Influence of exercise on the fiber composition of skeletal muscle

Summary Biopsy samples from the vastus lateralis muscle (VLM) of man were examined for fiber composition at rest and at selected intervals during prolonged exercise ranging in intensity from 40% to 75% of the total body maximal oxygen uptake (VO _2max) and one-min bouts of exercise at 150%VO _2max. Because of the heterogeneity of fibers in human VLM, studies were also completed where the effect of exercise on the fiber composition of the rat soleus muscle (SM) was examined. In some animals the SM from one hindlimb was removed 9 days prior to their being exercised after which the remaining SM was removed. Exercise reduced muscle glycogen in all experiments. In the studies with man, blood lactate exceeded 17 mmoles/l after the heavy exercise but was largely unchanged by endurance exercise. Colonic temperature of the exercised rats exceeded 40° C. In studies where fibers were identified only as type I and type II, type II fibers in the VLM of all samples (16) taken at rest averaged 61.2±12.5% as compared to 59.0±12.0% after exercise (54 biopsy samples). In a second series of studies with man where the subtypes of type II fibers were identified, there were also no differences in fiber composition of the VLM after varying periods of exercise. Glycogen content and percent fiber composition were the same in right and left SM obtained from rested rats. Exercise (30 to 40 min) did not alter the fiber composition of the rat SM. These data demonstrate that the histochemically demonstratable myofibrillar actomyosin ATPase of skeletal muscle is not altered by a single exercise bout.     

Virulence and viability of Yersinia pestis 25 years after lyophilization.

When equal volumes of 6% lactose and a broth culture of Yersinia pestis were mixed before freezing, approximately 50% of the cells survived lyophilization and reconstitution on the following day. Concomitantly, the number of viable cells per 50% lethal dose increased from about 16 to 125 organisms. On subsequent storage of the lyophilized cells under vacuum in glass ampoules at 4 degrees C for 25 years, more than 25% of the cells remained viable. When stored cultures were assayed immediately after reconstitution, virulence for mice was significantly reduced (as many as 4,000 cells/50% lethal dose), but the virulence was fully restored when reconstituted cultures were held for 24 h at room temperature, or when a subculture was prepared in fresh medium.     

Demonstration of potent, gonadotropin-like biological activity in the serum of rats during midpregnancy

The gonadotropin-like activity (GnLa) of serum from pregnant rats was measured using the rat interstitial cell testosterone (RICT) bioassay. Serum GnLA was elevated on day 9 of pregnancy, peaked at 7.2 μg rat LH-RPl equivalents/ml on day 11 and declined to undetectable levels by day 15. Serum LH, measured by homologous RIA, was consistently low (<20 ng/ml) during pregnancy, except near term.Rat placental lactogen (rPL), which was measured in the same serum samples by rat radioreceptor assay (RRA), reached maximal concentrations on days 12 and 13 of pregnancy.These data suggest the presence in pregnancy serum of a potent-gonadotropin-like hormone, different from pituitary LH, whose origin is unknown. Furthermore, there are discrepancies between the times of appearance of this GnLA and rPL.     

Purification and characterization of two G-proteins that activate the beta 1 isozyme of phosphoinositide-specific phospholipase C. Identification as members of the Gq class.

Plasma membranes from bovine liver contain a phosphatidylinositol 4,5-bisphosphate-specific phospholipase C (PLC) activity that is activated by guanine nucleotides. The G-proteins involved retained their ability to activate bovine brain PLC-beta 1 in a guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S)-dependent manner following extraction from the membranes with cholate and reconstitution with phospholipids. This reconstitution assay was used to purify the G-proteins by chromatography on heparin-Sepharose, DEAE-Sephacel, octyl-Sepharose, hydroxylapatite, Mono Q, and Sephacryl S-300 gel filtration. Gel electrophoresis showed that two alpha-subunits with molecular mass of 42 and 43 kDa were isolated to a high degree of purity, together with a beta-subunit. Neither alpha-subunit was a substrate for pertussis toxin-catalyzed ADP-ribosylation. Gel filtration of the final activity indicated an apparent molecular mass of 95 kDa, suggesting the presence of an alpha beta gamma heterotrimer. Immunological data revealed that the 42- and 43-kDa proteins were related to alpha-subunits of the Gq class recently purified from brain (Pang, I.-H., and Sternweis, P. C. (1990) J. Biol. Chem. 265, 18707-18712) and identified by molecular cloning (Strathmann, M., and Simon, M. I. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 9113-9117). The activation of PLC-beta 1 by the purified G-protein preparation was specific for nonhydrolyzable guanine nucleotides, the efficacy decreasing in order GTP gamma S greater than guanylimidodiphosphate greater than guanylyl(beta,gamma-methylene)-diphosphonate. Half-maximal activation required 4 microM GTP gamma S suggesting that the affinity of the G-proteins for GTP analogues is low. The GTP gamma S-dependent activation of PLC-beta 1 required millimolar Mg2+ and was inhibited by guanosine 5'-O-(2-thiodiphosphate) and by excess beta gamma-subunits. Aluminum fluoride also activated PLC-beta 1 in the presence of the G-proteins. The G-proteins were inactive toward PLC-gamma 1 or PLC-delta 1. In summary, these findings identify two G-protein activators of PLC-beta 1 that have the properties of heterotrimeric G-proteins and are members of the Gq class.     

Modulation of SLE induction in naive mice by specific T cells with suppressor activity to pathogenic anti-DNA idiotype.

T cells (CD8+) with specific suppressor activity against anti-dsDNA antibody (16/6 Id+) were generated in vitro. The cells were established from BALB/c-enriched T cells exposed in vitro to silica beads coated with the pathogenic anti-DNA idiotype, 16/6. The idiotype specificity of the suppressor cells was demonstrated by (a) specific induction of a decrease in proliferative response of T helper cell lines specific for the pathogenic idiotype (16/6 Id), when exposed to the idiotype, with no effect on T cell lines with other specificities, e.g., against human IgM or synthetic polypeptide. (b) Effectively suppressing in vitro antibody production of anti-16/6 antibody, employing 16/6-primed B cells and specific helper T cell line. The 16/6 Id-specific Ts cells were found to be MHC restricted. Weekly intravenous injections of 10(7) 16/6 Id-specific Ts cells given to BALB/c mice at different stages of experimental SLE disease prevented the clinical, serological, and pathological manifestations. This effect was characterized by decreased titers of autoantibodies (e.g., anti-DNA, anti-Sm antibodies) in the sera, by abolishment of the proteinuria, leukopenia, and the increased ESR, followed by decreased immunoglobulin deposition in the kidneys. Treating the mice with control IgM-specific T cells did not affect the above parameters. These studies demonstrate the ability to generate Ts cells specific for pathogenic idiotypes. The method might be employed therapeutically to modulate the course of autoimmune conditions.     

Addition to the article by Iu. E. Dubrova et al. "Influence of heterozygosity on the variation of anthropometric traits in newborns." Determination of intersample differences by covariation and correlation statistics]

Relationships between heterozygosity of 13 polymorphic loci and variation of the set of anthropometric traits were studied in 302 singleton newborns (174 boys, 128 girls). Statistically significant correlation between heterozygosity and all traits were not found. Variances of four traits--body weight, body length, circumference of head and breast measured by first principal component decrease with increase of heterozygosity in boys and girls. At the same time, variance of body proportions (second principal component) increase significantly in boys only. The highest values of correlation between four traits were found in the group of low heterozygous boys. The groups of newborns with different level of heterozygosity are characterized by different combinations of first principal component and the number of minor deviations from development (stigma). It is concluded from the whole set of data that newborn boys with the average level of heterozygosity have the highest level of viability.     

Synthesis of 2-chloro-2′-deoxyadenosine by washed cells ofE. coli

Summary Washed cells ofE. coli ATCC 5275, a thymine auxotroph, catalysed formation of 2-chloro-2-deoxyadenosine when incubated with 2-chloroadenosine and a variety of deoxynucleosides. This transdeoxyribosylation reaction was complete after 4 h of shaking at 37°C. The equilibrium reaction mixture favoured product formation when purine rather than pyrimidine deoxyribonucleosides were used as cosubstrates, and when the ratio of deoxysugar donor to 2-chloroadenosine was high. Using deoxyadenosine as cosubstrate, chlorodeoxyadenosine was purified from larger scale reaction mixtures by treatment with Dowex-1 (OH-form) or by high performance liquid chromatography.     

Erythrocyte shape and volume changes caused by an inhibitor of the glucose and anion transporters

Light scattering measurements and scanning electron microscopy show that p-azidobenzylphlorizin (p-AzBPhz) causes changes in the shape and volume of human erythrocytes by at least two, dose-dependent mechanisms: At nominal concentrations above 5 microM, the azide induces cell swelling by either enlarging a pre-existent channel or by creating pores between phase boundaries of the membrane through which salt and water enter, but sucrose remains excluded. However, over the range 0.03 to 0.3 microM, in either isosmotic NaCl or KCl media, when fewer than 1 million molecules of azide are bound per cell, the ligand causes membrane deformations that convert discocytes into cells resembling stage 2 echinocytes. Whereas a cell volume increase of about 10% accompanies these shape changes, (microhematocrit and electronic cell sizing measurements), no net influx of either Na+ or K+ during this stage of swelling was detectable. These cell alterations take place at p-AzBPhz concentrations which concurrently inhibit both chloride and 3-methoxyglucose equilibrium exchange transport. The results may indicate that when the membrane impermeable p-AzBPhz interacts with the anion and/or sugar transporter, some trans-membrane perturbation occurs which alters the cytoskeleton.