Biomedical subjects

K S Prostak

Publications and source records attributed to K S Prostak.

12 recordsLinked to original sources

PubMed1994

The loci of mineral in turkey leg tendon as seen by atomic force microscope and electron microscopy.

Transmission electron micrographs of fully mineralized turkey leg tendon in cross-section show the ultrastructure to be more complex than has been previously described. The mineral is divided into two regions. Needlelike-appearing crystallites fill the extrafibrillar volume whereas only platelike crystallites are found within the fibrils. When the specimen is tilted through a large angle, some of the needlelike-appearing crystallites are replaced by platelets, suggesting that the needlelike crystallites are platelets viewed on edge. If so, these platelets have their broad face roughly parallel to the fibril surface and thereby the fibril axis, where the intrafibrillar platelets are steeply inclined to the fibril axis. The projection of the intrafibrillar platelets is perpendicular to the fibril axis. The extrafibrillar volume is at least 60% of the total, the fibrils occupying 40%. More of the mineral appears to be extrafibrillar than within the fibrils. Micrographs of the mineralized tendon in thickness show both needlelike-appearing and platelet crystallites. Stereoscopic views show that the needlelike-appearing crystallites do not have a preferred orientation. From the two-dimensional Fourier transform of a selected area of the cross-sectional image, the platelike crystallites have an average dimension of 58 nm. The needlelike-appearing crystallites have an average thickness of 7 nm. The maximum length is at least 90 nm. Atomic force microscopy (AFM) of unstained, unmineralized turkey leg tendon shows collagen fibrils very much like shadow replicas of collagen in electron micrographs. AFM images of the mineralized tendon show only an occasional fibril. Mineral crystallites are not visible. Because the collagen is within the fibrils, the extrafibrillar mineral must be embedded in noncollagenous organic matter. When the tissue is demineralized, the collagen fibrils are exposed. The structure as revealed by the two modalities is a composite material in which each component is itself a composite. Determination of the properties of the mineralized tendon from the properties of its elements is more difficult than considering the tendon to be just mineral-filled collagen.

Animals↗

PubMed1991

Serum fluoride level and fluoride content of enameloid.

We investigated diverse groups of fish species to determine whether the fluorine (F) contents of the dental hard tissues were related to baseline serum F levels. Serum samples, enameloid, dentin, ganoid/enamel, and bone were analyzed for F by either electron microprobe or wet chemistry. Species were categorized into two groups based on the F content of the enameloid. One group contained greater than 2.6 wt% F in enameloid, whereas the other group had less than 0.45 wt% F in enameloid. The dentin and bone from all species (or, in skates, the cartilage), as well as the ganoid/enamel layer of a Holostean fish (alligator gar), showed consistently low F content. In those species whose teeth developed in sequential rows, the F content of enameloid increased with progressive tooth development. The serum F levels of all fish were below 0.05 microgram F/mL (2.63 mumol/L) and were not significantly related to the F content of the enameloid. The results substantiate the idea that F incorporation into enameloid is related to fish phylogeny, not food or habitat. It is suggested that specialized outer dental epithelial cell configurations may facilitate the incorporation of F into enameloid.

Animals↗

PubMed1990

Ultrastructural study of tracer permeability through the cat and ferret enamel organ.

The access of exogenous materials to the developing enamel surface has been intensively studied in rodents, but not in other mammalian species. This ultrastructural study investigates the permeability of injected horseradish peroxidase (HRP) and lanthanum tracers in cat and ferret tooth buds. In cat enamel organs fixed by immersion, lanthanum did not escape the capillaries overlying secretory stage tooth buds, but it did permeate up to the distal junctions of ruffle-ended (RA) and the proximal junctions of smooth-ended (SA) ameloblasts. Perfusion fixation with lanthanum compromised junctional integrity of cat ameloblasts at all stages of development. Similarly, HRP rarely escaped the capillaries associated with cat secretory stage enamel organs. However, unlike lanthanum, HRP was mostly confined to the vasculature of maturation stage enamel organs in immersion fixed cats at all time intervals examined. In ferrets, HRP penetrated up to, but not beyond, the distal junctional complexes of secretory ameloblasts. In maturation stage enamel organs, HRP coated the papillary and RA cells, but did not penetrate the RA distal cell junctions. HRP did permeate the extracellular spaces of SA to reach the underlying enamel surface. Ameloblasts in transitional phases of SA and RA endocytosed HRP at the distal cell surface. This data leads to several conclusions. First, HRP localization in the ferret paralleled that observed in rodents. Second, the results of cat enamel organs substantiate previous studies showing perfusion fixation can increase vascular and intercellular permeability to lanthanum. However, in cats fixed by immersion, both lanthanum and HRP were restricted to capillaries associated with the secretory stage enamel organ, and only lanthanum escaped maturation stage capillaries. It is suggested that variations in the fenestrations and distribution of capillaries associated with the cat enamel organ may differentially retain some materials and permit other materials to escape with relative ease.

Ameloblasts↗

PubMed1989

The penetration of exogenous tracers through the enameloid organ of developing teleost fish teeth.

In order to determine whether exogenous materials permeate to the forming tooth enameloid matrix, teleost species were injected intramuscularly with horseradish peroxidase (HRP) or myoglobin, or; intracardially with lanthanum nitrate or HRP, then killed a predetermined intervals post-injection. Tooth bearing bones were processed for transmission electron microscopy. At the enameloid matrix formation stage, capillaries associated with the enameloid organ were few in number and rarely fenestrated. Both organic tracers reached the matrix at cervical but not coronal, regions of the teeth in all species examined. Lanthanum was rarely observed extravascularly and never extended to the enameloid matrix at the secretion stage. At the enameloid mineralization stage, fenestrated capillaries were closely associated with the outer dental epithelial cells (ODE). All tracers were observed in the plasma membrane invaginations of the ODE. Only intracardially injected HRP compromised the apical intercellular junctions of the inner dental epithelial cells (IDE) to reach the mineralizing enameloid Lanthanum did not extend past the ODE-IDE cell junctions. It is concluded that the close association of mineralization stage fenestrated capillaries with the highly invaginated ODE cells result in increased tracer penetration compared to the secretory stage. The deeper penetration of the organic tracers, compared with lanthanum, between mineralization stage IDE cells may be due to longer in vivo circulation of the former material. The apical junctions of mineralization stage IDE cells, however, remained impermeable to the organic tracers. The absence of mineral in secretory stage enameloid mineral could not be due to specialized cell junctions preventing access of molecules to the matrix. It is suggested that controlling factors other than cellular permeability initiate enameloid mineralization.

Animals↗

PubMed1989

Increased pH-lowering ability of Streptococcus mutans cell masses associated with extracellular glucan-rich matrix material and the mechanisms involved.

Streptococcus mutans strain IB-1600 was cultivated in Todd-Hewitt broth (THB) or THB supplemented with sucrose (S). Cell mass obtained from THB exhibited a high cell density and negligible glucan-rich extracellular matrix material (EMM), whereas cell mass from 2% S-supplemented THB exhibited widely-spaced cells separated by EMM. The pH-lowering potential of the different cell masses was studied in vivo with an intra-oral enamel demineralization test and rinsing with glucose solution, and in vitro with a model which permits vertical penetration of glucose through the cell mass and pH evaluation at different depths within the cell mass. In vivo, the pH profile of EMM-rich cell mass derived from 2% S-supplemented THB was characterized by a lower pH minimum and a slower return of the pH as compared with THB-derived cell mass. In vitro, an increase in cell mass EMM content was associated with a more rapid initiation and an increase in the rate of pH drop in the depth of the cell masses. Evaluation of the acidogenic potential of the cells in cell masses derived from THB and 2% S-supplemented THB with suspensions of dispersed cell mass and added glucose indicated no difference. The buffering capacity of cell mass derived from 2% S-supplemented THB within the pH range of 6.5-4.0 was greatly reduced as compared with that of THB-derived cell mass, due to the relatively low buffering capacity of EMM. The presence of EMM also appeared to enhance the porosity of the cell mass.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Scanning electron microscopy of monkey secretory- and transitional-stage enamel organ cells.

This scanning electron microscope (SEM) study of secretory- and transitional-stage enamel organ cells of the permanent dentition of Macaca mulatta and Macaca arctoides was undertaken because the topography of these cells in primates has not been described in the literature. Comparison of our results with murine enamel organ morphology reported previously revealed not only many similarities, but also some significant differences. Tooth buds of the permanent dentition were routinely prepared for SEM. Murine secretory-stage ameloblasts have been described to be 65-70 microns long, with smooth lateral membranes, but those of monkeys were only 30-35 microns tall, with four different lateral plasma membrane configurations: smooth, filamentous, longitudinally ridged, and transversely ridged. The filamentous form was most common. Cells were seen with either transverse or longitudinal ridges in the basal half, and with filamentous ridges in the apical portion; this indicates modulation between these forms. Because of the extraordinary similarity between these lateral membrane modulations and those of rat incisor maturation ameloblasts, a comparable function is proposed--namely, that monkey secretory ameloblasts function, in part, in the resorption and mineralization of enamel matrix. There were several layers of rounded stratum intermedium cells basal to monkey secretory-stage ameloblasts, but only one layer of cuboidal stratum intermedium in rodents. The stellate reticulum cells of rats and monkeys appeared attenuated, with large extracellular spaces. There was little or no reduction in cell length of monkey transitional-stage ameloblasts. The position of the nuclear bulge differentiated transitional- from secretory-stage ameloblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Ameloblasts↗

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↗

PubMed1986

Campylobacter-like organisms isolated from gastric mucosa of ferrets.

Campylobacter-like organisms (CLO) were isolated from gastric lesions in 1 ferret and gastric mucosa of 2 healthy ferrets. The organism was not isolated from biopsies of gastric mucosa of 14 other healthy ferrets, 1 of which had small gastric lesions located at the pylorus. Lesions from which CLO were isolated were located in the antrum of 1 ferret and were classified as inflammation with repair. Affected gastric tissue was highly vascularized with fibrous connective tissue surrounding irregularly shaped glands. Necrosis and ulceration of adjacent mucosa also were observed. Using Warthin-Starry stain, Campylobacter-like organisms were seen on and in the glandular epithelium of the ferret with gastric lesions from which CLO were isolated.

Animal Diseases↗

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↗

PubMed1982

Proliferative colitis in ferrets.

During a 4-month period, 31 of 156 ferrets (Mustela putorius) in a biomedical research program developed protracted diarrhea. Clinical signs were green mucohemorrhagic fecal material, partially prolapsed rectum, anorexia, body weight loss, and dehydration. Nine of the affected animals were necropsied. On gross examination, the descending colon was grossly thick and histologically characterized by marked proliferation of the mucosa, relatively few goblet cells, mixed inflammatory cell infiltrate, and penetration of the mucosal glands through the muscularis mucosa into the submucosa and tunica muscularis. Campylobacter fetus subsp jejuni was isolated from 6 of 9 ferrets with proliferative colitis. Warthin-Starry stained sections of hyperplastic colon revealed large numbers of organisms in the apical portion of epithelial cells, and organisms similar to Campylobacter spp were observed by electron microscopy in hyperplastic colonic epithelium. The proliferative colitis in the ferret is compared with the pathologic and bacterial features of similar intestinal proliferative diseases in swine and hamsters.

Animals↗