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Biomedical subjects

R Alvarez

Publications and source records attributed to R Alvarez.

At least 19 recordsLinked to original sources
PubMed2003

Vitrification of turbot embryos: preliminary assays.

Successful fish embryo cryopreservation is still far from being achieved. Vitrification is considered the most promising option. Many factors are involved in the success of the process. The choice of a proper vitrification solution, the enzymatic permeabilization of embryos to increase cryoprotectant permeability, the adequate container for embryo loading, and the temperature for thawing, were the parameters considered at different developmental stages in the present study. After vitrification, embryo morphology was evaluated under stereoscopic microscopy, establishing the percentage of intact embryos. Two of the studied parameters yielded differences in this percentage, the volume of straw used for embryo loading (1 ml straws were significantly better than 0.5 ml straws, with regard to post-thawed embryo morphologies), and the thawing temperature, achieving 49% of embryos with intact morphology after thawing at 0 degrees C. After thawing, the intact embryos were incubated and periodically observed to detect morphological changes. Changes in the perivitelline space, shrinkage of the yolk and chorion ruptures as well as a progressive whitening of the embryo and yolk were observed. After 8 h all embryos showed clear signs of degradation and during this incubation period no embryo showed any developmental ability.

Animals↗
PubMed2002

Study of the composition of tars produced from blends of coal and polyethylene wastes using high-performance liquid chromatography.

Tars produced at semi-industrial scale in a coke oven of 6 x 10(3) kg capacity were used to investigate the effect of using polyethylene waste as an additive in the carbonization process with coal. The polyethylene wastes used were low-density polyethylene from the agriculture greenhouses and high-density polyethylene from domestic sources. The high-performance liquid chromatography analysis of the soluble fractions in toluene and carbon disulfide, using two polystyrene-divinylbenzene columns and a mixture of dichloromethane-methanol as a mobile phase, provides useful information on the composition of tars and their derived pitches in terms of the substitution and molecular topology of polynuclear aromatic compounds (PACs). Differences in composition of tars produced with polyethylene waste at 1% (w/w) have been found to be negligible, while a higher amount of the waste (3%, w/w) promoted the formation of peri-condensed PACs at the expense of the substituted cata-condensed PACs. This behaviour is due to more extensive secondary reactions of tar precursors via dealkylation and aromatic condensation taking place during the carbonization process as a consequence of a more viscous co-carbonizing system. Changes in tar composition caused by this amount of polyethylene waste addition were comparable to those promoted by an increase in the carbonization temperature at semi-industrial and industrial ovens and by the coal preheating before the carbonization process. The characteristic features in tar composition were also found for the derived pitches from tars obtained with the polyethylene waste addition.

Chromatography, High Pressure Liquid↗
PubMed2001

Role of tyrosine phosphorylation in ligand-independent sequestration of CXCR4 in human primary monocytes-macrophages.

The chemokine stromal cell-derived factor (SDF)-1 and its receptor, CXCR4, play important roles in human immunodeficiency virus type 1 (HIV-1) pathophysiology, leukocyte trafficking, inflammation, hematopoiesis, embryogenesis, angiogenesis, and cancer metastasis. The effects of cytokines on the regulation of CXCR4 function were investigated in human primary monocytes-macrophages. The expression of functional CXCR4 on the cell surface was demonstrated by the detection of ligand-induced Ca(2+) mobilization, chemotaxis, and ligand-induced receptor endocytosis. Surface CXCR4 expression was down-regulated by cytokines interleukin-4 (IL-4), IL-13, and granulocyte-macrophage colony-stimulating factor (GM-CSF) and up-regulated by IL-10 and transforming growth factor-beta 1. Down-regulation was mediated post-translationally, in the absence of protein degradation, through an endocytotic mechanism. In contrast to SDF-1 alpha-induced CXCR4 endocytosis, cytokine-induced endocytosis of this receptor was independent of actin filament polymerization. GM-CSF increased the expression of G protein-coupled receptor kinase 3 (GRK3), beta-arrestin-1, Pyk2, and focal adhesion kinase (FAK). Cytokine treatment also increased the total and tyrosine-specific phosphorylation of CXCR4 as well as the phosphorylation of FAK on tyrosine 397. It also induced the formation of GRK3.CXCR4 or FAK.CXCR4 complexes. Infection of macrophages by primary R5X4 and X4 isolates of HIV-1 was inhibited by IL-4, IL-13, and GM-CSF, an effect that was associated with down-regulation of surface CXCR4 expression. These data indicate that ligand-dependent and ligand-independent endocytoses of CXCR4 are mediated by different mechanisms. Cytokine-induced endocytosis of chemokine receptors may be of therapeutic value in HIV-1 infection, inflammation, tumor metastasis, and defective hematopoiesis.

Actins↗
PubMed2001

Ovine Echinococcus granulosus transmission dynamics in the province of Rio Negro, Argentina, 1980-1999.

In this work, the impact of a hydatidosis control programme for dogs on the intermediate ovine host was specifically analysed to determine the levels of prevalence achieved and the dynamics of parasite transmission, as well as to evaluate the quality of diagnostic systems in slaughterhouses. A field study was conducted in four slaughterhouses (Valcheta, Los Menucos, Jacobacci, Bariloche) that process animals coming from all the departments within the work area. The control programme for dogs entailed treating dogs with 5 mg/kg praziquantel at 2-month intervals for 20 years. Sample size was determined with a 10% error margin and a 95% significance level. Harvested viscera (liver, lungs, kidneys) were preserved in 5% formaldehyde and sent to the laboratory for diagnostic confirmation of both positive and negative specimens. The 61% initial prevalence dropped to 18.3% at the end of the 10-year period, observed differences proving significant (Chi-square=15.454, P=0.00). There were statistically significant increases in infection prevalence with age (Pearson's Chi-square=133.61, P=0.00). Overall, 37.2% of hydatidosis cases diagnosed in slaughterhouses were considered non-hydatid by histological study. On the other hand, 1.1% of those diagnosed as healthy were found to be infected with hydatidosis. The number of hydatid cysts per animal increased with age: 0.04 in lambs and 1.22 in adults (linear regression equation, -0.0539+0.0127 x age), whereas the average for the whole period was 3.7% in lambs and 20.5% in adults. Viability studies indicated that 63.8% of parasitised animals had viable cysts, out of which 53.3% were fertile. Diagnosis of infection in sheep made by means of an adjusted statistical design and with histological confirmation of the presumptive diagnosis made in slaughterhouses demonstrated the flaws of the official systems for epidemic surveillance of hydatidosis. However, there was no overall significant difference in slaughterhouse and laboratory data.Ro was 0.53 and could imply a decrease in reproductive capacity of the parasite and steady state extinction.

Abattoirs↗
PubMed2001

Gas chromatographic study of the volatile products from co-pyrolysis of coal and polyethylene wastes.

The aim of this study was to determine the volatile products distribution of co-processing of coal with two plastic wastes, low-density polyethylene from agriculture greenhouses and high-density polyethylene from domestic uses, in order to explain the observed decrease in coal fluidity caused by polyethylene waste addition. Polymeric materials, although they are not volatile themselves, may be analysed by gas chromatography through the use of pyrolysis experiments. In this way, a series of pyrolysis tests were performed at 400 and 500 degrees C in a Gray-King oven with each of the two plastic wastes, one high-volatile bituminous coal and blends made up of coal and plastic waste (9:1, w/w, ratio). The pyrolysis temperatures, 400 and 500 degrees C, were selected on the basis of the beginning and the end of the coal plastic stage. The organic products evolved from the oven were collected, dissolved in pyridine and analysed by capillary gas chromatography using a flame ionization detector. The analysis of the primary tars indicated that the amount of n-alkanes is always higher than that of n-alkenes and the formation of the alkenes is favoured by increasing the pyrolysis temperature. However, this effect may be influenced by the size of the hydrocarbon. Thus, the fraction C17-C31 showed a higher increase of n-alkenes/n-alkanes ratio than other fractions. On the other hand, the difference between the experimental and estimated values from tars produced from single components was positive for n-alkanes and n-alkenes, indicating that co-pyrolysis of the two materials enhanced the chemical reactivity during pyrolysis and produced a higher conversion than that from individual components.

Alkanes↗
PubMed2001

Variation in the LRP-associated protein gene (LRPAP1) is associated with late-onset Alzheimer disease.

The LRP-associated protein is involved in the amount of mature LRP expressed on liver and brain. LRP is the main ApoE receptor and also binds alpha2-macroglobulin (alpha2M), a protein that associates with the beta-amyloid protein (betaA). By binding to alpha2M, LRP is responsible for the clearance of secreted betaA, thus preventing fibril formation. Genetic variation at the APOE, A2M, and LRP genes has been associated with the risk of developing late-onset Alzheimer disease (LOAD). We genotyped 373 patients, 300 controls, and 100 healthy elderly controls for a common DNA-polymorphism at the LRPAP1 gene (Insertion/Deletion, intron 5). Homozygotes for the rare Insertion (I) allele were at a significantly lower frequency in patients compared with controls (P = 0.002; OR = 0.29; 95% CI = 0.13, 0.68), and in patients compared with healthy elderly controls (P = 0.0002; OR = 0.18; 95% CI = 0.07, 0.46). No patient with an age at the onset below 75 years was II (0 of 214) compared with 8 in the group above 75 years (8 of 159) (P = 0.0044), suggesting that this genotype delays the onset of the disease. According to our data, the variation at the LRPAP1 gene is associated with the risk of developing LOAD. This is in agreement with the role of the LRPAP1 protein in the amyloidogenic pathway.

Aged↗
PubMed2001

Association between the NOS3 (-786 T/C) and the ACE (I/D) DNA genotypes and early coronary artery disease.

DNA polymorphisms at the endothelium constitutive nitric oxide synthase gene (NOS3) have been linked to the risk of developing coronary artery disease (CAD). In vitro, a polymorphism in the 5' region of the NOS3 gene (-786 T/C) influences promoter activity. This polymorphism has been associated with coronary spasms among Japanese. The genetic variation at the angiotensin-converting enzyme (ACE) is associated with plasma ACE activities and has also been linked with susceptibility to cardiovascular disease. Our objective was to determine if DNA polymorphisms in the NOS3 and ACE genes were associated with early CAD. We analyzed the -786 T/C polymorphism in the 5' flanking region and the 27-bp repeat polymorphism in NOS3 intron 4, as well as the ACE-I/D polymorphism. A total of 170 male smokers (CAD patients) younger than 50 years and 300 male smokers (healthy controls) were genotyped. Frequencies were compared by the chi(2) test, and odds ratios (ORs) and their 95% confidence intervals (CI) were also calculated. Only the -786 T/C polymorphism in the 5' flanking region of the NOS3 gene was significantly associated with early CAD in our population. The frequency of the CC genotype was significantly increased (P = 0.039) in patients compared to controls (OR = 1.67; 95% CI = 1.01, 2.72). We found a synergistic effect between the NOS3-CC and the ACE-DD genotypes in the risk of developing early CAD. The frequency of CC + DD was significantly increased among patients (P = 0.002). Thus, those with a NOS3-CC and an ACE-DD genotype would have a significantly increased risk of suffering an early episode of coronary artery disease (OR = 2.82; 95% CI = 1.40, 5.70). Although based on a limited number of patients, our work suggests that individuals who are NOS3-CC + ACE-DD are at a higher risk for early CAD, probably as a consequence of increased endothelial dysfunction.

Adult↗
PubMed2001

Congenital dermoid cyst of the anterior fontanel in mestizo-mulatto children.

OBJECTS: Twenty-seven cases of histologically confirmed congenital dermoid cysts of the anterior fontanel in children are reported. METHODS: The age, sex and race of each patient was recorded. CONCLUSIONS: Ages ranged between 2 months and 6 years. There was a female predominance, and 77.7% of these patients were children of mixed race. Surgical excision resulted in complete cure without complications or recurrences.

Child↗
PubMed2001

Salt stress increases the Ca2+-independent phosphoenolpyruvate carboxylase kinase activity in Sorghum leaves.

In C4 plants, the photosynthetic enzyme phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) is subjected to a phosphorylation process via the light-dependent up-regulation of a Ca2+-independent PEPCase-kinase. The present work aimed to study the effect of salt stress on PEPCase phosphorylation in Sorghum vulgare Pers. leaves. The growth of salt-treated plants was reduced compared with that of the control plants. PEPCase activity modestly increased (around 20-40%) whereas PEPCase phosphorylation was markedly enhanced, on a protein basis, in extracts from illuminated leaves. The enhanced protein kinase activity was found to display a low molecular mass in the range 32-35 kDa, to be independent of Ca2+ and to be up-regulated by light. Furthermore, up-regulation was blocked in vivo by the cytosolic protein synthesis inhibitor cycloheximide. Collectively, these data demonstrated that salinity stress altered the Ca2+-independent PEPCase-kinase, presumably by increasing the mesophyll content of the enzyme. Potassium chloride, but not abscisic acid, mimicked the effect of NaCl on PEPCase-kinase activity.

Abscisic Acid↗
PubMed2001

Early response gene expression during differentiation of cultured Leishmania donovani.

The promastigote form of the unicellular parasite, Leishmania donovani, must differentiate into the amastigote form to establish an infection in a mammalian host. Identification of genes whose expression changes during differentiation could help reveal mechanisms of Leishmania gene regulation and identify targets for controlling the diseases caused by this human pathogen. Two genomic clones were isolated, P9 that is more highly expressed in promastigotes than in axenic amastigotes and A14 that is preferentially expressed in axenic amastigotes. Analysis of the DNA sequences revealed open reading frames that would encode 55.5 kDa and 100 kDa proteins, respectively, with no homology to known proteins. The mRNA level for these genes during 24 h time courses of parasite differentiation in culture was compared to two genes known to be differentially expressed, c-lpk2 and mkk. Changes in RNA level occurred within 2 h for each gene and continued in advance of morphological changes. The expression levels of these four genes in axenic amastigotes correlated with results from animal-derived parasites.

Animals↗
PubMed2001

Photoinduced transformation of 14-F-bacteriorhodopsin gelatin films based on both wild type and D96N mutant.

Spectral and kinetic transformations were studied in gelatin films made with 14-F wild type (WT) bacteriorhodopsin (BR) and 14-F D96N mutant BR. Unlike the recent study of water suspensions of the same pigments, where a red shifted species at 660 nm was shown to form under the light in 14-F WT only, there are no drastic differences in photoinduced behavior between gelatin films based on 14-F WT and 14-F D96N. It is not observed any photoinduced formation of red shifted species at 660 nm for both types of films as it is observed for corresponding pigments in water suspension. The observed results are explained in a terms of relationship between the rates of two photoinduced processes that occur in suspensions and films of corresponding pigments. Kinetic characteristics of the photoinduced processes for the films with chemical additives suggest that there are no advantages in using 14-F D96N films when compared to films based on 14-F WT.

Bacteriorhodopsins↗
PubMed2001

Parenteral nutrition and immature neonates. Comparative study of neonates weighing under 1000 and 1000-1250 g at birth.

UNLABELLED: We studied the nutritional requirements of 53 neonates with a birth-weight of 1250 g or less and analysed the parenteral and enteral nutrition provided, the weight-gain curves, the incidence of prior pathology and complications. We compared those weighing under 1000 g at birth (n=25) with those weighing 1001-1250 g (n=28). All neonates received central parenteral nutrition at an average age of 42.3 h. The liquid requirements of the lower birth-weight group were significantly greater. No differences were found in the supply of glucose, proteins, lipids and calories until after the first 15 days of life, when the <1000 g group required a greater liquid and caloric intake. Parenteral nutrition was suspended earlier for the >1000 g group (32.6 vs. 48.1 days). Maximum weight loss (12.56%) for the two groups occurred at 5.23 days. No differences in weight gain (g/kg/day) between the groups were observed. The >1000 g group began enteral nutrition significantly earlier and presented greater tolerance. The incidence of complications (bronchopulmonary dysplasia, enterocolitis, nosocomial sepsis, Candidas A sepsis, osteopenia) was greater in the lower birth-weight group, as was that of hyaline membrane disease and mechanically assisted respiration. There were no differences in the incidence of intracraneal haemorrhage, ductus arteriosus, early sepsis, delayed intrauterine growth or hypoglucemia. CONCLUSIONS: The severity of the initial pathology and the greater incidence of complications among the lower birth-weight neonates (<1000 g) influenced both the need for parenteral nutrition and the reduced tolerance to enteral nutrition. Although the rate of weight gain was similar for the two groups, the <1000 g group required a longer period of parenteral nutrition.

Aging↗
PubMed2001

Genetic variation at the chemokine receptors CCR5/CCR2 in myocardial infarction.

Our objective was to examine the association between myocardial infarction (MI) and two DNA-polymorphisms at the proinflammatory chemokine receptors CCR2 (I64V) and CCR5 (32 bp deletion, (Delta)ccr5), defining if these polymorphisms influence the age for the onset of MI. A total of 214 patients with an age at the first MI episode <55 years, 96 patients that suffered the first MI episode when older than 60 years, and 360 population controls were polymerase chain reaction genotyped for the CCR2-V64I and CCR5-Delta32/wt polymorphisms. Patients and controls were male from the same Caucasian population (Asturias, northern Spain). The frequency of the Deltaccr5 allele was significantly higher in controls compared to patients <55 years (P = 0.004), or in patients >60 years compared to patients <55 years (P = 0.002). Taking the patients >60 years as the reference group, non-carriers of the (Delta)ccr5-allele would have a three-fold higher risk of suffering an episode of MI at <55 years of age (OR = 3.06; 95% CI = 1.46-6.42). Gene and genotype frequencies for the CCR2 polymorphism did not differ between patients <55 years and controls or patients >60 years. Our data suggest that the variation at the CCR5 gene could modulate the age at the onset of MI. Patients carrying the (Delta)ccr5-allele would be protected against an early episode of MI. CCR5 and the CCR5-ligands are expressed by cells in the arteriosclerotic plaque. Thus, the protective role of (Delta)ccr5 could be a consequence of an attenuated inflammatory response, that would determine a slower progression of the arteriosclerotic lesion among (Delta)ccr5-carriers. Our work suggests that the pharmacological blockade of CCR5 could be a valuable therapy in the treatment of MI.

Adult↗
PubMed2001

Hereditary non-spherocytic haemolytic anaemia due to red blood cell glutathione synthetase deficiency in four unrelated patients from Spain: clinical and molecular studies.

In four unrelated patients with chronic haemolysis and markedly reduced red blood cell (RBC) glutathione (49.5%, 12.6%, 11.5% and 15% of the normal concentration respectively), a severe glutathione synthetase (GSH-S, EC 6.3.2.3) deficiency was found. One case exhibited a neonatal haemolytic anaemia associated with oxoprolinuria, but without neurological manifestations. The family study revealed GSH-S activity in both parents to be around half the normal level, a finding consistent with the presumed autosomal recessive mode of inheritance of this enzymopathy. Two cases exhibited a well-compensated haemolytic syndrome without anaemia or splenomegaly at steady state. One of these cases was diagnosed after an episode of acute haemolytic anaemia after fava bean ingestion. The remaining patient suffered from moderate to severe chronic non-spherocytic haemolytic anaemia and splenomegaly, and required occasional blood transfusion for a haemolytic crisis associated with drug ingestion. In this patient, the anaemia was corrected by splenectomy. In addition to GSH-S, a panel of 16 other RBC enzyme activities was also studied in all the patients. Hexokinase, aldolase, glucose-6-phosphate dehydrogenase and pyruvate kinase activities all increased; these increases were to be expected, given the rise in the number of circulating reticulocytes. In two patients, the incubation of RBCs with hydrogen peroxide revealed an enhanced production of malonyldialdehyde. DNA analysis showed a homozygous state for 656 A-->G mutation in patients 2 and 3. The GSH-S gene of patient 1, studied elsewhere, revealed an 808 T-->C. The GSH-S gene of patient 4 was not available for study. The present study demonstrates that GSH-S deficiency is also present in Spain and further supports the molecular and clinical heterogeneity of this enzymopathy

Adult↗
PubMed2001

Shock wave therapy for chronic proximal plantar fasciitis.

Three hundred two patients with chronic heel pain caused by proximal plantar fasciitis were enrolled in a study to assess the treatment effects consequent to administration of electrohydraulicall-generated extracorporeal shock waves. Symptoms had been present from 6 months to 18 years. Each treated patient satisfied numerous inclusion and exclusion criteria before he or she was accepted into this study, which was approved by the Food and Drug Administration as a randomized, double-blind evaluation of the efficacy of shock wave therapy for this disorder. Overall, at the predetermined evaluation period 3 months after one treatment, 56% more of the treated patients had a successful result by all four of the evaluation criteria when compared with the patients treated with a placebo. This difference was significant and corroborated the fact that this difference in the results was specifically attributable to the shock wave treatment, rather than any natural improvement caused by the natural history of the condition. The current study showed that the directed application of electrohydraulic-generated shock waves to the insertion of the plantar fascia onto the calcaneus is a safe and effective nonsurgical method for treating chronic, recalcitrant heel pain syndrome that has been present for at least 6 months and has been refractory to other commonly used nonoperative therapies. This technology, when delivered using the OssaTron (High Medical Technology, Kreuz-lingen, Switzerland), has been approved by the Food and Drug Administration specifically for the treatment of chronic proximal plantar fasciitis. The results suggest that this therapeutic modality should be considered before any surgical options, and even may be preferable to cortisone injection, which has a recognized risk of rupture of the plantar fascia and recurrence of symptoms.

Adult↗
PubMed2001

Variation at the Angiotensin-converting enzyme and endothelial nitric oxide synthase genes is associated with the risk of esophageal varices among patients with alcoholic cirrhosis.

Esophageal varices are a frequent complication among patients with liver cirrhosis. Nitric oxide and other vasoactive molecules regulate the vascular tone in both the liver microcirculation and the systemic and splanchnic circulation. Several genes that encode proteins involved in the maintenance of vascular tone, such as the endothelial-constitutive nitric oxide synthase (ecNOS), the angiotensinogen (AGT), the angiotensin-converting enzyme (ACE), and the angiotensin II receptor type 1 (AT1R) are polymorphic, and these polymorphisms have been associated with several cardiovascular diseases. Our aim was to define a possible role for DNA polymorphisms at these genes in the risk of developing esophageal varices among patients with alcoholic cirrhosis. We analyzed 145 male patients with liver cirrhosis. Patients and 200 healthy controls were genotyped by polymerase chain reaction for the ACE-I/D, the AGT-M235T, the AT1R-A1166C, and the ecNOS-4/5 (intron 4) polymorphisms. Ninety-five patients had varices and 50 did not show this complication. Carriers of the ACE-I allele (ID + II genotypes) were at a significantly higher frequency among patients with varices (p = 0.013). Patients without varices had a higher frequency of the ecNOS-4 allele compared with patients with varices (p = 0.026). ACE-I carriers + ecNOS-55 were at a significantly higher frequency (p = 0.0012; odds ratio = 3.19; 95% CI = 1.55-6.55) among patients with varices (51 of 95, 54%) compared with patients without (18 of 50, 36%). Allele and genotype frequencies for the AGT and AT1R polymorphisms did not differ between the two groups. The genotypes associated with an increased risk for varices have been linked to higher plasma levels of nitric oxide and reduced levels of ACE. These genotypes could have a vasodilatory effect in the systemic and splanchnic circulation, thus favoring the development of portocollaterals.

Adult↗