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G Suárez

Publications and source records attributed to G Suárez.

At least 19 recordsLinked to original sources
PubMed2005

Oil spill in the Rio de la Plata estuary, Argentina: 1. Biogeochemical assessment of waters, sediments, soils and biota.

Aliphatic (ALI) and aromatic (ARO) hydrocarbon concentrations, composition and sources were evaluated in waters, sediments, soils and biota to assess the impact of approximately 1000 tons of oil spilled in Rio de la Plata coastal waters. Total ALI levels ranged from 0.4-262 microg/l in waters, 0.01-87 microg/g in sediments, 5-39 microg/g in bivalves, 12-323 microg/g in macrophytes to 948-5187 microg/g in soils. ARO varied from non-detected 10 microg/l, 0.01-1.3 mug/g, 1.0-16 microg/g, 0.5-6.9 microg/g to 22-67 microg/g, respectively. Offshore (1, 5, 15 km) waters and sediments were little affected and contained low background hydrocarbon levels reflecting an effective wind-driven transport of the slick to the coast. Six months after the spill, coastal waters, sediments, soils and biota still presented very high levels exceeding baseline concentrations by 1-3 orders of magnitude. UCM/resolved aliphatic ratio showed a clear trend of increasing decay: coastal waters (3.3) < macrophytes (6.7) < soils (9.4) < offshore sediments (13) < coastal sediments (17) < clams (52). All environmental compartments consistently indicated that the most impacted area was the central sector close to Magdalena city, specially low-energy stream embouchures and bays which acted as efficient oil traps. The evaluation of hydrocarbon composition by principal component analysis indicated the predominance of biogenic (algae, vascular plant cuticular waxes), background anthropic, pyrogenic and diagenetic hydrocarbons, offshore and in non-impacted coastal sites. In contrast, polluted stations presented petrogenic signatures characterized by the abundance of isoprenoids, low molecular weight n-alkanes and methylated aromatics in different stages of alteration. The petrogenic/biogenic ratio ( n-C23) and petrogenic/pyrogenic relationship (methylated/unsubstitued PAH) discriminated the samples according to the different degree of impact. The following paper present the results of the study of the progress of hydrocarbon disappearance in sediments and soils 13 and 42 months after the spill.

Alkanes↗
PubMed2004

Effect of cervical spinal cord stimulation on regional blood flow and oxygenation in advanced head and neck tumours.

BACKGROUND: Tumour ischaemia leads to decreased delivery of oxygen, chemotherapy and radiosensitisers. Hypoxia in head and neck (H&N) tumours is an important adverse prognostic factor. Spinal cord stimulation (SCS) is a well-established neurosurgical technique in the treatment of several ischaemic syndromes. This prospective study evaluated the effect of cervical-SCS on common carotid artery (CCA) blood flow and tumour oxygenation in patients with advanced H&N cancer. PATIENTS AND METHODS: Sixteen patients with advanced H&N tumours were enrolled. Cervical-SCS devices were inserted subcutaneously prior to commencement of scheduled chemoradiotherapy. Pre- and post-SCS measurements were as follows: (i) tumour oxygenation (mmHg) using polarographic probes; (ii) blood flow quantification (ml/min) and diastolic and systolic velocimetry (cm/s) in the CCA using colour Doppler. RESULTS: After SCS, median tumour oxygenation increased in two-thirds of patients (34%; P = 0.023), all patients had improved CCA blood flow (50%; P <0.001) and almost all patients showed an increased CCA diastolic velocity (26%; P = 0.003) and systolic velocity (20%; P = 0.011). CONCLUSIONS: Cervical-SCS increased tumour oxygenation and CCA blood flow, and could enhance the loco-regional delivery of oxygen, radiosensitising and chemotherapeutic drugs. Cervical-SCS as adjuvant in chemoradiotherapy of these tumours warrants further investigation.

Adult↗
PubMed2000

Reagentless biosensors based on self-deposited redox polyelectrolyte-oxidoreductases architectures.

Reagentless fructose and alcohol biosensors have been produced with a versatile enzyme immobilisation technique which mimics natural interactions and flexibility of living systems. The electrode architecture is built up on electrostatic interactions by the sequential adsorption of redox polyelectrolytes and redox enzymes giving rise to the efficient transformation of substrate fluxes into electrocatalytic currents. All investigated multilayer structures were self-deposited on 3-mercapto-1-propanesulfonic acid monolayers self-assembled on gold electrodes. Fructose dehydrogenase, horseradish peroxidase (HRP) and the couple HRP-alcohol oxidase were electrochemically connected with a cationic poly[(vinylpyridine)Os(bpy)2Cl] redox polymer (RP) interface in a layer-by-layer self-deposited architecture. The dependence of the distance on the electrochemical response of this interface was also studied showing a clear decrease in the Faradaic current when the distance to the electrode surface was increased. The sensitivities obtained for each biosensor were 19.3, 58.1 and 10.6 mA M(-1) cm(-1) for fructose, H2O2 and methanol, respectively. The sensitivity values can be easily controlled by a rational deposition and manipulation of the charge in the catalytic layers. The electrostatic assembly of the electrochemical interface and the catalytic layers resulted in integrated biochemical systems in which mass transfer diffusion and heterogeneous catalytic and electron transfer steps are efficiently coupled and can be easily manipulated.

Alcohol Oxidoreductases↗
PubMed2000

In vitro infection of cells of the monocytic/macrophage lineage with bovine leukaemia virus.

The oncogenic retrovirus bovine leukaemia virus (BLV) primarily infects B cells. Most infected animals remain asymptomatic for long periods of time before an increase in circulating B cells or localized tumours can be observed. This long clinical latency period may be explained by cells of the monocyte/macrophage lineage (M/M) becoming infected and acting as a reservoir for the virus, as shown for other retroviruses (human immunodeficiency virus-1, feline immunodeficiency virus). M/M cells in different stages of differentiation (HL-60, THP-1, U-937, J774, BGM, PM2, primary macrophages of sheep and cows) were cultured with BLV produced by permanently infected donor cells (FLKBLV and BLV-bat(2)). Donor cells were inhibited from multiplying by either irradiation or treatment with mitomycin C. In other experiments, supernatant from donor cells containing virus was used. In co-culture with the donor cells, the less differentiated monocytic cells showed severe cellular changes such as differentiation, vacuolization, cell lysis and membrane blebbing; apoptosis was a frequent phenomenon. Budding and extracellular viruses were also observed. The more differentiated macrophage cells, although they showed less signs of infection by microscopy, had a complete BLV protein profile, as seen by Western blotting; bands corresponding to p24CA (Gag) and its precursors were clearly seen. In addition, gp51SU was identified by syncytia formation assays. It is concluded that M/M cells may be infected by BLV, the consequences of the infection differing according to the type of cell.

Animals↗
PubMed2000

Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot of nonspecific and specific viral proteins frequently detected in different antigen preparations of bovine leukemia virus.

Bovine leukemia virus (BLV) infection in cattle is seldom manifested clinically, and is routinely diagnosed by serologic tests such as enzyme-linked immunosorbent assay or Western blot (WB). Because of the difficulty in interpreting WB results, the aim of the present study was to determine which of the bands observed in WB were specifically produced by BLV and which corresponded to nonspecific proteins, either derived from medium components or of a cellular nature. Five different BLV antigen preparations from 2 cell lines (FLK-BLV and BLV-bat2) frequently used for the production of BLV antigen were compared. The protein profiles of these antigen preparations were analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis and WB. Fetal calf serum, required for cellular growth and important in induction of viral transcription in vitro, was identified as a source of irrelevant proteins. In this study, 15 nonspecific protein bands in the growth medium were observed. These bands interfered with the interpretation of results. A nonspecific protein (25 kD) that was highly reactive in cell lysate preparation from BLV-bat2 was also detected. The unequivocal identification of protein bands, both specific and nonspecific, seen in WB is important not for understanding the protein profile of antigen preparations but also for determining if an animal is BLV positive or negative.

Animals↗
PubMed1998

Comparison of four tests to evaluate the reactivity of rabbit sera against envelope or Gag-related proteins of bovine leukemia virus (BLV).

Bovine leukemia virus (BLV) has a long latency period during which animals are inapparently infected, may spread the disease, and are only detected by serological techniques or by the most cumbersome molecular biology techniques. We have compared techniques for detecting either total antibodies (ELISA), anti-p24 and Gag-related proteins (Western blot), or anti-gp51 (agar gel immunodiffusion, AGID, and syncytia inhibition, SI) in rabbits inoculated experimentally with inocula of variable immunogenicity. The two tests to detect antibodies to gp51 correlated well in sera clearly positive or clearly negative by either one, but correlation was poor in the intermediate groups. All sera positive by AGID were also positive by ELISA, but results did not agree in sera negative by AGID, ELISA proving to be more sensitive. Western blot was a good technique for detecting antibodies against Gag-related proteins. However, no band was identified to clearly correspond to anti-Env-related proteins. As for other retroviruses, testing of animals for infection with BLV should include the detection of antibodies anti-Gag and anti-Env proteins.

Animals↗
PubMed1998

Differential inhibition of Maillard protein fluorescence by nitric oxide donors.

The nitric oxide donors nitroprusside (NP) and S-nitroso-N-acetylpenicillamine (SNAP) were added repeatedly over a prolonged period into a protein fructation system of 0.05 M fructose and BSA. These additions inhibited Maillard reaction advanced-stage fluorescence generation in a dose-dependent manner without affecting initiation of glycation. NP caused 66% inhibition whereas SNAP caused only 30% inhibition at maximum dose. The lower inhibition by SNAP possibly reflects an interference caused by N-acetylpenicillamine and mediated by a metal-dependent enhanced free-radical generation. We propose that the inhibition of fluorescence results from mutual annihilation between nitric oxide and free radicals, such as OH*, produced during fructation. In vivo generated nitric oxide may play a protective role in cells against the deleterious effect of free radicals that are associated with the augmented fructose autoxidation and fructation that occurs in diabetes.

Fluorescence↗
PubMed1998

Inhibition of zinc metallopeptidases by flavonoids and related phenolic compounds: structure-activity relationships.

Flavonoids and other benzopyrone substances, having an appropriate hydroxylation profile, may inhibit the metalloenzymes leucine aminopeptidase (LAP), aminopeptidase M (AP-M), and carboxypeptidase A (CP-A). A structural feature that evidently favours the interaction between flavonoids and the three metalloenzymes is the 2,3-double bond conjugating the A and B rings and conferring a planar structure. This can be considered virtually indispensable for inhibition of the three metallopeptidases, though the hydroxylation profile required differed for each of the enzymes, and the interaction mechanism and behaviour also differed. The inhibitory effect of flavonoids on LAP was reversible, and to be effective the flavonoid had to have conjugated A and B rings and ortho-dihydroxylation on at least one of the aromatic rings. This same requirement was essential for inhibition by coumarins and was attributed to a catechol-like mechanism of interaction. The inhibitory effects on AP-M were due to inactivation of the enzyme, irreversibly altered by flavonoids with a 2,3-double bond and a minimum of one hydroxyl substituent on each of the aromatic rings. With CP-A, conjugation of the A and B rings enhanced the inhibitory effect of flavonoids, though it was not strictly required. The interaction between the polyphenolic substances tested and the two zinc aminopeptidases was not reversed by adding zinc to the reaction medium, indicating that the inhibition is not due to the coordination of the phenolic hydroxyl groups with the catalytical zinc of active site, though the presence of zinc affected the interaction behaviour differently according to each substance's hydroxylation profile.

Carboxypeptidases↗
PubMed1997

Macrophages infected with bovine leukaemia virus (BLV) induce humoral response in rabbits.

BLV is a lymphotropic retrovirus which infects mainly B-cells. However, the possible infection of cells of the monocyte/macrophage lineage (M/M) might explain some aspects of the disease such as latency or disease progression. We infected sheep M/M with BLV either by culturing M/M with supernatant containing virus, or coculturing M/M with persistently infected cell lines. These BLV-infected M/M were inoculated into rabbits and the serological response was followed for two years. ELISA results using adsorbed sera showed a persistent production of specific antibodies from as early as the first week post inoculation. Two tests were used to detect the response against envelope glycoprotein gp51: Agar gel immunodiffusion (AGID) and a virus neutralization test read as syncytia inhibition (SI). Sera were positive by AGID after the second or third inoculation. Neutralizing titres (SI) were higher than those seen in control rabbits inoculated with persistently infected cell lines, suggesting that the virus may be expressed better in M/M. Gag-related proteins were analyzed by Western Blot (WB). Sera from rabbits inoculated with BLV-infected M/M recognized as many viral proteins as sera from BLV immunized control rabbits or infected cows, and this profile did not change with repeated inoculations. All these results suggest that BLV may infect M/M, where viral proteins are actively expressed to the point that they induce a humoral immune response in animals, and that animals get persistently infected.

Animals↗
PubMed1996

Taxonomic note: a proposal for reviewing the interpretation of the CAMP reaction between Listeria monocytogenes and Rhodococcus equi.

The discrepancies between the current description of the CAMP test between Listeria monocytogenes and Rhodococcus equi in the latest edition of Bergey's Manual of Determinative Bacteriology (L. monocytogenes is described as CAMP test negative with R. equi) and routine findings (positive reactions are usually described in many laboratories) make it advisable to review the current interpretation of the CAMP test to avoid confusion among people working in microbiological laboratories. Overall, 98.4% of the L. monocytogenes strains examined in this study, regardless of their source or the intensity of their hemolytic activity, displayed a synergic hemolytic reaction (CAMP phenomenon) with R. equi, indicating that L. monocytogenes can generally be considered CAMP positive with R. equi. We propose that L. monocytogenes, together with Listeria ivanovii, should be considered CAMP test positive with R. equi (circular or racket and semicircular or shovel shapes, respectively).

Hemolysis↗
PubMed1996

Cholesterol oxidase from Rhodococcus equi is likely the major factor involved in the cooperative lytic process (CAMP reaction) with Listeria monocytogenes.

The CAMP reaction between Listeria monocytogenes and Rhodococcus equi was studied by a diffusion assay. Listeria monocytogenes displayed identical cooperative haemolytic effect with supernatant cultures of R. equi or with commercial cholesterol oxidase (COX). This result, even with enzymes of different sources (commercial COX is obtained from Pseudomonas spp.) suggests that this enzyme secreted by R. equi has a crucial role in the synergistic haemolytic (CAMP) reaction with L. monocytogenes. The mechanism of the cooperative lytic process between L. monocytogenes and R. equi may represent a different and novel mechanism reaction, in which the COX may not act as a conventional second-step factor, and a reaction different to the direct interaction with the cholesterol of the erythrocyte membrane may be involved.

Cholesterol Oxidase↗
PubMed1996

Hartmannella vermiformis isolated from the cerebrospinal fluid of a young male patient with meningoencephalitis and bronchopneumonia.

Meningoencephalitis and bronchopneumonia were documented in a patient from Peubla, Mexico. The patient began with symptoms and signs of a common flu and 12 days after the onset of his disease he was admitted to the hospital presenting symptoms and signs of meningoencephalitis. The clinical course evolved into an endocraneal hypertension syndrome with bronchopneumonia, coma and death. Wide-spectrum antibiotics, immunosuppressive and anti-tuberculosis therapy were unsuccessfully administered. Important antecedents were degree I malnutrition and repeated contact with polluted water. Post-mortem autopsy was not performed. Gram-positive cocci were isolated from the spinal fluid 2 days after admission, and then active amebae were isolated from three different samples of the spinal fluid at days 16, 18 and 19 after admission. Such samples were concentrated and inoculated onto specific culture media. Identification of amebae was based on their morphology and biochemistry. All amebae were Hartmannella vermiformis. Amebae were apparently not the cause of the disease and might be considered as an opportunistic colonizer which may have caused the evolution of the disease to become worse.

Acid Phosphatase↗
PubMed1995

Fructated protein is more resistant to ATP-dependent proteolysis than glucated protein possibly as a result of higher content of Maillard fluorophores.

Glycation by fructose (fructation) renders bovine serum albumin more refractory to degradation by an ATP-dependent proteolytic system from reticulocytes than glycation by glucose (glucation). It appears that the decrease in the protein's susceptibility to degradation is a complex effect of the various protein-bound moities that are generated at the different stages of the Maillard reaction and not only the result of primary amino group blockage. Advanced Maillard reaction fluorescent components may induce a decrease in proteolysis, whereas the intermediate Amadori groups possibly may enhance degradation. However, the inhibitory effect on degradation of the fluorophores would predominate at higher levels of glycation. Resistance of intracellular fructated proteins to ATP-dependent degradation may lead to alterations in the function of cells with an active sorbitol pathway and, in this way, underlie the complications of diabetes.

Adenosine Triphosphate↗
PubMed1995

Prediction on admission of in-hospital mortality in patients older than 70 years with acute myocardial infarction.

STUDY OBJECTIVE: To identify the differential characteristics regarding risk factors, presentation, and clinical status on hospital admission in patients aged 70 years or older with acute myocardial infarction (MI) of less than 24 h of evolution, compared with patients younger than 70 years, and to analyze possible factors that could affect mortality on admission in the group of patients older than 70 years. STUDY DESIGN: Of 1,289 patients admitted in the coronary care unit with acute MI during the period 1988 to 1991, with a delay from onset of symptoms of less than 24 h, we defined two groups according to age: younger than 70 years (group 1) and 70 years or older (group 2) in order to analyze the possible predictive factors for mortality on hospital admission in patients older than 70 years (n = 322). By means of univariate analysis, we studied clinical variables that were present on admission; age; sex; medical history of diabetes, cerebrovascular accident, stable angina, previous MI, cardiac failure, right bundle branch block, and atrial fibrillation; previous treatment with digoxin, calcium antagonists, angiotensin-converting enzyme inhibitors (ACEI), antiaggregants or beta-blockers; location and extension of the acute MI, and thrombolysis. The association between mortality, as the dependent variable, and all other variables, as independent variables, was evaluated using a stepwise logistical regression procedure. RESULTS: In patients older than 70 years of age, the model included the following as independent predictors of mortality: female sex (odds ratio [OR], 2.59); complete right bundle branch block (CRBBB) (OR, 4.88); Q-wave MI (OR, 0.35 for non-Q-wave MI); and Forrester grade 2 to 3 (OR, 6.36) and 4 (OR, 80.14). CONCLUSIONS: In patients with acute MI and older than 70 years at the time of admission to the coronary care unit, together with the variables indicating the degree of hemodynamic involvement and the extension of the acute MI, factors such as female sex and CRBBB stand out as independent predictors of mortality.

Aged↗
PubMed1995

[The effect of gallopamil and propranolol in patients with ischemic cardiopathy and moderate depression of ventricular function].

BACKGROUND: Calcium channel blockers have been wide and successfully used in the treatment of coronary heart disease. Gallopamil, a metoxylic derivative of verapamil, has many of its properties and so, caution is recommended when given to patients with depressed left ventricular function. Clinical studies about this effect are scarce, and we have assessed it in patients with coronary heart disease and diminished left ventricular function. METHODS: We studied 20 patients in a cross-over, randomized, double-blind study during three weeks active periods with two intercalating washout placebo periods of one week. Patients had history of previous myocardial infarction, positive exercise stress test and ejection fraction ranging from 30% to 50% by echocardiography. RESULTS: There were no significant differences between each drug and corresponding placebo on either systolic or diastolic function. When we compared both drugs, patients showed a milder increase in area under E after propranolol than after gallopamil (p < 0.008). Clinical episodes of cardiac failure were not reported, and ejection fraction did not change. CONCLUSIONS: Both gallopamil and propranolol can be used in patients with coronary heart disease and moderately depressed left ventricular ejection fraction.

Adrenergic beta-Antagonists↗
PubMed1994

Transformation of Aspergillus parasiticus using autonomously replicating plasmids from Aspergillus nidulans.

A genetic transformation system for the aflatoxin-producing fungus Aspergillus parasiticus using two autonomously replicating plasmids from A. nidulans (ARp1 and pDHG25) is reported. Transformation frequencies using the plasmid pDHG25 were from 5 x 10(2) to 2.5 x 10(4) transformants per 10(6) viable protoplasts and microgram DNA. The stability of the plasmids in the transformants was also studied. This transformation system offers a new opportunity to clone genes related to aflatoxin production using appropriate aflatoxin-defective mutants.

Aspergillus↗
PubMed1994

A red pigment synthesized by an Aspergillus parasiticus mutant as a possible new intermediate in the aflatoxin biosynthetic pathway.

The isolation of a red pigment from an Aspergillus parasiticus mutant obtained by 366 nm u.v. light treatment of A. parasiticus NRRL 2999 is described. Studies of conversion in aflatoxin B1 and G1 suggest that the red pigment could be a possible new intermediate in the aflatoxin biosynthetic pathway not described to date, and this has been verified by studies in gas chromatography/mass spectrometry. The solubility and stability characteristics under refrigeration storage, and the influence of the temperature and the pH on its production by the A. parasiticus mutant were also studied. It grew best at 30 degrees C and pH 6. The red pigment was most soluble in ethyl acetate. The results obtained in water are emphasized where there was high stability.

Aflatoxin B1↗