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THE EFFECT OF BRAIN HOMOGENATES ON DIRECTLY MEASURED WATER FLUXES THROUGH THE PRONOTUM OF PERIPLANETA AMERICANA (1992)
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BibTeX
@MISC{Machin92theeffect,
author = {J. Machin and P. Kestler and G. J. Lampert},
title = {THE EFFECT OF BRAIN HOMOGENATES ON DIRECTLY MEASURED WATER FLUXES THROUGH THE PRONOTUM OF PERIPLANETA AMERICANA},
year = {1992}
}
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Abstract
Measurements of tritiated water (THO) efflux using a cup, ventilated with dry air, attached to the pronotum of Periplaneta, have been used to obtain unam-biguous measurements of the permeability of this structure. Permeability values were 53 % of those determined gravimetrically. Our results support the proposal that cockroach cuticle permeability is hormonally controlled, to the extent that compounds extracted from the brain have been shown to be capable of inducing permeability change over relatively short periods. Fresh brain homogenate injections from hydrated donors produced a 28 % increase in pronotal per-meability in 5 h, rising to 46 % the day after. Injections of saline or of fresh brain extracts from dehydrated and normally hydrated cockroaches had no effect. However, previously frozen brain homogenates, from donors at all hydration levels, significantly increased pronotal permeability the day following injection. The capacity of the pronotum to undergo increases in permeability over relatively short periods was also evident in other experiments. THO permeabili-ties of excised pronotal discs (5.16xl0~l o±0.31xl0~1 0ms"') were an order of magnitude higher than those of intact pronota (O.49xlO~1(l±O.O6x 10"10 ms " ' ). In vivo permeability of pronota of accidentally injured cockroaches was significantly higher than that of uninjured animals, even though the pronota themselves were not damaged. We argue that the observed changes in cuticle permeability are too small primarily to serve osmoregulatory functions. We suggest, instead, that the changes might be associated with the control of secondary processes in which the cuticle is involved and which unavoidably promote water loss.
Keyphrases
pronotum periplaneta americana short period secondary process vivo permeability observed change intact pronota dry air water loss cockroach cuticle permeability fresh brain extract tritiated water osmoregulatory function tho permeabili-ties cuticle permeability injured cockroach excised pronotal disc pronotal permeability pronotal per-meability uninjured animal unam-biguous measurement fresh brain homogenate injection hydrated cockroach hydration level frozen brain homogenate permeability change permeability value
