Degeneration secondary

Olah et al. (1976a) continued the studies of potentially degenerate secondary cyclopropylcarbinyl cations incorporated into polycyclic carbon skeletons with the preparation of 2,4-dehydro-5-homoadamantyl cation [144 R = H]. This ion and two 5-substituted tertiary derivatives were prepared from the corresponding 5-R-2,4-dehydrohomoadamantyl alcohols [145 R = H, CH3... 

In single pulse and spin-echo spectra of normal human and animal plasma, there are few resonances in the chemical shift range to high frequency of 85.3 when measured in the pH range 3 to 8.5. However, on acidification of the plasma to pH <2.5, resonances from histidine and phenylalanine become detectable. In plasma from patients with Wilson s disease (liver degeneration secondary to an inborn error of caeruloplasin/copper metabolism), weak signals from histidine and tyrosine are seen in spin-echo spectra at pH 7.6, but... 

Bevacizumab Age-related macular degeneration, secondary to choroidal... 

The analogous equilibrium isotope effects in two-fold degenerate secondary cyclopropylmethyl cations [8] (Koch, 1985) and [128] (Schneider, 1985) have also been investigated by nmr spectroscopy. The results are similar and confirm the interpretation of the isotope effect in cation [9]. 

Rodrigues de Cerqueira AC, Costa dos Reis M, Novis FD, Bezerra JMF, Canedo de Magalhaes G. Cerebellar degeneration secondary to acute lithium carbonate intoxication. Arq Neuropsiquiatr 2008 66(3-A) 578-80. 

Isotope effect between the HH, HD, DH, and DD isotopomers was used as an important tool to determine the mechanism of the double-proton transfer. For concerted degenerate double-proton transfers in the absence of tunneling, the rule of the geometrical mean (RGM) should hold in good approximation, which states that /chh/ hd = /cdh/ dd-Tunneling may lead to a breakdown of this rule but the relation /chh > hd = dh > dd should remain valid. In the absence of secondary isotope effects the relation /chh HD = DH = 2 /cdd sliould liold for a stepwise pathway, even if tunneling is involved. 

What concerns us here are three topics addressing the fates of bromonium ions in solution and details of the mechanism for the addition reaction. In what follows, we will discuss the x-ray structure of the world s only known stable bromonium ion, that of adamantylideneadamantane, (Ad-Ad, 1) and show that it is capable of an extremely rapid degenerate transfer of Br+ in solution to an acceptor olefin. Second, we will discuss the use of secondary a-deuterium kinetic isotope effects (DKie) in mechanistic studies of the addition of Br2 to various deuterated cyclohexenes 2,2. Finally, we will explore the possibility of whether a bromonium ion, generated in solution from the solvolysis of traAU -2-bromo-l-[(trifluoromethanesulfonyl)oxy]cyclohexane 4, can be captured by Br on the Br+ of the bromonium ion, thereby generating olefin and Br2. This process would be... 

Secondary cell cultures, which can be prepared by taking cells from some types of primary culture, usually those derived from embryonic tissue, dispersing them by treatment with trypsin and inoculating some into a fresh batch of medium. A limited number of subcultures can be performed with these sorts of cells, up to a maximum of about 50 before the cells degenerate. 

Low concentrations of solubilised jS-albumin inhibit ACh release in slices from rat hippocampus and cortex areas which show degeneration in AzD, but not in slices from the striatum which is unaffected. While not totally specific to ACh, since some inhibition of NA and DA and potentiation of glutamate release have been reported, this effect is achieved at concentrations of A/i below those generally neurotoxic. Since jS-amyloid can inhibit choline uptake it is also possible (see Auld, Kar and Quiron 1998) that in order to obtain sufficient choline for ACh synthesis and the continued function of cholinergic neurons, a breakdown of membrane phosphatidyl choline is required leading to cell death (so-called autocannibalism), /i-amyloid can also reduce the secondary effects of Mi receptor activation such as GTPase activity... 

From examination of Fig. 11, it is inferred that the zn-n state is less reactive, and a biradical mechanism should be the major reaction pathway. The degenerate stabilizing perturbation of the bonding levels is missing, and concerted pathways are not likely if stabilized only by much smaller secondary interactions. If the hi-n singlet state could be intercepted in some way, the all-suprafacial concerted mechanism would be favored [K(ji ) -0(jr )] relative to the suprafacial-antarafacial mechanism [O(tt) - -K( i )]. 

Other diseases with disruptions in neurofilament organization include diabetic neuropathy and Charcot-Marie-Tooth disease. For these diseases, the disruption of neuro filaments may be a secondary effect as in the case of trembler axons or a direct effect. For example, some forms of Charcot-Marie-Tooth peripheral neuropathy result from mutations in a neurofilament subunit [22, 43]. In most cases, neuronal degeneration is an eventual consequence, but neuronal function may be impaired prior to substantial loss of neurons. Generally, disruptions of neurofilaments have the most severe consequences in large motor neurons, which is consistent with the fact that the largest neurons have the highest levels of neurofilament expression. 

Wallerian degeneration is the secondary disruption of the myelin sheath and axon distal to the injury 518... 

The cyclopentyl cation (39) undergoes a rapid degenerate rearrangement which can be frozen out at cryogenic temperatures as shown by solid state CPMAS 13C NMR spectra.57 MP2/6-31G(d,p) calculations show that cyclopentyl cation has a twisted conformation 4058 in which the axial hydrogens are bend toward the carbocation center. This is due to the pronounced geometrical distortion caused by the hyper-conjugative interaction of the /i-cr-C-H-bond with the formally vacant 2pz-orbital at the C+ carbon of this secondary carbocation. 

Recently, this view of secondary a-deuterium KIEs has had to be modified in the light of results obtained from several different theoretical calculations which showed that the Ca—H(D) stretching vibration contribution to the isotope effect was much more important than previously thought. The first indication that the original description of secondary a-deuterium KIEs was incorrect was published by Williams (1984), who used the degenerate displacement of methylammonium ion by ammonia (equation (4)) to model the compression effects in enzymatic methyl transfer (SN2) reactions. 

Other Systemic Effects. Endocrine lesions related to 1,2-dibromoethane exposure were reported in the NCI (1978) gavage bioassay. These consisted of adrenal cortical cell degeneration in a small number of exposed male and female Osborne-Mendel rats. The possibility exists that this adrenal change represents a secondary (stress-related) effect rather than a primary effect of 1,2-dibromoethane exposure. 

In the chronic gavage study of 1,2-dibromoethane conducted by NCI (1978), high-dose male Osborne-Mendel rats and B6C3P mice developed testicular atrophy. Because study animals had high compound- and gavage- related mortality and early onset of forestomach squamous cell carcinomas, it is difficult to determine from these results whether testicular atrophy (degeneration) was a primary (compound-induced) or secondary nonspecific) event. 

Menkes disease Deficient cross-linking secondary to functional copper deficiency Depigmented (steely) hair Arterial tortuosity, rupture Cerebral degeneration Osteoporosis, anemia... 

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