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T J Chambers

Publications and source records attributed to T J Chambers.

At least 181 records · Page 10Linked to original sources
PubMed1986

The effect of human calcitonin on the cytoplasmic spreading of rat osteoclasts.

We previously found that calcitonin (CT), which inhibits osteoclastic bone resorption, abolished the cytoplasmic motility of isolated osteoclasts. The transition from motility to immotility was accompanied by a characteristic change in cell shape which coincided with the loss of pseudopodial ruffling activity and gradual cytoplasmic retraction. In this report we used computer-assisted morphometry to quantify the reduction in cytoplasmic spreading induced by human CT (hCT). Osteoclasts, isolated from neonatal rat long bones, were allowed to spread on a plastic surface for 120 min. The outlines of six osteoclasts were recorded on a time-lapse video recorder. hCT, other hormones, or plasma samples were then added. The outlines of the same six osteoclasts were recorded after incubation, and the area covered by the cells after incubation was calculated as a percentage of the area covered by the same cells before hormone addition. Osteoclastic spreading was reduced by hCT in a dose-dependent manner and was significantly decreased by concentrations of 2 pg/ml and above. High concentrations of PTH and 1,25-dihydroxyvitamin D3 had no effect on osteoclasts. This technique is a sensitive and quantitative assay of hCT concentration which is unaffected by the presence of other calcium-regulating hormones likely to be present in plasma.

Aged↗
PubMed1986

Monoclonal antibodies against osteoclasts inhibit bone resorption in vitro.

Several recently-derived monoclonal antibodies (mcabs) that bind with a high degree of specificity to membrane antigens of osteoclasts were tested for their effects on the function of giant cells from osteoclastomas. None of the antibodies stimulated bone resorption when incubated with giant cells on bone slices, nor did we find any evidence that the mcabs were able to block calcitonin-inhibition of bone resorption. However, three of the mcabs strongly inhibited bone resorption. This inhibition was unaccompanied by impaired survival or morphological evidence of toxicity, but the same mcabs induced a state of cytoplasmic quiescence we have previously found to be characteristic of the response of osteoclasts to local and systemic inhibitors of osteoclastic bone resorption. These results suggest that the mcabs bind to antigens of functional importance in bone resorption or its regulation, and the similarity between the response of giant cells to mcabs and hormonal inhibitors of bone resorption raises the possibility that the mcabs may bind to and cause activation of surface receptors for one or more of these hormones. Whether this is so or not, the mcabs which influence giant cell function may represent valuable probes for an analysis of the mechanism and regulation of osteoclastic bone resorption.

Antibodies, Monoclonal↗
PubMed1986

Human osteoclast-specific antigens are expressed by osteoclasts in a wide range of non-human species.

A series of monoclonal antibodies have been developed which react specifically with human osteoclasts in human fetal bone and a range of neoplastic and non-neoplastic bone lesions. We have examined whether such antibodies retain reactivity and specificity with osteoclasts isolated from the bone of newborn non-human mammals and embryonic chickens. Of seven osteoclast-specific monoclonal antibodies, three retain their reactivity with rabbit and two with guinea-pig; none react with mouse or rat osteoclasts; two antibodies detect avian osteoclasts. The extensive retention of some osteoclast antigens during phylogeny suggests that they might represent functionally important molecules in the regulation of osteoclast activity. Moreover, the existence of antibodies capable of defining multi- and mononuclear osteoclasts, from species where osteoclast function is well characterized, suggests possible experimental routes towards the isolation, and hence study of purified populations of osteoclasts and their precursors.

Animals↗
PubMed1985

The effects of calcium regulating hormones on bone resorption by isolated human osteoclastoma cells.

Cells were disaggregated from osteoclastomas, and the response of the giant cells to calcium-regulating hormones, prostaglandin (PG)E1 and dibutyryl cyclic AMP (dbcAMP) was observed by phase-contrast time-lapse video microscopy. The pattern and nature of their response was very similar to that previously found to be characteristic of osteoclasts: calcitonin (CT), PGE1 and dbcAMP induced cytoplasmic quiescence, while parathyroid hormone (PTH) showed no influence on cytoplasmic motility or behaviour. The cells were also cultured on slices of devitalized cortical bone for 5 or 18 h. After this time the giant cells were associated with the appearance in the scanning electron microscope of characteristic resorption pits, the volume of which was calculated by computer-assisted morphometric and stereophotogrammetric techniques after removal of cells. Calcitonin caused a dramatic reduction in the volume of bone resorbed by these isolated cells compared with control cultures, while PTH was without significant effect. This result supports the view that PTH does not increase bone resorption in intact bone through a direct effect on osteoclasts. PGE1, which stimulates bone resorption when added to intact bone, paradoxically reduced resorption in our cultures. It thus appears possible that PGE1 acts as a direct inhibitor of osteoclastic bone resorption but has an additional effect on other cells in bone, which are induced by PGE1 to cause osteoclastic stimulation.

Alprostadil↗
PubMed1985

Mammalian collagenase predisposes bone surfaces to osteoclastic resorption.

The cell-free endocranial surface of young adult rat parietal bones was used as a substrate for bone cell-derived mammalian collagenase. Incubation of parietal bones in a concentration of enzyme comparable to that secreted by osteoblastic cells in vitro caused destruction of surface osteoid, and resulted in exposure of mineral onto the bone surface. Bones so pre-treated were considerably more susceptible to osteoclastic resorption than bones pre-incubated in the absence of collagenase. These results are consistent with the view that the osteoid layer which covers bone surfaces acts as a barrier to osteoclastic contact with underlying, resorption-stimulating bone mineral; and that cells of the osteoblastic lineage induce osteoclastic resorption through collagenase secretion which, by digestion of the surface osteoid, exposes bone mineral to osteoclastic contact.

Animals↗
PubMed1985

On the origin of the osteoclast: the cell surface phenotype of rodent osteoclasts.

The origin and development of the osteoclast is not well defined; although it is derived from a bone marrow stem cell, it is not proven whether the osteoclast progenitor comes from the multipotential hemopoietic stem cell or comprises an entirely separate cell lineage. We have studied the cell lineage relationship of osteoclasts isolated from newborn rodent bone to other bone marrow cell types, in particular the monocyte-macrophage cell line, by the use of cell surface phenotyping. In studies in mouse and rat we failed to detect the expression of markers characteristic of mononuclear phagocytes or other bone marrow cell types, including the hemopoietic tissue restricted common leucocyte antigen (T200). Our findings cast further doubt on the view that osteoclasts arise by fusion of mononuclear phagocytes in a similar fashion to the formation of multinucleate inflammatory giant cells.

Animals↗
PubMed1985

Cutaneous malignant histiocytosis--a clinicopathological review of five cases.

Malignant histiocytosis is a rare, and usually fatal, tumour which may involve the skin. The clinical and pathological changes are described in five patients who presented with skin nodules as the initial feature. We witnessed spontaneous healing of lesions, a previously described phenomenon which may cause diagnostic confusion. It is suggested that patients presenting with malignant histiocytosis confined to the skin form a sub-group with a more favourable prognosis.

Adult↗
PubMed1985

The pathobiology of the osteoclast.

This article reviews recent information concerning the origin of osteoclasts and the local and systemic regulation of their activity. It appears that much of the environmental responsiveness of osteoclasts is mediated by cells of the osteoblastic lineage, which exert a major influence on the localisation, induction, stimulation, and inhibition of osteoclastic bone resorption. Some of the mechanisms by which osteoclast function may be disturbed by inflammatory and neoplastic diseases are discussed, and it is suggested that many pathological disturbances of osteoclastic bone resorption may be explicable as mimicry of physiological regulatory mechanisms by local hormones introduced into bone as the local regulators of the diseased tissue.

Animals↗
PubMed1985

The effect of calcium-regulating hormones and prostaglandins on bone resorption by osteoclasts disaggregated from neonatal rabbit bones.

It has previously only been possible to assess osteoclastic bone resorption in intact bone, where other cell types may modify or mediate osteoclastic responses to environmental agents. We have recently developed techniques which enable us to measure bone resorption by osteoclasts extracted from bone and have used these techniques to assess the effects of prostaglandins (PGs) and calcium-regulating hormones on bone resorption by these cells. Osteoclasts were mechanically disaggregated from neonatal rabbit long bones and cultured on slices of devitalized cortical bone for 8 or 24 h. After this time, osteoclasts were associated with the appearance in the scanning electron microscope of characteristic resorption pits, the volume of which was calculated by computer-assisted morphometric and stereophotogrammetric techniques after removal of cells. Salmon calcitonin inhibited osteoclastic bone resorption at concentrations of 1 pg/ml and above, while PTH and 1,25-dihydroxyvitamin D3 were without significant effect. This suggests that the latter hormones do not increase bone resorption in intact bone through a direct effect on osteoclasts. PGI2, PGE1, and PGE2, all of which are known to stimulate resorption when added to intact bone, paradoxically reduced resorption in our cultures. It appears likely that PGs act as direct inhibitors of osteoclastic bone resorption but have an additional effect on other cells in bone, which are induced by PGs to cause osteoclastic stimulation.

Alprostadil↗
PubMed1985

Bone cells predispose bone surfaces to resorption by exposure of mineral to osteoclastic contact.

The cell-free endocranial surface of young adult rat parietal bones was used as a substrate for osteoclastic bone resorption, either without prior treatment, or after incubation of the parietal bones with collagenase or neonatal rat calvarial cells. Untreated, the endocranial surface consisted of unmineralized organic fibres; incubation with calvarial cells or collagenase caused disruption and removal of these fibres, with extensive exposure of bone mineral on the endocranial surface, without morphologically detectable mineral dissolution. Neonatal rabbit osteoclasts resorbed bone to a greater extent from parietal bones pre-incubated with calvarial cells or collagenase than from untreated bones; mineral exposure and subsequent osteoclastic resorption were both increased if calvarial cells were incubated with parathyroid hormone; removal of bone mineral after incubation with calvarial cells removed the predisposition to osteoclastic resorption. These experiments demonstrate that calvarial cells are capable of osteoid destruction, and indicate that one mechanism by which osteoblasts induce osteoclastic bone resorption may be through digestion of the unmineralized organic material that covers bone surfaces, to expose the underlying resorption-stimulating bone mineral to osteoclastic contact.

Animals↗
PubMed1985

Human fetal osteoclasts fail to express macrophage antigens.

A method for the isolation of osteoclasts from human fetal long bones in sufficient numbers for phenotypic studies has been devised. Using this technique we have studied the expression of cell surface antigens characteristic of mononuclear phagocytes and other haemopoietic cell types on fetal osteoclasts and compared their phenotype with mononuclear cells in the same preparations. We found that osteoclasts failed to express DrW(Ia) and 24 of 26 antigens (in 6 of 7 antigenic clusters) found on mononuclear phagocytes of the same developmental stage. This implies that osteoclasts represent the maturational end-stage of a cell lineage separate from that of conventional blood cells, and of mononuclear phagocytes in particular.

Antibodies, Monoclonal↗
PubMed1985

The permeability of normal, adenomatous, ulcerative colitic and malignant large bowel epithelial cell membranes to inulin.

We measured the permeability of normal, adenomatous, colitic and malignant large bowel epithelial cells by immersing fragments of large bowel mucosa in radiolabelled inulin and comparing autoradiograph grain density inside and outside cells after incubation. All the carcinomas studied showed extensive uptake of inulin within 5 min, while normal, adenomatous and colitic epithelial cells completely excluded inulin for 30 min. We found no difference in the proportion of epithelial cells incorporating uridine into RNA in carcinomatous and normal mucosa, and this suggests that the increased inulin permeability of carcinoma cell membranes was not due to leakage into non-viable cells. Experiments with cytochalasin B also showed that increased pinocytosis by carcinoma cells could not account for the difference. The relative impermeability of adenomatous and colitic cells suggests that increased permeability is not caused by increased proliferation. The consistent finding of increased permeability in the plasma membranes of carcinoma cells suggests that this may be more than an epiphenomenon of malignancy. It also suggests that measurement of cell permeability may have a role in distinguishing malignant from benign epithelial neoplasms.

Adenoma↗
PubMed1985

Monoclonal antibodies to osteoclastomas (giant cell bone tumors): definition of osteoclast-specific cellular antigens.

The cellular origin of the osteoclast, the major agent of bone resorption, remains controversial despite the demonstration that osteoclasts form by fusion of mononuclear cells that are ultimately derived from a bone marrow stem cell. One view is that they are the terminally differentiated progeny of mononuclear phagocytic cells. However, we have previously provided evidence, from functional and phenotypic studies of rodent and human osteoclasts, that raises the possibility that osteoclasts form a separate cell lineage from conventional hemopoietic cells and macrophages in particular. In an attempt to elucidate this question, we have used monoclonal antibody techniques to examine the relationship between osteoclasts and other bone marrow-derived cells. By using osteoclasts from osteoclastomas (giant cell tumors of bone) for immunizations, we have produced 11 mouse hybridomas secreting monoclonal antibodies reacting with osteoclasts in normal human fetal bone and a variety of neoplastic and non-neoplastic bone lesions. Eight antibodies in 4 reactivity sets have been shown to recognize membrane antigens, whereas a further 3 react with cytoplasmic determinants. In 7 there is no cross-reactivity with macrophages in a wide range of tissues, thus effectively differentiating between these two cell types. These antibodies will prove useful for the identification of osteoclasts in tissues and in the separation of their circulating precursors, thus allowing an experimental approach to be made to many of the outstanding questions regarding the developmental pathobiology of the osteoclast.

Antibodies, Monoclonal↗
PubMed1984

Cell surface characterization of the human osteoclast: phenotypic relationship to other bone marrow-derived cell types.

Among the differentiated progeny of stem cells transplantable by bone marrow are osteoclasts, the multinucleate cells which are the major agents of bone resorption. Although the osteoclast is well characterized from a structural and functional standpoint, its development and origin are still far from clear. We have used monoclonal antibodies to investigate the interrelationship between osteoclasts and other haemopoietic cells in man. We have analysed the distribution of 19 granulocyte-monocyte antigens in eight reactivity clusters on the non-neoplastic osteoclasts present within nine osteoclastomas (syn. giant cell tumours of bone) and a single example of aneurysmal bone cyst. We found that osteoclasts are antigenically effete, failing to express granulocyte-monocyte, common leucocyte or other haemopoietic determinants; the only monocyte antigens detected on osteoclasts are My-7 and two closely related specificities, MCS.2 and DüHL60.4, which are also expressed by tissues outside the haemopoietic system. Our findings, taken together with recent transplantation studies, cast further doubt on the view that osteoclasts are specialized bone-resorbing macrophage-derived giant cells, and support a hypothesis that they are the end product of fusion of a hitherto unidentified circulating mononuclear cell type, the preosteoclast, which constitutes a cell lineage separate from those originating from the conventional multipotential haemopoietic stem cell, although still of bone marrow origin.

Antibodies, Monoclonal↗