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Biomedical subjects

M Peterka

Publications and source records attributed to M Peterka.

82 records · Page 5Linked to original sources
PubMed1977

Influence of cleft palate on growth of the maxilla in mouse embryos.

Cortisone acetate (7.5 mg on day 12, or 4 X 2.5 mg on days 12-15) and single dose of 6-aminonicotinamide (0.5 mg on day 14) were administered to pregnant females of random bred strain H-Velaz mice. The width of the alveolar arch of the developing maxilla was measured in drawings of the roof of the mouth of 600 fixed embryos taken between days 16 and 19. The width of the maxilla of experimental embryos with a closed secondary palate was the same as in the control embryos throughout the observation period, whereas the maxilla of all embryos with cleft palates was wider than in the controls. Final expansion of the maxilla was the same in all experimental groups.

6-Aminonicotinamide↗
PubMed1977

The role of the mandible in mouse palatal development revisited.

Growth changes associated with formation of the secondary palate were studied in H-Velaz mouse embryos by morphometric measurement of medial sagittal sections of the heads between days 13 and 15 of embryonic development. Horizontalization of the palatine processes depends primarily on the length of the mandible and is effected by a shift of palatine process material into the supralingual space. The administration of 7.5 mg cortisone acetate im to the female on day 12, of 0.5 mg 6-aminonicotinamide im on day 14, or amniocentesis on day 14 significantly retards growth of the embryo in general and of the mandible in particular without significantly affecting deflexion of the skull base. The different spatial conditions created by disproportion between deflexion of the base and the length of the mandible cause irregularities in the course of horizontalization which lead, as a rule, to cleft palate.

6-Aminonicotinamide↗
PubMedDate not supplied

Teratogenic and lethal effects of long-term hyperthermia and hypothermia in the chick embryo.

The teratogenic effect of maternal hyperthermia is well known in laboratory animals and is presumed to exist also in humans. The aim of our study was to describe the embryotoxic effect of long-term higher and lower incubation temperatures on the chick embryo. Chick embryos were incubated within days 1 to 9 at 12 different incubation temperatures ranging from 31 to 42 degrees C. On the basis of our results, we estimated that there are three upper and lower critical thresholds of the incubation temperature: the first thresholds are 31 and 42 degrees C, at which all embryos died; the second thresholds are 32 and 41 degrees C, at which all living embryos were malformed; the third thresholds are 33 and 40 degrees C, at which some of the living embryos were without structural malformations, but their weight was shifted down and up with lower and higher temperature, respectively. The incubation temperature of 37 to 38 degrees C was optimal. Typical malformations detected on day 9 of incubation were microphthalmia, gastroschisis, caudal regression syndrome, and hyperlordosis, all of which occurred in dead embryos several times more frequently than in living embryos. CNS malformations were only sporadically present on day 9, as most of specimens bearing CNS defects died during the first days of incubation.

Animals↗
PubMedDate not supplied

Light irradiation increases embryotoxicity of photodynamic therapy sensitizers (5-aminolevulinic acid and protoporphyrin IX) in chick embryos.

Photodynamic therapy (PDT) of malignant processes is based on the ability of a photosensitizer to first, accumulate in malignant (immature) tissue and second, to be destroyed following light irradiation. Because of the similarity between malignant and embryonic immature tissues, we investigated the deleterious effect of the PDT procedure on day 4 chick embryos in ovo. We compared experimentally the photodynamic effect (light-toxic) and the side effect (dark-toxic) of the clinically attractive photosensitizers 5-aminolevulinic acid (ALA) and protoporphyrin IX (PP IX). The dark and light embryotoxicity (i.e. lethality plus teratogenicity) was determined after intra-amniotic injection of one of a range of dose of each compound. Under dark conditions, PP IX exhibited embryotoxicity at a dose of 10 microg/embryo; however ALA did not exhibit embryotoxicity even at the highest dose (300 microg/embryo). Light irradiation of embryos following injection induced strong embryotoxic effects of both substances even at dark-ineffective doses.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

Position and growth of upper and lower tooth primordia in prenatal mouse--3D study.

The secondary palate formation in mouse has been associated with the period of fast growth of the mandible from embryonic days (ED) 13.0 to 16.0. During that time, the incisors and first molars develop from the bud to the bell stage. We investigated the position and growth of the tooth during prenatal elongation of the lower and upper jaws, and searched for the developmental stage when alignment of opposing teeth was achieved. Computer-aided 3D representations allowed us to represent the position of incisors and molars in the embryonic head from ED 13.5 to 18.0 on the basis of data obtained from histological sections. The atlas-hypophysis connection exhibited minimum change in length and orientation during the prenatal period, and thus was used as a reference line. The length of the teeth was calculated from 3D data. The upper first and second molars were longer than the lower ones. When viewed from the upper side, the upper and lower molar primordia were parallel from ED 13.5 to 15.0. During this period, the upper molars had a more lateral position than the lower ones. This situation was maintained in the anterior extremity of the first molars at later stages, while the posterior part of the upper and lower molar epithelia reached opposition in the medio-lateral direction from ED 16.0. The lower incisors exhibited an apparently backward position when compared to the upper incisors at earlier stages. However, the distance between the prospective anterior tips of the opposing incisors gradually decreased. The part of Meckel's cartilage associated with the lower dental quadrant elongated more than 3-fold from ED 13.5 to 18.0, and the lower jaw grew faster than the upper one. This difference resulted from the fast growth of the lower diastema from ED 14.0 to 18.0. The different growth speeds of the upper and lower jaws did not change the relative antero-posterior adjustment of the upper and lower molars, but contributed to achieving the opposition of the gnawing ends of the incisors.

Animals↗
PubMedDate not supplied

Dentition development and budding morphogenesis.

The development of functional teeth in the mouse has been widely used as a model to study general mechanisms of organogenesis. Compared with other mammals, in which three incisors, one canine, four premolars, and three molars may occur even in each dental quadrant, the mouse functional dentition is strongly reduced. It comprises only one incisor separated from three molars by a toothless gap diastema at the location of the missing teeth. However, mouse embryos also develop transient vestigial dental primordia between the incisor and molar germs in both the upper and lower jaws. These rudimental structures regress, and epithelial apoptosis is involved in this process. The existence of the vestigial dental structures allowed a better assessment of the periodicity in the mouse dentition, which extends opportunities for the interpretation of molecular data on tooth development. We compared the dentition development with tentative models of budding morphogenesis in other epithelial appendages lungs and feathers. We suggested how developmental control by signaling molecules, including bone morphogenetic protein (Bmp), sonic hedgehog (Shh), and fibroblast growth factor (Fgf), can be similarly involved during budding morphogenesis of dentition and other epithelial appendages. We propose that epithelial apoptosis plays an important role in achieving specific features of dentition, whose development involves both budding and its more complex variant branching. The failure of segregation of the originating buds supports the participation of the concrescence of several tooth primordia in the evolutionary differentiation of mammalian teeth.

Animals↗
PubMedDate not supplied

[Effect of the Tabby mutation on the dentition of mice].

The X-linked hypohidrotic ectodermal dysplasia in man leads to dental defects and is homologous to the Tabby (Ta) mutation in mouse. We currently investigate the effects of the Ta mutation on odontogenesis. The incisor germ of Ta showed an abnormal size and shape, a change in the balance between prospective crown- and root-analogue tissues and retarded cytodifferentiation. Although the enamel organ in Ta incisors was smaller, a larger proportion of the dental papilla was covered by preameloblasts-ameloblasts. The independent development of the labial and lingual parts of the enamel organ in rodent lower incisor might reflect their heterogeneous origin, as demonstrated for the upper incisor. The mandibular cheek dentition in Ta mice exhibits large variations classified in five morphotypes, based on the tooth number, shape, size and position. In Ta embryos, the mesio-distal extent of the dental epithelium was similar to that in WT, but its segmentation was altered. These morphotypes could be explained by a tentative model suggesting that 1) the positions of tooth boundaries differ in Ta and WT molars and among the Ta morphotypes; 2) the tooth patterns are determined by the distal boundary of the most mesial tooth primordium while the distal teeth take advantage of the remaining dental epithelium; 3) one tooth primordium in Ta mice might derive from adjacent parts of two primordia in WT.

Ameloblasts↗
PubMedDate not supplied

Morphometric analysis of potential maxillary diastemal dental anlagen in three strains of mice.

By means of histomorphometric analysis of temporo-spatial changes of the thickness of oral maxillary epithelium in day 11 and 12 ICR, Swiss, and DBA/2 x B6 mouse embryos, the transitory existence of two potential tooth anlagen was documented. The mesial primordium appeared slightly later and disappeared earlier than the distal one. Their development culminated at dental lamina and bud stage, respectively. These potential vestigial tooth anlagen might correspond to the third and fourth upper premolars present in some recent rodent families and in Paramyidae, the supposed ancestors of actual rodents.

Animals↗