Seiki Hori

Calpain inhibitor entrapped in liposome rescues ischemic neuronal damage

Transient forebrain ischemia induces activation of calpain and proteolysis of a neuronal cytoskeleton, fodrin, in gerbil hippocampus. This phenomenon precedes delayed neuronal death in hippocampal CA1 neurons. We examined effects of a calpain inhibitor on delayed neuronal death after transient forebrain ischemia. In gerbils, a selective calpain inhibitor entrapped in liposome was given transvenously and 30 min later, 5-min forebrain ischemia was produced by occlusion of both common carotid arteries. On day 7, CA1 neuronal damage was examined in the hippocampal slices stained with cresyl violet. Calpain-induced proteolysis of fodrin was also examined by immunohistochemistry and immunoblot. Additionally, to assure entrapment of the inhibitor by CA1 neurons, the inhibitor-liposome complex was labeled with FITC and given to gerbils. Fluorescence in the hippocampal slices was examined by confocal laser scanning microscope. Selective CA1 neuronal damage induced by forebrain ischemia was prevented by administration of the inhibitor in a dose-dependent manner. Calpain-induced proteolysis of fodrin was also extinguished by the calpain inhibitor in a dose-dependent manner. Bright fluorescence of the FITC-labeled inhibitor was observed in the CA1 neurons. The data show an important role of calpain in the development of the ischemic delayed neuronal death. Calpain seems to produce neuronal damage by degrading neuronal cytoskeleton. Our data also show a palliative effect of the calpain inhibitor on the neurotoxic damage, which offers a new and potent treatment of transient forebrain cerebral ischemia.

Role of xanthine oxidase in delayed lipid peroxidation in rat liver induced by acute exhausting exercise

Abstract The aim of this study was to examine whether xanthine oxidase (XOD)-derived hepatic oxidative damage occurs in the main not during but following strenuous exercise. The degree of damage to hepatic tissue catalyzed by XOD was investigated immediately and 3 h after a single bout of exhausting exercise, in allopurinol and saline injected female Wistar rats. Allopurinol treatment resulted in increased hypoxanthine and decreased uric acid contents in the liver compared with the saline treated group, immediately and 3 h after the exercise. Analysis immediately after the exercise showed no changes in hepatic hypoxanthine, uric acid, and thiobarbituric acid-reactive substance (TBARS) contents in the saline treated group, when compared with the resting controls. However, significant increases in uric acid contents in the saline treated livers were observed 3 h after the exercise, relative to the controls. Hepatic TBARS content in the saline treated group were markedly greater than those in both the control and allopurinol treated groups after 3 h of recovery following the exercise. It was concluded that a single bout of exhausting exercise may impose XOD-derived hepatic oxidative damage, primarily during the recovery phase after acute severe exercise.

Effects of tension at the site of coaptation on recovery of sciatic nerve function after neurorrhaphy: evaluation by walking-track measurement, electrophysiology, histomorphometry, and electron probe X-ray microanalysis.

The effects of tension at the site of coaptation on recovery of sciatic nerve function after neurorrhaphy were studied by evaluating walking‐track measurements, nerve conduction velocity measurements, histomorphometry, and electron probe X‐ray microanalysis. Forty adult male Lewis rats underwent right sciatic nerve (SN) transection followed by one of four different nerve repair procedures (N = 10 rats per group). In Group 1, the gap was repaired by end‐to‐end epineural coaptation. In Group 2, a 5‐mm segment of SN was resected, and the defect was repaired under high tension by epineural neurorrhaphy. In Group 3, a 5‐mm segment of SN was resected, and the defect was repaired with a 5‐mm interposition nerve graft. In Group 4, a 5‐mm segment of SN was resected. Then, to lessen the tension that follows neurorrhaphy, an anchoring suture was added. Finally, end‐to‐end coaptation was performed. Walking‐track analysis showed better functional recovery in Group 1 than in Group 2, and better recovery in Group 3 than in Group 2. Group 4 showed a tendency toward better recovery comparing with Group 2. Electron probe X‐ray microanalysis revealed higher Na, Cl, and K peaks in axoplasm accompanied by increase in the endoneural fluid pressure (EFP) in Group 2 than those of Group 1. This higher level of Na, Cl and K may be due to impairment of axonal sodium and potassium transport mechanism in Group 2. Increase in EFP may affect nerve regeneration.

Changes in element concentrations induced by agonist in pig pancreatic acinar cells

Changes in electrolytes of pig pancreatic acinar cells following application of gastrin-cholecystokinin (CCK) were investigated using the technique of X-ray microanalysis of hydrated and dehydrated sections of freshly frozen pancreas. After stimulation by CCK (10−9 M), Na and Cl increased significantly in the cytoplasm [Na, from 10 mmol/kg wet wt. (48 mmol/kg dry wt.) to 19 mmol/kg (95 mmol/kg); Cl, from 22 mmol/kg (105 mmol/kg) to 49 mmol/kg (245 mmol/kg)] as well as in the luminal interspace [Na, from 53 mmol/kg (189 mmol/kg) to 65 mmol/kg (283 mmol/kg); Cl, from 65 mmol/kg (232 mmol/kg) to 102 mmol/kg (443 mmol/kg)]. In the secretory granules Cl increased significantly from 30 mmol/kg (86 mmol/kg) to 67 mmol/kg (203 mmol/kg). K decreased significantly from 120 mmol/kg (571 mmol/kg) to 81 mmol/kg (405 mmol/kg) in the cytoplasm, while both increased from 38 mmol/kg (109 mmol/kg) to 58 mmol/kg (176 mmol/kg) in the granules and from 46 mmol/kg (164 mmol/kg) to 48 mmol/kg (209 mmol/kg) in the luminal interspace. Ca increased significantly in the cytoplasm as well as in the luminal interspace, and decreased significantly in the secretory granules. CCK evoked Ca release from secretory granules in the secretory pole of acinar cells. The values were measured from dehydrated sections, and agreed well with those from hydrated sections. The effect of furosemide, an inhibitor of the Na+-K+-2Cl− co-transporter, on the ion transport of acinar cell was studied. When furosemide (10−5 M) was added to the external solution, the cytoplasmic Cl and Ca concentrations decreased significantly, while there was a little decrease in Na and K concentrations under the secretory condition. These results indicate that Na+-K+-2Cl− co-transport, and Na+, Cl− and K+ exits into the lumen are involved in the mechanism of ion secretion in pig pancreatic acinar cells.

Effects of decreased plasma glutamine concentrations on peripheral lymphocyte proliferation in rats

Abstract The relationship between exercise-induced lowering of plasma glutamine concentrations and proliferation of peripheral lymphocytes was investigated in male Wistar rats. The T-lymphocyte proliferative responses to the mitogen, concanavalin A, were determined by incorporation of radiolabelled thymidine into the DNA in vitro. The rats ran 2 h · day−1, 6 days · week−1 for 4 weeks. Analysis immediately after the final period of exercise showed T-lymphocyte proliferation to be significantly depressed, together with a marked decrease in plasma glutamine concentrations. There were also significant increases in serum corticosterone concentrations immediately after exercise. However, following 24-h recovery, this exercise-induced immunosuppression was not statistically significant when compared with the age-matched control group. In the second experiment, in order to clarify the importance of glutamine for immunological function in vivo, methionine sulfoximine, an effective inhibitor of glutamine synthetase was injected intraperitoneally (12.5 mg · kg body mass−1). Plasma glutamine concentrations were decreased 4 h after the injection, compared with the placebo control group, and this resulted in a significant decrease in the rate of T-lymphocyte proliferation. This treatment had no effects on serum corticosterone concentrations. These results would suggest that the chronic exercise-induced reduction in proliferation of peripheral T-lymphocytes is a transient reversible phenomenon, which returns to normal levels within 24 h of the final training period. It is also conceivable that this exercise-induced immunosuppression is associated with a decrease in circulating glutamine concentrations.

Seasonal variations of physiological responses to heat of subtropical and temperate natives.

In an attempt to compare the physiological responses of subtropical natives to heat with those of temperate natives, seasonal variations in physiological responses to heat were observed in young male residents of Okinawa who were born and raised in Okinawa, subtropical zone (group O) and young male residents of Okinawa who were born and raised on the Japan mainland, temperate zone, but moved to Okinawa in less than two years (group M). In both seasons, group O showed less sweat loss, lower Na concentration in sweat, lower rise in rectal temperature and less increase in heart rate during heat exposure than group M. In both groups, greater sweat loss, lower Na concentration in sweat and lower rise in rectal temperature in summer than in winter were observed. Seasonal differences in Na concentration in sweat, rise in rectal temperature and increase in heart rate for group O were smaller than those for group M. It was assumed the efficiency of sweat for cooling the body for group O was better than that for group M, and heat tolerance for group O was superior to that for group M.

Effects of the endothelin receptor antagonist TAK-044 on hepatocyte element alterations in the ischemic-reperfused liver in Beagle dogs

BACKGROUND/AIMS This study was designed to investigate elemental alterations of subcellular organelles (cytoplasm, nucleus, mitochondria) after ischemia of the liver, and the effects of the pre-ischemic administration of an endothelin ETA/ETB receptor antagonist (TAK-044) on subcellular elements. METHODS We determined serial changes in subcellular elements by X-ray microanalysis using liver biopsy specimens, and we compared the liver functions of a control and a TAK-044-treated group of Beagle dogs, before and after 70% partial ischemia (60 min). TAK-044 was given intravenously at a dose of 3 mg/kg before ischemia. RESULTS In the control, the Ca concentration in the cytoplasm showed a slight increase after ischemia and a marked increase immediately after reperfusion. It returned to approximately pre-ischemic levels at 6 h after reperfusion. In contrast, in the TAK-044 group, the increase was significantly suppressed. The changes in Na and Cl, which increased in parallel with Ca, were also suppressed in the TAK-044 group. The alterations in K were opposite to those Ca. These changes were also suppressed to a significant degree in the TAK-044 group. Elemental alterations in the nucleus and mitochondria were similar to those in the cytoplasm in both the control and TAK-044 groups. The changes in the liver functions and the electron microscopic findings supported the differences in serial changes in subcellular elements between the two groups. CONCLUSIONS TAK-044 exhibited a hepatoprotective effect on ischemia-reperfusion injury from the aspect of subcellular elemental dynamics and liver functional and morphologic changes.

Comparison of physical characteristics, body temperature and resting metabolic rate at 30‡C between subtropical and temperate natives

Anthropometric measurements, measurements of skin temperatures, rectal temperature, heart rate and metabolic rate at 30‡C were made on 25 young male residents of Okinawa who were born and raised in Okinawa (group O) and 25 young male residents of Okinawa who were born and raised on the Japan mainland but moved to Okinawa less than 2 years before the test (group M) in summer. Group O showed significantly shorter height, lighter body weight, and slender body shape than group M. Group O showed thinner skinfold thickness and smaller percentage of body fat content than group M. Skin temperatures for group O were higher than those for group M, and rectal temperature for group O was slightly lower than that for group M. Group O showed, less metabolic rate per body surface area and slower heart rate than group M. It is concluded that physical characteristics of subtropical natives is favorable for heat dissipation, and subtropical natives have superior capacity for non-evaporative heat dissipation than migrants of temperate natives to a subtropical zone.

Effect of serotonin on ouabain-sensitive, K+-dependent, p-nitrophenylphosphatase activity in strial marginal cells of normal and reserpinized guinea pigs

Na+,K+-ATPase activity is abundant on the basolateral infoldings of the strial marginal cells and contributes to the maintenance of the characteristic electrolyte composition of the endolymph. However, the stria vascularis of the cochlea is known not to be innervated. In order to clarify its humoral regulation by serotonin, the K+-p-nitrophenylphosphatase activity of strial marginal cells was investigated with a cerium-based method in normal guinea pigs and in guinea pigs treated with reserpine, 5-hydroxytryptamine or reserpine plus 5-hydroxytryptamine. K+-p-nitrophenylphosphatase activity was almost completely depressed 3--20 days after reserpine administration. Ten days after reserpinization, followed by repeated 5-hydroxytryptamine treatment, the enzyme activity was detectable. These results suggest that 5-hydroxytryptamine increases the phosphatase activity. Thus, the function of the stria vascularis in producing cochlear endolymph may be regulated by 5-hydroxytrypt amine.

Decreased energy expenditure during prolonged sub-maximal exercise in a warm environment

Abstract The purpose of this study was to investigate the influence of a warm environment on thermoregulation and energy expenditure during sub-maximal prolonged exercise in humans. Six healthy male subjects cycled for 120 min at an intensity of 60% maximal oxygen uptake (Vo2max) at three environmental temperatures (10°C, CT; 20°C, MT; and 30°C, WT). Although oxygen uptake at WT showed a significantly lower value compared to those at MT and CT, no significant differences of respiratory exchange ratio were observed among the three environmental trials. A remarkable decrease in total energy expenditure during the 120-min exercise at WT was observed in comparison with those at MT and CT (p<0.05). Changes in rectal temperature, mean skin temperature, and mean body temperature at WT were significantly higher than those at both MT and CT. Although increases in mean body temperature from rest every five minutes during exercise were not different among three environmental temperatures, mean energy expenditures every five minutes at WT were lower compared with those at MT and CT (p<0.05). These results suggest that the increase in energy expenditure for physical exertion is substantially reduced during prolonged sub-maximal exercise in a warm environment. This acute alteration in the energy metabolism may contribute to inhibition of excess heat production and enable prolonged exercise in a warm environment.