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11.
Mohammed Safwat Abdel-Salam Walter Klingmüller 《Molecular & general genetics : MGG》1987,210(1):165-170
Summary A method for transposon mutagenesis in Azospirillum lipoferum 29708 is reported with transposon Tn5. The suicide plasmid pSUP2021 was used to deliver Tn5 in A. lipoferum using Escherichia coli SM10 as the donor. Neomycin-resistant transconjugants were detected at a frequency of 6x10-6 per recipient. Different types of mutants were isolated, e.g. auxotrophic, coloured, IAA-negative, and IAA-overproducers. Among the auxotrophic mutants, cysteine and methionine requirers prevailed. Random Tn5-insertion with only one copy per mutant was demonstrated by Southern blotting and hybridization. Tn5-induced mutants are relatively stable, with reversion rates of 2–20×10-8. A gene which is a part of the carotenoid pathway is closely linked to the histidine genes. The existence of two pathways for IAA production in A. lipoferum is discussed. 相似文献
12.
Nina Safar-Hermann Mohammed N. Ismail Han Sun Choi Erich Mstl Elmar Bamberg 《Zoo biology》1987,6(2):189-193
Estrogen concentration in feces was investigated in five different herbivorous species of zoo animals. Using a nonspecific estrogen radioimmunoassay, in four species (red buffalo, yak, Grevy's zebra, and Nubian ibex) pregnancy was revealed by measuring estrogen concentration in feces. In hippopotamus, the levels of fecal estrogens were not different between pregnant and nonpregnant animals. 相似文献
13.
Shobha Thangada Keith Alvares Mario Mangino Mohammed I. Usman M.Sambasiva Rao Janardan K. Reddy 《FEBS letters》1989,250(2):205-210
Using the normal adult rat hepatocytes, plated on rat tail collagen-coated dishes and fed a chemically defined medium, we demonstrate here that ciprofibrate at 0.1 mM concentration, increases significantly the mRNA levels of fatty acyl-CoA oxidase, enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional protein, and thiolase (the three enzymes of the β-oxidation system), and causes peroxisome proliferation. Increase in mRNA levels of these genes was evident within 1 h and was maximal 24 h after the addition of ciprofibrate. In hepatocytes cultured in the absence of ciprofibrate, the basal levels of these enzymes were low and further declined with time. Concomitant treatment of hepatocytes with cycloheximide did not inhibit or superinduce the mRNA levels, indicating that this induction may represent a primary (direct) effect of this compound on the expression of these genes and does not apparently involve short-lived repressor protein(s). 相似文献
14.
α-[3 H]Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid Binding to Rat Striatal Membranes: Effects of Selective Brain Lesions 总被引:1,自引:0,他引:1
The binding of alpha-[3H]amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid ([3H]AMPA), a structural Glu analog, to rat striatal membranes was studied. In the absence of potassium thiocyanate and Cl-/Ca2+, saturation-curve analysis of [3H]AMPA binding suggested that a single class of noninteracting binding sites with a KD value of 340 +/- 27 nM was involved, although AMPA inhibition of [3H]AMPA binding set at a concentration of 100 nM suggested, in contrast, the presence of multiple populations of striatal binding sites. Several other excitatory amino acid receptor agonists and antagonists were tested, and the most potent and selective quisqualic acid (QA) receptor agonists (QA, L-Glu, and AMPA) were found to represent the most potent inhibitors of [3H]AMPA binding. N-Methyl-D-aspartate receptor agonists and antagonists were ineffective as displacers of the [3H]AMPA binding. Lesions of intrastriatal neurons (using kainic acid local injections) and of corticostriatal afferent fibers led 2-3 weeks later to large decreases (63 and 30%, respectively) in striatal [3H]AMPA binding, whereas selective lesion of the nigrostriatal dopaminergic pathway (using nigral injection of 6-hydroxy-dopamine) was without any influence. Taken together, these results suggest that [3H]AMPA binding is primarily associated with postsynaptic intrastriatal neurons. Some [3H]AMPA binding sites may also be located presynaptically on corticostriatal nerve endings. So, in addition to the possibility that [3H]AMPA binding sites may be involved in corticostriatal synaptic transmission, it is interesting that these putative QA-preferring excitatory amino acid receptor sites may also play some role in autoregulatory processes underlying this excitatory synaptic transmission. 相似文献
15.
Pterygodermatites variabilis n. sp. (Nematoda: Rictulalarioidea) from the Indian gerbils Tatera indica collected from Sind and Baluchistan Provinces of Pakistan is described and compared with closely related species of the genus
recovered from small mammalian hosts. The new species is characterised by a combination of the following characters: it possesses
a regular crown of 26 and 14–38 denticles in male and female specimens respectively, 40–47 pairs of pre-vulvar spines, and
a variable position of the vulva in specimens collected from different localities: it also differs in the size of the spicules
and gubernaculum. 相似文献
16.
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18.
Summary Isotope dilution provides a method for measuring plant competition for mineral N and transfer of biologically fixed N from
a legume to a grass. A plant growth medium was enriched with15N, and used to grow Siratro (Macropitilium atropurpureum D.C. Urb.) and Kleingrass 75 (Panicum coloratum L.) in 20 liter pots for 98 days in a glasshouse. The plants were grown in pure stand and in mixtures. When grown in 50∶50
mixture the grass obtained 59% of the labelled N and the legume obtained 41%. The grass produced nearly as much root mass
as the legume even though biomass of the shoots were less than half that of the legume. Reducing the proportion of either
plant species in the mixture reduced the proportion of the mineralized N absorbed by that species. The shoots of the grass
were significantly more enriched (1.166 atom%15N excess) than the roots (1.036). The grass received 12% of its N as biologically fixed N from the legume. 相似文献
19.
Mohammed A. Khidhir Serge Casaregola I. Barry Holland 《Molecular & general genetics : MGG》1985,199(1):133-140
Summary The mechanism of the inhibition and of the recovery of DNA synthesis in E. coli following UV-irradiation was analysed in several mutants defective in repair or in the regulation of the RecA-LexA dependent SOS response. Several lines of evidence indicated that inhibition is not an inducible function and is probably due to the direct effect of lesions in the template blocking replisome movement.Recovery of DNA synthesis after UV was largely unaffected by mutations in the uvrA, recB or umuC genes. Resumption of DNA synthesis does however require protein synthesis and the regulatory action of recA. Experiments with a recA constitutive mutant and recA 200 (temperature sensitive RecA) demonstrated that RecA protein itself is directly required but is not sufficient for recovery of DNA synthesis. We therefore propose that recovery of DNA synthesis depends upon the concerted activity of RecA and the synthesis of an inducible Irr (induced replisome reactivation) factor under RecA control. We suggest that the mechanism of recovery involves the action of Irr and RecA to promote movement of replisomes past non-instructive lesions, uncoupled from polymerisation and/or that Irr and RecA are required to promote re-initiation of a stalled replication complex downstream of a UV-lesion subsequent to such an uncoupling step. 相似文献
20.
Synopsis
Sardinella aurita were sampled from catches of the lampara fishery at Tripoli, Libya during October 1979 through to September 1980. Landings
consisted mainly of adult fish with large (mode 21–26 cm total length), relatively fast growing 3–5-group individuals in winter
and spring and smaller (mode 14–20 cm total length), slow growing 2- and 3-group fish in summer. Gonad growth commenced in
April, when the fish were feeding on zooplankton, and continued at the expense of mesenteric fat until July. It is suggested
that the older and bigger fish spawn first, probably after having moved westwards, and that this results in spatial and temporal
differences in length at age within the population. There was no consistent difference in growth rate between the sexes, but
because first maturity in males tends to occur earlier than in females, there were length distribution differences between
the sexes in the youngest (2+) age group as sampled. 相似文献