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81.
Marion S. R?der Mark E. Sorrells Steven D. Tanksley 《Molecular & general genetics : MGG》1992,232(2):215-220
Summary The long-range structure of 5S rRNA gene clusters has been investigated in wheat (Triticum aestivum L.) by means of pulsed field gel electrophoresis. Using aneuploid stocks, 5S rRNA gene clusters were assigned to sites on chromosomes 1B, 1D, 513 and 5D. Cluster sizes were evaluated and the copy number of 5S DNA repeats was estimated at 4700-5200 copies for the short repeating unit (410 bp) and about 3100 copies for the long repeat (500 bp) per haploid genome. A comparison of wheat cultivars revealed extremely high levels of polymorphism in the 5S rRNA gene clusters. With one restriction enzyme digest all varieties tested gave unique banding patterns and, on a per fragment basis, 21-fold more polymorphism was detected among cultivars for 5S DNA compared to standard restriction fragment length polymorphisms (RFLPs) detected with single copy clones. Experiments with aneuploid stocks suggest that the 5S rRNA gene clusters at several chromosomal sites contribute to this polymorphism. A number of previous reports have shown that wheat cultivars are not easily distinguished by isozymes or RFLPs. The high level of variation detected in 5S rRNA gene clusters therefore offers the possibility of a sensitive fingerprinting method for wheat. 5S DNA and other macro-satellite sequences may also serve as hypervariable Mendelian markers for genetic and breeding experiments in wheat. 相似文献
82.
The effect of the cerebral 5-hydroxytryptamine system on the turnover of striatal 3,4-dihydroxyphenyl-ethylamine (dopamine) was investigated by measuring the level of dopamine and one of its metabolites in rats depleted of cerebral 5-hydroxytryptamine or treated with a 5-hydroxytryptamine receptor blocker. Treatment with p-chlorophenylalanine induced, in addition to a reduction in striatal 5-hydroxytryptamine and 5-hydroxyindol-3-ylacetic acid, an increase in the striatal concentration of dopamine, a diminution in the concentration of homovanillic acid in the same cerebral area, and a reduction in the rise of this acid after the administration of a butyrophenone derivative or tetrabenazine. Treatment with methysergide also reduced the increase of homovanillic acid induced by the butyrophenone. When probenecid was given to rats treated with p-chlorophenylalanine, homovanillic acid failed to accumulate, whereas the accumulation of 5-hydroxyindol-3-ylacetic acid was unaffected. The decay of dopamine after alpha-methyl-p-tyrosine administration was normal for the first 6 h but was later reduced in rats given p-chlorophenylalanine or methysergide. The results suggest that the lack of activation of 5-hydroxytryptamine receptors leads to a reduction in the turnover of dopamine in the nigrostriatal pathway. 相似文献
83.
Enhanced Noradrenergic Neuronal Activity Increases Homovanillic Acid Levels in Cerebrospinal Fluid 总被引:2,自引:2,他引:0
Harry Scheinin 《Journal of neurochemistry》1986,47(3):665-667
Idazoxan, a highly specific and selective alpha 2-adrenoceptor antagonist, caused a dose-dependent increase in the concentration of homovanillic acid (HVA) a metabolite of 3,4-dihydroxyphenylethylamine, in cisternal CSF of freely moving rats. This increase in HVA level could be antagonized by the alpha 2-adrenoceptor agonist medetomidine. The increase was directly proportional to the concurrent elevation in level of 3-methoxy-4-hydroxyphenylglycol, a metabolite of noradrenaline, in the CSF of individual rats and followed a similar time course. It is suggested that the HVA level in CSF may be increased under conditions of enhanced noradrenergic activity and that, in such situations, it reflects noradrenergic rather than dopaminergic neuronal activity. Care should be taken, therefore, when changes in central dopaminergic activity are assessed by measurements of HVA level in CSF. 相似文献
84.
5-Hydroxytryptamine (5-HT; 3 x 10(-8)-1 x 10(-5)M) produced a dose-dependent increase in phosphatidylinositol/polyphosphoinositide (PI) turnover in mouse cortical slices, as measured by following production of 3H-labelled inositol phosphates (IPs) in the presence of 10 mM LiCl. Analysis of individual IPs, in slices stimulated for 45 min, indicated substantial increases in inositol monophosphate (IP1; 140%) and inositol bisphosphate (IP2; 95%) contents with smaller increases in inositol trisphosphate (IP3; 51%) and inositol tetrakisphosphate (IP4; 48%) contents. The increase in IP3 level was solely in the 1,3,4-isomer. This response was inhibited by the nonselective 5-HT antagonists methysergide, metergoline, and spiperone. It was also inhibited by the selective 5-HT2 antagonists ketanserin and ritanserin but not by the 5-HT1 antagonists isapirone, (-)-propranolol, or pindolol. 5-HT-stimulated IP formation was also unaltered by atropine, prazosin, and mepyramine. Lesioning brain 5-HT neurones using 5,7-dihydroxytryptamine (5,7-DHT; 50 micrograms i.c.v.) produced a 210% (p less than 0.01) increase in the number of 5-HT2-mediated head-twitches induced by 5-methoxy-N,N-dimethyltryptamine (2 mg/kg). However, 5,7-DHT lesioning had no effect on 5-HT-stimulated PI turnover in these mice. Similarly, an electroconvulsive shock (90 V, 1 s) given five times over a 10-day period caused an 85% (p less than 0.01) increase in head-twitch responses but no change in 5-HT-stimulated PI turnover. Decreasing 5-HT2 function by twice-a-day injection of 5 mg/kg of zimeldine or desipramine (DMI) produced 50% (p less than 0.01) and 56% (p less than 0.01), respectively, reductions in head-twitch behaviour.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
85.
R L Melnick L G Monti S M Motzkin 《Biochemical and biophysical research communications》1976,69(1):68-73
The mechanism of integration of λll, which is deleted of all the known λ recombination genes, was studied using deleted hosts as recipients. The presence of BC DNase and I in the recipient cells affected the fate of λll DNA. In nine of ten transductants, insertion of the λll genome took place somewhere between J and N and the remaining one had abnormally permuted prophage λ. In this lysogen (#42), the sequence of prophage genes was similar to that of vegetative phage λ. The properties of lysogen #42 were compared with those of other lysogens. 相似文献
86.
Bernd Höffken Reinhard Ködding Alexander von zur Mühlen Tainer Hehrmann Rolf-Dieter Hesch 《Biochimica et Biophysica Acta (BBA)/General Subjects》1978,539(1):114-124
The nature of the conversion of thyroxine (T4) to triiodothyronine (T3) and reverse triiodothyronine (rT3) was investigated in rat liver homogenate and microsomes. A 6-fold rise of T3 and 2.5-fold rise of rT3 levels determined by specific radioimmunoassays was observed over 6 h after the addition of T4. An enzymic process is suggested that converts T4 to T3 and rT3. For T3 the optimal pH is 6 and for rT3, 9.5. The converting activity for both T3 and rT3 is temperature dependent and can be suppressed by heat, H2O2, merthiolate and by 5-propyl-2-thiouracil. rT3 and to a lesser degree iodide, were able to inhibit the production of T3 in a dose related fashion. Therefore the pH dependendy, rT3 and iodide may regulate the availability of T3 or rT3 depending on the metabolic requirements of thyroid hormones. 相似文献
87.
Christian Paech John Pierce Stephen D. McCurry N.E. Tolbert 《Biochemical and biophysical research communications》1978,83(3):1084-1092
Xylulose-1,5-bisphosphate in preparations of ribulose-1,5-bisphosphate (ribulose-P2) arises from non-enzymic epimerization and inhibits the enzyme. Another inhibitor, a diketo degradation product from ribulose-P2, is also present. Both compounds simulate the substrate inhibition of ribulose-P2 carboxylase/oxygenase previously reported for ribulose-P2. Freshly prepared ribulose-P2 had little inhibitory activity. The instability of ribulose-P2 may be one reason for a high level of ribulose-P2 carboxylase in chloroplasts where the molarity of active sites exceeds that of ribulose-P2. Because the KD of the enzyme/substrate complex is ≤1 μM, all ribulose-P2 generated in situ may be stored as this complex to prevent decomposition. 相似文献
88.
89.
ADAM SKINNER 《Biological journal of the Linnean Society. Linnean Society of London》2007,92(2):347-366
The Australian Sphenomorphus group is a morphologically and ecologically diverse clade of lygosomine scincids, collectively comprising more than one‐half of the Australian scincid fauna. A previous phylogenetic analysis of mitochondrial 12S and 16S rRNA, and ND4 and adjacent tRNA sequences for a series of Australian Sphenomorphus group scincids recovered several well‐supported, major clades, although these were generally separated by relatively short branches associated with low support values. Applying a recently described methodology for inferring lineage‐level polytomies, I employ ATP synthetase‐β subunit intron sequences and the existing mitochondrial (mt)DNA data set (with sequences for additional taxa) to assess the hypothesis that the poorly resolved basal relationships within the Australian Sphenomorphus group are a consequence of the major clades having originated essentially simultaneously. Phylogenetic analyses of the separate mtDNA and intron sequence data reveal a number of congruent clades, including Anomalopus, Calyptotis, Ctenotus, Lerista, the Eulamprus quoyii group, the Glaphyromorphus crassicaudis group (including Glaphyromorphus cracens, Glaphyromorphus darwiniensis, and Glaphyromorphus fuscicaudis), Glaphyromorphus gracilipes + Hemiergis, Coeranoscincus reticulatus + Ophioscincus truncatus + Saiphos, and Eulamprus amplus + Eulamprus tenuis + Gnypetoscincus + Nangura. The relationships among these clades indicated by the two data sets, however, are generally incongruent. Although this may be partially ascribed to error in estimating phylogenetic relationships due to insufficient data, some incongruence is evident when uncertainty in inferred relationships is allowed for. Moreover, the congruent clades are typically separated by very short branches, several having a length insignificantly different from zero. These results suggest that initial diversification of Australian Sphenomorphus group scincids was rapid relative to the substitution rates of the mtDNA and intron fragments considered, if not essentially simultaneous. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92 , 347–366. 相似文献
90.