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1.
Characterization of temperature-sensitive [3H]serotonin (5-HT) binding sites (1 and 4 nM Kd sites) revealed complex inhibition by neuroleptics and serotonin antagonists. There was no simple correlation with affinities for S1 and S2 receptors. pretreatment (48 h before) with mianserin did not alter Bmax or Kd for the 1 nM Kd [3H]5-HT site, although [3H]ketanserin (S2) densities were decreased by 50%. This suggested that possible S2 components of [3H]5-HT binding must be negligeable, even though ketanserin competed with high affinity (IC50 = 3 nM) for a portion of the 1 nM Kd [3H]5-HT site. Low concentrations of mianserin inhibited the 1 nM Kd [3H]5-HT site in a non-competitive manner, as shown by a decrease in Bmax with no change in Kd after incubation. The complex inhibition data may therefore represent indirect interactions through another site. 相似文献
2.
Acetylcholine stimulates hydrolysis of 32 P-labeled phosphatidic acid in guinea pig synaptosomes 总被引:3,自引:0,他引:3
[3H]-inositol or [3H]-arachidonate was injected intracerebrally into guinea pigs. Labeled nerve endings were incubated with Ach1 or CCh, both of which stimulate labeling of PhA and PhI from 32Pi by > 100% and 70% respectively. Their addition did not affect the labeled phosphatidyl-[3H]-inositol or [3H]-arachidonyl-diglyceride and -PhI. Enhanced hydrolysis of [3H]-inositol-PhiP and -PhIP2 in the presence of ACh, CCh or choline was not reversed by atropine. In a two-step experiment, PhA was labeled with 32Pi, and DNP was added to block further formation. Addition of ACh stimulated an atropine-sensitive in [32P]-PhA. 相似文献
3.
Labeled n-alkanes administered to the grasshopper are hydroxylated at or near the middle of the carbon chain. The secondary alcohols formed are then esterified. Chain length specificity is evident in both the hydroxylation of n-alkanes and the esterification of secondary alcohols, with the shorter chain C23, C21, C19, and C25 compounds converted to secondary alcohol wax esters more readily than the longer chain C27, C29, and C31 compounds. Secondary alcohols and ketones are not reduced to alkanes. 相似文献
4.
Timothy S. Gaginella Thomas J. Rimele Thomas M. ODorisio Robert J. Dorff 《Life sciences》1980,26(19):1599-1608
Muscarinic receptors in the smooth muscle of the cat pylorus (pyloric sphincter) were identified by binding of the ligand (±) [3H]-quinuclidinyl benzilate ([3H]-QNB). Receptor related binding of [3H]-QNB reached steady-state in thirty minutes at 37°C, was saturable, showed pharmacologic specificity and was stereoselective. An apparent equilibrium dissociation constant, KD, of 1.9 ± 0.3 nM and maximum receptor concentration of 122 ± 13 femtomoles per mg of protein (means ± S.E.M.) were determined from Scatchard plots of [3H]-QNB binding. Hill coefficients of 0.99 and 1.01 indicated the absence of cooperative interactions. The muscarinic antagonists atropine and propantheline inhibited binding with IC50 values in the nanomolar range, whereas bethanechol was over four orders of magnitude less potent. Noncholinergic agents had little or no effect on [3H]-QNB binding. The isomer of QNB was about seventy times more effective at inhibiting binding than its isomer while benzetimide was greater than two thousand fold more active than benzetimide. The isomers of another anticholinergic compound, tropicamide, also competed for [3H]-QNB binding sites in a stereoselective manner, the isomer being eighty-five times more potent than the isomer. 相似文献
5.
The conversion of a 5β-pregnan-3-one into a 3-thia-A-nor-pregnane is described. The single epimer, characterized as the 5β-isomer by nmr spectroscopy, was obtained.A previous report [1] from this laboratory described the synthesis of the epimeric 3-oxa-A-norpregnan-20-ones and from A-norprogesterone. Recently, the total synthesis of the related A-nor-3-thiaestra-1,-5(10)-diene derivative has been described [2]. Continuing interest [3] in A-ring-modified steroids as probes of drug-receptor interactions prompts this report of the preparation of the 3-thia-5β-A-norpregnan-20-one . 相似文献
6.
Sun-Shine Yuan 《Steroids》1982,39(3):279-289
A-ring enollactones , or derived from 4-cholesten-3-one, testosterone benzoate or 3-oxo-4-estren-17β-yl benzoate were condensed with [1,2-13C2]acetyl chloride to give intermediates , or . and were cyclized by acid or base to give 3,4-13C2-labeled 4-cholesten-3-one and testosterone, respectively. [3,4-13C2]4-Cholesten-3-one was converted via reduction of its trimethylsilyl enol ether to [3,4-13C2]cholesterol. Acetyl enollactone was cyclized in acetic acid to [3,4-13C2]3-oxo-4-estren-17β-yl benzoate followed by aromatization and hydrolysis to produce [3,4-13C2]estradiol-17β. Alternatively, cyclization of with base afforded [3,4-13C2]3-oxo-4-estren-17β-ol directly, which was then oxidized and aromatized to yield [3,4-13C2]estrone. Ozonolysis of progesterone, conversion to the diketal ester and acylation followed by acid hydrolysis furnished [3,4-13C2]progesterone. 相似文献
7.
E A Meighen I G Bogacki A Bognar G A Michaliszyn 《Biochemical and biophysical research communications》1976,69(2):423-430
Bioluminescence rises very rapidly in the later stages of growth of due to the induction of luciferase activity. This enzyme catalyzes the oxidation of FMNH2 and a long chain aliphatic aldehyde resulting in the emission of light. The present experiments report the discovery of an aldehyde dehydrogenase in which is remarkably similar to luciferase in its specificity for long chain aliphatic aldehydes. Furthermore, the activity of this enzyme is shown to be induced at the same time as luciferase thus providing strong evidence for a functional implication of aldehyde dehydrogenase in the bioluminescent system of . 相似文献
8.
Fourier analysis of sequences along edges of the type I collagen molecule constructed from two α1(I) and one α2 chains shows that the molecule is two-sided if the supercoil pitch of the α chains along the molecular axis, P, is 39 residues (, where D = 234 residues or 67 nm). One side has alternating charged and hydrophobic regions with spacings of , while the other side has an excess of hydrophobic residues with a spacing of . These characteristics arise from sequence regularities in the α chains and the geometric relationship between the chains. The pattern is marginally strongest with α2 as chain 1. The sides could form the inside of a helical microfibril where contacts between molecules would fall P apart along the α chains. The sides could form the outside of the microfibril where contacts between microfibrils would be spaced apart by the α chain supercoil along the microfibril axis, P′. If the microfibril is a 54 helix of D-staggered collagen molecules with a left-handed supercoil of pitch , P′ is close to (43 residues). subsets in the α chains give rise to the spacing along the molecule. The microfibril has 41 screw symmetry satisfying X-ray diffraction evidence that microfibrils pack in a tetragonal unit cell.This model is the same as proposed previously by us (Trus & Piez, 1976: Piez & Trus, 1977) except that P = 39 rather than 30 residues. Contrary to our earlier assumption, P = 39 residues is within the range allowed by X-ray diffraction measurements. The present results favor P = 39 since it relates regularities in the α chain sequences to helical parameters in a direct way. Furthermore, model studies show that geometric arguments which support P = 30 are equally strong at P = 39 residues. 相似文献
9.
Relationships between perinatal mortality, disrupted uteroplacental function and prostaglandin metabolism have been studied in Zn-deficient rats. Uterine contractility , placental blood flow , and uterine and placental prostaglandin synthesis from [1?14C] arachidonic acid were investigated at day 22 of pregnancy. High amplitude uterine contractions were almost completely eliminated and utero-placental blood flow was decreased by 85% by Zn deficiency. Synthesis of [1?14C]-prostaglandin E2, F2α and 6-keto-F1α from [1?14C] arachidonic acid decreased significantly in uterine tissue but increased in placentae. These possibly inter-related effects may contribute to the high perinatal mortality observed in Zn deficiency. 相似文献
10.
In vivo biosynthesis of -linolenic acid in plants 总被引:6,自引:0,他引:6
C G Kannangara B S Jacobson P K Stumpf 《Biochemical and biophysical research communications》1973,52(2):648-655
[1-14C]acetate was readily incorporated into unsaturated fatty acids by leaf slices of spinach, barley and whole cells of and . In these systems the [14C] label in newly synthesized oleate and linoleate was approximately equally distributed in the C1–9 and the C10–18 fragments obtained by reductive ozonolysis of these acids, whereas in a-linolenic acid over 90% of the total [14C] was localized in the C1–9 fragment. While [1-14C]oleic acid was converted by whole cells of to [1-14C]linoleic and [1-14C]linolenic acids, [U-14C]oleic acid yielded [U-14C]linoleic acid but a-linolenic acid was labeled only in the carboxyl terminal carbon atoms. When spinach leaf slices were supplied with carboxyl labeled octanoic, decanoic, dodecanoic, tetradecanoic and octadecanoic acids, only the first three acids were converted to a-linolenic acids while the last two acids were ineffective. Thus we suggest that (a) linoleic acid is not the precursor of a-linolenic acid and (b) 12:3(3, 6, 9) is the earliest permissible trienoic acid which is then elongated to a-linolenic acid. 相似文献
11.
The biosynthesis of 2-methylalkanes was studied in the crickets and . Labelled acetate, valine, and isobutyric acid were incorporated into the cuticular hydrocarbon of at levels of 6.0 ± 1, 6.5 ± 2, and 1.5 ± 0.7 percent respectively. The hydrocarbons of this insect are 20 percent 2-methylalkanes, primarily of even numbered carbon chain lengths, and 80% n-alkanes. Of the label incorporated into the hydrocarbon fraction, 28 ± 2 percent of sodium [1-14C] acetate, 98 ± 1 percent of L-[G-3H] valine, and 75 ± 10 percent of [1-14C] isobutyric acid were incorporated into the 2-methylalkanes. This suggests that valine is converted to isobutyric acid and is incorporated into the even numbered carbon chain length 2-methylalkanes during the initial stages of chain elongation. Similar data obtained in suggests that leucine is converted to isovaleric acid which is then incorporated into the odd numbered carbon chain length 2-methylalkanes. 相似文献
12.
Plasma membranes were isolated from HM7 melanoma cells grown in the presence of [3H]glucosamine and Na235SO4 or [3H]mannose and [14C]glucosamine. The labelled glucoconjugates were solubilized with 0.6 M lithium diiodosalicylate/0.5% Triton X-100. Fractionation of glycoconjugates by repeated chromatography on columns of Sepharose CL-6B and DEAE-Sepharose and by affinity chromatography on WGA-Sepharose yielded three radiochemically homogenous glycoproteins. One of these having an apparent molecular weight of 100 000 was found to contain clusters of (AcNeu)1 or in2 å [Gal å GalNAc] linked to the protein. One other glycoprotein contained both and oligosaccharides, and the third contained only carbohydrates. Preliminary results indicate that the 100 000 molecular weight mucin-type glycoprotein is present in significantly reduced quantities in cultured human fetal uveal melanocytes. Further, the bulk of the glycoproteins from the melanocytes were of lower molecular size compared to those from the melanoma cells. 相似文献
13.
Galactaric acid, C6H10O8, (CAS Reg. No. 526-99-8), is triclinic, P, with cell dimensions at ?147° [and 20°], a = 4.900(1) [4.918(1)], b = 5.728(1) [5.816(1)], c = 6.784(1) [6.849(1)] Å, α = 92.32(2) [92.31(2)], β = 93.74(2) [94.16(2)], γ = 93.08(2) [93.49(2)]°, V = 189.5 Å3, Z = 1, Dx = 1.831 [1.800], Dm = [1.790] g.cm?3, molecular symmetry . The structure was solved by the direct method, MULTAN, and refined to R = 0.034, Rw = 0.039 for 787 reflections with FObs > 3σ(Fobs). The crystal structure has a system of strong, intermolecular hydrogen-bonds, which accounts for the high crystal density and low solubility in water. 相似文献
14.
I.K. Adzamli R.A. Henderson H. Ong A.G. Sykes R. Cammack K.K. Rao 《Biochemical and biophysical research communications》1982,105(4):1582-1589
When parsley [2Fe-2S] and 2[4Fe-4S] proteins in the normal oxidised state are reduced 1:1 with Cr(II) (15-aneN4) (H2O)22+ the Cr(III) product remains attached to the protein and reduction is by an inner-sphere mechanism. With high potential [4Fe-4S] protein and rubredoxin the Cr(III) product is not attached to the protein and the mechanism is outer-sphere. Results are discussed in the context of protein crystallographic information. The Cr(III) product is not attached to the Fe2S2 core (extrusion experiments) or to the cysteinyl S-atoms (ESR). Negative patches close to the active site remain possible alternatives. 相似文献
15.
C Hedgcoth K Thomas K Scheets S Allen 《Biochemical and biophysical research communications》1980,95(2):880-886
When murine sarcoma virus-transformed cells are labeled with [3H]lysine for various periods, 5 of 6 isoaccepting lysine tRNAs separable by RPC-5 chromatography are aminoacylated in 1 hr to the same extent that they are aminoacylated . The sixth isoacceptor, tRNA6Lys, is not aminoacylated to a measurable extent in 1 hr, although it is present in the tRNA prepared from the cells. All six isoacceptors are aminoacylated with [3H]lysine when the labeling period is 2 or 3 hr. These results further show that correlations of the amount of tRNA4Lys with cell division accurately reflect the situation . Results of differential centrifugation indicate that tRNA6Lys occurs in mitochondria. 相似文献
16.
(1) a photoactivable derivative of 5-adenylyl imidodiphosphate (AdoPP[NH]P), was synthesized. (2) Binding of 3H]NAP4-AdoPP[NH]P to soluble ATPase from beef heart mitochrondria (F1) was studied in the absence of photoirradiation, and compared to that of . The photoactivable derivative of AdoPP[NH]P was found to bind to F1 with high affinity, like AdoPP[NH]P. Once had bound to F1 in the dark, it could be released by AdoPP[NH]P, ADP and ATP, but not at all by NAP4 or AMP. Furthermore, preincubation of F1 with unlabeled AdoPP[NH]P, ADP, or ATP prevented the covalent labeling of the enzyme by upon photoirradiation. (3) Photoirradiation of F1 by resulted in covalent photolabeling and concomitant inactivation of the enzyme. Full inactivation corresponded to the binding of about 2 mol . Photolabeling by NAP4-AdoPP[NH]P was much more efficient in the presence than in the absence of MgCl2. (4) Bound was localized on the α- and β-subunits of F1. At low concentrations (less than 10 μM), bound was predominantly localized on the α-subunit; at concentrations equal to, or greater than 75 μM, both α- and β-subunits were equally labeled. (5) The extent of inactivation was independent of the nature of the photolabeled subunit (α or β), suggesting that each of the two subunits, α and β, is required for the activity of F1. (6) The covalently photolabeled F1 was able to form a complex with aurovertin, as does native F1. The ADP-induced fluorescence enhancement was more severely inhibited than the fluorescence quenching caused by ATP. The percentage of inactivation of F1 was virtually the same as the percentage of inhibition of the ATP-induced fluorescence quenching, suggesting that fluorescence quenching is related to the binding of ATP to the catalytic site of F1. 相似文献
17.
B.V. Chernyak P.A. Dibrov A.N. Glagolev M.Yu. Sherman V.P. Skulachev 《FEBS letters》1983,164(1):38-42
Motility of a marine alkali-tolerant bacterium, Vibrio alginolyticus, can be observed in the presence of high concentrations of a protonophorous uncoupler, CCCP. Motility in the CCCP-containing media is completely inhibited by decrease in extracellular [Na+] or by monensin-induced increase in intracellular [Na+]. A mutant has been selected that grows only in media supplemented with a substrate such as acetate requiring no ΔNa to be transported into the cell. Motility of the mutant was found to be completely inhibited by CCCP. Cyanide, CCCP and vanadate added separately or in twos inhibit motility only partially. The three poisons added together completely paralyse the cells. In this inhibitor cocktail, arsenate can substitute for CCCP + vanadate; cyanide can be replaced by anaerobiosis. It is concluded that (i) ΔNa rather than ΔNH powers the flagellar motor of V. alginolyticus in the presence of CCCP, and (ii) in addition to the Na+-motive respiratory chain [Tokuda, H. and Unemoto, T. (1982) J. Biol. Chem. 257, 10007–10014] there is a vanadate and arsenate-sensitive oxygen-independent mechanism of ΔNa generation, presumably an ion-motive ATPase. A suggestion is put forward that circulation of Na+ can replace that of H+ in V. alginolyticus, ΔNa being formed by the Na+-motive respiratory chain and utilized by Na+-solute symporters, the Na+-driven flagellar motor and maybe by a reverse ion-motive ATPase. 相似文献
18.
Tomasz Twardowski Janet M. Hill Herbert Weissbach 《Biochemical and biophysical research communications》1976,71(3):826-833
Extracts of 40 hr nauplii can convert a heavy form of elongation factor 1 (EF-1H) to a light species (EF-1L). The data indicate that a protease in the extracts is responsible for this reaction, and these findings may explain the observation that extracts from nauplii have only EF-1L whereas before hatching of the embryos EF-1H is the predominant species (Slobin and M?ller [1975] Nature 258, 452–454). 相似文献
19.
V D Ghanekar R J Lin R E Coffman R L Blakley 《Biochemical and biophysical research communications》1981,101(1):215-221
Exposure to nitrous oxide (N2O) is accompanied by oxidation of cob[I]alamin to the inactive cob[III]alamin [1] and to loss of methionine synthetase activity [2]. There is a steady increase in thymidylate synthetase activity in marrow collected from rats exposed to N2O and this returns to normal on restoring the animals to an air environment. 相似文献
20.
(1) (a penetrating SH- reagent) inactivated l-[14C]leucine entrance (binding and translocation) into Saccharomyces cerevisiae, the extent of inhibition depending on the time of preincubation with , concentration, the amino acid external and internal concentration, and the energization state of the yeast cells. With d-glucose-energized yeast, inhibited l-[14C]leucine entrance in all the assayed experimental conditions, but with starved yeast and low (0.1 mM) amino acid concentration, it did not inhibit l-[14C]leucine binding, except when the cells were preincubated with l-leucine. With the rho? respiratory-deficient mutant (energized cells), inhibited l[14C]leucine entrance as with the energized wild-type, though to a lesser extent. (2) Analysis of the effect as a function of l-[14C]leucine concentration showed a significant decrease of values of the high- (S1) and low- (S2) affinity amino acid transport systems, but values were not significantly modified. (3) When assayed in the presence of d-glucose, inhibition of d-glucose uptake and respiration contributed significantly to inactivation of l-[14C]leucine entrance. Pretreatment of yeast cells with 2,4-dinitrophenol enhanced the effect of l-[14C]leucine binding and translocation. (4) Bromoacetylsulfanilic acid and bromoacetylaminoisophthalic acid, two non-penetrating SH- reagents, did not inactivate l-[14C]leucine entrance, while , a slowly penetrating SH- reagent, inactivated it to a limited extent. When compared with the effect of , these negative results indicate that thiol groups of the l-[14C]leucine carrier were not exposed on the outer surface of the yeast cell permeability barrier. 相似文献