HLA-DR residues accessible under the peptide-binding groove contribute to polymorphic antibody epitopes

Many residues involved in polymorphic antibody-binding epitopes on class II molecules are located on the -helix of DRβ chains. Although they have received less attention, residues in the peptide-binding groove and second domain of the DRβ chain may also be critical for polymorphic anti-DR antibody epitopes. In this study, we used transfectants expressing site-directed mutations at positions in the HLA-DR β₁ and β₂ domains and flow cytometry to define the epitopes of several polymorphic anti-DR antibodies. Both DR(β 1^*0403) residues 14 and 25 were shown to be involved in the epitopes of mAbs DA6. 164, HU-20, Q5/6, and 50D6, and DR(β 1^*0701) residue 14 was shown to be critical for the epitopes of two DR7-specific mAbs, SFR16-DR7M and TAL 13. 1. Unlike most other residues shown to be important in antibody-binding epitopes, residue 14 is located in the floor of the peptide-binding groove and residue 25 is in an outer loop, each with their side chains pointing down, such that antibodies may directly contact these residues from below the binding groove. Two residues in the β₂ domain, β180 and β181, were also shown to be involved in the epitopes of three polymorphic anti-DR mAbs, NFLD.D1, NFLD.M1, and LY9. Although these two residues are close to the transmembrane domain in the linear sequence, their solvent accessibility in the DR1 structures is quite impressive. Our data provide new evidence that residues accessible under the peptidebinding groove contribute to polymorphic antibody-binding epitopes.     

Y chromosome microdeletions, in azoospermic or near-azoospermic subjects, are located in the AZFc (DAZ) subregion

Submicroscopic deletions of the Y chromosome and polymorphisms of the androgen receptor (AR) gene in the X chromosome have been observed in men with defective spermatogenesis. To further define the subregions/genes in the Y chromosome causing male infertility and its relationship to polymorphisms of the AR polyglutamine tract, we screened the genomic DNA of 202 subfertile males and 101 healthy fertile controls of predominantly Chinese ethnic origin. Y microdeletions were examined with 16 sequence-tagged site (STS) probes, including the RBM and DAZ genes, spanning the AZFb and AZFc subregions of Yq11, and related to the size of trinucleotide repeat encoding the AR polyglutamine tract. Y microdeletions were detected and confirmed in three out of 44 (6.8%) of azoospermic and three out of 86 (3.5%) severely oligozoospermic patients. No deletions were detected in any of the patients with sperm counts of >0.5 x 10(6)/ml, nor in any of the 101 fertile controls. All six affected patients had almost contiguous Y microdeletions spanning the entire AZFc region including the DAZ gene. The AZFb region, containing the RBM1 gene, was intact in five of the six subjects. Y deletions were not found in those with long AR polyglutamine tracts. Our study, the first in a Chinese population, suggest a cause and effect relationship between Y microdeletions in the AZFc region (possibly DAZ), and azoospermia or near-azoospermia. Y microdeletions and long AR polyglutamine tracts appear to be independent contributors to male infertility.      

Evaluation of API 20 STREP system for identifying Listeria species.

The API 20 STREP system was used to identify 146 known strains from seven species of the genus Listeria, including both pathogenic and environmental strains. The gallery was easy to use and tests, with the exception of leucine arylamidase (LAP) and starch fermentation (AMD), were simple to interpret. Identification to genus level was satisfactory but differentiation between species was poor. Using the API 20 STREP the haemolytic species L monocytogenes, seeligeri, and ivanovii could easily be differentiated from the non-haemolytic species L welshimeri, innocua, grayii and murrayi. Of the haemolytic species, L monocytogenes could not be distinguished from L seeligeri but L ivanovii could be separated from the two other haemolytic species because it fermented ribose. Non-haemolytic L welshimeri could not be differentiated from non-haemolytic L innocua, but mannitol and ribose fermenting non-haemolytic L grayi and L murrayi were easily differentiated from the other two non-haemolytic species. The API 20 STREP identified Listeria in four hours and therefore might be used for rapid identification of strains causing infection in man. It would, however, not be useful to identify environmental isolates when speciation is important.     

Glomerular epithelial cell lesions in rat renal isografts

Visceral glomerular epithelial cell lesions--microvillus formation, loss of foot processes, osmiophilic inclusion droplets, balloon-like malformation of cell processes, degeneration, necrosis, and loss of cell processes from capillary basement membranes--are found in rat renal isografts 1 mth after transplantation. The lesions, which are most readily recognized in perfusion-fixed material, are essentially focal, affecting neither all glomeruli, nor all cells in any glomerulus, bear no relation to the degree of interstitial nephritis in the graft, and are associated with albuminuria and with focal capillary sclerosis in some glomeruli. They are not restricted to renal isografts but are found in aging rats, in different experimental models of glomerular disease and in clinical glomerular disorders, again in association with proteinuria and glomerulosclerosis. It is therefore proposed that glomerular epithelial cell damage increases capillary permeability and impairs maintenance of the integrity of the capillary wall, leading to proteinuria and focal glomerulosclerosis.     

Pathogenesis of infectious bronchitis nephritis. 2. Studies of water and electrolyte balance in colostomised chickens

Water and electrolyte balance was examined throughout the course of an experimental infection with T strain infectious bronchitis virus in colostomised chickens. Significant losses of water and negative sodium and potassium balances were observed. The major change in the electrolyte balance was the increased output of sodium in urine and this was associated with a diuresis. A decrease in food intake was the most important contribution to the negative potassium balance. Death resulted from acute renal failure. The implication of the results for electrolyte replacement therapy is discussed and a method for colostomies in birds weighing less than 0.5 kg is described.