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Biomedical subjects

M Rivera

Publications and source records attributed to M Rivera.

At least 145 records · Page 8Linked to original sources
PubMed1993

Blood levels of organochlorine residues and risk of breast cancer.

BACKGROUND: Organochlorines such as DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane] and PCBs (polychlorinated biphenyls), which have been used extensively as insecticides and as fluid insulators of electrical components, respectively, are known to be persistent environmental contaminants and animal carcinogens. These agents have been found in human tissue due to their inefficient metabolism and their solubility in lipids, which lead to lifelong sequestration in adipose tissue. Their association with human cancer occurrence, however, has been explored only marginally, with most studies having 20 or fewer cases. PURPOSE: This blinded study was designed to determine whether exposure to PCBs and to DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene], the major metabolite of DDT, is associated with breast cancer risk in women. METHODS: We analyzed sera from the stored blood specimens of 14,290 participants enrolled between 1985 and 1991 in the New York University Women's Health Study, a prospective cohort study of hormones, diet, and cancer. Cohort members who developed breast cancer were included as case patients in our nested case-control study. DDE and PCBs were measured by gas chromatography in the sera of 58 women with a diagnosis of breast cancer 1-6 months after they entered the cohort and in 171 matched control subjects from the same study population who did not develop cancer. RESULTS: Mean levels of DDE and PCBs were higher for breast cancer case patients than for control subjects, but paired differences were statistically significant only for DDE (P = .031). After adjustment for first-degree family history of breast cancer, lifetime lactation, and age at first full-term pregnancy, conditional logistic regression analysis showed a fourfold increase in relative risk of breast cancer for an elevation of serum DDE concentrations from 2.0 ng/mL (10th percentile) to 19.1 ng/mL (90th percentile). For PCBs, the relative risk for a change in serum levels from 3.9 ng/mL (10th percentile) to 10.6 ng/mL (90th percentile) was less than twofold, a nonsignificant association that was further reduced after adjustment for DDE. CONCLUSION: In this population of New York City women, breast cancer was strongly associated with DDE in serum but not with PCBs. IMPLICATIONS: These findings suggest that environmental chemical contamination with organochlorine residues may be an important etiologic factor in breast cancer. Given the widespread dissemination of organochlorine insecticides in the environment and the food chain, the implications are far-reaching for public health intervention worldwide.

Adult↗
PubMed1993

Porins and lipopolysaccharide of Escherichia coli ATCC 25922 and isogenic rough mutants.

The lipopolysaccharide and porin profile of Escherichia coli ATCC 25922, a smooth strain commonly used in antibiotic susceptibility testing, and five isogenic rough mutants was examined. The lipopolysaccharide of the parent strain had the characteristic ladder pattern on polyacrylamide gels, while that of the mutants appeared similar to chemotypes Ra and Rc of Salmonella typhimurium with some changes in chemical composition. Of the porins, OmpC appeared markedly reduced in the parent strain while OmpF appeared markedly reduced in the mutants. In addition, a new outer-membrane protein of size intermediate to that of OmpC and OmpF was detected in all mutants. Neither parent nor mutants were susceptible to the LPS core-specific P1 phage or the porin-specific PA2 and K20 phages.

Bacterial Outer Membrane Proteins↗
PubMed1993

Laser flash photolysis studies of electron transfer to the cytochrome b5-cytochrome c complex.

Rate constants for electron transfer in the complex between recombinant rat mitochondrial outer membrane cytochrome b5 or the tryptic fragment of bovine liver cytochrome b5 and horse mitochondrial cytochrome c were measured by laser flash photolysis of 5-deazariboflavin-EDTA solutions. When an excess of cytochrome b5 was titrated with increasing amounts of cytochrome c at low ionic strength and electron transfer was initiated by a laser flash, both proteins were rapidly reduced by deazariboflavin semiquinone. The initial photoreduction was followed by a slower second-order reduction of b5 complexed oxidized cytochrome c by free reduced cytochrome b5. At an 8:1 ratio of cytochromes b5 to c, the pseudo-first-order rate constant for reduction of complexed cytochrome c increased 3-5-fold between ionic strengths of 5 and 40 mM, and then dropped precipitously at higher ionic strengths. The ionic strength dependent increase in rate constant is likely to be due to relief of steric hindrance via rearrangement of cytochrome c in the complex. The reaction rate showed no sign of saturation at any ionic strength, indicating a first-order rate constant greater than 10(4) s-1 within a transient ternary protein complex; i.e., interprotein electron transfer approaches the largest values previously reported for the stable binary protein complex (approximately 4 x 10(5) s-1). Our results emphasize the flexibility of electron-transfer protein complexes, which had previously been modeled in a single conformation with specific salt bridges. It appears that a variety of orientations can exist within such protein-protein complexes and that the population of conformations changes with ionic strength.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Zymosan-induced luminol-amplified chemiluminescence of whole blood phagocytes in experimental and human hyperthyroidism.

Luminol-amplified CL of whole blood phagocytes was studied in rats given 3 consecutive doses of 0.1 mg L-triiodothyronine T3/kg or in hyperthyroid patients, after stimulation by zymosan. In both cases, CL was significantly increased, an effect which was produced independently of the opsonization of the zymosan particles and markedly inhibited by azide. The in vitro addition of T3 or L-thyroxine (T4) to whole blood phagocytes from normal rats did not modify the opsonized zymosan-dependent CL, when assayed at the concentrations found in euthyroid subjects or in hyperthyroid patients. Administration of propylthiouracil (400 mg/day for 2-3 months) to hyperthyroid patients reduced the CL response observed prior to treatment, to values comparable to those found in the euthyroid group. These data indicate that hyperthyroidism elicits an enhanced respiratory burst activity of whole blood phagocytes, probably related to adaptive changes induced by thyroid hormone on the mieloperoxidase-H2O2 system, rather than to direct actions of the hormone molecule or changes in the opsonic capacity of plasma.

Adult↗
PubMed1993

Prevalence of ectopic ventricular activity after left ventricular mass regression.

To assess the effects of left ventricular mass reduction on the prevalence of ventricular ectopic activity, we conducted a double-blind, placebo-controlled trial measuring ambulatory 48 h premature ventricular depolarizations in 27 patients with mild-to-moderate hypertension and an increased left ventricular mass index. Data was obtained at baseline and 6 +/- 2 months after randomization to either 25 mg captopril or placebo twice a day. Patients on captopril attained reduction in blood pressure from 167 +/- 11/103 +/- 6 to 136 +/- 10/85 +/- 5 mm Hg (P = .001), left ventricular mass index regression from 149 +/- 17 to 96 +/- 23 g/m2 (P = .001), and ventricular ectopic activity reduction from 413 +/- 172 to 77 +/- 27 ventricular extrasystoles/day (P = .001). Patients on placebo had no significant change in blood pressure (from 162 +/- 11/101 +/- 6 at baseline to 160 +/- 8/100 +/- 8 mm Hg after 6 months; P = NS). In the placebo group left ventricular mass index increased from 155 +/- 40 to 182 +/- 51 g/m2 (P = .01), and ventricular ectopic activity decreased from 634 +/- 293 to 562 +/- 260 ventricular extrasystoles/day (P = NS). Eight out of 14 patients on captopril (57%) and 1 out of 13 patients on placebo (8%) achieved reduction > 85% in ventricular ectopic activity per day (P = .004). Using multivariate logistic regression analysis, left ventricular mass index regression and reduction in systolic blood pressure were the most important correlates for this effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Captopril↗
PubMed1993

Prognosis of acute tubular necrosis: an extended prospectively contrasted study.

The ability to predict the outcome in acute tubular necrosis (ATN) remains elusive despite considerable efforts. Accurate prediction is a crucial priority and has large economical and ethical implications, mainly to judge when treatment is futile and further efforts only prolong miserable agony. To analyze the influence of risk factors in the prognosis of ATN, we applied, in an initial phase, a prospective protocol of demographic data, cause of renal failure, diuresis, need of dialysis and clinical conditions in 228 patients using multiple linear and logistic regression models. In a control phase with 100 consecutive patients, we checked the accuracy of the results previously obtained, evaluating further the overall population of 328 patients in a synthetic phase. Finally, the validation of the equations obtained was verified in 25 patients from another hospital. As a complement of this 4-phase study, detailed statistical comparisons between both linear and logistic multiple regression models were undertaken. Correlation between probability of death obtained with equations from the initial phase applied to control patients and real evolution of these patients, survival or death, was excellent. The study of the synthetic phase revealed coma, assisted respiration, hypotension, oliguria and jaundice as having an independent positive influence on mortality and nephrotoxic etiology and normal consciousness on good prognosis. For the linear model, the same cut-off point of discriminant score (0.9) above which there were no chances for survival could be established in the 4 phases. With the logistic model, it only was found at later phases. The multiple linear was better than the logistic regression model in terms of better correlation with real mortality, better sensitivity and specificity intervals, easier use of discriminant cut-off point and better adjustment of distribution of standardized residuals to expected normal function. Early prognosis of ATN is possible and can be given using simple clinical features. A discriminant score allows to distinguish patients without chances for survival. The multiple linear is better than the logistic regression model in the prediction of the outcome in ATN.

Acute Disease↗
PubMed1993

Risk assessment for human immunodeficiency virus among pregnant Hispanic adolescents.

Inner-city adolescents are believed to be at increased risk for HIV infection because of their high-risk behaviors, and black and Hispanic teenagers may be at greatest risk as a consequence of these behaviors and inadequate AIDS education. In the present paper, the HIV risk status of pregnant Hispanic adolescents presenting for prenatal care to an inner-city municipal outpatient clinic located in New York City was assessed. The assessment consisted of a confidential structured interview. Based on known adult risk factors, adolescents were identified as being at increased risk or low risk. One-third of the 87 teenagers were identified as being at increased risk for HIV infection. Nobody reported symptoms suggestive of AIDS, had had a transfusion, or reported use of intravenous drugs or crack cocaine. Sexual risk-taking behavior was the most common factor that increased HIV risk. Sixteen adolescents were at increased risk solely because of a sexually transmitted disease and seven others reported an STD with at least one other risk factor. Although 86% of the pregnant teenagers reported the risk-taking behavior of substance use by self or partner, only four were at increased risk based on this factor alone. However, many adolescents were unaware of their partners' past substance use and sexual history and, therefore, may have underestimated their own risk. Birthplace (United States vs. foreign born) and nationality (Puerto Rican vs. non-Puerto Rican Hispanic) were significantly associated with the adolescents' HIV risk assessment via an interaction effect. None of the adolescents had previously considered themselves to be at increased risk for HIV infection. The overwhelming majority who were at increased risk declined referral for further counseling or testing. It is recommended that pregnant Hispanic adolescents be assessed for HIV risk and receive risk reduction counseling as part of their general health care.

Acquired Immunodeficiency Syndrome↗
PubMed1993

[Female non-surgical sterilization: use of endo-uterine quinacrine and betamethasone pellets. Review of the subject: experimental bases--pharmacology--toxicology--efficacy].

Quinacrine produces obstruction of the region of the uterine tube by its fibroblastic granulomatous action. Factors such as the Zn++ and Cu++ content of tubal tissue, as well as the use of anti-prostaglandins, potentialise this action. Two groups of patients were evaluated in this study: Group A--95 women. 180 mg of quinacrine +0.6 mg of betamethasone were inserted into the uterine cavity, on the basis of two insertions separated by a one month interval. Two pregnancies were found by the end of the 2nd year, the percentage failure rate being 2.2 and the Pearl index 0.58. Group B--129 women. 216 mg of quinacrine +1.2 mg of betamethasone were inserted into the uterine cavity, on the basis of two insertions separated by a one month interval. Two pregnancies were found by the end of the 1st year, the percentage failure rate being 0.59 and the Pearl index 0.54. Iatrogenic adverse reactions associated with quinacrine only were not seen in either of these two study groups. None of the pregnancies was ectopic.

Adult↗
PubMed1993

[Non-surgical female sterilization using quinacrine: efficacy of two insertions of quinacrine pellets].

In a group of 159 women at Santiago du Chili, fertility control by means of chemical occlusion of the utero-tubular junction was assessed. Two transcervical intra-uterine insertions of 216 mg of quinacrine, carried out at an interval of one month and associated with 50 mg of intra-uterine diclofenac and 150 mg of intra-muscular diclofenac resulted in a pregnancy rate after 12 months of 2.1 per 100 women and a Pearl index of 1.63 at 27 months after the sterilization process. The complications and adverse events appear to be similar to those which occur during insertion of an IUD and were minor and transient, disappearing within a few hours or at most 2 days after the procedure.

Adult↗
PubMed1992

Gene synthesis, bacterial expression, and 1H NMR spectroscopic studies of the rat outer mitochondrial membrane cytochrome b5.

The gene coding for the water-soluble domain of the outer mitochondrial membrane cytochrome b5 (OM cytochrome b5) from rat liver has been synthetized and expressed in Escherichia coli. The DNA sequence was obtained by back-translating the known amino acid sequence [Lederer, F., Ghrir, R., Guiard, B., Cortial, S., & Ito, A. (1983) Eur. J. Biochem. 132, 95-102]. The recombinant OM cytochrome b5 was characterized by UV-visible, EPR, and 1H NMR spectroscopy. The UV-visible and EPR spectra of the OM cytochrome b5 are almost identical to the ones obtained from the overexpressed rat microsomal cytochrome b5 [Bodman, S. B. V., Schyler, M. A., Jollie, D. R., & Sligar, S. G. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 9443-9447]. The one-dimensional 1H NMR spectrum of the OM cytochrome b5 indicates that the rhombic perturbation of the ferric center is essentially identical to that in the microsomal beef, rabbit, chicken, and rat cytochromes b5. Two-dimensional 1H NMR spectroscopy (NOESY) and one-dimensional NOE difference spectroscopy were used to assign the contact-shifted resonances that correspond to each of the two isomers that result from the rotation of the heme around its alpha-gamma-meso axis. The assignment of the resonances allowed the determination of the heme orientation ratio in the OM cytochrome b5, which was found to be 1.0 +/- 0.1. It is noteworthy that the two cytochromes b5 that have similar populations of the two heme isomers (large heme disorder) originate from the rat liver.

Amino Acid Sequence↗
PubMed1992

Effects of captopril on regional segment motion during acute coronary occlusion.

The effects of captopril on myocardial segment function in different degrees of transient coronary occlusion were studied using ultrasonic dimension gauges in 15 open-chest dogs. The occlusion procedures (OP) were performed on the left anterior descending coronary artery (LAD) in eight dogs and on the left circumflex coronary artery (Cx) in seven dogs. To measure the changes in segment shortening in the subendocardium we used eight dogs (ischemic and control zones: four dogs LAD and four dogs Cx). To measure the changes in wall thickening we used seven dogs (ischemic and control zones: three dogs LAD and four dogs Cx). Total coronary OP lasting 1 min and partial OP (70-80%) lasting 1 min and 2 min 30 s, before and after captopril (0.25 mg/kg i.v.) were performed. Left ventricular pressure, dP/dt, coronary flow, and ECG were monitored. Total coronary OP (1 min) changed segment shortening (18% LAD; 14% Cx) and wall thickening (19% LAD; 18% Cx) to values of dyskinesis (-3% and -4% for shortening; -6% and -5% for thickening). Captopril improved regional function maintaining positive values for shortening (4% LAD; 3% Cx) and thickening (0.3% LAD; 4% Cx). Similar responses were obtained during partial OP and captopril. Results suggest that captopril produced a significant improvement in the regional function parameters affected by ischemia both in total and partial obstructions.

Animals↗
PubMed1992

Cardiac tamponade as presentation of systemic amyloidosis.

We present a patient with pericardial tamponade due to amyloid heart disease. A 64-yr-old man was admitted to the hospital because of fatigue and the abrupt development of chest pain and dyspnea. Echocardiography showed severe pericardial effusion and total pericardiectomy was necessary. Ten months later laboratory studies revealed proteinuria and high serum creatinine. A rectal biopsy showed amyloid deposition that was also found in the pericardial tissue. Pericardial tamponade is an extremely rare complication of cardiac amyloidosis. To our knowledge, only one previous case of cardiac tamponade due to amyloid heart disease has been reported.

Amyloidosis↗