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Biomedical subjects

K Müller

Publications and source records attributed to K Müller.

At least 325 records · Page 18Linked to original sources
PubMed1987

Haemodilution therapy in ischaemic stroke: plasma concentrations and plasma viscosity during long-term infusion of dextran 40 or hydroxyethyl starch 200/0.5.

In 21 patients with ischaemic strokes we have monitored plasma viscosity, total plasma concentration, numeric average molecular weight (Mn), and weight average molecular weight (Mw) of Dextran 40 (dextran) and hydroxyethylstarch 200/0.5 (HES) during 10 days of treatment (days 1-4, 2 X 500 ml; days 5-10, 1 X 500 ml). Plasma concentrations of dextran increased during the first 4 days (8.3 mg X ml-1 on the first day to 18.0 mg X ml-1 on the fifth day), reached an apparent steady state of 17.2 mg X ml-1 during the next 6 days, and declined subsequently with a half-time (t1/2) of 4.03 days. After ten days treatment Mn and Mw were shifted towards higher values. Plasma viscosity increased from 1.26 mPas to 1.69 mPas on Day 10 (p less than 0.01) and was linearly correlated with the total plasma concentration of dextran (p less than 0.001; r = 0.88). Total plasma concentrations of HES averaged 11.7 mg X ml-1 on Day 1 and 12.4 mg X ml-1 on Day 5. The molecular weight distribution did not change during the infusions but decreased in comparison with the administered solution. Plasma viscosity fell from 1.40 mPas to 1.30 mPas at Day 10 (p less than 0.05) and was not related to the concentration of HES. The haemodiluting effect, as indicated by a decrease of the haematocrit, was 22% and 16.8% for dextran and HES respectively. These data suggest several advantages of HES compared with dextran in haemodilution therapy of ischaemic stroke.

Aged↗
PubMed1987

The increase in skin 7-dehydrocholesterol induced by an hypocholesterolemic agent is associated with elevated 25-hydroxyvitamin D3 plasma level.

Vitamin D3 is generated in skin by UV irradiation of 7-dehydrocholesterol (7-DEHC). Whether the 7-DEHC amount in skin affects vitamin D3 formation, and thereby the plasma level of 25-hydroxyvitamin D3 (25[OH]D3) is not known. In the present work we report on the influence on vitamin D and Ca metabolism of a new hypocholesterolemic agent, HCG-917 (0-2-[hydroxy-3-]N'-(2-chlorophenyl)-N-piperazinyl-1- [propyl]-4-chloro-benz-aldoxim-hydrochloride) which inhibits 7-DEHC reductase and thereby increases skin 7-DEHC. Rats were treated with HCG 917 (0.3 and 5.0 mg/kg, orally) for 13 days. HCG 917 caused a dose-dependent decrease in cholesterol and concomitant accumulation of 7-DEHC in plasma and skin. In skin, 7-DEHC was: control: 1.05 +/- 0.20; HCG 917, 0.3 mg/kg: 1.41 +/- 0.22; HCG 917, 5.0 mg/kg: 2.35 +/- 0.35 mg/g. At a dose of 0.3 mg/kg, HCG 917 had no significant influence on the plasma level of neither 25(OH)D3 nor 1,25(OH)2D3. However, at a dose of 5.0 mg/kg, HCG 917 induced a significant increase in plasma 25(OH)D3 (control: 36.2 +/- 2.2; HCG 917 5.0 mg/kg: 57.6 +/- 6.5 nmol/l) and a slight but not significant rise in 1,25(OH)2D3. Calcium balance studies indicated that HCG 917 did not influence intestinal Ca absorption nor urinary Ca excretion. At a dose of 5.0 mg/kg HCG 917 slightly induced a decrease in total plasma Ca. In conclusion, HCG 917 treatment can induce a significant rise in skin 7-DEHC with an increase in plasma 25(OH)D3. These results suggest that variation in the skin level of 7-DEHC can directly influence the cutaneous production of vitamin D3 and thereby the vitamin D status of the organism.

Animals↗
PubMed1987

Structure and thermodynamics of the dihexadecylphosphatidylcholine-water system.

X-ray small- and wide-angle diffraction, differential scanning calorimetry (DSC), temperature scanning densitometry (TSD) and electron microscopy were used to study the lyotropic and thermotropic properties of the system 1,2-O-dihexadecyl-sn-glycero-3-phosphocholine-water over a wide range of compositions from the dry lipids to a large excess of water, and in the temperature range between 0 degrees C and 150 degrees C. The results were used to construct a temperature-composition phase diagram. The phases have been characterized with respect to their molecular arrangements and hydrocarbon chain packing subcells. In the fully hydrated state (greater than 45 wt% H2O) four thermotropic phases were found, with readily reversible transitions at 5 degrees C, 32.5 degrees C and 43.6 degrees C, respectively. The two lower temperature phases deviate from all others in consisting of bilayers with fully interdigitated hydrocarbon chains, while above 32.5 degrees C the structures resemble closely those of the analog diester lipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). At hydrations between 30 and 45 wt% H2O, and below 32 degrees C, interdigitated and non-interdigitated multilayers coexist in one coherent phase. A bilayer tilting mechanism is proposed for the formation of this coexistence of two regular structures. Below 30 wt% H2O, hydrated 1,2-O-dihexadecyl-sn-glycero-3-phosphocholine (DHPC) exists in lamellar, non-interdigitated bilayers, showing very weak interbilayer swelling. There, the water molecules appear to occupy voids between the polar headgroups.

Calorimetry, Differential Scanning↗
PubMed1987

Thermal phase behaviour and structure of hydrated mixtures between dipalmitoyl- and dihexadecylphosphatidylcholine.

Mixtures of 1,2-dipalmitoyl- and 1,2-O-dihexadecyl-sn-glycero-3-phosphocholine (DPPC and DHPC) in dispersion with excess water were studied by differential scanning calorimetry (DSC) and X-ray diffraction techniques. The transition parameters of the main gel-to-liquid crystalline transition show a monotonous dependence on the composition, indicating ideal miscibility of the two lipids, in keeping with the closely similar structures of the pure, hydrated lipids in the P beta' and L alpha states. The pre-transition shows a depression to a minimum temperature of 23 degrees C occurring around equimolar mixtures. Below the pre-transition temperatures, the L beta' gel phase of DPPC maintains bimolecular structure up to DHPC admixtures of 50 mol%, with adaptations in hydrocarbon chain packing and multilayer periodicity. On the side of DHPC, the interdigitated gel structure shows full solubility for DPPC up to equimolarity without major structural changes. The crystalline Lc-phase of DPPC exhibits immiscibility with DHPC, demonstrated by the fact that the subtransition is abolished already at less than 15 mol% DHPC. DHPC, below its subtransition, can accommodate up to 50 mol% DPPC within an interdigitated layer structure with unperturbed, crystalline hydrocarbon chain packing.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Mutants of an influenza A reassortant which are cold-sensitive (cs) as well as temperature-sensitive (ts): on the role of the neuraminidase activity for influenza virus infection.

Temperature-sensitive (ts) mutants were obtained by undiluted passage of the cold-sensitive (cs) influenza A reassortant 113/Ho. This reassortant produces normal yields of infectious virus with negligible neuraminidase (NA) at 40 degrees. The mutants obtained from it had a narrow temperature optimum for plaque formation in chick embryo cells, since they were cs as well as ts. Such cs/ts mutants have not been described before. In contrast to mutants derived from FPV, most of the mutants derived from 113/Ho carried a ts defect in the NA gene. NA activity was not detectable after infection with these mutants at 40 degrees. The results are interpreted to mean that, although NA activity is not completely dispensible for influenza A virus replication in tissue cultures, the viruses possess a surplus of NA activity. The normally high activity of NA of influenza viruses seems to be necessary only for the natural infection of the respiratory tract.

Animals↗
PubMed1987

[Reuse of angiography catheters. II. Effect of multiple sterilizations on the properties of the catheter material--physicochemical studies].

The reuse of sterile medical devices designated for single use is a controversial practice, known to be performed in many countries. As far as catheters for angiography are concerned, various methods for cleaning and sterilisation are in use. However, interactions of detergents and ethylene oxide used in reprocessing with polyethylene materials of the catheters have not been investigated systematically. This paper presents a physico-chemical characterisation of common angiographic catheters. The interaction of polyethylene and ethylene oxide is examined.

Angiography↗
PubMed1987

[Recycling of angiography catheters. III. Effect of multiple sterilizations on the characteristics of catheter material. Experimental studies on mechanical behavior].

Reprocessing of angiographic catheters is becoming common practice. Physico-chemical and mechanical integrity of polyethylene, however, is conditional for any method of reprocessing in use. In this paper data are presented concerning mechanical stability of polyethylene catheters when repeatedly exposed to ethylene oxide, leading to the conclusion that reuse of catheters seems to be possible without loss of mechanical safety.

Angiography↗