Intracellular responses of antennal chordotonal sensilla of the American cockroach

The responses of mechanoreceptor neurons in the antennal chordotonal organ have been examined in cockroaches by intracellular recording methods. The chordotonal organ was mechanically stimulated by sinusoidal movement of the flagellum. Stimulus frequencies were varied between 0.5 and 150 Hz. Receptor neurons responded with spike discharges to mechanical stimulation, and were classed into two groups from plots of their average spike frequencies against stimulus frequency. Neurons in one group responded to stimulation over a wide frequency range (from 0.5 to 150 Hz), whereas those in a second group were tuned to higher frequency stimuli. The peak stimulus frequency at which receptor neurons showed maximum responses differed from cell to cell. Some had a peak response at a stimulus frequency given in the present study (from 0.5 to 150 Hz), whereas others were assumed to have peak responses beyond the highest stimulus frequency examined. The timing for the initiation of spikes or of a burst of spikes plotted against each stimulus cycle revealed that spike generation was phase-locked in most cells. Some cells showed phase-independent discharges to stimulation at lower frequency, but increasing stimulus frequencies spike initiation began to assemble at a given phase of the stimulus cycle. The response patterns observed are discussed in relation to the primary process of mechanoreception of the chordotonal organ.     

Modulation of synaptic plasticity by brain estrogen in the hippocampus

The hippocampus is a center for learning and memory as well as a target of Alzheimer's disease in aged humans. Synaptic modulation by estrogen is essential to understand the molecular mechanisms of estrogen replacement therapy. Because the local synthesis of estrogen occurs in the hippocampus of both sexes, in addition to the estrogen supply from the gonads, its functions are attracting much attention.     

The beta c component of the granulocyte-macrophage colony-stimulating factor (GM-CSF)/interleukin 3 (IL-3)/IL-5 receptor interacts with a hybrid GM-CSF/erythropoietin receptor to influence proliferation and beta-globin mRNA expression.

BACKGROUND: The interaction of different members of the hematopoietic growth factor receptor family may be relevant to the increased proliferation and the failure of differentiation that characterizes the myeloid leukemias. We recently demonstrated that a chimeric receptor (GMER) that is composed of the extracellular and transmembrane domains of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha-chain (GMR alpha) and the cytoplasmic domain of the murine erythropoietin receptor mEpoR binds hGM-CSF with low affinity (3 nM) and confers both proliferative and differentiation signals to stably transfected murine Ba/F3 cells. MATERIALS AND METHODS: To investigate whether the common beta-subunit of the GM-CSF receptor (beta c) can interact with GMER, either the entire beta-subunit or a mutant, truncated beta-subunit that completely lacks the cytoplasmic domain (beta tr) was introduced into Ba/F3 cells that express GMER, and the binding of GM-CSF as well as proliferation and differentiation responses were measured. RESULTS: Scatchard analysis showed that both GMER + beta c and GMER + beta tr bound hGM-CSF with high affinity (Kd 40 pM to 65 pM). Proliferation assays showed that the maximum growth of cells expressing GMER + beta c was identical to that of cells with GMER alone. However, proliferation of the cells that expressed GMER + beta tr was reduced by 80-95% of GMER. Dose-response curves showed that the concentration of GM-CSF required for half-maximal growth was 0.5-5.0 pM for GMER + beta c and 0.5-5 nM for GMER and GMER + beta tr. The EpoR cytoplasmic domain of GMER also undergoes ligandinducible tyrosine phosphorylation. However, the tyrosine phosphorylation did not correlate with growth in cells expressing beta tr. Coexpression of beta c with GMER in Ba/F3 cells grown in hGM-CSF markedly enhanced beta-globin mRNA expression. CONCLUSIONS: These results indicate that beta c can transduce a unique signal in association with GMER to influence both proliferative and differentiation signal pathways.     

Large scale preparation of PA-oligosaccharides from glycoproteins using an improved extraction method

We have developed a new method for the large scale preparation of pyridylaminated (PA-) oligosaccharides from glycoproteins. Phenol/chloroform extration was adapted for the removal of protein and excess 2-aminopyridine, improving the efficiency of preparation. From a 2.5 g sample of human apo-transferrin, 25–30 mol of agalacto biantennary PA-oligosaccharide could be obtained. By increasing the concentration of PA-oligosaccharide substrate, we were able to detect a very low level ofN-acetylglucosaminlytransferase IV activity in CHO cell extracts.Abbreviations PA 2-aminopyridine - SDS sodium dodecyl sulfate - GlcNAc N-acetylglucosamine - GnT N-acetylglucosaminyltransferase - Gn,Gn-bi-PA GlcNAc1-2Man1-3(GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc-2-aminopyridine - Gn,Gn,Gn-tri-PA GlcNAc1-2(GlcNAc1-4)Man1-3(GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc-2-aminopyridine - Gn,Gn,Gn-trí-PA GlcNAc1-2Man1-3({GlcNAc1-2(GlcNAc1-6)Man1-6})Man1-4GlcNac1-4GlcNAc-2-aminopyridine - Gn,(Gn),Gn-bi-PA GlcNAc1-2Man1-3(GlcNAc1-4)(GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc-2-aminopyridine     

Differential distribution of receptors for two fucose-binding lectins in embryos and adult tissues of the mouse

Ulex europaeus agglutinin-I (UEA-I) recognizes the Fuc alpha 1----2 Gal linkage. Receptors for UEA-I were not detected in mouse embryos until the 13th day of embryo-genesis, except for their temporary expression in early trophectoderm cells. In adult mice, UEA-I receptors were detected at various sites, including cells of the digestive tracts, the bronchial epithelium, Hassall's corpuscle of the thymus, and the skin. The fucose-binding protein of Lotus tetragonolobus (FBP) is another lectin that recognizes fucosyl residues. The distribution of FBP receptors was significantly different from that of UEA-I receptors. FBP receptors were first detected in late 8-cell embryos and were expressed in the embryonic ectoderm, visceral endoderm, and trophoblastic giant cells in egg-cylinders. At later stages, the distribution of FBP receptors became restricted to certain parts of the embryo. In the adult, the distribution of FBP receptors was more restricted than that of UEA-I receptors. Particularly in embryos before the 11th day of gestation, the distribution of FBP receptors resembled that of SSEA-1, which is defined by the Gal beta 1----4(Fuc alpha 1----3) GlcNAc linkage. From the specificity of FBP, we inferred that the disappearance of SSEA-1 and FBP receptors during embryogenesis is not the result of alpha 1----2 fucosylation of the terminal galactosyl residue in the determinant. The fact that the expression of two fucose-related cell-surface markers, i.e., UEA-I receptors and SSEA-1 (or FBP receptors), is developmentally regulated in an entirely different fashion is an excellent example illustrating the precise control of differentiation-dependent alterations in cell-surface carbohydrates.     

Aplysia myoglobins with an unusual amino acid sequence

The complete amino acid sequence of the myoglobin from Aplysia juliana, a species distributed world-wide, has been determined and compared with the sequence of the myoglobin of Aplysia limacina, a Mediterranean species, and of Aplysia kurodai, a Japanese and Asian species. Unlike mammalian myoglobins, Aplysia myoglobins contain only a single histidine residue, lacking the distal one, the homology being 76% between A. juliana and A. limacina, 74% between A. juliana and A. kurodai, and 83% between A. limacina and A. kurodai. The hydropathy profiles of the Aplysia myoglobins are very similar, but completely different from that of sperm whale myoglobin, taken as the reference.     

Oxidation of oxymyoglobin to metmyoglobin with hydrogen peroxide: involvement of ferryl intermediate

Hydrogen peroxide, one of the potent oxidants in muscle tissues, can induce very rapid oxidation of oxymyoglobin (MbO2) to metmyoglobin (metMb) with an apparent rate constant of 7.5 X 10(4) h-1 M-1 (i.e., 20.8 s-1 M-1) over the wide pH range of 5.5-10.2 in 0.1 M buffer at 25 degrees C. Its molecular mechanism, however, is quite different from that of the autoxidation of MbO2 to metMb. Kinetic analysis has revealed that the hydrogen peroxide oxidation proceeds through the formation of ferryl-Mb(IV) from deoxy-Mb(II), which is in equilibrium with MbO2, by a two-equivalent oxidation with H2O2. Once the ferryl species is formed, it reacts rapidly with another deoxy-Mb(II) in a bimolecular fashion so as to yield 2 mol of metMb(III). Under physiological conditions, the rate-determining step was the oxidation of the deoxy species by H2O2, its rate constant being estimated to be on the order of 3.6 X 10(3) s-1 M-1 at 25 degrees C. These findings leads us to the view that a good supply of dioxygen provides rather an important defense against the oxidation of myoglobin with hydrogen peroxide in cardiac and skeletal muscle tissues.     

A new species of the genus <Emphasis Type="Italic">Stathmopoda</Emphasis> (Lepidoptera: Stathmopodidae) closely related to the persimmon pest, <Emphasis Type="Italic">S. masinissa</Emphasis>, from Ryukyu Islands,Japan

A new species of the genus Stathmopoda from the Ryukyu Islands, Japan, is described. The new species is associated with Diospyros maritima Blume and is very similar to S. masinissa Meyrick, which is a notorious pest of persimmon, D. kaki L., in Japan and Korea. The adult external features, wing venation, and male and female genitalia of both species are illustrated and compared in detail.