The analysis of PO2 difference between air space and arterialized blood in chicken eggs with respect to widely altered shell conductance

The gas exchange of chicken eggs takes place by molecular diffusion. The diffusion barrier between ambient atmosphere and erythrocyte hemoglobin of the gas exchanger (the vascularized chorioallantoic membrane) is conveniently divided into two parts by the air space in the fibrous shell membranes; i.e., the outer barrier (mainly the porous eggshell) and the inner barrier (the chorioallantoic membrane and the chemical reaction with hemoglobin). In contrast to the alveolar-arterial Po2 difference in vertebrate lungs, the difference of Po2 between the air space and the arterialized blood in the allantoic vein (delta PAo2.Pao2) is large in chick embryos. The present study analyzed the delta PAo2.Pao2 in relation to the diffusing capacity of the chorioallantoic membrane (inner barrier) and physiological shunt in the allantoic circulation with respect to widely altered diffusive conductance of the shell (outer barrier). The shell diffusive conductance (Go2) was altered of the beginning of incubation, and the O2 consumption (Mo2) was measured on day 16. The Mo2 increased hyperbolically with increasing Go2, reached a maximum at control values of Go2 and decreased with further increases in Go2. From Go2 and Mo2, the air space Po2 was determined. The delta PAo2.Pao2 was increased in eggs with augmented Go2 (from about 50 torr in control eggs to 70 torr in conductance-increased eggs). The diffusing capacity and allantoic shunt which produce a given delta PAo2.Pao2 were estimated employing a microcomputer performing the Bohr integration procedure so that a calculated Pao2 agreed with the measured Pao2. The allantoic shunt is not more than 20%; 10% is likely. The diffusing capacity becomes maximum in intact control eggs and is decreased at both lowered and augmented Go2. At lowered Go2, diffusion limitation is responsible for about 90% of delta Pao2.Pao2 even in the presence of a 10% shunt. The diffusion limitation to blood oxygenation decreases as Go2 increases, but it is still predominant at augmented Go2. In control eggs, the resistance of the inner barrier to O2 diffusion is about 1.7-fold that of the shell (outer barrier) which agrees with the previous reports.

Cooling rates of living and killed chicken and quail eggs in air and in helium-oxygen gas mixture

1. In a helium atmosphere, heat is dissipated from a surface 3.5 times faster than it is in air. Eggs in a helium-oxygen atmosphere cool only 1.4 times faster than they cool in air. This signifies that internal resistance to heat flow is a significant factor in the cooling rates of eggs. 2. Heat flow occurs inside an egg in two ways: by conduction through the tissues and in flowing blood. Killing an embryo stops the latter, but not the former. Eggs cool more slowly after they have been killed, signifying that blood flow can be an important component in an egg's internal flows of heat. 3. Blood flow should be a relatively more important component of heat flow in large eggs than in small eggs. The difference in conductance between living and killed eggs is larger in 60 g chicken eggs than it is in 10 g quail eggs.

[Clinical study of cefotetan in complicated urinary tract infections]

Clinical effectiveness and safety of Cefotetan were evaluated in 28 patients with complicated urinary tract infections. The results were excellent in 12 patients (42.9%), moderate in 10 patients (35.7%) and poor in 6 patients (21.6%), and the effectiveness rate was 78.6%. Bacteriologically, 24 (75%) out of 32 strains were eradicated. Subjective side effects, nausea and abdominal discomfort, were observed in one patient. Abnormal laboratory findings were observed in 6 patients, eosinophilia in 3 patients and slight elevation of transaminase in 3 patients.

A case of recurrent malignant pheochromocytoma complicated by watery diarrhea, hypokalemia, achlorhydria syndrome

A patient is reported who had undergone right adrenalectomy for pheochromocytoma and 15 yr later developed a recurrence in the same site complicated by the watery diarrhea, hypokalemia, achlorhydria syndrome. This tumor was histologically defined as a composite malignant pheochromocytoma-ganglioneuroblastoma (well differentiated type). Vasoactive intestinal polypeptide and catecholamine concentrations were elevated in both plasma and the tumor. The tumor somatostatin content also was high. The tumor was immunohistochemically determined to contain both vasoactive intestinal polypeptide and somatostatin.

Comparative model analysis of central shunts in vertebrate cardiovascular systems

The incomplete double circulation of air-breathing fishes and lungfishes, amphibians, reptiles and embryonic birds and mammals has been analyzed using a simplified mode comprising the intra- and extracardiac shunts and compartments for the gas exchange (gills, lungs, skin, etc.) as well as systemic tissue gas exchange. The intracardiac shunting is defined and given common symbols for all species of animals analyzed. Two types of equations, fluid-flow and mass-flow equations, are derived for each model, which are solved to give shunting rate as a function of blood O2 content of the principal cardiac compartments and vessels. The model analysis not only offers possibility for an overall average evaluation of central shunts, but also suggests which blood samples must be determined for evaluation of the shunt patterns.

The problems of digitalis therapy from the viewpoint of serum concentration with special reference to the sampling time, to the overlapping range of serum concentration where intoxicated and non-intoxicated patients are located and to atrial fibrillation

Clinical studies were carried out during digoxin maintenance therapy to clarify three questions concerning digitalis therapy: optimal time for blood sample collection for serum digoxin concentration (SDC), the overlapping range of SDC levels in which some patients may be intoxicated while others are not, and both resistance and sensitivity of atrial fibrillation (AF) to digitalis. The SDC curve after a single dose of digoxin or beta-methyldigoxin shows the appropriate sampling time to be at least 12 hours after the administration. The optimal time is 24 hours. The overlapping SDC range was 1.7-2.7 ng/ml. There were significant differences in CTR and ventricular rates in AF between intoxicated and non-intoxicated groups. This suggests that susceptibility to digitalis increases with the severity of underlying heart disease. Precipitating factors such as CTR should be taken into consideration, if the SDC is in the overlapping level. Digitalis resistance occurs in 6.7% of 105 patients with AF, and more frequently in hypertensive heart disease than others. Digitalis sensitivity occurs more often in the elderly and in patients with dilated cardiomyopathy. But it is not necessary to attain higher therapeutic levels for AF than for sinus rhythm. Clearly optimal digitalis therapy for AF can be best accomplished when precise clinical findings, SDC and EKG recordings are carefully monitored and used to correct treatment.

Tolerance of chick embryos to low temperatures in reference to the heart rate

Ten-day-old embryos were exposed to 28, 18 and 8 degrees C environments and their electrocardiograms (ECG) monitored. Embryos in 28 and 18 degrees C environments maintained a constant heart rate averaging 97 and 25 beats/min, respectively, followed by arrhythmias and cardiac arrest at 101 and 59 hr. Embryos in an 8 degrees C environment went into cardiac arrest after 2-4 hr, but recovered 20 hr later upon rewarming to 38 degrees C. Six to 20-day-old embryos exposed to 8 degrees C were examined for tolerance time after cardiac arrest. The younger the embryo the longer its tolerance to prolonged cardiac arrest.

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.

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).

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.

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.

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.

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.

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.

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.

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.

Effect of O2 and CO2 in N2, He, and SF6 on chick embryo blood pressure and heart rate

Arterial pressure of chick embryos was measured electromanometrically to investigate the effect of altered gaseous environments on blood pressure (BP) and heart rate (HR). The experiments were made in eggs incubated for 14-16 days at 38 degrees C without impeding the diffusive respiratory gas exchange through the shell and chorioallantois. In air, the HR was counted 260-270 beats/min and the BP increased from 14/7 Torr at day 14 to 21/12 Torr at day 16. Both the BP and HR decreased with hypoxia, whereas hyperoxia affected a slight increase in BP and little change in HR. Hypercapnia decreased the HR and tended to enhance a systolic maximum pressure. The effect of hypoxia was augmented markedly in the presence of hypercapnia and vice versa. When N2 was replaced with helium (He), the effect of hypoxia was mitigated significantly. On the contrary, replacement of N2 with sulfur hexafluoride (SF6) augmented the effect of hypoxia. Because the respiratory gas exchange of the egg takes place by diffusion through the shell and chorioallantoic capillaries, the effect of He and SF6 atmospheres on BP and HR is attributed to an altered diffusivity of O2 and CO2 in these inert gases.

Measurement of blood pressure of chick embryo with an implanted needle catheter

A catheter, consisting of a hypodermic needle and polyethylene tube, was implanted in the allantoic artery and/or vein of chick embryos ranging in incubation ages from 13 to 17 days. The procedure was performed through a small hole opened in the shell (less than 1 cm2). The hole was covered after implantation of the catheter, ensuring the adequate gas exchange by the chorioallantois and physiological values of blood gases. Blood pressure was measured with an electromanometric transducer. The arterial pressure lacked a dicrotic elevation. Both the systolic and diastolic pressures increased markedly with days of incubation, but the heart rate showed no significant change. The venous pressure was pulsatile in some eggs, and the pulsations became prominent after administration of epinephrine.

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).

Relationship between venoarterial CO2 content difference and venoalveolar PCO2 difference in acute hypercapnia in dogs

When mixed venous blood is oxygenated in alveolar air with higher PCO2, the PCO2 within the red cell is though to exceed the alveolar PCO2 due to the Haldane effect and to block the inward CO2 diffusion. If the direction of the CO2 diffusion is not reversed during the contact time, the HCO2-gain in the plasma will not exceed the amount estimated from venoalveolar PCO2 difference by using a CO2 dissociation curve of separated plasma. In order to clarify the validity of the above thought, the venoarterial CO2 content difference was measured by using a van Slyke apparatus and a PCO2 electrode at various alveolar PCO2 levels in rebreathing dogs. The HCO3-rise in the whole blood was obviously reduced when acute hypercapnia was administered in both normoxia and hyperoxia. Quantitatively, the decrease of CO2 content under hypercapnia corresponded to the difference in CO2 content between the true and separated plasma. The reduction, however, was slightly stronger in normoxia than in hyperoxia with alveolar PO2 of 300 to 420 mmHg. These data seem to support the following explanation: When venous blood was oxygenated in normoxic air with PCO2 higher than true venous, the inward CO2 diffusion was inhibited by the Haldane effect and the reversed diffusion after the oxygenation could also be disregarded during the contact time. Because the oxygenation was accelerated in hyperoxia and the direction of the CO2 diffusion was reversed earlier than in normoxia, the plasma CO2 content became higher in hyperoxia than in normoxia.

Adverse effect of failure to turn the avian egg on the embryo oxygen exchange

Fertile chicken eggs belonging to the same flock of hens were divided into two groups and incubated for 16 days. During incubation, group 1 eggs were turned twice a day and group 2 eggs were left unturned. Blood sampled from the allantoic vein or artery was analyzed for gas tensions (PO2 and PCO2), pH and Hct. These values were compared by unmpaired t-test for significance differences between the two groups. While the differences of PCO2 and pH were found insignificant, failure to turn the eggs caused a pronounced fall in the arterialized PO2 which was accompanied with an increase in Hct. In addition, the embryo weight was reduced in unturned eggs. Lack of turning retarded the absorption of albumen. The unabsorbed albumen interposed between the chorioallantoic membrane and inner shell membrane, impeding the blood oxygenation through the chorioallantois. Little change in PCO2 might be attributed to a large diffusive conductance of the chorioallantois for CO2. The present results suggest that the eggs must be turned periodically during incubation to prevent the distortion of normal oxygen exchange especially for the study of egg respiration.

Repetitive and simultaneous sampling from the air cell and blood vessels in the chick embryo

A catheterization procedure is described for repeated and simultaneous removal of gas samples from the air cell and of blood from the allantoic vein and artery of the developing chick embryo. The partial pressures of O2 and CO2 determined using this method do not differ from those obtained by conventional methods.

Analysis of chorioallantoic gas exchange in the chick embryo

To analyze the gas exchange mechanisms in the chorioallantois, PO2 and PCO2 were measured in air cell gas, in the allantoic artery and in the allantoic vein in chicken embryos on the 16th day of incubation. In addition, the O2 dissociation curve of blood, and O2 uptake and CO2 output of the embryo were determined. From O2 measurements performed in hypoxia (FIO2=0.14), normoxia and hyperoxia (FIO2=0.67), it was concluded that there was a sizable functional arterio-venous shunt amounting to 10-15% of the total chorioallantoic blood flow and that the diffusing capacity of the air cell-blood barrier for O2 was about 7 microliter . min-1. Torr-1. The CO2 measurements are in agreement with the model. In hypoxia, the air cell-blood transfer of O2 was markedly diffusion limited. The diffusion limitation effect was slight in normoxia, and not detectable in hyperoxia. At all oxygenation levels the effect of the shunt on blood arterialization was marked, particularly so in hyperoxia where the air cell-arterialized blood PO2 difference averaged 180 Torr.

Respiratory gas transport by the incompletely separated double circulation in the bullfrog, Rana catesbeiana

To investigate respiratory gas transport in the bullfrog, Rana catesbeiana (mean body weight 249 g. ambient temperature 25 degrees C), O2 uptake and CO2 output were determined, and blood gas parameters (PO2, PCO2, pH, O2 content, O2 capacity and hematocrit) were measured in blood samples taken from various heart cavities and blood vessels. Analysis of the data on the basis of a simplified circulatory gas transport model allowed to estimate the cardiac output and its distribution, and to describe the O2 and CO2 exchange in lungs, skin and tissues. The total cardiac output (average 20.5 ml/min) was estimated to be distributed about equally to the pulmocutaneous (56%) and systemic arterial vessels (44%), whereas the systemic venous return (62%) was larger than the pulmonary venous return (38%). The marked difference in oxygenation between aortic and pulmocutaneous arterial blood (average O2 saturation 85% and 47%, respectively) showed a highly effective separation of systemic venous and pulmonary venous blood in the ventricle and conus arteriosus. After enlargement of the ventricle produced by incision of the pericardium, the separation of arterialized and venous blood was markedly reduced, but not abolished.

Oxygen transport in chicken embryos under hypothermal exposure

Fertile hens' eggs incubated for 16 days at 38 degrees C were abruptly exposed to a temperature of 30 degrees C for 2 h and then determinations of blood gas parameters and the O2 dissociation curve were performed. In addition, O2 uptake was measured. Under hypothermal exposure the O2 dissociation curve showed a marked leftward shift in accordance with the increase in pH. The O2 saturation in arterialized blood of the allantoic vein reached almost 100%, and the blood S(O2) of the allantoic artery also increased up to about 50% in contrast with about 20% in normothermal controls. The blood flow rate through the chorioallantoic capillary plexus seemed to be almost identical with that of normothermal embryos. Because of the increased O2 affinity and the decreased O2 consumption, the systemic venous O2 reserve should be raised by hypothermal exposure. In connection with this conjecture, the redistribution of blood flow and O2 quantity by hypothermal exposure were calculated using the same circulation model as used in normothermal embryos. The result came closer to fetal lambs than to normothermal embryos.

Oxygen analyses of chicken embryo blood

According to data obtained previously on the blood gas tensions and the oxygen dissociation curve of chicken embryos, the arteriovenous oxygen saturation difference in the allantoic circulation has been conjectured fairly large. In order to confirm this conjecture as well as to check the validity of the in vitro dissociation curve, both the blood oxygen capacity and content in allantoic artery and vein were measured. The in vivo O2 saturation measured here resulted in a similar value to that estimated from the dissociation curve. The O2 content in allantoic vein ranges from about 7 to 11.5 vol% during the 10th to the 18th days of incubation and that in artery is pronouncedly low in a range of 1 to 2.5 vol%, suggesting that the blood flow rate through the body tissues is fairly larger than that through the gas exchange capillary plexus. Then, the distribution of blood flow was estimated from the analyzed data based on a model of blood circulation and some assumptions. In connection with this estimation, the diffusing capacity for deoxygenation in the tissues was speculated to be much larger than that for oxygenation in the chorioallantoic capillaries.

Estimation of contact time and diffusing capacity for oxygen in the chorioallantoic vascular plexus

The contact time of erythrocyte in the chorioallantioc capillaries of chicken embryos was estimated by referring to the oxygenation rate measured with a microphotometer. The chorioallantioc membrane was excised from an incubated egg and the SO2 of blood in it's capillary was changed by varying the gas composition around the membrane from the venous blood PO2 level to the air space gas. The oxygenation time (te) required to attain the level of arterialized blood SO2 was measured as the contact time (tc) in the capillaries, which resulted in 0.87, 0.74, 0.57, 0.49 and 0.36 sec for 10, 12, 14, 16 and 18 days of incubation, respectively. The obtained te value coincided with the contact time calculated from the CO diffusing capacity referring to the reaction rate of CO with oxygenated erythrocyte. Using the te value, the diffusing capacity for O2 in the chorioallantoic capillary was calculated; 1.1, 2.2, 4.4, 6.0 and 6.6 x 10(-3) ml-min-1 - mm Hg-1 for the same incubation days as above. The capillary blood volume (Vc) was also estimated, which increased from about 16 to 35 mul during development from 10 to 18 days. The values of DO2 and Vc converted per kg weight of embryo at the days near hatching were similar to those per kg body weight estimated in human lung.

Oxygen dissociation curve for chorioallantoic capillary blood of chicken embryo

Oxygen dissociation curves for blood in the chorioallantoic capillary of chicken embryos were determined using a microphotometric apparatus made for measuring the reaction velocity of a red blood cell with oxygen and carbon monoxide. The modified Hill's equations expressing the dissociation curve during development were calculated by two methods. P50's at pH of 7.4 were found to be 60.0, 54.4, 46.2, 33.1, and 28.6 mmHg for 10, 12, 14, 16 and 18 days of incubation, respectively. Although the Bohr factor did not show a clear relation to age, the oxygen affinity and the oxygen capacity tended to increase with the lapse of days, and the power of heme-to-heme interaction, to decrease with age. The findings imply that there is a respiratory adaptation of embryos during development.

Oxygenation and deoxygenation velocity factors of chorioallantoic capillary blood

The oxygenation and deoxygenation rates of capillary blood of chicken embryo were measured precisely with a microphotometric reaction apparatus. The velocity factors expressed as Fcox and Fcdeox in ml O2-ml RBC-1-S-1-mmHg-1 were calculated as functions of oxygen saturation. They were similar to results previously obtained in human blood using the rapid flow apparatus. The continuous registration of the reaction with oxygen enables us to estimate the equilibrium time of blood when passing through the chorioallantoic capillary. The value obtained was almost identical to the contact time indirectly assessed from the CO reaction. The diffusing capacity of the chorioallantoic capillary plexus of the 16-day-old embryos was estimated as 7.3 x 10(-3) ml-min-1mmHg-1 by using the values of the Fcox and the equilibrium time determined here together with the values of the blood flow and hematocrit which had been obtained in the previous experiments.

Microphotometric method for measuring the oxygenation and deoxygenation rate in a single red blood cell

A new reaction apparatus combining a microscope and a photometric device was developed for kinetic studies of a single red cell. A monolayer of red cells was placed in a closed reaction cuvette set on a microscope stage, a light beam of 5 to 10 mum in diameter was directed into one of the red cells, and the light transmission change in the cell was analyzed. The light beam with a wavelength range shorter than 460 nm was made by placing a narrow iris diaphragm in the light path. The space in the cuvette prevented the red cells from drying thereby providing favorable physiological conditions during measurements. The cuvette was filled with reagent gas mixtures of O2, CO2, and N2 which came in contact with the red cells. Transmission change due to the reaction was detected separately at two wavelengths of 418 and 402 nm by means of two photomultipliers mounted on the microscope. The linearity was tested by comparison between SO2 measured with a Van-Slyke apparatus and the microphotometer. Both SO2 measurements agreed well with each other, but the latter was about 3% greater than the former at around 50% SO2. Using this apparatus the oxygenation and deoxygenation velocities were measured over an entire O2-saturation range. The velocity factors showed good agreement with those obtained by using conventional flow methods.