Binding of opiates and endogenous opioid peptides to neuroleptic receptor sites in the corpus striatum.

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 $\text{in vitro}$ (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 $\text{in vivo}$ 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 $\text{in vitro}$ and their potency to evoke “bizarre behavior” in rats $\text{in vivo}$. In contrast, a wide variety of other opiates having morphine-, morphinone- or oripavine-structure showed no affinity for neuroleptic binding sites $\text{in vitro}$ (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.     

Enriched populations of rat retinal ganglion cells: Studies using a cell-type specific surface marker

Cells dissociated from adult and neonatal rat retinas were separated by density gradient centrifugation. Previous work had shown that rat retinal cells labelled by an immunofluorescence assay for the Thy-1 antigen were chiefly or exclusively ganglion cells, and so the proportion of Thy-1 positive cells in the density gradient fractions was used as an index of the enrichment of ganglion cells. The proportion of Thy-1 positive neonatal cells was increased from about 0.4% in the initial dissociate to about 8% in the most enriched fraction of a Percoll step gradient. Amongst adult cells the initial 0.7% Thy-1 positive cells were increased to roughly 2% in the best fraction of a metrizamide step gradient.

The presence of relatively large numbers of Thy-1 positive cells in other fractions suggested that it would be difficult to further increase the proportion of rat ganglion cells by methods based on their sedimentation properties. These results demonstrate the importance of cell-type specific markers in attempts to purify cells from the central nervous system.     

Ubiquitous soluble Mg(2+)-ATPase complex. A structural study.

We have performed a detailed structural analysis of the soluble Mg(2+)-ATPase complex purified from Xenopus laevis ovary, which is an abundant and ubiquitous homo-oligomeric protein complex located in the nucleus and in the cytoplasm, belonging to a novel multigene-family of putative Mg(2+)-ATPases. Enzyme activity staining after non-denaturing polyacrylamide gel electrophoresis revealed that Mg(2+)-ATPase activity of the native protein is dependent on oligomerization and could not be detected in dissociated subunits. For the native protein a sedimentation coefficient of 15.3 S and a corresponding relative molecular mass of 612,000 was determined by analytical ultracentrifugation and a relative molecular mass of 590,000 was estimated from scanning transmission electron microscopy, supporting our previous conclusion that the oligomer comprises six 97,000 Mr subunits. Conventional electron microscopy of negatively stained specimens revealed the Mg(2+)-ATPase complex to be a hexagonal molecule in its favoured "end-on" projection and a double-banded molecule in its "side-on" projection (approx. 12 nm diameter; approx. 9 nm height). In addition, dimerized complexes could be observed in negatively stained specimens, yielding pronounced hexameric images and four-banded images in their end-on and side-on orientations, respectively (approx. 12 nm diameter; approx. 18.5 nm height). Two-dimensional (2D = mono-molecular) crystals have been produced from the dimerized complexes by the negative staining carbon film technique. Hexagonal crystals with a p6 plane group symmetry were obtained from molecules in their end-on orientation and longitudinal arrays with a p2 symmetry from complexes in their side-on orientation. A low-resolution molecular model of the native protein, derived from averages of these two 2D crystals, is presented. From our results we propose oligomerization as an inherent structural principle of organization for this whole newly defined Mg(2+)-ATPase multigene-family, that includes such seemingly diverse functionally defined proteins as mammalian and yeast "vesicle fusion" and "peroxisome assembly" proteins and the product of the yeast cell cycle gene CDC48.     

Root-microbial effects on plant iron uptake from siderophores and phytosiderophores

Collaborative experiments were conducted to determine whether microbial populations associated with plant roots may artifactually affect the rates of Fe uptake and translocation from microbial siderophores and phytosiderophores. Results showed nonaxenic maize to have 2 to 34-fold higher Fe-uptake rates than axenically grown plants when supplied with 1 μM Fe as either the microbial siderophore, ferrioxamine B (FOB), or the barley phytosiderophore, epi-hydroxymugineic acid (HMA). In experiments with nonsterile plants, inoculation of maize or oat seedlings with soil microorganisms and amendment of the hydroponic nutrient solutions with sucrose resulted in an 8-fold increase in FOB-mediated Fe-uptake rates by Fe-stressed maize and a 150-fold increase in FOB iron uptake rates by Fe-stressed oat, but had no effect on iron uptake by Fe-sufficient plants. Conversely, Fe-stressed maize and oat plants supplied with HMA showed decreased uptake and translocation in response to microbial inoculation and sucrose amendment. The ability of root-associated microorganisms to affect Fe-uptake rates from siderophores and phytosiderophores, even in short-term uptake experiments, indicates that microorganisms can be an unpredictable confounding factor in experiments examining mechanisms for utilization of microbial siderophores or phytosiderophores under nonsterile conditions.     

Structure of the central spacer region of extrachromosomal ribosomal DNA in Physarum polycephalum

We have analyzed the sequence organization of the central spacer region of the extrachromosomal ribosomal DNA from two strains of the acellular slime mold Physarum polycephalum. It had been inferred previously from electron microscopy that this region, which comprises about one third of the 60 kb³ palindromic rDNA, contains a complex series of inverted repetitious sequences. By partial digestion of end-labeled fragments isolated from purified rDNA and from rDNA fragments cloned in Escherichia coli, we have constructed a detailed restriction map of this region. The 11 kb of spacer DNA of each half molecule of rDNA contains the following elements: (a) two separate regions, one of 1.1 kb and one of 2.1 kb, composed of many direct repeats of the same 30 base-pair unit; (b) a region of 4.4 kb composed of a complex series of inverted repeats of a 310 base-pair unit; (c) another region of 1.6 kb composed of inverted repeats of the same 310 base-pair unit located directly adjacent to the center of the rDNA; (d) two copies of a unique sequence of 0.85 kb, which probably contains a replication origin. Some of the CpG sequences in the spacer resist cleavage by certain restriction endonucleases and thus appear to be methylated. The lack of perfect symmetry about the central axis and the arrangement of inverted repeated sequences explain the complex pattern of branches and forks of the fold-back molecules previously observed by electron microscopy. Comparison of the rDNA restriction maps from the two strains of Physarum suggests that the repeat units in the spacer are undergoing concerted evolution. We propose a model to explain the evolutionary origin of the several palindromic axes in the Physarum rDNA spacer.     

Zur sozialen Organisation des BienenfressersMerops apiaster

Zusammenfassung Beobachtungen zur sozialen Organisation wurden in einer Bienenfresserkolonie (16 Paare) in Nordost-Griechenland von April bis August 1979 vorgenommen:Die zeitliche Abstimmung der Brutaktivitäten wurde während der einzelnen Stadien des Brutzyklus ermittelt. Die Synchronisation verbesserte sich signifikant zwischen der Fertigstellung der Höhle und dem Beginn der Eiablage.Balzfütterungen und Kopulationen häufen sich wenige Tage vor der Eiablage, werden gegen Ende der Eiablage wieder seltener und treten danach nicht mehr auf.Jedes Paar verteidigt einen Abschnitt der Uferböschung, obwohl es darin nur die Höhle und wenige Sitzplätze benutzt. Territoriale Auseinandersetzungen treten vor allem zwischen angesiedelten Paaren und Neuankömmlingen auf. Obwohl die Angriffe um ein Mehrfaches häufiger von den Territoriumsbesitzern ausgehen, ziehen sich diese später aus einem Teil des Territoriums zurück, und ein neues Paar rückt nach. Diese Streitigkeiten halten nur wenige Tage an.

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On the social organization of the European Bee-eater(Merops apiaster)

Summary Several aspects of the social organization have been studied in a breeding colony (16 pairs) in North-eastern Greece from April until August 1979:Colony synchronization was measured at the beginning and at the end of nest-hole excavation, egg-laying and incubation. The degree of synchrony increased between the end of excavation and the onset of laying.The rates of courtship-feeding and copulation increased a few days before the first egg was layed and decreased again at the end of the laying period.Every pair defended a part of the river bank although it only used the burrow and one or some perches there. Territorial conflicts especially appeared between a settled and an intruding pair. Although the attacks were performed several times more frequently by the territory owners, that pair withdrew from a part of its territory and the other moved up. These territorial conflicts only lasted a few days.

     

The murine bone marrow macrophage,a sensitive indicator cell for murine migration inhibitory factor and a new method for their harvest

Murine bone marrow macrophages grown on Teflon-coated petri dishes for a period of 8–16 days can be removed with a yield of 90–95% and a viability greater than 95% following incubation in 1 mM EDTA. Bone marrow cells cultured on Teflon-coated dishes did not differ in their replication rate, peroxidase and nonspecific esterase content, pinocytosis, secretion of lysozyme and neutral proteinases from bone marrow cells cultured on plastic dishes. Murine bone marrow macrophages were found to be sensitive indicator cells for mouse migration inhibitory factor (MIF). Large numbers of cells for the MIF assay can be obtained, since their yield is 10–15 times higher than the yield of oil-induced peritoneal exudate macrophages from the same number of mice.