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41.
Summary The nervous system of the most primitive fresh-water Turbellaria of the order Catenulida was investigated. Neurosecretory
cells were found to occur in it. These cells have a structure similar to that of nerve cells, they only differ by the presence
of neurosecretion granules and a more developed golgi complex. In the simplest Catenulida,Stenostomun, neurosecretory granules are found both in the brain cells and in the trunks in the nerve fibres where they are rather randomly
distributed. Another representative of this family, the more highly organizedCatenula, exhibits specialized brain and nerve trunk regions containing neurosecretion granules.
This work was supported in part by the Committee on Cytobiology of the Polish Academy of Sciences 相似文献
42.
Andrzej Myśliwski Jolanta Myśliwska Zbigniew Kmieć 《Histochemistry and cell biology》1977,52(1):91-96
Summary A comparsion of the Feulgen hydrolysis curves and the chromatin compactness of the liver cell nuclei of young and old rats was made. It was found that the rate of DNA depurination and chromatin compactness are higher in the liver cell nuclei of old rats, both in di-and tetraploidal cells. The effect of fixation upon the course of the hydrolysis curves is discussed.This investigation was supported by grant 474/VI Committee of Cell Pathology, Polish Academy of Sciences 相似文献
43.
Some opiates with morphinan- and benzomorphan-structures possess affinities for neuroleptic receptors as revealed by their abilities to compete with 3H-spiroperidol for common binding sites in rat striatum (IC50 in the range between 10?6 and 10?5M). The binding of these opiates to neuroleptic receptors appears to be of pharmacological significance, since studies in mice revealed a small but significant displacement of spiroperidol by high doses of the opiate antagonist levallorphan from specific binding sites in the striatum. In addition, there exists some correlation between the ability of opiates to bind to neuroleptic receptor sites and their potency to evoke “bizarre behavior” in rats . In contrast, a wide variety of other opiates having morphine-, morphinone- or oripavine-structure showed no affinity for neuroleptic binding sites (IC50 greater than 10?4 M). Of the opioid peptides (methionine-enkephalin, leucine-enkephalin and β-endorphin) none has an affinity for neuroleptic binding sites. A variety of other peptides were also investigated but did not interfere with spiroperidol binding. Only ACTH showed a moderate affinity for neuroleptic binding sites. 相似文献
44.
CD study of four modified nucleosides, constituents of tRNA molecules, revealed that 2-thio-5-methyluridine and 5-methyluridine in aqueous solution, 0.1N HCl, and organic solvents essentially occur in an anti-conformation. 5-Methylcytidine also occurs in an anti-conformation similar to cytidine in aqueous solution and organic solvents, while 2-thiocytidine dihydrate appears to occur in an anti-conformation. It is stressed that the CD data of thionucleosides might be applied to the successfully conformational analysis of tRNA molecules. 相似文献
45.
Actin-binding proteins involved in the capping of epidermal growth factor receptors in A431 cells. 总被引:3,自引:0,他引:3
K Kwiatkowska I A Khrebtukova D A Gudkova G P Pinaev A Sobota 《Experimental cell research》1991,196(2):255-263
A capping process of epidermal growth factor receptors (EGF-Rs) was used for the study of the relation between the receptors and the actin-binding proteins (spectrin, vinculin, annexin I) that may be involved in EGF-R-cytoskeleton interaction. In intact, adherent A431 cells, EGF-Rs were diffusively distributed on the cell surface. Spectrin, vinculin, and annexin I were located beneath the plasma membrane. An abundance of EGF-Rs as well as submembrane proteins was observed in regions of membrane ruffles and cell-cell contacts. Annexin I was localized also in cytoplasm being attached to filamentous structures surrounding the nucleus and extending to the cell periphery. Under polyvalent ligand treatment, EGF-Rs of adherent cells were aggregated on one side of the cell. Spectrin, vinculin, and annexin I dislocated together with EGF-Rs and were concentrated under plasma membrane at regions where cap formation took place. In suspended A431 cells only spectrin was located under the plasma membrane whereas annexin I and vinculin were diffusively distributed through the cells. During cap formation only spectrin was colocalized with EGF-Rs. The results confirmed the major role of spectrin as a receptor-microfilament linking protein. 相似文献
46.
Andrzej Slominski 《In vitro cellular & developmental biology. Animal》1991,27(9):735-738
Summary Crosslinking of [14C]l-tyrosine to at least five hamster melanoma cell surface proteins is reported. This effect was abolished by addition of nonradioactivel-tyrosine,l-phenylalanine, orl-dopa, but not byd-tyrosine, tyramine, dopamine, norepinephrine, or epinephrine. The above proteins can be purified by tyrosine-affinity chromatography.
They have molecular weights different from proteins staining for dopa oxidase and proteins that bind anti-tyrosinase antibody
in Western blots. It is suggested that they may be a hithergo unrecognized part of the cellular apparatus governing melanogenesis. 相似文献
47.
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49.
The C-peptide of ribonuclease A (residues 1 to 13) is obtained by cyanogen bromide cleavage at Met13, which converts methionine to a mixture of homoserine lactone (giving C-peptide lactone) and homoserine carboxylate (giving C-peptide carboxylate). The helix-forming properties of C-peptide lactone have been reported. The helix is formed intramolecularly in aqueous solution, is stabilized at low temperatures (0 to 20 °C) and also by a pH-dependent interaction between sidechains. The C-peptide lactone helix is about 1000-fold more stable than expected from “host-guest” data for helix formation in synthetic polypeptides.Here we report the failure of C-peptide carboxylate to form an α-helix in comparable conditions. Formation of a salt-bridge between the α-COO? group and the imidazolium ring of His12+ appears to be responsible for the suppression of helix formation. The presence of the Hse13-COO? … His12+ salt-bridge in C-peptide carboxylate is shown by 1H nuclear magnetic resonance titration of the amide proton resonances of His12 and Hse13, and is expected from model peptide studies. The most probable reason why C-peptide carboxylate does not form an α-helix is that the Hse13-COO? … His12+ salt-bridge competes successfully with a helix stabilizing salt-bridge (Glu9? … His12+).S-peptide (residues 1 to 20 of ribonuclease A) does form an α-helix with properties similar to those of the C-peptide (lactone) helix, which shows that the lactone ring of C-peptide lactone is not needed for helix formation.These results support the hypothesis that a Glu9? … His12+ salt-bridge stabilizes the C-peptide (lactone) helix, and they show that specific interactions between side-chains can be important in preventing as well as in promoting α-helix formation. 相似文献
50.
Andrzej Piekarowicz 《Journal of molecular biology》1982,157(2):373-381
HineI is a restriction enzyme isolated from Haemophilus influenzae strain Re. Like other type III restriction endonucleases it requires ATP for cleavage and S-adenosyl-methionine for methylation of DNA. This enzyme recognises the same sequence as HinfIII (Piekarowicz et al., 1981) and cleaves and methylates DNA in a manner similar to all type III restriction enzymes. 相似文献