Faculty Bibliography

Alpha cells are a type of ganglion cell whose morphology appears to be conserved across a number of mammalian retinas. In particular, alpha cells display the largest somata and dendritic arbors at a given eccentricity and tile the retina as independent on- (ON) and off-center (OFF) subtypes. Mammalian alpha cells also express a variable tracer coupling pattern, which often includes homologous (same cell type) coupling to a few neighboring alpha cells and extensive heterologous (different cell type) coupling to two to three amacrine cell types. Here, we use the gap junction-permeant tracer Neurobiotin to determine the architecture and coupling pattern of alpha cells in the mouse retina. We find that alpha cells show the same somatic and dendritic architecture described previously in the mammal. However, alpha cells show varied tracer coupling patterns related to their ON and OFF physiologies. ON alpha cells show no evidence of homologous tracer coupling but are coupled heterologously to at least two types of amacrine cell whose somata lie within the ganglion cell layer. In contrast, OFF alpha cells are coupled to one another in circumscribed arrays as well as to two to three types of amacrine cell with somata occupying the inner nuclear layer. We find that homologous coupling between OFF alpha cells is unaltered in the connexin36 (Cx36) knockout (KO) mouse retina, indicating that it is not dependent on Cx36. However, a subset of the heterologous coupling of ON alpha cells and all the heterologous coupling of OFF alpha cells are eliminated in the KO retina, suggesting that Cx36 comprises most of the junctions made with amacrine cells

Spinal motor neurons acquire specialized 'pool' identities that determine their ability to form selective connections with target muscles in the limb, but the molecular basis of this striking example of neuronal specificity has remained unclear. We show here that a Hox transcriptional regulatory network specifies motor neuron pool identity and connectivity. Two interdependent sets of Hox regulatory interactions operate within motor neurons, one assigning rostrocaudal motor pool position and a second directing motor pool diversity at a single segmental level. This Hox regulatory network directs the downstream transcriptional identity of motor neuron pools and defines the pattern of target-muscle connectivity

Advances in high throughput cloning strategies have led to sequencing of the human genome as well as progress in the sequencing of the genome of several other species. Consequently, the field of molecular genetics is blossoming into a multidisciplinary entity that is revolutionizing the way researchers evaluate a myriad of critical concepts such as development, homeostasis, and disease pathogenesis. There is tremendous interest in the quantitative assessment of tissue-specific expression of both newly identified and well characterized specific genes and proteins. At present, an ideal approach is to assess gene expression in single elements recorded physiologically in living preparations or by immunocytochemical or histochemical methods in fixed cells in vitro or in vivo. The quantity of RNA harvested from individual cells is not sufficient for standard RNA extraction methods. Therefore, exponential polymerase-chain reaction based analyses, and linear RNA amplification including amplified antisense RNA amplification and a newly developed terminal continuation RNA amplification methodology have been developed for use in combination with microdissection procedures and cDNA/oligonucleotide microarray platforms. RNA amplification is a series of intricate procedures to amplify genetic signals from minute quantities of starting materials for microarray analysis and other downstream genetic methodologies. RNA amplification procedures effectively generate quantities of RNA through in vitro transcription. The present report illustrates practical usage of RNA amplification technologies within the context of regional, population cell, and single cell analyses in the brain

The molecular organization of ribbon synapses in photoreceptors and ON bipolar cells is reviewed in relation to the process of neurotransmitter release. The interactions between ribbon synapse-associated proteins, synaptic vesicle fusion machinery and the voltage-gated calcium channels that gate transmitter release at ribbon synapses are discussed in relation to the process of synaptic vesicle exocytosis. We describe structural and mechanistic specializations that permit the ON bipolar cell to release transmitter at a much higher rate than the photoreceptor does, under in vivo conditions. We also consider the modulation of exocytosis at photoreceptor synapses, with an emphasis on the regulation of calcium channels

The right ventricle (RV) of the heart is responsible for pumping blood to the lungs. Its kinematics are not as well understood as that of the left ventricle (LV) due to its thin wall and asymmetric geometry. In this study, the combination of tagged MRI and three-dimensional (3-D) image-processing techniques was used to reconstruct 3-D RV-LV motion and deformation. The reconstructed models were used to quantify the 3-D global and local deformation of the ventricles in a set of normal subjects. When compared with the LV, the RV exhibited a similar twisting pattern, a more longitudinal strain pattern, and a greater amount of displacement

Decreases in behavioral investigation of novel stimuli over time may be mediated by a variety of factors including changes in attention, internal state, and motivation. Sensory cortical adaptation, a decrease in sensory cortical responsiveness over prolonged stimulation, may also play a role. In olfaction, metabotropic glutamate receptors on cortical afferent pre-synaptic terminals have been shown to underlie both cortical sensory adaptation and habituation of odor-evoked reflexes. The present experiment examined whether blockade of sensory cortical adaptation through bilateral infusion of the group III metabotropic glutamate receptor antagonist cyclopropyl-4-phosphonophenylglycine (CPPG) into the anterior piriform cortex could reduce habituation of a more complex odor-driven behavior such as investigation of a scented object or a conspecific. The results demonstrate that time spent investigating a scented jar, or a conspecific, decreases over the course of a continuous 10 minute trial. Acute infusion of CPPG bilaterally into the anterior piriform cortex significantly enhanced the time spent investigating the scented jar compared to investigation time in control rats, without affecting overall behavioral activity levels. Infusions into the brain outside of the piriform cortex were without effect. CPPG infusion into the piriform cortex also produced an enhancement of time spent investigating a conspecific, although this effect was not significant

Munc13 proteins are essential in neurotransmitter release, controlling the priming of synaptic vesicles to a release-ready state. The sequences responsible for this priming activity are unknown. Here we identify a large alpha-helical domain of mammalian Munc13-1 that is autonomously folded and is sufficient to rescue the total arrest in neurotransmitter release observed in hippocampal neurons lacking Munc13s.

The primary objective of this study was to characterize the drug exposure for children hospitalized in the authors' institution's pediatric intensive care unit for the year 2002. Secondary objectives included the examination of drug utilization differences among various age criteria and the suitability of the most prevalent resources for pediatric dosing guidance. Many of the most commonly prescribed agents in the pediatric intensive care unit fall into the broad categories of pain management/sedation and anti-infectives. Based on the generally narrow windows afforded by each of these drug classes, it is obvious that more, well-defined investigations in critically ill children are warranted. The existing dosing guidance for many of these agents is neither generalizable nor sufficient to accommodate the diversity in pediatric intensive care unit patients, and the current drug monographs fall short of any practical dosing information

To evaluate molecular events associated with the aging process in animal models and human tissues, microarray analysis is performed at the regional and cellular levels to define transcriptional patterns or mosaics that may lead to better understanding of the mechanism(s) that drive senescence. In this review, we outline the experimental and analytical issues associated with high-throughput genomic analyses in aging brain and other tissues for a comprehensive evaluation of the current state of microarray analysis in aging paradigms. Ultimately, the goal of these studies is to apply functional genomics and proteomics approaches to aging research to develop new tools to assess age in cell- and tissue-specific manners in order to develop aging biomarkers for pharmacotherapeutic interventions and disease prevention