The interaction of phosphorus and potassium with seed alkaloid concentrations, yield and mineral content in narrow-leafed lupin (Lupinus angustifoliusL.)

We tested the impact of P deficiency, K deficiency, and their interaction on seed alkaloid concentrations and profile, yield and mineral content in sweet (low-alkaloid) and bitter (high-alkaloid) varieties of narrow-leafed lupin (Lupinus angustifolius L.). P deficiency reduced seed alkaloid concentrations in sweet, but not in bitter, varieties. Under P deficiency, the alkaloid profile in harvested seed of sweet varieties mimicked that of the bitter variety Fest, with 13-hydroxylupanine dominating over lupanine. With adequate or abundant P, lupanine was the predominant alkaloid in sweet varieties. K deficiency was associated with an 8-fold increase of seed alkaloid concentrations in the sweet variety Danja (from 1000 to 8000 mg kg^–1 DM), mostly due to the stimulation of lupanine production. There was a significant interaction between P and K that affected seed alkaloid concentrations in two ways: (i) the inhibitory effect of P deficiency was only apparent under K deficiency and (ii) the lowest seed alkaloid concentrations occurred with abundant K (240 mg K kg^–1) and P (60 mg P kg^–1). Seed yield of all varieties increased asymptotically with increasing P and reached a maximum at adequate P (30 mg P kg^–1). There was no impact of K deficiency on seed yield. In sweet and bitter varieties P supply increased seed N, P and Zn concentrations, but not K. In contrast, seed K concentrations increased and P concentrations decreased with increasing K supply. These findings suggest that P fertiliser should be supplemented with K, to avoid high seed alkaloid concentrations stimulated by asymptomatic K deficiency at high P levels.     

Ultrastructural features of oogenesis in a free-living marine Platyhelminth, Vorticeros luteum

The female gonad of the prolecithophoran turbellarian Voticeros luteum has a heterocellular organization as is typical in the neoophoran Platyhelminthes. It is composed of an ovarian and a vitellarian area that are not well separated from one another and from the surrounding tissues by a tunica. Each oocyte during maturation becomes completely surrounded by a single accessory cell whose function has been hypothesized on the basis of the present investigation. The main feature in oocyte differentiation appears to be the synthesis and accumulation of small electron-dense inclusions; these are about 1-2 mum in size, are elaborated by the Golgi apparatus and have a content which reacts partially to the cytochemical test for polyphenols. The genesis, composition and cortical localization of the inclusions suggest that they could be homologous to the egg-shell granules present in the oocytes of 'archoophoran' species. A comparative analysis and discussion of the oocyte inclusions observed to date in other turbellarians is undertaken and the hypothetical use of these structures as characters providing some new insights in clarifying the phylogenetic relationships among free-living Platyhelminthes is finally discussed.     

DjPum, a homologue of Drosophila Pumilio, is essential to planarian stem cell maintenance

As stem cells are rare and difficult to study in vivo in adults, the use of classical models of regeneration to address fundamental aspects of the stem cell biology is emerging. Planarian regeneration, which is based upon totipotent stem cells present in the adult--the so-called neoblasts--provides a unique opportunity to study in vivo the molecular program that defines a stem cell. The choice of a stem cell to self-renew or differentiate involves regulatory molecules that also operate as translational repressors, such as members of PUF proteins. In this study, we identified a homologue of the Drosophila PUF gene Pumilio (DjPum) in the planarian Dugesia japonica, with an expression pattern preferentially restricted to neoblasts. Through RNA interference (RNAi), we demonstrate that gene silencing of DjPum dramatically reduces the number of neoblasts, thus supporting the intriguing hypothesis that stem cell maintenance may be an ancestral function of PUF proteins.     

Ultrastructural and cytochemical studies of the female gonad of Prorhynchus sp. (Platyhelminthes,Lecithoepitheliata)

The female gonad of Prorhynchus is heterocellular (neoophoran organization) and consists of an unpaired, elongate germovitellarium enveloped by a finely granular extracellular lamina. It is composed of a posterior germinative area where early oocytes are randomly associated with differentiating vitellocytes and a growth area with follicular organization. In each follicle a single oocyte is surrounded by a layer of vitellocytes. By electron microscopy, the oocytes showed features typical of non-vitellogenic germ cells; they had chromatoid bodies, annulate lamellae, lipid droplets and R.E.R. and Golgi complexes producing small granules with a multilamellar pattern. Vitellocytes showed features typical of secretory cells with the R.E.R. and Golgi complex developed to a great extent and involved in the production of type A and type B globules, respectively. We speculate that type A globules are shell-globules and type B globules are yolk. The structure, composition and role of vitellocyte globules of Prorhynchus are compared with those of homologous inclusions from other Platyhelminthes.Abbreviations A type A globule - B type B globule - ECL extracellular lamina - GC Golgi complex - L lipid - RER rough endoplasmic reticulum - O oocyte - V vitellocyte     

The ultrastructure of the germanium in some Rhabdocoela

Two Daphnia clones were isolated from different day depths during the period of diel vertical migration and were tested for their life-history responses to a fish exudate released by juvenile perch. Animals were exposed to fish exudate every 24 or 48 h. Both clones responded to the exudate by exhibiting earlier maturation and larger sizes of first clutches, which resulted in higher rates of population increase. Also, neonates were smaller in the presence of the exudate. It was found that the clone isolated from a deeper day depth (migrating clone) was less sensitive to the exudate than the clone isolated from the surface waters, which was presumed to be non-migrating. The non-migrating clone responded by having smaller neonate sizes and smaller sizes at maturity than the migrating clone. The non-migrating clone responded to the fish chemical when it was exposed to it every 24 or 48 h, whereas the migrating clone only responded to the exudate if exposed to it every 24 h.     

Ultrastructural features of oogenesis in some marine neoophoran turbellarians

An ultrastructural study of oogenesis has been undertaken in some marine species of neoophoran turbellarians belonging to the Tricladida, Proseriata, and Prolecithophora. Among marine triclads, Cercyra hastata has oocytes with a remarkable amount of what appears to be autosynthetic proteinaceous yolk, while Procerodes dohrni and P. lobata have alecithal oocytes. Among the Proseriata, several species of the primitive family Monocelididae (subfamily Monocelidinae) have oocytes with a discrete amount of what appears to be autosynthetic yolk, while Parotoplana macrostyla, of the derived family Otoplanidae, has alecithal eggs. Finally preliminary observations on Plagiostomum maculatum (order Prolecithophora) suggest that oocytes have autosynthetic yolk globules.These results support the hypothesis (previously formulated on the basis of similar ultrastructural investigations on freshwater triclads) that the presence of autosynthetic yolk in some neoophoran turbellarians can be interpreted as a primitive character inherited from an ancestor with archoophoran organization. This plesiomorphic character would still be maintained in some species while lost in others following differentiation of vitellaria which are characteristic of the Neoophora.     

TSPO over-expression increases motility, transmigration and proliferation properties of C6 rat glioma cells

Gliomas are one of the most malignant cancers. The molecular bases regulating the onset of such tumors are still poorly understood. The translocator protein (TSPO), formerly known as the peripheral-type benzodiazepine receptor, is a mitochondrial permeability transition (MPT)-pore protein robustly expressed in gliomas and involved in the regulation of apoptosis and cell proliferation. TSPO expression levels have been correlated with tumor malignancy. Here we describe the production of C6 rat glioma cells engineered to over-express the TSPO protein with the aim of providing the first direct evidence of a correlation between TSPO expression level and glioma cell aggressiveness. We observed that TSPO potentiates proliferation, motility and transmigration capabilities as well as the ability to overcome contact-induced cell growth inhibition of glioma cells. On the whole, these data demonstrate that TSPO density influences metastatic potential of glioma cells. Since several data suggest that TSPO ligands may act as chemotherapeutic agents, in this paper we also demonstrate that TSPO ligand-induced cell death is dependent on TSPO density. These findings suggest that the use of TSPO ligands as chemotherapeutic agents could be effective on aggressive tumor cells with a high TSPO expression level.     

Yolk utilization in stick insects entails the release of vitellin polypeptides into the perivitelline fluid

This study investigates the developmental fate of vitellin (Vt) polypeptides generated by limited proteolysis in an insect embryo. To this end, a number of polyclonal (pAb) and monoclonal antibodies (mAb) were raised against the yolk sac and the perivitelline fluid of late embryos of the stick insect Carausius morosus. Two dimensional immuno gel electrophoresis and Western blotting demonstrate that polypeptides resulting from Vt processing are present both in the yolk sac and the perivitelline fluid. At the confocal microscope, different labelling patterns were detected in the ooplasm depending on the stage of development attained by the embryo. At early developmental stages, label is associated with large unsegmented portions of the fluid ooplasm. During embryonic development, the fluid ooplasm is gradually transformed into yolk granules by intervention of vitellophages. Prior to dorsal closure, the yolk sac is separated from the perivitelline fluid by interposition of serosa cells (the so called serosa membrane). Several mAbs raised against the perivitelline fluid react specifically with this membrane suggesting that the release of Vt polypeptides from the yolk sac occurs by intracellular transit through the serosa cells. By immunocytochemistry, gold label appears associated with the cell surface and a number of vacuoles of the serosa membrane. These data are interpreted as suggesting that Vt polypeptides resulting from limited proteolysis in stick insect embryos are not exhaustively degraded within the yolk sac, but are instead transferred transcytotically to the perivitelline fluid through the serosa membrane.