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K Frick

Publications and source records attributed to K Frick.

32 records · Page 2Linked to original sources
PubMed1986

A new quantitative approach to the assessment of stages of vigilance as defined by spatiotemporal EEG patterning.

Electroencephalographically oriented research on vigilance needs valid measures for assessing the level of vigilance between wakefulness and sleep. When studying different psychologically, psychopathologically, and pharmacologically induced states, special attention has to be paid to minor alterations of the level of vigilance which are reflected, essentially, in topographical changes of alpha-activity (Stage A). Since vigilance is a dynamic process, brief fluctuations in the range of a few seconds must also be recorded. In our opinion existing methods of quantification do not fully meet these demands. We have, therefore, developed a relatively simple procedure which can be characterized as an attempt quantitatively to reconstruct visually, i.e., spatiotemporally defined patterns of vigilance. The usefulness of this method, which also has certain limitations, has been demonstrated in psychopharmacological studies.

Alpha Rhythm↗
PubMed1985

The lateralization of occipital alpha-power under resting conditions in the EEG of healthy volunteers. A state- and a trait-variable.

Using a structural analysis of lateralization of occipital alpha-power in 20 healthy volunteers under resting conditions, a clear vigilance-dependence could be shown for the great majority. In contrast the state of four subjects showed almost no dependence on vigilance. Additional findings according to which these two subgroups also differ in a characteristic manner with regard to various other aspects, especially occipital alpha-quantity and vigilance dynamics, point to a maturational dimension.

Adult↗
PubMed1985

Asymmetry of occipital alpha-rhythm under resting conditions: a neurophysiological measure of "hemisphericity".

Using the resting EEGs of 20 healthy subjects in semirecumbent position with eyes closed and left undisturbed, we studied the question whether and, if so, to what extent, lateralization of occipital alpha-rhythm depends on level of vigilance. As a simple indicator of vigilance, the relative alpha-power for each 2-sec. epoch of 02-CZ (occipital right) was calculated. Lateralization was defined as the ratio of absolute alpha-powers in 01-CZ and 02-CZ (occipital left and right). This was also calculated epoch by epoch. The results of individual analysis of data from each subject allowed categorization into 3 types. This typological differentiation obtained quantitatively could be supported by visual pattern analysis. The findings are discussed in relation to the state- vs trait-problem which constantly confronts us when we interpret experimentally obtained functional asymmetries of hemispheres.

Adult↗
PubMed1984

Interrelation between changes in the EEG and psychopathology under pharmacotherapy for endogenous depression. A contribution to the predictor question.

With the predictor problem in mind, we studied in-patients with endogenous depression whether relationships exist among the EEG, the therapeutic response, and the severity of psychopathology. We found that clinically defined responders and non-responders differ in respect of their average power spectra calculated for the two occipital regions. In addition, it was shown that there is a statistically significant correlation between the EEG before treatment and the severity of AMP-documented psychopathology after a 4-week treatment period. This correlation was stronger for the left occipital region than for the right.

Amitriptyline↗
PubMed1980

[Quantitative microbiologic studies of the sulcus fluid in patients with immunodeficiencies].

Quantitative microbiologic examinations of fluid taken from gingival sulci were carried out with patients suffering from chronic lymphatic leukemia (CLL), i.e. with disturbed immune response, and with healthy subjects. The pathogen count in each case was correlated with the gingival index, the plaque index, the amount of fluid in the gingival sulcus, and the pocket depth. Patients with chronic lymphatic leukemia with gingiva clinically free of inflammation showed one to 20 times more bacterial flora in fluid from the gingival sulcus than fluid from healthy control subjects. The quantitative values tend to equalize only if imflammation is severe. If the pathogen count is considered a function of the amount of plaque or pocket depth, markedly more microorganisms/mm3 of sulcus fluid were found with CLL patients than in the control group. It therefore may be concluded that immunologic reactions contribute decisively to the causation and maintenance of gingivitis with all of its consequences and that these reactions play an important role in the destruction of pathogens found in the region of the gingival pocket.

Aged↗
PubMed1977

[Bacterial count in the sulcus fluid of healthy and inflamed marginal gingiva].

Even with a plaque index of 1, peak values of germ count per micronl were found which remained almost constant with plaque increasing up to an index of 3. Germ count and degree of inflammation correlated in the range of the gingival indices 0 to 2. A further intensification of the inflammation showed a significant reduction of germ count per micronl. When studying the relationship between germ count and depth of pocket, the same behavior was observed, starting at a pocket depth of 4.5 mm.

Adolescent↗
PubMed1976

Siderophore protection against colicins M, B, V, and Ia in Escherichia coli.

A variety of natural and synthetic siderophores capable of supporting the growth of Escherichia coli K-12 on iron-limited media also protect strain RW193+ (tonA+ ent-) from the killing action of colicins B, V, and Ia. Protective activity falls into two categories. The first, characteristic of enterobactin protection against colicin B and ferrichrome protection against colicin M, has properties of a specific receptor competition between the siderophore and the colicin. Thus, enterobactin specifically protects against colicin B in fes- mutants (able to accumulate but unable to utilize enterobactin) as predicted by our proposal that the colicin B receptor functions in the specific binding for uptake of enterobactin (Wayne and Neilands, 1975). Similarly ferrichrome specifically protects against colicin M in SidA mutants (defective in hydroxamate siderophore utilization). The second category of protective response, characteristic of the more general siderophore inhibition of colicins B, V, and Ia, requires the availability or metabolism of siderophore iron. Thus, enterobactin protects against colicins V and Ia, but only when the colicin indicator strain is fes+, and hydroxamate siderophores inhibit colicins B, V, and Ia, but only when the colicin indicator strain is SidA+. Moreover, ferrichrome inhibits colicins B, V, and Ia, yet chromium (III) deferriferrichrome is inactive, and ferrichrome itself does not prevent adsorption of colicin Ia receptor material in vitro. Although the nonspecific protection against colicins B, V, and Ia requires iron, the availability of siderophore iron for cell growth is not sufficient to bring about protection. None of the siderophores tested protect cells against the killing action of colicin E1 or K, or against the energy poisons azide, 2, 4-dinitrophenol, and carbonylcyanide m-chlorophenylhydrazone. We suggest that nonspecific siderophore protection against colicins B, V, and Ia may be due either to an induction of membrane alterations in response to siderophore iron metabolism or to a direct interference by siderophore iron with some unknown step in colicin action subsequent to adsorption.

Azides↗
PubMed1976

Relationship between the transport of iron and the amount of specific colicin Ia membrane receptors in Escherichia coli.

Strains of Escherichia coli K-12 defective in their ability to utilize exogenously supplied iron due to genetic defects in the entF, tonB, fes, or fep gene exhibited elevated levels of the specific outer-membrane receptor for colicin Ia when compared with parental strains. Although entF, fes, and fep strains showed a higher degree of Ia sensitivity than did the parental strains, tonB strains were resistant to colicin action. The colicin insensitivity of tonB strains was not due to hyperproduction of enterochelin. Growth in medium containing 101.8 muM Fe2+ led to a lowering of receptor levels in all the above strains and resulted in decreased colicin Ia sensitivity in all strains except tonB, which was already at maximal resistance. Growth in citrate plus iron (1.8 muM) or in ferrichrome resulted in a substantial reduction in both receptor levels and Ia sensitivity in ent, fes, and fep strains but had no effect on receptor levels in tonB strains. Growth in citrate did not lead to an alteration in receptor levels in a mutant specifically defective in citrate-mediated iron transport. The presence of enterochelin during growth led to a reduction in the number of receptors in the parental and ent strains but not in tonB, fes, or fep strains. Thus, in all cases examined, there was an inverse relationship between the number of colicin receptors per cell and the ability of the strain to take up iron from the growth medium. This suggests that under conditions of iron limitation there is a derepression of colicin Ia receptor biosynthesis. These results may point to a role of the colicin I receptor in iron uptake.

Binding Sites↗
PubMed1976

[Psychophysiological studies of EEG, operational performance and the dynamics of vigilance regulation. I. The EEG during performance of Brickenkamp's attention-concentration test (test d 2) (author's transl)].

During the performance of the d 2 test developed by Brickenkamp (standardized test of attention and concentration), occipital EEG activity was registered telemetrically in 10 male students aged 25 to 32 years. Simultaneously, the pencil markings performed by the subjects, indicating the time course of their pattern recognition and discrimination, were recorded by means of a piezo-electrical transducer. The EEG behavior during test performance was evaluated by serial spectral analysis. The analysis of the EEG parameters derived from it (total power, absolute and relative alpha-power) showed that there is a relationship between these EEG measures reflecting the regulation of cortical vigilance and the error rate in the concentration test. While subjects with low error rate present a heightening of cortical arousal focused in the right occipital area, subjects with higher error rate tend to have a higher degree of general cortical activation.

Adult↗
PubMed1976

[Psychophysiological studies of EEG, operational performance and the dynamics of vigilance regulation. II. EEG activity and reactivity during tracking performance in a control loop with varying degrees of difficulty (author's transl)].

In ten male students the EEG occipital activity was recorded during a visuo-motor task consisting of pursuit-tracking. The degree of task difficulty varied systematically depending on the modification of the transfer function of control element dynamics. The EEG data were evaluated by serial spectral analysis. The distribution functions of the total power estimates and their minima and maxima reflect the dynamics of the regulation of cortical vigilance and permit to differentiate the degree of effort which corresponds to the varying degree of task difficulty. The study of task-irrelevant acoustically evoked potentials showed that with increasing cortical activation the amplitudes of N1-P2 and P2-N2 are diminished. These results might suggest that evoked potentials induced by task-irrelevant stimuli can serve as indicators of the neuronal capacity available for information processing that is not task-oriented.

Adult↗
PubMed1976

[Signal analysis of EEG-changes induced by nomifensin - a new antidepressant (author's transl)].

Ten healthy volunteers received a single oral dose of 100 mg nomifensive, a new antidepressant (tetragtdriusiqyubikube deruvatuve; Hoe 36-984). The drug-induced effects on the EEG were compared with those of placebo. The statistically proved results show that nomifensine causes a distinct shift in vigilance with two different partial processes. After an initially occurring stabilization of the dominant alpha-frequency there appears a polyrhythmic disintegration of the alpha-rhythm with increase of slower and faster frequencies. At the same time a shifting takes place within the beta-range with increasing of 23.5-32.0 Hz-components. Accordingly it is evident that nomifensine results in a typical pharmaco-electroencephalographic profile.

Alpha Rhythm↗
PubMedDate not supplied

Increased blink rates in schizophrenics. Influences of neuroleptics and psychopathology.

During a standardized visuomotor task, eye blinking, a possible parameter of central dopaminergic activity, was studied in 18 previously medicated and eight drug-naive schizophrenic in-patients in the acute state and during remission. Whereas schizophrenics executed the visuomotor task with the same precision as age- and sex-matched normal control subjects did, the mean blink rate was increased in both schizophrenic groups. During neuroleptic treatment, the mean blink rate was reduced only in the group of drug-naive patients, but not in the previously neuroleptic treated schizophrenics. This varying blinking activity is discussed with respect to the development of neuroleptic tolerance and influence of psychopathology.

Adult↗
PubMedDate not supplied

EGF receptor-associated DNA-nicking activity is due to a Mr-100,000 dissociable protein.

The receptor for epidermal growth factor (EGF) is a single-chain transmembrane polypeptide of relative molecular mass (Mr) 170,000 (170K) which has been implicated in the regulation of both normal and abnormal cell proliferation. It has an externally facing EGF-binding domain and a cytoplasmically facing tyrosine-specific protein kinase site. Although the receptor has been well characterized, the mechanism by which it transmits the growth stimulatory signal from the plasma membrane to the nucleus is unclear. EGF binding to cells has been shown to enhance topoisomerase activity within the cells. Topoisomerases catalyse the interconversion of topological isomers of DNA and thus may influence replication and transcription. Mroczkowski et al. reported that purified EGF receptors of both human and murine origin can nick supercoiled double-stranded (ds) DNA in an ATP-dependent fashion, an activity related to those of topoisomerases. Another related tyrosine kinase, pp60src, has also been reported to have a similar DNA-nicking activity. We have now characterized the EGF receptor-associated DNA-nicking activity by sucrose gradient centrifugation. Our results, presented here, indicate that the DNA-nicking activity is not intrinsic to the EGF receptor, but is found in a distinct molecular species.

DNA Topoisomerases, Type I↗