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Biomedical subjects

R Alvarez

Publications and source records attributed to R Alvarez.

At least 55 records · Page 3Linked to original sources
PubMed2000

Measurement of proton release and uptake by analogs of bacteriorhodopsin.

Proton release and subsequent uptake by several forms of bacteriorhodopsin (bR), including 4-keto analogs of wild-type (WT) and D96N and D85N mutants as well as the 9-demethylretinal analog of WT and D96N mutants, have been measured using a highly sensitive electrochemical technique. Release and uptake of protons by bR in membrane patches on a tin oxide electrode produce a current transient whose amplitude is proportional to the rate of pH change at the electrode surface. Profiles of proton release by the analogs vs. pH are substantially different from the profiles of the native proteins.

Bacteriorhodopsins↗
PubMed2000

Microtubule binding to Smads may regulate TGF beta activity.

Smad proteins are intracellular signaling effectors of the TGF beta superfamily. We show that endogenous Smad2, 3, and 4 bind microtubules (MTs) in several cell lines. Binding of Smads to MTs does not require TGF beta stimulation. TGF beta triggers dissociation from MTs, phosphorylation, and nuclear translocation of Smad2 and 3, with consequent activation of transcription in CCL64 cells. Destabilization of the MT network by nocodazole, colchicine, or a tubulin mutant disrupts the complex between Smads and MTs and increases TGF beta-induced Smad2 phosphorylation and transcriptional response in CCL64 cells. These data demonstrate that MTs may serve as a cytoplasmic sequestering network for Smads, controlling Smad2 association with and phosphorylation by activated TGF beta receptor I, and suggest a novel mechanism for the MT network to negatively regulate TGF beta function.

Activin Receptors, Type I↗
PubMed2000

Serum inhibin B determination is predictive of successful testicular sperm extraction in men with non-obstructive azoospermia.

Recent work indicates that serum inhibin B is a useful marker of spermatogenesis and inhibin B production sufficient to maintain detectable serum concentrations in adults depends on spermatogenic activity. The purpose of the present study was to investigate the usefulness of serum inhibin B measurement to predict the success of testicular sperm extraction (TESE) in 17 men with nonobstructive azoospermia to be treated by intracytoplasmic sperm injection (ICSI) (group 1). Two additional groups were used as positive controls; group 2 comprised 22 infertile men having obstructive azoospermia, and group 3, which included 29 semen donors having normal seminal parameters. Follicle stimulating hormone (FSH) was significantly higher (P < 0.01) and inhibin B significantly lower (P < 0.001), in group 1 as compared with groups 2 and 3. Serum inhibin B concentrations were significantly higher (P < 0.001) among successful TESE men as compared with those having failed TESE. In contrast, no differences were detected between these two groups with respect to serum FSH or testicular size. In addition, serum inhibin B but not FSH discriminated between successful and failed TESE in group 1 subjects as compared with control groups. According to the receiver operating characteristics curve analysis, the best inhibin B value for discriminating between successful and failed TESE was >40 pg/ml (sensitivity 90%, specificity 100%). It is concluded that inhibin B measurement is a useful non-invasive predictor of spermatogenesis and thus, all azoospermic males should have serum inhibin B concentrations determined in addition to FSH measurement and karyotyping prior to undergoing TESE.

Adult↗
PubMed2000

Interaction of D-600 with the transmembrane domain of the sarcoplasmic reticulum Ca(2+)-ATPase.

Experiments were performed to determine whether the organic Ca(2+) channel blocker D-600 (gallopamil), which penetrates into muscle cells, affects sarcoplasmic reticulum (SR) Ca(2+) uptake by directly inhibiting the light SR Ca(2+)-ATPase. We have previously shown that at 10 microM, D-600 inhibits LSR ATP-dependent Ca(2+) uptake by 50% but has no effect on ATPase activity (21). These data suggest that the SR Ca(2+)-ATPase might be a potential target for D-600. The ATPase activity of the enzyme is associated with its hydrophilic cytoplasmic domain, whereas Ca(2+) binding and translocation are associated with the transmembrane domain (18). In the present experiments, we determined which of the two domains of the ATPase is affected by D-600. Thermal inactivation experiments using the SR Ca(2+)-ATPase demonstrated that D-600 decreased the thermal stability of Ca(2+) transport but had no effect on the stability of ATPase activity. In addition, D-600 at a concentration of 160 microM did not have any leaking effect of Ca(2+) on the Ca(2+)-loaded SR. Thermal denaturation profiles of SR membranes revealed that D-600 interacts directly with the transmembrane domain of the Ca(2+)-ATPase. No evidence for interaction with the nucleotide domain was obtained. We conclude that the Ca(2+) blocker D-600 inhibits the SR Ca(2+) pump specifically by interacting with the transmembrane Ca(2+)-binding domain of the Ca(2+)-ATPase.

Adenosine Triphosphatases↗
PubMed2000

Inhibitory tagging in inhibition of return is affected in schizophrenia: evidence from the stroop task.

L. J. Fuentes, A. B. Vivas, and G. W. Humphreys (1999b) showed that stimulus processing is affected when stimuli are presented to locations subject to inhibition of return. They argued that activated representations of stimuli presented at inhibited locations are disconnected from their associated responses through an "inhibitory tagging" mechanism occurring in inhibition of return. In the present research, the authors asked whether such a mechanism is affected in people with schizophrenia. Healthy adults and patients with schizophrenia performed a Stroop task in an inhibition of return paradigm. Healthy adults showed a reduction in the Stroop interference when stimuli were presented at inhibited locations, a result that agrees with the inhibitory tagging mechanism hypothesis and replicates previous findings. However, patients with schizophrenia did not show such a reduction, a result suggesting that they have a deficit in inhibitory processing occurring in inhibition of return.

Adult↗
PubMed2000

Co-existence of hereditary spherocytosis and a new red cell pyruvate kinase variant: PK mallorca.

BACKGROUND AND OBJECTIVE: A partial red blood cell (RBC) pyruvate-kinase (PK-R) deficiency was found in a patient with concomitant hereditary spherocytosis (HS) and chronic hemolytic anemia. Clinical, biological and molecular studies were performed in the patient, his parents and a brother, in order to characterize the specific PK-R gene mutation and the inheritance mechanism of the transmission of both red cell defects in this particular family. DESIGN AND METHODS: Conventional biological studies were used to identify the PK-LR gene mutation responsible for hereditary transmission of PK-R deficiency and HS. The family study was completed with genotypic and RBC membrane protein analyses in the patient and his family. RESULTS: Molecular study of the PK deficiency was performed in all the family members and demonstrated a heterozygous condition for the 1516 G->A (506Val->Ile) mutation at the PK-LR gene in both the patient and his mother. Since this mutation has not been reported previously, it is provisionally named PK "Mallorca". The study of RBC membrane proteins demonstrated the existence of partial band 3 and protein 4.2 deficiencies in the propositus and his father but not in the mother and brother, who were also studied. These results support the dominant mode of inheritance of HS and PK-LR gene in this family. INTERPRETATION AND CONCLUSIONS: HS and PK deficiency are not exceptional in Spain. The co-existence of both RBC defects in the same patient, however, is very rare; only a few cases have been described to date. Our findings suggest that performing an elementary RBC enzyme survey in all patients with HS would help to determine the real frequency of this apparently rare association.

Amino Acid Substitution↗
PubMed2000

[The prolonged administration of intravenous immunoglobulins as a treatment for refractory fistulous Crohn's diseases].

Fistulating Crohn's disease is present in 17-35% of non-surgically treated patients and in up to 45% of surgically treated ones. Among the several therapeutic alternatives for this disease is intravenous immunoglobulin administration. We present a 28-year-old woman with refractory fistulating Crohn's disease who improved after prolonged immunoglobulin administration (32 months).

Adult↗
PubMed2000

[Prognostic factors for survival following transarterial chemoembolization in advanced hepatocellular carcinoma].

The efficacy of transarterial chemoembolization in the palliative treatment of non-resectable hepatocellular carcinoma is controversial. To determine the possible existence of clinical and analytical variables with independent predictive value for survival related to the tumor and the treatment given, a multivariate analysis in a series of 111 patients who underwent transarterial chemoembolization was carried out. Overall actuarial survival was 54%, 31% and 24% at 1, 2 and 3 years respectively. Child-Pugh score (p < 0.05), tumor size (p < 0.05) and arterial occlusion after intraarterial chemotherapy (p < 0.05) reached independent predictive value. The group of patients in whom two or three of these factors were simultaneously present had a very poor prognosis with a survival of 20% and 0% at 1 and 2 years respectively, compared with 60%, 50% and 37% at 1, 2 and 3 years respectively in the group with one or none of these factors (p < 0.01). Grouping on the basis of these variables may be useful in the design of future controlled prospective studies that aim to determine the efficacy of transarterial chemoembolization.

Adult↗
PubMed2000

[Percutaneous intrahepatic portosystemic shunting in the treatment of veno-occlusive disease of the liver after bone marrow transplantation].

Veno-occlusive disease of the liver is a frequent cause of morbidity and mortality after bone-marrow transplantation. Its clinical manifestations are primarily related to the development of portal hypertension and sinusoidal congestion. The efficacy of the different therapeutic options used is controversial. We present a 22-year-old woman with veno-occlusive liver disease histologically confirmed after autologous bone-marrow transplantation, with progressive alteration in liver biochemistry and ascites. She was treated by percutaneous intrahepatic portosystemic shunting. After the procedure there was a marked improvement in ascites and an increase in diuresis with liver function progressively returning to normal. The safety and efficacy of this approach in the treatment of patients with veno-occlusive liver disease should be evaluated in controlled studies.

Adult↗
PubMed2000

[Detection of viral genomes of the Herpesviridae family in multiple sclerosis patients by means of the polymerase chain reaction (PCR)].

BACKGROUND: The multiple sclerosis seems to be the junction between genetics alteration and an unknown environmental factor, that they would originate an autoimmune alteration, that they would be the reason of the inflammation and demyelinization responsible of the disease. Our objective has been the determination of this possible environmental factor and to reach it, we have studied the appearance of Herpesviridae family viruses. MATERIALS AND METHODS: 204 blood samples were studied: 102 from relapsing-remitting multiple sclerosis patients (43 were undergoing beta-interferon treatment), and 102 from blood donors with the same age and sex than multiple sclerosis patients. From this samples, we extracted the DNA of peripheral blood mononuclear cells (PBMCs), and we analyzed by polymerase chain reaction (PCR) to detect the appearance of herpes simplex virus, varicella zoster virus, Epstein-Barr virus, cytomegalovirus, human herpesvirus 6 (HHV-6), human herpesvirus 7 and human herpesvirus 8. RESULTS: a) we only found significative difference (p = 0.0001) in HHV-6: 21.5% donors positive samples (22/102), opposite to 49.02% of positivity in mulytiple sclerosis patients (50/102); b) we didn't found significative differences in none of other viruses studied, between patients treated with beta-interferon and non-treated ones. CONCLUSIONS: Our results suggest us that HHV-6 can play an important role in the multiple sclerosis development. The beta-interferon treatment doesn't affect to DNA prevalence of none of studied viruses.

Adult↗
PubMed2000

Synergistic effect between apolipoprotein E and angiotensinogen gene polymorphisms in the risk for early myocardial infarction.

BACKGROUND: Several studies based on different populations worldwide have described an association between cardiovascular diseases and genetic variations in the apolipoprotein E (A:POE), angiotensinogen (A:GT), angiotensin receptor type 1 (A:T1R), and angiotensin-converting enzyme (A:CE) genes. In addition, there is growing evidence of an interaction between hypercholesterolemia and the renin-angiotensin system in the risk for hypertension and atherosclerosis. METHODS: To determine whether the DNA polymorphisms in A:POE (epsilon2, epsilon3, and epsilon4 alleles), A:GT (M235T), A:T1R (1166 A:/C:), and ACE (I:/D:) are associated with early onset of myocardial infarction (MI), we genotyped 220 patients and 200 controls <55 years of age. Patients and controls were males from the same homogeneous Caucasian population. Data concerning hypertension, diabetes, and tobacco consumption were recorded. The lipid profiles of patients and controls were also determined. RESULTS: APOE, ACE, AGT, and AT1R allele and genotype frequencies did not differ between patients and controls. None of these polymorphisms was related to the biochemical values in patients or controls. The frequency of individuals who were both APOE epsilon4 allele carriers and AGT-TT homozygotes was significantly higher in patients than in controls (11% vs 3.5%; P: = 0.0037). In patients, the frequency of epsilon4 carriers was significantly higher (P: <0.00001) in those who were AGT-TT (46%) than those who were AGT-MT/MM (14%). Mean cholesterol was significantly higher in AGT-TT + APOE epsilon34/44 patients than in the TM/MM + epsilon34/44 or TT + epsilon23/33 genotypes (P: = 0. 029). CONCLUSIONS: Our data suggest a synergistic effect between the APOE and AGT polymorphisms and early MI. The increased risk could be mediated in part through higher cholesterol concentrations among individuals who are AGT-TT + APOE epsilon4 allele carriers.

Adult↗
PubMed1999

Inhibitory processing in visuospatial attention in healthy adults and schizophrenic patients.

This study assessed visuospatial attention in healthy adults and medicated schizophrenic patients. Participants performed a visual orientation task in which a peripheral cue was followed. at different intervals, by a target presented either at valid or invalid locations. When the long stimulus onset asynchrony (SOA) was used, participants were presented with either a single peripheral cue (single-cue condition) or two cues, the peripheral cue followed by a central cue (the double-cue condition). Healthy adults showed marginal facilitation effects with the short SOA and similar inhibition of return effects with the long SOA in both single-cue and double-cue conditions. Schizophrenic individuals showed a big facilitation effect with the short SOA and normal inhibition of return with the long SOA in both cue conditions. Results with the short SOA replicated previous findings (Huey, E.D., Wexler, B.E., 1994. Schizophrenia Research 14, 57-63) but, in contrast, we did not observe blunted inhibition of return with the long SOA. An inspection of the differences in the procedures used in both studies may help both to account for the discrepancies and to reveal what processes involved in visuospatial attention are affected in schizophrenia.

Adult↗
PubMed1999

Treadmill exercise-induced stress causes a rise of blood histamine in normotensive but not in primary hypertensive humans.

We have previously shown an interaction between noradrenergic and histamine-containing neurons in the rat vas deferens. As a generalized phenomenon, this interaction is involved in a novel peripheral reflex that, in an inhibitory way, modulates sympathetic activity and arterial pressure. Consistent with this, an activation of postganglionic sympathetic neurons causes a rise in rat blood histamine. In the present study, we showed that enhanced sympathetic activity due to treadmill exercise in normotensive humans, is accompanied by a rise in blood histamine, suggesting the presence of a similar neuronal interaction in humans. In contrast, the rise in blood histamine does not occur in primary hypertensive humans during the same degree of physical exercise, suggesting that this interaction is faulty in such hypertensives and could be involved in the pathophysiology of the disease.

Adult↗
PubMed1999

[Frequency of the APOE-4 allele in Alzheimer's disease and its variation with age in Asturias (Spain)].

BACKGROUND: Patients with late-onset Alzheimer's disease show a higher frequency of the APOE-4 than controls. The usefulness of the APOE genotyping in the diagnosis of the disease is controversial. Recently, an age dependent prevalence of APOE-4 in Alzheimer's disease has been described, with a maximum frequency for patients with an age at onset between 65 and 80 years. Additionally, the APOE-4 frequency in healthy controls is similar among the different age-groups, including healthy octogenarians. These data suggest that APOE-4 determines when and not who will develop the disease. PATIENTS AND METHODS: The APOE genotype was defined following a previously described PCR-protocol. We analysed 120 patients with clinically defined probable Alzheimer's disease and 250 controls from the same Caucasian population (Austrias, Northern Spain). RESULTS: We found a significantly higher frequency of the APOE-4 in patients, compared to controls (p = 0.00001). The prevalence of this allele was 65% among patients with an age at onset 66-70, falling to 36% and 18% in patients younger than 65 and older than 80 years, respectively. The average age (SD) at onset did not differ between the E-44 (69 years), E-34 (73 years) and E-33 (73 years). APOE-4 frequency was similar between the different age-groups of controls, including healthy octogenarians. CONCLUSIONS: In Asturias, APOE genotyping can not be used for the presimptomatic diagnosis of Alzheimer's disease. However, individuals carrying this allele would have a higher probability of developing the disease at an age between 65 and 80 years if they are predisposed (genetically and/or environmentally) to the disease.

Adult↗
PubMed1999

Association between an alpha(2) macroglobulin DNA polymorphism and late-onset Alzheimer's disease.

An association between a five-base-pair deletion/insertion DNA polymorphism at the alpha(2) macroglobulin gene (A2M) and late-onset Alzheimer's disease (LOAD) has been recently described. We developed a PCR assay to analyze this polymorphism in 190 LOAD patients (older than 65 years) and 400 controls from Spain. Controls were stratified into three groups: <65 years (n = 200), 65 to 80 years (n = 100), and 81 years or older (n = 100). We found a significantly higher frequency of carriers of the D allele in patients older than 81 years compared to controls older than 81 years (p = 0.0012). In addition, the frequency of the D allele was significantly lower in controls older than 81 years compared to controls younger than 65 (p = 0.048). Our work suggests that the D allele confers an age-dependent increased risk to develop late-onset Alzheimer's disease.

Age of Onset↗