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J Drescher

Publications and source records attributed to J Drescher.

At least 37 records · Page 2Linked to original sources
PubMed1997

Cardiovascular regulation: a modelling approach.

A detailed analysis of autonomic cardiovascular control (ACVC) may provide a key to a better understanding of the mechanisms underlying postflight orthostatic hypotension. The central substrate of human ACVC is not directly accessible to measurements and observation in space research. Modelling--supporting inference and physiological reasoning--is a valuable tool to disclose its involvement We are currently determining the suitability of artificial neural networks (ANN's) as a model of the central substrate of ACVC. Having conducted a number of experiments with simulated tilt test data to clarify the choice of input coding and of architectural biases in network training we will now report on the approximation of data obtained from human subjects during preparation of the German MIR'97 and D-2 missions.

Adaptation, Physiological↗
PubMed1997

Two-crew operations: stress and fatigue during long-haul night flights.

BACKGROUND: As part of a research program concerning legal aspects of two-pilot operations on long-haul routes, the purpose of the study was to investigate two-crew extended range operations during a flight roster with two consecutive night flights and a short layover. HYPOTHESIS: Present flight time regulations may not be adequate for two-crew minimum operations. METHODS: The study was conducted in cooperation with a German airline company on the route Frankfurt (FRA)-Mahe (SEZ). There were 11 rotations (22 flights) that were investigated by pre-, in- and post-flight data collection each time from the two pilots. Recordings included sleep, taskload, fatigue and stress by measurement of EEG, ECG, motor activity, and subjective ratings. The average actual flight times were 9:15 h (FRA-SEZ) and 9:53 h (SEZ-FRA). All flights took place at night. The layover duration in Mahe was 13:30 h during day-time. RESULTS: During layover, sleep was shortened by 2 h on average compared with 8-h baseline sleep. The two consecutive night duties resulted in a sleep loss of 9.3 h upon return to home base. Inflight ratings of taskload showed moderate grades, but for fatigue ratings an increasing level was observed. Fatigue was more pronounced during the return flight and several pilots scored their fatigue at a critical level. Motor activity, brainwave activity (occurrences of micro-events) and heart rate indicated drowsiness and a low state of vigilance and alertness during both night flights, but these effects were more pronounced during the second flight. CONCLUSIONS: From the findings it is concluded that a duty roster, as conducted in this study, may impose excessive demands on mental and physiological capacity.

Adult↗
PubMed1996

Development of a regional cohort of very-low-birthweight children at six years: cognitive abilities are associated with neurological disability and social background.

The authors studied the intelligence, memory, visuomotor skills and la nguage of 298 six-year-old children with very low birthweight (VLBW) (less that 1500g). Of 591 VLBW childern born July 1983 to June 1986 within 50km of the centre of Hamburg, Germany, 330 were traceable at age six years and 298 of these were seen by a neuropaediatrician and a psychologist; the other 19 were too severely disabled for psychological assessment with the standardized tests used. The mean memory performance of VLBW children at age six years was below the standard mean in all diagnostic and socio-economic subgroups. As expected, visuomotor development was clearly influenced by neurological but not socio-economic status. Intelligence and language skills were much more closely related to socio-economic background that to neurological morbidity. However, VLBW children with hyperactivity, clumsiness or cerebral palsy differed significantly in intelligence and visuomotor performance from those without neurological symptoms.

Cerebral Palsy↗
PubMed1995

Determination of the concentration of influenza virus antihaemagglutinin antibody molecules of the IgG class and of the equilibrium constant by use of enzyme immunoassay titres determined for graded epitope concentrations.

A new technique for determining the concentration of influenza virus antihaemagglutinin antibody molecules of the IgG class (A) and of the equilibrium constant K of paratope-epitope interaction is described. The method is based on determining enzyme immunoassay (EIA) titres of antibody with graded epitope concentrations: EIA titres were defined in terms of the antibody dilution yielding a fixed amount of antibody adsorbed per ml (= 6.21 x 10(10)). Adsorption of antibody depends on the concentration of paratopes and epitopes allowed to react and on the equilibrium constant. For the use of a constant concentration of epitopes, the paratope concentration needed to yield the desired degree of antibody adsorption decreases with increasing avidity. Therefore, the EIA titres increase both with increasing avidity and increasing antibody concentration. When graded epitope concentrations are used for determining the EIA titres of a given serum, the titres are influenced in a similar manner by the antibody concentration of the serum and the increase of titres with increasing epitope concentration reflects avidity. The equilibrium constant found is subsequently used to determine the concentration of free antibody at the dilution meeting the definition of EIA titre and the product of EIA titre and the sum of free and bound antibody at this dilution gives the number of antibody molecules present in the test serum. A panel of 118 antisera was tested comparatively for A and K using the new method and by means of the guanidine titre ratio test and equilibrium filtration. The values obtained agreed well with each other. This novel technique offers the advantage that it can be easily adapted for use with other viruses.

Animals↗
PubMed1995

Sleepiness of civil airline pilots during two consecutive night flights of extended duration.

Sleepiness of civil airline pilots was studied in a two-crew cockpit during two consecutive night flights of about 10 h duration each. Sleepiness was assessed by EEG recordings and subjective ratings during hourly recurrent short experimental phases. On the second night flight, the alertness component that is related to the preceding sleep showed a modification due to reduced quality and quantity of sleep between flights. The daytime sleep during layover was not sufficient to maintain the same alertness level as observed during the initial flight. This result is in coincidence with investigations in shift workers starting a period of night shifts. It is concluded that improvements such as the introduction of a nap schedule should be considered to alleviate spontaneous sleepiness in the cockpit.

Adult↗
PubMed1995

Psychosocial aspects of HIV and AIDS.

Psychiatrists see human immunodeficiency virus (HIV)-infected patients who suffer from several types of psychiatric disorders and personality disorders. These syndromes can arise (1) in people who have had a previous history of a similar illness; (2) in people in whom the HIV infection exacerbates a borderline condition; (3) from the stress of the HIV infection and its known prognosis; and (4) only rarely is a person who is not HIV infected but becomes unduly or unrealistically concerned about acquiring the infection.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Forehead skin microcirculation during tilt table testing and lower body negative pressure.

Noninvasive skin microcirculation measurements based on a new Near Infrared sensor technique (NIR/Fa. Silicon Sensor GmbH; Berlin) were embeded in a tilt table experiment for simulation of acute effects of weightlessness (HDT -6 degrees) and active standing with the Russian Tschibis-LBNP device. The phenomenon of orthostatic intolerance depends on complex interactions among functional characteristics of central and peripheral cardiovascular control. The purpose of this study was to assess the blood volume and flow motion changes as well as pulsatile spectral pattern during orthostatic and antiorthostatic stress.

Adult↗
PubMed1995

Heart rate variability during head down tilt and lower body negative pressure in the Russian Tschibis.

The cardiovascular function in space seems to be normal. However, abnormalities of cardiovascular responses have been found during lower body negative pressure suction in space. The etiology of the cardiovascular deconditioning in space is still unknown. A previous study showed, that short periods of head down tilt (HDT-6 degrees) induce changes in the spectral pattern of heart rate variabilty (HRV) and an increase in the sympathethic activation caused by orthostatic stress. The aim of this study was to test following hypotheses: 1. The dynamic of heart rate variability is different in the head down tilt and supine positions. 2. The application of lower body negative pressure (LBNP) during head down tilt induces similar heart rate variability patterns like the standing position. 3. After short term head down tilt the cardiovascular response to lower body negative pressure stressor is altered.

Adult↗
PubMed1995

[Q-fever associated myocarditis in a 14-year-old boy].

A 14-year-old boy presented with the symptoms and clinical signs of myocarditis. Ventricular arrhythmias were the main manifestation. Dilated left ventricle with slightly impaired contractility and spongy appearance of the myocardium were also noted. Laboratory signs of an acute infectious disease were absent, but a significant rise in the complement fixation titer for Coxiella burnetii was observed. Treatment with oral tetracycline for 6 months resulted in improvement of ventricular arrhythmias and normalization of left ventricular dimensions and structure over the following months. Cardiac involvement in Q fever is rare, and with it endocarditis is usually seen as a chronic form of the disease. Myocarditis associated with Q fever has been reported only in some rare cases but not in children. The case reported here illustrates that the diagnosis of Q fever should also be considered in a case of myocardial involvement in an infectious disease of unknown etiology.

Adolescent↗
PubMed1994

Method for determining the equilibrium constant and the concentration of influenza virus IgG antihaemagglutinin antibody molecules by use of EIA titres determined with and without guanidine hydrochloride.

A novel technique for determining the concentration of influenza virus antihaemagglutinin antibody molecules (A) of the IgG class and their equilibrium constant (K) is described which is based on recording EIA (enzyme-linked immunosorbent assay) guanidine titre ratios R (EIA titre determined in the absence of guanidine divided by EIA titre determined in the presence of 0.25 M guanidine hydrochloride). K is determined by using a regression line relating values of K to values of R. The line was established by testing antisera comparatively for K by means of equilibrium filtration and for R by EIA. The assay of A is based on the finding that the concentration of antibody molecules adsorbed at serum dilutions yielding an O.D. reading of 0.9 in the EIA test is within the experimental limits constant. Since K is known, this point of reference can be used to calculate A. For a panel of 57 influenza antisera, the A and K values determined by equilibrium filtration agreed well with the respective values determined by use of the novel technique.

Animals↗
PubMed1994

Nosocomial hepatitis B virus infections in cardiac transplant recipients transmitted during transvenous endomyocardial biopsy.

Between March 1986 and September 1990, 67 of 243 cardiac transplant recipients in outpatient care at our clinic became hepatitis B virus surface antigen (HBsAg) positive after operation. The HBsAg of 63 patients belonged to the subtype ay, suggesting a common source of infection. These 63 cases and 103 controls with negative hepatitis B virus (HBV) serology were studied in order to analyse the outbreak. The sources of infection were patients who were chronic HBsAg carriers. Infection was transmitted at the time of endomyocardial biopsy, if performed on the same day and in the same room after biopsy of an HBsAg positive patient. The most likely mode of HBV transmission was droplet contamination of instruments and/or medication vials used for subsequent patients. Performing biopsies on HBsAg positive and negative patients in separate rooms resulted in the termination of the outbreak.

Adult↗
PubMed1994

Acute effects of simulated microgravity on heart rate variability.

Microgravity is known to stress the heart and blood vessels and to perturb the normal neural regulation of the cardiovascular system. In an effort to gain greater insight into the adjustments of neural control of the cardiovascular system in space, we have used a model of simulated microgravity, the -6 degrees head-down tilt body position (HDT). As a common method for the description of the functional state of the cardiovascular system the power spectral analysis of the heart rate can be used. The following working hypotheses were postulated: 1. HDT causes an acute activation of the parasympathetic nerve traffic to the heart, which is detectable by a reduction in heart rate and by the spectral power distribution of the heart rate variability. 2. HDT induces changes in the autonomic nervous response to upright posture which can be detected after a 45-minute period of head-down tilt.

Adult↗
PubMed1993

Comparative investigation of the hemagglutinin epitopes of influenza virus A/Brazil/11/78 (H1N1). and its escape variants.

A method described previously for determining the concentration of influenza virus antihemagglutinin antibody molecules, the number of epitopes per virus particle and the equilibrium constant of virus antibody interaction was adapted to the use with escape variants (EVs), produced by multiplication of influenza virus A/Brazil (H1N1) in presence of monoclonal antibody directed to each of the four hemagglutinin sites (Sa, Sb, Ca and Cb). The EVs were found to possess an altered antigenic site, which was both antigenic and immunogenic. By use of selected EVs and antibody preparations, the number of epitopes per antigenic site was determined and it was found that each of the four sites was represented by about 390 epitopes per virus particle, suggesting that each of the about 400 hemagglutinin spikes per virion possessed one epitope of the specificity Sa, Sb, Ca and Cb. Alteration of site Sa but not of site Ca increased the avidity of antibody to react with the unchanged sites.

Antibody Affinity↗
PubMed1992

The evaluation of biological efficiency of electromagnetic fields generated by implanted radiotelemetric transmitters used in space research on animals.

The study was carried out in 50 male rats abdominally implanted with biotelemetric systems (BTS) or mock-up. The animals were provided with 12/12 light/dark schedule during 6-week experiment. The electromagnetic field (EMF) frequency was 455 kHz, magnetic induction near transducer was about 10(-2) mT. Circadian rhythm of the body temperature and locomotor activity was controlled in course of the experiment. The latter been finished, some tissues and the blood of the animals have been sampled to test corticosterone, testosterone, T3, T4 level in serum with radioimmunoassay and membrane permeability for Ca2+, Na+, K(+)-ATPase activity and charge changes in liver microsomes was detected. The probable ways of the EMF influence on whole body are discussed.

Animals↗