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Biomedical subjects

A Sierra

Publications and source records attributed to A Sierra.

At least 19 recordsLinked to original sources
PubMed1998

Expression of death-related genes and their relationship to loss of apoptosis in T1 ductal breast carcinomas.

Expression of the death-related proteins (DRPs) Bcl-2, Bax, Bcl-x and Bak that regulate cell survival and death was examined using immuno-histochemical methods in a group of 142 T1 (<2 cm) ductal breast carcinomas. Immunostaining results were correlated with loss of apoptosis and clinicopathological parameters such as histological grade (HG) and lymph node involvement. Expression of anti-apoptotic proteins Bcl-2 and Bcl-x was found in 57.0% and 62.75% of tumors, respectively. Bcl-2 expression, but not Bcl-x expression, was related to loss of apoptosis. Expression of the apoptotic proteins Bax and Bak was present in 58% of Bcl-2-negative tumors and associated significantly with an increase in apoptosis. Expression of these DRPs was associated significantly with the HG of the tumors: Bcl-2 and Bak expression was predominant in HG I/II tumors, whereas expression of Bcl-xL and Bax was commonly observed in HG III tumors, as occurs for p53 over-expression. Our results suggest that the loss or gain of apoptosis is regulated tightly in T1 breast carcinomas through the expression of different effectors along with tumor cell differentiation.

Apoptosis↗
PubMed1998

Risk factors for surgical site infections diagnosed after hospital discharge.

A prospective cohort study on 1103 consecutive patients undergoing general surgery with a follow-up of up to 30 days was undertaken to analyse the risk factors for surgical-site infection (SSI). Relative risks (RRs), crude and multiple-risk factors adjusted for by logistic regression analysis, and their 95% confidence intervals were calculated. One hundred and four patients (9.4%) developed infection, 81 in hospital and 23 at home. Predictors for in-hospital SSI differed from those for post-discharge SSI. In a crude analysis, an increased risk of post-discharge SSI occurred after clean-contaminated surgery (but not contaminated surgery). Stepwise logistic regression failed to identify any significant predictor for post-discharge SSI.

Adult↗
PubMed1998

A randomized, blinded, comparative trial of one pepsin-digested and two whole IgG antivenoms for Bothrops snake bites in Uraba, Colombia. The Regional Group on Antivenom Therapy Research (REGATHER).

The therapeutic efficacy and the incidence of early antivenom reactions (EARs) were compared in a clinical trial performed in 79 patients bitten by Bothrops sp. in Urabá, Colombia. Patients were randomized into three groups according to the antivenom administered: A (n = 30, Butantan polyspecific, pepsin-digested Bothrops antivenom); B (n = 27, Butantan polyspecific, whole IgG Bothrops antivenom); and C (n = 22, Colombian commercial, monovalent, whole IgG Bothrops antivenom). The groups were comparable in all clinical and epidemiologic aspects; 33 patients had mild, 22 moderate, and 24 severe envenoming. At the doses used (two, four, and six vials [10 ml/vial] for mild, moderate, and severe envenomings, respectively) there were no differences between the antivenoms in restoring normal hemostatic parameters within 24 hr. The evolution of local envenoming was comparable in the three groups. Serum venom/antivenom kinetics determined by ELISA showed a complete clearance of venom levels 1 hr after treatment in mild/moderate envenomings. In severe cases, venom levels remained detectable up to 24 hr and recurrence of antigenemia was observed in some cases. Antivenom concentrations remained at high levels up to 24 hr of treatment. The incidence of EARs was significantly different in the groups: A (36.7%), B (11.1.%), and C (81.8%). There were no life-threatening anaphylactic reactions. We conclude that the efficacy of the three antivenoms was similar in neutralizing human Bothrops envenomings and that the production of whole IgG antivenoms by caprylic acid fractionation is a good alternative for reducing the incidence of EARs.

Adolescent↗
PubMed1998

[Impact of zidovudine treatment and the pneumocystis carinii prophylaxis in natural history of patients with HIV infection].

INTRODUCTION: Early use of prophylactic regimens against Pneumocystis carinii and zidovudine therapy, may have modified the natural history of patients with HIV-1 infection. We describe the incidence of opportunistic infections and analize the mortality rate in those patients to check the occurrence of any change in the above mentioned natural history. PATIENTS: Clinical charts of patients with HIV-1 infection attending our hospital are reviewed, from november 1987 to june 1994. RESULTS: We found 200 patients with AIDS, documenting 64 (32%) deaths and 69 (34.5%) patients lost to follow-up. Seven HIV-1 infected patients (3.5%) received primary prophylaxis against Pneumocystis carinii and 17 (8.5%) zidovudine therapy before developing AIDS. Patients with AIDS receiving zidovudine therapy had a higher survival (median 50 months) than those not receiving such therapy (median 17 months; p < 0.001). Ninety one patients with tuberculosis receiving zidovudine therapy had also a higher survival than those not receiving antirretroviral therapy (p < 0.01). Eighty six patients with Pneumocystis carinii pneumonia receiving zidovudine had also a higher survival (p < 0.001). Likewise, patients on zidovudine treatment had a lower reduction on CD4 lymphocyte count. CONCLUSIONS: The spectrum of AIDS-defining illnesses is similar to the whole country. We have not found any difference in the incidence of opportunistic infections, but we observed a trend to reduction in the incidence rate of PCP. The introduction of zidovudine therapy seems to have a positive influence on the survival of AIDS patients. This advantage is highlighted in those patients more immunodeficients at first.

AIDS-Related Opportunistic Infections↗
PubMed1997

D2 receptor-mediated inhibition of GABA release by endogenous dopamine in the rat globus pallidus.

Attempting to better understand the role of the dopaminergic innervation in the rat globus pallidus, we examined here whether or not endogenous dopamine modulates the release of [3H]GABA in superfused pallidal slices. The superfusion medium contained elevated (15 mM) potassium. The release of endogenous dopamine was induced by the dopamine releaser drug, methamphetamine. Methamphetamine (100 microM) inhibited by 46% the release of [3H]GABA. Methamphetamine inhibition was completely blocked by reserpinization of the rats. It was also completely blocked by the D2 dopamine receptor antagonist sulpiride (10 microM). Sulpiride alone caused a 105% increase in GABA release. The increase was not observed in slices from reserpinized rats. Quinpirole (10 microM), a D2 dopamine receptor agonist, inhibited (43%) [3H]GABA release. The results suggest that endogenous dopamine exerts an inhibitory effect on GABA release in the rat globus pallidus. The effect is mediated by D2 receptors presumably located on striatopallidal axon terminals.

Animals↗
PubMed1997

Astrocyte-derived cytokines contribute to the metastatic brain specificity of breast cancer cells.

The occurrence of breast cancer metastases is preferential to certain organs. Astrocytes may play an important role in the development of brain metastases, as these cells have been shown to respond to extracellular stimuli by producing many cytokines and growth factors that can modulate tumor cell proliferation, growth, and/or metastases. To test this hypothesis, we analyzed the responses of the human breast cancer cell line MDA-MB-435 and its metastatic sublines to astrocyte primary cultures from newborn rat cerebra. Astrocyte purity of the glial cell cultures was demonstrated by glial fibrillary acidic protein and rat neural antigen-2 (Ran-2) immunopositive staining. The 435-Br1 cell line, which was derived from a brain metastases in a nude mouse, showed increased adhesion to astrocytes and enhanced growth in vitro in the presence of media from Con A-stimulated astrocytes, relative to the parental MDA-MB-435 and the lung metastasis-derived variant 435-Lung2. Furthermore, the growth-stimulatory effect was partially reversed by anti-IL-6, anti-transforming growth factor beta (anti-TGF beta), and anti-IGF-I antibodies, indicating that these metastatic cells use exogenous cytokines as paracrine growth factors. In an attempt to elucidate the role of several biologic-response modifiers produced by astrocytes, we tested the responses of MDA-MB-435 cells to purified cytokines and growth factors. We found that the addition of recombinant human or mouse IL-6 produced a variety of responses in the different 435 metastatic variants. Furthermore, IL-6 receptor (IL-6R) expression was slightly increased in the 435-Br1 cells, and exogenous IL-6 rescued 435-Br1 cells from apoptosis in serum-depleted cultures. No apoptotic protective effect was observed in either MDA-MB-435 parental cells or 435-Lung2 cells. Thus, responses to exogenous IL-6 might determine the differences among these metastatic variants by extending cell survival of selected subpopulations, giving them the opportunity to respond to growth factors or other favorable conditions that might be present. These results suggest that cytokines produced by glial cells in vivo may contribute, in a paracrine manner, to the development of brain metastases by breast cancer cells.

Adult↗
PubMed1997

Ductal carcinoma in situ of the breast: correlation between histologic classifications and biologic markers.

The expression of hormone receptors (estrogen and progesterone), c-erb-B2 (neu), p53, and Ki-67) was studied by immunohistochemical analysis in a series of 94 carcinomas in situ of the breast. The tumors were classified in two (high grade vs. low grade) and three (high grade vs. intermediate grade vs. low grade) categories. High-grade carcinomas were well defined by biologic markers showing statistically significant differences for all of the parameters tested. No clear biologic distinction, however, between low-grade and intermediate-grade cancers could be obtained. Negative progesterone receptors and a high proliferative index are the best discriminant parameters for the final assignment of doubtful cases.

Adult↗
PubMed1996

Muscarinic antagonists microinjected into the subthalamic nucleus decrease muscular rigidity in reserpinized rats.

The ability of anticholinergic agents microinjected into the subthalamic nucleus to reduce reserpine-induced muscular rigidity was assessed in rats. The electromyographical activity of the gastrocnemius-soleus muscle was used as a parameter of muscular rigidity. Reserpine (5 mg/kg i.p.) produced the appearance of electromyographical activity. The muscarinic antagonists M3 (1.27 nmol of 4-DAMP) and M1 (2.36 nmol of pirenzepine) markedly reduced the reserpine-induced electromyographical activity, whereas the M2 antagonist AFDX-116 (2.37 nmol) had no effect. These results suggest that a high cholinergic tone in the subthalamic nucleus is associated with the reserpine-induced muscular rigidity. Moreover, the M3 muscarinic antagonist is more effective than the M1 muscarinic antagonist in reducing the muscular rigidity in reserpinized rats, a model of Parkinson's disease, by blocking the high cholinergic tone in the subthalamic nucleus.

Anesthetics, Intravenous↗
PubMed1996

M3 muscarinic receptors mediate cholinergic excitation of the spontaneous activity of subthalamic neurons in the rat.

The effect of the muscarinic antagonist on carbachol-induced increase in spontaneous activity of neurons of the subthalamic nucleus was examined by recording the extracellular unitary activity in an in vitro slice preparation. Carbachol produced (98% of the 263 neurons tested) an increase (twofold of the basal at 500 nM) of the discharge frequency. The EC50 for the carbachol-induced effect was 375 +/- 8.7 nM (mean +/- SEM). The response was blocked by muscarinic antagonists in a dose dependent manner. However, the IC50 (94 +/- 3 nM) for the M3 antagonist 4-diphenyl acetoxy-N-methyl piperidine methobromide (4-DAMP) was considerably less than the other muscarinic antagonists (M1 antagonist pirenzepine, IC50 1340 +/- 110 nM; M2 antagonist AF-DX-116, IC50 6780 +/- 690 nM). These results suggest that the cholinergic input to the rat subthalamic nucleus exerts a postsynaptic excitatory action and this effect is likely mediated via muscarinic receptor type 3.

Animals↗
PubMed1996

High frequency of altered HLA class I phenotypes in invasive breast carcinomas.

We studied 105 tumor samples obtained from patients diagnosed as having breast carcinomas for HLA class I and II (DR) antigen expression, using a panel of mAbs defining HLA-monomorphic, locus-specific and allele-specific determinants. Peripheral blood lymphocytes from patients were also typed for HLA alleles. The results indicated total HLA class I losses in 55 patients (52.3%), HLA-A locus losses in four patients (3.8%), HLA-B locus losses in eight patients (7.6%), and A, B, locus losses in 10 patients (9.5%). The remaining 28 patients whose tissues reacted positively with monomorphic- and locus-specific mAbs were tested for HLA allelic losses using several anti-HLA mAbs defining A2, A3, A9, B8, B12, etc. Of these 28 patients, 16 (57%) showed one or more losses of HLA reactivity. These results indicated that in 88.5% of patients we detected a particular HLA-altered tumor phenotype. The downregulation of HLA class I antigens in breast carcinomas may thus be more frequent than previously reported, and patients without HLA class I downregulation may be the exception rather than the rule. It cannot be ruled out that HLA alterations are present in some of the 12 patients with an apparently normal HLA phenotype, as some HLA alleles could not be studied because of the lack of appropriate mAbs. These HLA alterations could represent an important step associated with tumor invasion, conferring to the tumor cells the ability to escape from T-lymphocyte recognition.

Antibodies, Monoclonal↗
PubMed1995

Cadmium and mercury toxicity in a human fetal hepatic cell line (WRL-68 cells).

The toxic effects of cadmium (Cd) and mercury (Hg), as chloride salts, were studied using an hepatic human fetal cell line (WRL-68 cells). From viability curves and the proliferative capacity of the cell in the presence of the metal, three different cell treatments were chosen, (1) 0.5 microM of the metal chloride for 24 h (acute low dose treatment), (2) 0.5 microM of the metal chloride for 7 days (chronic treatment), and (3) 5 microM of the metal chloride for 24 h (acute high dose treatment). WRL-68 cells grown in the presence of Cd exhibited the same proliferative curve as control cells, whereas in the case of Hg, the cells increased their proliferative capacity. Both metals produced ultrastructural alterations in different degrees, mainly observed as mitochondrial and RER structural changes, depending of the treatment and concentration of the metal used. Cytotoxicity was assessed by measuring the release of lactate dehydrogenase from the cells. Acutely high dose-treated cells showed the highest value for this parameter, and Cd-treated cells presented higher lactate dehydrogenase release than the Hg-treated ones. Cell damage was also measured by alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) activities. Acute high dose Cd treatment caused the highest value of enzymatic release. Lipid peroxidation was significantly different with respect to control cells in chronic and acute high dose treatments with both metals. Metallothionein (MT) induction in response to Hg treatment was not detected. However, a dramatic induction of this protein occurred in Cd-treated cells. WRL-68 cells differentially respond to Cd and Hg making this hepatic fetal human cell line a useful tool in investigating the mechanism of toxicity of these heavy metals.

Cadmium↗
PubMed1995

5-Hydroxytryptamine increases spontaneous activity of subthalamic neurons in the rat.

The effect of 5-hydroxytryptamine on the spontaneous activity of neurons of the subthalamic nucleus was examined by recording the extracellular unitary activity in an in vitro slice preparation. The most frequent response to 5-hydroxytryptamine (84% of 57 neurons tested) was an increase (twofold of basal at 10 microM) of the discharge frequency. The EC50 for the 5-hydroxytryptamine-induced effect was 1.8 +/- 0.5 microM (mean +/- SEM). The response was dose-dependently blocked by the serotoninergic antagonist mianserin and was not prevented by removal of calcium ions from the perfusing buffer. These results indicate that the serotoninergic input to the rat subthalamic nucleus exerts a postsynaptic excitatory action on most neurons of the nucleus.

Animals↗
PubMed1995

Bcl-2 expression is associated with lymph node metastasis in human ductal breast carcinoma.

The Bcl-2 proto-oncogene product blocks apoptosis. We retrospectively studied Bcl-2 expression in 124 primary tumors from patients diagnosed with T1 (2 cm or less) breast carcinoma with (T1N1) or without (T1N0) lymph-node metastasis. Bcl-2 protein was detected by immunohistochemistry on paraffin-embedded tissue sections. Multivariate logistic regression modeling was used to estimate prevalence odds ratios for lymph-node metastasis. Bcl-2 was widely expressed among T1 tumors showing a strong positive relationship with estrogen (ER)- and progesterone (PR)-receptor-positive tumors. However, a significant inverse correlation was seen between Bcl-2 expression and histological grade, Bcl-2 being absent in the majority of T1 undifferentiated tumors (grade-III carcinomas). Furthermore, Bcl-2 was more frequently expressed in T1N1 cases (72.2%) than in T1N0 specimens (45.7%). The odds for lymph-node metastasis in the Bcl-2-positive group was 3.6 times larger than that in the Bcl-2-negative group. The co-expression of PR significantly modified the effect of Bcl-2 on the odds for lymph-node metastasis, suggesting the existence of a synergistic interaction between the 2 parameters. We studied the percentage of dead cells in primary tumors by in situ DNA fragmentation (FDNA), and found an inverse correlation between Bcl-2 expression and FDNA. This supported the hypothesis that Bcl-2 extends cell survival. In conclusion, our study provides evidence that Bcl-2 expression is involved in breast-cancer progression, at least in a subset of well-differentiated and PR-positive tumors.

Adult↗
PubMed1995

D-1 receptor mediated modulation of the release of gamma-aminobutyric acid by endogenous dopamine in the basal ganglia of the rat.

1. Presynaptic D1 receptors are present on GABAergic terminals of neostriatal projections. 2. By activating these receptors, exogenous dopamine enhances the release of GABA. 3. Here the authors have explored whether endogenous dopamine was also able to activate the receptors, thus enhancing GABA release. 4. The effect of methamphetamine, a dopamine releaser, on the release of tritiated GABA was studied in slices of substantia nigra pars reticulata, entopeduncular nucleus and caudate-putamen, targets of the striatal projections. 5. Methamphetamine enhanced the release of the label. However the enhancement required an intact dopaminergic innervation, since it was lost in slices isolated from rats with 6-hydroxydopamine-induced lesions of the dopaminergic nigrostriatal system. 6. The activation of the receptors by endogenous dopamine was also judged by the effect of the selective D1 antagonist SCH 23390 in potassium depolarized slices. By preventing activation of the receptors by dopamine released as result of depolarization, the antagonist reduced GABA release. In 6-OHDA lesioned slices, no reduction was observed, even though the slices were also depolarized. 7. The results indicate that endogenous dopamine enhances GABA release from striatal terminals in the pars reticulata of the substantia nigra, entopeduncular nucleus and caudate-putamen. This would facilitate GABAergic neurotransmission. 8. The study suggests that the function of DA in the basal ganglia is widespread, modulating not only the firing of the striatal efferent neurons but also the transmission of the fired impulses across synapses in the target nuclei of these neurons.

Animals↗
PubMed1995

Determination of the susceptibility in vitro of 54 isolates of Mycobacterium fortuitum against three fluoroquinolones using two methods.

The in vitro susceptibility to ofloxacin, norfloxacin and ciprofloxacin or 54 Mycobacterium fortuitum isolates originating from clinical samples (7) of patients attending the Hospital Universitario de Canarias and Hospital del Tórax, and from environmental (47) sources, were determined. For this, two methods were used: dilution in agar with Middlebrook 7H10 Agar as a base medium culture, and broth microdilution, with Mueller-Hinton Broth without supplement. The different isolates under study revealed a uniform susceptibility by both methods against ciprofloxacin. 100% inhibition was obtained from a Minimum Inhibitory Concentration (MIC) of 0.25 microgram/ml, and 2 micrograms/ml of ciprofloxacin, for broth microdilution and dilution in agar, respectively. For ofloxacin and norfloxacin, all the isolates were inhibited at an MIC of 0.5 microgram/ml, by the broth microdilution method, which contrasted sharply with an MIC of 32 micrograms/ml, in the case of dilution in agar. In this study, we have observed the existence of differences in the in vitro susceptibility of the isolates of M. fortuitum against the three fluoroquinolones assayed, mainly for ofloxacin and norfloxacin, by both methods. We, therefore, consider it necessary to establish a standardized, reproducible assay method, for the study of sensitivity to atypical mycobacteria.

Anti-Infective Agents↗