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A Romero

Publications and source records attributed to A Romero.

At least 37 records · Page 2Linked to original sources
PubMed2003

A newly identified buccal interneuron initiates and modulates feeding motor programs in aplysia.

Despite considerable progress in characterizing the feeding central pattern generator (CPG) in Aplysia, the full complement of neurons that generate feeding motor programs has not yet been identified. The distribution of neuropeptide-containing neurons in the buccal and cerebral ganglia can be used as a tool to identify additional elements of the feeding circuitry by providing distinctions between otherwise morphologically indistinct neurons. For example, our recent study revealed a unique and potentially interesting unpaired PRQFVamide (PRQFVa)-containing neuron in the buccal ganglion. In this study, we describe the morphological and electrophysiological characterization of this novel neuron, which we designate as B50. We found that activation of B50 is capable of producing organized rhythmic output of the feeding CPG. The motor programs elicited by B50 exhibit some similarities as well as differences to motor programs elicited by the command-like cerebral-to-buccal interneuron CBI-2. In addition to activating the feeding CPG, B50 may act as a program modulator.

Action Potentials↗
PubMed2003

Effect of cadmium on 24-h variations in hypothalamic dopamine and serotonin metabolism in adult male rats.

This study was designed to analyze the possible cadmium effects on time-of-day variations of anterior, mediobasal, and posterior hypothalamic contents of dopamine (DA), serotonin (5-HT), and norepinephrine (NE) content in adult male rats. Also DA and 5-HT metabolism, as expressed by the ratio 3,4-dihydroxyphenyl acetic acid (DOPAC) to DA and 5-hydroxyindoleacetic acid (5-HIAA) to 5-HT, respectively, were studied. Adult male rats were given cadmium at a dose of 25 ppm of cadmium chloride in drinking water for 1 month. Age-matched rats having access to cadmium-free water were used as controls. Weight gain for the whole period was not changed by cadmium exposure. The metal accumulated in the hypothalamus of rats. In the three hypothalamic regions, significant 24-h variations of NE and 5-HT concentration were found in controls, while DA content changed rhythmically in mediobasal hypothalamus only. Mean content of NE, 5-HT, and DA of anterior, mediobasal, and posterior hypothalamus decreased after cadmium exposure. After cadmium the 24-h pattern of NE changed only in mediobasal hypothalamus, whereas the metal changed significantly the pattern of 5-HT in all regions. DOPAC to DA and 5-HIAA to 5-HT ratios decreased and were differentially changed in all hypothalamic regions analyzed in cadmium-treated rats. There was a statistically significant relationship between time of administration of metal and time that the change took place in biogenic amines in the hypothalamus. These results indicate that cadmium may depress hypothalamic biogenic amine release.

Aging↗
PubMed2003

Effect of cadmium on lymphocyte subsets distribution in thymus and spleen.

This work was designed to analyze the possible dose dependent effects of cadmium on the distribution of lymphocyte subsets within the thymus and spleen. Cadmium accumulation was also evaluated in these tissues. For this purpose, adult male rats were exposed for one month to 0, 5, 10, 25, 50 or 100 ppm of cadmium chloride (CdCl2) in the drinking water. In both spleen and thymus, the B lymphocytes increased with the doses of 5 and 10 ppm of CdCl2, and decreased with the doses of 25-100 ppm. In spleen, the doses of 25 and 50 ppm decreased CD4+ cells and the doses of 5 and 10 ppm increased CD8+ cells, while the percentage of thymus T, CD4+, CD8+ and CD4(+)-CD8+ cells was not modified by cadmium treatment at any dose used in this study. After cadmium exposure, the metal was accumulated in the spleen only from the dose of 50 ppm on, and in the thymus, from the dose of 10 ppm on. In conclusion, although the accumulation of the metal is higher in thymus than in spleen, the metal affected CD4+ and CD8+ lymphocytes at the spleen but not at the thymus.

Animals↗
PubMed2002

Aprotinin mediated antioxidant effect in Cardiosurgery with mechanical cardiorespiratory support (CMCS).

BACKGROUND: Aprotinin has been used in cardiosurgery as a hemostatic agent. Considering the implication of oxygen reactive species and proteases in the pathogenesis of Systemic Inflammatory Response Syndrome, we hypothesized that aprotinin may exert an antioxidant effect. This work was designed to evaluate the antioxidant capacity of aprotinin in vitro and in vivo in child patients undergoing cardiosurgery with mechanical cardiorespiratory support. METHODS: Colorimetric techniques and chemiluminiscent emission assays. A blind controlled clinical trial was performed with a control (G-1, n=14, without aprotinin) and treated with aprotinin (G-2, n=12) groups (both assessed by medical decision) of child patients undergoing cardiosurgery with mechanical cardiorespiratory support. Blood samples were taken at: T-0 (induction of anesthesia), T-1 (10 minutes after begining of perfusion), T-2 (5 minutes after anoxic heart arrest), T-3 (ending operation) and T-4 (24 hours after operation). RESULTS: We proved that aprotinin has no hydroxyl radical, superoxide anion nor H2O2 scavenger capacity as well as its capacity for inhibiting in vitro activated-leukocyte chemiluminiscence. Malonildialdehyde levels were higher in G-1 than G-2 with the greatest difference at T-2 (7.2+/-3.6 nmol/ml in G-1 vs 4+/-1.65 in G-2). Phospholipase A2 activity showed a tendency of higher values in G-1 than G-2 although there was no statistical significance. Uric acid concentration was greater in G-2 at T-1, T-2, T-3 and T-4 than G-1 and catalase activity was higher in G-2 at T-0, T-2 and T-3 than G-1 with noteworthy difference only at 5 minutes after anoxic heart arrest. Low cardiac output, arrhythmias and sudden death in the early postoperative phase were less frequent in the treated group. CONCLUSIONS: These results suggest that aprotinin exerts a primary antioxidant activity and its protective effects in cardiosurgery seem to be associated with reduction of systemic oxidative stress.

Antioxidants↗
PubMed2002

Comparison of the quantity and quality of the microbiological content of sludge in countries with low and high content of pathogens.

The parasites present in the residual sludge generate by the diverse treatment processes of residual water vary, depending on the socioeconomic and epidemiological conditions of different communities. And although data exist at the global level regarding the microbiological quality of sludge, these data are practically nonexistent in developing countries. Therefore, this project compares the content of the four principal groups of parasites in residual sludge from the United States and Mexico. The marked differences between the orders of magnitude found in the two countries (coliphages 10(3)-10(6) and 1.3 x 10(5) PFU/gTS, fecal coliforms 10(7)-10(10) and 10(7), Salmonella typhi 10(6)-10(8) and 10(3) MPN/gTS, Giardia lamblia 10(2)-10(4) and 10(2) cysts/gTS and helminth ova from 73-177 and <1 to 10 viable HO/gTS, respectively) will permit proposing real, effective and economical stabilization processes (undoubtedly different from those of industrialized countries), and will thus take advantage of the benefits represented by the reuse and disposal of sludge, in addition to developing regulations in agreement with the conditions of each region.

Animals↗
PubMed2001

NMR investigations of protein-carbohydrate interactions: insights into the topology of the bound conformation of a lactose isomer and beta-galactosyl xyloses to mistletoe lectin and galectin-1.

A hallmark of oligosaccharides is their often limited spatial flexibility, allowing them to access a distinct set of conformers in solution. Viewing each individual or even the complete ensemble of conformations as potential binding partner(s) for lectins in protein-carbohydrate interactions, it is pertinent to address the question on the characteristics of bound state conformation(s) in solution. Also, it is possible that entering the lectin's binding site distorts the low-energy topology of a glycosidic linkage. As a step to delineate the strategy of ligand selection for galactosides, a common physiological docking point, we have performed a NMR study on two non-homologous lectins showing identical monosaccharide specificity. Thus, the conformation of lactose analogues bound to bovine heart galectin-1 and to mistletoe lectin in solution has been determined by transferred nuclear Overhauser effect measurements. It is demonstrated that the lectins select the syn conformation of lactose and various structural analogues (Galbeta(1-->4)Xyl, Galbeta(1-->3)Xyl, Galbeta(1-->2)Xyl, and Galbeta(1-->3)Glc) from the ensemble of presented conformations. No evidence for conformational distortion was obtained. Docking of the analogues to the modeled binding sites furnishes explanations, in structural terms, for exclusive recognition of the syn conformer despite the non-homologous design of the binding sites.

Binding Sites↗
PubMed2001

Characterization of typical pepper-isolates of PVY reveals multiple pathotypes within a single genetic strain.

Potato virus Y (PVY) isolates originally coming from infected pepper plants, were biologically and genetically characterized, especially in comparison with PVY potato-isolates. Pepper PVY isolates could be differentiated from potato isolates in their host range, aphid transmission efficiencies, Mab serology, and genetic status. The genetic distances estimated for PVY pepper-isolates, based on their restrictotypes with five restriction enzymes and on their coat protein gene sequences, indicated that they form a single genetic strain with different pathotypic properties. This situation is essentially different to that of PVY potato-isolates.

Base Sequence↗
PubMed2001

The enterins: a novel family of neuropeptides isolated from the enteric nervous system and CNS of Aplysia.

To identify neuropeptides that have a broad spectrum of actions on the feeding system of Aplysia, we searched for bioactive peptides that are present in both the gut and the CNS. We identified a family of structurally related nonapeptides and decapeptides (enterins) that are present in the gut and CNS of Aplysia, and most of which share the HSFVamide sequence at the C terminus. The structure of the enterin precursor deduced from cDNA cloning predicts 35 copies of 20 different enterins. Northern analysis, in situ hybridization, and immunocytochemistry show that the enterins are abundantly present in the CNS and the gut of Aplysia. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry we characterized the enterin-precursor processing, demonstrated that all of the precursor-predicted enterins are present, and determined post-translational modifications of various enterins. Enterin-positive neuronal somata and processes were found in the gut, and enterins inhibited contractions of the gut. In the CNS, the cerebral and buccal ganglia, which control feeding, contained the enterins. Enterin was also present in the nerve that connects these two ganglia. Enterins reduced the firing of interneurons B4/5 during feeding motor programs. Such enterin-induced reduction of firing also occurred when excitability of B4/5 was tested directly. Because reduction of B4/5 activity corresponds to a switch from egestive to ingestive behaviors, enterin may contribute to such program switching. Furthermore, because enterins are present throughout the nervous system, they may also play a regulatory role in nonfeeding behaviors of Aplysia.

Amino Acid Sequence↗
PubMed2001

Purification, crystallization and identification by X-ray analysis of a prostate kallikrein from horse seminal plasma.

The purification, crystallization and identification by X-ray diffraction analysis of a horse kallikrein is reported. The protein was purified from horse seminal plasma. Crystals belong to space group C2 and the structure was solved by the MIRAS method, with two heavy-atom derivatives of mercury and platinum. X-ray diffraction data to 1.42 A resolution were collected at the ESRF synchrotron-radiation source.

Amino Acid Sequence↗
PubMed2001

Crystal structure of native and Cd/Cd-substituted Dioclea guianensis seed lectin. A novel manganese-binding site and structural basis of dimer-tetramer association.

Diocleinae legume lectins are a group of oligomeric proteins whose subunits display a high degree of primary structure and tertiary fold conservation but exhibit considerable diversity in their oligomerisation modes. To elucidate the structural determinants underlaying Diocleinae lectin oligomerisation, we have determined the crystal structures of native and cadmium-substituted Dioclea guianensis (Dguia) seed lectin. These structures have been solved by molecular replacement using concanavalin (ConA) coordinates as the starting model, and refined against data to 2.0 A resolution. In the native (Mn/Ca-Dguia) crystal form (P4(3)2(1)2), the asymmetric unit contains two monomers arranged into a canonical legume lectin dimer, and the tetramer is formed with a symmetry-related dimer. In the Cd/Cd-substituted form (I4(1)22), the asymmetric unit is occupied by a monomer. In both crystal forms, the tetrameric association is achieved by the corresponding symmetry operators. Like other legume lectins, native D. guianensis lectin contains manganese and calcium ions bound in the vicinity of the saccharide-combining site. The architecture of these metal-binding sites (S1 and S2) changed only slightly in the cadmium/cadmium-substituted form. A highly ordered calcium (native lectin) or cadmium (Cd/Cd-substituted lectin) ion is coordinated at the interface between dimers that are not tetrameric partners in a similar manner as the previously identified Cd(2+) in site S3 of a Cd/Ca-ConA. An additional Mn(2+) coordination site (called S5), whose presence has not been reported in crystal structures of any other homologous lectin, is present in both, the Mn/Ca and the Cd/Cd-substituted D. guianensis lectin forms. On the other hand, comparison of the primary and quaternary crystal structures of seed lectins from D. guianensis and Dioclea grandiflora (1DGL) indicates that the loop comprising residues 117-123 is ordered to make interdimer contacts in the D. grandiflora lectin structure, while this loop is disordered in the D. guianensis lectin structure. A single amino acid difference at position 131 (histidine in D. grandiflora and asparagine in D. guianensis) drastically reduces interdimer contacts, accounting for the disordered loop. Further, this amino acid change yields a conformation that may explain why a pH-dependent dimer-tetramer equilibrium exists for the D. guianensis lectin but not for the D. grandiflora lectin.

Binding Sites↗
PubMed2001

Stereoselection in the Prins-pinacol synthesis of acyltetrahydrofurans.

[reaction: see text]. Depending upon the nature of the alkene and allylic substituents, acid-promoted rearrangements of acetals derived from anti allylic diols give 12 or stereoisomeric acyltetrahydrofurans 13. Stereoelectronic effects of the allylic substituents and the extent of bonding in the Prins cyclization transition state are central features of a proposed new model for predicting stereoselection in the Prins-pinacol synthesis of acyltetrahydrofurans.

Chemistry, Organic↗
PubMed2001

A novel solenoid fold in the cell wall anchoring domain of the pneumococcal virulence factor LytA.

Choline binding proteins are virulence determinants present in several Gram-positive bacteria. Because anchorage of these proteins to the cell wall through their choline binding domain is essential for bacterial virulence, their release from the cell surface is considered a powerful target for a weapon against these pathogens. The first crystal structure of a choline binding domain, from the toxin-releasing enzyme pneumococcal major autolysin (LytA), reveals a novel solenoid fold consisting exclusively of beta-hairpins that stack to form a left-handed superhelix. This unique structure is maintained by choline molecules at the hydrophobic interface of consecutive hairpins and may be present in other choline binding proteins that share high homology to the repeated motif of the domain.

Amino Acid Motifs↗
PubMed2001

Estimates of illicit drug use during pregnancy by maternal interview, hair analysis, and meconium analysis.

OBJECTIVE: To compare the sensitivity and specificity of maternal interview, maternal hair analysis, and meconium analysis in detecting perinatal exposure to cocaine, opiate, and cannabinoid. DESIGN/METHODS: The use of cocaine, opiate, and cannabinoid during pregnancy was determined prospectively in 58 women by 3 methods: structured maternal interview, maternal hair analysis, and meconium analyses. The results of the 3 methods were compared with one another. RESULTS: The maternal interview showed the lowest sensitivity in detecting cocaine and opiate exposures (65% and 67%, respectively), but it had the highest sensitivity in detecting cannabinoid exposure (58%). Both hair and meconium analyses had high sensitivity for detecting cocaine or opiate exposures. Hair analysis had a sensitivity of 100% for cocaine and 80% for opiate detection. However, it had a false-positive rate of 13% for cocaine and 20% for opiate, probably as a result of passive exposure. Meconium analysis had a sensitivity of 87% for cocaine and 77% for opiate detection, but unlike hair analysis, it had no false-positive test results for cocaine. Both hair and meconium analyses had low sensitivity in detecting cannabinoid exposure (21%-22.7%), most probably because of the sporadic use of cannabinoid. CONCLUSION: Meconium and hair analyses had the highest sensitivities for detecting perinatal use of cocaine and opiate, but not for cannabinoid. The principal drawback of hair analysis is its potential for false-positive test results associated with passive exposure to drugs. Maternal interview is a time-consuming test of low sensitivity. The high sensitivity of meconium analysis and the ease of collection make this test ideal for perinatal drug screening.

Adult↗
PubMed2001

Low molecular weight heparin versus oral anticoagulants in the long-term treatment of deep venous thrombosis.

PURPOSE: The purpose of this study was to evaluate whether low molecular weight heparin (LMWH) could be equal or more effective than conventional oral anticoagulants (OAs) in the long-term treatment of deep venous thrombosis (DVT). METHODS: One hundred fifty-eight patients with symptomatic DVT of the lower limbs confirmed by means of duplex ultrasound scan were randomized to receive 3 to 6 months' treatment with nadroparine calcium or acenocoumarol. Quantitative and qualitative duplex scan scoring systems were used to study the evolution of thrombosis in both groups at 1, 3, 6, and 12 months. RESULTS: During the 12-month surveillance period, two (2.5%) of the 81 patients who received LMWH and seven (9%) of the 77 patients who received OAs had recurrence of venous thrombosis (not significant). In the LMWH group no cases of major bleeding were found, and four cases (5.2%) occurred in the OA group (not significant). The mortality rate was nine (11.1%) in the LMWH group and 7.8% in the OA group (not significant). The quantitative mean duplex scan score decreased in both groups during the follow-up and had statistical significance after long-term LMWH treatment on iliofemoral DVT (1, 3, 6, and 12 months), femoropopliteal DVT (1-3 months), and infrapopliteal DVT (first month). Duplex scan evaluation showed that the rate of venous recanalization significantly increased in the common femoral vein at 6 and at 12 months and during each point of follow-up in the superficial and popliteal veins in the LMWH group. Reflux was significantly less frequent in communicating veins after LMWH treatment (17.9% vs 32.2% in the OA group). The reflux rates in the superficial (22.4% in the LMWH group, 30.6% in OA group) and deep (13.4% vs 17.7%) venous system showed no significant differences between groups. CONCLUSIONS: The unmonitored subcutaneous administration of nadroparine in fixed daily doses was more effective than oral acenocoumarol with laboratory control adjustment in achieving recanalization of leg thrombi. With nadroparine, there was less late valvular communicating vein insufficiency, and it was at least as efficacious and safe as oral anticoagulants after long-term administration. These results suggest that LMWHs may therefore represent a real therapeutic advance in the long-term management of DVT.

Acenocoumarol↗
PubMed2001

Systematic study of occult pulmonary thromboembolism in patients with deep venous thrombosis.

PURPOSE: This study was carried out to evaluate the prevalence and extension of pulmonary thromboembolism (PTE) in symptom-free patients with symptomatic deep venous thrombosis (DVT) of lower limbs and to evaluate their possible implication in the adequate treatment of thromboembolic disease. MATERIALS AND METHODS: We prospectively studied, using noninvasive examination (pulmonary spiral computed tomography [CT] angiography), 159 consecutive patients with acute DVT confirmed by duplex scanning without symptoms of PTE. CT was repeated at 30 days to study evolution of these clinically occult PTE. RESULTS: We observed silent PTE in 65 patients (41%) in all levels of lower limb venous thrombosis. Prevalence of PTE showed significant association with male sex (P =.001) and previously diagnosed heart disease (P =.023). There was no significant association between the level of DVT and the presence of PTE nor the DVT side and thromboembolic pulmonary localization. Of the 65 patients with positive CT exploration results for PTE, 52 had characteristics of acute PTE, 10 had chronic PTE, and 3 patients had both. Chronic PTE was found more frequently in patients with previous episodes of DVT (P =.024). A total of 165 pulmonary artery-affected segments were found at several locations: 5 main, 35 lobar, 58 interlobar, and 67 segmental. Multiple segments were affected in 59% of patients. Repeat CT examinations were performed at 30 days in 53 of 65 patients with positive CT scanning results. In 48 cases (90.6%) PTE had completely disappeared. CONCLUSIONS: Silent PTE occurred frequently in association with clots of lower limbs. The CT scan had a good availability and cost-effectiveness to detect clinically underestimated PTE. The incorporation of this exploration in the systematic diagnostic strategy of most patients with DVT to establish the extension of thromboembolic disease at diagnosis may be useful in the evaluation of added pulmonary artery symptoms and treatment strategies.

Adolescent↗
PubMed2001

Towards defining the role of glycans as hardware in information storage and transfer: basic principles, experimental approaches and recent progress.

The term 'code' in biological information transfer appears to be tightly and hitherto exclusively connected with the genetic code based on nucleotides and translated into functional activities via proteins. However, the recent appreciation of the enormous coding capacity of oligosaccharide chains of natural glycoconjugates has spurred to give heed to a new concept: versatile glycan assembly by the genetically encoded glycosyltransferases endows cells with a probably not yet fully catalogued array of meaningful messages. Enciphered by sugar receptors such as endogenous lectins the information of code words established by a series of covalently linked monosaccharides as letters for example guides correct intra- and intercellular routing of glycoproteins, modulates cell proliferation or migration and mediates cell adhesion. Evidently, the elucidation of the structural frameworks and the recognition strategies within the operation of the sugar code poses a fascinating conundrum. The far-reaching impact of this recognition mode on the level of cells, tissues and organs has fueled vigorous investigations to probe the subtleties of protein-carbohydrate interactions. This review presents information on the necessarily concerted approach using X-ray crystallography, molecular modeling, nuclear magnetic resonance spectroscopy, thermodynamic analysis and engineered ligands and receptors. This part of the treatise is flanked by exemplarily chosen insights made possible by these techniques.

Cell Communication↗