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Biomedical subjects

M Friedemann

Publications and source records attributed to M Friedemann.

At least 19 recordsLinked to original sources
PubMed1995

Effects of glial cell line-derived neurotrophic factor on developing and mature ventral mesencephalic grafts in oculo.

The search for trophic factors that can support injured dopaminergic neurons and can enhance dopaminergic graft survival and outgrowth for therapeutic uses in Parkinson's disease has lately focused on members of the transforming growth factor (TGF) beta super-family. In this paper we have studied the effects of a member of the TGB beta family, glial cell line-derived neurotrophic factor (GDNF), on immature and mature ventral mesencephalic tissue grafted to the anterior chamber of the eye. The results confirm that GDNF increases survival of TH-positive neurons and enhances TH-immunoreactive nerve fiber formation when the grafts are treated during their development. The distribution of nerve terminals is densest within the area of TH-immunoreactive neurons and at the surface of the grafts. However, there is no change in the number of calcium-binding protein (CaBP)-positive neurons, suggesting that the subpopulation of TH-positive neurons that is increased are the CaBP-negative neurons of the ventral tier of pars compacta. Terminals from those neurons form the striatal patches during normal development. When the grafts are treated with GDNF after maturation, no change in TH-positive cell survival is seen but an increase of nerve terminals is still found within the cell dense area of the graft. Potassium-evoked dopamine release, measured using in vivo chronoamperometry, revealed significantly increased extracellular overflow in transplants treated with GDNF during development. The dopamine uptake blocker nomifensine significantly increased the time for clearance of the released dopamine. These data suggest that GDNF treatment of immature grafts enhances survival of TH-positive neurons, which would have innervated the striatal patches, and also increases TH-immunoreactive nerve fiber formation and dopamine release. Furthermore, GDNF treatment of mature grafts also increases dopamine fiber formation within the TH-positive neuronal area, indicating that adult dopaminergic neurons are also responsive to this agent.

Animals↗
PubMed1993

In vivo electrochemical measurements and electrophysiological studies of rat striatum following neonatal 6-hydroxydopamine treatment.

The effects of neonatal treatment (one day after birth) with the neurotoxin, 6-hydroxydopamine (75 micrograms/10 microliters intracisternal), were studied in the striatum of normal adult and treated Sprague-Dawley rats. Measurements of monoamine levels in the dorsal striatum and nucleus accumbens, by high-performance liquid chromatography coupled with electrochemical detection, showed that neonatal 6-hydroxydopamine treatment produced a permanent and massive destruction of striatal dopamine. The effects were more pronounced in the dorsal striatum than in the nucleus accumbens. In addition, serotonin levels were elevated in the rat striatum as a consequence of the neonatal treatment. Rapid chronoamperometric recordings of K(+)-evoked monoamine overflow using Nafion-coated recording electrodes were investigated in both the dorsal and ventral striatum of control and neonatally lesioned rats. The potassium-evoked responses recorded from the dorsal striatum of the 6-hydroxydopamine-treated rats were significantly reduced in amplitude as compared to controls. In addition, the reduction/oxidation current ratios of the responses were more serotonin-like, in contrast to the dopamine-like current ratios measured in the striatum of untreated animals. In ventral striatum, the amplitudes of the K(+)-evoked responses were not significantly reduced versus control. However, the K(+)-evoked signals were more serotonin-like in their electrochemical characteristics as compared to controls. In addition to the release studies, extracellular single-unit electrophysiological recordings were performed in normal and neonatally 6-hydroxydopamine-treated rats. The spontaneous discharge rate of striatal neurons in the neonatally 6-hydroxydopamine-treated rats was similar to that of control rats. This is in contrast to dopamine lesions in adult animals, where a marked elevation of the discharge rate is observed. Local applications of dopamine and serotonin into the striatum of neonatally 6-hydroxydopamine-treated rats elicited excitations of striatal cells rather than the normal inhibitory effects seen in control animals. Taken together, these data suggest that loss of striatal dopamine terminals at birth leads to both pre- and postsynaptic alterations in monoamine pathways.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

[The use of echocardiography in intensive care medicine].

Transthoracic echocardiography is an easily accessible, non-invasive imaging procedure for evaluation and follow-up of critically ill patients. It is particularly helpful in evaluating patients with thoracic pain, low-output syndrome or heart murmur, and has prognostic value in acute myocardial infarction. It makes a diagnostic contribution in 60 to 90% of cases, and has therapeutic implications in 50 to 65%. New ultrasound technics are briefly discussed.

Aortic Dissection↗
PubMed1992

[Bicavitary cardiac stimulation. Re-assessment and results].

In each indication for cardiac stimulation, dual chamber pacing must be considered if stimulation or sensing in the atrium is possible. It is of particular importance in patients with diastolic ventricular dysfunction. The Heart rate is the most important parameter in stress-adaptation; for this reason we propose to use exclusively the VVIR or DDDR stimulation mode in physically active patients. Complications of dual chamber pacing are rare. During follow-up it is important to limit the energy of impulses and so to enhance the longevity of the generator, and to verify other parameters such as adaptation of the rate adaptation sensor and the AV delay intervals for sensed and paced atrial events. Modern technology allows us to reach the two most important goals of cardiac stimulation: avoid syncopes due to excessive bradycardia or asystole and optimize the quality of life of our patients.

Adaptation, Physiological↗
PubMed1989

The effects of cholecystokinin (CCK-8) on dopamine-containing nerve terminals in the caudate nucleus and nucleus accumbens of the anesthetized rat: an in vivo electrochemical study.

The action of cholecystokinin (CCK) on presynaptic function of dopaminergic nerve terminals has been the subject of much debate in the literature. In efforts to resolve some of the reported ambiguities, high speed in vivo electrochemical recordings were carried out in the caudate nucleus and nucleus accumbens of the urethane anesthetized rat, to determine effects of locally applied sulfated (CCK-8S) and unsulfated (CCK-8US) CCK octapeptide. Locally-applied CCK-8S and CCK-8US caused no increase in the baseline electrochemical signals recorded from either brain region. However, locally applied CCK-8S potentiated the potassium-evoked overflow of dopamine (DA) into the extracellular space in both the caudate and nucleus accumbens. In contrast, pressure ejection of CCK-8US produced no significant effects on the potassium-evoked overflow of DA in either structure. These data support a facilitatory effect of CCK-8S on potassium-evoked overflow from DA-containing nerve terminals in the urethane anesthetized rat that is likely mediated through a peripheral type CCK receptor.

Anesthesia↗
PubMed1988

The effects of delta 9-tetrahydrocannabinol on potassium-evoked release of dopamine in the rat caudate nucleus: an in vivo electrochemical and in vivo microdialysis study.

The effect of systemically administered delta 9-tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana, on the potassium-evoked release of dopamine (DA) was examined in the neostriatum of the chloral hydrate anesthetized rat. Both in vivo electrochemical and in vivo microdialysis techniques were employed. A low dose of THC (0.5 mg/kg, i.p.) increased the time course of potassium-evoked in vivo electrochemical signals corresponding to released extracellular DA. In vivo microdialysis showed an increase in potassium-evoked DA release following 0.5 and 2.0 mg/kg doses of THC. Potassium-evoked electrochemical signals corresponding to released extracellular DA were augmented in time course following i.p. administration (5.0 mg/kg) of nomifensine, a recognized and potent catecholaminergic reuptake blocker. In addition, in vivo brain microdialysis studies of nomifensine (5.0 mg/kg i.p.) on neostriatal potassium-evoked DA release showed that DA levels were augmented in magnitude over the time course of the microdialysis. Taken together, these studies indicate that THC has a potent presynaptic augmenting effect on at least the neostriatal portions of the mesotelencephalic DA system in the rat, although the possibility that this effect could be mediated transsynaptically cannot be ruled out. Given the previous extensive evidence for an involvement of portions of the mesotelencephalic DA system in mediating the reinforcing and euphorigenic properties of many classes of abused drugs, and in mediating direct electrical brain stimulation reward, we suggest that the presently demonstrated effects of THC on forebrain dopamine function may be related to marijuana's euphorigenic properties and, thus, to its abuse potential.

Caudate Nucleus↗
PubMed1986

[Significance of reciprocal ST-segment depression in the acute stage of transmural myocardial infarct].

19 patients with transitory ST-segment depression in the wall opposite the infarcted territory during acute transmural myocardial infarction (AMI) were studied. We investigated the reproducibility of this reciprocal ST depression induced by stress testing and correlated the ECG changes with coronary angiographic evaluation of arteries supplying the remote area. We tried to derive criteria for detection of simple mirror image. 3 different groups were defined according to ECG evolution: Group 1 consisted of 7 anterior and 3 inferior AMI where reciprocal ECG changes disappeared appeared within 24 to 48 hours independently of the ECG changes in the infarcted area. These ST depressions were reproduced by stress testing one to two months later, and correlated angiographically with an anatomic lesion. 7 out of 10 patients later had bypass graft surgery. Group 2 consisted of 7 patients in whom posterior wall extension of an inferior AMI made the diagnosis of anterior ischemia impossible. In another two patients (one anterior and one inferior AMI) reciprocal ST depression and infarcted area ECG changes showed a simultaneous evolution. The reciprocal ST depression could not be reproduced during stress testing and did not correlate with any angiographic lesion. It is concluded that reciprocal ST depression during the acute phase of transmural anterior or purely inferior myocardial infarction is correlated with multivessel coronary disease if their regression is not strictly simultaneous to the infarction-related ECG changes. Further investigations are indicated in these patients.

Acute Disease↗
PubMed1984

[Unstable angina pectoris].

The treatment of unstable angina pectoris should take into account self-regulation, the possibilities for improved oxygen transport, and a reduction of myocardial oxygen requirement. It consists primarily of drug therapy (nitrates, Ca-antagonists, amiodarone, beta-blockers). Secondarily, coronarography is performed with a view to surgical therapy.

Adrenergic beta-Antagonists↗
PubMed1983

[The anti-arrhythmia drug quinidine as an alternative in the treatment of severe falciparum malaria].

Parenteral quinine is the most effective treatment for severe falciparum malaria. It is not easily available in Switzerland and so dangerous delays treating patients may occur. The antiarrhythmic drug quinidine, usually stocked by hospitals, is an alternative drug for malaria treatment. We report the cases of two patients with severe malaria imported from Kenya. They were treated first with intravenous quinidine sulfate over 3 days and for another 4 days with peroral quinidine sulfate. The therapeutic response was excellent. During the 2 months posttherapeutic period no recrudescence of Plasmodium falciparum occurred. 20 mg/kg b.w./die of quinidine given intravenously seems to be an adequate dose in severe falciparum malaria.

Administration, Oral↗
PubMed1980

[Systolic time intervals in the evaluation of changes in circulation].

The current literature on the clinical application of measurement of systolic time intervals is reviewed. The values in question are defined and discussed and their position in clinical medicine is critically evaluated. It emerges the PEP/LVET (defined in text) is the best indicator for clinical evaluation of circulatory changes during the course of heart disease. The heart diseases in which this method cannot be employed are discussed. The fact that this non-invasive method can provide information on important functional changes in the circulation accounts for the interest in the method shown in intensive care units.

Cardiac Output↗
PubMed1979

[A case of acute left myocardial insufficiency after tocolysis by means of beta stimulation].

A case is presented to demonstrate that tocolysis by beta adrenergic stimulation can be complicated by metabolic myocardial infarction. The possible role of pathophysiologic and pharmacologic facts is discussed, but additional clinical features involved in this particular case may be partly responsible for the above-mentioned complication. Finally, some recommendations are made with a view to assessing risk factors and improving cardioprotective effects.

Adrenergic beta-Agonists↗
PubMed1975

[Treatment of rhythm disorders following acute heart infarction using a beta receptor blockader (Visken)].

In a group of 40 patients with acute myocardial infarction and ectopic ventricular or atrial beats or tachycardia, the effect of Visken has been tested by means of 3 i.v. injections of 0.4 mg each at intervals of 15 min. The results showed that Visken has a good effect on these rhythm disturbances and can be administered without danger, provided due regard is had to the contraindications. Beta-blockade is especially indicated when the sinus rate is raised and the conventional antiarrhythmic drugs have proved ineffective.

Blood Pressure↗