Recognition of HLA-B27 by mouse cytotoxic T-cell clones: a transgenic mouse

As a basis for the characterization of mouse T cells involved in the recognition of xenogeneic HLA molecules, a panel of HLA-B27-reactive cytotoxic T-cell clones was generated upon stimulation by cells from HLA-B27-transgenic mice. The HLA-B27-induced T-cell response was found to comprise two categories of clones: some recognizing HLA-B27 independent of H-2 molecules expressed by the target cells (unrestricted clones), others recognizing HLA-B27 in an H-2 restricted manner. The unrestricted clones exhibited diverse specificities, as judged from their various cross-reactivities with other xenogeneic (HLA) or allogeneic (H-2) molecules. In addition, although most of the unrestricted clones were able to react with both mouse and human HLA-B27-transgenic mice. The HLA-B27 induced T-cell which reacted only with HLA-B27-positive mouse, and not human cells. These findings illustrate that both H-2-restricted and unrestricted T cells with diverse species contribute to HLA-B27-xenorecognition.     

The root-knot nematode resistance gene (Mi) in tomato: construction of a molecular linkage map and identification of dominant cDNA markers in resistant genotypes

A dominant allele at the Mi locus on chromosome 6 of tomato (Lycopersicon esculentum Mill) confers resistance to three species of root-knot nematodes (Meloidogyne). The resistance, which is associated with a localized necrotic response, was originally introduced into tomato from the wild species Lycopersicon peruvianum. As a step towards the molecular cloning of Mi, we have identified closely linked DNA markers from both cDNA and genomic DNA libraries as restriction fragment length polymorphisms (RFLPs). DNA from tomato populations segregating for nematode resistance was analyzed to generate a high-resolution genetic map of this region. Additional information on gene order was obtained by comparing the size of the introgressed L. peruvianum chromosomal segment within a collection of nematode-resistant tomato lines. Among the four cDNA markers that are tightly linked to Mi, three are dominant, i.e. L. peruvianum-specific. One cDNA marker corresponds to a gene family comprising 20-30 members, one of which is diagnostic for all nematode-resistant genotypes tested. The presence of non-homologous sequences around the Mi gene may contribute to the suppression of recombination in this region of the genome in crosses heterozygous for Mi. The potential of 'walking' from closely linked markers to Mi is discussed.     

Plant-microbial interaction under gnotobiotic conditions: A scanning electron microscope study

Inoculation of canola seeds withPseudomonas putida GR12-2 stimulates root elongation under gnotobiotic conditions. Transformation ofP. putida GR12-2 with the broad-host-range plasmid pGSS15 abolishes the enhancement of root elongation. With scanning electron microscopy it was found that both transformed and nontransformedP. putida GR12-2 are capable of binding to canola seed coats. In addition, it was observed that 4 days after the initial inoculation the roots of bothP. putida GR12-2- and GR12-2/pGSS15-treated seedlings were free of adhering bacteria despite the fact that it was subsequently shown that both bacterial strains are capable of binding to roots. Thus, adhesion to roots is not necessary for the initial phase of enhanced root elongation that is induced byP. putida GR12-2 under gnotobiotic conditions.     

Chromosome banding and genome compartmentalization in fishes

The diploid chromosome number of the Chinese raccoon dog varies from 54 (no B chromosomes) to 58 (4 B chromosomes). The B chromosomes are totally heterochromatic. An electron microscopic study was made of the synaptonemal complexes (SC) in spermatocytes of these animals. The SC karyotype consists of 27 regular chromosome pairs (autosomes and the sex chromosomes) plus the B chromosomes. The Bs pair effectively with one another at pachytene, but the SC axes of the B chromosomes are much denser than those of the A chromosomes. Depending on the number of Bs, both bivalents and multivalents have been observed. When three B chromosomes are present in a cell, parallel alignment of all three SCs can be seen. Formation of multivalents indicates high homology among these supernumerary heterochromatic chromosomes. Fusiform bulges are found along unpaired regions of all chromosomes which are particularly pronounced in diplotene.     

Outer root sheath cells of human hair follicle are able to regenerate a fully differentiated epidermis in vitro

During wound healing, interfollicular epidermis can be regenerated from the outer root sheath of hair follicles, showing that the cells of this structure can shift toward an interfollicular epidermal phenotype. Similarly, it has been shown that a multilayered epithelium originating from outer sheath cells can be obtained in vitro by culturing hair follicles. However, in the culture systems developed so far, the phenotypical shift was incomplete since the cells retained some of their original characteristics and did not acquire several key markers of terminally differentiated epidermis. In this paper, we describe a new tissue culture method for obtaining a multilayered epithelium from outer sheath cells. This is performed by implanting human hair follicles vertically into dermal equivalents and then raising the culture at the air-liquid interface. The morphological, immunological, and biochemical features of the in vitro reconstructed tissue are very similar to those observed in normal interfollicular epidermis, including those specific for terminally differentiated keratinocytes. Thus, under appropriate in vitro conditions, outer root sheath cells are able to express an interfollicular epidermal phenotype as occurs in vivo during wound healing.     

Chemical modification of essential carboxyl group and histidine residue in the plasma-membrane 5'-nucleotidase

An investigation, using specific chemical reagents, of the amino acids involved in the catalytic activity of the purified 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) from bovine liver plasma membranes, was carried out. The enzyme was irreversibly inactivated by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The inhibition kinetics were of the first-order type and decreased partially in the presence of nucleotides and divalent cations. These results indicate for the first time that a carboxyl group is essential for the catalytic process of 5'-nucleotidase. Moreover, chemical modification by diethylpyrocarbonate also produced inactivation of the enzyme and showed a differential spectrum with a peak at 240 nm characteristic of N-carbethoxyhistidine residues. This inactivation was efficiently released upon decarbethoxylation by hydroxylamine only when the extent of inactivation, due to low concentration of diethylpyrocarbonate, was limited. The time-dependent inactivation followed first-order kinetics and nucleotides afforded significant protection against diethylpyrocarbonate modification. The results indicate the involvement of the histidine residue in catalysis.     

Pseudoterminalisation,terminalisation, and non-chiasmate modes of terminal association

Terminal associations occur commonly between meiotic homologues of the two smallest (S10, S11) chromosomes in the northern race of Cryptobothrus chrysophorus when they are either heterozygous or homozygous for distal supernumerary heterochromatic segments. A detailed examination of the origin and behaviour of these associations provides convincing evidence that they are non-chiasmate in character and so cannot be explained by either pseudoterminalisation or terminalisation. The same is true of the terminal associations involved in the persistent pseudomultiples that develop between non-homologues of Heteropternis obscurella when one or both of these carry distal heterochromatic segments. In both situations the C-bands involved in such terminal associations are entire and are never interrupted by non-banded material. In Cryptobothrus, similar associations can also develop between centromere regions when these are heterozygous or homozygous for proximal supernumerary heterochromatic segments.     

31P-NMR study of high-energy phosphorylated compounds metabolism and intracellular pH in the perfused rat heart

Using 31P-NMR and haemodynamical measurements, this work assesses different aspects of myocardial preservation improvement during a global ischaemia, based on a simultaneous and correlated study of high-energy phosphorylated compounds, intracellular pH and left ventricular function. Isolated perfused working rat hearts were subjected to 2 or 3 h of hypothermic ischaemia followed by 30 or 45 min of reperfusion. A study of the influence of pH and buffer used in cardioplegic solutions has demonstrated a better preservation of high-energy phosphates and an improved functional recovery when using a pH 7.0, glutamate - containing solution. Protection provided by cardioplegia can be enhanced by the appropriate use of a fluorocarbon-oxygenated cardioplegic reperfusate. The use of nifedipine, a calcium antagonist, in the cardioplegic solutions, does not provide any additional protection under hypothermic conditions.     

H-2-linked Ir gene control of T cell recognition of the Sm nuclear autoantigen and the aberrant response of autoimmune MRL/Mp-+/+ mice

We have examined T cell recognition of the nuclear autoantigen Sm. Rabbit Sm-primed cells from autoimmune MRL/Mp-+/+ (+/+) mice and from all normal strains tested were able to proliferate to rabbit Sm in vitro. In contrast, the reactivity of normal strains to Sm of murine origin was genetically restricted; only H-2f strains B10.M and A.CA, and H-2s strains B10.S and A.SW could recognize mouse Sm, suggesting that responsiveness to mouse Sm was under the control of H-2-linked Ir genes. Although five Iak-bearing normal strains (B10.A, B10.A(2R), B10.BR, A/Sn, and CBA) did not recognize mouse Sm, autoimmune +/+ (Iak) mice were responders. The responsiveness of the +/+ mice to Sm was probably not due to differences in their Iak region, compared with other strains, because the Iak region of normal strains and the autoimmune +/+ strain were indistinguishable by interstrain MLC, immune response gene product function, and recognition by anti-Iak mAb. Inhibition of Sm-induced proliferation by mAb demonstrated that T cells from autoimmune +/+ mice, responder normal strains, and nonresponder normal strains recognized rabbit and mouse Sm in the context of I region-encoded products. The T cell response to Sm antigen in normal mice is therefore Ia region restricted and, for the murine antigen, under Ir gene control. Autoimmune mice that spontaneously make anti-Sm antibodies (+/+) also perceive Sm in an Ia-restricted manner, but their responder status abrogates H-2-linked Ir gene control.