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Biomedical subjects

B Kerebel

Publications and source records attributed to B Kerebel.

At least 73 records · Page 4Linked to original sources
PubMed1979

Ultrastructural studies of enamel crystallites.

High resolution electron microscopy has provided precise measurements of human enamel crystallites from the first stages of enamel development to the last stage of maturation, through counting of lattice planes and statistical analysis. Thickness and width measurements of human enamel crystallities in their mature stage are 263 A (21.9 standard error) and 683 A (134 standard error), respectively. The growth curve of enamel crystallites was drawn, the increase in the number of lattice planes in the course of enamel development was demonstrated. Fusions and dislocations related to the maturation process were visualized and discussed. Difficulties linked to the use of ultrastructural techniques were mentioned. The question of the organic stroma of the crystals remained unsettled.

Ameloblasts↗
PubMed1978

[A method for measuring apatite crystals in human dentine by high resolution transmission electron microscopy].

High resolution electron microscopy now makes it possible to use an original method for measuring biological apatite crystals. The crystals of intertubular sound dentine have an average width of 296 A (standard deviation: 37) and an average thickness of 32 A (standard deviation: 5). During the course of so-called arrested caries, crystals get twice as thick compared to those sound dentine, whereas their width remains unchanged.

Apatites↗
PubMed1978

Osteodentine and vascular osteodentine of Anarhichas lupus (L.).

TEM, SEM and X-ray diffraction analysis demonstrate the heterogeneity of the dentinal tissue on Anarhichas lupus, a vascular osteodentine. The disordered aspect of collagen fibres, incompletely mineralized (the periodical striation being still visible), explains the scattered distribution of crystallites since they are responsible for their arrangement. The low degree of mineralization revealed by the visible collagen striation is confirmed by X-ray diffraction analysis (the crystallinity of vascular osteodentine being much lower than that of the peripheral dental tissue) as well as by high resolution TEM, since no lattice planes could be observed. Osteodentine, supporting bone and proper bone have in common a mineral phase, more or less organized, different from the apatite system.

Animals↗
PubMed1977

Ultrastructural study of amelogenesis imperfecta.

An ultrastructural study of teeth with amelogenesis imperfecta revealed various aspects of microcavities in the enamel surface, which ranged from isolated imprints of ameloblasts corresponding to the mildest lesions at the end of amelogenesis, to pits caused by the death of 20 to 30 ameloblasts at the beginning of amelogenesis. Abnormalities in the shape of the prisms can be observed. Further, crystals are distributed randomly within a prism or at the junction of 2 contiguous prisms while intercrystalline spaces are widened, indicating in various places the lack of a preferred orientation of the crystals. In amelogenesis imperfecta, two different crystalline periods are found: 1 of about 250 A, the other of about 500 A and over. The fact that amorphous areas are found among the crystals of enamel may be related to different stages of crystallization. However, it was not possible to find any lattice defect.

Ameloblasts↗
PubMed1977

Some ultrastructural aspects of biological apatite dissolution and possible role of dislocations.

High resolution electron microscope techniques now make it possible to study the mineralization of calcified tissues at the crystal structure level. Dislocations play an important part in the course of crystal maturation and modifications. At least two origins of dislocations are known. The first is due to phenomena related to the incorporation of fluoride ions into the lattice. The second is due to mechanical stresses occurring between crystals during their maturation. Dislocations are the starting-points of acid dissolution which proceeds along dislocation-lines, sometimes inducing a splitting of the crystals. In the present study, dislocations have been visualized, either isolated in the crystal core and perhaps the two-dimensional surface representation of a screw-shaped dislocation, or forming nets of dislocations producing a spiral staircase on the sides faces of the crystals. There is evidence of a maturation cycle of the crystals, which may grow, split, coalesce or dissolve; liberated elements and small crystal fragments may allow development of near-by crystals. This remodelling explains the existence of a standard size as well as the perfect fitting of the crystals. These morphological data involve physico-chemical properties of biological apatites.

Acid Etching, Dental↗
PubMed1977

[Study of a non-collagen protein fraction of dentin during minerlization].

A protein fraction of mineralizing porcine dentine was analysed after E.D.T.A. demineralization. This fraction of heterogeneous composition had a high content of phosphorus. Its acid character, deductible from the amino acid analysis, was confirmed by electrophoresis. After Sephadex gel filtration, five fractions were obtained. They could be characterized by amino acid analysis and phosphorus dosage. Two fractions contained phosphorus and were very rich in aspartic acid and serine. The three other fractions were characterized by their very high content of glycine.

Amino Acids↗
PubMed1977

[Semiquantitative study of periodontolysis and experimental bone repair in the golden hamster].

80 golden hamsters received Keyes high carbohydrate diet 2 000 and a therapy with the unsaponified fraction of corn germ oil extract (UCOE). 40 hemialveolar molar sockets were preserved and a quantitative study was carried out with the scanning electron microscope and the use of two statistical methods. The effects of UCOED are: a reduction of resorption areas, a decrease in size of resorption lacunae and an increase in the attachment surface of periodontal fibres. These results are connected to the quantity of UCOED ingested. Further, the quantifying of the resorption areas indicates that the periodontal lesions induced by Keyes diet 2 000 are balanced by the ingestion of 20 mg/kg/per day of UCOED, whereas the ingestion of 50 mg/kg/per day induced a larger increase in bone apposition.

Alveolar Process↗
PubMed1976

[Amelogenesis imperfecta--structural, ultrastructural and radiocrystallographic study].

Teeth with amelogenesis imperfecta were obtained from three members of the same family, and studied through convergent technics of investigation: classical histology, scanning electron microscopy, high resolution electron microscopy, and crystallographic analysis. The results were compared with theoretical computer calculations. Enamel abnormalities related to the shape and irregular distribution of the crystals. Some needle-shaped crystals were found together with large ones, roughly rectangular. 42% of the crystals were distorted. Widened interplanar spacings were evidence of an hypomineralization. However, the interplanar spacings observed in high resolution electron microscopy, as well as the crystalline degree of the crystals, studied through classical crystallographic methods, revealed an apparently sound hydroxyapatite

Amelogenesis Imperfecta↗