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241.
Abstract 3-Chlorobiphenyl-degrading bacteria were obtained from the mating between Pseudomonas putida strain BN10 and Pseudomonas sp. strain B13. Strains such as BN210 resulted from the transfer of the genes coding the enzyme sequence for the degradation of chlorocatechols from B13 into BN10, whereas B13 derivatives such as B131 have acquired the biphenyl degradation sequence from BN10. During growth of the hybrid strains on 3-chlorobiphenyl 90% chloride was released. Activities of phenylcatechol 2,3-dioxygenase, benzoate dioxygenase, catechol 1,2-dioxygenase, chloromuconate cyloisomerase and 4-carboxymethyl-enebut-2-en-4-olide hydrolase were found in 3-chlorobiphenyl-grown cells. The hybrid strains were found to convert some congeners of the Aroclor 1221 mixture such as mono- and dichloro-substituted biphenyls. 相似文献
242.
Synopsis The behaviour of three piranha species,Serrasalmus marginatus, S. spilopleura, andPygocentrus nattereri, and their prey fishes was studied underwater in the Pantanal region, Mato Grosso, Brazil. General habits, predatory tactics, feeding behaviour, and social interactions while foraging, as well as defensive tactics of prey fishes were observed.S. marginatus is solitary whereas the other two species live in shoals; their agonistic behaviour varies accordingly, the simplest being displayed by the solitary species. Predatory tactics and feeding behaviour also vary:S. spilopleura shows the most varied diet and highly opportunistic feeding strategy, which includes aggressive mimicry. The solitaryS. marginatus, besides fin and scale-eating, occasionally cleans larger individuals ofP. nattereri. Several cichlid species display defensive tactics clearly related to piranha attacks: tail protecting, watching, and confronting the predator are the most commonly observed behaviours. Piranhas seem to strongly influence use of habitat, social structure, and foraging mode of the fish communities. 相似文献
243.
244.
245.
大鼠隔—海马通路损伤对海马内递质含量及酶活力的影响 总被引:3,自引:0,他引:3
单侧切断大鼠海马缴和部分穹窿可使海马部分去神经。损伤后7d,海马内胆碱能系统中乙酰胆碱(ACh)含量下降72.5%,胆碱乙酰基转移酶(ChAT)活力下降45.7%,胆碱酯酶活力下降52.2%,在单胺能系统中,去甲肾上腺素(NA)含量下降16.3%,多巴胺(DA)含量下降31.3%,5-羟色胺含量下降30.3%。在损伤过程中,海马内氨基酸含量没有改变。实验结果表明,海马缴和穹窿是脑内胆碱能和单胺能传入神经到达海马靶区的部分共同通路。 相似文献
246.
Garry J. Smith Heinz W. Kunz Harold A. Dunsford Thomas J. Gill III 《Cell biology and toxicology》1990,6(2):205-217
The histopathological response and cell culture characteristics of liver cells from the R16 (grc
–) strain of rats, which carries an MHC-linked deletion, were examined one week after a single intraperitoneal injection of 200 mg/ kg body weight diethylnitrosamine (DEN) and were compared with the response of liver cells from wild type (grc+) rats. The DEN exposure induced hydropicl vacuolar changes in the parenchymal cells and a limited proliferation of oval cells in the periportal areas of the livers of both grc+ and grc rats. Primary culture of collagenase-digested livers consisted of parenchymal, bile ductular and oval-related cells as determined by cell-specific immunohistochemistry. Subpassaged cells from grc+ rats exhibited oval cell ultrastructural morphology, inducible histochemical staining for gammaglutamyl transpeptidase (GGT), and DEN-associated onset of anchorage-independent growth. Primary cultures of liver cells from R16 rats consistently failed to form cell strains upon subpassage.Abbreviations DEN
diethylnitrosamine
-
grc
growth and reproduction complex
- GGT
gamma-glutamyl transpeptidase
- MHC
major histocompatibility complex 相似文献
247.
Recombinant AtT-20 cells expressing human growth hormone (hGH) secreted the hormone at a constant, basal rate of 0.3–0.5 ng/105 cells-hour when exposed to medium without secretagogues. When triggered with 8 bromo-cyclic AMP, cells secreted hGH at an initial rate of 1.7 ng/105 cells-hour while intracellular hGH declined sharply. Upon extended exposure to secretagogue, secretion decreased gradually to the basal rate and intracellular hGH stabilized at a value 40% the initial. In cells switched from secretion to growth medium, the total rate of hGH accumulation intracellularly and in medium was 2.2 times that observed with cells never exposed to secretagogue; however, only a fraction of the hormone was stored intracellularly and the rest was secreted. When cells were exposed alternately to growth and secretion medium, induced cells secreted at rates at least two times higher than uninduced controls during the first five cycles. The induced response deteriorated with time, however, in parallel with outgrowth of attached cells by foci of round cells, and by the eighth cycle induced secretion did not occur. Operational modifications that may improve the performance of cycling schemes are discussed. 相似文献
248.
The effects of the seaweed concentrate Kelpak on the growth and mineral nutrition of lettuce plants grown under conditions of varying nutrient supply were investigated. Kelpak significantly increased the yield and the concentration and amounts of Ca, K and Mg in the leaves of lettuce receiving an adequate supply of nutrients, but had little effect on nutrient stressed plants. Results are discussed in relation to the physiological mechanisms that have been proposed to explain the beneficial effects of seaweed concentrate on plants.author for correspondence 相似文献
249.
Initial steps in the degradation of benzene sulfonic acid, 4-toluene sulfonic acids,and orthanilic acid in Alcaligenes sp. strain O-1 总被引:2,自引:0,他引:2
Thomas Thurnheer Daniel Zürrer Otmar Höglinger Thomas Leisinger Alasdair M. Cook 《Biodegradation》1990,1(1):55-64
Alcaligenes sp. strain O-1 grew with benzene sulfonate (BS) as sole carbon source for growth with either NH4
+ or NH4
+ plus orthanilate (2-aminobenzene sulfonate, OS) as the source(s) of nitrogen. The intracellular desulfonative enzyme did not degrade 3- or 4-aminobenzene sulfonates in the medium, although the enzyme in cell extracts degraded these compounds. We deduce the presence of a selective permeability barrier to sulfonates and conclude that the first step in sulfonate metabolism is transport into the cell. Cell-free desulfonation of BS in standard reaction mixtures required 2 mol of O2 per mol. One mol of O2 was required for a catechol 2,3-dioxygenase. When meta ring cleavage was inhibited with 3-chlorocatechol in desalted extracts, about 1 mol each of O2 and of NAD(P)H per mol of BS were required for the reaction, and SO3
2- and catechol were recovered in high yield. Catechol was shown to be formed by dioxygenation in an experiment involving 18O2. 4-Toluene sulfonate was subject to NAD(P)H-dependent dioxygenation to yield SO3
2- and 4-methylcatechol, which was subject to meta cleavage. OS also required 2 mol of O2 per mol and NAD(P)H for degradation, and SO3
2- and NH4
+ were recovered quantitatively. Inhibition of ring cleavage with 3-chrorocatechol reduced the oxygen requirement to 1 mol per mol of OS SO3
2- (1 mol) and an unidentified organic intermediate, but no NH4
+, were observed. 相似文献
250.
Summary The toxicity of chromium and tin on growth, photosynthetic carbon-fixation, oxygen evolution, heterocyst differentiation and nitrogenase activity ofAnabaena doliolum and its interaction with bivalent cations has been studied. Some interacting cations, viz. Ca2+, Mg2+ and Mn2+, substantially antagonised the toxic effects of chromium and tin with reference to growth, heterocyst differentiation and nitrogenase activity in the following hierarchal sequence: Ca2+ > Mg2+ > Mn2+. However, the sequence of hierarchy was Mg2+ > Ca2+ > Mn2+ for carbon fixation and Mn2+ > Mg2+ > Ca2+ for photosynthetic oxygen evolution. Synergistically inhibitory patterns were noticed for all the parameters, viz. growth,14CO2 uptake, oxygen evolution, heterocyst differentiation and nitrogenase activity ofA. doliolum when Ni2+, Co2+ and Zn2+ were combined with the test metals in the growth medium. These cations followed the following sequence of synergistic inhibition: Ni2+ > Co2+ > Zn2+. Among all the interacting cations, Ca2+, Mg2+ and Mn2+ exhibited antagonistic effects which relieved the test cyanobacterium from metal toxicity. In contrast to this, Ni2+, CO2+ and Zn2+ showed synergistic inhibition which potentiating the toxicity of test metals in the N2-fixing cyanobacteriumA. doliolum. It is evident from the present study that bivalent cations, viz. Ca2+, Mg2+, Mn2+, Ni2+, Co2+ and Zn2+, may appreciably regulate the toxicity of heavy metals in N2-fixing cyanobacteria if present in aquatic media. 相似文献