Perrin C.,Central University of Costa Rica
American Journal of Dermatopathology | Year: 2013
This second part of the review categorizes the site-specific nail tumors, as proposed in the first part, according to their clinical presentations. Acquired localized longitudinal pachyonychia allows for the specific recognition of onychogenic nail tumor, which can be classified into 2 groups according to the predominant compartment of origin within the nail unit as follows: epithelial tumors encompassing onychocytic matricoma and onychocytic carcinoma, and fibroepithelial tumors: the so-called onychomatricoma. As onychomatricoma is neither an epithelial matrical tumor nor a tumor with a limited differentiation toward the matrix, the author proposes instead the descriptive term of panonychoma fibropapilliferum (POP). The designation of POP does convey to the surgical pathologist or the dermatopathologist the key morphological pattern of this tumor. It should be noted that the proposed term of panonychoma is analogous to the nomenclature that is well established for follicular neoplasms with differentiation toward all elements of the normal hair follicle, that is panfolliculoma. The second term fibropapilliferum is used to highlight the mixed fibroepithelial nature of this neoplasm, which forms multiple rudimentary nail units. These nail units construct multiple nail plates that join together and form a single thick nail plate. According to nail anatomy, 2 types of POP are described: POP of the apical matrix/eponychium, with a pseudo-condylomatous pattern, and POP of the ventral matrix with a foliated pattern in transverse sections and a fibrokeratoma-like pattern in the longitudinal sections. Suggestions for the evaluation and clinical management of localized longitudinal pachyonychia are proposed. On histology of a nail clipping, 2 patterns with clinical significance can be individualized. A horizontal alignment of large cavities indicates POP of the ventral matrix. A haphazard arrangement of smaller cavities in the nail plate, including an arrangement in the inferior two-thirds of the nail clipping, should prompt a biopsy of the distal ventral matrix to rule out a malignant lesion. In the setting of the "masked "nail tumor, a clinical subtype with some significance can be individualized, the subungual keratotic nodule growing rapidly. Three nail bed tumors are discussed within this latter group. Two new clinicopathological variants of subungual keratoacanthoma are described, and a new nail bed tumor is discussed: the infundibulocystic nail bed squamous cell carcinoma. The absence of striking nuclear atypia and the giant cystic to multicystic pattern distinguishes infundibulocystic nail bed squamous cell carcinoma from follicular infundibulocystic squamous cell carcinoma. The last section proposes a classification of folliculogenic nail bed tumors. The follicular microcysts of the nail bed have previously been called subungual epidermoid inclusions or onycholemmal cysts, but the term follicular microcysts of the nail bed is more pertinent, because of the multiple lines of follicular differentiation (infundibular, tricholemmal, apocrine, and sebaceous) seen in their benign and malignant counterparts. Absent in a large portion of the normal nail bed, the follicular microcysts seem to have a peculiar propensity for the formation of tumors that vary in maturity from simple follicular microcystic hyperplasia associated with acquired longitudinal melanonychia to microcystic nail bed hamartoma and microcystic nail bed carcinoma (the so-called onycholemmal carcinoma). The concluding tables emphasize the key and essential histological features required to make the diagnosis of site-specific nail tumors and guide appropriate therapy. The author proposes to categorize subungual tumors into 2 types: subungual skin tumors (including subungual skin metastasis from internal malignancies) and nail tumors. Nail tumors can be accurately classified using a combined clinical and histogenetic approach. This new and expanding group of appendageal tumors is important for both dermatologists and dermatopathologists for the potential early detection of a malignant lesion or for the avoidance of overtreatment of a benign lesion. © 2013 Lippincott Williams & Wilkins.
Nangia A.,Central University of Costa Rica
Journal of Chemical Sciences | Year: 2010
Advances in supramolecular chemistry and crystal engineering reported from India within the last decade are highlighted in the categories of new intermolecular interactions, designed supramolecular architectures, network structures, multi-component host-guest systems, cocrystals, and polymorphs. Understanding self-assembly and crystallization through X-ray crystal structures is illustrated by two important prototypes - the large unit cell of elusive saccharin hydrate, Na16(sac)16 · 30H2O, which contains regular and irregular domains in the same structure, and by the Aufbau build up of zinc phosphate framework structures, e.g. ladder motif in [C3N 2H12][Zn(HPO4)2] to layer structure in [C3N2H12][Zn2(HPO 4)3] upon prolonged hydrothermal conditions. The pivotal role of accurate X-ray diffraction in supramolecular and structural studies is evident in many examples. Application of the bottomup approach to make powerful NLO and magnetic materials, design of efficient organogelators, and crystallization of novel pharmaceutical polymorphs and cocrystals show possible future directions for interdisciplinary research in chemistry with materials and pharmaceutical scientists. This article traces the evolution of supramolecular chemistry and crystal engineering starting from the early nineties and projects a center stage for chemistry in the natural sciences. © Indian Academy of Sciences.
Zhai L.,Central University of Costa Rica
Chemical Society Reviews | Year: 2013
Stimuli-responsive polymer films undergo interesting structural and property changes upon external stimuli. Their applications have extended from smart coatings to controlled drug release, smart windows, self-repair and other fields. This tutorial review summarizes non-covalent bonding, reversible reactions and responsive molecules that have played important roles in creating stimuli-responsive systems, and presents the recent development of three types of responsive polymer systems: layer-by-layer polymer multilayer films, polymer brushes, and self-repairing polymer films, with a discussion of their response mechanism. Future research efforts include comprehensive understanding of the response mechanism, producing polymer systems with controlled response properties regarding single or multiple external signals, combining polymer film fabrication with nanotechnology, improving the stability of polymer films on substrates, and evaluating the toxicity of the degradation products. © 2013 The Royal Society of Chemistry.
Babu N.J.,University of Nottingham |
Nangia A.,Central University of Costa Rica
Crystal Growth and Design | Year: 2011
The current phase of drug development is witnessing an oncoming crisis due to the combined effects of increasing R&D costs, decreasing number of new drug molecules being launched, several blockbuster drugs falling off the patent cliff, and a high proportion of advanced drug candidates exhibiting poor aqueous solubility. The traditional approach of salt formulation to improve drug solubility is unsuccessful with molecules that lack ionizable functional groups, have sensitive moieties that are prone to decomposition/racemization, and/or are not sufficiently acidic/basic to enable salt formation. Several novel examples of pharmaceutical cocrystals from the past decade are reviewed, and the enhanced solubility profiles of cocrystals are analyzed. The peak dissolution for pharmaceutical cocrystals occurs in a short time (<30 min), and high solubility is maintained over a sufficiently long period (4-6 h) for the best cases. The enhanced solubility of drug cocrystals is similar to the supersaturation phenomenon characteristic of amorphous drugs. However, in contrast to the metastable nature of amorphous phases, cocrystals are stable owing to their crystalline nature. Yet, cocrystals can exhibit dramatic solubility advantage over the stable crystalline drug form, often comparable to amorphous pharmaceuticals. The "spring and parachute" concept for amorphous drug dissolution is adapted to explain the solubility advantage of pharmaceutical cocrystals. Thus (1) the cocrystal dissociates to amorphous or nanocrystalline drug clusters (the spring), which (2) transform via fast dissolving metastable polymorphs to the insoluble crystalline modification following the Ostwalds Law of Stages, to give (3) high apparent solubility for cocrystals and optimal drug concentration (the parachute) in the aqueous medium. © 2011 American Chemical Society.
Tripuramallu B.K.,Central University of Costa Rica |
Das S.K.,Central University of Costa Rica
Crystal Growth and Design | Year: 2013
Two new metal organophosphonate oxide materials with formulas [Cu II 4CuI 2(L)2(2,2′- bpy)6(HPW12O40)]n·4nH 2O (1) and [Cu(2,2′-bpy)VO2(OH)(H 2L)]n (2) have been synthesized starting from the Cu(II) salts, 2,2′-bipyridine (2,2′-bpy), p-xylylenediphosphonic acid (H4L), and sodium tungstate (for 1)/ammonium metavanadate (for 2). Both the compounds 1 and 2 are characterized by routine elemental analyses, IR spectroscopy, thermogravimetric (TG) analysis, and unambiguously characterized by single crystal X-ray crystallography. The crystal structure of compound 1 consists of 2D copper phosphonate layers connected by the Keggin heteropolyanion to form a three-dimensional (3D) framework. The copper phosphonate layers in compound 1 are fabricated by the rare copper hexanuclear clusters in which the four terminal Cu(II) centers form two eight-membered Cu-dimer (Cu 2P2O4) rings (top and the bottom) that are connected to each other by the two central Cu(I) atoms of four-membered Cu 2O2 rings. These hexanuclear assemblies are connected to each other along the plane through the p-xylyl linkers to form a two-dimensional (2D) layer. Compound 1 is a unique example in terms of the existence of a hexanuclear copper phosphonate cluster in the 3D coordination matrix. Compound 2 has a 2D structure, in which the one-dimensional [Cu(2,2′-bpy)(H 2L)]n chains are connected by the VO2OH subunits to from a 2D layer. The formation of VO2OH in compound 2 ceases the formation of eight-membered Cu-dimer rings. The self-assembly of the polyoxometalates plays an important role in the formation of the metal organophosphonate phases. © 2013 American Chemical Society.