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Biomedical subjects

F González

Publications and source records attributed to F González.

At least 91 records · Page 5Linked to original sources
PubMed1999

Biosorption of copper and zinc by Cymodocea nodosa.

The adsorption of the two metal ions Cu and Zn in a single-component system by Cymodocea nodosa, a brown alga, under different pH conditions was investigated. The solution pH significantly affected the exhibited uptake, being maximum at a pH value of 4.5. Multi-component mixture biosorption in aqueous solutions is also reported. A comparison was made between the single-component saturation uptake and the multi-component uptakes. To evaluate the two-metal sorption system performance, simple isotherm curves had to be replaced by three-dimensional sorption isotherm surfaces. In order to describe the isotherm surfaces mathematically, three Langmuir-type models were evaluated. The isotherms indicate a competitive uptake with Cu being preferentially adsorbed. In addition, different tests were carried out to compare the process efficiency working continuously in small columns.

Adsorption↗
PubMed1999

[CEA, CA 19.9 and CA 195 in patients with colorectal carcinoma. ROC analysis].

The aim of this study was to assess the utility of determining serum levels of the CEA, CA 19.9 and CA 195 tumor markers in 906 patients with colorectal carcinoma for a 5-year follow-up period. In addition to calculating sensitivity and specificity for the common normal limits, the results were analyzed with RO curves. Sensitivity values for 90% and 95% specificity were also obtained. The results of the areas under the curve (CEA: 0.887; CA 19.9: 0.802; CA 195: 0.971) and sensitivities and specificities at different normality limits showed better behavior for CEA with respect to CA 19.9 and CA 195, the last two presenting similar results. CEA continues to be the best tumor marker to monitor patients with colorectal carcinoma.

Adenocarcinoma↗
PubMed1999

Tranexamic acid inhibits fibrinolysis, shortens the bleeding time and improves platelet function in patients with chronic renal failure.

BACKGROUND: A defect in platelet function is the main determinant of the prolonged bleeding time in chronic renal failure (CRF). We previously reported a significant correlation between platelet abnormalities and elevated plasma markers of plasmin and thrombin generation. Our aim was to explore the effect of inhibiting both plasmin action with tranexamic acid (TA) and thrombin production with low molecular weight heparin (LMWH), on the bleeding time (BT) and platelet function in patients with CRF. METHODS: 37 patients with CRF (mean creatinine 8.6 +/- 4.4 mg/dl) under conservative treatment, with prolonged BT, entered this study and received TA during 6 days, with (n = 24) and without LMWH (n = 13). BT, platelet aggregation/secretion, platelet granule contents, von Willebrand factor and parameters of coagulation and fibrinolysis were recorded before and at the end of treatment. RESULTS: The BT was shortened in 26/37 (67%) patients. This effect was associated with significant improvement of platelet aggregation and secretion, with decrease to a normal range of fibrin/fibrinogen degradation products, mild increase in plasmin-antiplasmin complexes and pronounced reduction of circulating plasminogen. No differences were seen among patients with or without LMWH. No serious side effects or complications were observed. INTERPRETATION: These findings indicate that the activation of fibrinolysis plays a significant role in the defect of primary hemostasis in patients with CRF. Inhibition of plasmin activity with TA shortens the BT and improves platelet function in the majority of patients with severe disease.

Antifibrinolytic Agents↗
PubMed1999

[Chemical disturbance of the phytoplankton structure in an artificial pond (Guaicaipuru, Edo. Miranda, Venezuela)].

When an ecosystem is disturbed, it reverts to an early successional state, characterized by changes in community structure and function, that can be anticipated as response to stress. The purpose of this paper was to check the effect of a disturbance caused by application of chemical compound (Copper Sulfate, to 100 micrograms L-1 granular of 92%) on the phytoplankton community in a pond located in Guaicaipuro, Edo. Miranda (Venezuela), and compare the diversity and composition of the community before and after the chemical application. An additional purpose was, to test the Odum's hypothesis about the community response to chemical stress. The chemical compound was apply in different random points to assure homogeneous distribution in the water body. Only one application of the chemical was used 6 hours after the first sample was taken. Dissolved oxygen in surface and depth were measured. In order to estimate the diversity and composition of phytoplankton community, samples were taken in 5 random points of the pond, until a 2 liter sample was completed in an intermediary basis, during 30 days in the beginning of rainy season, between june and july of 1994. Oxygen showed a maximum value at surface of 9.3 mg O2/L and minimal value at depth (2.3 mg O2/L). Species richness varied between 4 and 18. Phytoplankton community varied between 7.1 x 10(4) and 7.8 x 10(6) cel/L, and diversity index between 0.12 and 1.39. Oxygen, species richness and phytoplankton minimal values were noticed at the fifth day after chemical application. Before chemical application, phytoplankton community was dominated by filamentous microalgae, especially Chlorophyta. After the fifth day, this group decreased in abundance and species number. On the seventh day small-size Cyanobacteria became dominant, particularly Chroococcoid forms. The community reverted to an early stage of ecological succession. Since the ninth day, community showed the following abundance sequence: Chrysophyta, Pyrrophyta, Bacillariophyta, and Euglenophyta, with an increased species richness. At the end of the study period, filamentous Chlorophyta species appeared. These results support Odum's hypothesis.

Animals↗
PubMed1998

Effects of verapamil, sodium nitroprusside and calcium deprivation on the phenylephrine-induced contraction of smooth muscle strips from the reticular groove of adult cattle.

The effects of verapamil, sodium nitroprusside and calcium deprivation on the smooth muscle strips from the floor of the reticular groove of adult cattle were studied. The mechanical activity of the muscle strip was recorded isometrically. Contraction was induced with phenylephrine (10(-6) mol/l) in Tyrode solution. Verapamil (10(-6) mol/l) produced a high inhibition of the response, phasic and tonic (P < 0.05). Sodium nitroprusside (10(-6) mol/l) reduced mainly the phasic contraction (P < 0.05). Deprivation of Ca2+ from extracellular medium produced a high inhibition of the tonic phase. This study indicates that the action of verapamil on the reticular groove smooth muscle may be partially related to blockade of calcium entry through voltage-dependent channels, opened during phenylephrine stimulation. However, the nitroprusside action could be attributed to effect on the extrusion of calcium.

Animals↗
PubMed1998

[Epidemic outbreaks of salmonellosis caused by eating eggs].

BACKGROUND: Investigation of outbreaks of foodborne infections (OFI) by Salmonella associated with the consumption of hens' eggs from a same classification center of Castellón, and determination of origin, extension and to take measures of control and prevention. METHODS: Descriptive and case-control studies, microbiologic analysis of feces, suspicious foods, and eggs. Sampling of eggs in the classification center for estimation the prevalence of Salmonlla. RESULTS: In 1992, 5 OFI were detected, 4 collective (1 school, 2 restaurants, and 1 residence) and 1 at home, by the consumption of food prepared with eggs: fried or boiled eggs, omelette, soufflé, 2 times, and home-made russian salad. Five hundred and forty-five persons were exposed and 364 were studied, with 100 case patients and 16 hospitalized. The range of attack rates was 10.5-87.0%. Samonella enteritidis (3 OFI) and S. typhimurium (3 OFI) were the infectious agents. In February 1993, the prevalence of Salmonella in eggs from the center was 0.26% (4/1.524) (S. enteritidis, 2 isolates, and S. typhimurium, 2 isolate), three on the shell, and one in the yolk. Two farmhouses of the six supplied were infected. CONCLUSIONS: These outbreaks indicate that salmonellosis by egg's consumption are frequent here and investigation of infection sources is necessary.

Adolescent↗
PubMed1997

Endothelial cell markers in chronic uremia: relationship with hemostatic defects and severity of renal failure.

Plasma von Willebrand factor antigen, soluble thrombomodulin, and tissue factor were increased in 31 patients with severe chronic renal failure (creatinine clearance <20 ml/min) under conservative treatment, whereas plasminogen activator inhibitor antigen did not differ significantly from healthy controls. No correlation among plasma levels of these proteins was found. Three patterns of relationship between endothelial cell markers and hemostatic defects were identified: 1) Plasma thrombomodulin, a marker of endothelium damage, was found an independent predictor of bleeding time and platelet aggregation, and secretion defects, and was also related to the severity of renal failure; 2) von Willebrand factor antigen, an index of endothelial cell activation and secretion, was significantly correlated with intravascular markers of thrombin and plasmin generation and with platelet adenosine triphosphate content, but not with plasma creatinine levels; and 3) tissue factor and plasminogen activator inhibitor antigen levels were not statistically correlated with the diverse hemostatic defects. Activation of coagulation and fibrinolysis, secondary to endothelial cell activation, appearing early during the evolution of chronic renal failure, is pathogenically related to the platelet dysfunction, and probably to development of atherosclerosis and thrombotic events in this disease. The progression of chronic renal failure, through endothelial cell damage, would lead to aggravation of the platelet functional defect potentiating the hemorrhagic risk.

Antigens↗
PubMed1997

The effect of ageing on RNA content in neurons from the thalamic reticular nucleus visual sector.

In this paper we investigate nucleic acid content in neurons from the dorsocaudal region of the thalamic reticular nucleus in ageing Wistar rats. Nucleic acid per surface unit was analysed by calculating mean extinction using cytophotometric methods. Once the mean extinction and nuclear and cytoplasmic areas were known, nucleic acid total content was calculated. There was an increase in nucleic acid total content and in nuclear and cytoplasmic areas from the age of 3 months onwards. We interpreted these findings as a compensatory response, by 'neuronal hypertrophy', to the deterioration process occurring in the ageing rats. Between the 24th and 30th month, i.e. old age, nucleic acid per surface unit and total content in the cytoplasm exhibited a considerable decrease.

Aging↗
PubMed1997

Human immunodeficiency virus infection modifies the natural history of chronic parenterally-acquired hepatitis C with an unusually rapid progression to cirrhosis.

BACKGROUND/AIMS: To investigate the possible role of HIV infection in the natural history of chronic parenterally-acquired hepatitis C. METHODS: A multicenter cross-sectional study was performed in 547 patients with chronic parenterally-acquired hepatitis C with or without HIV infection (116 HIV-positive and 431 HIV-negative). Approximate duration of HCV infection was estimated in all patients included, and histologic diagnoses made at different time intervals following HCV infection were analyzed in both groups. Factors related to serum HCV-RNA levels were also investigated. RESULTS: Histologic findings were similar in liver biopsies from both HIV-infected and noninfected patients. However, in the first 10 years, 13 out of 87 (14.9%) HIV-positive subjects developed cirrhosis, in comparison with 7 out of 272 (2.6%) in the HIV-negative group (p < 0.01). Similar results were found in the first 5 and 15 years, respectively, and most of the HIV-negative patients with cirrhosis (42 out of 56) developed cirrhosis in a time interval longer than 15 years. Consequently, mean interval from estimated time of HCV infection to cirrhosis was significantly longer in HIV-negative than HIV-positive patients (23.2 vs. 6.9 years; p < 0.001). Chronic active hepatitis (with and without cirrhosis) and long duration of HCV infection were significantly associated with higher HCV load (p < 0.05). Finally, HIV-positive patients with CD4+ cell counts > 500 cells/ml showed a lower HCV load than those with < 500 cells/ml (p < 0.05). CONCLUSIONS: HIV infection modifies the natural history of chronic parenterally-acquired hepatitis C with an unusually rapid progression to cirrhosis. HIV-related immunodeficiency may be a determinant of higher hepatitis C viremia levels and more severe liver damage.

Adult↗
PubMed1997

Corneal graft after drug-induced toxic epidermal necrolysis (Lyell's disease).

Toxic epidermal necrolysis (TEN) is a clinical syndrome characterized by extensive epidermal loss similar to that found in scalding. Drug sensitization is generally considered to be the mechanism leading to this condition. Severe ocular manifestations are present in nearly all patients. We report a case of TEN with severe ocular involvement, on whom two penetrating keratoplasties were performed in the same eye. Although the prognosis of keratoplasty is reported to be poor when cicatricial changes are present, after the second graft, our patient's symptoms of pain decreased and her visual acuity from light perception improved to 20/40. The graft remains transparent under immunosuppressive therapy twenty-three months after surgery.

Adult↗
PubMed1997

Age-related differences in norfloxacin pharmacokinetic behaviour following intravenous and oral administration in sheep.

The pharmacokinetics of norfloxacin after intravenous (i.v.) and oral (PO) administration in lambs (n = 5) and adult sheep (n = 5) were studied. After i.v. administration (10 mg.kg-1) plasma concentrations were best fitted by a three-compartment open model in both age groups. Distribution volumes were significantly larger in lambs (approximate 4.0 fold difference between 4 week old and adult sheep). There was no significant difference (p < 0.05) between the groups in terms of elimination halflife but plasma clearance was significantly higher in lambs. Norfloxacin was poorly absorbed after oral administration (60 mg.kg-1) in sheep (F = 4.04%). Mean oral bioavailability was 73.51% in lambs (30 mg.kg-1). Norfloxacin elimination was faster in lambs after oral administration. MRTt was significantly prolonged in both age groups when compared with the respective data for i.v. administration.

Absorption↗