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221.
222.
Calcium Dependence of Muscarinic Receptor-Mediated Catecholamine Secretion from the Perfused Rat Adrenal Medulla 总被引:9,自引:4,他引:5
Orna E. Harish Lung-Sen Kao Robert Raffaniello Arun R. Wakade Allan S. Schneider 《Journal of neurochemistry》1987,48(6):1730-1735
It had previously been thought that muscarinic cholinergic receptors utilize an influx of extracellular calcium for activation of adrenomedullary catecholamine secretion. However, it has recently been demonstrated that muscarinic receptors on isolated adrenal chromaffin cells can elevate cytosolic free calcium levels in a manner independent of extracellular calcium, presumably by mobilizing intracellular calcium stores. We now demonstrate that muscarinic receptor-mediated catecholamine secretion from perfused rat adrenal glands can occur under conditions of extracellular calcium deprivation that are sufficient to block both nicotine- and electrically stimulated release. Three independent conditions of extracellular calcium deprivation were used: nominally calcium-free perfusion solution (no calcium added), EGTA-containing calcium-free perfusion solution, and perfusion solution containing the calcium channel blocker verapamil. Secretion was evoked from the perfused glands by either transmural electrical stimulation or injection of nicotine or muscarine into the perfusion stream. Each condition of calcium deprivation was able to block nicotine- and electrically stimulated catecholamine release in an interval that left muscarine-evoked release largely unaffected. The above results demonstrate that muscarine-evoked catecholamine secretion from perfused rat adrenal glands can occur in the absence of extracellular calcium, presumably by mobilization of intracellular calcium. The latter may be due to muscarinic receptor-mediated generation of inositol trisphosphate. 相似文献
223.
Correlation of kinetic parameters of nitroreductase enzymes with redox properties of nitroaromatic compounds 总被引:2,自引:0,他引:2
The well-established mechanism of regeneration of the parent nitro compound by the reaction of the nitro anion radical with oxygen in aerobic systems is the basis of the correlation of kinetic parameters of purified flavoenzymes with electron affinities of some selected nitroaryl and nitroheterocyclic compounds. We have found that there is a linear relationship between log Vmax/Km and the one-electron reduction potentials of these compounds and that the measured values of redox dependence for these compounds is similar to that determined by other methods. Our results support the proposal of a rate-determining single electron-transfer as the initial step in the reduction of nitro compounds by purified flavoenzymes and are discussed in terms of the Marcus electron transfer theory. 相似文献
224.
Naftali A. Langberg 《Mathematical biosciences》1980,50(3-4):263-271
A group of n susceptible individuals exposed to a contagious disease isconsidered. It is assumed that at each point in time one or more susceptible individuals can contract the disease. The progress of this simple batch epidemic is modeled by a stochastic process Xn(t), t∈[0, ∞), representing the number of infectiveindividuals at time t. In this paper our analysis is restricted to simple batch epidemics with transition rates given by . This class of simple batch epidemics generalizes a model used and motivated by McNeil (1972) to describe simple epidemic situations. It is shown for this class of simple batch epidemics, that Xn(t), with suitable standardization, converges in distribution as n→∞ to a normal random variable for all t∈(0, t0), and t0 is evaluated. 相似文献
225.
Leonarda Ianzano Maria d'Apolito Marta Centra Maria Savino Orna Levran Arleen D. Auerbach Anne-Marie Cleton-Jansen Norman A. Doggett Jan C. Pronk Alex J. Tipping Rachel A. Gibson Christopher G. Mathew Scott A. Whitmore Sinoula Apostolou David F. Callen Leopoldo Zelante Anna Savoia 《Genomics》1997,41(3):309
226.
227.
Oron U Halevy O Yaakobi T Hayam G Gepstein L Wolf T Ben-Haim S 《International journal of cardiovascular interventions》2000,3(4):227-230
BACKGROUND: The next clinical frontier in the therapeutics of ischemic heart disease may involve the development and delivery of specific molecules and cells into the myocardium. The aim of the present study was to evaluate the efficiency and safety of the MyoStar injection catheter (Biosense-Webster Inc.) that has recently been developed to deliver molecules and cells to the myocardium. The 8 Fr (110 cm length) catheter comprises a navigation sensor with a 27 gauge needle at the distal tip. METHODS: Mouse myogenic cells (C2) were delivered to a tissue culture dish through different modalities: a standard laboratory pipette, a syringe needle (27 gauge) and the injection catheter. The cells were counted and monitored for growth and differentiation in the tissue culture immediately after delivery and two, three and six days later. Cells that were injected through a regular syringe needle or through the injection catheter demonstrated the same capacity to proliferate in tissue culture up to six days. RESULTS: The behavior of the cells in culture (fusion) was identical for the cells delivered to the tissue culture by a pipette or by the injection catheter. CONCLUSION: The results of the present study indicate that delivery of cells through the MyoStar injection catheter is a method with no significant loss or adverse effects to the cells along the path of the catheter. The catheter, which possesses both injection and navigation capabilities, can be used to deliver cell therapy to patients with ischemic heart disease. 相似文献
228.
Rom I Faicevici A Almog O Neuman-Silberberg FS 《Biochimica et biophysica acta》2007,1773(10):1526-1533
During oogenesis in Drosophila, mRNAs encoding determinants required for the polarization of egg and embryo become localized in the oocyte in a spatially restricted manner. The TGF-alpha like signaling molecule Gurken has a central role in the polarization of both body axes and the corresponding mRNA displays a unique localization pattern, accumulating initially at the posterior and later at the anterior-dorsal of the oocyte. Correct localization of gurken RNA requires a number of cis-acting sequence elements, a complex of trans-acting proteins, of which only several have been identified, and the motor proteins Dynein and Kinesin, traveling along polarized microtubules. Here we report that the cytoplasmic Dynein-light-chain (DDLC1) which is the cargo-binding subunit of the Dynein motor protein, directly bound with high specificity and affinity to a 230-nucleotide region within the 3'UTR of gurken, making it the first Drosophila mRNA-cargo to directly bind to the DLC. Although DDLC1 lacks known RNA-binding motifs, comparison to double-stranded RNA-binding proteins suggested structural resemblance. Phenotypic analysis of ddlc1 mutants supports a role for DDLC1 in gurken RNA localization and anchoring as well as in correct positioning of the oocyte nucleus. 相似文献
229.
230.
Miriam Altstein Yoav Gazit Orna Ben Aziz Tal Gabay Ruth Marcus Zvi Vogel Jacob Barg 《Archives of insect biochemistry and physiology》1996,31(4):355-370
PBAN (also termed melanization and reddish coloration hormone, MRCH) is a cerebral factor known to regulate sex pheromone biosynthesis and cuticular melanization in moths. In the present study we developed a quantitative method (based on computerized image analysis of cuticles) to determine the effect of Helicoverpa zea PBAN (Hez-PBAN) on cuticular melanization and to study the structure-activity relationship of the neuropeptide in Spodoptera littoralis larvae. The results indicate that Hez-PBAN stimulates cuticular melanization in an interspecific manner, and that the minimal dose evoking formation of melanins is between 3–10 pmol/larva. Higher doses of Hez-PBAN did not stimulate melanization any further. Examination of the structure-activity relationship of Hez-PBAN revealed that the first eight N-terminal amino acids are not essential for the melanotropic activity and that the activity resides in the C-terminal region. Within this region the C-terminal amide was found to play a very important role. © 1996 Wiley-Liss, Inc. 相似文献