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Biomedical subjects

E Contreras

Publications and source records attributed to E Contreras.

At least 19 recordsLinked to original sources
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

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 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↗
PubMed1992

Pharmacological characterization of adenosine A1 and A2 receptors in the bladder: evidence for a modulatory adenosine tone regulating non-adrenergic non-cholinergic neurotransmission.

1. The nerve-evoked contractions elicited by transmural electrical stimulation of mouse urinary bladders superfused in modified Krebs Ringer buffer containing 1 microM atropine plus 3.4 microM guanethidine were inhibited by adenosine (ADO) and related nucleoside analogues with the following rank order of potency: R-phenylisopropyladenosine (R-PIA) greater than cyclohexyladenosine (CHA) greater than 5'N-ethylcarboxamido adenosine (NECA) greater than ADO greater than S-phenylisopropyladenosine (S-PIA). Tissue preincubation with 8-phenyltheophylline (8-PT) displaced to the right, in a parallel fashion, the NECA concentration-response curve. 2. The contractions elicited by application of exogenous adenosine 5'-triphosphate (ATP) were also inhibited by ADO and related structural analogues. The rank order of potency to reduce the motor response to ATP was: NECA greater than 2-chloroadenosine (CADO) greater than R-PIA greater than ADO greater than CHA greater than S-PIA. 3. The ADO-induced ATP antagonism was of a non-competitive nature and was not specific. Tissue incubation with 10 microM NECA not only reduced the motor responses elicited by ATP, but also 5-hydroxytryptamine, acetylcholine and prostaglandin F2 alpha. The action of NECA was antagonized following tissue preincubation with 8-PT. The inhibitory action of NECA was not mimicked by 10 microM CHA. 4. The maximal bladder ATP contractile response was significantly increased by tissue preincubation with 5-30 microM 8-PT. 5. The 0.15 Hz evoked muscular twitch was significantly increased by 8-PT while dipyridamole consistently reduced the magnitude of the twitch response. These results are consonant with the hypothesis that an endogenous ADO tone modulates the bladder neurotransmission. 6. A working model is proposed suggesting the presence of ADO-Al and A2 receptors in the mouse urinary bladder. The A1 receptor subpopulation is probably of presynaptic origin whereas the smooth muscle membranes contain a population of the A2 receptor subtype.

Adenosine↗
PubMed1991

Demonstration of the need for end point validation of putative biomarkers: failure of aberrant crypt foci to predict colon cancer incidence.

Seven-week-old Sprague-Dawley rats were fed a semipurified AIN76 diet and were given a weekly injection of the colon carcinogen 1,2-dimethylhydrazine for 8 weeks (initiation stage of carcinogenesis). The rats were divided into seven groups and each group of rats was placed on one of seven different modifications of the AIN76 diet for the next 24 weeks (promotional stage of carcinogenesis). The mean numbers of aberrant crypt foci/rat and the incidence of adenocarcinomas from some of the seven dietary groups were found to be significantly different. However, all attempts to show a significant correlation between the mean number of aberrant crypt foci/rat and the incidence of adenocarcinomas failed. Therefore, the number of aberrant crypt foci/rat cannot by itself be used as a reliable quantitative predictor (biomarker) of the efficacy of dietary intervention or of chemopreventive procedures on modulating the risk of developing colon cancer. This conclusion emphasizes the need for end point validation of potential cancer biomarkers before the biomarkers can be considered predictive of modulation of the risk for colon cancer.

Adenocarcinoma↗
PubMed1991

Adenosine analogs attenuate tolerance-dependence on alprazolam.

1. Tolerance to and physical dependence on alprazolam were induced in mice by administering two doses of a slow release preparation. 2. Physical dependence was evaluated by the abstinence syndrome induced by flumazenil. Tolerance was studied by measuring the motor incoordination induced by a test dose of alprazolam. 3. The intensity of tolerance was decreased by the administration of L-phenylisopropyl adenosine (L-PIA), cyclopentyl adenosine (CPA), cyclohexyl adenosine (CHA), N-ethylcarboxamide adenosine (NECA), 8-phenyltheophylline (8-PTP) and theophylline (TP). 4. The intensity of the abstinence syndrome induced by flumazenil was attenuated by L-PIA, CPA NECA, TP and 8-PTP. 5. The results suggest that benzodiazepines may exert, at least in part, their effects by involving adenosine in the central nervous system.

Adenosine↗
PubMed1991

Systemic atropine administration during cardiac arrest does not cause fixed and dilated pupils.

OBJECTIVES: Systemic administration of atropine during CPR may postpone brain death determination because of its reputed ability to produce fixed and dilated pupils. We studied the effect of atropine administered in the usual doses as an adjunct to endotracheal intubation and for cardiac arrest to determine if it would interfere with neurological assessment. DESIGN: Two groups of children were studied. Group 1 consisted of 28 patients who received atropine (0.03 +/- 0.003 mg/kg) prior to endotracheal intubation. Group 2 consisted of 21 patients previously without evidence of brainstem disease who suffered a witnessed arrest and had prompt return of spontaneous circulation and received an atropine dose of 0.03 +/- 0.01 mg/kg. RESULTS: In group 1, pupillary size averaged 4.02 +/- 0.78 mm before and 4.75 mm +/- .84 mm after atropine (P less than .001). In group 2, the pupillary examination was conducted 30 minutes after return of spontaneous circulation. The pupillary diameter was 4.80 +/- 0.91 mm. All pupils were reactive to light in both groups. CONCLUSION: Atropine administration in conventional dose causes slight pupillary dilation but does not abolish pupillary light reactivity.

Adolescent↗
PubMed1990

Bradykinin facilitates the purinergic motor component of the rat bladder neurotransmission.

The motor activity of the rat bladder elicited by transmural electrical stimulation was abolished in the presence of 200 nM tetrodotoxin but not of 1 microM atropine plus 3.4 microM guanethidine. Tissue preincubation with 20 microM, alpha, beta-methylene ATP reduced but did not obliterate the electrically-induced motor effect. Bradykinin (BK) caused a short-lasting motor response while it potentiated, in a concentration-dependent fashion, the 0.15-5 Hz-induced muscle twitching. The facilitatory action of the peptide lasted for at least 5 min and was blocked by the BK-B2 receptor antagonist D-Arg0 [Hyp3, Thi5,8, D-Phe7]-BK. The motor response caused by the exogenous application of adenosine 5'-triphosphate (ATP) was almost immediate and lasted less than 30 s; it was also potentiated by BK-B2 receptor activation, an effect that was reduced in a concentration-dependent manner by pretreatment with the BK-receptor antagonist.

Action Potentials↗
PubMed1990

Effects of some adenosine analogs on morphine-induced analgesia and tolerance.

1. The analogs of adenosine D- and L-phenylisopropyladenosine (D- and L-PIA) and chloroadenosine (CADO) induced analgesia in mice (hot-plate test). 2. The antinociceptive effects of the three adenosine agonists were antagonized by caffeine but were unaffected by naloxone. 3. Morphine-induced antinociception was increased by pretreatment with adenosine agonists. 4. Whereas CADO significantly attenuated the induction of morphine tolerance, D- and L-PIA did not affect the process.

2-Chloroadenosine↗