Transient cranial hemorrhage does not cause depressed contractility in cardiac neural crest-ablated chick embryos

The aim of this experiment was to study the osteogenesis in vivo of allogenic osteoblast combined culture with calcium phosphate composites. The osteoblasts were obtained by enzymatic digestion of periosteum from fibula subcultured to 13 generations, the cells were combined culture with hydroxyapatite and biphasic calcium phosphate. Subseguently, the composite was implanted into rabbits subcutaneously or intramuscularly. The blank material was implanted in the contralateral side as control. Four weeks later, all animals were sacrificed. All the implants were examined by gross observation, histological examination and EDXA. The results showed: 1. obvious ingrowth of connective tissue with very little inflammatory reaction; 2. new bone formation in the composites with deposit of Ca and P on the surface of osteoblast, but none in the blank materials; 3. no significant difference of new bone formation between the different sites of implantation or different materials, but those implanted intramuscularly had lamellae form of new bone while those implanted subcutaneously had only mineralization of extracellular matrix. The conclusion were: 1. the composites are biocompatible with prior osteogenesis property; 2. periosteal-derived allogenic osteoblasts obatined by enzymatic digestion could survive following implantation with bioactivity; 3. rich blood supply might be advantageous to new bone formation and its maturation.     

Resistance pattern of middle ear fluid isolates in acute otitis media recently treated with antibiotics

The incorporation of fluoride into restorations is desirable because of its cariostatic action. The purpose of this study was to determine fluoride release and fluoride uptake by enamel and cementum from three visible light-cured fluoride-containing composites. Seven circular discs of each composite were prepared and the amount of fluoride released into distilled water was determined at daily intervals for 14 days and then after 30, 60 and 90 days. The fluoride concentration in enamel and cementum was determined in three successive depths by an acid etch biopsy procedure. The composite slabs were made and ligated to the enamel and cementum surfaces and the teeth were immersed in synthetic saliva for 7 days. After removal of the composite slabs, three successive biopsies were again performed. Then the teeth were immersed in 1 M KOH for 24 h and similar biopsies done. The fluoride concentrations were adjusted to standardized depths of 10microm, and the total and bound fluoride uptake calculated. The amounts of fluoride released were significantly different among the three composites. The fluoride released decreased sharply after 1 day and then gradually reached a plateau. As for the enamel and cementum fluoride uptake, FluorEver showed the largest uptake followed by FluoroCore and then Pertac-Hybrid.     

Preparation of cross-linked human serum albumin labelled with 125I for studies of reticuloendothelial system function

A method is described to prepare a new test substance for reticuloendothelial system (RES) function studies. Glutaraldehyde was used for the cross-linking of human serum albumin. The polymeric product was fractionated by repeated chromatography on Sepharose 6B. Cross-linked material with a particle size of approximately 18 nm, as evidenced by electron microscopy, was pooled and labelled with 125I. The surface charge of the albumin polymers, determined by agarose gel electrophoresis, was not significantly changed compared with that of the original albumin monomer. Cross-linking takes place almost entirely between the epsilon-amino groups of lysine in the albumin molecules, as confirmed by amino acid analysis. Preliminary biological tests on mice indicate that the cross-linked polymers are phagocytosed mainly by RE cells of the liver and spleen. The disappearance rate was similar to that of other RE test substances. Intravenous administration of more than 50 times the usual dose caused no deaths, indicating a very low toxicity. Trace amounts of glutaraldehyde were not detectable by gas chromatography. Judging from these experiments, this new preparation of cross-linked albumin fulfils many of the criteria stated for an ideal RES test substance.     

充氢反应球磨法制备氢化态Mg-3Ni-2MnO2复合物的水反应制氢性能

将95％Mg+3％Ni+2％MnO2混合粉末在行星式高能球磨机中充氢反应球磨100 h,利用X射线衍射(XRD)和扫描电镜(SEM)对球磨后的粉体进行表征,并研究其与水反应的动力学性能.结果表明,充氢球磨能对Mg-3Ni-2MnO2进行充分的氢化,Mg全部形成MgH2.制备的氢化态Mg-3Ni-2MnO2复合粉末的颗粒...     

Study on Preparation and Property of Poly－Aminosilicone－Rare Earth Composite

The poly-aminosilicone-rare earth composite was prepared by poly-aminosilicone cross-linked with rare earth and active silanol. The thermal stability of the composites was studied by thermogravimetric analysis (TG). Force condition of the composites in electric field was analyzed and relative polarizability was derived. It is found that the composites containing different rare earth ions have different relative polarizability. The experiment results reveal that organosilicon materials with different electrical performance can be obtained by this way. Meanwhile, the absorption and flourescene spectrum of composites were also investigated. Compared to rare earth chloride, the spectrum properties of the composite are changed obviously. The possible reasons for these phenomena were discussed.     

A method for preparing collagen graft materials

The aim of this research was to develop a method of local production of collagen graft materials which are presently imported. The following methods were used to produce collagen membrane and sponge from human placentas and rat tail tendons. Collagen type I was isolated from human placenta and rat tail tendon by acetic acid extraction and characterised by SDS-PAGE. The collagen sponge was prepared by dissolving the collagen in HCl. The resulting dispersion was poured into a glass container, freeze-dried and then cross-linked by immersion in glutaraldehyde solution. It was then washed with distilled water and freeze-dried again. The collagen membrane was also similarly prepared by dispersing lyophilized collagen in HCl but then mixed with glutaraldehyde, exposed to U.V. light and later air dried.     

Fluoride release from tooth-colored restorative materials: a 12-month report

BACKGROUND: This study measured the amount of fluoride released from three light-activated glass polyalkenoate (ionomer) cements, a conventional glass polyalkenoate, a compomer and a fluoridated composite over a period of 12 months. METHODS: Five discs (7 x 2 mm) of each material were sequentially immersed in 4 mL portions of deionized water at 37 degrees C and before each measurement, the test specimen was rinsed with 1 mL of deionised water. An Orion Model 901 microprocessor digital Ionalyzer was used for the measurements and the data obtained were converted into microgram/cm2. The amount of fluoride released was measured 86 times during the 12-month test period. RESULTS: It was found that the pattern of fluoride release from the light-activated glass polyalkenoates was similar to that of the conventional glass polyalkenoate. The light-activated glass polyalkenoates, however, released significantly more fluoride than the conventional material. The composite and the compomer released significantly less fluoride than any glass polyalkenoate tested and the difference between the composite and the compomer was not significant. CONCLUSION: It was concluded that the light-activated glass polyalkenoates tested released more fluoride than a conventional glass polyalkenoate, a compomer or a composite, and that with regard to fluoride release the compomer behaved more or less like the composite.     

Intrastrand cross-linked actin between Gln-41 and Cys-374. III. Inhibition of motion and force generation with myosin

Structural and functional properties of intrastrand, ANP (N-(4-azido-2-nitrophenyl)-putrescine) cross-linked actin filaments, between Gln-41 and Cys-374 on adjacent monomers, were examined for several preparations of such actin. Extensively cross-linked F-actin (with 12% un-cross-linked monomers) lost at 60 degrees C the ability to activate myosin ATPase at a 100-fold slower rate and unfolded in CD melting experiments at a temperature higher by 11 degrees C than the un-cross-linked actin. Electron microscopy and image reconstruction of these filaments did not reveal any gross changes in F-actin structure but showed a change in the orientation of subdomain 2 and a decrease in interstrand connectivity. Rigor and weak (in the presence of ATP) myosin subfragment (S1) binding and acto-S1 ATPase did not show major changes upon 50% and 90% ANP cross-linking of F-actin; the Kd and Km values were little affected by the cross-linking, and the Vmax decreased by 50% for the extensively cross-linked actin. The cross-linking of actin (50%) decreased the mean speed and the number of sliding filaments in the in vitro motility assays by approximately 35% while the relative force, as measured by using external load in these assays, was inhibited by approximately 25%. The mean speed of actin filaments decreased with the increase in their cross-linking and approached 0 for the 90% cross-linked actin. Also examined were actin filaments reassembled from cross-linked and purified ANP cross-linked dimers, trimers, and oligomers. All of these filaments had the same acto-S1 ATPase and rigor S1 binding properties but different behavior in the in vitro motility assays. Filaments made of cross-linked dimers moved at approximately 50% of the speed of the un-cross-linked actin. The movement of filaments made of cross-linked trimers was inhibited more severely, and the oligomer-made filaments did not move at all. These results show the uncoupling between force generation and other events in actomyosin interactions and emphasize the role of actin filament structure and dynamics in the contractile process.     

Insulin-like growth factors-I and -II stimulate chemotaxis of osteoblasts isolated from fetal rat calvaria

Repair and regeneration of damaged bone is believed to be regulated in part by growth factors stored in the bone matrix. These growth factors are synthesized and secreted by osteoblasts and are incorporated into the developing bone. This pool of stored growth factors is then released into the immediate area following resorption of the matrix. One of the initial steps in bone repair is the recruitment of osteoblasts to the repair site. Growth factors, such as TGF-beta and PDGF, which are present in bone matrix, have been shown to be chemotactic for osteoblasts. In this study, primary cultures of osteoblasts isolated from fetal rat calvaria were examined for chemotaxis in response to IGF-I and IGF-II. IGF-I stimulated a dose-dependent increase in osteoblast chemotaxis, while IGF-II stimulated chemotaxis maximally at the lowest concentration studied (0.1 ng/ml), and had no effect at the highest concentration studied (100 ng/ml). IGF-I and -II had no effect on osteoblast proliferation at any of the concentrations examined. These results indicate that IGFs may be playing an important role in the early stages of bone repair by stimulating osteoblast chemotaxis to the repair site.     

Macrophage colony-stimulating factor release and receptor expression in bone cells

Colony-stimulating factors (CSF) may play a role in bone resorption. To examine whether osteoblasts secrete colony-stimulating activity (CSA) in response to parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrP), conditioned medium (CM) from ROS 17/2.8 cells and primary rat osteoblasts were examined for induction of clonal growth of cultured rat bone marrow cells. Untreated cells constitutively secreted CSA, which increased with PTH and PTHrP treatment. The colonies formed were principally comprised of macrophages, and preincubation of CM with antiserum to murine macrophage colony-stimulating factor (M-CSF) neutralized most of the CSA, suggesting that the osteoblast-derived CSA was predominantly due to M-CSF. PTHrP treatment upregulated steady-state M-CSF mRNA levels. To investigate a paracrine role for M-CSF in bone we examined bone tissue and cells for the M-CSF receptor c-fms using immunohistochemical techniques and demonstrated staining of mature osteoclasts both in situ and after isolation. We conclude that M-CSF is responsible for the majority of the CSA released by PTH- and PTHrP-treated rat osteoblasts. In addition we identified CSF-1 receptor expression in mature osteoclasts. These data suggest that M-CSF is a mediator of osteoblast-osteoclast interaction in PTH- and PTHrP-induced bone resorption.     

Expression of interleukin-1 system genes in human gametes

Elevation of extracellular calcium has been shown to inhibit osteoclastic bone resorption and stimulate proliferation and chemotaxis of osteoblasts. Therefore, calcium released by bone resorption may have important roles in the coupling of bone resorption and bone formation. Although both osteoclasts and osteoblasts have calcium-sensing mechanisms, the responsible molecule in these cells seems to be different. Functional and histological studies show that calcium-sensing mechanism in osteoclasts is a ryanodine receptor-like molecule in plasma membrane. In contrast, calcium-sensing mechanism in osteoblasts has similar functional property to parathyroid calcium-sensing receptor (CaSR), but is a different molecule from CaSR. In addition, several bone marrow cells express CaSR. The elucidation of the identity and the physiological roles of these calcium-sensing mechanisms would give us a more clear view of bone remodeling.     

Bone regeneration by basic fibroblast growth factor complexed with biodegradable hydrogels

The objective of this study is to enhance the bone induction activity of basic fibroblast growth factor (bFGF) for reconstruction of skull bone defects which has been clinically recognized as almost impossible. For this purpose, we prepared biodegradable hydrogels from gelatin with an isoelectric point of 4.9 which is capable of polyionic complexing with basic bFGF. When implanted in rabbit skull defects of 6 mm in diameter (6 defects per experimental group), the gelatin hydrogels incorporating 100 microg of bFGF promoted bone regeneration at the defect in marked contrast to free bFGF of the same dose, finally closing the bone defects after 12 weeks of implantation as is apparent from histological examination. In dual energy X-ray absorptometry analysis, the bone mineral density at the skull defects enhanced by the hydrogels was significantly higher than that by free bFGF at doses ranging from 2 to 200 microg/defect (P < 0.05). The extent of bone regeneration induced by gelatin hydrogels incorporating 100 microg of bFGF increased with a decrease in their water content. Histological examination indicated that more slowly degrading hydrogels of lower water content prolonged the retention period of osteoblasts in the bone defects. This led to enhanced bone regeneration compared with faster degrading hydrogels of higher water content. It was concluded that this biodegradable hydrogel system was a promising surgical tool to assist self-reconstruction of the skull bone.     

A five year study. Fluoride release of four reinforced composite resins

PURPOSE: The purpose of this study was to record the fluoride released measured in parts per million of four fluoride composite resins for five years. MATERIALS AND METHODS: Four fluoridated composites were separated into four groups. Two composite resins with high viscosity were core materials, Ti-Core with titanium (group 1) and Ti-Core Natural (group 2) and the other two resins studied were low viscosity post cements Flexi-Flow cement with titanium (group 3) and Flexi-Flow Natural (group 4). The fluoride release was studied under four experimental conditions. Three replications were studied in each condition. Fluoride release was measured for 260 weeks (5 years). STATISTICAL METHODS: A one-way analysis of variance (ANOVA) was used to compare the average weekly release followed by a Student-Newman-Keuls (SNK) pairwise multiple comparison test. All results were considered statistically significant if p < 0.05. RESULTS: The ANOVA analysis released a significant statistical interaction between group and week (p < 0.0001). Further analysis showed that the average weekly release for Ti-Core with titanium did not differ from Ti-Core Natural, and that Ti-Core with titanium and Ti-Core Natural differed from both Flexi-Flow Natural and Flexi-Flow with titanium, which were not different from one another. CONCLUSIONS: Ti-Core with titanium (Group 1) and Ti-Core Natural (Group 2) released a greater amount of fluoride than Flexi-Flow with titanium (Group 3) and Flexi-Flow Natural (Group 4). The fluoride released from these fluoridated resin composites are similar to reported ranges of other fluoride releasing dental restoration materials.     

Persistent papillomavirus infection in a cat

The purpose of this study was to further define the cellular response to titanium and polymethylmethacrylate (PMMA) particles in aseptic loosening, and to determine if the use of pamidronate may be effective in inhibiting bone resorption associated with this response. Macrophages and osteoblasts were cocultured to simulate the environment around an aseptically loose prosthesis. Macrophages were plated on the bottom of six well plates and osteoblasts were plated on culture dish inserts, and placed into the wells with the macrophages. Incubation of macrophages with PMMA in this system led to release of prostaglandin E (PGE2), granulocyte macrophage-colony stimulating factor (GM-CSF), and interleukin-6 (IL-6). Incubation with titanium led to release of tumor necrosis factor (TNF) and IL-6. Exposure of calvaria to media from cells exposed to either PMMA or titanium led to release of calcium 45. Incubation of calvaria with pamidronate was able to inhibit release of calcium 45 associated with exposure to the macrophage/osteoblast/particle conditioned medium. Bone resorption at the interface between implant and bone is a consistent feature leading to loosening of orthopedic implants. By inhibiting bone resorption associated with the inflammatory response to implant particulates, pamidronate or other bisphosphonates may have clinical utility in the treatment or prevention or aseptic loosening.     

Growth and differentiation of human bone marrow osteoprogenitors on novel calcium phosphate cements

Materials that augment bone cell proliferation and osteogenic activity have important therapeutic implications for bone regeneration and for use in skeletal reconstruction and joint replacement. We have studied the growth and interactions of human bone marrow cells on a variety of new cement composites in vitro. These cement materials are composed of calcium-deficient hydroxyapatites, carbonated apatite and amorphous calcium phosphate. Cell proliferation was significantly reduced and cell differentiation increased in the presence of these cements compared with cells cultured on tissue culture plastic. Alkaline phosphatase, one of the markers of the osteoblast phenotype, was dramatically stimulated by 3 of the 4 cements examined between day 4 and day 10, above levels observed following culture of human osteoblasts on plastic alone. Photomicroscopic examination demonstrated growth and close integration of bone marrow cells and 3 of the composites. Longer term marrow cultures (15 day) on the cements confirmed the stimulation of cell differentiation over proliferation. From these studies, enhanced osteoblastic differentiation was observed on a 70% carbonated apatite, which has a composition similar to bone mineral, whereas, cell toxicity was observed on cells grown on amorphous calcium phosphate. This in vitro culture system demonstrates the use of human bone marrow cells for the potential evaluation of new biomaterials and the development of a novel carbonated apatite that may be of potential use in orthopaedic implants.     

Chemical and swelling evaluations of amino group crosslinking in gelatin and modified gelatin matrices

PURPOSE: To determine the extent of amino group crosslinking in gelatin matrices by chemical assay, and to compare these results to crosslinking evaluations from swelling measurements. METHODS: Matrices crosslinked with a water soluble carbodiimide (EDC/G), glutaraldehyde (GTA/G), as well as a GTA crosslinked matrix prepared from gelatin modified to contain 230% greater crosslinking sites (GTA/Mod) were evaluated. Crosslinking extent, Xc, was determined by a UV assay of uncrosslinked amino groups before and after crosslinking, and was used to obtain crosslinking densities. Equilibrium swelling ratios, Qm, at 37 degrees C in isotonic pH 7.4 were used to calculate crosslinking degree from the Flory equation for swelling of ionic polymers for comparison to the chemically determined crosslinking densities. RESULTS: Of the original 33 x 10(-5) moles epsilon-amino groups/g gelatin, 91 to 95% were crosslinked in EDC/G and GTA/G. GTA/Mod lost 95% of the original 108 x 10(-5) moles amino groups/g gelatin. Crosslinking densities were 4.1 x 10(-4) and 4.2 x 10(-4) moles/mL for EDC/G and GTA/G, respectively. The value for GTA/Mod increased to 14.2 x 10(-4) moles/mL. Values of Qm followed the same trend. The Flory crosslinking degrees for both gelatin matrices were 12 x 10(-4) and 13 x 10(-4) moles/mL, respectively. The value for the more extensively crosslinked GTA/Mod was 280 x 10(-4) moles/mL. CONCLUSIONS: The swelling and chemical evaluations of crosslinking are in general agreement for matrices with the lower of two crosslinking levels. The chemical determination appears suitable for evaluating amino group crosslinking in gelatin and it may be suitable for other proteinaceous materials.     

Evaluation of integrin molecules involved in substrate adhesion

Integrins were cross-linked to their extracellular matrix ligands using non-penetrating chemical cross-linkers. This procedure did not disturb the distribution of integrin in the adhesion structure and adhesion plaque integrin staining remained even when the cultures were extracted with ionic detergents. 80-90% of the beta 1 integrin in the cross-linked culture was extracted with RIPA buffer and the remaining 10-20% was recovered following reversal of the cross-linking. This separated two distinct integrin pools, one which can be cross-linked to substrate bound extracellular matrix and one which is not. The specificity of this procedure for cross-linking of integrins involved in substrate adhesion was demonstrated using NIH 3T3 cells which express both alpha 5 beta 1 and alpha 6 beta 1 integrins. alpha 6 was cross-linked only in cells plated on laminin whereas alpha 5 was cross-linked when fibronectin was present. Using antisera directed to the cytoplasmic domains of either alpha 5 or beta 1 integrin, it was demonstrated that these domains can be blocked in the intact cell but the blocking can be removed using ionic detergent extraction after chemical cross-linking. The extracellular matrix associated with the substrate surface but not that associated with the media exposed surface is both cross-linked and retained on the plastic dish following cross-linking.     

Temporal expression of PTHrP during endochondral bone formation in mouse and intramembranous bone formation in an in vivo rabbit model

Expression of parathyroid hormone-related protein (PTHrP) messenger RNA (mRNA) and protein was investigated throughout the developmental progression of endochondral bone formation in mouse and intramembranous bone formation in an in vivo model in rabbit, using in situ hybridization and immunohistochemistry. Endochondral bone formation was investigated in a developing embryo, newborn, and adult mouse. In fetal long bones through to newborn (day 7), PTHrP mRNA and protein were consistently expressed in chondrocytes within the proliferative, transitional, and hypertrophic zones. In addition, high levels of PTHrP were also detected in osteoblasts on the surface of trabecular bone surfaces. Similarly, at the adult stage (week 7), PTHrP mRNA and protein were consistently expressed in chondrocytes at epiphyseal ends of the subarticular cartilage, within cortical periosteum, as well as in osteoblasts located at the metaphyseal trabecular bone surfaces. Using an in vivo intramembranous bone formation model in rabbits, expression of PTHrP mRNA and protein was demonstrated in preosteoblasts prior to trabecular bone formation (1-week bone harvest). As bone formed (2-, 3-, and 4-week bone tissue harvests), PTHrP mRNA and protein were highly expressed in actively synthesizing osteoblasts and in those osteocytes embedded within the superficial layers of the bone matrix. Lining osteoblasts and osteocytes buried deeply in the bone matrix displayed weak or no signal for PTHrP. The pattern of spatial and temporal expression of PTHrP demonstrated in cartilage cells and osteoblasts in the two systems suggests an important role of PTHrP in both endochondral and intramembranous bone formation.     

Effect of additives on gelation and tissue adhesion of gelatin-poly(L-glutamic acid) mixture

Gelation and tissue adhesion of mixtures of gelatin and poly (L-glutamic acid) (PLGA) aqueous solution were investigated in the presence of additives following the addition of a water-soluble carbodiimide (WSC) that induced chemical cross linking between gelatin and PLGA. To prevent spontaneous gelation of the mixed solution through physical cross linking between gelatin molecules at room temperature, additives were added to the mixed solution. Among the additives studied, starch and urea were effective in preventing the spontaneous physical gelation. The mixed gelatin and PLGA solution set to a cross-linked hydrogel within scores of second by WSC addition, irrespective of the presence of urea, whereas the viscosity of the solution with added starch was too high to measure the gelation time. The cross-linked gelatin-PLGA hydrogels with and without urea showed higher bonding strength to soft tissues than fibrin glue. This was in marked contrast to gelatin-PLGA hydrogels with soluble starch. Irrespective of the presence of urea, the gelatin-PLGA hydrogels gradually biodegraded in the back subcutis of mice over 3 months and no severe inflammatory response to the hydrogels was observed. These findings indicate that urea is promising as an additive to prevent spontaneous physical gelation of the mixed gelatin and PLGA aqueous solution without changing the characteristics of WSC-induced cross linking and tissue adhesion of the formed hydrogel.     

Sugar cross-linked gelatin for controlled release: microspheres and disks

The aim of the present paper was to find a 'biocompatible' means to cross-link gelatin-based pharmaceutical devices. In particular, we have studied the ability of native and oxidized mono- and di-saccharides to induce the cross-linking of gelatin. To this end, gelatin discs and gelatin microspheres were produced and their dissolution kinetics at 37 degrees C were examined. In order to find evidence of sugar-mediated cross-linking, DSC and FTIR experiments were performed. The obtained results indicated that both native and oxidized sugars resulted to different extents, in the formation of a cross-linked gelatin network able to reduce the dissolution of gelatin. These results suggest that oxidized mono- and disaccharides could be an interesting method by which to cross-link gelatin thereby reducing the risk of toxic side effects arising from the use of synthetic cross-linkers.