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Biomedical subjects

A Ríos

Publications and source records attributed to A Ríos.

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

Determination of chlorophenols in human urine based on the integration of on-line automated clean-up and preconcentration unit with micellar electrokinetic chromatography.

A new method was developed and validated for the determination of chlorophenols in human urine by using micellar electrokinetic chromatography (MEKC) coupled via a mechanic arm to an on-line automatic clean-up and preconcentration unit for urine samples. Separation is accomplished by using a selective buffer consisting of 15 mM borate, 25 mM phosphate and 100 mM sodium dodecyl sulfate (SDS) at pH 9.1 in addition to a positive power supply of 25 kV at 18 degrees C. The proposed capillary electrophoresis (CE) method allows the separation of 11 chlorophenols within 7 min with a reproducibility as relative standard deviation (RSD) between 2.6% and 7.2%, and limits of detection (LODs) between 0.08 and 0.46 microg/mL for all chlorophenols. Urine samples were previously hydrolyzed with 37% HCl at 80 degrees C for 60 min and then cleaned on a C-18 mini-column. Recoveries ranged from 58% to 103%. The preconcentration treatment affords limits of determination between 4 and 12 ng/mL for all chlorophenols except pentachlorophenol and 4-chlorophenol, which could not be determined. The overall analysis time, including on-line clean-up, preconcentration and electrophoretic separation is 20 min per sample.

Chlorophenols↗
PubMed1999

Experimental colitis induced by trinitrobenzenesulfonic acid: an ultrastructural and histochemical study.

Inflammatory bowel disease (IBD) of humans is a chronic and devastating disease of unknown etiology. Models of acute colitis in animals have been achieved by intrarectal administration of agents such as 2,4,6-trinitrobenzenesulfonic acid (TNBS) into rat colon. This agent induces focal inflammation and alterations in the colon with features similar to those found in chronic inflammatory diseases in humans. The aim of this study was to assess the effect of TNBS administration on histological and ultrastructural features of the rat colon, especially in areas not affected by transmural inflammation. Also in areas without transmural inflammation, we observed a significant increase in crypt diameter and in the number and area of the goblet cells, as well as alterations in the contents of mucin in goblet cells. We conclude that TNBS treatment in rats led to severe changes in normal architecture of the colon and also in damaged areas where no direct inflammation was produced.

Animals↗
PubMed1998

Determination of anti-carcinogenic polyphenols present in green tea using capillary electrophoresis coupled to a flow injection system.

A capillary electrophoresis (CE) method was developed for the simultaneous determination of a number of major ingredients of green tea. The components analysed were caffeine, adenine, theophylline, epigallocatechin-3 gallate, epigallocatechin, epicatechin-3 gallate, (-)-epicatechin, (+)-catechin, gallic acid, quercetin and caffeic acid. Separation was achieved using a fused capillary column with 0.15 M H3BO3 as buffer at a pH of 8.5, UV detection at 210 nm and 20 kV of voltage. Analysis was carried out after treatment (extraction, filtration and dilution) of the samples in a flow injection system which was coupled to a CE equipment via a programmable arm. The procedure allows the determination of these compounds in less than 20 min. Quantitative analysis was performed by the standard addition method. Limits of detection ranged between 0.04 microgram ml-1 for flavonols and 1.2 micrograms ml-1 for caffeine.

Anticarcinogenic Agents↗
PubMed1998

Direct determination of biogenic amines in wine by integrating continuous flow clean-up and capillary electrophoresis with indirect UV detection.

A flow-injection manifold for automating the determination of biogenic amines in wine using capillary electrophoresis (CE) with indirect UV detection was developed. The ensuing method involves clean-up and solid-phase extraction (SPE) of the target analytes in the sample. Various treatments involving different SPE minicolumns were tested and compared. The C18 minicolumn was chosen to concentrate the amines following addition of ammonium chloride and ammonium hydroxide as buffer to neutralize them. Additions of amine standards were used to determine recoveries. Biogenic amines can be separated and detected after SPE with limits of detection in the range 0.05-0.1 microgram ml-1 by using 4 mM copper(II) sulphate, formic acid and 18-crown-6 as running buffer. All the amines studied are eluted within 15 min under the optimum conditions established. The overall process was successfully used to identify biogenic amines in various types of wine from different Spanish regions.

Biogenic Amines↗
PubMed1998

Changes in cultured arterial smooth muscle cells isolated from chicks upon cholesterol feeding.

We have developed cultures of smooth muscle cells (SMC) isolated from arterial hypercholesterolemic chicks (cholesterol-SMC). These cultures are suitable for the study at the molecular level of the changes in arterial SMC induced by a cholesterol diet. By using a strong dose of cholesterol (5%) for 10 d, we obtained very proliferative SMC which became foam cells after 30 d in culture. On the other hand, SMC cultures isolated from control-fed chicks had a lower growth rate than the SMC ones under the same culture conditions. DNA synthesis was fourfold greater in cholesterol-SMC than in control-SMC cultures. Intracellular cholesterol concentrations were the same in both cholesterol and control SMC during the first 14 d of culture but afterward increased in differing ways: after 20 d of culture the cholesterol-SMC increased their cholesterol content to double the control. We give here the results obtained from transmission electron microscopy, lipid analysis, proliferation studies, DNA, RNA and protein synthesis, and then discuss their implications.

Animals↗
PubMed1998

Dietary nucleotides have cytoprotective properties in rat liver damaged by thioacetamide.

Liver cirrhosis has been induced with thioacetamide administered via different routes in rats and other species. The oral intake of thioacetamide causes nodular liver cirrhosis in rats characterized by extensive fibrosis occupying most of the hepatic parenchyma. To characterize the cytological features of cirrhosis induced by thioacetamide, and the degree of recovery obtained with dietary nucleotides, we made a morphometric study of the hepatocytes in rats administered 300 mg/l of thioacetamide for 4 months, and in rats receiving the same hepatotoxic treatment but allowed a 2-weeks recovery period on a nucleotide-free diet or a 250 mg/100 g nucleotide-supplemented diet. Thioacetamide caused to cell damage and affected the ultrastructure of hepatocytes leading to a decrease in cytoplasmic area together with increased nuclear and nucleolar size. Dietary supplementation with nucleotides favoured recovery, restoring the cytoplasmic (TN=491.7+/-9.6 vs TAA=305.1+/-3.7), nuclear (73.6+/-2.8 vs 97.4+/-2.9), and nucleolar area of damaged hepatocytes (5.6+/-0.3 vs 14.0+/-0.9). The injury from thioacetamide intake increased liver collagen, but dietary nucleotides prevented hepatic deposition of this protein. This study supports the hypothesis that dietary supplementation with nucleotides is decisive in ensuring hepatocyte recovery after thioacetamide-induced liver damage, and that dietary nucleotides have antifibrotic properties.

Animals↗
PubMed1998

Dietary nucleotides correct plasma and liver microsomal fatty acid alterations in rats with liver cirrhosis induced by oral intake of thioacetamide.

BACKGROUND/AIMS: Dietary nucleotides modulate a number of metabolic processes, including long-chain polyunsaturated fatty acid metabolism. In this study, we evaluated the effect of dietary nucleotides on plasma and liver microsomal fatty acid profiles in a rat model of liver cirrhosis induced by oral intake of thioacetamide. METHODS: Fifty-four female Wistar rats were assigned to one of the following groups: rats in the thioacetamide group (n=45) were given 300 mg thioacetamide/l in their drinking water for 4 months, and rats in the control group (n=9) received water during the same period. After 4 months of treatment, 9 rats in each group were killed. The remaining rats in the thioacetamide group were divided into two new groups, and the animals in each were allowed to recover for 1 or 2 weeks on either a nucleotide-free diet or the same diet supplemented with 50 mg of each of the following: AMP, GMP, CMP, IMP and UMP per 100 g diet. RESULTS: Saturated (mainly stearic acid), monounsaturated, and n-6 long-chain polyunsaturated fatty acids (mainly arachidonic acid), and also the unsaturation index decreased in plasma of rats with experimental cirrhosis. Administration of the diet supplemented with nucleotides to thioacetamide-treated rats corrected plasma levels of saturated, n-6 long-chain polyunsaturated fatty acids and the unsaturation index. In liver microsomes, the cirrhotic rats showed lower levels of protein and higher levels of palmitic, oleic, linoleic and arachidonic acids. Protein concentrations and levels of all the above-mentioned fatty acids were corrected with the nucleotide-enriched diet. CONCLUSIONS: Dietary nucleotides contribute to correcting plasma and liver microsomal fatty acid alterations in rats with liver cirrhosis induced by chronic oral administration of thioacetamide.

Administration, Oral↗
PubMed1998

Dietary monounsaturated n-3 and n-6 long-chain polyunsaturated fatty acids affect cellular antioxidant defense system in rats with experimental ulcerative colitis induced by trinitrobenzene sulfonic acid.

The intrarectal administration of trinitrobenzene sulfonic acid in rats induces ulcerative colitis, which results in histological alterations of colonic mucosa, severe modification of the cellular antioxidant defense system, and enhanced production of inflammatory eicosanoids. This study evaluated the influence of different dietary fatty acids, i.e., monounsaturated, n-3, and n-3 + n-6 polyunsaturated fatty acids, on the recovery of the colonic mucosa histological pattern, the cellular antioxidant defense system of colon, and PGE2 and LTB4 colonic mucosa contents in a model of ulcerative colitis induced by intrarectal administration of trinitrobenzene sulfonic acid. Administration of dietary n-3 polyunsaturated fatty acids led to a minimum stenosis score, a higher histological recovery, lower colon alkaline phosphatase and gamma-glutamyltranspeptidase activities, and lower mucosal levels of PGE2 and LTB4 compared with the other two experimental groups. However, glutathione transferase, glutathione reductase, glutathione peroxidase, and catalase activities were lower in the group treated with n-3 polyunsaturated fatty acids than in the groups fed with either the monounsaturated or the n-6 + n-3 polyunsaturated enriched diet. We conclude that n-3 polyunsaturated fatty acids can be administered to prevent inflammation in ulcerative colitis, but they cause a decrease in the colonic antioxidant defense system, promoting oxidative injury at the site of inflammation.

Animals↗
PubMed1998

Sensitive determination of paraquat and diquat at the sub-ng ml-1 level by continuous amperometric flow methods.

Two methodologies are described for the determination of paraquat and diquat. The first is based on the pre-treatment of an electrode with a surfactant solution, which improves the electrochemical determination of the herbicides. Linear calibration graphs were obtained in the ranges 10-80 and 10-100 ng ml-1 for paraquat and diquat, respectively. The limits of detection were 6.32 for paraquat and 4.80 ng ml-1 for diquat. The method was applied to the determination of the herbicides in synthetic water samples. The second methodology is based on the preconcentration of paraquat and diquat in a minicolumn packed with a cation-exchange material. The determination ranges and detection limits depend on the sample volume used (5-50 ml). Thus, 50 ml of sample provides limits of detection of 0.016 and 0.020 ng ml-1 for paraquat and diquat, respectively. The applicability of the method was demonstrated with the determination of the herbicides in both synthetic and real water samples.

Diquat↗
PubMed1998

IL-4 improves the detection of cytogenetic abnormalities in multiple myeloma and increases the proportion of clonally abnormal metaphases.

In the present study the incidence of abnormal karyotypes and the number and proportion of abnormal metaphases obtained in multiple myeloma (MM) using three culture conditions were compared: unstimulated culture (72 h), IL-6/GM-CSF-stimulated culture (120 h) and IL-4-stimulated culture (120 h). The three types of culture conditions were assessed simultaneously on bone marrow samples from 30 consecutive myeloma patients. In addition DNA content (DNA ploidy and cell cycle) was analysed by flow cytometry. The number of MM samples with clonal karyotypic abnormalities was higher after IL-4-stimulated cultures (53%) than it was after IL-6 + GM-CSF (37%) and unstimulated (30%) cultures. The benefit of IL-4 was also observed in cases with low numbers of plasma cells in the bone marrow, in early clinical stages and in untreated patients. In those cases in whom clonal chromosomal abnormalities were detected by the three culture methods. the cytogenetic findings were always identical. According to our results the addition of IL-4 to the cultures of bone marrow cells in MM increases the number of abnormal metaphases.

Aged↗
PubMed1998

Severe malnutrition alters lipid composition and fatty acid profile of small intestine in newborn piglets.

The goal of this study was to evaluate the influence of severe protein-energy malnutrition (PEM) on lipid composition and fatty acid profile in the small intestinal mucosa of lactating pigs. Malnutrition was achieved by 80% protein-energy restriction for 30 d (20% of the food intake in the control group) in 7-d-old newborn piglets. Malnourished piglets had significantly lower concentrations of cholesterol, phospholipid and triglycerides in the jejunum and ileum compared with freely fed controls. Fatty acid composition of the intestinal mucosa was severely affected by malnutrition. A sharp decline in the relative percentages of (n-3) and (n-6) long-chain polyunsaturated fatty acids (LC-PUFA) in malnourished piglets paralleled higher (n-9) fatty acid proportions in the total mucosa, microsomes and phospholipids of the jejunum. The structure of the small intestine was severely affected as assessed by light and electron microscopy, and alkaline phosphatase and disaccharidase activities in the intestinal mucosa were also significantly impaired. Plasma from malnourished piglets had significantly lower concentrations of (n-3) and (n-6) LC-PUFA than that of control piglets; however, the fatty acid composition of red blood cell membrane was unaffected. Our results suggest that early severe PEM dramatically modifies intestinal membrane lipid composition. Changes in the lipid composition of the small intestinal mucosa and in phospholipid distribution as well as in the fatty acid profile may alter membrane fluidity and organization. These alterations appear to affect the activity of membrane-bound hydrolytic enzymes.

Alkaline Phosphatase↗
PubMed1997

[Syndrome of abnormal chromatin clumping in leucocytes with a high fraction of bone marrow cells in S-phase and in vitro autonomous growth].

Syndrome of abnormal chromatin clumping in leucocytes syndrome (ACCLS) is an uncommon entity which shares clinical and biological features with the myelodysplastic (MDS) and chronic myeloproliferative syndrome. In fact, as some authors consider ACCLS a new type of MDS, others maintain that it is in Ph'negative/bcr-abl negative chronic myeloid leukaemia. A new case of ACCLS appeared in a 68 year old woman, who presented with anaemic symptoms, bleeding and recurrent infections, and a haematological picture including progressive macrocytic anemia, thrombocytopenia and leuco-erythroblastosis. Marrow hypercellularity with granulocytic hyperplasia, and mature granulocytes presenting nuclear hyposegmentation and large peripheral blocks of chromatin separated by clear zones were the characteristic features of this case. No cytogenetic abnormalities were found and DNA flow-cytometry content was normal (euploid), supporting the thought that a disequilibrium exists in the hetero-chromatin/eucromatin ration in AACLS. Reverse PCR for bcr-abl transcripts was negative. The cell-cycle-phase analysis showed a high fraction of S-cells in the bone marrow (27%) in contrast to a very low S-phase (0.2%) in the peripheral blood, pattern that is different from both CMML and CML. In vitro clonogenic assays showed a high colony forming capacity and a certain grade of autonomous proliferation of the bone marrow cells, which is reminiscent of the CMML growth behaviour in culture. The patient was treated with vitamin D3, low dose Ara-C, prednisone and hydroxyurea until her demise, fifteen months after diagnosis. In total, the patient received 47 units of packed cells and 114 of platelet concentrates, and was transfused only when she presented anaemic or hemorrhagic symptoms. These clinical and haematological features suggest that ACCLS is a distinct entity that should be considered a sixth type of MDS, beside CMML, with which it has much in common.

Aged↗
PubMed1997

Steatosis and collagen content in experimental liver cirrhosis are affected by dietary monounsaturated and polyunsaturated fatty acids.

BACKGROUND AND METHODS: We used thioacetamide administered orally to induce cirrhosis in rats, and after these had recovered for 1 and 2 weeks we examined the effects of dietary supplementation with monounsaturated and n-3 polyunsaturated fatty acids, or with a combination of n-3 and n-6 polyunsaturated fatty acids, on the extent of steatosis and collagen content in the liver. RESULTS: Nodular cirrhosis, increased collagen content, and lipid accumulation were established after 4 months of treatment with thioacetamide. When the animals were fed a diet rich in oleic acid for 2 weeks, the steatosis and fibrosis decreased. Supplementation with n-3 polyunsaturated fatty acids favored reductions in collagen content but did not reduce the fat accumulation. With a diet supplemented with a mixture of n-3 and n-6 fatty acids we found no reduction in either lipid accumulation or collagen content. CONCLUSIONS: Fibrosis and steatosis may be influenced by dietary fat, and monounsaturated fat appears to influence favorably the histologic recovery of the damaged liver.

Animals↗
PubMed1996

In vitro inhibition of Ca2+/calmodulin-dependent kinase II activity by melatonin.

Recent evidence suggests that a melatonin (MEL) mechanism of action may be through modulation of Ca2+-activated calmodulin (CaM). MEL binds to CaM with a high affinity, and has been shown to act as a CaM antagonist. Among the CaM-dependent enzymes, Ca2+/Calmodulin-dependent protein kinase II (CaM-kinase II) is a particularly abundant enzyme in the nervous system. In the brain it phosphorylates a broad spectrum of substrates, thus modulating important neuronal functions. We describe the MEL effect on CaM-kinase II activity in vitro. CaM-kinase II was purified from rat brain by column chromatography, and identified by Western immunoblotting. CaM-kinase II activity was assessed in the presence of Ca2+/CaM by the kinase's ability to phosphorylate the synthetic substrate syntide-2 and by enzyme autophosphorylation. MEL inhibited CaM-kinase II activity, and enzyme autophosphorylation. Inhibition of the enzyme by 10(-9) M MEL was nearly of 30%. Trifluoperazine (10 microM), W7 (10 microM), and compound 48/80 (30 micrograms/ml), inhibited CaM-kinase II activity by 40%, 42%, and 93%, respectively. Both EGTA (5 mM) and MEL (10(-5) M) abolished autophosphorylation. The effect of MEL on CaM-kinase II activity was specific, since neither serotonin, N-acetylserotonin, nor 6-hydroxymelatonin inhibited its activity. Our results support the hypothesis that MEL acts as a CaM antagonist and cellular functions may be rhythmically regulated by MEL modulation of CaM-dependent protein phosphorylation.

Animals↗
PubMed1996

Serum amino acid changes in rats with thioacetamide-induced liver cirrhosis.

To date, no attempt has been made to study alterations occurring in the amino acid profile in chronic models of thioacetamide-induced liver cirrhosis. In this work, changes in serum amino acids and proteins in rats with thioacetamide-induced liver cirrhosis are reported, together with changes in enzyme activities in the liver and serum. Seventeen female Wistar rats were used. Eight rats were given 300 mg thioacetamide/l in drinking water for 4 months and nine rats were given water ad libitum during the same time-period. Significant increases in glycine, alanine, serine, methionine, glutamate, ornithine, phenylalanine, tyrosine, histidine and proline were observed in rats with the resulting experimental liver cirrhosis. Threonine, taurine, glutamine, lysine and citrulline tended to increase while isoleucine, leucine, aspartate, arginine and tryptophan tended to decrease. Total and nonessential amino acids increased significantly in cirrhotic animals. Total essential and aromatic amino acids tended to increase in the thioacetamide-treated group, whereas branched chain amino acids tended to decrease in the same group. Regarding serum proteins, a decrease in albumin concentration in the thioacetamide-treated animals was the only change detected. The liver enzyme activities under observation (aspartate and alanine aminotransferases, glutamate dehydrogenase and threonine deaminase) were lower in the thioacetamide group. Decreases were significant for both transaminases and threonine deaminase. Results for serum activities showed that transaminases did not change in thioacetamide-treated rats in comparison with controls. In contrast, alkaline phosphatase rose dramatically in cirrhotic rats. We conclude that the serum amino acid pattern in this chronic model of liver cirrhosis resembles in part that of the corresponding human disease.

Administration, Oral↗