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Biomedical subjects

K Krause

Publications and source records attributed to K Krause.

At least 91 records · Page 5Linked to original sources
PubMed1984

Magnetic field of the earth as additional zeitgeber for endogenous rhythms?

The influence of 50% decrease and increase of the earth magnetic field on the activity of the enzymes hydroxyindole-O-methyltransferase (HIOMT) and N-acetyl-serotonintransferase (NAT) is proved in vivo and in vitro. NAT and HIOMT catalyse the melatonin biosynthesis in the pineal gland and in the retina. Our results support the hypothesis of Leask and Schulten, that molecular magnetic field sensitivity is the basis of animals' magnetic field detection.

Acetylserotonin O-Methyltransferase↗
PubMed1983

Influence of low magnetic-field-strength variations on the retina and pineal gland of quail and humans.

Recently, Schulten postulated on the basis of his experiments and quantum-mechanical calculations that variations of the strength of the earth's magnetic field may influence reactions in biological systems. In this paper groups of birds were subjected to different variations of low magnetic-field strength. The influence of these variations on the enzyme hydroxyindol-O-methyl transferase (HIOMT) was determined. HIOMT is unique to the retina and the pineal gland and seems to be involved in regulation of light-adaptation processes. A significant effect was found, which can be interpreted as being in agreement with Schulten's theory. These observations were further supported by our examination of the influence of magnetic field variation on human night-vision acuity. Whereas the magnetic influence on the avian retina may be interpreted in connection with navigation, the importance for the human retina remains to be elucidated.

Acetylserotonin O-Methyltransferase↗
PubMed1982

Sex differences in refraction errors up to the age of 15.

A health inquiry concerning vision and corrective lenses at the age of 14 was carried out in a northern Finland series about 12,000 children followed up since birth. Data were obtained from more than 99% of cases. 34% of the girls and 18% of the boys had corrective lenses. 55% of the study population were living in the province of Oulu, and the ophthalmological records of these children were analysed (N 1939). The ophthalmological records covered 67% of the children with lenses in the province of Oulu. 71% of the girls with lenses, and 66% of the boys had these for myopia, both myopia and hyperopia were less common among the boys, but the cases were more pronounced. The children with lenses were on average taller and heavier and the myopic children had a better mean ability at school.

Adolescent↗
PubMed1978

[Contribution to deep electron pendulous therapy. VIII. Communication: concerning the problem of diverging contours in telecentric electron pendulous irradiation using the electron energies 10 MeV and 20 MeV (author's transl)].

The mode of correction of the isodose curves from telecentric electron pendulous technique using a constant patient radius rp = 30 cm (Isodosenatlas, Siemens, 1973) is represented with regard to its application in patients with diverging surface contours. Correction is possible by two different methods: 1st by experimental determination of an air gap factor for the shift of isodoses, and 2nd by two factors depending on the focus-skin distance and on the angle of incidence of the electron beam. Determination of the factors is performed either by means of fixed fields measured by vertical and at oblique incidence of the beam and a depth dose distribution measured at the central axis, with oblique incidence of the electrons.

Electrons↗
PubMed1978

New individual tissue compensators for high-energetic photons. Part I. Principle and procedure.

Part I. The inhomogeneity of absorbed dose caused by irregular body surface contour in the treatment port for external photon radiation is shown as a problem. The discussion of the physical fundamentals and technical possibilities of missing tissue compensators leads to a practical solution. A new handy procedure is presented allowing easy and rapid preparing of geometrically minified as well as absorption- and stray radiation corrected individual compensators. The achievable dose homogeneity within the target volume is shown as better than +/-5%. Systematical errors are investigated for the different parameters. In Part II systematical preclinical tests and first practical clinical experiences will be discussed.

Absorption↗
PubMed1978

[Homogenization of the dose to the target volume in case of irregular body-surface by means of compensation (author's transl)].

Irregular body-surface contours in the treatment part of high-energetic photon fields are producing an inhomogeneous dose distribution within the target volume. Homogenization of the dose is necessary in order to avoid over- or underdosage. A technique of making compensators is described. These are individual compensation filters substituting tissue layers which are lacking, they are correctly scaled down and optimally corrected in view of absorption and scattering according to the actual irradiation conditions. A simple mechanical device makes possible the production of a mould for heavy-metal compensators immediately in the course of scanning of the body-surface. A universal semi-automatic version of this method is appropriate to clinical practice; it records optically, and therefore without contact and quickly, all body-contours desired. By means of the image of moiré contour-lines thus obtained can be made the mould for the compensator in a second operation using an electronically controlled copy-milling machine.

Filtration↗
PubMed1977

[The methodological position of frontal feedbacks during work with large groups of dental students].

Single-channel feedback installations without revertive communication to the single work place and without possibility for evaluating the student's performance may be used with success in lectures and diagnostic exercises for large groups of dental students. Dispensing deliberately with the evaluation of performance permits to carry on a dialogue with the student, which offers the possibility of acting rapidly on the learning process during the very same teaching event. This control procedure allows to activate and motivate the students considerably. The methodical approach is explained.

Computers↗
PubMed1977

On a simple method for routine check of the constancy of radiation quality of bremsstrahlung emitted by therapeutic particle accelerators.

The constancy of radiation quality of therapeutically employed particle accelerators has to be checked at weekly intervals. Any change in radiation quality may have considerable therapeutic effects owing to its influence on dose distribution. It can be recommended to make measurements instead of, or in addition to, the axial reference-point measurement at 5 and 15 cm depth in the phantom, at 5 cm depth in the beam axis and at a reference-point about 1 cm within the geometric edge of the field, for checking the constancy of the radiation quality of bremsstrahlung. Only then, if routine checks carried out for the axial and the lateral reference-point dose ratios do not show any deviations greater than e.g. +/- 2%, radiation quality is deemed to have remained sufficiently constant for radiotherapeutical applications.

Radiotherapy, High-Energy↗
PubMed1976

Procedure for field axes measurement, beam indication adjustment, and figure of convergence determination within performance tests for radiation therapy equipment.

A routine measuring procedure for the verification of radiation field axes and figure of convergence within a spatial resolution of +/- 0.5 mm is described. Measurements are done in two parallel planes in a certain distance before and behind the presumed isocentre. The used test arrangement permits rapid check and controlled adjustment of the alignment of beam or isocentre indicating devices for all isocentic radiation therapy equipment.

Mathematics↗
PubMedDate not supplied

[Acceptance of progressive lenses].

BACKGROUND: The wearing of progressive lens poses a problem to two kinds of patients: those who are practically emmetropic and use reading glasses only, and ametropic patients whose eyes have been corrected for years with bifocals. The wearing of progressive lenses is generally not recommended for those presbyopes. METHODS: A group of individuals (n = 50) underwent refraction, and their addition was adjusted to their work and their age (44-72 years). They were then divided into two groups, one of which (n = 25) was equipped with bifocals (Telarc, Essilor) and the other (n = 25) with progressive lenses (Varilux Comfort, Essilor). After four weeks, the types of glasses were exchanged. After a further four weeks, each group used the original pair of glasses for another week. At the end of this phase, each of the test subjects was asked his opinion in favour of one or the other types of glasses. At each change of glasses, factors such as duration of the adaptation period, assessment of sight, general impression and time of use were recorded. RESULTS: At the determination of refraction much attention must be given to mildly astigmatic patients in order to optimise the prescription of progressive lenses. Progressive lenses were just as well tolerated by the group of convinced bifocal wearers, even though the familiarisation period took up to two weeks, especially for the older patients. Once the progressive lenses had been accepted, bifocals were generally abandoned for good. This is mainly due to the quality of the progressive lenses, which favour precise vision even in intermediate zones. For most of the individuals who were previously fitted with reading glasses only, the demarcation line between the distant and near parts of the bifocal lens pose major problems. Whereas progressive lenses were accepted as readily as in the group previously fitted with bifocals, about 40% of the total individuals tested refused bifocal lenses. CONCLUSION: In all, 96% of the participants considered progressive lenses good or very good. All recognised that progressive lenses represent the most aesthetic solution. However, in certain cases bifocal lenses together with progressive lenses remain interesting. For patients who were previously accustomed to reading glasses only, the duration of use of glasses with progressive lenses rose from 40% to 60% of the working day.

Adult↗
PubMedDate not supplied

[Idiopathic varus gonarthrosis: diminished nociceptive vs. unchanged somatosensory sensitivity].

Neuromuscular control deficits are supposed to contribute to the development of osteoarthritis (OA). Pain measurements were performed to clarify whether nociceptive afferents differ between OA patients and healthy subjects. Thermal pain thresholds were significantly higher in OA subjects as compared to controls, but there was no difference in perceptual thresholds after electrical stimulation. Lateralization, gender, site of OA changes, previous operations, or medication did not affect these findings.

Adult↗
PubMedDate not supplied

The use of the ophthalmological services during the preschool age, ocular findings and family background.

The series consists of 12,059 children followed-up since their mothers' pregnancy. Of these children, 5.2 percent had visited an ophthalmological department during their first five years. Visits were significantly more frequent among the children of social classes I to III than among those of class IV and the farmers', and thus the frequencies of the diseases based on diagnoses given in the ophthalmological departments were also higher in social classes I to III. These children clearly had the best opportunities to have their diseases diagnosed at an early age. Squint was the most common diagnosis with the prevalence being 18.4 per thousand for the children in social classes I to III and 15.9 for the total series. The second largest group consisted of children without any positive ocular finding. These were mainly risk children having some other disease. The third most common diagnosis was dacryostenosis--its incidence in social classes I to III being 9.4 per thousand and that in the total series 7.9 per thousand. Squint correlated negatively with birth weight and was more common among children with some other disease, especially some nervous or mental disease. Dacryostenosis correlated positively with gestational age. If the mother smoked during the pregnancy she was more likely to give birth to a child with squint and less likely to bear a child with dacryostenosis.

Agriculture↗