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M Peterka

Publications and source records attributed to M Peterka.

At least 19 recordsLinked to original sources
PubMed1996

Timing of exchange of the maxillary deciduous and permanent teeth in boys with three types of orofacial clefts.

Timing of exchange of the deciduous and permanent maxillary teeth was investigated using dental plaster casts of 163 boys with total unilateral cleft (UCLP), 82 boys with bilateral cleft (BCLP), and 97 boys with isolated cleft palate (CP). All patients were treated at the Prague Plastic Surgery Clinic. The results were compared with a control group of 294 schoolboys. To evaluate the course of eruption, the proportion of each erupted teeth in each year of age was employed. In boys with UCLP, eruption of the permanent maxillary lateral incisors and the permanent maxillary second molar was retarded on the cleft side. On the non-affected side, no delay of eruption was observed, but earlier eruption was found in the permanent maxillary canine and in the permanent maxillary first and second premolars. In boys with BCLP, the highest retardation of eruption was found in the permanent maxillary lateral incisor and in the permanent maxillary first molar. The permanent maxillary canine and both permanent maxillary premolars erupted earlier than in the control group. In boys with CP, only the permanent maxillary central incisors erupted earlier. The maxillary deciduous canines and the second molars were both lost early. We conclude that the developmental disturbances of the maxillary jaw and teeth in patients with orofacial clefts are also associated with alteration of timing of dental exchange.

Adolescent↗
PubMed1996

Apoptosis is involved in the disappearance of the diastemal dental primordia in mouse embryo.

Three transient dental primordia (D1, D2 and D3) exist in the upper diastema in mouse embryos and their regression is associated with the presence of cell death. In order to specify the type of cell death and its temporo-spatial distribution, staining with hematoxylin, supravital staining with Nile Blue, TUNEL method, electron microscopic analysis and computer assisted 3-D reconstructions were performed. These data demonstrated that apoptosis is involved in the disappearance of the diastemal dental rudiments. Apoptosis occurred first with prevalence in the buccal part of the epithelium of the diastemal dental primordia and extended later to the whole epithelium of the dental rudiments and the dental lamina interconnecting them with the incisor and molar epithelia. Cell death occurred only sporadically in the adjacent mesenchyme. The prospective upper diastema in mouse embryos may provide a model for studies of developmental determination of toothless areas in the jaw as well as a tool for analyses of regulatory mechanisms of programmed cell death in morphogenesis.

Animals↗
PubMed1995

Contribution of 3-D computer-assisted reconstructions to the study of the initial steps of mouse odontogenesis.

The specific arrangement of mouse dentition in each dental quadrant (1-0-0-3) is supposed to result from the initiation of two independent dental laminae--one for the incisor and one for the three molars. In order to verify whether the adult mouse dental pattern really corresponds to the initial patterning, an analysis of development of the mouse antemolar part of the upper dental quadrant was performed in 10-13 day embryos using histological sections and computer-assisted 3-D reconstructions. Six primary dental laminae contributed to the formation of the upper incisor anlage, which is, therefore, a structure of multiple origin. In contrast to the lower diastema, where only a low epithelial band extended mesially from the first lower molar in 12-13 day embryos, in the upper diastema a dental lamina existed interconnecting transiently the incisor and molar anlagen and giving rise to 3 distinct epithelial rudiments. The rudiments exhibited growth retardation and regressed after reaching a maximum at the bud stage. Our results showed a discrepancy between the embryonic and adult dental patterns in the mouse upper jaw. The specific arrangement of the mouse dentition implied a reduction of the embryonic dental anlagen, which was achieved either by their integration into the one incisor primordium or regression in the prospective diastema. Odontogenesis in the mouse upper jaw provides a model of hypodontia of evolutionary origin, which can be employed in molecular studies of the control mechanisms of initiation, spatial organization and specific morphogenesis of teeth.

Animals↗
PubMed1994

Development of nucleolar apparatus in the chick primitive erythroid cells.

The primitive erythroid line cells of chick embryos were studied during embryonic days 2-14 by means of a cytochemical method to investigate the appearance and frequency of the main nucleolar types. The populations of erythroblasts and erythrocytes were classified according to the presence of functionally dominant nucleoli in their nuclei. In the course of primitive erythroid cell differentiation and maturation, compact nucleoli and nucleoli with nucleolonemas (both supposed to be RNA biosynthetically active) were gradually replaced by ring-shaped nucleoli and finally by micronucleoli reflecting the reversible and irreversible inhibition of RNA synthesis, respectively. The occurrence of the main nucleolar types and their values in primitive erythroid cells of the developing chick depend not only on the maturation stage of the blood cells, but also on the developmental stage of the chick embryo. In comparison with the definitive erythroid line of the post-hatching chick and hen, the cells of the chick embryonic primitive erythroid line possess relatively high values of "active" nucleolar types. These are still present in advanced maturation stages, and occur also as definitive erythroid lines of lower vertebrates.

Animals↗
PubMed1994

Maternal hyperthermia and infection as one of possible causes of orofacial clefts.

It has been proposed that the hyperthermia in pregnant women may be associated with birth defects in their offsprings. We analysed the retrospective interview data on probable febrile illness during critical period of orofacial clefts development in 992 mothers of boys and girls with three types of orofacial clefts--cleft lip, unilateral or bilateral cleft lip and palate and cleft palate. A number of mother that gave the positive answer was relatively high and varied from 24% to 33%. There were no significant differences of the incidence of mother febrile illness between three groups of orofacial clefts in boys and girls. These data support presumption on the harmful effect of febrile illness during early pregnancy on craniofacial development.

Cleft Lip↗
PubMed1994

Teratogenic effects of bilirubin--a study using chick embryotoxicity screening test (CHEST).

Using the Chick Embrotoxicity Screening Test (CHEST), two samples of bilirubin of different commercial origin were tested on 2, 3 and 4- day old chick embryos. Water soluble Bilirubin Lachema (containing 20 mg albumin per 1 ml) had no teratogenic effect. On the opposite, Bilirubin Merck (containing 8 mg albumin per 1 ml) manifested an apparent teratogenic potential when single doses 0.2 and 0.6 micrograms were administered intraamniotically on day 4. Dose-dependent malformations of brain and eyes, cleft beak and reduction deformities of limbs were observed. No such effects could be produced by administration of Bilirubin Merck on either day 2 and 3. A tentative explanation of the difference between teratogenic properties of Merck and Lachema bilirubin preparations may be sougth in the different proportion of the free and albumin bound fractions.

Abnormalities, Drug-Induced↗
PubMed1994

The effect of cyclosporin A on the proliferating chick embryo erythroblasts.

The proportion of proliferating erythroblasts, i.e. proerythroblasts, basophilic erythroblasts and polychromatophilic erythroblasts in blood islands of the chick embryo yolk sac, were counted during embryonic days 2-10. From day 2 when high amounts of erythroblasts signalized the onset of embryonic erythropoiesis, the percentage of less mature erythroid cells gradually decreased. Intraamniotic injection of cyclosporin A in doses 1.5 or 15.0 micrograms per embryo on day 5 led to significant changes in the proportion of proliferating erythroblasts in the yolk sac blood islands. We speculate that these changes were caused initially by the release of the more mature cells into the circulation and later by a dose-dependent decrease in the number of stem cells. The estimation of proerythroblast percentage from all proliferating erythroblasts in the yolk sac blood islands may serve as a valuable indication of toxic damage in the late avian embryo.

Animals↗
PubMed1994

rRNA synthesis in proerythroblasts and hepatocytes after cyclosporin A administration in chick embryo.

The ribosomal RNA (rRNA) synthesis in the proerythroblasts and hepatocytes of the chick embryo was examined using the nucleolar test during embryonic days 5-10 after intraamniotic administration of single doses of cyclosporin A (CsA). Administration of the 0.75 or 7.5 g of CsA 5th day of embryonic development caused a significant decrease in proerythroblasts and hepatocytes numbers with active rRNA synthesis. Five days after the CsA administration, the percentage of proerythroblasts with biosynthetically active nucleoli already did not differ from the control while the decreased numbers of hepatocytes actively synthetizing rRNA remained statistically significant. Our results indicate, that CsA inhibits the rRNA biosynthesis in embryonic immature cells. Depending on the cell type, the effect of CsA and its dynamics may be apparently different.

Animals↗
PubMed1994

Differing embryotoxic effects of senecionine and senecionine-N-oxide on the chick embryo.

The embryotoxic properties of pyrrolizidine alkaloids senecionine (water insoluble) and senecionine-N-oxide (water soluble) were examined using the CHEST method (Chick Embryotoxicity Screening Test). The beginning of the embryotoxicity range for senecionine was found to be between 3-30 micrograms; senecionine-N-oxide, on the other hand, showed no effect even with 100 micrograms dose. On the basis of the theoretical calculation, it can be expected that senecionine embryotoxicity for mammals ranges between 10-100 mg/kg maternal body weight, overlapping in this way the known adult toxicity range. The rat LD50 of most alkaloids known to be significant for human health are in the range of 34-300 mg/kg.

Animals↗
PubMed1993

Tooth eruption in patients with cleft lip and palate.

In boys with a total unilateral cleft the course of eruption of deciduous and permanent teeth in the quadrant of the maxilla with the cleft was investigated and compared with the intact quadrant of the maxilla. The greatest retardation (two years) during eruption was found in deciduous and permanent second incisors in the maxillary quadrant affected by the cleft. This retardation is according to the authors associated with gross morphological changes such as duplication of the second incisor and its altered shape. The second upper permanent incisor erupts only in 60% of the patients and this can be explained by frequent hypodontia. Retarded eruption was observed also in the maxillary quadrant with the cleft in the permanent canine (one year), the first (one and a half year) and second permanent premolar (six months). In these teeth the crowns are not perceptibly malformed and the delayed eruption may be associated with lack of space in the hypoplastic quadrant of the maxilla on the side of the cleft. The permanent first incisor and permanent first and second molar erupt symmetrically in both maxillary quadrants.

Adolescent↗
PubMed1993

Multiple developmental origin of the upper incisor in mouse: histological and computer assisted 3-D-reconstruction studies.

Heads of 11-15-day-old mouse embryos were cut in frontal serial sections. Early development of the maxillary incisor was analyzed using series of thick (5 and 7 microns) and semi-thin (1 micron) frontal sections and computer assisted 3-D-reconstructions of the epithelial component. The enamel organ of the mouse maxillary incisor was found to be a complex structure of multiple origin, involving several epithelial anlagen--primary dental laminae--, which could hypothetically correspond to the 5 upper incisors of early mammals. The transitory existence of at once distinct and then fusing dental primordia could reflect heterochronic changes in ontogeny which might be related to phyletic trends.

Animals↗
PubMed1993

Drug-induced changes of rRNA biosynthesis--a marker of toxic damage to embryonal cell population.

The nucleolar test was used for evaluation of the rRNA biosynthesis in two populations of chick embryonic cells. In chick embryos, practically 100 per cent of proerythroblasts (starting from embryonic day 3) as well as hepatocytes (starting with embryonic day 5) synthetized nucleolar, i.e. ribosomal RNA. In consequence of a single administration of the well known teratogens--actinomycin D, cyclophosphamide or hydrocortisone--the percentage of rRNA synthetizing proerythroblasts and hepatocytes decreased characteristically--in dependence on the teratogenic drug. The presented method can be employed when toxicity of drugs or other chemical compounds is evaluated in cell populations possessing high metabolic and proliferative activity.

Animals↗
PubMed1992

Embryotoxicity of 25 psychotropic drugs: a study using CHEST.

Twenty five psychotropic drugs were ranked according to the embryotoxicity dose ranges estimated by the Chick Embryotoxicity Screening Test (CHEST). The chick results were compared with some data for common laboratory mammals. In 17 psychotropic drugs a deleterious dose-dependent effect upon the embryonic cardiovascular system was disclosed, terminating in immediate cardiac arrest.

Animals↗
PubMed1991

A modification of tooth germ cultivation in vitro and in ovo.

Mandibular molar anlages excised from 17-day mouse foetuses were cultured in vitro or in ovo (on the chorioallantoic membrane). In both cases, the explants were underlain either with a Millipore filter or with a piece of fibrin foam. Tooth germs were harvested after 7 days of cultivation and processed histologically. Spatial arrangement was highly preserved in the tooth germs cultured in vitro on fibrin foam. In vitro cultures on Millipore filters revealed significant flattening of tooth germs, caused especially by the collapse of enamel organ and the pulp. The cytodifferentiation of tooth germs cultured in vitro on both substrates (Millipore filter, fibrin foam) was characterized by the presence of odontoblasts, polarizing ameloblasts and predentine. The cytodifferentiation of tooth germs cultured in ovo on Millipore filters placed on chorioallantoic membrane was characterized by the presence of odontoblasts, ameloblasts, predentine, dentine and enamel. However, the flattening of these explants was identical with the changes of the explants cultured on Millipore filters in vitro. In ovo cultivation on the fibrin foam failed to bring satisfactory results.

Ameloblasts↗
PubMed1988

Orofacial clefts. A theoretical basis for their prevention and treatment.

In spite of the existing huge number of data on palate development as well as the incidence, experimental induction and clinical treatment of orofacial clefts, no unitary concept has been made available that would make possible their sorting out, further interpretation and extrapolation. The aim of this monograph has been to provide firm grounds for managing the data within categories consistent with the general principles of teratogenesis reformulated and extended upon the theory of morphogenetic systems, and, upon this basis, to evaluate the present chances of preventing the origin of orofacial clefts. Chapter 1 introduces the problem of birth defects that possess some distinct features in common with the recognised prime problems of present medicine, that is neoplastic and cardiovascular diseases. Orofacial clefts represent a substantial component of the human birth-defect spectrum that is a mere remnant of the original volume of teratogenesis estimated as affecting about 35% of human embryos. The merciful process of prenatal extinction of abnormal conceptuses, or terathanasia, reduces this eminent figure by approximately one order of magnitude. Basing upon the prevalence of clefts in embryos and infants we may say that the prenatal extinction of individuals with orofacial clefts lies somewhere between 70-90%. Chapter 2 deals with the history of recognising and formulating the general principles of teratology that go back to Isidore Geoffroy Saint-Hilaire. Estimating the contribution of the great personalities such as Dareste, Schwalbe, and J. G. Wilson, the chapter enumerates and describes the ten principles of teratogenesis as having arisen from the known rules extended and reformulated by the original theory of morphogenetic systems. In their sum, the principles constitute a deductive system defining teratogenesis at several levels of bioorganisation, capable of predicting the large-scale effects of environmental impact on animal and human reproduction. Chapter 3 presents the orofacial clefts in the light of the theory of morphogenetic systems. Palatal morphogenesis is accomplished under the conditions of extraordinary spatial complexity and extends over a relatively long period of development. Several morphogenetic subsystems may be distinguished, namely the morphogenetic subsystem (smgs) of facial outgrowths, the smgs of palatal shelves, the smgs of the glossomandibular complex and, eventually, the smgs of the axial cervical region, acting at different phases of palatal development.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1987

Prenatal development of rugae palatinae in mice: scanning electron microscopic and histologic studies.

The development and spatial arrangement of rugae palatinae was investigated using sagittal histological sections through the heads of 12- to 19-day mouse (ICR) embryos (appearance of vaginal plug = day 1) and scanning electron microscopy (SEM) visualization. Three distinct, consecutively occurring types of developing rugae were described: 1) rugal anlage (formed by thickened epithelium mostly burrowed in mesenchyme), 2) primitive ruga (transversally oriented band of thickened epithelium protruding to the oral cavity), and 3) definitive ruga (transversally oriented mesenchymal ridge protruding to the oral cavity, covered by epithelium). As the characteristic configuration and spatial patterns were found on each of days 13-19, rugae could be utilized as a natural positional marker (eg, in odontogenesis or palatogenesis studies). The foremost rugae start to differentiate between days 12 and 13. Between days 13 and 14 the number of rugae conspicuously increases in the anterior third of palatal shelf, and by palatal shelf horizontalization (day 15, a.m.) new rugae originate in the middle third. We presume that the origin of rugae is dependent upon inductive epithelial-mesenchymal interactions. The presence of developing rugae and the timing of their origin (occurrence of tissue interactions) in the middle versus the anterior third of the palatal shelf appears to be reflected in the mode of cellular arrangement, extracellular matrix (ECM) composition, and, probably, even in the elevation mechanism. Six stages of formation of the ruga were defined, and stage-dependent arrangements of epithelial and mesenchymal cells within the developing ruga were documented. A rearrangement of cells precedes the occurrence of the primitive ruga as well as its transformation to the definitive one. These events are discussed in relation to the hypothetical integrated function of cytoskeletal and ECM components. Regarding the developmental relation of rugae to maxillary dentition in the mouse, a comparison of particular stages of teeth and rugae development and analysis of their similarities and dissimilarities may extend the knowledge of general rules of morphogenesis and differentiation in oral biology.

Animals↗
PubMed1987

[Sensitivity of the primordia of various organs to chemical substances].

In the experiments performed in chick embryos, using the chick embryo screening test (CEST)-1 and CEST-2 technique, 100 various classes of chemical substances have been tested for teratogenic activity. Estimation of three morphogenetic systems (caudal part of the body, facial skull and extremities) has demonstrated that some of the substances do not produce any damaging effect, other produce some lesions in selected germs, the third influence two or three germs simultaneously. Similar picture is also specific for the effect of the chemical substances to the rat intrauterine development. Owing to data obtained, we come to the conclusion that for screening of embryotoxicity of various xenobiotics under in vivo and in vitro experimental conditions one should not orient to one single germ.

Animals↗