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  • pharmacokinetics  (239)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 68 (1993), S. 219-229 
    ISSN: 1570-7458
    Schlagwort(e): Hymenoptera ; Aphidiidae ; Homoptera ; Aphididae ; Schizaphis graminum ; wheat ; tritrophic interactions ; learning ; host-habitat location
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of experience on the responsiveness of the aphidiid parasitoidLysiphlebus testaceipes (Cresson) (Hymenoptera: Aphidiidae) to host-associated cues was investigated using a wind-tunnel bioassay. Naive females were able to discriminate between uninfested wheat (Triticum aestivum L.) and wheat infested withSchizaphis gramimum (Rondani) (Homoptera: Aphididae), but oviposition experience significantly increased the parasitoid's propensity to respond to aphid-infested plants with upwind, targeted flight. The behavioural change associated with such experience was acquired rapidly (within five minutes) and persisted for at least 24 h. The parasitoid could be successfully conditioned to associate a novel odour with the presence of hosts, suggesting that the increase in response to aphid-infested plants which occurs as a result of experience is probably due to associative learning of olfactory cues from the plant-aphid complex.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 4 (1987), S. 61-66 
    ISSN: 1432-0789
    Schlagwort(e): Stem nodulation ; Aeschynomene afraspera ; Legume ; Nitrogen fixation ; Acetylene reduction assay (ARA)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Aeschynomene afraspera is a wild annual legume growing in periodically waterlogged soils in western Africa. This legume is characterized by a profuse stem nodulation. Nodules are formed on the stem at the emergence of lateral root primordia, called nodulation sites. These sites are irregularly distributed on vertical rows all along the stem and branches. Stem nodules are hemispherically shaped. Their outside is dark green and they contain a red-pigmented central zone. Stem nodules exhibit a high nitrogen-fixing potential. Acetylene reduction assays result in stem nodule activity of 309 μmol C2H4 g−1 dry nodule h−1. Field-grown stem nodulated Aeschynomene accumulated more N (51 g N m−2 in 10 weeks) than the root nodulated one. Because of this nitrogenfixing potential and its ability to grow in waterlogged conditions, A. afraspera could probably be introduced into tropical rice cropping systems.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 5 (1987), S. 83-87 
    ISSN: 1432-0789
    Schlagwort(e): Inoculation ; Inoculum dose ; Nitrogen fixation ; Chickpea ; Rhizobium spp. ; Cicer arietinum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The influence of three inoculum rates on the performance of three chickpea (Cicer arietinum L.) Rhizobium strains was examined in the field on a Mollisol soil. Increasing amounts of inoculum improved the performance of the strains. A normal dose (104 cells per seed) applied at different intervals gave non-significant increases in nodulation, nitrogenase activity (acetylene reduction assay), nitrogen uptake and grain yield. A ten-fold increase in inoculum increased nodule number, shoot dry weight, nitrogenase activity (ARA) and grain yield, but increases over the control were significant only for nodule dry weight and nitrogen uptake by shoot and grain. The highest level of inoculum (100 × normal) significantly increased nodule dry weight, grain yield, total nitrogenase activity (ARA) and nitrogen uptake by shoot and grain. Strain TAL 620 was more effective than the other two. Combined nitrogen (60 kg N ha−1) suppressed nodulation and nitrogenase activity (ARA).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1432-0789
    Schlagwort(e): Triticum aestivum ; T. turgidum ; Nitrogen fixation ; Field inoculation ; Acetylene reduction assay (ARA)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Eight commercial Israeli spring wheat cultivars (six Triticum aestivum and two T. turgidum) grown with 40 and 120 kg N/ha were tested for responses to inoculation with Azospirillum brasilense. At the low level of N fertilization (40 kg/ha), five cultivars showed significant increases in plant dry weight measured at the milky ripe stage; however, by maturation only the cultivar “Miriam” showed a significant increase in grain yield. Two cultivars, which had shown a positive inoculation effect at the earlier stages, had a significant decrease in grain yield. No significant effect of inoculation was found at the high N level. To confirm those results, four wheat (T. aestivum) cultivars were tested separately over 4 years in 4 different locations under varying N levels. Only Miriam showed a consistently positive effect of Azospirillum inoculation on grain yield. Inoculation increased the number of roots per plant on Miriam compared with uninoculated plants. This effect was found at all N levels. Nutrient (N, P and K) accumulation and number of fertile tillers per unit area were also enhanced by Azospirillum, but these parameters were greatly affected by the level of applied N. It is suggested that the positive response of the spring wheat cultivar “Miriam” to Azospirillum inoculation is due to its capacity to escape water stresses at the end of the growth season.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 4 (1987), S. 15-19 
    ISSN: 1432-0789
    Schlagwort(e): Nitrogen fixation ; N-balance studies ; Azolla ; Blue-green algae ; Chemical N fertilization ; Rice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary A nitrogen balance study conducted in ceramic pots under net house conditions for four seasons showed that flooded rice soil leaves a positive nitrogen balance (N increase) in soil after rice cropping in both fertilized and unfertilized soil. Recovery of nitrogen from rice soil was more than its input in unfertilized soil, but it was reverse in fertilized soil. Incorporation of Azolla or BGA twice as basal and 20 days after transplanting (DAT) alone or in combination showed higher nitrogen balance and N2-fixation (N gain) in soil than in that where it was applied once either as basal or 20 DAT. Planted soil showed more N2-fixation than that of fallow rice, and flooded soil fixed more nitrogen in comparison to non-flooded soil in light but less in dark. Soil exposed to light fixed more nitrogen than that of unexposed soil in both flooded and non-flooded conditions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 4 (1987), S. 9-14 
    ISSN: 1432-0789
    Schlagwort(e): Rhizosphere ; Nitrogen fixation ; Root exudates ; Soil bacteria ; Carbon budget ; Rice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The association of rice seedlings (cv. Delta) with different strains of Azospirillum was studied under monoxenic conditions in the dark. Axenic 3-day-old seedlings were obtained on a C- and N-free medium and inoculated with 6 · 107 bacteria per plant in a closed vial. Seven days later, different components of a carbon budget were evaluated on them and on sterile controls: respired CO2, carbon of shoot and roots, bacterial and soluble carbon in the medium. Two strains (A. lipoferum 4B and A. brasilense A95) isolated from the rhizosphere of rice caused an increase in exudation, + 36% and + 17% respectively compared with sterile control. Shoot carbon incorporation and respiration were reduced by inoculation. A third strain (A. brasilense R07) caused no significant change in exudation. A. lipoferum B7C isolated from maize did not stimulate rice exudation either. We further investigated a possible effect of nitrogen fixation on this phenomenon: inhibition of nitrogen fixation by 10% C2H2 did not modify the extent of C exudation by rice associated with A. lipoferum 4B or with the non-motile A. lipoferum 4T.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 26 (1987), S. 347-357 
    ISSN: 1432-1432
    Schlagwort(e): Ribosome structure ; Electron microscopy ; Image analysis ; Evolutionary lineages
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Multivariate statistical analysis and classification techniques are powerful tools in sorting noisy electron micrographs of single particles according to their principal features, enabling one to form average images with an enhanced signal-to-noise ratio and a better reproducible resolution. We apply this methodology here to determining the characteristic views of the large (50S) ribosomal subunits from the eubacteriumEscherichia coli and the archaebacteriaMethanococcus vannielii, Sulfolobus solfataricus, andHalobacterium marismortui. Average images were obtained of the subunit in the common crown and kidney projections, but views of the particle in orientations intermediate between these two extremes were also elucidated for all species. These averages show reproducible detail of up to 2.0 nm resolution, thus enabling the visualization and interspecies comparison of many structural features as a first step toward comparing the actual three-dimensional structures. Our results disprove evolutionary lineages recently postulated on the basis of electron microscopical images of ribosomal subunits.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1432-1351
    Schlagwort(e): Photoreception ; Extraretinal Photoreceptor ; Chromophore ; Opsin ; Reptile ; Immunocytochemistry ; HPLC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Since the beginning of this century evidence has accumulated which demonstrates that non-mammalian vertebrates possess photoreceptors situated deep within the brain. While many attempts have been made to localize these sensory cells, studies have either failed or been inconclusive. In this report we have used several experimental approaches to localize the deep brain photoreceptors of the lizard Anolis carolinensis. Using 3 antibodies that bind vertebrate cone opsins, we have immunolabelled cerebrospinal fluid (CSF)-contacting neurons located at the ventricular border within the nucleus ventromedialis of the septum. Western blot analysis indicates that these antibodies recognized a single 40 kD protein in ocular, anterior brain, and pineal extracts. Immunoblots of rodent brain did not show a similar protein band. We have also identified specific retinoids associated with phototransduction (11-cis and all-trans-3,4-didehydroretinaldehyde) within anterior brain extracts. This combined data provides the most detailed analysis of deep brain photoreceptors in any vertebrate. Consequently, we feel Anolis provides an excellent model to study this unexplored sensory system of the vertebrates.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 1432-1351
    Schlagwort(e): Egg laying hormone ; Aplysia ; Binding protein ; Immunocytochemistry ; Reproductive system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract A protein solubilized from a membrane preparation of the gonad of Aplysia californica has been isolated by affinity chromatography, using bag cell egg-laying hormone (ELH) as the bound ligand, and partially purified and characterized by gel electrophoresis. The protein has an apparent molecular weight of 52 kDa and consists of two disulfide-linked subunits of about 30 kDa each. The protein is glycosylated and has an acidic pI. Approximately 10–15 μg of this protein can be isolated from a single ovotestis, representing less than 1% of the total protein in the gonad; but the protein could not be detected in buccal mass or body wall, tissues which do not have apparent response to ELH. Antibodies generated against this ELH-binding protein (ELHBP) were used to localize sites in the ovotestis which might contain this molecule and thus represent targets for egg-laying hormone. Immunocytochemical results indicate that the oocytes are a rich source of this protein, since their cytoplasm was the only detectable site of immunoreactivity. Whether this binding protein represents an egg-laying hormone receptor is uncertain, but its prevalence in oocytes suggests that ELH plays a signaling role on these gametes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Trees 8 (1993), S. 75-84 
    ISSN: 1432-2285
    Schlagwort(e): Picea abies (L.) Karst ; Freezing injury ; Acid rain ; Carbohydrate histochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The cellular structures of acid rain-irrigated needles of several provenances of Norway spruce (Picea abies L. Karst) seedlings were studied after winter experimental freezing. Frost injuries and recovery were characterized by visual damage scoring and classification of mesophyll cell alterations, also using histochemical methods for carbohydrate fluorescent staining. The treatment with-30° C during the late dormancy period was sufficient to cause significant injuries and intracellular degradation in the tissues of the green needles. The most affected seedlings in terms of visual injury scoring were found among those treated with clean water or at pH 3, while freezing injury, defined as an occlusion of phenolic substances in the central vacuole of the mesophyll cells, was most abundant in the needles from spruces irrigated either with clean water or at pH 4 or pH 3. Electron microscopy revealed the details of the injury, e. g. thinning out of the cytoplasm and chloroplast stroma, darkening of the chloroplasts and eventually swelling of the chloroplasts and protoplast. PAS and ConA reactions in the needle tissue revealed intense starch accumulation in the mesophyll and transfusion tissues as early as in March, with a tendency to increase, especially in the untreated needles during the recovery period. Plasma membrane disturbances were indicated by histochemical identification of callose deposits in the mesophyll cell walls, these being most abundant in the acid rain-treated needles. All these findings suggest that freezing at −30° C was more deleterious to the seedlings pretreated with acid or clean water than to those not given additional irrigation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Trees 8 (1993), S. 99-103 
    ISSN: 1432-2285
    Schlagwort(e): Robinia pseudoacacia L. ; Hydrogen uptake ; Hydrogenase ; Nitrogen fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Hydrogen uptake is thought to increase the efficiency of nitrogen fixation by recycling H2 produced by nitrogenase that would otherwise be lost by diffusion. Here we demonstrate the capacity of eight Rhizobium strains to take up molecular hydrogen. Uptake by nodule homogenates from Robinia pseudoacacia was measured amperometrically under nitrogenase repression. Markedly lower activities were found than in soybean nodules. In addition hydrogenase activity was detected by the ability of bacteroids to reduce methylene blue in the presence of hydrogen. It was demonstrated that hydrogenase structural genes are present in the black locust symbiont, Rhizobium sp. strain R1, using hybridization with a plasmid, which contained hydrogenase genes from R. leguminosarum bv. viceae.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Trees 8 (1993), S. 23-30 
    ISSN: 1432-2285
    Schlagwort(e): Wound responses ; Hardwoods ; Xylem parenchyma ; Suberization ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Wound responses of xylem parenchyma by suberization were investigated in some hardwoods by light and electron microscopy. Suberized ray and axial parenchyma cells form a distinct boundary around the wound in all investigated species. Vessels and fibres within and close behind the suberized area appeared more or less occluded; vessels in Fagus, Quercus, and Populus contained suberized tyloses, those in Betula and Tilia contained amorphous and fibrillar deposits. A common mechanism for suberin deposition in the parenchyma cells became evident. Cisternae of the endoplasmic reticulum were apparently involved in suberization. Suberin compounds are extruded by cytoplasmic vesicles, which fused with the plasma membrane, in order to release their content. The suberin layer exhibited the typical lamellated structure; cytoplasmic continuity between suberized cells by plasmodesmata was maintained through the suberin layer. Fagus revealed the most intense suberized area as compared with the other species. Within the reaction zone of Fagus and Quercus, some individual ray and axial parenchyma cells exhibited a subdivision into 2 or 3 compartments prior to suberization. Subdivision was achieved by the formation of a primary wall-like layer. Subsequently, the compartments became individually suberized. Wounding during winter did not induce suberization. Also, samples wounded and kept under water during the vegetation period showed no response. The role of suberization in the effectivity of wound-associated compartmentalization is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    ISSN: 1432-2285
    Schlagwort(e): Cambial activity ; Frost hardiness ; Phenology ; Salix ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The ultrastructure of cells in the cambial region of Salix dasyclados Wim. (clone 78056) was studied during the development of winter hardiness and the onset of cambial activity in spring. Plants were grown at relative growth rates (RG) of 8% and 12% respectively, resulting in different nitrogen content in the stems. Frost hardiness of the plants was estimated by standardized freezing tests. Plants with a higher nitrogen status ceased growth later and started re-growth earlier in spring than plants with lower nitrogen content. Differences in ability to withstand low temperatures during autumn and spring were found between plants grown in the two nutrient treatments. During the development of frost hardiness in the autumn, the number of meristematic cells in the cambial region decreased. The cessation of meristematic activity was accompanied by cell wall thickening and ultrastructural changes in the cells. Frost hardiness increased from the ability to survive -6° C in October to survival of -80° C at the beginning of December. From November to February the cambial region comprised a layer of 2–3 thick-walled cells with conspicuous ultrastructural features. Starch accumulated in plastids in September, decreased during November to March and then increased again in accordance with changes of frost hardiness. Onset of cambial activity began between the end of March and the beginning of April, as shown by increased vacuolization of meristematic cells and mitotic activity. By April, the starch content had increased and lipolysis was observed. Frost hardiness had decreased, and plants with low and high nitrogen content were able to survive -15° C and -10° C, respectively. After budburst, all axillary shoot parts were damaged at temperatures below-3° C.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Mycopathologia 121 (1993), S. 143-147 
    ISSN: 1573-0832
    Schlagwort(e): Electron microscopy ; Farmer's lung ; Saccharopolyspora rectivirgula ; Thermoactinomyces vulgaris
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The fine structure ofThermoactinomyces vulgaris andSaccharopolyspora rectivirgula is described by transmission electron microscopy. These two bacteria are the most common microbes causing farmer's lung. The fine structure of hyphae, germination of endospores and the details of conidial wall layers ofT. vulgaris, as well as the fine structure of septate hypha and globose, polygonal conidia ofS. rectivirgula are described. The conidial wall ofT. vulgaris consisted of an inner multilayered spore coat, intermediate spore coat and outer spore coat. The findings are important for the investigations to find fragments of these bacteria in the lungs of exposed patients and experimental animals.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 12 (1987), S. 201-218 
    ISSN: 1573-0867
    Schlagwort(e): relative effectiveness ; apatites ; wheat ; initial and residual effectiveness ; bicarbonate extractable phosphorus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The initial and residual agronomic effectiveness of six apatite rock phosphates from India, one from the USA (North Carolina) and one from Australia (Queensland) were evaluated in a pot trial with wheat on a lateritic soil. All of the Indian rock phosphates were very poor sources of phosphorus. Values of initial effectiveness relative to monocalcium phosphate ranged from 〈 0.0001 to 0.02 and from 〈 0.0001 to 0.008 for measurements based on yield and phosphorus uptake respectively. The residual effectiveness relative to freshly applied monocalcium phosphate was determined by growing a second crop on the fertilized soils. The effectiveness of the Indian rock phosphates remained very low ranging from 〈 0.0001 to 0.002 and from 〈 0.0001 to 0.0004 for yield and phosphorus uptake respectively. Queensland and North Carolina rock phosphates were much superior to the Indian sources with initial effectiveness values in terms of yield of 0.08 and 0.37 and residual effectiveness values of 0.02 and 0.15 respectively. For each crop there was a single relationship between yield and phosphorus uptake (i.e. internal efficiency) for all phosphorus sources showing that variations in yield response were due solely to differences in phosphorus availability. Sodium bicarbonate extractable phosphorus values for fertilized soils sampled shortly after fertilization were not predictive of yield unless different calibration curves were used for the different phosphorus fertilizers.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 13 (1987), S. 191-197 
    ISSN: 1573-0867
    Schlagwort(e): chemical extractants ; critical levels ; semi-arid region soils ; wheat ; zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract To find critical tissue levels of Zn for wheat, and to evaluate various chemical extractants, a screen-house experiment was conducted on 21 diverse soils representing semi-arid regions in Haryana State, India. The extractants differed in the amounts of Zn extracted and the order was: 0.1 N HC1 〉 EDTA-NH4OAc 〉 EDTA-(NH4)2CO3 〉 DTPA + CaCl2. The amounts (mg kg−1) of extractable Zn associated with a yield reduction of 20% were: DTPA + CaCl2, 0.60; EDTA — (NH4)2CO3, 0.80; EDTA-NH4OAc, 0.92 and 0.1 N HCl, 1.20. The corresponding critical Zn concentration in ten weeks old plants was found to be 17 mg gm−1. The DTPA + CaCl2 method gave the best correlation (r = 0.85) between extracted Zn and Bray's per cent yield. It is recommended for assessing Zn status of soils of semi-arid region.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    ISSN: 1573-0832
    Schlagwort(e): Capsule ; Cryptococcus neoformans ; Deep-etching ; Quick-freezing ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The three-dimensional ultrastructure ofCryptococcus neoformans was studied by quick-freezing and deep-etching (QF-DE) method.C. neoformans, strain CDC551, was cultured on agar. The viable yeast cells (107 cells) were inoculated into each mouse from the tail vein. Three weeks after the inoculation, the brains of the mice were perfused with fixatives, quickly frozen, freeze-fractured, deeply etched and rotary shadowed with platinum and carbon. In addition, the viable cells ofC. neoformans on agar were picked up and quickly frozen, and replica membranes were prepared as described above. The ultrastructure ofC. neoformans was three-dimensionally demonstrated by the QF-DE method. The capsule was composed of fine meshworks of microfibrils (10–13 nm in diameter), which were directly attached to the cell walls. The capsule of the in vivo yeasts (yeast cells in the brain lesion) was thicker than that of the in vitro yeasts (yeast cells on agar culture). At the outer part of the cell wall, a particle-accumulating layer was observed. This layer in vivo was thicker than that in vitro. Occasionally, the yeast cells were ingested by phagocytes in the mouse brain. Although the cytoplasm of such yeast cells was destroyed, the capsular meshworks were well preserved. The ultrastructure of the capsule was the same both in cultured and phagocytized yeasts in the cystic lesions of the brains. This lack of morphological changes of the capsular meshworks suggests that they are resistant to the digestion by phagocytes. This stability of capsular structures may provide one of the important pathogenic factors in cystic lesions byC. neoformans.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 203 (1993), S. 18-27 
    ISSN: 1432-041X
    Schlagwort(e): Oogenesis ; Germ line cell cluster ; Oocyte determination ; Ultrastructure ; Mayflies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Germ line cell cluster formation in ovarioles of three different stages, each from a different mayfly species, was studied using ultra-thin serial sectioning. In the analysed ovariole of Cloeön sp., only one linear, zigzag germ line cell cluster was found, consisting of sibling cells connected by intercellular bridges which represent remnants of preceding synchronized mitotic cycles followed by incomplete cytokinesis. A polyfusome stretched through all sibling cells. At the tip of the ovariole, cytokinesis occurred without preceding division of nuclei; thus, intercellular bridges were lined up but the remaining cytoplasm between the bridges had no nuclei. The analysed Siphlonurus armatus vitellarium contained five oocytes at different stages of development. Each oocyte in the vitellarium was connected via a nutritive cord to the linear cluster of its sibling cells in the terminal trophic chamber. Each cluster had the same architecture as was found in Cloëon. The 3-dimensional arrangement and distribution of closed intercellular bridges strongly suggest that all five clusters are derived from a single primary clone. The position of oocytes within each cluster is random. However, each oocyte is embraced by follicular or prefollicular cells whilst all other sibling cells are enclosed by somatic inner sheath cells, clearly distinguishable from prefollicular cells. In the analysed ovariole of Ephemerella ignita, two small linear clusters were found in the tropharium beside two single cells, two isolated cytoplasmic bags with intercellular bridges but no nuclei, and some degenerating aggregates. One cluster was still connected to a growing oocyte via a nutritive cord. In all species the nurse cells remained small and no indications of polyploidization were found. We suggest that this ancient and previously unknown telotrophic meroistic ovary has evolved directly from panoistic ancestors.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 196 (1987), S. 367-371 
    ISSN: 1432-041X
    Schlagwort(e): Vitellogenesis ; Bufo marinus oocyte ; Yolk-platelet membrane ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Oocytes of the toad Bufo marinus have been studied by means of thin section and particularly freeze-fracture electron microscopy to characterize the cytoplasmic membranes around the yolk organelle, and the storage of yolk material in precursors and platelets. This appears to be a previously unknown type of yolk-platelet formation. During yolk-organelle development from the primordial precursor to the bi-partite fully grown yolk platelet, numerous lipoid droplets are attached to the periphery of the platelet, indicating an intense uptake of lipids. As is typical for amphibians, the fully grown yolk platelet has a crystalline internum covered by a dense osmiophilic externum, and the whole organelle is enveloped by a plasma membrane that shows no direct connection or fusion with endocytotic vesicles. The yolk membrane exhibits few intramembraneous particles (IMPs) at the core areas and some more where it borders fields of lipoid droplets. Here the IMPs show a net-like arrangement in the furrows between adjacent droplets.
    Materialart: Digitale Medien
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  • 20
    ISSN: 1432-0827
    Schlagwort(e): Chondrocytes ; High-density suspension culture ; Electron microscopy ; Matrix vesicle ; Apatite formation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Chondrocyte cultures grown in centrifuge tubes with intermittent centrifugation differentiate into hypertrophic chondrocytes and form calcification. We examined chondrocytes cultured in this system electron microscopically. Rat growth-plate chondrocytes were seeded in a plastic centrifuge tube and cultured in the presence of Eagle's minimum essential medium supplemented with 10% fetal bovine serum and 50 μg of ascorbic acid per ml. Specimens were examined by using electron microscopy and selected-area electron-diffraction techniques. In the early stage of culture, a few chondrocytes were scattered and extracellular matrices were not observed. In the middle stage of the cultures, the chondrocytes resembled proliferative cells. Matrix vesicles appeared to be budding from the cell surfaces of chondrocytes and were observed sparsely in the extracellular matrices, which were well formed around the chondrocytes. Matrix vesicles increased substantially during the following cultures. In the mature stage of the cultures, crystal formation related to matrix vesicles was observed. In the 33-day cultures, several masses of calcified matrix were formed and it was confirmed to be apatite by selected-area electron diffraction analysis. The chondrocytes appeared hypertrophic during this same stage. The 56-day culture was similar to the 33-day culture. It was concluded that this culture system provides an extracellular-matrix mineralization which is produced by chondrocytes per se.
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  • 21
    ISSN: 1432-2048
    Schlagwort(e): Carbohydrate and nitrogen distribution ; Nitrate ; Nitrogenase activity ; Nitrogen fixation ; Respiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This study was undertaken to determine how carbon utilization of fruit production might affect symbiotic activity in hydroponically cultured white bean (Phaseolus vulgaris L.) cv. Rico and its supernodulating genotype R32-BS15 (abbreviated as RBS15). Total plant biomass production of both genotypes was similar. Nodule dry weight of RBS15 consistently scored approximately twice the amount recorded for Rico, while nodule numbers in the mutant were almost six times as high. Nodule respiration on a per-plant basis and specific respiration was initially (day 37) disproportionally higher in the mutant, reaching up to three times the values recorded for Rico, while plant N2 fixation estimated by 15N dilution was almost identical. This indicates a lower fixation efficiency of RBS15 nodules, which we suggest to be a result of the larger number of smaller nodules with a higher proportion of growth and maintenance respiration per unit nodule mass. During reproductive development, specific respiration of the mutant dropped below that of Rico without a reduction in fixation, indicating a change in relative efficiency of fixation. Continuous removal of fruits from day 37 onwards stimulated respiration of nodules in both genotypes with highest values per plant being documented for RBS15, while specific activity was higher for Rico. The results indicate that symbiotic activity was not detrimentally affected by competition for carbohydrates between fruits and nodules. It appeared that nodules did not possess excess N2-fixation capacity which could be stimulated by additional provision of photosynthate. Hence, the early onset of reproduction during the life cycle of P. vulgaris is unlikely to be responsible for inadequate fixation performance in the field.
    Materialart: Digitale Medien
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  • 22
    ISSN: 1432-1939
    Schlagwort(e): Plant defenses ; Polyphenols ; Herbivory ; Savanna ; Nitrogen fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In East African savanna we found that leaves of mature tree species with symbiotic N2 fixation contained lower concentrations of polyphenols than leaves of species without this symbiosis. We suggest that the root symbiosis is costly to the plant in terms of photosynthate that otherwise could be used in chemical defense. Further, a negative relationship between concentration of polyphenols and the height of the species was found, independent of their ability to fix N2. These findings suggest that root symbioses and apparency to herbivory are important factors mediating the production of chemical defenses in plants.
    Materialart: Digitale Medien
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  • 23
    ISSN: 1432-1939
    Schlagwort(e): Actinorhizal plants ; Evolutionary tradeoffs ; Nitrogen fixation ; Nutrient resorption ; Phosphorus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nutrient resorption was measured in an actinorhizal nitrogen-fixing shrub,Comptonia peregrina, for five years in the understory of a deciduous oak forest in Rhode Island, USA. Mean resorption of nitrogen was extremely inefficient (11%) compared to most deciduous species (50%+), yet resorption of phosphorus was efficient (53%) and comparable to other species. Of the seven additional nutrients studied, only copper (6%) and zinc (10%) were resorbed from senescing leaves. Resorption of nitrogen (5%–20%) and phosphorus (40%–71%) varied significantly among years. Copper was resorbed from leaves in three years and accreted into leaves in two years. Five-year resorption means differed among individual genets by as much as a factor of 2.5 for nitrogen, and 1.3 for phosphorus. Resorption of nitrogen, copper, and zinc were highly correlated, yet resorption of phosphorus remained autonomous from other nutrients. The ecophysiological tradeoffs inComptonia which have resulted in the cooccurence of actinorhizal nitrogen fixation, inefficient nitrogen resorption, and efficient phosphorus resorption suggest that plant nutrient status does have an impact on resorption efficiency and that the evolution of nutrient conservation strategies is nutrient-specific.
    Materialart: Digitale Medien
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  • 24
    ISSN: 1432-1939
    Schlagwort(e): Lupinus succulentus ; Fabaceae ; Lupine ; Quinolizidine alkaloids ; Nitrogen fixation ; Defoliation ; Plant-herbivore interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We examined the effects of nitrogen nutrition and defoliation on the alkaloids, nitrogen levels, and growth of Lupinus succulentus by growing plants under five nitrogen/defoliation treatments: 1) fertilization with a high-nitrate nutrient solution, 2) fertilization with a low-nitrate solution, 3) inoculation with N-fixing bacteria but without available soil nitrogen, 4) high-nitrate solution plus periodic partial defoliation, and 5) low-nitrate plus defoliation. In the absence of defoliation, plants from both the N-fixing and high-N treatments had higher concentrations of alkaloids and nitrogen, and higher growth rates than the low-N plants. Periodic defoliation had little effect on the high-N plants, but defoliated N-fixing plants were severely stunted and had lower alkaloid and nitrogen levels. The experimental treatments also affected the relative concentrations of the alkaloids. Our results indicate that 1) alkaloid composition and concentration in L. succulentus are determined by both nitrogen availability and developmental state, 2) plants relying solely on N-fixation respond quite differently to defoliation than those with adequate soil nitrogen, and 3) the food value of the plant tissue can be affected by an interaction between the effects of defoliation and nitrogen status.
    Materialart: Digitale Medien
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  • 25
    ISSN: 1432-2145
    Schlagwort(e): Cytoplasmic male sterility ; Ultrastructure ; Mitochondria morphometry ; Beta vulgaris L
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The development of microspore mother cells (MMC) and tapetum in male-fertile and male-sterile anthers of Beta vulgaris L. was compared at the electron microscope level. These studies were complemented by morphometric analyses of mitochondria in both tissues through successive stages of microsporogenesis. The earliest irregularities in the ultrastructure of male-sterile anthers were noted within the tapetum at the tetrad stage. These disturbances were initially expressed by a slight reduction in mitochondrial size and the appearance of concentric configurations of endoplasmic reticulum. As development proceeded, a further decrease in mitochondrial size become more conspicuous and was accompanied by a reduction in ribosome population and a failure of the tapetum to produce Ubisch bodies. This failure to produce Ubisch bodies is reflected in the underdevelopment of sterile microspore exine.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 6 (1993), S. 98-107 
    ISSN: 1432-2145
    Schlagwort(e): Selaginella ; Megaspore ; Exospore ; Ultrastructure ; Tapetal cells ; Plasmodesmata
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Structures have been found in the locular space between the tapetal cells and megaspores in Selaginella argentea and S. kraussiana that enter the megaspore wall and extend to the plasma membrane of the megaspore cytoplasm. We have called these structures “wicks”. Unless special fixation procedures are used wicks are either very poorly preserved or not apparent. Wicks appear to be routes for the transport of materials from the tapetum to developing megaspores. The entry of the wicks into the megaspore wall and their passage throughout the wall implies that the megaspore wall of Selaginella is a three-dimensional mesh-work of inter-connecting spaces. Wicks have several macromolecular-sized subunits, and the results of our histochemical reactions indicated the presence of glycoprotein and/or mucopolysaccharide. X-ray microanalysis of the S. convoluta exospore showed that silicon is present in rod-shaped structures between units of the exospore in mature megaspores. Because of the size and form of the structures between the exospore units we consider that they are remnants of wicks stabilized by silicon.
    Materialart: Digitale Medien
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  • 27
    ISSN: 1432-2145
    Schlagwort(e): Wheat pollen ; Chemical hybridizing agents ; Male sterility ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Phenylcinnoline carboxylate compounds SC-1058 and SC-1271 cause complete male sterility in wheat when applied at suitable dosages at the pre-meiotic stage of anther development. Anthers from treated and untreated plants were compared using light and electron microscopy from the pre-meiotic stage through the formation of nearly mature pollen. Overall anther development is gradually slowed in treated plants and pollen development is generally arrested in the late prevacuolate or early vacuolate microspore stage, although the first pollen mitosis does sometimes occur. The sporopollenin-containing exine walls are thinner, and show abnormally developed foot and tectum layers with sparse connecting baculi. Microspore cytoplasm degenerates and the cells eventually collapse. At the early, prevacuolate, free microspore stage treated tapetal cells hypertrophy, expanding into the locule. They contain abnormally large vacuoles that appear to form from the fusion of secretory vesicles, and some vacuoles contain electrondense deposits. The sporopollenin-containing orbicular wall and Ubisch bodies are retarded in their development and are structurally deformed. Acetolysis of whole anthers and of thick sections shows that the sporopollen-in-containing structures of treated materials are greatly reduced in thickness and are less rigid than in the control. We conclude that application of these compounds causes interference with the secretory function of tapetal cells which supplies sporopollenin cell-wall polymers to the exine of the microspores and to the tapetal orbicular wall and associated Ubisch bodies. Interference with the tapetal secretion of other nutrients required for microspore development is strongly suggested.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 6 (1993), S. 191-198 
    ISSN: 1432-2145
    Schlagwort(e): Micropyle ; Transfer cells ; Ultrastructure ; Nucellus ; Poaceae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Several kinds of outgrowth from the grass ovule are known. Attention is focused here on one outgrowth that occurs within or around the micropyle and is of nucellar origin. Grass species in which it is currently known to occur are listed and examples of variants briefly described. Attention is concentrated upon Pennisetum, where the cell structure is described in detail with a series of electron photomicrographs. The tissue representing an aggregation of these transfer cells is newly named with the term ‘embellum’, and its significance for pollen tube growth is considered.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 6 (1993), S. 153-170 
    ISSN: 1432-2145
    Schlagwort(e): Appendix ; Sauromatum guttatum ; Ultrastructure ; Mitochondrion ; Amyloplast ; Peroxisome
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ultrastructure of the epidermal and sub-epidermal cells of the appendix of the Sauromatum guttatum inflorescence reveals developmental changes during anthesis. These changes precede, and probably make possible, heat and odor production. Two days before D-day (the day of heat production and inflorescence-opening) the mitochondria of the epidermis divide; apparent division of the amyloplasts was observed at the same time. The presence of lipid bodies and peroxisomes in the epidermis was clearly evident. On D-day, the epidermis becomes a continuous layer in which the cell walls separating two adjacent cells disappear. At the same time, in the sub-epidermal cells, the mitochondria and the amyloplasts undergo division. The mitochondria become electron-dense, and their DNA is clearly visible. On that day, lipids as well as starch are being depleted. The peroxisomes change in structure every day, from D-2 to D-day. It has also been demonstrated by histochemical techniques that during anthesis the activity of cytochrome c oxidase (3,3-diaminobenzidine as a substrate) decreases whereas the activity of NADH dehydrogenase [tetrazolium salts: nitro-blue tetrazolium chloride (NBT) or neotetrazolium chloride (NT) in the presence of NADH], increases. Oxygen consumption of isolated mitochondria from the D-day appendix was inhibited in the presence of the two tetrazolium salts to a different degree: oxidation of NADH in the presence of NBT was the most sensitive to inhibition, more so than the oxidation of malate and succinate. NT was less effective as an inhibitor in the presence of those three respiratory substrates.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 631-634 
    ISSN: 1432-1041
    Schlagwort(e): salbutamol ; albuterol ; pharmacokinetics ; bioavailability ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Salbutamol was administered to sixteen healthy male volunteers intravenously and by mouth in liquid, tablet, and capsule form using a Latin-Squares design. Pharmacokinetic parameters from intravenous data were similar to previously reported values obtained with oral administration, with a mean terminal half-life of 3.8 h and a mean clearance of 439 ml·min−1·1.73 m−2. Peak plasma concentrations of 10–20 ng·ml−1 were obtained 1–3 h following oral administration. The absolute bioavailability of each of the oral preparations was 44%. While statistically significant differences in lag time and time to peak concentration were noted among the various oral preparations, the drug is rapidly absorbed in all three dosage forms and the observed differences are unlikely to be of clinical significance.
    Materialart: Digitale Medien
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  • 31
    ISSN: 1432-1041
    Schlagwort(e): Liver cirrhosis ; Spirapril ; ACE inhibitor ; pharmacokinetics ; haemodynamic effects ; liver function tests
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and haemodynamic effects of orally administered spirapril, a novel angiotensinconverting enzyme (ACE) inhibitor, have been investigated in patients with liver cirrhosis (n=10), in patients with chronic, non-cirrhotic liver disease (n=8) and in a control group of healthy subjects (n=16). The absorption and elimination of spirapril did not differ between patients with liver disease and control subjects. In contrast, the bioavailability of spiraprilat, the metabolite responsible for the pharmacological action of spirapril, was significantly reduced in patients (AUC 820 μg·h·l−1, 923 μg·h·l−1 and 1300 μg·h·l−1 in patients with cirrhosis, patients with non-cirrhotic liver disease and in healthy subjects, respectively. Compared to healthy subjects, cirrhotic patients had a reduced rate constant of spiraprilat formation (1.10 h−1 in patients vs. 2.00 h−1 in control subjects) while the elimination half-life of spiraprilat was not different. The effect of spirapril on diastolic blood pressure was decreased in patients with chronic liver disease as compared to the controls. Thus, the pharmacokinetics of spirapril was unchanged in patients with different types of liver disease, including cirrhosis. However, the bioavailability of spiraprilat and hypotensive effect of spirapril were reduced in patients.
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 45 (1993), S. 357-361 
    ISSN: 1432-1041
    Schlagwort(e): Circadian rhythms ; Indomethacin ; Ketoprofen ; pharmacokinetics ; time-varying models ; nonsteroidal anti-inflammatory drugs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A one-compartment model with first-order absorption has provided good fits to five sets of indomethacin data and four sets of ketoprofen data taken at different times of day. There was substantial variation in the model parameters with time of administration and most of the features of this variation applied equally to both drugs. From the data examined, the source of variation appears to be mainly in the absorption phase and this was confirmed using a chronokinetic analysis, in which simultaneous fits were obtained with time-variant rate parameters. However, there may also be circadian variation in protein binding. The danger of quoting parameter values for either of these two drugs based on administration at a single time of day has been illustrated, and this may well be true for other drugs.
    Materialart: Digitale Medien
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  • 33
    ISSN: 1432-1041
    Schlagwort(e): Gamma-hydroxybutyric acid ; pharmacokinetics ; dose-proportionality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Gamma-hydroxybutyric acid (GHB) is effective in treatment of the alcohol and opiate withdrawal syndromes. Its absorption and disposition kinetics have been studied in 8 healthy male volunteers following oral administration of single doses of 12.5, 25 and 50 mg kg−1. The AUC increased disproportionately with the dose and so the apparent oral clearance decreased significantly as the dose was increased, whereas the terminal half-life and mean residence time increased. The peak plasma concentrations normalised to the lowest dose fell significantly with increasing doses, whilst the corresponding peak times increased. These findings suggest that both the oral absorption and the elimination of GHB are capacity-limited processes. GHB did not bind to significant extent to plasma proteins over the therapeutic concentration range. The pharmacokinetic parameters in healthy volunteers were not significantly different from those previously observed in alcohol-dependent patients with compensated alcoholic liver disease.
    Materialart: Digitale Medien
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  • 34
    ISSN: 1432-1041
    Schlagwort(e): Glyceryl trinitrate spray ; pharmacokinetics ; a/b-ratio ; pulmonary artery diastolic pressure ; finger pulse curve ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The time course and the magnitude of the effect of glyceryl trinitrate (GTN) on central venous (pulmonary artery diastolic pressure-PAPd) and peripheral arterial (a/b-ratio of the finger pulse wave) haemodynamics were compared in a randomized double-blind cross-over study in 12 patients suffering from congestive heart failure (NYHA II–III) with elevated PADd at rest (≥15 mm Hg). The data were obtained in a bioavailability study of two sprays of glyceryl trinitrate, which differed in their galenical characteristics and in the dose of GTN (0.4 mg vs. 0.8 mg). Following sublingual administration of each spray, PAPd, a/b-ratio and the plasma concentrations of GTN and its metabolites were measured up to 30 min. The relative bioavailability of GTN of the test preparation was estimated to be 157%, 161% and 147%, when calculated from the plasma concentration-time data or the integrated effect of GTN on a/b-ratio or PAPd, respectively. The mean time courses of the decrease in PAPd and the increase in the a/b-ratio of the finger pulse curve were mirror images. Thus, there was a strong correlation between the mean values of PAPd and a/b-ratio following the administration of glyceryl trinitrate. Since the slope of the relationship differed considerably between the patients, the magnitude of effect of GTN on PAPd in the individual patient could not be predicted from the changes in a/b-ratio.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 463-466 
    ISSN: 1432-1041
    Schlagwort(e): Benazepril ; Proteinuria ; benazeprilat ; ACE inhibitor ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have investigated whether the pharmacokinetics and pharmacodynamics of the ACE inhibitor benazepril hydrochloride are altered with proteinuria by studying 8 patients with major proteinuria of different causes who were given a single dose of 10 mg p.o. The maximum plasma concentration of benazepril was found between 0.5 and 2 h after dosing (median 1 h). Its elimination was almost complete within 6 h. Peak plasma levels of benazeprilat, the active metabolite of benazepril, were observed between 1 and 6 h (median 2.5 h). The elimination of benazeprilat from plasma was biphasic, with mean initial and terminal half-lives of 3.0 and 17.3 h, respectively. On average, the pharmacokinetic parameters of benazepril and benazeprilat in the patients did not differ from those in a historical control group of healthy volunteers, but intersubject variability in the AUC and half-lives of benazeprilat was greater in the patients. Plasma ACE was completely inhibited from 1.5 to 6 h after dosing, and at 48 h the mean inhibition was still 42 %. Plasma renin showed substantial intersubject variation. Mean supine blood pressure (systolic/diastolic) was reduced from baseline by a maximum of 18/13 mm Hg at 6 h. Proteinuria was diminished after benazepril in 7 patients. In conclusion, the results of this study suggest that proteinuria in the nephrotic range does not require a change in benazepril dosage.
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  • 36
    ISSN: 1432-1041
    Schlagwort(e): dDAVP ; bioavailability ; gastrointestinal tract ; healthy volunteers ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The absolute bioavailability of an aqueous solution of 1-deamino-8-D-arginine vasopressin (dDAVP) from different regions of the gastrointestinal (GI) tract (stomach, duodenum, jejunum, ileum, colon, rectum) has been studied in 6 healthy, male volunteers aged 24 to 35 years, followed for 12 h after each drug administration. For i. v. administration the subjects received 4 μg dDAVP. For intestinal administration 400 μg dDAVP was directly applied to six distinct sites in the GI tract via two or four channel tubes with or without a distal occlusive balloon. Biological effects were assessed and plasma and urinary levels of dDAVP were measured using a specific, sensitive RIA. Urine osmolality remained elevated and diuresis decreased for 12 h following dDAVP administration irrespective of the site of application. After i. v. administration, the half-life of elimination of dDAVP was 60.0 min, plasma clearance 1.7 ml·min−1·kg−1, amount excreted in urine 2.0 μg and renal clearance was 0.8 ml·min−1·kg−1. The mean bioavailability (f) after gastric application was 0.19% (range 0.02–0.35%). f was 0.24% after duodenal application (range 0.04–0.62%), 0.19% after jejunal (range 0.01–0.41%), 0.03% after distal ileal (range 0.01–0.08%), 0.04% after proximal colonic (range 0.01–0.12%) and 0.04% after rectal (0.01–0.10%) application. The bioavailability was significantly higher in the three upper GI regions in comparison to the three lower regions. The bioavailability of dDAVP after gastric, duodenal and jejunal application was similar to that after swallowing a tablet in a previous study. Absorption from the ileum was lower than expected and no preferential site of absorption was found.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 247-251 
    ISSN: 1432-1041
    Schlagwort(e): Proguanil ; Pregnancy ; Malaria ; cycloguanil ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma and whole blood concentrations of proguanil, its active metabolite cycloguanil, and the inactive metabolite 4-chlorophenyl-biguanide, were measured by HPLC in 10 healthy Karen women in the last trimester of pregnancy, following a 200 mg single oral dose of proguanil. Four of these women were restudied 2 months after delivery. The pharmacokinetic properties of proguanil were similar during and after pregnancy. Median peak plasma concentrations of proguanil during pregnancy and following delivery were 212 and 215 ng·ml−1, and occurred at 4.5 and 5 h, respectively. Mean plasma AUC values for proguanil during and following pregnancy were 94 and 98 ng·h·ml−1·kg−1, respectively. Corresponding whole blood AUC values were 361 and 396 ng·h·ml−1·kg−1. The mean elimination half lives and mean residence times of proguanil in plasma and whole blood were 12.3 and 19.6 h and 13.8 and 20.7 h respectively during pregnancy. Following pregnancy these values were 17.1 and 19.7 h for plasma and 19.7 h and 20.2 h for whole blood respectively. Mean peak plasma and whole blood concentrations of cycloguanil following pregnancy were 25 and 22 ng·ml−1 respectively. During pregnancy peak cycloguanil concentrations in both plasma and whole blood were markedly lower, 13 and 12 ng ml−1, respectively. Two pregnant women (neither of whom were restudied) were probably poor metabolisers of proguanil. The mean ratio of proguanil to cycloguanil plasma AUC was 16.7 in the third trimester of pregnancy and 7.8 following pregnancy, compared with less than 5 in previously reported studies. The concentrations of 4-chlorophenylbiguanide in both plasma and whole blood in pregnant subjects were also lower than those after pregnancy. These data show that blood concentrations of the active antimalarial metabolite cycloguanil are reduced in late pregnancy and that the currently recommended dose of proguanil could be inadequate for antimalarial prophylaxis in pregnant women.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 265-269 
    ISSN: 1432-1041
    Schlagwort(e): Cyclosporine ; Renal transplantation ; pharmacokinetics ; intraindividual variation ; circadian variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The intraindividual variability and circadian variation of oral cyclosporine (CsA) pharmacokinetics were studied over 24 h in 18 renal transplant recipients at steady state, and in 10 of the patients during a second 24 h period. The absolute percentage intraindividual difference in daytime AUC (0–12 h) ranged from 2% to 54% (mean 30%), and the corresponding variability in nighttime AUC (0–12 h) ranged from 5% to 80% (mean 34%). The pharmacokinetic variables t1/2, tmax and Cmax were more variable than the AUC (0–12 h) both during the day and at night. The evening trough level was significantly lower than the morning trough level; 185 ng · ml−1 versus 223 ng · ml−1. This, together with a significantly longer t1/2 in the night than the day, suggested circadian variability in the pharmacokinetics of CsA. In a separate retrospective study in 162 renal transplant recipients given CsA by constant intravenous infusion, repeated CsA blood concentration measurements at steady state showed lower concentrations during the day than the night, suggesting higher CsA clearance during daytime. It is concluded that CsA pharmacokinetics in renal transplant recipients, besides the well-known interindividual variability, also displays large intraindividual variability as well as circadian variation. Our findings further emphasize the necessity and difficulty of pharmacological monitoring in the clinical use of CsA in organ transplantation.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 301-302 
    ISSN: 1432-1041
    Schlagwort(e): Adriamycin ; Haemodialysis ; adriamycinol ; pharmacokinetics ; moment analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 305-306 
    ISSN: 1432-1041
    Schlagwort(e): Atenolol ; bioavailability ; intestinal absorption ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We investigated the dose proportionality after the intake of oral atenolol 25, 50, 100 and 150 mg. Standard tablets were taken by 8 healthy volunteers in randomised order of doses. The area under the curve divided by dose did not differ between the doses, indicating that the absorption of this hydrophilic compound, with known incomplete bioavailability, was constant over the range tested.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 45 (1993), S. 255-260 
    ISSN: 1432-1041
    Schlagwort(e): Ramipril ; Propranolol ; interaction ; pharmacokinetics ; pharmacodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the pharmacodynamic effects of ramipril, propranolol, and their combination, as well as the effect of propranolol on the pharmacokinetics of ramipril in 12 healthy men (age 24 (SD 6) y, weight 72 (7) kg). Propranolol and placebo, ramipril and placebo, or propranolol and ramipril were given orally for four days in a crossover, double-blind fashion. The pharmacokinetics of ramipril and ramiprilat were investigated on day 4. Effects on plasma renin activity, ACE activity, and heart rate and blood pressure both before and after a standardized exercise test were measured on days 1 and 4. On day 4 the combination reduced the mean arterial pressure by 2.8 mmHg compared with propranolol alone and by 3.7 mmHg compared with ramipril alone. Ramipril had no effect on the bradycardia induced by propranolol. Propranolol reduced exercise mean arterial pressure by 9 mmHg (day 4) and heart rate by 7 beats.min−1 (day 4) compared with ramipril; this was not affected by co-administration of ramipril. On day 4 the average plasma renin activity was not significantly higher than after the combination. ACE activity was not affected by propranolol. The pharmacokinetics of ramipril and ramiprilat were not influenced by propranolol. The combination of ramipril and propranolol has additive pharmacodynamic effects that may be useful in the treatment of hypertension.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 45 (1993), S. 275-277 
    ISSN: 1432-1041
    Schlagwort(e): Fenoterol ; Pregnancy ; pharmacokinetics ; premature labour
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of the β2-adrenergic drug fenoterol, which is used as a tocolytic agent in pregnancy, has been investigated in pregnant (n=9) and nonpregnant (n=5) women during a constant rate intravenous infusion. Clearance and mean residence time were found to be 1990 (1879/2220; Median, Q25/Q75) ml/min and 9.2 (8.0/14.0) min in the pregnant and 2126 (1915/2130) ml/min and 16.6 (16.5/32.1) min in the nonpregnant women, respectively. In addition, fenoterol clearance was estimated in 88 women from a single blood sample collected at steady state during IV therapy and the effect of gestational age on clearance was studied. Clearance displayed large inter-individual variation. There was no apparent correlation between clearance and gestational age. We conclude that there is no need to adjust the dose on pharmacokinetic grounds in the course of pregnancy.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 195-197 
    ISSN: 1432-1041
    Schlagwort(e): Cefotaxime ; Renal insufficiency ; desacetylcefotaxime ; pharmacokinetics ; children
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary It is generally assumed that the renal clearance of drugs in patients with renal impairment are affected to a similar extent regardless of the type of renal disease (intact nephron hypothesis). We have studied the effect of underlying renal disease on the pharmacokinetics of cefotaxime and desacetylcefotaxime in two groups of children (ages 7 to 16 y) with varying degrees of renal dysfunction. Patients in group 1 (n=5) had intrinsic renal disease and those in group 2 (n=5) had extrinsic renal disease, as identified by the primary renal lesion. After a single intravenous dose of cefotaxime timed blood and urine samples were collected for 24 h; cefotaxime and desacetylcefotaxime were measured by HPLC. There were no significant differences between the groups in age, body surface area, urine output, creatinine clearance, total body clearance, nonrenal clearance, renal clearance, and volume of distribution at steady state of cefotaxime, and renal clearance of desacetylcefotaxime. However, the renal clearance: creatinine clearance (CLR:CLCR) ratios for both cefotaxime [1.34 in group 1 vs. 0.51 in group 2] and desacetylcefotaxime [1.58 in group 1 vs. 0.75 in group 2] were statistically significant between the two groups. Group 1 patients had an average CLR:CLCR ratio greater than 1 for both the parent compound and the metabolite, suggesting that net tubular secretion was still intact, despite a diminished glomerular filtration rate (CLCR=24 ml·min−1·1.73 m−2). In contrast, patients in group 2 (CLCR=49) ml·min−1·1.73 m−2) had an average CLR:CLCR ratio less than 1 for both cefotaxime and desacetylcefotaxime, suggesting that renal tubular transport mechanisms did not remain functional in these patients. Our findings suggest that the effect of renal insufficiency on the renal elimination of cefotaxime and its metabolite desacetylcefotaxime may depend on the cause of renal insufficiency.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 253-258 
    ISSN: 1432-1041
    Schlagwort(e): Bioelectrical impedance ; Gentamicin ; non-invasive technique ; neonates ; predictive models ; pharmacokinetics ; plasma levels
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The use of bioelectrical impedance (BI) analysis as a non-invasive approach for individualising gentamicin therapy in newborn infants has been investigated in a two phase study. In Phase I, 1/impedance and length2 were identified as statistically significant predictors of the distribution volume of gentamicin (Adj R2=0.78, CV=12.42%), and length2/impedance and post-conceptual age were predictors of total systemic clearance (Adj R2=0.83, CV=14.5%), following the administration of 2.5 mg·kg−1 gentamicin to 17 neonates (gestational age (GA) 27 to 36 weeks). In a prospective validation of these relationships in an independent (Phase II) group of 27 infants (GA 26 to 41 weeks), predicted serum gentamicin concentrations were close to those achieved. Several instances of high prediction errors (predicted minus achieved levels) were observed in infants with known or suspected renal impairment and they caused significant (P〈0.05) perturbation in the bias and accuracy of the models. Daily BI measures over a four to five day period were able to detect individual changes in the fat-free body compartments, which were translated into alterations in gentamicin regimens. This simple, non-invasive and relatively inexpensive bedside technique provides a potentially valuable means to individualise gentamicin therapy without relying on the measurement of serum gentamicin concentration.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 357-360 
    ISSN: 1432-1041
    Schlagwort(e): Famotidine ; Reflux oesophagitis ; intraoesophageal long-term pH-metry ; pharmacodynamics ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics, pharmacodynamic effect and clinical efficacy of famotidine were studied in 10 patients with reflux oesophagitis Grades I and II. For the pharmacokinetic studies the patients received 20 mg famotidine i. v. The half-life of famotidine was 3.8 h, the total plasma clearance was 297 ml·min−1, and a steady state volume of distribution of 1.21·kg−1 was found. For pharmacodynamic assessment, intraoesophageal pH-metry was performed without and after acute treatment with famotidine 20 mg i. v. and following 3 weeks of oral famotidine 80 mg b. d. The resultant percentage total acid exposure time (pH〈4 within 24 h) were 23.9%, 19.0% and 19.2% (median), respectively (NS). At the end of 6 weeks of oral therapy, symptomatic and endoscopic improvement had occurred in 9 and 5 patients, respectively. Our study shows that the pharmacokinetics of famotidine in patients with reflux oesophagitis is comparable to that in healthy volunteers and peptic ulcer patients. The clinical response to the treatment appeared comparable to that found after other H2-receptor antagonists.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 365-367 
    ISSN: 1432-1041
    Schlagwort(e): Ciprofloxacin ; Diazepam ; quinolone ; benzodiazepine ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effects of pretreatment with a seven day course of ciprofloxacin on pharmacokinetics and pharmacodynamics of an intravenous (5 mg) dose of diazepam were investigated in a group of 12 healthy volunteers in a double-blind placebo-controlled crossover study. Ciprofloxacin pretreatment significantly reduced diazepam CL (without ciprofloxacin: 19.5 ml·h−1kg−1; with ciprofloxacin: 12.3 ml·h−1kg−1). Diazepam t1/2 was also prolonged (without ciprofloxacin: 36.7 h; with ciprofloxacin: 71.1 h), but volume of distribution was unaltered (without ciprofloxacin: 1.1 l·kg−1; with ciprofloxacin: 1.1 l·kg−1). However, no significant changes were detected in psychometric tests of digit symbol substitution, tapping rate and short memory, as well as levels of concentration, vigilance and tension measured by visual analogue scales.
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  • 47
    ISSN: 1432-1041
    Schlagwort(e): Temocapril ; Liver dysfunction ; angiotensin converting enzyme inhibitor ; diacid ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Six subjects with normal liver function (Group 1) and 7 patients with liver dysfunction (Group 2; mean ICGR15 value 30.5 (5.2) %; range 16 to 56) received a single oral dose of 1 mg temocapril, a prodrug-type ACE inhibitor, with preferentially excreted by the biliary route. The plasma temocapril concentrations in Group 2 at 30 min and 1 h postdose were significantly higher than in Group 1, but the difference had disappeared 2 h postdosing. Although the half life of temocapril diacid in Group 2 was significantly longer than in Group 1, there was no significant difference between the two groups in AUC, Cmax or tmax. In Group 2, urinary recovery of temocapril was significantly increased, suggesting a possible delay in the bioactivation of temocapril into the diacid, but recovery of the diacid itself was not abnormal. ACE inhibitory action in Group 2 remained unchanged. Temocapril is regarded as an ACE inhibitor the disposition and efficacy of which are little affected in patients with impaired liver function.
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  • 48
    ISSN: 1432-1041
    Schlagwort(e): Isradipine ; Diclofenac ; pharmacokinetics ; platelet aggregation ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In this open, two-period crossover study in 18 healthy male volunteers, a single oral dose of 50 mg diclofenac was administered alone and on day 7 of multiple oral dosing of 5 mg b.i.d. isradipine to assess a possible pharmacokinetic interaction. The effect of these drugs on ex vivo platelet function was also determined. Serial blood samples were obtained over 12-hour periods on three occasions: after the single diclofenac dose; after the morning dose of isradipine on day 6 and after co-administration of both drugs on day 7 of steady-state isradipine administration. Additional samples were taken at 2 h post dose for determination of ex vivo platelet aggregation. Isradipine plasma concentrations were determined by a gas chromatographic method and diclofenac plasma concentrations by an HPLC method. The pharmacokinetic characteristics of diclofenac were unaltered during co-administration. The maximum plasma concentration of isradipine was increased 19.6% during co-administration from 5.06 to 6.05 ng·ml−1. This is not expected to be of clinical importance. Isradipine's apparent total body clearance and steady-state AUC remained unchanged. Ex vivo induced platelet aggregation was not affected by any of the treatments.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 45 (1993), S. 555-558 
    ISSN: 1432-1041
    Schlagwort(e): Glucagon ; pharmacokinetics ; i.v. infusion ; intranasal spray ; intramuscular administration ; insulin-dependent diabetes mellitus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of intranasal, an intravenous infusion, and intramuscular glucagon has been studied in 5 healthy subjects and 11 patients with insulin-dependent diabetes mellitus. After infusion the elimination half-life was significantly longer in diabetics (11.9 vs 6.6 min) and the apparent volume of distribution was twice as high in diabetics (0.19 vs 0.37 l·kg−1). The metabolic clearance rates were the same in the two groups (18.9 and 21.3 ml·min−1·kg−1 in controls and in diabetics) and were about twice those previously reported. After 1 mg intranasally the Cmax of immunoractive glucagon (IRG) was similar in diabetic and in healthy subjects. Administration of a higher dose (2 mg) to diabetic patients produced a higher plasma level, although not proportionately so. The AUC after 1 mg was also similar in controls and in diabetics. The elimination half-life in both groups was similar to the value found after IV infusion; it was significantly shorter in controls (5.5 min) than in diabetics (13.8 min). In both groups, mean Cmax was significantly lower than after IM glucagon, the relative bioavailability of 1 mg intranasally vs IM injection being less than 30%. After IM administration, the Cmax and AUC of IRG in controls and in diabetic patients, were identical. The apparent elimination half-life was also similar in the two groups, and was three- to four-times longer (28.6 and 31.4 min) than after infusion or intranasal administration, possibly because estimation of the t1/2 was affected by slow release of the hormone from the site of injection.
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 45 (1993), S. 563-569 
    ISSN: 1432-1041
    Schlagwort(e): Chlorpromazine ; metabolites ; N-oxide ; sulfoxide ; 7-hydroxy ; conjugates ; pharmacokinetics ; first pass metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A study was carried out in 11 healthy young men to investigate the pharmacokinetics of chlorpromazine (CPZ) after a bolus intravenous (IV) dose (10 mg) and three single oral doses (25, 50 and 100 mg), with a washout period of two weeks between doses. Plasma levels of CPZ, CPZ N-oxide (CPZNO), CPZ sulfoxide (CPZSO) and both free and conjugated 7-hydroxy-CPZ (7-HOCPZ) were measured by extraction radioimmunoassays. CPZ exhibited multicompartmental pharmacokinetics in most subjects. There was wide between-subject variability in half life (11.05 h), volume of distribution (1215 l), volume of distribution at steady state (642 l) and mean residence time (8.88 h), whereas systemic clearance was somewhat less variable (76.6 l·h−1). All metabolites were present in measurable concentrations in the plasma of 9 of 11 subjects after IV CPZ, whereas free 7-HOCPZ was not detected in the other 2 individuals. With the exception of CPZNO, the biological half lives of the primary metabolites were longer than the half life of CPZ. After oral administration, the percentage of CPZ reaching the systemic circulation intact (F%) was very low (4–38%) and dose dependant. Moreover, both within-subject and between-subject variances were very high. The maximum plasma concentration (Cmax) and area under the plasma concentration versus time curve extrapolated to infinite time (AUC) showed evidence of nonlinearity, whereas half life did not appear to be dose dependant. These data suggest that the high degree of variability in the pharmacokinetics of CPZ is a result of extensive first pass metabolism rather than variation in half life. The mean AUC for the total conjugates of 7-HOCPZ was about two fold higher than that of the parent drug or any other metabolite. This shows that phase II metabolism plays a very significant role in the disposition of CPZ. As a result, the role of CYP2D6 in the 7-hydroxylation of CPZ cannot be fully assessed without taking phase II metabolism into account.
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 45 (1993), S. 585-587 
    ISSN: 1432-1041
    Schlagwort(e): Flumazenil ; benzodiazepine ; absorption ; disposition ; elderly volunteers ; pharmacokinetics ; aging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In an open design, randomised, two-way cross-over study, a single 2 mg i.v. dose and a single 30 mg oral dose of flumazenil were each administered to a group of healthy young (n=6) and elderly (n=12) volunteers (male: female 2/1). Plasma samples were collected at intervals and intact drug was assayed. Both the IV and oral doses of flumazenil were very well tolerated by both age groups and no severe or unexpected adverse effects were observed. The main complaints were dizziness and headache, mainly after oral dosing, probably due to the higher Cmax and AUC following this route of administration. After 2 mg i. v. the disposition parameters in the two age groups (elderly/young) were very similar: volume of distribution (Vss): 0.88/0.901·kg−1; total body clearance (ClPL): 0.86/0.99 l·min−1; terminal elimination half-life (t1/2β): 1.02/0.91 h. After the 30 mg oral dose the mean Cmax of 87.6 ng·ml−1 (elderly) and 78.4 ng·ml−1 (young) were generally reached within 0.5 to 1 h. In 26% (elderly) and 23% (young), the absolute bioavailability of flumazenil was very similar. It is concluded that the absorption and disposition paramters of flumazenil were not significantly affected by aging.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 27-33 
    ISSN: 1432-1041
    Schlagwort(e): Nicorandil ; vasodilator ; tolerance study ; blood pressure ; pharmacokinetics ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the effects of intravenous nicorandil, a mixed arterial and venous vasodilator, in 48 healthy volunteers. Nicorandil (20, 28, 39, 54, 74, 103, 144, or 200 μg·kg−1) or placebo were given over 5 min to subjects supine (16 subjects, 2 doses) or sitting (32 subjects, 1 dose) in a single-blind crossover design. Electro-cardiographic intervals, blood pressure, and heart rate were measured before and for 8 h after dosing. Blood and urine safety laboratory studies were also performed before and after dosing. All intravenous infusions of nicorandil and placebo were well tolerated and there were no clinically important safety concerns. The most frequent adverse event after nicorandil was headache (24 events by 19 subjects), although its occurrence was not strictly dose related. One subject experienced transient symptomatic hypotension (144 μg·kg−1). Mean plasma nicorandil concentrations were dose-related and fell with a half-life of 0.7 to 1.2 h. Systemic clearance and volume of distribution tended to decrease as dose increased. Sitting subjects showed marginally lower (〈20%) systemic clearances and larger values of Cmax and AUC. Nicorandil produced dose-related reductions in blood pressure, with consistent statistically significant differences from placebo after the 144 and 200 μg·kg−1 doses. The falls in blood pressure were greater for diastolic pressure and in this supine position. At 200 μg·kg−1, the mean falls in systolic/diastolic pressures (mm Hg) during the first hour were 10.9/14.7 supine and 6.1/9.1 sitting; systolic pressure returned to baseline after 8 h and diastolic pressure after 4 h. Heart rate increased transiently (mean peak increase of 17–24 bpm at the end of the 144 and 200 μg·kg−1 infusions). Blood pressure and heart rate changes over time were statistically significantly correlated with plasma nicorandil concentrations. Individual areas under the blood pressure and heart rate change curves likewise correlated with plasma concentration curve areas.
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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. S31 
    ISSN: 1432-1041
    Schlagwort(e): Cefmenoxime ; Renal failure ; continuous haemofiltration ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The elimination of cefmenoxime after single and repeated i. v. dosing was studied in 12 patients with severe renal failure and sepsis during continuous haemofiltration. More than 30 % of the drug was found in the filtrate. The sieving coefficient (S) was 0.54. Vss % was unchanged 0.311 · kg−1 in comparison with patients with normal renal function, whereas the mean t/12ß was prolonged to about 16 h, and total clearance was reduced 20.8 ml · min−1 · 1.73 m−2. Once daily administration of 1 g cefmenoxime is suggested as the appropriate dose under such circumstances.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 171-176 
    ISSN: 1432-1041
    Schlagwort(e): Oxprenolol ; β-adrenoceptor blockade ; circadian rhythm ; haemodynamics ; pharmacokinetics ; exercise ; healthy volunteers ; kinetic-dynamic model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the effect of dosage time of oxprenolol (Trasicor®) on its pharmacokinetics and pharmacodynamics in six healthy volunteers. The drug effects measured were heart rate and systolic blood pressure during exercise. Oxprenolol was taken orally at 08.00 h, 14.00 h, 20.00 h, and 02.00 h in randomized order, with 1 week between successive doses. There were differences in the pharmacokinetics of oxprenolol for the ratio between the apparent volume of distribution and systemic availability (P=0.04) and for elimination half-life (P=0.006). Both were lowest after administration at 14.00 h (163 (77) l and 1.2 (0.6) h; mean (SD)) and highest after administration at 02.00 h (229 (100) l, and 1.7 (0.6) h). The systolic blood pressure during exercise before oxprenolol did not vary with dosage time, but heart rate during exercise before intake was lowest before dosage time 08.00 h and highest before dosage time 20.00 h (P=0.03). The time-course of heart rate during exercise after oxprenolol was described by a model that incorporated the factors drug concentration and spontaneous diurnal variation. EC50 and Emax did not vary between dosage times. The spontaneous diurnal variation in heart rate during exercise was unaffected by oxprenolol, leading to an apparently greater effect of oxprenolol during the night than during the day.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. S53 
    ISSN: 1432-1041
    Schlagwort(e): Quinapril ; Renal failure ; quinaprilat ; haemodialysis ; ACE inhibitor ; pharmacokinetics ; pharmacodynamics ; peritoneal dialysis ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics and pharmacodynamics of the ACE inhibitor quinaprilat have been studied in six chronic haemodialysis (HD) patients and in six patients undergoing continuous ambulatory peritoneal dialysis (CAPD) after a single oral dose of 2.5 mg quinapril. Mean tmax and Cmax values (SEM) for quinaprilat in interdialytic HD patients were 4.0 (0) h and 84 (8.4) ng · ml−1 respectively, and they did not differ significantly from those in CAPD patients (4.7 (0.7) h and 64 (5.7) ng · ml−1). Elimination half lives were 30 (10.1) h (HD) and 34 (7.3) h (CAPD). Cmax, tmax, t/12, and AUC were increased and CL was decreased compared to data reported previously after giving 2.5 mg to healthy subjects. Peritoneal clearance was calculated as 0.1 (0.1) ml · min−1, thus less than 0.5 % of the dose were removed within 24 h by CAPD. ACE activity was suppressed by more than 93 % between 4 and 24 h postdose (P 〈 0.001). It decreased in both groups with increasing plasma quinaprilat levels. Angiotensin II concentration compared to baseline was significantly decreased at 4 hours (−30.4±10 %) and 24 h (−30±9.9 %) (P 〈 0.05,n=11), while active plasma renin concentration was still significantly increased at 48 h postdose (+60.2±14.5 %,P 〈 0.01). Mean arterial pressure 24 h postdose was significantly (P 〈 0.05) decreased in HD (−12 mm Hg) and CAPD patients (− 20 mm Hg). Only two patients reported unwanted effects (fatigue, dizziness, nausea, and weakness). In conclusion, due to its long lasting effect on ACE activity and on blood pressure in terminal renal failure a starting dose of quinapril 2.5 mg o. d. may be used in hypertensive HD and CAPD patients.
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 361-364 
    ISSN: 1432-1041
    Schlagwort(e): Tulobuterol ; β2-adrenoceptor agonist ; aerosol inhalation ; transdermal delivery ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the pharmacokinetics of tulobuterol given transdermally or by aerosol inhalation in healthy male volunteers. Tulobuterol was rapidly absorbed after inhalation, with a tmax of 0.8–1.5 h. The Cmax and the AUC increased linearly with dose. Tulobuterol was well absorbed after transdermal administration, with an absorption lag-time of about 4 h. The Cmax and AUC increased linearly with dose and the tmax was about 9–12 h. The mean percentage of drug absorbed during the application of a patch for 24 h was 82–90% after a single dose and 82–85% during repeated dosing. The mean urinary recoveries as unchanged drug after a single inhalation and patch application were 3–4% and 5–6% respectively. Tulobuterol did not accumulate during repeated inhalation or transdermal application. It was well tolerated, except for an increase in heart rate of 10–20 beats · min−1 after five repeated applications of a 4 mg patch.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 44 (1993), S. 387-389 
    ISSN: 1432-1041
    Schlagwort(e): Flosequinan ; Congestive heart failure ; elderly ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have investigated the pharmacokinetics of the direct vasodilator flosequinan in elderly patients with congestive heart failure. Eight patients received a single dose of 50 mg, and 8 patients received once-daily treatment with 25 mg for two weeks. In the single dose study, the tmax of flosequinan was 2.5 h, Cmax was 1.17 μg · ml−1 and t1/2 was 5.63 h. The tmax of the metabolite BTS 53554 was 20.3 h, Cmax was 1.44 μg · ml−1 and t1/2 was 62.0 h. BTS 53554 accumulated gradually in the 14-day repeated dose study and steady-state was reached after approximately 2 weeks. Flosequinan was not found to accumulate. Adverse reactions were not observed in either the single or repeated dose study. It is advisable to consider renal function and body weight when flosequinan is to be administered to elderly patients with congestive heart failure. The initial dose should be 25 mg.
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  • 58
    ISSN: 1432-1041
    Schlagwort(e): Metoprolol ; controlled-release formulation ; hydrochlorothiazide ; pharmacokinetics ; pharmacodynamics ; healthy volunteers ; efficacy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied a controlled-release formulation containing metoprolol 100 mg and hydrochlorothiazide 12.5 mg. We compared the pharmacokinetics of both substances and the pharmacodynamics of metoprolol with those of a conventional combination tablet. The controlled-release formulation gave less variable plasma metoprolol concentrations, Cmax 138 nmol·l−1 and Cmin 74 nmol·l−1, whereas for the conventional formulation the mean Cmax of metoprolol was 629 nmol·l−1 and the Cmin 20 nmol·l−1. Despite lower relative systemic availability (68%) for metoprolol from the controlled-release formulation and a smaller AUC, metoprolol from the controlled-release formulation produced a greater total effect, calculated as the area under the curve of the effect on exercise heart rate vs. time (303 vs. 259%·h; P〈0.05). Hydrochlorothiazide was rapidly absorbed from both formulations and the plasma concentration profiles were almost superimposable. Controlled-release metoprolol with hydrochlorothiazide combines effective β1-adrenoceptor blockade for 24 h without affecting the pharmacokinetics of hydrochlorothiazide.
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  • 59
    ISSN: 1432-0983
    Schlagwort(e): Electron microscopy ; Replicative intermediates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Some physicochemical properties of the mitochondrial DNAs (mtDNA) from plants of flax, broad bean and mung bean, and from tissue culture cells of jimson weed, soybean, petunia and tobacco were determined. Circular molecules were observed in electron microscope preparations of each mtDNA. In soybean, petunia, broad bean and mung bean mtDNAs, the circular molecules had a continuous distribution of lengths (ranges between 1 to 36 kb, and 1 to 126 kb), heavily skewed toward smaller molecules. Eighty-six percent of the flax circular molecules were from 27 to 54 kb in size, and 78% of the jimson weed circular molecules were from 4 to 15 kb. Replicative forms of 1.2–1.6 kb circular molecules were observed in electron microscope preparations of broad bean mtDNA.
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 411-418 
    ISSN: 1432-1041
    Schlagwort(e): 5-fluorouracil ; colorectal carcinoma ; pharmacokinetics ; product-inhibition ; blood clearance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The nonlinear disposition kinetics of 5-fluorouracil (5-FU) were investigated in 6 patients with colorectal carcinoma. Each patient randomly received two single, intravenous doses of 5-FU (7.5 and 15 mg/kg) on separate days. Venous blood and urine samples were collected just prior to and for 5 h after drug administration. In addition to the kinetic studies, the in vitro whole blood/plasma concentration ratio and stability of 5-FU at 37°C were determined in whole blood from normal volunteers and from 5 patients with colorectal carcinoma. A disproportionate increase in area under the curve and corresponding decrease in total body clearance with increasing dose was observed suggesting dose-dependent behavior of 5-FU. Doubling the dose was accompanied by a 36% decrease in nonrenal clearance but no apparent change in renal clearance. Therefore, the mechanism for dose-dependent elimination appears to be primarily associated with nonrenal processes. The mean 5-FU half-life following the high dose was nearly twice as long as that observed for the low dose (12.3 versus 6.2 min). The log-linear decline in plasma concentrations and increase in half-life with dose suggest the potential role of product-inhibition as an explanation for the observed nonlinearity in 5-FU elimination. The present study demonstrates that 5-FU degrades when incubated in whole blood. This most likely reflects metabolism in red blood cells or other blood-formed elements since 5-FU was stable in plasma. Although degradation in whole blood occurs, the estimated whole blood clearance does not contribute significantly to the observed total body clearance value. These findings suggest the possibility of pulmonary clearance of 5-FU.
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 431-432 
    ISSN: 1432-1041
    Schlagwort(e): theophylline ; fluoroquinolones ; drug interaction ; pharmacokinetics ; ofloxacin ; norfloxacin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Pretreatment for 3 days with oral ofloxacin or norfloxacin had no significant effect on the disposition of a single i.v. dose the theophylline in healthy volunteers.
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  • 62
    ISSN: 1432-1041
    Schlagwort(e): growth hormone releasing factor ; radio-immunoassay ; pharmacokinetics ; variance model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Three ranges of doses of growth hormone releasing factor (2.5–80 µg, 80–320 µg and 75–600 µg) were intravenously administered to healthy young volunteers in three double blind studies. Serum circulating GRF levels were determined by radioimmunoassay. Experimental concentration curves were fitted, using the extended least squares method, to a biexponential model for the structural model and power function for the variance model. The power variance model, compared to the constant variance model greatly reduced the coefficient of variation of the biexponential parameters. The power of the variance model was estimated to be 1.95. The distribution half-life was 6.6 min and the elimination half-life was 39.0 min (harmonic means). Total clearance was 0.12±0.01 µg/l/min. No difference between these parameters was found for the various doses. GRF kinetics was linear established in the range 10 to 600 µg which means that elimination was not altered by the increased doses.
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 563-568 
    ISSN: 1432-1041
    Schlagwort(e): nitrendipine ; pharmacokinetics ; hepatitis ; liver cirrhosis ; protein binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Twenty one patients with liver disease (cirrhosis 11, chronic hepatitis 5 and acute hepatitis 5) and 6 healthy volunteers were given a single i.v. dose of nitrendipine 5 mg. Afterwords nitrendipine 20 mg once daily were administered orally for seven days. With the intravenous injection a significant increase in the AUC and elimination half-life of nitrendipine was found in patients with cirrhosis as compared to the normal volunteers. After chronic oral dosing, the area under the plasma concentration-time curve, AUC (0–24), was 94.5 ng ml−1 h and the plasma clearance CL was 1380.6 ml/min in the healthy controls; in patients with cirrhosis the AUC (0–24) h was significantly greater at 309.4 ng ml−1 h and CL had fallen to 686.6 ml/min. Considerable accumulation of nitrendipine was also found in the patients with chronic hepatitis. Nitrendipine could not be detected in urine from any of the subjects. Blood pressure and heart rate were not significantly influenced by the treatment in the various groups investigated. Antipyrine clearance in the patients with cirrhosis was correlated with the nitrendipine plasma clearance. Thus, accumulation of nitrendipine has been demonstrated in the patients with cirrhosis and chronic hepatitis.
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 597-605 
    ISSN: 1432-1041
    Schlagwort(e): iloprost ; prostacyclin analogue ; pharmacokinetics ; pharmacodynamics ; radiolabeled study ; volunteers ; side-effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma levels and excretion of tritium-labeled iloprost in healthy elderly male and female volunteers have been measured after i.v. infusion of 2 ng·kg−1·min−1 for 4 h and oral administration of 0.1 and 0.48 μg/kg. During infusion, a steady-state of labeled compounds in the plasma was not achieved. Total radioactivity declined from a mean of 408 pg equiv/ml in three phases, with half-lives of 24 min, 1.7 h and 5.0 h, respectively. A steady-state of unchanged iloprost was reached rapidly with a peak of 81 pg/ml. Plasma levels declined biphasically with half-lives of 6 min and 31 min. Total clearance was 24 ml· min−1·kg−1. Maximum concentrations of labeled substances after oral administration were 307 and 1,051 pg equiv/ml after 29 and 39 min respectively. The peak of unchanged iloprost (116 pg/ml) was observed 7.5 min after an oral dose of 0.48 μg/kg. Bioavailability was 16%. Iloprost was totally metabolized and the metabolities were mainly excreted in urine. The main biotransformation products in plasma and urine were tentatively identified by cochromatography as dinor-and tetranoriloprost and their glucuronides. ADP-induced platelet aggregation was reduce by 60% during the i.v. infusion and 15 min after oral administration of 0.48 μg/kg. Heart rate and blood pressure were virtually unaffected. Common side-effects were facial flush, headache and nausea.
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 625-629 
    ISSN: 1432-1041
    Schlagwort(e): disopyramide ; bioavailability ; saturable binding ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of disopyramide were determined in 10 healthy volunteers after a 300 mg oral dose and again after a 2mg/kg i.v. dose. The unbound clearance was 599 ml/min and the unbound renal clearance 310 ml/min. The terminal elimination rate constant of unbound drug was 0.180 h−1 after the i.v. dose and 0.203 h−1 after the oral dose. The absorption rate constant was 0.53−1 and the maximum peak concentration occurred after 3.2 h. The bioavailability was 0.809 using the area under the unbound plasma concentration time curve. Although a saturable plasma protein binding was found in all subjects the bioavailability using the total concentration, in contrast to theoretical expectations, showed the same value (0.813) as the unbound concentrations.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 197-201 
    ISSN: 1432-1041
    Schlagwort(e): ceftazidime ; renal impairment ; plasmapheresis ; pharmacokinetics ; cephalosporins ; autoimmune disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of plasmapheresis (PA) on the elimination kinetics of ceftazidime (Cef) has been investigated. A single dose of Cef was administered intravenously to 11 patients with autoimmune diseases and varying degrees of renal impairment (Group I CLCR〈50 ml/min, Group II CLCR〉50 ml/min). In Groups I and II the mean total clearance of Cef (CL) was 30 and 116 ml/min−1, respectively. The elimination half-life (t1\2β) and the volume of distribution (V) were significantly higher in Group I than in Group II (11.9 vs 2.0 h, 27.1 vs 18.5 l). PA had no influence on the plasma level-time profile of Cef. The amount of Cef recovered from separated plasma accounted for only 2 to 9% of the administered dose, being particularly low in patients with normal renal function (4.6%). Thus, since elimination of Cef via PA is negligible, dosage calculations should be based solely on renal function.
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 227-230 
    ISSN: 1432-1041
    Schlagwort(e): enoxacin ; theophylline ; drug interaction ; healthy volunteers ; adverse effects ; pharmacokinetics ; renal tubular excretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The mechanism of the theophylline-enoxacin interaction has been studied in six healthy subjects. Theophylline 250 mg was administered p.o., twice daily for 11 days in a sustained release dosage form. On the 4th day of treatment, blood samples were taken every 2 h and urine was collected over 1 dose interval. From Days 5 to 11 coated tablets of enoxacin 400 mg b.i.d. were coadministered. On Day 11 blood and urine were collected as on Day 4. The mean plasma theophylline concentration rose from 4.4 to 15.1 mg/l, corresponding to a 73.6% reduction in total clearance. The urinary excretion of unchanged theophylline increased from 12.7 to 35.3%, whereas the production of metabolites was reduced (1-demethylation 81.4%; 3-demethylation 83.1%, 8-hydroxylation 74.6%). The results indicate that the theophylline-enoxacin interaction may be due to inhibition of the cytochrome P-450 isozymes responsible for theophylline metabolism. Unexpectedly, the renal clearance of theophylline metabolites was found to be drastically reduced when enoxacin was coadministered. This led to unchanged or even to elevated plasma levels of the metabolites. The mechanism of this interaction is still to be elucidated, but it may be due to competition for renal tubular secretion.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 323-325 
    ISSN: 1432-1041
    Schlagwort(e): iron deficiency anaemia ; sulphadimidine ; absorption ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effect of iron deficiency anaemia and its treatment on the absorption of sulphadimidine has been investigated in adult patients. The absorption judged by total % of the dose excreted in urine and Cmax, tmax, AUC and Kabs in plasma, was not significantly different before and after iron therapy or correction of anaemia. However, sulphadimidine absorption by the anaemic patients was significantly greater than in normals.
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 315-318 
    ISSN: 1432-1041
    Schlagwort(e): propranolol ; pharmacodynamics ; pharmacokinetics ; beta-blockade ; sustained-release propranolol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The duration and extent of cardiac beta-blockade and their relationship to propranolol pharmacokinetics were assessed in nine healthy volunteers. Each subject received 160 mg of regular propranolol (R), 160 mg of sustained-release propranolol (SR) and no drug (control), both as single doses and once daily for 7 days. After single doses and at steady-state, both products caused a decrease in exercise heart rate for at least 24 h, compared to control. The time course of effect was similar to the time course of serum propranolol concentration. The oral clearance of propranolol decreased from single doses to steady-state for both R and SR; however, the difference achieved statistical significance only for R. These changes were reflected in mean accumulation ratios (AUC steady-state 0–24 h/AUC single dose 0-infinity) of 1.49 and 1.68 for R and SR, respectively. The pharmacokinetic data are consistent with a decrease in intrinsic hepatic clearance of propranolol, leading to an increase in bioavailability at steady-state. Despite a two-fold difference in the bioavailability of R and SR, there was no difference in the area under the effect-time curve at steady-state.
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  • 70
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 355-361 
    ISSN: 1432-1041
    Schlagwort(e): metoprolol ; smoking ; gender ; pharmacokinetics ; HPLC ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The purpose of this study was to examine the influence of cigarette smoking and gender on the pharmacokinetics of metoprolol. Eighteen volunteers with no evidence of clinical disease each randomly received the following doses of metoprolol tartrate: 100 mg orally, 200 mg orally and 20 mg as a constant-rate intravenous infusion over 20 min. The only significant difference between smokers (S) and nonsmokers (NS) was that S had a larger steady-state volume of distribution (3.3 vs 2.5 l/kg). There were no differences in half-life, systemic clearance or bioavailability (f). No differences were observed between males (M) and females (FM) for any of the kinetic parameters examined. Systemic bioavailability varied markedly between subjects (range: 15 to 92%). In fifteen of the eighteen subjects, f was higher after the 200-mg dose compared to the 100-mg dose. These results suggest that metoprolol may be subject to saturable presystemic elimination and extend the previous observations of Johnsson et al. [1] who showed that f increased from 31% to 46% when doses were increased from 20 to 100 mg. However, the difference in f as the dose is increased is unlikely to be clinically significant since the mean difference is smaller than the variation in f among subjects.
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  • 71
    ISSN: 1432-1041
    Schlagwort(e): amodiaquine ; Plasmodium falciparum malaria ; monodesethylamodiaquine ; HPLC ; pharmacokinetics ; prophylaxis ; metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The disposition of monodesethylamodiaquine was studied in four healthy subjects after a single oral dose of 10 mg/kg amodiaquine base. Amodiaquine was not found in any sample, but the major metabolite monodesethylamodiaquine was detected and was assumed to be the sole derivative that contributed significantly to antimalarial activity in the blood. The best fit for the decay of the metabolite was obtained with a three-compartment model. The half-lives of the first two phases were 3.2 to 11.4 h for t1/2α1 and 22.7 to 50.3 h for t1/2α2 in plasma. The half-life of the terminal phase ( t1/2β) was between 9 and 18.2 days. The concentration in whole blood was 4- to 6-times higher than in plasma. Three schedules (alternate days, weekly, daily) of the conventional prophylactic dose of 10 mg/kg per week were compared in six other healthy subjects. There were significant differences in the plasma monodesethylamodiaquine levels between the three schedules.
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  • 72
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 423-426 
    ISSN: 1432-1041
    Schlagwort(e): Ketanserin ; pharmacokinetics ; hypertension ; ketanserinol ; predicted plasma concentration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the pharmacokinetics of ketanserin in 6 hypertensive patients after a single oral 40 mg dose and at steady-state after 4 weeks treatment with 20 mg and then 40 mg 12-hourly. Pharmacokinetic variables after a single dose were similar to those reported in healthy volunteers, with median values for Cmax 112 ng·ml−1, tmax 1 h, and t1/2 19 h. The corresponding values for the metabolite ketanserinol were Cmax 155 ng·ml−1, tmax 2 h, and t1/2 25 h. The median AUC was 3.3 times greater for ketanserinol than for the parent drug. These results were used to predict the mean steady-state plasma concentrations of ketanserin and ketanserinol. Predicted values were on average similar to those observed after four weeks treatment with 40 mg 12-hourly, although there were marked differences between the observed and predicted values in some patients. There was no evidence of time- or dose-dependent kinetics for ketanserin, but the study had insufficient power to exclude the occurrence of these phenomena entirely.
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 531-534 
    ISSN: 1432-1041
    Schlagwort(e): ketoconazole ; pharmacokinetics ; antimycotic drug
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the pharmacokinetics of the anti-mycotic ketoconazole in seven patients who took it for 1–6 months at a dose of 200 mg daily. The mean elimination half-life of the drug was 3.3 h, and although the ketoconazole was given only once daily, a satisfactory clinical response was obtained in all seven individuals. Only a small fraction of the absorbed drug (mean 0.22%) was excreted unchanged in the urine, suggesting almost complete metabolism. Our results support the concept that anti-mycotic activity in the tissues continues after the plasma drug concentration has fallen below a critical level. Our results also support the concept of a change in pharmacokinetics with chronic dosing.
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 67-72 
    ISSN: 1432-1041
    Schlagwort(e): cisplatin ; pharmacokinetics ; modelling ; drug dispositions ; cancer patients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have fitted a first-order multicompartment pharmacokinetic model to plasma platinum concentrations measured in nine ovarian cancer patients who received intravenous infusions of cisplatin for 6 h. The time-course of ultrafilterable plasma platinum was similar in all patients studied, and was fitted by a single compartment within the limits of experimental detection. However, the time-course of protein-bound platinum showed marked differences between patients, the differences being explained by distribution to two peripheral compartments. The wide inter-patient variation observed in protein-bound plasma platinum concentrations supports the view that pharmacokinetic modelling should be carried out separately for each patient, since averaging plasma concentrations would have obscured some individual pharmacokinetic characteristics.
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 59-65 
    ISSN: 1432-1041
    Schlagwort(e): indoramin ; 6-hydroxyindoramin ; debrisoquine ; hydroxylators ; genetic polymorphism ; blood pressure ; pharmacokinetics ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Five poor metabolisers (PM) and seven extensive metabolisers (EM), of debrisoquine, all healthy volunteers, received 50 mg indoramin orally following an overnight fast. Plasma concentrations of indoramin and 6-hydroxyindoramin were determined by HPLC with fluorimetric detection. In PM subjects, mean values of Cmax (158 ng/ml) and AUC(0–24) (2556 ng·h·m−1) for indoramin were substantially elevated and t1/2β (18.5 h) prolonged by comparison with values in the EM subjects (21.6 ng/ml, 151 ng·h·ml−1 and 5.2 h respectively). For 6-hydroxyindoramin, on the other hand, Cmax (12.4 ng/ml) and AUC(0–8) (47.5 ng·h·ml−1) in PM subjects were significantly lower than in the EM subjects (28.2 ng/ml and 94.7 ng·h·ml−1). There was a tendency to a higher incidence of side-effects in the PM group. Although the difference did not achieve statistical significance (0.1〉p〉0.05), all the PM subjects experienced sedation compared to only two in the EM group. Differences in blood pressure and pulse rate between the two groups were small. It is concluded that the oxidative metabolism of indoramin is subject to genetic polymorphism, which is probably under the control of the same gene locus as that influencing debrisoquine oxidation. The clinical consequences are discussed.
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 179-183 
    ISSN: 1432-1041
    Schlagwort(e): aminoglycosides ; haemodialysis ; gentamicin ; tobramycin ; pharmacokinetics ; renal failure ; kanamycin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The study was undertaken to look for a correlation between the measured elimination rate constants (k) of aminoglycosides and creatinine during haemodialysis. The pharmacokinetics of aminoglycosides were studied during 44 courses of haemodialysis in 21 patients. The measured k of gentamicin and tobramycin from the start until 30 min after the end of haemodialysis (mean 0.18 h−1; t1/2=3 h 51 min) was significantly correlated with the measured k of creatinine (mean 0.13 h−1; t1/2=5 h, 20 min), and also with the gentamicin and tobramycin k during haemodialysis (mean 0.20 h−1, t1/2=3 h, 28 min), as predicted by a computer program. Thus, serum concentrations of aminoglycosides 30 min after haemodialysis can be estimated by simple regression equations. However, because the measured and predicted values may diverge considerably in the individual patient, monitoring of aminoglycoside concentrations in serum after haemodialysis remains necessary.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 287-292 
    ISSN: 1432-1041
    Schlagwort(e): praziquantel ; cysticercosis ; pharmacokinetics ; cerebrospinal fluid ; parasite drug level
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Two patients with cysticercosis received praziquantel (PZQ) 75 mg/kg/day orally together with 30 mg prednisone daily for 3 weeks. The first patient presented with grand-mal seizures, a pyramidal tract syndrome and subcutaneous cysticerci, and the other had internal hydrocephalus necessitating drainage. Serial plasma samples were taken after the first dose of PZQ. Lumbar CSF was obtained from the first patient and ventricular CSF from the second. Subcutaneous cysticerci were removed from the first patient. PZQ in the specimens was assayed by GLC. For distribution between plasma and CSF a rate constant of 4.9 h−1 for free PZQ, corresponding to a t1/2 of 8 min or less for the non-protein bound fraction was calculated for Patient 1. In the second patient the distribution was so rapid that the rate constant could not be calculated. The difference in distribution rate might have been due to use of different sampling times or to a time lag in the entry of PZQ between the ventricles and the lumbar sac. The rate constant for distribution of the drug between plasma and parasites was 1.4 h−1, corresponding to a t1/2 of 30 min or less. Thus PZQ penetrates rapidly into the CSF. It enters the parasite more slowly, although still more rapidly than the plasma half-life of PZQ (1–1 1/2 h).
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  • 78
    ISSN: 1432-1041
    Schlagwort(e): metoprolol ; neonates ; amniotic fluid ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Seven women were treated with metoprolol 50–100 mg twice daily for hypertension in pregnancy. The disposition of metoprolol and one of its metabolites alfa-OH-metoprolol was studied in venous plasma and amniotic fluid during labour, in mixed cord plasma and in capillary blood of the newborn. Peak concentrations of metoprolol and alfa-OH-metoprolol were reached 60 to 120 min after dosing in maternal plasma while the amniotic fluid levels of these compounds continued to increase from 60 to 180 min to the end of the study and were substantially higher than in the plasma after 4 to 5 h. It is postulated that a major fraction of metoprolol and alfa-OH-metoprolol reaches the amniotic fluid via the fetal urine and that the elimination from the amniotic fluid mainly proceeds via diffusion across fetal membranes and transfer across the fetal capillary bed. No measurable concentrations of metoprolol were found in two of the newborns 2 h after delivery. In the remaining four neonates the 2-h concentrations exceeded the corresponding cord plasma levels. In all neonates the alfa-OH-metoprolol levels in the capillary blood were higher 2 h after birth than in cord blood. In two newborns the metabolite levels continued to increase for 5 h and in one the highest blood concentrations of this metabolite was found 20 h after birth. Redistribution of metoprolol from tissue stores followed by metabolism might be the cause of these temporary elevations of the blood levels of metoprolol and alfa-OH-metoprolol.
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 431-434 
    ISSN: 1432-1041
    Schlagwort(e): phenylethylmalonamide ; pharmacokinetics ; elderly
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of phenylethylmalonamide (PEMA) were studied in 6 elderly men after oral administration of a single 400 mg dose. Peak PEMA serum levels were obtained within 4 h of intake, half-life values ranged from 30.7–57.9 h in these elderly men. The elimination half-life was twice as long when compared to a study previously performed in young volunteers.
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 493-498 
    ISSN: 1432-1041
    Schlagwort(e): amiloride ; pharmacokinetics ; renal failure ; liver disease ; urinary excretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of the antikaliuretic amiloride has been studied in healthy controls and in patients with chronic renal failure or hepatitis. It was 40% bound to protein. In healthy volunteers 49% of an oral dose was recovered unchanged in the urine. The renal clearance of amiloride was about 3 times the creatinine clearance, which means that it was predominantly excreted via tubular secretion. Renal impairment reduced the clearance of amiloride, causing a prolongation of the t1/2 and drug accumulation in plasma. In hepatitis the t1/2 of amiloride was prolonged and the AUC increased. Urinary recovery (Ae) of amiloride was greater in hepatitis patients than in controls.
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 33 (1987), S. 499-504 
    ISSN: 1432-1041
    Schlagwort(e): morphine ; epidural administration ; pharmacokinetics ; CSF/plasma concentrations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In order to determine the rate and degree of redistribution of morphine within the cerebrospinal fluid (CSF), and whether it was affected by the site of and volume of the injection, morphine was given to 23 elderly patients undergoing thoracotomy — in 10 ml saline in the lumbar epidural interspace (n=5), in 10 ml saline in the thoracic epidural interspace (n=5), in 2 ml saline in the thoracic interspace (n=8) and in 10 ml saline in the lumbar epidural interspace (n=5). The plasma concentration of morphine in all patients was comparable and was much lower than in the CSF. The CSF morphine concentration, measured as the area under the CSF concentration curve (AUC), the maximal CSF concentration (Cmax) and the time to reach maximal CSF concentration (tmax), varied between the four groups. The variation was related to the site of the injection; the AUC and Cmax were lower and tmax appeared later after thoracic than lumbar injection. Lumbar CSF morphine concentrations were further reduced by thoracic epidural injection of morphine in a small as compared to a large volume. The permeability of the dura to morphine was not influenced by the volume used. The results show that morphine is not homogenously distributed within the CSF. The availability of morphine to CSF from the epidural space is not altered by the injection volume, but the drug remains more localized in CSF after epidural injection of morphine in a small volume. The findings imply that epidural injection of morphine in a small volume at a site of nociceptive input should evoke spinal analgesia with least risk of supraspinally mediated side effects.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 273-277 
    ISSN: 1432-1041
    Schlagwort(e): pentobarbital ; hexobarbital ; dipyrone ; intensive care ; D-glucaric acid ; pharmacokinetics ; drug interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effect of pentobarbital treatment in a mean dose of 30 mg/kg/day on the clearance of hexobarbital (Evipan) and dipyrone (Novalgin) has been evaluated in critical care patients receiving a large number of drugs as comedication. Eleven patients treated with pentobarbital showed a hexobarbital half-life of 2.79 h and a total plasma clearance of 9.80 ml·min−1·kg−1 as compared to 10 patients without pentobarbital administration in whom there was a significantly longer half life (6.92 h) and lower clearance (2.97 ml·min−1·kg−1). The kinetics of hexobarbital were correlated with the urinary excretion of D-glucaric acid, a non-invasive parameter of drug metabolising activity. In 10 patients on pentobarbital, the total plasma clearance of N-4-methylaminoantipyrine, the active form of dipyrone, did not differ from that in 8 patients not receiving pentobarbital. As drug kinetics show great variability in these patients, it is difficult to discriminate enzyme induction from other mechanisms, for example competitive inhibition or changes in volume of distribution. In the presence of pentobarbital, however, induction of drug metabolising enzymes should be considered as a possible reason for the higher clearance of hexobarbital.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 367-372 
    ISSN: 1432-1041
    Schlagwort(e): endralazine ; severe hypertension ; food intake ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A sensitive HPLC assay has been used to determine the effect of food on plasma endralazine levels in 8 patients with essential hypertension. Subjects were investigated whilst on maintenance therapy with endralazine combined with a fixed antihypertensive baseline treatment for at least 4 weeks, samples being collected after the usual oral morning dose of endralazine (5 mg and 10 mg), on two occasions at least 7 days apart. Endralazine was administered with the concomitant therapy in randomised order once 90 min before and once immediately after a standard breakfast. Acetylator status did not affect its pharmacokinetics in the postprandial study after a 5 mg dose, the peak endralazine concentration averaged 57.5% lower and the AUC had fallen significantly by 49.9%, whereas after 10 mg the postprandial peak level and the AUC were 82.9% and 64.7%, lower. In the 5 mg study the mean arterial blood pressure was decreased by 30 mm Hg in the fasting subjects and by 21 mm Hg in the post-prandial group. For the 10 mg dose the corresponding values were 35 and 24 mm Hg. The blood pressure lowering effect was only weakly correlated with the food — related reduction in the plasma endralazine levels. The results suggest that endralazine has a similar kinetic interaction with food as that found for hydralazine.
    Materialart: Digitale Medien
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  • 84
    ISSN: 1432-1041
    Schlagwort(e): triazolam ; troleandomycin ; benzodiazepines ; antibiotics ; drug interaction ; pharmacokinetics ; first-pass effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Seven healthy volunteers received a single oral dose of triazolam 0.25 mg after 7 days on troleandomycin 2 g/day p.o. or placebo in a double-blind cross-over study. Plasma triazolam and psychometric and memory tests (including Critical Flicker Fusion threshold, Choice Reaction Time, Digit Symbol Substitution and Self-Rating Scales) were assessed at regular intervals after the final treatment. Troleandomycin was found to prolong the psychomotor impairment and amnesia produced by triazolam. There was a significant enhancement of the AUC, the peak concentration and the delay to tmax of triazolam after 7 days treatment with troleandomycin compared to placebo. Thus, there is a pharmacokinetic interaction, and the combination of triazolam and troleandomycin should be avoided or the dose of triazolam should be adjusted. The most likely mechanism is a diminished hepatic first-pass effect, and a decrease in the apparent oral clearance of triazolam.
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 577-582 
    ISSN: 1432-1041
    Schlagwort(e): yohimbine ; pharmacokinetics ; plasma levels ; renal elimination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetic disposition of yohimbine was examined in eight young male subjects following a single oral dose of 10 mg yohimbine hydrochloride. The drug was rapidly absorbed (absorption half-time 0.17±0.11 h) and rapidly eliminated from the plasma (elimination half-life 0.60±0.26 h). This clearance of yohimbine from plasma was constant over approximately 10 elimination half-lives, suggesting that distribution into a second pharmacokinetically distinct compartment was not responsible for the rapid decline in plasma yohimbine levels. Urinary excretion and the partitioning of the drug into red blood cells (RBC) was investigated. In the 24 h following oral administration of the drug, virtually no yohimbine was eliminated in the urine (0.35±0.50% of the administered dose). Furthermore, only 20% of blood-borne yohimbine was located in RBC. These results suggest that yohimbine is eliminated primarily through metabolism since the rapid plasma clearance of yohimbine was not the result of renal elimination or sequestration by RBC.
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  • 86
    ISSN: 1432-1041
    Schlagwort(e): moracizine·HCl ; antiarrhythmic ; ethmozine ; radiolabelled ; pharmacokinetics ; material balance ; healthy subjects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Moracizine (ethmozine) is a phenothiazine derivative with demonstrated antiarrhythmic activity. To characterize the pharmacokinetics and material balance relationships in humans, we have given14C-moracizine·HCl as a single oral dose of 500 mg (50 μCi) to six healthy men. Plasma, urine, and faecal samples were collected for 7 days after administration and the concentrations of total radioactivity and intact moracizine were determined by liquid scintillation counting and HPLC, respectively. Urine and faecal recovery accounted for 95% of the administered radioactivity. Most of this radioactivity was found in the faeces (59%). Only 0.05% of the dose was recovered from urine as intact moracizine. The Cmax and AUC for moracizine equivalents of total radioactivity were 4- and 18-fold higher, respectively, than the corresponding values for intact moracizine. Additionally, both the disappearance of total radioactivity from plasma and its excretion rate into urine were slower in comparison to intact drug. Terminal t1/2 values calculated from plasma concentration-time data were 85.2 and 3.5 h for total radioactivity and intact moracizine, respectively. However, based on urinary excretion rates, the t1/2 for total radioactivity was shorter (29.3 h) while the t1/2 for intact drug was comparable (2.7 h) to the results obtained from the plasma data. The oral plasma clearance of moracizine was relatively large (2.2l·min−1), suggesting first-pass metabolism. The estimated oral systemic availability of moracizine was 34%.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 31 (1987), S. 711-714 
    ISSN: 1432-1041
    Schlagwort(e): flecainide ; pharmacokinetics ; moderate renal failure ; variability of elimination half-time
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the pharmacokinetics of flecainide after the oral administration of 100 mg to 8 patients without renal impairment and 8 patients with mild to moderate renal failure. Both groups gave comparable results with respect to the peak plasma concentrations and the time to peak. There was a significant correlation between renal flecainide clearance and endogenous creatinine clearance. The elimination half-time in the patients with impaired renal function was significantly longer (19.9, SD 9.9 h) than that in the patients with normal renal function (11.5, SD 4.2 h), but the variability in the elimination half-time in renal failure could not be explained on the basis of the available results.
    Materialart: Digitale Medien
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  • 88
    ISSN: 1432-1041
    Schlagwort(e): captopril ; uraemia ; captopril disulfide ; dialysis ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have measured the plasma concentrations of captopril and total disulfide conjugates of captopril after a 50 mg oral dose in 6 uraemic patients on maintenance dialysis and in 8 hypertensive subjects with normal renal function. The mean peak plasma concentration of captopril was 2.5 times higher (0.447 µg·ml−1 vs 0.181 µg·ml−1) and the concentrations of the disulfides 4 times higher (3.62 µg·ml−1 vs 0.924 µg·ml−1) in the uraemic patients. Moreover captopril disulfide conjugates in the uraemic subjects reached peak concentrations at 8 h after the dose and subsequently felt. The apparent plasma half-time was 46±19 h. Only 15% of these conjugates were removed by dialysis. This marked accumulation of captopril conjugates was associated with a sustained fall in both systolic and diastolic blood pressures. In uraemic patients the mean maximum reduction in systolic and diastolic blood pressures were 37±7 mmHg and 24±9 mmHg respectively, occurring 6 h after the dose, compared with 8±7 and 8±1 mmHg respectively at 30 min in normal renal function patients. These results are consistent with the results of animal experiments, which show that captopril disulfides can be converted back to free captopril and can contribute to the antihypertensive effect of the drug. They provide a reationale for reducing the dose and frequency of administration of captopril in patients with significant renal impairment.
    Materialart: Digitale Medien
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  • 89
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 309-311 
    ISSN: 1432-1041
    Schlagwort(e): digoxin ; verapamil ; cirrhosis ; drug interaction ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of a single low dose of verapamil (80 mg) on the serum levels of digoxin (single dose of 0.5 mg) was studied in 6 patients with hepatic cirrhosis and in 6 healthy volunteer controls. In the cirrhotic patients verapamil increased the peak serum level and the total AUC of digoxin by 98% and 32%, respectively. There was an associated 23% decrease in the renal digoxin clearance. In normal subjects only marginal alterations in digoxin kinetics were observed following verapamil administration. The results indicate that cirrhosis magnifies the influence of verapamil on digoxin kinetics.
    Materialart: Digitale Medien
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 303-307 
    ISSN: 1432-1041
    Schlagwort(e): azapropazone ; arthritis ; pharmacokinetics ; synovial fluid level ; synovial tissue level
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The concentration-time curves of azapropazone in synovial fluid and tissues have been studied in arthritic patients after an i.v. bolus (600 mg) and under steady-state conditions. Synovial fluid and tissue samples were taken intraoperatively 0.45–60 h after administration. The azapropazone concentrations in synovial fluid, synovial tissue and plasma were correlated. The levels in synovial fluid were usually lower than corresponding plasma levels. Under steady-state conditions azapropazone did not accumulate in synovial tissues.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 317-320 
    ISSN: 1432-1041
    Schlagwort(e): ranitidine ; amitriptyline ; drug interaction ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The possibility of an interaction of ranitidine with amitriptyline was assessed by means of amitriptyline and nortriptyline plasma concentration measurements, blood pressure and pulse rate, digit symbol substitution, and visual analogue scales. Ranitidine had no effect on amitriptyline or nortriptyline concentrations. Responses recorded by the digit symbol substitution and visual analogue scale tests correlated with changes in concentrations of amitriptyline and nortriptyline in plasma. No effects on blood pressure or pulse rate were observed. We concluded that there was no effect of ranitidine on amitriptyline kinetics or response in the conditions of our study.
    Materialart: Digitale Medien
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 351-355 
    ISSN: 1432-1041
    Schlagwort(e): nifedipine ; cimetidine ; pharmacokinetics ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma pharmacokinetics of nifedipine and the formation of its metabolites have been studied in volunteers under conditions which would affect the activity of the cytochrome P-450 system. The pharmacokinetics of a 10-mg capsule of nifedipine were not significantly different between smokers and non-smokers of similar age. After pretreatment with cimetidine, which inhibits the activity of cytochrome P-450, the peak plasma concentration and area under the plasma-time concentration curve for nifedipine were increased by a mean 84%. In contrast, pre-treatment with ranitidine which has little effect on cytochrome P-450, did not significantly alter nifedipine pharmacokinetics. Smoking does not contribute significantly to the variability in nifedipine pharmacokinetics. However, the interaction between nifedipine and cimetidine, but not ranitidine, may be of clinical importance.
    Materialart: Digitale Medien
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 377-382 
    ISSN: 1432-1041
    Schlagwort(e): morphine ; renal failure ; pharmacokinetics ; morphine-3-glucuronide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetics of morphine and its glucuronidated metabolites were investigated in seven patients with advanced renal failure. The terminal elimination half life of morphine varied between 1.5 and 4.0 h (mean 2.4 h), the volume of distribution between 2.5 and 6.3 l·kg−1 (mean 4.4 l·kg−1) and the total plasma clearance between 13.3 and 31.3 l·min−1·kg−1 (mean 21.1 l·kg−1). There were no statistically significant differences between the pharmacokinetic data in the uraemic patients and in a control group of cancer patients with normal kidney function. The concentrations of the glucuronidated metabolites rapidly rose to levels above those of morphine. The elimination half-life of M3G varied between 14.5 and 118.8 h (mean 49.6 h) in the renal failure patients, which is distinctly different from the 2.4 to 6.7 h (mean 4.0 h) found in patients with normal kidney function. There was a significant correlation between the half-life of M3G and renal function estimated as serum urea. Thus, the metabolism of morphine in patients with kidney disease is not significantly impaired. The clinical importance of the high concentrations of glucuronides in uraemic patients is not known.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 395-401 
    ISSN: 1432-1041
    Schlagwort(e): probenecid ; Michaelis-Menten kinetics ; protein binding ; pharmacokinetics ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Six healthy volunteers were given probenecid 0.5, 1 and 2 g p.o. and 0.5 g i.v. The protein binding of probenecid at different concentrations in human plasma was estimated by equilibrium dialysis. The free fraction was found to increase nonlinearly with increasing total probenecid concentration, up to a maximum free fraction of 26%. The plasma concentration-time data after the oral doses were described by a one-compartment open model with first-order absorption and Michaelis-Menten elimination. The mean absorption rate constant 0.0072 min−1 was dose-independent, and the maximal rate of elimination (mean 1429 µg/min) did not differ between doses whether calculated from the total or free concentrations. The Michaelis-Menten constant decreased significantly from 67.1 to 55.5 µg/ml as the dose increased from 1 g to 2 g, while the unbound Michaelis-Menten constant remained unchanged. The elimination of probenecid after the 0.5 g dose was in the linear region of the Michaelis-Menten elimination when calculated from the total and the free concentrations. The volume of distribution increased only slightly from 9.5 to 11.4 l as the dose increased from 0.5 to 2 g, but the unbound volume of distribution decreased significantly from 164 to 99 l. Absorption was complete and was independent of the dose administered.
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 31 (1987), S. 667-672 
    ISSN: 1432-1041
    Schlagwort(e): adrenergic beta-receptors ; propranolol ; beta-blockade ; pharmacokinetics ; leukocyte beta-receptors ; leukocytes ; exercise tachycardia ; 4—OH-propranolol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The chronotropic response to a single oral dose of propranolol in 23 healthy subjects has been related to the plasma propranolol concentration and the density of β-adrenoceptors on peripheral polymorphonuclear leucocytes. The percentage reduction in exercise-induced tachycardia was significantly correlated with the log plasma propranolol concentration within subjects but not between subjects. Taking the concentration of the active metabolite 4-hydroxypropranolol into account did not improve the interindividual correlation. The reduction in exercise-induced tachycardia was significantly correlated with the maximum binding density of (125I)-hydroxybenzylpindolol on polymorphonuclear leucocyte membrane fragments measured before medication. A response index (% reduction in exercise-induced tachycardia/plasma propranolol concentration) was correlated with the maximum binding density of (125I)-hydroxybenzylpindolol (predrug) at 2 h (rs=0.72), 4 h (rs=0.84) and 6 h (rs=0.73) after dosing. The data suggest that interindividual variation in the response to propranolol after a single oral dose is determined by interindividual differences both in plasma propranolol and adrenoceptor density.
    Materialart: Digitale Medien
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 31 (1987), S. 695-699 
    ISSN: 1432-1041
    Schlagwort(e): doxorubicin ; sarcoma ; pharmacokinetics ; polychemotherapy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of doxorubicin has been studied in 26 sarcoma patients receiving polychemotherapy. Mean elimination half-life was 34.7±16.6 h and the total plasma clearance was 29.5±9.31·h−1·m−2. No relationship was found between the pharmacokinetic parameters and the response to treatment, or its toxicity. Special attention was paid to the early-phase kinetics of the drug (3–20 min after injection). A correlation between the early clearance and the ages of the patients was observed. The early clearance was clearly correlated with the total plasma clearance measured over 48 h after injection, indicating the importance of the distribution phase in the overall kinetics of the drug.
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 31 (1987), S. 701-704 
    ISSN: 1432-1041
    Schlagwort(e): theophylline ; miocamycin ; drug interaction ; metabolism ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The interaction between a new macrolide antibiotic, miocamycin, and theophylline was evaluated in a single cross-over study in 5 asthmatic children. Each patient received a single dose of theophylline (4.3 mg/kg) delivered in 15 min using a constant-rate infusion pump, immediately before and after a 10 day course of miocamycin 17.5 mg/kg b.d. The pharmacokinetics of theophylline were calculated for each phase of the study. The elimination rate constant (3.92 vs 3.74 h−1), the mean total body clearance (1.71 vs 1.8 ml·min·kg−1) and the mean apparent volume of distribution (0.57 vs 0.58 l·kg−1) did not differ. The result can be explained by the inability of the antibiotic to form inactive cytochrome P-450 metabolite complexes which can interfere with the metabolism of theophylline. Thus, miocamycin can safely be administered to asthmatic children requiring theophylline treatment, when they have an infection due to susceptible pathogens.
    Materialart: Digitale Medien
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 31 (1987), S. 733-736 
    ISSN: 1432-1041
    Schlagwort(e): meptazinol ; pharmacokinetics ; elderly patients ; healthy volunteers ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have determined the pharmacokinetics of meptazinol after its intravenous and intramuscular administration in a crossover study in 7 elderly hospital in-patients (〉70 years), and have compared with the results from 14 healthy, young volunteers (ages 20–40 years). The systemic availability after i.m. administration was comparable to that after i.v. administration, a result consistent with the physicochemical properties of the drug. There was a slight, but statistically significant (p〈0.01) prolongation in t1/2z in the elderly (mean 2.93 h) compared with the young (mean 2.06 h). This was associated with a 25% lower clearance in the elderly rather than with any alteration in volume of distribution. However, these changes would not appear to be substantial enough to require a revised dosage recommendation for meptazinol for this age group.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 31 (1987), S. 743-743 
    ISSN: 1432-1041
    Schlagwort(e): chloroquine ; dose dependence ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 32 (1987), S. 17-22 
    ISSN: 1432-1041
    Schlagwort(e): felodipine ; calcium antagonist ; normal man ; renal function ; albumin excretion ; beta2-microglobulin excretion ; adverse effects ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The acute renal effects of a single oral dose of felodipine 0.15 mg/kg were studied in 8 healthy males. Thirty minutes after administration the mean plasma concentration was 25.7 nmol/l. There was a significant reduction in diastolic blood pressure (24%) and a concomitant rise in heart rate (38%), leaving the systolic pressure unchanged. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured by the constant infusion technique using the clearance of125I-iothalamate and131I-hippuran respectively. GFR was unchanged and the filtration fraction (FF) was reduced, whilst there was a decrease in renal vascular resistance (RVR). The glomerular filter characteristics were unchanged, as estimated by the unchanged excretion rate of albumin. There was a significant rise in the clearance of sodium (176%) but only a small and insignificant increase in urine volume. Clearance of potassium was decreased. An increase in the clearance of uric acid and a rise in the beta-2-microglobulin excretion rate were found, both suggesting a proximal tubular effect of felodipine. The excretion rate of calcium was increased.
    Materialart: Digitale Medien
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