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Biomedical subjects

B J Rolls

Publications and source records attributed to B J Rolls.

At least 91 records · Page 5Linked to original sources
PubMed1987

Effects of aging on vasopressin secretion, water excretion, and thirst in man.

Disorders of water balance are common among elderly patients. A number of factors may contribute. Osmoreceptor-mediated release of AVP is increased, but the response to volume stimuli may be reduced. The capacity of the kidney to concentrate urine is reduced by age, but this impairment cannot be correlated with coincident loss of glomerular filtration (GFR); there may rather be a failure of cAMP response to AVP in aging kidneys. Free water clearance is reduced in the old in proportion to the loss of GFR. Thirst mechanisms are also significantly impaired in healthy as well as sick old people. This combination of factors renders old people particularly liable to develop disorders of water homeostasis during episodes of acute or chronic ill health.

Aging↗
PubMed1986

Lactation in lean and obese rats: effect of cafeteria feeding and of dietary obesity on milk composition.

Changes in milk composition associated with maternal dietary obesity and cafeteria feeding were investigated. Protein, lactose and fat contents, and the fat composition, were determined for lean and obese rats given a cafeteria diet at different stages of reproduction. Feeding the cafeteria diet during lactation resulted in an increase in long-chain fatty acids and a fall in the characteristic medium-chain fatty acids. This effect was modified by obesity and the diet during pregnancy. Feeding the cafeteria diet in lactation reduced the milk protein and increased the fat. The milk of obese rats contained more energy, with more fat but less protein than that of lean rats. Increases in fat and long-chain fatty acid content, and decreases in protein and medium-chain fatty acid content of the milk were correlated with increased maternal intake of energy, total fat and long-chain fatty acids. Thus, the greatest influence on milk composition is exerted by the maternal diet during lactation. However, these effects are modified by pre-existing maternal obesity and the diet during pregnancy.

Animals↗
PubMed1985

Angiotensin II-induced thirst and vasopressin release in man.

1. The thirst and plasma vasopressin responses to single-blind controlled intravenous angiotensin II infusions (2-16 ng min-1 kg-1) were investigated in ten healthy young men. 2. Thirst and vasopressin secretion were stimulated in four out of ten subjects. These effects occurred at plasma angiotensin concentrations well above those measured under physiological conditions associated with thirst and vasopressin secretion such as water deprivation. 3. Further studies are needed to define why only certain individuals respond to intravenous angiotensin II infusions and to determine whether potentiation of angiotensin-induced thirst and vasopressin secretion by other stimuli (e.g. hypovolaemia and hypertonicity) might occur in man, in particular under pathological conditions when plasma angiotensin levels are above the physiological range.

Adult↗
PubMed1985

Experimental analyses of the effects of variety in a meal on human feeding.

Satiety can be relatively specific to particular foods, and this is an important factor in influencing human food selection and the amount of food eaten. As a food is eaten, its taste and appearance decrease in pleasantness, but the taste and appearance of other foods remain relatively unchanged. The changes in pleasantness are highly correlated with the amounts of foods that will be eaten subsequently in a meal. Therefore more is eaten during a meal consisting of a variety of foods than during a meal with just one of the foods, even if that food is the favorite. This enhancement depends at least in part on the sensory properties of foods in that change in just the flavor or shape of foods affect intake. Although changes in the color of foods do not affect intake, the taste of colors that have been eaten becomes less pleasant and this probably affects food selection. The more dissimilar foods are, the greater the enhancement of intake by variety in a meal will be. As well as affecting food intake, the change in the pleasantness of foods which occurs while eating is an important determinant of food selection in that it promotes consumption of a varied diet.

Color↗
PubMed1985

Osmotic thirst and vasopressin release in humans: a double-blind crossover study.

Thirst is a subjective sensation. Therefore to investigate further the nature, intensity, and specificity of osmotic thirst, we studied the effects of double-blind infusions of hypertonic (0.45 M) and isotonic (0.15 M) saline on subjective ratings and sensations of thirst, water intake, plasma vasopressin, and body fluids in seven healthy volunteer young men. Only the hypertonic saline significantly increased plasma sodium concentration, plasma osmolality, plasma vasopressin concentration, and visual analog ratings of thirst sensations. Both infusions expanded blood volume, which was greater with the hypertonic saline infusion. Neither solution significantly altered mean arterial blood pressure nor plasma angiotensin levels. Throughout a 60-min drinking period after the infusions, water intake was always significantly greater after the hypertonic saline than after the isotonic saline. The subjects described the thirst sensations as mainly due to a dry unpleasant tasting mouth, which was promptly relieved by drinking. Visual analog rating changes confirmed the subjective reports. Finally, the effects on thirst and vasopressin secretion were observed at plasma sodium concentration and osmolality changes that are well within the physiological range.

Adult↗
PubMed1984

Reduced thirst after water deprivation in healthy elderly men.

To determine whether responses to dehydration are altered with age, we investigated the thirst, fluid and electrolyte responses, and hormonal responses to 24 hours of water deprivation in seven healthy active elderly men (67 to 75 years old) and seven healthy young men (20 to 31 years old) who were matched for weight loss during water deprivation. After water deprivation, the older men had greater increases in plasma osmolality, sodium concentration, and vasopressin levels. However, their urinary osmolality was lower and they were less thirsty and drank less after water deprivation, so that their plasma and urine were not diluted to predeprivation levels. Regression analysis indicated increased sensitivity of vasopressin osmoreceptors in the older group, although this difference was not statistically significant. We conclude that after 24 hours of water deprivation, there is a deficit in thirst and water intake in healthy elderly men, as compared with younger men, although vasopressin osmoreceptor responsiveness is maintained or even increased. Our findings also suggest that the well-known deficit in urinary concentrating ability that occurs with age reflects renal causes and not a lack of circulating vasopressin.

Adult↗
PubMed1984

Effects of diet and obesity on body weight regulation during pregnancy and lactation in the rat.

The effects of obesity level and cafeteria feeding were studied in rats during pregnancy and lactation. The non-fetal weight gain in pregnancy was three times greater with the cafeteria diet than with chow, indicating that fat deposition is not regulated at an optimal level during pregnancy. There was a strong negative correlation between postpartum weight and weight change during lactation. Obese rats were finicky in that their weight changes in lactation were exaggerated when the diet was changed between pregnancy and lactation. Pup growth rate was proportional to maternal energy intake but in this experiment not related to maternal protein, fat or carbohydrate intake. In obese rats switched to chow, intake was inadequate for normal pup growth. Thus, the weight gains in pregnancy are not regulated at a set level, and the weight change in lactation appears to compensate for the weight gain in pregnancy.

Animals↗
PubMed1984

Body fluid changes, thirst and drinking in man during free access to water.

To investigate whether human thirst and drinking during ad lib access to water occur in response to body fluid deficits, we obtained blood samples and visual analog scale thirst ratings from five healthy, volunteer, young men at hourly intervals and when they were thirsty during a normal working day. Although there were significant increases in ratings of thirst, pleasantness of drinking water, mouth dryness and unpleasantness of the taste in the mouth when subjects were thirsty enough to drink compared with intervening intervals, there were no concomitant changes in body fluid variables (microhematocrit, plasma osmolality and plasma sodium, potassium, protein and angiotensin II concentrations). Subjects drank mainly in association with eating and were not overhydrated as indicated by constantly hypertonic urine and significant tubular reabsorption of free water over the experimental period. The results indicate that during free access to water humans become thirsty and drink before body fluid deficits develop, perhaps in response to subtle oropharyngeal cues, and so provide evidence for anticipatory thirst and drinking in man.

Adult↗
PubMed1984

Pleasantness changes and food intake in a varied four-course meal.

Satiety can be specific to a food which has been eaten. This is shown by a decrease in the pleasantness of foods eaten relative to foods which have not been eaten. The aim of the present experiment was to determine whether this specificity still remained after a meal with a very different food in each of four courses. Forty-eight human subjects were given a four-course lunch with either a different food in each course (varied meal), or the same food in each course (plain meal). Energy intake was elevated by 60% in the varied meal primarily because of the increase food consumption in the third and fourth courses. The pleasantness of the taste of foods eaten decreased rapidly, whereas the pleasantness of foods which had not been eaten remained relatively unchanged. The change in pleasantness of a food correlated well with the subsequent intake of that food. Therefore, sensory-specific satiety is still found after eating four different courses in a meal and general satiety does not result. Some selective interactions between different foods were also found. For example, when a savory food was eaten, the pleasantness of (uneaten) savory foods decreased more than that of (uneaten) sweet foods. The converse was found when sweet foods were eaten. It is concluded that sensory-specific satiety and the effect of variety in enhancing food intake can operate throughout a meal with four very different foods, and that there are interactions between foods similar in savoriness or sweetness.

Adolescent↗
PubMed1983

High-energy diets produce different effects on fatty acid synthesis in brown adipose tissue, white adipose tissue and liver in the rat.

The influence of feeding rats a high-energy diet for 7 days on fatty acid synthesis in brown adipose tissue, white adipose tissue and liver of the rat was investigated. The incorporation of 3H2O and [U-14C]glucose into fatty acid was measured in vivo. The rats fed the high-energy diets had higher rates of fatty acid synthesis in white adipose tissue than the controls fed on chow, while fatty acid synthesis in brown adipose tissue and liver was either decreased or unchanged relative to that of controls fed on chow. After an oral load of [U-14C]glucose the incorporation of radioactivity into tissue fatty acid was several-fold higher in brown adipose tissue than in white adipose tissue in rats fed on chow. In rats fed the high-energy diets, incorporation of radioactivity into fatty acid in brown adipose tissue was decreased while that into white adipose tissue was either increased (Wistar rats) or unchanged (Lister rats).

Adipose Tissue↗
PubMed1983

Sensory-specific and motivation-specific satiety for the sight and taste of food and water in man.

In normal weight humans it was shown first that the sight of food is pleasant when hungry, and that the pleasantness of the sight of a food which has been eaten to satiety decreases more than the pleasantness of the sight of foods which have not been eaten. Thus the specificity of satiety extends to the visual modality, and this may be an important factor in influencing which foods are selected for ingestion. Second, it was shown that the pleasantness of both the sight and taste of food are modulated in a motivation-specific manner, in that in hungry and thirsty humans the pleasantness of the sight and taste of food but not water is decreased by eating to satiety, and the pleasantness of the sight and taste of water but not food is decreased by drinking water to satiety. Third, it was shown that sensory-specific decreases in the pleasantness of the taste of a particular food produced by its ingestion are associated with only minor changes in the intensity of its taste, which do not account for the changes in pleasantness as shown by an analysis of covariance and by the relation between pleasantness and intensity, so that it is unlikely that sensory adaptation is an important part of the mechanism of sensory-specific satiety.

Adult↗
PubMed1983

Variety in the diet enhances intake in a meal and contributes to the development of obesity in the rat.

Male and female rats were given three palatable, high energy foods either simultaneously or in succession during three 40 min courses. Both simultaneous and successive variety enhanced energy intake compared to the intake of single palatable foods, which was itself enhanced compared to the intake of chow. Rats deprived of food for 24 hr showed a compensatory increase in chow intake (84%) but only a 20% increase in intake in the single palatable food conditions, and no increase in the variety conditions. Male and female rats showed a similar response to variety and deprivation. The effect of variety on body weight was also examined in rats offered either chow, or chow and one palatable food, or chow and three palatable foods in succession (changed every 12 hr) or simultaneously, for seven weeks. All rats offered the palatable foods were hyperphagic compared to chow-fed controls. Rats given the simultaneous but not the successive variety diet were more hyperphagic than the other palatable food groups and showed significantly greater body weight and fat gains. The availability of a variety of foods is an important factor in the amount eaten in the meal and in the etiology of obesity.

Adipose Tissue↗
PubMed1983

The effects of supplementation of the diet with highly palatable foods upon energy balance in the rat.

Full energy balance studies have been performed for 9 weeks on four groups of four adult female rats housed in a continuously running indirect calorimeter; for four weeks two of the groups received highly palatable foods in addition to a standard pelleted diet. A further sixteen groups, of which eight received the palatable foods, provided additional carcass composition data. All practicable precautions were taken to measure energy exchange accurately. Comparison of 'start-to-finish' apparent energy balance with carcass composition changes showed a systematic error of approx. +3% of energy throughput. This was most probably caused by losses of energy in food and excreta, which led to over-estimation of energy intake. Variations among individual balance periods added a standard error of approx. +/- 1%: the source of error here was probably imperfect matching of animals analysed at intermediate stages. The rats offered the palatable foods increased their metabolizable energy (m.e.) intake by 106 kJ/day, 51% of the control groups' intake, in the first week of supplementation. Over the whole 4 weeks of supplementation the increase was 64 kJ/day, or 31%. Withdrawal of the palatable foods led to an immediate fall in intake to about two-thirds of control level, and a return to control level over the next 2-3 weeks. Energy expenditure rose more slowly than intake, reaching a fairly steady level ca. 5 days after introduction of the palatable foods. Expenditure was then ca. 22 kJ/day above control level; an increase of 12% above control expenditure or, allowing for systematic and random errors, 33-37% of the additional m.e. intake. Expenditure returned to control level over the 2 weeks after ceasing supplementation. The experimental groups gained weight at a declining rate throughout the period of supplementation. The gain in live body weight at the end was ca. 32 g, but this comprised a carcass weight gain of 37 g and a loss of 5 g gastrointestinal tract contents. The carcass weight gain comprised 27 g fat (i.e. ca. 70% of the weight gained), 9 g lean tissue and 1 g additional water. The gain of carcass energy was 1100 kJ. There was a small increase in body length, an increase in liver weight, and an increase in the weight of the interscapular brown adipose tissue pad. Regression analysis showed that the increase in the weight of the interscapular brown adipose tissue pad reflected the increase in total body fat.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Obese rats develop hyperketonaemia and a fatty liver during lactation.

Lactating rats made obese before conception by feeding high energy foods show a decreased rate of lipogenesis in vivo in mammary gland, but not in liver. Obese lactating rats have an increased hepatic fat content, together with moderate increase in blood ketone bodies. It is suggested that these changes are due to mobilization during lactation of the expanded adipose tissue lipid pool in the obese rats which results in overloading the liver with fatty acids. The concomitant increase in ketone body concentrations may inhibit glucose utilization and hence lipogenesis in the lactating mammary gland of obese rats.

Animals↗
PubMed1982

Effects of environmental temperature on dietary obesity and growth in rats.

We have investigated how differences in environmental temperature interact with diet-content and palatability to affect body weight and energy intake. Adult male hooded Lister rats kept at 18 degrees C or 25 degrees C became obese after over-consumption of palatable, high energy foods. The difference in body weight between the obese rats kept at 18 degrees C and their chow-fed control group was in part attributable to reductions in the growth of the controls kept at 18 degrees C. The obese rats at 18 degrees C had greater body weight gains relative to chow-fed controls than equivalent groups at 25 degrees C. All groups at 18 degrees C had greater energy intakes than equivalent groups at 25 degrees C. Withdrawal of high energy foods led to greater weight loss in rats which had been eating a diet which was varied every day than in rats which had been eating three constantly available high energy foods. Weight losses after diet withdrawal were also greater in obese groups kept at 18 degrees C than in those kept at 25 degrees C. Carcass fat determinations demonstrated that the varied diet-withdrawn rats kept at 18 degrees C did not have persistently elevated body fat stores, but the other diet-withdrawn groups were persistently obese. Therefore lower environmental temperature, and enhanced diet-palatability interact additively to increase energy intakes during cafeteria feeding, and to increase weight losses after withdrawal of palatable foods.

Animals↗
PubMed1982

Pregnancy and lactation in the obese rat: effects on maternal and pup weights.

Lister hooded female rats, fed palatable high energy foods and chow, weighed significantly more than chow-fed control rats before mating. A smaller proportion of the obese rats became pregnant, and they lost more litters in lactation. When litters survived (7 +/- 1 pups), maternal weight changes differed between groups during lactation. The controls gained 6.2 +/- 3.2 g. whereas the obese rats lost variable amounts of weight despite the continued availability of the palatable diet. The rats that were heaviest at mating and parturition and which showed the largest non-fetal weight gains in pregnancy (i.e., the "large weight loss group") lost 60.6 +/- 4.8 g, while less obese rats which showed similar non-fetal gains to controls (i.e., the "small weight loss group") lost 24.6 3.2 g. Thus the weights of all groups converged and were similar after three weeks of lactation, but diverged again after weaning. During lactation the total energy intakes and amounts of protein consumed by the obese rats were significantly below those of controls, and total fat intake was significantly elevated. Although litter size and pup weights did not differ significantly at birth, pups of obese mothers weighed significantly less than those of controls at weaning. Maternal obesity in lactation appears to influence both body weight regulation and lactational performance.

Animals↗