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Biomedical subjects

F Acevedo

Publications and source records attributed to F Acevedo.

29 records · Page 2Linked to original sources
PubMed1980

The glucose transport activity of human erythrocyte membranes. Reconstitution in phospholipid liposomes and fractionation by molecular sieve and ion exchange chromatography.

Human erythrocyte membranes, at a protein concentration of 1-2 g/l, were solubilized with 0.12 M cholate in the presence of 0.06 M phospholipid (egg yolk phospholipids or phosphatidylcholine). More than 40% of the protein was solubilized. Cholate was removed by molecular sieve chromatography, whereby liposomes formed. These liposomes exchanged D-glucose faster than L-glucose. The recovery of glucose transport activity in the reconstituted system was estimated to be higher than 16%. The liposomes were heterogenous in size, as shown by molecular sieve chromatography on Sepharose 4B, and small liposomes predominated. In liposomes formed with phosphatidylcholine, the distribution of glucose transport activity did not parallel the distribution of protein or phospholipid, and the activity was found mainly in the smallest liposomes. The proteins were incorporated mainly in the liposomes that eluted at the lowest ionic strength upon ion exchange chromatography. The glucose transport activity separated into three main peaks upon ion exchange chromatography of egg yolk phospholipid liposomes. The activity eluted at low ionic strength. The liposomes contained proteins mainly from the 3- and 4.5-regions (nomenclature according to Steck, T.L. (1974) J. Cell Biol. 62, 1-19). The activity peaks were highest in the first part of the chromatogram. The protein distribution did not coincide with the variation in activity over each peak. Therefore, it cannot be excluded that a minor component not seen in the electrophoretic analyses might be responsible for the glucose transport activity.

Biological Transport, Active↗
PubMed1980

A molecular sieving method for preparing erythrocyte membranes.

The most widely used methods for preparing erythrocyte membranes are time-consuming, since they involve repeated steps of centrifugation and washing. We have found that membranes can be prepared in a rapid and simple way by molecular-sieve chromatography on a Sepharose 4B column. Two sizes of columns have been used, one 9-ml column to prepare about 1 mg of membrane proteins in 10 min and one 2-litre column for larger amounts (up to 200 mg in 15 min). The optimal pH and phosphate concentration for the separation of hemoglobin from the membranes were found to be 7.5 and 5 mM, respectively. Sodium dodecyl sulphate (SDS) electrophoretic analysis of the membrane proteins prepared by centrifugation and by this new method shows similar protein compositions.

Blood Proteins↗
PubMed1977

Theoretical conversion yields for penicillin synthesis.

The efficiency of conversion of the carbon-energy source to product is of primary importance in many fermentation processes. In order to assess the efficiency of a process, one must know how close the actual conversion yield is to the theoretical maximum. Theoretical conversion yields are useful, therefore, as guides in improving a process. This knowledge is particularly important today because the cost of raw materials is rapidly rising. In this study, the biochemical pathway of penicillin synthesis was used to estimate the theoretical yield of penicillin from glucose, ammonia, and sulfate. These values are compared with experimental data from the literature. An analysis of the role of glucose in the synthesis of cell mass and penicillin and in the maintenance of cells makes it possible to assess the efficiency of carbon-source utilization and to direct further advances in penicillin fermentations.

Ammonia↗
PubMedDate not supplied

Comparison of intervention strategies for control of Triatoma dimidiata in Nicaragua.

The effectiveness of three operational strategies for the control of Triatoma dimidiata was compared by a field trial in the Department of Madriz, Nicaragua. One strategy involved full pretrial evaluation, followed by spraying of all houses irrespective of whether or not they had been found to be infested. The second strategy minimised the pretrial evaluation by considering the locality infested as soon as one house was found to be positive, followed by spraying all houses. The third strategy involved full pretrial evaluation, followed by spraying only those houses found to be positive. Evaluation after twelve months indicated that all three strategies were similarly effective, since all sprayed houses remained free of infestation. However, comparative estimates of the unit intervention costs indicated that strategies 1 and 2 were substantially less efficient than the third strategy of spraying only positive houses.

Animals↗
PubMedDate not supplied

Clinical, epidemiologic, and virologic features of dengue in the 1998 epidemic in Nicaragua.

From July to December 1998, a hospital- and health center-based surveillance system for dengue was established at selected sites in Nicaragua to better define the epidemiology of this disease. Demographic and clinical information as well as clinical laboratory results were obtained, and virus isolation, reverse transcriptase-polymerase chain reaction, and serologic assays were performed. World Health Organization criteria were used to classify disease severity; however, a number of patients presented with signs of shock in the absence of thrombocytopenia or hemoconcentration. Therefore, a new category was designated as "dengue with signs associated with shock" (DSAS). Of 1,027 patients enrolled in the study, 614 (60%) were laboratory-confirmed as positive cases; of these, 268 (44%) were classified as dengue fever (DF); 267 (43%) as DF with hemorrhagic manifestations (DFHem); 40 (7%) as dengue hemorrhagic fever (DHF); 20 (3%) as dengue shock syndrome (DSS); and 17 (3%) as DSAS. Interestingly, secondary infection was not significantly correlated with DHF/DSS, in contrast to previous studies in Southeast Asia. DEN-3 was responsible for the majority of cases, with a minority due to DEN-2; both serotypes contributed to severe disease. As evidenced by the analysis of this epidemic, the epidemiology of dengue can differ according to geographic region and viral serotype.

Adolescent↗
PubMedDate not supplied

Squamous papilloma of the esophagus diagnosed by cytology. Report of a case with concurrent occult epidermoid carcinoma.

Esophageal material for cytologic smears was obtained by the gel-foam technique from an 84-year-old man with dysphagia and symptoms of obstruction in whom initial attempts at endoscopic biopsy were nondiagnostic. The smears contained cells with koilocytotic atypia, similar to those described in smears from uterine cervix lesions produced by human papilloma virus. The cytologic diagnosis of an esophageal papilloma of viral origin was confirmed by the second biopsy. A third biopsy, from a lower level of the esophagus following dilatation procedures, revealed an epidermoid carcinoma in situ contiguous with the papilloma.

Aged↗
PubMedDate not supplied

[Effect of the medium composition on the synthesis of protease by Aspergillus sp].

The main regulatory mechanisms controlling the synthesis of neural protease in batch cultures of a strain of Aspergillus were studied. Protease was inducible in this strain. No activity appeared during the trophophase when the organism was grown in a minimal medium, unless an inducer was added. Gelatine had the best induction effect among all the tested substances. The growth kinetics and enzyme production in a culture medium containing gelatine as the sole carbon and nitrogen source was determined. In spite of these results, protease activity was clearly detectable during the idiophase in absence of an external inducer. Furthermore, the addition of gelatine to cultures during the idiophase resulted in a decrease of the enzyme activity. This behaviour could be due to internal autoinduction generated by accelerated protein turnover of the nitrogen starved cells. The addition of gelatine probably reduced the protein starvation. Protease synthesis was sensitive to repression by rapidly assimilable carbon sources such as glucose and glycerol. Ammonia also caused an important repression, while nitrate and amino nitrogen had no effect. It was concluded that the synthesis of this enzyme is controlled by induction, catabolite repression, and ammonia repression, and that the enzyme production period could be adjusted by adequate formulation of the culture medium.

Aspergillus↗
PubMedDate not supplied

[5 years' experience with parietal cell vagotomy].

The authors presents five years experience with the Parietal Cell Vagotomy in 65 cases. In this group 54 of them had duodenal ulcer, 7 cases presented duodenal ulcer and Hiatal hernia. Only 4 cases presented hiatal hernia. Clinical, radiological and gastric secretion controls show a satisfactory evolution and considerable reduction in the ion H+ concentration. The authors presented in their series 4.6% recurrence in the D.U. group, the morbidity was 1.5%, they did not report operative mortality.

Adolescent↗
PubMedDate not supplied

[Use of esophageal cytology. Comparative study on the value of various methods (III)].

Several esophageal cytologic tecniques (sponge biopsy, sponge smear, and espohageal washings) were assessed and compared with endoscopy and biopsy of esophageal tumors. Esophageal cytology rendered better results than esophagoscopy or biopsy, with a 97% positivity in cases of esophageal carcinoma, when using sponge biopsy and sponge smear techniques, and of 91.4% for esophageal and gastric carcinoma of the fundus invading gastroesophageal junction, when considered together. The combination of sponge techniques was better for diagnosisng esophageal carcinoma than the application of esophageal washings, a more difficult, time consuming, and sometimes unfeasible method. However, the utilization of three mehtods enhanced the overall diagnostic possibilities in all cases of esophageal tumors when considered together.

Biopsy↗