Dissociation between murine spleen cell mitogenic activity of enterotoxin contaminants and anti-tumor activity of staphylococcal protein A

Soluble staphylococcal protein A (SpA) in the form of high m.w. complexes with IgG has been shown to significantly inhibit the growth of Meth A fibrosarcomas in BALB/c mice. Although SpA reportedly is a potent T cell mitogen that can induce immune cell proliferation and production of humoral factors with anti-tumor activity, it has been suggested that mitogenic enterotoxin contaminants might be responsible for these effects. The purpose of the present study was to investigate the nature of SpA-induced cell proliferation and the relationship between mitogenicity and the anti-tumor effect that we observed in our mouse model. SpA stimulated the proliferation of a mixed population of splenic B and T cells from BALB/c mice, but activity did not require the presence of IgG in the culture medium. Furthermore, mitogenic activity could be inhibited completely by anti-SEA plus anti-SEB, but was unaffected by anti-SpA. HPLC-purified SpA was inactive while the mitogenic factor(s) had the same retention time as authentic enterotoxin and its activity was inhibited by anti-SEA and anti-SEB, but not by anti-SpA. Enterotoxin-free rSpA produced in Escherichia coli had the same IgG binding capacity as the staphylococcal product but was not mitogenic. These data indicate that SEA and SEB completely account for mitogenicity in SpA preparations. In contrast, we found that optimal concentrations of rSpA as well as crude and HPLC purified staphylococcal SpA were equally effective in inhibiting the growth of established Meth A fibrosarcomas demonstrating that SpA is responsible for antitumor activity without any apparent role for enterotoxins.     

Reconstitution of denatured E. coli alkaline phosphatase with E. coli ribosome.

E. coli alkaline phosphatase was denatured by physical/chemical means. In vitro reconstitution of this denatured enzyme was assisted by 70S E. coli ribosome, as shown by the recovery of its catalytic competence. Almost total recovery of activity of the totally inactivated enzyme was obtained in presence of equimolar concentration of 70S ribosome at 50 degrees C.     

Maternal Control of PIN1 Is Required for Female Gametophyte Development in Arabidopsis

Land plants are characterised by haplo-diploid life cycles, and developing ovules are the organs in which the haploid and diploid generations coexist. Recently it has been shown that hormones such as auxin and cytokinins play important roles in ovule development and patterning. The establishment and regulation of auxin levels in cells is predominantly determined by the activity of the auxin efflux carrier proteins PIN-FORMED (PIN). To study the roles of PIN1 and PIN3 during ovule development we have used mutant alleles of both genes and also perturbed PIN1 and PIN3 expression using micro-RNAs controlled by the ovule specific DEFH9 (DEFIFICENS Homologue 9) promoter. PIN1 down-regulation and pin1-5 mutation severely affect female gametophyte development since embryo sacs arrest at the mono- and/or bi-nuclear stages (FG1 and FG3 stage). PIN3 function is not required for ovule development in wild-type or PIN1-silenced plants. We show that sporophytically expressed PIN1 is required for megagametogenesis, suggesting that sporophytic auxin flux might control the early stages of female gametophyte development, although auxin response is not visible in developing embryo sacs.     

Sensory Neuron-Derived Eph Regulates Glomerular Arbors and Modulatory Function of a Central Serotonergic Neuron

Olfactory sensory neurons connect to the antennal lobe of the fly to create the primary units for processing odor cues, the glomeruli. Unique amongst antennal-lobe neurons is an identified wide-field serotonergic neuron, the contralaterally-projecting, serotonin-immunoreactive deutocerebral neuron (CSDn). The CSDn spreads its termini all over the contralateral antennal lobe, suggesting a diffuse neuromodulatory role. A closer examination, however, reveals a restricted pattern of the CSDn arborization in some glomeruli. We show that sensory neuron-derived Eph interacts with Ephrin in the CSDn, to regulate these arborizations. Behavioural analysis of animals with altered Eph-ephrin signaling and with consequent arborization defects suggests that neuromodulation requires local glomerular-specific patterning of the CSDn termini. Our results show the importance of developmental regulation of terminal arborization of even the diffuse modulatory neurons to allow them to route sensory-inputs according to the behavioural contexts.     

The binding of aromatic derivatives of β-d-galactopyranosides to the fab' of immunoglobulin J539. Observation on the nature of ligand-antibody interactions

A number of d-galactopyranosides bearing aromatic substituents have been prepared, and their binding to immunoglobulin J539 (Fab') has been studied. It appears that the main contribution of the 6-O-aromatic moiety to binding arises from the fact that it imparts an increased hydrophobicity to the ligand, causing a decrease in its hydration (solubility) that results in a greater free-energy of binding. In the d-galactosides having an aromatic aglycon, the phenyl group appears to partake in actual interactions with the protein.