Newsgroup: it.scienza.biologia
Titolo: La ricerca di Purdey e Mucca pazza

Non so quanti di voi ne abbiano avuto notizia. Si tratta di un
ricercatore indipendente che avrebbe individuato come una delle cause
della BSE sia la sostituzione nel prione del rame col manganese, dovuto
ad un'infelice concomitanza di fattori esterni.
In quanto ho letto, è riportato che un'equipe di biochimici di Cambrige
avrebbe condotto uno studio che conferma quest'ipotesi.
Mi sapete dare ulteriori dettagli circa questa ricerca?
Grazie,
  All

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TITLE:  Ecosystems supporting clusters of sporadic TSEs demonstrate
excesses of the radical-generating divalent cation manganese and
deficiencies of antioxidant co factors Cu, Se, Fe, Zn. Does a foreign
cation substitution at prion protein's Cu domain initiate TSE? 
AUTHORS:  Purdey M 
AUTHOR AFFILIATION:  High Barn Farm, Elworthy, Taunton, UK. 
SOURCE:  Med Hypotheses 2000 Feb;54(2):278-306 
CITATION IDS:  PMID: 10790765 UI: 20253832 
ABSTRACT:  Analyses of food chains supporting isolated clusters of
sporadic TSEs (CWD in N Colorado, scrapie in Iceland, CJD in Slovakia)
demonstrate a consistent 2 1/2+ fold greater concentration of the
pro-oxidant divalent cation, manganese (Mn), in relation to normal
levels recorded in adjoining TSE-free localities. Deficiencies of the
antioxidant co factors Cu/Se/Zn/Fe and Mg, P and Na were also
consistently recorded in TSE foodchains. Similarities between the
clinical/pathological profile of TSEs and Mn delayed
psycho-neurotoxicity in miners are cited, and a novel theory generated
which suggests that sporadic TSE results from early life dependence of
TSE susceptible genotypes on ecosystems characterised by this specific
pattern of mineral imbalance. Low Cu/Fe induces an excessive
absorption of Mn in ruminants and an increased oxidation of Mn2+ into
its pro oxidant species, Mn3+, which accumulates in mitochondria of
CNS astrocytes in Mn SOD deficient genotypes. Deficiencies of
scavenger co factors Cu/Zn/Se/Fe in the CNS permits Mn3+ initiated
chain reactions of auto-oxidant mediated neuronal degeneration to
proliferate, which, in turn, up-regulates the expression of the
Cu-metalloprotein, prion protein (PrP). Once the rate of PrP turnover
and its demand for Cu exceeds the already depleted supply of Cu within
the CNS, PrP can no longer bind sufficient Cu to maintain its
conformation. Mn3+ substitutes at the vacated Cu domain on PrP, thus
priming up a latent capacity for lethal auto-oxidative activity to be
carried along with PrP like a 'trojan horse'; where Mn 3+ serves as
the integral 'infectious' transmissible component of the misfolded
PrP-cation complex. The Mn overactivation of concanavalin A binding to
glycoprotein and Mn-initiated autoxidation results in a diverse
pathological profile involving receptor capping,
aggregation/modification of CNS membrane/cytoskeletal proteins. TSE
ensues. The BSE/nv CJD strain entails a 'synthetic' induction of the
same CNS mineral disturbance, where 'in utero' exposure to
Cu-chelating insecticides/Mn supplements accelerates the onset of a
more virulent 'strain' of adolescent TSE. Copyright 2000 Harcourt
Publishers Ltd. 
 

 
Ti ringrazio per la celerità della risposta. Io cercavo di sapere
qualcosa anche in merito allo studio dei ricercatori di Cambridge.
Grazie,
  All

Non facciamo confusione,il Prione cioé la proteina prionica Prpc(normale)ha
la funzione di legare il rame nel cervello;ovvero funge da shuttle per gli
ioni rame destinati a legarsi agli enzimi che prevengono i danni
ossidativi.Lo ione rame é stato dimostrato legarsi alla proteina
sana.Siccome la proteina prionica non sana,Prpsc ha molti foglietti beta al
posto delle alfa eliche(di quella normale) ecco che questo potrebbe spiegare
il non legame con il rame .