Oligosaccharide Le(a)-Le(x): a cell surface marker for carcinomas derived from embryonic endoderm.

An immunohistochemical evaluation of Le(a)-Le(x) expression by adenocarcinomas of the biliary tree, pancreas, colon and stomach was undertaken as examples of epithelial tumors derived from embryonic endoderm. This complements previous studies showing that Lea-Lex was present on the cell surface of non-small cell lung carcinomas, some non-lung carcinomas, and is a prognostic marker for squamous cell lung carcinomas. All of the tumor specimen evaluated were positive and no expression of Le(a)-Le(x) was detected in derivatives of neural, connective or muscle tissues. These findings indicate that it could be informative to examine the biological significance of Le(a)-Le(x) not only in carcinogenesis but during embryogenesis, as well.

Virus-like particles in the aquatic fungus, Rhizidiomyces.

Isometric virus-like particles (VLPs), 60 nm in diameter, have been observed by electron microscopy in eight isolates of thermal-shocked Rhizidiomyces, a zoosporic, unicellular member of the Hyphochytridiales. VLP pathogenesis was observed in all fungal developmental stages from the zoospores to the mature sporangia. Paracrystalline structures associated with mitochondria preceded VLP occurrence in multinucleate sporangia. Particles appeared first in the intact nucleus, and subsequently VLPs completely replaced the nucleus and cytoplasm of the fungal host. Cell wall breakdown followed with release of VLPs into the medium. Approximately 50% of each fungal isolate was destroyed by the VLPs under stress conditions of heat, low nutrition, or aging. However, sufficient numbers of zoospores were capable of maturing into sporangia which produced zoospores to maintain the isolates in culture. After cloning 10 generations of zoospores, VLPs could still be produced in the offspring, thus indicating vertical transmission of the VLPs from generation to generation.

Isolation and characterization of a double-stranded DNA mycovirus infecting the aquatic fungus, Rhizidiomyces.

Isometric particles 60 nm in diameter were isolated from the culture filtrate of the aquatic fungus, Rhizidiomyces, via pressure dialysis. The virus particles had a sedimentation coefficient of 625 S and a buoyant density of CsCI of 1.314 g/ml. The nucleic acid was dsDNA present as a single molecule (MW = 16.8 x 10(6)). Gel electrophoresis revealed 14+ protein bands ranging from MW of 84,500 to 26,000, with the largest one being dominant. This mycovirus appears to be distinct from all previously characterized viruses.

Differential effect of 2-thiouracil on synthesis of two plant viruses in the same host.

In cowpea leaves singly or doubly infected with cowpea chlorotic mottle virus (CCMV) and/or southern bean mosaic virus (SBMV), treatment with 2-thiouracil increased the accumulation of CCMV particles and strongly decreased the accumulation of SBMV particles. Thiouracil prevented the usual inhibition of synthesis of CCMV particles at about 6 days after inoculation, and 2-3 times as many CCMV particles accumulated as in water-treated plants. A single treatment of thiouracil 48 h before, at the time of, or 24 h after inoculation caused at least 90% decrease in the amount of SBMV particles extracted from inoculated leaves for at least 15 days. When virus particles were extracted from plants treated with thiouracil, the specific infectivity of CCMV was increased 2.3 times and SBMV was decreased 0.46 times as compared to virus from control plants.