Biomedical subjects

D E Mark

Publications and source records attributed to D E Mark.

7 recordsLinked to original sources

PubMed1991

A comparison of four particulate bone derivatives.

Samples of four types of particulate bone matrix derivatives were prepared and surgically inserted into standardized critical-sized defects in calvariae of Long-Evans rats. Implantation of demineralized bone matrix (DBM), bone regenerative matrix, and two types of particulate chemosterilized, antigen-extracted, autolyzed, allogeneic (AAA) bone from endochondral (eAAA) and intramembranous (iAAA) sources will result in the regeneration of bone in orthotopic skull defects. The four preparations were tested in orthotopic, 8-mm calvarial wounds to compare the quantity of new bone that formed 28 days postimplantation. Quantitative computer imaging was used to measure roentgenographic gray levels and bone volume of new trabeculae (calcified plus osteoid). All experimental bone matrix derivatives produced more bone volume than the nontreated control wounds. Bone volume regenerated from iAAA was significantly less than eAAA and DBM-regenerated bone.

Analysis of Variance↗

PubMed1990

Repair of calvarial nonunions by osteogenin, a bone-inductive protein.

Efforts were taken to determine the dose of bovine osteogenin (OG) that would induce more bone than that induced by 20 mg of rat particulate demineralized bone matrix (DBM), the amount allowed by the confines of an 8-mm rat craniotomy defect. Dose-response studies were performed for demineralized bone matrix alone and osteogenin, partially purified from bovine demineralized bone matrix, plus rat insoluble collagenous bone matrix (M). Demineralized bone matrix alone (2.5, 5.0, 10, 20, or 40 mg) or osteogenin (0.0625, 0.125, 0.250, 0.50, or 1.0 mg) plus 25 mg insoluble collagenous bone matrix was implanted into the pectoralis muscle for 3, 5, and 7 weeks. Both materials induced time- and dose-dependent formation of bone. The three highest dosages of osteogenin (plus insoluble collagenous bone matrix) induced more bone than 20 mg demineralized bone matrix and seemed to accelerate bone repair. However, when implanted into the 8-mm rat craniotomy defect for 4 weeks, 20 mg demineralized bone matrix and 0.5 mg osteogenin (plus insoluble collagenous bone matrix) induced comparable amounts of bone. These results suggest different mechanisms for bone formation in heterotopic and orthotopic sites.

Animals↗

PubMed1990

Osseous wound healing with xenogeneic bone implants with a biodegradable carrier.

Human antigen-extracted, autolyzed (AA) bone and a bovine bone morphogenetic protein were prepared as implants within biodegradable carriers and compared with autogenous bone grafts and controls in the healing of critical-size bony defects in nonhuman primates. The treated craniotomy sites were studied 3 and 6 months after surgery; radiodensity and volume of newly deposited trabecular bone were assessed by radiomorphometric and histomorphometric methods, respectively. There was no evidence of adverse immunologic response to the experimental implants. The autografts resulted in the greatest volume of new bone formation (p less than 0.01), but the AA implants elicited a significantly greater response than either the bovine bone morphogenetic protein derivatives or the controls (p less than 0.05). By 6 months, the AA derivatives had healed with actively coalescing islands of new bone, displaying normal-appearing outer and inner tables along with well-developed marrow cavities. It appears that xenogeneic AA implants have the ability to elicit an excellent osseous response in critical-size calvarial wounds. In addition, the carrier polymer for the implants acted as an effective soft-tissue spacer before being absorbed.

Animals↗

PubMed1989

Calvarial bone regeneration using osteogenin.

This experimental study reports on the application of a partially purified noncollagenous protein extracted from cortical bone to restore craniotomy defects in Papio species (baboon). The partially purified protein (osteogenin) produced significantly more bone formation in calvarial wounds than was found in the untreated controls. There were no adverse tissue reactions from the implanted xenogeneic osteogenin.

Animals↗

PubMed1989

Scanning electron microscopic study of cell attachment to biodegradable polymer implants.

The biodegradable polymers--polylactic acid (PLA) and polyglycolic acid (PGA)--are currently being studied as carriers for bioactive bone regeneration compounds. The inclusion of osteo-inductive substances in poly-(DL, lactide-co-glycolide) copolymer alloplastic implants has been shown to enhance the repair of osseous defects. The purpose of this study was to examine, by SEM, the attachment relationship of biodegradable polymer implants to cells and tissue matrix. Three groups of copolymer implants were studied: (1) plain 50:50 PLA-PGA copolymer, (2) PLA-PGA copolymer with hydroxyapatite (HA), and (3) PLA-PGA copolymer with autolyzed, antigen-extracted (AA) bone particles. Polymer discs were surgically implanted into the pectoralis muscles of rats. At seven, 14, and 21 days post-implantation, the baskets were removed and the contents prepared for SEM. Results showed that at one week, implants were coated primarily with red and white blood cells in a fibrinoid clot. Degradation of the polymers was evidenced by irregular enlarging of polymer surface pores. At two and three weeks, polymers became lobular and then fibrinoid as degradation progressed. Inflammatory cell and red blood cell adhesions were increasingly replaced by fibroblasts and collagen matrix deposition. As polymer degradation progressed, AA and HA particles were exposed; however, the lack of cell or tissue adhesion in these areas suggests that degradation may be more influenced by the fluid environment than by direct cell attachment. Furthermore, degradation may inhibit direct cell attachment.

Animals↗

PubMed1988

The role of transmembrane cationic gradients in immune complex stimulation of human polymorphonuclear leukocytes.

The role of monovalent cationic gradients in human polymorphonuclear leukocyte (PMNL) stimulation was investigated by monitoring immune complex-stimulated transmembrane depolarization and superoxide production, events which accompany--and have been used as indicators of --PMNL activation. Abolishing only the Na+ gradient by substitution of choline for extracellular Na+ did not affect the resting membrane potential but reduced the rate of stimulus-induced transmembrane depolarization to 50% of control. In contrast, collapsing both Na+ and K+ gradients by suspension in K+ buffer (high K-PRK) depolarized the cells and reduced the stimulus-induced rate of depolarization to 11% of control. Pretreatment of cells suspended in Na+ buffers with 5-(N,N-dimethyl)amiloride hydrochloride (DMA) or with valinomycin reduced by one-half the rate of immune complex induced membrane depolarization. Conversely, in the absence of either or of both Na+ or K+ gradients, or in the presence of valinomycin, immune complex elicited an enhanced rate of superoxide production. However, PMNL prepared via NH4Cl (NH4Cl-PMNL) instead of H2O (H2O-PMNL) lysis of residual red blood cells exhibited an absolute requirement for an intact Na+ gradient in cell stimulation. The present results thus demonstrate that: 1) both Na+ and K+ gradients participate equally in the membrane depolarization elicited by immune complex; 2) neither a Na+ or a K+ gradient is required for immune complex activation, or for activity of the respiratory burst; and 3) an artifactual requirement for an intact Na+ gradient occurs in neutrophils prepared by the NH4Cl lysis technique.

Ammonium Chloride↗

PubMed1988

Are serine proteases involved in immune complex activation of neutrophils?

Soybean polypeptides and diisopropylfluorophosphate (DFP) have been reported to inhibit neutrophil functions such as the oxidative burst, chemotaxis, and/or phagocytosis in response to soluble stimuli; these observations would be compatible with the involvement of an active serine protease in neutrophil stimulation. We have investigated the possibility of such involvement when particulate stimuli such as immune complexes are utilized. The depolarization of the neutrophils' membrane potential, one of the earliest indicators of stimulation, and superoxide production, which is detectable 30-45 sec later, were our indicators of neutrophil response to immune complexes. The neutrophils were equilibrated with, and after 5 min washed free of, up to 60 mM DFP, a potent covalent serine protease inhibitor. At DFP concentrations below 24 mM, such treatment did not perturb neutrophil activation as measured by either of the above parameters, nor did F- alone under comparable conditions. Additionally, the immune complex induced responses of neutrophils preincubated for 3 min with N-alpha-p-tosyl-L-lysine chloromethylketone (TLCK), L-1-tosylamido-2-phenyl-ethyl-chloromethylketone (TPCK), or phenyl-methyl-sulfonyl-fluoride (PMSF), covalent serine protease inhibitors which have, however, been shown to function in other capacities, e.g., as superoxide dismutases; 1 mM PMSF or 0.5 mM TLCK consistently reduced the observed membrane depolarization, one of the earliest consequences of neutrophil activation, by 20-30%, while 0.1 mM TLCK and 0.01 mM TPCK had little or no effect. The inhibition of superoxide production, a slightly later stimulus response, by PMSF, TLCK, and TPCK was more profound (50-75%); these compounds have, however, been shown to have activities other than serine protease inhibitors--for example, as superoxide dismutases. Since DFP is purely a serine protease inhibitor, and since the three other compounds do not affect depolarization (the earlier and superoxide independent event), our results indicate that active serine proteases do not appear to be necessary for immune-complex-initiated neutrophil stimulation. Other stimuli, which are known to activate neutrophils by different pathways, were not investigated.

Antigen-Antibody Complex↗