PubMed Health⌕ Search

Biomedical subjects

Z Skobe

Publications and source records attributed to Z Skobe.

At least 37 records · Page 2Linked to original sources
PubMed1988

Ultrastructure of odontogenic cells during enameloid matrix synthesis in tooth buds from an elasmobranch, Raja erinacae.

The ultrastructure of the inner dental epithelial cells (IDE) and odontoblasts in elasmobranch (Raja erinacae) tooth buds was investigated by transmission electron microscopy to determine what contribution each cell type makes to the forming enameloid matrix. Row II, early stage, IDE cells contained few organelles associated with protein synthesis, whereas preodontoblasts appeared competent to initiate extracellular matrix production. Row III IDE cells are also devoid of organelles related to secretory protein synthesis, although these IDE cells accumulated large pools of intracellular glycogen. The glycogen appeared to be packaged into vesicles and exocytosed into the lateral extracellular space toward the forming enameloid matrix. Row III odontoblasts had a morphology consistent with an active protein secretory cell. No procollagen granules were present within the odontoblasts, however, nor were many collagen fibers observed in the enameloid matrix. Instead, non-collagenous "giant" fibers having 17.5-nm periodic cross striations were associated with the invaginations of odontoblast cell processes. Giant fibers, which spanned a clear zone adjacent to the odontoblasts, terminated within the enameloid matrix. Smaller 25-nm-wide "unit" fibers emanated from the giant fiber tips to form the bulk of the enameloid matrix. The clear zone, which separated the odontoblasts from the enameloid matrix at early stages, diminished in size at later stages until the odontoblast processes were completely embedded in the enameloid matrix. Nascent enameloid crystallites were observed only after a layer of unmineralized predentin was deposited beneath fully formed enameloid matrix. The results suggest that the major constituent of the enameloid matrix in skates is a non-collagenous protein derived from the odontoblasts. The inner dental epithelial cells appear to contribute large quantities of carbohydrates to the forming enameloid matrix.

Animals↗
PubMed1988

A light and electron microscope study of aging parotid and submandibular salivary glands of Swiss-Webster mice.

Light and electron microscope comparisons were made of parotid and submandibular glands from male Swiss-Webster white mice 3, 13, and 18 months old. The glands from the 13- and 18-month-old mice were less organized and the parenchyma was not as dense. Fibrous connective tissue, intracellular lipofuscin granules, and residual body formation increased with age. In the cells of the parotid glands of 18-month-old mice, the nucleus-to-cytoplasm ratio was greater than in the specimens from the younger two ages. The granular convoluted tubules in submandibular glands of 18-month-old mice were the smallest of all age groups. The age changes appear comparable to those of rat and human salivary glands, yet this is an inexpensive animal model that achieves old age in less time than other animal models.

Aging↗
PubMed1988

A scanning electron microscope study of monkey maturation-stage ameloblasts.

The maturation-stage enamel organs of Macaca arctoides and Macaca mulatta were examined in order to determine whether the cells were similar to those of the continuously erupting rat incisor. Tooth buds of the permanent dentition were fixed in formaldehyde-glutaraldehyde and post-fixed in OsO4. The enamel organs were separated from the enamel during dehydration, critical-point-dried, metal-coated, and examined in a scanning electron microscope. The results showed that there were few differences in the morphology of maturation-stage ameloblasts of these primates compared with those of other species reported in the literature. The apical plasma membranes were either smooth- or ruffle-ended, while the later membranes had maze, microvillous, or ridge configurations, also seen in rats, and an additional configuration of interdigitating bulbous extensions. The blood vessels of the papillary layer in monkeys were about 7 micron in diameter, considerably larger than those of the rat.

Ameloblasts↗
PubMed1987

Lingual changes in ageing mice by light- and scanning electron-microscopy.

Tongues from young, old and senescent Swiss-Webster white mice were compared. Sections and tissues were taken from the anterior, posterior, and ventral regions. The epithelium became atrophic and hyperkeratotic in the senescent animals. The filiform papillae were blunted, atrophic and disorganized across the entire dorsal surface in the older animals. The ventral aspect in the senescent animals had thinning epithelium, a hyperchromatic germinal layer, and a roughened, disorganized surface.

Aging↗
PubMed1986

Ultrastructure of the dental epithelium during enameloid mineralization in a teleost fish, Cichlasoma cyanoguttatum.

Secretory-stage inner dental epithelial cells (IDE) of tooth buds deposited an unmineralized, ectodermally-derived, enameloid collagen matrix. Pharyngeal plates bearing tooth buds were fixed: some were demineralized, others treated with guanidine-EDTA, then fixed and post-fixed in osmium tetroxide with potassium ferricyanide. Thin Epon sections were viewed in a Jeol 100B TEM. Nascent enameloid crystals were orientated parallel to the collagen fibres and attained widths of 200 nm. Enameloid collagen was absent in demineralized mature enameloid. The outer dental epithelial plasma membrane was deeply invaginated forming extensive channels associated with elongated fuzzy-coated vesicles. Four configurations of IDE cells were characterized by cellular constituents, including elongated granules, Golgi complexes, multivesicular bodies, large electron-dense granules and extracellular amorphous material which was also adjacent to cells containing few organelles associated with protein synthesis, within infoldings of ruffled apical membranes and multivesicular bodies. This material was considered to be resorbed enameloid collagen, not a secretory product.

Amelogenesis↗
PubMed1985

Individual variation in enamel structure of human mandibular first premolars.

Nine human mandibular first premolars were examined to assess variation in external morphology and enamel structural organization within a tooth type. The relationship of enamel ultrastructure to gross dental morphology was also studied. The teeth were cut in the mesiodistal direction just lingual to the buccal cusp, and etched. Montages were constructed of the cut enamel surface photographed in the scanning electron microscope at 100 X magnification. Parameters were measured and correlation coefficients were calculated for the comparison of various odontometric features. The mesiodistal and buccolingual dimensions were highly correlated and the occlusal thickness of enamel was significantly correlated to crown height but not crown width. Hunter-Schreger bands were less pronounced in fossa areas than at lateral aspects, cusps, or ridges; these bands were directly related to the geometry of the tooth. It was concluded that within this tooth type, there is a large amount of individual variation not only in gross morphology but also in enamel ultrastructure. This result underscores the fact that interspecific comparisons must be made with care.

Bicuspid↗
PubMed1985

Scanning electron microscope study of cat and dog enamel structure.

Scanning electron microscopy revealed several similarities as well as significant differences in the enamel structure between cat and dog teeth. Three enamel layers were present in both species; a surface rodless (aprismatic) layer, an outer layer of parallel rods (only at some sites), and an inner layer with prominent Hunter-Schreger bands. In the inner layer of both carnivores, the diameter of individual rods varied significantly and frequently their course changed abruptly with respect to neighboring rods. In dog teeth the cross-sectional shape of inner enamel rods was pleomorphic, but hexagonal in outer enamel. In contrast, cat enamel rods were rounded in both inner and outer enamel layers. Hunter-Schreger bands of cats circumscribed the teeth in relatively straight segments, but these bands showed pronounced waviness in dog teeth. In cats and dogs the surface rodless layer was structurally continuous with subjacent interrod enamel and covered all tooth surfaces with the exception of the cervical areas. The data show that the structure of inner and outer enamel layers differ between these two carnivore species and that the enamel structure of the cat was most similar to that described in humans. One principal difference between carnivore and human teeth is that the growth lines of carnivores do not terminate at perikymata on the tooth surface.

Animals↗
PubMed1985

Correlation of apical and lateral membrane modulations of maturation ameloblasts.

Maturation ameloblasts of rat incisor teeth have smooth-ended and ruffle-ended apical membrane configurations. It has also been reported that maturation ameloblasts have several lateral membrane configurations. The purpose of this study was to determine the correlation between the modulations of lateral and apical cell membranes of murine incisor ameloblasts in the maturation stage of amelogenesis. Maxillary and mandibular incisors were dissected, demineralized, embedded in paraffin, sectioned and then de-paraffinized, and the enamel organs were prepared for scanning electron microscopy. Additional mouse and rat incisor enamel organs were fixed and teased apart during dehydration, then observed in the SEM. The lengths of smooth- and ruffle-ended ameloblast segments were measured, and the site, length, and frequency of each lateral membrane configuration were determined within each segment. The lateral membrane configuration with folds forming from 12 to 14 channels around the periphery of the cells was most predominant in both smooth- and ruffle-ended cells. Cells surrounded by from six to eight channels were the only other lateral membrane configuration observed in ruffle-ended ameloblasts. Smooth-ended ameloblasts had lateral membrane configurations with either dense or sparse microvillous projections in addition to both types of channel cells. The observation that channelled extracellular spaces are always associated with ruffle-ended cells suggests that channels somehow function in conjunction with the ruffled apical membrane in resorption and removal of enamel matrix proteins. The smooth-ended ameloblasts lack tight apical junctions, and their microvillous lateral membranes permit the passage of plasma fluids around cells to the maturing enamel surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Ameloblasts↗
PubMed1985

The effects of colchicine on the ultrastructure of the dental epithelium and odontoblasts of teleost tooth buds.

Secretory granule ultrastructure of teleost inner dental epithelial (IDE) cells has been reported to be similar to procollagen granules of other cells synthesizing collagen. This study describes the ultrastructure of secretory products in odontogenic cells during enameloid matrix formation in cichlids after inhibition of granule secretion with colchicine. Thirty-six fish were injected with 0.1 mg colchicine, then three were killed first at 2-hr intervals for 12 hr, then daily for 5 days. Tooth buds were processed for transmission electron microscopy, and ultrastructural alterations were assessed for each post-injection interval. Four hours post-injection, IDE cells contained increased numbers of secretory granules, lightly stained granules, dilated cisternae of the granular endoplasmic reticulum, and intercellular amorphous material. After 6 hr, the IDE intercellular amorphous material additionally contained electron dense deposits, and after 8 hr, the intercellular material had fibers similar in appearance to enameloid collagen. No ultrastructural changes were detected in odontoblasts that were in close proximity to the enameloid matrix. Only odontoblasts synthesizing predentin were affected by colchicine, and the observed alterations were similar to those seen in IDE cells. It is concluded that IDE cells synthesize and secrete ectodermal enameloid matrix collagen.

Amelogenesis↗
PubMed1983

Association of fimbriae with the hydrophobicity of Streptococcus sanguis FC-1 and adherence to salivary pellicles.

A nonhydrophobic mutant of Streptococcus sanguis FC-1 was isolated which has a greatly diminished capacity for attaching to experimental salivary pellicles on hydroxyapatite surfaces and for aggregating with salivary components. The mutant appears to be defective in the synthesis of fimbriae, as judged by electron microscopic observations and by its inability to exhibit twitching motility.

Adhesiveness↗
PubMed1981

Ultrastructure of differentiating preameloblasts from tooth germs of the permanent dentition of Macaca mulatta and Macaca arctoides.

Cytodifferentiation of inner enamel epithelium and the adjacent connective tissue from the tip of the cervical loop to the initiation of enamel elaboration in two Macaca species was examined. Ten- to twelve-month-old specimens were fixed by perfusion and the permanent tooth buds were prepared for transmission electron microscopy. At the cervical loop proper, inner enamel epithelium cells have lobed nuclei, a paucity of cytoplasm, and wide extracellular spaces; the basal lamina facing the dental papilla is straight. With increasing distance from the tip of the cervical loop, the following changes occur gradually: (a) preameloblasts elongate from 15 to 45 micrometers, and their organelles, particularly mitochondria and profiles of rough endoplasmic reticulum, become more numerous; (b) extracellular spaces decrease between preameloblasts starting at the basal (infranuclear) end; (c) the basement membrane becomes convoluted and associated with aperiodic fibers; (d) preodontoblast projections penetrate the aperiodic fibers; (e) collagen fibers subjacent to the basement membrane increase in density, with particularly thick fibers paralleling the aperiodic fibers. These modifications occur within three-fourths of the distance from the tip of the cervical loop to the mineralization front. The condensation of preodontoblasts is followed immediately by predentin synthesis. Concomitantly, the basement membrane breaks down and the aperiodic fibers are engulfed by preameloblasts. Preameloblast projections penetrate junctional predentin, contact mineralized dentin, and enamel synthesis ensues. At this stage the ameloblast is 45 micrometers long, the nucleus is central or basal, the Golgi apparatus has migrated apically, but the Tomes' process has not yet formed. The results indicate that odontogenesis in Macaca monkeys more closely resembles human odontogenesis than does that in the murine rodents.

Ameloblasts↗
PubMed1981

Ultrastructure of secretory ameloblasts in a monkey Macaca mulatta.

A 13-month-old animal was fixed by perfusion; the tooth buds of the permanent dentition were removed and prepared for transmission electron microscopy. Secretory ameloblasts were about 35 micrometers long and Tomes processes varied from 6 to 16 micrometers in length. The organelles included a basal nucleus, a Golgi apparatus concentrated in a spherical region about 4 micrometers in diameter in the supranuclear region, rough endoplasmic reticulum situated between the basal and apical terminal webs, and mitochondria dispersed throughout the cytoplasm, including Tomes processes. Many ameloblasts also contained a variety of granules, rosettes of small vesicles, and multivesicular bodies interpreted as parts of a lysosomal or GERL system. Stippled material was observed only at the distal end of the Tomes process of some ameloblasts. The results demonstrate that the Tomes process in the macaque was longer than reported in cats or man, otherwise the secretory ameloblast ultrastructure is similar among the three species.

Ameloblasts↗
PubMed1980

The pathway of enamel rods at the base of cusps of human teeth.

Enamel increases in volume and surface area with distance from the dentin-enamel junction, particularly at cusps, while the number of rods remains constant. Our results indicate that the increase in volume may be due to the increased rod diameter near the tooth surface, a circumferential winding of rods in the parazone orientation of Hunter-Schreger bands, and the migration of rods from a mid-coronal origin at the dentin surface to a cuspal terminaton at the tooth surface. Increased surface area can be explained by the increased rod diameter and the oblique approach of rods to the tooth surface.

Acid Etching, Dental↗
PubMed1980

The vascular pattern in the papillary region of rat incisor and molar tooth enamel organ.

Scanning electron microscopy of the enamel organ of rat incisor and molar teeth in the maturation stage of amelogenesis revealed two vascularization patterns of the papillary layer. In one pattern, the anastomosing capillaries formed loops of varying sizes around spherical or somehwat oblong papillae. In the second pattern, the capillaries were parallel to each other embedded in furrows between long ridges of papillary cells. It is postulated that each of these two patterns may be associated with a specific stage in the process of enamel maturation.

Animals↗