Livestock microbial landscape patterns: Retail poultry microbiomes significantly vary by region and season

Microbes play key roles in animal welfare and food safety but there is little understanding of whether microbiomes associated with livestock vary in space and time. Here we analysed the bacteria associated with the carcasses of the same breed of 28 poultry broiler flocks at different stages of processing across two climatically similar UK regions over two seasons with 16S metabarcode DNA sequencing. Numbers of taxa types did not differ by region, but did by season (P = 1.2 × 10-19), and numbers increased with factory processing, especially in summer. There was also a significant (P < 1 × 10-4) difference in the presences and abundances of taxa types by season, region and factory processing stage, and the signal for seasonal and regional differences remained highly significant on final retail products. This study therefore revealed that both season and region influence the types and abundances of taxa on retail poultry products. That poultry microbiomes differ in space and time should be considered when testing the efficacy of microbial management interventions designed to increase animal welfare and food safety: these may have differential effects on livestock depending on location and timing.

480Right ventricular dysfunction is associated with late mortality in severe aortic stenosis: results from a multi-centre outcome study in patients undergoing aortic valve replacement

Background

The right ventricle (RV) is relatively understudied and often not routinely assessed in aortic stenosis (AS). However, there are several potential reasons for its importance. RV function is sensitive to left-sided afterload changes which can result in pulmonary hypertension (PH) in severe AS. PH is also a recognised predictor of poor prognosis in AS, but RV afterload and function can be difficult to assess. Cardiovascular magnetic resonance (CMR) may reveal unrecognised RV dysfunction and simultaneously evaluate other prognostic markers in AS.

Purpose

To investigate preoperative RV function assessed by CMR in severe AS and its association with mortality after aortic valve replacement (AVR).

Methods

674 severe AS patients listed for either surgical or percutaneous AVR at six cardiothoracic centres underwent preoperative CMR (for ventricular function, mass and scar) along with echocardiography for valve severity. Scans were core-lab analysed for LV and RV volumes, function and scar quantification. Eight patients were excluded due to inadequate RV image quality for a total of 666 patients finally included. All-cause mortality was tracked for a minimum of 2 years after AVR.

Results

107 (16%) of severe AS undergoing invasive AVR had a RV ejection fraction (RVEF) <55%. CMR detected overt RV dysfunction (RVEF <50%) in 61 (9%) patients. During a median 3.6 years follow-up, 145 (22%) patients died. Baseline RV dysfunction was the most powerful predictor of all-cause mortality (hazard ratio [HR] 2.5, 95% CI 1.6–3.9, p<0.0001). RV function was independent from other clinical characteristics but associated with signs of LV maladaptation (LV ejection fraction [LVEF] and late gadolinium enhancement [LGE]). The strongest Cox multivariable model for all-cause mortality accounted for RV dysfunction, age and LGE (adjusted HRs 1.7, 1.1, 2.2, respectively). Even early stages of pre-procedural RV dysfunction (RVEF 45–50%) were associated with reduced long-term survival.

Cox and Kaplan-Meier for all-cause death

Conclusion

One out of 6 patients with severe AS undergoing valve replacement manifests a reduction in RV function detectable by CMR. Those with RV dysfunction (RVEF<50%) have a 2.5-fold increase in all-cause mortality after AVR at 3.6 years. Whilst RV dysfunction is associated with LV maladaptation (LGE, LVEF), it is a powerful independent factor associated with all-cause mortality and impacts survival even at early stages. Thus, the RV appears to be important in cardiac adaptation to AS and longevity after AS intervention.

Acknowledgement/Funding

British Heart Foundation and National Institute of Health Research

Cyclic vomiting syndrome is a prevalent and under-recognized condition in the gastroenterology outpatient clinic

BACKGROUND

Cyclic vomiting syndrome (CVS) is a functional gastrointestinal disorder (FGID) characterized by intermittent episodes of nausea and vomiting. Our aim was to report its prevalence and associated features.

METHODS

Data concerning demographics, symptoms, and psychiatric comorbidity were collected. Symptoms compatible with CVS were classified as per Rome III criteria. We recorded whether a diagnosis of CVS was considered in patients after negative investigation. We compared demographics and association with other FGIDs in patients with and without CVS.

KEY RESULTS

920 of 1002 patients provided data. Of the 920 patients, 112 (12.2%) had symptoms compatible with CVS. Thirteen (11.6%) of these had an organic cause for their symptoms, but 99 patients (88.4%) were deemed to have CVS (prevalence=10.8%). Organic causes for symptoms compatible with CVS included gastroparesis, large hiatus hernia, achalasia, and small bowel obstruction. Only 39.4% of patients with CVS were asked about vomiting symptoms at their initial consultation, and a diagnosis of CVS was considered in only four (4.0%) of the 99 patients. CVS was associated with younger age, tobacco smoking, never having married, psychiatric comorbidity, and presence of symptoms compatible with other FGIDs (P≤.01).

CONCLUSIONS AND INFERENCES

Prevalence of CVS in this outpatient gastroenterology adult population was 10.8%. Identified associations included younger age, tobacco smoking, psychiatric comorbidity, and symptoms compatible with other FGIDs. The condition was considered as a possible diagnosis in <5% of patients who met the diagnostic criteria.

Derivation and validation of a diagnostic test for irritable bowel syndrome using latent class analysis

BACKGROUND

The accuracy of symptom-based diagnostic criteria for irritable bowel syndrome (IBS) is modest.

AIMS

To derive and validate a new test that utilises latent class analysis.

METHODS

Symptom, colonoscopy, and histology data were collected from 1981 patients and 360 patients in two cohorts referred to secondary care for investigation of their gastrointestinal symptoms in Canada and the UK, respectively. Latent class analysis was used to identify naturally occurring clusters in patient-reported symptoms in the Canadian dataset, and the latent class model derived from this was then applied to the UK dataset in order to validate it. Sensitivity, specificity, and positive and negative likelihood ratios (LRs) were calculated for the latent class models.

RESULTS

In the Canadian cohort, the model had a sensitivity of 44.7% (95% CI 40.0-50.0) and a specificity of 85.3% (95% CI 83.4-87.0). Positive and negative LRs were 3.03 (95% CI 2.57-3.56) and 0.65 (95% CI 0.59-0.71) respectively. A maximum positive LR of 3.93 was achieved following construction of a receiver operating characteristic curve. The performance in the UK cohort was similar, with a sensitivity and specificity of 52.5% (95% CI 42.2-62.7) and 84.3% (95% CI 79.3-88.6), respectively. Positive and negative LRs were 3.35 (95% CI 2.38-4.70) and 0.56 (95% CI 0.45-0.68), respectively, with a maximum positive LR of 4.15.

CONCLUSIONS

A diagnostic test for IBS, utilising patient-reported symptoms incorporated into a latent class model, performs as accurately as symptom-based criteria. It has potential for improvement via addition of clinical markers, such as coeliac serology and faecal calprotectin.

Systematic review with meta-analysis: the accuracy of diagnosing irritable bowel syndrome with symptoms, biomarkers and/or psychological markers

BACKGROUND

Irritable bowel syndrome (IBS) is a complex, heterogeneous disease which can be challenging to diagnose. No study has identified and assessed the accuracy of all available methods of diagnosing IBS.

AIM

To conduct a systematic review of the literature to identify and assess accuracy of symptom-based diagnostic criteria, biomarkers, psychological markers or combinations thereof.

METHODS

MEDLINE, EMBASE and EMBASE Classic were searched (until April 2015) to identify studies reporting accuracy of available methods to diagnose IBS in adult populations. Eligible studies assessed accuracy of these diagnostic tests against an accepted reference standard. Data were extracted to calculate positive and negative likelihood ratios, with 95% confidence intervals (CIs), of the diagnostic test utilised. Where more than one study used the same test, data were pooled in a meta-analysis.

RESULTS

Twenty-two studies (7106 patients) were eligible. Positive and negative likelihood ratios of the current gold standard, the Rome III criteria, were 3.35 (95% CI: 2.97-3.79) and 0.39 (95% CI: 0.34-0.46), similar to other symptom-based criteria. Eleven biomarkers performed no better than symptom-based criteria. Psychological markers performed well in one study. Five different combinations were assessed. The best in terms of positive likelihood ratio was faecal calprotectin, intestinal permeability and Rome I criteria (26.4; 95% CI: 11.4-61.9), and in terms of negative likelihood ratio serum-based biomarkers and psychological markers (0.18; 95% CI: 0.12-0.25).

CONCLUSIONS

Symptom-based diagnostic criteria, biomarkers and psychological markers performed modestly in predicting IBS. Combining symptoms with markers appears more effective, and may represent the way forward in the diagnosis of IBS.

Measuring placental transfusion for term births: weighing babies with cord intact

OBJECTIVE

To estimate the volume and duration of placental transfusion at term.

DESIGN

Prospective observational study.

SETTING

Maternity unit in Bradford, UK.

POPULATION

Twenty-six term births.

METHODS

Babies were weighed with umbilical cord intact using digital scales that record an average weight every 2 seconds. Placental transfusion was calculated from the change in weight between birth and either cord clamping or when weighing stopped. Start and end weights were estimated using both a B-spline and inspection of graphs. Weight was converted to volume, 1 ml of blood weighing 1.05 g.

MAIN OUTCOME MEASURES

Volume and duration of placental transfusion.

RESULTS

Twenty-six babies were weighed. Start weights were difficult to determine because of artefacts in the data as the baby was placed on the scales and wrapped. The mean difference in weight was 116 g [95% confidence interval (CI), 72-160 g] using the B-spline and 87 g (95% CI, 64-110 g) using inspection. Converting this to the mean volume of placental transfusion gave 110 ml (95% CI, 69-152 ml) and 83 ml (95% CI, 61-106 ml), respectively. Placental transfusion was usually complete by 2 minutes, but sometimes continued for up to 5 minutes. Based on the B-spline, placental transfusion contributed 32 ml (95% CI, 30-33 ml) per kilogram of birth weight to blood volume, but 24 ml (95% CI, 19-32 ml) based on inspection. This equates to 40% (95% CI, 37-42%) and 30% (24-40%), respectively, of total potential blood volume.

CONCLUSION

Inspection of the graphs probably underestimates placental transfusion. For term infants, placental transfusion contributes between one-third and one-quarter of total potential blood volume at birth.

Haplotype uncertainty in association studies

Inferring haplotypes from genotype data is commonly undertaken in population genetic association studies. Within such studies the importance of accounting for uncertainty in the inference of haplotypes is well recognised. We investigate the effectiveness of correcting for uncertainty using simple methods based on the output provided by the PHASE haplotype inference methodology. In case-control analyses investigating non-Hodgkin lymphoma and haplotypes associated with immune regulation we find little effect of making adjustment for uncertainty in inferred haplotypes. Using simulation we introduce a higher degree of haplotype uncertainty than was present in our study data. The simulation represents two genetic loci, physically close on a chromosome, forming haplotypes. Considering a range of allele frequencies, degrees of linkage between the loci, and frequency of missing genotype data, we detail the characteristics of genetic regions which may be susceptible to the influence of haplotype uncertainty. Within our evaluation we find that bias is avoided by considering haplotype probabilities or using multiple imputation, provided that for each of these methods haplotypes are inferred separately for case and control populations; furthermore using multiple imputation provides the facility to incorporate haplotype uncertainty in the estimation of confidence intervals. We discuss the implications of our findings within the context of the complexity of haplotype inference for larger marker rich regions as would typically be encountered in genetic analyses.

Leukaemia incidence near coastal features

BACKGROUND

The aim of the study was to independently test the hypothesis that leukaemia incidence is higher in proximity to estuaries.

METHODS

Electoral wards were classified as to whether they included estuarine, coastal or only inland features. Rates of different adult and childhood leukaemias were computed for each ward category; that is, acute lymphoblastic leukaemia (ALL), acute myeloid leukaemia (AML), chronic myeloid leukaemia (CML) aged 0-79 and for all childhood leukaemias combined (aged 0-14).

RESULTS

Poisson regression analysis controlling for the effects of sex, age, and socioeconomic and urban-rural status, showed no statistically significant differences in incidence between wards with different levels of estuarine classification.

CONCLUSION

The hypothesis created from an earlier dataset that a link exists between leukaemia and residence near estuaries is not upheld.

Population mixing, childhood leukaemia, CNS tumours and other childhood cancers in Yorkshire

We tested the hypothesis that variation in population mixing attributable to the diversity of migrants moving to an area is associated with the incidence of childhood leukaemia and other childhood cancers. An ecological analysis was performed on 954 children (<15 years) diagnosed with a malignancy between 1986 and 1996 in 532 electoral wards in Yorkshire, UK. Incidence rate ratios (IRR) were calculated for all childhood leukaemias (n=325), acute lymphoblastic leukaemia (ALL) (n=248), central nervous system (CNS) tumours (n=236) and other solid tumours (n=393) Incidence of all childhood leukaemias was significantly lower in areas of high (top decile) population mixing (IRR 0.72, 95% Confidence Interval (CI) 0.54-0.97) and higher in areas of low (bottom decile) population mixing (IRR 1.56, 95% CI 0.73-3.34), but similar patterns of incidence were not observed for central nervous system or other solid tumours. Population mixing may be a proxy for the range of infections circulating in a community and these results are consistent with the hypothesis that greater exposure to infections reduces the risk of developing childhood leukaemia by conferring efficient modulation of the immune system.

The importance of full participation: lessons from a national case-control study

Differential participation between cases and controls can lead to biased estimates of risk. However, the effects of participation are often ignored. We report a detailed analysis of locations of residence for participants and non-participants in a large, national case-control study of childhood cancer in Great Britain, using the 1991 census. The initial selection of 7669 controls, taken from lists of those registered with a General Practitioner, was representative of the British population in respect to an areal-based index of material deprivation. However, parents of controls agreeing to participate were living in more affluent areas than initially selected controls and their matched 3838 cases. The three components of the deprivation index, persons unemployed, households not owning a car or their home were similarly associated with participation. Other census characteristics, such as proportion of flat dwellers and centrally heated households were also associated with control participation. Population density of the local area was not different between participating controls and their matched cases. However, initially selected controls lived in more urban areas than their cases. Such differences are not unique to this study, as they are an inevitable consequence of incomplete participation. The implications of these differences are discussed, in relation to the difficulty this imposes in the interpretation of studies of disease aetiology.

Population mixing and childhood diabetes

BACKGROUND

Exposure to infections, particularly in early life, may modify the risk of developing childhood diabetes. Population mixing, based on the number and diversity of incoming migrants to an area can be used as a proxy measure for exposure to infections. We tested the hypothesis that incidence of childhood Type 1 diabetes is higher in areas of low population mixing.

METHODS

Children (<15 years) diagnosed with diabetes between 1986--1994 in Yorkshire, UK (n = 994) were analysed with demographic data and denominator populations from the 1991 UK Census. Population mixing was estimated separately for 'any age' (>1 year) and children (1--15 years) for each area, using the proportion of migrants and an index of diversity based on numbers and origins of migrants. Regression models calculated the effect of 'any age' and childhood population mixing on the incidence of diabetes, controlling for population density, ethnicity and proportion of migrants.

RESULTS

Areas with low levels of population mixing of children (bottom decile), were significantly associated with higher incidence of childhood diabetes for 0-14 years (incidence rate ratio [IRR] = 1.46, 95% CI : 1.01--2.11). When stratified by age different effects were observed for childhood population mixing with raised IRR for ages 5-9 (2.23, 95% CI : 1.20--4.11) and 10-14 (1.47, 95% CI : 0.89--2.42), and decreased IRR for 0--4-year-olds (0.56, 95% CI : 0.17--1.82).

CONCLUSION

The incidence of childhood diabetes is highest in areas where limited childhood population mixing occurs and the diversity of origins of incoming children is low; those over 4 years are at greatest risk. This is consistent with an infectious hypothesis where absence of stimulation to the developing immune system increases vulnerability to late infectious exposure, which may precipitate diabetes.

Large tables

The traditional exploration of large contingency tables leads to multiple comparisons with the inherent generation of chance associations. To allow for this, a simple empirical Bayesian approach is used here to derive estimates of association 'shrunk' towards a global mean. Estimates are displayed on ordered normal plots, to allow visual detection of outliers, with the addition of 'guide rails', derived from simulation, to facilitate their detection. The methods, and the interpretation of results, are illustrated using a large table of occupations for cancer registrations in England and Wales for 1971-90.

Residential radon exposure and adult acute leukaemia

Exposure to radioactive radon gas in homes, from natural sources, is an important public-health issue for many countries. We found no association between household exposure to radon and leukaemia in adults in the UK.

Early social mixing and childhood Type 1 diabetes mellitus: a case-control study in Yorkshire, UK

AIMS

Evidence from animal models shows an increased risk of Type 1 diabetes mellitus associated with the absence of early life exposure to pathogens. To test this 'hygiene hypothesis', patterns of social mixing and infections in the first year of life and the risk of developing autoimmune diabetes in childhood were examined.

METHODS

Personal interviews were conducted with the mothers of 220 children with Type 1 diabetes (0-15 years) and 433 age/sex matched controls from a population-based case control study in Yorkshire, UK. Social mixing including attendance at daycare, and infections occurring under 1 year of age were measures of exposure. Adjusted odds ratios (OR) were derived using conditional logistic regression.

RESULTS

Frequency of attendance at daycare during the 1st year of life was inversely associated with childhood diabetes (OR 0.71, 95% confidence interval 0.51-1.00, P = 0.05), a finding not explained by mother's age, level of education or maternal diabetes. Increasing numbers of children in the daycare setting and numbers of sessions attended were significantly associated with increasing protection from diabetes. The strongest effect was observed in children with diabetes diagnosed aged 0-4 years.

CONCLUSIONS

Social mixing through attendance at daycare in early infancy appears to confer protection against the development of childhood diabetes. This may be mediated through exposure to infectious agent(s) as a significant dose-response effect was evident with increasing numbers of child 'contacts'. These findings suggest early infectious exposure may play a role in the development of immunoregulatory mechanisms which protect against diabetes and further work is warranted.

Perinatal and neonatal determinants of childhood type 1 diabetes. A case-control study in Yorkshire, U.K

OBJECTIVE

To identify environmental factors that exert their effect in the perinatal and neonatal period and influence the subsequent onset of insulin dependent (type 1) diabetes during childhood.

RESEARCH DESIGN AND METHODS

A population-based case-control study of data abstracted from the hospital obstetric and neonatal records of 196 children with type 1 diabetes and 325 age- and sex-matched control subjects. Analysis of matched sets by conditional logistic regression was conducted for a range of perinatal and neonatal factors.

RESULTS

A significantly raised risk was observed for illnesses in the neonatal period (OR 1.61, 95% CI 1.06-2.44), the majority of which were infections and respiratory difficulties. Exclusive breast feeding as the initial feeding method was significantly protective (OR 0.65, 95% CI 0.45-0.94). There were no significant associations with high- or low-birth weight, being firstborn or small-for-dates. All factors significant (5% level) for the entire dataset, that is, maternal age, type 1 diabetes in mothers, preeclampsia, delivery by cesarean section, neonatal illnesses, and initial breast feeding were modeled and the OR remained significant for all variables other than cesarean section.

CONCLUSIONS

The findings are based on medical record data that cannot be subject to biased recall of mothers. Neonatal illnesses increased and initial breast feeding decreased the risk of childhood type 1 diabetes. Further determinants of risk are mothers with type 1 diabetes, older mothers, and preeclampsia during pregnancy.

Mortality and diabetes from a population based register in Yorkshire 1978-93

OBJECTIVE

To investigate mortality of children diagnosed with insulin dependent diabetes mellitus (IDDM) and to identify common factors before death.

DESIGN

Follow up of a population based cohort of children diagnosed with IDDM to ascertain deaths.

SETTING

Children were diagnosed in Yorkshire but followed up throughout the United Kingdom.

SUBJECTS

From the Yorkshire Children's Diabetes Register details of 1854 children aged 0-16 years (1978-93) were submitted to the NHS Central Register.

MAIN OUTCOME MEASURE

Notification and causes of death.

RESULTS

98.3% of cases were traced and 26 deaths identified. Follow up ranged from 1-18 years (median 9.3 years), providing 17,350 person-years of IDDM. Fifteen deaths (58%) were attributed to diabetes or its complications; 11 (42%) were unrelated and included one suicide. For mortality from all causes, the standardised mortality ratio (SMR) of 247 (95% confidence interval (CI) 163 to 362) was significantly increased for those under 34 years. The largest number of deaths (n = 10) occurred in the 15-19 year age range, with an SMR of 442 (95% CI 209 to 802). Case note examination showed a clear tendency towards poor diabetic control, and worries over control were expressed before death by health care professionals.

CONCLUSIONS

Despite advances in treatment, IDDM still carries an increased mortality for young people, particularly in the "transition" age range.

Nitrate in drinking water and the incidence of gastric, esophageal, and brain cancer in Yorkshire, England

OBJECTIVES

This small-area ecologic study in Yorkshire, northern England, examines the hypothesis that exposure to higher levels of nitrate in drinking water increases the risk of stomach, esophageal, or brain cancer in adults.

METHODS

Nitrate levels over the period 1990-95 and numbers of incident cancers from 1975-94 were available for 148 water supply zones, geographically defined areas each supplying water of homogeneous chemical composition to an average population of around 20,000.

RESULTS

No relationship was found between nitrate concentrations and the incidence of stomach or esophageal cancers. The incidence of cancer of the brain and central nervous system was found to be higher in areas with higher nitrate levels, with a relative risk of 1.18 (95 percent confidence interval = 1.08-1.30) in the quartile of the population with the highest average levels (mean 29.8 mg/l) compared with the lowest quartile (mean 2.4 mg/l). The increase in risk remained statistically significant (P < 0.01) after allowing for other covariates and for extra-Poisson variation in a regression model.

CONCLUSIONS

This study does not support the hypothesis of an increased risk of stomach or esophageal cancer associated with higher nitrate levels in drinking water. The observed relationship with brain cancer requires confirmation in other studies, including those involving data on individuals.

Small area variation in the incidence of childhood insulin-dependent diabetes mellitus in Yorkshire, UK: links with overcrowding and population density

BACKGROUND

The incidence of insulin-dependent diabetes mellitus (IDDM) incidence varies between and within countries. The origins of this variation are disputed, but they involve both genetic and non-genetic influences. To explore the role of environmental factors in the aetiology of IDDM we have examined the incidence in small geographical areas and related it to variables derived from national censuses.

METHODS

This is an ecological analysis of incidence data from a register of children with IDDM covering the counties of West Yorkshire, North Yorkshire and Humberside in the north of England. All children aged < or = 16, diagnosed with IDDM between 1978 and 1990 were eligible for inclusion. Spatial variation in incidence between electoral wards was investigated using Poisson regression, in relation to socioeconomic status, population density, urban-rural status and measures of geographical isolation. Ward child populations varied in size from 84 to 7197 (mean = 1545).

RESULTS

Rates were significantly lower in wards of high population density and with many overcrowded houses. The rate ratio for areas in the upper half of the childhood density distribution was 0.88 (95% confidence interval (CI): 0.78-0.99) and for the two upper tertiles of household overcrowding the rate ratios were 0.84 (95% CI: 0.74-0.95) and 0.68 (95% CI: 0.58-0.79) respectively.

CONCLUSIONS

The incidence of childhood IDDM was associated with environmental factors including population density and overcrowded homes. A possible inference from these data is that patterns of infection are involved in the occurrence of IDDM. Analytical epidemiological studies will be needed to investigate these ideas further.

Clustering of childhood IDDM. Links with age and place of residence

OBJECTIVE

To improve understanding of the etiology of IDDM by analyzing spatial and space-time distribution of the incidence in children.

RESEARCH DESIGN AND METHODS

Statistical tests to detect clustering were applied to a population-based register of 1,490 children (aged 0-16 years) with IDDM in Yorkshire, northern England. The Knox test analyzed clustering in space and time, and the Potthoff-Whittinghill test quantified spatial differences in incidence between small-area census units (electoral wards). The Potthoff-Whittinghill test was conditioned for childhood population density and deprivation (Townsend index).

RESULTS

Both tests demonstrated clustering of IDDM in Yorkshire children. Space-time and spatial clustering is strongest in the younger children (0-4 and 5-9 years of age), even after conditioning for known associations. Clustering was more common in the county of Humberside during the years 1982-1985 and in wards of low population density (< 0.26 0- to 16 year-old subjects per hectare).

CONCLUSIONS

The study revealed a nonrandom space-time distribution of IDDM in children not accounted for by known covarying demographic factors. The Potthoff-Whittinghill test has not previously been applied to childhood IDDM. The new finding of strong clustering in young children is consistent with early exposure, possibly in utero, to infectious agents or localized environmental sources.

Incidence of childhood diabetes mellitus in Yorkshire, northern England, is associated with nitrate in drinking water: an ecological analysis

The relationship between the incidence of childhood-onset insulin-dependent diabetes mellitus and levels of nitrate in drinking water in the former Yorkshire Regional Health Authority was investigated by means of an ecological analysis. A population-based register contributed 1797 0-16-year-olds diagnosed with diabetes between 1978 and 1994. Nitrate data were based on 9330 samples of drinking water tested between 1990 and 1995 in 148 water supply zones, for which 1991 census small area statistics were taken on population density, ethnicity and socio-economic status. Diabetes incidence was positively associated with raised mean nitrate levels with a standardised incidence ratio of 115 in zones with greater than 14.85 mg.1-1 (chi2 = 26.81, 1 df, p < 0.001). Significant negative trends were found between standardised incidence ratios and proportion of non-whites in the population (chi2 = 33.57, 1 df, p < 0.001), childhood population density (chi2 = 30.81, 1 df, p < 0.001) and the Townsend deprivation score (chi2 = 33.89, 1 df, p < 0.001). Poisson regression modelling, adjusting for the other factors, showed a significant increase in relative incidence rate ratio from a baseline of 1 at nitrate levels below 3.22 mg.1-1 to 1.27 (95% confidence interval 1.09, 1.48) for mean nitrate levels above 14.85 mg.1-1. An association between higher nitrate levels in domestic drinking water and incidence of childhood diabetes has been demonstrated. This was not explained by the ethnic composition of the population, population density or socioeconomic status. Nitrate in drinking water may be a precursor of chemicals which are toxic to the pancreas.

Geographical mapping of childhood diabetes in the northern English county of Yorkshire

This study aimed to highlight geographical differences in childhood Type 1 (insulin dependent) diabetes mellitus (IDDM) by mapping incidence at 3 different geographical scales, within the northern English county of Yorkshire. Mapping techniques are applied to incident cases from a population-based regional register of childhood IDDM. The Yorkshire Children's Diabetes Register (YCDR) comprises 1310 children (0-14 years) diagnosed with IDDM from 1978-1990. Age standardized incidence rates (cases/100000/year) are given for administrative county, standardized incidence ratios (SIRs) are mapped by local government district and electoral ward. Heterogeneity between areas was assessed by a chi 2 test. At county level, incidence is 25% higher in Humberside (16.82 per 100000 per year) compared to West Yorkshire (12.21 per 100000 per year) (p < 0.001). SIRs for the 22 districts display significant heterogeneity (p < 0.001) with deficits in the urban areas of Kirklees (70 95% CI 57-85) and Bradford (81 95% CI 68-95) and significant excesses in the rural districts of Ryedale (147 95% CI 106-198), Beverley (149 95% CI 113-193), Holderness (166 95% CI 112-237) and Boothferry (186 95% CI 134-250). At the smallest scale, variation between wards is significant (p < 0.001) and low incidence in urban areas is notable. Geographical variation in the incidence of childhood IDDM may provide strong clues to its aetiology. Within Yorkshire, geographical distribution shows significant heterogeneity at three different scales. The magnitude of the variation is not explained by ethnic or genetic differences in the population and underlines the important influence of environmental factors in disease aetiology.

Maternal vitamin E alters passively acquired immunity of chicks

Passively transferred antibody levels were significantly increased in plasma of two- and seven-day-old chicks when the dams were fed 150 and 450 p.p.m. vitamin E prior to immunization with Brucella abortus. However, if the hens were fed 90, 300 and 900 p.p.m. vitamin E before immunization, the chicks evidenced no increase in antibody titers relative to controls. This nonlinear antibody response by the reticulo-endothelial system to vitamin E confirms in Gallus domesticus similar results reported for other species.

Purification of ribonuclease T 1 by diethylaminoethylcellulose chromatography

A procedure is described for isolating the enzyme ribonuclease T(1) from Takadiastase, an extract of the mould Aspergillus oryzae. It involves an initial concentration of the enzyme by adsorption on DEAE-cellulose followed by gradient elution. Later the enzyme is chromatographed on the same adsorbent with an eluent of constant composition. Yields of 350-380mg of ribonuclease T(1) from 500g of Takadiastase were obtained.

Alkaline phosphatase and leucine aminopeptidase association in plasma of the chicken

Two electrophoretic vari ants of leucine aminopeptidase show direct association with two genetically controlled forms of alkaline phosphatase. Treatment of plasma with neuraminidase converted the faster-migrating form of both enzymes to slower-moving forms, but plasmas with slowermigrating forms were unaffected by this treatment. The two forms of the enzymes may be due to the presence or absence of a single gene controlling the attachment of sialic acid to the enzyme molecules.

Inheritance of two alkaline phosphatase variants in fowl plasma

Starch-gel electrophoresis of plasina reveals two mnutually exclusive forms of alkaline phosphatase. Analysis of the plasma of 931 birds from 96 sib families of two inbred lines through two generations shows that the faster-moving isozymne is determined by an autosomal gene Ap(2) which is completely dominant to its allele Ap(4) determining the slower form.