Brillouin microscopy for the evaluation of hair micromechanics and effect of bleaching.

Brillouin microscopy is a new form of optical elastography and an emerging technique in mechanobiology and biomedical physics. It was applied here to map the viscoelastic properties of human hair and to determine the effect of bleaching on hair properties. For hair samples, longitudinal measurements (i.e. along the fibre axis) revealed peaks at 18.7 and 20.7 GHz at the location of the cuticle and cortex, respectively. For hair treated with a bleaching agent, the frequency shifts for the cuticle and cortex were 19.7 and 21.0 GHz, respectively, suggesting that bleaching increases the cuticle modulus and-to a minor extent-the cortex modulus. These results demonstrate the capability of Brillouin spectroscopy to address questions on micromechanical properties of hair and to validate the effect of applied treatments.

Viscoelastic properties of biopolymer hydrogels determined by Brillouin spectroscopy: A probe of tissue micromechanics.

Many problems in mechanobiology urgently require characterization of the micromechanical properties of cells and tissues. Brillouin light scattering has been proposed as an emerging optical elastography technique to meet this need. However, the information contained in the Brillouin spectrum is still a matter of debate because of fundamental problems in understanding the role of water in biomechanics and in relating the Brillouin data to low-frequency macroscopic mechanical parameters. Here, we investigate this question using gelatin as a model system in which the macroscopic physical properties can be manipulated to mimic all the relevant biological states of matter, ranging from the liquid to the gel and the glassy phase. We demonstrate that Brillouin spectroscopy is able to reveal both the elastic and viscous properties of biopolymers that are central to the structure and function of biological tissues.

Brillouin microspectroscopy data of tissue-mimicking gelatin hydrogels.

Brillouin spectroscopy, based on the inelastic scattering of light from thermally driven acoustic waves or phonons [1], holds great promise in the field of life sciences as it provides functionally relevant micromechanical information in a contactless all-optical manner [2]. Due to the complexity of biological systems such as cells and tissues, which present spatio-temporal heterogeneities, interpretation of Brillouin spectra can be difficult. The data presented here were collected from gelatin hydrogels, used as tissue-mimicking model systems for Brillouin microspectroscopy measurements conducted using a lab-built Brillouin microscope with a dual-stage VIPA spectrometer. By varying the solute concentration in the range 4-18% (w/w), the macroscopic mechanical properties of the hydrogels can be tuned and the corresponding evolution in the Brillouin-derived longitudinal elastic modulus measured. An increase in Brillouin frequency shift with increasing solute concentration was observed, which was found to correlate with an increase in acoustic wave velocity and longitudinal modulus. The gels used here provide a viable model system for benchmarking and standardisation, and the data will be useful for spectrometer development and validation.

Image analysis applied to Brillouin images of tissue-mimicking collagen gelatins.

Brillouin spectroscopy is an emerging analytical tool in biomedical and biophysical sciences. It probes viscoelasticity through the propagation of thermally induced acoustic waves at gigahertz frequencies. Brillouin light scattering (BLS) measurements have traditionally been performed using multipass Fabry-Pérot interferometers, which have high contrast and resolution, however, as they are scanning spectrometers they often require long acquisition times in poorly scattering media. In the last decade, a new concept of Brillouin spectrometer has emerged, making use of highly angle-dispersive virtually imaged phase array (VIPA) etalons, which enable fast acquisition times for minimally turbid materials, when high contrast is not imperative. The ability to acquire Brillouin spectra rapidly, together with long term system stability, make this system a viable candidate for use in biomedical applications, especially to probe live cells and tissues. While various methods are being developed to improve system contrast and speed, little work has been published discussing the details of imaging data analysis and spectral processing. Here we present a method that we developed for the automated retrieval of Brillouin line shape parameters from imaging data sets acquired with a dual-stage VIPA Brillouin microscope. We applied this method for the first time to BLS measurements of collagen gelatin hydrogels at different hydration levels and cross-linker concentrations. This work demonstrates that it is possible to obtain the relevant information from Brillouin spectra using software for real-time high-accuracy analysis.

Current measurement by Faraday effect on GEPOPU.

The design of an optical current sensor to be used in a pulsed power generator is presented. The current sensor is based on the polarization rotation by the Faraday effect. GEPOPU is a pulsed power generator, 110 kA, 120 ns double transit time, 1.5 Ω coaxial geometry, and current rise time of 50 ns. Two different optical geometries surrounding the conductor were tried, using Amici roof prism and pentaprism to go around the current once, as a way to preserve the state of polarization along the optical path by means of complementary reflections within the sensing element. We believe this to be the first time that such large and rapidly varying currents have been measured with this configuration. The values obtained for both geometries agree with the values obtained with a Rogowski coil. The traces obtained are completely noise-free and no significant time lag has been observed between the current determined from the Faraday rotation and the current measured using a Rogowski coil.

Bebé colodión. Comunicación de 14 casos / Collodion baby. Report of fourteen patients

El término bebé colodión se refiere a una condición transitoria del recién nacido que consiste en la presencia de una membrana translúcida y adherente que recubre casi completamente la superficie corporal. Constituye una manifestación inicial común a varias entidades; las más frecuentes son la ictiosis lamelar y la eritrodermia ictiosiforme congénita no ampollar. A continuación presentamos una serie de 14 pacientes que nacieron como bebé colodión y una revisión actualizada de la literatura.

Infantile myofibromatosis: report of nine patients.

Infantile myofibromatosis is a rare fibrous tumor of infancy that can be solitary or multiple. Although most of the cases are limited to the skin, in some instances systemic involvement can be present. Solitary tumors limited to the skin usually present a good prognosis with spontaneous regression. We performed a retrospective observational review of the clinical and pathologic characteristics of nine patients diagnosed as having infantile myofibromatosis, followed during a 10-year period in a Pediatric Dermatology Department.

Hemangioma hemosiderótico targetoide: revisión a propósito de cuatro casos / Targetoid Hemosiderotic Hemangioma: Revision based on four cases

El hemangioma hemosiderótico targetoide, conocido también como hobnail hemangioma, es un tumor vascular benigno que se localiza preferentemente en tronco y miembros. La forma clásica (o targetoide) se presenta como una pápula pequeña, solitaria, violácea-amarronada, rodeada por una zona pálida y un anillo equimótico periférico. Existe controversia acerca del origen vascular capilar o linfático de este tumor, aunque estudios inmunohistoquímicos recientes avalan su naturaleza linfática. Presentamos cuatro casos pediátricos de hemangioma hemosiderótico targetoide con manifestaciones clínicas atípicas.

Targetoid hemosiderotic hemangioma, also known as hobnail hemangioma, is a benign vascular tumor that mainly affects the trunk and limbs. Its classical (or targetoid) appearance is that of a small, solitary, violaceus to brown papule surrounded by a pale halo and a peripheral equimotic ring. Controversy exists about the vascular capillary or lymphatic origin of this tumor; however, recent immuhistochemical studies support its lymphatic nature. We discuss four pediatric cases of targetoid hemosiderotic hemangioma with atypical presentation.

Eruptive pseudoangiomatosis.

We describe two children with acute onset and spontaneous resolution of angioma-like papules during a viral illness. The biopsy specimens from both patients showed a unique histologic appearance consisting of dilated dermal blood vessels with plump, hobnail-shaped endothelial cells. On the basis of the natural history and the histopathologic features we suggest the diagnosis of eruptive pseudoangiomatosis.

Fotoprotección en la infancia / Photoprotection in childhood

La radiación ultravioleta (UV) es sólo una parte de las radiaciones electromagnéticas emitidas por el sol y tiene un especial interés dermatológico por los diversos efectos que causa sobre la piel. En este trabajo analizamos los distintos tipos de radiaciones, su participación en los procesos de bronceado y de fotoenvejecimiento y carcinogénesis e intentamos recomendar sencillas medidas de protección solar para que puedan llevar a cabo padres y niños. Si bien hoy en día la exposición solar, el desarrollo de la vida al aire libre y el hecho de estar bronceado son aspectos saludables, creemos que como pediatras jugamos un rol importante en la educación para la fotoprotección

Fotoprotección en la infancia / Photoprotection in childhood

La radiación ultravioleta (UV) es sólo una parte de las radiaciones electromagnéticas emitidas por el sol y tiene un especial interés dermatológico por los diversos efectos que causa sobre la piel. En este trabajo analizamos los distintos tipos de radiaciones, su participación en los procesos de bronceado y de fotoenvejecimiento y carcinogénesis e intentamos recomendar sencillas medidas de protección solar para que puedan llevar a cabo padres y niños. Si bien hoy en día la exposición solar, el desarrollo de la vida al aire libre y el hecho de estar bronceado son aspectos saludables, creemos que como pediatras jugamos un rol importante en la educación para la fotoprotección (AU)