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Biomedical subjects

L L Key

Publications and source records attributed to L L Key.

At least 37 records · Page 2Linked to original sources
PubMed1995

Characterization of M-CSF and its receptor in microphthalmic mice.

The macrophage colony-stimulating factor (M-CSF) gene expression in osteopetrotic mice (op/op) is defective due to a point-mutation in the M-CSF gene [1]. However, almost all osteopetrotic patients have been shown to have a normal or elevated circulating level of bioactive M-CSF [2]. To investigate the action of the M-CSF in mi/mi mice (microphthalmic; another osteopetrotic mouse mutant), M-CSF levels and its receptors were studied. We found that serum levels of M-CSF in mi/mi mice were not significantly different from normal control mice. The M-CSF receptor binding affinity of spleen-adherent cells was similar to that of control mice. In spleen cells from mi/mi mice, the receptor binding sites per cell (normalized to total spleen cells, M-CSF receptor positive cells, or M-CSF receptor RNA positive cells) were present in a greater number than in spleen cells from phenotypically normal siblings. Northern blot analysis showed that there is no significant difference in transcripts of the M-CSF receptor (c-fms) in the mi/mi and phenotypically normal mice. Unlike the op/op mutant, M-CSF levels, as well as the affinity and number of M-CSF receptors, do not explain the defect in osteoclastic function in the mi/mi mutation.

Animals↗
PubMed1994

Calcium needs of adolescents.

Adolescents grow at the greatest rate of any age group after infancy and accumulate 37% of their total bone mass during this growth spurt. Because maximum bone mass is acquired during adolescence, the calcium deposited during adolescence determines the risk of osteoporosis and fracture in adulthood. Bone mass is dependent on calcium intake, growth and pubertal development, exercise, and genetic and racial factors. Unfortunately, during this time of tremendous calcium need, most adolescents eat a diet that is very deficient in calcium. Girls are twice as likely to be deficient as boys (85% vs 43%). Other factors contributing to poor bone mineralization include adolescent pregnancy, anorexia nervosa, excessive exercise, and various chronic medical conditions. To avoid osteoporosis in later life, adequate dietary calcium intake should be recommended and calcium supplementation considered in all adolescent patients.

Adolescent↗
PubMed1993

Combination macrophage-colony stimulating factor and interferon-gamma administration ameliorates the osteopetrotic condition in microphthalmic (mi/mi) mice.

Malignant osteopetrosis is a fatal congenital bone disorder characterized by defective osteoclastic function. Death frequently occurs within the first decade of life. The precise molecular defect(s) that causes osteopetrosis is not known. The possibility that osteoclasts, like macrophages, are controlled by interactions with cytokines suggests that these agents may provide a means of increasing osteoclastic function. Macrophage-colony stimulating factor (M-CSF), a cytokine known to enhance macrophage and osteoclast generation, and recombinant human interferon-gamma (rIFN), a cytokine known to stimulate superoxide generation by white cells, were administered to microphthalmic (mi/mi) mice in an attempt to improve the osteopetrotic condition. Each cytokine was administered separately and in combination to neonatal mi/mi mice for 7 consecutive d. Bone turnover, osteoclast numbers, superoxide generation by white cells, and hematocrit were assessed. rIFN, M-CSF, and a combination of the cytokines stimulates oxygen-derived free radical production by white cells and increased bone resorption. rIFN resulted in a reduction in the number of osteoclasts. This reduction in number was ameliorated by M-CSF. M-CSF alone and in combination with rIFN resulted in improved hematopoietic function, increased weight gain, and increased physical activity of the affected mutants.

Animals↗
PubMed1993

Osteopetrosis. The pharmaco-physiologic basis of therapy.

Medical treatments of osteopetrosis have attempted to improve hematologic function, reduce the osteosclerotic condition, and/or improve immune function. Prednisone therapy has improved hematologic function in some patients, but has not resulted in a reduction in bone mass. Calcium deficient diets have limited further sclerosis in some patients. High-dose calcitriol and parathormone infusions have stimulated osteoclastic activity. In some patients, high-dose calcitriol has resulted in clinical improvement. Newer treatments, such as interferon gamma and macrophage colony stimulating factor, may alter the osteoclastic and immune defects by stimulating cellular formation and function. These therapies, alone or in combination, ameliorate but do not cure the osteopetrotic condition.

Adjuvants, Immunologic↗
PubMed1992

Nitroblue tetrazolium reduction and bone resorption by osteoclasts in vitro inhibited by a manganese-based superoxide dismutase mimic.

Oxygen-derived free radicals are produced by osteoclasts. Oxygen radical formation occurs at the osteoclast/bone surface interface. This location next to bone implies that oxygen radicals, including but not limited to superoxide, are needed for bone resorption. Compounds that scavenge superoxide are being developed as pharmaceutical agents to inhibit the damaging effects of oxygen radical formation on tissues. One such scavenger is the Desferal-manganese complex (DMnC). DMnC reduced the amount of formazan staining produced by the interaction of oxygen radicals with nitroblue tetrazolium (NBT) in both individual mouse calvarial osteoclasts in tissue explants and isolated osteoclasts. As a result of the reduced concentrations of oxygen radicals, DMnC inhibited bone resorption by calvarial explants and isolated osteoclasts. Superoxide dismutase (SOD) inhibited NBT reduction and bone resorption by isolated osteoclasts but to a lesser degree than DMnC. Inhibition of bone resorption in the isolated osteoclast system increased in parallel to the concentration of DMnC in cultures. Desferal without Mn had no effect on bone resorption by isolated osteoclasts. These results support the hypothesis that osteoclasts produce oxygen radicals as part of the process of bone resorption.

Analysis of Variance↗
PubMed1992

Recombinant human interferon gamma therapy for osteopetrosis.

A defect in leukocytic superoxide formation has been demonstrated in patients with congenital osteopetrosis. This leukocyte defect appears to be related to defective bone resorption. Because recombinant human interferon gamma therapy enhances superoxide production in patients with chronic granulomatous disease, we sought to determine whether a similar strategy could reverse the osteopetrotic condition. Interferon gamma, 1.5 micrograms/kg three times a week, was administered by subcutaneous injection for 6 months to eight patients with osteopetrosis. Urinary hydroxyproline and urinary calcium excretion increased markedly during therapy in parallel with a significant decrease in trabecular bone volume. Bone marrow scans demonstrated increased bone marrow production. The hemoglobin concentration, platelet count, and leukocyte production of superoxide increased significantly. No serious infections were encountered during the therapy. These data suggest that interferon gamma administration enhances bone resorption and leukocyte function in patients with osteopetrosis.

Bone Marrow↗
PubMed1992

Autosomal recessive osteopetrosis: bone marrow imaging.

Technetium-99m sulfur colloid scintigraphy was performed prospectively in 12 infants and children with autosomal recessive osteopetrosis, to correlate the appearance of bone marrow stores with advancing age. Baseline images were obtained in all patients, and one to five follow-up images were obtained in eight patients after they began therapy with calcitriol, interferon-gamma, or both. Conventional radiography was performed along with the nuclear studies in all cases. Magnetic resonance (MR) images of the head or lower extremities were also obtained in six patients and were correlated with the scintigraphic findings. Patterns of abnormal distribution of bone marrow appeared to be age-dependent. In patients younger than 1 year, marrow stores were primarily in the skull base and at the ends of the long bones. In patients aged 3-5 years, marrow stores shifted to the diaphyseal regions of long bones and to the calvarium. In the appendicular skeleton, areas of greatest bone marrow activity corresponded to regions of relative decreased opacity on radiographs and areas of intermediate or high signal intensity on T2-weighted MR images. The skull base showed appreciable marrow activity in spite of densely sclerotic bone on radiographs.

Bone Marrow↗
PubMed1992

Cranial imaging in autosomal recessive osteopetrosis. Part I. Facial bones and calvarium.

Cranial imaging studies (radiographs, computed tomographic [CT] scans, magnetic resonance [MR] images, and bone marrow scintigrams) in 13 infants and children with autosomally recessive osteopetrosis were reviewed to characterize patterns of facial and calvarial involvement at presentation and with progression of disease. In the mandible, a characteristic triangular opacity representing calcification within the secondary condylar cartilage ossification center was seen in 10 of the 13 patients. Defective dentition with incomplete enamel formation and/or caries was encountered in all patients. The paranasal sinuses were poorly pneumatized in all patients, but the ethmoid sinuses tended to be the least severely affected. Hypertelorism was present in five of the 13 patients, with a characteristic "space-alien" appearance on frontal radiographs. In younger patients, the calvarium demonstrated a high-attenuation inner table, a broad, low-attenuation diploic space, and a less high-attenuation outer table at CT. In three older children, a "hair-on-end" appearance was seen, which, at bone marrow scintigraphy, corresponded to areas of marked hematopoietic activity. Regions of sclerotic bone demonstrated low signal intensity on both T1- and T2-weighted MR images; areas containing marrow had intermediate signal intensity. These many new radiologic features of osteopetrosis are related to its pathophysiologic characteristics.

Child↗
PubMed1992

Cranial imaging in autosomal recessive osteopetrosis. Part II. Skull base and brain.

The authors reviewed cranial imaging studies (radiographs, computed tomographic scans, and magnetic resonance [MR] images) in 13 infants and children with the autosomal recessive form of osteopetrosis to characterize patterns of skull base, brain, and cranial nerve involvement at presentation and with progression of disease. Marked sclerosis and deposition of osteopetrotic bone was noted along the anterior (but not posterior) occipitomastoid suture (n = 8), at the basioccipital-exoccipital synchondrosis (n = 9), and along the sphenooccipital synchondrosis (n = 8). Endobones, presumably representing unresorbed primitive ossification centers, were seen in the sphenoidal body and basioccipital bone in 11 of the 13 patients. Marked cupping at the basioccipital-exoccipital synchondrosis was observed in three. Neurologic deficits included blindness (n = 11), conductive hearing loss (n = 11), and facial nerve palsies (n = 4). Delayed myelination was seen with MR imaging in two of five retarded infants, including one with a documented coexisting neuronal storage defect. Prominent extracerebral cerebrospinal fluid spaces were present over the frontal lobes in five of the eight developmentally normal patients, representing either subclinical parenchymal disease or a phenomenon related to discordant growth rates between skull and brain.

Brain↗
PubMed1992

Six-year follow-up of a case of radiation injury following treatment for medulloblastoma.

Recent reports in the literature have documented long-term sequelae of radiation treatment in children, the most notable of which are diminished endocrine functioning and decline in intellectual ability. A case is presented in which both these long-term effects were seen 7 years after radiation treatment for medulloblastoma. Growth hormone and thyroid hormone deficiencies were identified and treated. Full-Scale IQ dropped from the 79th percentile to the 3rd percentile, and neuropsychological functioning ranged from normal to impaired. However, magnetic resonance imaging reveals few direct imaging correlates of J.M.'s neuropsychological deficits. If identified, hormone deficiencies in such patients can be successfully treated; intellectual deficits may present more of a management problem. In this case, cognitive deficits have contributed to considerable difficulty in school; however, with special classes and modifications, the patient is making progress. Our findings indicate that the long-term outcome for children with radiation injury may be improved significantly with hormone therapy and appropriate academic intervention, and argue strongly for systematic, sequential follow-up of such children so that appropriate intervention can be implemented and continued as necessary.

Body Height↗
PubMed1992

Osteoclastic superoxide generation: taking control of bone resorption using modulators of superoxide concentrations.

We have examined the role of superoxide in bone resorption by stimulating defective superoxide production and bone resorption in patients with osteopetrosis and inhibiting superoxide production and bone resorption in murine calvarial explants. Interferon gamma treatment did stimulate superoxide generation and bone resorption in patients with osteopetrosis as evidenced by a reduction in bone volume and an increase in biochemical markers of bone resorption. Further, lowering the superoxide concentrations within calvarial osteoclasts using a scavenger, desferal manganese, decreased bone resorption. We conclude that superoxide generation by osteoclasts is necessary for normal osteoclastic function.

Animals↗
PubMed1992

Circulating macrophage colony-stimulating factor is not reduced in malignant osteopetrosis.

Malignant osteopetrosis is a disorder characterized by a deficiency in osteoclast number or function. In one animal model of osteopetrosis, the op/op mouse, macrophage colony-stimulating factor (M-CSF) is absent, and the administration of M-CSF corrects the defects. We evaluated the serum of 13 patients with malignant osteopetrosis by an M-CSF radioimmunoassay to determine if a quantitative M-CSF deficiency existed in these patients. All patients had M-CSF present in levels equal to or higher than control serum. In addition, serum from 6 osteopetrotic patients was tested in a bioassay to determine if the M-CSF present is biologically active, and in all cases there was demonstrable activity in these samples. We provide evidence that deficiency of circulating M-CSF is unlikely to be a major contributor to the etiologic basis for the majority of children with malignant osteopetrosis.

Child, Preschool↗
PubMed1990

The vitamin K-dependent carboxylation system in human osteosarcoma U2-OS cells. Antidotal effect of vitamin K1 and a novel mechanism for the action of warfarin.

An osteoblast-like human osteosarcoma cell line (U2-OS) has been shown to possess a vitamin K-dependent carboxylation system which is similar to the system in human HepG2 cells and in liver and lung from the rat. In an 'in vitro' system prepared from these cells, vitamin K1 was shown to overcome warfarin inhibition of gamma-carboxylation carried out by the vitamin K-dependent carboxylase. The data suggest that osteoblasts, the cells involved in synthesis of vitamin K-dependent proteins in bone, can use vitamin K1 as an antidote to warfarin poisoning if enough vitamin K1 can accumulate in the tissue. Five precursors of vitamin K-dependent proteins were identified in osteosarcoma and HepG2 cells respectively. In microsomes (microsomal fractions) from the osteosarcoma cells these precursors revealed apparent molecular masses of 85, 78, 56, 35 and 31 kDa. When osteosarcoma cells were cultured in the presence of warfarin, vitamin K-dependent 14C-labelling of the 78 kDa precursor was enhanced. Selective 14C-labelling of one precursor was also demonstrated in microsomes from HepG2 cells and from rat lung after warfarin treatment. In HepG2 cells this precursor was identified as the precursor of (clotting) Factor X. This unique 14C-labelling pattern of precursors of vitamin K-dependent proteins in microsomes from different cells and tissues reflects a new mechanism underlying the action of warfarin.

Antidotes↗
PubMed1990

Oxygen derived free radicals in osteoclasts: the specificity and location of the nitroblue tetrazolium reaction.

Oxygen derived free radicals are generated by osteoclasts. In a novel culture system, isolated rat osteoclasts were stained when nitroblue tetrazolium (NBT) was reduced by cellular oxidants to formazan, an insoluble precipitate. Superoxide dismutase (SOD) inhibited the accumulation of formazan by the isolated osteoclasts. Osteoclasts in mouse calvarial organ cultures also reduced NBT to formazan. The reaction products were localized to the area of the osteoclast-bone interface. At the light microscopic level, the formazan granules appeared to be concentrated within the cytoplasm. Formazan accumulation was significantly inhibited by calcitonin (hCT). The inhibition of NBT reduction by SOD indicates that the isolated osteoclasts were capable of producing superoxide. The localization of the formazan granules between the external osteoclastic membrane and the bone, and the inhibition of this reaction during hCT exposure suggests that oxygen derived free radicals may contribute to bone resorption.

Animals↗
PubMed1990

Pituitary gland: MR imaging of physiologic hypertrophy in adolescence.

The size and shape of pituitary glands in 169 children, adolescents, and young adults were analyzed with T1-weighted sagittal magnetic resonance (MR) images. In patients younger than 12 years old, no pituitary gland was found to be more than 6 mm in height. In adolescents, definite evidence for physiologic (pubertal) pituitary hypertrophy was seen in both sexes, although it was much more prominent in girls. The pituitary glands of four of 32 teenage girls measured 8-10 mm, but no teenage boy had a gland taller than 7 mm. Young adults aged 21-30 years had significantly (P less than .05) smaller glands than teenagers of the same sex. Significant (P = .0001) variations in the shape of the pituitary glands according to patient age and sex were also noted. Convex upper margins were seen in 56% of teenage girls, while this shape was noted in only 18% of the remaining patients of either sex. In eight of 32 teenage girls (25%) the pituitary glands were nearly spherical on sagittal images; this shape was not recorded in any other group. The normal maturation sequence of the pituitary gland apparently involves a period of physiologic hypertrophy in teenagers. This is manifest in girls by a significant change in both pituitary size and shape, while the glands of boys undergo a transformation in size only.

Adolescent↗