On the regulation of tyrosine transaminase, glutamatic dehydrogenase and aspartic transaminase in Tetrahymena

Aspartic transaminase, tyrosine transaminase, lactic dehydrogenase, and glutamic dehydrogenase were studied in Tetrahymena pyriformis in order to gain a better understanding of the control of the entrance and exit of metabolic intermediates to and from the major carbohydrate pathways. Glucose decreased the activity of aspartic transaminase, tyrosine transaminase and glutamic dehydrogenase but not lactic dehydrogenase. Actinomycin D (6 and 12 μg/ml) blocked the decrease in glutamic dehydrogenase and aspartic transaminase activity caused by glucose; 12 μg/ml partially prevented the decrease in tyrosine transaminase activity. Actinomycin D alone had little effect on enzyme activity. Uracil incorporation into RNA was doubled by 6 μg/ml actinomycin D, a concentration which did not alter the RNA content of the cells. At 12 μg/ml this drug caused a small decrease in RNA spec. act. Cycloheximide at 10 μg/ml, a concentration which inhibited protein synthesis by 70%, caused a three-fold increase in aspartic transaminase and a two-fold increase in glutamic dehydrogenase. In the presence of both cycloheximide and glucose, the drug effect predominated. Thus both actinomycin D and cycloheximide blocked the glucose-induced decrease in enzyme activity. These results suggest that the levels of aspartic transaminase, glutamic dehydrogenase, and probably tyrosine transaminase are regulated at least in part by a degradative control system.     

苯酚对多刺裸腹溞糖及蛋白质代谢酶的影响

采用急性毒性方法,研究了苯酚对多刺裸腹溞(Moina macrocopa)糖及蛋白质代谢的影响。实验设对照组和5个苯酚处理组,苯酚浓度分别为0.25、0.75、1.25、1.75、2.25 mg/L。分别在苯酚处理24 h和48 h后用分光光度法测定丙酮酸激酶(PK)、乳酸脱氢酶(LDH)、琥珀酸脱氢酶(SDH)、谷草转氨酶(GOT)和谷丙转氨酶(GPT)的活力。结果显示,随着苯酚浓度的增加和处理时间的延长,LDH活力呈现升高趋势,PK和SDH活力与对照组相比没有显著性差异。GOT活力在处理24 h后先升后降,处理48 h后活力降低;GPT活力在处理24 h、48 h后活力均升高。结论是:苯酚中毒需要高水平的代谢能量,导致裸腹溞代谢发生重大改变,诱导能量代谢一定程度上由碳水化合物分解代谢向蛋白分解代谢转变。     

Influence of testosterone propionate during storage on livability and metabolism of bovine spermatozoa

Bovine spermatozoa, stored in the presence of 25, 50, 100 or 150 μg testosterone propionate/ml of extender for either 4 hours at 5° C or 2 weeks at ?196° C, elicited a decreased O₂ uptake. The O₂ uptake decreased with each increase in the level of testosterone added to the media. Part of this decrease in O₂ uptake particularly at higher concentrations of the testosterone was due to a decrease in the number of live spermatozoa. There was also an increase in the release of glutamic oxalacetic transaminase enzyme from the spermatozoa in the testosterone containing diluents. The depressed respiration and the higher accumulation of Kreb's cycle intermediates are suggestive that testosterone at 25 μg/ml extender may be beneficial for storage of spermatozoa at ?196° C.     

Effect of dieldrin injection on the level of certain amino acids and some enzymes in rat brain

The present investigation revealed the effect of the organochlorine insecticide dieldrin at the dose level 0.25 LD50 at different time intervals on the concentration of 11 rat brain amino acids, on the activities of glutamic oxyacetic transaminase (GOT), glutamic pyruvic transaminase (GpT) and cholinesterase. The study was also extended to include the total protein content during the tested periods. The daily injection of dieldrin caused a marked decrease in the levels of glutamic acid, glutamine and taurine and an increase in the levels of aspartic acid, asparagine, GABA, glycine, lysine, serine, alanine and histidine. However, the maximal increase and decrease were recorded for most of the tested amino acids at the end of the tested period. The activity of the transaminases increased significantly. The recorded values of GOT were usually higher than GPT. Cholinesterase activity was inhibited thoroughly during all the experimental periods. Total protein content was decreased in the experiment; the minimal value was given 3 days after the injection.     

Effect of static magnetic field on some enzymes activities in rats

The magnetic field of 0.008 T and 0.15 T inductions influence lasting 7 weeks (7 days a week), 1 h daily determines the increase of the activity of cytoplasmatic enzymes (glutamic pyruvic transaminase, glutamic oxalacetic transaminase, lactic dehydrogenase), the decrease of cholinesterase activity and the growth of alkaline phosphatase activity in the plasma of the examined animals. The observed changes were reversible. 2 months after the exposure had been stopped, the tested parameters were back to normal.     

Temporal response of uterine prostaglandins to estradiol treatment in the ovariectomized-prenant rat

Previous studies in our laboratory have shown that 24 hours of estradiol treatment significantly enhanced uterine prostaglandin (PG)F, PGE and thromboxane B₂ (TxB₂) leels but had no effect on 6-Keto-PGF_1α (6KF) concentrations in ovariectomized-pregnant rats. One explanatior for the lack of an augmentation in 6KF was a temporal differences in response (i.e. 6KF increased and decreased within the 24 hour period). To test this possibility rats were ovariectomized on day 19 of pregnancy and sacrificed 0, 4, 8, 12, 16, 20 and 24 hours after estradiol treatment. Uterine tissue and venous plasma were analyzed for PGs by radioimmunoassay. No significant (p > .05) alterations were detected for any of the uterine PGs at 0, 4, 8 and 12 hours. However, at 16 hours PGF, TxB₂ and PGE all showed significant (p > .05) increases (2.4, 3.4 and 2.1 fold, respectively) compared to 12 hours. In contrast, no significant augmentation in 6KF levels (p > .05, 1.3 fold) was detected at 16 compared to 12 hours although it was enhanced relative to 0 and 4 hours. In addition, PGF, TxB₂ and PGE, but not 6KF, showed further increases 24 hours after estradiol administration. No alterations were found (p > .05) for any of the PGs in uterine venous plasma at the time points studied. In summary, uterine PGF, PGE and TxB₂ net production appears to be more enhanced by estradiol treatment than 6KF at the time points studied. In addition, there is a slight, but significant, difference in the temporal response characteristics of 6KF compared to the other PGs. The data suggest that the dramatic increase in uterine PGF, PGE and TxB₂ levels at parturition in the rat are probably significantly related to enhanced levels of estradiol. However, the majority of the increase in uterine 6KF levels at labor is more likely caused by factors other than augmented plasma estradiol.     

Activation of mitogen activated protein kinase (MAPK) during D-galactosamine intoxication in the rat liver

A significant increase in plasma glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase was observed 6 h after intraperitoneal administration of D-galactosamine (D-Galn). Three hours after administration of D-Galn, the vitamin C concentration in the liver decreased significantly compared to that in a control group and thereafter the hepatic vitamin C concentration remained at a significantly lower level. Phosphorylated JNK (c-Jun NH2-terminal kinase) and phosphorylated ERK (extracellular signal-regulated kinase) started increasing 3 h after D-Galn treatment and remained at a high level for 6-12 h after the treatment, while phosphorylated p38 MAPK increased significantly 6 h after D-Galn administration. These results indicated that oxidative stress and the activation of JNK and ERK took place almost simultaneously, followed by the activation of p38 MAPK.     

Temporal response of uterine prostaglandins to estradiol treatment in the ovariectomized-pregnant rat

Previous studies in our laboratory have shown that 24 hours of estradiol treatment significantly enhanced uterine prostaglandin (PG)F, PGE and thromboxane B2 (TxB2) levels but had no effect on 6-Keto-PGF1 alpha (6KF) concentrations in ovariectomized-pregnant rats. One explanation for the lack of an augmentation in 6KF was a temporal difference in response (i.e. 6KF increased and decreased within the 24 hour period). To test this possibility rats were ovariectomized on day 19 of pregnancy and sacrificed 0, 4, 8, 12, 16, 20 and 24 hours after estradiol treatment. Uterine tissue and venous plasma were analyzed for PGs by radioimmunoassay. No significant (p greater than .05) alterations were detected for any of the uterine PGs at 0, 4, 8 and 12 hours. However, at 16 hours PGF, TxB2 and PGE all showed significant (p less than .05) increases (2.4, 3.4 and 2.1 fold, respectively) compared to 12 hours. In contrast, no significant augmentation in 6KF levels (p greater than .05, 1.3 fold) was detected at 16 compared to 12 hours although it was enhanced relative to 0 and 4 hours. In addition, PGF, TxB2 and PGE, but not 6KF, showed further increases 24 hours after estradiol administration. No alterations were found (p greater than .05) for any of the PGs in uterine venous plasma at the time points studied. In summary, uterine PGF, PGE and TxB2 net production appears to be more enhanced by estradiol treatment than 6KF at the time points studied. In addition, there is a slight, but significant, difference in the temporal response characteristics of 6KF compared to the other PGs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased serum enzyme activity in microwave-exposed rats

Heat stable serum enzymes were studied in rats exposed to microwaves (2.45 GHz, 120 Hz amplitude modulated) 24 hr after a single 4-hr exposure or immediately after 3 and 10 exposures to 0.1 to 55 mW/cm2. In addition, stable colonic temperature at 41.5 degrees C for 30 min was maintained by microwave exposure in a group of five rats under barbiturate anesthesia. Alkaline phosphatase and lactic dehydrogenase did not increase as a result of microwave exposure. Increased serum glutamic pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) were noted in the 41.5 degrees C group 24 hr after exposure. A threshold body temperature for acute cellular injury after microwave exposure was demonstrated. The acute cellular injury could be in the liver. These mild elevations in the serum enzyme levels (mean +/- SE, GOT = 167 +/- 40 U/liter: GPT = 74 +/- 26 U/liter) indicated that the injuries were not accompanied by any significant sequelae in the rat. From this threshold and colonic temperature (41.5 degrees C for 30 min) in barbiturate-anesthetized, microwave-exposed rats, we derived a tentative threshold for the whole-body average absorption rate at 14 W/kg (70 mW/cm2 at 2.45 GHz for adult rats) for 4 hr. This tentative threshold is subject to changes by duration of exposure and by compounding variables influencing maintenance of body temperature.     

Proliferative response and renewal of hepatic function following cocaine administration in mice

Experiments were undertaken to investigate the hepatic, temporal and spatial sequence of events following a single injection of cocaine, a known hepatotoxin. Centrilobular necrosis was induced in male mice (DBA/2Ha) 24 hr post-injection (PI). The time course of hepatic damage was monitored by assaying microsomal cytochrome P450 content, the activity of microsomal FAD-containing monooxygenase (FAD-M) and by determining the levels of serum glutamic pyruvic transaminase (SGPT). Kinetics of the onset of DNA synthesis were determined by autoradiography of thin liver sections and the incorporation of 3H-methyl thymidine into perchloric-acid-precipitable material. There was no increase in the labelling index (LI) and thymidine (TdR) incorporation in the first 24 hr PI. The LI rose to 14.6% and TdR incorporation showed a 5-fold increase over control values 48 hr PI. Both indices declined slightly at 72 hr PI and returned to control values by 96 hr PI. In contrast, the cytochrome P450 content declined by 69%, the FAD-M activity dropped by 40% and the SGPT levels showed an 18-fold increase at 24 hr PI, coincident with cytological signs of necrosis. Although the patterns of recovery differed between these selected enzymes, normal values were attained by 96 hr PI. These results demonstrate that cell damage and hepatic dysfunction precede the onset of DNA synthesis and subsequent proliferation.     

Accidental methyl methacrylate inhalation toxicity in a rhesus monkey (Macaca mulatta).

A rhesus monkey (Macaca mulatta), accidentally exposed to vapors of methyl methacrylate for 22 hours was found in a comatose condition. Attempts to revive the animal were unsuccessful. Necropsy revealed a diffusely mottled liver, pulmonary edema, and atelectasis. The thoracic cavities each contained 30 ml of clear yellow fluid. Histopathologic review of the tissues showed central lobular liver necrosis, pulmonary edema, pulmonary emphysema, and atelectasis. Analysis of a blood sample obtained from the monkey 1.5 hours prior to death showed a normal hemogram, but elevated values for serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, lactate dehydrogenase, phosphohexose isomerase, blood urea nitrogen, and serum sodium. The pathologic findings, laboratory results, and clinical history suggested a diagnosis of methyl methacrylate poisoning.     

Proliferative Response and Renewal of Hepatic Function Following Cocaine Administration In Mice

ABSTRACT Experiments were undertaken to investigate the hepatic, temporal and spatial sequence of events following a single injection of cocaine, a known hepatotoxin. Centrilobular necrosis was induced in male mice (DBA/2Ha) 24 hr post-injection (PI). the time course of hepatic damage was monitored by assaying microsomal cytochrome P₄₅₀ content, the activity of microsomal FAD-containing monooxygenase (FAD-M) and by determining the levels of serum glutamic pyruvic transaminase (SGPT). Kinetics of the onset of DNA synthesis were determined by autoradiography of thin liver sections and the incorporation of ³H-methyl thymidine into perchloric-acid-precipitable material. There was no increase in the labelling index (LI) and thymidine (TdR) incorporation in the first 24 hr PI. the LI rose to 14.6% and TdR incorporation showed a 5-fold increase over control values 48 hr PI. Both indices declined slightly at 72 hr PI and returned to control values by 96 hr PI. In contrast, the cytochrome P₄₅₀ content declined by 69%, the FAD-M activity dropped by 40% and the SGPT levels showed an 18-fold increase at 24 hr PI, coincident with cytological signs of necrosis. Although the patterns of recovery differed between these selected enzymes, normal values were attained by 96 hr PI. These results demonstrate that cell damage and hepatic dysfunction precede the onset of DNA synthesis and subsequent proliferation.     

Enzyme changes associated with mitoichondrial malic enzyme deficiency in mice

A genetically determined absence of mitochondrial malic enzyme (EC 1.1.1.40) in c3H/c6H mice is accompanied by a four-fold increase in liver glucose-6-phosphate dehydrogenase and a two-fold increase for 6-phosphogluconate dehydrogenase activity. Smaller increases in the activity of serine dehydratase and glutamic oxaloacetic transaminase are observed while the level of glutamic pyruvate transaminase activity is reduced in the liver of deficient mice. Unexpectedly, the level of activity of total malic enzyme in the livers of mitochondrial malic enzyme-deficient mice is increased approximately 50% compared to littermate controls. No similar increase in soluble malic enzyme activity is observed in heart of kidney tissue of mutant mice and the levels of total malic enzyme in these tissues are in accord with expected levels of activity in mitochondrial malic enzyme-deficient mice. The divergence in levels of enzyme activity between mutant and wild-type mice begins at 19--21 days of age. Immunoinactivation experiments with monospecific antisera to the soluble malic enzyme and glucose-6-phosphate dehydrogenase demonstrate that the activity increases represent increases in the amount of enzyme protein. The alterations are not consistent with a single hormonal response.     

Primary structure of mitochondrial glutamic oxaloacetic transaminase from rat liver: Comparison with that of the pig heart isozyme

The complete amino acid sequence of the mitochondrial glutamic oxaloacetic transaminase isozyme from rat liver is presented. The sequence contained 401 amino acid residues, 10 of which are methionine. Cyanogen bromide cleavage of mitochondrial glutamic oxaloacetic transaminase produced 12 peptides, one of which contained an internal homoserine residue resulting from incomplete cleavage by cyanogen bromide. The calculated molecular weight was 44,358. The sequence showed 94% homology with that of the corresponding isozyme from pig heart. These findings support the conclusion that the rate of evolution of the mitochondrial isozymes is lower than that of their cytosolic isozymes.     

Cold acclimation of wheat (Triticum aestivum): Properties of enzymes involved in proline metabolism

Two cultivars of wheat ( Triticum aestivum L.), a winter wheat, Kharkov, and a spring wheat, Glenlea, were acclimated under controlled conditions at 2 temperatures, 5°C and 25°C with a 12-h photoperiod. Water content, protein and proline concentrations were determined. Enzymatic properties (activity and apparent energy of activation) were investigated for enzymatic systems involved in 2 pathways of proline metabolism, the glutamic acid and ornithine pathways. Four enzymes were studied, proline dehydrogenase (PDH, EC 1.5.1.2), glutamate dehydrogenase (GDH, EC 1.4.1.2-4), glutamine synthetase (GS, EC 6.3.1.2) and ornithine transaminase (OT, EC 2.6.1.13). Cold acclimation led to an accumulation of proline, a decrease in water content and an increase in soluble protein, especially in winter wheat. For both cultivars, cold acclimation modulated enzyme properties of PDH and GDH. Increased activities of GS and OT were observed as a result of cold acclimation in both cultivars, with the greatest increase in Kharkov. The apparent energy of activation of these 2 enzymes decreased, particularly for Kharkov, which accumulated proline in cold conditions.     

Recovery of stress-induced increases in noradrenaline turnover is delayed in specific brain regions of old rats

Male Wistar rats at 2 and 12 months of age were sacrificed before, immediately following, and at 6 and 24 hours after a 3-hour immobilization stress period. Levels of noradrenaline (NA) and its major metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), in eight brain regions and plasma corticosterone levels were fluorometrically determined. Immobilization stress caused significant increases of MHPG-SO4 levels in all brain regions examined and significant elevations in plasma corticosterone levels in both 2 and 12 month old rats. In 2 month old rats, the MHPG-SO4 levels in all brain regions returned to control levels within 6 hours after release from the stress. However, in 12 month old rats, the metabolite levels in the hypothalamus, amygdala, pons plus medulla oblongata (pons+med. obl .) and midbrain still remained at significantly increased levels at 6 and 24 hours after the stress. Moreover, in the amygdala of older rats, stress-induced decreases in NA levels persisted even 6 hours after stress. Plasma corticosterone levels also showed significant elevations at 6 and 24 hours after the stress only in 12 month old rats. These results suggest that brain NA metabolism during recovery periods from an acute exposure to a stressful situation is altered by the aging process in such a manner that NA neurons in the hypothalamus, amygdala, pons+med. obl . and midbrain in older rats remain activated by stressful stimuli for prolonged periods of time following release from stress.     

Effects of an intrauterine copper device on serum copper, endometrial histology, and ovarian, hepatic, and renal functions in the Japanese monkey (Macaca fuscata fuscata).

A copper intrauterine device (Cu-IUD) was inserted transabdominally into the uterine cavity of eight Japanese monkeys (Macaca fuscata fuscata) for 4 to 6 months, and effects on various organ functions were examined. Results showed no significant effects on the menstrual cycle length, serum levels of LH, estradiol-17 beta, progesterone or clinical biochemical data such as serum copper, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, lactic dehydrogenase, and blood urea nitrogen. Histology revealed edema and infiltration of eosinophilic leukocytes in the endometrium treated with a Cu-IUD.     

Effect of picroliv on low density lipoprotein receptor binding of rat hepatocytes in hepatic damage induced by paracetamol.

Picroliv from root and rhizome of Picrorhiza kurroa showed reversal of low density lipoprotein (LDL) binding to paracetamol-induced damaged hepatocytes of rats. Changes in levels of glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, alkaline phosphatase, conjugated dienes and lipids of hepatocytes were significantly prevented by picroliv at different doses. The effect of picroliv on enzyme levels, LDL receptor binding and lipids in damaged hepatocytes was found to be comparable to silymarin, a known hepatoprotective agent.     

SOME EFFECTS OF DIETARY VITAMIN B6 DEFICIENCY ON γ-AMINOBUTYRIC ACID METABOLISM IN DEVELOPING RAT BRAIN

Abstract— Severe vitamin B₆ deficiency induced in pregnant rats during the last 2 weeks of gestation resulted in a reduction of brain weight in the new born rat. This indicates that the foetus was affected in utero . However, no significant changes were observed in other measured parameters in brains of the neonates at birth. Subjecting these neonates to vitamin B6 deficiency during lactation severely retarded the development of their body and brain weights. There is evidence to suggest that B₆ deficiency also leads to increased levels of glutamic acid decarboxylase apoenzyme, although the in vivo activity of the enzyme appears to be reduced as a result of marked reduction in coenzyme saturation. The level of γ-aminobutyric acid transaminase apoenzyme was reduced. Its coenzyme saturation was also reduced, but the level of reduction was less than with the decarboxylase. The progressive increase in whole brain γ-aminobutyric acid level was also retarded by the deficiency. Five days after administration of pyridoxine hydrochloride to 2-week-old deficient neonates, whole brain γ-aminobutyric acid levels and the activities of whole brain glutamic acid decarboxylase and γ-aminobutyric acid transaminase were almost restored to normal. However, brain and body weight showed a slow recovery during the same period. It was found that in the recovering neonates both enzymes follow changes in age rather than changes in brain weight.