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Biomedical subjects

U Roth

Publications and source records attributed to U Roth.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Value of Doppler color ultrasonography in diagnosis of arterial occlusive disease of the lower extremity. A direct comparison with percutaneous angiography].

UNLABELLED: A Direct Comparison with Percutaneous Angiography: AIM: To compare colour-coded Doppler sonography (CCDS) with conventional angiography in severe occlusive vascular disease of the lower limb. METHODS: In 55 patients 1141 vessel segments were evaluated, 700 of them with atheromatous plaques, 270 with stenoses, 208 with occlusions and 6 with aneurysms. RESULTS: Deeper-seated vessels such as the abdominal aorta, the pelvic arteries, the superficial femoral artery at the level of the adductor canal and parts of the lower leg arteries are less accessible for direct CCDS. Many pathological changes however can be diagnosed indirectly by changes in the spectral wave form distal to the lesion. In superficial vascular segments (the common femoral artery, the profunda femoris artery, the superficial femoral artery above the adductor canal and the popliteal artery) image quality was excellent, more pathological changes were found, and the degree of stenosis was better estimated in comparison to angiography. CONCLUSION: The value of CCDS in patients with intermittent claudication is limited to those who have been examined with angiography e.g. before angioplasty, to follow-up examinations after vascular dilatation or surgery and to supplementary visualisation after angiography especially in readily accessible (superficial) vascular segments.

Adult↗
PubMed1996

Membrane protein subunit fractionation by means of inverse pore gradient elution polyacrylamide gel electrophoresis.

We report here the preparative scale isolation of the four subunits of the nicotinic acetylcholine receptor (nAChR) applying short inverse pore gradient SDS gels on an elution-PAGE apparatus. The nAChR subunits are of similar molecular weights (alpha, 50.2 kDa; beta, 53.7 kDa; gamma, 56.3 kDa; delta, 57.6 kDa) and isoelectric point (approx 5.5) and share the typical properties of amphiphatic membrane proteins that are difficult to separate by chromatographic procedures. Preparative PAGE, which has proved to be the method of choice for nAChR-subunit fractionation, however, is time-consuming and achieves only moderate resolutions yielding dilute fractions. We present here the fractionation of a membrane preparation of Torpedo electric organ (2 mg of total protein) on short gels (2 cm) with linear or concave inverse pore gradients. All of the four subunits are isolated in homogeneous fractions of approx 70 micrograms/ml within only 4 h. Compared to the standard method, this means a 50% reduction in separation times with threefold higher concentrated protein fractions. We also give the theoretical explanation and experimental validation of the improved features resulting from short inverse-gradient polyacrylamide gels.

Animals↗
PubMed1996

Agonist responses of neuronal nicotinic acetylcholine receptors are potentiated by a novel class of allosterically acting ligands.

Similar to the gamma-aminobutyric acidA receptor and the N-methyl-D-aspartate subtype of glutamate receptor, neuronal nicotinic acetylcholine receptors are subject to positive modulatory control by allosterically acting ligands. Exogenous ligands such as galanthamine and the neurotransmitter 5-hydroxytryptamine, when applied in submicromolar concentrations with nicotinic agonists, significantly increase the frequency of opening of nicotinic receptor channels and potentiate agonist-activated currents. Because these effects have been shown to be blocked by the monoclonal antibody FK1, they are mediated by binding sites that are located on alpha subunits of nicotinic receptors and distinct from those for acetylcholine and acetylcholine-competitive ligands. At higher concentrations, the potentiating effect of these ligands decreases and is eventually overcome by an inhibition of the agonist-induced response. The sensitizing actions of galanthamine, 5-hydroxytryptamine, and related compounds, at submicromolar concentrations, may reflect the existence of cross-talk between adjacent neuroreceptors and synapses in the central nervous system and thus suggests the formation of transiently active chemical networks in the vertebrate brain.

Allosteric Site↗
PubMed1995

[The value of color Doppler ultrasound in follow-up of percutaneous transluminal angioplasty of the thigh area].

The value of colour-coded Doppler sonography to evaluate results of percutaneous transluminal angioplasty of the superficial femoral artery was tested in 26 patients. Because of good accessibility, morphology may be demonstrated similar to intravenous DSA. However, accurate evaluation of dilatation success also requires haemodynamic measurements. Numerous parameters were determined one day before, one day after and one month after angioplasty at various points of the extremity (dilated segment, popliteal artery, lower leg arteries). Results were compared with those of normal individuals. Because of the large range of scatter and overlapping between normal and pathological values, only a few parameters can be used as valuable indicators for successful PTA. Spectral wave form becomes bi- or triphasic pattern and due to this the Pulsatility Index rises distal to the dilated area. An increasing systolic acceleration rate, peak systolic velocity and prestenotic Pulsatility Index have excellent predictive value. Using a Damping Factor, the later walking range may be predicted.

Adult↗
PubMed1994

[Principles of quantitative color Doppler ultrasound of pelvic and leg arteries. Normal sample].

Statistical analysis of a group of 25 healthy individuals, examined via angiodynography, shows a large range of scatter for all measured parameters in pelvic and lower extremity arteries. Blood flow and velocity values, systolic acceleration and vessel diameter decrease whereas the pulsatility index rises from the centre towards the periphery. Problem areas for morphological and quantitative evaluation are the abdominal aorta, pelvic vessels, superficial femoral artery in the distal adductor canal and the fibular artery. Nearly all vessels showed tri- or multiphasic spectral patterns. Biphasic waveform, however, may be normal in lower extremity arteries. The data yielded by colour-coded Doppler sonography were comparable to results obtained with other procedures.

Adolescent↗
PubMed1994

Identification of purine binding sites on Torpedo acetylcholine receptor.

Electrophysiological studies from this and other laboratories have suggested a direct action of ATP on nicotinic acetylcholine receptors (nAChR). To determine the site of binding of this purine derivative, we have covalently modified the nAChR from Torpedo marmorata electrocytes employing 2-[3H]-8-azido-ATP as a photoactivable affinity label. Covalently attached radioactivity was predominantly found in the beta-polypeptide of the receptor. Based on the results of protection studies with several nAChR ligands whose target sites at the receptor are known, we conclude that the purine site(s) differ from those of acetylcholine and of physostigmine, galanthamine and related ligands, and those of local anesthetics.

Adenosine Triphosphate↗
PubMed1992

Role of the oral calcium-loading test with measurement of intact parathyroid hormone in the diagnosis of symptomatic subtle primary hyperparathyroidism.

BACKGROUND: This study was designed to assess the diagnostic value of the oral calcium tolerance test with measurement of intact parathyroid hormone by the immunoradiometric assay (IRMA PTH) in the diagnosis of primary hyperparathyroidism in patients with symptoms who have minimal, intermittent, or no elevation of the levels of total calcium and/or intact PTH. METHODS: After baseline levels of IRMA PTH and total calcium were measured, an oral calcium load of 1000 mg elemental calcium was administered to 10 patients with hyperparathyroidism and 18 normal control subjects. Total calcium and IRMA PTH levels were measured at 30, 60, and 120 minutes after the oral calcium load was administered. RESULTS: The mean suppression of the baseline level of IRMA PTH in the patients with hyperparathyroidism was 83.7% +/- 6.5% (mean +/- 1 SEM), but the levels of the normal control subjects fell significantly (p < 0.05) lower to 58.8% +/- 3.7% (mean +/- 1 SEM). CONCLUSIONS: This study suggests that the oral calcium tolerance test may be a valuable adjunct in confirming the diagnosis of primary hyperparathyroidism in patients with symptoms who have minimal, intermittent, or no elevation of the levels of total calcium and/or IRMA PTH:

Administration, Oral↗
PubMed1991

[The value of angiodynography in follow-up of surgical vascular prostheses].

Apart from the proximal anastomosis, aortoiliac/-femoral bypass is accessible to angiodynography. The spectral waves can mostly be derived and analyzed very well. Femoropopliteal grafts can be demonstrated over the whole length, including the anastomoses if they are not located in the adductor (Hunter's) canal. Pathological findings such as stenosis or aneurysms can be easily detected. Because of a large range of scatter, blood velocity or flow are no suitable parameter to determine functioning and prognosis of the bypass. A triphasic spectral waveform in the graft, the failing of aneurysms, stenosis or turbulent blood flow in the anastomosis, a high "Pulsatility Index" and a short systolic blood flow acceleration distal to the bypass, proved to be more important parameters, that can be easily determined via colour coded Doppler sonography.

Adult↗
PubMed1991

[Phantom studies using echo contrast media to improve the Doppler color sonographic imaging of the superficial femoral artery in the adductor canal].

The adductor canal was simulated using 2.6 cm muscular tissue and 2 fasciae to analyse the limits of colour-coded Doppler sonography (angiodynography) in this region. Defects in the spectral signal cause a significant underestimation of mean, peak systolic and peak diastolic (backflow) velocities and of calculated blood flow. Furthermore the pulsatility index is overestimated and the colour-coded visualisation of the arteries is almost lost. For the most part, these changes can be compensated by administration of a sonographic contrast agent (SH U 454). A minimum of 9 mg microbubbles/ml blood is required. Nevertheless, the adjustment of system controls (e.g. transducer power) becomes more difficult and an ideal setting impossible.

Contrast Media↗
PubMed1990

[Duplex sonography: accuracy, reproducibility and possibilities for error. Checking quantitative flow measurements against an in vitro model].

Using a pulsatile model of tubes, duplex-sonographic measurements of flow were compared with actual flow. The correlation coefficient between actual and duplex-sonographically obtained flow was 0.975, mean percentage deviation being -18.1% (P less than 0.0001). The obvious scatter (margin of error -69.2 to +50%) is to be explained by the simulation closely imitating a real situation: the transducer was hand-held and tubes were placed in muscle or fat tissue. Accuracy was increased by multiple measurements, especially when taking into account only the maximal value of any series of measurements. Vessel diameter was easy to measure accurately (mean error less than 0.01% [-18.7 to +9.4%]). Repeated measurements of flow velocity had only a small scatter (coefficient of variance 0.064). In muscle or fat the Doppler signal was attenuated and the error the greater the deeper the level at which measurements were made. Low flow (common in patients with obstructive vascular disease) can also cause faulty results.

Analysis of Variance↗
PubMed1990

[A realistic cardiovascular model for evaluating clinical applicability of duplex and color-Doppler equipment].

To evaluate the accuracy and reliability of colour-coded Doppler devices (CCDD) for practical use, a circulatory phantom with in vivo characteristics was developed. The experimental design consists of a piston-diaphragm metering pump with an adjustable piston volume and frequency of stroke as well as silicone tubings with different elasticity and diameters comparable with cadaver arteries. Depending on physiological conditions, blood as a circulating fluid and the surrounding soft tissues of the artery near the Doppler probe should be employed. The transducer should be manually guided. Thus, comparable to physiological frequency spectral displays, different types of wave forms (e.g. monophasic, triphasic) were initiated to analyze the reliability of CCDDs for practical use.

Blood Flow Velocity↗
PubMed1990

[Phantom studies of the value of color-coded Doppler sonography in arterial occlusive disease of the lower extremities].

A new practically orientated phantom for evaluating Doppler Duplex equipment was developed and used to determine the possibilities and limits of color coded Doppler Sonography (Angiodynography) in the diagnosis of arterial occlusive disease of the lower extremity. The problems that may occur in quantifying flow in these arteries are analyzed. The influence of superimposed slices of various soft-tissues on flow quantification, on the spectral waves and on color coded visualisation of the arteries and the possibility to compensate those changes by the use of sonographic contrast agents are discussed.

Arterial Occlusive Diseases↗