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Biomedical subjects

T W Wilson

Publications and source records attributed to T W Wilson.

At least 73 records · Page 4Linked to original sources
PubMed1990

Dynamic mechanical properties of straight titanium alloy arch wires.

Eight straight-wire materials were studied: an orthodontic titanium-molybdenum (Ti-Mo) product, TMA; three orthodontic nickel-titanium (Ni-Ti) products, Nitinol, Titanal, and Orthonol; three prototype alloys, a martensitic, an austenitic, and a biphasic alloy; and a hybrid shape-memory-effect product, Biometal. Each wire was prepared with a length-to-cross-sectional area of at least 3600 cm-1. With an Autovibron Model DDV-II-C used in the tensile mode, each sample was scanned from -120 to +200 degrees C at 2 degrees C/min. From the data base, plots of the log storage modulus, log tan delta, and percent change in length vs. temperature were generated. Results showed that the dynamic mechanical properties of the alloys within this TI system are quite different. The Ti-Mo alloy, TMA, was invariant with temperature, having a modulus of 7.30 x 10(11) dyne/cm2 (10.6 x 10(6) psi). The three cold-worked alloys--Nitinol, Titanal, and Orthonol--appeared to be similar, having a modulus of 5.74 x 10(11) dyne/cm2 (8.32 x 10(6) psi). The biphasic shape-memory alloy displayed a phase transformation near ambient temperature; whereas the hybrid shape-memory product, Biometal, underwent a 3-5% change in length during its transformation between 95 and 125 degrees C. Among the Ni-Ti wires tested, several different types of alloys were represented by this intermetallic material.

Dental Alloys↗
PubMed1990

Effect of furegrelate on renal plasma flow after angiotensin II infusion.

We had previously shown that selective thromboxane synthetase inhibition with furegrelate increases urinary excretion of 6-ketoPGF1 alpha, the hydrolysis product of prostacyclin after stimulation of renal prostaglandin synthesis with furosemide. The present study assessed the functional significance of this "redirection" of prostaglandin formation using a more physiologic stimulus, angiotensin II. Sprague-Dawley rats (n = 27) were fitted with a transabdominal bladder cannula. Five days later they were given angiotensin II (10 mg.kg-1.min-1) by intravenous infusion. After 30 min, an infusion of furegrelate, 2 mg/kg, then 2 mg.kg-1.h-1, (n = 9); indomethacin, 2 mg/kg, then 2 mg.kg-1.h-1 (n = 9); or vehicle, 250 microL, then 0.018 mL/min (n = 9) was begun for 60 min. Clearance of [14C]para-aminohippuric acid was taken as a measure of renal plasma flow. Angiotensin II raised the mean arterial pressure in all groups. Administration of furegrelate or indomethacin did not change mean arterial pressure or heart rate. Angiotensin II reduced [14C]p-aminohippuric acid clearance by about 32% (1.42 +/- 0.18 to 0.97 +/- 0.07 mL.min-1.100 g-1, p less than 0.05). Furegrelate attenuated this renal vasoconstriction (0.97 +/- 0.07 to 1.38 +/- 0.17 mL.min-1.100 g-1, p less than 0.05), while indomethacin increased it by a further 32% (1.78 +/- 0.12 to 1.20 +/- 0.12 mL.min-1.100 g-1, p less than 0.05). Vehicle alone had no effect. Furegrelate reduced serum thromboxane B2 by 90% (6.52 +/- 0.030 to 0.7 +/- 0.21 ng/100 microL, p less than 0.05), while indomethacin reduced it by 73% (5.9 +/- 0.99 to 1.4 +/- 0.20 ng/100 microL, p less than 0.05). We conclude that furegrelate attenuates the renal vasoconstriction of angiotensin II, presumably by enhancing the formation of vasodilator prostaglandins.

Angiotensin II↗
PubMed1990

Blood pressure in blacks. Twin studies in Barbados.

We have recently reported that there are significant genetic influences on the population variation in blood pressure in black twins in Los Angeles. The present cross-sectional study was undertaken to replicate these findings in a black twin population that lives in a different biosocial environment. We chose the Caribbean island nation of Barbados, where 96% of the population is black, the literacy rate is 99%, and the access to health care is guaranteed. The goals were 1) to test the feasibility of twin studies in blood pressure research in a developing country and 2) to estimate the relative contribution of genes and environment to blood pressure variability in blacks in the Caribbean. The names of 200 twin sets were obtained with the assistance of community resources including a twin club, by media advertisement, and by asking people at public blood pressure screenings if they knew any twins. By using these methods, we identified 200 sets of twins. Of these, 37.5% (75/200) met our criteria for study. Although 97% of the sets of twins (73/75) said they were willing to participate, only 69% (52/75) were able to be scheduled during the 1 week of the study when the full team of investigators was in Barbados. Of those scheduled, 83% (43/52) were examined. Examination included medical history, physical examination, recumbent blood pressure measurements by two observers, anthropometric measurements, 24-hour urine collections for sodium and potassium tests, and blood tests for zygosity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Increased prescribing of antidepressants subsequent to beta-blocker therapy.

Using records of the Saskatchewan Prescription Drug Plan, we determined the incidence of antidepressant use (a marker for depressive symptoms) in patients who received beta-blockers or other treatments for chronic diseases (diuretics, antihypertensives, and hypoglycemics) during 1984, but not in the previous 6 months. Antidepressants initiated within 12 months after the study drug were counted. Of the 3218 new beta-blocker users, 6.4% received concurrent prescriptions (ie, within 34 days) for an antidepressant and beta-blocker. Only 2.8% of the reference group (no study drug use) received an antidepressant. A greater proportion of patients prescribed propranolol (9.5%) received an antidepressant than those prescribed other "lipophilic" (3.9%) or "hydrophilic" (2.5%) beta-blockers. Incidence ratios for propranolol revealed the overall risk antidepressant use was 4.8 (95% confidence interval [CI], 4.1 to 5.5) times that of the reference group and 2.1 (95% CI, 1.7 to 2.5) times that of all other study drug users. For propranolol, relative risk of antidepressant use (drug/reference group) varied with age and was greatest in the 20- to 39-year-old group (17.2; 95% CI, 13.7 to 21.5).

Adrenergic beta-Antagonists↗
PubMed1990

Image processing by computer analysis--potential use and application in civil and criminal litigation.

The image processing by computer analysis has established a data base for applications in the industrial world. Testing has proved that the same system can provide documentation and evidence in all facets of modern day life. The medicolegal aspects in civil and criminal litigation are no exception. The primary function of the image processing system is to derive all of the information available from the image being processed. The process will extract this information in an unbiased manner, based solely on the physics of reflected light energy. The computer will analyze this information and present it in pictorial form, with mathematical data to support the form presented. This information can be presented in the courtroom with full credibility as an unbiased, reliable witness. New scientific techniques shown in the courtroom are subject to their validity being proven. Past imaging techniques shown in the courtroom have made the conventional rules of evidence more difficult because of the different informational content and format required for presentation of these data. I believe the manner in which the evidence can now be presented in pictorial form will simplify the acceptance. Everyone, including the layman, the judge, and the jury, will be able to identify and understand the implications of the before and after changes to the image being presented. In this article, I have mentioned just some of the ways in which image processing by computer analysis can be useful in civil and criminal litigation areas: existing photographic evidence; forensic reconstruction; correlation of effect evidence with cause of evidence; medical records as legal protection; providing evidence of circumstance of death; child abuse, with tracking over time to prevent death; investigation of operating room associated deaths; detection of blood at the scene of the crime and on suspected objects; use of scales at the scene of the crime; providing medicolegal evidence beyond today's technology; and a new theory and technique on using polygraph information in litigation. I am sure that the professionals in the forensic field will be able to think of many more applications where the image processing by computer analysis tool will be able to provide solutions to complex problems. The next time you say to yourself, "I wish they would have preserved this," or, "It's too bad they didn't do an autopsy," think of this new tool that is available to help you get the documentation and answers that will stand up to the scrutiny of the civil and criminal litigation system.

Accidents, Traffic↗
PubMed1990

Prostaglandins, the kidney, and hypertension.

Prostaglandins are part of the family of oxygenated metabolites of arachidonic acid known collectively as eicosanoids. While they are formed, act, and are inactivated locally and rarely circulate in plasma, they can affect blood flow in some tissues and so might contribute to the control of peripheral vascular resistance. Few studies have shown any derangement of total body prostaglandin synthesis or metabolism in hypertension, but increased renal synthesis of one prostanoid, thromboxane A2, has been noted in spontaneously hypertensive rats and some hypertensive humans. This potent vasoconstrictor may account for the increased renal vascular resistance and suppressed plasma renin activity seen in many patients with hypertension. Increased renal vascular resistance could increase the blood pressure directly as a component of total peripheral resistance or indirectly by increasing glomerular filtration fraction and tubular sodium reabsorption. Specific thromboxane synthesis inhibitors not only decrease renal thromboxane production but also increase renal vasodilator prostaglandin synthesis when prostaglandin synthesis is stimulated. This redirection of renal prostaglandin synthesis toward prostacyclin might be of benefit in correcting a fundamental renal defect in patients with hypertension.

Animals↗
PubMed1990

Outpatient management of traumatic microhyphemas.

Traumatic microhyphema is an entity encountered in emergency rooms and general ophthalmology practices. The management of traumatic microhyphema has not been well defined in the literature. We discuss the effectiveness of our treatment regimen and the incidence of rebleed in patients with microhyphema.

Adult↗
PubMed1990

Aminocaproic acid prophylaxis in traumatic hyphema.

Oral aminocaproic acid has been shown to be effective in clot stabilization and in the reduction of secondary bleeding rates in cases of traumatic hyphema. In a retrospective study of 105 patients treated during a 1-year period, we found the incidence of rebleeding in patients with traumatic hyphema who received aminocaproic acid prophylaxis was 2%; the incidence in those who did not was 25%.

Administration, Oral↗
PubMed1989

Effects of aging on responses to furosemide.

Furosemide causes both diuretic and non-diuretic changes in renal function. We compared responses to intravenous furosemide 0.5 mg.kg-1 in 38 subjects (30 males, 8 females) aged 18 to 30 with those in 14 subjects (9 males, 5 females) aged 50 and over. There were no consistent differences attributable to gender. Older persons showed greater natriuresis (47 percent in males and 26 percent in females) but their increment in plasma renin activity was markedly reduced. The urinary excretion of thromboxane B2 was elevated in older subjects (58 +/- 10 vs. 30 +/- 4 ng/4 h, p less than 0.05 for males; 48 +/- 7 vs. 29 +/- 4 ng/4 hr, p less than 0.05 for females) while that of 6-keto prostaglandin F1 alpha was not different. While differences in the diuretic response to furosemide may be due to pharmacokinetic differences, the non-diuretic response differences may reflect age related changes in renal prostaglandin synthesis.

Adolescent↗
PubMed1989

Sulindac does not spare renal prostaglandins.

It has been suggested that the nonsteroidal anti-inflammatory drug, sulindac, selectively spares renal prostaglandin synthesis. We compared the effect of placebo and sulindac 300 mg daily for one week on furosemide-stimulated renal prostaglandin synthesis in twelve healthy young men. Sulindac reduced serum thromboxane B2, a measure of platelet thromboxane A2 production, from 21 +/- 3.9 to 10.9 +/- 2.2 ng/ml (p less than 0.01) but had no effect on body weight, blood pressure or serum creatinine. Sulindac did, however, decrease the natriuretic effect of intravenous furosemide, and reduced the increment in plasma renin activity. The excretion rates of 6-keto-prostaglandin F1 alpha and thromboxane B2 in urine were reduced by 34 and 27% respectively (p less than 0.001 for both). The reduced excretion rate was particularly prominent in the first ten minutes after furosemide injection. While these decreases are less marked than those seen with indomethacin, the reduction in platelet thromboxane A2 production is also of lesser degree. We conclude that, in the dose used, sulindac is a less potent inhibitor of cyclo-oxygenase than indomethacin and has no selective renal sparing effect.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Hypertension in the elderly.

As many as forty percent of Canadians over age sixty-five have blood pressure readings of 160/90 or higher. They are at greater risk for stroke, congestive heart failure, myocardial infarction and sudden death. Hypertension appears to be an exaggeration of the normal circulatory changes of aging--increased systemic vascular resistance and a slight decrease in cardiac output at rest and during exercise. The major trials of treatment for hypertension have included subsets of elderly hypertensives who have enjoyed about the same overall benefit from treatment as younger subjects. Two treatment trials specifically for elderly hypertensives also show that treating systolic-diastolic hypertension does more good than harm. Isolated systolic hypertension appears to be a risk factor of equal magnitude to systolic/diastolic hypertension. Although it is possible to treat isolated systolic hypertension, the definitive clinical trial comparing mortality and morbidity in treated and untreated groups is not yet published. Thiazides, while inexpensive and effective antihypertensives for the elderly, are relatively contraindicated in as many as half. Other classes of drugs, particularly calcium channel blockers, can be effective alternatives. Many, if not most, elderly hypertensives will be prescribed more than one type of antihypertensive in addition to other types of drugs. The possibility of drug interactions as well as the danger of overly rapid blood pressure reduction must be kept in mind.

Aged↗
PubMed1989

Eye injuries in childhood: demography, etiology, and prevention.

A 1-year survey was conducted of all children with eye injuries seen in the Wills Eye Hospital emergency room to determine demographic, etiologic, and prophylactic factors. There were 810 children with ocular trauma. Childhood ocular injuries are frequent, often resulting in serious visual impairment. Many of these injuries are preventable.

Accidents↗
PubMed1988

The effects of continuing medical education on family doctor performance in office practice: a randomized control study.

A randomized controlled study was conducted to determine if specifically designed continuing medical education in the fields of cardiovascular and cancer medicine could change doctor office behaviour significantly. Thirty-one volunteer family doctors from 25 offices participated. Six (three cardiovascular and three cancer) learning objectives were defined. Two educational formats were selected as the independent variables: (1) group interaction opportunities (face-to-face and teleconference); and (2) concisely written newsletters. Chart measures of doctor performance prior to and 6 and 12 months following education served as the dependent variables. The family doctors receiving education were found to perform the recommended behaviours significantly more than those who did not receive the education (P less than 0.05) at 6 months post-education. This difference was maintained at the 12-month post-educational period for one of the educational programmes offered. A carefully planned programme of continuing medical education will result in favourable changes in the office practice of volunteer doctors. These changes can persist for as long as 12 months. Adherence to several essential learning principles is required.

Cardiology↗
PubMed1988

Effects of atenolol and enalapril on blood pressure, plasma renin activity and urinary prostanoids.

In order to assess whether blood pressure reduction with atenolol or enalapril is associated with changes in renal prostaglandin (PG) synthesis, we studied the effects of 10 weeks therapy in 20 subjects with mild or moderate hypertension. After a four week placebo run-in period, subjects were randomized to receive either atenolol 50-100 mg/day or enalapril 5-20 mg/day for 10 weeks, then crossed over to the alternate active drug. Both drugs lowered blood pressure: placebo 147/97, atenolol 135/87, enalapril 132/87 (p less than 0.05, for both). Atenolol reduced resting heart rate but neither drug changed body weight, serum sodium or potassium or creatinine clearance. Intravenous furosemide was used as a standardized stimulus of renal PG synthesis. Neither drug changed the excretion rates of 6ketoPGF1 alpha or thromboxane B2 (hydrolysis products of PGI2 and thromboxane A2 respectively). Diuretic, kaliuretic, and natriuretic effects of furosemide were also not affected. Plasma renin activity was increased by enalapril but reduced slightly by atenolol. Subjects with more marked blood pressure reduction showed responses to furosemide no different than those with less effect. We conclude that blood pressure reduction with atenolol or enalapril does not change the response of renal eicosanoid synthesis to acute stimulation with furosemide.

Adult↗
PubMed1987

Indomethacin increases the formation of lipoxygenase products in calcium ionophore stimulated human neutrophils.

Arachidonic acid metabolism in human neutrophils stimulated in vitro with the calcium ionophore A23187 was studied using combined HPLC and radioimmunoassays. Indomethacin (0.1 and 1.0 microM) caused a 300% increase in LTB4 formation in neutrophils stimulated with A23187. 5-, 12- and 15-HETE levels were also increased. In the presence of exogenous arachidonic acid 1.0 microM Indomethacin caused a 37% increase in LTB4 formation. Acetyl Salicylic Acid and Ibuprofen had no effect on the formation of lipoxygenase metabolites. The effect of indomethacin on LTB4 formation does not appear to be due to a simple redirection of substrate arachidonic acid from the cyclooxygenase to the lipoxygenase pathways.

Aspirin↗
PubMed1987

Testing the "redirection hypothesis" of prostaglandin metabolism in the kidney.

Furosemide increases the synthesis of two major renal eicosanoids, prostacyclin (PGI2) and thromboxane A2 (TXA2), by stimulating the release of arachidonic acid which in turn is metabolized to PGG2/PGH2, then to PGI2 and TXA2. PGI2 may mediate, in part, the early increment in plasma renin activity (PRA) after furosemide. We hypothesized that thromboxane synthetase inhibition should direct prostaglandin endoperoxide metabolism toward PGI2, thereby enhancing the effects of furosemide on renin release. Furosemide (2.0 mg . kg-1 i.v.) was injected into Sprague-Dawley rats pretreated either with vehicle or with U-63,557A (a thromboxane synthetase inhibitor, 2 mg/kg-1 followed by 2 mg/kg-1 X hr-1). Urinary 6ketoPGF1 alpha and thromboxane B2 (TXB2), reflecting renal synthesis of PGI2 and TXA2, as well as PRA and serum TXB2, were measured. Serum TXB2 was reduced by 96% after U-63,557A. U-63,557A did not affect the basal PRA. Furosemide increased PRA in both vehicle and U63,557A treated rats. However, the PRA-increment at 10, 20 and 40 min following furosemide administration was greater in U-63,557A-treated rats than in vehicle-treated rats and urine 6ketoPGF1 alpha excretion rates were increased. These effects of thromboxane synthesis inhibition are consistent with a redirection of renal PG synthesis toward PGI2 and further suggest that such redirection can be physiologically relevant.

6-Ketoprostaglandin F1 alpha↗