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PubMed1978

Compartmentalization and growth of the Drosophila abdomen.

An analysis of the cell lineage of the adult Drosophila abdomen is reported. Genetically marked clones are produced in the tergites in the embryo and in the sternites and pleura during larval life. The spatial disposition of the segment primordia is also studied in a series of 250 gynandromorphs. We conclude that in the embryo the segments are all separate polyclones soon after blastoderm and these are probably adjacent to each other. Gynandromorph analysis suggests that segments 2--6 develop from similarly sized cell groups but that the first tergite develops from a primordium which is equal to that of two other segments. We suggest that presumptive adult and larval cells are not separated at blastoderm. Our estimate from clonal analysis of the number of larval cells (12) which construct the sternites and pleura is equal to the number observed directly in the ventral nest of histoblasts.

Abdomen↗
PubMed1990

Horizontal compartmentation in the germinal matrices and intermediate zone of the embryonic rat cerebral cortex.

Cellular compartmentation was studied in the germinal matrices and the intermediate zone of the cerebral cortex of rat embryos that survived for 1 or more days after injection with [3H]thymidine. In contrast to the vertical compartmentation seen in the neuroepithelium with short-survival thymidine autoradiography, sequential-survival autoradiography revealed a horizontal compartmentation both in the germinal matrices and the intermediate zone. In the neuroepithelium of embryos that survived for 24 h, the differentially labeled cells form two distinct horizontal bands. The band overlapping with the mitotic zone is composed of heavily labeled cells, whereas the band overlapping with the synthetic zone is composed of lightly labeled cells. This indicates that there are two proliferative cell populations within the neuroepithelium, one turning over fast and the other more slowly. In the cortical intermediate zone of the same embryos several horizontal bands are present. Of these, the dispositions of two bands of heavily labeled cells--the superior band and the inferior band--were followed for several days. The superior band is apparently composed of glial cells that disperse in the direction of the internal capsule and the corpus callosum. In contrast, the inferior band (which overlaps with the subventricular zone where many cells are horizontally oriented) is apparently composed of sojourning young neurons. The cells of the inferior band resume their migration toward the cortical plate after a pause of 1-2 days. These observations call for a reappraisal of the view that young cortical neurons follow a direct radial path to the cortical plate.

Animals↗
PubMed2000

Expression of spicule matrix proteins in the sea urchin embryo during normal and experimentally altered spiculogenesis.

During its embryonic development, the sea urchin embryo forms an endoskeletal calcitic spicule. This instance of biomineralization is experimentally accessible and also offers the advantage of occurring within a developmental context. Here we investigate the time course of appearance and localization of two proteins among the four dozen that constitute the protein matrix of the skeletal spicule. SM50 and SM30 have been studied in some detail, and polyclonal antisera have been prepared against them (C. E. Killian and F. H. Wilt, 1996, J. Biol. Chem. 271, 9150-9159). Using these antibodies we describe here the localization and time course of accumulation of these two proteins in Strongylocentrotus purpuratus, both in the intact embryo and in micromere cultures. We also investigate the disposition of the matrix proteins, SM50, SM30, and PM27, in the three-dimensional spicule by studying changes in protein localization during experimental manipulation of isolated skeletal spicules. We conclude that SM50, PM27, and SM30 probably play different roles in biomineralization, based on their localization and patterns of expression. It is unlikely that these proteins are solely structural elements within the mineral. SM50 and PM27 may play a role in defining the extracellular space in which spicule deposition occurs, while SM30 may play a role in secretion of spicule components. Finally, we report on the effects of serum on expression of some primary mesenchyme-specific proteins in micromere cultures; withholding serum severely depresses accumulation of SM30 but has only modest effects on the accumulation of other proteins.

Animals↗
PubMed1989

Elevations in the endogenous levels of the putative morphogen retinoic acid in embryonic mouse limb-buds associated with limb dysmorphogenesis.

Retinoic acid, an endogenous metabolite of vitamin A (retinol), possesses striking biological activity akin to a morphogen in developing and regenerating vertebrate limbs. Systemic administration of retinoic acid (RA) to pregnant mammals during the period of limb organogenesis invariably results in dose-dependent dysmorphogenesis. In an attempt to uncover the mode of action of RA in the developing limb bud we analyzed, by HPLC methods, the levels of RA and its metabolic precursor, retinol, in embryonic mouse tissues prior to and following maternal exposure to a teratogenic dose of RA. Detectable levels of both RA and its isomer 13-cis-retinoic acid were found in the limb buds of Day 11 mouse embryos (40 +/- 2 somites). Although retinol was the major retinoid found in ethanolic extracts of either whole embryo or the limb buds, the latter is enriched in RA compared to the whole embryo. This indicated either a higher degree of retinol metabolism or a sequestration of RA in the limb bud compared to the rest of the embryo at this stage of development. A study of the time course of retinoid levels in treated embryos showed that changes occur rapidly, are stable for several hours, and then begin to return to pretreatment levels. After a maternal dose of 10 mg/kg RA, which resulted in a mild degree of limb anomalies, peak RA levels in the limb bud increased 50-fold over the endogenous level; a full 300-fold increase was found after a 100 mg/kg dose which results in 100% incidence of phocomelia. Interestingly, a dose-dependent depression in retinol levels was observed after RA treatment both in maternal plasma as well as the embryo. Studies are in progress to trace the intracellular disposition of both retinol and RA as well as any further active metabolite of RA in the limb buds and other embryonic tissues.

Abnormalities, Drug-Induced↗
PubMed1993

Diabetes in pregnancy: experimental aspects.

Substantial literature indicates that diabetes in pregnant rats and mice induces embryo lethality, growth retardation, and a variable incidence of birth defects. All these embryopathic effects appear to be mediated by several factors, e.g. genetic disposition and the composition of the diets eaten by the animals. Studies carried out on rodent embryos cultured in vitro showed that numerous components of the diabetic state (ketone bodies, somatomedin inhibitors, low concentrations of insulin) display a dysmorphogenic potential. Besides, diabetes-induced malformations have been often related, both in vivo and in vitro studies, to morphological and physiological alterations of the yolk sac, the principal organ for the passage of nutrients from the mother to the rodent embryo. On the whole, in vivo and in vitro experiments indicate that hyperglycemia itself is not a major factor in producing diabetic embryopathies that are more likely ascribable to severe alterations of the embryonic energetic balance.

Animals↗
PubMed2006

Stepwise enforcement of the notochord and its intersection with the myoseptum: an evolutionary path leading to development of the vertebra?

The notochord constitutes the main axial support during the embryonic and larval stages, and the arrangement of collagen fibrils within the notochord sheath is assumed to play a decisive role in determining its functional properties as a fibre-wound hydrostatic skeleton. We have found that during early ontogeny in Atlantic salmon stepwise changes occur in the configuration of the collagen fibre-winding of the notochord sheath. The sheath consists of a basal lamina, a layer of type II collagen, and an elastica externa that delimits the notochord; and these constituents are secreted in a specific order. Initially, the collagen fibrils are circumferentially arranged perpendicular to the longitudinal axis, and this specific spatial fibril configuration is maintained until hatching when the collagen becomes reorganized into distinct layers or lamellae. Within each lamella, fibrils are parallel to each other, forming helices around the longitudinal axis of the notochord, with a tangent angle of 75-80 degrees to the cranio-caudal axis. The helical geometry shifts between adjacent lamellae, forming enantiomorphous left- and right-handed coils, respectively, thus enforcing the sheath. The observed changes in the fibre-winding configuration may reflect adaptation of the notochord to functional demands related to stage in ontogeny. When the vertebral bodies initially form as chordacentra, the collagen lamellae of the sheath in the vertebral region are fixed by the deposition of minerals; in the intervertebral region, however, they represent a pre-adaptation providing torsional stability to the intervertebral joint. Hence, these modifications of the sheath transform the notochord per se into a functional vertebral column. The elastica externa, encasing the notochord, has serrated surfaces, connected inward to the type II collagen of the sheath, and outward to type I collagen of the mesenchymal connective tissue surrounding the notochord. In a similar manner, the collagen matrix of the neural and haemal arch cartilages is tightly anchored to the outward surface of the elastic membrane. Hence, the elastic membrane may serve as an interface between the notochord and the adjacent structures, with an essential function related to transmission of tensile forces from the musculature. The interconnection between the notochord and the myosepta is discussed in relation to function and to evolution of the arches and the vertebra. Contrary to current understanding, this study also shows that notochord vacuolization does not result in an increased elongation of the embryo, which agrees with the circular arrangement of type II collagen that probably only enables a restricted increase in girth upon vacuolization, not aiding elongation. As the vacuolization occurs during the egg stage, this type of collagen disposition, in combination with an elastica externa, also probably facilitates flexibility and curling of the embryo.

Animals↗
PubMed1989

Patterns of engrailed protein in early Drosophila embryos.

By the onset of gastrulation during nuclear cycle 14 of Drosophila embryogenesis, the engrailed gene is expressed in fourteen one-cell-wide stripes. Each stripe defines the anlagen of the posterior compartment of a metameric segment. We report here several observations relating to the role and disposition of the engrailed protein during the embryonic stages that precede cellularization. We demonstrate that in embryos mutant for the engrailed gene, there were characteristic morphological abnormalities as early as the 6th cleavage cycle. In addition, the engrailed protein was detected in pre-cycle-9 embryos by Western blot analysis. When localization of engrailed protein begins during cycle 14, engrailed expression was first present in broad anterior and posterior regions before the fourteen-stripe pattern appeared.

Animals↗
PubMed1979

[The inner surface of chick embryo small intestine by scanning electron microscope].

The inner surface of the midgut of chick embryos aged seven to fifteen days of incubation has been examined by scanning electron microscopy. At this period, the surface of the mucous membrane undergoes significant morphological changes; in fact, while at seven days of incubation it appears to be smooth and regular, in the following days it begins to show longitudinal folds increasingly higher, more numerous and complicated. After eleven days of incubation some folds take a zig-zag appearance that progressively becomes more evident and extends to all the folds. In the mean time, the enterocytes undergo a gradual differentiation and represent the only type of epithelial cells at this stage of development. Their apex until seven days of incubation is dome-shaped, provided with short microvilli and separated from the surrounding cells by deep circular grooves. At about thirteen days the apex appears to be less swollen, with longer and more numerous microvilli and delimited by microplicae arranged in a hexagonal disposition.

Animals↗
PubMed2003

Cryopreserved embryos in the United States and their availability for research.

OBJECTIVE: To determine the number of embryos stored at assisted reproductive technology (ART) clinics in the United States and their current disposition. DESIGN: A targeted survey instrument sent by the SART-RAND team to all medical practices providing in vitro fertilization services in the United States. RESULTS: The SART-RAND team surveyed all 430 ART practices in the United States. Of these practices, 340 returned surveys for analysis. The data from these surveys were merged with data taken from the 1999 SART dataset, which contains information about practice size and success rates. Responding clinics reported a total of 396,526 embryos in storage as of April 11, 2002. The vast majority of the embryos (88.2%) were targeted for patient use. Small numbers of embryos were available for research, donation, destruction, quality assurance, or other uses. CONCLUSIONS: Nearly 400,000 embryos are stored in the United States, the majority of which (88.2%) are targeted for patient use. Few are available for research (2.8%), limiting possible conversion into embryonic stem cell lines.

Cryopreservation↗
PubMed1979

[Scanning electron microscopy of the inner surface of small intestine in chick embryos].

The inner surface of the midgut of chicken embryos ageing between seven and fifteen days incubation has been examined by scanning electron microscope. In this period the surface of the mucous membrane undergoes significant morphological changes; in fact, while at seven days incubation it appears to be smooth and regular, in the following days it begins to show longitudinal folds increasingly higher, more numerous and complicated. Since eleven days incubation some folds take a zigzag appearance that progressively becomes more evident and extends to all the folds. In the mean time, the enterocytes undergo a gradual specialization and represent the only type of epithelial cells in this stage of development. Their apex until seven days incubation is dome-shaped, provided with short microvilli and separated from the surrounding cells by deep circular grooves. About thirteen days the apex appears to be less swollen, with longer and more numerous microvilli and bounded by microplicae arranged in an hexagonal disposition.

Animals↗
PubMed2006

Left-right asymmetry in the vertebrate embryo: from early information to higher-level integration.

Although vertebrates seem to be essentially bilaterally symmetrical on the exterior, there are numerous interior left-right asymmetries in the disposition and placement of internal organs. These asymmetries are established during embryogenesis by complex epigenetic and genetic cascades. Recent studies in a range of model organisms have made important progress in understanding how this laterality information is generated and conveyed to large regions of the embryo. Both commonalities and divergences are emerging in the mechanisms that different vertebrates use in left-right axis specification. Recent evidence also provides intriguing links between the establishment of left-right asymmetries and the symmetrical elongation of the anterior-posterior axis.

Animals↗
PubMed1992

Legal and ethical issues arising with preimplantation human embryos.

The development of in vitro fertilization has led to ethical and legal controversies concerning actions with externalized preembryos. A legal and ethical consensus is emerging that preembryos are not legal persons or moral subjects, although they are owed special respect because of their ability to implant and come to term. In addition, gamete providers are recognized as having dispositional authority over whether preembryos will be created, cryopreserved, placed in a uterus, discarded, donated, or used in research. Prior agreements over preembryo disposition are the best way to minimize disputes between the gamete providers.

Embryo Transfer↗
PubMed1988

A freeze-fracture study on the developing satellite cells of spinal ganglia in the chick embryo.

A freeze-fracture analysis of the satellite cells of spinal ganglia of the chick embryo was performed in 8 successive stages of development, from the 5th incubation day to hatching. The characteristic laminar disposition of the cells were first observed on the 7th day. Tight junctions were found at the 20th incubation day. Small groups or irregular aggregates of particles, but not gap junctions, were described on the 7th and 8th days. Pinocytotic vesicles were pointed out in the different stages considered.

Animals↗
PubMed2004

Population pharmacokinetic modelling of Emfilermin (recombinant human leukaemia inhibitory factor, r-hLIF) in healthy postmenopausal women and in infertile patients undergoing in vitro fertilization and embryo transfer.

AIMS: The aim of this analysis was to develop a population pharmacokinetic model for Emfilermin (recombinant human leukaemia inhibitory factor, r-hLIF) following subcutaneous administration to healthy postmenopausal women and to infertile patients undergoing in vitro fertilization and embryo transfer (IVF-ET). METHODS: Data from three studies, a single and a repeat dose Phase I study in postmenopausal women as well as a proof of concept study in patients undergoing in vitro fertilization and embryo transfer were combined and analyzed. The structural pharmacokinetic model was developed using the rich data from the Phase I studies and the full pharmacostatistical model was then derived using all the data. RESULTS: The pharmacokinetics of r-hLIF after repeated subcutaneous administration were described by a one-compartment disposition model with a zero order input. The duration of the absorption phase was short (0.8 h) and invariant. The apparent clearance in postmenopausal women was 57 l h(-1) (CV = 17%). In in vitro fertilization and embryo transfer patients, the apparent clearance was decreased by 35% compared with postmenopausal women. The apparent volume of distribution was 235 l (interindividual CV = 28%) and exhibited an interoccasion variability of 23%. It increased (for weight above 62 kg) or decreased (for weight below 62 kg) by 29% for every 10 kg body weight. The median posthoc estimates of apparent clearance and volume of distribution and their variability were consistent with the population estimates. In postmenopausal women, the results were consistent with those obtained by noncompartmental analysis. The residual variability on r-hLIF serum concentrations was 20%. CONCLUSIONS: The pharmacokinetics of r-hLIF after repeated SC administration were described by a one compartment disposition model, with zero order input, in postmenopausal women and those undergoing IVF or intracytoplasmic sperm injection and embryo transfer. Absorption of r-hLIF was rapid as was its subsequent clearance. The apparent volume of distribution of r-hLIF was moderate to high, depended on body weight and showed interoccasion variability.

Administration, Cutaneous↗
PubMed1998

Evaluation of the placenta: suggestions for a greater role in developmental toxicology.

Both in human and in rat, two types of placenta are present: the yolk sac (YS) and the chorioallantoic placenta. Histiotrophy, alpha-fetoprotein synthesis and blood cell formation occur in YS of both species. Besides, the midgut, primordial germ cells and possibly immunological structures originate from the YS tissue. The specialised cells of the chorioallantoic placenta attach the embryo to the uterus and form the vascular connections necessary for the nutrient transport. The placenta redirects maternal endocrine, immune and metabolic functions to conceptus advantage. These complex activities are sensitive to direct toxicity. Indirect effects on the placental functions might be elicited by immunomodulators and endocrine disrupters. Some experimental models could be utilised to identify possible toxic effects on placenta. Among the in vitro models the rodent giant yolk sac culture may be used to study the transport of materials, morphological and/or biochemical alterations and biotransformation activity of the visceral YS epithelium. Other in vitro approaches utilise human derived trophoblastic cells and tissues to investigate implantation and perimplantation toxicology. Besides specific studies, in vivo reproductive toxicity tests could pay more attention to the evaluation of placental tissues. Nowadays, some physiologically based pharmacokinetic models for developmental toxicity are also available to describe the disposition of toxic substances and their metabolites during pregnancy in rodents. Thus, more detailed studies on the embryo-foetal placenta may provide an important tool to understand developmental toxicity mechanisms, with particular regard to embryolethality and delayed development.

Allantois↗