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Biomedical subjects

I Pollard

Publications and source records attributed to I Pollard.

At least 37 records · Page 2Linked to original sources
PubMed1986

Prenatal stress effects over two generations in rats.

Persistent effects of stress were found in second generation rats bred from females whose own mothers had been stressed during pregnancy. The second generation rats grew more slowly, with a plateau in the growth being reached at the same age as in the controls. This resulted in adult animals of both sexes being permanently smaller than their control counterparts. When these offspring were subjected to short-term stress (one session) in adulthood, the response was not significantly different to that for the controls, indicating an intact emergency response. The male offspring from the stressed group, however, had a significantly (P less than 0.01) higher plasma progesterone concentration, and a significantly (P less than 0.01) lower testicular enzymic 3 beta-hydroxysteroid dehydrogenase activity at rest, when compared with the control offspring. The fertility of the mature female from the stressed group was not affected as a third generation of litters born did not differ from the controls. It is suggested that a changed genetic programme in the ovarian germ cells of the first generation and/or a changed uterine environment in the second generation may be implicated.

3-Hydroxysteroid Dehydrogenases↗
PubMed1985

Effect of stress administered during pregnancy on the development of fetal testes and their subsequent function in the adult rat.

When maternal stress, containing a large anxiety component, was administered during pregnancy there was a significant decrease in 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity in the fetal testis from days 16 to 20 of gestation, but not at birth nor in the first week after birth. However, persistent effects were found in adult males of 90 days of age. Basal testosterone concentrations in both plasma and testes and testicular 3 beta-HSD activity were significantly lower whilst basal plasma progesterone concentrations were significantly higher in the stressed group. When the stressed offspring were subjected to short-term stress (one session), their plasma testosterone concentration was significantly below that of the controls. It is suggested that suppressed gonadotrophin secretion during critical periods of development alters fetal testicular function, and that raised circulating levels of stress-induced hormones such as beta-endorphin may be responsible for changes in gonadotrophin secretion.

3-Hydroxysteroid Dehydrogenases↗
PubMed1984

Effects of stress administered during pregnancy on reproductive capacity and subsequent development of the offspring of rats: prolonged effects on the litters of a second pregnancy.

The effects of high-anxiety-producing stress administered to rats during pregnancy were studied. The birthweight of offspring of both sexes from the stressed group was found to be significantly lower compared to birthweights of rats, however, were not affected. Mortality rate was significantly higher in the stressed group, although litter size, gestation length and sex ratios were not affected. Mean plasma resting corticosterone levels of the young pups did not differ between the two groups although they rose significantly as they aged in all groups. The offspring of both sexes from stressed mothers responded differently from the controls when subjected to short-term stress (one session) in adulthood. Their increase in plasma corticosterone concentration was significantly below that of the controls. This difference in response was abolished with long-term stress (10 days) when the males, but not the females, had habituated to the stressor. The observed inability to respond adequately to a sudden environmental change suggests a defective emergency response. Lingering effects due to stressing were also found. Male offspring of a second litter, conceived by the original mothers 8 weeks after the discontinuation of stress, had significantly lower birthweights than those of the controls. The subsequent growth rate of neither sex was affected nor was the response to short-term stress.

Animals↗
PubMed1983

Participation of the intermediate lobe of the pituitary gland after prolonged exposure to unpredictable stress in the rat.

An ultrastructural study is described which related cellular activity in the intermediate lobe of the pituitary gland with circulating levels of corticosterone. Exposure of male CSF rats to a signalled, unpredictable 60-day stress regimen induced intense secretory activity in all cells of the pars intermedia for the first 5 days of stressing, and thereafter secretory activity reverted back to the control condition. Blood corticosterone levels showed an initial extreme increase lasting for the first 5 days of exposure to the stress before gradually falling to re-establish a new stable level of secretion by 40 days. The possible involvement of the intermediate lobe in emotional or psychological stress when corticosterone levels are high is discussed.

Adrenal Glands↗
PubMed1980

The involvement of coated vesicles in the secretion of corticosterone by the zona fasciculata of the rat adrenal cortex.

Following exposure of rats to unpredictable stress there was a marked increase in the number of 'coated' vesicles in contact with or close to the cell membrane of the zona fasciculata cells. The close correlation between the vesicle numbers and the plasma levels of corticosterone led to the hypothesis that the coated vesicles were intimately involved in the secretory process. The use of horseradish peroxidase as a tracer protein confirmed that the coated vesicles were not involved in pinocytosis and the inward movement of materials, this function being performed by a much larger uncoated vesicle. The presence of microtubules associated with the coated vesicles and radiating through the Golgi body region, the site of formation of the vesicles, suggested that they may be involved in the transport of the secretory product to the cell membrane. The use of microtubules inhibitors, colchicine and vinblastine, were found to significantly reduce the plasma steroid response to stress. On the basis of these findings a new secretory mechanism was postulated.

Adrenal Cortex↗
PubMed1980

Estimation of thyroid gland activity in the Snell dwarf mouse by ultrastructural observation of the thyroid gland, measurement of plasma thyroxine concentration and thyroid hormone binding capacity.

An ultrastructural study of the thyroid gland of the Snell dwarf mouse showed cellular activity to be very low. Follicle cell diameters were significantly lower than in controls whilst the nucleocytoplasmic ratio was significantly higher. The observed cellular activity of the thyroid cells was associated with circulating levels of thyroxine which were found to be significantly lower than in controls. Measurement of the free thyroxine index showed very little free hormone available for tissue uptake. No differences in thyroid function due to age or sex in the dwarf mice were seen. Possible endocrine imbalances contributing to the low thyroid activity in the Snell dwarf mouse are discussed.

Animals↗
PubMed1980

Plasma testosterone levels and delta 5-3 beta-hydroxysteroid dehydrogenase activity in the testis of the rat following prolonged exposure to stress.

Exposure of male CSF rats to a signalled, unpredictable 60-day stress regimen induced a significant elevation in circulating testosterone levels at Days 1 and 60 which was abolished by castration. Small morphological changes were seen in the Leydig cells in the early days of stressing. A significant increase in 3 beta-HSD activity was seen by 5 days of stress, indicating increased steroidogenic activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1979

Plasma thyroid hormone and glucocorticosteroid concentrations in the male rat following prolonged exposure to stress.

Exposure of male CSF rats to a signalled unpredictable 60-day stress regimen induced a significant elevation in circulating triiodothyronine (T3) concentration above the control for the first 20 days of stress before the rate of secretion returned to normal. On the other hand, circulating thyroxine (T4) concentration fell significantly below the control value for the first 5 days of stress before the normal rate of secretion was reached in 10 days. A histological study of the thyroid gland revealed no change in activity among any of the control and stressed groups. At the same time this regimen also induced an initial extreme corticosterone elevation which was maintained for the first 5 days of stress and thereafter gradually fell to re-establish a new level by 40 days with no further change up to 60 days of stress. The possible physiological significance of the marked elevation in T3/T4 ratio as a result of stress is discussed, in particular with relation to higher glucocorticoid secretion.

Animals↗
PubMed1977

Ultrastructural changes in the adenohypophysis, adrenal gland activity, and desynchronization of the oestrous cycle following unpredictable stress in the rat.

An ultrastructural study of the adenohypophysis, after exposure of female Wistar rats to a signalled unpredictable 5- and 15-day stress regimen, is described. Cellular activity of the adenohypophysis correlated well with the circulating levels of corticosterone. Intense secretory activity was observed in all tropic cell types at 5 and 15 days although the observed differences generally were greater in the 5-day stressed group. It was observed that the oestrous cycles of 40 and 100% of the rats became desynchronized over the 5- and 15-day stress period respectively.

Animals↗
PubMed1976

Plasma glucocorticoid elevation and ultrastructural changes in the adenohypophysis of the male rat following prolonged exposure to stress.

A morphological and ultrastructural study is described which indicates that cellular activity in the adenohypophysis correlates well with the circulating levels of corticosterone. Intense secretory activity is observed in all tropic cells of the adenohypophysis over 10 days; thereafter the cellular morphology shows a return to the control condition. There are, however, differences in the degree of adaptation between the different tropic cells. After its initial hyperactivity, corticotrope activity returned to a control level by 20 days. Thyrotrope activity was also found to adapt to control activity, but only after 40 days. Similar patterns were observed in the stomatotrope and gonadotrope, where the initial hypertrophy returned to control levels by 20 days; thereafter, however, an inhibition was observed. The luteotrope however, seems to be an exception in that its level of activity increased throughout the duration of the stress procedure.

Adaptation, Physiological↗