Low Occupational Level Research Articles

Richness and distribution of sponge megabenthos in continental margin canyons off southeastern Australia

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 340:73-88 (2007) - doi:10.3354/meps340073 Richness and distribution of sponge megabenthos in continental margin canyons off southeastern Australia Thomas A. Schlacher1,*, Monika A. Schlacher-Hoenlinger1,2, Alan Williams3, Franziska Althaus3, John N. A. Hooper2, Rudy Kloser3 1Faculty of Science, Health & Education, The University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia 2Biodiversity Program, Queensland Museum, PO Box 3300, South Brisbane, Queensland 4101, Australia 3Commonwealth Scientific and Industrial Research Organisation (CSIRO) Marine & Atmospheric Research, PO Box 1538, Hobart, Tasmania 7001, Australia *Email: tschlach@usc.edu.au ABSTRACT: Submarine canyons are spectacular topographical features that intersect the continental margins of the world’s oceans. Canyons comprise unique habitats in terms of complexity, instability, material processing, and hydrodynamics, and they may support diverse assemblages of larger epibenthos. Yet, quantitative data on the biodiversity of the megabenthos in canyons are scant. Consequently, we quantified the diversity of sponges (a key and dominant group of the megabenthos) in 5 canyons located on the continental margin off southeastern Australia at depths from 114 to 612 m. The canyons harboured a rich sponge fauna, with a total of 165 species, belonging to 65 genera, 41 families, 10 orders, and 2 classes in 14 sled samples. Species richness declined with depth, but was positively linked to spatial heterogeneity of bottom types. Areas comprised of a broader range of bottom types (e.g. mixed rocky and sandy/muddy bottoms) contained more species than areas with more uniform substratum properties. Spatial patterns of the sponge assemblages were characterized by (1) high species turnover both between sites in individual canyons and between different canyons, and (2) low levels of site occupancy of the component species, with most species recorded from single canyons only. Variations in depth, substratum type and topographic relief resulted in heterogeneous environmental conditions of benthic habitats in canyons that corresponded to changes in the assemblage structure of sponges. A broad comparison with other abrupt topographical features in the bathyal zone of the region suggests that canyon assemblages may rival the diversity of sponges on seamounts. Site-to-site variation in diversity and species composition within individual canyons suggests that biological patterns may be finer-grained than the spatial scale of conventional geomorphological units. Consequently, from a perspective of conservation planning, a single or a few canyons are unlikely to accurately represent the regional faunal diversity, because of the strong biotic separation of communities between canyons and the limited distributional ranges of the component species. KEY WORDS: Submarine canyons · Megabenthos · Porifera · Diversity · Species-range sizes Full text in pdf format Supplementary appendix PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 340. Online publication date: June 18, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Ethnic disparities in problem behaviour in adolescence contribute to ethnic disparities in social class in adulthood

It is important for prevention of social class disparities to know how ethnic disparities in social class arise among migrant children. We contribute to this understanding by examining the role of problem behaviour in adolescence. Prospective observational study with 753 Dutch native and 217 Turkish migrant adolescents (11-18 year) followed for 10 years. Internalising and externalising problems were assessed in adolescence and employment status and occupational level were assessed in adulthood. The difference in odds ratios (OR) before and after adjustment for internalising and externalising problems was an indication of the predictive value of disparities in internalising and externalising problems for the development of social class disparities. A total of 135 (62%) of the Turkish and 602 (80%) of the Dutch adults were employed. Internalising and externalising problems were not associated with employment status. Of the employed, 65 (48%) Turkish and 179 (30%) Dutch adults worked in low-level occupations (p < 0.0001). Internalising and externalising problems were associated with both ethnicity and occupation. The OR for low-level occupation for Turkish adults was 1.78 (1.19-2.65), indicating ethnic disparities. Adjustment for internalising problems lowered the OR with 36% to 1.50 (0.97-2.31), and adjustment for externalising problems lowered it with 8% to 1.72 (1.15-2.57). Findings were similar for men and women and did not vary by age. Ethnic disparities in occupational level in adulthood could partly be attributed to disparities in mental health between Turkish migrants and Dutch natives in adolescence. Prevention of ethnic disparities in mental health at young age may therefore also contribute to the prevention of occupational differences in adulthood.

Sertindole: efficacy and safety in schizophrenia

Sertindole is an antipsychotic drug with affinity for dopamine D2, serotonin 5-HT2A and 5-HT2C, and α1-adrenoreceptors. Preclinical studies suggest that sertindole acts preferentially on limbic and cortical dopaminergic neurons and clinical trials have confirmed that sertindole is effective at a low dopamine D2 occupancy level. The active substance has a long half-life. Oral administration once daily yields highly stable plasma levels. These features may explain the clinically observed low frequency of extrapyramidal side effects, including tardive dyskinesia. In contrast to most antipsychotics, sertindole seems to be void of sedative effects. However, although not strictly proven by objective neuropsychological tests, this asset of sertindole does not add to the cognitive problems inherent in schizophrenia. Administration of sertindole is more often associated with prolongation of QTc compared with most other currently used antipsychotics. However, large cohort analyses do not suggest that all-cause mortality is higher with sertindole than with, for example, risperidone or olanzapine. The effective antipsychotic dose range of sertindole is 12 – 20 mg/day, with small variations among patients. The frequency of most adverse events, for example extrapyramidal symptoms and somnolence, with such a dose does not differ from placebo. Three side effects have been more common than with placebo/haloperidol in short-term studies: weight gain, rinithis and a decreased ejaculation volume. Two head-to-head comparisons (one in treatment-resistant patients) of sertindole and risperidone showed equivalent effects on positive symptoms. For negative symptoms, one study obtained equivalent effects and one a superior effect of sertindole. Sertindole should not be used as first-line treatment for first-episode patients with schizophrenia because of the QTc prolongation. It has a side-effect profile that makes it an interesting alternative for many patients who do not respond well to the initial choice of antipsychotic drug.

Neighbourhood non-employment and daily smoking: a population-based study of women and men in Sweden

To examine whether neighbourhood non-employment is associated with daily smoking after adjustment for individual characteristics, such as employment status. Cross-sectional study of a simple, random sample of 31,164 women and men aged 25-64, representative of the entire population in Sweden. Data were collected from the years 1993-2000. The individual variables included age, sex, employment status, occupation and housing tenure. Logistic regression was used in the analysis with neighbourhood non-employment rates measured at small area market statistics level. There was a significant association between neighbourhood non-employment rates and daily smoking for both women and men. After adjustment for employment status and housing tenure the odds ratios of daily smoking were 1.39 (95% CI = 1.22-1.58) for women and 1.41 (95% CI = 1.23-1.61) for men living in neighbourhoods with the highest non-employment rates. The individual variables of unemployment, low occupational level and renting were associated with daily smoking. Neighbourhood non-employment is associated with daily smoking. Smoking prevention in primary health care should address both individuals and neighbourhoods.

Lower levels of occupation, income and education are strongly associated with a longer smoking duration: Multivariate results from the 2001 Australian National Drug Strategy Survey

Our aim was to investigate the association of socio-economic status (SES) with duration of smoking among ever smokers. We used a subsample of ever smokers (n = 9973) aged 18+ years from the 2001 National Drug Strategy Household Survey (conducted by the Australian Institute of Health and Welfare), which involved a multistage area sample and mainly self-administered questionnaires. The outcome was smoking duration from onset to cessation. We used survival analysis to predict smoking duration. Results showed that smoking duration from onset to cessation was 14% longer for blue-collar workers than for professionals. Respondents who earned under 300 US dollars/week smoked for 38% longer than those earning 800 US dollars+/week. Individuals with less than 10 years of education smoked for 13% longer than those with 12+ years of education. Smokers from lower social strata smoke for much longer durations. This finding and the fact that smoking increases the likelihood of financial stress suggest that lower SES smokers who experience financial stress are more likely to suffer a longer period of compromised living standards than their counterparts in the higher strata. The financial and health burdens of smoking coupled with social inequalities in smoking behaviour suggest that smoking may exacerbate social class differences in health and standards of living. Thus, targeting smoking among disadvantaged groups would not only represent a public health policy but also a social policy to reduce social inequalities.

Low socioeconomic status is associated with chronic musculoskeletal complaints among 46,901 adults in Norway

A study was undertaken to evaluate the relationship between socioeconomic status (SES) and chronic musculoskeletal complaints (MSC), and to determine how this relationship is influenced by change in SES. Two consecutive public health surveys within the county of Nord-Trøndelag, Norway, were conducted in 1984-86 (HUNT-1) and 1995-97 (HUNT-2). Among 46,901 adults who participated in both surveys, 24,127 persons (51%) in HUNT-2 who reported MSC continuously for at least 3 months during the past year were defined as having chronic MSC. Prevalence of chronic MSC was estimated at nine anatomical sites using multiple logistic regression with odds ratio (OR) and 95% confidence interval (CI) as measures of association with SES. When defining SES by educational level, type of occupation, or income, low status was associated with increased prevalence of chronic MSC (age-adjusted analyses). The negative influence of low education or low occupation level was not eliminated by increasing the level of education or occupation from HUNT-1 to HUNT-2, in contrast with what was found for individuals with higher income level in HUNT-2 than in HUNT-1. The relationship with SES was more evident among individuals with musculoskeletal symptoms 15 days during the past month than among those with less than 15 days, evident at all nine different anatomical sites. The strongest relationship was found between low SES and prevalence of widespread chronic MSC. Individuals with low SES had higher prevalence of chronic MSC than those with high SES. Future studies should try to clarify whether chronic MSC are a cause or consequence of low SES.

Single-molecule studies of repressor–DNA interactions show long-range interactions

We have performed single-molecule studies of GFP-LacI repressor proteins bound to bacteriophage lambda DNA containing a 256 tandem lac operator insertion confined in nanochannels. An integrated photon molecular counting method was developed to determine the number of proteins bound to DNA. By using this method, we determined the saturated mean occupancy of the 256 tandem lac operators to be 13, which constitutes only 2.5% of the available sites. This low occupancy level suggests that the repressors influence each other even when they are widely separated, at distances on the order of 200 nm, or several DNA persistence lengths.

The Long-Term Labor Market Consequences of Graduating from College in a Bad Economy

This paper studies the labor market experiences of white male college graduates as a function of economic conditions at time of college graduation. I use the National Longitudinal Survey of Youth whose respondents graduated college between 1979 and 1988 and are followed for 14 to 23 years after college graduation. I employ both national and state variation in economic conditions at time of college graduation to identify the effect. Because timing and location of college graduation could potentially be affected by economic conditions, I also instrument for the national unemployment rate usinf year of birth and for the state unemployment rate using year of birth and state of residence at age 14. I find large, negative wage effects to graduating in a worse economy which persist for the entire period studied. I find that cohorts who graduate in worse economies are in lower level occupations and have slightly higher educational attainment. Labor supply is unaffected.

Social consequences in adult life of end-stage renal disease in childhood

To describe employment achievement and social independence of adults with childhood end-stage renal disease (ESRD) and to explore determining factors. Employment, occupational level, living arrangements, social engagements, and subjective health perception were cross-sectionally established between 1998 and 2000 in 144 of all living 187 adult Dutch patients with ESRD with an onset at age 0 to 15 years between 1972 and 1992. Potential clinical determinants were established by means of a review of all medical charts. Compared with age-matched Dutch citizens, patients were more often involuntarily unemployed (19.4% vs 11.1%), had a lower occupational level, more often still lived with their parents, and more often had no partner. A low occupational level was associated with a dialysis duration >8 years (OR, 9.6; 95% CI, 1.9-47.6); living at the parental home was associated with the male sex (OR, 3.4; 95% CI, 1.5-7.8) and with a dialysis duration >8 years (OR, 3.7; 95% CI, 1.3-10.2). Prolonged dialysis during childhood may decrease the ability to gain high-skilled professions and social independence. Unemployment is twice as high in adult patients with childhood ESRD than in healthy persons, but more than twice as low as compared with young ESRD patients with an adult onset of the disease, according to previous reports.

Anxiogenic properties of an inverse agonist selective for α3 subunit‐containing GABAA receptors

Alpha3IA (6-(4-pyridyl)-5-(4-methoxyphenyl)-3-carbomethoxy-1-methyl-1H-pyridin-2-one) is a pyridone with higher binding and functional affinity and greater inverse agonist efficacy for GABA(A) receptors containing an alpha3 rather than an alpha1, alpha2 or alpha5 subunit. If doses are selected that minimise the occupancy at these latter subtypes, then the in vivo effects of alpha3IA are most probably mediated by the alpha3 subtype. Alpha3IA has good CNS penetration in rats and mice as measured using a [(3)H]Ro 15-1788 in vivo binding assay. At doses in rats that produce relatively low levels of occupancy (12%) in the cerebellum (i.e. alpha1-containing receptors), alpha3IA (30 mg kg(-1) i.p.), like the nonselective partial inverse agonist N-methyl-beta-carboline-3-carboxamide (FG 7142), not only caused behavioural disruption in an operant, chain-pulling assay but was also anxiogenic in the elevated plus maze, an anxiogenic-like effect that could be blocked with the benzodiazepine antagonist Ro 15-1788 (flumazenil). Neurochemically, alpha3IA (30 mg kg(-1) i.p.) as well as FG 7142 (15 mg kg(-1) i.p.) increased the concentration of the dopamine metabolite 3,4-dihydroxyphenylacetic acid in rat medial prefrontal cortex by 74 and 68%, respectively, relative to vehicle-treated animals, a response that mimicked that seen following immobilisation stress. Taken together, these data demonstrate that an inverse agonist selective for GABA(A) receptors containing an alpha3 subunit is anxiogenic, and suggest that since alpha3-containing GABA(A) receptors play a role in anxiety, then agonists selective for this subtype should be anxiolytic.

The role of psychosocial factors in explaining socio-economic differences in mobility decline in a chronically ill population: results from the GLOBE study

In chronically ill patients, mobility develops more unfavorably in persons with low socio-economic status (SES) than in their better-off counterparts. Using longitudinal data from the Dutch GLOBE study (a study of health and living conditions in Eindhoven and its surroundings), the present study examines whether psychosocial factors can explain socio-economic differences in mobility decline, independent of disease severity, co-morbidity, and health-related behavior in a chronically ill population. Data were from 1384 men and woman, aged 15–74 years, suffering from at least one of the four chronic diseases: asthma/COPD, heart disease, diabetes mellitus, and low back pain. Three indicators of SES were used: education, occupational class, and income. Change in physical mobility between 1991 and 1997 was measured with the Nottingham Health Profile (NHP). Psychosocial factors were measured extensively and included life events, long-term difficulties, coping styles, social support, and personality characteristics. Low occupational level and low income predicted an increased risk of mobility decline in comparison to people with a higher occupational level and income, even after controlling for sociodemographics, disease severity, co-morbidity, and health-related behavior. Additional adjustment for psychosocial factors hardly reduced the SES-related odds ratios of mobility decline. We conclude that psychosocial factors (and also health-related behaviors, disease severity and co-morbidity) cannot explain socio-economic differences in mobility decline in a chronically ill population. Our findings will not give us new tools for prevention and intervention strategies in order to reduce physical disability and particularly the SES differences therein.

Oral health-related knowledge, attitudes, and beliefs among 11 to 12-year-old Finnish schoolchildren with different oral health behaviors

The aim of this study was to explore oral health-related knowledge, attitudes, and beliefs among 11 to 12-year-old schoolchildren with favorable, moderate, or poor behavior related to oral health. The data were gathered by questionnaire. Recommendations commonly used in Finland in oral health education were chosen as the criteria for selection of groups of children with favorable, moderate, and poor oral health behavior. Differences between groups were analyzed using cross-tabulations and factors related to unfavorable behavior using logistic regression analysis. The percentage of children with appropriate knowledge was higher in the good behavior group (GB) than in the other groups. The groups differed most in the children's knowledge of the recommendation to use fluoride toothpaste at least twice a day. Most children in the GB group considered it important to brush their teeth for the fresh feeling this gave. The majority of children in all groups considered it important to brush their teeth when going to the dentist. The majority also considered brushing important for avoiding tooth decay and tooth discoloration as well as for having fresh breath. Unfavorable knowledge, attitudes, beliefs, and behavior tended to accumulate in the same children. Factors associated with unfavorable behavior were male sex, mother's low skill occupation level, and child's poor knowledge of oral health-related facts.

Chemoattractant Signals and β2 Integrin Occupancy at Apical Endothelial Contacts Combine with Shear Stress Signals to Promote Transendothelial Neutrophil Migration

Lymphocyte transendothelial migration (TEM) is promoted by fluid shear signals and apical endothelial chemokines. Studying the role of these signals in neutrophil migration across differently activated HUVEC in a flow chamber apparatus, we gained new insights into how neutrophils integrate multiple endothelial signals to promote TEM. Neutrophils crossed highly activated HUVEC in a beta(2) integrin-dependent manner but independently of shear. In contrast, neutrophil migration across resting or moderately activated endothelium with low-level beta(2) integrin ligand activity was dramatically augmented by endothelial-presented chemoattractants, conditional to application of physiological shear stresses and intact beta(2) integrins. Shear stress signals were found to stimulate extensive neutrophil invaginations into the apical endothelial interface both before and during TEM. A subset of invaginating neutrophils completed transcellular diapedesis through individual endothelial cells within <1 min. Our results suggest that low-level occupancy of beta(2) integrins by adherent neutrophils can mediate TEM only if properly coupled to stimulatory shear stress and chemoattractant signals transduced at the apical neutrophil-endothelial interface.

Using [11C]diprenorphine to image opioid receptor occupancy by methadone in opioid addiction: clinical and preclinical studies.

Substitute methadone prescribing is one of the main modes of treatment for opioid dependence with established evidence for improved health and social outcomes. However, the pharmacology underpinning the effects of methadone is little studied despite controversies about dosing in relation to outcome. We therefore examined the relationship between methadone dose and occupation of opioid receptors in brain using the positron emission tomography (PET) radioligand [(11)C]diprenorphine in humans and rats. Eight opioid-dependent subjects stable on their substitute methadone (18-90 mg daily) had an [(11)C]diprenorphine PET scan at predicted peak plasma levels of methadone. These were compared with eight healthy controls. No difference in [(11)C]diprenorphine binding was found between the groups, with no relationship between methadone dose and occupancy. Adult male Sprague-Dawley rats that had been given an acute i.v. injection of methadone hydrochloride (0.35, 0.5, 0.7, or 1.0 mg kg(-1)) before [(11)C]diprenorphine showed a dose-dependent increase in biodistribution but no reduction in [(11)C]diprenorphine binding. We suggest that the lack of a dose-dependent relationship between methadone dose, either given chronically in human or acutely in rat, and occupancy of opioid receptor measured with [(11)C]diprenorphine PET is related to efficacy of this opioid agonist at very low levels of opioid receptor occupancy. This has implications for understanding the actions of methadone in comparison with other opioid drugs such as partial agonists and antagonists.

Measurement of the affinity and cooperativity of annexin V–membrane binding under conditions of low membrane occupancy

We developed a method for measuring the binding affinity of annexin V for phospholipid vesicles and cells at very low levels of membrane occupancy. The annexin V-117 mutant was labeled with fluorescein iodoacetamide on its single N-terminal cysteine residue; binding to phospholipid vesicles containing phosphatidylserine (PS) and 2% rhodamine–phosphatidylethanolamine was measured by fluorescence quenching due to resonance energy transfer; binding to cells with exposed PS was measured by fluorometry after elution of bound protein. The equilibrium constant was calculated as a function of the midpoint of the calcium titration curve, the Hill coefficient, and the concentration of membrane binding sites. Calcium titrations at very low ratios of protein to membrane revealed Hill coefficients of approximately 8 for both vesicles and cells, far higher than previously measured, but as the protein–membrane ratio was increased above 3% of maximum membrane occupancy, the value of the Hill coefficient progressively decreased to a limiting value of about 2. High Hill coefficients were also observed for measurements performed at different ionic strengths and with membrane PS content varied over the range from 20 to 50%. This method allows the accurate determination of the affinity and cooperativity of annexin V–membrane binding and will be useful for the evaluation of modified annexin V derivatives intended for diagnostic and therapeutic applications.

What types of home are closing? The characteristics of homes which closed between 1996 and 2001

Closures of care homes have received considerable public attention. Fee levels and the cost of upgrading homes to meet the national minimum standards have been identified as the main factors influencing closures. The present paper compares private residential homes, dual-registered homes and nursing homes for older people which have closed between 1996 and 2001 with homes which have remained open. Homes which closed tended to be: smaller; to have had lower occupancy levels in 1996; to be the only home run by the organisation; to occupy converted buildings; to occupy multi-storey buildings, and if so, to have no lift; to have more shared bedrooms; and to have en suite facilities in none or only some of the bedrooms. These factors were interrelated and the effect of these variables in combination was examined using multivariate (logistic regression) analysis. Among the homes which remained open, only 34% provided at least 80% of places in single rooms, which was to have become the national minimum standard for existing homes until the standards were amended in March 2003. A separate analysis of data on social climate found that the homes with a more positive social environment were those most likely to have closed. The findings support the view that there is likely to be an increase in the importance of homes run by corporate providers relative to homes run as single, owner-managed homes, with a consequent reduction in choice for potential residents. At the same time, projections of future demand in a range of countries indicate that a considerable increase in provision will be required to meet the expected growth in the population of dependent older people, while developments in alternative forms of accommodation are unlikely to meet the growth in demand in the foreseeable future.

Widening socioeconomic inequalities in mortality in six Western European countries.

During the past decades a widening of the relative gap in death rates between upper and lower socioeconomic groups has been reported for several European countries. Although differential mortality decline for cardiovascular diseases has been suggested as an important contributory factor, it is not known what its quantitative contribution was, and to what extent other causes of death have contributed to the widening gap in total mortality. We collected data on mortality by educational level and occupational class among men and women from national longitudinal studies in Finland, Sweden, Norway, Denmark, England/Wales, and Italy (Turin), and analysed age-standardized death rates in two recent time periods (1981-1985 and 1991-1995), both total mortality and by cause of death. For simplicity, we report on inequalities in mortality between two broad socioeconomic groups (high and low educational level, non-manual and manual occupations). Relative inequalities in total mortality have increased in all six countries, but absolute differences in total mortality were fairly stable, with the exception of Finland where an increase occurred. In most countries, mortality from cardiovascular diseases declined proportionally faster in the upper socioeconomic groups. The exception is Italy (Turin) where the reverse occurred. In all countries with the exception of Italy (Turin), changes in cardiovascular disease mortality contributed about half of the widening relative gap for total mortality. Other causes also made important contributions to the widening gap in total mortality. For these causes, widening inequalities were sometimes due to increasing mortality rates in the lower socioeconomic groups. We found rising rates of mortality from lung cancer, breast cancer, respiratory disease, gastrointestinal disease, and injuries among men and/or women in lower socioeconomic groups in several countries. Reducing socioeconomic inequalities in mortality in Western Europe critically depends upon speeding up mortality declines from cardiovascular diseases in lower socioeconomic groups, and countering mortality increases from several other causes of death in lower socioeconomic groups.

Feedback inhibition by RALT controls signal output by the ErbB network.

The ErbB-2 interacting protein receptor-associated late transducer (RALT) was previously identified as a feedback inhibitor of ErbB-2 mitogenic signals. We now report that RALT binds to ligand-activated epidermal growth factor receptor (EGFR), ErbB-4 and ErbB-2.ErbB-3 dimers. When ectopically expressed in 32D cells reconstituted with the above ErbB receptor tyrosine kinases (RTKs) RALT behaved as a pan-ErbB inhibitor. Importantly, when tested in either cell proliferation assays or biochemical experiments measuring activation of ERK and AKT, RALT affected the signalling activity of distinct ErbB dimers with different relative potencies. RALT deltaEBR, a mutant unable to bind to ErbB RTKs, did not inhibit ErbB-dependent activation of ERK and AKT, consistent with RALT exerting its suppressive activity towards these pathways at a receptor-proximal level. Remarkably, RALT deltaEBR retained the ability to suppress largely the proliferative activity of ErbB-2.ErbB-3 dimers over a wide range of ligand concentrations, indicating that RALT can intercept ErbB-2.ErbB-3 mitogenic signals also at a receptor-distal level. A suppressive function of RALT deltaEBR towards the mitogenic activity of EGFR and ErbB-4 was detected at low levels of receptor occupancy, but was completely overcome by saturating concentrations of ligand. We propose that quantitative and qualitative aspects of RALT signalling concur in defining identity, strength and duration of signals generated by the ErbB network.

Application of a Latent Variable Model for a Multicenter Study on Early Effects Due to Mercury Exposure

A latent variable model was applied to the results of an Italian multicenter nation-wide cross-sectional study to assess the earliest health effects due to mercury (Hg) exposure caused by occupation, dental amalgams (DENTAM) and fish eating (FISH). The studied population included subjects recruited from four different geographical areas. A total number of 122 workers from chloroalkali plants and production of thermometers and neon lamps formed the occupationally exposed group, whereas 196 subjects, recruited from the same areas and not occupationally exposed to mercury, formed the control group. Neuropsychological functions were assessed with neurobehavioral testing including vigilance, motor and cognitive function, tremor measurements, and with symptoms concerning neuropsychological and mood assessment. Neuroendocrine function was examined with the measurement of prolactin (PRL) level. Parameters of immunological and renal function were also measured. The target population was characterized by the number and surface of dental amalgams and consumption of fish. In the exposed workers the average urinary mercury (U-Hg) was 10.4±6.9 (geometric mean 8.3, range 0.2–35.2) μg/g creatinine, whereas in the control group it was 1.9±2.8 (geometric mean 1.2, range 0.1–33.2) μg/g creatinine. The preliminary results indicated that finger tapping (FT) and the Branches alternate movement task (BAMT) coordination test were associated with the occupational exposure (OCCEXP). PRL was significantly decreased among the exposed workers, and inversely related to U-Hg. Among the immunological and renal parameters, cytokine serum interleuchin-8 (sIL8) and β 2 micro globulin (β 2MG) were lower in the exposed group and negatively correlated to U-Hg. Small-size fish consumption was associated to a beneficial effect on symptoms reporting. No effects were observed concerning dental amalgams. After first evaluating the relationship between mercury exposure and each indicator of effect, further assessment was performed to identify the earliest effects related to mercury exposure among those who resulted in being associated in the preliminary elaboration. Two latent variables “exposure” and “effect” were identified, integrating respectively the different forms of exposure (occupational, due to dental amalgams and fish consumption) and the indicators of effects (FT, BAMT, PRL, sIL8, β 2MG). Confounding factors (age, alcohol, body mass index (BMI)) were considered in the same model. This further analysis showed that an inverse association of occupational exposure to mercury with PRL and BAMT, with Hg-U mediating the effect on PRL, was predominant with respect to the other form of mercury exposure, the other indicators of effect and the confounders. In conclusion, this study supports the finding of alterations of neuroendocrine secretion and motor coordination at very low occupational exposure levels of inorganic mercury, below the current ACGIH Biological Exposure Index. These changes occur at lower levels than other subtle effects on the renal function and the immunitary system. On the contrary, dental amalgams and small-size fish consumption do not seem to be associated to any adverse health effect at these exposure levels.

Comment — Economics of a nest-box program for the conservation of an endangered species: a re-appraisal

Spring et al. (D.A. Spring, M. Bevers, J.O.S. Kennedy, and D. Harley. 2001. Can. J. For. Res. 31: 1992–2003) recently published a paper on the economics of a nest-box program for the endangered arboreal marsupial, Leadbeater's possum (Gymnobelideus leadbeateri) in southeastern Australian forests. While their paper is a useful one, there are some important limitations of nest-box programs that need to be highlighted. In the case of Leadbeater's possum, we have undertaken extensive nest-box studies in Victoria mountain ash (Eucalyptus regnans F. Muell.) forests, where the vast majority of populations of the species now occur. Although large numbers of nest boxes have been deployed, very few have actually been occupied, which is a major problem since the effectiveness of any nest-box program will depend on patterns of use by the target species. Given very low levels of nest-box occupancy, harvesting regimes such as those that lead to on-site tree retention are needed to better conserve hollow-dependent species like Leadbeater's possum. Moreover, the need for nest boxes in the first place indicates that logging practices are presently not ecologically sustainable, and modified forestry practices need to be adopted.