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Biomedical subjects

S J Schuster

Publications and source records attributed to S J Schuster.

33 records · Page 2Linked to original sources
PubMed1997

Wholistic care. Healing a "sick" system.

A contemporary health system seeks to overcome the excesses and shortcomings of the medical model by integrating wholistic concepts and practices into the medical care it provides. Established on the grounds of an acute care hospital as one of its departments, the Franciscan Wholistic Health Center's (FWHC) goal-explicit spirituality and the involvement of FWHC staff in their own as well as their client's spiritual development-distinguishes it from other efforts.

Delivery of Health Care↗
PubMed1993

Distribution of erythropoietin producing cells in rat kidneys during hypoxic hypoxia.

We have used in situ hybridization to determine the localization and distribution of cells expressing the erythropoietin (EPO) gene in kidneys of rats exposed to reduced oxygen tensions to characterize the control of renal EPO formation during hypoxic hypoxia. Animals were subjected to severe hypoxia (7.5% O2) for 4, 8 and 32 hours to assess changes related to the duration of hypoxic exposure, and additionally to 9% and 11.5% O2 for eight hours to define changes related to the degree of hypoxia. The number of cells containing EPO mRNA were counted on tissue sections and compared to tissue concentrations of EPO mRNA and to the serum hormone concentrations. In situ hybridization revealed expression of the EPO gene exclusively in peritubular cells that were predominantly located in the cortical labyrinth under all conditions tested. After four hours of severe hypoxia (7.5% O2) approximately 170-fold more cells were found to contain EPO mRNA than under normoxic conditions. The number of EPO producing cells did not change significantly between four and eight hours exposure to 7.5% O2, but the amount of EPO mRNA per kidney increased approximately threefold. Further continuation of hypoxia resulted in down-regulation of renal EPO mRNA levels, which was mainly due to a reduction in the number of cells containing EPO mRNA. Comparison of graded degrees of hypoxia applied for eight hours showed an inverse exponential relationship between oxygen tension and the number of EPO producing cells. This recruitment of cells expressing the EPO gene occurred along a gradient extending from the corticomedullary border to the subcapsular tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗
PubMed1992

Plasminogen activator inhibitor-1 messenger RNA expression is induced in rat hepatocytes in vivo by dexamethasone.

Plasminogen activator inhibitor-1 (PAI-1), the major physiologic inhibitor of tissue plasminogen activator (tPA), plays a crucial role in the regulation of fibrinolysis. Both hepatocytes and endothelial cells have been implicated as major sources of plasma PAI-1. To study the relative contribution of these cell types to hepatic PAI-1 production, we have separated hepatocytes and hepatic sinusoidal endothelial cells by fractionation of freshly isolated rat livers using metrizamide density gradients and centrifugal elutriation. In untreated animals, PAI-1 messenger RNA (mRNA) was detected only in the purified endothelial cell fraction, and not in the hepatocyte fraction or in unfractionated liver. However, when the animals were treated with dexamethasone, PAI-1 mRNA expression was transiently induced in the liver. This induction paralleled the appearance of PAI-1 mRNA in purified hepatocytes, while PAI-1 expression in sinusoidal endothelial cells was unchanged. Four hours after dexamethasone treatment, plasma PAI-1 levels were increased approximately twofold over levels measured in animals treated with the diluent alone. These data suggest that PAI-1 production by hepatocytes may contribute to elevated plasma PAI-1 levels in the setting of acute injury and stress.

Animals↗
PubMed1992

Cellular sites of extrarenal and renal erythropoietin production in anaemic rats.

The cellular origins of erythropoietin were investigated in the rat using a probe derived from a cloned rat erythropoietin cDNA. In anaemic-hypoxic rat liver, in situ hybridization detected erythropoietin mRNA primarily in hepatocytes and less frequently in nonparenchymal sinusoidal or perisinusoidal liver cells. An RNase protection assay was used to compare the erythropoietin mRNA contents of separated rat liver cell fractions and also suggested that hepatocytes are the major source of extrarenal erythropoietin with nonparenchymal liver cells contributing less than 1% to total hepatic erythropoietin production. In kidney, in situ hybridization localized erythropoietin mRNA in nonepithelial cells, as yet of undefined lineage, in the cortical and outer medullary interstitium. These results indicate that, in the rat, the primary sources of erythropoietin in liver and kidney are different types of cells.

Anemia↗
PubMed1991

Parenchymal versus reticuloendothelial iron overload in the liver: distinction with MR imaging.

Parenchymal iron deposition occurs in hemochromatosis, while iron is deposited in reticuloendothelial (RE) cells after blood transfusions or rhabdomyolysis. Magnetic resonance images of patients with decreased liver signal intensity on T2-weighted images at 1.5 T were blindly compared in an effort to distinguish these conditions. In each of five patients with hemochromatosis, the pancreas had low signal intensity, but splenic signal intensity was decreased in only one. In contrast, only three of the 16 patients with RE iron overload had low pancreatic signal intensity, while all of these patients either had low splenic signal intensity (n = 14) or previously underwent splenectomy (n = 2). Distinction among these causes of iron deposition is clinically important because parenchymal iron overload from hemochromatosis may produce significant tissue damage, while the RE iron of transfusions and rhabdomyolysis is of little clinical consequence.

Adolescent↗
PubMed1989

Stimulation of erythropoietin gene transcription during hypoxia and cobalt exposure.

Erythropoietin, a plasma glycoprotein produced primarily by the kidney, is a growth and differentiation factor for erythroid progenitor cells. Production of renal erythropoietin is regulated by modulation of mRNA levels in response to changes in tissue oxygenation. Exposure to cobalt, a nonphysiologic stimulus for erythropoietin production, also acts by inducing mRNA accumulation. To determine whether variations in erythropoietin mRNA levels result from enhanced transcription of the erythropoietin gene, in vitro transcription reactions were performed using isolated rat kidney cell nuclei. Quantitation of specific nuclear RNAs labeled during in vitro transcription revealed active erythropoietin gene transcription in kidney nuclei from anemic-hypoxic and cobalt-treated animals while erythropoietin transcriptional activity was undetectable in normal kidney nuclei. Time course studies showed that stimulation of transcription begins between two and four hours following cobalt treatment and parallels the kinetics of mRNA and plasma erythropoietin accumulation. These results indicate that tissue hypoxia and cobalt exposure specifically enhance erythropoietin gene expression. This increase in erythropoietin production is regulated at least in part at the level of gene transcription.

Animals↗
PubMed1987

Regulation of erythropoietin production in a human hepatoblastoma cell line.

Production of immuno and biologically active erythropoietin was documented to occur in the human hepatoblastoma cell line HepG-2. The expression of the erythropoietin gene was further verified by Northern blot analysis using a single stranded RNA probe. In vitro studies showed that erythropoietin production by these cells was not stimulated by hypoxia or cobalt chloride, but was related to the proliferative activity of the cells in culture. In addition it was found that the secretion of erythropoietin was almost completely abrogated by tunicamycin, an inhibitor of N-linked glycosylation. This effect of tunicamycin was also observed in a permanently transfected cell line that secretes erythropoietin in large quantities.

Animals↗
PubMed1987

Physiologic regulation and tissue localization of renal erythropoietin messenger RNA.

Although erythropoietin (Epo) is produced primarily by the kidneys in response to hypoxia, the precise cell type(s) and mechanisms by which these cells regulate production are poorly understood. In the experiments we report, the kinetics of renal Epo production in response to acute hypoxia and the intrarenal localization of cellular Epo synthesis were studied at the level of Epo mRNA. Erythropoietin mRNA expression was determined by Northern blot analysis of rat kidney RNAs using a probe derived from the mouse Epo gene. Renal Epo mRNA content increased as early as 1 hour after initiation of hypoxia and continued to accumulate during 4 hours of stimulation. Discontinuation of the hypoxic stimulus resulted in rapid decay of mRNA levels. Kidney and plasma Epo levels measured by radioimmunoassay paralleled, with respective lag times, the changes in renal Epo mRNA content, suggesting that Epo production in response to acute hypoxia represents de novo synthesis and is regulated by changes in Epo mRNA. Northern blot analysis of RNAs extracted from separated glomerular and tubular tissue fractions revealed Epo mRNA in the tubular fraction, whereas glomerular tissue did not contain Epo mRNA. Thus, the site of cellular Epo synthesis is located in the renal tubule or its interstitium and not in the glomerular tuft.

Animals↗