Alterations in diaphragmatic oxidative and antioxidant enzymes in the senescent Fischer 344 rat.

We investigated age-related changes in antioxidant, glycolytic, beta-oxidation, and tricarboxylic acid cycle enzyme activity in the diaphragm and plantaris muscle of female Fischer 344 rats. Tissue samples from the costal and crural diaphragm and plantaris muscle were obtained from 30 animals in the following age groups: 1) 6 mo old (n = 10), 2) 26 mo old (n = 10), and 3) 30 mo old (n = 10). Aging had no effect (P greater than 0.05) on the activities of citrate synthase (CS) and 3-hydroxyacyl-CoA dehydrogenase (HADH) in the costal or crural diaphragm. Similarly, no age-related differences existed (P greater than 0.05) in the crural diaphragm in lactate dehydrogenase (LDH) or glutathione peroxidase (GPX) activity. In contrast, the activities of LDH and GPX were significantly (P less than 0.05) higher in the costal diaphragm in the 30- than in the 6-mo old animals. In addition, the ratio of LDH to CS activity increased (P less than 0.05) as a function of age in the costal diaphragm. Conversely, the ratio of CS to GPX activity in the costal diaphragm was lower (P less than 0.05) in the 30- than in the 6-mo old animals. No significant (P greater than 0.05) age-related differences existed in LDH-to-CS or CS-to-GPX activity ratios in the crural diaphragm. Finally, aging resulted in a significant decrease (P less than 0.05) in the activities of LDH, CS, and HADH in the plantaris muscle. These data demonstrate that, unlike many hindlimb locomotor muscles, the oxidative capacity of the Fischer 344 rat diaphragm does not decrease in old age.     

大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育

本实验用免疫组织化学ＡＢＣ法研究了大鼠胼胝体内神经肽Ｙ免疫反应阳性（ＮＰＹ－ＩＲ）纤维的生后发育。结果发现,许多ＮＰＹ－ＩＲ纤维在大鼠出生时便存在于胼胝体内。ＮＰＹ－ＩＲ胼胝体纤维的密度在生后１周内继续逐渐增高,在第２周内达到最高峰。之后,ＮＰＹ－ＩＲ胼胝体纤维的密度逐渐下降,至第３周末时接近成年时的水平,即仅有少量ＮＰＹ－ＩＲ纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多ＮＰＹ－ＩＲ胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。     

Activation of microcarrier-attached lymphocytes in microgravity

A technology has been developed to achieve optimal attachment of adhesion-independent lymphocytes to microcarrier beads. The activation of T-lymphocytes by concanavalin A was tested under microgravity conditions in an experiment carried out in space during the first Spacelab Life Science Mission. Activation, measured as the synthesis of deoxyribonucleic acid (DNA) and the production of interferon-gamma, more than doubled in attached lymphocytes in microgravity. The depression of the activation discovered in previous space experiments is due to an impairment not of the lymphocyte but of the macrophage function. The system described here may be useful for radiobiological investigations on the effect of high-energy particles and for testing the efficiency of the immune system in humans during the long-duration space flight planned in the future. The biotechnological significance of the increased lymphokine production in space remains to be assessed.     

Growth and sporulation of Metarrhizium anisopliae and Beauveria bassiana on media containing various peptone sources

Two entomogenous fungi, Metarrhizium anisopliae and Beauveria bassiana, were cultured in liquid culture media containing various commercial peptone sources to determine the effect of the sources on growth and sporulation. Each fungus responded differently to the various peptone sources. Tryptone, Casitone, and yeast extract were effective for mycelial growth of M. anisopliae; however, yeast extract was the most effective in production of spores. Soytone Casitone, Neopeptone, and casein hydrolysate were used effectively for mycelial growth of B. bassiana, but the latter two were not as effective for production of spores. Gelatone and Peptone (Bacteriological) were not effective for production of growth or sporulation for either fungus.     

Endurance-training-induced cellular adaptations in respiratory muscles

Controversy exists concerning the adaptability of mammalian respiratory muscles in response to endurance training. We examined the effects of 8 wk of progressive treadmill exercise (45 min/day 5 days/wk) on the biochemical adaptations of rat diaphragm and intercostal muscles. Female Sprague-Dawley rats were randomly assigned to a sedentary control (n = 10) or an exercise-training group (n = 10). Endurance training resulted in an enhanced oxidative capacity in the anterior costal diaphragm as evidenced by a 29% increase (P less than 0.05) in the activity of succinate dehydrogenase (SDH) in trained animals compared with controls (4.15 +/- 0.13 vs. 3.21 +/- 0.17 mumol.g-1.min-1). Similarly, SDH activity in the intercostal muscles was 32% greater (P less than 0.05) in the trained animals than in the untrained animals (1.72 +/- 0.11 vs. 1.30 +/- 0.06 mumol.g-1.min-1). In contrast, the crural region of the diaphragm showed no significant increase (P greater than 0.05) in oxidative capacity as a result of the training program (3.28 +/- 0.12 vs. 3.13 +/- 0.18). Furthermore, training did not alter (P less than 0.05) lactate dehydrogenase activity in the intercostals or in the crural or the costal diaphragm. These data demonstrate that the oxidative capacity of the costal diaphragm and the intercostal muscles can be enhanced by increasing respiratory loads via regular endurance exercise. We speculate that the lack of metabolic adaptation in the crural region of the diaphragm was not due to limited plasticity of the fibers in this area but to failure to the exercise-training program to provide the appropriate stimulus for cellular adaptation.     

Sustained inhibition of rat myometrial gap junctions and contractions by lindane

Background  

Gap junctions increase in size and abundance coincident with parturition, forming an intercellular communication network that permits the uterus to develop the forceful, coordinated contractions necessary for delivery of the fetus. Lindane, a pesticide used in the human and veterinary treatment of scabies and lice as well as in agricultural applications, inhibits uterine contractions in vitro, inhibits myometrial gap junctions, and has been associated with prolonged gestation length in rats. The aim of the present study was to investigate whether brief exposures to lindane would elicit sustained inhibition of rat uterine contractile activity and myometrial gap junction intercellular communication.     

BiP and calreticulin form an abundant complex that is independent of endoplasmic reticulum stress

BiP is found in association with calreticulin, both in the presence and absence of endoplasmic reticulum stress. Although the BiP-calreticulin complex can be disrupted by ATP, several properties suggest that the calreticulin associated with BiP is neither unfolded nor partially or improperly folded. (1) The complex is stable in vivo and does not dissociate during 8 hr of chase. (2) When present in the complex, calreticulin masks epitopes at the C terminus of BiP that are not masked when BiP is bound to an assembly-defective protein. And (3) overproduction of calreticulin does not lead to the recruitment of more BiP into complexes with calreticulin. The BiP-calreticulin complex can be disrupted by low pH but not by divalent cation chelators. When the endoplasmic reticulum retention signal of BiP is removed, complex formation with calreticulin still occurs, and this explains the poor secretion of the truncated molecule. Gel filtration experiments showed that BiP and calreticulin are present in distinct high molecular weight complexes in which both molecules interact with each other. The possible functions of this complex are discussed.     

Evidence for Four Cytoplasmic Dynein Heavy Chain Isoforms in Rat Testis

Recent studies have revealed the expression of multiple putative cytoplasmic dynein heavy chain (DHC) genes in several organisms, with each gene encoding a separate protein isoform. This finding is consistent with the hypothesis that different isoforms do different things, as is the case for the axonemal dyneins. Furthermore, the large number of tasks ascribed to cytoplasmic dynein suggests that there may be additional isoforms not yet identified. Two of the mammalian cytoplasmic dynein heavy chains are DHC1a and DHC1b. DHC1a is conventional cytoplasmic dynein and is found in all organisms examined. DHC1b is expressed in organisms that have multiple dyneins, and has been implicated in the intracellular trafficking of molecules in unciliated and ciliated cells. In the present study, we examined the DHC1b protein from rat testis. Testis cytoplasmic dynein contains a large amount of dynein heavy chain reactive with an antibody raised against a peptide sequence of rat DHC1b. The testis anti-DHC1b immunoreactive protein is slightly smaller than testis DHC1a, as assessed by SDS-PAGE. In Northern blots, the DHC1b mRNA is smaller than the DHC1a mRNA. In sucrose gradients made in low ionic strength, DHC1a sedimented at approximately 20S, and the anti-1b immunoreactive heavy chains sedimented in a broad band centered at approximately 14S. The V1-photolysis reaction of individual sucrose gradient fractions revealed three distinct patterns of photolysis, suggesting that there are at least three separate 1b-like heavy chain isoforms in testis. Using a high-stringency Western blotting protocol, the anti-1b antibody and the anti-DHC2 antibody recognized the same heavy chain and specifically bound to one of the three 1b-like heavy chains. We conclude that rat testis contains three 1b-like dynein heavy chains, and one of these is the product of the DHC1b/DHC2 gene previously identified.