The innervation of some proboscis structures involved in feeding behavior of the blowfly (Calliphora vicina)

The microtopology of the motoneurons involved in protraction and retraction of the proboscis of the blowfly (Calliphora vicina) has been studied. In addition, taste input from the labellar hairs was investigated. As a result of this study it appears that protraction movements are controlled by two while retraction movements are guided by three motoneurons on each side. The neurons in each group apear to be in ipsicontralateral communication with each other. The musculi protractores fulcri (MPF) probably contain a proprioceptive cell group which projects to the MPF motoneurons. It is proposed that the proboscis motor system can be modulated by proprioception as well as by chemosensory labellar input. Neurosecretory cells may be involved in adjusting muscle power.     

Tactical Voting in Plurality Elections

How often will elections end in landslides? What is the probability for a head-to-head race? Analyzing ballot results from several large countries rather anomalous and yet unexplained distributions have been observed. We identify tactical voting as the driving ingredient for the anomalies and introduce a model to study its effect on plurality elections, characterized by the relative strength of the feedback from polls and the pairwise interaction between individuals in the society. With this model it becomes possible to explain the polarization of votes between two candidates, understand the small margin of victories frequently observed for different elections, and analyze the polls'' impact in American, Canadian, and Brazilian ballots. Moreover, the model reproduces, quantitatively, the distribution of votes obtained in the Brazilian mayor elections with two, three, and four candidates.     

Characterization of O-glycosidically linked oligosaccharides of rat erythrocyte membrane sialoglycoproteins

The carbohydrate units of the rat erythrocyte membrane sialoglycoprotein rSGP-4 [Edge, A. S. B., & Weber, P. (1981) Arch. Biochem. Biophys. 209, 697-705] have been characterized. All of the carbohydrate of this Mr 19,000 glycoprotein occurs in O-glycosidic linkage to the peptide; following alkaline borohydride treatment and chromatography on Bio-Gel P-2, sialic acid containing oligosaccharides terminating in N-acetylgalactosaminitol were obtained. Their structures were determined by compositional analysis, exoglycosidase digestions, alkaline sulfite degradation, and periodate oxidation. The oligosaccharides were characterized for molecular weight and linkage by direct chemical ionization and gas-liquid chromatography/mass spectrometry, respectively. The structures are proposed to be NeuAc alpha 2----3Gal beta 1----3GalNAc-ol, Gal beta 1----3(NeuAc alpha 2----6)GalNAc-ol, NeuAc alpha 2----3Gal beta 1----3(NeuAc alpha 2----6)GalNAc-ol, and NeuAc alpha 2----3Gal beta 1----3(NeuAc alpha 2----3Gal beta 1----4GlcNAc beta 1----6)GalNAc-ol. Two of the N-acetylglucosamine-containing hexasaccharides were present per molecule of rSGP-4 along with two trisaccharides and seven tetrasaccharides.     

Chemiluminescence associated with phagocytosis of foreign particles in rabbit alveolar macrophages

Rabbit alveolar macrophages exhibit a chemiluminescent response which is associated with phagocytosis of zymosan and polystyrene-butadiene particles. The chemiluminescence reaches a peak in 15 to 25 minutes and then gradually diminishes over the next 1 to 3 hours. During the time of maximal light emission there appears to be no actual uptake of particles, but the response is dependent upon the particle concentration. The metabolic inhibitor, DNP (2,4-dinitrophenol), causes a rapid inhibition of the chemiluminescent response. The addition of ATP to the medium prior to exposure of the cells to particles causes the chemiluminescent response to be greatly diminished, i.e., 0.3mM ATP virtually abolishes the response. These experiments suggest that some metabolic response of the cell to phagocytosis is responsible for the chemiluminescence.     

Immunocytochemical localization of the elongation factor Tu in E. coli cells

The localization of the elongation factor Tu (EF-Tu) in ultrathin cryosections of E. coli cells was determined with the electron microscope using a highly specific immunological labelling technique. EF-Tu is distributed almost homogeneously throughout the cytoplasm. Although it has often been suggested that EF-Tu could be part of a putative prokaryotic cytoskeleton, we did not find any evidence for supramolecular assemblies, such as fibres or filaments, containing a large amount of EF-Tu. EF-Tu was not observed in association with the outer cell membrane and periplasmic space. A topological relationship with the inner membrane is not apparent in our micrographs. In cells in which the EF-Tu level is raised significantly, the protein piles up in discrete cell regions.     

Fluorimetric determination of carbamoyl phosphate

A simple fluorimetric assay for the determination of carbamoyl phosphate in tissue extracts is described. In the assay, production of ATP from carbamoyl phosphate and ADP by carbamate kinase is coupled to the formation of NADPH, using glucose, hexokinase, NADP⁺, and glucose-6-phosphate dehydrogenase. Production of NADPH in this system proved to be equal to the amount of carbamoyl phosphate present.     

Cell surface heparan sulfate proteoglycans from human vascular endothelial cells. Core protein characterization and antithrombin III binding properties.

Human aortic endothelial cells (HAEC) and human umbilical vein endothelial cells (HUVEC) were labeled with 35SO(4)2- for 48 h. The membrane-associated proteoglycans were solubilized from these monolayers with detergent and purified by ion-exchange chromatography on Mono Q, incorporation in liposomes, and gel filtration. The liposome-intercalated proteoglycans were 125I-iodinated and treated with heparitinase before SDS-polyacrylamide gel electrophoresis. Radio-labeled proteins with apparent molecular masses of 130, 60, 46, 35, and 30 kDa (HAEC) and 180, 130, 62, 43, and 35 kDa (HUVEC) were detected by autoradiography. Further characterization by affinity chromatography on immobilized monoclonal antibodies and by Northern blot analysis provided evidence for the expression of syndecan, glypican, and fibroglycan in human endothelial cells. Most of the heparan sulfate which accumulated in the subendothelial matrix was implanted on a 400-kDa core protein. This protein was immunologically related to perlecan and bound to fibronectin. Binding studies on immobilized antithrombin III suggested that all membrane-associated heparan sulfate proteoglycan forms had the capacity to bind to antithrombin III but that high affinity binding was more typical for glypican. Most of the proteoglycans isolated from the extracellular matrix also bound only with low affinity to antithrombin III. These results imply that glypican may specifically contribute to the antithrombotic properties of the vascular wall.     

A quantitative histochemical study of NADPH-ferrihemoprotein reductase activity

Summary A quantitative histochemical assay for NADPH-ferrihemoprotein (P450) reductase had been developed. For optimal activity, it is necessary to use a relatively electropositive tetrazolium salt such as neotetrazolium chloride as the final acceptor. The apparentK _m of the reaction is 0.83 mM. Its specificity has been proven in two ways: (i) activity is increased selectively in the pericentral zone of liver from rats treated with phenobarbitone, an inducer of the reductase, though not in liver of rats injected with 3-methylcholanthrene, which induces NAD(P)H dehydrogenase; (ii) it is competitively inhibited by NADP⁺ (K _i=1.50mm) though unaffected by dicumarol, an inhibitor of NAD(P)H dehydrogenase activity. An NADP⁺ concentration ten times greater than the substrate concentration inhibits the histochemical reaction and the reaction in a microsomal fraction assayed biochemically to the same degree (70% inhibition). The amount of inhibition is independent of temperature, of the zone of the acinus and of the treatment of the animal.Continuous microdensitometric monitoring of the reaction product as it is formed has shown that the specific reaction is linear with incubation up to 10 min, thus allowing end-point measurements to be used for cytophotometric analysis.