Martin Wilson - US grants

A necessary precondition for the understanding of visual system pathology is that the normal visual system be understood in sme detail. A quantitative description of the retina at the level of single cells is likely to be the cornerstone for this broader understanding. Over the last two years may colleagues and I have made progress towards such a quantitative description of the first stages of visual processing in the salamander retina. This proposal continues the same basic strategy. By selectively destroying receptors in an isolated retina viewed under the microscope, I plan to isolate either one, or a pair of receptors from the neighbors to which they would otherwise be electrically coupled. This experimental simplification will allow me to examine in detail the properties of the connections between individual receptors. A second part of this proposal sets out to use simultaneous microelectrode impalement of cones and bipolar cells to establish the spatial extent and fine structure of bipolar cell receptive fields. Bipolar cell responses to small currents injected into receptors should also allow a preliminary analysis of the physiology of the receptor to bipolar cell synapse.

Much of the power of the retina to process and package information is derived from the properties of retinal synapses. It is known, from anatomical studies, that retinal synapses have structural features suggesting they work differently from more familiar synapses elsewhere in the nervous system. Presently though, the physiology of retinal synapses is very imperfectly understood. This proposal describes electrophysiological experiments to investigate the normal working of retinal synapses, concentrating in particular, on the first synapse of the visual system: the synapse between photoreceptors and bipolar cells. Four sets of questions are addressed here, each of which is a continuation of our present work. A first set of questions concerns the properties of channels, on bipolar cells, that are opened by the photoreceptor transmitter, glutamate. We have recently discovered that these channels have some unorthodox and surprising properties that we intend to examine in more detail. A second set of questions is concerned with the presynaptic mechanisms involved in the release of transmitter from photoreceptors. To tackle these questions we have developed the sparse culture of chick retinal cells as a preparation that avoids the technical problems associated with the intact retina. The third group of questions centers on the role of the peptide, somatostatin, in the outer retina. This peptide, which in the amphibian retina is probably the neurotransmitter of an interplexiform cell, has been shown to have diverse, modulatory actions in other parts of the nervous system. We propose to describe somatostatin's effects in the intact retina and uncover the underlying mechanisms by examining isolated retinal neurons. Lastly, we want to find out more about two important membrane currents found in chick cone cells. One of these currents is the calcium current involved in transmitter release.

[unreadable] DESCRIPTION (provided by applicant): The long-term goal of this work is to understand the retina as a neuronal machine, much like the rest of the brain for which it serves as a model. Synaptic transmission between amacrine cells forms the focus of this proposal since there is evidence that novel mechanisms of transmitter release are present in these cells. Elucidation of these fundamental mechanisms will help in understanding the design and role of this class of neuron in the retina and will likely have wide relevance to synaptic transmission throughout the brain. The experiments proposed here will combine patch clamp electrophysiology with high resolution calcium imaging of isolated, cultured amacrine cells to achieve 3 specific aims. Our first aim is to determine the relationship between calcium release from internal stores and synaptic transmission. At present the connection between calcium release and transmitter release is strong but essentially circumstantial. We will establish a causal connection by pharmacologically interfering with calcium release and showing that this alters synaptic transmission. Using light and electron microscopy we will examine the spatial relationship between calcium stores and synapses to see if it is consistent with a functional relationship. Our second aim is to define the mechanism of the calcium amplifier in dendrites that takes the small amount of calcium admitted through calcium channels and boosts it with calcium from internal stores. To achieve this aim we will use calcium imaging to examine, through the use of selective blockers, the interaction between Ryanodine receptors and IP3 receptors, both of which we know are involved in the calcium amplifier. We will examine the biochemical pathway producing IP3, again using pharmacological agents. The storage capacity of the calcium stores and the relative independence of adjacent stores will be addressed. Our third aim is to understand the role of calcium entry through TRP channels for the release of transmitter. We have preliminary evidence that these calcium permeable but voltage independent channels admit calcium to the dendritic cytoplasm when internal stores are depleted, and perhaps under other circumstances too. To reveal their role in transmitter release we will block calcium entry through these channels while monitoring synaptic transmission. [unreadable] [unreadable]

organ culture; retinal bipolar neuron; biomedical facility; image processing; voltage /patch clamp;

DESCRIPTION (provided by applicant): The broad goal of this application is to accelerate and facilitate the seamless integration of physical and mathematical sciences into the undergraduate biology curriculum of a large public university. The plans outlined in this proposal will enable us to design and execute a critical component of a broader reorganization of the undergraduate biology curriculum, which was initiated one year ago. We have identified two overarching goals. The first goal is to cultivate a substantial cadre of students with advanced skills in both biology on the one hand and mathematics, engineering, chemistry, computer science or physics on the other. The second goal, which supports the first, is to educate all biology students to be much more familiar with quantitative approaches than is traditional in biology programs. To achieve these goals we propose 4 specific aims. We will develop and launch a required freshman class introducing students to the application of mathematics in biology. This class will show students how to use a mathematical software toolbox that they will carry with them throughout their undergraduate careers. Subsequently, we will systematically introduce quantitative examples and exercises into high enrollment intermediate level biology courses. At the same time, we will launch a minor degree in Quantitative Biology and Bioinformatics that will take students majoring in either biology or a mathematical or physical science, and complement their coursework with interdisciplinary studies. In the steady state we expect to have about 20% of biology students graduate with this minor degree. As part of the Quantitative Biology and Bioinformatics minor, we will institute a program of undergraduate interdisciplinary research in which well-prepared undergraduates will be placed in the research labs of faculty members from different departments. An integral part of this proposal is a plan to disseminate our ideas and progress through participation in national meetings, partnering with organizations already established as hubs of national networks, and the open dissemination of course material from our website.

Abstract Not Provided.

DESCRIPTION (provided by applicant): The broad goal of this application is to accelerate and facilitate the seamless integration of physical and mathematical sciences into the undergraduate biology curriculum of a large public university. The plans outlined in this proposal will enable us to design and execute a critical component of a broader reorganization of the undergraduate biology curriculum, which was initiated one year ago. We have identified two overarching goals. The first goal is to cultivate a substantial cadre of students with advanced skills in both biology on the one hand and mathematics, engineering, chemistry, computer science or physics on the other. The second goal, which supports the first, is to educate all biology students to be much more familiar with quantitative approaches than is traditional in biology programs. To achieve these goals we propose 4 specific aims. We will develop and launch a required freshman class introducing students to the application of mathematics in biology. This class will show students how to use a mathematical software toolbox that they will carry with them throughout their undergraduate careers. Subsequently, we will systematically introduce quantitative examples and exercises into high enrollment intermediate level biology courses. At the same time, we will launch a minor degree in Quantitative Biology and Bioinformatics that will take students majoring in either biology or a mathematical or physical science, and complement their coursework with interdisciplinary studies. In the steady state we expect to have about 20% of biology students graduate with this minor degree. As part of the Quantitative Biology and Bioinformatics minor, we will institute a program of undergraduate interdisciplinary research in which well-prepared undergraduates will be placed in the research labs of faculty members from different departments. An integral part of this proposal is a plan to disseminate our ideas and progress through participation in national meetings, partnering with organizations already established as hubs of national networks, and the open dissemination of course material from our website.