A modified power control scheme for remedying the effects of traffic nonuniformity in LEO satellite communications systems

It has been shown in our previous studies that the geographical traffic nonuniformity considerably affects the performance of the low earth orbit satellite communications systems. In this paper, a new scheme for improving the throughput characteristics of these systems at nonuniform traffic distribution is proposed. In this method, some parts of the users under the satellite which is flying over the area with high traffic load are assigned to its neighbor satellites with lower transmitting power levels. It is shown that the method equalizes the traffic loads of the satellites to some degree and, hence, can improve the throughput characteristics of the system.     

Effect of nicardipine, a Ca2+ channel blocker, on pyruvate dehydrogenase activity and energy metabolites during cerebral ischemia and reperfusion in gerbil brain

The purpose of this study was to determine if nicardipine, a calcium ion channel blocker, affects pyruvate dehydrogenase (PDH) activity and improves energy metabolism during cerebral ischemia and reperfusion. Cerebral ischemia was induced, using the bilateral carotid artery occlusion method, for 60 min followed by reperfusion up to 120 min in gerbils. Nicardipine (1 mg/kg) or saline (vehicle-treated) was given to gerbils 30 min prior to the occlusion of the common carotid arteries. PDH activity and metabolites (ATP, PCr, and lactate) were measured in cortex prior to ischemia, immediately following ischemia, and after each reperfusion period. After 60 min ischemia, PDH activity increased in both groups, and was significantly higher in the nicardipine-treated group. After 20 min reperfusion, PDH activity in the nicardipine-treated group recovered to control levels, whereas, the PDH activity in the vehicle-treated group remained elevated, and was higher than the nicardipine-treated animals. At 60 and 120 min reperfusion, the activities in the vehicle-treated group were significantly below control levels, there were no differences, however, between the two groups. ATP and PCr concentrations were markedly depleted immediately after ischemia in both groups. ATP levels at 20 min reperfusion and PCr levels at 60 min reperfusion were significantly higher in the nicardipine-treated group. Lactate concentrations in both groups increased 7-8 fold, similarly, immediately after ischemia. During reperfusion, the lactate remained elevated in both groups, though the levels in the nicardipine-treated group were lower than those in the vehicle-treated group, but not significantly. Nicardipine treatment normalized PDH activity quickly and improved energy metabolism after reperfusion.     

Comparison of clinical pictures of mitochondrial encephalomyopathy with tRNA(Leu(UUR)) mutation in 3243 with that in 3254]

We compared clinical pictures of a case of mitochondrial encephalomyopathy with tRNA(Leu(UUR)) point mutation at nucleotide position 3254 of mitochondrial DNA with those at position 3243. The mutation 3254 was a 19-year-old male patient with cardiomyopathy accompanied with muscle atrophy. The first mutant 3243 was a 31-year-old female patient showing clinical features of MELAS and endocrinological abnormalities. The second 3243 mutant was a 27-year-old male patient who had an external ophthalmoplegia and slight mental decline. In all cases, muscle biopsy specimen showed ragged red fibers and strongly SDH-reactive blood vessels, but their limb weakness were unremarkable. These results suggest that tRNA(Leu(UUR)) point mutation 3254 exhibits similar clinical phenotypes as those observed in 3243 mutant.     

Increased serum vascular endothelial growth factor levels and intrathyroidal vascular area in patients with Graves' disease and Hashimoto's thyroiditis

Vascular endothelial growth factor (VEGF) is one of the angiogenic factors. We examined both thyroid volume and intrathyroidal vascular area by color flow Doppler ultrasonography in patients with Graves' disease (GD), Hashimoto's thyroiditis (HT), and subacute thyroiditis. The serum concentrations of thyroid hormones, TSH, TSH receptor antibodies, and VEGF were also examined. There was a significant increase in serum VEGF levels in patients with untreated GD and goitrous HT compared with those in healthy subjects. The serum VEGF levels in untreated patients with subacute thyroiditis were significantly higher than those in patients with untreated GD or HT. There was a significant correlation between serum VEGF levels and the ratio of intrathyroidal vascular area and thyroid area in untreated patients with GD who had a goiter larger than or equal to 40 cm3. There was also a significant correlation between serum VEGF and TSH levels in patients with HT who were hypothyroid and had a goiter. Serum VEGF levels decreased significantly in these patients after treatment; this was accompanied by a significant decrease in intrathyroidal vascular area and thyroid volume. Our study demonstrates that VEGF appears to play an important role in intrathyroidal angiogenesis in patients with GD and goitrous HT.     

Daily wheel running activity modifies the period of free-running rhythm in rats via intergeniculate leaflet

The period of free-running rhythms (tau) in rats, as measured using a running wheel, is different from that measured using an Automex. The aim of this work was to examine the effects of lesions of the intergeniculate leaflet (IGL) on the tau of these two activity rhythms. When blind rats were transferred from a cage with a running wheel to a cage without a running wheel, the tau lengthened. The tau of the wheel-running activity was associated with the number of wheel revolutions per day. A complete lesion of the IGL lengthened the tau of the wheel-running activity, and caused a reduction in the number of wheel revolutions per day in all rats. In rats housed in cages without a running wheel, locomotor activity was reduced by IGL lesions, although the tau was unaffected. When IGL-lesioned rats were transferred from a cage with a running wheel to a cage without a running wheel, no further change was observed. These results indicate that the tau is modified by the daily activity of wheel-running, but not by general locomotor activity, and that the IGL may be involved in this modification.