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Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections 总被引:15,自引:4,他引:11
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A method of rapid freezing in supercooled Freon 22 (monochlorodifluoromethane) followed by cryoultramicrotomy is described and shown to yield ultrathin sections in which both the cellular ultrastructure and the distribution of diffusible ions across the cell membrane are preserved and intracellular compartmentalization of diffusabler ions can be quantitated. Quantitative electron probe analysis (Shuman, H., A.V. Somlyo, and A.P. Somlyo. 1976. Ultramicros. 1:317-339.) of freeze-dried ultrathin cryto sections was found to provide a valid measure of the composition of cells and cellular organelles and was used to determine the ionic composition of the in situ terminal cisternae of the sarcoplasmic reticulum (SR), the distribution of CI in skeletal muscle, and the effects of hypertonic solutions on the subcellular composition if striated muscle. There was no evidence of sequestered CI in the terminal cisternae of resting muscles, although calcium (66mmol/kg dry wt +/- 4.6 SE) was detected. The values of [C1](i) determined with small (50-100 nm) diameter probes over cytoplasm excluding organelles over nuclei or terminal cisternae were not significantly different. Mitochondria partially excluded C1, with a cytoplasmic/ mitochondrial Ci ratio of 2.4 +/- 0.88 SD. The elemental concentrations (mmol/kg dry wt +/- SD) of muscle fibers measured with 0.5-9-μm diameter electron probes in normal frog striated muscle were: P, 302 +/- 4.3; S, 189 +/- 2.9;C1, 24 +/- 1.1;K, 404 +/- 4.3, and Mg, 39 +/- 2.1. It is concluded that: (a) in normal muscle the "excess CI" measured with previous bulk chemical analyses and flux studies is not compartmentalized in the SR or in other cellular organelles, and (b) the cytoplasmic C1 in low [K](0) solutions exceeds that predicted by a passive electrochemical distribution. Hypertonic 2.2 X NaCl, 2.5 X sucrose, or 2.2 X Na isethionate produced: (a) swollen vacuoles, frequently paired, adjacent to the Z lines and containing significantly higher than cytoplasmic concentrations of Na and Cl or S (isethionate), but no detectable Ca, and (b) granules of Ca, Mg, and P = approximately (6 Ca + 1 Mg)/6P in the longitudinal SR. It is concluded that hypertonicity produces compartmentalized domains of extracellular solutes within the muscle fibers and translocates Ca into the longitudinal tubules. 相似文献
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AV Shevchenko IG Budzanivska TP Shevchenko VP Polischuk D Spaar 《Archives Of Phytopathology And Plant Protection》2013,46(2):139-146
The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants. 相似文献
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Lukyanetz EA Sotkis AV Kostyuk PG 《Biochemical and biophysical research communications》2002,293(1):132-138
Action of serotonin (5-HT) on single Ca(2+) channel activity was studied in identified neurons of snail Helix pomatia. Only one type of Ca(2+) channels of 5 pS unitary conductance was determined under patch-clamp cell-attached mode. Kinetic analysis have shown a monotonically declining distribution of channel open times (OT) with mean time constant of 0.2 ms. The distribution of channel closed times (CT) could be fitted by double-exponential curve with time constants 1 and 12 ms. We established that 5-HT acts on Ca(2+) channel activity indirectly via cytoplasm. 5-HT prolonged the OT (up to 0.3 ms) and shortened the CT proportionally for both constants to 0.4 and 6 ms correspondingly. A conclusion is made that enhancement of Ca(2+) macro-current by 5-HT is determined by kinetic changes, increase of the number of active channels, and increase of the probability of OT. At the same time the transmitter did not affect the unitary channel conductance. 相似文献
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Usdin K; Chevret P; Catzeflis FM; Verona R; Furano AV 《Molecular biology and evolution》1995,12(1):73-82
The single most difficult problem in phylogenetic analysis is deciding
whether a shared taxonomic character is due to common ancestry or one that
appeared independently due to convergence, parallelism, or reversion to an
ancestral state. Mammalian L1 retrotransposons undergo periodic
amplifications in which multiple copies of the elements are interspersed in
the genome. Because these elements apparently are transmitted only by
inheritance and are retained in the genome, a shared L1 amplification event
can only be an inherited ancestral character. We propose that L1
amplification events can be an excellent tool for analyzing mammalian
evolution and demonstrate here how we addressed several refractory problems
in rodent systematics using L1 DNA as a taxonomic character.
相似文献
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R Alan Harris Dorottya Nagy-Szakal Sabina AV Mir Eibe Frank Reka Szigeti Jess L Kaplan Jiri Bronsky Antone Opekun George D Ferry Harland Winter Richard Kellermayer 《Epigenetics》2014,9(8):1131-1137
Inflammatory bowel diseases (IBD) are emerging globally, indicating that environmental factors may be important in their pathogenesis. Colonic mucosal epigenetic changes, such as DNA methylation, can occur in response to the environment and have been implicated in IBD pathology. However, mucosal DNA methylation has not been examined in treatment-naïve patients. We studied DNA methylation in untreated, left sided colonic biopsy specimens using the Infinium HumanMethylation450 BeadChip array. We analyzed 22 control (C) patients, 15 untreated Crohn’s disease (CD) patients, and 9 untreated ulcerative colitis (UC) patients from two cohorts. Samples obtained at the time of clinical remission from two of the treatment-naïve UC patients were also included into the analysis. UC-specific gene expression was interrogated in a subset of adjacent samples (5 C and 5 UC) using the Affymetrix GeneChip PrimeView Human Gene Expression Arrays. Only treatment-naïve UC separated from control. One-hundred-and-twenty genes with significant expression change in UC (> 2-fold, P < 0.05) were associated with differentially methylated regions (DMRs). Epigenetically associated gene expression changes (including gene expression changes in the IFITM1, ITGB2, S100A9, SLPI, SAA1, and STAT3 genes) were linked to colonic mucosal immune and defense responses. These findings underscore the relationship between epigenetic changes and inflammation in pediatric treatment-naïve UC and may have potential etiologic, diagnostic, and therapeutic relevance for IBD. 相似文献
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AV. H. HEWOOD EDITAE 《Botanical journal of the Linnean Society. Linnean Society of London》1979,78(3):235-236
Following the publication of the last of the series of Flora Europaea Notulae, No. 20 in the Botanical Journal of the Linnean Society , 76: 297–384 (1978), a number of additions or alterations have been drawn to our attention. These are published in continuation. 相似文献
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Peracchia C Sotkis A Wang XG Peracchia LL Persechini A 《The Journal of biological chemistry》2000,275(34):26220-26224
Cytosolic changes control gap junction channel gating via poorly understood mechanisms. In the past two decades calmodulin participation in gating has been suggested, but compelling evidence for it has been lacking. Here we show that calmodulin indeed is associated with gap junctions and plays a direct role in chemical gating. Expression of a calmodulin mutant with the N-terminal EF hand pair replaced by a copy of the C-terminal pair dramatically increases the chemical gating sensitivity of gap junction channels composed of connexin 32 and decreases their sensitivity to transjunctional voltage. The increased chemical gating sensitivity, most likely because of the higher overall Ca(2+) binding affinity of this mutant as compared with native calmodulin, and the decreased voltage sensitivity are only observed when the mutant is expressed before connexin 32. This indicates that the mutant, and by extension native calmodulin, must interact with connexin 32 before gap junctions are formed. Immunofluorescence data suggest further that this interaction leads to incorporation of native or mutant calmodulin into the connexon as an integral regulatory subunit. 相似文献
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Sotkis A Wang XG Yasumura T Peracchia LL Persechini A Rash JE Peracchia C 《Cell communication & adhesion》2001,8(4-6):277-281
The direct calmodulin (CaM) role in chemical gating was tested with CaM mutants, expressed in oocytes, and CaM-connexin labeling methods. CaMCC, a CaM mutant with greater Ca-sensitivity obtained by replacing the N-terminal EF hand pair with a duplication of the C-terminal pair, drastically increased the chemical gating sensitivity of Cx32 channels and decreased their Vj sensitivity. This only occurred when CaMCC was expressed before Cx32, suggesting that CaMCC, and by extension CaM, interacts with Cx32 before junction formation. Direct CaM-Cx interaction at junctional and cytoplasmic spots was demonstrated by confocal immunofluorescence microscopy in HeLa cells transfected with Cx32 and in cryosectioned mouse liver. This was confirmed in HeLa cells coexpressing Cx32-GFP (green) and CaM-RFP (red) or Cx32-CFP (cyan) and CaM-YFP (yellow) fusion proteins. Significantly, these cells did not form gap junctions. In contrast, HeLa cells expressing only one of the two fusion proteins (Cx32-GFP, Cx32-CFP, CaM-RFP or CaM-YFP) revealed both junctional and non-junctional fluorescent spots. In these cells, CaM-Cx32 colocalization was demonstrated by secondary immunofluorescent labeling of Cx32 in cells expressing CaM-YFP or CaM in cells expressing Cx32-GFP. CaM-Cx colocalization was further demonstrated at rat liver gap junctions by Freeze-fracture Replica Immunogold Labeling (FRIL). 相似文献