首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The metabolic conversion of α-l-acetylmethadol (LAM) to α-l-noracetylmethadol (NAM) and α-l-dinoracetylmethanol (NNAM), has been studied in three opiate addicts being maintained on 100 mg of LAM three times weekly. Plasma levels of NAM and NNAM were established shortly after the initial dose of LAM. The plasma level of NNAM was substantially higher following repeated dosing than following the initial dose. The combined daily urinary excretion of LAM, NAM and NNAM was 6–8 times greater after repeated dosing than after the initial dose. Since NAM and NNAM, which are formed by the sequential N-demethylation of LAM are both considerably more active morphine-like agonists than is LAM itself, it is likely that the pharmacological effects of LAM are due to NAe NAM and NNAM. Variations in the rates of formation and elimination of NAM and NNAM may partially explain the variability in response seen in LAM maintenance therapy.  相似文献   

2.
The stereoisomers of N6-phenylisopropyladenosine elicit accumulations of cyclic AMP in brain slices via interaction with adenosine-receptors. The response in guinea pig cerebral cortical slices and in rat hippocampal slices is blocked by theophylline and potentiated by biogenic amines. A chelator, EGTA, potentiates the response to phenylisopropyladenosine in guinea pig cerebral cortical slices. The 1-isomer (EC50 25 μM) is four- to five-fold more potent than the d-isomer in eliciting accumulations of cyclic AMP in brain slices. In a rat coronal hippocampal slice in vitro, 1-phenylisopropyladenosine (IC50 ~ 0.7 μM) reduces the amplitude of evoked synaptic responses generated via a monosynaptic pathway to the CA1 pyramidal neurons. The d-isomer is nearly one hundred-fold less potent. Thus, the adenosine-receptors involved in the electrophysical response appear much more stereoselective for the 1-isomer of phenylisopropyladenosine than the adenosine-receptors involved in cyclic AMP-generation in brain slices.  相似文献   

3.
PGA1 was incubated with rabbit renal cortical homogenates containing HSA (0–4.5%). The ability of this tissue to readily metabolize PGA1 progressively decreased with increasing HSA levels in the incubates The rate of disappearance of 3H-PGA1 was twice as rapid in rats treated with salicylic acid (S. A.) in comparison to control animals; since only 30% of the injected radioactivity was bound to the plasma of the S.A. treated rats, as compared to 90% bound to control plasma, an association may exist between the degree of binding of 3H-PGA1 and its rate of clearance. The studies indicate that PGA1 interaction with HSA decreases its metabolism in vitro, and slows down its clearance in vivo, implicating HSA as a possible factor in prostaglandins metabolism in vivo.  相似文献   

4.
Homovanillic acid (HVA) labelled with two deuterium atoms (d2-HVA) was used to determine the contribution of HVA in the blood to HVA in the urine and CSF of monkeys. During and after a six-hour intravenous infusion of d2-HVA at a constant rate, the levels of both d2-HVA and endogenous HVA (d0-HVA) in plasma, urine, and CSF were determined by gas chromatography-mass spectrometry, and the relative enrichments of d2-HVA in each of these fluids calculated. Results indicate that HVA in the urine is derived exclusively from the blood, with no contribution from renal metabolism of dopamine (DA). Furthermore, less than one percent of HVA in either lumbar or ventricular CSF is derived from circulating HVA. The plasma elimination curve of d2-HVA was biexponential, with a terminal phase half-life (t12) of 44 minutes and an apparent volume of distribution of 0.8 liters/kg.  相似文献   

5.
The effects of methylglyoxal bis(guanylhydrazone) on S-adenosyl-l-methionine decarboxylase (EC 4.1.1.50) activity were studied in the mouse kidney stimulated to growth by testosterone administration. The drug was found to be a potent inhibitor of the enzyme in vitro. Administration of methylglyoxal bis(guanylhydrazone) in vivo resulted in a transient inhibition followed by a strong enhancement of the enzyme activity. Dialysis of the kidney extract, to remove remaining methylglyoxal bis(guanylhydrazone), revealed a great and rapid increase in the activity of S-adenosyl-l-methionine decarboxylase. Injections of testosterone to castrated mice resulted in a marked increase in kidney weight and an accumulation of renal putrescine, spermidine and spermine. These effects of testosterone could not be blocked by simultaneous injections of methylglyoxal bis(guanylhydrazone). It appears that due to secondary effects by which the inhibition of methylglyoxal bis(guanylhydrazone) on S-adenosyl-l-methionine decarboxylase activity is circumvented the inhibitor seems to be of uncertain value in attempts to decrease selectively the in vivo levels of polyamines.  相似文献   

6.
An antiserum to βh-lipotropin (LPH) which does not cross react with βh-endorphin has been obtained utilizing two different methods of affinity chromatography. This was employed in studies of three normal human subjects in whom the metabolic clearance rate (MCR) apparent volume of distribution (Vd) and fractional rate of disappearance (Kd) of ACTH and βh-LPH were determined following bolus simultaneous injection of 270 μg highly purified βh-LPH and 230 μg of synthetic human ACTH. A biphasic disappearance curve was noted for both hormones. βh-LPH: MCR-0.571, 0.519, and 0.461 L/minute; Vd-30.7, 27.7, 25.0 liters, representing 49, 46 and 35% of body weight; Kd-0.0186, 0.0187, 0.0185 min?1. ACTH: MCR-0.274, 0.266, and 0.332 L/minute; Vd-6.5, 6.5, 14.5 liters, representing 10.4, 10.8 and 20.4% of body weight; Kd-0.0418, 0.0409, 0.0229 min?1. The observed larger MCR of βh-LPH can account for previous observations of basal plasma ACTH/LPH ratios greater than unity, even though these peptides are present in the pituitary in equimolar concentrations.  相似文献   

7.
Acid-catalysed monobutylidenation of 3-deoxy-d-ribo-hexitol yields the 2,4-acetal as the sole, detected product. 3-Deoxy-l-xylo-hexitol yields the 4,5-acetals as kinetic products, and the 4,6-acetal as the thermodynamic product.  相似文献   

8.
High avidity antisera against β-endorphin h-EP) were obtained in two of five rabbits immunized with unconjugated synthetic human βh-EP. One of these antisera (K-7762) cross-reacted 1.5% on a molar basis with β-lipotropin h-LPH) and did not recognize leucine-enkephalin in a concentration as high as 0.2 mmol/l. The cross-reaction with methionine-enkephalin h-LPH 61–65) was 9%, while that with α-endorphin (βh-LPH 61–76) was 69%. This implied that the specific recognition site was in the amino-terminal region of βh-EP. Although this sequence is present in βh-LPH it was poorly recognized by the antiserum, suggesting that the free amino-terminal is essential. This interpretation was supported by the finding that α-N-acetylh-EP was equally poorly recognized by the antiserum. The sensitivity of the radioimmunoassay was 1.9 pmol/l. βh-EP was not detectable (< 3 pmol/l) in 26 of 27 extracted plasma samples in healthy blood donors, in one it was 5 pmol/l. In five of six patients with an enlarged sella turcica, but without clinical and laboratory evidence of pituitary dysfunction, βh-EP was detectable (5 ± 3 pmol/l; mean ± S.D.) after metyrapone. βh-EP was elevated in Addison's disease (23, 54 and 76 pmol/l), Nelson's syndrome (37, 39 and 109 pmol/l), ectopic ACTH production (27, 59 and 76 pmol/l), but only detectable in one of three samples from patients with Cushing's disease (7 pmol/l). Gel chromatography of extracts of porcine pituitary revealed only one immunoreactive peak co-eluting with synthetic human βh-EP. The specificity of the antiserum K-7762 was such that the βh-EP concentration in plasma extracts could be reliably estimated by radioimmunoassay without prior chromatography.  相似文献   

9.
Biosynthesis of N-methyl-l-glucosamine moiety of streptomycin from d-glucose by Streptomyces griseus was studied. A mixture of d-[1-14C]glucose and d-[6-3H]glucose was given to the culture of S. griseus. The 3H/14C ratio found in N-methyl-d-glucosamine further supports a mechanism that the conversion of d-glucose to l-hexose is carried out without scission of carbon skeleton. When d-[1-14C]glucose and d-[3-3H]glucose were used, the fall of 3H/14C ratio in N-methyl-l-glucosamine showed that the hydrogen atom at C-3 plays a rôle in such a transformation.  相似文献   

10.
The capsular polysaccharide from Klebsiella K44 has been investigated by the techniques of methylation, base-catalyzed elimination, Smith degradation, and partial hydrolysis. The last-named yielded an oligosaccharide corresponding to one repeating unit. The anomeric configutations of the sugar residueswere determined by 1H- and 13C-n.m.r. spectroscopy. The polysaccharide has a fractional acetyl content and is the first in this series to be based on a linear, pentasaccharide repeating unit. →3)-β-d-Glcp-(1→4)-αd-Glcp-(1→4)-β-d-GlcpA-(1→2)α-l-Rhap-(1→3)-α-l-Rhap-(1→  相似文献   

11.
Behavioral comparisons of the stereoisomers of tetrahydrocannabinols   总被引:1,自引:0,他引:1  
The potencies of (?)-trans9-THC, (+)-trans9-THC, (+)-cis9-THC, (?)-trans8-THC and (+)-trans8-THC were compared in several different species. (?)-trans9-THC was 100 times more potent than (+)-trans9-THC in depressing schedule-controlled responding in monkeys. The (+)-trans isomers were less effective than their corresponding (?)-trans isomers in the dog static-ataxia test, but potency ratios could not be determined due to a lack of dose-responsiveness of the (+)-trans isomers. However, it appeared that their potency differed by at least ten fold. The potency of (+)-cis9-THC in the dog static-ataxia test was comparable to that of (+)-trans9-THC. The hypothermia in mice produced by the (?) isomers of trans9-THC and trans8-THC were 9.1 and 30.4 times greater than that produced by their respective (+)-isomers. Also, the potency ratio of the (+)- and (?)-trans9-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   

12.
As part of a program to synthesize the ceramide trisaccharide (1) related to Fabry's disease, methyl 4-O-(4-O-α-d-galactopyranosyl-β-d-galactopyranosyl)-β-d-glucopyranoside (12) was prepared. Methyl β-lactoside (2) was converted into methyl 4-O-(4,6-O-benzylidene-β-d-galactopyranosyl)-β-d-glucopyranoside (4). Methyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl-β-d-galactopyranosyl)-β-d-glucopyranoside (7) was synthesized from 4 through the intermediates methyl 2,3,6-tri-O-benzoyl-4-O-(4,6-O-benzylidene-2,3-di-O-benzoyl-β-d-galactopyranosyl)-β-d-glucopyranoside (5) and methyl 2,3,6-tri-O-benzoyl-4-O-(2,3-di-O-benzoyl-β-d-galactopyranosyl)-β-d-glucopyranoside (6). The halide-catalyzed condensation of 7 with 2,3,4,6-tetra-O-benzyl-d-galactopyranosyl bromide (8) gave methyl 2,3,6-tri-O-benzoyl-4-O-[2,3,6-tri-O-benzoyl-4-O-(2,3,4,6-tetra-O-benzyl-α-d-galactopyranosyl)- β-d-galactopyranosyl]-β-d-glucopyranoside (10). Stepwise deprotection of 10 led to 12, the methyl β-glycoside of the trisaccharide related to Fabry's disease.  相似文献   

13.
The metabolism of the prostaglandin F analogues, 15-methyl-Δ4-cis-PGF and 16,16-dimethyl-Δ4-cis-PGF, has been investigated in the cynomolgus monkey and the human female. The two analogues, tritium labelled in the 9β-position, were administered by intramuscular injections into the monkeys and by subcutaneous injections into the human. Excretion of tritium labelled products were followed in urine (in both species) and feces (in monkeys only) and several metabolites were identified by GC/MS. The analogues were found to be resistant to the 15-hydroxy dehydrogenase and furthermore the degradation by β-oxidation was delayed. About 13% of the given dose of 15-methyl-Δ4-cis-PGF was excreted unchanged into urine and feces from the monkey. The corresponding figure for 16,16-dimethyl-Δ4-cis-PGF was about 20%. In addition, a large part of the metabolites had the carbon skeleton intact and were only metabolized by ω-oxidation. The relative resistance to degradation of these two analogues is likely to be the basis for their prolonged pharmacological activity.  相似文献   

14.
A reaction of 2-acetyl-3-acylaminobenzo[b]furans (9do) with Vilsmeier (VM) reagent afforded a mixture of (E)- and (Z)-{(E)-2-aralkenylbenzo[b]furo[3,2-d][1,3]oxazin-4-ylidene}acetaldehydes (5) with a characteristic exo-formylmethylene group on the oxazine ring. The Z-isomer was more stable than the E-isomer. The Z-isomers ((Z)-5) were reacted with phosphonate reagents under two different conditions to obtain various butadiene derivatives (12) containing benzo[b]furo[3,2-d][1,3]oxazine skeleton. Typical compounds (5 and 12) were evaluated for their anti-osteoclastic bone resorption activity, antagonistic activity for the cysLT1 receptor and growth inhibitory activity for MIA PaCa-2 and MCF-7. Compounds 12f and 12j showed potent anti-osteoclastic bone resorption activity comparable to E2 (17β-estradiol).  相似文献   

15.
d1-Prostaglandin E1 and d1-11-deoxyprostaglandin E1 are conveniently synthesized via the copper (I) catalyzed conjugate addition of the Grignard reagent prepared from 3-trityloxy-trans-1-octenyl bromide to the appropriate cyclopentenone precursor. The Grignard reagent also afforded the synthesis of a novel structure, d1-15-hydroxy-9-oxo-13-cis-prostenoic acid.  相似文献   

16.
Human factor XII was activated by adsorption onto kaolin in the presence of high molecular weight kininogen. The washed kaolin-containing precipitates activate prekallikrein to kallikrein. When antithrombin III was added to the reaction mixture, the conversion of prekallikrein to kallikrein was inhibited, the degree of inhibition depending on the concentration of antithrombin and the time of incubation. Heparin had a slight enhancing effect with low concentrations of antithrombin and short incubation times. However, the inhibition of the generated kallikrein by antithrombin III was markedly enhanced by heparin. Antithrombin III inhibited also the effect of activated factor XII on the partial thromboplastin time, using factor XII-deficient plasma. Of other plasma proteinase inhibitors used (α1-antitrypsin, α2-macroglobulin, Cl-inactivator) only Cl-inactivator inhibited activated factor XII.  相似文献   

17.
Batch and continuous production of high fructose syrup from Jerusalem artichoke tubers has been studied using yeast cells immobilized in open pore gelatin matrix. In a batch reactor, the hydrolysis was 93% (d-fructose/d-glucose = 90/10) and 42 mg d-fructose per ml was produced from the artichoke tuber extract by immobilized cells in 3 h. The same immobilized cells were recycled and used repeatedly for 10 batch cycles starting with fresh juice at the beginning of each cycle. It was found that immobilized cells were extremely stable and the percent hydrolysis was almost constant for all 10 batch cycles. In a continuous reactor using an immobilized cell concentration of 65.7 g (dry wt) l?1 of total working bioreactor volume, the percent hydrolysis was found to remain constant at ~100% at dilution rates <1.26 h?1, but beyond that it decreased. Volumetric productivity attained its maximum value at D = 2.08 h?1 and was found to be 100 g l?1 h?1. This was achieved at a feed sugar conversion of 80%. At 90% conversion and D = 1.66 h?1, the productivity was found to be 90 g l?1 h?1. Continuous operation of the immobilized cell bioreactor at a constant dilution rate of 1.65 h?1 for 240 h resulted in only 2% loss of original activity.  相似文献   

18.
We propose the existence of a previously unrecognized enzymatic pathway in man which allows for optical inversion (epimerization) at saturated carbon, employing R(?)-p-iso-butyl hydratropic acid (I) and an analog in which the chiral center and methyl group were deuterium labeled [R(?)d4]. We have proposed a detailed enzymatic pathway for this optical inversion in which we postulate the existence of an R-aryl propionic acid isomerase system. The results make understandable the bioequivalence of a variety of (S) and (R) isomers of non-steroidal anti-inflammatory agents.  相似文献   

19.
Sun-Shine Yuan 《Steroids》1982,39(3):279-289
A-ring enollactones 1a, 1b or 9 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 2a, 2b or 10. 2a and 2b 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 10 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 10 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 16 and acylation followed by acid hydrolysis furnished [3,4-13C2]progesterone.  相似文献   

20.
(1) The t12 for 1.3 mM D-allose uptake and efflux in insulin-stimulated adipocytes is 1.7 ± 0.1 min. In the absence of insulin mediated uptake of D-allose is virtually eliminated and the uptake rate (t12 = 75.8 ± 4.99 min) is near that calculated for nonmediated transport. The kinetic parameters for D-allose zero-trans uptake in insulin-treated cells are Kztoi = 271.3 ± 34.2 mM, Vztoi = 1.15 ± 0.12 mM · s?1. (2) A kinetic analysis of the single-gate transporter (carrier) model interacting with two substrates (or substrate plus inhibitor) is presented. The analysis shows that the heteroexchange rates for two substrates interacting with the transporter are not unique and can be calculated from the kinetic parameters for each sugar acting alone with the transporter. This means that the equations for substrate analogue inhibition of the transport of a low affinity substrate such as D-allose can be simplified. It is shown that for the single gate transporter the Ki for a substrate analogue inhibitor should equal the equilibrium exchange Km for this analogue. (3) Analogues substituted at C-1 show a fused pyranose ring is accepted by the transporter. 1-Deoxy-D-glucose is transported but has low affinity for the transporter. High affinity can be restored by replacing a fluorine in the β-position at C-1. The Ki for d-glucose = 8.62 mM; the Ki for β-fluoro-d-glucose = 6.87 mM. Replacing the ring oxygen also results in a marked reduction in affinity. The Ki for 5-thio-d-glucose = 42.1 mM. (4) A hydroxyl in the gluco configuration at C-2 is not required as 2-deoxy-d-galactose (Ki = 20.75 mM) has a slightly higher affinity than d-galactose (Ki = 24.49 mM). A hydroxyl in the manno configuration at C-2 interferes with transport as d-talose (Ki = 35.4 mM) has a lower affinity than d-galactose. (5) d-Allose (Km = 271.3 mM) and 3-deoxy-d-glucose (Ki = 40.31 mM) have low affinity but high affinity is restored by substituting a fluorine in the gluco configuration at C-3. The Ki for 3-fluoro-d-glucose = 7.97 mM. (6) Analogues modified at C-4 and C-6 do not show large losses in affinity. However, 6-deoxy-d-glucose (Ki = 11.08 mM) has lower affinity than d-glucose and 6-deoxy-d-galactose Ki = 33.97 mM) has lower affinity than d-galactose. Fluorine substitution at C-6 of d-galactose restores high affinity. The Ki for 6-fluoro-d-galactose = 6.67 mM. Removal of the C-5 hydroxymethyl group results in a large affinity loss. The Kid-xylose = 45.5 mM. The Ki for l-arabinose = 49.69 mM. (7) These results indicate that the important hydrogen bonding positions involved in sugar interaction with the insulin-stimulated adipocytes transporter are the ring oxygen, C-1 and C-3. There may be a weaker hydrogen bond to C-6. Sugar hydroxyls in non-gluco configurations may sterically hinder transport.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号