Intracellular mammalian cell

All phosphoinositides are found in the cytosolic half of the lipid bilayer of the plasma or intracellular compartment membranes (left part). The different kinases acting on phosphoinositides in mammalian cells are shown in solid lines and the phosphoinositide 3-kinases, in bold. The phosphoinositides counterpart pathways catalysed by known phosphatases are represented by dashed lines. The best known phosphatases are PTEN (Phosphatase and tensin homolog deleted on chromosome 10) and SHIP (SH2 domain-containing inositol 5-phosphatase). 

Figure 4. Percentage survival (dashed lines) vs. percentage cells undergoing intracellular freezing (solid lines) in three mammalian cells frozen at various rates to -20 °C (HeLa) or to -78 °C to -196 °C (ova and red blood cells (RBC)). (Modified from Leibo, 1977. Sources of data for individual curves are given there.)...

Cells are normally kept at osmotic (water activity) equilibrium by the action of the Na-pump. Inhibition of the pump with the specific Na -K -ATPase inhibitor, ouabain, causes cell swelling as does inhibition of it by hypothermia. The intracellular environment contains a high concentration of K (100 to 120 mM, in most mammalian cells), lower concentrations of Na (about 10 to 30 mM), and high... 

Induction of apoptosis has been reported in various mammalian cell lines. In previous studies, it has been reported that TBT induces apoptosis in isolated thymocytes at concentrations which are relevant to those causing thymus atrophy in vivo. TBT can also induce apoptosis in PC12 cells, and in human T-lymphoblastoid CEM cells. While the mechanism of TBT-induced apoptosis is still unknown, it has been reported that TBT stimulates thymocyte apoptosis by a mechanism independent of protein synthesis and under conditions where intracellular ATP levels are severely depleted. ... 

Cyclic AMP was the first intracellular signal identified in mammalian cells. Several components comprise a system for the generation, degradation, and action of cAMP. 

Dopp E, voLLMER G, HAHNEL c, GREVESMUHL Y and SCHIFFMANN D (1999) Modulation of tile intracellular calcium level in mammalian cells caused by ivp-estradiol, different phytoestrogens and the anti-estrogen ICl 182780. JSteroid Biochem Mol Biol. 68 (1-2) 57-64. 

Subjecting cells to oxidative stress can result in severe metabolic dysfunctions, including peroxidation of membrane lipids, depletion of nicotinamide nucleotides, rises in intracellular free Ca ions, cytoskeletal disruption and DNA damage. The latter is often measured as formation of single-strand breaks, double-strand breaks or chromosomal aberrations. Indeed, DNA damage has been almost invariably observed in a wide range of mammalian cell types exposed to oxidative stress in a number... 

As far as we are aware, OPCs are the only normal mammalian cells, other than eggs and blastomeres, that have been shown to survive, proliferate and differentiate in serum- and extract-free culture in the absence of other cell types. Indeed, a single OPC can survive and proliferate in these conditions in the absence of any other cells, suggesting that diffusible autocrine factors are not required (Y. Tokumoto, unpublished work). These properties make OPCs especially attractive for studying how intracellular programmes and extracellular signals can combine to control when the cells exit the cell cycle and differentiate. It seems likely that similar mechanisms operate in other cell lineages. 

Trichinellosis is caused by the parasitic nematode Trichinella spiralis. This parasite has a complex life cycle that alternates between intestinal and muscle cell compartments of the host. This nematode infection is unusual because 7. spiralis is an intracellular parasite of mammalian cells. In addition, the broad host range of this parasite includes most mammals. The disease in humans has intrigued parasitologists, other biologists and public health workers for over a century (Cambell, 1983). The attraction to trichinellosis pardy stems from the debilitating and sometimes fatal effects that characterize this disease. 

Iron homeostasis in mammalian cells is regulated by balancing iron uptake with intracellular storage and utilization. As we will see, this is largely achieved at the level of protein synthesis (translation of mRNA into protein) rather than at the level of transcription (mRNA synthesis), as was the case in microorganisms. This is certainly not unrelated to the fact that not only do microbial cells have a much shorter division time than mammalian cells, but that one consequence of this is that the half-life of microbial mRNAs is very much shorter (typically minutes rather than the hours or often days that we find with mammals). This makes it much easier to control levels of protein expression by changing the rate of specific mRNA synthesis by the use of inducers and repressors. So how do mammalian cells... 

WRF presents an intracellular enzymatic system, cytochrome P450 monooxigenases, similar to those mammalian cells, that catalyzes a broad range of intracellular degradation reactions of released metabolites after the pollutants breaking by extracellular enzymes. 

For these proteins, mammalian cells proved better hosts, as they could process the protein with intracellular machinery similar to that in humans. However, large-scale production of proteins in cell culture was problematic. Mammalian cells had to grow attached to a solid surface, such as glass in roller bottle culture. While the Federal Drug Administration (FDA) had approved some processes for vaccine production that used cell cultures, it required that these cells be normal. Normal mammalian cells can divide only a few times before they stop growing, making scale-up to large volumes difficult. 

GENERAL MECHANISMS OF INTRACELLULAR MEMBRANE TRAFFICKING IN MAMMALIAN CELLS INCLUDE BOTH UNIVERSAL AND HIGHLY SPECIALIZED PROCESSES 139... 

Mammalian cells maintain a lower concentration of Na+ (around 12 mM) and a higher concentration of K+ (around 140 mM) than in the surrounding extracellular medium (respectively, 145 and 4 mM). The system (Na+-K+)-ATPase, which maintains high intracellular K+ and low intracellular Na+, is localized in the plasma membrane, and belongs to the family of P-type ATPases. Other members of the family in eukaryotes are the sarcoplasmic reticulum and plasma membrane Ca2+ ATPases and, in plants, the H+-ATPases. The overall reaction catalysed is ... 

This results in the extrusion of three positive charges for every two that enter the cell, resulting in a transmembrane potential of 50-70 mV, and has enormous physiological significance. More than one-third of the ATP utilized by resting mammalian cells is used to maintain the intracellular Na+-K+ gradient (in nerve cells this can rise up to 70%), which controls cell volume, allows neurons and muscle cells to be electrically excitable, and also drives the active transport of sugars and amino acids (see later). 

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