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High-resolution x-ray scattering studies of the nonpolar thermotropic liquid crystal 4-n-pentylphenylthiol-4'-n-octyloxybenzoate (8S5) in aerosil gel nanonetworks reveal that the aerosil-induced disorder significantly alters both the nematic to smectic-A and smectic-A to smectic-C phase transitions. The limiting 8S5 smectic-A correlation length follows a power-law dependence on the aerosil density in quantitative agreement with the limiting lengths measured previously in other smectic-A liquid crystal gels. The smectic-A to smectic-C liquid crystalline phase transition is altered fundamentally by the presence of the aerosil gel. The onset of the smectic-C phase remains relatively sharp but there is an extended coexistence region where smectic-A and smectic-C domains can exist.

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The simultaneous presence of two disparate neoplasms occurring in the same specimen has been well documented, albeit uncommonly. The juxtaposition of malignant melanoma and basal cell carcinoma (BCC) has been rarely reported in case reports, with most cases describing melanoma in situ and BCC. We present two cases of invasive melanoma (Clark level IV, no microscopic satellites present) intimately associated with BCC, and in areas distinction of the two lesions was difficult. Immunohistochemical studies delineated the two cell populations. In addition, one patient presented with multiple cutaneous metastases, all simulating blue nevi. The metastases occurred in the same anatomical region as the primary tumor, and histologically consisted of pigmented dendritic melanocytes and melanophages in the superficial and mid-dermis and arranged in a blue nevus-like lesion. Histologic clues suggesting the possibility of a metastatic melanoma included a sparse lymphocytic infiltrate, the presence of an epithelioid component and atypia of the dendritic melanocytes. However, without appropriate clinical history, the lesions could be overlooked as ordinary blue nevus. Collision tumors containing invasive melanoma and BCC are rare and this is the first report of a collision tumor with blue nevus-like metastasis. Awareness of this phenomenon and pattern of metastasis, together with the clinical findings will aid in the correct classification of these lesions.

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The importance of gastroesophageal reflux disease (GERD) to managed health care systems cannot be overestimated. It contributes significantly to the use of health care resources, including doctor's services, medication consumption, and diagnostic testing. A roundtable meeting of 13 managed care experts was convened January 23, 2001 in Dallas, to discuss the implications of GERD on the managed care system. The following proceedings are published in five sections. In the first part, Jeffrey Danzig, MD, a gastroenterologist, provides the clinical foundation for the discussion, based on the existing literature and his personal practice.

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OBJECTIVE: To analyze the presentation, evaluation, and treatment of a subset of patients with well-differentiated thyroid carcinoma who present with a lateral neck mass and no palpable disease in the thyroid gland. STUDY DESIGN: A retrospective review of all patients undergoing thyroidectomy for malignancy. METHODS: A database of all thyroidectomies performed for malignancy by the Vanderbilt University Department of Otolaryngology-Head and Neck Surgery from 1992 to 1997 was created. Patients who presented with an isolated neck mass without evidence of palpable disease in the thyroid were selected for the study population. RESULTS: There were 60 cases of thyroid malignancy, with 14 cases (23.3%) that presented as isolated lateral neck mass. The characteristics of this group (compared with the population of all thyroid malignancies) include younger age at presentation (37.7 +/- 15.2 y vs. 49.8 +/- 15.6 y; Student t test: P = .019) and long-standing presence of symptoms (27.4 +/- 39.6 mo vs. 3.6 +/- 3.9 mo; P = .023). These patients generally presented from a referring facility after having an excisional biopsy, which was 100% accurate. Fine-needle aspiration is becoming more useful and was 66.7% accurate. Histological examination revealed cancer in the thyroid gland in all patients, 11 cases of papillary carcinoma, 2 follicular carcinomas, and one medullary carcinoma The mean size of the primary focus was 10.9 +/- 8.7 mm, with 29% demonstrating bilateral disease and 14% demonstrating multifocal disease in the ipsilateral gland. The neck specimens revealed an average of 5.3 +/- 3.2 metastatic nodes in levels II-IV and 3.9 +/- 4.6 metastatic nodes in the paratracheal region. CONCLUSION: Based on this patient population, the long-standing lateral neck mass in the young patient should raise the physician's index of suspicion for thyroid carcinoma Fine-needle aspiration should be used in conjunction with judicious excisional biopsy. The bilateral and multifocal nature of otherwise occult primary disease argues for total thyroidectomy in this setting.

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OBJECTIVE: To evaluate the functional and histological effects of a single application of topical mitomycin-C after laser injury in the posterior canine glottis. STUDY DESIGN: A prospective, randomized study of 16 canines. METHODS: A supersaturated (1%) solution of topical mitomycin-C was applied to a unilateral, laser-induced injury near the cricoarytenoid joint in eight dogs. The mitomycin-soaked pledget was placed immediately after induction of the injury and was left in contact with exposed cartilage for 3 minutes. The opposite side was not injured to provide an internal control. In eight additional dogs, the same laser injury was allowed to heal untreated. After 6 weeks, the animals were sacrificed and their larynges harvested. Arytenoid adduction sutures were placed bilaterally, and the force required to bring the vocal folds to midline was measured for each side using tensiometry. Gross and microscopic histological analysis was performed. Statistical analysis was accomplished using a two-tailed Student t test of unpaired samples, and the Wilcoxon Signed Rank Test where appropriate. RESULTS: The mitomycin-C treated larynges demonstrated improved cricoarytenoid joint mobility (P = .007), decreased granulation tissue development (P = .03), and complete prevention of secondary "vocal granuloma" formation (P = .0004) when compared with eight dogs with identical laser injuries allowed to heal untreated. No complications were noted. CONCLUSIONS: This study demonstrates functional preservation and improved histological appearance of the injured glottis after a single treatment with topical mitomycin-C. Potential applications of these findings include prophylactic use of topical mitomycin-C on glottic insults that commonly progress from granulation tissue formation to scarring and decreased vocal fold function.

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Preparations of rat liver sinusoidal plasma membrane have been tested for their ability to metabolize the hepatotoxin carbon tetrachloride (CCl4) to reactive free radicals in vitro and compared in this respect with standard preparations of rat liver microsomes. The sinusoidal plasma membranes were relatively free of endoplasmic reticulum-associated activities such as the enzymes of the cytochrome P450 system and glucose-6-phosphatase. CCl4 metabolism was measured as (i) covalent binding of [14C]-CCl4 to membrane protein, (ii) electron spin resonance spin-trapping of CCl3. radicals and (iii) CCl4-induced lipid peroxidation. By all of these tests, purified sinusoidal plasma membranes were found unable to metabolize CCl4. The fatty acid composition of the plasma membranes was almost identical to that of the microsomal preparation and both membrane fractions exhibited similar rates of the lipid peroxidation that was stimulated non-enzymically by gamma-radiation or incubation with ascorbate and iron. The absence of CCl4-induced lipid peroxidation in the plasma membranes seems to be due, therefore, to an absence of CCl4 activation rather than an inherent resistance to lipid peroxidation. We conclude that damage to the hepatocyte plasma membrane during CCl4 intoxication is not due to a significant local activation of CCl4 to CCl3. within that membrane.

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The Wachstein-Meisel ATPase histochemical method has been previously used to demonstrate the ultrastructural localization of this enzyme in both whole liver and isolated plasma membranes following fixation in glutaraldehyde. In the present study biochemical assay, of liver plasma membrane enzymes following fixation in cold 2.5% glutaraldehyde showed that approximately 40% of Mg2+-ATPase, but only 4% of (Na+-K+)-ATPase activity remained in membranes from either control or ANIT-treated rats. In addition, 5'-nucleotidase activity was almost abolished by fixation. The present results indicate that the Wachstein-Meisel method, when applied to biliary canaliculi, can reliably be used to demonstrate the ultrastructural, histochemical localization of Mg2+-ATPase but not that of (NA+-K+)-ATPase. Furthermore, the method permits a valid comparison to be made of the relative Mg2+-ATPase activity in normal and chemically damaged biliary canaliculi.

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Oral administration of a single dose of alpha-naphthyl-isothiocyanate (ANIT) to rats produced a conjugated hyperbilirubinaemia, maximal at 2 days and which subsided by 7. The activities of 3 liver plasma membrane enzymes, Mg-2+-ATPase, (Na-+-K-+)-ATPase and 5-nucleotidase, and serum bilirubin levels were studied for up to 7 days after treatment. Activities of the 3 enzymes were significantly decreased at 2 days after treatment and returned to normal by 7, thus varying inversely with the degree of hyperbilirubinaemia. Enzyme histochemistry used to demonstrate canalicular localization of Mg-2+-ATPase in sections of whole liver and of isolated plasma membrane pellets showed that the reduction in activity was not a uniform partial loss, but represented a range of reductions in most canaliculi with a few retaining normal staining intensity. The results suggest that after ANIT intoxication there is a membrane lesion which may be responsible for the observed hyperbilirubinaemia due to the failure of secretion of biliary constituents into the canaliculus. However, more direct studies are necessary to determine whether any one of these enzymes is directly involved in the transport of biliary constituents across the bile canalicular membrane.

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