EVOLUTIONARY SHIFTS IN THE SPECTRAL PROPERTIES OF SPIDER SILKS

We measured the reflectance properties of unpigmented silks spun by a systematic array of primitive (Deinopoidea) and derived (Araneoidea) aerial, web-spinning spiders, as well as silks spun by Araneomorphae and Mygalomorphae spiders that do not spin aerial webs. Our data show that all of the primitive aerial web spinners produce catching silks with a spectral peak in the ultraviolet (UV), and cladistic analysis suggests that high UV reflection is the primitive character state for silk spectral properties. In contrast, all of the derived aerial web spinners produce silks that are spectrally flat or characterized by reduced reflectance in the UV. Correlated with the evolution of these catching silks is a 37-fold increase in species number and apparent habitat expansion. This suggests that the unique silk proteins spun by the araneoids have been important to their ecological and evolutionary diversity.     

Support for association of schizophrenia with genetic variation in the 6p22.3 gene,dysbindin, in sib-pair families with linkage and in an additional sample of triad families

Genetic variants in a gene on 6p22.3, dysbindin, have been shown recently to be associated with schizophrenia (Straub et al. 2002a). There is no doubt that replication in other independent samples would enhance the significance of this finding considerably. Since the gene is located in the center of the linkage peak on chromosome 6p that we reported earlier, we decided to test six of the most positive DNA polymorphisms in a sib-pair sample and in an independently ascertained sample of triads comprising 203 families, including the families for which we detected linkage on chromosome 6p. Evidence for association was observed in the two samples separately as well as in the combined sample (P=.00068 for SNP rs760761). Multilocus haplotype analysis increased the significance further to .00002 for a two-locus haplotype and to .00001 for a three-locus haplotype. Estimation of frequencies for six-locus haplotypes revealed one common haplotype with a frequency of 73.4% in transmitted, and only 57.6% in nontransmitted, parental haplotypes. All other six-locus haplotypes occurring at a frequency of >1% were less often transmitted than nontransmitted. Our results represent a first successful replication of linkage disequilibrium in psychiatric genetics detected in a region with previous evidence of linkage and will encourage the search for causes of schizophrenia by the genetic approach.     

Childhood obesity and parental smoking as risk factors for childhood ADHD in Liverpool children

ADHD prevalence has risen in parallel with rising prevalence of pregnancy smoking and childhood obesity. The objective was to determine the epidemiological association of pregnancy smoking and childhood obesity with ADHD. A cross-sectional community study was conducted in 2006 using a parental questionnaire. A total of 1,074 schoolchildren aged 5-11 years were enrolled from 15 primary schools in a lower socio-economic area of Merseyside. ADHD was defined by the question "does your child have Attention Deficit Hyperactivity Disorder, (ADHD), which has been diagnosed by a doctor?" The prevalence estimates for childhood obesity, maternal smoking during pregnancy and childhood ADHD were 14.9% (116/777), 28.0% (269/955), and 3.4% (32/945), respectively. ADHD prevalence increased fivefold in children with obesity (RR, 4.80, 95% CI 2.2-10.4, P < 0.001) and more than twofold in children of mothers who smoked during pregnancy (RR, 2.44, 95% CI 1.2-4.9, P = 0.02). Regression analysis adjusting for obesity, overweight, maternal smoking during pregnancy, heavy maternal smoking, household member smoking during pregnancy, doctor-diagnosed asthma, preterm birth, and low birthweight showed significant independent associations of ADHD prevalence with obesity (AOR, 4.66, 95% CI 1.57-13.89, P = 0.006) and pregnancy smoking (AOR, 3.19, 95% CI 1.08-9.49, P = 0.04). There was a positive dose-response association of ADHD with the number of maternal cigarettes smoked during pregnancy. Measures to reduce both smoking among pregnant women and childhood obesity might reduce prevalence of childhood ADHD.     

The intron 7 donor splice site transition: a second Tay-Sachs disease mutation in French Canada

Mutations at the hexosaminidase A (HEXA) gene which cause Tay-Sachs disease (TSD) have elevated frequency in the Ashkenazi Jewish and French-Canadian populations. We report a novel TSD allele in the French-Canadian population associated with the infantile form of the disease. The mutation, a GA transition at the +1 position of intron 7, abolishes the donor splice site. Cultured human fibroblasts from a compound heterozygote for this transition (and for a deletion mutation) produce no detectable HEXA mRNA. The intron 7+1 mutation occurs in the base adjacent to the site of the adult-onset TSD mutation (G805A). In both mutations a restriction site for the endonuclease EcoRII is abolished. Unambiguous diagnosis, therefore, requires allele-specific oligonucleotide hybridization to distinguish between these two mutant alleles. The intron 7+1 mutation has been detected in three unrelated families. Obligate heterozygotes for the intron 7+1 mutation were born in the Saguenay-Lac-St-Jean region of Quebec. The most recent ancestors common to obligate carriers of this mutation were from the Charlevoix region of the province of Quebec. This mutation thus has a different geographic centre of diffusion and is probably less common than the exon 1 deletion TSD mutation in French Canadians. Neither mutation has been detected in France, the ancestral homeland of French Canada.     

Characterization of two human cAMP-specific phosphodiesterase subtypes expressed in baculovirus-infected insect cells.

Recombinant baculoviruses were constructed to express cDNAs encoding two distinct subtypes of human cAMP-specific phosphodiesterase (hPDE4A and hPDE4B). Infection of Spodoptera frugiperda insect cells with the appropriate recombinant baculoviruses resulted in high level production of biologically-active protein as measured by enzymatic activity and immunoblotting using subtype-specific anti-hPDE4 antisera. Both recombinant proteins showed catalytic activity with a low K_m (～ 3 μM) for cAMP (with no cGMP hydrolyzing activity) and were inhibited by R-rolipram with apparent K_is of 0.38 and 0.25 μM, respectively. The recombinant enzymes also contained saturable, stereoselective and high-affinity rolipram-binding sites (K_d ～ 2 nM). Thus, insect cell-derived hPDE4s possess kinetic properties analogous to native enzymes as well as to recombinant enzymes produced in yeast.     

Effect of dung burial by the dung beetle Bubas bison on numbers and viability of Cryptosporidium oocysts in cattle dung

Cryptosporidium oocysts were inoculated into fresh dung (∼1.2 × 10⁴ oocysts per gram wet weight) and fed to dung beetles to assess the effect of dung burial by the dung beetle Bubas bison on the distribution of the oocysts in small cores of soil in the laboratory. The experiment consisted of five replicates of each of two treatments; controls (dung but no dung beetles) and the experimental treatment (inoculated dung and seven pairs of dung beetles). After 5 days, when approximately 90% of the dung was buried, the surface and buried dung was recovered and subsampled. The oocysts in the subsamples were recovered and enumerated using qPCR. Oocyst viability was evaluated using an assay based on the exclusion or inclusion of two fluorogenic vital dyes, 4′,6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI). Results revealed that overall 13.7% of oocysts remained on the surface and 86.3% of oocysts were buried. The viability of oocysts in buried dung was only 10% compared to oocysts the surface dung (58%). Therefore, widespread dung burial by B. bison during the winter months could substantially reduce the numbers of Cryptosporidium oocysts available to be washed into waterways following winter rains.     

Plant functional traits capture species richness variations along a flooding gradient

Local species coexistence is the outcome of abiotic and biotic filtering processes which sort species according to their trait values. However, the capacity of trait‐based approaches to predict the variation in realized species richness remains to be investigated. In this study, we asked whether a limited number of plant functional traits, related to the leaf‐height‐seed strategy scheme and averaged at the community level, is able to predict the variation in species richness over a flooding disturbance gradient. We further investigated how these mean community traits are able to quantify the strength of abiotic and biotic processes involved in the disturbance–productivity–diversity relationship. We thus tested the proposal that the deviation between the fundamental species richness, assessed from ecological niche‐based models, and realized species richness, i.e. field‐observed richness, is controlled by species interactions. Flooding regime was determined using a detailed hydrological model. A precise vegetation sampling was performed across 222 quadrats located throughout the flooding gradient. Three core functional traits were considered: specific leaf area (SLA), plant height and seed mass. Species richness showed a hump‐shaped response to disturbance and productivity, but was better predicted by only two mean community traits: SLA and height. On the one hand, community SLA that increased with flooding, controlled the disturbance‐diversity relationship through habitat filtering. On the other hand, species interactions, the strength of which was captured by community height values, played a strong consistent role throughout the disturbance gradient by reducing the local species richness. Our study highlights that a limited number of simple, quantitative, easily measurable functional traits can capture the variation in plant species richness at a local scale and provides a promising quantification of key community assembly mechanisms.