Statistics for forensic toxicology - mechanisms of toxicity

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Hint	Answer	% Correct
	activation of Ca2+-dependent hydrolytic enzymes (leads to disintegration of membranes, proteins etc.)	100%
	activation of Ca2+-dependent proteases (convert xanthine dehydrogenase to xanthine oxidase, which also produces superoxide and hydrogen peroxide)	100%
	activation of constitutively-expressed nitric oxide synthases in neuronal and endothelial cells (increases NO production, which reacts with superoxide to form highly reactive peroxynitrite)	100%
how are these species generated indirectly?	activation of cytochrome P450, increased intracellular Ca2+	100%
how do these species cause oxidative stress?	activation of dehydrogenases in the TCA cycle (increases electron output via the electron transport chain, causing increased production of superoxide)	100%
what is Ca2+ involved in?	activation of enzymes (e.g. TCA cycle), cytoskeletal polymerisation, muscle contraction, neurotransmission, regulation of signal transduction and exocytosis, transporters	100%
how are these species generated directly?	activation of foreign compounds (e.g. benzene), redox cycling (e.g. paraquat), transition metals, inhibition of mitochondrial electron transport (blocking the electron transport chain)	100%
what do we need ATP for?	active transport, especially ion transport, biosynthetic reactions, cell division, cell morphology, cytoskeletal polymerisation, essential part of DNA, muscle contraction, regulation of signal transduction	100%
what other issues can these species cause?	affecting the function of oxidise proteins, mutate DNA causing cellular dysfunction and reducing ATP synthesis, lipid peroxidation, cell swelling, cell lysis	100%
when does calcium become toxic in the cytoplasm?	at high levels	100%
what are the 3 primary causes of necrosis?	ATP depletion	100%
why are the levels of calcium ions tightly regulated within a cell?	because it is so important and so reactive	100%
what are four consequences of excitotoxicity?	depletion of ATP (Mitochondrial ATP production is decreased; activation of Ca2+ ATPase uses ATP)	100%
what kind of 'essential function disruption' are these causes?	disruption to energy generation & protein synthesis	100%
what do these species do to ATP?	drain the ATP reserves	100%
	endoplasmic reticulum Ca2+ ATPase	100%
what eventuates?	eventually the lipid fragments release reactive aldehydes and more free radicals	100%
	excitotoxicity	100%
what is the consequence of increased intracellular Ca2+?	excitotoxicity	100%
what are the 4 mechanisms of calcium removal from the cell?	extracellular Ca2+ ATPase	100%
	extracellular Na+/Ca2+ exchanger	100%
what will dying cells do during apoptosis?	fragment into membrane-bound apoptotic bodies	100%
	inhibition of ADP phosphorylation (eg. DDT)	100%
what are the 4 key mechanisms by which ATP can be depleted?	inhibition of electron transport (eg. cyanide inhibits cytochrome oxidase)	100%
	inhibition of oxygen delivery to the ETC (eg. cocaine, carbon monoxide)	100%
how can oxidative stress be avoided within a cell?	it can be quenched by enzymes	100%
what affect will this have on neighbouring cells?	it can trigger an inflammatory response or long term inflammation	100%
how does it stop oxidative stress?	it converts the superoxide radical (O2-) into H2O2 using metals such as Cu, Fe, Mn, or Ni. H2O2 is then degraded to H2O by catalase	100%
what is the role of ion gradients in necrosis?	it sets off a positive feedback loop of Na+ and Ca2+ entering the cell, opening voltage-gated channels, which lets more ions enter etc.	100%
what does this ion gradient cause that leads to necrosis?	loss of volume control: water influx & cell swelling until the cell lyses (dies)	100%
what do dying cells do during necrosis?	membrane integrity is lost and the cell body swells and bursts open	100%
	microfilament dysfunction (disrupted morphology and function, impaired motility)	100%
	mitochondrial Ca2+ uniporter	100%
what are oxidants?	molecules that can accept an electron	100%
what are antioxidants?	molecules that can donate an electron	100%
what affect will this have on neighbouring cells?	none, the membrane makes it so cellular contents are not released, so cannot effect neighbouring cells	100%
what is necrosis?	non-programmed cell death	100%
which is more reactive?	oxidants	100%
	oxidative stress	100%
what is lipid peroxidation?	peroxidative degradation of lipids by removal of hydrogen from fatty acids, producing a lipid radical.	100%
	physical damage to mitochondria (eg. chronic ethanol abuse)	100%
	production of reaction oxygen and nitrogen species (leads to disintegration of membranes, proteins etc.)	100%
what is apoptosis?	programmed cell death	100%
what causes oxidative stress?	reactive oxygen (ROS) and reactive nitrogen (RNS) species	100%
which is most important?	superoxide dismutase (SOD)	100%
what is narcosis?	the bigger picture, downstream cellular effects that toxins can have	100%
how is this further broken down?	this can be further broken down by reaction w oxygen, forming a lipid peroxyl radical	100%
what is oxidative stress?	when the balance of oxidants and antioxidants is disrupted, meaning that more oxidants are present	100%