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K Fuller

Publications and source records attributed to K Fuller.

51 records · Page 3Linked to original sources
PubMed1987

Hormonal regulation of acid phosphatase release by osteoclasts disaggregated from neonatal rat bone.

Osteoclasts disaggregated from neonatal rat long bones and incubated on plastic or glass substrates were found to release a considerable proportion of tartrate-resistant acid phosphatase into culture supernatants. Enzyme release was detectable in the supernatant medium of cultures containing as few as ten cells after 1 hr of incubation and proceeded in a linear manner for the ensuing 6 hr. Calcitonin (1 pg/ml) and cytochalasin B (5 micrograms/ml) inhibited release into the supernatant, suggesting that release represents enzyme secretion. Prostaglandin E1 induced transient inhibition followed by recovery; parathyroid hormone and 1,25(OH)2 vitamin D3 were without influence. Acid phosphatase release in these cultures shows a pattern of hormone responsiveness that coincides with the effects of these hormones on bone resorption by isolated osteoclasts. The extent of acid phosphatase release and its regulation by calciotropic hormones imply a central role for acid hydrolase secretion in osteoclastic bone resorption. The experimental system described in this study may facilitate analysis of the pharmacological hormonal and cellular regulation of osteoclastic function.

Acid Phosphatase↗
PubMed1987

Generation of osteoclasts in cultures of rabbit bone marrow and spleen cells.

The primary and specific function of the osteoclast is the resorption of bone. We have applied this criterion, and a monoclonal antibody that binds specifically to osteoclasts, to cultures of tissues that may contain osteoclastic precursors. Bone marrow and spleen cells were incubated for up to 4 weeks in the presence or absence of parathyroid hormone, interleukin 1, or 1,25(OH)2 vitamin D3, on plastic coverslips or slices of devitalised bone. Osteoclasts (as judged by the presence of resorption cavities and the appearance of monoclonal antibody-positive cells) did not develop in cultures incubated without added hormones, nor in cultures containing parathyroid hormone or interleukin 1, but were regularly observed when bone marrow cells were incubated with 1,25(OH)2 vitamin D3. Although multinucleate giant cells were common after incubation, especially in the presence 1,25(OH)2 vitamin D3, monoclonal antibody bound not to these cells but to a minor and distinctive population of mononuclear cells and cells of low multinuclearity. We found no excavations and no monoclonal antibody-positive cells after incubation of peritoneal macrophages with 1,25(OH)2D3. These results provide direct evidence of osteoclastic function arising in cultures of haemopoietic tissues.

Animals↗
PubMed1987

Calcitonin gene-related peptide inhibits osteoclastic bone resorption: a comparative study.

Besides the calcitonin (CT) precursor, the calcitonin gene also encodes another peptide--calcitonin gene-related peptide (CGRP). We have previously reported that CGRP lowers plasma calcium in the rat. In the present study we have evaluated the effect of CGRP on resorption of bone by isolated rat osteoclasts and have compared these effects to those produced by calcitonins from three species (salmon, pig, and human calcitonins). There was a significant inhibition of bone resorption with rat calcitonin gene-related peptide (rCGRP) at a 1000-fold higher dose than that used for human CT. This effect well explains the CT-like effect of CGRP seen in the in vivo rat CT bioassay. Our results suggest that though CGRP may not be involved in the hormonal control of plasma calcium, the peptide may be an important local regulator of bone cell function.

Animals↗
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↗
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

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↗
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↗
PubMed1984

Resorption of bone by isolated rabbit osteoclasts.

A carborundum wheel was used to prepare slices of cortical bone that demonstrate a predictable surface appearance in the scanning electron microscope. Osteoclasts were mechanically disaggregated from neonatal rabbit long bones and settled onto these slices. After 24h in culture osteoclasts were associated with areas of excavation in the bone surface. These excavated areas typically showed a well-defined outline and a distinctive fibrillar base, which resembled the pattern of collagen fibrils in bone. The majority of such concavities were of approximately circular outline and of smaller diameter than the associated osteoclast, but other excavations were elongated or of complex morphology, and may have been produced by osteoclasts that were resorbing bone while they migrated. Irregular concavities tended to be more shallow but to occupy a greater area of the bone surface than circular concavities. Roughening of the bone surface without detectable excavation was also seen adjacent to osteoclasts. Calcitonin and cytochalasin B, which inhibit osteoclastic motility, also inhibited bone resorptive activity by these cells. The techniques described in this paper represent a model system with which to assess the direct and indirect effects of hormones, cells and substrate composition on the induction, stimulation and inhibition of osteoclastic bone resorption and to investigate the mechanisms by which cells degrade extracellular matrices.

Animals↗
PubMed1984

Effect of substrate composition on bone resorption by rabbit osteoclasts.

Slices of human femoral cortical bone were prepared with a carborundum wheel. Osteoclasts were isolated from neonatal rabbit long bones and incubated on either untreated, demineralized or anorganic preparations of these bone slices. Anorganic bone showed extensive tracts of uninterrupted surface excavation after incubation, while untreated bone tended to show discontinuous excavations of smaller total volume; demineralized bone was not resorbed. The endosteal surface of adult rat calvaria was also used as a substrate for osteoclastic bone resorption. The endosteal surface was exposed and rendered acellular, and was used either without further treatment or after incubation in collagenase. Bone resorption occurred only in those calvaria pre-treated with collagenase. These experiments imply that osteoclastic contact with bone mineral rather than the endosteal surface is the stimulus that initiates bone-resorptive behaviour in osteoclasts. The mechanism by which osteoblasts induce osteoclastic bone resorption may be through the known ability of osteoblasts to secrete collagenase, which, by digestion of the unmineralized lamina limitans of endosteal surfaces, exposes bone mineral to osteoclastic contact.

Animals↗
PubMed1984

Effect of parathyroid hormone and calcitonin on the cytoplasmic spreading of isolated osteoclasts.

Osteoclasts, the major agents of bone resorption, were isolated from neonatal rat bone, and the cytoplasmic spreading of these cells was measured after incubation in the presence or absence of hormones or other cell types. Salmon calcitonin, which inhibits osteoclastic bone resorption, reduced spreading in a dose-dependent manner and caused significant inhibition at concentrations as low as 6.7 pg/ml. Parathyroid hormone (PTH) had no effect on the spreading of isolated osteoclasts but if osteoblasts and osteoclasts were co-cultured the addition of PTH caused a marked increase in spreading at concentrations of 0.025 i.u./ml and above. The results suggest that while calcitonin is a direct inhibitor of osteoclastic activity, PTH may stimulate osteoclasts through a primary action on osteoblasts.

Animals↗
PubMed1984

The effect of prostaglandins I2, E1, E2 and dibutyryl cyclic AMP on the cytoplasmic spreading of rat osteoclasts.

We isolated osteoclasts from neonatal rat bone and assessed the effects of prostaglandins (PGs) I2, E1 and E2 on osteoclastic spreading. We found that although the PGs and dibutyryl cyclic AMP (DB-cAMP) acted as direct inhibitors of osteoclastic spreading, if osteoblasts and osteoclasts were co-cultured, the addition of PGs or DB-cAMP caused a considerable increase in spreading. This suggests that the PGs and DB-cAMP induce osteoblasts to stimulate osteoclasts. Osteoblasts are known to produce PGs, and thus possess the capacity to either inhibit (through PGs) or stimulate osteoclasts. Our results suggest that the balance between stimulation and inhibition of osteoclasts by osteoblasts may be determined by osteoblastic cyclic AMP levels.

Alprostadil↗
PubMedDate not supplied

Identification and characterization of the murine Rag1 promoter.

Rag1 and Rag2 are required for the somatic rearrangement of immunoglobulin genes and T-cell receptor genes and the subsequent development of B and T cells. We describe the pattern of DNase I hypersensitive sites surrounding the Rag1 gene that accompanies mouse B-cell development and show that one of these sites corresponds to the murine Rag1 promoter. Transcription initiates over a 30 bp region, with approximately 70% of the transcripts initiating within a 5 bp region. The promoter contains neither a consensus TATA box nor an initiator, but does contain an AT rich sequence that could serve as a non-consensus TATA box. The Rag1 promoter directs only negligible levels of expression in transient transfection assays, but when combined with a heterologous enhancer, it is capable of driving significant levels of expression in pre-B cells, pre-T cells, and mature B cells. Methylation interference and mutation analysis reveal that the Rag1 promoter contains binding sites for E-box binding proteins, NF-Y proteins, and Ikaros proteins. These findings are discussed with respect to B-cell development and regulation of differential Rag expression by the promoter in pre-B, pre-T, and CNS cells.

Animals↗