Aspartate Aminotransferase Activity Levels Research Articles

Efficacy of nutritional selenium nanoparticles on growth performance, immune response, antioxidant capacity, expression of growth and immune-related genes, and post-stress recovery in juvenile Sobaity seabream (Sparidentex hasta)

This study evaluated the impacts of nano-Se on the growth, immunity, antioxidant capacity, physiological parameters, gene expression, and stress resistance of fingerling Sobaity seabream (Sparidentex hasta). The fish with an average weight of 21.5 ± 0.1 g were divided into four treatment groups in triplicates that received one of the test diets supplemented with varying levels of nano-Se: 0 (control), 0.5 (Se-0.5), 1 (Se-1), and 2 (Se-2) mg/Kg for 60 days. The results showed that final weight, weight gain rate, specific growth rate, feed intake, and feed conversion ratio improved with significant linear and quadratic trends (P < 0.05) in response to nano-Se-supplemented diets, and the best values were measured in the Se-2 group. Superoxide dismutase activity level remained unaffected among the four groups (P > 0.05). Catalase activity increased in nano-Se-supplemented groups, with the highest level measured in fish fed the Se-0.5 diet. Glutathione peroxidase activity levels were not significantly different between the control and nano-Se groups, but the lowest malondialdehyde concentration was detected in the Se-2 group. Nano-Se had no marked effect on total plasma Ig levels; however, the highest lysozyme activity and alternative complement activity (ACH50) were observed in the Se-0.5 and Se-2 groups, respectively. No significant differences (P > 0.05) were observed in plasma total protein, albumin, globulin, triglyceride, and thyroid hormone (T3 and T4) contents among the groups. However, the lowest cholesterol and low-density lipoprotein values and the highest high-density lipoprotein concentration were measured in the Se-2 group. The Se-0.5 and Se-1 groups exhibited significantly lower levels of aspartate aminotransferase activity, and the lowest alkaline phosphatase activity level was detected in the Se-1 group. The expression level of insulin-like growth factor I gene in all nano-Se-fed groups was significantly higher than the control. Also, the expression of interleukin-1β and lysozyme genes was significantly upregulated in nano-Se-supplemented groups, with the highest values in the Se-2 group. Following acute crowding stress, plasma cortisol and lactate levels at all post-stress time intervals were not significantly different among the experimental groups. Fish fed the Se-0.5 and Se-2 diets tended to have lower plasma glucose concentrations than other groups. In conclusion, dietary nano-Se at 2 mg/kg is recommended to promote growth performance and enhance antioxidant and immune parameters in Sobaity juveniles.

PREVENTION OF PATHOLOGICAL EFFECT OF ISCHEMIA-REPERFUSION IN LIVER RESECTION BY SEVOFLURANE PRECONDITIONING.

The intermittent Pringle maneuver remains the major technique for controlling hemorrhage during liver surgery. Nevertheless, this procedure involves a risk of triggering a cascade of pathological changes resulting in the ischemia-reperfusion injury (I/R) effect. The pharmacological prevention of this I/R injury represents a promising approach. The aim of the study was to compare the effects of pharmacological preconditioning with sevoflurane and propofol-based intravenous anesthesia on the postoperative function of the liver as the primary end-point. A prospective cohort study includes the analysis of the data of 73 patients who underwent liver surgery. In the study group (n = 41), preconditioning with sevoflurane inhalation was provided 30 minutes prior to liver resection. In the control group (n = 32), sevoflurane preconditioning was not provided. The primary endpoints were blood lactate concentration shortly after the surgery and one day later; alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities on postoperative Days 1, 3, and 5 as markers of hepatocyte damage. On postoperative Day 1, in patients of the study group, lactate decreased to preoperative levels, while in the control group, lactate content increased as compared to both preoperative levels and the levels immediately after liver resection. A significant difference in AST activity levels between the groups was registered on Day 5, although this difference was not clinically relevant. The decrease in the prothrombin index in the study group on Day 3 was superior to that in the control group. The multiple regression analysis demonstrated a moderate positive association between the number of resected liver segments and the markers of the functional state of the liver in the study group while in the control group, such association was not significant. The protective effect of sevoflurane on the postoperative function of the liver is manifested by the lower level of blood lactate and the stable level of transaminase activity.

B-088 Estimation of Antibodies to Hbsag and Liver Function Markers From a Large Laboratory Database in São Paulo, Brazil

Abstract Background The Hepatitis B virus (HBV) infection can lead to chronic hepatitis B and severe hepatic disease. The Gamma Glutamyl Transferase (GGT), Aspartate Aminotransferase (AST), and Alanine Aminotransferase (ALT) tests are commonly used to assess liver function. Despite having an effective vaccine schedule, many people in Brazil are still susceptible to HBV. Vaccines use the surface protein (AgHBs) of the virus to induce immunity, and patients with antibody levels above 10 mUL/mL to this protein are considered to have vaccine-induced immunity. The study aims to analyze the pattern of hepatitis B markers and liver function in HBV-positive populations. Methods A retrospective analysis from 2020 to 2022 was conducted from a large laboratory database in São Paulo, Brazil selecting all individuals from whom the following serological diagnostic markers for Hepatitis B were requested: HBsAg, total Anti-HBc, IgM Anti-HBc, and Anti-HBs. HBV groups were classified based upon results for the following serological diagnostic markers: HBsAg, total Anti-HBc, IgM Anti-HBc, and Anti-HBs. The HBV susceptible group was identified as negative for all markers, the naturally immune group with Anti-HBc and Anti-HBs markers, and the vaccinated group with Anti-HBs only. Liver function was evaluated in two conditions: naturally immune and vaccinated, using liver cell injury markers: GGT, AST, and ALT. The Mann-Whitney U and Kruskal-Wallis tests were used for statistical analysis with P &amp;lt; 0.05 considered significant. Results Results from a total of 57 311 (32%) men and 121 404 (68%) women were evaluated. The study observed a lower frequency of individuals in the male vaccinated group (36%) compared to the susceptible group (56%). Conversely, the female group showed a higher frequency of individuals immunized by vaccination (51%) in relation to the susceptible group (45%). The rate of individuals exposed to natural infection was higher in the male group (9%) compared to the female group (4%). Regarding Anti-Hbs antibody levels, higher levels were observed in the population with natural infection markers compared to those immunized by HBV vaccination (527.5 ± 4.0 SEM vs 332.3 ± 1.1 mUI/mL, P &amp;lt; 0.001). Analyzing the age ranges with the greatest susceptibility (31–40 and 41–50 years), a gradual decrease in antibodies was observed over the years when compared: Naturally, P = 0.03, and immunized, P &amp;lt; 0.001). Indicator exams of liver function in both conditions showed average GGT levels above the reference value for the naturally infected groups: female 62.4 ± 5.34 SEM U/L; male 86.7 ± 5.4 SEM U/L, P &amp;lt; 0.001. No significant values of ALT and AST activity levels were seen. Conclusion The study results showed that this specific male population was more susceptible to HBV infection, while the female population has higher concentrations of Anti-HBs antibodies. Individuals who had a natural Hepatitis B infection exhibit GGT values above the standard.

THE IMPACT OF CHOLECALCIFEROL ON THE SEX HORMONES LEVEL AND SERUM BIOCHEMICAL INDICES IN RAT MALES WITH EXPERIMENTAL GONADOPATHY

THE IMPACT OF CHOLECALCIFEROL ON THE SEX HORMONES LEVEL AND SERUM BIOCHEMICAL INDICES IN RAT MALES WITH EXPERIMENTAL GONADOPATHY

Gastrodin Improves Nonalcoholic Fatty Liver Disease Through Activation of the Adenosine Monophosphate-Activated Protein Kinase Signaling Pathway.

NASH is currently one of the most common causes of liver transplantation and hepatocellular carcinoma. Thus far, there is still no effective pharmacological therapy for this disease. Recently, Gastrodin has demonstrated hepatoprotective effects in a variety of liver diseases. The aim of this study is to investigate the function of Gastrodin in NASH. In our study, Gastrodin showed potent therapeutic effects on NASH both in vivo and in vitro. In high-fat diet or high-fat and high-cholesterol diet-fed mice, the liver weight, hepatic and serum triglyceride and cholesterol contents, and serum alanine aminotransferase and aspartate aminotransferase activity levels were markedly reduced by Gastrodin treatment as compared with the corresponding vehicle groups. Notably, Gastrodin showed minimal effects on the function and histological characteristics of other major organs in mice. We further examined the effects of Gastrodin on lipid accumulation in primary mouse hepatocytes and human hepatocyte cell line and observed that Gastrodin showed a significant decrease in lipid accumulation and inflammatory response in hepatocytes under metabolic stress. Furthermore, RNA-sequencing analysis systemically indicated that Gastrodin suppressed the pathway and key regulators related to lipid accumulation, inflammation, and fibrosis in the pathogenesis of NASH. Mechanistically, we found that Gastrodin protected against NASH by activating the adenosine monophosphate-activated protein kinase (AMPK) pathway, which was supported by the result that the AMPK inhibitor Compound C or AMPK knockdown blocked the Gastrodin-mediated hepatoprotective effect. Gastrodin attenuates steatohepatitis by activating the AMPK pathway and represents a therapeutic for the treatment of NASH.

Application infusion drugs based on sorbitol for normalization of aminotransferase activity blood cancer patients operated cardia of the stomach

Objective. To study the effect of intravenous infusions of Rheosorbilact on the activity of alanine aminotransferase and aspartate aminotransferase in the plasma of operated patients with gastric cardiac cancer after proximal gastrectomy.&#x0D; Materials and methods. Alanine aminotransferase and aspartate aminotransferase activity levels were studied in plasma of 40 operated patients with gastric cardiac cancer after proximal gastrectomy immediately after surgery, on the 1st, 2nd, 3rd, 5th day after intravenous infusions of the drug. The infusion of Rheosorbilact was administered intravenously, drip, for 5 days at a rate of 40 drops per minute. The daily dose of the drug was 1000.0 ml.&#x0D; Results. In patients with gastric cardiac cancer after proximal gastrectomy in the first days after surgery revealed changes in aminotransferases, which are accompanied by an increase in the activity of alanine aminotransferase and aspartate aminotransferase in blood plasma. To correct the activity of plasma aminotransferases in such patients, Rheosorbilact was administered intravenously immediately after surgery. After repeated intravenous infusions of Rheosorbilact for 5 days, a significant decrease in the activity of alanine aminotransferase and aspartate aminotransferase in blood plasma in the operated patients was revealed.&#x0D; Conclusions. In the first days after proximal gastrectomy in patients with gastric cardiac cancer, an increase in the activity of aminotransferases in blood plasma was revealed. Repeated intravenous infusions of Rheosorbilact normalize the activity of alanine aminotransferase and aspartate aminotransferase in the blood plasma of such patients in the early postoperative period. Infusion drug Rheosorbilact is recommended for widespread medical use in patients with cardiac gastric cancer after proximal gastrectomy, especially in the early postoperative period.

The effect of purslane hydroextract and zinc on performance, antioxidant capacity and immunity of broiler chickens during summer conditions

Abstract. Due to negative effects of high ambient temperature, the present study was conducted to investigate the effects of Portulaca oleracea hydroextract (PHE) and zinc (Zn) on the growth performance and immunity of broiler chickens reared under high summer ambient temperature conditions. A total of 420 day-old male broiler chickens (Ross 308) were randomly allocated to seven dietary treatments each replicated four times with 15 birds per replicate. The basal diet as the control diet was supplemented with 100 mg kg−1 butylated hydroxytoluene (BHT), or 300 and 600 mg kg−1 of PHE, 100 mg kg−1 of zinc and 100 mg kg−1 of zinc plus 300 or 600 mg kg−1 of PHE (ZP300 and ZP600). The result of the present study showed that Zn, PHE and their combination did not alter daily feed intake and feed conversion ratio. Although there was a tendency toward an increase in broiler body weight at 24 and 44 days of age (P=0.059 and P=0.061), the body weight of birds fed the basal diet supplemented with Zn reduced at day 10. The birds fed diets supplemented with BHT or ZP600 showed lower aspartate aminotransferase (ASAT) and lactate dehydrogenase activity at 24 days of age (P&lt;0.05), but it remains lower in the ZP600 group only for ASAT activity level at day 44. The results of the present study suggest that dietary PHE and Zn supplementation partially improved body weight and serum antioxidant capacity, superoxide dismutase activity and antibody titer against sheep red blood cells and Newcastle diseases in the broiler chickens during summer conditions.

Hepatoprotective effects of allyl isothiocyanate against carbon tetrachloride-induced hepatotoxicity in rat

We evaluated the hepatoprotective activity of allyl isothiocyanate (AITC) against carbon tetrachloride (CCl4)-induced liver injury in rats. Sprague Dawley rats were orally administered AITC at doses of 5 (AITC 5) and 50 (AITC 50) mg/kg body weight once daily for 3 days, with or without intraperitoneal injection of CCl4. Serum chemistry was assessed for changes in alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The enzyme activities of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) were examined in liver tissues, while pro-inflammatory cytokines including tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) mRNA expression were analyzed using real-time polymerase chain reaction. And heme oxygenase-1 (HO-1) and ionized calcium binding protein-1 (Iba-1) immunoreactivities were evaluated by Western blot analysis and immunohistochemistry, respectively. In serum chemistry, the oral administration of AITC itself did not affect the serum levels of ALT or AST, furthermore pretreatment with AITC 5 and AITC 50 significantly reduced the ALT and AST activity levels that were elevated in CCl4-intoxicated rats. In addition, AITC significantly suppressed the reduction of SOD and CAT, and the elevation of MDA, TNF-α mRNA expression, on the other hands, induced the expression of HO-1 compared with those of the vehicle-treated CCl4 group. The histopathological evaluation and Iba-1 immunoreactivity also supported the hepatoprotective effects of AITC against CCl4-induced liver injury. These results suggest that AITC ameliorates oxidative liver injury, possibly through reducing lipid peroxidation, enhancing antioxidant enzymes, and suppressing Kupffer cells and macrophages.

Genome-wide association study identifies genetic variants in GOT1 determining serum aspartate aminotransferase levels

We carried out a genome-wide association study of serum aspartate aminotransferase (AST) activity in 866 Amish participants of the Heredity and Phenotype Intervention Heart Study and identified significant association of AST activity with a cluster of single nucleotide polymorphisms located on chromosome 10q24.1 (peak association was rs17109512; P=2.80E-14), in the vicinity of GOT1, the gene encoding cytosolic AST (cAST). Sequencing of GOT1 revealed an in-frame deletion of three nucleic acids encoding asparagine at position 389 c.1165_1167delAAC (p.Asn389del) in the gene. Deletion carriers had significantly lower AST activity levels compared with homozygotes for the common allele (mean±s.d.: 10.0±2.8 versus 18.8±5.2 U l(-1); P=2.80E-14). Further genotyping of the deletion in other Amish samples (n=1932) identified an additional 20 carriers (minor allele frequency (MAF)=0.0052). The deletion was not detected in 647 outbred Caucasians. Asn at codon 389 is conserved among known mammalian cASTs. In vitro transient transfection of wild-type and mutant cAST indicated that mutant cAST protein was barely detectable in the cells. Furthermore, even after correction for cAST expression, mutant cAST had markedly diminished enzymatic activity. Remarkably, we did not find any association between the deletion and metabolic traits including serum fasting glucose or insulin, fasting and post-meal lipids, inflammatory markers, or sub-clinical markers of cardiovascular disease. In conclusion, we discovered a rare in-frame deletion in GOT1 gene, which inactivates cAST enzyme in the Old Order Amish. This finding will help us to understand structure and function of the enzyme and would be useful for predicting serum AST levels.

Change in dental pulp parameters in response to different modes of orthodontic force application

(1) To evaluate dental pulp sensitivity by electrical pulp testing and measure aspartate aminotransferase activity in the pulp after 14 days of orthodontic intrusion, and (2) to compare those measurements with measurements obtained in teeth after 7 days of intrusion and 7 days of rest. The study sample included 13 subjects (mean age = 16.5 +/- 2.7 years). For every subject, before extraction, two contralateral premolars were included in a spring and loaded by a force. Two study groups were formed: Group A, teeth with 14 days of mechanical load, and Group B, teeth with 7 days of mechanical load plus 7 days of rest. Electrical pulp testing and aspartate aminotransferase activity measurements were performed after 14 days in all tested teeth. After extraction, aspartate aminotransferase activity in the pulp was determined spectrophotometrically at 20 degrees C. Mean aspartate aminotransferase activity values were 0.21 U/mg (SD = 0.15) in Group A and 0.27 U/mg (SD = 0.17) in Group B. Mean electrical pulp testing readings were 38.92 microA (SD = 24.61) in Group A and 36.77 microA (SD = 26.84) in Group B. Mean values of the intrusive force magnitude did not differ in both groups. Different durations of orthodontic intrusion, defined as 14 days of load and 7 days of load followed by 7 resting days, were not reflected by electrical pulp testing or by aspartate aminotransferase activity levels in the pulp of the affected teeth. However, the response threshold to electrical pulp stimulation was elevated in all tested teeth.

Metabolic Profile Test in Iran: Variations of Metabolites Around Parturition at Dairy Cattle

profile or profile was defined as a set or combination of blood constituents analyzed together in one test. Metabolic Profile test (MPT) was used as a diagnostic approach in Iran in recent years. Reference values of metabolites were determined by Seifi (1996). Calving, with the demands for initiating milk production, places high-producing cows in a critical nutrient balance and may affect profiles for 60 or more days after calving. Production level is one aspect of the periparturient flux that may reflect in the profile. Glucose and PCV are negatively correlated and total proteins; Mg and cholesterol are positively correlated with the post parturient rise in milk production. The aim of this study was to evaluate the variations of serum metabolites around parturition. The investigation was conducted in two dairy farms in Mashhad city in north east of Iran. One hundred cows were bled on four occasions: 20-10 days prepartum, 3-7 days, 30 days and 56-60 days postpartum. Blood samples were drawn from Jugular vein and analyzed by computerized analyzer (RA1000 Technicon). The following metabolites and enzymes were measured on serum samples: glucose, urea nitrogen, cholesterol, albumin, total protein, calcium, inorganic phosphorus and Aspartate Aminotransferase (AST). Data were analyzed for statistical significance by analysis of variance using SPSS program for Windows. A p value less than 0.05 were considered as significant. In farm 1, prepartum variations in urea nitrogen, cholesterol, albumin, calcium, AST, PCV and total protein and in farm 2 prepartum variations in glucose, cholesterol, calcium, phosphorus, AST, PCV, and total protein were significant (p< 0.05). Serum glucose level decreased markedly 3-7 days postpartum and gradually increased at 30 and 5660 days postpartum. At least 92% of dairy cows suffer negative energy balance at early lactation. At this stage, the level of milk production reaches to peak earlier than dry matter intake and the result is low blood glucose. The peak of urea nitrogen concentration was found preparturition and it decreased postpartum. The concentration of serum cholesterol was lower at 10-20 days prepartum and after calving gradually increased. The peak of serum calcium levels was found 10-20 days before calving and it was markedly decreased after parturition. Serum total protein and PCV values were lowest at preparturition sampling. AST activity levels were lower at first sampling and reached highest after parturition. AST relates to metabolism, and it seems increased activity of the enzyme in high producing dairy cows is due to increased of body metabolic and hepatic activities . Reference

Chemical anatomy of excitatory endings in the dorsal cochlear nucleus of the rat: differential synaptic distribution of aspartate aminotransferase, glutamate, and vesicular zinc.

In order to identify cytochemical traits relevant to understanding excitatory neurotransmission in brainstem auditory nuclei, we have analyzed in the dorsal cochlear nucleus the synaptic distribution of aspartate aminotransferase, glutamate, and vesicular zinc, three molecules probably involved in different steps of excitatory glutamatergic signaling. High levels of glutamate immunolabeling were found in three classes of synaptic endings in the dorsal cochlear nucleus, as determined by quantitation of immunogold labeling. The first type included auditory nerve endings, the second were granule cell endings in the molecular layer, and the third very large endings, better described as "mossy." This finding points to a neurotransmitter role for glutamate in at least three synaptic populations in the dorsal cochlear nucleus. The same three types of endings enriched in glutamate immunoreactivity also contained histochemically detectable levels of aspartate aminotransferase activity, suggesting that this enzyme may be involved in the synaptic handling of glutamate in excitatory endings in the dorsal cochlear nucleus. There was also extrasynaptic localization of the enzyme. Zinc ions were localized exclusively in granule cell endings, as determined by a Danscher-selenite method, suggesting that this ion is involved in the operation of granule cell synapses in the dorsal cochlear nucleus.

Aspartate aminotransferase (AST) levels in human periodontium-derived cells.

The ability to objectively assess periodontal disease activity can significantly affect periodontal therapy. Aspartate aminotransferase (AST) is released extracellularly upon tissue destruction which suggests its potential as a key index in a quantitative assay for evaluating periodontal disease activity. The purpose of the present research was to assess the origin of AST in gingival crevicular fluid (GCF) in vitro. An experimental kit was used for the measurement of AST level in human gingival epithelial cells (HGEs), human gingival fibroblasts (HGFs), human periodontal ligament fibroblasts (HPLFs), polymorphonuclear leukocytes (PMNs), and plasma in peripheral blood. AST activity levels were observed in all of the periodontally derived cells, PMNs, and plasma. A significantly high level of AST activity was observed in HGEs (104.93 +/- 8.13 KU/1000 cells). The level of AST activity in HPLFs was 18.09 +/- 3.73 KU/1000 cells. AST activity in PMNs was significantly low, approximately 2% of that observed in HPLFs. These findings may suggest that AST level in GCF is correlated with the destruction of periodontal tissue.

Sarcocystis fusiformis: some protein metabolic enzymes in various fractions of sarcocysts of buffalo ( Bubalisbubalis)

An investigation on the relative presence of some protein metabolic enzymes, namely aspartate aminotransferase (AST), alanine aminotransferase (ALT), NAD + and NADP + dependent glutamate dehydrogenase (GLDH) and arginase in cyst wall (CW), cyst fluid (CF) and zoite (ZP) fractions of the sarcocysts of Sarcocystis fusiformis in the oesophageal muscles of Indian water buffalo was carried out. Both the transaminases were present in all the fractions of the cyst, although in variables amounts. There was a higher level of AST activity than of ALT activity. AST activity was the highest in ZT, whereas ALT activity was at a maximum in the CF fraction. The levels of activity of NAD + and NADP + dependent GLDH and arginase remained beyond detectable limits. The study revealed that the intermediates of carbohydrate metabolism are linked to protein metabolism by transaminases. The possibility of concomitant removal of ammonia and its subsequent incorporation into the urea cycle is ruled out in this parasitic protozoan.

Aspartate aminotransferase activity is required for aspartate catabolism and symbiotic nitrogen fixation in Rhizobium meliloti

A mutant of Rhizobium meliloti, 4R3, which is unable to grow on aspartate has been isolated. The defect is specific to aspartate utilization, since 4R3 is not an auxotroph and grows as well as its parent strain on other carbon and nitrogen sources. The defect was correlated with an inability to fix nitrogen within nodules formed on alfalfa. Transport of aspartate into the mutant cells was found to be normal. Analysis of enzymes involved in aspartate catabolism showed a significantly lower level of aspartate aminotransferase activity in cell extracts of 4R3 than in the wild type. Two unrelated regions identified from a genomic cosmid bank each complemented the aspartate catabolism and symbiotic defects in 4R3. One of the cosmids was found to encode an aspartate aminotransferase enzyme and resulted in restoration of aspartate aminotransferase activity in the mutant. Analysis of the region cloned in this cosmid by transposon mutagenesis showed that mutations within this region generate the original mutant phenotypes. The second type of cosmid was found to encode an aromatic aminotransferase enzyme and resulted in highly elevated levels of aromatic aminotransferase activity. This enzyme apparently compensated for the mutation by its ability to partially utilize aspartate as a substrate. These findings demonstrate that R. meliloti contains an aspartate aminotransferase activity required for symbiotic nitrogen fixation and implicate aspartate as an essential substrate for bacteria in the nodule.

Relationship Between Vitamin B-6 Status and Elevated Pyridoxal Kinase Levels Induced by Theophylline Therapy in Humans

Theophylline administration to seven healthy male volunteers resulted in a rapid and significant decline in both plasma and erythrocyte pyridoxal-5'-phosphate levels. Total erythrocyte pyridoxal kinase levels increased during 15 wk of theophylline treatment from a mean initial activity of 19.23 +/- 5.03 (mean +/- SD) to 62.64 +/- 11.59 nmol pyridoxal-5'-phosphate formed/(g hemoglobin.h). Although plasma pyridoxal levels remained normal, the threefold increase in total erythrocyte pyridoxal kinase activity levels did not normalize plasma and erythrocyte pyridoxal-5'-phosphate levels. Pyridoxal-5'-phosphate hydrolysis was not affected by theophylline therapy. Increased pyridoxal oxidation was confirmed by elevated urinary 4-pyridoxic acid excretion after 15 wk of theophylline treatment. Mean erythrocyte alanine aminotransferase activity declined by 70%, and aspartate aminotransferase activity declined by 50%, indicating that decreased availability of pyridoxal-5'-phosphate can have widespread metabolic consequences. We conclude that the effect of theophylline on vitamin B-6 metabolism is not transitory and cannot be overcome by elevated intracellular levels of pyridoxal kinase. However, pyridoxine supplementation (10 mg/d for 1 wk) normalized indices of vitamin B-6 status and reversed the downward trend in both alanine aminotransferase and aspartate aminotransferase activity levels.

Interactive Effects of Cadmium, Polychlorinated Biphenyls, and Fuel Oil on Experimentally Exposed English Sole (Parophrys vetulus)

Investigation of the interactive effects of representatives of three classes of compounds was performed, using English sole (Parophrys vetulus) as the test organism, juvenile fish were exposed orally to cadmium chloride and Aroclor 1254 (PCB), either independently or simultaneously, for a 4-wk period, followed by exposure to seawater-accommodated No. 2 diesel fuel for 2 wk. Blood was collected for analysis of serum constituents, and tissue samples were examined for histological changes. Hepatocellular necrosis, regeneration, and karyomegaly were observed. Differential lesion prevalences were observed among the exposure groups, with high proportions among cadmium-exposed fish, low proportions among PCB-exposed fish, and intermediate proportions in combination cadmium- plus PCB-exposed fish. Levels of aspartate aminotransferase activity and magnesium in the sera of these groups exhibited similar patterns. Depressed serum calcium levels in both PCB-exposed and cadmium- plus PCB-exposed groups were found after the first week, and lower serum albumin concentrations occurred in all cadmium- and PCB-exposed groups following the third week. Subsequent exposure to No. 2 diesel fuel produced few effects in any of the exposure groups. The observed antagonistic effect of Aroclor 1254 against cadmium toxicity emphasizes the importance of employing multiple as well as single contaminant exposure in toxicity studies.

Magnesium sensitivity of l-aspartate: 2-oxoglutarate aminotransferase in Escherichia coli

Strains 619 and 961, derived from Escherichia coli K12, show growth inhibition by 0.4 M Mg 2+. The inhibition is overcome by l-aspartate. The related strain 977 exhibits Mg 2+, which arose concurrently with a mutation to argR − . Transduction experiments indicated that the genetic determinant for Mg 2+ sensitivity is closely linked to, but not identical with, argR. Since aspartate reverses the inhibition, aspartate aminotransferase ( l-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1), an enzyme of aspartate synthesis, was examined. Incubation of 961 in a growth medium containing Mg 2+ leads to a sharp decrease in the specific activity of aspartate aminotransferase in 2 h, followed by a gradual increase. In similar experiments with 977, a greatly reduced drop and a much sharper rise occur. Extracted aspartate aminotransferase is virtually insensitive to Mg 2−. Extracts of Mg 2+-treated 961, on incubation at 37°C, show nearly full restoration of aspartate aminotransferase activity within several hours. The reversible inactivation appears to affect the finished enzyme, in the absence of protein synthesis, as demonstrated in cell suspension experiments. Under these conditions, the inactivating effect of Mg 2+ is enhanced by aspartate. Tests with growing cells suggest that aspartate may repress aspartate aminotransferase formation. Growth of 961 in the presence of 0.4 M Mg 2+ plus aspartate leads to relatively elevated levels of aspartate aminotransferase activity. In this case, on extractiion, no appreciable restoratiion occurs, and in cell suspension experiments, the aspartate aminotransferase shows no Mg 2+ sensitivity. The aminotransferase from Mg 2+ plus aspartate-grown cells and the normal enzyme are similar in affinity for aspartate, sedimentation behaviour, and inactivation at 60°C, but differ in their response to heat treatment at 50°C. It is thought that the two enzymes may be specified by the same gene, but may differ structurally, as a function of availability of Mg 2+ during their formation.