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W Halangk

Publications and source records attributed to W Halangk.

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

Capacities of oxidative metabolism in digitonin-treated bovine epididymal spermatozoa.

Treatment of bull spermatozoa from epididymal cauda with 5 micrograms digitonin per microliter cells removed the permeability barrier of plasma membrane for mitochondrial substrates and effectors. Such preparations yielded a high portion of coupled mitochondria characterized by ratios of active respiration to carboxyatractyloside-inhibited respiration greater than 13 in the presence of efficient substrates. Bull sperm mitochondria oxidized pyruvate and lactate in the presence of malate as well as glycerol-3-phosphate with much higher rates than succinate or palmitoyl carnitine. For the efficient substrates the respiration coupled to ADP phosphorylation amounted to 77 to 100% of the uncoupled rate. Comparable rates of active respiration were also observed with ATP indicating the high ATPase activity present in digitonin-treated spermatozoa. Uncoupled rates of respiration corresponded to rates of intact spermatozoa, but the capacity of the phosphorylating respiration exceeded the respiration rates of intact motile spermatozoa remarkably. This indicates that the spermatozoal ATP turnover at sufficient supply of substrate is mostly controlled by ATP utilizing reactions.

Animals↗
PubMed1986

Effect of improved hydrogen supply on energy state, ureogenesis and gluconeogenesis in isolated hepatocytes.

The cellular energy state as well as ureogenesis and gluconeogenesis as ATP-consuming processes were studied as a function of hydrogen supply of mitochondria in isolated hepatocytes. Even though the ATP turnover was quite different during ureogenesis and gluconeogenesis and in the absence of these syntheses both the safranine signals (as a probe for the mitochondrial membrane potential) and the total ATP contents of the cells did not vary to a great extent. Partial uncoupling by FCCP destroyed the mitochondrial membrane potential and decreased the cellular ATP totally. Under these conditions the presence of ornithine plus lactate maintained a measurable membrane potential and ATP level. In order to demonstrate the relevance of hydrogen supply of mitochondria to the syntheses of glucose and urea, the load on energy metabolism was additionally increased by partial uncoupling, and the cells were incubated in a parallel mode in Krebs-Henseleit buffer and an 80 mM succinate containing medium, the latter forcing succinate into the cells. After partial uncoupling, ureogenesis and gluconeogenesis as well as the ATP level were seen to decrease markedly in Krebs-Henseleit buffer, whereas in the succinate medium the improved hydrogen supply of mitochondria counteracted the drain by FCCP, and substantially higher rates of the syntheses and elevated ATP levels were maintained.

Adenosine Diphosphate↗
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

Effect of various substrates on mitochondrial and cellular energy state of intact spermatozoa.

Ejaculated bull spermatozoa separated from seminal plasma by repeated washing were used to study the effects of various substrates on respiration, mitochondrial energization, cellular ATP/ADP ratios, and motility. The respiratory rate in the presence of lactate, pyruvate, acetate or glycerol was about two to three times higher compared to cells oxidizing amino acids, fatty acids, or endogenous substrates. When well oxidizable substrates were present, the uncoupler FCCP produced a marked increase in respiration (two to three times at optimal FCCP concentrations). Mitochondrial energization was monitored in intact spermatozoa by spectrophotometry with the dye safranin. Lactate and pyruvate yielded more pronounced mitochondrial energization than did alanine or endogenous substrates. Cellular ATP/ADP ratios, with lactate, pyruvate, acetate or glycerol, were found to range from 6 to 10, whereas endogenous substrates and amino acids were able to establish ATP/ADP quotients as low as about 1 only. The capacity to oxidize various substrates was clearly reflected by the amount of motile cells. Motility in the presence of lactate, acetate or glycerol was seen in more than 60% of spermatozoa, while spermatozoa in the presence of alanine or butyrate showed a motility not above the endogenous level (approx. 30% motile cells). The experiments demonstrated that cellular performance is highly dependent on the energy state as made possible by the capacity of substrate utilization.

Acetates↗
PubMed1982

A quick test for the simultaneous determination of intactness and concentration of spermatozoa.

The fluorescence of ethidium bromide bound to the DNA of bull spermatozoa can be used for the estimation of intactness and concentration of spermatozoa of washed sperm samples. For the full permeability of the spermatozoal membrane for ethidium bromide digitonin is used in a concentration of 50 micrograms/ml. The fluorescence signals before and after digitonin treatment reflect the portion of cells with intact cellular membrane in the sample. The signal after addition of digitonin correlates to a high degree with the sperm concentration. The method exhibits a sufficient accuracy for the estimation of sperm quality. That applies for the reproducibility with individual ejaculates as well as for the correlation to other methods determining the intactness and sperm concentration. This simple single-step technique requires only about 2 X 10(7) spermatozoa corresponding to 10 to 20 microliters of an average bull ejaculate.

Animals↗
PubMed1982

[Effect of temperature decrease on the intactness of the cell membrane of ejaculated bull spermatozoa].

Respiration of washed ejaculated bull spermatozoa with exogenous succinate is drastically increased after a sudden cooling of spermatozoa (cold shock). Loss of intactness of the cellular membrane occurs in a small temperature range between about 16 degrees C and 8 degrees C. A low cooling rate in critical temperature range connected with a sufficient equilibration time at this temperatures strongly restricts the damage of the spermatozoal membrane.

Animals↗
PubMed1980

[Relation between intactness and adenine nucleotide pattern of ejaculated bull spermatozoa].

The intactness of bull spermatozoa was determined by exclusion of external succinate. This was oxygraphically measured in the presence of cytochrome c after inhibition of the cell respiration with rotenone. An addition of cytochrome c was necessary for a reproducible respiration of damaged cells. The portion of intact cells determined in this way correlated with that obtained by the fluorescent dye primuline. The content of adenine nucleotides and the percentage of ATP of washed fresh spermatozoa depended on the intactness of the sperm sample. The adenine nucleotide pattern of spermatozoa after deep freezing corresponded to that of washed fresh ejaculates with a high percentage of damaged cells. The major part of ejaculates tested showed only a small increase of damaged cells during substrate-free incubations at 38 degrees C up to 4 h under aerobic and anaerobic conditions. Ejaculates which had shown a drastic increase of damaged cells were not recognizable by the initial portion of damaged cells. Also a lowered content of ATP in the cells was no indicator of an increased fragility of the cell membrane. A remarkable loss of total adenine nucleotides was observed under conditions of cold shock. It indicates that the changes in the sperm membrane induced by cold shock were qualitatively different in comparison with changes caused by storage and by a slow decrease in temperature.

Adenine Nucleotides↗
PubMed1979

The lipoxygenase of reticulocytes. Purification, characterization and biological dynamics of the lipoxygenase; its identity with the respiratory inhibitors of the reticulocyte.

A lipoxygenase has been purified from rabbit reticulocyte-rich anaemic blood cells. It possesses a molecular weight of 78 000 and an isoelectric point of 5.5 and contains 5% neutral sugars and two iron atoms per enzyme molecule. The lipoxygenase has proved to be identical with the inhibitors of respiratory proteins described formerly. The actions of the lipoxygenase on linoleic acid, phospholipids, mitochondrial and erythrocyte membranes and electron transfer particles were studied. A special feature of the reticulocyte lipoxygenase is the suicidal character of its action on lipids. With electron transfer particles the reticulocyte lipoxygenase causes a loss of acid-labile sulfur which accompanies respiratory inhibition; the strong respiratory inhibition is not exerted by soybean lipoxygenase. The reticulocyte lipoxygenase acts preferably on mitochondrial membranes as compared with cell membranes of the erythrocyte; erythrocyte cytosol moderates the action on mitochondrial membranes. Furthermore, the lipoxygenase reaction can concomitantly and irreversibly inactivate sulfhydryl enzymes as demonstrated with muscle glyceraldehyde-3-phosphate dehydrogenase. The occurrence of the lipoxygenase here described is restricted to reticulocytes; very low amounts were observed in bone marrow and no lipoxygenase was detectable in normal blood. During the course of an experimental anaemia the lipoxygenase is produced owing to superinduction in large amounts, which may persist for a long time since they escape inactivation. Preliminary evidence was obtained for the occurrence of other lipoxygenases in tissues of lung, spleen, kidney and also epithelial tumours.

Amino Acids↗
PubMed1977

Degradation of mitochondria by cytosolic factors in reticulocytes.

The degradation process of mitochondria in rabbit reticulocytes proceeds predominately directly in the cytosol rather than in secondary lysosomes as judged by electronmicroscopy. At least five cytosolic protein factors are present in reticulocytes, which could be related to the degradation of mitochondria: the two inhibitory proteins of the respiratory chain RF and RC and three enzymes which cause a lysis of mitochondria in vitro (lipoxygenase, proteinase, phospholipase A). The properties of these factors are the subject of this paper. A hypothetic scheme of the degradation of mitochondria in reticulocytes is proposed. The degradation of mitochondria in reticulocytes is viewed as a complex interplay of various cytosolic factors and the functional state of the mitochondrial membranes. The lipoxygenase damages the membranes and triggers the penetration of the respiratory inhibitors. In this manner, a catastrophic cycle is initiated which leads to the complete breakdown of the mitochondria.

5-Aminolevulinate Synthetase↗
PubMed1977

Some properties of the lipoxygenase from rabbit reticulocytes.

A lipoxygenase was enriched from the stoma-free supernatant of rabbit reticulocytes. The enzyme causes drastic deterioration of mitochondrial membranes. The release of matrix enzymes is paralleled by formation of products of lipid peroxidation. The enzyme reacts with isolated phospholipds and free cis-unsaturated fatty acids. Some properties were determined: molecular weight, isoelectric point, temperature and pH-dependence and Km value for linoleic acid. The enzyme is inhibited by reaction products and a variety of inhibitors, especially antioxidants and chelating agents.

Animals↗
PubMed1977

[Relationship between the conformation of isolated rat liver mitochondria and their susceptibility to rabbit reticulocyte lipoxygenase].

Lipoxygenase from rabbit reticulocytes cause disruption of mitochondrial membranes and peroxidation of their lipids as judged by electronmicroscopy, release of matrix enzymes and formation of malonyldialdehyde. Without substrate mitochondria become orthodox and strong lysis by lipoxygenase appears. The lysis is prevented by ATP or ADP plus succinate; in this case mitochondria remain condensed or partly condensed. The protection by substrate was even observed in the presence of 2,4-DNP, although the mitochondria were transformed to the condensed state. Lysis was more pronounced in hypotonic than in hypertonic sucrose, condensed mitochondria are also attacked. No relation seems to exist between lipoxygenase attack and the conformational state of mitochondria. Lysis of mitochondria is dependent on the susceptibility of the fatty acid moiety of phospholipids, which may be influenced by both metabolic and structural events via alteration of protein-lipid interactions.

Adenosine Diphosphate↗
PubMed1975

[Action of the systemic fungicide dexon on several NADH dehydrogenases].

The fungicide dexon (p-dimethylaminobenzenediazosulfonate, Na-salt) inhibits the NADH oxidase activity of submitochondrial particles (ETP) from beef heart (semi-inhibition concentration 1.4 muM), while the succinate oxidase activity is unaffected. Measurements of the activity of several enzymatic partial reactions of the respiratory chain of ETP suggest that dexon acts directly on the flavine of NADH dehydrogenase. Soluble NADH-cytochrome c-oxidoreductase (MAHLER) and rotenone-insensitive NADH ubiquinone reductase are also inhibited by dexon. At low concentrations of dexon, inhibition of ETP starts slowly only after addition of NADH. Preincubation without NADH increases the amount of inhibition, but does not prevent the time delay. It is assumed that an electron flux through the respiratory chain, or reduction of flavine is prerequisite for the reaction of dexon with the action site. Furthermore, dexon inhibits the NADH dehydrogenase located at the outer surface of the inner membrane of plant mitochondria, accessible to extramitochondrial NADH and insensitive to rotenone, as has been shown on isolated mitochondria from cauliflower (Brassica oleracea L). In addition, dexon inhibits selectively the NADH dehydrogenase of the DT diaphorase (ERNSTER) from rat liver cytosol. In contrast, the dicoumarol-insensitive NADH dehydrogenase (ZINSMEYER et al.) from rat liver cytosol, the NADH-cytochrome b5-reductase (STRITTMATTER) from rat liver microsomes, the rotenone-insensitive NADH-cytochrome c-oxidoreductase of the outer membrane of rat liver mitochondria, soluble NADH-oxidase from Escherichia coli, and NADH-dehydrogenase from human erythrocytes are not inhibited. The results suggest that dexon is a group reagent to certain pyridine nucleotide-dependent flavine enzymes.

Animals↗
PubMedDate not supplied

Oxidative stress affects pancreatic proteins during the early pathogenesis of rat caerulein pancreatitis.

Rats received up to four subcutaneous injections of caerulein (20 microg/kg) in hourly intervals to induce a mild edematous pancreatitis. A single dose of caerulein resulted in significant oxidative modification of proteins in pancreatic homogenates as compared to saline-injected controls (p < 0.01). Repeated injections of the secretagogue were unable to induce a further increase in modified proteins. Protein oxidation preceded the formation of the lipid peroxidation product malondialdehyde as well as edema and the increase in serum amylase by 1-2.5 h. Western blotting for oxidatively modified proteins confirmed the results of the quantitative measurements and did not reveal individual, selectively modified proteins. These findings indicate that oxidative stress and oxidative protein modification are very early events in the initial period of caerulein pancreatitis. This may explain the poor success rate of most studies that administered antioxidants therapeutically during or after initiation of pancreatitis.

Amylases↗