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Topic: Feedback inhibition

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positive feedback

linear feedback shift registers

feedback loops

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audio feedback

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force feedback

negative feedback loop

feedback amplifier

Soma to germline feedback

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	Regulation of Metabolism
		The process of feedback inhibition regulates the activity of preexisting enzymes in the cells.
		Feedback inhibition (or end product inhibition) is a mechanism for the inhibition of preformed enzymes that is seen primarily in the regulation of whole biosynthetic pathways, e.g.
		Note: In the case of feedback inhibition (above), the signal molecule, tryptophan, is a negative effector of Enzyme a in the pathway of tryptophan biosynthesis, because when it binds to Enzyme a, it inactivates the enzyme.
	textbookofbacteriology.net /regulation.html (3878 words)

	Enzyme Inhibition
		In feedback inhibition, there is a second binding site on the enzyme where the inhibitor binds, so that the inhibitor is not necessarily similar in structure to the substrate.
		In feedback inhibition, the inhibitor binds to the enzyme at a site away from the active site and acts by altering the shape of the enzyme in such a way that it is incapable of catalyzing the reaction.
		Feedback inhibition is a natural part of the process by which an organism regulates the chemical reactions that take place in its cells.
	dl.clackamas.cc.or.us /ch106-08/enzyme1.htm (654 words)

	Decreased hypothalamic-pituitary-adrenal axis sensitivity to cortisol feedback inhibition in human aging. (Site not responding. Last check: 2007-10-17)
		This study assessed the influence of aging on the sensitivity of the human HPA axis to feedback inhibition induced by cortisol.
		Endogenous cortisol feedback inhibition was removed by treatment with metyrapone, which reduces cortisol synthesis by inhibiting 11 beta-hydroxylase.
		Feedback sensitivity was estimated by the latency to and extent of decline of plasma ACTH concentration during and following the cortisol infusion.
	www.arclab.org /medlineupdates/abstract_9032777.html (292 words)

	feedback inhibition - OneLook Dictionary Search
		Tip: Click on the first link on a line below to go directly to a page where "feedback inhibition" is defined.
		feedback inhibition : The American Heritage® Dictionary of the English Language [home, info]
		Feedback inhibition : Biological Sciences Dictionary [home, info]
	www.onelook.com /?w=feedback+inhibition&ls=a (142 words)

	AllRefer.com - cortisol (Biochemistry) - Encyclopedia
		Cortisol is synthesized and secreted by the adrenal cortex in response to the stimulating substance adrenocorticotropic hormone (ACTH).
		In turn, cortisol is the major regulator of ACTH production in the pituitary gland; it acts by negative feedback inhibition, i.e., a rise in the level of cortisol in the blood inhibits ACTH secretion by the pituitary.
		Cortisol, usually referred to as hydrocortisone when used medicinally, is more potent than cortisone with respect to metabolic and anti-inflammatory effects.
	reference.allrefer.com /encyclopedia/C/cortisol.html (250 words)

	Search Results for feedback - Encyclopædia Britannica
		To correct this flaw, the principle of feedback was added to the model and provided a closer approximation of interpersonal human interaction than was known theretofore.
		Ranking prominently among experimental variables are so-called feedback contingencies (aftereffects, knowledge of results) that may be controlled by the experimenter so as to occur concurrently with...
		Inhibition or activation of an enzyme by a small regulatory molecule...
	www.britannica.com /search?miid=1152704&query=feedback (464 words)

	Feedback inhibition of valine, leucine and isoleucine biosynthesis - Branched chain amino acid and lysine biosynthesis ...
		Feedback inhibition of valine, leucine and isoleucine biosynthesis - Branched chain amino acid and lysine biosynthesis - HORT640 - Metabolic Plant Physiology - Department of Horticulture and Landscape Architecture - Purdue University
		Feedback inhibition of threonine dehydratase (TD) [EC 4.2.1.16] by isoleucine would prevent this imbalance (Singh and Shaner, 1995).
		Control appears to be exerted at the threonine dehydratase (TD) step which is feedback inhibited by isoleucine (Aubert et al, 1998).
	www.hort.purdue.edu /rhodcv/hort640c/branch/br00006.htm (373 words)

	feedback inhibition -- Encyclopædia Britannica
		Synthesis is stopped by the inhibition of the first enzyme in the pathway by the...
		Overview of the laboratory procedures involved in the inhibition, destruction, and removal of microorganisms.
		Information on how lateral inhibition creates a discrepancy between what is really seen by the eyes and what is made up by the brian.
	www.britannica.com /eb/article-9033914?tocId=9033914 (782 words)

	NEUROSCIENCE: ON MICROCIRCUIT INHIBITION FLOW
		In contrast, feedback inhibition is triggered by recurrent collaterals of the pyramidal cells, which therefore activate interneurons only when an output spike is generated [5].
		Feedforward and feedback inhibition thus provide complementary controls of excitability: feedforward inhibition is regulated by the level of excitatory input, while feedback inhibition is proportional to the rate of output.
		This shift of inhibition is apparently due to sequential activation of inhibitory synaptic conductances onto the soma and dendrite of the pyramidal neurons.
	scienceweek.com /2004/sb041203-1.htm (1320 words)

	JSMF - 1998 McDonnell - Pew Program in Cognitive Neuroscience
		An initial experiment will document more carefully the existence of auditory feedback inhibition as indexed by the amplitude of the M100 response in auditory cortex to self-produced speech, as compared with the responses to a recording of the same speech.
		The second experiment will consider the hypothesized cause of this inhibition by using the MEG paradigm of the first study to examine the effects of exposure to various manipulations of auditory feedback (including delayed auditory feedback) on the inhibition of auditory feedback.
		Two hypotheses about this issue are proposed for evaluation: a) auditory feedback is inhibited by a fixed amount; b) auditory feedback is inhibited dynamically, with the level of inhibition a function of the speed of production of the speech movement.
	www.jsmf.org /grants/historical/mcpew/1998/houde.htm (472 words)

	Feedback Inhibition (Site not responding. Last check: 2007-10-17)
		Catabolic pathways are organized in the same manner, but they break down molecules.
		Feedback regulation is the mechanism by which biosynthetic and catabolic pathways regulate themselves.
		These pathways have evolved self-regulation such that, if too much of the end product is around (E in the pathway above), it, or a byproduct, acts as an inhibitor of an earlier reaction.
	web.mit.edu /esgbio/www/eb/feedback.html (173 words)

	Irreversible steps in computer models (2/4)
		2b and 3c, in which weak feedback inhibition is seen to be sufficient to maintain a steady state at low demand.
		This observation is easily rationalized, and it illustrates a practical difference between inhibition and activation that may have important implications for the regulatory design of metabolic systems in nature.
		By contrast, reported activation effects are often hyperbolic, in the sense that an enzyme subject to activation often shows some activity in the absence of activator, and in addition, the amount of activation possible is limited by the limiting rates of the enzymes involved.
	bip.cnrs-mrs.fr /bip10/irrev2.htm (2757 words)

	Negative Feedback Regulation of Hormone Release in the Hypothalamic-Pituitary Axis
		The usefulness of negative feedback inhibition is that it results in hormonal homeostasis, that is the maintenance of hormone levels within a particular appropriate physiological range.
		An important place to consider negative feedback inhibition is in evaluating disorders of secretion (see table at right).
		When Cushing's syndrome is due to a tumor in the adrenal cortex, increased negative feedback inhibition has the effect of decreasing secretion of tropic hormones.
	courses.washington.edu /conj/bess/feedback/newfeedback.html (751 words)

	Feedback inhibition control by lysine and threonine - Branched chain amino acid and lysine biosynthesis - HORT640 - ...
		Feedback inhibition control by lysine and threonine - Branched chain amino acid and lysine biosynthesis - HORT640 - Metabolic Plant Physiology - Department of Horticulture and Landscape Architecture - Purdue University
		These two amino acids completely inhibit the activity of all AK isoenzymes, resulting in methionine starvation.
		Homoserine dehydrogenase (HSD) [EC 1.1.1.3] activity could play only a secondary role in limiting threonine synthesis in plants, because in contrast to bacteria, plants contain at least one HSD isoenzyme that is insensitive to feedback inhibition (Galili, 1995).
	www.hort.purdue.edu /rhodcv/hort640c/branch/br00008.htm (374 words)

	branchedpathreg (Site not responding. Last check: 2007-10-17)
		Isofunctional enzyme inhibition: same as above except that have two enzyme 1's, that catalyze the same reaction, but each sensitive to feedback inhibition by different endproducts.
		Cumulative feedback inhibition: In cumulative feedback have only one enz 1, and two allosteric sites, but as each endproduct binds activity of enzyme is reduced by 1/2.
		Inhibition plus activation: Not all endproducts are negative feedback inhibitors.
	faculty.washington.edu /jclara/410/Outlines/branchedpathreg.htm (193 words)

	13. Enzymes and Enzyme Complexes (Site not responding. Last check: 2007-10-17)
		Allosteric inhibitions are frequently exerted by products of metabolic pathways and may be of great physiological significance by permitting precise control of the reaction by feedback inhibition (end product inhibition).
		The pathway is branched and its regulation includes feedback inhibition of the initial reaction before the branching point, as well as inhibition of the two separate branches independently.
		The enzyme activities were assayed as follows: one of the fractions that is unable to respond to the negative effector (fraction 6) was mixed in the presence of CTP with the fraction to be sampled for inhibitory activity.
	www.albany.edu /~abio304/text/13part2.html (5902 words)

	Chapter11 Transparencies
		Inhibition of the enzymes at the branchpoints causes intermediate to accumulate, and this intermediate then feeds back to inhibit the enzyme catalyzing the first commited step for the entire pathway.
		Enzyme is feedback inhibited by 9 small molecules, most of which obtain nitrogen from glutamine: carbamoyl-phosphate, glucosamine-6-phosphate, tryptophan, histidine, alanine, serine, glycine, CTP and AMP.
		In nitrogen-limited conditions, GS is present in higher amounts in cells, is deadenylylated, and less sensitive to feedback inhibition.
	www.bmb.psu.edu /courses/micro401/Ch11Nt.htm (2079 words)

	Methoxyestrogens Exert Feedback Inhibition on Cytochrome P450 1A1 and 1B1 -- Dawling et al. 63 (12): 3127 -- Cancer ...
		Inhibition assay of CYP1A1 with alternate substrates 2-MeOE2 and E2-d4.
		Inhibition assay of CYP1B1 with alternate substrates 2-MeOE2 and E2-d4.
		This feedback inhibition reduces the formation of estradiol semiquinones (E2–2,3SQ and E2–3,4SQ) and quinones (E2–2,3Q and E2–3,4Q), which may form quinone-DNA adducts or cause oxidative DNA damage by reactive oxygen species arising during redox cycling.
	cancerres.aacrjournals.org /cgi/content/full/63/12/3127 (3634 words)

	Enzymes
		The inhibition is called competitive because if you increase the ratio of succinic to malonic acid in the mixture, you will gradually restore the rate of catalysis.
		In the case if feedback inhibition and precursor activation, the activity of the enzyme is being regulated by a molecule which is not its substrate.
		In feedback inhibition, the allosteric effect lowers the affinity of the enzyme for its substrate.
	users.rcn.com /jkimball.ma.ultranet/BiologyPages/E/Enzymes.html (1853 words)

	Human glucocorticoid feedback inhibition is reduced in older individuals: evening study. (Site not responding. Last check: 2007-10-17)
		To confirm this finding and to determine whether aging-related changes in feedback responsiveness are exaggerated near the time of the circadian nadir in adrenocortical secretion, we performed a similar study in the evening.
		When corrections were made for differences in circulating cortisol concentrations achieved among age and gender subgroups, feedback inhibition of ACTH was found to be significantly greater in young than in old subjects of both genders.
		Our studies support the hypothesis that glucocorticoid responses to stress in aging individuals are likely to be prolonged due to blunted and delayed inhibition of ACTH secretion, thus increasing the total exposure to glucocorticoids.
	www.arclab.org /medlineupdates/abstract_11158007.html (242 words)

	Density-Dependent Feedback Inhibition of Oligodendrocyte Precursor Expansion -- Zhang and Miller 16 (21): 6886 -- ...
		Density-Dependent Feedback Inhibition of Oligodendrocyte Precursor Expansion -- Zhang and Miller 16 (21): 6886 -- Journal of Neuroscience
		The inhibition of precursor expansion was cell-type-specific and dependent on the presence of oligodendrocyte lineage cells.
		We propose that this density-dependent feedback inhibition of oligodendrocyte precursor expansion may play a primary role in regulating the number of oligodendrocytes in the developing spinal cord.
	www.jneurosci.org /cgi/content/short/16/21/6886 (502 words)

	Feedback inhibition of the cholesterol biosynthetic pathway in patients with Smith-Lemli-Opitz syndrome as demonstrated ... (Site not responding. Last check: 2007-10-17)
		Feedback inhibition of the cholesterol biosynthetic pathway in patients with Smith-Lemli-Opitz syndrome as demonstrated by urinary mevalonate excretion -- Pappu et al.
		Feedback inhibition of the cholesterol biosynthetic pathway in patients with Smith-Lemli-Opitz syndrome as demonstrated by urinary mevalonate excretion
		The long-term effects of dietary cholesterol upon the plasma lipids, lipoproteins, cholesterol absorption, and the sterol balance in man: the demonstration of feedback inhibition of cholesterol biosynthesis and increased bile acid excretion.
	www.jlr.org /cgi/content/full/43/10/1661 (4707 words)

	Effect of Overall Feedback Inhibition in Unbranched Biosynthetic Pathways -- Alves and Savageau 79 (5): 2290 -- ...
		The horizontal arrows represent biochemical reactions, whereas the vertical arrows represent inhibitory feedback interactions.
		feedback inhibition is present and that the concentration of final
		be smaller in pathways with overall feedback inhibition.
	www.biophysj.org /cgi/content/full/79/5/2290 (6947 words)

	Irreversible Reactions in Metabolic Simulations
		The four versions of the model thus include all possibilities necessary for deciding whether taking proper account of feedback inhibition is more or less important than allowing for the small degree of reversibility in a reaction with a very large equilibrium constant.
		If allowing for this small degree of reversibility is trivial, whereas ignoring a feedback loop is crucial, we should expect the results from models 1a and 1b to resemble one another and to differ from those from models 1c and 1d.
		If there is a feedback loop that allows communication around an irreversible step then the behaviour is virtually identical whether the reversibility of the nearly irreversible step is allowed for or not.
	bip.cnrs-mrs.fr /bip10/stellen.htm (2238 words)

	[No title] (Site not responding. Last check: 2007-10-17)
		Model of Feedback Inhibition using a metabolic pathway to illustrate this concept.
		The biosynthesis of amino acids is often regulated by Feedback Inhibition (in those organisms that make amino acids since not all do).
		This is of course related to non-competitive inhibition of the enzyme, but we discussed only the case where the enzyme loses activity but can still bind its substrate normally, which we called a classic non-competitive inhibitor.
	www.bio.mtu.edu /campbell/401lec17p4.html (462 words)

	Nitric oxide exerts feedback inhibition on EDHF-induced coronary arteriolar dilation in vivo -- Nishikawa et al. 279 ...
		Nitric oxide exerts feedback inhibition on EDHF-induced coronary arteriolar dilation in vivo -- Nishikawa et al.
		Nitric oxide exerts feedback inhibition on EDHF-induced coronary arteriolar dilation in vivo
		that arteriolar dilation to BK was inhibited in the presence of
	ajpheart.physiology.org /cgi/content/full/279/2/H459 (4596 words)

	Dynamics of Electrosensory Feedback: Short-Term Plasticity and Inhibition in a Parallel Fiber Pathway -- Lewis and ...
		The indirect feedback pathway of the ELL consists of PFs arising from cerebellar granule cells in the eminentia granularis
		Feedback pathways are prevalent at all levels of the nervous system and they appear to play diverse functional roles.
		Berman NJ, and Maler L. Inhibition evoked from primary afferents in the electrosensory lateral line lobe of the weakly electric fish (Apteronotus leptorhynchus).
	jn.physiology.org /cgi/content/full/88/4/1695 (7756 words)

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