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Biomedical subjects

H Igisu

Publications and source records attributed to H Igisu.

At least 55 records · Page 3Linked to original sources
PubMed1993

Brain energy metabolites in mice after an acute exposure to carbon monoxide.

Brain energy metabolites were determined in mice over 8 days after an acute exposure to carbon monoxide (CO). The exposure of 0.5% CO for 15 min caused 33% mortality. Survived mice recovered completely within 30 min in room air. Lactate increased markedly immediately after the exposure, while glucose increased 30 min later. Four hours, 1 day, 4 days and 8 days after the exposure, the levels of brain energy metabolites including phosphocreatine and ATP did not differ from those of the control. Thus, energy metabolism in the whole brain in mice appears not to be impaired after they survive an acute CO intoxication.

Adenosine Triphosphate↗
PubMed1992

Preservation of energy metabolites by carnitine in the mouse brain under ischemia.

Ischemia (decapitation) caused marked changes of energy metabolites in the mouse brain. However, the changes were clearly less severe, when the mouse was pre-treated with L-carnitine. This suggests that L-carnitine may protect the brain from the ischemic attack. Since D-carnitine showed a similar effect, the effects may be due to mechanism(s) other than the 'classical' function of carnitine.

Animals↗
PubMed1992

["Toxins" and nerve--a discussion on the pathogenesis of acrylamide intoxication, giant axonal neuropathy and Krabbe disease].

A common mechanism appears to play a pathogenetic role in acrylamide intoxication, which is due to an exogenous cause, and in giant axonal neuropathy, an intrinsic disorder. In giant axonal neuropathy, a genetic defect in the processing of an intrinsic acrylamide or acrylamide-like substance may be postulated. On the other hand, the devastating pathology in Krabbe disease (a genetic disorder affecting almost exclusively the nervous system) appears to be due to the effects of psychosine, a toxic lipid produced in the nervous system. These suggest that the "toxicological approach" can be more diverse and of greater use than usually considered.

Acrylamide↗
PubMed1992

[Effects of methylmercury chloride on creatine kinase activity in the rat brain].

The effects of methylmercury chloride (MMC) on creatine kinase (CK) activity in the rat brain were studied. Male Wistar rats were injected subcutaneously with 10 mg MMC/kg body weight/day for 7 consecutive days, and sacrificed on the 15th day when all rats showed a crossing phenomenon of the hind limbs. CK activity was mildly inhibited in the anterior, mid and posterior cerebral cortex. Aspartate aminotransferase and lactate dehydrogenase activities were also inhibited in some parts of the cerebral cortex, almost to the same extent as the CK activity. No definite inhibition of the enzyme activity was found in the striatum and the cerebellum. From this study we concluded that the mild inhibition of CK activity does not seem to play an important role in the genesis of neurotoxicity of MMC.

Animals↗
PubMed1992

Brain energy metabolites in mice intoxicated with acrylamide: effects of ischemia.

Concentrations of phosphocreatine, creatine, ATP, ADP, AMP, glucose and lactate in the whole brain did not differ between the mice intoxicated with acrylamide and the controls. When the brain was made ischemic, these concentrations changed to the same extent in both groups. The only difference was the lower pyruvate in acrylamide-intoxicated mice under the ischemia. Thus, as far as the whole brain is concerned, acrylamide does not cause gross alterations of energy metabolites, even under ischemia.

Acrylamide↗
PubMed1991

Suppression of neurotoxicity of ammonia by L-carnitine.

Administration of ammonium acetate to mice caused seizures and alterations of brain energy metabolites. Pretreatment of animals with L-carnitine suppressed the frequency of the seizures and prolonged the latency to the first fit. When examined using the 'freeze clamp' method, brain energy metabolites were well preserved and the elevation of ammonia was less marked on administration of L-carnitine. Thus, L-carnitine suppresses ammonia-induced seizures and biochemical alterations of the brain in mice.

Ammonia↗
PubMed1990

Effects of acrylamide and N,N'-methylene-bis-acrylamide on creatine kinase activity.

In vitro, both acrylamide and N,N'-methylene-bis-acrylamide inhibited creatine kinase (CK) activity from brain or sciatic nerve with almost the same potency. In vivo, only acrylamide (50 mg/kg b. wt./day, 8 days) caused paralysis of hind limbs and suppressed CK activity in cerebrum, cerebellum, spinal cord and muscle in rats. Bis-acrylamide (50 mg or 100 mg/kg b. wt./day, 8 days) caused no paralysis nor inhibition of CK activity in any tissue examined. Definite inhibition of CK was not found in sciatic nerve from rats given either chemical. The inhibition of CK may play a role in the genesis of toxicity of acrylamide especially in the central nervous system.

Acrylamide↗
PubMed1990

Binding of galactosylsphingosine (psychosine) by albumin.

On applying [3H]galactosylsphingosine (psychosine) and albumin to a gel filtration column, either as a pre-incubated mixture or as separate solutions, the lipid and albumin co-eluted. When albumin and [3H]galactosylsphingosine were incubated with Sephadex G-50, the concentration of galactosylsphingosine outside the gel increased as the concentration of albumin increased. These observations indicate that albumin binds galactosylsphingosine. By using an equilibrium gel procedure, it was estimated that one molecule of albumin has 7.4 binding sites for galactosylsphingosine, and that the dissociation constant is 3.9 X 10(-6) M. These values appear compatible with the potency of albumin to suppress galactosylsphingosine-induced hemolysis.

Binding Sites↗
PubMed1990

Inhibition of creatine kinase activity by ethylene oxide.

Exposure of rats to 500 ppm ethylene oxide for six hours a day, three times a week, for 12 weeks, lowered serum creatine kinase activity by more than 40%. The only other change was a slightly decreased triglyceride concentration. After four weeks of exposure, neither aspartate aminotransferase nor lactate dehydrogenase activity in brain, spinal cord, and muscle was affected but creatine kinase activity was clearly inhibited. In vitro, ethylene oxide inhibited creatine kinase activity in brain homogenate and in a purified muscle enzyme preparation. Dithiothreitol did not counteract the effect of ethylene oxide. Though the amount of sulphydryl groups in purified creatine kinase was decreased considerably by exposure to ethylene oxide, the enzyme still showed moderate activity. Thus ethylene oxide inhibits creatine kinase activity in vivo and in vitro and the inhibition appears to be unrelated to the disruption of sulphydryl groups in the enzyme.

Animals↗
PubMed1989

[Psychosine: a "toxin" produced in the brain--its mechanism of action].

Psychosine (galactosylsphingosine) is enzymatically synthesized from UDP-galactose and sphingosine and degraded by galactosylceramidase. Galactosylceramidase is genetically deficient in Krabbe disease (globoid cell leukodystrophy) and psychosine accumulates in the brain of humans, dogs or mice affected by the disease. Psychosine has a very potent inhibitory effect on cytochrome c oxidase (COX) in mitochondria. When COX is purified, psychosine does not suppress the enzyme activity. However, a clear inhibitory effect is seen when the enzyme is "reconstituted" with sonicated phosphatidylcholine, suggesting that the inhibition of the enzymatic activity is caused by perturbation of the environment of COX in the mitochondrial membrane. Studies using analogues suggest that the free amino group in the sphingosine moiety plays an important role in exerting the effects of psychosine. The effects of psychosine are not only potent but fast and reversible. It is noteworthy that a powerful inhibitor of cellular respiration is synthesized in mammals' brain, an organ vulnerable to hypoxia.

Animals↗
PubMed1989

Acrylamide and thiamine.

Acrylamide administration to rats caused clear alteration of blood thiamine content, which appeared to reflect suppressed intake and/or utilization of the vitamin in the body. Decreased utilization of thiamine does not seem to be induced by decreased binding of thiamine pyrophosphate (TPP) and apotransketolase, because acrylamide did not affect the Km of TPP for transketolase activity.

Acrylamides↗
PubMed1988

[Effects of repeated inhalation-exposure to fenitrothion powder on blood cholinesterase activity in rats].

Effects of repeated exposure to Fenitrothion (Sumithion) powder on erythrocyte membrane acetylcholinesterase (AChE) and plasma cholinesterase (PChE) were studied. Rats (Wistar, male) were exposed to fenitrothion powder for 2 hrs/day, 5 days/week for up to 3 months. The suppression of AChE and PChE increased as the exposure period and exposure concentration increased, although no suppression of AChE was found after a single 4-hr exposure. The persistence of AChE inhibition after the termination of exposure increased with the increase of the exposure period and was longer than that of PChE. Therefore, the AChE activity seems to be useful in examining the response to the repeated exposure to fenitrothion powder.

Administration, Inhalation↗
PubMed1988

Inhibition of cytochrome c oxidase and hemolysis caused by lysosphingolipids.

Galactosylsphingosine, glucosylsphingosine and sphingosine all inhibited cytochrome c oxidase activity in mitochondria from rat liver; more than 50% inhibition was caused by 5 microM lipid (0.1 mumol/mg mitochondrial protein). However, these lysosphingolipids did not suppress the activity of purified cytochrome c oxidase. When the enzyme was "reconstituted" with phosphatidylcholine, the lysosphingolipids clearly inhibited the activity. On the other hand, galactosylsphingosine, glucosylsphingosine and sphingosine all hemolyzed erythrocytes, indicating that lysosphingolipids can disrupt the membrane. Thus, it appears that the inhibition of cytochrome c oxidase, a membrane-bound enzyme in mitochondria, is due to perturbation of the environment of the enzyme and that the primary attacking site of the lysosphingolipids is the membrane. Because the potency to inhibit cytochrome c oxidase and to hemolyze erythrocytes did not differ among these lysosphingolipids and because galactosylceramide caused neither inhibition of cytochrome c oxidase nor hemolysis, the free amino group in the lysosphingolipids seems to be essential to give the effects. In addition, both inhibition of cytochrome c oxidase and hemolysis caused by lysosphingolipids were completely abolished by albumin, suggesting that toxic effects of lysosphingolipids may not be apparent in blood.

Animals↗
PubMed1987

[The inhaled effects of fenitrothion powder on blood cholinesterase in rats].

Effects of fenitrothion (Sumithion) powder on red cell acetylcholinesterase (AChE) and plasma cholinesterase (PChE) were studied in vitro and in vivo. Experiments in vitro revealed that fenitrothion has almost the same potency to inhibit AChE (in pre-washed red cell membrane) and PChE. Rats (Wistar, male) were exposed to fenitrothion powder for 4 hours using a new apparatus which can generate powder constantly over a long period. In this experiment, however, no apparent suppression of AChE was found while PChE was markedly inhibited. This inhibition persisted for 3 days after the exposure. This discrepancy was interpreted to be due to the inevitable procedure in preparing red cell specimens, i.e., washing of the red cells. After acute exposure in vivo, fenitrothion appears to be easily removed from the red cells by washing. Thus, PChE, rather than AChE, seems to be a good indicator of an acute exposure to fenitrothion powder in vivo.

Animals↗