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Laurence J. Dorr 《Brittonia》1994,46(1):62-65
Notes that augment an earlier essay on R. S. Williams’ botanical activities and the distribution of his collections from Bolivia and Peru are presented. Twelve species based on Williams’ vascular plant collections are added to a catalog that was previously published. Synonymies of an additional 22 taxa are corrected or updated. Notes also are provided concerning the typification or orthography of two species. 相似文献
3.
Laurence A. Greenbaum 《The Yale journal of biology and medicine》1987,60(1):54-Feb;60(1):54
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Summary The actions of cyclic AMP are subject to several levels of post-receptor modulation in cardiac tissue. Isoproterenol and prostaglandin E1 both stimulate cAMP accumulation, but only isoproterenol causes activation of particulate cAMP-dependent protein kinase, leading to activation of phosphorylase kinase and glycogen phosphorylase, and inhibition of glycogen synthase. Through the use of isolated, adult ventricular myocytes, we have determined that the hormone-specific activation of glycogen phosphorylase is due to subcellular compartmentation of cAMP. There is some evidence that cyclic nucleotide phosphodiesterases, whose activity is stimulated by alpha1-adrenergic agonists in isolated myocytes, may have a role in compartmentation. Phosphoinositide hydrolysis is stimulated by alpha, and muscarinic agonists, presumably leading to activation of protein kinase C, which in turn has multiple effects on hormone-sensitive adenylate cyclase.Abbreviations cAMP
Adenosine-3,5-Cyclic Monophosphate
- cGMP
Guanosine-3,5-Cyclic Monophosphate
- Gi, GS
Guanine nucleotide-binding proteins linked to inhibition and stimulation, respectively, of adenylate cyclase
- GTP
Guanosine-5-triphosphate
- PDE
Cyclic Nucleotide Phosphodiesterase
- PGE1
Prostaglandin E1 相似文献
5.
The ribulose-1,5-bisphosphate carboxylase (Rubisco) large- and small-subunit genes are encoded on the chloroplast genome of the eukaryotic chromophytic alga Olisthodiscus luteus. Northern blot experiments indicate that both genes are co-transcribed into a single (>6 kb) mRNA molecule. Clones from the O. luteus rbc gene region were constructed with deleted 5 non-coding regions and placed under control of the lac promoter, resulting in the expression of high levels of O. luteus Rubisco large and small subunits in Escherichia coli. Sucrose gradient centrifugation of soluble extracts fractionated a minute amount of carboxylase activity that cosedimented with native hexadecameric O. luteus Rubisco. Most of the large subunit synthesized in E. coli appeared insoluble or formed an aggregate with the small subunit possessing an altered charge: mass ratio compared to the native holoenzyme. The presence in O. luteus of a polypeptide that has an identical molecular mass and cross reacts with antiserum generated against pea large-subunit binding protein may indicate that a protein of similar function is required for Rubisco assembly in O. luteus. 相似文献
6.
Cattolico RA 《Trends in ecology & evolution》1986,1(3):64-67
Eukaryotes contain a chimeric assembly of genomes, each localized in a specialized subcellular compartment. The successful survival of an organism requires that these sequestered genomes be viewed as dependent variables in a coevolutionary complex. This discussion focuses on chloroplast evolution. A selected review of information available on chloroplast diversity is presented, followed by an analysis of the genetic modifications which may have occurred in the conversion of a free-living ancestral photosynthetic prokaryote into an organelle that has an obligately dependent and highly efficient interplay with the nuclear genome. 相似文献
7.
Laurence S. Kaminsky F.Peter Guengerich Ghazi A. Dannan Steven D. Aust 《Archives of biochemistry and biophysics》1983,225(1):398-404
R- and S-warfarin metabolite profiles (regio- and stereoselectivity) have been determined with hepatic microsomes from untreated rats and rats treated with nine individual polybrominated biphenyl (PBB) congeners, a commercial mixture of PBBs, and, for comparison with phenobarbital and 3-methylcholanthrene. The metabolic rates have been correlated with cytochrome P-450 (P-450) isozyme concentrations in the microsomes determined by immunochemical quantitation techniques (G. A. Dannan, F. P. Guengerich, L. S. Kaminsky, and S. D. Aust, (1983) J. Biol. Chem., 258, 1282–1288). The warfarin hydroxylase activities of the P-450 isozyme components of the various microsomal preparations (F. P. Guengerich, G. A. Dannan, S. T. Wright, M. V. Martin, and L. S. Kaminsky (1982) Biochemistry, 21, 6019–6030) were multiplied by the corresponding isozyme concentrations to obtain an assessment of the potential warfarin hydroxylase capacity of the microsomes, and the results were compared with actual activities. The results of these studies and comparisons indicate that substrate regio- and stereoselectivities of microsomal-bound P-450s are essentially retained on purification of the isozymes to homogeneity and reconstitution, that warfarin metabolism by microsomal preparations can be used to predict microsomal P-450 isozyme compositions, and that microsomal warfarin hydroxylase activity is greater than would be predicted based on the approx 20:1 ratio of P-450 to NADPH-P-450 reductase in the microsomes and on the known activities of constituent isozymes. Two P-450 isozymes which are induced by treatment of rats with phenobarbital appear to be more tightly linked to NADPH-P-450 reductase than does an isozyme induced by β-naphthoflavone. 相似文献
8.
The total parasite load, helminths and arthropods, was measured in wild antelopes (Antilopinae and Alcelaphinae) in Kenya. Two parasite faunas were present, one consisting of endemic species and the other of species introduced into Africa with human livestock, presumably within the last 2000 years. There was little evidence of natural immunity to helminthic infection and gazelle restricted by ranching died of acute helminth infection. The helminth fauna of antelopes was dissimilar from that of zebra and giraffe which graze in the same savannah area, although species of tick were shared. New host records from Kenya are given for Bigalkenema curvispiculum Gibbons, Paracooperia raphicerci Ortlepp, Trichostrongylus axei Cobbold and T. colubriformis Giles from Gazella thomsonii Gilnther, B. curvispiculum from G. granti Brooke, Cooperia fulleborni Hung from Connochaetes taurinus Burchell and Moniezia expansa Rudolphi from Giraffa camelopardalis tippel-skirchi L. The implication of parasitic infection to conservation programmes and the possible future erosion of the conservation areas in East Africa is discussed briefly. 相似文献
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