Biomedical subjects
D A Wilkinson
Publications and source records attributed to D A Wilkinson.
Visual-motor control loop: a linear system?
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Glyoxylate aminotansferases from oat leaves.
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Mu-opioid ([3H]DAGO) binding in slices of rat brain: inhibition by sodium ions, guanyl-5'-yl imidodiphosphate and by the adrenergic neurotoxins DSP4 and xylamine.
We have characterized and quantified the specific binding of the mu-agonist [3H] DAGO to 300 microM slices of hypothalamus and cerebral cortex. The receptors have many of the opioid characteristics previously demonstrated in homogenate assays. Binding is reversible, saturable, stereospecific and of high affinity. The delta-opioids DTLET and DSLET are 36- and 30-fold respectively, less effective than DAGO in competing for the binding site. Assays can be routinely performed in the presence of physiological concentrations of sodium, though in TRIS buffer the affinity and the number of receptors is increased. Protection of the ligand against proteolytic degradation is unnecessary. Unexpectedly, we observed that GppNHp inhibits [3H] DAGO binding to brain slices. This suggests an allosteric modification of the mu-receptor in the membranes of intact cells. The mu-receptors are also blocked by the adrenergic neurotoxins DSP4 and xylamine. This re-emphasizes our contention that care should be exercised in the use of these drugs. The technique is simple, rapid and involves minimal disruption of tissue. It should provide new opportunities for the study of cell surface opioid receptor subtypes in intact tissue.
Hypothermia following whole-body heating of mice: effect of heating time and temperature.
We have observed an acute and prolonged lowering of body temperature (hypothermia) following whole body heating (WBH) of mice. This phenomenon of heat-induced hypothermia and the subsequent recovery of normal temperatures have been systematically investigated. The hypothermic period can be characterized by two parameters: Tnadir and a recovery time constant (tau). For treatment temperatures below 41 degrees C and treatment durations of 1 h or less, a mild hypothermia (Tnadir greater than 33 degrees C) and fast recovery (tau less than 1 h) occur. Tnadir and tau vary slightly with treatment temperature and are almost independent of treatment length. At treatment temperatures 41 degrees C and above for up to 1 h, we observed acute hypothermia (Tnadir as low as 28 degrees C) and slow recovery (tau = several hours). This region of prolonged hypothermia is characterized by a rapid change of Tnadir and tau with temperature, and a much less rapid change with treatment duration. The WBH temperature-time range causing prolonged hypothermia is very narrow, and if exceeded results in lethality. Critical lethal temperatures have been estimated for several treatment durations from the time constant data. Post-WBH hypothermia can be minimized by keeping the animals in a 37 degrees C environment. However, we find that neither survivability nor intestinal cell repopulation is enhanced by this procedure.
Calorimetric evaluation of antennas used for microwave interstitial hyperthermia.
Several quasi-adiabatic calorimeters have been constructed for determining the heating efficiency of microwave antennas. The absorber is 0.9% saline which is stirred continuously, making equilibration times short (several seconds). Depth of insertion data have been obtained for standard BSD and CTC antennas at 915 MHz. Efficiency varies only slightly with insertion depth in the range 7-16 cm and can be as high as 65%. At shallower depths efficiency drops off, while reflected power and leakage fields increase. Data obtained in site visits conducted by the Hyperthermia Physics Center show that antenna efficiency of the BSD and CTC models can vary by as much as 35% within sets of functional 'identical' antennas.
Communicating alcohol and drug prevention strategies and models across cultural boundaries: preliminary report on an ILO/WHO/UNDCP [International Labour Office/World Health Organization/United Nations International Drug Control Program] Interagency Program.
The joint ILO/WHO/UNDCP collaborative program "Prevention of Drug and Alcohol Problems among Workers and their Families" represents transfer of an innovative model to a culturally diverse group of nations: Egypt, Mexico, Namibia, Poland, and Sri Lanka. The concept is to move from reactive programs-led by alcohol and drug experts, reactive to problem employees-to proactive prevention led by management. Nontechnical language and metaphors have been developed to secure the commitment of managers in the private and public sectors. Participating countries and enterprises adapt the program to local conditions, fostering "local ownership" with the objective of creating self-sustaining activities. The objective is to describe elements of the program which may be readily transferable worldwide across the cultural borders that characterize nations, enterprises, and public sector workplaces.
"Dare to be different.
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