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71.
Analogues of the des-1-tryptophan,3-beta-cyclohexylalanine-alpha-factor of Saccharomyces cerevisiae, where the glycyl residue of position 9 was replaced by D-Ala, L-Ala, D-Leu, and L-Leu, were synthesized and evaluated by morphogenesis assays and circular dichroism spectroscopy. Synthesis was accomplished in solution phase with mixed anhydrides and p-nitrophenyl active esters as the coupling agents. All crude dodecapeptides were purified to greater than 98% homogeneity by preparative high-performance liquid chromatography on a reversed-phase column. The Gly9, D-Ala9, and D-Leu9 analogues elicited morphogenic alterations in MATa strains of S. cerevisiae at concentrations of 1-2 micrograms/mL and exhibited similar CD patterns in both trifluoroethanol and tris(hydroxymethyl)aminomethane buffer, pH 7.4. In contrast, the L-Ala9 and L-Leu9 analogues were more than 200 times less active in the morphogenesis assay and had markedly different CD spectra. These results demonstrate that the position 9 residue plays an important role in determining the biological activity and solution conformation of alpha-factor. We suggest the presence of a type II beta-turn in the Lys7-Gln10 region when the alpha-factor assumes its biologically active conformation. 相似文献
72.
The inhibition of neutrophil granule enzyme secretion and chemotaxis by pertussis toxin 总被引:21,自引:2,他引:19 下载免费PDF全文
E L Becker J C Kermode P H Naccache R Yassin M L Marsh J J Munoz R I Sha'afi 《The Journal of cell biology》1985,100(5):1641-1646
Pertussis toxin treatment of rabbit peritoneal neutrophils causes a concentration-dependent inhibition of granule enzyme secretion induced by formylmethionyl-leucyl-phenylalanine, C5a, and leukotriene B4. It also inhibits chemotaxis induced by formylmethionyl-leucyl-phenylalanine. The same toxin treatment, however, has no effect on granule enzyme secretion induced by the calcium ionophore A23187 or phorbol 12-myristate 13-acetate. Moreover, pertussis toxin treatment does not affect either the number or affinity of the formylpeptide receptors on the neutrophil nor does it have any effect on the unstimulated levels of cyclic AMP (cAMP) or the transient rise in cAMP induced by chemotactic factor stimulation in these cells. We hypothesize that pertussis toxin, as in other cells, interacts with a GTP binding regulatory protein identical with or analogous to either Ni or transducin which mediates the receptor-induced inhibition or activation of a target protein or proteins required in neutrophil activation. The nature of the target protein is unknown, but it is not the catalytic unit of adenylate cyclase. The target protein acts after binding of chemotactic factor to its receptor in the sequence that leads to the receptor-induced rise in intracellular Ca2+. It does not affect the responses elicited by the direct introduction of calcium into the cells or the activity of protein kinase C. 相似文献
73.
Pseudomonas aeruginosa strain PAO1 was compared to PAO1 strains containing an IncP-1 R plasmid (RP1, R68, or R68.45) in an experimental mouse burn infection model. All R plasmids tested caused a 10- to 400-fold increase in mean lethal dose (LD50). The decrease in virulence produced by plasmids R68 and R68.45 was significantly greater than the decrease caused by the closely related plasmid RP1. All plasmids also led to an increased sensitivity of strain PAO1 to human serum bactericidal activity. Virulence and serum resistance of strain PAO1 were restored by curing of the entire plasmid R68.45 but not by deletions in the plasmid's transfer gene regions. 相似文献
74.
Sensitization to stress: the enduring effects of prior stress on amphetamine-induced rotational behavior 总被引:2,自引:0,他引:2
In rats with a unilateral 6-OHDA lesion of the substantia nigra exposure to footshock or immobilization stress produced a long-lasting enhancement in the rotational behavior evoked by a subsequent injection of amphetamine. However, the effect was dependent on the environmental context in which stress was applied. It is suggested that stress may induce enduring changes in brain and behavior similar to those produced by psychomotor stimulant drugs. 相似文献
75.
Clifford A. L. Becker 《Inorganica chimica acta》1985,100(2):227-233
Equilibrium constants, Kdis, for the solvent- dependent, solution-phase disproportionation equilibria of monosubstituted pentakis(arlisocyanide)cobalt(I) complexes: 2[Co(CNR)4L]+?[Co(CNR)3L2]+ + [Co(CNR)5]+, Kdis = are measured by planimeter-integration of proton- NMR spectra at ambient temperature. The complexes, [Co(CNR)4L]ClO4, R = 2,6-Me2C6H3, L = P(C6H5)3, P(C6H4Cl-p)3, P(OC6H5)3, P(OC6H4Cl-p)3; R = o-MeC6H4, L = P(C6H4Cl-p)3, P(OC6H5)3, P(OC6H4Cl-p)3; R = 2,4,6-Me3C6H2, L = P(C6H5)3; R = 2,6-Et2C6H3, L = P(C6H5)3; are investigated in the deuterated solvents, CDCl3, CD3CN, (CD3)2CO, C5D5N, CD3NO2, and (CD3)2SO. Disproportionation seems to occur in all [Co(CNR)4L]+, but NMR study is facilitated by utilizing equivalent alkyl protons (i.e., Me-groups) on the RNC ligands.Correlation of Kdis values with steric-hindrance of the RNC in sets of complexes with the same P-ligand is evident in all solvents: Kdis decreases with increased steric-hindrance in RNC. The Kdis values for complexes with the same RNC and analogous triarylphosphine, triarylphosphite ligands (i.e., PR3, P(OR)3, same R) are approximately equal. The Kdis values for complexes of P-ligands with Cl-substituent are significantly larger than Kdis values for complexes with the corresponding unsubstituted P-ligands (e.g., [Co(CNR)4P(C6H4Clp)3]ClO4vs. [Co(CNR)4P(C6H5)3]ClO4) in (CD3)2CO and C5D5N solution, but are smaller in CDCl3 and CD3CN, and approximately equal in CD3NO2 and (CD3)2SO. Properties of the solvents are also considered. 相似文献
76.
Zusammenfassung Regionale und artliche Unterschiede der Rückstände von Quecksilber in Eiern von sieben Brutvogelarten der deutschen Nordseeküste wurden untersucht. Bei vier Arten stellten wir deutliche geographische Unterschiede in der Kontamination fest (Abb. 1). Höchstgehalte fanden wir in Eiern von der Elbmündung (Region V). Austernfischer- und Flußseeschwalbeneier von der inneren Deutschen Bucht (Region VI) enthielten größere Mengen als solche von Nordfriesland (Region VII). Der gesetzliche Richtwert für Eier (0,03 mg/kg) wurde von 353 der 355 untersuchten Eier überschritten. Fluß- und Brandseeschwalbe waren am stärksten, Brandgans, Austernfischer und Lachmöwe am wenigsten mit Quecksilber kontaminiert (Abb. 2, 4.2.). Mit Ausnahme von Brandgans und Silbermöwe erreichten die Rückstände in vielen Eiern der anderen Arten, an der Elbe sogar in allen Eiern, eine den Bruterfolg gefährdende Größenordnung, insbesondere bei der Flußseeschwalbe.
Pollutants in eggs of birds breeding at the German North Sea Coast. II. Mercury
Summary Regional and interspecific differences of mercury residues were investigated in the eggs of seven species breeding at the German North Sea Coast (Tadorna tadorna, Haematopus ostralegus, Charadrius hiaticula, Larus argentatus, L. ridibundus, Sterna hirundo, S. sandvicensis). We found distinct geographical differences in contamination (Fig. 1): In eggs from the Elbe Eastuary (region V) maximum residues of mercury were ascertained. Eggs of Oystercatcher and Common Tern from the Bay of Helgoland (region VI) contained larger quantities than eggs from Northern Frisia (region VII). 353 from 355 eggs examined showed a value exceeding the legal standard value for eggs which is 0,03 mg/kg in Germany. Common Tern and Sandwich Tern eggs had the highest, Shelduck, Oystercatcher and Blackheaded Gull eggs the lowest mercury contamination (Fig. 2, 4.2.). With the exception of Shelduck and Herring Gull, residues in many eggs of the other species — at the river Elbe in all eggs — came up to a range endangering breeding success, especially in Common Terns.相似文献
77.
Temporal Profiles of Proteins Responsive to Transient Ischemia 总被引:4,自引:3,他引:1
The responses of long and short half-lived proteins to ischemia were measured in rat brain during 6 days of recovery from 30 min of transient forebrain ischemia produced by four-vessel occlusion. At the end of the ischemic interval, the neocortical activities of four vulnerable enzymes [ornithine (ODC) and S-adenosylmethionine (SAMDC) decarboxylases, and RNA polymerases I and II] were unchanged, but within 30 min of reperfusion, their activities dropped by 25-50%. The loss of substance P in the striatum and substantia nigra was slower, reaching about 50% by 12 h. On the other hand, the activities of 5 long half-lived enzymes did not change in the neocortex at 5 and 15 h of reperfusion and regional protein concentrations were essentially unaffected over 6 days survival. The rate and extent of normalization of the amounts or activities of the vulnerable proteins varied. RNA polymerase II and ODC activities were restored within 4 h, and ODC showed a biphasic increase in activity, with peaks at 10 h and 2-3 days. RNA polymerase I and SAMDC activities were restored by 18 h and 5 days, respectively, whereas substance P concentrations did not completely recover, even at 6-15 days. The greater the regional reduction of blood flow during ischemia, the larger the net change (gain or loss) of SAMDC or ODC activity and the longer the time required to normalize the activities of these enzymes. The average rate of proteolysis, assessed by measuring the rate of clearance of 14C from protein prelabeled with [14C]bicarbonate, was abnormal during the first 2 days of reperfusion. Postischemic changes in both protein synthesis and degradation could affect the amounts of some of the proteins responsive to transient ischemia. 相似文献
78.
Deprenyl Protects Dopamine Neurons from the Neurotoxic Effect of 1-Methyl-4-Phenylpyridinium Ion 总被引:3,自引:2,他引:1
1-Methyl-4-phenylpyridinium ion (MPP+) is the product of the metabolic oxidation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by monoamine oxidase (MAO). MPP+ is toxic to 3,4-dihydroxyphenylethylamine (dopamine, DA) neurons in explant cultures of rat embryonic midbrain. Addition of 2.5 microM MPP+ to the feeding medium for 6 days results in significant reduction of the DA levels in the cultures (to 19% of control) as well as in the uptake of [3H]DA (to 32% of control). When the cultures are treated with the MAO inhibitor deprenyl (10 microM) 24 h prior to and during exposure to MPP+, the DA neurons are protected from the toxicity of the drug. In the combined deprenyl plus MPP+ treatment, the levels of DA in the cultures remain at the control range and the [3H]DA uptake is reduced to only 73% of control. These results indicate that MAO is involved in the toxicity of MPP+ on DA neurons. 相似文献
79.
In this review, we have mainly included studies in which whole-body autoradiography was used. In lipid research, most studies have been done with fatty acids. These studies showed some common characteristics in the pattern of tissue distribution. A major uptake was seen in the brown fat, liver and adrenal cortex but also to some extent in other tissues with a high metabolic activity or high cell turn-over, e.g. the gastric and intestinal mucosa, diaphragm, kidney cortex and bone marrow. Low levels of radioactivity were generally found in the brain, testes, thymus, white fat, skeletal muscles, lungs and spleen. Most fatty acids showed some specific features, e.g the strong uptake of erucic, arachidonic and docosahexaenoic acid in myocardium and of eicosapentaenoic acid in the adrenal cortex. Studies with PGE1 and LTC3 showed that the liver and kidney and to a lesser degree the lungs were the major sites of metabolism. The distribution of free cholesterol and triolein emulsion labelled in the fatty acid moieties did show some similarities with respect to the general pattern found with most fatty acids. Specific for cholesterol was a very strong uptake in the adrenal cortex. There was also a significant uptake in the spleen whereas the uptake in the brown fat was not as marked as for most fatty acids. Specific for triolein was a marked uptake in the spleen and myocardium, in fed animals also in the white adipose tissue. These studies show that whole-body autoradiography can give much valuable information of the uptake and distribution of lipids that would be rather difficult to obtain with conventional methods. Combined with electron-microscopy, autoradiography can be used to study cellular and even subcellular distribution, and thus given further data on the metabolism of lipids in the body. 相似文献
80.
Gerald D. Fasman 《Journal of biosciences》1985,8(1-2):15-23
The Chou-Fasman predictive algorithm for determining the secondary structure of proteins from the primary sequence is reviewed.
Many examples of its use are presented which illustrate its wide applicability, such as predicting (a) regions with the potential
for conformational change, (b) sequences which are capable of assuming several conformations in different environments, (c)
effects of single amino acid mutations, (d) amino acid replacements in synthesis of peptides to bring about a change in conformation,
(e) guide to the synthesis of polypeptides with definitive secondary structure,e.g. signal sequences, (f) conformational homologues from varying sequences and (g) the amino acid requirements for amphiphilicα-helical peptides. 相似文献