Evaluation of biophysical alterations in the epithelial and endothelial layer of patients with Bullous Keratopathy

The cornea is a fundamental ocular tissue for the sense of sight. Thanks to it, the refraction of two-thirds of light manages to participate in the visual process and protect against mechanical damage. Because it is transparent, avascular, and innervated, the cornea comprises five main layers: Epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. Each layer plays a key role in the functionality and maintenance of ocular tissue, providing unique ultrastructural and biomechanical properties. Bullous Keratopathy (BK) is an endothelial dysfunction that leads to corneal edema, loss of visual acuity, epithelial blisters, and severe pain, among other symptoms. The corneal layers are subject to changes in their biophysical properties promoted by Keratopathy. In this context, the Atomic Force Microscopy (AFM) technique in air was used to investigate the anterior epithelial surface and the posterior endothelial surface, healthy and with BK, using a triangular silicone tip with a nominal spring constant of 0.4 N/m. Six human corneas (n = 6) samples were used for each analyzed group. Roughness data, calculated by third-order polynomial adjustment, adhesion, and Young's modulus, were obtained to serve as a comparison and identification of morphological and biomechanical changes possibly associated with the pathology, such as craters and in the epithelial layer and exposure of a fibrotic layer due to loss of the endothelial cell wall. Endothelial cell membrane area and volume data were calculated, obtaining a relevant comparison between the control and patient. Such results may provide new data on the physical properties of the ocular tissue to understand the physiology of the cornea when it has pathology.

Layer-by-Layer Investigation of Ultrastructures and Biomechanics of Human Cornea

The cornea is an avascular, innervated, and transparent tissue composed of five layers: the epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium. It is located in the outermost fraction of the eyeball and is responsible for the refraction of two-thirds of light and protection from external mechanical damage. Although several studies have been done on the cornea on the macroscopic scale, there is a lack of studies on the micro-nanoscopic scale, especially an analysis evaluating the cornea layer by layer. In this study, atomic force microscopy (AFM) was employed to assess four layers that form the cornea, analyzing: adhesion, stiffness, and roughness. The results showed microvilli in the epithelial and endothelial layers, pores in the basement membrane, and collagen fibers in the Stroma. These data increase the knowledge about the human cornea layers’ ultrastructures and adds new information about its biophysical properties.

Severe Cutaneous Adverse Drug Reactions in Children: Epidemiological, Clinical and Etiological Aspects in Dermatology-Venereology Unit at National and Teaching Hospital of Cotonou

BACKGROUND

The aim of this study was to describe the epidemiological, clinical and etiological aspects of severe cutaneous adverse drug reactions in children in dermatologyvenereology unit at National and Teaching Hospital of Cotonou.

METHODS

A retrospective and descriptive study was carried out for 10 years in dermatology-venereology unit at the National and Teaching Hospital of Cotonou to document the epidemiological, clinical and etiological aspects of severe cutaneous adverse drug reactions in children. It included all children aged from 0 to 18 years with clinical diagnosis of severe cutaneous adverse drug reactions. Drug imputability was based on the criteria of the French pharmacovigilance group.

RESULTS

Severe cutaneous adverse drug reactions accounted for 47.3% of paediatric cases (35/74 cases). The mean age was 9.3 years ± 5.2. The sex-ratio was 1.1. Self-medication was noted in 76.5% of children, on the initiative of parents in 66.7% of cases. There were 51.4% cases of Steven Johnson syndrome, 22.8% cases of Lyell syndrome, 8.5% cases of generalized and bullous fixed drug eruption, 2.9% cases of acute generalized exanthematous pustulosis and erythrodermic maculo-papular rash. Drug combinations was noted in 20% of cases. Penicillins (26.5%), paracetamol and sulfonamides (16.3%) were the drugs frequently incriminated.

CONCLUSION

Steven Johnson syndrome and Lyell syndrome were the main severe cutaneous adverse drug reactions in children, mostly of school age. Penicillins, paracetamol and sulfonamides were the drugs frequently used and administered most often on self-medication.

A new mammography dosimetric phantom

Breast phantoms produced with tissue-equivalent materials are used in an attempt to simulate glandular and adipose tissues, in terms of X-ray attenuation and density. In this work, a set of breast tissue-equivalent phantoms (BTE phantoms) with semicircular shapes of different thicknesses and compositions were produced. Such phantoms may be used in the measurement of the incident air kerma (K(i)) and the mean glandular dose (D(G)) delivered to patients undergoing mammography. To characterise the materials used to produce the phantoms, a series of 17-keV X-ray attenuation coefficient measurements were performed. The carbon-nitrogen-hydrogen elemental composition and the densities of the tissue-equivalent materials were also determined and compared with values available in the literature. Linear attenuation coefficients of 0.724 and 0.923 cm(-1) were determined, respectively, for adipose and glandular tissues. Such values agree with data available in the literature. On the basis of the results obtained in this work, it is suggested that BTE phantoms are used instead of polymethyl methacrylate phantoms to select exposure parameters (kV, mAs and target/filter combination) specific for breast glandularities from 0 to 50 % in the optimisation of doses in mammography.