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Biomedical subjects

K Beck

Publications and source records attributed to K Beck.

At least 109 records · Page 6Linked to original sources
PubMed1981

Locomotion of Xenopus epidermis cells in primary culture.

The locomotion of single epidermis cells, grown out from Xenopus laevis tadpole tails has been investigated by time-lapse cinemicrography using phase-contrast and reflection-contrast optics. The cells develop a large, mostly 200-250 nm thick, lamella, which adheres homogeneously to the supporting coverglass and exceeds the projection area of the cell body. From the comparison of RIC-pictures taken at high (1.06) and low (0.62) numerical aperture of illumination (I.N.A.) we deduce that at low I.N.A. the embossment of the medium-facing side of the lamella is visualized. By this method microcolliculi are demonstrated, which form at the edge of the lamellipodium and move backward. They resemble ruffles, but are flatter and no membrane flow towards the perinuclear region is observed. Indirect immunofluorescence reveals an enhanced staining for actin and alpha-actinin in the lamellipodium and in the transition region of cell body and lamella. Tonofilaments do not participate in lamella formation, the relatively few microtubules seem to be oriented in the direction of cytoplasmic flow. Electron micrographs demonstrate the course of fibrils in the cell body and a meshwork of actin filaments and membranous tubules in the lamella. Based on these findings a model for cell locomotion is presented: the motive force is generated by the cell body causing a flow of cytoplasm towards the periphery and extension of the lamella at its edge. The activity of the lamellipodium has to ensure the flat form of the advanced edge; microcolliculi are assumed to represent a small membrane store for the extension of the lamella. The lamellipodium is not involved in the production of motive force. The cell body is anchored to the lamella by radiating fibrils and the fibrillar meshwork is inserted at the 'dorsal' membrane of the lamella and the basal filament cortex of the cell body. This anchorage provides the structural basis for the uptake of lamella material into the cell body in the transition region.

Animals↗
PubMed1981

Evaluation of reflection interference contrast microscope images of living cells.

Reflection contrast microscope methods are generally used for studies of those portions of the cell that are turned towards the glass coverslip, to comprehend the structure of the cytoskeleton and the dynamics of cell movement, as well as formation of cell-glass contacts. In incident illumination only reflected light contributes to picture formation. The intensity of which in the case of observation of unstained cells is small because of small refraction differences. To overcome this problem a reflection contrast system was developed by Leitz according to Ploem [49], in which by using contrast preserving measures the reflection becomes prominent in comparison with the lens reflexes. The emerging pictures are a result of interferences of reflections at glass-cell, cell-culture medium and culture medium-cell interfaces. According to Fresnel's equations the reflected intensity depends on the differences of the particular refractive indices and the thickness of the layers, which determine the phase of interfering beams. In idealized systems of thin films the reflected intensity is a measure for their optical constants. Relative reflection measurements from glass-cell areas is comparison with the known glass-medium reflection, can therefore be revealing as far as refraction index, cell-glass distance or cell thickness are concerned. The estimates by Bereiter-Hahn et al. [15] were made in the assumption of vertical illumination neglecting its actual conical shape: the comparison of two Fresnel functions of cytological relevant measurements show - in accordance with Gingell and Todd [24] - that this is only permitted under certain conditions, depending on the required accuracy of the measurements; an incidence angle of about 30 degrees leads to an error of about 10%, an angle of 50 degrees to more than 50%.

Animals↗
PubMed1980

Investigation on the thermostability of steroid hormone receptors in lyophilized calf uterine tissue powder.

Powdered calf uteri were lyophilized and sealed in a vacuum. The effects of lyophilization and the thermostability of the binding activity of uterine steroid hormone receptors were studied. The lyophilized powder was analyzed for its ability to bind estrogen, progestin, androgen, and glucocorticoid steroids. Lyophilization had no deleterious effects on the binding activity. Storage of the lyophilized powder at +20 C for more than 14 days did not reduce the binding activity. No reduction of the binding capacity was also observed when the storage temperature was at +30 C for 16 hours. However, a slight loss of specific binding sites was observed for 17 beta-estradiol (-12%) at the storage temperature of +40 C, but the other steroid binding proteins were more stable. When the storage temperature was at +60 C for 16 hours, a loss of about 24% was observed for the specific estrogen binding sites, whereas the binding capacity of progestin, androgen, and glucocorticoid receptors was reduced by only less than 10%. Storage at the high temperature of +80 C for 16 hours resulted in a loss of only 36% for the estrogen binding capacity and less than 30% loss for the other binding proteins. The freeze-dried uterine powders can be useful quality control specimens for steroid receptor assays.

Animals↗
PubMed1976

[Rotor syndrome. A long-term study].

A patient with Rotor syndrome has been followed up for 28 years. The subject was in good health and exhibited marked jaundice due to a hyperbilirubinemia ranging between 5 and 8 mg bilirubin per 100 ml, about 70% of the bilirubin giving direct van den Berg reaction. The liver was slightly enlarged and of normal color. Histologically it showed traces of a brown pigment and marked siderosis in the hepatocytes. In addition, mild hypersideremia and hypercholesteremia were observed together with increased amounts of bilirubin and urobilinogen in urine. Menthol glucuronide formation was normal. Hepatic excretion of bilirubin, sulfobromophthalein and radio-opaque dyes was impaired. There was no change in liver histology of biopsies taken at an interval of 6 years, the siderosis in particular remaining constant. During the observation a moderate increase in the activities of serum transaminases occurred but no longer recurred when physical and dietetic stress was avoided.

Adult↗