Surface mediated death of unconditionedTetrahymena cells: Effect of physical parameters, growth factors, hormones, and surfactants

Abstract

A new form of cell death has been observed. The death occurs at liquid-air interfaces when Tetrahymena cells are grown in a chemically defined medium (CDM) at low inocula. The cells die by lysis at the liquid-air interface (medium surface), which they reach due to negative gravitaxis as well as positive aerotaxis. When the cells are grown in a closed compartment, with no liquid-air interface, the death is not observed, and the cells proliferate. Cloning of cells in CDM is thus possible. The addition of effectors such as NGF (10(-11) M), EGF (10(-10) M), PDGF (10(-10) M), and insulin (10(-7) M) to cells in CDM prevents the surface mediated death. Since detergents/surfactants like SDS (7 x 10(-5) M), NP-40 (2 x 10(-5) M), Tween 80 (10(-4))% w/v), Pluronic F-68 (10(-7) M), and the biosurfactant surfactin (10(-6) M) have the same effect, we suggest that the effectors act by stimulating the cells to exudate surfactant(s) of their own. Furthermore, lyzed cells and exudates from living cells (pre-conditioned medium) prevent the death. In conditions with liquid-air interfaces, certain physical parameters are of great importance for the survival of cells at low inocula. The parameters are the distance to the surface, the temperature, and the inoculum. By increasing the height of the medium, lowering the temperature, and increasing the inoculum of the culture, the survival can be greatly enhanced. There is no evidence for programmed cell death (PCD) or apoptosis.

Swelling of Ionic and Nonionic Surfactant Micelles by High Pressure Gases

“…Pluronic amphiphilic block copolymers are used extensively in a wide range of applications, including detergents, , separations, , drug solubilization and delivery, − and the controlled release of drugs. − As a result there have been a significant number of small-angle scattering studies on the structural properties of nonionic Pluronic surfactants, especially in low concentration aqueous environments, including a number of review articles. , One of the first structural studies of Pluronic surfactants was conducted by Zhou et al who used dynamic light scattering to investigate the structure and assembly of micelles. Since then a lot of research has been conducted into probing the structural characteristics of copolymer micelles using small angle scattering techniques. − The ionic surfactant cetyltrimethylammonium bromide (CTAB) has also been widely studied because of its use as a template in the synthesis of mesoporous silicas, , as a detergent, in the stabilization of nanoparticles, , and also in separation science .…”