Biomedical subjects

W Ching

Publications and source records attributed to W Ching.

22 records · Page 2Linked to original sources

PubMed1987

Growth of bone marrow cells on porous ceramics in vitro.

Following the transplantation of bone marrow cells to extra-osseous sites, bone formation occurs in those sites. This osteogenic potential of bone marrow cells might be utilized for filling defects in bone if they could be transported on porous ceramic materials. Before such an approach becomes feasible, it is important to know what happens to the cells in the presence of the ceramics that might be used. In order to investigate the interaction between bone marrow cells and ceramics, in vitro, a system for culturing bone marrow cells on ceramic materials has been developed. Bone marrow cells adhered well to the surface of calcium hydroxyapatite and tricalcium phosphate ceramics, and this was followed by the formation of fibrous tissue on and within the ceramics. These ceramics were compatible with bone marrow cells even in culture conditions in which there was a large surface area of ceramic interfacing with cells. The results support the proposal that calcium hydroxyapatite and tricalcium phosphate are appropriate as bone replacement materials. In contrast, calcium aluminate had an adverse effect on bone marrow cells when there was a high proportion of ceramic to culture medium. However, this effect was not present if the proportion of ceramic to culture medium was low. Therefore, a large amount of biodegradable porous calcium aluminate ceramic should not be used as an alternative to autogeneous bone grafting.

Aluminum↗

PubMed1985

Bone ingrowth into three different porous ceramics implanted into the tibia of rats and rabbits.

Three different porous ceramics--calcium aluminate, calcium hydroxyapatite, and tricalcium phosphate--were implanted into the proximal tibia in rats and rabbits to study the interactions between these ceramics and a bony site that is abundant in bone marrow. New bone was consistently formed within the bone marrow surrounding and adjacent to all three types of ceramics. Calcium hydroxyapatite and tricalcium phosphate ceramics permitted bone ingrowth into their pores. The newly formed bone was found only in the part of the ceramic intruding into the bone, not in the portion protruding in the soft tissues outside the tibia. Partial replacement of the new bone opposite the medullary portion by new hemopoietic marrow occurred with longer implantation times. In contrast, no bone was seen within the pores of any of the calcium aluminate implants.

Aluminum↗

PubMed1984

The use of ceramics for bone replacement. A comparative study of three different porous ceramics.

Ceramics have many properties which might make them suitable alternatives to bone grafts. This present study was done to find a suitable biodegradable porous ceramic for human bone replacement. Three different porous ceramics (calcium aluminate, calcium hydroxyapatite and tricalcium phosphate), with interlinked pores of two size ranges (150 to 210 micron), were implanted into the skulls of rats and rabbits for up to six months; the interaction with surrounding bone, which is virtually devoid of bone marrow, was then assessed. The ceramics caused no adverse biological response. Tissue ingrowth into pores throughout the implant was seen in all three types and in both pore sizes of ceramic, but the density of the penetrating tissue was far less for calcium aluminate than for calcium hydroxyapatite or tricalcium phosphate. For each type of ceramic, the soft-tissue ingrowth was more dense with the larger pore size, and with a longer period of implantation. Bone ingrowth was not usually seen within the pores of any ceramic. There were no differences in the histological findings between the rats and the rabbits. The results demonstrate that it is possible to produce ceramic materials with a porous structure which allows ingrowth of tissue and biological fluids.

Aluminum↗

PubMedDate not supplied

Clustering of neuronal sodium channels requires contact with myelinating Schwann cells.

Efficient and rapid conduction of action potentials by saltatory conduction requires the clustering of voltage-gated sodium channels at nodes of Ranvier. This clustering results from interactions between neurons and myelinating glia, although it has not been established whether this glial signal is contact-dependent or soluble. To investigate the nature of this signal, we examined sodium channel clustering in co-cultures of embryonic rat dorsal root ganglion neurons and Schwann cells. Cultures maintained under conditions promoting or preventing myelination were immunostained with antibodies against the alpha subunit of the sodium channel and against ankyrin(G), a cytoskeletal protein associated with these channels. Consistent with previous in vivo studies (Vabnick et al., 1996), sodium channels and ankyrin G cluster at the onset of myelination. These clusters form adjacent to the ends of the myelinating Schwann cells and appear to fuse to form mature nodes. In contrast, sodium channels and ankyrin G do not cluster in neurons grown alone or in co-cultures where myelination is precluded by growing cells in defined media. Conditioned media from myelinating co-cultures also failed to induce sodium channel or ankyrin G clusters in cultures of neurons alone. Finally, no clusters develop in the amyelinated portions of suspended fascicles of dorsal root ganglia explants despite being in close proximity to myelinated segments in other areas of the dish. These results indicate that clustering of sodium channels requires contact with myelinating Schwann cells.

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