Effects of Population Density on Sex Expression in Onoclea sensibilis L. on Agar and Ashed Soil

Population density affected the sex expression of agar-growngametophytes of Onoclea sensibilis L. The time of onset of sexualitywas advanced, the proportion of females was increased, and thegrowth rate of individuals was greater at lower densities. Populationdensity had no effect on the sex expression of Onoclea grownon ashed soil, and there was no difference in growth rate ofindividuals grown on ashed soil at different densities. Covariateanalysis, using thallus width as a measure of growth rate, indicatedthat the effect of density on sex expression was mostly associatedwith growth rate. The differing effects of population densityon agar and ashed soil demonstrate that substrate influencessex expression in Onoclea. This influence is most dramatic insingle-gametophyte cultures, where agar cultures produced 97per cent females and ashed soil cultures 100 per cent males. Onoclea sensibilis L., sensitive fern, fern gametophytes, sexuality, population density     

Technical comment on Boersma et al. (2016) Temperature driven changes in the diet preference of omnivorous copepods: no more meat when it's hot? Ecology Letters, 19, 45–53

A recent study concluded that omnivorous plankton will shift from predatory to herbivorous feeding with climate warming, as consumers require increased carbon:phosphorous in their food. Although this is an appealing hypothesis, we suggest the conclusion is unfounded, based on the data presented, which seem in places questionable and poorly interpreted.     

Recycling cell surface glycoproteins undergo limited oligosaccharide reprocessing in LEC1 mutant Chinese hamster ovary cells

The ability of particular cell surface glycoproteins to recycle and become exposed to individual Golgi enzymes has been demonstrated. This study was designed to determine whether endocytic trafficking includes significant reentry into the overall oligosaccharide processing pathway. The Lec1 mutant of Chinese hamster ovary (CHO) cells lack N - acetylglucosaminyltransferase I (GlcNAc-TI) activity resulting in surface expression of incompletely processed Man5GlcNAc2 N -linked oligosaccharides. An oligosaccharide tracer was created by exoglycosylation of cell surface glycoproteins with purified porcine GlcNAc-TI and UDP-[3H]GlcNAc. Upon reculturing, all cell surface glycoproteins that acquired [3H]GlcNAc were acted upon by intracellular mannosidase II, the next enzyme in the Golgi processing pathway of complex N -linked oligosaccharides (t1/2= 3-4 h). That all radiolabeled cell surface glycoproteins were included in this endocytic pathway indicates a common intracellular compartment into which endocytosed cell surface glycoproteins return. Significantly, no evidence was found for continued oligosaccharide processing consistent with transit through the latter cisternae of the Golgi apparatus. These data indicate that, although recycling plasma membrane glycoproteins can be reexposed to individual Golgi-derived enzymes, significant reentry into the overall contiguous processing pathway is not evident.      

Topological studies on the enzymes catalyzing the biosynthesis of Glc-P- dolichol and the triglucosyl cap of Glc3Man9GlcNAc2-P-P-dolichol in microsomal vesicles from pig brain: use of the processing glucosidases I/II as latency markers

In the current model for Glc3Man9GlcNAc2-P-P-Dol assembly, Man5GlcNAc2- P-P-Dol, Man-P-Dol, and Glc-P-Dol are synthesized on the cytoplasmic face of the ER and diffuse transversely to the lumenal leaflet where the synthesis of the lipid-bound precursor oligosaccharide is completed. To establish the topological sites of Glc-P-Dol synthesis and the lipid-mediated glucosyltransfer reactions involved in Glc3Man9GlcNAc2-P-P-Dol synthesis in ER vesicles from pig brain, the trypsin-sensitivity of Glc-P-Dol synthase activity and the Glc-P- Dol:Glc0-2Man9GlcNAc2-P-P-Dol glucosyltransferases (GlcTases) was examined in sealed microsomal vesicles. Since ER vesicles from brain do not contain glucose 6-phosphate (Glc 6-P) phosphatase activity, the latency of the lumenally oriented, processing glucosidase I/II activities was used to assess the intactness of the vesicle preparations. Comparative enzymatic studies with sealed ER vesicles from brain and kidney, a tissue that contains Glc 6-P phosphatase, demonstrate the reliability of using the processing glucosidase activities as latency markers for topological studies with microsomal vesicles from non-gluconeogenic tissues lacking Glc 6-P phosphatase. The results obtained from the trypsin-sensitivity assays with sealed microsomal vesicles from brain are consistent with a topological model in which Glc-P-Dol is synthesized on the cytoplasmic face of the ER, and subsequently utilized by the three Glc-P-Dol-mediated GlcTases after "flip-flopping" to the lumenal monolayer.      

The Growth and Carbon Economy of Selection Lines of Lolium perenne cv. S23 with Differing Rates of Dark Respiration: 2. Grown as Young Plants from Seed

Young plants of two selection lines of Lolium perenne cv. S23with ‘fast’ and ‘slow’ rates of ‘maturetissue’ respiration were individually grown from seed,together with plants of S23, their common parent, in 9.2 cmpots in a controlled environment at 20/15 °C day/night temperatures. No significant differences were found between the genotypesin leaf extension and tiller production during this early stageof their growth. They did differ however, by an average of 26%,in the rate of dark respiration of fully expanded leaf laminae.The use of a simple model demonstrated that such a differencein respiration could alone account for the different rates ofdry matter production shown by the selection lines when grownas young crops from seed. Possible penalties of ‘slow’respiration are also considered. Lolium perenne L., ryegrass, respiration, maintenance respiration, stimulated swards, leaf growth, tiller production, carbon economy     

The Movement of Zinc through Excised Stems of Seedlings of Pinus radiata D. Don.

Radioactive Zn solns were drawn through 10 cm stem sectionsexcised from seedlings of P. radiata to determine the locationand quantity of ⁶⁵Zn remaining in the stems and the concn of⁶⁵Zn in the exudate. Zinc was removed from solns passing through the excised stemsby processes which appeared to be non-metabolic because coolingthe inflow solns did not decrease the proportion of Zn removedand non-specific because Ca competed with Zn for ‘exchangesites’. The formation of anionic or uncharged complexes between Zn andEDTA, or citrate resulted in more Zn passing through the excisedstems. Consistent with the greater stability of Zn-EDTA complexesmore Zn passed through stems treated with EDTA than with citrate.Decreasing the pH of solns containing Zn, Ca and potassium citrateincreased the amount of Zn deposited in the basal (inflow) endof the stems, probably by decreasing the amount of Zn boundto citrate. Increasing the conen of Zn in test solns containingZn, Ca and potassium citrate did not change the distributionof ⁶⁵Zn in the stems as the capacity of the stems to removeZn from soln was large enough to remove all the free Zn in allthe solns Pinus radiata D. Don, pine, zinc, movement, stems     

A feature selection approach for identification of signature genes from SAGE data

Background  

One goal of gene expression profiling is to identify signature genes that robustly distinguish different types or grades of tumors. Several tumor classifiers based on expression profiling have been proposed using microarray technique. Due to important differences in the probabilistic models of microarray and SAGE technologies, it is important to develop suitable techniques to select specific genes from SAGE measurements.