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Biomedical subjects

M Perez

Publications and source records attributed to M Perez.

At least 73 records · Page 4Linked to original sources
PubMed1998

Tumor necrosis factor-induced apoptosis stimulates p53 accumulation and p21WAF1 proteolysis in ME-180 cells.

Tumor necrosis factor (TNF)-mediated apoptotic signaling has been characterized by activation of specific protease or protein kinase cascades that regulate the onset of apoptosis. TNF has also been shown to induce oxidative or genotoxic stress in some cell types, and apoptotic potential may be determined by the cellular response to this stress. To determine the role of genotoxic stress in TNF-mediated apoptosis, we examined cellular accumulation of p53 in TNF-treated ME-180 cells selected for apoptotic sensitivity (ME-180S) or resistance (ME-180R) to TNF. Although TNF was able to activate receptor-mediated signaling in either cell line, p53 accumulation was measurable only in apoptotically sensitive ME-180S cells. TNF-induced changes in p53 levels were detected 1 h after treatment, and peak levels were measurable 4-8 h after TNF exposure. TNF was unable to induce p21WAF1 in either cell line but affected the stability of this protein in apoptotically responsive ME-180S cells. Evidence of p21WAF1 proteolysis was detected by monitoring the appearance of a 16-kDa immunoblottable p21WAF1 fragment, which became detectable 4 h after TNF addition and increased in content before the onset of DNA fragmentation (16-24 h). The kinetics of p21WAF1 proteolysis closely paralleled those of poly(ADP-ribose) polymerase, suggesting cleavage of p21WAF1 by activation of an apoptotic protease. Pretreatment of ME-180S cells with the apoptotic protease inhibitor YVAD blocked TNF-induced apoptosis and prevented both poly(ADP-ribose) polymerase and p21WAF1 degradation but did not affect p53 induction. These results provide evidence for the early onset of genotoxic stress in cells committed to TNF-mediated apoptosis and for divergence in propagation of this signal in non-responsive cells. In addition, TNF-induced p21WAF1 proteolysis may be mediated by an apoptotic protease and may contribute to the apoptotic process by disrupting p53 signaling, altering cell cycle inhibition, and limiting cellular recovery from genotoxic stress.

Amino Acid Chloromethyl Ketones↗
PubMed1998

Dimerization of 8-OH-DPAT increases activity at serotonin 5-HT1A receptors.

[35S]GTPgammaS binding responses can be used to measure differences between the intrinsic activity of ligands at human 5-hydroxytrypamine-(1A) (h 5-HT1A) receptors expressed in recombinant cell lines. The maximal [35S]GTPgammaS binding response to 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) was lower than that to 5-HT in a recombinant C6-glial membrane preparation and dependent on the GDP concentration: it was attenuated by about 60% vs 5-HT by increasing the concentration of GDP from 0.3 to 30 and 300 microM. Whereas dimerization of 8-OH-DPAT almost did not affect its potency at h 5-HT1A receptors (pEC50: 7.45 and 7.40 for 8-OH-DPAT and its dimer at 30 microM GDP), it increased efficacy at h 5-HT1A receptors. The maximal response to the 8-OH-DPAT dimer was systematically greater than the response to 8-OH-DPAT and identical to that to 5-HT; moreover in contrast to the 8-OH-DPAT monomer, the maximal response to the dimer was unaffected by increasing the GDP concentration. An enhanced 135S]GTPgammaS binding response (44 to 63% vs 8-OH-DPAT) was also observed in the hippocampus, lateral septum, dorsal raphe and cingulate cortex of guinea-pig brain sections using autoradiography of 5-HT1A receptor-activated G-proteins. Hence, the 8-OH-DPAT dimer shows increased efficacy at 5-HT1A receptors compared to 8-OH-DPAT. The differential regulation of the maximal agonist responses by GDP suggests that the [35S]GTPgammaS binding responses to these two ligands could be mediated by different G-protein subtypes upon activation of the 5-HT1A receptor.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1998

Introduction of cyclofem once-a-month injectable contraceptive in Mexico.

A large introductory study of Cyclofem, a once-a-month injectable contraceptive, was conducted in three Mexican provinces. A total of 3457 healthy women participated: 640 women from rural areas (community-based component) and 2817 women from urban and suburban areas (health center-based component). A total of 20,316 women-months of treatment experience were accumulated during a one year period. Cyclofem proved its use-effectiveness (pregnancy rate of 0.03%) and its safety under routine service conditions of family planning facilities in Mexico. The overall life table continuation rate at 1 year was 26.1%. Higher continuation rates were observed in the community-based component (36.6%) as compared to the health center component (23.7%). The most common reason for method discontinuation was change of address. Only 15% of the discontinuations were attributable to the injectable contraceptive method, with the overall 1 year discontinuation rate for bleeding problems (including amenorrhea) was < 11%. These observations underscore the importance of appropriate counseling and follow-up measures, providing convenient access to repeat injections, and other service delivery issues related to continuation of Cyclofem. The results of this trial have once again demonstrated that Cyclofem is a highly effective method with an acceptable side effect profile. In addition, the study provided the elements for its approval by local health authorities and its inclusion into the Ministry of Health Family Planning Program.

Adolescent↗
PubMed1998

Relationship between helminthic infection and IgE response in atopic and nonatopic children in a tropical environment.

BACKGROUND: Although IgE antibody is clearly involved in allergic reactions to environmental allergens, this immunoglobulin is an important component of host-protective immune responses against the helminthic parasites that are endemic in the majority of the world population. However, these infections not only stimulate the production of antiparasite IgE antibody but can nonspecifically induce polyclonal IgE synthesis that results in highly elevated total serum IgE levels. Such polyclonal stimulation can diminish specific IgE antibody responses and cause saturation of mast cell Fc epsilon receptors, thus inhibiting allergic reactivity. This may represent a mechanism of immune evasion by the parasite. OBJECTIVE: Because an atopic disposition is generally recognized to be associated with elevated IgE synthesis against environmental allergens, the aim of this study was to evaluate the influence of atopy on the antiparasite response. To this end, we examined two groups of Venezuelan children in whom the intestinal helminth Ascaris lumbricoides is endemic but that differ greatly in their level of atopy. One group was from an island population (Coche Island) that has a very strong atopic background and in which the prevalence of allergic disease is extremely high. The other was a group of nonatopic children belonging to a mainland population (Barrio Los Erasos) that is of comparable socioeconomic level and has an exposure to helminthic infection similar to that of the island group but a relatively low expression of allergic diseases. RESULTS: Although the living conditions and the prevalence of Ascaris infection of the two groups were comparable, the intensity of the parasitic infection was considerably higher in the nonatopic mainland children (geometric mean values of eggs per gram of feces: Barrio Los Erasos, 7621; Coche Island, 1435; p < 0.001). In addition, their total serum IgE levels were significantly more elevated than in the atopic island group (geometric mean: Barrio Los Erasos, 2172; Coche Island, 941 IU/ml; p < 0.001). In contrast, the specific anti-Ascaris response was much stronger in the atopic children (geometric mean: Barrio Los Erasos, 0.30; Coche Island, 0.91 PRU/ml; p < 0.001), which resulted in the ratio of specific to total IgE being nine times higher than in the nonatopic mainland subjects. These differences were maintained even when the children were matched on the basis of infection intensity, thus indicating that the atopic children have an intrinsic propensity to favor specific over polyclonal IgE responses to the parasite. CONCLUSIONS: The children with a strong atopic background demonstrated IgE responses concordant with an enhanced protective response against helminthic parasites and had significantly lower intensities of infection than their nonatopic counterparts. These observations support the concept that the atopic state has conferred a selective evolutionary advantage that could compensate for its involvement in allergic disease.

Animals↗
PubMed1998

p300/MDM2 complexes participate in MDM2-mediated p53 degradation.

Control of p53 turnover is critical to p53 function. E1A binding to p300/CBP translates into enhanced p53 stability, implying that these coactivator proteins normally operate in p53 turnover control. In this regard, the p300 C/H1 region serves as a specific in vivo binding site for both p53 and MDM2, a naturally occurring p53 destabilizer. Moreover, most of the endogenous MDM2 is bound to p300, and genetic analysis implies that specific interactions of p53 and MDM2 with p300 C/H1 are important steps in the MDM2-directed turnover of p53. A specific role for p300 in endogenous p53 degradation is underscored by the p53-stabilizing effect of overproducing the p300 C/H1 domain. Taken together, the data indicate that specific interactions between p300/CBP C/H1, p53, and MDM2 are intimately involved in the MDM2-mediated control of p53 abundance.

Cell Line↗
PubMed1998

The importance of family functioning to caregiver adaptation in mothers of child cancer patients: testing a social ecological model.

This study was designed to investigate associations between family relationships, personal-psychological caregiver adaptation (ie, depressive symptomatology, sense of burden), and ability to function within the health care system (perceived doctor-parent relationship) in mothers of child cancer patients. Data were collected through a survey of a sample of 29 mothers whose children were diagnosed with some form of childhood cancer, mainly leukemia. Family functioning was positively related to both caregiver adaptation and doctor-parent relationship. Mothers who reported decreased maternal depression and burden were significantly more likely to report respectively improved spousal relationships and improved spousal communication. Mothers reporting more positive doctor-parent relationships also described themselves as having improved relationships with spouse and child, and improved spousal communication. Maternal well-being and doctor-parent relationship were not directly related. By suggesting that both intrapsychic and instrumental maternal adaptation are influenced by positive relationships in the family, this study provides support for the social ecological model of stress. The possibility that family factors exert a direct influence on both caregiver intrapsychic well-being and instrumental skills argues for the importance of their being carefully considered in any models evaluating caregiver adaptation.

Adaptation, Psychological↗
PubMed1998

Phospholipase D- and protein kinase C isoenzyme-dependent signal transduction pathways activated by the calcitonin receptor.

The calcitonin receptor expressed by the porcine LLC-PK1 renal tubule cells is a seven-transmembrane domain, G protein-coupled receptor activating adenylyl-cyclase and phospholipase C. Salmon calcitonin stimulated dose- and time-dependent release of the phospholipase D-dependent phosphatidylcholine product [3H] choline with an EC50 = 2.5 +/-0.3 x 10(-8) M, similar to that determined for phosphoinositide metabolism (EC50 = 4.5 +/-1.0 x 10(-8)M). The hormone failed to induce release of [3H]phosphocholine and [3H]glycerophosphocholine, ruling out activation of phosphatydilcholine-specific phospholipase C and phospholipase A. Calcitonin stimulated phosphatidic acid, a product of phospholipase D-dependent phosphatydilcholine hydrolysis. Activation of phospholipase D was confirmed by release of [3H]phosphatydilethanol, a specific and stable product in the presence of a primary alcohol. Activation of calcitonin receptor induced diacylglycerol formation, with a rapid peak followed by a prolonged increase, due to activation of phospholipase C and of phospholipase D. Consequently, the protein kinase-C alpha, but not the delta isoenzyme, was cytosol-to-membrane translocated by approximately 50% after 20 min exposure to calcitonin, whereas protein kinase-C zeta, which was approximately 40% membrane-linked in unstimulated cells, translocated by approximately 19%. The human calcitonin receptor expressed by BIN-67 ovary tumor cells, although displaying higher affinity for calcitonin, failed to activate phospholipase D and protein kinase-C in response to the hormone. This receptor lacks the G protein binding consensus site due to the presence of a 48-bp cassette encoding for a 16-amino acid insert in the predicted first intracellular loop. This modification is likely to prevent the calcitonin receptor from associating to phospholipase-coupled signaling.

Animals↗
PubMed1998

Binding characteristics of antibodies to the TSH receptor.

We have used fragments of the TSH receptor (TSHR) expressed in E. coli as glutathione S-transferase fusion proteins to produce rabbit polyclonal antibodies and a panel (n=5) of monoclonal antibodies to the extracellular fragment of the TSHR. The binding characteristics of the antibodies to linear, conformational, glycosylated and unglycosylated forms of the receptor in different assay systems have been investigated. The reactivity of these antibodies with the TSHR was assessed by Western blotting with both native and recombinant human TSHR expressed in CHO cells, immunoprecipitation of 35S-labelled full-length TSHR produced in an in vitro transcription/ translation system, immunoprecipitation of 125I-TSH/TSHR complexes, inhibition of 125I-TSH binding to the TSHR and fluorescence activated cell sorter (FACS) analysis of binding to CHO-K1 cells expressing the TSHR on their cell surface. Fab fragments of monoclonal antibodies were isolated, labelled with 125I and used to determine the affinity constants of these antibodies with receptor, bound and free Fab being separated by polyethylene glycol (PEG) precipitation. Rabbit polyclonal and mouse monoclonal antibodies reacted with the TSHR in Western blotting and one monoclonal antibody (3C7) was able to inhibit 125I-TSH binding to native human TSHR (74% inhibition), recombinant human TSHR (84% inhibition) and porcine TSHR (65% inhibition). Affinity constant values for TSHR monoclonal antibody Fab fragments calculated using Scatchard analysis were about 10(7) M(-1). Four out of five monoclonal antibodies reacted in FACS analysis with TSHR expressed on the surface of CHO-K1 cells. The FACS unreactive monoclonal (3C7) bound well to detergent solubilised TSH receptors and this emphasised the importance of using a combination of FACS analysis and radioactively-labelled probes in analysis of the TSH receptor. The monoclonal antibodies produced in this study were found to be of relatively low affinity but proved useful for detection of the receptor by Western blotting and by FACS analysis.

Animals↗
PubMed1997

5-HT1B receptor antagonist properties of novel arylpiperazide derivatives of 1-naphthylpiperazine.

A new series of arylpiperazide derivatives of 1-naphthylpiperazine of general formula 4 has been prepared and evaluated as 5-HT1B antagonists. Binding experiments at cloned human 5-HT1A, 5-HT1B, and 5-HT1D receptors show that these derivatives are potent and selective ligands for 5-HT1B/1D subtypes with increased binding selectivity versus the 5-HT1A receptor when compared to 1-naphthylpiperazine (1-NP). Studies of inhibition of the forskolin-stimulated cAMP formation mediated by the human 5-HT1B receptor demonstrate that the nature of the arylpiperazide substituent modulates the intrinsic activity of these 1-NP derivatives. Among them, 2-[[8-(4-methylpiperazin-1-yl)naphthalen-2-yl]oxy] -1-(4-o-tolylpiperazin-1-yl)ethanone (4a) was identified as a potent neutral 5-HT1B antagonist able to antagonize the inhibition of 5-HT release induced by 5-CT (5-carbamoyltryptamine) in guinea pig hypothalamus slices. Moreover, 4a was found to potently antagonize the hypothermia induced by a selective 5-HT1B/1D agonist in vivo in the guinea pig following oral administration (ED50 = 0.13 mg/kg).

Animals↗
PubMed1997

Synthesis of a new zinc finger peptide; comparison of its 'code' deduced and 'CASTing' derived binding sites.

Using two synthetic oligonucleotides, we have constructed a new gene containing three zinc finger motifs of the Cys2-His2 type. We named this artificial gene 'Mago'. The Mago nucleotide triplets encoding the amino acid positions, described to be crucial for DNA binding specificity, have been chosen on the basis of the proposed recognition 'code' that relates the zinc finger's primary structure to the DNA binding target. Here we demonstrate that Mago protein specifically binds the 'code' DNA target, with a dissociation constant (Kd) comparable to the Kd of the well known Zif268 protein with its binding site. Moreover, we show that the deduced Mago 'code' and the 'experimental' selected DNA binding sites are almost identical, differing only in two nucleotides at the side positions.

Amino Acid Sequence↗
PubMed1997

Membrane permeability changes induced in Escherichia coli by the SH protein of human respiratory syncytial virus.

The small hydrophobic (SH) protein of human respiratory syncytial virus (HRSV) has been efficiently expressed in Escherichia coli. In analogy to small hydrophobic proteins encoded by other RNA viruses, membrane permeability changes to low-molecular-weight compounds were detected in bacteria expressing HRSV SH protein. These changes implied, at least, the entry of both the protein synthesis inhibitor hygromycin B and the beta-galactoside substrate o-nitrophenyl-beta-d-galactopyranoside and the exit of preloaded [3H]uridine from bacterial cells. Site-directed mutagenesis indicated that the C-terminal end of SH is needed for induction of membrane permeability changes. In addition, amino acid substitution at residue 32 (Ile to Lys) abolished that activity. This was correlated with a drastic increase in SH electrophoretic mobility and a decrease of the predicted values of alpha-helix for all residues of the SH transmembrane domain. Other sequence changes have either partial effect or no effect on the membrane permeability changes induced by the SH protein. However, none of the mutations abrogated the association of SH protein with bacterial membranes, indicating that incorporation of SH protein to membranes is not sufficient to induce the observed changes. Membrane permeability changes then might provide a useful test for the identification of key amino acid residues in this unique HRSV gene product.

Amino Acid Sequence↗
PubMed1997

Loss of low-affinity nerve growth factor receptor during malignant transformation of the human prostate.

BACKGROUND: The low-affinity nerve growth factor receptor (LNGFR) exhibits an inverse association of epithelial expression with the degree of differentiation of prostate adenocarcinoma tissue. However, the stage at which loss of LNGFR expression is first manifested in the malignant prostate has not been determined. METHODS: In order to characterize loss of LNGFR expression in the clinically localized malignant prostate of untreated patients, the pattern of expression of the LNGFR was examined in nonmalignant tissues, consisting of normal and prostatic intraepithelial neoplastic tissues, and in malignant tissues that had been graded by Gleason's scores and categorized into well, moderately, and poorly differentiated adenocarcinomas. In order to determine whether there was an inverse correlation between LNGFR expression and prostate-specific antigen (PSA) secretion, preoperative concentrations of PSA in the serum were also analyzed in relation to the differentiative state of the adenocarcinomas. RESULTS: Premalignant prostate tissues exhibited expression of the LNGFR on all epithelia, whereas in malignant prostate tissues a proportion of epithelia exhibited loss of expression of the LNGFR. An increase in Gleason score of the adenocarcinoma tissue was associated with an increase in the proportion of epithelia that exhibited loss of expression of the LNGFR. Moreover, the proportion of epithelia expressing the LNGFR was inversely correlated with an increase in the concentration of serum PSA. The loss of LNGFR expression was first manifested in epithelia that occurred toward the center of adenocarcinoma tissue. Furthermore, extensive loss of expression of the LNGFR of approximately 63% occurred in well-differentiated adenocarcinomas. CONCLUSIONS: These observations demonstrate that loss of LNGFR expression is first observed in well-differentiated malignant epithelia. Hence, loss of the LNGFR may be indicative of the initial stages of malignant transformation of prostate epithelia, as well as all subsequent stages of prostate adenocarcinomas.

Adenocarcinoma↗
PubMed1997

Short-term effects of prone position in critically ill patients with acute respiratory distress syndrome.

OBJECTIVE: Changing the position from supine to prone is an emerging strategy to improve gas exchange in patients with the acute respiratory distress syndrome (ARDS). The aim of this study was to evaluate the acute effects on gas exchange, hemodynamics, and respiratory system mechanics of turning critically ill patients with ARDS from supine to prone. DESIGN: Open, prospective study. SETTING: General intensive care units. PATIENTS: 23 patients [mean age 56 +/- 17 (SD) years] who met ARDS criteria and had a Lung Injury Score > 2.5 (mean 3.25 +/- 0.3). INTERVENTIONS: The decision to turn a patient was made using a protocol based on impaired oxygenation despite the use of positive end-expiratory pressure and a fractional inspired oxygen (FIO2) of 1. MEASUREMENTS AND RESULTS: We measured gas exchange and hemodynamic variables in all patients and in 16 patients calculated respiratory system compliance when they were supine and 60 to 90 min after turning them to a prone position. This latter position was remarkably well tolerated and no clinically relevant complications or events were detected either during turning or while prone. The partial pressure of oxygen in arterial blood (PaO2)/FIO2 ratio improved from 78 +/- 37 mm Hg supine to 115 +/- 31 mm Hg prone (p < 0.001), and intrapulmonary shunt decreased from 43 +/- 11 to 34 +/- 8% (p < 0.001). Cardiac output and other hemodynamic parameters were not affected. Respiratory system compliance slightly improved from 24.7 +/- 10.2 ml/cmH20 supine to 27.8 +/- 13.2 ml/cmH20 prone (p < 0.05). An improvement in PaO2/FIO2 of more than 15% from changing from supine to prone was found in 16 patients (responders). Responders had more hypoxemia (PaO2/FIO2 70 +/- 23 vs 99 +/- 53 mm Hg in non-responders, p < 0.01), more hypercapnia (partial pressure of carbon dioxide in arterial blood (70 +/- 27 vs 64 +/- 9 mm Hg, p < 0.01) and a shorter elapsed time to the onset of ARDS and turning to the prone position (11.8 +/- 16 vs 32.8 +/- 42 days, p < 0.01). CONCLUSIONS: Turning critically ill, severely hypoxemic patients from the supine to the prone position is a safe and useful therapeutic intervention. Our data suggest that prone positioning should be carried out early in the course of ARDS.

Adult↗
PubMed1997

Advances in dermatologic surgery.

The major advances in dermatologic surgery for this period reside in the areas of diagnosis and management of cutaneous melanoma, laser surgery, tumescent liposuction, and tumorigenesis. A closer look at these advances is presented.

Forecasting↗