Search PubMed⌕ Search

Biomedical subjects

G Romero

Publications and source records attributed to G Romero.

At least 55 records · Page 3Linked to original sources
PubMed1995

The pharmacology of VA21B7: an atypical 5-HT3 receptor antagonist with anxiolytic-like properties in animal models.

VA21B7 (3-[2-(4'-piperonylpiperazinyl) indolyl] carboxaldehyde) was synthesized as a potential 5-HT3 receptor antagonist. Even though VA21B7 showed a higher affinity towards 5-HT3 receptors as compared to other receptors studied, it was not a potent 5-HT3 receptor antagonist either in the periphery or in the brain. In a simple animal model of anxiety such as the two-compartment box in mice, a remarkable anxiolytic-like effect was found at doses of 2-500 micrograms/kg IP and also at low oral doses, in the microgram range. These drug doses did not produce any significant effect on spontaneous motor activity of mice. The anxiolytic profile of VA21B7 was further explored using other models of anxiety in rats such as the elevated plus-maze and punished-drinking. VA21B7 was compared with standard 5-HT3 receptor antagonists such as ondansetron, tropisetron and granisetron, with the 5-HT1A agent buspirone and with diazepam. In the plus-maze, VA21B7 showed an anxiolytic-like profile after doses of 0.25-0.5 mg/kg IP or 2-4 mg/kg PO which did not modify the number of total entries into the open and closed arms of the maze. Diazepam, granisetron and tropisetron were also effective in this test but not ondansetron and buspirone. VA21B7 was also able to release suppressed behaviour in the punished-drinking test. The dose-response curve was bell-shaped with a peak at 2-4 mg/kg. At variance with other studies, 5-HT3 receptor antagonists also increased the number of shocks taken in this test and the dose-response curve was also bell-shaped. VA21B7 was not anticonvulsant like diazepam, its anxiolytic action in the light/dark test was not flumazenil-sensitive and there was no rebound anxiogenic effect on withdrawal from chronic VA21B7 treatment for 15 consecutive days. Moreover, VA21B7 was not amnesic like the benzodiazepines but low doses of 2-4 mg/kg reduced the memory deficits induced in rats by scopolamine. Much higher doses were necessary to decrease spontaneous motor activity in rats. Since VA21B7 appears to be well tolerated in rodents at high doses, we think that it is of potential interest as an anxiolytic in humans.

Analgesics↗
PubMed1995

Role of glycosyl-phosphatidylinositol hydrolysis as a mitogenic signal for epidermal growth factor.

We have investigated the role of the hydrolysis of glycosyl-phosphatidylinositol (GPI) as one of the signalling pathways elicited after interaction of epidermal growth factor (EGF) with its specific plasma membrane receptor (EGFR). Endogenous GPI was characterized in both NIH 3T3 mouse fibroblast cells and in EGFR-transfected NIH 3T3 cells (designated EGFR T17). GPI molecules isolated from both cell lines were identical and they incorporated radioactivity from both sugar and fatty acid substrates. Incubation of EGFR T17 cells with EGF, produced a rapid and transient hydrolysis of GPI. Maximum hydrolysis occurred after a 1-min incubation with 50 nM EGF. No such effects of EGF were observed in the parental cell line. Both inositol phosphoglycan (IPG)- and EGF-induced cell proliferation was inhibited in the presence of an IPG-antibody to different extents. The relationship between GPI hydrolysis and the activity of the EGFR was studied using the tyrosine kinase inhibitors tyrphostin (RG50864) and genistein. These agents were able to significantly inhibit EGF-mediated cell proliferation, EGF-dependent hydrolysis of GPI and EGF-regulated autophosphorylation of the EGFR. It is concluded that GPI hydrolysis is one of the earliest intracellular events generated in response to EGF.

3T3 Cells↗
PubMed1994

Synthesis of 2-piperazinylbenzothiazole and 2-piperazinylbenzoxazole derivatives with 5-HT3 antagonist and 5-HT4 agonist properties.

New 2-piperazinylbenzothiazole and 2-piperazinylbenzoxazole derivatives were prepared and tested as 5-HT3 receptor antagonists. Some of the new compounds antagonized the effect of 5-HT at the longitudinal muscle myenteric plexus (LMMP) preparation of the guinea pig ileum, and two benzothiazole derivatives, compounds 2e and 2f, were more potent than ondansetron in this regard. However, these two compounds were much weaker than the typical 5-HT3 receptor antagonist as displacers of [3H]BRL-43694 binding to rat cerebral cortex homogenates or as antagonists of the bradycardia response to 5-HT in the anaesthetized rat. Like the prokinetic agent cisapride, some of the new compounds enhanced gastric emptying in rats. Compound 2f not only markedly enhanced gastric emptying but was also a potent agonist at the isolated rat oesophageal tunica muscularis mucosae, a preparation sensitive to 5-HT4 receptor stimulation, and enhanced the twitch response in the LMMP preparation. The latter effect was blocked by a high concentration of tropisetron or by previous desensitization with 5-methoxytryptamine. Compound 2f appears to show a promising pharmacological profile as a potential gastrokinetic agent.

Animals↗
PubMed1994

Protective effects of calcium channel blockers in carbon tetrachloride-induced liver toxicity.

The effects of calcium channel blockers, verapamil, nifedipine and diltiazem, on CCl4-induced liver damage were determined. A single dose of CCl4 (0.5 ml/kg p.o.) led to a five-fold increase in liver calcium content. The toxic effect of CCl4 was also observed in other hepatic processes: the protein synthesis rate in the liver showed an important decrease, liver glycogen content and bile flow was decreased, and lipid peroxidation was approximately doubled. The plasma levels of cholesterol, triglycerides and transaminases (AST and ALT) also increased. When the calcium channel blockers were administered 2 hr prior to and 7 hr after the administration of the toxic agent at doses of 25 mg/kg (diltiazem) and 10 mg/kg (nifedipine and verapamil), the liver showed a significant reestablishment of several of these parameters: a considerable reduction in liver calcium content, a decrease in AST and ALT levels, and a significant increase in protein synthesis rate. There was also a partial inhibition of lipid peroxidation.

Animals↗
PubMed1994

Effect of prenatal exposure to antidepressants on 5-HT-stimulated phosphoinositide hydrolysis and 5-HT2 receptors in rat brain.

1. Female rats were given antidepressants, with different effects on 5-HT uptake, from day 6 of pregnancy until delivery. 2. 5-HT-stimulated inositol phosphate accumulation as well as 5-HT2 receptor density were measured at two different times in the pups. 3. Prenatal exposure to fluoxetine or iprindole reduced phosphoinositide hydrolysis in 25-day-old pups. However, chronic treatment of adult rats with fluoxetine or prenatal exposure to either desipramine or tianeptine did not modify inositol phosphate accumulation. 4. After prenatal exposure, only desipramine significantly decreased the density of [3H]ketanserin-labelled 5-HT2 receptors in the pups. 5. No correlation was found between changes in inositol phosphate formation and 5-HT2 receptor number.

Animals↗
PubMed1994

Antibody binding to the juxtamembrane region of the insulin receptor alters receptor affinity.

The effect of three antibodies that interact with distinct regions of the insulin receptor (the alpha subunit (83-7), the juxtamembrane region near tyrosine 960 (960) or the carboxy terminal region of the beta subunit (CT-1) on insulin binding was examined. Detergent-solubilized insulin receptors from IM-9 cells immobilized on Sepharose beads by 960 antisera bound 2-3 times more 125I-insulin tracer (25-60 pM) than receptors immobilized with either 83-7 or CT-1. Pre-incubation of solubilized receptors with either 83-7 or 960 resulted in equivalent depletion (90%) of insulin binding activity from solubilized IM-9 cell extracts, suggesting that both antibodies were in excess and capable of binding a similar population of receptors. Antibody 960, but not CT-1 or 83-7, also increased insulin binding 2 fold to solubilized receptors precipitated with polyethylene glycol. To determine whether the altered binding observed with antibody 960 was due to increased affinity of the receptor for insulin or appearance of more insulin binding sites, binding studies were performed over a wide range of insulin concentrations. Analysis of the resulting binding curves indicated that 960 increased the affinity of the receptor for insulin 3 fold over control (kd = 0.3 nM for 960, and 0.9 nM for 83-7, respectively). The antibody 960 also specifically increased insulin binding to intact, saponin-permeabilized IM-9 cell membranes. These results indicate that binding of 960 antibody to the juxtamembrane region of the insulin receptor alters the affinity of the receptor for insulin. Since tyrosine 960 in the juxtamembrane region has been suggested to play a role in receptor signalling, changes in receptor conformation in this region that are likely to account for the change in affinity may play a role in signal transduction.

Antibodies↗
PubMed1994

VIP suppression in the intestine and cerebral cortex following administration of VIP antiserum to newborn rats.

The administration of vasoactive intestinal peptide (VIP) antiserum to newborn rats significantly reduced the VIP content, both in the cerebral cortex and in intestinal epithelial cells. The decrease was observed at postnatal days 14 and 21 and also in 90 day-old animals. The neonatal treatment produced a significant increase in the density of high- and low-affinity binding sites for VIP in the cerebral cortex at post-natal days 14 and 21 whereas in the intestinal epithelial cells only the low-affinity binding sites were up-regulated at the same time points. VIP suppression induced by neonatal administration of the corresponding antiserum may represent a useful approach to further characterize the physiological role of this neuropeptide.

Age Factors↗
PubMed1993

Novel antagonists of 5-HT3 receptors. Synthesis and biological evaluation of piperazinylquinoxaline derivatives.

A series of piperazinylquinoxalines has been synthesized and studied as 5-HT3 receptor antagonists in different preparations. Antagonism to 5-HT in the longitudinal muscle of the guinea pig ileum was particularly prominent in cyanoquinoxaline derivatives with an alkyl substitutuent on the piperazine moiety. The pA2 of some selected compounds against the 5-HT3 agonist 2-methyl-5HT in the guinea pig ileum was in the range of tropisetron or ondansetron, and one of them, 7e, was more potent than these reference compounds by approximately 2 or 3 orders of magnitude. However, these compounds were markedly less potent than either tropisetron or ondansetron as displacers of 3H-BRL 43694 binding to rat cortical membranes or as antagonists of the Bezold-Jarisch reflex in rats. Piperazinylcyanoquinoxalines represent a new class of 5-HT3 antagonists with a selective effect on guinea pig peripheral receptors.

Animals↗
PubMed1993

In vitro activation of the transcription factor ISGF3 by interferon alpha involves a membrane-associated tyrosine phosphatase and tyrosine kinase.

Interaction of interferon alpha (IFN alpha) with its cell surface receptor rapidly activates the formation of the transcription complex ISGF3, which subsequently translocates to the nucleus and stimulates the expression of a variety of early response genes. We have recently developed a cell-free system where IFN alpha can activate the formation of ISGF3 in vitro. This system has enabled us to demonstrate that the component of the ISGF3 transcription complex which is modified by IFN alpha treatment (ISGF3 alpha) is membrane-associated and that its activation involves a protein kinase. Using a combination of specific tyrosine kinase and phosphatase inhibitors and monoclonal anti-phosphotyrosine antibodies we now are able to demonstrate that IFN alpha-activated transcription involves at least a two-step process where a membrane-associated tyrosine phosphatase and a tyrosine kinase lead to modification of ISGF3 alpha and subsequent formation of the complete complex. Furthermore, formation of the ISGF3 complex is specifically disrupted by protein tyrosine phosphatase and can be reversibly dissociated by the phosphotyrosine analogue phenylphosphate. The latter observation suggested that SH2 and/or SH3 domains may be required for the stable formation of this transcription complex.

Base Sequence↗
PubMed1993

Brain-derived neurotrophic factor and neurotrophin-3 induce cell proliferation in the cochleovestibular ganglion through a glycosyl-phosphatidylinositol signaling system.

We have investigated the role of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in the regulation of cell proliferation in the early developing cochleovestibular ganglion (CVG). Ganglia were isolated from 72-hr chick embryos and cultured for 24 hr. Both BDNF and NT-3 had a powerful mitogenic effect, at doses of 1-5 ng/ml, consistent with an involvement of the high-affinity receptor. Evidence for the participation of the glycosyl-phosphatidylinositol (GPI)/inositol phosphoglycan (IPG) signaling system in the mediation of proliferative effects of BDNF and NT-3 is presented. Both of these neurotrophins elicited a fast and transient hydrolysis of labeled GPI, approximately 60% in 30 sec. The dose-response profile of GPI hydrolysis overlaps the neurotrophin-induced cell proliferation response profile. Anti-IPG antibodies were able to block the growth-promoting effects of BDNF and NT-3. Anti-IPG antibodies immunoprecipitated a CVG-endogenous IPG, induced upon BDNF treatment, which exhibited proliferative stimulating properties. Both BDNF and NT-3 are proposed as potential candidates for regulation of growth during CVG development, with this mitogenic effect being mediated by the GPI/IPG signaling system.

Animals↗
PubMed1993

Brain-derived neurotrophic factor and neurotrophin-3 support the survival and neuritogenesis response of developing cochleovestibular ganglion neurons.

The effects of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) on the differentiation of avian cochleovestibular ganglion and their possible association with the hydrolysis of glycosyl-phosphatidylinositol (GPI) were studied. BDNF and NT-3 (2 ng/ml) promoted neurite outgrowth in explants of both cochlear and vestibular ganglia. This effect on neuritogenesis was stage-dependent, reaching a maximum at E7 for NT-3 and at E9 for BDNF. The magnitude of the response of the vestibular ganglion to BDNF was always smaller than that of the cochlear ganglion of an equivalent stage. BDNF and NT-3 stimulation of neuronal survival and neurite extension was also demonstrated in dissociated neuronal cell cultures. The effect was concentration-dependent with saturation of the response occurring at 4 ng/ml for BDNF and at 2 ng/ml for NT-3, the half-maximal effect occurring at 2 and 1 ng/ml, respectively, for the most sensitive stages of the chick cochlear ganglion. Inositol phosphoglycan (IPG) did not mimic the effects of BDNF or NT-3 on neuronal survival and neurite outgrowth, nor was it able to potentiate their responses. Antibodies raised against IPG did not block the effects of these neurotrophins. The results suggest that BDNF and NT-3 may act in cooperation to establish the innervation pattern of the inner ear. Unlike their early proliferative effects, neurotrophic effects are uncoupled from the GPI/IPG signal transduction system.

Animals↗
PubMed1993

Activation of the mitogen-activated protein kinase pathway in Triton X-100 disrupted NIH-3T3 cells by p21 ras and in vitro by plasma membranes from NIH 3T3 cells.

We describe a novel Triton-disrupted mammalian cell system wherein the pathways for activation of mitogen-activated protein (MAP) kinases (MAPKs) are capable of direct biochemical manipulation in vitro. MAPKs p42mapk and p44mapk are activated in signal transduction cascade(s) initiated by occupancy of plasma membrane receptors for peptide growth factors, hormones, and neurotransmitters. One likely activation pathway for MAPKs consists of sequential activations of c-ras, c-raf-1, and a protein-tyrosine/threonine kinase, MAP kinase kinase. Triton-disrupted cells retained capacity for activation of the pathway by both peptide growth factors and by addition of GTP-loaded p21 rasVal12. Incubation of disrupted cells with an antibody that neutralized the function of c-ras (Y13-259) abolished receptor-mediated stimulation of MAPK as did acute addition of 200 microM azatyrosine. Activation of the pathway was reconstituted in a cell-free system using high-speed supernatants generated from Triton-disrupted cells together with purified plasma membranes from parental cells and as a heterogeneous system using purified plasma membranes from v-ras-transformed cells. These systems will allow biochemical dissection in vitro of the interaction(s) between c-ras and the MAPK pathway in mammalian cells.

3T3 Cells↗
PubMed1993

The involvement of inositol phosphoglycan mediators in the modulation of steroidogenesis by insulin and insulin-like growth factor-I.

We have investigated the mechanisms by which insulin and insulin-like growth factor-I (IGF-I) regulate the synthesis of progesterone by swine ovary granulosa cells. Analysis of the cell density dependence of the effects of insulin and IGF-I showed that the induction of progesterone synthesis by these growth factors is consistent with an autocrine or paracrine model of action, which involves the insulin- and IGF-I-stimulated release of a soluble factor(s) into the culture medium. We have tested the hypothesis that this soluble factor(s) may be structurally related to inositol phosphoglycans, a class of putative second messengers of the action of insulin. Consistent with this hypothesis, we isolated an activator of pyruvate dehydrogenase (PDH) phosphatase from culture medium obtained from cells treated with insulin or IGF-I. Further analysis showed that specific antibodies raised against the inositol phosphoglycan anchor of the variant surface glycoprotein of Trypanosoma brucei blocked the activation of PDH phosphatase by the material isolated from the culture medium, suggesting a close structural relationship between this putative PDH phosphatase activator and inositol phosphaglycans. Pertussis toxin treatment, shown to inhibit the generation of inositol phosphoglycans in other systems, was found to inhibit the effects of insulin on progesterone synthesis in granulosa cells. Finally, the stimulatory effects of insulin and IGF-I on progesterone synthesis by intact granulosa cells were markedly inhibited by the addition of antiinositol phosphoglycan antibodies to the culture medium. Based on these observations, we propose that the release of inositol phosphoglycans into the extracellular medium plays an important role in the signaling mechanisms by which insulin and IGF-I regulate the synthesis of progesterone in swine ovary granulosa cells.

Animals↗
PubMed1993

[The verbal autopsy on children with a respiratory infection and acute diarrhea. An analysis of the disease-care-death process].

The study focuses on children between 72 hours and five years of age who died of acute respiratory infection (ARI) or acute diarrhea (AD) in the State of Tlaxcala. Peer Review Mortality Committee of the State contributed with the staff to the deaths analysis. Cases were included only when diagnosis was confirmed by verbal autopsy (VA). One hundred and thirty two cases were included (98 corresponding to ARI deaths and 34 to AD). The process related to medical care-seeking behaviors and prescribing practices by private and non-private physicians was analyzed through the VA. During the study period, 60% of children with ARI and 58.9% of children with AD died at home. More than 80% of these children had received medical care within three days preceding their death, and 50% of them had been seen by a physician within 12 hours prior to their death. Most of these visits were to a private doctor (71% for ARI and 86% for AD). Forty seven percent of treatments prescribed for ARI were judged to be wrong, either because of a bad choice of antibiotic or because the physician did not prescribe an antibiotic when the patient required it. Similarly, 65% of treatments for AD were considered erroneous, either due to the use of an antibiotic which was not justified or due to the lack of oral rehydration therapy when it was needed. Additionally, late referral to a hospital was considered as having direct influence at the death in half of the consultation. Families were too late in demanding medical care or demanded no care at all in 21.9% of cases of ARI and in 6.1% of cases of AD. We have found the VA to be useful in identifying problems related to the process of health-seeking behaviors and medical care. Our results suggest interventions that may lower the high mortality rates in Tlaxcala, such as training workshops directed to institutional and private physicians, and the implementation of top-of-line treatment centers where high-risk patients can be referred and also the health care workers can learn the correct treatment of both diseases. Future studies should focus on the identification of alarm signs and risk factors that may help to lower mortality due to ARI or AD, when recognized and treated at early stages.

Acute Disease↗
PubMed1992

The generation of inositolglycan mediators from rat liver plasma membranes: the role of guanine nucleotide binding proteins.

The guanine nucleotide dependence for the generation of inositolglycan second messengers from rat liver plasma membranes has been investigated. Plasma membranes, when treated with insulin release a soluble mediator substance which activates pyruvate dehydrogenase (PDH). Guanosine 5'-[3-thio]triphosphate (GTP gamma S) was found to be as potent as insulin in stimulating mediator release. The stimulatory effects of GTP gamma S required the presence of magnesium and following preincubation of membranes with guanosine 5'-[2-thio]diphosphate (GDP beta S) the stimulation of mediator release by either insulin or GTP gamma S was blocked. The activation of PDH by mediator fractions produced in response to either insulin or GTP gamma S was abolished following treatment of the fractions with anti-inositolglycan antibodies. The significance of these observations with respect to the possible involvement of a regulatory guanine-nucleotide binding protein (G-protein) in the generation of insulin mediators is discussed.

Adenosine Triphosphate↗