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Biomedical subjects

D R Williams

Publications and source records attributed to D R Williams.

At least 235 records · Page 13Linked to original sources
PubMed1984

Metal binding by pharmaceuticals. Part 5. Interaction of Cd(II), Ni(II) and Pb(II) with the intracellular hydrolysis products of the anti-tumour agent ICRF 159 and its inactive homologue ICRF 192.

Formation constants for the cadmium(II), nickel(II) and lead(II) complexes of DL-NN'-dicarboxamidomethyl-NN'-dicarboxymethyl-1,2-diaminopr opane (ICRF 198) and the 1,2-diaminobutane homologue (ICRF 226) have been measured potentiometrically at 37 degrees C and I = 150 mmol dm-3 [NaCl]. In all titrations a competing ligand, known to complex strongly with the metal ion, and having its formation constants predetermined, was employed. The constants are used in computer simulation models to assess the relative efficacy of the agents in mobilizing these metals from plasma proteins into low-molecular-weight complexes and the results are compared to those for known chelating agents. It is shown that the lead mobilizing potential of the agents is greater than either EDTA or D-penicillamine; they are, however, less adept in the removal of cadmium and nickel than other established agents.

Antineoplastic Agents↗
PubMed1984

Computer simulation of metal ion equilibria in biofluids. IV. Plutonium speciation in human blood plasma and chelation therapy using polyaminopolycarboxylic acids.

An investigation by computer simulation into the nature of Pu(IV) binding to low-molecular ligands in human blood plasma is described. Particular consideration is given to the interactions of various chelating agents which have been or might be used for treating plutonium intoxication. Formation constants of EDTA and DTPA with Cu(II), Mg(II), Mn(II), Zn(II), and Cd(II) have been measured under biologic conditions of temperature and background electrolyte. The relative ability of these and other chelating agents to cause excretion of plutonium and the concomitant loss of certain essential trace metals has thus been assessed.

Chelating Agents↗
PubMed1984

Disappearance of afterimages at 'impossible' locations in space.

An eccentrically positioned afterimage, viewed in the dark, will disappear if the eye is positioned so that the afterimage now projects to a more extreme location relative to straight ahead. It was found that the afterimage disappeared when it projected to a location which corresponded to the edge of the visual field defined by the brow, cheek, and nose. This suggests that visibility of stimuli from those retinal regions shadowed by the head is influenced by eye-position information.

Afterimage↗
PubMed1984

Trends in bowel cancer in selected countries in relation to wartime changes in flour milling.

Wartime changes in flour milling have been estimated to have more than doubled the intake of cereal fiber in England and Wales, Ireland, and Switzerland for periods of at least 6 years. These circumstances were used to test the hypothesis that cereal fiber inhibits colon carcinogenesis. Age-standardized rates for deaths attributed to bowel cancer were plotted from 1931 to the mid-1970s for England and Wales, Ireland, Switzerland, New Zealand, the US, and Australia. The ratio of the mortality rate observed 11 to 15 years after the change in extraction rates to that predicted from the prewar trend correlated with the increase in estimated cereal fiber consumption. The slope of the regression line suggested that any protective effect from cereal fiber was more modest than that inferred from other studies. The disparity between studies would be less if cereal fiber inhibited more than one stage of the process of carcinogenesis. Trends in six other countries with insufficient data for quantitative analysis were generally consistent (with the exception of those for Norway). The limitations of historical cause-of-death registrations as measures of cancer onset rates and the multiplicity of other changes during wartime require that our results be interpreted with caution.

Australia↗
PubMed1984

Localized granuloma annulare is associated with insulin-dependent diabetes mellitus.

The prevalence of diabetes mellitus in 557 patients with granuloma annulare (GA) has been assessed by a retrospective study, using age-matched population data. A definite association was confirmed between GA and insulin-dependent diabetes with 16 observed cases compared with 0.9 expected, and in all but one case the diabetes was associated with the localized form of GA. Two further cases developed insulin-dependent diabetes within 5 years of presentation with GA.

Adolescent↗
PubMed1983

Consequences of spatial sampling by a human photoreceptor mosaic.

The short wavelength color mechanism in the human visual system can distinguish gratings from uniform fields of the same average radiance at spatial frequencies that are twice as high as the highest at which it can resolve bars in the grating. This discrimination above the resolution limit is associated with a splotchy or mottled appearance of the grating similar to two-dimensional noise. The most plausible explanation for the mottled pattern is that it is a moiré pattern produced by aliasing (spatial undersampling) by an irregular and sparse mosaic of short wavelength cones.

Color Perception↗
PubMed1983

Historical outline of the biological importance of trace metals.

A historical review of the discoveries that trace elements are involved in biological processes and relationships between trace metals and inherited disease. Ongoing experiments are appraised and a better understanding of the pathologies of inherited diseases anticipated.

Animals↗
PubMed1983

Metal binding by pharmaceuticals. Part 3. Copper (II) and zinc (II) interactions with isoniazid.

Formation constants for copper(II) and zinc(II) complexes of isonicotinoylhydrazine (isoniazid) and guanosine-5'-monophosphate have been measured potentiometrically at 37 degrees C, I = 150 mmol dm-3 [NaCl]. These constants have been used in computer models to assess the extent of complex formation by the drug in vivo. The simulations indicate that the predominant complexes existing in blood plasma are ternary species formed with histidinate. However, at clinical levels of isoniazid, it seems unlikely that these complexes are physiologically significant. On the other hand, ternary complex formation with nucleosides may be involved in the binding of isoniazid to viral RNA.

Copper↗
PubMed1983

Quality assessment of blood glucose monitors in use outside the hospital laboratory.

The quality of analytical results required in clinical practice is generally dictated by analytical rather than clinical criteria. The increasing availability of analytical technology that can be used outside the hospital laboratory challenges this situation. In an attempt to highlight this dilemma one method of glucose analysis outside the laboratory has been assessed using a pilot external quality assessment scheme (EQAS) and the results have been compared with the performance of the same machines in the laboratory. In the laboratory reliable results were obtained when the Glucometer was used by experienced laboratory personnel giving a good correlation of results (r = 0.96) when compared with an automated method. The results of the EQAS revealed that 44% of hospital ward glucose estimations and 63% of general practice estimations would be considered unsatisfactory by conventional laboratory criteria--that is, greater than +/- 2 SD of the mean laboratory result. This level of performance must, however, be considered in relation to the number of times that a clinically misleading result is obtained. No analytical system should be used in clinical practice without a continuous, objective assessment of its performance.

Blood Glucose↗
PubMed1982

Metal binding by pharmaceuticals. Part 2. Interactions of Ca(II), Cu(II), Fe(II), Mg(II), Mn(II) and Zn(II) with the intracellular hydrolysis products of the antitumour agent ICRF 159 and its inactive homologue ICRF 192.

Formation constants for the calcium(II), copper(II), iron(II), magnesium(II), manganese(II) and zinc(II) complexes of dl-NN'-dicarboxamidomethyl-NN'-dicarboxymethyl-1,2-diaminopropane (ICRF 198) and the 1,2-diamino-butane homologue (ICRF 226) have been measured potentiometrically at 37 degrees C and I=150 mmol dm-3 [NaCl]. The constants are used in computer simulation models to assess the relative avidity of these compounds for biologically essential metal ions in vivo. It is shown that the agents interact similarly with all of the ions studied except those of zinc(II), which are particularly strongly chelated by the hydrolysis product of ICRF 192. This effect could be responsible for the difference in cytotoxicity exhibited by the antitumour agent ICRF 159 (Razoxane) and its inactive homologue ICRF 192. However, the mechanism through which this might occur remains unclear.

Antineoplastic Agents↗
PubMed1982

Cardinal directions of color space.

Thresholds for detecting changes in color are raised following viewing a field sinusoidally modulated in color over time. This effect is highly selective. For example, thresholds for detecting reddish and greenish changes from white are raised following viewing a field varying in a reddish-greenish direction, but not after viewing one varying in a yellowish-bluish direction. Similarly thresholds for yellowish and bluish changes from white are raised following viewing a field varying along a yellowish-bluish axis but not altered by exposure to reddish-greenish variation. Thresholds for chromatic changes are not raised following viewing a field varying in luminance. Thresholds for changes in luminance are raised following viewing a field varying in luminance but not altered by exposure to purely chromatic variation. Since this selectivity is found only for these directions and not intermediate directions in color space we conclude that these directions are cardinal, that is, signals varying along these directions are carried along separate, fatiguable, second stage pathways. The results conform to the expectations of opponent process theory with the important exception that the yellowish-bluish cardinal direction is a tritanopic confusion line and not a red-green equilibrium line.

Color Perception↗