Biomedical subjects

B A Pappas

Publications and source records attributed to B A Pappas.

75 records · Page 5Linked to original sources

PubMedDate not supplied

Pinealectomy: behavioral and neuropathological consequences in a chronic cerebral hypoperfusion model.

This experiment determined if pinealectomy (PX) affects the consequences of chronic, moderate brain ischemia. Rats were pinealectomized at 25 days of age and trained at 9 months on a tactile radial maze. They then underwent permanent occlusion of the common carotid arteries (2VO) or sham surgery, followed by maze retraining and then neurohistological assessment at 16 months. Combined PX + 2VO rats committed more working memory errors on the maze. 2VO itself caused a 10% reduction in hippocampal CA1 pyramidal cell number. PX alone caused a 21% reduction. Combined PX and 2VO caused the greatest reduction (32%) of CA1 cells. Similar results were seen for CA4. PX also increased glial fibrillary acidic protein immunoreactivity in both CA1 and CA4. Thus PX not only augmented the consequences of chronic brain ischemia but notably, PX itself caused hippocampal damage. These effects seemed not to result from the small cortical lesion caused by the PX procedure. The results are consistent with the hypothesis that endogenous melatonin is a neuroprotectant in the aging brain.

Animals↗

PubMedDate not supplied

Perinatal manganese exposure: behavioral, neurochemical, and histopathological effects in the rat.

Manganese chloride (Mn) was dissolved in the drinking water (0, 2, or 10 mg/ml) of dams and their litters from conception until postnatal day (PND) 30. Parturition was uneventful in the Mn-exposed rats and no physical abnormalities were observed. The rats exposed to 10 mg/ml Mn showed a 2.5-fold increase in cortical Mn levels. Their weight gain was attenuated from PND 9-24 and they were hyperactive at PND 17. Neither the 2 nor the 10 mg/ml Mn-exposed groups differed from the controls on the elevated plus apparatus or on the Morris water maze and the radial arm maze. Brain monoamine levels and choline acetyltransferase activity were affected. Tyrosine hydroxylase immunohistochemistry showed that dopamine cells of the substantia nigra were intact. Glial fibrillary acidic protein immunoreactivity was not increased in cortex, caudate, and hippocampus. However, both the low- and high-dose Mn-exposed groups showing thinning of the cerebral cortex. This could have resulted from perinatal malnutrition or from a direct effect of Mn on cortical development.

Analysis of Variance↗

PubMedDate not supplied

Intrauterine diazepam exposure: effects on physical and neurobehavioral development in the rat.

Primiparous timed-pregnant Wistar dams were administered a single daily SC injection of diazepam (1.0 or 5.0 mg/kg) or vehicle, over gestation days 14-20. The offspring were assessed on a number of developmental parameters. Pups exposed to the lower dose exhibited a decrease in birth weight and a delay in hair growth. Although these parameters were apparently not affected in the higher dose group, a significant dose-dependent decrease in pup viability was observed, both at birth and at one week of age. No differences were manifested for incisor eruption, pinna uncurling, eye opening, righting, geotaxis, acoustic startle, swimming, or forward locomotion. Rotarod performance was affected in the prenatal DZP animals and body weight at 60 days of age was depressed in the males of the 1.0 mg/kg group. The high dose of diazepam produced an increased susceptibility to minor metrazol-induced seizures in a kindling paradigm, but these altered seizure thresholds were not evidenced in an acute metrazol dose-response study. The NE and DA contents of hypothalamus, brainstem, hippocampus, and cortex of adult brains were assessed in each group. DA was not altered in any brain region while a single significant effect on NE was found. In the 1.0 mg/kg exposed rats only males, but not females, showed higher brainstem levels than controls. These results indicate that in the rat, prenatal exposure to clinically relevant doses of diazepam causes both fetal toxicity and long-term neurobehavioral alterations.

Animals↗