Some metabolic disorders affecting the carotenoid-linked haemolymph proteins inRhynchosciara americana (Diptera,Sciaridae)

Summary Disorders in the carotenoid metabolism are proposed to explain the absence of the yellow and violet or only the violet carotenoid-linked proteins from the haemolymph of someR. americana larvae. The lack of only the yellow chromoprotein is considered to be due to a failure in the biosynthesis of its apoprotein.Supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Conselho Nacional de Pesquisas (CNP_q). W.R.T. and A.G. de B. are indebted to Prof.F. J. S. Lara for advice, encouragement and for laboratory facilities. We thank Mr.A. Malavasi for collecting larvae in nature, Mrs.R. M. Zanelato for larvae culture and MissI. L. Jorge for typing.     

The sodium and glucose transports byin vitro intestinal preparations

Riassunto L'assorbimento di glucosio da parte del digiuno di ratto, rovesciato ed incubatoin vitro, appare relativamente poco sensibile al trasporto attivo del sodio, mentre il trasporto di glucosio dalla mucosa alla sierosa è fortemente correlato e nello stesso senso, con il trasporto attivo di sodio.

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This work has been supported by a research grant of the Consiglio Nazionale delle Ricerche, Roma.     

Feminist Systems Theory: Learning by Praxis

Feminist Systems Theory (FST) is an emerging theory grounded in cultural ecofeminism and critical systems theory. FST’s contribution is in a set of principles that contain implications for community development and social research. FST brings to the fore the importance of valuing and considering the voices of people at the margins of social research and community development projects and is an effort towards a new ontology and language of person and nature to adequately address environmental marginalization. The ‘systems’ theory contribution to FST enriches our repertoires of methods and tools with an emphasis on systems thinking characterised by the use of boundary analysis. FST is ideally situated to enhance systemic intervention practice, an application of action research and participatory research practices. This paper will examine ‘process philosophy’ necessary to understand the nature of boundary analysis and the implications for FST and praxis with relevant examples drawn from case studies of current applications of FST in action research settings; (1) economic analysis and transition pathways; (2) policy analysis of the Close the Gap strategy for Indigenous equality and equity in Australia; (3) a community food distribution system; and, (4) a community health and diabetes prevention program.     

Postnatal loss of Dlk1 imprinting in stem cells and niche astrocytes regulates neurogenesis

The gene for the atypical NOTCH ligand delta-like homologue 1 (Dlk1) encodes membrane-bound and secreted isoforms that function in several developmental processes in vitro and in vivo. Dlk1, a member of a cluster of imprinted genes, is expressed from the paternally inherited chromosome. Here we show that mice that are deficient in Dlk1 have defects in postnatal neurogenesis in the subventricular zone: a developmental continuum that results in depletion of mature neurons in the olfactory bulb. We show that DLK1 is secreted by niche astrocytes, whereas its membrane-bound isoform is present in neural stem cells (NSCs) and is required for the inductive effect of secreted DLK1 on self-renewal. Notably, we find that there is a requirement for Dlk1 to be expressed from both maternally and paternally inherited chromosomes. Selective absence of Dlk1 imprinting in both NSCs and niche astrocytes is associated with postnatal acquisition of DNA methylation at the germ-line-derived imprinting control region. The results emphasize molecular relationships between NSCs and the niche astrocyte cells of the microenvironment, identifying a signalling system encoded by a single gene that functions coordinately in both cell types. The modulation of genomic imprinting in a stem-cell environment adds a new level of epigenetic regulation to the establishment and maintenance of the niche, raising wider questions about the adaptability, function and evolution of imprinting in specific developmental contexts.