共查询到20条相似文献,搜索用时 31 毫秒
1.
Sam W. Woo Anthony W. Linnane Phillip Nagley 《Biochemical and biophysical research communications》1982,109(2):455-462
strain DC5-E2 that lacks mtDNA () can be cotransformed with a mixture of mtDNA and the plasmid YEp13 (LEU2/2μ/pBR322) to produce Leu+ transormants which, on being mated to tester strains, generate respiratory competent diploids (such events are denoted marker rescue). In this work strain DC5-E2 was transformed with recombinant molecules consisting of a mtDNA segment including the gene inserted into YEp13. The Leu+ transformants made with the recombinant plasmids were unable to rescue testers carrying mutations in the region, in contrast to Leu+ cotransformants made with mixtures of YEp13 and mtDNA. We conclude that marker rescue events occur as a result of interactions between the mtDNA of the tester and the mtDNA sequences introduced by transformation. Such interactions cannot occur when the latter mtDNA is forced to replicate in covalent association with YEp13, probably in the nucleus. 相似文献
2.
A third melanotropin coding fragment named γ-MSH was discovered by Nakanishi et al (Nature , 423–427 (1979)) in the cryptic region outside the portion coding for ACTH and β-LPH in the ACTH/β-LPH precursor mRNA isolated from the intermediate lobe of bovine pituitary. Four possible γ-MSH peptides derived from this coding fragment were synthesized by solid-phase methodology and their bioactivity determined in an MSH assay as well as the anterior pituitary primary culture assay. Relative to α-MSH, the melanotropic activities of Ac-γ1-MSH, γ1-MSH, γ2-MSH and γ3-MSH are 7.3 × 10?4, 3.3 × 10?5, 1.4 × 10?4 and 4.6 × 10?7 respectively. None of these γ-MSH peptides releases LH, FSH, PRL, GH and TSH in the pituitary culture medium at a dose as high as 100 ng per dish. 相似文献
3.
The effects of prolyl-leucyl-glycinamide and cyclo (leucyl-glycine) on morphine-induced antinociception in mice and on binding of 3H-ligands for opiate receptor subtypes (μ, δ and κ) the mouse brain homogenate were determined. Subcutaneous administration of either of the above peptides (1, 2, and 4 mg/kg) 10 min prior to the injection of morphine did not affect morphine-induced antinociception as evidenced by the identical ED50 values of morphine in vehicle and peptide treated groups. The binding of 3H-dihydromorphine and 3H-naloxone ( μ receptors), 3HDAla2DLeu5-enkephalin (δ receptors), and 3H-ethylketocyclazocine (κ receptors) to opiate receptors in the mouse brain homogenate was also unaffected by both the peptides over a large concentration range. It is concluded that these peptides do not interact with brain opiate receptors. 相似文献
4.
Some opiates with morphinan- and benzomorphan-structures possess affinities for neuroleptic receptors as revealed by their abilities to compete with 3H-spiroperidol for common binding sites in rat striatum (IC50 in the range between 10?6 and 10?5M). The binding of these opiates to neuroleptic receptors appears to be of pharmacological significance, since studies in mice revealed a small but significant displacement of spiroperidol by high doses of the opiate antagonist levallorphan from specific binding sites in the striatum. In addition, there exists some correlation between the ability of opiates to bind to neuroleptic receptor sites and their potency to evoke “bizarre behavior” in rats . In contrast, a wide variety of other opiates having morphine-, morphinone- or oripavine-structure showed no affinity for neuroleptic binding sites (IC50 greater than 10?4 M). Of the opioid peptides (methionine-enkephalin, leucine-enkephalin and β-endorphin) none has an affinity for neuroleptic binding sites. A variety of other peptides were also investigated but did not interfere with spiroperidol binding. Only ACTH showed a moderate affinity for neuroleptic binding sites. 相似文献
5.
An agonist of chicken hypothalamic luteinizing hormone-releasing hormone (cLH-RH). [D-Trp6] cLH-RH, was synthesized and tested for luteinizing hormone (LH)-releasing activity using dispersed chicken anterior pituitary cells, as well as for binding to rat anterior pituitary membrane receptors. cLH-RH and mammalian LH-RH (mLH-RH) gave identical dose-response curves in stimulating chicken LH release ( and respectively) and similar estimates of potency. The [D-Trp6] analogs of cLH-RH and mLH-RH stimulated LH release at lower doses ( and respectively) and were approximately 20-fold more potent. In contrast to the activity in the chicken bioassay, cLH-RH bound to rat anterior pituitary membrane receptors with a much lower affinity than did mLH-RH and had a relative potency of 2%. [D-Trp6] cLH-RH was approximately 100-fold more potent than cLH-RH in the rat receptor assay while [D-Trp6] mLH-RH was 28-fold more active than mLH-RH. These data demonstrate that substitution of Gly6 of LH-RH with D-Trp enhances the LH release from chicken pituitary cells to a similar extent to that observed in mammals, and indicate that the approaches used to produce active LH-RH analogs in mammals are likely to be applicable to birds. 相似文献
6.
Mahmoud Sharkawi 《Life sciences》1980,27(21):1939-1945
Disulfiram inhibited mouse and rat liver alcohol dehydrogenase (LADH) . Inhibition of LADH by disulfiram appears to be non-competitive. The inhibition constants (Ki) were about 1.5 × 10?4 M and 4.3 × 10?5 M for mouse and rat LADH respectively. Ethanol elimination was significantly reduced in mice pretreated with disulfiram. At identical time intervals after ethanol administration, the concentration of ethanol in blood from disulfiram-, cyanamide-, or dimethyl formamide-treated mice were significantly higher than the ethanol concentration in blood from control mice. Both cyanamide and dimethyl formamide (DMF) can precipitate a disulfiram-like reaction in man when ethanol is ingested. These and previous experiments suggest that elevated concentrations of ethanol should be considered in the etiology of some of the symptoms seen in the disulfiram-ethanol reaction. 相似文献
7.
Impaired negative cooperativity of the semisynthetic analogues human [LeuB24]- and [LeuB25]-insulins
Linda M. Keefer Marie-Agnès Piron Pierre De Meyts Hans-Gregor Gattner Cornelia Diaconescu Derek Saunders Dietrich Brandenburg 《Biochemical and biophysical research communications》1981,100(3):1229-1236
Several semisynthetic analogues of human insulin were prepared by enzyme-assisted coupling of synthetic octapeptides to the C-terminal of porcine desoctapeptide insulin. We report the receptor-binding and biological properties of [LeuB24]- and [LeuB25]-insulins, one of which has the same sequence as a “mutant” insulin recently found in a diabetic patient (Tager, H. et al.(1979) Nature :121–125). [LeuB24]- and [LeuB25]-insulins had, respectively, 8–12% and 0.9–1.1% of the binding affinity of human insulin, and 11% and 2.7% of its potency in stimulating lipogenesis in isolated rat fat cells. Neither one was an antagonist of the biological effects of native insulin. While the ability of [LeuB24]-insulin to induce negative cooperativity was clearly impaired, that of [LeuB25]-insulin was almost abolished. [LeuB25]-insulin was also a potent antagonist of the negative cooperativity induced by native insulin. 相似文献
8.
tRNACUGLeu from E. Coli was purified by column chromatography on benzoylated DEAE-cellulose, followed by hydroxyapatite prepared by an improved method. Crystals obtained by vapour diffusion gave X-ray diffraction out to 7 Å in the hk0 projection and 10 Å in h0?. The space group was P42212 with , and 8 molecules in the unit cell. Birefringence showed preferred orientation of RNA helical regions in the ab plane. 相似文献
9.
Daniela Cocchi Angela Santagostino Irit Gil-Ad Sergio Ferri Eugenio E. Müller 《Life sciences》1977,20(12):2041-2046
The effect of Leu5-enkephalin on growth hormone (GH) and prolactin (PRL) release was studied in the infant rat and compared to that of morphine. In 10 day-old pups, intracerebroventricular injection of Leu5-enkephalin (50, 75 and 100 μg) resulted in a dose-related increase in plasma GH; morphine was active as GH releaser at the dose of 5 and 10 μg, but not at 2.5 μg. Pretreatment with naloxone (2 mg/kg ip) suppressed the GH-releasing effect of either Leu5-enkephalin (100 μg) or morphine (10 μg). Leu5-enkephalin (75 and 100 μg) induced a rise in plasma PRL which was neither dose-related nor antagonized by naloxone; morphine (5 and 10 μg) was active as PRL releaser and its effect was antagonized by naloxone. These results indicate that: 1) Leu5-enkephalin stimulates both GH and PRL release; 2) the release of GH by Leu5-enkephalin but likely not that of PRL involves specific opiate receptors; 3) morphine releases GH and PRL through specific opiate receptors. 相似文献
10.
Proton and 13C magnetic resonance studies are reported on the synthetic polypentapeptide of elastin, HCO-(Val(1)-Pro(2)-Gly(3)-Val(4)-Gly(5))n-Val-OMe, where n ∼- 18. Temperature and solvent dependence of peptide N chemical shift and solvent dependence of peptide carbonyl chemical shift were used to delineate these moieties preliminary to identification of secondary structure.Based on these studies it is proposed, for the organic solvents of dimethyl sulfoxide, methanol, and low-temperature trifluoroethanol, that dynamic hydrogen bonds form in order of decreasing frequency of occurrence between the Val(1)O and the Val(4) N (a β-turn), between the Gly(3) N and the Gly(5)O (an 11-atom, hydrogen-bonded ring), and a more limited interaction between the Gly(3)O and the Gly(5) N (a γ-turn).Arguments are presented that relate the conformational features proposed above to the coacervate, which is a filamentous state. 相似文献
11.
John T. Dombrosky John A. Thomas Michael G. Mawhinney John W. Lloyd 《Life sciences》1973,13(7):795-804
Varying doses of morphine sulfate (10, 20 or 40 mg/kg daily × 10) were observed to suppress metabolic activities in the mouse prostate gland. Prostate gland fructose, an index of androgenic activity, was significantly reduced by these dose regimes of morphine (P < 0.01). Injections of morphine sulfate (20 mg/kg daily × 10) led to an inhibitition in the synthesis of both fructose?14C and sorbitol?14C from glucose?14C by the prostate gland, part of which may have been due to decreased uptake of glucose by the gland. The assimilation of 2-deoxyglucose?14C by the prostate was also reduced by morphine treatment. The actions of morphine (2 × 10?3M) on the metabolism of radioactive glucose by the mouse prostate gland likewise revealed a significant reduction in the formation of sorbitol?14C, but no decrease in fructose?14C formation. These results indicate that both the and actions of morphine can inhibit fructose metabolism in the prostate gland. 相似文献
12.
J R Giglio 《Analytical biochemistry》1975,69(1):207-221
The neurotoxin crotamine, which is a basic low molecular weight protein, was isolated, in the form of its hydrochloride, from a South Brazilian rattlesnake (Crotalus durissus crotaminicus, Crotalus durissus terrificus) venom.Disc electrophoresis, carried out in 7% acrylamide by the method of Reisfeld, at pH 4.5, showed a single band for the purified toxin.The toxin showed the following amino acid composition: Asx2, Ser3, Glx2, Pro3, Gly5, Cys5, Met1, Ileu1, Leu1, Tyr1, Phe2, Trp2, Lys9, His2, and Arg2, which corresponds to a minimum molecular weight of 4760. This assignment of minimum molecular weight is supported by the recovery of 1.0 mole of N-terminal of crotamine by the Sanger dinitrophenol (DNP) method, 1.0 mole of by the Udenfriend method, and by uv analysis, which gave a value of 4820. The odd number of half-cystine residues () cannot be explained on the basis of available analytical data.Tyrosine was the only amino-terminal residue detectable by the Sanger DNP method. Glycine was identified as the only carboxyl-terminal residue by the hydrazinolysis method of Akabori and by release upon treatment with yeast carboxypeptidase.The H+ electrometric and Cl? complexometric titrations of crotamine hydrochloride showed that about 13 moles of HCl are bound per 4760 g of the free base. 相似文献
13.
C.Channa Reddy Nan-qian Li Chen-Pei D. Tu 《Biochemical and biophysical research communications》1984,121(3):1014-1020
A new glutathione -transferase has been purified to homogeneity from 105,000 × g supernatant of Sprague-Dawley rat liver homogenates. The purified enzyme exhibited specific activities of approximately 1.8, and 0.12 μmoles. min?1. mg?1 toward 1-chloro 2,4-dinitrobenzene and cumene hydroperoxide respectively. The SDS gel electrophoresis data on subunit composition revealed that the new transferase is composed of two subunits with an identical Mr of 24,400 (Yα Family). Our translation experiments with rat liver poly(A) RNAs and substrate specificity data suggest that this subunit is different from the previously reported Ya, Yb and Yc subunits of rat liver glutathione -transferases. Comparatively, the new isozyme showed significant activity toward 1,2 epoxy-3-(P-nitrophenoxy)-propane, ethacrynic acid and P-nitrophenyl acetate, 0.4, 0.34 and 0.18 μ moles. min?1. mg?1 respectively. 相似文献
14.
The kinetics of fructose uptake was determined in perfused rat liver during steady-state fructose elimination. On the basis of the corresponding values of fructose concentration in the affluent and in the effluent medium, and the fructose and ATP concentration in biopsies, the kinetics of membrane transport and intracellular phosphorylation in the intact organ was calculated according to a model system. Carrier-mediated fructose transport has a high (67 mM) and (30 μmoles · min?1 ·g?1). The calculated kinetic constants of the intracellular phosphorylation were compared with values obtained with an acid-treated rat liver high speed supernatant (values given in parentheses). with fructose 1.0 mM (0.7 mM), with ATP 0.54 mM (0.37 mM), 10.3 μmoles · min?1 · g?1 (10.1 μmoles · min?1 · g?1, calculated on the basis of the highest measured rate of fructose uptake correcting the ATP concentration to saturating values). The kinetics of fructose uptake reveals that at Physiological fructose concentrations the membrane transport limits the rate of fructose uptake, thus protecting the liver from severe depletion of adenine nucleotides. 相似文献
15.
Jiahua Yu Yeon Jun Jeong Kang-Beom Kwon Sung-Zoo Kim Suhn Hee Kim Jin-Woo Park Hee-Chul Yu Byung-Hyun Park 《International journal of peptide research and therapeutics》2008,14(2):167-172
Atrial natriuretic peptide (ANP) was recently shown to promote triacylglycerol hydrolysis in human white adipocytes both in vitro
and in vivo through a cGMP-dependent pathway. The ANP-stimulated lipolytic effect is known to be specific to primates. In
this study, we compared the lipolytic effect of different natriuretic peptides obtained from several species, including ANP
from human, rat, chicken, frog, and eel, brain natriuretic peptide (BNP) from porcine and rat, C-type natriuretic peptide
(CNP) from human, chicken, and frog, Dendroaspis natriuretic peptide (DNP), urodilatin, and des-[Gln18, Ser19, Gly20, Leu21, Gly22]-ANP (C-ANP), on human and rat adipocytes. We also compared the amount of intracellular cGMP produced in both human and rat
adipocytes that were treated with natriuretic peptides. Among these NPs, rat ANP, as well as porcine and rat BNP, DNP and
urodilatin showed the ability to elevate intracellular cGMP and to stimulate lipolysis as human ANP. No natriuretic peptide
showed the ability to stimulate lipolysis in rat adipocytes, though some of them induced significant elevation of intracelluar
cGMP concentrations. These results suggest that ANP and BNP from species close to human have the ability to induce lipolysis
in human adipocytes.
Jiahua Yu and Yeon Jun Jeong contributed equally. 相似文献
16.
17.
N Yanihara K Tsuji C Yanaihara T Hashimoto T Kaneko A Arimura A V Schally 《Biochemical and biophysical research communications》1973,51(1):165-173
Syntheses are described of [Pro1]-LH-RH, [Orotic acid1]-LH-RH, [Glu1]-LH-RH, [Ser2]-LH-RH, [Leu2]-LH-RH, [Gln2]-LH-RH and [Phe2]-LH-RH. The LH-releasing hormone (LH-RH) activity of each of these peptides was compared with that of natural LH-RH . [Glu1]-LH-RH and [Phe2]-LH-RH had significant LH-RH activity, while all the other analogs possessed extremely low activities. These findings are briefly discussed in the light of the structure-activity relationship for LH-RH. 相似文献
18.
András Patthy László Gráf Ágnes Kenessey József I. Székely Sándor Bajusz 《Biochemical and biophysical research communications》1977,79(1):254-259
β-endorphin was incubated with rat brain homogenate, and the amino acids released were measured by amino acid analysis. Phe, Leu, Tyr, and Lys were liberated in the greatest amount indicating that the cleavage of Leu77-Phe78 and some Lys-X peptide bonds with endopeptidases followed by the removal of the terminal residues by exopeptidases are the main routes of β-endorphin degradation in the brain. Bacitracin considerably reduced the amino acid release from β-endorphin incubated with rat brain homogenate, and its action is suggested to be due to the inhibition of brain amino- and carboxypeptidases. Bacitracin also potentiated and prolonged the analgesic activity of β-endorphin. 相似文献
19.
- and - octopamine have been identified in beef and rat adrenal gland and in rat salivary gland by means of gas chromatography-mass spectrometry. The tritrifluoroacetyl derivatives of -, - and - octopamine were resolved by gas chromatography and shown to produce two characteristic ions at 315 and 328. The di-O-trimethylsilyl-N-trifluoroacetyl derivatives of these three isomers were also resolved by gas chromatography and shown to produce a characteristic ion at 267. Biological samples were homogenized in formic acid:acetone, subjected to ion-exchange chromatography and then derivatized. When the derivatized biological extracts were examined for each characteristic ion, peaks were observed at the exact retention times of the standards. The three isomers are present in adrenal gland in concentrations of ~1 μg g?1 and in rat salivary gland in concentrations of ~0.1 μg g?1. This evidence confirms a previous report of the presence of -octopamine in rat salivary gland measured by a radiochemical enzyme assay and is the first report of the presence of -octopamine in biological tissue. 相似文献
20.
Gianfranco Delle Fave Anna Kohn Laura de Magistris Marcello Mancuso Claudio Sparvoli 《Life sciences》1980,27(11):993-999
The effect of bombesin on gastrin release and gastric acid secretion was investigated in 10 healthy volunteers. Bombesin (0.6 μg · Kg?1 · hr?1) produced a significantly higher increase in plasma gastrin levels (86.7 11.1 pmo/1 than after a protein meal (39.6 ± 5.6 pmol1/1). The gastric acid secretory response to bombesin (12.1 ± 2.9 mEq · hr?1) was however significantly lower than the maximal response produced by pentagostrin (20.9 ± 3.5 mEq · hr?1) at the dose of 6 μg · Kg?1. Atropine did not modify gastrin release induced by bombesin but significantly reduced gastric acid secretion . From the data presented it may be hypothesized that less biologically active forms of gastrin and/or other peptides inhibiting the gastrin effect upon gastric acid secretion may be released by bombesin. 相似文献