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Biomedical subjects

H Tazawa

Publications and source records attributed to H Tazawa.

At least 109 records · Page 6Linked to original sources
PubMed1985

Variability of shell conductance and gas exchange of chicken eggs.

In 395 fertilized chicken eggs (strain Warren) obtained from a commercial hatchery the following coefficients of variation (SD/mean) were found: egg shell conductance for water vapor, GH2O, 22%; freshly laid egg weight, W, 8%; the specific conductance, gH2O (= GH2O/W), 22%. In 20 eggs selected for widely varying gH2O (range 57%-195% of the mean, 0.246 mg/(day X torr X g), the specific O2 uptake and the CO2 output, measured on days 16-19 of incubation, showed a maximum at medium gH2O values, decreasing at both lower and higher gH2O. The variations of gH2O in the selected eggs were shown to cause a variation of water loss up to hatching from 9 to 26% (average 15%), and a variation of the O2 tension from 84 to 123 torr, and of the CO2 tension from 18 to 54 torr, in the perichorioallantoic air space on days 16-19 of incubation. Mechanisms responsible for the observed changes in the metabolic rate and for the physiological adjustments to varied egg shell conductance are discussed.

Animals↗
PubMed1985

Direct measurement of allantoic blood flow in the chicken, Gallus domesticus. Responses to alteration in ambient temperature and PO2.

A technique is described for direct measurement of allantoic blood flow in chicken embryos in situ using an electromagnetic flow meter. A branch of the allantoic artery was catheterized non-obstructively for simultaneous pressure measurement. In 15-day-old embryos at 39 degrees C the mean heart rate was 278 beats/min falling to 124 beats/min at 26 degrees C. Despite this fall in heart rate, blood flow fell only 10% from 4.4 ml/min at 39 degrees C to 4.0 ml/min at 26 degrees C. Mean allantoic blood pressure was similarly nearly unaffected by temperature. Allantoic blood flow was insignificantly altered by hyperoxic as well as hypoxic exposure (6% O2).

Allantois↗
PubMed1984

Carbon dioxide dissociation and buffering in chicken blood during development.

Carbon dioxide dissociation curves of oxygenated and deoxygenated bloods, the Haldane effect, the buffer value and other blood and true plasma buffering indices, O2 capacity and hematocrit were determined in bloods withdrawn from chicks before, during and after hatching and 8-month-old hens. Blood CO2 dissociation curves shifted upwards in the developing embryo till pipping, and moved downwards after pipping and hatching. In accordance with the position of the CO2 dissociation curves, the true plasma bicarbonate and red cell CO2 standardized to PCO2 = 40 torr changed. The Haldane factor at standard PCO2 increased from 0.12-0.13 on days 10-14 of incubation to 0.34 in young hens. The buffering power changed in parallel with O2 capacity and hematocrit, increasing steadily during incubation, dropping at hatching and then increasing again to the adult value. The observed changes in the CO2 dissociation curves and buffering variables during the development enable the chick to minimize the changes in the acid-base status and are favorable for coping with the increasing demand for CO2 transport and buffering of the developing bird.

Acid-Base Equilibrium↗
PubMed1983

Blood gases and acid-base status in chicken embryos with naturally varying egg shell conductance.

In chicken eggs selected for widely varying values of specific water vapor conductance, gH2O (= water vapor conductance per freshly laid egg mass), PCO2, pH, PO2 and hematocrit were measured in arterialized blood sampled from an allantoic vein (after 16 days of incubation) or in blood termed 'venous', sampled from an allantoic artery (after 18 days of incubation). Both arterialized and 'venous' PCO2 were inversely related to gH2O. Since the variations of blood plasma pH with PCO2 were smaller than predicted for true plasma, partial compensation by appropriate non-respiratory changes of plasma bicarbonate concentration must have occurred. Only with extremely high and low gH2O a definite alkalosis and acidosis, respectively, were observed. Both arterialized and 'venous' PO2 tended to diminish with decreasing gH2O. The hematocrit value showed a tendency to increase with decreasing gH2O and with decreasing arterialized PO2.

Acid-Base Equilibrium↗
PubMed1983

Gas exchange, blood gases and acid-base status in the chick before, during and after hatching.

To study the transition from chorioallantoic to pulmonary gas exchange in birds, blood gases and acid--base variables were measured in chicks of domestic fowl before, during and after hatching. Measurements were made in samples of 'venous' blood (from allantoic arteries or the right ventricle, respectively) entering the gas exchanger (chorioallantois or lungs, respectively) and arterialized blood (from allantoic veins or the left ventricle, respectively) leaving the gas exchanger. Also, O2 uptake was measured and blood flow of the gas exchanger was determined according to the Fick principle. During the last days of incubation PO2 decreased PCO2 increased in both arterialized and 'venous' blood, but the changes of pH were small due to a concomitant increase in bicarbonate concentration, in accordance with the results of previous studies. After external pipping and hatching pronounced hypocapnia developed, but the respiratory alkalosis was partiallY compensated by a transitory non-respiratory reduction of bicarbonate. In spite of arterial hypoxia at the end of incubation and some loss of blood during hatching, blood O2 transport was not seriously impaired during pipping and hatching as revealed by 'venous' blood gases. The blood gases and pH of 17-day-old chicks were close to those of adult chickens.

Acid-Base Equilibrium↗
PubMed1983

Derivation of theoretical equations of the CO2 dissociation curve and the carbamate fraction in the Haldane effect.

The simultaneous Henderson-Hasselbalch equations in plasma and red cell were solved in order to obtain the CO2 dissociation curve of oxygenated blood. In order to solve the above two equations the following equation was added, in which the relationship between the intracellular (delta pHC) and the extracellular pH change (delta pHP) was defined as follows: pHC = (1 + sigma) delta pHP, where 1 + sigma is a factor to be determined from experimental data on Donnan's ratio for H+. From the solution, the ratio of bicarbonate shift to the CO2 quantity released out of or combined with hemoglobin was calculated. The solution was validated by comparing the above ratio between the theoretical and experimental data. The CO2 contents calculated at 12 Torr in whole blood, red cell, and plasma compartments show good agreement with the respective analyzed values. When the buffer values of hemoglobin and plasma buffer protein were 70.0 and 7.5 mmol/(liter plasma X pH), respectively, sigma = -0.21 + 0.05 X delta pHP, and the Donnan's ratio for HCO3- was assumed to be 0.7 at pH = 7.33, the theoretical CO2 dissociation curve fitted well with the experimental curve. The CO2 dissociation curve of deoxygenated blood was expressed by adding the measured Haldane effect to the CO2 content of oxygenated blood. This additive characteristic in turn made it possible to estimate carbamate contribution in the Haldane effect.

Carbamates↗
PubMed1983

Quantitative analyses of the CO2 dissociation curve of oxygenated blood and the Haldane effect in human blood.

The theoretical equations for the CO2 dissociation curve derived by MOCHIZUKI et al. (1983) have made it possible to estimate the CO2 contents in blood at any PCO2 by putting the intra- and extracellular bicarbonate contents at a certain PCO2 into them. Moreover, according to their Haldane effect equation, the carbamate and bicarbonate contributions are evaluated, when the Haldane effect and its plasma component are known along the PCO2 range. In order to accomplish the above calculation the water shifts due to the PCO2 and O2 saturation changes were measured as the changes of hematocrit. The hematocrit of oxygenated blood was linearly correlated to pH with a factor of -0.037, and the difference in hematocrit between oxygenated and deoxygenated bloods was 0.004 in terms of fractional hematocrit. The blood and plasma CO2 contents measured at four different PCO2's were compared with the ones calculated by use of the intra- and extracellular bicarbonate contents at 42 Torr PCO2. The measured and calculated CO2 contents coincided fairly well with each other. Using intra- and extracellular bicarbonate contents in oxygenated blood together with the Haldane effect and its plasma component, the carbamate contribution was then calculated. The carbamate content was about 1.2 mmol/liter blood over a PCO2 range of 20 to 100 Torr, and its ratio to the total Haldane effect decreased from 50 to 40%, as PCO2 was increased. The ratio of the bicarbonate shift to the total bicarbonate change due to the Haldane effect, ranging from 0.82 to 0.66, was significantly greater than that measured by changing PCO2.

Carbamates↗
PubMed1982

Regulatory processes of metabolic and respiratory acid-base disturbances in embryos.

First, preliminary experiments were designed in the 16-day-old individual chick embryo to elucidate the effect of electrolyte infusion and blood samplings on hemodilution, which might influence the acid-base balance. Three kinds of hemodilution were observed: 1) hemodilution caused by four repetitive samplings, which had no influence on acid-base balance; 2) hypervolumic hemodilution caused by infusion of solution whose volume equaled about 5-6% of total blood volume, which induced dilution acidosis; and 3) hypertonic hemodilution caused by hypertonic electrolyte infusion, which also induced dilution acidosis. The embryo recovered from the hypertonic dilution acidosis in 6 h after infusion, but it did not recover from hypervolumic acidosis. Second, the time course of changes in metabolic and respiratory acid-base disturbances was studied in the individual embryo. Metabolic acid-base disturbances made by hypertonic NaHCO3 infusion were restored to control state in 6 h. Respiratory acid-base disturbances were also regulated in terms of changes in plasma[HCO-3] and pH. The renal function and redistribution of HCO-3 may in part be responsible for the regulation.

Acid-Base Equilibrium↗
PubMed1982

Mathematical formulation of CO2 dissociation curve and buffer line of human blood at rest.

The CO2 content and pH of tonometered blood were measured in nine healthy subjects. The CO2 content in the whole blood (Cb) was found to be expressed by an exponential function of PCO2 including only one parameter (B) as follows: Cb = 1.15 . B-2.548 . PBCO2. The B value was specific to the sampled blood and ranged from 0.4 to 0.45 in the deoxygenated and from 0.45 to 0.52 in the oxygenated blood. The relationship between pH and log PCO2 was also expressed by using one characteristic parameter (D) as follows: for the deoxygenated blood, log PCO2 = 2.144-D . (pH-7.045), and for the oxygenated blood, log PCO2 = 2.037-D . (pH-7.085). The D values were in a range of 1.38 to 1.58. The linear relation between log [HCO3-] and pH was also expressed by using only one parameter. Next, between Cb and [HCO3-] obtained at the same PCO2 of 40 mmHg, a high correlation was observed: the regression line was given, independently of O2 saturation, by Cb40 = 1.942 . [HCO3-]40-3.193, where [HCO3-] was expressed in mM. Using the above equations, it was possible to evaluate the approximate B and D values from a pair of pH and PCO2 measurements and subsequently to depict the CO2 dissociation curve as well as the buffer line in the true plasma.

Adult↗
PubMed1981

Changes in acid-base balance of chick embryos exposed to a He or SF6 atmosphere.

On day 16 of the chick embryo, a catheter was implanted in the allantoic vein carrying arterialized blood, and a syringe was attached to the blunt end of the shell connecting to the air cell. This technique allowed for repetitive sampling and analysis of air cell gas and arterialized blood when these eggs were exposed to a He-O2 or SF6-O2 atmosphere. Exposure to He-O2 reduced the arterial CO2 tension(PaCO2) from 36 to 17 Torr and increased pH by 0.17 units; exposure to SF6-O2 increased PaCO2 from 37 to 62 Torr and reduced the pH by 0.14 units. These responses were brought about by changes in the gas conductance of the shell, resulting in a diffusive hypocapnia and respiratory alkalosis in He-O2 and a diffusive hypercapnia and respiratory acidosis in SF6-O2. During a 4-h exposure to these foreign gases the observed pH changes were smaller than predicted because of marked shifts of HCO3- into the blood (SF6-O2) or out of the blood (He-O2).

Acid-Base Equilibrium↗