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Biomedical subjects

W Kunz

Publications and source records attributed to W Kunz.

At least 73 records · Page 4Linked to original sources
PubMed1987

The kinetics of nuclear polyploidization and tumour formation in livers of CF-1 mice exposed to dieldrin.

The kinetics of nuclear polyploidization in livers of CF-1 mice exposed to dieldrin were studied at concentrations of 0, 0.1, 1, 5 and 10 p.p.m. in the diet, in 'steady-state' situations (which are reached within a few weeks after initiation of treatment). Animals were killed at five time intervals (after 1.85, 3, 6, 9 and 14 months of exposure). The changes in the percentage of octaploid nuclei (8C) were used as an indicator of the kinetics of overall polyploidization. Polyploidization in control mice increased proportionally (linearly) with time (age). The enhancement of polyploidization by dieldrin was found to be proportional to dietary concentration. The slopes of the linear regressions of polyploidization, as a function of age, were identical in all dieldrin-treated groups and controls, indicating that there was no cumulative effect of dieldrin in time. A comparative analysis of the observed dieldrin dietary concentration: response relationship of polyploidization and of tumour formation in CF-1 mouse liver indicates that liver tumour formation is associated with a constant degree of polyploidization. Assuming that polyploidization reflects the ageing process, the data suggest that liver tumour formation is imminent at a constant biological age and that tumour promoters, such as dieldrin, could operate by advancing the biological age of mouse liver in the initial phases of treatment. The results of this study suggest that the analysis of ploidy changes may serve as an aid to perspective in evaluating risks associated with exposures to liver tumour promoters.

Aging↗
PubMed1987

Phenobarbital induction of cytochrome P-450 in normal and preneoplastic rat liver: comparison of enzyme and mRNA expression as detected by immunohistochemistry and in situ hybridization.

The expression levels of the major phenobarbital-inducible cytochromes P-450 were analyzed immunohistochemically in liver sections obtained from rats treated sequentially with diethylnitrosamine and phenobarbital. In parallel sections expression of the corresponding messenger RNAs was investigated by in situ hybridization using an appropriate 35S-labeled cDNA probe. A phenobarbital-mediated increase in enzyme protein and a concomitant enhancement of the corresponding mRNA was seen in hepatocytes of the centrilobular areas of the liver acinus. A comparable increase in P-450 protein and mRNA expression was detected in large carcinogen-induced nodules present in animals maintained on phenobarbital until killing. This result was confirmed by Northern analysis of nodular RNA. No such induction was seen in liver nodules obtained from animals which were withdrawn from the phenobarbital-containing diet 10 days prior to killing. These findings demonstrate that phenobarbital induction of cytochrome P-450 enzymes occurs in neoplastic liver tissue as it does in normal liver and, in addition, suggest that the increase in the levels of the major phenobarbital-inducible P-450s in normal and neoplastic liver is mediated by an enhancement of the steady-state concentrations of their mRNAs.

Animals↗
PubMed1987

Respiratory function of rat brain mitochondria after hypobaric hypoxia and piracetam treatment.

After an acute hypobaric hypoxia the mitochondrial respiratory control index is reduced in consequence of a decreased active-state respiration. The finding is paralleled by decreased uncoupled respiration and a not significantly changed resting-state respiration. Long term hypoxic exposures show adaptive traits of this criterion of mitochondrial energy metabolism. The antihypoxic effect of piracetam may be reflected in a delayed normothermic in vitro aging of mitochondrial suspension.

Animals↗
PubMed1987

Cause and consequences of dynamic compartmentation of adenine nucleotides in the mitochondrial intermembrane space in respect to exchange of energy rich phosphates between cytosol and mitochondria.

By means of reconstituted systems consisting in rat heart mitochondria and pyruvate kinase it was shown, that the mitochondrial ATP-production is remarkable increased if ADP is produced by enzymes localized in the mitochondrial intermembrane space as creatine kinase or adenylate kinase. This result and different amount of inhibition by atractyloside or carboxyatractyloside of hexokinase- and creatine kinase stimulated respiration further support the concept of dynamic compartmentation of adenine nucleotides in the mitochondrial intermembrane space.

Adenine Nucleotides↗
PubMed1987

Gender-specifically expressed genes in Schistosoma mansoni.

Using a genomic gene bank in phage lambda and two cDNA banks in the expression vector lambda-gt11 we have cloned and characterized genes that are expressed preferentially or exclusively in females. One of these genes transcribes two predominant RNA molecules of 0.8 and 3.9 kb which comprise more than 5% of the mRNA population of adult female worms. Transcription of these two RNAs occurs in close proximity on the genome, probably in an overlapping fashion. Experiments are presently in progress to sequence the genes and to produce antibodies against their polypeptide products which will be used to determine in which tissue and at what time in development these genes are expressed. The gene products are probably used for egg shell formation. The final long-term perspective of this project is to interfere with the schistosome parasite's cycle and to reduce its pathogenicity by interrupting egg production.

Animals↗
PubMed1987

[ATP-metabolizing enzymes in suspensions of isolated coupled rat brain mitochondria].

An improved method for the isolation of rat brain mitochondria is described. The preparation exhibits a respiratory control index (RCI) of 6 or 7.3 in the presence of pyruvate and malate or glutamate and malate, respectively. RCI decreases to 2.5 in the presence of Mg++. When the phosphorylation of extramitochondrially added or formed ADP is suppressed by carboxyatractyloside (CAT) inhibition of the adenine nucleotide translocator, the remaining respiration amounts to 6 nmol O2/min X mg mitochondrial protein. These results and the ratio of 16 to 19 from the quotient of phosphorylating active-state respiration to CAT inhibited respiration refer to a high degree of mitochondrial coupling of respiration. Therefore the remaining respiration in the presence of Mg++ is due to a phosphokinase activity located outside the inner membrane of intact mitochondria or at nonphosphorylating mitochondrial fragments. The following activities were observed: Oligomycin sensitive ATPase, 47 mU/mg protein; hexokinase, 272 mU/mg protein; creatinphosphokinase, 116 mU/mg protein; and a surprisingly low activity of adenylatekinase, 57 mU/mg protein.

Adenosine Monophosphate↗
PubMed1986

Urinary polyamine excretion by tumor-bearing and tumor-free mice exposed to cyclophosphamide, 5-fluorouracil and 6-mercaptopurine.

The effects of cytostatic treatment on urinary polyamine excretion have been investigated in tumor-bearing (either Ehrlich carcinoma of S 180 sarcoma) and in tumor-free mice. The animals were exposed to single or multiple treatment with various doses of cyclophosphamide, 5-fluorouracil, or 6-mercaptopurine. Treatment invariably enhanced polyamine excretion dependent on dose and effectiveness of the cytostatic drug. The most pronounced increases were observed in the excretion of spermine and putrescine, with peak excretion usually occurring after 1-2 and 3-4 days, respectively. The urinary excretion of spermidine was relatively modest in untreated mice, but the increases observed following drug treatment were high in proportion. Significant differences in urinary polyamine excretion were observed between tumor-free and tumor-bearing animals following treatment with all cytostatic agents. Peak values were invariably higher in tumor-bearing mice even in those with small, barely detectable tumors. After discontinuation of treatment polyamine excretion returned to normal values and stabilized in groups in which regression predominated, whereas in those groups of animals which showed little or no tumor regression urinary polyamine levels gradually increased again during a 2-week observation period.

Animals↗
PubMed1986

Polychlorinated biphenyls, classified as either phenobarbital- or 3-methylcholanthrene-type inducers of cytochrome P-450, are both hepatic tumor promoters in diethylnitrosamine-initiated rats.

The cytochrome P-450 isozymes, cytochrome P-450 MC1 and MC2, purified from rats treated with 3-methylcholanthrene (MC), were found by immunohistochemical staining to be strongly induced in the livers of rats treated with 3,3', 4,4'-tetrachlorobiphenyl (TCBP), while the cytochrome P-450 isozymes, PB1 and PB2, purified from the livers of rats treated with phenobarbital (PB), were shown to be induced in the livers of rats treated with 2,2', 4,4', 5,5'-hexachlorobiphenyl (HCBP). The latter compound also strongly induced NADPH-cytochrome P-450-reductase. Following induction, all 5 enzymes were located preferentially in the centrilobular and midzonal region of the liver acinus. The influence of these polychlorinated biphenyls (PCBs) on diethylnitrosamine (DEN)-initiated hepatocarcinogenesis was investigated by analyzing the evolution of adenosine triphosphatase-deficient focal lesions. Whereas DEN alone produced very few islets, the administration of either PCB congener (150 mumol/kg, i.p., once weekly over a period of 8 weeks) subsequent to DEN treatment (50 ppm in the drinking water, 10 days) strongly enhanced the number of islets as well as the relative volume of liver occupied by islet tissue. These effects were evident, both 1 and 9 weeks, after cessation of PCB treatment. Unexpectedly the less persistent PCB congener, TCBP, showed a much more potent enhancing effect after the 9 weeks recovery period than did (HCBP).

Animals↗
PubMed1986

Expression of albumin messenger RNA detected by in situ hybridization in preneoplastic and neoplastic lesions in rat liver.

The process of chemical hepatocarcinogenesis is characterized by the appearance of preneoplastic lesions showing changes in the expression of various marker enzymes. We have analyzed the phenotype of small preneoplastic foci and expansively growing nodules in liver sections obtained from rats treated with various carcinogens. Changes within the lesions in canalicular adenosine triphosphatase, gamma-glutamyl transpeptidase, NADPH-(cytochrome P-450) reductase, cytochrome P-450 PB2, epoxide hydrolase, and glycogen content were detected by means of enzyme histochemical and immunohistochemical staining procedures. In parallel sections the expression of albumin messenger RNA was investigated by in situ hybridization using a 35S-labeled albumin specific complementary DNA probe. In general, small preneoplastic lesions showed unchanged levels of albumin messenger RNA. In contrast, the expression of albumin messenger RNA was found to be reduced to varying degrees in large hepatic nodules. An expression of alpha-fetoprotein messenger RNA could not be detected in any of the nodules. No direct correlation between the enzyme phenotype of the lesions and the degree in reduction of albumin messenger RNA could be established except that the reduction was most pronounced in nodules which had lost their ability to store glycogen. Since the synthesis and excretion of albumin is a typical function of the differentiated hepatocyte in the adult animal, the observed decrease in albumin messenger RNA expression in large hepatic nodules is in accordance with the hypothesis of a gradual dedifferentiation or retrodifferentiation of the cell population during carcinogenesis. Hyperplastic nodules produced by continuous treatment of rats with 4-dimethylaminoazobenzene showed increased rather than decreased albumin levels. The analysis of albumin messenger RNA expression might therefore be used as a tool to discriminate between nodules of differing biological nature and fate.

Adenosine Triphosphatases↗
PubMed1985

Contribution of different enzymes to flavoprotein fluorescence of isolated rat liver mitochondria.

The fluorescence signal of flavoproteins of rat liver mitochondria was investigated to determine the respective contributions of the various flavoenzymes. About 50% of the overall signal were found to be NAD-linked and caused by alpha-lipoamide dehydrogenase flavin (Em7.4 = -283 mV). Roughly 25% were due to a flavoprotein reducible in a non-NAD-linked reaction. This fluorescent flavoenzyme (Em7.4 = -52 mV) has been tentatively identified as a flavoprotein of the fatty-acid-oxidizing system, most probably the electron transfer flavoprotein. The remaining 25% of the signal are accounted for by flavoenzymes which are reducible by dithionite only. These flavoenzymes were not involved in the flavoprotein fluorescence alterations accompanying changes in electron flow through the respiratory chain. Contributions of other mitochondrial flavoproteins such as succinate dehydrogenase, NADH dehydrogenase, alpha-glycerophosphate dehydrogenase, proline dehydrogenase, and choline oxidase, to the overall flavin fluorescence signal of isolated rat liver mitochondria can be neglected.

Animals↗
PubMed1985

Interdependence of mitochondrial ATP production and extramitochondrial ATP utilization in intact spermatozoa.

The dependence of both respiration and total activity of ATP-consuming reactions on the cellular adenine nucleotide pattern was investigated in intact bovine spermatozoa. ATP consumption was manipulated by inhibition with vanadate and activation with caffeine, leading to a decrease or increase in the rate of respiration up to 70% or 20%, respectively. Oligomycin blocked the respiration to the same extent as did vanadate, suggesting that the total extramitochondrial ATP-consuming activity is vanadate-sensitive. The major part of ATP utilization must be linked to dynein ATPase, since inhibition of (Na+, K+) ATPase by ouabain showed only a small effect on respiration (-17%). Being a potent inhibitor of dynein ATPase, vanadate drastically reduced the amount of motile cells, whereas caffeine tended to increase the intensity of motion. The effects of vanadate or caffeine on respiration were paralleled by changes in cellular ATP, reflecting the response of mitochondrial respiration on the cellular ATP/ADP ratio. Respiration was found to depend on changes in the ATP/ADP ratio in the range from about 3 (+caffeine) to 9 (+vanadate). The range of response of ATP consumption to the ATP/ADP ratio was determined by varying the mitochondrial ATP production via the concentration of lactate which was used as substrate. The measured effects on both respiratory rate and ATP/ADP ratio suggested that ATP consumption was markedly dependent on ATP/ADP ratios below 5. It is concluded that lactate concentrations above 1 mM sufficiently supply bovine spermatozoa with substrate and the energy turnover is mainly limited by the activity of dynein ATPase rather than by the capacity of mitochondrial oxidative phosphorylation.

Adenosine Diphosphate↗
PubMed1985

rDNA in Locusta migratoria is very variable: two introns and extensive restriction site polymorphisms in the spacer.

Cloned ribosomal DNA (rDNA) of Locusta migratoria was analyzed by restriction site mapping and SI nuclease experiments. The repeat unit is 18 kb long. The nontranscribed spacer region (NTS) is very large (11 kb) and homogeneous in length, but many of the restriction sites are heterogeneous among the repeat units. Two introns of different length were found at different positions in the 28S gene. They are present in less than 5% of the genes.

Animals↗
PubMed1985

The effect of methotrexate pretreatment on 5-fluorouracil kinetics in sarcoma 180 in vivo.

Synergy of sequential MTX and 5-FU has been shown in several in vitro and in vivo systems. In the present study the influence of time interval between MTX and 5-FU and MTX dose on 5-FU accumulation in tumor cells has been examined in Sarcoma 180 in vivo. There was a clear relationship between MTX dose applied and amount of 5-FU detected in the acid-soluble fraction, the RNA fraction and the thymidylate synthase complex fraction. Also, the MTX-5-FU time interval affected clearly the amount of 5-FU detected in all three fractions, the optimum time interval being 8-12 hr. The results indicate that for sequential application of MTX and 5-FU selection of an adequate MTX dose and a sufficient time interval is crucial to achieve synergistic action.

Animals↗
PubMed1985

Regulation and expression of four cytochrome P-450 isoenzymes, NADPH-cytochrome P-450 reductase, the glutathione transferases B and C and microsomal epoxide hydrolase in preneoplastic and neoplastic lesions in rat liver.

Nitrosamine-induced hepatocarcinogenesis has been used to investigate the regulation and expression of different drug-metabolizing enzymes in preneoplastic and neoplastic lesions in the female Wistar rat. The enzymes investigated were two phenobarbital-inducible cytochrome P-450 (cyt. P-450) isoenzymes (PB1 and PB2, mol. wt. 52 000 and 53 500, respectively), two 3-methylcholanthrene-inducible forms (MC1 and MC2, mol. wt. 54 500 and 57 000, respectively), NADPH-cytochrome P-450 reductase, the cytosolic glutathione transferases (GSTs) B and C and the microsomal epoxide hydrolase with broad substrate specificity (mEHb). Carcinogen-induced lesions were identified by use of the known markers of hepatocarcinogenesis adenosinetriphosphatase and gamma-glutamyl transpeptidase. While the GSTs and mEHb were increased in all preneoplastic and neoplastic lesions, the levels of the individual cyt. P-450 isoenzymes were characteristically different from each other. In many of the early ATPase deficient islets PB1 was elevated, whereas the content of the other cyt. P-450 forms and NADPH-cytochrome P-450 reductase was either unchanged or slightly lowered. At later stages of hepatocarcinogenesis PB1 returned to the levels of the surrounding tissue, while the other cyt. P-450 isoenzymes were decreased, the most prominent reduction being found in MC1. In neoplastic nodules all the cyt. P-450s and NADPH-cyt. P-450 reductase were diminished, some of them dramatically. These findings indicate that in spite of a common response of groups of P-450s to inducing agents, individual P-450 isoenzymes are also regulated separately. Moreover, the constant elevation of mEHb and GSTs in all lesions investigated in this study demonstrates that these enzymes, which are largely involved in deactivation, are regulated in a different fashion from the predominantly carcinogen-activating monooxygenases. The observed differences in enzyme pattern may provide a useful method for subdividing and categorizing preneoplastic and neoplastic lesions.

Animals↗
PubMed1985

Effect of phenobarbital and other liver monooxygenase modifiers on dimethylnitrosamine-induced alkylation of rat liver macromolecules.

The effects of phenobarbital (PB) and other liver monooxygenase modifiers on dimethylnitrosamine (DMN)-induced alkylation of rat liver DNA and protein were investigated at different carcinogen doses. In rats given single injections of radioactively labeled DMN, pretreatment with PB (80 mg/kg body weight, administered for 5 days) resulted in a small but significant decrease in the formation of 7-methylguanine and O6-methylguanine per mole of guanine in liver DNA associated with a decrease in the O6/N7-methylguanine ratio. The specific radioactivity of liver protein was also lowered in PB-pretreated rats. The degree of PB interference was independent of DMN dose within a carcinogen dose range of 0.5 microgram to 10 mg/kg body weight. In parallel experiments, the effects of pretreatment with PB, Aroclor 1254, pregnenolone-16 alpha-carbonitrile, butylated hydroxytoluene, beta-naphthoflavone, and ethanol on DMN-induced alkylation of liver DNA were studied at a DMN dose of 5 micrograms/kg body weight. In general, pretreatment with these modifiers of liver monooxygenase resulted in a decrease in specific alkylation of DNA and in the ratio of 7-methylguanine to guanine. If, however, 7-methylguanine levels were related to total liver DNA, these differences in DNA alkylation between controls and pretreated rats became substantially smaller, partially being negligible, since these inducers led to an increase in relative liver weight with concomitant increase in the content of liver DNA. Thus, when expressed per total liver, no significant changes in the overall extent of metabolic activation of DMN were evident. These findings are not consistent with the results of in vitro studies on DMN metabolism in microsomal systems which favored the hypothesis that changes in the metabolism of hepatocarcinogens are responsible for the reduction of liver tumor response in animals treated simultaneously with inducers of the liver monooxygenase system and hepatocarcinogens. Our findings suggest that these effects might rather be related to drug-mediated changes on the cellular level.

Alkylation↗