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Biomedical subjects

J Rosenbaum

Publications and source records attributed to J Rosenbaum.

At least 73 records · Page 4Linked to original sources
PubMed1995

Human myofibroblastlike cells obtained by outgrowth are representative of the fibrogenic cells in the liver.

During human fibrogenesis, myofibroblastlike cells proliferate and are the main source of fibrosis components. We have used cultured myofibroblastlike cells obtained by outgrowth from explants of human liver to study the expression of extracellular matrix (ECM) components and matrix-metalloproteinase-2 (MMP-2) These cells contained types I, III, IV, and V procollagen messenger RNAs (mRNAs). They also expressed mRNAs for laminin B1 chain and for cellular and plasma fibronectin. The corresponding proteins were detected by immunocytochemistry. MMP-2 expression was shown by Northern blot and gelatin zymography. Because transforming growth factor beta 1 (TGF beta 1) is considered an important mediator in liver fibrogenesis, we examined its effect on expression of ECM components by cultural human myofibroblastlike cells. TGF beta 1 increased collagen mRNAs steady-state levels and total collagen secretion in the culture medium. It also increased fibronectin mRNA levels but had no effect on laminin mRNA or MMP-2 expression. In summary, cultured human myofibroblastlike cells express those ECM components that accumulate during hepatic fibrogenesis, indicating the usefulness of this model to study mechanisms of human liver fibrogenesis. In addition to the mitogenic effect of TGF beta 1 on human myofibroblastlike cells, we now demonstrate its stimulation of ECM accumulation in these cells, thus emphasizing the central role of TGF beta 1 and myofibroblastlike cells in the pathophysiology of human hepatic fibrosis.

Cells, Cultured↗
PubMed1995

Interferon alfa and gamma inhibit proliferation and collagen synthesis of human Ito cells in culture.

During the course of ongoing liver fibrogenesis, Ito cells acquire myofibroblastic features, proliferate, and synthesize increased amounts of extracellular matrix components. Interferon (IFN) alfa and IFN gamma have been shown to elicit antiproliferative and/or antifibrogenic effects in various cell cultures of mesenchymal origin. The aim of this study was to investigate the effects of IFN-alpha and IFN-gamma on cultured human myofibroblastic Ito cells (MFBIC) proliferation and collagen synthesis and secretion. Serum-stimulated incorporation of [3H]-thymidine into DNA of MFBIC was dose-dependently decreased by both cytokines. IFN-alpha (10(4) U/mL) and IFN-gamma (10(3) U/mL) decreased DNA synthesis by 69% and 66%, respectively. Inhibition of cell proliferation was confirmed by cell counting. Similar results were observed when cell growth was stimulated with platelet-derived growth factor (PDGF-BB, PDGF-AA) or transforming growth factor (TGF)-beta 1. Collagen secretion per cell was inhibited by both cytokines, as assessed by [3H]-hydroxyproline incorporation. After a 6-day treatment, IFN-gamma showed a greater potency than IFN-alpha in inhibiting secretion of newly synthetized collagen (41% and 4% of control in the presence of 10(2) U/mL of IFN-gamma and 10(4) U/mL of IFN-alpha, respectively). Both IFN-alpha and IFN-gamma concurrently decreased steady-state expression of type I and type III procollagen messenger RNAs (mRNAs) in quiescent MFBIC. Viability assays ruled out cytotoxic effects of the two molecules. Finally, both IFNs decreased smooth muscle alpha-actin (SM alpha-actin) expression, whether assayed by immunoblotting or by Northern blot analysis. We conclude that IFN-alpha and IFN-gamma inhibit proliferation as well as collagen synthesis in human MFBIC.

Actins↗
PubMed1994

Effect of simvastatin, an inhibitor of hydroxy-methylglutaryl coenzyme A reductase, on the growth of human Ito cells.

During hepatic fibrogenesis, Ito cells proliferate, acquire a myofibroblastlike phenotype and synthesize increased amounts of extracellular matrix components. In this study, we have assessed the effects of simvastatin, an inhibitor of hydroxy-methylglutaryl-coenzyme A reductase, on the growth of human myofibroblastlike Ito cells. Cells were grown from explants of normal human liver and characterized by a positive staining for desmin and smooth muscle alpha-actin. Simvastatin (0.1 to 10 mumol/L) induced a marked dose-dependent decrease of [3H]thymidine incorporation in human Ito cells, whether stimulated by human serum or by purified growth factors. Simvastatin-induced inhibition of DNA synthesis was confirmed by nuclear autoradiography and was not explained by a cytotoxic effect. The growth inhibitory effect of simvastatin was specifically due to inhibition of hydroxy-methylglutaryl-coenzyme A reductase because it was overcome by addition of mevalonic acid, the product of the enzymatic reaction. The reduction in [3H]thymidine incorporation was not affected by supplementation of culture medium with purified cholesterol-low-density lipoprotein or isopentenyl adenine. It was partially reversed by addition of farnesol. These results show that simvastatin decreases the growth of human Ito cells, independently of its effect on cholesterol synthesis. This decrease may be due in part either to reduced farnesylation of proteins involved in growth factor signaling pathway or to inhibition of N-linked protein glycosylation. Whether this effect exists in vivo and could thus lead to a parallel decrease of fibrosis deposition within the liver requires further study.

Actins↗
PubMed1993

Immunolocalization of heparin-binding growth factors (HBGF) types 1 and 2 in rat liver. Selective hyperexpression of HBGF-2 in carbon tetrachloride-induced fibrosis.

Ito cells play a major role in liver fibrosis but the mechanisms controlling their activation in vivo are poorly understood. Heparin-binding growth factors (HBGF) types 1 and 2 are mitogenic for cultured Ito cells. They have been found in liver extracts but their cellular localization is unknown. We have studied by immunohistochemistry HBGF-1 and -2 expression in normal rat liver and in carbon tetrachloride (CCl4)-induced fibrosis. In normal liver, HBGF-1 was present only in sinusoidal cells whereas HBGF-2 was also detected in endothelial cells lining major vessels. At the acute stage of CCl4 intoxication, HBGF-2 was expressed in centrilobular clusters of mononuclear phagocytes that were surrounded by many HBGF-2-negative Ito cells. In the later stages, HBGF-2 was expressed by Ito cells within the fibrous bands. No modulation of HBGF-1 expression was noted at any stage. These results suggest that (1) at the acute stage of CCl4 intoxication, HBGF-2 produced by mononuclear phagocytes could participate in the recruitment of Ito cells; and (2) during the CCl4-induced fibrotic process, HBGF-2 could contribute to Ito cell proliferation and the synthesis of fibrosis components. In this in vivo model of hepatic fibrosis, the hyperexpression of HBGF-2 is a relatively specific event since the expression of a structurally related molecule, HBGF-1 was not modulated.

Animals↗
PubMed1993

Private sector response against the cholera threat in Trinidad and Tobago.

During the first half of 1992 the threat of cholera to Trinidad and Tobago prompted a strong health education effort by public authorities and the private sector. To help assess the private sector effort, the cost of cholera-related advertisements and private announcements placed in the country's two leading newspapers during January-June 1992 were reviewed. The review indicated that an estimated TT$ 540,660 was spent on these ads and announcements, that they contributed strongly to keeping cholera prevention continuously in the public eye, and that most of the messages published were accurate, specific, and safe. The strength and success of the private contribution to cholera prevention in this case suggests that similar approaches could be applied to other health problems and to the cholera problem outside Trinidad and Tobago. Overall, the lesson appears to be that if one can find congruence between private sector motives and public health interests, then the potential prospects for a successful partnership are great.

Advertising↗
PubMed1993

Mitogenic effect of transforming growth factor-beta 1 on human Ito cells in culture: evidence for mediation by endogenous platelet-derived growth factor.

We assessed the effect of transforming growth factor-beta 1 on the proliferation of human Ito cells. Ito cells in their myofibroblastlike phenotype were grown from explants of human liver and were characterized with electron microscopy and positive immunostaining for desmin and smooth muscle alpha-actin. Transforming growth factor-beta 1 was mitogenic for human Ito cells whatever the culture conditions, although it was, as previously described, inhibitory of growth for rat Ito cells. The mitogenic effect of transforming growth factor-beta 1 was likely due to induction of autocrine platelet-derived growth factor chain secretion by Ito cells themselves because (a) the mitogenic effect of transforming growth factor-beta 1 was blocked by specific platelet-derived growth factor antibodies, (b) transforming growth factor-beta 1 increased platelet-derived growth factor-A chain messenger RNA expression and platelet-derived growth factor-AA secretion by human Ito cells and (c) human Ito cells expressed the alpha-type platelet-derived growth factor-A receptor messenger RNA. Exogenous platelet-derived growth factor-AA was also mitogenic for human Ito cells, mimicking the effect of transforming growth factor-beta 1. Our data suggest that results obtained with rat Ito cells must be extrapolated with caution to human ones. The mitogenic effect of transforming growth factor-beta 1 on human Ito cells probably has pathophysiological relevance because transforming growth factor-beta 1 has been demonstrated in vivo at sites of active liver fibrogenesis.

Actins↗
PubMed1992

Are tiny polyps important when found on sigmoidoscopy in asymptomatic people?

To determine the occurrence of synchronous large bowel polyps located proximal to the sigmoid, in persons undergoing screening flexible sigmoidoscopy, we examined those who had diminutive polyps (less than or equal to 0.5 cm) as the only finding in the distal colon by further colonoscopy. One hundred one asymptomatic persons (mean age 61 +/- 13 years) had 143 diminutive polyps; a single polyp was found in 76%, and 64% of all polyps were located in the rectum. Thirty (21%) were hyperplastic and 86 (60%) were neoplastic, including 14 with moderate and one with severe dysplasia. The others were inflammatory (five) or unclassified (hot biopsy changes or normal mucosa, 14 polyps), and eight were lost before processing. Colonoscopy revealed that 16 (16%) of the 101 patients had 21 additional polyps proximally, mostly less than 1 cm in diameter. These included one hyperplastic and 18 neoplastic polyps, and two specimens showed hot biopsy changes. Age, histological type, number or location of the index diminutive polyps, were not associated with proximal lesions. We question whether immediate colonoscopy is justified in asymptomatic patients with only diminutive polyps at flexible sigmoidoscopy.

Adult↗
PubMed1990

Decreased toxicity of polymorphonuclear neutrophils toward hepatocytes isolated from rats with acute inflammatory reaction.

We have recently demonstrated that polymorphonuclear neutrophils were toxic to hepatocytes through a protease-mediated mechanism. Since synthesis of antiproteases is markedly increased during acute inflammatory reaction, the aim of this work was to investigate the toxicity of neutrophils against normal vs. inflammatory rat hepatocytes. Acute inflammatory reaction was induced by subcutaneous injection of turpentine 24 hr before the experiments. Hepatocytes from normal and turpentine-treated rats were isolated by collagenase digestion. They were incubated with human neutrophils stimulated by 1 mg/ml opsonized zymosan. Cytotoxicity was quantified by the percentage of alanine aminotransferase activity released by hepatocytes in culture medium after an 18-hr incubation period. By comparison to normal hepatocytes, inflammatory hepatocytes were more resistant to the toxicity of neutrophils. At a neutrophil/hepatocyte ratio of 20:1, the alanine aminotransferase activity releases were 53.7% +/- 5.4% (mean +/- 1 S.E.) and 27.4% +/- 4.8% for normal and inflammatory hepatocytes, respectively. Similarly, inflammatory hepatocytes were found to be less sensitive than normal hepatocytes to the toxic effect of purified neutrophil cathepsin G. In contrast, both types of hepatocytes exhibited the same sensitivity to H2O2 generated by a system consisting of glucose and glucose oxidase. Two arguments suggested that the resistance of inflammatory hepatocytes to protease toxicity was explained by an increased production of antiproteases by these cells: (a) when tested against cathepsin G and porcine pancreatic elastase activities, the protease inhibitory capacity of conditioned medium from inflammatory hepatocytes was higher than that of conditioned medium from normal hepatocytes; (b) conditioned medium from inflammatory hepatocytes markedly reduced the toxicity of stimulated neutrophils as that of cathepsin G.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1990

Interstrand duplexes in hnRNA: the occurrence of retrotransposon antisense sequences.

We have previously identified a class of non-polyadenylated hnRNA molecules (CLASS IA-) which hydrogen bond to polyadenylated hnRNA molecules. Characterization of clones from a Drosophila Class IA- cDNA library reveals that 18S rRNA and transcripts derived from intermediate repeat DNA constitute the bulk of such molecules. The most abundant non-ribosomal clone in the library derives from the antisense strand of the Copia retrotransposon and occurs in Drosophila Kc cell Class IA- hnRNA as non-polyadenylated transcripts of 10 and 15 kb.

Animals↗
PubMed1989

Demonstration of a basic fibroblast growth factor-like molecule in mouse hepatic endothelial cells.

We have investigated whether isolated mouse hepatic sinusoidal endothelial cells (HSEC) synthesized basic FGF. HSEC lysate was fractionated by heparin-Sepharose chromatography. A peak of mitogenic activity for Balb/c 3T3 fibroblasts was eluted with 3M NaCl. Several arguments suggested that the mitogenic factor was related to bFGF: a) its affinity for heparin; b) the loss of its mitogenic activity by heating at 65 degrees C, which was prevented in the presence of heparin; c) the abolition of its mitogenic activity in the presence of protamine sulfate; d) finally, its mitogenic effect was reduced in the presence of antibody to bFGF. These data demonstrate the presence of a bFGF-like molecule in HSEC. This molecule could be involved in the regulation of the neighboring Ito cell proliferation.

Animals↗
PubMed1989

Mouse hepatic endothelial cells in culture secrete a growth inhibitor for hepatic lipocytes and Balb/c 3T3 fibroblasts.

Hepatic lipocytes are sinusoidal cells in close contact to endothelial cells. They proliferate, switch to a fibroblastic phenotype and synthetize collagen during hepatic fibrosis. Since it is known that vascular endothelial cells can influence the proliferation of neighboring cells such as smooth muscle cells, we investigated the role of hepatic endothelial cells on the growth of lipocytes and Balb/c 3T3 fibroblasts. Concentrated conditioned medium from endothelial cells inhibited both [3H]thymidine incorporation and actual growth of lipocytes and Balb/c 3T3 fibroblasts. The inhibition was lost when conditioned medium was treated with heat or trypsin, or when medium was conditioned in the presence of cycloheximide. We conclude that hepatic endothelial cells secrete a proteic growth inhibitor for lipocytes and hepatic Balb/c 3T3 fibroblasts. This inhibitor could be of importance in limiting lipocyte proliferation in the liver and possibly in preventing hepatic fibrosis.

Animals↗
PubMed1988

Influence of ethanol consumption on maternal-fetal transfer of zinc in pregnant rats on day 14 of pregnancy.

The hypothesis that a biochemical lesion underlying the development of fetal alcohol syndrome is an ethanol-induced reduction in placental zinc transfer was tested. Placental zinc transfer was assessed in control and ethanol-fed dams on d 14-15 of pregnancy. Litters from ethanol-fed dams were characterized by a high resorption frequency and fewer live fetuses per litter than litters from control dams. In addition, fetuses from the ethanol-fed dams weighed less than control fetuses. However, despite the negative effects of ethanol intake on litter outcome, placental and fetal retention of 65Zn was similar in the two groups. Therefore, an ethanol-induced fetal zinc deficiency does not seem to have a role in the production of the gross structural malformations associated with fetal alcohol syndrome when adequate zinc is provided in the diet.

Animals↗