Loading...
(1/330) Resistance training affects GLUT-4 content in skeletal muscle of humans after 19 days of head-down bed rest.

This study assessed the effects of inactivity on GLUT-4 content of human skeletal muscle and evaluated resistance training as a countermeasure to inactivity-related changes in GLUT-4 content in skeletal muscle. Nine young men participated in the study. For 19 days, four control subjects remained in a -6 degrees head-down tilt at all times throughout bed rest, except for showering every other day. Five training group subjects also remained at bed rest, except during resistance training once in the morning. The resistance training consisted of 30 isometric maximal voluntary contractions for 3 s each; leg-press exercise was used to recruit the extensor muscles of the ankle, knee, and hip. Pauses (3 s) were allowed between bouts of maximal contraction. Muscle biopsy samples were obtained from the lateral aspect of vastus lateralis (VL) muscle before and after the bed rest. GLUT-4 content in VL muscle of the control group was significantly decreased after bed rest (473 +/- 48 vs. 398 +/- 66 counts. min-1. microgram membrane protein-1, before and after bed rest, respectively), whereas GLUT-4 significantly increased in the training group with bed rest (510 +/- 158 vs. 663 +/- 189 counts. min-1. microgram membrane protein-1, before and after bed rest, respectively). The present study demonstrated that GLUT-4 in VL muscle decreased by approximately 16% after 19 days of bed rest, and isometric resistance training during bed rest induced a 30% increase above the value of GLUT-4 before bed rest.  (+info)

(2/330) A five-year assessment of controlled trials of in-patient and out-patient treatment and of plaster-of-Paris jackets for tuberculosis of the spine in children on standard chemotherapy. Studies in Masan and Pusan, Korea. Fifth report of the Medical Research Council Working Party on tuberculosis of the spine.

In two centres in Korea 350 patients with a diagnosis of tuberculosis of the thoracic and/or lumbar spine were allocated at random: in Masan to in-patient rest in bed (IP) for six months followed by out-patient treatment or to ambulatory out-patient treatment (OP) from the start; in Pusan to out-patient treatment with a plaster-of-Paris jacket (J) for nine months or to ambulatory treatment without any support (No J). All patients recieved chemotherapy with PAS with isoniazid for eighteen months, either supplemented with streptomycin for the first three months (SPH) or without this supplement (PH), by random allocation. The main analysis of this report concerns 299 patients (eighty-three IP, eighty-three OP, sixty-three J, seventy No J; 143 SPH, 156 PH). Pre-treatment factors were similar in both centres except that the patients in Pusan had, on average, less extensive lesions although in a greater proportion the disease was radiographically active. One patient (J/SPH) died with active spinal disease and three (all No J/SPH) with paraplegia. A fifth patient (IP/PH) who died from cardio respiratory failure also had pulmonary tuberculosis. Twenty-three patients required operation and/or additional chemotherapy for the spinal lesion. A sinus or clinically evident abscess was either present initially or developed during treatment in 41 per cent of patients. Residual lesions persisted in ten patients (four IP, two OP, one J, three No J; six SPH, four PH) at five years. Thirty-two patients had paraparesis on admission or developing later. Complete resolution occurred in twenty on the allocated regimen and in eight after operation or additional chemotherapy or both. Of the remaining four atients, all of whom had operation and additional chemotherapy, three died and one still had paraparesis at five years. Of 295 patients assessed at five years 89 per cent had a favourable status. The proportions of the patients responding favourably were similar in the IP (91 per cent) and OP (89 per cent) series, in the J (90 per cent) and No J (84 per cent) series and in the SPH (86 per cent) and PH (92 per cent) series.  (+info)

(3/330) Energy expenditure and balance during spaceflight on the space shuttle.

The objectives of this study were as follows: 1) to measure human energy expenditure (EE) during spaceflight on a shuttle mission by using the doubly labeled water (DLW) method; 2) to determine whether the astronauts were in negative energy balance during spaceflight; 3) to use the comparison of change in body fat as measured by the intake DLW EE, 18O dilution, and dual energy X-ray absorptiometry (DEXA) to validate the DLW method for spaceflight; and 4) to compare EE during spaceflight against that found with bed rest. Two experiments were conducted: a flight experiment (n = 4) on the 16-day 1996 life and microgravity sciences shuttle mission and a 6 degrees head-down tilt bed rest study with controlled dietary intake (n = 8). The bed rest study was designed to simulate the flight experiment and included exercise. Two EE determinations were done before flight (bed rest), during flight (bed rest), and after flight (recovery). Energy intake and N balance were monitored for the entire period. Results were that body weight, water, fat, and energy balance were unchanged with bed rest. For the flight experiment, decreases in weight (2.6 +/- 0.4 kg, P < 0.05) and N retention (-2. 37 +/- 0.45 g N/day, P < 0.05) were found. Dietary intake for the four astronauts was reduced in flight (3,025 +/- 180 vs. 1,943 +/- 179 kcal/day, P < 0.05). EE in flight was 3,320 +/- 155 kcal/day, resulting in a negative energy balance of 1,355 +/- 80 kcal/day (-15. 7 +/- 1.0 kcal. kg-1. day-1, P < 0.05). This corresponded to a loss of 2.1 +/- 0.4 kg body fat, which was within experimental error of the fat loss determined by 18O dilution (-1.4 +/- 0.5 kg) and DEXA (-2.4 +/- 0.4 kg). All three methods showed no change in body fat with bed rest. In conclusion, 1) the DLW method for measuring EE during spaceflight is valid, 2) the astronauts were in severe negative energy balance and oxidized body fat, and 3) in-flight energy (E) requirements can be predicted from the equation: E = 1.40 x resting metabolic rate + exercise.  (+info)

(4/330) Low-dose T(3) improves the bed rest model of simulated weightlessness in men and women.

This study tested the hypothesis that low-dose 3,5, 3'-triiodothyronine (T(3)) administration during prolonged bed rest improves the ground-based model of spaceflight. Nine men (36.4 +/- 1. 3 yr) and five women (34.2 +/- 2.1 yr) were studied. After a 5-day inpatient baseline period, subjects were placed at total bed rest with 6 degrees head-down tilt for 28 days followed by 5-day recovery. Fifty micrograms per day of T(3) (n = 8) or placebo (n = 6) were given during bed rest. Serum T(3) concentrations increased twofold, whereas thyroid-stimulating hormone was suppressed in treated subjects. T(3)-treated subjects showed significantly greater negative nitrogen balance and lost more weight (P = 0.02) and lean mass (P < 0.0001) than placebo subjects. Protein breakdown (whole body [(13)C]leucine kinetics) increased 31% in the T(3) group but only 8% in the placebo group. T(3)-treated women experienced greater changes in leucine turnover than men, despite equivalent weight loss. Insulin sensitivity fell by 50% during bed rest in all subjects (P = 0.005), but growth hormone release and insulin release were largely unaffected. In conclusion, addition of low-dose T(3) to the bed rest model of muscle unloading improves the ground-based simulation of spaceflight and unmasks several important gender differences.  (+info)

(5/330) Serum levels of hyaluronan, antigenic keratan sulfate, matrix metalloproteinase 3, and tissue inhibitor of metalloproteinases 1 change predictably in rheumatoid arthritis patients who have begun activity after a night of bed rest.

OBJECTIVE: To evaluate whether and how moderate physical activity following a night of rest influences serum levels of matrix metalloproteinase 3 (MMP-3), tissue inhibitor of metalloproteinases 1 (TIMP-1), antigenic keratan sulfate (Ag KS), and hyaluronan (HA) in 10 normal subjects and 38 patients with rheumatoid arthritis (RA). METHODS: Blood was obtained from 20 RA patients before they arose from a night's sleep, and again 1 and 4 hours after they had begun to perform moderate physical activity. Another 18 RA patients remained in bed and blood was sampled at the same time periods. Serum levels of MMP-3, TIMP-1, Ag KS, and HA were measured by enzyme-linked immunosorbent assay. Clinical activity was evaluated by the Lansbury index. RESULTS: Both in normal subjects and in RA patients who did not remain in bed throughout the period of blood sampling, levels of HA, Ag KS, and MMP-3 increased significantly during the first hour after the subjects arose: the increase in HA and Ag KS correlated with the Lansbury index in the RA group. Three hours later, levels of Ag KS had dropped to baseline values in both groups of subjects. Levels of HA remained significantly and moderately elevated in the RA group but not in the control group, while levels of MMP-3 did not drop significantly in either group. In contrast, levels of HA, Ag KS, and MMP-3 did not change significantly in RA patients who had remained in bed. Unlike the other markers, the levels of TIMP-1 remained unchanged at the different time periods in all 3 groups studied. CONCLUSION: Significant changes in serum levels of some metabolic markers occur during the first hour after one arises from a night of sleep, especially in patients with RA. Measurement of the magnitude of these changes at different times in individual patients provides very different information about metabolic changes occurring in joint tissue than does measurement of the level of the markers at a single time point, as is usually currently reported.  (+info)

(6/330) Contributions of MSNA and stroke volume to orthostatic intolerance following bed rest.

We examined whether the altered orthostatic tolerance following 14 days of head-down tilt bed rest (HDBR) was related to inadequate sympathetic outflow or to excessive reductions in cardiac output during a 10- to 15-min head-up tilt (HUT) test. Heart rate, blood pressure (BP, Finapres), muscle sympathetic nerve activity (MSNA, microneurography), and stroke volume blood velocity (SVV, Doppler ultrasound) were assessed during supine 30 degrees (5 min) and 60 degrees (5-10 min) HUT positions in 15 individuals who successfully completed the pre-HDBR test without evidence of orthostatic intolerance. Subjects were classified as being orthostatically tolerant (OT, n = 9) or intolerant (OI, n = 6) following the post-HDBR test. MSNA, BP, and SVV during supine and HUT postures were not altered in the OT group. Hypotension during 60 degrees HUT in the post-bed rest test for the OI group (P < 0.05) was associated with a blunted increase in MSNA (P < 0.05). SVV was reduced following HDBR in the OI group (main effect of HDBR, P < 0.02). The data support the hypothesis that bed rest-induced orthostatic intolerance is related to an inadequate increase in sympathetic discharge that cannot compensate for a greater postural reduction in stroke volume.  (+info)

(7/330) Increase in epinephrine-induced responsiveness during microgravity simulated by head-down bed rest in humans.

The epinephrine (Epi)-induced effects on the sympathetic nervous system (SNS) and metabolic functions were studied in men before and during a decrease in SNS activity achieved through simulated microgravity. Epi was infused at 3 graded rates (0.01, 0.02, and 0. 03 microg. kg(-1). min(-1) for 40 min each) before and on the fifth day of head-down bed rest (HDBR). The effects of Epi on the SNS (assessed by plasma norepinephrine levels and spectral analysis of systolic blood pressure and heart rate variability), on plasma levels of glycerol, nonesterified fatty acids (NEFA), glucose and insulin, and on energy expenditure were evaluated. HDBR decreased urinary norepinephrine excretion (28.1 +/- 4.2 vs. 51.5 +/- 9.1 microg/24 h) and spectral variability of systolic blood pressure in the midfrequency range (16.3 +/- 1.9 vs. 24.5 +/- 0.9 normalized units). Epi increased norepinephrine plasma levels (P < 0.01) and spectral variability of systolic blood pressure (P < 0.009) during, but not before, HDBR. No modification of Epi-induced changes in heart rate and systolic and diastolic blood pressures were observed during HDBR. Epi increased plasma glucose, insulin, and NEFA levels before and during HDBR. During HDBR, the Epi-induced increase in plasma glycerol and lactate levels was more pronounced than before HDBR (P < 0.005 and P < 0.001, respectively). Epi-induced energy expenditure was higher during HDBR (P < 0.02). Our data suggest that the increased effects of Epi during simulated microgravity could be related to both the increased SNS response to Epi infusion and/or to the beta-adrenergic receptor sensitization of end organs, particularly in adipose tissue and skeletal muscle.  (+info)

(8/330) Myonuclear domain and myosin phenotype in human soleus after bed rest with or without loading.

After 2 or 4 mo of bed rest (6 degrees head-down tilt) and 1 mo of ambulation, there was a tendency toward a higher percentage of fibers expressing fast myosin heavy chain (MHC) isoforms and a de novo appearance of fibers coexpressing type I+IIa+IIx and IIa+IIx MHC in human soleus fibers. After 2 and 4 mo of bed rest, the mean size of type I fibers decreased by 12 (P > 0.05) and 39%, respectively. Because myonuclear number/mm of fiber length was unchanged, myonuclear domain was smaller after bed rest than before. The mean size and myonuclear domain of type I fibers were largest after 1 mo of recovery. The effects of wearing an antigravity device (Penguin suit), which had a modest but continuous resistance at the knee and ankle (Penguin-1) or knee resistance without loading on the ankle (Penguin-2), for 10 consecutive h/day were determined during 2 mo of bed rest. Mean fiber sizes in Penguin-1, but not Penguin-2, group were maintained at or above pre-bed-rest levels, whereas neither group showed phenotype changes. Myonuclear domain in type I fibers was larger in Penguin-1 and smaller in Penguin-2 group post- compared with pre-bed rest, indicating that a single daily 10-h bout of modest muscle loading can prevent bed-rest-induced soleus fiber atrophy but has minimal effect on myosin phenotype. The specific adaptive cellular strategies involved may be a function of the duration and magnitude of the adaptive stimulus as well as the immediate activity history of the fiber before the newly changed functional demands.  (+info)