Search PubMed⌕ Search

Biomedical subjects

T Kawashiro

Publications and source records attributed to T Kawashiro.

At least 109 records · Page 6Linked to original sources
PubMed1976

Measurement of Krogh's diffusion constant of CO2 in respiring muscle at various CO2 levels: evidence for facilitated diffusion.

Krogh's diffusion constant for CO2, KCO2, was determined in respiring muscle tissue at various levels of tissue PCO2, between 10 and 160 torr, using a technique described previously (Kawashiro et atl, 1975). With increasing mean tissue PCO2, KCO2 declined towards an apparently asymptotic value. The relationship between KCO2 (10(-9) mmol-cm(-1)-min(-1)-tor(-1)) and PCO2 (torr) at 37 degrees C could be approximated by the equation KCO2 = 17.3 [1 + 1.72 - exp(--0.027 - PCO2)]-At PCO2 = 0 torr KCO2 exceeded the asymptotic value, which was virtually attained at PCO2 = 100 torr, by more than a factor of two. Thus CO2 diffusion in muscle appears to be facilitated in the low PCO2 range. Specific CO2 production rate of tissue, which was determined simultaneously, did not vary with CO2 in the PCO2 range studied. Effects of facilitated CO2 transport on CO2 exchange in muscle are assessd using simple models. In the presence of CO2 facilitation muscle PCO2 is reduced, particularly during exercise.

Animals↗
PubMed1976

Problems in determination of oxygen dissociation of avian blood.

No appreciable errors are expected in determination of blood gas values and pH using classical techniques provided time of anaerobic storage is kept small and is, if unavoidable performed on ice. In particular, dissociation curves may safely be analyzed with the Van Slyke technique which is in disagreement with the conclusions of Lutz et al. (1973). For measurement of PO2 and PCO2, delay time is mainly dictated by response time of the electrodes; measurements may have to be corrected for metabolism, particularly in high PO2 range.

Animals↗
PubMed1976

Measurement of diffusivity and metabolic rate of O2 and CO2 in respiring tissue.

The method described is apt to measure, at the same time, Krogh's diffusion constant and specific metabolic rates for O2 and CO2 in intact, respiring tissues. Due to metabolism tissue thickness for this method is limited to about 500 mum unless hyperbaric conditions are used. The results suggest that both KO2 and KCO2 are similar in alive and in dead tissue. Due to tissue inhomogeneity and to possible facilitation of O2 or CO2 transport our values of K have to be considered as effective mean values for the physiological range of PO2 and PCO2 in muscle at rest and at exercise.

Animals↗
PubMed1976

Study of CO2 sensitive vagal afferents in the cat lung.

Single unit activity was recorded in the cat vagus in order to detect possible receptors firing in response to changing lung CO2 concentration. The cats were ventilated at a high rate (60-120 breaths per min) and inspired CO2 concentration was altered between 0 and 8% in a step-like fashion, each phase consisting of about 10 breaths. Thus the effects of changing intrapulmonary CO2 concentration could be differentiated from the effects of stretch of lung tissue. Activity was recorded in 7 cats from 120 units firing in phase with ventilation. Many receptors showed some CO2 sensitivity, but no fiber was found discharging in response to CO2 exclusively. The results provide no evidence for the occurence of specific CO2 receptors in the feline lung with vagal afferents functionally similar to those reported for the avian lung.

Animals↗
PubMed1975

Solubility of various inert gases in rat skeletal muscle.

For the determination of solubility coefficients, isolated rat abdominal muscles were equilibrated at 37 degrees C with various inert gases saturated with water vapor. After rapid transfer into a closed chamber containing room air the amount of gas extracted from the sample by diffusion was measured by gas chromatography. Corrections for unextracted gas and for gas lost during the transfer of the sample were applied. The following mean values for the solubility coefficients, in mumol-1(-1)-torr(-1), were found: chloro-difluoro-methane (Freon 22), 56.0; acetylene, 55.5; nitrous oxide, 27.7; methane, 2.42; hydrogen, 1.13; helium, 0.608; sulfur hexafluoride, 0.559. The relationships between solubility in tissue, in water and in olive oil are discussed.

Abdominal Muscles↗
PubMed1975

Diffusivity of various inert gases in rat skeletal muscle.

Krogh's diffusion constant (K) was determined for various inert gases in isolated rat abdominal muscle at 37 degrees C by measuring the amount of gas diffusing per unit time and partial pressure difference through a portion of the muscle of known surface area and thickness. The following mean values for K, in 10(-9) mmol-min-1-cm-1-torr-1, were obtained: C2H2, 42.2; N2O, 20.0; CHClF2, 18.8; H2, 1.67; He, 1.42; CH4, 1.27; SF6, 0.081. From Krogh's diffusion constant, the diffusion coefficient (D) was calculated using the solubility coefficient determined previously in the same preparation. The D values thus obtained were found to be about half the D values in water at 37 degrees C. Model calculations show that for gases with high lipid/water partition coefficient, D in tissues containing lipid is underestimated by this method. Graham's law (inverse proportionality between D and square root of molecular mass) was found to represent a useful approximation for these gases. A better correlation, however, was obtained between D and the molecular diameter.

Abdominal Muscles↗
PubMed1975

Determination of diffusivity of oxygen and carbon dioxide in respiring tissue: results in rat skeletal muscle.

Gas transfer rates for O2 and CO2 through freshly excised respiring rat abdominal muscle were measured. The tissue separated as a thin membrane two chambers, one of which was ventilated with a constant gas mixture. The other chamber was closed and the time course of changes of PO2 and PCO2, initially set at varied levels, was followed by electrodes. A plot of rate of change of PO2 and PCO2 in the closed chamber against the partial pressure difference across the tissue yielded both Krogh's diffusion constant, KO2 and KCO2, and metabolic rate of tissue, i.e. specific O2 consumption and CO2 production, mo2 and mco2. The mean values at 37 degrees C, KO2 = 1.31 x 10(-9) mMol-cm-1-min-1-torr-1 and KCO2 = 28.0 x 10(-9) mMol-cm-1-min-1-torr-1, did not differ significantly from values determined by other authors in various tissue preparations in which metabolism had been suppressed. Average O2 consumption, mo2 = 0.87 mMol-min-1-L-1, was not different from the values obtained in the same tissue by the Warbung manometric method, 0.74 mMol-min-1-L-1. The mean respiratory quotient, calculated as the ratio of mean CO2 production and mean O2 consumption, was 0.85.

Abdominal Muscles↗
PubMed1975

Metabolic changes in avian blood and their effects on determination of blood gases and pH.

Oxygen consumption. MO2 and CO2 production rates, Cco2, of duck blood samples anaerobically stored at 41 degrees C were 0.041 and 0.036 mMol (L blood)minus 1 min minus 1, respectively, and were independent of O2 saturation in the range of 100 to 10% saturation; the resulting metabolic respiratory quotient of blood was 0.88. The pH decreased linearly with time at a rate of 0.0014 unit min minus 1. The lactic acid production rate was independent of Po2, and was about 0.033 MMol L minus 1 min minus 1. Errors were assessed that may be introduced in blood gas analysis when the high metabolic activity of avian blood is not accounted for. Thus the O2 dissociation curve established using the Van Slyke analysis will be shifted to the right; however, the displacement around P50 is only about 1 torr for a time lag of 5 min between sampling and analysis and is even less at higher Po2 values. When using electrodes, P02 will be underestimated and PCO2 overestimated. The magnitude of these errors depends on both delay time and slope of the dissociation curves. It is concluded that the standard blood gas analytical methods are applicable to avian blood, but that in some cases corrections for metabolic effects are neccessary. Any delay between blood sampling and analysis should be kept as short as possible; storage, if neccessary, should be on ice.

Animals↗
PubMed1975

Arterial blood gases in undisturbed resting birds: measurements in chicken and duck.

Arterial blood was sampled in resting, unrestrained and undisturbed birds using a remote-controlled sampling device. With this technique a blood sample of 0.45 ml was obtained for analysis of PO2, PCO2 and pH at the body temperature of the animal. In 5 domestic hens the following mean values were obtained: PA02-82 torr; PACO2=33 torr; pHA=7.52. The average body temperature was TB=41.0 degrees C. In 6 domestic ducks the analysis yielded values of PAO2=82 torr; PACO2=38 torr; pH2=7.49; Tb=41.0 degrees C. Although these values are close to those reported in the literature some discrepancies may be recognized; they can be attributed to respiratory and metabolic changes of blood composition possibly induced by classical sampling procedures.

Animals↗
PubMed1975

Oxygen and carbon dioxide dissociation of duck blood.

Oxygen and CO2 dissociation of duck blood was studied in blood samples equilibrated with known gas mixtures at the bird's body temperature (41 degrees C) and analyzed in the Van Slyke manometric apparatus and in pH electrodes. At various pH values between 7.38 and 7.55 the Hill plots yielded straight and parallel lines over a wide range of O2 saturation, the Hill coefficient being 2.9. Half saturation pressure P50 at pH = 7.50 was 36 torr. The Bohr effect factor was -0.53. Buffering properties were analyzed by equilibrating blood samples with gas mixtures of different PCO2 at 41 degrees C. The buffer value for whole blood in the range of 3-7% CO2 was 19.3 mMol-L-1-pH-1, the buffer value for true plasma 22.9 mMol-L-1-pH-1. The CO2 dissociation curve constructed using the buffer values had a slope of 0.17 mMol-L-1-torr-1 in the PCO2 range from 40 to 50 torr. The CO2 content of oxygenated blood at PCO2 = 40 torr was 21.7 mMol-L-1. The Haldane effect factor at PCO2 = 35 torr equalled 0.30 mMol of combined CO2 per mMol HbO2. With the values of PO2, PCO2 and pH measured in arterial blood of undisturbed and unrestrained, resting ducks effective dissociation curves for both O2 and CO2 were constructed assuming a metabolic R.Q. of 0.8. These curves are expected to resemble closely the actual in vitro dissociation curves of resting ducks.

Animals↗