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[1.] Sng/Fragment 045 01 - Diskussion
Zuletzt bearbeitet: 2016-05-09 20:12:25 WiseWoman
Fragment, Gesichtet, KomplettPlagiat, SMWFragment, Sajikumar 2005, Schutzlevel sysop, Sng

Typus
KomplettPlagiat
Bearbeiter
SleepyHollow02
Gesichtet
Yes.png
Untersuchte Arbeit:
Seite: 45, Zeilen: 1 ff. (komplett)
Quelle: Sajikumar 2005
Seite(n): 43-44, Zeilen: 43:5-25 - 44:1-10
[Biochemical studies have shown that metabolic stability is reached in slices after 2-4 h, i.e., metabolite levels require 2-4 h to stabilize, and these levels are then maintained for at] least 8 h of incubation (Whittingham et al., 1984). This includes parameters for the activity of enzymes, second messengers, pH, and others. Interestingly, the value for bio-active molecules which stabilizes at a very low level, if strong electrical stimulation was not delivered to the tissue. We suppose that in addition to processes of the acute slice preparation, low electrical activity may result in the delayed but prolonged metabolic stability at a low level after about 4 h if no stimulation is applied to the tissue. This may lead to a reduction of PRPs to an amount near zero if the half life of the proteins is considered with about 2 h. Thus, starting with functional experiments after a preincubation time of 4-5 h may rectify all slices and neurons to a low but very comparable basal metabolic and plasticity level. Tetanization for instance, would then activate a machinery of processes ‘from zero’ (a situation never occurring in behaving animals) which is mechanistically more useful to determine time constants during plastic events, than it would be the case by using freely behaving untreated rats. If in intact rats protein synthesis is blocked by a pharmacological reversible inhibitor a similar situation as in slices can be created revealing similar time constants for early-LTP in vitro. Unfortunately, currently available reversible protein synthesis inhibitors reduce the synthesis of macromolecules in the intact animal for several hours, making this preparation probably unusable to directly study processes of synaptic tagging with the methods used so far. Thus, slice preparations represent an ideal, however also partially artificial model to determine properties of tagging and late-associativity. Although, most of the problems concerning brain slice incubation are known for a long time, most laboratories start their ‘physiological’ slice experiments after a very short preincubation period of even less than 1 h. Knowing the metabolic instability during that period we prolonged the preincubation of hippocampal slices to at least 4 h to obtain comparable [and more physiological results in describing functional processes in slice preparations.] [Seite 43]

Biochemical studies have shown that metabolic stability is reached in slices after 2-4 h, i.e., metabolite levels require 2-4 h to stabilize, and these levels are then maintained for at least 8 h of incubation (Whittingham et al., 1984). This includes parameters for the activity of enzymes, second messengers, pH, and others. Interestingly, the value for bio-active molecules which stabilizes then at a very low level, if strong electrical stimulation was not delivered to the tissue. We suppose that in addition to processes of the acute slice preparation, low electrical activity may result in the delayed but prolonged metabolic stability at a low level after about 4 h if no stimulation is applied to the tissue. This may lead to a reduction of PRPs to an amount near zero if the half life of the proteins is considered with about 2 h. Thus, starting with functional experiments after a preincubation time of 4-5 h, may rectify all slices and neurons to a low but very comparable basal metabolic and plasticity level. Tetanization for instance, would then activate a machinery of processes ‘from zero’ (a situation never occurring in behaving animals) which is mechanistically more useful to determine time constants during plastic events, than it would be the case by using freely behaving untreated rats. If in intact rats protein synthesis is blocked by a pharmacological reversible inhibitor a similar situation as in slices can be created revealing similar time constants for early-LTP in vitro. Unfortunately, currently available reversible protein synthesis inhibitors reduce the synthesis of macromolecules in the

[Seite 44]

intact animal for several hours, making this preparation probably unusable to directly study processes of synaptic tagging with the methods used so far. Thus, slice preparations represent an ideal, however also partially artificial model to determine properties of tagging and late-associativity. Although, most of the problems concerning brain slice incubation are known for a long time, most laboratories start their ‘physiological’ slice experiments after a very short preincubation period of even less than 1 h. Knowing the metabolic instability during that period we prolonged the preincubation of hippocampal slices to at least 4 h to obtain comparable and more physiological results in describing functional processes in slice preparations.

Anmerkungen

Weiter unten, auf der Folgeseite, findet sich zwar ein Hinweis auf Sajikumar and Frey, 2004a, nicht aber auf die hier tatsächlich verwendete Quelle.

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