Gonda M A, Arthur L O, Zeve V H, Fine D L, Nagashima K
Cancer Res. 1976 Mar;36(3):1084-93.
A chronically infected continuous mouse mammary tumor cell line containing virus particles of type B morphology, free of contaminating type C virions, has been grown in tissue culture. These cells were treated with dexamethasone, a synthetic glucocorticoid, a potent stimulator of mouse mammary tumor virus expression. Surfaces of untreated and dexamethasone-treated cells were investigated by scanning electron microscopy. Untreated cells demonstrated a moderate expression of mouse mammary tumor virus (80 particles/cell) distributed diffusely over the cell surface. However, virions on dexamethasone-treated cells were localized in clusters of 100 to greater than 2000 virus particles, often with more than one cluster per cell. Dexamethasone-treated cells typically showed a 10-fold increase in cell-associated virus over untreated cells. Concentrated extracellular fluids from untreated and dexamethasone-treated cultures were quantitated for free virus. Dexamethasone-treated culture fluids demonstrated a similar 10-fold increase of extracellular particles, in contrast to untreated cultures. This increase in virus particles on the cell surfaces as well as in the extracellular fluids supports the theory that dexamethasone has a stimulatory effect on viral replication, not just on the release of budding particles. The ultrastructure of budding mouse mammary tumor virus during dexamethasone stimulation, determined by scanning and transmission electron microscopy, and the significance of such an in vitro system for viral immunodiagnosis are discussed.
一种长期感染的连续传代小鼠乳腺肿瘤细胞系已在组织培养中生长，该细胞系含有B型形态的病毒颗粒，无C型病毒粒子污染。这些细胞用合成糖皮质激素地塞米松处理，地塞米松是小鼠乳腺肿瘤病毒表达的强效刺激剂。通过扫描电子显微镜研究未处理和地塞米松处理细胞的表面。未处理的细胞显示出小鼠乳腺肿瘤病毒的适度表达（80个颗粒/细胞），分散分布在细胞表面。然而，地塞米松处理细胞上的病毒粒子聚集在100至超过2000个病毒粒子的簇中，每个细胞通常有不止一个簇。与未处理的细胞相比，地塞米松处理的细胞通常显示与细胞相关的病毒增加10倍。对未处理和地塞米松处理培养物的浓缩细胞外液中的游离病毒进行定量。与未处理的培养物相比，地塞米松处理的培养液显示细胞外颗粒同样增加10倍。细胞表面以及细胞外液中病毒粒子的这种增加支持了地塞米松对病毒复制有刺激作用的理论，而不仅仅是对出芽颗粒的释放有刺激作用。讨论了通过扫描和透射电子显微镜确定的地塞米松刺激过程中出芽小鼠乳腺肿瘤病毒的超微结构，以及这种体外系统对病毒免疫诊断的意义。
