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11.
N-Methylaspartate-Evoked Liberation of Taurine and Phosphoethanolamine In Vivo: Site of Release 总被引:2,自引:1,他引:1
The effect of N-methyl-D,L-aspartic acid (NMA) on extracellular amino acids was studied in the rabbit hippocampus with the brain dialysis technique. Administration of 0.5 or 5 mM NMA caused a concentration-dependent liberation of taurine and phosphoethanolamine (PEA). Taurine increased by 1,200% and PEA by 2,400% during perfusion with 5 mM NMA whereas most other amino acids rose by 20-100%. The effect of NMA appeared to be receptor-mediated, as coperfusion with D-2-amino-5-phosphonovaleric acid curtailed the NMA response by some 90%. The NMA-stimulated release of taurine and PEA was suppressed when Ca2+ was omitted and further inhibited when Co2+ was included in the perfusion medium. The effect of NMA was mimicked by the endogenous NMA agonist quinolinic acid and the partial NMA agonist D,L-cis-2,3-piperidine dicarboxylic acid. Although the NMA-evoked release of taurine and PEA was Ca2+-dependent in vivo, NMA had no effect on Ca2+ accumulation in hippocampal synaptosomes. The previously reported NMA-induced activation of dendritic Ca2+ spikes and the lack of effect on synaptosomal Ca2+ uptake suggest that taurine and PEA are released from sites other than nerve terminals, possibly from dendrosomatic sites. This notion was strengthened by the absence of an effect of NMA on the efflux of radiolabelled taurine from hippocampal synaptosomes. In contrast, high K+ stimulated synaptosomal uptake of Ca2+ and release of taurine. 相似文献
12.
Jerzy Witwicki Mankulathu V. Chidambaram Earl Frieden 《Biological trace element research》1983,5(2):81-90
The influence of several commercial albumin preparations on the ferroxidase activity of ceruloplasmin (ferroxidase I, ferrous: O2 oxidoreductase EC 1.16.3.1) at pH 6.0 was determined using ferric-transferrin formation. The ability of several albumin preparations to inhibit the ferroxidase activity of ceruloplasmin differs more than three hundredfold. It appears to depend on the method of isolation of albumin rather than the source of albumin, suggesting the existence of an inhibitor bound to albumin. The inhibitor was isolated after chromatography of an albumin preparation on Sephadex G-200. It was identified as citrate by thin layer chromatography and by comparison of the spectrum of the sulfide-pentabromoacetone derivative. Albumin preparations, even with bound citrate, do not exert a significant inhibitory effect at pH 7.4. 相似文献
13.
14.
Red clover (Trifolium pratense L.) seedlings were screened for the ability to regenerate plantlets from hypocotyl-derived callus tissue. Media sequences described by Beach and Smith (1979) and Collins and Phillips (1982) and a variation using media from both sequences were tested. Plantlets were regenerated from three out of 642 genotypes. In all three cases, callus was initiated on B5C medium and regeneration was accomplished on SPL medium. Attempts to regenerate plants from petiole-derived callus tissue have so far been successful only with regenerants of clone F49. Petiole callus from epicotyl-derived F49 plants proved to be non-regenerative. Pollen viability varied significantly among individuals regenerated from callus cultures of clone F49. Root tip squashes from F49 regenerants revealed the normal diploid chromosome number (2n=14). The frequency of regeneration within progeny from reciprocal crosses between F49 regenerants and several non-regenerative genotypes was 29%.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- BAP
benzylaminopurine
- KN
kinetin
- NAA
-naphthaleneacetic acid 相似文献
15.
Abstract: Histamine (HA) potently stimulated cyclic AMP accumulation in intact pineal glands taken from light-exposed chicks. The action of HA was stronger in the presence of forskolin and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). The effect of HA was mimicked by HA H1- and H2-receptor-selective agonists in the following order of potency: HA > 4-methylhistamine (H2) > 2-methylhistamine (H1) > 2-thiazolylethylamine (H1) ≫ dimaprit (H2). The HA H3-receptor-selective agonist (R)α-methylhistamine was poorly active. The effect of HA was antagonized by selective H2-receptor blockers (tiotidine > oxmetidine > cimetidine = ranitidine) and was not significantly affected by the selective H1- and H3-receptor blockers mepyramine and thioperamide. A detailed analysis of an antagonistic action of ranitidine (versus HA) revealed a noncompetitive mode of action of the H2 blocker. The stimulatory action of the H1 agonist 2-thiazolylethylamine (both under basal conditions and in the presence of forskolin or IBMX) was not significantly influenced by three H1-receptor-selective blockers (mepyramine, triprolidine, and diphenhydramine), but it was totally counteracted by ranitidine. Using accepted selective agonists and antagonists of the HA H1, H2, and H3 receptor we were unable to identify clearly the receptor subtype mediating the HA action on the cyclic AMP-generating system of the chick pineal. It is suggested that the receptor under consideration may represent either an H2-like (in terms of mammalian criteria) or avian-specific HA receptor. The data suggest that HA may be considered a modulator of the pineal activity in chicks. 相似文献
16.
The precision of extrachromosomal homologous recombination and gene targeting in plant cells was investigated. Recombination was directed to introns of selectable marker genes where potential changes could persist without affecting the function and therefore the selectability of the genes. Approximately 9 kb of crossover regions was rescued and sequenced. Changes were detected at a frequency below one point mutation per 1000 bp, indicating that extrachromosomal recombination and gene targeting both appear to occur with high fidelity. 相似文献
17.
A crude nuclear fraction of resting wheat embryos was used as the source of putative plant minichromosomes: unique DNA sequences
the size of genes and flanked by telomere-type repeats. Preliminary separation of low-molecular-weight DNA species from chromosomal
DNA (Hirt's method), velocity sedimentation, and isopycnic centrifugation were followed by PCR amplification of minichromosome-like
sequences. The most abundant PCR product was cloned and sequenced. In addition to telomeric repeats (defined by a PCR primer),
which were the expected sequences, the linear DNA molecule (637 pb) contained an ARS-like element, RAP1-binding site, and
two relatively long ORFs. The whole sequence seems to represent a naturally occurring plant minichromosome. 相似文献
18.
Ana J. Coito Maria de Sousa Jerzy W. Kupiec-Weglinski 《Cell communication & adhesion》1994,2(3):249-255
The specific adhesion of cells to other cells or to particular tissue microenvirorvments is a basic function of cell migration and recognition, and underlines many biologic processes including embryogenesis, repair and immunity. Leukocytes express an array of surface receptors broadly known as “accessory adhesion molecules.” which mediate most cell -cell interactions, direct lymphocyte traffic between anatomical compartments, and facilitate cellular adhesion to the inflammation or alloantigenic sites (Springer 1990). In addition, adhesion molecules are involved in the process of antigen recognition, and may costimulate cell activation and transformation. These proteins are thought to affect the very early antigen independent events between host leukocytes and vascular endothelium. Because of these activities, the subject of adhesion molecules is gaining interest in the field of organ transplantation, in both conceptualization and development of novel therapeutic strategies (de Sousa et al. 1991, Kupiec-Weglinski et al. 1993a, Heemann et al. 1993). 相似文献
19.
Summary DNA fingerprints generated by the Jeffreys' probes, 33.6 and 33.15, indicated the presence of minisatellite-like sequences
in the red clover genome. The fingerprints generated by probe 33.6 gave less background and fewer but better defined bands
than those obtained with probe 33.15. Assay of a regenerative somaclonal variant (F49R) by DNA fingerprinting with probe 33.6
detected mutation that was unlinked to the regenerative trait. The fingerprints obtained under the applied conditions also
demonstrated genetic stability of consecutive generations of the regenerants in tissue culture. DNA fingerprints of F1 plants revealed that each polymorphic band was inherited from either one or the other parent. Both probes distinguished individual-specific
genotypes in seven cultivars of red clover. Greater variability in DNA fingerprints was detected between (V=0.899) than within
(0.417≤V≤0.548) cultivars. 相似文献
20.
Phytochemistry Reviews - Sea buckthorn (Elaeagnus rhamnoides; syn. Hippophae rhamnoides) is a thorny shrub or a small tree belonging to the Elaeagnaceae family, native to Eurasia. Sea buckthorn... 相似文献