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M Pietschmann

Publications and source records attributed to M Pietschmann.

6 recordsLinked to original sources
PubMed1988

Oxygen binding properties, capillary densities and heart weights in high altitude camelids.

The oxygen binding properties of the blood of the camelid species vicuna, llama, alpaca and dromedary camel were measured and evaluated with respect to interspecific differences. The highest blood oxygen affinity, not only among camelids but of all mammals investigated so far, was found in the vicuna (P50 = 17.6 Torr compared to 20.3-21.6 Torr in the other species). Low hematocrits (23-34%) and small red blood cells (21-30 microns 3) are common features of all camelids, but the lowest values are found in the Lama species. Capillary densities were determined in heart and soleus muscle of vicuna and llama. Again, the vicuna shows exceptional values (3720 cap/mm2 on average in the heart) for a mammal of this body size. Finally, heart weight as percent of body weight is higher in the vicuna (0.7-0.9%) than in the other camelids studied (0.5-0.7%). The possibility that these parameters, measured in New World tylopodes at sea level, are not likely to change considerably with transfer to high altitude, is discussed. In the vicuna, a unique combination of the following features seems to be responsible for an outstanding physical capability at high altitude: saturation of blood with oxygen in the lung is favored by a high blood oxygen affinity, oxygen supply being facilitated by low diffusion distances in the muscle tissue. Loading, as well as unloading, of oxygen is improved by a relatively high oxygen transfer conductance of the red blood cells, which is due to their small size and which compensates the negative effect of a low hematocrit on the oxygen conductance of blood.(ABSTRACT TRUNCATED AT 250 WORDS)

2,3-Diphosphoglycerate↗
PubMed1988

The Bereitschaftspotential in preparation to mental activities.

Earlier studies had investigated the Bereitschaftspotential (Bp) under different aspects of muscular activities. The present experiments were designed to test whether the Bp will be affected by the degree of mental load while motor activity is kept constant. Fourteen healthy male subjects had to solve arithmetical tasks under a graduated time pressure (3 categories of tasks). The subjects had to indicate by pressing one of three keys (trigger), which category of task they wanted to solve next. As soon as a key had been pressed, a task appeared on the computer display and disappeared after the time interval corresponding to the selected category. The results had to be entered into a computer via a keyboard. The EEG signals (5 s time constant, 15 Hz upper frequency cut-off) were averaged time-locked to the movement onset, starting 1.5 s before the pressing of the key. Trials with artefacts were rejected from averaging. The Bp was found to be significantly higher when the tasks were to be solved under higher time pressure. We assume that this might be rather an expression of an appropriate self-activation for the expected mental task than due to a different motor preparation.

Adult↗
PubMed1987

P300 and anticipated task difficulty.

Recently, it has been shown that P300 measures depend on stimulus evaluation processes. This paper explores the effect of messages informing about the degree of difficulty of subsequent tasks on the P300 component. Ten healthy volunteers were asked to solve mental arithmetic tasks of graduated difficulty. The degree of difficulty was announced by messages which preceded the tasks and which were used as P300 eliciting stimuli. Measurements of the amplitude and latency of P300 components from 3 brain regions (Fz, Cz, Pz) were collected selectively for each category of task difficulty announced. Subjective ratings of difficulty and the frequency of errors confirmed the monotonic increase of task difficulty from categories I to VI. The mean P300 amplitude in categories I-VI showed a U-shaped trend, i.e. the highest amplitude occurred in the extreme categories 'extremely easy' and 'very difficult'. No significant effect of stimulus categories on P300 peak latencies was found. It is concluded that the P300 amplitude reflects an evaluation in the sense of distance judgements on an internal scale which in this study concerned the task difficulty.

Adult↗
PubMed1985

Cellular hyperplasia and hypertrophy, capillary proliferation and myoglobin concentration in the heart of newborn and adult rats at high altitude.

Newborn rats and their mothers were subjected to a simulated altitude of 5000 m for 4-5 weeks. Weight, capillary density (CD), fiber cross-sectional area (AF) and capillary-to-fiber ratio (C/F) of right (RV) and left (LV) ventricles and myocardial myoglobin (Mb) concentration were measured weekly in the newborns and at the end of the high altitude sojourn in the adults. Results were compared to sea level controls. In the adults, adaptive changes were only observed in the right ventricle. In newborns both, RV and LV, exhibited significant alterations. After 2 weeks at 5000 m the ventricular weight increase was 223% (RV) and 40% (LV) in the newborns and 96% in the adults' RV. Whereas only fiber hypertrophy was detectable in the RV of the dams, cardiac weight increase of the acclimatized neonates resulted from both, hypertrophy and hyperplasia of the myocytes. Appropriate capillary proliferation kept CD constant. Cardiac Mb concentration did not change. We conclude, that capillary neoformation primarily counteracts the increase of the O2 diffusion distance due to fiber hypertrophy and/or hyperplasia.

Altitude↗
PubMed1978

[Activation-dependent characteristics of the electroencephalogram during visual information processing: II Results of an automatic amplitude analysis based on momentary values of signal voltage (author's transl)].

EEG was recorded in 16 Ss. under conditions of a modified "Konzentrations-Leistung-Test" including four levels of performance (balanced change-over design), and histograms of the momentary values of the signal voltages (derivation F3/01) constructed for frequency bands 4...8 Hz, 8...13 Hz and 13...26 Hz. The type of performance affected significantly standard deviations and the excesses in all frequency bands (multivariate analysis of variance, F-Test). Similar to the results of an interval analysis (Activ. ner. sup. 18, 1976, p. 244), the differences in mean values indicated the preponderant relevance of perceptual factors (NEWMAN-KEULS-Test). Four characteristics showed a significant activation dependence: the standard deviations of the amplitude distributions in the frequency bands 4...8 Hz and 13...26 Hz, corresponding to the root-mean--square values of the signal voltages, as well as the excesses in the frequency bands 8...13 Hz and 13...26 Hz. Only and amplitude of the theta waves were influenced notably by mental arithmetics, significantly though only when this was done under conditions of time stress.

Analysis of Variance↗