Detection of Viral Antigens in Mouse and Rat Tumor Cells by Immunoelectron Microscopy Following Periodate-Lysine-Paraformaldehyde (PLP) Fixation

Author(s):  
Y. Ohtsuki ◽  
G. Seman ◽  
J. M. Bowen ◽  
M. Scanlon ◽  
L. Dmochowski

Recently, periodate-lysine-paraformaldehyde (PLP) fixation was reported for immunoelectron microscopy (1). In PLP fixation, carbohydrates are oxidized by periodate and cross-linked by lysine; paraformaldehyde stabilizes proteins and lipids. By using PLP fixation, intracytoplasmic type A viral antigens have been previously demonstrated by immunoperoxidase labeling (2). In the present study, PLP fixation has been applied for the detection of the same antigens in mouse mammary tumor culture cells by both immunoferritin and immunoperoxidase methods. Rabbit anti-intracytoplasmic type A virus serum (anti-A), kindly provided by Dr. M. Muller (3), rabbit anti-strain A mouse mammary tumor virus (anti-MMTV) and preimmune rabbit serum as control were used to detect viral antigens in cells of C3H/HeJ strain mouse mammary tumor culture. Attempts have been also made to demonstrate peroxidase labeling of type C virus particles in frozen sections of an SD-MSV-induced NZB rat bone tumor tissue by rabbit anti-MuLV serum.

1999 ◽  
Vol 73 (6) ◽  
pp. 5166-5171 ◽  
Author(s):  
Jong-Seo Lee ◽  
Tatsuya Haruna ◽  
Akinori Ishimoto ◽  
Tasuku Honjo ◽  
Shin-ichi Yanagawa

ABSTRACT The int3 oncogene was discovered as a frequent target in mouse mammary tumor virus-induced mammary tumors and encodes the intracellular domain of a Notch4/int3 protein. In one spontaneous mammary tumor, no. 9, that developed in a BALB/c mouse, we have found an insertion of a 1.2-kb sequence, consisting of a 5′ long terminal repeat and gag sequences of an intracisternal type A particle (IAP) as well as an extra copy of the Notch4/int3genomic sequences containing exons 23 and 24, into the intron between exons 24 and 25 of the Notch4/int3 gene. In this tumor, unique splicing events between the IAP and the Notch4/int3sequences generated two types of IAP-Notch4/int3 fusion transcripts encoding two different portions of the intracellular domain of Notch4/int3 proteins: one with a RAM domain and the other without. Interestingly, these two proteins showed different subcellular localizations in a mouse mammary epithelial cell line, HC-11.


Author(s):  
N. H. Sarkar ◽  
Dan H. Moore

Mouse mammary tumor virus (MTV) is believed to contain about 0.8% single stranded ribonucleic acid (RNA). This value of RNA content was estimated on a dry weight basis. The subject of this report is an attempt to visualize the RNA molecules of MTV particles.MTV particles were isolated from RIII mouse (tumor incidence approximately 80%) milk according to the method described by Lyons and Moore. Purified virions from 5 ml of milk were finally suspended in 0.2 ml of PBS, pH 7.4 and was mixed with an equal volume of pronase (5 mg/ml). This mixture was incubated at 37°C for an hour. RNA was extracted three times using freshly prepared cold phenol. It was then treated three times with cold ethyl ether to remove any trace of phenol. The RNA thus extracted was divided into two parts. One part was diluted four fold with 8M urea to avoid aggregation of the molecules. The other part was left untreated. Both samples were then mixed with an equal volume of 1M ammonium acetate, adjusted to pH 8.0 with NH3 containing chymotrypsin at a concentration of 0.01%.


Author(s):  
W. J. Hamilton

The study of RNA tumor viruses has been greatly facilitated by the use of immunochemical tagging methods. In the past these methods have been constrained to antibody conjugates with ferritin or peroxidase. In order to avoid the disadvantages of using conjugated antisera, investigators have applied the unlabeled antibody enzyme method of Sternberger to mammary tumor derived mouse cells prior to embedding for electron microscopy. The current study has successfully applied the Sternberger method to virusproducing cells and purified virus pellets after epoxy-embedding and ultrathin sectioning. The results demonstrate the distinct advantages of this “post-embedding” method for viral antigen localization.Purified Rauscher leukemia virus (RLV) and mouse mammary tumor virus (MMTV) were pelleted, fixed in buffered 2% paraformaldehyde and washed thoroughly. These were dehydrated in acetone, infiltrated and embedded in Spurr resin according to common procedures. A tumor derived cell line, Mm5mt, producing MMTV was embedded by parallel methods.


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