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Biomedical subjects

H Schwartze

Publications and source records attributed to H Schwartze.

At least 19 recordsLinked to original sources
PubMed1996

A report on pathological changes of the dipole moment in children suffering from anthracycline cardiomyopathy.

Cardiomyopathy is a severe complication of the tomour therapy with anthracyclines. Since even minor disturbances of myocardial cell membranes could influence the dipole moment of the heart the noninvasive measurements of this parameter might be useful, particularly in the paediatric population. 17 children aged 2-15 years treated clinically for various malign blood diseases were examined repeatedly with a modified Nelson lead-system up to 3 years. The dipole moment was evaluated by visual comparison of the calculated horizontal and frontal VCGs, evaluation of 3 distinctive vectors, as well as of the magnitude curves and the velocity curves, all of them compared with the normal age dependent percentiles of each respective child. Conventional 12-lead ECGs were used to confirm rhythm disturbances and alterations of P-, PQ-, QRS-, and QT-durations. Our results show that damages of the heart are different during the time of the drug administration, then consisting of acute toxic reactions such as sudden dilatation and/or rhythm disturbances, and of long-term disturbances leading to growth retardation of the heart with the danger of chronic congestive heart failure months or years after the end of the anthracycline treatment. Morphological and biochemical damages of myofibrils caused by the toxicity of anthracyclines precede functional restraints of the heart. A noninvasive method for an early and reliable diagnosis of these damages is urgently needed, particularly for children. Measurements of the dipole moment with the Nelson-lead system seem to offer this diagnostic tool which aims possible changes of the drug administration protocol. (Fig. 3, Ref. 15.)

Antibiotics, Antineoplastic↗
PubMed1993

[Studies of fetal and neonatal isolated guinea pig lung on the effect of electric tissue resistance on the ECG].

The results of measurements of the electrical resistance of lung tissue are reported in order to estimate quantitatively the influence of air and blood filling on the conductivity. Experiments were done on isolated lung tissue of fetal and infantile guinea pigs. The ohmic resistance was measured by a minimised 4-electrode technique: isolated fetal lungs empty of air, or artificially aerated ones on the one hand, isolated lungs of infantile animals with spontaneous respiration and normal lung blood flow on the other hand. The increase of the electrical resistance produced by aeration is reduced by at least 50% by the synchronously increasing blood flow in spontaneously respired lungs. These experiments in the described animal model offer an opportunity for a more precise interpretation of the electrocardiogram of human adults changing with respiratory phases.

Animals↗
PubMed1992

[Electrocardiography in pediatrics. 1: Critical considerations of methods and experimental findings].

The results of experimental cardiology are reported on the basis of the electrophysiology of the heart. The QRS complex of the ECG, representing the spread of excitation through the ventricles, is used as an example to reflect the physiological and pathological events of the heart. The limitations of this example arise from the uncorrected recordings of the potential differences from the body surface. The need to use corrected lead systems is pointed out. The most commonly used FRANK lead system is extremely sensitive to the inaccurate positioning of lead points on the thorax. Evidence for this drawback is given by experimental findings in infantile and juvenile rats. It is clear that inaccurate positioning of electrodes is especially crucial in small subjects. A fundamental criticism of the FRANK lead system used in growing subjects is the impossibility of eliminating the errors caused by the changing geometry of the thorax of children of different ages. Improvement of the physical correction of ECG recordings in children for the purpose of reliable diagnostics is vital.

Animals↗
PubMed1992

[Electrocardiography in pediatrics. 2: Recommendations for a newly introduced recording and evaluation procedure].

ECG recordings were made by means of a modified NELSON-lead system in a total of 100 children aged between 2 weeks and 59 months. Software developed by ourselves served for on-line calculations of the dipole moment D which is graphically represented by vector loops in three projection planes, horizontal, frontal and sagittal. In addition, the maximum spatial vector Dmax and the mean vector A are calculated by the program. The examination of one child including positioning of 20 electrodes and production of a hard-copy of the results takes no longer than 15 minutes. The children were unsedated and awake when the ECGs were recorded. The results show the continuously growing dipole moment and its gradually changing direction from the right posterior or left anterior to the left posterior quadrant in parallel with the growth of the body and the heart, respectively. The smallest vector magnitudes and smallest vector loops of the dipole moment are measured in the youngest infants (0-2 months) while very high voltages in conventional ECGs of infants are regularly seen, predominantly in the precordial region. Two examples of pathological NELSON-ECGs are reported. One case is a boy aged 4 years 10 months with aortic supravalvular stenosis, the other one is a girl aged 4 years 3 months with pulmonic valve stenosis. These cases demonstrate the excellent suitability of this noninvasive method as a diagnostic tool for pediatric cardiology.

Child↗
PubMed1991

Quantitative electrocardiography and vectorcardiography in postnatally developing rats.

The aim of this study was to provide quantitative descriptions of developmental changes of the cardiac electrical activity of rats as background information useful for assessing abnormal development, for example, in spontaneously hypertensive rats. The data are based on the findings of serial examinations of 11 animals, slightly anesthetized by ether, on whom Frank-ECGs were recorded on days 6, 14, 21, 30, 38, and 53 of life. Typical features of the electrocardiograms during the physiologic development are P waves consisting of one positive deflection in all three leads (x, y, and z); and PQ intervals decreasing between days 6 and 14, whereas the heart rate increases during this period. QRS vector loops and the maximum spatial vector (R) shift to the left, whereas the amplitudes of R first increase but decrease with later age. The shape of the QRS magnitude curves is described, the peaks of which occur later during QRS in relation to increasing age. QRS intervals are considerably shorter than in the adult even at day 53. At this age rats have attained the adult configuration of the QRS loop. From day 30 onward, QRS frequency merges with the T wave. It is concluded that the ontogenetic development of the major electrical forces of the rat heart shows peculiarities compared to those seen with the development of other mammalian species. The most probable morphologic and functional postnatal adjustments are discussed with reference to the causes of the developmental electrocardiographic changes.

Aging↗
PubMed1991

[Physiology and physiopathology of postnatal pulmonary adaptation. 1: Physiology].

The aim of the review consists of the help to understand the complex physiological mechanisms of the onset of breathing and the regulation of the respiration during the early newborn period. The lungs of the newborn contain nearly no alveoli. Postnatal formation of alveoli enlarges the gas exchange surface until the 20th year of life, the lung volume increases by a factor of 27. Immediately postnatal the aeration of the lungs is performed by several deep inspirations with breath hold and following crying. The fetal lung liquid is resorbed via both, lymph and blood vessels. Stability of the functional residual capacity is reached very rapidly. The inflation augmenting reflex and sighing support effectively this process. The significant importance of the surfactant for the successful begin of air breathing is described. Onset of respiration is combined with the decrease of the pulmonary arterial resistance and the remarkable increase of the pulmonary blood flow. The hypoxic response in the newborn is biphasic. An initial short hyperventilation is regularly followed by ventilatory depression. Neurophysiological causes are evident. Hyperventilation by inhalation of gas mixtures with higher CO2 concentrations is low, at least in preterm infants. The causes are believed to ly in the limitation of the efficiency of the respiratory muscles. Peripheral chemoreceptors in the glomus caroticum and in the bronchial mucosa, stretch receptors in the bronchial muscles, and muscle spindles in the intercostal muscles are functioning in newborns as well as in preterm infants.

Adaptation, Physiological↗
PubMed1991

[Physiology and pathophysiology of postnatal pulmonary adaptation. 2: Pathophysiology].

Subject of this review is the pathophysiology of the respiratory distress syndrome (RDS), the apnea, and the sudden-death infant syndrome (SIDS). The fatality rate of the RDS yet amounts to 24%. Preterm infants are preferably involved because of their deficient surfactant synthesis. The lack of surfactant causes atelectases, hyaline membranes, lung oedema, and augmentation of respiration work. Only towards the very end of gestation the amount of surfactant of the fetal lung increases rapidly so that the normal postnatal respiration is guaranteed. RDS produces a pathological circulatory situation with insufficiency of the right heart and congestion. The atrial natriuretic hormone is increased about tenfold in the serum of RDS-infants. Modern treatment of the RDS uses instillations of exogenous surfactants before the first breath. Apneic attacks are observed predominantly during REM-sleep. They seem to have pathological value only if they exceed 15 seconds. Infants with recurrent apnoea breathe periodically, they were mostly preterm newborns. Probably, the cause of recurrent apneic attacks are central regulatory deficits and adenosine may play an important pathological role as neurotransmitter. Arrhythmias of the heart including the QT-syndrome observed in SIDS-infants at risk may have the same central pathophysiological source.

Apnea↗
PubMed1990

[Recent findings in fetal lung development: structure, surfactant, lung fluid].

A great deal of lung development takes place after birth; new alveoli continue to develop until 8-11 years. However, the differentiation of epithelial cells is characteristic of the fetal lung from 24 weeks of gestation onwards: this is the point at which the surfactant containing type II cells can first be identified. Lung blood flow and the metabolic rate of type II cells increase in parallel rates the last 20% of the gestation period. The timely synthesis of surfactant depends on the availability of the fetal hormones T3, cortisol and prolactin, whereas this synthesis is inhibited by insulin and testosterone. Endogenous surfactant consists of 80% phosphatidylcholine and 10% protein. A sufficient quantity of surfactant is only available at term. Nowadayx, surfactant deficiency can be treated successfully with various exogenous surfactant preparations. Fetal lung liquid contributes about one half to the amniotic fluid. It is partly secreted by an active transport system. Secretion is inhibited by the stimulation of beta-adrenergic receptors in the lung tissue. The epithelial surface of the alveoli is a barrier which limits protein penetration considerably; lung liquid contains minimal amounts of protein. Under pathological conditions (RDS, haemorrhagic lung oedema) the alveolar barrier is disturbed so that plasma protein penetrate into the air spaces and form hyaline membranes.

Female↗
PubMed1990

[Fetal respiratory movements and their regulation].

In 1972, fetal breathing movements were clinically rediscovered. Details of their episodic occurrence, frequency, inspired volume, pleural pressure, and the nearly absolute independence of fetal blood gases were investigated in animal experiments. In the human being, there is also an association between fetal breathing and sleep state: fetal breathing movements were confined almost exclusively to periods of REM sleep. The pattern of respiratory frequency changes as gestation progresses; the rates decrease as term approaches. Hardly any breathing movement can be detected during labor. The fetal respiratory centre is capable of rhythmic movements, but there is a lack of response to basic chemical stimuli from the periphery of the body. The association between fetal breathing and REM sleep implies that the connection between breathing and behaviour is already established before birth; but in the fetus, the link between breathing and metabolism is not yet forged. Throughout postnatal life this linkage predominantly regulates breathing. The difference between fetus and newborn in the reaction to chemical stimuli implies a change at birth related to the glomera cells of the carotid bodies. Under the influence of the marked increase in the sympathetic tone there is a major increase in the sensitivity of the receptor cells to oxygen deficiency immediately after birth.

Asphyxia Neonatorum↗
PubMed1989

Effect of mild chronic hypoxia on the infantile heart: ECGs of guinea pigs pre- and postnatally treated with carbon monoxide.

Contrary to rats, developing guinea pigs don't react with a hypertrophy of their hearts following sublethal chronical intoxication with CO (200 ppm in room air applied to the pregnant mothers and subsequently to the infant animals). Since birth weight and postnatal growth remained in normal ranges, tissue oxygenation must have been sufficient despite a concentration of 30 +/- 4.5% COHb. Hence, ECGs didn't show characteristic parameters of heart hypertrophy. However, alterations of QRS vector loops consist in a more pronounced but retarded rightward accentuation during the first 4 days of life and afterwards in an accelerated turnover to the left relative to controls. We suppose a pathological volume loading of both the ventricles during the first week of postnatal life, caused by the chronically acting hypoxia.

Aging↗
PubMed1988

[Recent physiologic and pathophysiologic findings on fetal circulation].

Venous return of the fetal circulation consists of 70% blood from the lower body and of 30% blood from the upper body. Blood of the left V. hepatica contains more oxygen than that of the right hepatic vein. This rather well oxygenated blood from the left hepatic lobe joins the blood of the Ductus venosus, carrying high concentrations of O2 and glucose predominantly to the left ventricle, Aorta ascendens, and Truncus brachiocephalicus. Less oxygen saturated blood of the right hepatic lobe together with the venous return of V. cava superior reaches the right ventricle via the tricuspid valve, then the Ductus arteriosus and Aorta descendens. The hepatic microcirculation seems to be of importance for regulations of the fetal venous return. However, the supply of organs with oxygen and nutrients is mainly dependent on regional vascular resistances.

Ductus Arteriosus, Patent↗
PubMed1988

[The influence of exhausting training on the development of the motor pattern of swimming and on the sleep-wake behavior of growing rats].

At present it is generally accepted that programs of physical training which require coordinate performances of the central and the vegetative nervous system may be conducive to the complex development of central nervous functions. The aim of the study was to investigate the effect of an exhausting swim training with albino rats aged 6-30 days on the development of motor pattern of swimming and on the sleep-wake behaviour. Daily training rats performed the adult motor pattern of swimming earlier than controls which were not trained. Trained animals are more active and longer awake than control rats which were treated daily only by a short stress (stay in cold water for 10 s). During the growth period before puberty exhausting training produces complex effects: the development of motor patterns is accelerated and the central vigilance level is raised. It is unknown which consequences might possibly arise as to the central nervous integration in adult mammals which were strongly trained in early infancy.

Animals↗
PubMed1988

[Recent physiologic and pathophysiologic studies in heart function in the perinatal period].

Recent investigations of the cardiac output in fetal lambs have shown that left ventricular output reaches nearly exclusively the upper circulation of the body (head, neck, forelegs) via the ascending aorta. Right ventricular output supplies predominantly the descending aorta via the ductus arteriosus. Increasing afterload results in reductions of stroke volumes in the fetus as well as in the neonate. The Frank-Starling-mechanism is only weakly developed in lambs before and after birth. Immediately after birth the rise of myocardial contractility in the newborn is related to his important endogenic sympathoadrenergic stimulation. This large postnatal increase of contractility depends strictly on a normally functioning thyroid gland during the last trimester of gestation. Presumably, T3 influences the prenatal development of the cardiac beta-receptors.

Animals↗
PubMed1986

[The red blood cells in growing guinea pigs (Cavia cobaya). I. Communication: pre- and perinatal changes in bone marrow and blood].

118 blood samples, 98 bone-marrow smears of guinea pig fetuses, 156 blood samples of spontaneously born guinea pigs 1 to 5 days of age, and 119 bone-marrow smears of the same age group were analysed quantitatively. The normoblasts show significant differences in pre- and early postnatal animals: a peak of the cell count is found in the late fetus which decreases immediately after birth. The prenatal development of the red blood picture is characterised by an increase of erythrocyte count and hematocrit and a decrease of cell size, and reticulocyte count. This development continues postnatally. The perinatal bone-marrow and blood picture findings suggest a true postnatal increase of the erythrocyte count in the guinea pig during the first 3 to 5 days of life which likely is due to the grown demand for oxygen transport capacity.

Aging↗
PubMed1986

[The red blood cells in growing guinea pigs. (Cavia cobaya). II. Communication: erythropoiesis and red blood cells in the postnatal development period].

Bone-marrow smears of 175 guinea pigs aged 1-27 days and venous blood samples of 351 animals aged 1-25 days were prepared for cell counting. A significant increase of erythroblasts were found between life day 1 and 2; normoblasts increased in number synchronously with a decrease of erythroblasts after the 5th day. The percentage of the erythroid bone marrow increased from 10 to 14 during the developmental period. Beyond the perinatal period the red blood picture is characterized by the following changes: a decrease of erythrocyte count, hematocrit, hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin; a constant mean corpuscular hemoglobin concentration; an increase of the reticulocyte count. The decrease of the red cell count is compensated by a decreasing oxygen affinity attained by an important increase of 2,3-DPG. Nevertheless, the stimulus for a raising erythropoiesis remains constant which can be shown by the growing percentage of erythroid cells and reticulocytes. The difference between the human postnatal development and that of the guinea pig becomes obvious. Cell counts in dependence of body masses in postnatally growing guinea pigs, veil the perinatal finding of the increase in erythrocytes up to the 5th day and the decrease of the mean corpuscular volume after the 3rd day.

Animals↗
PubMed1986

[Pathophysiology of circulatory regulation in hypoxia and asphyxia in the perinatal period].

Asphyxia is defined as hypoxia with hypercapnia; the physiology and pathophysiology of the O2-saturation-curve in maternal and fetal blood is given. Recent results about the redistribution of the cardiac output in chronically instrumented fetal lambs under the conditions of asphyxia, hypoxia and acidosis are reported. The life-threatening consequences of ischaemic situations in the regional circulations for liver, gut, kidney and lung are described, particularly in the newborn. It is stressed that in asphyxiated babies which show circulatory and/or cerebral disturbances, further organ functions (e.g. respiration, excretion) may be seriously damaged.

Animals↗
PubMed1986

[Postnatal development of the brain mass in guinea pigs (Cavia cobaya)].

The quantitative development of body mass (BoM) and brain mass (BrM) has been studied in guinea pigs during postnatal life from the 1st day until adulthood. The increase of both the parameters (BoM, BrM) was statistically significant from the 7th day on (p less than or equal to 0.05). The growth curves of BoM and BrM can be described mathematically by non linear regression functions of which the correlation coefficients were r = 0.96 and r = 0.82, respectively. The two growth rates of BoM and BrM show negative allometry, the rate of increase of BoM being 2.45 and that of BrM 1.16 between the 1st day and day 19-25. The correlation coefficient of the BoM/BrM ratio was r = 0.87. During the postnatal brain development of the guinea pig no particular growth spurt could be observed, as it is known from other species, e.g. the rat. This finding seems to be coherent with the advanced state of the newborn guinea pig with his functioning sensory mechanisms and an important motor activity.

Animals↗