Biomedical subjects
D W Jones
Publications and source records attributed to D W Jones.
Cyclosporine treatment for intractable polymyositis.
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X-ray refinement of the crystal and molecular structure of 1,12-dimethylbenz[a]anthracene.
The molecular and crystal structure of 1,12-dimethylbenz[a]anthracene, one of the least carcinogenic of the benz[a]anthracenes, has been refined, from new X-ray diffractometric data collected at room temperature, to an R index 0.047 over 1217 independent reflections. Improved determination of molecular geometry shows that steric strain arising from the presence of two bay-methyl substituents causes even greater molecular distortion than in the highly carcinogenic 7,12-dimethylbenz[a]anthracene, with the benzo A ring inclined at about 29 degrees to the furthest C and D rings. Methyl carbon atoms are displaced 1.0 and 1.3 A on opposite sides of the mean molecular plane and the beach bond of the bay region is 1.480(4) A long, flanked by C-C-C angles of 124.3 and 125.0 degrees. The shortest carbon-carbon bond is C5-C6 = 1.327(5) A at the K region, with the next shortest C8-C9 = 1.346(6) A. Close intramolecular approaches of methyl hydrogens across the bay and to nearest aromatic hydrogens are 2.3-2.6 A.
Institutional care utilization by the elderly: a critical review.
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Renal abnormalities in ankylosing spondylitis.
The incidence of renal abnormalities is increased in patients with ankylosing spondylitis (AS). Possible mechanisms include the effects of nonsteroidal anti-inflammatory drugs (NSAIDs), an increased incidence of glomerulonephritis and the deposition of amyloid. We assessed renal function in 51 patients with AS randomly selected from those attending routine rheumatology clinics. Five patients were found to have a definite renal abnormality and three of them underwent renal biopsy. These showed one case each of IgA glomerulonephritis, focal segmental glomerulosclerosis and nonspecific tubulo-interstitial damage. A sixth patient had recurrent haematuria and borderline renal functional impairment but refused further investigation. The urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) was elevated in four patients; two had other biochemical evidence of renal damage while the other two patients appeared normal, although they had both received spinal irradiation in the past. The finding of a significant renal abnormality in 10% of AS patients suggests that evidence of renal involvement should be actively sought in this disease.
Chronic knee effusion and aspiration: the effect on quadriceps inhibition.
Inhibition of the non-weight-bearing quadriceps was studied in ten patients with chronic knee effusions. The muscles were tested with the knees both flexed and extended, before and after joint aspiration. More inhibition was seen when the knees were extended (p less than 0.005). There was no relationship between muscle inhibition and the size of effusion, pain experienced during contraction or the extent of weakness. Aspiration of joints did not reduce the amount of inhibition. Acute effusions have previously been shown to cause muscle inhibition, even when pain-free, and we suggest that the known changes in the compliance of chronically effused joints are responsible for the observed differences in the effect of acute and chronic effusions.
Evaluation of a new elastomeric impression material.
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Conformational changes in von Willebrand's factor protein: effects on the binding of factor VIII-coagulant.
The effects of conformational changes in purified canine von Willebrand's factor (VWF) were investigated to explore the relationship between its factor VIII-related antigen (VIII:AG) and ristocetin cofactor (RCoF) properties and the factor VIII-coagulant (VIII:C) binding site(s). Binding of VIII:C from canine von Willebrand's disease (VWD) plasma by VWF was used to measure the combining reaction of these proteins. The VWF was denatured to varying degrees by exposure to temperature and pH extremes, low ionic strength, and 6 M urea. Various treatments resulted in three types of change: elimination of RCoF, VIIIR:Ag, and VIII:C binding, removal of RCoF activity alone; or elimination of RCoF and retarded elution of VIII:Ag and VIII:C. As long as VIIIR:Ag reactivity was maintained, binding of VIII:C could be demonstrated; but in the absence of VIIIR:Ag, neither RCoF activity nor VIII:C binding remained. These results suggest that VIII:C binding and RCoF sites are separate on VWF and that interaction between VIII:C and VWF is possible even after significant structural changes occur in VWF. Furthermore, RCoF is more vulnerable to denaturation than the antigenic site. The spectrum of conformational changes that affect the properties of VWF may parallel the various recognized subtypes of VWD.
Fracture resistance of teeth with resin-bonded restorations.
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Molecular structure of 1,8-dimethylfluoren-9-one.
The molecular and crystal structure of the synthetic 1,8-dimethyl derivative of 9H-fluoren-9-one (F-9-one) has been determined by direct methods from X-ray diffractometric data and refined to an R index of 0.035 over 1216 independent reflections. With a mutual inclination between benzene rings of 178.6 degrees, the molecule is closely planar; of the non-hydrogen atoms, only the oxygen is as much as 0.08 A out of the plane defined by the ring-joining carbons C(10), C(11), C(12) and C(13). Neither the carbonyl bond nor the beach bond C(11)-C(12) differs significantly from the corresponding bonds in F-9-one and the 2,7-diamino compound; C-C bonds involving methyl carbons and the keto carbon are all very close to 1.50 A long (e.s.d. 0.003 A). The C-C(methyl) bonds are bent so that angles C(10)-C(1)-C(14) and C(13)-C(8)-C(15) are about 123 degrees, while the methyl groups are orientated with one hydrogen from each pointing away from the carbonyl group.
Influence of plasticizer on soft polymer gelation.
An evaluation has been made of the soft polymer gel systems of the type used as prosthodontic short-term denture-lining materials. The purpose of the study was to determine the effect upon gel strength and gelation time produced by variations in the composition of the plasticizer liquids. Poly(ethylmethacrylate) co-polymers were mixed with combinations of ethyl alcohol and the esters dibutyl phthalate (DBP), butylphthalyl butylglycolate (BPBG), and benzyl salicylate (BS). The relative rate of gelation of plasticizer polymer compositions was obtained by means of a reciprocating rheometer. The gelation rate was found to increase rapidly with an increase in the ethyl alcohol content. Significantly shorter gelation times were also found with liquids containing the lower-molecular-weight esters. A linear relationship was found between the ethyl alcohol content and the log of the gelation time. The higher-molecular-weight esters produced the strongest gel. A linear relationship was found between the gelation (log) times and the seven-day puncture strength. The ratio of polymer to plasticizer liquid was found to have a very significant influence upon the puncture strength and gelation time. Molecular weight or molecular volume of the ester plasticizers was found to have a greater influence on gel formation than the cohesive energy parameter. The strong polar bonding of ethyl alcohol was found to have a significant influence on both the rate of gel formation and the subsequent gel strength. The data indicate that controlled variations in the characteristics of plasticity and gel strength of dental soft polymer systems can be made to suit different clinical prosthodontic requirements.
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Labetalol analysis with the TOXI-LAB. A Drug-Detection system.
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The response of dental amalgam to dynamic loading.
A conventional (gamma 2-containing) dental amalgam was fatigue-tested at 1800 and 80 cycles/min, employing uni-axial, sinusoidal loading, with R = -8. Compressive, tensile, and creep tests were conducted to characterize the alloy's static mechanical behavior. Tests were performed at 37 degrees C on specimens which were aged for seven days, at 37 degrees C. Fatigue-tested specimens were microscopically examined for fracture surface appearance and crack path. The amalgam demonstrated a frequency dependence and a significant reduction in fracture strength due to fatigue loading. The fatigue crack path was primarily intergranular in the gamma 1 phase and inclined at approximately 45 degrees to the principal stress axis. These observations are characteristic of some metals when subjected to low-frequency, elevated temperature testing where significant grain boundary sliding occurs, and therefore suggest a creep-fatigue interaction for this alloy.
In vitro crevice corrosion behavior of implant materials.
The crevice corrosion susceptibility of cold-worked Type 316LVM stainless steel, cast Co-Cr-Mo, wrought Co-Cr-W-Ni, non-nitrided and nitrided Ti-6Al-4V ELI, and c.p. Ti, Grades 1 and 4, was studied in vitro by means of a crevice cell. Occlusion was created by interfacing a disc specimen and a Teflon bar. Specimens were mechanically prepared through 2-4 micron Al2O3 and passivated in 30% HNO3, followed by steam sterilization. Tests were performed in a deaerated Ringer's solution, maintained at pH = 7 and 37 degrees C. Anodic polarization was conducted potentiostatically at pre-selected levels, and resultant currents were monitored: stainless steel, 50 and 100 mV (S.C.E.), 450 min; non-stainless materials, 600 mV, 1000 min. Results for the stainless steel demonstrated that a HNO3 passivation treatment reduced its crevice corrosion susceptibility. For the non-stainless steel materials, no crevice corrosion susceptibility was observed, although a dulling and discoloration of c.p. Ti was evident. Recognizing that 600 mV is in excess of the O2 reduction potential in vivo, it was concluded that, in the absence of fretting, implants of these non-stainless steel materials would not experience significant corrosion loss under crevice conditions.
Shapes of benz[a]anthracenes: the crystal and molecular structure of 2-methylbenz[a]anthracene.
The crystal structure of 2-methylbenz[a]anthracene (2-MBA), the least carcinogenically active of the monomethylbenz[a]anthracenes, has been determined by application of direct methods to single-crystal X-ray diffractometric data and refined by least squares to R = 0.033 (Rw = 0.035). Deviations of the carbon atoms from the mean molecular plane are much smaller than in the rather more active 1-MBA; in 2-MBA, the benzo-ring A is inclined at about 2 degrees to each of the three rings in the anthracene moiety and even the methyl carbon atom is displaced by only 0.07 A from the ring-carbon atom plane of 2-MBA (and by 0.01 A from the ring-A plane). As in other MBA, the shortest C-C bond in this accurately determined structure is at the K-region (C(5)-C(6) = 1.330(3) A) but three other bonds are short; C(8)-C(9) = 1.347(4), C(10)-C(11) = 1.353(3) and the M-region bond C(3)-C(4) = 1.359(4) A (0.003 A longer if corrected for rigid-body librations). The 2-methyl group appears to take up two orientations with one trio of hydrogen positions more favored than the other.
Development of dental ceramics. An historical perspective.
This article covers the inception and development of porcelain and its adoption into dentistry as a restorative material substituting for natural tooth. The turbulent years of development of dental porcelain with the innumerable waxing and waning fortunes of its acceptance and success are outlined. The major milestones in the historical and scientific development and refinements of dental porcelain materials are covered from its earliest beginnings to modern day materials.