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Biomedical subjects

K Langner

Publications and source records attributed to K Langner.

33 records · Page 2Linked to original sources
PubMed1985

Detection of melanogenic proteins in cultured chick-embryo melanocytes.

The phorbol ester, 12-0-tetradecanoylphorbol-13-acetate (TPA), was used as a reversible inhibitor of melanogenesis. Chick-melanocyte cultures of the black genotype, E/E, were grown in conditioned medium plus TPA. After growth in TPA and after its removal, the cells were pulse labeled with 3H-leucine. The membrane fraction, which included all tyrosinase activity as well as both mature and immature melanosomes, was solubilized with Triton X-100. The proteins were separated using two-dimensional electrophoresis and visualized by fluorography. One defined melanogenic protein, tyrosinase, was isolated, and its location was determined in the two-dimensional protein pattern. The protein patterns for both the TPA-inhibited cells and the cells in which the TPA effects were reversed after removal were compared. In addition to tyrosinase, at least nine TPA-sensitive proteins were found. These were designated as being putative melanogenic proteins which, along with tyrosinase, may be responsible for melanin-granule synthesis.

Age Factors↗
PubMed1985

Reliability of transcutaneous measurement of oxygen and carbon dioxide partial pressure with a combined Po2-Pco2 electrochemical sensor in the fetus during labor.

A combined single electrochemical sensor designed to measure synchronously and transcutaneously oxygen partial pressure and carbon dioxide partial pressure (RADIOMETER prototype) was applied onto the scalp in 21 fetuses during labor. The values of tcPo2 respectively tcPco2 were compared with the values of fetal blood analysis (FBA) and blood from the umbilical artery (UA): Comparing the tcPco2 with the values of the FBA we found the values to be very consistent (r = 0.95, p less than 0.001). For the comparison of the tcPco2 with the values of the umbilical artery, the correlation coefficient was lower (r = 0.76, p less than 0.05). The transcutaneous measurement of Po2 as compared with the values of the fetal blood analysis was also quite accurate (r = 0.83, p less than 0.001). Looking at the values of the transcutaneous measurement during the expulsion of the fetus and its comparison with the values of the umbilical artery, it was an interesting finding that values of the transcutaneous estimation of Po2 were much lower in some cases and no statistical correlation was found (p greater than 0.05). We conclude that the combined electrochemical sensor for measuring tcPco2 and tcPo2 is a new additional tool for studying the physiology and pathophysiology of the fetus during labor, but as the accuracy of Po2 and Pco2 in the fetal blood is influenced by the progress of labor, the special characteristic of the transcutaneous measurement has to be taken into account when values are interpreted.

Carbon Dioxide↗
PubMed1985

The influence of the progress of labor on the reliability of the transcutaneous PCO2 of the fetus.

Transcutaneous PCO2 measurements were performed on 105 fetuses during labor. A modified Severinghaus electrode was calibrated with 5% and 10% carbon-dioxide gas at 33 and 66torr. This corresponds to a drop in the PCO2 levels measured transcutaneously of about 13% and to an adjustment to the blood gas level. The levels measured transcutaneously were compared with data compiled from the fetal blood analysis and values of blood gas analysis from the umbilical artery immediately after delivery. The object of the study was to find out to what extent the progress of labor influences the conformity between the PCO2 levels measured transcutaneously and measured in blood. Comparing the data of the transcutaneous measurement (pb PCO2) with the pb PCO2 of the peripheral blood (pb PCO2) in cases without a caput succedaneum, we found a correlation coefficient of r = 0.79 and a slope of 1.1. On the other hand with the development of a caput succedaneum the correlation coefficient was lowered to r = 0.72 and the slope to 0.85. An influence of the propulsion of the fetal head in the birth canal on the accuracy of the transcutaneous measurement was also obvious. When the position of the fetal head was either above or in the interspinal plane, the correlation coefficient amounted to r = 0.85. With the progression below the interspinal plane, the correlation coefficient was clearly lowered. While our results show a good overall conformity between PCO2 levels measured transcutaneously and those from peripheral blood, our analysis shows also to what extent the conformity can be influenced both by the existence of a caput succedaneum and by the propulsion of the presenting part.

Carbon Dioxide↗
PubMed1984

Correlation between transcutaneous pCO2 and the corresponding values of fetal blood--a study at a measuring temperature of 39 degrees C.

Continuous transcutaneous monitoring of fetal carbon dioxide partial pressure (tcpCO2) may become an important new method for investigating the physiology and pathophysiology of the fetus during labor, as well as an additional tool for fetal surveillance. In order to contribute to the standardization of this newly developed method, we measured tcpCO2 during labor in 105 fetuses. We then compared the transcutaneous pCO2 with the pCO2 of fetal blood gas analysis; the correlation between these two parameters was significant. The relationship between transcutaneous pCO2 and the pH from fetal scalp blood is described, as is the influence of the stage of labor on the correlation between transcutaneous monitoring and blood samples. tcpCO2 during labor appears to be a helpful additional tool, especially in fetuses with pathologic heart rate patterns in whom multiple fetal blood gas analysis would otherwise be necessary.

Carbon Dioxide↗
PubMed1984

A new perfusion circuit for the newborn with lung immaturity: extracorporeal CO2 removal via an umbilical arteriovenous shunt during apneic O2 diffusion.

In spite of improved prophylaxis and therapy, the respiratory distress syndrome is still a major cause of morbidity and mortality in premature babies. Owing to the fact that a number of patients are unresponsive to other methods of neonatal care, an increasing number of perinatal centers have started to treat this group of patients with extracorporeal membrane oxygenation successfully. To make the extracorporeal gas exchange more practicable for the neonate directly after birth, a modification of this method using an umbilical arteriovenous shunt for CO2 removal in apneic premature lambs as an animal model was evaluated. A miniaturized low-resistance extracorporeal circuit that is totally incorporated in a regular intensive care baby incubator was developed. The benefit of using extracorporeal CO2 removal in very low birth weight newborns could be a conditioning of the premature lung during a short period of bypass, after which ventilation at nontraumatic pressures and nontoxic O2 concentrations would become possible.

Animals↗
PubMed1984

Glycosylated hemoglobin (HbA1), glucose tolerance and neonatal outcome in gestational diabetic and non-diabetic mothers.

Glycosylated hemoglobin (HbA1) was determined in three subject groups: 69 non-diabetic mothers who were delivered of normal weight infants at term (Group I), 33 non-diabetic mothers who were delivered of macrosomic infants (greater than 4000 g) at term (Group II), 51 gestational diabetics in the 3rd trimester--before onset of the diabetes therapy (Group III). In all three groups diagnostic assessment of glucose regulation was done by means of the oral glucose tolerance test during the 3rd trimester. Glycosylated hemoglobin was assayed by cation-exchange chromatography in small disposable columns. The mean values and standard deviations of HbA1 were 6.51 +/- 0.46% in Group I, 6.59 +/- 0.42% in Group II and 7.11 +/- 0.56% in Group III. Between the HbA1 values of Group III (gestational diabetes) on the one hand and those of the non-diabetic groups I and II on the other, there were highly significant differences (p less than 0.001; x2-test). HbA1 values above 7.4%--i.e. above mean + 2 s. d. of HbA1 in the non-diabetic mothers--were with 95% probability abnormal and indicative of gestational diabetes. HbA1 values between 7.0% and 7.4% were suspected of impaired glucose tolerance and gestational diabetes respectively. Between the HbA1 levels in the non-diabetic groups and those in the gestational diabetic group there was a vast zone with overlapping values. HbA1 data situated in this transitional area could be found both in non-diabetic subjects and also in those with abnormal glucose regulation. HbA1 values below 6.0% excluded gestational diabetes or otherwise impaired glucose tolerance with a high degree of probability.

Birth Weight↗
PubMed1983

[Transcutaneously measured carbon dioxide partial pressure in non-hypoxic fetuses during labor].

Using the newly developed Severinghaus electrode we performed measurements of the transcutaneous carbon dioxide partial pressure (tcPco2) in 81 non-hypoxic fetuses during labor. The calibration and measuring temperature was 39 degrees C. After a correction with a factor of 13% the transcutaneous Pco2 values corresponded well with the blood values of the Pco2 from FBA respectively the umbilical artery. While during the first stage of labor we found only a gradual rise in the tcPco2 level, we observed a rapid rise at the end of the second stage. Analysing the influence of clinical factors on the fetal tcPco2 level we found statistically significant higher levels during the first stage of labor in primipara compared with multipara. However there was no significant difference dependent on gestational age, the age of the mother and the birthweight.

Birth Weight↗
PubMed1982

[A new ECG electrode concept for the conduction of fetal heart action potentials without penetration of the skin].

Internal cardiotocography is an important method for reliable supervision of the fetus during labor. The main task is the prevention of fetal hypoxia. However, there is a considerable disadvantage as the electrodes used penetrate the fetal skin, creating a possible entry point for organisms. The concept we have developed forms a new way of decreasing the risk of infection during labor by conducting the fetal heart rate potentials without penetrating the skin. The electrode is fixed to the skin of the presenting part by tissue adhesive and electrical contact between the fetal skin and the wire of the electrode is established through using electrolyte fluid.

Electrocardiography↗
PubMed1982

[Effect of diffusion potentials and various stomach regions on the behavior of the potential difference after pentagastrin].

Junction potentials at the tip of a 0.15 M NaCl- and a 3 M KCl-flowing bridge dependent on the surrounding electrolyte solution were measured and calculated. There was a close correlation between the calculated and measured junction potentials. The magnitude of the calculated and experimentally determined junction potentials at the tip of the 0.15 M NaCl-bridge was found to be almost identical. Provided that junction potentials were not subtracted from the measured potential difference pentagastrin diminished the simultaneous measured antrum and corpus potential difference in 11 volunteers. When however junction potentials from the experimentally determined potential difference had been subtracted pentagastrin induced a transient significant decline in the corpus potential difference but no significant changes of PD could be registered in the antrum. The observation that pentagastrin did not change the antrum-PD suggests that the pentagastrin effect is related to the parietal cells.

Humans↗
PubMedDate not supplied

[Changes in lung compliance during extracorporeal gas exchange in the premature lamb].

Changes in the function of the lungs were investigated in 14 premature lambs during extracorporeal CO2 removal via membrane lungs with alveolar oxygen diffusion of the nonventilated lung by measuring the pressure volume curves at various moments after the start of perfusion via the endotracheal tube. During the course of the perfusion the static compliance clearly increases. In less than 6 hours the optimum of the "conditioning" appears to have been reached using this treatment.

Animals↗
PubMedDate not supplied

[Circulatory adaptation of the newborn infant immediately post partum by bilocal measurement of transcutaneous PCO2].

In addition to cardio-respirography, non-invasive intermittent blood pressure measurement, temperature measurement and transcutaneous oxygen partial pressure measurement, a further non-invasive method for monitoring the post partuant adaptation of the newborn has emerged with the development of an electrode for measuring the transcutaneous carbon dioxide partial pressure. In order to achieve the correct interpretation of measuring data in depressed newborns, a transcutaneous carbon dioxide partial pressure measurement was performed on 36 vigorous newborns directly post partum. The levels of the transcutaneous carbon dioxide measurement exceeded those from arterial PCO2 measurements. After using the Severinghaus corrective formula which takes into account a tissue factor as well as a temperature factor, the levels did correspond well with the results from arterial CO2 partial pressure determinations. In order to be able to investigate the adaptation of the circulation, we performed synchronous measurements of the tcPCO2 infraclavically and in the regio pubica. The significant difference between the measuring data of both electrodes up to an interval of 26 minutes post partum suggests that during the early adaptation phase of the vigorous newborn, there is a right to left shunt with venous admixture.

Adaptation, Physiological↗
PubMedDate not supplied

[Extracorporeal gas exchange--an alternative to ventilation of the premature newborn infant with respiratory insufficiency].

In spite of improvements in its prophylaxis and therapy the membrane syndrome is still one of the main causes of morbidity and mortality in newborns. In many perinatal centers in the United States extracorporeal gas exchange via an artificial lung is the ultimate step in therapy for this group of patients today. As a result of our own research work we are able to introduce an extracorporeal circulation system which is especially suited to the particular situation of the immature newborn and which enables a complete immobilization of the lung to avoid baro-trauma with alveolar oxygen diffusion and CO2-removal through the membrane lung. Using appropriate dimensions the system can be housed in a newborn incubator. With low total resistance the perfusion in the newborn is performed via an arterio-venous shunt of the umbilical vessels alternatively with and without a mechanical pump. We tested this perfusion system on premature lambs with a gestational age of 128 to 130 days. During a test period of from 6 to 8 hours at a low blood flow rate (200 ml/min) we achieved a sufficient CO2-removal via the membrane lung with enough oxygen supply through the non-ventilated lung. By means of suitable materials, and using CO2 gas priming procedure and employing prostacyclin analogons to inhibit thrombocyte aggregation, it was possible to lower the heparine dosage to a minimum.

Animals↗