Development of the MapMe intervention body image scales of known weight status for 4-5 and 10-11 year old children

Background

Parents tend to visually assess children to determine their weight status and typically underestimate child body size. A visual tool may aid parents to more accurately assess child weight status and so support strategies to reduce childhood overweight. Body image scales (BIS) are visual images of people ranging from underweight to overweight but none exist for children based on UK criteria. Our aim was to develop sex- and age-specific BIS for children, based on British growth reference (UK90) criteria.

Methods

BIS were developed using 3D surface body scans of children, their associated weight status using UK90 criteria from height and weight measurements, and qualitative work with parents and health professionals.

Results

Height, weight and 3D body scans were collected (211: 4–5 years; 177: 10–11 years). Overall, 12 qualitative sessions were held with 37 participants. Four BIS (4–5-year-old girls and boys, 10–11-year-old girls and boys) were developed.

Conclusions

This study has created the first sex- and age-specific BIS, based on UK90 criteria. The BIS have potential for use in child overweight prevention and management strategies, and in future research. This study also provides a protocol for the development of further BIS appropriate to other age groups and ethnicities.

Concentration-dependent Toxicity after Subcutaneous Administration of Meloxicam to C57BL/6N Mice (Mus musculus)

Studies using the Mouse Grimace Scale have shown that for many NSAID, including meloxicam, minimal doses of at least 20 mg/kg may be necessary to achieve adequate peri- and post-operative analgesia in mice. However, more data are needed to determine whether such NSAID doses exceed the threshold for gastrointestinal ulceration or induce other relevant pathology. We administered equal volumes of saline or injectable meloxicam (1 or 5 mg/mL) at a dose of 20 mg/kg SC to 20 young adult male and female C57BL/6N mice daily for 6 d and performed necropsies on all mice on the seventh day. Mice given 5 mg/mL meloxicam subcutaneously developed significantly more severe pathology at the injection site than saline controls. Pathology was characterized by full-thickness epidermal necrosis; cavitary lesions within subcutis, muscle, or fat; steatitis; and myositis. Mice that received 1 mg/mL meloxicam subcutaneously developed lesions that were qualitatively similar but far less severe than those after 5 mg/mL. However, no pathologic lesions typically associated with NSAID toxicity, such as gastric ulceration and liver and kidney lesions, were seen. These results demonstrate that although meloxicam injected subcutaneously causes concentration-dependent skin pathology at the injection site, a dose of 20 mg/kg can be safely administered subcutaneously at a concentration of 1 mg/mL for as long as 6 d.

Whole-genome sequencing reveals clinically relevant insights into the aetiology of familial breast cancers

BACKGROUND

Whole-genome sequencing (WGS) is a powerful method for revealing the diversity and complexity of the somatic mutation burden of tumours. Here, we investigated the utility of tumour and matched germline WGS for understanding aetiology and treatment opportunities for high-risk individuals with familial breast cancer.

PATIENTS AND METHODS

We carried out WGS on 78 paired germline and tumour DNA samples from individuals carrying pathogenic variants in BRCA1 (n = 26) or BRCA2 (n = 22) or from non-carriers (non-BRCA1/2; n = 30).

RESULTS

Matched germline/tumour WGS and somatic mutational signature analysis revealed patients with unreported, dual pathogenic germline variants in cancer risk genes (BRCA1/BRCA2; BRCA1/MUTYH). The strategy identified that 100% of tumours from BRCA1 carriers and 91% of tumours from BRCA2 carriers exhibited biallelic inactivation of the respective gene, together with somatic mutational signatures suggestive of a functional deficiency in homologous recombination. A set of non-BRCA1/2 tumours also had somatic signatures indicative of BRCA-deficiency, including tumours with BRCA1 promoter methylation, and tumours from carriers of a PALB2 pathogenic germline variant and a BRCA2 variant of uncertain significance. A subset of 13 non-BRCA1/2 tumours from early onset cases were BRCA-proficient, yet displayed complex clustered structural rearrangements associated with the amplification of oncogenes and pathogenic germline variants in TP53, ATM and CHEK2.

CONCLUSIONS

Our study highlights the role that WGS of matched germline/tumour DNA and the somatic mutational signatures can play in the discovery of pathogenic germline variants and for providing supporting evidence for variant pathogenicity. WGS-derived signatures were more robust than germline status and other genomic predictors of homologous recombination deficiency, thus impacting the selection of platinum-based or PARP inhibitor therapy. In this first examination of non-BRCA1/2 tumours by WGS, we illustrate the considerable heterogeneity of these tumour genomes and highlight that complex genomic rearrangements may drive tumourigenesis in a subset of cases.

Depth perception in disparity-defined objects: finding the balance between averaging and segregation

Deciding what constitutes an object, and what background, is an essential task for the visual system. This presents a conundrum: averaging over the visual scene is required to obtain a precise signal for object segregation, but segregation is required to define the region over which averaging should take place. Depth, obtained via binocular disparity (the differences between two eyes’ views), could help with segregation by enabling identification of object and background via differences in depth. Here, we explore depth perception in disparity-defined objects. We show that a simple object segregation rule, followed by averaging over that segregated area, can account for depth estimation errors. To do this, we compared objects with smoothly varying depth edges to those with sharp depth edges, and found that perceived peak depth was reduced for the former. A computational model used a rule based on object shape to segregate and average over a central portion of the object, and was able to emulate the reduction in perceived depth. We also demonstrated that the segregated area is not predefined but is dependent on the object shape. We discuss how this segregation strategy could be employed by animals seeking to deter binocular predators.

This article is part of the themed issue ‘Vision in our three-dimensional world’.

Mistaken Identity: Temporal-Order Biases in the Perception of Speed

Biases in the perceived speed of a moving stimulus have been observed for various spatial configurations of a motion stimulus (eg Norman et al, 1996 Perception25 815 – 830). In general, psychophysical studies are designed to remove any possible source of bias due to the temporal order of presentation. Here, we examined biases in speed perception between the first and second temporal interval in a 2IFC procedure. The stimulus was a circular patch (∼ 2 deg) containing 50 translating dots. A standard speed was always presented in the first interval (∼ 6 deg s−1), with one of 7 test speeds in the second interval. A range of ISIs (0 – 2.3 s) and stimulus durations (100 – 900 ms) was tested. We also dissociated spatial location (left/right of fixation point) and direction of dot travel (left/right and vertical/horizontal) of the two stimuli, whilst maintaining the temporal separation.

In all cases we found an increase in perceived speed from 1st to 2nd interval and further, the effect was independent of direction, ISI, duration, and the spatial position of the 1st and 2nd stimuli. We can suggest no simple account of the results based upon neural fatigue in motion detectors, temporal sampling windows, or representational momentum. Tentative models are currently being explored with three interval stimuli.

Women and their birth partners' experiences following a primary postpartum haemorrhage: a qualitative study

Background

Postpartum haemorrhage (PPH) is a common obstetric complication. Rates of PPH are increasing in a number of developed countries. This is concerning as PPH is recognised as a leading cause of maternal morbidity and mortality which includes psychological and emotional distress. There is limited understanding of the emotional impact of PPH experienced by women and their birth partners. This study qualitatively describes the experiences of women and their birth partners who experienced a primary PPH.

Methods

Semi-structured interview study. Couples were recruited via maximum variation sampling, which, by purposive sampling drew participants from three groups depending on the degree of PPH: minor (500–1000 ml), moderate (1000–2000 ml) and severe (>2000 ml). Interviews took place from 4 to 14 months post birth, and data were analysed via Framework analysis.

Results

In this qualitative study, 11 women and six partners were interviewed. Data were organised into four interrelated themes; Control, Communication, Consequence, Competence. Just over half of the women and their birth partners were unaware they had a PPH, and would have preferred more information either at the time or in the postnatal period. The findings suggest that birth partners also required more information, especially if separated from their partner during the PPH.

Conclusions

This study provides valuable insights into women’s reports of their feelings and experiences during and after a PPH, and how their partners feel having observed a PPH. This study suggests that women who have had a PPH of any volume would like more information. Further investigations into the timings, methods and effectiveness of discussions following a PPH are recommended.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-016-0870-7) contains supplementary material, which is available to authorized users.

Genome-wide association study of lifetime cannabis use based on a large meta-analytic sample of 32 330 subjects from the International Cannabis Consortium

Cannabis is the most widely produced and consumed illicit psychoactive substance worldwide. Occasional cannabis use can progress to frequent use, abuse and dependence with all known adverse physical, psychological and social consequences. Individual differences in cannabis initiation are heritable (40-48%). The International Cannabis Consortium was established with the aim to identify genetic risk variants of cannabis use. We conducted a meta-analysis of genome-wide association data of 13 cohorts (N=32 330) and four replication samples (N=5627). In addition, we performed a gene-based test of association, estimated single-nucleotide polymorphism (SNP)-based heritability and explored the genetic correlation between lifetime cannabis use and cigarette use using LD score regression. No individual SNPs reached genome-wide significance. Nonetheless, gene-based tests identified four genes significantly associated with lifetime cannabis use: NCAM1, CADM2, SCOC and KCNT2. Previous studies reported associations of NCAM1 with cigarette smoking and other substance use, and those of CADM2 with body mass index, processing speed and autism disorders, which are phenotypes previously reported to be associated with cannabis use. Furthermore, we showed that, combined across the genome, all common SNPs explained 13-20% (P<0.001) of the liability of lifetime cannabis use. Finally, there was a strong genetic correlation (rg=0.83; P=1.85 × 10(-8)) between lifetime cannabis use and lifetime cigarette smoking implying that the SNP effect sizes of the two traits are highly correlated. This is the largest meta-analysis of cannabis GWA studies to date, revealing important new insights into the genetic pathways of lifetime cannabis use. Future functional studies should explore the impact of the identified genes on the biological mechanisms of cannabis use.

The effects of lebrikizumab in patients with mild asthma following whole lung allergen challenge

Background

Interleukin 13 (IL13) is a T-helper type 2 (Th2) cytokine associated with inflammation and pathology in allergic diseases such as bronchial asthma. We have shown that treatment with lebrikizumab, an anti-IL13 monoclonal antibody, significantly improves prebronchodilator forced expiratory volume in 1 s (FEV₁) in a subset of subjects with uncontrolled asthma.

Objective

To evaluate efficacy and safety of lebrikizumab in subjects with mild asthma who underwent bronchial allergen challenge.

Methods

Twenty-nine subjects were randomized 1: 1–5 mg/kg lebrikizumab (n = 13) or placebo (n = 16) administered subcutaneously every 4 weeks over 12 weeks, a total of four doses. Primary efficacy outcome was late asthmatic response (LAR) at Week 13, defined as area under the curve of FEV₁ measured 2–8 h following inhaled allergen challenge. Serum biomarkers were measured to verify IL13 pathway inhibition and identify patients with an increased response to lebrikizumab.

Results

At Week 13, the LAR in lebrikizumab subjects was reduced by 48% compared with placebo subjects, although this was not statistically significant (95% confidence interval, −19%, 90%). Exploratory analysis indicated that lebrikizumab-treated subjects with elevated baseline levels of peripheral blood eosinophils, serum IgE, or periostin exhibited a greater reduction in LAR compared with subjects with lower baseline levels of these biomarkers. Lebrikizumab exerted systemic effects on markers of Th2 inflammation, reducing serum immunoglobulin E (IgE), chemokine ligands 13 and 17 by approximately 25% (P < 0.01). Lebrikizumab was well tolerated.

Conclusion and Clinical Relevance

Lebrikizumab reduced the LAR in subjects with mild asthma. Clinical trial number NCT00781443.

Rat-specific IgG and IgG₄ antibodies associated with inhibition of IgE-allergen complex binding in laboratory animal workers

OBJECTIVES

The relationship between exposure to rodent allergens and laboratory animal allergy is complex; at highest allergen exposures there is an attenuation of sensitisation and symptoms which are associated with increased levels of rat-specific immunoglobulin (Ig)G and IgG4 antibodies. We set out to examine whether the increased levels of rat-specific IgG and IgG4 antibodies that we have previously observed at high allergen exposure in our cohort of laboratory animal workers play a functional role through blockage of the binding of IgE-allergen complex binding to CD23 receptors on B cells.

METHODS

Cross-sectional survey of laboratory animal workers (n=776) in six UK pharmaceutical companies were surveyed. IgE-allergen complex binding to B cells was measured in 703 (97.9%) eligible employees; their exposure was categorised by either job group or number of rats handled daily.

RESULTS

We observed a significant decrease in IgE-allergen complex binding to B cells with increasing quartiles of both rat-specific IgG and IgG4 antibodies (p<0.001). IgE-allergen complex binding to B cells was lower in workers with high allergen exposure, and significantly so (p=0.033) in the subgroup with highest exposures but no work-related chest symptoms.

CONCLUSIONS

These findings demonstrate a functional role for rat-specific IgG/G4 antibodies in laboratory animal workers, similar to that observed in patients treated with high dose immunotherapy who become clinically tolerant, suggesting a potential explanation for the attenuation of risk at highest allergen exposures.

Fluorescence correlation spectroscopy with patterned photoexcitation for measuring solution diffusion coefficients of robust fluorophores

Patterned fluorescence correlation spectroscopy is developed as a new technique for measuring diffusion coefficients of photostable fluorescent probe molecules. In this method, interference between two intersecting, coherent laser beams creates an excitation fringe pattern from which fluorescence emission is monitored. Spontaneous concentration fluctuations of fluorescent molecules within the excitation volume are detected as excess noise on a fluorescence transient; concentration fluctuations are driven primarily by diffusion of these molecules between interference fringes although contributions from photobleaching and diffusion over the entire pattern dimensions can also be observed. Autocorrelation of the fluorescence transient allows analysis of the temporal characteristics of the fluctuations, which were used to determine solution diffusion coefficients; the method was applied to study the diffusion of Rhodamine 6G (R6G) in water/methanol solutions containing added electrolyte and in pure ethanol. The method can be used to characterize the diffusive transport of fluorescently labeled species, which is an important issue in designing small-volume detection experiments.

Identification of a novel prostate cancer susceptibility variant in the KLK3 gene transcript

Genome-wide association studies (GWAS) have identified more than 30 prostate cancer (PrCa) susceptibility loci. One of these (rs2735839) is located close to a plausible candidate susceptibility gene, KLK3, which encodes prostate-specific antigen (PSA). PSA is widely used as a biomarker for PrCa detection and disease monitoring. To refine the association between PrCa and variants in this region, we used genotyping data from a two-stage GWAS using samples from the UK and Australia, and the Cancer Genetic Markers of Susceptibility (CGEMS) study. Genotypes were imputed for 197 and 312 single nucleotide polymorphisms (SNPs) from HapMap2 and the 1000 Genome Project, respectively. The most significant association with PrCa was with a previously unidentified SNP, rs17632542 (combined P = 3.9 × 10⁻²²). This association was confirmed by direct genotyping in three stages of the UK/Australian GWAS, involving 10,405 cases and 10,681 controls (combined P = 1.9 × 10⁻³⁴). rs17632542 is also shown to be associated with PSA levels and it is a non-synonymous coding SNP (Ile179Thr) in KLK3. Using molecular dynamic simulation, we showed evidence that this variant has the potential to introduce alterations in the protein or affect RNA splicing. We propose that rs17632542 may directly influence PrCa risk.

How Do Reliability and Timing Influence Cue-Combinations for Shading and Stereo-Disparity?

Cue-conflict studies have been used with considerable success to examine the mechanisms underlying the integration of different sensory cues. Our recent studies have used these methods to examine the combination of stereo-disparity and shading cues in realistically rendered stimuli. The stimuli featured circular convexities with cyclopean shading and a stereo-cue based upon a densely dotted surface texture—other cues (shape outline and surface texture gradient) were controlled for. In our first experiment observers made depth discriminations while disparity noise was manipulated; we were able to demonstrate that for most observers cues are combined optimally—ie, PSEs and response variances shifted towards the more reliable channel. In a follow-on study we have examined how these cue-combinations are affected by presentation timing—with forwards and backwards masking. For most observers the adage that shading provides a quick and dirty mechanism for making depth judgements seems to be supported. Observers can make reliable depth judgements based upon shading when the difference in depth is relatively fine. However, for fine discriminations more time is required, and by this time the more accurate information from the stereo-channel has become available and is used.

Temporal changes in UK birth order and the prevalence of atopy

BACKGROUND

Many studies have reported an inverse association between birth order and the risk of respiratory allergic disease. In recent decades, the prevalence of atopy has increased alongside reductions in fertility rates.

AIMS OF THE STUDY

To quantitate how much of the increased prevalence of atopy, measured by skin prick test or specific IgE, can be attributed to temporal changes in family size in the United Kingdom.

METHODS

Through a systematic literature review (MEDLINE, 1965-2009), five studies of UK populations were identified and their data were included in the calculation of a summary odds ratio for the risk of atopy for each birth order. Information on changes in UK family sizes between 1960 and 2001 was obtained from Eurostat. On this basis, expected increases in the prevalence of atopy were calculated by weighting the proportion in each birth order category for 1960 and 2001 by the summary odds ratio for that category and then calculating the relative risk of atopy in 2001 compared with 1960.

RESULTS

The pooled summary odds ratios for atopy were 0.90, 0.69 and 0.69 for those born second, third and fourth (or higher), respectively. The expected relative increase in the prevalence of atopy resulting from a change in family size between 1960 and 2001 was 3%.

CONCLUSIONS

Despite the strong associations between birth order and atopy, reductions in family size in the last 40 years account for little of the increase in atopy.

Use of radiolabelled thymidine and leucine to estimate bacterial production in soils from continental antarctica

Tritiated thymidine incorporation (TTI) into DNA was used to examine bacterial production in two soil types from the Robertskollen group of nunataks in northwestern Dronning Maud Land, providing the first estimates of bacterial production in soil habitats on the Antarctic continent. Although estimates of bacterial productivity in soils near to bird nests (344 (plusmn) 422 ng of C g [dry weight](sup-1) h(sup-1)) were higher than those for soils from beneath mosses (175 (plusmn) 90 ng of C g [dry weight](sup-1) h(sup-1); measured by TTI at 10(deg)C), these differences were not significant because of patchiness of bacterial activity (P > 0.05). TTI- and [(sup14)C]leucine ([(sup14)C]Leu)-derived estimates of bacterial production were similar when incubations of 3 h were used, although incubations as short as 1 h were sufficient for measurable uptake of radiolabel. Dual-label incorporation of [(sup3)H]thymidine ([(sup3)H]TdR) into DNA and [(sup14)C]Leu into protein indicated that TTI did not reflect bacterial production of in situ assemblages when incubations were longer than 3 h. Isotope dilution analysis indicated that dilution of the specific activity of exogenously supplied [(sup3)H]TdR by de novo synthesis of TdR precursor could be limited by additions of [(sup3)H]TdR at a concentration of 1 nmol per ca. 115 mg of soil. TTI exhibited a psychrotrophic response to variation in temperature, with a temperature optimum of ca. 15(deg)C and a Q(inf10) value for 0 to 10(deg)C of 2.41.

Specific cognitive deficits in a group at genetic high risk of schizophrenia

BACKGROUND

Neuropsychological deficits in schizophrenia patients and their relatives have been thought to represent possible genetic vulnerability markers or endophenotypes of the disorder. The present study describes results from the Edinburgh High Risk Study of computerized testing using the Cambridge Neuropsychological Test Automated Battery (CANTAB) on a group at genetic high risk (HR) of schizophrenia and a control group.

METHOD

A total of 97 HR and 25 control participants were assessed on three tests from the CANTAB - spatial span, spatial working memory, and Stockings of Cambridge. Analyses of covariance were used to compare the HR and control groups on the main outcome measures whilst controlling for intelligence quotient (IQ). Subsequent analysis examined the effects of the presence of symptoms on group differences.

RESULTS

HR participants had significantly reduced spatial memory capacity [F(1, 118)=4.06, p=0.046] and significantly reduced planning processing speed [F(1, 116)=4.16, p=0.044] compared with controls even after controlling for general intelligence (IQ). Although HR individuals made more errors and showed poorer problem-solving and strategy performance compared with controls, these differences were not significant after controlling for IQ. Subsequent analysis indicated that the presence or absence of psychotic symptoms in the HR group did not influence these specific cognitive deficits.

CONCLUSIONS

Spatial memory capacity and planning processing speed may represent cognitive endophenotypes characterising the genetic predisposition to schizophrenia in this HR group.

Differential gene expression during compensatory sprouting of dendrites in the auditory system of the cricket Gryllus bimaculatus

Neurones that lose their presynaptic partners because of injury usually retract or die. However, when the auditory interneurones of the cricket Gryllus bimaculatus are denervated, dendrites respond by growing across the midline and forming novel synapses with the opposite auditory afferents. Suppression subtractive hybridization was used to detect transcriptional changes 3 days after denervation. This is a stage at which we demonstrate robust compensatory dendritic sprouting. Whereas 49 unique candidates were down-regulated, no sufficiently up-regulated candidates were identified at this time point. Several candidates identified in this study are known to influence the translation and degradation of proteins in other systems. The potential role of these factors in the compensatory sprouting of cricket auditory interneurones in response to denervation is discussed.

Prefrontal gyral folding and its cognitive correlates in bipolar disorder and schizophrenia

OBJECTIVE

We sought to address whether dorsal or ventral prefrontal gyrification is abnormal in bipolar disorder and to determine its diagnostic specificity and cognitive associations.

METHOD

Forty-two out-patients with bipolar disorder, 28 with schizophrenia and 37 controls underwent magnetic resonance imaging. All subjects also underwent IQ and executive assessments using tasks whose performance has been localized to the ventral or dorsal prefrontal cortex. Cortical folding was quantified using the gyrification index (GI) and related to the cognitive measures.

RESULTS

Patients with bipolar disorder showed reduced prefrontal gyrification compared with controls but did not differ from patients with schizophrenia. Neither ventral nor dorsal GI was preferentially affected in either disorder. Current IQ was positively and significantly correlated with GI.

CONCLUSION

Patients with bipolar disorder and patients with schizophrenia have reduced prefrontal gyrification affecting both ventral and dorsal subregions. These reductions were significantly associated with cognitive impairments occurring in both disorders.

Early allergen exposure and atopic eczema

BACKGROUND

The relationship between exposure to indoor aeroallergens in early life and subsequent eczema is unclear. We have previously failed to show any significant associations between early life exposure to house dust mite and cat fur allergens and either sensitization to these allergens or wheeze. We have also previously reported a lower prevalence of parent-reported, doctor-diagnosed eczema by age 2 years for children exposed to higher concentrations of house dust mite, but no other associations with other definitions of eczema or for exposure to cat allergen.

OBJECTIVES

To extend the exposure-response analysis of allergen exposure and eczema outcomes measured up to age 8 years, and to investigate the role of other genetic and environmental determinants.

METHODS

A total of 593 children (92 x 4% of those eligible) born to all newly pregnant women attending one of three general practitioner surgeries in Ashford, Kent, were followed from birth to age 8 years. Concentrations of house dust mite and cat allergen were measured in dust samples collected from the home at 8 weeks after birth. The risk of subsequent eczema as defined by the U.K. diagnostic criteria was determined according to different levels (quintiles) of allergen exposure at birth.

RESULTS

By age 8 years, 150 (25 x 3%) children had met the diagnostic criteria for eczema at least once. Visible flexural dermatitis was recorded at least once for 129 (28 x 0%). As in other studies, parental allergic history was positively associated with most eczema outcomes, as were higher maternal education and less crowded homes. No clear linear associations between early exposure to house dust mite or cat allergen were found, regardless of the definition of eczema used. The risk of eczema appeared to increase for the three lowest quintiles of house dust mite allergen exposure (odds ratio, OR 1 x 37 for third quintile compared with first), and then to fall for the two highest quintiles (OR 0 x 66 and 0 x 71) even after controlling for confounding factors.

CONCLUSIONS

The lack of any clear exposure-disease relationship between allergens in early life and subsequent eczema argues against allergen exposure being a major factor causing eczema. If the lower levels of eczema at higher levels of house dust mite are confirmed, then interventions aimed at reducing house dust mite in early infancy could paradoxically increase the risk of subsequent eczema.

Sixty years on: the price of assembling military gas masks in 1940

BACKGROUND

Between 1940 and 1944 military gas masks with filter pads containing 20% crocidolite were assembled in a Nottingham factory.

METHODS

Records supplied by the late Professor Stephen Jones were of 1154 persons, mainly women, who had worked in the factory during this period; they included many deaths from mesothelioma. A systematic effort was therefore made to establish causes of death for the whole cohort.

RESULTS

Of 640 employees with full name and sex recorded, 567 (89%) were traced. Of these, 491 had died, including 65 from mesothelioma, though only 54 were certified as such. After exclusion of these 54, standardised mortality ratios were significantly raised for respiratory cancer (SMR 2.5) and carcinomatosis (SMR 3.2). The pattern of mortality in the remaining 514 employees without full identification was similar, but a low tracing rate (40%) did not justify their further analysis. The first death from mesothelioma was in 1963 (22 years after first exposure) and the last in 1994, whereas a further 5.0 cases would have been expected between 1996 and 2003 (p = 0.0065).

CONCLUSION

These findings in a cohort followed over 60 years after brief exposure to crocidolite confirm a high and specific risk of mesothelioma (28% peritoneal) and perhaps of lung cancer some 20-50 years later. The statistically significant absence of further mesothelioma cases during the past eight years suggests that crocidolite, though durable, is slowly removed.

Distribution, habitat and conservation status of the eastern pygmy-possum Cercartetus nanus in Victoria

We review the distribution, habitat and conservation status of the eastern pygmy-possum (Cercartetus nanus) in Victoria. Data on the habitat occurrences and rates of detection were gleaned from 133 published and unpublished fauna surveys conducted from 1968 to 2003 in Gippsland; northern Victoria; the Melbourne area and south-western region. C. nanus was reported from a broad range of vegetation communities, which predominantly included a dense mid-storey of shrubs rich in nectar-producing species such as those from the families Proteaceae and Myrtaceae. Survey effort using a range of methods was immense across surveys: 305,676 Elliott/cage trap-nights, 49,582 pitfall trap-nights, 18,331 predator remains analysed, 4424 spotlight hours, and 7346 hair-sampling devices deployed, 1005 trees stagwatched, and 5878 checks of installed nest-boxes. The surveys produced 434 records of C. nanus, with Elliott/cage trapping, pitfall trapping and analysis of predator remains responsible for the vast majority of records (93%). These data and those from the Atlas of Victorian Wildlife indicate that although C. nanus has a widespread distribution in Victoria, it is rarely observed or trapped in fauna surveys. Only 11 (8%) of the surveys we reviewed detected >10 individuals. C. nanus is likely to be sensitive to several recognised threatening processes in Victoria (e.g., feral predators, high frequency fire, feral honeybees). There is also evidence of range declines in several regions, which suggests that the species is vulnerable to extinction. Therefore, we recommend that it be nominated as a threatened species in Victoria.

Detection of the eastern pygmy-possum Cercartetus nanus (Marsupialia: Burramyidae) at Barren Grounds Nature Reserve, New South Wales

THE eastern pygmy-possum (Cercartetus nanus) has an extensive distribution, from south-eastern Queensland to south-eastern South Australia, and also into Tasmania (Strahan 1995). Despite this it is rarely detected in fauna surveys (Bowen and Goldingay 2000). This rarity in detection suggested that the species may be characterised by small and isolated populations, and therefore vulnerable to extinction. Consequently, it became listed as a 'Vulnerable' species in New South Wales (NSW) in 2001. Unless resolved, the low rate of detection of C. nanus will continue to hinder the acquisition of basic ecological information that is needed to more clearly define its conservation status and that is fundamental to the development of a recovery plan. An extensive body of survey data for NSW involving C. nanus has been reviewed by Bowen and Goldingay (2000). Among a range of survey methods aimed at detecting this species, trapping within flowering banksias and checking installed nest-boxes had the highest rates of detection. Indeed, one study in northern NSW captured 98 individuals over a 3- year period from within nest-boxes (Bladon et al. 2002). All other studies detected fewer than 15 C. nanus. It is clear that further research is required to investigate the effectiveness of a range of detection methods.

Early allergen exposure, skin prick responses, and atopic wheeze at age 5 in English children: a cohort study

BACKGROUND

For many years it has been assumed that the risk of childhood respiratory allergies is related to allergen exposures in early life. There are, however, few prospective data in support. We aimed to examine this relationship in a representative cohort of children born in Ashford, Kent (UK).

METHODS

625 children (94% of those eligible) were followed from birth to the age of 5.5 years at which time 552 underwent skin prick testing to extracts of house dust mite and cat fur allergens. Maternal reports of wheeze in the last year were collected by interview. These outcomes were related to individual domestic concentrations of Der p 1 and Fel d I allergens estimated from dust collection at the age of 8 weeks.

RESULTS

10% of children were sensitised to house dust mite or cat at age 5.5 years; 7% had atopic wheeze. No significant relationships between allergen exposure and either sensitisation or wheeze were found but, on examination, the exposure-response relationships for both allergens and for each outcome rose steeply at low levels of exposure and were attenuated at high levels of exposure. These patterns were modified by paternal atopy and by birth order.

CONCLUSIONS

There are no linear relationships between early allergen exposure and the induction of childhood respiratory allergy; rather, the risks of IgE sensitisation and asthma rise at very low levels of exposure and are attenuated thereafter. These patterns are influenced by parental atopy and birth order. These findings suggest important gene-environment interactions in the development of atopy and asthma and imply that reductions in domestic allergen exposure alone are unlikely to have a major impact in decreasing the incidence of these diseases in childhood.

A polymorphic variation in the interleukin 1A gene increases brain microglial cell activity in Alzheimer's disease

OBJECTIVE

To investigate the impact of possession of the -889 C/T polymorphism of the interleukin 1A gene (IL-1A) and the -511 C/T polymorphism of the interleukin 1B gene (IL-1B) on the extent of neuroinflammation in the brain in Alzheimer's disease (AD), as demonstrated by the degree of microglial cell activity associated with each IL-1A and IL-1B genotype.

METHOD

Microglial cell activity within the frontal cortex was determined in 68 patients with necropsy confirmed AD by image analysis as the percentage area of tissue occupied by ferritin immunostained material (microglial cell load). IL-1A, IL-1B, and apolipoprotein E (APOE) genotyping were performed by polymerase chain reaction on DNA extracted from frontal cortex or cerebellum.

RESULTS

The microglial cell load was 31% greater in patients with IL-1A T allele, 62% greater with IL-1A TT genotype, but 108% greater with IL-1A TT genotype in combination with APOE epsilon4 allele. No effects on microglial cell load occurred with polymorphisms in IL-1B, or APOE alone.

CONCLUSIONS

Polymorphisms within IL-1A influence the degree of brain microglial cell activation, especially in bearers of APOE epsilon4 allele, reinforcing the importance of neuroinflammatory processes in the pathogenesis of AD, and supporting the rationale for treating the disease with inflammation modulating drugs.

Association between chronic fatigue syndrome and the corticosteroid-binding globulin gene ALA SER224 polymorphism

Chronic fatigue syndrome (CFS) is characterized by idiopathic fatigue of greater than 6 months' duration with postexertional exacerbation and many other symptoms. A trend toward relative hypocortisolism is described in CFS. Twin and family studies indicate a substantial genetic etiologic component to CFS. Recently, severe corticosteroid-binding globulin (CBG) gene mutations have been associated with CFS in isolated kindreds. Human leukocyte elastase, an enzyme important in CBG catabolism at inflammatory sites, is reported to be elevated in CFS. We hypothesized that CBG gene polymorphisms may act as a genetic risk factor for CFS. A total of 248 patients with CFS defined by Centers for Disease Control criteria, and 248 controls were recruited. Sequencing and restriction enzyme testing of the CBG gene coding region allowed detection of severe CBG gene mutations and a common exon 3 polymorphism (c.825G-->T, Ala-Ser224). Plasma CBG levels were measured in 125 CFS patients and 198 controls by radioimmunoassay. Total and free (calculated and measured) cortisol levels were ascertained in single samples between 8-10 a.m. The age of onset (mid 30s) and gender ratio (2.2:1, female:male) of the patients were similar to those reported in U.S. epidemiologic studies. A trend toward a preponderance of serine224 homozygosity among the CFS patients was noted, compared with controls (chi2 = 5.31, P = 0.07). Immunoreactive-CBG (IR-CBG) levels were higher in Serine/Alanine (Ser/Ala) than Ala/Ala subjects and higher again in Ser/Ser subjects, this effect was strongest in controls; Ser/Ser: 46.1+/-1.8 (n = 31, P = 0.03) vs. Ser/Ala: 42.4+/-1.0 (n = 56, P = 0.05) vs. Ala/Ala: 40.8+/-1.7 microg/mL (n = 21). Despite higher CBG levels, there was a nonsignificant trend toward lower total and free plasma cortisol in serine allele positive patients, total cortisol: Ser/Ser: 13.3+/-1.4 (n = 34) vs. Ser/Ala: 14.0+/-0.7 (n = 66) vs. Ala/Ala: 15.4+/-1.0 (n = 23). Homozygosity for the serine allele of the CBG gene may predispose to CFS, perhaps due to an effect on hypothalamic-pituitary-adrenal axis function related to altered CBG-cortisol transport function or immune-cortisol interactions.

New pregnancies and loss of allergy

BACKGROUND

Inverse associations between allergic disease and sibship have been consistently described and are frequently explained by purported lower rates of early infection among children from small families. Alternative explanations include the possibility that pregnancy itself determines maternal atopic status.

OBJECTIVE

To test the hypothesis that atopy defined by skin prick test (SPT) declines with increasing numbers of pregnancies.

METHODS

At enrollment to a birth cohort, mothers were skin prick tested to three common allergens. Seven years later these women underwent a second SPT and provided information on their reproductive histories. At both visits, information on allergic disease was also sought.

RESULTS

Twenty five (15%) women who were initially atopic were no longer so at the second visit; loss of hayfever symptoms was reported by 33 (29%) women. Women with higher numbers of intervening pregnancies were more likely to 'lose' their atopy (P=0.05) and symptoms of hayfever (P=0.02); this was not true for asthma. The findings could not be accounted for by maternal age.

CONCLUSION

Successive pregnancies may in part determine a mother's atopic state. Since maternal atopy is a risk factor for childhood atopic disease, this process may affect the atopic state of successive children. These findings suggest an alternative explanation for the sibship effect in allergic disease.

Can early infection explain the sibling effect in adult atopy?

Atopy is strongly and inversely related to family size, a pattern which is plausibly assumed to reflect a protective effect of early infection. The current study tested this hypothesis by case-referent analysis of an adult cohort in the UK. The study established that atopy, defined by prick tests to common aeroallergens, was less common among those from larger families after adjustment for potentially confounding factors. In particular, a higher number of brothers appeared to offer protection. The current authors attempted to explain this distribution by examining contemporary family-doctor records of early childhood infections; and by a number of other indirect indices of early-life "hygiene". The sibling effect was unexplained by evidence of infection with either hepatitis A or Helicobacter pylori, or by counts of infections or antibiotic prescriptions in early life. There was a significant and independent negative association between the number of gastrointestinal infections before the age of 5 yrs and the odds of atopy. Dog ownership and home moving in early life also displayed potentially protective associations. Although the current study replicates the finding that atopy is inversely associated with family size this could not be explained by documentary or serological evidence of early infection. The findings support the suggestion that the "sibling effect" in atopy may not simply reflect protection by early infection.

A polymorphism in the angiotensin 1-converting enzyme gene is associated with damage to cerebral cortical white matter in Alzheimer's disease

The impact of the insertion (I)/deletion (D) (I/D) polymorphism in the angiotensin 1-converting enzyme (ACE) gene on the extent of white matter myelin loss (ML) was investigated in four regions of the cerebral cortex in an autopsy-confirmed series of 93 patients with Alzheimer's disease (AD). The possible influence of APO E epsilon4 allele acting in concert with ACE D allele was assessed. The extent of ML did not differ between D/D, I/D and I/I genotype groups when data from all four brain regions were combined. However, separate analysis showed that the frontal and temporal cortex tended to be affected more severely by ML in patients with D/D genotype compared to those with I/D and I/I genotypes. Stratification according to APO E epsilon4 allele revealed a greater overall ML in patients bearing at least one copy of ACE D allele and one APO E epsilon4 allele, especially in individuals homozygous for both. The APO E epsilon4 allele may therefore act synergistically in patients with AD (and other subjects) bearing ACE D/D genotype to increase the risk of ML, perhaps through transient ischaemic episodes consequent upon poor cardiac output associated with coronary atherosclerosis in patients with the APO E epsilon4 allele.

Genetic variation of the APOE promoter and outcome after head injury

The APOE-epsilon4 allele is associated with risk for Alzheimer's disease (AD) and poorer outcome after head injury. Several studies show that polymorphisms in the promoter that influence APOE expression also increase risk for AD. The authors' data from a study of 92 patients are consistent with a possible influence of the G-219T promoter polymorphism on outcome after head injury. The group with unfavorable outcome had a genotype frequency distribution similar to that found in AD.

A community-based survey of the koala Phascolarctos cinereus in the Lismore region of north-eastern New South Wales

A community-based survey was undertaken in the Lismore Local Government Area (LGA) of north-eastern New South Wales to provide a basis for the development of a Shire-wide koala management plan. A questionnaire and maps were distributed to identify community attitudes towards P. cinereus conservation and management, as well as to document locations of sightings. There were 1121 surveys returned from 23,751 distributed (4.7% returned) across 18,000 ratepayers (6.2% response). Respondents indicated the frequency with which P. cinereus were seen in different suburbs, whether they had young or were sick, and provided 840 map-based records. Ten percent of respondents saw P. cinereus on at least a weekly basis, highlighting the importance of this LGA for the conservation of this species. More than 80% of respondents considered that roving dogs, land clearing, road traffic and housing development were serious threats to long-term P. cinereus survival. More than 90% of respondents supported restrictions on dogs, tree-planting programs, as well as planning activities to protect P. cinereus habitat while 85% approved of protection zones to control development within P. cinereus habitat. These results if representative of the entire community suggest strong support for the development of conservation options for P. cinereus. The study also confirms the usefulness of conducting such community-wide surveys for conspicuous threatened species.

The angiotensin 1-converting enzyme insertion (I)/deletion (D) polymorphism does not influence the extent of amyloid or tau pathology in patients with sporadic Alzheimer's disease

An insertion (I)/deletion (D) polymorphism in the angiotensin 1-converting enzyme (ACE) gene has, in some studies, been associated with increased risk for Alzheimer's disease (AD), and functionally the enzyme has been implicated in the degradation of amyloid beta protein (Abeta). We have investigated the frequency of the I/D polymorphism in a clinic-based and autopsy-confirmed series of cases of AD, and investigated what impact the I/D polymorphism in ACE gene might have on the extent of Abeta and tau pathology in the frontal cortex in the autopsy-confirmed series. We found no differences in I/D allele or genotype frequencies between the clinic-based and autopsy-confirmed AD cases, or between the pooled clinic-based and autopsy-confirmed AD cases and a series of normal control subjects. Moreover, Abeta (Abeta(40) and Abeta(42)) load, tau load or extent of amyloid angiopathy did not differ between D/D, I/D and I/I genotype groups, though Abeta(42) load tended to be higher in bearers of I/I genotype (compared to D/D genotype). Neither age at onset nor duration of illness differed according to genotype. We conclude therefore that the frequency of ACE I-allele is not increased in AD and, in autopsy-confirmed AD cases, possession of the ACE I allele has no impact upon the pathology of AD, at least in terms of the amount of Abeta or tau deposited in the brain.

Contribution of APOE promoter polymorphisms to Alzheimer's disease risk

OBJECTIVE

To determine whether the effects of APOE promoter polymorphisms on AD are independent of the APOE-epsilon4 allele.

BACKGROUND

Recently, the -491 A-->T and -219 G-->T polymorphisms located in the APOE promoter have been suggested to be risk factors for AD. However, the effects of these polymorphisms have not always been reproduced in case-control studies, possibly because of the strong linkage disequilibrium existing at this locus or the characteristics of the populations studied.

METHODS

Data collection was performed from six independent samples (1,732 patients with AD and 1,926 control subjects) genotyped for APOE exon 4 and the two APOE promoter polymorphisms. The risks associated with the APOE polymorphisms for developing AD were estimated using logistic regression procedures and calculation of odds ratios with 95% CI adjusted by age, sex, and collection center. Independence of the APOE promoter polymorphisms was tested by stratification for APOE-epsilon4 and tertile design was used for age stratification.

RESULTS

The independence of the -491 AA genotype was observed in the whole sample whereas the independence of the -219 TT genotype was observed only in the oldest population.

CONCLUSION

The -491 and -219 APOE promoter polymorphisms incur risk for AD in addition to risk associated with the APOE-epsilon4 allele, with age accentuating the effect of the -219 TT genotype. Because these polymorphisms appear to influence apoE levels, these results suggest that APOE expression is an important determinant of AD pathogenesis.

Chemistry for peptide and protein PEGylation

Poly(ethylene glycol) (PEG) is a highly investigated polymer for the covalent modification of biological macromolecules and surfaces for many pharmaceutical and biotechnical applications. In the modification of biological macromolecules, peptides and proteins are of extreme importance. Reasons for PEGylation (i.e. the covalent attachment of PEG) of peptides and proteins are numerous and include shielding of antigenic and immunogenic epitopes, shielding receptor-mediated uptake by the reticuloendothelial system (RES), and preventing recognition and degradation by proteolytic enzymes. PEG conjugation also increases the apparent size of the polypeptide, thus reducing the renal filtration and altering biodistribution. An important aspect of PEGylation is the incorporation of various PEG functional groups that are used to attach the PEG to the peptide or protein. In this paper, we review PEG chemistry and methods of preparation with a particular focus on new (second-generation) PEG derivatives, reversible conjugation and PEG structures.

Are interleukin-1 gene polymorphisms risk factors or disease modifiers in AD?

Polymorphisms in the interleukin-1 genes, IL-1A and IL-1B, have been associated with AD, but not in all studies. The authors genotyped the IL-1A(-889) and IL-1B(-511) polymorphisms in large independent cohorts of 503 control individuals and 395 patients with AD, and a further 100 with brain Abeta load. No evidence was found of risk for AD with these variants, nor of an effect on age at onset. However, an impact of IL-1B(-511) on Abeta(40) load (p < 0.05) was detected.

A polymorphism within intron 11 of the tau gene is not increased in frequency in patients with sporadic Alzheimer's disease, nor does it influence the extent of tau pathology in the brain

There are numerous polymorphisms within the tau gene but these are in complete linkage disequilibrium and exist as two common extended haplotypes H1 and H2. We have investigated the frequency of these haplotypes in 83 cases of sporadic Alzheimer's disease (AD) using the +34 polymorphism in intron 11 of the tau gene as a marker of H1 and H2 haplotypes. The total amount of hyperphosphorylated tau protein (tau load), present as neurofibrillary tangles, neuropil threads or plaque neurites, was quantified in the frontal cortex of these patients and related to tau haplotype. We found no increase in H1H1 haplotype in this autopsy population of cases with AD compared to published control data. Stratification of cases for apolipoprotein E (APO E) genotype showed a slight, but not statistically significant, overrepresentation of epsilon 4 allele amongst bearers of H2 haplotype. There were no overall differences in tau load between haplotype groups though cases within each haplotype group bearing APO E epsilon 4 allele had a significantly higher tau load than those without epsilon 4 allele. Neither age at onset or duration of illness differed according to tau haplotype. We conclude that the frequency of tau gene H1 haplotype is not elevated in AD and possession of this has no impact upon the amount of tau pathology in AD.

Pegylation: a novel process for modifying pharmacokinetics

The use of liposomal carriers and the modification of therapeutic molecules through the attachment of poly(ethylene glycol) [PEG] moieties ('pegylation') are the most common approaches for enhancing the delivery of parenteral agents. Although 'classical' liposomes (i.e. phospholipid bilayer vehicles) have been effective in decreasing the clearance of encapsulated agents and in passively targeting specific tissues, they are associated with considerable limitations. Pegylation may be an effective method of delivering therapeutic proteins and modifying their pharmacokinetic properties, in turn modifying pharmacodynamics, via a mechanism dependent on altered binding properties of the native protein. Pegylation reduces renal clearance and, for some products, results in a more sustained absorption after subcutaneous administration as well as restricted distribution. These pharmacokinetic changes may result in more constant and sustained plasma concentrations, which can lead to increases in clinical effectiveness when the desired effects are concentration-dependent. Maintaining drug concentrations at or near a target concentration for an extended period of time is often clinically advantageous, and is particularly useful in antiviral therapy, since constant antiviral pressure should prevent replication and may thereby suppress the emergence of resistant variants. Additionally, PEG modification may decrease adverse effects caused by the large variations in peak-to-trough plasma drug concentrations associated with frequent administration and by the immunogenicity of unmodified proteins. Pegylated proteins may have reduced immunogenicity because PEG-induced steric hindrance can prevent immune recognition. Two PEG-modified proteins are currently approved by the US Food and Drug Administration; several others, including cytokines such as interferon-alpha (IFNalpha), growth factors and free radical scavengers, are under development. Careful assessment of various pegylated IFNalpha products suggests that pegylated molecules can be differentiated on the basis of their pharmacokinetic properties and related changes in pharmacodynamics. Because the size, geometry and attachment site of the PEG moiety play a crucial role in determining these properties, therapeutically optimised agents must be designed on a protein-by-protein basis.

Genetic fieldwork for hereditary prostate cancer studies

The success of a genetic family study depends on the recruitment of a sufficient number of unaffected family members. We present our experiences from interviews performed in two family studies, a genetic family study of prostate cancer (PC) and a medical, anthropological, qualitative study. In the genetic family study, 949 PC patients were contacted, and 29% responded. Response rates were higher (44%) among subjects contacted by health providers participating in the study, compared to only 18% of those contacted by letter. Thirty-six pedigrees were ascertained. On average, each family had 3.3 affected relatives. Average age at time of diagnosis was 61.9 years in the probands. 58% of the families reported additional cancers. Breast cancer was reported in 12 families; colon cancer was the second most reported cancer, followed by lung, stomach, and throat cancers. Beliefs about the inheritance of PC were explored with 20 participants. The parental origin of the proband's PC in each family did not significantly affect participants' beliefs about the inheritance of PC. 95% agreed that PC could be inherited from a father to a son. Participants thought that a mother (n = 12) or daughter of a patient (n = 11) could not give PC to their sons. This misperception of the inheritance of PC can result in (1) an underreporting of PC cases in a kindred, and (2) healthy men underestimating their risk of developing PC when the disease runs in the mother's family. Thus health educators and genetic counselors might consider these findings when teaching patients and their relatives about hereditary PC.

Source regions for atmospheric aerosol measured at Barrow, Alaska

Aerosol data consisting of condensation nuclei (CN) counts, black carbon (BC) mass concentration, and aerosol light scattering coefficient at the wavelength of 450 nm (SC) measured at Barrow, AK, from 1986 to 1997 have been analyzed. BC and SC show an annual cycle with the Arctic haze maxima in the winter and spring and the minima in the summer. The CN time series shows two maxima in March and August. Potential source contribution function (PSCF) that combines the aerosol data with air parcel backward trajectories was applied to identify potential source areas and the preferred pathways that give rise to the observed high aerosol concentrations at Barrow. Ten-day isentropic back trajectories arriving twice daily at 500 and 1500 m above sea level were calculated for the period from 1986 to 1997. The PSCF analyses were performed based on the 80th percentile criterion values for the 2- and 24-h averages of the measured aerosol parameters. There was a good correspondence between PSCF maps for the 2- and 24-h averages, indicating that 1-day aerosol sampling in the Arctic adequately represents the aerosol source areas. In winter, the high PSCF values for BC and SC are related to industrial source areas in Eurasia. The trajectory domain in winter and spring is larger than in summer, reflecting weaker transport in summer. No high PSCF areas for BC and SC can be observed in summer. The result is related to the poor transport into the Arctic plus the strong removal of aerosol by precipitation in summer. In contrast to the BC and SC maps, the CN plot for summer shows high PSCF areas in the North Pacific Ocean. High CN values appearto be mostly connected with the long-range transport from Eurasia in winter and spring and with the reduced sulfur compound emission from biogenic activities in the ocean in the summer. PSCF analysis was found to be effective in identifying potential aerosol source areas.

Quantitative dosing of surfaces with fluorescent molecules: characterization of fractional monolayer coverages by counting single molecules

Quantitative deposition of dye molecules onto a substrate has been achieved at very low surface concentrations, in the range of 5 x 10(-8) - 1 x 10(-6) monolayer, using the technique of controlled substrate withdrawal from solution. These small surface populations were determined with high (>96%) efficiency by single-molecule counting using an epi-illumination, fluorescence microscope with charge-coupled device detector. The fluorescence imaging resolution (3sigma) is 0.78 microm; over a uniform excitation area of 67 x 67 microm2, a large number (>7,500) of spatially resolved channels are available for counting individual molecules. At low coverages, the number density of fluorescence spots on the surface agrees with the expected surface concentration of molecules, based on the concentration of dye in solution and the solution film thickness predicted from theory. When the surface density of molecules is high enough that fluorescence spot overlap is likely to occur within the optical resolution of the instrument, the observed fewer number of spots can be corrected for overlap through a site occupation model based on Poisson statistics.

The effects of dot density and motion coherence on perceptual fading of a target in noise

A peripherally presented target embedded in dynamic texture perceptually disappears (or 'fills-in') after around 10 s of steady fixation. This phenomenon was investigated for a target containing moving dots. The effects of manipulating the coherence of the motion within the target and the density of dots across the whole screen were explored. Coherence thresholds for the detection of a target at different dot densities were recorded for comparison. Fading occurred faster as either motion coherence or dot density was reduced. Coherence thresholds for target detection were unaffected by manipulations of dot density. There appeared to be no relationship between the stimulus exposure time needed for fading and the coherence threshold for detection of a target. The results suggest that the time taken for a target to fade is not a simple function of its motion detection threshold.

Detecting binocular 3D motion in static 3D noise: no effect of viewing distance

Relative binocular disparity cannot tell us the absolute 3D shape of an object, nor the 3D trajectory of its motion, unless the visual system has independent access to how far away the object is at any moment. Indeed, as the viewing distance is changed, the same disparate retinal motions will correspond to very different real 3D trajectories. In this paper we were interested in whether binocular 3D motion detection is affected by viewing distance. A visual search task was used, in which the observer is asked to detect a target dot, moving in 3D, amidst 3D stationary distractor dots. We found that distance does not affect detection performance. Motion-in-depth is consistently harder to detect than the equivalent lateral motion, for all viewing distances. For a constant retinal motion with both lateral and motion-in-depth components, detection performance is constant despite variations in viewing distance that produce large changes in the direction of the 3D trajectory. We conclude that binocular 3D motion detection relies on retinal, not absolute, visual signals.

Poor CD4 T cell restoration after suppression of HIV-1 replication may reflect lower thymic function

OBJECTIVE

To characterize immune phenotype and thymic function in HIV-1-infected adults with excellent virologic and poor immunologic responses to highly active antiretroviral therapy (HAART).

METHODS

Cross-sectional study of patients with CD4 T cell rises of > or = 200 x 10(6) cells/l (CD4 responders; n = 10) or < 100 x 10(6) cells/l (poor responders; n = 12) in the first year of therapy.

RESULTS

Poor responders were older than CD4 responders (46 versus 38 years; P < 0.01) and, before HAART, had higher CD4 cell counts (170 versus 35 x 106 cells/l; P = 0.11) and CD8 cell counts (780 versus 536 x 10(6) cells/l; P = 0.02). After a median of 160 weeks of therapy, CD4 responders had more circulating naive phenotype (CD45+CD62L+) CD4 cells (227 versus 44 x 10(6) cells/l; P = 0.001) and naive phenotype CD8 cells (487 versus 174 x 10(6) cells/l; P = 0.004) than did poor responders (after 130 weeks). Computed tomographic scans showed minimal thymic tissue in 11/12 poor responders and abundant tissue in 7/10 responders (P = 0.006). Poor responders had fewer CD4 cells containing T cell receptor excision circles (TREC) compared with CD4 responders (2.12 versus 27.5 x 10(6) cells/l; P = 0.004) and had shorter telomeres in CD4 cells (3.8 versus 5.3 kb; P = 0.05). Metabolic labeling studies with deuterated glucose indicated that the lower frequency of TREC-containing lymphocytes in poor responders was not caused by accelerated proliferation kinetics.

CONCLUSION

Poor CD4 T cell increases observed in some patients with good virologic response to HAART may be caused by failure of thymic T cell production.