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101.
Heng Xu John S. Partilla Brian R. de Costa Kenner C. Rice Richard B. Rothman 《Peptides》1992,13(6):1207-1213
Recent pharmacological data strongly support the hypothesis of δ receptor subtypes as mediators of both supraspinal and spinal antinociception (δ1 and δ2 receptors). In vitro ligand binding data, which are fully supportive of the in vivo data, are still lacking. A previous study indicated that [3H][
-Ala2,
-Leu5]enkephalin labels two binding sites in membranes depleted of μ binding sites by pretreatment with the site-directed acylating agent, 2-(p-ethoxybenzyl)-1-diethylaminoethyl-5-isothiocyanatobenzimidazole-HCI (BIT). The main goal of the present study was to develop a ligand-selectivity profile of the two δncx binding sites. The data indicated that naltrindole and oxymorphindole were relatively selective for site 1 (20-fold). [
-Ser2,Thr6]Enkephalin and deltorphin-II were only 2.7-fold and 2.2-fold selective for site 1. [
-Pen2,
-Pen5]Enkephalin and deltorphin-I were 80-fold and 38-fold selective for site 2.3-Iodo-Tyr-
-Ala-Gly-Phe-
-Leu was 52-fold selective for site 1. Morphine had moderate affinity for site 1 (Ki = 16 nM), and was about 11-fold selective for site 1. Thus, of the 10 drugs studied, only DPDPE and DELT-I were selective for site 2. Viewed collectively with other data, it is likely that the δ1 receptor and the δncx binding site are synonymous. 相似文献
102.
103.
BsuBI--an isospecific restriction and modification system of PstI: characterization of the BsuBI genes and enzymes. 下载免费PDF全文
The enzymes of the Bacillus subtilis BsuBI restriction/modification (R/M) system recognize the target sequence 5'CTGCAG. The genes of the BsuBI R/M system have been cloned and sequenced and their products have been characterized following overexpression and purification. The gene of the BsuBI DNA methyltransferase (M.BsuBI) consists of 1503 bp, encoding a protein of 501 amino acids with a calculated M(r) of 57.2 kD. The gene of the restriction endonuclease (R.BsuBI), comprising 948 bp, codes for a protein of 316 amino acids with a predicted M(r) of 36.2 kD. M.BsuBI modifies the adenine (A) residue of the BsuBI target site, thus representing the first A-N6-DNA methyltransferase identified in B. subtilis. Like R.PstI, R.BsuBI cleaves between the A residue and the 3' terminal G of the target site. Both enzymes of the BsuBI R/M system are, therefore, functionally identical with those of the PstI R/M system, encoded by the Gram negative species Providencia stuartii. This functional equivalence coincides with a pronounced similarity of the BsuBI/PstI DNA methyltransferases (41% amino acid identity) and restriction endonucleases (46% amino acid identity). Since the genes are also very similar (58% nucleotide identity), the BsuBI and PstI R/M systems apparently have a common evolutionary origin. In spite of the sequence conservation the gene organization is strikingly different in the two R/M systems. While the genes of the PstI R/M system are separated and transcribed divergently, the genes of the BsuBI R/M system are transcribed in the same direction, with the 3' end of the M gene overlapping the 5' end of the R gene by 17 bp. 相似文献
104.
Female Wistar rats were trained in a Skinner-box, 30 trials per day in a dark room to establish operant defence conditioning. Training started with a light (15 s), then combined with footshock for further 8 s. When the rats learned to press the key to avoid footshock within 15 s, conditioned response was considered established. After the rats reached a conditioning rate (CR) above 80% for 5 days, cannulae were implanted into caudate-putamen. Two to three days later, Met-enkephalin (MEK) or bestatin (an aminopeptidase inhibitor) was injected bilaterally into caudate-putamen. 30 min, 2 h, 24 h and 48 h after injection, conditioning tests were conducted, with each session consisting of 30 trials. Control experiments were done when 0.9% NaCl (NS) was injected. After injection of NS, CR maintained above 80% in all 4 test sessions. MEK (60 ng/rat) or bestatin (10 micrograms/rat) significantly lowered the CR during the 30 min and 2 h test session. In the latter case, the latency (L) was also prolonged. However both CR and L returned to the control level in the 24 h and 48 h test sessions. Naloxone (2 mg/kg, i.p.) blocked the conditioning-depression effect of bestatin. No significant alteration was seen in locomotor activity after MEK or bestatin injection. The results suggest that enkephalin in caudate-putamen may be involved in the regulation of retrieval of conditioning. Bestatin mimics the effect of MEK on conditioning reflex probably by increasing production of endogenous enkephalin. 相似文献
105.
The m gamma delta-1 element, a small gamma delta (Tn1000) derivative useful for plasmid mutagenesis, allele replacement and DNA sequencing. 总被引:9,自引:0,他引:9
C M Berg N B Vartak G Wang X Xu L Liu D J MacNeil K M Gewain L A Wiater D E Berg 《Gene》1992,113(1):9-16
Transposon gamma delta (Tn1000), a 6-kb member of the Tn3 family, is widely used for plasmid mutagenesis. A 1.8-kb derivative of gamma delta was constructed that contains the kan gene from Tn5 and the resolution (res) site from gamma delta cloned between 40-bp inverted repeats of gamma delta's delta (delta) end. This element, named m gamma delta-1, lacks the genes encoding transposase and resolvase, and therefore depends on its host to supply transposition and resolution functions. Thus, in strains lacking gamma delta, m gamma delta-1 will not transpose. The m gamma delta-1 element is shown to be useful for mutagenesis of plasmids, DNA sequencing, and allele replacement (in Streptomyces avermitilis). 相似文献
106.
Nucleotide sequence, function, activation, and evolution of the cryptic asc operon of Escherichia coli K12. 总被引:13,自引:0,他引:13
The cryptic asc (previous called "SAC") operon of Escherichia coli K12 has been completely sequenced. It encodes a repressor (ascG); a PTS enzyme IIasc for the transport of arbutin, salicin, and cellobiose (ascF); and a phospho-beta-glucosidase that hydrolyzes the sugars which are phosphorylated during transport (ascB). ascG and ascFB are transcribed from divergent promoters. The cryptic operon is activated by the insertion of IS186 into the ascG (repressor) gene. The ascFB genes are paralogous to the cryptic bglFB genes, and ascG is paralogous to galR. The duplications that gave rise to these paralogous genes are estimated to have occurred approximately 320 Mya, a time that predates the divergence of E. coli and Salmonella typhimurium. 相似文献
107.
Protection by salvianolic acid A against adriamycin toxicity on rat heart mitochondria. 总被引:5,自引:0,他引:5
It was found that salvianolic acid A (Sai A) has potent antioxidant activity. The effects of Sai A on adriamycin-induced heart mitochondrial toxicity of rats in vitro and on adriamycin antitumor activity are investigated in this article. Malondialdehyde (MDA) formation and membrane rigidification of rat heart mitochondria intoxicated with adriamycin were significantly reduced by Sai A. In the electron spin resonance (ESR) studies, Sai A has no significant effect on the formation of adriamycin semiquinone radicals (AQ.), while hydroxyl radicals generated by electron transfer from AQ. to H2O2 were scavenged by Sai A dose-dependently. On the other hand, Sai A was shown to have no effects on the antitumor activity of adriamycin in cultured L1210 ascitic tumor cells and in mice with P388 ascite tumor. These results indicate that Sai A protects against adriamycin induced heart mitochondrial toxicity of rats, while Sai A has no antagonizing effect on the antitumor activity of adriamycin. 相似文献
108.
Using O-phosphotyrosine as a substrate, human platelets were shown to contain a highly active phosphotyrosine phosphatase (PTPase) activity. This activity was potently inhibited by vanadate, molybdate, and HgCl2. About 80% of the PTPase activity was particulate. When Triton-solubilized PTPase activity from whole platelets was applied to a DEAE Sephacel column about 40% came through unbound. The activity that bound was eluted by a NaCl gradient as a broad, heterogeneous peak. The possibility is raised for the existence of multiple forms of phosphotyrosine phosphatases in human platelets. That one or more of these forms may be regulated by activators of platelet aggregation and secretion, such as thrombin and collagen, is discussed. 相似文献
109.
Summary The sequence and genetic organization was determined of the 2508 by lactococcal portion of pFX2, which was derived from a
crypticLactococcus lactis subsp.lactis plasmid and used as the basis for construction of a series of lactococcal vectors. A lactococcal plasmid plus origin and
two replication protein-coding regions (repA andrepB) were located. RepA has a helix-turn-helix motif, a geometry typical of DNA-binding proteins. RepB shows a high degree of
homology to the plasmid replication initiation proteins from other gram-positive bacteria andMycoplasma. The transcribed inverted repeat sequence betweenrepA andrepB could form an attenuator to regulate pFX2 replication. Upstream of theori site, and in a region which was non-essential for replication, a 215 by sequence identical to the staphylococcal plasmid
pE194 and carrying the RSA site was identified. The genetic organization of this lactococcal plasmid replicon shares significant similarity with pE194
group plasmids. 相似文献
110.
Renmei Ren Kanhui Yan Yanjie Su Hanjun Qi Bin Liang Wunyong Bao Frans B. M. de Waal 《Primates; journal of primatology》1991,32(3):321-327
Observations were made following 130 spontaneous aggressive incidents in two small breeding groups of captive golden monkeys
(Rhinopithecus roxellanae roxellanae). Participants were observed both during the first 10 min following these incidents and during matched control observations.
An increased contact rate was observed between opponents following the aggressive incident. Post-conflict contacts were characterized
by a number of behavior patterns: open mouth, rapid grooming, embrace, and crouching. Adult males played an important role
as mediator in agonistic disputes among females: males intervened in 93.6% of female fights. It is speculated that this intervention
behavior is related to the species' organization into one-male units. 相似文献