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Biomedical subjects

J Rocha

Publications and source records attributed to J Rocha.

At least 19 recordsLinked to original sources
PubMed2005

The epidemiology of moderate and severe injuries in a Nicaraguan community: a household-based survey.

Although injuries constitute a major public health problem worldwide, the magnitude and nature of this problem is difficult to establish in low-income settings due to the lack of valid and representative data. In Nicaragua, several parallel studies have been carried out attempting to assess levels and patterns of injury using various sources of information. The objective of this study was to describe the magnitude and profile of moderate and severe injuries in a well-defined community in Nicaragua. The study was conducted using a household-based survey design. Randomized cluster sampling provided information from 10,797 households (63,886 inhabitants). The outcomes included fatal and non-fatal injuries registered during a recall period of 6 weeks. Seven percent of all injuries were classified as moderate or severe. The estimated annual incidence rate of moderate/severe injuries was 27.6 per 1000 [95% confidence intervals (CI): 26.4-29.2], while the mortality and impairment rates were 108.9 (95% CI: 83.5-134.4) and 95.3 (95% CI: 71.4-119.2) per 100,000 inhabitants, respectively. Home and traffic areas were the main environments associated with injury occurrence. The most affected groups were the elderly, children and males. No differences were found between urban and rural areas. Only 9% of all cases, including minor injuries, sought hospital treatment. The main causes of non-fatal injuries were falls, traffic and cuts, whereas fatalities were largely associated with intentional injuries. For every death due to injury, there was one permanent disability, 25 moderate/severe injuries and 354 minor injuries. This study provides a broad description of injury magnitudes and patterns in a defined Nicaraguan community, and demonstrates the aggregate injury pyramid of the same community. It also identifies the issue of severity and concludes with a recommendation to apply different criteria of severity. Our results support the call for a careful evaluation of injury data sources and severity scores when planning injury prevention programmes.

Adolescent↗
PubMed2005

A family of metrics for biopolymers based on counting independent sets.

We introduce a new family of metrics for graphs of fixed size, based on counting-independent sets. Our definition is simpler and easier to calculate than the edge ideal metric family defined by Llabrés and Rosselló without loosing any of its abstract properties. We contrast them on some examples with graphs that represent protein secondary and three-dimensional (3D) structures. We conclude that although the edge ideal metrics are faster to calculate on some sparse graphs, in general, the independent set metrics are more tractable.

Algorithms↗
PubMed2005

Transitory gliosis in the CA3 hippocampal region in rats fed on a ketogenic diet.

The ketogenic diet (KD) is a high-fat, low-protein and low-carbohydrate diet included as medical practice against seizure disorders, particularly in children refractory to conventional anti-epileptic drug treatment. However, the molecular basis of its therapeutic effect remains unclear. Considering the growing evidence for the importance of glial cells for neuronal development, survival and plasticity, we investigated astrocyte protein markers from KD fed rats, in different regions of hippocampus, a brain structure commonly involved in seizure disorders. We found a transitory increment in GFAP in the CA3 hippocampal region, but not in the CA1 or dentate gyrus (DG). This change was not accompanied by changes in S100B content or glutamine synthetase activity. In order to evaluate possible hippocampal involvement we investigated spatial-cognitive behavior using the water-maze task. No changes were observed. This transitory gliosis in CA3 could be related to, or precede, other associated changes proposed to be involved in the attenuation of seizure disorders. These data reinforce the importance of hippocampal astrocytes as cell targets during KD feeding.

Animals↗
PubMed2004

Mg,Al layered double hydroxides with intercalated indomethacin: synthesis, characterization, and pharmacological study.

Magnesium aluminium layered double hydroxides (LDH) with a molar Mg/Al ratio of 2.0 have been prepared with intercalated indomethacin following two routes: reconstruction from a previously calcined Mg(2)Al-CO(3) LDH, and coprecipitation from the corresponding chlorides. The solids have been characterized by powder X-ray diffraction, FTIR, and (13)C CP/MAS NMR spectroscopies and thermal stability (differential thermal analysis and thermogravimetric analysis). Intercalation of the drug is attained by both routes; however, while coprecipitation leads to a single layered structure, contamination with another layered MgAl-CO(3) phase occurs by the reconstruction method. The amount of drug intercalated, as well as the height of the gallery, are larger by the coprecipitation than by the reconstruction one. The data obtained support a somewhat tilted, upwards orientation of the drug molecules forming an interdigited bilayer, in the case of the sample prepared by coprecipitation, with the carboxylate groups pointing towards the hydroxyl layers. However, in the case of the sample prepared by reconstruction, the molecules are forming a tilted, upwards monolayer. The solids prepared are stable up to 250 degrees C. Pharmacological studies in vivo show that intercalation of the drug in the LDH reduces the ulcerating damage of the drug.

Aluminum Hydroxide↗
PubMed2004

Tracing the origin of the most common thiopurine methyltransferase (TPMT) variants: preliminary data from the patterns of haplotypic association with two CA repeats.

Thiopurine methyltransferase (TPMT) is an essential enzyme for normal metabolism of thiopurine drugs. In humans TPMT activity is largely dependent upon genetic variation at the TPMT locus, with TPMT*3A and TPMT*3C being the most frequent mutant alleles associated with reduced activity. TPMT*3C is a widespread allele reaching the highest frequencies in Africans, whereas TPMT*3A is virtually restricted to Caucasian descendent populations. To estimate the time of origin of these two alleles, we analyzed the levels of diversity at two CA repeats flanking the TPMT gene. In accordance to its pattern of geographical distribution, the study of the decay in linkage disequilibrium over time indicated that TPMT*3A was the younger allele. The estimated age was 5700 years, which coincides with the Neolithic, a period characterized by major population expansion that could have been responsible for the spread of TPMT*3A from its place of origin, maybe a western Eurasian population. TPMT*3C was found to have arisen earlier, roughly 14000 years ago, which could explain the worldwide dispersal of TPMT*3C.

Age Distribution↗
PubMed2004

Occupational injuries identified by an emergency department based injury surveillance system in Nicaragua.

OBJECTIVES: To identify and describe the work related injuries in both the formal and informal work sectors captured in an emergency department based injury surveillance system in Managua, Nicaragua. SETTING: Urban emergency department in Managua, Nicaragua serving 200-300 patients per day. METHODS: Secondary analysis from the surveillance system data. All cases indicating an injury while working and seen for treatment at the emergency department between 1 August 2001 and 31 July 2002 were included. There was no exclusion based on place of occurrence (home, work, school), age, or gender. RESULTS: There were 3801 work related injuries identified which accounted for 18.6% of the total 20 425 injures captured by the surveillance system. Twenty seven work related fatalities were recorded, compared with the 1998 International Labor Organization statistic of 25 occupational fatalities for all of Nicaragua. Injuries occurring outside of a formal work location accounted for more than 60% of the work related injuries. Almost half of these occurred at home, while 19% occurred on the street. The leading mechanisms for work related injuries were falls (30%), blunt objects (28%), and stabs/cuts (23%). Falls were by far the most severe mechanism in the study, causing 37% of the work related deaths and more than half of the fractures. CONCLUSIONS: Occupational injuries are grossly underreported in Nicaragua. This study demonstrated that an emergency department can be a data source for work related injuries in developing countries because it captures both the formal and informal workforce injuries. Fall prevention initiatives could significantly reduce the magnitude and severity of occupational injuries in Managua, Nicaragua.

Accidents, Home↗
PubMed2003

Controlling hydrolysis and dispersion of AlN powders in aqueous media.

Aqueous suspensions of aluminum nitride (AlN) powders have been prepared in the presence of different surface-active agents, namely, H3PO4 and an anionic surfactant, to avoid the hydrolysis of AlN powders and to enhance dispersion. The most determinant parameters to the hydrolysis process (DeltapH and time of contact) and the stabilization of AlN particles in water (surface crystallinity, surface chemical modification, and surface ionic charge) were seen to be strongly dependent on the acidic agent. The H3PO4 treatment was effective against hydrolysis of AlN due to the formation of a phosphate-based protection layer on the particles' surface, and, although it keeps the pH of the suspension below 4, it does not guarantee a good dispersion. The individual adsorption of the anionic surfactant at the surface of AlN particles suspensions did not completely suppress the hydrolysis but it did enhance the degree of dispersion. A proper combination of the two types of surface-active agents enabled the preparation of AlN aqueous suspensions of relatively low viscosity and high AlN concentration, which can be a good starting point for aqueous-based colloidal shaping techniques or for freeze granulation or spray drying to obtain suitable granulate powder characteristics for dry-pressing technologies. An adsorption mechanism of the surface-active agents onto the particles' surface is proposed and supported by NMR and FT-IR analyses.

Journal Article↗
PubMed2002

alpha1-Antitrypsin null alleles: evidence for the recurrence of the L353fsX376 mutation and a novel G-->A transition in position +1 of intron IC affecting normal mRNA splicing.

alpha1-Antitrypsin (PI) deficiency is a common autosomal recessive disorder associated with emphysema and liver disease, which may result from a wide spectrum of mutations causing a reduction of serum levels (deficient alleles) or a total lack of circulating protein (null alleles). We report two different alleles associated with the absence of isoelectric focusing banding patterns in Portuguese patients with emphysema. The first allele, Q0(ourém), results from the recurrence of the defining mutation of the Q0(mattawa) variant (L353fsX376) on a M3 normal background. The second allele, Q0(porto), has a novel G-->A mutation at position +1 of the intron IC (IVS1C+1G-->A), which restricts mononuclear phagocyte transcripts to mRNA species resulting from the direct splice of exon IA to exon II. The absence of this normal splice alternative in the liver, where PI is primarily synthesized, provides a basis for the pathogenic effects of this mutation.

Emphysema↗
PubMed2001

Pyrochlore-type tin niobate.

A single crystal of Sn(1.59)Nb(1.84)O(6.35) was grown at 1273 K from a mixture of sodium niobate and tin(II) chloride. The structure is of pyrochlore type A(2)B(2)O(7). The tin is partially oxidized to tin(IV) and competes with niobium for the occupation of site B. The stereoactivity of the Sn(2+) lone pair induces displacement of tin towards the O atoms of the tunnel.

Journal Article↗
PubMed2001

Ab initio structure determination of a small-pore framework sodium stannosilicate.

The structure of a small-pore framework sodium stannosilicate Na(2)SnSi(3)O(9).2H(2)O (AV-10) has been determined ab initio from powder X-ray diffraction data (XRD). The unit cell is orthorhombic (space group C222(1), Z = 4) with cell dimensions a = 7.9453(5), b = 10.3439(7), c = 11.6252(7) A, V = 955 A(3). The structure of AV-10 is composed of corner sharing SnO(6) octahedra and SiO(4) tetrahedra, forming a three-dimensional framework structure. The SiO(4) tetrahedra form helix chains along [001] interconnected by SnO(6) octahedra. The SnO(6) octahedra are isolated by SiO(4) tetrahedra and, thus, there are no Sn-O-Sn linkages. AV-10 has been characterized by chemical analysis, powder XRD, scanning electron microscopy, (29)Si, (119)Sn, single- and (FAM) triple-quantum (23)Na MAS NMR spectroscopy, thermogravimetry (TGA), and nitrogen adsorption isotherms. The zeolitic water of AV-10 is reversibly lost. The dehydrated material has been studied in situ by powder XRD, TGA, and, in particular, triple-quantum (23)Na MAS NMR.

Journal Article↗
PubMed2001

Novel microporous europium and terbium silicates.

The synthesis and structural characterization of the first examples of microporous europium(III) and terbium(III) silicates (Na(4)K(2)X(2)Si(16)O(38) x 10H(2)O, X = Eu, Tb) are reported. The structure of these solids was solved by powder X-ray diffraction ab initio (direct) methods and further characterized by chemical analysis (EDS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), (23)Na and (29)Si magic-angle spinning (MAS) NMR, and luminescence spectroscopy. Both materials display interesting photoluminescence properties and present potential for applications in optoelectronics. This work illustrates the possibility of combining in a given silicate microporosity and optical activity.

Journal Article↗
PubMed2001

Determination of the degree of acetylation of chitin materials by 13C CP/MAS NMR spectroscopy.

13C CP/MAS NMR spectroscopy has been shown to be a powerful tool to quantify the degree of acetylation of chitin and chitosan. In order to optimise the parameters which afford quantitative 13C cross-polarisation magic-angle spinning NMR spectra, a detailed relaxation study has been carried out on selected chitin and deacetylated chitin samples. A relaxation delay of 5 s and a contact time of 1 ms have been found to yield quantitative NMR spectra of samples with deacetylation degree values of 0.68 and 0.16. The measured spin-lattice relaxation times in the rotating frame, T(1rhoH), are in the range 6.4-8.9 ms for chitin and 4.3-7.3 ms for deacetylated chitin, while TCH values for both samples are very similar and range from 0.03 to 0.19 ms. Spin-counting experiments indicate that, within experimental error, all carbon is detected by NMR indicating that the samples studied contain no (or very few) paramagnetic centres.

Acetylation↗
PubMed2001

(MeLi)4(dem)1.5]infinity] and [(thf)3Li3M3[(NtBu)3S--how to reduce aggregation of parent methyllithium.

Organolithium compounds play the leading role among the organometallic reagents in synthesis and in industrial processes. Up to date industrial application of methyllithium is limited because it is only soluble in diethyl ether, which amplifies various hazards in large-scale processes. However, most reactions require polar solvents like diethyl ether or THF to disassemble parent organolithium oligomers. If classical bidentate donor solvents like TMEDA (TMEDA= N,N,N',N'tetramethyl-1,2-ethanediamine) or DME (DME=1,2-dimethoxyethane) are added to methyllithium, tetrameric units are linked to form polymeric arrays that suffer from reduced reactivity and/or solubility. In this paper we present two different approaches to tune methyllithium aggregation. In [[(MeLi)4(dem)1,5)infinity] (1; DEM = EtOCH2OEt, diethoxymethane) a polymeric architecture is maintained that forms microporous soluble aggregates as a result of the rigid bite of the methylene-bridged bidentate donor base DEM. Wide channels of 720 pm in diameter in the structure maintain full solubility as they are coated with lipophilic ethyl groups and filled with solvent. In compound 1 the long-range Li3CH3...Li interactions found in solid [[(MeLi)4]infinity] are maintained. A different approach was successful in the disassembly of the tetrameric architecture of [((MeLi)4]infinity]. In the reaction of dilithium triazasulfite both the parent [(MeLi)4] tetramer and the [[Li2[(NtBu)3S]]2] dimer disintegrate and recombine to give an MeLi monomer stabilized in the adduct complex [(thf)3Li3Me-[(NtBu)3S]] (2). One side of the Li3 triangle, often found in organolithium chemistry, is shielded by the tripodal triazasulfite, while the other face is mu3-capped by the methanide anion. This Li3 structural motif is also present in organolithium tetramers and hexamers. All single-crystal structures have been confirmed through solid-state NMR experiments to be the same as in the bulk powder material.

Journal Article↗
PubMed2001

Patterns of haplotype diversity within the serpin gene cluster at 14q32.1: insights into the natural history of the alpha1-antitrypsin polymorphism.

The levels of haplotype diversity associated with different alpha1-antitrypsin (PI) alleles were assessed by the analysis of three microsatellites located within or close to corticosteroid-binding globulin (CBG), alpha1-antitrypsin [PI-(TG)n] and protein C inhibitor [PCI-(TG)n] loci in three populations with different historic backgrounds: Portugal, the Basque Country and São Tomé Príncipe (Gulf of Guinea). Unlike the more distant PCI-(TG)n repeat, allelic variation at PI-(TG)n reflected distinct phases of mutational recovery of microsatellite diversity around different founder alleles and showed a considerable differentiation between alpha1-antitrypsin protein variants. In accordance with population history, the Basque sample presented overall reduced levels of microsatellite variation. The African sample, although presenting the highest PCI-(TG)n diversity, showed a lineage-specific reduction in PI-(TG)n heterozygosity within the oldest M1Ala213 variant that could have been caused by (1) selection at a closely linked locus or (2) biases in the microsatellite mutation process leading to a stable equilibrium distribution. Age estimates of alpha1-antitrypsin variants based on microsatellite variation suggest that the Z deficiency allele appeared 107-135 generations ago and could have been spread in Neolithic times. The S mutation has an older 279- to 470-generation age, indicating that its high frequencies in Iberia did not result from a recent bottleneck and that PI*S could have originated in this region. M2 and M3 types had lower age estimates than would be expected from their wide geographical distributions, suggesting that their dispersion in Europe might have been preceded by important bottlenecks.

Alleles↗
PubMed2001

Localization of a recessive juvenile cataract mutation to proximal chromosome 7 in mice.

OBJECTIVE: To localize the chromosomal position of a novel cataract mutation (juvenile recessive cataract; jrc) in mice. METHODS: A mapping population was developed by crossing cataract males (albino MH) to wild-type females (black C57BL/6J). F1 females were backcrossed to albino MH males with cataracts. RESULTS: The results were consistent with a model of a single autosomal recessive gene [153 cataract, 169 wild-type; chi2 = 0.8, 1 degree of freedom (d.f.), p > 0.35]. Linkage with the albino (tyrosinase; Tyr) locus was evident (chi2 = 61.5, 1 d.f., p < 0.0001), implicating chromosome 7 as the location of jrc. Recombination percentages (+/- SE) between jrc and D7Mit340 (1.2 cM location), D7Mit227 (16.0 cM) and D7Mit270 (18.0 cM) were 17.1 +/- 2.1, 3.7 +/- 1.1 and 6.2 +/- 1.3%, respectively. Multi-point mapping determined that the most likely order of these loci is D7Mit340 - jrc - D7Mit227 - D7Mit270 - Tyr. Although animals with the mutant phenotype appeared to have little or no sense of sight, their growth was not different (p >0.20) from that of normal mice. CONCLUSION: The jrc mutation model may be useful in the study of the genetics of cataracts in other animal species, including humans.

Animals↗
PubMed2000

The phylogeography of Brazilian Y-chromosome lineages.

We examined DNA polymorphisms in the nonrecombining portion of the Y-chromosome to investigate the contribution of distinct patrilineages to the present-day white Brazilian population. Twelve unique-event polymorphisms were typed in 200 unrelated males from four geographical regions of Brazil and in 93 Portuguese males. In our Brazilian sample, the vast majority of Y-chromosomes proved to be of European origin. Indeed, there were no significant differences when the haplogroup frequencies in Brazil and Portugal were compared by means of an exact test of population differentiation. Y-chromosome typing was quite sensitive in the detection of regional immigration events. Distinct footprints of Italian immigration to southern Brazil, migration of Moroccan Jews to the Amazon region, and possible relics of the 17th-century Dutch invasion of northeast Brazil could be seen in the data. In sharp contrast with our mtDNA data in white Brazilians, which showed that > or =60% of the matrilineages were Amerindian or African, only 2.5% of the Y-chromosome lineages were from sub-Saharan Africa, and none were Amerindian. Together, these results configure a picture of strong directional mating between European males and Amerindian and African females, which agrees with the known history of the peopling of Brazil since 1500.

Black People↗