Growth of the pig: changes in red cell and plasma volumes.

In the pig, plasma volume increased from 58.0 +/- 2.53 ml/kg on day 1 to 66.7 +/- 3.35 (P less than 0.05) on day 2, and decreased between days 7 and 9 to 56.4 +/- 1.16 (P less than 0.02). The next significant change in volume occurred at weaning: from 53.1 +/- 1.24 ml/kg at week 4 to 44.16 +/- 2.2 at week 5. It then increased to 56.1 +/- 1.41 ml/kg by week 7 and decreased to 48.5 +/- 1.44 by week 9; then between weeks 10 and 11 it increased to 59.33 +/- 3.01 (P less than 0.005). Red cell volume on day 1 was 32.3 +/- 1.25 ml/kg and decreased to 20.2 +/- 1.37 (P less than 0.01) on day 2. The only other change of significance in red cell volume over the 12-week growth period was a small increasan 0.05) at week 6. The mean for BVRcells was 0.88 +/- 0.01 for the growth period. The pattern of changes in plasma and red cell volumes differed from those for the beagle.     

Preoptic recess lesions, body fluid compartments, and the renin-aldosterone system

The effects of electrolytic ablation of the periventricular tissue surrounding the anteroventral third ventricle (AV3V) of the rat brain on body fluid distribution and the renin-aldosterone system were determined. Rats underwent either ablation of AV3V periventricular tissue or control surgeries. After recovery, animals were implanted with femoral arterial and jugular venous catheters, and sodium space and plasma volume were measured by calculating the dilution of intravenous injections of 22Na- and 125I-labeled serum albumin, respectively. Total body water was determined in separate groups of rats by desiccation. Other animals with AV3V lesions and control rats were used to measure urinary sodium excretion and plasma renin (Prenin) and aldosterone (Paldo) concentrations while volume replete and after volume depletion. Animals with AV3V lesions had expanded extracellular fluid volume and decreased plasma volume, but total body water was comparable with control-operated rats. Volume-replete and volume-depleted rats with AV3V lesions had significantly higher Prenin than control animals in similar volume states. Although Paldo was not different between groups in the volume-replete state, it was significantly greater in rats with AV3V lesions than in control animals after volume depletion. These data demonstrate that AV3V periventricular ablation results in chronic alterations in the normal body fluid distribution but does not diminish the rats' ability to increase Prenin and Paldo or decrease sodium excretion during volume depletion.     

Growth of the pig: patterns of changes in electrolytes, water, and protein.

In 246 pigs studied from day of birth through week 12, mean plasma concentration of Na was 144.2; K, 3.89; and Cl, 103 mEq/1. Fifty-five pigs were analyzed for total body water (TBW), Na, K, Cl, protein, and fat. TBW was 83% fat-free wet weight (FFWW) at birth and declined, but not significantly, over the 12 weeks. Water content of tissues differed from each other as well as in the rates at which their water content changed. Concentration of electrolytes Na, K, Cl (mEg/100 g FFWW) decreased significantly in whole pig, viscera, brain, and skin; while Na increased and K and Cl decreased significantly in skeletal muscle. Of the tissues, skeletal muscle contributed 32% (fat-free tissue weight as per cent of total FFWW) at birth and 44% at week 12; and viscera, 15% at birth and 21% at week 12. The contribution of skeleton decreased over the same period from 22 to 15%, skin from 14 to 6%, and brain from 2 to 0.5%. The contribution of total water by the various organs changes in the same direction as the contribution to total FFWW. Na, K, Cl, and protein as a per cent of total in skin also show the same directional change. In skeletal muscle there was a decrease in conribution to total Na and Cl, but an increase to total K and protein. In the skeleton, except for protein, there is an increase in contribution of total Na, K, and Cl. There was a correlation of 0.99 and 0.94 between the sum of total Na and K in milliequivalents and TBW in millimeters for the whole pig and skeletal muscle respectively.     

Dynamic body weight and body composition changes in response to subordination stress

Social stress is prevalent in many facets of modern society. Epidemiological data suggest that stress is linked to the development of overweight, obesity and metabolic disease. Although there are strong associations between the incidence of obesity with stress and elevated levels of hormones such as cortisol, there are limited animal models to allow investigation of the etiology of increased adiposity resulting from exposure to stress. Perhaps more importantly, an animal model that mirrors the consequences of stress in humans will provide a vehicle to develop rational clinical therapy to treat or prevent adverse outcomes from exposure to chronic social stress. In the visible burrow system (VBS) model of chronic social stress mixed gender colonies are housed for 2 week periods during which male rats of the colony quickly develop a dominance hierarchy. We found that social stress has significant effects on body weight and body composition such that subordinate rats progressively develop characteristics of obesity that occurs, in part, through neuroendocrine alterations and changes in food intake amount. Although subordinate rats are hyperphagic following social stress they do not increase their intake of sucrose solution as control and dominants do suggesting that they are anhedonic. Consumption of a high fat diet does not appear to affect development of a social hierarchy and appears to enhance the effect that chronic stress has on body composition. The visible burrow system (VBS) model of social stress may be a potential laboratory model for studying stress-associated metabolic disease, including the metabolic syndrome.     

Obstructive sleep apnoea in adults: body postures and weight changes interactions

The aim of this work was to study the relationship between changes of body posture dominance and changes of body weight overtime in adults with obstructive sleep apnoea. The participants were 112 non-treated adults with obstructive sleep apnoea who underwent two polysomnographic evaluations at our Sleep Disorders Unit during an average of 6.2years interval. Positional patients - having most of their breathing abnormalities in the supine posture and who became non-positional patients - had a significant gain in weight and a significant increase in apnoea-hypopnoea index, mainly in lateral apnoea-hypopnoea index. On the contrary, non-positional patients who became positional patients had a significant decrease in weight (but less than the increase in weight of positional patients who became non-positional patients) and showed a significant improvement in apnoea-hypopnoea index, again mainly in lateral apnoea-hypopnoea index. These non-positional patients who became positional patients initially had a less severe disease, as judged by apnoea-hypopnoea index, lateral apnoea-hypopnoea index and minimum SaO(2) during non-rapid eye movement sleep, and were less obese than non-positional patients who remained non-positional patients. The later were the patients who showed initially the worst disease and were more obese than the rest of the patients, and their condition did not change significantly over time. Non-positional patients who converted to positional patients showed a decrease in body weight and improvement of obstructive sleep apnoea, while positional patients who converted to non-positional patients showed an increase in body weight and worsening of obstructive sleep apnoea. It appears that weight changes have a modulatory effect on positional dominance, and lateral apnoea-hypopnoea index appears to be a sensitive parameter of these changes.     

Lipectomy, body weight, and body weight set point in rats.

Adult, Wistar male rats were lipectomized or sham lipectomized. The food-hoarding behavior was measured repeatedly and plotted against the animals' body weights. Body weight set point was estimated as the intercept of regression line of hoarding with the X axis. Body fat content was measured with a TOBEC body composition analyzer. Body weight set point, fat content, and girth were obtained initially, after surgery, and after recovery. The hoarding threshold was lowered for 2 weeks after surgery, from 561 +/- 20 to 512 +/- 19 g (lipectomized), and from 582 +/- 15 to 558 +/- 14 g (sham lipectomized). After a 4-week recovery, all rats reached their prelipectomy body weight set point and regained their initial body fat. Five weeks after surgery, no significant difference was found between the body weight set points of lipectomized and sham-lipectomized rats. This indicates that the body weight set point was not mainly modulated by fat depots. The transient lowering of the set point is thought to be due to surgical stress.     

Assessment of fluid shifts of body compartments using both bioimpedance analysis and blood volume monitoring

Fluid shifts are commonplace in chronic hemodialysis patients during the intra- and interdialytic periods. In this study, we evaluated fluid shifts of body compartments using both bioimpedance spectroscopy and blood volume monitoring from the start to the end of hemodialysis. 24 stable hemodialysis patients were included on the study. Relative change of blood volume was progressively reduced from the start to the end of hemodialysis (1 hr, -7.22+/-3.23%; 2 hr, -9.78+/-4.69%; 3 hr, -12.88+/-5.65%; 4 hr, -15.41+/-6.54%, respectively). Mean % reduction of intracellular fluid was not significantly different to that of extracellular fluid at the end of hemodialysis (delta ICF, -6.58+/-5.34% vs. delta ECF, -7.07+/-5.12%). Mean % fluid reduction of arms, legs and trunk was -11.98+/-6.76%, -6.43+/-4.37% and -7.47+/-4.56%, respectively at the end of hemodialysis. There were 3 characteristic patterns in blood-volume change. Similar amounts of fluid were removed from the extracellular and intracellular compartments during hemodialysis, with the arms showing the greatest loss in terms of body segments. The pattern of blood volume change measured by blood volume monitoring may be useful for more accurate determination of dry-weight and for correcting volume status in hemodialysis patients.     

Alcohol drinking, food and fluid intakes and body weight gain in rats

Body weight (BW) and food and fluid intakes were compared in rats receiving a 10% or a 20% alcohol solution as the only source of fluid and in water-drinking rats. Intake of the 20% alcohol solution caused a marked reduction in BW gain without affecting energy intake. Meal size (alcohol plus powder) and meal number over the 24-hour circadian cycle were not modified. Examination of simultaneous recordings of eating and drinking revealed that preprandial drinking increased significantly in rats drinking alcohol solutions. The reduced BW gain may be due to increased energy expenditure through increased alcohol metabolism and/or postprandial thermogenesis. Thus, in rats drinking alcohol solutions up to 20%, energy input is unchanged while energy output is increased.     

Taste preferences, body weight gain, food and fluid intake in singly or group-housed rats.

Two behavioral experiments were performed to determine if the housing conditions modify taste preferences, body weight gain, food and fluid intake, and alimentary diurnal pattern in adult male rats. In Experiment 1, a two-bottle 24-h preference test (salt, sweet, sour, bitter solutions versus deionized water) was performed in singly, dually or multiply housed rats. In Experiment 2, the same sapid solutions as Experiment 1 and water were contemporaneously offered to singly, dually, or multiply housed rats. Crowded rats drank more water, sweet solution, and total fluid, but less salt solution than singly or dually housed rats during dark and whole-day periods. All rats preferred sour solution, but not bitter solution, to water. In both experiments, crowded rats gained less body weight and ate less food than dually or isolated rats. These results suggest that the housing conditions influence taste preferences, food and fluid intake, body weight gain, but not alimentary diurnal pattern in rats. An important implication of these results is that in experiments in which appetite and taste are dependent variables, all rats should be housed under the same social and environmental conditions.     

Personality, body image, and eating pattern changes in overweight persons after weight loss.

A group of overweight persons who achieved a substantial weight loss over a 6-month period were compared with a group of overweight persons who showed an unsubstantial weight change and a normal weight control group. All groups were evaluated before the weight program began and at a 6-month follow-up. The substantial weight loss group showed a number of significant changes after weight reduction. Body image rating shifted in the direction of evaluating onself as less heavy, eating was rated as less good and more heavy, and a greater feeling of self-control was indicated. Over time, the change group learned to limit the number of emotional and environmental cues that were discriminative stimuli for eating behavior. There also were more frequent reports of eating in response to cues of hunger after substantial weight loss.     

Cardiovascular,hormonal and body fluid changes during prolonged exercise

Summary During prolonged heavy exercise a gradual upward drift in heart rate (HR) is seen after the first 10 min of exercise. This secondary rise might be caused by a reduction in stroke volume due to reduced filling of the heart, which is dependent upon both hemodynamic pressure and blood volume. Swimming and bicycling differ with respect to hydrostatic pressure and to water loss, due to sweating. Five subjects were studied during 90 min of bicycle exercise, and swimming the leg kick of free style. The horizontal position during swimming resulted in a larger cardiac output and stroke volume. After the initial rise in heart rate the secondary rise followed parallel courses in the two situations. The rises were positively related to the measured increments in plasma catecholamine concentrations, which continued to increase as exercise progresssed. The secondary rise in HR could not be explained by changes in plasma volume or in water balance, nor by changes in plasma [K]. The plasma volume decreased 5–6% (225–250 ml) within the first 5 to 10 min of exercise both in bicycling and swimming, but thereafter remained virtually unchanged. The sweat loss during bicycling was four times greater than during swimming; but during swimming the hydrostatic conditions induced a diuresis, so that the total water loss was only 25% less than during bicycling.     

The perinatal rat: body weight, hematocrit and regional changes in heart weight and lactate dehydrogenase isozyme composition and activity

Body weight (BW), hematocrit (Hct), heart weight (HW) and cardiac lactate dehydrogenase (LDH) activity and isozyme pattern were studied in the perinatal rat. BW increased linearly, from 5 days before birth till 10 days after birth, while Hct increased from 30 to 34% within 1 day of birth. HW increased in step with BW. However, the relative contribution to total HW of right ventricle (RV), interventricular septum (S) and atria declined relative to the left ventricle free wall (LVW) beginning 2 to 3 days before birth. RV/LVW declined steadily throughout the study period. LDH specific activity in LVW, RV, S and atria increased greatly prior to birth and less so afterwards, with atria showing the lowest values throughout the study. Total LDH activity in each portion of the heart paralleled the respective regional weight changes. LDH isozyme composition (percent M subunit) declined at the time of birth in LVW, RV and S from 63 to 43%; change in atrial M subunit was smaller. The change in LDH isozyme composition could be accounted for in LVW, RV and S by increasing H subunit activity alone. In atria, both M and H subunit activity increased.     

Comparison of methods to evaluate changes in relative body mass index in pediatric weight control.

Our objective was to compare three BMI-based adiposity measures to assess change in pediatric weight control: LMS z-BMI, BMI sympercent, and percent overBMI. Comparison 1 presents changes of +1.0, -1.0, and -2.0 BMI units for 36 hypothetical children (7-, 11-, and 15-year-old children with BMI values from 19-39 kg/m(2)). Comparison 2 presents effect sizes over 12 months and the relationship between baseline and change for 140 8-12-year-old children with BMI values ranging from 21 to 37 kg/m(2). Comparison 1 showed smaller changes in z-BMI than BMI sympercent or percent overBMI for equal changes in BMI when initial BMI values are greater. Comparison 2 showed similar effect sizes for the three measures, since there is a reduction in both standard deviation and magnitude of LMS z-BMI values as the BMI values increase. The three measures perform differently when considering the relationship of initial value to change. Initial percent overBMI shows a negative relationship with change, as heavier children show larger changes, LMS z-BMI shows a positive relationship, as children with lower baseline values show larger changes, and BMI sympercent changes were inconsistently related to baseline BMI sympercent values. Although all three measures result in similar effect sizes when evaluating treatment over time, we conclude that LMS z-BMI is less appropriate for comparing individuals and percent overBMI is the only measure that shows heavier children have greater change.