Metabolic changes following eccentric exercise in trained and untrained men

The effects of one 45-min bout of high-intensity eccentric exercise (250 W) were studied in four male runners and five untrained men. Plasma creatine kinase (CK) activity in these runners was higher (P less than 0.001) than in the untrained men before exercise and peaked at 207 IU/ml 1 day after exercise, whereas in untrained men the maximum was 2,143 IU/ml 5 days after exercise. Plasma interleukin-1 (IL-1) in the trained men was also higher (P less than 0.001) than in the untrained men before exercise but did not significantly increase after exercise. In the untrained men, IL-1 was significantly elevated 3 h after exercise (P less than 0.001). In the untrained group only, 24-h urines were collected before and after exercise while the men consumed a meat-free diet. Urinary 3-methylhistidine/creatinine in the untrained group rose significantly from 127 mumol/g before exercise to 180 mumol/g 10 days after exercise. The results suggest that in untrained men eccentric exercise leads to a metabolic response indicative of delayed muscle damage. Regularly performed long distance running was associated with chronically elevated plasma IL-1 levels and serum CK activities without acute increases after an eccentric exercise bout.     

Radiosensitivity of peripheral blood lymphocytes in autoimmune disease

The proliferation of peripheral blood lymphocytes, cultured with Con A, can be inhibited by ionizing radiation. Lymphocytes from patients with conditions associated with autoimmunity, such as rheumatoid arthritis, systemic lupus erythematosus and polymyositis, are more radiosensitive than those from healthy volunteers or patients with conditions not associated with autoimmunity. The nuclear material isolated from the lymphocytes of patients with autoimmune diseases is, on average, lighter in density than the nuclear material from most healthy controls. This difference in density is not related to increased sensitivity to ionizing radiation but the degree of post-irradiation change in density (lightening) is proportional to the initial density, i.e. more dense nuclear material always shows a greater upward shift after radiation. The recovery of preirradiation density of nuclear material, 1 h after radiation exposure, taken as an indication of DNA repair, correlates with the radiosensitivity of lymphocyte proliferation (Con A response); failure to return to pre-irradiation density being associated with increased sensitivity of proliferative response. These results require extension but, taken with previously reported studies of the effects of DNA methylating agents, support the idea that DNA damage and its defective repair could be important in the aetio-pathogenesis of autoimmune disease.     

Tropomyosin isoforms in chicken embryo fibroblasts: purification, characterization, and changes in Rous sarcoma virus-transformed cells

Seven polypeptides (a, b, c, 1, 2, 3a, and 3b) have been previously identified as tropomyosin isoforms in chicken embryo fibroblasts (CEF) (Lin, J. J.-C., Matsumura, F., and Yamashiro-Matsumura, S., 1984, J. Cell. Biol., 98:116-127). Spots a and c had identical mobility on two-dimensional gels with the slow-migrating and fast-migrating components, respectively, of chicken gizzard tropomyosin. However, the remaining isoforms of CEF tropomyosin were distinct from chicken skeletal and cardiac tropomyosins on two-dimensional gels. The mixture of CEF tropomyosin has been isolated by the combination of Triton/glycerol extraction of monolayer cells, heat treatment, and ammonium sulfate fractionation. The yield of tropomyosin was estimated to be 1.4% of total CEF proteins. The identical set of tropomyosin isoforms could be found in the antitropomyosin immunoprecipitates after the cell-free translation products of total poly(A)+ RNAs isolated from CEF cells. This suggested that at least seven mRNAs coding for these tropomyosin isoforms existed in the cell. Purified tropomyosins (particularly 1, 2, and 3) showed different actin-binding abilities in the presence of 100 mM KCl and no divalent cation. Under this condition, the binding of tropomyosin 3 (3a + 3b) to actin filaments was significantly weaker than that of tropomyosin 1 or 2. CEF tropomyosin 1, and probably 3, could be cross-linked to form homodimers by treatment with 5,5'-dithiobis-(2-nitrobenzoate), whereas tropomyosin a and c formed a heterodimer. These dimer species may reflect the in vivo assembly of tropomyosin isoforms, since dimer formation occurred not only with purified tropomyosin but also with microfilament-associated tropomyosin. The expression of these tropomyosin isoforms in Rous sarcoma virus-transformed CEF cells has also been investigated. In agreement with the previous report by Hendricks and Weintraub (Proc. Natl. Acad. Sci. USA., 78:5633-5637), we found that major tropomyosin 1 was greatly reduced in transformed cells. We have also found that the relative amounts of tropomyosin 3a and 3b were increased in both the total cell lysate and the microfilament fraction of transformed cells. Because of the different actin-binding properties observed for CEF tropomyosins, changes in the expression of these isoforms may, in part, be responsible for the reduction of actin cables and the alteration of cell shape found in transformed cells.     

Effects of psoralen on replicon size and mean rate of DNA synthesis in partially synchronized cells of Pisum sativum L.

We have examined by fibre autoradiography the spacing of replicons in pea root meristems during synchronized entry into S phase from arrest at the G1/S boundary. Pretreatment with the DNA cross-linking agent, psoralen, produces a marked shortening of replicon spacing, suggesting that premature arrest of the replication fork results in the recruitment of additional initiation points within a given replicon family. This is discussed in relation to models for the control of DNA replication.     

Hypothermia-inducing peptide promotes recovery of vesicular stomatitis virus from persistent animal infections.

A single injection of the hypothermia-inducing neuropeptide bombesin resulted in an excellent recovery system for reisolating viruses from Swiss albino mice infected with vesicular stomatitis virus even up to 90 days after infection. The virus was recovered from a cell homogenate prepared from whole brain tissue 24 h after intracerebral injection of bombesin; brain cells were cocultivated with BHK-21 cell monolayers and then plaqued on BHK-21 cells at 31 degrees C. All of the recovered viruses were identified as vesicular stomatitis virus by antibody neutralization and peptide analyses of some of the structural proteins. However, some of the recovered viruses were altered with regard to tryptic peptide maps, temperature sensitivity, and central nervous system disease induced compared with the viruses used to initiate the infection. Most of the recovered viruses induced a similar disease when reinoculated intracerebrally into mice, characterized by hind-leg paralysis 4 to 6 days after infection. Two of the recovered viruses were lethal, however, resulting in a relatively rapid generalized wasting disease and death in 3 to 4 days.     

Application of X-ray microanalysis to cell suspensions of oil palm (Elaeis guineensis Jacq.)

X-ray microanalysis has been used to determine the elemental composition of oil-palm (Elaeis guineesis) cell suspensions without the use of cryoprotectants. Results based on individual cells were gathered over a typical growth cycle of 14 d. During the log phase (5–7 d) there is an increase in the number of cells containing high concentrations of both K (400 mmol kg^-1 dry weight) and P (400 mmol kg^-1 dry weight). Morphologically these cells had thin cell walls and were frequently joined to other cells (two to five cells per clump).     

Long term regeneration by somatic embryogenesis in barley (Hordeum vulgare L.) tissue cultures derived from apical meristem explants

Callus cultures were initiated from apical meristem explants of one to four-week-old aseptically-grown barley (Hordeum vulgare L. cv. Atlas 57) plants. Embryogenic callus and plants were produced in three separate experiments; the cultures have retained regenerative capacity for three years after initiation. Our results demonstrate that explants other than immature embryos are embryogenically competent in barley and that regeneration occurs by both somatic embryogenesis and organogenesis.     

Evidence for isofunctional enzymes in the degradation of phenol, m- and p-toluate, and p-cresol via catechol meta-cleavage pathways in Alcaligenes eutrophus.

A study of the degradation of phenol, p-cresol, and m- and p-toluate by Alcaligenes eutrophus 345 has provided evidence that these compounds are metabolized via separate catechol meta-cleavage pathways. Analysis of the enzymes synthesized by wild-type and mutant strains and by strains cured of the plasmid pRA1000, which encodes m- and p-toluate degradation, indicated that two or more isofunctional enzymes mediated several steps in the pathway. The formation of three catechol 2,3-oxygenases and two 2-hydroxymuconic semialdehyde hydrolases was indicated from an examination of the ratio of the specific activities of these enzymes against various substrates. Evidence for two 2-hydroxymuconic semialdehyde dehydrogenases, two 4-oxalocrotonate isomerases and decarboxylases, and three 2-ketopent-4-enoate hydratases was derived from the induction of these enzymes under different growth conditions. Each activity was detected when the wild type was grown in the presence of m-toluate, but not when grown with phenol (except for a hydratase) or p-cresol, whereas in strains cured of pRA1000, growth with phenol or p-cresol, but not with m-toluate, induced these enzymes. Hydroxylation of phenol and p-cresol appears to be mediated by the same enzyme.     

Cleavage of growth hormone by rabbit liver plasmalemma enhances binding

Several studies have shown that proteolytic cleavage can enhance the biological activity of the growth hormone (GH) molecule. It seemed possible, therefore, that proteolytic modification of GH might be a normal function of GH-target tissues. Plasmalemma-enriched fractions isolated from rabbit liver were found to contain a proteinase(s) which cleaves the large disulfide loop of human and rat GH. The proteolytic activity was specific to plasmalemma-enriched fractions in that much lower activities were observed in microsomal-enriched fractions prepared from the same livers. The plasmalemmal proteinase(s) may be a trypsin-like enzyme because proteolytic activity was decreased by two serine proteinase inhibitors. Inhibition by unlabeled human GH of 125I-GH binding to receptors did not prevent cleavage of the tracer; therefore, hormone-receptor interaction was not required for cleavage of the GH molecule. In binding studies, cleaved GH associated more readily than did intact hormone with rabbit liver receptors. These studies suggest that plasmalemma-enriched fractions prepared from rabbit liver contain a proteinase which cleaves the GH molecule in a highly specific manner. Moreover, it is unlikely that inactivation of GH is the function of this limited proteolysis because cleaved hormone is bound preferentially by at least a subset of receptors in rabbit liver.     

Isolation and sequence of a cDNA clone that contains the entire coding region for chicken smooth-muscle alpha-tropomyosin

We have constructed a cDNA-expression library of approximately 100,000 members from embryonic chicken smooth-muscle mRNA using the plasmid-expression vectors pUC8 and pUC9. Using an immunological screening procedure and 32P-labeled cDNA probes, we have identified and isolated clones encoding smooth-muscle tropomyosin. Plasmid pSMT-10 (approximately 1100 base pairs) was found to hybrid-select mRNA for smooth-muscle alpha-tropomyosin. DNA-sequence analysis revealed that pSMT-10 contained the entire coding region for alpha-tropomyosin and portions of the 5'- and 3'-untranslated regions. Comparison of the derived amino acid sequence of smooth-muscle alpha-tropomyosin with known skeletal-muscle (rabbit and chicken) and platelet (equine) sequences revealed extensive homology between the various proteins. The smooth-muscle tropomyosin shows the greatest sequence divergence from the skeletal-muscle tropomyosins at the COOH-terminal region. In contrast, the smooth-muscle tropomyosin is most homologous to the platelet tropomyosin at the COOH-terminal end. The relationship of the various tropomyosin sequences to function (e.g. interactions with troponin) are considered.