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1.
2.
Contribution of Noradrenergic Neurons to the Regulation of Dopaminergic (D1 ) Receptor Denervation Supersensitivity in Rat Prefrontal Cortex 总被引:2,自引:1,他引:1
J. P. Tassin J. M. Studler D. Hervé G. Blanc J. Glowinski 《Journal of neurochemistry》1986,46(1):243-248
3,4-Dihydroxyphenylethylamine (DA, dopamine) levels in the rat prefrontal cortex were selectively decreased by 52%, leaving noradrenaline (NA) levels unaffected, 4 weeks following restricted bilateral electrolytic lesions of the ventral mesencephalic tegmentum (VMT). These lesions also induced a significant increase in DA-sensitive, but not isoproterenol-sensitive, adenylate cyclase activity in tissue homogenates (+38%). We had shown previously that chemical (6-hydroxydopamine, 6-OHDA) lesions of the VMT destroy both ascending DA and NA fibers but do not alter the D1-receptor density in the prefrontal cortex. In this study, electrolytic lesions of the VMT were combined with bilateral injections of 6-OHDA made laterally in the pedunculus cerebellaris superior to assess the role of NA fibers in the development of D1-receptor supersensitivity. This combined treatment produces a large decrease of cortical NA levels (-95%), an increase in beta-adrenergic-sensitive adenylate cyclase activity (+110%), and a decrease in DA levels (-60%), but does not alter D1-receptor density in the prefrontal cortex. These results indicate that the development of D1-receptor supersensitivity in the prefrontal cortex following electrolytic lesion of the VMT depends on the presence of an intact NA innervation. 相似文献
3.
Biological and physical properties of a beta-endorphin analog containing only D-amino acids in the amphiphilic helical segment 13-31 总被引:2,自引:0,他引:2
Our approach to the modeling of beta-endorphin has been based on the proposal that three basic structural units can be distinguished in the natural peptide hormone: a highly specific opiate recognition sequence at the N terminus (residues 1-5) connected via a hydrophilic link (residues 6-12) to a potential amphiphilic helix in the C-terminal residues 13-31. Our previous studies showed the validity of this approach and have demonstrated the importance of the amphiphilic helical structure in the C terminus of beta-endorphin. The present model, peptide 5, has been designed in order to evaluate further the requirements of the amphiphilic secondary structure as well as to determine the importance of this basic structural element as compared to more specific structural features which might occur in the C-terminal segment. For these reasons, peptide 5 retains the three structural units previously postulated for beta-endorphin; the major difference with regard to previous models is that the whole C-terminal segment, residues 13-31, has been built using only D-amino acids. In aqueous buffered solutions as well as in 2,2,2-trifluoroethanol-containing solutions, the CD spectra of peptide 5 show the presence of a considerable amount of left-handed helical structure. Enzymatic degradation studies employing rat brain homogenate indicate that peptide 5 is stable in this milieu. In delta- and mu-opiate receptor-binding assays, peptide 5 shows a slightly higher affinity than beta-endorphin for both receptors while retaining the same delta/mu selectivity. In opiate assays on the guinea pig ileum, the potency of peptide 5 is twice that of beta-endorphin. In the rat vas deferens assay, which is very specific for beta-endorphin, peptide 5 displays mixed agonist-antagonist activity. Most remarkably, peptide 5 displays a potent opiate analgesic effect when injected intracerebroventricularly into mice. At equal doses, the analgesic effect of peptide 5 is less than that of beta-endorphin (10-15%) but longer lasting. In conjunction with our previous model studies, these results clearly demonstrate that the amphiphilic helical structure in the C terminus of beta-endorphin is of predominant importance with regard to activity in rat vas deferens and analgesic assays. The similarity between the in vitro and in vivo opiate activities of beta-endorphin and peptide 5, when compared to the drastic change in chirality in the latter model, demonstrates that even a left-handed amphiphilic helix formed by D-amino acids can function satisfactorily as a structural unit in a beta-endorphin-like peptide. 相似文献
4.
The inhibitory effect of propionic acid P and biomass concentration X is studied in batch and continuous fermentations with cell recycle.In batch fermentations, the specific growth rate decreases and cancels out at a critical propionic acid concentration Pc
1; the formerly decreasing specific production rate becomes constant after Pc
1 and cancels out when a second critical propionic acid concentration Pc
2 is reached.In continuous fermentation with cell recycle, a similar inhibition is observed with biomass. The specific rates decrease and become constant at a critical biomass concentration Xc. They cancel out at different high biomass concentrations.In both cases, the specific production rate can be related to the specific growth rate by the Luedeking and Piret expression: =+, [1], where the constants and are determined by the fermentation parameters.List of Symbols
t h
time
-
X kg/m3
biomass concentration
-
P kg/m3
propionic acid concentration
-
A kg/m3
acetic acid concentration
-
S kg/m3
lactose concentration
- dX/dt kg/(m3h)
instantaneous rate of cell growth
- dP/dt kg/(m3h)
instantaneous rate of propionic acid production
-
h–1
specific growth rate
-
h–1
specific propionic acid production rate
-
D h–1
dilution rate 相似文献
5.
J P Blanc J W Taylor R J Miller E T Kaiser 《The Journal of biological chemistry》1983,258(13):8277-8284
In our approach to beta-endorphin modeling, we have proposed that the biological properties of the natural peptide are determined by the combination of three basic structural units: a highly specific opiate recognition sequence at the NH2 terminus (residues 1-5) connected via a hydrophilic peptide link (residues 6-12) to a potential amphiphilic helix in the COOH-terminal residues 13-31. In the alpha-helical conformation the hydrophobic domain twists around the length of the helix and covers almost one-half of its surface. The other distinctive features of the helix include its basicity and the two aromatic residues Phe18 and Tyr27. In contrast to previous models we have studied, peptide 4 is a "negative" model in the sense that it was designed and examined in order to determine how the lack of a well defined amphiphilic structure affects the biological properties of beta-endorphin. For this purpose, peptide 4 retains the three structural units previously postulated for beta-endorphin, but the amino acids of the 13-31 region are arranged in such a way that no definite continuous hydrophobic zone could be formed in an alpha- or pi-helical conformation of this region. In aqueous buffered solutions, peptide 4 showed almost the same amount of alpha-helical structure as beta-endorphin, with a slight tendency toward less helicity in 50% aqueous 2,2,2-trifluoroethanol. In rat brain homogenate, peptide 4 was degraded slightly slower than beta-endorphin, in contrast to the apparently much higher stability of previous models under the same conditions. With regard to opiate receptor binding, peptide 4 was twice as potent as beta-endorphin in mu-receptor assays but half as potent in delta-receptor assays. The opiate potency of peptide 4 on the guinea pig ileum was higher than that of beta-endorphin. In contrast, in the rat vas deferens assay, which is very specific for beta-endorphin, the potency of peptide 4 was very low and could be shown not to be mediated by the same opiate mechanism or by the same opiate receptor. A comparison of these results with those of previous model peptides provides further evidence for the importance of an amphiphilic helical structure in beta-endorphin residues 13-31, which determines the resistance to proteolysis of the natural molecule and contributes to the delta- and mu-opiate receptor interaction. The amphiphilicity of this helical structure must also be essential for high opiate activity on the rat vas deferens (epsilon-receptors), whereas no such structural requirement appears to be necessary for interaction with the opiate receptors on the guinea pig ileum. 相似文献
6.
Summary The morphological features of intestinal epithelium have been studied by light and electron microscopy in two species; in the rat which is able to absorb proteins, such as antibodies and in the rabbit which does not present any transfer upon oral administration of antibodies.The structure of intestinal absorptive cells of the foetus at term and of the newborn from the first day up to the 20th day of life showed a marked evolution. In the foetal cells the apical quarter of the space between the nucleus and the terminal web presents a well developed smooth endoplasmic reticulum. This reticulum is progressively replaced from the first days of life by large numerous vacuoles which diminish in size and number from the 10th day until they disappear on the 20th day. At that time the cells present the adult picture.This evolution as well as other described structural features of the absorptive cells are similar in the two species, despite functional differences in neonatal protein absorption.
Nous remercions le chef du Centre de Microscopie électronique Monsieur A. Gautier pour ses conseils et ses suggestions intéressantes, Madame M. Probst et Monsieur O. Jenni pour leur aide technique. 相似文献
Nous remercions le chef du Centre de Microscopie électronique Monsieur A. Gautier pour ses conseils et ses suggestions intéressantes, Madame M. Probst et Monsieur O. Jenni pour leur aide technique. 相似文献
7.
Mainul Hassan Philippe J. Blanc Alain Pareilleux Gérard Goma 《Biotechnology letters》1994,16(8):819-824
Summary A search was carried out for mutants, defective in the conversion of stearic acid to oleic acid in effort to improve the quality of lipids produced by Cryptococcus curvatus ATCC, 20509. Mutants were selected as unsaturated fatty acid (Ufa) auxotrophs. After treatment of parent organism with Ethyl methanesulfonate (EMS), 11 oleate-requiring auxotrophs were isolated. Only 3 of them were real unsaturated fatty acid (Ufa) mutants, while the other 8 were designated as fatty acid synthetase (Fas) mutants. The amount of saturated fatty acid (SFA) was about 65.2 % in the lipids extracted from an Ufa mutant named UfaM3 and it was significantly higher than that of the wild-type (WT) (46.6 %) and similar to that of cocoa butter (60.4 %). 相似文献
8.
TIF4631 and TIF4632: two yeast genes encoding the high-molecular-weight subunits of the cap-binding protein complex (eukaryotic initiation factor 4F) contain an RNA recognition motif-like sequence and carry out an essential function. 总被引:25,自引:9,他引:16
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C Goyer M Altmann H S Lee A Blanc M Deshmukh J L Woolford Jr H Trachsel N Sonenberg 《Molecular and cellular biology》1993,13(8):4860-4874
The 5' ends of eukaryotic mRNAs are blocked by a cap structure, m7GpppX (where X is any nucleotide). The interaction of the cap structure with a cap-binding protein complex is required for efficient ribosome binding to the mRNA. In Saccharomyces cerevisiae, the cap-binding protein complex is a heterodimer composed of two subunits with molecular masses of 24 (eIF-4E, CDC33) and 150 (p150) kDa. p150 is presumed to be the yeast homolog of the p220 component of mammalian eIF-4F. In this report, we describe the isolation of yeast gene TIF4631, which encodes p150, and a closely related gene, TIF4632. TIF4631 and TIF4632 are 53% identical overall and 80% identical over a 320-amino-acid stretch in their carboxy-terminal halves. Both proteins contain sequences resembling the RNA recognition motif and auxiliary domains that are characteristic of a large family of RNA-binding proteins. tif4631-disrupted strains exhibited a slow-growth, cold-sensitive phenotype, while disruption of TIF4632 failed to show any phenotype under the conditions assayed. Double gene disruption engendered lethality, suggesting that the two genes are functionally homologous and demonstrating that at least one of them is essential for viability. These data are consistent with a critical role for the high-molecular-weight subunit of putative yeast eIF-4F in translation. Sequence comparison of TIF4631, TIF4632, and the human eIF-4F p220 subunit revealed significant stretches of homology. We have thus cloned two yeast homologs of mammalian p220. 相似文献
9.
Cloning and analysis of structural genes from Streptomyces pristinaespiralis encoding enzymes involved in the conversion of pristinamycin IIB to pristinamycin IIA (PIIA): PIIA synthase and NADH:riboflavin 5'-phosphate oxidoreductase. 总被引:4,自引:4,他引:0
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V Blanc D Lagneaux P Didier P Gil P Lacroix J Crouzet 《Journal of bacteriology》1995,177(18):5206-5214
In Streptomyces pristinaespiralis, two enzymes are necessary for conversion of pristinamycin IIB (PIIB) to pristinamycin IIA (PIIA), the major component of pristinamycin (D. Thibaut, N. Ratet, D. Bisch, D. Faucher, L. Debussche, and F. Blanche, J. Bacteriol. 177:5199-5205, 1995); these enzymes are PIIA synthase, a heterodimer composed of the SnaA and SnaB proteins, which catalyzes the oxidation of PIIB to PIIA, and the NADH:riboflavin 5'-phosphate oxidoreductase (hereafter called FMN reductase), the SnaC protein, which provides the reduced form of flavin mononucleotide for the reaction. By using oligonucleotide probes designed from limited peptide sequence information of the purified proteins, the corresponding genes were cloned from a genomic library of S. pristinaespiralis. SnaA and SnaB showed no significant similarity with proteins from databases, but SnaA and SnaB had similar protein domains. Disruption of the snaA gene in S. pristinaespiralis led to accumulation of PIIB. Complementation of a S. pristinaespiralis PIIA-PIIB+ mutant with the snaA and snaB genes, cloned in a low-copy-number plasmid, partially restored production of PIIA. The deduced amino acid sequence of the snaC gene showed no similarity to the sequences of other FMN reductases but was 39% identical with the product of the actVB gene of the actinorhodin cluster of Streptomyces coelicolor A(3)2, likely to be involved in the dimerization step of actinorhodin biosynthesis. Furthermore, an S. coelicolor A(3)2 mutant blocked in this step was successfully complemented by the snaC gene, restoring the production of actinorhodin. 相似文献
10.
Phenotypically Vif- human immunodeficiency virus type 1 is produced by chronically infected restrictive cells. 总被引:2,自引:1,他引:1
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M Bouyac F Rey M Nascimbeni M Courcoul J Sire D Blanc F Clavel R Vigne B Spire 《Journal of virology》1997,71(3):2473-2477
The permissivity of CD4+ transformed T cells for the replication of human immunodeficiency virus type 1 (HIV-1) vif mutants varies widely between different cell lines. Mutant vif-negative viruses propagate normally in permissive CD4+ cell lines but are unable to establish a productive infection in restrictive cell lines such as H9. As a consequence, elucidation of the function of Vif has been considerably hampered by the inherent difficulty in obtaining a stable source of authentically replication-defective vif-negative viral particles produced by restrictive cells. vif-negative, vpr-negative HIV-1 strain NDK stock, produced by the permissive SupT1 cell line, was used to infect restrictive H9 cells. By using a high multiplicity, infection of H9 cells was achieved, leading to persistent production of viral particles displaying a dramatically reduced infectious virus titer when measured in a single-cycle infectivity assay. Although these viral particles were unable to further propagate in H9 cells, they could replicate normally in CEM and SupT1 cells. Comparison of unprocessed and processed Gag proteins in the persistently produced vif-negative viral particles revealed no defect in the processing of polypeptide precursors, with no inversion of the Pr55gag/p24 ratio. In addition, there was no defect in Env incorporation for the vif-negative viral particles. Despite their apparently normal protein content, these particles were morphologically abnormal when examined by transmission electron microscopy, displaying a previously described abnormally condensed nucleoid. Chronically infected restrictive cell lines producing stable levels of phenotypically vif-negative HIV-1 particles could prove particularly useful in further studies on the function of Vif in the virus life cycle. 相似文献