American Journal of Physiology-Heart and Circulatory Physiology, 2001
We hypothesized that O2 wasting of Ca2+handling in the excitation-contraction coupling in ryanodi... more We hypothesized that O2 wasting of Ca2+handling in the excitation-contraction coupling in ryanodine-treated failing hearts might derive from an increased external Ca2+extrusion via Na+/Ca2+ exchanger and futile Ca2+ cycling via sarcoplasmic reticulum (SR) Ca2+-ATPase. We tested this hypothesis by mechanoenergetic studies using rat left ventricular slices. After the slices were treated with ryanodine (0.1 μM), 1-Hz free shortening significantly decreased by 78–85%, whereas the observed O2consumption (V˙o 2) required for total Ca2+ handling, increased from 0.79 to 1.13 ml O2 · min−1 · 100 g LV−1 (155.6% of control). We reconfirmed that cyclopiazonic acid (10 μM), a blocker of SR Ca2+-ATPase, decreased V˙o 2 by 75–80% in normal slices. However, 100 μM of cyclopiazonic acid was needed to inhibit the V˙o 2 by 80% after ryanodine treatment. Blockade of a sarcolemmal Na+/Ca2+exchanger by KB-R7943 (10 μM) significantly decreasedV˙o 2 by 45% after ryanodine treatment without significant effe...
Under the conditions of both an increased red cell affinity for O(2) at a constant rate of O(2) d... more Under the conditions of both an increased red cell affinity for O(2) at a constant rate of O(2) delivery (arterial O(2) content x flow) and a decrease in the rate of O(2) delivery induced by hypoxic hypoxia at constant blood flow, we have obtained a linear relationship between the partial pressure of O(2) in the muscle venous effluent (P(v,)(O(2))) and O(2) uptake (.V(O(2))). The relationship is described by the equation .V(O(2)) = D(a) x P(v,)(O(2)) + .V(O(2)conv)) where D(a) is the apparent O(2) diffusion capacity and .V(O(2)conv)) is O(2) delivery-limited .V(O(2)), and D(a) x P(v,)(O(2)) represents the O(2) diffusion-limited .V(O(2)) .V(O(2)diff)). From these observations, we propose the hypothesis that .V(O(2)) consists of two additive values, .V(O(2)conv)) and .V(O(2)diff)). The mechanism underlying the reduction in .V(O(2)) that is induced by reducing O(2) delivery to markedly below the .V(O(2)conv)) value has only been investigated using a model based on the single compartment of diffusion-limited .V(O(2)), and has not been investigated in terms of this additive .V(O(2)) model. The single compartment analysis appears to overestimate the role of O(2) diffusion in limiting the reduction of .V(O(2)) that occurs in response to a decrease in O(2) diffusion capacity, as reflected by the .V(O(2))/P(v,)(O(2)) ratio. To gain better insight into the mechanism involved, we altered the rate of O(2) delivery by changing arterial P(O(2)) from normoxia (with inhalation of air) to hypoxia (by inhalation of 10-11 % O(2)) and blood flow (with high and low flow rates (n = 7 for both groups), and very low and ischaemic flow rates (n = 4 for both groups)) in pump-perfused dog gastrocnemius preparations during tetanic isometric contractions at 1 Hz. As rates of O(2) delivery were reduced from 23.2 to 10.9 ml min(-1) (100 g)(-1), significant decreases in P(v,)(O(2)) and .V(O(2)) were observed (P < 0.05). From the data of P(v,)(O(2)) and .V(O(2)) values within this range of O(2) delivery rates, we obtained the regression equation .V(O(2)) = 0.22 x P(v,)(O(2)) + 8.14 (r = 0.58). From the equation, the intercept of the .V(O(2))-axis was significantly different from zero (P < 0.05), in accordance with the observation that the .V(O(2)) /P(v,)(O(2)) ratio (ml min(-1) (100 g)(-1) Torr(-1)) increased from 0.54 to 1.35 (P < 0.05). However, at extremely low rates of O(2) delivery (5.6 and 7.3 ml min(-1) (100 g)(-1) the .V(O(2))/P(v,)(O(2)) ratio was 1.51 and 2.80 (P < 0.05), respectively. This indicates a break in the linear .V(O(2))-P(v,)(O(2)) relationship as the rate of O(2) delivery was reduced to below the .V(O(2)conv)) value of the .V(O(2))-axis intercept. These results suggest that the reduction in .V(O(2)) caused by extreme reductions in the rate of O(2) delivery is not attributable to a reduction in O(2) diffusion capacity, as expected from the .V(O(2))/P(v,)(O(2)) ratio, but to a reduction in the O(2) delivery-limited .V(O(2)) component, as evaluated by the .V(O(2))-axis intercept of the linear .V(O(2))-P(v,)(O(2)) relationship.
Journal of Molecular and Cellular Cardiology, 2007
The aim of this study was to examine whether short-and long-term gene transfer of Ca 2+ handling ... more The aim of this study was to examine whether short-and long-term gene transfer of Ca 2+ handling proteins restore left ventricular (LV) mechanoenergetics in aortic banding-induced failing hearts. Aortic banded rats received recombinant adenoviruses carrying sarcoplasmic reticulum Ca 2+-ATPase (SERCA2a) (Banding+SERCA), parvalbumin (Banding+Parv) or β-galactosidase (Banding +βgal), or an adeno-associated virus carrying SERCA2a (Banding+AAV.SERCA) by a catheterbased technique. LV mechanoenergetic function was measured in cross-circulated hearts. "Banding", "Banding+βgal" and "Banding+saline" groups showed lower end-systolic pressure at 0.1 ml intraballoon water (ESP 0.1), higher end-diastolic pressure at 0.1 ml intraballoon water (EDP 0.1) and slower LV relaxation rate, compared with "Normal" and "Sham". However, "Banding+SERCA" and "Banding+Parv" showed high ESP 0.1 , low EDP 0.1 , and fast LV relaxation rate. In "Banding", "Banding+βgal" and "Banding+saline", slope of relation between cardiac oxygen consumption and systolic pressure-volume area, O 2 cost of total mechanical energy, was twice higher than normal value, whereas slope in "Baning+SERCA" and "Banding+Parv" was similar to normal value. Furthermore, O 2 cost of LV contractility in the 3 control banding groups was ∼3 times higher than normal value, whereas O 2 cost of contractility in "Banding+SERCA", "Banding+AAV.SERCA" and "Banding+Parv" was as low as normal value. Thus, high O 2 osts of total mechanical energy and of LV contractility in failing hearts indicate energy wasting both in chemomechanical energy transduction and in calcium handling. Improved calcium handling by both short-and long-term overexpression of SERCA2a and parvalbumin transforms the inefficient energy utilization into a
American Journal of Physiology-Heart and Circulatory Physiology, 2001
The aim of the present study was to examine the mechanisms of Ca2+ overload-induced contractile d... more The aim of the present study was to examine the mechanisms of Ca2+ overload-induced contractile dysfunction in rat hearts independent of ischemia and acidosis. Experiments were performed on 30 excised cross-circulated rat heart preparations. After hearts were exposed to high Ca2+, there was a contractile failure associated with a parallel downward shift of the linear relation between myocardial O2 consumption per beat and systolic pressure-volume area (index of a total mechanical energy per beat) in left ventricles from all seven hearts that underwent the protocol. This result suggested a decrease in O2consumption for total Ca2+ handling in excitation-contraction coupling. In the hearts that underwent the high Ca2+ protocol and had contractile failure, we found marked proteolysis of a cytoskeleton protein, α-fodrin, whereas other proteins were unaffected. A calpain inhibitor suppressed the contractile failure by high Ca2+, the decrease in O2 consumption for total Ca2+ handling, and ...
Clinical and Experimental Pharmacology and Physiology, 1999
1. It has previously been shown that perfusion with high O2-affinity-erythrocytes decreases venou... more 1. It has previously been shown that perfusion with high O2-affinity-erythrocytes decreases venous PO2 (PVO2) and decreases O2 uptake (VO2) in contracting muscle at the same O2 delivery (arterial O2 concentration x flow). A linear VO2-PVO2 relationship has been obtained with a VO2-axis intercept, suggesting that, during this type of hypoxia, VO2 is composed of a PVO2-dependent and -independent VO2. However, the VO2-PVO2 relation during hypoxic hypoxia has not been examined. 2. To clarify this relation, PVO2 and VO2 have been measured in contracting gastrocnemius (1 Hz trains of 0.2 s isometric tetani) under both normoxic and hypoxic conditions during 5 min of stimulation. 3. Venous O2 changes proportionally with O2 delivery. Each VO2-PVO2 relation was linear, with the mean described by the equation VO2 = 5.06 + 0.41 x PVO2 (n = 6, r = 0.81, P < 0.05). The VO2-axis intercept was significantly different from zero (P < 0.05). 4. These results were similar to those obtained during hypoxia induced by high O2-affinity-erythrocytes. We conclude that there is a linear relationship between PVO2 and VO2 above the VO2-axis intercept, regardless of the type of hypoxia.
We have examined whether mouse plasma erythropoietin (EPO) can be measured by an improved enzyme-... more We have examined whether mouse plasma erythropoietin (EPO) can be measured by an improved enzyme-linked immunosorbent assay (ELISA) using milk proteins (Block Ace) both as a blocking reagent and as a diluent for standard recombinant human EPO (rHuEPO) and for plasma samples. Block Ace brought about high slope sensitivity of the standard curve, with a low background. The dose-response curves of normal or anaemic mouse plasma and of rHuEPO were linear and parallel to each other. The anaemic plasma had an additive effect with rHuEPO by increasing the absorbance at 405 nm. The coefficients of variation in the intra-and interassays ranged from 4.2% to 15.3%. The plasma EPO levels in 22 normal mice were 18.3 ___ 10.3 mU/ml. An inverse relationship between the logarithm of plasma EPO concentrations and blood haemoglobin concentrations, red blood cell counts or packed cell volumes was found in normal mice and in mice with iron deficiency anaemia (IDA). These results show the validity for the use of the new improved ELISA method for measuring circulating murine EPO.
... In agreement with an observation on rats with IDA (McCall et al. 1962), reticulocytosis durin... more ... In agreement with an observation on rats with IDA (McCall et al. 1962), reticulocytosis during the development of IDA was enhanced depending on the severity of anaemia or the plasma EPO levels (Fig. ... Br J Haematol 38:291-294 Jansson LT, Perkki6 MV, Clemons Get al. ...
It is still uncertain that hyperoxia affects muscle oxygen consumption (VO 2) during repetitive c... more It is still uncertain that hyperoxia affects muscle oxygen consumption (VO 2) during repetitive contractions [1]. There is both theoretical and experimental support for the idea that all precapillary O 2 losses, i.e., a longitudinal decrease in arteriolar oxygen tension (PO 2), an arteriovenous diffusion shunt, and diffusive exchange between arterioles and capillaries contribute significantly to limitations on O 2 extraction in the resting muscle [2]. Furthermore, O 2-diffusion shunt as an ineffective O 2 supply may affect VO 2 in tetanically contracting muscle during hyperoxia. We examined the influence of hyperoxia on VO 2 and peripheral O 2 exchange during repetitive tetanic contractions with the canine gastrocnemius muscle group. Possible mechanisms for limiting VO 2 by increasing PaO 2 have been discussed in relation to peripheral O 2 diffusion limitation for muscle VO 2 [3-8] using both muscle venous effluent PO 2 (PvO 2), reflecting O 2 driving force of diffusion from erythrocyte to mitochondria, and VO 2 /PvO 2 ratio, reflecting O 2 diffusion conductance [9, 10]. Methods Eight mongrel dogs (mean weight 13.2Ϯ0.9 kg) were anesthetized with pentobarbital sodium (I.P., 30 mg/kg). The animals were ventilated by a respirator
The Otsuka-Long-Evans Tokushima Fatty rat represents a model for spontaneous non-insulindependent... more The Otsuka-Long-Evans Tokushima Fatty rat represents a model for spontaneous non-insulindependent type II diabetes mellitus (DM), characterized by diastolic dysfunction and associated with abnormal calcium handling and decrease in sarcoplasmic reticulum Ca 2+ -ATPase (SERCA2a) expression. The aim of this study was to examine whether SERCA2a gene transfer can restore the energetic deficiency and left ventricular (LV) function in this model. DM rats were randomized to receive adenovirus carrying either the SERCA2a gene (DM + Ad.SERCA2a) or the B-galactosidase gene (DM + Ad.BGal) or saline (DM + saline). LV mechanoenergetic function was measured in crosscirculated heart preparations 3 days after infection. In DM, end-systolic pressure at 0.1 ml intraballoon water (ESP 0.1 ) was low and end-diastolic pressure at 0.1 ml intraballoon water (EDP 0.1 ) was high (22 mm Hg), compared with non-DM (EDP 0.1 12 mm Hg). In DM + Ad.SERCA2a, however, ESP 0.1 was increased over 200 mm Hg and EDP 0.1 was decreased to 7 mm Hg. LV relaxation rate was fast in DM + Ad.SERCA2a, but slow in the other DM groups. There was no difference in relation between cardiac oxygen consumption per beat and systolic pressure-volume area among all groups. Finally, the oxygen cost of LV contractility in DM was about three times as high as that of normal. In DM + Ad.SERCA2a, the oxygen cost decreased to control levels, but in DM + Ad.BGal/DM + saline it remained high. In DM failing hearts, the high oxygen cost indicates energy wasting, which contributes to the contractile dysfunction observed in diabetic cardiomyopathy. SERCA2a gene transfer transforms this inefficient energy utilization into a more efficient state and restores systolic and diastolic function to normal.
The plasma concentrations of both immunoreactive erythropoietin (EPO) and lactate were determined... more The plasma concentrations of both immunoreactive erythropoietin (EPO) and lactate were determined in four healthy untrained subjects at sea level and on the 2nd or 3rd day at altitudes (1,300 and 3,500 m). The mean plasma EPO (18.8 +/- 1.6 mU/ml at sea level) increased significantly on the 3rd day at 1,300 m (25.5 +/- 2.0 mU/ml, p < 0. 05) and showed an almost three-fold increase on the 2nd day at 3,500 m (53.5 +/- 3.7 mU/ml, p < 0.001). Likewise, the mean plasma lactate at 3,500 m (3.98 +/- 0.27 mmol/l) was 3.6 times as high as that at sea level (1.11 +/- 0.05 mmol/l) (p < 0.001). The plasma EPO concentrations were found to correlate well with the lactate concentrations at sea level and altitudes (r = 0.86, p < 0.01). These results are consistent with the well-known EPO/lactate response to altitudes and suggest that the circulating EPO concentration as well as blood lactate concentration can be used as an index of anaerobic condition.
The different response of O2 uptake (VO2) of resting skeletal muscle to the changes in blood flow... more The different response of O2 uptake (VO2) of resting skeletal muscle to the changes in blood flow has been thought to reflect a species difference. To scrutinize this notion, we investigated the relation between O2 delivery (arterial O2 content multiplied by blood flow) and VO2 in isolated dog gracilis muscle perfused solely with normal hematocrit (Ht) blood (n = 9), or alternately with normal and low Ht blood (n = 6), or alternately with normal and high Ht blood (n = 3) at varying perfusion rates. Eleven out of the 18 preparations showed an autoregulation of blood flow, and the others did not. But, in all preparations, the VO2 was delivery-independent above a critical O2 delivery (0.45 ml/(min.100 g muscle)) and showed the constant VO2 of 0.30 ml/(min.100 g), while below the critical level it turned out to be delivery-dependent. The maximal extraction ratio was 0.67. The same relationship was found with the low and high Ht perfusion. The pattern observed in dog gracilis muscle was essentially the same as that in rat gracilis muscle (KOLAR and JANSKY, 1984).
The aim of the present study was to clarify the effects of O2 diffusion limitation resulting from... more The aim of the present study was to clarify the effects of O2 diffusion limitation resulting from hypoxic interventions on O2 uptake (V.O2) in unloaded (that is, near-zero initial force) and loaded skeletal muscle in a high-frequency stimulation. We measured V.O2, muscle venous PO2 (PvO2) and initial force in gastrocnemius-plantaris muscle in situ of anesthetized dogs: (1) during hypoxic hypoxia at 1 Hz tetanic stimulation, and (2) during hypoxia induced by the perfusion with high O2-affinity erythrocytes (having a low value of PO2 at 50% saturation of hemoglobin (P50)) at 4 Hz twitch stimulation. Averaged unloaded V.O2 during normoxia was 10.2 ml.min-1.100 g-1 at averaged blood flow of 74 ml.min-1.100 g-1 (n = 6). Hypoxic hypoxia of a decreased O2 delivery (arterial O2 concentration x flow) significantly decreased both unloaded and loaded V.O2 with a decrease in PvO2 (p<0.05). The unloaded V.O2 was reduced to 8.5 ml.min-1.100 g-1. Low P50-hypoxia decreased V.O2 at high and low initial force conditions with a decrease in PvO2 (p<0.05) at the same O2 delivery. If these decreases in V.O2 correspond with a decrease in V.O2 at zero initial force (unloaded V.O2), the unloaded V.O2 value is calculated to be 7.57 ml.min-1.100 g-1 from V. O2-initial force data. Despite the different conditions of O2 delivery, the unloaded V.O2 decreased by both hypoxia showed similar values. Thus the decreased unloaded V.O2 does not seem to be derived from only the limited O2 delivery. Some other factors such as the limitation of O2 diffusion may contribute to the decreased V.O2.
A nutritional survey was carried out among residents (39 males and 46 females) of Dzong village i... more A nutritional survey was carried out among residents (39 males and 46 females) of Dzong village in the northern area of the Gandaki region of Nepal. The results were compared with our previous findings. The mean body mass index value was under 21 for both sexes, but the mean percentage of body fat of females (17-19 years old, 25.8 +/- 9.4%; 20-29 years old, 31.0 +/- 8.4%) was higher than that of males (17-19 years old, 12.0 +/- 1.0%; 50-59 years old, 24.4 +/- 7.6%). Most serum nutritional markers for both sexes were generally at normal levels although the iron levels were lower and packed red cell volume levels were higher than normal. As determined by results of the 24-hr dietary recall survey, the main food groups consumed by both sexes were cereals, potatoes, pulses, meats and vegetables. The mean daily intake of nutrients was similar for both sexes, with a few exceptions. The relatively high serum TG levels of the subjects may have been due to the high consumption of carbohydrate-laden cereals. The amounts of food consumed were not adequate, resulting in a latent and chronic deficiency of nutrients, especially calcium and iron. These results suggest that improvements in the nutritional status of this group of people are necessary.
The Otsuka Long-Evans Tokushima fatty rat is an animal model of Type 2 diabetes mellitus (DM), wh... more The Otsuka Long-Evans Tokushima fatty rat is an animal model of Type 2 diabetes mellitus (DM), which is characterized by diastolic dysfunction associated with decreased sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a). The aim of this study was to examine whether gene transfer of SERCA2a can influence coronary blood flow and cardiomyocyte diameter in this model. DM rats were injected with adenovirus carrying SERCA2a (DM+SERCA) or beta-galactosidase gene (DM+betaGal). Coronary blood flow was measured in cross-circulated excised hearts 3 days after infection. Although in all groups coronary blood flow remained unchanged even if left ventricular (LV) volume or intracoronary Ca(2+) infusion was increased, the DM+SERCA group showed a sustained increase in coronary blood flow compared with the other groups. This result suggests that the sustained high coronary blood flow is a specific response in SERCA2a-overexpressed hearts. Although the LV weight-to-body weight ratio (LV/BW) and cardiomyocyte diameter were higher in the DM and DM+betaGal groups than in the non-DM group, in the DM+SERCA group, these measurements were restored to non-DM size. The percentages of collagen area in the three DM groups was significantly higher than results shown in non-DM rats, and there were no significant differences in collagen area percentage among the three DM groups. These results suggest that a lowered LV/BW by SERCA2a overexpression is due mainly to reduced size of cardiomyocytes without any changes in collagen area percentage. In conclusion, in DM failing hearts, SERCA2a gene transfer can increase coronary blood flow and reduce cardiomyocyte size without reduction in collagen production.
American Journal of Physiology-Heart and Circulatory Physiology, 2001
We hypothesized that O2 wasting of Ca2+handling in the excitation-contraction coupling in ryanodi... more We hypothesized that O2 wasting of Ca2+handling in the excitation-contraction coupling in ryanodine-treated failing hearts might derive from an increased external Ca2+extrusion via Na+/Ca2+ exchanger and futile Ca2+ cycling via sarcoplasmic reticulum (SR) Ca2+-ATPase. We tested this hypothesis by mechanoenergetic studies using rat left ventricular slices. After the slices were treated with ryanodine (0.1 μM), 1-Hz free shortening significantly decreased by 78–85%, whereas the observed O2consumption (V˙o 2) required for total Ca2+ handling, increased from 0.79 to 1.13 ml O2 · min−1 · 100 g LV−1 (155.6% of control). We reconfirmed that cyclopiazonic acid (10 μM), a blocker of SR Ca2+-ATPase, decreased V˙o 2 by 75–80% in normal slices. However, 100 μM of cyclopiazonic acid was needed to inhibit the V˙o 2 by 80% after ryanodine treatment. Blockade of a sarcolemmal Na+/Ca2+exchanger by KB-R7943 (10 μM) significantly decreasedV˙o 2 by 45% after ryanodine treatment without significant effe...
Under the conditions of both an increased red cell affinity for O(2) at a constant rate of O(2) d... more Under the conditions of both an increased red cell affinity for O(2) at a constant rate of O(2) delivery (arterial O(2) content x flow) and a decrease in the rate of O(2) delivery induced by hypoxic hypoxia at constant blood flow, we have obtained a linear relationship between the partial pressure of O(2) in the muscle venous effluent (P(v,)(O(2))) and O(2) uptake (.V(O(2))). The relationship is described by the equation .V(O(2)) = D(a) x P(v,)(O(2)) + .V(O(2)conv)) where D(a) is the apparent O(2) diffusion capacity and .V(O(2)conv)) is O(2) delivery-limited .V(O(2)), and D(a) x P(v,)(O(2)) represents the O(2) diffusion-limited .V(O(2)) .V(O(2)diff)). From these observations, we propose the hypothesis that .V(O(2)) consists of two additive values, .V(O(2)conv)) and .V(O(2)diff)). The mechanism underlying the reduction in .V(O(2)) that is induced by reducing O(2) delivery to markedly below the .V(O(2)conv)) value has only been investigated using a model based on the single compartment of diffusion-limited .V(O(2)), and has not been investigated in terms of this additive .V(O(2)) model. The single compartment analysis appears to overestimate the role of O(2) diffusion in limiting the reduction of .V(O(2)) that occurs in response to a decrease in O(2) diffusion capacity, as reflected by the .V(O(2))/P(v,)(O(2)) ratio. To gain better insight into the mechanism involved, we altered the rate of O(2) delivery by changing arterial P(O(2)) from normoxia (with inhalation of air) to hypoxia (by inhalation of 10-11 % O(2)) and blood flow (with high and low flow rates (n = 7 for both groups), and very low and ischaemic flow rates (n = 4 for both groups)) in pump-perfused dog gastrocnemius preparations during tetanic isometric contractions at 1 Hz. As rates of O(2) delivery were reduced from 23.2 to 10.9 ml min(-1) (100 g)(-1), significant decreases in P(v,)(O(2)) and .V(O(2)) were observed (P < 0.05). From the data of P(v,)(O(2)) and .V(O(2)) values within this range of O(2) delivery rates, we obtained the regression equation .V(O(2)) = 0.22 x P(v,)(O(2)) + 8.14 (r = 0.58). From the equation, the intercept of the .V(O(2))-axis was significantly different from zero (P < 0.05), in accordance with the observation that the .V(O(2)) /P(v,)(O(2)) ratio (ml min(-1) (100 g)(-1) Torr(-1)) increased from 0.54 to 1.35 (P < 0.05). However, at extremely low rates of O(2) delivery (5.6 and 7.3 ml min(-1) (100 g)(-1) the .V(O(2))/P(v,)(O(2)) ratio was 1.51 and 2.80 (P < 0.05), respectively. This indicates a break in the linear .V(O(2))-P(v,)(O(2)) relationship as the rate of O(2) delivery was reduced to below the .V(O(2)conv)) value of the .V(O(2))-axis intercept. These results suggest that the reduction in .V(O(2)) caused by extreme reductions in the rate of O(2) delivery is not attributable to a reduction in O(2) diffusion capacity, as expected from the .V(O(2))/P(v,)(O(2)) ratio, but to a reduction in the O(2) delivery-limited .V(O(2)) component, as evaluated by the .V(O(2))-axis intercept of the linear .V(O(2))-P(v,)(O(2)) relationship.
Journal of Molecular and Cellular Cardiology, 2007
The aim of this study was to examine whether short-and long-term gene transfer of Ca 2+ handling ... more The aim of this study was to examine whether short-and long-term gene transfer of Ca 2+ handling proteins restore left ventricular (LV) mechanoenergetics in aortic banding-induced failing hearts. Aortic banded rats received recombinant adenoviruses carrying sarcoplasmic reticulum Ca 2+-ATPase (SERCA2a) (Banding+SERCA), parvalbumin (Banding+Parv) or β-galactosidase (Banding +βgal), or an adeno-associated virus carrying SERCA2a (Banding+AAV.SERCA) by a catheterbased technique. LV mechanoenergetic function was measured in cross-circulated hearts. "Banding", "Banding+βgal" and "Banding+saline" groups showed lower end-systolic pressure at 0.1 ml intraballoon water (ESP 0.1), higher end-diastolic pressure at 0.1 ml intraballoon water (EDP 0.1) and slower LV relaxation rate, compared with "Normal" and "Sham". However, "Banding+SERCA" and "Banding+Parv" showed high ESP 0.1 , low EDP 0.1 , and fast LV relaxation rate. In "Banding", "Banding+βgal" and "Banding+saline", slope of relation between cardiac oxygen consumption and systolic pressure-volume area, O 2 cost of total mechanical energy, was twice higher than normal value, whereas slope in "Baning+SERCA" and "Banding+Parv" was similar to normal value. Furthermore, O 2 cost of LV contractility in the 3 control banding groups was ∼3 times higher than normal value, whereas O 2 cost of contractility in "Banding+SERCA", "Banding+AAV.SERCA" and "Banding+Parv" was as low as normal value. Thus, high O 2 osts of total mechanical energy and of LV contractility in failing hearts indicate energy wasting both in chemomechanical energy transduction and in calcium handling. Improved calcium handling by both short-and long-term overexpression of SERCA2a and parvalbumin transforms the inefficient energy utilization into a
American Journal of Physiology-Heart and Circulatory Physiology, 2001
The aim of the present study was to examine the mechanisms of Ca2+ overload-induced contractile d... more The aim of the present study was to examine the mechanisms of Ca2+ overload-induced contractile dysfunction in rat hearts independent of ischemia and acidosis. Experiments were performed on 30 excised cross-circulated rat heart preparations. After hearts were exposed to high Ca2+, there was a contractile failure associated with a parallel downward shift of the linear relation between myocardial O2 consumption per beat and systolic pressure-volume area (index of a total mechanical energy per beat) in left ventricles from all seven hearts that underwent the protocol. This result suggested a decrease in O2consumption for total Ca2+ handling in excitation-contraction coupling. In the hearts that underwent the high Ca2+ protocol and had contractile failure, we found marked proteolysis of a cytoskeleton protein, α-fodrin, whereas other proteins were unaffected. A calpain inhibitor suppressed the contractile failure by high Ca2+, the decrease in O2 consumption for total Ca2+ handling, and ...
Clinical and Experimental Pharmacology and Physiology, 1999
1. It has previously been shown that perfusion with high O2-affinity-erythrocytes decreases venou... more 1. It has previously been shown that perfusion with high O2-affinity-erythrocytes decreases venous PO2 (PVO2) and decreases O2 uptake (VO2) in contracting muscle at the same O2 delivery (arterial O2 concentration x flow). A linear VO2-PVO2 relationship has been obtained with a VO2-axis intercept, suggesting that, during this type of hypoxia, VO2 is composed of a PVO2-dependent and -independent VO2. However, the VO2-PVO2 relation during hypoxic hypoxia has not been examined. 2. To clarify this relation, PVO2 and VO2 have been measured in contracting gastrocnemius (1 Hz trains of 0.2 s isometric tetani) under both normoxic and hypoxic conditions during 5 min of stimulation. 3. Venous O2 changes proportionally with O2 delivery. Each VO2-PVO2 relation was linear, with the mean described by the equation VO2 = 5.06 + 0.41 x PVO2 (n = 6, r = 0.81, P < 0.05). The VO2-axis intercept was significantly different from zero (P < 0.05). 4. These results were similar to those obtained during hypoxia induced by high O2-affinity-erythrocytes. We conclude that there is a linear relationship between PVO2 and VO2 above the VO2-axis intercept, regardless of the type of hypoxia.
We have examined whether mouse plasma erythropoietin (EPO) can be measured by an improved enzyme-... more We have examined whether mouse plasma erythropoietin (EPO) can be measured by an improved enzyme-linked immunosorbent assay (ELISA) using milk proteins (Block Ace) both as a blocking reagent and as a diluent for standard recombinant human EPO (rHuEPO) and for plasma samples. Block Ace brought about high slope sensitivity of the standard curve, with a low background. The dose-response curves of normal or anaemic mouse plasma and of rHuEPO were linear and parallel to each other. The anaemic plasma had an additive effect with rHuEPO by increasing the absorbance at 405 nm. The coefficients of variation in the intra-and interassays ranged from 4.2% to 15.3%. The plasma EPO levels in 22 normal mice were 18.3 ___ 10.3 mU/ml. An inverse relationship between the logarithm of plasma EPO concentrations and blood haemoglobin concentrations, red blood cell counts or packed cell volumes was found in normal mice and in mice with iron deficiency anaemia (IDA). These results show the validity for the use of the new improved ELISA method for measuring circulating murine EPO.
... In agreement with an observation on rats with IDA (McCall et al. 1962), reticulocytosis durin... more ... In agreement with an observation on rats with IDA (McCall et al. 1962), reticulocytosis during the development of IDA was enhanced depending on the severity of anaemia or the plasma EPO levels (Fig. ... Br J Haematol 38:291-294 Jansson LT, Perkki6 MV, Clemons Get al. ...
It is still uncertain that hyperoxia affects muscle oxygen consumption (VO 2) during repetitive c... more It is still uncertain that hyperoxia affects muscle oxygen consumption (VO 2) during repetitive contractions [1]. There is both theoretical and experimental support for the idea that all precapillary O 2 losses, i.e., a longitudinal decrease in arteriolar oxygen tension (PO 2), an arteriovenous diffusion shunt, and diffusive exchange between arterioles and capillaries contribute significantly to limitations on O 2 extraction in the resting muscle [2]. Furthermore, O 2-diffusion shunt as an ineffective O 2 supply may affect VO 2 in tetanically contracting muscle during hyperoxia. We examined the influence of hyperoxia on VO 2 and peripheral O 2 exchange during repetitive tetanic contractions with the canine gastrocnemius muscle group. Possible mechanisms for limiting VO 2 by increasing PaO 2 have been discussed in relation to peripheral O 2 diffusion limitation for muscle VO 2 [3-8] using both muscle venous effluent PO 2 (PvO 2), reflecting O 2 driving force of diffusion from erythrocyte to mitochondria, and VO 2 /PvO 2 ratio, reflecting O 2 diffusion conductance [9, 10]. Methods Eight mongrel dogs (mean weight 13.2Ϯ0.9 kg) were anesthetized with pentobarbital sodium (I.P., 30 mg/kg). The animals were ventilated by a respirator
The Otsuka-Long-Evans Tokushima Fatty rat represents a model for spontaneous non-insulindependent... more The Otsuka-Long-Evans Tokushima Fatty rat represents a model for spontaneous non-insulindependent type II diabetes mellitus (DM), characterized by diastolic dysfunction and associated with abnormal calcium handling and decrease in sarcoplasmic reticulum Ca 2+ -ATPase (SERCA2a) expression. The aim of this study was to examine whether SERCA2a gene transfer can restore the energetic deficiency and left ventricular (LV) function in this model. DM rats were randomized to receive adenovirus carrying either the SERCA2a gene (DM + Ad.SERCA2a) or the B-galactosidase gene (DM + Ad.BGal) or saline (DM + saline). LV mechanoenergetic function was measured in crosscirculated heart preparations 3 days after infection. In DM, end-systolic pressure at 0.1 ml intraballoon water (ESP 0.1 ) was low and end-diastolic pressure at 0.1 ml intraballoon water (EDP 0.1 ) was high (22 mm Hg), compared with non-DM (EDP 0.1 12 mm Hg). In DM + Ad.SERCA2a, however, ESP 0.1 was increased over 200 mm Hg and EDP 0.1 was decreased to 7 mm Hg. LV relaxation rate was fast in DM + Ad.SERCA2a, but slow in the other DM groups. There was no difference in relation between cardiac oxygen consumption per beat and systolic pressure-volume area among all groups. Finally, the oxygen cost of LV contractility in DM was about three times as high as that of normal. In DM + Ad.SERCA2a, the oxygen cost decreased to control levels, but in DM + Ad.BGal/DM + saline it remained high. In DM failing hearts, the high oxygen cost indicates energy wasting, which contributes to the contractile dysfunction observed in diabetic cardiomyopathy. SERCA2a gene transfer transforms this inefficient energy utilization into a more efficient state and restores systolic and diastolic function to normal.
The plasma concentrations of both immunoreactive erythropoietin (EPO) and lactate were determined... more The plasma concentrations of both immunoreactive erythropoietin (EPO) and lactate were determined in four healthy untrained subjects at sea level and on the 2nd or 3rd day at altitudes (1,300 and 3,500 m). The mean plasma EPO (18.8 +/- 1.6 mU/ml at sea level) increased significantly on the 3rd day at 1,300 m (25.5 +/- 2.0 mU/ml, p < 0. 05) and showed an almost three-fold increase on the 2nd day at 3,500 m (53.5 +/- 3.7 mU/ml, p < 0.001). Likewise, the mean plasma lactate at 3,500 m (3.98 +/- 0.27 mmol/l) was 3.6 times as high as that at sea level (1.11 +/- 0.05 mmol/l) (p < 0.001). The plasma EPO concentrations were found to correlate well with the lactate concentrations at sea level and altitudes (r = 0.86, p < 0.01). These results are consistent with the well-known EPO/lactate response to altitudes and suggest that the circulating EPO concentration as well as blood lactate concentration can be used as an index of anaerobic condition.
The different response of O2 uptake (VO2) of resting skeletal muscle to the changes in blood flow... more The different response of O2 uptake (VO2) of resting skeletal muscle to the changes in blood flow has been thought to reflect a species difference. To scrutinize this notion, we investigated the relation between O2 delivery (arterial O2 content multiplied by blood flow) and VO2 in isolated dog gracilis muscle perfused solely with normal hematocrit (Ht) blood (n = 9), or alternately with normal and low Ht blood (n = 6), or alternately with normal and high Ht blood (n = 3) at varying perfusion rates. Eleven out of the 18 preparations showed an autoregulation of blood flow, and the others did not. But, in all preparations, the VO2 was delivery-independent above a critical O2 delivery (0.45 ml/(min.100 g muscle)) and showed the constant VO2 of 0.30 ml/(min.100 g), while below the critical level it turned out to be delivery-dependent. The maximal extraction ratio was 0.67. The same relationship was found with the low and high Ht perfusion. The pattern observed in dog gracilis muscle was essentially the same as that in rat gracilis muscle (KOLAR and JANSKY, 1984).
The aim of the present study was to clarify the effects of O2 diffusion limitation resulting from... more The aim of the present study was to clarify the effects of O2 diffusion limitation resulting from hypoxic interventions on O2 uptake (V.O2) in unloaded (that is, near-zero initial force) and loaded skeletal muscle in a high-frequency stimulation. We measured V.O2, muscle venous PO2 (PvO2) and initial force in gastrocnemius-plantaris muscle in situ of anesthetized dogs: (1) during hypoxic hypoxia at 1 Hz tetanic stimulation, and (2) during hypoxia induced by the perfusion with high O2-affinity erythrocytes (having a low value of PO2 at 50% saturation of hemoglobin (P50)) at 4 Hz twitch stimulation. Averaged unloaded V.O2 during normoxia was 10.2 ml.min-1.100 g-1 at averaged blood flow of 74 ml.min-1.100 g-1 (n = 6). Hypoxic hypoxia of a decreased O2 delivery (arterial O2 concentration x flow) significantly decreased both unloaded and loaded V.O2 with a decrease in PvO2 (p<0.05). The unloaded V.O2 was reduced to 8.5 ml.min-1.100 g-1. Low P50-hypoxia decreased V.O2 at high and low initial force conditions with a decrease in PvO2 (p<0.05) at the same O2 delivery. If these decreases in V.O2 correspond with a decrease in V.O2 at zero initial force (unloaded V.O2), the unloaded V.O2 value is calculated to be 7.57 ml.min-1.100 g-1 from V. O2-initial force data. Despite the different conditions of O2 delivery, the unloaded V.O2 decreased by both hypoxia showed similar values. Thus the decreased unloaded V.O2 does not seem to be derived from only the limited O2 delivery. Some other factors such as the limitation of O2 diffusion may contribute to the decreased V.O2.
A nutritional survey was carried out among residents (39 males and 46 females) of Dzong village i... more A nutritional survey was carried out among residents (39 males and 46 females) of Dzong village in the northern area of the Gandaki region of Nepal. The results were compared with our previous findings. The mean body mass index value was under 21 for both sexes, but the mean percentage of body fat of females (17-19 years old, 25.8 +/- 9.4%; 20-29 years old, 31.0 +/- 8.4%) was higher than that of males (17-19 years old, 12.0 +/- 1.0%; 50-59 years old, 24.4 +/- 7.6%). Most serum nutritional markers for both sexes were generally at normal levels although the iron levels were lower and packed red cell volume levels were higher than normal. As determined by results of the 24-hr dietary recall survey, the main food groups consumed by both sexes were cereals, potatoes, pulses, meats and vegetables. The mean daily intake of nutrients was similar for both sexes, with a few exceptions. The relatively high serum TG levels of the subjects may have been due to the high consumption of carbohydrate-laden cereals. The amounts of food consumed were not adequate, resulting in a latent and chronic deficiency of nutrients, especially calcium and iron. These results suggest that improvements in the nutritional status of this group of people are necessary.
The Otsuka Long-Evans Tokushima fatty rat is an animal model of Type 2 diabetes mellitus (DM), wh... more The Otsuka Long-Evans Tokushima fatty rat is an animal model of Type 2 diabetes mellitus (DM), which is characterized by diastolic dysfunction associated with decreased sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a). The aim of this study was to examine whether gene transfer of SERCA2a can influence coronary blood flow and cardiomyocyte diameter in this model. DM rats were injected with adenovirus carrying SERCA2a (DM+SERCA) or beta-galactosidase gene (DM+betaGal). Coronary blood flow was measured in cross-circulated excised hearts 3 days after infection. Although in all groups coronary blood flow remained unchanged even if left ventricular (LV) volume or intracoronary Ca(2+) infusion was increased, the DM+SERCA group showed a sustained increase in coronary blood flow compared with the other groups. This result suggests that the sustained high coronary blood flow is a specific response in SERCA2a-overexpressed hearts. Although the LV weight-to-body weight ratio (LV/BW) and cardiomyocyte diameter were higher in the DM and DM+betaGal groups than in the non-DM group, in the DM+SERCA group, these measurements were restored to non-DM size. The percentages of collagen area in the three DM groups was significantly higher than results shown in non-DM rats, and there were no significant differences in collagen area percentage among the three DM groups. These results suggest that a lowered LV/BW by SERCA2a overexpression is due mainly to reduced size of cardiomyocytes without any changes in collagen area percentage. In conclusion, in DM failing hearts, SERCA2a gene transfer can increase coronary blood flow and reduce cardiomyocyte size without reduction in collagen production.
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Papers by S. Sakata