Search PubMed⌕ Search

Biomedical subjects

J Krieger

Publications and source records attributed to J Krieger.

At least 199 records · Page 11Linked to original sources
PubMed1981

Cerebrospinal fluid adenosine 3',5'-monophosphate, 5-hydroxyindoleacetic acid and homovanillic acid in patients with sleep apnoea syndrome.

Adenosine 3',5'-monophosphate (cyclic AMP), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were determined in the cerebrospinal fluid of patients with respiratory disorder and hypersomnia and in control patients. Patients with the sleep apnoea syndrome confirmed polygraphically showed elevated levels of cyclic AMP and 5-HIAA. Cyclic AMP levels were inversely correlated with arterial Po(2), measured under resting conditions. The level of HVA also was raised, but the change was not statistically significant.

Cyclic AMP↗
PubMed1980

hCG-Leydig cell functional binding kinetics: threshold and nonlinearity in response.

Functional kinetic methods, developed to measure the interaction of human chorionic gonadotropin (hCG) with rat Leydig-cell receptors, appear to be useful tools for correlating response with receptor occupancy. In the functional procedures, hCG was allowed to bind to the cells (period I), the free hormone was removed by washing and/or antiserum treatment (period II), and the response of the cells was measured at 37 degrees C (period III). Once initiated, the response to hCG was stable throughout period III. Assuming a one-to-one relationship between occupancy and response during period III, we estimated the rate of association to be 10(8) M-1/min at 37 degrees C with an activation energy of 14-17 kcal/mol. Removal of sialic acid from hCG increased this rate; removal of other carbohydrate residues decreased it. Similar values for the kinetics of binding were observed when either steroidogenesis or cyclic AMP accumulation was measured, suggesting that the same receptor may mediate both processes. Use of either functional or direct (i.e., 125I-labeled hCG) methods to estimate response as a function of occupancy gave equal results, suggesting that most binding sites were coupled to a response. Response was nonlinearly coupled to occupany. Threshold amounts of hormone-receptor complex (0.1% total receptors testosterone synthesis; 2.7% total receptors cyclic AMP accumulation) were required to induce any response. Increased stimulation required progressively larger increments of receptor occupancy. The threshold was inversely proportional to the efficacy of the hCG derivative used and was reduced by the presence of isobutylmethylxanthine.

Animals↗
PubMed1978

EMG activity of cricothyroid and chin muscles during wakefulness and sleeping in the sleep apnea syndrome.

The authors studied the direct and integrated EMG activities of the cricothyroid (CT) and chin muscles in 7 patients with the sleep apnea syndrome. They noted: (1) A tonic activity with phasic inspiratory reinforcements in the CT during wakefulness. (2) A decrease in the tonic activity without any modification of the phasic inspiratory reinforcement during sleep. (3) A decrease or even disappearance of the phasic activity during sleep-induced hypopneas. (4) A complete cessation of both the tonic and the phasic activities of the CT during obstruction apneas: resumption of respiration is marked by the reappearance first of the phasic inspiratory activity and secondly of the tonic one. (5) In some patients similar activities are recorded in the chin muscles during wakefulness, sleep and sleep apnea. These results favor possible obstruction of the upper airway at the laryngeal level: the conjunction of inhibition of the inspiratory activity of the laryngeal muscles with the subsequent closing of the glottis and inspiratory depressure could produce an obstruction.

Adult↗
PubMed1978

[Respiratory arrest during sleep. Facts and hypothyses].

The writers analyze 29 nyctohemeral recordings in 20 patients with sleep apneas. In addition to the standard polygraphy, use is made of pneumotachography and capnography. The results (central apnea with open or secondarily closed glottis; obstructive apnea with closed glottis or with expiratory valve phenomenon) raise the hypothesis of a central physiopathological mechanism common to the various types of apneas through a more or less dissociated inhibition of the activity of the respiratory, laryngeal, intercostal, and diaphragmatic muscles:--in central apnea: inhibition of the thoracoabdominal activity and maintenance of the tonicity of the laryngeal muscles, keeping the glottis open;--in obstructive apnea: persistence of the thoracic and/or abdominal activity with inhibition of the activity of the laryngeal muscles, leading to a passive obstruction due to the effect of inspiratory depression.

Airway Obstruction↗
PubMed1977

[Opsoclonia: oculographic study].

Oculographic study of a case of opsoclonus associated with infectious meningoencephalitis was used to determine the criteria of definition of this abnormal ocular movement, distinguishing it from the other abnormal movements of flutter and dysmetria. The authors first discuss, on the basis of these recordings, the possible relationship between opsoclonus and myoclonia, and then the role of the cerebellum. The disturbances noted in the course of study of saccadian movement lead them to suggest the hypothesis of overall involvement of the saccadian oculomotor system. They stress the value of oculographic recording in better understanding the general mechanisms of saccadian movement and the pathogenesis of the various changes which may be encountered.

Adult↗
PubMedDate not supplied

Elements of the olfactory signaling pathways in insect antennae.

Owing to their enormous ability to recognize airborne molecules, insects have long been used as model systems for studying various aspects of olfaction. Modern biological techniques have opened new avenues for exploring the molecular mechanisms underlying the complex signaling processes in chemosensory neurons. Biochemical and molecular analyses have allowed the identification of molecular elements of the olfactory reaction pathways and have shed light on mechanisms that account for the sensitivity and specificity of the chemosensory system.

Amino Acid Sequence↗
PubMedDate not supplied

Apnea following hyperventilation in man.

To assess the incidence of posthyperventilation apnea (PHA), breathing patterns after active voluntary hyperventilation were determined during EEG recording by means of: (1) a thermocouple in 1060 patients; (2) a pneumotachograph coupled with a capnograph in 100 further patients. All the patients were randomly chosen. PHA of 12.6 +/- 0.48 occurred in only 18% of awake subjects and was not related to the magnitude of the lowering of end-tidal FECO2 during the test. PHA frequency increased when sleep followed hyperventilation and in patients with clinical or EEG evidence of cerebral pathology and seemed to be age-related. This study supports the hypothesis that in man a central neural mechanism closely linked to vigilance and connected with active breathing supplies sufficient neural facilitation to prevent the apnea consequent on the decrease in chemical humoral stimulation. Posthyperventilation sleep reduces this neural facilitation, allowing the lack of chemical stimulation to induce apnea. The high incidence of PHA reported in some studies might be due to a decrease in vigilance which was not detected by the usual behavioral or electroencephalographic tests.

Adolescent↗
PubMedDate not supplied

Auditory event-related potentials in obstructive sleep apnea: effects of treatment with nasal continuous positive airway pressure.

Event-related potentials (ERPs) were recorded in 47 patients with obstructive sleep apnea (OSA) syndrome prior to and after 6 weeks of treatment with continuous positive airway pressure (CPAP). Compared with a control group, the OSA patients showed ERP abnormalities: lengthened P3 latencies and decreased N2-P3 amplitudes. After 6 weeks of CPAP treatment, there was a highly significant improvement in the abnormal ERPs: the P3 and N2 latencies were shortened, but remained longer than in controls, and the N2-P3 and N1-P2 amplitudes were increased. No correlations could be established with various sleep variables. ERPs may be used as an electrophysiological marker of brain dysfunction; treatment of OSA with CPAP is probably responsible for functional brain modifications. On the other hand, possible relationships between the ERP abnormalities and the neuropsychological disorders observed in OSA remain to be established.

Adult↗
PubMedDate not supplied

[Sleep apnea synrome : effects of chlorimipramine in subjects with stable body weight (author's transl)].

Beneficial effects have been attributed to Chlorimipramine in the treatment of sleep apnea syndrome (SAS). However, there were no quantitative evaluations of these effects. Polygraphic studies were made before and after chlorimipramine treatment (75 mg per day for 3 to 16 months). The 3 SAS subjects, whose weight remained stable throughout the course of treatment, showed no evidence of reduced hypopnea and apnea during sleep.

Adult↗
PubMedDate not supplied

[Post-traumatic coma from diffuse brain lesions. A correlative study of the levels of dysfunction and the EEG nyctohemeral aspects (author's transl)].

Thirteen EEG and polygraphic recordings were performed during a 24-hour period in 11 patients with post-traumatic coma. Spontaneous fluctuations, reactivity, and the organization of electrical activity were studied throughout the nyctohemeral period. The results were compared with the data obtained from clinical examinations evaluated in terms of the level of neurological dysfunction. The level of impairment of the EEG was usually a valid indication of the level of neurological dysfunction, the EEG results being sometimes more precise than the clinical data. In regard to the prognosis, the disappearance in the EEG of any fluctuations coincided with an unfavourable evolution.

Brain↗
PubMedDate not supplied

[Nycterohemeral variations in plasma growth hormone (GH) levels and sleep apnea syndromes: their relationship with obesity (author's transl)].

The authors suggest the hypothesis that the obesity often associated with sleep apnea syndromes is related to changes in HG secretion. Indeed, as HG secretion is sleep related any disturbances due to apnea during may alter the GH secretion. In order to test their hypothesis the authors studied, during the course of 24-hour polygraphic recordings, the levels of HG, blood glucose and free fatty acids, in 16 subjects, 14 of whom were obese and 9 of whom had the sleep apnea syndrome. The results obtained confirmed the relationship between the number of apnea and the stability of sleep. They also demonstrated a relationship between GH secretion and both the stability of sleep and obesity. These results, therefore, suggest that apnea plays a role in obesity development.

Adult↗