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PubMed1995

Sixth Annual Stuart Reiner Memorial Lecture: embryonic development of nerve and muscle.

This article provides a basic scheme of sequential anatomic and some physiologic events occurring during the course of embryonic development of motor neurons and muscles, leading to the establishment of mature nerve-muscle relationships. Motor neurons and muscles begin their development independently and during embryogenesis they become dependent on each other for further development and survival. Aspects of development which occur independently and those requiring mutual interactions are identified. The development of motor neurons is discussed with respect to their production, projection, neuromuscular transmission, myelination, sprouting, survival, and death. The development of muscles is discussed with respect to the origin, differentiation, and muscle fiber types. Discussion on the development of neuromuscular junction includes differentiation of presynaptic nerve terminal, postsynaptic components, and elimination of multiple axons.

Animals↗
PubMed1986

Embryonic development of the chicken external cloaca and phallus.

The use of the scanning electron microscope has provided new detailed information about the embryonic development of the chicken external cloaca and phallus and has consequently clarified the origin of the differences between the anatomy of the chicken and turkey phallus. At Day 6 (of incubation), the genital (g.) tubercle is formed in the ventral aspect of the embryo between the caudal fold of the amnion and the tail bud. On the ventral surface of the tail bud are paired g. swellings which flank the g. tubercle. Originating at the midline between the g. swellings is the g. crest which is joined cranially to the g. tubercle and later in development forms the ventral floor of the proctodeum (the most caudal cloacal compartment). By Day 8 the base of the g. tubercle has expanded caudolaterally to merge with the craniolateral extensions of the g. swellings. The g. swellings have likewise merged medially thus completing a collar-like structure around the g. tubercle. By Day 16, the dorsal and ventral lips of the cloaca have differentiated from the collar-like structure and the rounded, apical region of the g. tubercle gives rise to the primitive phallus. Further development of the external cloaca and phallus is limited primarily to the rotation of the phallus toward the ventral floor of the proctodeum and the concurrent shortening (longitudinally) of the proctodeum. Additional differentiation of the phallus occurs after hatching.

Animals↗
PubMed1990

[Influence of tubal and uterine milieu in the embryonic development].

Establishment of pregnancy in mammals is a process resulting of closely concerted events. The participation of the embryo through its development and secretory activity on the one hand, and on the other, the oviductal and endometrial tissues, by means of their secretions, give the optimal conditions to let the embryo establish creating a proper milieu for its nutrition and development. In this review, we analyze the influence of the oviductal and uterine secretions upon early embryonic development and differentiation and some transport systems of nutritional elements required in the early stages of the blastogenesis.

Embryo Implantation↗
PubMed2006

GLUT1 deficiency links nutrient availability and apoptosis during embryonic development.

GLUT1 is essential for human brain development and function, as evidenced by the severe epileptic encephalopathy observed in children with GLUT1 deficiency syndrome resulting from inherited loss-of-function mutations in the gene encoding this facilitative glucose transporter. To further elucidate the pathophysiology of this disorder, the zebrafish orthologue of human GLUT1 was identified, and expression of this gene was abrogated during early embryonic development, resulting in a phenotype of aberrant brain organogenesis consistent with the observed expression of Glut1 in the embryonic tectum and specifically rescued by human GLUT1 mRNA. Affected embryos displayed impaired glucose uptake concomitant with increased neural cell apoptosis and subsequent ventricle enlargement, trigeminal ganglion cell loss, and abnormal hindbrain architecture. Strikingly, inhibiting expression of the zebrafish orthologue of the proapoptotic protein Bad resulted in complete rescue of this phenotype, and this occurred even in the absence of restoration of apparent glucose uptake. Taken together, these studies describe a tractable system for elucidating the cellular and molecular mechanisms of Glut1 deficiency and provide compelling in vivo genetic evidence directly linking nutrient availability and activation of mitochondria-dependent apoptotic mechanisms during embryonic brain development.

Animals↗
PubMedDate not supplied

[The determination of the cytodifferentiation of the adenohypophysis in embryonic development].

This is a review of the literature and author's own data on determination of various cell types of adenohypophysis during embryonic development. Recent studies using techniques of organ culture and immunohistochemistry have established the time of determination of glandular cells of adenohypophysis. It has been shown in rat embryos that the direction of differentiation of all major cell types of adenohypophysis is programmed late during the development of the epithelial anlage of this organ. Similar data as concerns somatotropic and prolactin cells have been obtained on chick embryos. Chick embryos possess regional type of determination of prolactin and somatotropin-containing cells in the anlage in correspondence with their location in definitive adenohypophysis.

Animals↗
PubMed1989

Lack of expression of HLA-B27 gene in transgenic mouse trophoblast. Conserved genetic pressures underlying extra-embryonic development.

The mechanisms that regulate developmental control of the expression of MHC class I genes during generation of extra-embryonic tissues are largely unknown. In the present study, we studied the levels of transcripts of the human HLA-B27 gene in extra-embryonic tissues of transgenic mice containing the HLA-B27 (heavy chain) gene by in situ hybridization with biotinylated single-stranded RNA probes. In contrast to extra-embryonic stromal cells and embryonic tissues which contain (varying levels of) messenger RNA coding for HLA-B27, specific transcripts were not detected in labyrintho-, or spongiotrophoblast, nor in trophoblastic giant cells. These cells are devoid of HLA A and B locus class I transcripts in man. Regulation of expression of human MHC class I genes in extra-embryonic trophoblast in transgenic animals is thus under conserved selective pressure that is retained across a species barrier. Thus, in extra-embryonic tissues, regulation of expression of MHC class I genes is distinct from the mechanisms operating in developing embryonic cells.

Animals↗
PubMed2002

The dynamic expression pattern of B lymphocyte induced maturation protein-1 (Blimp-1) during mouse embryonic development.

We have analyzed the spatial and temporal patterns of B lymphocyte-induced maturation protein-1 (Blimp-1) expression during mouse embryonic development. Blimp-1 expression is induced early in the anterior definitive endoderm, mesoderm of head process, and prechordal plate. In ectoderm-derived tissues at later stages, Blimp-1 expression is found in the primitive photoreceptors of neural retina, in differentiated epithelial cells of epidermis, tongue, oral and nasal cavities, and in the precursors of internal root sheaths of hair follicles. In mesoderm-derived tissues, Blimp-1 expression is observed in splanchnopleure, a subset of somatopleure-derived cells in limb buds, and myotomes of somites. Blimp-1 is also expressed in mesenchyme of developing hand plates, digits, branchial arches, nasal processes, and external genitalia. Blimp-1 is present in mesenchyme-derived chondroblasts, supporting cells of taste buds, and papilla of teeth, hair follicles and taste buds. In endoderm-derived tissues, Blimp-1 expression in the foregut region is restricted to a subset of epithelial cells at the headfold stage while expression in the endodermal epithelium of midgut and hindgut persists from the headfold stage to birth. Finally, Blimp-1 is expressed in the migrating primordial germ cells.

Animals↗
PubMed1998

Effects of pulsed ultrasound on embryonic development: an in vitro study.

Whole-embryo culture was used as the model system to study the effects of pulsed ultrasound on embryonic development. Rat embryos (9.5 days old) were exposed to a wide range of ultrasound levels at ultrasound frequencies between 1-4 MHz for 30 min in vitro. After 48 h in culture, absolute control, sham and treatment embryos were assessed for viability, morphology, growth and development. At an ambient temperature of 37 degrees C, no significant effects were observed for spatial peak temporal average intensities below 4 W/cm2 or peak negative pressures below 1.9 MPa. At higher acoustic levels, there was a significant increase in the number of nonviable embryos and the number of morphological abnormalities in viable embryos increased. Abnormal cephalocaudal flexion and abnormal head development were the most common gross morphological abnormalities. Both thermal and nonthermal bioeffect mechanisms are involved.

Analysis of Variance↗
PubMed2006

Complete loss of iron regulatory proteins 1 and 2 prevents viability of murine zygotes beyond the blastocyst stage of embryonic development.

Iron regulatory proteins 1 and 2 (IRPs) are homologous mammalian cytosolic proteins that sense intracellular iron levels and post-transcriptionally regulate expression of ferritin, transferrin receptor, and other iron metabolism proteins. Adult mice with homozygous targeted deletion of IRP2 develop microcytic anemia, elevated red cell protoporphyrin IX levels, high serum ferritin, and adult-onset neurodegeneration. Mice with homozygous deletion of IRP1 develop no overt abnormalities, but mice that lack both copies of IRP2 and one copy of IRP1 develop a more severe anemia and neurodegeneration than mice with deletion of IRP2 alone. Here, we have demonstrated that IRP1-/- IRP2-/- embryos do not survive gestation, and that although IRP1-/- IRP2-/blastocysts can be genotyped and harvested, implanted embryos with the IRP1-/- IRP2-/genotype are undetectable at embryonic day 6.5 and beyond. Blastocysts derived from a cross in which 25% of the fertilized embryos were expected to have the IRP1-/- IRP2-/genotype often showed brown discoloration and abnormal morphology. These abnormal blastocysts likely have the IRP1-/- IRP2-/- genotype, and the brown discoloration may be attributable to ferritin overexpression and sequestration of ferric iron in ferritin, whereas abnormal morphology may be due to concomitant functional iron deficiency. These results demonstrate that IRPs are indispensable for regulation of mammalian iron homeostasis at the post-implantation stage of murine embryonic development.

Animals↗
PubMed2006

Loggerhead sea turtle (Caretta caretta) egg yolk concentrations of persistent organic pollutants and lipid increase during the last stage of embryonic development.

Data are scarce describing the concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides in sea turtle eggs. The purpose of this study was to establish appropriate sample collection methodology to monitor these contaminants in sea turtle eggs. Contaminant concentrations were measured in yolk samples from eggs that failed to hatch from three loggerhead sea turtle (Caretta caretta) nests collected in southern Florida to determine if concentrations change through embryonic development. One to three egg yolk samples per nest were analyzed from early, middle, and late developmental stages (n=22 eggs total). PCB and pesticide concentrations were determined by gas chromatography with electron capture detection (GC-ECD). Geometric mean concentrations of summation operatorPCBs (52 congeners), summation operatorDDTs, summation operatorchlordanes, and dieldrin in all eggs were 65.0 (range=7.11 to 3930 ng/g lipid), 67.1 (range=7.88 to 1340 ng/g lipid), 37.0 (range=4.04 to 685 ng/g lipid), and 11.1 ng/g lipid (range=1.69 to 44.0 ng/g lipid), respectively. Early and middle developmental stage samples had similar concentrations of PCBs and organochlorine pesticides on a wet-mass basis (ng/g tissue extracted), but the concentrations doubled by the late stage. This increase is most likely attributable to the 50% increase in lipid content observed in the late-stage yolk. These findings indicate that an early-stage sample cannot be directly compared to a late-stage sample, especially from different nests. These preliminary findings also allowed us to calculate the minimum number of eggs per nest required for analysis to obtain an acceptable mean concentration per nest. More research is required to investigate geographical trends of contaminant concentrations and potential health effects (i.e., abnormalities) caused by these contaminants on sea turtle development.

Animals↗
PubMed1988

Embryonic development in superovulated dairy cattle exposed to elevated ambient temperatures between Days 1 to 7 post insemination.

Holstein heifers (n = 29) were used to determine whether thermal stress during the first 7 d of embryonic development may increase the incidence of embryonic abnormalities in dairy cattle. Heifers were acclimated to environmental chambers at 20 degrees C for 9 d and superovulated with follicle stimulating hormone-pituitary (FSH-P; 40 mg total), beginning on Days 9 to 11 of the estrous cycle. Prostaglandin F(2)alpha (Lutalyse; 50 mg total) was administered on Day 3 of FSH-P. Heifers were inseminated artificially at estrus and then maintained at either thermal neutrality (20 degrees C) or under hyperthermic conditions (daily exposure up to 16 h at 30 degrees C and 8 h at 42 degrees C) for 7 d beginning at 30 h after the onset of estrus. On Day 7 post estrus, embryos were recovered nonsurgically and evaluated morphologically for stage of development and quality. The distribution of embryos classified as normal, abnormal, retarded or as unfertilized ova, differed (P<0.001) between heat stress and thermoneutral treatments. Only 20.7% of 82 embryos recovered from stressed heifers were normal compared with 51.5% of 68 embryos from thermoneutral animals. Stressed heifers had a higher incidence of abnormal and retarded embryos with degenerate nonviable blastomeres. Responses indicated that thermal stress from 30 h after the onset of estrus to Day 7 post estrus increases the incidence of abnormal and retarded embryos in superovulated heifers.

Journal Article↗
PubMed2000

Embryonic development of the nervous system of the rhabdocoel flatworm Mesostoma lingua (Abilgaard, 1789).

We have analyzed the embryonic development of the Mesostoma nervous system, using a combination of histology, transmission electron microscopy, and wholemount immunohistochemistry. Neural progenitors are formed at an early stage when the Mesostoma embryo constitutes a multilayered mesenchymal mass of cells. A neurectoderm as in vertebrates or arthropods is absent. Only after neurons in the deep layers of the embryo have started differentiating do superficial cells reorganize into an epithelium that will give rise to the epidermis. Neurons are clustered in two anterior, bilaterally symmetric brain hemispheres. An antibody against acetylated beta-tubulin (anti-acTub) that labels neurotubules reveals an invariant pattern of pioneer neurons in the brain of midstage embryos. Pioneer neurons are grouped in several small clusters at characteristic positions. They pioneer several commissural tracts of the brain and two pairs of ventral and dorsal connectives, respectively.

Animals↗
PubMed1988

Localization of c-myc expression during oogenesis and embryonic development in Xenopus laevis.

The expression of the proto-oncogene c-myc during oogenesis and embryonic development was followed by in situ hybridization using a cytological protocol adapted to amphibian embryos. The c-myc RNA was highly expressed in the cytoplasm of young oocytes and was further diluted during oocyte growth without specific localization. From the neurula stage on, new myc transcripts were detected and the whole embryo appeared positive with antisense myc RNA probes relative to control sense RNA probes. In addition, a spatial localization of high levels of the transcript was also observed in specific areas of the developing embryo, including the epidermis, gill buds, optic vesicles and lens placodes. These observations might indicate a specific role of the c-myc gene during the differentiation of these tissues. Alternatively, this high level of myc expression might prevent such tissues from entering into terminal differentiation during the growth of the embryo.

Animals↗
PubMed1989

[Late embryonic development of the vomeronasal complex of the cat (Felis silvestris)].

An examination of 2 feline embryos in different stages of development (overall length 60 and 115 mm respectively) reveals a well developed vomeronasal complex in each case. Jacobson's Organs embedded within the paraseptal cartilage form long blind tubes at the base of the septum nasi. The cartilage is caudally tub-shaped and embraces rostrally completely the organ over a considerable length. In this manner a long, nearly tunnel-like tube is formed which represents a modified form of the original outer bar and which has not been described so far in cats. It stretches rostro-ventrally across the branching region of the paraseptal cartilage as far as the mouth of Jacobson's Organ. The dorsal branch of the cartilago paraseptalis on the other hand forms a vertically oriented strip which connects to the lamina transversalis anterior. The ductus nasopalatinus passing through the palate is laterally supported by a cartilago ductus nasopalatini which rostrally to the mouth of Jacobson's Organ forms a unified element with the ventral branch of the cartilago paraseptalis. In the case of the younger cat embryo, this cartilago ductus nasopalatini is yet weakly developed. The ductus nasopalatini of the embryos studied are in an amazingly retarded state of development. The ductus, which are blocked in the early stages of the embryonic development during secondary palate formation, form predominantly solid strands of epithelium. By dissolving the cemented epithelium, the ductus are open. But even in the case of the older embryo of the cat, this process is not completed yet. The short duct connecting Jacobson's Organ with the ductus nasopalatinus is also still closed in both embryos. Such cemented sections of epithelium of the younger embryo reveals an interesting relation between the ductus nasopalatinus and the ductus nasolacrimalis which so far has not been pointed out for mammals. From the point of view of phylogenetics, the locally specialized vomeronasal complex of cats exhibits all the criteria of a progressive development of characteristics.

Animals↗
PubMed1981

Variation with embryonic development and regional localization of specific [3H]phorbol 12,13-dibutyrate binding to brain.

We have previously characterized specific binding of the phorbol ester tumor promoter [20-3H]phorbol 12,13-dibutyrate to several tissues, including mouse skin and brain. We report here that specific binding activity in chicken brain increases dramatically during development. In whole embryonic chicken brain, binding increased from 2.0 to 6.8 to 10.6 pmol/mg of protein at 7, 14, and 20 days, respectively. Adult chicken brain bound 15 pmol/mg of protein. In contrast to specific binding activity, binding affinity remained constant. Substantial regional localization of binding activity within the brain was found. For calf brain, representative values ranged from 4.6 pmol/mg for medulla to 38.1 pmol/mg for frontal lobe. Binding affinity did not vary. Inhibition of binding by postulated neurotransmitters and antagonists was examined. D-Propranolol and quinidine, membrane-stabilizing drugs, inhibited binding competitively, although at mM concentrations.

Animals↗
PubMed1987

Early implantation and embryonic development of the baboon: stages 5, 6 and 7.

Implantation stages of the olive baboon, Papio cynocephalus anubis, showing embryonic development equivalent to Carnegie stages 5, 6 and 7 of development, were collected by hysterotomy and examined histologically. The younger specimens (stage 5) consisted of a thick trophoblastic plate composed of cytotrophoblast and syncytiotrophoblast with multiple small clefts, and a bilaminar disk embryo with a small slit-like amniotic cavity. An epithelial plaque response was present in the uterine epithelium immediately peripheral to the implantation site, within an area of pronounced uterine edema. The bilaminar embryonic disk consisted of columnar epiblast cells underlying the amniotic cavity, and thickened visceral endodermal cells that form part of the yolk sac. The slightly further developed placenta (stage 6) consisted predominantly of cytotrophoblast including primary villi and syncytiotrophoblast lining large spaces containing maternal blood. Secondary placental villi were present in the oldest group (stage 7), and there was modest decidualization of the uterine stroma. An epithelial plaque response persisted, but varied in extent. The sequence of events in early development in the baboon is similar to that in the rhesus monkey insofar as blood space formation and endometrial responses are concerned. However, the plaque response is not so great as in the rhesus; there is no secondary placenta, and the decidual response is slightly more extensive.

Animals↗