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691.
The effect of toluene on Escherichia coli has been examined. In the presence of Mg2+, toluene removes very little protein, phospholipid, or lipopolysaccharide from E. coli. In the absence of Mg2+, or in the presence of EDTA, toluene removes considerably more cell material, including several specific cytoplasmic proteins such as malate dehydrogenase (EC 1.1.1.37). In contrast, glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and glutamate dehydrogenase (EC 1.4.1.4) are not released at all under the same conditions.Cells treated with toluene in the presence of Mg2+ remain relatively impermeable to pyridine nucleotides, while cells treated with toluene in the presence of EDTA become permeable to these compounds. Freeze-fracture electron microscopy shows that toluene causes considerable damage to the cytoplasmic membrane, while the outer membrane remains relatively intact. These results indicate that the permeability characteristics of toluene-treated cells depend at least partly on the state of the outer membrane after the toluene treatment. 相似文献
692.
The biofiltration of dimethyl sulphide (Me2S) and other volatile sulphur compounds results in the accumulation of the metabolite sulphuric acid in the carrier material.
Regeneration of an acidified (pH 4.7), Hyphomicrobium-MS3-inoculated compost biofilter degrading Me2S was not possible by trickling tap water (days 0–28) or a KH2PO4/K2HPO4 buffer solution (1.26 g PO3-
4 l-1, pH 7) (days 29–47) over the bioreactor at a superficial liquid flow rate of 34 lm-2 day-1. Since the protons produced displaced nutrient cations (Na+, K+, Ca2+, Mg2+, NH+
4) from the cation-exchange sites on the compost material, 95% of the SO2-
4 was leached as the corresponding sulphate salts and not as sulphuric acid. Concomitantly, the pH of the compost material
decreased from 4.7 to 3.9 over the 47 days rinsing period. Moreover, the rinsing procedure resulted in the leaching of essential
microbial nutrients from the compost material, such as NH+
4 (22.3% wash-out over the 47-day rinsing period) and PO3-
4 (39.3% washout over the 28-day tap-water rinsing period). However, mixing limestone powder into the Me2S-degrading compost biofilter was a successful approach to controlling the pH in the optimal range for the inoculum Hyphomicrobium MS3 (pH 6–7). A stoichiometric neutralisation reaction (molar ratio CaCO3/H2SO4=1.1) was observed between the CaCO3 added and the metabolite of the Me2S degradation, while high elimination capacities (above 100 g Me2S m-3 day-1) were obtained over a prolonged (more than 100 days) period.
Received: 1 December 1995/Received revision: 26 April 1995 Accepted: 29 April 1996 相似文献
693.
Albert P. Bos Annemieke M. Pattenier Rick E. Grobbee Dick Lindhout Dick Tibboel Jan C. Molenaar 《Human genetics》1994,94(4):445-446
We report the results of a parental questionnaire concerning possible etiological and teratological factors, such as exposure to herbicides, in the development of congenital diaphragmatic hernia (CDH). The herbicide Nitrofen interferes with lung development in rats, can induce diaphragmatic hernia and greatly resembles thyroid hormone. No association with the studied teratogens nor with maternal thyroid dysfunction was found. The questionnaire was completed by 33 parents whose baby had CDH, and by 43 couples whose baby had oesophageal atresia. The resemblance of Nitrofen to thyroid hormone, a well-known growth factor for the developing lung, is of particular interest from a pathogenetic point of view in the development of CDH. 相似文献
694.
695.
Data point fields of values of the dependence of nitrogen and potassium concentration in shoot dry matter on dry matter weight
in the course of the vegetation cycle at four stages of development of spring barley (Hordeum vulgare L. cv. Ametyst) plants were derived from a four-year-cycle of stationary field nutrition experiments at two localities. Three
selection procedures of the boundary data are described. Graphical outputs and their subsequent mathematical expression enable
an objective construction of regressive upper and lower boundary curves of the data point fields. The shape of the curves
is characteristic of each investigated element. The position of the upper boundary curve can characterize the maximum uptake
ability, that of the lower curve the maximum efficiency of utilization of absorbed nutrients, and their amplitude the requirement
extent of the species or cultivar investigated. The boundary curves can be objectively constructed for individual nutrients
from a sufficiently vast set of data from a very broad spectrum of ecological conditions (for example from stationary field
nutrition experiments at various localities). 相似文献
696.
Klaas de Smet 《Hydrobiologia》1998,391(1-3):81-86
Middle Holocene remains and rock paintings show that the Nile crocodile (Crocodylus niloticus Laurenti) used to occur across the whole Sahara. It also occurred at the South Mediterranean shores, in swamps and rivers and it may even have been circum-mediterranean. Until the beginning of this century, many permanent waters in the Sahara still housed relict populations. Nowadays, only few specimens survive in pools in few river canyons of the Ennedi plateau (N. Chad), where they are threatened with extinction. Another relict population, in the Tagant hills of Mauretania, was found to be probably extinct in 1996. 相似文献
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