Histological and histomorphometric study of human palatal mucosa: Implications for connective tissue graft harvesting.

AIMS: To analyse the histological structure and histomorphometric characteristics of human hard palatal mucosa in order to determine the donor site of choice for connective tissue grafts from a histological point of view. MATERIALS AND METHODS: Palatal mucosa samples from six cadaver heads were harvested at four sites: incisal, premolar, molar and tuberosity. Histological and immunohistochemical techniques were performed, as was histomorphometric analysis. RESULTS: In the current study, we found that the density and size of cells were higher in the superficial papillary layer, whereas the thickness of the collagen bundles increased in the reticular layer. Excluding the epithelium, the mean percentage of lamina propria (LP) and submucosa (SM) was 37% and 63%, respectively (p < .001). LP thickness showed similar values in the incisal, premolar and molar regions, and a significantly greater thickness in tuberosity (p < .001). The thickness of SM increased from incisal to premolar and molar, disappearing in the tuberosity (p < .001). CONCLUSIONS: As dense connective tissue of LP is the tissue of choice for connective tissue grafts, the best donor site from a histological point of view is tuberosity because it is composed only of a thick LP without the presence of a loose submucosal layer.

Immunohistological study of the density and distribution of human penile neural tissue: gradient hypothesis.

Immunohistological patterns of density and distribution of neural tissue in the human penis, including the prepuce, are not fully characterized, and effects of circumcision (partial or total removal of the penile prepuce) on penile sexual sensation are controversial. This study analyzed extra- and intracavernosal innervation patterns on the main penile axes using formalin-fixed, paraffin-embedded human adult and fetal penile tissues, single- and double-staining immunohistochemistry and a variety of neural and non-neural markers, with a special emphasis on the prepuce and potential sexual effects of circumcision. Immunohistochemical profiles of neural structures were determined and the most detailed immunohistological characterizations to date of preputial nerve supply are provided. The penile prepuce has a highly organized, dense, afferent innervation pattern that is manifest early in fetal development. Autonomically, it receives noradrenergic sympathetic and nitrergic parasympathetic innervation. Cholinergic nerves are also present. We observed cutaneous and subcutaneous neural density distribution biases across our specimens towards the ventral prepuce, including a region corresponding in the adult anatomical position (penis erect) to the distal third of the ventral penile aspect. We also describe a concept of innervation gradients across the longitudinal and transverse penile axes. Results are discussed in relation to the specialized literature. An argument is made that neuroanatomic substrates underlying unusual permanent penile sensory disturbances post-circumcision are related to heightened neural levels in the distal third of the ventral penile aspect, which could potentially be compromised by deep incisions during circumcision.

Merkel cells of human oral mucosa express the pluripotent stem cell transcription factor Sox2.

Merkel cells are neuroendocrine cells associated to a neural sensitive ending and localized primarily in the epidermis, although they are also found in oral mucosa. Sox2 or SRY-box2 is a key transcription factor important in the maintenance of embryonic neural crest stem cell pluripotency. Sox2 has been described in Merkel cells of skin and in Merkel cell carcinomas, but not specifically in oral Merkel cells. The aims of the present study were to analyze the density of Merkel cells in human oral mucosa and to study the expression of Sox2 in these cells. For these purposes, immunohistochemical analyses for Sox2 and CK20 (the best marker for Merkel cells) were automatically performed on sections of normal human oral mucosa. Double immunofluorescence for Sox2 and CK20 was also performed. To analyze the density of Merkel cells, CK20 positive cells were counted in each sample and the length of the epithelial apical edge was measured (cells/mm). Merkel cells, demonstrated by CK20 immunoreactivity, were found in 95% of oral mucosa specimens studied (n=21). Mean density of Merkel cells in oral mucosa was 1.71±2.34 cells/mm. Sox2 immunoreactivity was found in the nuclei of scattered cells located at the basal layer. Serial sections immunostained for Sox2 and CK20 showed that Sox2-positive cells of oral mucosa coexpressed CK20, confirming that they were Merkel cells. Immunofluorescence for Sox2 and CK20 showed colocalization of both markers, demonstrating that virtually all oral Merkel cells expressed Sox2. This transcription factor could play a role in Merkel cell maturation and maintenance.

Effect of temperature in bursting of thalamic reticular cells / Efecto de la temperatura en las descargas en ráfaga de la célula del núcleo reticular del tálamo

Abstract Objective: To show the relation between the four parameters associated to bursting discharges of the thalamic reticular cells (TRNn): the maximum firing frequency (fmax) and the temperature at which it occurs (Tfmax), the range of temperatures defined as the full width at half maximum (∆Th) and the maximum specific low threshold calcium conductance (GT). Materials and Methods: In order to simulate the TRNn bursting activity, a computational simulation model was implemented using the NEURON software, which incorporates morphological and electrophysiological data, and stimuli properties closely related to reality. Results: It was found that there are nonlinear relations between the parameters. The fmax frequency follows a quadratic growth with temperature and tends asymptotically towards a limit value with the maximum calcium conductance. In the same manner, ∆Th increases until reaching a limit value as function of fmax and GT. However, the increment per frequency unit is bigger than the increment per conductance unit. Conclusions: Four equations were obtained that model the relations between the parameters associated to bursting discharges of the TRNn in rats and other neurons with similar characteristics in different animal species.

Resumen Objetivo: Mostrar la relación entre los cuatro parámetros asociados a las descargas en ráfaga de las neuronas del núcleo reticular del tálamo (TRNn): la frecuencia máxima de descarga (fmax) y la temperatura a la cual se produce (Tfmax), el rango de temperaturas definido como ancho a media altura (∆Th) y la conductancia máxima de calcio de bajo umbral (GT). Materiales y métodos: Para simular las descargas en ráfaga de las TRNn se implementó un modelo de simulación computacional usando el software NEURON, que incorpora datos morfológicos, electrofisiologicos y las propiedades de los estímulos en estrecha relación con la realidad. Resultados: Se encontraron relaciones no lineales entre los parámetros. La frecuencia fmax crece de forma cuadrática con la temperatura y tiende asintóticamente a un valor límite con la conductancia. Así mismo, ∆Th también se incrementan hasta alcanzar un valor límite en función de fmax y GT. No obstante, es mayor el incremento por cada unidad de frecuencia que por cada unidad de conductancia. Conclusiones: Se obtuvieron cuatro ecuaciones que modelan las relaciones entre los pará- metros asociados a las descargas en ráfaga de las neuronas TRN en ratas y otras neuronas con características similares en diferentes especies animales.