Anaerobic degradation of 3,4,5-trimethoxybenzoate by a defined mixed culture of Acetobacterium woodii, Pelobacter acidigallici, and Desulfobacter postgatei

Abstract Acetobacterium woodii was continuously grown on 3,4,5-trimethoxybenzoate as pure culture or in commensalistic combination with Pelobacter acidigallici and Desulfobacter postgatei . Under pure culture conditions the following growth parameters were determined: μ _max= 0.112 h⁻¹, K _s= 1.07 mM, Y _max= 35 g/mol, and m = 0.22 mmol·g⁻¹·h⁻¹. In coculture with P. acidigallici the affinity for the substrate increased and the K _s value was found to be 135 μM. Under batch culture conditions mixed populations of A. woodii, P. acidigallici , and D. postgatei completely mineralized 3,4,5-trimethoxybenzoate to CO₂, whereas under continuous culture conditions more than 3 mM acetate remained unused.     

Mengovirus-Induced Cytopathic Effect in L-Cells: Protective Effect of Interferon

The effect of interferon on mengovirus-induced cytopathic effect (CPE) in L cells, the cut-off of host-cell protein synthesis, and production of mature virus were found to be dependent on the concentration of interferon. CPE and inhibition of host protein synthesis were not affected until the concentration of interferon was increased 100-fold over that required to reduce viral yields by 90%.     

Monoclonal Antibodies for Detection and Serotyping of Cucumber Mosaic Virus

Two monoclonal antibodies (MAbs) to cucumber mosaic virus (CMV) were selected from a panel of MAbs for use in the direct DAS (double antibody sandwich)-ELISA. Two different test procedures were developed: an ELISA with polyclonal and monoclonal antibodies (mixed ELISA) for the routine detection of CMV and a MAb-ELISA with two MAbs directed against different epitopes for the specific detection of the N serotype which is prevalent in GDR. The conventional two-step incubation of plates precoated with IgG was compared with simultaneous incubation of test sample and labelled antibody (one-step incubation). The mixed ELISA proved to be more sensitive than the direct DAS-ELISA with polyclonal antisera in detecting CMV in crude sap of infected plants. On the other hand, the MAb-ELISA could be used for serotyping of CMV isolates which is important in epidemiological investigations and in resistance breeding. Both the two-step and the one-step procedures gave similar results with some advantages of the latter procedure. One-step incubation is not only time-saving but seems to be also more sensitive with regard to the detection limit. However, care must be taken to circumvent the hook-effect occurring at high virus concentrations.     

Augmentation of host antitumor immunity by low doses of cyclophosphamide and mafosfamide in two animal tumor models

Summary By cloning in vitro we have obtained two sublines of the L5222 rat leukemia, one with high (L5222-S) and the other with low (L5222-R) in vivo sensitivities to non-toxic doses of mafosfamide, a stabilized derivative of 4-hydroxy-cyclophosphamide. This sensitivity in vivo was not related to the cytotoxic activity of the drug in vitro. Treatment of rats bearing the L5222-S and of mice transplanted with the MOPC-315 plasmocytoma with low doses of mafosfamide or cyclophosphamide resulted in a high percentage of surviving animals, which were resistant to a subsequent tumor challenge. Viable leukemic cells were needed to establish antitumor immunity, since it was not possible to induce resistance by injection of mitomycin-C-treated, non-viable L5222 cells. The adoptive transfer of spleen cells from animals immune against the L5222-S and the MOPC-315 resulted in resistance of the syngeneic recipients against a rechallenge with tumor cells, provided that the animals were treated with an immunosuppressive dose (100 mg/kg) of cyclophosphamide prior to the spleen cell implantation. In nude mice treatment of the L5222 with low doses of mafosfamide also resulted in surviving animals, however resistance to a second tumor challenge occurred only sporadically.The data presented confirm that therapy with cyclophosphamide or mafosfamide enhances host antitumor immunity but, contrary to previous reports, it could be demonstrated that successful tumor rejection was independent of T cells.Supported by the Federal Ministry of Research and Technology (BMFT), Bonn-Bad Godesberg, FRG     

Microtubules are involved in the secretion of proteins at the apical cell surface of the polarized epithelial cell, Madin-Darby canine kidney

Microtubule-disrupting drugs (nocodazole, colchicine) and cytochalasin D, which inhibits the polymerization of the actin microfilaments, were used to study the role of the cytoskeleton in protein secretion in the polarized Madin-Darby canine kidney (MDCK) epithelial cells. Two proteins were analyzed. The gp 80 glycoprotein complex, which in untreated cells is sorted into the apical pathway and lysozyme, which is released randomly at both cell surfaces in transfected MDCK cells. Our results show that cytochalasin D has no influence on the transport of the gp 80 complex and lysozyme to either cell surface. However, in the presence of nocodazole or colchicine the secretion of both proteins at the apical cell surface is reduced by 50% with a concomitant increase in the basolateral release. These data suggest that microtubules are necessary for an efficient secretion of proteins at the apical cell surface of MDCK cells. In regard to the yet unresolved discrepancy concerning the involvement of microtubules in the transport of membrane proteins to the apical surface of MDCK cells, our results are consistent with the data of Rindler et al. (Rindler, M. J., Ivanov, I. E., and Sabatini, D. D. (1987) J. Cell. Biol. 104, 231-241) who observed a nonpolarized delivery of the influenza virus hemagglutinin in the presence of nocodazole or colchicine.     

Community composition and soil properties in northern Bolivian savanna vegetation

Abstract. Direct gradient analysis (Canonical Correspondence Analysis) of northern Bolivian savanna vegetation revealed correlations between the composition of plant communities and physical and chemical soil properties. Cover/abundance values for 193 species from 27 sites were related to data on eight soil factors. A water-regime variable and the percentage of sand and silt were correlated with the first axis of the species-environment biplot and explained most of the variation in community composition. Along this axis, species and sites of flood-plain vegetation were separated from sites not affected by flooding rivers. The second axis of the biplot was correlated with soil-chemical variables, namely extract-able phosphate, base saturation, organic carbon, pH, and effective cation exchange capacity. Part of the variation in community composition can be explained by these soil nutrient variables. Grassland communities were separated from woody vegetation along the soil nutrient gradient, and floodplain communities of white-water rivers from those of clear-water rivers. The results of the gradient analysis indicate that the soil texture-moisture gradient is the prime factor determining the variation in the floristic composition of the savanna communities examined, and that, in addition, the soil nutrient gradient accounts for some of the variation.     

HSP25 in isolated perfused rat hearts: Localization and response to hyperthermia

Recent investigations concentrate on the correlation between the myocardial expression of the inducible 70-kDa heat shock protein (HSP70i) by different stress conditions and its possible protective effects. Only few studies have focused on the involvement of small heat shock proteins in this process. We analyzed the location of the small heat shock protein HSP25 in isolated cardiomyocytes as well as its location and induction in isolated perfused hearts of rats. By immunofluorescence microscopy HSP25 was found to colocalize with actin in the I-band of myofibrils in cardiomyocytes of isolated perfused hearts as well as in isolated neonatal and adult cardiomyocytes. Hyperthermic perfusion of isolated hearts for 45 min resulted in modulation of different parameters of heart function and in induction of HSP25 and HSP70i. Temperatures higher than 43°C (44–46°C) were lethal with respect to the contractile function of the hearts. Compared to control hearts perfused at 37°C, significant increases during hyperthermic perfusion at 42°C and 43°C were obtained for heart rate, contraction velocity and relaxation velocity. In response to hyperthermia at 43°C and after subsequent normothermic perfusion for 135 min at 37°C, left ventricular pressure, contraction velocity and relaxation velocity remained significantly elevated. However, heart rate returned to control values immediately after the period of heat treatment. HSP25 is constitutively expressed even in normothermic perfused hearts as shown by Western blotting. Hyperthermia increased the content of HSP25 only in the left ventricular tissue. In contrast, HSP70i was strongly induced in all analyzed parts of the myocardium (left ventricle, right ventricle, septum). Our findings suggest a differential regulation of HSP25 and HSP70i expression in response to hyperthermia in isolated perfused hearts. The constitutively expressed HSP25 seems to be located adjacent to the myofibrils which implies a specific role of this protein even under unstressed conditions for the contractile function of the myocardium.     

Induction and ionic basis of slow wave potentials in seedlings of Pisum sativum L.

Slow wave potentials (SWPs) are transient depolarizations which propagate substantial distances from their point of origin. They were induced in the epidermal cells of pea epicotyls by injurious methods such as root excision and heat treatment, as well as by externally applied defined steps in xylem pressure (Px) in the absence of wounding. The common principle of induction was a rapid increase in Px. Such a stimulus appeared under natural conditions after (i) bending of the epicotyl, (ii) wounding of the epidermis, (iii) rewatering of dehydrated roots, and (iv) embolism. The induced depolarization was not associated with a change in cell input resistance. This result and the ineffectiveness of ion channel blockers point to H(+)-pumps rather than ion channels as the ionic basis of the SWP. Stimuli such as excision, heat treatment and pressure steps, which generate SWPs, caused a transient increase in the fluorescence intensity of epicotyls loaded with the pH-indicator DM-NERF, a 2',7'-dimethyl derivative of rhodol, but not of those loaded with the pH indicator 2',7'bis(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF). Matching kinetics of depolarization and pH response identify a transient inactivation of proton pumps in the plasma membrane as the causal mechanism of the SWP. Feeding pump inhibitors to the cut surface of excised epicotyls failed to chemically simulate a SWP; cyanide, azide and 2,4-dinitrophenol caused sustained, local depolarizations which did not propagate. Of all tested substances, only sodium cholate caused a transient and propagating depolarization whose arrival in the growing region of the epicotyl coincided with a transient growth rate reduction.