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At least 469 records · Page 26Linked to original sources
PubMed1981

A genetic factor controlling morphogenesis of the laryngotracheo-esophageal complex the mouse.

A new autosomal, recessive lethal mutation in the mouse cause failure of division of the embryonic foregut into totally separate digestive and respiratory ducts. The newborn homozygote has a cleft that extends between the laryngotracheal and esophageal tubes, allowing excessive air to pass into the stomach and subsequently into the peritoneal cavity. This mutation has been designated lec (laryngotracheo-esophageal cleft). The common region shared by the respiratory and digestive tubes has features characteristic of both structures. Development of cartilage around the laryngotracheo-esophageal complex is also affected in the mutant.

Animals↗
PubMed2002

Drosophila APC2 and APC1 have overlapping roles in the larval brain despite their distinct intracellular localizations.

The tumor suppressor APC and its homologs, first identified for a role in colon cancer, negatively regulate Wnt signaling in both oncogenesis and normal development, and play Wnt-independent roles in cytoskeletal regulation. Both Drosophila and mammals have two APC family members. We further explored the functions of the Drosophila APCs using the larval brain as a model. We found that both proteins are expressed in the brain. APC2 has a highly dynamic, asymmetric localization through the larval neuroblast cell cycle relative to known mediators of embryonic neuroblast asymmetric divisions. Adherens junction proteins also are asymmetrically localized in neuroblasts. In addition they accumulate with APC2 and APC1 in nerves formed by axons of the progeny of each neuroblast-ganglion mother cell cluster. APC2 and APC1 localize to very different places when expressed in the larval brain: APC2 localizes to the cell cortex and APC1 to centrosomes and microtubules. Despite this, they play redundant roles in the brain; while each single mutant is normal, the zygotic double mutant has severely reduced numbers of larval neuroblasts. Our experiments suggest that this does not result from misregulation of Wg signaling, and thus may involve the cytoskeletal or adhesive roles of APC proteins.

Adenomatous Polyposis Coli Protein↗
PubMedDate not supplied

NuMA expression and function in mouse oocytes and early embryos.

Nuclear mitotic apparatus protein (NuMA), originally described as a nuclear protein, is an essential component in the formation and maintenance of mitotic spindle poles. In this study, we analyze the expression pattern and function of NuMA in mouse oocytes and early embryos. In germinal vesicle-stage oocytes, NuMA was detected both at the centrosome and in the nucleus. However, after nuclear maturation and extrusion of the first polar body, NuMA was concentrated at the broad meiotic spindle poles and at cytasters (centers of cytoplasmic microtubule asters) of mature metaphase II oocytes. Cold-induced depolymerization of microtubules appeared to disassociate NuMA foci from the cytoplasmic cytasters. During fertilization, NuMA was relocated into the re-formed male and female pronuclei. Microinjection of anti-NuMA antibody into 1 of 2 cells of 2-cell-stage embryos inhibited normal cell division. These results suggest that NuMA might play an important role in cell division during early embryonic mitosis.

Animals↗
PubMed1997

Bronchogenic cysts and esophageal duplications: common origins and treatment.

BACKGROUND/PURPOSE: Bronchogenic cysts and esophageal duplications are usually considered as separate foregut malformations. Yet, both are thought to arise from the same embryological event, division of the embryonic foregut, and they share common histological characteristics, often making their clinical differentiation difficult. METHODS: A retrospective review of the cases of 68 children treated at a single institution between 1937 and 1995 was performed. Thirty children were girls (44%) and 38 were boys (56%). Ages ranged from newborn to 24 years. Complete records were available in all children. Fourteen of these 68 children were asymptomatic. RESULTS: Respiratory (54%) or gastrointestinal (13%) symptoms were the most frequent presenting problems. The majority of children were treated by resection of the cyst (52 of 68; 76%), while 9 of 68 (13%) required lobectomy for intraparenchymal lesions. Three children underwent marsupialization, with all of these children requiring additional surgery for recurrent disease. Five children (5 of 68; 7%) had multiple cysts. The mortality rate from this series was 10% (7 of 68). Two deaths were caused by perioperative exsanguination, one related to bleeding from a cyst lined with gastric mucosa with subsequent ulceration and hemorrhage into the esophagus. Two deaths occurred secondary to septic complications, one from an esophageal leak and the other from an intraparenchymal abscess. Two deaths were caused by respiratory failure; one was unrelated (SIDS). The majority of cysts found on histological review were lined by respiratory epithelium or bronchial glands (51 of 68; 75%). Gastrointestinal epithelium was present in cysts of nine children, only two of which were clinically diagnosed as esophageal duplications. Twenty-one cases (21 of 68; 31%) were classified as esophageal duplications based on the intramural location of the cyst, yet 15 of 21 (71%) contained respiratory epithelium, substantiating the hypothesis of the common origin of these lesions. CONCLUSIONS: The histological similarity and anatomic proximity of the "bronchogenic cysts" and the intramural "esophageal duplications" supports their common origin. The possible complications of bleeding, ulceration, infection, and obstruction of the esophagus or airway, should generally lead to prompt resection.

Adolescent↗
PubMed2001

The C. elegans gon-2 gene encodes a putative TRP cation channel protein required for mitotic cell cycle progression.

The C. elegans gon-2 gene is required for the post-embryonic mitotic cell divisions of the gonadal precursor cells. A single major transcript of approximately 6.7 kb is derived from the gon-2 locus. This mRNA encodes a protein related to the TRP family of cation channels and has a high degree of similarity to several vertebrate genes, including melastatin. Mutant alleles of gon-2 affect evolutionarily conserved amino acid residues. Northern analyses suggest that gon-2 expression is not limited to gonadal tissues.

Alleles↗
PubMed1998

Identification and developmental expression of a 5'-3' exoribonuclease from Drosophila melanogaster.

In multicellular organisms, very little is known about the role of mRNA stability in development, and few proteins involved in degradation pathways have been characterized. We have identified the Drosophila homologue of XRN1, which is the major cytoplasmic 5'-3' exoribonuclease in Saccharomyces cerevisiae. The protein sequence of this homologue (pacman) has 59% identity to S. cerevisiae XRN1 and 67% identity to the mouse homologue (mXRN1p) in certain regions. Sequencing of this cDNA revealed that it includes a trinucleotide repeat (CAG)9 which encodes polyglutamine. By directly measuring pacman exoribonuclease activity in yeast, we demonstrate that pacman can complement the yeast XRN1 mutation. Northern blots show a single transcript of approximately 5.2 kb which is abundant only in 0-8-h embryos and in adult males and females. In situ hybridization analysis revealed that the pcm transcripts are maternally derived, and are expressed at high levels in nurse cells. During early embryonic syncytial nuclear divisions, pcm transcripts are homogenously distributed. pcm mRNA is expressed abundantly and ubiquitously throughout the embryo during gastrulation, with high levels in the germ band and head structures. After germ band retraction, pcm transcripts are present at much lower levels, in agreement with the Northern results. Our experiments provide the first example of an exoribonuclease which is differentially expressed throughout development.

Amino Acid Sequence↗
PubMed2004

Ubiquitin-like protein activation.

Post-translational covalent attachment of ubiquitin and ubiquitin-like proteins (ubls) has emerged as a predominant cellular regulatory mechanism, with important roles in controlling cell division, signal transduction, embryonic development, endocytic trafficking and the immune response. Ubls function by remodeling the surface of their target proteins, changing their target's half-life, enzymatic activity, protein-protein interactions, subcellular localization or other properties. At least 10 different ubiquitin-like modifications exist in mammals, and attachment of different ubls to a target leads to different biological consequences. Ubl-conjugation cascades are initiated by activating enzymes, which also coordinate the ubls with their downstream pathways. A number of biochemical and structural studies have provided insights into the mechanism of ubl-activating enzymes and their roles in ubl conjugation cascades.

Amino Acid Sequence↗
PubMed2006

Early diagnosis of conjoined twins by real-time three-dimensional ultrasound--case report and review of the literature.

In 1:50 000 to 1:100 000 births, conjoined twins occur, caused by incomplete division of the embryonic disc more than 13 days after fertilisation. We present a case of cephalothoracopagus janiceps, a very rare form of conjoined twins, which was diagnosed at 13 weeks of gestation. Three-dimensional and colour Doppler ultrasound enabled precise prenatal visualisation of the fusion of the foetal head and chest up to the umbilicus. We could demonstrate the presence of two foetal hearts connected by an arterio-arterial shunt as well as two pairs of upper and lower extremities. After the clear 3-D presentation of the anomaly, making the poor prognosis visible, the mother decided to have the pregnancy terminated. Autopsy confirmed the prenatal diagnosis.

Adult↗
PubMed2006

Correction of massive hydrocephalus and brain wound in holoprosencephaly.

Holoprosencephaly is a rare disorder of embryologic development that denotes an incomplete or absent division of the embryonic forebrain (prosencephalon) into distinct lateral cerebral hemispheres. In most cases of holoprosencephaly, the fetus fails to survive to term, and those that do survive have severe functional limitations, including mental retardation. We present a case report of cranial vault remodeling in a 20-month-old female who was born with holoprosencephaly and a severe number 0/14 cleft. The patient developed chronic nonhealing ulcers secondary to hydrocephalus, ventriculoperitoneal shunts, and the underlying architecture of her cranial vault.

Absorbable Implants↗
PubMed2000

Sox2 regulatory sequences direct expression of a (beta)-geo transgene to telencephalic neural stem cells and precursors of the mouse embryo, revealing regionalization of gene expression in CNS stem cells.

Sox2 is one of the earliest known transcription factors expressed in the developing neural tube. Although it is expressed throughout the early neuroepithelium, we show that its later expression must depend on the activity of more than one regionally restricted enhancer element. Thus, by using transgenic assays and by homologous recombination-mediated deletion, we identify a region upstream of Sox2 (-5.7 to -3.3 kb) which can not only drive expression of a (beta)-geo transgene to the developing dorsal telencephalon, but which is required to do so in the context of the endogenous gene. The critical enhancer can be further delimited to an 800 bp fragment of DNA surrounding a nuclease hypersensitive site within this region, as this is sufficient to confer telencephalic expression to a 3.3 kb fragment including the Sox2 promoter, which is otherwise inactive in the CNS. Expression of the 5.7 kb Sox2(beta)-geo transgene localizes to the neural plate and later to the telencephalic ventricular zone. We show, by in vitro clonogenic assays, that transgene-expressing (and thus G418-resistant) ventricular zone cells include cells displaying functional properties of stem cells, i.e. self-renewal and multipotentiality. We further show that the majority of telencephalic stem cells express the transgene, and this expression is largely maintained over two months in culture (more than 40 cell divisions) in the absence of G418 selective pressure. In contrast, stem cells grown in parallel from the spinal cord never express the transgene, and die in G418. Expression of endogenous telencephalic genes was similarly observed in long-term cultures derived from the dorsal telencephalon, but not in spinal cord-derived cultures. Thus, neural stem cells of the midgestation embryo are endowed with region-specific gene expression (at least with respect to some networks of transcription factors, such as that driving telencephalic expression of the Sox2 transgene), which can be inherited through multiple divisions outside the embryonic environment.

Animals↗
PubMed1999

Utilization of the aquatic research facility and fertilization syringe unit to study sea urchin development in space.

Methods were developed for the investigation of the effects of microgravity on early development in sea urchins within the Canadian Space Agency's Aquatic Research Facility (ARF). The ARF payload provided light, temperature control, automated fixation capability, and a 1 G on-orbit centrifuge control. Eggs and embryos of either the sea urchin species Lytechinus pictus or Strongylocentrotus purpuratus were loaded into Standard Container Assemblies (SCAs) which comprised the experimental aquaria (33 mL volume) contained within the ARF. A newly developed Fertilization Syringe Unit (FSU) was used to achieve "in-flight" fertilization capability. Fixative solutions were preloaded into fixation blocks maintained adjacent to the SCAs and injected at pre-selected time points, resulting in final (diluted) concentrations of either 0.5% or 2% glutaraldehyde (depending upon embryonic stage). Light, scanning, and transmission electron microscopy determined that all desired embryonic and cell division stages (16-cell stage, blastula, gastrula, and pluteus) were preserved using the experimental protocols and fixation capability provided by the ARF/FSU system.

Animals↗
PubMed1985

Diagnosis and management of fetal holoprosencephaly.

The holoprosencephalies are a spectrum of cerebral and facial malformations resulting from incomplete division of the embryonic forebrain. Using ultrasound to search for structural defects in the fetal brain and to measure interorbital distances, the alobar variety can be diagnosed antenatally. A series of seven cases is presented. Criteria for diagnosis and guidelines for obstetric management are presented.

Brain↗
PubMed2001

Inactivation of M-phase promoting factor at exit from first embryonic mitosis in the rat is independent of cyclin B1 degradation.

Exit from M-phase and completion of cell division requires inactivation of M-phase promoting factor (MPF), a heterodimer composed of the regulatory cyclin B1 and the catalytic p34cdc2 kinase. Inactivation of MPF is associated with cyclin B1 degradation that is brought about by the ubiquitin-proteasome pathway. Our study examined the role of the proteasome in the first mitosis of rat embryos and its participation in the regulation of cyclin B1 degradation and MPF inactivation. We show that in the early zygote the proteasome is evenly distributed in the ooplasm and the nucleus, whereas during mitosis it accumulates on the spindle apparatus. We further demonstrate that inhibition of proteasomal catalytic activity prevents 1-cell embryos from undergoing mitosis. This mitotic arrest is associated with the presence of relatively high amounts of cyclin B1, which unexpectedly does not result in elevated MPF activity. Our findings strongly imply that completion of the first embryonic division depends on proteasomal degradation and that cyclin B1 is included among its target proteins. They also provide the first evidence that MPF inactivation at this stage of development is not solely dependent upon cyclin B1 degradation and is insufficient to allow the formation of the 2-cell embryo.

Animals↗
PubMed2001

Roles for 147 embryonic lethal genes on C.elegans chromosome I identified by RNA interference and video microscopy.

Early embryonic development involves complex events such as the regulation of cell division and the establishment of embryonic polarity. To identify genes involved in these events, we collected four-dimensional time-lapse video recordings of the first three cell divisions and analysed terminal phenotypes after RNA interference of 147 embryonic lethal genes previously identified in a systematic screen of Caenorhabditis elegans chromosome I. Over half gave defects in early processes such as meiosis, the assembly or position of the first mitotic spindle, cytokinesis, and proper nuclear positioning. For some phenotypic classes, the majority of genes are involved in a shared biochemical process. In addition, we identified loss-of-function phenotypes for genes of unknown function, but for which homologues exist in other organisms, shedding light on the function of these uncharacterized genes. When applied to the whole genome, this approach should identify the vast majority of genes required for early cell processes, paving the way for a greatly improved understanding of these processes and their regulation at the molecular level.

Animals↗
PubMed1988

Role of cell displacement, cell division, and fragment size in pattern formation during embryonic retinal regeneration in Xenopus.

Studies on the regenerating vertebrate retina provide, for the first time, a detailed view of how cells respond to removal of 2/3 of the eyebud, how their displacements, new juxtapositions, and extra mitotic activity correlate with stable changes in the retinotectal projection. They provide insight into how retinal ganglion cells encode "position", and how they use this information to form specific neural connectivity patterns.

Animals↗
PubMed1986

Cell growth and cell division: dissociated and random initiated? A study performed on embryonal carcinoma cell lines. II.

The 'random transition probability' cell-cycle models have so far failed to convincingly link the transition events with phenomena describable by biochemical methods. The study presented was carried out on the F9 and PCC3 N/1 embryonal carcinoma (EC) cell lines. We now report an extended analysis of the two-random transition probability (TP) model and preliminary results are presented showing that the deterministic L period in that model can be regarded as reflecting the 'cell-growth cycle'. Evidence is presented that suggests that the 'cell-growth cycle' is a supramitotic deterministic phase--i.e. starting in one cell cycle and being completed in the next following G1 period and dissociated from the 'DNA-division cycle'. This phenomenon makes an interesting contribution to the old knowledge of a stepwise G1 prolongation during early embryogenesis in yielding a mechanism by which the cell can alter the ratio of nucleus to cytoplasm prior to the onset of gene expression.

Animals↗
PubMed2004

Effects of methoxychlor, dieldrin and lindane on sea urchin fertilization and early development.

We have studied the effects of methoxychlor (MXC), dieldrin, and lindane on fertilization and early development of sea urchin egg. These organochlorine pesticides have often been found in polluted ground and water near agricultural sites, and have therefore been detected from time to time in the food chain and in drinking water. They have been reported to alter various reproduction functions in various animals including marine populations. We observed that the rate of fertilization decreased when the sperm was incubated with dieldrin or lindane. Treatment of eggs with each pesticide did not prevent fertilization, but increased the rate in polyspermy, delayed or blocked the first mitotic divisions, and altered early embryonic development. Moreover, all pesticides could alter several intracellular biochemical pathways that control first mitotic divisions and early development, including intracellular calcium homeostasis, MPF (mitosis promoting factor) activity and formation of the bipolar mitotic spindle. We found that lindane was the most potent of the three pesticides to alter all biochemical events. All these effects were observed at relatively high concentrations. However, bio-accumulation in sediments and aquatic organisms have been reported. Sea urchin eggs may then be in contact with very high concentrations of these pesticides in areas where these pesticides are not handled or stocked properly, and then develop into abnormal embryos.

Animals↗
PubMed2001

A requirement for Notch in the genesis of a subset of glial cells in the Drosophila embryonic central nervous system which arise through asymmetric divisions.

In the Drosophila central nervous system (CNS) glial cells are known to be generated from glioblasts, which produce exclusively glia or neuroglioblasts that bifurcate to produce both neuronal and glial sublineages. We show that the genesis of a subset of glial cells, the subperineurial glia (SPGs), involves a new mechanism and requires Notch. We demonstrate that the SPGs share direct sibling relationships with neurones and are the products of asymmetric divisions. This mechanism of specifying glial cell fates within the CNS is novel and provides further insight into regulatory interactions leading to glial cell fate determination. Furthermore, we show that Notch signalling positively regulates glial cells missing (gcm) expression in the context of SPG development.

Animals↗