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Biomedical subjects

S Schmidt

Publications and source records attributed to S Schmidt.

At least 451 records · Page 25Linked to original sources
PubMed1985

Low dose streptozotocin induced diabetes in mice. Metabolic, light microscopical, histochemical, immunofluorescence microscopical, electron microscopical and morphometrical findings.

The experimental animal model of human insulin-dependent diabetes mellitus (IDDM, type I diabetes), which was for the first time described by Like and Rossini (1976) for Charles River CD-1 mice and produced by the application of multiple subdiabetogenic streptozotocin (SZ) doses, has been reproduced in the mouse strain C57 Bl/KsJ which has been bred over several generations at the Central Institute for Diabetes Karlsburg (since 1975). Male mice were given subdiabetogenic intraperitoneal injections of SZ (40 mg/kg b.w.) on five days running.--The simultaneously performed metabolic, light and electron microscopical, histochemical, fluorescence microscopical, and morphometric examinations show that the small doses of SZ lead to a metabolic disturbance in the islets of Langerhans already on the third day of the experiment (after the first two SZ injections) which is associated with a high-degree reduction or an interruption of the insulin production. Subsequently, on the 8th day (three days after the last SZ injection) up to the 20th day an insulitis occurs which is characterized by a target cell reaction of lymphocytes against the beta cells and leads to the lysis of the majority of the beta cells. In the course and after the insulitis, a persisting insulin deficiency diabetes develops with lacking signs of an attempt to replace the perished beta cells. For the time being, the nature of this target beta cell destruction by lymphocytes remains unclear. According to the enzyme-histochemical and electron microscopical results, the involved lymphocytes are natural killer cells (NK cells) rather than T cells. The release of the target cell reaction is obviously effected by the initial metabolic disturbances in the beta cells intervening in the insulin synthesis. Virus bodies do not play any role in this process. The importance of this animal model to human insulin-dependent diabetes mellitus is discussed.

Animals↗
PubMed1985

Growth of phenol-mineralizing microorganisms in fresh water.

A method was developed to enumerate the procaryotic and eucaryotic phenol-mineralizing microorganisms present in samples of fresh water. Sixty-five percent or greater mineralization of [U-14C]phenol was considered a positive tube (contained phenol-mineralizing microorganisms) in the most-probable-number technique. Replicate most-probable-number tubes contained no microbial inhibitors, streptomycin and tetracycline, or cyclohexamide and nystatin plus 200 pg to 100 micrograms of phenol per ml. Phenol mineralization rates were obtained by measuring the amount of exogenous phenol that disappeared from solution over time in the presence or absence of the microbial inhibitors. Initially, less than 100 phenol-mineralizing bacteria per ml and 1 phenol-mineralizing fungus per ml were present at both 200 pg and 100 micrograms of phenol per ml. Phenol mineralization rates were 6.3 times greater for the mineralizing bacteria than for the fungi at 200 pg of phenol per ml. Phenol concentrations above 10 micrograms/ml were inhibitory to the microorganisms capable of mineralizing phenol. The phenol mineralizers grew in the water samples in the absence of phenol, indicating that there were sufficient indigenous nutrients in the lake water to support growth. There was no difference in the growth rate of these microorganisms in the presence or absence of 1 ng of phenol per ml, whereas the growth rate was more rapid at 1 microgram of phenol per ml than in its absence. There was a correlation between microbial growth and the amount of phenol mineralized at 1 microgram but not at 1 ng of phenol per ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
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↗
PubMed1985

Cytotoxicity of MHC antisera against rat islets: detection by release of 51Cr and leakage of hormones.

Antisera directed to major histocompatibility complex (MHC) antigens are able to mediate complement-dependent cytotoxicity against rat islets of Langerhans. This cytotoxic action was detected by the release of 51Cr from prelabeled islets or by the loss of glucagon, but beta-cell damage as measured by insulin leakage was less pronounced. In addition, MHC antigens were demonstrated on dispersed islet cells by indirect immunofluorescence. These results suggest that islet cells bear MHC antigens and that antibodies directed to these antigens can mediate a complement-dependent cytotoxic reaction against islets of Langerhans.

Animals↗
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

[Accuracy in the diagnosis of renal masses. Computed tomography, sonography, urography, angiography].

One hundred and twelve renal masses, whose histology was confirmed at operation, as well as renal vein thrombosis and renal infiltration, were examined by urography, sonography, CT and angiography. In general the results showed good agreement. For the diagnosis of the type of tumour, its size, infiltration into the renal capsule, demonstration of regional lymph node metastases and infiltration into neighbouring organs and for the diagnosis of liver metastases, CT was superior to the other methods.

Abscess↗
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

Photochemical (PUVA) treatment of isolated rat islets.

Isolated rat islets were irradiated with long-wave ultraviolet light alone or in combination with the photosensitizer 8-methoxypsoralen. The influences on specific beta cell functions were determined with the aim of finding out experimental conditions which allow the use of such islets for transplantation. Short-term effects: Ultraviolet light affected [3H]leucine incorporation into (pro)insulin (5 J/cm2: 53.8%, 10 J/cm2: 41.0% of the controls) and insulin release was slightly reduced. 8-methoxypsoralen enhanced the irradiation effect. Long-term effects: A restoration of irradiation-affected beta cell function was detected after 5 days of culture unless the dose exceeded 2 J/cm2 (0.1 microM 8-methoxypsoralen) or 1 J/cm2 (1 microM 8-methoxypsoralen). After functional restoration islets can be used for transplantation experiments.

Animals↗
PubMed1984

Protective effect of uridine on D-galactosamine-induced deficiency in brain uridine phosphates.

In the rat, 2 h after intraventricular application of 10 mumoles D-galactosamine as well as 10 and 20 mumoles uridine, opposite effects on brain content of UDP-glucose and uracil nucleotides were observed. While D-galactosamine caused a strong decrease in content of uridine phosphates, the brain content of the latter substances was markedly increased after uridine application. Furthermore, 20 mumoles uridine applied 10 min prior to D-galactosamine administration prevented the D-galactosamine-induced drop in brain uridine phosphates. The results are discussed in the light of behavioural findings in which D-galactosamine-induced impairment of retention performance of an acquired behaviour could be abolished by uridine pretreatment.

Animals↗