Analysis of UDP-galactose 4'-epimerase mutations associated with the intermediate form of type III galactosaemia

Type III galactosaemia is a hereditary disease caused by reduced activity in the Leloir pathway enzyme, UDP-galactose 4'-epimerase (GALE). Traditionally, the condition has been divided into two forms-a mild, or peripheral, form and a severe, or generalized, form. Recently it has become apparent that there are disease states which are intermediate between these two extremes. Three mutations associated with this intermediate form (S81R, T150M and P293L) were analysed for their kinetic and structural properties in vitro and their effects on galactose-sensitivity of Saccharomyces cerevisiae cells that were deleted for the yeast GALE homologue Gal10p. All three mutations result in impairment of the kinetic parameters (principally the turnover number, k(cat)) compared with the wild-type enzyme. However, the degree of impairment was mild compared with that seen with the mutation (V94M) associated with the generalized form of epimerase deficiency galactosaemia. None of the three mutations tested affected the ability of the protein to dimerize in solution or its susceptibility to limited proteolysis in vitro. Finally, in the yeast model, each of the mutated patient alleles was able to complement the galactose-sensitivity of gal10 Delta cells as fully as was the wild-type human allele. Furthermore, there was no difference from control in metabolite profile following galactose exposure for any of these strains. Thus we conclude that the subtle biochemical and metabolic abnormalities detected in patients expressing these GALE alleles likely reflect, at least in part, the reduced enzymatic activity of the encoded GALE proteins.

Fractal rotation isolates mechanisms for form-dependent motion in human vision

Here, we describe a motion stimulus in which the quality of rotation is fractal. This makes its motion unavailable to the translationbased motion analysis known to underlie much of our motion perception. In contrast, normal rotation can be extracted through the aggregation of the outputs of translational mechanisms. Neural adaptation of these translation-based motion mechanisms is thought to drive the motion after-effect, a phenomenon in which prolonged viewing of motion in one direction leads to a percept of motion in the opposite direction. We measured the motion after-effects induced in static and moving stimuli by fractal rotation. The after-effects found were an order of magnitude smaller than those elicited by normal rotation. Our findings suggest that the analysis of fractal rotation involves different neural processes than those for standard translational motion. Given that the percept of motion elicited by fractal rotation is a clear example of motion derived from form analysis, we propose that the extraction of fractal rotation may reflect the operation of a general mechanism for inferring motion from changes in form.

Characterisation and glucoregulatory actions of a novel acylated form of the (Pro(3))GIP receptor antagonist in type 2 diabetes

In this study, we tested the biological activity of a novel acylated form of (Pro(3))glucose-dependent insulinotropic polypetide [(Pro3)GIP] prepared by conjugating palmitic acid to Lys(16) to enhance its efficacy in vivo by promoting binding to albumin and extending its biological actions. Like the parent molecule (Pro(3))GIP, (Pro(3))GIPLys(16)PAL was completely stable to the actions of DPP-IV and significantly (p <0.01 to p <0.001) inhibited GIP-stimulated cAMP production and cellular insulin secretion. Furthermore, acute administration of (Pro(3))GIPLys(16)PAL also significantly (p <0.05 to p <0.001) countered the glucose-lowering and insulin-releasing actions of GIP in ob/ob mice. Daily injection of (Pro(3))GIPLys(16)PAL (25 nmol/kg bw) in 14-18-week-old ob/ob mice over 14 days had no effect on body weight, food intake or non-fasting plasma glucose and insulin concentrations. (Pro(3))GIPLys(16)PAL treatment also failed to significantly alter the glycaemic response to an i.p. glucose load or test meal, but insulin concentrations were significantly reduced (1.5-fold; p <0.05) after the glucose load. Insulin sensitivity was enhanced (1.3-fold; p <0.05) and pancreatic insulin was significantly reduced (p <0.05) in the (Pro(3))GIPLys(16)PAL-treated mice. These data demonstrate that acylation of Lys(16) with palmitic acid in (Pro(3))GIP does not improve its biological effectiveness as a GIP receptor antagonist.

Levels and distribution of genetic diversity of coconut (Cocos nucifera L., var. Typica form typica) from Sri Lanka assessed by microsatellite markers

The coconut variety Typica, form typica, commonly known as Sri Lanka tall coconuts is the most widely exploited and grown variety in Sri Lanka. Under the coconut bio-diversity conservation programme, several Typica populations have been collected by island-wide surveys and planted ex situ. Thirty-three coconut populations were subjected to microsatellite assay with eight coconut-specific microsatellite primer pairs in order to study the levels and distribution of genetic variation of the collected materials for formulating future collection strategies and selecting parents for the breeding programme. A total of 56 alleles were detected ranging from 3 to 10 alleles per primer pair with an average of 7 alleles per locus. Overall a very high level of genetic diversity was detected (0.999) for all the populations studied ranging from 0.526 for population Debarayaya to 0.683 for population Dickwella. Only four introduced coconut populations, i.e. Clovis, Margeret, Dickwella, Mirishena and an embryo-cultured population were clearly separated from the resulting dendrogram. A very high level of within population variation (99%) accounted for native populations suggests a common history and a restricted genetic base for native Sri Lankan tall coconuts. Categorization of alleles into different classes according to their frequency and distribution confirmed the results of the dedrogram and concluded the adequacy of single large collection from the entire target area to represent the total genetic diversity in Sri Lanka. This study discusses useful information regarding conservation and breeding of coconut in Sri Lanka.