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  • caspase  (1)
  • coated pits  (1)
  • 1
    ISSN: 1432-1424
    Keywords: antidiuretic hormone ; coated pits ; cortical collecting tubule ; endocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Antidiuretic hormone increases the water permeability of the cortical collecting tubule and causes the appearance of intramembrane particle aggregates in the apical plasma membrane of principal cells. Particle aggregates are located in apical membrane coated pits during stimulation of collecting ducts with ADHin situ. Removal of ADH causes a rapid decline in water permeability. We evaluated apical membrane retrieval associated with removal of ADH by studying the endocytosis of horseradish peroxidase (HRP) from an isotonic solution in the lumen. HRP uptake was quantified enzymatically and its intracellular distribution examined by electron microscopy. When tubules were perfused with HRP for 20 min in the absence of ADH, HRP uptake was 0.5±0.3 pg/min/μm tubule length (n=6). The uptake of HRP in tubules exposed continuously to ADH during the 20-min HRP perfusion period was 1.3±0.8 pg/min/μm (n=8). HPR uptake increased markedly to 3.2±1.1 pg/min/μm (n=14), when the 20-min period of perfusion with HRP began immediately after removal of ADH from the peritubular bath. Endocytosis of HRP occurred in both principal and intercalated cells via apical membrane coated pits. We suggest that the rapid decline in cortical collecting duct water permeability which occurs following removal of ADH is mediated by retrieval of water permeable membrane via coated pits.
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  • 2
    ISSN: 1573-675X
    Keywords: Annexin V ; apoptosis ; caspase ; gemcitabine ; ovarian cancer ; staurosporine.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A variety of chemotherapeutic agents induce cell death via apoptosis. We had shown previously that gemcitabine (2′,2′-difluorodeoxycytidine) induced an atypical apoptosis in BG-1 human ovarian cancer cells; therefore, further studies were conducted to characterize more precisely gemcitabine-induced apoptosis in BG-1 cells compared to a general inducer of apoptosis, staurosporine. BG-1 cells exposed to 0.5, 1.0 and 10 μM gemcitabine for 8 h, or staurosporine (1.0 μM) for 6 h, exhibited high molecular weight DNA fragmentation (50 kbp); however, only staurosporine treatment produced internucleosomal DNA fragments (200 bp) in a laddered pattern on the agarose gel. Staurosporine (1.0 μM) rapidly induced phosphatidylserine plasma membrane translocation that increased linearly with time as measured by annexin V-FITC binding, and similar kinetics were observed for caspase activation by staurosporine in BG-1 cells. In contrast, 10 μM gemcitabine increased phosphatidylserine expression in a small fraction of cells (5–10%) vs. untreated controls over the course of 48 h and significant caspase activity was detected within 12 h of drug exposure. Time-lapse video microscopy of BG-1 cells exposed to 1.0 μM staurosporine or 10 μM gemcitabine for up to 72 h showed that the morphologic changes and kinetics of cell death induced by these agents differed significantly. We also evaluated the apoptosis induced by paclitaxel (a mitotic poison) and cisplatin (an agent not dependent on cell cycle functions) in BG-1 cells by these methods because these drugs are used clinically to treat ovarian cancer. Our findings demonstrate that the kinetics of apoptotic cell death induced by gemcitabine and other chemotherapeutic agents should be taken into account when designing treatment strategies for ovarian cancer.
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