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551.
At the August 1995 meeting of the General Council of the CMA, a resolution supporting school-based health promotion (comprehensive School Health) was adopted. This article briefly reviews the research supporting this integrated approach to school and community programs, applies the recommended approach to reducing tobacco use and outlines a role for physicians in promoting Comprehensive School Health in their communities. 相似文献
552.
553.
The objective of this study was to characterize the extracellular proteolytic activity of Streptococcus bovis. Strains KEG, JB1, NCFB 2476, and K11.21.09.6C produced very similar large molecular weight (160–200 kDa) extracellular proteases
that were specifically inhibited by PMSF, a serine protease inhibitor. Further experiments with S. bovis KEG indicated that cultures grown with casein as the sole added N source produced the greatest level of proteolytic activity,
and the level of proteolytic activity was independent of growth rate. Clarified ruminal fluid (CRF) decreased proteolytic
activity by 54% compared with cultures grown with casein alone, and addition of exogenous peptides and carbohydrates (CHO)
to the CRF further reduced the level of proteolytic activity by 44% and 52%, respectively. These results suggested that the
proteolytic activity of S. bovis KEG was modulated by available N source and that the proteolytic activity was present for reasons other than providing N
for growth. The role of S. bovis in ruminal proteolysis requires further definition, but phenotypic similarity among some ruminal strains would suggest a
common niche in ruminal proteolysis. The uniformity of proteolytic activities could make S. bovis a prime candidate for manipulation in ruminal proteolysis control strategies.
Received: 12 January 1999 / Accepted: 19 May 1999 相似文献
554.
555.
C.J. Giffard S. Ladha A.R. Mackie D.C. Clark D. Sanders 《The Journal of membrane biology》1996,151(3):293-300
Nisin, a prominent member of the lantibiotic family of antimicrobial agents, has wide application as a food preservative despite
poor understanding of its mode of action. Fluorescence recovery after photobleaching has been used with planar lipid bilayers
as a model membrane system to examine how nisin might interact with the surface of bacterial cells. Nisin associates with
planar lipid bilayers in the absence of an applied membrane potential causing an array of effects consistent with adsorption
of nisin onto the membrane surface which involves inhibition of the lateral diffusion and fluorescence of the lipid probe
N-(7--1,2,3-benzoxadiazol-4-yl) phosphatidylethanolamine (NBD-PE) and a reduction of the capacitance of the bilayer. Nisin
adsorption is dependent on phospholipid composition. In the presence of dioleoylphosphatidylcholine (PC): cardiolipin (CL)
4:1, the rate of lateral mobility of phospholipid is reduced to 61% of the control level which decreases to a value of 46%
when CL is replaced by 1-palmitoyl-2-oleoylphosphatidylserine (PS). These effects on bilayer parameters are transient, and
with time the values return to near original levels. High electrical conductivity is observed on application of a voltage
ramp suggesting that insertion into the membrane follows surface association. Results have been interpreted in terms of a
model in which nisin initially binds to the surface of the membrane causing a modulation of bilayer properties.
Received: 14 August 1995/Revised: 22 February 1996 相似文献
556.
Summary Microfibrils composed of mannan have been shown to occur in the cells walls of the green algae Codium fragile and Acetabularia crenulata. Unlike cellulosic microfibrils, these structures were exceedingly sensitive to the usual physical and chemical procedures used for isolating cell walls, and were preserved in electron microscope preparations only when mild treatments were employed. 相似文献
557.
Mannan-rich plant cell walls were mechanically disintegrated and chemically extracted in order to ascertain their morphology and structure by electron microscopy and electron diffraction. For Acetabularia crenulata and Codium fragile, the cell-wall fragments were found to consist of alkali-resistant fibrillar mannan II encrusted with alkali-soluble granular mannan I. In the case of ivory nuts (Phytelephas macrocarpa) there is, in addition, a microfibrillar cellulose component which was also identified. The mannan I—mannan II polymorphism was also obtained when various mannan fractions were recrystallized from solution. In these recrystallizations, the occurrence of one or the other polymorph was found to depend on several parameters: the molecular weight of the mannan, the temperature of crystallization and the polarity of the crystallization medium.Abbreviations DP
degree of polymerization
- EDTA
ethylenediaminetetraacetic acid
Affiliated with the Scientific and Medical University of Grenoble 相似文献
558.
559.
By using the fluorescence enhancement of ethidium bromide when it binds to RNA, a very rapid, simple and sensitive assay for the concentration of ribosomal RNA in complex mixtures has been devised. 相似文献
560.
Semi-quantitative estimation of the composition of alginates by infra-red spectroscopy 总被引:3,自引:0,他引:3
W. Mackie 《Carbohydrate research》1971,20(2):413-415