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PubMed2002

Role of gravitational loading in the development of rat soleus muscle fibers.

Effects of hindlimb unloading during the first 3 months after birth on the development of soleus muscle fibers were studied in rats. The mean absolute weigh and cross-sectional area of whole soleus muscle in the unloaded rats were -1/3 and 1/4 of those in the controls, respectively. But the unloading did not affect the lengths of muscle, at 90 degrees of ankle joint angle, and of muscle fibers sampled from tendon to tendon, and the total sarcomere number. Since the total number of fibers in soleus was not affected either, the inhibited increase of muscle mass following unloading was mainly due to the smaller CSA of individual fibers. Numbers of both myonuclei and satellite cells were significantly less in unloaded than control rats. The % distribution of fibers expressing pure type I myosin heavy chain was significantly less in unloaded than controls (-23 %). Further, muscle fibers with multiple innervation were noted in the unloaded rats. It is suggested that the development and/or differentiation of soleus muscle fibers are closely associated with gravitational loading and that the growth-associated increase in fiber number may be genetically programmed.

Journal Article↗
PubMed2002

Mitochondrial adaptations in skeletal muscle cells in mammals exposed to gravitational unloading.

It is known that exposure to actual or simulated weightlessness is often accompanied by decreased muscle dynamic performance, and increased level of blood lactate accumulation. Decreased mitochondrial content found in fibers of the working muscles is considered to be one of the possible causes for those changes. Studies on oxidative potential of the muscle cell (i.e. capacity of the cell to oxidative energy production) under conditions of altered gravity have been carried out since late 70-ties. It was shown that the relatively short term spaceflight and hindlimb suspension induced significant decrease oxidative enzyme activities and mitochondrial volume density in rat fast muscle. However postural soleus muscle failed to exhibit similar changes, although the absolute mitochondrial content was found to be sufficiently lower after exposure to simulated microgravity. This phenomenon allowed to conclude that the pronounced soleus fiber atrophy masked the proportional absolute decrease in oxidative potential which failed to be revealed as subsequent changes in mitochondrial volume density and oxidative enzyme activity. It is also important, that biosatellite studies exposed considerable changes in mitochondria distribution pattern inside m. soleus fibers: volume density of mitochondria (and, correspondingly, activity of oxidative enzymes) increases (or does not change) in the center of fiber, and decreases at its periphery, in subsarcolemmal area. However the time course of mitochondrial alterations development (particularly during long-duration exposures to real or simulated microgravity) and some peculiarities of the mitochondria distribution were not described yet. Also, materials dealing with simultaneous time-course comparative analysis of mitochondrial characteristics and indices of physiological cost of submaximal exercise are very rare. The present paper is purposed to compare the data, obtained in several experimental studies, allowed to analyze the possible contribution of muscle mitochondria changes to changes in metabolic cost of submaximal exercise and the time-course dynamics of mitochondrial characteristics under conditions of actual or simulated gravitational unloading.

Journal Article↗
PubMed2002

Gravitational unloading induces osteoclast-like differentiation of FLG 29.1 cells.

FLG 29.1 cells, cultured at 1xg, are able to switch on a differentiating process only when they are suitably induced by chemical factors. On the contrary, when FLG 29.1 cells are cultured in conditions of gravitational unloading, simulated by a Random Positioning Machine, the switching on of the differentiation process occurs in the absence of any added differentiating agent or any stimulating factor. The phenotypic characterization of the cells and quantitative measures of their bone resorption activity are consistent with a differentiation process through the osteoclastic pathway.

Journal Article↗
PubMedDate not supplied

Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials.

OBJECTIVES: To determine whether parachutes are effective in preventing major trauma related to gravitational challenge. Design Systematic review of randomised controlled trials. DATA SOURCES: Medline, Web of Science, Embase, and the Cochrane Library databases; appropriate internet sites and citation lists. STUDY SELECTION: Studies showing the effects of using a parachute during free fall. MAIN OUTCOME MEASURE: Death or major trauma, defined as an injury severity score > 15. RESULTS: We were unable to identify any randomised controlled trials of parachute intervention. CONCLUSIONS: As with many interventions intended to prevent ill health, the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials. Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute.

Journal Article↗
PubMed1994

[A case of generalized disseminated atypical mycobacteriosis caused by M. avium complex with a giant gravitation abscess].

A case of generalized disseminated atypical mycobacteriosis caused by M. avium complex (MAC) was reported. The case was a female of 52 years of age. She was admitted to our hospital due to high fever and polyarthralgia. Her chest X-ray and CT scan revealed infiltrative shadows in the right S2b and S4 segments, and multiple accumulation shadows were seen on osteoscintigraphy. Pus aspirated from a lesion of the right fifth rib were acid-fast bacilli positive by smear (Gaffky v). The administration of four drugs, INH, RFP, EB and SM, was introduced, then corticosteroid was added, and the case became afebrile. Later, acid-fast bacilli were also isolated from bronchial washing and aspirated specimen from bone marrow, and all of them were identified as MAC. Based on these findings, the case was diagnosed as generalized disseminated mycobacteriosis. After several months remission, tenderness over the fifth lumbar vertebra deteriorated, and MRI scan on lumbar vertebrae showed high-intensity area both on T1-weighted and T2-weighted images. MAC was isolated from the pus of the fifth lumbar vertebra. Lumbar lesions deteriorated gradually, and a giant gravitation abscess which involved right ilium was revealed by CT scan of the pelvis. In spite of vigorous treatment including chemotherapy, aspiration of pus and drainage, general condition of the case deteriorated, and the case finally died of renal insufficiency.

Abscess↗
PubMed1964

GRAVITATIONAL STRESS: CHANGES IN CORTICAL EXCITABILITY.

Evoked responses, recorded from the visual cortex, are enhanced during positive (head to tail) acceleration, and during cerebral hypotension induced by hemorrhage. The phenomenon observed during positive acceleration may therefore be due, at least in part, to its hypotensive effect, but the increased somatic stimulation must also be considered.

Acceleration↗