Biomedical subjects

W N Tapp

Publications and source records attributed to W N Tapp.

60 records · Page 4Linked to original sources

PubMed1979

Circadian variations in the effect of alpha-methyl-p-tyrosine on avoidance learning.

Circadian variations in alpha-methyl-p-tyrosine's (alpha MT) disruption of active avoidance acquisition were studied, alpha MT administered between 11.0 and 13.00 h, 17.00 and 19.00 h and 23.00 and 01.00 h impaired learning, but alpha MT administered between 05.00 and 07.00 h did not impair learning. The time of alpha MT ineffectiveness corresponds with the reported circadian peak in brain catecholamines, suggesting that the circadian susceptibility rhythm of alpha MT depends upon circadian fluctuations of brain catecholamines.

Animals↗

PubMed1979

Effects of cortical, hypothalamic, and hippocampal lesions on chronic alcohol intake and preference in rats.

The effects of cortical, hippocampal, and suprachiasmatic (hypothalamic) lesions on forced alcohol consumption, alcohol preference and the distribution of alcohol intake throughout the day were examined in rats. Controls included by hypothalamic sham-operated and unoperated groups. Baseline water intake during light and dark and initial alcohol preference (10% alcohol versus water) were determined. All animals then were placed on a forced alcohol consumption regimen consisting of ad lib lab-chow and 10% ethanol in water. On the sixth day of each week during the alcoholization regimen, light and dark phase alcohol intake was assessed and on the seventh day of each week, a 24-hr, two-bottle alcohol preference test (10% ethanol) was given. After nine weeks on the forced alcohol regimen, all animals were given a seven day "withdrawal" period consisting of access to plain water and to 10% alcohol in water. Throughout both the forced alcoholization and withdrawal periods, the lesioned groups, especially the cortically lesioned group, displayed a significantly greater preference for the 10% alcohol solution than any of the control groups. Control and lesion groups did not differ significantly in their preference for a 5% alcohol solution or for a quinine solution, suggesting that simple taste threshold changes probably would not account for these data. The results are discussed in terms of the possibility that the brain lesions may have rendered the animals more sensitive to the "addictive" and/or reinforcing properties of ethanol.

Alcohol Drinking↗

PubMed1977

Unilateral catecholamine depletion of the corpus striatum and amphetamine-induced turning: an ontogenetic study.

Unilateral intrastriatal microinjections of alpha-methyl-p-tyrosine followed by systemic amphetamine treatment produced turning ipsilateral to the side of the injection in rats from 12 days of age to maturity, but not in rats younger than 12 days. These results are consistent with other findings that indicate rapid development of the striatal dopaminergic system and dopaminergic component of the amphetamine stereotypy in the second postnatal week.

Aging↗

PubMedDate not supplied

An analysis of some sensitizing agents in the pathogenesis of stress-induced gastric erosive disease.

Prior surgical implantation of a venous catheter sensitized rats to cold-immobilization stress. Three of six catheterized females succumbed during the stress. The remaining rats fell into two groups in terms of their core temperature at the end of the stress period: Male uncatheterized rats had higher temperatures than rats in the other three groups. No relation was found between catheter patency and magnitude of hypothermia. Degree of gastric disease paralleled the core temperature findings in that the male uncatheterized rats had significantly fewer gastric erosions than the rats in the other three groups. Additionally, a robust effect of gender was found with uncatheterized females showing more hypothermia and more gastric disease than uncatheterized males. A subsequent experiment was conducted to evaluate whether anesthesia or wearing the protective spring was responsible in part for the sensitization seen. Here, the gender difference was less although females consistently averaged lower core temperatures after stress than did males. Despite similar core temperatures after stress, females that were prepared with the protective spring apparatus developed more gastric disease than female controls or similarly treated males. Thus, the additional sensitization exhibited by females in the first experiment may relate to the fact that both catheterization and the taping procedure were sensitizers while only catheterization was a sensitizer for males.

Animals↗

PubMedDate not supplied

Cardiovascular aging in Syrian hamsters: similarities between normal aging and disease.

The functional status of the cardiovascular system in health and cardiomyopathic (CM) hamsters was assessed throughout their lives by measuring heart weight and fluid in the pleural and peritoneal cavities. An index of cardiovascular age was developed from a multiple regression model of changes in these variables with chronological age. This index showed parallel changes in healthy and CM hamsters with increasing age, but CM hamsters with shorter lifespans underwent the changes at earlier ages. It was also a better predictor of viability than chronological age. The cardiovascular age index correctly predicted the early death of those hamsters which died before the average death age, whereas they should have been alive according to their chronological age. Conversely, hamsters which lived beyond the average death age had cardiovascular ages younger than the average death age, whereas their chronological ages erroneously indicated they should have been dead. This index may have been able to assess viability because it was correlated with histopathological signs of congestive heart failure in both strains of hamsters, as well as with the total amount of pathology found in them. Hamsters which die naturally at a particular age should have older cardiovascular indices than those sacrificed at the same age, and CM hamsters which died at 11-13 months of age did have older cardiovascular ages than hamsters that were sacrificed at these ages. Three experiment examined the effects of various treatments on the index of cardiovascular age. Life in constant light decreased the cardiovascular age of CM hamsters by 30% and extended life by 25%. Chronic digitalis treatment will improve cardiovascular performance, and it prevented increases in cardiovascular age during the end stages of heart failure. Finally, life-threatening chronic stress increased cardiovascular age in CM hamsters, which suggested that severe stress brought CM hamsters nearer to death. However, it was not possible to determine whether the effects of these treatments were on aging or health. Thus, the data suggested that aging, at least in hamsters, may be closely related to the natural development of heart failure which represents a common end stage of life in both cardiomyopathic hamsters and very old, supposedly healthy hamsters.

Aging↗

PubMedDate not supplied

Hamsters with coronary vasospasm are at increased risk from stress.

Results of earlier experiments suggested that hamsters with inherited heart disease were at a higher risk of succumbing to stress during the vasospastic, lesion-forming period of their lives rather than later when the process of congestive heart failure had begun. To test this hypothesis, we stressed cardiomyopathic hamsters (CMH) whose ages differed by about 3 months; the younger of the two groups of stressed hamsters was in the vasospastic phase of the disease. The stressor was cold immobilization in which stressor intensity was manipulated using two durations of cold exposure. Log rank survival curves revealed no difference in mortality with the more intense stressor. However, significantly fewer of the older hamsters succumbed to the less intense stressor (46% as compared with 85% of the younger CMHs). Examination of the hearts in the experiment where mortality rate was the same for both groups revealed evidence of cardiac dilatation, indicative of heart failure, only in the older hamsters following stress. Since the younger hamsters did not show these changes and since they, but not the older animals, have coronary microvascular spasm and an increased susceptibility to stress, it would appear that the process of coronary vasospasm should be viewed as an independent and additional risk factor in determining the consequences of stress. Because of the effects of stress in the younger cardiomyopathic hamster, we believe that a neural link--which can be activated by stress--may be involved in the pathogenetic process of coronary vasospasm.

Age Factors↗