The effect of compounds altering the cAMP level on reversing the 2-cell block induced by hypoxanthine in mouse embryos in vitro.

The possibility of reversing the hypoxanthine induced 2-cell block in mouse embryos when cultured in conditions supplemented with compounds that increase (FSH, hMG, IBMX, hCG) or inhibit (GnRH-analogue) cAMP was assessed. When embryos were cultured in Ham's F-10 without hypoxanthine supplemented with each of the above compounds, no inhibition of blastocyst development was observed. Embryos were then cultured in Ham's F-10 with hypoxanthine supplemented again with each compound. For the addition of GnRH-analogue or FSH, the rate of blastocyst formation was comparable with that of the control medium with hypoxanthine alone. Instead, the addition of IBMX or hMG reversed the induced block. There was no reversible effect for the addition of 2 micrograms/ml hCG while the latter was observed with higher doses. The results from GnRH-analogue and IBMX addition show that, contrary to what was found for oocytes, stimulation of cAMP reverses the hypoxanthine-induced block in mouse embryos. FSH and hCG also had effects opposite to those observed for oocytes. It is unknown why hMG (FSH + LH) reverses the block. A lower cAMP degradation rate resulting in a higher cAMP level is a possible explanation. Our results provide further evidence that cleavage arrest by hypoxanthine has a different mechanism than the hypoxanthine-induced arrest of meiosis.

[The use of sodium gamma-oxybutyrate and gutimine for decreasing metabolic disorders in the heart, caused by exotoxic shock in acetic acid poisoning]. / Primenenie gamm-oksibutirata natriia i gutimina dlia umen'sheniia metabolicheskikh narushenii v serdtse, vyzvannykh ékzotoksicheskim shokom pri otravlenii ukusnoi kislotoi.

Exotoxic shock was simulated in non-linear rat males anesthetized with barbital after intragastric administration of 70% acetic acid at a dose of 4 ml/kg using a gastric tube. Energy metabolism and the rate of lipid peroxidation were studied in heart muscle during the decompensated and terminal periods of exotoxic shock. Sodium hydroxybutyrate (200 mg/kg) and gutimine (75 mg/kg), administered alone within 30 min after the poisoning, prolonged the period before manifestation of the decompensated and terminal steps of the shock; these drugs decreased the rate of metabolic impairments in the myocardium by decreasing the rates of adenine nucleotide catabolism, of glycolysis, lipolysis and lipid peroxidation.

Effect of nucleoside transport inhibition on adenosine and hypoxanthine accumulation in the ischemic human myocardium.

The effect of nucleoside transport inhibition on the adenylate catabolism was studied in the human myocardium under normothermic ischemic conditions. Ten hearts from cardiac transplant recipients and two hearts from cardiac homograft donors were used in this study. The hearts were excised under hypothermic conditions (25 degrees C body temperature), the coronary arteries flushed with 500 ml ice-cold Ringer solution (n = 6; group I) or with ice-cold Ringer solution containing 1 mg/l of the nucleoside transport inhibitor R75231 (n = 6; group II). After transportation at 0 degree C from the operation room, the hearts were quickly rewarmed to 37 degrees C. Serial transmural biopsy specimens were taken during normothermic ischemia for determination of purine catabolites. The level of ATP before normothermic ischemia was 17.5 +/- 1.0 mumol/g dry weight in the control group (group I) and 19.3 +/- 0.4 mumol/g dry weight in the drug group. ATP, expressed as percentage of total purine content, was similar in both groups before rewarming (79.5 +/- 4.3% in group I and 79.5 +/- 2.9% in group II). There was no significant difference in the rate of ATP breakdown in both groups throughout the experiment (ATP was 3.0 +/- 1.4% of total purines in group I and 1.4 +/- 0.2% in group II at 120 min of normothermic ischemia). Adenine nucleotide content changed also similarly in both groups. Adenosine accumulation was, however, significantly higher in group II than in group I (peak values: 4.6 +/- 1.0% of total purines in group I vs 14.0 +/- 1.7% in group II; p < 0.01). The ratio between adenosine and inosine was significantly higher in group II throughout normothermic ischemia (p < 0.01). In spite of a larger accumulation of adenosine in group II, the increase in inosine was similar in both groups. We conclude that nucleoside transport inhibition significantly delays the breakdown of adenosine and the formation of hypoxanthine in the ischemic human myocardium.

Mutagenicity of active oxygen species in bacteria and its enzymatic or chemical inhibition.

The mono-electronic reduction of oxygen in the hypoxanthine-xanthine oxidase system led to the formation of active species eliciting an evident and highly reproducible mutagenic response in strain TA104 of S. typhimurium. Similar effects were observed by generating oxy radicals either extracellularly or inside bacterial cells. Mutagenicity was selectively detected in TA104 and not in other Salmonella strains, which points out the importance of the hisG428 mutation and of the deletion excising the uvrB gene, as far as sensitivity to oxy radicals is concerned. The mutagenicity of the system was further enhanced in the presence of superoxide dismutase. Catalase did not affect the mutagenicity of hypoxanthine plus xanthine oxidase, whereas it inhibited the mutagenicity induced by the mixture of hypoxanthine with xanthine oxidase and superoxide dismutase. This demonstrates that not only hydrogen peroxide but also the superoxide radical anion is positive in this system. Glutathione and 2 synthetic thiols, i.e., N-acetylcysteine and alpha-mercaptopropionylglycine, besides decreasing the high spontaneous mutagenicity of TA104, efficiently prevented the mutagenicity of active oxygen species.

Cytotoxicity of the hypoxanthine-xanthine oxidase system on V79 cells: comparison of the effects of SOD and CuDIPS.

The hypoxanthine - xanthine oxidase system generates an extracellular flux of superoxide anion radical (O2.-) and hydrogen peroxide (H2O2). Catalase but not superoxide dismutase (SOD) protects V79 cells exposed to the hypoxanthine - xanthine oxidase system, showing that H2O2 is the major reactive oxygen species involved in the cytotoxicity of such a system. In contrast to SOD, the lipophilic SOD like compound CuII (diisopropylsalicylate)2 (CuDIPS) exhibits some protection at non cytotoxic concentration. It is also found that methanol partially protects cells exposed to the hypoxanthine-xanthine oxidase system. It appears that in our experimental conditions (temperature, ionic strength and pH) the protective effect afforded by methanol and CuDIPS is due to the inhibition of the xanthine oxidase activity.

Output of (14C)adenine nucleotides and their derivatives from cerebral tissues. Tetrodotoxin-resistant and calcium ion-requiring components.

1. Neocortical tissues, exposed briefly to [(14)C]adenine and containing over 98% of their (14)C as adenine nucleotides, when superfused with glucose-bicarbonate salines released about 0.1% of their (14)C content/min to the superfusate. 2. Addition of unlabelled adenosine to the superfusing fluid increased the (14)C output three- to four-fold; half-maximal increase was given by about 40mum-adenosine, and reasons are adduced for considering the activity of adenosine kinase to be a major factor in conditioning the (14)C output. Adenosine similarly increased the enhanced (14)C output caused by electrical excitation of the superfused tissue; it brought about only a small increase in tissue glycolysis. 3. Output of (14)C from the [(14)C]adenine-labelled tissues was increased when Ca(2+) was omitted from the superfusing fluids, but electrical stimulation did not then liberate more (14)C. Nevertheless, such tissues still responded to electrical stimulation by increased glycolysis, and their (14)C output again became susceptible to increase by electrical stimulation when Ca(2+) was restored. 4. The six-fold increase in tissue glycolysis caused by electrical excitation was almost completely inhibited by tetrodotoxin at 0.1mum and above, but this was associated with about 50% inhibition only in the output of (14)C from tissues preincubated with [(14)C]adenine. The (14)C-labelled compounds of which output was most inhibited by tetrodotoxin were adenosine, inosine and hypoxanthine whereas output in a nucleotide fraction was little affected.