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Biomedical subjects

J R Heath

Publications and source records attributed to J R Heath.

17 recordsLinked to original sources
PubMed1991

Evaluation of biodegradable ampicillin anhydrate microcapsules for local treatment of experimental staphylococcal osteomyelitis.

Successful treatment of chronic osteomyelitis requires sustained high concentrations of antibiotics locally within the infected bone. The efficacy of biodegradable (poly-DL-lactide-co-glycolide) microspheres containing 30.7% ampicillin anhydrate for the local treatment of experimental staphylococcal osteomyelitis was evaluated in rabbits. In the initial experiment, antibiotic therapy was initiated immediately following injection of Staphylococcus aureus into the proximal tibial metaphysis. A single intramedullary injection of microencapsulated ampicillin (100 mg) prevented osteomyelitis in all seven animals tested and was as effective as a two-week course of parenteral ampicillin administration. When antibiotic therapy was delayed for seven days, osteomyelitis developed in four of eight animals treated locally with microencapsulated ampicillin and in six of eight animals that received parenteral ampicillin therapy. When antibiotic therapy was delayed for seven days and was preceded by debridement, all ten animals treated locally with microencapsulated ampicillin had sterile bone cultures. In contrast, seven of ten animals treated locally with unencapsulated ampicillin powder developed osteomyelitis. Biodegradable antibiotic-loaded microspheres may be of clinical benefit for the local treatment of chronic osteomyelitis.

Ampicillin↗
PubMed1990

Pathogenic potential of Eubacterium yurii subspecies.

Several mechanisms that could contribute to the periodontopathogenic potential of Eubacterium yurii were investigated. All 18 strains examined produced RNAase and the metabolites H2S, indole and butyrate. Some strains produced phosphatase and DNAase. Methanol extracts of whole cells of E. yurii subspp. yurii and margaretiae stimulated bone resorption in vitro comparable to that produced by recognised periodontal pathogens. These results suggest that further studies should be performed to elucidate the role of E. yurii in periodontal disease.

Bone Resorption↗
PubMed1990

Finishing composite restorative materials.

A clinically realistic in vitro study was performed to determine the best method for smoothing trimmed surfaces of seven composite restorative materials. Soflex discs produced the smoothest surface, and little advantage appeared to be gained by prior smoothing of the surface with stones or points. A polishing paste, even when used with intermediate finishing agents, produced a rougher surface than that left by the discs.

Composite Resins↗
PubMed1989

A scanning electron microscopic study of in vitro toxicity of ethylene-oxide-sterilized bone repair materials.

Polylactic acid (PLA) and polyglycolic acid (PGA) have been under investigation for use in the management of hard- and soft-tissue wounds. Current research has included the incorporation of osteo-inductive substances into a PLA-PGA copolymer alloplastic implant material for enhancement of the healing of osseous defects. Conventional methods of sterilization--such as dry heat, steam heat, or 60Co--tend either to destroy or attenuate osteo-inductive activity and alter polymer biodegradation. Ethylene oxide (EO) gas sterilization is currently being tested as an alternate method. This study examined the relationship of EO-induced cytotoxicity to the length of time of polymer aeration following EO sterilization. Three groups of copolymer implant discs were studied: (1) 50:50 PLA-PGA copolymer, (2) PLA-PGA polymer with hydroxyapatite (HA), and (3) PLA-PGA with autolyzed, antigen-extracted (AA) bone particles. Polymer discs, as well as particulate HA and AA bone controls, were sterilized with EO for 12 hours. Following periods of two weeks, one week, one day, or no subsequent vacuum aeration, samples were placed into 24-well culture plates. A suspension of human fibroblasts was added to each well. Cell growth and attachment were permitted for 24 hours. Medium was then removed, and solutions for cell fixation, buffer washing, and dehydration were added to each well. SEM examination revealed changes in cell growth with increasing periods of aeration suggestive of increasing cell vitality. Cells growing on discs having no aeration were small, round, and lobulated, whereas those of seven to 14 days' aeration were more numerous, and flattened with many microvilli, pseudopodia, and dendritic processes, features consistent with normal cell morphology. These results suggest that EO-sterilized polymer implants should be aerated for least seven to 14 days prior to surgical use.

Bone and Bones↗
PubMed1988

Simple methods for denture identification: a clinical trial.

The persistence of identification marks applied to dentures with two spirit solvent based fibre tip pens and graphite pencil covered with an experimental and a proprietary sealant were studied under service conditions. In general, the marks applied with the pens were rapidly lost, but those covered with the sealants persisted satisfactorily. The experimental sealant performed slightly better than the proprietary product.

Aged↗
PubMed1976

Abrasion of restorative materials by toothaste.

The procedure developed in this investigation is suitable for determining the abrasion resistance of restorative materials to toothbrush/dentifrice abrasion. Ideally, a restoration should have an abrasion resistance similar to that of enamel. Of the materials tested, gold was the only one that wore slightly less than enamel, whilst amalgam wore almost twice as quickly. The silicate material and composites (excluding TD.71) wear away 2-4 times faster than enamel. TD.71 and especially the unfilled resin exhibited very high rates of abrasion. After prolonged toothbrush/dentifrice abrasion, the surfaces of gold and amalgam were considerably smoother than those of the silicate and composite materials.

Dental Amalgam↗
PubMed1975

Enzyme activities and properties of lysosomes and brush borders in jejunal biopsies from control subjects and patients with coeliac disease.

1. Reduced activities of four enzymes from brush borders were found in intestianl biopsies from patients with untreated coeliac disease. The activities returned towards control values after treatment by gluten withdrawal. Parallel changes were noted for the cytosol enzyme lactate dehydrogenase. 2. Measurement of brush-border integrity by differential centrifugation of biopsy extracts indicated increased fragility of the brush borders in biopsies from untreated patients. Normal values were obtained for biopsies from treated patients. 3. Increased activites of six acid hydrolases (lysosomal enzymes) were found in biopsies from untreated coeliac patients. Normal values were obtained for biopsies from treated patients. 4. Assement of lysosomal integrity by assay of latent N-acetyl-beta-glucosaminidase and of sedimentable activity of four acid hydrolases demonstrated increased lysosomal fragility in untreated coeliac mucosa. These lysosomal changes return to within the normal range after treatment by gluten withdrawal. 5. The lysosomal changes are consistent with their having a pathogenic role in the enterocyte damage of coeliac disease. Possible mechanisms for the lysosomal changes are discussed.

Acetylglucosaminidase↗
PubMed1975

Effect of bile-duct ligation on organelle marker enzymes in the liver and serum of rats.

1. Marker enzymes for the principal subcellular organelles of rat liver were asayed in the liver of rats 1 day and 8 days after bile-duct ligation or after laparotomy as a control procedure. 2. The microsomal enzymes in liver tissue showed complex changes. Benz[alpha]pyrene hydroxylase activity, predominantly found in the smooth endoplasmic reticulum, was decreased. Glucose 6-phosphatase activity and ribonucleic acid, which are localized predominantly in the rough endoplasmic reticulum, were increased. 3. The plasma membrane enzyme, alkaline phosphatase, increased in activity after bile-duct ligation. 4. No changes in mitochondrial enzyme activities were noted after 1 day but there was a 50% reduction 8 days after ligation. Lysosomal enzyme activities did not change in the liver tissue. 5. Liver catalase and D-amino acid oxidase activities showed a slight increase at 1 day postligation but a significant fall by 8 days. 6. Lactate dehydrogenase, a cytosol enzyme, showed a decrease in activity after 1 day but an increase in tissue activities 8 days after ligation. 7. Serum activities of mitochondrial, plasma membrane, microsomal, lysosomal and cytosol marker enzymes tended to increase post-ligation, particularly at 8 days. 8. Monoamine oxidase, a predominantly mitochondrial enzyme, was greatly elevated in the serum after 1 day but had returned to normal activities by 8 days.

Acetylglucosaminidase↗