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Biomedical subjects

M Rivera

Publications and source records attributed to M Rivera.

At least 127 records · Page 7Linked to original sources
PubMed1994

Breast cancer and serum organochlorines: a prospective study among white, black, and Asian women.

BACKGROUND: Five small case-control studies have examined the relationship between exposure to organochlorines and the risk of breast cancer and have found inconsistent results. In these studies, organochlorine levels in breast cancer patients were measured after (or at most 6 months before) diagnosis. PURPOSE: We tested the hypothesis that organochlorines are a risk factor for breast cancer, using prospectively gathered data on serum levels of DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] (the main metabolite of the pesticide DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane]) and polychlorinated biphenyls (PCBs). METHODS: Study subjects belonged to a cohort of 57,040 women (46,629 white, 8123 black, and 2288 Asian) from the San Francisco Bay Area who took a multiphasic health examination, independent of concern about risk of breast cancer, in the late 1960s. At that time, a sample of blood was obtained, then frozen and stored. Follow-up was through December 31, 1990. We conducted a nested case-control study of 150 case patients and 150 matched control subjects. A random sample of 50 women per racial/ethnic group who had been diagnosed with breast cancer more than 6 months after the multiphasic examination (mean follow-up = 14.2 years) was selected, and each case patient was matched to a cancer-free control subject. RESULTS: Matched analyses found no differences in the case patients' and control subjects' serum levels of DDE (mean difference = 0.2 parts per billion [ppb]; 95% confidence interval [CI] = -6.7, 7.2) or PCBs (mean difference = -0.4 ppb; 95% CI = -0.8, 0.1). DDE levels, however, tended to be higher among black case patients compared with black controls (mean difference = 5.7 ppb; 95% CI = -3.3, 14.8), and PCBs were lower among white case patients compared with white controls (mean difference = -0.6 ppb; 95% CI = -1.2, -0.1). Organochlorine levels were significantly higher among black and Asian women compared with white women. The mean difference for DDE was 11.0 ppb for black women (95% CI = 4.3, 17.6) and 12.6 ppb for Asian women (95% CI = 6.0, 19.2); for PCBs, the respective differences were 0.8 ppb for black women (95% CI = 0.2, 1.4) and 1.4 ppb for Asian women (95% CI = 0.8, 1.9). The results were not altered by adjusting for relevant confounders, and the lack of association between exposure to organochlorines and breast cancer was present regardless of length of follow-up, year of diagnosis, or the case patient's menopausal and estrogen-receptor status. CONCLUSION: The data do not support the hypothesis that exposure to DDE and PCBs increases risk of breast cancer. IMPLICATIONS: Future investigations must consider the biologic mechanisms involved and variations in exposure to chemical pollutants and of breast cancer incidence rates among diverse groups of women.

Adult↗
PubMed1994

Hydration and localization of diacylglycerol in the insect lipoprotein lipophorin. A 13C-NMR study.

In order to probe the organization of diacylglycerol (DG) in lipophorin, 13C-enriched lipophorin was prepared for NMR investigations. We obtained 13C-enriched lipophorin labeled exclusively in DG by feeding insects tobacco leaves coated with [1-13C]palmitic acid or [1-13C]oleic acid. Lipophorins enriched up to 5% with a [13C]fatty acid were obtained by this procedure. NMR studies of the isolated lipophorin DG showed that palmitic acid accumulates almost entirely (> 90%) in the sn-1 position. Oleic acid was found equally distributed between the sn-1 and sn-2 positions, yielding a DG enriched equally at both positions. The 13C-NMR spectra of both [13C]palmitate- and [13C]oleate-enriched lipophorins showed that DG had one narrow carbonyl resonance indicative of rapid motion. A comparative analysis of the 13C carbonyl chemical shift data for DG in organic solvents, aqueous solutions, and dispersions with the DG carbonyl chemical shift of native lipophorin enriched in [13C]palmitate or [13C]oleate shows a high degree of water exclusion from the DG carbonyls in lipophorin. This result is consistent with the existence of a lipophorin lipid core containing most of the lipophorin DG. This study represents the first attempt to elucidate the organization of DG in lipophorin. The possibility of obtaining [13C]DG-enriched lipophorins, selectively enriched in one or both acyl chains of DG, should provide a powerful tool for further analysis of the organization and the dynamic properties of DG in native lipoproteins.

Animals↗
PubMed1994

Cation-promoted cyclic voltammetry of recombinant rat outer mitochondrial membrane cytochrome b5 at a gold electrode modified with beta-mercaptopropionic acid.

Reversible cyclic voltammetry of recombinant rat outer membrane (OM) cytochrome b5 was observed at a gold electrode modified with beta-mercaptopropionic acid. Electron transfer between the negative electrode surface and the negatively charged OM cytochrome b5 was promoted by the addition of divalent metal ions such as Mg2+ or Ca2+ and by the positively charged species poly-L-lysine. The titration of OM cytochrome b5 (0.1 mM) with poly-L-lysine resulted in a gradual positive shift of the E1/2 value which leveled off at +8 mV vs NHE when the poly-L-lysine:cytochrome b5 ratio reached a value of 2:1. Since the further addition of poly-L-lysine had no effect on the E1/2 value of the protein, it was concluded that a complex is formed in which two molecules of poly-L-lysine bind to each molecule of OM cytochrome b5. When the OM cytochrome b5-poly-L-lysine complex (0.1 mM) was titrated with Mg2+ or Ca2+ ions, the E1/2 value shifted gradually in the negative direction and leveled off at -40 mV vs NHE when the concentration of divalent ions reached 85 mM. When the voltammetric response of 0.1 mM cytochrome b5 was promoted by Mg2+ or Ca2+ ions, the minimum concentration of divalent cation necessary to produce a reversible voltammogram was 40 mM and the observed E1/2 was -46 mV vs NHE. On the other hand, only 0.2 mM [Cr(NH3)6]3+ was necessary to promote the reversible electrochemistry of 0.1 mM cytochrome b5. The half-wave potential observed under these conditions was -78 mV vs NHE. This indicates that there is a large dependence of the reduction potential of cytochromes b5 on the kind and concentration of multivalent ions in solution. A reduction potential of -102 mV vs NHE was obtained for OM cytochrome b5 (0.60 mM) by spectroelectrochemical titration in the presence of 0.4 mM [Ru(NH3)6]3+ and 1 mM methyl viologen, pH 7.0, mu = 0.1 M. This value is approximately 100 mV more negative than the reduction potentials reported for microsomal cytochromes b5 obtained from other sources under the same conditions. The binding interactions between OM cytochrome b5 and poly-L-lysine or Mg2+ ions were probed by investigating the isotropically shifted 1H NMR resonances arising from the heme in the OM cytochrome b5.(ABSTRACT TRUNCATED AT 400 WORDS)

3-Mercaptopropionic Acid↗
PubMed1994

Bone marrow oxygen consumption and erythropoiesis in chronically hypoxic rats.

Bone marrow oxygen consumption (VO2) was determined weekly in 16 Holtzman rats exposed to continuous hypobaric hypoxia (CHH) during 30 days. The results were compared with those obtained in 10 sea level control animals (SL). The VO2 expressed as ng.at.O2/min, decreased progressively with time of exposure to hypoxia. VO2 (mean +/- SD) was 0.0936 +/- 0.135 in SL rats. In CHH animals, it was 0.1001 +/- 0.0292 after 8 days of hypoxia, 0.1030 +/- 0.0206 after 16 days, 0.0594 +/- 0.0148 (p = 0.002) after 24 days and 0.0136 +/- 0.404 (p = 0.000) after 30 days. Protein concentration in bone marrow was progressively higher in hypoxics when compared to control, with significant differences since the first week of exposure. Blood hemoglobin increased in parallel to protein concentration in the bone marrow. These findings suggest an increase in the cells of the erythroid series whose oxygen consumption is less than cells in the early stages of differentiation. The increased protein concentration is in agreement with the fact that globin mRNA appears in cells with a progressively increasing anaerobic metabolism at relatively late stages of erythropoiesis.

Animals↗
PubMed1994

Ventilatory response to severe acute hypoxia in guinea-pigs and rats with high hemoglobin-oxygen affinity induced by cyanate.

Baseline ventilation, hemoglobin concentration (Hb) and P50 were significantly lower in guinea-pigs than in rats. Chronic sodium cyanate (NaOCN) administration did not significantly increase hemoglobin concentration in either guinea-pigs or rats. It decreased the P50 significantly less in guinea-pigs than in rats. The high Hb-O2 affinity experimentally induced did not modify the hypoxic ventilatory response (HVR) of guinea-pigs and rats. At the same level of acute hypoxia, HVR was significantly lower in NaOCN guinea-pigs than in NaOCN rats. Guinea-pigs, genotypically adapted animals to high altitude, displayed relatively minor ventilatory and Hb-O2 affinity changes to NaOCN, and a relatively minor HVR to acute hypoxia. They probably use tissue and biochemical adaptive mechanisms, in addition to their limited extracellular responses to successfully tolerate ambient hypoxia.

Acute Disease↗
PubMed1994

Maternal immunity to measles and infant immunity at less than twelve months of age relative to maternal place of birth.

Sera from infants aged 5 to 11 months and from their mothers were used to investigate the level and duration of transplacentally derived measles antibody. The infants of foreign-born, inner-city mothers were more likely to have measles antibody and were less likely to get measles. Infants of foreign-born mothers, because they are less likely to respond to measles vaccine, may require different vaccine strategies than infants of mothers born in the United States.

Antibodies, Viral↗
PubMed1994

Prevalence of antiphospholipid antibodies in nephropathies not due to systemic lupus erythematosus.

Renal involvement by some types of thrombotic microangiopathy has been associated with the presence of antiphospholipid antibodies in both patients with systemic lupus erythematosus (SLE) and in those with other types of connective tissue disorders. To assess the prevalence and clinical significance of these antibodies in renal disease we prospectively studied anticardiolipin antibodies and lupus anticoagulant activity in 138 patients. These patients were classified into four groups: chronic glomerulonephritis (n = 57), acute and non-SLE systemic nephropathies (n = 13), non-immune-related nephropathies (n = 39), and SLE nephropathies (n = 29). The prevalence of antiphospholipid antibodies in patients with chronic primary glomerulonephritis (9%) was lower than in the SLE group (34%) and higher, but not significantly, than in patients with non-immunologically mediated renal diseases (2.6%). Positive patients in this group correspond to atypical "lupus-like" SLE forms or sporadic cases. In the group of patients with acute nephropathy and non-SLE systemic disorders, lupus anticoagulant was present in sic and anticardiolipin was present in four. In most cases the finding was transient and probably related to concomitant infection or active immune response. We conclude that there is a low prevalence of antiphospholipid antibodies in primary chronic glomerulonephritides, similar to that found in non-immunologically based nephropathies. The presence of these antibodies associated with chronic glomerulonephritis should raise the suspicion of SLE. On the other hand, positivity of these antibodies is a frequent finding in acute and systemic nephropathies. Therefore, the clinical and prognostic significance of their presence in these disorders should be further studied in a larger series of patients.

Adolescent↗
PubMed1994

Aortic graft infection due to Pasteurella haemolytica and group C beta-hemolytic streptococcus.

Although infection is a rare complication of aortic bypass grafting, we treated a 50-year-old patient who developed aortic graft infection due to Pasteurella haemolytica and group C beta-hemolytic streptococcus. The source of the infection could not be verified; however, after removal of the infected graft and administration of a 6-week course of intravenous ampicillin, he recovered fully. We discuss the etiology and pathogenesis of this rare infection.

Aorta↗
PubMed1994

Anti-neutrophil cytoplasmic antibody-associated paraneoplastic vasculitis.

A 68 year old man presented with a systemic necrotizing vasculitis and elevated levels of anti-neutrophil cytoplasmic antibody (ANCA) which responded to treatment with steroids and cyclophosphamide, with a decrease in the titre of ANCA until its disappearance. Four months later he presented with weakness, loss of weight, aphonia and dysphagia. A computerized tomography scan showed a solid mass in the anterior mediastinum, and histological studies revealed an undifferentiated adenocarcinoma. Vasculitis improved although the malignancy progressed and ANCA was persistently negative. Our case demonstrates an association between ANCA and paraneoplastic vasculitis.

Adenocarcinoma↗
PubMed1994

Influence of body iron stores on the serum erythropoietin concentration in hemodialyzed patients.

The influence of body iron stores on the concentration of serum erythropoietin was studied in 48 hemodialyzed patients not receiving human recombinant erythropoietin, androgens or iron supplements. The serum erythropoietin concentration was 11.6 +/- 10.4 mIU/ml. There was no correlation between the serum erythropoietin and the hematocrit or hemoglobin concentration; however, there was a correlation between the serum erythropoietin and the log of serum ferritin (r = -0.5699, p < 0.01). Serum erythropoietin levels were higher in the 18 ferropenic patients (serum ferritin < 50 ng/ml) than in the 30 patients with normal serum ferritin concentration (18 +/- 13.8 vs. 7.8 +/- 4.7 mIU/ml, p < 0.01). The administration of intravenous iron to the ferropenic patients resulted in a reduction in serum erythropoietin independent of the response of the anemia (18 +/- 13.8 basal and 7.9 +/- 6.5 mIU/ml at 4 weeks, p < 0.01). Our data would suggest that the concentration of erythropoietin in hemodialyzed patients is influenced by the serum ferritin level.

Adult↗
PubMed1994

Progression of renal failure in chronic primary glomerular diseases.

The rate of progression of renal failure was analyzed in 19 patients with biopsy-proven chronic primary glomerular diseases, by the slope (regression coefficient) of the linear regression of reciprocal serum creatinine on time. The relative importance of proteinuria, sex, underlying disease and components of arterial pressure (systolic, diastolic and mean) was tested using stepwise multiple linear regression, the dependent variable being the slope of progression. We found that the only variable significantly related with slopes of progression was arterial pressure. Hypertension was found in 14 of the 19 patients. There was a significant linear relationship (p < 0.05) between mean arterial pressure and slopes of progression. Notwithstanding, the best fit to the data follows a quadratic function (p < 0.001 for mean arterial pressure), which corresponds to a negative parabolic curve. Therefore, either low or high values of mean arterial pressure were associated with faster mean progression rates. Thus, an accurate approach of this relationship fits a nonlinear regression model.

Adolescent↗
PubMed1994

[Adrenal insufficiency in patients with kidney failure secondary to amyloidosis. Its detection by a stimulation test].

In order to know the prevalence rate of adrenal insufficiency among patients with renal failure due to amyloidosis; we have performed a stimulation test with synthetic corticotropin hormone (Nuvacthen test) in nine patients diagnosed of renal amyloidosis and in five controls. We also measured ACTH and plasma cortisol levels. In two out of nine patients (22%) a low ACTH, low plasmatic cortisol and an abnormal response to Nuvacthen test were detected being diagnosed of primary adrenal insufficiency. We conclude that adrenal insufficiency is not an infrequent finding in systemic amyloidosis and may be due to secondary amyloidotic infiltration of adrenal or pituitary glands. Though Nuvacthen test is a useful test to diagnose subclinical adrenal insufficiency, in our series patients with an abnormal response also had low levels of basal cortisol and ACTH and no one patient with normal basal levels had an abnormal response to the stimulation test.

Adrenal Insufficiency↗
PubMed1994

[Diagnostic yield of Echo-Doppler in dysfunction of the grafted kidney].

The study's goal is to analyze the usefulness of Eco-Doppler in the knowledge of renal graft hemodynamics and the description of its dysfunction. 234 examinations were performed in 110 patients. Acceleration, mean rate (MR), maximum systolic rate (MXSR) and minimal diastolic rate (MNDR), as well as resistance index (RI) and pulsatility index (PI) were determined in the external iliac, renal, segmentary, interlobular and arcuate arteries. RI and PI, as well as MXSR and the acceleration are higher in the extra-parenchymatous versus the intra-parenchymatous beds. Peak MR and MNDR values are reached in the renal artery. Termino-lateral to external iliac arterial anastomosis conditions higher MXSRs in the renal artery as opposed to termino-terminal to hypogastric artery (p < 0.05). In the arcuate artery, RI > 0.8 is reached in 51.6% of acute tubular necrosis (ATN), 46.9% of acute rejections (CR), 46.3% of chronic rejection (AR), 21% of grafts with cyclosporin-induced nephrotoxicity (NFX) and 12.5% of normal functioning kidneys isolated chance analysis with Eco-Doppler does not distinguish between AR and ATN. A dysfunctional graft with an RR in the arcuate artery of nearly 9.7 suggests NFX, but AR with interstitial predominance cannot be ruled out.

Acute Disease↗
PubMed1994

[Gastrointestinal complications in renal transplantation].

Seventy-nine gastrointestinal complications in 480 recipients of a renal transplant (RT) (16%) are described. The most frequent complication was high digestive haemorrhage (HDH) (19/480) (2.9%); other complications were: esophagitis, gastroenteritis, diverticulitis, cholecystitis, intestinal tuberculosis, rectal ulcer and colonic polyps. Mortality secondary to gastrointestinal complications was 1.1%. Sixty-seven percent of cases with peptic ulcer developed HDH, an incidence higher than that observed in the general population (20%). Twenty-one percent of transplanted patients with DH had ulcer background. Cholecystitis and diverticulitis were complications with a low incidence (0.2% and 0.6%, respectively) which do not seem to justify aggressive diagnostic and therapeutic manoeuvres prior to the transplant. Prevalence of intestinal tuberculosis in this series (0.4%) was higher to that described in the literature.

Adolescent↗