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Biomedical subjects

M Perez

Publications and source records attributed to M Perez.

At least 91 records · Page 5Linked to original sources
PubMed1997

Thyrotropin (TSH) receptor autoantibodies do not appear to bind to the TSH receptor produced in an in vitro transcription/translation system.

An in vitro transcription/translation (TnT) system was used to produce 35S-labeled full-length TSH receptor (TSHR) and TSHR extracellular domain (TSHRex). The interaction of the labeled proteins with TSHR autoantibodies in Graves' sera was then studied using an immunoprecipitation assay. In the assay, 35S-labeled TSHR or TSHRex were incubated with test sera, and any immune complexes formed were precipitated with protein A-Sepharose (in the case of mouse monoclonal antibodies, antimouse IgG-agarose was used). Rabbit antibodies to the TSHR and a mouse monoclonal antibody precipitated as much as 50% of the 35S-labeled TSHR preparations compared with about 2% for normal rabbit serum and 4% for a control monoclonal antibody. However, none of 34 Graves' sera (TSHR autoantibody levels ranging from 14-95% inhibition of [125I]TSH binding) were able specifically to immunoprecipitate 35S-labeled TSHR or TSHRex. These negative findings were confirmed by analysis of the immunoprecipitates on SDS-PAGE followed by autoradiography. Our results indicate that the TnT system is not useful for producing labeled TSHR preparations that can bind TSHR autoantibodies well. This is in contrast to TnT produced 35S-labeled glutamic acid decarboxylase, thyroid peroxidase, and 21-hydroxylase, which react well with their respective autoantibodies. One main difference between these 3 autoantigens and the TSHR is that the receptor is highly glycosylated, and this extensive glycosylation may be of critical importance for correct folding of the receptor. Consequently, the inability of the TnT system to glycosylate proteins could explain in part why TnT-produced 35S-labeled TSHR and TSHRex do not bind TSHR autoantibodies.

Animals↗
PubMed1997

The toxic and accumulative effects of short-term exposure to cadmium in rainbow trout (Oncorhynchus mykiss).

Groups of 20 trout (Oncorynchus mykiss) were exposed for 3-w periods to different subacute oral doses of Cl2Cd (0.01, 0.025 or 0.05 microgram Cd/mL). Cadmium toxicity and accumulation were studied in kidney, liver, gills, muscle and brain weekly. Cadmium determination was carried out using atomic absorption spectrocopy (AAS) with graphite furnace. After 21 d exposure, cadmium concentrations increased significantly. In all tissues studied except muscle and brain. Cadmium storage presented the following sequence: kidney > liver > gills. At the beginning, cadmium accumulation was linearly dose dependent (r = 0.999). Then, at the highest dose (0.05 microgram Cd/mL) accumulation increased rapidly during the second week of exposure until equilibrium was reached. In contrast, liver did not accumulate cadmium selectively, suggesting that liver is able to eliminate cadmium, perhaps through metallothionein formation. Cadmium levels in gills were higher than controls (P < 0.05) and showed signs of equilibrium after the first week. According to organ weight/body weight ratios, there was similar accumulation behavior. Liver and kidney ratios increased dose dependently, but gills and brain did not have significant differences.

Absorption↗
PubMed1996

Serotonin dimers: application of the bivalent ligand approach to the design of new potent and selective 5-HT(1B/1D) agonists.

A series of serotonin dimers of formula 4 in which two serotonin moeities are linked together through their 5-hydroxyl residue has been prepared and evaluated as 5-HT(1B/1D) receptor agonists. Binding experiments at cloned human 5-HT(1B), 5-HT(1D), and 5-HT(1A) receptors show that all of these dimers are very potent ligands at 5-HT(1B/1D) receptors with increased binding selectivity vs the 5-HT(1A) receptor when compared to serotonin. Studies of inhibition of the forskolin-stimulated c-AMP formation mediated by the human 5-HT(1B) receptor (formerly the 5-HT(1Dbeta) receptor) demonstrate that all of these serotonin dimers behave as full agonists. Among them, the piperazide derivatives of bis-serotonin, 4g,j, were also identified as very potent agonists in contracting the New Zealand white rabbit saphenous vein (pD2 = 7.6 in each case compared to 5.8 for sumatriptan). Results analysis supports the hypothesis that the important increase in potency of the serotonin dimers can be attributed to the presence of two serotonin pharmacophores in the same molecule, while the enhanced selectivity for 5-HT(1B/1D) receptor subtypes may be due to the position of the spacer attachment to serotonin.

Animals↗
PubMed1996

Regulation of epidermal growth factor receptor activity by crotoxin, a snake venom phospholipase A2 toxin. A novel growth inhibitory mechanism.

Crotoxin (CT), a phospholipase A2 (PLA2) derived from the venom of Crotalus durissus terrificus, is a heterodimeric protein composed of subunit B with enzymatic activity and a binding regulatory subunit (A) without enzyme activity. Although the PLA2 activity of CT may be important in its anti-proliferative activity, its cytostatic mechanism is unknown. In this study, we examined the cytostatic effect of PLA2-associated CT activity on squamous carcinoma cells expressing distinct levels of epidermal growth factor receptor (EGFr). CT was most effective in suppressing growth on cells expressing high intrinsic levels of EGFr. Cardiotoxin, another membrane active toxin with no intrinsic PLA2 activity, had no differential anti-proliferative activity on cells expressing high EGFr levels, suggesting a correlation between EGFr expression and CT-directed anti-proliferative activity. Both chemically modified CT (MCT) devoid of PLA2 activity and covalently cross-linked CT (CCT), which is functionally unable to utilize cellular membranes as PLA2 substrate, were also without growth inhibitory activity. No evidence for direct binding of CT to EGFr was found, although pretreatment with EGF was able to partially suppress the anti-proliferative activity of CT. Tyrosine phosphorylation of EGFr, however, was stimulated by CT in intact A431 cells. Tyrosine phosphorylation of EGFr was concentration-dependently stimulated (3- to 8-fold) in cellular membranes of A431 cells treated in vitro with CT but not with anti-proliferatively inactive MCT or CCT. The data provide evidence for transmembrane receptors involved in growth signaling (namely EGFr) as cellular targets and potential effectors of PLA2-mediated anti-proliferative activity of snake venom.

Animals↗
PubMed1996

Zfp60, a mouse zinc finger gene expressed transiently during in vitro muscle differentiation.

The complete cDNA coding sequence of the zinc finger gene Zfp60 is reported. The predicted amino acid sequence of the Zfp60 protein has been found to contain 19 zinc finger motives clustered at the C-terminus. At its N-terminus, Zfp60 shares with other members of the zinc finger gene family two additional conserved amino acid modules named Kruppel Associated Boxes (KRAB). The expression patterns of Zfp60, MyoD and MHC mRNAs have been followed during in vitro myogenic differentiation of C2 cells. We show that the bacterial produced Zfp60 protein binds DNA only in presence of zinc ions. Zfp60 locus has been mapped in chromosome 7, where other Zfp loci are localised.

Amino Acid Sequence↗
PubMed1996

Total body calcium and bone mineral content: comparison of dual-energy X-ray absorptiometry with neutron activation analysis.

The aim of this study was to compare the dual-energy X-ray absorptiometry (DXA) measurement of bone mass with an independent measure of body calcium obtained by neutron activation analysis (NAA). Total body bone mineral content (BMC) was measured using DXA in 46 subjects in the age range 5-47 years (17 children, 28 young women, and 1 adult male). Total body calcium (TBCa) was measured in the same subjects by in vivo NAA. The correlation between the two measures of bone mass was highly significant (BMC[g] = 3.22 x TBCa[g] - 51.4, r > 0.98, p < 0.0001, SEEBMC = 122.7 g). When BMC was the independent parameter, the SEETBCa was 37.5 g. Bland-Altman analysis indicated a mean difference of 2.8 g with a standard error +/- 4.7 g for TBCaNAA versus TBCaDXA when the BMC values were converted to TBCa. The relative change in bone mass (delta TBCa/delta BMC) for DXA was higher than that reported for dual-photon absorptiometry versus NAA. The findings presented in this study provide translational equations among the DXA and NAA measurements and for the conversion of total body BMC to TBCa in children and young adults.

Absorptiometry, Photon↗
PubMed1996

Gas generation and preconcentration coupled to gas phase molecular absorption spectrometry: a powerful tool for the simultaneous determination of analytes forming volatile compounds.

Different methods for a simultaneous determination of several analytes forming volatile compounds at room temperature are described. The main steps of these methods are: continuous generation, collection in a cryogenic trap, revolatilization, measurement of the volatile compounds by Gas Phase Molecular Absorption Spectrometry and resolution by multi-wavelength methods. Several mixtures containing 2, 3 or 4 components have been studied: 1) elements forming covalent hydrides; 2) arsenic organometallic compounds forming volatile gases with a similar structure to arsine; and 3) sulphur species that can evolve volatile compounds. Under the optimum conditions obtained for each mixture, detection limits range from 0.8 ng/mL (dimethylarsinic acid) to 2 microg/mL (SCN(-)).

Journal Article↗
PubMed1996

The behavioral treatment of auditory hallucinatory responding of a schizophrenic patient.

This study assessed the efficacy of a behaviorally based treatment package to decrease the frequency of verbal responding to auditory hallucinations and to increase attention to important external stimuli, rather than to the hallucinations. The subject, a 49-year-old male, with a 20-year history of auditory hallucinatory responding (AHR), laughing and talking to himself, was seen in an outpatient clinic. Observations were made during management skill training, given usually twice a week. Observation sessions were divided into 15-minute intervals. The intervention package included reinforcement in the form of praise, pats on the back, and token reinforcement contingent on the absence of auditory hallucinations. Cancellation tests were given to measure his ability to attend to external tasks. Using an ABCAD design, it was seen that the data indicated that the intervention resulted in both a sharp decrease in auditory hallucinations and an increase in the subject's ability to attend to external tasks.

Attention↗
PubMed1996

Activation of epidermal growth factor receptor tyrosine phosphorylation by tumor necrosis factor correlates with loss of cytotoxic activity.

TNF induces cytotoxicity in human tumor cells through a receptor-mediated process with unknown signaling characteristics. Evidence suggests that overexpression of transmembrane growth factor receptors with intrinsic tyrosine kinase activity may suppress the antiproliferative or cytotoxic activity of TNF, suggesting antagonism between these two signaling pathways in tumor cells. To investigate TNF cytotoxic signal transduction, ME-180 cervical carcinoma cell variants were isolated that expressed complete cytotoxic sensitivity (ME-180S) or resistance (ME-180R) to TNF but identical levels of p55 TNF receptor expression. ME-180R cells expressed threefold higher EGFR than the ME-180S cell line and TNF treatment stimulated EGFR tyrosine phosphorylation only in resistant cells. Activation of tyrosine phosphorylation in ME-180R cells was TNF concentration dependent and maximally stimulated (three- to-five-fold) after 10-15 minutes of treatment. Other tyrosine phosphoproteins were not affected by TNF incubation demonstrating specific TNF-stimulated tyrosine phosphomodulation of EGFR. Pretreatment with the tyrosine kinase inhibitor tryphostin before incubation with TNF resulted in partial reversal of TNF cytotoxic resistance in ME-180R cells and enhanced TNF responsiveness in ME-180S cells, suggesting a "protective" role for tyrosine phosphorylation in TNF-induced cytotoxicity. Together these results demonstrate that TNF-mediated tyrosine phosphorylation is differentially regulated in sensitive and resistant tumor cells and may play a critical role in the cytotoxic signaling process through differential expression or regulation of tyrosine protein kinases and phosphatases.

Cell Survival↗
PubMed1996

Ehrlichia canis-like agent isolated from a man in Venezuela: antigenic and genetic characterization.

We report the first isolation and molecular and antigenic characterization of a human ehrlichial species in South America. A retrospective study was performed with serum specimens from 6 children with clinical signs suggestive of human ehrlichiosis and 43 apparently healthy adults who had a close contact with dogs exhibiting clinical signs compatible with canine ehrlichiosis. The evaluation was performed by the indirect fluorescent-antibody assay with Ehrlichia chaffeensis Arkansas, Ehrlichia canis Oklahoma, and Ehrlichia muris antigens. The sera from two apparently healthy humans were positive by the indirect fluorescent-antibody assay for all three antigens. Of the three antigens, samples from humans 1 and 2 showed the highest antibody titers against E. chaffeensis and E. muris, respectively. The remaining serum samples were negative for all three antigens. One year later examination of a blood sample from subject 1 revealed morulae morphologically resembling either E. canis, E. chaffeensis, or E. muris in monocytes in the blood smear. The microorganism, referred to here as Venezuelan human ehrlichia (VHE), was isolated from the blood of this person at 4 days after coculturing isolated blood leukocytes with a dog macrophage cell line (DH82). The organism was also isolated from mice 10 days after intraperitoneal inoculation of blood leukocytes from subject 1. Analysis by electron microscopy showed that the human isolate was ultrastructurally similar to E. canis, E. chaffeensis, and E. muris. When the virulence of VHE in mice was compared with those of E. chaffeensis, E. canis, and E. muris, only VHE and E. muris induced clinical signs in BALB/c mice at 4 and 10 days, respectively, after intraperitoneal inoculation. VHE was reisolated from peritoneal exudate cells of the mice. Only E. chaffeensis- and E. muris-infected mice developed significant splenomegaly. Western immunoblot analysis showed that serum from subject 1 reacted with major proteins of the VHE antigen of 110, 80, 76, 58, 43, 35, and 34 kDa. Human serum against E. chaffeensis reacted strongly with 58-, 54-, 52-, and 40-kDa proteins of the VHE antigen. Anti-E. canis dog serum reacted strongly with 26- and 24-kDa proteins of VHE. In contrast, anti-E. sennetsu rabbit and anti-E. muris mouse sera did not react with the VHE antigen. Serum from subject 1 reacted with major proteins of 90, 64, or 47 kDa of the E. chaffeensis, E. canis, and E. muris antigens. This reaction pattern suggests that this serum sample was similar to serum samples from E. chaffeensis-infected human patients in Oklahoma. The base sequence of the 16S rRNA gene of VHE was most closely related to that of E. canis Oklahoma. On the basis of these observations, we suggest that VHE is a new strain or a subspecies of E. canis which may cause asymptomatic persistent infection in humans.

Adult↗
PubMed1996

Recency effect in multiple sclerosis.

The main object of this study was to test acquisition-retrieval deficits in multiple sclerosis (MS) patients A Spanish version of the Rey Auditory-Verbal Test (RAVLT) (Rey 1964) was used with an MS group (n=10 subjects) and a control group (n=10) Different measurements were obtained with the RAVLT memory span, a learning curve, and a curve of serial position of words The results revealed no differences between groups in memory span and learning curve, but significant differences were found in the curve of serial position No revency effect in the immediate form of theRAVLT was seen These results are discussed with reference to the work of Baddelaey and Hitch (1993) regarding recency effects and related literature on the acquisition-retrieval deficits in MS patients.

Journal Article↗
PubMed1996

[Multifocal choroiditis associated with herpes zoster ophthalmicus. Apropos of a case].

We describe a patient with multifocal choroidal lesions affecting the midperipheral fundus, with an atrophic and scattered punched-out pale aspect. Lesions were discovered seven months after an ipsilateral herpes zoster ophthalmicus. Fluorescein angiography findings exhibited a delay of choroidal injection and late moderate staining during the venous phase. The etiological arguments refer to a previous herpes zoster infection. The pathogeny would involve an occlusion of posterior ciliary arteries, lesions of posterior ciliary nerves and/or direct cytopathogenic involvement of chorioretina by neurotropic virus from ciliary ganglion.

Adolescent↗
PubMed1995

Synthesis and serotonergic activity of arylpiperazide derivatives of serotonin: potent agonists for 5-HT1D receptors.

A series of new arylpiperazide derivatives of serotonin has been prepared and evaluated as 5-HT1D receptor agonists. Binding experiments at cloned human 5-HT1D alpha, 5-HT1D beta, and 5-HT1A receptors show that all the compounds are very potent and selective ligands for 5-HT1D receptor subtypes. Functional activity studies (contraction of the New Zealand white rabbit saphenous vein) demonstrate that most of the derivatives behave as full agonists. Among them, the aryl sulfonamide derivative 5q (pD2 = 8.33 compare to 5.75 for sumatriptan) was also identified as a very potent agonist in inhibiting the forskolin-mediated cyclase coupled to 5-HT1D beta receptors (EC50 = 0.52nM).

Animals↗
PubMed1995

E5531, a pure endotoxin antagonist of high potency.

Shock due to Gram-negative bacterial sepsis is a consequence of acute inflammatory response to lipopolysaccharide (LPS) or endotoxin released from bacteria. LPS is a major constituent of the outer membrane of Gram-negative bacteria, and its terminal disaccharide phospholipid (lipid A) portion contains the key structural features responsible for toxic activity. Based on the proposed structure of nontoxic Rhodobacter capsulatus lipid A, a fully stabilized endotoxin antagonist E5531 has been synthesized. In vitro, E5531 demonstrated potent antagonism of LPS-mediated cellular activation in a variety of systems. In vivo, E5531 protected mice from LPS-induced lethality and, in cooperation with an antibiotic, protected mice from a lethal infection of viable Escherichia coli.

Animals↗
PubMed1995

T-cell responses in photoimmune therapy.

The extracorporeal inactivation of a lymphocyte rich buffy coat suspension with ultraviolet A light and 8 methoxypsoralen can lead to dramatic clinical improvements following reinfusion of the damaged cells. This therapy is reviewed in the context of the disease it is most commonly used for: cutaneous lymphoma. Studies with cutaneous lymphoma patients have shown an active immune response against purified tumor cells. In addition a mouse model for an impact of therapy on a T-cell lymphoma has demonstrated results that parallel those from clinical studies in humans. The impact of photoimmune therapy on in vivo and in vitro T-cell responses to cutaneous lymphoma is discussed.

Antibody Formation↗
PubMed1995

Results of Delorme's procedure for rectal prolapse. Advantages of a modified technique.

PURPOSE: A retrospective study was undertaken to assess the results of Delorme's procedure for rectal prolapse and to determine the advantages of an innovative extended transrectal repair, which aims at performing a total pelvic floor repair. METHODS: A total of 85 patients, ranging in age from 21 to 97 years, were operated on. Sixty-five (82 percent) patients had varying degrees of fecal incontinence. Similar groups of patients were compared with regard to control of the prolapse and restoration of continence according to 1) age and medical condition and 2) operative technique: original vs. extended operation. RESULTS: Twelve patients (14 percent) developed postoperative complications. There was one perioperative death (1.2 percent). Eighty patients were followed for 6 to 136 (median, 33) months. Eleven (13.5 percent) developed recurrent full-thickness prolapse. The recurrence rate was significantly different 1) between 44 elderly and poor operative risk patients not suitable for abdominal surgery (22.5 percent) and 41 younger patients without concurrent medical conditions, electively submitted to perineal repair (5 percent) (P < 0.05), and 2) between the original procedure (21 percent of 44 patients) and the modified technique (5 percent of 41 patients) (P < 0.05). Forty five patients (69 percent) improved or regained full continence. No patient worsened. No residual dysfunction was induced. Restoration of continence was not influenced by selection of patients or surgical technique. CONCLUSIONS: Despite increased morbidity (22 percent; P < 0.05), advantages of the modified technique were 1) over the original procedure, a reduced recurrence rate, 2) over perineal proctectomy, the absence of coloanal anastomosis and better functional outcome, and 3) over abdominal rectopexy, a less aggressive approach without disturbing effects on bowel habits.

Adult↗