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Biomedical subjects

G Perez

Publications and source records attributed to G Perez.

At least 37 records · Page 2Linked to original sources
PubMed1998

Structural models of antibody variable fragments: a method for investigating binding mechanisms.

The value of comparative molecular modeling for elucidating structure-function relationships was demonstrated by analyzing six anti-nucleosome autoantibody variable fragments. Structural models were built using the automated procedure developed in the COMPOSER software, subsequently minimized with the AMBER force field, and validated according to several standard geometric and chemical criteria. Canonical class assignment from Chothia and Lesk's [Chottin and Lesk, J. Mol. Biol., 196 (1987) 901; Chothia et al., Nature, 342 (1989) 877] work was used as a supplementary validation tool for five of the six hypervariable loops. The analysis, based on the hypothesis that antigen binding could occur through electrostatic interactions, reveals a diversity of possible binding mechanisms of anti-nucleosome or anti-histone antibodies to their cognate antigen. These results lead us to postulate that antinucleosome autoantibodies could have different origins. Since both anti-DNA and anti-nucleosome autoantibodies are produced during the course of systemic lupus erythematosus, a non-organ specific autoimmune disease, a comparative structural and electrostatic analysis of the two populations of autoantibodies may constitute a way to elucidate their origin and the role of the antigen in tolerance breakdown. The present study illustrates some interests, advantages and limits of a methodology based on the use of comparative modeling and analysis of molecular surface properties.

Amino Acid Sequence↗
PubMed1998

Behavioral and demographic risk factors for transmission of human immunodeficiency virus type 1 in heterosexual couples: report from the Heterosexual HIV Transmission Study.

We compared 224 heterosexual couples who were discordant for human immunodeficiency virus (HIV) type 1 infection (one partner HIV infected) with 78 HIV-concordant couples (both partners HIV infected) to identify demographic and behavioral risk factors for HIV transmission. Among the 229 couples whose male partner was first infected, HIV-concordant couples had engaged in anal sex more frequently before and after knowing that the male was infected than had HIV-discordant couples. Pap smears of grade 2 or higher (inflammation) were more prevalent among the second-infected female partners in HIV-concordant couples than among uninfected women in discordant couples (58% vs. 23%; P < .001). Anal sex and unprotected vaginal sex after knowledge of a male partner's infection were significant correlates of concordance in a multivariate logistic model, as were ethnicity, marital status, and antiviral therapy. Ethnicity strongly predicted concordance, even after controlling for sexual risk behaviors and stage of disease.

Adult↗
PubMed1998

Rates of tuberculosis infection in healthcare workers providing services to HIV-infected populations. Terry Beirn Community Programs for Clinical Research on AIDS.

OBJECTIVE: To assess the prevalence of tuberculosis (TB) or a positive skin test in healthcare workers (HCWs) providing services to human immunodeficiency virus (HIV)-infected individuals and to determine prospectively the incidence of new infections in this population. DESIGN: This prospective cohort study enrolled 1,014 HCWs working with HIV-infected populations from 10 metropolitan areas. Purified protein derivative (PPD) tuberculin skin tests were placed at baseline and every 6 months afterwards on those without a history of TB or a positive PPD. Demographic, occupational, and TB exposure data also were collected. SETTING: Outpatient clinics, hospitals, private practice offices, and drug treatment programs providing HIV-related healthcare and research programs. PARTICIPANTS: A voluntary sample of staff and volunteers from 16 Community Programs for Clinical Research on AIDS units. RESULTS: Factors related to prior TB or a positive skin test at baseline included being foreign-born, increased length of time in health care, living in New York City, or previous bacille Calmette-Guerin vaccination. The rate of PPD conversion was 1.8 per 100 person years of follow-up. No independent relation was found between the amount or type of contact with HIV-infected populations and the risk of TB infection. CONCLUSION: These data provide some reassurance that caring for HIV-infected patients is not related to an increased rate of TB infection among HCWs in these settings.

AIDS-Related Opportunistic Infections↗
PubMed1997

A comparative trial of zidovudine administered every four versus every twelve hours for the treatment of advanced HIV disease.

Zidovudine is approved for administration in doses given every 4 hours. Less frequent dosing has been used in many clinical trials, but the toxicity and efficacy of such regimens have not been formally compared with the approved regimen. In this multicenter, randomized, double-blind, controlled trial, the safety, tolerance and efficacy of 600 mg of zidovudine given daily in two or six divided doses were compared. Three hundred and twenty patients with a CD4 lymphocyte count < 250 cells/mm3 (mean, 104 cells/mm3) or a prior AIDS-defining illness were treated with zidovudine 100 mg every 4 hours (regimen A) or 300 mg every 12 hours (regimen B). Eighty-eight patients (56%) and 94 patients (58%), assigned to regimens A and B, respectively, completed the planned 48 weeks of treatment. Serious anemia (hemoglobin < or = 7.5 g/dl) occurred in 13% and 7% of patients treated with regimens A and B, respectively (difference, 6%, 95% confidence interval [CI], 2, 12%; p = .13). The mean duration of treatment and the frequency of neutropenia and symptomatic complaints including nausea and headache were similar in the two treatment groups. The number of patients experiencing a new opportunistic infection (18% versus 20% for regimens A and B, respectively), and the number of deaths (five in each group) did not differ significantly between groups. The effect of treatment on CD4 lymphocyte counts and HIV p24 antigenemia also was similar for both regimens. Zidovudine given at the more convenient dose of 300 mg twice daily has similar safety, and tolerance and appears to have similar efficacy to the currently approved regimen. Use of this regimen should help simplify the treatment of HIV disease.

Adult↗
PubMed1997

A controlled trial of isoniazid in persons with anergy and human immunodeficiency virus infection who are at high risk for tuberculosis. Terry Beirn Community Programs for Clinical Research on AIDS.

BACKGROUND: Patients with human immunodeficiency virus (HIV) infection and latent tuberculosis are at substantial risk for the development of active tuberculosis. As a public health measure, prophylactic treatment with isoniazid has been suggested for HIV-infected persons who have anergy and are in groups with a high prevalence of tuberculosis. METHODS: We conducted a multicenter, randomized, double-blind, placebo-controlled trial of six months of prophylactic isoniazid treatment in HIV-infected patients with anergy who have risk factors for tuberculosis infection. The primary end point was culture-confirmed tuberculosis. RESULTS: The study was conducted from November 1991 through June 1996. Over 90 percent of the patients had two or more risk factors for tuberculosis infection, and nearly 75 percent of patients were from greater New York City. After a mean follow-up of 33 months, tuberculosis was diagnosed in only 6 of 257 patients in the placebo group and 3 of 260 patients in the isoniazid group (risk ratio, 0.48; 95 percent confidence interval, 0.12 to 1.91; P=0.30). There were no significant differences between the two groups with regard to death, death or the progression of HIV disease, or adverse events. CONCLUSIONS: Even in HIV-infected patients with anergy and multiple risk factors for latent tuberculosis infection, the rate of development of active tuberculosis is low. This finding does not support the use of isoniazid prophylaxis in high-risk patients with HIV infection and anergy unless they have been exposed to active tuberculosis.

AIDS-Related Opportunistic Infections↗
PubMed1997

Effects of hemodialysis on left ventricular diastolic filling.

Diastolic Doppler filling parameters were measured before and after hemodialyses, performed once with and once without fluid removal. Changes occurred only with fluid removal and correlated with weight loss, indicating that they are the result of reduction in preload.

Aged↗
PubMed1997

Lymphocyte shedding from genital tract of human immunodeficiency virus-infected women: immunophenotypic and clinical correlates.

OBJECTIVE: Our purpose was to describe the lymphocyte subpopulations in genital tract samples from human immunodeficiency virus-infected women and the clinical correlates associated with lymphocyte shedding. STUDY DESIGN: Genital tract samples of women infected with human immunodeficiency virus-1 were processed for immunophenotyping analysis with a FACScan flow cytometer. Immunologic and virologic characteristics of women with and without lymphocyte shedding were compared with t test, Wilcoxon rank test, or Fisher's exact test. RESULTS: The rate of genital lymphocyte shedding among human immunodeficiency virus-1-infected women was 39%. Genital shedding was not related to age, race, use of antiretroviral therapy, or positive human immunodeficiency virus-1 culture. A negative rank correlation (r = -0.71, p = 0.047) between CD3+ CD4+ counts in peripheral blood and genital tract was observed. The majority of the lymphocyte cells were CD3+ CD8+, and > 80% of the CD3+ CD4+ cells were memory cells. CONCLUSION: The immune profile of the genital tract lymphocytes is suggestive of a local mucosal immune response.

Adult↗
PubMed1997

Modeling of anti-nucleosome immunoglobulin Fv domains: analysis of electrostatic interactions.

Three-dimensional structural models of six murine anti-(H2A-H2B) monoclonal autoantibody variable fragments were built by comparative molecular modeling using the COMPOSER software. Analysis of the antibody combining sites is based on the hypothesis that ionic and/or electrostatic interactions predominate in antigen antibody binding, as suggested by the cationic nature of histones and the amino acid sequences of the antibody hypervariable regions. The study of the electrostatic potentials of their combining site surfaces, computed with the MOLCAD software, and the comparison with the electrostatic potentials of 13 selected control mAbs show the lack of a unique electrostatic pattern. One group of three mAbs expresses a strong and large electronegative area, supporting the hypothesis that ionic interactions predominate in antigen recognition. The second group, containing the other three mAbs, exhibits an alternation of electropositive and electronegative areas. All, however, present a localized electronegative area in the vicinity of H-CDR1 and H-CDR2 loops that is generated by the presence of at least one acidic residue. The model suggesting that the binding activity may depend on charged residues at the same site is reminiscent of what was previously reported in anti-DNA mAbs. In addition, the alternation of electropositive areas and electronegative areas in second group mAbs is also frequently observed in certain anti-DNA mAbs. These data argue for the existence of relationships between these two autoantibody populations and suggest that they share a common immunogenic particle formed by anionic and cationic components, such as a nucleosome.

Amino Acid Sequence↗
PubMed1997

Dichotomizing stroke outcomes based on self-reported dependency.

Patients participating in a clinical trial of stroke therapy were assessed 3 months after randomization using the Barthel Index, the Modified Rankin Scale, questions on activities of daily living, and extent of recovery. Those who needed help in performing the activities of daily living and had not recovered completely were classified as dependent. Self-reported dependency had a sensitivity of 94% and specificity of 80% against the Barthel Index dichotomized at 16 or below, or a sensitivity of 85% and specificity of 87% against the Modified Rankin Scale dichotomized at 2 or above.

Activities of Daily Living↗
PubMed1996

Lymphocyte immunoregulatory cells present in semen from human immunodeficiency virus (HIV)-infected individuals: a report from the HIV Heterosexual Transmission Study.

The purpose of this study was to determine the types and distribution of immune subsets present in semen from human immunodeficiency virus (HIV)-infected (HIV+) individuals and to compare these values with those measures in semen from HIV-negative (HIV-) individuals. To accomplish this, a direct three-color monoclonal antibody labeling technique was employed to identify immune cells in fresh ejaculates. Once labeled, the percent of each immune subset present in the ejaculate was determined by flow cytometric analysis. The percent of CD3+ cells present in the semen of the HIV+ group showed no significant difference when compared with semen from the HIV- group. Analysis of the CD4+ subset yielded a significantly lower percent in the HIV+ group than in the HIV- group. The analysis of the CD8+ subset yielded a higher percent of cells present in semen from HIV+ individuals. The CD8 higher value along with lower CD4 value results in a lower CD4/CD8 ratio in the HIV+ group. Further subset studies showed that the percent of cells expressing naive (CD4+ CD45RA+) and memory (CD4+ CD45RO+) markers was lower in the HIV+ group. This study provides additional data supporting the utility of flow cytometry and monoclonal antibodies to immunophenotypic cells present in semen ejaculates. It is also the first reported application of the technique to a disease-based model and may be useful to better understand issues of mucosal immunity and transmission of sexually transmitted diseases such as HIV.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Expression and folding of an interleukin-2-proinsulin fusion protein and its conversion into insulin by a single step enzymatic removal of the C-peptide and the N-terminal fused sequence.

We report the expression in E. coli of a proinsulin fusion protein carrying a modified interleukin-2 N-terminal peptide linked to the N-terminus of proinsulin by a lysine residue. The key aspects investigated were: (a) the expression of the fused IL2-PI gene, (b) the folding efficiency of the insulin precursor when still carrying the N-fused peptide and (c) the selectivity of the enzymatic cleavage reaction with trypsin in order to remove simultaneously the C-peptide and the N-terminal extension. It was found that this construction expresses the chimeric proinsulin at high level (20%) as inclusion bodies; the fused protein was refolded at 100-200 micrograms/ml to yield about 80% of correctly folded proinsulin and then it was converted into insulin by prolonged reaction (5 h) with trypsin and carboxypeptidase B at a low enzyme/substrate rate (1:600). This approach is based on a single enzymatic reaction for the removal of both the N-terminal fused peptide and the C-peptide and avoids the use of toxic cyanogen bromide.

Amino Acid Sequence↗
PubMed1995

Sequential methotrexate, 5-fluorouracil (5-FU), and high dose leucovorin versus 5-FU and high dose leucovorin versus 5-FU alone for advanced colorectal cancer. A multi-institutional randomized trial.

BACKGROUND: The primary objective of this study was to compare the single-biochemical modulation of 5-fluorouracil (5-FU) and leucovorin with that of the double-biochemical modulation of methotrexate and leucovorin. Because of the Martin et al. study in which an experimental model showed similar effects of 5-FU at maximum tolerated doses to the modulation with leucovorin at standard doses, a third treatment arm of 5-FU alone was also studied. METHODS: A randomized trial was performed using a 500-mg/m2 intravenous (i.v.) 1-hour infusion of methotrexate, and 12 hours later, a 600-mg/m2 i.v. bolus of 5-FU plus a 200-mg/m2 i.v. 1-hour infusion of leucovorin (MFL) every 2 weeks versus 5-FU plus leucovorin at an equal dose and schedule (FL), versus a 1200-mg/m2 i.v. dose of 5-FU every 2 weeks. Of 186 patients included in the study, 178 were evaluable. RESULTS: In a preliminary analysis with 94 evaluable patients, two significant statistical differences were shown. First, the toxicity rate of the 5-FU--alone (F) treatment arm was higher than that of the other arms (MFL vs. F, P = 0.0002; FL vs. F, P = 0.00001). Second, the median survival was worse in the F treatment arm with a rate of 12.6 months for the MFL and FL arms and 7.5 months for the F arm (P < 0.05). Considering these results, the F treatment arm was discontinued. The final results included 70 evaluable patients for MFL and 74 patients for FL. No difference was found in the distribution of prognostic factors. The response rates were 25.7% for MFL (95% CI, 16-37.5) and 14.8% for FL (95% CI, 7.6-25), (P = 0.1). The median survival was 14.3 months for patients treated with MFL and 12.3 months for those treated with FL. The hematologic toxicity was mild, with no grade 3/4 leukopenia in either treatment arm. The major nonhematologic toxicity in the MFL and FL treatment arms was ocular; nongrade 3/4 diarrhea also was observed. CONCLUSIONS: The results of MFL double-biochemical modulation failed to show a significant statistical difference from that of single-biochemical modulation for this dose and schedule.

Adenocarcinoma↗
PubMed1995

Purification and characterization of a lectin from the seeds of Erythrina costaricensis.

This work compares three methods used for the purification of the lectin of Erythrina costaricensis and presents new data regarding its physicochemical properties and N-terminal sequence. The lectin was isolated from the seeds of Erythrina costaricensis using O-alpha-D galactosyl polyacrylamide, galactose-derivatized Sepharose and ConA-Sepharose as affinity chromatography supports. The lectin content is about 110 mg/100 g dry flour. The protein agglutinates human and rabbit erythrocytes; other animal erythrocytes were not agglutinated. The agglutination is inhibited by galactosyl moieties, p-nitrophenyl-beta-galactoside being the strongest inhibitor. The lectin is a dimeric protein (56 kDa) with identical subunits, each with a mol. wt of 27.2 kDa. The lectin is a glycoprotein with 3.6% neutral sugars. The amino acid content shows a high proportion of acidic and hydroxy residues; cysteine is absent and there are 6 methionines/mol protein. The N-terminal sequence is similar to those of Erythrina lectins; Ala is the N-terminal amino acid. In summary this paper reports the isolation of a lectin which shares many structural and functional properties with other Erythrina lectins. However, differences in some of its characteristics (pI, interactions with animal erythrocytes, mitogenic ability) indicate some distinctions in structure amongst this group of proteins.

Amino Acid Sequence↗
PubMed1995

Malondialdehyde-modified low density lipoproteins in patients with atherosclerotic disease.

The murine monoclonal antibody mAb-1H11 raised against malondialdehyde (MDA)-modified LDL, was used to detect cross-reacting material in human atheromatous tissue and in plasma. MDA-modified LDL levels in plasma were 0.19 +/- 0.02 mg/dl (mean +/- SEM) in 44 control subjects, 0.24 +/- 0.02 mg/dl in 15 patients with chronic stable angina pectoris (P = NS vs LDL cholesterol matched controls), 1.4 +/- 0.1 mg/dl in 60 patients with acute myocardial infarction (P < 0.001 vs controls), and 0.86 +/- 0.11 mg/dl in 22 patients with carotid atherosclerosis (P < 0.001 vs controls). Modified LDL, isolated from pooled LDL of 10 patients, showed a higher electrophoretic mobility on agarose gels, a higher content of thiobarbituric acid reactive substances, and a higher cholesterol/protein ratio than native LDL and had a similar reactivity (antigen/protein ratio) in the assay as the in vitro MDA-modified LDL used for calibration. Its apo B-100 moiety was not fragmented. Uptake of this modified LDL by macrophages resulted in foam cell generation. In conclusion, elevated plasma levels of atherogenic MDA-modified LDL may be a marker for unstable atherosclerotic cardiovascular disease.

Aged↗