Ocular Surface Fibroma: Clinical, Histopathological, and Immunohistochemical Features of 10 Cases.

AIM: To describe the clinical, histological, and immunohistochemical (IHC) features of a series of 10 cases of ocular surface fibroma (OSF) and correlate the findings with other similar histological entities. METHOD: The patient demographics and features of the lesions were analysed from the clinical notes. All cases in the series had routine diagnostic excisional biopsies with standard histopathological and IHC evaluation. Each case was analysed by histology and immunohistochemistry with antibodies to: CD34, Factor XIIIa, desmin, smooth muscle actin, S100, Melan-A, ß-catenin, neurofilament, and Ki67. RESULTS: OSF occurred on the bulbar, tarsal, or forniceal conjunctiva, and typically presented as a white, pink, or yellow sheet-like or nodular lesion. The most common symptom was irritation or a foreign-body sensation. Lesions ranged in size from 4 to 13 mm. Only 1/10 cases showed a recurrence after an incomplete excision. Histologically, OSF comprised bland spindle cells in a collagen stroma. The spindle cells were CD34-positive (in 10/10 cases) and a smaller subset was positive for Factor XIIIa (6/10 cases). Normal resident spindle cells in the conjunctival stroma, Tenon's capsule, and tarsal plate were positive for CD34 and Factor XIIIa, implicating these cells in the origin of OSF. CONCLUSION: OSF is a benign lesion of resident CD34- and Factor XIIIa-positive spindle cells in the conjunctiva and Tenon's capsule. We have called to attention another lesion to be included by clinicians in the differential diagnosis of benign ocular surface lesions composed of CD34- and Factor XIIIa-positive spindle cells.

Controlling the Messenger: Regulated Translation of Maternal mRNAs in Xenopus laevis Development.

The selective translation of maternal mRNAs encoding cell-fate determinants drives the earliest decisions of embryogenesis that establish the vertebrate body plan. This chapter will discuss studies in Xenopus laevis that provide insights into mechanisms underlying this translational control. Xenopus has been a powerful model organism for many discoveries relevant to the translational control of maternal mRNAs because of the large size of its oocytes and eggs that allow for microinjection of molecules and the relative ease of manipulating the oocyte to egg transition (maturation) and fertilization in culture. Consequently, many key studies have focused on the expression of maternal mRNAs during the oocyte to egg transition (the meiotic cell cycle) and the rapid cell divisions immediately following fertilization. This research has made seminal contributions to our understanding of translational regulatory mechanisms, but while some of the mRNAs under consideration at these stages encode cell-fate determinants, many encode cell cycle regulatory proteins that drive these early cell cycles. In contrast, while maternal mRNAs encoding key developmental (i.e., cell-fate) regulators that function after the first cleavage stages may exploit aspects of these foundational mechanisms, studies reveal that these mRNAs must also rely on distinct and, as of yet, incompletely understood mechanisms. These findings are logical because the functions of such developmental regulatory proteins have requirements distinct from cell cycle regulators, including becoming relevant only after fertilization and then only in specific cells of the embryo. Indeed, key maternal cell-fate determinants must be made available in exquisitely precise amounts (usually low), only at specific times and in specific cells during embryogenesis. To provide an appreciation for the regulation of maternal cell-fate determinant expression, an overview of the maternal phase of Xenopus embryogenesis will be presented. This section will be followed by a review of translational mechanisms operating in oocytes, eggs, and early cleavage-stage embryos and conclude with a discussion of how the regulation of key maternal cell-fate determinants at the level of translation functions in Xenopus embryogenesis. A key theme is that the molecular asymmetries critical for forming the body axes are established and further elaborated upon by the selective temporal and spatial regulation of maternal mRNA translation.

Keratin dynamics: modeling the interplay between turnover and transport.

Keratin are among the most abundant proteins in epithelial cells. Functions of the keratin network in cells are shaped by their dynamical organization. Using a collection of experimentally-driven mathematical models, different hypotheses for the turnover and transport of the keratin material in epithelial cells are tested. The interplay between turnover and transport and their effects on the keratin organization in cells are hence investigated by combining mathematical modeling and experimental data. Amongst the collection of mathematical models considered, a best model strongly supported by experimental data is identified. Fundamental to this approach is the fact that optimal parameter values associated with the best fit for each model are established. The best candidate among the best fits is characterized by the disassembly of the assembled keratin material in the perinuclear region and an active transport of the assembled keratin. Our study shows that an active transport of the assembled keratin is required to explain the experimentally observed keratin organization.

Stability analysis and simulations of coupled bulk-surface reaction-diffusion systems.

In this article, we formulate new models for coupled systems of bulk-surface reaction-diffusion equations on stationary volumes. The bulk reaction-diffusion equations are coupled to the surface reaction-diffusion equations through linear Robin-type boundary conditions. We then state and prove the necessary conditions for diffusion-driven instability for the coupled system. Owing to the nature of the coupling between bulk and surface dynamics, we are able to decouple the stability analysis of the bulk and surface dynamics. Under a suitable choice of model parameter values, the bulk reaction-diffusion system can induce patterning on the surface independent of whether the surface reaction-diffusion system produces or not, patterning. On the other hand, the surface reaction-diffusion system cannot generate patterns everywhere in the bulk in the absence of patterning from the bulk reaction-diffusion system. For this case, patterns can be induced only in regions close to the surface membrane. Various numerical experiments are presented to support our theoretical findings. Our most revealing numerical result is that, Robin-type boundary conditions seem to introduce a boundary layer coupling the bulk and surface dynamics.

Noise in restaurants: levels and mathematical model.

Noise affects the dining atmosphere and is an occupational hazard to restaurant service employees worldwide. This paper examines the levels of noise in dining areas during peak hours in different types of restaurants in Hong Kong SAR, China. A mathematical model that describes the noise level in a restaurant is presented. The 1-h equivalent continuous noise level (L(eq,1-h)) was measured using a Type-1 precision integral sound level meter while the occupancy density, the floor area of the dining area, and the ceiling height of each of the surveyed restaurants were recorded. It was found that the measured noise levels using Leq,1-h ranged from 67.6 to 79.3 dBA in Chinese restaurants, from 69.1 to 79.1 dBA in fast food restaurants, and from 66.7 to 82.6 dBA in Western restaurants. Results of the analysis of variance show that there were no significant differences between means of the measured noise levels among different types of restaurants. A stepwise multiple regression analysis was employed to determine the relationships between geometrical and operational parameters and the measured noise levels. Results of the regression analysis show that the measured noise levels depended on the levels of occupancy density only. By reconciling the measured noise levels and the mathematical model, it was found that people in restaurants increased their voice levels when the occupancy density increased. Nevertheless, the maximum measured hourly noise level indicated that the noise exposure experienced by restaurant service employees was below the regulated daily noise exposure value level of 85 dBA.

Nanoscale memory devices.

This article reviews the current status and future prospects for the use of nanomaterials and devices in memory technology. First, the status and continuing scaling trends of the flash memory are discussed. Then, a detailed discussion on technologies trying to replace flash in the near-term is provided. This includes phase change random access memory, Fe random access memory and magnetic random access memory. The long-term nanotechnology prospects for memory devices include carbon-nanotube-based memory, molecular electronics and memristors based on resistive materials such as TiO(2).

Thin-film enhanced nerve guidance channels for peripheral nerve repair.

It has been demonstrated that nerve guidance channels containing stacked thin-films of aligned poly(acrylonitrile-co-methylacrylate) fibers support peripheral nerve regeneration across critical sized nerve gaps, without the aid of exogenous cells or proteins. Here, we explore the ability of tubular channels minimally supplemented with aligned nanofiber-based thin-films to promote endogenous nerve repair. We describe a technique for fabricating guidance channels in which individual thin-films are fixed into place within the lumen of a polysulfone tube. Because each thin-film is <10 microm thick, this technique allows fine control over the positioning of aligned scaffolding substrate. We evaluated nerve regeneration through a 1-film guidance channel--containing a single continuous thin-film of aligned fibers--in comparison to a 3-film channel that provided two additional thin-film tracks. Thirty rats were implanted with one of the two channel types, and regeneration across a 14 mm tibial nerve gap was evaluated after 6 weeks and 13 weeks, using a range of morphological and functional measures. Both the 1-film and the 3-film channels supported regeneration across the nerve gap resulting in functional muscular reinnervation. Each channel type characteristically influenced the morphology of the regeneration cable. Interestingly, the 1-film channels supported enhanced regeneration compared to the 3-film channels in terms of regenerated axon profile counts and measures of nerve conduction velocity. These results suggest that minimal levels of appropriately positioned topographical cues significantly enhance guidance channel function by modulating endogenous repair mechanisms, resulting in effective bridging of critically sized peripheral nerve gaps.

Reversible canal wall down mastoidectomy for acquired cholesteatomas: preliminary results.

OBJECTIVES: The educational objectives were to discuss a new technique to manage acquired cholesteatomas and to compare this with standard approaches used for cholesteatoma removal. The study objective was to determine the feasibility of using a new approach, the reversible canal wall down approach, in conjunction with bone cement to remove acquired cholesteatomas and, potentially, preserve the ossicular chain. STUDY DESIGN: Retrospective review of five patients who underwent resection of their acquired cholesteatomas using a technique that maximizes exposure, yet preserves the posterior canal wall and, potentially, the ossicular chain. METHODS: In the setting of a tertiary otological referral center, five consecutive patients with acquired cholesteatomas underwent reversible canal wall down surgery. Four patients were male (ages, 41, 53, 26, and 10 y), and one patient was a woman [age, 51 y]). A reversible canal wall down mastoidectomy approach was used in the patients. Main outcome measures were intraoperative findings with respect to cholesteatoma removal and postoperative clinical examination, including postoperative audiograms. RESULTS: Five patients had dry ears postoperatively. One patient initially had granulation tissue forming on the posterior ear canal. This eventually resolved. The patients who had a postoperative audiogram after cholesteatoma resection with ossicular chain preservation noted an improvement or stabilization in their hearing. CONCLUSIONS: Using the reversible canal wall down approach in conjunction with bone cement, one is able to obtain excellent exposure of the cholesteatoma and, potentially, preserve the ossicular chain. This approach may be particularly useful in revision cholesteatoma surgery or in cases of acquired cholesteatoma in which the surgeon may be able to preserve the ossicular chain.

Effect of round window membrane application of nitric oxide on hearing and nitric oxide concentration in perilymph.

Nitric oxide (NO), a free radical, has been found to be important in the development of middle ear effusions. However, the effect of NO in the middle ear effusion on cochlear function and on perilymph concentrations of NO has not been reported. We placed S-nitroso-N-acetylpenicillamine (SNAP), a NO donor compound, on the round window membrane (RWM) of adult chinchillas. Auditory brainstem response (ABR) thresholds were measured before and after the placement of SNAP on the RWM and hourly for 8 h after SNAP placement. Samples of perilymph were collected 2 h after application of SNAP and were assayed for total nitrate and nitrite, the end products of NO. Experimental ears demonstrated significant ABR threshold elevations after 5 h and elevated nitrate/nitrite in the perilymph. These findings suggest that NO present in the middle ear passes through the RWM into the inner ear and can cause significant hearing loss.