Necrotizing enterocolitis (NEC) remains a leading cause of morbidity and mortality in premature infants. Both human surgical specimens and animal models suggest a potential involvement of Paneth cells in NEC pathogenesis. Paneth cells play critical roles in epithelial homeostasis, innate immunity and host-microbial interactions. Yet, the complex interplay between Paneth cell disruption, epithelial barrier dysfunction and microbial-driven inflammation remains unclear in the immature intestine. In this study, mucosal intestinal injury consistent with human NEC was induced in postnatal day 14-16 (P14-P16) mice by disrupting Paneth cells, followed by gavage with Klebsiella pneumonia. Mucosal injury was determined by histology, serum cytokine levels and epithelial barrier dysfunction. Toll-like receptor 4 (TLR4) activation was examined using protein expression, gene expression, and TLR4−/− mice. Finally, the role of bacteria was evaluated using heat-killed bacteria, conditioned media, Bacillus cereus and cecal slurries. We found that live bacteria were required to induce injury; however, TLR4 activation was not required. NEC induced by Paneth cell disruption results in altered localization of tight junction proteins and subsequent loss of barrier function. Prior research has shown a requirement for TLR4 activation to induce NEC-like damage. However, many infants develop NEC in the absence of Gram-negative rod bacteremia, raising the possibility that alternative pathways to intestinal injury exist. In this study, we show a previously unknown mechanism for the development of intestinal injury equivalent to that seen in human NEC and that is not dependent on TLR4 pathways. These data are congruent with the new hypothesis that NEC may be the consequence of several disease processes ending in a final common inflammatory pathway.

Background. Premature infants are commonly subject to intestinal inflammation. Since the human small intestine does not reach maturity until term gestation, premature infants have a unique challenge, as either acute or chronic inflammation may alter the normal development of the intestinal tract. Tumor necrosis factor (TNF) has been shown to acutely alter goblet cell numbers and villus length in adult mice. In this study we tested the effects of TNF on villus architecture and epithelial cells at different stages of development of the immature small intestine. Methods. To examine the effects of TNF-induced inflammation, we injected acute, brief, or chronic exposures of TNF in neonatal and juvenile mice. Results. TNF induced significant villus blunting through a TNF receptor-1 (TNFR1) mediated mechanism, leading to loss of villus area. This response to TNFR1 signaling was altered during intestinal development, despite constant TNFR1 protein expression. Acute TNF-mediated signaling also significantly decreased Paneth cells. Conclusions. Taken together, the morphologic changes caused by TNF provide insight as to the effects of inflammation on the developing intestinal tract. Additionally, they suggest a mechanism which, coupled with an immature immune system, may help to explain the unique susceptibility of the immature intestine to inflammatory diseases such as NEC.

The vertebrate retina is a specialized photosensitive tissue comprised of six neuronal and one glial cell types, each of which develops in prescribed proportions at overlapping timepoints from a common progenitor pool. While each of these cells has a specific function contributing to proper vision in the mature animal, their differential representation in the retina as well as the presence of distinctive cellular subtypes makes identifying the transcriptomic signatures that lead to each retinal cell's fate determination and development challenging. We have analyzed transcriptomes from individual cells isolated from the chick retina throughout retinogenesis. While we focused our efforts on the retinal ganglion cells, our transcriptomes of developing chick cells also contained representation from multiple retinal cell types, including photoreceptors and interneurons at different stages of development. Most interesting was the identification of transcriptomes from individual mixed lineage progenitor cells in the chick as these cells offer a window into the cell fate decision-making process. Taken together, these data sets will enable us to uncover the most critical genes acting in the steps of cell fate determination and early differentiation of various retinal cell types.

Recent research into the rapid antidepressant effect of subanesthetic doses of ketamine have identified a series of relevant protein cascades activated within hours of administration. Prior to, or concurrent with, these activation cascades, ketamine treatment generates dissociative and psychotomimetic side effects along with an increase in circulating glucocorticoids. In rats, we observed an over 3-fold increase in corticosterone levels in both serum and brain tissue, within an hour of administration of low dose ketamine (10 mg/kg), but not with (2R, 6R)-hydroxynorketamine (HNK) (10 mg/kg), a ketamine metabolite shown to produce antidepressant-like action in rodents without inducing immediate side-effects. Hippocampal tissue from ketamine, but not HNK, injected animals displayed a significant increase in the expression of sgk1, a downstream effector of glucocorticoid receptor signaling. To examine the role conscious sensation of ketamine’s side effects plays in the release of corticosterone, we assessed serum corticosterone levels after ketamine administration while under isoflurane anesthesia. Under anesthesia, ketamine failed to increase circulating corticosterone levels relative to saline controls. Concurrent with its antidepressant effects, ketamine generates a release of glucocorticoids potentially linked to disturbing cognitive side effects and the activation of distinct molecular pathways which should be considered when attempting to delineate the molecular mechanisms of its antidepressant function.

Despite the myriad social and health benefits of exercise, humans display heterogeneous levels of participation. Significant progress has been made in identifying molecular events, systems, and mechanisms that support exercise’s beneficial effects, but it is not clear yet what regulates exercise behavior itself or serves to maintain prolonged chronic exercise behavior. The human heterogeneity in voluntary exercise can be recapitulated in a rodent model of wheel running, a behavior with high rewarding properties. While rats given continuous access to running wheels all began with low running activity, a 3‐week training program dramatically increased running activity and uncovered a wide range of individual differences in running behavior. In addition, we have identified intriguing sex differences in this model. Compared to age‐matched males, female rats exhibited significantly higher levels of average daily running. When assessing individual female rats’ running behavior, we also observed a repetitive peak‐valley pattern of running activity, with peaks coinciding with the proestrus stage (highest estrogen level) in the rat estrous cycle. Bilateral ovariectomy (OVX) not only lowered their overall running activity, but also completely eliminated cyclical variations. Furthermore, low dose estrogen replacement via osmotic mini‐pumps in an OVX background restored running activity to pre‐OVX levels, and acute estradiol injections were able to replicate running peaks. Collectively, those results suggest estrogen exerts strong regulation of female running activity. By taking individual and sex differences into consideration in the experimental design, we anticipate our subsequent biochemical assays will identify signaling molecules and pathways involved in running activity that is driven by a surge of estradiol.