Comparison of muscle force,muscle endurance,and electromyogram activity during an expedition at high altitude

Handgrip force (HF), maximal pinch force (MF), muscle endurance (ME), and the median power frequency (MdPF) of the activity shown in the electromyogram (EMG) were studied at various altitudes in eight normal healthy subjects. MF and ME were measured between the index finger and thumb, and all measurements were obtained at altitudes ranging from 610 to 4860 m during an expedition in the Qinghai Plateau in China. With the change in altitude HF, ME, and MF showed no significant change. Compared to the MdPF at 2260 m on ascent, the MdPF at other altitudes showed a significant decrease (P<0.01). Thus, we conclude that muscle performance (HF, MF, and ME) was not affected by the environment at high altitude. However, MdPF was affected and the mean MdPF at 610 m after the expedition did not recover to initial values of MdPF. We suggest these results may have been affected by fatigue and chronic exposure to the hypobaric hypoxic environment, since the members of the expedition party expressed feelings of sluggishness and fatigue after the expedition.     

31P nuclear magnetic resonance study on changes in phosphocreatine and the intracellular pH in rat skeletal muscle during exercise at various inspired oxygen contents

We measured ATP, phosphocreatine (PCr), inorganic phosphate (P_i), and the intracellular pH in rat hindlimb muscles during submaximal isometric exercise with various O₂ deliveries using³¹P nuclear magnetic resonance spectroscopy (³¹P NMR) to evaluate changes in energy metabolism in relation to O₂ availability. Delivery of O₂ to muscles was altered by controlling the fractional concentration of inspired oxygen (F _IO₂) at 0.50, 0.28, 0.21, 0.11 and 0.08 with monitoring partial pressure of oxygen and carbon dioxide, and bicarbonate at the femoral artery. The steady-state ratio of PCr : (PCr + P_i) during exercise decreased as a function ofF _IO₂ even at 0.21. Significant acidification of the intracellular pH during exercise occurred at 0.08F _IO₂. Change in the PCr : (PCr + P_i) ratio demonstrated that the oxidative capacity, i.e. the maximal rate of the oxidative phosphorylation reaction, in muscle was not limited by O₂ delivery at 0.50F _IO₂, but was significantly limited at 0.21F _IO₂ or below. Change in the intracellular pH at 0.08F _IO₂ could be interpreted as an increase in lactate, suggesting activation of glycolysis. Correlation between the PCr : (PCr + P_i) ratio and the intracellular pH revealed the existence of a critical PCr : (PCr + P_i) ratio and pH for glycolysis activation at around 0.4 and 6.7, respectively.     

Micropropagation of horseradish hairy root by means of adventitious shoot primordia

Adventitious shoot primordia were formed on horseradish hairy root cultured in dark. Plantlet formation frequency from the primordia was higher than that from root fragments. Culture for 26 days provided the adventitious shoot primordia, which had the highest potential for plantlet formation (53% explants at 40 days). Benzyladenine supplementation in the dark caused primordium enlargement, but did not increase the number of primordia formed. After adventitious shoot primordia were encapsulated with calcium alginate, kinetin supplementation (2.0–4.0 M) increased the shoot formation frequency (65–80% explants at 20 days) in the light, but also promoted the undesirable formattion of multiple shoots. Supplementation with naphthaleneacetic acid (0.27–5.4 M) in the calcium alginate beads in light enhanced the root emergence from primordia without inhibition of plantlet formation when the encapsulated beads were put on the agar-medium without naphthaleneacetic acid.     

Glycosphingolipids in cultured lens epithelial cells from dog and rhesus monkey

Vertebrate lens tissues contain several species of acidic andneutral glycosphingolipids in relatively high amounts. However,the epithelia with capsule from dog and rhesus monkey lenseshad a simpler composition and lower content of glycosphingolipidsthan whole lenses. Gangliosides and neutral glycosphingolipidsin monolayer cultures of lens epithelial cells were also differentfrom those in whole lenses. Although -galactosyl (Gal1-3Ga1-R)or Lewis^x (Galß1-4[Fuc1-3]GlcNAc-R) epitopes werefound in glycosphingolipids from whole lenses, they were notdetected in those from monolayer cultures of dog and rhesusmonkey lens cells. In addition, significant changes in ganglio-seriesgangliosides were induced in monolayer cultures of both cells,where GM3 and GD3 were predominant. Immunofluorescence studyrevealed a characteristic distribution of cell surface gangliosidesin confluent monolayers. These findings suggest that glycosphingolipidsynthesis in lens epithelia is intrinsically different fromthat in cortical and nuclear fibres, and that the expressionof Lewis^x and -galactosyl epitopes in glycosphingolipids appearsto be associated with the differentiation of epithelial cellsto fibres. gangliosides glycosphingolipids lens epithelial cells Lewis^x rhesus monkey.     

Data on the CGG repeat at the fragile X site in the non-retarded Japanese population and family suggest the presence of a subgroup of normal alleles predisposing to mutate

The fragile X mutation is the result of amplification in the repeat number of p(CGG) _n in FMR-1; alleles with more than 52 repeats have been shown to be so unstable as to mutate in the repeat number in almost every transmission. To improve our understanding of mutations in normal alleles of FMR-1, the following studies were carried out in the Japanese population: a study on length variation in the repeat to determine the allele distribution of the repeat length in a non-retarded population, family studies to observe new mutations in normal allele, and haplotype analyses with microsatellite markers flanking the repeat to confirm estimated mutation rates and founder chromosomes in the fragile X syndrome. Analysis of the p(CGG) _n in 370 unrelated males detected 24 distinct alleles with repeats of 18–44. A comparison with previously reported data suggests the presence of racial/ethnic differences in the allele distribution. No premutation allele was found in 824 unrelated X chromosomes examined by the polymerase chain reaction and Southern blot analysis. Family studies detected one new mutation in a total of 303 meioses. However, the mutation rate was not in accordance with the expected or observed heterozygosities in the population or with linkage disequilibrium observed between the repeat numbers and the haplotypes of the markers flanking the CGG. The haplotype in the chromosome in which the new mutation was found was the same as that frequently found in the Japanese fragile X chromosomes, and the variance in the CGG repeat number was wider in chromosomes with the haplotypes frequently found in the fragile X chromosome than in those with the other haplotypes. These observations suggest that a subgroup is present in normal alleles and that this subgroup is more liable to mutate than others.     

Nitroprusside and Cyclic GMP Stimulate Na+-Ca2+ Exchange Activity in Neuronal Preparations and Cultured Rat Astrocytes

Abstract: The effects of nitric oxide (NO)-generating agents on ⁴⁵Ca²⁺ uptake in rat brain slices and cultured rat astrocytes were studied in the presence of monensin, which is considered to drive the Na⁺-Ca²⁺ exchanger in the reverse mode. Sodium nitroprusside (SNP) at >10 µ M increased monensin-stimulated Ca²⁺ uptake in the slices, although it did not affect high K⁺-stimulated Ca²⁺ uptake. Another NO donor, 3-morpholinosydnonimine, was effective. The effect of SNP was antagonized by hemoglobin (50 µ M ), a NO scavenger, and mimicked by 8-bromo-cyclic GMP (100 µ M ). In rat brain synaptosomes, SNP increased monensin-stimulated Ca²⁺ uptake, but it did not affect high K⁺-stimulated Ca²⁺ uptake. 8-Bromocyclic GMP, but not SNP, increased Na⁺-dependent Ca²⁺ uptake significantly in synaptic membrane vesicles in the absence of monensin. In cultured rat astrocytes, SNP and 8-bromo-cyclic GMP increased Ca²⁺ uptake in the presence of ouabain and monensin, which were required for the Ca²⁺ uptake in the cells. These findings suggest that NO stimulates the Na⁺-Ca²⁺ exchanger in neuronal preparations and astrocytes in a cyclic GMP-dependent mechanism.     

Purification and characterization of a 22-kDa protein in chloroplasts from green spores of the fern Osmunda japonica

Changes in the polypeptide composition of chloroplasts were investigated during germination of green spores of the fern Osmunda japonica . The polypeptide composition of chloroplasts was appreciably changed during a germination time course of 48 h. Levels of five polypeptides with apparent molecular masses of 47, 44, 42, 22 and 18.5 kDa in the soluble fraction of chloroplasts and three polypeptides with molecular masses of 24, 22 and 15 kDa in the thylakoid membranes decreased during germination. In contrast, no decrease of chloroplast polypeptides was observed in the spores incubated with cycloheximide for 48 h. A new 22-kDa protein was isolated from thylakoid membranes of spores and the amino-terminal sequence of the purified protein was determined. High levels of alanine and glycine were found in the basic protein (pl > 10.3). This protein, with a native molecular mass of 80 kDa, was characterized by a subunit band observed at a molecular mass of 22 kDa on SDS-PAGE and by the disappearance of the band during spore germination. Protease activity against the 22-kDa protein was observed in an extract prepared from chloroplasts of quiescent spores. A hypothetical cytosolic proteinaceous factor is implicated in the regulation of protein degradation in chloroplasts.     

3-Methylaspartate ammonia-lyase from a facultative anaerobe,strain YG-1002

3-Methylaspartase was purified 24-fold and crystallized from the crude extract of the cells of a facultative anaerobic bacterium from soil, strain YG-1002. The molecular mass of the native enzyme was about 84 kDa and that of the subunit was about 42 kDa. The pH optimum for the deamination reaction of (2S, 3S)-3-methylaspartic acid and those for the amination reaction of mesaconic acid were 9.7 and 8.5; its optimum temperature was 50°C. The enzyme was stable at pH 5.5–11.0 and up to 50°C. The enzyme required both divalent and monovalent cations such as Mg²⁺ and K⁺. The enzyme was inhibited by sulfhydryl reagents, metal-chelating reagents and some divalent cations. The enzyme catalyzed the reversible amination/deamination reactions between several 3-substituted (S)-aspartic acids and their corresponding fumaric acid derivatives. The enzyme preferentially acted on (2S, 3S)-3-methylaspartic acid and mesaconic acid in the deamination and the amination reactions respectively. The enzyme showed high similarities in several enzymological properties and N-terminal amino acid sequence with 3-methylaspartase from an obligate anaerobic bacteriumClostridium tetanomorphum.