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Biomedical subjects

J M Hamilton

Publications and source records attributed to J M Hamilton.

At least 73 records · Page 4Linked to original sources
PubMed1986

Effects of diet and photoperiod on NE turnover and GDP binding in Siberian hamster brown adipose tissue.

This experiment examined the effects of diet and photoperiod on food intake, body weight, and brown adipose tissue (BAT) activity in female Siberian hamsters (Phodopus sungorus sungorus). BAT function was assessed by measuring both the sympathetic nervous system activity of BAT [estimated by the rate of norepinephrine (NE) turnover] and BAT thermogenic activity (estimated by GDP binding to BAT mitochondria). Nineteen weeks of high-fat feeding in long photoperiod [16:8 light-dark cycle (LD)] caused a 20% increase in food intake but did not affect body weight. Both NE turnover rate and GDP binding in interscapular BAT (IBAT) were increased four- to eightfold relative to that from chow-fed controls. Thus it appears that in Siberian hamsters BAT can serve the same energy-dissipating function during diet-induced overeating previously established in rats and mice. Nineteen-week exposure to a short photoperiod (LD 8:16) produced a reduction in body weight but did not affect food intake. Both NE turnover rate and GDP binding in IBAT were increased two- to fourfold relative to that from long-photoperiod controls. Thus it appears that in Siberian hamsters the photoperiod-induced improvements in thermogenic capacity are mediated via the same mechanisms as are cold- or diet-induced thermogenesis.

Adipose Tissue, Brown↗
PubMed1986

Dissociation of sympathetic and thermogenic activity in brown fat of Syrian hamsters.

Syrian hamsters (Mesocricetus auratus) were fed a high-fat (HF) diet for up to 16 wk. Sympathetic and thermogenic activities in their brown adipose tissue (BAT) were assessed by measuring norepinephrine content and turnover and mitochondrial GDP binding and cytochrome c oxidase activity. Chronic ingestion of the HF diet resulted in significant increases in carcass lipid and interscapular BAT wet weight by the end of the second week. HF-fed hamsters were slightly hyperphagic during the first 2 wk of HF feeding only. Significant weight gains persisted beyond the period of hyperphagia. Hypertrophy of interscapular BAT after 16 wk on the HF diet was accompanied by increases in protein and DNA content, indicating growth of functional tissue. Norepinephrine turnover and content in BAT were decreased throughout the entire period of HF feeding, regardless of changes in caloric intake or body weight. Mitochondrial cytochrome c oxidase activity and GDP binding were increased after 16 wk on the HF diet, a time when the HF-fed animals were obese but not hyperphagic. These results demonstrate a dissociation of BAT thermogenesis from sympathetic activity in the tissue. It appears that sympathetic nervous system activity in BAT was suppressed by the HF diet, whereas thermogenic activity of the tissue was activated when the hamsters became obese.

Adipose Tissue, Brown↗
PubMed1985

Eversion of frown lines.

A method of everting frown lines by undermining the glabellar area through a lower stab wound and suturing the frown line into a ridge with vertical mattress sutures tied over small cotton rolls is presented. This has proven 90 percent successful over a 2-year follow-up.

Dermatologic Surgical Procedures↗
PubMed1984

Possible role of histamine in the genesis of pulmonary arterial disease in cats infected with Toxocara cati.

Kittens between 12 and 20 weeks of age were orally dosed with 6000 infective ova of Toxocara cati. Animals were sacrificed at intervals between one and eight weeks after infection to study the development of pulmonary arterial lesions. After two weeks, marked leucocyte infiltration and mild thickening of the media of some of the smaller arteries was apparent histologically . Cellular inflammatory activity progressively increased up to four weeks after infection when intimal proliferation was evident in many of the arteries. After six weeks, the arterial walls were grossly thickened with pronounced intimal proliferation which after eight weeks had resulted in complete occlusion of some vessels. The progressive arterial occlusion was associated with a three- to four-fold increase in the parenchymal mast cell population and a corresponding increase in lung histamine content. The possible role of histamine in the genesis of the arteriopathy is discussed.

Animals↗
PubMed1984

Adipose tissue lipoprotein lipase activity in rats maintained at a reduced body weight.

Male rats fed a cellulose-diluted diet maintained a reduced body weight. Adipose tissue lipoprotein lipase (LPL) activity decreased after two days of cellulose feeding, but was not different from chow-fed control levels with weight stabilized at 90% or 70% of the control group. Plasma triglyceride concentration decreased with weight loss and remained depressed with stabilized reduced weight. Regaining lost weight had no effect on LPL activity when compared with chow-fed controls or with levels obtained for the weight-reduced group. However, plasma triglyceride concentration returned to chow-fed control levels with weight gain. The disparity between these results and those obtained in obese human beings lends support to the hypothesis that the increase in adipose tissue LPL activity in weight-reduced obese human beings is indicative of a defect in regulation of adipose tissue metabolism.

Adipose Tissue↗
PubMed1983

Copulatory behavior and hypothalamic estrogen and progestin receptors in chronically insulin-deficient female rats.

The effects of relatively short- or long-term diabetes on sexual receptivity and and proceptivity and on hypothalamic estrogen and progestin receptors were examined in rats fed regular chow or high fat diet. Ovariectomized, streptozotocin-induced chronically insulin deficient and normal rats received sequential treatments with 2 micrograms estradiol benzoate (EB) and 1 mg progesterone (P) 10 days following the induction of diabetes and were tested for lordosis and soliciting behaviors. Nondiabetic rats fed either diet displayed significantly higher lordosis and solicitation behaviors than chow-fed diabetics, and fat-fed diabetic animals displayed behavior levels intermediate to those of nondiabetic and chow-fed rats. Ten days after the induction of diabetes, the levels of hypothalamic estrogen receptors of chow-fed diabetics were significantly lower than nondiabetics with the fat-fed diabetic group showing intermediate levels. However, 70 days after streptozotocin treatment diabetic rats had significantly lower estrogen receptors than nondiabetics regardless of the diet. Treatment of long-term (70 days) diabetic rats with 1-2 U of U-100 Lente insulin for 24 hr or 7 days was ineffective in restoring the hypothalamic estrogen receptor concentrations to those of nondiabetics. Three weeks following induction of diabetes, induction of cytoplasmic progestin receptors by EB treatment was significantly impaired in diabetic animals fed either chow or high fat diet. Although the reproductive dysfunctions present in short-term diabetic female rats may be due in part to chronic fuel deprivation, it appears that the long-term maintenance of cytosol estrogen receptor level is dependent on other actions of insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗