Biomedical subjects

J F Marini

Publications and source records attributed to J F Marini.

34 records · Page 2Linked to original sources

PubMed1996

Effects of strenuous exercise on serum myosin heavy chain fragments in male triathletes.

During the Nice Triathlon (June 26, 1994), the serum levels of type I myosin heavy chain (MHC) fragments and creatine kinase (CK and CK-MB) activities were assessed in 12 athletes in order to evaluate the exercise-induced muscle damage. Blood samples (BS) were taken 2 days before the event (baseline), on arrival, 6 and 24 h later, and 2 and 4 days later. The mean results (and SD) were respectively: MHC (microU.I-1): 142 (69), 156 (116), 242 (144), 1183 (574), 2603 (1405), 1002 (523); CK (U.I-1): 109 (27), 626 (267), 1188 (562), 1159 (442), 633 (385), 224 (119). The CK peak occurred at BS-6h for 8 subjects, and at BS-24h for the other ones. The MHC peak occurred at BS-48h in all the subjects. The CK-MB/CK ratios exhibited a profile similar to those described previously. Serum MHC peak values were correlated with CK ones (r = 0.67; p < 0.05). After a four-day recovery period, as the CK values had decreased, the MHC levels were still elevated. The main result of the study is the MHC peak occurrence at BS-48h in all the subjects.

Adult↗

PubMed1995

Mitochondria changes in human muscle after prolonged exercise, endurance training and selenium supplementation.

The functional and structural responses to acute exercise (E) and training, (T) with or without selenium supplementation (Sel), were investigated in a double-blind study on 24 young male subjects. The Sel or the placebo were given over 10 weeks of an endurance training programme. Prior to the programme and on its conclusion muscle biopsies were taken from the vastus lateralis muscle before and after an exhausting treadmill test of maximal endurance capacity (Capmax). The muscle samples were examined by electron microscopy to make a quantitative analysis of the mitochondria population in the muscle fibres. The number of mitochondria per area (QA) and the relative surface occupied by the total mitochondria profile area (AA) were estimated. The mean area per mitochondrion (â) was obtained by the quotient AA/QA. The effects of the isolated or combined independent variables T, E and Sel were analysed by nonparametric tests. Training induced significant increases in both QA (30%, P < 0.001) and AA (52%, P < 0.001), without changing â; T + Sel produced a slight rise of AA (27%, P < 0.001), which resulted in larger (24%, P < 0.001) â. The E produced an enlargement of â resembling swelling. This phenomenon was also found for the combinations E + T and E + T + Sel, but it was then far more pronounced in E + T. The training effects observed are in agreement with previous descriptions. In contrast, the changes observed after acute exercise seem to indicate a remarkable short-term plasticity of muscle mitochondria. The results in Sel would seem to suggest a dampening effect of the selenium on the mitochondria changes, both in chronic and acute exercise. The mechanism of this action on mitochondrial turnover is uncertain, but might be related to a higher efficiency of the selenium-dependent enzyme glutathione peroxidase.

Adult↗

PubMed1995

Muscle strength during bedrest with and without muscle exercise as a countermeasure.

Bedrest is known to be a useful experimental model for simulating weightlessness and studying its effects on human skeletal muscle activity. We therefore conducted a study in which 12 healthy male subjects underwent 28 days of continuous exposure to 6 degrees head-down bedrest. Our main objective was to test a set of preventive countermeasures for maintaining the stability of the human body. Of the subjects 6 performed deadlifts in the supine position for 30 to 45 min each day. The isometric actions were performed for 5-30 s at 90, 120 and 150 degrees knee angles and isokinetic training at speeds of 30 and 180 degrees.s-1. In vivo quadriceps muscle strength was measured under controlled experimental conditions with a commercial dynamometer. The hypothesis that intense daily isometric and isokinetic leg exercise and lower body negative pressure (LBNP) might serve to maintain muscle strength under conditions of weightlessness was tested. Of the subjects 6, who did not perform any exercise, served as the control population under conditions of simulated weightlessness. The results showed that a significant reduction (P < or = 0.0001) in the muscle force [-10.3 (SD 6.7%)] occurred in the control group whereas no significant changes were observed in the trained group [+3.9 (6.8%)]. From these studies we conclude that intense muscle training and LBNP constitute efficient countermeasures to compensate for the biomechanical effects of weightlessness on human lower limbs and to limit other factors such as cardiovascular deconditioning.

Adult↗

PubMed1995

Characteristics of the venous hemodynamics of the leg under simulated weightlessness: effects of physical exercise as countermeasure.

In order to test the hypothesis that increases in calf venous distensibility in microgravity are partly due to the changes affecting the surrounding skeletal muscles (muscular atrophy), 12 healthy volunteers were exposed for 28 d to microgravity simulated by -6 degrees head-down bed rest. Half these subjects were exposed to countermeasures during bed rest: a) repeated LBNP (Lower Body Negative Pressure) sequences starting on the 15th d with one 15 min sequence at -35 mb, every other day from the 15th until the 21st d, and then every day until the end of bed rest; b) physical training including isotonic type exercise and isometric or isokinetic work by all muscle mass of upper and lower limbs (from the 8th until the 28th d). The other six subjects forming the control group were not subjected to any countermeasure. Calf venous hemodynamics were determined by mercury strain gauge plethysmography with venous occlusion. Distensibility (delta Vmax) and venous emptying (venous outflow at the 6th s of emptying: VO6, half-emptying time: T1/2, maximum venous outflow (MVO) could also be measured. Nuclear magnetic resonance (NMR) was used to study changes in volume of calf muscles. Plethysmographic measurements made for each subject prior to, during (once a week), and after bed rest show a parallel increase in calf venous distensibility in both groups of subjects until the 20th d of bed rest. Filling and emptying times then tended to stabilize in the group treated with countermeasures (group CM) whereas high venous distensibility was observed until the end of bed rest and 5 d thereafter in the control group (group C).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Does utrophin expression in muscles of mdx mice during postnatal development functionally compensate for dystrophin deficiency?

We correlated utrophin expression with the physiopathological course in mdx mice. Evolution of the pathology was assessed by monitoring expression of developmental MHC in mdx mice versus control. Utrophin expression is detected by dystrophin/utrophin cross-reacting antibodies and can only be evaluated in mdx mouse muscles (in absence of dystrophin). This protein was expressed at the periphery of all myotubes and myofibers during the first postnatal week. It began declining in fast muscles before the third week and disappeared from the soleus between the 3rd and the 4th week. The decrease was concomitant with a sudden degenerative/regenerative process affecting slow muscle earlier and more massively than fast muscles. The pathological process became stable in all muscle types (except the diaphragm), with greater utrophin expression in the soleus. These results in mdx mice along with observed utrophin expression in severely affected DMD patients suggest that overexpression of utrophin is not enough to explain the stability of regenerated fibers in mdx mice.

Animals↗

PubMed1994

Effect of 28-day head-down bed rest with countermeasures on heart rate variability during LBNP.

The effect of exercise and LBNP countermeasures on the cardiovascular deconditioning response have been evaluated by the study of heart rate variability during progressive LBNP tests before, during (day 15), and after 28 d continuous 6 degrees head-down tilt bed rest. Twelve healthy men (age 27-42 years) were studied in two groups. Six were assigned to a countermeasure regime (CM) consisting of strenuous short-term resistance exercise once per day, 6 days per week from day 7 to day 28, combined with lower body negative pressure (LBNP, -28 mm Hg) for 15 min on days 16, 18, 20, and 22-28. Results were compared with data from six subjects, matched on the basis of maximum oxygen uptake, who received no countermeasures (No-CM). The main effects of bed rest were seen in reductions in RR-interval, and in total spectral power. The results of spectral analysis showed a significant reduction in an index of parasympathetic activity with a nonsignificant increase in a sympathetic indicator. The fractal component of heart rate variability was reduced also, suggesting a change in cardiovascular control mechanisms. Although there were significant differences between CM and No-CM for a number of variables, there were no bed rest by countermeasure interaction effects in the statistical analysis. These results suggested that this particular series of countermeasures was ineffective in preventing at least certain changes indicative of cardiovascular deconditioning with 28 d head-down tilt bed rest.

Adult↗

PubMed1992

Rat soleus muscle fiber responses to 14 days of spaceflight and hindlimb suspension.

Morphological and enzymatic responses in fibers expressing fast, slow, or both types of myosin heavy chain (MHC) were studied in rats after 14 days of spaceflight (COSMOS 2044) or hindlimb suspension. Although the percentage of slow-twitch fibers was unchanged, a higher percentage of fibers that expressed both slow and fast MHC was observed in flight and suspended rats than in synchronous ground-based controls. The soleus was 25 and 34% smaller than control after 14 days of flight and suspension, with the reduction in fiber cross-sectional area (CSA) being greater in slow- than in fast-twitch fibers in both experimental groups. The activities of succinate dehydrogenase (SDH) and alpha-glycerophosphate dehydrogenase (GPD) were not significantly affected by flight or suspension. The total SDH activity (i.e., SDH activity x CSA) decreased significantly in the slow-twitch fibers of the flight and the fast-twitch fibers of the suspended rats, in large part due to fiber atrophy. A shift in MHC expression in 14 and 9% of the fibers in flight and suspended rats occurred without a change in myosin adenosinetriphosphatase activity. The SDH and GPD activities of the fibers that expressed both slow and fast MHC were slightly higher than the slow-twitch fibers and slightly lower than the fast-twitch fibers. These data indicate that events were initiated within 14 days of spaceflight or suspension that began to reconfigure the protein profiles of 9-14% of the slow-twitch fibers from typical slow-twitch toward those of fast-twitch fibers, while all fibers were dramatically losing total protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗

PubMed1992

Effects of acute exercise on attenuated vagal baroreflex function during bed rest.

We measured carotid baroreceptor-cardiac reflex responses in six healthy men, 24 h before and 24 h after a bout of leg exercise during 6 degrees head-down bed rest to determine if depressed vagal baroreflex function associated with exposure to microgravity environments could be reversed by a single exposure to acute intense exercise. Baroreflex responses were measured before bed rest and on day 7 of bed rest. An exercise bout consisting of dynamic and isometric actions of the quadriceps at graded speeds and resistances was performed on day 8 of bed rest and measurements of baroreflex response were repeated 24 h later. Vagally-mediated cardiac responses were provoked with ramped neck pressure-suction sequences comprising pressure elevations to +40 mm Hg, followed by serial, R-wave triggered 15 mm Hg reductions, to -65 mm Hg. Baroreceptor stimulus-cardiac response relationships were derived by plotting each R-R interval as a function of systolic pressure less the neck chamber pressure applied during the interval. Compared with pre-bed rest baseline measurements, 7 d of bed rest decreased the gain (maximum slope) of the baroreflex stimulus-response relationship by 16.8 +/- 3.4% (p < 0.05). On day 9 of bed rest, 24 h after exercise, the maximum slope of the baroreflex stimulus-response relationship was increased (p < 0.05) by 10.7 +/- 3.7% above pre-bed rest levels and 34.3 +/- 7.9% above bed rest day 7. Our data verify that vagally-mediated baroreflex function is depressed by exposure to simulated microgravity and demonstrate that this effect can be acutely reversed by exposure to a single bout of intense exercise.

Adult↗

PubMed1991

Expression of myosin heavy chain isoforms in Duchenne muscular dystrophy patients and carriers.

The expression of MHC isoforms in the skeletal muscles of nine patients with Duchenne muscular dystrophy (DMD) (from 2.5 to 15 yr of age) and three DMD carriers was studied using different specific anti-MHC MAbs. We also analyzed muscle fiber size and fiber reactivity with acridine orange and/or with a surface antigen marker. One-quarter of all fibers of DMD patients, or less with age, were of normal size and contained only adult slow MHC. Half of the muscle fibers contained adult and developmental MHCs. Only half of these fibers were representative of an active regenerative process. MHC co-expression also altered the proportion of normal fast or slow fibers. Adult fast MHCs were expressed as unique MHC only in small and very small fibers in the oldest DMD patients. In DMD carrier muscles, the greatest alterations in MHC expression were observed in patients with the most reduced dystrophin expression. However, MHC changes in dystrophin-positive fibers were similar to those observed in dystrophin-free fibers. In conclusion, disruptions or delays in the switching of all genes coding for adult fast and slow MHC and developmental MHC coincided with dystrophin deletion and with perturbations in its expression.

Adolescent↗

PubMed1990

Metabolic and morphologic properties of single muscle fibers in the rat after spaceflight, Cosmos 1887.

The adaptation of a slow (soleus, Sol) and a fast (medial gastrocnemius, MG) skeletal muscle to spaceflight was studied in five young male rats. The flight period was 12.5 days and the rats were killed approximately 48 h after returning to 1 g. Five other rats that were housed in cages similar to those used by the flight rats were maintained at 1 g for the same period of time to serve as ground-based controls. Fibers were classified as dark or light staining for myosin adenosine triphosphatase (ATPase). On the average, the fibers in the Sol of the flight rats atrophied twice as much as those in the MG. Further, the fibers located in the deep (close to the bone and having the highest percentage of light ATPase and high oxidative fibers in the muscle cross section) region of the MG atrophied more than the fibers located in the superficial (away from the bone and having the lowest percentage of light ATPase and high oxidative fibers in the muscle cross-section) region of the muscle. Based on quantitative histochemical assays of single muscle fibers, succinate dehydrogenase (SDH) activity per unit volume was unchanged in fibers of the Sol and MG. However, in the Sol, but not the MG, the total amount of SDH activity in a 10-microns-thick section of a fiber decreased significantly in response to spaceflight. Based on population distributions, it appears that the alpha-glycerophosphate dehydrogenase (GPD) activities were elevated in the dark ATPase fibers in the Sol, whereas the light fibers in the Sol and both fiber types in the MG did not appear to change. The ratio of GPD to SDH activities increased in the dark (but not light) fibers of the Sol and was unaffected in the MG. Immunohistochemical analyses indicate that approximately 40% of the fibers in the Sol of flight rats expressed a fast myosin heavy chain compared with 22% in control rats. Further, 31% of the fibers in the Sol of flight rats expressed both fast and slow myosin heavy chains compared with 8% in control rats. Immunohistochemical changes in the MG were minimal. These data suggest that the magnitude and direction of enzymatic activity and cell volume changes are dependent on the muscle, the region of the muscle, and the type of myosin expressed in the fibers. Further, the ability of fibers to maintain normal or even elevated activities per unit volume of some metabolic enzymes is remarkable considering the marked and rapid decrease in fiber volume.

Adenosine Triphosphatases↗

PubMed1989

Anti-myosin heavy chain monoclonal antibodies reveal two IIB (fast) fiber subtypes.

Indirect immunofluorescence analysis of different rat skeletal muscles using anti-myosin heavy chain (MHC) monoclonal antibodies (MAb) revealed the presence of two immunologically distinct kinds of fibers within the IIB fibers, histochemically identified by myosin ATPase staining. Some IIB fibers (designated here as IIB1) were unreactive with one anti-fast MHC MAb, whereas they did react with another anti-fast MHC MAb; other IIB fibers (designated here as IIB2) reacted with both anti-fast MAbs. Neither of the two IIB fiber subtypes was significantly reactive with a neonatal MHC MAb. The number of each IIB fiber subtype was age-dependent, at least in the plantaris muscle. IIB1 fibers were observed only in the superficial portion of the plantaris and gastrocnemius muscle. The ratio of IIB1:IIB2 fibers was about the same throughout the extensor digitorum longus and extraocular muscles. Therefore, the two kinds of IIB fibers here observed have a different myosin heavy chain content. On the basis of their specific immunoreactivities, we suggest that IIB1 fibers contain the previously described MHCB. IIB2 fibers contain either a unique new MHC isoform or a mixture of at least two MHC, possibly composed of the MHCB and either the previously described MHCA or a new MHC isoform.

Adenosine Triphosphatases↗

PubMed1989

[A case of sciatica with hypertrophy of the calf].

Hypertrophy of the calf associated with sciatica is rare. In the present case there was hypertrophy, predominantly of type I fibers, which showed a high percentage to the detriment of type II fibers. In the previously reported cases, the type of hypertrophied fibers was variable and pseudomyotonic discharges were inconstantly recorded. The mechanism underlying the hypertrophy is unknown. Inequality of size of muscle fibers could result from proximity of atrophic fibers and those with compensatory hypertrophy. The increased proportion of type I fibers could be the consequence of compensatory hypertrophy induced by lesions of synergic muscles and/or muscle compartments.

Female↗

PubMed1988

Tendon and myo-tendinous junction in an overloaded skeletal muscle of the rat.

Overloading of rat plantaris muscles was produced by aseptic ablation of the synergists. The morphological changes occurring after 1 or 2 weeks were investigated at the light and electron microscopical level in the distal tendon of the plantaris and at the myotendinous junction. Sham-operated rats were prepared as controls. In the tendon, quiescent fibrocytes were replaced by activated fibroblasts displaying a vesicular nucleus with prominent nucleoli and an outstanding increase in cytomembranes, particularly the rough endoplasmic reticulum and the Golgi complex. The plasmalemma of the fibroblasts was modified by the presence of caveolae and the surbsurface cytoplasm contained many membrane-bound vacuoles. In the tendon, the collagen bundles were disrupted, resulting in the formation of empty longitudinally oriented spaces; in these spaces, as in the pericapillary areas, no inflammatory cells were observed. At the myotendinous junction, fibroblast activation was consistently observed in both control and overloaded specimens. At this level, the sarcolemma of the finger-like projections of muscle fibres presented many caveolae close to clusters of large subsurface vacuoles. These observations indicate that, at the beginning of the compensatory hypertrophy, the adaptative changes to overloading include a non-inflammatory reaction of the tendon characterized by enhanced collagen synthesis and intensive membrane renewal and recycling. From the mechanical point of view this reaction can impair the tendon resistance to stretch. At the myotendinous junction the increased membrane turnover of the sarcolemma and the fibroblast activation can be considered permanent phenomena consequent to the increased stress exerted upon the interface connecting the contractile apparatus to the stroma.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Fibre type transition and stiffness modification of soleus muscle of trained rats.

Rat soleus muscles were subjected to two types of overload with intent to induce fibre type transitions and modifications in muscular stiffness. The overloading techniques were respectively an endurance training program and a strength training program. The method of controlled releases was used to obtain tension-extension curves characterizing the elastic behaviour of the soleus. Fibre typing was made by myofibrillar ATPase staining and the effectiveness of the training programs was also evaluated by assessing enzymatic activities. Endurance training resulted in an increase of stiffness associated with a decrease of type II fibers. The opposite change was found as a result of strength training. These results demonstrate that endurance training and strength training induce opposite modifications in muscular stiffness which are correlated with fibre type transitions.

Alanine Transaminase↗

PubMedDate not supplied

Analysis of altered gene expression in rat soleus muscle atrophied by disuse.

The present study involved a global analysis of genes whose expression was modified in rat soleus muscle atrophied after hindlimb suspension (HS). HS muscle unloading is a common model for muscle disuse that especially affects antigravity slow-twitch muscles such as the soleus muscle. A cDNA cloning strategy, based on suppression subtractive hybridization technology, led to the construction of two normalized soleus muscle cDNA libraries that were subtracted in opposite directions, i.e., atrophied soleus muscle cDNAs subtracted by control cDNAs and vice versa. Differential screening of the two libraries revealed 34 genes with altered expression in HS soleus muscle, including 11 novel cDNAs, in addition to the 2X and 2B myosin heavy chain genes expressed only in soleus muscles after HS. Gene up- and down-regulations were quantified by reverse Northern blot and classical Northern blot analysis. The 25 genes with known functions fell into seven important functional categories. The homogeneity of gene alterations within each category gave several clues for unraveling the interplay of cellular events implied in the muscle atrophy phenotype. In particular, our results indicate that modulations in slow- and fast-twitch-muscle component balance, the protein synthesis/secretion pathway, and the extracellular matrix/cytoskeleton axis are likely to be key molecular mechanisms of muscle atrophy. In addition, the cloning of novel cDNAs underlined the efficiency of the chosen technical approach and gave novel possibilities to further decipher the molecular mechanisms of muscle atrophy.

Age Factors↗

PubMedDate not supplied

Respective effects of hindlimb suspension, confinement and spaceflight on myotendinous junction ultrastructure.

This study compares the effects of 14-day confinement and spaceflight with the respective effects of 8, 18 and 29-day hindlimb suspension on rat soleus and plantaris MTJ ultrastructure. Independently of the experimental situation, greater morphological changes were observed in the soleus as compared to the plantaris MTJ. 18 days of suspension and 14 days of confinement resulted in ultrastructural modifications of the digit-like processes in the soleus MTJ. Additional changes were observed in the myofibrils, microtendon and tendon after 29 days of suspension and 4 days of spaceflight. These results emphasize the influence of the intensity and duration of the muscle loading on the MTJ ultrastructure.

Animals↗