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Biomedical subjects

D F Williams

Publications and source records attributed to D F Williams.

At least 127 records · Page 7Linked to original sources
PubMed1988

Results and prognostic factors in penetrating ocular injuries with retained intraocular foreign bodies.

Of 105 eyes with ocular injuries involving retained intraocular foreign bodies, 63 (60%) had a final visual acuity of 20/40 or better; 20 (19%) were 20/50 to 5/200; and 15 (14%) were worse than 5/200. Six eyes (6%) were enucleated. The extent of visual recovery was limited in selected cases by the characteristics of the initial injury. Multivariate analysis was used to identify prognostic factors. Predictive of a good visual outcome (greater than or equal to 20/40) were: (1) initial visual acuity better than 20/40 and (2) the need for only one or two operations in the treatment of the injury. Predictive of a poor visual outcome (less than 5/200) were: (1) initial visual acuity worse than 5/200 and (2) a wound 4 mm or longer in length, independent of wound location. The visual outcome in this series of patients was compared with other large series of intraocular foreign bodies reported before the development of vitreous microsurgical techniques. The percentage of patients with a visual outcome of 20/40 or better has remained the same, whereas the incidence of enucleation has diminished.

Adolescent↗
PubMed1988

Validation of the exchange assay for the measurement of androgen receptors in human and dog prostates.

This study describes an exchange assay for measurement of cytosolic and nuclear androgen receptors (AR) in human and dog prostates. Efficient replacement of endogenously bound ligand from the receptor with [3H] mibolerone was achieved by incubation of cytosolic or nuclear fractions at 0 degree C for 72 h in the presence of 0.15M NaSCN and 15% sucrose. It was demonstrated that in the presence of the chaotropic salt rapid steroid dissociation took place at 0 degree C followed by [3H] mibolerone binding; sucrose protected the AR from denaturation by NaSCN. Combination of these two reagents, therefore, allowed quantitative androgen exchange at 0 degrees C. Receptors determined by this exchange procedure are specific for androgens, of high affinity (KD 2-5 nM), and sedimented on sucrose gradients as 4-4.6S entities. Use of [3H] mibolerone minimized interference from plasma proteins and reduced nonspecific binding. This exchange assay has now been applied to quantitation of cytosolic and nuclear AR in small tissue samples (50 mg). Thus it is possible to measure AR in tissue samples obtained by needle biopsies and attempt to correlate receptor values to clinical response of prostatic cancer patients.

Animals↗
PubMed1987

Evulsion of the retina associated with optic nerve evulsion.

We examined two patients with optic nerve evulsion as well as nasal peripapillary retinal and retinal pigment epithelial evulsion after ocular trauma. Fluorescein angiography demonstrated an intact peripapillary choriocapillaris, loss of peripapillary retina and retinal pigment epithelium, and complete disruption of retinal perfusion. We have postulated a mechanism for traumatic peripapillary retinal evulsion involving severe anterior displacement and abduction of the globe that may explain how the disruptive force was transmitted to the nasal retinal nerve fiber layer. We have provided a clinical correlation with magnetic resonance imaging of the optic nerve and globe of a normal individual.

Adult↗
PubMed1987

Intraocular Echinococcus multilocularis.

Alveolar hydatid disease, caused by the organism Echinococcus multilocularis, is a potentially lethal helminthic infection. After initial hepatic infestation, the organism may spread locally and hematogenously to distant sites. Death occurs secondary to hepatic failure, local extension into vital structures, or metastasis to the brain or lungs. A 67-year-old male Alaskan Eskimo developed decreased visual acuity secondary to a choroidal mass in the right eye eight years after an initial diagnosis of alveolar hydatid disease and four years before the development of symptomatic cerebral metastasis. A pathologic examination disclosed characteristic parasitic membranes involving the posterior pole of the right eye. To our knowledge, this is the first report of ocular involvement in alveolar hydatid disease.

Aged↗
PubMed1987

The enzymatic degradation of polymers in vitro.

Specimens of 14C-labeled poly(ethylene terephthalate), nylon 66, and poly(methyl methacrylate) have been synthesized and exposed, in vitro, to a number of enzyme solutions. Poly(ethylene terephthalate) was found to be affected by esterase and papain, although in different ways, but not by trypsin or chymotrypsin. Nylon 66 was unaffected by esterase but degraded by the other three. Poly(methyl methacrylate) was not affected by any of these enzymes. This indicates that some nominally stable polymers are susceptible to degradation by enzymes under some circumstances. The amount of degradation is small, but could have significant sequelae should it be reproduced in vivo.

Chymotrypsin↗
PubMed1987

On the biodegradation of poly-beta-hydroxybutyrate (PHB) homopolymer and poly-beta-hydroxybutyrate-hydroxyvalerate copolymers.

The known biodegradability of PHB in certain biological environments has led to its proposed use as a 'biodegradable' implant material. Monofilaments of PHB homopolymer and two PHV-PHB copolymers have been studied in vivo and in vitro and assessed for changes in mechanical properties and topography. In vivo biodegradation was only observed with PHB when pre-degraded by 10.0 Mrad of gamma-irradiation before implantation. High temperature in vitro hydrolysis suggested that PHV copolymer additions retarded the rate of degradation of PHB. Hydration reactions had most effect on the ultimate tensile properties of the materials. In contrast, the elastic properties appeared to be relatively unaffected.

Animals↗
PubMed1987

The effect of environmental aging on the fracture toughness of dental composites.

The effect of aging four commercially-available dental composites in water or ethanol at 37 degrees C for periods of up to 28 days was assessed by measuring changes in the materials' plane-strain fracture toughness (KIC). The results, obtained by means of a mini Short Rod Fracture Toughness Test specimen design, suggest that while water aging does not produce significant changes in KIC, aging in ethanol does cause significant increases in fracture toughness for three of the four dental composites studied. In view of previously-reported loss of wear resistance for dental composites aged in ethanol solutions, the present study emphasizes the difficulties in using fracture toughness to predict wear properties.

Air↗
PubMed1985

Protein absorption and desorption phenomena on clean metal surfaces.

The noncompetitive adsorption of the proteins albumin and fibrinogen onto 17 different metal surfaces has been studied in vitro using 125I-labeled proteins. Although many of the metals showed very similar adsorption characteristics to polymers, several of them adsorbed considerably greater amounts. Copper, gold, and silver were the most significant in this respect, all three being face-centered cubic, group 1B metals known to bind to many types of protein in vitro and in vivo. The desorption of the proteins was studied in an in vivo model in which preproteinized metals were implanted in rats. There was considerable variations in the amounts of the proteins removed from the various metal surfaces. Generally those metals onto which protein is most readily adsorbed tend to lose the protein quickly, whereas others, such as iron, with only moderate adsorbed amounts, may retain a large part of the adsorbed layer for a long time.

Adsorption↗
PubMed1985

Changes in the sedimentation properties of cytosolic androgen receptors associated with activation in vitro and in vivo.

In cell-free systems androgen receptor (AR) labeled with (3H)DHT at 0 degrees C in the presence of 50mM molybdate remains unactivated (less than 3% binding to nuclei) and untransformed (7-8S on sucrose density gradients containing 0.4M KCl and 50mM molybdate). In the absence of molybdate, however, these complexes undergo activation and transformation even at 0 degrees C, albeit, very slowly. Incubation of unactivated, untransformed AR complexes at 18 degrees C, or at 0 degrees C in the presence of 0.4M KCl, greatly accelerated both activation and transformation. Activation and transformation are also associated with formation of high affinity (3H)DHT-receptor complexes as indicated by decreased rates of (3H)DHT dissociation from the receptor. Cytosolic AR complexes labeled with (3H)DHT in tissue slices at 37 degrees C, or in vivo, undergo rapid activation, transformation and nuclear translocation. The data suggest that activation and transformation of cytosolic AR in cell-free systems is associated with changes in the physicochemical properties of AR similar to those occurring upon hormone binding in intact cells and in vivo.

Animals↗