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Biomedical subjects

E R Schwartz

Publications and source records attributed to E R Schwartz.

At least 19 recordsLinked to original sources
PubMed1995

Human osteoblasts in culture metabolize both 1 alpha, 25-dihydroxyvitamin D3 and its precursor 25-hydroxyvitamin D3 into their respective lactones.

1 alpha, 25-Dihydroxyvitamin D3 [1 alpha, 25-(OH)2D3], the hormonal form of vitamin D3, is further metabolized in the kidney and intestine through the carbon 24 (C-24) oxidation pathway initiated by C-24 hydroxylation, and the carbon 23 (C-23) oxidation pathway initiated by C-23 hydroxylation. The C-24 oxidation pathway leading to the formation of calcitroic acid has been previously reported to be present in bone cells, but the C-23 oxidation pathway leading to the formation of 1 alpha, 25-(OH)2D3-26,23-lactone has not been described in bone cells, even though 1 alpha, 25-(OH)2D3-26,23-lactone is noted to have a significant effect on bone formation. Therefore, in the present study, we investigated the production of 1 alpha, 25-(OH)2D3-26,23-lactone in normal human osteoblasts, and our studies revealed that human osteoblasts possess the activity of both 24- and 23-hydroxylases constitutively. Thus, 1 alpha, 24(R),25-(OH)3D3, 1 alpha, 25-(OH)2-24-oxo-D3, 1 alpha, 23(S), 25-(OH)3-24-oxo-D3, 1 alpha, 23-(OH)2-24,25,26,27-tetranor D3, and calcitroic acid formed through the C-24 oxidation pathway and 1 alpha, 23(S),25-(OH)3D3 and 1 alpha, 25-(OH)2D3-26,23-lactone formed through the C-23 oxidation pathway were detected under basal conditions. Also, the synthesis of these metabolites was increased significantly when the cells were treated with 1 alpha, 25-(OH)2D3 (50 nM) for 24 h before incubation with the tracer. As 25-hydroxyvitamin D3 (25OHD3) follows similar side-chain modifications as 1 alpha, 25-(OH)2D3, the metabolism of 25OHD3 in normal human osteoblasts was studied under basal conditions. We found that 25OHD3 was also metabolized through both C-24 and C-23 oxidation pathways, resulting in significant synthesis of 24(R),25-(OH)2D3 along with 25OH-24-oxo-D3, 23(S),25-(OH)2-24-oxo-D3, 23(S),25-(OH)2D3, and 25OHD3-26,23-lactone. Under the same experimental conditions, we looked for 1 alpha, 25-(OH)2D3 synthesis, as earlier studies have shown production of 1 alpha, 25-(OH)2D3 in human bone cells. During a time-course study ranging from 1-24 h, we found that by 2 h, the 24(R), 25-(OH)2D3 concentration rose and accumulated considerably during the following 24 h, but 1 alpha, 25-(OH)2D3 did not accumulate at any time. However, other 1-hydroxylated metabolites, 1 alpha, 23(S),25-(OH)3D3, 1 alpha, 23(S),25-(OH)3-24-oxo-D3, as well as 1 alpha, 25-(OH)2D3-26,23-lactone were detected.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcifediol↗
PubMed1991

Osteoarthritis.

Explore the source record for details and available documents.

Animals↗
PubMed1987

Animal models: a means to study the pathogenesis of osteoarthritis.

A number of animal models have been developed to investigate the pathogenesis of osteoarthritis. In general, rabbits, guinea pigs, and dogs have been the animals of choice, although rats, mice, and birds have also been used. The techniques used to induce disease development include: destabilization of a knee joint either by extra- or intraarticular surgical manipulation; immobilization of the knee joint to alter load impact and distribution; or introduction of a foreign substance into the joint space. The success of a particular animal model rests in the ability to parallel, on a temporal basis, the biological changes which characterize osteoarthritic development as seen in the human population. Macroscopic, microscopic, and biochemical evaluations then permit the detailing of the steps which lead to cartilage erosion. In this manner, link proteins have been found to be deficient in osteoarthritic guinea pig cartilage.

Animals↗
PubMed1986

The phosphorylation of human link proteins.

Three link proteins of 48,44 and 40 kDa were purified from human articular cartilage and identified with monoclonal anti-link protein antibody 8-A-4. Two sets of lower molecular weight proteins of 30-31 kDa and 24-26 kDa also contained link protein epitopes recognized by the monoclonal antibody and were most likely degradative products of the intact link proteins. The link proteins of 48 and 40 kDa were identified as phosphoproteins while the 44 kDa link protein did not contain 32P. The phosphorylated 48 and 40 kDa link proteins contained approximately 2 moles PO4/mole link protein.

Aged↗
PubMed1986

Monensin stimulation of arylsulfatase B activity in human chondrocytes.

Secreted and intracellular arylsulfatase B (ASB) activities were measured in normal and osteoarthritic (OA) human chondrocyte cultures in the absence and presence of monensin, ammonium chloride, and chloroquine. Of the three agents added, only monensin produced a significant stimulation of secreted enzyme activity. Osteoarthritic cells consistently exhibited a three-fold higher level of secreted specific ASB activity than did normal cells, with or without monensin. When compared with normal cells, OA cells also consistently exhibited a twofold heightened intracellular specific enzyme activity both in the absence or presence of monensin. With increasing dosage of monensin, secreted and intracellular ASB activity increased for both OA and normal cells. Total enzyme activity of secreted and intracellular ASB was found to be cell density dependent. No inhibition of secreted or intracellular ASB activity was observed for sparsely plated cultures. In contrast to sparse cultures, an inhibition of secreted ASB, with or without monensin, was observed in densely plated cultures. Intracellular total activity was not inhibited by high-density cultures. Secreted ASB activity was found to be time-dependent after passage. Enzyme activity was maximal at 6 h in both OA and normal cells and decreased by the end of 24 h both in serum-free medium and in serum-free medium with monensin. When compared with normal cells, OA cells expressed higher levels of ASB activity under all test conditions. This heightened activity therefore appears to be a property inherent in the OA chondrocyte.

Aged↗
PubMed1985

Phosphorylation of proteoglycans. Identification of phosphorylation sites in chondroitin sulfate-rich region of core protein.

Serine residues, which are the sites of phosphorylation in proteoglycans, were demonstrated to be located on chondroitin sulfate-containing peptides. These peptides appeared to be derived primarily from the chondroitin sulfate-rich region of the proteoglycan core protein. The localization of phosphate moieties in the chondroitin sulfate-containing peptides was observed in all experiments. The phosphate moieties were retained on chondroitin sulfate-containing peptides after the protein core was treated with either papain or trypsin. Two phosphopeptide preparations, derived from chondroitin sulfate-containing peptides of proteoglycan subunits, were extensively purified. These 2 phosphopeptide preparations were shown by carbohydrate analysis to be free of keratan sulfate-containing peptides or peptides from the hyaluronic acid binding region of the core protein. One of the phosphopeptide preparations had a phosphate: serine molar ratio of 0.40. This indicated that nearly one-half of the serine residues were phosphorylated rather than glycosylated. Peptides derived from the core protein that contained keratan sulfate had no phosphate moieties.

Cartilage, Articular↗
PubMed1985

Characterization of human bone cells in culture.

Cultures of human bone cells were established, maintained, and characterized with respect to several metabolic parameters. These studies were undertaken with a view to using the bone culture system as a means of studying mechanisms of bone metabolism. The donor patients' ages ranged from 1 to 90 years and their disease states included congenital limb anomalies, exostosis, and osteo- and rheumatoid arthritis. Cultures were maintained up to 5 months. The osteoblast-like character of these cells was confirmed with the use of measurements applied to bone cells from other systems. Analyses showed that (a) the cells' appearance resembled that of cultured osteoblasts from other animal sources, b) intracellular cAMP was stimulated by human parathyroid hormone, c) osteocalcin was detected in the medium of all tested bone cell cultures and its production was found to be stimulated by 1,25-dihydroxycholecalciferol, and d) newly synthesized collagen was almost exclusively type I. In contrast, cultures of human fibroblasts, established in one instance from tissue specimens of the same donor patient, grew faster, reached a higher limiting density, and produced a greater proportion of type III collagen than the corresponding bone cells. Furthermore, fibroblasts did not accumulate osteocalcin in their culture medium. The conditions described in this report to maintain human bone cells in culture should provide a suitable test system to study the regulation of human bone metabolism.

Bone and Bones↗
PubMed1985

The pediatrician's approach to the preschool child with language delay.

A systematic approach to the child with suspected language disorder includes screening of expressive language, receptive language, general development, and hearing. Various screening approaches and tools are discussed. Diagnostic categories and associated referral patterns are recommended.

Child, Preschool↗
PubMed1984

Phosphorylation of proteoglycans from human articular cartilage.

Previous studies have shown that sulfated proteoglycans from human articular and epiphyseal cartilage were phosphorylated. These macromolecules contribute to the stiffness and resiliency of this tissue. We demonstrate here that the phosphate moieties are an integral part of proteoglycan subunits. Specifically, evidence is presented which indicates that proteoglycan monomers contain 3 to 4 phosphate moieties per core protein and that these appear to exist as phosphoserine residues. Furthermore, the data illustrate that human articular cartilage also contains more than 20 different phosphoproteins, some of which are closely associated with proteoglycan aggregates. Proteoglycan subunits were purified from extracts of articular cartilage or from media fractions which had been used to label tissue specimens with 32P-orthophosphate. Chemical and radiographic analyses revealed that the phosphate concentration with respect to sulfate and uronic acid content remained constant when purified proteoglycan monomers were subjected to equilibrium ultracentrifugation and size-exclusion chromatography. That the phosphate moieties were bound to proteoglycan monomers via monoester linkages was indicated by the release of 32P-orthophosphate from proteoglycan subunits incubated under mild alkaline conditions or reacted with acid or alkaline phosphatases. Identification of serine residues in the core protein as the sites of phosphorylation was made by autoradiography of thin layer plates on which hydrolyzed samples of purified 32P-proteoglycan subunits had been subjected to 2-dimensional electrophoresis/chromatography. Quantification of 3 to 4 phosphate moieties per core protein of 200,000 daltons was made by chemical analysis of inorganic phosphate released from proteoglycans by acid hydrolysis.

Adult↗
PubMed1984

Phosphorylation of proteoglycans from human articular cartilage by a cAMP-dependent protein kinase.

Purified proteoglycan subunits from human articular, bovine articular and nasal cartilages, and a rat chondrosarcoma were phosphorylated in vitro by beef heart cAMP-dependent protein kinase in the presence of gamma 32P-ATP. In these experiments, a maximum of 1.7 moles of 32P were incorporated per mole of proteoglycan from human cartilage. Phosphorylation was dependent on the presence of cAMP. Analysis by autoradiography revealed that serine residues in the core protein of the proteoglycan were the sites of phosphorylation. Treatment of proteoglycan subunits with chondroitinase ABC and alkaline phosphatase prior to reaction with cAMP-dependent protein kinase increased the incorporation of 32P by 12-30% when compared with untreated proteoglycans. These data indicate that proteoglycans in cartilage can be phosphorylated by cAMP-dependent protein kinase.

Animals↗
PubMed1982

Characteristics of human chondrocyte cultures in completely defined medium.

Chondrocytes derived from normal human adult articular cartilage were established and maintained for over 5 months in a completely defined medium without the addition of serum or any other growth factors. At the end of 5 months, these cells were still metabolically active. The cells incorporated [3H] thymidine into DNA, incorporated [35S] sulfate into proteoglycans, and exhibited lysosomal enzyme activities. The 35S-labeled proteoglycans isolated from the culture medium had elution profiles on high pressure liquid chromatography (HPLC) similar to those observed for proteoglycans from other mammalian sources. This self-contained growth competence may reflect a need produced by the unusual avascular and alymphatic character of articular cartilage.

Adult↗
PubMed1982

Effect of ascorbate on lysosomal enzyme activities in guinea pig cartilage and adrenals.

The effect of ascorbic acid on adrenal and cartilage lysosomal enzyme activity was evaluated in guinea pigs maintained on either 2.4 mg, or 150 mg of ascorbate per day. When compared to adrenal enzyme activities in animals on high dietary levels of ascorbate, the adrenals of animals on 2.4 mg of ascorbate per day expressed 50% increase in the activities of acid phosphatase, arylsulfatase A, and arylsulfatase B (p less than 0.02). In cartilage, the activity of acid phosphatase was significantly elevated in animals on low dietary levels of ascorbate (p less than 0.01), but arylsulfatase A and arylsulfatase B activities were not affected by varying the dietary intake of ascorbate. These data indicate an inverse relationship between tissue vitamin C concentrations and lysosomal enzyme activities.

Acid Phosphatase↗
PubMed1981

Experimentally induced osteoarthritis in guinea pigs: metabolic responses in articular cartilage to developing pathology.

Developing osteoarthritis, surgically induced in the right hind knee joint of guinea pigs by different procedures (A or B), was studied in animals maintained on either minimal or supplemented levels of dietary vitamin C. Procedure A, consisting of transecting the anterior cruciate and major portion of the medial collateral ligaments, resulted in a slower developing and less severe form of the disease than procedure B which also included a partial menisectomy. Regardless of the surgical procedure used, animals on minimal levels of ascorbate always exhibited more severe pathology than those on high levels. When compared with controls, a significant enhancement of acid phosphatase characterized arthritic cartilage in both supplemented and minimal diet groups, although the increase was 2-fold greater in the latter. In addition, a significant elevation of arylsulfatase A and B activities was observed only in the minimal diet group. Early stages of pathology in both diet groups were characterized by formation of repair cartilage which stained strongly with Safranin O on histologic sections. As the disease progressed, pitting, ulcerations, and eburnation occurred in the minimal diet group. Cartilage weight in normal joints was greater for guinea pigs kept on high levels of vitamin C. It is likely that this stimulated synthesis of cartilage in the supplemented animals protected against the erosion of the articular cartilage which characterized the more severe disease process in the guinea pigs on minimal levels of ascorbate.

Animals↗
PubMed1981

Proteoglycan structure and metabolism in normal and osteoarthritic cartilage of guinea pigs.

Sulfated proteoglycan structure and metabolism in osteoarthritic articular cartilage from the hind-limb joints of guinea pigs in which the disease had been surgically induced were evaluated and compared with those from nonoperated or sham-operated controls. In these studies, conducted on animals receiving high and low dietary levels of ascorbic acid, the effect of vitamin C on these variables was also examined. Sulfated proteoglycan biosynthesis per unit of DNA as reflected by in vivo uptake of 35S-sulfate was stimulated both by arthritic development and high dietary vitamin C. Under these conditions, the specific activities, 35S-cpm/micrograms uronic acid, of the proteoglycans were elevated. Neither arthritic development nor variation in dietary levels of vitamin C altered the structure of the proteoglycans. Two species of proteoglycans that exhibited the same electrophoretic mobilities in agarose/acrylamide gels, the same elution profiles on high performance liquid chromatography,, and the same galactosamine/glucosamine ratios were found in all normal and osteoarthritic cartilage specimens tested. The specific activities of these two specimens tested. The specific activities of these two species were dissimilar. In all samples, the larger of the two species had a higher specific activity.

Animals↗
PubMed1981

Experimentally-induced osteoarthritis in guinea pigs: effect of surgical procedure and dietary intake of vitamin C.

The effect of variation in dietary ascorbic acid on surgically induced osteoarthritis was examined in the stifle joints of guniea pigs. Two different surgical procedures were used to induce osteoarthritis in the right stifle joint of these animals. Guinea pigs were maintained either on a high (150 mg/day) or low (2.4 mg/day) dietary intake of vitamin C. Regardless of the surgical procedure used to induce osteoarthritis, the animals maintained on the high level of vitamin C consistently showed severe joint damage than animals on the low level of the vitamin.

Animals↗