Food limitation of asexual reproduction in a spionid polychaete

Summary

The rate of asexual fragmentation in the spionid polychaete Pygospio elegans is shown to increase in the presence of augmented food levels and is a density-dependent response. Asexual reproduction does not occur when the animals are reproducing sexually.     

Oxidative stress mediates neuronal DNA damage and apoptosis in response to cytosine arabinoside

Cytosine arabinoside (AraC) is a nucleoside analog that produces significant neurotoxicity in cancer patients. The mechanism by which AraC causes neuronal death is a matter of some debate because the conventional understanding of AraC toxicity requires incorporation into newly synthesized DNA. Here we demonstrate that AraC-induced apoptosis of cultured cerebral cortical neurons is mediated by oxidative stress. AraC-induced cell death was reduced by treatment with several different free-radical scavengers (N-acetyl-L-cysteine, dipyridamole, uric acid, and vitamin E) and was increased following depletion of cellular glutathione stores. AraC induced the formation of reactive oxygen species in neurons as measured by an increase in the fluorescence of the dye 5-(6)-carboxy-2',7'-dichlorodihydrofluorescein diacetate. AraC produced DNA single-strand breaks as measured by single-cell gel electrophoresis and the level of DNA strand breakage was reduced by treatment with the free radical scavengers. These data support a model in which AraC induces neuronal apoptosis by provoking the generation of reactive oxygen species, causing oxidative DNA damage and initiating the p53-dependent apoptotic program. These observations suggest the use of antioxidant therapies to reduce neurotoxicity in AraC chemotherapeutic regimens.     

Fine structure of a murine mammary carcinoma cell line

Summary A fine structural study was made of cells from the epithelioid MCF-8/5-2A cell line derived from a MuMTV-free, D2 transplantable hyperplastic outgrowth. Electron microscopy shows the cells to be truly epithelial with many cell-to-cell junctions and microvilli. The cells are similar in many respects to normal mouse mammary gland and some of the conventional mammary tumor derived cell lines. This study supports previous observations of the absence of MuMTV in MCF-8 within the limits of morphological detection, and demonstrates the presence of numerous virus particles within, or budding into, cisternae of the endoplasmic reticulum and nuclear envelope. These intracisternal A particles have not been previously described in such abundance in mammary tumor tissue culture cells. This study was supported by Contract NIH-NCI-E-71-2421, with the NIH and by an institutional grant to the Michigan Cancer Foundation from the United Foundation of Detroit, Michigan.     

Revisiting species delimitation within the genus Oxystele using DNA barcoding approach

The genus Oxystele, a member of the highly diverse marine gastropod superfamily Trochoidea, is endemic to southern Africa. Members of the genus include some of the most abundant molluscs on southern African shores and are important components of littoral biodiversity in rocky intertidal habitats. Species delimitation within the genus is still controversial, especially regarding the complex O. impervia / O. variegata. Here, we assessed species boundaries within the genus using DNA barcoding and phylogenetic tree reconstruction. We analysed 56 specimens using the mitochondrial gene COI. Our analysis delimits five molecular operational taxonomic units (MOTUs), and distinguishes O. impervia from O. variegata. However, we reveal important discrepancies between MOTUs and morphology-based species identification and discuss alternative hypotheses that can account for this. Finally, we indicate the need for future study that includes additional genes, and the combination of both morphology and genetic techniques (e.g. AFLP or microsatellites) to get deeper insight into species delimitation within the genus.     

Anser brachyrhynchus Baillon undAnser erythropus (L.) als Winterg?ste am Jadebusen

Ohne Zusammenfassung