PubMed · 6855601
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J K Inman, R N Perham, G C DuBois, E Appella. 1983. Amidination.. https://doi.org/10.1016/s0076-6879(83)91051-0
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The aim of this study was to investigate oxidative cell injury in rat thymocytes under conditions of radical generation exterior to the cell utilizing the thermolabile azocompound 2,2'-azobis(2-amidinopropane) dihydrochloride to generate peroxyl radicals at a constant and reproducible rate. This initiator, being water-soluble and endowed with a positive charge, is suitable for studies on oxidative damage of biomembranes induced in the external water environment. The relationship between cell viability, lipid and thiol oxidation and chain-breaking antioxidant depletion was studied. During the first hour of treatment cell viability decreased slightly, protein sulfhydryl groups were consumed slowly and no significant production of conjugated dienes occurred. After 90 min of incubation, when thymocyte permeability started to increase, the concentration of alpha-tocopherol decreased gradually, significant changes of polyunsaturated fatty acids occurred and a rapid phase of thio oxidation commenced. It can be concluded that, under conditions of an exogenous oxidant challenge, initially the cell membrane provides a physical barrier to the entrance of radicals to the thymocyte. When peroxyl radicals gain access to the membrane and the molecular barrier begins to disorganize, the oxidizable cellular components become susceptible to massive attack.
We investigated the role of oxygen free radicals in the modulation of glyceraldehyde-3-phosphate dehydrogenase binding to the erythrocyte membrane. Previous studies have demonstrated that in vitro tyrosine phosphorylation of Band 3 prevents the binding of various glycolytic enzymes to its cytoplasmic domain. Since these enzymes are inhibited in their bound state, the functional consequence of Band 3 tyrosine phosphorylation in red blood cells should be to increase glycolysis. To generate free radicals, we used an azo-compound, the hydrophilic 2,2'-azobis(2-amidinopropane) hydrochloride, which, at 37 degrees C and in the presence of oxygen, decomposes and produces peroxyl radicals at a constant rate. The reaction of peroxyl radicals with intact red cells induced a time-dependent loss of the membrane-bound glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase, associated with a concomitant decrease in enzyme activity. At the same time, Band 3 was phosphorylated in tyrosine. These results were completely reversible in plasma after removal of the oxidative stress. The peroxyl radicals also enhanced the production of lactate in intact cells. Our data reveal a powerful mechanism of erythrocyte metabolic regulation that can boost or reduce energy production in times of special need such as during a free radical attack.
To determine the origin of the calbindin-containing laminar nerve endings in the myenteric ganglia of the rat esophagus, retrograde tracing experiments combined with immunohistochemistry using an antibody for calbindin were carried out. After Fast blue was injected into the cervical portion of the esophagus, labeled neurons were found bilaterally in the nodose ganglion and dorsal root ganglia of C1 to T3. 80% of the total neurons in the nodose ganglion and 20% of those in the dorsal root ganglia showed calbindin immunoreactivity. Moreover, 79% of Fast-blue-labeled neurons found in the nodose ganglion and 18% of those in the dorsal root ganglia were immunoreactive for calbindin. These results suggest that the calbindin antibody we used is useful as a marker for identifying esophageal vagal afferents derived from the nodose ganglion. The calbindin-immunoreactive nerve fibers forming the laminar endings in the myenteric ganglia of the rat cervical esophagus are mainly derived from sensory neurons in the nodose ganglion and partly derived from those in the cervical and upper thoracic dorsal root ganglia. Calbindin-containing laminar nerve endings may be related to mechanoreceptors in the esophagus.