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Biomedical subjects

R D Bowen

Publications and source records attributed to R D Bowen.

7 recordsLinked to original sources
PubMed2006

Permeation of bioactive constituents from Arnica montana preparations through human skin in-vitro.

This study investigated and characterised transdermal permeation of bioactive agents from a topically applied Arnica montana tincture. Permeation experiments conducted over 48 h used polydimethylsiloxane (silastic) and human epidermal membranes mounted in Franz-type diffusion cells with a methanol-water (50:50 v/v) receptor fluid. A commercially available tincture of A. montana L. derived from dried Spanish flower heads was a donor solution. Further donor solutions prepared from this stock tincture concentrated the tincture constituents 1, 2 and 10 fold and its sesquiterpene lactones 10 fold. Permeants were assayed using a high-performance liquid chromatography method. Five components permeated through silastic membranes providing peaks with relative retention factors to an internal standard (santonin) of 0.28, 1.18, 1.45, 1.98 and 2.76, respectively. No permeant was detected within 12 h of applying the Arnica tincture onto human epidermal membranes. However, after 12 h, the first two of these components were detected. These were shown by Zimmermann reagent reaction to be sesquiterpene lactones and liquid chromatography/diode array detection/mass spectrometry indicated that these two permeants were 11,13-dihydrohelenalin (DH) analogues (methacrylate and tiglate esters). The same two components were also detected within 3 h of topical application of the 10-fold concentrated tincture and the concentrated sesquiterpene lactone extract.

Administration, Topical↗
PubMed1982

The effects of gating delays on ejection estimates: concise communication.

We have examined the effects of gating delays on the left-ventricular ejection fraction as measured by gated blood-pool studies. Patients with normal ventricular function were shown to have greater errors introduced by gate delays than those with poor function. The magnitude of the error depends on the shape of the ventricular time-activity curve. Actual delay measurements were performed on several commercial gates.

Cardiac Output↗
PubMed1980

Detection of obstructive uropathy using 99mtechnetium diethylenetriaminepentaacetic acid.

A simple, accurate test with no morbidity and effective for the detection of urinary tract obstruction in patients with normal and impaired renal function would be of significant clinical use. We herein evaluate the ability of 99mtechnetium diethylenetriaminepentaacetic acid to detect the presence or absence of obstruction. Of 107 patients who underwent recent studies 31 had confirmation of the presence or absence of obstruction by excretory urography, retrograde pyelography or other definitive procedures. Patients were studied in the posterior projection wtih perfusion images after intravenous injection of 20 millicuries 99mtechnetium diethylenetriaminepentaacetic acid. Static images of the urinary tract were obtained from 1 to 30 minutes after injection with delayed images up to 24 hours. Obstruction were defined as abnormal retention of activity in the collecting system persisting in the delayed images. Diethylentriaminepentaacetic acid identified correctly 13 of 13 patients proved to have obstruction and 17 of 18 without obstruction. One falsely positive result was owing to pyelocaliectasis. These data indicate a sensitivity of 100 per cent, specificity of 94 per cent and accuracy of 97 per cent.

Aged↗
PubMedDate not supplied

Radionuclide measurement of differential glomerular filtration rate.

The authors sought to determine whether radionuclides could provide a reasonable estimate of differential renal function in five normal dogs and six dogs with unilateral segmental renal infarction. Glomerular filtration rate (GFR) of each kidney was measured by the standard technique using constant infusions of 99mTc-DTPA, iothalamate, and creatinine following ureteral catheterization. These results were correlated with total GFR estimated by bolus injection of 99mTc-DTPA and analysis of the plasma 99mTc-DTPA disappearance curve obtained by blood sampling. Differential GFR was then calculated by multiplying the total GFR from double exponential analysis of this curve (DTPA2) by each of three measures of differential function. These include the percent differential uptake of 99mTc-DTPA and 99mTc-DMSA in the posterior projection as well as the geometric mean of 99mTc-DMSA uptake. There were good correlations between differential GFR calculated from iothalamate clearances obtained at ureteral catheterization and all noninvasive methods involving radionuclides and DTPA2 (r = 0.85 - 0.99). Single exponential analysis of the 99mTc-DTPA plasma disappearance curve was less satisfactory. The authors suggest that measurement of total and differential GFR calculated from plasma clearance of 99mTc-DTPA and external counting may be a useful method with potential clinical applications.

Animals↗
PubMedDate not supplied

Radionuclide measurement of differential glomerular filtration rate in urinary tract obstruction.

In a previous study using dogs whose renal function was rendered asymmetric by unilateral infarction, the efficacy of technetium-99m (99mTc) DTPA and DMSA in measuring differential glomerular filtration rate (GFR) was demonstrated. The present study was undertaken to determine whether the same techniques were applicable to unilateral ureteral obstruction. Five normal dogs and nine dogs with partial unilateral ureteral obstruction had determination of glomerular filtration rate by standard techniques using constant infusions of iothalamate and creatinine after ureteral catheterization. These results were compared with total GFR as measured by single injection of 99mTc DTPA and analysis of the plasma disappearance curve. Calculated differential GFR was obtained by multiplying total GFR from double exponential analysis of this curve (DTPA2) by each of three measures of differential function. These included the percent differential uptake of 99mTc DTPA and 99mTC DMSA in the posterior projection as well as the geometric mean of 99mTc DMSA uptake. There were good correlations between differential GFR determined by iothalamate clearances at ureteral catheterization and all noninvasive methods involving radionuclides and DTPA2 ( r = 0.93-0.99). Single exponential analysis of the 99mTc DTPA plasma disappearance curve was less satisfactory than double exponential analysis. These results and those reported previously support the use of radionuclides in the determination of differential GFR in a variety of clinical situations.

Animals↗
PubMedDate not supplied

Noninvasive measurement of an index of renal blood flow.

A new technique for the noninvasive measurement of an index of renal blood flow is described. The method utilizes ultrasound determined renal volume and radionuclide assessment of the mean transit time of a pertechnetate bolus through the kidneys. From this information a value for flow is calculated according to compartmental analysis principles. There is good correlation between renal blood flow estimated by this technique and that determined by microsphere injection, r = 0.96.

Animals↗