Plasmid Rolling-Circle Replication.

Plasmids are DNA entities that undergo controlled replication independent of the chromosomal DNA, a crucial step that guarantees the prevalence of the plasmid in its host. DNA replication has to cope with the incapacity of the DNA polymerases to start de novo DNA synthesis, and different replication mechanisms offer diverse solutions to this problem. Rolling-circle replication (RCR) is a mechanism adopted by certain plasmids, among other genetic elements, that represents one of the simplest initiation strategies, that is, the nicking by a replication initiator protein on one parental strand to generate the primer for leading-strand initiation and a single priming site for lagging-strand synthesis. All RCR plasmid genomes consist of a number of basic elements: leading strand initiation and control, lagging strand origin, phenotypic determinants, and mobilization, generally in that order of frequency. RCR has been mainly characterized in Gram-positive bacterial plasmids, although it has also been described in Gram-negative bacterial or archaeal plasmids. Here we aim to provide an overview of the RCR plasmids' lifestyle, with emphasis on their characteristic traits, promiscuity, stability, utility as vectors, etc. While RCR is one of the best-characterized plasmid replication mechanisms, there are still many questions left unanswered, which will be pointed out along the way in this review.

An integrated view of data quality in Earth observation.

Data quality is a difficult notion to define precisely, and different communities have different views and understandings of the subject. This causes confusion, a lack of harmonization of data across communities and omission of vital quality information. For some existing data infrastructures, data quality standards cannot address the problem adequately and cannot fulfil all user needs or cover all concepts of data quality. In this study, we discuss some philosophical issues on data quality. We identify actual user needs on data quality, review existing standards and specifications on data quality, and propose an integrated model for data quality in the field of Earth observation (EO). We also propose a practical mechanism for applying the integrated quality information model to a large number of datasets through metadata inheritance. While our data quality management approach is in the domain of EO, we believe that the ideas and methodologies for data quality management can be applied to wider domains and disciplines to facilitate quality-enabled scientific research.

Genetic and biochemical characterization of the Streptococcus pneumoniae PcrA helicase and its role in plasmid rolling circle replication.

PcrA is a chromosomally encoded DNA helicase of gram-positive bacteria involved in replication of rolling circle replicating plasmids. Efficient interaction between PcrA and the plasmid-encoded replication initiator (Rep) protein is considered a requirement for the plasmid to replicate in a given host, and thus, the ability of a Rep protein to interact with heterologous PcrA helicases has been invoked as a determinant of plasmid promiscuity. We characterized transcription of the Streptococcus pneumoniae pcrA gene in its genetic context and studied the biochemical properties of its product, the PcrA(Spn) helicase. Transcription of the pneumococcal pcrA gene was directed by promoter Pa, consisting of an extended -10 box. Promoter Pa also accounted for expression of a second essential gene, radC, which was transcribed with much lower efficiency than pcrA, probably due to the presence of a terminator/attenuator sequence located between the two genes. PcrA(Spn) displayed single-stranded DNA-dependent ATPase activity. PcrA(Spn) showed 5'-->3' and 3'-->5' helicase activities and bound efficiently to partially duplex DNA containing a hairpin structure adjacent to a 6-nucleotide 5' or 3' single-stranded tail and one unpaired (flap) nucleotide in the complementary strand. PcrA(Spn) interacted specifically with RepC, the initiator of staphylococcal plasmid pT181. Although the pneumococcal helicase was able to initiate unwinding of the RepC-nicked pT181 DNA, it was much less processive in this activity than the cognate staphylococcal PcrA protein. Accordingly, PcrA(Spn) was inefficient in in vitro replication of pT181, and perhaps as a consequence, this plasmid could not be established in S. pneumoniae.

[Eating attitudes and body satisfaction in adolescents: a prevalence study]. / Actitudes alimentarias y satisfacción corporal en adolescentes: un estudio de prevalencia.

OBJECTIVES: To determine the prevalence of possible TCA in a sample of adolescents of either sex, in habitants of Girona, as well as to determine the relations between eating attitudes and body shape concerns in adolescent girls. SU BJECTS AND METHOD: The study sample was composed of all adolescent man and women (n=1025), students from Girona, with ages comprised between 14 and 19. The questionnaires used where the EAT-40 (being values over 30 the cut-off point) and the BSQ. RESULTS: While a 16.3% of adolescent women present potential risk of TCA, only 0.4% adolescent men have the same risk. A 9% of adolescent women show an extreme concern for her body shape and weight, and 13.1% show a moderate worry. Adolescent women that showed the highest symptomatology associated with eating disorders also present a higher dissatisfaction and concern with body shape (r=.65). CONCLUSIONS: The prevalence of possible TCA in Girona city is similar to the one found in other studies. This high prevalence makes necessary the implementation of prevention strategies in younger people.

Actitudes alimentarias y satisfacción corporal en adolescentes: un estudio de prevalencia / Eating attitudes and body satisfaction in adolescents: a prevalence study

Objetivos. Determinar la prevalencia de posibles TCA en una muestra de adolescentes de ambos sexos de la ciudad de Girona y la relación de las actitudes alimentarias con la actitud hacia el propio cuerpo en las mujeres adolescentes. Sujetos y método. La muestra de estudio estuvo formada por todos los hombres y mujeres adolescentes (n= 1.025), estudiantes de secundaria de la ciudad de Girona, con edades comprendidas entre los 14 y 19 años. Los cuestionarios utilizados fueron el EAT-40 (considerando positivos valores superiores a 30) y el BSQ. Resultados. Un 16,3 por ciento de las mujeres adolescentes presentan riesgo potencial de TCA, frente a un 0,4 por ciento en los hombres adolescentes. Un 9 por ciento de las mujeres adolescentes manifiesta una preocupación extrema por su figura y peso, mientras que el 13,1 por ciento mostraba una preocupación moderada. Las mujeres adolescentes que manifiestan una mayor sintomatología propia de los trastornos de la alimentación, también presentan asociada una mayor insatisfacción y preocupación con la imagen corporal (r=.65) Conclusiones. La prevalencia de posibles TCA en la cuidad de Girona es similar a la hallada en otros estudios. Esta elevada prevalencia hace necesaria la implantación de estrategias de prevención en edades más precoces (AU)

[Low flow cavernous sinus fistula. Treatment by highly selective embolization]. / Fístulas carótido-cavernosas de bajo flujo. Tratamiento con embolización supraselectiva.

Carotid-cavernous sinus fistulae are anomalous communications between the carotid artery and the cavernous sinus. They are classified according to whether they are traumatic or spontaneous, but distinction in relation to the anatomical origin of the branches of the carotid artery which supplies them is more important. The anatomy of the regional vasculature is analysed in this article. The vessels most frequently involved in spontaneous dural fistulae are the internal maxillary artery (from the external carotid) and the meningohypophyseal trunk (from the internal carotid) which anastomose respectively with the inferior cavernous sinus artery and with the ascending pharyngeal artery. We present two cases of spontaneous carotid-cavernous fistulae. Both were type D of Barrow's classification, and in view of progressive changes in the visual fields, it was decided to proceed with invasive treatment by highly selective embolization of the branches of the external carotid artery, which is currently the treatment of choice in such cases. Good results were obtained.

The effect of fetal infection with human immunodeficiency virus type 1 on birthweight and length of gestation. SIGO Study Group of HIV Infection in Pregnancy.

We sought to evaluate the effect of vertical transmission of human immunodeficiency virus type 1 (HIV-1) on birthweight and length of gestation. For this purpose we used maternal and pregnancy data of 559 HIV-1-seropositive pregnant women delivered at 13 Italian centers from 1985 to 1991. The mother-to-child transmission rate of HIV infection was 18.2% (84/461). After adjustment for potential confounders with multiple linear regression analysis, there were no differences in birthweight, gestational age, and proportion of expected birthweight (observed birthweight/expected birthweight) between infected and uninfected children. Intravenous drug abuse during current pregnancy was the factor which correlated best with a reduction in birthweight (mean reduction, 214.4 g; 95% confidence interval (CI), 61.7-367.1), length of gestation (mean reduction, 9.3 days; 95% CI, 3.9-14.7) and proportion of expected birthweight (mean reduction, 12.1%; 95% CI, 4.7-19.5%). In our population, HIV-1 infection of the fetus has little effect on length of gestation and birthweight.

AIDS in Italy and proposals for a new therapeutic strategy.

In Italy, the number of AIDS cases reported up to September 1993 was 18,832. Of these, 3,544 were women (21%), mainly of fertile age. AIDS in pregnancy has aroused great interest in Italy, mainly due to the extent of the phenomenon, which is not equalled in other Western countries. In this contribution to the study of HIV infection in pregnancy, the Authors propose a new procedure for monitoring, asymptomatic HIV-positive pregnant women, using fetal Fibronectin as an indicator of aspecific chorionamnionitis and the threat of premature birth, both considered as a risk factors for transmission of the virus from mother to child.

Application of pulse polarography with anodic stripping voltammetry to biological and toxicological analyses for lead and cadmium.

The development of polarographic techniques within the last thirty years has made possible exceptional increases in sensitivity ; thus the order of concentration studied has passed from 10-3 g ion/1. to 10-10 g ion/1. Pulse polarography with anodic stripping voltammetry is, therefore, particularly suitable for the determination of a large number of the so-called " biologically essential " and " highly toxic " metals, more often than not present in extremely low concentrations in biological samples which may be of limited volume (blood, for example). Our principal concern has been to describe and apply a method for the determination of lead and cadmium, sufficiently sensitive, precise, practical and rapid for everyday use by biologists and toxicologists. A fortiori this method is applicable in hydrology to the determination of traces of these metals in water.