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A Díaz

Publications and source records attributed to A Díaz.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Identification, by Western blot, of Fasciola hepatica immunogens recognized by the sera of experimentally infected rats].

This paper was aimed at identifying the main components present in the excretory-secretory antigens of adult parasite which are recognized by the sera of rats experimentally infected with metacercariae of Fasciola hepatica, by using the Western Blot technique. The cynetics of antibodies was also determined with and indirect ELISA. The results obtained allowed to find 31 components with approximate molecular weights from 11 to 136 kD. The predominant fractions were the following: 11-13 kD, 14-16 kD, 23-33 kD, 55-57 kD, 65-71 kD, and 86-136 kD. Antibodies were detected from the 2nd. week of infection in 80% of the animals and from the 3rd. week in 100% of them. There were no antibodies during the first week. The identification of these antibodies may contribute to a better understanding of the mechanisms of immunity linked with the infection by F. hepatica.

Animals↗
PubMed1997

Complement evasion by Echinococcus granulosus: sequestration of host factor H in the hydatid cyst wall.

Hydatid disease, which affects humans and various livestock species, is caused by the larval stages of the cestode parasite Echinococcus granulosus. The disease involves the growth of a fluid-filled cyst in the host's internal organs. The hydatid cyst wall is generally thought to preclude the access of host immune cells to the cyst, while allowing passage of macromolecules. Thus, evasion of humoral effector mechanisms, in particular the complement system, may be crucial to parasite survival. Evasion of complement might involve inhibition of the C3b deposition step, which can in principle be achieved through parasite-derived or host-derived and parasite-bound regulatory molecules. In this work, extracts from bovine hydatid cysts were analyzed for the presence of factor H-like function, namely the cofactor activity for the breakdown of amidated bovine C3 by bovine factor I. Both this activity and antigenically detectable bovine factor H were found in most extracts. The cofactor activity was retained by an anti-bovine factor H Ab column; as no factor H-cross-reactive parasite molecules were detected in the active extracts, the activity was indeed due to host factor H. The pattern of extraction of host factor H from the parasite tissue indicated that at least part of it was selectively bound to the cyst wall, and that a strong charge component was involved in the binding. Our results indicate that the selective concentration of host factor H from plasma/interstitial fluid may contribute to complement evasion by E. granulosus.

Animals↗
PubMed1997

Reduction of bone mass in women after bone marrow transplantation.

Osteoporosis is a common disease among patients undergoing transplantation. Its prevalence and complications have been well described in solid organ recipients, especially kidney, liver, and heart. However, studies in bone marrow transplantation (BMT) are scarce. Among the mechanisms invoked in the pathogenesis of BMT osteoporosis are the baseline disease, the use of immunosuppressive drugs and, more remarkably, secondary hypogonadism. We present a study of 27 women who underwent BMT, all of them suffering ovarian failure. We studied different biochemical markers of bone formation/resorption and also evaluated the presence of osteopenia/osteoporosis by dual energy X-ray absorptiometry (DXA) of the lumbar spine. Osteopenia was observed in nine patients (33%) and osteoporosis in another five (18%), according to the World Health Organization criteria. We also detected a subgroup showing elevation of several bone turnover biochemical markers, indicating high osseous remodeling. A remarkable increase in urine hydroxyproline/creatinine was detected in 95% of cases, although an explanation is lacking. We outline a reasonable therapeutic approach for osteoporosis in BMT emphasizing the need to monitor these patients after transplantation.

Adolescent↗
PubMed1997

A comparative study of alpha2- and beta-adrenoceptor distribution in pigeon and chick brain.

The pharmacological properties and anatomical distribution of alpha2-, beta1- and beta2-adrenoceptors in pigeon and chick brains were studied by both homogenate binding and tissue section autoradiography. [3H]Bromoxidine (alpha2-adrenoceptor-), [3H]CGP 12177 (beta-adrenoceptor) and [125I]cyanopindolol (beta-adrenoceptor) were used as radioligands. In both species, [3H]bromoxidine binding to avian brain tissue showed a pharmacological profile similar to that previously reported for alpha2-adrenoceptors in mammals. Regarding the anatomical distribution, the areas with the highest densities of alpha2-adrenoceptors in the pigeon brain included the hyperstriatum, nuclei septalis, tectum opticum and some brainstem nuclei. Most beta-adrenoceptors found in tissue membranes and sections from chick and pigeon brain were of the beta2 subtype, in contrast to what has been reported in the mammalian brain, where the beta1 subtype is predominant. A striking difference was found between the two species regarding the densities of these receptors: while pigeon brain was extremely rich in [125I]cyanopindolol binding throughout the brain (mainly cerebellum) in the pigeon, the levels of labelling in the chick brain were much lower; the exception was the cerebellum, which displayed a higher density than other parts of the brain in both species. Overall, our results support the proposed anatomical equivalences between a number of structures in the avian and mammalian encephalon.

Adrenergic alpha-Agonists↗
PubMed1997

The genus Rhodosporidium: a potential source of beta-carotene.

Four wild-type species of the genus Rhodosporidium have been studied as as possible sources for the industrial production of beta-carotene. HPLC-based studies showed that their carotenoid composition consisted of almost pure beta-carotene at concentrations ranging from 226 to 685 micrograms/g of dried yeast biomass. These results are consistent with those obtained by spectrophotometry at 480 nm.

Basidiomycota↗
PubMed1997

[Severe-grade tetanus in a multipurpose ICU: review of 13 cases].

BACKGROUND: The mortality of severe tetanus (grades II-III) remains high today, being greater than 20% with a large number of complications, due to the lengthy stay of these patients in the ICU. METHODS: A review of 13 cases of severe tetanus over the last 5 years was performed analyzing age, entrance, previous immunization, ICU stay, grade of severity, complications and mortality. RESULTS: The ages ranged between 35 to 79 years (mean 54 years). No patient had been previously immunized. Entrance was determined in 11 patients (84.6%). The mean ICU stay was 27.3 days. Complications were presented in 76.8% of the patients, with the most frequent being vegetative alterations (38%). The global mortality was 30.7% (4 patient), 3 secondary to sepsis of pulmonary origin and one from a cardiac arrest of vegetative etiology. CONCLUSIONS: The authors believe that prophylaxis is fundamental in prevention of the disease but an important sector of the population remains unvaccinated. On appearance of severe tetanus, admission to the ICU is essential since many complications may appear requiring specialized techniques and personnel.

Acinetobacter Infections↗
PubMed1997

[Prevention of infections in patients with lymphoproliferative syndromes and myeloma by nebulization of an IgA concentrate].

Infection of the upper respiratory tract is a major cause of morbidity and mortality in patients with lymphoproliferative syndromes and multiple myeloma. Nebulizations with IgA tested in a randomized double blind trial to evaluate its efficacy to prevent respiratory infections in patients with lymphoproliferative syndromes and multiple myeloma. Forty nine patients were evaluated (chronic lymphocytic leukaemia, 22; multiple myeloma, 11; lymphoma, 8; HCL, 6; Waldenström and lymphoepiteliod tymoma, 1 patient each) were randomized to receive nebulizations every 12 hours during 3 months of IgA or placebo. Seven infectious episodes (4 respiratory tract infections) in 25 IgA treated patients and 25 episodes (16 respiratory tract infections) in 24 control patients were recorded (p <0.0002). Eighteen patients belonging to the treated group remained free of infections against only 5 from the control group (p < 0.001). No difference related to the grade of infections was observed between groups. The arithmetic media for the first infection observed in each group was 45.6 +/- 22.0 days for the IgA treated and 28.6 +/- 17.5 days for the placebo (p < 0.025). According to this study, IgA nebulization therapy was useful to prevent respiratory tract infections and also delay the onset of infection in patients with lymphoproliferative syndromes and myeloma.

Administration, Intranasal↗
PubMed1996

A comparative thermodynamic analysis by laser-flash absorption spectroscopy of photosystem I reduction by plastocyanin and cytochrome c6 in Anabaena PCC 7119, Synechocystis PCC 6803 and Spinach.

A comparative thermodynamic analysis of photosystem I (PSI) reduction by plastocyanin (Pc) and cytochrome c6 (Cyt) has been carried out by laser-flash absorption spectroscopy in the cyanobacteria Anabaena PCC 7119 and Synechocystis PCC 6803 as well as in spinach. These three organisms have been reported to exhibit different reaction mechanisms [Hervas, M., Navarro, J. A.. Díaz, A., Bottin, H., & De la Rosa, M. A. (1995) Biochemistry, 34, 11321-11326]. Whereas the activation free energy for the overall reaction is mainly enthalpic in nature, long-range electrostatic interactions appear to be attractive in Anabaena, but repulsive in Synechocystis and spinach. The net interaction between PSI and its two donor proteins in Anabaena is similarly affected by ionic strength (the rate constant decreases with increasing salt concentration), but the activation parameters delta H+/+ delta S+/+ show different dependencies on ionic strength. A compensation effect between entropy and enthalpy at varying ionic strength is found in all these Pc/PSI and Cyt/PSI systems, except with Cyt and PSI from Anabaena. Such a compensation effect is proposed to be mainly due to stabilization of the intermediate electrostatic complex by hydrophobic forces. The electron transfer step seems to be well optimized in the Anabaena Cyt/PSI couple, which exhibits a temperature-independent fast kinetic phase and, therefore, a low activation energy barrier. Short-distance forces appear to have gained relevancy in the reaction mechanism of PSI reduction by Cyt and Pc throughout evolution, whereas long-range interactions are prevalent in less evolved organisms.

Anabaena↗
PubMed1996

Ontogenetic development of 5-HT1D receptors in human brain: an autoradiographic study.

The pattern of pre- and postnatal appearance of 5-HT1D receptors throughout the different areas of the human brain was studied by quantitative in vitro autoradiography, using [125I]GTI (serotonin O-carboxymethyl-glycyl-[125I]tyrosinamide) as a ligand. The anatomical distribution of 5-HT1D receptors in neonatal, infant and children's brain was in good agreement with that observed in the adult, the basal ganglia and substantia nigra being the most intensely labelled areas. The development of these receptors throughout the human brain was mainly postnatal: low densities of [125I]GTI binding sites were observed at the fetal/neonatal stage in most regions analyzed, in contrast with the high levels of labelling found in infant and children's brains. Indeed, in a number of regions, including the globus pallidus, substantia nigra and visual cortex, a peak of overexpression of 5-HT1D receptors was observed in the first decade of life. Such overexpression could support a regulatory role for 5-HT1D receptors in advanced periods of the CNS developmental process. Our results also indicate that the administration of drugs acting on 5-HT1D receptors during the early postnatal period of life could result in modifications of their properties, as these receptors are already functional in this period.

Adult↗
PubMed1996

[Outbreak of Shigella boydii dysentery in the county of El Bierzo].

BACKGROUND: Investigation of an outbreak of bacillar dysentery of possible transmission by water produced by Shigella boydii. METHODS: The strains were isolated in the stools and studies of identification, serotyping, susceptibility to antibiotics and plasmid profile were carried out according to standard methods. The epidemiological investigation was carried out retrospectively. RESULTS: 51 strains were isolated from 48 patients. All were identified as S. boydii serotype 4. The pattern of susceptibility was variable, all of them showed resistance to ampicillin, tetracycline and chloramphenicol. The plasmid profile was homogeneous. Of the 41 patients who completed the questionnaire all were living in the same town or nearby localities. CONCLUSIONS: The serotype 4 of S. boydii, infrequent in Spain, the homogeneous plasmid profile and the relationship between time and place of the cases, suggest that we find ourselves faced with an outbreak epidemiologically relationed. The localisation of the cases and the network of the drinking water supply represented on the plan of the town, support the hypothesis of the origin of hte outbreak as being in the lack of chlorination of one of the tanks of the network of supply.

Adolescent↗
PubMed1995

Laser-flash kinetic analysis of the fast electron transfer from plastocyanin and cytochrome c6 to photosystem I. Experimental evidence on the evolution of the reaction mechanism.

The reaction mechanism of electron transfer from the interchangeable metalloproteins plastocyanin (Pc) and cytochrome c6 (Cyt) to photooxidized P700 in photosystem I (PSI) has been studied by laser-flash absorption spectroscopy using a number of evolutionarily differentiated organisms such as cyanobacteria (Anabaena sp. PCC 7119 and Synechocystis sp. PCC 6803), green algae (Monoraphidium braunii), and higher plants (spinach). PSI reduction by Pc or Cyt shows different kinetics depending on the organism from which the photosystem and metalloproteins are isolated. According to the experimental data herein reported, three different kinetic models are proposed by assuming either an oriented collisional reaction mechanism (type I), a minimal two-step mechanism involving complex formation followed by intracomplex electron transfer (type II), or rearrangement of the reaction partners within the complex before electron transfer takes place (type III). Our findings suggest that PSI was able to first optimize its interaction with positively charged Cyt and that the evolutionary replacement of the ancestral Cyt by Pc, as well as the appearance of the fast kinetic phase in the Pc/PSI system of higher plants, would involve structural modifications in both the donor protein and PSI.

Biological Evolution↗
PubMed1995

Echinococcus granulosus: interactions with host complement in secondary infection in mice.

Complement has been shown to lyse protoscoleces of Echinococcus granulosus, but products from this parasite are able to consume complement, and this has been proposed as an evasion mechanism. The murine secondary hydatidosis model, with intraperitoneal inoculation, is used in this work to assess the occurrence in vivo of complement consumption by the parasite as well as the role of complement during the establishment of infection. Although the measurement of systemic levels of C3 activation, total C3, and hemolytic complement in challenged mice yielded no evidence of complement consumption, the relevance of local consumption at the site of infection cannot be ruled out. The role of complement during establishment of infection was assessed by comparing parasite burdens in normal and complement-depleted mice. Complement depletion by treatment with cobra venom factor caused a 79% reduction in cyst numbers (P < 0.05). Possible explanations of this unexpected result are discussed. The results presented suggest that lysis or opsonization by host complement are not effective against the establishing parasite in this model. They also indicate the significance of complement activation by the parasite needs to be studied at a local level.

Animals↗
PubMed1995

Reagents that activate GTP-binding proteins trigger the acrosome reaction in human spermatozoa.

The acrosome reaction is a specialized exocytotic process. In the mouse there is compelling evidence that receptor-mediated activation of GTP-binding proteins by factors in the zona pellucida of oocytes is a central event in the acrosome reaction. Several reagents are able to affect GTP-binding proteins directly, bypassing the receptor-ligand step for activation. We have assessed the effect of several of these compounds on human spermatozoa, monitoring cell vitality and the acrosome reaction simultaneously using the triple-stain technique. GTP gamma S and aluminium fluoride complexes promote sperm activation very efficiently; amphiphilic peptides capable of activating G(o) and Gi, also elicit the acrosome reaction. The results indicate that activation of heterotrimeric GTP-binding proteins is sufficient to trigger acrosome exocytosis in human spermatozoa.

Acrosome↗
PubMed1995

Regulation of dihydropyridine-sensitive Ca++ channels during opioid tolerance and supersensitivity in rats.

The changes in cerebral dihydropyridine (DHP)-sensitive Ca++ channels (L-type) associated with tolerance and supersensitivity to the antinociceptive effect of the mu-opioid receptor agonist sufentanil were analyzed in rats. The tail-flick test was used to assess the nociceptive threshold. DHP binding and autoradiographic assays were performed with [3H]nimodipine and [3H]PN 200-110 [isopropyl 4-(2,1,3-benzoxadizol-4-yl)- 1,4-dihydro-2,6-dimethyl-5-methoxycarbonylpyridine-3-carboxylate], respectively. Chronic s.c. infusion of sufentanil (2 micrograms/hr) for 7 days induced tolerance (tolerance index, 5.6) in association with up-regulation of DHP binding sites in cerebral cortex membranes (+36%), as well as in brain sections. Animals were rendered hypersensitive to the antinociceptive effect of sufentanil by chronic and simultaneous infusion of sufentanil (2 micrograms/hr) and nimodipine (1 microgram/hr) for 7 days (potentiation index, 40 vs. tolerant). Under these conditions, a greater increase in the number of DHP binding sites was observed in cortex membranes (+71%), and more evidently in brain sections. In these animals, withdrawal of nimodipine for 48 hr returned the dose-response curve of sufentanil to the tolerant values, whereas Ca++ channels remained increased. The role of an increased influx through L-type channels in opioid tolerance is reinforced. Our results also suggest that, although changes in neuronal Ca++ fluxes are not the only underlying mechanism, the increase and the sustained blockade of Ca++ channels with nimodipine is essential for the expression of opioid supersensitivity.

Analgesics, Opioid↗