The effect of NADH and NAD+ on the proteolysis of lactate dehydrogenase isozymes by trypsin

Résumé L'effet de la NADH et NAD⁺ sur la protéolyse de la lacticodéhydrogénase isoenzyme 1 (LDH 1) et isoenzyme 5 (LDH 5) par la trypsine fut étudié. Les résultats montrent que la NAD⁺ exerce une protection contre la protéolyse de la LDH 1. Mais ni la NADH ni la NAD⁺ ne protègent contre la protéolyse de la LDH 5.     

Genetic and developmental basis of evolutionary pelvic reduction in threespine sticklebacks

Hindlimb loss has evolved repeatedly in many different animals by means of molecular mechanisms that are still unknown. To determine the number and type of genetic changes underlying pelvic reduction in natural populations, we carried out genetic crosses between threespine stickleback fish with complete or missing pelvic structures. Genome-wide linkage mapping shows that pelvic reduction is controlled by one major and four minor chromosome regions. Pitx1 maps to the major chromosome region controlling most of the variation in pelvic size. Pelvic-reduced fish show the same left-right asymmetry seen in Pitx1 knockout mice, but do not show changes in Pitx1 protein sequence. Instead, pelvic-reduced sticklebacks show site-specific regulatory changes in Pitx1 expression, with reduced or absent expression in pelvic and caudal fin precursors. Regulatory mutations in major developmental control genes may provide a mechanism for generating rapid skeletal changes in natural populations, while preserving the essential roles of these genes in other processes.     

Insights into assembly from structural analysis of bacteriophage PRD1

The structure of the membrane-containing bacteriophage PRD1 has been determined by X-ray crystallography at about 4 A resolution. Here we describe the structure and location of proteins P3, P16, P30 and P31. Different structural proteins seem to have specialist roles in controlling virus assembly. The linearly extended P30 appears to nucleate the formation of the icosahedral facets (composed of trimers of the major capsid protein, P3) and acts as a molecular tape-measure, defining the size of the virus and cementing the facets together. Pentamers of P31 form the vertex base, interlocking with subunits of P3 and interacting with the membrane protein P16. The architectural similarities with adenovirus and one of the largest known virus particles PBCV-1 support the notion that the mechanism of assembly of PRD1 is scaleable and applies across the major viral lineage formed by these viruses.     

Tungsten isotope evidence that mantle plumes contain no contribution from the Earth's core

Osmium isotope ratios provide important constraints on the sources of ocean-island basalts, but two very different models have been put forward to explain such data. One model interprets (187)Os-enrichments in terms of a component of recycled oceanic crust within the source material. The other model infers that interaction of the mantle with the Earth's outer core produces the isotope anomalies and, as a result of coupled (186)Os-(187)Os anomalies, put time constraints on inner-core formation. Like osmium, tungsten is a siderophile ('iron-loving') element that preferentially partitioned into the Earth's core during core formation but is also 'incompatible' during mantle melting (it preferentially enters the melt phase), which makes it further depleted in the mantle. Tungsten should therefore be a sensitive tracer of core contributions in the source of mantle melts. Here we present high-precision tungsten isotope data from the same set of Hawaiian rocks used to establish the previously interpreted (186)Os-(187)Os anomalies and on selected South African rocks, which have also been proposed to contain a core contribution. None of the samples that we have analysed have a negative tungsten isotope value, as predicted from the core-contribution model. This rules out a simple core-mantle mixing scenario and suggests that the radiogenic osmium in ocean-island basalts can better be explained by the source of such basalts containing a component of recycled crust.     

Differential distribution of TASK-1, TASK-2 and TASK-3 immunoreactivities in the rat and human cerebellum

In this work, the distributions of some acid-sensitive two-pore-domain K⁺ channels (TASK-1, TASK-2 and TASK-3) were investigated in the rat and human cerebellum. Astrocytes situated in rat cerebellar tissue sections were positive for TASK-2 channels. Purkinje cells were strongly stained and granule cells and astrocytes were moderately positive for TASK-3. Astrocytes isolated from the hippocampus, cerebellum and cochlear nucleus expressed TASK channels in a primary tissue culture. Our results suggest that TASK channel expression may be significant in the endoplasmic reticulum of the astrocytes. The human cerebellum showed weak TASK-2 immunolabelling. The pia mater, astrocytes, Purkinje and granule cells demonstrated strong TASK-1 and TASK-3 positivities. The TASK-3 labelling was stronger in general, but it was particularly intense in the Purkinje cells and pia mater.Received 25 February 2004; received after revision 19 April 2004; accepted 28 April 2004     

Quantitative evidence for the two-gradient hypothesis in the primary induction

Zusammenfassung Die Einwirkung quantitativer Unterschiede induzierender Agenzien wurde untersucht. HeLa-Zellen, mit und ohne Wärmebehandlung, wurden in zwei verschiedenen Proportionen (4:1 bzw. 1:4) gemischt und als Induktor in Epidermisexplantaten des Molchkeimes benutzt. Das Resultat (Fig.) zeigt, dass der Induktor, der mehr Zellen ohne Wärmebehandlung enthält, mehr mesodermale, aber auch mehr deuterencephale Gebilde induziert. Das Resultat wird mit der Zwei-Gradienten-Hypothese der induzierenden Agenzien erklärt.

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The investigation was supported by research grants from the Finnish State and the Sigrid Juselius Fund.     

Stimulation of pyruvate carboxylation by gastric secretagogues

Summary Pyruvate carboxylation was stimulated by 2 gastric secretagogues, histamine and dibutyryl cyclic AMP, and by butyrate. Thiocyanate, an inhibitor of acid secretion, produced a slight decrease. Avidin significantly reduced acid secretion and this effect was overcome by biotin and oxalacetate. The results suggest that carboxylation of pyruvate is one of the reactions controlling oxidative metabolism and acid secretion in toad gastric mucosa.This investigation was supported by Consejo de Desarrollo Científico y Humanístico de la Universidad del Zulia, and by CONICIT Grant S1-0455.     

A simple method for cultivating the early chick embryo in vitro

Summary A method for cultivating the early chick embryo in an artificial medium has been developed that permits the determination of the stage at the onset of the treatment and the continuous observation of the embryogenesis.Kungliga Fysiografiska Sällskapet, Lund, supported this work.