Foetal dilated cardiomyopathy with left ventricular thrombosis.

Serial foetal echocardiography showed the development of severe left ventricular systolic dysfunction and thrombosis in a previously healthy foetus. Normal cardiac findings in a mid-trimester foetus do not exclude subsequent dilated cardiomyopathy.

Study of the ureter structure in anencephalic fetuses

Purpose The objective of this paper is to analyze the structure of the ureter in normal and anencephalic human fetuses. Materials and Methods We studied 16 ureters from 8 human fetuses without congenital anomalies aged 16 to 27 weeks post-conception (WPC) and 14 ureters from 7 anencephalic fetuses aged 19 to 33 WPC. The ureters were dissected and embedded in paraffin, from which 5 µm thick sections were obtained and stained with Masson trichrome, to quantify smooth muscle cells (SMC) and to determine the ureteral lumen area, thickness and ureteral diameter. The samples were also stained with Weigert Resorcin Fucsin (to study elastic fibers) and Picro-Sirius Red with polarization and immunohistochemistry analysis of the collagen type III fibers to study collagen. Stereological analysis of collagen, elastic system fibers and SMC were performed on the sections. Data were expressed as volumetric density (Vv-%). The images were captured with an Olympus BX51 microscope and Olympus DP70 camera. The stereological analysis was done using the Image Pro and Image J programs. For biochemical analysis, samples were fixed in acetone, and collagen concentrations were expressed as micrograms of hydroxyproline per mg of dry tissue. Means were statistically compared using the unpaired t-test (p < 0.05). Results The ureteral epithelium was well preserved in the anencephalic and control groups. We did not observe differences in the transitional epithelium in the anencephalic and control groups. There was no difference in elastic fibers and total collagen distribution in normal and anencephalic fetuses. SMC concentration did not differ significantly (p = 0.1215) in the anencephalic and control group. The ureteral lumen area (p = 0.0047), diameter (p = 0.0024) and thickness (p = 0.0144) were significantly smaller in anencephalic fetuses. Conclusions Fetuses with anencephaly showed smaller diameter, area and thickness. These differences could indicate ...

Fetal-maternal interactions in the synepitheliochorial placenta using the eGFP cloned cattle model.

BACKGROUND: To investigate mechanisms of fetal-maternal cell interactions in the bovine placenta, we developed a model of transgenic enhanced Green Fluorescent Protein (t-eGFP) expressing bovine embryos produced by nuclear transfer (NT) to assess the distribution of fetal-derived products in the bovine placenta. In addition, we searched for male specific DNA in the blood of females carrying in vitro produced male embryos. Our hypothesis is that the bovine placenta is more permeable to fetal-derived products than described elsewhere. METHODOLOGY/PRINCIPAL FINDINGS: Samples of placentomes, chorion, endometrium, maternal peripheral blood leukocytes and blood plasma were collected during early gestation and processed for nested-PCR for eGFP and testis-specific Y-encoded protein (TSPY), western blotting and immunohistochemistry for eGFP detection, as well as transmission electron microscopy to verify the level of interaction between maternal and fetal cells. TSPY and eGFP DNA were present in the blood of cows carrying male pregnancies at day 60 of pregnancy. Protein and mRNA of eGFP were observed in the trophoblast and uterine tissues. In the placentomes, the protein expression was weak in the syncytial regions, but intense in neighboring cells on both sides of the fetal-maternal interface. Ultrastructurally, our samples from t-eGFP expressing NT pregnancies showed to be normal, such as the presence of interdigitating structures between fetal and maternal cells. In addition, channels-like structures were present in the trophoblast cells. CONCLUSIONS/SIGNIFICANCE: Data suggested that there is a delivery of fetal contents to the maternal system on both systemic and local levels that involved nuclear acids and proteins. It not clear the mechanisms involved in the transfer of fetal-derived molecules to the maternal system. This delivery may occur through nonclassical protein secretion; throughout transtrophoblastic-like channels and/or by apoptotic processes previously described. In conclusion, the bovine synepitheliochorial placenta displays an intimate fetal-maternal interaction, similar to other placental types for instance human and mouse.

Study of the ureter structure in anencephalic fetuses.

PURPOSE: The objective of this paper is to analyze the structure of the ureter in normal and anencephalic human fetuses. MATERIALS AND METHODS: We studied 16 ureters from 8 human fetuses without congenital anomalies aged 16 to 27 weeks post-conception (WPC) and 14 ureters from 7 anencephalic fetuses aged 19 to 33 WPC. The ureters were dissected and embedded in paraffin, from which 5 µm thick sections were obtained and stained with Masson trichrome, to quantify smooth muscle cells (SMC) and to determine the ureteral lumen area, thickness and ureteral diameter. The samples were also stained with Weigert Resorcin Fucsin (to study elastic fibers) and Picro-Sirius Red with polarization and immunohistochemistry analysis of the collagen type III fibers to study collagen. Stereological analysis of collagen, elastic system fibers and SMC were performed on the sections. Data were expressed as volumetric density (Vv-%). The images were captured with an Olympus BX51 microscope and Olympus DP70 camera. The stereological analysis was done using the Image Pro and Image J programs. For biochemical analysis, samples were fixed in acetone, and collagen concentrations were expressed as micrograms of hydroxyproline per mg of dry tissue. Means were statistically compared using the unpaired t-test (p < 0.05). RESULTS: The ureteral epithelium was well preserved in the anencephalic and control groups. We did not observe differences in the transitional epithelium in the anencephalic and control groups. There was no difference in elastic fibers and total collagen distribution in normal and anencephalic fetuses. SMC concentration did not differ significantly (p = 0.1215) in the anencephalic and control group. The ureteral lumen area (p = 0.0047), diameter (p = 0.0024) and thickness (p = 0.0144) were significantly smaller in anencephalic fetuses. CONCLUSIONS: Fetuses with anencephaly showed smaller diameter, area and thickness. These differences could indicate that anencephalic fetal ureters tend to have significant structural alterations, probably due to cerebral lesions with consequent brain control damage of ureter nerves.

The great auricular nerve in fetuses / El nervio auricular mayor en fetos

The great auricular nerve (GAN) is the largest branch of the superficial cervical plexus that winds around the posterior border of the sternocleidomastoid muscle, accompanied by the external jugular vein. Forty fetuses (right side: 40/80; left: 40/80) with gestational ages between 15 to 28 weeks were microdissected to document the anatomy of the GAN. The results obtained were classified as: i) Incidence and morphometry: GAN was present in 100 percent of the fetal specimens with average length on the right and left sides recorded as 12.65 +/- 2.14 mm and 12.55 +/- 2.82 mm respectively. ii) Course: GAN was located parallel to the transverse cervical nerve and the external jugular vein. Duplicate external jugular veins were observed in 5 percent (4/80) with GAN located anterior to one of the tributaries; iii) Branching Pattern: 16 percent (13/80) of specimens depicted a single branch. Duplicate branches in 67 percent (54/80) (referred to as Type I: anterior and posterior branches and 33 percent (26/80) referred to as Type II: anterior and posterior branches; iv) Variation: the transverse cervical nerve formed a communication with GAN, inferior to the parotid gland in 1 percent. The anatomical knowledge of the course, bifurcation pattern and variations of GAN may prevent complications during surgical procedures such as parotidectomies.

El nervio auricular mayor (NAM) es el ramo más grande del plexo cervical superficial que gira alrededor del margen posterior del músculo esternocleidomastoideo, acompañado de la vena yugular externa. Cuarenta fetos (lado derecho: 40/80; izquierdo: 40/80), con edades gestacionales de 15 a 28 semanas fueron microdisecados para describir la anatomía del NAM. Los resultados obtenidos se clasificaron en: i) Incidencia y morfometría: NAM estaba presente en el 100 por ciento de las muestras fetales con una longitud media de los lados derecho e izquierdo de 12,65+/-2,14mm y 12,55+/-2,82mm, respectivamente. ii) Curso: NAM se encuentra paralelo al nervio cervical transverso y la vena yugular externa. Duplicación de las venas yugulares externas se observaron en el 5 por ciento (4/80) con el NAM situado por delante de uno de los afluentes, iii) Patrón de ramificación: 16 por ciento (13/80) de las muestras presentaba una solo ramo. Ramos duplicados en el 67 por ciento (54/80) de Tipo I, ramos anterior y posterior y, el 33 por ciento (26/80) Tipo II, ramos anterior y posterior, y iv) Variación: el nervio cervical transverso formando una comunicación con NAM, inferior a la glándula parótida en el 1 por ciento. El conocimiento anatómico del curso, patrón de bifurcación y variaciones del NAM pueden prevenir las complicaciones durante los procedimientos quirúrgicos como la parotidectomía.

Back to the debate: sternalis muscle / Volver al debate: músculo esternal

The sternalis muscle (SM) is an anatomical variant found in the anterior thoracic wall. While the attachment sites of SM are generally agreed upon, the innervation and function of this muscle are not well established. Cadaveric and surgical explorations to date report that SM is innervated by either the pectoral nerves or the anterior branches of the intercostal nerves, or a combination of both. Knowledge of SM is relevant to health care providers specialising in imaging and/or surgery of the anterior thoracic wall. This paper aims to raise awareness in the medical community of the clinical relevance of SM through two case reports and a brief literature review.

El músculo esternal (ME) es una variante anatómica en la pared torácica anterior. Mientras que los sitios de fijación del ME estan acordados, la inervación y la función de este músculo no están bien establecida. Exploraciones cadavéricas y quirúrgicas han informado que el ME está inervado por los nervios pectorales o ramos anteriores de los nervios intercostales, o una combinación de ambos. El conocimiento del SE es relevante para los proveedores de atención de salud especializada de imágenes y/o cirugía de la pared torácica anterior. Este documento tiene como objetivo crear conciencia en la comunidad médica de la relevancia clínica de ME a través de dos reportes de caso y una breve revisión bibliográfica.

Placentation in Sigmodontinae: a rodent taxon native to South America.

BACKGROUND: Sigmodontinae, known as "New World rats and mice," is a large subfamily of Cricetidae for which we herein provide the first comprehensive investigation of the placenta. METHODS: Placentas of various gestational ages ranging from early pregnancy to near term were obtained for five genera, i.e. Necromys, Euryoryzomys, Cerradomys, Hylaeamys, and Oligoryzomys. They were investigated by means of histology, immunohistochemistry, a proliferation marker, DBA-lectin staining and transmission electron microscopy. RESULTS: The chorioallantoic placenta was organized in a labyrinthine zone, spongy zone and decidua and an inverted yolk sac persisted until term. The chorioallantoic placenta was hemotrichorial. The interhemal barrier comprised fetal capillary endothelium and three layers of trophoblast, an outermost, cellular layer and two syncytial ones, with interspersed trophoblast giant cells (TGC). In addition, accumulations of TGC occurred below Reichert's membrane. The junctional zone contained syncytial trophoblast, proliferative cellular trophoblast, glycogen cells and TGC that were situated near to the maternal blood channels. In three of the genera, TGC were also accumulated in distinct areas at the placental periphery. PAS-positive glycogen cells derived from the junctional zone invaded the decidua. Abundant maternal uNK cells with positive response to PAS, vimentin and DBA-lectin were found in the decidua. The visceral yolk sac was completely inverted and villous. CONCLUSION: The general aspect of the fetal membranes in Sigmodontinae resembled that found in other cricetid rodents. Compared to murid rodents there were larger numbers of giant cells and in some genera these were seen to congregate at the periphery of the placental disk. Glycogen cells were found to invade the decidua but we did not identify trophoblast in the walls of the deeper decidual arteries. In contrast these vessels were surrounded by large numbers of uNK cells. This survey of wild-trapped specimens from five genera is a useful starting point for the study of placentation in an important subfamily of South American rodents. We note, however, that some of these rodents can be captive bred and recommend that future studies focus on the study of time dated pregnancies.

Calcium levels in the maxillae of human foetuses / Niveles de calcio en los maxilares de fetos humanos

Calcium along with phosphorus and carbonate imparts hardness and strength to skeletal system. Most of the human studies in this context are based on informations in postnatal life. There are different theories to explain the manner in which the matrix of bone becomes impregnated with the two inorganic salts, calcium phosphate and calcium carbonate. In our study, 29 human foetuses were obtained from the museum section of Department of Anatomy, J .N. Medical College, Aligarh, and divided into five groups. Maxillae were cleaned by separating the soft tissue and dissolved in concentrated nitric acid to determine calcium. Results were analysed by using Student's 't' test. The most striking feature of our findings was a reduction in aforementioned relative calcium in subsequent groups of foetuses. This decrease was highly significant in foetuses of last three groups i.e. III, IV and V. On the other hand, when total amount of calcium in foetal maxillae of adjacent groups were compared, a steady rise in concentration of calcium was noticed but no definite pattern was observed. Sexual dimorphism could be considered only in groups IV and V foetuses due to lack of female foetuses in first three groups. Some scientists did consider the human foetal bones but their interests were confined to parietal bone, femur and teeth. None of the earlier studies considered calcium concentration in maxillae of human foetuses. Therefore, our study aimed at measuring the level of calcium in maxillae of developing human foetuses in different age groups to find pattern, if any, during development for medicolegal purposes.

El calcio junto con el fósforo y el carbonato otorgan la dureza y la fuerza al sistema esquelético. La mayoría de los estudios en seres humanos se basan en la información de la vida postnatal. Existen diferentes teorías para explicar la manera en que la matriz del hueso se impregna con las de sales inorgánicas, fosfato de calcio y carbonato de calcio. Fueron utilizados 29 fetos humanos del Museo del Departamento de Anatomía, Facultad J. N. Medical, Aligarh, divididos en cinco grupos. Los maxilares fueron limpiados separando los tejidos blandos, luego se disolvieron en ácido nítrico concentrado para determinar el nivel de calcio. Los resultados se analizaron a través de la prueba t de Student. La característica más notable fue la reducción de calcio en los grupos subsecuentes de los fetos. Esta disminución fue muy significativa en los fetos de los tres últimos grupos es decir, III, IV y V. Por otro lado, cuando se comparó la cantidad total de calcio en maxilares fetales de los grupos adyacentes, se observó un aumento constante en la concentración de calcio, sin ningún patrón definido. El dimorfismo sexual pudo ser considerado sólo en los grupos IV y V de los fetos, ya que la falta de fetos femeninos en los primeros tres grupos impidió su comparación. Algunos científicos han examinado los huesos del feto humano, pero sus intereses se limitan a los huesos parietales, al fémur y los dientes. Ningún de los primeros estudios considera la concentración de calcio en los maxilares de los fetos humanos. Así el objetivo de este estudio fue medir el nivel de calcio durante desarrollo de fetos humanos en maxilares de fetos de diferentes edades para determinar algún patrón, si los hubiera, con fines médico-legales.

Diferentes índices volumétricos dos pulmões de feto com hernia diafragmática congênita avaliados pela ultrassonografia tridimensional / Different volumetric indices of lung in fetuses with congenital diaphragmatic hernia by three-dimensional ultrasonography

Objetivo: avaliar o potencial dos diferentes índices volumétricos de pulmões de fetos com hérnia diafragmática congênita isolada (HDC) medidos pela ultrassonografia tridimensional (US-3D) para predizer o resultado perinatal. Forma de estudo: Cinquenta e cinco fetos apresentando HDC foram avaliados pela US-3D entre janeiro de 2002 e maio de 2007. Os volumes pulmonares foram calculados pelo método rotacional na ultrassonografia tridimensional nos fetos com HDC (volumes observados) e comparados com aqueles descritos previamente em fetos normais (volumes esperados para determinada idade gestacional).

Objective: To evaluate the potencial of different lung mesurements using three-dimensional ultrasonography (3DUS) to predict perinatal outcome in cases of isolated congenital diaphragmatic hernia (CDH). Study design: Fifty-five fetuses presenting isolated CDH were prospectively evaluated by 3DUS between January 2002 and May 2007. Observed/expected total, contralateral and ipsilateral fetal lung volume ratios TFLV, CFLV and IFLV, respectively were calculated using the VOCAL™ technique and ultrasonographic fetal total lung volume to body weight ratio (US-FLW)...

The connective tissue of the adductor canal--a morphological study in fetal and adult specimens.

The adductor canal is a conical or pyramid-shaped pathway that contains the femoral vessels, saphenous nerve and a varying amount of fibrous tissue. It is involved in adductor canal syndrome, a claudication syndrome involving young individuals. Our objective was to study modifications induced by aging on the connective tissue and to correlate them to the proposed pathophysiological mechanism. The bilateral adductor canals and femoral vessels of four adult and five fetal specimens were removed en bloc and analyzed. Sections 12 microm thick were obtained and the connective tissue studied with Sirius Red, Verhoeff, Weigert and Azo stains. Scanning electron microscopy (SEM) photomicrographs of the surfaces of each adductor canal were also analyzed. Findings were homogeneous inside each group. The connective tissue of the canal was continuous with the outer layer of the vessels in both groups. The pattern of concentric, thick collagen type I bundles in fetal specimens was replaced by a diffuse network of compact collagen bundles with several transversal fibers and an impressive content of collagen III fibers. Elastic fibers in adults were not concentrated in the thick bundles but dispersed in line with the transversal fiber system. A dynamic compression mechanism with or without an evident constricting fibrous band has been proposed previously for adductor canal syndrome, possibly involving the connective tissue inside the canal. The vessels may not slide freely during movement. These age-related modifications in normal individuals may represent necessary conditions for this syndrome to develop.

Morphology of the lateral pterygoid muscle associated to the mandibular condyle in the human prenatal stage

El músculo pterigoideo lateral (MPL) establece una relación directa con el cóndilo y el disco articular, desempeñando un rol importante en el movimiento mandibular a través del complejo articular temporomandibular (CATM). El objetivo de este trabajo fue determinar la correspondencia entre las características morfológicas de los haces musculares del MPL y el grado de mineralización del cóndilo mandibular en la etapa prenatal, mediante un análsisi estructgural, ultraestructural y microanalítico. Se utilizaron 16 fetos humanos de 11 a 37 semanas de gestación, procedentes de abortos espontáneos y sin patologías aparentes. Se obtuvieron muestras del músculo pterigoideo lateral y cóndilo mandibular, para ser examinadas meidante microscopía ñoptica, electrónica y técnicas de microanálisis. Muestras incluidas en parafina se emplearon en los estudios de inmunomarcación con desmina (dilución 1:25 Dako) y alfa actina sarcómerica (dilución 1:50 Dako), visualizados con sistema avidina-biotina. El lado contralateral de cada una se utilizó para microscopía electrónica de transmisión. En 4 cóndilos de 17 y 21 semanas de desarrollo se analizó el contenido relativo de calcio y fósforo con la técnica microanalítica por difracción de rayos X. Entre las 11 y 16 semanas, el MPL estuvo contituido por miotubos secundarios asociados a céluals satélites y fascículos. La organización del músculo a las 37 semanas fue más compleja, con aspecto multipeniforme y con la edad se redujo la intensidad de la inmunomarcación con alfa actina sarcomérica. Estos resultados sugieren que entre las 16 y 22 semanas, el proceso de diferenciación y maduración de las fibras musculares precede y prevalece sobre el desarrollo y mineralización del cóndilo mandibular. La funcionalidad aún rudimentaria del MPL prenatal sería uno de los factores reguladores del proceso de osificación a nivel del cóndilo mandibular, cuyo ritmo aumentaría a partir de las 22 semanas de gestación (AU)

Morphology of the lateral pterygoid muscle associated to the mandibular condyle in the human prenatal stage

El músculo pterigoideo lateral (MPL) establece una relación directa con el cóndilo y el disco articular, desempeñando un rol importante en el movimiento mandibular a través del complejo articular temporomandibular (CATM). El objetivo de este trabajo fue determinar la correspondencia entre las características morfológicas de los haces musculares del MPL y el grado de mineralización del cóndilo mandibular en la etapa prenatal, mediante un análsisi estructgural, ultraestructural y microanalítico. Se utilizaron 16 fetos humanos de 11 a 37 semanas de gestación, procedentes de abortos espontáneos y sin patologías aparentes. Se obtuvieron muestras del músculo pterigoideo lateral y cóndilo mandibular, para ser examinadas meidante microscopía ñoptica, electrónica y técnicas de microanálisis. Muestras incluidas en parafina se emplearon en los estudios de inmunomarcación con desmina (dilución 1:25 Dako) y alfa actina sarcómerica (dilución 1:50 Dako), visualizados con sistema avidina-biotina. El lado contralateral de cada una se utilizó para microscopía electrónica de transmisión. En 4 cóndilos de 17 y 21 semanas de desarrollo se analizó el contenido relativo de calcio y fósforo con la técnica microanalítica por difracción de rayos X. Entre las 11 y 16 semanas, el MPL estuvo contituido por miotubos secundarios asociados a céluals satélites y fascículos. La organización del músculo a las 37 semanas fue más compleja, con aspecto multipeniforme y con la edad se redujo la intensidad de la inmunomarcación con alfa actina sarcomérica. Estos resultados sugieren que entre las 16 y 22 semanas, el proceso de diferenciación y maduración de las fibras musculares precede y prevalece sobre el desarrollo y mineralización del cóndilo mandibular. La funcionalidad aún rudimentaria del MPL prenatal sería uno de los factores reguladores del proceso de osificación a nivel del cóndilo mandibular, cuyo ritmo aumentaría a partir de las 22 semanas de gestación (AU)

Quantitative study using semithin section of the rat fetal myocardium

Durante el desarrollo embrionario el corazón es muy dependiente de la proliferación de miocitos, la que continúa hasta el recién nacido. La regeneración del miocardio durante este período varía directamente con el potencial de proliferación celular. Es aún discutible las capacidades proliferativas e hipertróficas del miocardio desde el periodo embrionario al perinatal. Utilizamos 5 fetos de ratas no consanguíneos de l8, 5 y 2O, 5 días de gestación, obteniéndose fragmentos de su pared ventricular izquierda, fijados y procesados para la microscopía de electrónica de rutina. Efectuamos la estimación estereológica en delgadas secciones, en cada corazón, que fue obtenida en 10 campos microscópicos escogidos al azar, con el Sistema test M-42 montada en un ocular Nikon CFW(IOX) y con uno objetivo de immersion IOOX). Se realizó un estudio cualitativo a través de microscopía electrónica. Los resultados muestran los promedios de los valores de densidad volumétrica: a) Miocitos (incluyendo núcleos) =69,3 por ciento; b) El núcleo del micocito aislado=6,5; c) Tejido conjuntivo (incluyendo vasos) = 30,7 por ciento. El núcleo de los micotitos tiene un promedio de densidad de superficie igual a= 0,073 Úm2/Úm3. El promedio de densidad numérica de núcleos se obtuvo utilizando el método disector y el valor encontrado fue de 2357160/mm3. El diámetro de núcleos de los miocitos, considerándolos como una esfera fue 3,7 Úm3. La ME presentó miocitos bien fijados con buen desarrollo de los sarcómeros, dispuestos en forma irregular en el citoplasma de esta célula. El intersticio cardíaco mostró fibroblastos con características de una gran síntesis proteica. El volumen de núcleos de cardiomiocitos es menor al encontrado en el miocardio humano durante este período. Hay diferencias en la densidad numérica de núcleos si se comparan rata y humano. Este artículo sugiere la presencia de cardiomiocitos binucleados durante el período fetal en la rata en mayor número que los reportados en trabajos previos

Ultrastructure of developing human muscle: the problem of multinucleation of striated muscle cells

As células musculares estriadas dos vertebrados säo de origem mesodérmica, particularmente do mesoderma para-axial localizado nos somitos. No embriäo humano de 32 dias cada somito inicia um processo de diferenciaçäo em três porçöes: o miótomo que dá origem ao músculo, o dermátomo e o esclerótomo. No miótomo proliferam as células musculares embrionárias mononucleadas, os mioblastos. A partir da oitava semana de vida embrionária já säo observadas células musculares mais diferenciadas, os miotubos: säo células com mais de um núcleo de localizaçäo central. Ao redor dos núcleos, säo observadas as miofibrilas. A partir do quinto mês de vida intra-interina, os núcleos migram para a periferia do citoplasma, para as porçöes sub-sarcolêmicas, dando origem às fibras musculares propriamente ditas. Há três teorias sobre o mecanismo de multinucleaçäo das células musculares: a) cada célula muscular multinucleada é um sincício resultante da fusäo de várias células musculares mononucleadas; b) divisäo do núcleo, sem divisäo do citoplasma (amitose); c) ocorrência de ambos os processos. No presente trabalho, foram estudadas por microscopia eletrônica células musculares provenientes de 27 fetos humanos variando de 9 semanas de vida embrionária até 9 meses. Foi possível se observar que mioblastos em mitose säo comuns entre os miotubos e que os mesmos localizam-se entre a membrana plasmática e a membrana basal dos miotubos. Foi possível ainda se observar em vários campos examinados a presença de mioblastos situados nas extremidades de miotubos ou entre dois miotubos longitudinalmente dispostos cujas membranas plasmáticas justapostas encontravam-se em degeneraçäo sugerindo uma possível anexaçäo das células mais jovens (mioblastos) pelas células mais diferenciadas (miotubos). Se isoo realmente ocorre, o fato poderia em parte explicar o fenômeno da multinucleaçäo das células musculares estriadas

The developing human muscle: ultrastructural differences between myoblasts and fibroblasts.

Material from foetuses of nine weeks to nine months development was examined by electron microscopy to obtain some information about the various stages in the development of skeletal muscle and structures which are intimately related to it, such as blood vessels, nerves, neuromuscular spindles, fibroblasts and their product, i.e., collagen. Regarding the myoblasts and fibroblasts it was interesting to compare their ultrastructural features since there has been some difficulty in the identification of these two types of mononucleated cells by the authors which deal with light microscopy in the study of developing skeletal muscle. It was possible to note that between nine and eighteen weeks of development the muscle is different from mature skeletal muscle and is composed predominantly of two populations of muscle cells. These are the myoblasts which are mononucleated cells and the myotubes which are multinucleated muscle cells. After eighteen weeks of development there occur only muscle fibres similar to those of adult muscle. Fibroblasts also occur frequently in the developing muscle: they too are mononucleated cells. Fibroblasts and collagen fibrils are seen between the muscle cells and structures related to them as early as nine weeks of development. Bundles of collagen were also seen in the cytoplasm of fibroblasts.