Survival of patients treated for end-stage renal disease by dialysis and transplantation.

The results of treatment in 213 patients with end-stage renal disease who underwent hemodialysis, peritoneal dialysis or transplantation, or a combination, between 1962 and 1975 were analysed. Comparison by censored survival analysis showed significantly better (P less than 0.01) patient survival with the integrated therapy of dialysis and transplantation than with either form of dialysis alone. There was no significant difference in survival of males and females but survival at the extremes of age was poorer. Analysis of survival by major cause of renal failure indicated best survival in patients with congenital renal disease. Graft and patient survival rates at 1 year after the first transplantation were 42% and 69%. The major cause of death in this series was vascular disease but infection was responsible for 50% of deaths after transplantation. While integration of dialysis with transplantation produces best patient survival, this course is possible only when sufficient cadaver kidneys are available.     

Stereospecificity of peptide transport by germinating barley embryos

The stereospecific requirements for peptide transport in the scutellum of germinating barley (Hordeum vulgare) embryos are described. Replacement of an L-amino acid residue in a peptide by its D-stereoisomer decreases the affinity of the peptide for the transport site, leading to a reduction in transport. Substitution of a second D-residue reduces affinity still further. The extent to which transport is inhibited depends upon the position of the D-residue in the primary sequence, with D-residues at the C-terminus of the peptide having the greatest effect. Competition between D- and L-peptides indicates that they both enter via the same transport system. Although D-amino acids can be accumulated when presented as a peptide, these same D-residues are not transported when supplied as the free amino acids. L-Leu-D-leu is accumulated intact against a concentration gradient, indicating the operation of an active transport mechanism that can function without the involvement of peptidase activity.     

Topoisomerase mutants and physiological conditions control supercoiling and Z-DNA formation in vivo.

The influence of topoisomerase I and gyrase mutations in Escherichia coli on the supercoiled density of recombinant plasmids and the stability of left-handed Z-DNA was investigated. The formation of Z-DNA in vivo by dC-dG sequences of different lengths was used to determine the effective plasmid supercoil densities in the mutant strains. The presence of Z-DNA in the cells was detected by linking number and EcoRI methylase inhibition assays. A change in the unrestrained superhelical tension in vivo directly effects the B- to Z-DNA transition. Alterations in the internal or external environment of the cells, such as the inactivation of gyrase or topoisomerase I, a gyrase temperature-sensitive mutant, or starvation of cells, have a dramatic influence on the topology of plasmids. Also, E. coli has significantly more superhelical strain than Klebsiella, Morganella, or Enterobacter. These studies indicate that linking deficiency and effective supercoil density are mutually independent variables of plasmid tertiary structure. A variety of factors, such as protein-DNA interactions, activity of topoisomerases, and the resulting supercoil density, contribute to the B to Z transition inside living cells.     

The NC1 domain of type IV collagen promotes axonal growth in sympathetic neurons through interaction with the alpha 1 beta 1 integrin

We have examined the effects of collagen IV on the morphological development of embryonic rat sympathetic neurons in vitro. In short-term (less than or equal to 24 h) culture, collagen IV accelerated process outgrowth, causing increases in the number of neurites and total neuritic length. Analysis of proteolytic fragments of collagen IV indicated that the NC1 domain was nearly as active as the intact molecule in stimulating process outgrowth; in contrast, the 7S domain and triple helix-rich fragments of collagen IV were inactive. Moreover, anti-NC1 antiserum inhibited neuritic outgrowth on collagen IV by 79%. In long-term (up to 28 d) cultures, neurons chronically exposed to collagen IV maintained a single axon but failed to form dendrites. Thus, the NC1 domain of collagen IV can alter neuronal development by selectively stimulating axonal growth. Comparison of collagen IV's effects to those of laminin revealed that these molecules exert quantitatively different effects on the rate of initial axon growth and the number of axons extended by sympathetic neurons. Moreover, neuritic outgrowth on collagen IV, but not laminin, was blocked by cycloheximide. We also observed differences in the receptors mediating the neurite-promoting activity of these proteins. Two different antisera that recognize beta 1 integrins each blocked neuritic outgrowth on both collagen IV and laminin; however, an mAb (3A3) specific for the alpha 1 beta 1 integrin inhibited collagen IV but not laminin-induced process growth in cultures of both sympathetic and dorsal root neurons. These data suggest that immunologically distinct integrins mediate the response of peripheral neurons to collagen IV and laminin.     

An embryo-specific protein of barley (Hordeum vulgare).

An immunological approach has been used to identify embryo-specific products that can be used as molecular markers of embryogenesis. Immunoadsorption of antisera to remove antigens common to embryos, meristematic cells and callus, revealed one major embryo-specific antigen, a polypeptide of 17 kDa. The antigen appeared at mid-stages of zygotic embryo formation and remained at similar levels up to six days post-germination of the seedling. The polypeptide could not be detected by protein staining, suggesting it is a non-abundant product. Appearance of the antigen could be induced by culture of zygotic embryos in vitro on abscisic acid (1 microM) or mannitol (9% mass/vol.). Cross-reactive products of near-identical molecular mass were observed in embryos of wheat, rye and oats but not distantly related cereals, nor embryos from dicotyledonous species. The timing of the appearance of the antigen was different in embryos formed from microspores during anther culture in vitro. In the cultured material, the 17-kDa polypeptide preceded the appearance of morphologically distinct embryonic structure.     

Molecular characterization of a second abortive phage resistance gene present in Lactococcus lactis subsp. lactis ME2.

The fifth phage resistance factor from the prototype phage-insensitive strain Lactococcus lactis subsp. lactis ME2 has been characterized and sequenced. The genetic determinant for Prf (phage resistance five) was subcloned from the conjugative plasmid pTN20, which also encodes a restriction and modification system. Typical of other abortive resistance mechanisms, Prf reduces the efficiency of plaquing to 10(-2) to 10(-3) and decreases the plaque size and burst size of the small isometric-headed phage p2 in L. lactis subsp. lactis LM0230. However, normal-size plaques occurred at a frequency of 10(-4) and contained mutant phages that were resistant to Prf, even after repeated propagation through a sensitive host. Prf does not prevent phage adsorption or promote restriction and modification activities, but 90% of Prf+ cells infected with phage p2 die. Thus, phage infections in Prf+ cells are aborted. Prf is effective in both L. lactis subsp. lactis and L. lactis subsp. cremoris strains against several small isometric-headed phages but not against prolate-headed phages. The Prf determinant was localized by Tn5 mutagenesis and subcloning. DNA sequencing identified a 1,056-nucleotide structural gene designated abiC. Prf+ expression was obtained when abiC was subcloned into the lactococcal expression vector pMG36e. abiC is distinct from two other lactococcal abortive phage resistance genes, abiA (Hsp+, from L. lactis subsp. lactis ME2) and abi416 (Abi+, from L. lactis subsp. lactis IL416). Unlike abiA, the action of abiC does not appear to affect DNA replication. Thus, abiC represents a second abortive system found in ME2 that acts at a different point of the phage lytic cycle.