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Biomedical subjects

A Boyde

Publications and source records attributed to A Boyde.

At least 181 records · Page 10Linked to original sources
PubMed1981

The arrangement of ameloblasts on the surface of maturing enamel of the rat incisor tooth.

The location of striated border cells versus non-striated border cells during enamel maturation in the rat incisor was studied by light microscopy. Serial cross sections of the lower incisors were examined from a segment of the incisor in sections which also included the first molar tooth. In the series recorded here every cross section showed both striated and non-striated border cells. A map showing the distribution of cells on the enamel surface, as plotted from their position in each of the cross sections, reveals that the non-striated border cells traverse the enamel as oblique bands. Between the narrow bands of non-striated border cells were wide bands of striated border cells. The non-striated border cells were joined at their basal nuclear poles by contacts which appeared to separate the lateral inter-ameloblast space from the space between the papillary-ridge cells. Neither the striated border cells nor the non-striated border cells went entirely to the edge of the enamel organs. The above pattern of striated border cells and non-striated border cells is regarded to be a manifestation of the cyclical activity of maturation ameloblasts.

Ameloblasts↗
PubMed1981

The production of putative osteoclasts in tissue culture - ultrastructure, formation and behavior.

A system for culture of cat bone marrow produces multinucleate cells (50-100 nuclei) of large proportions (300 micrometer diameter). Scanning and transmission electron microscopy indicates that these cells (not virally induced syncytia) are true osteoclasts, which exhibit ultrastructural aspects of bone resorption (ruffled border and clear zones in TEM section, active spatulate cytoplasmic extensions in the SEM) even after 6 weeks culture on a plastic substratum. Observations have also been made regarding the formation of the multinucleate cells from apparently specific mononuclear precursors, and the behaviour of these cells on various substrata is also reported.

Animals↗
PubMed1980

Lack of Fc receptors on osteoclasts.

Fc and C3 receptors, which are characteristically present on macrophages, could not be demonstrated on osteoclasts maintained in situ on their normal substrates when assayed for by use of sheep red blood cells coated with immunoglobulin (Shapiro et al. 1979). The present study tested the hypotheses that Fc receptors are present only on the osteoclast surface adjacent to bone and that Fc receptors on osteoclasts can be uncovered by enzymes or stimulated to appear. Freeze-dried, inverted osteoclasts (and osteoblasts) obtained from the endocranium of newborn rats were tested for Fc receptors using the rosette assay and examined by scanning electron microscopy. No rosettes were observed on the surfaces of the osteoclasts that had been approximal to the bone. Bone specimens were cultured for 30 min at 37 degrees C in control medium, or in medium with the addition of 10, 50 or 100 microgram/ml trypsin, 0.5 U/ml parathyroid extract (PTE), or 0.5 or IU/ml parathyroid hormone 1--34 (PTH). Additionally, two week-old rats were injected intraperitoneally with PTE (1.5 U/g body weight or 1 USP/g body weight) or with PTH (1 U/g body weight) or with vehicle alone, 6 h before sacrifice. The specimens were assayed for Fc receptors and examined by scanning electron microscopy. Macrophages were always used as controls for the assay. No rosettes were present on osteoclasts subjected to any of these treatments. Accordingly, the hypotheses were not supported.

Animals↗
PubMed1980

Treatment with lithium salts reduces ethanol dehydration shrinkage of glutaraldehyde fixed tissue.

Changes in the area of glutaraldehyde fixed 15 day p.c. mouse embryo limbs were recorded using a Quantimet 720 image analysing computer attached to a light microscope: during a period of treatment with an isotonic salt solution (mostly halides of the alkali or alkaline earth metals); a subsequent wash with distilled water; and dehydration through a 30, 50, 70, 80, 90, and 100% ethanol series. Pretreatment with NaCl, KCl, RbCl had no significant effect. Treatment with LiCl, LiNO3, LiF (0.03 M), CsF and CsCl caused an increase (relative to Na, K or Rb treated samples) in the specimen volume during dehydration, which persisted in 100% ethanol. Li treated samples showed the largest post-critical-point-drying (CPD) volumes, followed by Cs treated tissue. Pretreatment with Be, Mg, Ca, Sr and Ba chlorides caused shrinkage and the 100% ethanol and post-CPD volumes of these samples were all lower than those treated with the monovalent cation containing salts.

Aldehydes↗
PubMed1980

Energy dispersive X-ray elemental analysis of isolated epiphyseal growth plate chondrocyte fragments.

Isolated cells of matrix fragments of freeze fractured and freeze dried growth plate from the four species was analyzed by EDX. Cells were removed from the tissue by stereoscopic microdissection using an SEM and mounted on thin film supports on TEM grids: this approach eliminated specimen X-ray background and reduced instrumental and support background levels to insignificant proportions. Chondrocyte and matrix fragments were dissected and analyzed. Cell Ca reaches EDX detectable levels in hypertrophic cells close to the mineralization front. At all stages of maturation, the cells exhibit high P; however, matrix Ca levels are elevated before P. This data suggests that the early cartilage matrix is accumulating Ca and that the cells' role in this process may be to elevate the matrix Ca and P concentration. All cells showed clear S peaks although these are reduced in late hypertrophic cells. With mineralization, matrix S levels fall, indicating a loss of sulfated proteoglycans. Matrix before mineralization contains more K than would be expected from data of previous studies. It is suggested that while this K may be bound to fixed anionic sites in the matrix, reported values for cartilage lymph and extracellular fluid should be reviewed.

Animals↗
PubMed1980

Scanning electron microscope histochemistry: the use of backscattered electrons to identify epidermal Langerhans cells in the scanning electron microscope.

Epidermal sheets reacted for ATPase were examined in the scanning electron microscope and images based on atomic number contrast formed by collecting the backscattered electrons. Langerhans cells lying within the tissue were revealed and could be related to surface structures by reference to conventional secondary electron images.

Adenosine Triphosphatases↗
PubMed1980

Characteristic molar ratios of magnesium, carbon dioxide, calcium and phosphorus in the mineralizing fracture callus and predentine.

From fracture callus in different stages of mineralization the contents of Mg, CO2, Ca and P were determined and compared with those found in predentine. It was found that the Mg- and CO2-contents are high in relation to Ca and P values during the prestages and early stages of mineralization. These relatively high Mg- and CO2-values are connected with high Mg/Ca, Mg/P, CO2/Ca and CO2/P ratios which strongly decrease with the increasing degree of mineralization. These results seem to be part of a general controlling mechanism of the calcification.

Animals↗
PubMed1980

Further studies of specimen volume changes during processing for SEM: including some plant tissue.

The dimensions of specimens undergoing preparation for examination in the SEM were measured throughout the preparative sequence or at various important stages. The tissues studied included 15-day mouse embryo limbs (MEL), small blocks of adult mouse liver and brain, and potato tuber. The animal tissues were fixed in 3% glutaraldehyde (GA) in 0.15M cacodylate buffer, and the potatoe tissue in 2% GA in water. The effects of various secondary fixation and other treatments were investigated. The results show that lithium salts cause a reduction in the shrinkage of MEL in 100% ethanol but this effect was not significant in the other tissues investigated, and did not persist in specimens stored after critical point drying (CPD). All CPD specimens were shrunken. However postosmication and treatment with uranyl acetate (UAc) and cetyl pyridinium chloride (CPC) all reduced specimen shrinkage in 100% ethanol and after critical point drying. The volume gains with Os + UAc and Os + CPC are both very significant, but it was found that these larger specimens shrank more on storage. Thus rapid examination in the SEM is recommended. Ethanol and Freon 113 were compared as intermediate fluids and it was found that ethanol-CO2 critical point dried specimens shrank more before and after CPD than Freon 113-CO2 specimens. The latter technique is, therefore, to be recommended. Potato tissue shrinks in 30% ethanol, whereas animal tissues all swell in this concentration. The potato tissue also shrank very litte on critical point drying in contrast to the animal tissue specimens.

Animals↗
PubMed1979

A correlated scanning and transmission electron microscopic study of maturation ameloblasts in developing molar teeth of rats.

Maturation ameloblasts of developing molar teeth of the rate were studied by both scanning and transmission electron microscopy. After fixation, teeth were frozen and split. One face of the fractured tooth was used for SEM, the other for TEM. It was found that in some regions proximal junctional complexes separate the interameloblast space from the intercellular space of the papillary layer. Thereby an intercellular ameloblastic compartment is delineated which in some specimens contains a substance interpreted to be colloidal. Elsewhere the proximal junctions of ameloblasts are not present and free communication between the extracellular spaces is evident. The apical pole of ameloblasts varies in structure. Over some areas there is a distinct distal border zone with membranous infoldings which in some regions resembles a striated or ruffled border, but in other regions the membranes show whorl configurations. The distal border zone also contains granules with flocculent material. Elsewhere the ameloblasts display no distal border zone and the cells show a smooth membrane (except for pinocytotic vesicles and hemidesmosomes) facing the enamel surface. The lateral surface of ameloblasts exhibits a variety of surface configurations similar to but not as pronounced as those reported previously in rat incisor maturation ameloblasts.

Aging↗
PubMed1979

Colonization of various natural substrates by osteoblasts in vitro.

The ability of osteoblasts to transfer from normal rat growing skull bone to small fragments of various biological materials was tested in an organ culture system. The substrates were tested as overlays and included intact or anorganic cut, polished or fractured bone, osteoid, cementum, dentine and enamel. Osteoblasts migrated on to and over all these materials, whether collagenous or not and whether mineralized or not. The culture medium affected the cell shape, elongation, alignment and dorsal ruffling activity of the cells similarly on the original bone surfaces and on the overlays. The position of the cells on the overlay was influenced by constraints due to space available for each cell, sharp edges and corners, and fine textural patterns, in that order. It is concluded that the ability of such substrates to support new bone formation cannot rest with the readiness of the osteoblasts to coat them. The procedures outlined constitute a valuable, simple and rapid means of testing one aspect of the biocompatibility of potential prosthetic bone implant materials.

Animals↗
PubMed1978

Intercellular attachments between calcified collagenous tissue forming cells in the rat.

Osteoblasts of the young rat cranium, and cementoblasts and odontoblasts of young rat molars were prepared by ethanol freeze-fracture prior to critical point drying for scanning electron microscopy (SEM) as well as conventional transmission electron microscopy (TEM) techniques. Critical point drying causes shrinkage which separates the lateral intercellular contacts between neighbours in the same sheet in the case of cementoblasts and osteoblasts, but not those between odontoblasts. These differences are considered to be of functional significance and need to be taken into consideration when formulating theories of calcium influx into the mineralizable matrix of the respective tissues.

Animals↗
PubMed1978

Histochemical and electron probe analysis of secretory ameloblasts of developing rat molar teeth.

Calcium was not found in secretory ameloblasts and stratum intermedium cells when treated with OsO4-pyroantimonate or when surfaces prepared by fracturing fresh, rapidly frozen, developing molar tooth germs were subject to electron probe X-ray analysis. Pyroantimonate reaction product, considered to be calcium, was found in mitochondria of enamel organ cells which were first placed in a bath containing calcium and potassium. The plasma membrane was disrupted in cells ehich showed mitochondrial localization of reaction product. The results provide no data which indicates that enamel organ cells have a direct, active role in the movement of calcium into the enamel. Rather, it is suggested that the secretory enamel organ might serve as a selective barrier in regulating the initial mineralization of enamel.

Ameloblasts↗