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Biomedical subjects

A Boyde

Publications and source records attributed to A Boyde.

At least 199 records · Page 11Linked to original sources
PubMed1978

Electron probe analysis of maturation ameloblasts of the rat incisor and calf molar.

Rapidly frozen upper incisor teeth of rats and molar teeth of calves were freeze fractured, freeze dried and dry dissected in preparation for energy dispersive x-ray emission microanalysis in the scanning electron microscope. Successive zones of ameloblasts adjacent to maturing rat incisor enamel were examined, beginning with cells adjacent to the least mature enamel and progressing to cells over increasingly more mature enamel. Pronounced Kalpha1,2 x-ray peaks were obtained for P, S, Cl, K and Fe but not for Ca. Ca levels were also very low compared with P, S, Cl and K in calf molar maturation ameloblasts, whereas they were high in the distal poles of the secretory odontoblasts in the same specimens. The findings indicate that both intra- and extracellular Ca levels are extremely low in maturation ameloblasts. It is concluded that Ca is neither stored nor concentrated in large amounts by the maturation ameloblasts prior to its entry into the enamel. The suggestion is made that the maturation ameloblasts might regulate entry of calcium into enamel by serving as a selective barrier.

Ameloblasts↗
PubMed1977

Some morphological observations on osteoclasts.

Osteoclasts of the peripheral portions of the endocranial aspect of young rat parietal and frontal bones were studied by scanning electron microscopy of glutaraldehyde fixed, critical point dried specimens. These studies show osteoclasts to have a much more complicated form than has previously been realised. Extensively branching, elongated, smooth-surfaced cells, which are for the most part elevated above the level of the surrounding bone matrix surface and sometimes above portions of osteoblasts or other osteoclasts, were identified as motile non-resorbing cells. Portions of the former and other entire cells may be embowered in Howship's lacunae, have microvilli on their dorsal surface, and are surrounded by a serrated border of microprojections which have an apparently firm attachment to the matrix surface. Osteoclasts in short term culture show additional free surface ruffles which are not encountered in specimens taken fresh from the animal. No evidence of recruitment of osteoblasts or osteocytes into osteoclasts was found. Disinterred osteocytes retained an ability to migrate from their lacunae on to surrounding bone matrix surface.

Animals↗
PubMed1977

Further observations on the relationship between the matrix and the calcifying fronts in osteosarcoma.

Human osteosarcoma biopsies were studied with the SEM using sequential etching with sodium hypochlorite solutions after removal of aluminium or gold coatings. Osteosarcomas differ from normal hard tissues in that the matrix never proceeds to complete mineralization, so that the specimens fragment on hypochlorite treatment. Details of the fibrillar pattern and calcospheritic type of mineralization pattern can be seen in hypochlorite etched, fractured surfaces and mineralizing fronts.

Bone Matrix↗
PubMed1977

The migration of osteoblasts.

The endocranial matrix surfaces of parietal bones of 2-week old Albino Wistar rats were partly denuded of osteoblasts and then cultured for various periods up to 24 h, in control or PTE-enriched medium. They were examined by scanning electron microscopy and evidence for cell locomotion was found. Osteoblasts traversed the denuded bone surface and cut edges of bone in either medium, and cells also migrated out from vascular channels. Glass spicules were placed on the otherwise undisturbed osteoblast layer in similar organ cultures for 2, 3 or 5 days. Osteoblasts migrated from the bone to populate the glass, negotiating any angle. The cells in PTE-enriched media were always aligned parallel to one another and elongated, tended to align with the edges of the glass and, in time, formed a substrate of aligned fibrils whose axes were parallel to those of the cells. Osteoblasts in control medium on glass showed variable degrees of alignment and elongation and were less influenced by edges of the glass. Non-locomotory, nearly equidiametrical cells on glass in 5d control cultures had formed a substrate of randomly oriented fibrils. Migrating osteoblasts on bone matrix did not have leading edge ruffles; isolated, migrating ones on glass did.

Animals↗
PubMed1977

Observations on the marginal ruffles of an established fibroblast-like cell line.

LW13K2 cells, a clone of a spontaneously in vitro transformed derivative of embryonic Lewis rat fibroblastic cells, were studied by phase contrast cine-light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ruffles found at the advancing edge of cells grown on glass substrates in vitro form and recede in a period of less than one min if they do not make an attachment of the substrate. If they fail to make an attachment they may form pinocytotic channels near the leading edge as described by Price (1972) and/or collapse, generally backwards, towards the cell body. The "spines" which appear to reinforce the membranous ruffles are the last structures to disappear, and accumulate in an irregular array behind the ruffling edge; this area is behind that in which pinocytosis occurs. In comparison with the sparse numbers of ribosomes found in the trailing edge, they are present in notable concentrations near the leading, ruffling edge of the cell. No membrane vesicles have been found in or near the ruffling edges at the ruffle-spine concentration zone.

Animals↗
PubMed1977

Scanning electron microscopy of rat maturation ameloblasts.

Post-secretory, maturation-phase ameloblasts were studied by scanning electron microscopy of freeze-fractured or dry-dissected rat incisors. These cells are in contact with the enamel which they secreted at an earlier time and which undergoes a process of continuing mineralization. The lateral intercellular compartment between maturation ameloblasts is sometimes continuous with the intercellular space of the papillary layer of the enamel organ, but often closed by basal ring contacts which correspond to terminal bars seen in transmission electron microscopy. The distal poles of the cells sometimes possess striated borders. Lateral cell surfaces may show longitudinal gutter-like depressions between ridges from which numerous intercellular connections arise; or a maze of lateral folds and ridges; or they may have mostly microvillous surface projections bordering a minimal intercellular space compartment. Preliminary correlations of groupings of basal, lateral and distal cell features indicate that "basal-closed plus distal striated border" cells may show every type of lateral surface. Cell without a striated border, whether open or closed basally, have ridge or maze lateral surfaces bordering a wide intercellular compartment. "Basal-open plus striated border" cells have microvillous or maze-like surfaces. These combinations of features are encountered a few times along the length of the maturation zone of individual incisors and suggest tha existence of cyclical changes in the type of activity of maturation ameloblasts.

Ameloblasts↗
PubMed1977

Electron microprobe investigations into the process of hard tissue formation.

The electron microprobe microanalyser has been used to measure the concentrations of Ca, P and S in the predentine of young rat incisors. The specimens were prepared as alcohol embedded ultrathin sections, unfixed vacuum embedded dry cut ultrathin sections and as thin cryostat sections. The results show the influence of preparation on the measured compositions and indicate that Ca is tightly bound to the matrix, whereas P can be easily washed out. Measurements along the dentine-predentine border demonstrated zones of Ca enrichment, the average size of which suggests that the zones could be the prestages of calcospherites. A mineralisation mechanism is discussed in which the high Ca concentration activates pyrophosphosphatase or ATPase before the onset of nucleation.

Animals↗
PubMed1977

Qualitative electron probe analysis of secretory ameloblasts and odontoblasts in the rat incisor.

Rapidly frozen growing rat incisors were freeze fractured and freeze dried in preparation for energy dispersive X-ray emission microanalysis in a scanning electron microscope. Ca levels were found to be elevated in the distal cell body of odontoblasts, whereas Ca was uniformly low over all parts of the cell body of secretory ameloblasts. The results suggest fundamental differences in the mechanisms by which these two cell types process Ca, and that Ca possibly diffuses through the secretory ameloblast layer on its way to the enamel.

Ameloblasts↗
PubMed1977

Cyanide removal of gold from SEM specimens.

The cyanide method is highly recommended for the purposes of the removal of gold coatings from SEM specimens prior to (a) further treatment before further SEM, and (b) staining and mounting for LM.

Animals↗
PubMed1977

Facial and visceral arch development in the mouse embryo: a study by scanning electron microscopy.

The morphogenesis of the face and visceral arch region were studied by scanning electron microscopy in 63 mouse embryos between 8 and 13 days post coitum. The developmental stages were determined by reference to Theiler's (1971) scheme for the categorization of the normal stages of development. After the cervical fold is formed (stage 12) the mandibular primordium appears (stage 13) followed by the primordia of arches II and III (stage 14 with arch IV forming last (stage 15). Arches II, III and IV regress in reverse order, with no evidence that a cervical sinus pouch is formed. Placodes of the sensory ganglia from cranial nerves 7, 9 and 10 are formed in the first, second and third visceral grooves respectively. Formation of the external auditory meatus and its surrounding tubercles were also observed. Morphogenesis of the upper face is dominated by the midsagittal grove, which extends into the stomatodeum; and by the medial nasal, lateral nasal and maxillary processes. The temporal changes in shape and the interrelationships of the structures mentioned are described in detail.

Animals↗
PubMed1976

Experimental study of changes in osteoblastic shape induced by calcitonin and parathyroid extract in an organ culture system.

Neonate rat endocranial osteoblasts were cultured on their bone surfaces in control medium (CC) or medium to which either parathyroid extract (PTE) or calcitonin (CT) had been added for 2, 4, 8 or 24 h. Some were cultured for 24 h in CC, then for 2, 4, 8 or 24 h in either CT or PTE medium; or for 24 h in PTE, then for 2, 4, 8 or 24 h in either CC or CT; or 24 h in CT and 2, 4, 8 or 24 h in CC. The dorsal ruffling of the cells in CC was found to be suppressed by later culturing with PTE and the disoriented cells reorganized to form arrays of parallel cells. The effects of PTE were also reversed by CC or CT: the osteoblasts in the second culture (CC) lost elongation and order, and proceeded through a proliferative phase before exhibiting the ruffling form similar to a single CC 24 h culture. PTE-cultured osteoblasts showed an increase in cell overlap and contact so that a more competent barrier was formed separating the bone from the medium. In control or CT medium, however, intercellular gaps were greater than in vivo.

Animals↗
PubMed1976

Disorders of bone and fracture of the femoral neck. Evaluation of computer image analysis in diagnosis.

The quantity of bone and osteoid has been measured in undecalcified sections of iliac-crest biopsy specimens taken from patients with fracture of the femoral neck. A control group of bone samples was obtained from post-mortem material. The 'Quantimet 720' image-analysing computer system was used to measure the area of bone and osteoid. An eye-piece graticule was used to measure the proportion of bone-surfaces covered with osteoid, and there was good correlation between the results obtained by these two methods. Little difference was found between the proportion of bone in the fracture and control groups, but the fracture group contained many more individuals with an increased proportion of trabecular osteoid measured with the quantimet and of osteoid-covered surfaces measured with an eyepiece graticule.

Age Factors↗
PubMed1976

Scanning electron microscopy of bone cells in culture.

Embryonic and young rat bone cells have been growing in culture and examined in the scanning electron microscopy (SEM). Compared with cells fixed in situ and taken directly from the animal, the cultured osteoblastic cells were smoother, flatter and more extensive and showed tighter intercellular contacts. Some matrix is formed in culture and undergoes at least partial mineralization as judged by the accumulation of Ca and P measured by energy dispersive x-ray analysis. Findings concerning the morphology of the collagen arrangement were indecisive. Some superficial cells, free of surrounding matrix, resembled osteocytes in normal in vivo bone. This may indicate that a proportion of the extracellular matrix produced by the cultured cells failed to polymerise into recognizable bone matrix, and that osteocytic morphology is not dependent upon the physical characteristics of the bone matrix.

Animals↗
PubMed1976

Morphological changes of osteoblasts in vitro.

The appearance of neonate rat endocranial osteoblasts exposed in situ and fixed immediately was compared with that of similar osteoblasts organ cultured for short periods of up to 48 hours in control medium and serum alone, or with added parathyroid extract (PTE). Normal osteoblasts showed a range of variation in size and shape, degree of elongation and orientation. Culturing the osteoblasts resulted in an overall loss of elongation and ordering of the cells, and the production of dorsal ruffles which were more complex and larger in the longer culture times. PTE added to the culture medium caused an increase in cell elongation and a striking recordering of the osteoblasts into domains of parallel cells. The swirling patterns made by these domains were similar to those of the underlying bone collagen. Ruffles, where present, were small and more often peripheral than dorsal. The results indicate that fully differentiated osteoblasts are able to adapt very rapidly to survival and function in culture conditions, and that the endocytosis necessary for synthetic activity is suppressed by PTE although some cell movement may continue.

Animals↗
PubMed1976

Scanning electron microscopy of the lateral cell surfaces of rat incisor ameloblasts.

Dry dissected rat incisor ameloblasts studied in the scanning electron microscope show remarkable specializations of their lateral surfaces. Four or five cycles of a change from a surface with longitudinal gutterlike folds associated with large intercellular spaces, to one with microvilli and reduced intercellular spaces, are found along the length of the lower incisor maturation zone. It is argued that these changes indicate cyclical activity in maturation ameloblasts.

Activity Cycles↗
PubMed1976

Three-dimensional anatomy of the 8-day mouse concepts: a study by scanning electron microscopy.

The three-dimensional anatomy of the 8-day mouse concepts was studied by scanning electron microscopy aided by microdissection within the microscope specimen chamber. Attention was given to the relationship of the extra-embryonic membranes and their subtended compartments and particular emphasis was placed on the 'inverted' condition of the embryo at this stage of development. The main points brought forth in this study are: (1) the five basic brain segments are discernible on the basis of surface contour; (2) the cervical fold, extending from the ventrum of the metencephalon to the somatopleure, forms a partition which separates the branchial region from the rest of the amniotic space; (3) the procephalic membrane bifurcates in a vertical plane to form the splanchnopeure and somatopleure lateral to the forebrain, and it bifurcates horizontally to form the dorsal and ventral coverings of the pericardial coelom; (4) the anttrum of the pericardial-peritoneal canal opens into the lateral coelom posterior to the cervical fold; (5) the midgut of the embryo is delineated laterally by longitudinal grooves connecting the foregut and hindgut antra; (6) embryonic ectoderm in the neural-fold region is formed by a single layer of pseudostratified columnar cells; (7) the allantois is hollow near its base and the inner surface is formed by a discontinuous layer of squamous cells; (8) blood islands in the extra-embryonic mesoderm form a ring of bulges around the middle of the exocoel. Other structures such as the ectoplacental cavity, the ectoplacental cone and the parietal capsule are also described.

Animals↗