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K S Tweedell

Publications and source records attributed to K S Tweedell.

21 records · Page 2Linked to original sources
PubMedDate not supplied

Culture of PNKT-4B cells at invasion permissive and restrictive temperatures. I. Chromosomal analysis.

PNKT-4B is an aneuploid cell line derived from a herpesvirus-induced renal adenocarcinoma of Rana pipiens that displays restricted invasion at 21 degrees C or cooler and invasion at 23 degrees C through 28 degrees C. Metaphase chromosomes obtained from subcultures (passages 297; 345-347) grown at 18 degrees C or 28 degrees C were Giemsa stained or N-banded with acidic silver nitrate. Cells grown at 18 degrees C displayed a modal chromosome number of 41, while 28 degrees C cultures displayed a modal number of 40. The distribution of the chromosomes suggests that the two temperatures may be allowing growth of different subclonal populations. N-banding of chromosomes at both temperatures revealed an increase of active nucleolar organizer regions (NORs) over normal frog tissues, 2/2N. Analysis of 200 N-banded spreads from cells grown at each temperature revealed modal numbers of 9 NORs/cell and modal numbers of 6 NOR-containing chromosomes/cell. Nine specific NOR-containing chromosomes were identified and scored. Similar distributions were observed at 18 degrees C and 28 degrees C. The data imply that the modal number of PNKT-4B has shifted since it was first described, 39, and differs at invasion-permissive and -restrictive temperatures. Increased numbers of active NORs and alterations of NOR-containing chromosomes imply an amplification of rDNA over the amount in normal frog.

Adenocarcinoma↗
PubMedDate not supplied

Temperature-dependent malignant invasion in vitro by frog renal carcinoma-derived PNKT-4B cells.

The northern leopard frog, Rana pipiens, may be afflicted with a herpesvirus-transmitted renal carcinoma which has the interesting property that its metastatic behavior is temperature-related. PNKT-4B is a cell line derived from a pronephric carcinoma arising in a tadpole. We sought to ascertain if invasion of normal tissue by PNKT-4B cells in three-dimensional confrontation culture in vitro is similarly temperature-dependent. Normal fragments of tadpole and frog organs are invaded by PNKT-4B cells at 28 degrees C but not at 20 degrees C or 21 degrees C. PNKT-4B cells failed to invade tadpole tissues at 7 degrees C. A temperature critical for invasion was sought. Temperatures of 21 degrees C and cooler are invasion-restrictive and 23 degrees C and warmer are invasion-permissive under the conditions of this study. Identification of a critical permissive temperature allows for the characterization of biochemical events which may be activated at the same temperature. The biochemical changes, which are selectively activated and subsequently repressed as tumor cells are cycled through invasion-permissive and invasion-restrictive temperatures, become compelling candidates as reactions involved in, or causal for, malignant invasion.

Animals↗