Biomedical subjects

W Gerok

Publications and source records attributed to W Gerok.

At least 19 recordsLinked to original sources

PubMed1992

Cell volume and bile acid excretion.

The interaction between cell volume and taurocholate excretion into bile was studied in isolated perfused rat liver. Cell swelling due to hypo-osmotic exposure, addition of amino acids or insulin stimulated taurocholate excretion into bile and bile flow, whereas hyperosmotic cell shrinkage inhibited these. These effects were explained by changes in Vmax of taurocholate excretion into bile: Vmax. increased from about 300 to 700 nmol/min per g after cell swelling by 12-15% caused by either hypo-osmotic exposure or addition of amino acids under normo-osmotic conditions. Steady-state taurocholate excretion into bile was not affected when the influent K+ concentration was increased from 6 to 46 mM or decreased to 1 mM with iso-osmoticity being maintained by corresponding changes in the influent Na+ concentration. Replacement of 40 mM-NaCl by 80 mM-sucrose decreased taurocholate excretion into bile by about 70%; subsequent hypo-osmotic exposure by omission of sucrose increased taurocholate excretion to 160%. Only minor, statistically insignificant, effects of aniso-osmotic cell volume changes on the appearance of bolus-injected horseradish peroxidase in bile were observed. Taurocholate (400 microM) exhibited a cholestatic effect during hyperosmotic cell shrinkage, but not during hypo-osmotic cell swelling. Both taurocholate and tauroursodeoxycholate increased liver cell volume. Tauroursodeoxycholate stimulated taurocholate (100 microM) excretion into bile. This stimulatory effect was strongly dependent on the extent of tauroursodeoxycholate-induced cell swelling. During continuous infusion of taurocholate (100 microM) further addition of tauroursodeoxycholate at concentrations of 20, 50 and 100 microM increased cell volume by 10, 8 and 2% respectively, in parallel with a stimulation of taurocholate excretion into bile by 29, 27 and 9% respectively. There was a close relationship between the extent of cell volume changes and taurocholate excretion into bile, regardless of whether cell volume was modified by tauroursodeoxycholate, amino acids or aniso-osmotic exposure. The data suggest that: (i) liver cell volume is one important factor determining bile flow and biliary taurocholate excretion; (ii) swelling-induced stimulation of taurocholate excretion into bile is probably not explained by alterations of the membrane potential; (iii) bile acids modulate liver cell volume; (iv) taurocholate-induced cholestasis may depend on cell volume; (v) stimulation of taurocholate excretion into bile by tauroursodeoxycholate can largely be explained by tauroursodeoxycholate-induced cell swelling.

Amino Acids↗

PubMed1992

Liver cell volume and protein synthesis.

Protein synthesis in isolated rat hepatocytes was determined from the incorporation of [3H]leucine (4 mM) into acid-precipitable material in the presence of amino acids at twice their physiological concentration. Protein synthesis increased linearly with time and incubated cell protein, and was inhibited by cycloheximide by more than 95%. In normo-osmotic incubations containing amino acids at twice the physiological concentration the rate of [3H]leucine incorporation was 5.8 +/- 0.2 nmol/h per mg of cell protein (n = 26). Hyperosmotic cell shrinkage due to addition of 60 mM-NaCl or 120 mM-raffinose inhibited [3H]leucine incorporation into acid-precipitable material by 60 and 74% respectively, whereas hypo-osmotic cell swelling was ineffective. Inhibition of protein synthesis by adding 120 mM-raffinose was largely counteracted by simultaneous lowering of the NaCl concentration by 60 mM. Glutamine (10 mM) had no effect on protein synthesis in normo-osmotic incubations (320 mosM), but stimulated protein synthesis in hyperosmotically (440 mosM) pre-shrunken cells almost to rates found in normo-osmotic (320 mosM) control incubations. Cyclic AMP and vasopressin inhibited protein synthesis by 23% and 8% respectively, whereas insulin and phenylephrine were ineffective. However, inhibition of protein synthesis by cyclic AMP was about twice as strong in the presence of vasopressin or phenylephrine. When protein synthesis was preinhibited by cyclic AMP, [3H]leucine incorporation was stimulated by glutamine (10 mM), insulin or hypo-osmotic exposure. There was a close relationship between the inhibition of protein synthesis and the extent of hepatocyte shrinkage induced by the above-mentioned effectors, suggesting a role of cell volume in the regulation of hepatic protein synthesis.

Animals↗

PubMed1992

Inhibition of protein N-glycosylation by 2-deoxy-2-fluoro-D-galactose.

The effects of 2-deoxy-2-fluoro-D-galactose (dGalF) on N- and O-glycosylation of proteins was studied in rat hepatocyte primary cultures and in human monocytes. In hepatocytes, dGalF at concentrations of 1 mM or higher completely inhibited N-glycosylation of alpha 1-antitrypsin and alpha 1-acid glycoprotein, whereas 4 mM-2-deoxy-D-galactose (dGal) only slightly impaired N-glycosylation. In monocytes, 1 mM- or 4 mM-dGalF blocked N-glycosylation of alpha 1-antitrypsin and of interleukin-6, while O-glycosylation of interleukin-6 remained unaffected. In monocytes, dGal had no effect on protein N-glycosylation. Addition of uridine effectively prevented the UTP deficiency induced by dGalF, but had no effect on the inhibition of protein N-glycosylation by dGalF. Using 19F-n.m.r. spectroscopy, 2-deoxy-2-fluoro-D-galactose 1-phosphate (dGalF-1-P), UDP-dGalF and UDP-dGlcF could be identified as the major metabolites of dGalF in hepatocytes as well as in monocytes. In conclusion, compared with dGal, dGalF is a more efficient inhibitor of protein N-glycosylation. The effect is not caused by the depletion of UTP induced by dGalF, but rather by metabolites of dGalF. dGalF is metabolized not only in hepatocytes but also in peripheral blood monocytes, which can be used for ex vivo studies of disturbances in D-galactose metabolism.

Animals↗

PubMed1992

[Current insights on the pathogenesis of chronic inflammatory bowel diseases].

The pathogenesis and etiology of inflammatory bowel disease (IBD) is poorly understood. As a matter of fact, it is not even certain whether either one is a single entity with different forms of clinical manifestations, or whether each one represents a single clearly separable entity. Common features of both diseases are chronic persistence, recurrent exacerbation and remission, the production of autoantibodies, as well as the expression of aberrant HLA-class II molecules on the surface of epithelial cells on the site of inflammation gut. It is likely that these events involve a disturbed immunoregulatory function or autoimmune process. Since the beginning of investigation the cause of IBD, infectious agents (bacteria, virus, mycobacterium paratuberculosis and others) or bacterial products (endotoxin, peptidoglycans from the bacterial cell wall) have been considered as primary causes. Epidemiological studies showed a marked increase of the incidence rates of IBD in industrial countries leading to the hypothesis, that environmental factors could play a role in the pathogenesis of the disease. So far it is clear that the major identified risk factor for IBD is a genetic susceptibility confirmed by studies showing a positive family history.

Colitis, Ulcerative↗

PubMed1992

[Primary prevention of varicose bleeding: current status].

1. Surgical shunts should be abandoned for prevention of the first bleeding because of an increased mortality rate, despite a marked reduction in frequency of bleeding. 2. Sclerotherapy is not recommended for clinical practice in preventing the first bleeding. The meta-analysis of numerous randomized clinical trials shows a small effect on bleeding risk and mortality rate. But these effects are remarkably heterogenous in various studies and are compensated by the complications of sclerotherapy. 3. Prophylactic treatment with beta-blockers has similar results as sclerotherapy documented by meta-analysis of several studies. In contrast to sclerotherapy both risk and side effects are minimal. More controlled clinical trials are needed to define subgroups of patients with higher benefit of the prophylaxis. In individual high-risk patients (size of varices, liver dysfunction, red-colour-signs) beta-blocker prophylaxis may have possible benefit.

Adrenergic beta-Antagonists↗

PubMed1992

Increased prostaglandin PGE2 and 6-keto-PGF1 alpha immunoactivity in incubates of gastric mucosa and forestomach of nephrectomized rats.

Prostaglandin E2 (PGE2)- and 6-keto-PGF1 alpha-like immunoactivity was measured in incubates of forestomach and gastric corpus mucosa in (a) unoperated rats, (b) rats with sham-operation of the kidneys and (c) rats with bilateral nephrectomy. In addition the mean ulcer area in the forestomach and gastric mucosa was assayed in all three groups of rats. The PGE2- and 6-keto-PGF1 alpha-like immunoactivity in gastric mucosa incubates and 6-keto-PGF1 alpha in the forestomach incubates was almost the same in unoperated and sham-operated rats. Increased 6-keto-PGF1 alpha in the forestomach and of PGE2 and 6-keto-PGF1 alpha in the gastric mucosa was found in rats with bilateral nephrectomy before gastric lesions were seen. A higher mean ulcer area occurred in the forestomach and gastric mucosa 24-48 h after bilateral nephrectomy. We conclude, that the increased PGE2- and 6-keto-PGF1 alpha production by the gastric mucosa and forestomach was associated with the loss of normal renal tissue function. Despite the protection of PGE2 and PGI2 by gastric tissue, gastric lesions nevertheless occur in acute uraemic rats.

6-Ketoprostaglandin F1 alpha↗

PubMed1992

Biosynthesis and excretion of gangliosides by the isolated perfused rat liver.

De novo synthesis and excretion into perfusate and bile fluid of hepatic gangliosides were studied in isolated perfused rat livers. Addition of N-acetyl-[6-3H(n)]D-mannosamine to the perfusate resulted in radioactive synthesis of at least eight gangliosides labeled in their sialic acid residues. About 10% of total de novo synthesized gangliosides were excreted into the perfusate, less than 1% into the bile fluid. Labeled gangliosides were tentatively identified by cochromatography with known standards. All of them are known to occur in rat liver and sera. The results indicate that most, if not all, normal serum gangliosides are synthesized in the liver; excretion with bile fluid is negligible. They explain previous observations, and indicate clinical implications, which are discussed.

Animals↗

PubMed1992

Cell swelling increases bile flow and taurocholate excretion into bile in isolated perfused rat liver.

The effects of aniso-osmotically and amino-acid-induced cell-volume changes on bile flow and biliary taurocholate excretion were studied in isolated perfused rat liver. With taurocholate (100 microM) in the influent perfusate, hypo-osmotic exposure (225 mosmol/l) increased taurocholate excretion into bile and bile flow by 42 and 27% respectively, whereas inhibition by 32 and 47% respectively was observed after hyperosmotic (385 mosmol/l) exposure. The effects of aniso-moticity on taurocholate excretion into bile was observed throughout aniso-osmotic exposure, even after completion of volume-regulatory ion fluxes and were fully reversible upon re-exposure to normo-osmotic media. Hypo-osmotic cell swelling (225 mosmol/l) increased the Vmax. of taurocholate translocation from the sinusoidal compartment into bile about 2-fold. Also, cell swelling induced by glutamine and glycine stimulated both bile flow and biliary taurocholate excretion. There was a close relationship between the aniso-osmotically and amino-acid-induced change of cell volume and taurocholate excretion into bile. The data suggest that liver cell volume plays an important role in regulating bile-acid-dependent bile flow and biliary taurocholate excretion.

Amino Acids↗

PubMed1992

High concentrations of soluble tumor necrosis factor receptors in ascites.

Ascites and plasma concentrations of soluble tumor necrosis factor receptors p55 and p75 were measured in a prospective study in 34 patients (35 occasions of ascites) with hepatic (5 infected and 21 uninfected) and malignancy-related (9) ascites. All patients had high concentrations of both soluble tumor necrosis factor receptors in ascites and plasma; these were about 500 times higher than the corresponding tumor necrosis factor-alpha concentrations. Ascites levels of soluble tumor necrosis factor receptors p55 and soluble tumor necrosis factor receptors p75 were significantly elevated in patients with malignancy-related (p55: 26.0 +/- 8.6 ng/ml; p75: 20.5 +/- 17.4 ng/ml; mean +/- S.D.) and infected ascites (p55: 25.1 +/- 10.9 ng/ml, p75: 22.6 +/- 11.0 ng/ml) compared with patients with uncomplicated hepatic ascites (p55: 10.1 +/- 4.4 ng/ml; p75: 6.0 +/- 2.6 ng/ml). Patients with infected or malignancy-related ascites also showed higher soluble tumor necrosis factor receptor concentrations in plasma than did patients with plain hepatic ascites. Successful antibiotic treatment of peritonitis reduced soluble tumor necrosis factor receptor p55 and p75 ascites levels in three patients from 24.2 +/- 15.2 ng/ml to 10.7 +/- 1.9 ng/ml and from 20.2 +/- 14.4 ng/ml to 7.5 +/- 1.8 ng/ml, respectively. Soluble tumor necrosis factor receptors p55 and p75 at cutoff levels of 16.5 ng/ml and 9.5 ng/ml, respectively, differentiated between infected or malignant and plain hepatic ascites with diagnostic accuracies of 94% and 89%, respectively. They did not differentiate between infected and malignant ascites. The concentrations of soluble tumor necrosis factor receptor p55 were usually higher in ascites than in plasma in all subgroups of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Cause and frequency of posttransfusion hepatitis after open-heart surgery.

A total of 1476 patients who underwent open-heart surgery between 1986 and 1988 participated in a prospective study examining posttransfusion hepatitis. They received a total of 8327 units of whole blood, packed erythrocytes, or fresh frozen plasma. The aminotransferase activities were measured preoperatively and 1, 2, 3, 4, 6, 9, 12, and 24 weeks after the operation. Thirty-four patients in all (2.3% of the transfused patients) developed posttransfusion hepatitis, which could be identified as hepatitis B in 1 patient and hepatitis C in 14 patients. No cause for posttransfusion hepatitis could be found in 19 cases (hepatitis of unknown origin). Hepatitis C became chronic in 5 patients. In contrast to hepatitis C, the 19 patients with hepatitis of unknown origin all showed a milder clinical course with lower maximal aminotransferase activities and a shorter duration of the hepatitis. A chronic course was not observed among them. The cause of hepatitis of unknown origin is discussed.

Adult↗

PubMed1992

Metabolic alkalosis as driving force for urea synthesis in liver disease: pathogenetic model and therapeutic implications.

Despite a marked reduction of the urea cycle capacity, patients with well-compensated chronic liver disease excrete near-normal amounts of urea. Compensation of the urea cycle defect apparently occurs through the activation of liver glutaminase, as suggested by an inverse relationship between the in vitro ureagenic capacity and the flux through glutaminase in liver tissue from patients with a normal, fatty, or cirrhotic liver. In these patients, the flux through glutaminase, as determined in vitro, increases in parallel with the plasma bicarbonate level and plasma pH determined in vivo. In view of this and results from previous studies, the following hypothesis is suggested: The decrease of urea cycle enzyme activities in liver cirrhosis produces metabolic alkalosis due to an impaired bicarbonate elimination. Alkalosis in turn activates and stabilizes hepatic glutaminase and accordingly mitochondrial ammonia provision for carbamoylphosphate synthetase. This results in a compensatory stimulation of the urea cycle flux in the cirrhotic patient to near-normal rates, despite the marked reduction of urea cycle enzyme activity. Accordingly, alkalosis is an important driving force for urea synthesis in the cirrhotic patient. With respect to clinical medicine, attention must be paid to acid-base disturbances in the hyperammonemic patient.

Alkalosis↗

PubMed1992

N-glycosylation of membrane glycoproteins in retinol-deficient rat liver.

The effect of vitamin A deficiency on N-linked oligosaccharides of membrane glycoproteins was studied in rat liver in order to evaluate the suggested role of retinol in protein N-glycosylation. First, oligosaccharides of newly synthesized glycoproteins from rough endoplasmic reticulum of vitamin A deficient liver were compared with that of pair-fed controls. Oligosaccharides were metabolically labelled with D-[2-3H]mannose, released from the glycoproteins with endoglycosidase H, purified by reversed phase HPLC and ion exchange chromatography, and were reduced with sodium borohydride. HPLC fractionation of the oligosaccharide alditols showed that the glycoproteins carried mainly four oligosaccharide species, Glc1Man9GlcNAc2, Man9GlcNAc2, Man8GlcNAc2 and Man7GlcNAc2, in identical relative amounts in the vitamin A deficient and the control tissue. In particular, no increase in the proportion of short chain oligosaccharides was noted in vitamin A deficient liver. Second, the number of N-linked oligosaccharides was estimated in dipeptidylpeptidase IV (DPP IV), a major glycoprotein constituent of the hepatic plasma membrane, comparing the newly synthesized glycoprotein from rough endoplasmic reticulum and the mature form of DPP IV from the plasma membrane. No evidence was obtained that retinol deficiency caused incomplete glycosylation of this membrane glycoprotein. From these data, the suggested role of retinol as a cofactor involved in the synthesis of N-linked oligosaccharides of glycoproteins must be questioned.

Animals↗

PubMed1992

Human serum gangliosides in hypercholesterolemia, before and after extracorporeal elimination of LDL.

Total content, pattern and transport by lipoproteins of gangliosides have been studied in the sera of 10 patients with hypercholesterolemia and manifest cardiovascular disease. Half of the patients with hypercholesterolemia and 3 healthy controls were treated with heparin-induced extracorporeal LDL precipitation (HELP). In the sera of the untreated group total gangliosides and cholesterol were elevated about 2-fold. Ratios of normal ganglioside components were not altered and abnormal ganglioside species not detected. Treatment with HELP resulted in an almost selective removal of lipid-bound sialic acid carried on LDL. The re-increase of total serum gangliosides was strictly correlated to that of LDL-cholesterol and apolipoprotein B. Total gangliosides and ratios of individual components carried on single LDL- and HDL-particles were not altered by the HELP treatment. Our results indicate that gangliosides are excreted into the serum along with nascent apolipoprotein B-containing lipoproteins, which are of hepatic origin. In hypercholesterolemia excretion of gangliosides into the circulation is elevated and surplus of circulating gangliosides is bound to increased numbers of 'atherogenic' LDL. Biosynthesis of different ganglioside components, most probably by the liver, and total amount of gangliosides bound to lipoprotein particles seem not to be altered.

Adult↗

PubMed1992

Evidence for the production of high amounts of interleukin-6 in the peritoneal cavity of patients with ascites.

The ascites and serum concentrations of interleukin-6 (IL-6) and interleukin-1 (IL-1) were determined in 21 patients with hepatic ascites and in 9 patients with malignancy-associated ascites. There was no evidence for bacterial peritonitis in any patients. All ascites samples contained high amounts of immunoreactive IL-6 [hepatic ascites 1730 +/- 2130 pg/ml (mean +/- SD), 1160 pg/ml (median); malignant ascites 4020 +/- 1510 pg/ml (mean), 3820 pg/ml (median)] but no IL-1. The mean ascites to serum ratios of IL-6 were 96 (median 49) in patients with hepatic ascites and 587 (median 480) in patients with malignant ascites. Ascites IL-6 was biologically active as determined by the B9 cell bioassay. The results indicate that even in the absence of infection IL-6 is produced in high amounts in the peritoneal cavity of patients with hepatic or malignant ascites.

Adult↗

PubMed1992

Uridine catabolism by the isolated perfused rat liver.

A new approach in the treatment of gastrointestinal tumors with 5-fluorouracil involves the infusion of high doses of uridine to improve the chemotherapeutic efficiency of the former. High amounts of uracil formed from uridine can interfere with the hepatic catabolism of 5-fluorouracil and thus increase its bioavailability and toxicity. In our study, we analysed the metabolite pattern of uridine in the effluent of isolated perfused rat livers in relation to portal uridine levels. The livers were perfused hemoglobin-free without recirculation at a constant flow. In the perfusate, uridine was changed from 0.5 to 100 mumol/l. The complete degradation of [2-14C]uridine and [2-14C]uracil was monitored via the release of labeled CO2. Radioactive catabolites of uridine including uracil and the sum of dihydrouracil and beta-ureidopropionate were separated by high-performance liquid chromatography and counted using a radioactivity flow monitor. Portal uridine concentrations were increased from 0.5 to 100 mumol/l and were accompanied by a rise in the relative amount of non-metabolized uridine in the effluent from 13 to 78%. At uridine concentrations above 50 mumol/l, there was a constant release of uracil into the effluent, indicating saturation of uridine phosphorolysis or transport. The amount of 14CO2 formed by the liver reflecting complete uridine breakdown was higher than any other uridine metabolite when uridine concentration varied from 0.5 to 15 mumol/l. Saturation of 14CO2 formation was achieved at a uridine concentration of 25 mumol/l. Higher peak values of 14CO2 release were observed after direct infusion of equivalent amounts of uracil into the portal vein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Anisoosmostic liver perfusion: redox shifts and modulation of alpha-ketoisocaproate and glycine metabolism.

1) In isolated perfused rat liver, 14CO2 production from [1-14C]alpha-ketoisocaproate or [1-14C]glycine as well as ketogenesis from alpha-ketoisocaproate were stimulated upon exposure to hypoosmotic perfusion media, whereas hyperosmotic exposure inhibited. The effects of anisotonicity were preserved when ketogenesis from alpha-ketoisocaproate and 14CO2 production from [1-14C]glycine were already stimulated by glucagon. On the other hand, ketogenesis from tyrosine (2 mM) or octanoate (0.1 mM) were almost unaffected by anisoosmotic exposure. 2) With all ketogenic substrates studied, hypoosmotic (hyperosmotic) cell swelling (shrinkage) decreased (increased) the beta-hydroxybutyrate/acetoacetate ratio in effluent perfusate. A shift of the mitochondrial and cytosolic NADH systems to a more oxidized (reduced) state following hypoosmotic (hyperosmotic) exposure was also found upon infusion of beta-hydroxybutyrate/acetoacetate and lactate/pyruvate as redox indicator metabolite couples. The effects of anisotonicity on the beta-hydroxybutyrate/acetoacetate ratio were reversible upon normoosmotic reexposure and persisted throughout anisoosmotic exposure despite completion of volume regulatory K+ fluxes within 10-15 min. Hepatic oxygen consumption decreased by about 10% during hyperosmotic cell shrinkage and was transiently stimulated during hypoosmotic exposure. 3) There was a close relationship between ketogenesis from alpha-ketoisocaproate (0.5 mM) and the mitochondrial redox state, as assessed by the beta-hydroxybutyrate/acetoacetate ratio in effluent, regardless of whether the pathway was modulated by anisotonicity or glucagon. 4) Isoosmotic cell swelling induced by addition of glutamine (3 mM) was without significant effect on ketogenesis from octanoate and stimulated ketogenesis and 14CO2production from [1-14C]alpha-ketoisocaproate only slightly (i.e. by less than 10%); however, in each case the hydroxybutyrate/acetoacetate ratio in effluent perfusate decreased by about 20% upon addition of glutamine. 5) Stimulation of 14CO2production from [1-14C]glycine by hypoosmotic exposure and glucagon was only slightly affected when the accompanying decrease of the beta-hydroxybutyrate/acetoacetate ratio was reversed by addition of beta-hydroxybutyrate. 6) The data are compatible with a hypotonicity (hypertonicity)-induced shift of the mitochondrial NADH system to a more oxidized (reduced) state, probably due to a alterations of respiration. Mitochondrial swelling probably also occurs under the influence of glutamine. Modulation of ketogenesis from alpha-ketoisocaproate, but not of glycine oxidation by anisoosmotic exposure and glucagon can be related to the accompanying redox shifts. The observations support the concept that cell volume may be an important parameter determining liver cell function.

Animals↗

PubMed1991

Cell volume is a major determinant of proteolysis control in liver.

Hepatic proteolysis is inhibited by insulin, amino acids and hypoosmotic cell swelling and is stimulated by glucagon. These effectors simultaneously modulate cell volume in the intact liver, as shown by measurements of the intracellular water space. A close relationship exists between the effect on proteolysis and the accompanying cell volume change, regardless of whether hepatic proteolysis was modified by insulin, glucagon, cyclic AMP, glutamine, glycine, barium of hypoosmotic exposure. It is suggested that cell volume changes exerted by hormones and amino acids play a crucial role in the regulation of hepatic proteolysis.

Animals↗

PubMed1991

A simple and rapid method for the detection of RNA in formalin-fixed, paraffin-embedded tissues by PCR amplification.

A simple and rapid method for the extraction, reverse transcription and PCR amplification of RNA from formalin-fixed, paraffin-embedded tissue is described. The procedure can be completed within 24 hours. In a first application of this method we detect human albumin mRNA in liver tissue, demonstrating the feasibility to retrospectively analyze gene expression and RNA viruses in fixed tissue.

Albumins↗