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Biomedical subjects

R L Williams

Publications and source records attributed to R L Williams.

At least 127 records · Page 7Linked to original sources
PubMed1996

In-vitro corrosion and wear of titanium alloys in the biological environment.

Cyclic anodic polarization studies were undertaken for several titanium alloys of varying composition and phase structures. All materials were exposed to an accelerated corrosion test using a potentiostat and their electrochemical behaviour was analysed within a potential range of 0 to 5000 mV. The electrolyte used was a phosphate buffered saline (PBS) solution at pH = 5, 7.4 and 9. The polarization curves obtained represented both the passive and active regions of the materials and these curves were used to compare the resistance to pitting corrosion of each material. The sliding-wear of these materials was studied in both non-corrosive and corrosive environments. A simple pin-on-disc type wear apparatus was designed and built to simulate the co-joint action of corrosion and sliding-wear. Using this apparatus, it was also possible to evaluate the effect of wear-accelerated corrosion, which was also evaluated by wearing the surface of the specimens prior to corrosion. It was evident that the mixed phase alpha-beta alloys (Ti-6AI-4V and Ti-6AI-7Nb) possessed the best combination of both corrosion and wear resistance, although commercially pure titanium and the near-beta (Ti-13Nb-13Zr) and beta (Ti-15Mo) alloys displayed the best corrosion resistant properties.

Alloys↗
PubMed1996

Excision of the distal ulna in rheumatoid arthritis. Is the price too high?

Patients with rheumatoid arthritis who underwent excision of the distal ulna were reviewed and the operated wrist was compared with the non-operated side in the 40 patients who had the procedure performed unilaterally. Radiological assessment showed that the radiocapitate measurement of carpal translocation was the most consistent and that excision of the distal ulna was not associated with statistically significant collapse, ulnar translocation or radial rotation of the carpus. 61% of wrists spontaneously developed a radial shelf or limited radiocarpal fusion following excision of the distal ulna, compared to 21% of non-operated wrists. However, there was no statistically significant difference in carpal collapse or ulnar translocation between these two groups.

Adult↗
PubMed1996

Absorption rate vs. exposure: which is more useful for bioequivalence testing?

PURPOSE: The goals were to evaluate the usefulness of Cmax/AUClqc, ratio of the maximum plasma drug concentration to the area under the plasma concentration-time curve to the time of the last quantifiable concentration, in bioequivalence testing and to explore the use of exposure as a replacement for the concepts of rate and extent of drug absorption. METHODS: The bioequivalence of products differing in both rate (ka) and extent (F) of absorption was assessed under conditions similar to those encountered in a typical trial. A one-compartment model drug with first-order absorption (rate constant = ka) and eliminations was used. Variability was introduced in all model parameters using Monte Carlo techniques. The results were expressed in terms of the probability of declaring bioequivalence in a cross-over trial with 24 subjects using Cmax/AUClqc, AUClqc, and Cmax as bioequivalence measures. RESULTS: The outcome of a bioequivalence trial was shown to depend on the measure. Cmax/AUClqc reflected changes in ka, but not in F. AUClqc showed dependence on F, but virtually no dependence on ka. For Cmax, a 3- to 4-fold increase in ka and a concomittant 20% decrease in F, as well as corresponding changes in the opposite directions, resulted in bioequivalent outcomes. CONCLUSIONS: It was concluded that use of Cmax/AUClqc should be discouraged and that defining bioequivalence in terms of rate and extent of absorption has major problems. The goal of bioequivalence trials should be to assure that the shape of the concentration-time curve of the test product is sufficiently similar to that of the reference product. To this end, the use of "exposure" rather than "rate and extent of absorption" concepts is encouraged.

Absorption↗
PubMed1996

C2 domain conformational changes in phospholipase C-delta 1.

The structure of the PH-domain truncated core of rat phosphoinositide-specific phospholipase C-delta 1 has been determined at 2.4 A resolution and compared to the structure previously determined in a different crystal form. The stereochemical relationship between the EF, catalytic, and C2 domains is essentially identical. The Ca2+ analogue Sm3+ binds at two sites between the jaws of the C2 domain. Sm3+ binding ejects three lysine residues which bridge the gap between the jaws and occupy the Ca2+ site in the apoenzyme, triggering a conformational change in the jaws. The distal sections of the C2 jaws move apart, opening the mouth by 9 A and creating a gap large enough to bind a phospholipid headgroup.

Animals↗
PubMed1996

Selection of key community descriptors for community-orientated primary care.

BACKGROUND: Community-oriented primary care (COPC) requires the development of practical tools if it is to be carried out. A previous study demonstrated a practical approach to carrying out one portion of a community assessment for COPC using a few representative health indicators. OBJECTIVE: To determine the validity of this process elsewhere, we tested whether these findings were generalizable to other settings and to the same setting a decade later. METHOD: In a cross-sectional study design, data on 18 health indicators were collected for census tracts in two target areas and for the entire state of Ohio, USA, for 1990. A factor analysis was performed to identify factors underlying the health indicators in the three areas examined. RESULTS: Two underlying factors, termed age and poverty, were present in all locations and over time. Each factor was defined by core indicators and a cluster of associated indicators. CONCLUSIONS: These results suggest that one part of a COPC community assessment can be done by selecting very few indicators. The distribution of indicators of age and income explains the variability of most of the health related indicators studied. These factors are stable over time and location. A community assessment should include indicators which, at a minimum, provide information on these two factors.

Adolescent↗
PubMed1996

Specific killing of lymphoma cells by cytotoxic T-cells mediated by a bispecific diabody.

Antibody fragments produced by bacterial fermentation lack natural effector functions. Bispecific antibody fragments, however, can be endowed with effector functions, for example cell-mediated killing, by binding to and retargeting of cytotoxic cells. Diabodies are a class of engineered antibody fragments with two antigen binding sites, consisting of two associated chains; each chain consists of heavy and light chain variable domains linked by a short polypeptide linker. In contrast to IgG, or other antibody fragments in which the two binding sites can take up a range of orientations and spacings, the diabody structure is more rigid and compact, with the two binding sites separated by 65 łA (less than half the distance in IgG). To establish whether diabodies could also be used in cell-mediated killing, we have explored the use of a bispecific diabody binding to an idiotypic marker on mouse B-cell lymphoma (BCL-1) and to mouse CD3. The bispecific diabody activated naive T-cells and also mediated the specific killing of the lymphoma cells by cytotoxic T-cells. The diabody was less active in T-cell activation but 10-fold more active (w/v) in killing than an analogous bispecific IgG.

Animals↗
PubMed1996

Office laboratory procedures, office economics, patient and parent education, and urinary tract infection.

This review updates our readers on four important areas of office practice: office laboratory procedures, office economics, patient and parent education, and urinary tract infection. Michael Aldous reviews the recent literature on office laboratory procedures, which includes a report on the ongoing heated discussion of the Clinical Laboratory Improvement Amendments, an update of recent studies on new and better rapid streptococcal tests, and improved methods for urinalysis. Rickey Williams provides a report on office economics that includes a discussion of the effects of capitation, how preventive care can be cost effective, and the future prospects for greatly expanded office computerization. Burris Duncan discusses patient and parent education with an in-depth review of the potential economic value of a full implementation of the American Academy of Pediatrics' The Injury Prevention Program, and in addition he chronicles the rapid growth and development of school-based health centers. John Ey reviews the recent literature on urinary tract infections in children, including how we can make the diagnosis, methods for preventing recurrent urinary tract infections, the most effective studies for evaluating the urinary system, and what follow-up is necessary. We hope this review will provide the pediatrician with important information to help in the care of their patients.

Adolescent↗
PubMed1996

Ewing's sarcoma of the skull in an infant. A case report and review.

A 1-year-old female infant presented with a large 7-8 cm Ewing's sarcoma of the left parietal calvarium. It deeply indented the subjacent hemisphere. Wide surgical excision was followed by chemotherapy but not radiation. The patient was clinically free of tumor when she expired 9 months later of sepsis. Though primary Ewing's sarcoma of the skull is said to be relatively rare, we have tabulated 37 cases of this disorder, including the present one (we excluded mandibular tumors (> 100 cases) since they are not usually treated by neurosurgeons). The mean age was 11 years and of those available to follow-up, three quarters were tumor-free 6 months to 7 years postsurgery. The remainder survived an average of 21 months. Ewing's tumors of the calvarium generally grant a favorable prognosis following surgery and/or radiation and chemotherapy. Those at the base of the brain may be more difficult to eradicate. In addition to primary Ewing's tumors, metastases to the skull and the brain from other primary sources in the skeleton have been documented in several reports.

Chemotherapy, Adjuvant↗
PubMed1996

Use of assisted reading to increase correct reading rates and decrease error rates of students with learning disabilities.

The effects of assisted reading on 3 elementary students with learning disabilities were evaluated using a multiple baseline design. Data were collected from the students' oral reading from their basal texts. The results indicated an increase in number of words read correctly as well as a decrease in the number of words read incorrectly when assisted reading was used in the classroom.

Behavior Therapy↗
PubMed1996

Academic achievement of successful candidates for tenure and promotion to associate professor.

BACKGROUND AND OBJECTIVES: For faculty to achieve promotion and tenure, a clear understanding is needed of the measures by which performance will be judged. This study describes the specific academic achievements of successful candidates for tenure and promotion to associate professor in family medicine. METHODS: A survey questionnaire was mailed to all members listed in the Society of Teachers of Family Medicine database as holding the rank of associate professor. The questionnaire sought information about items as they were at the time the individual was being considered for promotion to associate professor with tenure. The items included scholarly accomplishments, time for research, areas of scholarly expertise, and departmental policy regarding promotion and tenure. RESULTS: Of the 296 eligible faculty, 197 (67%) returned a completed survey. The mean number of publications of these successfully promoted individuals was 10. The respondents averaged 78% of their publications in peer-reviewed journals and were first author on 64% of their peer-reviewed articles. The mean number of peer-reviewed publications per year was 1.5. Research grant support as principal or coinvestigator was reported by 44%, and respondents averaged 9 hours a week on scholarly activities. Scholarly activity was found to vary significantly by type of school, degree, and tenure track status. CONCLUSIONS: Information reported here can be of value for prospective promotion and tenure candidates, their advisors, and members of review committees.

Achievement↗
PubMed1996

Impact of MRI on a knee arthroscopy waiting list.

As part of a waiting list initiative, magnetic resonance imaging (MRI) scans were arranged for 69 patients waiting for knee arthroscopy. All patients had a clinical diagnosis of a meniscal tear. With 11 non-attenders, 58 scans were performed. Of the patients scanned, 35 had demonstrable meniscal tears, and five patients had other pathology on their scans. All patients were reviewed clinically after their scans, and 24 patients were removed from the waiting list. After a further 9 months, only one of the 24 patients removed had been re-listed for therapeutic arthroscopy. This initiative proved a cost-effective method of reducing waiting times for knee arthroscopy.

Arthroscopy↗
PubMed1996

Value of intraoperative image intensifier prints in trauma surgery.

We have studied the use of image intensification in a trauma theatre over a period of 6 months with particular reference to the acquisition of intraoperative image intensifier thermal prints instead of formal radiographs. The quality of the prints and the savings generated have been assessed. During the study period, 476 patients underwent orthopaedic trauma procedures. The image intensifier was used for intraoperative screening in 280 patients. In 278 of these a thermal print was obtained. This was used, instead of formal check radiographs, to plan further management in 210 patients (75%). In 68 patients, the printout was insufficient in its coverage of the operated area, and a check radiograph was also obtained. In no case did the clarity of the thermal image hinder accurate interpretation. We believe that thermal images are a useful substitute for formal postoperative radiographs in many trauma cases, and that, with notable exceptions, their use could decrease costs, reduce patient discomfort and radiation dose and spare overloaded radiology services.

Bone and Bones↗
PubMed1995

Phospholipase C delta 1 requires a pleckstrin homology domain for interaction with the plasma membrane.

The structural requirements of phospholipase C delta 1 for interaction with the plasma membrane were analysed by immunofluorescence after microinjection into living cells. Microinjection of deletion mutants revealed that the region required for membrane attachment and binding of inositol 1,4,5-trisphosphate in vitro corresponded to the pleckstrin homology domain, a structural module described in more than 90 proteins.

3T3 Cells↗