Heterophilic NCAM-Mediated Cell Adhesion to Proteoglycans from Chick Embryonic Brain Membranes

The vertebrate neural cell adhesion molecule NCAM mediates adhesion by both homophilic and heterophilic mechanisms, with heparan sulfate proteoglycans (HSPGs) being likely heterophilic ligands. In this study, transfected chicken NCAM polypeptides expressed on mouse L cells mediated the adhesion of these cells to several different heparan sulfate proteoglycans in nonionic detergent extracts of Embryonic Day 10 chicken brain membranes. In addition, adhesion inhibition experiments suggested a hitherto-undetected role for chondroitin sulfate proteoglycans in the stimulation of NCAM-mediated adhesion to some, but not all, of the HSPG ligands. Our experiments support the view that NCAM is a multivalent adhesive molecule whose function is affected by interactions with extracellular matrix and cell surface molecules.     

DNA-dependent protein kinase catalytic subunit: a target for an ICE-like protease in apoptosis.

Radiosensitive cell lines derived from X-ray cross complementing group 5 (XRCC5), SCID mice and a human glioma cell line lack components of the DNA-dependent protein kinase, DNA-PK, suggesting that DNA-PK plays an important role in DNA double-strand break repair. Another enzyme implicated in DNA repair, poly(ADP-ribose) polymerase, is cleaved and inactivated during apoptosis, suggesting that some DNA repair proteins may be selectively targeted for destruction during apoptosis. Here we demonstrate that DNA-PKcs, the catalytic subunit of DNA-PK, is preferentially degraded after the exposure of different cell types to a variety of agents known to cause apoptosis. However, Ku, the DNA-binding component of the enzyme, remains intact. Degradation of DNA-PKcs was accompanied by loss of DNA-PK activity. One cell line resistant to etoposide-induced apoptosis failed to show degradation of DNA-PKcs. Protease inhibitor data implicated an ICE-like protease in the cleavage of DNA-PKcs, and it was subsequently shown that the cysteine protease CPP32, but not Mch2alpha, ICE or TX, cleaved purified DNA-PKcs into three fragments of comparable size with those observed in cells undergoing apoptosis. Cleavage sites in DNA-PKcs, determined by antibody mapping and microsequencing, were shown to be the same for CPP32 cleavage and for cleavage catalyzed by extracts from cells undergoing apoptosis. These observations suggest that DNA-PKcs is a critical target for proteolysis by an ICE-like protease during apoptosis.     

Restoration of regeneration potentiality in prolonged culture of Digitalis purpurea

Regeneration potential was restored in 2-year-old cultures of proliferating shoots of Digitalis purpurea L. under the influence of 14.43 M gibberellic acid, while cytokinins were ineffective. The retrieved shoots grew normally in a modified Murashige and Skoog's medium supplemented with 0.98 M indole-3-butyric acid (IBA) and 27.1 M adenine sulphate and rooted 100% in the presence of 0.49 M IBA alone.NBRI Research Publication No. 415 (N.S.)     

Inorganic soil phosphate fractions as related to soil-test values by common methods

Summary An attempt to find the relationship among the soil inorganic phosphate fractions and the soil test values determined with various common methods, has been made in the present studies. Out of the methods tried (Olsenet al., Bray and Kurtz, Datta and Kamath, Bingham) the soil-test values obtained with only Bray and Kurtz's method no. 2 have shown a positive significant relationship with Ca-P fraction while the others have shown more or less a positive significant correlation with saloid-bound P, Al-P and Fe-P fractions. Negative significant relationships of Al-P and Fe-P with Ca-P indicate that they increase or decrease at the expense of each other by fertilisation and cropping. Application of basic slag at the rate of 120 lbs P₂O₅ per acre indicate a maximum increase in most of the soil test values and the saloid bound P and Al-P fractions suggesting probably its high residual value in the soils. The use of the method of Datta and Kamath along with that of Olsenet al. and Bray and Kurtz no. 1 has been recommended.     

ISOLATION OF NERVE ENDINGS FROM THE POSTERIOR PITUITARY GLAND : Electron Microscopy of Fractions Obtained by Centrifugation

Bovine posterior pituitary glands were homogenized in 10 per cent sucrose and fractionated by differential centrifugation. The following centrifugation procedure resulted in the most satisfactory separation: 1000 g for 15 minutes—nuclei, connective tissue, basement membranes with associated endothelium, giant nerve endings, and whole pituicytes; 4200 g for 15 minutes—free nerve endings, including Herring bodies; 17,000 g for 15 minutes—mitochondria; 68,000 g for 15 minutes—neurosecretory granules. Electron microscopic examination was carried out on whole tissue and on the isolated fractions. Isolated nerve endings were examined also by negative staining techniques. Isolated nerve endings retain an apparently normal complement of mitochondria, neurosecretory granules, and microvesicles ("synaptic" vesicles). The free nerve endings closely resemble those observed in sections of intact posterior pituitary tissue. Free microvesicles were not observed in any of the fractions isolated and apparently sediment at centrifugal forces higher than those employed in this study.     

Cutting edge: Rac GTPases sensitize activated T cells to die via Fas

In activated CD4(+) T cells, TCR restimulation triggers apoptosis that depends on interactions between the death receptor Fas and its ligand, FasL. This process, termed restimulation-induced cell death (RICD), is a mechanism of peripheral immune tolerance. TCR signaling sensitizes activated T cells to Fas-mediated apoptosis, but what pathways mediate this process are not known. In this study we identify the Rho GTPases Rac1 and Rac2 as essential components in restimulation-induced cell death. RNA interference-mediated knockdown of Rac GTPases greatly reduced Fas-dependent, TCR-induced apoptosis. The ability of Rac1 to sensitize T cells to Fas-induced apoptosis correlated with Rac-mediated cytoskeletal reorganization, dephosphorylation of the ERM (ezrin/radixin/moesin) family of cytoskeletal linker proteins, and the translocation of Fas to lipid raft microdomains. In primary activated CD4(+) T cells, Rac1 and Rac2 were independently required for maximal TCR-induced apoptosis. Activating Rac signaling may be a novel way to sensitize chronically stimulated lymphocytes to Fas-induced apoptosis, an important goal in the treatment of autoimmune diseases.     

Molecular mapping and transfer of a novel brown planthopper resistance gene bph42 from Oryza rufipogon (Griff.) To cultivated rice (Oryza sativa L.)

Molecular Biology Reports - Brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most destructive pests of rice accounting for 52% of annual yield loss. The breakdown of...     

Late signaling in the activated platelets upregulates tyrosine phosphatase SHP1 and impairs platelet adhesive functions: Regulation by calcium and Src kinase

Sustained stimulation of platelets with protease-activated receptor agonists in presence of extracellular calcium was associated with tyrosine dephosphorylation of specific proteins of relative mobilities 35, 67, and 75 kDa. From phosphatase assays and inhibitor studies SHP1, a Src homology 2 (SH2) domain-containing tyrosine phosphatase expressed abundantly in hemopoietic cells, was found to be upregulated in platelets between 25 and 30 min following thrombin stimulation. Concomitantly, SHP1 was tyrosine phosphorylated by, and coprecipitated with, Src tyrosine kinase. SHP1 activation, association with Src and dephosphorylation of specific proteins were dependent on extracellular calcium and maintenance of a higher cytosolic calcium plateau. There was progressive impairment of platelet functions like aggregability and clot retraction, associated with downregulation of fibrinogen-binding affinity of integrin alpha(IIb)beta(3), in the platelets exposed to thrombin for 45 min. This could reflect the late physiological changes in platelets when the cells are consistently exposed to stimulatory signals under thrombogenic environment in vivo.