PubMed Health⌕ Search

Biomedical subjects

G Hajak

Publications and source records attributed to G Hajak.

8 recordsLinked to original sources
PubMed1992

The metabolic fate of infused L-tryptophan in men: possible clinical implications of the accumulation of circulating tryptophan and tryptophan metabolites.

L-Tryptophan (Trp) was widely used as a natural tool for the support of serotonin-mediated brain functions and as a challenge probe for the assessment of serotonin-mediated neuroendocrine responses. The metabolic fate of the administered Trp and the kinetics of the accumulation of Trp metabolites in the circulation, however, have never thoroughly been investigated. This study describes the time- and dose-dependent alterations in the plasma levels of various Trp metabolites and large neutral amino acids after the infusion of Trp to healthy young men (1, 3 and 5 g; placebo-controlled, double-blind, cross-over study during day- and night-time). The major Trp metabolites (kynurenine, indole acetic acid and indole lactic acid) in plasma increased dose-dependently but rather slowly after Trp administration to reach their maximal plasma levels (up to 10-fold after the 5 g dose) at about 3 h p.i., and remained at an elevated level (about 5-fold) for up to 8 h. N-acetyl-Trp and 5-hydroxy-Trp rose rapidly and massively after Trp infusions, at the 5 g dose more than 200- and 20-fold, respectively, and declined rapidly to about 5-fold baseline levels within 2 h. Whole blood serotonin levels were almost unaffected by the Trp infusions. A rather slow increase of 5-hydroxyindole acetic acid was seen, reaching maximum values (3-fold at the 5 g dose) at about 2 h after the infusion of Trp. Additionally, a dose-dependent rise of circulating melatonin was observed after L-Trp infusions. The administration of L-Trp caused a depletion of the concentrations of the other large neutral amino acids and a dose dependent decrease of the ratio between plasma tyrosine and the sum of the plasma concentrations of the other large neutral amino acids. Apparently, none of the existing pathways of peripheral Trp metabolism is saturated by its substrate, Trp in men. At least some of the central effects reported after L-Trp administration may be mediated by the Trp-stimulated formation of neuroactive metabolites or by the decreased availability of tyrosine for catecholamine synthesis.

Adult↗
PubMed1992

Assessment of intracranial hemodynamics in sleep apnea syndrome.

BACKGROUND AND PURPOSE: Sleep apnea syndrome may lead to changes in cerebral hemodynamics due to altered alveolar ventilation. We investigated the dynamics of CO2- and blood pressure-regulated alterations of cerebral blood flow velocities during apneic episodes and evaluated CO2 reactivity during different sleep stages. METHODS: A computer-assisted pulsed Doppler system (2 MHz) was used for continuous overnight recordings of middle cerebral artery flow patterns together with simultaneous polysomnography, continuous blood pressure recordings, and measurements of end-expiratory CO2 in six patients with sleep apnea syndrome. RESULTS: Increases in mean flow velocity of 19-219% and in blood pressure of 12.5-83.1% could be observed during the apneic episodes, with maximum increases during rapid eye movement (REM) sleep. CO2 reactivity was in the normal range (4.4 +/- 1.2%) in the waking state and was markedly increased during sleep stages 1 and 2 (p less than 0.005 compared with awake). The greatest increase was found during REM sleep, with a rise of up to three times the waking value (p less than 0.0001 compared with sleep stage 2). CONCLUSIONS: The changes of mean flow velocity could be interpreted as reactive adaptation processes because of CO2 and blood pressure increases corresponding to apnea. The increased CO2 reactivity during sleep may indicate a "hypersensitivity" of intracranial vascular CO2 or pH receptors and a disturbance of central catecholaminergic and cholinergic systems. The pronounced velocity changes during apneic episodes and the concomitant alterations of vessel wall tension might lead to microangiopathies and macroangiopathies due to chronic strain on the brain vessels.

Adult↗
PubMed1992

[Somnambulism and pavor nocturnus--review and case report].

A case of night terror with sleepwalking in an adult patient is described. Sleep polygraphic data are presented. The literature related to sleepwalking, night terror and its treatment is reviewed. The psychopathologic patterns of sleepwalking and night terror are illustrated and the differentiations of parasomnias and epileptic seizures discussed. The clinical applications of these findings are described and practical recommendations made for the management of NON-REM parasomnia.

Arousal↗
PubMed1992

Problems in performing a double-blind multicenter study using a hypnotic in private practice.

1. The procedure described--the immediate data transfer and entry system (ITES)--is suitable to improve the quality of data collected in multicentre studies in private practice. 2. The results of the study show that regarding influence on sleep quality and daytime well-being the non-benzodiazepine Z is significantly superior to placebo and slightly superior to the benzodiazepines F and T. 3. The advantage of Z treatment is the better daytime well-being after taking the hypnotic for sleep induction the night before. 4. This study shows that a quality standard equal to that in clinical practice may be achieved in private practice.

Adolescent↗
PubMed1992

Changes in heart rate during obstructive sleep apnoea.

The mechanisms behind the decrease in heart rate during apnoeas in patients with obstructive sleep apnoea (OSA) are little known. Recent findings in animal experiments indicate that stimulation of the upper airway activates postinspiratory and cardiac vagal neurones in the medullary respiratory centre, causing alterations in heart rate and respiratory rhythm. Since OSA leads to a collapse of the airway and consequent stimulation of upper airway receptors, we studied the interrelations between heart rate and respiratory rhythm during apnoea and during negative intrathoracic pressure generated by the Mueller manoeuvre (MM). Fifteen patients with OSA (apnoea hypopnoea index (AHI) 45 +/- 28.h-1) were studied by polysomnography, during a MM and a Valsalva manoeuvre, each of 15 s duration. The heart rate decrease (delta HRA) and the increase in total respiratory cycle duration (TOT) were evaluated during apnoea in non-rapid eye movement (REM) sleep. Patients with OSA demonstrated a decrease in heart rate during apnoea (-14.4 +/- 9.0 beats.min-1), and during MM (-11.5 +/- 13.5 in OSA vs 3.1 +/- 7.8 beats.min-1 in a control group). TOT increased during apnoea (4.6 +/- 3.1 s). There was a significant correlation between delta HRA and AHI (r = -0.64) as well as between delta HRA and increase in TOT (r = 0.62). These findings indicate that upper airway obstruction may cause an activation of receptors at the site of airway collapse or distortion leading to changes in heart rate and respiratory rhythm.

Female↗
PubMed1991

The influence of intravenous L-tryptophan on plasma melatonin and sleep in men.

The sleep-inducing mechanisms of L-Tryptophan (L-Trp) are generally thought to be mediated by a central serotonergic activation. Evidence is presented that some effects of L-Trp on sleep may be mediated by melatonin, a Trp-metabolite with sedative properties. Trp effects on vigilance, sleep, and plasma-melatonin concentrations were measured after double-blind application of 0, 1, 3, and 5 g L-Trp in nine and five healthy probands during daytime and nighttime, respectively. A significant sleep-inducing effect was observed after L-Trp administration during daytime and nighttime. The infusions of L-Trp caused a massive elevation of plasma melatonin levels. This effect was significant both during the night and the day, indicating that the increment of circulating melatonin may be of extrapineal origin.

Adult↗
PubMed1991

[ST segmental changes and arrhythmias in obstructive sleep apnea].

Patients with obstructive sleep apnea show a fall in arterial oxygen saturation during apneas. Whether this is causing myocardial ischemia and consecutively ST segment depressions in the electrocardiogram is not known. Therefore 15 consecutive patients (53 +/- 8 years, apnea index 45 +/- 28, minimal oxygen saturation 71 +/- 14%) with OSA were studied by Holter electrocardiogram and polysomnography. History and exercise testing gave no evidence of coronary heart disease. Three patients had ventricular arrhythmias Lown IVA and 10 had Lown I or III. Three patients showed unspecific negative T waves or ST segment elevations. In no patient significant ST segment depression was found. It is concluded that OSA does not lead to ischemic ST segment depression in the absence of coronary heart disease. The cause of ventricular arrhythmias in OSA seems not be related to myocardial ischemia.

Adult↗