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Volume 48 (1998)
- Issue 6 Pages 397-
- Issue 5 Pages 301-
- Issue 4 Pages 219-
- Issue 3 Pages 173-
- Issue 2 Pages 99-
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Volume 48, Issue 2
Displaying 1-9 of 9 articles from this issue
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Review
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Tadaaki MANO1998 Volume 48 Issue 2 Pages 99-114
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSDownload PDF (1855K)
Regular Papers
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Tsukasa TAMEYASU, Tsuyoshi AKIMOTO, Yasuhisa HIROHATA, Ibuki SHIRAKAWA ...1998 Volume 48 Issue 2 Pages 115-121
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSTo investigate in vitro ATP-dependent sliding of regularly arranged myosin molecules on actin filaments, we prepared thick hybrid filaments in which myosin molecules isolated from rabbit skeletal muscle were arranged around the paramyosin core (length, 10-20 μm; diameter, ≤0.2 μm) obtained from a molluscan smooth muscle. A single to a few thick hybrid filaments were attached to a polystyrene bead (diameter, 4.5 μm; specific gravity, 1.5) and made to slide on actin filament arrays (actin cables) in the internodal cell of an alga, mounted on the rotor of a centrifuge microscope. The bead was subjected to centrifugal forces serving as external loads to the ATP-dependent actin-myosin sliding. The maximum unloaded sliding velocity of the thick filament attached-bead (mean, 3.4 μm/s; 20-23°C) was significantly higher than that of the bead coated with randomly oriented myosin molecules reported previously. The steady-state force-velocity (P-V) relations obtained were qualitatively similar to those in intact skeletal muscle fibers. These results indicate that this in vitro motility assay system retains the basic characteristics of contracting skeletal muscle fibers, and that it may be effectively used to study mechanisms underlying the steady-state P-V characteristics of ATP-dependent actin-myosin sliding using various recombinant myosins produced in nonmuscle cells.View full abstractDownload PDF (1433K) -
Yi SYUU, Junichi ARAKI, Shinyu LEE, Shunsuke SUZUKI, Ju MIZUNO, Satosh ...1998 Volume 48 Issue 2 Pages 123-132
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSWe investigated the effects of intracoronary Ca2+ and epinephrine on the intracellular Ca2+ recirculation fraction (RF) and total Ca2+ handling in the left ventricle (LV) of the excised cross-circulated canine heart preparation. We analyzed LV postextrasystolic potentiation (PESP) following a spontaneous extrasystole that occurred sporadically under constant atrial pacing. All PESPs decayed in alternans and none decayed monotonically. We extracted an exponential decay component from the alternans PESP, determined its beat constant (τe), and calculated RF=exp(−1/τe). Increased intracoronary Ca2+ slightly increased τe and RF, but epinephrine did not change them, although both agents enhanced LV contractility 2-3 times. Neither Ca2+ nor epinephrine affected the sinusoidal decay of the alternans PESP. These results indicate that RF via the sarcoplasmic reticulum was slightly augmented by Ca2+, but not by epinephrine. We combined these RF data with LV Ca2+ handling O2 consumption data and obtained 40-110 μmol/kg as the total amount of Ca2+ handled in one cardiac cycle in the control and enhanced contractile states. These results indicate that this new LV-level approach seems to better the understanding of the Ca2+ mass dynamics responsible for the mechanoenergetics enhanced by inotropic interventions.View full abstractDownload PDF (1209K) -
Yuzhen TAN1998 Volume 48 Issue 2 Pages 133-141
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSWe have attempted to evaluate whether, similar to the angiogenesis of blood vessels, cultures of lymphatic endothelial cells (LEC) isolated from dog thoracic ducts have an ability to induce lymphangiogenesis in response to basic fibroblast growth factor (bFGF), then to examine the effects of heparin on the bFGF-mediated morphogenesis. The effects of bFGF and/or heparin on the proliferation and migration of the LEC were evaluated by changing the number of the subconfluent cells and by wound migration assay, respectively. The effects of the agents on invasion and tube formation of the LEC into a three-dimensional collagen gel and on collagen gel induced tube formation of the LEC were also investigated by a phase-contrast microscope and an electron microscope. The bFGF (10 ng/ml) caused a significant induction of proliferation and migration of the LEC, the induction of which was augmented dose-dependently by an additional treatment with heparin ranging from 1 to 100 μg/ml. The bFGF produced invasion and tube formation of the LEC into a three-dimensional collagen gel. The bFGF also facilitated to form capillary-like tubes of the LEC between two layers of collagen gels. Heparin (10 μg/ml) accelerated both processes of bFGF-mediated lymphangiogenesis of the LEC. These findings suggest that the cultured LEC isolated from dog thoracic ducts have an ability to form lymphatic capillary-like tubes in response to bFGF and that heparin accelerates dose-dependently the process of the bFGF-mediated neo-vascularization of lymph vessels.View full abstractDownload PDF (2085K) -
Tetsuya YOSHIDA, Kei NAGASHIMA, Seiichi NAKAI, Akira YORIMOTO, Takashi ...1998 Volume 48 Issue 2 Pages 143-148
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSWe studied the difference of thermoregulatory responses between trained male athletes (TR, n=9) and untrained men (UT, n=7) during 60 min of cold exposure (15°C) without shivering, and examined the effects of physical fitness and body fat on these responses. Mean skin temperature (¯Tsk), esophageal temperature (Tes), and skin conductance (Kb) were similar between TR and UT, and heat production (¯M) for TR increased significantly during exposure at 15°C. The ¯M at 15°C correlated positively with maximal oxygen uptake and negatively with body fat (%BF), but not with Tes. The Kb correlated negatively with Tes and positively with ¯Tsk. The %BF also correlated negatively with Kb and ¯Tsk during exposure at 15°C, and the slope of %BF vs. ¯Tsk relationship was significantly steeper in TR than in UT. These results suggest that (1) body temperature is maintained by the reduction of skin conductance, and (2) heat insulation independent of body fat is enhanced in trained athletes during cold exposure without shivering.View full abstractDownload PDF (620K) -
Shin-Jung PARK, Hiromi TOKURA1998 Volume 48 Issue 2 Pages 149-156
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSThis study investigated the effects of three different types of clothing on the circadian rhythms of core temperature and urinary catecholamines. One type of clothing consisted of long-sleeved shirts, full-length trousers, and socks (Type L, 1, 042 g); the second type was of half-sleeved shirts and knee-length trousers (Type H, 747 g); the third type was of Type H during the daytime and Type L during night sleep (Type M). Six healthy females participated in this study where rectal temperature, skin temperatures, heart rate, and urinary catecholamines were continuously measured for 37.5 h at an ambient temperature of 23.8±0.2°C and a relative humidity of 60±5%. The results were as follows: (1) The nocturnal minimum of rectal temperature decreased significantly in the sequence Type L<Type M<Type H clothing, and 27.2 and 12.4% of the circadian amplitude were influenced by type of clothing during the daytime and the nighttime, respectively. (2) The rise of skin temperatures in the extremities increased significantly more after the subjects retired for sleep with Type M or Type H clothing than with Type L. (3) Urinary catecholamines decreased more in the evening and increased more in the morning with Type H and Type M clothing than with Type L. These results show that the circadian rhythm of core temperature, especially the nocturnal minimum value, was influenced by the type of clothing worn not only during the nighttime, but also during the daytime.View full abstractDownload PDF (940K) -
Toshio IZUOKA, Yasuo TAKAYAMA, Tetsuro SUGIURA, Hiroya TANIGUCHI, Teru ...1998 Volume 48 Issue 2 Pages 157-161
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSPlatelet-activating factor (PAF), one of the harmful substances released after coronary reperfusion, has been reported to increase pulmonary vascular permeability and induce pulmonary edema. In this study, we sought to examine the possible role of PAF in the genesis of pulmonary edema after coronary reperfusion. Extravascular lung water (EVLW) was measured by the thermal-dye double indicator dilution method during coronary ligation and after reperfusion in situ in dogs. The proximal left anterior descending coronary artery was occluded for 15 min and reperfused in 5 dogs (group 1), while five other dogs (group 2) were treated with PAF-antagonist (TCV-309, 1 mg/kg) before coronary artery occlusion. EVLW and hemodynamic indices were measured at baseline, 15 min of coronary occlusion, and 15 and 30 min after coronary reperfusion. EVLW increased at 15 min of coronary occlusion in both groups, but there was no significant difference between the two groups (6.4 to 10.3 ml/kg and 5.4 to 7.1 ml/kg in groups 1 and 2, respectively). After coronary reperfusion, EVLW increased further in group 1 (6.4 to 16.5 ml/kg, p<0.01), but no further increase was observed in group 2 at 30 min after coronary reperfusion. There were no significant differences in hemodynamic indices between the two groups throughout the test. Thus, PAF-antagonist attenuated the increase in EVLW after coronary reperfusion independent of hemodynamic indices, and hence, PAF may play an important role in the genesis of pulmonary edema caused by coronary reperfusion.View full abstractDownload PDF (522K)
Short Communications
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Naotoshi SUGIMOTO, Osamu SHIDO, Sotaro SAKURADA, Sukenaga ITO, Tetsuo ...1998 Volume 48 Issue 2 Pages 163-166
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSSpontaneous running in a running wheel has emerged as an alternative method of exercise in small animals. The present study investigated how exercise training with a running wheel affects core temperature level and thermoeffector thresholds in rats. Female rats were allowed to run freely in the wheel for 6 months. Sedentary controls did not exercise during the same period. After the exercise training period, they were loosely restrained and their threshold core temperatures for tail skin vasodilation and cold-induced thermogenesis were determined by warming or cooling the animals by use of a chronically implanted intravenous thermode. Resting and threshold core temperatures of the exercise-trained rats were higher than those of the sedentary controls. The results suggest that in rat, exercise training with a running wheel shifts threshold temperatures for heat loss and heat production to high levels, which may result in a rise in core temperature level.View full abstractDownload PDF (359K) -
A.S. MALHOTRA, K. PAL, R. PRASAD, A.C. BAJAJ, R. KUMAR, R.C. SAWHNEY1998 Volume 48 Issue 2 Pages 167-169
Published: 1998
Released on J-STAGE: May 31, 2002
JOURNAL FREE ACCESSCirculatory levels of insulin and growth hormone (GH) were estimated in nine tropical euglycemic men in New Delhi and during the first week of every month of stay in Dakshin Gangotri, Antarctica. Prolonged residency in Antarctica did not alter GH levels because mean GH values during Austral summer and Austral winter were not significantly different from the New Delhi values. Compared with GH, the insulin levels during March, April, and June were found to be significantly lower than the New Delhi values. In Antarctica, the insulin levels in March, April, May, June, July, and August were also found to be significantly lower than the December values. This decline in insulin in Antarctica might be important in increasing substrate availability for heat production by facilitating lipolysis and hepatic glucose output.View full abstractDownload PDF (328K)
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