Previous research indicates the presence of a feedback inhibitor of lactation (FIL) in milk (Peaker and Wilde, 1996). Recently, tryptophan hydroxylase I (TPH1), the rate-limiting enzyme in serotonin (5-HT) biosynthesis, was identified in the mouse mammary gland and to be regulated by prolactin (PRL). Furthermore, 5-HT was present in rodent milk and addition of 5-HT to in vitro mammary cultures and in vivo administration of 5-HT to lactating mice reduced milk protein synthesis. Studies were conducted to determine the presence of the enzymatic machinery necessary to produce 5-HT in the bovine mammary gland, the presence of specific 5-HT receptors within the bovine mammary gland, the effects of 5-HT and non-selective and selective receptor antagonists on milk protein gene expression in cultures of primary bovine mammary epithelial cells (BMEC), and to determine the effects of intra-mammary infusions of 5-HT and a non-selective 5-HT receptor antagonist on milk production and composition in lactating dairy cows. Tryptophan hydroxylase I, aromatic amino acid decarboxylase (AADC) and the 5-HT reuptake transporter (SERT) were detected in lactating bovine mammary tissue by qRT-PCR and immunohistochemical staining. Additionally, mRNA for the 5-HT 1B, 2A, 2B, 4 and 7 receptors were detected in bovine mammary tissue as well as BMEC by qRT-PCR and in situ hybridization. Tryptophan hydroxylase I mRNA is in BMEC and up-regulated by PRL. Serotonin down-regulates milk protein gene expression but has not apparent effects on apoptosis and methysergide, ritanserin, SB-224289, and pimozide (receptor antagonists) increased milk protein gene expression in BMEC. Intra-mammary 5-HT infusions decreased overall milk yield in late-lactating dairy cows by 11.1%. Intra-mammary infusions of METH increased overall milk yield by 10.9%. In conclusion, the enzymatic machinery for 5-HT biosynthesis and uptake, as well as receptors involved 5-HT signaling are present in the bovine mammary gland. Furthermore, 5-HT appears to be a FIL in the bovine, but further research regarding its cellular mechanism of action and the location of its receptor populations should be conducted.

Establishing adequate muscle mass is essential for metabolic health. Fetuses with intrauterine growth restriction (IUGR) are born with less muscle mass than appropriate for gestational age infants and never fully recover, as those born IUGR demonstrate persistent reductions in lean body mass in adulthood. Consequently, children and adults with IUGR have an increased risk of developing type 2 diabetes, obesity, and other complications associated with the metabolic syndrome. In order to better understand the in utero programming paradigm of IUGR on skeletal muscle growth and metabolism, we isolated satellite cells from one-month-old lambs and examined their function because of their role in muscle growth. In this series of experiments, we establish a differentiation protocol and show that satellite cells grown on Matrigel (P ≤ 0.05) and in the presence of a TGFβ inhibitor (P ≤ 0.05) have increased fusion events after 3 - 4 days of differentiation. Importantly we found that differentiation of IUGR satellite cells, measured by percent fusion, was greater than controls (P ≤ 0.05). However this difference was lost when cultures were exposed to a TGFβ inhibitor for 24 hours (P > 0.05). Using our optimized differentiation protocol to produce myotubes, we measured insulin-stimulated glucose uptake. IUGR myotubes were less responsive to insulin compared to controls (P < 0.01). These findings demonstrate for the first time that satellite cells from IUGR lambs exhibit disturbed glucose metabolism and differentiation capacity, which indicates that satellite cells become programmed by conditions associated with IUGR.

Despite mounting evidence, a question still exists as to the true clinical relevance of varying degrees of malnutrition, the role of currently measured nutritional parameters in identifying malnutrition and predicting clinical risk in individual patients, and the efficacy of nutritional therapy. This study was designed to document the usefulness of the Prognostic Nutritional Index (PNI) as a predictor of clinical course. The nutritional assessments and clinical records of 328 subjects in a Veterans Administration Hospital were reviewed, PNI and complication rates were determined for each of the subjects, and the data statistically analyzed. The PNI was found to be a useful indicator of malnutrition and predictor of clinical course. The PNI appeared to be a more sensitive index of clinical outcome than did comparison of individual nutritional parameters to accepted norms, although it accounted for only 17% of the information needed to predict clinical course perfectly.

Recently, high carbohydrate diets were recommended for the treatment of diabetes mellitus. All aspects of these diets, however, have not been fully tested — particularly in insulin dependent diabetes mellitus (IDDM). The present study was designed to investigate the effects of high carbohydrate, low fat diets (HCLFD) on blood glucose regulation, lipoprotein and apoprotein concentrations and nutritional status in IDDM. Six women with IDDM were studied in the Clinical Research Center for ten weeks. The study was divided into a control diet (CD) with 45% CHO, 40% fat, and 15% protein for four weeks, and a HCLFD with 65% CHO, 20% fat, and 15% protein for six weeks. Subjects were allowed free selection of their carbohydrate and fiber sources during both diet periods. The resulting selections produced diets with approximately equal proportions of complex and simple carbohydrates (49% and 51%, respectively) and moderate quantities of dietary fiber (50 g) during the HCLFD. Weekly fasting and pre-prandial serum glucose and glycosylated hemoglobin, and daily 24 hr. urine glucose excretion and insulin dose were not significantly different between the two periods. Total plasma, LDL and HDL cholesterol concentrations (p<.05). and apopproteins AI (p<.001), B (p<.01) and CIII (p<.05) were significantly lower, VLDL cholesterol (p<.05), total plasma (p<.01) and VLDL (p<.001) triglycerides were significantly higher, and apoproteins AII and E were unchanged during the HCLFD. Lipoprotein and apoprotein concentrations were independent of glycemic control. There were no significant changes in any of the nutritional parameters tested. All except vitamin B₆ were within their respective normal ranges. Whole blood and plasma vitamin B₆, and pyridoxal 5'-phosphate fell below the lower limits, even though dietary intakes were adequate. The present study suggest that HCLFD did not adversely affect glycemic control in IDDM, and demonstrated a potentially beneficial lowering of total and LDL cholesterol concentrations independent of glycemic control. Finally, nutritional status appeared unaltered as a result of HCLFD. The lower levels of the B₆ vitamers in IDDM demonstrated in this study suggest that the relationship between diabetes and vitamin B₆ status needs to be investigated further. / Graduation date: 1982

Dietary protein intake has been observed to influence the induction of cancer in animals exposed to carcinogens, presumably by affecting the activities of enzyme systems which metabolize them. One such carcinogen is aflatoxin B₁ (AFB₁) a mold metabolite and frequent contaminant of foodstuffs. Variations in the levels of dietary proteins fed rats and rainbow trout (Salmo gairdneri) influence the induction of hepatocellular carcinoma by AFB, in these animals. The following work was undertaken to provide an explanation of these results in terms of AFB₁ in vitro metabolism. The effect of dietary casein and fish protein concentrate (FPC) levels upon the activities of potential AFB₁ metabolizing enzyme systems were studied in the rainbow trout (Salmo gairdneri). Hepatic subcellular protein and cytochrome P-450 contents, and the activities of glutathione-S-epoxide transferase (GTr) epoxide hydrase (EH) cytochrome c reductase and aldrin epoxidase (AE) enzymes were determined in trout fed varying levels of casein or FPC. In addition, the reduction of AFB₁ to aflatoxicol (AFL) and conversion to an active mutagen for Salmonella typhimurium TA 98 were examined. A prerequisite for this study was the adaptation of the Ames mutagen assay system for use with fish hepatic enzymes. Lowered hepatic GTr and AE activities and increased conversion of AFB₁ to AFL and to a microbial mutagen were noted in trout fed high protein diets relative to those fed low protein diets. Cytochrome P-450 content was observed to decrease with increasing dietary casein and increase with increasing dietary FPC. Hepatic EH activity remained constant and decreased in trout fed increasing levels of casein or FPC respectively. These changes in enzyme activity are discussed in relation to dietary influences upon AFB₁ carcinogenesis in the rainbow trout. / Graduation date: 1978

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