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M Chojkier

Publications and source records attributed to M Chojkier.

At least 55 records · Page 3Linked to original sources
PubMed1986

Selective inhibition of collagen synthesis by the Ca2+ ionophore A23187 in cultured human fibroblasts.

The question of whether the Ca2+ ionophore A23187 affects collagen production relative to total protein synthesis or has possible effects on collagen degradation was investigated. Cultured normal human fibroblasts were incubated with radioactive proline, and the radioactivity of collagenase-sensitive and -resistant proteins was used to calculate the rates of protein production. The net production of collagen relative to total proteins was inhibited by A23187 in a dose-related manner, and 50% inhibition of basal collagen production was achieved with 0.6 microM A23187. There was a 70% decrease in the absolute rate of collagen production in the presence of 0.6 microM A23187 which represented a 4-fold greater inhibition of collagen production than of noncollagen protein production. The major mechanism for the decreased net production of collagen was decreased synthesis, rather than increased degradation. Ca2+ mobilization induced by cholecystokinin octapeptide was also associated with selective inhibition of collagen production in normal human fibroblasts. These studies establish that the Ca2+ ionophore A23187 induces a selective decrease in collagen polypeptide synthesis by normal human fibroblasts and suggest a modulatory role of Ca2+ on collagen metabolism.

Calcimycin↗
PubMed1986

A [4,5-3H]lysine:[14C]lysine dual-label method to measure lysine hydroxylation in collagen.

A new method has been developed to determine the extent of lysine hydroxylation in newly synthesized collagen. This method relies on the measurement of changes in the ratio of [3H]lysine:[14C]lysine in collagenase digests, resulting from loss of tritium from the C-5 position of lysine during hydroxylation. Lysine hydroxylation can be measured in the presence of large amounts of noncollagen proteins, and simultaneous quantitation of the relative rates of collagen and non-collagen protein production is obtained. The dual-label lysine method is simple, rapid, and accurate. There was a very good correlation between this method and column chromatography procedures currently used for the measurement of lysine hydroxylation.

Animals↗
PubMed1986

Predictors of outcome in massive upper gastrointestinal hemorrhage.

We reviewed 100 consecutive cases of massive upper gastrointestinal hemorrhage (UGIH). The criteria for inclusion were a decrease in hematocrit greater than or equal to 6%, unstable vital signs, and greater than or equal to units of blood transfused (16 +/- 18 units, mean +/- SD). A multiple regression analysis of 96 variables was employed to determine the most accurate predictors of outcome. The overall mortality was 35%. Hospital status (whether the patient was an inpatient or outpatient when the UGIH began) showed a striking association with mortality (70% for inpatients vs. 22% for outpatients, p less than 0.001). Nonsurvivors also had a greater number of life-threatening diseases than survivors (1.4 +/- 1.1 vs. 0.3 +/- 0.5, p less than 0.001) and greater transfusion requirements (27 +/- 20 units vs. 10 +/- 13 units, p less than 0.001). Age, the presence of cirrhosis, and recent excessive alcohol intake were not important risk factors. At presentation, the most reliable predictor of a fatal outcome was the brevity of the interval between the onset of bleeding and the initiation of a medical work-up. The primary predictor when considering the entire hospitalization was the number of life-threatening diagnoses. Our data indicate that stratification for hospital status and for other potentially predictive risk factors should be incorporated in future trials of therapy for UGIH.

Aged↗
PubMed1986

Asymptomatic primary biliary cirrhosis in an old man.

We report asymptomatic primary biliary cirrhosis (PBC) in an 83-year-old man. The diagnosis was based on an elevated alkaline phosphatase, a high titer antimitochondrial antibody, normal ERCP, and characteristic histological changes on liver biopsy.

Aged↗
PubMed1986

Hepatocyte collagen production in vivo in normal rats.

Although hepatocytes produce collagen in vitro, their contribution to hepatic collagen synthesis in vivo is unknown. To answer this question, we injected rats intraperitoneally with [3H]proline and [14C]ornithine. [3H]Proline labeled prolyl-t-RNA in both hepatocytes and nonparenchymal cells. In contrast, [14C]ornithine was rapidly converted to [14C]arginine via the urea cycle only in hepatocytes, labeling arginyl-t-RNA. Approximately 60% of the 14C in albumin and transferrin was present as arginine while the remainder was found in proline and related amino acids. As expected for proteins that have the same proline/arginine ratio and that are produced solely by the hepatocyte, the [3H]proline/[14C]arginine ratio was very similar in albumin and transferrin. Conversely, in nonparenchymal cells a negligible percentage of 14C was present as arginine. A sizeable percentage of the 14C in hepatic collagen was present as arginine; given the greater proline(+hydroxyproline)/arginine ratio in hepatic collagen, our data indicate that in normal rats, hepatocytes contribute most of newly synthesized hepatic collagen.

Animals↗
PubMed1986

Hepatic collagen production in the rat is unaffected by methotrexate.

Methotrexate (MTX) has been implicated in the pathogenesis of hepatic fibrosis. However, no information exists regarding the effects of MTX on hepatic collagen metabolism. Therefore, we studied the role of MTX in hepatic collagen production in vivo in rats receiving an 8-week course of varying doses of MTX. Twenty-four hours prior to sacrifice animals received an injection of [5-3H]proline. Collagen was extracted with hot trichloroacetic acid and the proteinbound [3H]hydroxyproline was used as a measure of de novo collagen production. The hepatic collagen content was essentially the same in the control and treatment groups in spite of evidence of hepatotoxicity. Similarly, no significant differences were present among the control and MTX-treated groups in the de novo absolute collagen production. In summary, we found no evidence of increased hepatic fibrogenesis in small groups of animals after 8 weeks of treatment with MTX. Data clearly supporting the claim that MTX itself is responsible for hepatic fibrosis are lacking.

Animals↗
PubMed1985

D-Galactosamine hepatotoxicity is associated with endotoxin sensitivity and mediated by lymphoreticular cells in mice.

Two strains of mice (C57BL/10ScN and C3H/HeJ) that carry the same mutant lipopolysaccharide gene (Lpsd) which makes them resistant to the toxic effects of endotoxin (LPS) are also partially resistant to the hepatotoxic effects of D-galactosamine. As measured by serum alanine aminotransferase, the degree of liver injury induced by D-galactosamine in the LPS-resistant strains is only 10%-30% that of closely related strains of LPS-sensitive mice. Similarly, histopathologic changes are less pronounced in the endotoxin-resistant strains than in LPS-susceptible mice. By transferring spleen cells from LPS-susceptible strains to lethally irradiated, LPS-resistant mice, we established that susceptibility to D-galactosamine is mediated by lymphoreticular cells. Radiation-resistant spleen cells transferred D-galactosamine sensitivity, suggesting a role for macrophages. We did not exclude the possibility that lymphocytes can also transfer the response to D-galactosamine. These results establish that in mice, D-galactosamine sensitivity is associated with endotoxin sensitivity and that the former is mediated by lymphoreticular cells, not by hepatocytes.

Animals↗
PubMed1984

[3H]tryptophan-[14C]proline dual label method for the simultaneous determination of collagen and noncollagen protein production.

A new method for the simultaneous determination of newly synthesized collagen and noncollagen proteins has been developed. Because tryptophan is not found in collagen noncollagen proteins were specifically labeled with [3H]tryptophan. [14C]Proline was used to label both groups of proteins. To calculate the 14C-labeled noncollagen protein the 3H radioactivity of the protein mixture was divided by the ratio of 3H:14C in noncollagen protein of a representative sample. This value was obtained by collagenase digestion. The remaining 14C radioactivity in the protein mixture was attributed to [14C]collagen. There was a very good correlation between the dual label method and the widely used collagenase digestion method for the measurement of collagen and noncollagen protein production and for the calculation of the relative rate of collagen synthesis. This new method provides a simple and accurate analysis of collagen production, and it is suitable for rapid processing of a large number of biological samples.

Animals↗
PubMed1983

Specifically decreased collagen biosynthesis in scurvy dissociated from an effect on proline hydroxylation and correlated with body weight loss. In vitro studies in guinea pig calvarial bones.

The question whether ascorbate regulates collagen production solely through its direct role in proline hydroxylation was investigated. Proteins in calvarial bones from control and scorbutic weanling guinea pigs were labeled in short-term cultures with radioactive proline. Proteins were digested with purified bacterial collagenase to distinguish between effects on collagen polypeptide production and hydroxyproline formation. There was a preferential decrease in the absolute rate of collagen biosynthesis beginning after 2 wk of ascorbate deficiency, and this effect was temporally dissociated from decreased proline hydroxylation. There were no significant changes in the absolute rates of collagen degradation or noncollagen protein production. In vitro inhibition of proline hydroxylation in normal bone with alpha, alpha'-dipyridyl did not affect the relative rate of collagen synthesis, further dissociating these functions. Ascorbate added to scorbutic bone cultures reversed defective proline hydroxylation but not defective collagen synthesis, suggesting that the latter was an indirect effect of scurvy. There was a linear correlation between the extent of body weight lost during the 3rd and 4th wk of scurvy and the rate of collagen synthesis in scorbutic bone. This correlation also applied to control animals receiving ascorbate, but with weight loss induced by food restriction. These studies establish for the first time that ascorbate deficiency in guinea pigs leads to a specific decrease in collagen polypeptide synthesis and suggest that this decrease results from the reduced food intake and/or weight-loss characteristic of scurvy.

Animals↗
PubMed1981

Measurement of portal-systemic shunting in the rat by using gamma-labeled microspheres.

A method for determining the extent of portal-systemic shunting (PSS) is described and evaluated in lightly anesthetized (ketamine) rats. This method relies on the intrasplenic injection of 15-micrometers gamma-labeled spheres and the subsequent measurement of liver and lung radioactivities. After the splenic injection of the microspheres, a fraction of microspheres shunting the hepatic sinusoidal bed will be entrapped in the lungs. Thus, the ratio, lung/(lung + liver) radioactivities, will indicate the degree of PSS. The percent of PSS was determined in normal (n = 13; 1.2 +/- 0.3%), in cirrhotic (n = 9; 15.0 +/- 4.5%; P less than 0.01), and in portal vein-ligated animals (n = 14; 95.0 +/- 0.9%; P less than 0.001 for normal and cirrhotic). In addition, PSS was sequentially quantitated (n = 3) before (3.0%) and after (89%) partial portal vein ligation. The variability of PSS found in cirrhotic rats (0.7-41.0%) is in agreement with the reported data for PSS in patients. This technique, which is simple, rapid, and reproducible, allows the quantitation of PSS in small laboratory animals.

Animals↗
PubMed1980

Esophageal tamponade in the treatment of bleeding varices. A decadel progress report.

Previous reports from this hospital in 1958 and 1967 have revealed that esophageal tamponade is a relatively dangerous type of treatment. Other investigators have been able to avoid many of the hazards of this technique. We have again assessed our results in 50 episodes of esophageal tamponade in bleeding esophageal varices in 39 patinets. Thirty-seven had alcoholic cirrhosis, one Wilson's disease, and one portal vein thrombosis. The diagnosis of variceal hemorrhage was established by endoscopy or angiography in virtually all. The great majority (86%) had had unsuccessful infusions of vasopressin previously. The Sengstaken-Blakemore tube (SBT) was used in 41 and the Linton tube (LT) in nine. Hemorrhage was controlled for at least 24 consecutive hours in 20 episodes (40%). Ninety percent of the patients died. Rupture of the esophagus following inflation of the gastric balloon in the esophagus caused three deaths (8%). Major nonfatal complications such as aspiration pneumonia occurred on five other occasions. Although the complications of esophageal tamponade were greatly reduced from our previous series, the efficacy of esophageal tamponade also decreased. There were no significant differences in the efficacy or complications of the SBT and LT. The high mortality and complication rates are still discouraging. We believe that the role of esophageal tamponade in the treatment of hemorrhage from varices is a secondary one.

Esophageal and Gastric Varices↗
PubMed1979

A controlled comparison of continuous intraarterial and intravenous infusions of vasopressin in hemorrhage from esophageal varices.

Infusions of intraarterial vasopressin (IAV) into the superior mesenteric artery have been shown to be effective in controlling hemorrhage from esophagogastric varices. Intravenous infusions of vasopressin (IVV), which can be initiated rapidly and require less sophisticated equipment and personnel, have also been reported to control variceal hemorrhage. We undertook a controlled clinical trial to compare these two routes of administration. Twenty-two cirrhotic patients with massive hemorrhage from varices were randomized to receive either IVV or IAV. Intraarterial vasopressin was begun at 0.1 U/min and increased progressively as needed to 0.2, 0.3, 0.4, and 0.5 U/min. Intravenous vasopressin was begun at 0.3 U/min and increased progressively as needed to 0.6, 0.9, 1.2, and 1.5 U/min. Hemorrhage was controlled in 5 of 10 episodes (50%) with IVV and in 6 of 12 episodes (50%) with IAV. Seven of the ten episodes treated with IVV (70%) ended fatally compared with 9 of 12 treated with IAV (75%). Side-effects and complications occurred with similar frequency in the two groups. The two routes of administration are equal in effects, side-effects, and complications. We recommend that IVV, which can be administered more easily, be given a brief therapeutic trial early in the management of hemorrhage from varices.

Adult↗
PubMed1978

Spontaneous meningococcal peritonitis: a report of two cases.

Two patients with spontaneous bacterial peritonitis caused by Neisseria meningitidis are described. In both cases immediate diagnosis was possible by examination of the ascitic fluid. Meningococcal peritonitis supports the hypothesis that the hematogenous spread of bacteria into the ascitic fluid may be one of the mechanisms of spontaneous bacterial peritonitis.

Adult↗
PubMedDate not supplied

Bioluminescence assays for bile acids in the detection and follow-up of experimental liver injury.

We evaluated the usefulness of recently developed bioluminescence assays for serum bile acids (BA) in the detection and follow-up of experimental liver injury. Liver damage was induced in rats by either D-galactosamine or CCl4, and BA were compared to SGPT and aminopyrine breath test (ABT). In severe liver injury, following D-galactosamine administration, all three methods revealed a significant difference from control values. The degree of abnormality was, however, far greater with SGPT and BA than with ABT. In moderate liver injury, induced by CCl4, the increase in BA was not significant. Values of SGPT and BA showed a very good correlation (3 alpha-OH: r = 0.88; 7 alpha-OH: r = 0.90; 12 alpha-OH: r = 0.83; p less than 0.001 for all correlations). Application of different assays for 3 alpha-OH, 7 alpha-OH and 12 alpha-OH BA allowed us to assess changes in individual BA. A 96-hr follow-up study in D-galactosamine-treated animals showed an increase in BA up to 48 hr and a decrease thereafter. The bioluminescence assays for BA are simple, rapid and require only 10 microliter of serum. Thus, these assays may be the method of choice in detecting and monitoring liver injury in small laboratory animals.

Alanine Transaminase↗
PubMedDate not supplied

Acetaldehyde stimulates collagen and noncollagen protein production by human fibroblasts.

The mechanisms responsible for the increased hepatic collagen deposition in alcoholic cirrhosis remain unknown. The question of whether ethanol or acetaldehyde has a direct effect on collagen and noncollagen protein production was investigated in human fibroblasts with no detectable activity of alcohol dehydrogenase to distinguish the effects of these metabolites. To eliminate environmental factors, protein production by confluent human skin, fetal and hepatic fibroblasts was studied after three passages. Cells were labeled with [5-3H]proline for 4 hr in the presence of 0.2 mM ascorbate alone or with addition of either ethanol (50 mM) or acetaldehyde (0 to 300 microM). Rates of protein production were calculated from the radioactivities of collagenase-sensitive and collagenase-resistant proteins. Skin fibroblasts from alcoholic individual either with cirrhosis or without liver disease have comparable rates of collagen and noncollagen protein production. Acetaldehyde, in a concentration found in the liver during ethanol abuse, significantly increased collagen production by human skin fibroblasts (up to 140%), fetal fibroblasts (up to 240%) and hepatic fibroblasts (up to 70%) but the addition of ethanol had no significant effect on basal collagen production. The effect of acetaldehyde was dose-related and affected noncollagen protein production in a similar manner. Acetaldehyde did not cause changes in either proline transport or the specific activity of the proline precursor pool. This newly recognized stimulation of collagen production by acetaldehyde may be a possible mechanism of fibrogenesis in alcoholic individuals.

Acetaldehyde↗