Influence of exercise on cardiac and skeletal muscle myofibrillar proteins

The purpose of this study was to examine the Ca²⁺-Mg²⁺ myofibrillar ATPase and protein composition of cardiac and skeletal muscle following strenuous activity to voluntary exhaustion. Sprague-Dawley rats (200 g) were assigned to a control and exercised group, with the run group completing 25 m·min^–1 and 8% grade for 1 hour. Following activity, the myocardial Ca²⁺–Mg²⁺ myofibrillar ATPase activity -pCa relationship had undergone a rightward shift in the curve. Electrophoretic analysis revealed a change in the pattern of cardiac myofibrillar protein bands, particularly in the 38–42 Kdalton region. Enzymatic analysis of myofibrillar proteins from plantaris muscle, revealed no change in Ca²⁺ regulation following exercise. Electronmicrographic and electrophoretic analysis revealed extensively disrupted sarcomeric structure and a change in the ratio of several plantaris myofibrillar proteins. No difference was observed for myosin: Actin: tropomyosin ratios; however a dramatic reduction in 58 and 95 Kdalton proteins were evident. The results indicate that prolonged running is associated with similar responses in cardiac and skeletal muscle myofibrillar protein compositions. The abnormalities in myofibrillar ultrastructure may implicate force transmission failure as a factor in exercised-induced muscle damage and/or fatigue.     

蚕豆叶片发育与衰老过程中超氧物歧化酶活性与丙二醛含量变化

蚕豆植株叶片随茎节自上而下表现出明显的发育与衰老顺序,可作为衰老特征的是叶绿素和蛋白质含量明显下降。蚕豆叶中SOD活性主要定位于12 000× g离心后所得的上清液和叶绿体组分。衰老叶片的SOD总活性和叶绿体组分的相对活性都有所下降,SOD同工酶谱也发生了改变。O_2~ 产生速率随叶龄增大而稍上升;而MDA含量在叶片外观表现枯黄衰老征兆前就急剧上升。可能因为衰老叶片过氧化氢酶活性大幅度下降与SOD之间的不平衡,致使O_2~ 代谢中间产物累积而引起膜的损伤.     

Biochemical adaptation of cardiac and skeletal muscle to physical activity.

1. Female Wistar rats were randomly assigned to control (C) or exercising (T) groups and subsequently portioned into 1, 3, 5 and 10 day T and C groups. The T groups completed a progressive endurance running program. Biochemical indices of adaptation were measured in cardiac muscle and in plantaris and soleus muscles of C and T animals after their last exercise bout. 2. In cardiac muscle, myofibrillar ATPase activity was significantly elevated in the 3T (0.241 +/- 0.031) and 5T (0.242 +/- 0.013) groups (P less than or equal to 0.05) compared to their respective controls (3C = 0.187 +/- 0.015 and 5C = 0.190 +/- 0.007). 3. After 10 days of training cardiac myofibrillar ATPase activity was elevated by 17% but this was not significant (P greater than or equal to 0.05). 4. No changes in myofibrillar ATPase activity were seen in skeletal muscle (P greater than or equal to 0.05), however, hexokinase activity progressively increased and was significantly elevated in the 3T, 5T and 10T soleus and plantaris muscles of rats over controls (P less than or equal to 0.05). 5. Minimal nonsignificant changes were noted in the hexokinase activity of the hearts of all T groups (P greater than or equal to 0.05). 6. These results indicate that metabolic adaptation of the heart and skeletal muscles takes place after as little as three training sessions. 7. Although the adaptation of the skeletal muscles continually progresses, the adaptation of the heart appears to be transitory.(ABSTRACT TRUNCATED AT 250 WORDS)     

Biosynthesis of lysosomal hydrolases: their synthesis in bound polysomes and the role of co- and post-translational processing in determining their subcellular distribution

By in vitro translation of mRNA’s isolated from free and membrane-bound polysomes, direct evidence was obtained for the synthesis of two lysosomal hydrolases, β-glucuronidase of the rat preputial gland and cathespin D of mouse spleen, on polysomes bound to rough endoplasmic reticulum (ER) membranes. When the mRNA’s for these two proteins were translated in the presence of microsomal membranes, the in vitro synthesized polypeptides were cotranslationally glycosylated and transferred into the microsomal lumen. Polypeptides synthesized in the absence of microsomal membranes were approximately 2,000 daltons larger than the respective unglycosylated microsomal polypeptides found after short times of labeling in cultured rat liver cells treated with tunicamycin. This strongly suggests that nascent chains of the lysosomal enzymes bear transient amino terminal signals which determine synthesis on bound polysomes and are removed during the cotranslational insertion of the polypeptides into the ER membranes. In the line of cultured rat liver cells used for this work, newly synthesized lysosomal hydrolases showed a dual destination; approximately 60 percent of the microsomal polypeptides detected after short times of labeling were subsequently processed proteolytically to lower molecular weight forms characteristic of the mature enzymes. The remainder was secreted from the cells without further proteolytic processing. As previously observed by other investigations in cultured fibroblasts (A. Gonzalez-Noriega, J.H. Grubbs, V. Talkad, and W.S. Sly, 1980, J Cell Biol. 85: 839-852; A. Hasilik and E.F. Neufeld, 1980, J. Biol. Chem., 255:4937-4945.) the lysosomotropic amine chloroquine prevented the proteolytic maturation of newly synthesized hydrolases and enhanced their section. In addition, unglycosylated hydrolases synthesized in cells treated with tunicamycin were exclusively exported from the cells without undergoing proteolytic processing. These results support the notions that modified sugar residues serve as sorting out signals which address the hydrolases to their lysosomal destination and that final proteolytic cleavage of hydrolase precursors take place within lysosome itself. Structural differences in the carbohydrate chains of intracellular and secreted precursors of cathespin D were detected from their differential sensitivity to digestion with endoglycosidases H and D. These observations suggest that the hydrolases exported into the medium follow the normal secretory route and that some of their oligosaccharides are subject to modifications known to affect many secretory glycoproteins during their passage through the Golgi apparatus.     

Calpain,calpastatin activities and ratios during myocardial ischemia-reperfusion

The purpose of this study was to test the hypothesis that myocardial ischemia-reperfusion (I/R) is accompanied by an early burst in calpain activity, resulting in decreased calpastatin activity and an increased calpain/calpastatin ratio, thereby promoting increased protein release. To determine the possibility of a calpain burst impacting cardiac calpastatin inhibitory activity, rat hearts were subjected (Langendorff) to either 45 or 60 min of ischemia followed by 30 min of reperfusion with and without pre-administration (s.c.) of a cysteine protease inhibitor (E-64c). Myocardial function, calpain activities (casein release assay), calpastatin inhibitory activity and release of CK, LDH, cTnI and cTnT were determined (n = 8 for all groups). As expected no detectable changes in calpain activities were observed following I/R with and without E-64c (p > 0.05). Both I/R conditions reduced calpastatin activity (p < 0.05) while E-64c pre-treatment was without affect, implicating a non-proteolytic event underlying the calpastatin changes. A similar result was noted for calpain–calpastatin ratios and the release of all marker proteins (p < 0.05). In regard to cardiac function, E-64c resulted in transient improvements (15 min) for left ventricular developed pressure (LVDP) and rate of pressure development (p < 0.05). E-64c had no effect on end diastolic pressure (LVEDP) or coronary pressure (CP) during I/R. These findings demonstrate that restricting the putative early burst in calpain activity, suggested for I/R, by pre-treatment of rats with E-64c does not prevent downegulation of calpastatin inhibitory activity and/or protein release despite a transient improvement in cardiac function. It is concluded that increases in calpain isoform activities are not a primary feature of I/R changes, although the role of calpastatin downregulation remains to be elucidated.     

Morphological and biomechanical analysis of a skeleton from Roman imperial necropolis of Casalecchio di Reno (Bologna, Italy, II-III c. A. D.). A possible case of crutch use

A Roman skeleton (T.130) from the roman necropolis of Casalecchio di Reno has been studied in order to understand if the hypothesis of crutch use, suggested by the severe articular degeneration at the hip joint that caused evident reduction of his locomotory possibilities, could be supported by the morphological alterations of other bones and joints. The pathological changes and muscular development of the upper limbs and shoulder girdle bones suggest that these parts were submitted to a great mechanical stress. The observations are consistent with the hypothesis of crutch use that would have involved a new weight-bearing function of the upper limbs in order to help locomotion, even though it is difficult to assess the number and type of the crutches. The comparison with other possible cases of crutch use reported in literature gives an additional support to the interpretation of the findings.     

Molecular evolution of P transposable elements in the genus Drosophila. III. The melanogaster species group

Phylogenetic relationships were determined for 76 partial P-element sequences from 14 species of the melanogaster species group within the Drosophila subgenus Sophophora. These results are examined in the context of the phylogeny of the species from which the sequences were isolated. Sequences from the P-element family fall into distinct subfamilies, or clades, which are often characteristic for particular species subgroups. When examined locally among closely related species, the evolution of P elements is characterized by vertical transmission, whereby the P-element phylogeny traces the species phylogeny. On a broader scale, however, the P-element phylogeny is not congruent with the species phylogeny. One feature of P-element evolution in the melanogaster group is the presence of more than one P-element subfamily, differing by as much as 36%, in the genomes of some species. Thus, P elements from several individual species are not monophyletic, and a likely explanation for the incongruence between P-element and species phylogenies is provided by the comparison of paralogous sequences. In certain instances, horizontal transfer seems to be a valid alternative explanation for lack of congruence between species and P-element phylogenies. The canonical P-element subfamily, which represents the active, autonomous transposable element, is restricted to D. melanogaster. Thus, its origin clearly lies outside of the melanogaster species group, consistent with the earlier conclusion of recent horizontal transfer.      

Environmental stress increases variability in the expression of dental cusps

Teeth are an important model for developmental studies but, despite an extensive literature on the genetics of dental development, little is known about the environmental influences on dental morphology. Here we test whether and to what extent the environment plays a role in producing morphological variation in human teeth. We selected a sample of modern human skulls and used dental enamel hypoplasia as an environmental stress marker to identify two groups with different stress levels, referred to as SG (“stressed” group) and NSG (“nonstressed” group). We collected data on the occurrence and the relative development of 15 morphological traits on upper molars using a standard methodology (ASU‐DAS system) and then we compared the frequencies of the traits in the two groups. Overall, the results suggest that (a) stressors like malnutrition and/or systemic diseases have a significant effect on upper molar morphology; (b) stress generates a developmental response which increases the morphological variability of the SG; and (c) the increase in variability is directional, since individuals belonging to the SG have more developed and extra cusps. These results are consistent with the expectations of the current model of dental development. Am J Phys Anthropol 153:397–407, 2014. © 2013 Wiley Periodicals, Inc.     

Noisy-threshold control of cell death

Background  

Cellular responses to death-promoting stimuli typically proceed through a differentiated multistage process, involving a lag phase, extensive death, and potential adaptation. Deregulation of this chain of events is at the root of many diseases. Improper adaptation is particularly important because it allows cell sub-populations to survive even in the continuous presence of death conditions, which results, among others, in the eventual failure of many targeted anticancer therapies.