Transitional pore

Kieffer, J., Investigation of the transitional pore stmeture of activated carbon fibers by small-angle neutron scattering, J. Appl. Phys., 1992, 72(12), 5649 5656. 

Carbons may have closed and open pores with a large variety of dimensions from a few Angstroms to several microns. In terms of structure, the pores in active carbons are divided into three basic classes [66, 69] macropores, transitional pores, and micropores. Pores are formed during the production of carbon (pyrolysis of its precursors), or can be formed by other means such as oxidation by 02, air, C02, or H20 [66]. According to Dubinin s... 

Andrabi, S. A., Sayeed, I., Siemen, D., Wolf, G. Horn, T. F. (2004). Direct inhibition of the mitochondrial permeability transition pore a possible mechanism responsible for anti-apoptotic effects of melatonin. FASEB J. 18, 869-71. 

Fas ligand and interleukin-ip), the neurotransmitter glutamate and thrombin. Like tumor necrosis factor (TNF) receptors, Fas is coupled to downstream death effector proteins that ultimately induce caspase activation (Ch. 22). Fas and TNF receptors recruit proteins called FADD and TRADD respectively FADD and TRADD then activate caspase-8, which, in turn, activates caspase-3 (Fig. 35-4). Calcium ion influx mediates neuronal apoptosis induced by glutamate receptor activation calcium induces mitochondrial membrane permeability transition pore opening, release of cytochrome c and caspase activation. Interestingly, in the absence of neurotrophic factors some neurotrophic factor receptors can activate apoptotic cascades, the low-affinity NGF receptor being one example of such a death receptor mechanism [23],... 

Several different changes in mitochondria occur during apoptosis. These include a change in membrane potential (usually depolarization), increased production of reactive oxygen species, potassium channel activation, calcium ion uptake, increased membrane permeability and release of cytochrome c and apoptosis inducing factor (AIF) [25]. Increased permeability of the mitochondrial membranes is a pivotal event in apoptosis and appears to result from the formation of pores in the membrane the proteins that form such permeability transition pores (PTP) may include a voltage-dependent anion channel (VDAC), the adenine nucleotide translocator, cyclophilin D, the peripheral benzodiazepine receptor, hexokinase and... 

Figure 11.6 Schematic representation of Ca2+ transport in and out of mitochondria, showing all the Ca2+ transporters and activation of matrix dehydrogenases. PTP—permeability transition pore. (From Carafoli, 2003. Copyright 2003, with permission from Elsevier.)...

A dissipation of mitochondrial membrane potential (A P/w) is often detectable dining apoptosis (Green, 1998 Shidoji et al, 1997). A loss of A Pm is thonght to be mediated by the opening of the mitochondrial permeability transition pore which is proposed to be involved in mitochondrial efflux of cytochrome c into the cytosol (Scarlett and Mnrphy, 1997). However, a recent report by Bossy-Wetzel et al (1998) provided... 

Bax interacts with the permeability transition pore to induce permeability transition and cytochrome c release in isolated mitochondria, Proc.Natl.Acad.Sci. U.S.A. 95 14681-14686. 

Crompton, M., 1999, The mitochondrial permeabUity transition pore and its role in cell death, Biochem J 341 233-249. 

Scorrano, L., PetroniUi, V., Di Lisa, F., and Bemardi, P., 1999, Commitment to apoptosis by GD3 ganglioside depends on opening ofthe mitochondrial permeability transition pore. J Biol Chem 274 22581-22585. 

Mattiasson G, Friberg H, Hansson M, Elmer E, Wieloch T. 2003. Flow cytometric analysis of mitochondria from CAl and CA3 regions of rat hippocampus reveals differences in permeability transition pore activation. J Neurochem 87 532-544. 

Kroemer G. The mitochondrial permeability transition pore complex as a pharmacological target. An introduction. Curr Med Chem 2003 10(16) 1469-1472. 

Kidd JF, Pilkington MF, Schell MJ, et al. Paclitaxel affects cytosolic calcium signals by opening the mitochondrial permeability transition pore. J Biol Chem 2002 277(8) 6504-6510. 

Porosity refers to the volume of pores in a solid. It contributes to the internal surface area of the sample and can influence the kinetics of adsorption. Diffusion into and out of pores is often considered responsible for slow adsorption and desorption processes. Pores vary in size and shape. They have been classified according to their average widths as micropores which are of the order of molecular dimensions (<2 nm), meso- or transitional pores which are between 2-50 nm and macropores which are larger than 50 nm (Sing et al., 1985). The sum of all the pores is called the pore volume (porosity). 

Critical for predictivity in a recent comprehensive study was the number and choice of parameters measured [4]. Early, sublethal effects on cell proliferation, cell morphology and mitochondria occurred consistently and ubiquitously with toxicity and when used collectively were most diagnostic. It is noteworthy that the toxicity of many drugs is attributable to various mitochondrial targets, including oxidative phosphorylation, fatty acid oxidation, Krebs cycling, membrane transport, permeability transition pore, proliferation and oxidative stress (Table 14.4). 

Permeability transition pore Opening by reactive oxygen species, reactive nitrogen species, bile adds, ihio crosslinkers, atractyloside, betu-liniate, lonidamidem various anticancer drugs, to collapse mitochondrial membrane potential and activate mitochondrial apoptotic pathway... 

Much progress has been made in understanding the different mechanisms that can cause mitochondrial dysfunction, such as (i) uncoupling of electron transport from ATP synthesis by undermining integrity of inner membrane (ii) direct inhibition of electron transport system components (iii) opening of the mitochondrial permeability transition pore leading to irreversible collapse of the transmembrane potential and release of pro-apoptotic factors (iv) inhibition of the... 

Drugs that Induce the Mitochondrial Permeability Transition Pore (MPT)... 

Juhaszova, M. et al. (2008) The identity and regulation of the mitochondrial permeability transition pore where the known meets the unknown. Annals of the New York Academy of Sciences, 1123, 197-212. 

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