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1.
Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones 总被引:1,自引:1,他引:0
A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer. 相似文献
2.
Gillian D Alton David L Pearl Ken G Bateman W Bruce McNab Olaf Berke 《BMC veterinary research》2010,6(1):42
Background
Ontario provincial abattoirs have the potential to be important sources of syndromic surveillance data for emerging diseases of concern to animal health, public health and food safety. The objectives of this study were to: (1) describe provincially inspected abattoirs processing cattle in Ontario in terms of the number of abattoirs, the number of weeks abattoirs process cattle, geographical distribution, types of whole carcass condemnations reported, and the distance animals are shipped for slaughter; and (2) identify various seasonal, secular, disease and non-disease factors that might bias the results of quantitative methods, such as cluster detection methods, used for food animal syndromic surveillance. 相似文献3.
Molecular modelling of the interactions of tetra-(4-N-methylpyridyl) porphin with TA and CG sites on DNA. 总被引:1,自引:1,他引:0
The molecular structure of the DNA-intercalating ligand tetra-(4-N-methylpyridyl) porphin has been determined by X-ray crystallography. The porphyrin has a precise centre of symmetry; the central core is planar, with the N-methylpyridyl groups inclined to it at angles of 66-72 degrees. Molecular modelling of this structure into TpA and CpG sites of intercalated DNA, has been performed, and approximate energetics calculated. It has been shown that only the CpG site can have full ligand intercalation, since the thymine methyl group sterically hinders such geometry at TpA sites. Modelling indicates the importance of electrostatic effects in the low-energy forms of intercalated and part-intercalated complexes at both sequences. 相似文献
4.
OBJECTIVE--To establish a baseline of knowledge to plan an effective health education programme in schools. The survey was repeated at five year intervals from 1969 to 1989. DESIGN--To preserve consistency, the same anonymous questionnaire, which was confidential to the research workers, was used throughout. SETTING--Three secondary schools in Wolverhampton in different parts of the town and representing different social groups. SUBJECTS--Sample sizes ranged from 471 fourth year pupils (aged 14 to 15) in 1969 to 540 in 1984 and 380 in 1989, the decrease being due mainly to the falling birth rate. There were slightly more girls than boys, and the pupils covered the whole range of academic ability. RESULTS--Over the 20 years the proportion of pupils who knew someone taking drugs more than doubled from 15% (71) to 31% (117) and the proportion who had been offered drugs almost quadrupled from 5% (24) to 19% (72). The changes taking place over the past five years were characterised by an increased knowledge about drugs and the first mention of "crack," a purified form of cocaine, and "ecstasy" (methylenedioxymethamphetamine). Peer influence continued to be given as the prime reason for taking drugs. Over the 20 years, though less often mentioned in 1989, television and newspapers remained the most common source of information. CONCLUSIONS--These results suggest the need for responsible coverage by the mass media and for more effective health and social education programmes to prevent the spread of drug misuse. 相似文献
5.
A molecular model has been derived for the intercalation of proflavine into the CpG site of the decamer duplex of d(GATACGATAC). The starting geometry of the intercalation site was taken from previous crystallographic studies on the d(CpG)-proflavine complex, and molecular mechanics used to obtain a stereochemically acceptable structure. This has widened grooves compared to standard A- or B- double helices, as well as distinct conformational, roll, twist and tilt features. 相似文献
6.
Nonocclusive main pulmonary arterial distension produces peripheral pulmonary hypertension. The mechanism of this response is unknown. The effects of total spinal anesthesia on the response were studied in halothane-anesthetized dogs. Before total spinal anesthesia, main pulmonary arterial balloon inflation increased pulmonary arterial pressure and resistance without affecting systemic hemodynamic variables. Both right and left pulmonary arterial pressures were monitored to exclude unilateral obstruction with main pulmonary arterial balloon inflation. Total spinal anesthesia decreased cardiac output and systemic arterial pressures. After total spinal anesthesia, main pulmonary arterial distension still increased pulmonary arterial pressure and resistance. Right atrial pacing, discontinuation of halothane anesthesia, and norepinephrine infusion during total spinal anesthesia partially reversed the hemodynamic changes caused by total spinal anesthesia. The percent increase in pulmonary vascular resistance due to main pulmonary arterial distension was similar before total spinal anesthesia and during all experimental conditions during total spinal anesthesia. The pulmonary hypertensive response is therefore not dependent on central synaptic connections. 相似文献
7.
Pearl Horn Cooper Irvin N. Hirshfield Werner K. Maas 《Molecular & general genetics : MGG》1969,104(4):383-390
Summary Mutants of Escherichia coli K-12 previously isolated in the authors' laboratory have reduced arginyl-tRNA synthetase activity. The mutants fall into two classes. All mutants grow slowly on arginine-free medium. On arginine-supplemented medium some mutants grow at a normal rate (Class I) while others still grow slowly (Class II). Matings were performed to located a Class I and a Class II mutation on the E. coli chromosome map, and on the basis of our results we have assigned both to one locus, argS. 相似文献
8.
Arthur O. Tucker Michael J. Maciarello Pearl W. Burbage George Sturtz 《Economic botany》1994,48(3):333-336
The essential oils of fresh leaves, twigs, and/or fruits of spicebush cultivated in Oregon (field distilled) and Delaware (laboratory distilled) are examined by GC/MS. The oil of leaves of spicebush is notably high in 6-methyl-5-hepten-2-one (1.94% in Oregon to 34.83 ± 9.69% in Delaware). β-caryophyllene (15.26% in Oregon to 48.44 ± 1.35% in Delaware), and/or (E)-nerolidol (10.20% in Oregon to 12.05 ± 2.02% in Delaware). The oil of the twigs of spicebush is notably high in 1,8-cineole (45.41 ± 0.35% in Delaware), while the oil of the fruits is notably high in a-phellandrene (64.62 ± 0.66% in Delaware) and β-phellandrene (11.23+0.17% in Delaware). 相似文献
9.
Marco Moracci Maria Ciaramella Roberto Nucci Laurence H. Pearl Ian Sanderson Antonio Trincone Mos Rossi 《Biocatalysis and Biotransformation》1994,11(2):89-103
The Sulfolobus solfataricus β-glycosidase (Sβgly) is a thermostable and thermophilic glycosyl-hydrolase with broad substrate specificity. The enzyme hydrolizes β-D-gluco-, fuco-, and galactosides, and a large number of /Winked glycoside dimers and oligomers, linked β1-3, β1-4, and β1-6, It is able to hydrolize oligosaccharides with up to 5 glucose residues. Furthermore, it is also able to promote transglycosylation reactions. The corresponding gene has been cloned and overexpressed both in yeast and Escherichia coli. Based on sequence and functional data, the Sβgly has been assigned to the so-called BGA family of glycosyl-hydrolases, including β-glycosidases, β-galactosidases and phosho-β-galactosidases from mesophilic and thermophilic organisms of the three domains. The Sβgly has been crystallized and the resolution of its structure is in progress. Because of its special properties, the enzymes has considerable biotechnological potential. 相似文献
10.
OBJECTIVE--To monitor young people''s knowledge and experience of illicit drugs between 1969 and 1994 at intervals of five years. DESIGN--The same anonymously completed questionnaire was used throughout. SETTING--Three Wolverhampton secondary schools representing three different socioeconomic groups. SUBJECTS--392 pupils aged 14 to 15 completed the questionnaire in 1994. Previous sample sizes were 471 in 1969, 523 in 1974, 648 in 1979, 540 in 1984, and 380 in 1989. MAIN OUTCOME MEASURES--Self reported levels of knowledge and experience of illicit drugs. RESULTS--Over 25 years the proportion of pupils who knew someone taking drugs more than quadrupled from 15% (71/471) to 65% (254/392), and the proportion who had been offered drugs increased ninefold from 5% (24) to 45% (175). Both of these proportions more than doubled over the past five years. In 1994 the proportions of pupils mentioning "ecstasy" (methylenedioxymethamphetamine), amphetamines, and crack cocaine increased significantly (P < 0.01) and the proportion mentioning opiates decreased significantly (P < 0.01). "Poppers" (amyl nitrite) were mentioned for the first time. "To feel big, to show off, look grown up" has continued to be the main perceived reason for taking drugs. Television has continued to be the main source of information. CONCLUSIONS--In the past five years in particular young people''s exposure to illicit drugs has increased dramatically. Despite more education about drugs, pupil''s knowledge remains limited. Social pressures remain the first perceived reason for taking drugs. The media have a responsibility not to glamorise drugs. 相似文献