SEARCH · PubMed Health

Results for “Embryogenesis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources

PubMed1991

The embryogenesis of Onchocerca volvulus over the first year after a single dose of ivermectin.

Adult Onchocerca volvulus, extracted from nodules before, and at intervals of two weeks to 12 months after, a single 150 micrograms/kg dose of ivermectin, were examined longitudinally and by sequential transverse sections. The mean number of male worms per nodule fell, and the proportion of nodules with no male worm rose, within two weeks of ivermectin and remained so for 12 months. In female worms, at intervals after ivermectin, the percentages of the length of the lower genital tracts occupied by embryos at each stage of development, or by degenerating ova, embryos and microfilariae (mfs), were recorded: (a) in un(re-)inseminated worms whose original embryogenesis was continuing and in those in which it was completed; and (b) in worms, reinseminated post-ivermectin, in which a new embryogenesis had begun. The results indicated that: (a) the time needed for the zygotes of O. volvulus to develop to mfs is 8-12 weeks; (b) nearly 40 percent of females had not resumed mf production by 12 months after treatment; (c) many intrauterine mfs had not degenerated within the first two weeks of ivermectin; (d) some of the last embryos to mature to mfs did not degenerate but accumulated temporarily in the anterior uteri 8-16 weeks after ivermectin.

Animals↗

PubMed1990

[Development of the ascending lumbar and azygos veins in human embryogenesis].

The ascending lumbar and azygos veins make a single magistral, but with different topography in the abdominal and thoracic cavities. The former runs more dorsolateral than the sympathetic trunk, and the latter--more ventromedial. These vessels are of different origin in human embryogenesis. The ascending lumbar vein develops from supracardinal veins of the abdominal cavity, that unite the dorsomedial tributaries of the postcardinal vein. The supramesonephral (thoracic) part of the latter makes the azygos vein trunk. Its beginning in the form of a plexus is determined by anastomosing supracardinal, postcardinal and mesocardinal veins. The mesocardinal vein serves as a longitudinal anastomosis for veins, connecting medial tributaries of the postcardinal vein. Differential peculiarities of its basin over the whole length and topographic peculiarities of the ascending lumbar and azygos veins depend on growth specificity of kidneys and adrenals, as well as on other organs in human embryogenesis.

Adrenal Glands↗

PubMedDate not supplied

[Effect of chronic low-intensity gamma irradiation on embryogenesis in the silkworm (Bombyx mori L.)].

Gamma irradiation of a grain during embryogenesis at an intensity only 100 times exceeding that of the natural radioactive background reduces by 4-7 h the average time of embryogenesis for different species and hybrids of thesilworm embryo. The 10- and 40-time increase in the radiation intensity decreases the stimulatory effect and leads to the delay in the development.

Animals↗

PubMed1979

[Cell cycles in the early embryogenesis of the peled].

The dynamics of cell cycles in early embryogenesis of the peled has been studied using various methofs: determination of mitotic and mitotic phase index, of cell doubling time and of coefficient of asynchrony. The desynchronization of divisions begins at the V division after the longitudinal furrow has passed and is completed after the beginning of the cell cycle lengthening. The animal-vegetative gradient in the distribution of mitotic phases is observed at the early stages of desynchronization. The lengthening of cell cycle begins in interphase of the XI-XII cleavage and markedly accelerates from the interphase of the XII-XIII cleavage on. The methods of analysis of the cell cycles in early embryogenesis and possible factors influencing the dynamics of desynchronization are discussed.

Animals↗

PubMed1980

[Embryogenesis and early postnatal development of rats following transplacental sex hormone administration].

A study was made of the effect of different doses of testosterone propionate, sinestrol, diethylstilbestrol and sigetin administered to rats during the last three days of pregnancy on the embryogenesis and postnatal development of the progeny. It was established that sex hormones (except sigetin) often disturb pregnancy, labor and lactation. They also exert a musculinizing and sterilizing effect on the progeny. Sigetin produces no action on embryogenesis or postnatal development of rats.

Animals↗

PubMedDate not supplied

[Immunofluorescence study of H-2 antigens in early mouse embryogenesis].

The time of appearance and degree of expression were studied for antigens of the main locus of histocompatibility of the mouse embryos by indirect immunofluorescence. H-2 antigens appeared on the 5.5 day of embryogenesis on the cells of still undifferentiated rudiments of embryonic endoderm and ectoderm. By the 8th day of embryogenesis, rather intensice fluorescence of the cells of amnion, yolk sac and embryonic ectoderm was observed suggesting a marked expression of H-2 antigens during this period. The cells of trophoblast gave practically no positive reaction with anti-H-2-serum.

Animals↗

PubMed1984

[Effect of lofenal on rat embryogenesis].

The embryotoxic and teratogenic effect of lofenal was studied at different stages of embryogenesis of albino rats. Postimplantation death of embryos and foetus anomalies are stated to depend on both the dose of the administered preparation and on the period of embryogenesis.

Abnormalities, Drug-Induced↗

PubMed1978

[Various patterns in the development of the periganglionic vascular bed of respiratory tube ganglia during human embryogenesis].

The investigation has been performed in 118 serial sections of human embryos. The development of vascular bed in ganglia of the respiratory tube at early embryogenesis has been studied. The main attention has been paid to the formation of periganglial vascular bed. Loop-like and arc-shaped connections between the developing vessels and galglia and rearrangement of periganglial vascular bed during embryogenesis are described. Three stages in the development of blood supply to the ganglia of the respiratory tube are noted: I stage--avascular (embryos are 17-30 mm long); II stage--formation of periganglial vascular bed (embryos are 33-50 mm long); III stage--formation of intraganglial vascular bed (embryos are 55 mm long and more). Within I and II stages, reorganization phases in the vascular bed are described. A suggestion is made that the vascular factor of the development and differentiation of ganglial elements starts acting since the formation of periganglial vascular bed; before this, the mesenchima surrounding the neuronal plexus performs their trophic.

Cell Differentiation↗

PubMedDate not supplied

[Effect of monosomy of the autosomes on the preimplantation stages of embryogenesis in laboratory mice].

The effects of monosomy for the autosomes 1, 2, 3, 5, 6, 16 and 19 were studied in mice with single or double Robertsonian translocations. The monosomy for different autosomes affects the preimplantation development of the mouse embryos in different ways. The monosomy for the autosomes 1, 3, 6, 16 or 19 does not affect cleavage, compactization or blastulation and is, in some cases, even compatible with the implantation. The most these embryos are eliminated at the blastocyst stage (monosomy for the autosomes 3, 6 or 19) or, sometimes, at the postimplantation stages (1 or 16). The monosomy for the autosomes 2 or 5 is realized during cleavage causing the developmental delay, pathological changes in the nuclei of blastomeres and elimination at the morula stage. The results obtained suggest differential activity of chromosomes at the preimplantation stages of embryogenesis. Possible reasons for the early death of the embryos with particular types of monosomy are discussed. A hypothesis of mutual activation of the homologous autosomes at the early developmental stages is put forward. According to this hypothesis, the loci of a single unpaired autosome, especially of paternal origin, remain inactive during the early embryogenesis.

Aneuploidy↗

PubMed1980

[Immunoglobulin-positive cells of the human spleen and thymus in embryogenesis].

The percentage and types of fluorescence of immunoglobulin-positive cells were studied in the spleen and thymus from 32 human fetuses aged from 11 to 32 weeks by indirect immunofluorescence. During embryogenesis the number of immunoglobulin-positive cells in the spleen rises from 13 to 33.7%, while in the thymus the percentage of these cells is 0--2 and does not depend on the period of the fetus development. Differentiated estimation of immunoglobulin-positive cells was performed for the first time during embryogenesis from the types of fluorescence. Thymocytes have solitary points of fluorescence on the surface. Lymphocytes with solitary and then with multiple points covering all the surface and at last with "caps" of fluorescence appear in the spleen during the period of the development. The different density of immunoglobulin receptors on the surface reflects the level of lymphocyte differentiation.

Female↗

PubMed1981

Cytoskeletal coordination and intercellular signalling during metazoan embryogenesis.

This article draws attention to certain recently discovered features of cell surface organization and cytoskeletal deployment that may be revealing a new basis for intercellular signalling during metazoan embryogenesis. It is a signal mode that could coordinate many aspects of 'Entwicklungsmechanik' by spatiotemporal integration of the cytoskeletal/motor network throughout developing tissues. Evidence that this is achieved by 'intercellular cytoskeletal/plasma membrane connecting systems' which coordinate the spinal organization of microtubules, microfilaments, and intermediate filaments in developing animal tissues is critically examined. It is argued that this system does operate but that it is not used to transmit positional information in embryonic fields. However, it probably responds to such information and might play an important part in establishing field boundaries during the very earliest stages of embryogenesis. Certain aspects of cell surface organization in contemporary protozoans reveal ways in which the Protozoa could have been pre-adapted for the employment of cytoskeletal/cell surface signalling during the advent of multicellularity. In marked contrast, such signalling does not appear to be exploited during plant morphogenesis. The extent to which cytoskeletal organization might be coordinated in sister cells by transmission of spatial instructions during cell division in both animal and plant tissues is also considered.

Animals↗

PubMed1982

[Ultrastructural study of the epithelium of the indifferent gonad in human embryogenesis].

Gonads from 10 human embryos (28 days -- 6 weeks of development) have been studied (stage of the indifferent gonad). The material is fixed in 3% glutaraldehyde, treated in 2% osmium tetraoxide solution and after dehydratation in alcohols embedded in araldit. Ultrathin sections are contrasted in uranyl-acetate saturated alcohol solution and then in lead citrate. The sections are studied by means of the electron microscope Tesla-613. At early stages of embryogenesis (28-32 days) the cells of the germ epithelium are polar; their main organells are localized in apical parts. The granular endoplasmic reticulum is especially well developed, its membranes have the form of either a spiral or concentric circuses, mitochondria accumulate as large clusters. The cells discharge, into the celoma, their secret containing certain structures which are morphologically identical to the elements of the agranular endoplasmic reticulum. By the 33d day of embryogenesis primary sex cords appear, their cells lose polarity. In these cells Golgi complex is especially well developed. Complex plexuses of cellular processes and powerful contacts of a lock type are formed. Divergent differentiation of the gonadal epithelium into superficial and sex cord epithelium is started. With an increasing size of the gonad, the latter predominates. It begins to perform the secretory function, while the superficial epithelium becomes less active.

Epithelium↗

PubMed1980

[Content and properties of different classes of membrane-bound polyribosomes during embryogenesis in chickens].

The quantitative ratio, chemical composition and sedimentation properties of three polyribosomal fractions (free polyribosomes and polyribosomes tightly and loosely bound to the endoplasmic reticulum) isolated from chicken embryos of different age were studied. The fraction of polyribosomes loosely bound to the membranes was obtained from the total preparation of membrane-bound polyribosomes by treatment with high ionic strength solutions. It was found that the polyribosomes loosely bound to the membranes and free polyribosomes possess similar chemical composition and sedimentation properties. All the fractions studied were characterized by a much higher polyribosomal content as compared to the 80S monomers. In the course of embryogenesis the amount of polyribosomes loosely bound to the membranes is decreased, whereas that of tightly bound ones is increased. These data are indicative of an enhanced synthesis of secreted proteins, particularly collagen, on tightly bound polyribosomes during embryogenesis in chicken.

Animals↗

PubMedDate not supplied

[State of rat embryogenesis and progeny during exposure to foreign substances contained in the food].

Examination of the action of different xenobiotics (pesticides, heavy metals) on embryogenesis and progeny allowed the methodological approaches to this line of research to be suggested. It is recommended that xenobiotics be administered in different periods of embryogenesis: from day 1 to day 7, from day 7 to day 15 and from day 1 to day 20. It has been established that at cross mating the most pronounced alterations arose in the progeny of experimental males. The main object was to study the effect dependence on the dose, time and administration of the substances in order to establish their threshold and subthreshold levels. Validation of these parameters required the use of a complex of integral, functional, biochemical and morpholgical findings that warrant as assessment of the changes from the standpoint of the entire body, individual systems, organs, cellular and subecellular structures.

Animals↗

PubMed1995

[Organ regeneration and somatic embryogenesis from young stems of Fritillaria sinica].

Regenerated bulbs and embryogenetic calli were inducted from young stems of Fritillaria sinica cultured on Murashige and Skoog (MS) medium supplemented with alpha-naphthale-neacetic acid (NAA), 2, 4-dichlophenexy-acetin acid (2, 4-D), 6-benzylaminopurine (6BA) and kenetin (Kt) respectively. The callus cultures used for the organ regeneration and somatic embryogenesis were subcultured at intervals of 30-40 days on MS medium+NAA 1mg/L + 6BA 0.5mg/L. In general, the bulbs can be obtained from cultured Fritillaria sinica through three ways: (1) induction from explants; (2) production of adventitious buds or (3) somatic embryogenesis.

Culture Media↗

PubMed1994

Quantitation of endogenous thyroid hormone receptors alpha and beta during embryogenesis and metamorphosis in Xenopus laevis.

Greater than 90% of the endogenous thyroid hormone receptor proteins TR alpha and TR beta in tissues of Xenopus laevis comigrate with their respective in vitro synthesized counterparts, and these major components are not phosphorylated detectably. Maternally inherited TR alpha protein is stable through early embryogenesis during a time in which there is no detectable TR alpha mRNA synthesis. At stage 35 when TR alpha mRNA is first detectable, the inherited TR alpha protein is present at about 100 molecules/cell. TR alpha protein subsequently increases to levels of about 1500 and 6000 molecules/cell in tail and head regions, respectively, in stage 52 tadpoles. Even though TR alpha mRNA gradually increases during metamorphosis (from stage 52 to 62), TR alpha protein remains constant, suggesting strongly that post-transcriptional events control the ultimate levels of TR alpha protein. In contrast, there is no detectable TR beta protein (less than 100 molecules/cell) throughout embryogenesis until stage 52. Both TR beta mRNA and protein rise along with the increase in endogenous thyroid hormone, reaching a maximum at the climax of metamorphosis, when TR beta protein exceeds TR alpha protein in concentration. As with TR alpha protein, TR beta protein in tail is consistently about one-fourth that of TR beta protein in the head region. The number of TR alpha protein molecules in extracts of premetamorphic tadpoles and cultured cells grown in the absence of thyroid hormone fully accounts for all of the sites to which 125I-T3 bind. We interpret this to mean that TR alpha protein must be a necessary, if not sufficient, component in the pathway toward metamorphosis triggered by thyroid hormone and required for the phenomenon of competence in tissues and cells.

Amino Acid Sequence↗

PubMed1993

Localization of RIHB (retinoic acid-induced heparin-binding factor) transcript and protein during early chicken embryogenesis and in the developing wing.

Previously, we isolated an avian protein which we named retinoic acid induced heparin binding factor (RIHB). RIHB is a 121 amino acid secreted polypeptide, rich in basic and cysteine residues (Vigny et al., Eur. J. Biochem. 186: 733-740, 1989). Northern blot analysis indicates that the RIHB gene is transiently expressed during embryogenesis (Urios et al., Biochem. Biophys. Res. Com. 175:617-624, 1991). Here we present an investigation of RIHB expression during early chicken embryogenesis by in situ hybridization and immunofluorescence studies. In the 3-day embryo (stage 20-21), the RIHB transcript is observed throughout the embryo, with the notable exception of the neural tube. At this stage the protein can be visualized in almost all of the basement membranes and around many types of cells. The localization of the RIHB protein does not strictly parallel that of its messenger. Between days 3 and 11 we focused our attention on wing development. The level of both the mRNA and protein decreases during this period but the disappearance is not uniform. The level of both the mRNA and protein decreases during this period but the disappearance is not uniform. The transcript becomes progressively restricted to epithelia and regions surrounding the forming cartilage. In contrast to the transcript, the protein accumulates in the epithelial basement membrane and, interestingly, in the central part of the embryonic cartilage (diaphysis) but not in the distal parts (epiphysis). These data are discussed in relation to the putative role(s) of RIHB in development.

Animals↗

PubMed1993

C-ski transcripts with and without exon 2 are expressed in skeletal muscle and throughout chick embryogenesis.

Overexpression of v-ski or c-ski cDNAs has a pronounced effect on proliferation, morphological transformation and myogenic differentiation in cells in culture and in transgenic animals. Yet, little is known about expression of the c-ski locus or the relationship between c-ski cDNAs and alternatively spliced c-ski transcripts in chicken tissues, particularly in skeletal muscle or during embryogenesis. We developed a series of probes and oligonucleotide primers specific for the eight coding exons and the long 3' noncoding region found in chicken c-ski mRNAs. The most abundant chicken c-ski mRNAs in a vast array of tissues are 8.5 kb, with additional, but less abundant, mRNAs of 7.5, 6.5 and 4.4 kb. Steady-state levels of c-ski mRNAs, indistinguishable from transcripts in other tissues, accumulate in skeletal muscle from embryonic, newly hatched, and adult chicks. Only exon 2, a small exon of 111 bp, was found to be alternatively spliced in c-ski mRNAs. Transcripts with and without exon 2 appear in all tissues, in somites, and from the earliest stages of chick embryogenesis. Thus, c-ski cDNA sequences, which extend about 4.3 kb, represent either the least abundant form of c-ski mRNAs in tissues or a severely truncated form of the major 8.5 kb transcripts.

Animals↗