Cloning and expression of a soluble sialidase from Chinese hamster ovary cells: sequence alignment similarities to bacterial sialidases

A cDNA encoding a soluble sialidase from Chinese hamster ovary(CHO) cells has been cloned and expressed. Completely degenerateoligonucleotide primers, which were based on the amino acidsequence of peptides obtained from the purified sialidase (Warneret al., Glycobiology, 3, 455–463, 1993), and the polymerasechain reaction, with single-stranded cDNA template, were employedto generate a unique oligonucleotide probe. The unique probeof 93 bp was used for screening a     

Evidence for the Predator Attraction Hypothesis in an amphibian predator–prey system

Many species possess damage-released chemical alarm cues that function in alerting nearby individuals to a predator attack. One hypothesis for the evolution and/or maintenance of such cues is the Predator Attraction Hypothesis, where predators, rather than prey, are the “intended” recipients of these cues. If a predator attack attracts additional predators, these secondary predators might interfere with the predation event, providing the prey with a better chance to escape. In this study, we conducted two experiments to explore this hypothesis in an amphibian predator/prey system. In Experiment 1, we found that tiger salamanders (Ambystoma mavortium) showed a foraging attraction to chemical cues from wood frog (Lithobates sylvaticus) tadpoles. Salamanders that were experienced with tadpole prey, in particular, were strongly attracted to tadpole alarm cues. In Experiment 2, we observed experimental encounters between a tadpole and either one or two salamanders. The presence of the second predator caused salamanders to increase attack speed at the cost of decreased attack accuracy (i.e., increasing the probability that the tadpole would escape attacks). We also found that the mere presence of visual and chemical cues from a second predator did not affect this speed/accuracy trade-off but did cause enough of a distraction to increase tadpole survival. Thus, our findings are consistent with the Predator Attraction Hypothesis for the evolution and/or maintenance of alarm cues.     

Isolation and properties of a soluble sialidase from the culture fluid of Chinese hamster ovary cells

A Soluble sialidase that can degrade recombinant glycoproteinsexpressed in Chinese hamster ovary (CHO) cells has been isolatedand purified to near homogeneity from the cell culture fluidof this host. Purification of     

Spontaneous Cell Fusion in Macrophage Cultures Expressing High Levels of the P2Z/P2X7 Receptor

Mouse and human macrophages express a plasma membrane receptor for extracellular ATP named P2Z/P2X₇. This molecule, recently cloned, is endowed with the intriguing property of forming an aqueous pore that allows transmembrane fluxes of hydrophylic molecules of molecular weight below 900. The physiological function of this receptor is unknown. In a previous study we reported experiments suggesting that the P2Z/P2X₇ receptor is involved in the formation of macrophage-derived multinucleated giant cells (MGCs; Falzoni, S., M. Munerati, D. Ferrari, S. Spisani, S. Moretti, and F. Di Virgilio. 1995. J. Clin. Invest. 95:1207– 1216). We have selected several clones of mouse J774 macrophages that are characterized by either high or low expression of the P2Z/P2X₇ receptor and named these clones P2Zhyper or P2Zhypo, respectively. P2Zhyper, but not P2Zhypo, cells grown to confluence in culture spontaneously fuse to form MGCs. As previously shown for human macrophages, fusion is inhibited by the P2Z/P2X₇ blocker oxidized ATP. MGCs die shortly after fusion through a dramatic process of cytoplasmic sepimentation followed by fragmentation. These observations support our previous hypothesis that the P2Z/P2X₇ receptor is involved in macrophage fusion.     

Mast Cells Contain Large Quantities of Secretagogue-Sensitive N-Acetylaspartate

Abstract: Mast cells play a central role in both immediate allergic reactions and inflammation. A functional nerve-mast cell interaction has been proposed, given the morphological association between mast cells and neuropeptide-containing peripheral nerves. We now show that purified rat peritoneal mast cells contain large quantities of N -acetylaspartate (NAA; 747.50 nmol/mg of protein). Mast cell levels of NAA were rapidly reduced, by 64.0 and 86.4%, following treatment with compound 48/80 and mastoparan, respectively. These secretagogues strongly decreased mast cell histamine content over the same time period, suggesting also that NAA is stored in secretory granules. The data are the first to show that NAA is present in an immune effector cell type. Because NAA may be involved in myelin synthesis and glutamyl peptide metabolism, NAA released from mast cells following nervous or other stimuli could participate in neuroimmune interactions. Mast cells in multiple sclerosis plaques may contribute to the reported elevations in brain NAA in this disease.     

Corticotropin releasing factor decidualizes human endometrial stromal cells in vitro. Interaction with progestin

Decidualization of endometrial cells is a hormone-dependent process of differentiation which occurs during the menstrual cycle and pregnancy. Recent in vitro studies have revealed that cAMP and its generators induce decidualization of stromal cells isolated from proliferative endometrium and that progestins enhance the effect of cAMP. Since corticotropin releasing factor (CRF) generates cAMP and prostaglandins in other organs, in the present study the effect of CRF, a hypothalamic factor also produced by decidua and fetal membranes, on in vitro decidualization of endometrial stromal cells was evaluated. The addition of CRF to a culture medium of stromal cells induced in vitro decidualization, as indicated by morphologic changes from elongated fibroblast-like cells into larger and round cells and by the release of prolactin in the medium. The effect of CRF on stromal cells and on prolactin release was significantly augmented by the coincubation in the presence of medroxyprogesterone acetate. This observation indicates CRF as a novel factor of decidualization and confirms that progestins act as enhancers of the expression of decidual products.     

The effect of antiserum quality on strain specificity assessment of foot and mouth disease virus by the neutralization reaction

The factors affecting the virus strain specificity of antibody to foot an mouth disease virus prepared by a variety of protocols in several species were evaluated by neutralization tests. The time at which the serum was taken, the antigen dose given, whether or not revaccination had occurred and the animal species in which the sera were prepared, did not appear to affect the strain specificity of serum prepared to inactivated antigens when measured in neutralization tests, probably because of the restricted nature of the antigenic site involved. However, variation was observed with convalescent animal sera or sera from animals which had received trypsin cleaved virus were used. For these reasons banks of reference antisera are prepared as pooled sera using one or two inoculations of inactivated antigen.     

The fine structure of HNK-1 (Leu7) positive cells

Summary The ultrastructural characteristics of HNK-1 (Leu7) positive cells, visualized with a peroxidase labelled anti-mouse IgM serum, were analysed. Our investigation demonstrates: 1) the majority of Leu7 positive cells has a low nuclear/cytoplasmic ratio (N/C), an irregular outline, a well developed smooth endoplasmic reticulum, parallel tubular arrays (PTA) and electron dense granules; 2) the minority of Leu7 positive cells has a high N/C, regular profiles and lacks electron dense granules. The presence of two distinct ultrastructural patterns within Leu7 positive cells may represent: 1) the expression of subsequent stages of cell differentiation; 2) two distinct Leu7 positive cell subpopulations.     

Efficient direct chromosome analyses and enzyme determinations from chorionic villi samples in the first trimester of pregnancy

Chorionic villi were obtained by an aspiration technique which proved to be the best of four alternative procedures. We report in detail the series of experiments which led to (1) successful, rapidly growing cell cultures practically free of maternal cell contamination (the use of hormone-supplemented Chang medium greatly increased the growth rate); (2) an efficient direct method to obtain high quality metaphases from the Langhans cells of the cytotrophoblast tissue and with which the fetal karyotype is defined within a few hours of chorionic villi sampling; and (3) successful testing for the activity of eight enzymes directly from the villi samples, thus showing that this material is suitable for a rapid, direct diagnosis of the related metabolic diseases.