A polymorphism in the porcine miR‐208b is associated with microRNA biogenesis and expressions of SOX‐6 and MYH7 with effects on muscle fibre characteristics and meat quality

MicroRNAs (miRNAs) encoded by the myosin heavy chain (MHC) genes are muscle‐specific miRNAs (myomiRs) and regulate the expression of MHC isoforms in skeletal muscle. These miRNAs have been implicated in muscle fibre types and their characteristics by affecting the heterogeneity of myosin. In pigs, miR‐208b and miR‐499 are embedded in introns of MYH7 and MYH7b respectively. Here, we identified a novel single nucleotide polymorphism (SNP) in intron 30 of MYH7 by which porcine miR‐208b is encoded. Based on the association study using a total of 487 pigs including Berkshire (n = 164), Landrace (n = 121) and Yorkshire (n = 202), the miR‐208b SNP (g.17104G>A) had significant effects on the proportions of types I and IIb fibre numbers (P < 0.010) among muscle fibre characteristics and on drip loss (P = 0.012) in meat quality traits. Moreover, the SNP affected the processing of primary miR‐208b into precursor miR‐208b with a marginal trend towards significance (P = 0.053), thereby leading to significant changes in the levels of mature miR‐208b (P = 0.009). These SNP‐dependent changes in mature miR‐208b levels were negatively correlated with the expression levels of its target gene, SOX‐6 (P = 0.038), and positively associated with the expression levels of its host gene, MYH7 (P = 0.046). Taken together, our data suggest that the porcine miR‐208b SNP differentially represses the expression of SOX‐6 by regulating miRNA biogenesis, thereby affecting the expression of MYH7 and the traits of muscle fibre characteristics and meat quality.     

Chemical modification of the hydroxylase of soluble methane monooxygenase gives one form of the protein with significantly increased thermostability and another that functions well in organic solvents

Proteolysis of the hydroxylase component of soluble methane monooxygenase (MMO) with trypsin yielded a protein which retained 50% activity in a standard MMO assay. In an H₂O₂-driven assay, in which H₂O₂ replaced two of the protein components, NADH and O₂ used in the standard assay, the proteolysed hydroxylase retained full activity for ethane, propane and propene, but had a 2–3 fold increase with methane as substrate. Several crosslinking reagents have been tested for their ability to stabilise the proteolysed form of the hydroxylase. Using polyoxyethylene bis(imidazolyl carbonyl) (M_r 3350) as the crosslinking agent, increased thermostability of the hydroxylase was observed. Activated methoxypolyethylene glycol (M_r 5000) was used to modify the hydroxylase which was now soluble in organic solvents as well as water and could be activated by H₂O₂. The glycol-modified hydroxylase functioned well in organic solvents in the catalysis of propene oxidation.     

Trehalose, the insect blood sugar, inhibits loading of diacylglycerol by lipophorin from the fat body in locusts

Trehalose, the insect blood sugar, was found to inhibit diacylglycerol uptake by lipophorin from the fat body in vitro. Trehalose inhibited diacylglycerol uptake by about 40%-50% at various physiological concentrations. This suggests that trehalose may play a dual role in the hemolymph, i.e. serving as the insect's fuel and as a regulator in lipid transport.     

Presence in invertebrate genomes of sequences characterized by the repetition of the triplet CCPurine

In Drosophila melanogaster (Dm), polypeptidic domains have been found in different morphogenetic genes. Two types of them are characterized by the repetition of nucleotidic triplets: the M repeat (CAX) and the paired repeat (CAXCCX). In this paper we described a third type of repeat isolated from the genome of a Polychaete annelid: Owenia fusiformis. This repeat is characterized by the repetition of the triplet CCPurine. Phylogenetic studies showed the presence of this repeat in all the invertebrate genomes tested (eight copies in Dm genome) while we failed to detect it in vertebrate genomes.     

Generation of inositol phosphates, cytosolic Ca and secretion of noradrenaline in PC12 cells treated with glutamate

Glutamate transiently stimulated rat pheochromocytoma PC12 cells and caused an inositol trisphosphate formation and an increase in levels of Ca⁺ in the cytosol. The rank order of potency of glutamate> N-methyl-D-aspartate (NMDA) > KAINATE = quisqualate is characteristic of an interaction with NMDA receptors. The effect of glutamate on inositol trisphosphate formation disappeared in a low Mg²⁺ buffer and was not blocked by DL-2-amino-5-phosphonovalerate, an antagonist for NMDA receptors coupled to ion channels. Although glutamate failed to stimulate noradrenaline secretion, glutamate enhanced the effect of bradykinin, but not of Ca ionophore A23187, or KC1. These results suggest the existence of metabotropic glutamate receptors, different from previously reported receptors, in PC12 cells.