Topography of the inferior alveolar nerve in human embryos and fetuses: an histomorphological study

The aim of this study is to establish the position of the inferior alveolar nerve in relation to the Meckel's cartilage, the anlage of the mandibular body and primordia of the teeth, and also to trace the change in nerve trunk structure in the human prenatal ontogenesis. serial sections (20µm) from thirty-two 6-12 weeks-old entire human embryos and serial sections (10µm) of six mandibles of 13-20 weeks-old human fetuses without developmental abnormalities were studied. histological sections were impregnated with silver nitrate according to Bilshovsky-Buke and stained with hematoxylin and eosin. during embryonic development, the number of branches of the inferior alveolar nerve increases and its fascicular structure changes. in conclusion, the architecture of intraosseous canals in the body of the mandible, as well as the location of the foramina, is predetermined by the course and pattern of the vessel/nerve branching in the mandibular arch, even before the formation of bony trabeculae. particularly, the formation of the incisive canal of the mandible can be explained by the presence of the incisive nerve as the extension of the inferior alveolar nerve. It has also been established that Meckel's cartilage does not participate in mandibular canal morphogenesis.

Desarrollo osteológico de la columna vertebral y del complejo caudal de larvas de Lutjanus guttatus (Perciformes: Lutjanidae) en condiciones de cultivo / Osteological development of the vertebral column and caudal complex of Lutjanus guttatus (Perciformes: Lutjanidae) larvae under rearing conditions

The spotted rose snapper (Lutjanus guttatus) is an important commercial species in Mexico with good culture potential. The osteological study at early stages in this species is an important tool to confirm normal bone structure and for the detection of malformations that may occur during early development. This study was carried out in order to evaluate and describe the normal osteological development of the vertebral column and caudal complex of this species grown under controlled conditions. For this, a total of 540 larvae of L. guttatus, between 2.1 and 17.5mm of total length (TL), were cultured during 36 days; culture conditions were 28ºC, 5.74mg/L oxygen and 32.2ups salinity with standard feeding rates. To detect growth changes, a sample of 15 organisms was daily taken from day one until day 36 of post-hatch (DPH). Samples were processed following standard techniques of clearing, and cartilage (alcian blue) and bone staining (alizarin red). Results showed that the vertebral column is composed of ten vertebrae in the abdominal region, and 14 vertebrae including the urostyle in the caudal region. The development of the axial skeleton starts with the neural arches and haemal arches at 3.8mm TL. Caudal elements such as the hypurals and parahypural began to develop at 4.1mm TL. Pre-flexion and flexion of the notochord and the formation of all hypurals were observed between 5.3 and 5.8mm TL. Ossification of the vertebrae in the abdominal region and in some neural arches initiated at 9.5mm TL. In the caudal region, all the neural and haemal arches ossified at 10.2mm TL. All the abdominal vertebrae and their respective neural arches and parapophyses ossified at 11.2mm TL, while the elements of the caudal complex that ossified were the hypurals, parahypurals and modified haemal spines. All caudal fin rays, 12 neural spines and 3 haemal arches were ossified by 15.5mm. The complete ossification process of this specie under laboratory culture conditions was observed when larvae reached 17.3mm TL on 36 DPH. Detailed analysis of the osteological structures will allow a reference description to evaluate and detect malformations that may occur during the larval culture of the spotted rose snapper.

El pargo flamenco (Lutjanus guttatus) es una especie de importancia comercial en México con un gran potencial para su cultivo. El estudio osteológico en estadios tempranos de esta especie bajo condiciones controladas, es una herramienta importante para el conocimiento de su estructura ósea normal y poder detectar las malformaciones que se puedan presentar. El objetivo del presente trabajo se realizó para conocer y describir el desarrollo osteológico normal de la columna vertebral y el complejo caudal de 540 larvas de 2.1 a 17.5mm de longitud total (LT) bajo condiciones de cultivo a 28°C, 5.74mg/L de oxígeno y 32.2UPS de salinidad. Diariamente se tomó una muestra de 15 organismos desde el día uno hasta el 36 después de la eclosión (DDE) y se procesaron con las técnicas de clareado y tinción de cartílago (azul aciano) y hueso (rojo alizarina) para llevar a cabo la descripción de las estructuras. La columna vertebral se divide en región abdominal con diez vértebras y región caudal compuesta por 14 vértebras incluido el urostilo. El desarrollo del esqueleto axial inicia con la formación de los arcos neurales y hemales a los 3.8mm de LT. A los 4.1mm de LT empieza la formación de los hipurales y parahipural que son elementos caudales. Entre los 5.3 y 5.8mm de LT se observó en pre-flexión y flexión del notocordio y la formación de todos los hipurales. La osificación de las vértebras en la región abdominal y en algunos arcos neurales inició a los 9.5mm de LT. A los 10.2mm de LT se osificó la región caudal y todos los arcos neurales y hemales. A los 11.2mm LT se osificaron todas las vértebras abdominales con sus respectivos arcos neurales y los parapófisis, mientras que los elementos del esqueleto caudal que se osificaron fueron los hipurales, parahipurales y las espinas hemales modificadas. A los 15.5mm de LT se osificaron los radios de la aleta caudal y 12 espinas neurales y 3 hemales. El proceso de osificación de las larvas de esta especie en condiciones de cultivo se completó a los 17.3mm LT o 36 DDE. El análisis detallado de las estructuras osteológicas, permitirá una descripción de referencia para evaluar y detectar las malformaciones que se puedan presentar durante el cultivo larvario.

gp130 is important for the normal morphogenesis of Meckel's cartilage and subsequent mandibular development

gp130-mediated signaling is involved in both chondrogenesis and osteogenesis, but its direct role in the formation of embryonic Meckel's cartilage and associated mandibular development has not yet been elucidated. In this study, we examined the influence of gp130 ablation on the developing mandibular Meckel's cartilage by evaluating the morphological and histological changes as well as the gene expression patterns in developing embryonic gp130-/- mice. The ablation of the gp130 gene showed no change in region-specific collagen mRNA expression except for a slight delay in its expression but caused shortened embryonic Meckel's cartilage, delayed hypertrophic chondrocyte maturation and subsequent bony replacement with characteristic bending of the intramandibular Meckel's cartilage. The bending of Meckel's cartilage led to a narrow mandibular arch at the rostral area with poor cortical plate formation. These findings indicate that gp130-mediated signaling is important for the normal morphogenesis of Meckel's cartilage and subsequent mandibular development.

Effects of cigarette smoke on the Meckel's cartilage of rat fetus: morphologic, morphometric and stereologic study

O objetivo deste estudo foi investigar os efeitos da fumaça de cigarros sobre o desenvolvimento da cartilagem mandibular (cartilagem de Meckel) do embrião de rato. Quando inalado por ratas Wistar, entre o 9º e o 12º dia de prenhez, a fumaça de cigarros (5/dia) provocou retardo do crescimento intrauterino, com fetos e placentas menores. Nos fetos do grupo experimental, o exame histopatológico revelou uma cartilagem de Meckel pouco desenvolvida, com condroblastos menores apresentando citoplasma escaso com núcleos mais pálidos, esféricos e centrais, assim como uma matrix cartilaginosa mais abundante. A análise morfométrica revelou que as lacunas da cartilagem de Meckel eram menores nos fetos do grupo experimental, não apresentando alteração significativa de sua forma. Os resultados sugeriram que a fumaça de cigarros inalada pelas ratas prenhes durante o período de organogênese induziu retardo tanto do crescimento quanto da diferenciação celular na cartilagem de Meckel dos fetos.

Histochemical study of developing cartilage of the primordial vertebrae in rat embryo

The aim of this study was to investigate the presence anddistribution of cell surface terminal sugars in developing cartilage of theprimordial vertebrae in rat embryo. Material and Fifty female and 25 male Wistar rats were chosenrandomly. After adaptation, mating was done. Vaginal plug observationwas performed on O-day of gestation. Specimens were collected from9-18 days old embryos and were fixed in B4G solution. After routinehistological processing and embedding in paraffin, blocks were cut into4-micrometer thickness sections. Then sections were stained byPAS-Alcian blue and Lectin histochemistry methods [VVA-B4, MPA, WFA].On the basis of intensity of staining, sections were graded andnonparametric statistical test [Kruskal Wallis] was used to comparedifferences between samples. The commencment of chondroblast differentiation in the centrumof future vertebrae was specified by appearance of D-Gal Terminal sugarin 13th day of embryonic period. On the 14th to 16th days of presence ofGal/GalNac, D-GalNac terminal sugars were detected in developingvertebrae. Reactions were first observed in centrum and then in pediclesand laminae of vertebrae. From the 17th day on ward, reaction with theabove mentioned lectins showed a significant reductions [P<0.05]. This study showed that changes in surface terminal sugarsregulate morphologic changes and the fate of the cell, during tissuegrowth and development

Embriogénesis del área mandibular en oveja y gato / Embryonic development of mandibule in sheep and cat

Se describe en forma comparada la ontogenia del cartílago del primer arco faríngeo y su relación con la formación de la mandíbula, en dos especies: oveja y gato, que presentan diferencias fenotípicas y funcionales a nivel de ese carácter. Se utilizó una muestra de 18 embriones y fetos felinos con un desarrollo entre 20 y 48 días de gestación y 12 fetos ovinos de 27 a 45 días. Un grupo de embriones fue procesado con la técnica de doble tinción "in toto" con alizarina y azul de Alcian, y el otro grupo fue analizado con técnica histológica corriente: hematoxilina eosina-azul de Alcian. En ovinos de 31 a 35 días y felinos de 32 a 39 días, se observa el cartílago diferenciado en sínfisis, centro o cuerpo y componente caudal. Los primeros componentes evidenciaron diferencias entre ambas especies. En la oveja, el centro del cartílago del primer arco no sufre osificación endocondral. La sínfisis mantiene el diámetro y se prolonga para formar el proceso rostral que promueve el crecimiento de la mandíbula. En gatos, la sínfisis es poco desarrollada y la parte anterior del centro del cartílago sufre osificación ondocondral, la que aumenta la distancia transversa entre las mandíbulas derecha e izquierda. Las diferencias encontradas en la estructura del cartílago de Meckel y su diferenciación posterior estarían relacionadas con la forma definitiva de la mandíbula en ovinos (dolicocefálicos) y en felinos (braquiocefálicos).