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Biomedical subjects

D F Williams

Publications and source records attributed to D F Williams.

At least 19 recordsLinked to original sources
PubMed1992

Recombinant basic fibroblast growth factor in red blood cell ghosts accelerates incisional wound healing.

The pharmacological manipulation of wound healing with locally applied growth factors is now a practical possibility. The effect of topical applications of recombinant basic fibroblast growth factor (bFGF) on the strength and cellularity of healing incisional rat skin wounds was investigated. Applications of bFGF in a simple vector (either a collagen suspension or saline) were not associated with any positive effects on wound breaking load at 7 days after injury in comparison with vector-treated control wounds; at the highest dose of 50 micrograms per wound, breaking loads were significantly decreased from a mean(s.e.m.) of 287(22) g/cm2 in controls to 201(23) g/cm2 (P < 0.005). Increasing doses of applied peptide were paralleled by increasing wound cellularity. Delay of bFGF release at the site of application was achieved by encapsulation into red blood cell ghosts. Wounds treated with bFGF in such ghosts were 50 per cent stronger than paired control wounds (388(27) versus 256(28) g/cm2, P < 0.002) 7 days after injury. Treated wounds were significantly more cellular at 4 days than paired control wounds. Topical applications of bFGF applied at the time of injury exert a positive effect on incisional wound strength only when a vector that delays release is used.

Administration, Topical↗
PubMed1992

Stimulation of neutrophil movement by metal ions.

The interaction between corrosion products of metallic implants and the surrounding tissue is important in determining the biocompatibility of the implant, in particular the interaction of corrosion products with inflammatory cells such as neutrophils and macrophages. Such cells are capable of releasing enzymes and high-energy oxygen radicals which can damage the tissue. Clearly, any factors that influence cell movement to the implant site could influence the biocompatibility of the implant. The present study examined the influence that copper and nickel ions had on neutrophil locomotion. Both copper and nickel ions stimulated a proportion of the neutrophil population to take up a nonspherical morphology and to locomote. These metal ion stimulated cells have higher circularity values and move slower than neutrophils incubated with FMLP. For both FMLP and nickel ion stimulated cells, there is a correlation between the speed of neutrophil locomotion and neutrophil circularity; as the neutrophil circularity value decreases, the speed of locomotion increases.

Biocompatible Materials↗
PubMed1992

Immune response in biocompatibility.

Biocompatibility is concerned with the interactions that occur between biomaterials and host tissues. As foreign objects in that host tissue these materials may initiate several types of response. It has often been postulated that the immune response, by which the host normally defends itself against invasion by foreign organisms, can be involved in the response to biomaterials. This review discusses the mechanisms by which this could occur and the evidence that suggests the immune response is indeed of significance in biocompatibility.

Animals↗
PubMed1992

Evaluation of soft tissue response to a poly(urethane urea).

Variations in the performance of vascular prostheses constructed of polyurethanes, and some evidence which suggested that these variations could be due not to the properties of the polymer itself, but to differences in the cellular response to the various microstructures of porous polyurethanes require investigation. Experiments were performed to evaluate quantitatively the extent of the cell behaviour adjacent to a series of polyurethane samples. It was shown that, with Biomer, a polyurethane urea, the profile of cell behaviour as a function of distance from the implant surface and of time following implantation, the response of cells in general and macrophages in particular, varied considerably with different internal microstructure. This supports the suggestion that the cellular response to different structures and susceptibility to degradation are related.

Animals↗
PubMed1992

Surgical management of subfoveal choroidal neovascularization.

BACKGROUND: Subfoveal choroidal neovascularization (CNV) usually is associated with a poor visual prognosis. Laser photocoagulation of certain subfoveal membranes secondary to age-related macular degeneration (ARMD) appears preferable to observation based on recent Macular Photocoagulation Study (MPS) findings but is associated with decreased vision. The authors explored the use of vitreoretinal surgical techniques as an alternative method of eradicating subfoveal CNV. METHODS: After vitrectomy, a small retinotomy technique was used to extract or disconnect from the choroidal circulation subfoveal CNV in 58 eyes. There were 33 eyes with ARMD, 20 eyes with presumed ocular histoplasmosis, and 5 eyes with miscellaneous etiologies. Five eyes also received subfoveal RPE patches. RESULTS: With limited follow-up, significant improvement in vision (defined as 2 Snellen lines) was achieved in 7 of 22 eyes with ARMD CNV removal (1 eye 20/20), 0 of 4 eyes with ARMD CNV removal and RPE patches, and 1 of 7 eyes with ARMD CNV disconnection. Significant improvement was achieved in 6 of 16 eyes with presumed ocular histoplasmosis removal and 0 of 4 eyes with presumed ocular histoplasmosis CNV disconnection. In 5 eyes with miscellaneous CNV, 2 improved (20/20 and 20/40). CNV recurred in 29%. CONCLUSIONS: Some patients with subfoveal CNV appear to benefit from surgical removal. Only rarely do eyes with ARMD improve. Longer-term follow-up and refined case selection are required before this approach can be widely recommended.

Aged↗
PubMed1992

Outcome and cost analysis of scheduled versus emergency scleral buckling surgery.

BACKGROUND: Retinal detachments are usually considered to be a surgical emergency. However, there are additional risks and costs for unnecessary emergency surgeries. The purpose of this study is to evaluate whether the conventional wisdom for treating all retinal detachments as emergencies needs to be re-examined. METHODS: Forty-eight patients who had an emergency scleral buckle and 89 patients who had a scheduled procedure were randomly selected from 884 consecutive patients who had a primary scleral buckling procedure during a 4 1/2-year period. The medical records of each patient were used to obtain detailed information related to prognosis. The visual acuity measurements of each patient, taken 6 months after the procedure, were obtained from the records of the ophthalmologist following the patient. Linear regression analysis was used to compare the final visual outcome for patients who had emergency surgery with patients who had scheduled surgery after taking into account patient factors related to prognosis. RESULTS: Patients selected for emergency surgery had better visual prognoses than scheduled patients but had the same risk of systemic complications and the same extent of detachment if the macula was not involved. None of the 18 patients with an attached macula experienced macular involvement while awaiting scheduled surgery. There were no differences between emergency and scheduled patients in ocular or systemic complications, rate of reattachment, rate of decreased visual acuity after surgery, visual outcome adjusted for prognosis, or, since 1985, length of hospital stay. A greater cost was incurred for the patients having emergency surgery due to difference in pay scales for support personnel. CONCLUSIONS: Because the study is not large and the patients were not randomized to treatment, the results are not definitive. However, they suggest that emergency surgery is unnecessary for many patients with a detached retina.

Appointments and Schedules↗
PubMed1991

Quantitative assessment of the tissue response to implanted biomaterials.

The tissue response to a small number of polymeric biomaterials was studied using monoclonal antibodies specific for certain inflammatory cell types, to develop a reliable and accurate method for the quantitative evaluation of biocompatibility. The sites of antibody binding were identified using an avidin-biotin staining procedure and the sections evaluated using a computer-aided image analysis system. The staining technique successfully demonstrated both polymorphonuclear leucocytes and macrophages in tissue samples containing polymeric biomaterials. The image analysis system facilitated the measurement of up to 30 cell-related parameters and allowed a large number of cells to be analysed.

Animals↗
PubMed1991

Neutrophil polarization and immunoelectrophoresis assays in the study of complement activation by biomaterials.

The neutrophil polarization assay, a technique used to measure chemotaxis, was adapted to examine complement activation. Complement activation in serum which had been incubated with metallic and polymeric biomaterials was examined using the neutrophil polarization assay and immunoelectrophoresis assay. In agreement with previous publications, nylon activated the complement cascade, but PTFE did not. The neutrophil polarization assay was found to be the most sensitive technique for examining complement activation by endotoxin but the immunoelectrophoresis assay is the technique most sensitive for detecting complement activation by cobalt powder. In both assays, complement activation was not detected in serum incubated with chromium powder. However, serum incubated with silver and nickel powder stimulated neutrophils to polarize indicating that these powders may activate complement.

Biocompatible Materials↗
PubMed1991

Relationship between chemotaxis and complement activation by ceramic biomaterials.

This paper examines the relationship between complement activation by ceramic biomaterials and chemotaxis. Complement activation was examined by both neutrophil polarization (a technique which has previously been used to examine chemotaxis) and immunoelectrophoresis assays. The results suggest that at increasing serum concentrations of both calcium hydrogen phosphate and coral (calcium carbonate) powder, the quantity of C3 activation increased, as did the quantity of serum-derived chemotactic factors. In the case of tricalcium phosphate powder, the quantity of C3 activation and the neutrophil polarization response to serum were similar for serum levels between 20 and 80 mg/ml. Complement C3 was not activated in serum incubated with calcium hydrogen phosphate powder and serum incubated with this material was not chemotactic for neutrophils.

Biocompatible Materials↗
PubMed1991

Vitrectomy for premacular fibroplasia. Prognostic factors, long-term follow-up, and time course of visual improvement.

Two hundred seventy eyes with premacular fibroplasia consecutively treated by pars plana vitrectomy and membrane peeling were reviewed. This study is among the largest series with long-term follow-up reported to date. Visual improvement of two or more lines was achieved in 43% of eyes at 6 to 12 months, in 54% at 1 to 2 years, in 60% at 2 to 3 years, and in 58% at 3 to 5 years. Overall, complications occurred in 34 eyes (13%). Cataract progression after vitrectomy was noted in 106 (57%) of phakic eyes at 3 to 5 years, and 43 of these eyes underwent subsequent cataract extraction. Mean time to best visual acuity after vitrectomy was slightly less than 1 year for all eyes unless they had cataract worsening with subsequent cataract extraction (1.9 years). Significant factors affecting visual outcome were: preoperative lens status, visual acuity before vitrectomy, duration of preoperative symptoms of distortion and/or blurred vision, and the occurrence of intraoperative complications.

Adolescent↗
PubMed1991

Red imported fire ant (Hymenoptera: Formicidae) control with a corn grit bait of fenoxycarb without soybean oil.

The standard fenoxycarb fire ant bait formulation (Logic), composed of pregel defatted corn grits and soybean oil toxicant, was modified by eliminating the soybean oil. This formulation without soybean oil contained greater than 2 times more fenoxycarb and was as effective as the standard bait formulation against laboratory colonies of red imported fire ant, Solenopsis invicta Buren. In field tests, the modified and standard baits were equally effective in controlling fire ants after 6, 12, and 18 wk. Individual worker ants obtained from plots treated with fenoxycarb baits without soybean oil had greater than 47 times less fenoxycarb than did workers from the plots treated with the standard fenoxycarb baits containing soybean oil.

Animals↗
PubMed1991

The mechanical and microscopic aspects of the deformation and fracture of a poly (ether urethane-urea) spun arterial prosthesis.

The mechanical properties of a microporous, electrostatically spun poly (ether urethane-urea), used in the construction of arterial prostheses, have been examined, with particular reference to anisotropic, crack initiation processes and preconditioning. The results demonstrate considerable anisotropy in relation to samples derived from circumferential and longitudinal directions of the tube wall structure related to the spinning process. There is also a considerable difference in crack initiation on inner and outer surface of the arterial wall, again related to the processing conditions. The results provide an important contribution to an understanding of structure-property relationships in microporous arterial prosthesis.

Biocompatible Materials↗
PubMed1991

Outcome and cost analysis of scheduled versus emergency scleral buckling surgery.

Conventional wisdom holds that a retinal detachment of recent onset should be regarded as a surgical emergency. A delay in surgery may result in an extension of detachment for patients with an attached macula and a worse visual outcome for patients with a detached macula. However, the potential disadvantages of performing surgery on an emergency basis must be weighed against the risks of delaying surgery; disadvantages include a greater frequency of operative complications resulting from fatigue factors among the operating personnel, an increased anesthetic risk due to inadequate time to assess and stabilize coexisting medical problems, and higher hospital costs. In this retrospective study covering 4 1/2 years, we compared the risks, benefits, length of hospitalization, and costs of scleral buckling surgery for retinal detachments performed as an emergency procedure or on the day following admission. After a 15% random selection from 884 consecutive operations, 48 emergency procedures were compared with 89 scheduled procedures. Patients selected for emergency surgery had better visual prognoses than scheduled patients. The potential for risk of systemic complications was not a reason for postponing surgery. None of the 18 patients with an attached macula experienced macular involvement while awaiting scheduled surgery. There were no differences between emergency and scheduled patients in ocular or systemic complications, rate of reattachment, rate of decreased visual acuity following surgery, visual outcome adjusted for prognosis, or, since 1985, length of hospital stay. Cost was greater for patients having emergency surgery, because of a difference in pay scales for support personnel.

Cost-Benefit Analysis↗
PubMed1990

Rebleeding in experimental traumatic hyphema treated with intraocular tissue plasminogen activator.

Tissue plasminogen activator has recently been shown to enhance the clearance of experimental nontraumatic hyphema in animals. However, hyphema in human eyes usually results from ocular trauma, and rebleeding is a serious complication. Hemorrhage is also a potential complication of fibrinolytic therapy. We assessed the incidence of rebleeding in an animal model of surgically induced traumatic hyphema after intracameral injection of tissue plasminogen activator (25 micrograms) or physiological saline. Eight eyes were each treated with tissue plasminogen activator or physiological saline at 10 minutes, 24 hours, 48 hours, or 72 hours after injury. Controls were 8 eyes with hyphema but no intracameral injection. No eyes treated with physiological saline (total, 32 eyes) or control eyes rebled. In contrast, the incidence of rebleeding from the injury site in eyes treated with tissue plasminogen activator was 88% (7/8) at 10 minutes, 75% (6/8) at 24 hours, 50% (4/8) at 48 hours, and 0% (0/8) at 72 hours after injury. Treatment of traumatic hyphema with tissue plasminogen activator prior to healing of damaged vascular endothelium may contribute to rebleeding.

Animals↗
PubMed1990

Clearance of experimental vitreous hemorrhage after panretinal cryotherapy is related to macrophage influx.

We investigated the effect of panretinal cryotherapy on blood clearance and on the inflammatory cellular response in rabbit eyes with experimental vitreous hemorrhage. Eyes treated with cryotherapy demonstrated less extensive vitreous opacity and more rapid clearance of blood than untreated eyes. The peak inflammatory cellular response measured by counts or radiolabeled cells in the optic nerve was 2.5 times greater in the cryotherapy-treated eyes. Panretinal cryotherapy may promote the clearance of vitreous hemorrhage by stimulating the influx of increased numbers of phagocytic inflammatory cells.

Animals↗