Activity of the hexose monophosphate shunt in the outer segments of normal and dystrophic rat retinae

The activity of the hexose monophosphate shunt in the outer segments of retinae from normal rats and from rats with retinal dystrophy has been measured cytochemically. The 1-week-old dystrophic retinae has less activity than retinae from 1-week-old normal animals. In rats of 2 weeks and older, there was more pentose shunt activity in the dystrophic than in the normal retinae. This difference between the normal and dystrophic retinae increased with age. The relationship of these findings to other biochemical effects observed in the dystrophic retina are discussed with regard to the progressive nature of the dystrophy.     

Effects on fracture healing of an antagonist of the vitamin K cycle

Summary The anticoagulant, dicumarol, inhibits the vitamin K cycle by blocking the conversion of the vitamin K epoxide. The effects of dicumarol on ossification have been tested by feeding it to rats in which a closed fracture of the metatarsals had been induced; the effects were studied up to 12 days postfracture. At 12 days, treatment with dicumarol caused a highly significant decrease in the amount of bone produced, without affecting the total size of the callus. Quantitative cytochemistry of unfixed, undemineralized sections showed that dicumarol also markedly affected the periosteal activities of glucose 6-phosphate dehydrogenase and of alkaline phosphatase in the first 2 mm from the fracture measured at 3 and 5 days postfracture when normally, new bone is first formed. In contrast, dicumarol had little effect on these activities in the fully formed callus.     

Mitochondrial oxidative activity in human rheumatoid synovial lining cells.

The activities of two mitochondrial enzymes, succinate dehydrogenase and cytochrome oxidase, have been measured by quantitative cytochemistry and microdensitometry in the synoviocytes of rheumatoid and non-rheumatoid synovial lining cells. Although both tended to be higher in the former, there was no statistically significant difference in the activities of either enzyme in these tissues. However, when cytochrome oxidase activity was measured without exogenous cytochrome c, the activity in the rheumatoid synoviocytes was highly significantly elevated. It is suggested that these findings may indicate only that the cytochrome c-cytochrome oxidase complex in the rheumatoid cells is more stable, possibly because of the increased availability of phospholipids in these cells.     

Agaridoxin: A fungal catecholamine which acts as an alpha 1 agonist of mammalian hypothalamic adenylate cyclase

Agaridoxin, a catecholamine isolated from mushrooms, and 4 synthetic analogues cause activation of adenylate cyclase in the presence of guanylyl imidodiphosphate (Gpp(NH)p) in membrane particles prepared from rat hypothalamus. These compounds also activate adenylate cyclase preparations from rat kidney, liver and cerebral cortex. In the presence of tyrosinase, these compounds are readily oxidized to quinones which lack agonist activity. Studies with selective adrenergic blockers suggest that agaridoxin acts at an alpha 1-type receptor. Agaridoxin-mediated adenylate cyclase stimulation is most effectively antagonized by WB-4101 and phenoxybenzamine, while propranolol and yohimbine are without inhibitory effect. Agaridoxin and the alpha 1 agonist methoxamine inhibited the binding of [3H]WB-4101 in rat hypothalamic and cerebral cortical membranes. The values of Ki for both compounds are lower than that of norepinephrine. The agaridoxin analogue, 4-aminocatechol hydrochloride, is a more effective and potent adenylate cyclase activator than agaridoxin or methoxamine.     

Application of image-guided surface coil P-31 MR spectroscopy to human liver, heart, and kidney

Localized phosphorus-31 magnetic resonance (MR) spectroscopy in humans has previously been accomplished with surface coils by means of depth-resolved surface coil spectroscopy or rotating frame experiments, in which the extent of tissue sampled critically depends on surface coil placement. The authors' goal was to modify the surface coil image-selected in vivo spectroscopy (ISIS) experiment to accomplish three-dimensional volume selection through application of selective pulses in the presence of B0 gradients. Advantages of ISIS include the ability to use proton images to define the volume of interest (VOI) and reduced dependence on exact positioning of the surface coil. However, rapid replication of the surface coil ISIS experiment can cause spectral contamination from signals originating outside the VOI. A modified version of the ISIS experiment was developed to alleviate contamination under conditions of rapid replication. Applications of localized P-31 MR spectroscopy for observation of high-energy phosphorus metabolites are presented in human liver, heart, and transplanted and normal kidney.