Orbital dermoid cysts: clinicopathologic correlations, classification, and management. The 1997 Josephine E. Schueler Lecture

The dermoid cyst is one of the most common space-occupying orbital lesions, but there has been no large series that details the clinical, pathologic, and therapeutic aspects of this condition. Furthermore, despite the various presentations and types of dermoid cysts, there is no clinically applicable classification of these lesions. We performed a retrospective histopathologic study of 197 consecutive orbital and periorbital dermoid cysts excised at Wills Eye Hospital during a 32-year period, correlated the histopathologic findings with the recorded clinical and radiographic observations, and devised a clinically applicable classification of orbital dermoid cysts. The mean age at excision was 17 years (range, 5 months to 85 years), and the most frequent clinical finding was a painless subcutaneous mass, present in 89% of cases. In 72% of patients, the mass was located in the superotemporal orbital region and produced no abnormalities of vision or intraocular pressure. Computed tomography and magnetic resonance imaging, performed mainly in the more recent cases, disclosed a characteristic round to ovoid cystic lesion with a well-defined lining. Histopathologically, 165 of the cysts (84%) were lined by keratinizing, stratified squamous epithelium. Ten (5%) were lined by nonkeratinizing epithelium resembling conjunctival epithelium. Hair shafts were present in the wall or lumen of the cyst in 195 (99%) of specimens, sebaceous glands in 148 (75%), and sweat glands in 39 (20%); inflammation was present in 75 cases (38%). Based on these personal observations and a review of the literature, a classification of orbital dermoid cysts is proposed that we believe will provide guidance for the ophthalmologist in the management of these lesions.     

Pore spectra from continuous scan mercury porosimetry

A method for obtaining pore spectra is described. Continuous pressure—volume data from mercury porosimetry were used to determine the volume distribution as a function of the intrusion and extrusion pressure or the pore radius for a number of porous samples.An explanation is offered for delayed intrusion of mercury into pores. Mercury vapor transfer has been postulated as a thermodynamically allowed mechanism in those few cases where pore size or constrictions prohibit liquid transfer.     

Flame retardant mechanism of polyamide 6-clay nanocomposites

The thermal and flammability properties of polyamide 6/clay (2 and 5% by mass fraction) nanocomposites were measured to determine their flame retardant (FR) performance. The gasification process of the nanocomposite samples at an external radiant flux of 50 kW/m² in a nitrogen atmosphere was observed, and the residues collected at various sample mass losses were analyzed by thermogravimetric analysis, transmission electron microscopy, and X-ray diffraction to determine the content of the residue and to understand the FR mechanism of the nanocomposites. The analysis of the floccules of blackened residues shows that up to 80% by mass of the residues consists of clay particles and the remainder is thermally stable organic components with possible graphitic structure. Furthermore, clay particles are stacked in the carbonaceous floccule residues and the d-spacing of the clay platelets is in the range of 1.3-1.4 nm as compared to the well exfoliated original sample. The accumulation of the initially well-dispersed clay particles in the sample on the burning/gasifying sample surface are due to two possible mechanisms. One is recession of the polymer resin from the surface by pyrolysis with the de-wetted clay particles left behind. Another mechanism is the transportation of clay particles pushed by numerous rising bubbles of degradation products and the associated convection flow in the melt from the interior of the sample toward the sample surface. Numerous rising bubbles may have another effect on the transport of clay particles. Bursting of the bubbles at the sample surface pushes the accumulated clay particles outward from the bursting area and forms the island-like floccules instead of forming a continuous net-like structure of a clay filled protective layer. Therefore, both PA6/clay nanocomposite samples did not produce sufficient amounts of protective floccules to cover the entire sample surface and vigorous bubbling was observed over the sample surface which was not covered by the protective floccules.     

Decompression illness in sports divers detected with technetium-99m-HMPAO SPECT and texture analysis

Diving for sport and recreation has increased in recent years, resulting in more incidences of diving illness. Therefore, we studied potential use of regional cerebral blood flow SPECT imaging with 99mTc-HMPAO in the management of divers who have experienced decompression illness (DCI). METHODS: A group of ten sports divers who had no experience of DCI were compared with ten sports divers who had experienced at least one episode of DCI. Transaxial SPECT images were first compared objectively using a first-order texture measure and then subjectively using a receiver operator characteristic (ROC) experiment. Experienced observers were asked to rate images subjectively in terms of the images' textural appearance. RESULTS: Both these techniques showed that there is a statistically significant difference between the two groups and the images produced by the DCI divers were generally more coarsely patchy when compared to the non DCI divers. The quantitative texture technique proved significantly better in identifying divers with DCI than the visual analysis by observers using ROC curves. CONCLUSION: Differences between the cerebral blood flow patterns of sports divers who have experienced DCI and sports divers who have no experience of DCI can be detected using 99mTc-HMPAO SPECT and a texture analysis technique.     

Effects of electrically induced fatigue on the twitch and tetanus of paralyzed soleus muscle in humans

We analyzed the twitch and summated torque (tetanus) during repetitive activation and recovery of the human soleus muscle in individuals with spinal cord injury. Thirteen individuals with complete paralysis (9 chronic, 4 acute) had the tibial nerve activated every 1,500 ms with a 20-Hz train (7 stimuli) for 300 ms and a single pulse at 1,100 ms. The stimulation protocol lasted 3 min and included 120 twitches and 120 tetani. Minimal changes were found for the acute group. The chronic group showed a significant reduction in the torque and a significant slowing of the contractile speeds of both the twitch and tetanus. The decrease in the peak twitch torque was significantly greater than the decrease in the peak tetanus torque early during the fatigue protocol for the chronic group. The twitch time to peak and half relaxation time were prolonged during fatigue, which was associated with improved fusion of the tetanus torque. At the end of the fatigue protocol, the decrease in the peak twitch torque was not significantly different from the decrease in the peak tetanus torque. After 5 min of rest, the contractile speeds recovered causing the tetanus to become unfused, but the tetanus torque became less depressed than the twitch torque. The differential responses for the twitch and the tetanus suggest an interplay between optimal fusion created from contractile speed slowing and excitation contraction coupling compromise. These issues make the optimal design of functional electrical stimulation systems a formidable task.     

Translating emerging research on the genetics of smoking into clinical practice: ethical and social considerations.

Despite decades of research aimed at improving the effectiveness of smoking treatment, available treatments are only modestly effective, and smoking remains the leading cause of preventable deaths in the United States. Recent research on genetic factors related to smoking behavior eventually may lead to the design of new tobacco dependence treatments and to the individualization of treatment based on genetic factors. Although this research is in its infancy, and data on the analytic and clinical validity of genetic tests to tailor smoking treatment are not yet available, it is not too soon to begin identifying and addressing key ethical issues associated with genetic testing in the context of tobacco dependence treatment. Key concerns include (a) potential harm (e.g., stigmatization, discrimination) to patients related to inappropriate use of genetic information, (b) implications of pleiotropic associations, (c) differential prevalence of risk-conferring genotypes among racial or ethnic subpopulations, (d) preparedness of primary care physicians to incorporate genetic testing into smoking treatment, (e) informed consent, and (f) ensuring an appropriate balance between individually tailored treatment by genotype and broad-based interventions that focus on social and environmental factors affecting smoking behavior. Additional research on these ethical and social issues must be conducted simultaneously with the scientific work currently under way. Failure to address these concerns will likely undermine efforts to translate knowledge emerging from the United States' substantial investment in genetic research on smoking into clinical practice and improved patient outcomes.     

Reversibility of hepatic failure following jejunoileal bypass

Jejunoileal bypass was performed in 50 morbidly obeses patients. The morbidity encountered compared favorably with that of other series. All patients manifesting hepatic failure demonstrated hyperbilirubinemia within the first three months postoperatively. Hyperbilirubinemia, if uncorrected, resulted in a mortality of 75%. Augmentation jejunal interposition was performed in three patients who demonstrated hepatic decompensation or severe electrolyte imbalance or both. This resulted in rapid correction of electrolyte disturbances, liver function measurements, and patient symptoms without significant postoperative weight gain. Persistent hyperbilirubinemia or recalcitrant electrolyte problems or both are indications for augmentation jejunal interposition.     

Zinc absorption in Crohn's disease

Zinc deficiency is a potential complication of Crohn's disease and we have searched for evidence of this and assessed the possibility that malabsorption of zinc might be a cause. Serum zinc concentrations in 33 patients suffering from Crohn's disease were significantly lower than in 58 normal control subjects (9 . 18 +/- 2 . 3 mumol compared with 13 . 6 +/- 1 . 73 mumol, P < 0 . 0005). Serum zinc correlated well with serum albumin concentrations and the low serum zinc may simply reflect the low serum albumin. Thus its value as an indicator of zinc deficiency is poor. We studied zinc absorption in seven patients with Crohn's disease and compared it with the results obtained previously in five normal subjects using a new technique involving a short-lived isotope of zinc (69mZn). Plasma appearance curves, constructed after an oral dose of isotope, and disappearance curves, after an intravenous dose, were used in a deconvolution computer programme to calculate zinc absorption. Compared with normal subjects, zinc absorption was considerably impaired in patients with Crohn's disease (range 9--45%, compared with 38--75%). This abnormality is a potential cause of zinc deficiency in patients with Crohn's disease.