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Relationship between lipid composition, frequency of ethanol-induced respiratory deficient mutants, and ethanol tolerance in Saccharomyces cerevisiae.

The frequency of ethanol-induced respiratory deficient mutants and lipid composition in two Saccharomyces cerevisiae strains showing different degrees of ethanol tolerance were investigated. The more ethanol-tolerant strain exhibited a lower frequency of ethanol-induced respiratory deficient mutants than the less ethanol-tolerant strain. In addition, the more ethanol-tolerant strain contained a higher ergosterol/phospholipid ratio, a higher proportion of phosphatidylcholine, a lower proportion of phosphatidylethanolamine, a higher incorporation of long-chain fatty acids in total phospholipids, and a slightly higher proportion of unsaturated fatty acids in total phospholipids than the less ethanol-tolerant strain. These results show a clear relationship between the lipid composition, the frequency of ethanol-induced respiratory deficient mutants, and the ethanol tolerance of S. cerevisiae. A possible explanation of this relationship is discussed.

Ethanol↗

Forskolin promotes the development of ethanol tolerance in 6-hydroxydopamine-treated mice.

Partial depletion of brain norepinephrine by 6-hydroxydopamine prevents the development of functional tolerance to ethanol in mice. This blockade of tolerance development was overcome by daily intracerebroventricular injections of forskolin. These results suggest that interaction of norepinephrine with post-synaptic beta-adrenergic receptors, and activation of adenylate cyclase, is important for the development of ethanol tolerance. Interaction of norepinephrine with alpha 1-adrenergic receptors may be less crucial, since treatment with a phorbol ester activator of protein kinase C did not restore the development of tolerance in mice treated with 6-hydroxydopamine. The importance of the beta-adrenergic receptor-coupled adenylate cyclase system for development of ethanol tolerance, in addition to its previously-reported role in long-term potentiation, suggests that this system may influence neuroadaptive processes in general.

Animals↗

Effect of ethanol tolerance on norepinephrine-ethanol inhibition of (Na+ + K+)-adenosine triphosphatase in various regions of rat brain.

Brain (Na+ + K+)-adenosine triphosphatase activity from untreated rats was inhibited by a combination of 1 microM norepinephrine + 50 mM ethanol (NE + EtOH), in preparations from cerebral cortex (CX), cerebellum (CB), hippocampus (HC), hypothalamus (HT), thalamus-midbrain and pons-medulla, but not from striatum. The rank order of inhibition in these regions was more similar to that of alpha-1 receptor density than of regional NE content. EtOH administration for 3 weeks produced tolerance to the hypothermic effect of EtOH; increased basal adenosine triphosphatase activity in CX, CB and HC, as measured 24 hr after withdrawal; and decreased the inhibitory effect of NE + EtOH in CX, HT, HC and CB preparations. Tolerance to the inhibitory effects of high concentrations (0.22 or 0.44 M) of EtOH alone was found only in CX, HT and HC preparations. Tolerance to NE + EtOH or to EtOH alone was greatest in HC and CX, intermediate in HT and CB and least or absent in other regions. Temperature-dependence of (Na+ + K+)-adenosine triphosphatase activity was studied in preparations from CX (high initial sensitivity to NE + EtOH, high tolerance development), CB (intermediate initial sensitivity, intermediate tolerance) and striatum (no initial sensitivity, no tolerance). Arrhenius plots showed differences between these regions, with respect to changes in transition temperature and activation energy after chronic EtOH treatment in vivo. These changes did not explain the regional differences in tolerance development. Therefore it seems unlikely that a single mechanism, such as "stiffening" of the cell membrane, can explain the varied pattern of tolerance development in different brain regions.

Animals↗

Ethanol-Induced Leakage in Saccharomyces cerevisiae: Kinetics and Relationship to Yeast Ethanol Tolerance and Alcohol Fermentation Productivity.

Ethanol stimulated the leakage of amino acids and 260-nm-light-absorbing compounds from cells of Saccharomyces cerevisiae. The efflux followed first-order kinetics over an initial period. In the presence of lethal concentrations of ethanol, the efflux rates at 30 and 36 degrees C were an exponential function of ethanol concentration: k(e) = k(e)e, where k(e) and k(e) are the efflux rate constants, respectively, in the presence of a concentration X of ethanol or the minimal concentration of ethanol, X(m), above which the equation was applicable, coincident with the minimal lethal concentration of ethanol. E is the enhancement constant. At 36 degrees C, as compared with the corresponding values at 30 degrees C, the efflux rates were higher and the minimal concentration of ethanol (X(m)) was lower. The exponential constants for the enhancement of the rate of leakage (E) had similar values at 30 or 36 degrees C and were of the same order of magnitude as the corresponding exponential constants for ethanol-induced death. Under isothermic conditions (30 degrees C) and up to 22% (vol/vol) ethanol, the resistance to ethanol-induced leakage of 260-nm-light-absorbing compounds was found to be closely related with the ethanol tolerance of three strains of yeasts, Kluyveromyces marxianus, Saccharomyces cerevisiae, and Saccharomyces bayanus. The resistance to ethanol-induced leakage indicates the possible adoption of the present method for the rapid screening of ethanol-tolerant strains. The addition to a fermentation medium of the intracellular material obtained by ethanol permeabilization of yeast cells led to improvements in alcohol fermentation by S. cerevisiae and S. bayanus. The action of the intracellular material, by improving yeast ethanol tolerance, and the advantages of partially recycling the fermented medium after distillation were discussed.

Journal Article↗

In vitro tolerance to inhibition by ethanol of N-methyl-D-aspartate-induced depolarization in locus coeruleus neurons of behaviorally ethanol-tolerant rats.

Intracellular recordings were made in pontine slice preparations of the rat brain containing the locus coeruleus (LC). Ethanol at 100 mM, but not at 10 or 30 mM inhibited depolarizing responses to pressure-applied N-methyl-D-aspartate (NMDA) in LC neurons of ethanol-naive rats. Ethanol (100 mM) had a similar effect in LC neurons of ethanol-naive rats, of rats treated with ethanol for 14 days (3 g/kg daily, i.p.) and of rats treated with equicaloric amounts of saccharose (5 g/kg daily, i.p.). The blood concentration of ethanol was markedly decreased at 4 h, and was below the detection limit at 24 h after the last injection. Behavioral measurements in the open-field system demonstrated the development of tolerance in rats receiving ethanol for 14 days. Moreover, an anxiety-related reaction was shown to develop when the acute effect of the last ethanol injection vanished. Therefore, in subsequent in vitro experiments, ethanol (10 mM) was continuously present in the superfusion medium in order to mimic a steady blood concentration and to prevent a withdrawal-like situation. Under these conditions, ethanol (100 mM) still continued to inhibit the NMDA-induced depolarization in slices of untreated rats, but became ineffective in slices of ethanol-treated rats at 4 h after the last injection. By contrast, a supersensitivity to ethanol developed in brain slices at 24 h after the last ethanol injection. In conclusion, in vitro tolerance between systemically and locally applied ethanol at LC neurons could only be demonstrated when a low concentration of ethanol was added to the superfusion medium to simulate the blood concentration of this compound.

Animals↗

Ethanol tolerance in bacteria.

The adverse effects of ethanol on bacterial growth, viability, and metabolism are caused primarily by ethanol-induced leakage of the plasma membrane. This increase in membrane leakage is consistent with known biophysical properties of membranes and ethanolic solutions. The primary actions of ethanol result from colligative effects of the high molar concentrations rather than from specific interactions with receptors. The ethanol tolerance of growth in different microorganisms appears to result in large part from adaptive and evolutionary changes in cell membrane composition. Different cellular activities vary in their tolerance to ethanol. Therefore, it is essential that the aspect of cellular function under study be specifically defined and that comparisons of ethanol tolerance among systems share this common definition. Growth is typically one of the most sensitive cellular activities to inhibition by ethanol, followed by survival, or loss of reproductive ability. Glycolysis is the most resistant of these three activities. Since glycolysis is an exergonic process, a cell need not be able to grow or remain viable for glycolysis to occur.

Bacteria↗

N-methyl-D-aspartate receptors, nitric oxide, and ethanol tolerance.

Several experimental models have been used to study tolerance to ethanol. The development of tolerance to the motor incoordinating effect of a single administration of ethanol occurs within 8-24 h after the effect of the first dose has disappeared. This form of tolerance is designated rapid tolerance and seems to involve functional rather than pharmacokinetic mechanisms. Like chronic tolerance, rapid tolerance has been shown to be influenced by processes related to learning and memory. It is known that N-methyl-D-aspartate (NMDA) receptor systems are involved in the expression and maintenance of one form of long-term potentiation (LTP), a synaptic adaptive process which has been suggested to be the cellular basis of memory or associative memory. Considering the similarities between learning and tolerance, the effects of NMDA agonists and antagonists on tolerance to ethanol were investigated. Our studies demonstrated that NMDA antagonists that impair learning, such as dizocilpine or ketamine, inhibit tolerance, while NMDA agonists that improve learning, such as D-cycloserine, increase tolerance. Moreover, the nitric oxide synthase inhibitor L-nitroarginine blocks tolerance to the effects of ethanol. Taken together, these data confirm the involvement of the NMDA system in ethanol tolerance and emphasize the participation of learning in this phenomenon.

Animals↗

Membrane fatty acid changes and ethanol tolerance in rat and mouse.

Ethanol tolerance and erythrocyte membrane lipids were studied in Sprague-Dawley rats at various times during and after chronic administration, by inhalation, of ethanol vapor. Tolerance increased during the three weeks treatment period and reverted to base line ten days after the treatment was stopped. Chronic ethanol treatment led to changes in the composition of membrane phospholipid fatty acids. These changes partially reverted after treatment ceased. At all times the changes in 16:0, 18:0, 18:1 and 18:2 were correlated with the degree of ethanol tolerance. Analysis of the effect of ethanol treatment (ip injections over a one week period) in three strains of mice showed that the changes of phospholipid fatty acids in erythrocyte membranes were related to whether the strain developed a tolerance to the hypnotic effect of ethanol (DBA, C 57), or not (Swiss). These results show that membrane phospholipid fatty acid composition and ethanol tolerance co-vary during chronic treatment. During the withdrawal period, ethanol sensitivity reverts to control values while the return of the fatty acids to the normal state is incomplete.

Animals↗

Effects of frontal polar cortical ablation and cycloheximide on ethanol tolerance in rats.

Thirty adult male Wister rats were pretrained to criterion on the moving belt test, and then made tolerant to ethanol by daily administration of increasing doses over a period of 3 weeks. After a one-month recovery period, they were divided into 3 groups, subjected to bilateral frontal polar cortical ablations, sham-operation and no operation respectively. After postoperative recovery, the cycle of ethanol treatment and testing was repeated. Only the lesioned group failed to reacquire tolerance. A pilot experiment showed that occipital cortical ablations also prevented tolerance. In a second experiment 32 rats, which had similarly undergone and then recovered from an initial period of ethanol tolerance, were divided into 4 groups which received daily treatment with sucrose plus cycloheximide (0.3 mg/kg), sucrose plus saline, ethanol plus cycloheximide, and ethanol plus saline respectively. Only the ethanol plus saline group re-acquired tolerance. Tt is concluded that frontal polar cortical lesions and cycloheximide can both block the development of tolerance to ethanol in animals previously shown to be capable of developing such tolerance.

Animals↗

Effects of post-ethanol administration of NMDA and non-NMDA receptor antagonists on the development of ethanol tolerance in C57B1 mice.

The effect of post-ethanol administration of NMDA and non-NMDA receptor antagonists on the development of environment-dependent ethanol tolerance was studied in C57B1 mice. Ethanol tolerance was produced by daily injections of ethanol (3.5 g/kg, IP) in the same experimental environment and measured as ethanol-produced "sleep-time" during 5 consecutive days. The non-competitive NMDA receptor antagonist, dizocilpine (MK-801; 0.1 mg/kg, IP), and the competitive NMDA receptor antagonist, CGP 39551 (5 mg/kg, IP), both given 120 min after the administration of ethanol, inhibited the development of tolerance to the hypnotic actions of ethanol. In contrast, the development of ethanol tolerance was not altered by administration of the specific AMPA/KA receptor blocking agents, NBQX (10 mg/kg, IP), and LY326325 (2.5 mg/kg, IP), respectively. Modulation of NMDA receptor activity by drugs like NMDA, d-cycloserine, and milacemide, which are known to enhance learning and memory in rodents, had no significant effect on the development of ethanol tolerance. Our present data confirm and extend previous findings which indicate that NMDA, but not non-NMDA, glutamate receptors may play an important role in the neuroadaptive processes associated with the development of ethanol tolerance.

Animals↗

Development of ethanol tolerance not altered by 6-OHDA lesions of dorsal bundle.

It has been demonstrated via intraventricular (IVT) 6-OHDA infusions that central nervous system norepinephrine is necessary for the development of tolerance to ethanol (ETOH) in the mouse. Because 6-OHDA IVT infusions are not specific, we tested the effects of destruction of a specific NE pathway on development of ETOH tolerance. Rats received 6-OHDA lesions of the dorsal noradrenergic bundle (DB) and the development of ethanol tolerance was measured using the sleeptime test. The time between loss and recovery of the righting reflex was determined after an acute challenge dose of ETOH. Rats were than placed on ETOH diet for 13 days followed by a repeat of the sleeptime test. Sham and 6-OHDA-DB-lesioned rats exhibited the same sleeptime prior to ETOH diet, consumed similar amounts of ETOH diet over the course of 13 days, and exhibited similar significantly (p less than 0.0005) shorter sleeptimes after ETOH diet. Our data suggest that destruction of the DB does not alter development of ETOH tolerance as measured by the sleeptime test.

Animals↗

Short-term metabolic ethanol tolerance in dogs.

Metabolic ethanol tolerance was studied in a cohort of five dogs with ethanol challenge repeated weekly over a 7-week period. During the 7-week period, the area under the blood alcohol versus time curve (AUC) increased slightly while the rate of ethanol elimination also increased slightly. During the repeated ethanol dosing, ethanol absorption shifted from approximately equal absorption in the stomach and intestine to three-fold more absorption in the intestine than in the stomach. The likely cause of the shift in absorption site was probably a concomitant change in gastric emptying that occurred with repeated dosing. This shift is significant since ethanol absorption in the small intestine has been shown to be over six-fold more rapid than ethanol absorption in the stomach.

Animals↗

Antisense oligonucleotide to c-fos blocks the ability of arginine vasopressin to maintain ethanol tolerance.

Administration of the neuropeptide, arginine vasopressin, can reduce the rate of dissipation of functional ethanol tolerance in mice that have acquired that tolerance. We previously showed that intracerebroventricular vasopressin administration can also produce an increase in septal c-fos mRNA levels. To evaluate the role of the increased expression of c-fos in the ability of vasopressin to maintain tolerance, ethanol-tolerant mice were given intracerebroventricular injections of vasopressin in the presence or absence of an antisense oligonucleotide to c-fos. The antisense oligonucleotide completely blocked the ability of vasopressin to maintain ethanol tolerance, while a missense oligonucleotide was without effect. The antisense oligonucleotide also attenuated the increase in septal c-fos mRNA levels caused by vasopressin. The results provide evidence for a role of c-fos expression in the maintenance of ethanol tolerance by vasopressin.

Analysis of Variance↗

Ethanol tolerance in hippocampal neurons: adaptive changes in cellular responses to ethanol measured in vitro.

The passive and synaptic membrane properties of hippocampal CA1 and dentate gyrus granule neurons have been compared in hippocampal slices obtained from control and ethanol-tolerant rats given ethanol up to 24 hr before sacrifice. In addition, the effects of in vitro exposure to a low concentration (20 mM) of ethanol have been examined in neurons obtained from both groups of animals. No differences were observed in the passive or synaptic membrane properties of dentate granule neurons obtained from control and chronically ethanol-exposed rats. Dentate granule neurons obtained from the two groups of animals also showed similar responses to in vitro exposure to 20 mM ethanol. Hippocampal CA1 neurons were also similar, except for the post-spike train afterhyperpolarization which was significantly prolonged in neurons from chronically ethanol-exposed animals. Exposure to 20 mM ethanol in vitro resulted in a significant increase in the amplitude and duration of the afterhyperpolarization in CA1 neurons obtained from control animals, but a significant decrease in CA1 neurons obtained from chronically ethanol-exposed rats. These results suggest that behavioral tolerance to ethanol is accompanied by adaptive changes in the electrophysiological responses of hippocampal CA1 neurons when tested with an acute exposure to ethanol. Chronic treatment with ethanol did not cause such adaptive changes in dentate gyrus granule neurons suggesting that they may be less sensitive to the effects of long-term exposure to ethanol than CA1 neurons.

Action Potentials↗

Interaction between N-methyl-D-aspartate (NMDA) and serotonin (5-HT) on ethanol tolerance.

Earlier work from this laboratory had shown that 5-HT is involved in the development of tolerance to ethanol, and that enhancement of 5-HT levels by L-tryptophan accelerated tolerance development. To explore the possibility that NMDA receptors are involved in the 5-HT effect on tolerance, we examined the effect of a noncompetitive N-methyl-D-aspartate (NMDA) antagonist [(+)MK-801] on the ability of L-tryptophan to enhance tolerance to the effect of ethanol on tilt-plane test performance by the rat. L-Tryptophan treatment resulted in the development of rapid tolerance to a dose of ethanol that failed to produce such tolerance by itself. However, prior administration of (+)MK-801 blocked the L-tryptophan effect on rapid tolerance development, in a dose-dependent manner. These results suggest that NMDA receptors are involved in the 5-HT enhancement of ethanol tolerance.

Analysis of Variance↗

Ethanol tolerance in yeasts.

It is now certain that the inherent ethanol tolerance of the Saccharomyces strain used is not the prime factor regulating the level of ethanol that can be produced in a high sugar brewing, wine, sake, or distillery fermentation. In fact, in terms of the maximum concentration that these yeasts can produce under batch (16 to 17% [v/v]) or fed-batch conditions, there is clearly no difference in ethanol tolerance. This is not to say, however, that under defined conditions there is no difference in ethanol tolerance among different Saccharomyces yeasts. This property, although a genetic determinant, is clearly influenced by many factors (carbohydrate level, wort nutrition, temperature, osmotic pressure/water activity, and substrate concentration), and each yeast strain reacts to each factor differently. This will indeed lead to differences in measured tolerance. Thus, it is extremely important that each of these be taken into consideration when determining "tolerance" for a particular set of fermentation conditions. The manner in which each alcohol-related industry has evolved is now known to have played a major role in determining traditional thinking on ethanol tolerance in Saccharomyces yeasts. It is interesting to speculate on how different our thinking on ethanol tolerance would be today if sake fermentations had not evolved with successive mashing and simultaneous saccharification and fermentation of rice carbohydrate, if distillers' worts were clarified prior to fermentation but brewers' wort were not, and if grape skins with their associated unsaturated lipids had not been an integral part of red wine musts. The time is now ripe for ethanol-related industries to take advantage of these findings to improve the economies of production. In the authors' opinion, breweries could produce higher alcohol beers if oxygenation (leading to unsaturated lipids) and "usable" nitrogen source levels were increased in high gravity worts. White wine fermentations could also, if desired, match the higher ethanol levels in red wines if oxygenation (to provide the unsaturated lipids deleted in part by the removal of the grape skins) were practiced and if care were given to assimilable nitrogen concentrations. This would hold true even at 10 to 14 degrees C, and the more rapid fermentations would maximize utilization of winery tankage.(ABSTRACT TRUNCATED AT 400 WORDS)

Ethanol↗

Relationship between ethanol tolerance, H+ -ATPase activity and the lipid composition of the plasma membrane in different wine yeast strains.

Ethanol tolerance, ATPase activity and the lipid composition of the plasma membrane to study potential relationship among them were examined in five different wine yeast strains. Yeast cells were subjected to ethanol stress (4% v/v). Principal component analysis of the results revealed that the wine yeasts studied can be distinguished in terms of ATPase activity and oleic acid (C18:1), and palmitoleic acid (C16:1), in plasma membrane. Multiple regression analysis was used to identify a potential influence of some components of the plasma membrane on ethanol tolerance and ATPase activity. Based on the results, the ergosterol, oleic acid and palmitoleic acid are highly correlated with ATPase activity and ethanol tolerance. Ethanol tolerance and the ATPase activity of the plasma membrane were correlated at the 96.64% level with the oleic acid and ergosterol in plasma membrane. The Saccharomyces cerevisiae var. capensis flor yeast strain, which exhibited the highest ergosterol concentration in plasma membrane when grown in the presence of 4% v/v ethanol, was found to be the most ethanol-tolerant.

Adenosine Triphosphatases↗

Selection for ethanol tolerance in two populations of Drosophila melanogaster segregating alcohol dehydrogenase allozymes.

Selection for ethanol tolerance was equally successful in two populations of D. melanogaster in both of which the frequency of AdhF was 0.5 at the start of the experiment. Increased tolerance to ethanol was not invariably associated with increased frequencies of AdhF. In one population alcohol dehydrogenase (ADH) activity was significantly higher in three of the four selected sublines compared with their controls but there was no difference in activity between the selected and control sublines in the second population. The level of ADH activity in the control and selected lines was significantly correlated with the frequency of AdhF, but not with ethanol tolerance. These results show that adaptation to environmental alcohols in populations of D. melanogaster can be independent of the ADH system.

Alcohol Oxidoreductases↗