Complementary DNA for a novel human interleukin (BSF-2) that induces B lymphocytes to produce immunoglobulin

When stimulated with antigen, B cells are influenced by T cells to proliferate and differentiate into antibody-forming cells. Since it was reported that soluble factors could replace certain functions of helper T cells in the antibody response, several different kinds of lymphokines and monokines have been reported in B-cell growth and differentiation. Among these, human B-cell differentiation factor (BCDF or BSF-2) has been shown to induce the final maturation of B cells into immunoglobulin-secreting cells. BSF-2 was purified to homogeneity and its partial NH2-terminal amino-acid sequence was determined. These studies indicated that BSF-2 is functionally and structurally unlike other known proteins. Here, we report the molecular cloning, structural analysis and functional expression of the cDNA encoding human BSF-2. The primary sequence of BSF-2 deduced from the cDNA reveals that BSF-2 is a novel interleukin consisting of 184 amino acids.     

Secretion of cytokinins in vivo and in vitro byAlternaria brassicicola and their role in pathogenesis

Summary Formation of green islands in the host (mustard leaves) beneath the infection-drops containing germinating conidia ofAlternaria brassicicola (Schw.) Wiltsch. has been correlated with the secretion of cytokinins by the pathogen.A. brassicicola also synthesized cytokinins in the liquid synthetic medium. Cytokinins produced in vitro were extracted, and their application on the detached mustard leaves evoked the formation of green islands.     

Analysis of T-cell subsets in rejection of Kb mutant skin allografts differing at class I MHC

The T-cell subpopulations which initiate and mediate tissue allograft rejection remain controversial. In the present study we attempted to identify the phenotype and function of the T-cell subset(s) primarily responsible for the rejection of skin allografts differing at a single class I locus in the major histocompatibility complex (MHC). We found that the rejection rates by B6 mice (H-2b) of four different class I mutant (Kbm) skin allografts form a distinct hierarchy. This hierarchy correlates strikingly and uniquely with the relative precursor frequencies of Lyt2+ interleukin-2-secreting T-helper cells reactive against the various Kbm mutants. To investigate the role of Lyt2+ T cells in the rejection of class I-disparate skin allografts directly, H-2b nude mice were engrafted with Kbm skin allografts and then reconstituted with L3T4+ or Lyt2+ T-cell subpopulations from syngeneic H-2b mice. Lyt2+ T cells were observed to be both necessary and sufficient for the rejection of class I-disparate Kbm skin allografts, whereas L3T4+ T cells were neither necessary nor sufficient. These results identify the Lyt2+ interleukin-2-secreting T-cell subset as the critical cell type determining the rejection rate of class I-disparate Kbm skin allografts.     

The Tetrahymena ribozyme acts like an RNA restriction endonuclease

A shortened form of the Tetrahymena self-splicing ribosomal RNA intervening sequence acts as an endoribonuclease, catalysing the cleavage of large RNA molecules by a mechanism involving guanosine transfer. The sequence specificity approaches that of the DNA restriction endonucleases. Site-specific mutagenesis of the enzyme active site alters the substrate sequence specificity in a predictable manner, so that endoribonucleases can be synthesized to cut at a variety of tetranucleotide sequences.     

Loss of a Harvey ras allele in sporadic Wilms' tumour

Genomic changes within chromosome band 11p13 appear to have a role in the initiation of Wilms' tumour. The human Harvey ras oncogene, c-Ha-ras 1, has been located by Jhanwar et al. immediately adjacent to this region at band 11p14 .1, although several groups have assigned the gene more distally at band 11p15 . We have examined tumour DNA from two cases of sporadic Wilms' tumour, and report here that in both cases one of the two constitutional c-Ha-ras 1 alleles was absent. One tumour had a reciprocal translocation between the short arm of chromosome 11 (at band 11p13), and the long arm of chromosome 12, with no visible loss of chromosomal material. The loss of a c-Ha-ras 1 allele in association with this translocation indicates that a submicroscopic deletion had occurred. The resulting hemizygosity may have had a role in tumour initiation. Our results indicate that the c-Ha-ras 1 gene and the 'Wilms' tumour locus' may be in close proximity. It would, therefore, be premature to exclude the possibility that these two sites are functionally related.     

Effect of 5-hydroxytryptamine antibodies on pigment migration in the erythrophores of the fiddler crab,Uca pugilator: Further evidence for 5-hydroxytryptamine as a neurotransmitter that stimulates release of red pigment-dispersing hormone

Summary 5-Hydroxytryptamine (5-HT) antibodies inhibit red pigment dispersion in the fiddler crab,Uca pugilator. This observation supports the hypothesis that 5-HT stimulates release of red pigment-dispersing hormone.The 5-HT antibody preparation was a generous gift from Dr S. Spector, Roche Institute of Molecular Biology, Nutley, New Jersey.     

Molecular structure of r(GCG)d(TATACGC): a DNA--RNA hybrid helix joined to double helical DNA

The molecule r(GCG)d(TATACGC) is self-complementary and forms two DNA--RNA hybrid segments surrounding a central region of double helical DNA; its molecular structure has been solved by X-ray analysis. All three parts of the molecule adopt a conformation which is close to that seen in the 11-fold RNA double helix. The conformation of the ribonucleotides is partly determined by water molecules bridging between the ribose O2' hydroxyl group and cytosine O2. The hybrid-DNA duplex junction contains no structural discontinuities. However, the central DNA TATA sequence has some structural irregularities.