Role of perfusion computed tomography in assessing submandibular gland radiochemotherapy-induced injury.

OBJECTIVE: We aimed to detect changes in the volume and perfusion parameters of the submandibular glands during and after radiochemotherapy. STUDY DESIGN: Twelve patients underwent computed tomography (CT) and perfusion CT before radiochemotherapy, after 40 Gy, after 70 Gy, and 3 months after radiochemotherapy. Submandibular gland volume, blood volume, permeability surface area product, and blood flow were quantified. RESULTS: Submandibular gland volumes during and after therapy were significantly lower compared with the baseline value (P < .001). Blood volume, blood flow, and permeability surface area product values showed statistically significant reduction during and 3 months after therapy. A significant linear correlation was found between changes in submandibular gland volume and of the perfusion parameter blood volume in the period between baseline and 3 months after therapy (P = .012; RP = -0.697). CONCLUSIONS: Changes in submandibular gland volume and dynamics of perfusion parameters imply that radiation-induced injury of submandibular glands develops early during radiochemotherapy.

Autoxidation of hydrazones. Some new insights.

Autoxidation of hydrazones is a generally occurring reaction, leading mostly to the formation of alpha-azohydroperoxides. All structural kinds of hydrazones, having at least one hydrogen atom on nitrogen, are prone to autoxidation; however, there are marked differences in the rate of the reaction. Hydrazones of aliphatic ketones are 1-2 orders of magnitude more reactive than analogous derivatives of aromatic ketones. Even less reactive are the hydrazones of chalcones, which function also as efficient inhibitors of autoxidation of other hydrazones. These differences can be attributed to the reduction of the rate of the addition of oxygen to a hydrazonyl radical, which is a reversible reaction. In the case of conjugated ketones, it becomes endothermic, making this elementary step slow down and the chain termination reactions become important. Substituents influence the stability of hydrazonyl radicals and, consequently, the bond dissociation energies of the N-H bonds. In acetophenone phenylhydrazones, the substituents placed on the ring of hydrazine moiety exhibit a higher effect (Hammett rho = -2.8) than those on the ketone moiety (rho = -0.82), which denotes higher importance of the structure with spin density concentrated on nitrogen in delocalized hydrazonyl radical. Electronic effects of the substituents also affect the transition state for the abstraction of hydrogen atom by electrophilic peroxy radicals; NBO analysis display a negative charge transfer of about 0.4 eu from hydrazone to a peroxy radical in the transition state.

Direct conversion of bromohydrins to ketones by a free radical elimination of hydrogen bromide.

Secondary beta-bromo alcohols can be transformed directly to ketones in very good yields by a free radical process. Tertiary beta-bromo alcohols do not react while the primary ones are transformed to aldehydes in lower yields. The reaction involves an abstraction of a hydrogen atom alpha to an OH group, followed by elimination of the bromine atom and subsequent tautomerization of an enol to a ketone.