Parnassia palustris: a genetically diverse species in Scandinavia

Patterns of variation at nine enzyme loci were examined in 528 plants representing diploid and tetraploid populations of Parnassia palustris s. l. in Europe to assess genetic variation patterns and migration history. Half of the plants showed a unique multilocus phenotype and 75% of all phenotypes occurred only in Scandinavia. Diploid populations showed similar levels of genetic diversity as other widespread outbreeding species with animal-mediated pollination and F -statistics indicated excessive heterozygosity and low rates of gene flow among them. In spite of dramatic population histories caused by the ice ages, diploid populations have maintained the same genetic diversity in Scandinavia as in central and southern Europe. Northern populations have apparently been established through the gradual advance of genetically variable populations and patterns of variation at individual loci indicate different migration routes, from the south-south-west and the east-north-east, respectively. The data strongly support a repeated autoploid origin of the tetraploid cytotype which has been much more successful than the diploid progenitors in colonizing new land since the last ice age. High genetic diversity in Scandinavia has apparently been obtained by a combination of immigration of plants from different source areas and recurrent formation of autotetraploids from diploid progenitors.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 347−372.     

Considerations for the use of SADIE statistics to quangify spatial patterns

The SADIE methodology has recently been developed to quangify spatial patterns, particularly in determining the randomness of observed patterns, estimating patches and gaps, and quangifying correlation between species. We used argificially generated data sets to investigate the relationship of the SADIE pattern and association statistics with patch number and spatial positions of the patches. Results showed that SADIE statistics are critically dependent on the absolute positions of quadrat counts, and not just on their relative positions. In particular, degree of patchiness increased as the patch was displaced away from the centre. Therefore, the dependence of SADIE statistics on absolute sampling positions should be taken into consideration when using and interpreting SADIE-based results.     

An integrative approach for studying the etiology of alcoholism and other addictions.

Studies of alcoholism etiology often focus on genetic or psychosocial approaches, but not both. Greater understanding of the etiology of alcohol, tobacco and other addictions will come from integration of these research traditions. A research approach is outlined to test three models for the etiology of addictions--behavioral undercontrol, pharmacologic vulnerability, negative affect regulation--addressing key questions including (i) mediators of genetic effects, (ii) genotype-environment correlation effects, (iii) genotype x environment interaction effects, (iv) the developmental unfolding of genetic and environmental effects, (v) subtyping including identification of distinct trajectories of substance involvement, (vi) identification of individual genes that contribute to risk, and (vii) the consequences of excessive use. By using coordinated research designs, including prospective assessment of adolescent twins and their siblings and parents; of adult substance dependent and control twins and their MZ and DZ cotwins, the spouses of these pairs, and their adolescent offspring; and of regular families; by selecting for gene-mapping approaches sibships screened for extreme concordance or discordance on quantitative indices of substance use; and by using experimental (drug challenge) as well as survey approaches, a number of key questions concerning addiction etiology can be addressed. We discuss complementary strengths and weaknesses of different sampling strategies, as well as methods to implement such an integrated approach illustrated for the study of alcoholism etiology. A coordinated program of twin and family studies will allow a comprehensive dissection of the interplay of genetic and environmental risk-factors in the etiology of alcoholism and other addictions.     

Spatial pattern analysis of the incidence of aster yellows disease in lettuce

The degree of aggregation of lettuce plants infected by aster yellows phytoplasma (AYP) was investigated in 12 fields from three experiments. Position of diseased and healthy plants was mapped in a 6–9×12-m section of each field; for most analyses, fields were divided into 10-plant quadrats. Mean disease incidence (p) ranged from 0.01 to 0.30. The frequency of diseased plants was described by the beta-binomial distribution, with an index of aggregation (θ) ranging from 0 to 0.17, positively correlated withp, and generally increasing over time within a field. Distance-class analysis revealed a core-cluster size of only a few plants. However, spatial autocorrelations ofp between quadrats were not significant, indicating that the scale of spatial pattern was small, generally less than 10 plants. An overall measure of aggregation was given by the slope parameter of the binary form of the power law, in which the log of the calculated variance is regressed on the log of the theoretical variance for a binomial distribution. The slope was 1.18 and significantly different from 1. Results for this “simple-interest” disease are interpreted in relation to the persistent transmission of AYP by its aster leafhopper vector.     

Prostatic Alpha-Linolenic Acid (ALA) Is Positively Associated with Aggressive Prostate Cancer: A Relationship Which May Depend on Genetic Variation in ALA Metabolism

Previous observational studies have reported associations between prostate cancer and alpha-linolenic acid (ALA). However, few investigations have been able to study this relationship prospectively and in well-controlled settings. Moreover, no studies have determined whether single nucleotide polymorphisms (SNPs) that influence ALA metabolism are associated with this common cancer. The purpose of this study was to explore associations between prostatic levels of ALA, SNPs and prostate cancer-specific biomarkers in samples collected from a previous randomized clinical trial conducted using a presurgical model and which tested the effects of flaxseed supplementation, a rich source of ALA, prior to prostatectomy (n = 134). Serum prostate-specific antigen (PSA) was determined and immunohistochemistry was used to assess tumor proliferation rate (Ki67). Prostatic ALA was determined with gas chromatography. Seven previously identified SNPs associated with delta-6 desaturase activity (rs99780, rs174537, rs174545, rs174572, rs498793, rs3834458 and rs968567) were tested for associations with prostatic ALA, PSA and Ki67. Despite consuming seven times more ALA per day, men in the flaxseed arm had similar amounts of prostatic ALA relative to men not consuming flaxseed. In unadjusted analysis, there were significant positive associations between prostatic ALA and PSA (ρ = 0.191, p = 0.028) and Ki67 (ρ = 0.186, p = 0.037). After adjusting for covariates (flaxseed, age, race, BMI and statin-use) the association between ALA and PSA remained (p = 0.004) but was slightly attenuated for Ki67 (p = 0.051). We did not observe associations between any of the SNPs studied and prostatic ALA; however, in models for PSA there was a significant interaction between rs498793 and ALA and for Ki67 there were significant interactions with ALA and rs99780 and rs174545. Independent and inverse associations were observed between rs174572 and Ki67. This study provides evidence that prostatic ALA, independent of the amount of ALA consumed, is positively associated with biomarkers of aggressive prostate cancer and that genetic variation may modify this relationship.     

Preliminary determination of mycotoxin binding to soil when leaching through soil with water

Mycotoxin-contaminated crops that are left in the field are potential contaminants of groundwater. Aflatoxin B₁ (AFB₁) and fumonisin B₁ (FB₁) distribution in soil-water systems and the comparative response of aflatoxin-contaminated corn and pure aflatoxin when leached through soil were investigated using columns. Each experiment was repeated once. Eluates and soil extracts were analyzed for AFB₁ and its metabolites and FB₁ along with different amounts of pure FB₁ and water mixtures. AFB₁ was detected in water samples from columns containing 10% and 20% silty clay loam soil and aflatoxin-contaminated corn mixtures and in the upper (top) 2.5 cm of soil from the 10 cm soil column. Aflatoxin B₂ (AFB₂) was detected in eluates from the column containing 10% soil and aflatoxin-contaminated corn mixture and from the column containing aflatoxin-contaminated corn alone. No AFB₂ was detected in eluates from the column containing 20% soil and aflatoxin-contaminated corn mixture. No detectable amount of aflatoxin was observed in eluates from the containing 50% silty clay loam soil and aflatoxin contaminated corn. No detectable amount of FB₁ was observed in eluates or soil extracts, but FB₁ was detected in the mixtures of pure FB₁ and water.     

Increased Dendritic Spine Density and Tau Expression Are Associated with Individual Differences in Steroidal Regulation of Male Sexual Behavior

Male sexual behavior (MSB) is modulated by gonadal steroids, yet this relationship is highly variable across species and between individuals. A significant percentage (∼30%) of B6D2F1 hybrid male mice demonstrate MSB after long-term orchidectomy (herein after referred to as “maters”), providing an opportunity to examine the mechanisms that underlie individual differences in steroidal regulation of MSB. Use of gene expression arrays comparing maters and non-maters has provided a first pass look at the genetic underpinnings of steroid-independent MSB. Surprisingly, of the ∼500 genes in the medial preoptic area (MPOA) that differed between maters and non-maters, no steroid hormone or receptor genes were differentially expressed between the two groups. Interestingly, best known for their association with Alzheimer’s disease, amyloid precursor protein (APP) and the microtubule-associated protein tau (MAPT) were elevated in maters. Increased levels of their protein products (APP and tau) in their non-pathological states have been implicated in cell survival, neuroprotection, and supporting synaptic integrity. Here we tested transgenic mice that overexpress tau and found facilitated mounting and intromission behavior after long-term orchidectomy relative to littermate controls. In addition, levels of synaptophysin and spinophilin, proteins generally enriched in synapses and dendritic spines respectively, were elevated in the MPOA of maters. Dendritic morphology was also assessed in Golgi-impregnated brains of orchidectomized B6D2F1 males, and hybrid maters exhibited greater dendritic spine density in MPOA neurons. In sum, we show for the first time that retention of MSB in the absence of steroids is correlated with morphological differences in neurons.     

<Emphasis Type="Italic">Ixodes heathi</Emphasis> n. sp. (Acari: Ixodidae), a co-endangered tick from the critically endangered mountain pygmy possum (<Emphasis Type="Italic">Burramys parvus</Emphasis>), with notes on its biology and conservation

A new species of co-endangered tick, Ixodes heathi n. sp., is described from specimens of the nymph collected on the critically endangered mountain pygmy possum (Burramys parvus Broom) from the alpine region of Victoria, Australia. Its biology is discussed along with strategies for its conservation.