The blood-brain barrier: an important concept in neuroimaging.
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Animals↗
Biomedical subjects
A J Wilson
Publications and source records attributed to A J Wilson.
The effect of intracarotid nonionic contrast media on the blood-brain barrier in acute hypertension.
PURPOSE: To determine whether acute hypertension (HT) is a risk factor for damage to the blood-brain barrier in carotid angiography with nonionic contrast media. METHODS: Anesthetized rats received intravenous injections of technetium-99m-pertechnetate and horseradish peroxidase. Two groups of rats received metaraminol to raise their blood pressure to between 165 and 190 mmHg peak systolic and then received intracarotid injections of saline or iopamidol. Two other groups remained normotensive and received intracarotid injections of saline or iopamidol. Animals were perfused with a fixative solution and their brains removed. Activity of extravasated Tc-99m-pertechnetate was determined to assess blood-brain barrier breakdown. Brains were then sectioned, treated histochemically to visualize extravasated horseradish peroxidase, and ranked visually according to horseradish peroxidase staining. RESULTS: Extravasation of both tracers was significantly greater in the hypertensive group that received contrast media than in the other three groups. CONCLUSIONS: Acute hypertension potentiates the blood-brain barrier-damaging effects of nonionic contrast media during carotid angiography in rats.
Acute Disease↗
Computed arthrotomography of glenohumeral instability.
In spite of recent advances in imaging technology, computed arthrotomography continues to be a useful imaging modality for shoulder evaluation. The spatial resolution of computed tomography (CT) and the longer clinical experience continue to provide advantages over magnetic resonance imaging (MRI). Computed arthrotomography remains a simple and reliable method for evaluation of the glenoid labrum in patients with shoulder instability.
Arthrography↗
The influence of age and gender on radial height.
Radial height was measured on carefully standardized posteroanterior x-ray films of the wrist in 25 male and 25 female patients. The range of radial height (10 to 18 mm) was the same for both male and female patients, with slightly different means for each sex. In females the mean was at the upper limit of the previously reported range, whereas in males the mean was outside the reported range. Our results suggest that previously published measurements underestimate radial height. Inasmuch as radial height may be used in planning management of distal radial fractures, it is important to redefine these measurements. We also believe that the wide range of normal makes comparison with a noninjured contralateral wrist essential for accurate assessment of radial shortening in each individual patient.
Adolescent↗
Opposing roles of cyclic AMP in the vascular control of edema formation.
Eight agents that increase the intracellular concentration of cyclic AMP were tested for their effect on edema formation. The specificity of the agents for vascular smooth muscle or the endothelium was determined by measuring vasodilation with a laser Doppler flow probe and cAMP production by endothelial cells and vascular smooth muscle cells in culture. The agents were injected intradermally in anesthetized rabbit skin and the local accumulation of 125I-labeled albumin in response to intradermal bradykinin was measured. Iloprost, prostaglandin E1, prostaglandin E2, pituitary adenylate cyclase activating polypeptide (PACAP), and vasoactive intestinal polypeptide (VIP) potentiated bradykinin-induced edema. These same agents also increased blood flow and vascular smooth muscle cAMP concentrations, but did not increase endothelial cell cAMP production. Albuterol suppressed edema formation, did not cause vasodilation, but did increase endothelial cell cAMP concentrations. The phosphodiesterase inhibitor rolipram did not cause vasodilation, but suppressed edema and potentiated the cAMP response to albuterol in cultured endothelial cells. L-Isoproterenol affected both cell types. At a lower concentration L-isoproterenol was a potent stimulus to endothelial cell cAMP production and inhibited edema formation; a higher dose had additional effects on vascular smooth muscle and significantly increased blood flow. These findings support the hypothesis that increasing intracellular cAMP concentrations in vascular smooth muscle promotes edema via increased blood flow. In contrast, increasing cAMP concentrations in endothelium may suppress edema by enhancing the permeability barrier.
Albuterol↗
Results of the 1992 survey of the American Association of Academic Chief Residents in Radiology.
RATIONALE AND OBJECTIVES: The authors conducted the annual American Association of Academic Chief Residents in Radiology (A3CR2) survey of chief residents of academic radiology programs to evaluate commonalities and differences among radiology training programs. METHODS: The surveys were mailed to 125 accredited programs in the United States and Canada. The analysis of the returned surveys took into account the geographic region of the respondents. RESULTS: Chief residents from 72 training programs (58%) returned their completed surveys. There are important variations among training programs related to requirements for entry, salary, and night call, and how residents prepare for Board examinations. CONCLUSIONS: The A3CR2 annual survey provides important information for program directors regarding how their training practices might differ from others so that they might better evaluate their programs.
Certification↗
Single-exposure conventional and computed radiography. The hybrid cassette revisited.
RATIONALE AND OBJECTIVES: The authors constructed and evaluated a hybrid cassette for single-exposure extremity imaging with storage-phosphor plates and conventional radiographic film. METHODS: A hybrid cassette was constructed using a fine radiographic screen and a storage-phosphor plate. Exposures of a Lucite step wedge and a line pair gauge were made with the hybrid cassette, a conventional radiographic cassette, and a storage-phosphor cassette. The spatial resolution and imaging speeds of the hybrid and standard systems were compared. RESULTS: Spatial resolution loss was less than 0.5 line pairs per mm with the hybrid cassette. Speed loss was characteristic of the hybrid cassette, requiring approximately 40% greater exposure to produce the same film density as standard cassettes. CONCLUSIONS: The speed difference between this and a previous study is probably due to differences in film-screen choice, kilovolt peak, and storage-phosphor plate generations. The sensitivity spectrum of our film and the emission spectrum of our screens were more closely matched than were the spectra in the previous study; we used lower kilovolt peak, and our storage-phosphor plates were a later, more efficient, generation. Despite slight speed losses, the hybrid cassette appears to be a better choice for obtaining matched images for clinical trials than the alternative of two separate exposures.
Extremities↗
Adenylate cyclase-mediated vascular responses of rabbit aorta, mesenteric artery and skin microcirculation.
1. The importance of adenylate cyclase-mediated vascular relaxation in the macro and microcirculation was assessed in rabbit aortic and coeliac artery bioassay rings in vitro and skin microvessels in vivo. 2. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP38), the beta-agonist, isoprenaline, and the prostaglandins, PGE1 and PGE2, were compared with the activity of nitroprusside, which acts by stimulating guanylate cyclase. 3. In aortic tissue the relative relaxant potencies were (-log M EC50, 100% = response to nitroprusside 10(-6) M): nitroprusside 7.0, PACAP38 6.8, isoprenaline 6.3; PGE1 and PGE2 were weak constrictors. In coeliac artery rings relative potencies were (-log M EC50, 100% = response to nitroprusside 10(-5) M): PACAP38 6.6, PGE1 6.6, nitroprusside 6.5, PGE2 4.9, and isoprenaline 4.3. 4. Comparative potencies when injected into anaesthetized rabbit skin in vivo were (-log mol/site required to increase blood red cell flux by 75%): PACAP38 13.0, PGE2 10.7, isoprenaline 9.7, PGE1 9.1, nitroprusside < 7. 5. Nitroprusside, the most effective relaxant tested in the aorta, was 10(7) fold less potent than PACAP in its effect on skin blood flow. PGE1 and PGE2 were constrictors of the aorta, of intermediate effect in the coeliac artery, but potent vasodilators of the microcirculation. 6. In this model, the importance of adenylate cyclase-mediated vascular relaxation increases with decreasing vessel size.
Adenylyl Cyclases↗
Role of beta 2-glycoprotein I and anti-phospholipid antibodies in activation of protein C in vitro.
AIMS: To investigate the effect of beta 2-glycoprotein I (beta 2 GPI) on the thrombin/thrombomodulin dependent activation of protein C; and to determine whether beta 2 GPI dependent anticardiolipin antibodies have any effect. METHODS: Protein C was activated by thrombin in the presence of thrombomodulin and phospholipid vesicles in an in vitro system. The effect of adding purified beta 2 GPI to this system was observed. Affinity purified anticardiolipin antibodies and total IgG from patients with anticardiolipin antibodies and the lupus anticoagulant were studied for their effects on protein C activation in the presence and absence of beta 2 GPI. RESULTS: beta 2-Glycoprotein I had no effect on the activity of preformed activated protein C. When the phospholipid vesicles were incubated with beta 2 GPI before the addition of protein C, the activation of protein C was inhibited in a dose dependent manner. With phosphatidylserine:phosphatidylcholine vesicles at a concentration of 1 microM:2 microM, beta 2 GPI began to inhibit the reaction at a concentration of 15 nM, and at 4 microM (the normal plasma concentration) the activation of protein C was reduced to 40%. Anticardiolipin antibodies had no demonstrable effect. CONCLUSIONS: beta 2-Glycoprotein I inhibits protein C activation in an in vitro system. Its physiological role is unknown but it has potential procoagulant as well as anticoagulant properties. An effect of antiphospholipid antibodies on protein C activation, which might explain their association with thrombosis, could not be shown.
Antibodies, Antiphospholipid↗
Lupus anticoagulant activity of some antiphospholipid antibodies against phospholipid bound beta 2 glycoprotein I.
AIMS: To determine whether beta 2 glycoprotein I (beta 2GPI) dependent anticardiolipin (aCL) antibodies detected in solid phase enzyme linked immunosorbent assays can also have lupus anticoagulant activity. METHODS: Six anticardiolipin antibodies were affinity purified from patients with these antibodies and lupus anticoagulant activity in their plasma. RESULTS: The anticardiolipin antibodies bound only to anionic phospholipids in the presence of beta 2GPI and bound to beta 2GPI in the absence of phospholipids. Four out of six had lupus anticoagulant activity in the dilute Russell viper venom time test. CONCLUSIONS: The results show that some beta 2GPI dependent aCL are lupus anticoagulants. It is unclear why only some should have lupus anticoagulant activity while others do not.
Anions↗
The normal shoulder: common variations that simulate pathologic conditions at MR imaging.
The appearance of the supraspinatus tendon and anterior capsular mechanism was analyzed in 60 asymptomatic shoulders with magnetic resonance (MR) imaging. The images were reviewed with special attention to findings that simulate pathologic conditions, as defined by means of currently accepted criteria. On T1-weighted and proton-density (PD) spin-echo (SE) images, intermediate signal intensity was present within the supraspinatus tendon in most shoulders. Focal signal intensity within the distal tendon was particularly common finding, being present in 95% (57 of 60) of shoulders on PD images. Focal obliteration of the subacromial-subdeltoid fat stripe and acromioclavicular joint arthrosis were seen in 95% (57 of 60) and 48% (29 of 60) of the subjects, respectively. There was considerable variation in the shape of the anterior glenoid labrum-glenohumeral ligament (GHL) complex. The labrum may appear triangular, round, crescentic, or absent. The middle and inferior GHLs lie in proximity to the upper half of the anterior labrum; the cleavage plane between the ligaments and the labrum can mimic a tear at MR imaging.
Adult↗
The injuries to JFK.
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Craniocerebral Trauma↗
Measuring animal well-being.
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Agriculture↗
Transport of live animals for slaughter.
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Animal Welfare↗
Wheelchair-mounted integrated control systems for multiply handicapped people.
Integrated control systems allow disabled people access to multiple functions from a single input device (for example a set of switches). Multiply handicapped users are thereby able to switch efficiently between wheelchair control, communication, computer access and control of their environment, without third-party help. Integrated systems have been developed for multiply handicapped children and adults in the Barnsley area. The design philosophy has concentrated upon utilizing, wherever possible, commercially available assistance devices and remotely controlling these via logic-based integrated control systems tailored to the needs and abilities of the individual client. This approach presents few problems as the inputs to commercially available devices are often based on simple switch control. The systems already supplied have proved, after an initial training period, to be easy to operate and have led to a considerable improvement in quality of life for the users. Computer-based, wheelchair-mounted integrated systems are now being developed. A prototype system currently emulates the logic-based controllers described above, employing the screen to display information on the current status of the system. Future development will move toward a more flexible system which will be able to read a variety of input signals and control a large number of outputs. The system will also have the facility to utilize software-based communications, keyboard emulation and environmental control packages as well as business and education software. Such a system could be easily set up, via software, for use by any disabled person.
Biomedical Engineering↗
Monitoring body fluid distribution in microgravity using impedance tomography (APT (applied potential tomography)).
For an astronaut, the excitement of going into orbit is accompanied by a shift of 1 to 1.5 l of fluid from the legs into the upper body. Information on the way the redistributed fluid is handled by the body is very useful to space physiologists studying the process of adaptation to zero-gravity. Applied potential tomography (APT) can be used to image changes in fluid distribution. To ensure that the technique was capable of measuring fluid shifts induced by changing gravitational forces on the body, a standard Sheffield APT system was used to study several subjects during the eight ESA parabolic flight campaign. The results clearly demonstrated the feasibility of using APT for monitoring fluid redistribution during space flight. A battery-powered, body-worn APT system has now been developed for use in space. The equipment was tested on the eleventh parabolic flight campaign. The data collected with the miniaturised system was comparable to that obtained in the earlier experiment. Ergonomic tests indicated that the equipment is no more difficult to operate and maintain under weightless conditions than on earth. The system is undergoing space qualification tests in Munich. If no problems arise it will be used by German astronauts on missions to MIR and Skylab.
Body Fluids↗
Characterization of radioactive petroleum piping scale with an evaluation of subsequent land contamination.
Scale formation in oilfield piping and equipment has been a problem for petroleum companies. In the past, scale waste from cleaning of piping and equipment has been considered nonhazardous. Naturally occurring radioactive material in the form of 226Ra and, to a lesser degree, 228Ra with their associated decay products have recently been discovered in the scale. Due to the lower abundance and short half-life, 228Ra is not addressed in this paper. 226Ra, an alpha emitter, is a potential internal hazard to workers from the inhalation and ingestion of the dust produced during descaling or pipe cleaning operations. Along with this, a higher-than-normal background gamma exposure rate is seen where the pipe cleaning was routinely done. An evaluation of the radiation hazards associated with a retired pipe cleaning field was performed. Gamma exposure rates, 226Ra concentration, and 226Ra leachability were examined using scale containing soil from the field. Radon emanation from the soil was also determined.
Alpha Particles↗