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The Minnesota Center for Twin and Family Research (MCTFR) comprises multiple longitudinal, community-representative investigations of twin and adoptive families that focus on psychological adjustment, personality, cognitive ability and brain function, with a special emphasis on substance use and related psychopathology. The MCTFR includes the Minnesota Twin Registry (MTR), a cohort of twins who have completed assessments in middle and older adulthood; the Minnesota Twin Family Study (MTFS) of twins assessed from childhood and adolescence into middle adulthood; the Enrichment Study (ES) of twins oversampled for high risk for substance-use disorders assessed from childhood into young adulthood; the Adolescent Brain (AdBrain) study, a neuroimaging study of adolescent twins; and the Siblings Interaction and Behavior Study (SIBS), a study of adoptive and nonadoptive families assessed from adolescence into young adulthood. Here we provide a brief overview of key features of these established studies and describe new MCTFR investigations that follow up and expand upon existing studies or recruit and assess new samples, including the MTR Study of Relationships, Personality, and Health (MTR-RPH); the Colorado-Minnesota (COMN) Marijuana Study; the Adolescent Brain Cognitive Development (ABCD) study; the Colorado Online Twins (CoTwins) study and the Children of Twins (CoT) study.
Here we provide an update of the 2013 report on the Nigerian Twin and Sibling Registry (NTSR). The major aim of the NTSR is to understand genetic and environmental influences and their interplay in psychological and mental health development in Nigerian children and adolescents. Africans have the highest twin birth rates among all human populations, and Nigeria is the most populous country in Africa. Due to its combination of large population and high twin birth rates, Nigeria has one of the largest twin populations in the world. In this article, we provide current updates on the NTSR samples recruited, recruitment procedures, zygosity assessment and findings emerging from the NTSR.
Smoking prevalence is higher amongst individuals with schizophrenia and depression compared with the general population. Mendelian randomisation (MR) can examine whether this association is causal using genetic variants identified in genome-wide association studies (GWAS).
We conducted two-sample MR to explore the bi-directional effects of smoking on schizophrenia and depression. For smoking behaviour, we used (1) smoking initiation GWAS from the GSCAN consortium and (2) we conducted our own GWAS of lifetime smoking behaviour (which captures smoking duration, heaviness and cessation) in a sample of 462690 individuals from the UK Biobank. We validated this instrument using positive control outcomes (e.g. lung cancer). For schizophrenia and depression we used GWAS from the PGC consortium.
There was strong evidence to suggest smoking is a risk factor for both schizophrenia (odds ratio (OR) 2.27, 95% confidence interval (CI) 1.67–3.08, p < 0.001) and depression (OR 1.99, 95% CI 1.71–2.32, p < 0.001). Results were consistent across both lifetime smoking and smoking initiation. We found some evidence that genetic liability to depression increases smoking (β = 0.091, 95% CI 0.027–0.155, p = 0.005) but evidence was mixed for schizophrenia (β = 0.022, 95% CI 0.005–0.038, p = 0.009) with very weak evidence for an effect on smoking initiation.
These findings suggest that the association between smoking, schizophrenia and depression is due, at least in part, to a causal effect of smoking, providing further evidence for the detrimental consequences of smoking on mental health.
Dietary Zn has significant impacts on the growth and development of breeding rams. The objectives of this study were to evaluate the effects of dietary Zn source and concentration on serum Zn concentration, growth performance, wool traits and reproductive performance in rams. Forty-four Targhee rams (14 months; 68 ± 18 kg BW) were used in an 84-day completely randomized design and were fed one of three pelleted dietary treatments: (1) a control without fortified Zn (CON; n = 15; ~1 × NRC); (2) a diet fortified with a Zn amino acid complex (ZnAA; n = 14; ~2 × NRC) and (3) a diet fortified with ZnSO4 (ZnSO4; n = 15; ~2 × NRC). Growth and wool characteristics measured throughout the course of the study were BW, average daily gain (ADG), dry matter intake (DMI), feed efficiency (G : F), longissimus dorsi muscle depth (LMD), back fat (BF), wool staple length (SL) and average fibre diameter (AFD). Blood was collected from each ram at four time periods to quantify serum Zn and testosterone concentrations. Semen was collected 1 to 2 days after the trial was completed. There were no differences in BW (P = 0.45), DMI (P = 0.18), LMD (P = 0.48), BF (P = 0.47) and AFD (P = 0.9) among treatment groups. ZnSO4 had greater (P ≤ 0.03) serum Zn concentrations compared with ZnAA and CON treatments. Rams consuming ZnAA had greater (P ≤ 0.03) ADG than ZnSO4 and CON. There tended to be differences among groups for G : F (P = 0.06), with ZnAA being numerically greater than ZnSO4 and CON. Wool staple length regrowth was greater (P < 0.001) in ZnSO4 and tended to be longer (P = 0.06) in ZnAA treatment group compared with CON. No differences were observed among treatments in scrotal circumference, testosterone, spermatozoa concentration within ram semen, % motility, % live sperm and % sperm abnormalities (P ≥ 0.23). Results indicated beneficial effects of feeding increased Zn concentrations to developing Targhee rams, although Zn source elicited differential responses in performance characteristics measured.
Identifying risk factors of individuals in a clinical-high-risk state for psychosis are vital to prevention and early intervention efforts. Among prodromal abnormalities, cognitive functioning has shown intermediate levels of impairment in CHR relative to first-episode psychosis and healthy controls, highlighting a potential role as a risk factor for transition to psychosis and other negative clinical outcomes. The current study used the AX-CPT, a brief 15-min computerized task, to determine whether cognitive control impairments in CHR at baseline could predict clinical status at 12-month follow-up.
Baseline AX-CPT data were obtained from 117 CHR individuals participating in two studies, the Early Detection, Intervention, and Prevention of Psychosis Program (EDIPPP) and the Understanding Early Psychosis Programs (EP) and used to predict clinical status at 12-month follow-up. At 12 months, 19 individuals converted to a first episode of psychosis (CHR-C), 52 remitted (CHR-R), and 46 had persistent sub-threshold symptoms (CHR-P). Binary logistic regression and multinomial logistic regression were used to test prediction models.
Baseline AX-CPT performance (d-prime context) was less impaired in CHR-R compared to CHR-P and CHR-C patient groups. AX-CPT predictive validity was robust (0.723) for discriminating converters v. non-converters, and even greater (0.771) when predicting CHR three subgroups.
These longitudinal outcome data indicate that cognitive control deficits as measured by AX-CPT d-prime context are a strong predictor of clinical outcome in CHR individuals. The AX-CPT is brief, easily implemented and cost-effective measure that may be valuable for large-scale prediction efforts.
The COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) project is a large international collaborative effort to analyze individual-level phenotype data from twins in multiple cohorts from different environments. The main objective is to study factors that modify genetic and environmental variation of height, body mass index (BMI, kg/m2) and size at birth, and additionally to address other research questions such as long-term consequences of birth size. The project started in 2013 and is open to all twin projects in the world having height and weight measures on twins with information on zygosity. Thus far, 54 twin projects from 24 countries have provided individual-level data. The CODATwins database includes 489,981 twin individuals (228,635 complete twin pairs). Since many twin cohorts have collected longitudinal data, there is a total of 1,049,785 height and weight observations. For many cohorts, we also have information on birth weight and length, own smoking behavior and own or parental education. We found that the heritability estimates of height and BMI systematically changed from infancy to old age. Remarkably, only minor differences in the heritability estimates were found across cultural–geographic regions, measurement time and birth cohort for height and BMI. In addition to genetic epidemiological studies, we looked at associations of height and BMI with education, birth weight and smoking status. Within-family analyses examined differences within same-sex and opposite-sex dizygotic twins in birth size and later development. The CODATwins project demonstrates the feasibility and value of international collaboration to address gene-by-exposure interactions that require large sample sizes and address the effects of different exposures across time, geographical regions and socioeconomic status.
Lifelong health is thought to be partially set during intrauterine life by persistent epigenetic changes induced by the prenatal environment. To evaluate this hypothesis, we initiated a prospective longitudinal study in monochorionic (MC) twins: the TwinLIFE study. MC twins are monozygotic, thus in origin genetically identical, and share a single placenta. Although MC twins have many environmental factors in common, in one-third of the MC twin pairs, one fetus has significantly less access to nutrients and resources during pregnancy than its co-twin often resulting in a significant discordance in prenatal growth. Hence, MC twins constitute a unique natural experiment to study the influence of the prenatal environment on health. In TwinLIFE, we will chart intrapair differences in DNA methylation focusing on mesenchymal stromal cells isolated from cord as an advanced proxy of epigenetic dysregulation relevant for long-term health consequences. Next, we will follow up the MC twins for growth, cardiovascular and neurodevelopmental outcomes during childhood and evaluate the impact of an epigenetic signature at birth on future health. The current target is to include 100 MC twin pairs, but we aim to continue enrollment after procuring additional funding. TwinLIFE will not only address an unmet clinical need in the high-risk group of MC twins, but may also advance early-life strategies to prevent adverse growth, cardiovascular and neurodevelopmental outcomes in the general population.
We have observed the G23 field of the Galaxy AndMass Assembly (GAMA) survey using the Australian Square Kilometre Array Pathfinder (ASKAP) in its commissioning phase to validate the performance of the telescope and to characterise the detected galaxy populations. This observation covers ~48 deg2 with synthesised beam of 32.7 arcsec by 17.8 arcsec at 936MHz, and ~39 deg2 with synthesised beam of 15.8 arcsec by 12.0 arcsec at 1320MHz. At both frequencies, the root-mean-square (r.m.s.) noise is ~0.1 mJy/beam. We combine these radio observations with the GAMA galaxy data, which includes spectroscopy of galaxies that are i-band selected with a magnitude limit of 19.2. Wide-field Infrared Survey Explorer (WISE) infrared (IR) photometry is used to determine which galaxies host an active galactic nucleus (AGN). In properties including source counts, mass distributions, and IR versus radio luminosity relation, the ASKAP-detected radio sources behave as expected. Radio galaxies have higher stellar mass and luminosity in IR, optical, and UV than other galaxies. We apply optical and IR AGN diagnostics and find that they disagree for ~30% of the galaxies in our sample. We suggest possible causes for the disagreement. Some cases can be explained by optical extinction of the AGN, but for more than half of the cases we do not find a clear explanation. Radio sources aremore likely (~6%) to have an AGN than radio quiet galaxies (~1%), but the majority of AGN are not detected in radio at this sensitivity.
To determine the impact of pre-operative intratympanic gentamicin injection on the recovery of patients undergoing translabyrinthine resection of vestibular schwannomas.
This prospective, case–control pilot study included eight patients undergoing surgical labyrinthectomy, divided into two groups: four patients who received pre-operative intratympanic gentamicin and four patients who did not. The post-operative six-canal video head impulse test responses and length of in-patient stay were assessed.
The average length of stay was shorter for patients who received intratympanic gentamicin (6.75 days; range, 6–7 days) than for those who did not (9.5 days; range, 8–11 days) (p = 0.0073). Additionally, the gentamicin group had normal post-operative video head impulse test responses in the contralateral ear, while the non-gentamicin group did not.
Pre-operative intratympanic gentamicin improves the recovery following vestibular schwannoma resection, eliminating, as per the video head impulse test, the impact of labyrinthectomy on the contralateral labyrinth.
To examine when cochlear fibrosis occurs following a translabyrinthine approach for vestibular schwannoma resection, and to determine the safest time window for potential cochlear implantation in cases with a preserved cochlear nerve.
This study retrospectively reviewed the post-operative magnetic resonance imaging scans of patients undergoing a translabyrinthine approach for vestibular schwannoma resection, assessing the fluid signal within the cochlea. Cochleae were graded based on the Isaacson et al. system (from grade 0 – no obstruction, to grade 4 – complete obliteration).
Thirty-nine patients fulfilled the inclusion criteria. The cochleae showed no evidence of obliteration in: 75 per cent of patients at six months, 38.5 per cent at one year and 27 per cent beyond one year. Most changes happened between 6 and 12 months after vestibular schwannoma resection, with cases of an unobstructed cochlear decreasing dramatically, from 75 per cent to 38.5 per cent, within this time.
The progress of cochlear obliteration that occurred between 6 and 12 months following vestibular schwannoma resection indicates that the first 6 months provides a safer time window for cochlear patency.
We studied the genetic diversity and the population structure of human isolates of Histoplasma capsulatum, the causative agent of histoplasmosis, using a randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) assay to identify associations with the geographic distribution of isolates from Mexico, Guatemala, Colombia and Argentina. The RAPD-PCR pattern analyses revealed the genetic diversity by estimating the percentage of polymorphic loci, effective number of alleles, Shannon's index and heterozygosity. Population structure was identified by the index of association (IA) test. Thirty-seven isolates were studied and clustered into three groups by the unweighted pair-group method with arithmetic mean (UPGMA). Group I contained five subgroups based on geographic origin. The consistency of the UPGMA dendrogram was estimated by the cophenetic correlation coefficient (CCCr = 0.94, P = 0.001). Isolates from Mexico and Colombia presented higher genetic diversity than isolates from Argentina. Isolates from Guatemala grouped together with the reference strains from the United States of America and Panama. The IA values suggest the presence of a clonal population structure in the Argentinian H. capsulatum isolates and also validate the presence of recombining populations in the Colombian and Mexican isolates. These data contribute to the knowledge on the molecular epidemiology of histoplasmosis in Latin America.
Introduction: Although use of point of care ultrasound (PoCUS) protocols for patients with undifferentiated hypotension in the Emergency Department (ED) is widespread, our previously reported SHoC-ED study showed no clear survival or length of stay benefit for patients assessed with PoCUS. In this analysis, we examine if the use of PoCUS changed fluid administration and rates of other emergency interventions between patients with different shock types. The primary comparison was between cardiogenic and non-cardiogenic shock types. Methods: A post-hoc analysis was completed on the database from an RCT of 273 patients who presented to the ED with undifferentiated hypotension (SBP <100 or shock index > 1) and who had been randomized to receive standard care with or without PoCUS in 6 centres in Canada and South Africa. PoCUS-trained physicians performed scans after initial assessment. Shock categories and diagnoses recorded at 60 minutes after ED presentation, were used to allocate patients into subcategories of shock for analysis of treatment. We analyzed actual care delivered including initial IV fluid bolus volumes (mL), rates of inotrope use and major procedures. Standard statistical tests were employed. Sample size was powered at 0.80 (α:0.05) for a moderate difference. Results: Although there were expected differences in the mean fluid bolus volume between patients with non-cardiogenic and cardiogenic shock, there was no difference in fluid bolus volume between the control and PoCUS groups (non-cardiogenic control 1878 mL (95% CI 1550 – 2206 mL) vs. non-cardiogenic PoCUS 1687 mL (1458 – 1916 mL); and cardiogenic control 768 mL (194 – 1341 mL) vs. cardiogenic PoCUS 981 mL (341 – 1620 mL). Likewise there were no differences in rates of inotrope administration, or major procedures for any of the subcategories of shock between the control group and PoCUS group patients. The most common subcategory of shock was distributive. Conclusion: Despite differences in care delivered by subcategory of shock, we did not find any significant difference in actual care delivered between patients who were examined using PoCUS and those who were not. This may help to explain the previously reported lack of outcome difference between groups.
Introduction: Point of care ultrasound has been reported to improve diagnosis in non-traumatic hypotensive ED patients. We compared diagnostic performance of physicians with and without PoCUS in undifferentiated hypotensive patients as part of an international prospective randomized controlled study. The primary outcome was diagnostic performance of PoCUS for cardiogenic vs. non-cardiogenic shock. Methods: SHoC-ED recruited hypotensive patients (SBP < 100 mmHg or shock index > 1) in 6 centres in Canada and South Africa. We describe previously unreported secondary outcomes relating to diagnostic accuracy. Patients were randomized to standard clinical assessment (No PoCUS) or PoCUS groups. PoCUS-trained physicians performed scans after initial assessment. Demographics, clinical details and findings were collected prospectively. Initial and secondary diagnoses including shock category were recorded at 0 and 60 minutes. Final diagnosis was determined by independent blinded chart review. Standard statistical tests were employed. Sample size was powered at 0.80 (α:0.05) for a moderate difference. Results: 273 patients were enrolled with follow-up for primary outcome completed for 270. Baseline demographics and perceived category of shock were similar between groups. 11% of patients were determined to have cardiogenic shock. PoCUS had a sensitivity of 80.0% (95% CI 54.8 to 93.0%), specificity 95.5% (90.0 to 98.1%), LR+ve 17.9 (7.34 to 43.8), LR-ve 0.21 (0.08 to 0.58), Diagnostic OR 85.6 (18.2 to 403.6) and accuracy 93.7% (88.0 to 97.2%) for cardiogenic shock. Standard assessment without PoCUS had a sensitivity of 91.7% (64.6 to 98.5%), specificity 93.8% (87.8 to 97.0%), LR+ve 14.8 (7.1 to 30.9), LR- of 0.09 (0.01 to 0.58), Diagnostic OR 166.6 (18.7 to 1481) and accuracy of 93.6% (87.8 to 97.2%). There was no significant difference in sensitivity (-11.7% (-37.8 to 18.3%)) or specificity (1.73% (-4.67 to 8.29%)). Diagnostic performance was also similar between other shock subcategories. Conclusion: As reported in other studies, PoCUS based assessment performed well diagnostically in undifferentiated hypotensive patients, especially as a rule-in test. However performance was similar to standard (non-PoCUS) assessment, which was excellent in this study.
We assessed whether paternal demographic, anthropometric and clinical factors influence the risk of an infant being born large-for-gestational-age (LGA). We examined the data on 3659 fathers of term offspring (including 662 LGA infants) born to primiparous women from Screening for Pregnancy Endpoints (SCOPE). LGA was defined as birth weight >90th centile as per INTERGROWTH 21st standards, with reference group being infants ⩽90th centile. Associations between paternal factors and likelihood of an LGA infant were examined using univariable and multivariable models. Men who fathered LGA babies were 180 g heavier at birth (P<0.001) and were more likely to have been born macrosomic (P<0.001) than those whose infants were not LGA. Fathers of LGA infants were 2.1 cm taller (P<0.001), 2.8 kg heavier (P<0.001) and had similar body mass index (BMI). In multivariable models, increasing paternal birth weight and height were independently associated with greater odds of having an LGA infant, irrespective of maternal factors. One unit increase in paternal BMI was associated with 2.9% greater odds of having an LGA boy but not girl; however, this association disappeared after adjustment for maternal BMI. There were no associations between paternal demographic factors or clinical history and infant LGA. In conclusion, fathers who were heavier at birth and were taller were more likely to have an LGA infant, but maternal BMI had a dominant influence on LGA.
The Japanese Murrelet Synthliboramphus wumizusume is a rare, globally ‘Vulnerable’ seabird, endemic to Japan and South Korea. However, little is known of its at-sea distribution, habitat or threats. We conducted several years of at-sea surveys around Japan to model Japanese Murrelet density in relation to habitat parameters, and make spatial predictions to assess the adequacy of the current Japanese marine Important Bird and Biodiversity Area (IBA) network for the species. During a five-year period, 3,485 km of at-sea surveys recorded 3,161 Japanese Murrelets around four breeding locations. Maximum murrelet group size was 90 individuals with a mean group size of 2.9 ± 4.2 individuals. Models of Japanese Murrelet at-sea density around the two largest breeding locations predicted that almost all murrelets occur within 30 km of the breeding colony and most within 10 km. Murrelets were predicted closer to the colony in May than in April and closer to the colony at a neritic colony than at an offshore island colony. Additionally, murrelets breeding on an offshore island colony also commuted to mainland neritic habitat for foraging. The marine habitat used by Japanese Murrelets differed between each of the four surveyed colonies, however oceanographic variables offered little explanatory power in models. Models with colony, month and year generated four foraging radii (9–39 km wide) containing murrelet densities of > 0.5 birds/km2. Using these radii the Japanese marine IBA network was found to capture between 95% and 25% of Japanese Murrelet at-sea habitat while breeding and appears appropriately configured to protect near-colony murrelet distributions. Given the range of marine habitats that breeding murrelets inhabit, our simple models offer an applicable method for predicting to unsampled colonies and generating ecologically-informed seaward extension radii. However, data on colony populations and further at-sea surveys are necessary to refine models and improve predictions.
We investigated risk factors for severe acute lower respiratory infections (ALRI) among hospitalised children <2 years, with a focus on the interactions between virus and age. Statistical interactions between age and respiratory syncytial virus (RSV), influenza, adenovirus (ADV) and rhinovirus on the risk of ALRI outcomes were investigated. Of 1780 hospitalisations, 228 (12.8%) were admitted to the intensive care unit (ICU). The median (range) length of stay (LOS) in hospital was 3 (1–27) days. An increase of 1 month of age was associated with a decreased risk of ICU admission (rate ratio (RR) 0.94; 95% confidence intervals (CI) 0.91–0.98) and with a decrease in LOS (RR 0.96; 95% CI 0.95–0.97). Associations between RSV, influenza, ADV positivity and ICU admission and LOS were significantly modified by age. Children <5 months old were at the highest risk from RSV-associated severe outcomes, while children >8 months were at greater risk from influenza-associated ICU admissions and long hospital stay. Children with ADV had increased LOS across all ages. In the first 2 years of life, the effects of different viruses on ALRI severity varies with age. Our findings help to identify specific ages that would most benefit from virus-specific interventions such as vaccines and antivirals.
Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) represent a disease continuum with common genetic causes and molecular pathology. We recently identified mutations in the T-cell restricted intracellular antigen-1 (TIA1) protein as a cause of ALS +/− FTD. TIA1 is an RNA-binding protein containing a low complexity domain (LCD) that promotes the assembly of membrane-less organelles, such as stress granules (SG). Whole exome sequencing of two family members with fALS/FTD revealed a novel missense mutation in the TIA1 LCD (P362L). Subsequent screening identified five more TIA1 mutations in six additional ALS patients, but none in controls. All mutation carriers presented with weakness, behavioral abnormalities or language impairments and had a final diagnosis of ALS +/− FTD. Autopsy on five TIA1 mutation carriers showed widespread neurodegeneration with TDP-43 pathology. Round eosinophilic inclusions in lower motor neurons were a consistent feature. Cellular assays revealed abnormal SG dynamics in the presence of TIA1 mutations. In summary, missense mutations in the LCD of TIA1 are a newly recognized cause of ALS/FTD with TDP-43 pathology and strengthen the role of RNA metabolism in the pathogenesis in this disease.
We performed a new series of measurements on samples that were part of early measurements on radiocarbon (14C) dating made in 1948–1949. Our results show generally good agreement to the data published in 1949–1951, despite vast changes in technology, with only two exceptions where there was a discrepancy in the original studies. Our new measurements give calibrated ages that overlap with the known ages. We dated several samples at four different laboratories, and so we were also able to make a small intercomparison at the same time. In addition, new measurements on samples from other Egyptian materials used by Libby and co-workers were made at UC Irvine. Samples of tree rings used in the original studies (from Broken Flute Cave and Centennial Stump) were obtained from the University of Arizona Laboratory of Tree-Ring Research archive and remeasured. New data were compared to the original studies and other records.
Incorporation of cover crop residue into the soil has been suggested as a means for reducing weed seedbanks. To explore this hypothesis, we buried mesh bags of seeds mixed with sand at 15-cm depth in late fall in plots that had been planted with rye (Secale cereale L.) or hairy vetch (Vicia villosa Roth.) or left unplanted. Separate bags contained either velvetleaf (Abutilon theophrasti Medik.), giant foxtail (Setaria faberi Herrm.), Powell amaranth (Amaranthus powellii S. Watson), or common lambsquarters (Chenopodium album L.). The experiment used a randomized complete block design with five replications, and enough bags were buried to allow a final recovery in each of the following three springs. Each spring, bags were exhumed, and seeds were either counted and tested for viability or mixed with chopped cover crop material or simply stirred for control bags, and the material was reburied. The experiment was completed twice with initial burials in fall of 2011 and 2013. Rye had no consistent effect on persistence of seeds of any of the species. For two observation intervals, rye increased persistence of a species; for another two intervals, it decreased persistence relative to the control; but mostly rye did not affect persistence. Hairy vetch decreased persistence of C. album and A. powellii in both runs of the experiment but had no effect on persistence of A. theophrasti and S. faberi. Germination of the first two species is promoted by nitrate, whereas A. theophrasti germination is not sensitive to nitrate, and S. faberi is only rarely nitrate sensitive. We suggest that nitrate released during decomposition of hairy vetch may have promoted fatal germination of C. album and A. powellii. Incorporation of legume cover crops like hairy vetch may provide a means for decreasing the seedbanks of the many weed species whose germination is promoted by nitrate. The lack of any reduction of A. theophrasti and S. faberi seed persistence in response to hairy vetch and the inconsistent and mostly negligible effect of rye indicate that a general increase in readily decomposable organic matter through incorporation of cover crops may be ineffective at reducing weed seedbanks.