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Biomedical subjects

G Guerra

Publications and source records attributed to G Guerra.

At least 37 records · Page 2Linked to original sources
PubMed1997

Bile salt-induced cytotoxicity and ursodeoxycholate cytoprotection: in-vitro study in perifused rat hepatocytes.

OBJECTIVES: Membrane toxicity induced by hydrophobic bile salts may be important in liver diseases. Administration of ursodeoxycholate reduces serum liver enzymes in chronic liver diseases, but the nature of this effect is still unclear. We aimed at establishing a convenient in-vitro system for investigating the hepatotoxic properties of hydrophobic bile salts and the putative hepatoprotective effect of ursodeoxycholate. METHODS: About 100 mg of freshly isolated rat hepatocytes were suspended on a resin column (Bio-Gel P4 fine) and perifused with different concentrations of bile salts. The effluent was collected at 5-min intervals and assayed for lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity. Enzyme leakage induced by bile salts was compared with that induced by Triton X-100 (Union Carbide, Danbury, CT, USA) at different concentrations. After perifusion, hepatocytes were collected for electron microscopic observation. RESULTS: Cytotoxicity of individual bile salts, assessed by enzyme release, was time and concentration dependent and corresponded to their hydrophilic-hydrophobic balance. Perifusion with hydrophilic bile salts, cholate and ursodeoxycholate, did not result in a significant enzyme release in concentrations up to 5 mmol/l, whereas hydrophobic bile salts, chenodeoxycholate and deoxycholate, induced significant enzyme leakage even in low concentrations, 0.5 and 0.1 mmol/l, respectively. Addition of ursodeoxycholate significantly reduced the hepatotoxic effect of deoxycholate. This protective effect was evident within minutes. The ultrastructural appearance of hepatocytes exposed to hydrophobic bile salts was very similar to the non-specific cellular lysis observed after exposition to Triton X-100, suggesting that they act mainly in a detergent-like fashion. CONCLUSION: Perifused rat hepatocytes seem a convenient in-vitro system for investigating the hepatotoxic properties of bile salts and hepatoprotective effect of ursodeoxycholate, offering the opportunity to investigate the effects of bile salts under dynamic conditions, mimicking the in-vivo situation, and allowing continuous enzyme release monitoring. Hydrophobic bile salts seem to act mainly in a detergent-like fashion; ursodeoxycholate-related hepatoprotection could be due not only to a dilution effect of toxic bile salts, but also to a direct cytoprotective effect.

Animals↗
PubMed1996

Changes in human plasma nerve growth factor level after chronic alcohol consumption and withdrawal.

Numerous studies reported in recent years have shown that withdrawal from chronic consumption of drugs induces high levels of anxiety, both in humans and in animal models. In the present study, we demonstrated that withdrawal from chronic consumption of either ethanol or heroin causes a significant increase in plasma nerve growth factor, suggesting that the resulting anxiety condition triggers the release of this molecule. Although the functional significance of this phenomenon needs to be better defined, it is hypothesized that the increased levels of circulating nerve growth factor might be involved in homeostatic adaptive and/or reparative mechanisms.

Adult↗
PubMed1996

The determination of plasma transferrin receptor as good index of erythropoietic activity in renal anemia and after renal transplantation.

Both the plasma determinations of erythropoietic (EPO) and transferrin receptor (TfR) would provide a good characterization of anemia especially when mixed erythron disorders underlie, such as in renal failure. Immunologic assays of EPO and TfR, as well as standard hematologic determinations (hematocrit, reticulocyte count, serum iron, transferrin, ferritin) were performed in patients with chronic renal failure (CRF), in regular dialysis treatment (RDT) and in transplanted (TX) patients. In nonanemic TX patients both EPO and TfR ranged normally, whereas in anemic TX ones (Hct < 40%) both values were increased suggesting the physiologic response both of the kidney and of the erythron to decreased red cell mass. In transitory posttransplant erythrocytosis the increased values of TfR, with normal EPO values, would hypothesize a defective feedback to EPO release. Both EPO and TfR values were found increased in TX patients with adult polycystic kidney disease with persistent erythrocytosis (Hct > 50%), thus confirming previous observations. In CRF and RDT patients, all anemic, both EPO and TfR were normal, even though significantly low with respect to the degree of anemia. In RDT seriously anemic patients, the administration of recombinant human EPO induced different patterns of bone marrow response. We conclude that the determination of TfR would provide further information on renal anemia since the receptor increase mostly preceded the rise of Hct, evidencing those patients who will not have an effective bone marrow response to the therapy.

Adult↗
PubMed1996

Red blood cells expressing fetal antigens: their presence in adults with certain forms of anemia.

Using the IgG fraction of an antiserum against cord red blood cell (RBC) membranes (F-IgG), antigenic properties of RBC of newborns (n = 24) and patients suffering from anemia (n = 46) [either due to beta-thalassemia intermedia (n = 37) or hemorrhage (n = 9)] as compared to those of normal adults (n = 18) were examined with fluorescence microscopy, flow cytometry and radioimmunoassays (RIA). With fluorescence microscopy and flow cytometry 1.01 +/- 0.31 and 0.82 +/- 0.28% (mean +/- SD), respectively, of cord RBC and 0.79 +/- 0.31 and 0.53 +/- 0.28% of RBC from anemic patients reacted with F-IgG. RBC of normal adults showed virtually no F-IgG reactivity. In anemic patients there was a good correlation between the percent of F-IgG-reactive cells and the percent of reticulocytes, although the former were only two thirds of the latter; the ratio of F-IgG-reactive cells to reticulocytes was higher in posthemorrhagic anemia than in thalassemia. Moreover, double stainings revealed that the majority of F-IgG-reactive RBC were at the reticulocyte stage (80%), and coexpressed transferrin receptor (96%). Furthermore, the F-IgG-positive RBC correlated inversely with Hb levels. When RIA was employed, F-IgG binding to RBC of anemic patients and newborns was similar and considerably and significantly higher than that to RBC from healthy adults. The results demonstrate the reappearance in certain forms of anemia of F-IgG-reactive RBC, which are likely to represent a subpopulation of reticulocytes.

Adult↗
PubMed1996

Molecular analysis of CYP21 and C4 genes in Brazilian families with the classical form of steroid 21-hydroxylase deficiency.

The most common enzymatic defect of steroid synthesis is deficiency of the adrenal steroid 21-hydroxylase. Inhibition of the formation of cortisol results in an increased pituitary release of ACTH which in turn drives the adrenal cortex to overproduce androgens. This hormonal setting affects the development of genetic females by misdirecting the differentiation of external genitalia towards the male type. Since the isolation of the gene encoding 21-hydroxylase enzyme in 1984, gene deletions, large gene conversions, and microconversions have been reported to be responsible for the disease. In this paper, we report a study of this genetic defect in 22 families with one or more affected offspring diagnosed as having the classical form of congenital adrenal hyperplasia. The DNA from 30 patients was analyzed with three restriction enzymes. Hybridization with a 21-hydroxylase cDNA probe and the 5' end of a C4 genomic probe disclosed gene deletion in 7.3% (3/41) of the disease-related chromosomes. The rate of large gene conversion was 17.1% (7/41), and no abnormality in the hybridization pattern was observed in 75.6% (31/41) of the disease alleles. Densitometry of the autoradiographs was used to determine the ratio of the copy-number of the 21-hydroxylase gene (CYP21B) to the copy-number of its pseudogene (CYP21A). Differences in phenotype, the low frequency of gene deletion, and the high frequency of gene conversion compared with other studies in different populations indicated that 21-hydroxylase deficiency in the Brazilian population may involve different molecular mutations.

Adrenal Hyperplasia, Congenital↗
PubMed1995

Reactivity of the H(+)-ATPase from Kluyveromyces lactis to sulfhydryl reagents.

N-Ethylmaleimide (NEM) inhibited the H(+)-ATPase (EC 3.6.1.35) from Kluyveromyces lactis with a second-rate constant of 200 M-1 min-1. H(+)-ATPase was partially protected by Mg-ADP. Low concentrations of Mg protected ATPase from the effects of NEM, while high Mg sensitized ATPase to NEM. The reaction of 14C-NEM with the native enzyme modified three cysteine residues/monomer, two of which were involved in 80% of the inactivation of the enzyme. In the presence of Mg-ADP, NEM binding to the first residue had only a slight effect on the activity (10-20% inhibition). After further incubation, the modification of a second cysteine residue (probably cys-221) inactivated the ATPase. Methyl methanethiosulfonate did not inhibit the H(+)-ATPase but resulted in a NEM-resistant H(+)-ATPase. There seems to be at least one cys (probably cys-532) at, or near, the nucleotide binding site of the H(+)-ATPase, which does not appear to be essential for activity. Modification of a second cys residue (cys-221) also resulted in inactivation by NEM; this residue was not protected by ADP and thus probably is not at the ATP binding site.

Adenosine Diphosphate↗
PubMed1995

Perception of gastric distension. Influence of mode of distension on perception thresholds and gastric compliance.

Gastric distension has been used to evaluate gastric sensory function in humans, but the methodology is poorly validated and studies in vivo comparing different distension protocols are lacking. We aimed to compare the influence of the mode of gastric distension on sensation and gastric compliance utilizing a barostat device. In seven healthy volunteers, we positioned a barostat bag in the proximal stomach and tested in random order (in triplicate) four different distension protocols: (1) standard ramp distension with 4 mm Hg pressure step increments of 20 sec duration; (2) slow ramp distension with 2 mm Hg pressure increments of 40 sec duration; (3) random distension using a pressure ramp consisting of 2 mm Hg increments of 40 sec duration with randomly interposed pressure steps 50% below the preceding pressure step; and (4) rapid random distension with 4 mm Hg pressure increments of 10 sec duration with randomly interposed pressure steps 50% below the preceding pressure step. The distension procedures yielded mean airflow rates during the different distension protocols between 2.4 ml/sec for standard ramp and 18.4 ml/sec for rapid random distension. First perception and maximal tolerable pressure were 10.9 +/- 1.1 mm Hg and 19.6 +/- 1.5 mm Hg, respectively. First perception and maximal tolerable pressures were significantly correlated (r = 0.93, P < 0.005). The gastric pressure at occurrence of perception and the maximal tolerated pressure were not significantly different for the different distension protocols but gastric compliance was significantly reduced during rapid ramp distension (P < 0.01 vs slow ramp and P < 0.05 vs random distension) but not during standard ramp distension. We conclude that gastric sensory pressure thresholds as assessed by isobaric distension are not influenced by the mode of distension. The high correlation of pressure thresholds at first perception and maximal tolerated distension suggest a single population of gastric mechanoreceptors that mediate first sensation at low intensity stimulation and pain at intense stimulation.

Adult↗
PubMed1994

Sulfhydryl groups essential for the volume-sensitive release of taurine from astrocytes.

The volume-sensitive [3H]taurine efflux from cultured astrocytes was found to be strongly inhibited by the sulfhydryl group-modifying reagent N-ethylmaleimide (NEM). This maleimide inhibited taurine efflux evoked by 50% hyposmotic solutions with an IC50 of 54 microM. The inhibition by NEM followed pseudo-first order reaction kinetics. A double log plot of the pseudo-first order constant against NEM concentration gave a linear relationship with a slope of 1.2. The data are consistent with a simple bimolecular reaction mechanism in which one molecule of NEM reacts with one sulfhydryl group per transport unit. The membrane-impermeant maleimide derivative 5-eosin maleimide did not affect the volume-stimulated taurine efflux. The sulfhydryl-modifying mercurial reagents mersalyl and p-chloro mercuribenzenesulfonate (0.5-1 mM) increased [3H]taurine efflux under isosmotic conditions and concomitantly decreased the hyposmolarity-evoked efflux. The results demonstrate an essential requirement for sulfhydryl groups for the volume-sensitive taurine efflux.

Animals↗
PubMed1994

Pulmonary infections in lung cancer patients at diagnosis.

We carried out a prospective study involving 96 consecutive lung cancer patients at diagnosis, in order to determine through quantitative cultures of the bronchoalveolar lavage (BAL) fluid, the prevalence of pulmonary infections; we also evaluated the relationship between a patient's performance status, immunocompetence, lung cancer stage, histotype and the occurrence of respiratory infections. The patients (81 males, 15 females) had a mean age of 64 +/- 9 years. Of these, 62 were smokers, 30 were ex-smokers and four had never smoked. Sixty-seven patients had a prior history of chronic bronchitis. A total of 42 micro-organisms were cultured from the BAL fluids of 33 patients (34.3%). Fifty percent of these micro-organisms were gram-negative, 33.3% were gram-positive and the remaining 16.7% were other micro-organisms. The bacilli most often isolated were the Haemophilus species, accounting for 38.8% of all gram-negative bacilli. The most frequently isolated gram-positive pathogen was the Staphylococcus aureus. We have not found a significant relationship between the presence of a respiratory infection and the different cell types separately analyzed, nor with SCLC and NSCLC patient groups, nor with the stage of the disease. The performance status, the immunoregulatory ratio and the lymphocyte subsets were not significantly different in patients with or without a pulmonary infection. We think that the identification of a definite etiologic agent is of great importance for a rational anti-microbial treatment of pulmonary infections.

Adult↗
PubMed1991

[Heart arrhythmias in chronic respiratory failure due to chronic obstructive bronchopneumopathy: the incidence and correlations with nocturnal respiratory disorders].

The aim of this study was to assess: frequency and type of cardiac arrhythmias in patients with severe stable chronic obstructive lung disease (COLD) and chronic respiratory failure (CRF); diurnal or nocturnal predominance of the detected arrhythmias; prospective relationships between arrhythmias and nocturnal hypoxemic-hypercapnic episodes. All patients were examined with careful and complete medical history, chest roentgenogram, standard electrocardiogram, mono and bidimensional echocardiogram, respiratory function tests, arterial blood gases at rest, 24-hour dynamic electrocardiographic recording and, simultaneously, transcutaneous nocturnal monitoring of respiratory gases (TCNM). We studied 14 men: all complained of exercise-induced dyspnoea for 8 +/- 6 years; 10 of them reported usual nocturnal snoring. Respiratory function tests provided the following values (expressed in percentage compared with theoretical ones): vital capacity 58.6 +/- 15, forced expiratory volume/s 36 +/- 19, Tiffeneau index 60 +/- 19, Motley index 160 +/- 35, carbon monoxide diffusion capacity 48 +/- 26. Arterial blood gas analysis at rest resulted: PO2 47 +/- 4.5 mmHg, PCO2 49 +/- 7.9 mmHg, pH 7.38 +/- 0.3. Right ventricular diameter obtained with mono and bidimensional echocardiogram was 32 +/- 4.6 mm. Right pulmonary descending artery measured on chest roentgenogram was 23 +/- 3.8 mm. Nocturnal transcutaneous monitoring of respiratory gases showed mean PO2 of 40 +/- 9.7 mmHg and mean PCO2 of 75 +/- 19 mmHg. During night-time maximum percentage reductions of PO2 (36 +/- 17%) were measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Combined lectin-affinity and metal-interaction chromatography for the separation of glycophorins by high-performance liquid chromatography.

Human erythrocyte sialoglycoproteins, or glycophorins, were chromatographed by lectin-affinity and metal-interaction chromatography on high-performance liquid chromatographic columns. Glycophorins A, B and C were separated from other proteins and from glycophorin E by using a column containing wheat germ agglutinin, immobilized on a microparticulate silica support. The glycophorins were adsorbed on the lectin column from a mobile phase containing 0.25 M sodium chloride and recovered by stepwise desorption with 0.2 M N-acetylglucosamine solution. Glycophorins A, B and C were separated into the individual components on a silica-bound iminodiacetic acid stationary phase in the copper(II) chelate form. The separation of the glycophorins by metal-interaction chromatography was accomplished by decreasing salt gradient elution. Retention times and resolution of the individual glycophorins were sensitive to the initial sodium chloride concentration and the pH of the eluent. Addition of methanol to the eluent increased the resolution. The effects of linear, decreasing gradients of pH and methanol in 25 mM phosphate buffer on the resolution of glycophorins were also investigated. In both types of chromatography the mobile phases contained 0.05% (w/v) sodium dodecyl sulfate. With octylglycoside or CHAPS in the eluent glycophorins A and C could not be eluted. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was used to analyze all the chromatographic results.

Chromatography, Affinity↗
PubMed1988

The influence of thyroid hormones on colony growth of peripheral CFU-GM from normal and leukemic subjects.

In order to clarify the alterations of granuloblastic cells in chronic and acute myeloid leukemia, the colony growth behavior of cultured CFU-GM from the peripheral blood of normal and leukemic subjects was examined in basal conditions and after adding to the medium T3 or T4 and/or thioproline and/or flurbiprofen. These drugs had in previous investigations proved their ability to modify cellular receptors and the uptake of thyroid hormones. The study was carried out in semisolid (double agar layer) and liquid medium, utilizing the techniques described previously. Both thyroid hormones enhanced the colony growth from normal peripheral blood CFU-GM and the response was more evident with T4 than T3. The effect on leukemic CFU-GM (from CML and AML) was less clear, probably due to the presence in leukemic cells of a defect of cellular uptake and to the utilization of T3 and T4. Indeed, on addition to the culture medium of thioproline, which modifies membrane permeability, and of fluorbiprofen, which inhibits PGE synthesis, the colony number and growth from leukemic CFU increased considerably in accordance with the results of our previous studies on these substances showing that they are able to modify cellular receptors for thyroid and several other hormones.

Cells, Cultured↗