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L L Key

Publications and source records attributed to L L Key.

49 records · Page 3Linked to original sources
PubMed1989

Interleukin-2 stimulates osteoclastic activity: increased acid production and radioactive calcium release.

Recombinant human interleukin-2 (IL-2) was studied to determine effects on acid production by individual osteoclasts in situ on mouse calvarial bones. This analysis was performed using a microspectrofluorimetric technique to quantify acid production in individual cells. Radioactive calcium release was determined using calvarial bones in a standard tissue culture system. This allowed us to correlate changes in acid production with a measure of bone resorption. IL-2 stimulated acid production and bone resorbing activity. Both effects were inhibited by calcitonin. No stimulation of bone resorption occurred when IL-2-containing test media was incubated with a specific anti-IL-2 antibody and ultrafiltered. Our data demonstrated a correlation between acid production and bone resorbing activity in mouse calvaria exposed to parathyroid hormone (PTH). The data obtained from cultured mouse calvaria exposed to IL-2 demonstrated similar stimulatory effects to those seen during PTH exposure. These data suggest that calvaria exposed to IL-2 in vitro have increased osteoclastic acid production corresponding with increased bone resorption.

Acids↗
PubMed1988

Vitamin D and retinoblastoma. The presence of receptors and inhibition of growth in vitro.

The vitamin D receptor has been found in several human organs not involved in calcium metabolism and in several malignant neoplasms found in humans. The role of the receptor in these tissues is unclear. There is, however, a relationship between the presence and quantity of the vitamin D receptor in a malignant cell line and the antineoplastic effect of vitamin D on that cell line. We found that Y-79 retinoblastoma cells have receptors specific for calcitriol (1,25-dihydroxycholecalciferol). Scatchard analysis of the receptor data shows a quantity of 56,000 receptors per retinoblastoma cell. These receptors have a dissociation constant of 1.18 nmol/L. Retinoblastoma cells treated with 10(-9) mol/L of calcitriol for nine days had 15% less cell growth than the control cells. Further studies of the effect of vitamin D on retinoblastoma may warrant its inclusion in chemotherapeutic protocols for the treatment of this childhood affliction.

Calcitriol↗
PubMed1988

Variable osteoclast appearance in human infantile osteopetrosis.

A light and transmission electron microscopic (TEM) study of iliac crest metaphyseal bone from nine patients with infantile osteopetrosis demonstrates a variable spectrum of osteoclast abnormalities. All bone was obtained at biopsy before treatment. The average age at biopsy was 6 months with a range from 1 to 12 months. Osteoclast number was always increased and the cells were always appropriately positioned in relation to bone and cartilage. Osteoclast number, size, and nucleation varied from midly to markedly increased. In those with only a mild-to-moderate osteoclast increase, the marrow had an otherwise near-normal appearance with a good complement of hematopoietic cells. In those with markedly increased osteoclasts (hyperosteoclastic state) there were only scanty collections of hematopoietic cells. Light microscopic histomorphometry documented the percentage of bone and cartilage surfaces covered by osteoclasts. Controls from areas of greatest osteoclast presence documented a 5% coverage. One osteopetrotic patient registered a 4.8% value with all others elevated from 7.6 to 27.9%. Quantitative electron microscopy showed the ruffled border-clear zone complex to be absent or markedly diminished in seven of the nine patients. In two, however, osteoclast profiles had abundant ruffled border-clear zone complexes. Patients with the hyperosteoclastic bone marrow were more severely affected clinically. Light and TEM studies of marrow biopsies in initial assessment of osteopetrosis establish a baseline profile, may provide prognostic information, and allow for more meaningful treatment follow-up.

Child, Preschool↗
PubMed1988

A link between calcitriol and bone resorption.

Calcitriol exposure stimulated a human osteosarcoma cell line, U2-OS, to produce a factor(s) which stimulated bone degradation in human monocyte cultures and osteoclastic bone resorption in fetal rat long bone cultures. The factor(s) was elicited by as little as 10(-10) M calcitriol. The factor is effective in stimulating peripheral blood monocytes to degrade bone, suggesting a direct effect on cellular bone breakdown. The fetal long bone assays suggest that the osteoblast-like cells produce a factor(s) which stimulates osteoclasts. This is confirmed by the fact that human calcitonin added to the long bone cultures blocks the stimulation. The effect of PTH appears to be through the production of factors which stimulate osteoblasts. The present study suggests that a similar factor(s) may be responsible for the effect of calcitriol on bone resorption.

Bone Resorption↗
PubMed1986

Monocyte bone degradation: in vitro analysis of monocyte activity in patients with juvenile rheumatoid arthritis.

We examined the ability of the mononuclear phagocyte in vitro to degrade 45Ca-labeled bone particles to determine whether this assay allowed us to monitor disease activity in patients with juvenile rheumatoid arthritis. The monocytes from patients with juvenile rheumatoid arthritis receiving no anti-erosive therapy (n = 10) degraded significantly more bone than did cells obtained from normal controls (n = 10, P less than 0.001) or patients with juvenile rheumatoid arthritis receiving either gold thioglucose (n = 4, P less than 0.001) or D-penicillamine (n = 6, P less than 0.005). In two patients monitored for either 8 or 11 months, results of monocyte assays were found to parallel the clinical course. We conclude that in vitro monocyte bone degradation assays may provide a means of assessing joint activity in patients with juvenile rheumatoid arthritis. Further, this study and others indicate that mononuclear phagocytes are capable of causing erosive changes.

Adolescent↗
PubMed1986

In vitro degradation of bone particles by human monocytes is decreased with the depletion of the vitamin K-dependent bone protein from the matrix.

The bone vitamin K-dependent protein osteocalcin has been suggested to play a role in bone resorption. By administering sodium warfarin to rats, it is possible to inhibit the vitamin K-dependent addition of the their gamma-carboxyglutamic acid residues to osteocalcin. This results in reduced amounts of osteocalcin bone, probably because devoid of the calcium-binding Gla residues, the protein no longer accumulates in bone. Preparations of bone obtained from rats treated with sodium warfarin for 6 weeks contained only 0.2% of normal levels of osteocalcin and were 90% reduced in the concentration of Gla. This bone could not be degraded by human monocytes in vitro as well as control bone (only 54% of control; P less than 0.003). Defects in the movement of cells to the bone were documented by phase contrast microscopy. Only 60% as many monocytes attached to the osteocalcin-depleted bone as to control bone in an in vitro attachment assay. These effects do not appear to be related to direct cellular toxicity. The degradation of bone in this in vitro system appears to be dependent on the osteocalcin content in matrix. This may result from defective movement of cells to bone and/or attachment to the bone.

Animals↗
PubMed1983

Platelet-derived growth factor stimulates bone resorption by monocyte monolayers.

Resorption of devitalized bone particles by monocytes grown in culture was stimulated by platelet-derived growth factor (PDGF) in a dose-dependent manner. Bone resorption in response to PDGF was time-dependent with a significant increase over control cultures evident by 72 hours. These data are the first to demonstrate stimulation of bone resorption by PDGF in a specific cell type known to resorb bone in vivo and in vitro.

Bone Resorption↗
PubMedDate not supplied

Superoxide and bone resorption.

The reaction of superoxide with nitroblue tetrazolium produces an electron-dense diformazan precipitate which can be used to localize areas of superoxide production. Transmission electron microscopy was used to demonstrate that diformazan granules formed by the reaction of nitroblue tetrazolium with excess superoxide are electron dense, whereas monoformazan granules generated by hydrogen peroxide were not. On the basis of these observations, superoxide formed along the osteoclast-bone interface was localized by demonstrating the electron-dense diformazan granules between the osteoclastic membrane and the bone surface. The formation of this reaction product was inhibited by a superoxide scavenger, the deferoxamine mesylate-manganese complex (the "green" complex), confirming the specificity of the reaction product. The scavenger also inhibited bone resorption. High concentrations of superoxide generated in vitro at a neutral pH degraded osteocalcin into numerous peptide fragments, demonstrating the ability of superoxide to break peptide bonds. These studies localize superoxide production to the ruffled border space and suggest that superoxide generated at the osteoclast-bone interface is involved in bone matrix degradation.

Animals↗
PubMedDate not supplied

Cranial MR imaging of osteopetrosis.

BACKGROUND AND PURPOSE: The purpose of this study was to describe the cranial MR imaging manifestations of osteopetrosis. These features have not previously been reported in the literature. METHODS: Cranial MR studies, obtained with a uniform imaging protocol, were reviewed in 47 patients with osteopetrosis. Thirty-four patients had autosomal recessive (malignant) osteopetrosis (AROP), seven had intermediate osteopetrosis (IOP), and six had either type I or type II autosomal dominant osteopetrosis (ADOP I or II). The prevalence of abnormalities was tabulated and compared with the specific osteopetrosis variants. RESULTS: All patients with osteopetrosis had thickening and sclerosis of the calvaria. Ventriculomegaly, tonsillar herniation, proptosis, and dural venous sinus stenosis were observed in the majority of patients with AROP and ADOP I. Optic nerve sheath dilatation occurred in many of the patients with AROP and in all patients with ADOP I. Acquired cephaloceles were also observed only in these two groups. Optic nerve atrophy and optic canal stenosis were observed in a majority of patients with AROP, IOP, and ADOP II. Middle ear fluid was prevalent in AROP and IOP, present in over half the patients in each group. Features seen most prevalently, or exclusively, in AROP included stenosis of the internal carotid and vertebral arteries and extramedullary hematopoiesis. CONCLUSION: The cranial MR imaging features of osteopetrosis are both shared and unique among the various subtypes of the disease. The specific cranial and intracranial manifestations reflect the predominant calvarial or skull base patterns of bone thickening. The unique features seen in patients with AROP probably reflect the early age of onset and the greater severity of this form of the disease.

Adolescent↗