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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Changes in the ultrastructure, and distribution of phosphatases in the intestinal epithelium of Rana temporaria during development were consistent with other developmental changes. Alkaline phosphatase AMP-ase and ATP-ase were always associated with sites of absorption of foodstuffs into the cell. Initially, these were only the yolk platelets but at the onset of feeding the brush border lateral wall, membranes and associated absorption vesicles all became sites of activity. At metamorphosis when the larvae cease feeding, the enzyme activities decreased and became difficult to detect. In the early larval stages, acid phosphatase activity was confined principally to the lateral cell-wall membranes. This soon disappeared but was followed at metamorphosis by a dramatic increase in both the number of sites and their activity. In general, acid phosphatase appeared to be associated with areas of degeneration. The new epithelial cells which developed during metamorphosis appeared under the old epithelium. The cell debris from the larval epithelium was then expelled into the lumen of the intestine. The new epithelium contained sites of enzyme activity similar to those of the adult. Acid phosphatase was now present only in lysosome-like bodies and very sparsely on the brush border. These results are discussed in relation to dietary and structural changes. It is suggested that the presence of the enzymes at any site can be related to and anticipate these changes, possibly under hormonal control.
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  • 2
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron microscope studies of the distribution of four phosphatases (Alkaline phosphatase, Acid phosphatase, ATP-ase and AMP-ase) have been made on rat jejunum from birth to ten days after weaning. The results showed that a considerable change in the location of alkaline phosphatase occurred in the early stages of post-natal development. Acid phosphatase was confined primarily to vesicles, vacuoles and lysosomes. A maximum number of lysosomes were found 25 days after birth but thereafter they decreased in number. The ATP-ase and AMP-ase showed little change with age. From the results presented, it is tentatively suggested that alkaline phosphatase may be one of the factors associated with the increase in cell adhesion noted. A pathway for the development of lysosomes from the large invaginatory inclusions to the normal granular type of lysosome is also proposed.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 65 (1965), S. 607-621 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Studies have been made on the effects of an intramuscular injection of aminopterin on the crypts of Lieberkühn in rats. A decrease in the mitotic counts was accompanied by a rapid increase in the number of abnormal cells present in the epithelium of the crypt. Three hours after administration of the aminopterin, an almost complete absence of true metaphase chromosoms was found. By 24 hours, a partial return towards normal mitotic activity was observed but the number of abnormal cells present was still very high. It is suggested that the mitotic changes are in keeping with the conclusion of Grampa and Dustin (1952) of an arrest at interphase but that a secondary arrest at metaphase cannot be excluded. A morphological feature of some of the abnormal cells was the presence of a Feulgen positive granule in the cytoplasm, which by electron microscopy was also shown to contain many cytoplasmic constituents. It is suggested that material is lost from the nucleus and incorporated into a granule in the cytoplasm. A possible explanation of the purpose and function of the granule, as a means of disposing of unwanted or aberrant material, is put forward.
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  • 4
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron microscope studies on collagen from rat-tail tendon using the negative staining technique indicate the presence of fine filaments 15–30 Å in diameter within the fibres. The banding of the fibrils was only slightly affected by aminoacetylnitrile bisulphate, but an increased amount of fine fibrous material was present in preparations from experimental animals. It is suggested that this material represents a soluble form of collagen which is known to predominate after administration of the drug. Despite the fact that this would be a chemically abnormal collagen, its structure by electron microscopy corresponds remarkably well with the form suggested from X-ray diffraction and physico-chemical studies on normal soluble collagen.
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  • 5
    ISSN: 1432-0878
    Keywords: Skin ; Internal surfaces ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The scanning electron microscope has been used to investigate the surfaces of epidermis, hair follicles, fat cells, glands and blood vessels in sections of human skin. The appearances of structures associated with these surfaces have been described. The results demonstrate that this new instrument can become an important tool in the investigation of surface changes that might accompany the application of loads (extensive, compressive or torsional), or physiological or pathological abnormalities.
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  • 6
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Synopsis Alkaline phosphatase activity has been measured in mucosal scrapings of rat small intestine from birth to weaning. The levels of activity were then compared with those found in brush border fractions and cell residues over the same period. The amount of activity found in the residues was too high and variable to be accounted for in terms of diffusion, and it was concluded that during the developmental period considerable quantities of enzyme were present in the cytoplasm. The duodenal changes were similar, in form, in both mucosal scrapings and brush border, but the changes in the ileal brush borders were markedly different from those found in the ileal mucosal scrapings. A peak in the activity measured in the brush border fraction was observed during the weaning period. A partial explanation for the observed changes is suggested but a detailed analysis was not possible at the present stage in the work.
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  • 7
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 8
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Attempts to remove brush borders from rat intestinal mucosal scrapings in a saline medium are described. Variation of the pH of the medium showed that at about pH 6.5, morphologically intact columnar epithelial cells could be isolated and a suitable method for preparing whole cells is suggested. When the pH was raised to 8.5, the brush borders were liberated. Studies by electron microscopy revealed that a considerable amount of granular cytoplasmic material remained attached to the terminal web. This attached material could be removed, however, by adding EDTA to a suspension of the brush borders. The supernatants and the brush borders sedimented by centrifugation were investigated for contaminants from other regions of the cell. In general, the levels of contamination were higher in the brush borders isolated in saline than when isolated in the presence of EDTA. Phospholipid: cholesterol ratios for brush borders isolated in saline varied from 1.12∶1 to 1.21∶1, whereas in whole cells the ratio was about 3.5∶1. The results are discussed in relation to previous studies.
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  • 9
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The potential application of a DEM cell for the electrolysis of hydrogen bromide in the Ispra Mark 13A process for flue gas desulphurization has been tested in a number of laboratory experiments and in long-duration tests in a bench-scale plant of the process. Satisfactory electrode materials have been found, i.e. Hastelloy C 276 for the cathode and a RuO2 coating on titanium for the anode. Both electrode materials showed a good stability during a 1500 hours experiment. Cell voltage/current density relationships have been determined during bench-scale plant operation. A typical value is 1.5V at a current density of 2.5 kA m−2. It has been shown that in an undivided cell a cathodic back reaction occurs which causes a decrease of the current efficiency. Under normal operation conditions current efficiencies of about 90% are obtained. A simplified flow model for the DEM cell was developed which is useful in understanding the phenomena which occur during scale-up of the cell. An industrial size installation for the production of 170 kg h−1 of bromine at a current density of 2 kA m−2 was constructed and has been in operation since August 1989.
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