Lynne A Oland

Interests

Research

Neuron-glial cell interactions in teh developing and mature brain

Courses

Scholarly Contributions

Journals/Publications

• Oland, L. A., Tolbert, L. P., Liu, K. E., Tran, C. T., Fetter, R. D., Cardona, A., & MacNamee, S. E. (2016). Astrocytic glutamate transport regulates a Drosophila CNS synapse that lacks astrocyte ensheathment. Journal of Comparative Neurology.
• Gibson, N. J., Tolbert, L. P., & Oland, L. A. (2012). Activation of glial FGFRs is essential in bidirectional axon-glia signaling during development of the moth olfactory system. PLoS One, 7, e33828.
• Mallory, H. S., Gibson, N. J., Hayashi, J. H., Nighorn, A. J., & Oland, L. A. (2011). Direct and glia-mediated effects of GABA on development of central olfactory neurons. Neuron Glia Bbiology, 7(2-4), 143-161.
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  Previously studied for its role in processing olfactory information in the antennal lobe, GABA also may shape development of the olfactory pathway, acting either through or on glial cells. Early in development, the dendrites of GABAergic neurons extend to the glial border that surrounds the nascent olfactory lobe neuropil. These neuropil glia express both GABAA and GABAB receptors, about half of the glia in acute cultures responded to GABA with small outward currents, and about a third responded with small transient increases in intracellular calcium. The neuronal classes that express GABA in vivo, the local interneurons and a subset of projection neurons, also do so in culture. Exposure to GABA in culture increased the size and complexity of local interneurons, but had no effect on glial morphology. The presence of glia alone did not affect neuronal morphology, but in the presence of both glia and GABA, the growth-enhancing effects of GABA on cultured antennal lobe neurons were eliminated. Contact between the glial cells and the neurons was not necessary. Operating in vivo, these antagonistic effects, one direct and one glia mediated, could help to sculpt the densely branched, tufted arbors that are characteristic of neurons innervating olfactory glomeruli.
• Oland, L. A., & Tolbert, L. P. (2011). Roles of glial cells in neural circuit formation: Insights from research in insects. Glia, 59(9), 1273-1295.
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  PMID: 21732424;Abstract: Investigators over the years have noted many striking similarities in the structural organization and function of neural circuits in higher invertebrates and vertebrates. In more recent years, the discovery of similarities in the cellular and molecular mechanisms that guide development of these circuits has driven a revolution in our understanding of neural development. Cellular mechanisms discovered to underlie axon pathfinding in grasshoppers have guided productive studies in mammals. Genes discovered to play key roles in the patterning of the fruitfly's central nervous system have subsequently been found to play key roles in mice. The diversity of invertebrate species offers to investigators numerous opportunities to conduct experiments that are harder or impossible to do in vertebrate species, but that are likely to shed light on mechanisms at play in developing vertebrate nervous systems. These experiments elucidate the broad suite of cellular and molecular interactions that have the potential to influence neural circuit formation across species. Here we focus on what is known about roles for glial cells in some of the important steps in neural circuit formation in experimentally advantageous insect species. These steps include axon pathfinding and matching to targets, dendritic patterning, and the sculpting of synaptic neuropils. A consistent theme is that glial cells interact with neurons in two-way, reciprocal interactions. We emphasize the impact of studies performed in insects and explore how insect nervous systems might best be exploited next as scientists seek to understand in yet deeper detail the full repertory of functions of glia in development. © 2010 Wiley-Liss, Inc.
• Koussa, M. A., Tolbert, L. P., & Oland, L. A. (2010). Development of a glial network in the olfactory nerve: role of calcium and neuronal activity. Neuron Glia Biology, 2(4), 1-17.
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  In adult olfactory nerves of mammals and moths, a network of glial cells ensheathes small bundles of olfactory receptor axons. In the developing antennal nerve (AN) of the moth Manduca sexta, the axons of olfactory receptor neurons (ORNs) migrate from the olfactory sensory epithelium toward the antennal lobe. Here we explore developmental interactions between ORN axons and AN glial cells. During early stages in AN glial-cell migration, glial cells are highly dye coupled, dividing glia are readily found in the nerve and AN glial cells label strongly for glutamine synthetase. By the end of this period, dye-coupling is rare, glial proliferation has ceased, glutamine synthetase labeling is absent, and glial processes have begun to extend to enwrap bundles of axons, a process that continues throughout the remainder of metamorphic development. Whole-cell and perforated-patch recordings in vivo from AN glia at different stages of network formation revealed two potassium currents and an R-like calcium current. Chronic in vivo exposure to the R-type channel blocker SNX-482 halted or greatly reduced AN glial migration. Chronically blocking spontaneous Na-dependent activity by injection of tetrodotoxin reduced the glial calcium current implicating an activity-dependent interaction between ORNs and glial cells in the development of glial calcium currents.
• Oland, L. A., Gibson, N. J., & Tolbert, L. P. (2010). Localization of a GABA transporter to glial cells in the developing and adult olfactory pathway of the moth Manduca sexta. The Journal of Comparative Neurology, 518(6), 815-38.
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  PMID: 20058309. Glial cells have several critical roles in the developing and adult olfactory (antennal) lobe of the moth Manduca sexta. Early in development, glial cells occupy discrete regions of the developing olfactory pathway and processes of gamma-aminobutyric acid (GABA)ergic neurons extend into some of these regions. Because GABA is known to have developmental effects in a variety of systems, we explored the possibility that the glial cells express a GABA transporter that could regulate GABA levels to which olfactory neurons and glial cells are exposed. By using an antibody raised against a characterized high-affinity M. sexta GABA transporter with high sequence homology to known mammalian GABA transporters (Mbungu et al. [1995] Arch. Biochem. Biophys. 318:489-497; Umesh and Gill [2002] J. Comp. Neurol. 448:388-398), we found that the GABA transporter is localized to subsets of centrally derived glial cells during metamorphic adult development. The transporter persists into adulthood in a subset of the neuropil-associated glial cells, but its distribution pattern as determined by light-and electron-microscopic-level immunocytochemistry indicates that it could not serve to regulate GABA concentration in the synaptic cleft. Instead, its role is more likely to regulate extracellular GABA levels within the glomerular neuropil. Expression in the sorting zone glial cells disappears after the period of olfactory receptor axon ingrowth, but may be important during ingrowth if GABA regulates axon growth. Glial cells take up GABA, and that uptake can be blocked by L-2,4-diaminobutyric acid (DABA). This is the first molecular evidence that the central glial cell population in this pathway is heterogeneous.
• Gibson, N. J., Oland, L. A., & Tolbert, L. P. (2009). Roles of specific membrane lipid domains in EGF receptor activation and cell adhesion molecule stabilization in a developing olfactory system. PloS One, 4(9), e7222.
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  PMID: 19787046. Reciprocal interactions between glial cells and olfactory receptor neurons (ORNs) cause ORN axons entering the brain to sort, to fasciculate into bundles destined for specific glomeruli, and to form stable protoglomeruli in the developing olfactory system of an experimentally advantageous animal species, the moth Manduca sexta. Epidermal growth factor receptors (EGFRs) and the cell adhesion molecules (IgCAMs) neuroglian and fasciclin II are known to be important players in these processes.
• Abeytunga, D. T., Oland, L., Somogyi, A., & Polt, R. (2008). Structural studies on the neutral glycosphingolipids of Manduca sexta. Bioorganic Chemistry, 36(2), 70-6.
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  Glycosphingolipids (GSLs) have been implicated as playing major roles in cellular interactions and control of cell proliferation in muticellular organisms. Moreover GSLs and other sphingolipids such as sphingomyelins, ceramides and sphingosines serve a variety of roles in signal transduction. Hence, identification of structures of GSLs in different biota will shed light in understanding their physiological role. During this study, the major glycosphingolipid component present in the extracts of stage-12 and stage-17/18 metamorphosing adults of Manduca sexta was identified as mactosyl ceramide. We report the isolation of several ceramide disaccharides, a ceramide trisaccharide and a ceramide tetrasaccharide. The GSL structures were confirmed by high-resolution mass spectrometry and tandem mass spectrometry. The identity of the monosaccharides was proved using exoglycosidases. The predominant sphingosine chain-length varied from C-14 (tetradecasphing-4-enine) to C-16 (hexadecasphing-4-enine) in these GSLs. Sphingosines of both chain lengths were accompanied by their doubly unsaturated counterparts tetradecasphinga-4,6-diene and hexadecasphinga-4,6-diene. It is also interesting to note the presence of tetradecasphinganine and hexadecasphinganine in minute amounts in the form of a GSL in the extracts of M. sexta. The varying degrees of unsaturation in the sphingosine moiety of GSLs in M. sexta may be biologically significant in insect metamorphosis. The ceramide trisaccharides and ceramide tetrasaccharide belong to the arthro-series, The observation of fucose in the M. sexta GSLs is the first report of the presence of fucose in an arthroseries GSL.
• Oland, L. A., Biebelhausen, J. P., & Tolbert, L. P. (2008). Glial investment of the adult and developing antennal lobe of Drosophila. The Journal of Comparative Neurology, 509(5), 526-50.
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  In recent years the Drosophila olfactory system, with its unparalleled opportunities for genetic dissection of development and functional organization, has been used to study the development of central olfactory neurons and the molecular basis of olfactory coding. The results of these studies have been interpreted in the absence of a detailed understanding of the steps in maturation of glial cells in the antennal lobe. Here we present a high-resolution study of the glia associated with olfactory glomeruli in adult and developing antennal lobes. The study provides a basis for comparison of findings in Drosophila with those in the moth Manduca sexta that indicate a critical role for glia in antennal lobe development. Using flies expressing GFP under a Nervana2 driver to visualize glia for confocal microscopy, and probing at higher resolution with the electron microscope, we find that glial development in Drosophila differs markedly from that in moths: glial cell bodies remain in a rind around the glomerular neuropil; glial processes ensheathe axon bundles in the nerve layer but likely contribute little to axonal sorting; their processes insinuate between glomeruli only very late and then form only a sparse, open network around each glomerulus; and glial processes invade the synaptic neuropil. Taking our results in the context of previous studies, we conclude that glial cells in the developing Drosophila antennal lobe are unlikely to play a strong role in either axonal sorting or glomerulus stabilization and that in the adult, glial processes do not electrically isolate glomeruli from their neighbors.
• Heil, J. E., Oland, L. A., & Lohr, C. (2007). Acetylcholine-mediated axon-glia signaling in the developing insect olfactory system. European Journal of Neuroscience, 26(5), 1227-1241.
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  PMID: 17767501;Abstract: In the olfactory system of the sphinx moth Manduca sexta, migration of neuropil glial cells is triggered by olfactory receptor axons and depends on intraglial Ca2+ signaling. It is not known, however, how receptor axons and glial cells communicate and whether Ca2+ signaling is a consequence of this communication. We studied Ca2+ increases in glial cells in vivo and in situ, evoked by electrical stimulation of olfactory receptor axons in pupae and by odor stimulation of receptor neurons in adult moths. Axonal activity leads to Ca2+ increases in neuropil glial cells that are blocked by nicotinic acetylcholine receptor antagonists and can be mimicked by acetylcholine and carbachol application. In addition, Ca 2+ transients were abolished by removal of external Ca2+ and blockage of voltage-gated Ca2+ channels. During development, acetylcholine-mediated Ca2+ signaling could first be elicited at stage 6, the time when neuropil glial cells start to migrate. Glial migration was reduced after injection of nicotinic antagonists into pupae. The results show that Ca2+ signaling can be induced by acetylcholine release from olfactory receptor axons, which activates nicotinic acetylcholine receptors and leads to voltage-gated Ca2+ influx. The results further suggest that cholinergic signaling in the olfactory system is required for glial cell migration in Manduca. © The Authors (2007).
• Abeytunga, D. T., Glick, J. J., Gibson, N. J., Oland, L. A., Somogyi, A., Wysoki, V. H., & Polt, R. (2004). Presence of unsaturated sphingomyelins and changes in their composition during the life cycle of the moth Manduca sexta. Journal of Lipid Research, 45(7), 1221-1231.
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  PMID: 15102888;Abstract: NMR and electrospray ionization tandem mass spectrometry were used to show for the first time the presence of sphingomyelins in extracts of the tobacco hornworm Manduca sexta (Lepidoptera). The sphingosine in the ceramide was identified as tetradecasphing-4-enine, and the fatty acids were C188:0, C20:0, C22:0, and C24:0 (compound 1). Heterogeneity in the ceramide was observed in sphingomyelins from M. sexta. All of the sphingomyelins were associated with their doubly unsaturated sphingosine, tetradecasphing-4,6-dienine (compound 2), which contained the same set of fatty acids as compound I and represents a novel set of sphingomyelins not previously reported in Lepidoptera. Lipid rafts were isolated from brains of M. sexta, and the association of these novel sphingomyelins with rafts was confirmed. The existence of the additional double bond was also observed in ceramide and ceramide phosphoethanolamine isolated from M. sexta. The levels of the doubly unsaturated ceramide showed modest changes during metamorphosis of M. sexta. These results suggest that Manduca sphingomyelins may participate in the formation of lipid rafts, in keeping with their function in vertebrates.
• Slavish, J. P., Friel, D. K., Oland, L. A., & Polt, R. (2004). New PDMP analogues inhibit process outgrowth in an insect cell line. Bioorganic and Medicinal Chemistry Letters, 14(6), 1487-1490.
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  PMID: 15006387;Abstract: D-threo-1-Phenyl-2-aminodecanoyl-3-morpholinopropanol (D-threo-PDMP) has previously been shown to inhibit the biosynthesis of glycosphingolipids (GSLs) in mammals and mammalian cell lines by the inhibition of glucosylceramide synthase. New D-threo-PDMP analogues were synthesized from D-serine, and found to suppress neurite extension in an embryonic insect cell line from the moth Manduca sexta, and in explanted neural tissue from insect pupae. Inhibition occurred at lower concentrations than D-threo-PDMP. The observed suppression of neurite formation was found to be reversible after the removal of the compounds. Due to their small size and short life cycle, M. sexta is shown to be an ideal model organism for studies of GSL effects in cellular development, and for drug development studies. © 2004 Elsevier Ltd. All rights reserved.
• Tolbert, L. P., Oland, L. A., Tucker, E. S., Gibson, N. J., Higgins, M. R., & Lipscomb, B. W. (2004). Bidirectional influences between neurons and glial cells in the developing olfactory system. Progress in Neurobiology, 73, 73-105.
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  invited review, PMID: 15201035
• Tucker, E. S., Oland, L. A., & Tolbert, L. P. (2004). In vitro analyses of interactions between olfactory receptor growth cones and glial cells that mediate axon sorting and glomerulus formation. Journal of Comparative Neurology, 472, 478-95.
• Oland, L. A., & Tolbert, L. P. (2003). Key interactions between neurons and glial cells during neural development in insects. Annual Review of Entomology, 48, 89-110.
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  invited review
• Oland, L. A., Pott, W. M., Howard, C. T., Inlow, M., & Buckingham, J. (2003). A diffusible signal attracts olfactory sensory axons toward their target in the developing brain of the moth. Journal of Neurobiology, 56(1), 24-40.
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  PMID: 12767030;Abstract: The signals that olfactory receptor axons use to navigate to their target in the CNS are still not well understood. In the moth Manduca sexta, the primary olfactory pathway develops postembryonically, and the receptor axons navigate from an experimentally accessible sensory epithelium to the brain along a pathway long enough for detailed study of regions in which axon behavior changes. The current experiments ask whether diffusible factors contribute to receptor axon guidance. Explants were made from the antennal receptor epithelium and co-cultured in a collagen gel matrix with slices of various regions of the brain. Receptor axons were attracted toward the central regions of the brain, including the protocerebrum and antennal lobe. Receptor axons growing into a slice of the most proximal region of the antennal nerve, where axon sorting normally occurs, showed no directional preference. When the antennal lobe was included in the slice, the receptor axons entering the sorting region grew directly toward the antennal lobe. Taken together with the previous in vivo experiments, the current results suggest that an attractive diffusible factor can serve as one cue to direct misrouted olfactory receptor axons toward the medial regions of the brain, where local cues guide them to the antennal lobe. They also suggest that under normal circumstances, in which the receptor axons follow a pre-existing pupal nerve to the antennal lobe, the diffusible factor emanating from the lobe acts in parallel and at short range to maintain the fidelity of the path into the antennal lobe. © 2003 Wiley Periodicals, Inc.
• Tolbert, L. P., Oland, L. A., Christensen, T. C., & Goriely, A. R. (2003). Neuronal and glial morphology in olfactory systems: Significance for information processing and underlying developmental mechanisms. Brain and Mind, 4, 27-49.
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  Invited review
• Lohr, C., Tucker, E. S., Oland, L. A., & Tolbert, L. P. (2002). Development of depolarization-induced calcium transients in insect glial cells is dependent on the presence of afferent axons. Journal of Neurobiology, 52, 85-98.
• Gibson, N. J., Roessler, W. R., Nighorn, A. J., Oland, L. A., Hildebrand, J. G., & Tolbert, L. P. (2001). Neuron-glia communication via nitric oxide is essential in establishing antennal-lobe structure in Manduca sexta. Developmental Biology, 240, 326-39.
• Lohr, C., Oland, L. A., & Tolbert, L. P. (2001). Olfactory receptor axons influence the development of glial potassium currents in the antennal lobe of the moth Manduca sexta. Glia, 36, 309-320.
• Wegerhoff, R., Roessler, W. R., Higgins, M. R., Oland, L. A., & Tolbert, L. P. (2001). Fenvalerate treatment affects development of olfactory glomeruli in Manduca sexta. Journal of Comparative Neurology, 430, 533-41.
• Oland, L. A., & Evans, S. (2000). The tracheal system of the developing primary olfactory pathway of Manduca sexta: Tracheae do not play a guidance or targeting role for ingrowing receptor axons. Arthropod Structure and Development, 29(3), 185-196.
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  PMID: 18088926;Abstract: Axons navigate to their targets by detecting signals within the environment through which they are growing. The surfaces of tracheae, which are prominent features of the insect body plan, could be detected as favorable pathways for sensory axons growing toward the brain. The pattern of the tracheal investment of the adult antennal lobe of the moth Manduca sexta suggested two specific possibilities for interaction between tracheae and axons during development: That tracheae might be involved in guiding olfactory receptor axons to their target region of the brain, the antennal lobe; and that tracheae could provide an address system within the lobe that defines the sites of glomeruli, which are olfactory-axon target areas within the lobe. To determine whether tracheae contribute to development of the primary olfactory pathway, the distribution of tracheae in the adult and developing antennal lobes was examined with both confocal and electron microscopes. During the major stages in which axons are growing into the antennal lobe and in which glomeruli are forming, the tracheal investment of the nerve and lobe was found to be minimal. Tracheae thus cannot serve as axon guides or as local address sites for newly forming glomeruli during the initial targeting of receptors onto the antennal lobe. © 2001 Elsevier Science Ltd.
• Kent, K., Oland, L. A., & Hildebrand, J. G. (1999). Development of the labial pit organ glomerulus in the antennal lobe of the moth Manduca sexta: The role of afferent projections in the formation of an identified olfactory glomerulus. Journal of Neurobiology, 40, 28-44.
• Oland, L. A., Marrero, H. G., & Burger, I. (1999). Glial cells in the developing and adult olfactory lobe of the moth Manduca sexta. Cell and Tissue Research, 297(3), 527-545.
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  PMID: 10460499;Abstract: The antennal lobe of the moth contains several classes of glial cells that are likely to play functional roles in both the developing and mature lobe. In this study, confocal and electron microscopy were used to examine in detail the morphology of two classes of glial cells, those associated with olfactory receptor axons as they course to their targets in the lobe and those that form borders around the synaptic neuropil of the olfactory glomeruli. The former, the nerve-layer glia, have long processes with multiple expansions that enwrap axon fascicles; the latter, the neuropil glia, constitute two subgroups: complex glia with large cell bodies and branching, vellate arbors; and simple glia, with multiple, mostly unbranched processes with many lamellate expansions along their lengths. The processes of complex glia appear to be closely associated with axon fascicles as they enter the glomeruli, while those of the simple glia surround the glomeruli as part of a multi-lamellar glial envelope, their processes rarely invading the synaptic neuropil of the body of the glomerulus. The full morphological development of antennal-lobe glial cells requires more than two-thirds of metamorphic development. During this period, cells that began as cuboidal or spindle-shaped cells that were extensively dye-coupled to one another gradually assume their adult form and, at least under nonstimulated conditions, greatly reduce their coupling. These changes are only weakly dependent on the presence of olfactory receptor axons. Glial processes are somewhat shorter and less branched in the absence of these axons, but basic structure and degree of dye-coupling are unchanged.
• Roessler, W. R., Oland, L. A., Higgins, M. R., Hildebrand, J. G., & Tolbert, L. P. (1999). Development of a glia-rich axon-sorting zone in the olfactory pathway of the moth Manduca sexta. Journal of Neuroscience, 19, 9865-77.
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  PMID: 10559396
• Oland, L. A., & Tolbert, L. P. (1998). Glomerulus development in the absence of a set of mitral-like neurons in the insect olfactory lobe. Journal of Neurobiology, 36, 41-52.
• Oland, L. A., Pott, W. M., Higgins, M. R., & Tolbert, L. P. (1998). Targeted ingrowth and axon-glial cell relationships of olfactory receptor axons in the primary olfactory pathway of an insect. Journal of Comparative Neurology, 398, 119-138.
• Baumann, P. M., Oland, L. A., & Tolbert, L. P. (1996). Glial cells stabilize axonal protoglomeruli in the developing olfactory lobe of the moth Manduca sexta. Journal of Comparative Neurology, 373, 118-128.
• Oland, L. A., & Tolbert, L. P. (1996). Multiple factors shape the development of olfactory glomeruli: insights from an insect model system. Journal of Neurobiology, 30, 92-109.
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  review
• Oland, L. A., Müller, T., Kettenmann, H., & Hayashi, J. (1996). Preparation of primary cultures and acute slices of the nervous system of the moth Manduca sexta. Journal of Neuroscience Methods, 69(1), 103-112.
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  PMID: 8912940;Abstract: Interactions among receptor neurons, glial cells and neurons intrinsic to the antennal lobe of the moth underlie the formation of olfactory glomeruli. To isolate these interactions, as well as to understand the effect of a variety of humoral agents on differentiation of the neurons and glia, we generate primary cultures of neurons or glia. These methods are described. In addition, we describe a protocol for producing slice preparations of the developing moth brain that we are using to study the biophysical and morphological development of glial cells. This technique allows us to examine a class of glial cells associated with the glomeruli that otherwise are nearly inaccessible using standard intracellular recording techniques. It also preserves the 3-dimensional arrangement of glia that may strongly influence the development of glomeruli.
• Oland, L. A., Pott, W. M., Bukhman, G., Sun, X. J., & Tolbert, L. P. (1996). Activity blockade does not prevent the construction of olfactory glomeruli in the moth Manduca sexta. International Journal of Developmental Neuroscience, 14, 983-996.
• Oland, L. A., Kirschenbaum, S. R., Pott, W. M., Mercer, A. R., & Tolbert, L. P. (1995). Development of an identified serotonergic neuron in the antennal lobe of the moth and effects of reduction in serotonin during construction of olfactory glomeruli.. Journal of Neurobiology, 28, 248-267.
• Dagmar, M., Oland, L. A., & Tolbert, L. P. (1994). Uniglomerular projection neurons participate in the early development of olfactory glomeruli in the moth Manduca sexta. Journal of Comparative Neurology, 350, 1-22.
• Krull, C. E., Oland, L. A., Faissner, A., Schnachner, M., & Tolbert, L. P. (1994). In vitro analysis of neurite outgrowth indicates a potential role for tenascin-like molecules in the development of insect olfactory glomeruli.. Journal of Neurobiology, 25, 989-1004.
• Oland, L. A., & Oberlander, H. (1994). Factors that influence the development of cultured neurons from the brain of the moth Manduca sexta. In Vitro Cellular and Developmental Biology - Animal, 30 A(10), 709-716.
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  PMID: 7842172;Abstract: During metamorphic adult development, neurons and glial cells in the developing olfactory (antennal) lobes of the moth undergo characteristic and extensive changes in shape. These changes depend on an interplay among these two cell types and ingrowing sensory axons. All of the direct cellular interactions occur against a background of changing steroid hormone titers. Antennal-lobe (AL) neurons dissociated from stage-5 (of 18 stages) metamorphosing animals survive at least 3 wk in primary cell culture. We describe here the morphological influences on AL neurons of (1) exposure to the steroid hormone 20-hydroxyecdysone, (2) exposure to sensory axons, and (3) interactions among the AL neurons. Cultured AL neurons respond only weakly, if at all, to 20-hydroxyecdysone. They do, however, show greater total outgrowth and branching when they had been exposed in vivo to sensory axons. Because there is no direct contact between some of the neuronal types and the sensory axons at the time of dissociation, the increase in outgrowth must have been mediated via a diffusible factor(s). When AL cells (neurons and glia) are plated at high density in low volumes of medium, or when the cells are plated at low density but in the presence of medium conditioned by high-density cultures, neurite outgrowth and cell survival are increased. Nerve growth factor (NGF), epidermal growth factor (EGF), fibroblast growth factor-basic (bFGF), transforming growth factor-β (TGF(β)) and insulin- like growth factor (ILGF) had no obvious effect on neuronal morphology and thus are unlikely to underlie these effects. Our results suggest that the mature shape of AL neurons depends on developmental interactions among a number of diffusible factors.
• Oland, L. A., & Hayashi, J. H. (1993). Effects of the steroid hormone 20-hydroxyecdysone and prior sensory input on the survival and growth of moth central olfactory neurons in vitro. Journal of Neurobiology, 24(9), 1170-1186.
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  PMID: 8409976;Abstract: Neurons in the developing (antennal) olfactory lobe of the moth Manduca sexta undergo a period of extensive process outgrowth and branching that coincides temporally with both a rising titer of the steroid hormone 20- hydroxyecdysone and the ingrowth of sensory axons from receptors in the antenna. To evaluate the contribution of these two influences to the morphological development of antennal-lobe neurons, we placed the neurons in cell culture. Antennal-lobe neurons were dissociated from normal and chronically unafferented lobes at different stages of development and were exposed to different doses of hormone. Six neuronal cell types with distinctive and stable morphologies appeared in cultures from all stages of pupal development. Morphological changes in these neuronal types were examined quantitatively by comparison of the total length and number of branches. We found that 20-hydroxyecdysone had little direct effect on the morphological development of antennal-lobe neurons, but brief exposure to sensory axons in vivo prior to dissociation significantly enhanced subsequent outgrowth in culture.
• Oland, L. A., Orr, G., & Tolbert, L. P. (1990). Construction of a protoglomerular template by olfactory axons inititates the formation of olfactory glomeruli in the insect brain.. Journal of Neuroscience, 10, 2096-2112.
• Tolbert, L. P., & Oland, L. A. (1990). Glial cells form boundaries for developing insect olfactory glomeruli. Experimental Neurology, 109, 19-28.
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  invited review
• Oland, L. A., & Tolbert, L. P. (1989). Patterns of glial proliferation during formation of olfactory glomeruli. Glia, 2, 10-24.
• Tolbert, L. P., & Oland, L. A. (1989). A role for glia in the development of organized neuropilar structures. Trends in Neuroscience, 12, 70-75.
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  Review
• Oland, L. A., & Tolbert, L. P. (1988). Effects of hydroxyurea parallel the effects of radiation in developing olfactory glomeruli in insects. Journal of Comparative Neurology, 278, 377-387.
• Oland, L. A., Tolbert, L. P., & Mossman, K. L. (1988). Radiation-induced reduction of the glial population during development disrupts the formation of olfactory glomeruli in an insect.. Journal of Neuroscience, 8, 353-367.
• Oland, L. A., & Tolbert, L. P. (1987). Glial patterns during early development of antennal lobes of Manduca sexta: A comparison between normal lobes and lobes deprived of antennal axons.. Journal of Comparative Neurology, 255, 196-207.
• Oland, L. A., Stuart, A. E., Hayashi, J. H., & Callaway, J. C. (1987). Voltage spread in an identified interneuron of the barnacle's visual system. Journal of Neurophysiology, 58(6), 1420-1430.
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  PMID: 2449517;Abstract: The interneuron that is postsynaptic to barnacle photoreceptors (the inverting, or I-cell) receives similar synaptic input from the receptors onto its two distinct and separate arbors. We compared the spread of light-evoked synaptic potentials from the proximal and distal arbors with the cell's soma in order to ascertain how well voltages spread in this cell. The proximal and distal arbors are connected by a commissural process ~200 μm in length and 2 μm in diameter. Voltages spreading from the distal arbor along this process were 20-60% of their original value, and delayed 15-20 ms, when recorded at the cell's soma. The reversal potential of the receptor's input to the distal arbor, determined by injecting current into the soma, appeared substantially negative (-150 mV) to that of the identical input to the proximal arbor (-80 mV). Assuming identical reversal potentials in the two arbors, this difference indicates that more current must be injected into the I-cell's soma to change the voltage of the distal arbor to a given potential than to change that of the proximal arbor to the same potential. Comparison of input from a lateral eye to the ipsilateral arbor with that from the median eye to the same arbor indicates that these two inputs are at an electrically equivalent distance from the soma. Uneven illumination of the eyes may, through local conductance changes, cause the arbors to function independently, even to the point where one arbor may depolarize when the other is hyperpolarized.
• Oland, L. A., & Stuart, A. E. (1986). Pattern of convergence of the receptors of the barnacle's three ocelli onto second-order cells.. Journal of Neurophysiology, 55(5), 882-895.
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  PMID: 3711970;Abstract: The giant barnacle, Balanus nubilus, has three simple eyes, two lateral and one median. We have studied the convergence of the receptors of these ocelli by recording from the second-order cell (I-cell) and from the receptors' terminals. The I-cell's responses to illumination of the median and lateral eyes are similar in shape, dynamic range, and reversal potential, but the response to lateral input has a longer latency, a slower rise time, and a smaller amplitude. These differences primarily reflect the different voltage changes in the terminals of the decrementally conducting median and lateral receptors. Simultaneous recordings from the terminals of median and lateral receptors showed that the responses to light recorded in lateral terminals had a longer latency, a slower rise time, and smaller amplitude than signals in median terminals. The differences in the I-cell's responses to median and lateral input were essentially eliminated by stimulating the median and lateral ocellar nerves with extracellular suction electrodes positioned at equal distances from the receptors' terminals. The similarity of the I-cell's responses to median and lateral input suggests that lateral photoreceptors, like median receptors, contact the I-cell directly. No evidence was found for interaction between median and lateral receptors. Simultaneous fills of median and lateral receptors with cobalt showed minimal overlap between their terminal arbors. No voltage change was detected in the second receptor when the voltage in the first was changed with current pulses or when action potentials were elicited in the presence of tetraethylammonium ions. The absence of a detectable response in the terminals of one eye's receptors when the receptors of the other eye were stimulated with current or light suggests that there is no feedback from the I-cell to the receptors. Simultaneous illumination of the median and lateral eyes produced responses in the I-cell expected from two independent inputs. The first synaptic stage of the visual pathway in the barnacle is thus unusually simple, consisting of a small number of electrically isolated photoreceptors converging upon the same pair of second-order cells with no feedback interaction.
• Oland, L. A., French, K. A., Hayashi, J. H., & Stuart, A. E. (1983). Lateral visual pathway of giant barnacle. Journal of Neurophysiology, 49(2), 516-527.
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  PMID: 6300348;Abstract: We have studied the responses to light, conduction down the axons, and anatomical projections of the photoreceptors of the lateral eye in the giant barnacle, Balanus nubilus. By recording intracellularly from ganglion cells that respond to visual input, we have described convergence of the lateral and median visual pathways. Each lateral eye contains three photoreceptor cells, two large and one small. Cobalt filling of single large lateral receptor axons demonstrated that they end in a restricted ovoid bush on the ipsilateral side of the ganglion in approximately the same region in which the median receptors arborize. The lateral receptors have dark resting potentials and responses to light similar to those previously described for the receptors of the median eye. Like the median receptors, the lateral receptors conduct visual signals decrementally, although their axons may be twice as long (14-25 mm). Passing current of either polarity into either of the large receptors produced no detectable voltage change in the other cell. Action potentials elicited in either cell by stimulating it in the presence of tetraethylammonium ion were not detected in the other cell. Light-induced membrane noise in one cell did not correlate with noise in the other. Thus, like the receptors of the median eye, the large receptors of the lateral eye are not electrically coupled. By shadowing each ocellus individually, we have shown that the signals from the median and lateral photoreceptors converge at the level of the second-order cells described for the median pathway. Shadowing the median or a lateral eye gave rise to synergistic responses in second-, third-, and all higher order ganglion cells studied. No cells were found that were driven solely by the lateral eyes. Thus, the lateral and median visual pathways are highly convergent.

Presentations

• MacNamee, S. E., Tolbert, L. P., & Oland, L. A. (2014, Fall). Physiology of Drosophila astrocyte-like glial cells: intrinsic properties and response to channelrhodopsin-mediated neuronal activity. Society for Neuroscience. Washington, DC.
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Poster Presentations

• Hernandez, E., Macnamee, S. E., Kaplan, L. R., Charlton, J. A., Farhadi, D. S., Lance, K. L., Tolbert, L. P., & Oland, L. A. (2016, Nov). Drosophila astrocytes span functional neural domains. Society for Neuroscience.
• Hernandez, E., Lance, K. N., Charlton, J. A., MacNamee, S. E., Oland, L. A., & Tolbert, L. P. (2015, Fall). Morphological analysis of astrocyte-like glial cells in the Drosophila ventral nerve cord. Society for Neuroscience annual meeting. Chicago, IL: Society for Neuroscience.
• MacNamee, S. E., Liu, K., Gerhard, S., Fetter, R., Tolbert, L. P., Cardona, A., & Oland, L. A. (2015, Fall). Drosophila Astrocytes transport glutamate at identified non-tri-partite synapses. Society for Neuroscience annual meeting. Chicago, IL: Society for Neuroscience.
• Oland, L. A., Tolbert, L. P., & MacNamee, S. E. (2015, Fall). Astrocytic glutamate transport via dEEAT1 regulates a pre-motor synapse. Cold Spring Harbor Drosophila Neurobiology meeting. Cold Spring Harbor, NY: Cold Spring Harbor.
• Oland, L. A., Tolbert, L. P., Charlton, J. A., Lance, K. N., & Tran, C. T. (2015, Fall). Modulation of neural activity affects astrocyte morphology in Drosophila melanogaster. Society for Neuroscience annual meeting. Chicago, IL: Societyfor Neuroscience.
• MacNamee, S. E., & Oland, L. A. (2013, October). Astrocyte-like glial cells respond to neuronal activity with an inward current. Cold Spring Harbor Laboratory Neurobiology of Drosophila Meeting. Cold Spring Harbor, NY.
• MacNamee, S. E., Lee, S. W., & Oland, L. A. (2013, Fall). Drosophila astrocyte-like glia show heterogeneity in their morphology and voltage-gated currents. Society for Neuroscience. San Diego, CA.
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