Sex differences in neurotransmission parameters in response to repeated mild restraint stress exposures in intact male, female and ovariectomised female rats

The present study determined whether a repeated mild restraint stress exposure would differentially alter neuronal activity in male and female rats to gain insights into neurobiological substrates involved in sex differences in stress-induced behavioural responses. In our first set of experiments, we used Western blot analysis to determine whether alterations in several synaptic proteins were elicited by the repeated stress treatment. We found bidirectional changes in synaptophysin levels in female cerebral cortex and hippocampus that diverged between intact and ovariectomised females. There were persistent elevations in spinophilin levels in the male, but not female, hippocampus following the repeated mild restraint stress exposure. By contrast, levels of the NMDA receptor scaffolding protein, PSD-95, were altered only in intact female cerebral cortex and ovariectomised female hippocampus. We next used immunohistochemical evaluation of Fos expression as a marker for neuronal activation. We found significant increases in Fos immunoreactivity in all sex conditions across multiple brain regions in response to the repeated mild stress. Fos protein induction was greatest in the frontal cortex, piriform cortex and amygdala, with the degree of induction varying by sex condition. Fos induction was dramatically higher in amygdala and piriform cortex only in intact females following repeated stress compared to a single restraint stress exposure, suggestive of sensitisation rather than habituation. By contrast, the frontal cortex of intact and ovariectomised females showed habituation to the repeated stressor. Males displayed modest sensitisation in both the frontal cortex and dentate gyrus with no changes in other brain areas. Taken together, these findings show that exposure to a mild repeated stress results in sex differences in synaptic adaptations and patterns of brain activation that likely contribute to observed sex differences in stress-induced behaviours. This approach provides valuable insights into interactions between the hormonal milieu and responses to a repeated mild stress, and further supports the importance of considering hormonal status in treatment of stress-related disorders.

Insulin patterns in equivocal glucose tolerance tests (chemical diabetes)

Hyperinsulinemic patterns are a well recognized feature of equivocal glucose tolerances of the chemical diabetes type, i.e. those that are neither definitely nondiabetic nor clearly diabetic. A more complete characterization of such insulin responses is obtained when the data are expressed in terms of increments in insulin from the zero time point.

Thus, two patterns of insulin increments after oral glucose become evident when the equivocal zone of glucose tolerance is divided into lower and upper segments. Tests in the lower segment show normal increments at the halfhour point of the test; at one hour these tests show excessive increments which persist throughout the five hours of observation. On the other hand, tests in the upper zone show delays in the serum insulin rise at the half-hour point, followed by normal increments at one hour and excessive increments thereafter. The pattern is the same whether or not obesity is present.

It is suggested that tests in the equivocal zone of Glucose Tolerance Sum values be taken to be indicative of chemical diabetes. Tests with the Sum in the lower half of the equivocal zone could then represent chemical diabetes with mild intolerance stemming from insulin ineffectiveness, since insulin increments in this group are at or above the mean values recorded in nondiabetic controls. On the other hand, chemical diabetes with moderate glucose intolerance and Glucose Tolerance Sums in the upper half of the equivocal zone would be understood to result from a combination of an initial delay in the serum insulin rise followed by normal and then excessive increments in serum insulin with the latter two indicative of insulin ineffectiveness. However, insulin ineffectiveness may also be present at the time of the insulin delay.

High glucose:insulin ratios in tests indicative of chemical diabetes are almost always attributable to higher glucose increments with insulin increments normal or excessive compared to normal glucose tolerances. Deficient insulin increments contribute to the high ratios only at the half-hour point in tests with Glucose Tolerance Sums in the upper zone of equivocal glucose tolerances.

Fractional and partial hypopituitarism in anorexia nervosa

Increases in serum growth hormone which characterize acute starvation in non-obese individuals were usually absent in anorexia nervosa. Serum LH was decreased with serum FSH apparently normal in the majority. Increased adrenocortical activity as indicated by high basal 11 (OH)-corticosteroids and their incomplete suppression by dexamethasone and hyperresponsiveness to exogenous ACTH was recorded in about one-half of the patients tested. Urinary steroid responses to intravenous metyrapone were normal in all but one patient who had hypothalamic-pituitary hypofunction. Thyroid function was normal but TSH shortage has been reported. Resistance to insulin and a waning of insulin responses to hyperglycemia were noted in these individuals with anorexia nervosa.

Reactive hypoglycemia in women. Results of a health survey

1. Reactive hypoglycemia (for the purpose of this evaluation: blood glucose levels of 59 mg. per 100 ml. or less at the second, third, fourth or fifth hours of an oral glucose tolerance test) occurred in about 17 per cent of a group of 285 adult females participating in a survey.

2. This degree of reactive hypoglycemia occurred more often in the younger members (twenty to forty-five years of age), i.e., in 19 per cent of those with body weight less than 146 lbs. and in 31 per cent of those whose weight was above this range. Hypoglycemia was distinctly less frequent in the older nonoverweight females (2 per cent) and in the older obese group (11 per cent).

3. The lesser frequency of this degree of reactive hypoglycemia in the older nonobese and obese groups is attributable to higher fasting levels of glucose and to greater increments in blood glucose levels following upon an oral glucose load and not to any decrease in the usual increments in insulin.

4. In the two younger groups (twenty to forty-five years of age and either less than 146 lbs. or 146 lbs. or more in weight), those with reactive hypoglycemia as defined above had lower fasting blood glucose levels. This fact alone accounted for the subsequent occurrence of hypoglycemia. This conclusion is supported by the finding that the responses of those with and those without the stated degree of hypoglycemiaare Indistinguishable in terms of increments in blood glueose increments in insulin, and in the rations of the two.

5. Our data permit the generalization that blood glucose levels between 59 and 41 mg. per 100 ml. in the later hours of an oral glucose tolerance test are so common in young individuals, nonobese and obese, that this must be taken into account in any evaluation of so-called functional or reactive hypoglycemia in persons of this age. This degree of hypoglycemia is much less frequent in persons above forty-five of age.