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  • 1
    Electronic Resource
    Electronic Resource
    Age- and sex-related differences in nuclear lipid content and nucleoside triphosphatase activity in the JCR:LA-cp corpulent rat (1997)
    Springer
    Molecular and cellular biochemistry 176 (1997), S. 327-335 
    Details
    ISSN: 1573-4919
    Keywords: nucleoside triphosphatase ; hypercholesterolemia ; nuclear membrane ; nuclear pore complex ; nucleocytoplasmic transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The putative role of the nuclear nucleoside triphosphatase (NTPase) is to provide energy to the nuclear pore complex for poly A(+) mRNA export. Previous work has demonstrated that liver nuclear NTPase activity is greater in 6 month old corpulent (cp/cp) female JCR:LA rats, a hyperlipidemic rat model, compared to lean (+/?) animals. This increase appeared to be related to increases in nuclear membrane cholesterol content. The current study extended these initial data to compare NTPase activity as a function of age and sex in isolated JCR:LA-cp rat liver nuclei, to further test the hypothesis that nuclear membrane cholesterol may modulate NTPase activity. NTPase activity was increased in cp/cp female animals compared to +/? females at all ages studied, with Vmax values increased by 60-176%. Membrane integrity of cp/cp female nuclei was reduced compared to +/? female nuclei. Nuclear membrane cholesterol levels increased linearly with age by 50, 150 and 250% in 3, 6 and 9 month old cp/cp females over leans. In contrast, nuclei from cp/cp males exhibited only minor, isolated changes in NTPase activity. Furthermore, there were no significant changes in nuclear cholesterol content or membrane integrity in the less hyperlipidemic male animals at any age. These data suggest that altered lipid metabolism may lead to changes in nuclear membrane structure, which in turn may alter NTPase activity and functioning of the nuclear pore complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006877818372
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  • 2
    Electronic Resource
    Electronic Resource
    Spectroscopic determination of sarcoplasmic reticulum Ca2+ uptake and Ca2+ release (1997)
    Springer
    Molecular and cellular biochemistry 172 (1997), S. 159-170 
    Details
    ISSN: 1573-4919
    Keywords: ryanodine receptor ; sarcoplasmic reticulum ; Ca2+ release ; Calcium Green-2 ; antipyrylazo III
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In this report we describe the application of spectroscopic methods to the study of Ca2+ release by isolated native sarcoplasmic reticulum (SR) membranes from rabbit skeletal muscle. To date, dual-wavelength spectroscopy of arsenazo III and antipyrylazo III difference absorbance have been the most common spectroscopic methods for the assay of SR Ca2+ transport. The utility of these methods is the ability to manipulate intraluminal Ca2+ loading of SR vesicles. These methods have also been useful for studying the effect of both agonists and antagonists upon SR Ca2+ release and Ca2+ uptake. In this study, we have developed the application of Calcium Green-2, a long-wavelength excitable fluorescent indicator, for the study of SR Ca2+ uptake and release. With this method we demonstrate how ryanodine receptor Ca2+ channel opening and closing is regulated in a complex manner by the relative distribution of Ca2+ between extraluminal and intraluminal Ca2+ compartments. Intraluminal Ca2+ is shown to be a key regulator of Ca2+ channel opening. However, these methods also reveal that the intraluminal Ca2+ threshold for Ca2+-induced Ca2+ release varies as a function of extraluminal Ca2+ concentration. The ability to study how the relative distribution of a finite pool of Ca2+ across the SR membrane influences Ca2+ uptake and Ca2+ release may be useful for understanding how the ryanodine receptor is regulated, in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006879926286
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear membrane cholesterol can modulate nuclear nucleoside triphosphatase activity (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 63 (1996), S. 442-452 
    Details
    ISSN: 0730-2312
    Keywords: cholesterol ; NTPase ; nuclear membrane ; pore complex ; hepatic tissue ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Previous work has suggested that changes in nuclear membrane cholesterol may induce a stimulation in nuclear nucleoside triphosphatase (NTPase) activity. The purpose of the present study was to directly investigate if nuclear membrane cholesterol can stimulate nuclear NTPase activity. The cholesterol content of nuclei was altered with a liposomal methodology. The cholesterol content of nuclei isolated from hepatic tissue was relatively low in comparison to that typically exhibited by other membrane fractions. Because of this, it was difficult to further deplete the nuclear membrane of cholesterol, but we could successfully increase the cholesterol content after exposure to cholesterol-enriched liposomes. Nuclear NTPase activity was potently stimulated (∼ 150-200% of control) by an increase in the nuclear membrane cholesterol content. The Vmax of the NTPase activity in the presence of ATP or GTP was significantly increased after cholesterol enrichment without altering the affinity of the enzyme for these moieties. Mg2+ dependency of NTPase activity was also altered by cholesterol incorporation into the nuclear membrane. Cholesterol enrichment of the nuclear membrane also left the nuclei more susceptible to damage by salt-induced lysis than control nuclei. Our results clearly demonstrate that the cholesterol content of the nuclear membrane will have significant, direct effects on nuclear integrity and NTPase activity. © 1996 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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