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Biomedical subjects

R Rivera

Publications and source records attributed to R Rivera.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

IUDs and PID: a comparative trial of strings versus stringless devices.

An international multicentered clinical trial was designed to determine the possible role of intrauterine device (IUD) marker strings in the etiology of pelvic inflammatory disease (PID). A total of 1265 women were admitted and randomly allocated to receive either a standard TCu200 IUD or a TCu200 IUD without marker strings. These patients were followed-up through 12 months postinsertion. No statistically significant differences were found between the two groups of IUD users with respect to the incidence of PID or other types of infection or inflammation. The 12-month life table termination rates and overall continuation rates were also similar for users of the respective devices, with the exception of removal rates for bleeding/pain, which were significantly higher in the strings group than in the stringless group. However, the number of bleeding/pain complaints ever reported during the study were not statistically different in the two study groups. The study results indicate that the IUD string does not play an important role in the etiology of PID associated with the use of IUDs.

Adult↗
PubMedDate not supplied

Determination of protein loading in biodegradable polymer microspheres containing tetanus toxoid.

Various methods to determine loading of vaccine in biodegradable polymer microspheres encapsulating tetanus toxoid were evaluated. The microspheres were composed of poly (D-lactic acid) (PLA) and poly (DL-lactic-co-glycolic acid) (PLGA). Dissolution of microspheres in organic solvents such as methylene chloride, chloroform, or dimethyl sulfoxide and extraction of vaccine antigen or total protein with phosphate buffered saline gave variable results which depended upon the characteristics of the microspheres, such as type of polymer, excipients used in the microspheres and formulation conditions. Microspheres made from low molecular weight PLGA polymer and showing a large burst release exhibited up to 25% extraction of antigen whereas microspheres made from PLA microspheres with low burst release showed < 1% extraction. Extraction of total protein with 0.1 N NaOH and 5% sodium dodecyl sulfate showed results similar to those obtained with organic solvent extraction method. Partial digestion of microspheres with 6 N HCl at 60 degrees C for 20 h resulted in approximately 30% loss in TT protein by micro-bicinchoninic acid (BCA) assay. The major problem with this method was strong reactions in the micro-BCA assay of stabilizers, particularly sugars (glucose, sucrose) used in the microsphere formulations. Complete digestion of microspheres with 6 N HCl at 110 degrees C for 20 h or with 13.5 N NaOH at 121 degrees C for 1 h and quantitation of amino acids by a modified ninhydrin assay showed reproducible results on the protein loading in the microspheres. However, this method was affected by the presence of stabilizers, such as gelatin, which contain amino acids. Further, sucrose concentrations higher than 10% caused interference in the ninhydrin assay on samples hydrolyzed with 6 N HCl. In contrast, hydrolysis with 13.5 N NaOH did not show any interference by sucrose. Stabilizers used outside the microspheres for lyophilization purposes may be removed by washing the microspheres before loading determination or by dialysis but stabilizers used inside the microspheres would still cause interference. For reliable determination of total protein in the microspheres containing vaccines, we suggest complete digestion of microspheres with acid or base followed by amino acid analysis by colorimeteric assays such as ninhydrin method or using amino acid analyzers. The method needs to be optimized for each type of formulation to eliminate interference by the excipients. Alternatively, total protein nitrogen in the microspheres may be determined by the Kjel-dahl method if no amino acids or other nitrogen containing stabilizer is used inside the microspheres.

Antigens, Bacterial↗
PubMedDate not supplied

HLA antigens on red cells. Implications for achieving low HLA antigen content in blood transfusions.

HLA antigens on red cells were measured using the W6/32 monoclonal antibody as well as with other monoclonal antibodies directed to monomorphic determinants of HLA Class I molecules. Antibody binding was quantitated indirectly by either radioimmunoassay or flow cytometry. Red cells from approximately 50 percent of blood donors bound HLA-A, B, and C antibodies but not antibodies to HLA-DR or those directed to other leukocyte-specific antigens. Persons with HLA-B7-positive lymphocytes consistently expressed measurable red cell HLA antigens. However, 35 percent of donors with HLA-B7-negative lymphocytes also expressed HLA on red cells, and this expression did not correlate with any other HLA antigen. Storage did not affect expression of HLA antigens in red cells stored at 4 degrees C for 21 days or in red cells that had been cryopreserved. Contrary to previous reports, red cells expressing HLA antigens also had beta-2-microglobulin detected, suggesting that the HLA molecules in red cells are similar to those in lymphocytes and other cells, and consequently, that they have the potential to be immunogenic. These results demonstrate that patients requiring multiple transfusions will be exposed to HLA antigens even if they receive blood units depleted of leukocytes and platelets.

Blood Donors↗
PubMedDate not supplied

Serum alkaline phosphatase activity and skeletal maturation in Guatemalan adolescents.

Serum alkaline phosphatase activity (AP), stature and Tanner-Whitehouse-2 RUS skeletal age (SA) were determined for 873 rural Guatemalan youth and young adults 11-25 years of age. Mean AP decreases systematically with chronological age (CA) in girls, while an adolescent increase in mean AP occurs at 14 years in boys. When mean AP is calculated within SA groups, clear adolescent increases are apparent in girls, peaking at 11 years SA, and at 14 years SA in boys. Correlations between AP and relative skeletal age (SA-CA) decrease systematically from moderately positive at the youngest CA groups to moderately negative at the older ages, crossing zero at the chronological ages of maximum adolescent AP values. Analyses suggest the patterns of mean AP in adolescence follow closely the timing and patterns of growth velocity in stature in each sex, and are only indirectly related to SA as it is a proxy for the maturational timing of the adolescent spurt in stature.

Adolescent↗
PubMedDate not supplied

Quantitative trait loci influencing honeybee alarm pheromone levels.

Quantitative trait loci (QTL) mapping procedures were used to identify loci that influence the levels of alarm pheromones found in the stinging apparatus of worker honeybees. An F1 queen was produced from a cross between a queen of European origin and a drone descended from an African subspecies. Haploid drones from the hybrid queen were individually backcrossed to European queens to produce 172 colonies. Samples of stings were taken from backcross workers of these colonies. Alarm pheromone levels were determined by gas chromatography. RAPD markers were scored from the haploid drone fathers of these colonies. The multiple-QTL model (MQM) of MapQTL was used to identify QTLs that influence the levels of four alarm pheromone components. Seven independent, potential QTLs were identified with LOD scores greater than two, and one at LOD 1.88. We identified one QTL for n-decyl acetate, three for n-octanol, four for isopentyl acetate, and one for hexyl acetate. One region of linkage group XI shows a strong influence on body size and the levels of three alarm pheromone components. This locus explained 40% of the variance for the amount of n-decyl acetate (LOD 6.57). In general, the QTLs influencing alarm pheromone levels were independent of previously identified loci that influenced the stinging behavior of these colonies. The only exception was a potential locus influencing levels of n-octanol, which was inversely correlated with stinging behavior.

1-Octanol↗
PubMedDate not supplied

Obtaining family consent for participation in Alzheimer's research in a Cuban-American population: strategies to overcome the barriers.

Cultural values and beliefs affect family attitudes toward participation in research. Significant resistance to allowing their elders with dementia to participate in clinical research was encountered in Cuban-American families. These families expressed concern about disturbing the elder's comfort (tranquilidad) and solitude (soledad). Furthermore, most believed that intervention would be futile. Feelings of guilt associated with nursing home placement may have been exacerbated by the suggestion that active intervention could be effective. Strategies to overcome these barriers included reduced emphasis on the potential superiority of the intervention to be tested, reassurance that contact with research staff was usually appreciated by participants, arrangements to talk with the family as a group about the study, and increased use of Spanish-language consent forms.

Aged↗
PubMedDate not supplied

Role of the ouabain-like factor and Na-K pump in rat and human genetic hypertension.

Endogenous ouabain-like factor (OLF) is present in mammal tissues and after standardized extraction procedure can be similarly quantified by two independent assays: RIA and Na-KATPase inhibition. OLF was quantified both from plasma and tissues obtained from MHS hypertensive and MNS normotensive rats, maintained under the same environmental and dietary conditions, and from plasma of healthy volunteers and essential hypertensive patients. OLF biochemical characterization shows that it behaves like ouabain except for a 1000-fold higher affinity for the ouabain low-affinity Na-KATPase isoforms than ouabain. Tissue and plasma levels of OLF are higher in MHS than in MNS rats and are not influenced by exogenous OLF sources. Plasma OLF is also increased in a subgroup of hypertensive patients. Both in rats and humans a primary cell membrane alteration affecting ion transports seems to be linked to the increased levels of OLF. An antihypertensive compound which selectively antagonizes the pressor effect of OLF and corrects the ion transport defect is under development and can represent a new pharmacological approach to the treatment of hypertension.

Adrenal Glands↗
PubMedDate not supplied

[Alterations of cardiac output during bicarbonate hemodialysis and its relationship with other hemodynamic parameters].

PURPOSE: Time course of cardiac output (CO) and other hemodynamic parameters were measured during hemodialysis (HD). Our aims were to identify a characteristic CO profile and investigate the relationship with other hemodynamic parameters. PATIENTS AND METHODS: CO was measured with ultrasound dilution method in 45 chronic hemodynamically stable HD patients. Diabetics and patients with heart diseases were excluded. Ultrafiltration rate (UFR) was fixed at 649 +/- 244 mL/min. Pre/post statistical comparisons were performed for CO, cardiac index (IC), central blood volume (CBV) and total peripheral resistance (TPR). RESULTS: CO was pre 5.7 +/- 1.8 and post 4.5 +/- 1.4 L/min (p=0.001); IC was pre 3.2 +/- 0.9 and post 2.6 +/- 0.7 L/m2 (p=0.001); CBV was pre 1.28 +/- 0.39 and post 1.09 +/- 0.32 L (p=0.001). TPR increased from 18.7 +/- 5.6 to 22.7 +/- 6.1 mmHg/L/min (p=0.001). Maximal CO reduction rate was found at 60 min, thereafter it reduced progressively. Log(CO1) increased in a non-linear way with body weight gain and similarly it decreased during UFR. A negative correlation was found between log(TPR1) and log(CO1-QA). CO reduction was associated with UFR and not with age, dialysis duration, left ventricular hypertrophy, sex and hemoglobin (Hb) in a multiple regression model (r2 =0.31, p=0.05). Qa/CO1 was 0.16 +/- 0.12. CBV/CO increased from 0.23 +/- 0.06 to 0.25 +/- 0.07%. CONCLUSIONS: Progressive CO reduction and TPR increase appear to be the typical hemodynamic features of bicarbonate HD with a UFR of moderate degree. Volume overload and CO increase were related in a non-linear way. TPR1 was strongly correlated with CO1-Qa, suggesting that a large arterovenous shunt was associated with increased resistance.

Adult↗
PubMedDate not supplied

[Severe digestive hemorrhage by duodenal injury of Dieulafoy lesion].

The Dieulafoy lesion is a vascular anomaly generally located in proximal stomach. and consist of the presence of an artery of heavy caliber in the submucosa and mucosa, although the definitive diagnosis is anatomopathologic, with the endoscopic examination we can obtained a high precision approach. Is a rare cause of gastrointestinal bleeding although potentially fatal etiology of gastrointestinal hemorrhage. It occurs in fewer than 2% of the episodes of acute digestive hemorrhage. The injury of duodenal Dieulafoy has been communicated in a reduced number of cases and in some of them it has needed surgical treatment. We effectively presented and treat this case of a young man diagnosed in the initial endoscopy and was treated by means of injection of adrenalin and absolute alcohol.

Adolescent↗