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Biomedical subjects

M Alvarez

Publications and source records attributed to M Alvarez.

At least 91 records · Page 5Linked to original sources
PubMed2001

How partial nitrification could improve reclaimed wastewater transport in long pipes.

Reclaimed wastewater transport is studied in a concrete-lined cast iron pipe, where a nitrification-denitrification process occurs. The pipe is part of the Reuse System of Reclaimed Wastewater of South Tenerife (Spain), 0.6 m in diameter and 61 km long. In order to improve wastewater quality, at 10 km from the inlet there is injection of fresh water saturated in dissolved oxygen (DO), after which a fast nitrification process usually appears (less than two hours of space time). The amount of oxidized nitrogen compounds produced varies between 0.8 and 4.4 mg/l NOx(-)-N. When DO has disappeared, a denitrification process begins. The removal of nitrite is complete at the end of the pipe, whereas the nitrate does not disappear completely, leaving a concentration of about 0.4-0.5 mg/l. For a COD/NOx(-)-N ratio higher than 5, a first order nitrification rate in NOx(-)-N has resulted, with the constant k20 = 0.079 h-1, for a NOx(-)-N concentration range of 0.8-4.4 mg/l. Finally the following temperature dependency for the first order denitrification rate constant has been found: k = k20 x 1 x 15T-20. Although nitrogen could be used as nutrient in the agricultural reuse, its removal from reclaimed wastewater could be useful in order to diminish the chlorine needs for reclaimed wastewater disinfection.

Agriculture↗
PubMed2001

[Diagnosis of Clostridium difficile diarrhea: in search of a more efficient clinical focus].

BACKGROUND: The clinical parameters for the suspicion of Clostridium difficile infections, namely the use of antimicrobials and diarrhea, have a low predictive value for the diagnosis. AIM: To search other clinical variables and determine a clinical prediction model for (Clostridium difficile diarrhea. PATIENTS AND METHODS: All patients to whom a Clostridium difficile study was requested, were prospectively studied during 5 months. Clinical variables of these patients were registered. The diagnosis of Clostridium difficile was done using the cytotoxicity test in fibroblast cultures. RESULTS: Ninety two patients were analyzed and in 26, the diagnosis of Clostridium difficile was confirmed. A logistic regression model disclosed an age over 60 years old, the presence of mucus in the stools and a temperature over 37.8 degrees C in the previous 24 h, as significant predictors of the infection. The correlation of the model, between the predicted probability and the observed condition, was 81.5%. CONCLUSIONS: The presence of the clinical variables identified in this study are associated with a high probability of an infection by Clostridium difficile in patients with diarrhea and the recent use of antimicrobials.

Aged↗
PubMed2001

Contributions to the study of the foetal development of physiological intimal thickening in the human uterine artery.

The morphological study of the development of "intimal thickenings" of the human uterine artery in physiological condition was performed on 72 uterine arteries obtained from foetuses from the 12th week of gestation up to birth. Our results indicate that intimal thickening is formed by the migration and displacement of mesenchymal cells around the site of origin of collateral vessel from uterine mesothelium. These cells firstly differentiate into the myoblasts and then into the myocites. During the development the internal limitans membrane separates the intimal thickening from the tunica media and the elastic fibres appearing inside possessing a muscle-elastic nature. The function of intimal thickenings is the regulation of local blood flow by means of the control of myocitic contractile capacity; these cells play a fundamental role in endothelium-intimal smooth muscle cell contact.

Arteries↗
PubMed2001

Is carbohydrates-deficient transferrin the best test of the alcoholic etiology in acute pancreatitis?

AIM: To demonstrate if carbohydrates deficient transferrin (CDT) is the best marker to detect an excessive alcohol consumption as a cause of acute pancreatitis. MATERIAL AND METHODS: Prospective study of 60 patients consecutively admitted in our hospital. Acute pancreatitis were classified according to their different etiologies, alcoholic (11), probably alcoholic (4), biliary (25) and others (20). In all cases, we have compared CDT with classical quemical markers of alcohol abuse such as mean corpuscular volumen (MCV), gamma-glutamyltransferase (GGT) and aspartateaminotransferase (AST). Statistic correlations were done between the quantity of alcohol consumed and CDT, GGT, AST and MCV variables. RESULTS: Correlation between CDT and MCV with the excessive alcohol consumption was statistically significant. The acute pancreatitis caused by alcohol and the suspicious alcoholic group had a average CDT higher than the rest of the groups (p < 0.05). Taking a cut point with a CDT value of 20, the diagnosis capacity of the test to detect the alcoholic etiology was 82 and 92% of specificity. Taking a cut point with a MCV value higher than 95, sensibility was 67% and specificity was 82%. CONCLUSION: In our experience, the most efficient marker of the alcoholic etiology in acute pancreatitis was CDT.

Acute Disease↗
PubMed2001

Immunoreactivity of the fungal cell wall.

The cell wall is the major fungal structure involved in the interaction with the host and most of the immunological effects observed with intact fungal cells have been reproduced with cell-wall components. As a result of the exposure to fungal antigens, most individuals develop both cellular and antibody responses intended to limit the invasiveness or to eradicate the fungus from the infected tissues. However, a number of fungi including Candida albicans, Cryptococcus neoformans, Blastomyces dermatitidis, Coccidioides immitis, Trichophyton spp. and Histoplasma capsulatum can also induce T- and B-suppressive activities. A wide diversity of immunodominant cell-wall antigens for both cell-mediated and humoral responses have been identified in the most important fungal pathogens, although considerable differences exist in the information available at the molecular level among the different mycoses. Cellular responses require macrophage and Th1 activation, whereas humoral responses comprise the activation of the complement system and the induction of antibodies. The ability of fungal cell-wall components to elicit cellular or humoral immune responses has been traditionally used in the serodiagnosis of mycoses, the identification of fungal organisms and the development of vaccines for the prevention of mycoses. In the future, the analysis of such molecules will provide critical information in understanding the nature of host-fungus interactions.

Antibodies, Fungal↗
PubMed2001

Environmental reprogramming of the expression of protein kinase CK2beta subunit in fish.

The dramatic segregation of the nucleolar components in winter-acclimatized carp is the most striking cellular-phenotypical feature observed during the seasonal adaptation of this fish toward the circannual changes in its habitat. Our studies also show that the carp habitat temperature and photoperiod winter conditions provoke a remarkable reduction of both rRNA transcription and the processing of their precursors. To gain knowledge on the mechanisms involved in the regulation of nucleolar activity during the seasonal adaptation process, we studied the behavior of some genes, specifically snoRNA U3 and protein kinase CK2. Consistent with the reduction in the synthesis and processing of pre-rRNA observed during the cold season, the level of CK2beta expression decreases in winter when compared to that attained in summer. Similarly, in winter, liver and kidney cells contain lower levels of CK2beta subunit protein compared to summer. CK2 is associated with or modifies different factors and enzymes involved in the nucleolar activity; therefore, its higher or lower content could be part of the molecular mechanisms underlying the nucleolar seasonal changes that occur during the compensatory acclimatization process.

Animals↗
PubMed2001

[Biomedical images segmentation by the regions growth method].

The study of the different fiber types present in muscle tissue sample images allows the investigators to identify some metabolic and contractile muscle properties, and in general, its physiological state. The image segmentation, which identifies regions or contours of objects within the image, is a fundamental step of the on-line image analysis that can help in this study. However, this kind of images, in general, are very diffuse and with low contrast, so it is difficult to identify the different objects within the image. The main objective of this work is to propose a two-phase method for segmentation of digitized images of cross sections of rat muscle tissue. The first phase allows obtaining an initial group of homogeneous regions by using a uniformity criterion. In this phase we use a division and union of regions algorithm. The purpose of the second phase is to group together in an image the regions corresponding to a given fiber type. The results obtained show an appropriate identification of the regions of interest on the images studied.

Algorithms↗
PubMed2001

[Mollusc diversity in an Arca zebra (Mollusca: Bivalvia) community, Chacopata, Sucre, Venezuela].

The diversity of a subtidal epifaunal mollusk community was studied from September, 1990 to September, 1991 in Chacopata, Sucre State, Venezuela. There were 40 species (24 bivalves and 16 gastropods). The diversity indexes (H' = 2.087, J' = 0.392, 1/D = 0.528) were low when compared with other tropical zones. Monthly diversity reached its maximum in September, 1990 (1.63 bits/ind.) and July, 1991 (1.60 bits/ind.); minimum diversity occurred in June, 1991 (0.52 bits/ind.). A Log series model applied to species abundance data showed a straight line with a diversity index alpha of 5.56. Of 40 species identified, the turkeywing Arca zebra was dominant (69% in number of individuals and 72% of biomass) followed by Pinctada imbricata, Modiolus squamosus, Chama macerophyla and Anadara notabilis. The predatory snails Phyllonotus pomum, Chicoreus brevifrons and Murex recurvirostris seemed to have trophic relationships with A. zebra. The total mean biomass in wet weight (469.20 +/- 263 g m-2, shell included) was high which indicates that A. zebra, a species with a rapid growth rate, occupies a central role in the assemblage as an efficient filter feeder that converts planktonic food into available biomass, supporting one of the most important fisheries in Venezuela.

Animals↗
PubMed2001

Involvement of the nuclear matrix in the control of skeletal genes: the NMP1 (YY1), NMP2 (Cbfa1), and NMP4 (Nmp4/CIZ) transcription factors.

The functional role of the osteoblast nuclear matrix has been a matter of supposition. Its presumed function as an architectural agent of transcription derives primarily from the low solubility of nuclear matrix proteins and their typical localization into discrete subnuclear domains. In addressing how the nuclear matrix regulates skeletal genes, the authors compare Nmp4, Cbfal, and YY1 for the purpose of profiling osteoblast nuclear matrix transcription factors. All three proteins contribute to the transcription of ECM genes and partition into the osteoblast nuclear matrix via a nuclear matrix targeting domain. The authors propose that osteoblast nuclear matrix transcription factors involved in ECM regulation generally have the capacity to alter DNA geometry and reciprocally respond to DNA as an allosteric ligand. This may allow these proteins to adapt to the local nuclear architecture and generate the pattern of regulation specified by that architecture via unmasking of the appropriate transactivation domains. Osteoblast nuclear matrix transcription factors may also act as transcriptional adaptor molecules by supporting the formation of higher order protein complexes along target gene promoters. The genes encoding all three proteins considered here have trinucleotide repeat domains, although the significance of this is unclear. There is no canonical nuclear matrix binding motif, but finger-like structures may be suited for anchoring proteins to discrete subnuclear domains. Finally, the ability to leave the osteoblast nuclear matrix may be as important to the function of some nuclear matrix transcription factors as their association with this subcompartment.

Animals↗
PubMed2000

Inhomogeneous integral equation approach to pair and triple correlations in a glass-forming simple liquid.

A simple model of glass-forming liquid modeled via Dzugutov's pair potential is studied by means of the triplet hypernetted chain approximation as formulated by Attard [P. Attard, J. Chem. Phys. 93, 7301 (1990)]. This system, which is known to be mostly dominated by microscopic icosahedral ordering, eludes a correct description in terms of classical two-body integral equation theories. However, it is found here that the simple hypernetted chain approximation when applied at the three-particle level can yield a correct semiquantitative description of both the pair and triplet structure of the supercooled state, capturing features which escape more sophisticated closures implemented on the two-particle level.

Journal Article↗
PubMed2000

Epidemiologic studies on Dengue in Santiago de Cuba, 1997.

A small, isolated outbreak of dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) due to dengue virus type 2 (DEN-2) was documented in Santiago de Cuba on the island of Cuba beginning in January 1997. There were 205 DHF/DSS cases, all in persons older than age 15 years. All but three had evidence of a prior dengue infection, with the only known opportunity being the islandwide dengue virus type 1 (DEN-1) epidemic of 1977-1979. Virtually complete clinical and laboratory surveillance of overt disease was achieved. From December 1997 to January 1998, a random, age-stratified serum sample was obtained from 1,151 persons in 40 residential clusters in Santiago. Sera were tested for DEN-1 and DEN-2 neutralizing antibodies. The prevalence of DEN-2 antibodies in children age 15 years and under, born after the 1981 DEN-2 epidemic, was taken as the 1997 DEN-2 infection rate. This was adjusted slightly to accommodate observed cases, resulting in an estimated infection rate of 4.3%. Dengue fever and DHF/DSS attack rates were calculated from estimated total primary and secondary DEN-2 infections. Only 3% of 13,116 primary infections were overt. The DHF/DSS attack rate for adults of all ages was 420 per 10,000 secondary DEN-2 infections.

Adolescent↗
PubMed2000

The relationship between glycogen synthesis, biofilm formation and virulence in salmonella enteritidis.

Salmonella enteritidis accumulated large quantities of intracellular polysaccharide when grown in unrestricted nutrient conditions. Dense, abundant cytoplasmic granules were observed by electron microscopy in sections stained by the periodic acid-chlorite technique, indicating that the polysaccharide was of the glycogen type. When biofilm-producing S. enteritidis was pre-incubated in media containing increasing levels of glucose concentration, the levels of both cytoplasmic glycogen and biofilm rose correlatively to a point where a ceiling effect was observed. Studies carried out with activators and inhibitors of glycogen biosynthesis confirmed that biofilm was formed from glycogen cell stores. On the other hand, the virulence of the biofilm-producing strain in infected chickens increased proportionally to the amount of stored glycogen, suggesting a possible role of the glycogen depot in the virulence of S. enteritidis.

Animals↗
PubMed2000

Persistence of well-defined collective excitations in a molten transition metal

Well-defined microscopic collective excitations are found in liquid Ni at 1763 K by means of inelastic neutron scattering. Such excitations are supported by the liquid despite an anharmonic character of its thermodynamic functions. Consideration of the detailed shape of the interionic pair potential provides a way to understand why atomic motions at microscopic scales behave in a way much closer to the alkali metals than to the liquefied rare gases.

Journal Article↗
PubMed2000

Long-term evolution of local, proximal and remote astrocyte responses after diverse nucleus basalis lesioning (an experimental Alzheimer model): GFAP immunocytochemical study.

A study on long-term astrocytic responses (from 1 day to 20 months after lesioning in 4-month-old rats, and from 1 day to 6 months in 20-month-old rats) to diverse unilateral damage of the nucleus basalis (nbM) by injection of 40 nmol of ibotenic acid, or 50 or 100 nmols of quisqualic acid was performed using a histochemical method (immunoreactivity against the glial fibrillary acidic protein GFAP). Glial reactivity (i.e., isolated or clustered hypertrophic and/or hyper-reactive astrocytes) was evaluated in several ipsilateral and contralateral brain regions: the 'local response' within the damaged nbM region; the 'proximal response' (a new concept proposed by us) in the non-damaged structures neighbouring the nbM; and the 'remote response' in the ipsilateral brain cortex and in the contralateral cortex and nbM. In 4-month-old animals, the remote cortical glial responses, independent of the involution of cortical cholinergic activity and randomly located in layers I-V of motor and somatosensory cortical regions, were similar in appearance over a long period (13-20 months), with the highest reactivity 45 days after lesioning. The proximal response lasted from 1 day to 13 months and afterwards tended to disappear. Contralateral reactivity and ipsilateral cortical scars were observed. The local (nbM) glial response was maintained throughout the period studied. Subsets of astrocytes of different reactivities were observed, most of their elements being highly intermeshed. In 20-month-old animals, nbM lesions produced less positive, but similar, glial reactive patterns. This glial reactivity was superposed onto the glial reactivity of old age. All these results are discussed. The maintenance of reactive astrocytes many months after lesioning suggests the existence of cellular factors other than those produced by damaged nbM neurons. Taking into account the role of glial cells under pathological conditions, it is possible that these reactive astrocytes in humans could promote neurodegenerative processes, such as amyloid plaque formation and neurodegeneration (Alzheimer's disease). Along this line, nbM cholinergic involution could then originate cortical involution through induced reactive astrocytosis.

Age Factors↗
PubMed2000

[Prevalence of anti-HAV antibodies and efficacy of pre-vaccine detection at institutions for mentally retarded of the city of Alicante].

OBJECTIVE: The aim of this study was to investigate the prevalence and efficacy of the anti-HAV antibodies detection in institucions for mentally retarded people in the city of Alicante. DESIGN: Prevalence study. SETTING: Two institucions for mentally retarded people in the city of Alicante. PARTICIPANTS: One hundred and seven residents and seventy seven in care of them. MEASUREMENTS AND MAIN RESULTS: We have investigated the anti-HAV antibodies prevalence by enzymeinmunoanalysis of microparticle test. The efficacy of the anti-HAV antibodies detection before the vaccination has been studied by calculating the threshold of prevalence with the following formula: unit cost of detection + (1 - X) x unit cost vaccination anti-HAV negative subjects = unit cost vaccination. RESULTS: The global prevalence of anti-HAV antibodies was 56.5% (95% CI, 49-63.7). The prevalence of the residents was 55.1% (95% CI, 45.2-64.7) and 58.4% in care of them (95% CI, 46.6-69.5). Among the sociodemographic variables evaluated only the age was associated with the prevalence of anti-HAV antibodies (p < 0.001). The unit cost of prevaccination detection of anti-HAV antibodies was calculated as 998 pesetas and the unit cost of the vaccination as 3595, obtaining a prevalence anti-HAV threshold of 27.8%. CONCLUSIONS: The prevalence of anti-HAV antibodies in this collective studied is similar to the prevalence of anti-HAV antibodies of the spaniard population. The direct vaccination without a previous marker study is recommended to people under the age of 31 in this population group.

Adolescent↗
PubMed2000

Determination of beta-globin gene cluster haplotypes and prevalence of alpha-thalassemia in sickle cell anemia patients in Venezuela.

Sickle cell anemia and alpha-thalassemia have a heterogeneous distribution in Venezuela with a high frequency in the coastal area (sea level) and few cases in the mountains. Most of our population is an ethnic admixture of Europeans (Spaniards colonists), Africans (slaves), and Amerindians. The purpose of our study was to determine the origin of the beta(s) globin haplotype, age and survival dependency, and the admixture among the different African groups in our population. The alpha(3.7) globin gene deletion status was also studied and found in a very high frequency. DNA from peripheral blood of 191 non-related patients (81 with HbS homozygous and 15 patients compound heterozygous for HbS, HbC, HbD with beta-thalassemia, and 95 with sickle cell trait) were studied. The beta(s) chromosome was linked 51% to the Benin Haplotype, 29.5% with the CAR, 12.5% to the Senegal, and 2.5% to the Cameroon. We did not find any significant difference between the haplotype distribution among adults and children and among sickle cell patients and traits. Only 8.6% of the patients have homozygosity for the Benin haplotype. These results show a very high frequency of admixture in our African origin population.

Age Distribution↗