Effects of isoflurane and xenon on Ba2+-currents mediated by N-type calcium channels.

BACKGROUND: Isoflurane and xenon are inhalation general anaesthetics with differing clinical profiles and contrasting synaptic actions. Both agents have been shown to depress excitatory synaptic responses. Whether this is via pre-synaptic or post-synaptic mechanisms has not been determined clearly. N-type calcium channels are a putative pre-synaptic target for these agents. We tested whether N-type calcium channels were sensitive to isoflurane and xenon and whether there was any stereoselectivity in the effect of isoflurane. METHODS: We used patch-clamp electrophysiology on isolated HEK293 cells stably expressing N-type calcium channels to investigate the effects of isoflurane and xenon on barium currents mediated by N-type calcium channels. RESULTS: Racemic isoflurane caused a concentration-dependent reduction (11-35%) in the peak current through the N-type channels in the concentration range 0.15-1.22 mM. In the clinically relevant concentration range the inhibition was small. At an isoflurane concentration of 0.31 mM (equivalent to 1 MAC), the peak N-type current was inhibited by 14 (1)%. The optical isomers of isoflurane were found to be equally potent at inhibiting currents through N-type channels. The inert gas anaesthetic xenon was found to have no measureable effect on N-type channels at a concentration of 3.4 mM (approximately 1 MAC). CONCLUSIONS: These results suggest that N-type calcium channels are not the targets mediating general anaesthesia with these two inhalation agents.

Clinical evaluation of occlusal glass ionomer, resin, and amalgam restorations.

The purpose of the study was to evaluate four materials (a glass ionomer (polyalkenoate) silver cermet, two composite resin restoratives and a high copper content dental amalgam) placed in either conventional Class I cavities or in modified odontotomy-enameloplasty-sealant (OES) fissure preparations. One experienced operator inserted 438 occlusal. Class I restorations in the posterior permanent teeth of 124 patients in a private dental practice. Restorations were assessed for bulk loss of material, surface voids and cracking, restoration margin fractures and staining, and surface staining and roughness, by using colour transparencies taken at baseline and at recalls for up to 3 years. The glass ionomer cermet was the most difficult material to handle and also gave the least satisfactory clinical result. Loss of material and surface voids were common in the cermet restorations with surface cracking or crazing being seen in 11.4 per cent of the restorations, especially in the larger, conventional Class I preparations. One posterior resin was more viscous and difficult to handle than the other resin and exhibited more surface voids. The amalgam alloy was used in Class I preparations only and showed more restoration margin fractures and surface staining than did the other three materials. However, there were no unsatisfactory clinical assessments given for either restoration margin fracture and staining, or surface staining and roughness for any of the materials. Patient acceptance of the modified OES fissure preparation was extremely good.

Hyperparathyroidism, hypercalcemia and the otolaryngology head and neck surgeon.

Ability to successfully accomplish parathyroid surgery, as well as to understand the pathophysiology of parathyroid disease and hypercalcemia, is essential to the Otolaryngology Head and Neck surgeon (who must treat parathyroid disease), because of the more frequent identification of parathyroid adenomata and parathyroid hyperplasia (with their inherent hypercalcemia). Today many more cases are recognized because of hypercalcemia identified by now routine multiphasic biochemical screening tests. The etiology of hypercalcemia is discussed in considering the differential diagnosis of pseudohyperparathyroidism, and true hyperparathyroidism of parathyroid hyperplasia and parathyroid adenomata. Pseudohyperparathyroidism, secondary to ectopic elaboration of parathormone-like substance is treated medically. Parathyroid hyperplasia can sometimes be controlled medically, but the only definitive treatment for hyperplasia and parathyroid adenomata is surgery, to the extent indicated, in these often critically ill patients with this multisystem disease. Medical, as well as surgical treatment, is described. A patient is described who demonstrated in a slowly moving montage all the classic history and findings of severe hyperparathyroidism in successive phases to her ultimate demise, manifesting neurological, renometabolic , skeletal, cardiovascular and gastrointestinal multisystem symptoms which are described. The complete relief of the acute symptoms following excision of a massive parathyroid adenomata is described and the spectacular pathologic specimen is demonstrated. This patient's course is compared with that of a typical case of pseudohyperparathyroidism.

Squamous cell carcinoma arising in thyroglossal duct remnant cyst epithelium.

The extremely rare occurrence of invasive squamous cell carcinoma arising from normal epithelial lining of a thyroglossal duct remnant cyst is documented by demonstrating the histopathologic transition from normal squamous epithelium to squamous cell carcinoma. The requirements that must be fulfilled to accept a lesion as arising de novo from the epithelial lining are outlined, and all requirements are achieved. The lesion is differentiated from the less rare papillary or papillary-follicular adenocarcinoma of residual thyroid tissue of the thyroglossal duct tract remnants. This is the sixth report in the world literature of invasive squamous cell carcinoma arising from benign thyroglossal remnant squamous epithelium, and the second demonstrating the transition from normal squamous epithelium to invasive squamous cell carcinoma.

Severe complication of a Zenker's diverticulum with endoscopic diverticulotomy rescue.

Persistent pharyngoesophageal obstruction precipitated by lodgement of a foreign body in a Zenker's diverticulum, with abscess formation, was successfully treated by endoscopic diverticulotomy. The symptoms and pathogenesis of Zenker's diverticula are fully described, emphasizing the importance of the cricopharyngeus and party wall in its development and relentless progress. Transcutaneous resection of diverticula is reviewed. Detailed description of the technique of endoscopic diverticulotomy is outlined. The rationale and indications for the endoscopic approach are delineated.

Occult medullary carcinoma of thyroid: an unusual clinical and pathologic presentation.

High calcitonin levels noted on a totally healthy 49-year-old man participating in a calcitonin control project led to a presumptive diagnosis of medullary carcinoma. Complete thyroid studies augmented by selective catheterization and quantitative calcitonin studies confirmed the clinical impression of medullary carcinoma. Surgery was recommended and a total thyroidectomy was performed. On gross examination no nodules or tumefactions were palpable. Histopathology showed diffuse C-cell hyperplasia in the midst of which a C-cell tumor and micromedullary carcinoma of the thyroid were found. Morphologically the full spectrum of changes from focal C-cell hyperplasia through the stages of diffuse and nodular hyperplasia to the final development of medullary carcinoma are demonstrated by light and electron microscopy. The patient's postoperative course was benign and for the subsequent three years he had continued asymptomatic with normal calcitonin levels.

Place of total thyroidectomy in rhinolaryngologists' surgical treatment of thyroid disease.

Total thyroidectomy is more frequently performed and is becoming more widely accepted as the treatment of choice for more surgical diseases of the thyroid gland. Improvement in anesthesia, presurgical and post-operative care, as well as more meticulous surgical technique, have decreased the complications associated with this operation. As is demonstrated, morbidity and complications of total thyroidectomy are no more frequent nor severe than when subtotal thyroidectomy is performed. This allows boadening of the indications for total thyroidectomy to include more cases which will be better controlled, but for which total thyroidectomy had been withheld because of the fear of increased morbidity.