The Lability and Relative Reactivities of Organic Radicals

Studies have been made of the rates of many reactions involving organometallic compounds, by means of the color test of Gilman and Schulze. These rate studies comprise: (1) the relative reactivities of a variety of compounds towards a typical organometallic compound; (2) the relative reactivities of a series of related compounds like nitriles or azo compounds with an organometallic compound; (3) and, the differences in rate of reaction of a series of organometallic compounds towards other compounds.. The same method has been used in a study of the effect of concentration, temperature and catalysts on reaction rates. Also, it has been shown to be of service in a study of the mechanism of reactions, like the two-stage conversion of esters to ketones to tertiary alcohols; and the lability and relative electronegativities of radicals

G-proteins coupled to phosphoinositide hydrolysis in the cochlear and vestibular sensory epithelia of the rat are insensitive to cholera and pertussis toxins

In the cochlear (CSE) and vestibular sensory epithelia (VSE), phosphoinositides are hydrolyzed in response to stimulation of phospholipase C (PLC) by cholinergic muscarinic and purinergic P2y agonists. Such receptor-mediated activation of PLC is expected to be coupled through guanine nucleotide-binding proteins (G-proteins). Although several classes of G-proteins have been identified in the inner ear, nothing is known about the type of G-proteins associated with the phosphoinositide second messenger system in CSE and VSE. Phosphoinositide hydrolysis was determined by the release of radiolabeled inositol phosphates (InsPs). Ten mM NaF plus 10 [mu]M AlCl3 increased basal InsPs accumulation 2-fold in both CSE and VSE of the rat. Release of InsPs was also enhanced by guanosine 5'-O-(3-thiotriphosphate) (GTP-[gamma]-S) in saponin-permeabilized tissues. Furthermore, release of InsPs stimulated by both carbamylcholine (CCh) and adenosine 5'-O-[3-thiotriphosphate](ATP-[gamma]-S) was significantly inhibited by 100 [mu]M guanosine 5'-O-[2-thiodiphosphate](GDP-[beta]-S). These results strongly suggest the involvement of G-proteins in the receptor-PLC coupling in CSE and VSE. ADP-ribosylation in membrane fractions of CSE and VSE in the presence of cholera toxin (CTX) or pertussis toxin (PTX) indicated the existence of Gs- and Gi-type G-proteins. However, neither CTX nor PTX affected basal or agonist-stimulated release of InsPs. These observations suggest that muscarinic and P2y purinergic receptors are coupled to PLC via CTX- and PTX-insensitive G-proteins in CSE and VSE.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31661/1/0000595.pd

Note sur l'autoxydation chimiluminescente des réactifs de Grignard

SCOPUS: ar.jinfo:eu-repo/semantics/publishe