Medical Library

Species Richness and the Analytic Geometry of Latitudinal and Altitudinal Gradients.

Extensive empirical work has shown that species richness decreases roughly exponentially or quadratically with latitude. What appears to be a latitudinal gradient in fact may simply be a negative correlation of latitude with area at that latitude, due to convergence of lines of meridian at the poles. There is simply less area at high latitudes, which means fewer niches and fewer opportunities for speciation, hence diminished biodiversity at high latitudes. Similarly, analytic geometry of a cone shows that species number should decrease linearly with altitude on a conical mountain. Here, I provide an explicit mathematical model of the area hypothesis of species richness along latitude and altitude gradients. I re-analyze a previously published latitudinal gradient dataset and show that species number is a linear function of the predicted area and that species number is more fully explained by predicted area than by a quadratic function of latitude. However, analytic geometry is not needed if precise measures of area are known.

Gorelick R.

Department of Biology, School of Mathematics and Statistics, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada, K1S 5B6, Root_Gorelick@carleton.ca.

Expression, purification and characterization of TAT-high mobility group box-1A peptide as a carrier of nucleic acids.

High mobility group box 1 (HMGB1) is an abundant nuclear protein that binds to double-stranded DNA. HMGB1 is composed of high mobility (HMG) box A, box B, and C-terminal acidic regions. In this study, a recombinant TAT linked HMGB1 box A (rTAT-HMGB1A) peptide was expressed, purified, and characterized as a carrier of nucleic acids. The HMGB1A cDNA was amplified by PCR, and cloned into the pET21a expression vector with the TAT domain located at the N-terminus. The rTAT-HMGB1A peptide was overexpressed and purified using Nickel affinity chromatography. A recombinant HMGB1A (rHMGB1A) peptide without the TAT domain was also overexpressed and purified as a control. In gel retardation assays, both the rHMGB1A and rTAT-HMGB1A peptides formed complexes with DNA equally well. However, transfection assays showed that the rTAT-HMGB1A peptide had a higher gene transfer efficiency than rHMGB1A. Finally, rTAT-HMGB1A had no cytotoxicity to HEK 293 cells suggesting that rTAT-HMGB1A may be useful as a non-toxic gene delivery carrier.

Kim K, Han JS, Kim HA, Lee M.

Department of Bioengineering, College of Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791, Republic of Korea.

Species segregation in one-dimensional granular-system simulations.

We present one-dimensional molecular dynamics simulations of a two-species, initially uniform, freely evolving granular system. Colliding particles swap their relative position with a 50% probability allowing for the initial spatial ordering of the particles to evolve in time and frictional forces to operate. Unlike one-dimensional systems of identical particles, two-species one-dimensional systems of quasi-elastic particles are ergodic and the particles\’ velocity distributions tend to evolve towards Maxwell-Boltzmann distributions. Under such conditions, standard fluid equations with merely an additional sink term in the energy equation, reflecting the non-elasticity of the interparticle collisions, provide an excellent means to investigate the system\’s evolution. According to the predictions of fluid theory we find that the clustering instability is dominated by a non-propagating mode at a wavelength of the order 10piL/Nvarepsilon, where N is the total number of particles, L the spatial extent of the system and varepsilon the inelasticity coefficient. The typical fluid velocities at the time of inelastic collapse are seen to be supersonic, unless Nvarepsilon less, similar 10pi. Species segregation, driven by the frictional force occurs as a result of the strong temperature gradients within clusters which pushes the light particles towards the clusters\’ edges and the heavy particles towards the center. Segregation within clusters is complete at the time of inelastic collapse.

Pantellini F, Landi S.

LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris Diderot, 5 Place Jules Janssen, 92195, Meudon, France, filippo.pantellini@obspm.fr.

Novelty and spatio-temporal heterogeneity in the bacterial diversity of hypersaline Lake Tebenquiche (Salar de Atacama).

Lake Tebenquiche is one of the largest saline water bodies in the Salar de Atacama at 2,500 m above sea level in northeastern Chile. Bacteria inhabiting there have to deal with extreme changes in salinity, temperature and UV dose (i.e., high environmental dissimilarity in the physical landscape). We analyzed the bacterioplankton structure of this lake by 16S rRNA gene analyses along a spatio-temporal survey. The bacterial assemblage within the lake was quite heterogeneous both in space and time. Salinity changed both in space and time ranging between 1 and 30% (w/v), and total abundances of planktonic prokaryotes in the different sampling points within the lake ranged between two and nine times 10(6) cells mL(-1). Community composition changed accordingly to the particular salinity of each point as depicted by genetic fingerprinting analyses (denaturing gradient gel electrophoresis), showing a high level of variation in species composition from place to place (beta-diversity). Three selected sites were analyzed in more detail by clone libraries. We observed a predominance of Bacteroidetes (about one third of the clones) and Gammaproteobacteria (another third) with respect to all the other bacterial groups. The diversity of Bacteroidetes sequences was large and showed a remarkable degree of novelty. Bacteroidetes formed at least four clusters with no cultured relatives in databases and rather distantly related to any known 16S rRNA sequence. Within this phylum, a rich and diverse presence of Salinibacter relatives was found in the saltiest part of the lake. Lake Tebenquiche included several novel microorganisms of environmental importance and appeared as a large unexplored reservoir of unknown bacteria.

Demergasso C, Escudero L, Casamayor EO, Chong G, Balagué V, Pedrós-Alió C.

Centro de Biotecnología, Universidad Católica del Norte, Avda. Angamos 0610, Antofagasta, Chile.

Diversifying and Purifying Selection in the Peptide Binding Region of DRB in Mammals.

The class II genes of the major histocompatibility complex encode proteins which play a crucial role in antigen presentation. They are among the most polymorphic proteins known, and this polymorphism is thought to be the result of natural selection. To understand the selective pressure acting on the protein and to examine possible differences in the evolutionary dynamics among species, we apply maximum likelihood models of codon substitution to analyze the DRB genes of six mammalian species: human, chimpanzee, macaque, tamarin, dog, and cow. The models account for variable selective pressures across codons in the gene and have the power to detect amino acid residues under either positive or negative selection. Our analysis detected positive selection in the DRB genes in each of the six mammals examined. Comparison with structural data reveals that almost all amino acid residues inferred to be under positive selection in humans are in the peptide binding region (PBR) and are in contact with the antigen side chains, although residues outside of but close to the PBR are also detected. Strong purifying selection is also detected in the PBR, at sites which contact the antigen and at sites which may be involved in dimerization or T cell binding. The analysis demonstrates the utility of the random-sites analysis even when structural information is available. The different mammalian species are found to share many positively or negatively selected sites, suggesting that their functional roles have remained very similar in the different species, despite the different habitats and pathogens of the species.

Furlong RF, Yang Z.

Department of Biology, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK.

The determinants and outcomes of long-stay psychiatric admissions : A case-control study.

BACKGROUND: Acute psychiatric admissions lasting over 6 months (long-stays) continue to occur in England. Previous studies have suggested an association between long-stay and both schizophrenia and challenging behaviour, as well as rehousing or placement difficulties, but no UK study to date has compared such cases with control admissions. METHODS: We performed a case-control study. All long-stay patients present on acute general psychiatric wards serving the London Boroughs of Croydon, Lambeth, Lewisham and Southwark on November 1st 2004 were compared with a group of [Symbol: see text]next admitted\’ controls. We followed up long-stay cases 1 year later to determine whether they were still in hospital, and, if not, where they were living. RESULTS: In unadjusted comparisons long stay was associated with schizophrenia, non-white ethnicity, admission not due to suicidality, violence, severe illness and need for rehousing. A logistic regression was used to adjust for associations among exposures and only violence, severity of illness and need for rehousing remained associated with long-stay. After 1 year, two-thirds of cases were living out of hospital. CONCLUSIONS: Case-control studies may usefully contribute to the study of the complex social phenomenon of long-stay. Further research should address how the combination of individual and socially-determined effects that we found operate together over the course of admission to generate long-stays.

Tulloch AD, Fearon P, David AS.

Division of Psychological Medicine and Psychiatry, Institute of Psychiatry, King\’s College London, De Crespigny Park, London, SE5 8AF, UK.

[Access to Cervical Cytology in Medellín, Colombia during 2006.]

Background: The burden of illness of cervical cancer has not decreased enough in developing countries. For that reason is important to improve coverage, access and effectiveness of cervical cancer screening programs. The objective of this paper is to analyze women\’s access to the cervical cytology programme of the Secretary of Health of Medellín (Colombia). Methods: An analysis was made of 1.519 records of women from a cross-sectional study conducted in an urban area of Medellín (Colombia). Descriptive analysis was conducted and a Logit model was estimated for analysing recent cervical cytology (cytology performed less than 36 months prior to the survey). Results: 68,7% of women had a recent cytology, 17,2% did not have recent cytology and 14,2% of women attended for the first time to the service. The probability of having a recent cytology increased with age, women with family history of cervical cancer, women with personal history of sexually transmitted infections, women with some education and women who are (or were) married or in a stable union. Conclusions: The demand for cytology appears to be concentrated; a limited number of women assist frequently while others dont practice it or stop assisting.

Restrepo Zea J, Mejía Mejía A, Valencia Arredondo M, Tamayo Acevedo L, Salas Zapata W.

Facultad de Ciencias Económicas, Universidad de Antioquia.

[Prevalence of Certain Osteoporosis-Determining Habits among Post Menopausal Women in the Basque Country, Spain, in 2003.]

Backgound: On planning health promotion strategies for a disease or condition, one must know the current situation of the factors which have a bearing thereon. This study is aimed at analyzing, in the Basque Country, those living habits which interact to control the maximum bone density peak in postmenopausal women. Methods: This study was conducted in February-May 2003 on a sample of 555 women over 45 years of age selected at random in the Basque Country. A total of 82.8% thereof answered a living habit survey and a three-day recall diet survey. A descriptive core trend study was made for quantitative variable and frequencies for qualitative variables. A comparison was drawn between the prevalence among groups selected by way of the chi-square test and Student\’s t-test. Results: A total of 27.4% of the women studied were over 65 years of age (average age 58.51). Forty percent (40%) of the women were actively involved in physical exercise. A total of 4.1% of the women had sun exposure occasionally or exceptionally. The average calcium intake was 788.17 mg/day (SD=218.35). A total 0.3% had risk-level alcohol consumption and 14.7% moderate consumption. In relation to smoking, 12.6% of the women in the sample smoked less than a pack a day, and 3.5% more than one pack a day. Conclusions: The women studied showed as risk factors for having osteoporosis: a low level of active exercise, low calcium intake and in those women younger that 65 years of age and high degree of smoking.

Arana-Arri E, Gutiérrez-Ibarluzea I, Ecenarro Mugaguren A, Asua Batarrita J.

Servicio de Urgencias Generales, Hospital de Cruces, Barakaldo.

[Design and validation of a questionnaire to evaluate satisfaction of patients of the hospital outpatient clinics in Madrid, Spain, 2006.]

Background: In order to improve the quality of health care it is necessary to know the point of view of the patients through satisfaction surveys. Satisfaction surveys need some psychometric properties to guarantee its reliability and validity. The aim of this paper is to design and to validate a questionnaire to determine the satisfaction of patients of the hospital outpatient clinics. Methods: Validation of a satisfaction questionnaire, designed by an expert group and composed for 12 questions. The questionnaire was given to a sample of 677 patients attended in the hospital Gregorio Marañón outpatient clinics. The psychometric properties of the questionnaire were established: construct validity, concurrent criterion validity, predictive capacity and internal consistency. Results: Two dimensions were identified in the construct validity analyses, explaining 63% of the variance: \”clinical quality\” and \”administrative quality\”. The concurrent validity analysis showed a Spearmans rank correlation coefficient of 0.85 related to the standard criterion \”global satisfaction with the attention provided in outpatient clinics\” and an OR of 1.19 related to the criterion \”do you know the name of the physician who attended you?\” The predictive capacity of the questionnaire was measured by discriminated analysis, obtaining 84% of correct classified, and the internal consistency test gave a Cronbach s alpha of 0.90. Conclusions: Our questionnaire has enough psychometric properties to be considered an useful and feasible tool to measure the satisfaction of patients of the hospital outpatient clinics.

Granado de la Orden S, Rodríguez Rieiro C, Olmedo Lucerón MD, Chacón García A, Vigil Escribano D, Rodríguez Pérez P.

Servicio de Medicina Preventiva y Gestión de Calidad, Hospital General Universitario Gregorio Marañón, Madrid.

[Functional Capacity for Daily Living Activities among Senior Citizens Attending Community Centers in the City of Zaragoza, Spain, 2005.]

Background: To study the dependence related to aging is of particular interest in Aragon, where the population is one of the most aged in Spain. The objective of this study is that of quantifying the degree of functional dependence for daily living activities (DLA) and identifying the personal traits related thereto among individuals age 65 and above who are living at home and attend Community Centers in the city of Zaragoza. Methods: Cross-sectional study with 380 individuals selected by two-stage sampling. The OARS-MFAQ questionnaire was used by way of personal interviews, analyzing questions which assess the functional capacity to carry out the DLAs and their scoring (dependent variable), sociodemographic variables, self-assessed health condition and actual and hypothetical informal help (independent variables). The chi-square was used for evaluating classified residual data (p<0.05) and multiple correspondence analyses. Results: A total of 9.6% of the subjects showed \”major/total dependence\”, this percentage increasing to 15.5% and 18.7% for those individuals above age 75 and 80, respectively. The \”minor/moderate dependence\” is related to being a female (p<0.01), health condition self-assessed as poor-passable (p<0.0001), being a widow(er) (p<0.01), having no elementary school education (p<0.01). Conclusions: Those individuals who are more elderly, females, widow/widowers, having a lesser degree of education and worse self-assessed health condition are more dependent. Practically one out of every ten non-institutionalized individuals 65 years of age or over shows a severe deterioration of their functional capacity. Extrapolating, nearly 11,000 individuals in the city of Zaragoza would require daily help for the DLAs or should stay institutionalized.

Lázaro Alquézar A, Rubio Aranda E, Sánchez Sánchez A, García Herrero JC.

Facultad de Derecho, Universidad de Zaragoza.