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  • creatine kinase  (2)
  • Calcium influx  (1)
  • Key words:Body composition – Bone density – Densitometry – Femur – Spine – Total body  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 183 (1998), S. 193-202 
    ISSN: 1432-1351
    Schlagwort(e): Key words Fura-2 ; Fluorescence ; Limulus ventral photoreceptors ; Mn2+ ; Calcium influx
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract In contrast to insect species, light-activated influx of divalent ions into Limulus ventral photoreceptors has proven difficult to demonstrate. We used the quench of the fluorescent indicator dye, fura-2, to measure Mn2+ influx. Limulus ventral photoreceptors were injected with fura-2 and excited at 360 nm. When the photoreceptors were bathed in 1 mmol · l−1 Mn2+, an approximately 1% per 10 s decline in the fura-2 fluorescence during intervals between 50-ms flashes was taken as a measure of Mn2+ entry in darkness. Fluorescence decline during 10-s flashes was used to monitor Mn2+ entry during the photoresponse. During the 10-s flashes we observed a small rapid decline of the fura-2 fluorescence even in the absence of Mn2+. This reflected a contamination of the fluorescence signal arising from light-induced release of intracellular calcium stores. A subsequent slower decline in fluorescence during the 10-s flash, amounting to approximately 9% per 10 s, was only observed in the presence of extracellular Mn2+ and was attributed to Mn2+ influx. This light-activated influx was not through voltage-gated calcium channels since it persisted under voltage clamp, was not stimulated by depolarizing current injections, nor blocked by NiCl2. Depletion of internal calcium stores by cyclopiazonic acid treatment did not accelerate Mn2+ influx.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Molecular and cellular biochemistry 133-134 (1994), S. 235-243 
    ISSN: 1573-4919
    Schlagwort(e): creatine kinase ; mitochondria ; metabolism ; creatine phosphate shuttle ; gene expression ; muscle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Mitochondrial Creatine Kinase (MtCK) is responsible for the transfer of high energy phosphate from mitochondria to the cytosolic carrier, creatine, and exists in mammals as two isoenzymes encoded by separate genes. In rats and humans, sarcomere-specific MtCK (sMtCK) is expressed only in skeletal and heart muscle, and has 87% nucleotide identity across the 1257 bp coding region. The ubiquitous isoenzyme of MtCK (uMtCK) is expressed in many tissues with highest levels in brain, gut, and kidney, and has 92% nucleotide identity between the 1254 bp coding regions of rat and human. Both genes are highly regulated developmentally in a tissue-specific manner. There is virtually no expression of sMtCK mRNA prior to birth. Unlike cytosolic muscle CK (MCK) and brain CK (BCK), there is no developmental isoenzyme switch between the MtCKs. Cell culture models representing the tissue-specific expression of either sMtCK or uMtCK are available, but there are no adequate developmental models to examine their regulation. Several animal models are available to examine the coordinate regulation of the CK gene family and include 1) Cardiac Stress by coarctation (sMtCK, BCK, and MCK), 2) Uterus and placenta during pregnancy (uMtCK and BCK), and 3) Diabetes and mitochondrial myopathy (sMtCK, BCK, and MCK). We report the details of these findings, and discuss the coordinate regulation of the genes necessary for high-energy transduction.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Molecular and cellular biochemistry 184 (1998), S. 153-167 
    ISSN: 1573-4919
    Schlagwort(e): creatine kinase ; transcription factors ; myogenesis ; mitochondrion ; energy ; gene family
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Over the last 15 years, molecular characterization of the creatine kinase (CK) gene family has paralleled the molecular revolution of understanding gene structure, function, and regulation. In this review, we present a summary of advances in molecular analysis of the CK gene family with a few vignettes of historical interest. We describe how the muscle CK gene provided an essential model system to examine myogenic regulatory mechanisms, leading to the discovery of the binding site for the MyoD family of basic helix-loop-helix transcription factors essential in skeletal myogenesis and the characterization of the MEF2 family of factors with an A/T rich consensus binding site essential in skeletal myogenesis and cardiogenesis. Cloning and characterization of the four mRNAs and nuclear genes encoding the cytosolic CKs, muscle and brain CKs, and the mitochondrial (Mt) CKs, sarcomeric MtCK and ubiquitous MtCK, has allowed intriguing study of tissue-specific and cell-specific expression of the different CKs and analysis of structural, functional, regulatory, and evolutionary relationships among both the four CK proteins and genes. Current and future studies focus on understanding both cellular energetics facilitated by the CK enzymes, especially energy channelling from the site of production, the mitochondrial matrix and inner membrane, to various cytosolic foci of utilization, and regulation of MtCK gene expression at the cell and tissue-specific level as models of regulation of energy producing genes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Osteoporosis international 11 (2000), S. 158-166 
    ISSN: 1433-2965
    Schlagwort(e): Key words:Body composition – Bone density – Densitometry – Femur – Spine – Total body
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract: We assessed a new dual-energy bone densitometer, the PRODIGY, that uses a narrow-angle fan-beam (4.5°) oriented parallel to the longitudinal axis of the body (i.e., perpendicular to the usual orientation). High-resolution scans across the body can be stepped at 17 mm intervals. The energy-sensitive array detector uses cadmium zinc telluride, which allowed rapid photon counting. Spine and femur scans required 30 s, and total-body scans required 4–5 min; the dose was only 3.7 mrem and 0.04 mrem respectively, or about 5 to 10 times lower than conventional fan-beam densitometry. We found only a small influence of soft-tissue thickness on bone mineral density (BMD) results. There was also a small ( ± 1%) influence of height above the tabletop on BMD results. A software correction for object height allowed a first-order correction for the large magnification effects of position on bone mineral content (BMC) and area. Consequently, the results for BMC and area, as well as BMD, with PRODIGY corresponded closely to those obtained using the predecessor DPX densitometer, both in vitro and in vivo; there was a generally high correlation (r= 0.98–0.99) for BMD values. Spine and femur values for BMC, area and BMD averaged within 0.5% in vivo (n= 122), as did total-body BMC and BMD (n= 46). PRODIGY values for total-body lean tissue and fat also corresponded within 1% to DPX values. Regional and total-body BMD were measured with 0.5% precision in vitro and 1% precision in vivo. The new PRODIGY densitometer appears to combine the low dose and high accuracy of pencil-beam densitometry with the speed of fan-beam densitometers.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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