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Biomedical subjects

D T Kopp

Publications and source records attributed to D T Kopp.

12 recordsLinked to original sources
PubMed1991

Effect of strict glycemic control on renal hemodynamic response to amino acids and renal enlargement in insulin-dependent diabetes mellitus.

BACKGROUND: Many patients with insulin-dependent diabetes mellitus have an increase in the glomerular filtration rate and renal enlargement early in the course of their disease. Both these changes may be risk factors for the later development of diabetic nephropathy. Their cause is not known, but they could be due to augmented renal responses to the increase in plasma amino acid concentrations that occurs when dietary protein intake is high, a factor known to increase glomerular filtration and renal blood flow in normal subjects. METHODS: We measured the glomerular filtration rate and renal plasma flow after an overnight fast and during an infusion of amino acids in 12 patients with insulin-dependent diabetes mellitus and 9 normal subjects. The diabetic patients were studied when they were hyperglycemic, when they were euglycemic after an insulin infusion for 36 hours, and after intensive insulin therapy for 3 weeks. Kidney volume was measured by ultrasonography before and after the period of intensive insulin therapy. RESULTS: The glomerular filtration rate and renal plasma flow were normal after fasting when the patients were hyperglycemic (mean [+/- SE] fasting plasma glucose level, 11.5 +/- 0.7 mmol per liter). After the amino acid infusion, these values increased more in the patients (glomerular filtration rate, 2.65 +/- 0.07 ml per second per 1.73 m2 of body-surface area; renal plasma flow, 13.30 +/- 0.68 ml per second per 1.73 m2; P less than 0.05 for both) than in the normal subjects (2.25 +/- 0.08 and 11.20 +/- 0.65 ml per second per 1.73 m2, respectively). The 36-hour infusion of insulin in the diabetic patients did not alter the glomerular filtration rate or renal plasma flow either before or during the amino acid infusion. After three weeks of intensive insulin therapy (fasting plasma glucose level, 5.3 +/- 0.2 mmol per liter), the glomerular filtration rate and renal plasma flow after the amino acid infusion (2.33 +/- 0.03 and 11.30 +/- 0.43 ml per second per 1.73 m2, respectively) were similar to those in the normal subjects. The kidney volumes in the normal subjects and the patients with diabetes were 219 +/- 14 and 312 +/- 14 ml per 1.73 m2, respectively (P less than 0.01); the volume decreased to 267 +/- 22 ml per 1.73 m2 (P less than 0.001) in the diabetic patients after three weeks of intensive insulin therapy, which was not significantly different from the volume in the normal subjects (P = 0.1). CONCLUSIONS: Conventionally treated diabetic patients who have normal renal function while fasting have augmented renal hemodynamic responses to increased plasma amino acid concentrations. The concomitant decrease in these hemodynamic responses and in kidney size with strict glycemic control suggests that these phenomena are related and influenced by the metabolic state.

Adult↗
PubMed1987

Normal and stenotic renal arteries: experimental balloon-expandable intraluminal stenting.

Elastic recoil of the vessel wall is a common cause of failure of percutaneous transluminal angioplasty in renal arteries. To oppose such recoil, balloon-expandable metal stents were implanted in artificially stenotic renal arteries in pigs and normal renal arteries in dogs and pigs. The stents were then examined angiographically and histologically at regular intervals. All stents were completely covered with endothelialized neointima in 3 weeks. There was no difference in intimal thickness between the stenotic and nonstenotic renal arteries. A large stent diameter and a large open or nonmetal surface may cause less intimal hyperplasia, but nonturbulent, fast arterial flow is probably the most important factor in ensuring long-term patency of the vessel.

Angioplasty, Balloon↗
PubMed1986

Expandable intrahepatic portacaval shunt stents in dogs with chronic portal hypertension.

A canine experimental model was used to investigate the feasibility of using balloon-expandable portacaval shunts in humans with chronic portal hypertension. Intrahepatic portacaval shunts were created in nine dogs with stable portal hypertension previously induced by intraportal injections of polyvinyl alcohol (Ivalon). Embolic material was injected periodically through a subcutaneous port that allowed repeated access to the portal system. Shunts were placed 14 weeks after the last embolization. A shunt patency rate of 100% was observed up to 48 weeks. Low portacaval pressure gradient and high shunt flow accounted for the good results.

Animals↗
PubMed1985

Effect of errors in reangulation on planar and tomographic thallium-201 washout profile curves.

Cardiac phantom studies were performed with and without a defect present to test the hypothesis that myocardial 201TI quantitative circumferential washout profile curves calculated from planar and rotating slant hole (RSH) collimator tomographic images are equally affected by errors in axial repositioning. Simulated stress images were acquired with the long axis of the phantom perpendicular to the camera surface and redistribution images were acquired to represent 50% 201TI washout with axial repositioning errors relative to the stress position ranging from 0 to 20 degrees in 5 degrees increments. There was a decrease in the 201TI washout profile curves compared to that expected (50%) in the wall tilted away from the camera surface, and a reciprocal increase in the 201TI washout profile curves in the wall tilted towards the camera surface for both imaging techniques whether a lesion was present or not. This effect became more pronounced as the error in axial repositioning was increased for both the planar (p less than 0.001) and the RSH tomographic (p less than 0.001) techniques. However, the deviation of the 201TI washout profile curves from that expected (50%) was greater for the planar imaging technique with or without a lesion (p less than 0.05 to 0.001). Thus, we conclude that 201TI quantitative circumferential washout profile curves calculated using this tomographic imaging technique are less affected by errors in axial repositioning than those calculated using an equivalent projection by standard planar imaging methods. These data emphasize the importance which must be placed on the repositioning of patients to obtain valid 201TI washout profile curves for the detection and localization of coronary artery disease.

Coronary Disease↗
PubMed1985

Practical gamma camera quality control with a four-point phantom.

A gamma camera QC phantom for practical assessment of resolution (average FWHM), spatial calibration (pixels/mm), nonhomogeneity of spatial calibration, and average point-source sensitivity (cpm/muCi) was developed and evaluated. The phantom consists of four 57Co-point sources mounted on a Plexiglas base at corners of a square 10 cm on each side. Computer acquisition and processing are fully automated and require less than 1 min for point sources totaling 100 muCi (3.7 MBq) activity. The normal range of variability of measured QC parameters from a 12 wk evaluation period with four different gamma cameras (assumed to be operating normally) yielded coefficients of variation ranging from 0.3% for spatial calibration (pixels/mm) to 2.3% for sensitivity (cpm/muCi) assessments. From the normal range of variability a minimum detectable difference (MDD) was determined for each measured parameter and each gamma camera. The range of acceptable operation of a gamma camera system was set as the measured value +/- MDD for each QC parameter. The ability to detect and track small changes in the measured QC parameters was evaluated.

Cobalt Radioisotopes↗
PubMed1983

Factors affecting radiation exposure and radiographic image contrast in urology.

An evaluation of certain radiographic factors affecting patient exposure during urography is made. Factors considered include selection of tube kilovoltage, total beam filtration and film-screen combination. The effect on image quality is also considered. Experimental results suggest specific actions which would result in decreased patient exposure without compromising quality of the examination.

Humans↗
PubMed1982

Predicting splenic abnormality in Hodgkin disease using volume response to epinephrine administration.

The change in relative splenic volume following epinephrine administration was used to determine splenic abnormality noninvasively. Selective splenic imaging was accomplished with 99mTc-labeled heat-treated red blood cells, an LFOV gamma camera, a 30 degrees bilateral rotating slant hole collimator, and bilateral slant hole tomographic software. Relative splenic volumes were plotted over time, and correlated with clinical and histologic data. Eight patients with Hodgkin disease and other lymphomas were examined. Volume response to epinephrine appears to be significantly less in abnormal spleens, and may serve to identify patients with unequivocally normal spleens prior to treatment.

Epinephrine↗
PubMed1977

Simultaneous measurement of triiodothyronine and thyroxine in unextracted serum samples using a double-tracer radioimmunoassay method.

A method is described for the simultaneous measurement of triiodothyronine (T3) and thyroxine T4) in 0.04 ml of unextracted serum. Antibodies were prepared by immunization of rabbits with T3 and T4 conjugated with human serum albumin. Bound and free labeled hormones were separated by the double-antibody technique, and 8-anilino-1-naphthalene sulfonic acid was used to inhibit binding of the two hormones to thyroxine-binding globulin. The validity of the assay using 125I-T3 and 131I-T4 is shown by the excellent recovery of T3 and T4 added to serum and by the finding that curves obtained by assaying various dilutions of a hyperthyroid serum run parallel to the standard curves. In all clinical serum T3 and T4 values obtained using the double-tracer radioimmunoassay method were in excellent agreement with those obtained by single-tracer RIA techniques. The combined T3-T4 method appears to be accurate, sensitive, and specific, thus making the assay highly desirable as a technical time-saver.

Anilino Naphthalenesulfonates↗
PubMedDate not supplied

Distance and depth measurements of radioactive objects utilizing rotating slant-hole collimators.

It is desirable to have an accurate method to determine the depth of various organs which are commonly imaged in nuclear medicine. The method presented here utilizes the geometrical characteristics of the rotating slant-hole collimator to calculate distances and depth. The accuracy of the calculated distance was evaluated for point sources in air separated by 11 cm. The reproducibility of the calculated distance was evaluated as a function of the extent of collimator rotation between observations for angular differences of 45 degrees, 90 degrees, 135 degrees, and 180 degrees. The theory of the method is discussed and the relative error in distance calculation analyzed mathematically as a function of (1) collimator rotation angle error, (2) collimator slant angle error, and (3) position calculation error. Our findings indicate this method to be accurate to within 2% with a reproducibility range of 3%-5% for point sources.

Humans↗