Clear cell odontogenic tumor: histochemical and ultrastructural features

Clear cell odontogenic tumor, a rare epithelial jaw lesion of putative odontogenic origin, histologically resembles clear cell adenocarcinomas. Ultrastructural and histochemical features are described and support a non-glandular derivation. The intraosseous neoplasm is characterized by ovoid nests of clear or finely stippled cells with a mature collagenous stroma. These cells are PAS-positive, diastase labile and fail to bind alcian blue. Enzyme histochemical reactions disclose dehydrogenase, non-specific esterase, and acid phosphatase positivity. Fine structural characteristics include plasma membrane microvilli, desmosomes, endoplasmic reticulum, free ribosomes, glycogen rosettes and lysosomes. Many cells exhibit a paucity of cytoplasmic organelles with prominent vacuolization. Centrioles and annulate lamellae are also encountered. Summarily, clinical, radiographic, histochemical and ultrastructural features indicate that this neoplasm is probably of epithelial odontogenic origin with cytodifferentiation emulating glycogen-rich presecretory ameloblasts.     

Outpatient lumbar myelography. Initial results in 79 examinations using a low-dose metrizamide technique

Seventy-nine patients underwent lumbar myelography on an outpatient basis, with a low (3.75 g) dose of metrizamide as the radiocontrast agent and a 25-gauge spinal needle used for lumbar puncture. No patient experienced significant neurotoxicity following the examination; 70.8% (56 of 79) experienced minimal (23%) or no (48%) side effects. Three patients (3.8%) were admitted to the hospital for management of common side effects (headache, nausea/vomiting, back pain). We obtained postmyelographic computed tomographic scans on 96% (76 of 79) of the patients. Our initial results suggest that outpatient lumbar myelography is safe and can be performed with a very acceptable incidence of side effects.     

Deterioration of axonal membranes induced by phenolic pro-oxidants: Roles of superoxide radicals and hydrogen peroxide

The susceptibility of axons to oxidative free radicals generated by pro-oxidant neurotoxins and related compounds was tested by applying the reagents to the disheathed ventral nerve trunk of the crayfish. Electrophysiological characteristics of the axons, including spike amplitude and rise time, were recorded, using intracellular glass microelectrodes. L-Dopa, or L-dopa in the presence of copper-(bis)-histidine (Cu-his), did not change significantly the electrophysiological characteristics of the axon. A 20 mM concentration of 6-hydroxydopamine (6-OHDA), 20 mM 6-OHDA in an anaerobic environment, and 20 mM 6-OHDA with inactivated catalase-SOD accelerated the rate of decline of the spike amplitude with time to 5–8 times the control rate. Simultaneously, parallel increases in rise time and spike duration were observed, consistent with partial depolarization of the resting membrane presumably resulting from increased permeability. Catalase, Superoxide dismutase (SOD), or a mixture of catalase and SOD all afforded partial protection, catalase having the least protective effect, and catalase + SOD the greatest. In contrast, 20 mM H₂O₂, 2 mM H₂O₂, or Cu-his alone did not significantly accelerate deterioration of the axon. Most of the damage results from the interaction of H₂O₂ with O^?₂, rather than from the direct action of either species. p-Hydroxyphenylpyruvate (pHPP) in the presence of Cu-his induced a similar accelerated deterioration of the axon to 4.2 times the control rate. Catalase plus SOD partially protected against this effect, but either enzyme alone was not significantly protective.     

Monozygotic twins discordant for Wiedemann-Beckwith syndrome and the implications for genetic counselling.

A pair of monozygous twins discordant for Wiedemann-Beckwith syndrome is described and published reports reviewed to establish the mode of inheritance. Single gene control seems unlikely and it is proposed that the condition arises from the interaction of "at risk" genes in the fetus and metabolic factors in the mother, which suggests multifactorial control.