Effects of endurance training on myosin heavy-chain isoforms and enzyme activity in the rat diaphragm

We investigated the effects of endurance training (20 m/min, 60 min/day, 5 days/week) on myosin heavy-chain (MHC) isoforms and succinic dehydrogenase (SDH) activity in rat crural and costal diaphragms, and plantaris muscles. Although the 4-week endurance training produced significant (P<0.05) increases, both in SDH activity and the percentage of isoform HCIIa in the plantaris of the trained rat compared with the sedentary control rat, these alterations did not occur in either the crural or costal diaphragms. After 10 weeks of endurance training, trained animals had significantly (P<0.05) higher SDH activity in the costal diaphragm and the plantaris. Moreover, a significant (P<0.05) decrease occurred in the percentage of HCIIb in the costal diaphragm, and a significant (P<0.01) decrease in the percentage of HCIIb concomitant with a significant (P<0.05) increase of HCIIa resulted in the plantaris. However, the crural diaphragm did not show any significant changes after 10 weeks of endurance training. These results indicate that endurance training induces an alteration in the expression of an MHC phenotype, in addition to causing an increase in oxidative enzyme activity. However, the alterations in response to endurance training are apparently not uniform, varying between regions and/or kinds of muscles.     

Skeletal muscle metabolism during short duration high-intensity exercise: influence of creatine supplementation

Seven male subjects performed repeated bouts of high-intensity exercise, on a cycle ergometer, before and after 6 d of creatine supplementation (20 g Cr H₂O day^-1). The exercise protocol consisted of five 6-s exercise periods performed at a fixed exercise intensity, interspersed with 30-s recovery periods (Part I), followed (40 s later) by one 10 s exercise period (Part II) where the ability to maintain power output was evaluated. Muscle biopsies were taken from m. vastus lateralis at rest, and immediately after (i) the fifth 6 s exercise period in Part I and (ii) the 10 s exercise period in Part II. In addition, a series of counter movement (CMJ) and squat (SJ) jumps were performed before and after the administration period. As a result of the creatine supplementation, total muscle creatine [creatine (Cr) + phosphocreatine (PCr)] concentration at rest increased from (mean + SEM) 128.7 (4.3) to 151.5 (5.5)mmolkg^_1 dry wt (P < 0.05). This was accompanied by a 1.1 (0.5) kg increase in body mass (P < 0.05). After the fifth exercise bout in Part I of the exercise protocol, PCr concentration was higher [69.7 (2.3) vs. 45.6 (7.5) mmol kg“‘ dry wt, P < 0.05], and muscle lactate was lower [26.2 (5.5) vs. 44.3 (9.9) mmol kg”¹ dry wt, P < 0.05] after vs. before supplementation. In Part II, after creatine supplementation, subjects were better able to maintain power output during the 10-s exercise period (P < 0.05). There was no change in jump performance as a result of the creatine supplementation (P > 0.05). These findings show that enhanced fatigue resistance during short duration high-intensity exercise following creatine supplementation is associated with a greater availability of PCr and a lower accumulation of lactate in the muscle. The finding that jump performance was not enhanced suggests that short-term creatine feeding does not influence peak power output.     

Effect of vibration on red cell metabolism

Summary In investigating the influence of vibrational energy on the metabolism of the erythrocyte, it was hypothesized that under conditions of normal PaO₂ and SaO₂ in arterial blood, vibration induced vasoconstriction would decrease local blood flow and induce hypokinetic hypoxia. This decreased blood flow and therefore decreased delivery of oxygen to the tissue would markedly lower tissue PO₂ (hypokinetic hypoxia), which would influence the energetics and metabolism of the erythrocyte. The metabolism of the red blood cell (RBC) was evaluated by measuring the enzymatic activities of PFK (2.7.1.11), PGI (5.3.1.9), PK (2.7.1.40), and aldolase (4.1.3.13) from the anaerobic glycolytic cycle and D-G-6-P (1.1.1.49) from the pentose cycle. Also measured were the levels of ATP and 2,3 DPG and the in-vitro production of lactic acid. In the group of workers showing early changes (vibration angioneurosis) associated with the vibration syndrome, changes in RBC metabolism were demonstrated. Statistically significant were increases of PFK, PK and the production of lactic acid, indicating the activation of anaerobic glycolysis. Furthermore statistically significant were the increased 2,3 DPG and decreased ATP levels.     

Clinical toxicity associated with tiazofurin

Summary Tiazofurin, an investigational antimetabolite, is undergoing clinical evaluation in leukemia. We analyzed the data base of 198 patients entered in Phase I trials to characterize the incidence and severity of toxicities associated with tiazofurin according to dose and schedule. Severe myelosuppression occurred infrequently, and was not dose-dependent. A five day bolus schedule had a higher incidence of severe or life-threatening neutropenia than other schedules. Tiazofurin produced lymphopenia which was not dose-dependent in the range of 23–36% decrease from baseline, and the effect on lymphocyte count was generally greater than the decline in neutrophil count. Non-hematologic toxicity of a moderate or worse severity ( grade 2) included nausea and vomiting (18% of all courses), serum transaminase elevations (SGOT, 16%; SGPT, 9%), rash (9%), stomatitis (3%), conjunctivitis (3%), headache (10%), other signs of central nervous system toxicity (8%), and cardiac toxicity, primarily pleuropericarditis (4%). Dose-related cutaneous toxicity, headache, and nausea and vomiting were evident in the five day bolus schedule, and myalgia was more frequently reported at higher doses on the single dose schedule. The five day continuous infusion (CI) schedule had a higher incidence of neurotoxicity, cardiac toxicity, SGPT elevations and ocular toxicity than the daily for five days bolus schedule, but none of these differences attained statistical significance. Although the peak plasma concentrations of tiazofurin achieved with the five day bolus schedule were 3-fold higher than the steady-state plasma levels seen with an equal dose given by CI, the area under the concentration-time curve (AUC) was approximately 1.6-fold higher with CI. These observations suggest that both high peak plasma concentrations (above 400 uM) and prolonged exposure to plasma levels exceeding 50 uM may result in a higher incidence of serious non-hematologic toxicity.     

I269S Mutation in horse liver alcohol dehydrogenase S isoenzyme and its reactivity for steroids and retinoids

Ile-269 in horse liver alcohol dehydrogenase isoenzyme S(HLADH-S) was mutated to serine by phosphorothioate-based site-directed mutagenesis in order to study the role of the residue in coenzyme binding. The specific activity of the mutant(I269S) enzyme to ethanol was increased 49-fold. All turnover numbers of I269S enzyme toward 9 primary alcohols were increased. The mutant enzyme showed 3.6, 4.6, 11.6-fold higher catalytic efficiency for 5β-androstane-3,17-dione, 5β-cholanic acid-3-one and retinal than wild-type, respectively. The reaction mechanism of I269S enzyme was ordered bi bi as wild-type's. These results indicate that the hydrophobic interaction of Ile-269 residue with coenzyme plays an important role in dissociation of coenzyme from enzyme-coenzyme complex, which has been known as the rate limiting step of ADH reaction.     

The Pichia pastoris HIS4 gene: nucleotide sequence,creation of a non-reverting his4 deletion mutant,and development of HIS4-based replicating and integrating plasmids

We have obtained a clone of the Pichia pastoris HIS4 gene and have determined its nucleotide sequence. Based upon its deduced amino-acid sequence, the product of the P. pastoris HIS4 gene has the same structural organization as the Saccharomyces cerevisiae His4 protein and appears to encode a trifunctional enzyme catalyzing the second (phosphoribosyl-ATP pyrophosphohydrolase), third (phosphoribosyl-AMP cyclohydrolase), and tenth (histidinol dehydrogenase) steps in histidine biosynthesis. The chromosomal copy of the HIS4 gene was disrupted by homologous recombination, creating the strain SGY58. The his4 deletion mutation in this strain lacks the entire coding region of this gene and has a reversion rate that is undetectable. A set of complementary plasmids that carry the HIS4 gene was also developed. Among these are nine E. coli-P. pastoris shuttle vectors that transform the His4 deletion mutant at high efficiency and an integration vector for creating site-specific alterations of the P. pastoris genome.     

The Effect of Basic Fibroblast Growth Factor on the Reversion of Omental Adipocytes from Lean and Obese Patients

Background: this study was designed to characterize some of the biochemical and molecular genetic changes during reversion of human fat cells. Methods: mature adipocytes were isolated from greater omental fat tissue of eight lean and 14 massively obese persons by established methodology. Results: at day 7 of adherence to Leighton tubes, there was appreciable depletion of triacylglycerol, as well as assumption of an elongated contour. Relatedly, there was an increase in the expression of β-actin mRNA and a significant decrease in the specific activity of cytosolic glycerophosphate dehydrogenase. The decrement in the specific activity of glycerophosphate dehydrogenase, after 7 days in culture, was significant at p < 0.001. Basic fibroblast growth factor at 10 ngml^-1 accelerated significantly (p < 0.03) the decrease in the specific activity of glycerophosphate dehydrogenase in adipose cells from lean subjects. In contrast, basic fibroblast growth factor had no significant influence on cells from massively obese persons. Conclusion: such resistance may contribute to the intractability of massive obesity.     

心肌细胞培养方法和活细胞噻唑兰法测定

目的:介绍心肌细胞培养方法和研究比色分析法测定活心肌细胞.方法:接种不同数量细胞培养后行噻唑兰(MTT)比色分析;正常培养、含不同浓度维拉帕米培养的细胞行MTT代谢比色分析,并测乳酸脱氢酶(LDH)活性.结果:比色值与接种细胞数量、细胞释放的LDH活性呈高度相关(r=0.996、-0.986,P<0.01).结论:MTT比色分析法可用于测定活心肌细胞.     

犬失血性休克早期血浆3种酶活性值的变化

用１０只犬复制失血性休克模型,观察休克前、休克３０ｍｉｎ及回输血后３０ｍｉｎ时,血浆中心肌相关酶—肌酸激酶（ＣＫ）、谷草转氨酶（ＧＯＴ）、α－羟丁酸脱氢酶（ＨＢＤ）活性值的变化。结果发现：失血性休克３０ｍｉｎ时,ＣＫ、ＧＯＴ较休克前显著下降（Ｐ＜０．０５,Ｐ＜０．０１）;ＨＢＤ值也下降,但无统计学意义（Ｐ＞０．０５）。输血后３０ｍｉｎ时,ＣＫ、ＧＯＴ、ＨＢＤ值回升,与休克３０ｍｉｎ时比显著升高（Ｐ＜０．０５）,与休克前比无显著性差别（Ｐ＞０．０５）。提示：失血性休克早期心肌细胞可能存在有一种保护性反应,心肌细胞没有发生明显损伤。