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Biomedical subjects

J Dich

Publications and source records attributed to J Dich.

At least 37 records · Page 2Linked to original sources
PubMed1993

Inhibition of fatty acid synthesis in rat hepatocytes by exogenous polyunsaturated fatty acids is caused by lipid peroxidation.

Rat hepatocyte long-term cultures were utilized to investigate the impact of different polyunsaturated fatty acids (PUFA) on the insulin-induced de novo fatty acid synthesis in vitro. The addition of 0.5 mM albumin-complexed oleic, linoleic, columbinic, arachidonic, eicosapentaenoic or docosahexaenoic acid resulted in a marked suppression of fatty acid synthesis. By evaluation of cell viability (determined as the leakage of lactate dehydrogenase (LDH) it turned out, that the antioxidant used (50 microM alpha-tocopherol phosphate) had a low antioxidant activity, resulting in cytotoxic effects by the peroxidized PUFA. Arachidonic acid and eicosapentaenoic acid showed a dose- and time-dependent cytotoxicity. Two other antioxidants: 50 microM alpha-tocopherol acid succinate and 1 microM N,N'-diphenyl-1,4-phenylenediamine, both proved more efficient than alpha-tocopherol phosphate. There was a significant correlation between LDH-leakage and inhibition of fatty acid synthesis. Lipid peroxidation, measured as thiobarbituric acid-reactive substances, also showed a significant correlation with the degree of inhibition of fatty acid synthesis. Furthermore, PUFA had no inhibitory effect on fatty acid synthesis when peroxidation was minimized by the use of proper antioxidants. These data indicate that PUFA in vitro inhibit the insulin-induced de novo fatty acid synthesis in hepatocytes from starved rats, due to cytotoxic effects caused by lipid peroxidation.

Animals↗
PubMed1992

Regulation by growth hormone and glucocorticoid of testosterone metabolism in long-term cultures of hepatocytes from male and female rats.

The activities of 2-, 6 beta-, 7 alpha- and 16 alpha-testosterone hydroxylase and 5 alpha-testosterone reductase were measured in intact hepatocytes from male and female rats cultured for 8 days in a modified Waymouth medium supplemented with 0.1 or 1.0 microM dexamethasone with or without addition of 1 microgram/mL growth hormone. During culture of hepatocytes from female rats the activity of the male-specific 16 alpha-testosterone hydroxylase increased. This increase was significantly inhibited at day 8 by 1 microM dexamethasone as well as by growth hormone. Furthermore, in cultures of hepatocytes from male rats, the activity of the constitutive 16 alpha-testosterone hydroxylase was decreased by 1 microM dexamethasone as well as by growth hormone. The induction of 6 beta-testosterone hydroxylase by dexamethasone was suppressed by growth hormone in hepatocytes from both male and female rats, while the 7 alpha-testosterone hydroxylase activity was unaffected by culture time, hormone additions and gender. The decrease in female-specific 5 alpha-reductase activity with culture time in hepatocytes from female rats was significantly attenuated by growth hormone at 0.1 microM dexamethasone. The effects of growth hormone on testosterone hydroxylase activities in hepatocyte cultures from male and female rats are in accordance with the concept of growth hormone as a "feminization signal". The results suggest that the glucocorticoid-dependent expression of the male constitutive 16 alpha-hydroxylase requires periods of low levels of growth hormone.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1992

A perifusion system for cultured hepatocytes.

A perifusion system for primary cultures of hepatocytes is described. The system accommodates 20 rotated petri dishes (60 mm) and allows individual medium composition and sampling for each dish. Cell number and insulin (15 pM to 7.7 nM) were stable in the system for at least 24 h. The dose-response relationship for induction by insulin of glucokinase and pyruvate kinase was shifted to the left by a factor of 9 and 5, respectively, as compared to conventional, stationary cultures. The system is useful for studies at low and/or constant concentrations of substrates, hormones, growth factors, etc., with monolayers of cells having a high metabolic capacity.

Animals↗
PubMed1989

Effects of cytochrome P450-inducing agents on the monooxygenation of testosterone in long-term cultures of hepatocytes from male and female rats.

Hepatocytes from male or female rats were cultured for up to 2 weeks in a modified Waymouth medium supplemented with 0.1 or 1.0 microM dexamethasone, 10 nM insulin, and 0.1 nM glucagon with or without addition of phenobarbital, methylcholanthrene, or isoniazid. The activities of testosterone hydroxylases were measured in the intact cell monolayer and in the corresponding microsomal fraction. Aniline hydroxylase was measured in cell homogenates. In the presence of 0.1 microM dexamethasone the testosterone hydroxylase activities varied differently in hepatocytes from male and female rats during the culture period. The activities of 6 beta- and 15 alpha-hydroxylases increased in female and were unchanged in male hepatocytes, while 16 alpha-hydroxylase activity increased in female and decreased in male, and 2 alpha- and 7 alpha-hydroxylase activities were unchanged in both male and female hepatocytes during the culture period. Increasing the dexamethasone concentration to 1.0 microM caused an increase in 6 beta- and 15 alpha-hydroxylase activities in cultures of hepatocytes from both sexes, whereas an increase of 2 alpha- and a decrease of 7 alpha- and 17-hydroxylase activities were found only in cultures of hepatocytes from female rats. Addition of phenobarbital caused an increase in the activity of 7 alpha-hydroxylase in both male and female hepatocytes, while the effect on the other hydroxylases differed with the sex. In hepatocytes from male rats phenobarbital addition decreased the activities of 2 alpha- and 16 alpha-hydroxylases, while these were increased or stable after addition of phenobarbital to hepatocytes from female rats. The activity of aniline hydroxylase was increased at Day 1 and declined afterward. The results demonstrate that the activities of different steroid hydroxylases are inducible and can be directly measured in monolayers of hepatocytes from rats.

Animals↗
PubMed1989

Characterization of a co-culture system of neurons and hepatocytes.

A co-culture system of cerebellar granule cells (glutamatergic neurons) and hepatocytes has been developed. Petri dishes divided in halves by a temporary septum were coated with poly-L-lysine and cerebellar granule cells plated in one of the compartments. Five days later hepatocytes were plated in the other compartment and after 2 days the septum was removed and the two cell types shared the same culture medium for a period of 5 days. During this period of time cultures of neurons and hepatocytes kept separately or in co-culture exhibited identical characteristics with regard to activities of pyruvate kinase and glucokinase (hepatocytes), aspartate aminotransferase (neurons) as well as evoked transmitter release (neurons) and content of cytochrome P-450 (hepatocytes). The results show that it is possible to maintain neurons and hepatocytes in co-culture sharing the same culture medium for a prolonged period of time. Such a system may serve as a pharmacological model to study interactions between liver and brain cells with regard to neuroactive drugs.

Animals↗
PubMed1989

Maintenance of alcohol dehydrogenase activity in long-term culture of hepatocytes from female rat.

Conditions for maintaining the activity of alcohol dehydrogenase in cultures of hepatocytes isolated from female rats were studied. The activity of alcohol dehydrogenase in freshly isolated cells was 1.7 U/mg DNA. When cultured, the activity declined 20% after one day of culture, irrespective of the culture conditions. In a conventional medium with 5 mM glucose the activity after one week of culture was only 30% of that initially measured in culture. Addition of 25 mM glucose or a high concentration of amino acids delayed the decrease. When these compounds were added together it was possible to maintain the initial activity for one week, but the activity declined during the following week. Addition of growth hormone had no effect during the first week of culture but abolished the fall during the second week. The initial metabolism of ethanol was 0.65 mumol/min x mg DNA and declined to two-thirds during the 2 weeks of culture.

Acetylcholinesterase↗
PubMed1989

Risk of cancer in pesticide applicators in Swedish agriculture.

The risk of cancer was analysed in a cohort of 20,245 licensed pesticide applicators in agriculture who had licences issued between 1965 and 1976. Most were men (99%) and about 50% had been born in 1935 or later. The cohort was followed up in the Swedish Cancer Register from date of licence until death or 31 December 1982. The mean follow up time was 12.2 years. Average time since first exposure was longer, however, since one fifth of the cohort was exposed in the 1950s. A total of 558 malignant tumours was found compared with 649.8 expected, which resulted in a statistically significantly decreased standardised incidence ratio (SIR) of 0.86 (95% confidence interval (CI): 0.79-0.93). Significantly decreased risks of cancer were also found for liver (SIR = 0.45, 95% CI: 0.18-0.93), pancreas (SIR = 0.50, 95% CI: 0.26-0.87), lung (SIR = 0.50, 95% CI: 0.35-0.68), and kidney (SIR = 0.53, 95% CI: 0.32-0.84). No statistically significantly increased risks or any time trends were observed. SIR for testicular cancer was increased (SIR = 1.55, 95% CI: 0.92-2.45) and increased with period since licence. Eighteen cases with testicular cancer were found. For those born in 1935 or later a non-significant increased overall risk of cancer was observed (SIR = 1.07, 95% CI: 0.82-1.37). Comparisons were made with agricultural workers in general since pesticide applicators are mainly farmers that use or have used pesticides to a greater extent. Higher risks for pesticide applicators were found for testicular cancer, tumours of the nervous system and endocrine glands, and Hodgkin's disease.

Agricultural Workers' Diseases↗
PubMed1988

The content and activity of cytochrome P-450 in long-term culture of hepatocytes from male and female rats.

The content of cytochrome P-450 and the capacity for O-demethylation have been measured in cultures of hepatocytes from male and female rats for a period of 21 days. The effect of dexamethasone, insulin, glucagon, phenobarbital and hemin was investigated. In hepatocytes from female rats the content of cytochrome P-450 was unchanged after one day of culture. From day 1 to day 3 the content of cytochrome P-450 decreased by 65% and only the combined addition of dexamethasone, phenobarbital and hemin diminished the fall. After the initial fall, addition of 0.1 microM dexamethasone resulted in a stable value. Addition of 1 microM dexamethasone or 1 mM phenobarbital gave rise to an induction of cytochrome P-450 (285%). The high level of cytochrome P-450 was maintained for 3 weeks. In hepatocytes from male rats the content of cytochrome P-450 decreased by 40% after one day of culture. From day 1 to day 3 the content decreased by 45% and the decrease continued irrespective of the presence of hormones and/or phenobarbital. The O-demethylase activity in cultures of hepatocytes from female rats correlated to the cytochrome P-450 content independent of medium composition and age of the cultures, whereas no correlation was found in cultures from male rats. The present study demonstrates that hepatocytes from female rats in cultures retain O-demethylase activity for at least 3 weeks and that, with the experimental conditions used, the response to the hormones and inducers is different for hepatocytes from male and female rats.

Animals↗
PubMed1988

Soft tissue sarcoma risk in Swedish licensed pesticide applicators.

Two Swedish studies have suggested that exposure to phenoxy acid herbicides may cause soft tissue sarcoma. This association has been subsequently investigated in a number of epidemiologic studies. Results are inconsistent. In this study the risk of soft tissue sarcoma in a cohort of 20,245 Swedish pesticide applicators, of whom 72% were estimated to have been exposed to phenoxy acid herbicides, was analyzed. The cohort was observed by means of the Swedish Cancer Register from date of license until Dec 31, 1984, or until death if it occurred prior to that date. The mean follow-up time was 13.9 years. Seven patients with soft tissue sarcoma were observed compared with 7.7 expected on the basis of the incidence in Sweden. The relative risk was found to be 0.9 (95% confidence interval, 0.4 to 1.9). This finding is consistent with the hypothesis that exposure of phenoxy acid herbicides does not increase risk of soft tissue sarcoma.

Adult↗
PubMed1987

Risk of malignant lymphoma in Swedish pesticide appliers.

The risk of Hodgkin's disease (HD) and non-Hodgkin lymphoma (NHL) was studied in a cohort of 20,245 Swedish pesticide appliers, who had the licence issued between 1965 and 1976. In this cohort 72% were estimated to have been exposed to phenoxy acid herbicides. The cohort was followed-up in the Swedish Cancer Register from date of licence until Dec. 31, 1982 or until death if prior to that date. The mean follow-up time was 12.2 years. A total of 11 cases with HD and 21 cases with NHL were observed compared to 9.1 and 20.8 expected. The relative risks and the 95% confidence intervals were for HD 1.20 (0.60-2.16) and for NHL 1.01 (0.63-1.54). The relative risk rose, but not to statistical significance however, with increased time since licence for both diagnoses.

Agricultural Workers' Diseases↗
PubMed1987

Long-term culture of hepatocytes: ethanol oxidation and effect of ethanol on enzyme activities and albumin secretion.

Rat hepatocytes were cultured in a modified HI-WO/BA medium for 13 days, and the combined effect of dexamethasone, 10(-7) M, insulin, 10(-8) M, and glucagon, 10(-9) M on the DNA-content, and on the activity of several enzymes, the secretion of albumin and the rate of ethanol oxidation was investigated. The effect of ethanol on these parameters was also studied. All parameters measured declined with time in the hormone-free cultures. In hormone-supplemented cultures, the DNA-content, the activity of glucokinase, pyruvate kinase, hexokinase and lactate dehydrogenase and the secretion of albumin was maintained at reasonable levels throughout the 13 days, whereas both the activity of alcohol dehydrogenase and the rate of ethanol oxidation fell significantly, although less than in hormone-free cultures. Addition of 50 mM ethanol to the hormone-supplemented culture medium caused a ca. 20% fall in the activity of glucokinase and pyruvate kinase and a 20% increase in alcohol dehydrogenase activity. No effect of ethanol was observed on the activity of hexokinase and lactate dehydrogenase or on the secretion of albumin.

Albumins↗
PubMed1987

Ethanol-induced accumulation of triacylglycerol in cultured hepatocytes: dependency on ethanol metabolism.

Calculations based on net changes and [1-14C]oleate incorporation data suggest that fatty acids are the only precursor of acetylCoA and that extensive lipolysis takes place in hepatocyte cultures incubated with 1 mM oleate in the absence or presence of ethanol. The effect of 4-methylpyrazole on fatty acid metabolism as affected by ethanol has been studied. The ethanol-induced increase in fatty acid uptake was found to be an effect of ethanol per se, whereas the decreased oxidation of fatty acids and secretion of VLDL-triacylglycerol was found to be due to ethanol metabolism.

Animals↗
PubMed1986

Periportal and perivenous hepatocytes retain their zonal characteristics in primary culture.

Periportal and perivenous hepatocytes from rat liver were isolated by combined digitonin-collagenase perfusion, and gluconeogenesis, urea synthesis and fatty acid synthesis was measured both in freshly isolated cells and in primary culture. A periportal zonation of gluconeogenesis and urea synthesis of about 3 and 1.5 fold, respectively, was observed. This zonation persisted unchanged for 23 hours in culture under identical conditions of incubation for periportal and perivenous cells. Fatty acid synthesis was not zonated.

Alanine Transaminase↗
PubMed1985

Effect of ethanol on lipid metabolism in cultured hepatocytes.

Isolated rat hepatocytes were cultured in a modified HI-WO/BA medium for 16 h. In the following 24 h oleate or oleate plus ethanol was added to the medium. After this period the medium was changed again and the cultures were further incubated with [1-14C]oleate alone or with [1-14C]oleate plus ethanol for 6 h. This allowed a comparison of effects of short-term (6 h) and long-term (24 + 6 h) exposure to ethanol on fatty acid metabolism. The increased intracellular accumulation of triacylglycerol in the presence of ethanol was quantitatively accounted for by increased fatty acid uptake, by decreased fatty acid oxidation in the tricarboxylic acid cycle and by decreased VLDL (very-low-density lipoprotein)-triacylglycerol secretion. Ketone-body production was not affected. After short-term exposure the rate of accumulation of triacylglycerol was increased by 50%. This increase was accounted for by increased fatty acid uptake (44%), decreased tricarboxylic acid-cycle activity (49%) and decreased VLDL-triacylglycerol secretion (7%). After long-term exposure, the rate of accumulation of triacylglycerol was increased by 74%. This increase was accounted for by increased fatty acid uptake (34%), decreased tricarboxylic acid-cycle activity (34%) and decreased VLDL-triacylglycerol secretion (32%). The larger increase in accumulation of triacylglycerol after long-term exposure to ethanol was entirely accounted for by increased inhibition of secretion of VLDL-triacylglycerol. The biochemical mechanisms underlying the observations are discussed.

Animals↗
PubMed1983

Accumulation of triacylglycerol in cultured rat hepatocytes is increased by ethanol and by insulin and dexamethasone.

Isolated hepatocytes from female rats were cultured in HI-WO/BA medium for 6 days. To the medium was added oleate, ethanol, dexamethasone and insulin. With oleate To alone, triacylglycerol accumulated; ethanol augmented the accumulation by 90%. To the best of our knowledge, this is the first demonstration that ethanol in vitro increases the content of triacylglycerol in liver cells. Further addition of dexamethasone or insulin did not alter the accumulation of triacylglycerol, indicating that these hormones did not play permissive roles for the effect of ethanol in the present system. Dexamethasone and insulin, in the absence of ethanol, increased the accumulation of triacylglycerol by 30% and 50% respectively. The concentration of glycerol 3-phosphate was increased in the presence of ethanol; however, with time the concentration of glycerol 3-phosphate declined almost to control values, while the accumulation of triacylglycerol continued linearly; this suggests that the effect of ethanol was not mediated via fluctuations in the concentration of glycerol 3-phosphate. These results are discussed in relation to earlier investigations in vivo and in vitro.

Animals↗