Biomedical subjects

D L Carnes

Publications and source records attributed to D L Carnes.

At least 55 records · Page 3Linked to original sources

PubMed1997

Cells with osteoblastic phenotypes can be explanted from human gingiva and periodontal ligament.

Considerable phenotypic heterogeneity has been reported in gingival fibroblasts. Similarly, cells from the periodontal ligament (PDL) can be isolated with different phenotypes. Although it has been suggested that cells from the gingiva do not contribute to the formation of hard tissue, it is theoretically possible that under appropriate stimuli, immature mesenchymal cells in gingiva could differentiate along an osteoblastic pathway. Differentiation of immature mesenchymal cells into osteoblasts following stimulation with osteoinductive factors has been demonstrated in muscle. We undertook experiments to establish whether cells with osteoblastic characteristics could be identified from human gingiva as well as from human periodontal ligament. Some cell populations from each of these tissues were found to have high basal alkaline phosphatase activity, to release osteocalcin in response to 1,25(OH)2 VitD3, and to form a mineralized matrix. Thus, cells can be isolated from the gingiva and PDL that exhibit phenotypic markers, which taken together are characteristic of osteoblastic cells. Other cell populations derived from the PDL and gingival connective tissue were isolated that had fibroblastic characteristics. These studies support the concept that gingival tissue can give rise to cells which may differentiate along either a fibroblastic or an osteoblastic pathway.

Adult↗

PubMed1996

Pro-inflammatory cytokines downregulate platelet derived growth factor-alpha receptor gene expression in human osteoblastic cells.

Platelet derived growth factor (PDGF) is thought to play a significant role in bone repair and regeneration. We previously demonstrated that PDGF-AA binding can be modulated by interleukin-1 (IL-1). We now report that TNF-alpha significantly reduces PDGF-AA binding by decreasing the number of PDGF-alpha receptor subunits on the surface of normal human osteoblastic cells. This inhibition is likely due to a decrease in synthesis of PDGF-alpha receptors since TNF-alpha causes a relatively rapid decrease in PDGF-alpha receptor mRNA levels as determined by Northern blot analysis. The physiologic importance of this inhibition is demonstrated by a TNF-alpha induced decrease in PDGF-AA stimulated tyrosine kinase activity. When saturating concentrations of TNF-alpha were used, the addition of IL-1 further inhibited PDGF-AA binding and further decreased surface expression of PDGF-alpha receptors. In contrast, other mediators such as IL-6, PTH, 1,25(OH)2 vit D3, hydrocortisone, PGE2, bFGF, and IGF-1 had no effect. These results suggest that binding to the PDGF-alpha receptor is decreased by the strong pro-inflammatory cytokines such as IL-1 beta and TNF-alpha rather than as a general response to mediators important in bone resorption or bone formation. TNF-alpha and IL-1 are often co-expressed during destructive inflammatory processes. Thus, TNF-alpha and IL-1 may work in concert to limit the response of osteoblastic cells to PDGF-AA during periods of osseous inflammation.

Cell Line↗

PubMed1996

Longitudinal sealing ability of mineral trioxide aggregate as a root-end filling material.

This study evaluated the ability of mineral trioxide aggregate (MTA) to seal the root end effectively. Seventy-six single-rooted, extracted human teeth were cleaned and shaped using a step-back technique. After root-end resection and ultrasonic preparation, 72 root sections were randomly allocated to three groups and filled with dental amalgam and cavity liner, Super-EBA, or MTA. Microleakage was assessed at 24 h, 72 h, 2 wk, 4 wk, 8 wk, and 12 wk, using a fluid filtration measurement system. MTA demonstrated excellent sealing ability throughout 12 wk of fluid immersion, comparable with that observed for Super-EBA. Microleakage in the MTA group, as well as the Super-EBA group, was significantly less (p < 0.05) than in the amalgam group at 24 h, 72 h, and 2 wk. At the subsequent periods, there were no significant differences among the three materials. In this study, MTA was determined to be superior to amalgam, and comparable with Super-EBA in preventing microleakage when used as a root-end filling.

Aluminum Compounds↗

PubMed1996

pH changes at the surface of root dentin when using root canal sealers containing calcium hydroxide.

The purpose of this study was to investigate long-term pH changes in cavities prepared in root surface dentin of extracted teeth after obturation of the root canal with gutta-percha and a variety of sealers containing calcium hydroxide. After cleaning and shaping, root canals in 50 recently extracted, human single-rooted teeth were divided into five groups. Each of four groups was obturated with gutta-percha and either Sealapex, Sealer 26, Apexit, or CRCS, all of which contain calcium hydroxide. The remaining group served as the control and was not obturated with gutta-percha or sealer. Cavities were prepared in the facial surface of the roots in the cervical and middle regions. The pH was measured in these dentinal cavities at the initiation of the experiment, and 3, 7, 14, 21, 28, 45, 60, 90, and 120 days after obturation. Results indicate that the pH at the surface of the root does not become alkaline when calcium hydroxide cements are used as root canal sealers. Regardless of the sealer used, the observed pattern of pH change was not different from that seen in the control group of roots that were not treated with sealer. It is concluded that calcium hydroxide-containing cements, although suitable for use as root canal sealants, do not produce an alkaline pH at the root surface. If such a pH change is related to treatment of root resorption, these sealants do not contribute to this treatment.

Bismuth↗

PubMed1996

Changes in pH at the dentin surface in roots obturated with calcium hydroxide pastes.

The purpose of this study was to determine the pH, after defined periods of time, in cavities prepared in the facial surface of the cervical, middle, and apical regions of roots obturated with calcium hydroxide pastes. Root canal instrumentation was performed on 40 recently extracted, single-rooted human teeth. Cavities 1.5 mm in diameter and 0.75 mm in depth were prepared in the cervical, middle, and apical regions of the facial surface of each root. Teeth were randomly divided into four groups. One group was left unobturated and served as a control. The three remaining groups were obturated with either aqueous calcium hydroxide, calcium hydroxide mixed with camphorated monochlorophenol. or Pulpdent pastes. Access cavities and apical foramina were closed with Cavit. Each tooth was stored individually in a vial containing unbuffered isotonic saline. pH at the surface was measured in the cervical, middle, and apical cavities at 0 and 3, 7, 14, 21, 28, 45, 60, 90, and 120 days. Results indicate that hydroxyl ions derived from calcium hydroxide pastes diffused through root dentin at all regions over the experimental period of 120 days. The pattern of pH change at the tooth surface was similar in all regions of the root, regardless of the type of calcium hydroxide paste used. This was a rapid rise in pH from a control value of pH 7.6, to greater than pH 9.5 by 3 days, followed by a small decline to pH 9.0 over the next 18 days, before finally rising and remaining at, or above pH 10.0 for the remainder of the experimental period. Pulpdent paste in the apical region was the only exception in this pattern, producing a pH rise nearly one full unit below the other pastes, pH 9.3. These results indicate that, for all pastes tested, a high pH is maintained at the root surface for at least 120 days.

Analysis of Variance↗

PubMed1996

Ability of commercial demineralized freeze-dried bone allograft to induce new bone formation.

Demineralized freeze-dried bone allograft (DFDBA) has been used extensively in periodontal therapy. The rationale for use of DFDBA includes the fact that proteins capable of inducing new bone; i.e., bone morphogenetic proteins, can be isolated from bone grafts. Commercial bone banks have provided DFDBA to the dental practitioner for many years; however, these organizations have not verified the osteoinductive capacity of their DFDBA preparations. The aim of this study was to determine the ability of commercial DFDBA preparations to induce new bone formation. DFDBA with particle sizes ranging from 200 to 500 microns was received from six bone banks using various bone production methods. Different lots of DFDBA from the same tissue bank were sometimes available. A total of 14 lots were examined. The surface area of bone particles in each sample was measured morphometrically and the pH of a solution containing the particles after suspension in distilled water determined. Samples from each DFDBA lot were implanted intramuscularly (10 mg) or subcutaneously (20 mg) into three different animals and tissue biopsies harvested after 4 weeks. One sample from each tissue bank was implanted and harvested after 8 weeks. At harvest, each area where DFDBA had been implanted was excised and examined by light microscopy. The ability of DFDBA to produce new bone was evaluated and the amount of residual bone particles measured. The results show that bone particles from all tissue banks had a variety of shapes and sizes, both before implantation and after 1 or 2 months of implantation. The pH of particle suspensions also varied between batches, as well as between tissue banks. None of the DFDBA induced new bone formation when implanted subcutaneously. Intramuscular implants from three banks induced new bone formation after 1 and 2 months. DFDBA from two banks caused new bone formation only after 2 months. However, DFDBA from one bank did not induce new bone at all. Particle size before implantation correlated with particle size after implantation. However, particle size did not correlate with ability to induce bone. The results show that commercial DFDBA differs in both size and ability to induce new bone formation, but that the two are not related. The study also indicates that wide variation in commercial bone bank preparations of DFDBA exist and that ability to induce new bone formation also varies widely. Furthermore, the results suggest that methods or assays for evaluating the ability of DFDBA to induce new bone should be developed and standardized.

Adolescent↗

PubMed1995

Microcomputed tomography: an advanced system for detailed endodontic research.

This study evaluated the value of microcomputed tomography (MCT) for use in endodontic research. Four periodontally involved highly calcified maxillary first molars were extracted and then scanned for evaluation by a MCT system. The teeth were then instrumented, and 2 of the 4 obturated before rescanning for comparison evaluation. Several capabilities of the MCT to advance endodontic research significantly were observed: the ability of the MCT to present accurately the external and internal morphologies of the tooth without tooth destruction; the possibility of showing changes over time in surface areas and volumes of tissues; the ability to assess area and volume changes after instrumentation or obturation; and the capability of evaluating canal transportation following instrumentation or instrumentation and obturation. The tremendous potential of this scientific tool was discussed.

Dental Pulp Calcification↗

PubMed1994

Development of an in vitro culture system for the study of osteoclast activity and function.

Resorption is a difficult process to study in vivo because of the complex organization of mineralized tissue. The objective of this study was to develop an in vitro culture system for studying osteoclast attachment and activity. Transparent, microporous substrata were prepared using radio frequency-sputtering techniques to apply a thin layer of hydroxyapatite on polycarbonate filters previously coated with Type I collagen. Dentinoclasts isolated from the root surface of rat molar teeth undergoing inflammatory resorption and osteoclasts isolated from the endosteal surfaces of rat long bones were incubated on the experimental substrata. The culture system proved successful, supporting osteoclast viability and activity as demonstrated by cellular attachment and spreading seen by scanning electron microscopy. Activity was further demonstrated by monitoring acid production using a fluorescent probe, acridine orange. Isolated osteoclasts or dentinoclasts, when combined with synthetically prepared substrata, were observed to respond by mechanisms comparable to those that occur in vivo. Therefore, the system developed permits basic observations of osteoclasts in an in vitro system.

Animals↗

PubMed1993

Anti-inflammatory effects of dexamethasone on periapical tissues following endodontic overinstrumentation.

An animal model was developed in which the anti-inflammatory effects of dexamethasone could be examined histologically in periapical tissues following endodontic overinstrumentation. Mandibular first molars containing vital or partially necrotic pulp tissue were instrumented beyond the apical foramen in rats. Fifty microliters of sterile saline or dexamethasone sodium phosphate (0.4 mg/ml) were administered in a blind manner by supraperiosteal infiltration into the buccal vestibule. The rats were killed after 6, 24, and 48 h. Block sections of the mandibular molars were processed for histological examination and stained with hematoxylin and eosin. The number of polymorphonuclear neutrophils present in the periapical tissues was counted in a blind manner and statistical analysis of the results was performed by two-way analysis of variance. Following endodontic overinstrumentation, local infiltration of dexamethasone produced a significant anti-inflammatory effect on the periapical tissues of teeth with vital or partially necrotic pulp tissue.

Analysis of Variance↗

PubMed1992

Dissociation of phosphaturia and 25(OH)D-1 alpha-hydroxylase trophism using a novel analogue of parathyroid hormone.

Certain parathyroid hormone (PTH) analogues have been shown to selectively impair some but not all physiological actions of PTH. In this study, transaminated rat (r) PTH [TA-rPTH-(1-34)], a PTH analogue that differs from the rPTH-(1-34) fragment in that the NH2-terminal alanine is converted to pyruvate, was infused into mice to determine its properties in vivo and specifically to determine whether stimulation of 25-hydroxyvitamin D-1 alpha-hydroxylase (1 alpha-hydroxylase) activity was more dependent on concomitant renal handling of phosphate or on generation of adenosine 3',5'-cyclic monophosphate (cAMP). High-performance liquid chromatography-purified TA-rPTH-(1-34) was infused into C57BL mice at 10 or 30 pmol/h for 24 h. At 30 pmol/h, TA-rPTH-(1-34) was comparable with rPTH-(1-34) in its hypophosphatemic and phosphaturic effects but was less potent than rPTH-(1-34) in raising serum calcium. TA-rPTH-(1-34) was markedly less effective in stimulating renal 1 alpha-hydroxylase than rPTH-(1-34). Stimulation of urinary cAMP excretion occurred after infusion with TA-rPTH-(1-34), but this effect was significantly less than that seen with rPTH-(1-34). These findings indicate that PTH-induced hypophosphatemia and phosphaturia can be uncoupled from PTH stimulation of 1 alpha-hydroxylase. Furthermore, cAMP-related signal transduction appears to be more significant in regulation of 1 alpha-hydroxylase than mechanisms that mediate PTH-sensitive phosphate transport, independent of cAMP.

Animals↗

PubMed1992

Epithelial cell lines that induce bone formation in vivo produce alkaline phosphatase-enriched matrix vesicles in culture.

Hypertrophic chondrocytes and osteoblasts produce alkaline phosphatase (ALPase)-enriched matrix vesicles in vivo and in vitro and, along with certain epithelial cell lines and osteoblast precursors, induce bone when implanted in mesenchymal tissues. This study examined whether ALPase-enriched matrix vesicle production in vitro was a general property of cells that induce bone in vivo. Epithelial cell lines FL, WISH, and OK 16; connective tissue cell lines HEPM 1 and HEPM 2; neonatal rat muscle cells; rat costochondral chondrocytes; and human fibroblasts were implanted intramuscularly into nude mice. The FL and WISH cells produced tumors and induced large islands of bone with focal areas of cartilage immediately adjacent to the tumors. The chondrocytes formed cartilage nodules but did not induce bone, indicating that the ability of the cells to form a solid mass was not an a priori requirement for bone formation. No other cell type produced tumors or nodules or induced bone formation, although connective tissue cells have been shown to induce chondrogenesis in vitro and osteogenesis in vivo. Only matrix vesicles from normal chondrocytes, FL, WISH, and OK16 cultures exhibited enriched ALPase-specific activity. Matrix vesicles from FL and WISH cultures exhibited ALPase specific activities similar to those isolated from osteoblast or chondrocyte cultures. These data suggest that the ability to produce ALPase-enriched matrix vesicles in culture may be associated with the ability of cells to induce bone or cartilage in vivo.

Alkaline Phosphatase↗

PubMed1992

Initial effects of partially purified bone morphogenetic protein on the expression of glycosaminoglycan, collagen, and alkaline phosphatase in nonunion cell cultures.

Bone morphogenetic protein (BMP) stimulates mesenchymal cells to differentiate, resulting in de novo endochondral ossification in vivo. The response of fibrocartilage and periosteal cells from human and canine nonunion tissues to partially purified BMP was examined in culture. Cells derived from neonatal rat muscle explants were used for comparison. Alkaline phosphatase activity and expression of alkaline phosphatase and Types I and II collagen mRNAs were compared to that of rat chondrocytes. Synthesis of Type II collagen by the muscle cells was verified by enzyme-linked immunosorbent assay (ELISA). Addition of BMP to the muscle cell and nonunion cell cultures resulted in a dose-dependent decrease in cell number. There was a decrease in matrix vesicle and plasma membrane alkaline phosphatase activity concomitant with an increase in mRNA levels for alkaline phosphatase and collagen genes. Synthesis of immunoreactive Type II collagen increased. These data indicate that neonatal rat muscle cells and nonunion cells may respond in a similar fashion to BMP. Bone morphogenetic protein stimulated hyaluronic acid synthesis at three days, but chondroitin sulfate synthesis did not increase until ten days exposure to BMP. These data, together with those summarized above, suggest that more than three days may be required for complete expression of the chondrocyte phenotype typical of endochondral ossification.

Alkaline Phosphatase↗

PubMed1991

The solvent effects of calcium hydroxide irrigating solution on bovine pulp tissue.

The solvent effects of calcium hydroxide irrigating solution (used alone and in combination with sodium hypochlorite) on bovine pulp tissue were studied. Forty pieces of pulp tissue weighing 90 mg each were treated with calcium hydroxide solution alone, calcium hydroxide and sodium hypochlorite alternated, sodium hypochlorite alone, and saline alone. Each piece of tissue was treated for 32 min. Desiccated pretreatment and posttreatment weights were compared. There was no significant difference between the dissolution capability of calcium hydroxide solution used alone and of saline. No significant difference was noted between calcium hydroxide solution and sodium hypochlorite used alternately, and sodium hypochlorite used alone. However, both of these groups were significantly more effective at dissolving tissue than calcium hydroxide solution alone or saline. Calcium hydroxide solution was an ineffective solvent of pulpal tissue. If tissue dissolution is desired during root canal therapy, the use of calcium hydroxide solution as the sole irrigant is no more effective than saline.

Analysis of Variance↗

PubMed1991

Monoclonal antibodies to periodontal ligament cells.

Ten mouse monoclonal antibodies were prepared against cultured bovine periodontal ligament cells to be used as reagents for the study of periodontal disease and wound healing. Using standard immunohistochemical methods, these antibodies were found to recognize cell surface antigens in formalin-fixed bovine periodontium. Three of the 10 monoclonal antibodies (i.e., PDL-1, PDL-2, and PDL-10) cross-reacted with cells found in primate periodontium. While the isolated monoclonal antibodies appeared to distinguish subpopulations of cells located in the supporting tissues of teeth, immunohistological examination of other organs (dermis, kidney, skeletal muscle, thyroid, and parotid gland) indicated that a number of cell types of mesenchymal origin share an antigen(s) found on periodontal cells. The monoclonal antibodies described in this report should prove to be useful in studies of periodontal disease and guided tissue regeneration by providing both analytical reagents and immunochemical methods for isolating selected cell populations of the periodontium.

Animals↗

PubMed1989

Structure-activity relationships of parathyroid hormone analogs in the opossum kidney cell line.

Structural alterations in the parathyroid hormone (PTH) molecule produce marked changes in biologic activity. We examined the relative sensitivity of PTH-stimulated cAMP formation and PTH-inhibitable Na+-dependent phosphate transport responses to bovine PTH analogs [bPTH-(1-34), bPTH-(1-84), 8,18-norleucine-34-tyrosinamide bPTH-(1-34), bPTH-(7-34)-amide, 8,18-norleucine-34-tyrosinamide bPTH-(3-34), transaminated bPTH-(1-34)] and the human PTH-related peptide of malignancy (1-34) in cultured opossum kidney cells. The rank order of potency for stimulation of cAMP formation was bPTH-(1-34) = hPTHrP-(1-34) greater than nle bPTH-(1-34) greater than bPTH-(1-84) much greater than TAbPTH-(1-34). Nle bPTH-(3-34) and bPTH-(7-34) did not affect cAMP formation in intact cells at concentrations up to 10 microM. The rank order of potency for the inhibition of phosphate transport was bPTH-(1-34) = hPTHrP-(1-34) greater than nle bPTH-(1-34) greater than bPTH-(1-84) = TAbPTH-(1-34) greater than nle bPTH-(3-34). TAbPTH-(1-34) was a full agonist and inhibited phosphate transport at concentrations that did not increase cAMP formation, but nle bPTH-(3-34) was a partial agonist in spite of its inability to stimulate cAMP formation. Bovine PTH-(7-34) had no effect on phosphate transport. This study indicates that changes in the PTH molecule produce analogs that apparently discriminate between the cAMP-stimulating activity and phosphate transport-inhibiting activities of the native hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Amination↗

PubMed1989

Initial characterization of cells derived from human periodontia.

The studies presented in this report describe an initial characterization of cell types derived from explants of human periodontia. Cell cultures were established from human periodontal ligament (PL4, PL7), gingival tissue (GF2), and alveolar bone (BP1) by means of explant techniques and monolayer culture. Cells were studied at passage numbers 2-4 and were characterized on the basis of morphological, biochemical, and proliferative parameters. Subconfluent cells did not have distinct morphologies useful in distinguishing them from one another. At confluence, PL4 and BP1 cells formed multilayered cultures of randomly oriented cells, while PL7 and GF2 cells grew in a monolayer of parallel cells. Biochemically, PL4 and BP1 cells exhibited characteristics consistent with an osteoblast-like phenotype. These included a significant increase in PTH-stimulated cyclic AMP and high basal levels of alkaline phosphatase activity, which were decreased on exposure to PTH and increased after stimulation by 1.25 dihydroxyvitamin D3. In contrast, PL7 and GF2 cells exhibited basal alkaline phosphatase levels that were low, and cyclic AMP levels were not modulated by PTH stimulation. Cell populations PL7 and GF2 did not proliferate in culture medium supplemented with 3% platelet-poor plasma. After the addition of platelet-derived growth factor (PDGF) to this medium, the proliferation of these cell populations was equal to that in media supplemented with 10% fetal bovine serum. In contrast, PL4 and BP1 cells did proliferate in culture medium supplemented with 3% platelet-poor plasma. The addition of PDGF to the medium resulted in only a moderate increase in the proliferation of cell populations PL4 and BP1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1988

Differential expression of phenotype by resting zone and growth region costochondral chondrocytes in vitro.

This study establishes an in vitro model for examining endochondral cartilage cell metabolism. Chondrocytes derived from the resting cell zone and adjacent growth zone of rat costochondral cartilage were compared for retention of phenotype in culture. At third passage confluence, two cell populations differ morphologically and biochemically. Resting zone cells are fibroblast-like, with smooth cell membranes and little rough endoplasmic reticulum. Growth zone cells are more polygonal, smaller in diameter, with numerous cytoplasmic extensions of the plasma membranes and abundant rough endoplasmic reticulum. Both cell populations produce matrix vesicles that are comparable morphologically to matrix vesicles isolated enzymatically from epiphyseal cartilage. While membrane vesicles are released into the media by cells derived from the resting zone as well as from the growth cartilage, alkaline phosphatase activity is enriched in media vesicles produced by growth cartilage cells. Alkaline phosphatase enriched vesicles appear to be preferentially incorporated into the extracellular matrix. Both the plasma membrane marker enzyme activity and the membrane phospholipid composition are differentially expressed in matrix vesicles and plasma membranes and are cell specific. Matrix vesicles produced by resting zone cells are enriched in alkaline phosphatase, 5'-nucleotidase, ouabain sensitive Na+/K+ ATPase and cardiolipin when compared to the cell membrane. In addition, the plasma membranes of these cells contain more phosphatidylcholine plus sphingomyelin than do growth cartilage plasma membranes. Resting zone cell matrix vesicles have less phosphatidylethanolamine than do vesicles from growth cartilage cultures. Matrix vesicles produced by growth cartilage cells contain one proteolipid at 43,000 Mr which comigrates with plasma membrane proteolipid and an additional proteolipid at approximately 3,000 Mr. These data indicate that both cells retain differential expression of phenotype in culture and that one expression of this phenotype is production of specific extracellular matrix vesicles.

Animals↗

PubMed1988

The effects of vitamin D metabolites on the plasma and matrix vesicle membranes of growth and resting cartilage cells in vitro.

This study compares the effects of vitamins 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and 24,25-(OH)2D3 on populations of chondrocytes at different developmental stages. Confluent third passage chondrocytes derived from the resting zone and adjacent growth region of rat costochondral cartilage were cultured in Dulbecco's Modified Eagle's Medium containing 10% fetal bovine serum and increasing concentrations of hormone. After determination of cell number, matrix vesicles and plasma membranes were isolated by differential centrifugation. The effects of hormone on alkaline phosphatase, 5'-nucleotidase, ouabain-sensitive Na+/K+-ATPase, and phospholipid composition were dependent on vitamin D metabolite and were cell specific. Growth cartilage chondrocytes responded primarily to 1,25-(OH)2D3, whereas resting zone cells responded primarily to 24,25-(OH)2D3. 1,25-(OH)2D3 inhibited growth cartilage cell number at pharmacological concentrations and had no effect on resting cartilage cell number. In contrast, 24,25-(OH)2D3 appeared to stimulate resting cartilage cell number at physiological concentrations and inhibit these cells at pharmacological doses, but had no effect on growth cartilage chondrocytes. These data were supported by [3H]thymidine incorporation studies. 1,25-(OH)2D3 stimulated alkaline phosphatase, 5'-nucleotidase activity, and Na+/K+-ATPase activity in the matrix vesicles of growth cartilage cells. 1,25-(OH)2D3 also stimulated Na+/K+-ATPase activity in the matrix vesicles and plasma membranes of resting zone cells. Incubation with 24,25-(OH)2D3 stimulated alkaline phosphatase, 5'-nucleotidase, and Na+/K+-ATPase in the matrix vesicles produced by resting zone cells. In addition, 24,25-(OH)2D3 stimulated Na+/K+-ATPase activity in the plasma membranes of resting zone cells as well as in both matrix vesicles and plasma membranes of growth cartilage cells.

24,25-Dihydroxyvitamin D 3↗