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Biomedical subjects

D Sadler

Publications and source records attributed to D Sadler.

28 records · Page 2Linked to original sources
PubMed1986

The effects of age, dietary restriction, exercise and maternity on the abundance and volume of adipocytes in twelve adipose depots of adult guinea-pigs.

1. The mean adipocyte volume and cellularity of adipose tissue in twelve anatomically defined depots were measured in 190 virgin and reproductive guinea-pigs aged 6 months to 2 years, maintained on five different regimens of diet and exercise. 2. The total adipocyte complement was constant up to the age of about 10 months and increased by 65-70% during the 2nd year of life. At constant percentage body-weight as fat, age-related accumulation of adipocytes was accompanied by reduction in average adipocyte volume. A period of high percentage body-weight as fat was not a necessary antecedent to age-related accumulation of adipocytes, and the effect was not observed in specimens that exercised regularly. 3. In guinea-pigs over 13 months old, changes in adipose tissue cellularity made a major contribution to total fatness. The mean volume of samples of adipocytes was a satisfactory indicator of fatness only in younger specimens in which adipose tissue cellularity was not changing. 4. The lean body mass and the total adipocyte complement were lower in guinea-pigs on the sedentary, restricted-diet regimen, whether the regimen began at the age of 19 weeks or 31 weeks, but the depots studied were not equally affected. Both moderate and strenuous exercise on an ad lib. diet caused a reduction in the percentage body-weight as fat in males but not in females. The total adipocyte complement and lean body mass were unchanged, although the males became almost as thin following exercise as those on the restricted-diet regimen. 5. Among guinea-pigs under 400 d old, there were no significant differences between males and virgin females in the site-specific volume of adipocytes relative to the size of those in other depots of the same specimen; there was only one significant difference in this index between the older and the younger specimens. The diet and exercise regimens modified the site-specific adipocyte volume relative to those in other depots; adipocytes under the trapezius muscle of the neck (UMN), at the interscapular depot (HUMP) and those in the depots anterior to the forelimb became relatively smaller following exercise, while those in the popliteal fat mass were relatively larger. Adipocytes in the UMN and HUMP also became more numerous relative to those in the other depots following both moderate and strenuous exercise. Those in the groin site, the intra-abdominal depots and the intermuscular depots became relatively smaller following dietary restriction without exercise.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue↗
PubMed1985

Maternal behavior in rats and the effects of neonatal progestins given to the pups.

This paper reports changes in maternal behavior of rats following progestin treatment of the neonates. There have been recent reports that hormonal treatment of pups can alter maternal behavior, particularly licking of pups, and that such effects might have implications for the later development of those pups. Accordingly, the major objective of the experiments described was to test the hypothesis that the effects of neonatal progestins on later behavioral development that we have previously described (Birke & Sadler, 1983; 1984) might in part be mediated by changes in maternal behavior. This was done by investigating the behavior of dams, including pup-directed behavior, following the hormone treatments that we have used previously. In the first experiment, medroxyprogesterone acetate (MPA), given via maternal milk, was found to increase rates of pup licking by dams. In the second experiment, anogenital licking was increased to litters containing pups that had received either MPA or progesterone by direct injection. No significant changes in licking following pup treatment with the antiserum to progesterone were observed, however. The results are discussed in relation to our previous work on progestin effects on later behavior, and in relation to the suggestion that hormonal effects on sexually dimorphic behaviors might, at least partly, be mediated through interactions with the mother during the neonatal period.

Animals↗
PubMed1984

Modification of juvenile play and other social behaviour in the rat by neonatal progestins: further studies.

The effects of altering neonatal levels of progestins on the later development of social play behaviour was studied. Progestin levels were raised in experiment one by administering injections of either progesterone or medroxyprogesterone acetate. This indicated that exposure to either hormone led to reduced levels of social play in juvenile rats of both sexes, confirming earlier reports of lowered levels of play following medroxyprogesterone obtained via maternal milk. In Experiment 2, endogenous progestin levels were lowered by administration of the antiserum to progesterone. The prediction that this should result in raised levels of juvenile play was supported for males, but not for females. Females in Experiment 2 by contrast showed a decrease in play. Possible reasons for this sex difference in response to progesterone antiserum are discussed.

Animals↗
PubMed1984

The effects of food restriction and exercise on site-specific differences in adipocyte volume and adipose tissue cellularity in the guinea-pig. 1. Superficial and intra-abdominal sites.

The volume and number of adipocytes were measured in fourteen anatomical sites of adult guinea-pigs kept in small cages and fed ad lib., kept in small cages and on restricted diet or fed ad lib. and exercised. In the sedentary ad lib.-fed animals, there was no significant correlation between percentage body-weight as adipose tissue, as determined by direct dissection, and mean adipocyte volume based on samples from many different sites. The correlation was significant, though not high, for sedentary, restricted-diet animals and for exercised specimens. The correlations between the volume of adipocytes from left-right pairs of sites, and from sites around the same limb, were highly significant under all conditions studied. The correlation between the volume of adipocytes from sites other than left-right pairs of sites was weaker and in some cases statistically insignificant in sedentary ad lib.-fed guinea-pigs. The volume of adipocytes from sites in the groin region, the mesenteries and medial to the trapezius muscle failed to correlate in many cases with the volume of adipocytes from other sites sampled. The number of adipocytes at each site was similar in the exercised and sedentary ad lib.-fed animals. The restricted-diet, sedentary group had fewer adipocytes at all sites studied except the omental and mesenteric fat mass and the groin sites. It is suggested that moderate regular exercise or fasting gives rise to closer coordination between adipocytes at different sites because central factors regulating adipocyte volume become more prominent than local factors.

Abdomen↗
PubMed1984

The effects of food restriction and exercise on site-specific differences in adipocyte volume and adipose tissue cellularity in the guinea-pig. 2. Intermuscular sites.

Two intermuscular adipose depots, the popliteal mass (POP) and the fat under the gluteus superficialis muscle ( GLS ) were studied in guinea-pigs maintained under three different regimes of diet and exercise. Eleven different sites in POP and four sites in GLS were defined using associated muscle and fascia as 'landmarks'. Samples of twenty to twenty-five adipocytes from each site were removed and their mean volume measured; a consistent pattern of distribution of larger and smaller adipocytes within POP and GLS was found in all animals. The correlation between the volume of adipocytes from sites between the same pairs of muscles was substantially greater than the correlation between the volume of adipocytes from comparable sites between different muscles, whether the sites were within the same fat mass (POP) or in different fat masses (POP and GLS ). The volume of adipocytes from the edge of the fat mass correlated more closely with those from the edge of the same or a synergistic muscle than with the volume of cells from the centre sites or edge sites from an interface with another muscle. These effects were most pronounced in exercised animals and weak or insignificant in sedentary ad lib.-fed animals. The volume of adipocytes from edge sites correlated with the gross weight of the adjacent muscles in exercised animals only. It is concluded that muscle activity has a local effect on the volume of adjacent adipocytes. It is suggested that the mechanism involved is mechanical rather than biochemical.

Adipose Tissue↗
PubMed1984

Effects of neonatal medroxyprogesterone acetate on postnatal sexual differentiation of female rats.

Medroxyprogesterone acetate (MPA), 5 micrograms/g body wt, was given to lactating female rats 1 day after parturition. Group 1 females suckled 10-12 young, with equal numbers of males and females, while Group 2 females each suckled 10 female young. The young were weaned at 21 days of age. Exposure to MPA advanced the day of vaginal opening by 1 day, and increased anogenital distance in Group 2 young. At autopsy between 80 and 100 days of age, the clitoris of Group 2 females was significantly greater than in controls, and ovarian and adrenal weights were reduced.

Adrenal Glands↗
PubMed1983

Progestin-induced changes in play behaviour of the prepubertal rat.

The effects of neonatal exposure to medroxyprogesterone acetate on later play behaviour was studied. The experiments reported here indicate that animals of both sexes exposed to the hormone neonatally show lower levels of rough-and-tumble play in the prepubertal period. The effect is primarily one on play initiation: the organisation of play behaviour once initiated is not significantly affected, and the effect on play does not seem to be secondary to effects on some other behaviour. Several hypotheses are considered that might account for these findings.

Animals↗
PubMed1983

The rate of scent marking by male rats and consequent olfactory preferences of female rats.

An experiment is reported designed to test the hypothesis that female rats might discriminate between males that differed in the quantity of odor deposited by scent marking. Male odor donors were selected by prior screening for high or low rates of scent marking in an open arena. Females were then tested to determine whether they showed any preference for males that marked at a high rate. It was found that female rats did discriminate, but that they preferred to remain near males selected for low rates of scent marking.

Animals↗