共查询到20条相似文献,搜索用时 15 毫秒
1.
Chester Meyers Akira Arimura Ariel Gordin R. Fernandez-Durango David H. Coy Andrew V. Schally Jacques Drouin Louise Ferland Michele Beaulieu Fernand Labrie 《Biochemical and biophysical research communications》1977,74(2):630-636
Three analogs of somatostatin, [-Cys14] -, [Ala2, -Cys14] - and [-Trp8, -Cys14] - somatostatin, were synthesized by the solid phase method, characterized by several means, and tested for their effects on the release of insulin, glucagon, and growth hormone. The peptides sharply suppressed the release of growth hormone and glucagon , but had less effect on insulin secretion . These analogs, particularly [-Trp8, -Cys14] - somatostatin, could possibly be useful for the treatment of diabetes mellitus. 相似文献
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C. Mombers P.W.M. Van Dijck L.L.M. Van Deenen J. De Gier A.J. Verkleij 《生物化学与生物物理学报:生物膜》1977,470(2):152-160
Using differential scanning calorimetry and freeze fracture electron microscopy interactions were studied between lipids and a spectrin · action complex isolated from human erythrocyte membranes. With dispersions of , and mixtures of these two compounds, which for experimental reasons were chosen as the lipid counterpart, such an interaction could clearly be deduced from changes in the temperature and the enthalpy of the phase transition. Furthermore it was demonstrated that the interaction with this membrane protein protects the bilayer against the action of Ca2+ and Mg2+ and prevents fusion of lipid vesicles which easily occurs in some of the systems when divalent ions were added to the pure lipid vesicles. 相似文献
4.
The potencies of (?)--Δ9-THC, (+)--Δ9-THC, (+)--Δ9-THC, (?)--Δ8-THC and (+)--Δ8-THC were compared in several different species. (?)--Δ9-THC was 100 times more potent than (+)--Δ9-THC in depressing schedule-controlled responding in monkeys. The (+)- isomers were less effective than their corresponding (?)- isomers in the dog static-ataxia test, but potency ratios could not be determined due to a lack of dose-responsiveness of the (+)- isomers. However, it appeared that their potency differed by at least ten fold. The potency of (+)--Δ9-THC in the dog static-ataxia test was comparable to that of (+)--Δ9-THC. The hypothermia in mice produced by the (?) isomers of -Δ9-THC and -Δ8-THC were 9.1 and 30.4 times greater than that produced by their respective (+)-isomers. Also, the potency ratio of the (+)- and (?)--Δ9-THC was 5.6 as measured by depression of spontaneous activity in mice. The magnitude of the potency ratios of the THC stereo-isomers is dependent upon the species and the pharmacological test used. 相似文献
5.
Secretory vesicles isolated from adrenal medulla were found to fuse in vitro in response to incubation with Ca2+. Intervesicular fusion was detected by electron microscopy and was indicated by the appearance of twinned vesicles in freeze-fractured suspensions of vesicles and in thin-sectioned pellet. Two types of fusion could be distinguished: Type I, occurring between 10?7 M and 10?4 M Ca2+, was specific for Ca2+, was inhibited by other divalent cations and was abolished by pretreatment of vesicles with glutaraldehyde, neuraminidase or trypsin. Fusion type I was linear with temperature. A second type of intervesicular fusion was elicited by Ca2+ in concentrations higher than 2.5 mM and was morphologically characterized by multiple fusions of secretory vesicles. This type of fusion was found to be similar to fusion of liposomes prepared from the membrane lipids of adrenal medullary secretory vesicles: Ca2+ could be replaced by other divalent cations, the effect of different divalent cations was additive and pretreatments attacking membrane proteins were ineffective. Fusion type II of intact secretory vesicles as well as liposome fusion was discontinuous with temperature. Liposome fusion could be detected within 35 ms and persisted for 180 min. Using liposomes containing defined Ca2+ concentrations we have not found a major influence of Ca2+ asymmetry on fusion. Incorporation of the ganglioside GM3, which is present in the membranes of intact adrenal medullary secretory vesicles did not change the properties of liposomes fusion. Using a Ca2+-selective electrode we have identified in secretory vesicle membranes both high affinity binding sites for Ca2+ () and low affinity sites (). 相似文献
6.
Mohammad Ali Ghalambor Christopher D. Warren Roger W. Jeanloz 《Biochemical and biophysical research communications》1974,56(2):407-414
Incubation of UDP-[14C]--acetylglucosamine with calf pancreas microsomes in the presence of Mn++ and potassium thiocyanate gave a labeled glycolipid, tentatively identified as 1-2-acetamido-2-deoxy--glucosyl 2-dolichyl pyrophosphate on the basis of cochromatography with synthetic 1-2-acetamido-2-deoxy-α--glucopyranosyl 2-dolichyl pyrophosphate, similar chemical and enzymic hydrolyses of the biosynthetic and synthetic compounds, and stimulation of the biosynthesis by addition to the incubation mixture o dolichyl phosphate or a crude lipid fraction extracted from microsomes. 相似文献
7.
-3-dehydro-D, L-ornithine and -1, 4-diamino-2-butene have been synthesized and shown to be potent competitive inhibitors of ornithine decarboxylase. The KI′S for -3-dehydro-L-ornithine and -1, 4-diamino-2-butene are 2.2 and 2.0 μM respectively. Both analogs bind much more tightly to the enzyme than either ornithine or putrescine. Studies of chick embryo muscle cells in culture show results consistent with reversible inhibition of division and/or fusion by addition of -3-dehydro-D, L-ornithine to the culture medium. 相似文献
8.
- 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
9.
W.J. Burrows 《Biochemical and biophysical research communications》1978,84(3):743-748
Cytokinin-autonomous tobacco callus was incubated in defined mineral medium containing 3H-adenine for 60 minutes. Radioactivity was incorporated into the four predominant free cytokinins, ribosyl--zeatin, -zeatin, N6-(Δ2-isopentenyl) adenosine and N6-(Δ2-isopentenyl) adenine. The bases were more abundant than their respective ribosides, N6-(Δ2-isopentenyl) adenine being the most abundant cytokinin. No discrete peaks of radioactivity could be detected on the HPLC column eluate corresponding to the elution volumes of -zeatin and ribosyl--zeatin. 相似文献
10.
D E Sok C O Han W R Shieh B N Zhou C J Sih 《Biochemical and biophysical research communications》1982,104(4):1363-1370
Human leukocytes converted [3H]-(S)-15-HPETE into [3H]-14,15-LTA. Rat basophilic leukemia cells transformed 14,15-LTA into two bioactive C(14)-S-linked peptides, which have been characterized as 15(S)-hydroxy-14(R)-S-glutathionyl-5,8,10,12-icosatetraenoic acid and 15-(S)-hydroxy-14(R)-S-cysteinylglycyl-5,8,10,12-icosatetraenoic acid by comparison with synthetic specimens. 相似文献
11.
M S Kilberg H N Christensen M E Handlogten 《Biochemical and biophysical research communications》1979,88(2):744-751
The rapid transport of -cysteine into isolated rat hepatocytes escapes detectable inhibition by 2-(methylamino)-isobutyric acid at levels up to 50 mM. The system transporting cysteine instead is convincingly similar to the system described for the Ehrlich cell in structural and steric specificity and in pH sensitivity. The Na+-dependent uptake of 2-aminoisobutyric acid is almost evenly divided between Systems and , showing better accommodation of its two α-methyl groups by than in the Ehrlich cell. The hepatocyte system tolerates Li+-for-Na+ substitution better than does System , although the tolerance depends on amino acid structure. Adaptive regulation and insulin and glucagon stimulation were not seen under conditions producing these effects for System . 相似文献
12.
J Humphries T Wasiak Y P Wan K Folkers C Y Bowers 《Biochemical and biophysical research communications》1978,85(2):709-713
Ac-[Pro1, , -Trp3, -Trp6]-LH-RH completely inhibited ovulation in cycling rats at 200μg/rat and is comparable in activity to the corresponding D-1-analogue. This Ac-Pro1-analogue is the most potent antiovulatory peptide yet known having an -amino acid residue in position 1. This result shows that for the design of potent inhibitors of ovulation, a -amino acid residue is not essential in position 1. The corresponding Ac--Pro1- and Kic1-analogues completely inhibited ovulation at 750μg/rat, but not at 200μg/rat, and the Cpc1-analogue was inactive at these dosages. 相似文献
13.
S Lemaire L Chouinard D Denis M Panico H R Morris 《Biochemical and biophysical research communications》1982,108(1):51-58
Deliberate miscompartmentalization of liver outer mitochondrial membrane (OMM) proteins and liver mitochondrial proteins has been achieved by polyethylene-glycol mediated OMM vesicle-hepatocyte or mitochondrial-hepatocyte fusion. Reductively methylated OMM and mitochondrial proteins (3H) are destroyed at rates remarkably similar to those for OMM (, 60–70 h) or mitochondrial proteins (, 84–104 h) in liver when studied over 4–5 days in hepatocyte monolayers cultured in conditions giving stabilized endogenous protein catabolic rates mimicking endogenous rates. Destruction of transplanted OMM proteins is partially sensitive to chloroquine, supporting some lysosomally mediated autophagic destruction of long-lived transplanted OMM proteins in hepatocyte monolayers. 相似文献
14.
A heterogeneous particulate fraction of mouse brain homogenates binds NRDC 157 (3-phenoxybenzyl [1,]-3-(2,2-dibromovinyl)-2,2- dimethylcyclopropanecarboxylate), a potent pyrethroid insecticide, stereospecifically and with high affinity. Stereospecific binding is a minor component of total binding (2.8%); the remainder of observed binding is predominantly nonspecific and unsaturable. Stereospecific binding is half-saturated at 4×10?8 and fully saturated at concentrations in excess of 1×10?7. The stereospecific binding capacity of this preparation was 200–250 pmoles of NRDC 157 per gram equivalent of brain tissue (2.3–2.8 pmol/mg protein). This binding site may represent the neural receptor involved in the stereospecific toxic action of pyrethroids. 相似文献
15.
The relationship between cell fusion, DNA synthesis and the cell cycle in cultured embryonic normal and dysgenic () mouse muscle cells has been determined by autoradiography. The experimental evidence shows that the homozygous mutant myotubes form by a process of cell fusion and that nuclei within the myotubes do not synthesize DNA or undergo mitotic or amitotic division. The duration of the total cell cycle and its component phases was statistically the same in 2-day normal and mutant () myogenic cultures with the approximate values: T, 21.5 hr; G1, 10.5 hr; S, 7.5 hr; and G2, 2.5 hr. In both kinds of cultures, labeled nuclei appeared in myotubes 15–16 hr after mononucleated cells were exposed to [3H]thymidine, and the rate of incorporation of labeled nuclei into multinucleated muscle cells was comparable in control and dysgenic cultures. Thus, homozygous muscle cells in culture are similar to control cells with respect to their mechanism of myotube formation and the coordinate regulation of DNA synthesis and the cell cycle during myogenesis. 相似文献
16.
Hasan Mukhtar Insu P. Lee John R. Bend 《Biochemical and biophysical research communications》1978,83(3):1093-1098
Glutathione -transferase activity was found in sperm of the rat and and C57 mice. In rat sperm activities with benzo(a)pyrene 4,5-oxide, styrene 7,8-oxide, and 1-chloro-2,4-dinitrobenzene were 0.88, 1.07, and 26.1 nmoles/min/mg protein, respectively. Δ5-3-Ketosteroid isomerase activity of rat sperm was 4.9 nmoles/min/mg protein. These specific glutathione -transferase and Δ5-3-ketosteroid isomerase activities in sperm represent 0.4–4.1% of rat liver cytosol values. Human semen also contained significant glutathione -transferase activity. It is postulated that these enzymes could function in the metabolism and detoxification of certain electrophilic xenobiotics, if present in sperm. 相似文献
17.
The enzyme system for the synthesis of the pteridine pigment, sepiapterin, from triphosphate (dihydroneopterin triphosphate) has been found in extracts of . NADP+ or NADPH and Mg2+ are required for this enzymatic transformation. No sepiapterin is produced when dihydroneopterin is supplied as substrate in place of dihydroneopterin triphosphate. 相似文献
18.
One juvenile hormone was isolated from culture medium containing isolated corpora allata of the grasshopper (Orthoptera: Acrididae) and was shown by microchemical methods to be methyl (2, 6) - (10) - 10, 11-epoxy-3, 7, 11-trimethyldodeca-2, 6-dienoate. This compound (JH III), which occurs in a sphingid moth , is the first juvenile hormone identified in an insect order other than the Lepidoptera. Grasshopper organs incorporate both [2?14C] acetate and [methyl-14C] methionine into JH III showing biosynthesis, but no indication of the synthesis of JH I or JH II was seen. 相似文献
19.
J Germershausen D Goodman E W Somberg 《Biochemical and biophysical research communications》1978,82(3):871-878
RNA (guanine-7) methyltransferase, partially purified from mycelia, catalyzed the transfer of the methyl group from S-adenosylmethionine to the 5′ terminus of both poly A(+) RNA and reovirus unmethylated mRNA. RNase T2 digestion of the methylated poly A(+) RNA from yielded the “cap” structures m 7G(5′)pppAp and m 7G(5′)pppGp in a ratio of 2:1 respectively. RNase T2 digestion of the methylated reovirus mRNA yielded m 7G(5′)pppGp exclusively. The absence of mRNA 2′-0-methyltransferase activity in the enzyme preparation is consistent with the absence of 2′-0-methylation in mRNA [Seidel, B. L. and Somberg, E. W. (1978) Arch. Biochem. Biophys. , 108–112]. This is the first isolation of an eucaryotic, cellular RNA (guanine-7) methyltransferase that has been shown to methylate homologous substrate. 相似文献
20.
Expression and subcellular distribution of mouse cytochrome P1-450 mRNA as determined by molecular hybridization with cloned P1-450 DNA 总被引:1,自引:0,他引:1
Cytochrome P1-450 (P1-450) is defined as that cytochrome most closely associated with 3-methylcholanthrene (MC)-induced aryl hydrocarbon hydroxylase (AHH) activity. Recently a cloned DNA sequence (clone 46) was shown to represent a portion of the P1-450 structural gene [Negishi : 800–804 (1981)]. Poly(A+)-enriched RNA was isolated from total liver homogenate, membrane-bound polysomes and from free polysomes at various times after MC treatment of -responsive (B6) and -nonresponsive (D2) inbred mice. The poly(A+)-enriched RNA was separated by methylmercury-agarose gel electrophoresis and hybridized to nick-translated [32P]DNA from clone 46. By means of this RNA-DNA hybridization, only 6% of total polysomal P1-450 mRNA exists in free polysomes after 24 h of MC treatment. The data indicate that the endoplasmic reticulum is the principal site of synthesis for this integral microsomal protein.Studies of induction kinetics following MC treatment provided the evidence of the rapid increase of total liver and membrane bound P1-450 mRNA preceding the synthesis of apo-P1-450 and the increase of AHH activity. 相似文献