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  • Ultrastructure  (410)
  • Electron microscopy  (378)
  • pharmacokinetics  (182)
  • kinetics
  • Springer  (997)
  • American Chemical Society
  • 1975-1979  (997)
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  • Springer  (997)
  • American Chemical Society
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 6 (1977), S. 203-216 
    ISSN: 1572-8927
    Schlagwort(e): Glucose ; kinetics ; mixed solvent ; kinetic isotope effect ; enthalpy of activation ; entropy of activation ; tetrahydrofuran ; tert-butanol ; mutarotation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The mutarotation rates of glucose in aqueous mixtures of tetrahydrofuran andtert-butanol in the mole fraction (xi) range 0〈xi〈0.2 have been measured at 5° intervals in the range 5–35°C. The kinetic deuterium isotope effects have been determined for the same solvent compositions at 25 and 35°C. A statistical analysis of the Arrhenius plots indicates that the experimental errors, although small, are too large for the establishment of any compensation behavior between ΔH
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 5 (1976), S. 163-169 
    ISSN: 1572-8927
    Schlagwort(e): Solvent effects ; tetramethylurea ; hydrolysis ; hydrogen bonding ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Tetramethylurea was hydrolyzed in aqueous hydrochloric acid at temperatures of 80, 90, and 100°C. All reactions were carried out in an excess of both tetramethylurea and water, with first-order dependence on acid concentration being observed. As the concentration of water was increased, the rate of hydrolysis decreased until equimolar amounts of water and tetramethylurea were present. Subsequent addition of water had no effect on the observed rate.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 25 (1978), S. 145-159 
    ISSN: 1432-0827
    Schlagwort(e): Bird egg shell ; Ultrastructure ; Calcification ; Electron diffraction ; Microanalysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The egg-shell of Japanese quail was studied by several techniques. Semithin sections (1μm thick) of non-decalcified shell were observed by normal and polarized light microscopy. Thin sections of non-decalcified shell, examined by transmission electron microscopy, permitted us to observe the forms and dimensions of crystals of calcite within different layers of the shell: mammilary layer, layer of cones, palissade layer and surface crystal layer. There appears to be two distinct zones in the layer of cones as well as in the superficial crystal layer. Electron microdiffraction revealed the orientation of calcite crystals in the columns. Some crystal defects (twins?) were described and the possibility of their artefactual formation during ultramicrotomy is discussed. Localization of Ca, Mg, P and S were made by X-ray microanalysis of semithin sections. This technique shows that shell membranes, and chiefly the true cuticle, are also mineralized but, in these layers, minerals are not crystallized. Otherwise the distribution of Mg is not uniform throughout the shell thickness; it is less concentrated in the external zone of the layer of cones. These results together with observation of developing shells by scanning electron microscopy allowed us to propose a scheme for shell organization of the quail egg. This organization was related with decalcification which occurs during hatching.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 25 (1978), S. 217-222 
    ISSN: 1432-0827
    Schlagwort(e): Bone mineral ; Electron microscopy ; X-ray diffraction ; Dark field
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Electron microscopical observations of the size and shape of bone mineral crystallites have not been in complete agreement with X-ray diffraction findings. The two prevalent viewpoints consider bone mineral crystals to be either rod, or plate like in habit. There appears to be agreement that the smallest dimension of the crystals is about 5 nm, but there is discrepancy in the reported c-axial lengths. The method of dark field imaging is used to obtain a quantitative measurement of the c-axial length distribution in rabbit, ox and human bone: mean c-axial lengths 32.6 nm, 36.2 nm and 32.4 nm, respectively, show no significant difference at the 5% level to the mean c-axial length measured by X-ray line broadening. Both bright and dark field images strongly suggest that bone mineral has a plate like form. Reasons for past discrepancies are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 24 (1977), S. 215-222 
    ISSN: 1432-0827
    Schlagwort(e): Mineralization ; Osteodentin ; Intracellular ; Ultrastructure ; Microanalysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Newly formed osteodentin obtained from the anterior extremities of fetal or young rat incisors was observed by means of electron microscopy and electron probe X-ray microanalysis. Cells related to osteodentin formation frequently showed membrane bound intracellular bodies containing varying amounts of fine, needle-shaped crystals, which were identified as apatite. The intracellular clusters of apatite crystals were extruded from the cells through membrane fusion or cellular degeneration. These extracellular clusters seemed to be gradually incorporated into the mineralizing collagenous matrix, which developed around them. Frequent occurrence of dense, dotshaped or filamentous profiles suggested that the dense bodies seen in the perinuclear regions or in the Golgi area were the sites of crystal formation. Energy dispersive X-ray point analysis showed that the intracellular or extracellular apatite clusters contained sulfur in a concentration higher than was present in the mineralizing collagenous matrix. Furthermore, wave dispersive X-ray line analysis showed that the concentration of sulfur was higher in the osteodentin matrix than in the dentin matrix. The sulfur detected is presumed to be contained in acid mucopolysaccharides, which were distributed more heavily in the osteodentin matrix than in the dentin matrix. On the basis of these data, it was concluded that the unique chemical and structural characteristics of the osteodentin result primarily from the incorporation of apatite clusters of intracellular origin and associated acid mucopolysaccharides.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 28 (1979), S. 43-56 
    ISSN: 1432-0827
    Schlagwort(e): Bone resorption ; Osteogenesis ; Fish bone ; Osteocytes ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The comparative ultrastructure of fish bone osteogenesis and resorption induced by scale removal was described in the osteocytic (cellular-boned)Carassius auratus and the anosteocytic (acellular-boned)Tilapia macrocephala. Osteocytes, present in osteocytic bone, were lacking in anosteocytic bone. In osteocytic bone the osteoblast secreted a collagenous preosseous matrix in which it became enmeshed and then was termed a preosteocyte. When the preosseous matrix mineralized, the preosteocyte was termed an osteocyte and was completely surrounded by bone. In anosteocytic bone the osteoblasts receded from the mineralizing front and never became trapped as osteocytes. During resorption, types A and B resorptive cells, present in both bone types, invaded the matrix and demineralized the osseous zone. These cells were characterized by large amounts of granular endoplasmic reticulum and intracellular inclusions containing crystal-like material. Although functionally similar to mammalian osteoclasts, these cells lacked a characteristic ruffled border and were not multinucleated. The osteocytes of cellular bone did not appear to be involved during demineralization.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 1432-0827
    Schlagwort(e): Parathyroid hormone ; Osteoclasts ; Electron microscopy ; Morphometry ; Metaphysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The effects of parathyroid hormone (PTH) on the size of the osteoclasts, nuclei, ruffled borders, and clear zones in long bones of thyroparathyroidectomized (TPTX) rats were quantitated as a function of time. These data were compared with the number of osteoclasts in the bone and with plasma calcium levels. A significant increase in the average size of the ruffled borders was demonstrated 30 min after injection of 50 U of purified bovine PTH, and of the clear zones 30–90 min after PTH. This was followed at 90 min by an increase in the average size of the cells. The sizes of ruffled borders and clear zones dropped sharply to control levels after 6 h, whereas the size of the cells remained elevated up to 12 h and returned to control values at 24 h. Plasma calcium levels were increased, but not significantly, between 30 min and 6 h. An increase in the number of osteoclasts was significant after 12 h. Removal of the parathyroid glands did not diminish the normal activity of osteoclasts. In animals with intact glands injection of 50 U of PTH did not cause a significant change in cell size or resorbing apparatus. It is concluded that PTH acts to rapidly stimulate the bone resorptive activity of osteoclasts and to cause a delayed increase in their number.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Mycopathologia 59 (1976), S. 117-123 
    ISSN: 1573-0832
    Schlagwort(e): Ultrastructure ; Zygospore ; Mycorrhizal fungus ; Flaming crown
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The ultrastructural organization of the spores of the sporocarp of Endogone flammicorona was studied. Two types of organization are described. Initially the spore possessed a vacuolate protoplasm and was bound by two cell wall layers. The spore was surrounded by a hyphal mantle formed of a sheet of vacuolized hyphae with uniformly thin walls. Secondly, although the ultrastructural features of the spore appeared the same, it was now surrounded by a hyphal mantle with unevenly thickened walls (i. e., the so-called flaming crown) due to the gradual and irregular deposition of granules and lamellae. This crown gives the spore its most commonly observed morphological feature and is the preminent character employed taxonomically to speciate Endogone flammicorona Trappe & Gerdemann.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Mycopathologia 60 (1977), S. 175-177 
    ISSN: 1573-0832
    Schlagwort(e): Aspergillus fumigatus ; Spore formation ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Mycopathologia 61 (1977), S. 117-119 
    ISSN: 1573-0832
    Schlagwort(e): Prototheca ; Colorless alga ; Plastids ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract An ultrastructural investigation of six different species of Prototheca showed that all of them contained starch grains enclosed in double-membrane-bounded structures recognized as plastids. It is concluded that these unicellular species of Prototheca must be considered as non-photosynthetic algae.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 11
    ISSN: 1573-0832
    Schlagwort(e): Trichophyton mentagrophytes ; Thiocyanatopyrazole derivatives ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Four thiocyanatopyrazole derivatives were synthesized and their fungistatic activity was demonstrated in vitro against a number of dermatophytic fungi. In Trichophyton mentagrophytes, the most active compound induced an unusual increase of the plasma membrane with production of intra and extracytoplasmic complexes, a deterioration of nuclear and mitochondrial membranes and a formation of autophagic-like vacuoles. Plasmolysis, accompanied by an almost complete disorganization of cytoplasmic structures, seemed to be the final event. A possible mechanism of action of the compounds was discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 8 (1975), S. 319-331 
    ISSN: 1432-0630
    Schlagwort(e): Self-interstitials in silicon ; Swirls ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Point defect agglomerates in dislocation-free silicon crystals, usually called “swirls”, have been investigated by means of high-voltage electron microscopy. It was found that a single swirl defect consists of a dislocation loop or a cluster of dislocation loops. By contrast experiments it could be shown that these loops are formed by agglomeration of self-interstitial atoms. Generally the loops have a/2〈110〉 Burgers vectors, but in specimens with high concentrations of carbon (∼1017 cm−3) and oxygen (∼1016 cm−3) also dislocation loops including a stacking fault were observed. In crystals grown at growth rates higher thanv=4 mm/min no swirls are observed; lower growth rates do not markedly affect the size and shape of the dislocation loops. With decreasing impurity content (particulary of oxygen and carbon) the swirl density decreases, whereas the dislocation loop clusters become larger and more complex. A model is presented which describes the formation of swirls in terms of agglomeration of silicon self-interstitials and impurity atoms.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    ISSN: 1432-041X
    Schlagwort(e): Ultrastructure ; Scanning cytophotometry ; Chromatin ; Chondrocytes ; Regeneration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé Les cellules cartilagineuses des membres postérieurs deTriturus cristatus en régénération après amputation, ont été étudiées en microscopie électronique et par cytophotométrie à balayage. Nous nous sommes intéressés à la structure et à la distribution de la chromatine mais aussi à différents organites cytoplasmiques. Dans l'étude de cytophotométrie à balayage, la chromatine a été considérée à travers son constituant majeur, l'ADN, coloré par la réaction de Feulgen. Au cours de la régénération du membre, l'hétérochromatine initialement condensée, essentiellement accolée à la membrane nucléaire se décondense. Les vacuoles du cytoplasme, caractéristiques des animaux âgés par rapport aux animaux jeunes, disparaissent, les mitochondries et le reticulum endoplasmique rugueux deviennent plus abondants. Les caractéristiques nucléaires de l'activation cellulaire apparaissent précocement, précédent les modifications cytoplasmiques et conduisent à des cellules en tous points identiques aux cellules d'animaux jeunes en dehors de tout processus régénératif. Cette phase d'euchromatisation et de restructuration cytoplasmique est peut-être nécessaire à l'accroissement d'activité métabolique et à la division cellulaire qui suivent. Son déroulement peut expliquer tout au moins le ralentissement de la régénération observé chez les animaux âgés par rapport aux animaux jeunes.
    Notizen: Summary Cartilaginous cells of aged newts (Triturus cristatus) were studied during hind limb regeneration. The electron microscope was used to study the structure and distribution of chromatin in the cell nuclei, while the DNA content of the chromatin was measured by means of a scanning cytophotometer. Changes in the ultrastructure of the cytoplasm during regeneration were also studied. It was observed that the structure and distribution of chromatin in the activated cell is greatly modified. In the non-activated cell of the aged newt, the chromatin is found highly condensed and distributed peripherally close to the nuclear membrane. In contrast, in the activated cells, the chromatin is much less condensed and is distributed throughout the nucleus. Moreover, cytoplasmic vacuoles, found only in the non-activated aged cells, disappear and an increase in the mitochondria and rough endoplasmic reticulum is also observed. Changes in the nuclear structure are observed prior to the cytoplasmic modifications. It is interesting to note that the process of activation induces structural changes in the aged cells which make these cells appear to be structurally identical to the young cells. This process of rejuvenation takes 3–5 days in the newt. We suggest that these structural changes of the chromatin and cytoplasm in the aged cells are necessary to increase the metabolic activity which precedes cell division. It may also explain why regeneration takes a longer time in the aged animals than in the young ones.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 183 (1977), S. 233-248 
    ISSN: 1432-041X
    Schlagwort(e): Cytoplasmic architecture ; Ultrastructure ; Insect egg ; Pattern formation ; Yolk ; Cytoplasma-Architektur ; Ultrastruktur ; Insekten-Ei ; Musterbildung ; Dotter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung 1. Das Ei der ZuckmückeSmittia spec. wurde licht- und elektronenmikroskopisch untersucht. Die vorliegende Arbeit beschreibt den Bau des Periplasmas und des Dotter-Endoplasma-Systems vor Bildung der Polzellen. 2. Das Periplasma, nach außen vom Oolemm und einer mehrschichtigen Eihülle begrenzt, besteht aus einer ribosomenreichen cytoplasmatischen Matrix, in die vor allem Mitochondrien und ER-Zisternen, wenig annulate lamellae und gelegentlich Golgi-Apparate eingelagert sind. Mikrotubuli wurden nur selten nachgewiesen. Öfters sind Anhäufungen einer dichten granulierten Substanz zu beobachten, die in ihrer Struktur dem Oosom-Material ähnelt. 3. Das Dotter-Endoplasma-System stellt ein Netzwerk aus Cytoplasma dar, in das Proteid-Dotterkugeln, Lipidtröpfchen sowie Glycogen-Anhäufungen eingelagert sind. Das Endoplasma, das sich zu 3–7 Plasma-Inseln erweitern kann und unmittelbar in das Periplasma übergeht, besteht wie dieses aus einer cytoplasmatischen Matrix und enthält die gleichen Zellelemente wie das Periplasma. Rosettenförmige Membran-Strukturen werden als “nuclear envelope organizing center” gedeutet. 4. Drei der sorgfältig analysierten Eier enthielten je 2 Kerne; sie lagen in Plasma-Inseln in der hinteren Eihälfte. 5. Sowohl im Periplasma wie im Dotter-Endoplasma-System sind alle Zellelemente unregelmäßig verteilt. Eine besondere Anordnung oder Zonierung ist nicht zu erkennen. 6. Die räumliche Verteilung der erfaßten Eikomponenten liefert keine Hinweise auf eine Funktion dieser Komponenten als Determinanten für die embryonale Musterbildung.
    Notizen: Summary 1. Eggs of the midgeSmittia were investigated by light microscopy and transmission electron microscopy. This paper describes elements and architecture of periplasm and yolk endoplasm before the formation of pole cells. 2. The periplasm is coated externally by the oolemma and a multilayered egg shell. The periplasm consists of a cytoplasmic matrix rich in ribosomes; it contains mitochondria and ER cisternae, some annulate lamellae and an occasional Golgi complex. Microtubuli were demonstrated only rarely. Accumulations of a dense granulated substance resembling in its structure the oosome material were frequently observed. 3. The yolk endoplasm is a cytoplasmic network embodying proteid yolk particles, lipid droplets and accumulations of glycogen. The endoplasm is continuous with the periplasm and shows the same cell constituents. It may form between 3 and 7 cytoplasmic islands free of yolk particles. Rosette-shaped membranous structures in the yolk endoplasm are interpreted as nuclear envelope organizing centres. 4. Three carefully analysed eggs contained 2 nuclei each. both nuclei were situated in the posterior egg half. 5. Periplasm and yolk endoplasm are characterized by random distribution of cell elements. No zonation or special accumulations could be recognized. 6. The spatial distribution of the egg components studied did not indicate that any of these components could function as a determinant in embryonic pattern formation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 181 (1977), S. 333-355 
    ISSN: 1432-041X
    Schlagwort(e): Barnacle eggs ; Constriction rings ; Microfilaments ; Ultrastructure ; Peristalsis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary 1. The egg ofPollicipes polymerus, the common intertidal gooseneck barnacle, has been studied by electron microscopy. Constriction rings, similar to the contractile rings of cleaving cells and polar lobes, move unidirectionally from the animal to the vegetal pole of newly fertilized eggs. This is referred to as peristaltic constriction. The present paper describes the fine structure of the egg during first polar body formation and peristalsis. 2. During formation of the polar body, dense bodies are produced by the Golgi and extracellular plaques are observed. Thin microfilaments (40–60 Å) are in the egg adjacent to the polar body. 3. In eggs undergoing peristalsis, the appearance of extracellular spheres, flocculent material and filaments is observed. Intracellularly large numbers of multivesiculate bodies, glycogen granules, mitochondria and protein-carbohydrate and lipid yolk bodies are seen at the level of constriction. 4. Thin microfilaments are found in the cortical area of newly-fertilized eggs exclusively in peristaltic constriction rings. Filaments are oriented primarily in a meshwork, although circumferentially-oriented filaments are also found in rings near the vegetal pole. Microvilli extend into the space created between a constriction and the elevated egg membrane. 5. A model is proposed to explain the peristalsis in this species. It is suggested that information from a pacemaker region activates peristalsis by affecting filament polymerization and orientation. One function of peristalsis may be elongation of the egg from a sphere to an ovoid, although other possibilities such as elevation of the egg membrane, segregation of the lipid yolk to the vegetal pole and predetermination of the first cleavage plane are also discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 186 (1979), S. 65-70 
    ISSN: 1432-041X
    Schlagwort(e): Sea urchin ; Embryo ; Collagen ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Collagen fibrils with a main period banding of 610 Å and 220 Å in width were observed in the blastocoel of 72-h embryos of the sea urchin,Strongylocentrotus purpuratus. Non-striated fibrils of 50 Å diameter were also observed. The collagen is seen in highest concentration in the vicinity of mesenchyme cells which are richly endowed with endoplasmic reticulum and secretory vesicles. A role for collagen in cell attachment, orientation and spicule formation is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 185 (1978), S. 235-248 
    ISSN: 1432-041X
    Schlagwort(e): Liver ; Primary culture ; Ultrastructure ; Albumin synthesis ; Xenopus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Electron microscopic analysis of primary cultures derived from larvalXenopus liver has shown that these cells, although they form only two-dimensional aggregates, retain and presumably also develop structural characteristics typical of liver parenchyma cells, such as bile canaliculi with microvilli and epithelial junctional complexes. As judged from structural criteria, primary cultures contain 80–90% hepatocytes. In contrast to the intact tissue, primary cultures showed excessive development of microfilaments, however. Incorporation of labeled amino acids has revealed further that the capacity for protein synthesis is maintained in culture and that synthesis of liverspecific protein albumin is maintained in vitro, even in liver cultures derived from thyrostatic tadpoles. This latter result suggests that initiation of albumin synthesis in the larval liver is probably not dependent upon thyroid hormones but rather reflects the protodifferentiated state of this tissue.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 18
    ISSN: 1432-041X
    Schlagwort(e): Synaptogenesis ; Electron microscopy ; Visual acuity ; Fish development
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The morphogenetic differentiation of synapses of the optic tectum of the rainbow trout was investigated at different stages of development (from hatching to adult) and compared with the improvement in visual discrimination (minimum separable). (1) The main phase of synaptogenesis (increase in number of synapses, length of contact zone and number of vesicles) begins about one week after hatching and continues up to the age of one month, when the larvae start swimming freely. (2) Myelination begins 26 days after hatching and induces the end of the synaptogenesis period. (3) The visual discrimination (minimum separable) of trout larvae improves from 30 degrees of arc on the 10th day after hatching to 1 degree on day 30, then to about 14 to 18 min of arc in the adult. The results are discussed with special reference to previous biochemical investigations on changes in the ganglioside composition of the trout brain during comparable periods of development.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 185 (1979), S. 333-346 
    ISSN: 1432-041X
    Schlagwort(e): Chick embryo ; Limb bud ; Ultrastructure ; Cell death
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ultrastructural changes in the wing bud afterapical ectodermal ridge (A.E.R.) removal was studied to re-examine the issue of distal mesenchymal cell death. The A.E.R. of the right wing bud was removed microsurgically from chick embryos of stages 18 to 22 (HH 1951). The wing buds were examined at three hour intervals up to twelve hours after the operation with light, transmission and scanning electron microscopy. The main findings were: (1) Immediate and temporary shrinkage of the mesenchymal extracellular space 100 to 150 μm and chromatin condensation in the cells 50 to 75 μm from the wound. (2) Death of ectodermal and mesenchymal cells in the immediate vicinity of the wound. (3) Formation of a single squamous-like layer of mesenchymal cells to cover the wound. (4) Occasional evidence of cell death in the distal mesenchyme at later times after the operation. The pattern of cell death observed suggests only a traumatic etiology, and gives little evidence for the postulated developmental significance of cell death following A.E.R. removal.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 26 (1978), S. 181-190 
    ISSN: 1432-0827
    Schlagwort(e): Cellular calcium ; Electron microscopy ; Osteoblasts ; Chondrocytes ; Mineralization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The calcium distribution in cartilage and bone cells during beginning ossification of fetal mouse long bones was studied after fixation with 2% K-pyroantimonate in 1% osmium. In the developing periosteum, the future osteoblasts showed a sparse cation-antimonate precipitate over the cytoplasm. In young osteoblasts the precipitate was accumulated on the mitochondrial membranes and the plasmalemma. Both organelles were sharply outlined by precipitate in the mature osteoblasts at the onset of mineralization. X-Ray microprobe analysis of these organelles demonstrated the presence of both Sb and Ca. In the extracellular compartment, a collagen-associated precipitate with 50 to 60 nm periodicity appeared during osteoblastic differentiation. During the initial phase of matrix mineralization, a random gross precipitate appeared in the matrix and seemed to be accumulated by osmiophilic matrix vesicles while the collagen fibrils lost their precipitate. Subsequently, during the confluent phase of matrix mineralization, the precipitate rapidly disappeared from the cells, leaving them devoid of precipitate once they were surrounded by mineralized matrix. Similar changes were found in the chondrocytes of the growth plate, but cartilage collagen, unlike osteoid collagen, did not bind precipitate. The results indicate that both osteoblasts and calcifying cartilage cells bind calcium prior to matrix mineralization. Bone collagen has strong pyroantimonate binding capacity, but it is not directly involved with initial stages of matrix mineralization, which starts in close association with matrix vesicles.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 26 (1978), S. 271-282 
    ISSN: 1432-0827
    Schlagwort(e): Shell formation ; Free nerve endings ; Ultrastructure ; Lymnaea stagnalis ; Biomphalaria pfeifferi
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The mantle edge of the freshwater pulmonate snailsLymnaea stagnalis andBiomphalaria pfeifferi was investigated with histochemical and ultrastructural methods. The mantle edge gland, which is involved in shell formation, consists of the periostracal groove and the belt. This belt appears to be composed of various regions. In the area of the periostracal groove a number of subepithelial gland cell types occur; these release their products into the groove. Between the groove cells ciliated free nerve endings terminate; the corresponding perikarya occur in the subepidermal connective tissue. Also in the posterior belt region free nerve endings were observed between the epithelial cells; in addition, a particular type of subepithelial gland cell was found in this area. The epithelial cells of this part of the belt have the ultrastructural characteristics of ion and water transporting cells; they are probably involved in calcium deposition and resorption. The possible role of the free nerve endings and of the subepithelial gland cells is discussed.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 23 (1977), S. 215-223 
    ISSN: 1432-0827
    Schlagwort(e): Amorphous mineral ; Bone ; Electron microscopy ; Ultracryotomy ; Ultramicro-incineration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The fine structure of the extracellular phase of avian medullary bone and embryonic chick femur was examined in thin sections prepared by ultracryotomy and ultramicroincineration. Since contact with solutions was completely avoided, little or no loss or dislocation of mineral constituents could occur. Amorphous bone mineral (ABM) was present in two forms: as 15–30 nm spheres and as a structure-free haze. Removal of all organic material by low temperature ashing left the ABM intact. Crystals were usually associated with the ABM. In newly ossifying regions clusters or nodules of randomly oriented crystals and ABM appeared to coalesce when they reached approximately 1 μm in diameter. In highly calcified regions crystals appeared to be oriented along collagen fibers. ABM did not appear to be associated with collagen. Unmineralized collagen was visible in osteoid after staining with dry OsO4 vapor and it appeared to be diverted around nodules. Structures which resembled matrix vesicles were present. Selected area electron diffraction patterns indicated the presence of hydroxyapatite.
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 25 (1978), S. 179-190 
    ISSN: 1432-0827
    Schlagwort(e): Decalcification ; Electron microscopy ; Calcified matrices
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The ultrastructure of calcifying cartilage and bone has been examined under the electron microscope after using three different methods of decalcification. The first was carried out before embedding (by soaking specimens in EDTA or formic acid), the second after embedding (by floating ultrathin sections on formic acid), and the third after embedding (by soaking embedded specimens in EDTA or formic acid), and with later re-embedding. The first procedure invariably induces drastic changes in the fine structure of the cells and calcified matrix, probably as a results of the extraction of organic material along with extraction of mineral. The second and third procedures make it possible to preserve ultrastructural details perfectly in both cells and calcified matrix. Of the two, the third procedure is preferable because of its greater simplicity. In areas that are still calcifying, these post-embedding decalcification techniques reveal the presence of crystal-associated, filamentous organic structures which are not recognizable in specimens decalcified before embedding. These structures, which could have a key role in inducing and regulating crystal formation and growth, are less evident in fully calcified areas (but not at their borders). This may partly be due to the loss of glycan components in the matrix during calcification. The most important determinant, however, seems to be the fact that during calcification the components of the matrix, including collagen fibrils, are involved in an aggregation process which reduces the amounts of free chemical groups available for reaction with the stain solution. Because post-embedding decalcification does not disturb this state of aggregation, the stainability of the matrix and the electron microscopic evidence of its components remain very low.
    Materialart: Digitale Medien
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 24 (1977), S. 191-197 
    ISSN: 1432-0827
    Schlagwort(e): Amelogenesis imperfecta ; Hypocalcification ; Hypoplasia ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary An ultrastructural study of teeth with amelogenesis imperfecta revelaed various aspects of microcavities in the enamel surface, which ranged from isolated imprints of ameloblasts corresponding to the mildest lesions at the end of amelogenesis, to pits caused by the death of 20 to 30 ameloblasts at the beginning of amelogenesis. Abnormalities in the shape of the prisms can be observed. Further, crystals are distributed randomly within a prism or at the junction of 2 contiguous prisms while intercrystalline spaces are widened, indicating in various places the lack of a preferred orientation of the crystals. In amelogenesis imperfecta, two different crystalline periods are found: 1 of about 250 Å, the other of about 500 Å and over. The fact that amorphous areas are found among the crystals of enamel may be related to different stages of crystallization. However, it was not possible to find any lattice defect.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 24 (1977), S. 239-242 
    ISSN: 1432-0827
    Schlagwort(e): Cementum ; Lysis ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Examination of microradiographs from the deciduous teeth of pigs revealed large lacunae or radiolucent zones close to the cemento-dentinal junction. Electron microscopic studies of the ground sections showed areas or irregularly shaped zones devoid of mineral and filled with collagen fibers. In the wide unmineralized zones, spherical clusters of crystallites were noted. Several cementum lacunae bordered by a broad rim of unmineralized collagen fibers were noted and some lacunae also contained zones of a moderately electron dense material. This material did not yield a diffraction pattern, while the mineralized part of the cementum gave the diffraction pattern typical of hydroxyapatite.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 25 (1978), S. 45-51 
    ISSN: 1432-0827
    Schlagwort(e): CaCO3 ; Amino acids ; Sheaths ; Ligament ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The aragonite crystals in the molluscan bivalve hinge ligament are surrounded by an organic sheath which is distinct from the remainder of the ligament matrix. Methods have been developed to isolate these sheathed crystals from the ligaments ofSpisula solidissima andMercenaria mercenaria employing a papain digestion of the matrix protein. The sheathed crystals fromSpisula have a CaCO3/protein ratio of 11.1 and those fromMercenaria a ratio of 29.6. The sheathed crystals and the empty crystal sheaths have been examined by electron microscopy for structural integrity. The sheath proteins exhibit much smaller proportions of the amino acids glycine and methionine than the hinge ligaments. These are characteristic amino acids of high concentration in the hinge ligaments of both species. The concentrations of acidic and basic amino acids are increased about two fold in the sheaths over those of the ligaments. Otherwise there is little similarity in the amino acid composition of the sheaths in the two species. However, SDS electrophoresis shows the sheaths of both to contain a major protein component with a molecular weight of about 25,000. The sheath protein from theMercenaria ligament contains about 5% carbohydrate and that ofSpisula sheaths less than 1% carbohydrate.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 29 (1979), S. 101-105 
    ISSN: 1432-0827
    Schlagwort(e): Osteon ; X-ray diffraction ; Pole figures ; Electron microscopy ; Calcification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The X-ray diffraction method based on pole figures has been applied to single osteon samples in order to obtain information about the texture of the inorganic bone fraction and the way it changes during calcification. The osteon samples were cylindrically shaped, with axes corresponding to those of the haversian canals. Selection was carried out according to the degree of calcification and the orientation of collagen bundles and inorganic particles. Osteons at both the initial and final stages of calcification were chosen. Arrangements of fiber bundles and inorganic particles in successive lamellae characteristic of three types of osteons were selected: longitudinal, alternate, and transversal. The results indicate that in all three types of osteons, the long axis of the sample is apparently the only direction of orientation because the transversally oriented crystallites give an isotropic diffuse scattering as would be expected if all the inorganic particles were irregularly oriented around the osteon axis. The number of longitudinally oriented crystallites increases progressively from transversally oriented osteons to alternately and longitudinally oriented ones. The crystallite orientation in an axial direction increases in fully calcified osteons. This last result is in agreement with the electron microscopic finding that the long needle-shaped crystallites covering much more than a major collagen period and measuring 40–45 Å in width increase in number as calcification proceeds.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 25 (1978), S. 133-143 
    ISSN: 1432-0827
    Schlagwort(e): Osteon ; X-Ray diffraction ; Electron microscopy ; Calcification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary To obtain information on the changes in the inorganic bone fraction during calcification, low- and wide-angle X-ray diffraction techniques and electron microscopy have been applied to single osteon samples. The samples were cylindrically shaped and their axes corresponded to the axes of the Haversian canals. The selection was made according to the degree of calcification and the orientation of collagen bundles and inorganic particles. Osteons at both the initial and final stages of calcification were chosen. Arrangements of fiber bundles and inorganic particles in successive lamellae characteristic of three types of osteon were selected, that is, longitudinally structured osteons, transversely structured osteons, and alternately structured osteons. The results indicate that in osteonic lamellar bone there are two types of inorganic particles: (1) granules arranged in linear or needle-shaped entities with maximum width 40–45 Å, which are regularly distributed at the level of the main band of the collagen fibrils where their maximum length reaches the length of the main band itself; that is, about 400 Å; and (2) very long crystallites, with a diameter of 40–45 Å, which grow with their crystallographicc-axis parallel to the collagen fibrils and cover much more than a major collagen period.
    Materialart: Digitale Medien
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  • 29
    ISSN: 1432-2048
    Schlagwort(e): Festuca ; Frost damage ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Tillers of Festuca arundinacea Schreb. were subjected to-8°C in a bath of methylated spirits for three-quarters of an hour. They were thawed at room temperature and some material taken from the shoot apical meristem and leaf blade for electron microscopy. Similar material was taken from control plants for electron microscopy. Nine tillers subjected to-8°C and thawed subsequently failed to regrow. Nine control tillers regrew. All the treated meristem cells and about half the treated leaf mesophyll cells were extensively altered. Their nuclei were contracted, organelles were swollen or partly disrupted, plasmalemma and nuclear membranes were broken or absent and vacuoles were sometimes disrupted. Strongly osmiophilic material accumulated in the vicinity of membranes. About half the leaf mesophyll cells differed from the control mesophyll cells only in having more spherosomes and narrower thylakoids. Parallels with other ultrastructural studies of stress damage and the indications the results give of possible primary damaging events are discussed.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Planta 133 (1976), S. 15-19 
    ISSN: 1432-2048
    Schlagwort(e): Tropaeolum, Embryogenesis ; Differentiation ; Plastids ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Embryogeny in the nasturtium is characterized by the development of a large, tripartite suspensor and storing cotyledons. A light and electron microscopic study revealed an early diversification of the plastids in the various regions of the suspensor and the embryo proper. Amyloplasts are found in the developing cotyledons of the heart-like embryo, while chloroplasts occur within the meristematic part of the embryo and the adjacent portion of the suspensor. The cells between the meristem and the storing cotyledons display undifferentiated leukoplasts, whereas leukoplasts with an electron-dense matrix occur in the basal cell mass of the embryo-suspensor. Etioplasts develop in several cells of the placental haustorium of the suspensor. The carpel haustorium shows rather undifferentiated leukoplasts, which are transformed into electron-dense plastids during autolysis of the suspensor. This early plastidal differentiation in discussed with respect to its control and functional significance.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 97-105 
    ISSN: 1432-1041
    Schlagwort(e): Di-n-propylacetate ; 2-propyl-valeric acid sodium salt ; pharmacokinetics ; anti-epileptic ; drug monitoring ; man
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of the anti-epileptic drug di-n-propylacetate (DepakineR) have been studied in 7 patients, in whom plasma concentrations were determined during and following subchronic treatment. Elimination of the drug appeared to follow a monophasic exponential course; biological half lives were 8 to 15 hours. The data supported the assumption that an open one-compartment model can be used to describe the kinetics of dipropylacetate in man. The drug appeared to have a relatively restricted distribution: calculated relative distribution volumes ranged from 0.15 to 0.40 1/kg. There were large interindividual differences in clearance rate. The therapeutic range was considered to be between 50 and 100 mg/1 plasma. Plasma levels of phenobarbital were markedly raised during treatment with dipropylacetate for an unknown reason. Determination of the plasma concentrations of drugs at accurately fixed times appears to be a reliable method for pharmacotherapeutic monitoring of epileptic patients.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 157-160 
    ISSN: 1432-1041
    Schlagwort(e): Isosorbide dinitrate ; pharmacokinetics ; metabolism ; pharmacological action ; nitrates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary An oral dose of 5 mg of14C-isosorbide dinitrate was rapidly absorbed, biotransformed and excreted by human subjects. Peak whole blood concentrations of radioactivity were reached after 1.5 to 2 hours and declined relatively slowly. The radioactivity in whole blood mainly represented metabolites, isosorbide mononitrates. The peak concentrations found were 4.5, 11.7 and 34.3 ng/ml of isosorbide dinitrate, isosorbide 2-mononitrate and isosorbide 5-mononitrate, respectively, in the blood of one subject and 5.9, 15 and 61.3 ng/ml, respectively, in the blood of another subject. However, concentrations of the metabolites declined relatively slowly during 6 h after the oral dose. Up to 99% of an oral dose of isosorbide dinitrate was excreted during 5 days, mainly in the urine of the first day (ca. 78%). The results showed that isosorbide mononitrates were available to contribute to the pharmacological action.
    Materialart: Digitale Medien
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 241-248 
    ISSN: 1432-1041
    Schlagwort(e): pharmacokinetics ; experimental design
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary It is apparent from studying recent articles on pharmacokinetics that a number of misunder-standings exist, both about the design of experiments and the analysis of results. The purpose of this paper is to outline many of the common pitfalls associated with the design of experiments and also the limitations upon the analysis of results. The paper describes mathematical, laboratory and clinical aspects which must be examined in designing a protocol for pharmacokinetic experiments. Simulated data is presented to demonstrate the dangers of using standard computer programs for parameter estimation. Even when convergence is obtained the answers may be dependent on the method employed. A mathematical model is of little use unless a reasonable amount of good, accurate data is obtained.
    Materialart: Digitale Medien
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 249-254 
    ISSN: 1432-1041
    Schlagwort(e): Clonazepam ; 7-amino-clonazepam ; pharmacokinetics ; side-effects ; man
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Clonazepam (CNP) and its principal metabolite in plasma, 7-amino-CNP (ACNP), have been investigated in a prospective study of 27 newly diagnosed epileptics and correlated with specified side-effects. At a daily dose of 6 mg, the average plasma levels of both substances were about 50ng/ml, and individual values ranged from 30 to about 80ng/ml. There was a linear correlation between changes in dose and the resulting plasma levels, which indicates first order elimination kinetics. Side-effects were frequent, but neither their severity nor their occurrence could be related to plasma levels or to the rate of increase in plasma concentration of the drug. Three out of five patients who developed serious dysphoria had significantly high CNP levels. The concentration of ACNP was considerably increased in four patients who subsequently suffered from withdrawal symptoms. Drug interaction with diphenylhydantoin, i.e. decreased CNP level, was observed in all five patients who received both compounds. In general it is not yet possible to define an upper limit for the plasma levels of CNP and ACNP at which toxicity occurs. In patients treated with conventional doses of CNP, measurement of plasma concentration is not required, except in special circumstances, because of the lack of correlation between plasma level and side-effects.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 271-275 
    ISSN: 1432-1041
    Schlagwort(e): Fluorophenindione ; vitamin K antagonist ; pharmacokinetics ; loading dose ; anticoagulant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary After administration of a single loading dose (80 mg p.o.) of fluorophenindione, the prothrombin level decreased to 37 % in 24 h, and the effect lasted for 48 h. Accordingly, fluorophenindione can be classified as an anticoagulant with an “intermediate” effect. Its elimination half-life was 31 h, which is longer than that of phenindione, because of the greater stability of the fluorinated derivate.
    Materialart: Digitale Medien
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 343-347 
    ISSN: 1432-1041
    Schlagwort(e): Nortriptyline ; pharmacokinetics ; man ; two compartment model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma concentrations of nortriptyline have been assayed in four subjects after intravenous infusion of 57 mg nortriptyline hydrochloride. The data were evaluated according to a two compartment open model. The calculated best-fitting curves were in good agreement with the experimental data, better than could be expected from a simpler model. This justifies the assumption that the kinetics of nortriptyline in man may be described by this model with an appropriate input function. The data permitted estimation of all the parameters of the model. The meaning of the parameters is discussed, particularly in relation to individual variation.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 283-284 
    ISSN: 1432-1041
    Schlagwort(e): Newborn infants ; carbamazepine ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma elimination of carbamazepine (Tegretol®) was studied in five newborns who had got the drug transplacentally from their epileptic mothers. The half-lives ranged from 8.2 – 27.7 hours which is comparable or even shorter than those found in adults after a single oral dose, but in the same range as those found in adults after multiple oral doses. This suggests that the newborns' drug metabolizing capacity has been induced during fetal life.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1975), S. 1-8 
    ISSN: 1432-1041
    Schlagwort(e): Serum concentrations ; individual drug dosage ; pharmacokinetics ; individual variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The importance of individualizing the dosage of potent drugs in order to maximize their therapeutic effectiveness and safety is generally accepted. Whenever possible the dosage of a drug should be “titrated” directly in each patient against the intensity of its therapeutic or toxic actions. Unfortunately, for many drugs convenient clinical yardsticks of the intensity of their pharmacologic effects are lacking. Determination of the serum concentration of such compounds can help to guide adjustment of dosage during their therapeutic use. By measuring the serum level of drugs one bypasses the largest source of individual differences in doseeffect relationships — the pharmacokinetic variation between subjects. However, the relationship between the serum concentration of a drug and the intensity of its pharmacodynamic action is influenced by many other factors, which must always be considered in interpretation of serum levels. Therapeutic decisions should never be based solely on the serum concentration of a compound, nor can such measurements ever substitute for careful medical observation and judgement.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1975), S. 57-61 
    ISSN: 1432-1041
    Schlagwort(e): Furosemide ; gastrointestinal absorption ; diuretics ; glucuronides ; pharmacokinetics ; metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary 35S-furosemide was administered orally (n=7) or i.v. (n=2) to healthy subjects. The average gastrointestinal uptake estimated by comparison of the urinary recovery of label and the areas under the plasma curves after the two routes of administration was 65%. The half life of radioactivity in the plasma after oral35S-furosemide was 90 ± 17 min (estimated on the slope between 2 and 6 h); the corresponding figure after35S-furosemide i.v. was 47–53 min (slope 0.5–4 h). There was probably a slower phase after 4–6 h. Fractionation of labelled material in urine from two subjects demonstrated that approximately two thirds of the label recovered at 24 h had the same chromatographic properties as furosemide. A major part of the metabolite(s) was probably furosemide glucuronide. There was no evidence that 4-chloro-5-sulfamoylanthranilic acid was formed in man. The total urinary recovery of label (5–7 d) after oral and intravenous administration was 55.1±3.2 (mean±SD) and 82–84%, respectively. After35S-furosemide i.v., 6–9% of the label was recovered in faeces, and it could not be accounted for solely by biliary excretion of furosemide.
    Materialart: Digitale Medien
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  • 40
    ISSN: 1432-1041
    Schlagwort(e): Pivampicillin ; ampicillin ; probenecid ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Twenty male volunteers received oral doses (2100, 1050, and 525 mg) of a pivampicillin-probenecid salt in a 1 to 1 molar ratio (MK-356) at 12 hour intervals. After each dose peak serum concentrations of probenecid were observed 2 hours later than peak concentrations of ampicillin. Following the first dose of MK-356 the apparent elimination rate of ampicillin was dose-dependent and did not follow first order kinetics, as it showed a longer apparent half life after a higher dose. An equal dose of MK-356 administered 12 hours later caused an increase in the peak serum ampicillin level greater than expected from the concentration of ampicillin after the preceding dose. In twelve male volunteers who received at random 525 mg of MK-356 or 350 mg of pivampicillin, each three times daily for 4 days, the areas under the ampicillin concentration curve were the same after the first or last dose of either drug. When 2100 or 1050 mg of MK-356 was taken as an initial dose, 30 to 40 per cent of the ampicillin was recovered from urine in the ensuing 12 hours. The results indicate that when at least 400 mg probenecid was coadministered twice daily with 700 mg pivampicillin (MK-356), the peak serum concentrations of ampicillin were increased and its elimination rate slowed following successive doses.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1975), S. 135-145 
    ISSN: 1432-1041
    Schlagwort(e): Anturan® ; 14C-label ; man ; pharmacokinetics ; biotransformation ; C-glucuronidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The absorption, biotransformation and elimination of sulfinpyrazone, 1,2-diphenyl-3,5-dioxo-4-(2′-phenylsufinylethyl)-pyrazolidine, have been studied by administration of single 200 mg oral doses of a14C-labelled preparation to two male volunteers. Absorption from the gastro-intestinal tract was rapid and complete and the plasma concentration of unchanged drug reached maximum values of 22.67 and 13.04 µg/ml, respectively, after 1 – 2 hours. The elimination half-life in the two subjects, calculated from the decline between 3 and 8 hours, was 2.7 and 2.2 hours. The integrated concentration of unchanged sulfinpyrazone in plasma, estimated from the area under the concentration curves (AUC), was almost as high as that of total14C-substances, so the proportion of metabolized drug in plasma was low. In no case did the AUC of the three specifically determined metabolites, i.e. the sulphone G 31 442, the “para-hydroxy”-compound G 32 642 and the “4-hydroxy”-compound GP 52 097, exceed 4% of the sulfinpyrazone value. More than 95% of whole blood radioactivity was confined to plasma. The oral dose was rapidly and completely excreted, since within 4 days more than 95% was recovered, 85% from urine and 10% from faeces. A large proportion of the dose was excreted as unchanged drug in the two volunteers: 51 and 54% of total urinary radioactivity was present as sulfinpyrazone; 8.2 and 8.8% was present as “para-hydroxy”-metabolite, 2.7 and 3.0% as sulphone-metabolite, and 0.6 and 0.8% as “4-hydroxy”-metabolite. About 30% of urinary radioactivity consisted of highly polar metabolites. Spectroscopy of them showed that they were the C-β-glucuronides of sulfinpyrazone (28%) and the corresponding sulfone (2%). In these metabolites the C(4) of the pyrazolidine ring was directly attached to glucuronic acid, and thus they represent a new type of biosynthetic conjugate.
    Materialart: Digitale Medien
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1975), S. 155-159 
    ISSN: 1432-1041
    Schlagwort(e): Anticonvulsants ; benzazepines ; clonazepam ; pharmacokinetics ; gas chromatography ; man
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Eight healthy volunteers were given single i.v. and oral doses of clonazepam (2 mg). The disposition curves after i.v. administration showed a biexponential decline and the data were applied to a two-compartment open model. The volume of distribution ((Vd)β) ranged between 1.5 and 4.4 l/kg and the plasma half-life (t1/2) between 19 and 60 hours. Absorption after oral administration was fast, with peak plasma concentrations within 4 hours in all subjects. Five of the subjects received repeated oral doses of clonazepam 0.5 mg bid for 15 days. The plasma level during steady state (estimated as Cmin within the dose interval) could be predicted from the constants A, B, α and β obtained in the single dose study with a coefficient of variation of 6%. The plasma half-lives after cessation of the subchronic dosing were of the same magnitude as after single doses.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1975), S. 179-187 
    ISSN: 1432-1041
    Schlagwort(e): Etilefrine ; pharmacokinetics ; metabolism ; first-pass effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Pharmacokinetic and metabolic studies with3H-etilefrine were performed to assess the importance of a first-pass effect on the pharmacodynamic action of this sympathomimetic amine. Identical amounts of3H-activity, ca. 80% of the dose, were excreted in the urine after intravenous or oral administration, which indicates complete enteral absorption of the drug. Comparison of the areas under the plasma curves of unchanged etilefrine after both routes of administration resulted in a bioavailability factor of 0.55, which can be explained by an extensive first-pass effect. The time curve of plasma levels of etilefrine was compatible with an open 2-compartment model characterized by a rather large volume of distribution (Vd, β) of 160 1, and a predominant half life of 2 hours. The pharmacodynamic action corresponded to the amount of drug in the central compartment. The major pathway of metabolism of etilefrine was conjugation to form the phenolic sulphate, and a very minor proportion of the drug was excreted as the corresponding hydroxymandelic acid. This metabolic pattern seems to confirm our hypothesis that phenylalkylamines with the hydroxyl group in the m-position of the benzene ring are predominantly conjugated in contrast to p-hydroxylated compounds which are mainly deaminated.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1975), S. 169-178 
    ISSN: 1432-1041
    Schlagwort(e): Heptabarbital ; heptabarbital sodium ; pharmacokinetics ; plasma concentration ; single and multiple dose kinetics ; relative bioavailability ; urinary excretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A method has been developed for the quantitative determination of heptabarbital [5-(1-cyclohepten-1-yl)-5-ethylbarbituric acid] in human plasma after administration of single therapeutic doses of the drug. It involves a single extraction step followed by gas chromatography with alkali flame ionization detection, and the results were linear in the concentration range 0.125 – 5.0 µg/ml plasma. The pharmacokinetics and relative bioavailability of heptabarbital and heptabarbital sodium were studied in a crossover design in 7 healthy volunteers after oral administration of 20 tablets containing 200 mg heptabarbital and hard gelatine capsules containing an equivalent amount of its sodium salt. Heptabarbital concentrations in plasma were determined at regular intervals. The absorption of heptabarbital from the tablets was quite slow and peak level times varied from 1.5 to 4 h. The sodium salt was absorbed more rapidly and peak concentrations occurred between 1/3 and 2 h. In all cases the elimination of heptabarbital could be described by a single first-order process with an average half-life of 7.6 h (range 6.1 – 11.2 h). The half-life of the drug in each individual was about the same in the two trials. The relative bioavailability in each volunteer was estimated by comparing the areas under the plasma concentration curves. The sodium salt had an average bioavailability of 83% relative to the free acid. In some volunteers urinary excretion of unchanged heptabarbital was measured; cumulative excretion amounted to 0.16 – 0.30% of the administered dose. Four volunteers received one tablet each night for eight or ten days, but no accumulation was found. In three volunteers the half-life of the drug prior to and after these experiments did not change, whereas in the other volunteer the half-life decreased from 7.1 to 4.6 h. The possibility of enzyme induction should be considered when heptabarbital is taken regularly. It was concluded that heptabarbital was a suitable drug for the treatment of insomnia, since its half-life was rather short. Heptabarbital sodium may be used for induction of sleep, whereas Medomin® tablets, i.e. heptabarbital free acid, may be prescribed when the maintenance of sleep is the primary reason for treatment with a hypnotic drug.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1975), S. 199-207 
    ISSN: 1432-1041
    Schlagwort(e): Indomethacin ; acetylsalicylic acid ; drug interaction ; oral and rectal dosing ; serum levels ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A clinical-pharmacological study was performed to determine the effect of acetylsalicylic acid upon the serum concentration of indomethacin. 14 rheumatic patients were given indomethacin orally (25 mg × 4 for 4 days) and concurrently acetylsalicylic acid 3.7 g orally (0.9 g × 3 and 1.0 g × 1 daily), and 21 rheumatic patients were given indomethacin rectally in the morning (100 mg × 1) and concurrently acetylsalicylic acid 3.7 g orally (0.9 g × 3 and 1.0 g × 1 daily). On comparison with treatment with oral or rectal indomethacin alone, it was found that peak serum concentrations of indomethacin were significantly reduced (1% level), the times of the peaks were not shifted, and the areas beneath the serum concentration curves of indomethacin were smaller, but significantly so only if compared with rectal administration. In 12 rheumatic patients given indomethacin by rectum in the evening (100 mg × 1) and concurrently acetylsalicylic acid 3.7 g (0.9 g × 3 and 1.0 g × 1 daily), the serum level of indomethacin on the following morning (after 11 h) did not differ from that found after rectal treatment. A statistically but not biologically significant difference was observed between the mean serum half-lives of indomethacin given orally and rectally. For unknown reasons, concurrent doses of acetylsalicylic acid and indomethacin made the mean serum half-life of indomethacin longer than after its oral administration, but shorter than when the same dose of indomethacin was given rectally. There was no difference between serum levels of salicylate after oral administration of acetylsalicylic acid alone or after a concurrent oral or rectal dose of indomethacin. The results have been related to those reported previously, with respect to the interaction between indomethacin and acetylsalicylic acid, the serum levels of indomethacin after oral and rectal dosing, and the serum half-life of indomethacin based upon a one- or two-compartment model. The clinical relevance of the study is discussed.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1975), S. 229-234 
    ISSN: 1432-1041
    Schlagwort(e): Quercetin ; flavonoids ; pharmacokinetics ; absorption ; disposition ; metabolism ; man
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of quercetin, a flavonoid, have been studied in 6 volunteers after single intravenous (100 mg) and oral (4 g) doses. The data after iv administration were analyzed according to a two compartment open model with half lives of 8.8±1.2 min for the α phase and 2.4±0.2 h for the β phase (predominant half life), respectively. Protein binding was 〉98%. The apparent volume of distribution was small at 0.34±0.03 l/kg. Of the intravenous dose 7.4±1.2% was excreted in urine as a conjugated metabolite, and 0.65±0.1% was excreted unchanged. After oral administration no measurable plasma concentrations could be detected, nor was any quercetin found in urine, either unchanged or in a metabolized form. These results exclude absorption of more than 1% of unchanged drug. Recovery in faeces after the oral dose was 53±5%, which suggests extensive degradation by microorganisms in the gut. The data obtained show that oral administration of flavonoids may be of questionable value.
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1976), S. 327-332 
    ISSN: 1432-1041
    Schlagwort(e): Antipyrine ; pharmacokinetics ; half-life ; blood ; plasma ; saliva ; individual variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A previously described GLC method has been modified and applied to measurement of antipyrine levels in plasma, blood and saliva of man following administration of a single oral dose (10 mg/kg). The levels in blood and saliva were comparable to those in plasma at every time studied. The half life of antipyrine determined in blood, plasma or saliva in any given individual was similar. The intersubject variation in half-life was about two-fold (n=5). Antipyrine levels in saliva were not affected by the rate of saliva flow when collections were made continuously for 20 minutes. This study has demonstrated that kinetic data about antipyrine comparable to that from plasma may also be obtained from readily accessible tissue fluids, such as saliva and capillary blood.
    Materialart: Digitale Medien
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1976), S. 319-325 
    ISSN: 1432-1041
    Schlagwort(e): Chlorthalidone ; diuretics ; drug plasma concentration ; protein binding ; red blood-cell concentration ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A gas chromatographic method has been employed to determine chlorthalidone in plasma and whole blood after therapeutic doses. Radioactively labelled chlorthalidone was used for in vitro studies of the uptake of chlorthalidone from plasma by red blood cells. Chlorthalidone was markedly concentrated in red cells and as a compartment they would account for at least 30% of total drug in the body after multiple doses. The ratio between the plasma and red cell concentration of chlorthalidone varied between individuals. After a single oral dose of 50 mg in 6 healthy volunteers chlorthalidone was eliminated with a half-life of 51 to 89 hours. The apparent volume of distribution varied between 3 and 13 1/kg and the clearance between 53 and 145 ml/min. The mean steady-state plasma concentrations during treatment with a standard dose of 50 mg daily (n=10) varied 5-fold between individuals. During the steady state approximately 50% of the daily dose was excreted unchanged in the urine during 24 hrs. The plasma levels observed in patients were higher than those predicted from the single oral dose studies in healthy volunteers.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1976), S. 367-372 
    ISSN: 1432-1041
    Schlagwort(e): Sotalol ; β-adrenoceptor blocking drugs ; exercise tachycardia ; efficacy ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effects of sotalol after oral administration were measured on the tachycardia induced by strenuous exercise in normal subjects. Plasma sotalol levels were also determined. The oral administration of sotalol (50, 100, 200 and 400 mg) to 6 subjects produced a progressive reduction in the tachycardia induced by severe exercise. This was similar to the effects of 25, 50, 100, 200, 400 and 800 mg given to different subjects. Each increase in sotalol dose produced a successively greater reduction in exercise tachycardia. This did not appear to be maximum even with 800 mg. Oral sotalol was rapidly absorbed and produced peak blood levels in 2 – 3 hours. The plasma levels of sotalol measured 2 hours after the oral administration of 25 to 800 mg showed never more than a six-fold variation between different subjects. The half-life of sotalol in plasma was 12.7 ± SE 1.6 hours. There was a significant correlation between the logarithm of the plasma sotalol concentration and the percentage reduction of exercise heart rate. It is concluded that the oral administration of sotalol either once or twice daily (depending on dose level) will provide satisfactory 24-hour blockade of β-adrenoceptors.
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 9 (1976), S. 443-450 
    ISSN: 1432-1041
    Schlagwort(e): Cyclobarbital calcium ; pharmacokinetics ; plasma concentration ; relative bioavailability ; oral administration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and relative bioavailability of cyclobarbital calcium have been studied after oral administration of Phanodorm, of tablets according to the Formularium Nederlandse Apothekers (1968; FNA), and an aqueous solution. Six healthy volunteers participated in the investigation on three occasions and each received the three preparations. The dose administered was 300 mg cyclobarbital calcium. Plasma concentrations of cyclobarbital were determined at regular intervals. Absorption from the three preparations was rapid and was faster from the solution. Peak concentrations were usually attained within 1 h. The elimination of cyclobarbital could be described by a single first-order process with an average half-life of 11.6 h (range 8 – 17 h). There was little intra-subject variation of the half-life. Relative bioavailability for each volunteer was estimated by comparing the areas under the plasma concentration curves. The FNA-tablets and Phanodorm exhibited similar bioavailability, whereas the average bioavailability of the solution was 78% of that of FNA-tablets; the reason for this unexpected finding is unknown. It was concluded that cyclobarbital cannot be regarded as a uniformly suitable drug for the treatment of insomnia. The long half-life that was apparent in some of the volunteers (15 – 17 h) creates a substantial risk of residual effects on the following morning. In principle, however, the calcium salt of cyclobarbital may be used for induction of sleep, because of its rapid absorption.
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 63-69 
    ISSN: 1432-1041
    Schlagwort(e): Diabetes mellitus ; sulfonylurea ; glipizide ; glibenclamide ; pharmacokinetics ; excretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Four subjects received 5 mg14C-glipizide orally, 3 subjects 1 mg intravenously and 2 subjects 5 mg14C-glibenclamide orally. Plasma levels of radioactivity, and urinary and faecal excretion were measured. For both drugs the disappearance of radioactivity from plasma followed complex kinetics and the apparent half-lives increased steadily with time. The two sulfonylureas were extensively metabolized and were excreted in the urine as hydroxylated or conjugated metabolites. The effects of both drugs on blood glucose and immunoreactive insulin were comparable. The findings are compared with other published results.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 91-96 
    ISSN: 1432-1041
    Schlagwort(e): Carbamazepine ; pharmacokinetics ; man ; diphenylhydantoin ; phenobarbital ; plasma binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Carbamazepine (2.7–3 mg/kg) was administered orally as an alcoholic solution (50% v/v) to eight healthy volunteers. Two of the subjects were also given 50 mg and 100 mg of carbamazepine in alcoholic solution and 200 mg as a tablet. Plasma concentrations, which were analysed by mass fragmentography, reached a maximum 1 – 7 hours after dosing, and then declined monoexponentially with half-lives ranging from 24 to 46 hours. The half-lives were independent of dose. The apparent distribution volume ranged from 0.79 to 1.40 l/kg. It was found that 72% of carbamazepine was bound to plasma proteins with little interindividual variation, and this was not influenced by the presence of diphenylhydantoin or phenobarbital in therapeutic concentrations. The pharmacokinetic parameters calculated from single oral doses were used to predict the steady-state plasma concentration expected after treatment with multiple doses of 200 mg three times daily. The predicted steady-state concentration was 2 – 3 times higher than that reported in patients undergoing chronic treatment with carbamazepine at this dose level, i.e. the pharmacokinetics of carbamazepine apparently change during multiple dosing.
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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 217-222 
    ISSN: 1432-1041
    Schlagwort(e): Co-trimoxazole ; sulphamethoxazole ; trimethoprim ; pharmacokinetics ; paediatric-prescribing ; dosage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Co-trimoxazole, a mixture of one part trimethoprim (TMP) and five parts of sulphamethoxazole (SMX) in fixed ratio was given to 48 children aged between one and 48 months twice daily for up to seven days. Twenty were relatively healthy and 28 were very ill. Dosage was based on age. Plasma concentrations of both drugs were measured just before a dose was due and some three hours later. They were in the effective but not toxic range and serve to justify the simple regimen which generated them.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 255-260 
    ISSN: 1432-1041
    Schlagwort(e): Vitamin D ; renal osteodystrophy ; 5,6-trans-25-hydroxycholecalciferol ; rickets ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Vitamin D analogues of high biological activity are probably useful in the treatment of renal osteodystrophy. The pharmacokinetics of the synthetic compound 5,6-trans-25-hydroxycholecalciferol have been studied in healthy subjects who were of normal vitamin D status. In comparison to natural 25-hydroxy-cholecalciferol, serum levels of the analogue were lower and its half-life in blood after oral or intravenous administration was considerably shorter. In normal subjects no increase of dihydroxylated metabolites in serum was observed within seven days of an intravenous dose.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 8 (1975), S. 353-357 
    ISSN: 1432-1041
    Schlagwort(e): Chlormethiazole ; pharmacokinetics ; man ; plasma levels ; gas-liquid chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of chlormethiazole have been studied in six healthy volunteers following an intravenous infusion of the drug. The log. plasma concentration-time curve of chlormethiazole after cessation of the infusion was found to be curvilinear and was fitted therefore, by a bi-exponential equation computed by non-linear least squares regression analysis. Half-lives for the inital α-phase (0.54±0.05 h) and the terminal β-phase (4.05 ±0.60 h) were calculated together with other pharmacokinetic parameters of the two compartment open model. An explanation for the discrepancy between the presently reported plasma half-lives and those appearing in the literature has been presented. The pharmacokinetic treatment of the plasma concentration-time data obtained following intravenous infusion also enabled the prediction that the maximal systemic availability of an orally administered dose of chlormethiazole would be of the order of 15%.
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 16 (1979), S. 203-209 
    ISSN: 1432-1041
    Schlagwort(e): dantrolene sodium ; spasticity ; twitch tension ; dose response ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Dantrolen sodium is a muscle relaxant, which is used in the treatment of spasticity. Although it is given chronically, little is known about its pharmacokinetic behaviour. The relationship between the effect of a single oral dose of dantrolene sodium and its plasma concentration in healthy volunteers was studied by measuring the effect on the twitch tension, and in spastic patients on the decrease in muscle hypertonia. On the twitch tension dantrolene gave a depression of 49.1±9.4% (±SD) within 1.15 and 3.45 h after ingestion of 100 mg. The mean maximal plasma concentration was 1.24±0.32 µg/ml (±SD). The effect and the plasma concentration were correlated. No relationship between the plasma concentration of dantrolene sodium and its effect could be established in patients, although definite activity in 6 out of 7 patients was observed after a single oral dose of 100 mg, and plasma concentration of dantrolene sodium greater than 0.3 µg/ml were consistently associated with better results than placebo treatment in 6 out of 7 patients.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 16 (1979), S. 287-293 
    ISSN: 1432-1041
    Schlagwort(e): linear system theory ; perfusion model ; cardiac output ; pulmonary extraction ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Assessment of pharmacokinetics in terms of circulatory drug transport is proposed using the methods of linear system theory. In this model-independent approach drug distribution and disposition are characterized by the total extraction ratio, the mean residence time in the body and the volume of distribution at steady state. In analyzing concentration(c)-time(t) data, the procedure requires calculation only of the areas under the c(t)-and c(t)×t-curves to estimate kinetic parameters, and for prediction of the steady state concentration following continuous infusion or multiple doses. Pulmonary clearance of drugs is included in the theory.
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 251-256 
    ISSN: 1432-1041
    Schlagwort(e): Sisomicin ; pharmacokinetics ; bioavailability ; two-compartment analysis ; man
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of sisomicin, a new single component aminoglycoside antibiotic related to gentamicin c1a, were determined in four healthy volunteers after intravenous and intramuscular administration of a 1 mg/kg dose. The elimination profile of this antibiotic follows two-compartment model kinetics after I.V. administration. The fast (α) and slow (β) disposition rate constants averaged 0.072 and 0.004 min−1, respectively. The volume of distribution at the steady-state averaged 0.185 liters/kg which approximately corresponds to the volume of extracellular space. The physiological availability of an intramuscular dose appeared to be complete. A method of administration adapted to the kinetic properties of the drug is proposed.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 311-317 
    ISSN: 1432-1041
    Schlagwort(e): Hydralazine ; instability of impaired renal function ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Following a single 50 mg dose of hydralazine (Apresoline®) in 13 patients with impaired renal function, a decrease in glomerular filtration rate (GFR) was correlated with an increase in serum half-life (T1/2) of the drug (r=−0.69; p〈0.01). The T1/2 was 15.8 h in one patient with a GFR of 16 ml·min−1, as compared to a T1/2 of 1.7–3.0 h found previously in 16 healthy volunteers. In 49 patients on long-term antihypertensive treatment with hydralazine, the ratio between the minimum steady-state drug concentration and the daily dose of hydralazine (C SS min : Dose) increased as the GFR decreased. This accumulation of the drug was particularly evident in patients with a GFR less than 30 ml·min−1 (r=−0.63; p〈0.01; n=19). As renal excretion of unchanged hydralazine is generally regarded as unimportant, the slower elimination rate in chronic renal failure was probably caused by a slower rate of metabolic conversion. It was found, however, that the renal excretion of hydralazine could easily have been underestimated, as only 12.7% of an initial hydralazine concentration of 200 ng·ml−1 in urine could be recovered after storage of the samples at room temperature for 24 h.
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 325-330 
    ISSN: 1432-1041
    Schlagwort(e): Flutiorex ; pharmacokinetics ; sex ; anorectic agent ; sympathetic stimulation ; CNS stimulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effects of flutiorex, a new anorectic agent, and of a placebo on food intake and the activity of the sympathetic and central nervous systems have been compared in a double blind trial in two groups of healthy volunteers, one of five males and the other of five females. Flutiorex 20 mg orally had a significant anorectic effect both in males and females, the observed reduction in food intake being 34.0 and 27.5%, respectively. It caused α-adrenergic stimulation (blood pressure and pupil diameter) and central nervous system excitation (critical flicker frequency), both of which were more marked in males than in females. Flutiorex was better tolerated by women than by men. Measurement of the blood level of flutiorex and its de-ethylated metabolite, norflutiorex, showed that both compounds were detectable in four of the five male subjects, but in only one of the five females. Sex-linked differences in the pharmacokinetics of flutiorex may explain the greater intensity of its effects in males.
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 343-347 
    ISSN: 1432-1041
    Schlagwort(e): Methaqualone ; hypnotic ; pharmacokinetics ; combination formulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Concentrations of methaqualone have been measured in the serum of five male human subjects receiving five consecutive evening doses of a combination formulation containing methaqualone (250 mg), carbromal (300 mg) and benactyzine (0.33 mg) in each tablet. After administration of the first dose, mean peak serum concentrations of methaqualone (1.2 µg/ml) occurred at 3 h. After obtaining peak levels, mean concentrations of methaqualone declined rapidly during the next 6 h and there-after more slowly during the next 18 h. After administration of the last (fifth) dose, mean peak serum concentrations of methaqualone (1.9 µg/ml; 1.5 µg/ml above the predose level) occurred at 2 h. After attaining peak levels, mean concentrations of methaqualone declined rapidly during the next 6 h, and thereafter more slowly, with a half-life of approximately 10 h. Mean concentrations of methaqualone in serum samples 24 h after the second, third, fourth or fifth doses were not significantly different (0.3 µg/ml – 0.6 µg/ml) during this period of dosing. This suggests that significant accumulation of methaqualone in the serum did not occur during a period of five consecutive evening doses of the combination formulation.
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 137-145 
    ISSN: 1432-1041
    Schlagwort(e): Chlormethiazole ; pharmacokinetics ; metabolites ; oral administration ; young and elderly human subjects ; quantitative gas chromatographymass spectrometry ; whole blood distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma concentration of chlormethiazole and two of its metabolites has been measured in three young and three aged human subjects following administration of a single oral dose of chlormethiazole. A sensitive analytical method based on gas chromatography-mass spectrometry using the selective ion monitoring mode of operation was developed to permit quantitation of the plasma levels. The time course of the plasma concentration of chlormethiazole and metabolites showed wide inter-subject variation, particularly between the young and elderly subjects. Absorption of chlormethiazole was rapid in the subjects of both groups as assessed by the time taken to reach the peak plasma concentration. The mean peak plasma level of chlormethiazole was more than five times greater in the elderly (2.90±1.56 µg/ml) than in the young (0.55±0.58 µg/ml) subjects. The plasma level of chlormethiazole was consistently higher in the aged subjects and this was reflected by the larger area under the plasma curve in aged (7.62±5.37 µg.h/ml) than in young (0.94±0.66 µg.h/ml) individuals. Decreased pre-systemic elimination by the liver has been suggested as an important factor contributing to the higher plasma level in the elderly. Estimates of absolute systemic availability, calculated by reference to previous intravenous studies, were greater for the elderly subjects. The distribution of chlormethiazole in whole blood from six young and six elderly human subjects was investigated in vitro. The unbound fraction of chlormethiazole in plasma increased significantly from 0.308±0.035 in young subjects to 0.403±0.067 in the elderly. Distribution of the drug in whole blood was different for the two age groups; the fraction of drug distributed to plasma water was significantly greater and the fraction in blood cells was significantly less in the aged.
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 171-174 
    ISSN: 1432-1041
    Schlagwort(e): Tolamolol ; hypertension ; pharmacokinetics ; mean steady-state concentration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Tolamolol was administered in a “double-blind” study to fifteen hypertensive patients by dose-titration against arterial blood pressure. Mean steady-state plasma tolamolol concentrations (Css) were determined for each patient from the area under the plasma concentration — time curve during a dosage interval whilst patients were receiving optimal tolamolol doses. No significant correlation was observed between daily tolamolol dose and Css; the relationship between fall in lying mean arterial pressure and Css also failed to reach conventional levels of statistical significance, but Css was observed to be correlated with the fall in standing pressure. The results suggest that plasma concentrations in excess of 200 ng/ml may be required to achieve an effective hypotensive response with the drug.
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 341-344 
    ISSN: 1432-1041
    Schlagwort(e): Muzolimine ; pharmacodynamics ; pharmacokinetics ; furosemide ; saluresis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In a biometrically planned, double-blind study on 12 Oedema-free male patients the saluretic effect of muzolimine 30 mg was compared with furosemide 40 mg. The plasma level of muzolimine was determined and correlated with its pharmacodynamics. In terms of excretion during the 12-hour observation period muzolimine 30 mg had as great a cumulative effect as furosemide 40 mg. There was a significant difference in the time-response curve. During the first two hours furosemide 40 mg had more saluretic effect than muzolimine 30 mg. Between two and four hours there was no significant difference between the two substances. Between four and six hours, however, muzolimine was somewhat more effective than furosemide, although the difference did not reach the level of significance. After 6 h there was no longer any difference between the two compounds. The half-life of the fall in concentration of muzolimine in plasma was 3.7 up to 10 h after its administration. The time-response curve of the increased urine excretion correlated well with the time course of the concentration of muzolimine in plasma.
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 125-132 
    ISSN: 1432-1041
    Schlagwort(e): Valproic acid ; pharmacokinetics ; saliva concentration ; urinary excretion ; serum protein binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of valproic acid (VPA) have been studied in 6 healthy subjects following a single 600 mg dose, and after multiple doses over 12 days (1200 mg daily) of enteric-coated sodium valproate. A time lag before absorption of 1 to 2 h was observed in each subject, and then absorption was rapid, peak concentrations being recorded 3 to 4 h after administration of the dose. The plasma level decline was biphasic with a terminal half-life of 15.9±2.6 h in the single dose and 17.3±3.0 h in the multiple dose experiments. There was no evidence of dose dependent kinetics or autoinduction. Total plasma clearance was 0.0064±0.0011 l/kg×h. The apparent volume of distribution was small at 0.15±0.2 l/kg. The mean steady state plasma concentration (Css) reached after 4 days was 81.3±13.0 µg/ml. Css observed was lower than Css predicted (99.2±14.7 µg/ml) from single dose kinetics (p〈0.001). The difference was probably due to a reduction in plasma protein binding at higher concentrations. VPA concentration in saliva was between 0.4 and 4.5% of the total plasma concentration and was not equal to the concentration of unbound drug in plasma (6.7±0.8% unbound). 3.2% of the dose was excreted in urine as the parent drug and 21.2% as conjugated metabolites.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 367-373 
    ISSN: 1432-1041
    Schlagwort(e): Sulphamethizole ; tetracycline ; doxycycline ; rest ; exercise ; pharmacokinetics ; excretion ; absorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The serum level and urinary excretion of sulphamethizole, tetracycline and doxycycline were studied in healthy volunteers subjected to intensive exercise and bed rest in a cross-over trial. Each group consisted of 7–8 subjects. The exercise or bed rest began 15 min before oral administration of the drug and was continued for the following 4 hours. During exercise serum drug concentration and the area under the serum concentration-time curve for each agent was significantly higher (p〈0.05) than the corresponding values at rest. Exercise greatly suppressed the renal excretion of tetracycline and doxycycline, but the decrease alone appeared insufficient to account for the pronounced increase in serum drug concentration. Total drug excretion in urine was unchanged. Thus, it seemed most unlikely that overall absorption from the gastrointestinal tract had been altered by exercise. However, the rate of absorption appeared to be more rapid in the exercise than in the rest period. Marked haemoconcentration was not produced by the exercise. In addition to changes in absorption and elimination rates, alteration in the volume of distribution might contribute to the higher serum drug concentration during exercise. Therefore, the level of physical activity should be considered in the interpretation of pharmacokinetic data both in clinical practice and in pharmacokinetic studies.
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 275-284 
    ISSN: 1432-1041
    Schlagwort(e): Diazepam ; pharmacokinetics ; pregnant women ; plasma clearance ; blood/plasma concentration ratio ; placental transfer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The disposition of diazepam has been studied in pregnant women at parturition. The plasma concentration of diazepam was monitored for at least 3 days in 18 women who received a single intravenous injection of 10 mg during the 10 h-period prior to delivery. Fourteen mothers had uneventful puerperia (Group I) and in 13 of these cases there was a pronounced postnatal increase in the plasma concentration of diazepam. The terminal phase half-life (t1/2) was significantly greater for Group I (mean = 65 h; range = 24–114 h) than for age-matched non-pregnant patients (mean = 29 h; range = 18–44 h from literature). The prolonged t1/2 appeared to be related to changes in the distribution of diazepam and not to a reduction in hepatic elimination since the total plasma clearance (Cltp) in these 14 pregnant patients (mean = 28 ml/min; range = 18–43 ml/min) was not reduced compared to that reported for non-pregnant controls (mean = 30 ml/min; range = 22–45 ml/min). Four mothers underwent postnatal surgery for tubal ligation (Group II) and the plasma concentration-time profiles for this group did not show the same postnatal phenomenon as did the profiles obtained for Group I. The t1/2 for Group II was shorter (mean = 31 h; range = 24–37 h) than for Group I and similar to that for the non-pregnant controls. The Cltp for Group II was greater (mean = 56 ml/min; range = 48–63 ml/min) than for both Group I and non-pregnant controls. These results suggest that delivery alters the disposition of diazepam and is generally associated with a postnatal re-distribution of diazepam into the systemic circulation. The blood/plasma concentration ratio was determined in 9 patients (mean = 0.62; range = 0.54–0.77). There was no difference in the total blood clearance between the pregnant patients of Group I and the non-pregnant controls. In most cases the umbilical venous plasma concentration (Cpuv) of diazepam was greater than the peripheral maternal venous plasma concentration (Cpmv) at delivery. The foetus appears to constitute a slowly equilibrating tissue-group in which diazepam does not reach equilibrium with the maternal systemic circulation for at least 5–10 h at which time the diazepam concentration in maternal and foetal plasma is similar.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 49-53 
    ISSN: 1432-1041
    Schlagwort(e): p-Chlorophenoxyisobutyric acid ; clofibrate ; steady-state plasma concentrations ; bioavailability ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma concentrations and bioavailability of clofibrinic acid have been estimated under conditions approaching the steady-state during a ten-day period of administration as clofibrate or as a calcium clofibrinate-carbonate combination (1:1 w/w) at a dosage interval of 12 h. Formulation — related differences in bioavailability were not significant, and the 95% confidence limits of these differences were within −2% to +8% of the mean for the reference formulation of clofibrate. The mean steadystate plasma concentrations of clofibrinic acid measured on the tenth day of dosing were 116 µg/ml±22 S.D. and 119 µg/ml±23 S.D. after administration of 885 mg as clofibrate and the calcium clofibrinate-carbonate combination respectively. The peaks of mean plasma concentrations were 70 µg/ml±15 S.D., 119 µg/ml±32 S.D. and 131 µg/ml±26 S.D. on the first, fifth and tenth day of dosing with clofibrate, and 62 µg/ml±13 S.D., 127 µg/ml±S.D. and 143 µg/ml±25 S.D. on the corresponding days of dosing with the calcium clofibrinate-carbonate combination. After the last dose on the tenth day of dosing, the mean apparent half-lives of elimination of clofibrinic acid from plasma were 24.2 h±4.4 S.D. and 25.5 h±3.2 S.D. after administration of clofibrate and the calcium clofibrinate-carbonate combination respectively.
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 69-72 
    ISSN: 1432-1041
    Schlagwort(e): Phenazone ; pharmacokinetics ; hydrocortisone ; elimination rate ; distribution volume
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of a high plasma concentration of hydrocortisone on the metabolism of phenazone in humans has been studied. Two series of experiments were carried out, Group A to demonstrate any enzyme-inducing effect of hydrocortisone, and Group B to study the immediate effect of hydrocortisone on the metabolism of phenazone. 9 subjects (Group A) received a total 250–400 mg hydrocortisone i.m. twice daily for three days and the 24-hour elimination of phenazone was studied before and afterwards. In a further 5 subjects (Group B) the elimination of phenazone was examined during administration of hydrocortisone or placebo. The elimination rate and the apparent volume of distribution of phenazone remained unchanged under both experimental conditions.
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  • 70
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 97-101 
    ISSN: 1432-1041
    Schlagwort(e): Clonidine ; plasma level ; pharmacokinetics ; steady state ; urinary excretion ; side-effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A single oral dose of clonidine 300 µg was administered to 8 healthy, normotensive subjects and the time course of its plasma concentrations was followed for 24 h. The plasma concentration of clonidine rose to a peak of 1.17±0.12 ng/ml at about 2 h: the absorption half-life was 0.6±0.2 h. Elimination followed first order kinetics with a half-life of 7.7±2.0 h. The correlation between the two most common side-effects of clonidine, sedation and dryness of the mouth, with the time course of its plasma concentrations was highly significant, p〈0.01. All the subjects complained of severe sedation. During continuous administration of clonidine (75 µg t.i.d.) for one week a steady state serum level of 0.30–0.35 ng/ml was achieved. One 75 µg tablet of clonidine raised the serum level to about 0.69±0.13 ng/ml in two hours. After cessation of dosing, the serum level declined with a half-life of 7.5±1.5 h. The urinary excretion of unchanged clonidine was found to be about onethird of the administered dose in 24 h during continuous administration and in the first 24 h after the single oral dose.
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 14 (1978), S. 203-212 
    ISSN: 1432-1041
    Schlagwort(e): Mepivacaine ; pharmacokinetics ; neonates ; healthy adults ; metabolism ; renal excretion ; lignocaine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and metabolism of mepivacaine has been studied in premature neonates dosed subcutaneously and in healthy adults dosed intravenously. The pharmacokinetics of mepivacaine in four neonates (N) was compared with that in six adults (A). Newborns had a significantly longer terminal phase half-life than adults (N mean 8.69 h; A mean 3.17 h). Total plasma clearance normalized on body weight was significantly smaller in neonates (mean 2.34 ml/min/kg) than in adults (mean 5.47 ml/min/kg), as was the hepatic blood clearance (N mean 1.37 ml/min/kg; A mean 5.10 ml/min/kg). The renal plasma clearance, however, was significantly greater in neonates (mean 0.76 ml/min/kg) than adults (mean 0.20 ml/min/kg). There was an average six-fold increase in the fraction of the dose excreted unchanged in newborns (mean 43.3%) compared to adults (mean 7.1%) with acidified urine (pH 5.5–6.0). There was significantly more of the mono-N-demethylated metabolite of mepivacaine excreted by newborns (mean 11.4%) than by adults (mean 2.2%), but their capacity to carry out aromatic hydroxylation of mepivacaine was negligible. These results for mepivacaine were compared with those previously reported for lignocaine in premature infants. The immaturity of hepatic function appears to have diminished more profoundly the ability of premature infants to metabolize mepivacaine than lignocaine. These findings are discussed in terms of perfusion theory of hepatic drug elimination.
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  • 72
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 14 (1978), S. 143-147 
    ISSN: 1432-1041
    Schlagwort(e): Children ; leukemia ; high-dose methotrexate ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of intravenous high-dose methotrexate were studied in two groups of children being treated for malignant diseases, mostly acute lymphatic leukemia. The peak serum level of methotrexate of 2.32·10−5 mol/l was found in children given 500 mg methotrexate/m2 by a 24 h infusion, and another group given 2790 mg/m2 during a 6 h infusion had serum levels as high as 2.16·10−4 mol/l. The decay of serum concentration of methotrexate after completion of the infusion followed a diphasic curve, with an initial serum half-life of 4.8 h, followed by a second half-life of 34.4 h at distribution equilibrium. The apparent volume of distribution was 56.8 litres/m2. Significant levels of methotrexate were found in cerebrospinal fluid, but penetration into cerebrospinal fluid was slow. Urinary excretion of methotrexate was considerable. Four to five days after commencement of the infusion, urinary concentrations of methotrexate still exceeded the serum levels.
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 14 (1978), S. 335-340 
    ISSN: 1432-1041
    Schlagwort(e): Drug binding to muscle ; interindividual differences ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Binding of 22 drugs to human muscle tissue has been determined by ultrafiltration. All drugs tested were bound, the bound fraction ranging from 13% (aminophenazone) to 〉98% (desipramine). Both linear and nonlinear binding was observed. For chemically related substances, binding to muscle tissue correlated with plasma binding and lipid solubility. There were significant differences in binding to muscle from different individuals. With respect to pharmacokinetics of drugs, it is suggested that binding to muscle tissue may be at least as important as plasma binding.
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 15 (1979), S. 275-280 
    ISSN: 1432-1041
    Schlagwort(e): Parkinson's disease ; bromocriptine ; pharmacokinetics ; plasma concentration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma kinetics of bromocriptine (BCT), a long-acting dopamine agonist, was studied in twelve patients with Parkinson's disease, using a newly developed gas chromatographic method of analysis. Each patient received BCT for at least three weeks in a constant but different dose regimen. Concomitant treatment with 1-DOPA was not allowed. During a 6-day hospitalization period, a blood sample was taken immediately before the afternoon dose at 14.00 h (Cmin) to determine the steady-state level. On the 6th day blood samples were collected every hour during two 8 h dose intervals. The results showed a significant correlation between the mean values of the AUC and the Cmin. First order elimination kinetics appeared to be followed by BCT, at least for the plasma concentrations commonly found. Considerable inter-individual variation was demonstrated both for the dose/plasma concentration ratio and for calculated plasma clearances. No serious side-effects were observed during the investigation.
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  • 75
    ISSN: 1432-1041
    Schlagwort(e): indobufen ; platelet aggregation ; food effect on bioavailability ; repeated administration ; pharmacodynamics ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effect of food on bioavailability of indobufen tablets was investigated in 6 healthy volunteers. Subsequently, the same subjects took 100 mg b.i.d. for 7 days. Plasma levels and urinary excretion of indobufen were determined by GLC. Platelet aggregation induced by several concentrations of adrenaline was determined turbidimetrically at various times after the first and last doses. The absorption of indobufen tablets was not substantially impaired by the presence of food in the GI tract, although peak plasma levels and AUCs were slightly reduced after food. Pharmacokinetic analysis of plasma and urinary levels of indobufen did not indicate any change in drug disposition after repeated dosing. Adrenaline-induced platelet aggregation was markedly inhibited for up to 12 h after the first dose and the intensity and duration of this effect did not change after repeated administration. A twice-daily dosing appears suitable for clinical trials.
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 15 (1979), S. 341-347 
    ISSN: 1432-1041
    Schlagwort(e): clofibrate ; chlorophenoxyisobutyric acid ; disposition ; hepatitis ; cirrhosis ; renal failure ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The disposition of clofibrate over 96 hours was observed following single oral dose in six patients with acute viral hepatitis, six patients with liver cirrhosis, seven patients with renal insufficiency, and six control subjects. No parameter of the disposition of CPIB (active form of clofibrate) was significantly altered in acute hepatitis. In liver cirrhosis, the mean plasma half-life was unchanged compared to controls (20.9 vs. 17.5 h), but plasma clearance of the non-protein bound drug was reduced (115 vs. 243 ml×min−1), plasma protein binding was reduced (92.8 vs. 97.2 percent), and the apparent volume of distribution was increased (0.20 vs. 0.141×kg−1). In renal insufficiency plasma half-life was prolonged 2 to 6-fold, depending on the degree of renal impairment. Total plasma clearance (3.4 vs. 7.1 ml×min−1) and plasma clearance of the unbound drug (81 vs. 243 ml×min−1 were reduced in patients with renal failure, the clearance of the unbound drug being inversely correlated with the serum creatinine concentration. Renal failure was also associated with decreased protein binding and an increased volume of distribution of CPIB, and with reduced urinary excretion of CPIB and its glucuronide metabolite. The dose of clofibrate should be halved in patients with cirrhosis. In renal insufficiency, the dose should be adjusted according to the individual serum creatinine level: only 10 to 15% of the usual weekly dose should be given in complete renal failure.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 15 (1979), S. 363-366 
    ISSN: 1432-1041
    Schlagwort(e): methotrexate ; protein binding ; ultrafiltration ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The protein binding of methotrexate by serum from eight normal volunteers was assessed by continuous ultrafiltration at pH 7.4 and 37°C. Methotrexate concentrations were measured by radioimmunoassay and the data analysed by the method of Scatchard. The major binding protein was albumin which bound 87.3% of the drug in serum. Analysis of the Scatchard plots indicated two distinct groups of binding sites. Class I was found to have 0.16±0.05 (S D) binding sites with an intrinsic association constant of 71.15±35.98 (S D)×104 M−1: Class II had 2.01±0.93 (S D) binding sites and an affinity of 0.18±0.15×104 M−1. No great change in the percentage of methotrexate bound occurred until the total concentration of the drug exceeded 50 µMol 1−1.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 257-262 
    ISSN: 1432-1041
    Schlagwort(e): Anti-inflammatory and analgesic drug ; indoprofen ; pharmacokinetics ; bioavailability ; man
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In a pharmacokinetic study of the new analgesic and anti-inflammatory drug indoprofen, plasma levels and urinary excretion were determined in four healthy volunteers after 100 mg and 200 mg iv, and after 100 mg (capsules) and 200 mg (tablets) oral doses. After iv administration, the mean biological half-life (t1/2 β) was about 2 h (range 1.4 to 3.2 h). The apparent volume of distribution Vdβ ranged between 11 to 17 % of body weight, indicating its limited extravascular distribution. Most of the drug was excreted in urine as glucuronide and a smaller proportion as unchanged indoprofen: the 24 h urinary excretion of these compounds accounted for 67 to 95 % of an iv dose. Peak plasma levels occurred between 30 and 120 minutes after oral administration of 100 mg as capsules or 200 mg as tablets. The mean biological half-life was about 2 h, as after iv administration. The bioavailability of oral doses was assessed using both plasma levels and urinary excretion data. The absorption of capsules and tablets was practically complete, that of the former being faster.
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 25-29 
    ISSN: 1432-1041
    Schlagwort(e): Digoxin ; exchange transfusion ; pharmacokinetics ; neonates ; 86Rb assay
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary By means of an86Rb-uptake inhibition assay, changes in the plasma concentration of digoxin and the amount of the glycoside removed during exchange transfusion have been studied in two newborns. For comparison, the exchange procedure was simulated by a computer on the basis of a two-compartment open model and available pharmacokinetic constants. A rapid decrease in plasma digoxin concentration during exchange transfusion was found when the glycoside was administered intravenously or intramuscularly within 60 min before the procedure. The amount of digoxin removed by the exchange was less than 6 per cent of the given dose. Computer simulation of the procedure also showed removal of only a minor amount of digoxin. It is concluded that the decrease in plasma concentration and the removal of only a small amount of glycoside by the exchange transfusion can be attributed mainly to extensive tissue distribution of digoxin. The results imply that replacement of digoxin after an exchange transfusion seems unnecessary.
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 43-48 
    ISSN: 1432-1041
    Schlagwort(e): Spironolactone ; acetylsalicylic acid ; fludrocortisone ; kinetics ; pharmacology ; interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of 600 mg acetylsalicylic acid (ASA) on the renal excretion and clearance of canrenone, the principal unconjugated metabolite of spironolactone, was examined in a double-blind crossover study in six healthy subjects. ASA significantly reduced the urinary excretion, and the fractional excretion, of canrenone between 4 — 6 hours after administration of 50 mg spironolactone. The pharmacological activity of spironolactone, assessed simultaneously by alterations in fludrocortisone-induced urinary electrolyte changes, was slightly but not significantly reduced. The reductions in urinary canrenone excretion correlated with changes in the urinary log 10 Na/K ratio. The results suggest that canrenone may be actively secreted at the proximal renal tubule, and that secretion is blocked by ASA or its conjugates. This is a possible mechanism for the pharmacological interaction between ASA and spironolactone which has been described previously.
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 121-126 
    ISSN: 1432-1041
    Schlagwort(e): Diazepam ; pharmacokinetics ; subchronic dosage in man ; desmethyldiazepam
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In seven healthy male volunteers the effects of the pattern of dosing on the pharmacokinetics of diazepam have been studied. A cross-over design was employed that consisted of three parts: a single intravenous dose (0.1 mg/kg), and oral dosing (10 mg/day) for six days followed by an intravenous bolus (0.1 mg/kg) on the seventh day, followed by re-examination of a single intravenous dose after diazepam (D) and its major metabolite desmethyldiazepam (DD) had been completely eliminated. Plasma levels of D and DD were monitored by a specific, sensitive GLC-method. In younger patients (n=5, age 29 – 35 years) the elimination half-life, T1/2 (β), of D was 33.9±10.6 h (mean±S.D.) after the single dose. The control study gave an almost identical result (35.7±12.1). After subchronic dosage in all patients T1/2 (β) showed a modest but significant prolongation (paired t-test p〈0.01) to 52.9±17.4 h. It was caused by a significant decrease (p=0.016) in total plasma clearance ( $$\overline {\user1{Cl}} $$ ), from 26.0±10.8 ml/min to 18.2±7.0 ml/min. Older patients (age 43–60 years) showed the same phenomenon. Blood/plasma ratios remained constant indicating no change in protein binding. Biliary excretion of D was measured in five patients with a T-tube. Only negligible amounts (0.3–0.4%) of administered D were excreted within 3 days after subchronic dosage, which demonstrates a lack of enterohepatic cycling of D. After multiple administration of D, there was accumulation of DD to levels approximately five times higher than after a single dose. The possibility that the slower elimination of D after subchronic treatment might be caused by DD was also supported by experiments in dogs and rabbits. After pretreating rabbits with DD and maintaining a high DD plasma level, there was prolongation of T1/2 (β) from 2.7 h to 5.2 h, with a corresponding decrease of $$\overline {\user1{Cl}} $$ from 101.6 ml/min to 23.4 ml/min. Similar results were obtained in dogs. It is concluded that the disposition of D is altered by subchronic use and may be regulated by the plasma DD concentration.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 11 (1977), S. 149-154 
    ISSN: 1432-1041
    Schlagwort(e): Hydroflumethiazide ; spectrofluorometry ; pharmacokinetics ; plasma half life ; renal excretion ; renal disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A spectrofluorometric method for determination of hydroflumethiazide in human plasma and urine has been developed. The limit of detection was 10 ng/ml plasma and 100 ng/ml urine. The plasma concentration of hydroflumethiazide was determined for 9–11 hours and excretion in urine for 24–37 hrs after oral administration of about 1 mg/kg body weight to 7 subjects. Plasma half life in healthy subjects was 1.9–2.1 h, and 2.7–8.6 h in patients during the period 4–9 hrs after dosing. Cumulative excretion in urine was 67–79% of the dose during 31–37 hrs in 6 subjects; one patient with renal disease was found to excrete only 25.8% of dose during 24 hours. Renal clearance of hydroflumethiazide was higher in the healthy subjects (0.29–0.44 1 h−1 kg−1) than in the patients (0.040–0.15 l h−1 kg−1). Plasma half life of hydroflumethiazide was not closely correlated with renal clearance of the drug, which suggests that other factors may play a role in determining plasma half life.
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 16 (1979), S. 243-249 
    ISSN: 1432-1041
    Schlagwort(e): timolol ; beta blockade ; pharmacokinetics ; pharmcodynamics ; acute administration ; chronic administration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and effects of various oral doses of timolol administered either acutely or after chronic medication for 7 days were studied in healthy volunteers. After acute administration of timolol maximum plasma concentrations were attained within 1–2 h and thereafter declined exponentially with time. The mean apparent half-life of elimination from plasma was 2.5 h and was independent of dose. Area under the plasma concentration-time curve (AUC) was proportional to the orally administered dose. Plasma concentrations, apparent elimination half-life and AUC were not altered after one week of chronic administration. The effect of timolol on heart rate and blood pressure response to three sequentially increasing ‘steady state’ work loads were studied. After acute administration of timolol maximum reduction of systolic blood pressure, resting heart rate, and the different parameters of the work-heart rate (or blood pressure) relationships were produced by 5 mg timolol. Increasing the dose prolonged the duration over which these variables were reduced. The relationship between timolol plasma concentration and inhibition of different parameters of the exercise response was hyperbolic with half maximum inhibition at concentrations of about 3–4 ng/ml of timolol and maximum inhibition above 30 ng/ml. Maximum drug effects and duration of action of timolol on the different variables were similar after acute and chronic administration.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 16 (1979), S. 263-270 
    ISSN: 1432-1041
    Schlagwort(e): diazepam ; alcoholic beverages ; plasma level ; pharmacokinetics ; co-ordination skills ; red wine ; white wine ; whisky
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Twenty paid healthy students ingested diazepam 10 mg 30 min after the administration of ethanol 0.8 g/kg. The alcoholic beverage used was varied in randomized double-blind experiments, which were repeated at one-month intervals. Psychomotor performance, plasma diazepam, and alcohol concentration in breath were measured 30, 60, 90 min and 2, 3, 4, 6 and 24 h after the ingestion of diazepam. Beer and white wine elevated the plasma level of diazepam and the effect lasted for up to 2 h. Whisky elevated the diazepam level for 90 min. Red wine did not affect it significantly. The alcohol-diazepam combination impaired tracking skills and oculomotor co-ordination and enhanced nystagmus, more than diazepam alone. Red wine produced a breath alcohol concentration higher than after white wine. More nystagmus was recorded after red wine and diazepam, although white wine led to a higher plasma diazepam concentration. It appears that simultaneous ingestion of alcohol and diazepam accelerates the absorption of diazepam. This pharmacokinetic alteration may not contribute much to the combined psychomotor effects of diazepam and alcohol, which were mainly due to pharmacodynamic interaction at receptor level.
    Materialart: Digitale Medien
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 16 (1979), S. 271-277 
    ISSN: 1432-1041
    Schlagwort(e): lithium ; litarex ; single dose ; multiple dose ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary An analysis of the single and multiple dose pharmacokinetics of lithium in 7 healthy volunteers is presented. A solution of lithium chloride was administered in single dose experiments and the same solution and a sustained release preparation were employed in multiple dose experiments, which were carried out at steady state. A fixed dose of 24 mmol was used in the single dose experiments and in the subsequent multiple dose experiments in the same subjects the same dose was administered once daily for a week. Distinct two-compartment characteristics were found, with a mean disposition rate constant (β) of 0.035 h−1±0.010 SD, corresponding to a mean biological half-life of about 19.8 h. The mean half-time of the distributory α-phase was about 1.15 h. The absorption of lithium from an orally administered solution took place with a half-time of about 0.15 h in the single dose experiments. The apparent volume of distribution of the central compartment (Vc) was 0.307 1 kg−1±0.046 SD, less than half that of Vde at equilibrium. Vdβ (Vdarea) was 0.8291 kg−1±0.184 SD and mean total body clearance was 27.6 ml kg−1 h−1±4.7 SD.
    Materialart: Digitale Medien
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 16 (1979), S. 255-262 
    ISSN: 1432-1041
    Schlagwort(e): spironolactone ; canrenone ; fluorimetry ; high performance liquid chromatography ; linear kinetics ; saturation kinetics ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In Study I 20 normal volunteers received a single oral dose of spironolactone 100 mg. In Study II a further 20 normal volunteers were given first spironolactone 100 mg b.i.d. and subsequently spironolactone 100 mg once a day for a further 4 days. In Study III 5 normal subjects were given a single dose of spironolactone 500 mg. The concentration of canrenone in serum was determined both by fluorimetry and HPLC for 0–48 h in Study I, 120–168 h in Study II and 0–36 h in Study III. The total AUCs after the single 100 mg dose did not differ from the AUCs within the dosing interval during steady state. The half-lives of the terminal log-linear phases were almost identical (14.99±0.80 h and 15.69±0,80 h) when determined by fluorimetry, and were sligthly, but significantly (p〈0.01), longer when determined by HPLC — 20.14±1.62 and 18.71±1.04. The mean ratio of the specific AUC determined by HPLC and the fluorimetrically determined AUC was 0.3 after the single 100 mg dose. It did not differ from the corresponding value during steady state (0.34). In contrast, the ratio after the single 500 mg dose was approximately 50% higher. Fluorimetrically determined AUCs after 100 and 500 mg doses did not show dose-proportionality in contrast to the HPLC-determined AUCs. It was concluded that Canrenone contributes much less to the conventional fluorimetric determination than was previously assumed. It may not provide more than 1/10 and 1/4 of the antimineralocorticoid activity of spironolactone after single dose and multiple doses, respectively. Whereas linear kinetics apply after single and multiple 100 mg doses of spironolactone, after 500 mg saturation kinetics must be assumed with respect to metabolism. Thus, in bioavailability studies high doses of spironolactone should be avoided. For such studies the fluorimetric assay seems to be the appropriate bioanalytical method in spite of its lower specificity.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 355-357 
    ISSN: 1432-1041
    Schlagwort(e): Nitrazepam ; placental transfer ; pharmacokinetics ; plasma levels ; protein binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Six women from 14 to 17 weeks pregnant, and 12 woman from 36 to 40 weeks pregnant, were given nitrazepam 5 mg orally about 12 h before legal abortion by hysterotomy in the former group and elective caesarean section in the latter group. The concentration of nitrazepam was determined by gas-liquid chromatography. Binding to plasma proteins was evaluated by separation of the protein-free fraction by ultracentrifugation. In the first group (early pregnancy) the level of nitrazepam was found to be lower in the fetal than in the maternal circulation. The concentration in amniotic fluid was still lower. In the latter group (late pregnancy) the concentration both of unbound and total nitrazepam in maternal and fetal plasma were in equilibrium, which indicated an increase in transplacental transfer in late pregnancy. The percentage of unbound nitrazepam in both cases was 12%.
    Materialart: Digitale Medien
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 383-386 
    ISSN: 1432-1041
    Schlagwort(e): Benzodiazepine ; temazepam ; pharmacokinetics ; bioavailability ; hard and soft gelatine capsules
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma levels of temazepam were determined in healthy subjects after single oral administration of soft and hard gelatin capsules, and after 7 consecutive night-time doses in soft capsules. Absorption from soft gelatin capsules was significantly faster and produced earlier and higher peak plasma levels. The two pharmaceutical forms did not show any significant difference in relative availability. The apparent half-life of temazepam after night-time administration was significantly shorter than after morning administration, but no change in half-life was observed between the first and seventh night-time doses.
    Materialart: Digitale Medien
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  • 89
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 41-48 
    ISSN: 1432-1041
    Schlagwort(e): Furosemide ; pharmacokinetics ; anephric patients ; metabolism ; protein binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of furosemide 40 mg i.v. were compared in 7 anephric patients and in 7 normal subjects. The average serum clearance was 66 ml/min in the patients and 219 ml/min in the normal subjects, and the corresponding weight corrected clearances were 1.33 ml/min · kg and 2.96 ml/min · kg. Binding to serum proteins was significantly decreased in the anephric subjects, in whom a significant negative correlation was found between the percentage binding and the volume of distribution VDss. In the patients, but not in the normal subjects, there was a significant positive correlation between $$V_{D_{ss} } $$ and serum clearance. Both in normal and anephric individuals 4-chlor-5-sulphamoylanthranilic-acid (CSA) was found, but there was no evidence of special accumulation either of CSA or anthranilic acid in the anephric patients. In the patients the initial increase in serum concentration of sodium and protein followed by a more conspicuous decrease were more pronounced, but none of the changes were statistically significant.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 387-392 
    ISSN: 1432-1041
    Schlagwort(e): Digoxin ; β-methyldigoxin ; prolonged administration ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Five healthy volunteers received digoxin 0.4 mg or β-methyldigoxin 0.4 mg i. v., daily for 14 days, in a randomized cross-over arrangement. By monitoring minimal plasma concentrations during multiple dosing, it was found that the steady state pharmacokinetics of digoxin and β-methyldigoxin could be estimated even better by a one-compartment than by a two-compartment model. The following mean parameters were calculated: the half life of digoxin of 1.54±0.31 days was significantly shorter than the half life of 2.29±0.34 days for β-methyldigoxin. The distribution volume of 807±187 liters for digoxin was not significantly larger than the 735±227 liters for β-methyldigoxin. Renal digoxin clearance of 191±25 ml/min was significantly higher than both the renal clearance of β-methyldigoxin of 111±23 ml/min and also the creatinine clearance, which indicates tubular secretion of digoxin. There was a 2.8-fold accumulation of β-methyldigoxin injected once a day, which was significantly higher than the 1.8-fold accumulation of digoxin.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 12 (1977), S. 451-456 
    ISSN: 1432-1041
    Schlagwort(e): Bioavailability ; carbamazepine ; elimination ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The time-courses of plasma carbamazepine concentrations were followed in six apparently healthy adult subjects who, at different times, took single oral drug doses of 200, 400, 500, 600, 700, 800 and 900 mg. There were some suggestions of impaired bioavailability of the drug when given in tablet form. The following values were obtained for various pharmacokinetic parameters:k abs =0.176±0.209 h−1;k=0.0203±0.0055 h−1; T1/2=37.5±13.1 h; VD=0.825±0.1041 · kg−1; Clearance=0.0163±0.0061 l · kg−1. The elimination rate constant showed a statistically significant increase with increasing drug dose. This may help explain the clinical observation that the rate of rise of steady state plasma carbamazepine concentrations tends to decrease with dose increase in patients taking carbamazepine alone.
    Materialart: Digitale Medien
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 29-33 
    ISSN: 1432-1041
    Schlagwort(e): Microcrystalline theophylline ; chronic obstructive airways disease ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma theophylline concentrations have been measured in 9 patients with chronic obstructive airways disease following the oral administration of a microcrystalline theophylline preparation. Some measurements of FEV1 were also made. Four patients were given 375 mg as a single dose and then subsequently 375 mg stat and 125 mg 4 times daily for 3 days, (Group I). A further 5 patients took 250 mg as a single dose and then 250 mg 4 times daily for 3 days, (Group II). In both groups, following the single dose and again after the last dose of chronic administration, blood samples were obtained at frequent intervals up to 24 h for plasma drug estimation. During the 3-day course, blood samples were drawn before and 2 h after each morning dose. In Group I patients, substantial plasma theophylline concentrations were seen only after the loading dose. Thereafter, the mean concentrations before or 2 h after the morning doese were always less than 4.0 µg/ml. Trough concentrations were usually below 2.0 µg/ml. In contrast patients in Group II achieved substantially higher plasma theophylline concentrations, with mean peak concentrations always 10 µg/ml or greater, and trough concentrations greater than 5 µg/ml on at least one occasion in every subject. The elimination half-lives after chronic administration in both groups were not significantly different from those obtained after single doses. Mean drug accumulation, measured as AUCss/AUC1, was 0.87±0.07 in Group I and 0.72±0.14 in Group II, indicating that accumulation had not occurred with either regimen. The mean increase in FEV1 2 h after the administration of a single dose was 19.2% after 375 mg and 16.7% after 250 mg. These results indicate that the recommended dosage regimen for microcrystalline theophylline preparation (375 mg stat and 125 mg 4 times daily) produces inadequate plasma theophylline concentrations: 250 mg 4 times daily would appear to be likely to result in satisfactory theophylline levels in more patients.
    Materialart: Digitale Medien
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 365-371 
    ISSN: 1432-1041
    Schlagwort(e): Etidocaine ; pharmacokinetics ; metabolism ; neonate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The urinary elimination of etidocaine and several of its metabolites was investigated in neonates whose mothers had received one or more doses of etidocaine during labour. The urine collection period ranged among the neonates from 21.4 to 47.0 h post-partum. The total amounts of etidocaine and its metabolites recovered in neonatal urine represented a mean of 0.12 per cent of the maternal dose. Some differences in the pattern of urinary metabolites were observed between neonates and adults. Mean half-life of elimination of etidocaine calculated from sigma-minus plots of the neonatal urinary data was 6.42 h. This is greater than that previously reported following intravenous administration of etidocaine to adults (2.6 h). The slower rate of elimination in neonates is probably due to an increased neonatal volume of distribution since there is evidence to show that etidocaine is extensively metabolised by the neonate.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 379-383 
    ISSN: 1432-1041
    Schlagwort(e): Antipyrine ; pharmacokinetics ; phenzone ; posture ; immobilization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of a single dose of phenazone was studied in six subjects while ambulant and during bed rest for 3 days. Elimination of the drug was followed for 12 h after oral and intravenous administration. The elimination rate constant and total body clearance were significantly increased during bed rest as compared to the ambulant period, but the differences were small. The apparent volume of distribution decreased significantly. No consistent change due to bed rest was found in the rate of absorption or bioavailability of the oral dose.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 13 (1978), S. 209-212 
    ISSN: 1432-1041
    Schlagwort(e): Paracetamol ; acetaminophen ; Gilbert's syndrome ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of paracetamol after intravenous and oral administration has been studied in 6 patients with Gilbert's syndrome, and 6 healthy controls. Paracetamol clearance was significantly less in the patients (255 ml/min SE±23 ml/min) than in the normal subjects (352 ml/min SE±40 ml/min). Moreover, whilst paracetamol concentrations declined monoexponentially in the patients, the decline was biexponential in the controls. No difference in the bioavailability of 500 mg paracetamol given orally was observed between the two groups. The results suggest that not only is paracetamol elimination impaired in Gilbert's syndrome, but that its distribution kinetics are also abnormal. Both these findings could be attributed to a decrease in hepatic glucuronyl transferase activity.
    Materialart: Digitale Medien
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  • 96
    ISSN: 1432-1041
    Schlagwort(e): Theophylline ; kinetics ; apnea ; premature newborns ; developmental pharmacology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Aminophylline (theophylline-ethylenediamine) was administered to 27 premature newborns to prevent apneic spells. Of the 22 patients monitored for theophylline concentration, a therapeutic blood level was reached in 19 in 1–2 days, and 3 stayed below it. ‘Toxic’ blood levels (≥20 µg/ml) were reached in 3 cases, one of whom showed signs of toxicity. Theophylline treatment was not efficient in the prevention of apnea when a serious underlying disease was present. Theophylline blood half-life (mean : 27.0 h) and clearance (mean 12.9 ml/h/kg) confirmed the slow elimination pattern of the drug in the premature infant.
    Materialart: Digitale Medien
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  • 97
    ISSN: 1432-1041
    Schlagwort(e): Aminopyrine ; pharmacokinetics ; 14CO2 breath test ; hepatic disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The time-course of aminopyrine in plasma and of14CO2 in breath was determined for 6 hours after oral administration of (14C-methyl) aminopyrine to healthy controls and to patients with hepatitis and hepatic fibrosis, cirrhosis and hepatic bilharziasis.14CO2 in breath declined about 1.8 times more slowly than aminopyrine plasma levels, which suggests the occurrence of metabolite demethylation. This was confirmed by the slow elimination of14C from plasma, the formation of14CO2 after aminopyrine had disappeared and the presence of a considerable amount of monomethyl-aminopyrine in plasma. The mean14CO2 concentration in breath was correlated with but was not proportional to aminopyrine clearance, which was attributed to individual differences in aminopyrine half-life. Both a correlation and proportionality were found when14CO2 extrapolated to zero time was used as a parameter of14CO2 production. Hepatic disease affected aminopyrine clearance to a variable extent. In the hepatitis and fibrosis group, aminopyrine clearance was affected in 2 out of five subjects. In all except one cirrhotic subject aminopyrine clearance was markedly decreased. Moreover, in three out of seven cases aminopyrine absorption was impaired, presumably due to decreased gastrointestinal blood-flow. This may produce an erroneously low14CO2 concentration in breath during the first two hours after aminopyrine administration. Hepatic bilharziasis was accompanied by very low aminopyrine clearance in all four cases. In two patients high apparent Vd values were observed, probably due to “first-pass” metabolism. Patients with ascites had Vd values within normal limits.
    Materialart: Digitale Medien
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 14 (1978), S. 57-67 
    ISSN: 1432-1041
    Schlagwort(e): Chemotherapy ; sulfadiazine ; trimethoprim ; pharmacokinetics ; acetylation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Sulfadiazine (SDZ) 800 mg and trimethoprim (TMP) 160 mg were given orally to 10 normal subjects and the concentration of SDZ and TMP in serum and urine was followed for 24 h. Both drugs showed a significant negative correlation between individual “peak” concentrations in serum and the body weight of the subject. Twelve hours after dosing the serum concentration was 12 to 25 µg/ml for SDZ and 0.3 to 1.1 µg/ml for TMP. Individual concentration ratios between SDZ and TMP in serum were 4.8 (1 h) – 145 (24 h), and in the urine the ratio was close to 6 throughout the 24 h collection period. The range of urinary concentrations was from 65 to 400 µg/ml for SDZ and from 13.8 to 93.4 µg/ml for TMP. The fraction acetylated SDZ/acetylated SDZ + SDZ was 21% during the 0–8 h period, 33% during the 8–15 h period and 41% during the 15–24 period. The average values for the notional volume of distribution, Vd, were 0.36±0.13 1/kg for SDZ and 1.39±0.25 1/kg for TMP. The average “t1/2” was 15.2±7.4 h for SDZ and 7.4±1.9 h for TMP. Individual subjects showed a significant correlation between the serum clearance of TMP and SDZ (p〈0.01) and also between the renal clearance of the two drugs (p〈0.05). The serum clearance was significantly correlated with the renal clearance for TMP but not for SDZ. For SDZ Vd was significantly negatively correlated with the elimination constant; for TMP no such correlation was found. The serum clearance of SDZ was significantly correlated with the percentage of SDZ which was excreted as the (presumably) acetylated compound. The renal clearance of SDZ was independent of the serum concentration of SDZ. There was a highly significant negative correlation between the renal clearance and serum concentration of TMP, as well as for “acetylated SDZ”. The renal clearance of “acetylated SDZ” averaged more than six times that of unconjugated SDZ. With increased urine flow the renal clearances of TMP and SDZ were significantly increased.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 14 (1978), S. 237-244 
    ISSN: 1432-1041
    Schlagwort(e): Furosemide ; arterial hypertension ; protein binding ; sodium excretion ; renal function ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Furosemide 40 mg was injected intravenously in 7 patients with severe hypertension and vascular complications. A two compartment, open model was used to describe the disappearance of the drug from serum. The mean serum clearance (Cls=1.83 ml/min · kg) was significantly reduced compared to the mean Cls-value of a group of normals (2.96 ml/min · kg). A significant correlation was found between Cls and mean blood pressure, as well as between Cls and renal clearance (mean Clr=0.83 ml/min · kg); extrapolation of the regression line yielded a Cls-value of 50 ml/min for Clr=0. The Clr was also significantly negatively correlated with mean blood pressure. Protein binding of furosemide was normal, except in one patient, who had considerable impairment of renal function. Apparently more than 90% of unchanged furosemide passed in urine was excreted by tubular transport. A highly significant negative correlation was found between Cls and the fraction of furosemide excreted as a glucuronide. During the first two hours, significantly less sodium was excreted by the patients than by a comparable group of normal subjects. The correlation between serum concentration of furosemide and the amount excreted of sodium was not significant, but highly significant correlations were found between the amounts of furosemide and sodium excreted by the kidney in 0–30 and 0–60 min. In all the individual patients an approximately linear relationship with wide variation in the slope was found between the cumulative excretion of furosemide and sodium from 0–30 min to 0–60 and to 0–120 min. After 120 min deviations were observed in the curves from 4 of the patients, which indicated that smaller and smaller additional amounts of sodium were excreted with constant additional amounts of furosemide.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 14 (1978), S. 267-271 
    ISSN: 1432-1041
    Schlagwort(e): Lithium ; sustained-release ; pharmacokinetics ; manic patients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary An ordinary and a sustained-release lithium carbonate preparation were administered acutely at equivalent dosage (1.80 g=24.3 mmol) in a crossover fashion to manic patients. Serum lithium levels were determined by atomic absorption spectroscopy and pharmacokinetic parameters were calculated. Maximum mean serum levels of 1.13 mmol/l and 0.78 mmol/l were achieved at 6 h and 12 h respectively with the ordinary and sustained-release forms. The mean half-lives of absorption, redistribution and elimination were 0.78 h±0.05 (SE), 5.06 h±0.23, 26.8 h±4.5 and 3.73 h±0.37 (SE), 4.42 h±0.28 and 25.6 h±5.5 for the ordinary and sustained-release forms respectively. In healthy volunteers the ordinary preparation was completely absorbed but only 85% of the sustained-release form was absorbed in the manic subjects. Lithium ion distributed into two kinetic compartments and the final compartment appeared to correspond to total body water.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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