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Biomedical subjects

A Y Sun

Publications and source records attributed to A Y Sun.

At least 73 records · Page 4Linked to original sources
PubMed1983

Chronic ethanol administration induced an increase in phosphatidylserine in guinea pig synaptic plasma membranes.

Chronic ethanol administration to guinea pigs via intragastric intubation elicited a specific increase (50%) in phosphatidylserine in the synaptic plasma membrane. The ethanol-treated group also showed a 53% increase in synaptosomal (Na,K)-ATPase activity. Analysis of the acyl group composition of individual phospholipids in the same membrane fraction revealed only small changes which varied depending on the type of phospholipids. Since the (Na,K)-ATPase is known to be specifically activated by phosphatidylserine, the adaptive increase in enzyme activity during chronic ethanol treatment may be related to the increase in this type of negatively charged phospholipid.

Animals↗
PubMed1983

Effects of ATP on calcium binding to synaptic plasma membrane.

The release of labeled norepinephrine from preloaded synaptosomes requires the presence of potassium and calcium. ATP-dependent binding of calcium to synaptic plasma membranes (SPM) may provide a means of maintaining the cation in a readily available pool for the triggering of transmitter release. A high Ca-binding capacity was demonstrated in SPM. The Km for calcium is 5.5 X 10(-5) M. The dependence of the system on the gamma phosphate of ATP was demonstrated by an increase in Ca-binding with increasing ATP concentration and by competitive inhibition of binding by ADP and AMP. Magnesium is also required for ATP-dependent Ca-binding. The optimum pH for the Ca binding was 7.0. Pretreatment of SPM with phospholipase A2 lowered the binding capacity. Sulfhydryl groups are also critical for ATP-dependent Ca binding to occur. A model for ATP-dependent Ca-binding was proposed.

Adenosine Triphosphate↗
PubMed1981

Effects of acute administration of chlorinated water on liver lipids.

An acute administration of chlorinated water to rats caused "fatty liver" and indicated a more than 2-fold increase in liver triacylglycerols at 2 days after administration. The acyl group composition of triacylglycerols and phospholipids in both liver mitochondria and liver whole homogenate were also altered by the chlorine treatment. Among the phospholipid acyl groups, there was an increase in the proportion of 20:4 but a decrease in most other polyunsaturated acyl groups. The acyl group changes were more obvious with phosphatidylcholines than with phosphatidylethanolamines. Other phospholipids, including cardiolipin in the mitochondrial membranes, were not greatly altered. Both morphological and biochemical changes were maximum at 2 days after the treatment and were fully recovered after 10 days. The disturbance of a number of enzymatic processes in the liver membranes may account for a large part of the changes observed.

Animals↗
PubMed1980

Physicochemical approaches to the alcohol-membrane interaction in brain.

The effects of ethanol on physicochemical and enzymatic perturbations of neuronal membranes were examined. Using synaptic plasma membrane (SPM) isolated from cerebral cortex of Sprague-Dawley rats, a biphasic mode of action for ethanol was observed with (Na+ + K+)-ATPase, but not with Ca2+-ATPase or acetylcholinesterase. (Na+ + K+)-ATPase was found to be more sensitive to low concentration of sodium deoxycholate treatment than Ca2+-ATPase. A sharp transition break of (Na+ + K+)-ATPase activity in response to temperature changes was found with SPM preparation. Arrhenius plots of the response also indicated that (Na+ + K+)-ATPase is more sensitive to temperature changes than Ca2+-ATPase. The fluorescence polarization of TNS-membrane complex decreases as ethanol concentration increases, indicating an increase in membrane fluidity. However, ethanol, at low concentration (less than 0.3%) appears to elevate TNS fluorescence, but at higher concentration (3%) ethanol tends to lower the intensity of maximal emission. The results of this study indicate that ethanol may interact with the synaptic plasma membranes and elicit specific biochemical responses depending on the concentration of the alcohol used.

Animals↗
PubMed1980

Extraction and determination of chloroform in rat blood and tissues by gas chromatography-electron-capture detection: distribution of chloroform in the animal body.

We have developed a simple, sensitive, and accurate method for the determination of chloroform in rat blood, brain, kidney, liver, and fat. The detection limit is 2.5 ng of chloroform per gram of tissue. Studies of in vivo distribution of chloroform in rat blood and target tissues after intragastric intubation of chloroform/water show that the amount of chloroform accumulated in the different tissues increases with increasing doses. Fat tissue contains the greatest amount of chloroform. The accumulation of chloroform in rat blood and target tissues seems to be maximum 1.5 h after administration, and the apparent chloroform concentration is almost at baseline value 8 h later.

Adipose Tissue↗
PubMed1979

Effect of ethanol on cholesteryl ester hydrolases in adrenal.

An assay of cholesteryl ester hydrolase activity of microsomes from guinea pig adrenal indicated maximal activity at pH at pH 4.0 and 5.5. When ethanol was added to the microsomes, these enzymes showed differences in response with increasing ethanol concentration. Rats administered 15% ethanol as drink for 4--5 months showed a small (20%) increase in cholesteryl ester hydrolase (pH 4.0) activity in adrenal as compared to controls. However, a 50% decrease in cholesteryl ester hydrolase activity resulted when rats were administered ethanol by intragastric tubing technique (15 days) as compared to controls treated similarly with saline. The decrease in cholesteryl ester hydrolase activity was correlated with an increase in cholesteryl ester level in serum. In a different study, rats intubated with an acute dose of ethanol showed an increase in adrenal cholesteryl ester hydrolase activity as early as 1 hr after administration. This effect seemed to last for about 24 hr before activity returned to control level. It is concluded that different modes of ethanol administration to rats may elicit a change in cholesteryl ester hydrolase activity in the adrenal. An increase in cholesteryl ester hydrolase activity may be related to an increase in steroidogenic activity and activation of adrenocortical function.

Adrenal Glands↗
PubMed1979

Effect of chronic ethanol administration on phospholipid acyl groups of synaptic plasma membrane fraction isolated from guinea pig brain.

Guinea pigs were induced chronic alcoholism with a liquid diet containing 5% (w/v) ethanol. There was no apparent change in acyl group composition in the myelin lipids; however, acyl group changes were observed in the phosphoglycerides of synaptic plasma membranes (SPM). In general, acyl group changes are related to a decrease in the proportion of monoenes in both choline and ethanolamine phosphoglycerides and an increase in polyenes (15%) in the ethanolamine phosphoglycerides. The changes observed may be associated to the increased membrane-dependent transport activities observed after chronic ethanol treatment.

Alcoholism↗
PubMed1979

The effect of chronic ethanol administration on myelin lipids.

Myelin was isolated from the brain stem region of rats which were administered chronically with ethanol either through intragastric tubing (8gm/kg) for 3 weeks or by giving a 15% ethanol ad lib as drink for 1 year. The protein, phospholipid and cholesterol content and the acyl group composition of major phosphoglycerides of myelin were examined. Based on the protein content, there was less myelin isolated from the chronic alcoholic brain samples as compared to controls. Intrinsic changes in membrane components were observed. The phospholipid to protein ratio of myelin was approximately 20% lower in the group subjected chronically to ethanol by drink and 10% lower in the group given ethanol through intubation technique. The cholesterol to protein ratio was also lower in the group given ethanol as drink but the intubated group was not different from controls. Changes in phosphoglyceride acyl group composition were also observed. In general, there was an increase in the proportions of 16:0, 18:0 and 18:1 and a decrease in 20:1, 20:4 and 22:6. The acyl group changes reflected an increase in cellular phospholipase A2 or a decrease in chain desaturation and elongation activity due to chronic ethanol administration. These changes are also reflective of degenerative changes possibly associated with demyelination.

Alcoholism↗
PubMed1978

Dihydroergotoxine and ethanol: physiological and neurochemical variables in male mice.

The residual effects of dihydroergotoxine mesylate (DHET: active substance of Hydergine), ethanol, and DHET + ethanol were investigated in aging male mice. Prolonged alcohol or DHET consumption was found to prolong hexobarbital sleeping time and increase oxygen consumption. Administration of alcohol combined with DHET inhibited the ability of each drug to prolong hexobarbital sleeping time and increase oxygen consumption. There were no significant differences between groups in forebrain synaptosomal (Na+-K+) adenosine- triphosphatase and acetylcholinesterase activity or cerebellar protein, DNA and RNA content. The relative proportion of phospholipid to protein in isolated myelin of the medulla was significantly reduced, whereas the sphingomyelin content of total phospholipid was highest in alcohol-treated mice. Conocomitant treatment of mice with alcohol combined with DHET prevented the physiological and neurochemical changes caused by alcohol and, in some cases, DHET, administered alone.

Acetylcholinesterase↗
PubMed1978

The effects of chronic ethanol administration on acyl group composition of mitochondrial phospholipids from guinea pig adrenal.

The acyl groups of diacyl-glycerophosphocholine1 (GPC) and diacyl-glycerophosphoethanolamine (GPE) in guinea pig adrenals are comprised mainly of 16:0, 18:0, 18:1, 18:2 and 20:4(n-6) with only trace amounts of the longer chain polyunsaturated fatty acids. There was an increase in the proportions of 18:2 and a decrease in the 20:4(n-6) of diacyl-GPC and diacyl-GPE with respect to chronic ethanol administration. Acyl group changes were more obvious in diacyl-GPC than in diacyl-GPE. It is conceivable that these changes may lead to an alteration of other membrane transport activities as well as functions of the adrenal gland.

Adrenal Glands↗
PubMed1978

Effects of ethanol and dihydroergotoxine on mouse brain myelin components.

The effects of prolonged consumption of ethanol, dihydroergotoxine (Hydergine) and Hydergine-plus-ethanol on brain myelin components isolated from the medulla oblongata of mouse brain were examined. Based on protein content, the amount of myelin isolated from the brain tissue was not different with regard to the various treatments. However, there was a significant decrease (20%) in myelin phospholipid and cholesterol to protein ratios in the ethanol group as compared to controls and the Hydergine-treated group. On the contrary, the Hydergine and Hydergine-ethanol groups had higher cholesterol to phospholipid ratios than controls. In spite of the changes in membrane components, little change in acyl group composition of the phosphoglycerides was found in myelin.

Aging↗
PubMed1977

The effect of aging on synaptosomal Ca2+ transport in the brain.

The effect of aging on Ca2+ -transport in synaptosomal preparations from rat brains was assessed by measuring the accumulation of radioactive 45Ca within these particles. Four groups of rats at 6, 12 24 and 30 months of age were used for this study. Synaptosomal particles were isolated from the cerebral cortex of each animal and the radioactive 45Ca inside the particles were measured after incubating the particles with media containing an energy source and 45Ca Cl2. Results indicated that the transport of 45Ca was lower in the younger rats than the older groups. A 20% increase was consistent with the old rats (30 mo) as compared with the young ones (6 mo). The increase in Ca2+ -transport across synaptic plasma membranes may be related to the transmitter release and behavioral activity after senescence.

Adenosine Triphosphate↗
PubMed1977

The effect of chronic ethanol administration on arachidonyl transfer to 1-acyl-glycerophosphorylcholine in rat brain synaptosomal fraction.

Enzymatic transfer of arachidonate to synaptosomal diacyl-GPC in a group of rats (n=14) administered 30% ethanol by intragastric intubation for 21 days was 24% higher than controls (n=5) (P less than 0.05). No apparent difference in enzymic activity was observed with respect to different periods of withdrawal (8-24 hrs). The acyl transferase activity in another group of rats (n=5) which were given 15% ethanol as the sole drinking source for 13 months was 58% higher than controls (P less than 0.025). The increase in acyl transferase activity with respect to the two types of chronic ethanol administration may be due to an adaptive mechanism in brain to facilitate the increase in membrane transport activities which are known to occur under the influence of ethanol.

Acyltransferases↗
PubMed1977

Alcohol-membrane interaction: calcium uptake in mitochondria.

A biphasic effect of ethanol was observed on Ca2+-uptake activity, Ca2+-uncoupled respiratory control ratio (CURCR), and State 3 oxygen uptake. At low concentrations (0.1-0.5%) ethanol enhanced these activities, probably as the result of an increase in membrane fluidity. At higher levels (0.7-4.0%) ethanol had an inhibitory influence on mitochondrial activities as the membrane macromolecules were probably disturbed due to the hydrophobic alcohol-membrane interaction.

Animals↗