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Biomedical subjects

V E Mendel

Publications and source records attributed to V E Mendel.

33 records · Page 2Linked to original sources
PubMed1983

Effect of nutrient density and composition of liquid meals on gastric emptying in feeding rats.

Rats were fitted with gastric cannulas to determine gastric emptying rates of liquid test meals after a 16-h fast. They were allowed to drink [14C]polyethylene glycol (PEG) Vivonex High Nitrogen elemental diet (VHN) or Intralipid Fat Emulsion (IL) at 0.25, 0.50, and 1.00 kcal/ml under two conditions: drinking to satiety (VHN) or drinking to a constant volume of 15 ml (VHN and IL). Recovery of stomach contents through the cannula at the end of the drinking period allowed determination of rate of emptying. Average gastric emptying rate (ml/min) during a meal was found to vary inversely with the nutrient density of the test meal. However, the caloric emptying rate (kcal/min), as well as the total caloric load delivered to the intestine by the end of the meal, remained constant over the range of nutrient densities tested. The constancy of caloric emptying rate as diet caloric density increased was independent of diet composition, supporting the hypothesis that rate of gastric emptying is determined by caloric density of the diet. When rats were allowed to drink to satiety, caloric intake was not regulated but increased with increasing diet nutrient density, suggesting that control of meal size was independent of regulation of gastric emptying.

Animals↗
PubMed1983

Postgastric satiety in the sham-feeding rat.

A sham-feeding model using rats fitted with gastric and duodenal cannulas was employed to investigate the role of postgastric mechanisms of satiety in the short-term control of food intake. When fasted rats sham fed a liquid diet [Vivonex High Nitrogen (VHN), 0.5 kcal/ml], food drained freely from gastric fistulas, and mean first-meal size and 90-min intake increased more than threefold. Varying the rate of duodenal infusion of diet during sham feeding (0.06-0.44 kcal/min) decreased first-meal size and total intake in a dose-dependent manner. First meals ended when mean loads of 2-3 kcal had been delivered. The threshold rate (0.11 kcal/min) decreased meal size and total intake by more than 50%. When fasted rats consumed VHN to satiety with closed gastric fistulas, rate of gastric emptying of diet during feeding averaged 0.32 +/- 0.02 kcal/min and the load emptied by meal termination averaged 3.8 +/- 0.2 kcal. These results indicate that rates of gastric emptying of diet and loads delivered to the small intestine following ingestion of liquid food are sufficient to elicit postgastric satiety in the absence of gastric distension.

Animals↗
PubMed1980

Influence of the insulin-to-growth hormone ratio on body composition of mice.

To determine whether the insulin-to-growth hormone ratio was different in genetically related animals with known differences in food intake and amount of adipose tissue the following parameters were measured in lean (C57BL/6J) and yellow obese mice (Avy/a): food intake, body composition, energy intake, plasma concentrations, and ratios of insulin and growth hormone; these were determined in one experiment during a 24-h period. Yellow obese mice contained significantly greater amounts of body fat than the lean littermates, a significantly higher insulin-to-growth hormone ratio, and a higher daily food intake. In a second experiment, a shift in hormone concentrations and ratios occurred with increasing age and simultaneously with changes in body composition in the Avy/a mice; both changed without changes of food intake. The increased obesity may have resulted from an increase in the insulin-to-growth hormone ratio or more probably from an increase in the insulin level alone.

Animals↗
PubMed1976

Effect of ventromedial and dorsomedial hypothalamic lesions on circadian corticosterone rhythms.

Weanling rats received bilateral electrolytic lesions in the dorsomedial (DMH) or ventromedial (VMH) hypothalamic areas destroying primarily the dorsomedial (DMN) or ventromedial (VMN) hypothalamic nuclei. Sham-operated rats served as controls. Lesions in the VMN and DMN, both of which have previously been shown to disrupt normal diurnal feeding rhythms, were also observed to disrupt normal plasma corticosterone rhythms in the present study. The a.m. values of plasma corticosterone in the DMN-lesioned rats were higher than the sham-operated controls. In the p.m., the values of both VMN- and DMN-lesioned rats were lower than those of the controls but unchanged in comparison to their own a.m. concentrations. This disruption of the normal diurnal plasma corticosterone rhythm persisted for at least 9 post-operative weeks.

Animals↗
PubMed1975

Effect of deprivation and time of refeeding on food intake.

The amount of food eaten in a two hour trial by male Sprague Dawley rats was recorded after periods of food deprivation up to 42 hr in length. Rats ate 50-78% more when refed during the dark phase than when refed during the light phase. This occurred even when light fed animals were fasted for longer periods than the dark fed animals. Rats eat in a rhythmic pattern after deprivation. These data are in good agreement with data previously reported and extend it by increasing the number of observations, increasing the length of deprivation, and comparing different age groups.

Age Factors↗
PubMed1975

Effect of meal feeding on daily rhythms of plasma corticosterone and growth hormone in the rat.

After rats had adapted to regular meal feeding in the morning they demonstrated an altered circadian rhythm of plasma corticosterone (B) even under the normal light-dark cycle. The altered daily rhythm of plasma B consisted of two peaks, with one peak at 08.00 h in anticipation of meal feeding and a second peak corresponding to the normal peak of plasma B prior to lights-off seen in ad libitum-fed animals. Neither peak of plasma B in the meal-fed animals achieved the magnitude of the single peak observed in control animals. In spite of some quantitative differences during certain periods of the day, after the animals had adapted to meal feeding there was no difference in the basic profile of the daily rhythm of plasma immunoactive growth hormone (GH).

Adaptation, Physiological↗
PubMed1975

Hormone and glucose responses to serial cardiac puncture in rats (38465).

Serial, apparently basal radio-immunoassayable plasma insulin and growth-hormone values were obtained when fast-knock down ether anesthesia was used. Radioimmunoassayable prolactin was elevated at the second, third, and fourth bleedings but cause no apparent increase in circulating insulin levels. The elevation in plasma glucose may also have been a transient effect of sympathetic stimulation which simultaneous inhibited insulin release.

Anesthesia, Inhalation↗
PubMed1975

Amnion autografts, permanent structure.

Autografts of amniotic membrane were used to form tubes or conduits in lambs. These conduits survived for periods up to 9 months. The possibility of a clinical application has been explored.

Amnion↗
PubMed1974

Glucose metabolism and lipid mobilization by adipocytes from mice selected for growth.

1. Experiments were conducted to compare the abilities of epididymal adipocytes from mice selected for growth (line G) and from unselected mice (line C) to: (a) incorporate glucose, (b) respond to insulin, and (c) mobilize lipids, and to relate these abilities to the food intake of the donors.2. During the 3-week pre-experimental period, line G mice gained body weight 78% faster and ate 35% more food than line C mice; both lines had similar intakes per unit of metabolic body size.3. Line G epididymal fat pads weighed 227% more than those of line C and contained adipocytes which were 38% larger; it was estimated that they contained approximately 65% more cells.4. The basal rate of glucose incorporated into lipids (per unit protein) was highest in line C adipocytes, whereas the basal rates of glucose oxidation to CO(2) and the total glucose incorporation (uptake) were similar for adipocytes from both lines.5. Insulin (1000 muu./ml.) caused adipocytes from both lines of mice to increase significantly the incorporation of glucose into CO(2) and lipids; the largest elevation occurred when the incubation medium contained 0.1 mg glucose/ml. At this concentration of glucose, the minimum effective dose (MED) of insulin to produce a significant increase in glucose oxidation was similar for both lines. However, the MED of insulin necessary to significantly increase glucose incorporation into lipids and into the sum of CO(2) and lipids was highest in the larger, line G adipocytes. Furthermore, the magnitude of the insulin-induced increase in glucose incorporation was much less for line G than for the line C adipocytes.6. Epinephrine significantly elevated the rates of NEFA and glycerol release and NEFA re-esterification. The highest rates of NEFA and glycerol release occurred in line C adipocytes, whereas the highest rate of NEFA re-esterification occurred in the line G adipocytes.7. Glucose had no effect on NEFA release but significantly elevated the rates of glycerol release (in most instances) and NEFA re-esterification.8. The larger number of adipocytes in line-G adipose tissue allows for more total incorporation of glucose and a greater overall release of glycerol by this tissue. Consequently, a greater reduction of glucose concentration and a larger elevation of glycerol concentration in the blood can occur; either of these could be the feed-back signal which resulted in the larger long-term food intake by the line G mice.

Adipose Tissue↗
PubMed1974

Correlation of food intake in lambs with adipocyte glucose metabolism and NEFA release.

1. Experiments were conducted with lambs to determine the correlation between food intake, rate of glucose incorporation into CO(2) and lipids, and rate of lipid mobilization by their isolated omental adipocytes.2. During the interval between weaning and slaughter average daily dry matter (ADDM) intakes of the individual lambs were significantly correlated with average daily gains; however, the ratio of ADDM intake to body wt.((3/4)) was similar in all individuals.3. The average size of adipocytes for each lamb, as determined by lipid: protein ratios, was not significantly correlated with food intake.4. Oxidation of glucose to CO(2) and the total measured glucose incorporation by the adipocytes were significantly and negatively correlated with lamb ADDM intakes at low levels of glucose (0.1 mg/ml.), whereas rates of lipogenesis from glucose were similar for all intake levels.5. Insulin-induced increases in glucose utilization were positively and significantly correlated with ADDM intakes to the extent that insulin had over twice the effect on the adipocytes from high-intake lambs as it had on those from low-intake lambs. The minimum effective dose of insulin necessary to significantly increase glucose utilization by the adipocytes was also positively and significantly correlated with the ADDM intakes of the lambs.6. Basal NEFA release rates were higher for adipocytes from low-intake lambs. Epinephrine significantly increased NEFA release rates, independent of lamb intakes.7. A larger number of adipocytes in the high-intake lambs means that they would have a greater total potential to lower blood glucose, particularly when they are under the effects of normal circulating levels of insulin. The amount of glucose removed from the glucose pool could be the feed-back signal which results in a high long-term food intake.

Adipose Tissue↗
PubMed1966

Thermal response of intravascular and rectal tissue to temperature changes and chemical conditions in the rumen of sheep.

1. Experiments were conducted with two wether sheep which were fitted with rumen cannulae and chronically implanted intravascular thermocouples. An attempt was made to study the thermal response of intravascular and rectal tissue to temperature changes and chemical conditions in the rumen.2. When ice or hot water were placed in the rumen there was an immediate fall or rise in the intravascular temperature accompanied by a similar change in rectal temperature. The intravascular temperatures returned to their precooling or preheating level of 40 degrees C within 130 min, the rectal temperatures required 6-8 hr to return to their pretreatment values.3. When 0.5 M acetic acid was infused into the rumen there was a marked rise in the intravascular temperature, over and above the diurnal rhythm but not in rectal temperatures. Infusion of mixtures of acetic plus propionic or acetic plus n-butyric acids caused an intravascular temperature rise on feeding within the range of the diurnal pattern. In fasted animals, infusions of volatile fatty acids resulted in no rise in intravascular temperature.

Acetates↗