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T Weiss

Publications and source records attributed to T Weiss.

At least 19 recordsLinked to original sources
PubMed1992

Possible mechanism of ciliary stimulation by extracellular ATP: involvement of calcium-dependent potassium channels and exogenous Ca2+.

Ciliary motility was examined optically in tissue cultures from frog palate epithelium and frog's esophagus as a function of extracellular concentration of adenosine 5'-triphosphate (ATP) and related compounds. The addition of micromolar concentration of ATP caused a strong enhancement of frequency and wave velocity in the direction of the effective stroke. Since adenosine 5'-[beta,gamma imido]-triphosphate (AMP-PNP), a nonhydrolyzable analog of ATP, produces the same effects, ATP hydrolysis is not required. The overall potency is ATP approximately equal to AMP-PNP greater than ADP much greater than adenosine greater than AMP. It is suggested that both the phosphate and the base moieties are involved in ATP binding. The enhancement of ciliary activity by extracellular ATP is dependent on the presence of extracellular Ca2+, which can be replaced by extracellular Mg2+. The effect of a number of potent inhibitors of the voltage-gated calcium channels on the stimulation of ciliary activity by ATP were examined. No effect was detected in the concentration range within which these agents are specific. On the other hand, quinidine, a potent inhibitor of K+ (calcium-dependent) channels, inhibits the effect of ATP. The following model is suggested: exogenous ATP interacts with a membrane receptor in the presence of Ca2+, a cascade of events occurs which mobilizes intracellular calcium, thereby increasing the cytosolic free Ca2+ concentration which consequently opens the calcium-activated K+ channels, which then leads to a change in membrane potential. The ciliary response to these changes is the enhancement of ciliary activity.

Adenosine Triphosphate↗
PubMed1992

Effect of intensive walking exercise on skeletal muscle blood flow in intermittent claudication.

Walking exercise is generally accepted as a valid therapeutic regimen in the treatment of peripheral arterial occlusive disease (PAOD) of Fontaine stage II. In order to quantify the effect of walking exercise and/or drug therapy on regional muscular blood flow, PAOD Fontaine stage II was induced by multiple ligations of the femoral artery and of all side branches in one hindlimb of mongrel dogs; the contralateral extremity served as control. The animals underwent walking exercise with increasing intensities on a treadmill five days per week over one year; one group received 600 mg buflomedil (BF) per day orally in addition. At the end of the training period, the regional blood flow in all skeletal muscles of both hindlimbs was quantified by means of 15 microns radioactively labeled microspheres at resting conditions, after treadmill exercise (ten minutes) with or without preinjection of BF (3 mg/kg body weight) into the abdominal aorta. At resting condition and at the end of treadmill exercise the regional muscular blood flow did not differ significantly between the diseased and control extremity. Supplementary oral treatment with BF over one year had no significant effect; the increase in muscular blood flow during treadmill exercise was not enhanced after intra-aortic injection of BF. Consequently walking exercise has the potential to increase the functional capacity of collaterals in intermittent claudication and to restore blood supply to skeletal muscle.

Administration, Oral↗
PubMed1992

Intravascular ultrasound (IVUS) in patients with peripheral arterial occlusive disease (PAOD).

The new method of intravascular ultrasound (IVUS) permits an exact documentation of the pathomorphology of diseased arteries in a two-dimensional cross section image. Exact quantification of the vessel transverse diameters is achiveable. The different ultrasonic properties of fat, connective tissue and calcified tissue allow evaluation of intimal plaque composition. Thrombotic arterial occlusions can be detected. First experiences with IVUS prove, that this method is clearly superior to contrast arteriography and transcutaneous ultrasound, in terms of characterization and quantification of the extent of vessel wall disorders. Distinct structures, such as dissecting membranes or intimal flaps, which may escape arteriographic detection, are clearly visualized by IVUS. False adjustment of the physical parameters of the ultrasonic beam and non coaxial orientation of the ultrasound catheter within the vessel lead to false quantification of the transverse vessel diameters and to over- or underestimation of the echodensity and as a consequence of the intimal plaque composition. Simultaneous imaging of neighbouring arteries, veins or arterial branches allow longitudinal orientation within the vessel. Exact orientation however is only provided by simultaneous fluoroscopy. The present study demonstrates the value of IVUS as a guiding method of transcutaneous interventional procedures. The advantage could be an optimal selection of the recanalizing technique, appropriate to the arterial lesion. The result of interventional therapy can be documented immediately. Furthermore specific injuries of the vessel wall, leading to additional interventions and influencing short and long-term prognosis, can be imaged with high accuracy.

Angioplasty, Balloon↗
PubMed1991

Effect of reflex vagal activation on frequency of ventricular premature complexes.

To evaluate the antiarrhythmic effect of reflex-induced vagal activation, phenylephrine was infused in 17 patients with frequent ventricular premature complexes (VPCs). The role of heart rate reduction in suppressing VPCs was explored by pacing the atria at the preinfusion levels. Baroreceptor activation was considered effective when a greater than or equal to 20% decrease in heart rate was observed. Ten patients (59%) achieved the target heart rate decrease (-29 +/- 5%), whereas in 7 (41%) the baroreceptor reflex was considered inadequate. In the former group ("responders"), heart rate decreased from 73 +/- 7 to 52 +/- 6 beats/min (p less than 0.0001). When heart rate was allowed to fluctuate, ectopic activity was completely abolished in 9 of 10 patients; mean number of VPCs decreased from 38 +/- 8 to 0.2 +/- 0.6/100 beats (p less than 0.0001). During pacing, VPCs reappeared but their mean number (22 +/- 10/100 beats) was still significantly reduced compared with control values (p = 0.003). In the "nonresponders," despite adequate blood pressure increases, VPC frequency was not affected. The QT interval lengthened during phenylephrine (392 +/- 17 ms) versus control conditions (372 +/- 18 ms, p = 0.0008) in the responders group, whereas no change was observed in the nonresponders. These results demonstrate that reflex vagal activation markedly reduces VPCs. This effect is only partially rate-dependent; direct and indirect electrophysiologic changes secondary to baroreflex activation are also likely to be involved.

Adult↗
PubMed1991

Motor imagination--a model for motor performances?

The effect of training competition (TC) on central nervous activation was investigated in order to examine whether motor imagination could serve as a model for complex motor skills concerning information processing and motor control. EEG was recorded before and immediately after the TC. The mean alpha frequency (MAF) was computed from the EEG power density spectra. A significant increase of MAF was found after the TC. Similar changes were found during motor imagination. Thus, motor imagination seems to be a good model to examine activation processes.

Electroencephalography↗
PubMed1991

Effects of isoproterenol on T-wave amplitude and heart rate: a dose-response study.

This report examines the hypothesis that electrocardiographic T-wave amplitude is sensitive to graded increases in beta-sympathetic stimulation of the heart. Beta-adrenergic activity was manipulated pharmacologically in 9 healthy men by bolus infusion of isoproterenol in each of six doses: 0.1, 0.25, 0.5, 1.0, 2.0, and 4.0 micrograms. Results indicated that elevations in heart rate above placebo values increased as a linear function of isoproterenol dose. In contrast, the dose-response curve for T-wave amplitude was best described by a quadratic function: an initial reduction in T-wave amplitude at low levels of isoproterenol infusion was followed by a significant reversal of this effect at higher doses. Comparison of the heart rate and T-wave amplitude data points to limitations in the use of the latter as an index of beta-adrenergic activity. One of several possible explanations for the T-wave results would entail a mechanism that preserves ventricular function at high levels of beta-sympathetic stimulation.

Adult↗
PubMed1991

Periodic variations in skin perfusion in full-term and preterm neonates using laser Doppler technique.

In 37 full-term and preterm infants periodic oscillations of skin blood flux were studied by means of laser Doppler technique during the first week of life. The development of rhythmic oscillations of skin blood flux was similar in all infants. On the first postnatal day rhythmic oscillations were present in the heel skin of all full-term and preterm infants, but were rarely observed in the back and thigh skin. These flux motion patterns were not influenced by small changes in skin temperature. On day 4 rhythmic oscillations became predominant in all body regions. The oscillation frequencies of blood flux in the back, thigh and heel skin of full-term neonates reached the lower range of adult values at the end of the first postnatal week, whereas the oscillation frequencies in the preterm infants were still below the range of full-term neonates.

Back↗
PubMed1991

[Effect of intra-arterial and intravenous PGE1 infusions on transcutaneous oxygen pressure in patients with critical ischemia of the extremities].

In a randomized cross-over study 20 patients with peripheral arterial occlusive disease stage IV according to Fontaine received one i.a. infusion of 10 micrograms PGE1 in 25 ml saline over 30 min and one i.v. infusion of 40 micrograms PGE1 in 125 ml saline over 60 min. Transcutaneous PO2 was measured continuously (44 degrees C) on the forefoot and dorsum of the foot of the affected leg as well as on the forefoot of the contralateral limb. During i.a. infusion tcPO2 decreased by 73% on the forefoot combined with pain in the infused leg in 8 patients, whereas i.v. infusion induced a 83.1% increase in tcPO2. All in all i.v. PGE1 infusion resulted in a more pronounced increase of tcPO2 without causing side effects.

Alprostadil↗
PubMed1990

The effect of submandibular gland removal on testicular and epididymal parameters.

The effect of sialoadenectomy (submandibular gland removal) for four weeks duration was studied in five C3H mice and four sham-operated controls. This preliminary experiment using small numbers of animals indicated that sperm production parameters were lowered in sialoadenectomized animals although there were no significant differences between the sialodenectomized and sham-operated group. In a second experiment using larger numbers of animals, significant differences in testicular weights, epididymal weights, and testis weights were noted. These parameters were reduced only 10-14% from control levels. Epididymal sperm head counts were reduced 10% after sialoadenectomy but the two groups were not significantly different (P less than 0.05). No difference in testicular histology was observed. The present report contrasts to that of Tsutsumi et al. (1986) who indicate that submandibular removal with subsequent depletion of epidermal growth factor (EGF), is extremely deleterious (40-55% decreases in spermatid and sperm content) to the progress spermatogenesis.

Animals↗
PubMed1990

Dynamics of central nervous activation during motor imagination.

Central nervous processes of sensorimotor and behaviour control are prerequisites of skills and motor performance. Eight students (Ss) in sports were tested during motor imagination. They were requested to imagine their own movements when swimming over a distance of 100 m (sitting in a resting position, without any real or imitated movements). Electroencephalograms (EEG), heart rate (HR), skin conductance (SC), and respiration rate (RR) were recorded before, during and after one series of 3 periods of mental training (MT). HR, RR and SC increased during MT. The highest level of SC can be found at the beginning of the first period of imagination. Mean alpha-frequency of the EEG over the left occipital and precentral area in all Ss was higher during MT. The degree of these changes varied during the 3 imagination periods.

Brain↗
PubMed1990

Separation of left and right skull bones from low angle x-ray projections.

This study shows how two layers which are superposed in two low angle x-ray projections can be reconstructed separately without having any a priori knowledge of their shape. Similar to stereoscopic imaging, the projections of the two layers appear at different positions in the two superposition images. Matching one of the layers allows its elimination by subtraction. The resulting difference signal is the so-called 'movement artefact' of the second, mismatched layer. A filter method is developed to reconstruct this layer from the spectrum of its artefact within the Fourier domain. The second layer is reconstructed in an analogous way. So, for example, the bones of the left and the right side of the human skull can be imaged separately. This is used to reduce image artefacts caused by patient movements in subtraction angiography and tumourfluoroscopy of the brain.

Humans↗
PubMed1990

Activation and decreased deformability of neutrophils after intermittent claudication.

This study investigated local alterations in neutrophil activation and deformability after intermittent claudication. In 17 patients with one-sided peripheral arterial occlusive disease, neutrophil count, proportion of activated neutrophils (by nitro blue tetrazolium test), and neutrophil filterability as a measure of passive deformability were assessed in the femoral arterial and venous blood of the diseased leg and in the femoral venous blood of the healthy leg (n = 10). The values were obtained at rest, immediately after claudication, and 10 minutes after claudication induced by repetitive toe stands. Immediately after exercise, the arterial and venous blood differences in the diseased leg were 1) neutrophil count, 9% (95% confidence interval [CI], 5-14%; relative increase in the venous blood compared with arterial blood); 2) the proportion of activated neutrophils, 26% (CI, 10-42%); and 3) the neutrophil filterability, -10% (CI, -4% to -15%). At rest and 10 minutes after exercise, neutrophil parameters did not differ significantly between the femoral arterial and venous blood. Furthermore, no arterial and venous blood differences in the neutrophil parameters were found in the healthy leg. In addition to local changes, systemic changes occurred immediately after exercise. In the femoral arterial blood, the total neutrophil count had risen by 13% (CI, 8-18%), the proportion of activated neutrophils had risen by 41% (CI, 25-58%), and average neutrophil rigidity had risen 17% (CI, 11-22%) compared with the values obtained before exercise. At 10 minutes after exercise, all neutrophil parameters were still elevated. We conclude that even short periods of ischemia, as in intermittent claudication, cause local alterations in neutrophil function and distribution.

Arteries↗