Effect of dietary fibre on the mutagenicity and distribution of 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ)

Female BALB/c mice were fed either a fibre-free diet or one supplemented with 30% wheat-bran for 5 weeks. The ability of these mice to convert MeIQ to a bacteria mutagen in vivo was determined using intrasanguinous host-mediated bacterial mutation assays. Less mutagenic activity was detected in the livers of mice fed the bran-supplemented diet compared with those fed the fibre-free diet. Subsequent experiments demonstrated that the effect of brain was not due to modifications in hepatic metabolism, but to changes in uptake of MeIQ from the gastrointestinal tract.     

Production and characterization of polyclonal and monoclonal antibodies against Aflatoxin B1 oxime-BSA in an enzyme-linked immunosorbent assay

From a single aflatoxin B₁ oxime — bovine serum albumin conjugate, polyclonal and monoclonal antibody preparations were produced. The four rabbit polyclonal antisera were specific for aflatoxin Bi in a microtitration plate enzyme — linked immunosorbent assay. The monoclonal antibodies showed a wide range of differing specificities, recognizing, for example, aflatoxins B₁, B₂, G₁ and G₂; B₁ and B₂; B₁ and G₁; and G₁ alone. No antibody preparations reacted with aflatoxin M₁. The significance of these results to the strategy of anti-aflatoxin antibody production for use in quantitative enzyme immunoassays is discussed.     

Histological aspects of in situ hybridization. Detection of poly(A) nucleotide sequences in mouse liver sections as a model system

This study examined the detection of cellular poly(A) sequences in mouse liver sections by in situ hybridization using a 3H-labelled poly(dT) probe. Parameters examined included possible losses of target poly(A) sequences from sectioned cells, access of probe to target sequences, section thickness, hybridization conditions, autoradiographic efficiency, specific activity of probes and specificity of reaction. An improved protocol was devised that resulted in good preservation of histological detail in sectioned tissue blocks, and a calculated hybridization efficiency of 50%-100%. With the use of probes of defined sequence, the protocol should allow detection of unique mRNA sequences within single cells with an estimated sensitivity of 6-12 unique mRNA molecules per sectioned cell.     

Respiratory syncytial virus infection in anti-mu-treated mice.

BALB/c mice were depleted of B cells by anti-mu treatment to investigate the pathogenesis of respiratory syncytial virus (RSV) infection in the absence of antibody. Termination of RSV replication after primary infection occurred with the same kinetics in anti-mu-treated mice as in phosphate-buffered saline (PBS)-treated controls. Yet, when rechallenged, anti-mu-treated mice were more permissive to RSV replication than PBS-treated controls. Anti-mu-treated mice also experienced greater illness than PBS-treated controls during both primary infection and rechallenge. Passive transfer of RSV-specific immune serum to anti-mu-treated mice before rechallenge reconstituted complete protection from RSV replication and diminished illness. Thus, RSV-specific antibody is not required to terminate RSV replication in primary infection, but without antibody, only partial immunity against rechallenge is induced. While it is unknown whether the mechanism is a direct effect on RSV titer or modulation of the illness-causing cellular immune response, the presence of RSV-specific antibody reduces illness in both primary RSV infection and rechallenge of mice.     

Comparison of the Ruthenium hexammine trichloride method to other methods of chemical fixation for preservation of avian physeal cartilage

Summary Several methods of chemical fixation of avian physeal cartilage were compared. The Ruthenium hexammine trichloride method was compared to isotonic glutaraldehyde and neutral buffered formalin for light microscopy and paraffin embedment, and to two osmium-ferrocyanide methods and a combination of 1% glutaraldehyde and 4% formaldehyde for electron microscopy. Only the Ruthenium hexammine trichloride method prevented the loss of matrix proteoglycans and shrinkage of chondrocytes. In undecalcified paraffin-embedded cartilage, preservation of matrix and cellular detail was excellent, but Ruthenium hexammine trichloride interfered with Haematoxylin and Eosin staining. Glutaraldehyde gave more intense eosinophilia than neutral buffered formalin. Ultrastructurally, the Ruthenium hexammine trichloride method was the most consistent and gave the best overall fixation. Matrix elements and cellular and nuclear membranes were well preserved. It did result in vacuolation of the cytoplasm and mitochondria, and it increased granularity of the cytoplasm, chromatin, and rough endoplasmic reticulum. Other fixatives produced minimal vacuolation and finer granularity, but preservation was less consistent, cell/matrix contrast was often excessive, and they caused shrinkage of all chondrocytes. Large dilatations of the rough endoplasmic reticulum that appear to be cytoplasmic inclusions by light microscopy are described for the first time in avian cartilage.     

Genetic homogeneity at the Friedreich ataxia locus on chromosome 9

Classical Friedreich ataxia, a progressive, neurodegenerative disorder involving both the central and peripheral nervous systems, has been subclassified according to the observed clinical heterogeneity. The variations in the age at onset and in the spectrum and severity of symptoms have previously been interpreted as evidence of genetic heterogeneity. We have studied the linkage between the disorder and closely linked DNA markers in families of distinct ethnic origins, including the "typical" French-Canadians and the Acadian population of Louisiana. The disease in these two populations, both of continental French origin, has a very similar initial clinical picture. However, a marked difference in the rate of progression of the obligatory symptoms after 10 years of apparent disease is observed. A total of 553 individuals from 80 families with 202 affected members have been typed with the chromosome 9 marker MCT112, which we have previously shown to be closely linked to the disease locus. Evidence for linkage was observed in all families with the generation of a combined total lod score of 25.09 at a recombination fraction of theta = .00, providing strong evidence for genetic homogeneity at this locus for the classical form of this disease.     

Tn552, a novel transposable element from Staphylococcus aureus

Tn552, one of several closely related beta-lactamase-encoding transposons from Staphylococcus aureus, has a novel set of putative transposition functions. Each is homologous with a well-characterized function from a different type of mobile genetic element. Thus, Tn552 encodes: (i) resL-binL, a co-integrate resolution system homologous with those of Tn3 family elements; (ii) p480, a potential transposase significantly homologous with the DNA integrases of eukaryotic retroviruses and retrotransposons; and (iii) p271, a potential ATP-binding protein that shows homology with the B protein of phage Mu. The 3' terminal nucleotides of Tn552 (CA), adjacent to which p480 might cleave, are the same as those of retroviruses, retrotransposons and phage Mu. The presumptive resolvase (BinL) is very closely related to BinR, which was identified as a DNA invertase and is now shown to resolve an artificial co-integrate in vivo. Furthermore, the structure of the derivative of Tn552 found in the staphylococcal plasmid pI258 can be explained by a BinL (or BinR)-mediated site-specific deletion ('resolution') event. Thus, pI258 contains only the right-hand half of Tn552, which encodes the beta-lactamase and two regulatory proteins. The latter are homologous with the beta-lactamase gene repressor and co-inducer of Bacillus licheniformis. Interestingly, the order of the regulatory genes is reversed in S. aureus compared with Bacillus licheniformis.     

Trypanosoma cruzi: cross-reactive anti-heart autoantibodies produced during infection in mice

Preimmunization with attenuated Corpus Christi stain Trypanosoma cruzi provides survival to C3H mice and enhances resistance of C57 mice to Brazil strain infection. C3H(He) and C57 B1/6 mice surviving acute infection of T. cruzi are shown to have heart specific autoantibodies through acute and chronic infection. ELISA assays were performed using nondenatured extract of hearts from normal syngeneic mice as target antigen reacted with sera from immunized and/or infected mice. Surviving C3H mice developed a specific anti-heart response as early as Day 21 of infection and this response continued at a high level to Day 300. The response in C57 mice, both immunized-infected and infected only, increased to Day 100 followed by a decline in intensity. The heart specificity of the response in mice was suggested by negligible reaction of sera with smooth muscle preparations and a reduced autoreactivity with skeletal muscle. Laminin, a suggested target of autoimmunity in Chagas' disease, was shown not to be the target of the responses in these mice. Immunoaffinity-purified heart specific antibodies show strong cross-reactivity with parasite antigen and like purified parasite specific antibodies, reacted with heart antigen.