Blood lead concentrations in exposed forecourt attendants and taxi drivers in parts of South Africa.

BACKGROUND: Leaded fuel was banned in South Africa in 2006, in order to improve human health and reduce environmental pollution. Lead (Pb) has been suggested to contribute to the development of neurodegenerative disorders, and the role of respiratory exposure to Pb from petrol fumes should not be neglected in this context. In addition to Pb, petrol contains various harmful chemicals including other neurotoxic metals and hydrocarbons. OBJECTIVES AND METHODS: Here, we investigated concentrations of Pb and other metals in blood from petrol station forecourt attendants (n = 38), taxi drivers (n = 21), and unexposed controls (n = 36). Taxi drivers and forecourt attendants were divided into three groups each, based on number of years worked. A questionnaire was designed to investigate the health status of the participants. Blood samples were collected by medical professionals and analyzed for metal concentrations by ICP-MS. RESULTS: A positive correlation between number of years worked and Pb blood concentrations was found. The highest Pb concentration (60.2 µg/L) was observed in a forecourt attendant who had worked 11-20 years, and the average Pb concentration in this group (24.5 µg/L) was significantly (p < 0.05) higher than in forecourt attendants who had worked 2-5 years (10.4 µg/L). Some individuals had elevated concentrations of manganese, arsenic, cadmium, chromium and cobalt, yet not significantly elevated at the group level. The blood levels of arsenic appeared to be related to smoking. Mood swings, dizziness, headaches and tiredness were reported by the workers. CONCLUSION: Blood Pb concentrations in petrol station forecourt attendants and taxi drivers exposed to leaded petrol are elevated and correlate to exposure time. A health monitoring program should be erected for all individuals working in these industries, and preventive measures should be implemented to eliminate metal exposure from petrol.

Detecting national human enteric disease outbreaks linked to animal contact in the United States of America.

Enteric pathogens, such as non-typhoidal Salmonella, Campylobacter and Escherichia coli, can reside in the intestinal tract of many animals, including livestock, companion animals, small mammals and reptiles. Often, these animals can appear healthy; nonetheless, humans can become infected after direct or indirect contact, resulting in a substantial illness burden. An estimated 14% of the 3.2 million illnesses that occur in the United States of America (USA) each year from such enteric pathogens are attributable to animal contact. Surveillance for enteric pathogens in the USA includes the compilation and interpretation of both laboratory and epidemiologic data. However, the authors feel that a collaborative, multisectoral and transdisciplinary - or One Health - approach is needed for data collection and analysis, at every level. In addition, they suggest that the future of enteric illness surveillance lies in the development of improved technologies for pathogen detection and characterisation, such as genomic sequencing and metagenomics. In particular, using whole-genome sequencing to compare genetic sequences of enteric pathogens from humans, food, animals and the environment, can help to predict antimicrobial resistance among these pathogens, determine their genetic relatedness and identify outbreaks linked to a common source. In this paper, the authors describe three recent, multi-state human enteric illness outbreaks linked to animal contact in the USA and discuss how integrated disease surveillance was essential to outbreak detection and response. Additional datasharing between public health and animal health laboratories and epidemiologists at the local, national, regional and international level may help to improve surveillance for emerging animal and human health threats and lead to new opportunities for prevention.

Les agents pathogènes entériques tels que les Salmonella non typhiques, Campylobacter et Escherichia coli peuvent coloniser le tractus intestinal d'un grand nombre d'animaux y compris les espèces d'élevage, les animaux de compagnie, les petits mammifères et les reptiles. Les animaux porteurs sont souvent sains en apparence ; néanmoins, les humains peuvent contracter l'infection après un contact direct ou indirect avec un animal atteint, ce qui induit un fardeau significatif associé à ces maladies. D'après les estimations, environ 14 % des 3,2 millions de cas annuels d'infections par des agents pathogènes entériques aux États-Unis d'Amérique ont pour origine un contact avec des animaux. Aux États-Unis, la surveillance des agents pathogènes entériques est basée sur la collecte et l'interprétation des résultats de laboratoire et des données épidémiologiques. Les auteurs sont néanmoins convaincus de la nécessité de recourir à une approche collaborative, multisectorielle et transdisciplinaire (en d'autres termes, une approche Une seule santé) pour la collecte et l'analyse des données, à tous les niveaux. Ils considèrent également que la surveillance des infections entériques reposera à l'avenir sur le développement de technologies avancées dans le domaine de la détection et de la caractérisation des agents pathogènes, notamment le séquençage génomique et la métagénomique. En particulier, le recours au séquençage du génome entier afin de comparer les séquences d'agents pathogènes d'origine humaine, alimentaire, animale et environnementale permettra d'anticiper l'apparition d'antibiorésistances, de déterminer le degré de parenté génétique de ces agents et d'identifier les foyers provenant d'une même source. Les auteurs décrivent trois foyers récents d'infections entériques humaines survenus dans plusieurs états des États-Unis et soulignent à quel point l'exercice d'une surveillance sanitaire intégrée a été déterminant pour la détection de ces foyers et la mise en œuvre d'une réponse appropriée. Un partage accru d'informations entre les laboratoires et les épidémiologistes de santé publique et animale aux niveaux local, national, régional et international pourrait contribuer à améliorer la surveillance des menaces émergentes pesant sur la santé animale et humaine et à mettre en œuvre de nouvelles modalités de prévention.

En el tracto intestinal de muchos animales, entre ellos ganado, mascotas, pequeños mamíferos o reptiles, puede haber patógenos intestinales como salmonelas no tifoideas, Campylobacter o Escherichia coli. A menudo los animales parecen sanos, pese a lo cual las personas pueden infectarse por contacto directo o indirecto con ellos, lo que da lugar a una considerable carga de morbilidad. Se calcula que, de los 3,2 millones de casos de enfermedad que estos patógenos intestinales causan al año en los EE. UU., un 14% es atribuible al contacto con animales. La vigilancia de patógenos intestinales que se practica en los EE. UU. incluye la compilación e interpretación de datos tanto epidemiológicos como de laboratorio. En opinión de los autores, sin embargo, es preciso que la obtención y el análisis de datos respondan a un planteamiento de colaboración multisectorial y transdisciplinar ­ esto es, a la lógica de Una sola salud ­ que abarque todos los niveles. Los autores apuntan además que el futuro de la vigilancia de las enfermedades intestinales pasa por el desarrollo de tecnologías más eficaces de detección y caracterización de patógenos, como la secuenciación genómica o la metagenómica. En particular, el uso de la secuenciación de genomas completos para comparar entre sí las secuencias genéticas de patógenos intestinales presentes en personas, alimentos, animales y el medio ambiente puede ayudar a predecir la aparición de resistencias a los antimicrobianos en estos patógenos, determinar su parentesco genético e identificar brotes vinculados con un origen común. Los autores, tras describir tres recientes brotes de enfermedad intestinal humana ligados al contacto con animales que afectaron a varios estados de los EE. UU., explican la función esencial que cumplió la vigilancia integrada de enfermedades para detectar esos brotes y responder a ellos. El intercambio de más datos entre los laboratorios de salud pública y sanidad animal y los epidemiólogos a escala local, nacional, regional e internacional puede ser de ayuda para mejorar la vigilancia de amenazas sanitarias y zoosanitarias emergentes y abrir nuevas posibilidades de prevención.

Computerized testing augments pencil-and-paper tasks in measuring HIV-associated mild cognitive impairment(*).

BACKGROUND: Existing tools for rapid cognitive assessment in HIV-positive individuals with mild cognitive deficits lack sensitivity or do not meet psychometric requirements for tracking changes in cognitive ability over time. METHODS: Seventy-five nondemented HIV-positive patients were evaluated with the Montreal Cognitive Assessment (MoCA), a brief battery of standardized neuropsychological tests, and computerized tasks evaluating frontal-executive function and processing speed. Rasch analyses were applied to the MoCA data set and subsequently to the full set of data from all tests. RESULTS: The MoCA was found to adequately measure cognitive ability as a single, global construct in this HIV-positive cohort, although it showed poorer precision for measuring patients of higher ability. Combining the additional tests with the MoCA resulted in a battery with better psychometric properties that also better targeted the range of abilities in this cohort. CONCLUSION: This application of modern test development techniques shows a path towards a quick, quantitative, global approach to cognitive assessment with promise both for initial detection and for longitudinal follow-up of cognitive impairment in patients with HIV infection.

Full-genome RNAi profiling of early embryogenesis in Caenorhabditis elegans.

A key challenge of functional genomics today is to generate well-annotated data sets that can be interpreted across different platforms and technologies. Large-scale functional genomics data often fail to connect to standard experimental approaches of gene characterization in individual laboratories. Furthermore, a lack of universal annotation standards for phenotypic data sets makes it difficult to compare different screening approaches. Here we address this problem in a screen designed to identify all genes required for the first two rounds of cell division in the Caenorhabditis elegans embryo. We used RNA-mediated interference to target 98% of all genes predicted in the C. elegans genome in combination with differential interference contrast time-lapse microscopy. Through systematic annotation of the resulting movies, we developed a phenotypic profiling system, which shows high correlation with cellular processes and biochemical pathways, thus enabling us to predict new functions for previously uncharacterized genes.

Reafferent copies of imitated actions in the right superior temporal cortex.

Imitation is a complex phenomenon, the neural mechanisms of which are still largely unknown. When individuals imitate an action that already is present in their motor repertoire, a mechanism matching the observed action onto an internal motor representation of that action should suffice for the purpose. When one has to copy a new action, however, or to adjust an action present in one's motor repertoire to a different observed action, an additional mechanism is needed that allows the observer to compare the action made by another individual with the sensory consequences of the same action made by himself. Previous experiments have shown that a mechanism that directly matches observed actions on their motor counterparts exists in the premotor cortex of monkeys and humans. Here we report the results of functional magnetic resonance experiments, suggesting that in the superior temporal sulcus, a higher order visual region, there is a sector that becomes active both during hand action observation and during imitation even in the absence of direct vision of the imitator's hand. The motor-related activity is greater during imitation than during control motor tasks. This newly identified region has all the requisites for being the region at which the observed actions, and the reafferent motor-related copies of actions made by the imitator, interact.

The closest BLAST hit is often not the nearest neighbor.

It is well known that basing phylogenetic reconstructions on uncorrected genetic distances can lead to errors in their reconstruction. Nevertheless, it is often common practice to report simply the most similar BLAST (Altschul et al. 1997) hit in genomic reports that discuss many genes (Ruepp et al. 2000; Freiberg et al. 1997). This is because BLAST hits can provide a rapid, efficient, and concise analysis of many genes at once. These hits are often interpreted to imply that the gene is most closely related to the gene or protein in the databases that returned the closest BLAST hit. Though these two may coincide, for many genes, particularly genes with few homologs, they may not be the same. There are a number of circumstances that can account for such limitations in accuracy (Eisen 2000). We stress here that genes appearing to be the most similar based on BLAST hits are often not each others closest relative phylogenetically. The extent to which this occurs depends on the availability of close relatives present in the databases. As an example we have chosen the analysis of the genomes of a crenarcheaota species Aeropyrum pernix, an organism with few close relatives fully sequenced, and Escherichia coli, an organism whose closest relative, Salmonella typhimurium, is completely sequenced.

Codon bias and base composition are poor indicators of horizontally transferred genes.

Horizontal gene transfer is now recognized as an important mechanism of evolution. Several methods to detect horizontally transferred genes have been suggested. These methods are based on either nucleotide composition or the failure to find a similar gene in closely related species. Genes that evolve vertically between closely related species can be divided into those that retain homologous chromosomal positions (positional orthologs) and those that do not. By comparing open reading frames in the Escherichia coli and Salmonella typhi genomes, we identified 2,728 positional orthologs since these species split 100 MYA. A group of 1,144 novel E. coli genes were unusually diverged from their S. typhi counterparts. These novel genes included those that had been horizontally transferred into E. coli, as well as members of gene pairs that had been rearranged or deleted. Positional orthologs were used to investigate compositional methods of identifying horizontally transferred genes. A large number of E. coli genes with normal nucleotide composition have no apparent ortholog in S. typhi, and many genes of atypical composition do, in fact, have positional orthologs. A phylogenetic approach was employed to confirm selected examples of horizontal transmission among the novel groups of genes. Our analysis of 80 E. coli genes determined that a number of genes previously classified as horizontally transferred based on base composition and codon bias were native, and genes previously classified as native appeared to be horizontally transferred. Hence, atypical nucleotide composition alone is not a reliable indicator of horizontal transmission.

Time-related changes in task performance after lesions restricted to the frontal cortex.

Behavioural studies in patients and functional neuroimaging studies in normal subjects suggest that the right frontal cortex plays an important role in sustaining attention to a task. However, the contribution of different regions of the frontal lobe to performance changes has not been clearly established. First, the assessment of sustained attention has not been carried out in patients with lesions that are restricted to cortical regions of the frontal lobe. Second, although sustained attention is often measured by performance on a task requiring effortful attention, it may be more meaningful to measure changes in performance as a function of time-on-task. Two studies were carried out in five groups of subjects: patients with left or right frontal cortical resections, patients with left or right anterior temporal lobe resections, and normal controls. In the first experiment, a brief (4-min) selective attention task was performed. The right frontal group, unlike the other groups, did not show improved reaction times after the first minute on the task. The second experiment involved a long (30-min) shifting attention task. Both the left and right frontal groups were slower than control groups; however, reaction times in the right frontal group increased with time spent on the task. We conclude that the right frontal cortex plays an essential role in modulating arousal during performance of a task and may also underlie aspects of learning during the early stages of task performance.

Functional connectivity of the anterior cingulate cortex within the human frontal lobe: a brain-mapping meta-analysis.

A database of positron-emission-tomography studies published between January 1993 and November 1996 was created to address several questions regarding the function and connectivity of the human anterior cingulate cortex (ACC). Using this database, we have previously reported on the relationship between behavioural variables and the probability of blood-flow response in distinct subdivisions of the ACC. The goal of the current analysis was to discover which areas of the frontal cortex show increased blood-flow co-occurring consistently with increased blood-flow in the ACC. Analyses of the frequency distributions of peaks in the ACC and the remaining frontal cortex (FC) yielded several important findings. First, FC peaks in the precentral gyrus, superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus, medial frontal gyrus and orbitomedial frontal gyri were more frequent in subtractions that also yielded a peak in the ACC than in those that did not yield an ACC peak. Second, regional differences in the frequency distribution of these FC peaks were observed when the ACC peaks were subdivided into the rostral versus caudal ACC and supracallosal versus subcallosal ACC. Peaks in the precentral gyrus and in the vicinity of the supplementary motor area were more prevalent in subtractions with co-occurring peaks in the caudal than with the rostral ACC. Peaks in the middle frontal gyrus were more frequent in subtractions with co-occurring peaks in the paralimbic part of the supracallosal ACC, relative to the subcallosal or limbic supracallosal ACC. These observations are consistent with known differences in the anatomic connectivity in these cortical regions, as defined in non-human primates. Further analyses of the influence of behavioural variables on the relationships between the ACC and other regions of the frontal cortex suggested that this type of meta-analysis may provide testable hypotheses about functional and effective connectivity within the human frontal lobe.

Monoalleleic transcription of the insulin-like growth factor-II gene (Igf2) in chick embryos.

A polymorphism in the igf2 gene of chickens was identified using NlaIII (GenBank accession number AF218827). In some embryos, the igf2 alleles were expressed monoallelically from either maternal or paternal alleles. These data demonstrate that genomic imprinting is not confined to mammalian vertebrates and suggest that genomic imprinting evolved at an early stage of vertebrate evolution. The observations that the igf2 gene is imprinted in a minority of embryos suggest that the imprinting in birds is unrelated to embryonic growth. Genome imprinting may provide opportunities for evolution of genes in a nonexpressed state. In poultry breeding, the presence of imprinted genes may make a major contribution to unequal performance in reciprocal matings between commercial lines.

Increased blood flow in the basal ganglia when using cues to direct attention.

We used positron emission tomography (PET) in ten subjects to study the brain regions involved in voluntary shifts of attention. For six scans, subjects performed a visual target detection task in which the location of the target was indicated in advance on some proportion of trials by the appearance of an arrow cue at fixation. The informative cues were successful in speeding reaction time to the target. Blood flow in the left putamen was correlated with the proportion of informative cues provided within a scan. We discuss this finding in terms of three possible interpretations: attentional shifts, response inhibition, and motor preparation related to the use of the right hand to respond. Blood flow in cortical regions commonly associated with attention was not related to cue ratio, a finding that may reflect automatization of the processes involved in interpreting and using the cues.

Directed attention after unilateral frontal excisions in humans.

We investigated the ability of patients with frontal-lobe lesions to benefit from advance information in a simple reaction-time task. The task involved pressing a button in response to the appearance of a peripheral target (visual angle of 11.5 degrees). A cue, presented in the centre of the screen, preceded the target onset by either a short (average 500 ms) or a long (average 3000 ms) interval. In half of the trials, the cue was an arrow indicating the location, in the left or right hemifield, of the upcoming target; in the other half, the cue was an uninformative plus sign. In addition to patients with unilateral excisions of frontal cortex, we tested patients with anterior temporal-lobe excisions and normal controls. The frontal-lobe group was mildly impaired with respect to the temporal-lobe group in using advance spatial cues to speed response to the visual target. While the size of the cueing effect changed across the range of cue-target intervals tested, there was no variation across intervals in the size of the impairment exhibited by the frontal-lobe group. The site and the volume of the lesions were determined on the basis of magnetic resonance image (MRI) scans in 10 of the 17 patients in the frontal group. There was no correlation between lesion volume and benefit score in these patients.

Regional differences in the effects of task difficulty and motor output on blood flow response in the human anterior cingulate cortex: a review of 107 PET activation studies.

We reviewed 107 blood flow activation studies carried out with positron emission tomography and published between January 1993 and November 1996. These studies had reported their findings as peaks of significant difference in cerebral blood-flow (CBF) between two scans/tasks and had located the peaks in standardized stereotaxic space. We coded each task along several dimensions, including the type and rate of input and output, the types of cognitive processes, and the relative difficulty of tasks within a study. Based on this coding, a difference score (A-B) was calculated for each subtraction. Subsequently, the frequency distributions of the difference scores for subtractions yielding a peak in the anterior cingulate region (cingulate peak) were compared with those distributions obtained from subtractions without a cingulate peak (no cingulate-peak). The cingulate peak subtractions (n = 158) differed from the no cingulate peak subtractions (n = 229) in terms of difficulty level (p = 0.001) and the presence of a remote memory component (p = 0.01). Regional differences in the frequency distribution of certain task parameters, such as difficulty level, recent memory and the use of the hand for responding, were also observed when peaks found in the anterior cingulate cortex (ACC) were further classified as located in the rostral vs caudal ACC, supracallosal vs subcallosal ACC, and limbic vs paralimbic parts of the supracallosal ACC. We conclude that task difficulty plays a major role in modulating blood-flow response in the ACC, possibly interacting with other parameters such as the nature of the response and memory demands.