PubMed Health⌕ Search

Biomedical subjects

A Kropf

Publications and source records attributed to A Kropf.

13 recordsLinked to original sources
PubMed1982

[Differentiation of 2 paroxysmal reaction types in the EEG after sleep deprivation].

In the EEG after sleep deprivation paroxysms with spikes and spike wave-complexes as well as paroxysms with slow waves can be seen. The paroxysms occur either spontaneously (it means at any time during the record) or at moments of shifting vigilance. These moments are characterized by sudden changes of the EEG frequency for instance by transition from one sleep stage to another. Paroxysms with spikes or spike wave-complexes occur mainly at the transition from lower to higher levels of vigilance and are accompanied by abnormal K-complexes and abnormal photosensibility. Paroxysms of slow waves occur mainly at the transition from higher to lower levels of vigilance, abnormal K-complexes and abnormal photosensitivity are lacking but in some cases the before diffuse abnormal EEG is improved after sleep deprivation. It assumed that we are dealing with two different types of reaction.

Arousal↗
PubMed1981

Photochemical reactions of 13-demethyl visual pigment analogues at low temperatures.

The photobleaching reaction of 13-demethylisorhodopsin (hereafter designated as 9-cis- 13-dm-rhodopsin), which was synthesized from 9-cis- 13-demethylretinal and cattle opsin, was investigated by low-temperature spectrophotometry in order to elucidate the role of the 13-methyl group of retinal in photobleaching. When 9-cis- 13-dm-rhodopsin was irradiated at-190 degrees C, batho-13-dm-rhodopsin was produced. Its absorption maximum lay at 532 nm, 11 nm shorter than that of cattle bathorhodopsin (gamma max 543 nm), and batho-13-dm-rhodopsin had an extinction coefficient about 0.6 times that of bathorhodopsin. Batho-13-dm-rhodopsin was thermally unstable. Above-180 degrees C, it converted to a new intermediate, BL-13-dm-rhodopsin, which in turn changed to lumi-13-dm-rhodopsin- above -140 degrees C. BL-13-dm-rhodopsin was "photosensitive" at temperatures around -188 degrees C, though batho-13-dm-rhodopsin and lumi-13-dm-rhodopsin was "photosensitive" at the same temperature. In the photobleaching process, lumi-13-dm-rhodopsin and meta-I-13-dm-rhodopsin were observed. Their thermostabilities were very similar to those of lumirhodopsin and metarhodopsin I, but each dm intermediate differed from its methylated counterpart in its value of gamma max and extinction coefficient.

Animals↗
PubMed1970

13-desmethyl rhodopsin and 13-desmethyl isorhodopsin: visual pigment analogues.

The preparation and properties of three geometric isomers of 13-desmethyl retinal (13-dmr) are described. They are analogous to the all-trans, 11-cis, and 9-cis isomers of retinal since two of the cis isomers combine with cattle opsin to form pigments which are spectrally indistinguishable from rhodopsin and isorhodopsin and the all-trans isomer is unreactive.The pigment which resembles rhodopsin, 13-desmethyl (13-dm) rhodopsin, is formed at about one ninth the rate at which 11-cis retinal reacts with opsin at 20 degrees C. The reaction with 13-dmr does not go to completion; and 0.05 M hydroxylamine, to which rhodopsin is stable, decomposes 13-dm rhodopsin. Irradiation of 13-dm rhodopsin results in a cis --> trans isomerization of the chromophore; but the photosensitivity of 13-dm rhodopsin is only 40 per cent that of rhodopsin.13-dm isorhodopsin, the 13-desmethyl analogue of isorhodopsin, is formed at approximately the same specific rate as 13-dm rhodopsin. The reaction goes to completion and the pigment is not decomposed by 0.03 M hydroxylamine. 13-dm isorhodopsin can also be photolyzed to the all-trans chromophore plus opsin.

Animals↗