Biomedical subjects
Publications and source records attributed to D A Clarke.
This paper presents a detailed description of the construction of complete acrylic upper dentures reinforced with highly drawn linear polyethylene fibres. The work forms part of a continuing project to elucidate the properties and potential of the new system.
The results reported in this paper are part of a continuing study of the reinforcement of acrylic denture base resins with highly drawn linear polyethylene fibres. Water sorption is significantly reduced by incorporation of these fibres, even though the water diffusion processes as such remain broadly unaffected. Clinical trials are encouraging and the reinforced dentures have been well accepted by all the patients.
Rotavirus, a double-stranded RNA virus, has been implicated as a diarrhea-provoking agent in a variety of animal species. Several previous reports have shown that immunization with a single serotype may result in increased in vitro neutralization titers against serotypes not represented in the immunogen. This study was undertaken to determine whether antibody from cows immunized against simian rotavirus strain SA-11 (which is alien to pigs) could protect neonatal piglets from infection with a North Carolina isolate of porcine rotavirus. Accordingly, cows were immunized with SA-11 and an immunoglobulin G (IgG)-rich fraction was isolated from their colostrum. An IgG-rich fraction was similarly isolated from colostrum of nonimmunized cows. At equal concentrations, IgG from SA-11-immunized cows had two- to fourfold higher neutralization titers to seven of eight test strains of rotavirus, including SA-11 (serotype 3); human rotavirus serotypes 1, 3, and 4; North Carolina porcine rotavirus (serotype undetermined); Ohio State porcine rotavirus (serotype 5); and bovine rotavirus (serotype 6). The IgG-rich fractions were fed as dietary supplements to agammaglobulinemic piglets infected with the North Carolina porcine rotavirus. IgG from the SA-11-immunized cows was about eightfold more effective in protecting piglets than was IgG from nonimmunized cows.
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The pharmacokinetics of xamoterol, a beta-adrenoceptor partial agonist under clinical evaluation for the treatment of mild to moderate heart failure, have been studied in 12 healthy male subjects. They received 14 mg i.v. and oral doses of 50 and 200 mg as a tablet and 200 mg as a solution in a 4 way cross-over design. After i.v. dosing the elimination half-life was 7.7 h, the total body clearance was 224 ml.min-1 and the volume of distribution at steady-state (Vss) was 48 l. Sixty-two percent of the dose was recovered unchanged in urine. After oral doses, the absolute bioavailability of xamoterol was shown to be 5% irrespective of whether the dose was administered as a tablet or solution. Peak plasma concentrations occurred at about 2 h for the tablet dose and slightly earlier (1.4 h) for the solution. Peak plasma concentration, AUC and urinary recovery of unchanged drug increased in proportion to dose. The apparent elimination half-life after oral doses (16 h) was significantly longer than that observed after an intravenous dose. Despite the low bioavailability, the degree of inter-subject variability of oral bioavailability was small probably indicating that the controlling factor is the hydrophilic nature of the molecule rather than extensive first pass metabolism or poor dissolution of xamoterol from the tablet formulation.
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The rate of inactivation of metronidazole in vitro was determined during the course of time-kill curves against anaerobic and aerobic bacteria in the stationary phase of growth. Metronidazole at a concentration of 10 mug/ml, as measured by bioassay, was rapidly inactivated in broth culture by susceptible anaerobic bacteria (minimum bactericidal concentration </= 3 mug/ml), and this correlated closely with its bactericidal activity. In contrast, the drug was neither inactivated nor had any bactericidal activity against a resistant strain of Propionibacteriumacnes (minimum bactericidal concentration > 1,500 mug/ml). Three of four aerobic bacteria also inactivated metronidazole, although at generally slower rates than the anaerobes, but this was not associated with a bactericidal effect against these organisms. The presence of aerobic bacteria in mixed cultures with Bacteroides fragilis did not, moreover, inhibit the bactericidal activity of metronidazole against the latter organism. However, the possibility still remains that, in vivo, aerobic bacteria capable of inactivating metronidazole could inhibit the action of the drug against anaerobes in mixed infections.
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The mechanical and physical effects of the presence of nystatin in three denture liners were investigated. In general, the modified materials were softer, showed greater strain, and demonstrated permanent set under compression for the duration of the tests. However, the degree of change in properties appeared unlikely to lead to reduced clinical performance. The most significant change was a great increase in the equilibrium capacity for water in the case of the modified liners. This may enhance the pharmacologic effectiveness of these liners by encouraging the release of nystatin at the tissue surface. Bacteriologic and clinical studies continue to investigate the possibility that modified semipermanent liners (Coe-Supersoft) may reduce the recurrence of denture stomatitis.
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The mixed leukocyte reaction (MLR) responses of 29 patients with classic rheumatoid arthritis (RA) were compared with those of 24 age- and sex-matched healthy controls. Pools of stimulating cells were selected to include the major cross-reacting HL-A specificities. In pooled human serum the MLR response of the RA lymphocytes was significantly enhanced relative to the response controls (P less than 0.05). In autologous serum there was suppression of the MLR response in patients with RA which correlated with disease activity. The data suggest the presence of an intrinsically enhanced cellular reactivity of RA lymphocytes suppressed by serologic factor(s). The mechanisms of this enhancement of suppression are discussed.
The etched-metal, resin-bonded fixed partial denture has evolved rapidly from its origination as an extracoronal splint. Technologic advancements in both resin chemistry and retentive surface etching techniques have markedly improved the quality of the prosthesis. Today, resin-bonded fixed partial dentures are an effective, conservative means of replacing missing teeth when specific contra-indications--long spans, insufficient sound enamel, malocclusion, pathologic occlusal habits--are identified and avoided. A universally-accepted standard preparation does not exist for resin-bonded fixed partial dentures; rather, common principles of tooth reduction are agreed upon by most authors. This case report details necessary modifications in typical preparation and framework design that must be included to maintain a midline diastema when such spacing is required or preferred by the patient.