The regeneration of accessory limb parts following epidermal cap transplantation in urodeles

Résumé Les événements morphogénétiques qui suivent le greffage d'un blastème apical à la face préaxiale d'un membre antérieur en voie régénératrice, chezAmbystoma, sont tout à fait normaux, mais le niveau où se localise le régénérat accessoire est différent selon l'espèce utilisé. Ces résultats sont discutés au point de vue du stimulus d'agrégation des cellules appartenant au régénérat accessoire.

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This work was supported by a research grant (NB 04128) from the National Institute of Neurological Diseases and Blindness, National Institutes of Health.     

Evolution of the extracellular space in immature nervous tissue

Resumen En el cerebelo de rata recién nacida existen espacios extracelulares mayores que 1000 Å los cuales progresivamente se reducen hasta que en la tercera semana, como en el adulto, las celulas y fibras se hallan separadas por endiduras de 150–200 Å. Estas observaciones indican que el reducido espacio usualmente hallado en el adulto no es un artificio tecnico como ha sido sugerido por algunos autores.     

TRPC6 is a glomerular slit diaphragm-associated channel required for normal renal function

Progressive kidney failure is a genetically and clinically heterogeneous group of disorders. Podocyte foot processes and the interposed glomerular slit diaphragm are essential components of the permeability barrier in the kidney. Mutations in genes encoding structural proteins of the podocyte lead to the development of proteinuria, resulting in progressive kidney failure and focal segmental glomerulosclerosis. Here, we show that the canonical transient receptor potential 6 (TRPC6) ion channel is expressed in podocytes and is a component of the glomerular slit diaphragm. We identified five families with autosomal dominant focal segmental glomerulosclerosis in which disease segregated with mutations in the gene TRPC6 on chromosome 11q. Two of the TRPC6 mutants had increased current amplitudes. These data show that TRPC6 channel activity at the slit diaphragm is essential for proper regulation of podocyte structure and function.     

Secondary antibody responses of mice to bacterial somatic antigens

Zusammenfassung IgG- und IgM-Antikörper wurden mit 2 Injektionen vonSalmonella-antigenen (S.-newport-Zellen undS.-typhi-Lipopolysacchariden) in Mäusen erzeugt. Es ergab sich, dass die IgG-Antikörper bei ihrer zweiten Reaktion nur dann ein Maximum erreichten, wenn zwischen der ersten und zweiten Injektion ein Zeitraum von mindestens 4 Wochen verstrichen war. Weiter wurde gefunden, dass die Lipopolysaccharide, im Gegensatz zu den Bakterienzellen, die Bildung der IgM-Antikörper favorisierten.     

Exemplification and the use-values of cases and case studies

This paper provides an account of the ‘use-value’ of case-based research by showing how social scientists exploit cases, and case studies, in a variety of practices of inference and extension. The critical basis for making such extensions relies on the power of a case, or the account given of a case (the case-study account), to exemplify certain features of the social world in ways which prove valuable for further analysis: either of the same case, or in many domains beyond the original case study. Framing use-values in terms of exemplification compares favourably with understanding reasoning beyond the case either as a form of analogical reasoning or in taking cases as experimentable objects.     

Bacterial carbon processing by generalist species in the coastal ocean

The assimilation and mineralization of dissolved organic carbon (DOC) by marine bacterioplankton is a major process in the ocean carbon cycle. However, little information exists on the specific metabolic functions of participating bacteria and on whether individual taxa specialize on particular components of the marine DOC pool. Here we use experimental metagenomics to show that coastal communities are populated by taxa capable of metabolizing a wide variety of organic carbon compounds. Genomic DNA captured from bacterial community subsets metabolizing a single model component of the DOC pool (either dimethylsulphoniopropionate or vanillate) showed substantial overlap in gene composition as well as a diversity of carbon-processing capabilities beyond the selected phenotypes. Our direct measure of niche breadth for bacterial functional assemblages indicates that, in accordance with ecological theory, heterogeneity in the composition and supply of organic carbon to coastal oceans may favour generalist bacteria. In the important interplay between microbial community structure and biogeochemical cycling, coastal heterotrophic communities may be controlled less by transient changes in the carbon reservoir that they process and more by factors such as trophic interactions and physical conditions.