Skeletal muscle fiber type composition and performance during repeated bouts of maximal,concentric contractions

Summary Force output and fatigue and recovery patterns were studied during intermittent short-term exercise. 27 men performed three bouts of 30 maximal unilateral knee extensions on 2 different occasions. Blood flow was maintained or occluded during recovery periods (60 s). Blood flow was restricted by inflating a pneumatic cuff placed around the proximal thigh. Muscle biopsies from vastus lateralis were analyzed for identification of fast twitch (FT) and slow twitch (ST) fibers and relative FT area. Peak torque decreased during each bout of exercise and more when blood flow was restricted during recovery. Initial peak torque (IPT) and average peak torque (APT) decreased over the three exercise bouts. This response was 3fold greater without than with blood flow during recovery. IPT and APT decreased more in individuals with mainly FT fibers than in those with mainly ST fibers. It is suggested that performance during repeated bouts of maximal concentric contractions differs between individuals with different fiber type composition. Specifically, in high intensity, intermittent exercise with emphasis on anaerobic energy release a high FT composition may not necessarily be advantageous for performance.     

Importance of eccentric actions in performance adaptations to resistance training.

The inability of the exercises presently used during space-flight to maintain muscle strength and mass may reflect the absence of eccentric (ecc) muscle actions. This study examined the importance of ecc actions in performance adaptations to resistance training. Middle-aged males performed 4-5 sets of 6-12 repetitions (rep) per set of the leg press and leg extension exercises 2 d each week for 19 weeks. Group CON/ECC (n = 9) performed each rep with concentric (con) and ecc actions, group CON (n = 8) with only con actions. Group CON/CON (n = 10) performed twice as many sets with only con actions. The resistance per set was selected to induce failure within the prescribed number of rep. Eight subjects did not train and served as controls. The increase in the three rep maximum (3RM) after training, in general, showed a hierarchy such that CON/ECC greater than CON/CON greater than CON. The differences (p less than 0.05) were: leg press 3RM with con and ecc actions, CON/ECC greater than CON/CON greater than CON (26 greater than 15 greater than 8%); leg press 3RM with only con actions, CON/ECC or CON/CON greater than CON (22 or 18 greater than 14%); and leg extension 3RM with con and ecc actions, CON/ECC greater than CON (29 greater than 16%). These differences (p less than 0.05) were still evident after 1 month of de-training. The results indicate that omission of ecc actions from resistance training compromises increases in strength, probably because intensity is not optimal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of free and bound insulin-like growth factors on proteoglycan metabolism in articular cartilage explants.

This article describes the effects of bound forms of insulin-like growth factors (IGFs) on proteoglycan metabolism by bovine articular cartilage in explant culture. When these growth factors were added to articular cartilage explants complexed with their native serum binding proteins (BPs), both IGF-I-BP complex and IGF-II-BP complex stimulated proteoglycan synthesis to different degrees over a 3-day period. When added to the medium of cultures of articular cartilage over 5 days, IGF-II-BP complex induced high rates of synthesis and low rates of catabolism of proteoglycans, giving rise to tissue levels of proteoglycan similar to those observed in fresh tissue. When articular cartilage was maintained in culture with the same concentration of IGF-I-BP complex, tissue levels of proteoglycans fell over the culture period because of lower rates of proteoglycan synthesis. Analysis of the proteoglycans synthesized by articular cartilage in the presence of free or bound IGF-I or IGF-II showed that these growth factors stimulated the rate of synthesis of the large proteoglycan species present in cartilage but did not affect the synthesis of the small proteoglycans.     

Hydromechanical simulation of systemic circulation

A hydromechanical model is developed for the simulation of the arterial systemic circulation. The geometry and elastic properties of arteries, the pulse-rate and stroke volume of the left ventricle, the design of peripheral resistances and the viscosity of the model fluid are approximated to physiological conditions. The parameters, pulse rate, stroke volume, pulse volume, elasticity of arteries, as well as peripheral resistances, are independent variables.     

Median nerve entrapment. pronator teres syndrome

Summary The surgical anatomy of interest in the pronator teres syndrome was studied to shed light on the ramifying pattern of the median nerve, the number of its muscular branches and their branching levels and to pinpoint the location of the fibrous bands which may cause median nerve entrapment. The fibrous arch of the pronator teres muscle (pronator arch) was found to lie 3 cm to 7.5 cm below Hueter's line, that of the flexor digitorum superficialis muscle (superficialis arch), which is distal to the pronator arch, was found to lie 6.5 cm below Hueter's line in its most proximal position. Symptom patterns in terms of muscle weakness caused by median nerve entrapment at different levels were also evaluated.

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Compression du nerf médian. Syndrome du rond pronateur. Anatomie chirurgicale et corrélation aux tableaux cliniques

Résumé L'anatomie chirurgicale relative au syndrome du rond pronateur a été étudiée pour éclairer les modalités de ramification du n. médian, le nombre de ses branches musculaires et leur niveau d'origine, et pour préciser la situation des arcades fibreuses qui peuvent comprimer le n. médian. L'arcade fibreuse du m. rond pronateur a été trouvé'e à 3 à 7,5 cm au-dessous de la ligne de Hueter, celle du m. fléchisseur superficiel des doigts, qui est distale par rapport à celle du m. rond pronateur, a été retrouvée à 6,5 cm au-dessous de la ligne de Hueter dans sa position la plus proximale. Les tableaux cliniques de déficit musculaire causés par la compression du n. médian à divers niveaux sont également analysés.

     

Analysis of c-myc, bcl-1 and bcl-2 Translocations in Human Lymphoma by Pulsed-Field Gel Electrophoresis

Translocations of the c-myc, bcl-2 and the putative bcl-1 oncogene are recurrent events in B-cell lymphoma. Since it is likely that the rearranged genes contribute to the malignant phenotype of the tumor cells, such oncogene translocation is of major interest. The molecular detection of translocations using conventional Southern hybridization analysis is complicated by the fact that translocation breakpoints are dispersed over large chromosomal regions. In order to overcome this problem we used pulsed-field gel electrophoresis (PFGE) to detect c-myc, bcl-2 and bcl-1 translocations in 29 lymph node biopsies.

C-myc translocation could not be detected in this group, either with standard Southern analysis or PFGE. Translocations of the bcl-2 gene were detected by PFGE in 5 samples and the breakpoints were mapped in all cases to the third exon of bcl-2 by standard Southern analysis. Furthermore, we also found rearrangements of the bcl-1 locus in 3 samples. Mapping of the breakpoint failed in one of these cases, which strongly indicates the existence of a breakpoint outside the bcl-1 major breakpoint region. Thus, PFGE allows the rapid detection of translocations in human lymphomas within large stretches of DNA.