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Biomedical subjects

I Checiu

Publications and source records attributed to I Checiu.

At least 19 recordsLinked to original sources
PubMed1994

Developmental basis of severe neural tube defects in the loop-tail (Lp) mutant mouse: use of microsatellite DNA markers to identify embryonic genotype.

Mouse embryos homozygous for the mutation loop-tail (Lp) develop lethal defects in which the neural tube remains open from the hindbrain to the caudal extremity, a condition that closely resembles the human malformation craniorachischisis. Heterozygotes develop tail defects and occasional spina bifida, but are generally viable. In order to study the early development of these defects, it is necessary to determine the genotype of embryos at stages prior to the first appearance of the morphological abnormalities. We used a microsatellite DNA sequence, Crp, that is closely linked to the Lp locus and which segregates polymorphic variants in matings between Lp/+ mice, thus permitting identification of embryos of Lp/Lp, Lp/+ and +/+ genotypes. We found that the severe phenotype craniorachischisis is present at 9.5 and 10.5 days of gestation only in Lp/Lp embryos in utero, whereas Lp/+ and +/+ littermates show neural tube closure throughout most of the body axis. The open neural tube phenotype also develops in Lp/Lp embryos growing in whole embryo culture. A small proportion of Lp/+ embryos were found to develop this phenotype in vitro, but only when culture conditions were suboptimal. Analysis of 8.5-day embryos revealed that the initial defect in Lp/Lp embryos is failure to initiate neural tube closure at the cervical/hindbrain boundary when the embryo has 6-7 somites. Thereafter, the neural tube remains open throughout the body axis, with the exception of the midbrain and forebrain where neural tube closure is initiated independently. Closure at the midbrain/forebrain boundary does not appear to be defective in Lp/Lp embryos. Heterozygous Lp/+ embryos initiate neural tube closure at the cervical/hindbrain boundary with a slight delay compared with +/+ littermates. Moreover, at 10.5 days of gestation, Lp/+ embryos undergo delayed closure of the posterior neuropore. Thus, Lp/+ embryos are defective in several aspects of the neurulation process. The pattern of delayed neuropore closure in Lp/+ embryos resembles that caused by the ct and Sp mutations and is likely to be responsible for the development of tail defects (i.e., looped tails) and spina bifida in Lp/+ mice. The use of microsatellite markers to determine the genotype of mutant embryos has general application: microsatellites are widespread throughout the mouse genome, so that informative sequences are likely to be available with close linkage to the majority of mutant genes. Moreover, polymorphisms can be detected using the polymerase chain reaction, making it possible to determine the genotype of very early embryos when only small amounts of material are available.

Animals↗
PubMed1975

[Stratification in the central nervous system].

Stratigenesis in the optic tectum of developing chick embryos was investigated between the 4th and the 11th day of incubation. Stratification is achieved by successive emigration of cell contigents from the proliferative layer. In the opinion of the authors the main factor which determines this very regular cell migration would be a gradient of oxygen and of metabolites. The gradient has to appear in the wall of tectum due to its typical vascular network. Experiences with induced hypoxia or with selective damage of the proliferative layer strengthen the hypotesis of an oxygen gradient playing the role of a generally active epigenetic factor in the stratigenesis of the central nervous system.

Animals↗
PubMedDate not supplied

Quantitative and qualitative approach of glycan-glycan interactions in marine sponges.

Cell recognition and adhesion involving many kinds of cell surface molecules operate via homotypic and/or heterotypic protein-protein and protein-carbohydrate binding. Our investigations in marine sponges have provided direct evidence for a novel molecular mechanism of multivalent glycan-glycan binding related to cellular interactions. Biochemical characterization of purified proteoglycans revealed the presence of specific acidic glycans, different from classical glycosaminoglycans. Such acidic glycans of high molecular weight, containing fucose, glucuronic or galacturonic acids, and pyruvate and sulfate groups may represent a new class of primordial proteoglycans, named by us glyconectins. The thermodynamic and kinetic approaches of biological macromolecule interactions do not provide a direct measurement of the intermolecular binding forces that are fundamental for the function of the ligand-receptor association. Using the atomic force microscopy (AFM), we provided the first quantitative evaluation of the binding strength between cell adhesion proteoglycans. Measurement of binding forces intrinsic to cell adhesion glyconectin proteoglycans (AGPs) is necessary to assess their contribution to the maintenance of the anatomical integrity of multicellular organisms. (i) As a model, we selected the cell AGP isolated from the marine sponge Microciona prolifera; it mediates in vivo cell recognition and aggregation via homotypic, species-specific, multivalent, and calcium ion-dependent glycan-glycan interactions. (ii) Under physiological conditions, a large cohesive force theoretically able to hold the weight of approximately 1600 cells was measured. (iii) The C-2 autocomplementarity model for AGP-AGP interactions; and (iv) the requirement of the calcium ionic bridges suggest also that the self-recognition and multivalency of glycan-glycan interactions are essential for cell adhesion. (v) The evolution of glyconectin-like proteoglycan molecules may have been a fundamental prerequisite for the emergence of the first multicellular organisms. Glycan-glycan interactions may thus provide a new paradigm for molecular self-recognition.

Animals↗
PubMedDate not supplied

[Stratification in the central nervous system].

In the authors' opinion the neuroblasts (glioblasts respectively) are moving along an oxigen-gradient, out of the proliferative layers toward the source of O2 (the vascular plexi). Stratigenesis is influenced by "guiding structures" (fibrillar plate in the tectum opticum), by the elongations of ependymal cells and by the similarly oriented vascular-connectives.

Animals↗
PubMedDate not supplied

[Fine-structure and function of the primary proliferative layer of the embryonal central nervous system].

Results obtained by mechanical isolation of neuroblasts from the primary proliferative layer of the central nervous system in chick embryos by the aid of an original method and by electronmicroscopic investigations are consistent with Sauer's concept on neuroepithelial cell proliferation. The bipolar form of the undifferentiated neuroblast is maintained--at the beginning--by external factors of cell contact only. Each end-feet contains two centrioles, one of which represents the basal body of a cilium. During mitosis, the position parallel to the lumen of the spingle axis and the subsequent appearance of two identical daughter cells depend on the behaviour of the centrioles. The later may move in an abnormal direction, and induce thus an obliquely or perpendicularly laying spindle axis. These changes may influence--on the other hand--the mechanism of proliferation.

Animals↗
PubMedDate not supplied

[Vital fluorochroming showing the effect of cyclophosphamide on the embryo].

Besides the usual methods, vital fluorochroming may globally show the extent of the cytotoxic effect of Cyclophosphamide (CP). By intravital treatment with highly diluted fluorochromes (acridine-orange, etc.) necrobiotic and dead cells, cell debris and phagosomes appear electively fluorescent. Glycosaminoglycans and various mucopolysaccharides show a somewhat weaker fluorescence. Autopods and the mesencephalon were selected for comparative assessment of the effect of other cytotoxic agents. Important results were also obtained by the repeated examination of blood (erythrocytes) and of hemopoetic foci. Cytotoxic effect within the embryo, teratogenesis and chemotherapeutic action are strongly correlated.

Acridine Orange↗
PubMedDate not supplied

[The ultrastructure of embryonic capillaries in the neuroepithelium of the brain vesicles].

The electronmicroscopic control of the capillaries of the brain vesicles in 5--6-day-old chick embryos revealed an intimate contact between capillary walls and neuroblasts, and on the other hand the presence of a functional endoplasmic reticulum in the endothelial cells. These are only very few vacuoles for protein transport in the cytoplasm of endothelial cells.

Animals↗
PubMedDate not supplied

[Dynamics of the action of cyclophosphamide. Studies in the chick embryo].

The dynamics of the Cyclophosphamide (CPA) effect was investigated in the chick embryo by a vital fluorochroming method worked out previously. In the 4-day-old embryo the morphological changes (at the level of light microscopy) in the limbs and in the mesencephalon induced by 100 microgram CPA appeared after a period of latency of about 10 hours. Successive blood control in the same embryo, treated with 50 microgram CPA, revealed three consecutive modifications of the blood cells: a great number of abnormal mitoses, the appearance of a great number of multinucleated, nonviable cells and the recovery of the lost cells. No difference could be detected between the effect of freshly prepared and stored CPA solutions. The fate of CPA (a bifunctionally alkylating agent) in contact with living tissues is discussed.

Animals↗
PubMedDate not supplied

On the prenatal noxious effects of trypan blue and of a related azo dye.

Since 1948 trypan blue has been a well-known and extensively used experimental teratogen, belonging to the group of azo dyes. Chemically, trypan blue consists of a biphenyl molecule (0-tolidine or benzidine) combined by means of azo linkages with two molecules of a substituted naphthalene. Between 1987-89 the effect of the replacement of the biphenyl molecule by a molecule of p,p'-diaminobenzanilide upon the prenatal noxious action of trypan blue has been controlled. Investigations were carried out on three species: chick embryos, albino rats and albino mice. In the species used, the replacement annihilates the teratogenic properties of the dye, with the persistence of some embryotoxic effects. On the other hand, the control of o-tolidine and of p,p'-diaminobenzanilide revealed that no one had teratogenic properties (only some embryotoxic effect, more marked in the case of o-tolidine). It results that the teratogenic action of trypan blue cannot be attributed to the o-tolidine molecule proper but to an effect which results (in a for the moment unknown manner) from its combination with the other parts of the dye molecule.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

In vitro studies on normal and pathological preimplantation development. I. Events of normal mouse preimplantation development as revealed by microcinematography.

After briefly presenting the main historical data of in vitro culture of preimplantation mouse embryos and their filming, the first own observations on normal preimplantation development made by using microcinematography are presented: development from two-cell to eight-cell embryos; compaction and cavitation. The timing and the duration of various developmental events were recorded. Own observations were compared with previous cinematographic data reported by other authors. Some processes needing further investigations are evidenced: rotation within the zona pellucida, penetration of cytoplasmic emissions through the zona, contraction and reexpansion.

Animals↗
PubMedDate not supplied

Ultrastructural changes in the mouse fetal neocortex following chronic maternal alcoholization.

Female mice (RAP strain) were alcoholized for 30-50 days before mating and during pregnancy until killing, with a 20% solution of ethanol administered instead of drinking water. From foetuses of 16, 18, 20 days and from newborn puppies on day 1 parietal neocortex fragments were excised and examined electronmicroscopically. Chronic maternal alcoholization induces in the neocortex of mouse foetuses and newborn puppies various ultrastructural changes: swelling of mitochondria with the disappearance of cristae and vacuolation, both in the capillary endothelium and in the cells of the neural tissue; enlargement of intercellular spaces; in the neocortex zones rich in neuronal processes (marginal and intermediary zone) vacuolation and structural wastage of these processes are detected. Moderate chronic alcohol intake leads to persistent ultrastructural changes in the fetal and newborn neocortex which may contribute to the appearance of some neuro-psychical and behavioral symptoms in alcohol embryo- and fetopathy. The possible pathogenetic pathways leading to the pathological changes detected are discussed.

Animals↗
PubMedDate not supplied

Ultrastructural changes in the mouse fetal choroid plexuses following chronic maternal alcoholization.

Female mice (RAP strain) were alcoholized for 30-50 days before mating and during pregnancy until killing, with a 20% solution of ethanol administered instead of drinking water. From foetuses of 16, 18 and 20 days and from newborn puppies (day 1) choroid plexuses were excised and electronmicroscopically examined. Chronic maternal alcoholization induced the lowering of glycogen content in the choroid cells of 16 day old foetuses, the swelling and vacuolization of mitochondria with the disappearance of cristae and enlargement of the Golgi complex--in the choroid cells at all the developmental stages controlled, the enlargement of intercellular spaces within the choroid epithelium and between the capillaries and the epithelial layer. The changes detected are presumedly due to disturbances of intracerebral fluid homeostasis and may be responsible for at least some of the CNS pathology observed in alcohol embryo- and fetopathy.

Alcoholism↗
PubMedDate not supplied

Sulphonated phthalocyanine induced caudal malformative syndrome in the chick embryo.

Sulphonated phthalocyanine (Pht.) has been tested for its possible noxious effect on the developing chick embryo. When injected into the subembryonic cavity of 40-45 hours incubated chick embryos (mainly 10-20 somite pairs), Pht. induces a highly reproducible caudal malformative syndrome (trunk and taillessness, various anomalies of the limbs). The main effect is--in about 15% of the malformed specimens--associated with unilateral microphthalmy and, less frequently, with coelosomy. Microscopically developmental disturbances of the caudal axial organs, of the mesonephros and of the limbs are observed. The initial pathological changes, at microscopic level, are necrosis and hemorrhages in the caudal axial and paraxial area. The allantois is poorly developed or even absent. Skeletal changes involve anomalies of the ribs and of the vertebral column and total or partial absence of the pelvic girdle bones. The high mortality, mainly during the first week, is due--first of all--to the developmental disturbances including the poor development or absence of the allantois. Control experiments with CuCl2 suggest the ethiological role of Cu. Pathogenetic aspects are discussed.

Abnormalities, Drug-Induced↗