PubMed Health⌕ Search

Biomedical subjects

M A Zern

Publications and source records attributed to M A Zern.

65 records · Page 4Linked to original sources
PubMed1985

Increased type I procollagen mRNA levels and in vitro protein synthesis in the baboon model of chronic alcoholic liver disease.

We have investigated the molecular mechanisms responsible for the histologic changes induced by ethanol in the baboon model of alcoholic liver disease. Eleven ethanol-fed baboons and their pair-fed controls had histology evaluated and RNA extracted from percutaneous liver biopsy specimens. In 6 of the ethanol-fed animals, fatty liver developed, but no significant differences were found when the RNA from the control and ethanol-fed livers was translated in the reticulocyte lysate system or analyzed with specific cDNA probes. Five of the baboons given ethanol, however, developed significant fibrosis. Molecular evaluation revealed that the RNA from these livers was more active in in vitro protein synthesis, and the type I procollagen mRNA content was significantly higher per microgram of liver RNA as determined by hybridization analysis (183% +/- 23% SEM of control, p less than 0.02). In addition, there were higher levels of albumin mRNA content in the livers of ethanol-fed baboons that developed fibrosis (180% +/- 21% SEM of control, p less than 0.05). There was no change, however, in the levels of beta-actin mRNA, a representative constitutive protein. These findings in the baboon model of alcoholic fibrosis show that ethanol consumption increases type I procollagen mRNA, which may foster fibrogenesis; increases albumin mRNA content without causing an increase in serum albumin; and induces no change in levels of beta-actin mRNA. These studies also show that percutaneous needle biopsy can supply sufficient tissue to evaluate molecular changes in human liver disease.

Actins↗
PubMed1984

Effects of chronic renal failure on protein synthesis and albumin messenger ribonucleic acid in rat liver.

Previously we reported that chronic renal failure in rats leads to preferential disaggregation of liver membrane-bound polysomes associated with a decrease in albumin synthesis. To determine whether reduced albumin synthesis results from reduced cellular levels of albumin messenger RNA (mRNA) or some other molecular mechanism, we have employed mRNA-DNA hybridization in conjunction with cell-free protein synthesis to determine albumin mRNA sequence content and biological activity in subcellular fractions from control and uremic rat liver. Using high specific activity albumin [3H]-complementary DNA prepared from purified-albumin mRNA, we found that total liver polysomes and albumin mRNA sequence content are increased in uremic animals. The extra polysomes are located within the membrane-bound subcellular fraction. These polysomes, however, have reduced ability to synthesize albumin in the cell-free system, and mRNA isolated from membrane-bound polysomes of uremic liver showed reduced albumin synthesis. Evaluation of albumin mRNA size by hybridization analysis revealed a reduced content of intact albumin mRNA molecules per microgram of RNA in the liver of uremic animals. This was associated with increased ribonuclease activity in uremic cytosol. The diminished albumin synthesis by membrane-bound polysomes of uremic rat liver can, therefore, be explained by enhanced degradation of albumin mRNA.

Albumins↗
PubMed1983

Molecular mechanisms for changes in hepatic protein synthesis induced by schistosomiasis infection in mice.

Mice infected with Schistosoma mansoni and littermate controls were evaluated serially for 12 weeks. Infected mice gained weight at the same rate as controls, but starting with the sixth week their livers became enlarged with granulomas and fibrous tissue, and they developed hypoalbuminemia. To evaluate the regulation of the albumin and type I collagen gene expression, total RNA was isolated from infected and control mice and translated in an mRNA-dependent rabbit reticulocyte lysate system. Protein synthesis was decreased 1.5-3-fold with RNA from infected vs. control liver. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the cell-free products showed a reduction in albumin but an increase in type I procollagen synthesis in infected mice. Immunoprecipitation of the cell-free product confirmed that albumin synthesis was reduced in greater proportion than other liver proteins in schistosome-infected mice. Hybridization of RNA from infected liver with cloned mouse albumin cDNA (pmalb-2) demonstrated a reduction in albumin mRNA to 37% of control, while hybridization with a chick type I pro alpha 2 collagen cDNA probe (pCg-45) revealed increased procollagen mRNA in infected liver beginning at 6 weeks postinfection. These results suggest that in murine schistosomiasis a reduction in biologically active albumin mRNA results in decreased albumin synthesis and may be responsible in part for hypoalbuminemia. In addition, increased collagen mRNA is associated with increased collagen synthesis during hepatic fibrosis.

Albumins↗
PubMed1983

Use of in situ hybridization to identify collagen and albumin mRNAs in isolated mouse hepatocytes.

We present a simple and improved method for in situ localization of albumin and collagen mRNAs in isolated mouse hepatocytes. The cells were isolated by collagenase perfusion, mincing, and differential centrifugation. Nick-translated 3H-labeled mouse albumin cDNA (pmalb-2) and chicken pro-alpha 2(I) collagen cDNA (pCg45) probes were then hybridized with the cells in silane-treated microcentrifuge tubes. The cells were transferred and fixed to a microscope slide and hybridization was evaluated semiquantitatively by counting exposure of grains in autoradiographic emulsion placed over the cells. With this method of in situ hybridization, all hepatocytes appear to have significant, but highly variable, amounts of albumin mRNA. In addition, type I procollagen mRNA appears to be present at low abundance in hepatocytes. These results indicate that in situ hybridization can effectively demonstrate the presence of specific low- or high-abundance mRNAs in isolated well-differentiated eukaryotic cells.

Animals↗
PubMed1983

Changes in collagen and albumin mRNA in liver tissue of mice infected with Schistosoma mansoni as determined by in situ hybridization.

We have employed in situ hybridization to evaluate the molecular mechanisms responsible for hypoalbuminemia and increased liver collagen content in murine schistosomiasis. Results were compared using a simplified method of hybridizing isolated hepatocytes from Schistosoma mansoni-infected and normal mouse liver with mouse albumin (pmalb-2) and chick pro-alpha 2(l) collagen (pCg45) probes. Whereas hepatocytes from infected mice showed significantly less albumin mRNA than hepatocytes from control, there were more grains of procollagen mRNA in hepatocytes from infected as compared with control liver. Hybridization of infected liver tissue sections with the collagen probe showed more grains per field in granulomas than in liver regions, whereas with the albumin probe there was more hybridization in liver tissue than in granulomas. These results suggest that in murine schistosomiasis a reduction in albumin mRNA sequence content may be associated with decreased albumin synthesis and ultimately leads to hypoalbuminemia. In addition, although the granuloma seems to be the primary source of type I collagen synthesis, hepatocytes are also capable of synthesizing collagen, especially under fibrogenic stimulation.

Albumins↗
PubMedDate not supplied

Development and use of a rat albumin cDNA clone to evaluate the effect of chronic ethanol administration on hepatic protein synthesis.

A rat albumin cDNA probe (pBR alb 149) was developed in order to investigate the molecular mechanisms responsible for changes in hepatic protein synthesis after chronic administration of ethanol to rats. Rats fed a diet for up to 1 year in which 36% of calories were from ethanol, developed fatty livers but not cirrhosis. Cell-free protein synthesis with liver membrane-bound polysomes of ethanol-fed rats was increased as compared to control membrane-bound polysomes, whereas protein synthesis with free polysomes was unchanged. Total RNA extracted from liver membrane-bound polysomes and translated in a rabbit reticulocyte mRNA-dependent system showed a marked increase in albumin synthesis in the ethanol-fed group. Analysis of RNA molecules separated according to molecular weight by gel electrophoresis and hybridized with recombinant-cloned albumin cDNA demonstrated an increase in full-sized albumin mRNA species in ethanol-fed animals. Therefore, chronic ethanol administration appears to increase albumin synthesis by increasing the steady-state level of biologically active albumin mRNA in liver membrane-bound polysomes. Despite development of fatty liver, the protein synthesis machinery functions normally.

Albumins↗
PubMedDate not supplied

Effects of dexamethasone on albumin and collagen gene expression in primary cultures of adult rat hepatocytes.

To further our studies on collagen gene expression, we have evaluated the molecular basis for the finding that steroids decrease collagen synthesis in cultured hepatocytes. We studied the effects of dexamethasone on primary cultures of adult rat hepatocytes grown on tissue culture plastic in either serum-supplemented medium or a serum-free hormonally defined medium. Cells were plated and allowed to attach for 24 hr in a mixture of serum-supplemented medium + hormonally defined medium. Cultures were then fed every 24 hr for 4 days under 1 of 4 conditions: serum-supplemented medium, serum-supplemented medium + dexamethasone, hormonally defined medium or hormonally defined medium + dexamethasone. On the fifth day, RNA was extracted. Dexamethasone did not affect the amount of RNA isolated; nor did it influence the quantitative translation of the mRNA in the rabbit reticulocyte lysate mRNA-dependent system. Employing hybridization analysis, dexamethasone resulted in increased albumin mRNA content in hepatocytes grown in serum-supplemented medium but had no affect on hormonally defined medium, and decreased type I in collagen mRNA content in cells grown in either serum-supplemented medium or hormonally defined medium. In cells cultured in hormonally defined medium, the beta-actin and procollagen mRNA levels were lower than those in serum-supplemented medium, but albumin mRNA levels were higher, and in fact equivalent to those in vivo. beta-Actin mRNA levels were not affected by dexamethasone in either serum-supplemented medium or hormonally defined medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMedDate not supplied

Development of molecular hybridization technology to evaluate albumin and procollagen mRNA content in baboons and man.

We have developed the methodology for evaluating the effects of pathophysiological conditions on the molecular mechanisms of hepatic protein synthesis and fibrogenesis in baboons and man. Total RNA was extracted from percutaneous liver biopsies of five baboons who were chronically fed an ethanol-rich liquid diet, their pair-fed controls and from humans with a variety of liver abnormalities. Chronic alcohol administration in baboons with liver fibrosis and normal serum albumin levels increased in vitro protein synthesis as measured by [35S]methionine incorporation, albumin mRNA content and Type I procollagen mRNA content. There was no difference in the beta-actin (a constitutive protein) mRNA content. In humans, serum albumin levels correlated with albumin mRNA content as indicated by the intensity of dot blot hybridization and Type I procollagen mRNA levels correlated with the activity of liver fibrosis. The use of RNA-DNA hybridization to investigate procollagen mRNA from human biopsies appears to be a valuable tool for evaluating the potential for collagen synthesis and the future course of liver disease. Besides the use of RNA-DNA hybridization, we describe other methodologies which are useful in delineating the levels of gene expression responsible for hepatic mRNA regulation in normal liver and disease states in man. The use of molecular techniques to evaluate human liver disease provides an opportunity to develop clinically relevant information while at the same time offering the additional advantage of providing fundamental knowledge about fibrogenesis.

Albumins↗
PubMedDate not supplied

Cationic lipid polymerization as a novel approach for constructing new DNA delivery agents.

In vivo gene delivery mediated by cationic lipids is often compromised by aggregation due to complexation with proteins in the blood. To improve the stability of cationic lipid-DNA complexes, the present study aimed to develop a novel approach in which a poly(cationic lipid) (PCL) is utilized to form stable cationic polyplexes for gene transfection. Hydrogenation of the acrylamide analogue of betaAE-DMRI, the polymerizable precursor of PCL, provided a monomeric lipid derivative (MHL) which was used for direct comparison of corresponding lipoplex stability, toxicity, and transfection activity. Various formulations of cationic liposomes, such as MHL, MHL-cholesterol (Chol), PCL, PCL-Chol, DOTAP-Chol, and commercially available lipofectamine were generated and examined in this study. The new poly(cationic lipid) did not display any significant toxicity to rat hepatocytes or Hep G2 cells as indicated by an LDH leakage assay. Furthermore, PCL was significantly less toxic than MHL, DOTAP-Chol or lipofectamine. Suspensions of PCL were resistant to aggregation even after 24 h of exposure to solutions containing 50 and 100% fetal bovine serum (FBS). In contrast, suspensions of lipofectamine extensively aggregated after 24 h of exposure to 50% FBS. To examine the influence of lipid polymerization on gene transfer activity, liposome-mediated transfections of a luciferase vector (pGL3) were performed in Hep G2 and Alexander cell lines. The luciferase activity of the PCL formulations in Hep G2 cells were similar to those of the MHL, DOTAP-Chol and lipofectamine formulations, demonstrating that lipid polymerization does not compromise transfection activity. In comparison to the monomeric precursor MHL and to the industry transfection standards DOTAP and lipofectamine, the novel poly(cationic lipid) exhibited the lowest cytotoxicity, was the most resistant to serum-induced aggregation and had comparable transfection activity when coformulated with cholesterol. This novel polymerization approach for the development of stable and active polyplexes may prove a valuable alternative for in vivo gene delivery.

Animals↗
PubMedDate not supplied

Albumin and procollagen type I gene regulation in alcohol and viral-induced human liver disease.

Common features of chronic alcoholic liver disease are progressive hypoalbuminemia and liver fibrosis. The molecular mechanisms which account for these effects are still controversial. Therefore, in the present study we evaluated albumin and collagen gene expression in livers of alcohol abusers and patients with viral-induced liver disease. Albumin and pro-alpha 1 (I) collagen mRNA levels were determined in 30 patients who underwent diagnostic liver biopsy. Of 14 alcoholics, 7 had alcoholic hepatitis alone, while the other 7 had cirrhosis plus alcoholic hepatitis. Of 16 non-alcoholic patients with chronic viral infection, 6 had chronic active hepatitis and 10 cirrhosis plus chronic active hepatitis. Total RNA was extracted from a portion of each biopsy, hybridized with a human albumin or collagen cDNA clone and compared to 2 normal surgical specimens which served as controls. The Northern hybridization studies revealed that: despite the presence of inflammation and fibrosis, the albumin mRNA levels of alcoholics were similar to normal controls; these alcoholics had significantly higher levels of albumin mRNA than did patients with similar histological stages of disease due to viral infection; and all the categories of patients had markedly increased procollagen mRNA levels when compared to controls. Given these results it is tempting to speculate that alcohol may actually increase albumin mRNA content in man as it does in animals. Furthermore, the increased procollagen mRNA levels in fibrotic livers suggest that an increase in collagen synthesis may be a significant factor in the pathogenesis of hepatic fibrosis.

Albumins↗