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Biomedical subjects

U Schmidt

Publications and source records attributed to U Schmidt.

At least 415 records · Page 23Linked to original sources
PubMed1982

Frequency-dependence of early auditory evoked responses in the guinea pig.

Neural auditory responses in the guinea pig, monitored by surface electrodes (brain stem potentials and frequency-following responses) and by electrodes at the round window, were analyzed for evidence of frequency dependence in the range from 500 Hz to 15 kHz. The characteristics of the brain stem potentials and frequency-following responses with stimuli near threshold intensity for frequencies below 2 kHz indicate that this activity derives from the excitation of apical regions of the basilar membrane. The same interpretation applies to the potentials recorded at the round window. Comparison of the responses seen with surface electrodes and those appearing at the round window reveals that the broad potential PI of the brain stem response to low-frequency stimuli corresponds to the compound action potential, while the frequency-following responses correspond to phase-locked responses in the acoustic nerve.

Animals↗
PubMed1982

Release of gastric histamine in patients with urticaria and food allergy.

In a clinical study the participation of histamine in the allergenic response of patients with food allergy was investigated. The resting levels of gastric tissue and plasma histamines of 10 patients were slightly higher than the respective values of normal volunteers. 5 minutes after local intragastral allergenic provocation a decline of the mucosal histamine content of the allergen-treated area was noticed. Parallel investigations on the mast cell content of the stomach mucosa revealed a parallel decrease of the o-phthaldialdehyde stained cells, whereas the number of toluidine blue stained cells remained unchanged. These data are in accordance with an antigen-induced IgE-dependent liberation of the mast cell histamine stores.

Adult↗
PubMed1981

On the mechanism of vesicle release from ATP-depleted human red blood cells.

The release of spectrin-free vesicles from ATP-depleted human red blood cells (Lutz et al. (1977) J. Cell. Biol. 73, 548) can be considered the final step of a shape change from discocytes to echinocytes. The study of physical and chemical properties of released vesicles suggests that vesicle release is not merely a consequence of charge alterations within either monolayer of the budding membrane. Fresh membranes and released vesicles have within experimental error the same sialic acid content per surface area and the same electrophoretic mobilities. Vesicle release cannot be stimulated by doubling the charge density on the outer monolayer by means of a phospholipase D-treatment, but correlates with a breakdown of polyphosphoinositides to diacylglycerol on the inner monolayer. This breakdown does not lead to a significant change in the negative charge density on the inner monolayer, because an increased phosphatidate content compensates for this alteration. Furthermore, polyphosphoinositide breakdown and diacylglycerol production are not the rate-limiting step in vesicle release from ATP-depleting red blood cells. This is evident from the fact that 10 mM EDTA inhibits vesicle release to 75% without affecting polyphosphoinositide breakdown and diacylglycerol production. Hence, diacylglycerol formation may be sufficient for membrane budding as suggested earlier (Allan et al. (1976) Nature 261, 58), but vesicle release requires a second, as yet unidentified process.

Adenosine Triphosphate↗
PubMed1981

Scalp distribution of the auditory evoked brainstem potentials in the guinea pig during monaural and binaural stimulation.

Auditory evoked brainstem potentials in response to monaural and binaural sound stimuli were observed by monopolar recording at five positions on the skull of the guinea pig. With monaural presentation the amplitudes of the first two potentials in the complex had a maximum at ipsilateral positions, the third potential was of uniform size at all recording positions, and the fourth and fifth potentials were largest at contralateral positions. The differing maxima of the negative and positive components of the individual potentials proved to be consistent with the theory of volume conduction. When sounds were presented binaurally the amplitudes of all potentials were symmetrical with respect to the vertex. Moreover, binaural interactions at the neural level could be inferred from the brainstem responses. The results indicate that the individual potentials in the complex are associated with activation of specific structures in the auditory pathway. This finding and the observed differences between the two sound modes have implications for clinical practice.

Acoustic Stimulation↗
PubMed1981

On the mechanism of red blood cell shape change and release of spectrin-free vesicles.

Changes in the negative change densities on the outside (by raising the phosphatidic acid concentration) or on the inside of the red blood cell membrane (by a breakdown of the polyphosphoinositides and a concomitant diacylglycerol production) do not explain the last step in echinocytosis, the release of spectrin-free vesicles.

Adenosine Triphosphate↗
PubMed1981

[Peritoneal dialysis therapy in psoriasis].

Report about three patients suffering from psoriasis vulgaris, who were not responsive to common dermatological treatment for many years. After peritoneal dialysis the psoriasis cleared and has not recurred for three to six months. Immunological investigations before and after peritoneal dialysis showed an increasing number of E-rosettes and a decrease of the concentration of soluble immune complexes of the serum.

Adult↗
PubMed1980

[Driving behavior of cardiovascular patients as affected by beta receptor blockers].

18 male patients under betablocker therapy adapted to their individual stage of hypersympathicotonic circulatory regulation disturbances were tested in a motor-vehicle simulator to find out possible changes of their driving ability. Besides observing driving-style and reactions, the following parameters were controlled: blood pressure, time of pulse waves, heart rate. Speeds of deviation angles (= deviation from straight line per time unit) decreased significantly. No differences between tests under betablocker medication and without it could be demonstrated, neither in simple-reaction times nor in the more complex multiple-reaction times, which can be compared with realistic traffic situations. Blood pressure and heart rate showed more significant decreases after medication than in tests without previous betablocker treatment. The results prove that the betablocking agent Bupranolol does not influence the ability of car-driving, not even in case of semichronical application.

Attention↗