The fine structural cytochemistry of virus particles found in renal tumors of leopard frogs. I. An enzymatic study of the viral nucleoid

Temperature-dependent metastasis of the Lucke renal carcinoma and its significance for studies on mechanisms of metastasis

Metastasis is temperature dependent in the renal adenocarcinoma of the North American leopard frog, Rana pipiens. Widespread, multiple, metastatic colonies occur in tumor-bearing frogs kept at 28 degrees C for 50 days while tumor-bearing frogs kept at 7 degrees C for 98 days or more have either no secondary deposits or they have only an occasional small metastatic nodule. An attractive aspect of the frog tumor is that invasion and metastasis can be permitted or inhibited by the manipulation of temperature alone-no exogenous chemicals or drugs are required for the effect. Because of this, biological variables which reproducibly and specifically associate with metastasis permissive conditions when ambient temperature is cycled between permissive and inhibitory values are strong candidates for being causal elements in the multistep process leading to metastasis. Intravascularly injected labelled renal tumor cells reached all organs studied in as little as 15 minutes at both metastasis restrictive and permissive temperature. The results with tumor cell inoculation dispose of the possibility that failure of metastasis in chilled animals is due to cold-induced changes in blood flow. Histologically typical metastatic colonies developed in frogs, kept at the permissive temperature, after injection with disaggregated tumor cells which were previously cryopreserved. Frog tumors elaborate type I collagenase in a temperature dependent manner. Type IV collagenase has been demonstrated as well. Tumor cell detachment in vitro, assembly and disassembly of tumor cell cytoplasmic microtubules, and invasion in vitro, are all temperature dependent.

Herpesviruses in metastatic Lucké renal adenocarcinoma

The etiologic agent of the renal adenocarcinoma of leopard frogs, Rana pipiens, is the Lucké tumor herpesvirus (LTHV). The virus is easily detected with thin section electron microscopy in primary tumors of frogs which have been exposed to a cold environment. Several spontaneous metastatic nodules and a large primary tumor were detected at autopsy of a frog which had been maintained at 4 degrees C for 73 days. LTHV was found not only in the primary tumor, as previously reported, but also was present in metastatic tumor cells in the liver, fat body, and bladder. The presence of LTHV in metastatic cells demonstrates that the differentiated state of primary Lucké tumor cells is retained in its metastatic colonies even at the fine structure level revealed by electron microscopy.

Arrangement of herpesvirus deoxyribonucleic acid in the core

The core of the herpes simplex virion consists of an electron-dense toroidal structure 50 nm high, with an inside diameter of 18 nm and an outside diameter of 70 nm, penetrated by a less dense cylindrical mass. The toroid contains deoxyribonucleic acid (DNA), as evident from the observation that uranyl ion staining is removed by ethylenediaminetetraacetic acid under conditions which result in the extraction of uranyl ions bound to nuclear DNA. Studies on negatively stained preparations of purified capsids suggest that the toroid consists of DNA arranged as if it were spooled around the cylindrical mass.

Herpes-type virus particles associated with a fungus

A cultutre of the fungus Thraustochytrium, isolated from an estuary, was infected by ani enveloped virus. The nucleocapsid measured 110 nanometers in diameter and containied a core of DNA. The virus replicated in the nucleus. These findings stronigly suggest that the particles are a herpes-type virus.

Intracellular inclusions resulting from infection with African horsesickness virus

Intranuclear and intracytoplasmic inclusions in monkey kidney cells infected with African horsesickness virus were studied with the aid of electron microscopy.