Titia Luise King

Interests

Teaching

Anatomy, Physiology, Disease of Companion Animals, Disease of Wildlife, Equine Health Management, Mammalian Histology, Veterinary Pharmacology, One-Health, Laboratory and exotic animal medicine, veterinary medicine

Courses

Scholarly Contributions

Chapters

• King, T. L. (2021). INTEGUMENT AND MAMMARY GLAND/UDDER. In Comparative Veterinary Anatomy A Clinical Approach. Elsevier.

Journals/Publications

• Lago-Alvarez, Y., Podico, G., Segabinazzi, L. G., Cunha, L. L., Barbosa, L., Arnold, C. E., Lima, F. S., King, L. T., McLean, A. K., & Canisso, I. F. (2020). Donkey Epididymal Transport for Semen Cooling and Freezing. Animals : an open access journal from MDPI, 10(12).
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  The objectives of this study were to assess the cooling and freezing of donkey epididymal semen harvested immediately after castration (Experiment 1, = 4) or after the shipment (24 or 48 h) of epididymides attached to testicles (Experiment 2, = 14) or dissected apart (Experiment 3, = 36). In each experiment, semen was frozen immediately (Non-Centrif) in an egg yolk-based semen extender (EY) or after processing through cushion-centrifugation (Centrif) while extended in a skim milk-based extender (SC). In all three experiments, cooled, pre-freeze, and post-thaw epididymal semen was assessed for total motility (TM), progressive motility (PM), plasma membrane integrity (PMI), and high mitochondrial membrane potential (HMMP). Data were analyzed with R using mixed models and Tukey's test as posthoc. Results showed that the cooling of epididymal semen up to 24 h after harvesting did not affect motility parameters or plasma membrane integrity; furthermore, in Experiment 3, the post-thaw evaluation of both Centrif and Non-Centrif achieved similar TM and PM. Collectively, the post-thaw results revealed low motility parameters across groups; while, the PMI and HMMP did not reflect this trend, and the values remained high, suggesting that there was a lack of epididymal sperm activation with either centrifugation or extenders. In summary, freshly harvested and cooled-shipped and cooled semen had satisfactory semen parameters. Future studies need to address donkey epididymal semen fertility in mares and jennies.
• King, T. L., Ruyle, B. C., Kline, D. D., Heesch, C. M., & Hasser, E. M. (2015). Catecholaminergic neurons projecting to the paraventricular nucleus of the hypothalamus are essential for cardiorespiratory adjustments to hypoxia.. Am J Physiol Regul Integr Comp Physiol..
• King, T. L., Kline, D. D., Ruyle, B. C., Heesch, C. M., & Hasser, E. M. (2013). Acute systemic hypoxia activates hypothalamic paraventricular nucleus-projecting catecholaminergic neurons in the caudal ventrolateral medulla. American journal of physiology. Regulatory, integrative and comparative physiology, 305(10), R1112-23.
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  Hypoxia activates catecholamine neurons in the caudal ventrolateral medulla (CVLM). The hypothalamic paraventricular nucleus (PVN) modulates arterial chemoreflex responses and receives catecholaminergic projections from the CVLM, but it is not known whether the CVLM-PVN projection is activated by chemoreflex stimulation. We hypothesized that acute hypoxia (AH) activates PVN-projecting catecholaminergic neurons in the CVLM. Fluoro-Gold (2%, 60-90 nl) was microinjected into the PVN of rats to retrogradely label CVLM neurons. After recovery, conscious rats underwent 3 h of normoxia (21% O2, n = 4) or AH (12, 10, or 8% O2; n = 5 each group). We used Fos immunoreactivity as an index of CVLM neuronal activation and tyrosine hydroxylase (TH) immunoreactivity to identify catecholaminergic neurons. Positively labeled neurons were counted in six caudal-rostral sections containing CVLM. Hypoxia progressively increased the number of Fos-immunoreactive CVLM cells (21%, 19 ± 6; 12%, 49 ± 2; 10%, 117 ± 8; 8%, 179 ± 7; P < 0.001). Catecholaminergic cells colabeled with Fos immunoreactivity in the CVLM were observed following 12% O2, and further increases in hypoxia severity caused markedly more activation. PVN-projecting CVLM cells were activated following more severe hypoxia (10% and 8% O2). A large proportion (89 ± 3%) of all activated PVN-projecting CVLM neurons were catecholaminergic, regardless of hypoxia intensity. Data suggest that catecholaminergic, PVN-projecting CVLM neurons are particularly hypoxia-sensitive, and these neurons may be important in the cardiorespiratory and/or neuroendocrine responses elicited by the chemoreflex.
• King, T. L., Heesch, C. M., Clark, C. G., Kline, D. D., & Hasser, E. M. (2012). Hypoxia activates nucleus tractus solitarii neurons projecting to the paraventricular nucleus of the hypothalamus. American journal of physiology. Regulatory, integrative and comparative physiology, 302(10), R1219-32.
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  Peripheral chemoreceptor afferent information is sent to the nucleus tractus solitarii (nTS), integrated, and relayed to other brain regions to alter cardiorespiratory function. The nTS projects to the hypothalamic paraventricular nucleus (PVN), but activation and phenotype of these projections during chemoreflex stimulation is unknown. We hypothesized that activation of PVN-projecting nTS neurons occurs primarily at high intensities of hypoxia. We assessed ventilation and cardiovascular parameters in response to increasing severities of hypoxia. Retrograde tracers were used to label nTS PVN-projecting neurons and, in some rats, rostral ventrolateral medulla (RVLM)-projecting neurons. Immunohistochemistry was performed to identify nTS cells that were activated (Fos-immunoreactive, Fos-IR), catecholaminergic, and GABAergic following hypoxia. Conscious rats underwent 3 h normoxia (n = 4, 21% O(2)) or acute hypoxia (12, 10, or 8% O(2); n = 5 each). Hypoxia increased ventilation and the number of Fos-IR nTS cells (21%, 13 ± 2; 12%, 58 ± 4; 10%, 166 ± 22; 8%, 186 ± 6). Fos expression after 10% O(2) was similar whether arterial pressure was allowed to decrease (-13 ± 1 mmHg) or was held constant. The percentage of PVN-projecting cells activated was intensity dependent, but contrary to our hypothesis, PVN-projecting nTS cells exhibiting Fos-IR were found at all hypoxic intensities. Notably, at all intensities of hypoxia, ∼75% of the activated PVN-projecting nTS neurons were catecholaminergic. Compared with RVLM-projecting cells, a greater percentage of PVN-projecting nTS cells was activated by 10% O(2). Data suggest that increasing hypoxic intensity activates nTS PVN-projecting cells, especially catecholaminergic, PVN-projecting neurons. The nTS to PVN catecholaminergic pathway may be critical even at lower levels of chemoreflex activation and more important to cardiorespiratory responses than previously considered.
• Kline, D. D., King, T. L., Austgen, J. R., Heesch, C. M., & Hasser, E. M. (2010). Sensory afferent and hypoxia-mediated activation of nucleus tractus solitarius neurons that project to the rostral ventrolateral medulla. Neuroscience, 167(2), 510-27.
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  The nucleus tractus solitarius (nTS) of the brainstem receives sensory afferent inputs, processes that information, and sends projections to a variety of brain regions responsible for influencing autonomic and respiratory output. The nTS sends direct projections to the rostral ventrolateral medulla (RVLM), an area important for cardiorespiratory reflexes and homeostasis. Since the net reflex effect of nTS processing ultimately depends on the properties of output neurons, we determined the characteristics of these RVLM-projecting nTS neurons using electrophysiological and immunohistochemical techniques. RVLM-projecting nTS neurons were identified by retrograde tracers. Patch clamp analysis in the horizontal brainstem nTS slice demonstrated that RVLM-projecting nTS cells exhibit constant latency solitary tract evoked excitatory postsynaptic currents (EPSCs), suggesting they receive strong monosynaptic contacts from visceral afferents. Three distinct patterns of action potential firing, associated with different underlying potassium currents, were observed in RVLM-projecting cells. Following activation of the chemoreflex in conscious animals by 3 h of acute hypoxia, 11.2+/-1.9% of the RVLM-projecting nTS neurons were activated, as indicated by positive Fos-immunoreactivity. Very few RVLM-projecting nTS cells were catecholaminergic. Taken together, these data suggest that RVLM projecting nTS neurons receive strong monosynaptic inputs from sensory afferents and a subpopulation participates in the chemoreflex pathway.

Other Teaching Materials

• King, T. L. (2023. WHERE THE WILD DOGS ARE: A CASE STUDY ON ALPHA FEMALE DOMINANCE IN AFRICAN WILD DOGS. University of Arizona.