Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
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Item LONG-RANGE SIGNALING AT THE INTESTINAL-NEURAL AXIS PROMOTES ORGANISMAL HEME HOMEOSTASIS IN C. ELEGANS(2014) Sinclair, Jason Wallace; Hamza, Iqbal; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Metazoans synthesize and regulate intracellular heme in a cell autonomous manner although genetic evidence in vertebrates suggests that cell non-autonomous mechanisms may exist at the organismal level. In C. elegans, a heme auxotroph, extraintestinal tissues are intrinsically dependent on the intestine, which acquires dietary heme for sustenance, supporting the concept that intestinal heme status must be coordinated at the systemic level to regulate whole-organism heme homeostasis. Here we show, by conducting a functional genome-wide RNAi screen in an intestinal-restricted heme sensor worm, that an interorgan heme signaling pathway exists and that >30% of the genes identified from the RNAi screen altered heme homeostasis in the intestine even though these genes are not expressed in the intestine. The biological basis for this signaling is underscored by HRG-7, a cathepsin protease-like protein secreted by the intestine and internalized by distally-located neurons. HRG-7 is specifically secreted from the intestine during heme limitation and hrg-7 depletion causes embryonic lethality concomitant with a heme deficiency response. Reciprocally, neuron-to-intestine heme signaling is mediated by the bone morphogenic protein homolog DBL-1, which recapitulates hrg-7 deficiency when depleted. Remarkably, depletion of both genes simultaneously results in markedly enhanced growth and heme deficiency phenotypes, suggesting that bidirectional signaling between the intestine and neurons mediates systemic heme homeostasis. Our results have uncovered an unexpected role for a protease family member in long-range communication between organs at the intestinal-neural axis to regulate systemic heme homeostasis in metazoa. As humans have over thirty cathepsin and cathepsin-like proteases, several of which are secreted, we anticipate that these proteins may play analogous roles in mammalian biology.Item On-Farm Dry Matter Analysis to Improve Feed Delivery Precision on Dairy Farms(2011) French, Karin R.; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Uncertainty in dairy ration content impacts feed efficiency, milk production, expenses, and environmental losses. When measuring silage by weight, unknown changes in dry matter (DM) may change the total mixed ration. The objective of this study was to measure variation in silage DM on selected farms and evaluate an electronic method of on-farm DM analysis. Of 31 Maryland farms surveyed, 63% reported DM analysis by an on-farm method, 83% by any method including laboratory measurement. Eight producers performed DM analysis daily for 21 days using a Farmex 1210 Electronic Silage Tester (on-farm) and they recorded precipitation; matching samples were analyzed for DM in a laboratory after oven drying ("standard" method, 55°C followed by 100°C) and by using a Farmex 1210 (laboratory). The standard deviation of mean silage DM varied from 0.72% to 3.33% DM, depending on farm. The electronic method compared poorly to standard DM analysis for most farms.Item Effects of Aging and Moderate Calorie Restriction on the Reproductive Axis of the Male Rhesus Macaque (Macaca mulatta)(2007-04-25) Sitzmann, Brandon Dale; Ottinger, Mary Ann; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Calorie restriction (CR) has been established as the only non-genetic method of altering longevity and attenuating biological changes associated with aging. This nutritional paradigm has been effective in nematodes, flies, rodents, dogs and possibly non-human primates. Its long history notwithstanding, little is known regarding the exact mechanism(s) of CR action or its potential impact on the hypothalamic-pituitary-gonadal (HPG) axis. The objectives of this project were to: 1) analyze neuroendocrine changes to the HPG axis that occur with aging and 2) evaluate the effects of moderate CR on reproductive function in male rhesus macaques. Pituitary gene expression profiling, semi-quantitative RT-PCR (sqRT-PCR) and immunohistochemistry showed circadian clock mechanism components present in three age categories of macaques, demonstrated age differences in expression for Per2, indicated differential expression of Per2 and Bmal1 at opposing time points and revealed daily rhythmic expression of REV-ERBα protein. These data indicate the ability of the macaque pituitary to express core-clock genes, their protein products, and to do so in a 24-hour rhythm. Young Adult CON and CR pituitary gene expression profiles detected potential differential expression in <150 probesets. A decline in>TSHR and CGA was detected in CR macaques as measured by sqRT-PCR. Other genes investigated showed no diet-induced changes. Young Adult CON and CR testicular gene expression profiles detected potential differential expression in <300 probesets although mRNA expression was not altered based on sqRT-PCR and real-time RT-PCR. Age-related>and/or diet-induced changes in HSD17β3, INSL3, CSNK1E and CGA were observed in a separate experiment with CGA in Old Adult CR subjects returning to youthful levels. Semen samples were collected from Young Adult CON and CR macaques. Normal spermiogram measures, ZP-binding, AR assay and SCSA® were conducted and indicated no differences between CON and CR-treated animals. Both groups exhibited similar daily testosterone profiles with no differences in mean or maximum levels; however, daily minimum testosterone levels were lower in CON animals. It appears that moderate CR had limited impact on neuroendocrine or reproductive function in male rhesus macaques based on our selected endpoints. Thus, advantageous CR health benefits can be achieved without obvious negative consequences to the HPG axis.