Biomedical subjects
Publications and source records attributed to J Wittmann.
Embryogenesis of the quail can be induced under in vitro conditions by avoiding drying out of the germinal area. This is attained either by covering the surface of the egg content with diluted albumen or by regulating the water loss in the incubating system by means of a membrane.
Chick embryos were treated on day 17 of incubation with 32.8 mumol thiourea or 18.9 nmol L-thyroxine. As was already known from previous studies, hatching was delayed and accelerated, respectively, under these conditions. The premature induction of hatching by L-thyroxine was accompanied by an advanced development of the pulmonary structure and of the circulation and by a premature absorption of the parabronchial liquid. Thiourea exerted an opposite effect on these parameters. In several cases the structural formation of the parabronchii was suppressed after treatment with thiourea. Furthermore, parabronchial liquid accumulated in those embryos, the hatching of which was suppressed. It is suggested that these changes represent a toxic effect of thiourea rather than a retardation of pulmonary development.
With the development of higher organisms, the problem of gas exchange of each single cell had to be resolved. Nature gave preference to the development of a specific organ for gas exchange (lungs, gills) as opposed to a system of gas exchange involving the whole organism. In vertebrates, the latter has been developed only in lungless salamanders (Desmognatus fuscus) and in the embryos of the oviparous species. Mammalian embryos also do not use their lungs during the prenatal period, however, in contrast to the oviparous species gas exchange is performed via the maternal respiratory apparatus. The transition from the pre- to the neonatal period is more problematic in mammals than in oviparous species. The critical situation is caused by the fact that mammalian lungs must be inflated within a comparatively short period of time. In oviparous species, however, the development of lung respiration lasts several hours. Several lines of evidence indicate that lungs are also involved in blood pressure changes occurring during the perinatal period. In this context the pulmonary regulation of bradykinin and prostaglandin metabolism has been emphasized. It has been recognized that lungs of adults serve not only as a gas exchange organ, but are involved in the synthesis, activation or inactivation of substances which exert an influence mainly on blood pressure. In this function, lungs are especially suitable due to their position between the venous and arterial circulation. Therefore, it is not surprising that disturbances in the pulmonary function result in manifold pathological processes.
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In the experiments reported here, the effect of dexamethasone on hepatic and renal xanthine dehydrogenase toward the end of incubation was studied. Dexamethasone injected on day 17 of incubation into the chick eggs increased the hepatic and decreased the renal activity of xanthine dehydrogenase. Furthermore, dexamethasone was found to accelerate fetal development as measured by the precocious decrease of thymidine uptake into nuclear DNA and by the increased fetus weight/egg weight ratio. The data suggest that an activation of xanthine dehydrogenase is caused by a hatching-independent factor and by a factor related to the hatching process.
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A prospective study was performed to determine the side effects of fiberoptic bronchoscopy on cardiopulmonary function, the influence of bronchial lavage on cardiopulmonary function, and the functional efficacy of fiberoptic bronchoscopy in obstructive atelectasis due to retained secretions. In 17 patients endotracheal intubation was immediately followed by a significant (P less than 0.01) rise in arterial, pulmonary artery and pulmonary capillary wedge pressure, heart rate, and cardiac output. There were no statistically significant differences in arterial blood gases and intrapulmonary right-to-left shunt. Two patients showed circulatory changes indicative of a heart insufficiency on the left side. A significant increase (P less than 0.001) in intrapulmonary right-to-left shunt from 12% to 17.5%, a significant decline in arterial oxygen tension of 15 mm Hg, and a significant increase of cardiac output from 6.4 to 7.71/min following saline solution lavage (20 ml in each bronchus) were observed in nine patients. The results indicate that bronchial lavage is the essential mechanism for the decline in arterial oxygen tension induced by fiberoptic bronchoscopy. In patients with unstable cardiopulmonary status, the cardiovascular response during bronchoscopy may be hazardous and the bronchoscopist should be aware of the pathophysiologic side effects involved. Fifteen therapeutic bronchoscopies were performed in five critically ill patients with obstructive atelectasis, due to retained secretions. Following the procedure, Qs/Qt declined from 23.9% to 15%, cardiac output from 9.3 to 7.31/min, and arterial Po2 increased from 58.9 to 70.9 mm Hg. The differences were statistically significant (P less than 0.0001). The therapeutic value of fiberoptic bronchoscopy in the treatment of obstructive atelectasis is demonstrated by the significant improvement in cardiopulmonary status.
Treating chick embryos with high doses of thiourea (32.8 mumol) on day 17 of incubation resulted in prevention of hatching and of active breathing. Furthermore, thiourea also prevented the increase of O2 consumption and the marked increase of somatic activity associated with the final hatching act. These findings provide evidence for the importance of active breathing in the prenatal period to initiate pipping and hatching of the avian embryo.
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.
Xanthine dehydrogenase activity in the liver of embryonic chicks has been shown to be inducible by L-thyroxine, thiourea, and cycloheximide. Results reported here indicate different mechanisms underlying the activation through L-thyroxine on the one hand, and through thiourea and cycloheximide on the other. Using hepatocyte suspension and homogenized liver, it has been shown that prenatal activation of xanthine dehydrogenase results in increased rate of uric acid formation from nucleic acids and purine derivatives, but not from amino acids.
Pressure changes in the air cell and at the egg shell have been used to monitor respiratory and somatic movements of embryonic chicks. During the prehatching period a phase of reduced activity is observed. Pulmonary respiration is initiated during this phase. Exogenous L-thyroxine exerts an accelerating effect on the hatching process and on the onset of the phase of reduced motility and of lung respiration. In thiourea-treated embryos the opposite effects on the hatching process and on the motility and respiration pattern are registered. When, however, the egg shell above the air cell was sealed with glue, times of hatching and of the beginning of lung respiration were similar to those of controls, although pipping the egg shell occurred earlier than normal. It is suggested that the effects of L-thyroxine and thiourea on the hatching process are caused by a premature or delayed onset, respectively, of pulmonary respiration.
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In chick embryos, time of pipping is accelerated after repeated gassing the air cell with N2, CO2, or by sealing the egg shell in the area of the air cell with glue. Gassing the air cell with 95% O:2-5% CO2, or pure O2, was followed by a retardation of pipping. Furthermore, gassing with N2, or sealing the air cell with glue, exerted an accelerating effect on the decrease of hepatic glycogen and ATP. Following gassing with 95% O2-5% CO2, the reverse effect on glycogen and ATP was observed. It is suggested that the increase of the CO2/O2 ratio, occurring in the air cell at the end of incubation, acts as a stimulus for both pipping and metabolic changes in the liver.
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1. Isolated kidney tubules from chicken have been used to study the actions of ethanol, ouabain and aminooxyacetate on glucose formation from lactate and pyruvate. 2. In kidney tubules from well-fed chickens the rate of glucose production from lactate was higher than from pyruvate. Ethanol (10 mM) and ouabain (0.1 mM) were found to increase glucose formation from pyruvate but not from lactate. 3. It is concluded that in the presence of ethanol the fluxes of pyruvate through pyruvate dehydrogenase are in favour of the pyruvate carboxylase reaction restricted. 4. Glucose formation from lactate is decreased by aminooxyacetate (0.1 mM) and ouabain (0.1 mM). 5. Aminooxyacetate inhibited glucose formation from lactate, although chicken phosphoenolpyruvate carboxykinase is located intramitochondrially. 6. The results indicate that the effect of aminooxyacetate like that of ouabain is caused by the restricted formation of pyruvate.
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At the time of hatching, activities of both KDH and succinate thiokinase increased in heart, while in liver only an enhanced activity of KDH was observed. Glutamate injected into egg exerted a stimulatory effect on KDH activity in chicken embryos but not in newborn chickens. There seems to be an age-dependent response of ASAT and GDH to stimulating effectors. In chicken embryos, 2-oxoglutarate induced GDH activity and in newly hatched chickens, ASAT activity. Concomitantly, liver protein content increased also. Administration of glutamate, however, was not followed by a significant activity increase of ASAT or GDH. Thus, the stimulation of ASAT and GDH activities seems to be favoured when they support glutamate formation out of 2-oxoglutarate.