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Biomedical subjects

A Castro

Publications and source records attributed to A Castro.

At least 145 records · Page 8Linked to original sources
PubMed2000

Part of Xenopus translin is localized in the centrosomes during mitosis.

During oogenesis, maternal mRNAs are synthesised and stored in a translationally dormant form due to the presence of regulatory elements at the 3' untranslated regions (3'UTR). In Xenopus oocytes, several studies have described the presence of RNA-binding proteins capable to repress maternal-mRNA translation. The testis-brain RNA-binding protein (TB-RBP/Translin) is a single-stranded DNA- and RNA-binding protein which can bind the 3' UTR regions (Y and H elements) of stored mRNAs and can suppress in vitro translation of the mRNAs that contain these sequences. Here we report the cloning of the Xenopus homologue of the TB-RBP/Translin protein (X-translin) as well as its expression, its localisation, and its biochemical association with the protein named Translin associated factor X (Trax) in Xenopus oocytes. The fact that this protein is highly present in the cytoplasm from stage VI oocytes until 48 h embryos and that it has been described as capable to inhibit paternal mRNA translation, indicates that it could play an important role in maternal mRNA translation control during Xenopus oogenesis and embryogenesis. Moreover, we investigated X-translin localisation during cell cycle in XTC cells. In interphase, although a weak and diffuse nuclear staining was observed, X-translin was mostly present in the cytoplasm where it exhibited a prominent granular staining. Interestingly, part of X-translin underwent a remarkable redistribution throughout mitosis and associated with centrosomes, which may suggest a new unknown role for this protein in cell cycle.

Amino Acid Sequence↗
PubMed2000

Benzothiadiazine dioxide dibenzyl derivatives as potent human cytomegalovirus inhibitors: synthesis and comparative molecular field analysis.

The benzothiadiazine dioxide (BTD) derivatives are potent nonnucleoside human cytomegalovirus (HCMV) inhibitors. As part of our comprehensive structure-activity relationship study of these compounds, we have now synthesized N,N- and N,O-dibenzyl derivatives with different para-substituents (alkyl, phenyl, electron-donating, electron-withdrawing) in the phenyl ring of the benzyl moieties. The antiviral activity against HCMV (AD-169 strain) was also experimentally measured showing IC(50) values between 2.5 and 50 microM. Comparative molecular field analysis (CoMFA) was employed to generate a model, based upon 32 diverse BTD derivatives, to delineate structural and electrostatic features important for enhanced activity against HCMV. The steric (van der Waals) interactions with the receptor majoritary describes the variation in antiviral activity among the inhibitors. Finally, the CoMFA model was used to design two sets of novel BTD derivatives. Synthesis and subsequent anti-HCMV evaluation of these compounds enabled us to maintain the activity of this new kind of HCMV inhibitors.

Antiviral Agents↗
PubMed2000

Nonnucleoside human cytomegalovirus inhibitors: synthesis and antiviral evaluation of (chlorophenylmethyl)benzothiadiazine dioxide derivatives.

A second generation of benzothiadiazine dioxide (BTD) derivatives was synthesized employing benzylation reactions mainly. The chlorophenylmethyl BTD derivatives showed activity against human cytomegalovirus (HCMV) with IC(50) values ranging from 3 to 10 microM. Their 50% cytotoxic concentrations were often >200 microM to lung fibroblast HEL cell proliferation and between 20 and 35 microM for lymphocyte CME cell growth. When cytotoxicity for cell morphology was considered, the minimum cytotoxic concentration for the different BTD derivatives varied between 5 and 200 microM. Some of the anti-HCMV compounds also showed activity against HIV-1 and HIV-2. The chlorophenylmethyl derivative 21 was active against a variety of HCMV clinical isolates from patients with different clinical manifestations and fully maintained its activity against a ganciclovir-resistant HCMV strain. The dibenzyl BTD derivatives did not inhibit HCMV protease, and preliminary pharmacological experiments revealed that their anti-HCMV action stems from interference with an early stage of the viral replicative cycle.

Animals↗
PubMed2000

The polo-like kinase Plx1 prevents premature inactivation of the APC(Fizzy)-dependent pathway in the early Xenopus cell cycle.

Members of the polo-like family of protein kinases have been involved in the control of APC (anaphase-promoting complex) during the cell cycle, yet how they activate APC is not understood in any detail. In Xenopus oocytes, Ca2+-dependent degradation of cyclin B associated with release from arrest at second meiotic metaphase was demonstrated to require the polo-like kinase Plx1. The aim of the present study was to examine, beyond Ca2+-dependent resumption of meiosis, the possible role of Plx1 in the control of cyclin degradation during the early mitotic cell cycle. Plx1 was found to be dispensable for MPF to turn on the cyclin degradation machinery. However, it is required to prevent premature inactivation of the APC-dependent proteolytic pathway. Microcystin suppresses the requirement for Plx1 in both Ca2+-dependent exit from meiosis, associated with degradation of both cyclin B and A downstream of CaMK2 activation, and prevention of premature APC(Fizzy) inactivation in the early mitotic cell cycle. These results are consistent with the view that Plx1 antagonizes an unidentified microcystin-sensitive phosphatase that inactivates APC(Fizzy).

Anaphase-Promoting Complex-Cyclosome↗
PubMed2000

Search for scalar top and scalar bottom quarks in pp collisions at square root s=1.8 TeV.

We have searched for direct pair production of scalar top and scalar bottom quarks in 88 pb-1 of pp collisions at sqrt[s]=1.8 TeV with the CDF detector. We looked for events with a pair of heavy flavor jets and missing energy, consistent with scalar top (bottom) quark decays to a charm (bottom) quark and a neutralino. The numbers of events that pass our selections show no significant deviation from standard model expectations. We compare our results to the next-to-leading order scalar quark production cross sections to exclude regions in scalar quark-neutralino mass parameter space.

Journal Article↗
PubMed2000

Search for a W' boson via the decay mode W'-->munumu in 1.8 TeV pp collisions.

We report the results of a search for a W' boson produced in pp collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample recorded by the Collider Detector at Fermilab. We consider the decay channel W'-->&munumu and search for anomalous production of high transverse mass munumu lepton pairs. We observe no excess of events above background and set limits on the rate of W' boson production and decay relative to standard model W boson production and decay using a fit of the transverse mass distribution observed. If we assume standard model strength couplings of the W' boson to quark and lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c2 at 95% confidence level.

Journal Article↗
PubMed2000

Role of acidic sphingomyelinase in Fas/CD95-mediated cell death.

Engagement of the Fas receptor has been reported to induce ceramide generation via activation of acidic sphingomyelinase (aSMase). However, the role of aSMase in Fas-mediated cell death is controversial. Using genetically engineered mice deficient in the aSMase gene (aSMase(-/-)), we found that thymocytes, concanavalin A-activated T cells, and lipopolysaccharide-activated B cells derived from both aSMase(-/-) and aSMase(+/+) mice were equally sensitive to Fas-mediated cell death, triggered by either anti-Fas antibody or Fas ligand in vitro. Similarly, activation-induced apoptosis of T lymphocytes was unaffected by the status of aSMase, and aSMase(-/-) mice failed to show immunological symptoms seen in animals with defects in Fas function. In vivo, intravenous injection of 3 microg/25 g mouse body weight of anti-Fas Jo2 antibody into aSMase(-/-) mice failed to affect hepatocyte apoptosis or mortality, whereas massive hepatocyte apoptosis and animal death occurred in wild type littermates. Animals heterozygous for aSMase deficiency were also significantly protected. Susceptibility of aSMase(-/-) mice to anti-Fas antibody was demonstrated with higher antibody doses (>/=4 microg/25 g mouse). These data indicate a role for aSMase in Fas-mediated cell death in some but not all tissues.

Animals↗
PubMed2000

Benzyl derivatives of 2,1,3-benzo- and benzothieno[3,2-a]thiadiazine 2,2-dioxides: first phosphodiesterase 7 inhibitors.

The synthesis of a new family of benzyl derivatives of 2,1,3-benzo- and benzothieno[3,2-a]thiadiazine 2,2-dioxides was achieved. The biological data revealed the first heterocyclic family of compounds with PDE 7 inhibitory properties appearing to be a new objective for the treatment of T-cell-dependent disorders. The IC(50) values or percent inhibition values of the compounds against PDE 7 were calculated by testing them against human recombinant PDE 7 expressed in S. cerevisiae. In this expression system the only cyclic nucleotide hydrolyzing activity present in cell extracts corresponded to human PDE 7. Isoenzyme selectivity PDE 7 versus PDE 4 and PDE 3 was also measured. Considering simultaneously inhibition of the three different isoenzymes, monobenzyl derivatives 15 and 23 showed interesting PDE 7 potency (around 10 microM); although not statistically significant, a trend toward selectivity with respect to PDE 3 and PDE 4 was obtained. Benzothiadiazine 16, although less potent at PDE 7 (IC(50) = 25 microM), also showed a trend of selectivity toward PDE 3 and PDE 4. These compounds are considered the best leads for further optimization.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Classification of ancient Roman glazed ceramics using the neural network of Self-Organizing Maps.

Artificial neural networks with unsupervised learning strategy known as Self-Organizing Maps were applied to classify ancient Roman glazed ceramics. Their clay ceramic bodies were analyzed by Inductively Coupled Plasma-Atomic Emission Spectroscopy and the chemical composition obtained was processed by this neural algorithm. The results obtained provide two types of information: firstly, classification of ceramic samples with identification of several groups and secondly, differentiation between the elemental chemical information. It was found that there are certain chemical elements which can be considered as principal and which can serve to differentiate between ceramics, whereas other elements give redundant information and do not contribute to sample differentiation. Seven chemical elements were considered principal and provide the necessary information. Two types of element were identified: 1- a group formed by common elements, such as: Ca, Fe, Mg, Mn and 2- another formed by optional elements: K or Na and Ba or Sr and Al or Ti.

Journal Article↗
PubMed2000

Anti-rhinovirus activity of 3-methylthio-5-aryl-4-isothiazolecarbonitrile derivatives.

A series of 3-methylthio-5-aryl-4-isothiazolecarbonitriles has been evaluated as anti rhinovirus agents against a panel of 17 representative human rhinovirus (HRV) serotypes, belonging to both A and B groups. No anti rhinovirus activity was detected for 3-methylthio-5-phenyl-4-isothiazolecarbonitrile (IS-2). Isothiazole derivatives with bulky substituents (O-Bn or O-But groups) on the para position of the phenyl ring were the most effective compounds of this series. In fact, a reduction in virus-induced cytopathogenicity was demonstrated for the O-Bn substituted IS-50 compound against the majority (88%) of the rhinoviruses tested, whereas the compound with an O-Ts group (IS-44) was found to be a specific inhibitor of group B serotypes, exhibiting the lowest IC(50) against HRVs type 2, 85 and 89. Our studies on the mechanism of action of IS-44 demonstrated that it prevents the thermal inactivation of HRV 2 infectivity, probably due to a conformational shift in the viral capsid and a decrease in affinity for the cellular receptor, resulting in an inhibition of attachment of the virions.

Antiviral Agents↗
PubMed2000

N-Benzylpiperidine derivatives of 1,2,4-thiadiazolidinone as new acetylcholinesterase inhibitors.

A new family of 1,2,4-thiadiazolidinone derivatives containing the N-benzylpiperidine fragment has been synthesised. The acetylcholinesterase (AChE) inhibitory activity of all compounds was measured using Ellman's method and some of them turned out to be as potent as tacrine. Furthermore, compound 13 was as active as tacrine in reversing the blockade induced by tubocurarine at rat neuromuscular junction. Additionally, receptor binding studies provided new lead compounds for further development of alpha2-adrenergic and sigma-receptor antagonists. Molecular dynamic simulation using X-ray crystal structure of AChE from Torpedo californica was used to explain the possible binding mode of these new compounds.

Acetylcholinesterase↗
PubMed2000

Postcardioversion atrial electrophysiologic changes induced by oral verapamil in patients with persistent atrial fibrillation.

OBJECTIVES: The aim of our study was to verify the effect of oral administration of verapamil on atrial electrophysiologic characteristics after cardioversion of persistent atrial fibrillation (AF) in humans. BACKGROUND: Discordant findings have been reported regarding the efficacy of verapamil in preventing the electrical remodeling induced by AF. METHODS: We determined the effective refractory periods (ERPs) at five pacing cycle lengths (300 to 700 ms) and in five right atrial sites after internal cardioversion of persistent AF (mean duration 238.1+/-305.9 days) in 19 patients. Nine patients received oral verapamil (240 mg/day) starting four weeks before the electrophysiologic study, whereas the other 10 patients were in pharmacologic washout. RESULTS: The mean ERPs were 202.0+/-22.7 ms in the washout group and 189.3+/-18.5 ms in the verapamil group (p < 0.0001). The degree of adaptation of refractoriness to rate was similar in the two groups (mean slope value in the washout group and verapamil group: 0.07+/-0.03 and 0.08+/-0.05, respectively), showing a normal or nearly normal adaptation to rate in the majority of the paced sites in both groups. The mean ERP was slightly longer in the septum than in the lateral wall and in the roof, both in the washout and verapamil groups. CONCLUSIONS: In patients with persistent AF, long-term administration of verapamil before internal cardioversion resulted in 1) shortening of atrial ERPs; 2) no change in refractoriness dispersion within the right atrium; and 3) no change in atrial ERP adaptation to rate.

Administration, Oral↗
PubMed2000

Lipase-catalysed synthesis of new acetylcholinesterase inhibitors: N-benzylpiperidine aminoacid derivatives.

New acetylcholinesterase inhibitors were synthetized via a lipase-mediated regioselective amidation using Candida antarctica lipase B as a biocatalyst in the key step. The new compounds have two different structural fragments: a N-benzylpiperidine moiety to anchor the enzyme active site and a dicarboxylic aminoacid to act as a biological carrier. Some analogues of N-benzylpiperazine were also synthesised and studied but they did not display AChE inhibitor activity. A preliminary structure activity relationship study was performed employing some computational techniques as similarity indices and electrostatic potential maps.

Acetylcholinesterase↗
PubMed2000

Collection, processing and cryopreservation of umbilical cord blood for unrelated transplantation.

Umbilical cord blood (UCB) transplantation is being used as an alternative source of hematopoietic stem cells for bone marrow reconstitution. Separation and processing of UCB samples in large numbers for storage in cord blood banks ideally needs to be partially automated. The aim of this study was to establish and standardize a method for unrelated cord blood banking as well as the biological characterization of the samples. Up to October 1999, a total of 938 UCB units (mean volume 84.6 +/- 23.6 ml, nucleated cell (NC) count 0.90 +/- 0.37 x 109, total CFU-GM 79 +/- 72 x 104, CD34+ cell count 2.46 +/- 2.72 x 106) had been collected. Twenty-three per cent of all UCB samples had a NC count below 0.4 x 109 and were discarded. The initial bacterial contamination rate was reduced to less than 5% as a result of extensive training in collection procedures. Using a modification of a triple bag system and adding a solution of 6% hydroxyethyl starch, the UCB was separated by two centrifugation steps into three components: buffy coat, red cell and plasma fractions. The overall recoveries for NC, CFU-GM and CD34+ cells were 87.4 +/- 8.5%, 88.8 +/- 6.6% and 90.3 +/- 12.4%, respectively, in a mean final volume of 27 +/- 4.2 ml.

Blood Banks↗
PubMed2000

Interferon alfa-2b plus ribavirin for chronic hepatitis C patients who have not responded to interferon monotherapy.

BACKGROUND: The role of combination therapy is poorly defined in chronic hepatitis C patients who are non-responders to interferon. AIM: To assess the efficacy, safety and tolerance of interferon alfa-2b plus ribavirin in chronic hepatitis C patients who do not respond to interferon monotherapy. METHODS: A total of 127 non-responder patients with chronic hepatitis C received 3 mU t.i.w. of interferon alfa-2b plus 1000-1200 mg ribavirin daily for 48 weeks. Effects of therapy were evaluated by serum aminotransferases and hepatitis C virus (HCV) RNA levels. RESULTS: Twenty-nine (23%) patients had an end-of-treatment response. Six months after treatment, 20 (16%) patients were sustained responders. Early loss of HCV RNA was the strongest predictor of a sustained response (P < 0.0001). Remission was also more frequent in patients with genotype 1b (P < 0.02), elevated alanine aminotransferase (P < 0.03) and low gamma glutamiltranspeptidase (P < 0.002). Treatment was discontinued in 21 (17%) patients: in 14 for intolerance and in seven due to side-effects. CONCLUSIONS: Combination therapy with interferon plus ribavirin produced a sustained response in 16% of chronic hepatitis C patients who were non-responders to interferon. This combination was safe and well tolerated.

Adult↗
PubMed2000

Transoesophageal low-energy cardioversion of atrial fibrillation. Results with the oesophageal-right atrial lead configuration.

BACKGROUND: Low energy internal cardioversion is a safe and effective procedure to restore sinus rhythm in patients with atrial fibrillation refractory to external cardioversion. However the procedure is invasive and fluoroscopy is mandatory. Aim of the study To assess the efficacy, safety and tolerability of a new simplified procedure of low energy internal cardioversion. METHODS: Twenty-five consecutive patients (19 males and 6 females) with persistent atrial fibrillation were submitted to low energy internal cardioversion using a step-up protocol (in steps of 50 V, starting from 300 V). A large surface area lead (cathode) was positioned in the oesophagus, 45 cm from the nasal orifice. A second large surface area lead (anode) was positioned in the right atrium. A quadripolar lead was positioned at the right ventricular apex to achieve ventricular synchronization and back-up pacing. Oesophageal endoscopy was performed within 24 h of the end of the procedure and repeated after 48 h, if injury to the oesophageal mucosa had occurred. RESULTS: Sinus rhythm was restored in 23 patients (92%) with a mean delivered energy of 15.74 J (range 5-27) and a mean impedance of 48 Omega. In two patients, endoscopy revealed that small burns had occurred in the oesophageal mucosa. Such lesions spontaneously healed after 48 h. CONCLUSIONS: This new technique of performing low energy internal cardioversion is effective and safe and avoids the positioning of a lead in the coronary sinus or in the left pulmonary artery, thereby simplifying the procedure.

Aged↗