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R Otero

Publications and source records attributed to R Otero.

At least 19 recordsLinked to original sources
PubMed2006

Clustering of chemisorbed H(D) atoms on the graphite (0001) surface due to preferential sticking.

We present scanning tunneling microscopy experiments and density functional theory calculations which reveal a unique mechanism for the formation of hydrogen adsorbate clusters on graphite surfaces. Our results show that diffusion of hydrogen atoms is largely inactive and that clustering is a consequence of preferential sticking into specific adsorbate structures. These surprising findings are caused by reduced or even vanishing adsorption barriers for hydrogen in the vicinity of already adsorbed H atoms on the surface and point to a possible novel route to interstellar H2 formation.

Journal Article↗
PubMed2006

Metastable structures and recombination pathways for atomic hydrogen on the graphite (0001) surface.

We present scanning tunneling microscopy results which reveal the existence of two distinct hydrogen dimer states on graphite basal planes. Density functional theory calculations allow us to identify the atomic structure of these states and to determine their recombination and desorption pathways. Direct recombination is only possible from one of the two dimer states. This results in increased stability of one dimer species and explains the puzzling double peak structure observed in temperature programmed desorption spectra for hydrogen on graphite.

Journal Article↗
PubMed2004

Neutralization of the edema-forming, defibrinating and coagulant effects of Bothrops asper venom by extracts of plants used by healers in Colombia.

We determined the neutralizing activity of 12 ethanolic extracts of plants against the edema-forming, defibrinating and coagulant effects of Bothrops asper venom in Swiss Webster mice. The material used consisted of the leaves and branches of Bixa orellana (Bixaceae), Ficus nymphaeifolia (Moraceae), Struthanthus orbicularis (Loranthaceae) and Gonzalagunia panamensis (Rubiaceae); the stem barks of Brownea rosademonte (Caesalpiniaceae) and Tabebuia rosea (Bignoniaceae); the whole plant of Pleopeltis percussa (Polypodiaceae) and Trichomanes elegans (Hymenophyllaceae); rhizomes of Renealmia alpinia (Zingiberaceae), Heliconia curtispatha (Heliconiaceae) and Dracontium croatii (Araceae), and the ripe fruit of Citrus limon (Rutaceae). After preincubation of varying amounts of each extract with either 1.0 microg venom for the edema-forming effect or 2.0 microg venom for the defibrinating effect, the mixture was injected subcutaneously (sc) into the right foot pad or intravenously into the tail, respectively, to groups of four mice (18-20 g). All extracts (6.2-200 microg/mouse) partially neutralized the edema-forming activity of venom in a dose-dependent manner (58-76% inhibition), with B. orellana, S. orbicularis, G. panamensis, B. rosademonte, and D. croatii showing the highest effect. Ten extracts (3.9-2000 microg/mouse) also showed 100% neutralizing ability against the defibrinating effect of venom, and nine prolonged the coagulation time induced by the venom. When the extracts were administered either before or after venom injection, the neutralization of the edema-forming effect was lower than 40% for all extracts, and none of them neutralized the defibrinating effect of venom. When they were administered in situ (sc at the same site 5 min after venom injection), the neutralization of edema increased for six extracts, reaching levels up to 64% for C. limon.

Animals↗
PubMed2004

Scorpion envenoming in two regions of Colombia: clinical, epidemiological and therapeutic aspects.

To determine clinical and epidemiological features of scorpion stings in two departments of Colombia, a descriptive study was performed in the hospitals of 10 towns from Antioquia (2 256 071 inhabitants) and five from Tolima (630 424 inhabitants). One hundred and twenty-nine cases were admitted during one year, 51 in Antioquia, 78 in Tolima and 41 were children less than 15 years old. Most stings (70.5%) occurred inside the house; 27.9% were on the hands and 26.4% on the feet. The scorpion species involved were Tityus pachyurus (51), Centruroides gracilis (31), T. fuehrmanni (29), T. asthenes (7) and Chactas spp. (1). In 10 cases the scorpion involved was not identified. Systemic envenoming signs (e.g. vomiting, tachypnea) were significantly more frequent in children than in adults (P < 0.05). Four children had hypertension, but none developed pulmonary oedema. One 3-year-old girl, stung by T. asthenes, had acute oedematous pancreatitis. Ninety-eight patients had mild envenoming. Moderate (27 patients) and severe (four patients) envenoming was significantly more frequent in children than in adults (P = 0.003; relative risk = 2.97). A pepsin-digested anti-Centruroides spp. antivenom was administered to 19 of 31 patients presenting systemic envenoming signs. No adverse reactions to antivenom were observed.

Adolescent↗
PubMed2004

The outcome after treatment of venous thromboembolism is different in surgical and acutely ill medical patients. Findings from the RIETE registry.

BACKGROUND: The history of venous thromboembolism (VTE), and the rationale for thromboprophylaxis in surgical patients are well understood. The situation is less clear for acutely ill medical patients. OBJECTIVES: To compare the clinical presentation of VTE and clinical outcomes of immobile acutely ill medical patients with surgical patients. PATIENTS: RIETE (Registro Informatizado de la Enfermedad TromboEmbolica) is a Spanish registry of consecutively enrolled patients with objectively confirmed, symptomatic acute VTE. In this analysis, clinical characteristics of patients, details of anticoagulant therapy, and outcomes of all enrolled acutely ill medical patients with immobility >/= 4 days, and surgical patients are included. RESULTS: Of 6160 patients enrolled up to December 2003, 756 (12%) were acutely ill medical patients with immobility >/= 4 days, and 884 (14%) were surgical patients who developed VTE within 2 months of surgical intervention. Only 28% of acutely ill medical patients had received thromboprophylaxis, compared with 67% of surgical patients. During the 3-month follow-up period, both fatal pulmonary embolism (PE) and fatal bleeding occurred more frequently in acutely ill medical patients. Immobility in acutely ill medical patients, cancer, and PE were associated with a significantly higher risk of fatal PE or bleeding. CONCLUSIONS: In patients treated for VTE, the incidences of fatal PE, fatal bleeding, and major bleeding were significantly higher in acutely ill medical patients compared with surgical patients. Given the low percentage of acutely ill medical patients who had received thromboprophylaxis, increasing its use appropriately may reduce the incidence of VTE and associated complications.

Acute Disease↗
PubMed2001

Use of venous thromboembolism prophylaxis for surgical patients: a multicentre analysis of practice in Spain.

OBJECTIVE: To assess the use of venous thromboembolism prophylaxis in surgical patients. DESIGN: Retrospective multicentre study. SETTING: Eight acute-care teaching hospitals with more than 400 beds, Spain. PATIENTS: Medical records of all consecutive patients undergoing operations in the general surgical and trauma and orthopaedic services during the month of April, 1997, were randomly selected. INTERVENTION: The sample size for each type of operation (general, trauma-orthopaedic) was calculated from the number of operations done at each hospital (with an absolute precision of 5%, and an alpha error of 5%) and the prevalence of the use of venous thromboembolism prophylaxis obtained from a random sample of 50 records (25 from patients in general surgery and 25 from patients in orthopaedic surgery) from each centre. MAIN OUTCOME MEASURES: Appropriate and inappropriate pharmacological prophylaxis defined according to a combination of risk categories for venous thromboembolism, doses of antithrombotic agents given, time of starting prophylaxis, and its duration. RESULTS: A total of 1848 medical records (general surgery, n = 1025; trauma-orthopaedic surgery, n = 823) were included. Physical methods (elastic stockings, intermittent pneumatic compression) were used in only 0.3% of patients. Pharmacological prophylaxis consisted of low molecular weight heparin in 99% of cases. The percentage given heparin-based prophylaxis was 54%. Overall, appropriate prophylaxis was given in 1175 patients (64%). Use of thromboprophylaxis ranged from 27% to 70% among the participating hospitals. Prophylaxis was more likely to be appropriate in orthopaedic patients (577, 70%) than in general surgical patients (598, 58%) in both the high and moderate risk categories. CONCLUSIONS: Given the large variability between the participating hospitals, more specific protocols and recommendations about prophylaxis of thromboembolism in surgical patients are needed.

Adolescent↗
PubMed2000

Snakebites and ethnobotany in the northwest region of Colombia: Part I: traditional use of plants.

In Antioquia and Chocó, traditional healers attend 60% of snakebites. With the aim to produce an inventory of the plants used by the healers to treat snakebites and to document the methods of preparation, administration, the dosage, number of patients treated throughout their years of practice with treatment results, 20 healers with experience in Bothrops, Porthidium and Bothriechis envenomations were interviewed between August, 1996 and November, 1998. They belong to nine black and three indigenous rural communities located near the towns of Bojayá, Vigía del Fuerte, Unguía (Atrato river valley), Nuquí and Bahía Solano (Pacific coast). Based on field interviews, 101 species of plants were identified as used to treat snakebites. The part used of each plant varies according to the species. Sixty plants are used in the form of drinks prepared by infusion, decoction or maceration; 78 as external baths on the affected extremity; 11 for steam application and 39 for poultices; the latter is used mainly when the bite is complicated by local necrosis. In mild and moderate envenomations, they generally use a mixture of three plants, while in severe cases they mix from five to 12, a handful of each one. Treatment is generally performed for 1-3 days, when the patient reacts positively. They reported to have treated 454 patients during their years of experience, 20 of them (4.4%) died. With the guidance of the healers, 77 species of plants were collected and photographed. These plants belong to 41 families, of which Piperaceae (13 species), Araceae (six species), Asteraceae (five species) and Gesneriaceae (three species) have the highest number of species.

Animals↗
PubMed2000

Snakebites and ethnobotany in the northwest region of Colombia. Part III: neutralization of the haemorrhagic effect of Bothrops atrox venom.

Thirty-one of 75 extracts of plants used by traditional healers for snakebites, had moderate or high neutralizing ability against the haemorrhagic effect of Bothrops atrox venom from Antioquia and Chocó, north-western Colombia. After preincubation of several doses of every extract (7.8-4000 microg/mouse) with six minimum haemorrhagic doses (10 microg) of venom, 12 of them demonstrated 100% neutralizing capacity when the mixture was i.d. injected into mice (18-20 g). These were the stem barks of Brownea rosademonte (Caesalpiniaceae) and Tabebuia rosea (Bignoniaceae); the whole plants of Pleopeltis percussa (Polypodiaceae), Trichomanes elegans (Hymenophyllaceae) and Senna dariensis (Caesalpiniaceae); rhizomes of Heliconia curtispatha (Heliconiaceae); leaves and branches of Bixa orellana (Bixaceae), Philodendron tripartitum (Araceae), Struthanthus orbicularis (Loranthaceae) and Gonzalagunia panamensis (Rubiaceae); the ripe fruits of Citrus limon (Rutaceae); leaves, branches and stem of Ficus nymphaeifolia (Moraceae). Extracts of another 19 species showed moderate neutralization (21-72%) at doses up to 4 mg/mouse, e.g. the whole plants of Aristolochia grandiflora (Aristolochiaceae), Columnea kalbreyeriana (Gesneriaceae), Sida acuta (Malvaceae), Selaginella articulata (Selaginellaceae) and Pseudoelephantopus spicatus (Asteraceae); rhizomes of Renealmia alpinia (Zingiberaceae); the stem of Strychnos xinguensis (Loganiaceae); leaves, branches and stems of Hyptis capitata (Lamiaceae), Ipomoea cairica (Convolvulaceae), Neurolaena lobata (Asteraceae), Ocimum micranthum (Lamiaceae), Piper pulchrum (Piperaceae), Siparuna thecaphora (Monimiaceae), Castilla elastica (Moraceae) and Allamanda cathartica (Apocynaceae); the macerated ripe fruits of Capsicum frutescens (Solanaceae); the unripe fruits of Crescentia cujete (Bignoniaceae); leaves and branches of Piper arboreum (Piperaceae) and Passiflora quadrangularis (Passifloraceae). When the extracts were independently administered by oral, i.p. or i.v. route either before or after an i.d. venom injection (10 microg), neutralization of haemorrhage dropped below 25% for all the extracts. Additionally, B. rosademonte and P. percussa extracts were able to inhibit the proteolytic activity of B. atrox venom on casein.

Analysis of Variance↗
PubMed2000

Snakebites and ethnobotany in the northwest region of Colombia: Part II: neutralization of lethal and enzymatic effects of Bothrops atrox venom.

Twelve of 74 ethanolic extracts of plants used by traditional healers for snakebites in the northwest region of Colombia, were active against lethal effect of Bothrops atrox venom when they were i.p. injected into mice (18-20 g). After preincubation of sublethal doses of every extract (0.5-4.0 mg/mouse) with 1.5 i.p. lethal dose 50% (LD50) (99.3 microg) of venom, seven of them demonstrated 100% neutralizing capacity within 48 h. These were the stem barks of Brownea rosademonte (Caesalpiniaceae) and Tabebuia rosea (Bignoniaceae); rhizomes of Renealmia alpinia (Zingiberaceae) and Heliconia curtispatha (Heliconiaceae); the whole plants of Pleopeltis percussa (Polypodiaceae) and Trichomanes elegans (Hymenophyllaceae); and the ripe fruits of Citrus limon (Rutaceae). The other five extracts showing partial neutralization (45-80%; 10-30% survival rate in the control group receiving the venom alone; P<0.05) were: leaves, branches and stem of Costus lasius (Costaceae); the whole plant of Sida acuta (Malvaceae); rhizomes of Dracontium croatii (Araceae); leaves and branches of Bixa orellana (Bixaceae) and Struthanthus orbicularis (Loranthaceae). When the extracts were independently administered per oral or i.p. route 60 min before an i.m. venom injection (204 microg=1.5 i.m. LD50), C. limon, T. elegans, B. orellana and T. rosea extracts had partial and significant neutralizing capacity against B. atrox venom lethal effect. C. limon extract was also partially effective when it was administered either i.v. 15 min before or i.p. 5 min after an i.m. venom injection. Three of the 12 extracts with anti-lethal effect (C. limon, D. croatii and S. acuta) were devoid of antiphospholipase A2 activity, when they were tested against one minimum indirect hemolytic dose of B. atrox venom (2 microg) in agarose-erythrocyte-egg yolk gels.

Animals↗
PubMed2000

Excretion of hexachlorobenzene and metabolites in feces in a highly exposed human population.

A set of 53 individuals from a population highly exposed to airborne hexachlorobenzene (HCB) were selected to study the elimination kinetics of this chemical in humans. The volunteers provided blood, 24-hr urine, and feces samples for analysis of HCB and metabolites. The serum HCB concentrations ranged from 2.4 to 1,485 ng/mL (mean +/- SD, 124 +/- 278), confirming that this human population has the highest HCB blood levels ever reported. All analyzed feces samples contained unchanged HCB (range, 11-3,025 ng/g dry weight; mean +/- SD, 395 +/- 629). The HCB concentration in feces strongly correlated with HCB in serum (r = 0.85; p < 0.001), suggesting an equilibrium in feces/serum that is compatible with a main pulmonary entrance of the chemical and low intestinal excretion of nonabsorbed foodborne HCB. The equilibrium is also compatible with a nonbiliary passive transfer of the chemical to the intestinal lumen. Two HCB main metabolites, pentachlorophenol (PCP) and pentachlorobenzenethiol (PCBT), were detected in 51% and 54% of feces samples, respectively. All urine samples contained PCP and PCBT, confirming the conclusions of a previous study [Environ Health Perspect 105:78-83 (1997)]. The comparison between feces and urine showed that whereas daily urinary elimination of metabolites may account for 3% of total HCB in blood, intestinal excretion of unchanged HCB may account for about 6%, thus showing the importance of metabolism in the overall elimination of HCB. The elimination of HCB and metabolites by both routes, however, appears to be very small (< 0.05%/day) as compared to the estimated HCB adipose depots. Features of HCB kinetics that we present in this study, i.e., nonsaturated intestinal elimination of HCB and excretion in feces and urine of inert glutathione derivatives, may explain, in part, the absence of porphyria cutanea in this human population heavily exposed to HCB.

Adolescent↗
PubMed1999

Urinary porphyrin excretion in a human population highly exposed to hexachlorobenzene.

BACKGROUND: Data from an epidemic reported in Turkey (1955-1959) is the only information about the relationship between hexachlorobenzene (HCB) intake and porphyria cutanea tarda in humans. No information is available on the HCB threshold exposure level to induce porphyria cutanea tarda. OBJECTIVES: To study HCB serum levels and urinary porphyrin excretion in the inhabitants of a village located near an organochlorine compound factory with high HCB concentrations in the air and to detect possible alterations in urinary porphyrin excretion and examine their relationship with HCB serum levels. DESIGN: Cross-sectional study. SETTING: Unit of Porphyrias of a tertiary care facility in Barcelona, Spain. PARTICIPANTS: Six hundred four inhabitants of the village who were older than 14 years provided serum and urine samples (185 participants were factory workers). MAIN OUTCOME MEASURES: Serum HCB was analyzed by gas chromatography coupled to electron capture detection. Quantification of urinary total porphyrins was performed by spectrofluorimetry. Porphyrin profile was determined by high-pressure liquid chromatography. RESULTS: Hexachlorobenzene was detected in all serum samples (mean, 39.8 ng/mL; range, 1.1-1616.0 ng/mL), and levels were higher in factory workers. Mean +/- SD level urinary total porphyrin average concentration was 98 +/- 69 nmol/L (range, 9-1009 nmol/L). Only the urine sample with the highest porphyrin concentration showed an increase of highly carboxylated porphyrins, with a typical profile of porphyria cutanea tarda. In the remaining 603 urine samples, coproporphyrin was the predominant fraction. CONCLUSION: The airborne exposure to and increased body burden of HCB in the Flix village population are not enough to trigger a significant alteration of the heme biosynthesis pathway.

Adolescent↗
PubMed1999

Neutralization, by a monospecific Bothrops lanceolatus antivenom, of toxic activities induced by homologous and heterologous Bothírops snake venoms.

A monospecific Bothrops lanceolatus antivenom, currently used in Martinique, was tested for its efficacy in the neutralization of several toxic and enzymatic activities of the venoms of B. lanceolatus, B. atrox and B. asper. When tested by the i.p. route in mice, B. lanceolatus venom had an LD50 of 12.8 microg/g. In addition, it induced local tissue damage (hemorrhage, edema and myotoxicity) and showed indirect hemolytic activity, but was devoid of coagulant effect on human plasma in vitro and of defibrinating activity in mice. Antivenom was fully effective in the neutralization of lethal, hemorrhagic, edema-forming, myotoxic and indirect hemolytic effects of B. lanceolatus venom in assays involving preincubation of venom and antivenom. When tested against the venoms of B. asper and B. atrox, the antivenom completely neutralized the lethal, hemorrhagic, myotoxic and indirect hemolytic effects, and was partially effective in neutralizing edema-forming activity. In contrast, the antivenom was ineffective in the neutralization of in vitro coagulant and in vivo defibrinating effects induced by these two venoms.

Animals↗
PubMed1999

A randomized blinded clinical trial of two antivenoms, prepared by caprylic acid or ammonium sulphate fractionation of IgG, in Bothrops and Porthidium snake bites in Colombia: correlation between safety and biochemical characteristics of antivenoms.

A randomized blinded clinical trial was performed in 53 patients bitten by Bothrops sp. and Porthidium sp. in Antioquia and Chocó, Colombia, in order to compare the efficacy and safety of two antivenoms made of whole IgG obtained by either ammonium sulphate (monovalent anti-B. atrox) or caprylic acid (polyvalent) fractionation. Additionally, antivenoms were compared by electrophoretic and chromatographic analyses and anticomplementary activity in vitro. With a protocol of 2, 4 and 6 antivenom vials for the treatment of mild, moderate and severe envenomings, respectively, both antivenoms were equally efficient to neutralize the most relevant signs of envenoming and to clear serum venom levels in patients from the first hour and later on. Three patients with severe envenoming and initially treated with less than six vials on admission had persistent or recurrent venom antigenemia within 12-48 h. Monovalent antivenom fractionated by ammonium sulphate precipitation had higher amounts of protein aggregates and nonimmunoglobulin proteins than polyvalent antivenom fractionated by caprylic acid precipitation. Both antivenoms presented anticomplementary activity in vitro, being higher in the monovalent product. In agreement, monovalent antivenom induced a significantly higher incidence of early antivenom reactions (52%) than polyvalent antivenom (25%).

Adolescent↗
PubMed1999

Organochlorine in the serum of inhabitants living near an electrochemical factory.

OBJECTIVES: To measure the impact of occupational and lifestyle factors on concentrations of organochlorine compounds in a general population sample living near an electrochemical factory with a high airborne concentration of hexachlorobenzene (HCB). METHODS: Serum samples from 608 people (328 selected from a random sample) were collected in 1994. Information on lifestyles, occupation, and medical condition was obtained by questionnaire. RESULTS: HCB and polychlorinated biphenyls (PCBs) were detected in all samples (means 36.7 ng/ml and 4.3 ng/ml respectively), followed by dichlorodiphenyl dichloroethane (DDE) and beta-hexachlorocyclohexane (beta-HCH), found in 98.7% and 87.3% of the samples respectively (means 4.6 ng/ml and 2.5 ng/ml, respectively). Concentrations of HCB were the highest ever reported. Occupation in the factory was the main determinant of the variation in concentrations of HCB (regression coefficients 1.52 (SEM 0.14) in 1n (HCB) for workers in the production department, and 2.13 (0.23) for workers in maintenance department) and explained the highest concentrations of HCB found in men of middle age. In retired workers, concentrations of HCB declined with time since retirement. The PCBs, dichlorodiphenyl trichloroethane (DDT), and beta-HCH were independent of the occupation and concentrations were similar to those found in other populations. Concentrations of beta-HCH and DDE in the whole population, and HCB among non-workers, were higher in women than in men. Concentrations of all measured organochlorine compounds increased with age and body mass index. Consumption of locally caught fish was an independent determinant of HCB and PCB concentrations. CONCLUSIONS: This population incorporated HCB directly through occupation in the electrochemical factory, by airborne pollution, and consumption of locally caught fish. Concentrations of other common organochlorine compounds were not higher than expected. Environmental exposures to these compounds deserve attention due to their persistence and potential health effects.

Adolescent↗
PubMed1998

Comparative study of the venoms of three subspecies of Lachesis muta (bushmaster) from Brazil, Colombia and Costa Rica.

A comparative study was performed on the pharmacology and biochemistry of venoms from three subspecies of Lachesis muta (L. m. stenophrys, L. m. muta and L. m. rhombeata) from Brazil, Colombia and Costa Rica. All venoms induced lethal, hemorrhagic, edema-forming, myotoxic, coagulant and defibrinating effects, showing also proteolytic and indirect hemolytic activities. The venoms of L. m. stenophrys from Costa Rica and L. m. muta from Cascalheira, Brazil, had the highest lethal and hemorrhagic activities and the venom of L. m. rhombeata showed the highest coagulant activity, whereas no significant differences were observed in myotoxic and edema-forming activities at most of the time intervals studied. In addition, venoms showed similar electrophoretic patterns on SDS-polyacrylamide gel electrophoresis. In conclusion, despite quantitative differences in toxic and enzymatic activities, together with subtle variations in electrophoretic patterns, our results indicate that experimental envenomation by these venoms induce a qualitatively similar pathophysiological profile.

Animals↗
PubMed1998

Budesonide affects allergic mucociliary dysfunction.

Airway inflammation characterized by neutrophils and free elastase contributes to allergic mucociliary dysfunction. Glucocorticosteroids are the most important anti-inflammatory agents used in the treatment of asthma, but their effect on allergic mucociliary dysfunction is not known. Therefore, we assessed both the prophylactic and therapeutic effects of the glucocorticosteroid budesonide on antigen-induced mucociliary dysfunction in sheep. Tracheal mucus velocity (TMV), a marker of mucociliary clearance, was measured by using a roentgenographic technique. When budesonide was administered either 30 min before or 1 h after airway challenge with Ascaris suum, the antigen-induced fall in TMV at 6 h was prevented. The effects on TMV at 8 and 24 h after challenge were also determined when budesonide and, for comparative purposes, alpha1-protease inhibitor were given 6 h after antigen challenge. Budesonide treatment improved TMV at 8 h, but TMV was not significantly different from antigen alone at 24 h. Treatment with alpha1-protease inhibitor, however, caused only a significant reversal of the antigen-induced fall in TMV at 24 h after challenge; this indicates a more prolonged effect than budesonide. Our results suggest that antiproteases may have a potential role as a therapeutic approach to mucociliary dysfunction in asthma and provide evidence for another means by which glucocorticosteroids contribute to the control of the disease.

Aerosols↗