Biology of halophilic bacteria,Part II

Archaebacteria (archaea) are comprised of three groups of prokaryotes: extreme halophiles, methanogens and thermoacidophiles (extreme thermophiles). Their membrane phospholipids and glycolipids are derived entirely from a saturated, isopranoid glycerol diether,sn-2,3-diphytanylglycerol (archaeol) and/or its dimer, dibiphytanyldiglyceroltetraether (caldarchaeol). In extreme halophiles, the major phospholipid is the archaeol analogue of phosphatidylglycerolmethylphosphate (PGP-Me); the glycolipids are sulfated and/or unsulfated glycosyl archaeols with diverse carbohydrate structure characteristic of taxons on the generic level. Biosynthesis of these archaeol-derived polar lipids occurs in a multienzyme, membrane-bound system that is absolutely dependent on high salt concentration (4 M). The highly complex biosynthetic pathways involve intermediates containing glycerol ether-linked C₂₀-isoprenyl groups which are reduced to phytanyl groups to give the final saturated polar lipids. In methanogens, polar lipids are derived both from archaeol and caldarchaeol, and thermoacidophiles contain essentially only caldarchaeol-derived polar lipids. The function of these membrane polar lipids in maintaining the stability, fluidity and ionic properties of the cell membrane of extreme halophiles, as well as the evolutionary implications of the archaeol and caldarchaeol-derived structures will be discussed.     

Regulation of enzymes of ethanol metabolism in yeast (Rhodotorula gracilis).

The three enzymes of ethanol metabolism alcohol dehydrogenase, aldehyde dehydrogenase and acetyl-CoA synthetase in the obligate aerobic yeast Rhodotorula gracilis are repressed by glucose and induced by C2 metabolic fuels with a regulatory pattern indicating a correlation in the control mechanisms. To try an identification of the molecular signals involved in the transmission of the inducing stimulus, experiments were carried out by blocking with 2 mM pyrazole the ethanol acetaldehyde metabolic step. Results indicate that ethanol is not specifically required as a molecular signal for induction.     

Regulation of enzymes of ethanol metabolism in yeast (Rhodotorula gracilis)

Summary The three enzymes of ethanol metabolism alcohol dehydrogenase, aldehyde dehydrogenase and acetyl-CoA synthetase in the obligate aerobic yeastRhodotorula gracilis are repressed by glucose and induced by C₂ metabolic fuels with a regulatory pattern indicating a correlation in the control mechanisms. To try an identification of the molecular signals involved in the transmission of the inducing stimulus, experiments were carried out by blocking with 2 mM pyrazole the ethanol acetaldehyde metabolic step. Results indicate that ethanol is not specifically required as a molecular signal for induction.This work was supported by a grant from the Italian Consiglio Nazionale delle Ricerche.     

Responses ofDrosophila to environmental ethanol from ecologically optimal and extreme habitats

Summary Adult tolerances and larval behaviour in the presence of ethanol is more variable in populations derived from optimal habitats than those from extreme habitats. Since the habitat types are defined ecologically in terms of climatic and biotic factors, this result has biological significance for defining the properties of populations from extreme habitats.I thank Garry Spence for technical assistance, and the Australian Research Grants Committee for partial financial support.     

Ethanol from cellulose

Summary An excess of organic waste, containing up to 60% cellulose and hemicellulose is produced worldwide. The conversion of this cellulosic material to ethanol is discussed: The two-step process consisting of a hydrolysis step to glucose and the subsequent fermentation by yeasts; and the one-step process, a fermentation of the cellulose by the anaerobic thermophileClostridium thermocellum, or by a thermophilic, anaerobic, defined mixed culture. The use of the latter seems to be very feasible., To achieve an economic process, it is suggested to combine this approach with a thermophilic fermentation of the effluent and/or stillage obtained to produce methane.Acknowledgment. Part of this work was supported by Energy and Research Development Administration contract number EY-76-509-0888-M003, and by the Deutsche Forschungsgemeinschaft.     

Effects of ethanol and acetaldehyde on cultured pre-implantation mouse embryos

Pre-implantation 2-cell stage mouse embryos, obtained from superovulated CF-1 mice, were exposed to ethanol and acetaldehyde through the culture medium for 60 min followed by a 105-h incubation period. Control and ethanol exposed embryos survived equally well in ethanol concentrations as high as 800 mg/100 ml medium and acetaldehyde levels up to 10 mg/100 ml medium.     

Effect of sucrose on lipogenesis of rats chronically treated with ethanol

Summary The effect of chronic ethanol administration with and without sucrose on the lipogenic enzymes of liver and adipose tissue of rats was studied. Ethanol markedly influenced the adipose lipogenic enzymes at 28 days. Sucrose caused a 2-10fold increase in lipogenic enzymes of both adipose and liver.Acknowledgment. This work was supported in part by a grant from the North Carolina Alcohol Research Authority.     

Effect of ethanol intake on phenytoin metabolism in volunteers.

Ingestion of ethanol, 1 g/kg, did not influence the phenytoin half-life in 5 volunteers after single i.v. administration of 3 mg/kg phenytoin. The control phenytoin half-life was 12.4 h (SD +/- 4.4); with ethanol ingestion it was 12.3 h (SD +/- 5.2).     

Effects of ethanol and acetaldehyde on cultured pre-implantation mouse embryos

Summary Pre-implantation 2-cell stage mouse embryos, obtained from superovulated CF-1 mice, were exposed to ethanol and acetaldehyde through the culture medium for 60 min followed by a 105-h incubation period. Control and ethanol exposed embryos survived equally well in ethanol concentrations as high as 800mg/100 ml medium and acetaldehyde levels up to 10 mg/100 ml medium.     

Effect of sucrose on lipogenesis of rats chronically treated with ethanol

The effect of chronic ethanol administration with and without sucrose on the lipogenic enzymes of liver and adipose tissue of rats was studied. Ethanol markedly influenced the adipose lipogenic enzymes at 28 days. Sucrose caused a 2-10fold increase in lipogenic enzymes of both adipose and liver.     

Diurnal rhythm of ethanol metabolism in the rat

Summary Male Sprague-Dawley rats injected with 2.0 g/kg of ethanol and analyzed 1 h later at 8 specific times of the day showed diurnal rhythms for alcohol concentrations in the blood, urine, brain and liver tissues. The circadian fluctuation noted for the concentrations of blood and tissue ethanol might indicate a diurnal variation in the enzymatic metabolism of ethanol.Supported by a grant from the US National Aeronautics and Space Administration.     

Effect of ethanol on taurine concentration in the brain

Summary The taurine concentration in the brain was decreased in ethanol-dependent rats, but returned to normal soon after withdrawal of ethanol. It was not affected by acute ethanol administration.This research was supported by a grant from the Taisho Pharmaceutical Co., Ltd., Tokyo.     

Efficacy of ethanol as a discriminative stimulus in ethanol-preferring and ethanol-nonpreferring rats

Rats which exhibited a preference for drinking a 6% w/v solution of ethanol in a free choice situation did not differ in their sensitivity to ethanol from animals exhibiting an aversion for ethanol, as measured by leaning rates in a T-maze task in which ethanol served as a discriminative stimulus.     

Efficacy of ethanol as a discriminative stimulus in ethanol-preferring and ethanol-nonpreferring rats

Summary Rats which exhibited a preference for drinking a 6% w/v solution of ethanol in a free choice situation did not differ in their sensitivity to ethanol from animals exhibiting an aversion for ethanol, as measured by learning rates in a T-maze task in which ethanol served as a discriminative stimulus.The author is thankful to Miss Christine Currey for technical assistance.     

Diurnal rhythm of ethanol metabolism in the rat

Male Sprague-Dawley rats injected with 2.0 g/kg of ethanol and analyzed 1 h later at 8 specific times of the day showed diurnal rhythms for alcohol concentrations in the blood, urine, brain and liver tissues. The circadian fluctuation noted for the concentrations of blood and tissue ethanol might indicate a diurnal variation in the enzymatic metabolism of ethanol.     

Dexamethasone protection against the acute lethality of ethanol in mice

Summary The administration of dexamethasone (DXM, 2.00 mg/kg) 1 h prior to the injection of lethal doses of ethanol was found to offer complete protection against ethanol toxicity at doses up to 5.25 g/kg and partial protection using higher doses. It is suggested that DXM central action might be involved in the protection against ethanol toxicity.Supported by a grant from U.S. National Aeronautics and Space Administration.     

Assessment of the scavenging action of reduced glutathione, (+)-cyanidanol-3 and ethanol by the chemiluminescent response of the xanthine oxidase reaction

The free radical scavenging capacity of reduced glutathione (GSH), (+)-cyanidanol-3 and ethanol was assessed by their interference with the maximal chemiluminescent response produced by the xanthine oxidase reaction. GSH and (+)-cyanidanol-3 induce a progressive inhibition of chemiluminescence when increasing amounts are added to the reaction mixture. GSH and (+)-cyanidanol-3 added together at low concentrations (1 and 0.05 mM respectively) exhibit an additive effect. The addition of ethanol presents a biphasic effect. It inhibits chemiluminescence at low concentrations (10-50 mM) while at higher concentrations (75-500 mM) this effect is reversed. Estimation of the concentrations required to produce half of the maximal inhibition of chemiluminescence by these agents revealed that ethanol is less effective than GSH and (+)-cyanidanol-3 as a free radical scavenger in the system used.     

Effect of chronic ethanol treatment on peroxisomal acyl-CoA oxidase activity and lipid peroxidation in rat liver and heart

Chronic ethanol administration was shown to increase catalase and acyl-CoA oxidase activities in rat myocardium but did not alter the activity of liver peroxisomal enzymes. As a result of alcohol consumption a 2-3-fold increase in the level of lipid peroxidation was observed in the heart tissue while in the liver the induction was much less pronounced.     

The effect of ethanol on the biosynthesis and regulation of opioid peptides

Summary Alcoholism and alcohol abuse are serious health problems. Alcohol is known to influence the activity of a number of biological systems, for example the hormonal and neuronal systems. One of the biological systems whose activity is greatly influenced by alcohol is the endogenous opiate system. Alcohol modifies the function of both opiate receptors and opioid peptides. In fact it has been proposed that many of the effects of ethanol are mediated by its effects on the endogenous opiate system. This review will present results from various laboratories on the effects of acute and chronic ethanol treatments on various species, and on the release, biosynthesis and post-translational processing of the endorphins, enkephalins and dynorphins, the three known families of endogenous opioid peptides. Furthermore, the effect of acute and chronic ethanol consumption on the -endorphin system in man, and the possible implications of the functional activity of the endogenous opiate system for the genetic predisposition to alcoholism will be discussed.     

Differential effects of ethanol on prostaglandin responses of arterial and venous smooth muscles.

The present results, using isolated rat aortic strips and portal vein segments, demonstrate that ethanol, depending upon concentration, can either enhance or attenuate the contractile actions of PGF2alpha on at least 2 different types of vascular smooth muscle. At the very least, the present findings question that the use of ethanol as a solvent when investigating the contractile actions of PG molecules on smooth muscles.