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Biomedical subjects

F Vara

Publications and source records attributed to F Vara.

27 records · Page 2Linked to original sources
PubMed1981

Purification and characterization of a membrane-bound ATP diphosphohydrolase from Cicer arietinum (chick-pea)roots.

Microsomal membranes from Cicer arietinum (chick-pea) roots contained an ATP phosphohydrolase activity that could be solubilized by high-ionic-strength media. The enzyme has been purified to homogeneity by affinity and ion-exchange chromatography. It has the properties of an ATP diphosphohydrolase (apyrase, EC 3.6.1.5) that hydrolyses different nucleoside di- and tri-phosphates but has no activity towards monophosphoric esters and pyrophosphate. No stimulation by K+ could be demonstrated for either the membrane-bound or the purified enzyme, and therefore it would seem not to be related to the K+ -dependent ATPase postulated to mediate K+ transport in plants.

Apyrase↗
PubMed1980

Properties of soluble and membrane bound dopamine-beta-monooxygenase from bovine adrenal medulla cross-linked with dimethyl suberimidate.

Bovine dopamine-beta-monooxygenase from chromaffin granules in its soluble and membrane-bound forms was cross-linked with the bifunctional reagent dimethyl suberimidate, and its structural and kinetic properties were studied. 1. The cross-linking reaction does not affect the activity of soluble dopamine-beta-monooxygenase; it produces a ten percent inactivation in the membrane-bound enzyme, possibly because the linkage to other membrane proteins hinders its activity. 2. The soluble dopamine-beta-monooxygenase reaction mixture was analyzed by sodium dodecyl sulfate gel electrophoresis, showing appreciable amounts of dimer and tetramer, but only small amounts of trimer. In membrane-bound dopamine-beta-monooxygenase, subjected to the same treatment, appreciable amounts of dimer and higher aggregates were found. 3. The kinetic properties of soluble dopamine-beta-monooxygenase after the crosslinking reaction are the same as those of the native enzyme, with a ping-pong kinetic mechanism and the same real Michaelis constants for tyramine and ascorbate: KmT = 0.36 mM and KmA = 0.32 mM. Membrane-bound dopamine-beta-monooxygenase does not present a ping-pong mechanism before or after cross-linking; its real Michaelis constants are slightly modified by the cross-linking reaction: KmT = 0.4 mM and KMA = 0.4 mM.

Adrenal Medulla↗
PubMedDate not supplied

[Lung resection surgery in patients with functional limits].

To determine whether there exists in our area concordance between forced expiratory volume in one second (FEV1) estimated before surgery by ventilation/perfusion scintigraphy and real values after surgery in patients undergoing pneumonectomy and lobectomy. Prospective descriptive study. We studied 15 patients undergoing pneumonectomy (M/F 14:1, age 62 +/- 7.5 years) and 11 undergoing lobectomy (M/F 11:0 age 66 +/- 3.5 years) in the thoracic surgery unit of Hospital de Cruces between 1 March 1990 and 1 March 1993. The FEV1 of all patients before surgery was under 2.1 liters. Tumors were malignant in 23 patients and benign in 3. Ventilation/perfusion gammagrams were obtained for all patients before surgery in order to predict the loss of function after resection of the parenchyma. Two months after surgery spirometric testing was done. The FEV1 calculated based on the results of scintigraphy was compared to the real FEV1 after resection by way of graphic concordance and by calculation of a within-group correlation coefficient. A correlation coefficient of 0.82 (p < 0.001) was obtained for FEV1 estimated by ventilation and real FEV1 in patients who underwent pneumonectomy, indicating good concordance. The correlation coefficient was 0.59 (p < 0.001) indicating moderate agreement between FEV1 estimated by perfusion and real FEV1 after resection. Correlation was statistically insignificant in lobectomy patients (0.28 by the method of Ali and 0.35 by Wernly's; p = 0.19 and 0.13, respectively). Ventilation scintigraphy offers an acceptably reliable prediction of FEV1 after lung resection. The reliability of measurements estimated by scintigraphy in lobectomized patients is not acceptable.

Aged↗
PubMedDate not supplied

Vascular endothelial growth factor (VEGF) levels in peritoneal dialysis effluent.

BACKGROUND: Long-term peritoneal dialysis (PD) patients who develop peritoneal ultrafiltration failure have an abnormally large number of capillaries and sclerotic changes in peritoneal biopsy. Peritoneal vascular endothelial growth factor (VEGF) production has been suggested to explain the higher levels in peritoneal effluent than in plasma. The high effluent VEGF levels have been related to peritoneal changes consisting of increased permeability to small molecules. To further analyze the relationship between peritoneal neoangiogenesis induced by VEGF and peritoneal transport, we studied peritoneal effluent VEGF levels in active PD patients. METHODS: VEGF levels were determined in serum and plasma, and in peritoneal effluent (PE) after 4, 8 and 15 h dwell times. RESULTS: PE VEGF levels were 58.6+/-33.7 pg/mL, with a mean VEGF D/P ratio of 0.45+/-0.29 (range 0.06-0.93). In low-transport patients (n = 7) this ratio did not differ from high-average ones (n=5) (0.48+/-0.3 and 0.41+/-0.1, NS). In multivariate analysis, the VEGF D/P ratio showed no correlation with the independent variables included in this study. VEGF levels were higher in 15 h than in 8 h effluent; so the VEGF D/P ratios were higher as well. Regression analysis showed a direct correlation between PEVEGF levels and dwell time (r: 0.57, p = 0.03), but not between VEGF D/P ratio and dwell time. PEVEGF levels directly correlated with effluent protein content. Regression analysis showed no correlation between PEVEGF levels and age, time on PD, days of peritonitis, urea and creatinine-mass transfer coefficients, ultrafiltration capacity, and accumulated glucose dose. Multivariate regression analysis showed correlation only between PEVEGF levels and dwell time, but not with the other independent variables. CONCLUSIONS: This study confirms that VEGF is present in fresh PE from PD patients at levels that suggest local production and filtration from plasma. Peritoneal effluent VEGF levels are not significantly associated with peritoneal functional parameters and background, and seem to be influenced by ultrafiltration in a dilution process. We believe that the role of VEGF in peritoneal pathophysiology is part of a complex relationship involving multiple peritoneal structures and other growth factors, including local counteracting factors for VEGF that regulate neoangiogenesis.

Dialysis Solutions↗
PubMedDate not supplied

[Campylobacter gastroenteritis in patients with human immunodeficiency virus infection].

BACKGROUND: Campylobacter bacteria are frequent, and usually slight causes of diarrhea in a normal host while in an immunosuppressed host the diarrhea may lead to severe pictures. The aim of this study was to analyze the clinical features of gastroenteritis by Campylobacter spp. in hospitalized seronegative patients and in those with HIV infection. METHODS: A retrospective study of the cases of gastroenteritis by Campylobacter spp. in adult patients admitted in the authors' hospital from January 1988 to July 1993 was carried out. RESULTS: Of the 20 patients studied with gastroenteritis by Campylobacter spp., 13 (65%) had HIV infection. The mean age of the patients was 38 years (range: 18-68 years) with 70% of the cases being males. Seventy seven percent of the HIV positive patients showed diagnostic criteria for AIDS while 71% of the seronegative patients showed a base disease and/or received steroid therapy. The length of the diarrhea was greater in the patients with HIV infection on comparison with the seronegative patients (25 vs. 6 days). The diarrhea persisted for more than 2 weeks in more than half of the cases of seropositive patients. Fever continued a mean of 24 days in the HIV positive patients as compared with only 5 days in the HIV negative cases. Most of the former patients were treated with erythromycin with good response. Gastroenteritis recurred in one patient and another patient with HIV infection presented a pseudoappendicular picture. No case of bacteremia was detected in either the seropositive or seronegative patients. Campylobacter jejuni was isolated in most of the cases with a high percentage of resistence to quinolone drugs. The mean CD4 lymphocyte count in HIV positive patients was 131/mm3 (range: 1-774). Mean survival following diagnosis of gastroenteritis by Campylobacter spp. was 8.9 months (range: 1-17) in the patients with AIDS. CONCLUSIONS: Gastroenteritis by Campylobacter spp. in hospitalized patients was related with immunosuppressive states. A clinical profile of prolonged febrile diarrhea was common in HIV positive patients and was associated with a low number of CD4 lymphocytes, advanced HIV infection and short survival.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Transformed mesothelial cells in patients on CAPD for medium- to long-term periods.

OBJECTIVE: To describe the characteristics of abnormal cells present in the peritoneal effluent of 4 continuous ambulatory peritoneal dialysis (CAPD) patients; the cells were accidentally detected in a longitudinal study of cell populations in 83 patients. DESIGN: Descriptive study. PARTICIPANTS: Four stable CAPD patients (2 male, 2 female). INTERVENTIONS: Peritoneal cells were collected from nocturnal peritoneal effluent (NPE) by centrifugation. MEASUREMENTS: Light microscopy, ultrastructural, cytochemical, and immunohistochemical characteristics were studied. RESULTS: The abnormal cells were characterized by a flat appearance, large size (diameter 100 microns)--six to ten times larger than a normal macrophage, a broad acidophilic cytoplasm with rare granulations, and a low nucleus/cytoplasm ratio. The nucleus was pyknotic, with dense chromatin and sometimes appeared fragmented. Its number presented a considerable variability between the patients and was much higher in the 2 females. This number remained stable in each patient over time. These cells were negative for beta-glucuronidase and positive for PAS stain with variable intensity. A very low number of flat cells were positive for vimentin with weak intensity, whereas cytokeratin and epithelial membrane antigen (EMA) were positive in a higher number of cells with medium to strong intensity. Ultrastructural studies showed numerous short surface microvilli, cytoplasm well-developed with intracytoplasmic lumina and abundant, dispersed intermediate filaments, scattered mitochondria, and stacks of rough endoplasmic reticulum were observed. Dispersed secretory vacuoles and isolated lipid vacuoles were present. CONCLUSION: All these features imply that they are mesothelial in origin and are suggestive of a change known as peritoneal squamous metaplasia. To date, the clinical follow-up of our patients has shown a benign outcome; further studies are necessary to elucidate the significance of this peritoneal squamous metaplasia in CAPD patients.

Adult↗
PubMedDate not supplied

Long-term continuous ambulatory peritoneal dialysis reduces the expression of CD11b, CD14, CD16, and CD64 on peritoneal macrophages.

OBJECTIVE: To characterize phenotypically the macrophages from nocturnal peritoneal effluent (NPE) in patients on continuous ambulatory peritoneal dialysis (CAPD), and to determine the influence of the length of this therapy on macrophage (M phi) function. DESIGN: Cross-sectional descriptive study. PATIENTS: Fifty-five patients on CAPD who were classified into short-, medium-, and long-term groups according to their time on CAPD. Peritoneal macrophages (PM phi) were also characterized in 7 patients at the time of catheter placement, and there were 13 normal controls. INTERVENTIONS: Macrophages were collected from NPE by centrifugation. MEASUREMENTS: Membrane receptor expression was evaluated by flow cytometry analysis. RESULTS: Flow cytometry analysis revealed that the expression of CD11b, CD16, CD64, and CD14 on NPE macrophages was reduced during the course of CAPD treatment, reaching levels which represented a 40%-50% reduction of the cell surface expression detected at the start of the treatment or on normal control macrophages. Both normal and CAPD PM phi expressed CD4, CD69, and CD71 very weakly and lacked CD25. No changes in HLA-DR or in other adhesion protein (CD11a, CD11c, CD18, CD54) expression were detected, and levels were similar in both patients and normal controls. CONCLUSION: Our results show that long-term CAPD might affect Fc gamma receptor-mediated phagocytosis by reducing the expression of CD16, CD64, and CD11b. Lower CD11b and CD14 expression would also impair PM phi adhesion to mesothelial structures.

Adult↗