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Biomedical subjects

P Schwartze

Publications and source records attributed to P Schwartze.

At least 19 recordsLinked to original sources
PubMed1999

Oxygen uptake to work rate relation throughout peak exercise in normal subjects: relevance for rate adaptive pacemaker programming.

The oxygen uptake to work rate (VO2/WR) relationship observed throughout peak exercise testing is already being applied for rate adaptive pacemaker programming. However, the detailed curve design of VO2/WR with respect to the anaerobic threshold (AT) has not yet been investigated. It was the purpose of this study to determine the VO2/WR slope below and above the AT in a healthy control group. Seventy-eight healthy control subjects (45.9 +/- 17.4 years; 34 women: 49.9 +/- 18.6 years 44 men: 43.6 +/- 16.6 years) were exercised on a treadmill with "breath-by-breath" gas exchange monitoring using the symptom limited "ramping incremental treadmill exercise" (RITE) protocol. The slope of the VO2/WR relationship from rest to peak exercise (r-p), rest to AT (slope A), and AT to peak exercise (slope B) in mL oxygen uptake per watt of external treadmill work was determined by linear regression analysis. [table: see text] The oxygen uptake to work rate relationship throughout peak exercise in the entire study group generated a significant slope change at the AT (31%, P < 0.0001) with a decreasing slope during higher work load intensities. Female subjects demonstrated a greater percentage of slope change at AT (43%), as compared to men (22%, P < 0.01). When using the oxygen uptake to work rate relationship for the programming of the pacemaker's rate response to exercise, the significant slope change at the AT should be considered to more appropriately pace during higher work intensities supported by anaerobic metabolism. Female pacemaker patients should be programmed to generate a steeper VO2/WR slope below AT with a greater slope change at AT, as compared to men. Abnormally high oxygen uptake to work rate ratios above the AT may be possibly used as an indicator of overpacing.

Adult↗
PubMed1997

Oxygen uptake kinetics during low intensity exercise: relevance for rate adaptive pacemaker programming.

OBJECTIVE: To establish a normal database for oxygen uptake (VO2) kinetics during low intensity treadmill exercise (LITE) testing, to be used as a guideline for programming rate adaptive pacemakers, and to determine its relation to VO2 at anaerobic threshold and peak exercise. DESIGN: VO2 kinetics during LITE were compared with VO2 at anaerobic threshold and at peak exercise. SETTING: LITE testing is applicable during ambulatory or hospital care and can even be performed by patients with reduced cardiac capacity. PATIENTS: 60 healthy subjects (23 women, 51.6 (SD 20.4) years; 37 men, 42.2 (16.2) years). INTERVENTIONS: Treadmill exercise testing with "breath by breath" gas exchange monitoring using the LITE protocol for steady state, submaximal exercise, and the ramping incremental treadmill exercise (RITE) protocol for peak exercise. MAIN OUTCOME MEASURES: Mean response time of VO2, mean oxygen deficit, and VO2 at anaerobic threshold (VO2-AT) and at peak exercise (VO2-peak) were determined. RESULTS: (1) LITE protocol: mean response time of VO2 = 35.1 (9.9) s; oxygen deficit = 418.3 (47.9) ml; oxygen deficit/VO2 time index = 54.7 (7.4). (2) RITE protocol: VO2-AT = 22.1 (5.7) ml/kg/min; heart rate at anaerobic threshold = 120.1 (3.6) beats/min; VO2-peak = 37.6 (10.7) ml/kg/min; peak heart rate = 167.8 (19.3) beats/min. The mean response time and oxygen deficit/VO2 time index were significantly correlated to VO2-peak and VO2-AT (P < 0.01). CONCLUSIONS: VO2 kinetics calculated in healthy controls may serve as a control database for assessing the rate response programming of pacemakers and its influence on VO2 during LITE. Because aerobic capacity below the anaerobic threshold is more likely to represent activity in daily life and the kinetics of VO2 are significantly related to VO2 at anaerobic threshold and peak exercise, LITE may provide a clinically useful correlate to peak exercise testing.

Adult↗
PubMed1991

[Development of the sense of smell, a review].

The pre- and postnatal development of human olfaction is described. Data from animal experiments a partially reviewed as a base for understanding of the results of olfactory testing of babies and children. In rat fetuses the vomero-nasal-organ is used as detector of molecules in the amnion fluid. The perinatal aeration of the nasal cavity allows the adequate stimulation of the olfactory epithelium. The early postnatal olfaction is a brainstem function; later the olfactory cortical area are used for the discrimination between odorants. There are only a few investigations about the olfactory function in childhood, so that the testing of olfaction for detecting abnormal brain developments is just in the beginning.

Animals↗
PubMed1991

[Induction of optokinetic nystagmus in infants and young children by a horizontally, diagonally or vertically moving striped pattern].

Horizontal optokinetic nystagmus (H-OKN) in infants is often described in contrast to diagonal (D-OKN) and vertical (V-OKN) nystagmus. No systematic investigation has been carried out to test the elicitability of D- and V-OKN in relation to the direction of the moving stimulus or the effect of stimulating the two eyes simultaneously or separately. We examinated the elicitability of H-, D- and V-OKN in more than 400 infants between birth and 5 years of age in two test situations: with both eyes open and with one eye covered. The stimulation device was a (hand-driven) drum of 12.2 cm diameter, on which a paper sheet with a pattern of black and white stripes (20 mm) kept in a horizontal, diagonal and vertical position, respectively. The distance to the infant's face was kept at ca. 25 cm. The occurrence of OKN was studied in all the six stimulation situations. Results demonstrated a clear developmental course in the monocular tests situation of the occurrence of OKN: at first only horizontal OKNs can be elicited, thereafter diagonal and finally vertical OKNs appeared. In general OKNs in all 6 testsituations are evident from the age of 3-24 months. However, in risico infants, deficits in at least one of the test situations were observed until the age of 5 years. Our results point towards a role of testing OKN as a screening method for detecting visual or brain dysfunction.

Brain↗
PubMed1990

The influence of altered head, thorax and pelvis mass on the postnatal development of the air-righting reaction in albino rats.

The experiments were performed on 18 albino newborn rats of both sexes. The postnatal development of the air-righting-reaction (ARR) of the rats was tested for 4 different falling heights (30, 40, 50 and 60 cm) with 3 different loading conditions: artificial alteration of the head, thorax and pelvis mass, respectively. The reaction was analyzed in terms of a three-segment model of the rat (three rotatable parts: head-thorax-pelvis with only one degree of freedom between successive segments). Loading of the head resulted in a delayed development of the first phase of the ARR, whereas loading of the trunk or pelvis slowed the second phase of development. In general, it appears that loading of a body segment results in a delayed development of the rotation of that segment during free fall. Furthermore, loading of a caudal region was associated with an earlier rotation of cranial segments. The completion of the ARR maturation process showed no dependency on either the location or the size of the load, suggesting that the postnatal development of the ARR is pre-programmed.

Animals↗
PubMed1990

The postnatal development of the air-righting reaction in albino rats. Quantitative analysis of normal development and the effect of preventing neck-torso and torso-pelvis rotations.

The aim of this study was to describe the ontogenesis of the air-righting reaction (ARR) in rats. The first experiment was performed on 6 newborn albino rats of both sexes and followed the development of the ARR over postnatal days 1-21. The degree of rotation achieved after falling from different heights was quantified according to a rating scheme. It appeared that the air-righting reaction is effected by a spiral movement which spreads in a cranio-caudal direction. The reaction develops between postnatal day 8 and 18. On postnatal day 10 only a few animals are able to turn their heads, this being possible only from a falling height of 60 cm and corresponding to a falling time of 350 ms. A rapid development of the reaction was found between days 10 and 14. The second experiment on 8 rats involved the use of immobilization in order to isolate the mechanisms that trigger the ARR. The immobilization prevented neck-torso rotation, torso-pelvis rotation, and both rotations in different animals. Despite the disruption of important (afferent) feedback systems, the reaction developed within the same age period as in control rats. Thus, the Magnus "chain reflex hypothesis' as basis for the ARR is rejected in favor of a central motor program hypothesis.

Age Factors↗
PubMed1989

[Reflex time in relation to age and behavioral status studied in postnatal growing rats].

1. The central nervous system of neonatal albino rats showed age specific functional parameters, some of them are comparable with those of human prematures. 2. The reflex times (RT) of the lid closure reflex and of the withdrawal reflex of the foreleg, hindleg and tail were measured during the behavioral states quite sleep, active sleep, and wakefulness of rats between 1st and 20th postnatal day. 3. The RT of the investigated reflexes decreased with age in different degrees. 4. The RT was found to be different in the behavioral states; with increasing age the RT becomes longer in active sleep than in the other states. 5. The reflex time measurement of withdrawal reflexes during different behavioral states should be proved for its applicability as a test for normal brain development in humans newborns.

Aging↗
PubMed1986

[Bürger's efforts for a productive relationship between physiology research and internal medicine].

On the occasion of the 100th anniversary of Max Bürger's birthday his performances in the field of physiology are summarizingly valued and deduced from Bürger's philosophical conception. For his whole life Bürger felt obliged to the developmental biological ideas of the first half of the last century. So the observation and description of the age-depending change of physiological accomplishments and functions became his essential subject of research. Particular attention deserve his investigations of the intrathoracic pressure as well as his studies on the sex-dependence of courses of the disease. As clinician Max Bürger particularly identified himself successfully with the development of the pathological physiology as subject of instruction and education.

Germany↗
PubMed1986

[Saccadic eye movements during sinusoidal rotational stimulation in rabbits in the postnatal period].

Electro-oculograms were recorded from rabbits of the 5th, 11th, 18th and 25th day of life as well as from adult animals by means of chronically implanted silver wire electrodes. The sinusoidal rotation of the fixed alert animals in the horizontal plane were carried out by frequencies of 0.05, 0.2, 0.5 and 1.0 Hz using amplitudes of 15 degrees, 22.5 degrees and 45 degrees (peak to peak: 30 degrees, 45 degrees and 90 degrees). The saccade-(Sc)-threshold as well as the Sc-frequency were determined and the phase angle between stimulus and eye movement was measured. The Sc-threshold depends on the stimulation amplitude and shows a longer postnatal development in small 15 degrees-amplitude stimulations than in more intensive ones. The Sc-frequency appears to be an age-, amplitude- and frequency-dependent parameter. It rises with advancing age and increasing stimulation amplitude, respectively. The number of Sc increases also with growing rotational frequency up to a maximum and decreases when using further rising frequencies. In contrast to eye movements without Sc, the phase angle is diminished in movements interrupted by Sc-reactions. This phenomenon as well as the decreasing phase angle with increasing rotational frequency occur in all age groups. Thus, the Sc cause a better temporal precision of vestibular-guided stabilization of the retinal image during the postnatal ontogenesis from the first time of their appearance onward.

Aging↗
PubMed1983

[Chronotropic effects of carnitine derivatives in isolated rabbit atria at defined transmural pressures].

Acetylcarnitine isomers and gamma-betaine methylesters are closely structure-related to cholinergic agonists. With continuous perfusion at defined transmural pressures of 0.1 and 0.5 kPa their effects on the chronotropic autoregulation of isolated spontaneously beating atria were examined in comparison with acetylcholine. Independent of the transmural pressure, the two isomers of acetylcarnitine had no effects on the heart rate up to a concentration of 10(-3) mol/l. Among the carboxylesters of gamma-betaines, the crotonobetaine methylester was up to 100 fold more effective than acetylcholine. Hydrogenation of the double bond decreased the negative chronotropic response 10 times. The L(-)-carnitine-methylester did not influence the spontaneous heart rate up to 3 X 10(-3) mol/l, but the D-isomer inhibited it significantly. Increase of the transmural pressure caused the same level of heart rate in both controls and atria under free betaines. At transmural pressure of 0.5 kPa, in comparison with 0.1 kPa, a significantly greater impairment of heart rate, released by crotonobetaine-methylester, was observed. Atropine blocked the interactions of the gamma-betaine-methylesters with the muscarinic cholinergic receptors of the pacemaker cells.

Animals↗
PubMed1981

[Ontogenesis of the corneo-retinal potential in rabbits].

The postnatal ontogenesis of the corneo-retinal potential in rabbits are unknown up to date. Therefore, in 32 young animals between the 1st and the 40th day of life and 6 adult rabbits this potential was measured during 10 degrees bulb deviation. The potential increases with age from 35 micro V in adults. The potential's development shows temporal conformity to postnatal ontogenesis of retina and ERG.

Aging↗