Hybridization data indicate that germ line DNA from all mouse strains contains numerous endogenous retroviruses (1). In vivo expression of viral proteins and complete infectious viruses is variable and both mouse strain and tissue specific (2). Studies of the control of endogenous virus expression might be expected to provide insight into both the role of endogenous viruses in leukemogenesis an...

B-cell activation and proliferation can be induced by a variety of extracellular stimuli. The fate of an activated B cell following mitogen stimulation can be dictated by the strength or duration of the signal, the expression of downstream signaling components necessary to promote proliferation, and the cell intrinsic sensors and regulators of the proliferative program. Previously we have ident...

The central nervous system produces growth factors that stimulate proliferation of ameboid microglia during embryogenesis and after traumatic injury. Two microglial mitogens (MMs) are recovered from the brain of newborn rat. MM1 has an approximate molecular mass of 50 kD and a pI of approximately 6.8; MM2 has a molecular mass of 22 kD and a pI of approximately 5.2. These trypsin-sensitive prote...

The Ras proteins are key mediators of the early cellular response to mitogens; the way in which they influence the later events in the cell cycle is beginning to fall into place.

Thymomodulin (TMD), a thymic biological response modifier, stimulates the release of tumour necrosis factor (TNF) and granulocyte-macrophage-colony stimulating factor (GM-CSF) in macrophage-lymphocyte cultures. We investigated the effects of the cytokines released in cultures with TMD, on the expression of human leucocyte antigen-DR (HLA-DR) antigens by alveolar macrophages (AM) and the T-cell ...

There is abundant evidence implicating a role for intracellular pH (pHin) in the proliferative response of many cells to mitogenic agents. In mammalian cells, pHin is generally regulated by two systems: Na+/H+ exchange and HCO; transport. Activation of Na+/H+ exchange is one of the earliest responses of mammalian cells to mitogens. In the absence of HCO;, this activation raises the pHin. Howeve...