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At least 991 records · Page 55Linked to original sources
PubMed1996

Benextramine acts as an irreversible noncompetitive antagonist of U46619-mediated contraction of the rat small mesenteric artery.

We have studied the effects of benextramine on the U46619 (11 alpha,9 alpha-epoxymethano-15S-hydroxy-prosta-5Z,13E-dienoic acid)-mediated contraction of the rat isolated small mesenteric artery. U46619 (10 nM-10 microM) produced a concentration-dependent contraction of the small mesenteric artery. The selective prostanoid TP receptor antagonist, SQ 30,741 ([1S-[1 alpha,2 alpha(5Z),3 alpha,4 alpha]]-7- [[[[[(oxaheptyl)amino]acetyl]amino]-methyl]-7-oxabicyclo[2.2.1]hep t-2-yl]-5- heptenoic acid; 1 microM), produced a parallel, rightward shift of the U46619 curve with an associated pA2 value of 7.43 +/- 0.09. Treatment of tissues with 100 microM benextramine depressed the maximum response to U46619 in a time-dependent manner. However, neither SQ 30,741 (10 microM) nor U46619 (10 microM) incubation significantly protected against this effect. Thus, benextramine acts as an irreversible noncompetitive antagonist of U46619. The mechanism of this action is not yet clear.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1985

Three-dimensional arrangement of the Escherichia coli 16 S ribosomal RNA.

A model for the arrangement of the Escherichia coli 16 S ribosomal RNA in the 30 S ribosomal subunit is given. This model is based on the 16 S ribosomal RNA secondary structure, intramolecular RNA crosslinking results, protein-RNA interactions, and the locations of proteins within the 30 S subunit. These considerations allow placement of most of the RNA helices in approximate positions. The overall shape (that of an asymmetric Y) is very reminiscent of the description of the shape of the RNA made by direct determinations and is reasonably correlated to the appearance of the 30 S subunit. The identities of the three major secondary-structure domains of the 16 S ribosomal RNA are, for the most part, preserved. In addition, many close contacts between the 5' and middle RNA domains occur in the body of the particle. The 3'-terminal domain is situated in the central part of the model. This position corresponds to the region between the head and the platform structure in the 30 S subunit. The regions that represent the general locations of the messenger RNA and transfer RNA binding sites can be identified in the model.

Cross-Linking Reagents↗
PubMed1986

Thiol group may be involved in the irreversible blockade of presynaptic alpha 2-adrenoreceptors by pyrextramine and benextramine in the isolated guinea pig ileum.

This study, conducted on isolated guinea pig ileum, was designed to establish the mechanism of presynaptic alpha 2-adrenoreceptor blockade by the tetramine disulfides, benextramine and pyrextramine. At 1 microM these drugs irreversibly blocked norepinephrine (NE)-induced inhibition of the twitch response to electrical stimulation. This may be the result of covalent bond formation between the disulfide bridge of the inhibitor and a thiol function at the receptor level through an interchange reaction since the benextramine carbon analogue did not affect NE response under the same conditions. Furthermore, NE (10 microM) failed to protect presynaptic alpha 2-adrenoreceptors from pyrextramine blockade whereas idazoxan (O.T microM) completely abolished the irreversible antagonism of pyrextramine (1 microM). This finding suggests that the tetramine disulfide binding site may coincide with that of idazoxan and is different from the NE binding site.

Adrenergic alpha-Antagonists↗
PubMed1989

Benextramine and nifedipine distinguish between sub-classes of alpha 1-adrenoceptors.

The effects of benextramine and nifedipine were examined on the dose-diastolic pressure response to methoxamine in pithed normotensive rats. Benextramine (3, 6 and 12 mg/Kg) displaced the dose-response curve to methoxamine to the right. Maximum response was reduced after the administration of 12 mg/Kg benextramine. Nifedipine (0.1 and 0.3 mg/Kg) also caused the dose-response curve to methoxamine to be displaced to the right with reduction in maximum response. Nifedipine effects were additive with an increase in the EC50 values as well as reduction in the maximum response after pretreatment with benextramine (3 and 6 mg/Kg). However, at the highest dose of benextramine the effects of nifedipine were diminished and no longer apparent. It is concluded that benextramine may have alkylated a nifedipine sensitive site on the alpha 1-adrenoceptors.

Animals↗
PubMed1992

Benextramine, a putative neuropeptide Y receptor antagonist, attenuates the termination of receptivity.

Sexual behavior in female rats is dependent on gonadal steroids. In ovariectomized rats, progesterone treatment typically exerts a biphasic effect on copulatory behavior induced by prior treatment with estradiol. Thus, there is an initial augmentation of the facilitative effect of estradiol occurring 4-10 h after progesterone. This is followed by a profound inhibitory effect, essentially terminating receptivity. We hypothesized that the receptivity terminating effect of progesterone could be due to increased synthesis and release of neuropeptide Y in relevant brain regions. Rats were tested for female sexual behavior 4 h after progesterone (52 h postestradiol). Immediately following this test, benextramine was administered (0, 3, or 15 mg/kg, IP). Subsequently, behavioral tests were administered 24, 48, 72, and 96 h postbenextramine. Benextramine treatment attenuated the inhibitory effects of progesterone on receptivity (lordosis quotients and percent of responding animals) without affecting either proceptive or rejection behaviors. These data suggest that blockade of NPY (and alpha-adrenergic) receptors is associated with selective enhancements of specific components of sexual behavior in female rats. Specifically, blockade of NPY receptors by benextramine is associated with continued receptivity.

Adrenergic alpha-Antagonists↗
PubMed1992

Benextramine-neuropeptide Y (NPY) binding site interactions: characterization of 3H-NPY binding site heterogeneity in rat brain.

Pre-incubation of rat brain membranes with 200 microM benextramine followed by extensive dilution and washing to remove unbound ligand reduced Bmax for N-[propionyl-3H]-NPY (3H-NPY) specific binding by 61% relative to control membranes treated identically but in the absence of benextramine. When rat brain membranes were co-incubated with 3H-NPY and 57 microM benextramine, there was a significant shift to the right; the apparent Kd for 3H-NPY binding increased two-fold relative to control membranes. These data are consistent with the hypothesis that benextramine is a competitive and irreversible ligand for a population (60-65%) of rat brain NPY binding sites. 'Paired tube' assays were then used to determine the selectivity of these benextramine-sensitive and insensitive 3H-NPY binding site populations. PYY, NPY and NPY13-36 each displaced 100% of 3H-NPY from rat brain membrane binding sites both in the absence and presence of 1 mM benextramine. In contrast, [Leu31,Pro34]NPY displayed the same binding site selectivity as benextramine in displacing 65% of 3H-NPY from specific binding sites on untreated rat brain membranes, and it failed to displace 3H-NPY from membranes treated with 1 mM benextramine. Thus the selectivity of the benextramine-insensitive 3H-NPY binding site population--PYY > = NPY > NPY13-36 >> [Leu31,Pro34]NPY--is characteristic of a Y2-like NPY binding site population, while the benextramine-sensitive 3H-NPY binding sites appear to be a Y1-like binding site population.

Amino Acid Sequence↗
PubMed1994

The role of alpha-1 adrenergic receptors in the stimulating effect of neuropeptide Y (NPY) on rat behavioural activity.

The role of noradrenergic alpha-1 receptors in increasing the behavioural activity after neuropeptide Y (NPY) injection into the frontal cortex was examined in rats. NPY (1 micrograms/1 microliter) injected into the frontal cortex of rats with chronically implanted cannulae, increased their locomotor and exploratory activity in the open field test. Similar effects were observed after injection of the alpha-1-adrenergic agonist phenylephrine (PH) (3-19 micrograms/1 microliter). Behavioural stimulation after NPY or PH was totally abolished by pretreatment with benextramine (1.73-173 micrograms/1 microliter), a compound blocking NPY and alpha-adrenergic receptors. The NPY-induced activation of behaviour was also abolished by i.p. injection of prazosine (3 mg/kg), a specific alpha-1-adrenergic receptor antagonist. It is concluded that: 1) NPY injected into the rat frontal cortex induces an increase in the locomotor and exploratory activity of the animals; and 2) indirect activation of alpha-1-adrenergic receptor seems to play a crucial role in the observed behavioural effects.

Adrenergic alpha-Antagonists↗
PubMed1994

Benextramine, an NPY antagonist, improves sexual behavior in male rats.

In adult, sexually-experienced male rats, the NPY-antagonist benextramine--at the doses of 5 and 10 mg/kg i.p. and of 50 micrograms/rat i.c.v.--significantly and specifically improved several parameters of copulatory activity. These data may further support the idea that NPY plays a role in the complex regulation of male sexual function, seemingly at the brain level.

Animals↗
PubMed1981

A method for the determination of nitrate reductase.

A procedure for the assay of nitrate reductase based on Szekely's diaminodiphenylsulphone method of nitrate determination (Szekely, E. (1967) Talanta 14, 941-950) is described. The method is simple and sensitive, allowing determination of 1 microgram of nitrate in a volume of 1 ml or less. It is particularly suited to the determination of nitrate reductase.

Cystamine↗
PubMed1994

Intrathecal kynurenate but not benextramine blocks hypoxic sympathoexcitation in chemodenervated anesthetized rats.

In peripherally chemodenervated anesthetized and ventilated rats, inhalation of 100% N2 for 20 s rapidly excites reticulospinal vasomotor neurons of the rostroventrolateral reticular nucleus (RVL) and sympathetic nerves. After an initial fall, arterial pressure is also elevated. The sympathoexcitatory response and secondary increases in arterial pressure were abolished by microinjections of muscimol (250 pmol) into the RVL or by intrathecal administration of kynurenate (500 nmol), a broad-spectrum antagonist of excitatory amino acid receptors, but not by benextramine, an alpha-adrenoceptor antagonist. The results indicate that excitation of pre-ganglionic sympathetic neurons in the spinal cord by hypoxia results from excitation of RVL-spinal vasomotor neurons, probably the glutamatergic neurons.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Rapid isolation of double stranded RNA segments from disulphide crosslinked polyacrylamide gels.

A simple method was developed to isolate dsRNA segments from disulphide crosslinked polyacrylamide gels. The dsRNA preparations from the P4 killer virus strain 77 of Ustilago maydis containing 7 genomic segments with molecular sizes ranging from 0.36 to 6.7 kbp, the 20 kbp dsRNA associated with the '447' cytoplasmic male sterility in Vicia faba and the 23 kbp genomic dsRNA of citrus tristeza virus (CTV) were separated on disulphide crosslinked polyacrylamide gels. After UV visualisation, the dsRNA bands were excised from the gel and dissolved using 2-mercaptoethanol. The dsRNA were then purified from the solubilized fractions by specific adsorption on microgranular cellulose and elution with a small volume of water. The method is rapid, simple and convenient for the isolation of all the tested dsRNAs segments.

Cross-Linking Reagents↗