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Biomedical subjects

R M Castillo

Publications and source records attributed to R M Castillo.

6 recordsLinked to original sources

Abiotic transformation of perchloroethylene in homogeneous dithionite solution and in suspensions of dithionite-treated clay minerals.

The reductive dechlorination of perchloroethylene (PCE) in homogeneous solutions of dithionite and at the surfaces of dithionite-citrate-bicarbonate (DCB) treated ferruginous smectite and Na-montmorillonite was studied. Transformation products of PCE identified in dosed dithionite-treated samples included TCE, DCE, 1,1,2-trichloroethane (TCA), 1,1-dichloroethane (DCA), chloroacetylene, acetylene, ethene, and ethane. The decomposition of dithionite to sulfate yielded both protons and electrons necessary for hydrodechlorination (hydrogenolysis) of PCE. Dithionite treatment of the Fe-poor Na-montmorillonite enhanced reductive dechlorination of PCE relative to dithionite-treated Fe-rich ferruginous smectite, within the range of 11.5-137.8 mM dithionite. For the same dithionite concentration, the kinetics of the heterogeneous reactions of PCE was generally faster than that of the homogeneous reaction, and higher concentrations of TCE were measured in the heterogeneous reactions. Interestingly, increases in the mass of the clay minerals used, the Fe2+ content in the clay mineral structure, or the dithionite concentration used did not necessarily enhance the abiotic transformation of PCE, as would otherwise be predicted. The most efficient reductive dechlorination of PCE was observed with 0.5% clay (m/v) treated with 34.5 mM dithionite buffered at pH 8.5. The solid-state transfer of electrons to surfaces and edges, rather than the redox capacity, limited the dechlorination of PCE by reduced ferruginous smectite and/or suspensions containing a higher clay mass. The greater reactivity of dithionite-reduced montmorillonite than similarly treated ferruginous smectite is attributed to (i) the well-documented layer collapse and aggregation of chemically reduced clays that increases with the clay's iron content, (ii) the location of solid-phase Fe2+ in the reduced clay mineral and whether it is accessible or inaccessible for reaction with PCE at the mineral edges and surfaces where the reactions are thought to occur, and (iii) the greater swellability of montmorillonite versus ferruginous smectite. The faster dechlorination rate of PCE observed with dithionite-reduced Fe-poor montmorillonite than similarly reduced iron-rich ferruginous smectite suggests that the use of dithionite barriers for in-situ treatment of chlorinated solvent plumes should not be limited to aquifers with Fe-rich sediments.

Aluminum Silicates↗

A six-stranded double-psi beta barrel is shared by several protein superfamilies.

BACKGROUND: Six-stranded beta barrels with a pseudo-twofold axis are found in several proteins. One group comprises a Greek-key structure with all strands antiparallel; an example is the N-terminal domain of ferredoxin reductase. Others involve parallel strands forming two psi structures (the double-psi beta barrel). A recently discovered example of the latter class is aspartate-alpha-decarboxylase (ADC) from Escherichia coli, a pyruvoyl-dependent tetrameric enzyme involved in the synthesis of pantothenate. RESULTS: Visual inspection and automated database searches identified the six-stranded double-psi beta barrel in ADC, Rhodobacter sphaeroides dimethylsulfoxide (DMSO) reductase, E. coli formate dehydrogenase H (FDHH), the plant defense protein barwin, Humicola insolens endoglucanase V (EGV) and, with a circular permutation, in the aspartic proteinases. Structure-based sequence alignments revealed several interactions including hydrophobic contacts or sidechain-mainchain hydrogen bonds that position the middle beta strand under a psi loop, which may significantly contribute to stabilizing the fold. The identification of key interactions allowed the filtering of weak sequence similarities to some of these proteins, which had been detected by sequence database searches. This led to the prediction of the double-psi beta-barrel domain in several families of proteins in eukaryotes and archaea. CONCLUSIONS: The structure comparison and clustering study of double-psi beta barrels suggests that there could be a common homodimeric ancestor to ADC, FDHH and DMSO reductase, and also to barwin and EGV. There are other protein families with unknown structure that are likely to adopt the same fold. In the known structures, the protein active sites cluster around the psi loop, indicating that its rigidity, protrusion and free mainchain functional groups may be well suited to providing a framework for catalysis.

Amino Acid Sequence↗

Subacute methylphenidate treatment for moderate to moderately severe traumatic brain injury: a preliminary double-blind placebo-controlled study.

OBJECTIVE: To determine the effect of subacute administration of methylphenidate on recovery from moderate to moderately severe closed head injury. DESIGN: Double-blind placebo-controlled with random assignment. Patients were enrolled when their Galveston Orientation and Amnesia Test score was at least 65. Drug/placebo treatment began the day following baseline cognitive assessment and continued for 30 consecutive days. Follow-up evaluations were conducted at 30 and 90 days after baseline, after discontinuation of drug/placebo. SETTING: A level I trauma center. PATIENTS: Twenty-three patients ranging in age from 16 to 64 years. Head injury severity ranged from moderately severe (Glasgow Coma Score [GCS] < or = 8, no intracranial pressure monitor) to "complicated mild" (GCS from 13 to 15 with positive computed tomography brain scan). Thirty-day follow-up was based on 12 patients, whereas 90-day evaluation was based on 9 patients, with complicated mild head injuries excluded from the analyses. INTERVENTIONS: Methylphenidate administered twice daily at a dose of .30 mg/kg; placebo administered according to the same schedule in identical pill form. MAIN OUTCOME MEASURES: The Disability Rating Scale (DRS) and tests of attention, memory, and vigilance. RESULTS: The methylphenidate group was significantly better at 30 days on the DRS (p < .02), and on tests of attention (p < .03) and motor performance (p, .05). No significant differences were noted between groups at 90 days. CONCLUSIONS: Subacute administration of methylphenidate after moderately severe head injury appeared to enhance the rate but not the ultimate level of recovery as measured by the DRS and tests of vigilance. Problems with possible selection bias and small sample size limit generalization of results.

Adolescent↗

Effect of treatment on serum antibody to Hymenolepis nana detected by enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) was developed to measure serum immunoglobulin G antibodies in 65 patients infected with Hymenolepis nana and 30 noninfected patients. Antibody was detected in 51 of 65 (sensitivity, 79%) and 5 of 30 H. nana-negative patients (specificity, 83%). Nine patients infected with H. nana were treated with praziquantel (20 to 25 mg/kg of body weight). Antibody disappeared from the sera at 90 days in six patients, five of whom had eliminated H. nana. Antibody persisted in three patients in whom H. nana infection did not clear after treatment. The H. nana ELISA had a high rate of cross-reactions with sera from patients with cysticercosis (8 of 29 [28%]) and hydatidosis (8 of 23 [35%]). The ELISA for H. nana may be useful for defining the epidemiology of H. nana infections, especially in areas free from cysticercosis and hydatidosis.

Adolescent↗

Risk factors for protein-energy malnutrition in pre-school shantytown children in São Paulo, Brazil.

OBJECTIVES: To investigate the health and nutritional conditions of people living in a shantytown in the city of São Paulo in order to identify risk factors for infant malnutrition. DESIGN: A retrospective cohort study. PARTICIPANTS: Children living in a shantytown was conducted among children less than 72 months of age. METHODS: Home visits were made and information was collected regarding the risk factors for malnutrition. RESULTS: The prevalence of chronic malnutrition was 41.6% according to Gomez, 36.6% according to Waterlow, and 17.6% according to WHO. Risk factors for malnutrition, according to the weight-for-age index, included birthweight, presence of upper respiratory tract infections, number of pregnancies, number of births, maternal body mass index, birthplace of father, and home building material; according to the weight-for-height index, they included birthweight and maternal age at the time of birth; and according to the height-for-age index, they included the number of prenatal medical visits, birthweight, maternal height, maternal body mass index, father's employment being unregistered, and maternal birthplace. An instrument for identifying children at risk of malnutrition was devised from these major risk factors for future malnutrition, which may then be applied to newly-born children.

Brazil↗