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Biomedical subjects

D G Smith

Publications and source records attributed to D G Smith.

At least 235 records · Page 13Linked to original sources
PubMed1989

Threaded cup acetabuloplasty. Early clinical experience.

Loosening of the acetabular cup component in total hip arthroplasty (THA) remains a source of ongoing concern. Threaded cup acetabuloplasty (TCA) utilizes torque and compression to gain purchase of the acetabular cup into the bony margin of the acetabulum. In an earlier study of 121 patients who had THA with TCA, patient assessments and roentgenograms were examined at an average of 30 months after surgery. Twenty percent of the cases were carried out for failed arthroplasty and 20% of the procedures required bone-graft reconstruction. A 22% incidence of moderate to severe postoperative pain, a 3% incidence of cup dislodgement, and a 24% incidence of radiolucencies between 1-2 mm were observed. The four cup dislodgements occurred in patients with severe osteopenia or in those requiring extensive bone-graft acetabular reconstruction. Good clinical results were obtained for osteoarthritic patients treated with primary THA. These early findings suggest that there is no advantage, but there are possible disadvantages, to threaded cup acetabuloplasty when compared to cup fixation with cement.

Acetabulum↗
PubMed1988

Chronic enterovirus infection in patients with postviral fatigue syndrome.

76 patients with the postviral fatigue syndrome (PVFS) and 30 matched controls were investigated. Virus isolation was attempted from concentrated faecal samples by direct culture and after acid dissociation of virus from antibody. Positive cultures of enteroviruses were obtained from 17 (22%) patients and 2 (7%) controls. An enterovirus-group-specific monoclonal antibody, 5-D8/1, directed against the VP1 polypeptide, was used to detect enteroviral antigen in the circulation, either free or complexed with antibody. VP1 antigen was detected in the serum of 44 (51%) of a further group of 87 PVFS patients. The number of patients positive for VP1 antigen was greater (42/44) when IgM complexes were detectable than when they were not (2/23). 1 year later, the 17 patients of the first group of 76 with positive cultures were again studied. The same virus was again isolated from 5 (29%), 13 (76%) had detectable IgM responses to enteroviruses, and 9 (53%) were positive for VP1 antigen in the serum. These results show that chronic infection with enteroviruses occurs in many PVFS patients and that detection of enterovirus antigen in the serum is a sensitive and satisfactory method for investigating infection in these patients.

Antibodies, Monoclonal↗
PubMed1988

A comparison of charges for continuous ambulatory peritoneal dialysis and center hemodialysis.

Use of continuous ambulatory peritoneal dialysis (CAPD) is increasing, and it is being promoted as a less expensive alternative to center hemodialysis (CHD). The debate over the relative charges for CAPD and CHD cannot generally be answered without considering the relationship between modality selection and patient characteristics. When selection and patient characteristics are accounted for, the difference between annual charges for CAPD and CHD patients is insignificant, in part because of the current payment system. The analysis suggests that patients using CHD may have lower charges than if they were using CAPD; similarly, patients using CAPD may have lower charges than if they were using CHD. Charges during CAPD training are lower than CHD or CAPD charges. Charges during the transition between CHD and CAPD tend to be higher than either CHD or CAPD due to additional hospitalizations. Estimated results suggest that encouraging current CHD patients to transfer to CAPD (or vice versa) may not have the desired effect of reducing charges.

Fees and Charges↗
PubMed1988

Effect of calcium channel blockers on theophylline disposition.

Twelve healthy subjects received a single oral dose of theophylline, 5 mg/kg alone, and after 7 days of oral verapamil, 120 mg every 8 hours, diltiazem, 90 mg every 8 hours, and nifedipine, 20 mg every 8 hours, in randomized crossover fashion. Mean theophylline oral clearance decreased 18% and 12% after verapamil and diltiazem, respectively (p less than 0.05). No significant change in theophylline oral clearance was observed after nifedipine. Increases in mean theophylline half-life were observed after verapamil (10.8 +/- 3.2 hours) and diltiazem (9.9 +/- 2.4 hours) (p less than 0.05) but not after nifedipine (8.6 +/- 2.4 hours) when compared with control (8.6 +/- 1.9 hours). Apparent volume of distribution was unchanged. Urinary excretion data showed that the relative formation rate constants of 3-methylxanthine and 1,3-dimethyluric acid were decreased during verapamil and diltiazem (p less than 0.05) but not during nifedipine. No change in 1-methyluric acid excretion was observed. Increases in urinary elimination of unchanged theophylline were observed after verapamil, diltiazem, and nifedipine. The modest reduction in theophylline clearance observed after verapamil and diltiazem is not likely to produce clinically significant increases in theophylline concentrations in most patients.

Adult↗
PubMed1988

Closed flexible intramedullary biopsy of metastatic carcinoma.

Closed flexible intramedullary biopsy was performed in 24 patients requiring surgical stabilization of 17 pathologic and ten impending pathologic fractures from metastatic carcinoma. The biopsy was positive for carcinoma in 25 of 27 cases and either confirmed the diagnosis of metastatic disease or revealed a carcinoma cell type of unknown origin. The technique of closed biopsy using an intramedullary flexible, large bore, plastic catheter in patients with metastatic carcinoma produced information comparable to other biopsy techniques.

Biopsy↗
PubMed1988

Mechanical disruption of human patellar cartilage by repetitive loading in vitro.

Plugs of cartilage and subchondral bone from patellae were subjected to cyclic compression consisting of rapid ramp loading for 0.3 seconds followed by a 2.7 second pause. At 1000 psi cyclic load, surface abrasion of the cartilage was noted at 250 cycles of compression. Primary fissures, which penetrated to the calcified cartilage, developed at 500 cycles. Secondary fissures, emanating from the primary fissures at 30 degrees-90 degrees angles, and penetrating to varying depths, were observed at 1000 cycles. Coalescence of fissures and undermining of cartilage fragments were noted at 8000 cycles. With greater loads, the same sequence of events occurred with fewer cycles except that primary fissures appeared before the surface was abraided. Fissure formation did not occur in specimens subjected to loads of 250 psi to 500 psi even if the superficial 100 micron of cartilage was removed and specimens were loaded for 120,860 cycles. The deeper layers of cartilage appear to be of prime importance in resisting fissure formation.

Biomechanical Phenomena↗
PubMed1988

Selection of patients for through-the-knee amputation.

Forty-six adult patients had a through-the-knee amputation (disarticulation of the knee) in a four-year period. Thirty-four of the patients had peripheral vascular insufficiency and were judged to lack the potential for using a prosthesis functionally, although the evaluation indicated that they had the potential for healing of the wound at the below-the-knee level of amputation. At a minimum follow-up of one year, the amputation wound had healed in thirty of these patients, and no joint contracture had developed. Two patients died in the first postoperative month, and two had failure to heal and needed revision to an above-the-knee amputation. The remaining twelve patients who had a through-the-knee amputation were judged to be potentially able to use a prosthesis functionally, but they did not have the capacity for wound-healing at the below-the-knee level. Therefore, in these patients, a through-the-knee amputation was performed as an alternative to an above-the-knee amputation. The amputation wound healed in eight of these patients, but four (33 per cent) had failure to heal and needed subsequent revision to an above-the-knee amputation. All twelve patients were able to use a prosthesis. The through-the-knee amputation provides good muscular balance and has a low risk for the late development of joint contracture. The residual limb (stump) provides an excellent surface area for sitting balance and a lever-arm for transfer. In a patient who has the potential to use a prosthesis functionally, the residual limb allows direct load-transfer (end weight-bearing).(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1987

Characterization of a novel reaction by human O6-alkylguanine-DNA alkyltransferase with 1,3-bis(2-chloroethyl)-1-nitrosourea-treated DNA.

The reaction of partially purified human O6-alkylguanine-DNA alkyltransferase with 1,3-bis(2-chloroethyl)-1-nitrosourea-treated DNA produces a covalent DNA-protein complex. Evidence that the complex-forming and the alkyltransferase activities are one and the same includes their copurification, identical heat inactivation kinetics, and similar responses to inhibitors. This novel reaction thus provides a sensitive alternative assay for detecting the alkyltransferase. It also provides support for a model in which N1,O6-ethanoguanine is an intermediate in formation of chloroethylnitrosourea-induced DNA interstrand cross-links.

Carmustine↗
PubMed1987

Formation of DNA interstrand cross-links by the novel chloroethylating agent 2-chloroethyl(methylsulfonyl)methanesulfonate: suppression by O6-alkylguanine-DNA alkyltransferase purified from human leukemic lymphoblasts.

The formation of DNA interstrand cross-links was compared in DNA treated with either 1,3-bis(2-chloroethyl)-1-nitrosourea or 2-chloroethyl(methylsulfonyl)methanesulfonate. DNA that was pulse treated briefly with either of these drugs continued to form cross-links at 37 degrees C for over 8 h after drug removal, indicating that such DNA contained stable precursors of cross-links. When human O6-alkylguanine-DNA alkyltransferase was added to the drug-treated DNA further cross-link formation was prevented at all points during this protracted time course, indicating that these stable cross-link precursors also remained substrates for this repair enzyme. Although the pattern of 2-chloroethyl(methylsulfonyl)methanesulfonate-induced cross-link formation and susceptibility to suppression by O6-alkylguanine-DNA alkyltransferase resembled that for 1,3-bis(2-chloroethyl)-1-nitrosourea, quantitative differences in the rates of cross-link formation and in the amounts of O6-alkylguanine-DNA alkyltransferase required to suppress cross-link formation suggest that critical differences exist between these agents.

Carmustine↗
PubMed1987

Evidence that O6-alkylguanine-DNA alkyltransferase becomes covalently bound to DNA containing 1,3-bis(2-chloroethyl)-1-nitrosourea-induced precursors of interstrand cross-links.

The reaction of partially purified human O6-alkylguanine-DNA alkyltransferase with 1,3-bis(2-chloroethyl)-1-nitrosourea-treated DNA resulted in formation of a DNA-protein covalent complex. Complex formation required active alkyltransferase and brief treatment of DNA with the drug. DNA lost its capacity to form the complex once drug-induced DNA interstrand cross-links were completely formed. These results are consistent with a model in which the transferase catalyzes cleavage at O6-guanine and transfer of the alkyl moiety in a putative O6, N1-ethanoguanine intermediate of cross-link formation. DNA-protein complex formation presumably results when the transferase accepts the N1-ethanoguanine-DNA structure, analogous to its acceptance of simple alkyl groups.

Carmustine↗
PubMed1987

Mate choice by lineage in three captive groups of rhesus macaques (Macaca mulatta).

The hypothesis that the matrilineal affiliation of 410 infants born in three captive groups of rhesus macaques is independent of the patrilineal affiliation of these infants was tested. Preferential mating with particular patrilines was observed for matrilineal members. We conclude that lineage affiliation does influence mate choice of rhesus macaques, at least when a large number of matrilines and relatively few patrilines which include natal males are represented in the group. Such nonrandom mating might explain high levels of genetic heterogeneity reported among matrilines within rhesus groups, despite high rates of male emigration, and is consistent with the maintenance of high levels of within-matriline kinship which might promote cooperative behavior among matriline members.

Animals↗
PubMed1987

Impact of multiple comparisons in randomized clinical trials.

The randomized clinical trial is the preferred research design for evaluating competing diagnostic and therapeutic alternatives, but confidence in the conclusions from a randomized clinical trial depends on the authors' attention to acknowledged methodologic and statistical standards. This survey assessed the level of attention to the problem of multiple comparisons in the analyses of contemporary randomized clinical trials. Of the 67 trials surveyed, 66 (99 percent) performed multiple comparisons with a mean of 30 therapeutic comparisons per trial. When criteria for statistical impairment were applied, 50 trials (75 percent) had the statistical significance of at least one comparison impaired by the problem of multiple comparisons, and 15 (22 percent) had the statistical significance of all comparisons impaired by the problem of multiple comparisons. Although some statistical techniques are available, there still exists a great need for future work to clarify further the problem of multiple comparisons and determine how the impact of this problem can best be minimized in subsequent research.

Clinical Trials as Topic↗
PubMed1987

Repair of severe muscle belly lacerations using a tendon graft.

Fourteen patients with 58 severe forearm muscle belly lacerations had muscle repair using tendon grafts. At mean follow-up of 14 months, results of manual muscle testing (N = 58) were: grade 5, 42%, grade 4, 14%, grade 3, 9%, grade 2, 9%, grade 1, 12%, and grade 0, 15%. Mean grip strength of the injured extremity, in pounds per square inch, was 33.5 compared with 83.4 on the noninjured side. Tendon excursion and joint mobility were maintained, and there were no postoperative complications. Tendon grafting of severe muscle lacerations is an effective method to overcome extensive defects.

Adolescent↗