Biomedical subjects

G Stebbins

Publications and source records attributed to G Stebbins.

6 recordsLinked to original sources

PubMed1999

Estrogen receptor immunoreactivity within subregions of the rat forebrain: neuronal distribution and association with perikarya containing choline acetyltransferase.

Administration of the neuroactive steroid hormone estrogen has been shown to effect cholinergic basal forebrain neuronal function. Antibodies directed against the estrogen receptor alpha (ERalpha) revealed dark (type 1) and light (type 2) nuclear positive neurons within the islands of Calleja, endopiriform nucleus, lateral septum, subfields of the cholinergic basal forebrain, bed nucleus of the stria terminalis, striohypothalamic region, medial preoptic region, periventricular, ventromedial, arcuate and tuberal mammillary nuclei of the hypothalamus, reuniens and anterior medial thalamic nuclei, amygdaloid complex, piriform cortex and subfornical organ. In contrast, only a few scattered ERalpha labeled neurons were found in cortex and hippocampus. ERalpha stained cell bodies were not seen in the striatum. Counts of ERalpha labeled neurons in intact female rats revealed significantly more type 2 neurons within the basal forebrain subfields. Quantitation of ERalpha immunoreactive neurons revealed a significant decrease in the relative number of type 1 neurons within the medial septum (MS), horizontal limb of the diagonal band (HDB) and substantia innominata/nucleus basalis (SI/NB) following ovariectomy. Quantitation following choline acetyltransferease (ChAT) immunohistochemistry revealed a significant decrease in the number of ChAT positive neurons within the MS, HDB and SI/NB, but not VDB following ovariectomy. Following ovx, the percentage of double labeled cholinergic basal forebrain neurons also declined significantly within the MS, VDB, HDB and SI/NB. These observations suggest that estrogen effects a subpopulation of cholinergic basal forebrain neurons and may provide insight into the biologic actions of this steroid in Alzheimer's disease.

Animals↗

PubMed1999

Psychiatric and neurologic predictors of psychogenic pseudoseizure outcome.

OBJECTIVE: To investigate the patterns of occurrence of psychogenic pseudoseizures (PPS) of 45 consecutive patients during a 6-month period after diagnosis, and to determine whether psychiatric and neurologic variables identified previously in PPS patient series can predict their recurrence after diagnosis, and whether any of these variables are associated with a particular outcome pattern. METHOD: Postdiagnosis PPS recurrence was assessed twice: during the first month and during a period ranging from the second to the sixth month. Outcome was categorized as follows: class I, complete cessation of PPS; class II, PPS only during one of the two observation periods; and class III, persistent PPS during the two observation periods. The authors used a logistic regression model to identify predictors of PPS recurrence (versus no PPS) among four neurologic and nine psychiatric variables, and compared their frequency among the three outcome classes. RESULTS: Class I, n = 13 (29%); class II, n = 12 (27%); and class III, n = 20 (44%). The presence of an abnormal MR image predicted PPS recurrence during the second observation period with a 75% accuracy. The presence of all nine psychiatric variables predicted PPS recurrence during both the first and second observation periods with a 93% and an 89% accuracy respectively. Patients with a class III outcome had a markedly higher frequency of recurrent major depression, dissociative and personality disorders, and a history of chronic abuse. Patients with a class II outcome displayed a notably higher frequency of denial of stressors and psychosocial problems, refusal of treatment recommendations, and new somatic symptoms after disclosure of diagnosis. Conversely, one episode of major depression was the one common diagnosis in patients with a class I outcome. CONCLUSIONS: PPS outcome after disclosure of diagnosis can be predicted by the presence of certain psychiatric characteristics. More than one psychopathogenic mechanism appears to operate in PPS.

Adult↗

PubMed1999

Dopamine transporter-immunoreactive neurons decrease with age in the human substantia nigra.

Unbiased disector stereologic cell counting was applied to sections from the human substantia nigra that were immunostained by using a monoclonal antibody against the dopamine transporter (DAT). This antibody was found to penetrate the full thickness of the stained section. Quantification of the number of DAT immunostained neurons was performed in human cases stratified into three age groups, young (ages 0-49 years), middle aged (ages 50-69 years), and aged (ages 70-85 years). The number of DAT-immunoreactive nigral neurons was normalized for each case by constructing a ratio of the number of DAT-containing neurons to total number of neuromelanin-containing cells in each subject's sample. Three types of DAT nigral neurons were seen: type 1, intensely stained; type 2, lightly stained; and type 3, DAT-immunonegative neuromelanin-containing perikarya. By 50 years of age, the number of type 1 neurons decreased significantly (P < 0.0001), whereas the number of type 2 neurons increased with age (P < 0.0001). Type 3 neurons also increased with age (P < 0.01), although less robustly than type 2 neurons. Type 1 neurons decreased by 11.2% per decade, and the total number of nigral neurons (types 1-3) decreased by 6.7% per decade. Relative to the young group, there were 75% and 88% reductions in type 1 neurons in the middle-aged and aged groups, respectively. This contrasts with the 35% and 41% reductions in total number of neuromelanin-containing neurons seen in middle-aged and aged groups, respectively. The young group had significantly more type 1 neurons and fewer type 2 neurons compared with middle-aged and aged participants. Post-hoc analyses indicated that the young group had significantly fewer type 3 neurons compared with middle-aged and aged participants. These findings demonstrate an age-related reduction in the number of substantia nigra DAT-immunoreactive neurons. Therefore, insight into the mechanisms regulating the rate of DAT synthesis may aid in our understanding of the decline of DATs with aging and its functional significance.

Adolescent↗

PubMed1989

Multicenter study of autologous adrenal medullary transplantation to the corpus striatum in patients with advanced Parkinson's disease.

In 19 patients with severe Parkinson's disease, we replicated the surgical procedures developed by Madrazo et al. for transplantation of the adrenal medulla to the striatum, and followed them for six months after operation. We monitored their motor function with the use of standardized scales and determined the amount and quality of "on" and "off" time (the hours of the waking day when the antiparkinsonian medications were effective and ineffective, respectively). We found significant improvement in focal areas of motor function. The mean percentage of on time during the day increased from 47.6 percent to 75.0 percent (P = 0.012); the mean percentage of on time without chorea increased from 26.6 percent to 59.2 percent (P = 0.006); the mean severity of off time decreased as assessed by both the Activities of Daily Living subscale of the Unified Parkinson's Disease Scale (P = 0.002) and the Schwab and England scale (P = 0.037). In contrast to the finding of Madrazo et al., however, the dosages of antiparkinsonian medications could not be decreased and postoperative morbidity was substantial. Despite cautious optimism, we conclude that the widespread use of this procedure outside of research centers is premature, since the improvement we found was slighter than in the previous cases.

Activities of Daily Living↗

PubMed1987

Studies of the hypotensive effect of calcium injected into lateral brain ventricles.

Calcium chloride (1-2 mumole) injected into lateral brain ventricles of pentobarbital anesthetized rats markedly decreases blood pressure. The hypotensive response is not affected by vagotomy and is characteristic calcium and barium since other polyvalent cations do not have the same effect. The calcium channel blocker, verapamil given into brain ventricles prevents the depressor effect of calcium suggesting that the hypotensive action of calcium is initiated intracellularly. The well documented lowering of blood pressure by increases in dietary intake of calcium may be mediated by increases in free calcium in cerebrospinal fluid.

Animals↗

PubMed1985

Effects of calcium and verapamil on normal and tumor murine leukocytes.

Although no differences in membrane stabilization by calcium were noted between leukemic (P-388) and normal murine leukocytes, tumor cells were shown to be more resistant to damage by ethanol but not by desmethylchlorpromazine. Furthermore, verapamil protected tumor cells but not normal cells against the disruptive effect of desmethylchlorpromazine but not that of ethanol. The protective action of verapamil was evident even in the absence of calcium. Thus leukemic cells appear to be altered so that the effects of certain membrane active agents are changed but the membrane stabilizing function of calcium is normal.

Animals↗