Loss of thyroidal inducibility of Na,K-ATPase with neoplastic transformation in tissue culture

Thyroidal induction of the plasma membrane Na,K-ATPase is a characteristic of mammalian tissues that exhibit a thermogenic response to this hormone. To facilitate analysis of the pathways mediating this response, we defined the conditions needed for reproducible thyroidal induction of this enzyme, as well as mitochondrial cytochrome c oxidase, in established cell lines in tissue cultures. In confluent monolayers of nontransformed mouse embryo fibroblasts (C3H/10T1/2), triiodothyronine modulated Na,K-ATPase and cytochrome c oxidase activities in a concentration- and time-dependent manner. Similar increases in Na,K-ATPase activity were obtained in other rodent embryo cells (SWISS/3T3 and NIH/3T3) and in human fibroblasts (WI-38). In contrast, neoplastic transformation of all of these cell lines resulted in loss of inducibility of Na,K-ATPase by thyroid hormone, regardless of the initiating mechanism (i.e. spontaneous, x-ray, chemicals, viruses).     

Polymorphonuclear leukocyte migration through human amnion membrane

A new in vitro model has been developed for studying migration of human polymorphonuclear leukocytes (PMN) through living native cellular and matrix barriers. Human amnion membrane consists of a single layer of epithelium bound to a continuous basement membrane interfacing an avascular collagenous stroma. Living amnion was placed in plastic chambers with separate compartments on each side of the membrane. PMN were introduced on the epithelial side of the amnion, and a Millipore filter (Millipore Corp., Bedford, Mass.) was placed against the stromal side. In response to N-formylmethionyl-leucyl- phenylanlanine (FMLP) chemoattractant, PMN penetrated the full thickness of the amnion and were collected and counted on the filter. The rate of PMN traversal of the amnion was dependent on the concentration of FMLP (optimal at 10(-8)M) as well as the slope of the FMLP gradient across the amnion. The route of PMN migration was studied by transmission electron microscopy. PMN first attached to the epithelial surface, then infiltrated between intercellular junctions. PMN migrated around or through tight junction and hemidesmosome attachments. The PMN then penetrated the basement membrane and migrated through the dense collagenous stroma. The present amnion migration system has characteristics of the in vivo inflammatory state not described in any previous method for monitoring PMN migration in vitro. Prior methods have not used native epithelium, whole basement membrane, or collagenous stroma. PMN penetration of these barriers occurs in the normal inflammatory response and probably involves biochemical mechanisms not required for simple migration through the pores of an artificial filter. The amnion system can be useful for future biochemical and morphological studies of PMN penetration of these barriers and possible repair processes that may follow.     

Changes in some nitrogenous components during the germination of pea seeds

The changes in major nitrogenous components during the germination of pea seeds have been followed. During the period of rapid axis growth, 3 to 8 days following germination, the nitrogen content of the cotyledons declines rapidly with an accompanying increase of nitrogen in the developing axis. The accumulation of alcohol soluble nitrogen, primarily amino nitrogen, in the cotyledons and axis during germination indicates that the mobilization of nitrogen is facilitated by proteolysis and translocation of the products.     

Escape from X-ray-induced arrest for lens cells stimulated from quiescence: time relationship to RNA, protein, and DNA synthesis

Quiescent cells of the central zone region of the rat lens epithelium were stimulated to enter the proliferation cycle by wounding. RNA synthesis and a corresponding increase in poly(A)+/total RNA reached a peak by Hour 4. Cells progressed into the G1B compartment by Hour 10. A rise in protein synthesis began at Hour 8, and onset of DNA synthesis occurred by Hour 14. The timing of cell cycle progression that allowed escape from a dose of X irradiation that completely inhibited DNA synthesis was investigated. A growth-arrest point was identified at Hour 9 where 10 GY of X irradiation given before, but not after, completely inhibited earliest responding cells from entering DNA synthesis on schedule. Increased quantities of cells entered DNA synthesis on schedule as timing of the X irradiation was moved closer to the end of G1. Based on time relationships, the rise in protein synthesis is correlated with the "sufficient" event for the escape.