Labeling of fructans in winter wheat stems

Fructans synthesized from newly formed assimilates accumulate in wheat stems as nonstructural carbohydrates. Experiments performed tested the hypothesis that the fructose moiety from translocated sucrose is used preferentially in biosynthesis of these fructans. Results indicated: (a) a large percentage of labeled sucrose was translocated and unloaded in an unaltered state; and (b) sucrose contributed its fructose moiety to fructan synthesis in stems.     

Monoclonal antibodies that recognize a polypeptide antigenic determinant shared by multiple Caenorhabditis elegans sperm-specific proteins

Four monoclonal antibodies that are directed against antigens present in sperm and absent from other worm tissues were characterized. Antibody TR20 is directed against the major sperm proteins, a family of small, abundant, cytoplasmic proteins that have been previously described (Klass, M. R., and D. Hirsh, 1981, Dev. Biol., 84:299-312; Burke, D. J., and S. Ward, 1983, J. Mol. Biol., 171:1-29). Three other antibodies, SP56, SP150, and TR11, are all directed against the same set of minor sperm polypeptides that range in size from 29 to 215 kD. More than eight different sperm polypeptides are antigenic by both immunotransfer and immunoprecipitation assays. The three antibodies are different immunoglobulin subclasses, yet they compete with each other for antigen binding so they are directed against the same antigenic determinant on the multiple sperm proteins. This antigenic determinant is sensitive to any of six different proteases, is insensitive to periodate oxidation or N-glycanase digestion, and is detectable on a polypeptide synthesized in vitro. Therefore, the antigenic determinant resides in the polypeptide chain. However, peptide fragments of the proteins are not antigenic, thus the determinant is likely to be dependent on polypeptide conformation. The antigenic determinant shared by these proteins could represent a common structural feature of importance to the localization or cellular specificity of these proteins.     

An equilibrium between distorted and undistorted DNA in the adult chicken beta A-globin gene

We have used single strand specific nucleases to map DNA distortion in the adult chicken beta A-globin gene. We have detected two structures of that kind and have mapped nuclease-cutting sites at one base resolution. One prominent site is centered at -190 relative to the RNA capping site and is positioned at the center of a stretch of contiguous C residues. The second site is near the first intron/exon junction (+620) and appears as a series of discrete 1-base-long enzyme-cutting sites. Based upon the pattern of nuclease cutting and the kinetics of nuclease cutting we conclude that the "poly(C)" stretch may assume a looped geometry in supertwisted DNA molecules which is similar to that proposed by Felsenfeld (Nickol, J. M., and Felsenfeld, G. (1983) Cell 35, 467-477). We show that S1 nuclease cuts within the intron occur mainly at the end points of polypurine segments and suggest that such end points may assume a distorted transitional geometry. We find that Neurospora crassa endonuclease cuts both the promotor and intron sites in linear DNA molecules but that in linear DNA the cutting process is limited by a first order conformation change of the DNA substrate. Based upon those kinetics we propose that in unstressed DNA, each of the two sites can convert between a distorted and undistorted geometry. In the enzyme assay buffer at 37 degrees C, the time constant for the equilibrium is nearly 10 h for the promotor site and 7 h for the intron.     

Lymphokine-activated and natural killer cell activity in human intestinal mucosa

The activity of natural effector (NE) cells was studied in lamina propria lymphocytes (LPL) obtained from 61 histologically normal specimens of human intestine, which included 45 resected for colon carcinoma and 16 resected for nonmalignant conditions. The mean spontaneous natural killer (NK) cell activity in LPL (1.7 X 10(2) cytotoxic units (C.U.)/10(5) cells) was very low in contrast to that found in peripheral blood mononuclear cells (PBMC) (38.5 X 10(2) C.U./10(5) cells). Significant NK activity was detected in only 16 (47%) of the tissues resected for carcinoma, and in five (38%) of those removed for nonmalignant conditions. Exposure to human leucocyte interferon resulted in only minimal increases in cytotoxicity for K562 target cells. Consistent with these findings, large granular lymphocytes represented less than 0.5% of freshly isolated LPL. Cultures of LPL from both carcinoma and nonmalignant conditions in MLA144-conditioned medium (CM), a source of interleukin 2 (IL 2), generated marked increases in cytotoxicity to levels comparable with or exceeding those found in PBMC. (Mean cytotoxicities were 90.4 X 10(2) and 49 X 10(2) C.U./10(5) cells, respectively.) Cytotoxicity induced by culture in MLA144-CM could be blocked by pretreatment of LPL with the monoclonal antibody anti-Tac directed against the IL 2 receptor. In addition, LPL cultured in recombinant human IL 2 were induced to levels of cytotoxicity that were similar to those induced by MLA144-CM. These data indicate that IL 2 is the factor in MLA144-CM responsible for generating lymphokine-activated killer (LAK) cells in LPL. The IL 2-activated LPL killer cells were OKT11+, OKT3-, Leu-7-, Leu-11b-, as determined by antibody and complement-mediated lysis, and the precursor cells in the lamina propria necessary for generation of killer cells by IL 2 were also OKT11+, OKT3-, Leu-7-, Leu-11b-. These studies indicate that LAK cells may be an important potential source of nonspecific cytotoxicity in the intestinal mucosa.     

Calcium-Stimulated Proteolysis in Myelin: Evidence for a Ca2+-Activated Neutral Proteinase Associated with Purified Myelin of Rat CNS

Incubation of myelin purified from rat spinal cord with CaCl2 (1-5 mM) in 10-50 mM Tris-HCl buffer at pH 7.6 containing 2 mM dithiothreitol resulted in the loss of both the large and small myelin basic proteins (MBPs), whereas incubation of myelin with Triton X-100 (0.25-0.5%) and 5 mM EGTA in the absence of calcium produced preferential extensive loss of proteolipid protein (PLP) relative to MBP. Inclusion of CaCl2 but not EGTA in the medium containing Triton X-100 enhanced degradation of both PLP and MBPs. The Ca2+-activated neutral proteinase (CANP) activity is inhibited by EGTA (5 mM) and partially inhibited by leupeptin and/or E-64c. CANP is active at pH 5.5-9.0, with the optimum at 7-8. The threshold of Ca2+ activation is approximately 100 microM. The 150K neurofilament protein (NFP) was progressively degraded when incubated with purified myelin in the presence of Ca2+. These results indicate that purified myelin is associated with and/or contains a CANP whose substrates include MBP, PLP, and 150K NFP. The degradation of PLP (trypsin-resistant) in the presence of detergent suggests either release of enzyme from membrane and/or structural alteration in the protein molecule rendering it accessible to proteolysis. The myelin-associated CANP may be important not only in the turnover of myelin proteins but also in myelin breakdown in brain diseases.     

The murine Hox-2 cluster of homeo box containing genes maps distal on chromosome 11 near the tail-short (Ts) locus

Two probes derived from a mouse recombinant lambda-clone (H24.1), that contains a sequence closely homologous to the Drosophila antennapedia homeo box, were mapped to mouse chromosome (MMU) 11 by filter hybridization of somatic cell hybrid DNA. This sequence is highly homologous to a human homeo box gene (HOX2) and appears to represent one of the two genes in the Hox-2 cluster previously assigned to MMU 11. To regionally map the Hox-2 cluster, we have carried out in situ hybridization of the two H24.1 probes and of an independently isolated Hox-2 probe. The autoradiographic silver grain distributions were similar in all three experiments with a peak over band 11D. This region contains the locus for the tail-short (Ts) mutation which causes skeletal abnormalities in heterozygotes and early embryonic death in homozygotes.     

Proteolysis in quaking mouse brain and spinal cord

Six proteolytic enzymes were assayed for activity in quaking CNS in examining the hypothesis that increased proteolytic activity contributes to the hypomyelination characteristic of this mutant. Cathepsin B-like enzyme, cathepsin D, neutral proteinase, calcium-activated neutral proteinase, prolyl endopeptidase, and diaminopeptidase II were assayed in whole homogenate of brain or spinal cord and each was found to have activity similar to that in normal mice. These results do not support a relationship between proteolysis and the genetic defect and suggest that other factors should be investigated to delineate the pathogenesis of this mutant.     

Carbohydrate changes in pre- and peri-implantation mouse embryos as detected by a monoclonal antibody

We have examined the tissue and embryonic distribution of an antigen on a large polysaccharide that is recognized by a monoclonal antibody, IIC3, prepared against F9 teratocarcinoma cells. By immunofluorescence the antigen is first detected on compacted morulae and early blastocysts. It is strongly expressed on the primary endoderm and trophoblast of expanded blastocysts, but then disappears from the trophoblast of attached blastocysts in vitro. The binding of the antibody is completely inhibited by D-galactose and N-acetylgalactosamine. Fluoresceinated lectins were used to study further the changes in cell surface carbohydrates on trophoblast during implantation. Ricinus I, specific for terminal galactose, binds to preimplantation stages but does not bind to the trophoblast of the attached blastocyst. On the other hand, wheat germ agglutinin, specific for N-acetylglucosamine and sialic acid, binds to all preimplantation embryos and also to attached blastocysts (embryo proper and trophoblast). Neuraminidase treatment of blastocyst outgrowths enhances binding of both IIC3 and Ricinus I to the trophoblast; conversely, the binding of wheat germ agglutinin is decreased by this treatment. The results obtained in this study show changes of cell surface carbohydrates during early mouse development and suggest that sialic acid may be masking molecules on the surface of the trophoblast at the time of implantation.     

Isolation of cDNA clones for basal lamina components: type IV procollagen

We have isolated cDNA clones for mouse type IV procollagen from a library constructed from total poly A+RNA of 13.5 day mouse embryo parietal endoderm (PE) cells. In Northern analysis these clones hybridise to a 6.8 kb RNA which is abundant in embryonic PE cells and in differentiated F9 teratocarcinoma cells. Hybrid selection and in vitro translation of the cDNA specific mRNA produced a single polypeptide of Mr = 165 000. This polypeptide was specifically immunoprecipitated with mouse type IV procollagen antisera and comigrated on SDS-gel electrophoresis with one of the two in vitro synthesised chains of type IV procollagen. Undifferentiated F9 teratocarcinoma cells can be induced by retinoic acid and dibutyryl cAMP to differentiate in vitro into endoderm-like cells which resemble mouse PE cells in synthesising large amounts of basement membrane proteins, including type IV procollagen. Here we show, using one of the cDNA clones as a probe for type IV procollagen, that an increase in cellular concentration of type IV procollagen mRNA occurs within 24 to 48 hours of induction, reaching a constant high level by 72 hours.