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Effects of gravitational loading or unloading on the growth-associated increase in the cross-sectional area and length of fibers, as well as the total fiber number, in soleus muscle were studied in rats. Furthermore, the roles of satellite cells and myonuclei in growth of these properties were also investigated. The hindlimb unloading by tail suspension was performed in newborn rats from postnatal day 4 to month 3 with or without 3-mo reloading. The morphological properties were measured in whole muscle and/or single fibers sampled from tendon to tendon. Growth-associated increases of soleus weight and fiber cross-sectional area in the unloaded group were approximately 68% and 69% less than the age-matched controls. However, the increases of number and length of fibers were not influenced by unloading. Growth-related increases of the number of quiescent satellite cells and myonuclei were inhibited by unloading. And the growth-related decrease of mitotically active satellite cells, seen even in controls (20%, P > 0.05), was also stimulated (80%). The increase of myonuclei during 3-mo unloading was only 40 times vs. 92 times in controls. Inhibited increase of myonuclear number was not related to apoptosis. The size of myonuclear domain in the unloaded group was less and that of single nuclei, which was decreased by growth, was larger than controls. However, all of these parameters, inhibited by unloading, were increased toward the control levels generally by reloading. It is suggested that the satellite cell-related stimulation in response to gravitational loading plays an essential role in the cross-sectional growth of soleus muscle fibers.

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We examined whether oropharyngeal stimulation by drinking released the dehydration-induced suppression of cutaneous vasodilatation and decreased mean arterial pressure (MAP) in exercising subjects, and assessed the effects of hypovolaemia or hyperosmolality alone on these responses. Seven young males underwent four hydration conditions. These were two normal plasma volume (PV) trials: normal plasma osmolality (P(osmol), control trial) and hyperosmolality (DeltaP(osmol) = +11 mosmol (kg H(2)O)(-1)); and two low PV trials: isosmolality (DeltaPV = -310 ml) and hyperosmolality (DeltaPV = -345 ml; DeltaP(osmol) = +9 mosmol (kg H(2)O)(-1)), attained by combined treatment with furosemide (frusemide), hypertonic saline and/or 24 h water restriction. In each trial, the subjects exercised at 60% peak aerobic power for approximately 50 min at 30 degrees C atmospheric temperature and 50% relative humidity. When oesophageal temperature (T(oes)) reached a plateau after approximately 30 min of exercise, the subjects drank 200 ml water at 37.5 degrees C within a minute. Before drinking, forearm vascular conductance (FVC), calculated as forearm blood flow divided by MAP, was lowered by 20-40% in hypovolaemia, hyperosmolality, or both, compared with that in the control trial, despite increased T(oes). After drinking, FVC increased by approximately 20% compared with that before drinking (P < 0.05) in both hyperosmotic trials, but it was greater in normovolaemia than in hypovolaemia (P < 0.05). However, no increases occurred in either isosmotic trial. MAP fell by 4-8 mmHg in both hyperosmotic trials (P < 0.05) after drinking, but more rapidly in normovolaemia than in hypovolaemia. PV and P(osmol) did not change during this period. Thus, oropharyngeal stimulation by drinking released the dehydration-induced suppression of cutaneous vasodilatation and reduced MAP during exercise, and this was accelerated when PV was restored.

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We treated 64 hemodialysis patients with cerebral hemorrhage over an 18-year period between 1986 and 2003. Clinical features, prognostic factors, and therapeutic strategy were reviewed in these cases. Thirty of the cases were in the 13-year period between 1986 and 1998, and 34 cases, in the 5-year period between 1999 and 2003. In recent years, the incidence of cerebral hemorrhage has risen with the increase in the number of hemodialysis patients. There were 21 patients with at least a 10-year history of hemodialysis. The underlying cause of renal failure was diabetic nephropathy in 25 patients and glomerulonephritis in 24 patients. The most frequent sites of bleeding were the basal ganglia and thalamus, the cerebellum being involved in only one patient. Many patients had severe bleeding with hematomas greater than 61 ml. Outcome assessment by the Glasgow Outcome Scale showed 24 patients with good recovery, 8 with moderate disability, 4 with severe disability, and 28 who died. Good recovery was seen more often in patients in their 50s and 60s, whereas death occurred more often in patients aged 70 and older. Although there is now less morbidity than previously, the prognosis is not uniformly favorable in all cases. Factors associated with a poorer prognosis included mixed hemorrhage, hematomas greater than 61 ml, and age 70 and older. Hematoma size and age were particularly important prognostic factors. Improved management and prognosis in these patients requires acute intensive treatment similar to that for hypertensive cerebral hemorrhage.

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Effects of hindlimb suspension or exposure to 2-G between postnatal day 4 and month 3 and of 3-month recovery at 1-G environment on the characteristics of rat hindlimb muscles were studied. Pronounced growth inhibition was induced by unloading, but not by 2-G loading. It is suggested that the development and/or differentiation of soleus muscle fibers are closely associated with gravitational loading. The data indicated that gravitational unloading during postnatal development inhibits the myonuclear accretion in accordance with subnormal numbers of both mitotic active and quiescent satellite cells. Even though the fiber formation and longitudinal fiber growth were not influenced, cross-sectional growth of muscle fibers was also inhibited in association with lesser myonuclear domain and DNA content per unit volume of myonucleus. Unloading-related inhibition was generally normalized following the recovery.

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PURPOSE: We tested the suitability of triaxial accelerometry to evaluate walking efficiency in older subjects. METHODS: First, we verified the accuracy to estimate the oxygen consumption rate (.VO2, mL.min-1) from the total impulse (Itotal, N.min-1), the square root of summed accelerations of each direction, during graded walking on a flat ground in 13 male and 27 female older subjects (61 +/- 6 yr, mean +/- SD). Second, to examine the effects of endurance/resistance training on walking efficiency, we assessed the relations of maximal isometric knee extension force (Fmax, N.m), maximal walking velocity (Vmax, m.min-1), and three-dimensional impulses (Ix, anterior-posterior; Iy, mediolateral; Iz, vertical) in 13 male and 40 female older subjects (62 +/- 7 yr) before and after 6 and 9 months of training. RESULTS: The following analyses were performed in all the data from the male and female groups. First, .VO2 was highly correlated with Itotal (r = 0.958, P < 0.0001) over the range of 250-2200 mL.min-1. Second, Fmax and Vmax increased by 48 +/- 7% (P < 0.001) and 21 +/- 2% (P < 0.001), respectively, after 9 months of training. Ix/Itotal and Iy/Itotal increased by 18 +/- 2% (P < 0.001) and 10 +/- 2%, respectively, after 9 months of training (P < 0.001), whereas Iz/Itotal decreased by 14 +/- 2% (P < 0.001). Vmax was negatively correlated with Iz/Itotal (r = -0.522, P < 0.0001) while positively correlated with Ix/Itotal (r = 0.561, P < 0.0001) and Iy/Itotal in the pooled data from before, after 6 and 9 months of training. Similarly, the product of Vmax and body weight was positively correlated with Fmax (r = 0.633, P < 0.0001). CONCLUSIONS: These results suggest that increased Fmax improved walking efficiency by increasing energy utilization in the anterior-posterior/mediolateral directions while decreasing energy loss in the vertical direction.

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We assessed the effects of aerobic and/or resistance training on thermoregulatory responses in older men and analyzed the results in relation to the changes in peak oxygen consumption rate (VO(2 peak)) and blood volume (BV). Twenty-three older men [age, 64 +/- 1 (SE) yr; VO(2 peak), 32.7 +/- 1.1 ml. kg(-1). min(-1)] were divided into three training regimens for 18 wk: control (C; n = 7), aerobic training (AT; n = 8), and resistance training (RT; n = 8). Subjects in C were allowed to perform walking of ~10,000 steps/day, 6-7 days/wk. Subjects in AT exercised on a cycle ergometer at 50-80% VO(2 peak) for 60 min/day, 3 days/wk, in addition to the walking. Subjects in RT performed a resistance exercise, including knee extension and flexion at 60-80% of one repetition maximum, two to three sets of eight repetitions per day, 3 days/wk, in addition to the walking. After 18 wk of training, VO(2 peak) increased by 5.2 +/- 3.4% in C (P > 0.07), 20.0 +/- 2.5% in AT (P < 0.0001), and 9.7 +/- 5.1% in RT (P < 0.003), but BV remained unchanged in all trials. In addition, the esophageal temperature (T(es)) thresholds for forearm skin vasodilation and sweating, determined during 30-min exercise of 60% VO(2 peak) at 30 degrees C, decreased in AT (P < 0.02) and RT (P < 0.02) but not in C (P > 0.2). In contrast, the slopes of forearm skin vascular conductance/T(es) and sweat rate/T(es) remained unchanged in all trials, but both increased in subjects with increased BV irrespective of trials with significant correlations between the changes in the slopes and BV (P < 0.005 and P < 0.0005, respectively). Thus aerobic and/or resistance training in older men increased VO(2 peak) and lowered T(es) thresholds for forearm skin vasodilation and sweating but did not increase BV. Furthermore, the sensitivity of the increase in skin vasodilation and sweating at a given increase in T(es) was more associated with BV than with VO(2 peak).

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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.