Structural characterization of myosin from bovine brain

Myosins isolated from bovine brain, rabbit skeletal muscle, and chicken gizzard smooth muscle and their heavy meromyosin and light meromyosin fractions were studied in the electron microscope by negative staining with uranyl acetate. Under similar conditions of preparation and polymerization, the three myosins formed paracrystals of different structures. The light meromyosin portion of the skeletal muscle myosin also assembled in a different fashion than the brain or smooth muscle light meromyosins; the latter two assembled similarly. The heavy meromyosin portion from each of the three myosins was shown to interact with the actins isolated from each of the three tissue sources by the formation of the characteristic arrowhead patterns with similar periodicities. The brain heavy meromyosin attachment to both skeletal and brain actins was dissociated by ATP. It is suggested that differences in the light meromyosin portions of the three myosins may account in part for their differences in assembly in vivo.     

On the Stability of Clathrate Hydrates Encaging Polar Guest Molecules: Contrast in the Hydrogen Bonds of Methylamine and Methanol Hydrates

Abstract

The stability of clathrate hydrates encaging highly polar guests has been investigated in order to explain the experimental observation that some amines form clathrate hydrates but alcohols act as inhibitor to hydrate formation. We choose methylamine and methanol as guest species and examine the stable structure, at which the total potential energy has a minimum value. At the local minima of those two hydrates, the potential energies of water-water and guest-water, and their hydrogen bonded networks are compared. It is found that methanol does not retain the host lattice structure, while the host-network structure is kept in the presence of methylamine. It is shown that the difference in the magnitude of the partial charge on the hydrogen atom between the hydroxyl and amino groups plays a much more significant role on the stability of both clathrate hydrates than the difference in molecular geometry. This is supported from the result of a methylamine-like model that has the same partial charges on the atoms in the hydrophilic site as methanol.     

Comparison of performances of four ELISA kits in the detection of BLV antibodies in bulk tank milk or concentrated lactoserum from herds with low prevalence of infection

Performances of four ELISA kits in the detection of BLV antibodies in bulk tank milk was studied in 76 non-infected herds and 44 herds with low prevalence of BLV infection. None of the kits gave false positive results. On the other hand, there was an important variation in sensitivity. The kits with the highest sensitivity identified 43% of infected herds, which included 65% of infected cows. When concentrated lactoserum was tested, 59% of infected herds, which included 73% of infected cows, could be identified.     

Energy coupling sites in the electron transport chain of Zymomonas mobilis

Abstract Energy-coupling sites in the electron transport chain of the obligately fermentative aerotolerant bacterium Zymomonas mobilis were examined. The H⁺ /O stoichiometry of the electron transport chain in intact bacteria oxidizing ethanol was close to 3.3. Cytoplasmic membrane vesicles coupled NADH oxidation to ATP synthesis. With ascorbate/phenazine methosulfate they showed oxygen uptake which was sensitive to antimycin A, but no significant ATP synthesis could be detected. Cells with a defective coupling site I, prepared by cultivation on a sulfate-deficient medium, showed a decreased rotenone sensitivity of respiration, and they lacked almost all the respiration-driven proton translocation and ATP synthesis. We conclude that, despite the reported composition of the electron transport chain, only energy coupling site 1 was functional in Z. mobilis .     

Mechanisms of modulation of neuronal nicotinic receptors by substance P and OAG

Substance P is known to modulate neuronal nicotinicacetylcholine receptors (nAChRs) in the sympathetic nervous system.There are two conflicting proposals for the mechanism of this effect, an indirect action mediated by protein kinase C (PKC) and a direct interaction with receptor subunits. We studied the mechanisms of thiseffect in PC-12 cells. Substance P enhanced the decay of thenicotine-induced whole cell current. This effect was fast in its onsetand was not antagonized by guanosine5'-O-(2-thiodiphosphate), a G protein blocker, orstaurosporine, a nonselective PKC blocker. Staurosporine failed toreverse the inhibition by 1-oleoyl-2-acetyl-sn-glycerol (OAG), a synthetic diacylglycerol analog known to activate PKC. Theinhibitory effects of the peptide and OAG were preserved in excisedpatches, but substance P applied to the extra patch membrane wasineffective in the cell-attached patch configuration. We conclude thatsubstance P modulates neuronal nAChRs most likely by direct interactions with the receptors but independently from activation ofPKC or G proteins and that PKC does not participate in modulation by OAG.

     

Enhancement of γ-linolenic acid production by Mucor ambiguus with nonionic surfactants

Summary -Linolenic acid (GLA) production by Mucor ambiguus IFO 6742, immobilised in Biomass Support Particles (BSPs), has been investigated in a fluidized-bed fermenter in the presence of nonionic surfactants. In this system, repeated batch cultivation was achieved at higher yield and productivity than by conventional methods, since microbial lipids inlcuding GLA were significantly secreted into the culture broth and/or on the surface of the cell wall.     

A relationship between the inhibition of heparan sulfate and chondroitin sulfate synthesis and the inhibition of molting by selenate in the hemipteran Rhodnius prolixus

The insect Rhodnius prolixus synthesizes heparan sulfate and chondroitin sulfate after a blood meal containing [35S]-inorganic sulfate. A 40 to 80% inhibition of heparan sulfate synthesis was obtained when the meal was supplemented with 10(-5) and 10(-4) M sodium selenate respectively. Likewise an inhibition of the molting in the order of 30 to 60% was observed when the insects were fed with blood containing 10(-5) and 10(-4) M selenate respectively. The insects after a subsequent meal without selenate molted normally. Except for the inhibition of the ecdysis no gross physiological or morphological changes could be observed in the insects. Based on these and other findings the possible role of sulfated glycosaminoglycans in the control of cell growth is discussed.     

Cauliflower mosaic virus gene VI causes growth suppression, development of necrotic spots and expression of defence-related genes in transgenic tobacco plants

Summary In order to study possible functions of the inclusion body matrix protein (IBMP) encoded by gene VI of cauliflower mosaic virus (CaMV), the XbaI fragment containing the gene VI of a Japanese strain of CaMV (CaMV S-Japan) was transferred to tobacco plants by Ti mediated transformation. Eight out of 18 kanamycin resistant plants (40%) expressed detectable levels of IBMP. Those transgenic plants expressing IBMP produced leaves with light green color, and their growth was suppressed as compared with control plants. Symptom-like necrotic spots also appeared on the leaves and stems of the mature transgenic plants. Furthermore, in these transgenic plants, pathogenesis-related proteins 1a, 1b and 1c were highly expressed and the activity of 1,3--glucanase was increased up to eightfold. From these results, we concluded that expression of the IBMP is associated with symptom development.     

Characterization of Vegetal Plate Cells Separated from Cytochalasin B-Treated Blastulae of the Sea Urchin, Clypeaster japonicus

Vegetal plate forming cells (VPCs) of the vegetal plate blastulae of the sea urchin, Clypeaster japonicus , had a layer of microfilaments on the basal side. The VPCs specifically protruded from the embryos after a treatment with 1 μg/ml of cytochalasin B (CB). Based on scanning electron microscopy, unlike other epithelial cells the protruded VPCs possessed neither cilium nor microvilli on their surface. The protruded VPCs were easily separated from the embryos by stirring the embryo suspension with pipette. An in vitro immunohistochemistry using a primary mesenchyme cell (PMC) surface-specific monoclonal antibody (MAb) raised against PMCs of Strongylocentrotus purpuratus showed that the MAb also specifically bound to the PMCs in mesenchyme blastulae of C. japonicus . The MAb bound in 81% of the separated VPCs in C. japonicus vegetal plate blastulae examined. However, the MAb binding occurred only after the separated VPCs were incubated in artificial sea water (ASW) for at least 1 hr. In the VPC-deprived embryos, gastrulation occurred after they were transferred to normal ASW. However, the PMCs and the spicules were not formed in these embryos.
In conclusion, a majority of the VPCs separated from the CB-treated blastulae were presumptive PMCs. These VPCs provide an excellent source of presumptive PMCs.