Scanning microscopy of the early stages of embryonic development of baboons (Papio cynocephalus): oocyte, penetration of the zona pellucida, and morula]

The surface of ovarian oocytes is evenly covered with finger-like microvilli about 1 micron long. Penetration of capcitated spermatozoa in the zona pellucida apparently occurs after acrosome reaction and though a narrow slitmmorulae are constituted of rounded blastomeres, usually of similar size and microvillous covering. A few blastomeres may be smaller than others, probably as a result of faster mitotic rate in one of the blastomeres compared to adjacent ones. Microvilli are numerous in the interblastomeric furrows where junctional ridges are not observed at the 30-40 cell stage.     

Effect of 2 inhibitors of glycoprotein synthesis, tunicamycin and 2-deoxyglucose, on development of the sea urchin (Paracentrotus lividus) egg]

Tunicamycin, an inhibitor of glycoprotein synthesis, inhibits the development of the sea Urchin egg. Gastrulation is very sensitive to the Tunicamycin. Fertilization is not inhibited. 2-deoxy-D-glucose inhibits gastrulation and induces the hyperdevelopment of ectodermic structures.     

Über DPNH-Diaphorase und alkalische Phosphatase bei Präimplantationsstadien des Goldhamsters (Mesocricetus auratus Waterh.)

Summary The activity of the DPNH-diaphorase and the alkaline phosphatase were examined in golden-hamster eggs prior to fixation. The reactions for DPNH-diaphorase as well as for alkaline phosphatase were found to be positive already in the undivided egg and in early cleavage stages. The reaction products of both enzyme determinations showed a histophotometrically measurable polar distribution in the cytoplasm, in the one-cell stage as well as in the individual blastomeres of the examined early cleavage stages.     

Composition and functional role of the mucus layers in the intestine

In discussions on intestinal protection, the protective capacity of mucus has not been very much considered. The progress in the last years in understanding the molecular nature of mucins, the main building blocks of mucus, has, however, changed this. The intestinal enterocytes have their apical surfaces covered by transmembrane mucins and the whole intestinal surface is further covered by mucus, built around the gel-forming mucin MUC2. The mucus of the small intestine has only one layer, whereas the large intestine has a two-layered mucus where the inner, attached layer has a protective function for the intestine, as it is impermeable to the luminal bacteria.     

Purinergic signaling in embryonic and stem cell development

Nucleotides are of crucial importance as carriers of energy in all organisms. However, the concept that in addition to their intracellular roles, nucleotides act as extracellular ligands specifically on receptors of the plasma membrane took longer to be accepted. Purinergic signaling exerted by purines and pyrimidines, principally ATP and adenosine, occurs throughout embryologic development in a wide variety of organisms, including amphibians, birds, and mammals. Cellular signaling, mediated by ATP, is present in development at very early stages, e.g., gastrulation of Xenopus and germ layer definition of chick embryo cells. Purinergic receptor expression and functions have been studied in the development of many organs, including the heart, eye, skeletal muscle and the nervous system. In vitro studies with stem cells revealed that purinergic receptors are involved in the processes of proliferation, differentiation, and phenotype determination of differentiated cells. Thus, nucleotides are able to induce various intracellular signaling pathways via crosstalk with other bioactive molecules acting on growth factor and neurotransmitter receptors. Since normal development is disturbed by dysfunction of purinergic signaling in animal models, further studies are needed to elucidate the functions of purinoceptor subtypes in developmental processes.     

Molecular basis of morphogenesis during vertebrate gastrulation

Gastrulation is a crucial step in early embryogenesis. During gastrulation, a set of morphogenetic processes takes place leading to the establishment of the basic body plan and formation of primary germ layers. A rich body of knowledge about these morphogenetic processes has been accumulated over decades. The understanding of the molecular mechanism that controls the complex cell movement and inductive processes during gastrulation remains a challenge. Substantial progress has been made recently to identify and characterize pathways and molecules implicated in the modulation of morphogenesis during vertebrate gastrulation. Here, we summarize recent findings in the analysis of signaling pathways implicated in gastrulation movements, with the aim to generalize the basic molecular principles of vertebrate morphogenesis.     

一种高速铁路无砟轨道混凝土结构疲劳损伤模型

基于连续损伤力学理论和边界面概念,建立了高速铁路无砟轨道混凝土结构在循环荷载作用下的疲劳损伤模型.模型在主坐标系中采用了拉压两个边界面,根据加载面与极限断裂面、边界面之间的位置关系来计算高速铁路无砟轨道混凝土结构在复杂应力状态下的损伤,并由累积损伤与应变能释放率之间的关系确定循环加载中极限断裂面的变化规律.通过将该理论模型嵌入有限元软件ABAQUS的用户材料子程序UMAT,与同类模型进行比较验证了模型的可行性.最后对高速铁路双块式无砟轨道支承层进行了循环动荷载作用下的疲劳累积损伤分析.结果表明该模型不仅能够较好地反映支承层在循环荷载作用下疲劳损伤非线性演变规律,还可以展现其疲劳损伤分布形态的全过程,为研究高速铁路无砟轨道混凝土结构的疲劳损伤与寿命预测,提供了可行的理论分析方法.     

Teratogenic effects of cadmium on Bufo arenarum during gastrulation

Developing Bufo arenarum embryos were treated during gastrulation with cadmium chloride in concentrations ranging from 6x10(-7) to 1.5x10(-5)M Cd++ at 20 and 30 degrees C. Initial failures at gastrulation result mainly in axial incurvations, microcephaly, hydropsy and abnormal tail formation. The higher temperature has a dual effect: at high concentrations of Cd early malformations are significantly increased; whereas, at low concentrations the higher temperature prevents alterations.     

The effects of actinomycin D and chloramphenicol on the rat preimplantation embryos

Summary Actinomycin D and chloramphenicol, injected in the rat on day 3 or 4 of gestation, induce embryolethality and embryotoxicity. These effects are revealed on day 5 of pregnancy by reduced number of blastocysts and by decrease of mean blastomeres number.     

The effects of actinomycin D and chloramphenicol on the rat preimplantation embryos

Actinomycin D and chloramphenicol, injected in the rat on day 3 or 4 of gestation, induce embryolethality and embryotoxicity. These effects are revealed on day 5 of pregnancy by reduced number of blastocysts and by decrease of mean blastomeres number.     

基于二氧化硅的量子点荧光纳米颗粒制备

多步制备了Si02-CdTe QDs荧光纳米颗粒，包括表面氨基化SiO2纳米颗粒载体、组装于载体表面的CdTeQDs壳以及最外层的二氧化硅壳。制备的SiO2-CdTe QDs荧光纳米颗粒性能稳定，紫外吸收和荧光发射增强明显。最外层的SiO2壳保证量子点的化学和光学稳定性的同时，还有助于表面生物基团的修饰。可以预见，SiO2-CdTe QDs荧光纳米颗粒作为生物探针将来应用于生化分析研究的广阔前景。     

Gene expression in spermiogenesis

Germ cells convey parental genes to the next generation, and only germ cells perform meiosis, which is a mechanism that preserves the parental genes. The fusion of the products of germ cell meiosis, the haploid sperm and egg, creates the next generation. Sperm are the haploid germ cells that contribute genes to the egg. In preparation for this, the haploid round spermatids produced by meiosis undergo drastic morphological changes to become sperm. During this process of spermiogenesis, the nuclear form of the haploid germ cell takes shape, the mitochondria are rearranged in a specific manner, the flagellum develops and the acrosome forms. Spermatogenesis is supported by precise and orderly regulation of gene expression during the changes in chromatin structure, when protamine replaces histone. In this report, we summarize the molecular mechanisms involved in spermiogenesis.Received 2 September 2004; received after revision 7 October 2004; accepted 7 October 2004     

Fecundity of the blood-feeding insectRhodnius prolixus increases in successive periods of egg production

The fecundity of the blood-feeding insect,Rhodnius prolixus, was observed to increase in successive periods of egg production, each period being triggered by a single large blood meal. As previously published, the fecundity of mated animals was significantly higher than that of unmated animals for the first period of egg production. For a second period of egg production, fecundity increased significantly in both mated and unmated animals. By the fourth period, fecundity had returned to first-feed values for mated animals, but remained high for unmated animals, and the fecundity of mated and unmated animals was not significantly different. Thus, during successive periods of egg production, the processes which maintain fecundity of unmated animals below that of mated animals are overcome.     

Comparison of the in vitro development of mouse single blastomeres with and without the zona pellucida

No difference was observed during in vitro development between mouse single blastomeres with and without the zona pellucida, isolated from 2- and 4-cell stage eggs.     

Comparison of the in vitro development of mouse single blastomeres with and without the zona pellucida

Summary No difference was observed during in vitro development between mouse single blastomeres with and without the zona, pellucida, isolated from 2- and 4-cell stage eggs.     

A sperm GPI-anchored protein elicits sperm-cumulus cross-talk leading to the acrosome reaction

The acrosome reaction has long been thought to be induced by the zona pellucida. Here we report the identification and function of a novel human sperm glycosylphosphatidylinositol (GPI)-anchored membrane protein, NYD-SP8. The release of the protein during sperm-egg interaction and its binding to the cumulus, the first layer of egg investment, elicits cross-talk between the gametes and produces calcium dependant release of progesterone, which lead to the acrosome reaction. An in vivo mouse model of NYD-SP8 immunization is also established showing a reduced fertility rate. Thus, contrary to accepted dogma, our study demonstrates for the first time that, prior to reaching the zona pellucida, sperm may release a surface protein that acts on the cumulus cells leading to the acrosome reaction, which may be important for determining the outcome of fertilization. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Received 11 August 2008; received after revision 18 December 2008; accepted 22 December 2008     

Some aspects of the early development and implantation of the mammalian egg

Summary The early development and implantation of the mammalian egg is described for various species and the differing and often contradictory solutions proposed by different authors for the many problems arising from their investigations are exposed, compared and discussed.     

Fibronectin peptide DRVPHSRNSIT and fibronectin receptor peptide DLYYLMDL arrest gastrulation ofRana pipiens

Gastrulation is characterized by dramatic cell migration which is thought to require the interaction of cell adhesion molecules with extracellular molecules. We have tested two novel peptides, a fibronectin peptide and a fibronectin receptor peptide, for their effects on gastrulation of the leopard frogRana pipiens. The fibronectin peptide DRVPHSRNSIT corresponds to residues 1373–1383 of the cell-binding domain of fibronectin; the receptor peptide DLYYLMDL corresponds to residues 124–131 of 1 subunit of a variety of integrins including 51. Either of these peptides significantly inhibited gastrulation after being microinjected into mid-blastulae. These results indicate that these sequences may correspond to the ligand/receptor interaction sites of fibronectin and its receptor(s).     

Hensen's node — The ’Organizer’ of the amniote embryo

Conclusion If the hundred years of study on theHensen's node — i.e. on gastrulation and early determination of the embryos of amniote vertebrates — teach anything, they teach in the first place how limited and fragmentary our knowledge is about one of the most central problems of the whole developmental biology. We know that the events in early amniote development — or early avian development, on which our data and ideas are nearly all based — in many ways resemble those in early Amphibian development, which is only slightly better understood, but we also know that direct extrapolations from anamniotes to amniotes cannot be made without proper reservations and without studying the amniote embryos themselves. And we have practically no idea of what is really going on in the cells of the blastoderm when they move, invaginate, induce or are induced, interact, become determined and begin their differentiation. We know that at the stages of gastrulation, the node, and indeed the whole blastoderm, is in a very labile state and can be regulated in many ways to produce a harmonious whole — or a monster — although we only understand very poorly the modes of this regulation. The progress made during the decades, and particularly in recent years, shows, however, that useful information is accumulating to produce a coherent picture, and there is no reason to be pessimistic.Dedicated to ProfessorEtienne Wolff on the occasion of his retirement.