RESUMEN
In the present paper, a critical overview of the most commonly used techniques for the characterization and the determination of carbon nanotubes (CNTs) is given on the basis of 170 references (2000-2014). The analytical techniques used for CNT characterization (including microscopic and diffraction, spectroscopic, thermal and separation techniques) are classified, described, and illustrated with applied examples. Furthermore, the performance of sampling procedures as well as the available methods for the determination of CNTs in real biological and environmental samples are reviewed and discussed according to their analytical characteristics. In addition, future trends and perspectives in this field of work are critically presented.
Asunto(s)
Nanotubos de Carbono/química , Cromatografía en Gel , Electroforesis Capilar , Microscopía Electrónica , Microscopía de Sonda de Barrido , Nanotubos de Carbono/análisis , Espectroscopía de Fotoelectrones , Dispersión de Radiación , Espectrometría por Rayos X , Espectrofotometría , Espectrometría Raman , TermogravimetríaRESUMEN
New materials have significant impact on the development of new methods and instrumentation for chemical analysis. From the discovery of carbon nanotubes in 1991, single and multi-walled carbon nanotubes--due to their high adsorption and desorption capacities--have been employed as sorption substrates in solid-phase extraction for the preconcentration of metal species from diverse matrices. Looking for successive improvements in sensitivity and selectivity, in the past few years, carbon nanotubes have been utilized as sorbents for solid phase extraction in three different ways: like as-grown, oxidized and functionalized nanotubes. In the present paper, an overview of the recent trends in the use of carbon nanotubes for solid phase extraction of metal species in environmental, biological and food samples is presented. The determination procedures involved the adsorption of metals on the nanotube surface, their quantitative desorption and subsequent measurement by means of atomic spectrometric techniques such as flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry/mass spectrometry, among others. Synthesis, purification and types of carbon nanotubes, as well as the diverse chemical and physical strategies for their functionalization are described. Based on 140 references, the performance and general properties of the applications of solid phase extraction based on carbon nanotubes for metal species atomic spectrometric determination are discussed.
RESUMEN
Since the 90s there increasing interest in early detection of neonatal hearing loss due to the feasibility of universal neonatal screening as well as to the possibility of early intervention. This has led to set up neonatal screening programs based upon otoacoustic emissions and to a great increase in the number of publications in the field. Our hospital started a neonatal hearing loss screening program using otoacoustic emission in March 2000. We used a Capella Cochlear Emissions (MADSEN electronics) equipment. Until May 2003 we have performed the test in 6372 children with a median age of 71 days. In our study, the sensibility of the test was 90.9% and the specificity 99.7%. Our results are similar to those reported in the literature although the age of the children was higher and we have found an incidence of hearing loss lower than other studies.
Asunto(s)
Pérdida Auditiva/diagnóstico , Pérdida Auditiva/epidemiología , Tamizaje Neonatal/métodos , Femenino , Humanos , Lactante , Recién Nacido , Masculino , Emisiones Otoacústicas Espontáneas/fisiologíaRESUMEN
Elderly persons often have balance disorders, with dizziness that sometimes leads to falls. Changes in the peripheral vestibular system with age, with loss of the hair cells and neurons of Scarpa's nucleus, have been studied for years. However, the changes in the vestibular nuclear complex with age have not been examined. We studied paraffin-embedded brainstems from nine persons of different ages in order to analyze possible changes with age. No abnormalities were observed in the volume or length of the vestibular nuclei, except for a decrease in both dimensions in the superior vestibular nucleus (SNV). All the main vestibular nuclei showed an increase in lipofuscin content with age that seemed to be less marked in the SNV. The low lipofuscin concentration in the SNV could be related with the conservation of vestibular reflexes, the center of which seems to be the SVN, in elderly persons.
Asunto(s)
Envejecimiento/fisiología , Núcleos Vestibulares/citología , Adulto , Anciano , Anciano de 80 o más Años , Humanos , Lipofuscina/análisis , Persona de Mediana Edad , Núcleos Vestibulares/químicaRESUMEN
Although the use of antibiotic prophylaxis has significantly reduced the frequency of postoperative wound infections, they continue to be a critical issue in head and neck cancer surgery. A study was made of possible risk factors for the development of these infections. A prospective study was made of 159 patients with pharyngo-laryngeal squamous-cell carcinoma who underwent open-pharynx surgery in order to analyze the factors associated with wound infections. Postoperative wound infection was defined as purulent drainage or mucocutaneous fistula formation, or both, in the first 10 days after surgery. Potential risk factors examined were age, medical illnesses, prior surgery and radiotherapy, TNM stage, type of operative procedure, method of reconstruction, and operative time. The overall wound infection rate was 23%. Although the incidence of wound infection was higher in patients who received preoperative radiotherapy, in patients with advanced stage disease, and in those who required flap reconstruction, the only preoperative factor that significantly increased the rate of wound infection was the concurrence of medical illnesses (chronic obstructive pulmonary disease and diabetes mellitus; p = 0.018). In conclusion, the presence of prior medical diseases was the main risk factor in the development of postoperative wound infections.
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Carcinoma de Células Escamosas/cirugía , Neoplasias Laríngeas/cirugía , Neoplasias Faríngeas/cirugía , Infección de la Herida Quirúrgica/etiología , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Estado de Salud , Humanos , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Estudios Prospectivos , Factores de RiesgoRESUMEN
Dysfunction of the last cranial pairs can occur in some neurological diseases, such as Chiari's malformation. This entity causes herniation of the cerebellar amygdalas through the foramen magnum, producing descent of the brainstem and traction on the lower cranial pairs. This dysfunction occurs in 57-70% of patients with this malformation, which is why the disease may be diagnosed in the ENT clinic. Clinical suspicion of this entity after exhaustive examination of the patient, early disease diagnosis and correct selection of surgical treatment can alleviate major symptoms and prevent neurological complications in some cases.
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Malformación de Arnold-Chiari/etiología , Nervios Craneales/anomalías , Malformación de Arnold-Chiari/diagnóstico , Malformación de Arnold-Chiari/cirugía , Nervios Craneales/cirugía , Femenino , Humanos , Imagen por Resonancia Magnética , Persona de Mediana Edad , Tomografía Computarizada por Rayos XRESUMEN
A study was made of the incidence and predisposing factors in non-surgical infections in a group of 159 patients undergoing oncological head and neck surgery. The incidence of these infections was 5.7%; the most frequent was lung infection (3.8%), followed by septic phlebitis (1.3%) and urinary infection (0.6%). Risk factors for pulmonary infection included advanced tumor stage, prolonged surgery, and supraglottic laryngectomy. No relationship was found with age, previous illnesses, tumor site, or the antibiotic used in preoperative prophylaxis.
Asunto(s)
Neoplasias de Cabeza y Cuello/complicaciones , Neoplasias de Cabeza y Cuello/cirugía , Infecciones/complicaciones , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Estudios Retrospectivos , Factores de RiesgoRESUMEN
Surgical wound infections are a frequent complication of head and neck cancer surgery. In a group of 159 consecutive patients we analyzed bacteriological cultures from 21 with suppurative draining from the wound. In 3 cases cultures were monomicrobial, in 12 cultures were polymicrobial, and in 6 no bacterial isolate was obtained from the cultured material. Gram-positive aerobes were the most frequent bacteria (54%), followed by gram-negative aerobes (38%) and anaerobes (8%). No relation was found between bacteriological profile, antibiotic prophylaxis, tumor site, tumor stage, or surgical procedure.
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Bacteriemia/complicaciones , Bacteriemia/microbiología , Bacterias/aislamiento & purificación , Neoplasias de Cabeza y Cuello/complicaciones , Infección de la Herida Quirúrgica/microbiología , Humanos , Estadificación de Neoplasias , Estudios RetrospectivosRESUMEN
One of the most important parameters for success in free tissue transfer to the head and neck are a proper and careful recipient vessel dissection and meticulous vascular microanastomotic technique. The principle that govern vessel positioning in the head and neck are more complex than those used in extremity free flap transfers. In this report the vascular selection as well as technical details are discussed, based on the literature data and our own experience in 20 patients.
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Anastomosis Arteriovenosa/cirugía , Neoplasias Encefálicas/cirugía , Encéfalo/cirugía , Carcinoma/cirugía , Cráneo/cirugía , Colgajos Quirúrgicos , Adolescente , Adulto , Anciano , Encéfalo/patología , Neoplasias Encefálicas/patología , Carcinoma/patología , Humanos , Masculino , Microcirugia , Persona de Mediana Edad , Estudios Retrospectivos , Cráneo/fisiopatologíaRESUMEN
The denervation-induced changes on S-100 protein, glial fibrillary acidic protein (GFAP) and vimentin immunoreactivity (IR) of the lamellar cells from cutaneous Meissner-like sensory nerve formations (SNF), or corpuscles, of the adult rat hind limb foot-pads were studied, using combined immunohistochemical and image analysis (optic microdensitometry) techniques. Animals were allowed to survive for 1, 3 and 7 days following sciatic and saphenous nerves transection. Lamellar cells of Meissner-like corpuscles displayed S-100 protein- and vimentin-IR, but not GFAP-IR. Denervation caused a marked time-dependent decrease of S-100 protein IR whereas vimentin-IR did not change or weakly increased. No positive GFAP-IR was observed in denervated SNF. These findings suggest that continuity of SNF with nerve fibers supplying them is necessary to maintain some of the immunohistochemical characteristics of the non-neuronal cells of SNF.
Asunto(s)
Ganglios Sensoriales/metabolismo , Proteína Ácida Fibrilar de la Glía/metabolismo , Proteínas S100/metabolismo , Piel/metabolismo , Vimentina/metabolismo , Animales , Desnervación , Ganglios Sensoriales/ultraestructura , Inmunohistoquímica , Masculino , Ratas , Ratas Wistar , Piel/inervaciónRESUMEN
The non-neuronal distribution of nerve growth factor receptors (NGFr) in the adult rat brain was investigated immunohistochemically using an anti-NGFr monoclonal antibody (192-IgG). In addition to the neurons known to be NGF-dependent or containing NGF binding-sites, a moderate to strong NGFr immunoreactivity was observed in several non-nervous tissues such as the ependymal cells, the epithelial cells of the choroid plexus, the leptomeninge and the cerebral blood vessels. Vascular immunoreactivity for NGFr occurs in the adventitia and muscular layers of the large arteries (circle of Willis) and, apparently, in all the wall layers of the intermediate or small (pial-arachnoid) arteries. The present results provide direct evidence for the presence of non-neuronal NGFr in the brain of adult rats, and suggest a possible involvement of NGF in roles other than those classically thought.
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Química Encefálica , Receptores de Factor de Crecimiento Nervioso/análisis , Animales , Anticuerpos Monoclonales , Sitios de Unión , Encéfalo/irrigación sanguínea , Plexo Coroideo/química , Endotelio Vascular/química , Epéndimo/química , Femenino , Técnicas para Inmunoenzimas , Masculino , Meninges/química , Prosencéfalo/química , Células de Purkinje/química , Ratas , Ratas Wistar , Receptores de Factor de Crecimiento Nervioso/inmunologíaRESUMEN
The distribution of S-100 protein and their subunits (alpha and beta) in lumbar dorsal root ganglia of adult rat was investigated immunohistochemically using monoclonal antibodies against the S-100 protein, alpha-subunit and beta-subunit of S-100 protein. The conventional S-100 protein antibody stained both neurons (large and intermediate in size; 20.3% and 41 +/- 3.2 microns of diameter) and glial cells (satellite cells and Schwann cells). The immunoreaction for the alpha-subunit was observed in the perikarya of some large and intermediate sized neurons (17.2%, 45.6 +/- 6.1 microns of diameter), satellite cells and Schwann cells, whereas the beta-subunit immunoreactivity was found principally in glial cells, and in a scarce number of large and intermediate sized neurons (2.8%, 43.3 +/- 5 microns of diameter) Our results demonstrate that a subpopulation of large and intermediate sized neurons of lumbar DRG contain alpha- and beta-subunits of S-100 protein, being alpha-subunit predominant. Furthermore, the satellite glial and Schwann cells contain also the two subunits but mainly beta-subunit. These data confirm previous studies about the presence of S-100 protein in neurons of the central and peripheral nervous system.
Asunto(s)
Ganglios Espinales/química , Proteínas S100/análisis , Animales , Técnicas para Inmunoenzimas , Masculino , Neuroglía/química , Neuronas/química , Ratas , Ratas EndogámicasRESUMEN
The cartilages of vestibulum nasi in rats of different ages (newborns, 1 week, 1 month and 12 months old) were studied immunohistochemically using monoclonal antibodies against glial fibrillary acidic protein (GFAP) and S-100 protein. The immunoreaction for both GFAP and S-100 protein results positive in a variable number of chondrocytes. The number of chondrocytes displaying GFAP-like immunoreaction does not change during development and maturation, whereas those showing S-100 protein-like immunoreactivity increase from birth to the adult state. The formation of cartilaginous tissue from neuroectodermic cells of neural crest has been postulated by several authors and our results strongly support these opinions; moreover, according to present findings S-100 protein could be involved in chondroid tissue formation.