Three generations under low versus high neighborhood density affect the life history of a clonal plant through differential selection and genetic drift

We tested whether neighborhood density affects the clonal life history of the stoloniferous plant Ranunculus reptans through selection and genetic drift. After three generations of sexual reproduction of 16 low- and 16 high-density lines, we studied traits related to growth form and reproduction in a common competition free environment. A 7.7% lower branching frequency and slightly longer internodes indicated an evolutionary shift towards a less compact growth form under high neighborhood density, but because stolons grew also more vertically, horizontal spread per ramet was slightly decreased. Neighborhood density had no directional effects on the evolution of allocation to sexual and vegetative reproduction in R. reptans . Variation among replicated high-density lines was significantly lower than among replicated low-density lines in both growth form and reproductive characteristics, indicating less pronounced genetic drift under high neighborhood density. This study demonstrates that a clonal plant can respond to selection imposed by neighborhood density. Moreover, it shows that the effect of random genetic drift increases with decreasing neighborhood density. In a declining species, such as R. reptans in central Europe, this may lower the potential for adaptive evolutionary change and increase extinction risk.     

Compensation for Retinal Vessel Density Reduces the Variation of Circumpapillary RNFL in Healthy Subjects

This work intends to assess circumpapillary retinal vessel density (RVD) at a 3.46 mm diameter circle and correlate it with circumpapillary retinal nerve fiber layer (RNFL) thickness measured with Fourier-Domain Optical Coherence Tomography. Furthermore, it aims to evaluate the reduction of intersubject variability of RNFL when considering RVD as a source of information for RNFL distribution. For that, 106 healthy subjects underwent circumpapillary RNFL measurement. Using the scanning laser ophthalmoscope fundus image, thickness and position of retinal vessels were assessed and integrated in a 256-sector RVD profile. The relationship between local RVD value and local RNFL thickness was modeled by linear regression. RNFL was then compensated for RVD variation by regression formulas. A strong statistically significant intrasubject correlation was found for all subjects between RVD and RNFL profiles (mean R = 0.769). In the intersubject regression analysis, 247 of 256 RNFL sectors showed a statistically significant positive correlation with RVD (mean R = 0.423). RVD compensation of RNFL resulted in a relative reduction of up to 20% of the intersubject variance. In conclusion, RVD in a 3.46mm circle has a clinically relevant influence on the RNFL distribution. RVD may be used to develop more individualized normative values for RNFL measurement, which might improve early diagnosis of glaucoma.     

Argynnis paphia-valesina,ein fall geschlechtskontrollierter vererbung bei schmetterlingen

Ohne Zusammenfassung     

Effect of testosterone on long-term organ cultures of canine prostate

Summary Organ cultures of rodent and human prostate glands have shown marked differences in their morphological response to testosterone. In this study, explants from 19 canine prostate glands were cultivated for a minimum of 9 days in Trowell’s T-8 medium. Groups of explants were exposed to media containing from 0.05 to 100 μm testosterone. While the higher testosterone levels (50 and 100 μm) markedly decreased explant viability, explants cultivated at lower levels (0.05 to 5 μm) appeared similar to control explants in testosterone-free Trowell’s T-8 medium. Atmospheric mixtures containing either 95% or 50% oxygen were equally effective. Shortly after the cultures were initiated, large amounts of secretory product were liberated into the lumen. After 9 or more days in vitro, glandular epithelium appeared cuboidal and never revealed the acid phosphatase-rich secretory granules seen in the preculture control. However, the epithelium exhibited an increase in alkaline phosphatase and lipid content following cultivation. This project was supported by contract N01-CP-33331, Carcinogenesis Program, Division of Cancer Cause and Prevention, National Cancer Institute, Bethesda, Maryland.