Biomedical subjects

T Weiss

Publications and source records attributed to T Weiss.

At least 73 records · Page 4Linked to original sources

PubMed1996

The outcome of patients with acute myocardial infarction ineligible for thrombolytic therapy. Israeli Thrombolytic Survey Group.

PURPOSE: The aim of this study was to determine the proportion of patients with acute myocardial infarction (AMI) excluded from thrombolytic therapy on a national basis and to evaluate the prognosis of these patients by reasons of ineligibility and according to the alternative therapies that they received during hospitalization. PATIENTS AND METHODS: During a national survey, 1,014 consecutive patients with AMI were hospitalized in all the 25 coronary care units operating in Israel. RESULTS: Three hundred and eighty-three patients (38%) were treated with a thrombolytic agent and included in the GUSTO study. Ineligible patients for GUSTO were treated: (1) without any reperfusion therapy (n = 449), (2) by mechanical revascularization (n = 97), or (3) given 1.5 million units of streptokinase (n = 85) outside of the GUSTO protocol. The inhospital and 1-year post-discharge mortality rates were 6% and 2% in patients included in the GUSTO study; 6% and 5% in those mechanically reperfused; 15% and 10% in those treated with thromoblysis despite ineligibility for the GUSTO trial, and 15% and 13% among patients not treated with any reperfusion therapy. CONCLUSIONS: Ineligibility for thrombolysis among patients with AMI remains high. Patients ineligible for thrombolysis according to the GUSTO criteria, but nevertheless treated with a thrombolytic agent were exposed to an increased risk.

Actuarial Analysis↗

PubMed1996

[APC (activated protein C) resistance and oral contraceptives].

Resistance to activated protein C [1,2,3,4,5,6] is the most frequent hereditary cause of thromboses and is widespread through-out the population. Women with APC resistance have an enhanced risk of thrombosis compared to the total population. The risk increase, with the intake of oral contraceptives.

Blood Coagulation Tests↗

PubMed1996

[Obstructive sleep apnea in patients with coronary heart disease].

Patients with obstructive sleep apnea have an increased cardiovascular morbidity and mortality, those with co-existent coronary artery disease being particularly at risk. The object of our study was to evaluate the prevalence of obstructive sleep apnea in patients with coronary artery disease. 153 patients (117 men, 36 women) with verified coronary artery disease were given a highly sensitive standardized questionnaire. The 59 patients with pathological results were then checked with a 6-channel non-laboratory monitoring system. 22.2% of all patients had a respiratory disturbance index (RDI) above 5/h. and 14.4% above 10/h. 13.3% had a pathological RDI and additionally suffered from excessive daytime sleepiness. Patients with coronary artery disease have a high prevalence of obstructive sleep apnea and should consequently be screened for this sleep-related breathing disorder.

Aged↗

PubMed1995

Influence of coronary angioplasty on the progression of coronary atherosclerosis.

This study examines the effect of coronary angioplasty on the progression and appearance of new disease in sites of the coronary tree that were not dilated by the balloon. We examined 355 pairs of coronary angiograms from 252 patients. The study consisted of consecutive patients who were referred for catheterization > 1 month after successful angioplasty. Progression/regression and the appearance of new narrowings at sites not dilated by angioplasty were determined. The life-table method was used to determine outcome, and any event (progression, regression, and new narrowing) was analyzed according to the time of occurrence. The angioplasty artery was compared with the non-angioplasty artery and the effect of restenosis was determined by comparing arteries with and without restenosis. Progression/regression rates were not significantly different in angioplasty and non-angioplasty arteries. More new narrowings were identified in the angioplasty artery (p < 0.01). With regard to narrowings located in the angioplasty artery, progression was more common, regression less common, and the appearance of new narrowings more common in arteries with restenosis than in non-angioplasty arteries or arteries without restenosis. We believe that mechanical trauma to the artery during angioplasty could accelerate disease progression and the appearance of new narrowings in angioplasty arteries, whereas normalization of flow rate and pattern, especially in arteries without restenosis, attenuates the rate of progression and the appearance of new narrowings in these arteries. The final outcome depends on the balance between these factors.

Angioplasty, Balloon, Coronary↗

PubMed1995

Gene polymorphism but not catalytic activity of angiotensin I-converting enzyme is associated with coronary artery disease and myocardial infarction in low-risk patients.

BACKGROUND: An insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene has been postulated to be associated with an increased risk of coronary artery disease (CAD) and myocardial infarction (MI). METHODS AND RESULTS: In the present study, the effects of I/D gene polymorphism and of ACE activity on CAD and MI were investigated in 920 individuals who underwent coronary angiography for diagnostic purposes. In the total population and in all CAD and MI groups, a strong association was observed between the gene polymorphism and ACE activities; DD genotypes had approximately twofold higher ACE activities than II genotypes. Although classic risk and protective factors of CAD and MI were identified, associations of ACE genotype and of ACE activity to CAD and MI were not detected in the total population. Among subjects defined to be at lower risk of MI by low body mass index and low cigarette consumption, however, an association of the DD genotype with MI was found. Exclusion of individuals with triglyceride levels > 140 mg/dL and cholesterol levels > 180 mg/dL revealed an association of the DD genotype with CAD. An association of the ACE activity with CAD or MI could not be demonstrated in any of the low-risk populations. CONCLUSIONS: Increased ACE activity obviously is not a risk factor of CAD or MI. The importance of the deletion polymorphism for the development of CAD and MI may be restricted to individuals without classic risk factors.

Case-Control Studies↗

PubMed1995

Theta power decreases in preparation for voluntary isometric contractions performed with maximal subjective effort.

In order to find EEG parameters that can be attributed to movements performed with maximal subjective effort, EEG recordings and force measurements were realized in connection with isometric contractions (IMC). IMC were performed with submaximal and maximal subjective effort. Mean spectral power density within the theta band was found as an indicator for maximal subjective effort. The theta power across the parieto-occipital area decreases from rest through movements performed with submaximal force to movements performed with maximal effort. It is argued that this theta decrease possibly reflects a down-regulation of the posterior attention system in order to minimize the influences of external stimuli during the preparation for voluntary IMC performed with maximal subjective effort.

Adult↗

PubMed1995

Form and magnitude of beta-sympathetic and parasympathetic influences on pulse transit time.

In this study, we examined autonomic influences on pulse transit time measured from the R-wave of the electrocardiogram (R-PTT). Six subjects received three doses each of isoproterenol and atropine. Isoproterenol produced a significant linear decrease in R-PTT, a significant linear increase in heart rate (HR), and a significant linear decrease in diastolic blood pressure (DBP). Atropine produced a significant linear decrease in R-PTT and significant linear increases in HR and DBP. The R-PTT shortening effect of isoproterenol may reflect positive inotropic effects of beta-sympathetic myocardial stimulation. The R-PTT shortening effect of atropine may reflect reduction of parasympathetic inhibition of ventricular myocardial activity. However, possible vascular contributions to these effects remain to be determined. Nonetheless, the results encourage further examination of R-PTT in research concerning autonomic regulation of cardiovascular activity.

Adult↗

PubMed1994

Activation processes during mental practice in stroke patients.

In healthy subjects, mental practice is known to improve motor performance. It is also known to be accompanied by a higher central nervous activity. Since such effects seem to be desirable for rehabilitation, we investigated the possibility of detecting changes in central nervous activity by means of EEG in stroke patients, and whether these changes were similar to those observed in healthy subjects. 12 left-sided hemiplegic patients who underwent a specific post-stroke rehabilitation treatment were requested to perform a simple arm movement sequence. In the following mental practice period the patients were requested to image the same sequence without any real movement. EEG background activity was recorded during rest and imagination periods. After the calculation of z-transformed power values within the theta, alpha, and beta-1 band, differences between rest and imagination periods were evaluated for their significance. Stroke patients show significant decreases of theta, alpha, as well as beta-1 power during mental practice in comparison to the rest period. These changes are similar to those obtained in healthy subjects. Theta power decreases in central and parietal leads. Central alpha power diminishes only during imagination of the contralateral arm. This phenomenon as well as the decrease of beta-1 power in central derivation were also obtained during real motor performance and might indicate an activation of the sensorimotor cortex. In accordance with the hypothesis of internal feedback mechanisms, this activation is a necessary prerequisite for motor learning during mental practice.

Aged↗

PubMed1994

Reactive hyperemia of skin microcirculation in septic neonates.

Reactive hyperemia after 1 min of arterial occlusion was studied in back, thigh and heel skin of 40 preterm and full-term neonates using laser Doppler flowmetry. Twelve infants had clinical signs of septicemia, but normal laboratory tests at the time of fluxmetry. However, CRP, leukocyte count and the ratio of immature to total neutrophils increased during the following days and septicemia was confirmed by positive blood cultures (septic group). Seven neonates with clinical signs of septicemia had developed neither positive blood cultures nor laboratory signs (non-septic group). Fifteen were healthy neonates. In the septic neonates, time to reach maximal hyperemia, maximum post-occlusive hyperemia and recovery time of skin perfusion were increased significantly in back and thigh skin and the heal skin temperature was decreased when compared to healthy neonates. Healthy and non-septic neonates showed no significant difference in any of the parameters. We conclude that altered reactive hyperemia in the skin may be an earlier sign of neonatal septicemia than laboratory tests.

Humans↗

PubMed1994

Mental practice of motor skills used in poststroke rehabilitation has own effects on central nervous activation.

In the last years it has been shown that the use of the EMG triggered electrical myostimulation (ETEM) brings good results in poststroke rehabilitation. It has been hypothesized that the relearning effects obtained by means of ETEM are due to the reinstatement of proprioceptive feedback. However, the technique is most powerful if imagination of motor acts (the so called mental practice) is used as an initial part of ETEM. Since mental practice in healthy people leads to central nervous activation processes as well as to an improvement of motor skills, we investigated the effects of mental practice alone on central nervous activity by means of EEG in stroke patients. Twelve left-sided hemiplegic patients who underwent a specific poststroke rehabilitation treatment were requested to perform a simple arm movement sequence. In the following mental practice period the patients were requested to imagine the same sequence without any real movement. EEG background activity was recorded during baseline and imagination periods. After the calculation of z-transformed power values within the alpha and beta-1 band, differences between rest and imagination periods were evaluated for significance. Stroke patients showed significant decreases of alpha as well as beta-1 power during mental practice in comparison to the rest period. These changes are similar to those obtained in healthy subjects. Central alpha power diminished only during imagination of the contralateral arm. This phenomenon as well as the decrease of beta-1 power in central derivation were also obtained during real motor performance and might indicate an activation of the sensorimotor cortex. In accordance with the hypothesis of internal feedback mechanisms, this activation is a necessary prerequisite for motor learning during mental practice. We conclude that mental practice of motor skills might have own effects in poststroke rehabilitation.

Aged↗

PubMed1994

Very early thrombolysis in acute myocardial infarction--a light at the end of the tunnel.

Myocardial damage in acute myocardial infarction is a time-dependent process. Thrombolytic therapy effectively opens the coronary artery, restores coronary blood flow and prevents ongoing necrosis. We examined the effect of very early thrombolytic therapy (including prehospital administration) in a consecutive group of 510 patients with myocardial infarction on the following factors: mortality, complications and the preservation of left ventricular function. The treatment was given to 89 at home (time delay to treatment 1.2 +/- 0.6 h) and 421 in hospital (2.0 +/- 1.0 h). Twelve patients died in hospital and major hemorrhage occurred in 10. The arterial patency rate in 416 patients who underwent coronary angiography 6 days later was 82%. Infarct size measured by left ventriculography was determined by the area at risk, the delay time until the initiation of thrombolytic therapy, the total duration of ischemic pain and the degree of restoration of arterial blood flow. We conclude that early thrombolytic therapy, particularly prehospital management, is feasible and safe and reduces infarct size and mortality. A further decrease in the delay to initiation of treatment and more effective thrombolytic therapy will further decrease mortality and myocardial damage.

Aged↗

PubMed1993

Human sodium channel myotonia: slowed channel inactivation due to substitutions for a glycine within the III-IV linker.

1. Three families with a form of myotonia (muscle stiffness due to membrane hyperexcitability) clinically distinct from previously classified myotonias were examined. The severity of the disease greatly differed among the families. 2. Three dominant point mutations were discovered at the same nucleotide position of the SCN4A gene encoding the adult skeletal muscle Na+ channel alpha-subunit. They predict the substitution of either glutamic acid, valine or alanine for glycine1306, a highly conserved residue within the supposed inactivation gate. Additional SCN4A mutations were excluded. 3. Electrophysiological studies were performed on biopsied muscle specimens obtained for each mutation. Patch clamp recordings on sarcolemmal blebs revealed an increase in the time constant of fast Na+ channel inactivation, tau h, and in late channel openings as compared to normal controls. tau h was increased from 1.2 to 1.6-2.1 ms and the average late currents from 0.4 to 1-6% of the peak early current. 4. Intracellular recordings on resealed fibre segments revealed an abnormal tetrodotoxin-sensitive steady-state inward current, and repetitive action potentials. Since K+ and Cl- conductances were normal, only the increase in the number of non-inactivating Na+ channels has to be responsible for the membrane hyperexcitability. 5. Length, ramification and charge of the side-chains of the substitutions correlated well with the Na+ channel dysfunction and the severity of myotonia, with alanine as the most benign and glutamic acid as the substitution with a major steric effect. 6. Our electrophysiological and molecular genetic studies strongly suggest that these Na+ channel mutations cause myotonia. The naturally occurring mutants allowed us to gain further insight into the mechanism of Na+ channel inactivation.

Action Potentials↗

PubMed1993

[Comparison between argon and excimer laser angioplasty in patients with lesions of the femoral and popliteal arteries: clinical and angiography results after 1 year].

The aim of this study was to compare acute and long term results of thermic argon laser versus athermic XeCl-excimer laser for recanalization of femoropopliteal lesions in 43 patients with peripheral vascular disease stage IIb to IV according to Fontaine. The argon laser system was applied in 29 lesions (9 stenoses, 20 occlusions up to 31 cm length) and an excimer laser was used in 28 lesions (10 stenoses, 18 occlusions up to 30 cm length). In all cases balloon dilatation followed laser recanalization to achieve a sufficient primary result (< 25% stenosis rate). Primary success was obtained in 86% with both laser systems. After 1 year 62.5 of the recanalized vessels with excimer laser and 56% with argon laser were still patent. Neither acute nor long term results showed significant differences between both laser systems. Compared to the argon laser, the procedure with the excimer laser was of shorter duration which may be advantageous under routine conditions. After one year, combining the results of both systems, the reocclusion rates of stenoses amounted to 22%, the reocclusion rates of short distance occlusions to 35% and that of long occlusions more than 10 cm length to 71%. With regard to the high reocclusion rate after reopening of long occlusions the laser systems seem to be of advantage, compared to balloon angioplasty mainly in critical stenosis and short occlusions which cannot be passed with the guide-wire.

Angiography↗

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↗