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  • 1
    Online Resource
    Online Resource
    Berlin, Heidelberg :Springer Berlin / Heidelberg,
    Keywords: Human physiology. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (158 pages)
    Edition: 1st ed.
    ISBN: 9783540448341
    Series Statement: Reviews of Physiology, Biochemistry and Pharmacology Series ; v.148
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 433 (1996), S. 245-253 
    ISSN: 1432-2013
    Keywords: Key words Osmoregulation ; Regulatory volume decrease ; Cytosolic calcium ; Calcium stores ; IP3 ; Arachidonic acid ; Collecting duct
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In rat inner medullary collecting duct (IMCD) cells in primary culture, hypotonic stress induces Ca2+ transients consisting of an early peak phase caused by a Ca2+ release from intracellular stores and a subsequent plateau phase that involves Ca2+ entry from the extracellular milieu. In the present study, the mechanisms by which cell swelling is transduced into the Ca2+ release were investigated. The free intracellular Ca2+ concentration ([Ca2+]i) was measured using the fluorescent dye fura-2 and cell volume using a confocal laser scanning microscope. In control experiments, after reduction of extracellular osmolarity from 600 to 300 mosmol/l, by omission of sucrose, [Ca2+]i rapidly increased from 106 ± 9 nmol/l to a peak value of 405 ± 22 nmol/l (P≤ 0.05) and thereafter reached a steady-state of 230 ± 23 nmol/l. In low-Ca2+ conditions (10 nmol/l), the reduction of osmolarity evoked only a transient increase of [Ca2+]i by 182 ± 11 nmol/l (P≤ 0.05), which reflected Ca2+ release from intracellular stores. Hyposmotic stress had no effect on inositol 1,4,5-triphosphate (IP3) production measured by a [3H]IP3 radioreceptor assay. Preincubation with 100 μmol/l ETYA (a non-metabolisible derivative of arachidonic acid) reduced the Ca2+ response to hyposmotic stress under high and low Ca2+ conditions (87 and 85% inhibition respectively) as well as the regulatory volume decrease (RVD). Extracellular application of arachidonic acid in isotonic medium led to an increase in [Ca2+]i under high and low Ca2+ conditions. Pretreatment of IMCD cells with 50 μg/ml D609 (a phosphatidylcholine-directed phospholipase C inhibitor) or with 200 μmol/l propranolol (a phosphatidate phosphohydrolase inhibitor) reduced the hypotonic Ca2+ response more strongly than pretreatment with 5 μmol/l BPhB (a phospholipase A2 inhibitor). The Ca2+ response was also suppressed after preincubation with 200 μmol/l RHC 80267 (a diacylglycerol lipase inhibitor). Preincubation with 50 ng/ml pertussis toxin (a G-protein inhibitor) reduced the transient component of the Ca2+ response partially. We conclude that G-proteins, phosphatidylcholine-directed phospholipase C, phospholipase A2, diacylglycerol lipase and arachidonic acid, but not IP3, are involved in the mechanisms by which Ca2+ is released from the intracellular stores during RVD in IMCD cells.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 39 (2000), S. 194-200 
    ISSN: 1436-6215
    Keywords: Key words SGLT1 – GLUT1 – lactation – human milk ; List of abbreviations SGLT, sodium dependent glucose transporter; GLUT, sodium independent glucose transporter; RT, reverse transcription; DIG, digoxigenin--〉
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Notes: Summary Background. Human milk contains 60–80 g/l lactose and and oligosaccharides. To synthesize this large amount of carbohydrates, the lacting mammary gland has a high demand for precursor molecules. such as glucose and galactose. Aim of the study. In the present study we investigated the molecular basis for the uptake of glucose and galactose into the human mammary gland. Methods. Using RT-PCR, Southern and Western blotting we analyzed the expression of SGLT1 (sodium glocose cotransporter 1) and GLUT1 (sodium independent glucose transporter) in epithelial cells isolated from fresh human milk. Results. Southern blot analysis of the amplications revealed the expression of SGLT1 mRNA but not of GLUT1 mRNA in milk epithelial cells. Using Western blotting, SGLT1 protein was identified in human milk cells. Conclusions. Our findings indicate that 1) the cell fraction isolated from fresh human milk is a suitable model for investigating gene expression in the human mammary gland and 2) lactating human mammary gland epithelial cells are supplied with monosaccharides mainly via SGLT1.
    Type of Medium: Electronic Resource
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