Search PubMed⌕ Search

Biomedical subjects

S Biedert

Publications and source records attributed to S Biedert.

33 records · Page 2Linked to original sources
PubMed1985

Doppler sonography in basilar artery occlusion.

We have investigated 6,972 patients with directional continuous-wave Doppler sonography within the last three and a half years, and have derived criteria for the sonographic diagnosis of basilar artery occlusion or tight stenosis in conjunction with 1,071 retrograde brachial angiograms. By sonographic patterns, we have suspected obstruction of the basilar artery or of both distal vertebral arteries in nine cases. Either bilateral sonographic silence or the absence of a diastolic flow component of the vertebral arteries served as criteria in the sonographic evaluation. Angiography of the vertebro-basilar system, performed in eight cases, showed near or complete occlusion in the distal vertebrals or in the proximal basilar artery. Degrees of stenosis less than an 80 percent reduction in lumen diameter could not be detected sonographically. Two further basilar artery occlusions were detected by means of angiography despite negative Doppler sonography: one of these patients showed an extensive collateral circulation between the posterior inferior and the superior cerebellar arteries, and one patient had an occlusion only of the middle and rostral thirds of the basilar artery, the proximal third and the anterior inferior cerebellar arteries being widely patent. Thus, we believe that directional CW Doppler sonography is very useful in the diagnosis of near or complete occlusion of both distal vertebral arteries or of the proximal basilar artery.

Angiography↗
PubMed1985

[Doppler sonography in intracranial circulation disorders of the internal carotid artery. A comparative Doppler sonography-angiography study].

During the past 33 months we have investigated 6,587 patients using directional continuous-wave Doppler sonography of the carotid arteries. On the basis of 1,671 retrograde brachial and direct carotid angiograms we have developed criteria for demonstrating a significant increase in the peripheral resistance of the internal carotid artery. We distinguished stenoses proximal (15 cases) and distal (4) to the origin of the ophthalmic artery, supraclinoid internal carotid artery occlusions (8), stenoses (2) and obliterations (10) of the middle cerebral artery that developed suddenly. Stenoses in the carotid siphon (proximal or distal to the origin of the ophthalmic artery) showed a reduction of more than 40% in the relative end-diastolic flow velocity (modified Pourcelot's index); in addition, stenoses proximal to the origin of the ophthalmic artery exhibited an alternating flow, or flow reversal, in the supratrochlear artery to a variable extent. Stenoses distal to the origin of the ophthalmic artery only rarely revealed the increase in orthograde flow velocity that had been theoretically expected in the supratrochlear artery. Stenoses of the middle cerebral artery exceeding the extent of atherosclerotic irregularities proved to be an exception. Supraclinoid obliterations of the internal carotid artery were reliably demonstrated by Doppler sonography. However, the reliably demonstrated by Doppler sonography. However, the majority of the occlusions of the middle cerebral artery that developed suddenly could not be detected by this means, probably due to anastomoses between the anterior and middle cerebral arteries, which were detected by means of angiography. Thus, we believe that continuous-wave Doppler sonography is a reliable tool for detecting stenoses of the carotid siphon of more than 60% reduction in lumen diameter as well as supraclinoid carotid artery occlusions. Resistance to the cerebral blood flow that is located more peripherally cannot be diagnosed reliably by this method.

Brain Ischemia↗
PubMed1985

Cellular mechanisms of digitalis action.

Although the therapeutic actions of digitalis glycosides have been known for over 200 years, their direct inotropic actions on the heart were not established until the last 50 years. Digitalis has undergone intense research, particularly with respect to its mechanisms of action. Many authors have claimed to have found the true mechanism of action, compounding the complexity of literature. Recent subcellular studies have pointed to specific areas of action of the digitalis glycosides. Each discovery has been dependent on the greater understanding of the electrophysiologic characteristics of cardiac muscle and excitation-contraction coupling. The current hypothesis suggests that digitalis specifically inhibits Na-K ATPase. This produces an elevation in intracellular sodium level that in turn produces an increase in the intracellular calcium level. The increased quantities of calcium available to the contractile elements of cardiac muscle provide the observed increased inotropy.

Animals↗
PubMed1985

[Pathologic nystagmus and related phenomena. A review].

Pathological nystagmus may be spontaneous, positional, or gaze-evoked. Peripheral vestibular nystagmus is usually rotatory, the horizontal component being most prominent. It is - in contrast to a central vestibular nystagmus - strongly inhibited by fixation. Spontaneous congenital nystagmus is also prominent with fixation, but it can usually be distinguished from acquired fixation nystagmus based on its long duration, atypical waveforms and high frequency. Two general types of positional nystagmus can be identified on the basis of nystagmus regularity: static and paroxysmal. The most common variety of positional nystagmus is the so-called benign paroxysmal positional nystagmus, which in the majority of cases occurs as an isolated symptom of unknown cause. Gaze-evoked nystagmus, prominent with fixation, includes dissociated, rebound and gaze-paretic nystagmus forms. Symmetrical gaze-evoked nystagmus is most commonly produced by ingestion of certain drugs. Phenomena related to nystagmus include: amblyopic, voluntary, and convergence-retraction nystagmus, ocular dysmetria, ocular flutter, opsoclonus, ocular bobbing, and ocular myoclonus.

Amblyopia↗
PubMed1985

[Differential diagnosis of tinnitus and vertigo. A review].

Tinnitus and vertigo, two common neurological complaints, often challenge the physician's ability with respect to possible etiology. Objective tinnitus can result from an abnormally patent eustachian tube, from tetanic contractions of the muscles of the soft palate, or from vascular abnormalities within the head or neck. Subjective tinnitus refers to lesions involving the external ear canal, tympanic membrane, ossicles, cochlea, auditory nerve, brainstem, and cortex. As many as 50% of patients with tinnitus do not exhibit associated hearing loss; in these patients, the cause of the tinnitus is rarely identified. An illusion of movement is specific for vestibular system disease--a peripheral or central location depending upon associated audiologic and neurologic symptoms, respectively. However, a presyncopal, light-headed sensation is most commonly associated with diffuse cerebral ischemia: in the young patient, this may be caused by a hyperventilation syndrome; in the aged individual, this can result from diffuse atherosclerotic cerebrovascular disease and decreased cardiac output. Postural and gait imbalance associated with acute vertigo indicates a unilateral peripheral vestibular or a central vestibular lesion; if vertigo is absent, either a cerebellar, proprioceptive, or bilateral peripheral vestibular lesion is likely. Transient oscillopsia suggests unilateral peripheral vestibular lesions. Permanent oscillopsia indicates a bilateral peripheral vestibular lesion or--in the absence of severe vertigo--brainstem or cerebellar damage.

Brain Diseases↗
PubMed1984

[Doppler sonogram in basilar artery thromboses].

We have investigated 6,380 patients with directional c-w Doppler sonography within the last 3 1/2 years, and have suspected obstruction of the basilar artery or of both distal vertebral arteries in 7 cases. Either bilateral sonographic silence or an absent diastolic flow component of the vertebral arteries were employed as criteria in the sonographic evaluation. Angiography of the vertebro-basilar system, performed in 6 cases, confirmed the diagnoses: basilar artery occlusion was found in 4 patients, 1 patient revealed tight stenosis of the basilar artery in its entire length, and 1 patient exhibited occlusion of both distal vertebral arteries. Three further basilar artery occlusions were detected by means of angiography despite initially negative Doppler sonography within the same period of time; 1 of those patients, however, met the above criteria for basilar artery occlusion upon sonographic reevaluation on the following day. Thus, we believe that directional c-w Doppler sonography is very useful in the diagnosis of basilar artery obstruction.

Adult↗
PubMed1981

Changes in cellular Na+, K+, and Ca2+ contents, monovalent cation transport rate, and contractile state during washout of cardiac glycosides from cultured chick heart cells.

To delineate more clearly the importance of altered monovalent cation transport rate in the mediation of the positive inotropic effects of cardiac glycosides, we studied changes in the contractile state and rate of uptake of K+ and Rb+ by monolayer cultures of chick embryo ventricular cells during exposure to and washout of ouabain and dihydro-ouabain. These cardiac glycosides produced a positive inotropic effect in this system, accompanied by a significant reduction in monovalent cation transport rate, by increases in cellular contents of Na+ and Ca2+, and by a decrease in cellular content of K+ as judged by radioisotopic tracer studies. Following removal of glycosides from media bathing the cultures, monovalent cation transport rate returned to normal within 1 minute, followed by a loss of inotropy which was complete by 7 minutes, a time at which cellular [Ca2+] had returned to normal. The bulk cellular concentration of Na+ remained increased, however, and that of K+ depressed for longer periods. Veratrine (1 microgram/ml) induced a positive inotropic effect, but caused a less marked increase in cellular [Na+] than did equipotent concentrations of ouabain and dihydroouabain. These results indicate that there is not a simple relationship between bulk cellular [Na+] and magnitude of inotropic effect in these cells, and are consistent with the proposal that there is a subsarcolemmal space in which [Na+] regulates Ca2+ fluxes and contractility, and in which [Na+] is regulated primarily by the balance between transsarcolemmal influx and Na+ pump rate and, to a lesser degree, by bulk [Na+].

Animals↗
PubMed1980

[Adriamycin-cardiomyopathy induced by an increment of (Ca2+) (author's transl)].

As compared to the metabolic inhibitor 2,4-Dinitrophenol, the cytostatic drug Adriamycin influences the isolated embryo ventricular cells of the chicken, thus causing a decrease in the contraction amplitude, an increase in the heart-rate, and the occurrence of "after-contractions". With radioactive measurements it could be demonstrated, that the reason therefore is an increment of Ca2+i. This may be explained by a decreased Ca-uptake by the sarcoplasmic reticulum and the mitochondria. This increment of Ca2+i brought about a change in the action potential and the refractory-period, as well as the occurrence of "'after-contractions" by control of the potassium flux.

Action Potentials↗
PubMed1980

[Experimental study on elucidating pathogenesis of adriamycin induced cardiomyopathy (author's transl)].

For the determination of the pathophysiological mechanisms responsible for the adriamycin-induced cardiomyopathy we investigated the acute myocardial effects of this drug on contractile behavior in cultured embryonic ventricular cells in comparison to metabolic inhibitors, e.g., 2,4-dinitrophenol. There could be demonstrated a fall in contraction amplitude due to exposure to adriamycin, an increase in heart rate and the occurrence of "after-contractions". The fall in contraction could be explained by a decreased Ca-uptake by the sarcoplasmic reticulum (SR) and/or the mitochondria, leading to a rise in [Ca2+]i. This would tend to reduce spontaneous rate in pacemaker cells, to increase gK (conductance of potassium) and to influence the conduction. 10 microgram/ml adriamycin showed a 25% increment of K-flux above rest. A similar result was obtained by use of 10(-4) mmol/l 2,4-DNP which also caused cessation of spontaneous activity. This increment in K-flux, a parameter for K-permeability, might be caused by an increase in [Ca2+]i. The possible origin of this increment of [Ca2+]i might be of mitochondrial nature.l Thus an acute perturbance of mitochondrial function might give rise to [Ca2+]i, since mitochondria are known as Ca-buffering compartment. The pathophysiological mechanisms of the adriamycin cardiomyopathy therefore can be seen in the increase of [Ca2+]i.

Animals↗
PubMed1979

Inotropic effects and changes in sodium and calcium contents associated with inhibition of monovalent cation active transport by ouabain in cultured myocardial cells.

Cultured monolayers of spontaneously contracting chick embryo ventricular cells were perfused with culture medium containing ouabain. Contractile state was monitored by an optical-video system recording amplitude and velocity of cell wall motion. Positive inotropic effects of 2.5 x 10(-7) to 10(-6) M ouabain were manifest within 1.5-2 min, and reached a stable plateau within 5-6 min. The inotropic effect was fully reversed within 5 min after washout of ouabain. Inhibition of uptake of 42K+ (or the K+ analog 86Rb+) and efflux of 24Na+ occurred 1.5-2 min after exposure to ouabain. The degree of inhibition of transport was closely related to the magnitude of the positive inotropic effect throughout the ouabain concentration range 10(-7) to 10(-6) M. After washout of ouabain from monolayers, the monovalent cation active transport rate returned to normal within 1 min. Thus, both the onset and offset of inotropic action of ouabain were closely related temporally to inhibition of the sodium pump. Exposure to ouabain caused significant increases in exchangeable Na and Ca contents that appeared to be developed within 5 min. These data support the hypothesis that inhibition of monovalent cation active transport by ouabain is causally related to the development of positive inotropy and are consistent with modulation of Ca content by intracellular Na+ via the Na+-Ca2+ exchange carrier mechanism.

Animals↗
PubMed1976

Characterization of 20S component in tubulin from mammalian brain.

Tubulin from porcine brain, purified by at least two cycles of assembly and disassembly, was characerized at different pH values by sedimentation velocity analysis and turbidimetric measurements. At pH 6.4 the depolymerized material was composed of two major species sedimenting with so20,w values of 6 and 36 and a minor one of 20S. By raising the pH, the amount of the 20S component increased and that of the 36S decreased, whereas that of the 6S component was unaltered. At pH 7.6 the mixture contained 20S and 6S components but hardly any 36S. The 20S species can be separated from the 6S ones by gel filtration on agarose A-15m at pH 7.6. On electron microscopic examination this preparation contains far fewer double rings compared to the material at pH 6.4, but single rings could often be seen. Sodium dodecyl sulfate gel electrophoresis of the 20S and 36S components showed that they consist almost entirely of tubulin and some higher and lower molecular weight fractions. Turbidity measurements showed that the minimal protein concentration necessary for polymerization increases with increasing pH. The turbidity plateau reached at a given pH can be raised by decreasing the pH. From these results it is suggested that the 20S component is an intermediate of the 36S species. The results further indicate the existence of a pH-dependent equilibrium between the 20S species and the 36Soligomers.

Animals↗
PubMedDate not supplied

The value of transcranial Doppler sonography in the differential diagnosis of Alzheimer disease vs multi-infarct dementia.

Primary degenerative dementia of the Alzheimer type and multi-infarct dementia exhibit differences in cerebrovascular blood flow velocity profiles, which were investigated by means of transcranial Doppler sonography. The pulsatility indices, as angle-independent parameters of peripheral vascular resistance, measured in middle cerebral and basilar arteries of patients with multi-infarct dementia (MID), were significantly increased (p < 0.005) with respect to cases of primary degenerative dementia of the Alzheimer type and to healthy age-matched controls. Approximately 75% of all MID patients exhibited small vessel disease rather than thromboembolism from the extracranial arteries and the heart, as judged by extracranial and transcranial Doppler sonographies, computerized cerebral tomographies, EEGs, and, if necessary, 2-D echocardiographies.

Aged↗
PubMedDate not supplied

Senile dementia of Alzheimer type and multi-infarct dementia investigated by transcranial Doppler sonography.

Dementia of the Alzheimer type, senile onset (SDAT), and multi-infarct dementia (MID) exhibit differences in cerebrovascular blood flow velocity profiles, which were investigated by means of transcranial Doppler sonography. The pulsatility indices (PI), as angle-independent parameters of peripheral vascular resistance measured in the basal cerebral arteries, were significantly increased in MID patients with respect to SDAT cases. In an analysis of the correlations between several variables and the magnitude of PI, we found strong inverse correlations of the CAMCOG score, and strong direct correlations of the blood pressure and the duration of illness, with the PI of all basal cerebral arteries only in MID patients. In SDAT patients, we found a direct correlation between the Hachinski ischemia score and the PI of all basal cerebral arteries. All 3 ischemia scores (Hachinski, Rosen, Loeb and Gandolfo) were significantly correlated with the PI of the middle cerebral and basilar arteries. By analyzing the correlations of the single items of the 3 different ischemia scores with the PI values obtained, we only found a clearcut correlation with the item focal neurological signs. Thus, our findings stress the relative importance of a concomitant cerebrovascular factor in the development of dementia in old age, even in patients with probable SDAT. A raise of the PI in the basal cerebral arteries allows early suspicion of a cerebrovascular factor even in only slight dementia so that possible risk factors for further aggravation of this type of vascular dementia might be detected and treated early in the course of disease.

Aged↗
PubMedDate not supplied

Directional C-W Doppler sonography in the diagnosis of basilar artery disease.

Using directional continuous-wave Doppler sonography of the vertebral arteries, we have investigated 1,540 patients during the past 5 years. On the basis of unilateral and bilateral retrograde brachial angiograms in the same patients (a total of 1,989 angiograms) we have developed sonographic criteria for demonstrating a significant increase in the peripheral resistance of both distal vertebral arteries and/or the basilar artery. All 11 cases of basilar artery stenosis of at least 60% reduction in lumen diameter (as shown by angiography) exhibited an approximately 40% or higher reduction in the sum of the modified Pourcelot indices of both vertebral arteries with respect to age-matched controls. All 3 stenoses of less than 60% reduction in lumen diameter were not detected by sonography. Even a good collateral circulation through rete mirabile anastomoses did not normalize the modified Pourcelot indices. One case of a persistent primitive trigeminal artery with thin-calibered vertebral arteries was also detected by sonography. The high percent of patients with one hypoplastic vertebral artery in the group with basilar artery stenoses indicates an increased risk for atherosclerosis of the basilar and/or distal vertebral artery in these patients. All 14 angiographically verified occlusions of the basilar artery were detected by sonographic criteria independent of the occlusion localization. Thus, we believe that directional continuous-wave Doppler sonography is a reliable technique for detecting basilar artery stenoses of at least 60% reduction in lumen diameter and basilar artery occlusions.

Arterial Occlusive Diseases↗