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  • 1980-1984  (2)
  • 1975-1979  (1)
  • 1970-1974  (1)
  • 1920-1924
  • Water permeability  (2)
  • pharmacokinetics  (2)
Material
Years
  • 1980-1984  (2)
  • 1975-1979  (1)
  • 1970-1974  (1)
  • 1920-1924
Year
  • 1
    ISSN: 1432-0428
    Keywords: 14C-labelled glipizide ; pharmacokinetics ; pharmacodynamics ; metabolism ; protein-binding ; insulin concentration ; glucose determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Peak serum concentrations are reached after about 2 h following oral administration of 5 mg radioactive glipizide, and in the case of intravenous administration of 1 mg radioactive substance they are reached immediately following the injection. The half-life amounts to 36 min (compartment 1) and 3.6 h (compartment 2) resp. The distribution volume of the substance is11, 100 ml. — 5 metabolites were detected in the urine; 2 of them remained unidentified; the same metabolites could partly be detected in the serum. — As regards the insulin levels, two peaks can be seen following oral as well as following intravenous administration; the first peak is reached after absorption or after the injection as the case may be, the second one is reached at midday postprandially. — Of the orally administered substance, the greatest share of total activity eliminated in the urine is observed during the first 24 h, 65.2% of the administered activity are renally eliminated during 48 h. The corresponding value for 120 h being 65.4% after oral and 64.8% after intravenous administration. — These data verify complete absorption following oral administration.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Clivia ; Cuticle development and fine structure ; Water permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fine structure of the upper cuticular membrane (CM) of Clivia miniata leaves was investigated using electron microscopy. The CM is made up of a thin (130 nm) lamellated cuticle proper (CP) and a thick (up to 7 μm over periclinal walls) cuticular layer (CL) of marbled appearance. Evidence is presented to show that the electron lucent lamellae of the CP do not simply represent layers of soluble cuticular lipids (SCL). Instead, the lamellation is probably due to layers of cutin differing in polarity. It is argued that the SCL in the Cp are the main barrier to water. Thickening of the CM during leaf development takes place by interposition of cutin between the CM and the cellin wall. The cutin of young, expanding leaves has a high affinity for KMnO4 and is therefore relatively polar. As leaves mature, the external CL underneath the CP becomes non-polar, as only little contrast can be obtained with permanganate as the post fixative.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Periderm membranes ; Solanum, periderm ; Suberin ; Tuber ; Water permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fine structure and water permeability of potato tuber periderm have been studied. Periderm membranes (PM) were isolated enzymatically using pectinase and cellulase. They were composed of, about six layers of phellem cells arranged in radial rows. The walls of phellem cells consist of cellulosic primary and tertiary walls and suberized secondary walls which are lamellated. Middle lamellae and primary walls contain lignin. Since the PM did not disintegrate during enzymatic isolation it appears that lignin also extends into the secondary suberized walls. The water permeability of PM was low, ranging from 1–3·10-10 m s-1. This low water permeability developed only during storage of tubers in air. Periderm membranes from freshly harvested tubers had a relatively high permeability. The low permeability of PM from stored tubers is attributed to soluble lipids associated with suberin since: (1) extraction of soluble lipids from PM increased permeability by more than 100-fold, (2) a phase transition of soluble lipids was observed between 46 and 51° C, and (3) only the permeability of PM decreased during storage while the permeability of extracted PM remained unchanged. Evidence is presented that two pathways for water movement exist in parallel. Pathway 1 is represented by middle lamellae and primary walls extending in radial direction across the membranes. This pathway has a relatively high specific permeability. Pathway 2 is represented by a polylaminated structure made up of tangential walls of phellem cells which are orientated normal to the direction of water flow. This pathway has a low specific permeability because of the properties of secondary walls incrusted with soluble lipids. It is calculated that about 10% of the water flows across pathway 1 and 90% across pathway 2 which has a volume fraction of 0.995.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 16 (1979), S. 31-38 
    ISSN: 1432-1041
    Keywords: bezafibrate ; hyperlipoproteinemia ; bioavailability ; pharmacokinetics ; GC-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition kinetics of bezafibrate, a newly developed drug of great lipid-lowering potency, were investigated in normal male subjects. Five male volunteers received14C-labelled bezafibrate orally in solution, and a further 10 were given the same dose (300 mg) of un-labelled drug as tablets. The concentration of bezafibrate in serum and urine from the latter was determined by GC, and in the former total radioactivity in serum, urine and feces was followed for 48 h, and urinary excretion products were analysed by TLC and GC-MS. Rapid absorption from the gastrointestinal tract led to peak serum levels 30 min and 2 h after administration of solution and tablets, respectively. Since approximately 95% of the administered14C-bezafibrate was excreted in urine within 48 h, and almost all the remainder was detected in feces, absorption can be regarded as complete after administration in solution. The relative optimal bioavailability from the tablets was also complete, since in both cases approximately 50% of the administered dose was detected as unchanged bezafibrate in urine within 24 h by GC in the tablet study, and by TLC in the solution study. Of the decomposition products, more than 20% of the dose was present as glucuronides and the remainder consisted of several more polar compounds, one of which was identified as a hydroxyderivative of bezafibrate. Since the apparent halflife of bezafibrate in serum was 2.1 h, this new drug possesses favourable pharmacokinetic features: rapid and complete absorption, even from tablets, combined with a conveniently short half-life, and clearance which is half renal (56 ml/min) and half metabolic (43 ml/min), giving a total clearance of 99 ml/min.
    Type of Medium: Electronic Resource
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