Untersuchungen des β-Lipoproteinsystems nach Berg bei Gesunden,Kranken und Schwangeren

Ohne Zusammenfassung     

Fatty Acid Composition of the Peribacteroid Membrane and the ER in Nodules of Glycine max Varies after Infection by Different Strains of the Microsymbiont Bradyrhizobiumjaponicum

The fatty acid composition of ER, Golgi and peribacteroid membrane (PBM) from root nodules formed on Glycine max after infection with different strains of Bradyrhizobium japonicum has been analysed by gas chromatography. In each plant-microsymbiont combination the fatty acid composition (FAC) of the PBM is distinct from ER and Golgi. The similarity between ER and PBM fatty acid composition is significantly stronger than between Golgi and PBM. In addition the fatty acid composition of all membrane systems in nodules is affected by the microsymbiont strain. A comparison of four strains of Bradyrhizobium japonicum grown in agar surface culture and isolated as the symbiotic bacteroids reveals a decrease in oleic acid during bacteroid differentiation.     

Möglichkeiten zur Steigerung der Schwermetallsorptionsleistung von Mikroorganismen

The sorption capacity of silver on different biological materials has been investigated depending on physico-chemical pretreatments. The maximum silver loading values measured were compared with the values obtained with nontreated biomasses. The results show an increase of the loading capacity up to a factor of 10 in case of the alkalitreated biomasses. When the biomasses are extracted before being used as adsorbent with a solvent mixture of chloroform/methanol in a ratio of 2:1 the efficiency of the silver adsorbing power can be increased. Beyond that, the ability to adsorb silver can also be influenced when microorganisms are used as biocatalysts in a product synthesis before they are used as adsorbents. A strain of Acetobacter methanolicus possesses 1.8 times higher affinity to silver when it is employed in a process of gluconic acid production before adsorption. Physico-chemical pretreatments influence not only the loading capacity of the biological material, but also the contacting time required for the establishment of the adsorption equilibrium can be considerable reduced.     

Rate of erythropoietin formation in humans in response to acute hypobaric hypoxia

This study was carried out to investigate the early changes in erythropoietin (EPO) formation in humans in response to hypoxia. Six volunteers were exposed to simulated altitudes of 3,000 and 4,000 m in a decompression chamber for 5.5 h. EPO was measured by radioimmunoassay in serum samples withdrawn every 30 min during altitude exposure and also in two subjects after termination of hypoxia (4,000 m). EPO levels during hypoxia were significantly elevated after 114 and 84 min (3,000 and 4,000 m), rising thereafter continuously for the period investigated. Mean values increased from 16.0 to 22.5 mU/ml (3,000 m) and from 16.7 to 28.0 mU/ml (4,000 m). This rise in EPO levels corresponds to 1.8-fold (3,000 m) and 3.0-fold (4,000 m) increases in the calculated production rate of the hormone. After termination of hypoxia, EPO levels continued to rise for approximately 1.5 h and after 3 h declined exponentially with an average half-life time of 5.2 h.     

Pulmonary gas exchange in panting dogs

Pulmonary gas exchange during panting was studied in seven conscious dogs (32 kg mean body wt) provided with a chronic tracheostomy and an exteriorized carotid artery loop. The animals were acutely exposed to moderately elevated ambient temperature (27.5 degrees C, 65% relative humidity) for 2 h. O2 and CO2 in the tracheostomy tube were continuously monitored by mass spectrometry using a special sample-hold phase-locked sampling technique. PO2 and PCO2 were determined in blood samples obtained from the carotid artery. During the exposure to heat, central body temperature remained unchanged (38.6 +/- 0.6 degrees C) while all animals rapidly switched to steady shallow panting at frequencies close to the resonant frequency of the respiratory system. During panting, the following values were measured (means +/- SD): breathing frequency, 313 +/- 19 breaths/min; tidal volume, 167 +/- 21 ml; total ventilation, 52 +/- 9 l/min; effective alveolar ventilation, 5.5 +/- 1.3 l/min; PaO2, 106.2 +/- 5.9 Torr; PaCO2, 27.2 +/- 3.9 Torr; end-tidal-arterial PO2 difference [(PE' - Pa)O2], 26.0 +/- 5.3 Torr; and arterial-end-tidal PCO2 difference, [(Pa - PE')CO2], 14.9 +/- 2.5 Torr. On the basis of the classical ideal alveolar air approach, parallel dead-space ventilation accounted for 54% of alveolar ventilation and 66% of the (PE' - Pa)O2 difference. But the steepness of the CO2 and O2 expirogram plotted against expired volume suggested a contribution of series in homogeneity due to incomplete gas mixing.     

Muscle plasticity: comparison of a 30-Hz burst with 10-Hz continuous stimulation

The changes in the contractile properties induced by a 30-Hz phasic stimulation paradigm were measured and compared with the changes induced by a 10-Hz continuous stimulation paradigm. The study was performed on the tibialis anterior muscles of cats with one paradigm applied to one hindlimb muscle and the other to the contralateral limb. Both hindlimb muscles received the same number of stimuli in a day, making the average stimulation frequency 10 Hz. Two periods of daily stimulation were studied, 8 and 24 h/day. Muscles stimulated at 30 Hz produced greater overall tetanic tension and, during a prolonged stimulation test, exerted a greater mean tension than muscles stimulated at 10 Hz (50 and 32% increase for animals stimulated for 8 and 24 h/day, respectively). Muscle mass was least reduced and fewer pathological abnormalities were observed in the muscles stimulated at 30 Hz. There were no apparent differences in the histochemistry or biochemistry between muscles stimulated at 10 and 30 Hz, which could account for these differences in muscle properties. These results indicate the 30-Hz paradigm may be better suited than 10 Hz continuous stimulation for applications requiring sustained muscle tension such as correction of scoliosis or muscle conditioning for motor prostheses.     

Erythrocyte deformability and lung segmental vascular resistance: effect of hematocrit

We have investigated the role of erythrocyte (RBC) deformability and perfusate viscosity on lung segmental vascular resistance in 12 isolated perfused lungs of 3- to 5-wk-old rabbits. Each lung was perfused alternately with control and formaldehyde-fixed rabbit RBCs at a flow rate of 80 ml.kg-1.min-1, left atrial and airway pressures being 8 and 6 cmH2O, respectively (zone 3). Perfusate RBC concentration was kept constant at 3.2 x 10(6)/mm3 for group I lungs (n = 6) and 7.2 x 10(6)/mm3 for group II lungs (n = 6). In all lungs, we measured pressures in the pulmonary artery and in 20- to 50-microns-diam arterioles and venules with the micropipette servo-null method during both perfusion periods. Compared with control, fixed cells had a 60% decrease in deformability index (i.e., the volume of a dilute solution of RBCs filtered through a 5-microns Nuclepore filter in 1 min). In groups I and II, perfusate viscosity of fixed cells was 15 and 55% greater, respectively, than that of control cells. We found that perfusion with fixed cells in group I lungs did not alter total or segmental vascular pressure drops. However, in group II lungs, perfusion with fixed cells at twice the cell concentration resulted in an increase in total vascular pressure drop, mainly due to an increase in pressure drop in veins (50% of total) and arteries (33%). The relatively small (17%) increase in pressure drop in microvessels was probably due to distension and/or recruitment of capillaries resulting from increased venular pressures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood rheology in acute mountain sickness and high-altitude pulmonary edema.

The role of blood rheology in the pathogenesis of acute mountain sickness and high-altitude pulmonary edema was investigated. Twenty-three volunteers, 12 with a history of high-altitude pulmonary edema, were studied at low altitude (490 m) and at 2 h and 18 h after arrival at 4,559 m. Eight subjects remained healthy, seven developed acute mountain sickness, and eight developed high-altitude pulmonary edema. Hematocrit, whole blood viscosity, plasma viscosity, erythrocyte aggregation, and erythrocyte deformability (filtration) were measured. Plasma viscosity and erythrocyte deformability remained unaffected. The hematocrit level was lower 2 h after the arrival at high altitude and higher after 18 h compared with low altitude. The whole blood viscosity changed accordingly. The erythrocyte aggregation was about doubled 18 h after the arrival compared with low-altitude values, which reflects the acute phase reaction. There were, however, no significant differences in any rheological parameters between healthy individuals and subjects with acute mountain sickness or high-altitude pulmonary edema, either before or during the illness. We conclude that rheological abnormalities can be excluded as an initiating event in the development of acute mountain sickness and high-altitude pulmonary edema.