Isolation, characterisation and preliminary cross-protection studies with a new pathogenic avian infectious bronchitis virus (Strain PL-84084)

Virological 1 examination of a severe infectious bronchitis (IB)-like field case in laying hens, led to the isolation of a coronavirus anti-genically different from Massachusetts, Connecticut and four Dutch IB variant strains. The virulence of the isolate for the fowl, and its dual tropism for the respiratory and genital tracts were demonstrated. In preliminary cross-protection studies Commercial vaccines did not protect against challenge with this isolate. These points and the possible economic significance of the virus are discussed.     

Developmental expression of alpha- and gamma-enolase subunits and mRNA sequences in the mouse brain

Nonneuronal alpha alpha- and neuron-specific alpha gamma- and gamma gamma-enolase activities were measured in the mouse brain during development. The corresponding mRNA sequences were quantified directly by hybridization with cDNA probes. The variations in alpha- and gamma-monomer levels inferred from the enzymatic activities were very similar to those of their respective mRNAs. We conclude that monomer levels are primarily controlled by the amounts of their mRNAs during mouse brain development.     

Nephrotoxic serum nephritis in chickens

Biochemical and histopathological changes in experimental nephro‐toxic serum nephritis in chickens were studied. Immunofluorescence studies revealed linear deposits of IgG along the glomerular basement membrane with monospecific anti‐rabbit IgG and monospecific anti‐chicken IgG during heterologous and autologous phases of disease, respectively. The overall histopathological picture was of proliferative glomerulonephritis. Proliferative lesions of an equal or even greater severity were observed in chickens without IgG deposits on the glomerular basement membrane. Ultrastructurally, mesangium revealed hyperplasia. Glomerular basement membrane appeared thickened but prodocytes were normal.     

Chemical cleavage method for the detection of RNA base changes: Experience in the application to collagen mutations in osteogenesis imperfecta

We discuss the definition of mutations in osteogenesis imperfecta (OI) using a chemical cleavage method for detecting mismatched bases in patient mRNA: control cDNA hetero-duplexes. The method is based on the increased chemical modification of cytosines (Cs) by hydroxylamine and thymines (Ts) by osmium tetroxide when they are not paired with their complementary base. The DNA is then cleaved at the modified base with piperidine and the use of radioactively labeled DNA probes allows the position of the mismatched base to be determined by electrophoresis of the cleavage-product. The precise mutations are then determined by specific amplification and sequencing of the region containing the mismatched base. In perinatally lethal OI (OI type II) mismatches have been detected in all 17 cases studied; 12 of these have been fully characterized. In 7 of these 12 cases the mismatches were point mutations in the genes for proα1(I) or proα2(I) which resulted in glycine substitutions in the triple helical region of the protein. Sequence variation was detected in addition to the glycine substitutions in 2 cases. In 2 cases the RNA mismatch resulted from changes in the amino acid sequence of the C-propetide domain. In the 3 remaining cases the mismatch resulted from silent nucleotide sequence variants. In the less severe forms of OI we have studied, mismatches have been detected and characterized in 8 of 12 cases. In 4 of these 8 cases the mismatch resulted from presumably neutral sequence variation and in the other 4 cases mutations have been defined. Three of these were also glycine substitutions in the α1(I) or α2(I); and in one case, 014, the mutation was the deletion of exon 8 in the α1(I) seqence.     

Correlation of clinical and molecular biological abnormalities in osteogenesis imperfecta

Substitution of a glycine residue in the triple helix of the alpha 1(I) chain by either arginine, valine or alanine was associated with the type II lethal perinatal osteogenesis imperfecta phenotype. This phenotype was also produced by a frameshift mutation that resulted in an abnormal amino acid sequence of the carboxy-terminal propeptide of the pro-alpha 1(I) chain. The latter baby, however, showed some clinical and radiographic differences from the other babies with type II OI. The severity of the clinical and radiographic phenotypes are likely to be determined by both the type and site of the mutation as well as by the intra-uterine environment.     

Reduced collagen VI causes Bethlem myopathy: a heterozygous COL6A1 nonsense mutation results in mRNA decay and functional haploinsufficiency

We have identified a new pathogenic mechanism for an inherited muscular dystrophy in which functional haploinsufficiency of the extracellular matrix protein collagen VI causes Bethlem myopathy. The heterozygous COL6A1 mutation results in a single base deletion from the mRNA and a premature stop codon. The mutant mRNA is unstable, subject to nonsense- mediated mRNA decay, and is almost completely absent both from patient fibroblasts and skeletal muscle, resulting in haploinsufficiency of the alpha1(VI) subunit and reduced production of structurally normal collagen VI. This is the first example of a muscular dystrophy caused by haploinsufficiency of a structural protein or member of the dystrophin-glycoprotein complex, and identifies collagen VI as a critical contributor to cell-matrix adhesion in skeletal muscle.