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E T Li

Publications and source records attributed to E T Li.

27 records · Page 2Linked to original sources
PubMed1986

Effect of zinc status on the binding of prostaglandins to ovarian membranes and intact platelets of pregnant rats.

The effects of zinc deficiency on the binding of PGF2 alpha to ovarian membranes and of PGE1 to intact platelets prepared from pregnant rats were examined. On d 21 of gestation, rats fed low zinc (less than 1 ppm) diets throughout pregnancy had prostaglandin receptor characteristics significantly different from those of rats fed control diets (100 ppm zinc). The number of binding sites for PGF2 alpha was higher in the ovarian membranes prepared from deficient rats than in those from controls, whereas the affinity was not affected. In washed platelets from zinc-deficient rats there were fewer PGE1 binding sites but greater affinity for PGE1 than in platelets from controls. These results demonstrate that zinc status affects prostaglandin binding to membranes. The effects are not uniform with regard to different tissues and prostaglandin receptors but suggest an effect of zinc status on plasma membranes.

Alprostadil↗
PubMed1984

5-Hydroxytryptamine : a modulator of food composition but not quantity?

After a meal of protein, in contrast to a meal of carbohydrate (CHO) at 1915 hr, rats allowed to choose from high carbohydrate and high protein diets during 2000-2100 hr prefer CHO (1). Thus the hypothesis that this regulation of macronutrient selection involves brain 5-hydroxytryptamine (5-HT) metabolism was tested. Compared to three baseline days during which rats (250- 300g ) consumed 1 g CHO, rats fed tryptophan (TRP, 5-HT precursor; 15 mg in 1 g CHO) selected meals higher in protein concentration (35.4% vs 46.6%, F (1,12) = 20.05, p less than 0.001) from 10% and 60% casein diets during 2000-2100 hr. Associated with the higher protein selection was an elevated brain 5-HT turnover in rats killed 30 minutes after consuming CHO + TRP. Pretreating rats with p-chlorophenylalanine, an inhibitor of TRP hydroxylase, blocked this effect of TRP (36.3% vs 37.0%). Fenfluramine (1 and 2 mg/kg i.p. at 1945 hr), which transiently enhances neuronal 5-HT release, increased the rat's relative preference for protein from 28.8% to 37.5% (2 mg/kg, t = 3.21, p less than 0.025) during 2000-2100 hr. These rats, also exhibited a selective preference for CHO between 3-12 hrs post injection which paralleled the known subsequent depletion of 5-HT by fenfluramine. We conclude that the relative proportion of protein and carbohydrate selected in a meal is controlled, at least in part, by prior food effects on brain 5-HT metabolism.

Animals↗
PubMed1984

Brain mechanisms and the quantitative and qualitative aspects of food intake.

The brain receives a large number of signals from the ingestion of food. They provide the brain with information on both the adequacy of energy ingested and the macronutrient composition of the food. From this information brain feeding control systems are able to respond and direct the animal to make appropriate food choices so that both the quantitative (energy) needs as well as the qualitative (nutrient) needs are met. An understanding of brain mechanisms regulating feeding will only emerge if their dual purposes are recognized.

Amino Acids↗
PubMed1984

A role for vagus nerve in regulation of protein and carbohydrate intake.

The effects of vagotomy on long-term protein and carbohydrate selection or on short-term food selection following cholecystokinin octapeptide (CCK-8) injections, protein, or carbohydrate premeals and on brain 5-hydroxytryptamine (5HT) and catecholamine metabolism were examined in adult rats. Vagotomy was followed by a reduction in daily protein intake that by 3 wk had fallen to 50% of preoperative levels. A corresponding increase in carbohydrate intake occurred so that total food intake was maintained at approximately 93% of that consumed by the sham-operated controls. These changes in day-to-day macronutrient selection from a choice of high- and low-protein diets were associated with a vagotomy-induced decreased turnover of 5HT in the hypothalamus. In meal consumption studies vagotomy prevented a further reduction in meal size by CCK-8 but did not block decreased consumption of total food or of protein preference of the rats in meals taken subsequent to a protein meal. It was concluded that the vagus nerve plays a role in regulating long-term protein and carbohydrate preferences but not in the relationships among meal-to-meal composition and intake.

Animals↗
PubMed1982

Meal composition influences subsequent food selection in the young rat.

Food selection one-half hour after the ingestion (2 g) of either a protein containing or a protein-free (carbohydrate) diet was studied in young rats. Following a 12 hr fast the rats were allowed 15 minutes to consume the meal (premeal). Thirty minutes later, they had access to two isocaloric diets that differed only in protein and carbohydrate content. During the first hour of ad lib feeding, protein intake and protein concentration selected were lower in the 45% casein prefed group compared to the carbohydrate group. A further reduction in protein intake and protein concentration occurred when the protein content of the premeal was increased to 70% from 45% casein. Rats prefed with the 70% casein diet significantly reduced their daily total food intake (12 hr) compared to either the 45% casein or carbohydrate prefed group. It is concluded that both quantity and composition of food selected is influenced by the composition of the preceding meal.

Aging↗
PubMed1982

Self-selected meal composition, circadian rhythms and meal responses in plasma and brain tryptophan and 5-hydroxytryptamine in rats.

Relationship among food composition, plasma and brain tryptophan and 5-hydroxytryptamine (5-HT) were studied by measuring both carcadian feeding and meal responses in self-selecting rats. Under ad libitum feeding conditions in which young rats were given a choice between two isocaloric diets (0 and 60% casein) and groups were killed at 3-hour intervals throughout the day, several circadian rhythms become apparent. Protein and carbohydrate energy, the plasma tryptophan:neutral amino acid ratio (TRP:NAA) and brain TRP, but not 5-HT concentrations showed statistically significant circadian variations. During the dark hours of plasma TRP:NAA ratio and brain TRP concentrations were inversely associated with the protein concentration of meals previously selected. In meal response studies, rats were similarly given a choice of diets, but were killed 20 minutes after their selected meals. Plasma TRP:NAA ratios, brain TRP and 5-hydroxyindole levels were inversely correlated with the protein concentration of the meals selected. Absolute quantities of protein, but not carbohydrate, fat or total energy, were inversely related to the plasma TRP:NAA ratio and brain TRP concentration. It is concluded that the circadian changes in the plasma TRP:NAA ratio and in brain TRP amd 5-hydroxyindole concentrations are under the continual influences of food choices made during spontaneous feeding activity.

Amino Acids↗
PubMed1982

Dietary minerals modify the food intake suppressing effects of high casein diets fed to rats.

Food intake, growth, and urinary urea and ammonia excretion were studied in young rats undergoing adaptation to high protein diets (70% casein) containing varying amounts of potassium, sodium and chloride. Two commercial mineral mixtures were used. The Bernhart-Tomarelli (BT) mineral mixture is low in K, Na and Cl compared to the TD (modified Williams-Briggs) mineral mixture. Rats consumed significantly less food and had poor growth when fed 70% casein diets containing the BT mineral mixture. Food intake and feed efficiency improved significantly when the BT diets were supplemented with KCl and NaCl, Na acetate or K acetate but not 3-chloropropionate. Urinary urea and ammonia excretion were directly proportional to food (protein) intake. However, body weight gain during the last 3 days of the 9-day study (experiment 3) was negatively correlated with urinary ammonia nitrogen (milligrams per gram food eaten) but not with urinary urea nitrogen. It is concluded that dietary K and/or Na content affects food consumption in rats fed high casein diets. Alterations in renal capacity for handling ammonia may be responsible for the food intake enhancing effect of K or Na in rats fed a high casein diet.

Ammonia↗