Crab: snail size-structured interactions and salt marsh predation gradients

We studied size-structured predator-prey interactions between blue crabs (Callinectes sapidus) and marsh periwinkles (Littoraria irrorata) with a combination of field studies, laboratory experiments and individual-based modeling. Size distributions of Littoraria differed among years at the same sites in a salt marsh and could largely be explained by dominance of strong cohorts in the population. At a given site, abundance increased with elevation above tidal datum. Size-selective predation by blue crabs does not appear to be an important regulator of snail size distributions but may have a major effect on local abundance. Laboratory studies indicated that predator-prey interactions between Callinectes and Littoraria are strongly size-dependent. Crabs were generally effective at feeding on periwinkles at size ratios greater than approximately 6 (crab width: snail length). At lower size ratios crabs were far less effective at manipulating the snails, which often survived but with damaged shells. An individual-based model which incorporated information about incidence of snail shell scarring (resulting from non-lethal interactions) and snail density, predicted reduced predation rates and smaller average crab size with distance from the low tide refugium for crabs.     

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Solar lentigines are strongly related to sun exposure in contrast to ephelides

Solar lentigines and ephelides are different types of pigmented skin lesions predominantly present on sun-exposed skin. Both lesions are risk indicators for melanoma and non-melanoma skin cancer. Solar lentigines are considered as a sign of photodamage although well-conducted epidemiological studies are lacking on this subject. Ephelides are associated with fair skin type and red hair. The aim of the present study was to investigate the relation of sun-exposure estimates with solar lentigines and ephelides. In the Leiden Skin cancer Study 577 patients with malignant melanoma and/or non-melanoma skin cancer and 385 individuals without a history of skin cancer were studied. The presence of solar lentigines and ephelides in the face and on the back was assessed. Data on skin type, hair color, sun-exposure variables and cutaneous signs of photodamage were collected, by questionnaire and physical examination. Data were analyzed by chi-square or Student t-tests and with multivariable regression. Exposure odds ratios with 95% confidence intervals (95% CI) were calculated to estimate the relative risk for the presence of solar lentigines and ephelides dependent on signs of photodamage. The association with age was strongly positive for solar lentigines whereas it was strongly negative for ephelides (P-values for trend <0.0001). After adjustment for age, sex and skin type, solar lentigines on the back were positively associated with cumulative (P = 0.01) and intermittent (P = 0.0002) sun exposure. After adjustment, solar lentigines on the back were also associated with a history of sunburns before the age of 20 yr (P = 0.0003) and the number of sunburns in childhood (P = 0.002). Solar lentigines in the face were significantly associated with cutaneous signs of photodamage, i.e. elastosis (odds ratio 2.4, 95% CI 1.7-3.3) and actinic keratosis (odds ratio 1.8, 95% CI 1.3-2.4) whereas ephelides were not. Ephelides in the face and on the back showed an inverse association with chronic sun exposure but after adjustment theses associations disappeared. Sunburns before the age of 20 appeared to be positively associated with ephelides on the back (P = 0.04). In contrast to lentigines, ephelides were much more associated with constitutional host factors such as fair skin and/or red hair (both P < 0.0001). This study indicates that both chronic and acute sun exposure are important in the pathogenesis of solar lentigines.     

Analysis of plastid DNA-like sequences within the nuclear genomes of higher plants

A wide-ranging examination of plastid (pt)DNA sequence homologies within higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion with methylation-sensitive restriction enzymes and Southern analysis was used to distinguish plastid and nuclear DNA in order to assess the extent of variability of promiscuous sequences within and between plant species. Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum (tobacco), and Chenopodium quinoa, showed homogenity of these sequences, while intraspecific sequence variation was observed among different cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum aestivum (wheat). Hypervariability of plastid sequence homologies was identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta vulgaris (beet), in which individual plants were shown to possess a unique spectrum of nuclear sequences with ptDNA homology. This hypervariability apparently extended to somatic variation in B. vulgaris. No sequences with ptDNA homology were identified by this method in the nuclear genome of Arabidopsis thaliana.      

Cryotherapy with liquid nitrogen versus topical salicylic acid application for cutaneous warts in primary care: randomized controlled trial

Background

Cryotherapy is widely used for the treatment of cutaneous warts in primary care. However, evidence favours salicylic acid application. We compared the effectiveness of these treatments as well as a wait-and-see approach.

Methods

Consecutive patients with new cutaneous warts were recruited in 30 primary care practices in the Netherlands between May 1, 2006, and Jan. 26, 2007. We randomly allocated eligible patients to one of three groups: cryotherapy with liquid nitrogen every two weeks, self-application of salicylic acid daily or a wait-and-see approach. The primary outcome was the proportion of participants whose warts were all cured at 13 weeks. Analysis was on an intention-to-treat basis. Secondary outcomes included treatment adherence, side effects and treatment satisfaction. Research nurses assessed outcomes during home visits at 4, 13 and 26 weeks.

Results

Of the 250 participants (age 4 to 79 years), 240 were included in the analysis at 13 weeks (loss to follow-up 4%). Cure rates were 39% (95% confidence interval [CI] 29%–51%) in the cryotherapy group, 24% (95% CI 16%–35%) in the salicylic acid group and 16% (95% CI 9.5%–25%) in the wait-and-see group. Differences in effectiveness were most pronounced among participants with common warts (n = 116): cure rates were 49% (95% CI 34%–64%) in the cryotherapy group, 15% (95% CI 7%–30%) in the salicylic acid group and 8% (95% CI 3%–21%) in the wait-and-see group. Cure rates among the participants with plantar warts (n = 124) did not differ significantly between treatment groups.

Interpretation

For common warts, cryotherapy was the most effective therapy in primary care. For plantar warts, we found no clinically relevant difference in effectiveness between cryotherapy, topical application of salicylic acid or a wait-and-see approach after 13 weeks. (ClinicalTrial.gov registration no. ISRCTN42730629)Cutaneous warts are common.^1–3 Up to one-third of primary school children have warts, of which two-thirds resolve within two years.^4,5 Because warts frequently result in discomfort,⁶ 2% of the general population and 6% of school-aged children each year present with warts to their family physician.^7,8 The usual treatment is cryotherapy with liquid nitrogen or, less frequently, topical application of salicylic acid.^9–12 Some physicians choose a wait-and-see approach because of the benign natural course of warts and the risk of side effects of treatment.^10,11A recent Cochrane review on treatments of cutaneous warts concluded that available studies were small, poorly designed or limited to dermatology outpatients.^10,11 Evidence on cryotherapy was contradictory,^13–18 whereas the evidence on salicylic acid was more convincing.^19–23 However, studies that compared cryotherapy and salicylic acid directly showed no differences in effectiveness.^24,25 The Cochrane review called for high-quality trials in primary care to compare the effects of cryotherapy, salicylic acid and placebo.We conducted a three-arm randomized controlled trial to compare the effectiveness of cryotherapy with liquid nitrogen, topical application of salicylic acid and a wait-and-see approach for the treatment of common and plantar warts in primary care.     

Late immature mortality is the major influence on reproductive success of African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae), in a Mediterranean-climate region of Australia

In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival.     

Discovery of a New Human Polyomavirus Associated with Trichodysplasia Spinulosa in an Immunocompromized Patient

The Polyomaviridae constitute a family of small DNA viruses infecting a variety of hosts. In humans, polyomaviruses can cause infections of the central nervous system, urinary tract, skin, and possibly the respiratory tract. Here we report the identification of a new human polyomavirus in plucked facial spines of a heart transplant patient with trichodysplasia spinulosa, a rare skin disease exclusively seen in immunocompromized patients. The trichodysplasia spinulosa-associated polyomavirus (TSV) genome was amplified through rolling-circle amplification and consists of a 5232-nucleotide circular DNA organized similarly to known polyomaviruses. Two putative “early” (small and large T antigen) and three putative “late” (VP1, VP2, VP3) genes were identified. The TSV large T antigen contains several domains (e.g. J-domain) and motifs (e.g. HPDKGG, pRb family-binding, zinc finger) described for other polyomaviruses and potentially involved in cellular transformation. Phylogenetic analysis revealed a close relationship of TSV with the Bornean orangutan polyomavirus and, more distantly, the Merkel cell polyomavirus that is found integrated in Merkel cell carcinomas of the skin. The presence of TSV in the affected patient''s skin was confirmed by newly designed quantitative TSV-specific PCR, indicative of a viral load of 10⁵ copies per cell. After topical cidofovir treatment, the lesions largely resolved coinciding with a reduction in TSV load. PCR screening demonstrated a 4% prevalence of TSV in an unrelated group of immunosuppressed transplant recipients without apparent disease. In conclusion, a new human polyomavirus was discovered and identified as the possible cause of trichodysplasia spinulosa in immunocompromized patients. The presence of TSV also in clinically unaffected individuals suggests frequent virus transmission causing subclinical, probably latent infections. Further studies have to reveal the impact of TSV infection in relation to other populations and diseases.     

BRCT domains: Easy as one,two, three

BRCA1 C-terminal (BRCT) domains are integral signaling modules in the DNA damage response (DDR). Aside from their established roles as phospho-peptide binding modules, BRCT domains have been implicated in phosphorylation-independent protein interactions, DNA binding and poly(ADP-ribose) (PAR) binding. These numerous functions can be attributed to the diversity in BRCT domain structure and architecture, where domains can exist as isolated single domains or assemble into higher order homo- or hetero-domain complexes. In this review, we incorporate recent structural and biochemical studies to demonstrate how structural features allow single and tandem BRCT domains to attain a high degree of functional diversity.Key words: BRCT domain, DNA repair, phosphorylation, phospho-peptide interaction, protein interaction, DNA binding, DNA damage response     

Melanocortin-1 receptor gene variants determine the risk of nonmelanoma skin cancer independently of fair skin and red hair

Melanocortin-1 receptor (MC1R) gene variants are associated with fair skin and red hair and, independently of these, with cutaneous malignant melanoma. The association of MC1R gene variants with nonmelanoma skin cancer is largely unknown. A total of 838 subjects were included in the present study: 453 patients with nonmelanoma skin cancer and 385 subjects with no skin cancer. The coding sequence of the human MC1R gene was tested using single-stranded conformation polymorphism analysis followed by sequencing of unknown variants. Risk of skin cancer dependent on the various MC1R gene variants was estimated using the exposure odds ratio. We investigated whether subjects with MC1R variant alleles were at increased risk of developing nonmelanoma skin cancer and, if so, whether this increased risk was mediated by fair skin and red hair. A total of 27 MC1R gene variants were found. The number of carriers of one, two, or three MC1R gene variants was 379 (45.2%), 208 (24.8%), and 7 (0.9%), respectively. A strong association between MC1R gene variants and fair skin and red hair was established, especially the variants Arg151Cys and Arg160Trp (P < .0001). Carriers of two variant alleles were at increased risk for developing cutaneous squamous cell carcinoma (odds ratio 3.77; 95% confidence interval [CI] 2.11-6.78), nodular basal cell carcinoma (odds ratio 2.26; 95% CI 1.45-3.52), and superficial multifocal basal cell carcinoma (odds ratio 3.43; 95% CI 1.92-6.15), compared with carriers of two wild-type alleles. Carriers of one variant allele had half the risk. The highest relative risks of nonmelanoma skin cancer were found in carriers of the Asp84Glu, His260Pro, and Asp294His variant alleles, and the risk was only slightly lower for carriers of the Val60Leu, Val92Met, Arg142His, Arg151Cys, and Arg160Trp variant alleles. When subjects were stratified by skin type and hair color, analysis showed that these factors did not materially change the relative risks. These findings indicate that MC1R gene variants are important independent risk factors for nonmelanoma skin cancer.     

Ephelides are more related to pigmentary constitutional host factors than solar lentigines.

Ephelides and solar lentigines are benign pigmented spots, which are currently associated with an increased risk of skin cancer. These two pigmented spots are known to be discriminated by their clinical, histological, and electron microscopic characteristics, even though occasional misclassification can occur because of their similarity. It has also been questioned whether these spots are not one and the same. In this study, we have attempted to differentiate between these two pigmented spots with the use of a standardized protocol for clinical examinations on 272 healthy volunteers, paying particular consideration to their pigmentary and constitutional host factors. We found that solar lentigines 1) are more prevalent than ephelides, 2) increase in prevalence and number with higher age, and 3) are most prevalent on the trunk and occur more frequently in males than in females. A trend is also observed whereby ephelides 1) loose their prevalence with age, 2) become equally distributed on the face, arms, and trunk, and 3) occur more frequently in females. An intimate association of ephelides, but not solar lentigines, has been found with hair color and skin type. All of these findings are in agreement with most of those reported in the literature, supporting the view that ephelides and solar lentigines are different types of pigmented lesions.