Impacts of dispersal on rapid adaptation and dynamic stability of Daphnia in fluctuating environments

Prior ecological research has shown that spatial processes can enhance the temporal stability of populations in fluctuating environments. Less explored is the effect of dispersal on rapid adaptation and its concomitant impact on population dynamics. For asexually reproducing populations, theory predicts that dispersal in fluctuating environments can facilitate asynchrony among clones and enhance stability by reducing temporal variability of total population abundance. This effect is predicted when clones exhibit heritable variation in environmental optima and when fluctuations occur asynchronously among patches. We tested this in the field using artificial ponds and metapopulations composed of a diverse assemblage of Daphnia pulex clones. We directly manipulated dispersal presence/absence and environmental fluctuations in the form of nutrient pulses. Consistent with predictions, dispersal enhanced temporal asynchrony among clones in the presence of nutrient pulses; this in turn stabilized population dynamics. This effect only emerged when patches experienced spatially asynchronous nutrient pulses (dispersal had no effect when patches were synchronously pulsed). Clonal asynchrony was driven by strong positive selection for a single clone that exhibited a performance advantage under conditions of low resource availability. Our work highlights the importance of dispersal as a driver of eco-evolutionary dynamics and population stability in variable environments.     

Differential phagocytosis of Leishmania mexicana promastigotes and amastigotes by monocyte‐derived dendritic cells

Leishmania species are dimorphic protozoan parasites that live and replicate in the gut of sand flies as promastigotes or in mammalian hosts as amastigotes. Different immune cells, including DCs, and receptors differ in their involvement in phagocytosis of promastigotes and amastigotes and in recognition of different Leishmania species. In the case of L. mexicana, differences in phagocytosis of promastigotes and amastigotes by DCs and participation of C‐type lectin receptors (CLRs) have not been established. In the present study, flow cytometry and confocal microscopy were used to investigate the phagocytosis by monocyte‐derived dendritic cells (moDCs) of L. mexicana promastigotes and amastigotes in the presence or absence of immune serum during various periods of time. Blocking antibodies against mannose receptors and DC‐SIGN were used to explore the participation of these receptors in the phagocytosis of L. mexicana by moDC. The major differences in interactions of L. mexicana promastigotes and amastigotes with moDC were found to occur within the first 3 hr, during which phagocytosis of promastigotes predominated as compared with opsonization of promastigotes and amastigotes. However, after 6 hr of incubation, opsonized promastigotes were preferentially phagocytosed as compared with unopsonized promastigotes and amastigotes and after 24 hr of incubation there were no differences in the phagocytosis of promastigotes and amastigotes. Finally, after 3 hr incubation, DC‐SIGN was involved in the phagocytosis of promastigotes, but not of amastigotes.     

Electron microscope studies on the intermediate lobe of the embryonic mouse

The development of the intermediate lobe of the hypophysis was studied in the embryonic C3H mouse; at least four glands from embryos of every gestational day from 15 to 19 were examined. In the 16 day-old embryo prospective secretory cells proliferate at the centre of the intermediate lobe anlage. At the same stage cylindrical cells bordering the hypophyseal cleft begin to reorganize into marginal cells. By the end of fetal life marginal cells are well differentiated. In the 17 day-old embryo a few granular inclusions appear in some centrally located cells. Secretory cells increase in number during the following two embryonic days. Some of these cells contain polymorphic populations of granular and vesicular inclusions by gestational day 19. The possibility of a dual formation of secretory inclusions is discussed. The result implies that the onset of granule-formation by these cells is not contemporaneous with the start of production of melanophore-expanding substances, the presence of which has been detected by earlier biological assays.     

A synthesis of 3-O-(α-d-mannopyranosyl)-d-mannose and its protein conjugate

Methods for the synthesis of 3-O-(α-d-mannopyranosyl)-d-mannose and 2-(4-aminophenyl)ethyl 3-O-(α-d-mannopyranosyl)-α-d-mannopyranoside have been investigated by a number of sequences. Glycosidations with 2,3-di-O-acetyl-4,6-di-O-benzyl-d-mannopyranosyl and 2-O-benzoyl-3,4,6-tri-O-benzyl-d-mannopyranosyl p-toluenesulfonates were found to give better yields than the Helferich modification, the use of a peracylated d-mannopyranosyl halide, or the use of triflyl leaving group. Only the α anomer was obtained. Factors influencing glycosidation reactions are discussed. A mercury(II) complex was used for selective 2-O-acylation of 4,6-di-O-benzyl-α-d-mannopyranosides. A disaccharide—protein conjugate was prepared by the isothiocyanate method.     

Status and impact of rural aquaculture practice on Lake Victoria basin wetlands

Rural aquaculture in Lake Victoria basin is a fast increasing nontraditional farming activity which if not appropriately practised will lead to degradation of the wetlands. As part of a study to develop appropriate guidelines and model systems for wetlands‐based rural aquaculture in the basin a survey was conducted to assess the status and the ecological and socioeconomic impact of rural aquaculture on wetlands and wetlands communities. Aquaculture practice was found to be common but not as a major activity. Aquaculture in the wetlands can be described as a low input‐low output production activity and subsistence based on ponds under 400 m² using free seed from public agencies with hardly any supplementary feeding. Men owned most of the ponds and women only contributed to the management of the fishponds by feeding the fish. Poorly constructed ponds and loss during harvesting have led to the escape of cultured species into the wild. Introduction of nonnative species in the basin has already led to wide ranging ecological, environmental and socioeconomic changes whose impact and usefulness are still very much contentious. Repeat of such scenarios can be avoided if appropriate and science‐based models for rural aquaculture farming are developed, tested and disseminated to the communities.     

Evaluation of microarray data normalization procedures using spike-in experiments

Background  

Recently, a large number of methods for the analysis of microarray data have been proposed but there are few comparisons of their relative performances. By using so-called spike-in experiments, it is possible to characterize the analyzed data and thereby enable comparisons of different analysis methods.     

Age-dependent variations of the efficiency of iridoid biosynthesis in Verbena officinalis

²H Labelled deoxyloganin gave ca a 30 % incorporation into each of dihydrocornin and cornin in Verbena officinalis plants before their flow