Selection by climatic regime and neutral evolutionary processes in holocentric chromosomes (Carex gr. laevigata: Cyperaceae): A microevolutionary approach

The holocentric structure promotes chromosome rearrangements by fission, fusion, translocation, and inversion, which have been thought to promote differentiation and speciation. The Carex laevigata group (Cyperaceae) comprises four species: two restricted endemics from the western Mediterranean (Carex camposii, 2n = 72, and Carex paulo-vargasii, 2n = 74–75), and two more widespread species, found mostly in Western Europe (C. laevigata, 2n = 69–84, and Carex binervis, 2n = 72–74). We tested the selection for chromosome number by climatic variables by controlling for the non-independence of the data using generalized linear mixed model (GLMM). We obtained chromosome counts as well as DNA sequences for the 5′ trnK intron and the trnV-ndhC intergenic spacer in the chloroplast genome from 181 individuals from 53 populations representing these four species. We also climatically characterized the sites where the 53 populations were found using the WorldClim database. Our results show that the best predictor of chromosome number variation is the climatic environment rather than neutral evolutionary processes like founder events and migration patterns. These results support the adaptive value of the holocentric chromosomes and their role in promoting differentiation and eventually speciation.     

Authorizing Knowledge in Science and Anthropology

An analogy exists between today's "defenders" of science in the "science/culture wars" and 19th-century "defenders" of euclidean geometry. Current critics have appointed themselves as arbiters of truth in a manner analogous to that of 19th-century mathematicians and theologians who argued against noneuclidean geometry that challenge Euclid's mathematically, philosophically, and theologically entrenched fifth postulate. The science wars then and now are not about science versus antiscience, objectivity versus subjectivity, but about authority in science: what kind of science should be practiced, and who gets to define it?     

Cas1p is a membrane protein necessary for the O-acetylation of the Cryptococcus neoformans capsular polysaccharide

The capsule is certainly the most obvious virulence factor for Cryptococcus neoformans. The main capsule constituents are glucuronoxylomannans (GXM). Several studies have focused on the structure and chemistry of the GXM component of the capsule, yet little is known about the genetic basis of the capsule construction. Using a monoclonal antibody specific to a sugar epitope, we isolated a capsule-structure mutant strain and cloned by complementation a gene named CAS1 that codes for a putative membrane protein. Although no sequence homology was found with any known protein in the different databases, protein analysis using the PROPSEARCH software classified Cas1p as a putative glycosyltransferase. Cas1p is a well-conserved evolutionary protein, as we identified one orthologue in the human genome, one in the drosophila genome and four in the plant Arabidopsis thaliana genome. Analysis of the capsule structure after CAS1 deletion showed that it is required for GXM O-acetylation.     

Site of deposition and factors affecting clearance of aerosolized solute from canine lungs

We determined the influence of several factors on lung solute clearance using aerosolized 99mTc-diethylenetriaminepentaacetate. We used a jet nebulizer-plate separator-balloon system to generate particles with an activity median aerodynamic diameter of 1.1 micron, administered the aerosol in a standard fashion, and determined clearance half times (t1/2) with a gamma-scintillation camera. The following serial studies were performed in five anesthetized, paralyzed, intubated, mechanically ventilated dogs: 1) control, with ventilatory frequency (f) = 15 breaths/min and tidal volume (VT) = 15 ml/kg during solute clearance; 2) repeat control, for reproducibility; 3) increased frequency, with f = 25 breaths/min and VT = 10 ml/kg; 4) positive end-expiratory pressure (PEEP) of 10 cmH2O; 5) unilateral pulmonary arterial occlusion (PAO); and 6) bronchial arterial occlusion (BAO). Control t1/2 was 25 +/- 5 min and did not change in the repeat control, increased frequency, or BAO experiments. PEEP markedly decreased t1/2 to 13 +/- 3 min (P less than 0.01), and PAO increased it to 37 +/- 6 min (P less than 0.05). We conclude that clearance from the lungs by our method is uninfluenced by increased frequency, increases markedly with PEEP, and depends on pulmonary, not bronchial, blood flow.