Vitamin C supplementation does not alter high-intensity endurance training-induced mitochondrial biogenesis in rat epitrochlearis muscle

The purpose of this study was to investigate whether vitamin C supplementation prevents high-intensity intermittent endurance training-induced mitochondrial biogenesis in the skeletal muscle. Male Wistar-strain rats were assigned to one of five groups: a control group, training group, small dose vitamin C supplemented training group, middle dose vitamin C supplemented training group, and large dose vitamin C supplemented training group. The rats of the trained groups were subjected to intense intermittent swimming training. The vitamin C supplemented groups were administrated vitamin C for the pretraining and training periods. High-intensity intermittent swimming training without vitamin C supplementation significantly increased peroxisome proliferator-activated receptor-γ coactivator-1α protein content and citrate synthase activity in the epitrochlearis muscle. The vitamin C supplementation did not alter the training-induced increase of these regardless of the dose of vitamin C supplementation. The results demonstrate that vitamin C supplementation does not prevent high-intensity intermittent training-induced mitochondrial biogenesis in the skeletal muscle.

Myxococcus xanthus twin-arginine translocation system is important for growth and development

The twin-arginine translocation (Tat) system serves to export fully folded proteins across the cytoplasmic membrane. In many bacteria, three major components, TatA, TatB and TatC, are the functionally essential constituents of the Tat system. A Myxococcus xanthus tatB-tatC deletion mutant could aggregate and form mounds, but was unable to form fruiting bodies under nutritionally limiting conditions. When tatB-tatC mutant vegetative cells were cultured with 0.5 M glycerol, the cell morphology changed to spore-like spherical cells, but the spores were not resistant to heat and sonication treatments. In contrast to the wild-type strain, the tatB-tatC mutant also showed a decreased cell growth rate and a lower maximum cell concentration. These results suggest possibility that the Tat system may contribute to export of various important proteins for development and growth for M. xanthus.

Cloning and establishment of a line of rats for high levels of voluntary wheel running

We generated an original Wistar line of rats that displayed increased levels of wheel running, which we named SPORTS (Spontaneously-Running-Tokushima-Shikoku). Male SPORTS rats ran voluntarily in a running wheel almost six times longer than male control Wistar rats, established without selection for their running activity. The running phenotype of female SPORTS rats was the same as female control Wistar rats. However, male offspring from the cross-mating between a female SPORTS rat and a male control rat also showed a similar level of hyper-running activity as the original SPORTS line. Compared to control rats, male SPORTS rats had lower levels of mean body weight, abdominal fat and plasma insulin after 4 weeks of running. It is likely that all these beneficial changes observed in the SPORTS rats reflected the increases in glucose disposal we observed in oral glucose tolerance tests carried out on the animals. We also found hyper-running caused a significant increase in skeletal muscle oxidative capacity, measured as the ratio of malate dehydrogenase to phosphofructokinase activity, an index of aerobic metabolism. These results indicate that the SPORTS rat may be a good animal model for determining the mechanisms responsible for up-regulation of running motivation, in addition to investigating changes in nutrient metabolism induced by high intensity exercise.

A double mutant exhibits reduced uptake of amino acids and tolerance of some antimicrobials

Myxococcus xanthus RppA and MmrA are homologous to methyl-accepting chemotaxis proteins (MCPs) and to multidrug transporters, respectively. We reported previously that rppA-mmrA double mutant exhibited reduced colony expansion, agglutination, and polysaccharide levels. We have demonstrated here that the rppA-mmrA mutant also exhibited reduced amino acid uptake. Furthermore, the double mutant appeared to be more susceptible to some antimicrobial agents, such as streptomycin, ethidium bromide and norfloxacin, than the wild-type. These phenotypes were not shown in the rppA or mmrA single mutant. These results indicate that M. xanthus RppA and MmrA are also involved in the uptake of amino acids and efflux of some antimicrobial agents.

RppA, a transducer homologue, and MmrA, a multidrug transporter homologue, are involved in the biogenesis and/or assembly of polysaccharide in Myxococcus xanthus

Myxococcus xanthus cells move by gliding, and form multicellular fruiting bodies under conditions of starvation. The authors cloned a gene, designated rppA (for receptor for polysaccharide production), which encodes a methyl-accepting protein homologous to the chemotaxis transducers in eubacteria. The rppA gene was co-transcribed with mmrA, a gene homologous to various multidrug transporter genes. The rppA or mmrA single mutants showed almost identical phenotypes to the wild-type strain; however, the rppA-mmrA double mutant exhibited reduced colony expansion, cell-cell agglutination and cellular reversal frequency. The double-mutant cells also showed less binding to Congo red, which mainly binds to fibril polysaccharide, than wild-type cells. Analysis of total polysaccharide in stationary-phase cells demonstrated that in the double mutant, polysaccharide levels were decreased by about 30 % as compared with the wild-type strain. These results indicated that RppA and MmrA play a role in the biogenesis and/or assembly of polysaccharide, and the phenotypes of the double mutant may be due to the reduction in fibril polysaccharide.

Genomic DNA released by dying cells induces the maturation of APCs

Mature APCs play a key role in the induction of Ag-specific immunity. This work examines whether genomic DNA released by dying cells provides a stimulus for APC maturation. Double-stranded but not single-stranded genomic DNA triggered APC to up-regulate expression of MHC class I/II and various costimulatory molecules. Functionally, dsDNA enhanced APC function in vitro and improved primary cellular and humoral immune responses in vivo. These effects were dependent on the length and concentration of the dsDNA but were independent of nucleotide sequence. The maturation of APC induced by dsDNA may promote host survival by improving immune surveillance at sites of tissue injury/infection.

Graves' disease: a host defense mechanism gone awry

In this report we summarize evidence to support a model for the development of Graves' disease. The model suggests that Graves' disease is initiated by an insult to the thyrocyte in an individual with a normal immune system. The insult, infectious or otherwise, causes double strand DNA or RNA to enter the cytoplasm of the cell. This causes abnormal expression of major histocompatibility (MHC) class I as a dominant feature, but also aberrant expression of MHC class II, as well as changes in genes or gene products needed for the thyrocyte to become an antigen presenting cell (APC). These include increased expression of proteasome processing proteins (LMP2), transporters of antigen peptides (TAP), invariant chain (Ii), HLA-DM, and the co-stimulatory molecule, B7, as well as STAT and NF-kappaB activation. A critical factor in these changes is the loss of normal negative regulation of MHC class I, class II, and thyrotropin receptor (TSHR) gene expression, which is necessary to maintain self-tolerance during the normal changes in gene expression involved in hormonally-increased growth and function of the cell. Self-tolerance to the TSHR is maintained in normals because there is a population of CD8- cells which normally suppresses a population of CD4+ cells that can interact with the TSHR if thyrocytes become APCs. This is a host self-defense mechanism that we hypothesize leads to autoimmune disease in persons, for example, with a specific viral infection, a genetic predisposition, or even, possibly, a TSHR polymorphism. The model is suggested to be important to explain the development of other autoimmune diseases including systemic lupus or diabetes.

Treatment of Vogt-Koyanagi- Harada's disease during pregnancy

BACKGROUND

Caution should be exercised in treating patients with autoimmune diseases during pregnancy.

CASES

We successfully treated three cases of Vogt-Koyanagi-Harada's disease (VKH disease) during pregnancy.

OBSERVATIONS

In the second trimester (14-27 weeks) of 1 patient, inflammation was mild and could be treated by topical corticosteroid. There is the possibility that her immune response had been modified by pregnancy. Systemic corticosteroid in a high dose was administered to the two cases in the second and third trimesters of pregnancy (28-41 weeks). The severity of inflammation in these 2 patients was similar to that in nonpregnant women. Inflammation subsided immediately without recurrence in all cases. No abnormality was found during the deliveries or in the babies.

CONCLUSIONS

Treatment for VKH disease during pregnancy should be chosen according to the severity of inflammation, the stage of pregnancy, and the maternal and fetal conditions.

Does prolonged exercise alter diet-induced thermogenesis?

Diet-induced thermogenesis (DIT) is mainly an insulin-mediated response and the result of fat and glycogen synthesis. We investigated DIT at rest and after exercise to clarify the mechanism of exercise-induced changes in DIT in 6 healthy men (mean age 36 +/- 16 years). Subjects exercised for 1 h at 58% of maximal O2 consumption on a bicycle ergometer and then rested for 8 h sitting in a comfortable chair (exercise experiment). On a different day, subjects rested for 8 h without preceding exercising (non-exercise experiment). At 12.30 h, the subjects were given their second meal. DIT to individual meal did not differ significantly between the exercise and non-exercise days. Increased insulin sensitivity and increased free fatty acid oxidation by exercise may facilitate the conversion of glucose to glycogen in muscle. On the other hand, insulin secretion expressed as the ratio of plasma levels of insulin to glucose after the meal was significantly decreased in the exercise experiment (p < 0.05). Study of heart rate variability showed that sympathetic tone, a primary hormonal determinant of glucose metabolism during exercise, was increased and parasympathetic tone was decreased during the recovery period in the exercise experiment (p < 0.05). These findings suggest that changes in DIT are affected by many factors and may be related to the balance between these counteracting factors.

Relationship among oxygenation, myoelectric activity, and lactic acid accumulation in vastus lateralis muscle during exercise with constant work rate

The purpose of this study was to determine whether oxygenation in localized working muscle depended on the muscle activity and on the lactic acidosis level. Seven healthy male subjects underwent the five 6-min cycling exercises with work rates of 50 watts (25.0 +/- 5.0% VO2max), 100 watts (36.6 +/- 6.2% VO2max), 150 watts (50.6 +/- 7.7% VO2max), 200 watts (67.8 + 6.9% VO2max), and 250 watts (82.9 +/- 7.5% VO2max) while gas exchange parameters and blood lactate concentration (BL) were measured. We also measured oxygenated hemoglobin and myoglobin concentration (oxy-Hb/Mb) with continuous-wave near infrared spectroscopy (NIR) and surface myoelectric activity with surface electrodes (EMG). The NIR probe and electrodes were positioned on the vastus lateralis muscle of the right leg. The relative change in oxy-Hb/Mb was estimated by regarding oxy-Hb/Mb in the resting condition as 100% and that obtained during thigh occlusion as 0%. The mean values of oxy-Hb/Mb and integrated EMG (iEMG) were determined from 5'30" to 6'00" at each work rate. The percentage of oxy-Hb/Mb was sustained at the first two work rates corresponding to 25.0 +/- 5.0 and 36.6 +/- 6.2% VO2max and decreased slightly at 150 watts corresponding to 50.6 +/- 7.7% VO2max, which was followed by a linear decrease at 200 and 250 watts corresponding to 67.8 +/- 6.9 and 82.9 +/- 7.5% VO2max. The iEMG, however, was increased slowly at 25.0 +/- 5.0 to 50.6 +/- 7.7% VO2max, and a rapid increment of the iEMG occurred at 67.8 +/- 6.9 and 82.9 +/- 7.5% VO2max. BL was sustained at 25.0 +/- 5.0 to 50.6 +/- 7.7% VO2max and increased linearly at 67.8 +/- 6.9 and 82.9 +/- 7.5% VO2max. There was a significant negative correlation for each subject between the percentage of oxy-Hb/Mb and iEMG (r = -0.947 to -0.993), between the percentage of oxy-Hb/Mb and BL (r = -0.890 to -0.982), and between the percentage of oxy-Hb/Mb and VO2 (r = -0.929 to -0.994) These results indicated that oxygenated hemoglobin/myoglobin concentration measured with NIR reflected the muscle activity and the lactic acidosis.

Expression of transforming growth factor-beta1 and transforming growth factor-beta Type-II receptor mRNA in papillary thyroid carcinoma

Transforming growth factor-beta1 (TGF-beta1) is a potent inhibitor of epithelial cell proliferation. Signal transduction by TGF-beta1 involves direct binding to the TGF-beta Type-II receptor and then the formation of a heterodimeric complex of TGF-beta Type-I and Type-II receptor. To explore the role of TGF-beta1 in thyroid carcinoma, we examined the expression of TGF-beta1 and TGF-beta Type-II receptor mRNA by northern blotting analysis in both 14 papillary thyroid carcinomas and surrounding normal thyroid tissues. Relative mRNA level was determined by scanning densitometry of the autoradiogram and corrected for loading differences using a human beta-actin cDNA probe. The relative mRNA levels of TGF-beta1 in 12 out of 14 papillary thyroid carcinomas were higher than those in surrounding normal thyroid tissues. In contrast, the relative mRNA levels of TGF-beta Type-II receptor were reduced to 60.1+/-18.3% of those of normal thyroid tissues in 10 papillary thyroid carcinomas. There were no clear relationships between the relative mRNA levels for TGF-beta1 and TGF-beta Type-II receptor and the histological characteristics of papillary thyroid carcinomas. The relative mRNA levels for TGF-beta1 and TGF-beta Type-II receptor did not show significant differences in thyroid carcinomas with or without lymph node metastases. There was a negative correlation between the TGF-beta Type-II receptor mRNA level and tumor size, while no significant correlation was observed between the TGF-beta1 mRNA level and tumor size. In conclusion, most papillary thyroid carcinomas overexpress TGF-beta1 mRNA but exhibit a reduction in TGF-beta Type-II receptor mRNA. The reduction of TGF-beta Type-II receptor mRNA may play a role in the pathogenesis of papillary thyroid carcinoma.

Hyponatremia in a patient with chronic inflammatory disease

A 66-year-old man was admitted with destructive arthropathy, and calcium pyrophosphate dihydrate was demonstrated in the synovial fluid specimen. He was found to have a hyponatremia. The serum sodium concentration was 121 mmol/l, plasma arginine vasopressin (AVP) 6.6 pmol/l, and serum interleukin (IL)-6 96 pg/l. The clinical findings suggest the diagnosis of syndrome of inappropriate secretion of antidiuretic hormone (SIADH). However, destructive arthropathy with increased values of C-reactive protein and IL-6 is the only background of SIADH in this patient. We suggest the possibility that IL-6 produced at inflammatory lesions may have stimulated an excessive release of AVP resulting in the hyponatremia and hypochloremia of SIADH.

Serum androgen levels in hyperthyroid women

Thyroid hormone is known to affect androgen metabolism, however, there are few studies in which alterations of androgen metabolism are simultaneously examined in patients with clinical thyroid disorders. In this study, we investigated the alterations of thyroid hormone and androgens before and during treatment in patients with hyperthyroidism. Fifteen female patients with hyperthyroidism due to Graves' disease were studied. From these patients, blood samples were obtained before treatment and at 1 month (M), 2M, 3M, 4M and 6M after beginning of treatment. Concentrations of free T4(FT4), free T3(FT3), testosterone (T), androstenedione (delta 4A), dihydrotestosterone (DHT), 5 alpha-androstane-3 alpha, 17 beta-diol(3 alpha-diol) and androsterone (AD) and sex hormone binding globulin (SHBG) were measured by radioimmunoassays (RIAs) or immunoradiometric assay (IRMA). As normal controls, ten healthy women were also studied. Before treatment concentrations of DHT (mean +/- SD: 3.35 +/- 0.78 nmol/L), 3 alpha-diol (0.78 +/- 0.11 nmol/L), AD (6.73 +/- 0.64 nmol/L) and SHBG (184.9 +/- 68.1 nmol/L) were significantly elevated compared with those of normal controls. T and delta 4A levels were not significantly different from normal values. DHT/T ratio indicating 5 alpha-reductase activity was 4.62 +/- 2.55 and significantly higher than that in normal controls. At 2 months after beginning of treatment with anti-thyroid drugs, thyroid function (FT4 and FT3) became normal and at 3 months after beginning of treatment, DHT, 3 alpha-diol, AD and DHT/T ratio decreased to normal range. SHBG level was gradually decreased, however still higher than that of the normal control group at 6 months after beginning of treatment. There was a time lag in recovery between serum androgen levels and SHBG level.

Interferon-alpha-induced thyroid dysfunction in patients with chronic active hepatitis C: a transient, reversible and self-limited dysfunction

To survey the prognoses of interferon-alpha (IFNalpha)-induced thyroid dysfunction, a total of 100 patients (49 males and 51 females) with biopsy-proven chronic active hepatitis C were studied. Either during or after IFNalpha therapy, 29 patients (33.7%) revealed suppression/elevation of thyroid stimulating hormone (TSH) or both, transient thyrotoxicosis (TSH less than 0.1 microU/ml) or transient hypothyroidism (TSH 5.0-190.95 microU/ml). However, the thyroid function normalized without supplementation of the thyroid hormone in the follow-up period. In the same period, one of the 14 control patients (7.1%) developed thyroid dysfunction. Thyroid abnormalities developed significantly more in patients with IFNalpha therapy than in those without IFNalpha therapy. The findings suggest that the occult autoimmune disorder becomes overt with IFNalpha treatment in patients with pre-existent autoimmune thyroid disease. IFNalpha-induced thyroid dysfunction is transient, reversible and self-limited. It is not necessary to discontinue IFNalpha therapy when thyroid dysfunction develops.

Diffusion-weighted imaging of the human optic nerve: a new approach to evaluate optic neuritis in multiple sclerosis

The apparent diffusion coefficient (ADC) in the optic nerve was measured from diffusion-weighted magnetic resonance imaging using an intravoxel incoherent motion (IVIM) sequence. The subjects were seven normal volunteers and eight patients with multiple sclerosis (MS) with a total of four optic nerves with acute neuritis and nine nerves with chronic neuritis. The mean ADC (4.18 +/- 1.13 x 10(-3) mm2/s, n = 9) in the optic nerves with chronic neuritis was significantly higher than that in normal volunteers (1.56 +/- 0.675 x 10(-3) mm2/s, n = 14) and that in the nerves with acute neuritis (0.94 +/- 0.43 x 10(-3) mm2/s n = 4) (P < 0.001). The ADC is useful in assessing MS foci in the optic nerves.

Decreased contraction economy in mouse EDL muscle injured by eccentric contractions

The objective of this study was to find out whether basal and/or active energy metabolism are altered in isolated mouse extensor digitorum longus muscle injured by eccentric (Ecc) contractions. Measurements of basal O2 consumption and isometric tetanus O2 recovery cost were made at 25 degrees C on muscles that had done either 10 Ecc, 10 isometric (Iso), or no contractions (No). In parallel experiments, rates of lactate and pyruvate production were measured to estimate the anaerobic contribution. Basal O2 consumption was unaffected by the type of protocol performed (P = 0.07). However, the tetanus O2 cost per force-time integral was elevated by 30-36% for the Ecc protocol muscles over that for the Iso and No protocol muscles. When including the increased lactate production by the Ecc protocol muscles, the total energetic cost per force-time integral was 53% higher than that for the Iso protocol muscles [2.35 +/- 0.17 vs. 1.54 +/- 0.18 mumol O2/(N.m.s)]. The decreased economy was attributed to two factors. First, in skinned fibers isolated from the injured muscles, the ratio of maximal actomyosin adenosinetriphosphatase activity to force production was up by 37.5%, suggesting uncoupling of ATP hydrolysis from force production. Second, increased reliance on anaerobic metabolism along with the fluorescent microscopic study of mitochondrial membrane potential and histochemical study of ATP synthase suggested an uncoupling of oxidative phosphorylation in the injured muscles.

Insufficient expression of Fas antigen on helper T cells in Behçet's disease

AIMS

To investigate the lack of equilibrium in the regulatory mechanism of the immune system in Behçet's disease (BD), the expression of Fas antigen, an apoptosis related antigen, on peripheral blood lymphocytes from BD patients was analysed.

METHODS

Twenty one BD patients were the subjects in this study. Ten healthy adults were examined as controls. Cell surface antigens of lymphocytes were analysed with flow cytometry.

RESULTS

There was a significant (p < 0.01) difference in the proportion of CD4 positive cells with CD25 between BD patients with active uveoretinitis (27.6% (SD 8.4%)) and the controls (14.7% (2.3%)), but no significant difference in the proportion of CD4 or CD45RO positive cells with Fas. On the other hand, the proportion of CD8 positive cells with Fas was significantly (p < 0.01) higher in BD patients with active uveoretinitis (45.6% (11.6%)) than in those with inactive uveoretinitis (23.8% (8.1%)) or in the controls (24.4% (2.5%)). The proportion of CD19 positive cells with Fas was also significantly (p < 0.01) higher in BD patients with active uveoretinitis (13.0% (5.0%)) than in the controls (5.1% (2.1%)).

CONCLUSION

The insufficient expression of Fas on activated CD4 positive T cells and its high expression on CD8 positive T cells seem to play an important role in the chronic inflammation in BD.

Attenuation of Ca(2+)-induced increase in oxidative metabolism by cooling and calmodulin antagonist in mammalian brain neurons: a flow-cytometric study

Effects of cooling and calmodulin antagonist on ionomycin-induced increase in oxidative metabolism (or formation of reactive oxygen species) of rat cerebellar neurons was examined using a flow cytometer and 2',7'-dichlorofluorescin diacetate, a fluorescent dye for intracellular hydrogen peroxide. Cooling neurons to temperatures below 16 degrees C greatly attenuated ionomycin-induced augmentation of oxidative metabolism without affecting the Ca2+ influx produced by ionomycin. Rewarming neurons to 36 degrees C in presence of ionomycin increased the oxidative metabolism, indicating a temperature-sensitive metabolic process. Substitution of Ca2+ with Ba2+ or Sr2+ completely abolished an ionomycin-induced increase in the oxidative metabolism. Pretreatment with W-7, a calmodulin antagonist, at concentrations of 10 microM or higher (up to 100 microM) produced a dose-dependent attenuation of ionomycin-induced increase in oxidative metabolism. Results suggest that calmodulin is involved in the ionomycin-induced increase in oxidative metabolism of dissociated cerebellar neurons.

Changes in myosin heavy chain isoform expression of overloaded rat skeletal muscles

1. The effect of functional overload produced by tenotomy of synergistic gastrocnemius muscle on the expression of myosin heavy chain (MHC) isoforms in the plantaris and soleus muscles of the rat was studied using gradient sodium dodecyl sulfate-acrylamide gel electrophoresis. 2. Five weeks tenotomy, the plantaris and soleus muscle weights induced by tenotomy of the gastrocnemius muscle were 44.3% (P < 0.005) and 37.4% (P < 0.005), respectively, heavier than the contralateral control muscles. 3. Although four types of MHC isoforms were observed in both control and experimental plantaris, the percentage of MHC isoforms in the control and experimental muscles differed; the hypertrophied plantaris muscle contained more HCI (P < 0.05), HCIIa and HCIId (P < 0.05) and less HCIIb (P < 0.05) than the control muscle. 4. The control soleus muscle contained two MHC isoforms, HCI and HCIIa. However, there was only a single HCI isoform in the hypertrophied soleus muscle. 5. These results indicate that overloading a skeletal muscle by removing its synergists produces not only the muscle hypertrophy but also the changes in the expression of MHC isoforms.

Myosin light chain patterns in histochemically typed single fibers of the rat skeletal muscle

1. This study was conducted to investigate the relationship between histochemical fiber types and myosin light chain patterns in rat single muscle fibers. 2. The hybrid of fast and slow light chains was observed in type I and II fibers of the soleus and type II fibers of the red portion of lateral head of the gastrocnemius muscles. 3. We also observed 7 types of light chain composition. Of the 7 types, 5 types were explainable by assuming the coexistence of isomyosins with either fast or slow light chains. However, the other 2 types could not be accounted for without hypothesizing the presence of isomyosins with promiscuous light chain distribution.

Triphenyltin-induced increase in the intracellular Ca2+ of dissociated mammalian CNS neuron: its independence from voltage-dependent Ca2+ channels

To test the possibility that triphenyltin (TPT) increases the intracellular Ca2+ ([Ca2+]i) in neurons as found previously in thymocytes, the effect of TPT on [Ca2+]i was examined in rat cerebellar neurons by a flow-cytometer with fluorescent dyes. TPT at concentrations ranging from 3 x 10(-7) M to 1 x 10(-5) M dose-dependently increased the [Ca2+]i. The TPT-induced increase in [Ca2+]i was not attenuated by a Ca2+ channel blocker, suggesting that it was not dependent on voltage-dependent Ca2+ channels. As the concentration of external Ca2+ ([Ca2+]e) increased, TPT produced a more profound increase in the [Ca2+]i. However, the increase in the [Ca2+]i by TPT was observed even in nominally [Ca2+]e-free solution. These results suggest two possibilities. First, TPT may promote Ca(2+)-influx to the neuron. Secondly, TPT may affect the intracellular Ca-store sites. This study is relevant to the neurotoxicity of organotins because it has become progressively clear that sustained increases in the [Ca2+]i can activate various Ca(2+)-dependent degradative processes.

Myosin heavy chain isoform transition in ageing fast and slow muscles of the rat

Using gradient sodium dodecyl sulphate-polyacrylamide gel electrophoresis, myosin heavy chain (MHC) isoforms were studied in the extensor digitorum longus (EDL) and the soleus muscles of male Wistar rats at different ages (5, 10, 20 weeks, 1 and 2 years). In the EDL muscle, four types of MHC isoforms were observed in all age groups. There was an increase in the percentage of HCIId and a concomitant decrease in the percentage of HCIIb with increasing age. No significant difference was observed in the percentages of HCI and HCIIa isoforms in all the age groups. In contrast, the soleus muscle contained two MHC isoforms, HCI and HCIIa. There was an increase in the percentage of HCI and a concomitant decrease in the percentage of HCIIa with increasing age. These results suggest that age-related changes in the MHC isoforms in both the fast-twitch EDL and the slow-twitch soleus muscles are one factor underlying the age-related decrease in the speed of muscle contraction.

[Endophthalmitis in Japan--a nationwide study with reference to type and etiology]

A nationwide clinical study on bacterial and fungal endophthalmitis was done with special reference to their type and etiology. Two hundred and eighty cases of endophthalmitis were reviewed. All cases were divided into two categories such as exogenous (trauma, surgery, and ulcer) and endogenous (metastasis). Penetrating trauma was responsible for 93 cases (33.2%), surgery for 88 cases (31.4%), ulcer for 11 cases (3.9%) and metastasis for 88 cases (31.4%). Out of the 280 cases, 79 cases (28.2%) were microbiologically diagnosed through aqueous or vitreous tap or biopsy. The total numbers of isolated organisms amounted to 87 consisting of 43 Gram-positive bacteria, 30 Gram-negative bacteria and 14 fungi. The positive isolation was 31 out of 86 (36%) from the aqueous and 52 out of 103 (50%) from the vitreous. Exogenous types associated with trauma, surgery or ulcer were mainly caused by Gram-positive bacteria of 37 strains, led by coagulase-negative staphylococci in 14 cases. On the other hand, endogenous cases were mainly due to Gram-negative bacteria of 14 strains including Klebsiella pneumoniae in 5 cases, E. coli in 4 cases and fungi of 11 strains including candida spp in 9 cases.

Muscle responses of thoroughbreds to conventional race training and detraining

Ten healthy sedentary Thoroughbreds with previous race training experience were trained conventionally for 9 weeks. Muscle biopsy samples were obtained before and after training and after 6 weeks of detraining pasture rest. Biopsy samples were obtained from the right deltoid, triceps, vastus lateralis, middle gluteal, biceps femoris, and semitendinosus muscles. The deep-frozen biopsy samples were analyzed for activities of succinate dehydrogenase (SDH), 3-hydroxy-acylcoenzyme A dehydrogenase (HAD), and phosphorylase (PHOS) and for glycogen concentration. The triceps and gluteal muscle samples were also serially sectioned and stained for myofibrillar actomyosin adenosine triphosphatase (ATPase) activity after alkaline (pH 10.3) and sequential acidic (pH 4.34) ATPase inactivation. Fiber types I (alkaline preincubation), IIA1, IIA2, and IIA3 (sequential acidic preincubation over 5 minutes) were identified and were evaluated for fiber-type distribution and fiber areas. Increases in response to training were observed in deltoid and vastus muscle SDH and gluteal muscle HAD activities, and deltoid muscle glycogen concentration (P less than 0.05 to P less than 0.01). Changes in PHOS activity were not observed. Type-IIA1, -IIA2, and -IIA3 fiber areas in triceps muscle were increased in response to training (P less than 0.05 to P less than 0.01). Changes in fiber-type distribution did not occur in response to training. Changes in muscle enzyme activities, glycogen concentration, fiber types, and fiber areas were not seen from posttraining to detraining. Further increases were observed when detraining values were compared with pretraining values in deltoid, triceps, vastus, gluteal, and biceps femoris muscle SDH activities and in gluteal muscle glycogen concentration (P less than 0.05 to P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of fiber types in skeletal muscles from ten animal species based on sensitivity of the myofibrillar actomyosin ATPase to acid or copper

Comparisons were made of the histochemical characteristics of skeletal muscle from 10 animal species. The basic comparison was made from the staining patterns for the myofibrillar actomyosin ATPase produced by preincubation of fresh frozen cross-sections of muscle at alkaline pH (10.30) or acid pH (4.60) with those produced by preincubation in media containing Cu2+ at alkaline pH (10.30), near neutral pH (7.40), or acid pH (4.60). Muscle sections were also stained for reduced nicotinamide adenine dinucleotide tetrazolium reductase and alpha-glycerophosphate dehydrogenase to provide an indication of the relative oxidative and glycolytic capacity of the different fiber types. Type II fibers in mixed fibered muscles were either very sensitive, moderately sensitive, or relatively insensitive to inactivation of the myofibrillar actomyosin ATPase after acid preincubation. These fibers were identified as type IIA1, IIA2, and IIA3, respectively. The myofibrillar actomyosin ATPase of the type I fibers of these muscles, with the exception of those in mouse muscle, was activated by pretreatment with acid. A separation of animal species was possible based on the stability of the IIA1 fibers to inclusion of Cu2+ in the preincubation medium. For one group of animals (rat, mouse, monkey, man, dog, rabbit, and cow), a reciprocal relationship existed between lability to acid and stability to Cu2+ for type IIA1 and IIA3 fibers, respectively. For the second group of animals (horse, ass, and cat) there was a parallel relationship between lability or stability of the type IIA1 and IIA3 fibers to pretreatment with either acid or Cu2+.

Role of carbohydrate in exercise

Carbohydrate is an important energy source during exercise. During short, heavy exercise it may be the only energy source for the working muscle and may be derived exclusively from the glycogen stores within the muscle fibers themselves. During prolonged, submaximal exercise the magnitude of the contribution that carbohydrate makes to the total fuel consumed depends upon a number of factors, including (1) the intensity of the exercise, (2) the duration of the exercise, (3) the state or type of training that the individual has engaged in, or both, and (4) the diet previously consumed. Due to their limited storage in the body and the relative ease with which these stores can be manipulated by combinations of diet and/or training, a knowledge of the dynamics of carbohydrate metabolism is an important component in the arsenal of knowledge for coaches and athletes.

The muscle fiber composition of skeletal muscle as a predictor of athletic success. An overview

Human skeletal muscle is composed of varying percentages of fiber types. This percent composition varies widely between muscles and among individuals. The fiber composition of some skeletal muscle could be construed as being advantageous to successful performance in selected athletic event. However, this relationship is not sufficiently close to warrant the conclusion that the fiber composition of the muscle per se is the determinant of the superior performance of elite athletes. Reasonably good evidence exists to support the position that the fiber composition of a muscle is the result of a genetic endowment. Although muscle fibers are mutable, present evidence is equivocal as to whether habitual participation in given type of physical activity is responsible for high percentages of a given fiber type being present in the muscles of some athletes. Although considerable knowledge has come from the study of muscle samples obtained from sedentary individuals, athletes of a wide range of performance capacity, and individuals before and after training, a considerable gap remains for a full understanding of how the characteristics of muscle are related to performance capacity. The observation that considerable variation exists in the percent distribution of the fibers within a muscle and that athletes with a wide range of fiber populations in their muscles can be successful in the same athletic event cautions against the routine application of the biopsy technique to estimate the fiber distribution of muscles and also to use such data as a routine screening procedure for predicting athletic success. The point, as was made in an earlier paper, that the biopsy technique for studying muscle is a research tool, will probably continue to be true for the near future.

Response of skeletal muscle to training

Physical training induces adaptive changes in skeletal muscle. These changes are localised to the active muscle with their magnitude depending upon the nature, i.e. time and intensity, of the training regimen. The most notable changes are increased concentrations of mitochondria and glycogen. With endurance training there are major changes in metabolism in that there is a greater contribution of fat to the total metabolism during submaximal exercise. This results in a conservation of the stores of glycogen with the net result of increasing total exercise capacity. This increased use of fat during submaximal exercise appears to be more closely related to the elevations in the concentration of mitochondria in muscle than to changes in total body maximal oxygen uptake. The combination of a greater contribution of fat to the metabolism and the elevated concentration of stored glycogen are prime factors contributing to the enhanced endurance capacity after endurance training. The mechanism for the greater use of fat after endurance training is discussed. Evidence now supports the hypothesis that this is due to a tighter control over the Embden-Meyerhof pathway as a result of the greater concentration of mitochondria. The effect of heavy resistance exercise on the size and strength of skeletal muscle is discussed. Some attention is focused on the recently revived controversy concerning whether muscle enlargement is the result of a hypertrophy of pre-existing fibres or of hyperplasia. It is concluded that although there is considerable evidence to support the development of hypertrophy in response to heavy resistance exercise, the contention that a splitting of fibres occurs to produce a greater fibre number is presently poorly supported.

Identification of fiber types in rat skeletal muscle based on the sensitivity of myofibrillar actomyosin ATPase to copper

Experiments are reported demonstrating that differential rates of inactivation of the histochemical staining for myofibrillar actomyosin ATPase in rat skeletal muscle fibers exist following inclusion of low concentrations of Cu2+ in the preincubation medium. This response of rat muscle occurs at near neutral (7.40), acid (4.60), and alkaline (10.30) pH. The response to Cu2+ appears to result from a binding of Cu2+ onto the myofibrillar complex, probably on myosin itself, as it can be reversed by soaking of the pretreated muscle sections in sodium cyanide or the Cu2+ chelator diethyldithiocarbamate. The pattern of modification of the staining pattern following pretreatment with Cu2+ is the mirror image of that produced by pretreatment with acid. The results demonstrate that the inclusion of Cu2+ in the preincubation media for the myofibrillar actomyosin ATPase can be a useful tool to differentiate fiber types. They also support the earlier conclusion that three distinct types of type II fibers can be identified in rat skeletal muscle based on the histochemical staining for myofibrillar actomyosin ATPase.

Histochemical changes of rat skeletal muscles induced by cold acclimation

After cold acclimation of rats the augmentation of succinic dehydrogenase activity in the fast-twitch oxidative glycolytic (FOG) and the slow-twitch oxidative (SO) fibers was observed in entire regions of the soleus, the extensor digitorum longus, the plantaris, the longissimus and the gastrocnemius muscles. Furthermore, a tendency to increased proportion of the FOG and the SO fibers was observed more prominently in superficial regions than in deep regions of a large muscle such as the gastrocnemius muscle.