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Biomedical subjects

W O Thompson

Publications and source records attributed to W O Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1992

Repeatability of automated ambulatory blood pressure measurements.

BACKGROUND: The repeatability of 24-hour automatic ambulatory blood pressure measurements recorded by noninvasive equipment (Del Mar Pressurometer IV) was assessed to determine the intrapatient variability of this test. METHODS: The usual antihypertensive medications of 73 patients with documented essential hypertension (supine diastolic blood pressure of 95 to 119 mm Hg) were withdrawn, and the patients were treated with placebo medication for 6 weeks. At the end of the placebo period, ambulatory blood pressure measurements of each patient were recorded every 15 minutes for 24 hours on two separate occasions 1 week apart. RESULTS: There was no significant difference in either the 24-hour systolic or diastolic blood pressure for the entire group between weeks. A mean difference for individual patients between the first and second recording within 5 mm Hg was observed in 49.3% and 52.1% of patients for 24-hour systolic and diastolic blood pressure, respectively. The correlation coefficient for 24-hour systolic blood pressure was greater than 24-hour diastolic blood pressure (r = .87 vs r = .67). A difference greater than 18.1/14.9 mm Hg for systolic/diastolic blood pressure would be required to assign a significant (P less than .05) change in blood pressure between two recordings in the same patient. CONCLUSIONS: These data quantify the usefulness of 24-hour ambulatory blood pressure measurements for a group of subjects. However, mean 24-hour ambulatory blood pressure varies significantly for individuals. Intrapatient variability may limit the usefulness of a single 24-hour ambulatory recording for an individual patient and suggests the need for more than one measurement to establish a level of blood pressure.

Adult↗
PubMed1991

Shear bond strength of Scotchbond in vivo.

The shear bond strengths of Scotchbond, HEMA/Scotchbond, and Scotchbond 2 were measured in vivo in dog canine and molar enamel and dentin. Dentin bond strengths were compared in superficial, middle, and deep dentin. The acid-etched enamel bond strengths of the three bonding systems ranged from 10 to 11 MPa and were not statistically different. Scotchbond/Silux bonds to superficial and middle cuspid and molar dentin were 3 MPa and were not statistically different. HEMA-treated dentin did not consistently improve Scotchbond strengths to either tooth type at any dentin depth. Deep dentin from either tooth type yielded significantly lower bond strengths. Scotchbond 2/Silux shear bond strengths were significantly higher (6-8 MPa) in superficial and middle cuspid dentin but were not different from Scotchbond bonds made to deep cuspid dentin or to any depth of molar dentin. The observation that molar bond strengths are lower than those made to cuspid dentin indicates that there are important substrate differences between teeth as well as within dentin as a function of depth. The dog model may be useful for the screening of new dentin bonding systems prior to clinical trials.

Animals↗
PubMed1991

Serum lipid and fecal bile acid changes with cereal, vegetable, and sugar-beet fiber feeding.

Thirty-four subjects consumed six controlled formula diets for 3 wk each, supplemented with 0 g added fiber, 10 and 30 g dietary fiber as wheat bran (WB), 10 and 30 g dietary fiber as mixed vegetable fiber (VF), and 30 g dietary fiber as sugar-beet fiber (SBF). Serum cholesterol changes for fiber free, 10 g WB, 30 g WB, 10 g VF, 30 g VF, and 30 g SBF (-0.13, -0.18, -0.05, -0.17, -0.24, and -0.70 mmol/L, respectively) were significant for 30 g VF and 30 g SBF. Reduction in total cholesterol with SBF was largely due to significant lowering of low-density-lipoprotein cholesterol. Total fecal bile acid concentrations were significantly higher with the fiber-free diet than with 30 g WB, VF, and SBF (P less than 0.001) and were also higher with 30 g SBF than with 30 g WB and 30 g VF (P less than 0.005). Daily fecal bile acid excretion was not different on 30 g SBF compared with 30 g WB and 30 g VF. Differences in cholesterol reduction across the diets could not be explained by differences in fecal bile acid excretion.

Adult↗
PubMed1991

Reproducibility of P3.

The P3 event-related potential has been widely employed in both clinical and research investigations. In the present study, P3 latency and amplitude intersession reliability were evaluated in 4 sessions over an average of 33 days in 24 healthy adults using the P3 tonal oddball paradigm. Mean group latencies ranged from 302-305 ms and mean amplitudes ranged from 7.75-8.87 microV. No significant group differences were found across sessions for latency or amplitude. Intrasubject variability was large; the 95% confidence interval for the difference between the means of two combined sessions was +/- 20 ms for latency and +/- 4.63 microV for amplitude. The results suggest that P3 latency and amplitude are reliable and reproducible over weeks for groups, but have greater variability for individuals.

Adult↗
PubMed1991

Racial aspects of ambulatory blood pressure.

Ambulatory blood pressure measurements, recorded by a Del Mar Pressurometer IV, were performed in 71 patients (25 blacks and 46 whites) with documented essential hypertension (supine diastolic blood pressure 95-119 mmHg) after four weeks of placebo treatment. Each 24-hour ambulatory BP measurement was calibrated with manual measurements within 5 mmHg and was repeated according to the daily conditions (work status) of the original recording. Ambulatory BP measurements were recorded every 15 minutes over 24 hours on two separate occasions one week apart. The mean of two 24-hour measurements was the value for the individual patient. Analyses of variance indicated no significant difference in the mean age, height, weight, 24-hour ambulatory systolic or diastolic BP, 8 am to 12 noon systolic or diastolic ambulatory BP, or 12 midnight to 4 am ambulatory systolic or diastolic BP for blacks versus whites. Among the subset of females, the 20 blacks were older than the 23 whites. Despite this age difference, there was no significant difference in height, weight or 24-hour, 8 am to 12 noon, or 12 midnight to 4 am ambulatory BP measurements. Therefore, this study does not support a racial difference in the level of ambulatory blood pressure measurement in these hypertensive patients.

Ambulatory Care↗
PubMed1990

Cerebral vessel stenosis in sickle cell disease: criteria for detection by transcranial Doppler.

Ischemic stroke is a common and disabling complication of sickle cell disease (Hb SS). Most infarctions occur in the presence of intracranial stenotic lesions of the large vessels of the circle of Willis. Transcranial Doppler (TCD), by measuring flow velocity in these arterial segments, can detect focal stenosis on the basis of elevated flow velocity. We report the preliminary results of a prospective study to develop criteria for detection of stenotic lesions based on TCD and identification of patients with Hb SS at risk for stroke. Comparing the TCD findings from six patients with lesions demonstrated by angiography to those from 115 Hb SS children without stroke, we conclude: (a) middle cerebral (MCA), anterior cerebral (ACA), or internal carotid (ICA) artery mean velocities greater than 190 cm/s strongly suggest focal stenosis; (b) MCA or ACA mean velocities of 150 to 190 cm/s suggest abnormality but at present cannot be considered diagnostic of stenosis; (c) mean velocities up to 150 cm/s are possibly due to the effects of low hematocrit and/or young age, and cannot as yet be distinguished from velocity elevations due to vessel stenosis.

Adolescent↗
PubMed1990

Unilateral cerebral inactivation produces differential left/right heart rate responses.

We studied heart rate following unilateral hemispheric inactivation by intracarotid amobarbital in 25 patients undergoing preoperative evaluation for epilepsy surgery. Heart rate increased after left hemisphere inactivation, but decreased following right hemisphere inactivation. The results are consistent with differential left/right cerebral hemispheric effects on autonomic function, and appear related to functional and anatomic asymmetries in both the central and peripheral nervous systems.

Adolescent↗
PubMed1990

Comparison of in vivo and in vitro tests in the diagnosis of imported fire ant sting allergy.

The specificities and sensitivities of skin test reactivity to imported fire ant (IFA) whole body extract (WBE) and IFA venom were compared with IFA WBE RAST and IFA venom RAST in the diagnosis of IFA allergy. Study groups consisted of 18 IFA allergic patients and 21 control subjects with no history of allergy to insect stings. All IFA allergic patients had positive skin tests to both IFA WBE and IFA venom. Six of 21 (29%) control subjects also had positive skin tests to both IFA WBE and IFA venom. A commercial IFA WBE RAST was positive in 10 of 18 (56%) IFA-allergic patients and 2 of 21 (10%) control subjects. Imported fire ant aqueous venom RAST was positive in 11 of 11 (100%) IFA-allergic patients and three of ten (30%) control subjects. Vespa IFA venom RAST was positive in 16 of 18 (89%) IFA-allergic patients and 5 of 21 (24%) controls. The sensitivities and specificities of IFA WBE skin testing, IFA venom skin testing, and IFA venom RAST did not differ significantly. Imported fire ant WBE RAST was less sensitive than the other diagnostic methods.

Adolescent↗
PubMed1989

Differential cognitive effects of terfenadine and chlorpheniramine.

The H1-histamine antagonist, terfenadine, has been proposed to have reduced cognitive side effects. In the present study, the relative cognitive effects of terfenadine, 60 mg, chlorpheniramine maleate, 8 mg, and placebo were tested with a double-blind, randomized, three-period crossover design in 24 healthy adult subjects. The dependent variable was latency of the P3-evoked potential. The P3 is a cognitively evoked electroencephalographic response that is an objective and sensitive measure of sustained attention and cerebral processing speed. Disease and drug states that adversely affect the central nervous system can slow P3 latency. For example, the centrally active anticholinergic scopolamine slows cognitive processing speed and prolongs P3 latency. P3 latency (millisecond) means (+/- mean standard error) were pretreatment, 310 (+/- 1.7; placebo, 313 (+/- 3); terfenadine, 320 (+/- 3); and chlorpheniramine, 333 (+/- 3). The findings suggest that terfenadine may be particularly advantageous in patients who require alertness and intact cognitive abilities.

Adult↗
PubMed1989

Survey of whole body-extract immunotherapy for imported fire ant- and other hymenoptera-sting allergy. Report of the Fire Ant Subcommittee of the American Academy of Allergy and Immunology.

A survey of 5300 allergists was conducted to determine the number and geographic distribution of patients receiving immunotherapy for imported fire ant (IFA) allergy in the United States and Canada. Responses were received from 1293 physicians who reported a total of 2573 patients being treated in 28 states. Most patients were from the southeast, but some patients were reported to be receiving IFA immunotherapy in areas outside the boundaries of known IFA infestation. Although IFA is a widespread health hazard in the southeast, it appears to exert an uneven impact on allergy practice in this region. Of the 1293 physicians responding to the survey, 117 (9%) reported the use of whole body extract (WBE) in the treatment of 1746 patients with winged Hymenoptera-sting allergy. Continued use of WBE immunotherapy was reported by physicians from all regions of the United States and from Canada. The largest numbers of patients receiving winged WBE immunotherapy were reported from Texas (641), Pennsylvania (246), Florida (129), and Canada (127). The results of this survey suggest a need for continuing medical education regarding (1) the magnitude of the health hazard posed by the IFA and (2) the efficacy of venom versus WBE in the treatment of winged Hymenoptera-sting allergy.

Animals↗
PubMed1989

Bioavailability of oxalic acid from spinach, sugar beet fibre and a solution of sodium oxalate consumed by female volunteers.

Oxalate bioavailability from sugar beet fibre (40 g), spinach (25 g) and a solution of sodium oxalate (182 mg) was tested in nine women using a triplicated 3 x 3 Latin square arrangement. Each test substance provided 120 mg oxalic acid. Throughout the study the volunteers consumed a control diet and the test substances were administered at breakfast on specified days. After an initial 2-day control period, oxalate was administered in three test periods that consisted of one test day followed by one control day. Urine collected during 24-hr periods was analysed daily for oxalate. Oxalate excretion did not differ among the five control days and was not increased significantly following the ingestion of sugar beet fibre by the volunteers. Oxalate excretion was greater (P less than 0.0001) for the mean of the spinach and sodium oxalate solution diets than for the mean of the sugar beet fibre and control diets. Oxalate bioavailability from sugar beet fibre was 0.7% compared with bioavailabilities of 4.5 and 6.2% for spinach and oxalate solutions, respectively. The low bioavailability of oxalate from sugar beet fibre may be attributable to its high ratio of minerals (calcium and magnesium) to oxalate, its complex fibre matrix or the loss of the soluble oxalate during processing of sugar beets.

Administration, Oral↗
PubMed1989

Hemisphere asymmetry for eye gaze mechanisms.

To investigate left/right asymmetries in cerebral gaze mechanisms, eye deviation was evaluated in 90 patients following intracarotid sodium amylobarbitone injections. For right-handed subjects with left cerebral language dominance, the occurrence and severity of eye deviation were greater for right versus left hemisphere injections. In contrast, subjects with mixed cerebral dominance for language/handedness exhibited no left/right difference in the incidence of eye deviation. The results are consistent with right cerebral dominance for attentional/intentional mechanisms directed at external space. Further analysis suggests that the cerebral asymmetry for gaze may be due to an evolutionary loss of attentional/intentional mechanisms by the left cerebral hemisphere as language function developed.

Adolescent↗
PubMed1989

Imported fire ant as a health hazard.

Members of the American Medical Association in 13 southern states were surveyed to assess the magnitude of medical problems caused by stings of the imported fire ant (IFA). Of the 29,205 physicians surveyed, 2,022 (7%) reported treating approximately 20,755 patients annually for reactions to IFA stings. Most patients were treated for local reactions, but 413 (2%) required treatment for life-threatening anaphylaxis.

Acute Disease↗
PubMed1989

Plasma lipoproteins in cortical versus lacunar infarction.

We investigated the relation of plasma lipids to the risk for ischemic stroke by comparing clinical and biochemical characteristics of survivors of cortical (n = 48) and lacunar (n = 36) brain infarction. By analysis of variance, no differences were observed in the concentrations of total cholesterol, triglycerides, low density lipoprotein cholesterol, very low density lipoprotein cholesterol, or apoproteins A1 and B. Patients with lacunar infarction, however, had higher concentrations of high density lipoprotein (HDL)-cholesterol than patients with cortical stroke. This HDL-cholesterol difference was due primarily to a strikingly low HDL-cholesterol content in white patients with cortical stroke. These data suggest that previously demonstrated differences in HDL-cholesterol concentrations between patients with ischemic stroke and control subjects without stroke may apply to patients with cortical but not lacunar infarction. Separation of cerebral infarction into subtypes based on mechanism may help clarify lipid-related risk factors in cerebrovascular disease.

Age Factors↗
PubMed1989

Gingival resistance to probing forces. II. The effect of inflammation and pressure on probe displacement in beagle dog gingivitis.

This study was undertaken to determine the effect of gingival inflammation and probing pressure on probe tip placement in relation to the base of the gingival crevice and the most coronal connective tissue attachment fibers. Nine young male beagle dogs were divided into three groups as determined by clinical status of the gingiva following implementation of a protocol designed to produce gingival health and disease. An electromechanical device was used to advance 0.6 mm diameter probes into the facial gingival crevices of selected teeth and to obtain force-displacement curves. The instrument stopped the probe at pressure of either 80, 160, 320, 640, 1280, or 2560 kPa which were randomly allocated to 12 test teeth in each dog. After the probe came to rest, it was attached to the tooth. When all 12 probes were attached, the animal was sacrificed. Blocks consisting of gingiva, probe, and tooth were processed to obtain two buccolingual sections, one containing the probe and the other immediately adjacent to it. Clinical and histometric measurements were performed and the data evaluated. Although three groups of animals were discernable by clinical criteria, only two groups, health and disease, could be formulated based on the degree of histologic inflammation. The histologic grouping was used in data analysis. Histometric distances from the cemento-enamel junction to the base of the crevice (cJ), to most coronal connective tissue attachment (cC) and to the probe tip (cP) all increased with change from health to disease. However, changes in health/disease did not influence difference between distances (cP-cJ,cP-cC).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Right cerebral specialization for tactile attention as evidenced by intracarotid sodium amytal.

Although several components of neglect syndrome have been reported to occur more frequently following right cerebral lesions, a right cerebral predominance for directed tactile attention has not been demonstrated. The intracarotid sodium amytal procedure (ISA, or Wada test) offers the opportunity to investigate differential effects for symmetric acute dysfunction of each cerebral hemisphere in each subject. In the present study, 18 patients undergoing preoperative evaluation for epilepsy surgery were trained in a nonverbal task of tactile attention. Left/right mean ISA dosages and left/right tactile test times postinjection were matched. Results revealed more correct responses following left ISA, and greater tactile inattention with more extinction-type responses following right ISA. No effect of seizure focus, sex, order of injection, or dosage was present. The finding that tactile inattention occurs more frequently with right cerebral dysfunction is consistent with right cerebral dominance for scanning attentional mechanisms directed at the external milieu.

Adolescent↗