The germ cell lineage ensures reproduction and heredity. The mechanism for germ cell specification in primates, including humans, has remained unknown. In primates, upon implantation the pluripotent epiblast segregates the amnion, an extra-embryonic membrane eventually ensheathing an embryo, and thereafter initiates gastrulation to generate three germ layers. Here, we show that in cynomolgus monkeys, the SOX17/TFAP2C/BLIMP1-positive primordial germ cells (cyPGCs) originate from the dorsal amnion at embryonic day 11 (E11) prior to gastrulation. cyPGCs appear to migrate down the amnion and, through proliferation and recruitment from the posterior amnion, expand in number around the posterior yolk sac by E17. Remarkably, the amnion itself expresses BMP4 and WNT3A, cytokines potentially critical for cyPGC specification, and responds primarily to them. Moreover, human PGC-like cells in vitro exhibit a transcriptome similar to cyPGCs just after specification. Our study identifies the origin of PGCs and a unique function of the nascent amnion in primates.
This study examined the external morphology and morphometry of the human embryonic inner ear membranous labyrinth and documented its three-dimensional position in the developing embryo using phasecontrast X-ray computed tomography and magnetic resonance imaging. A total of 27 samples between Carnegie stage (CS) 17 and the postembryonic phase during trimester 1 (approximately 6-10 weeks after fertilization) were included. The otic vesicle elongated along the dorsoventral axis and differentiated into the end lymphatic appendage and cochlear duct (CD) at CS 17. The spiral course of the CD began at CS18, with anterior and posterior semicircular ducts (SDs) forming prominent circles with a common crus. The spiral course of the CD comprised more than two turns at the postembryonic phase, at which time the height of the CD was evident. A linear increase was observed in the length of anterior, posterior, and lateral SDs, in that order, and the length of the CD increased exponentially over the course of development. Bending in the medial direction was observed between the cochlear and vestibular parts from the latero-caudal view, with the angle decreasing during development. The position of the inner ear was stable throughout the period of observation on the lateral to ventral side of the rhombencephalon, caudal to the pontine flexure, and adjacent to the auditory ganglia. The plane of the lateral semicircular canal was approximately 8.08-14.68 with respect to the cranial caudal (z-)axis, indicating that the orientation of the inner ear changes during growth to adulthood. Anat Rec, 298:2081Rec, 298: -2090Rec, 298: , 2015. V C 2015 Wiley Periodicals, Inc.Abbreviations used: CD 5 cochlear duct; CS 5 Carnegie stage; IEL 5 Inner ear length; MRI 5 magnetic resonance imaging; PCXT 5 phase-contrast X-ray computed tomography; PE 5 postembryonic phase
The purpose of this study is to investigate the effects of number of graphite nodules on fatigue limit and fracture origins in spheroidal graphite cast iron where carbon content and the number of graphite nodules are changed. As specimens, spheroidal graphite cast irons with 3.0, 3.2, 3.4, 3.6 and 3.8 mass% carbon content were produced respectively. Matrix was conducted pearlite (PDI) and ausferrite (ADI) by heat treatment (normalizing and austempering). The mean diameter of the graphite nodule decreases as the carbon content increases, and the number of graphite nodules per unit area increases. No differences were observed in tensile strength as a result of variations in the number of graphite nodules. The rotating bending fatigue test was conformed to JIS (Japanese Industrial Standards). Load frequency was 47 rpm, number of cycle to discontinue test was 1.0 © 10 7 cycles, and the specimen used was the 1 type of 8.00 mm in diameter. All the fracture surfaces were observed with a scanning electron microscope. The relationship between the characteristics of fatigue strength and the size of fracture origins (defect size) was investigated.No differences were observed in fatigue limit as a result of variations in the number of graphite nodules. Fracture origins were microshrinkage, unspheroidizing graphite nodule and aggregate graphite nodules. The percentage of fracture origin of aggregate graphite nodules was increased by cluster of the graphite nodules. The reason of this phenomenon was due to the decrease of the graphite nodules spacing. The mean defect size in each sample was constant irrespective of the change of number of graphite nodules, which was good agreement with the results of the fatigue limit.
The precise mechanisms through which the digestive tract develops during the somite stage remain undefined. In this study, we examined the morphology and precise timeline of differentiation of digestive tract-derived primordia in human somite-stage embryos. We selected 37 human embryos at Carnegie Stage (CS) 11-CS13 (28-33 days after fertilization) and threedimensionally analyzed the morphology and positioning of the digestive tract and derived primordia in all samples, using images reconstructed from histological serial sections. The digestive tract was initially formed by a narrowing of the yolk sac, and then several derived primordia such as the pharynx, lung, stomach, liver, and dorsal pancreas primordia differentiated during CS12 (21-29 somites) and CS13 ( 30 somites). The differentiation of four pairs of pharyngeal pouches was complete in all CS13 embryos. The respiratory primordium was recognized in 26-somite embryos and it flattened and then branched at CS13. The trachea formed and then elongated in 35-somite embryos. The stomach adopted a spindle shape in all 34-somite embryos, and the liver bud was recognized in 27-somite embryos. The dorsal pancreas appeared as definitive buddings in all but three CS13 embryos, and around these buddings, the small intestine bent in 33-somite embryos. In 35-somite embryos, the small intestine rotated around the cranial-caudal axis and had begun to form a primitive intestinal loop, which led to umbilical herniation. These data indicate that the digestive tract and derived primordia differentiate by following a precise timeline and exhibit limited individual variations. Anat Rec,
The purpose of this study is to investigate that effects of graphite spheroidization ratio and microstructure on the characteristics of fatigue limit in spheroidal graphite cast iron. Ferritic spheroidal graphite cast iron (FDI), pearlitic spheroidal graphite cast iron (PDI) and austempered spheroidal graphite cast iron (ADI) were used as specimens. The graphite spheroidization ratio was varied between 63³94% by the addition of a spheroidizing agent. Tensile test was carried out in air at room temperature. The experiment conformed to JIS (Japan Industrial Standards). Rotating bending fatigue test was also carried out using these materials. The experiment conformed also to JIS. Stress ratio R was ¹1, and the specimen used was type 1(JIS) with a diameter of 8 mm. The test was carried out in air at room temperature. The relationship between fatigue limit and graphite spheroidization ratio was investigated, as well as the correlation between fatigue limit and defect size.When the graphite spheroidization ratio was over 80%, the fatigue limit was not influenced. Fracture origins were micro-shrinkage, aggregate graphite, and unspheroidized graphite. When graphite spheroidization decreased, the ratio of unspheroidized graphite at the fracture origin increased. The defect size that transitioned from region I to II differed according to the microstructure: the defect size of PDI was the smallest, and that of FDI was larger than ADI. When there are no large defects in FDI, the fatigue limit can be estimated by tensile strength. However, in PDI and ADI, it must be estimated taking into account the size of existing defects in specimens.
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