PubMed Health⌕ Search

Biomedical subjects

C Baumann

Publications and source records attributed to C Baumann.

17 recordsLinked to original sources
PubMed1992

Size and chirality of intracellularly applied anions affect the function of isolated photoreceptors.

The effect of intracellularly applied anions on the function of retinal rods of the frog Rana esculenta was investigated by means of the whole-cell patch-clamp technique. When the recording pipette contained a medium based on potassium chloride, a slow spontaneous hyperpolarization was observed presumably due to a diffusional loss of the photoreceptor's internal transmitter cyclic guanosine monophosphate (cGMP) and its precursor guanosine triphosphate (GTP). When chloride was replaced by organic anions such as acetate, aspartate, or gluconate the speed of hyperpolarization diminished and the dark voltage of the rods was stabilized. The extent of stabilization correlates with the molecular weight of the anions. A significant difference in the stabilizing effect was found for L-aspartate and D-aspartate, suggesting an additional influence of the chirality. Effects of some of the anions on the configuration of the light responses were also observed.

Animals↗
PubMed1992

[Ewald Hering's opponent colors. History of an idea].

Ewald Hering (1834-1918) was one of the founders of modern visual science. Among his contributions, his color concept gave rise to mostly fruitless controversies, because it appeared to be incompatible with the trivariance of vision theory put forward by Young and Helmholtz. It is now clear that the two color concepts can be reconciled with one another. Hering's theory is based upon an analysis of visual perception. Experience indicates that a conscious subject needs four unique colors in order to characterize perception: blue, yellow, red and green. Usually, two of these hues, but never more, constitute a color sensation, e.g., orange contains red and yellow while blue and green are the components of turquoise. The central idea in Hering's concept was that red and green are opposite hues because they are never elicited simultaneously by a color stimulus; the same is true for blue and yellow. Hering also postulated that the perception of opponent colors is mediated by opponent processes in certain elements of the nervous system, i.e., that there are neurons that respond in a qualitatively different way to spectral stimuli of different frequencies. Today we know that, in fact, the majority of neurons in the retina and the visual pathway is capable of opponent-type responses as anticipated by Hering. It was, however, a long way until his concept was understood and finally accepted by the science community. Among those who helped to acknowledge it were the German physiologist von Kries, the Austrian physicist Schrödinger, the Finnish neurophysiologist Svaetichin, and the American psychophysicists Hurvich and Jameson. In 1906, the German Ophthalmological Society honored Ewald Hering by awarding him the Albrecht von Graefe Medal.

Color Perception↗
PubMed1978

The equilibrium between metarhodopsin I and metarhodopsin II in the isolated frog retina.

1. Rapid and slow changes in the absorbance of isolated frog retinae produced by exposure to brief flashes were studied at temperatures between 5 and 30 degrees C.2. Rapid changes observed at 475 nm consist of a transient increase of absorbance followed by an exponential decay to a new level of absorbance which is lower than before the flash exposure.3. The new level of absorbance determines the initial conditions of slow changes following the rapid ones. At higher temperatures, the loss of absorbance during the rapid changes is greater than at lower temperatures. Accordingly, the slow reactions start at lower levels of absorbance when the temperature is high.4. Quantitative analysis showed that the rapid reactions can be described in terms of two consecutive reactions followed by an equilibrium reaction: the light-controlled formation of lumirhodopsin, decay of lumirhodopsin to metarhodopsin I, and the equilibrium reaction between the metarhodopsins I and II.5. The slow absorbance changes observed in the visible (lambda = 480 nm) are due to metarhodopsin I and to metarhodopsin III. Metarhodopsin I decays during the early phase of slow reactions but can noticeably influence the kinetics at lower temperatures.6. The activation energy of the lumirhodopsin decay is 22.5 kcal/mole, that of the conversion of metarhodopsin I into metarhodopsin II is 30.1 kcal/mole. The entropy change associated with the metarhodopsin I-II equilibrium amounts to +34 cal/mole. K.

Animals↗
PubMed1977

Franz Boll.

Explore the source record for details and available documents.

Germany↗
PubMed1977

[Respiratory complications in acute pancreatitis].

The analysis of 12 cases of severe hemorrhagic pancreatitis shows the importance of the detection of an early hypoxemia, which should be treated as soon as possible by a sufficient oxygenation. If the arterial p02 does not improve one should not delay the moment of endotracheal intubation with PEEP.

Acute Disease↗
PubMed1976

The formation of metarhodospin380 in the retinal rods of the frog.

1. The formation of metarhodopsin380 (metarhodopsin II) was studied in isolated frog retinas exposed to intense flashes of 120 mus duration. 2. A rapid increase in absorbance at 375 nm during the flash was followed by a slower absorbance increase in the subsequent dark period. The slower increase showed virtual completion after 5 ms. 3. The fast absorbance increase during the flash was due to the formation of metarhodopsin478. The rate of this reaction was dependent on the time course of the flash and on the decay rate of lumirhodopsin. 4. Kinetic analysis indicates that three consecutive reactions occur: the light-controlled formation of lumirhodopsin, its first-order decay to metarhodopsin478 and the conversion of metarhodopsin478 into metarhodopsin380. At 21 degrees C, the decay constants were 2 X 10(4) S-1 (lumirhodopsin) and 1 X 10(3) S-1 (metarhodopsin478), respectively.

Animals↗
PubMed1976

Biochemical and physiological parameters on the healthy skin surface of patients with common warts.

Biochemical and physiological examinations were carried out on the healthy surface of the skin of 24 test persons who had had contracted common warts during the 2 years prior to examination and on a control group of 46 healthy persons of the same age and sex. The following significant results were obtained: (1) There was a significant reduction in the percentage amount of squalene in the lipids of the skin surface in the patients with common warts as compared with the healthy control persons. (2) The alkali neutralization time in the patients with common warts was significantly shortened as compared with the healthy control group. (3) The degree of moistening of the skin with water was significantly less in the patients with common warts than in the control persons. These results indicate important predisposing factors for common warts.

Adolescent↗