Faculty Bibliography

The growing realization that neurotrophins, such as brain-derived neurotrophic factor (BDNF), are crucial in modulating synaptic plasticity has broadened the spectrum of their trophic actions. At the same time, it has become clear that Abeta peptides derived from amyloid precursor protein (APP) have dramatic effects on synaptic transmission before the onset of the neurodegenerative disease. Because neurotrophins and Abeta are responsible for affecting both synaptic and cognitive function, it is likely that their mechanisms of action will be related and might even intersect. This review highlights several recent findings that suggest trophic factors and APP use similar pathways to control neuronal activity

Antifungal efficacies of the echinocandin drugs caspofungin, micafungin, and anidulafungin were reduced significantly in the presence of 50% human serum, which yielded nearly equivalent MICs or minimum effective concentrations against diverse Candida spp. and Aspergillus spp. Consistent with a direct drug interaction, serum decreased the sensitivity of glucan synthase to echinocandin drugs.

Embryonic heart formation requires the union of bilateral populations of cardiomyocytes and their reorganization into a simple tube. Little is known about the morphogenetic mechanisms that coordinate assembly of the heart tube and determine its dimensions. Using time-lapse confocal microscopy to track individual cardiomyocyte movements in the zebrafish embryo, we identify two morphologically and genetically separable phases of cell movement that coordinate heart tube assembly. First, all cardiomyocytes undergo coherent medial movement. Next, peripherally located cardiomyocytes change their direction of movement, angling toward the endocardial precursors and thereby establishing the initial circumference of the nascent heart tube. These two phases of cardiomyocyte behavior are independently regulated. Furthermore, we find that myocardial-endocardial interactions influence the second phase by regulating the induction, direction and duration of cardiomyocyte movement. Thus, the endocardium plays a crucial early role in cardiac morphogenesis, organizing cardiomyocytes into a configuration appropriate for heart tube assembly. Together, our data reveal a dynamic cellular mechanism by which tissue interactions establish organ architecture

Leucine, as an essential amino acid and activator of mTOR (mammalian target of rapamycin), promotes protein synthesis and suppresses protein catabolism. However, the effect of leucine on overall glucose and energy metabolism remains unclear, and whether leucine has beneficial effects as a long-term dietary supplement has not been examined. In the present study, we doubled dietary leucine intake via leucine-containing drinking water in mice with free excess to either a rodent chow or a high-fat diet (HFD). While it produced no major metabolic effects in chow-fed mice, increasing leucine intake resulted in up to 32% reduction of weight gain (P < 0.05) and a 25% decrease in adiposity (P < 0.01) in HFD-fed mice. The reduction of adiposity resulted from increased resting energy expenditure associated with increased expression of uncoupling protein 3 in brown and white adipose tissues and in skeletal muscle, while food intake was not decreased. Increasing leucine intake also prevented HFD-induced hyperglycemia, which was associated with improved insulin sensitivity, decreased plasma concentrations of glucagon and glucogenic amino acids, and downregulation of hepatic glucose-6-phosphatase. Additionally, plasma levels of total and LDL cholesterol were decreased by 27% (P < 0.001) and 53% (P < 0.001), respectively, in leucine supplemented HFD-fed mice compared with the control mice fed the same diet. The reduction in cholesterol levels was largely independent of leucine-induced changes in adiposity. In conclusion, increases in dietary leucine intake substantially decrease diet-induced obesity, hyperglycemia, and hypercholesterolemia in mice with ad libitum consumption of HFD likely via multiple mechanisms.

Increased fat deposition in skeletal muscle is associated with insulin resistance. However, exercise increases both intramyocellular fat stores and insulin sensitivity, a phenomenon referred to as "the athlete's paradox". In this study, we provide evidence that augmenting triglyceride synthesis in skeletal muscle is intrinsically connected with increased insulin sensitivity. Exercise increased diacylglycerol (DAG) acyltransferase (DGAT) activity in skeletal muscle. Channeling fatty acid substrates into TG resulted in decreased DAG and ceramide levels. Transgenic overexpression of DGAT1 in mouse skeletal muscle replicated these findings and protected mice against high-fat diet-induced insulin resistance. Moreover, in isolated muscle, DGAT1 deficiency exacerbated insulin resistance caused by fatty acids, whereas DGAT1 overexpression mitigated the detrimental effect of fatty acids. The heightened insulin sensitivity in the transgenic mice was associated with attenuated fat-induced activation of DAG-responsive PKCs and the stress mediator JNK1. Consistent with these changes, serine phosphorylation of insulin receptor substrate 1 was reduced, and Akt activation and glucose 4 membrane translocation were increased. In conclusion, upregulation of DGAT1 in skeletal muscle is sufficient to recreate the athlete's paradox and illustrates a mechanism of exercise-induced enhancement of muscle insulin sensitivity. Thus, increasing muscle DGAT activity may offer a new approach to prevent and treat insulin resistance and type 2 diabetes mellitus.

Recent advances in cancer cell biology have focused on histone deacetylase inhibitors (HDACi's) because they target pathways critical to the development and progression of disease. In particular, HDACi's can induce expression of epigenetically silenced genes that promote growth arrest, differentiation and cell death. In glioma cells, one such repressed gene is the tetraspanin CD81, which regulates cytostasis in various cell lines and in astrocytes, the major cellular component of gliomas. Our studies show that HDACi's, trichostatin and sodium butyrate, promote growth arrest and differentiation with negligible cell death in glioma cells and induce expression of CD81 and cyclin-dependent kinase inhibitor 1A (p21(CIP/WAF-1)), another regulator of cytostasis in astrocytes. Interference RNA knock-down of CD81 abrogates cytostasis promoted by HDAC inhibition indicating that HDACi-induced CD81 is responsible for growth arrest. Induction of CD81 expression through HDAC inhibition is a novel strategy to promote growth arrest in glioma cells.

An optimal system for monitoring in vivo corneal wound healing is inexpensive, has utility for wounding and imaging, and is able to provide previews before photography. We outline such an imaging system that takes advantage of a consumer digital camera and an LED-based light source for fluorescein excitation. Using FVB/NJ mice, 2mm diameter, circular, axial corneal epithelial defects were created using a crescent blade. The corneal wounds were imaged every four hours until healed using a Nikon Coolpix 5400 camera attached to a Nikon SMZ-10A stereomicroscope, using the illumination from a 16 LED 464nm flashlight. The wound area was calculated, and the linear regressions of the linear phase of wound healing were compared using the F-test. The slopes of the linear regressions for the 6 trials of 4 mice/trial had an average of -52.95microm/h (SEM=0.55microm/h) and were statistically equivalent (p>0.05). The mean of the R(2) values for the linear regressions was 0.9546 (SEM=0.0121). The equivalent linear regressions and R(2)>0.90 suggest that the imaging system could precisely monitor the wound healing of multiple trials and of animals within each trial, respectively. Using a consumer digital camera and LED-based illumination, we have established a system that is economical, is used in both wounding and imaging, is operated by a single person, and is able to provide real-time previews to monitor corneal wound healing precisely

Here we review how prior experience with stress alters the response to a subsequent homotypic or heterotypic stressor, focusing on the catecholaminergic systems in the adrenal medulla and the locus coeruleus (LC). The changes in response to homotypic stress differ depending on the stressor applied. With immobilization stress (IMO), transcriptional responses in the adrenal medulla to a single exposure are pronounced and several of the transcription factors and signaling kinases induced or activated are reviewed and compared to the longer term alterations with repeated stress, consistent with persistent activation of gene expression of catecholamine (CA) biosynthetic enzymes. In the LC, transcriptional and post-transcriptional activation of gene expression are shown to be important. Repeated IMO stress triggers further activation of a number of signalling pathways. Neither adrenal medulla nor LC display habituation to long term repeated stress. In contrast, gene expression for CA biosynthetic enzymes habituates to prolonged cold stress in the adrenal medulla and LC, but displays an exaggerated response with exposure to a novel or heterotypic stressor such as IMO. Some of the transcriptional pathways displaying sensitization are described.

The genetic pathways that partition the developing nervous system into functional systems are largely unknown. The engrailed (En) homeobox transcription factors are candidate regulators of this process in the dorsal midbrain (tectum) and anterior hindbrain (cerebellum). En1 mutants lack most of the tectum and cerebellum and die at birth, whereas En2 mutants are viable with a smaller cerebellum and foliation defects. Our previous studies indicated that the difference in phenotypes is due to the earlier expression of En1 as compared with En2, rather than differences in protein function, since knock-in mice expressing En2 in place of En1 have a normal brain. Here, we uncovered a wider spectrum of functions for the En genes by generating a series of En mutant mice. First, using a conditional allele we demonstrate that En1 is required for cerebellum development only before embryonic day 9, but plays a sustained role in forming the tectum. Second, by removing the endogenous En2 gene in the background of En1 knock-in alleles, we show that Drosophila en is not sufficient to sustain midbrain and cerebellum development in the absence of En2, whereas En2 is more potent than En1 in cerebellum development. Third, based on a differential sensitivity to the dose of En1/2, our studies reveal a genetic subdivision of the tectum into its two functional systems and the medial cerebellum into four regions that have distinct circuitry and molecular coding. Our study suggests that an ;engrailed code' is integral to partitioning the tectum and cerebellum into functional domains