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Biomedical subjects

E Contreras

Publications and source records attributed to E Contreras.

At least 37 records · Page 2Linked to original sources
PubMed1997

Endogenous nitric oxide attenuates ethanol-induced vasoconstriction in the human placenta.

The purpose of this study was to clarify the role of endogenous nitric oxide and prostanoids in ethanol-induced perturbation of microcirculation in perfused human placenta. Infusion of ethanol into chorionic plate vessels at 10-65 mM increases perfusion pressure in a concentration-dependent fashion, and is an indicator of fetal-placental vasoconstriction. Simultaneous infusion of N(omega)-nitro-L-arginine, methylene blue and endothelial cell removal significantly enhances the ethanol-induced increase in perfusion pressure. In contrast, sodium nitroprusside attenuates this effect. Indomethacin did not significantly modify the ethanol-induced response. In conclusion, inhibition of the action of endogenous nitric oxide is associated with an increase in fetal-placental vasoconstriction. These results suggest that endogenous nitric oxide acts as a vasodilator that reduces ethanol-induced vasoconstriction, thus improving microcirculation, and leads to decreased placental damage.

Antidotes↗
PubMed1996

Influence of nitric oxide on transepithelial transport in toad skin: effects of cholinergic agents and morphine.

The effects induced by L-arginine (L-Arg) on the short-circuit current and potential difference of Pleurodema thaul skin were investigated. L-Arg, but not D-Arg significantly increased the short-circuit current and potential difference when applied to the serosal surface. The effects of L-Arg were antagonized by amiloride, NG-nitro-methyl-L-arginine (L-NAME) and by methylene blue. Carbachol and acetylcholine induced significant increases of both electrical parameters of the toad skin. These effects of the muscarinic cholinergic drugs were potentiated by a low concentration of L-Arg and antagonized by L-NAME or methylene blue. Carbachol and acetylcholine induced significant increases of both electrical parameters of the toad skin. These effects of the muscarinic cholinergic drugs were potentiated by a low concentration of L-Arg and antagonized by L-NAME or methylene blue. Addition of dibutyryl cyclic guanosyl monophosphate (db cGMP) or dibutyryl cyclic adenosine monophosphate (db cAMP) increased short-circuit current and potential difference. The effects of db cGMP, but not those of db cAMP were antagonized by L-NAME. The consecutive application of db cGMP and db cAMP induced additive effects. These results suggest that L-Arg increases transport in toad skin presumably acting through the formation of nitric oxide, which then stimulates cytoplasmic guanylate cyclase and leads to increased Na+ and K+ transport. The effects of L-Arg and carbachol were antagonized by acute application of morphine; however, a rebound response was observed when carbachol or noradrenaline were given after prolonged exposure of the skin to morphine, which suggests an adaptive response of the skin involving both cGMP and cAMP. Responses to both nucleotides were unchanged by morphine.

Acetylcholine↗
PubMed1996

Possible role of nitric oxide in the antinociceptive action of intraventricular bradykinin in mice.

The i.c.v. administration of bradykinin (4, 8 and 16 micrograms) induced antinociception in mice which was resistant to naloxone; furthermore, the induction of tolerance to morphine by a single s.c. injection (100 mg/kg, 24 h before test doses of the peptide) did not affect antinociception. Since bradykinin is known to increase nitric oxide (NO) in peripheral tissues, we studied the possibility that its antinociceptive action may be related to NO effects in the central nervous system. Bradykinin effects were antagonized by previous treatment with NG-nitro-L-arginine or concomitant i.c.v. administration of bradykinin and methylene blue. The immediate precursor of NO, L-arginine, which by itself produces analgesia, also reduced bradykinin effects; moreover, tolerance to L-arginine significantly decreased the response to the peptide. These results suggest that NO is involved in antinociception induced by i.c.v. administration of bradykinin.

Analgesics↗
PubMed1995

Diazepam induces tolerance in the isolated skin of Pleurodema thaul.

The effects of the long-term administration of diazepam on the potential difference and short-circuit current of the isolated skin of the toad Pleurodema thaul (P. thaul) were investigated. Diazepam applied in a concentration range of 4.6 x 10(-6) to 5.2 x 10(-5) M decreased both electrical parameters. This response was unaffected by flumazenil indicating that the action of diazepam is not induced through benzodiazepine receptors. Induction of tolerance to diazepam on its observed effects on potential difference and short-circuit current was obtained by the administration of a single dose of the drug in a slow release preparation. Skins tolerant to diazepam were also tolerant to the acute effects of verapamil on both electric parameters. Tolerance to diazepam effects was partly reversed by increasing Ca2+ concentration in the inner bathing solution. The results are consistent with a Ca2+ channel blocking effect of diazepam in the P. thaul skin.

Animals↗
PubMed1995

Nutritional value and content of antinutritional compounds and toxics in ten wild legumes of Yucatan Peninsula.

The chemical and toxicological composition of ten wild legumes collected in Yucatan, Mexico was determined. For each species the whole fruit, (seed and pod), were studied as well as the seed and pod separately. A higher protein content was found in the seeds of A. lebbeck and P. saman (37.07 and 37.60% respectively). In the seeds of L. longystilus, C. yucatanensis and P. keyense a high concentration of fat was found, especially in the first with 31.34%. A high quantity of fiber was found in the pods. In general, the samples were rich in lysine (especially seeds) and scant in sulfur amino acids and tryptophan. All the samples showed high concentration of potassium and calcium. Some of them exhibited significant concentrations of iron. The pods of P. saman and P. keyense showed a high content of lectins. In the seeds of C. yucatanensis and in the pod of P. keyense high concentrations of trypsin inhibitors were found 60 and 406.7 TUI/mg sample respectively. The presence of saponins, was detected in seven samples, of which the seed of P. keyense had the highest concentration. Alkaloids were found only in the whole fruit and pod of P. saman and cyanogenic glucosides were present in A. pennatula. In general terms, the whole legume showed better digestibility than the pods alone.

Alkaloids↗
PubMed1995

Diazepam decreases the response to the electrical stimulation of the nerve-skin preparation of the toad Caudiverbera caudiverbera.

1. The effect of diazepam was examined in the nerve skin preparation of the toad Caudiverbera caudiverbera. 2. Nerve stimulation was followed immediately by a transient increase in short-circuit current (SCC) and in the potential difference (PD), which consisted of a rapid and then a slow component. 3. Diazepam concentrations from 5.0 x 10(-5)M to 5.1 x 10(-4)M caused a dose-dependent block of both components to a 30% of their control values and also reduced the stimulatory responses to noradrenaline in this preparation. 4. Diazepam antagonized the potassium blocking effect of barium. 5. These results, based on electrophysiological and pharmacological evidence, are consistent with a calcium and sodium blocking effect of diazepam on the nerve skin junction of C. caudiverbera.

Adrenergic alpha-Agonists↗
PubMed1995

Intrathecal pertussis toxin but not cyclic AMP blocks kappa opioid-induced antinociception in rat.

The role of inhibitory G-proteins and cyclic AMP in spinal mechanisms of kappa opioid receptor-mediated antinociception was assayed by recording the withdrawal response latency of the rat tail following immersion into a water bath of 49 degrees C. Intrathecal administration of pertussis toxin (1 microgram/rat, five days before the behavioral evaluation) prevented the antinociceptive effect of the kappa receptor agonist U-50,488H, while administration of dibutyryl cyclic AMP (10 micrograms/rat, 17 min. after U-50,488H) did not antagonize the antinociceptive action of the kappa ligand. Results suggest that in the spinal cord the signal transduction mechanism subserving the antinociceptive effect of U-50,488H involves a Gi or Go protein, but also that cyclic AMP is not implicated in coupling Gi/Go proteins to the effector system.

Animals↗
PubMed1995

[Monocytoid B-cell lymphoma: clinico-pathologic study of 2 cases].

Monocytoid B-cell lymphoma, considered as a low-grade lymphoma, is seen most frequently in persons of advanced age, chiefly women. It is often diagnosed in lymph-node phase, in low stages (I-II), and peripheral blood, bone-marrow or spleen are seldom involved. The morphologic and immunohistochemical study of two patients with monocytoid B-cell lymphoma is presented. The characteristic cell morphology, with homogeneous nuclei, low number of mitoses, and clear, wide cytoplasm, was present in both. Tumour cells expressed CD45, CD20, HLA-DR and monoclonal IgM-lambda and lambda chains, respectively. Case no. 1 had more irregular nuclei, protruding nucleoli, advanced stage at diagnosis and shorter clinical course. An epithelioid granulomatous reaction was present in case no. 2, which delayed the diagnosis until relapse. The diverse forms of clinical onset of monocytoid B-cell lymphoma, as well as its possibly aggressive course, association with other types of lymphoma and the difficulties for an adequate morphologic identification are commented.

Female↗
PubMed1994

Purinergic drugs and calcium channel antagonists attenuate the withdrawal syndrome from barbital.

The effects of some adenosine agonists and calcium channel antagonists on the induction of tolerance to and dependence on barbital in mice have been studied. The concurrent administration of barbital and one of the following adenosine agonists, D- or L-phenylisopropyl adenosine, cyclopentyl adenosine and chloroadenosine, or the adenosine antagonists theophylline or 8-phenyltheophylline did not change the intensities of tolerance to and dependence on the barbiturate. N-ethylcarboxamide adenosine administered during the period of chronic administration of barbital significantly reduced the withdrawal syndrome. The administration of the calcium channel antagonists diltiazem, verapamil or nifedipine was also ineffective in altering the processes of tolerance and physical dependence when given concomitantly with barbital. Abstinence behavior was significantly reduced when mice were treated during the first 48 h of withdrawal from the barbiturate with either L-phenylisopropyl adenosine, N-ethylcarboxamide adenosine, nifedipine or verapamil. These results are discussed in relation to the attenuation of tolerance to and dependence on benzodiazepines induced by similar treatments.

Adenosine↗
PubMed1994

[Expression of p29, estrogen receptor related protein in primary breast carcinoma. Methodological, anatomoclinical, and DNA content analysis].

The aim of this work was to assess the immunohistochemical detection of a estrogen receptor related protein (p29) in 48 histological samples of primary mammary carcinoma and its relationship to clinical, morphological and ADN content parameters. p29 protein was positive in 62.5% of samples. Over 50% of samples had a moderate or intense immunohistochemical staining (staining index over 16) and 77% has a heterogeneous expression of p29 protein. Seventy six percent of p29 positive and 53% of p29 negative tumors had a proliferation fraction over 10% (determined by the S fraction with flux cytometry). No relationship between p29 expression and the analyzed anatomoclinical variables was found. These results highlight this immunohistochemical method as an alternative to more complex and difficult biochemical techniques. On the other hand, the good results obtained in formalin fixed tissues allow retrospective studies in mammary carcinoma samples.

Biomarkers, Tumor↗
PubMed1994

[Breast cancer and flow cytometry: comparative study of DNA ploidy pattern with clinicopathological parameters].

There is evidence that DNA quantization and histopathological classification of breast cancer may be useful for its therapeutic management. DNA flow cytometry, clinical and anatomopathological features of 60 paraffin embedded primary breast cancer tissue samples were studied. The aneuploidy percentage was 67%. There was a correlation between DNA index and degree of cellular pleomorphism, degree of differentiation and the fraction of cells in S phase. Likewise a correlation was found between the degree of cellular pleomorphism and the mitotic index. DNA cytophotometry was useful to solve cases of difficult diagnosis with flow cytometry ("near" diploid and tetraploid tumors). No correlation was found between aneuploidy, percentage of cells in phase S, degree of cellular atypia and mitotic degree with clinical stage, degree of lymph node involvement, tumoral size or age. It is suggested that these variables may have an independent behavior.

Adult↗
PubMed1994

[The control of arterial hypertension in primary care: the evaluation of a program of self-care].

OBJECTIVE: To evaluate the efficacy of a self-care hypertension programme within primary care. DESIGN: Two models of intervention by means of self-care were compared, both using individual education and family support, with one of them using group education. SETTING AND PATIENTS: All those attending 10 health centres in Andalucía and who had a recent diagnosis of light or moderate Hypertension or with their hypertension not monitored over the preceding 6 months, were included. MEASUREMENTS AND MAIN RESULTS: These 160 people were assigned at random to the intervention group (group education) or the control group (individual education). Data analysis provided the results for the 95 people who completed the study. Both systolic and diastolic arterial pressure (SAP and DAP) diminished significantly during the study period, both in the sample as a whole and in the intervention group. However, the lessening of systolic pressure only reached statistically significant differences in the control group. Over the study period, the lessening of SAP was 6.2 in the intervention group and 8.0 in the control group; whereas the lessening of DAP was 7.0 in the intervention group and 2.3 in the control group. CONCLUSIONS: Arterial hypertension can be controlled in primary care by health education for self-care. On the basis of this study's findings, it is not valid to conclude that group is more efficacious than individual education.

Adult↗
PubMed1993

Calcium channel blockers apparently decrease noradrenaline release from nerve-skin terminals in Caudiverbera caudiverbera.

1. The effects of three calcium channel blockers, verapamil, diltiazem and nifedipine were examined on the response of the skin neuroepithelial synapse of the toad Caudiverbera caudiverbera to electrical stimulation. 2. The stimulus induced a significant rise in potential difference (PD) and short-circuit current (SCC). The three calcium antagonists reduced the responses in a dose-dependent manner. The greatest reduction was induced by verapamil followed by diltiazem and nifedipine. 3. Amiloride treatment did not affect the responses to electrical stimulation, indicating that the response to nerve stimulation is not due to current flowing through sodium channels. 4. When the preparation was blocked by either of the three antagonists, the skin response to noradrenaline was not affected. 5. It may be concluded that verapamil, diltiazem or nifedipine reduce the release of noradrenaline at the neuroepithelial synapse of C. caudiverbera.

Amiloride↗
PubMed1993

Calcium channel antagonists and adenosine analogues decrease tolerance to opiate pentazocine and U 50488H.

1. A single dose of pentazocine induces cross-tolerance the analgesic effects of the kappa agonist U 50488H. Tolerance is observed by means of the hot plate test or by the i.p. administration of acetic acid 6 or 24 hr after the priming dose, respectively. 2. The administration of the calcium channel antagonists, diltiazem, nifedipine or verapamil, reduces the degree of tolerance as assessed by the hot plate test or acetic acid administration. 3. The adenosine agonist N6-cyclopentyl adenosine significantly reduced the intensity of the process; in contrast, N6-cyclohexyladenosine antagonized the analgesic response to the opiate obscuring its influence on the process. 4. The results are discussed in relation to the interaction of calcium channel function in the analgesic response to the kappa opiates.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1993

Calcium channel modulators modify K opioid-induced inhibition of C-fiber-evoked spinal reflexes in rat.

The role of L-type Ca2+ channels on the kappa opioid-induced depression of spinal afferent transmission was assessed in spinalized rats, through recording of the C-fiber-evoked spinal flexor reflex. Six successive i.t. doses of the K agonist U-50,488H produced a dose-dependent decrease of the C-reflex duration (ID50: 25.7 nmol), the log dose-response relationship being shifted to left by pretreatment with 5 mg/kg i.v. of the calcium channel blocker verapamil, or to right by pretreatment with .25 mg/kg i.v. of the calcium channel agonist Bay K8644. Verapamil and Bay K8644, administered i.v. after U-50,488H i.t., respectively potentiated or antagonized the depressor effect of the K ligand on the reflex. The results point to a role for Ca2+ availability as a factor involved in depression of afferent nociceptive transmission by K opioids at the spinal cord.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1992

Effects of calcium channel antagonists and Bay K 8644 on the analgesic response to pentazocine and U 50488H.

1. The effects of diltiazem, nifedipine and verapamil and the calcium channel agonist Bay K 8644 on the analgesic responses to the subcutaneous (s.c.) or intracerebroventricular (i.c.v.) administration of pentazocine and U 50488H were investigated in mice. 2. The three calcium channel antagonists and Bay K 8644 reduced the number of writhes induced by the intraperitoneal administration of acetic acid. 3. The analgesic responses to the low doses of pentazocine (s.c.) were additive with the effects of diltiazem, nifedipine or Bay K 8644; while, in contrast, the higher doses produced underadditive responses. Only verapamil increased the effects of the i.c.v. administration of the opioid. 4. The effects of U 50488H (s.c.) were additive with those of diltiazem and Bay K 8644; verapamil only increased the response to the lower dose of the opioid. Nifedipine plus pentazocine always induced underadditive responses. The i.c.v. effects of U 50488H were only increased by verapamil. 5. These findings are discussed in relation with a possible interaction of kappa agonists with calcium channels in the central nervous system.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗