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Biomedical subjects

S Levine

Publications and source records attributed to S Levine.

At least 505 records · Page 28Linked to original sources
PubMed1977

Maternal pituitary-adrenal responsiveness as a function of differential treatment of rat pups.

The effects of litter separation and pup treatment on the maternal pituitary-adrenal system were investigated in 3 experiments. Lactating females did not show a pituitary-adrenal response to separation from their pups. However, the lactating females showed an increase in plasma corticosterone when their pups had been briefly removed and then returned. If, in addition, the pups were subjected to a noxious stimulus (electric shock) during the 2-min separation, mothers showed a further increase in corticosterone. When pups were returned after 3 hr of separation, mothers again showed a differential pattern of corticoid responsiveness. The magnitude of the mother's pituitary adrenocortical response depended upon the intensity of treatment given to the pups. These data lend physiological support to behavioral studies which have shown that maternal behavior is differentially influenced by pup-produced stimuli.

Animals↗
PubMed1977

Early handling influences on behavioral and physiological responses during active avoidance.

The effects of early handling on behavioral and physiological responses of the rat during active avoidance learning were investigated. Handled and nonhandled males and females were run in a 2-way shuttlebox task with an unconditioned stimulus of either .5 mA or .8 mA. Animals exposed to .8 mA showed a higher corticosterone response, a shorter response latency, and increased defecation. Early handling did not affect performance of the task, however handling did alter the patterns of the plasma corticosterone response over the course of avoidance training. Handled females showed less elevation of plasma corticosterone than nonhandled females, but all females showed a decrease in corticosterone over the course of avoidance learning. All males showed the drop in corticoids if run at .5 mA shock, but only handled males showed this change at .8 mA shock.

Animals↗
PubMed1977

Alterations in the maternal behavior of rats rearing malnourished offspring.

Investigations of maternal behavior of mothers fed a low-protein diet indicated deficits in retrieval and in the rate of nest-building. In addition, they indicated a concomitant increase in time spent with young when assessed during periods not associated with the retrieval/nest-building test session. The adrenalectomized mother, another case that produces growth-stunted progeny, was compared with both low-protein and control mothers for maternal behavior. Unlike the low-protein mother, the adrenalectomized mother did not exhibit retrieval or nest-building deficits; however, the adrenalectomized mother did display an increase in time spent with young. These data suggest that although deficits in retrieval and nest-building can be attributed to the nutritional condition of the mother, the stimulus characteristics of the malnourished pup are important in eliciting the increased time spent with the litter.

Adrenalectomy↗
PubMed1977

Interaction-induced reduction in differential maternal responsiveness: an effect of cue-reduction or behavior?

Litters from donor mothers received differential treatments (handling or shocking) and were then placed in wire-mesh baskets affixed to the cage tops of test mothers. Pup-produced cues from donor litters elicited different patterns of maternal behavior from test mothers that interacted with their own litters. In addition to these differences in maternal behavior, cues from the donor litters elicited a differential pattern of pituitary-adrenal activity. Shocked pups elicited larger corticosterone elevations than handled pups. These data suggest that the elimination of differential pituitary-adrenal responsiveness evidenced when mothers interact directly with pups subseuqent to pup treatment resllts from the termination of pup-produced cues that normally accompany active mother-infant interactions.

Animals↗
PubMed1977

Ontogenetic changes in pup-elicited maternal pituitary-adrenal activity: pup age and stage of lactation effects.

Ontogenetic changes in pup-elicited maternal corticosterone responsiveness were investigated. Patterns of maternal corticosterone change were found to depend on pup treatment: shocked pups elicited larger corticosterone elevations than pups that had been handled. In addition both the age of the stimulus pups and the state of lactation when the mother was tested affected the pattern and magnitude of maternal pituitary-adrenal activity.

Age Factors↗
PubMed1977

Influence of experiential factors and gonadal hormones on pituitary-adrenal response of the mouse to novelty and electric shock.

Plasma corticosterone elevations have been shown to occur in response to exposure to a novel environment and to the delivery of painful stimulation, such as footshock. The present experiment investigated the effects of experience with these types of stimuli upon the responsivity of the pituitary-adrenal system. When mice were subjected to repeated footshock, the adrenocortical response was increased. When animals were repeatedly shocked in a specific environment, the adrenocortical-stimulating properties of the situational stimuli were also elevated. On the other hand, plasma corticosterone elevations in response to merely being placed in an experimental chamber were not affected by 10 exposures to the situation. Previous data showed that animals that had been shocked in one environment were generally more responsive to many types of stimulus changes. Such a pattern of results suggests that the pituitary-adrenal system is subject to sensitization processes and that the central nervous system substrate which controls its function is one that is normally involved with the production of states of arousal. This configuration of results was quite pronounced in the female mouse regardless of hormonal state, and it was absent in the intact male. The results of studies with gonadectomized males suggested that testosterone inhibits sensitization.

Animals↗
PubMed1977

Uncertainty, as defined by the contingency between environmental events, and the adrenocortical response of the rat to electric shock.

The pituitary-adrenal system is thought to be sensitive to the degree of uncertainty in a situation. In addition, there is some question whether the pituitary-adrenal system can be conditioned in a Pavlovian sense. Three experiments are reported here. The first and third sought to define uncertainty in terms of conditioned stimulus-unconditioned stimulus (CB-US) and US-US contingencies, which vary the amount of information that can be used to predict the occurrence of discrete shocks. The second experiment examined the possibility that the adrenocortical system was subject to the laws of Pavlovian conditioning, by using a conditioned emotional response paradigm. The results showed that the magnitude of the Pituitary-adrenal response varied in a curvilinear manner along the dimension of uncertainty. Very low and very high degrees of uncertainty resulted in greater corticosterone elevations than did moderate levels. No evidence for Pavlovian conditioning of the adrencortical system was found, although behavioral measures showed fear conditioning. The data presented were supportive of the hypothesis that the pituitary-adrenal response reflects the operation of an arousal system.

Animals↗
PubMed1977

Effect of respiratory syncytial virus infection of HeLa-cell macromolecular synthesis.

Cells infected with respiratory syncytial (RS) virus eventually die but there appears to be no specific mechanism for shutting off cellular synthesis of macromolecules. DNA and RNA synthesis, as measured by the incorporation of labelled thymidine or uridine, do not begin to shut down until some time between 11 and 18 h after infection. By 18 h their rates of synthesis are reduced to approx. 50% for DNA and 35% for RNA. Protein synthesis continues throughout the course of infection at approximately the same rate. Synthesis of most of the cellular polypeptides also continues, but the distribution of polypeptides of high and low mol. wt. shifts. The increase in the proportion of those of high mol. wt. includes a peak that represents one of the seven previously identified virion polypeptides. Another consequence of RS virus infection is an increase in glucosamine incorporation, beginning near the end of the virus eclipse period (12 h after infection), which may be associated with virion glycoprotein synthesis. Polyacrylamide-gel electrophoresis of glucosamine-labelled cells reveals that at 18 h after infection two of the three previously identified virion glycoproteins are present.

Cell Survival↗