Favourable associations between the myosin heavy-chain and light-chain isoforms in human skeletal muscle

Histochemical and biochemical analyses were performed in order to examine the relationship between myosin light-chain (LC) isoforms and fibre-type distributions in whole human skeletal muscle. Muscle biopsies were obtained from the vastus lateralis muscle in six healthy men, and analysed for the relative area occupied by each fibre type (percentage of fibre type area) and the molar ratio of each LC isoform. The percentage of type I fibre area was positively correlated with the molar ratio of slow LC (LC1s and LC2s) to total LC. The regression line was located below the line of unity. Also, the ratio of percentage of type II fibre area to that of type II fibre area was positively correlated with the molar ratio of the fast alkali LC LC1f to fast alkali LCs LC1f and LC3f. These results support previous study, having shown that in human skeletal muscle some type I fibres express various amounts of fast LC in addition to slow LC and suggest that fast myosin heavy-chain HCII a is favourably associated with LC1f, whereas HCIIb is favourably associated with LC3f.     

Immunohistochemical evaluation of the neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on dopaminergic nigrostriatal neurons of young adult mice using dopamine and tyrosine hydroxylase antibodies

The recovery of dopamine (DA) neurons in young adult mice from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) damage was analyzed at various times after MPTP treatment with DA and tyrosine hydroxylase (TH) immunohistochemistry and also by chemical DA assay. A remarkable discrepancy in the recovery rate of DA and TH reactivities of the nigral neurons was observed: the TH immunoreactivities of both cell bodies in the substantia nigra and terminals in the neostriatum were markedly reduced 4 days after MPTP. However, these reactivities progressively improved and almost fully recovered after 25 days, while the DA immunoreactivities were maximally depleted 10 days after, and the depletion continued even through the 25th day. The alteration of DA levels was correlated with that of DA immunoreactivity. These findings suggest that a major effect of MPTP on the DA neurons of young adult mice is a transient neurotoxicity, and that the TH content improves more promptly than that of DA.     

Somatic mosaicism of CAG repeat in dentatorubral-pallidoluysian atrophy (DRPLA)

An unstable expansion of CAG repeat in the coding region ofthe DRPLA gene on chromosome 12p is the mutation specific forhereditary dentatorubralpallidoluysian atrophy (DRPLA). We studiedthe CAG expansion in brain and other tissues from six unre latedDRPLA patients. The CAG repeat lengths showed distinct difterencesbetween tissues. The sizes of the CAG expansion in various regionsof the brain except the cerebellum were generally larger byseveral repeats than in other peripheral tissues. Brain samplesshowed greater variation of the expansion compared with othertissues, but neither the size of the CAG expansion nor the degreeof CAG repeat variation parallels the detailed findings of neuropathologicalinvolvement. We conclude that somatic instabilities of the CAGrepeat cause tissue variability of the CAG repeat size in DRPLAbut other region or cell type-specific factors would be involvedto explain the selectivity of cell damage in DRPLA.     

Muscle energetics in short-term training during hypoxia in elite combination skiers

Four well-trained combination skiers were studied through pre- and post-training for the effects of short-term intermittent training during hypoxia on muscle energetics during submaximal exercise as measured by Phosphorus-31 nuclear magnetic resonance and maximal aerobic power ( O_2max). The hypoxia and training in the cold was conducted in a hypobaric chamber and comprised 60-min aerobic exercise (at an intensity equivalent to the blood lactate threshold), using a cycle ergometer or a treadmill twice a day for 4, consecutive days at 5°C, in conditions equivalent to an altitude of 2000 m (593 mm Hg). No change in O_2max was observed over the training period, while in the muscle energetics during submaximal exercise, the values of phosphocreatine/(phosphocreatine + inorganic phosphate) and intracellular pH were found to be significantly increased by training during hypoxia. During recovery, the time constant of phosphocreatine was found to have been significantly reduced [pre, 27.9 (SD 6.7) s; post, 22.5 (SD 4.7) s, P < 0.01]. The observed inhibition of phosphocreatine as well as that of intracellular pH changes after training during hypoxia and quicker recovery of phosphocreatine in submaximal exercise tests, may indicate improved oxidative capacity (i.e. a high adenosine 5-triphosphate formation rate) despite the short-term hypoxia training. Present address: Department Life Sciences, Univ. of Tokyo, Komaba 3-8-1, Meguro-ku 153, Japan     

A comparative, well-controlled study of ceftizoxime suppository against ceftizoxime intravenous injection in infantile acute pneumonia

We have attempted to clinically define the therapeutic usefulness of ceftizoxime suppository (CZX-S) in children with bacterial pneumonia, in a randomized trial. Intravenous injection of ceftizoxime (CZX) was used as the control. The results are summarized below. Subjects were inpatients with bacterial pneumonia, ranging in age from 9 months to 7 years and 10 months. As a rule, the daily dose was either four 250 mg (in potency) suppositories given at 6-hour intervals or 60 mg/kg body weight intravenous CZX (control) given in 4 injections at 6-hour intervals over a period of 7 days. The number of children in the study was 67. These children were divided into 2 dosage groups (suppository, 35; injection, 32) with matching pretreatment background factors. The severity of the target disease in the majority of the children was "moderate". The rate of therapeutic effectiveness was 97.1% for the suppository and 93.8% for the injection, and did not differ significantly between the 2 groups. Rates of efficacy by severity, presence or absence of underlying diseases, daily dose and/or complications were high without exception, and did not differ significantly between the 2 groups. Eradication rates for causative microorganisms, as studied in 16 children of each group, were both 93.8%. The 2 most frequently isolated causative organisms were Haemophilus influenzae and Streptococcus pneumoniae. Side effects were examined for 36 children of each group. The frequency of side effects did not differ significantly between the suppository group (2 with diarrhea and 1 with abdominal pain) and the injection group (1 with urticaria), and 8.3% and 2.8%, respectively. The frequency of abnormal laboratory test findings differed significantly (P less than 0.01) with respect to eosinophilia which occurred in 7 (20.6%) of the injected subjects but was not encountered in the subjects treated with suppositories. Other abnormal laboratory findings included thrombocytosis in 3 (14.3%) of the injection group and increased GOT in 1 (3.2%) of the suppository group. The suppository formulation of CZX appears to be a highly useful substitute for the injectable form, and should find a special use in children whose treatment with injections experiences some difficulty.     

Second messengers and protein phosphorylation in cellular signal transduction

Protein phosphorylation has been recognized as a major mechanism by which cellular functions are controlled by neurotransmitters and hormones. In this review, applications of molecular biological techniques to the analyses of regulatory mechanisms of protein phosphorylation by four major second messengers, cAMP, cGMP, diacylglycerol, and Ca2+, are described. 1) Complementary DNA of the regulatory subunit of the cAMP-dependent protein kinase was cloned and expressed in E. coli. Point mutations were introduced in order to analyze functional domains of the subunit. 2) The soluble isoform of guanylate cyclase was purified, and a cDNA of its 70-KD subunit was cloned. Cyclic GMP binding to purified cGMP-dependent protein kinase was characterized using a rapid filtration assay. 3) Primary structure of the catalytic subunit of calmodulin-dependent protein phosphatase (calcineurin A) was determined and the presence of the second isoform of the enzyme was shown by the cDNA cloning technique. 4) The regulatory domain of the protein kinase C was expressed in E. coli. Analysis using site-directed mutagenesis revealed that a "zinc finger"-like structure is responsible for the binding of phorbol esters. In these studies, the molecular biological approach has proven to be useful for clarifying the molecular mechanisms of cellular signal transduction related to second messengers and protein phosphorylation.     

Hormone receptors and obesity in Japanese women with breast cancer

Summary An association between hormone receptors in primary breast cancer and obesity determined prior to mastectomy was investigated in 128 Japanese women. The following criteria for obesity were used: (1) weight 60 kg (132 lbs), (2) weight kg/height cm–105 1.3, (3) weight lbs/height in 2.30, (4) body surface area 1.56 m². In view of the 4 criteria, tumor estrogen receptor (ER) values 4 fmol/mg were observed in obese patients more often than in nonobese patients, though the difference was not statistically significant. The same tendency was observed in the postmenopausal subgroup, 62 patients, especially in the 36 patients more than 5 years beyond menopause. However, there was still no statistical difference between obese and nonobese patients because the number of subjects was small. The same tendency was observed in the case of progesterone receptor (PgR) (6 fmol/mg) as observed in the case of ER. Address for reprints: Dr. Keijiro Kuno, Department of Surgery, Cancer Institute Hospital, 1-37-1 Kami-Ikebukuro, Toshima-ku, Tokyo, Japan 170     

Phosphate kinetics in patients on chronic hemodialysis

To investigate the phosphate kinetics in hemodialysis (HD), 8 patients in a stable condition, who were receiving HD three times a week for 4 hours per session, were investigated. Plasma phosphate was under 7 mg/dl, and residual renal function had almost disappeared. Dialysate containing phosphate was prepared by adding Na2HPO4 using a micro-infusion pump from the inlet of single pass dialysate in the individual dialysate delivery system. In the first week, Na2HPO4 was not added as the control period. In the second session of the second and third week, Na2HPO4 was added to give a phosphate concentration of 1.0 and 2.0 mmol/l in the dialysate, respectively. Total phosphate mass removal was 777 +/- 46.64 mg in the control period, 403 +/- 67.21 mg in the second week, and -230 +/- 214.8 mg in the third week. Total phosphate mass removal in the second and third week was significantly lower than that of the control period. Plasma phosphate concentration was significantly decreased after the HD compared with before the HD in the control and second week. There was no significant difference in plasma phosphate concentration between the period before HD and at 48 hours in the control and the second week. Plasma phosphate concentration before HD not only depended on phosphate mass removal by HD, but also on other factors. We suggest that dialysate containing phosphate might prevent excessive phosphate removal from non-extracellular compartments during HD.     

Tumor-specific Activation of Mitogen-activated Protein Kinase in Human Colorectal and Gastric Carcinoma Tissues

To search for the signaling events in colorectal carcinoma relevant to its tumorigenesis, we investigated the activity of mitogen-activated protein kinase (MAPK) in human colorectal carcinoma tissues and paired normal tissues. Of 64 cases examined, approximately 75% (48 cases) showed tumor-specific activation of MAPK by in situ kinase renaturation assay, as well as in vitro kinase assay with immunoprecipitated MAPK. In addition, tumor-specific activation of MAPK was associated with the activation of MAPK kinase in the cases we examined. However, no clear correlation of MAPK activation with lymph node involvement, metastatic rate, stage, histological classification, age or sex was observed. These results suggest that the MAPK pathway is involved in colorectal tumor development, but its activation alone is not sufficient for malignant conversion. In contrast to colorectal carcinoma, gastric carcinoma tissues showed a lower rate of MAPK activation, suggesting that the signaling pathway activated in colorectal carcinoma tissues may differ in part from that of gastric carcinoma.