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61.
Summary The effects of cyclic GMP (cGMP), carbachol and diltiazem on a potassium-selective, delayed-rectifier current in freshly dissociated rabbit corneal epithelial cells were studied using a modified perforated-patch-clamp technique. The current was stimulated by both 500 m cGMP (2.3–4.5-fold, mean = 2.9) and 250 nm carbachol, a muscarinic agonist (1.12–7.04-fold, mean = 3.8), and the stimulated current was totally blocked by diltiazem (10 m). The effects of cGMP appeared to be, at least in part, different from those of carbachol as they required the presence of external calcium. Single-channel data suggest that cGMP and carbachol activate the potassium current by increasing the open probability of the channel via a second-messenger system and that the action of diltiazem is probably through a direct blocking effect on the open channel.We are grateful to Erika Wohlfiel for secretarial help, Helen Hendrickson for cell preparation, and Joan Rae for software development. The work was supported by NIH grants EY06005 and EY03282 and an unrestricted award from Research to Prevent Blindness.  相似文献   
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Arginine kinase displays a distinctive rise and fall in specific activity and specific protein levels during the prepupal stage of Drosophila development with maximal activity occurring at morphological stage P3. This developmentally regulated peak is under the influence of ecdysone. Altered doses of the major ecdysone-inducible "early" genes at cytological regions 75B and 2B5 alter this pattern of expression while altered doses of another major "early" gene at 74EF have no effect. We hypothesize that a product of the 2B5 locus and a product of the 75B locus interact to effect this developmental pattern of expression of Drosophila arginine kinase.  相似文献   
64.
A new single gene-recessive internode length mutant inPisum, lkc, is characterized. The internodes oflkc plants are 30–40% shorter than those of comparableLkc plants, and this is attributable to reductions in both cell length and the number of cells per internode. Dwarfism in the mutant is not due to modified gibberellin (GA) levels, as determined by gas chromatography-selected ion monitoring (GC-SIM) for GA1 and GA20, and bioassay (rice cv. Tan-ginbozu). Furthermore,lkc plants are not as responsive as the wild-type to applied GA1. The diminished stature oflkc plants appears to result from a direct or indirect interference with the transduction of the GA1 signal.  相似文献   
65.
Organ explant culture models offer several significant advantages for studies of patho-physiologic mechanisms like cell injury, secretion, differentiation and structure development. Organs or small explants/slices can be removed in vivo and maintained in vitro for extended periods of time if careful attention is paid to the media composition, substrate selection, and atmosphere. In the case of human tissues obtained from autopsy or surgery, additional attention must be paid to the postmortem interval, temperature, hydration, and cause of death. Explant organ culture has been effectively utilized to establish outgrowth cell cultures and characterize the histiotypic relationships between the various cell types within an organ or tissue.J. Resau is a visiting scientist at the NCI-LMO-DCE in Frederick, MD 21702, U.S.A.K. Sakamoto is a visiting scientist from the Department of Surgery, Gunma University School of Medicine, Maebashi, Japan  相似文献   
66.
A program has been developed that provides molecular biologistswith multiple tools for searching databases, yet uses a verysimple interface. PATMATcan use protein or (translated) DNAsequences, patterns or blocks of aligned proteins as queriesof databases consisting of amino acid or nucleotide sequences,patterns or blocks. The ability to search databases of blocksby ‘on-the-fly’ conversion to scoring matrices providesa new tool for detection and evaluation of distant relationships.PATMAT uses a pull-down, menu-driven interface to carry outits multiple searching, extraction and viewing functions. Eachquery or database type is recognized, reported, and the appropriatesearch carried out, with matches and alignments reported inwindows as they occur. Any of the high scoring matches can beexported to a file, viewed and recalled as a query using onlya few keystrokes or mouse selections. Searches of multiple databasefiles are carried out by user selection within a window. PATMATruns under DOS; the searching engine also runs under UNIX.  相似文献   
67.
Arginine kinase displays a distinctive rise and fall in specific activity and specific protein levels during the prepupal stage of Drosophila development with maximal activity occurring at morphological stage P3. This developmentally regulated peak is under the influence of ecdysone. Altered doses of the major ecdysone-inducible “early” genes at cytological regions 75B and 2B5 alter this pattern of expression while altered doses of another major “early” gene at 74EF have no effect. We hypothesize that a product of the 2B5 locus and a product of the 75B locus interact to effect this developmental pattern of expression of Drosophila arginine kinase. © 1992 Wiley-Liss, Inc.  相似文献   
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Abstract: Glycoproteins were isolated from a rat brain synaptic junction fraction by affinity chromatography on Concanavalin A-agarose. The isolated glycoproteins were digested with pronase and radiolabeled with 125I-Bolton Hunter reagent, and 125I-Concanavalin A-binding glycopeptides were isolated by chromatography on Concanavalin A-agarose. Treatment of the 125I-Concanavalin A-binding glycopeptides with either α-mannosidase or endo-β- N -acetylglucosaminidase-C11 abolished their interaction with Concanavalin A. The pronase digest was reacted with endo-β-N-acetylglucosaminidase-C11 and released oligosaccharides were reduced with NaB3H4. Following affinity chromatography on Concanavalin A-agarose, Concanavalin A-binding [3H]oligosaccharides were chromatographed on Biogel P4. Two major oligosaccharides corresponding to standard carbohydrates containing eight and five mannose residues were identified. Treatment of these oligosaccharides with α-mannosidase converted them to smaller saccharides having a mobility on Biogel P4 columns equal to the standard disaccharide mannose-β-1-4- N '-acetylglucosamine. These results demonstrate that the Concanavalin A receptor activity associated with CNS synaptic junctions resides in asparaginelinked oligosaccharides of the high-mannose type.  相似文献   
70.
Summary The order and stoichiometry of the binding of phlorizin and sodium to the renal brush-border membraned-glucose transporter are studied. The experimental results are consistent with a random-binding sites is one-to-one. When the kinetics of phlorizin binding are measured as a function of increasing sodium concentration no significant variation is found in the apparent number of binding sites; however, the apparent binding constant for phlorizin decreases rapidly from approximately 16 m at [Na]=0 to 0.1 m at [Na]=100mm and approaches 0.05 m as [Na]. The experimental data are fit to a random carrier-type model of the coupled transport of sodium andd-glucose. A complete parameterization of the phlorizin binding properties of this model under sodium equilibrium conditions is given.  相似文献   
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