Isolation and semi-synthesis of a bioactive taxane from Taxus canadensis

A minor bioactive taxane, isolated from the needles of Taxus canadensis and semi-synthesized, was shown to be taxcultine.     

Isolation of a relatively pure outer membrane fraction of Moraxella nonliquefaciens and a comparison of its characteristics with the cytoplasmic membrane-containing material

Cell envelope fractions of Moraxella nonliquefaciens were isolated by a slight modification of Osborn's method. Two main membrane fractions were characterized chemically and morphologically. The density of the fraction containing cytoplasmic membrane material was 1.17 to 1.18 g cm-3 compared with 1.24 to 1.27 g cm-3 for the outer membrane fraction. Lipopolysaccharide was detected almost exclusively in the outer membrane fraction and sodium dodecyl sulphate polyacrylamide gel electrophoresis of this fraction revealed one dominant protein band with an apparent molecular weight of 45 000. Cross-contamination of the fractions was estimated to be about 10%, as calculated on the basis of the lipopolysaccharide fatty acid 3-hydroxydodecanoic acid and on the relative activities of D-lactate dehydrogenase and succinate dehydrogenase.     

Effects of irradiation on the biomechanics of osseointegration. An experimental in vivo study in rats

The present study reports on the late effects of increasing doses of radiation on the biomechanics of commercially pure titanium implants (fixtures) installed in the proximal tibia in 26 rats. Twelve weeks after various doses (10, 20, 30, and 35 Gy) of irradiation, the fixtures were inserted into rat tibiae, and after another eight weeks these were tested mechanically in vivo. Acute dose dependent skin reactions developed after all doses except 10 Gy, but most subsided within two to three weeks. There was a statistically significant reduction in torsion but the pull-out load was not significantly reduced for single doses up to 30 Gy. Histological analysis showed that bone remodelling was impaired. Shear stresses and shear moduli were estimated for the bone-implant interface and in the surrounding bone tissue. These estimated stresses and moduli were not found to be correlated to the dose of radiation.     

Bioavailability and first-pass metabolism of oral pentazocine in man

The bioavailability of oral pentazocine was studied in 5 healthy volunteers. Plasma concentrations were determined from 30 min up to 6 hr following oral administration (two 50-mg tablets) and, at other occasions, after intravenous injection of 30 mg pentazocine. The average bioavailability was found to be 18.4 +/- 7.8% (SD, n = 5). It is shown that this low bioavailability depend almost entirely on the first-pass metabolism of pentazocine following oral administration by application of intravenous clearance concepts. The average beta-phase half-life was about the same following intravenous administration, 203 +/- 71 (SD, n = 5) min as following oral administration, 177 +/- 34 (SD, n = 5) min, with a total volume of distribution of 5.56 +/- 1.63 (SD, n = 5) L/kg. It is suggested that the variations in bioavailability of orally administered pentazocine have the potential to contribute to variations in pharmacologic effects in patients.     

Study of the possibility of stabilizing a levorin microbiological standard

The effect of a number of factors, providing increased stability of the levorin microbiological standard was studied. It was shown that air-tight packing and inert gas atmosphere (antibiotic storage in ampoules sealed under nitrogen) significantly increased the antibiotic stability. It was also shown that hydrochinone had the highest positive effect on levorin stability.     

In vivo incorporation of ribosomal proteins into HeLa cell ribosomal particles

Using high salt-washed ribosomal subunits from HeLa cells we detect three ribosomal proteins from the small subunit and five ribosomal proteins from the large subunit that enter ribosomal particles in the absence of ribosome formation (actinomycin D-treated cells); in untreated cells, they enter the ribosomal particles quickly, while the rest of the ribosomal proteins are incorporated gradually. At least two of the large subunit actinomycin D-resistant ribosomal proteins seem to be absent in the 55 S nucleolar ribosomal precursor.     

洪家渡水电站枢纽布置的优化调整

洪家渡水电站是乌江梯级开发的龙头电站 ,坝址处于高山峡谷岩溶地区 ,枢纽由拦河坝、洞式溢洪道、泄洪洞、引水发电系统等建筑物组成。电站初步设计于 1992年审查通过 ,2 0 0 0年正式开工建设 ,在其间的 8年中 ,结合国内外水电技术的进步 ,不断深化对峡谷岩溶地区水电枢纽布置的认识 ,并对枢纽布置进行了一系列优化调整 ,取得了巨大的技术经济效益