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Biomedical subjects

J M Palacios

Publications and source records attributed to J M Palacios.

At least 37 records · Page 2Linked to original sources
PubMed2000

Pharmacological characterization of almotriptan: an indolic 5-HT receptor agonist for the treatment of migraine.

Almotriptan (3-[2-(dimethylamino)ethyl]-5-(pyrrolidin-1-ylsulfonylmethyl )-1H-indo le) has been studied in several models predictive of activity and selectivity at 5-HT receptors. Almotriptan showed low nanomolar affinity for the 5-HT(1B) and 5-HT(1D) receptors in several species, including the human, while affinity for 5-HT receptors other than 5-HT(1B/1D) was clearly less. Affinity for 5-HT(7) and 5-HT(1A) receptors was approximately 40 and 60 times lower than that for 5-HT(1B/1D) receptors, respectively. Almotriptan did not exhibit significant affinity for several non-5-HT receptors studied up to 100 microM. Almotriptan inhibited forskolin-stimulated cyclic AMP accumulation in HeLa cells transfected with 5-HT(1B) or 5-HT(1D) human receptors. In this model, almotriptan had the same efficacy as serotonin and an affinity in the low nanomolar range. It induced vasoconstriction in several vessels in which it was compared with sumatriptan. In isolated dog saphenous veins, almotriptan elicited concentration-dependent contractions with an EC(50) of 394 nM. In both these systems, almotriptan behaved as a full agonist. Infusion of almotriptan into the porcine meningeal vasculature induced vasoconstriction. In contrast, in the pig renal and rabbit mesenteric arteries, it had a very low maximal efficacy even at 100 microM, with similar results obtained in the rabbit renal artery. The results suggest that almotriptan is a potent and selective 5-HT(1B/1D) receptor agonist, with selectivity for the cranial vasculature as compared with peripheral vessels.

Animals↗
PubMed2000

Functional profile of almotriptan in animal models predictive of antimigraine activity.

Almotriptan is a new 5-HT(1B/1D) receptor agonist whose clinical efficacy for the treatment of migraine attacks has been demonstrated in Phase III clinical trials. We now compare the functional profile of almotriptan (assessed using animal models) with that of sumatriptan. Almotriptan selectively increased carotid vascular resistance in anaesthetised cats after intravenous or intraduodenal administration (ED(100)=11 microg/kg, i.v.; ED(50)=339 microg/kg, i. d.) and in anaesthetised beagle dogs following intravenous administration (ED(50)=116 microg/kg). A study in anaesthetised cats also demonstrated that almotriptan acts by selectively increasing the resistance of the carotid arteriovenous anastomoses without adversely affecting brain irrigation. In addition, almotriptan inhibited meningeal extravasation produced by electrical stimulation of the trigeminal ganglion in anaesthetised guinea pigs in the dose range of 0.3-3 mg/kg, i.v. In conclusion, almotriptan is both a selective constrictor affecting intracranial blood vessels and an inhibitor of neurogenically evoked plasma protein extravasation of the dura mater.

Animals↗
PubMed2000

Cardiovascular safety profile of almotriptan, a new indolic derivative for the treatment of migraine.

Almotriptan is a new 5-HT(1B/1D) receptor agonist effective for treating acute migraine attacks with or without aura. As 3-5% of patients treated with sumatriptan experience chest symptoms thought to be of cardiac origin, we investigated the cardiovascular safety profile of almotriptan in comparison with that of sumatriptan in six animal models. Almotriptan did not modify blood pressure or heart rate in conscious telemetered normotensive Wistar rats (p.o.), in anaesthetised beagle dogs (i.v.), or in conscious beagle dogs (i.v.), and only produced transient increases when administered (s.c.) to telemetered cynomolgus monkeys. Almotriptan did not consistently affect the duration of the electrocardiogram (ECG) intervals in anaesthetised beagle dogs even when the drug was administered into the coronary artery, nor was ECG morphology altered in telemetered cynomolgus monkeys. In contrast, sumatriptan i.v. consistently increased mean blood pressure and heart rate in conscious beagle dogs. Finally, almotriptan did not modify coronary blood flow at a dose of up to 0.3 mg/kg i.v. in conscious beagle dogs. Thus, almotriptan has a favourable cardiovascular safety profile.

Animals↗
PubMed2000

Synthesis and biological evaluation of 2,5-dihydropyrazol.

A novel series of 2,5-dihydropyrazolo[4,3-c]quinolin-3-ones has been prepared. These compounds showed good PDE 4 inhibitory activity and weak affinity for rolipram's binding site. They also exhibited a good anti-inflammatory profile without emetic side effects.

Animals↗
PubMed2000

Distribution of the histamine H(2) receptor in monkey brain and its mRNA localization in monkey and human brain.

The distribution of histamine H(2) receptor mRNA was determined by in situ hybridization histochemistry in human and monkey brain. In the case of monkey brain, we combined this technique with receptor ligand autoradiography to compare the distribution of mRNA and receptor binding sites. [(125)I]Iodoaminopotentidine ([(125)I]-APT), a reversible, high specific activity antagonist with high affinity and selectivity for the H(2) receptor, was used for receptor autoradiography. Radiolabeled oligonucleotides derived from the human mRNA sequence encoding this receptor were used as hybridization probes. The highest density of the H(2) receptor mRNA in human and monkey brain was found in caudate and putamen nuclei and external layers of cerebral cortex. Moderate levels were seen in the hippocampal formation and lower densities in the dentate nucleus of cerebellum. Areas such as globus pallidus, amygdaloid complex, cerebellar cortex, and substantia nigra were devoid of hybridization signal. The distribution of H(2) receptor mRNA in monkey brain is generally in good agreement with that of the corresponding binding sites: prominent in caudate, putamen, accumbens nuclei, and cortical areas. The hippocampus showed lower densities of receptors and low levels were detected in the globus pallidus pars lateralis. No binding sites were seen in amygdaloid complex and substantia nigra. The distribution of histaminergic innervation is in good correlation with the areas of high density for H(2) receptors: caudate, putamen, and external layers of cerebral cortex in monkey and human brain. The presence of mRNA in caudate and putamen nuclei, together with its absence from substantia nigra, suggests that the H(2) receptors found in the striatum are synthesized by intrinsic cells and not by nigral dopaminergic cells. These striatal H(2) receptors may be located on short circuit striatal interneurons or somatodendritically on striatal projection neurons which project to the globus pallidus pars lateralis. In conclusion, the present results, which constitute, to our knowledge, the first report of the regional distribution of mRNA encoding H(2) receptors detected by in situ hybridization, define the sites of synthesis of H(2) receptors and are the basis for future, more detailed studies that should result in a better understanding of H(2) receptor function.

Adult↗
PubMed2000

Identification and nucleotide sequence of genes involved in the synthesis of lactocin 705, a two-peptide bacteriocin from Lactobacillus casei CRL 705.

The structural gene determinants of lactocin 705, a bacteriocin produced by Lactobacillus casei CRL 705, have been amplified from a plasmid of approximately 35 kb and sequenced. Lactocin 705 is a class IIb bacteriocin, whose activity depends upon the complementation of two peptides (705alpha and 705beta) of 33 amino acid residues each. These peptides are synthesized as precursors with signal sequences of the double-glycine type, which exhibited high identities with the leader peptides of plantaricin S and J from Lactobacillus plantarum, brochocin C from Brochotrix campestris, sakacin P from Lactobacillus sake, and the competence stimulating peptides from Streptococcus gordonii and Streptococcus mitis. However, the two mature bacteriocins 705alpha and 705beta do not show significant similarity to other sequences in the databases.

Amino Acid Sequence↗
PubMed2000

Benzyl derivatives of 2,1,3-benzo- and benzothieno[3,2-a]thiadiazine 2,2-dioxides: first phosphodiesterase 7 inhibitors.

The synthesis of a new family of benzyl derivatives of 2,1,3-benzo- and benzothieno[3,2-a]thiadiazine 2,2-dioxides was achieved. The biological data revealed the first heterocyclic family of compounds with PDE 7 inhibitory properties appearing to be a new objective for the treatment of T-cell-dependent disorders. The IC(50) values or percent inhibition values of the compounds against PDE 7 were calculated by testing them against human recombinant PDE 7 expressed in S. cerevisiae. In this expression system the only cyclic nucleotide hydrolyzing activity present in cell extracts corresponded to human PDE 7. Isoenzyme selectivity PDE 7 versus PDE 4 and PDE 3 was also measured. Considering simultaneously inhibition of the three different isoenzymes, monobenzyl derivatives 15 and 23 showed interesting PDE 7 potency (around 10 microM); although not statistically significant, a trend toward selectivity with respect to PDE 3 and PDE 4 was obtained. Benzothiadiazine 16, although less potent at PDE 7 (IC(50) = 25 microM), also showed a trend of selectivity toward PDE 3 and PDE 4. These compounds are considered the best leads for further optimization.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Synthesis and biological evaluation of 3,4-diaryloxazolones: A new class of orally active cyclooxygenase-2 inhibitors.

A series of 3,4-diaryloxazolones were prepared and evaluated for their ability to inhibit cyclooxygenase-2 (COX-2). Extensive structure-activity relationship work was carried out within this series, and a number of potent and selective COX-2 inhibitors were identified. The replacement of the methyl sulfone group on the 4-phenyl ring by a sulfonamide moiety resulted in compounds with superior in vivo antiinflammatory properties. In the sulfonamide series, the introduction of a methyl group at the 5-position of the oxazolone ring gave rise to very COX-2-selective compounds but with decreased in vivo activity. Selected 3,4-diaryloxazolones exhibited excellent activities in experimental models of arthritis and hyperalgesia. The in vivo activity of these compounds was confirmed with the evaluation of their antipyretic effectiveness and their ability to inhibit migration of proinflammatory cells. As expected from their COX-2 selectivity, most of the active compounds lacked gastrointestinal toxicity in vivo in rats after a 4-day treatment of 100 mg/kg/day. Within this novel series, sulfonamides 9-11 have been selected for further preclinical evaluation.

Animals↗
PubMed2000

Phosphodiesterase type 4 isozymes expression in human brain examined by in situ hybridization histochemistry and[3H]rolipram binding autoradiography. Comparison with monkey and rat brain.

We have examined the distribution of four different cyclic AMP-specific phosphodiesterase isozyme (PDE4A, PDE4B, PDE4C and PDE4D) mRNAs in the brain of different species by in situ hybridization histochemistry and by autoradiography with [3H]rolipram. We have compared the localization of each isozyme in human brain with that in rat and monkey brain. We have found that the four PDE4 isoforms display a differential expression pattern at both regional and cellular level in the three species. PDE4A, PDE4B and PDE4D are widely distributed in human brain, with the two latter appearing more abundant. In contrast, PDE4C in human brain, presents a more restricted distribution, limited to cortex, some thalamic nuclei and cerebellum. This is at variance with the distribution of PDE4C in rat brain, where it is found exclusively in olfactory bulb. In monkey brain, the highest expression for this isoform is found in the claustrum, and at lower levels in cortical areas and cerebellum. PDE4B presented a broad distribution, being expressed in both neuronal and non neuronal cell populations. In general, the distribution of binding sites visualized with [3H]rolipram correlated well with the expression of each PDE4 isozyme.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Alzheimer beta-amyloid precursor proteins display specific patterns of expression during embryogenesis.

The beta-amyloid precursor proteins (betaAPPs) are a family of glycosylated transmembrane proteins that include in their sequences the beta-amyloid peptide, a major component of the characteristic amyloid deposits or senile plaques found in the brains of Alzheimer's disease patients and aged Down's syndrome subjects. Various betaAPP isoforms, mainly betaAPP-695, betaAPP-714, betaAPP-751 and betaAPP-770, the number corresponding to the number of amino acids they encode, resulting from the alternative splicing of a single primary transcript have been described. Using oligonucleotides recognizing each of the four major Alzheimer's betaAPP mRNAs, we have found that each betaAPP mRNA displays a specific temporal and spatial pattern of expression. The prototype isoform betaAPP-695 occurs early in cells actively implicated in morphogenetic events, as those mesodermal cells invaginating at the level of the primitive streak, and it is later restricted to the neurectodermal (neural tube, neural crest and neurogenic placode) derivatives. By contrast, the longest isoform betaAPP-770 appears later and restricted to mesodermal and endodermal derivatives. The isoforms betaAPP-714 and betaAPP-751 are still expressed later than the other two isoforms and distributed ubiquitously, though betaAPP-714 transcripts predominate typically within the neural tube.

Amyloid beta-Protein Precursor↗
PubMed2000

A novel autoregulation mechanism of fnrN expression in Rhizobium leguminosarum bv viciae.

The fnrN gene from Rhizobium leguminosarum UPM791 controls microaerobic expression of both nitrogen fixation and hydrogenase activities in symbiotic cells. Two copies of fnrN are present in this strain, one chromosomal (fnrN1) and the other located in the symbiotic plasmid (fnrN2). Their expression was studied by cloning the regulatory regions in lacZ promoter-probe vectors. The fnrN genes were found to be autoregulated: they are expressed only at basal levels under aerobic conditions; they are highly expressed under microaerobic conditions; and they are expressed at basal levels in the double mutant DG2 (fnrN1 fnrN2) under any condition. The promoters of both genes contain two FnrN-binding sequences (anaeroboxes), centred at positions -12.5 (proximal anaerobox) and -44.5 (distal anaerobox). Expression analysis and gel retardation experiments with fnrN1-derivative promoter mutants altered in key bases of the anaerobox sequences demonstrated that binding of FnrN1 to the distal anaerobox is necessary for microaerobic activation of transcription, and that binding of FnrN1 to the proximal anaerobox results in transcriptional repression. The apparent affinity of FnrN1 for the proximal anaerobox was fivefold lower than for the distal anaerobox, resulting in repression of transcription of fnrN1 only at high-FnrN1 concentrations. This positive and negative autoregulation mechanism ensures an equilibrated expression of fnrN in response to microaerobic conditions.

Bacterial Proteins↗
PubMed2000

Pharmacological profile of LAS 31180, a new inotropic/vasodilator quinolone derivative.

LAS 31180 (3-methylsulphonylamino-1-methyl-4(1H)-quinolone, CAS 137338-43-3) was found to have positive inotropic and vasodilator properties through its inhibitory action on type 3 phosphodiesterase. The inotropic effects of LAS 31180 were demonstrated in vitro both in isolated guinea-pig ventricular strips (EC50 of 1.2 mumol/l) and in isolated guinea-pig working hearts. In conscious chronically instrumented Beagle dogs, LAS 31180 administered either by intravenous or oral route, showed a dose-dependent, long-lasting positive inotropic effect with minimal effects on heart rate. In hypertensive Beagle dogs LAS 31180 elicited a potent and long-lasting fall in blood pressure.

Administration, Oral↗
PubMed2000

Generation of new hydrogen-recycling Rhizobiaceae strains by introduction of a novel hup minitransposon.

Hydrogen evolution by nitrogenase is a source of inefficiency for the nitrogen fixation process by the Rhizobium-legume symbiosis. To develop a strategy to generate rhizobial strains with H(2)-recycling ability, we have constructed a Tn5 derivative minitransposon (TnHB100) that contains the ca. 18-kb H(2) uptake (hup) gene cluster from Rhizobium leguminosarum bv. viciae UPM791. Bacteroids from TnHB100-containing strains of R. leguminosarum bv. viciae PRE, Bradyrhizobium japonicum, R. etli, and Mesorhizobium loti expressed high levels of hydrogenase activity that resulted in full recycling of the hydrogen evolved by nitrogenase in nodules. Efficient processing of the hydrogenase large subunit (HupL) in these strains was shown by immunoblot analysis of bacteroid extracts. In contrast, Sinorhizobium meliloti, M. ciceri, and R. leguminosarum bv. viciae UML2 strains showed poor expression of the hup system that resulted in H(2)-evolving nodules. For the latter group of strains, no immunoreactive material was detected in bacteroid extracts using anti-HupL antiserum, suggesting a low level of transcription of hup genes or HupL instability. A general procedure for the characterization of the minitransposon insertion site and removal of antibiotic resistance gene included in TnHB100 has been developed and used to generate engineered strains suitable for field release.

Bacterial Proteins↗
PubMed2000

Nickel availability and hupSL activation by heterologous regulators limit symbiotic expression of the Rhizobium leguminosarum bv. viciae hydrogenase system in Hup(-) rhizobia.

A limited number of Rhizobium and Bradyrhizobium strains possess a hydrogen uptake (Hup) system that recycles the hydrogen released from the nitrogen fixation process in legume nodules. To extend this ability to rhizobia that nodulate agronomically important crops, we investigated factors that affect the expression of a cosmid-borne Hup system from Rhizobium leguminosarum bv. viciae UPM791 in R. leguminosarum bv. viciae, Rhizobium etli, Mesorhizobium loti, and Sinorhizobium meliloti Hup(-) strains. After cosmid pAL618 carrying the entire hup system of strain UPM791 was introduced, all recipient strains acquired the ability to oxidize H(2) in symbioses with their hosts, although the levels of hydrogenase activity were found to be strain and species dependent. The levels of hydrogenase activity were correlated with the levels of nickel-dependent processing of the hydrogenase structural polypeptides and with transcription of structural genes. Expression of the NifA-dependent hupSL promoter varied depending on the genetic background, while the hyp operon, which is controlled by the FnrN transcriptional regulator, was expressed at similar levels in all recipient strains. With the exception of the R. etli-bean symbiosis, the availability of nickel to bacteroids strongly affected hydrogenase processing and activity in the systems tested. Our results indicate that efficient transcriptional activation by heterologous regulators and processing of the hydrogenase as a function of the availability of nickel to the bacteroid are relevant factors that affect hydrogenase expression in heterologous rhizobia.

Gene Expression Regulation, Bacterial↗
PubMed1999

Adenosine inhibits macrophage colony-stimulating factor-dependent proliferation of macrophages through the induction of p27kip-1 expression.

Adenosine is produced during inflammation and modulates different functional activities in macrophages. In murine bone marrow-derived macrophages, adenosine inhibits M-CSF-dependent proliferation with an IC50 of 45 microM. Only specific agonists that can activate A2B adenosine receptors such as 5'-N-ethylcarboxamidoadenosine, but not those active on A1 (N6-(R)-phenylisopropyladenosine), A2A ([p-(2-carbonylethyl)phenylethylamino]-5'-N-ethylcarboxamido adenosine), or A3 (N6-(3-iodobenzyl)adenosine-5'-N-methyluronamide) receptors, induce the generation of cAMP and modulate macrophage proliferation. This suggests that adenosine regulates macrophage proliferation by interacting with the A2B receptor and subsequently inducing the production of cAMP. In fact, both 8-Br-cAMP (IC50 85 microM) and forskolin (IC50 7 microM) inhibit macrophage proliferation. Moreover, the inhibition of adenylyl cyclase and protein kinase A blocks the inhibitory effect of adenosine and its analogues on macrophage proliferation. Adenosine causes an arrest of macrophages at the G1 phase of the cell cycle without altering the activation of the extracellular-regulated protein kinase pathway. The treatment of macrophages with adenosine induces the expression of p27kip-1, a G1 cyclin-dependent kinase inhibitor, in a protein kinase A-dependent way. Moreover, the involvement of p27kip-1 in the adenosine inhibition of macrophage proliferation was confirmed using macrophages from mice with a disrupted p27kip-1 gene. These results demonstrate that adenosine inhibits macrophage proliferation through a mechanism that involves binding to A2B adenosine receptor, the generation of cAMP, and the induction of p27kip-1 expression.

Adenosine↗
PubMed1999

Anticholinergic effects of desloratadine, the major metabolite of loratadine, in rabbit and guinea-pig iris smooth muscle.

Allergic conjunctivitis is the most common ocular allergic disease. Although very symptomatic it does not endanger vision, and topical antihistamines or chromones are the first choice treatment in clinical practice. Recently, equivalent nanomolar affinities for histamine H and muscarinic M 1 and M3 cloned human receptors have been reported for desloratadine, the active metabolite of loratadine, a widely prescribed antihistamine. This property might enhance its utility in the treatment of asthma, but could induce adverse anticholinergic effects after topical administration. In the present study, we compare the anticholinergic activity of desloratadine with other known muscarinic antagonists and antihistamines on rabbit and guinea-pig iris smooth muscle. Desloratadine was found to be a competitive antagonist (pA2 = 6.67+/-0.09) of carbachol-induced contractions in isolated rabbit iris smooth muscle. Atropine (pA2 = 9.44+/-0.02) and NPC-14695 (pA2 = 9.18+/-0.03) also behaved as competitive antagonists, whereas tiotropium bromide (pD'2 = 9.06+/-0.02) exhibited a non-competitive behaviour in this tissue. Carebastine (pA2 = 5.64+/-0.04) and fexofenadine (pA2 < 4.0) were also studied. After topical administration on the guinea-pig eye conjunctiva, desloratadine produced a potent (ED50 = 2.3 mg/ml) and long lasting mydriasis (> 120 min at the ED50) in conscious animals. Fexofenadine and carebastine were inactive even at the highest concentration tested (10 mg/ml). Atropine (ED50 = 30 microg/ml) and tiotropium bromide (ED50 = 10 microg/ml) were much more potent than desloratadine or pirenzepine (ED50 = 3 mg/ml) in this model. The competitive muscarinic antagonism of desloratadine in vitro, and its potency and duration of action in vivo, suggest that topical treatment of allergic conjunctivitis and rhinitis with desloratadine could produce undesirable peripheral anticholinergic side effects such as mydriasis and xerostomia.

Animals↗
PubMed1999

Flip and flop variants of AMPA receptor subunits in the human cerebellum: implication for the selective vulnerability of Purkinje cells.

We investigated the distribution of messenger RNAs coding for flip and flop splice variants ofAMPA receptor subunits in the human cerebellum to determine the relevance of AMPA receptors in the selective vulnerability of Purkinje cells to ischemia. Purkinje cells more abundantly expressed transcripts for flip variant of GluR-A, GluR-C, and GluR-D than granule cells, whereas transcripts for flop variants and GluR-B flip were expressed at similar levels on Purkinje cells and granule cells. These results suggest that human Purkinje cells possess AMPA receptors of the slowly desensitizing class as compared to granule cells. This differential distribution may explain the selective vulnerability of Purkinje cells.

Cell Death↗