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Biomedical subjects

G Díaz

Publications and source records attributed to G Díaz.

At least 37 records · Page 2Linked to original sources
PubMed1998

Biotin deficiency induces changes in subpopulations of spleen lymphocytes in mice.

Biotin deficiency is known to affect immune function in both humans and experimental animals. In this study, we determined the effect of biotin deficiency on 4-wk-old Balb/cAnN mice during 20 wk of experimentation. The growth rate of mice slowed significantly during the first 6 wk of consumption of a diet designed to induce biotin deficiency; thereafter, from weeks 7 to 20 there was progressive weight loss in the mice receiving the biotin-deficient diet. In the livers of biotin-deficient mice, the specific activities of two biotin-dependent enzymes--pyruvate carboxylase and propionyl-CoA carboxylase--decreased by as much as 75% and 80%, respectively, and in spleen lymphocytes the specific activities of these two enzymes decreased by 63% and 75%, respectively. With respect to the effects of biotin deficiency on the immune system, we observed statistically significant changes in both the absolute number of spleen cells and in the proportions of spleen cells carrying different phenotypic markers: after 16 wk the percentage of cells expressing surface immunoglobulin (sIg) decreased from 47% (control and supplemented) to 27% (deficient) and CD3+ cells increased from 42% (control and supplemented) to 54% (deficient). The mitogen-induced proliferation of spleen cells from deficient mice was lower than that of spleen cells from the control mice. These findings suggest that biotin could have an important role in lymphocyte maturation and responsiveness to stimulation, and consequently in the capacity of the immune system to respond to an antigenic challenge.

Animals↗
PubMed1998

HLA-DPbeta residue 69 plays a crucial role in allorecognition.

To investigate the contribution to allorecognition of the individual polymorphic positions Glu 69 and Val 36 from the DPB1*02012 allele, DPB1*02012 cDNA was subjected to site-directed mutagenesis and alleles expressing Lys at 69 and Ala at 36 were generated. The lymphoblastoid cell line (LCL) 45.EM1, a previously generated mutant B-LCL which expresses normal levels of DPA mRNA but is not able to transcribe DPB, was transfected with wild-type or mutant DPB1*02012 cDNAs. The ability of two HLA-DPw2 alloreactive CD4+ cytotoxic T-lymphocyte (CTL) clones to lyse the panel of DPB1*02012 wild-type and site-directed mutant B-cell lines was tested. Both CTL clones (8.3 and 8.9) lysed the B-LCL 45.1, which is haploid for HLA and expresses wild-type DPB1*02012, and transfectants expressing Ala at 36 instead of Val, indicating that this polymorphic residue is not critical for T-cell recognition. However, the change of Glu to Lys at 69 prevented recognition by clones 8.3 and 8.9. These data demonstrate that the residue at peptide-binding position 69 is crucial for T-cell receptor recognition and suggest the requirement for a negatively charged residue at this position for allostimulation of these T-cell clones. The side chain of DPbeta-69 is predicted to point into the peptide-binding groove, and the existence of positive(Lys) or negative (Glu) residues probably leads to substantial differences in the allo- or auto-DP-bound peptides or to differences in the conformation of the peptide-MHC complex, which would therefore be responsible for specific DPw2 allorecognition. The binding of a panel of monomorphic and polymorphic anti-HLA-DP monoclonal antibodies (mAbs) to these transfectants was also tested by flow cytometry. The changes at Glu 69 and Val 36 did not affect recognition by any of the monomorphic antibodies tested. However, the binding pattern of some of the polymorphic mAbs was clearly modified. Therefore, even though it is not crucial for T-cell allorecognition, polymorphic residue 36 must be involved in epitopes recognized by some polymorphic anti-DP antibodies, while residue 69 of the DPB molecule is crucial both for T-cell allorecognition and recognition by some mAbs.

Alleles↗
PubMed1998

Serological markers of hepatitis A, B and C in first year student nurses.

OBJECTIVE: To know the prevalence of serological markers of hepatitis A, B and C virus in first year student nurses. SETTING: A transversal study of prevalence. SUBJECTS AND METHODS: 81 first year student nurses, mean age 20.6 years (18-37, S.D. 3.8), with demographic, epidemiologic and clinical variables, performing liver enzymes, anti-HAV IgG, anti-HBcore and anti-HCV. RESULTS: The anti-HAV IgG was positive in 9 students (11.1%), with a prevalence of 6.7% between 17 and 19 years (C.I.95% 1.7 to 19.3%), 8.7% between 20 and 22 years (C.I.95% 1.5 to 29.5%), 20% between 23 and 25 years (C.I.95% 10.5 to 70.1%), and 37.5% (C.I.95% 10.2 to 74.1) in those over 25 years (p < 0.001). No other significative variables existed according to age-group. Regarding hepatitis B virus, of the 65 not previously vaccinated, only 1 (1.5%, C.I.95% 0.08 to 9.4%) was immunized, and there were no cases of HBsAg positive. The anti-VHC was positive in one case (1.2%, C.I.95% 0.06 to 7.6%), RIBA indeterminate and with normal ALT. Only one student (1.2%) showed increased transaminase values, attributed to liver steatosis. None of the students had suffered any episode of acute clinic hepatitis. CONCLUSIONS: The anti-HAV IgG prevalence in first year student nurses in our area is very low, and it is not necessary to carry out prevacunal screening. The low prevalence of anti-Hbcore also rejects a similar screening with respect to HBV. There were no HBsAg or anti-HCV positive cases, but it should not be the cause of forgetting to take the universal precautions or giving a false sensation of security.

Biomarkers↗
PubMed1997

Petroleum pollution in the Gulf of Mexico and Caribbean Sea.

In 1976, IOC-UNESCO and UNEP convened a meeting in Port of Spain to analyze the marine pollution problems in the region, noting that petroleum pollution was of regionwide concern and recommended initiating a research and monitoring program to determine the severity of the problem and monitor its effects. The Wider Caribbean is potentially one of the largest oil-producing areas in the world. Major production sites include Louisiana and Texas in the U.S.; the Bay of Campeche, Mexico; Lake Maracaibo, Venezuela; and the Gulf of Paria, Trinidad. All these are classified as high-risk production accident zones. Main sources of petroleum pollution in the Wider Caribbean are production, exploitation, transportation, urban and municipal discharges, refining and chemical wastes, normal loading and unloading operations, and accidental spills. About 5 million barrels of crude oil are transported daily in the Caribbean, thus generating an intense tanker traffic. It has been estimated that oil discharges from tank washings within the Wider Caribbean could be as high as 7 million barrels/yr. The results of the Caribbean Pollution Regional Program (CARIPOL) conducted between 1980 and 1987 pointed out that significant levels of petroleum pollution exist throughout the Wider Caribbean, including serious tar contamination of windward exposed beaches, high levels of floating tar within the major current systems, and very high levels of dissolved and dispersed hydrocarbons in surface waters. Major adverse effects of this type of pollution include: high tar levels on many beaches that either prevent their recreational use or require very expensive cleanup operations, distress and death for marine life, and responses in the enzyme systems of marine organisms that have been correlated with declines in reproductive success. Finally, the presence of polycyclic aromatic hydrocarbons (PAHs) in tissues of important economic species has been reported, creating a risk for public health because of the potential carcinogenic effects.

Accidents, Occupational↗
PubMed1996

Endothelin stimulates phosphoinositide hydrolysis and PAF synthesis in brain microvessels.

Treatment of brain microvessels with the three endothelin (ET) isoforms resulted in an increase of phosphoinositide turnover by activation of phospholipase C in a dose- and time-dependent manner. Both ET-1 and ET-2 are maximally effective, whereas the effect evoked by ET-3 was smaller. Concomitantly, there was an enhanced production of a platelet-activating factor (PAF)-like material. This was identified by standard and biological probes in platelets, such as induction of aggregation, phosphatidic acid (PA) production, increase of endogenous protein phosphorylation, and reversal of these responses by a PAF antagonist. The effects evoked by endothelins on phosphoinositide metabolism and PAF production were, to a certain extent, dependent on the presence of extracellular Ca2+. In addition, ET induced changes in Ca2+ dynamics, evoking an initial and rapid intracellular mobilization and influx of Ca2+ and, later, a maintained Ca2+ influx. These findings contribute to the understanding of the pathophysiological role of ET in the blood-brain barrier (BBB).

Animals↗
PubMed1996

Vibrio mimicus diarrhea following ingestion of raw turtle eggs.

Clinical and epidemiological characteristics of diarrhea associated with Vibrio mimicus were identified in 33 hospitalized patients referred to the Costa Rican National Diagnostic Laboratory Network between 1991 and 1994. The relevant symptoms presented by patients included abundant watery diarrhea, vomiting, and severe dehydration that required intravenous Dhaka solution in 83% of patients but not fever. Seroconversion against V. mimicus was demonstrated in four patients, from whom acute- and convalescent-phase sera were obtained. Those sera did not show cross-reaction when tested against Vibrio cholerae O1 strain VC-12. All the V. mimicus isolates from these cases produced cholera toxin (CT) and were susceptible to commonly used antibiotics. Attempts to isolate this bacterium from stool samples of 127 healthy persons were not successful. Consumption of raw turtle eggs was recalled by 11 of the 19 (58%) individuals interviewed. All but two V. mimicus diarrheal cases were sporadic. These two had a history of a common source of turtle (Lepidochelys olivacea) eggs for consumption, and V. mimicus was isolated from eggs from the same source (a local market). Among the strains, variations in the antimicrobial susceptibility pattern were observed. None of the strains recovered from market turtle eggs nor the four isolates from river water showed CT production. Further efforts to demonstrate the presence of CT-producing V. mimicus strains in turtle eggs were made. Successful results were obtained when nest eggs were tested. In this case, it was possible to isolate CT- and non-CT-producing strains, even from the same egg. For CT detection we used PCR, enzyme-linked immunosorbent assay (ELISA), and Y-1 cell assay, obtaining a 100% correlation between ELISA and PCR results. Primers Col-1 and Col-2, originally described as specific for the V. cholerae O1 ctxA gene, also amplified a 302-bp segment with an identical restriction map from V. mimicus. These results have important implications for epidemiological surveillance in tropical countries where turtle eggs are used for human consumption, serving as potential sources of cholera-like diarrhea.

Adult↗
PubMed1996

[Asymptomatic Addison disease: cause of striking reduction of insulin requirements in a patient with diabetes, Hashimoto thyroiditis and Basedow disease].

We report a 30 years old woman with sporadic poliglandular autoimmune syndrome type II, first seen with an insulin-dependent diabetes mellitus and a Graves-Basedow disease that became spontaneously hypothyroid with positive antimicrosomal antibodies. Six years later she presented with persistent vomiting and a remarkable reduction in insulin requirements. She had low basal and stimulated-cortisol levels and the diagnosis of severe adrenal failure was reached. A CT scan showed normal adrenal glands, she did not have cutaneous hyperpigmentation nor evidences of mineralocorticoid deficit. A selective autoimmune damage of the fascicular zone was assumed but a selective damage of ACTH producing pituitary cells cannot be discarded. The importance of investigating adrenal function in cases of unexplained reduction of insulin requirements is emphasized.

Addison Disease↗
PubMed1995

[Diagnosis and treatment of myasthenia gravis. Experience 1974-1992].

Between 1974 and 1992, 118 patients with Myasthenia gravis (MG) were studied in our Hospital; 92 patients, followed up for longer than 6 months, were surveyed for therapeutical results. Patients were categorized according to Osserman criteria; 22 belonged to group I; 77 to group II; 4 to group III and 15 to group IV. MG predominated in females, the ratio was 1.87:1.0. This predominance was more obvious in patients below 35 years of age (2.68:1.0) than above (1.18:1.0). The greatest prevalence was found at the 3rd decade of life. The assessment of the diagnostic test is as follows: 1) edrophonium test was positive in 97% of 93 patients; 2) supramaximal repetitive stimulation performed in 3 different nerves yielded positive results in 83% of 118 patients. It is worth noting that the test was positive in 92% of patients with generalized MG while only 48% of those with ocular MG displayed positive results; 3) sera antiacetycholine receptor antibodies (ACRA) quantification produced positive results in 88% of the patients with generalized MG and in 33% of ocular MG. Altogether the positivity of this test was 83%; 4) passive transfer of patients sera (25 generalized and 2 ocular MG forms) to mice and measurement of mepp's amplitude in the phrenic-diaphragm in vitro preparation yielded positive results in 100% of the tested cases. Once the diagnosis was achieved, the characteristics of the thymus were studied combining pneumomediastinography and linear tomography (PT) in 60 patients. Thorax Computed tomography (CT) was performed in 51 patients. Of those patients who underwent thymectomy, the coherence between radiological and histological diagnosis for PT was 100% while for CT just 60%. More recently 14 patients were studied by combining both procedures. Reliability of this technique is currently under study. Therapeutical assessment was carried out adscribing patients to 5 different groups according to their response after treatment withdrawal; group 2: Improved, neither symptoms nor signs; group 1: Remission, neither symptoms nor signs while on medication or minimal disability without medication; group 3: Unchanged while on medication; group 4: Worse, patients with more severe or frequent signs and symptoms despite being on treatment, group 5: Death, patients who died due to respiratory failure. Groups 1 and 2 were considered successful while 3, 4 and 5 as unsuccessful. Treatment was based on the administration of anticholinesterase drugs (piridostigmine, neostigmine) in 113 patients. Of these, 35 received those drugs as the only medication of whom 39% obtained successful results. Steroids (methylprednisone) were administered to 75 patients, in 40 cases combined with anticholinesterase drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1995

[Quantitative evaluation of juxtatrabecular fibrosis in myelodysplastic syndromes].

PURPOSE: Myelofibrosis is a common, poor-prognosis feature of myelodysplastic syndromes (MDS). The aim of this work was to evaluate quantitatively the extent of the juxtatrabecular fibrosis in primary MDS and in secondary myelodysplasias, along with the presence of immature precursor cells in anomalous position, that is, the displacement of granulopoiesis from the paratrabecular area to central positions. PATIENTS AND METHODS: Twenty-seven bone marrow samples were examined: 9 from primary MDS, 9 from secondary myelodysplasias, and 9 normal. The percentage of myeloblasts and promyelocytes with nucleoli located in the central areas was estimated, in an attempt to correlate such feature with the degree of juxtatrabecular fibrosis. The analysis of data was performed with the Kruskal-Wallis test, values of p < 0.01 being significant. RESULTS: Sectorial juxtatrabecular fibrosis was present in all the myelodysplastic samples, ranging from 6% to 55% of the trabecular surface; the highest values found in the controls were about 3.6% (p < 0.01). Although the juxtatrabecular fibrosis figures are higher in secondary MDS, the difference is not significant with regard to the primary MDS in the number of patients studied here. The count of myeloblasts and promyelocytes with nucleoli present in the MDS was significantly greater than that of the control group. The number of promyelocytes with nucleoli was significantly higher in the primary MDS with respect to the secondary ones, whereas no significant difference was seen between the two types of MDS regarding the myeloblast count. CONCLUSIONS: The increased number of central immature precursor cells in MDS was not directly correlated with the extent of the juxtatrabecular fibrosis. Although the number of cases is small, the fact that the juxtatrabecular fibrosis was higher in the two deceased patients in the series (49% and 56%, respectively) suggests a poor-risk prognosis for such finding.

Anemia, Refractory↗
PubMed1993

Identification of GTP binding proteins in brain microvessels and their role in phosphoinositide turnover.

The identity of GTP binding proteins in cerebral microvessels was investigated by immunoblotting. Data indicate the presence of a characteristic pattern of Gi, Gs and Go. The most remarkable finding is the presence of Go protein in cerebral microvessels that consist predominantly of capillary segments free of neuronal contaminants. The pattern of pertussis toxin-catalyzed ADP-ribosylation of a 40 kDa polypeptide is characteristic of the Gi/Go type alpha-subunits. In addition, we have observed that GTP tau S, a non-hydrolyzable guanine nucleotide, exerts a dual regulatory effect on phosphoinositide metabolism depending on the concentration, thus 10(-7) M concentration inhibits the 32P incorporation into PIP2 and PA by a pertussis toxin-sensitive mechanism; on the contrary, the stimulatory effect of higher concentration than 10(-6) M of GTP tau S is pertussis toxin-insensitive.

Adenosine Triphosphate↗
PubMed1993

Platelet-activating factor stimulates protein kinase C translocation in cerebral microvessels.

The effects of platelet-activating factor (PAF) on distribution of protein kinase C activity in brain microvessels have been examined. Our results indicate that PAF caused an increase of protein kinase C activity in membrane, accompanied by a loss of activity in the cytosol. This effect resulted to be dose-dependent and the translocation was evident after 30 min of PAF treatment. These results suggest that PAF could play a role in transport processes in the blood-brain barrier, involving protein phosphorylation by activation of protein kinase C.

Animals↗
PubMed1991

Pertussis toxin-insensitive regulation of phosphatidylinositol hydrolysis by vanadate in brain microvessels.

Vanadate, over a concentration range from 0.1 to 0.5 mM, stimulated the incorporation of (32P)-orthophosphate into PI and PA in brain microvessels. At concentrations higher than 0.5 mM, the stimulatory effect of vanadate decreased. Concommitantly, an enhanced DAG production was observed, indicating that vanadate stimulated PI turnover. All these effects were evident at all the times tested. Experiments performed in the presence of pertussis toxin (IAP) indicated that a IAP-sensitive G-protein does not mediate the vanadate stimulated PI effect in brain microvessels.

Animals↗
PubMed1990

[Vipoma of the pancreas. Apropos of a case and review of the literature].

Pancreatic endocrine tumors are uncommon; of this type of tumors, the Verner-Morrison's syndrome, WDHA or vipoma is diagnosed very rarely. The present paper is a report of a pancreatic vipoma in a 60 year-old female; she presented with watery diarrhea, facial flushing, hypokalemia, hypochlorhydria, metabolic acidosis and reversible renal failure; these are the usual manifestations of the syndrome. The diagnosis was made on the basis of radiological imaging, CAT and arteriography as well as the finding or elevated levels of vasoactive intestinal peptide (VIP). The surgical resection of the tumor was followed by the remission of the symptoms and normalization of the plasmatic levels of VIP. It is necessary to recognize this type of tumors because the only way to achieve a curative surgical resection is after an early diagnosis.

Adenoma, Islet Cell↗
PubMed1989

Evidence for a regulatory action of vanadate on protein phosphorylation in brain microvessels.

We investigated the action of vanadate on protein phosphorylation in microvessels isolated from rat brain. We found that a stimulation of protein phosphorylation from 32P-ATP occurs, in the presence of different concentrations of vanadate, 10(-3) M being the most effective dose. This action was time-dependent, and it was more evident after 60 s of treatment. The contribution of ATPase inhibition caused by vanadate appears to be negligible. In addition a stimulation of cAMP-dependent protein kinase activity was observed. The pattern of protein phosphorylation showed that exposure to 10(-3) M vanadate resulted in a nonspecific stimulation of protein phosphorylation concomitantly with a selective inhibition of the 55 KDa protein phosphorylation. The nature of this protein is also discussed.

Animals↗
PubMed1989

Chronic activation of dopamine receptors in the female infantile rat: effect on hypophyseal hormones and on the onset of puberty.

In the female rat the period from days 7-20 of age is special with regard to regulation of hypophyseal hormone secretion. This period is characterized by high FSH levels and the occurrence of sporadic LH peaks. As it has been reported that haloperidol could enhance both gonadotropins at 12 days of age and not at later ages, it was of interest to treat rats during the infantile period with pergolide, a dopaminergic agent of long action, and evaluate its effect on hormone levels and puberty onset. Three different schedules of drug injections were applied: 1) daily injections (0.05 mg/kg.day) on days 1-10, 2) daily injections on days 5-14, and 3) daily injections on days 11-20. It was found that only animals treated with daily injections of pergolide on days 11-20 showed an advance in the age of vaginal opening and first estrus compared to distilled water-injected controls. Thus, the rest of the experiments were performed using injection schedule 3. In this group of animals serum LH and FSH levels were decreased 3 and 6 days after the beginning of pergolide treatment (13 and 16 days of age); at 19 days of age pergolide did not modify gonadotropin levels. One day after the end of pergolide treatment (day 21 of age), there was a rebound in LH levels in drug-injected rats, and a nonsignificant increment in FSH levels was observed. There were no differences in serum gonadotropin levels on days 22, 23, and 25 or peripubertally (29, 33, or 36 days of age). On the other hand, pergolide did not significantly modify PRL levels during the treatment, probably due to the already low values of PRL at these ages. Furthermore, PRL levels were not different between control and pergolide-injected rats at all other ages studied. After puberty onset, animals were observed for eight consecutive cycles, and both groups cycled regularly. Furthermore, PRL and gonadotropins levels were similar at diestrus and proestrus. To evaluate if pergolide treatment during the infantile period had caused permanent alteration in dopamine receptor sensitivity, animals were injected with haloperidol (0.1 or 0.25 mg/kg), and PRL release was evaluated. There were no differences in the hyperprolactinemic effect of the drug between groups. Finally, gonadotropin sensitivity to LHRH was similar in adult female rats in proestrus of both groups. The present results suggest that chronic activation of dopamine receptors during the infantile period evokes specific responses on gonadotropin secretion and advances the age of puberty onset.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗