Leslie S Ritter

Interests

Teaching

Physiology and Pathophysiology

Research

Stroke: 1. Mechanisms of inflammation in the cerebral microcirculation during reperfusion after stroke2. Stroke Systems of Care

Courses

Scholarly Contributions

Journals/Publications

• Laws, L. A., Ritter, L. S., Loescher, L. J., & McEwen, M. M. (2022). Stroke-Specific Refinements to Naylor's Transitional Care Model to Address the Storm of Uncertainty and Unmet Survivor and Caregiver Needs. J Neurosci Nurs, 54(1), 23-29. doi:doi: 10.1097/JNN.0000000000000629
• Ritter, L. S., Julian, G., Ruth, T., & Carolyn, M. (2019). Hidden Risks: Relationship Among Visceral Adipose Tissue, Interleukin-18, and Adiponectin in the Development of Type 2 Diabetes in Filipino Americans. Circulation.
• Haynes, H. N., Gallek, M. J., Sheppard, K. G., Drake, K. W., & Ritter, L. S. (2015). Transitions of care for stroke and TIA. Journal of the American Association of Nurse Practitioners, 27(10), 558-67.
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  The purpose of this study was to identify elements of a stroke population that may affect transitions of care (TOC).
• Martinez, M., Prabhakar, N., Drake, K., Coull, B., Chong, J., Ritter, L., & Kidwell, C. (2015). Identification of Barriers to Stroke Awareness and Risk Factor Management Unique to Hispanics. International journal of environmental research and public health, 13(1), ijerph13010023.
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  Barriers to risk factor control may differ by race/ethnicity. The goal of this study was to identify barriers to stroke awareness and risk factor management unique to Hispanics as compared to non-Hispanic whites (NHWs). We performed a prospective study of stroke patients from an academic Stroke Center in Arizona and surveyed members of the general community. Questionnaires included: the Duke Social Support Index (DSSI), the Multidimensional Health Locus of Control (MHLC) Scale, a stroke barriers questionnaire, and a Stroke Awareness Test. Of 145 stroke patients surveyed (72 Hispanic; 73 NHW), Hispanics scored lower on the Stroke Awareness Test compared to NHWs (72.5% vs. 79.1%, p = 0.029). Hispanic stroke patients also reported greater barriers related to medical knowledge, medication adherence, and healthcare access (p < 0.05 for all). Hispanics scored higher on the "powerful others" sub-scale (11.3 vs. 10, p < 0.05) of the MHLC. Of 177 members of the general public surveyed, Hispanics had lower stroke awareness compared to NHWs and tended to have lower awareness than Hispanic stroke patients. These results suggest that Hispanic stroke patients perceive less control over their health, experience more healthcare barriers, and demonstrate lower rates of stroke literacy. Interventions for stroke prevention and education in Hispanics should address these racial/ethnic differences in stroke awareness and barriers to risk factor control.
• Shaw, K. M., Gallek, M. J., Sheppard, K. G., Ritter, L., Vento, M. A., Asai, S. M., & Nakagawa, K. (2015). Ethnic Differences in Withdrawal of Life Support After Intracerebral Hemorrhage. Hawai'i journal of medicine & public health : a journal of Asia Pacific Medicine & Public Health, 74(6), 203-9.
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  Minorities are less likely to decide on withdrawal of life support (WOLS) after acute severe illness. However, the decision-making process for WOLS after intracerebral hemorrhage (ICH) among Native Hawaiians and other Pacific Islanders (NHOPI) has not been described. To address this gap in the literature, a retrospective study was conducted on consecutive spontaneous ICH patients admitted to a tertiary center in Honolulu between 2006 and 2010. The occurrence of WOLS and time-to-WOLS were the outcome measures. Unadjusted and multivariable logistic regression models were performed to determine associations between NHOPI ethnicity and WOLS. This study assessed 396 patients (18% NHOPI, 63% Asians, 15% non-Hispanic whites [NHW], 4% others) with ICH. NHOPI was associated with lower rate of WOLS than NHW in the univariate analysis (OR 0.35, 95% CI: 0.15, 0.80). However, NHOPI ethnicity was no longer significant when adjusted for age (OR 0.59, 95% CI: 0.25, 1.43) and in the fully adjusted model (OR 0.68, 95% CI: 0.20, 2.39). Although NHOPI with ICH were initially perceived to have less WOLS compared to NHW, this observed difference was largely driven by the younger age of NHOPI rather than from underlying cultural differences that are inherent to their ethnicity.
• Withycombe, J. S., Smith, L. M., Meza, J. L., Merkle, C., Faulkner, M. S., Ritter, L., Seibel, N. L., & Moore, K. (2015). Weight change during childhood acute lymphoblastic leukemia induction therapy predicts obesity: a report from the Children's Oncology Group. Pediatric blood & cancer, 62(3), 434-9.
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  Obesity is a well documented problem associated with childhood acute lymphoblastic leukemia (ALL) with increasing body mass index often observed during therapy. This study aims to evaluate if weight gain, early in therapy, is predictive of obesity at the end of treatment.
• Funk, J. L., Frye, J. B., Davis-Gorman, G., Spera, A. L., Bernas, M. J., Witte, M. H., Weinand, M. E., Timmermann, B. N., Mcdonagh, P. F., & Ritter, L. (2013). Curcuminoids limit neutrophil-mediated reperfusion injury in experimental stroke by targeting the endothelium. Microcirculation, 20(6), 544-554.
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  PMID: 23464666;PMCID: PMC3740077;Abstract: Objective: We sought to test the hypothesis that turmeric-derived curcuminoids limit reperfusion brain injury in an experimental model of stroke via blockade of early microvascular inflammation during reperfusion. Methods: Male Sprague Dawley rats subjected to MCAO/R were treated with turmeric-derived curcuminoids (vs. vehicle) 1 hour prior to reperfusion (300 mg/kg ip). Neutrophil adhesion to the cerebral microcirculation and measures of neutrophil and endothelial activation were assayed during early reperfusion (0-4 hours); cerebral infarct size, edema, and neurological function were assessed at 24 hours. Curcuminoid effects on TNFα-stimulated human brain microvascular endothelial cell (HBMVEC) were assessed. Results: Early during reperfusion following MCAO, curcuminoid treatment decreased neutrophil rolling and adhesion to the cerebrovascular endothelium by 76% and 67% and prevented >50% of the fall in shear rate. The increased number and activation state (CD11b and ROS) of neutrophils were unchanged by curcuminoid treatment, while increased cerebral expression of TNFα and ICAM-1, a marker of endothelial activation, were blocked by >30%. Curcuminoids inhibited NF-κB activation and subsequent ICAM-1 gene expression in HBMVEC. Conclusion: Turmeric-derived curcuminoids limit reperfusion injury in stroke by preventing neutrophil adhesion to the cerebrovascular microcirculation and improving shear rate by targeting the endothelium. © 2013 John Wiley & Sons Ltd.
• Ritter, L., Funk, J. L., Frye, J. B., Davis-Gorman, G., Spera, A. L., Bernas, M. J., Witte, M. H., Weinand, M. E., Timmermann, B. N., McDonagh, P. F., & Ritter, L. S. (2013). Curcuminoids limit neutrophil-mediated reperfusion injury in experimental stroke by targeting the endothelium. Microcirculation (New York, N.Y. : 1994), 20(6).
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  We sought to test the hypothesis that turmeric-derived curcuminoids limit reperfusion brain injury in an experimental model of stroke via blockade of early microvascular inflammation during reperfusion.
• Ritter, L., Rentfro, A. R., McEwen, M., & Ritter, L. S. (0). Perspectives for practice: translating estimated average glucose (eAG) to promote diabetes self-management capacity. The Diabetes educator, 35(4).
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  The purpose of this article is to facilitate translation of the Consensus Statement to practice for diabetes educators and other professionals who contribute to the care of individuals with diabetes.
• Siaki, L. A., Loescher, L. J., & Ritter, L. (2012). A cultural perspective of Samoans' perceived risk of cardiovascular disease and diabetes. Journal of Cardiovascular Nursing, 27(6), 468-475.
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  PMID: 21912273;Abstract: BACKGROUND: Cardiovascular disease (CVD) and diabetes, which are leading causes of morbidity and mortality in the United States, have a high incidence among Pacific Islanders. Risk of these conditions increases in the presence of metabolic syndrome. Risk-reducing behaviors for CVD and diabetes are driven partly by perceived risk of health threats and their consequences. Perceived risk is influenced by sociocultural beliefs and is a component of some health behavior models, yet it is understudied in Pacific Islanders. OBJECTIVE: This mixed-methods study explored the perceived risk of CVD and diabetes in at-risk Samoan Pacific Islanders. SUBJECTS AND METHODS: We used culturally sensitive strategies to recruit and enroll 43 adult Samoans from a community setting in Hawaii. Participants were obese with at least 1 other component of metabolic syndrome. Their objective risk was determined by the National Cholesterol Education Program Adult Treatment Program III risk categories. Participants provided demographic and health history information and answered 2 quantitative perceived risk questions. They also participated in 1 of 7 focus groups-the source of perceived risk qualitative data. Quantitative and qualitative data were analyzed using descriptive statistics and content analysis, respectively. The mixed-methods analysis targeted points of data convergence and complementarity for the 2 methods. RESULTS: More than 80% of participants who were at moderately high (10%-20%) objective risk for CVD and diabetes had high (>20%) perceived risk of these conditions. There was high concordance of perceived risk for CVD and diabetes (P < .05). Qualitative data revealed bidirectional codes that influenced and were influenced by perceived risk within the participants' cultural perspective: current and planned health behavior, physical health, and family history of CVD or diabetes. CONCLUSION: Using mixed methods facilitated better understanding of cultural perspectives of perceived risk of CVD and diabetes. These results provide a foundation for developing culturally appropriate interventions targeting CVD and diabetes risk reduction in Samoans. Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
• Gallek, M. J., & Ritter, L. (2011). Central nervous system genomics.. Annual review of nursing research, 29, 205-226.
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  PMID: 22891506;Abstract: In the past 25 years, remarkable progress has been made in our understanding of genomics and its influence on central nervous system diseases. In this chapter, common diseases of the central nervous system will be reviewed along with the genomics associated with these diseases. The diseases/injuries that will be investigated include neurovascular disorders such as ischemic stroke, hemorrhagic stroke, subarachnoid hemorrhage, and traumatic brain injury. This chapter will also explore Apolipoprotein E (APOE), a 299-aminoacid protein encoded by the APOE gene, and its associations with many of the previously named diseases. APOE was first tied to the risk of Alzheimer's disease and has since then been investigated in traumatic brain injury and hemorrhagic strokes. In addition, we will discuss the future of genomic research in central nervous system diseases.
• Morrison, H., Frye, J., Davis-Gorman, G., Funk, J., McDonagh, P., Stahl, G., & Ritter, L. (2011). The contribution of mannose binding lectin to reperfusion injury after ischemic stroke. Current Neurovascular Research, 8(1), 52-63.
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  PMID: 21208161;PMCID: PMC3512100;Abstract: After complement system (CS) activation, the sequential production of complement products increases cell injury and death through opsonophagocytosis, cytolysis, adaptive, and inflammatory cell responses. These responses potentiate cerebral ischemia-reperfusion (IR) injury after ischemic stroke and reperfusion. Activation of the CS via mannose binding lectin (MBL)-initiated lectin pathway is known to increase tissue damage in response to IR in muscle, myocardium and intestine tissue. In contrast, the contribution of this pathway to cerebral IR injury, a neutrophil-mediated event, is less clear. Therefore, we investigated the potential protective role of MBL deficiency in neutrophil-mediated cerebral injury after IR. Using an intraluminal filament method, neutrophil activation and cerebral injury were compared between MBL-deficient and wild type C57Bl/6 mice subjected to 60 minutes of MCA ischemia and reperfusion. Systemic neutrophil activation was not decreased in MBL-deficient animals after IR. In MBL-deficient animals, cerebral injury was significantly decreased only in the striatum (p < 0.05). Despite MBL deficiency, C3 depositions were evident in the injured hemisphere during reperfusion. These results indicate that while MBL deficiency results in a modest protection of a sub-cortical brain region during IR, redundant complement pathway activation may overwhelm further beneficial effects of MBL deficiency during reperfusion. © 2011 Bentham Science Publishers Ltd.
• Morrison, H., McKee, D., & Ritter, L. (2011). Systemic Neutrophil Activation in a Mouse Model of Ischemic Stroke and Reperfusion. Biological Research for Nursing, 13(2), 154-163.
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  PMID: 21044968;PMCID: PMC3555226;Abstract: As a natural response to injury and disease, neutrophils activate, adhere to the microvasculature, migrate into brain tissue, and release toxic substances such as reactive oxygen species and proteases. This neutrophil response occurs when blood flow is returned to brain tissue (reperfusion) after ischemic stroke. Thus, the presence of activated systemic neutrophils increases the potential for tissue injury during reperfusion after ischemic stroke. Although experiments in rat models suggest that activated neutrophils play a pivotal role in cerebral ischemia reperfusion injury, little is known about systemic neutrophil activation during reperfusion following ischemic stroke in a mouse model. The purpose of this study was to characterize systemic leukocyte responses and neutrophil CD11b expression 15-min and 24-hr post-reperfusion in a mouse model of ischemic stroke. The intraluminal filament method of transient middle cerebral artery occlusion (tMCAO) with reperfusion or a sham procedure was performed in male C57Bl/6 mice. Automated leukocyte counts and manual white blood cell (WBC) differential counts were measured. Flow cytometry was used to assess systemic neutrophil surface CD11b expression. The data suggest that the damaging potential of systemic neutrophil activation begins as early as 15 min and remains evident at 24 hr after the initiation of reperfusion. In addition, because transgenic mouse models, bred on a C57Bl/6 background, are increasingly used to elucidate single mechanisms of reperfusion injury after ischemic stroke, findings from this study are foundational for future investigations examining the damaging potential of neutrophil responses post-reperfusion after ischemic stroke in genetically altered mouse models within this background strain. © The Author(s) 2011.
• Ritter, L., Davidson, L., Henry, M., Davis-Gorman, G., Morrison, H., Frye, J. B., Cohen, Z., Chandler, S., Mcdonagh, P., & Funk, J. L. (2011). Exaggerated Neutrophil-Mediated Reperfusion Injury after Ischemic Stroke in a Rodent Model of Type 2 Diabetes. Microcirculation, 18(7), 552-561.
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  PMID: 21699626;Abstract: We tested the hypothesis that both chronic and acute inflammatory processes contribute to worse reperfusion injury and stroke outcome in an experimental model of T2DM. Materials and Methods: Twelve- to thirteen-week-old male Zucker Diabetic Fatty (ZDF) rats vs. Zucker Lean Controls (ZLC) rats were tested at baseline and after middle cerebral artery occlusion (ischemia) and reperfusion (I-R). Neutrophil adhesion to the cerebral microcirculation, neutrophil expression of CD11b, infarction size, edema, neurologic function, sICAM, and cerebral expression of neutrophil-endothelial inflammatory genes were measured. Results: At baseline, CD11b and sICAM were significantly increased in ZDF vs. ZLC animals (p
• Ritter, L., Gallek, M. J., & Ritter, L. S. (2011). Central nervous system genomics. Annual review of nursing research, 29.
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  In the past 25 years, remarkable progress has been made in our understanding of genomics and its influence on central nervous system diseases. In this chapter, common diseases of the central nervous system will be reviewed along with the genomics associated with these diseases. The diseases/injuries that will be investigated include neurovascular disorders such as ischemic stroke, hemorrhagic stroke, subarachnoid hemorrhage, and traumatic brain injury. This chapter will also explore Apolipoprotein E (APOE), a 299-aminoacid protein encoded by the APOE gene, and its associations with many of the previously named diseases. APOE was first tied to the risk of Alzheimer's disease and has since then been investigated in traumatic brain injury and hemorrhagic strokes. In addition, we will discuss the future of genomic research in central nervous system diseases.
• Ritter, L., Morrison, H., Frye, J., Davis-Gorman, G., Funk, J., McDonagh, P., Stahl, G., & Ritter, L. S. (2011). The contribution of mannose binding lectin to reperfusion injury after ischemic stroke. Current neurovascular research, 8(1).
  More info

  After complement system (CS) activation, the sequential production of complement products increases cell injury and death through opsonophagocytosis, cytolysis, adaptive, and inflammatory cell responses. These responses potentiate cerebral ischemia-reperfusion (IR) injury after ischemic stroke and reperfusion. Activation of the CS via mannose binding lectin (MBL)-initiated lectin pathway is known to increase tissue damage in response to IR in muscle, myocardium and intestine tissue. In contrast, the contribution of this pathway to cerebral IR injury, a neutrophil-mediated event, is less clear. Therefore, we investigated the potential protective role of MBL deficiency in neutrophil-mediated cerebral injury after IR. Using an intraluminal filament method, neutrophil activation and cerebral injury were compared between MBL-deficient and wild type C57Bl/6 mice subjected to 60 minutes of MCA ischemia and reperfusion. Systemic neutrophil activation was not decreased in MBL-deficient animals after IR. In MBL-deficient animals, cerebral injury was significantly decreased only in the striatum (p < 0.05). Despite MBL deficiency, C3 depositions were evident in the injured hemisphere during reperfusion. These results indicate that while MBL deficiency results in a modest protection of a sub-cortical brain region during IR, redundant complement pathway activation may overwhelm further beneficial effects of MBL deficiency during reperfusion.
• Ritter, L., Morrison, H., McKee, D., & Ritter, L. S. (2011). Systemic neutrophil activation in a mouse model of ischemic stroke and reperfusion. Biological research for nursing, 13(2).
  More info

  As a natural response to injury and disease, neutrophils activate, adhere to the microvasculature, migrate into brain tissue, and release toxic substances such as reactive oxygen species and proteases. This neutrophil response occurs when blood flow is returned to brain tissue (reperfusion) after ischemic stroke. Thus, the presence of activated systemic neutrophils increases the potential for tissue injury during reperfusion after ischemic stroke. Although experiments in rat models suggest that activated neutrophils play a pivotal role in cerebral ischemia reperfusion injury, little is known about systemic neutrophil activation during reperfusion following ischemic stroke in a mouse model. The purpose of this study was to characterize systemic leukocyte responses and neutrophil CD11b expression 15-min and 24-hr post-reperfusion in a mouse model of ischemic stroke. The intraluminal filament method of transient middle cerebral artery occlusion (tMCAO) with reperfusion or a sham procedure was performed in male C57Bl/6 mice. Automated leukocyte counts and manual white blood cell (WBC) differential counts were measured. Flow cytometry was used to assess systemic neutrophil surface CD11b expression. The data suggest that the damaging potential of systemic neutrophil activation begins as early as 15 min and remains evident at 24 hr after the initiation of reperfusion. In addition, because transgenic mouse models, bred on a C57Bl/6 background, are increasingly used to elucidate single mechanisms of reperfusion injury after ischemic stroke, findings from this study are foundational for future investigations examining the damaging potential of neutrophil responses post-reperfusion after ischemic stroke in genetically altered mouse models within this background strain.
• Wysocki, K., & Ritter, L. (2011). Diseasome: an approach to understanding gene-disease interactions.. Annual review of nursing research, 29, 55-72.
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  PMID: 22891498;Abstract: Using bioinformatics computational tools, network maps that integrate the complex interactions of genetics and diseases have been developed. The purpose of this review is to introduce the reader to new approaches in understanding disease-gene associations using network maps, with an emphasis on how the human disease network (HDN) map (or diseasome) was constructed. A search was conducted in PubMed using the years 1999-2011 and using key words diseasome, molecular interaction, interactome, protein-protein interaction, and gene. The information reviewed included journal reviews, open source and web-based databases, and open source computational tools. A review of the literature revealed the complexity of molecular, genetic, and protein structures that contribute to cellular function and possible disease, and how network mapping can help the clinician and scientist gain a better understanding of this complexity Using computational tools and databases of genetics, protein interactions, and diseases, scientists have developed a network map of human genes and human diseases referred to as a diseasome. The diseasome is composed of 22 disease classes represented in different colored circular nodes. Lines connecting nodes indicate shared genes among diseases. Thus, the diseasome map provides a colorfully visual display that helps the user conceptualize gene-disease relationships. This review provides an overview of the use of network maps to understand the interrrelationships of genomics and disease. One such map, the diseasome, could be used as a reference for biomedical researchers and multidiscipline health care providers, including nurse practitioners and genetic counselors, to enhance their conceptualization and understanding of the genetic origins of disease.
• Henry, M., Davidson, L., Cohen, Z., McDonagh, P. F., Nolan, P. E., & Ritter, L. S. (2009). Whole blood aggregation, coagulation, and markers of platelet activation in diet-induced diabetic C57BL/6J mice. Diabetes Research and Clinical Practice, 84(1), 11-18.
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  PMID: 19233499;Abstract: Aims: Type 2 diabetes in humans is associated with hypercoaguability; however, little is known about platelet function in mouse models of type 2 diabetes used to study this disorder. Therefore, the purpose of this study was to examine platelet aggregation, coagulation, and markers of platelet activation in a diet-induced mouse model of type 2 diabetes. Methods: Four week old, male, C57BL/6J mice were randomized to a standard chow or high fat (60% beef lard) diet for 4 months. To examine platelet function we measured ADP-induced whole blood aggregometry, whole blood coagulation by thromboelastography, tail bleeding times, platelet microparticle and platelet expression of p-selectin and platelet expression of CD61 by flow cytometry. Results: Diabetic mice exhibited less aggregation (p < 0.05), less coagulation (p < 0.01), prolonged tail bleeding times (n.s.), and lower agonist stimulated platelet CD61 expression (p < 0.001) compared to non-diabetic mice. There was no difference in platelet microparticle and platelet p-selectin expression. Conclusions: Diet-induced type 2 diabetic mouse do not demonstrate the hypercoagulability and platelet activation typically observed in humans with this disorder. More studies are warranted to further explore platelet function in this mouse model; to determine their applicability for studying these alterations in type 2 diabetes. © 2009 Elsevier Ireland Ltd. All rights reserved.
• Rentfro, A. R., McEwen, M., & Ritter, L. (2009). Perspectives for practice: Translating estimated average glucose (eAG) to promote diabetes self-management capacity. Diabetes Educator, 35(4), 581-594.
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  PMID: 19633165;Abstract: Purpose: The purpose of this article is to facilitate translation of the Consensus Statement to practice for diabetes educators and other professionals who contribute to the care of individuals with diabetes. Methods: The 2007 Consensus Statement from the American Diabetes Association (ADA), European Association for the Study of Diabetes (EASD), International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), and International Diabetes Federation (IDF) called for the standardization of glycated hemoglobin measurement in reporting and use of average glucose values in clinical practice. Results: Conversion of glycated hemoglobin percentage to average blood glucose was anchored historically in early laboratory techniques linked to disease outcomes rather than to definitive laboratory standardization. Recently, the A1C-Derived Average Glucose (ADAG) study demonstrated that A1C values can be accurately expressed as estimated average glucose (eAG) and endorsed eAG as the best way to standardize the expression of laboratory values of glycated hemoglobin. Conclusions: Adoption of the 2007 Consensus Statement will influence clinical practice and decision making and subsequently influence self-management for individuals with diabetes. © 2009 The Author(s).
• Cohen, Z., Davis-Gorman, G., McDonagh, P. F., & Ritter, L. (2008). Caspase inhibition of platelet activation. Blood Coagulation and Fibrinolysis, 19(4), 305-309.
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  PMID: 18469552;Abstract: The role of caspases in platelet function is not well understood. When platelets are activated, they express phosphatidylserine on the outer plasma membrane, form platelet microparticles, and aggregate (Pag). The aims of this study were to determine if caspases play a role in the platelet activation seen in type 2 diabetes. Diabetic rats (Zucker diabetic fatty) were treated with a broad-spectrum caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone, in vivo and platelets were evaluated for phosphatidylserine expression, platelet microparticle formation, and Pag. We found a decreased phosphatidylserine exposure in zVAD-Zucker diabetic fatty rats compared to Zucker diabetic fatty-phosphate-buffered saline when activated with 20 μmol/l ADP. Zucker diabetic fatty rats treated with benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone decreased platelet microparticle numbers compared to phosphate-buffered saline control Zucker diabetic fatty rats. Further, treatment with benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone significantly decreased Pag. These results indicate that caspases play a role in platelet activation, suggesting a unique physiologic role of these proteases and perhaps the underlying mechanisms involved in the chronic platelet activation observed in type 2 diabetes. © 2008 Lippincott Williams & Wilkins, Inc.
• Henry, M. L., Davidson, L. B., Wilson, J. E., McKenna, B. K., Scott, S. A., McDonagh, P. F., & Ritter, L. S. (2008). Whole blood aggregation and coagulation in db/db and ob/ob mouse models of type 2 diabetes. Blood Coagulation and Fibrinolysis, 19(2), 124-134.
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  PMID: 18277133;Abstract: Type 2 diabetes in humans is associated with a significant hypercoagulable state; however, the effects of this on stroke and cardiovascular disease are not completely understood. The genetic mutations in db/db and ob/ob mice produce metabolic abnormalities similar to type 2 diabetes, but little is known about their platelet or coagulation properties. The objective of this study was therefore to examine platelet function and coagulation in db/db and ob/ob mice to determine the degree of alteration induced by type 2 diabetes. Male db/db and ob/ob mice, 8-16 weeks old, and their respective genetic control mice were used for all experiments. To examine platelet function and coagulation, we measured ADP-induced whole blood aggregation at baseline and after inhibition with aspirin and fucoidan, whole blood coagulation by thromboelastography, and platelet CD61 expression by flow cytometry. Both db/db and ob/ob mice demonstrated significantly less ADP-induced whole blood aggregation compared with control mice (db/db mice, P < 0.001; ob/ob mice, P < 0.01). Aggregation was significantly inhibited with aspirin in all groups; however, fucoidan inhibited aggregation only in control mice. The db/db and ob/ob mice demonstrated significantly less maximal clot strength compared with control mice (P < 0.01), and ob/ob mice demonstrated premature clot fibrinolysis measured by thromboelastography. In conclusion, the db/db and ob/ob type 2 diabetes mouse models do not demonstrate a hypercoagulable state similar to humans with this disease. We caution their use for studying cardiovascular and cerebrovascular disease in the setting of type 2 diabetes. © 2008 Lippincott Williams & Wilkins, Inc.
• Ritter, L. (2008). Ischemia-reperfusion injury after stroke: From mechanisms to a nursing process. Nursing Science Quarterly, 21(1), 41-42.
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  PMID: 18246645;
• Ritter, L., & Ritter, L. S. (2008). Ischemia-reperfusion injury after stroke: from mechanisms to a nursing process. Nursing science quarterly, 21(1).
• Ritter, L., Cohen, Z., Davis-Gorman, G., McDonagh, P. F., & Ritter, L. S. (2008). Caspase inhibition of platelet activation. Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis, 19(4).
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  The role of caspases in platelet function is not well understood. When platelets are activated, they express phosphatidylserine on the outer plasma membrane, form platelet microparticles, and aggregate (Pag). The aims of this study were to determine if caspases play a role in the platelet activation seen in type 2 diabetes. Diabetic rats (Zucker diabetic fatty) were treated with a broad-spectrum caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone, in vivo and platelets were evaluated for phosphatidylserine expression, platelet microparticle formation, and Pag. We found a decreased phosphatidylserine exposure in zVAD-Zucker diabetic fatty rats compared to Zucker diabetic fatty-phosphate-buffered saline when activated with 20 micromol/l ADP. Zucker diabetic fatty rats treated with benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone decreased platelet microparticle numbers compared to phosphate-buffered saline control Zucker diabetic fatty rats. Further, treatment with benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone significantly decreased Pag. These results indicate that caspases play a role in platelet activation, suggesting a unique physiologic role of these proteases and perhaps the underlying mechanisms involved in the chronic platelet activation observed in type 2 diabetes.
• Ritter, L., Funk, J., Schenkel, L., Tipton, A., Downey, K., Wilson, J., Coull, B., & McDonagh, P. (2008). Inflammatory and hemodynamic changes in the cerebral microcirculation of aged rats after global cerebral ischemia and reperfusion. Microcirculation, 15(3), 297-310.
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  Abstract: Effects of aging on inflammation and blood flow in the brain are unclear. Young (three to six months) and aged (19-22 months) male Brown Norway Fisher rats were used to compare (i) leukocyte function in nonischemic conditions and (ii) leukocyte function and hemodynamic changes after ischemia-reperfusion (I-R). In nonischemic studies, polymorphonuclear (PMN) CD11b expression and reactive oxygen species (ROS) production were measured with flow cytometry and PMN chemotaxis was measured with a Boyden chamber (+/-fMLP). In I-R studies, ischemia was induced by bilateral carotid artery occlusion and hypotension (20 minutes). During early reperfusion (30 minutes), leukocyte adhesion and rolling and blood-shear rates were measured using fluorescence microscopy. During late reperfusion (48 hours), mortality, neurological function, and leukocyte infiltration were measured. Stimulated PMN chemotaxis was increased in nonischemic aged rats (p > 0.05). In early reperfusion, there was a significant increase in leukocyte rolling and adhesion in the cerebral microcirculation and a significant decrease in shear rate in aged rats, compared to the young (p > 0.05). During late reperfusion, neurologic function was worse in aged vs. young rats (p > 0.05). These findings suggest that increased intravascular PMN adhesion and vascular dysfunction may contribute to poor neurologic outcome after cerebral I-R in the aged brain.
• Ritter, L., Funk, J., Schenkel, L., Tipton, A., Downey, K., Wilson, J., Coull, B., & McDonagh, P. (2008). Inflammatory and hemodynamic changes in the cerebral microcirculation of aged rats after global cerebral ischemia and reperfusion. Microcirculation, 15(4), 297-310.
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  PMID: 18464159;Abstract: Effects of aging on inflammation and blood flow in the brain are unclear. Young (three to six months) and aged (19-22 months) male Brown Norway Fisher rats were used to compare (i) leukocyte function in nonischemic conditions and (ii) leukocyte function and hemodynamic changes after ischemia-reperfusion (I-R). In nonischemic studies, polymorphonuclear (PMN) CD11b expression and reactive oxygen species (ROS) production were measured with flow cytometry and PMN chemotaxis was measured with a Boyden chamber (+/-fMLP). In I-R studies, ischemia was induced by bilateral carotid artery occlusion and hypotension (20 minutes). During early reperfusion (30 minutes), leukocyte adhesion and rolling and blood-shear rates were measured using fluorescence microscopy. During late reperfusion (48 hours), mortality, neurological function, and leukocyte infiltration were measured. Stimulated PMN chemotaxis was increased in nonischemic aged rats (p < 0.05). In early reperfusion, there was a significant increase in leukocyte rolling and adhesion in the cerebral microcirculation and a significant decrease in shear rate in aged rats, compared to the young (p < 0.05). During late reperfusion, neurologic function was worse in aged vs. young rats (p < 0.05). These findings suggest that increased intravascular PMN adhesion and vascular dysfunction may contribute to poor neurologic outcome after cerebral I-R in the aged brain.
• Ritter, L., Henry, M. L., Davidson, L. B., Wilson, J. E., McKenna, B. K., Scott, S. A., McDonagh, P. F., & Ritter, L. S. (2008). Whole blood aggregation and coagulation in db/db and ob/ob mouse models of type 2 diabetes. Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis, 19(2).
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  Type 2 diabetes in humans is associated with a significant hypercoagulable state; however, the effects of this on stroke and cardiovascular disease are not completely understood. The genetic mutations in db/db and ob/ob mice produce metabolic abnormalities similar to type 2 diabetes, but little is known about their platelet or coagulation properties. The objective of this study was therefore to examine platelet function and coagulation in db/db and ob/ob mice to determine the degree of alteration induced by type 2 diabetes. Male db/db and ob/ob mice, 8-16 weeks old, and their respective genetic control mice were used for all experiments. To examine platelet function and coagulation, we measured ADP-induced whole blood aggregation at baseline and after inhibition with aspirin and fucoidan, whole blood coagulation by thromboelastography, and platelet CD61 expression by flow cytometry. Both db/db and ob/ob mice demonstrated significantly less ADP-induced whole blood aggregation compared with control mice (db/db mice, P < 0.001; ob/ob mice, P < 0.01). Aggregation was significantly inhibited with aspirin in all groups; however, fucoidan inhibited aggregation only in control mice. The db/db and ob/ob mice demonstrated significantly less maximal clot strength compared with control mice (P < 0.01), and ob/ob mice demonstrated premature clot fibrinolysis measured by thromboelastography. In conclusion, the db/db and ob/ob type 2 diabetes mouse models do not demonstrate a hypercoagulable state similar to humans with this disease. We caution their use for studying cardiovascular and cerebrovascular disease in the setting of type 2 diabetes.
• Maes, M. L., Davidson, L. B., McDonagh, P. F., & Ritter, L. S. (2007). Comparison of sample fixation and the use of LDS-751 or anti-CD45 for leukocyte identification in mouse whole blood for flow cytometry. Journal of Immunological Methods, 319(1-2), 79-86.
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  PMID: 17187818;PMCID: PMC1896319;Abstract: Flow cytometry methods used to measure leukocyte function often entail sample preparation procedures that cause artifactual cell activation. To avoid leukocyte activation by isolation techniques, some preparation methods use fluorescent markers to discriminate leukocytes from erythrocytes in whole blood. One of these markers, laser dye styryl-751(LDS-751), has been used to distinguish leukocytes by staining nucleic acid, but has been found to stain other blood cells and dead cells indiscriminately. Thus, LDS-751 may not be an appropriate reagent for leukocyte identification in whole blood. Fixing samples with formaldehydes increases cell permeability and causes surface protein cross-linking that may alter staining of both intra- and extracellular markers. The degree of this sample alteration by formaldehyde fixation, however, remains in question. In addition, little is known about flow cytometry and sample preparation methods in mouse whole blood. The purpose of this study was to determine if labeling leukocytes with a monoclonal antibody specific to leukocyte common antigen (CD45) was superior to labeling with LDS-751 and to determine the effect of sample fixation on a mouse whole blood preparation for flow cytometry. Samples were incubated with CD16/CD32 Fc receptor blocker, and either 10 μg/ml LDS-751 or phosphate buffered saline (PBS). The samples were then fixed with paraformaldehyde or diluted with PBS followed by incubation with 5 μg/ml PerCP-conjugated anti-CD45, 5 μg/ml FITC-conjugated anti-CD11b, or 80 μM dichlorofluorescein diacetate. We found that samples labeled with LDS-751 demonstrated decreased fluorescence intensity for granulocyte CD11b expression and ROS production compared to samples labeled with anti-CD45. In addition, sample fixation decreased mean fluorescence intensity in samples labeled with either LDS-751 or anti-CD45. We conclude that labeling leukocytes with monoclonal antibody CD45 in a mouse whole blood preparation is preferable, as it provides improved measurement of leukocyte indices compared to LDS-751. Also, while sample fixation prior to antibody staining caused a decrease in overall fluorescence; it can be used to successfully identify extra-cellular markers. © 2006 Elsevier B.V. All rights reserved.
• Ritter, L., Maes, M. L., Davidson, L. B., McDonagh, P. F., & Ritter, L. S. (2007). Comparison of sample fixation and the use of LDS-751 or anti-CD45 for leukocyte identification in mouse whole blood for flow cytometry. Journal of immunological methods, 319(1-2).
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  Flow cytometry methods used to measure leukocyte function often entail sample preparation procedures that cause artifactual cell activation. To avoid leukocyte activation by isolation techniques, some preparation methods use fluorescent markers to discriminate leukocytes from erythrocytes in whole blood. One of these markers, laser dye styryl-751(LDS-751), has been used to distinguish leukocytes by staining nucleic acid, but has been found to stain other blood cells and dead cells indiscriminately. Thus, LDS-751 may not be an appropriate reagent for leukocyte identification in whole blood. Fixing samples with formaldehydes increases cell permeability and causes surface protein cross-linking that may alter staining of both intra- and extracellular markers. The degree of this sample alteration by formaldehyde fixation, however, remains in question. In addition, little is known about flow cytometry and sample preparation methods in mouse whole blood. The purpose of this study was to determine if labeling leukocytes with a monoclonal antibody specific to leukocyte common antigen (CD45) was superior to labeling with LDS-751 and to determine the effect of sample fixation on a mouse whole blood preparation for flow cytometry. Samples were incubated with CD16/CD32 Fc receptor blocker, and either 10 microg/ml LDS-751 or phosphate buffered saline (PBS). The samples were then fixed with paraformaldehyde or diluted with PBS followed by incubation with 5 microg/ml PerCP-conjugated anti-CD45, 5 microg/ml FITC-conjugated anti-CD11b, or 80 microM dichlorofluorescein diacetate. We found that samples labeled with LDS-751 demonstrated decreased fluorescence intensity for granulocyte CD11b expression and ROS production compared to samples labeled with anti-CD45. In addition, sample fixation decreased mean fluorescence intensity in samples labeled with either LDS-751 or anti-CD45. We conclude that labeling leukocytes with monoclonal antibody CD45 in a mouse whole blood preparation is preferable, as it provides improved measurement of leukocyte indices compared to LDS-751. Also, while sample fixation prior to antibody staining caused a decrease in overall fluorescence; it can be used to successfully identify extra-cellular markers.
• Ritter, L. S., Stempel, K. M., Coull, B. M., & McDonagh, P. F. (2005). Leukocyte-platelet aggregates in rat peripheral blood after ischemic stroke and reperfusion. Biological Research for Nursing, 6(4), 281-288.
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  PMID: 15788737;Abstract: Ischemic stroke and reperfusion (ISR) is associated with an inflammatory response characterized, in part, by the formation of leukocyte-platelet aggregates (LPA). Aggregate formation may amplify the immunologic and hemostatic functions of both cell types and thus exacerbate reperfusion injury after ischemic stroke. LPA formation in peripheral blood may also serve as a biomarker of the severity of injury. However, it is not fully known whether ISR causes LPA formation that can be detected in the peripheral blood. Therefore, the purpose of this study was to measure LPA in the peripheral blood after ISR using a rat model. The filament method was used to perform ISR. Blood was collected from the jugular vein before ischemia, after 4 hours of ischemia, and after 1 hour of reperfusion. Flow cytometry was used to quantify LPA in peripheral blood. Separate ISR groups were treated with tirofiban, a platelet GPIIb/IIIa inhibitor, and fucoidan, a selectin adhesion molecule inhibitor, and analyzed for LPA. Leukocyte CD11b expression and reactive oxygen species production were also analyzed to note the role of polymorphonuclear neutrophilic (PMN) activation on LPA formation. After ISR, LPA levels in peripheral blood were twice as large as preischemic levels. Both GPIIb/IIIa and selectin adhesion molecule inhibition (p
• Cohen, Z., Wilson, J., Ritter, L., & McDonagh, P. (2004). Caspase inhibition decreases both platelet phosphatidylserine exposure and aggregation: Caspase inhibition of platelets. Thrombosis Research, 113(6), 387-393.
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  PMID: 15226093;Abstract: Apoptosis of nucleated cells is regulated by caspases, a group of cysteine proteases, and is characterized by phosphatidylserine expression on the outer leaflet of the plasma membrane. Reports indicate that platelets contain caspases. However, the role of caspases in platelet function is not well understood. When platelets become activated, they express phosphatidylserine (PS) on the outer leaflet of the plasma membrane. In addition, platelets aggregate when activated. The aims of this study were to determine if caspase inhibition (using the pan-caspase inhibitor zVAD-fmk): (1) decreased PS expression and (2) decreased platelet aggregation following activation. Flow cytometry was used to determine PS expression and a platelet aggregometer was used to assess aggregation. We found that platelets treated with zVAD-fmk significantly decreased both A23187-induced PS exposure (total fluorescence index, TFI: A23187=791.42±174; zVAD+A23187=92.97±57, p≤0.05) and ADP-induced PS exposure (TFI: ADP=669.24±145, zVAD+ADP=174. 6±151, p≤0.05). Further, treatment with zVAD-fmk significantly decreased ADP-induced platelet aggregation (%: untreated=80±1.5, zVAD treated=69±3.0, p≤0.05). These results indicate that caspases play a role in platelet activation, suggesting a unique physiologic role for these proteases. © 2004 Elsevier Ltd. All rights reserved.
• Funk, J. L., Migliati, E., Chen, G., Wei, H., Wilson, J., Downey, K. J., Mullarky, P. J., Coull, B. M., McDonagh, P. F., & Ritter, L. S. (2003). Parathyroid hormone-related protein induction in focal stroke: A neuroprotective vascular peptide. American Journal of Physiology - Regulatory Integrative and Comparative Physiology, 284(4 53-4), R1021-R1030.
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  PMID: 12456385;Abstract: Parathyroid hormone-related protein (PTHrP) is a multifunctional peptide that enhances blood flow in non-central nervous system (CNS) vascular beds by causing vasodilation. PTHrP expression is induced in non-CNS organs in response to ischemia. Experiments were therefore undertaken to determine whether PTHrP can be induced in brain in response to ischemic injury and whether PTHrP can act locally as a vasodilator in the cerebral vasculature, an effect that could be neuroprotective in the setting of stroke. PTHrP expression was examined by Northern analysis and immunohistochemical staining in male Sprague-Dawley rats subjected to permanent middle cerebral artery occlusion (MCAO). Vasodilatory effects of superfused PTHrP(1-34) on pial arterioles were determined by intravital fluorescence microscopy. Effects of PTHrP(1-34) peptide administration on MCAO infarction size reduction were assessed. PTHrP expression was induced in the ischemic hemisphere as early as 4 h after MCAO and remained elevated for up to 24 h. Increased immunoreactive PTHrP at sites of ischemic tissue injury was located in the cerebral microvessels. Superfusion with PTHrP(1-34) peptide for up to 25 min increased pial arteriolar diameter by 30% in normal animals. In animals with permanent MCAO, PTHrP(1-34) peptide treatment significantly decreased cortical infarct size (-47%). In summary, PTHrP expression increases at sites of ischemic brain injury in the cerebrovasculature. This local increase in PTHrP could be an adaptive response that enhances blood flow to the ischemic brain, thus limiting cell injury.
• Ritter, L., Funk, J. L., Migliati, E., Chen, G., Wei, H., Wilson, J., Downey, K. J., Mullarky, P. J., Coull, B. M., McDonagh, P. F., & Ritter, L. S. (2003). Parathyroid hormone-related protein induction in focal stroke: a neuroprotective vascular peptide. American journal of physiology. Regulatory, integrative and comparative physiology, 284(4).
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  Parathyroid hormone-related protein (PTHrP) is a multifunctional peptide that enhances blood flow in non-central nervous system (CNS) vascular beds by causing vasodilation. PTHrP expression is induced in non-CNS organs in response to ischemia. Experiments were therefore undertaken to determine whether PTHrP can be induced in brain in response to ischemic injury and whether PTHrP can act locally as a vasodilator in the cerebral vasculature, an effect that could be neuroprotective in the setting of stroke. PTHrP expression was examined by Northern analysis and immunohistochemical staining in male Sprague-Dawley rats subjected to permanent middle cerebral artery occlusion (MCAO). Vasodilatory effects of superfused PTHrP(1-34) on pial arterioles were determined by intravital fluorescence microscopy. Effects of PTHrP(1-34) peptide administration on MCAO infarction size reduction were assessed. PTHrP expression was induced in the ischemic hemisphere as early as 4 h after MCAO and remained elevated for up to 24 h. Increased immunoreactive PTHrP at sites of ischemic tissue injury was located in the cerebral microvessels. Superfusion with PTHrP(1-34) peptide for up to 25 min increased pial arteriolar diameter by 30% in normal animals. In animals with permanent MCAO, PTHrP(1-34) peptide treatment significantly decreased cortical infarct size (-47%). In summary, PTHrP expression increases at sites of ischemic brain injury in the cerebrovasculature. This local increase in PTHrP could be an adaptive response that enhances blood flow to the ischemic brain, thus limiting cell injury.
• Ritter, L., Ruehl, M. L., Orozco, J. A., Stoker, M. B., McDonagh, P. F., Coull, B. M., & Ritter, L. S. (2002). Protective effects of inhibiting both blood and vascular selectins after stroke and reperfusion. Neurological research, 24(3).
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  Early intervention after acute ischemic stroke is essential to minimize brain cell injury. Although reperfusion of the ischemic brain is the treatment of choice for acute stroke, reperfusion itself may cause additional injury. The inflammatory cascade, characterized in part by early leukocyte interaction with endothelium, may contribute to this additional injury to blood vessels and surrounding brain tissue, extending the area of infarction. The selectin family of adhesion molecules mediates the initial, rolling and tethering of leukocytes to endothelium. P-selectin is rapidly expressed on ischemic endothelium in the brain vasculature, and L-selectin is expressed on leukocytes. Blocking the selectin-mediated tethering step may limit the inflammatory component of reperfusion injury in the brain. Fucoidin (FCN), a competitive inhibitor of P- and L-selectin, has been reported to decrease leukocyte accumulation during reperfusion of other organs. The effect of both leukocyte and endothelial selectin inhibition after cerebral ischemia and reperfusion has not been previously examined. The purpose of this study was to determine the effects of selectin adhesion molecule blockade on cerebral infarction size and neurological function after middle cerebral artery occlusion and reperfusion (MCAO-R) in the rat. MCAO was induced using the filament method. All animals were subjected to 4 h of MCAO and 24 h of reperfusion. After 24 h, brains were analyzed for size of infarction. Neurological function was assessed during stroke and 24 h after reperfusion. Two groups were studied, an untreated control group (n = 9) and a group treated with the selectin inhibitor, fucoidin (25 mg kg(-1)) (n = 9). We found that selectin blockade significantly reduced cerebral infarction size by 50% (p < 0.05) and improved neurological function (p < 0.05). In addition, a trend toward decreased cerebral edema was demonstrated with selectin inhibition. These results indicate that treatment of the blood and the endothelium with a selectin anti-inflammatory agent is protective after focal stroke and reperfusion in the rat.
• Ruehl, M. L., Orozco, J. A., Stoker, M. B., McDonagh, P. F., Coull, B. M., & Ritter, L. S. (2002). Protective effects of inhibiting both blood and vascular selectins after stroke and reperfusion. Neurological Research, 24(3), 226-232.
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  PMID: 11958413;Abstract: Early intervention after acute ischemic stroke is essential to minimize brain cell injury. Although reperfusion of the ischemic brain is the treatment of choice for acute stroke, reperfusion itself may cause additional injury. The inflammatory cascade, characterized in part by early leukocyte interaction with endothelium, may contribute to this additional injury to blood vessels and surrounding brain tissue, extending the area of infarction. The selectin family of adhesion molecules mediates the initial, rolling and tethering of leukocytes to endothelium. P-selectin is rapidly expressed on ischemic endothelium in the brain vasculature, and L-selectin is expressed on leukocytes. Blocking the selectin-mediated tethering step may limit the inflammatory component of reperfusion injury in the brain. Fucoidin (FCN), a competitive inhibitor of P- and L-selectin, has been reported to decrease leukocyte accumulation during reperfusion of other organs. The effect of both leukocyte and endothelial selectin inhibition after cerebral ischemia and reperfusion has not been previously examined. The purpose of this study was to determine the effects of selectin adhesion molecule blockade on cerebral infarction size and neurological function after middle cerebral artery occlusion and reperfusion (MCAO-R) in the rat. MCAO was induced using the filament method. All animals were subjected to 4 h of MCAO and 24 h of reperfusion. After 24 h, brains were analyzed for size of infarction. Neurological function was assessed during stroke and 24 h after reperfusion. Two groups were studied, an untreated control group (n = 9) and a group treated with the selectin inhibitor, fucoidin (25 mg kg-1) (n = 9). We found that selectin blockade significantly reduced cerebral infarction size by 50% (p < 0.05) and improved neurological function (p < 0.05). In addition, a trend toward decreased cerebral edema was demonstrated with selectin inhibition. These results indicate that treatment of the blood and the endothelium with a selectin anti-inflammatory agent is protective after focal stroke and reperfusion in the rat.
• Gale, S. C., Hokama, J. Y., Ritter, L. S., Gorman, G. D., Copeland, J. G., & McDonagh, P. F. (2001). Pentoxifylline reduces coronary leukocyte accumulation early in reperfusion after cold ischemia. Annals of Thoracic Surgery, 71(4), 1305-1311.
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  PMID: 11308178;Abstract: Background. Ischemia/reperfusion injury can complicate recovery in cardiac operations. Ischemia induces endothelial dysfunction, which may contribute to leukocyte accumulation during reperfusion. Leukocyte-mediated injury may then occur. Using intravital microscopy we previously reported increased leukocyte retention in coronary capillaries and venules during early reperfusion during warm ischemia/reperfusion. In this study we investigated whether cold cardioplegic protection would limit leukocyte sequestration in coronary microvessels early in reperfusion. Pentoxifylline (PTX) has antiinflammatory effects and may limit endothelial dysfunction during ischemia/reperfusion. The effect of cardioplegia modification with PTX was also examined. Methods. Isolated rat hearts were subjected to 90 minutes of 4°C ischemia after arrest with cardioplegia. Hearts were reperfused with diluted whole blood containing fluorescent-labeled leukocytes. Leukocyte retention in coronary microvessels was observed with intravital microscopy. Three groups were studied, nonischemic control, cold ischemia, and PTX-modified cold ischemia. Results. In coronary capillaries, leukocyte trapping was nearly doubled in unmodified cold ischemia versus control. PTX modification significantly reduced leukocyte accumulation. In coronary venules, greater leukocyte adhesion was observed in unmodified cold ischemia compared to nonischemic controls. PTX modification significantly reduced leukocyte adhesion. Conclusions. Cold cardioplegia did not prevent leukocyte retention in the coronary microcirculation early in reperfusion. PTX modification of cardioplegia significantly reduced leukocyte sequestration in coronary capillaries and venules. Preserving endothelial function during ischemia may limit leukocyte accumulation and ischemia/reperfusion injury after cardiac operation. © 2001 by The Society of Thoracic Surgeons.
• Hokama, J. Y., Ritter, L. S., Davis-Gorman, G., Cimetta, A. D., Copeland, J. G., & McDonagh, P. F. (2000). Diabetes enhances leukocyte accumulation in the coronary microcirculation early in reperfusion following ischemia. Journal of Diabetes and its Complications, 14(2), 96-107.
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  PMID: 10959072;Abstract: Background: Diabetic hearts are particularly vulnerable to ischemia- reperfusion injury. For leukocytes to participate in ischemia-reperfusion injury, they must first sequester in the microcirculation. The aim of this study was to determine, by direct observation, if early leukocyte deposition was increased in the diabetic coronary microcirculation early in reperfusion following myocardial ischemia. Methods: Non-diabetic and streptozotocin (STZ)-induced diabetic rat hearts, subjected to 30 min of 37°C, no-flow ischemia, were initially reperfused with blood containing labeled leukocytes. The deposition of fluorescent leukocytes in coronary capillaries and venules was directly visualized and recorded using intravital fluorescence microscopy. In addition, flow cytometry was used to measure CD11b adhesion molecule expression on polymorphonuclear (PMN) leukocytes from non-diabetic and STZ-diabetic rats. Results: In the non-diabetic, control hearts, early in reperfusion, leukocytes trapped in coronary capillaries and adhered to the walls of post-capillary venules. In the diabetic hearts, leukocyte trapping in capillaries and adhesion to venules were both significantly increased (P < 0.05). PMN CD11b expression was also significantly increased in the diabetic blood compared to the non-diabetic blood (P < 0.05). Conclusions: Early in reperfusion following myocardial ischemia, leukocytes rapidly accumulate in greater numbers in the coronary microcirculation of the diabetic heart by both trapping in coronary capillaries and by adhering to venules. The enhanced retention of leukocytes in the diabetic coronary microcirculation increases the likelihood of inflammation-mediated reperfusion injury and may explain, in part, the poor recovery of diabetic hearts from an ischemic event. (C) 2000 Elsevier Science Inc.
• Ritter, L. S., Orozco, J. A., Coull, B. M., & McDonagh, P. F. (2000). Leukocyte accumulation and hemodynamic changes in the cerebral microcirculation during early reperfusion after stroke. Stroke, 31(5), 1153-1161.
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  PMID: 10797180;Abstract: Background and Purpose - Leukocytes contribute to cerebral ischemia- reperfusion injury. However, few experimental models examine both in vivo behavior of leukocytes and microvascular rheology after stroke. The purpose of the present study was to characterize patterns of leukocyte accumulation in the cerebral microcirculation and to examine the relationship between leukocyte accumulation and microcirculatory hemodynamics after middle cerebral artery occlusion and reperfusion (MCAO-R). Methods - Male rats (250 to 350 g) were anesthetized and ventilated. Tail catheters were inserted for measurement of arterial blood gases and administration of drugs. Body temperature was maintained at 37°C. Animals were subjected to 2 hours of MCAO by the filament method. A cranial-window preparation was performed, and the brain was superfused with warm, aerated artificial cerebrospinal fluid. Reperfusion was initiated by withdrawing the filament, and the pial microcirculation was observed by use of intravital fluorescence microscopy. Leukocyte accumulation in venules, arterioles, and capillaries; leukocyte rolling in venules; and leukocyte venular shear rate were assessed during 1 hour of reperfusion. Results - We found significant leukocyte adhesion in cerebral venules during 1 hour of reperfusion after 2 hours of MCAO. Leukocyte trapping in capillaries and adhesion to arterioles after MCAO-R tended to increase compared with controls, but the increase was not significant. We also found that shear rate was significantly reduced in venules during early reperfusion after MCAO. Conclusions - A model using the filament method of stroke and fluorescence microscopy was used to examine white-cell behavior and hemodynamics in the cerebral microcirculation after MCAO-R. We observed a significant increase in leukocyte rolling and adhesion in venules and a significant decrease in blood shear rate in the microcirculation of the brain during early reperfusion. Leukocytes may activate and damage the blood vessels and surrounding brain cells, which contributes to an exaggerated inflammatory component to reperfusion. The model described can be used to examine precisely blood cell-endothelium interactions and hemodynamic changes in the microcirculation during postischemic reperfusion. Information from these and similar experiments may contribute to our understanding of the early inflammatory response in the brain during reperfusion after stroke.
• Ritter, L. S., Copeland, J. G., & McDonagh, P. F. (1998). Fucoidin reduces coronary microvascular leukocyte accumulation early in reperfusion. Annals of Thoracic Surgery, 66(6), 2063-2072.
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  PMID: 9930494;Abstract: Background. Leukocytes rapidly accumulate in the heart early in reperfusion after ischemia, contributing to reperfusion injury. The purpose of this study was to determine whether treatment with the selectin blocker fucoidin (FCN) would attenuate early leukocyte retention in coronary venules and capillaries during low flow reperfusion. Methods. Isolated rat hearts subjected to 30 minutes of 37°C, no-flow ischemia were initially reperfused with blood containing labeled leukocytes, followed by reperfusion with a Krebs red cell solution. The deposition of leukocytes in coronary capillaries and venules was observed using intravital microscopy. Three groups were studied: nonischemic control hearts, untreated postischemic hearts reperfused at low flow, and postischemic hearts reperfused at low flow, where both the hearts and the blood reperfusate were pretreated with FCN (0.36 mg/mL blood). Results. In the ischemia-reperfusion group, we observed a rapid and significant increase in leukocyte accumulation in both capillaries and venules. Treatment with FCN significantly reduced the leukocyte accumulation in both capillaries and venules (p < 0.05). In addition, FCN significantly reduced the persistence of leukostasis in both capillaries and venules, indicating that FCN affected a transient adhesion process. Conclusions. These results suggest that the selectin family of leukocyte-endothelial cell adhesion proteins mediates the initial retention of leukocytes in both coronary capillaries and venules during reperfusion. Selectin blockade may be effective in reducing the contribution of leukocytes to early reperfusion injury.
• Ritter, L. S., & McDonagh, P. F. (1997). Low-flow reperfusion after myocardial ischemia enhances leukocyte accumulation in coronary microcirculation. American Journal of Physiology - Heart and Circulatory Physiology, 42(3), H1154-H1165.
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  Abstract: During early reperfusion after myocardial ischemia, the mechanisms responsible for leukocyte accumulation in the heart are unclear. We examined the effects of reducing coronary blood flow during reperfusion on leukocyte accumulation in coronary capillaries and postcapillary venules. Isolated rat hearts were perfused for 30 min and then subjected to 30 min of 37°C, no-flow ischemia. The deposition of fluorescently labeled leukocytes was observed directly in coronary capillaries and venules using intravital microscopy after 5, 20, and 35 min of reperfusion. Blood cell velocity was measured in venules after 5 min of reperfusion (Rs), and shear rate (s1) was calculated. Four groups were studied: nonischemic control (NIC) hearts and postischemic hearts reperfused at full flow (I/R100) and at 50 and 10% of full flow d/R50 and I/R10, respectively). In I/Rioo hearts, there was a significant increase in leukocyte trapping in capillaries compared with the NIC group (Rs-. 5.7 ±0.6 vs. 2.0 ±0.4 leukocytes/capillary field, respectively; P < 0.05). However, the increase in leukocyte adhesion to venules was not statistically significant compared with NIC (R5: 3.2 ±0.4 vs. 1.5 ±0.6 leukocytes/100-m venule, respectively; P < 0.2). In I/Rso hearts, a further increase in leukocyte accumulation occurred in the capillaries but not in the venules. However, in URW hearts, there was a statistically significant increase in both capillaries (R3: 9.2 ± 0.8; P < 0.05) and venules (R5: 4.4 ±0.5; P < 0.05). When leukocyte margination in coronary venules was examined as a function of venular shear rate, a significant correlation (r = 0.99, P < 0.05) was found. These results suggest that, after ischemia, a reduction in reflow enhances leukocyte trapping in capillaries and that leukocyte adhesion in venules is inversely related to shear rate. Enhanced leukocyte accumulation may in turn increase the leukocyte contribution to early reperfusion injury in the heart. heart; capillaries; venules; rat Copyright ©1997 the American Physiological Society.
• Ritter, L. S., & Mcdonagh, P. F. (1997). Low-flow reperfusion after myocardial ischemia enhances leukocyte accumulation in coronary microcirculation. American Journal of Physiology - Heart and Circulatory Physiology, 273(3 42-3), H1154-H1165.
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  PMID: 9321802;Abstract: During early reperfusion after myocardial ischemia, the mechanisms responsible for leukocyte accumulation in the heart are unclear. We examined the effects of reducing coronary blood flow during reperfusion on leukocyte accumulation in coronary capillaries and postcapillary venules. Isolated rat hearts were perfused for 30 min and then subjected to 30 min of 37°C, no- flow ischemia. The deposition of fluorescently labeled leukocytes was observed directly in coronary capillaries and venules using intravital microscopy after 5, 20, and 35 min of reperfusion. Blood cell velocity was measured in venules after 5 min of reperfusion (R5) and shear rate (s-1) was calculated. Four groups were studied: nonischemic control (NIC) hearts and postischemic hearts reperfused at full flow (I/R100) and at 50 and 10% of full flow (I/R50 and I/R10, respectively). In I/R100 hearts, there was a significant increase in leukocyte trapping in capillaries compared with the NIC group (R5: 5.7 ± 0.6 vs. 2.0 ± 0.4 leukocytes/capillary field, respectively; P < 0.05). However, the increase in leukocyte adhesion to venules was not statistically significant compared with NIC (R5: 3.2 ± 0.4 vs. 1.5 ± 0.6 leukocytes/100-μm venule, respectively; P < 0.2). In I/R50 hearts, a further increase in leukocyte accumulation occurred in the capillaries but not in the venules. However, in I/R50 hearts, there was a statistically significant increase in both capillaries (R5: 9.2 ± 0.8; P < 0.05) and venules (R5: 4.4 ± 0.5; P < 0.05). When leukocyte margination in coronary venucles was examined as a function of venular shear rate, a significant correlation (r = 0.99, P < 0.05) was found. These results suggest that, after ischemia, a reduction in reflow enhances leukocyte trapping in capillaries and that leukocyte adhesion in venules is inversely related to shear rate. Enhanced leukocyte accumulation may in turn increase the leukocyte contribution to early reperfusion in jury in the heart.
• Ritter, L. S., Wilson, D. S., Williams, S. K., Copeland, J. G., & McDonagh, P. F. (1996). Pentoxifylline reduces leukocyte retention in the coronary microcirculation early in reperfusion following ischemia. International Journal of Microcirculation-Clinical and Experimental, 16(4), 170-179.
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  PMID: 8923149;Abstract: Using direct visualization techniques, we recently confirmed earlier histologic studies that leukocytes accumulate primarily in the coronary capillaries of ischemic hearts during early reperfusion. The purpose of this study was to determine if pentoxifylline (PTX) would reduce leukocyte trapping in post-ischemic hearts. Isolated rat hearts were subjected to 30 min of 37°C, no-flow ischemia. Hearts were initially reperfused with diluted whole blood containing fluorescent leukocytes. At 5, (R5), 20, and 35 min of reperfusion, the deposition of leukocytes in the coronary capillaries and venules was observed directly using intravital fluorescence microscopy. Three groups were studied: a non-ischemic control group (group I) and postischemic groups reperfused with diluted whole blood treated with vehicle group II or PTX (5 mM; group III). Postischemic reperfusion with unactivated blood caused a significant trapping of leukocytes in coronary capillaries throughout reperfusion (R5, group I = 2.0 ± 0.3 vs. group II = 5.7 ± 0.6 leukocytes/capillary field, p < 0.05). The addition of PTX reduced capillary leukocyte trapping below control values throughout reperfusion (R5, group III = 1.6 ± 0.2 leukocytes/capillary field, p < 0.05). At R5, there was no statistically significant difference in leukocyte accumulation in venules for all groups (group I = 1.5 ± 0.6, group II = 3.2 ± 0.4, group III = 3.3 ± 0.4 leukocytes/100 μm venule). During the reperfusion period, leukocyte persistence in the capillaries of postischemic hearts (36%) was greater than in the venules (13%). These data indicate that early in reperfusion after myocardial ischemia, leukocyte trapping occurs primarily in the coronary capillaries. PTX reduced early leukocyte trapping in the capillaries. The results also demonstrate that during reperfusion, the mechanisms affecting capillary retention are more persistent than those in the venule. These findings suggest that attempts to attenuate the damaging potential of early leukostasis in capillaries consider the biophysical properties of the leukocyte. © 1996 S. Karger AG.
• Ritter, L. S., Wilson, D. S., Williams, S. K., Copeland, J. G., & McDonagh, P. F. (1995). Early in reperfusion following myocardial ischemia, leukocyte activation is necessary for venular adhesion but not capillary retention. Microcirculation, 2(4), 315-327.
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  PMID: 8714813;
• Henriksen, E. J., & Ritter, L. S. (1993). Effect of insulin-like factors on glucose transport activity in unweighted rat skeletal muscle. Journal of Applied Physiology, 75(2), 820-824.
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  PMID: 8226487;Abstract: We have previously demonstrated that mechanical unweighting of the soleus muscle by hindlimb suspension leads to increases in insulin receptor binding, muscle/fat-specific glucose transporter (GLUT-4) protein levels, and insulin- stimulated glucose transport activity. The present study used a novel approach to further evaluate the potential role of postreceptor binding mechanisms in this enhanced insulin effect after unweighting. Insulin-like growth factor I (IGF-I), vanadate, and phospholipase C were used to stimulate glucose transport activity independently of insulin receptor binding. Soleus glucose transport activity (assessed by 2-deoxyglucose uptake) was evaluated in vitro with soleus strips (~18 mg). Progressively increased responses to maximally effective doses of insulin or IGF-I were observed after 3 and 6 days of unweighting compared with weight-matched control strips. Enhanced maximal responses to vanadate (6 days only) and phospholipase C (3 and 6 days) for 2-deoxyglucose uptake were also observed. The results of this study 1) provide evidence that post-insulin receptor binding mechanisms also play a role in the enhanced response of the insulin-dependent pathway for stimulation of glucose transport in unweighted skeletal muscle and 2) indicate that IGF-I action on glucose transport is included in this enhanced response in unweighted muscle.
• Henriksen, E. J., & Ritter, L. S. (1993). Effect of soleus unweighting on stimulation of insulin-independent glucose transport activity. Journal of Applied Physiology, 74(4), 1653-1657.
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  PMID: 8514679;Abstract: Unweighting of the rat soleus by tail-cast suspension results in increased insulin action on stimulation of glucose transport, which can be explained, at least in part, by increased insulin binding and enhanced glucose transporter protein levels. Glucose transport is also activated by an insulin-independent mechanism stimulated by in vitro muscle contractions or hypoxia. Therefore, the purpose of this study was to determine if soleus unweighting leads to an enhanced response of the insulin-independent pathway for stimulation of glucose transport. The hindlimbs of juvenile male Wistar rats were suspended by a tail-cast system for 3 or 6 days. Glucose transport activity in isolated soleus strips (~18 mg) was then assessed by using 2- deoxy-[1,2-3H]glucose (2-DG) uptake. Insulin (2 mU/ml) had a progressively enhanced effect on 2-DG uptake after 3 and 6 days of unweighting (+44 and +72% vs. control, respectively; both P < 0.001). At these same times, there was no difference between groups for activation of 2-DG uptake by maximally effective treatments with contractions (10 tetanuses), hypoxia (60 min), or caffeine (5 mM). These results indicate that the enhanced capacity for stimulation of glucose transport after soleus unweighting is restricted to the insulin pathway, with no apparent enhancement of the insulin-independent pathway.
• Henriksen, E. J., Schneider, M. C., & Ritter, L. S. (1993). Regulation of contraction-stimulated system a amino acid uptake in skeletal muscle: Role of vicinal sulfhydryls. Metabolism, 42(4), 440-445.
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  PMID: 8487665;Abstract: Functional vicinal sulfhydryls are essential for insulin-stimulated system A neutral amino acid uptake in the rat epitrochlearis muscle. In skeletal muscle, system A uptake is also activated by contractile activity. Therefore, the purposes of this study were to characterize the stimulation of system A activity by contractions induced by electrical stimulation in vitro, and to assess the role of vicinal sulfhydryls in this process. System A activity in the isolated epitrochlearis muscle was measured using the nonmetabolizable analogue α-(methylamino)isobutyric acid (MeAIB). Contractions increased MeAIB uptake by increasing the apparent maximal velocity (Vmax), with no alteration in the apparent Km. The maximal stimulatory effects of insulin and contractions on MeAIB uptake were completely additive, demonstrating that these two stimuli exert their effects via different mechanisms. Phenylarsine oxide (PAO), a vicinal sulfhydryl antagonist, at greater than 20 μmol/L inhibited basal and contraction-stimulated MeAIB uptake by approximately 50% and 70%, respectively, by decreasing Vmax, with no change in Km. Both inhibitory effects were completely prevented by cotreatment with the vicinal dithiol dimercaptopropanol (DMP), indicating the effects were mediated by interactions with vicinal sulfhydryls. Contraction-stimulated MeAIB uptake was rapidly (half-time, ∼7 minutes) reversed by the addition of PAO. These results (1) define conditions under which contraction-stimulated system A amino acid uptake can be studied in an isolated mammalian skeletal muscle preparation, and (2) indicate that vicinal sulfhydryls are essential for stimulation of system A activity by muscle contractions. © 1993.

Presentations

• Ritter, L. S. (2020, January). Stroke Transitions of Care--Are we Meeting Post Stroke Families Needs?. Mercy Care Case Manager Conference. Tucson, AZ: Mercy Care.
• Ritter, L. S. (2019, Fall). Community Centered Stroke Transitions of Care. 5th Annual Arizona Stroke Conference. Tucson, Arizona: Tucson Stroke Leadership Group.
• Ritter, L. S. (2019, Spring 2020). Are We Reaching Those Living With Stroke?. Mercy Care Conference. Tucson, Arizona: Mercy Care.
• Ritter, L. S. (2019, Spring). What's New in Stroke Treatments. Stroke and Brain Injury Support Group. Tucson, Arizona: Encompass Health Rehabilitation Hospital of Tucson.
• Ritter, L. S. (2019, Summer 2019). Community Stroke Services. Hacienda at the River Partners Event.
• Ritter, L. S. (2019, Summer). Use it or Lose it-- Neuroplasticity After Stroke. Stroke Resource Center of Southern Arizona Retreat. Tucson, Arizona.
• Sillah, I., Ogutu, B., McArthur, D., & Ritter, L. S. (2019, Spring). Needs Assessment For Using a Stroke Scale in Urban and Rural Kenyan Hospital Settings. Sigma Theta Tau 30th International Nursing Research Congress. Calgary, Alberta, Canada.
• Ritter, L. S. (2017, June). Stroke and Aphasia: What's the Connection?. Living With Aphasia Conference. Tucson, AZ: Aphasia Center.
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  This invited presentation was part of the Aphasia Center's annual conference for community dwelling people affected by aphasia. It was attended by ~50 people.
• Ritter, L. S. (2017, May). Living With Stroke: The Value of Community Resource Support. Life After Stroke and Brain Injury Conference. Tucson, Arizona: Tucson Medical Center.
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  This conference was attended by ~200 people and was part of an annual Stroke and Brain Injury conference sponsored by Tucson Medical Center. I was one of 4 invited (PhD, MD) faculty to present. This type of presentation aligns with my relatively new area of research in Transitions of Care for stroke.

Poster Presentations

• Laws, L., Ritter, L. S., McEwen, M., & Loescher, L. (2019, Spring). Towards a community-based stroke transitional care model. Western Institute of Nursing (WIN) Annual Conference. San Diego, CA: WIN.
• Ritter, L. S., Gallek, M., Pace, T. W., Taylor-Piliae, R. E., & Gallegos Jr., J. L. (2019, March). Hidden Risks: Relationship among visceral adipose tissue, interleukin - 18, and adiponectin in the development of type 2 diabetes in Filipino Americans. American Heart Association's 2019 EPI/Lifestyle Scientific Sessions. Houston, TX: American Heart Association.
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  accepted for presentation