Dermenkephalin and deltorphin I reveal similarities within ligand-binding domains of mu- and delta-opioid receptors and an additional address subsite on the delta-receptor.

Dermorphin (Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2), dermenkephalin (Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2) and deltorphin I (Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2) are the first naturally occurring peptides highly potent for and almost specific to the mu- and delta-opioid receptors, respectively. The amino-terminal domains Tyr-D-X-Phe (where X is either Ala or Met) of these peptides behave as selective and potent mu-receptor ligands. Routing of Tyr-D-X-Phe to the delta- or the mu- receptor is associated with the presence or the absence at the C-terminus of an additional hydrophobic and negatively charged tetrapeptide by-passing the mu-addressing ability of the amino-terminal moiety. A study of 20 Tyr-D-X-Phe-Y-NH2 analogs with substitution of X and Y by neutral, hydrophobic, aromatic amino acids as well as by charged amino acid residues shows that tetrapeptides maintain high binding affinity and selectivity for the mu-opioid receptor. Although residue in position 4 serves a delta-address function, the tripeptide motif at the C-terminus of dermenkephalin and deltorphin I are critical components for high selectivity at delta-opioid receptor. Results demonstrate that mu- and delta-opioid receptors share topologically equivalent ligand-binding domains, or ligand-binding sequences similarities, that recognized Tyr-D-X-Phe as a consensus message-binding sequence. The delta-receptor additionally contains a unique address subsite at or near the conserved binding domain that accommodates the C-terminal tetrapeptide motif of dermenkephalin and deltorphin I.     

Ultrastructure of scales in a teleost (Carassius auratus L.) after use of rapid freeze-fixation and freeze-substitution

Summary New data on the ultrastructural features of the elasmoid scales ofCarassius auratus have been obtained by use of rapid freezing with subsequent freeze-substitution in anhydrous solvents. These are compared with the results obtained using conventional aqueous fixatives.The external layer of the scales is composed of randomly oriented collagen fibres. In the first stages of mineralization, mineral deposits are located in the interfibrillary substance where dense granules appear to be active sites of mineralization. Spheritic mineralization occurs in this layer.The fibrillary plate is composed of two kinds of collagen fibres. Most of them are organized in lamellae forming the plywood-like structure. They are thicker than the so-called TC fibres, which are oriented from the basal part towards the superficial layer. These TC fibres are involved in the first stages of mineral deposition in the fibrillary plate where inotropic mineralization occurs.The mineral phase is almost always located in the interfibrillary matrix in both layers of the elasmoid scale. In this respect, teleost scales differ from those described so far in other lower vertebrates.

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Resumé Des précisions concernant les aspects ultrastructuraux des dépôts minéraux dans les écailles deCarassius auratus ont été obtenues grâce à l'utilisation de la congélation ultra-rapide suivie d'une cryosubstitution en milieu anhydre. Ces données sont comparées à celles fournies par les méthodes usuelles utilisant des fixateurs aqueux.La couche externe des écailles comprend des fibres collagènes disposées sans ordre apparent. Les dépôts minéraux se produisent surtout dans la substance interfibrillaire où des granules denses semblent représenter des sites actifs au cours de la minéralisation apparentée au type sphéritique.La plaque basale comporte deux catégories de fibres collagènes. Les unes, les plus nombreuses, de plus fort diamètre, sont organisées en lamelles formant une structure en contre-plaqué; les autres appelées fibres TC, orientées de la base de l'écaille vers la zone superficielle, jouent un rôle important dans les premières phases de la minéralisation de type inotropique dans cette partie de l'écaille.Dans les deux couches de l'écaille, la phase minérale est surtout trouvée dans la substance interfibrillaire. De ce fait, les écailles élasmoides des Téleostéens peuvent être distinguées des autres écailles dermiques connues de Vertébrés inférieurs.

     

Disproportionate rDNA replication does occur in diploid tissue in Drosophila hydei

Summary The rDNA content in Drosophila hydei has been compared in wild-type and in two translocation genotypes possessing only one nucleolus organizer. In highly polyploid salivary glands where rDNA is underreplicated, an independent polytenization of the rDNA occurs resulting in about the same rDNA level in each genotype independently of the number of nucleolous organizers present in the genome. Thus, the situation in the salivary glands of D. hydei is similar to that in D. melanogaster (Spear and Gall 1973).In tetraploid thoracic muscle where rDNA is not underreplicated, the rDNA percentage in the two translocation genotypes is also considerably increased, although the wild-type level is not completely attained. This result shows that rDNA replication is independently controlled even in a non-underreplicating tissue.In larval diploid brain the situation in the two translocation stocks is dissimilar: in one genotype the rDNA content remains unaltered whereas in the other it is increased. This demonstrates for the first time that a gene compensation does occur in a diploid tissue.Supported by a grant from the Deutsche Forschungsgemeinschaft (Ku 282/7)     

Human glioma tumour-associated antigens

Conclusion From this brief review it appears that at least three categories of human glioma-associated antigens may exist. The first seems to be restricted and common to gliomas. The second is shared between gliomas, normal adult brain, and fetal brain. The third is present on cells from adult and fetal tissue and on cells from tumours derived from the neural crest. The expression of glioma-associated antigens is highly variable from one tumour, or tumour cell line, to another, and reflects the phenotypic heterogeneity of the glioma group. Moreover, this heterogeneity has been found in different clones of individual glioma cell lines [1]. The fact that gliomas share some antigens with normal brain is of critical importance for immunodiagnosis or immunotherapy. It is evident that active immunotherapy for gliomas should be performed with cultured cells and not with tumour extracts, because such extracts may contain MBP.The exact nature of the various glioma-associated antigens remains to be clearly defined, however. They may belong to a group of surface glycoproteins such as those described by Lloyd et al. [24] for melanoma or more recently by Lubitz et al. [25] for glial cells.     

Effects of anti-embryonal carcinoma serum on aggregation and metabolic cooperation between teratocarcinoma cells

Effects of rabbit anti-embryonal carcinoma IgG on embryonal carcinoma cells and their differentiated derivatives were studied at different levels of cell-cell interaction. Fab fragments of anti-EC IgG were found to inhibit aggregation of the majority of EC cell lines. Two, however, were insensitive. Anti-EC Fab fragments act also on the transfer of metabolites between EC cells: the rescue of HPRT^? EC cells by HPRT⁺ EC cells in selective medium is abolished. These findings are correlated with the disappearance of tight and gap junctions from the surface of EC cells (Dunia et al., 1979). The presence of the surface structure involved in the action of anti-EC Fab fragments was tested by absorption experiments followed by decompaction test on PCC4 Aza R1 cells. All EC cell lines and two embryonic cell lines—a trophectodermal and an endodermal line—were found to bear material absorbing the decompacting activity. The results are discussed in terms of state of differentiation of the cell lines and of complexity of aggregation of embyronic cells.     

Underreplication of satellite DNAs in polyploid ovarian tissue of Drosophila virilis

The satellite DNAs of Drosophila virilis have been examined in diploid and polyploid tissues by isopycnic ultracentrifugation and thermal denaturation experiments. Previous work has established that the satellite DNAs are under replicated in the polytene chromosomes of the salivary glands of D. virilis. The results of the present experiments demonstrate that this underreplication also takes place in the ovaries which contain nurse cells and follicle cells. These tissues are polyploid but do not show polytene chromosomes.     

Expermental contribution on the genesis of arteriosclerosis caused by hypertension]

Autoradiographic tests carried out on rats with renal hypertension using 3H-proline resulted in an acclerated collagen synthesis by media cells of aorta and coronary arteries. Electronmicroscopically an increased content of collagen fibers and an enrichment of ruthenium-red-positive substances in the extracellular space were found. The 35S-sulfate-incorporation in aorta and coronary arteries of animals with hypertension is also increased. These changes in the extracellular space of the vascular wall have an atherosclerosis promoting effect, probably caused by a distrubance of the permeability.