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Biomedical subjects

C Bauer

Publications and source records attributed to C Bauer.

At least 343 records · Page 19Linked to original sources
PubMed1982

Disinfectant usage and hygiene practises at Port Moresby General Hospital.

A survey was conducted during August-October 1981, to assess the need for disinfectant policy for the Port Moresby General Hospital. Data collected revealed confusion amongst the nursing staff regarding the correct use of various detergents and disinfectants, an unacceptably high incidence of post-operative infections, evidence of poor general cleaning of the hospital and evidence of contamination of the distilled water supply in the Central Sterilizing Department by Pseudomonas species. There is an urgent need for the formation of a committee to advise and promote a disinfectant policy for the hospital, to ensure that this is followed by nursing and cleaning staff and to establish continuous surveillance of hygiene standards within the hospital.

Disinfection↗
PubMed1981

Studies on microsomal metabolizing systems for mutagenesis tests. Stability of fortified fractions.

Rat liver S-9 microsomal fractions were fortified with NADP+, G-6-P, and MgCl2 and stored at -80 degrees C and -20 degrees C. At various times aminopyrine demethylase and lipid peroxidation were determined and compared with that of non-fortified fractions. No difference in stability was noted between fortified and not fortified fractions. The known stability pattern of non fortified fractions was confirmed. Lipid peroxidation was found blocked in the fractions stored at -80 degrees C whereas a small release of malonyl dialdehyde proceeded in the frozen state at -20 degrees C, contributing to the loss of activity at this temperature. The use of pre-fortified fractions stored at -80 degrees C is justified.

Aminopyrine N-Demethylase↗
PubMed1981

Analysis of bicarbonate binding to crocodilian hemoglobin.

Crocodilian hemoglobin has a high intrinsic oxygen affinity but does not react with those organic phosphate esters that normally control the oxygen affinity of blood in higher vertebrates. Instead, its oxygen affinity is greatly lowered by CO2. The present study was undertaken to determine the nature of the CO2 binding to the hemoglobin of a crocodilian species, the Caiman, both qualitatively and quantitatively. The following parameters were measured: (a) carbamino compounds of deoxy- and oxyhemoglobin, (b) the effect of CO2 (at constant pH) on the oxygen affinity of Caiman hemoglobin, (c) total CO2 concentration of hemoglobin solutions at different pH and pCO2 values, and (d) the effect of CO2 on CD spectra of Caiman aquomethemoglobin. An analysis of the results of these measurements revealed that CO2 binding in the form of carbamate was not oxygen-linked and cannot, therefore, mediate the CO2 effect on the oxygen affinity. It was found, however, that 2 mol of bicarbonate can be bound/hemoglobin tetramer and that the association constant of the bicarbonate anion greatly depends upon the state of ligation. At pH 7.02 and 25 degrees C, a numerical value of 2.0 X 10(3) M-1 was obtained for deoxyhemoglobin, while for oxyhemoglobin no significant bicarbonate binding could be observed. At more alkaline pH (pH greater than or equal to 7.5), the association constant for deoxyhemoglobin decreases. Circular dichroism of Caiman aquomethemoglobin decreased considerably in the 287-nm region upon addition of CO2 at constant pH, an effect very similar to the one caused by inositol hexaphosphate in human aquomethemoglobin.

Alligators and Crocodiles↗
PubMed1981

Concanavalin A, a receptor protein with apparently co-operative binding characteristics.

Laser nephelometry is a suitable technique for the quantitative determination and differentiation of both lectins and glycoconjugates in the low-picomolar range. Simultaneously this method renders possible investigations on the specificity and mode of interaction between lectins and different ligands. The results demonstrate that the degree of co-operativity between concanavalin A and the respective glycoconjugate is dependent on the presence of hydrophobic binding sites and can be substantially altered by conformational changes of the ligand. The transition from apotransferrin to Fe3+-transferrin induces a transformation of the sigmoidal-shaped binding curve to a hyperbolic one. Hence, at low concentrations, Fe3+-transferrin is bound far better than apotransferrin, whereas maximal binding is nearly identical. After removal of N-acetylneuraminate, concanavalin A is less efficient in differentiating between the Fe3+-charged and Fe3+-free (apo) forms of transferrin.

Apoproteins↗
PubMed1981

Studies on the incubation mixtures for the in vitro mutagenesis test with metabolic activation (microsomal assay) = 2. Behaviour of cytochromes P-450, P-420, b5, of NADPH-CYT. C-reductases, and p-nitroanisole demethylase.

Cytochromes P-450, P-420, b5, NADPH-cytochrome c-reductase, aminopyrine and p-nitroanisole demethylase and lipid peroxidation were determined at various times in the incubation mixtures for the in vitro microsomal assay for the mutagenic activity of xenobiotics. No effect was observed on cytochromes b5 and P-420. A decrease in cytochrome P-450 (about 50% in 2 hrs.) and a much faster decrease of aminopyrine demethylase and NADPH cytochrome c-reductase (about 50% in 30 min) was noted with mice microsomes. With S9 liver fraction of rat, p-nitroanisole demethylase activity was much more stable than aminopyrine demethylase activity in the presence of lipid peroxidation, but the decrease was faster and at comparable rates for both activities in the presence of 50 mM styrene. The use of simple colorimetric assay as proves of microsomal monooxygenase activity and the importance of this kind of enzyme studies for a better understanding of the in vitro mutagenesis results are discussed.

Animals↗
PubMed1981

[Role of cytochrome P-450 in strain D7 of the yeast Saccharomyces cerevisiae].

Usual "in vitro" mutagenesis tests combine microbial test systems with mammalian metabolism (microsomal assay). Some cases are known in which expected positive results are not obtained due to many factors operating between the microsomes in the incubation mixtures and the nucleus of the test microbial cells (detoxifying mechanisms, permeability effects, unstable intermediate, alternative targets in the pathway, etc.). In these cases, useful additional information could be obtained using microbial test systems with incorporated metabolism. Microbial systems and in particular yeasts in Cytochrome P-450 dependent metabolizing activity are known since many years. We studied under this aspect the strain D7 of Saccharomyces cerevisiae, used in our laboratory, in order to standardize the conditions for optimal metabolizing activity. The composition of the culture medium, the growth phase, and the effect of the amount of the initial inoculum, were studied. Cytochrome P-450 content was determined by the technique of difference spectra (reduced cytochrome +/- CO). Results on the effect of glucose and sodium phenobarbital concentration in the culture medium were in agreement with the literature. Moreover we found that the cytochrome P-450 contents was markedly dependent on the size of the initial inoculum, being higher and the smaller was the initial inoculum.

Cell Division↗
PubMed1981

Demonstration of high levels of erythropoietin in rat kidneys following hypoxic hypoxia.

Controversial hypotheses exist as to whether hypoxic kidneys produce biologically active erythropoietin (Ep) or an inactive erythropoietic factor that generates Ep from plasma protein in the blood. To clarify the role of the kidney in Ep production we attempted to extract Ep from kidneys of normal and of hypoxia exposed (6 h at 0.42 atm) Sprague-Dawley rats. Ep was measured in the microsomal fraction of kidney homogenates, using the exhypoxic polycythemic mouse assay for Ep. The Ep content was also determined in kidneys that were flushed free of blood with isotonic phosphate-buffer prior to extirpation. We found 0.04 U Ep/g in blood-depleted kidneys of normal rats. Upon exposure of the animals to hypoxia the Ep level increased to 0.92 U/g kidney. Ep levels were significantly higher in the kidney cortex than in the medulla. The erythropoietic activity in renal extracts was not enhanced after incubation of samples with homologous serum. Ep extracted from hypoxic kidneys behaved identically with plasma-Ep in the following biochemical tests: heat stability, affinity chromatography, with wheat germ lectin, ion exchange chromatography, molecular sieve chromatography, and neuraminidase inactivation. These studies support the hypothesis that kidney cortex cells are capable of producing biologically active Ep.

Animals↗
PubMed1981

High oxygen affinity of maternal blood reduces fetal weight in rats.

In order to obtain information on the physiological significance of the difference in oxygen affinity between maternal and fetal blood, we have examined the effect of an acute increase of the oxygen affinity of maternal blood in pregnant rats, on fetal body weight, fetal brain and liver weights, placental weight, and the hematocrit of fetal blood. The increase in oxygen affinity was produced by exchange-transfusing pregnant rats on day 19 of gestation with blood that had been treated previously with sodium cyanate. As a result of the exchange transfusion, the difference in oxygen affinity between maternal and fetal blood essentially disappeared. Pregnant rats exchanged with normal blood served as controls. On day 21 of gestation, the fetal body weight and the fetal liver weight were significantly smaller by 18% and 25% respectively, in the group where the oxygen affinity of the maternal blood was acutely raised when compared to the controls. Also, the hematocrit of the fetal blood was significantly higher in the group where mothers had the high blood oxygen affinity. Placental weight and fetal brain weight were not significantly altered. We infer, that the reduction of fetal weight is due to fetal hypoxia which is caused by the abolishment of the difference in oxygen affinity between maternal and fetal blood. Human infants, whose birth weight is too small for their gestational age have a significantly increased postnatal mortality compared to babies with normal weight. We suppose that the increased mortality of newborns who are too small for their gestational age, represents a selective pressure that has favoured the evolution of a high oxygen affinity of fetal in comparison with maternal blood.

Animals↗
PubMed1981

Genetic activity of vinylidene chloride in yeast.

Vinylidene chloride (VDC) was tested for its ability to induce both point mutation and mitotic gene conversion in a diploid strain (D7) of the yeast Saccharomyces cerevisiae in a suspension test with and without a mammalian microsomal activation system, and in the intrasanguineous host-mediated assay in mice. In suspension tests with D7, VCD was toxic but not genetically active without microsomal activation. When a mouse liver 10 000 X g supernatant was included in the suspension tests, dose-related increases in both point mutation and mitotic gene conversion were seen at survival levels greater than 50%, at doses of VCD above 20 mM. In the host-mediated assay, VDC induced both point mutation and mitotic gene conversion when recovered from the liver and kidneys after both acute and sub-acute dosing. Yeasts recovered from the lungs showed little, if any, increase in either point mutation or mitotic gene conversion.

Animals↗
PubMed1981

Regulation of red cell DPG metabolism in fetuses and adults.

We have compared red cell levels of 2,3-DPG in relation to the activities of certain glycolytic enzymes (DPGM, PK, PFK) between fetuses and adults in various rodents in order to find out the possible causes of the low intraerythrocytic concentration of 2,3-DPG in the fetal period. It was concluded that, in all species studied, 2,3-DPG synthesis was limited by a high activity of PK in fetal red cells. In addition, in species of the suborder Myomorpha, the activity of DPGM was lower in fetal red cells than in adults. In particular, the 2,3-DPG deficient fetal rat red cells completely lacked DPGM activity.

2,3-Diphosphoglycerate↗
PubMed1980

The problem of negative results for styrene in the in vitro mutagenesis test with metabolic activation (microsomal assay). - 2. Behaviour of epoxide hydrolase in the incubation mixtures.

The behaviour of epoxide hydrolase and monooxygenase was studied in incubation mixtures for the in vitro mutagenesis test with metabolic activation (microsomal assay) both in the presence and in absence of styrene 50mM. Epoxide hydrolase activity was much more stable than monooxygenase in all tested systems (S-9 fractions or microsomes of rats or mice, males or females) both in the presence and in absence of styrene. Membrane bound epoxide hydrolase was slightly less stable than the soluble one. These results further substantiate the explanation for the negative results of in vitro mutagenesis tests with styrene.

Aminopyrine N-Demethylase↗
PubMed1980

Genetic effects of vinylcyclohexene diepoxide in yeast.

Using D7 strain of S. cerevisiae where we can consider three genetic effects such as mitotic gene conversion, mitotic cross over and reverse mutation we tested vinylcyclohexene diepoxide "in vitro" without metabolic activation. In this condition VCD is very toxic and induces both three genetic effects namely mitotic gene conversion, mitotic cross over and reverse mutation.

Crossing Over, Genetic↗