Purification and Properties of Closteroviruslike Particles Associated with Grapevine Corky Bark Disease

Closteroviruslike particles, designated as grapevine corky bark-associated virus (GCBaV), were purified from mature leaves and stem phloem tissue of a corky bark-affected grapevine that had indexed negative for other grapevine viruses. Electron microscopy of purified preparations revealed the presence of flexuous rod-shaped viruslike particles that were about 13 nm in diameter and between 1,400 and 2,000 nm long, with a helical pitch of 3.4 nm. In purified preparations, the GCBaV particles degraded within a few weeks, unlike grapevine leafroll associated virus (GLRaV), which was stable for more than 1 mo under the same storage condition. The molecular weight of the coat protein of GCBaV was 24,000. A large dsRNA molecule (about 15.3 kbp), along with lower molecular weight species, was detected in tissues of corky bark-diseased grapevines, but not in healthy grapevines. Polyclonal antisera were produced in rabbits against purified or partially purified virus preparations. In direct enzyme-linked immunosorbent assay (ELISA), antisera to GCBaV did not react to the serologically distinct types (II and III) of the long closteroviruses associated with grapevine leafroll disease and grapevine virus A (GVA), and vice versa. This antiserum also reacted in ELISA with other corky bark-affected grapevines. Our data suggest that closteroviruslike particles, designated as GCBaV, may be the causal agent of corky bark disease. However, definitive proof is still lacking. The inclusion of GCBaV in the group of closteroviruses with citrus tristeza virus is proposed.

The invasive and metastatic properties of hormone-independent but hormone-responsive variants of MCF-7 human breast cancer cells

We have previously isolated a series of MCF-7 human breast cancer cell variants which no longer require estrogen-supplementation for tumor growth in nude mice (Clarke et al. Proc Natl Acad Sci USA 86: 3649-3653, 1989). We now report that these hormone-independent and hormone-responsive variants (MIII, MCF7/LCC1) can invade locally from solid mammary fat pad tumors, and produce primary extensions on the surface of intraperitoneal structures including liver, pancreas, and diaphragm. Both lymphatic and hematogenous dissemination are observed, resulting in the establishing of pulmonary, bone, and renal metastases. The pattern of metastasis by MIII and MCF7/LCC1 cells closely resembles that frequently observed in breast cancer patients, and provides the first evidence of metastasis from MCF-7 cells growing in vivo without supplementary estrogen. The interexperimental incidence of metastases, and the time from cell inoculation to the appearance of metastatic disease are variable. The increased metastatic potential is not associated with an increase in either the level of laminin attachment, laminin receptor mRNA expression, or secreted type IV collagenolytic activity. We also did not detect a significant decrease in the steady-state mRNA levels of the metastasis inhibitor nm23 gene. However, when growing without estrogen in vitro, MCF7/LCC1 cells produce elevated levels of the estrogen-inducible cathepsin D enzyme.

Study on microwave dielectric properties of epoxy resin mixtures used for rapid product development

This paper presents a preliminary study on the dielectric properties and curing of three different types of epoxy resins mixed at various stichiometric mixture of hardener, flydust and aluminium powder under microwave energy. In this work, the curing process of thin layers of epoxy resins using microwave radiation was investigated as an alternative technique that can be implemented to develop a new rapid product development technique. In this study it was observed that the curing time and temperature were a function of the percentage of hardener and fillers presence in the epoxy resins. Initially dielectric properties of epoxy resins with hardener were measured which was directly correlated to the curing process in order to understand the properties of cured specimen. Tensile tests were conducted on the three different types of epoxy resins with hardener and fillers. Modifying dielectric properties of the mixtures a significant decrease in curing time was observed. In order to study the microstructural changes of cured specimen the morphology of the fracture surface was carried out by using scanning electron microscopy.