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Biomedical subjects

S Levine

Publications and source records attributed to S Levine.

At least 55 records · Page 3Linked to original sources
PubMed2000

Adolescents' understanding of social class: a comparison of white upper middle class and working class youth.

PURPOSE: Social class is increasingly being recognized as an important factor in the development of population-based variation in health among teens. However, little consensus exists regarding its measurement or conceptualization. METHODS: This study examined beliefs about social class of 48 working class and 50 upper middle class 16-year-old, white teens. RESULTS: Working class teens were more likely to misclassify themselves with regard to social class position. Significant class differences were present in beliefs regarding social mobility, parents' equity, equality of opportunity within society, and financial status as adults. How this conceptualization of social class translates into population-based variation in health remains an important area for further inquiry.

Adolescent↗
PubMed2000

Investigation and control of aspergillosis and other filamentous fungal infections in solid organ transplant recipients.

Filamentous fungal infections are associated with high morbidity and mortality in solid organ transplant patients, and prevention is warranted whenever possible. An increase in invasive aspergillosis was detected among solid organ transplant recipients in our institution during 1991-92. Rates of Aspergillus infection (18.2%) and infection or colonization (42%) were particularly high among lung transplant recipients. Epidemiologic investigation revealed cases to be both nosocomial and community-acquired, and preventative efforts were directed at both sources. Environmental controls were implemented in the hospital, and itraconazole prophylaxis was given in the early period after lung transplantation. The rate of Aspergillus infection in solid organ transplant recipients decreased from 9.4% to 1.5%, and mortality associated with this disease decreased from 8.2% to 1.8%. The rate of Aspergillus infection or colonization among lung transplant recipients decreased from 42% to 22.5%; nosocomial Aspergillus infection decreased from 9% to 3.2%. Cases of aspergillosis in lung transplant recipients were more likely to be early infections in the pre-intervention period. Early mortality in lung transplant recipients decreased from 15% to 3.2%. Two cases of dematiaceous fungal infection were detected, and no further cases occurred after environmental controls. The use of environmental measures that resulted in a decrease in airborne fungal spores, as well as antifungal prophylaxis, was associated with a decrease in aspergillosis and associated mortality in these patients. Ongoing surveillance and continuing intervention is needed for prevention of infection in high-risk solid organ transplant patients.

Aspergillosis↗
PubMed2000

Proliferation of glial cells in vivo induced in the neural lobe of the rat pituitary by lithium.

Lithium salts are widely used for treatment of psychiatric illness. Lithium also affects cell proliferation. During investigation of the effect of lithium chloride on the central nervous system (CNS) of nephrectomized rats, we noted numerous mitotic figures in the neural lobe of the pituitary. Morphologic criteria established that the mitotic cells were astrocytes, the supporting glial cells of the CNS, also known as pituicytes. Equimolar doses of chlorides of chemically related cations (sodium, potassium, rubidium) had no such effect.

Animals↗
PubMed2000

Developmental myosin heavy chains in the adult human diaphragm: coexpression patterns and effect of COPD.

In preliminary experiments we noted developmental (i.e., embryonic and neonatal) myosin heavy chains (MHCs) in the diaphragms of patients with severe chronic obstructive pulmonary disease (COPD). We hypothesized that this finding represented new fiber formation secondary to injury associated with the mechanical stress of COPD or previously undescribed MHCs in the human diaphragm. To distinguish between these possibilities, we analyzed diaphragmatic biopsies obtained from 9 patients with severe COPD (forced expiratory volume in 1 s = 21 +/- 2% predicted, residual volume = 283 +/- 22% predicted) and 10 age-matched controls. First, using immunocytochemistry with specific monoclonal antibodies, we noted that control diaphragms had greater proportions of fibers expressing embryonic (50 +/- 2 vs. 28 +/- 3%, P < 0.0001) and neonatal (52 +/- 2 vs. 32 +/- 3%, P < 0.001) MHCs than COPD diaphragms. Second, SDS-PAGE demonstrated that these developmental MHCs represented only a very small fraction of the diaphragmatic MHC content. Third, the RT-PCR demonstrated mRNA coding for embryonic and neonatal MHCs in COPD and control diaphragms. Last, COPD and control diaphragms exhibited normal histology on light microscopy. We conclude that the presence of developmental MHC isoforms does not indicate new fiber formation in diaphragms of patients with severe COPD. Although these results represent the first systematic description of embryonic and neonatal MHCs in normal adult human diaphragms, their function remains to be elucidated.

Adult↗
PubMed2000

Stress-induced alterations in corticotropin-releasing hormone and vasopressin gene expression in the paraventricular nucleus during ontogeny.

From postnatal day (PND) 4 to 14, neonates display a minimal pituitary-adrenal response to mild stress, the so-called 'stress hyporesponsive period' (SHRP). During the SHRP, maternal deprivation (MD) alters the pituitary-adrenal system, enabling neonates to become endocrine responsive to specific stimuli. We have previously reported that during the SHRP, mild stress enhances corticotropin-releasing hormone (CRH) messenger RNA (mRNA) expression in the paraventricular nucleus (PVN). Insofar as elevated CRH mRNA was observed both in the presence and absence of adrenocorticotropin (ACTH) release, we hypothesized that other ACTH secretagogues may participate in the pituitary stress response. During the SHRP, does arginine vasopressin (AVP) complement the actions of CRH which might be reflected centrally by the enhanced biosynthesis of both neuropeptides? To test this hypothesis we examined the time course of stress-induced CRH and AVP mRNA in the PVN at PND 6, 12, and 18. As an index of neural activity, c-fos mRNA in the PVN was also examined. Restraint was used as the stressor and MD was employed to enable an endocrine response during the SHRP. Despite the absence of stress-induced ACTH, in nondeprived pups during the SHRP, CRH mRNA was rapidly enhanced. In their maternally deprived (DEP) counterparts, ACTH levels were increased, and a significant induction of CRH mRNA was only observed at day 12. AVP mRNA levels were elevated in DEP 12-day-old pups at 15, 30 and 60 min. In rats beyond the SHRP, plasma ACTH levels, CRH and AVP mRNA were all enhanced following restraint. At PND 18, elevated CRH mRNA was not observed until 4 h after stimulus. Following restraint, c-fos mRNA was increased at all three ages, although the magnitude of c-fos response was less during the SHRP. These results demonstrate that when restraint elicits prototypical ACTH release, the neonatal central response is to enhance the biosynthesis of both AVP and CRH. If nucleic acid changes correlate with release, the increased synthesis of both neuropeptides may indicate the potential for AVP to synergize with CRH during the neonatal stress response.

Adrenocorticotropic Hormone↗
PubMed2000

Training residents for community psychiatric practice: the resident perspective.

OBJECTIVE: To capture the views and experiences of psychiatry residents in 5 Canadian training programs with respect to community psychiatric training. METHOD: We sent a questionnaire regarding respondent demography, career interests, and community psychiatry training experiences to psychiatry residents at 5 training programs in Ontario. We undertook descriptive analyses and frequency comparisons on the returned data. RESULTS: The overall response rate was 48%, with considerable variation between programs. With respect to career planning, respondents indicated highest interest in urban hospital-based practice. An interest in additional community psychiatry training was, however, expressed, particularly by junior residents. Residents' suggestions for improving community psychiatry training included better promotion of training opportunities, improved quality of supervision in community settings, and more didactic teaching. CONCLUSION: Psychiatry residents are obtaining training experiences in community psychiatry, but objectives and guidelines are quite variable, as is reflected in their understanding of the definition of "community psychiatry." Residents' career paths are still focused on urban hospital-based practice or solo private practice, which likely reflects their prevalent training experiences. There is, however, interest in community psychiatry training. Junior residents may be more open to this type of practice, and curricula should allow more exposure to community psychiatry at this stage of training.

Adult↗
PubMed2000

Rapid induction of corticotropin-releasing hormone gene transcription in the paraventricular nucleus of the developing rat.

Neonates from postnatal days (pnd) 4-14 display a minimal pituitary-adrenal response to mild stress, the so-called stress hyporesponsive period (SHRP). However, during the SHRP, maternal deprivation (deprived) alters the pituitary-adrenal system, enabling neonates to become endocrine responsive to specific stimuli. Although neonates do display stress-induced ACTH, there is limited evidence for enhanced CRH gene expression early in development. The present experiment examined whether a mild stimulus (isotonic saline injection) administered to deprived and nondeprived neonates would enhance CRH biosynthesis in the paraventricular nucleus. Using in situ hybridization we measured the time course of CRH heteronuclear RNA (hnRNA) and messenger RNA at 15, 30, and 240 min poststimulus. Pnd 6, 12, and 18 were included to examine the CRH gene response during and outside of the SHRP. Despite the minimal endocrine response of nondeprived pups during the SHRP, CRH hnRNA and messenger RNA were elevated at 15 min (all ages). Both transcripts were enhanced at 15-30 min in deprived (pnd 12 and 18) pups; however, the magnitude of the response was less than that in nondeprived pups. These data indicate that during ontogeny there is a rapid stimulus-induced CRH biosynthesis. Thus, during development, the central components of the hypothalamic-pituitary-adrenal axis may be stress hyperresponsive rather than hyporesponsive.

Adrenocorticotropic Hormone↗
PubMed2000

Feeding sugar overnight maintains metabolic homeostasis in rats and is preferable to overnight starvation.

Rats are often starved overnight for many different reasons. Overnight starvation causes loss of body and liver weights, depletion of liver glycogen, decrease of blood glucose and loss of amino acids because of gluconeogenesis. Providing pure sucrose cubes as the sole overnight nutrient is a simple, inexpensive way to empty the gastrointestinal (GI) tract, while minimizing liver changes and preventing decrease of blood glucose and loss of amino acids. Adding sugars to the overnight drinking water as the sole nutrient has the same beneficial effects, provided the type of sugar and its concentration allow for sufficient intake and provided hyponatremia is avoided. Feeding sucrose cubes or sugar solutions will empty the gastrointestinal tract as effectively as starvation. In all instances, simple precautions against coprophagy and pica should be taken in order to secure optimal benefit.

Animals↗
PubMed1999

The ontogeny of the neuroendocrine response to endotoxin.

During development, the hypothalamic-pituitary-adrenal (HPA) axis is normally hyporesponsive between postnatal days (pnd) 4 and 14. This interval has been designated as the stress-hyporesponsive period (SHRP). Recent evidence indicates that the neonate can respond to selective stimuli, i.e., exposure to immune signals. The purpose of this study was to investigate the neural correlates of the neonatal stress axis in response to a stimulus that activates the pituitary-adrenal hormones. Thus, lipopolysaccharide (LPS) was administered to neonates at three ages (pnd 6, 12, and 18) during or after the SHRP. In an effort to understand the neonatal hypothalamic paraventricular nucleus (PVN) response to an endotoxin, we measured c-fos immunoreactivity and corticotrophin-releasing hormone (CRH) gene expression. At all ages tested, there was an increase in ACTH and corticosterone (CORT) following LPS compared to controls. During the SHRP, LPS treatment resulted in a marked increase in Fos-positive cells in the PVN, whereas a saline injection had no effect. However, at pnd 18, both LPS and a saline injection elicited equivalent PVN Fos expression. In contrast to the effect on Fos, LPS and a saline injection decreased CRH mRNA at pnd 6 and 12. Outside the SHRP, LPS resulted in an increase in CRH gene expression relative to saline-injected controls. Thus, while the LPS-induced activation of Fos protein and plasma hormones were concordant, CRH mRNA did not positively correlate with the peripheral response. This suggests that the SHRP is not absolute, and the brain is responsive to some stimuli during this period.

Adrenocorticotropic Hormone↗
PubMed1999

Postnatal experiences and genetic effects on squirrel monkey social affinities and emotional distress.

Most nonhuman primate research on risk factors underlying vulnerability to stress has focused on early psychosocial experiences in various species of macaques. To test for genetic and experiential effects on emotional vulnerability in randomly bred squirrel monkeys, here we combined a paternal half-sibling analysis with three postnatal rearing protocols that altered aspects of maternal availability. In one condition offspring were periodically removed from natal groups, whereas differences in maternal availability were produced in two other conditions by manipulating the effort required of lactating mothers to successfully locate food. After completion of these protocols at 21 weeks of age, social affinities, maternal separation induced peep-calls, and plasma levels of cortisol were assessed from 29 to 37 weeks of age. Significant postnatal rearing effects and the lowest heritabilities were detected in peak elevations of cortisol measured 1 day after the removal of mothers from otherwise undisturbed groups. Individual differences in cortisol 3-7 days later revealed negligible postnatal rearing effects and the highest heritabilities (h(2) approximately. 70), as offspring sired by certain fathers failed to return to the preseparation level found in undisturbed natal groups. Paternal half-siblings that responded with long lasting increases in cortisol spent more time near their mother in undisturbed groups and exhibited long-lasting increases in separation induced peep-calls. These findings concur with human twin studies that suggest genetic and experiential factors contribute to individual differences in vulnerability to emotional distress.

Analysis of Variance↗
PubMed1999

Separation induced changes in squirrel monkey hypothalamic-pituitary-adrenal physiology resemble aspects of hypercortisolism in humans.

When separated from groups, squirrel monkeys respond with significant increases in plasma cortisol and adrenocorticotropic hormone (ACTH). While cortisol remains elevated above pre-separation levels, significant reductions occur in ACTH. Monkeys that respond with greater increases in cortisol subsequently exhibit greater reductions in ACTH, which suggests that reductions in ACTH are mediated by corticosteroid feedback. Monkeys that respond with greater increases in cortisol also tend to exhibit greater cerebrospinal fluid levels of the dopamine metabolite HVA, but not the norepinephrine metabolite MHPG, or corticotropin-releasing factor (CRF). Attenuation of corticosteroid feedback with metyrapone results in significant increases in circulating ACTH, and in older monkeys increases plasma HVA. Similar findings in humans have been reported in clinical studies of hypercortisolism and major depression.

Adrenal Glands↗
PubMed1999

Pregnancy and laparoscopic surgery.

We reviewed the English literature regarding laparoscopic surgery during pregnancy and found that of 518 reported procedures, the most common was cholecystectomy (45%), followed by adnexal surgery (34%), appendectomy (15%), and other operations (6%). We add six cases to this list; three cholecystectomies, an adnexal procedure, and two for abdominal pain. Thirty-three percent were performed in the first trimester, 56% in the second, and 11% in the third trimester. This review demonstrates a definite trend, indicating that laparoscopy in pregnancy appears to be safe when performed by experienced practitioners. (J Am Assoc Gynecol Laparosc 6(3):347-351, 1999)

Abdominal Pain↗
PubMed1999

Persistent effects of maternal deprivation on HPA regulation can be reversed by feeding and stroking, but not by dexamethasone.

Maternal deprivation of neonatal rats for 24 h has immediate and persistent effects on hypothalamic-pituitary-adrenal (HPA) regulation. Immediately after deprivation corticosterone (CORT) is elevated. The primary purpose of our experiments was to determine if, by preventing this CORT elevation, the persistent effects could be reversed. In experiment 1, pups were injected with dexamethasone at the onset of the 24-h deprivation period on postnatal day 11 to suppress the rise in CORT. In experiment 2 some aspects of maternal behaviour known to suppress CORT levels were mimicked during deprivation from postnatal days 11-12. The pups were either: (1) left undisturbed; (2) stroked periodically; or (3) stroked and episodically fed. At postnatal day 20 basal and stress-induced adrenocorticotrophic hormone (ACTH) and CORT levels were measured as well as brain mineralocorticoid (MR) and glucocorticoid receptors (GR). Neonatal rats receiving dexamethasone prior to the onset of the deprivation on day 11 did not differ on day 20 from deprived pups that were exposed to elevated CORT levels. There were no detectable changes in the non-deprived pups that were treated with dexamethasone. In contrast, feeding and stroking during the period of deprivation obliterated the persistent effects both with regard to the reduced ACTH response and the decreased GR mRNA in hippocampus and hypothalamus. Stroking alone appears to have no influence. In conclusion, the persistent reduction of the ACTH response to mild stress and the decrease of GR mRNA is not mediated by deprivation-induced elevations in CORT, but appears to be reversible by reinstating specific aspects of the dam's nurturing behaviour.

Adrenal Glands↗
PubMed1999

Estimating maximum concentrations for open path monitoring along a fixed beam path.

Researchers have applied open path optical sensing techniques to a variety of workplace and environmental monitoring problems. Usually these data are reported in terms of a path-average (or path-integrated) concentration. When assessing potential human exposures along a beam path, this path-average value is not always informative, since concentrations along the path can vary substantially from the beam average. The focus of this research is to arrive at a method for estimating the upper-bound in contaminant concentrations over a fixed open beam path. The approach taken here uses a statistical model to estimate an upper-bound concentration based on a combination of the path-average and a measure of the spatial variability computed from point samples along the beam path. Results of computer simulations and experimental testing in a controlled ventilation chamber indicate that the model produced conservative estimates for the maximum concentration along the beam path. This approach may have many applications for open path monitoring in workplaces or wherever maximum concentrations are a concern.

Humans↗
PubMed1999

Effects of coprophagy on serum urea and the weight of the gastrointestinal tract of fed or fasted rats.

Coprophagy can be minimized by fitting rat cages with metal grids which allow faecal pellets to pass through to the floor of the cage. When bedding was omitted overnight, the extent of coprophagy could be estimated from the weight of the droppings on the cage floor or the weight of the gastrointestinal (GI) tract removed from rats housed with or without grids. The effect of coprophagy was also demonstrated by the elevation of serum urea nitrogen in rats that consumed faeces. Therefore, precautions against coprophagy, or their absence, should be specified in all experimental protocols and reports.

Animals↗