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  • 1980-1984  (2)
  • 1975-1979
  • 1970-1974  (1)
  • 1920-1924
  • Water permeability  (2)
  • Acid secretion  (1)
  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 50 (1972), S. 744-750 
    ISSN: 1432-1440
    Keywords: Acid secretion ; Parietal cells ; Chronic-atrophic gastritis ; Duodenal ulcer ; Säuresekretion ; Parietalzellen ; chronischatrophische Gastritis ; Ulcus duodeni
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei männlichen Kontrollpersonen, Patienten mit Ulcus duodeni und mit chronisch-atrophischer Gastritis wurde aus Biopsiematerial der Korpusschleimhaut die Parietalzellzahl pro Areal Schleimhautoberfläche mit Hilfe einer histochemischen Reaktion und die maximale Säuresekretion mit Hilfe des Pentagastrininfusionstestes bestimmt. Bei den Patienten mit Ulcus duodeni fand sich eine signifikante Zunahme und bei den Patienten mit chronisch-atrophischer Gastritis eine signifikante Abnahme der bestimmten Parameter. Zwischen der Parietalzelldichte in Biopsiematerial und maximaler Säuresekretion bestand eine deutliche lineare Korrelation, die sich allerdings auch als polynominale Regression 2. Grades ausdrücken ließ.
    Notes: Summary Male patients with duodenal ulcer, chronicatrophic gastritis, and controls without gastrointestinal diseases were examined with respect to the relationship of their maximal acid output and parietal cell mass in gastric mucosal biopsies. Maximal acid output was measured using the pentagastrin infusion test. Parietal cells were marked histochemically in fresh frozen sections by means of their SDH-activity. The following results were obtained: 1. Maximal acid output (MAO) and parietal cell mass were significantly increased in the duodenal ulcer group, while these values were significantly decreased in the patients with chronic-atrophic gastritis. 2. Parietal cell density in biopsy material was closely related to the MAO irrespective of the group investigated. 3. This relationship was calculated as a linear one and could be further improved when expressed as a binominal regression.
    Type of Medium: Electronic Resource
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