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.     

Issues in using whole slide imaging for diagnostic pathology: “routine” stains,immunohistochemistry and predictive markers

The traditional microscope, together with the “routine” hematoxylin and eosin (H & E) stain, remains the “gold standard” for diagnosis of cancer and other diseases; remarkably, it and the majority of associated biological stains are more than 150 years old. Immunohistochemistry has added to the repertoire of “stains” available. Because of the need for specific identification and even measurement of “biomarkers,” immunohistochemistry has increased the demand for consistency of performance and interpretation of staining results. Rapid advances in the capabilities of digital imaging hardware and software now offer a realistic route to improved reproducibility, accuracy and quantification by utilizing whole slide digital images for diagnosis, education and research. There also are potential efficiencies in work flow and the promise of powerful new analytical methods; however, there also are challenges with respect to validation of the quality and fidelity of digital images, including the standard H & E stain, so that diagnostic performance by pathologists is not compromised when they rely on whole slide images instead of traditional stained tissues on glass slides.     

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.     

LIFE CYCLE OF THE HETEROTROPHIC DINOFLAGELLATE PFIESTERIA PISCICIDA (DINOPHYCEAE)1

The putatively toxic dinoflagellate Pfiesteria piscicida (Steidinger et Burkholder) has been reported to have an unusual life cycle for a free‐living marine dinoflagellate. As many as 24 life cycle stages were originally described for this species. During a recent phylogenetic study in which we used clonal cultures of P. piscicida, we were unable to confirm many reported life cycle stages. To resolve this discrepancy, we undertook a rigorous examination of the life cycle of P. piscicida using nuclear staining techniques combined with traditional light microscopy, high‐resolution video microscopy, EM, and in situ hybridization with a suite of fluorescently labeled peptide nucleic acid (PNA) probes. The results showed that P. piscicida had a typical haplontic dinoflagellate life cycle. Asexual division occurred within a division cyst and not by binary fission of motile cells. Sexual reproduction of this homothallic species occurred via the fusion of isogamous gametes. Examination of tanks where P. piscicida was actively feeding on fish showed that amoebae were present; however, they were contaminants introduced with the fish. Whole cell probing using in situ hybridization techniques confirmed that these amoebae were hybridization negative for a P. piscicida‐specific PNA probe. Direct observations of clonal P. piscicida cultures revealed no unusual life cycle stages. Furthermore, the results of this study provided no evidence for transformations to amoebae. We therefore conclude that P. piscicida has a life cycle typical of free‐living marine dinoflagellates and lacks any amoeboid or other specious stages.     

Control of the exotic bulb, Yellow Soldier (Lachenalia reflexa) invading a Banksia woodland, Perth, Western Australia

Summary In recent times managers have become increasingly aware of the South African bulbous species Yellow Soldier ( Lachenalia reflexa ) becoming a serious weed of bushland on the Swan Coastal Plain. In 1998, trials were implemented to investigate control options for Yellow Soldier invading the understorey of a Banksia ( Banksia attenuata ) Woodland west of Perth. Our trials showed that hand removal over two seasons left all natives intact but was very labour intensive, only reducing cover of Yellow Soldier by 44%. It also triggered germination by ephemeral weeds. Wiping the leaves of individual plants with a 10% glyphosate solution was not effective and was also highly labour intensive. Spot spraying with metsulfuron methyl at 0.2 g/15 L (5 g/ha) reduced the cover of Yellow Soldier by 65%, was easier to implement and appeared to have had insignificant effects on natives. We hope that this trial will encourage other workers in the field to undertake controlled trials to refine treatments at restoration sites.     

Interactions between large African browsers and thorny Acacia on a wildlife ranch in Kenya

Some plants respond to browsing with compensatory regrowth of plant tissues and with increased thorn growth. Associations between browsers and their preferred forage were examined through wandering quarter vegetation sampling and observational studies in an effort to understand how some plants respond to browsing by large African herbivores. Acacia seyal (n = 2680) A. drepanolobium (n = 1850), and Balanites glabra (n = 960) were three species of frequently browsed indigenous plants examined on Game Ranching Ltd. in Kenya. There were several statistically significant associations revealed. Individual A. seyal exposed to intensive browser utilization were observed to lose shoot tips, produce long thorns, and have relatively few flowers and fruits. Browser utilization was associated with increased lateral branching in A. drepanolobium and with an increased occurrence of short, thickened spines in B. glabra. Thorns, spines and flowers were measurable indicators of relative browser utilization, and may be useful features to monitor in the management of large African mammals and their prickly forage