Building a vertically integrated genomic learning health system: The biobank at the Colorado Center for Personalized Medicine

Precision medicine initiatives across the globe have led to a revolution of repositories linking large-scale genomic data with electronic health records, enabling genomic analyses across the entire phenome. Many of these initiatives focus solely on research insights, leading to limited direct benefit to patients. We describe the biobank at the Colorado Center for Personalized Medicine (CCPM Biobank) that was jointly developed by the University of Colorado Anschutz Medical Campus and UCHealth to serve as a unique, dual-purpose research and clinical resource accelerating personalized medicine. This living resource currently has more than 200,000 participants with ongoing recruitment. We highlight the clinical, laboratory, regulatory, and HIPAA-compliant informatics infrastructure along with our stakeholder engagement, consent, recontact, and participant engagement strategies. We characterize aspects of genetic and geographic diversity unique to the Rocky Mountain region, the primary catchment area for CCPM Biobank participants. We leverage linked health and demographic information of the CCPM Biobank participant population to demonstrate the utility of the CCPM Biobank to replicate complex trait associations in the first 33,674 genotyped individuals across multiple disease domains. Finally, we describe our current efforts toward return of clinical genetic test results, including high-impact pathogenic variants and pharmacogenetic information, and our broader goals as the CCPM Biobank continues to grow. Bringing clinical and research interests together fosters unique clinical and translational questions that can be addressed from the large EHR-linked CCPM Biobank resource within a HIPAA- and CLIA-certified environment.

Decreased fucosylation impacts epithelial integrity and increases risk for COPD

COPD causes significant morbidity and mortality worldwide. Epithelial damage is fundamental to disease pathogenesis, although the mechanisms driving disease remain undefined. Published evidence from a COPD cohort (SPIROMICS) and confirmed in a second cohort (COPDgene) demonstrate a polymorphism in Fucosyltransferese-2 (FUT2) is a trans-pQTL for E-cadherin, which is critical in COPD pathogenesis. We found by MALDI-TOF analysis that FUT2 increased terminal fucosylation of E-cadherin. Using atomic force microscopy, we found that FUT2-dependent fucosylation enhanced E-cadherin-E-cadherin bond strength, mediating the improvement in monolayer integrity. Tracheal epithelial cells from Fut2-/- mice have reduced epithelial integrity, which is recovered with reconstitution of Fut2. Overexpression of FUT2 in COPD derived epithelia rescues barrier function. Fut2-/- mice show increased susceptibility in an elastase model of disease developing both emphysema and fibrosis. We propose this is due to the role of FUT2 in proliferation and cell differentiation. Overexpression of FUT2 significantly increased proliferation. Loss of Fut2 results in accumulation of Spc+ cells suggesting a failure of alveolar type 2 cells to undergo transdifferentiation to alveolar type 1. Using a combination of population data, genetically manipulated mouse models, and patient-derived cells, we present a novel mechanism by which post-translational modifications modulate tissue pathology and serve as a proof of concept for the development of a disease-modifying target in COPD.

Determinants of mosaic chromosomal alteration fitness

Clonal hematopoiesis (CH) is characterized by the acquisition of a somatic mutation in a hematopoietic stem cell that results in a clonal expansion. These driver mutations can be single nucleotide variants in cancer driver genes or larger structural rearrangements called mosaic chromosomal alterations (mCAs). The factors that influence the variations in mCA fitness and ultimately result in different clonal expansion rates are not well-understood. We used the Passenger-Approximated Clonal Expansion Rate (PACER) method to estimate clonal expansion rate for 6,381 individuals in the NHLBI TOPMed cohort with gain, loss, and copy-neutral loss of heterozygosity mCAs. Our estimates of mCA fitness were correlated (R 2 = 0.49) with an alternative approach that estimated fitness of mCAs in the UK Biobank using a theoretical probability distribution. Individuals with lymphoid-associated mCAs had a significantly higher white blood cell count and faster clonal expansion rate. In a cross-sectional analysis, genome-wide association study of estimates of mCA expansion rate identified TCL1A , NRIP1 , and TERT locus variants as modulators of mCA clonal expansion rate.

Dietary Sources of Linoleic Acid (LA) Differ by Race/Ethnicity in Adults Participating in the National Health and Nutrition Examination Survey (NHANES) between 2017-2018

Linoleic acid (LA) is a primary n-6 polyunsaturated fatty acid (PUFA), which is of interest to nutritional professionals as it has been associated with health outcomes. However, as some LA-rich foods offer protection against chronic diseases such as CVD (e.g., fatty fish), while others increase risk (e.g., red meat), the individual foods contributing to LA intake may be an important factor to consider. Therefore, this analysis sought to examine whether there are racial/ethnic differences in the proportion of overall LA intake accounted for by individual food groups, via a cross-sectional analysis of 3815 adults participating in the National Health and Nutrition Examination Survey (NHANES; 2017-2018 cycle). Separate multivariable linear regressions models specified the proportion of overall LA intake attributable to each of the nine food groups (dairy, eggs, fat, fish, fruits and vegetables, grains, meat, nuts, and sweets) as the outcome, and race/ethnicity as the predictor, with age, gender, and socioeconomic status (SES) as covariates, in order to estimate whether there were mean differences by race/ethnicity in the proportion of overall LA intake attributable to each of these foods seperately. After a Bonferroni correction for multiple testing, eggs, grains, fruits and vegetables, meat, and fish each accounted for a different proportion of overall LA intake according to racial/ethnic grouping (all p < 0.006 after a Bonferroni correction). These findings indicate the food sources of LA in the diet differ by race/ethnicity, and warrant future investigations into whether this plays a role in health disparities.

The genetic determinants of recurrent somatic mutations in 43,693 blood genomes

Nononcogenic somatic mutations are thought to be uncommon and inconsequential. To test this, we analyzed 43,693 National Heart, Lung and Blood Institute Trans-Omics for Precision Medicine blood whole genomes from 37 cohorts and identified 7131 non-missense somatic mutations that are recurrently mutated in at least 50 individuals. These recurrent non-missense somatic mutations (RNMSMs) are not clearly explained by other clonal phenomena such as clonal hematopoiesis. RNMSM prevalence increased with age, with an average 50-year-old having 27 RNMSMs. Inherited germline variation associated with RNMSM acquisition. These variants were found in genes involved in adaptive immune function, proinflammatory cytokine production, and lymphoid lineage commitment. In addition, the presence of eight specific RNMSMs associated with blood cell traits at effect sizes comparable to Mendelian genetic mutations. Overall, we found that somatic mutations in blood are an unexpectedly common phenomenon with ancestry-specific determinants and human health consequences.

Telomere Length and the Transition to Family Caregiving in the REGARDS Study

An increase in life expectancy and an aging population has resulted in increased risks and prevalence of age-related diseases. Previous studies have shown that factors, such as chronic stress, are associated with shorter telomere length. When telomeres become critically short, cells enter a state of senescence, which is a hallmark of aging. Several prior studies examining the relationship between caregiving and telomere length have reported mixed results. The present study utilized data from the Caregiving Transitions Study, an ancillary study to the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. The difference in telomere length across an average ~8.6 years was compared between 235 incident caregivers and 229 controls. Telomere length was determined using the qPCR telomere-to-single copy gene (IFNB1) ratio (T/S) for each participant at both baseline and follow-up timepoints. Regression models controlling for age, sex, race, and baseline telomere length examined the association between caregiving status (exposure) and the telomere length change (□T/S). Sensitivity models adjusted for potential lifestyle and socioeconomic factors, including income, education, BMI, cigarette smoking, and alcohol use. We did not observe a significant association between □T/S and caregiving (beta=0.041, p=0.615). Adding lifestyle and socioeconomic factors did not change the null relationship (beta=0.062, p=0.455). In conclusion, this study provides evidence against an association between caregiving and the change in telomere length. Ultimately, more research to address the complex relationship between caregiving and telomere attrition is needed in order to prevent or reduce adverse outcomes and improve the well-being of caregivers and care recipients.

The pharmacogenomics of inhaled corticosteroids and lung function decline in COPD

Inhaled corticosteroids (ICS) are widely prescribed for patients with chronic obstructive pulmonary disease (COPD), yet have variable outcomes and adverse reactions, which may be genetically determined. The primary aim of the study was to identify the genetic determinants for forced expiratory volume in 1 s (FEV₁) changes related to ICS therapy.In the Lung Health Study (LHS)-2, 1116 COPD patients were randomised to the ICS triamcinolone acetonide (n=559) or placebo (n=557) with spirometry performed every 6 months for 3 years. We performed a pharmacogenomic genome-wide association study for the genotype-by-ICS treatment effect on 3 years of FEV₁ changes (estimated as slope) in 802 genotyped LHS-2 participants. Replication was performed in 199 COPD patients randomised to the ICS, fluticasone or placebo.A total of five loci showed genotype-by-ICS interaction at p<5×10^-6; of these, single nucleotide polymorphism (SNP) rs111720447 on chromosome 7 was replicated (discovery p=4.8×10^-6, replication p=5.9×10^-5) with the same direction of interaction effect. ENCODE (Encyclopedia of DNA Elements) data revealed that in glucocorticoid-treated (dexamethasone) A549 alveolar cell line, glucocorticoid receptor binding sites were located near SNP rs111720447. In stratified analyses of LHS-2, genotype at SNP rs111720447 was significantly associated with rate of FEV₁ decline in patients taking ICS (C allele β 56.36 mL·year^-1, 95% CI 29.96-82.76 mL·year^-1) and in patients who were assigned to placebo, although the relationship was weaker and in the opposite direction to that in the ICS group (C allele β -27.57 mL·year^-1, 95% CI -53.27- -1.87 mL·year^-1).The study uncovered genetic factors associated with FEV₁ changes related to ICS in COPD patients, which may provide new insight on the potential biology of steroid responsiveness in COPD.

Impact of Rare and Common Genetic Variants on Diabetes Diagnosis by Hemoglobin A1c in Multi-Ancestry Cohorts: The Trans-Omics for Precision Medicine Program

Hemoglobin A1c (HbA1c) is widely used to diagnose diabetes and assess glycemic control in individuals with diabetes. However, nonglycemic determinants, including genetic variation, may influence how accurately HbA1c reflects underlying glycemia. Analyzing the NHLBI Trans-Omics for Precision Medicine (TOPMed) sequence data in 10,338 individuals from five studies and four ancestries (6,158 Europeans, 3,123 African-Americans, 650 Hispanics, and 407 East Asians), we confirmed five regions associated with HbA1c (GCK in Europeans and African-Americans, HK1 in Europeans and Hispanics, FN3K and/or FN3KRP in Europeans, and G6PD in African-Americans and Hispanics) and we identified an African-ancestry-specific low-frequency variant (rs1039215 in HBG2 and HBE1, minor allele frequency (MAF) = 0.03). The most associated G6PD variant (rs1050828-T, p.Val98Met, MAF = 12% in African-Americans, MAF = 2% in Hispanics) lowered HbA1c (-0.88% in hemizygous males, -0.34% in heterozygous females) and explained 23% of HbA1c variance in African-Americans and 4% in Hispanics. Additionally, we identified a rare distinct G6PD coding variant (rs76723693, p.Leu353Pro, MAF = 0.5%; -0.98% in hemizygous males, -0.46% in heterozygous females) and detected significant association with HbA1c when aggregating rare missense variants in G6PD. We observed similar magnitude and direction of effects for rs1039215 (HBG2) and rs76723693 (G6PD) in the two largest TOPMed African American cohorts, and we replicated the rs76723693 association in the UK Biobank African-ancestry participants. These variants in G6PD and HBG2 were monomorphic in the European and Asian samples. African or Hispanic ancestry individuals carrying G6PD variants may be underdiagnosed for diabetes when screened with HbA1c. Thus, assessment of these variants should be considered for incorporation into precision medicine approaches for diabetes diagnosis.

Development and Validation of an Analytical Method to Quantitate Tris(chloroisopropyl)phosphate in Rat and Mouse Plasma using Gas Chromatography with Flame Photometric Detection

Tris(chloropropyl)phosphate (TCPP) is an organophosphorus flame retardant (OPFR) and plasticizer increasingly used in consumer products and as a replacement for brominated flame retardants. Commercially available TCPP is a mixture of four structural isomers the most abundant of which is tris(1-chloro-2-propyl)phosphate (TCPP-1). Although there is a widespread use of TCPP and potential for human exposure, there is limited data on the safety or toxicity of TCPP. The National Toxicology Program is conducting long-term studies to examine the toxicity of the TCPP in rats after lifetime exposure, including perinatal oral exposure. Quantitative estimates of internal dose are essential to interpret toxicological findings in rodents. To aid in this, a method was fully validated to quantitate the most abundant isomer, TCPP-1, in female Harlan Sprague Dawley (HSD) rat and B6C3F1 mouse plasma with partial validation in male rat plasma, and male and female mouse plasma. The method used protein precipitation using trichloroacetic acid followed by the extraction with toluene, and analysis by gas chromatography with flame photometric detection. The performance of the method was evaluated over 5-70 ng TCPP-1/mL plasma. The method was linear (r ≥ 0.99), accurate (inter-day relative error: ≤ ± -7.2) and precise (inter-batch relative standard deviation: ≤27.5%). The validated method has lower limits of quantitation and detection of ~5 and 0.9 ng/mL, respectively, in female HSD rat plasma and can be used on samples as small as 50 μL demonstrating the applicability to plasma samples from toxicology studies.

Diabetes and Platelet Response to Low-Dose Aspirin

CONTEXT

Previous studies have suggested less cardioprotective benefit of aspirin in adults with diabetes, raising concerns about "aspirin resistance" and potentially reduced effectiveness for prevention of cardiovascular disease (CVD).

OBJECTIVE

To examine differences in platelet response to aspirin by diabetes status.

DESIGN, SETTING, PARTICIPANTS

We examined platelet response before and after aspirin (81 mg/day for 14 days) in 2113 adults (175 with diabetes, 1,938 without diabetes), in the Genetic Study of Aspirin Responsiveness cohort, who had family history of early-onset CVD.

MAIN OUTCOME MEASURES

In vivo platelet activation (urinary thromboxane B2), in vitro platelet aggregation to agonists (arachidonic acid, adenosine diphosphate, collagen), and platelet function analyzer-100 closure time.

RESULTS

Although adults with diabetes had higher in vivo platelet activation before aspirin, the reduction in in vivo platelet activation after aspirin was similar in those with vs without diabetes. Likewise, the reduction in multiple in vitro platelet measures was similar after aspirin by diabetes status. In regression analyses adjusted for age, sex, race, BMI, smoking, platelet counts, and fibrinogen levels, in vivo platelet activation remained higher in adults with vs without diabetes after aspirin (P = 0.04), but this difference was attenuated after additional adjustment for preaspirin levels (P = 0.10). No differences by diabetes status were noted for any of the in vitro platelet measures after aspirin in fully adjusted models that also accounted for preaspirin levels.

CONCLUSIONS

In vitro platelet response to aspirin does not differ by diabetes status, suggesting no intrinsic differences in platelet response to aspirin. Instead, factors extrinsic to platelet function should be investigated to give further insights into aspirin use for primary prevention in diabetes.

The genetics of smoking in individuals with chronic obstructive pulmonary disease

Background

Smoking is the principal modifiable environmental risk factor for chronic obstructive pulmonary disease (COPD) which affects 300 million people and is the 3rd leading cause of death worldwide. Most of the genetic studies of smoking have relied on self-reported smoking status which is vulnerable to reporting and recall bias. Using data from the Lung Health Study (LHS), we sought to identify genetic variants associated with quantitative smoking and cessation in individuals with mild to moderate COPD.

Methods

The LHS is a longitudinal multicenter study of mild-to-moderate COPD subjects who were all smokers at recruitment. We performed genome-wide association studies (GWASs) for salivary cotinine (n = 4024), exhaled carbon monoxide (eCO) (n = 2854), cigarettes per day (CPD) (n = 2706) and smoking cessation at year 5 follow-up (n = 717 quitters and 2175 smokers). The GWAS analyses were adjusted for age, gender, and genetic principal components.

Results

For cotinine levels, SNPs near UGT2B10 gene achieved genome-wide significance (i.e. P < 5 × 10^− 8) with top SNP rs10023464, P = 1.27 × 10^− 11. For eCO levels, one significant SNP was identified which mapped to the CHRNA3 gene (rs12914385, P = 2.38 × 10^− 8). A borderline region mapping to KCNMA1 gene was associated with smoking cessation (rs207675, P = 5.95 × 10^− 8). Of the identified loci, only the CHRNA3/5 locus showed significant associations with lung function but only in heavy smokers. No regions met genome-wide significance for CPD.

Conclusion

The study demonstrates that using objective measures of smoking such as eCO and/or salivary cotinine can more precisely capture the genetic contribution to multiple aspects of smoking behaviour. The KCNMA1 gene association with smoking cessation may represent a potential therapeutic target and warrants further studies.

Trial registration

The Lung Health Study ClinicalTrials.gov Identifier: NCT00000568. Date of registration: October 28, 1999.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0762-7) contains supplementary material, which is available to authorized users.

Surfactant protein D is a causal risk factor for COPD: results of Mendelian randomisation

Surfactant protein D (SP-D) is produced primarily in the lung and is involved in regulating pulmonary surfactants, lipid homeostasis and innate immunity. Circulating SP-D levels in blood are associated with chronic obstructive pulmonary disease (COPD), although causality remains elusive.In 4061 subjects with COPD, we identified genetic variants associated with serum SP-D levels. We then determined whether these variants affected lung tissue gene expression in 1037 individuals. A Mendelian randomisation framework was then applied, whereby serum SP-D-associated variants were tested for association with COPD risk in 11 157 cases and 36 699 controls and with 11 years decline of lung function in the 4061 individuals.Three regions on chromosomes 6 (human leukocyte antigen region), 10 (SFTPD gene) and 16 (ATP2C2 gene) were associated with serum SP-D levels at genome-wide significance. In Mendelian randomisation analyses, variants associated with increased serum SP-D levels decreased the risk of COPD (estimate -0.19, p=6.46×10^-03) and slowed the lung function decline (estimate=0.0038, p=7.68×10^-3).Leveraging genetic variation effect on protein, lung gene expression and disease phenotypes provided novel insights into SP-D biology and established a causal link between increased SP-D levels and protection against COPD risk and progression. SP-D represents a very promising biomarker and therapeutic target for COPD.

Uncovering the DNA methylation landscape in key regulatory regions within the FADS cluster

Genetic variants near and within the fatty acid desaturase (FADS) cluster are associated with polyunsaturated fatty acid (PUFA) biosynthesis, levels of several disease biomarkers and risk of human disease. However, determining the functional mechanisms by which these genetic variants impact PUFA levels remains a challenge. Utilizing an Illumina 450K array, we previously reported strong allele-specific methylation (ASM) associations (p = 2.69×10⁻²⁹) between a single nucleotide polymorphism (SNP) rs174537 and DNA methylation of CpG sites located in the putative enhancer region between FADS1 and FADS2, in human liver tissue. However, this array only featured 20 CpG sites within this 12kb region. To better understand the methylation landscape within this region, we conducted bisulfite sequencing of the region between FADS1 and FADS2. Liver tissues from 50 male subjects (27 European Americans, 23 African Americans) were obtained from the Pathobiological Determinants of Atherosclerosis in Youth (PDAY) study, and used to ascertain the genotype at rs174537 and methylation status across the region of interest. Associations between rs174537 genotype and methylation status of 136 CpG sites were determined. Age-adjusted linear regressions were used to assess ASM associations with rs174537 genotype. The majority of CpG sites (117 out of 136, 86%) exhibited high levels of methylation with the greatest variability observed at three key regulatory regions–the promoter regions for FADS1 and FADS2 and a putative enhancer site between the two genes. Eight CpG sites within the putative enhancer region displayed significant (FDR p <0.05) ASM associations with rs174537. These data support the concept that both genetic and epigenetic factors regulate PUFA biosynthesis, and raise fundamental questions as to how genetic variants such as rs174537 impact DNA methylation in distant regulatory regions, and ultimately the capacity of tissues to synthesize PUFAs.

Multiethnic Exome-Wide Association Study of Subclinical Atherosclerosis

BACKGROUND

The burden of subclinical atherosclerosis in asymptomatic individuals is heritable and associated with elevated risk of developing clinical coronary heart disease. We sought to identify genetic variants in protein-coding regions associated with subclinical atherosclerosis and the risk of subsequent coronary heart disease.

METHODS AND RESULTS

We studied a total of 25 109 European ancestry and African ancestry participants with coronary artery calcification (CAC) measured by cardiac computed tomography and 52 869 participants with common carotid intima-media thickness measured by ultrasonography within the CHARGE Consortium (Cohorts for Heart and Aging Research in Genomic Epidemiology). Participants were genotyped for 247 870 DNA sequence variants (231 539 in exons) across the genome. A meta-analysis of exome-wide association studies was performed across cohorts for CAC and carotid intima-media thickness. APOB p.Arg3527Gln was associated with 4-fold excess CAC (P=3×10^-10). The APOE ε2 allele (p.Arg176Cys) was associated with both 22.3% reduced CAC (P=1×10^-12) and 1.4% reduced carotid intima-media thickness (P=4×10^-14) in carriers compared with noncarriers. In secondary analyses conditioning on low-density lipoprotein cholesterol concentration, the ε2 protective association with CAC, although attenuated, remained strongly significant. Additionally, the presence of ε2 was associated with reduced risk for coronary heart disease (odds ratio 0.77; P=1×10^-11).

CONCLUSIONS

Exome-wide association meta-analysis demonstrates that protein-coding variants in APOB and APOE associate with subclinical atherosclerosis. APOE ε2 represents the first significant association for multiple subclinical atherosclerosis traits across multiple ethnicities, as well as clinical coronary heart disease.

Differential regulation of human and mouse IL33 expression in the lungs of human IL33 BAC transgenic mice

Interleukin-33 (IL33) is a member of the IL-1 cytokine family. IL33 polymorphisms are strongly associated with asthma susceptibility and IL33 deletion attenuates asthma in mice. However, the use of mouse models to elucidate the role of IL-33 in asthma is hampered by notably different tissue-specific patterns of IL33 expression in humans and mice.

To bypass this limitation, we generated mice carrying a 157 kB human BAC transgene (TG) that includes IL33 and its flanking sequences on chromosome 9. This TG contains protective alleles for a number of asthma-associated polymorphisms. Five founders with 1, 2, or 6 BAC copies were obtained. All were healthy, fertile, and transmitted the transgene at the expected Mendelian ratio.

To compare expression of transgenic human (h) and endogenous mouse (m)IL33, mice were challenged intranasally with Alternaria, which induces rapid release of mIL-33 in the lungs. Bronchoalveolar lavage fluid analysis showed that hIL-33 was also induced by Alternaria. Analysis of lung RNA by real-time PCR showed that Alternaria-induced hIL33 transcription was TG copy number-dependent and comparable with that of mIL33.

IL33 is known to be expressed by human but not mouse endothelial cells. Indeed, we found high levels of hIL33 RNA in endothelial cell-enriched mouse CD31+ lung cells while mIL33 was barely detectable.

These results suggest that tissue-specific hIL33 expression is controlled by cis-acting element(s) within the IL33 locus. More generally, our BAC TG appears to include all cis-regulatory elements necessary for faithful tissue-specific and copy number-dependent regulation of hIL33 expression, suggesting our mice are an ideal tool to study IL33 and its role in asthma.

Greater collagen-induced platelet aggregation following cyclooxygenase 1 inhibition predicts incident acute coronary syndromes

Greater ex vivo platelet aggregation to agonists may identify individuals at risk of acute coronary syndromes (ACS). However, increased aggregation to a specific agonist may be masked by inherent variability in other activation pathways. In this study, we inhibited the cyclooxygenase-1 (COX1) pathway with 2-week aspirin therapy and measured residual aggregation to collagen and ADP to determine whether increased aggregation in a non-COX1 pathway is associated with incident ACS. We assessed ex vivo whole blood platelet aggregation in 1,699 healthy individuals with a family history of early-onset coronary artery disease followed for 6±1.2 years. Incident ACS events were observed in 22 subjects. Baseline aggregation was not associated with ACS. After COX1 pathway inhibition, collagen-induced aggregation was significantly greater in participants with ACS compared with those without (29.0 vs. 23.6 ohms, p < 0.001). In Cox proportional hazards models, this association remained significant after adjusting for traditional cardiovascular risk factors (HR = 1.10, 95%CI = 1.06-1.15; p < 0.001). In contrast, ADP-induced aggregation after COX1 inhibition was not associated with ACS. After COX1 pathway inhibition, subjects with greater collagen-induced platelet aggregation demonstrated a significant excess risk of incident ACS. These data suggest that platelet activation related to collagen may play an important role in the risk of ACS.

Abstract 43: Increased Activation of Inflammatory Genes in Monocytes of Healthy People with Ischemic White Matter Disease

Introduction: White matter hyperintensities (WMH) on MRI represent small vessel ischemic cerebrovascular disease. Greater WMH burden is associated with higher levels of circulating inflammatory cytokines in persons > 65 years with dementia, suggesting a pro-inflammatory vascular process. We hypothesized that middle-aged, asymptomatic, apparently healthy high risk people with high WMH burden would demonstrate increased inflammatory gene expression in monocytes analyzed with microarray.

Methods: Subjects (N=70) were identified from a larger MRI study in 593 healthy family members of persons with early-onset CAD (< 60 years). We obtained monocytes and examined gene expression in all subjects (mean age 58.1 ± 10 years, range 30-73; 55% female; 36% African American). These included 35 subjects with the greatest WMH burden using volumetric methods in the larger study, and 35 unrelated age-sex-race matched controls with the lowest WMH burden. Monocyte mRNA was analyzed on Illumina Human HT12 v4 microarrays. We performed unsupervised principal component analysis (PCA) followed by ANOVA between high and low WMH groups. Genes with 2 SD differences in expression between groups were included for Gene Ontology permutation analysis using 1000 permutations within “GoMiner”. Only genes with the lowest false discovery rate (FDR) were summarized.

Results: PCA identified no significant clustering. A total of 1,315 genes were included in gene ontology analysis and resulted in 10 ontological categories with an FDR<0.01%. This included 164 genes all showing greater expression in the high WMH group. These were key inflammatory genes, such as tumor necrosis factor (TNF), interleukin-6 (IL-6), interleukin-8 (IL-8), toll like receptor 5 and 7 (TLR5, TLR7) and integrin alpha 5 and M (ITGA5, ITGAM).

Conclusions: Gene microarray ontological analysis of monocytes in healthy middle aged high risk people with greater WMH burden shows increased activation of genes of known innate inflammatory pathways. These findings likely reflect greater pro-inflammatory processes in persons with greater WMH, consistent with the presence of inflammation-mediated occult small vessel cerebrovascular disease in a healthy middle-aged population at increased risk for vascular diseases.

Genome-wide association study of lung function phenotypes in a founder population

BACKGROUND

Lung function is a long-term predictor of mortality and morbidity.

OBJECTIVE

We sought to identify single nucleotide polymorphisms (SNPs) associated with lung function.

METHODS

We performed a genome-wide association study (GWAS) of FEV1, forced vital capacity (FVC), and FEV1/FVC in 1144 Hutterites aged 6 to 89 years, who are members of a founder population of European descent. We performed least absolute shrinkage and selection operation regression to select the minimum set of SNPs that best predict FEV1/FVC in the Hutterites and used the GRAIL algorithm to mine the Gene Ontology database for evidence of functional connections between genes near the predictive SNPs.

RESULTS

Our GWAS identified significant associations between FEV1/FVC and SNPs at the THSD4-UACA-TLE3 locus on chromosome 15q23 (P = 5.7 × 10(-8) to 3.4 × 10(-9)). Nine SNPs at or near 4 additional loci had P < 10(-5) with FEV1/FVC. Only 2 SNPs were found with P < 10(-5) for FEV1 or FVC. We found nominal levels of significance with SNPs at 9 of the 27 previously reported loci associated with lung function measures. Among a predictive set of 80 SNPs, 6 loci were identified that had a significant degree of functional connectivity (GRAIL P < .05), including 3 clusters of β-defensin genes, 2 chemokine genes (CCL18 and CXCL12), and TNFRSF13B.

CONCLUSION

This study identifies genome-wide significant associations and replicates results of previous GWASs. Multimarker modeling implicated for the first time common variation in genes involved in antimicrobial immunity in airway mucosa that influences lung function.

Genome-wide association study of white blood cell count in 16,388 African Americans: the continental origins and genetic epidemiology network (COGENT)

Total white blood cell (WBC) and neutrophil counts are lower among individuals of African descent due to the common African-derived “null” variant of the Duffy Antigen Receptor for Chemokines (DARC) gene. Additional common genetic polymorphisms were recently associated with total WBC and WBC sub-type levels in European and Japanese populations. No additional loci that account for WBC variability have been identified in African Americans. In order to address this, we performed a large genome-wide association study (GWAS) of total WBC and cell subtype counts in 16,388 African-American participants from 7 population-based cohorts available in the Continental Origins and Genetic Epidemiology Network. In addition to the DARC locus on chromosome 1q23, we identified two other regions (chromosomes 4q13 and 16q22) associated with WBC in African Americans (P<2.5×10⁻⁸). The lead SNP (rs9131) on chromosome 4q13 is located in the CXCL2 gene, which encodes a chemotactic cytokine for polymorphonuclear leukocytes. Independent evidence of the novel CXCL2 association with WBC was present in 3,551 Hispanic Americans, 14,767 Japanese, and 19,509 European Americans. The index SNP (rs12149261) on chromosome 16q22 associated with WBC count is located in a large inter-chromosomal segmental duplication encompassing part of the hydrocephalus inducing homolog (HYDIN) gene. We demonstrate that the chromosome 16q22 association finding is most likely due to a genotyping artifact as a consequence of sequence similarity between duplicated regions on chromosomes 16q22 and 1q21. Among the WBC loci recently identified in European or Japanese populations, replication was observed in our African-American meta-analysis for rs445 of CDK6 on chromosome 7q21 and rs4065321 of PSMD3-CSF3 region on chromosome 17q21. In summary, the CXCL2, CDK6, and PSMD3-CSF3 regions are associated with WBC count in African American and other populations. We also demonstrate that large inter-chromosomal duplications can result in false positive associations in GWAS.

Although recent genome-wide association studies have identified common genetic variants associated with total white blood cell (WBC) and WBC sub-type counts in European and Japanese ancestry populations, whether these or other loci account for differences in WBC count among African Americans is unknown. By examining >16,000 African Americans, we show that, in addition to the previously identified Duffy Antigen Receptor for Chemokines (DARC) locus on chromosome 1, another variant, rs9131, and other nearby variants on human chromosome 4 are associated with total WBC count in African Americans. The variants span the CXCL2 gene, which encodes an inflammatory mediator involved in WBC production and migration. We show that the association is not restricted to African Americans but is also present in independent samples of European Americans, Hispanic Americans, and Japanese. This finding is potentially important because WBC mediate or have altered counts in a variety of acute and chronic disorders.

Platelet kainate receptor signaling promotes thrombosis by stimulating cyclooxygenase activation

RATIONALE

Glutamate is a major signaling molecule that binds to glutamate receptors including the ionotropic glutamate receptors; kainate (KA) receptor (KAR), the N-methyl-d-aspartate receptor, and the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor. Each is well characterized in the central nervous system, but glutamate has important signaling roles in peripheral tissues as well, including a role in regulating platelet function.

OBJECTIVE

Our previous work has demonstrated that glutamate is released by platelets in high concentrations within a developing thrombus and increases platelet activation and thrombosis. We now show that platelets express a functional KAR that drives increased agonist induced platelet activation.

METHODS AND RESULTS

KAR induced increase in platelet activation is in part the result of activation of platelet cyclooxygenase in a mitogen-activated protein kinase-dependent manner. Platelets derived from KAR subunit knockout mice (GluR6(-/-)) are resistant to KA effects and have a prolonged time to thrombosis in vivo. Importantly, we have also identified polymorphisms in KAR subunits that are associated with phenotypic changes in platelet function in a large group of whites and blacks.

CONCLUSIONS

Our data demonstrate that glutamate regulation of platelet activation is in part cyclooxygenase-dependent and suggest that the KAR is a novel antithrombotic target.

Sensitive detection of chromosomal segments of distinct ancestry in admixed populations

Identifying the ancestry of chromosomal segments of distinct ancestry has a wide range of applications from disease mapping to learning about history. Most methods require the use of unlinked markers; but, using all markers from genome-wide scanning arrays, it should in principle be possible to infer the ancestry of even very small segments with exquisite accuracy. We describe a method, HAPMIX, which employs an explicit population genetic model to perform such local ancestry inference based on fine-scale variation data. We show that HAPMIX outperforms other methods, and we explore its utility for inferring ancestry, learning about ancestral populations, and inferring dates of admixture. We validate the method empirically by applying it to populations that have experienced recent and ancient admixture: 935 African Americans from the United States and 29 Mozabites from North Africa. HAPMIX will be of particular utility for mapping disease genes in recently admixed populations, as its accurate estimates of local ancestry permit admixture and case-control association signals to be combined, enabling more powerful tests of association than with either signal alone.

Heritability of Platelet Responsiveness to Aspirin in Activation Pathways Directly and Indirectly Related to Cyclooxygenase-1

Background— The inability of aspirin (acetylsalicylic acid [ASA]) to adequately suppress platelet function is associated with future risk of myocardial infarction, stroke, and cardiovascular death. Genetic variation is a proposed but unproved mechanism for insufficient ASA responsiveness.

Methods and Results— We examined platelet ASA responsiveness in 1880 asymptomatic subjects (mean age, 44±13 years; 58% women) recruited from 309 white and 208 black families with premature coronary heart disease. Ex vivo platelet function was determined before and after ingestion of ASA (81 mg/d for 2 weeks) with the use of a panel of measures that assessed platelet activation in pathways directly and indirectly related to cyclooxygenase-1, the enzyme inhibited by ASA. The proportion of phenotypic variance related to CHD risk factor covariates was determined by multivariable regression. Heritability of phenotypes was determined with the use of variance components models unadjusted and adjusted for covariates. ASA inhibited arachidonic acid–induced aggregation and thromboxane B 2 production by ≥99% ( P <0.0001). Inhibition of urinary thromboxane excretion and platelet activation in pathways indirectly related to cyclooxygenase-1 was less pronounced and more variable (inhibition of 0% to 100%). Measured covariates contributed modestly to variability in ASA response phenotypes ( r 2 =0.001 to 0.133). Phenotypes indirectly related to cyclooxygenase-1 were strongly and consistently heritable across races (h 2 =0.266 to 0.762; P <0.01), but direct cyclooxygenase-1 phenotypes were not.

Conclusions— Heritable factors contribute prominently to variability in residual platelet function after ASA exposure. These data suggest a genetic basis for the adequacy of platelet suppression by ASA and potentially for differences in the clinical efficacy of ASA.

Susceptibility to ozone-induced airway inflammation is associated with decreased levels of surfactant protein D

Background

Ozone (O₃), a common air pollutant, induces exacerbation of asthma and chronic obstructive pulmonary disease. Pulmonary surfactant protein (SP)-D modulates immune and inflammatory responses in the lung. We have shown previously that SP-D plays a protective role in a mouse model of allergic airway inflammation. Here we studied the role and regulation of SP-D in O₃-induced inflammatory changes in the lung.

Methods

To evaluate the effects of O₃ exposure in mouse strains with genetically different expression levels of SP-D we exposed Balb/c, C57BL/6 and SP-D knockout mice to O₃ or air. BAL cellular and cytokine content and SP-D levels were evaluated and compared between the different strains. The kinetics of SP-D production and inflammatory parameters were studied at 0, 2, 6, 12, 24, 48, and 72 hrs after O₃ exposure. The effect of IL-6, an O₃-inducible cytokine, on the expression of SP-D was investigated in vitro using a primary alveolar type II cell culture.

Results

Ozone-exposed Balb/c mice demonstrated significantly enhanced acute inflammatory changes including recruitment of inflammatory cells and release of KC and IL-12p70 when compared with age- and sex-matched C57BL/6 mice. On the other hand, C57BL/6 mice had significantly higher levels of SP-D and released more IL-10 and IL-6. Increase in SP-D production coincided with the resolution of inflammatory changes. Mice deficient in SP-D had significantly higher numbers of inflammatory cells when compared to controls supporting the notion that SP-D has an anti-inflammatory function in our model of O₃ exposure. IL-6, which was highly up-regulated in O₃ exposed mice, was capable of inducing the expression of SP-D in vitro in a dose dependent manner.

Conclusion

Our data suggest that IL-6 contributes to the up-regulation of SP-D after acute O₃ exposure and elevation of SP-D in the lung is associated with the resolution of inflammation. Absence or low levels of SP-D predispose to enhanced inflammatory changes following acute oxidative stress.

Genome scan for loci linked to mite sensitivity: the Collaborative Study on the Genetics of Asthma (CSGA)

Mite sensitivity has been reported to be a major risk factor for asthma. As part of the Collaborative Study on the Genetics of Asthma (CSGA), a genome scan using mite reactivity (Dermatophagoides Pteronyssinus (Der p) and Dermatophagoides farinae (Der f)) as the phenotype was conducted. In 287 CSGA families, 122 were informative for linkage. Evidence supporting linkage was observed for regions on chromosome 19 (D19S591, lod=2.43, P=0.0008; D19S1037, lod=1.57, P=0.007) and chromosome 20 (D20S473/D20S604, lod=1.41, P=0.01). All three ethnic groups appeared to contribute to the evidence for linkage on chromosome 20. African-American families gave strongest support for linkage on chromosomes 3 (D3S2409, lod=1.33, P=0.01), 12 (D12S373, lod=1.51, P=0.008) and 18 (ATA82B02, lod=1.32, P=0.01). Caucasian families showed strong evidence for linkage on chromosome 19 (D19S591, lod=3.51, P=0.00006). Hispanic families supported linkage on chromosomes 11 (D11S1984, lod=1.56, P=0.007), 13 (D13S787, lod=1.30, P=0.01) and 20 (D20S470, lod=1.71, P=0.005). These results suggest that multiple genes may be involved in controlling skin reactivity to Dermatophoigoies.

Optical dysfunction of the crystalline lens in aquaporin-0-deficient mice

Aquaporin-0 (AQP0), a water transport channel protein, is the major intrinsic protein (MIP) of lens fiber cell plasma membranes. Mice deficient in the gene for AQP0 (Aqp0, Mip) were generated from a library of gene trap embryo stem cells. Sequence analysis showed that the gene trap vector had inserted into the first exon of Aqp0, causing a null mutation as verified by RNA blotting and immunochemistry. At 3 wk of age (postnatal day 21), lenses from null mice (Aqp0(-/-)) contained polymorphic opacities, whereas lenses from heterozygous mice (Aqp0(+/-)) were transparent and did not develop frank opacities until approximately 24 wk of age. Osmotic water permeability values for Aqp0(+/-) and Aqp0(-/-) lenses were reduced to approximately 46% and approximately 20% of wild-type values, respectively, and the focusing power of Aqp0(+/-) lenses was significantly lower than that of wild type. These findings show that heterozygous loss of AQP0 is sufficient to trigger cataractogenesis in mice and suggest that this MIP is required for optimal focusing of the crystalline lens.

Detection of immunoglobulin G in the lung and liver of hamsters with visceral leishmaniasis

Several organs are affected in visceral leishmaniasis, not only those rich in mononuclear phagocytes. Hypergammaglobulinemia occurs during visceral leishmaniasis; anti-Leishmania antibodies are not primarily important for protection but might be involved in the pathogenesis of tissue lesions. The glomerulonephritis occurring in visceral leishmaniasis has been attributed to immune complex deposition but in other organs the mechanism has not been studied. In the current study we demonstrated the presence of IgG in the lung and liver of hamsters with visceral leishmaniasis. Hamsters were injected intraperitoneally with 2 x 10(7) amastigotes of Leishmania (Leishmania) chagasi and the presence of IgG in the liver and lung was evaluated at 7, 15, 30, 45, 80 and 102 days postinfection (PI) by immunohistochemistry. The parasite burden in the spleen and liver increased progressively during infection. We observed a deposit of IgG from day 7 PI that increased progressively until it reached highest intensity around 30 and 45 days PI, declining at later times. The IgG deposits outlined the sinusoids. In the lung a deposit of IgG was observed in the capillary walls that was moderate at day 7 PI, but the intensity increased remarkably at day 30 PI and declined at later times of infection. No significant C3 deposits were observed in the lung or in the liver. We conclude that IgG may participate in the pathogenesis of the inflammatory process of the lung and liver occurring in experimental visceral leishmaniasis and we discuss an alternative mechanism other than immune complex deposition.

Proportion positive for Epstein-Barr virus, cytomegalovirus, human herpesvirus 6, Toxoplasma, and human immunodeficiency virus types 1 and 2 in heterophile-negative patients with an absolute lymphocytosis or an instrument-generated atypical lymphocyte flag

OBJECTIVES

To determine the proportion of patients with evidence of an acute infection due to Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpesvirus 6 (HHV-6), Toxoplasma, or human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2) in heterophile-negative patients with an absolute lymphocytosis or an instrument-generated atypical lymphocyte flag, and to develop a cost-effective testing algorithm for managing such heterophile-negative patients.

DESIGN

We conducted a prospective investigation of 70 selected outpatients who tested negative for heterophile antibody in association with an absolute lymphocytosis or instrument-generated atypical lymphocyte flag. The control population consisted of 50 patients who were heterophile negative and had a normal absolute lymphocyte count and no instrument-generated atypical lymphocyte flag.

SETTING

A large outpatient laboratory system.

INTERVENTION

Viral serology for HHV-6 was performed by immunofluorescence, and all other serologies were performed by enzyme-linked immunoassay. All testing was for immunoglobulin (Ig) M antibodies, except in the case of HIV.

RESULTS

The proportion of study patients positive for EBV was 40% (28/70); for CMV, 39% (27/70); for HHV-6, 25% (16/65); for Toxoplasma, 3% (2/70); and for HIV, 0% (0/70). All 50 control patients were negative for EBV IgM antibodies. When patients with more than 1 positive viral test were excluded from analysis, positivity was 20% (9/45) for EBV, 22% (10/45) for CMV, 9% (4/45) for HHV-6, and 2% (1/45) for Toxoplasma. Utilizing hypothesis-generating logistic regression models, Downey type II atypical lymphocytes were significantly associated with EBV positivity (P =.006), while Downey type III lymphocytes were significantly associated with HHV-6 positivity (P =.016), and there was a trend for the association of Downey type I lymphocytes with CMV positivity (P =.097).

CONCLUSIONS

A positive viral serology was identified in 70% of study patients. Multiple positive serologies complicate establishing a definitive diagnosis. Potential cost savings may be associated with the use of an appropriate testing algorithm.

Identifying the need for curriculum change. When a rural training program needs reform

OBJECTIVE

To identify what changes should be made in the University of British Columbia's rural family practice training program curriculum to help graduates be better prepared to practice.

DESIGN

Two cross-sectional surveys via mailed questionnaires: one designed to measure physicians' self-reported preparedness for practice and the other to measure the importance of various rural family medicine components.

SETTING

Rural training program graduates and preceptors representing rural communities in British Columbia.

PARTICIPANTS

Thirty-nine graduates of the rural training program between 1982 and 1991 and 14 community-based rural training program preceptors representing eight communities throughout the province participated in this study.

MAIN OUTCOME MEASURES

Percentage of graduates of the rural program who reported themselves to be underprepared on each family practice item and preceptors' mean scores for the attributed importance to rural practice of each item on this questionnaire.

RESULTS

A list of curriculum areas most in need of reform was created. This list included trauma, counseling skills, radiology, vacuum extraction, fracture care, exercising community leadership, cost-effective use of diagnostic tests, using community health resources, obtaining hospital privileges, ophthalmology, dermatology, otolaryngology, personal and professional growth, relationships with other physicians, and personnel issues.

CONCLUSIONS

Using both the level of graduates' self-reported underpreparedness and the attributed importance of elements of rural practice, as indicated by the preceptor survey, we developed a list of the areas of the rural training program curriculum most in need of reform.

Randomised double-blind placebo-controlled study on adverse effects of rubella immunisation in seronegative women

BACKGROUND

The objective of our study was to investigate the association of adverse clinical musculoskeletal and neurological events in healthy postpartum women with live attenuated (RA27/3 strain) rubella-virus vaccine, and to assess the frequency of acute and recurrent arthralgia and arthritis and associations with acute and recurrent muscle pain (myalgia) and neurological manifestations (paraesthesias).

METHODS

We used a randomised placebo-controlled, double-blind design in a community setting. 636 women were enrolled and, after 90 women dropped out, 546 healthy women aged 18-41 years, who were rubella seronegative on routine screening were immunised parenterally with either monovalent live attenuated (RA27/3 strain) rubella vaccine (n = 270) or saline placebo (n = 276) in the postpartum period. Outcome measures were the occurrence of acute and persistent or recurrent joint manifestations (arthralgia or arthritis) at 1, 3, 6, 9, and 12 months after immunisation. Occurrence of muscle pain (myalgia), and neurological symptoms (paraesthesia) was also assessed at the same times.

FINDINGS

543 women completed 1-month follow-up. 456 women completed the 12-month assessment. There were no differences at the time of immunisation between rubella vaccine and placebo groups in distribution of age, ethnic origin, parity, time between delivery and immunisation, breastfeeding history, or histories of earlier rubella vaccination or joint complaints. Results indicated a significantly higher incidence (p = 0.006; odds ratio = 1.73 [95% CI = 1.17-2.57]) of acute joint manifestations in rubella-vaccine recipients (30%) than in placebo recipients (20%). Frequency of chronic (recurrent) arthralgia or arthritis was only marginally significant (p = 0.042; 1.58 [1.01-2.45]).

INTERPRETATION

RA27/3 rubella vaccine given to seronegative women during the postpartum period was significantly associated with development of acute arthralgia or arthritis. Although the numbers of women assessed and length of follow-up revealed only marginally significant differences in persistent or recurrent joint manifestations between rubella vaccine and placebo recipients, it is possible that susceptible women who are given rubella vaccination may experience this outcome.

Training for rural practice. Are graduates of a UBC program well prepared?

OBJECTIVE

To evaluate preparedness for rural practice and to ascertain where graduates of a community-based rural training program practise.

DESIGN

Mailed cross-sectional survey.

SETTING

Rural communities in British Columbia.

PARTICIPANTS

Graduates of the University of British Columbia's (UBC) rural training program from 1982 to 1991 and a random sample of non-program-trained rural BC physicians.

MAIN OUTCOME MEASURES

Self-reported preparedness for rural practice in various areas of family medicine and in aspects of professional and personal life in rural settings. Locations of practice.

RESULTS

Rural program graduates reported themselves better prepared in family medicine, community medicine, practice management, and behavioural science. Non-program-trained rural physicians thought themselves better prepared in medical subspecialties. Responses in pediatrics, obstetrics and gynecology, and surgical preparation showed no important differences. Rural program residents were located in rural areas (51%), regional settings (20.5%), and metropolitan areas (17.9%).

CONCLUSION

Graduates of the UBC rural training program consider themselves better prepared for rural family practice than non-program-trained rural physicians in several areas of family practice. Most graduates of the program were practising in rural and regional settings.

Renal bone disease in pediatric and young adult patients on hemodialysis in a children's hospital

Renal bone disease has been well defined in adult patients receiving chronic dialysis and in children on peritoneal dialysis/continuous ambulatory peritoneal dialysis. However, little is known about the histologic features in patients undergoing chronic hemodialysis in a children's hospital center. Twenty one patients, aged 17.5 +/- 1.5 yr, on hemodialysis for 35 +/- 6 months underwent iliac crest bone biopsies and deferoxamine infusion tests. Nineteen of 21 patients were receiving oral calcitriol. The 21 patients were classified by histomorphometry as follows: osteitis fibrosa, 5; mild hyperparathyroidism, 3; normal histology, 3; aplastic, 6; and mixed lesions, 4. Four of 21 patients were surface positive for aluminum, and seven other patients stained positive for iron in bone. Serum parathyroid hormone (PTH) levels correlated directly with the bone formation rate (r = 0.84) and with eroded bone perimeter (r = 0.67). Eight of the nine patients with serum PTH levels above 125 pg/mL had marrow fibrosis. All patients with serum calcium levels < 10.0 mg/dL and serum PTH levels > 125 pg/mL had either osteitis fibrosa or mixed bone lesions--a group of patients that might benefit from aggressive vitamin D therapy. In contrast, an examination of patients with serum calcium levels > 10.0 mg/dL and serum PTH levels < 65 pg/mL correctly identified three out of three patients with aluminum-related bone disease. These findings suggest that measurements of serum intact PTH levels by the immunoradiometric assay method may be valuable in distinguishing high-turnover lesions from normal or low-turnover skeletal lesions in this population.

A case of a hepatitis B infected practitioner

The first case of a dental practitioner infected by a blood-borne pathogen to be identified to the College of Dental Surgeons of B.C. and reviewed by the Dental Profession Advisory Program's infected practitioner program committee is reported. After the committee was contacted, the infected practitioner's status was evaluated and guidelines were provided to him. This paper reviews the committee's decision-making process, particularly with respect to its management of the infected dental practitioner.

Quantitative risk approaches for formaldehyde

Formaldehyde presents unique data that highlight significant issues in the extrapolation of animal studies to human risk assessments. Formaldehyde causes rare nasal cancer in rats at 15 ppm, but not at lower levels of 2 ppm and 0.5 ppm in the range of human exposures. Mice and hamster studies even at high levels have results similar to low dose rats. Higginson et al. reviewed the human epidemiology studies and concluded that no excess cancer risk was observed; and if a risk exists, it is very low. Formaldehyde is a natural metabolite--the human body turns over 51 g/day. Cells, therefore, have detoxification and other defence mechanisms to formaldehyde. Recent CIIT biomechanism results elucidate these factors. These data raise two issues: First, the appropriateness of linear quantitative risk methodology given the non-linear nature of the biological data. Either a non-linear (threshold) statistical model or NOEL approach are appropriate risk assessment techniques for formaldehyde. Second, the rare nasal cancer observed in rats also occurs in control animals. A comparison of relative risk between background and low formaldehyde exposures has been calculated for both groups. Non-linear (MLE) 5 stage multistage models estimate 0 per million risk from both background and 1 ppm of formaldehyde exposure. Linear or upperbound (95%) estimates are 7,200/million from background and 5,000/million from 1 ppm formaldehyde. These estimates have a significant impact on formaldehyde regulatory programs for warning labels and "safe" exposure levels.

EEG sleep evaluation of depression in borderline patients

In this study the sleep of borderline patients and patients with primary nondelusional depression showed sleep continuity disturbance and greater REM activity and density (particularly during the first REM period) than that of normal control subjects. First-night REM latencies were more variable in the borderline than in the depressed group, but by the second night both groups showed shorter REM latencies than the controls. The similarities in EEG sleep suggest a relationship between borderline disorder and the affective spectrum and cast doubt on the definition of the borderline disorder as a pure character type.

Impaired renal and extrarenal potassium adaptation in old rats

Young (3 to 4 months) and old (21 to 22 months) rats were fed either a regular or high potassium (K) diet. After acute potassium chloride infusion, the fraction of infused K excreted (K efficiency) was similar in rats on a normal diet (57 +/- 3%, young, vs. 61 +/- 2%, old). With high K feeding there was a significant increase in the young, 69 +/- 4%, but not in the old rats, 62 +/- 2%. Na-K ATPase activity was markedly reduced in the renal medulla of old rats on a regular or high K diet. In addition, the response to acute K loading was compared in acutely nephrectomized rats. In the young rats on a regular diet plasma K increased from 3.72 +/- 0.09 to 5.28 +/- 0.16 mEq/liter while with K ingestion the increase was significantly less, 3.62 +/- 0.07 to 4.75 +/- 0.12 mEq/liter. In the old rats plasma K increased similarly on a regular or high K diet, 3.68 +/- 0.10 to 5.68 +/- 0.33 mEq/liter and 3.76 +/- 0.06 to 5.97 +/- 0.30 mEq/liter, respectively. Thus, old rats have impaired renal and extrarenal adaptation, but they have a normal response to an acute K challenge. A reduction in Na-K ATPase may account for the defect in renal adaptation in the aged rats.

Prophylaxis of recurring urinary tract infection in females: a comparison of nitrofurantoin with trimethoprim-sulfamethoxazole

Twenty-eight females with recurrent urinary tract infection were treated to eradicate their existing infections and then observed for recurrences while receiving one of the three following prophylactic regimens for 6 to 12 months: nitrofurantoin, 50 mg daily; one half tablet of trimethoprim-sulfamethoxazole (TMP-SMX) twice weekly; or one tablet of TMP-SMX once weekly. Preadolescent girls received half the adult doses. After completion of the course of prophylactic agent the patients were followed up at bimonthly intervals until infection recurred. After eradication of this new infection they were started on another prophylactic regimen. Six infections (1.0/patient-year) recurred in patients on nitrofurantoin, four infections (0.4/patients-year) reucrred in those receiving twice weekly TMP-SMX, and 12 infections (1.3/patient-year) in those receiving once weekly TMP-SMX. The mean interval between discontinuation of prophylaxis and recurrence of infection was 2.6 months. TMP-SMX in the doses used eliminated aerobic gram-negative rods from swabs from the anal canal in many patients. Gram-negative organisms resistant to trimethoprim did not cause infection either during or after therapy.