Reduction of Feeding by the Variegated Grasshopper, Zonocerus variegatus , Following Infection by the Fungal Pathogen, Metarhizium flavoviride

The effect of infection by the fungal entomopathogen , Metarhizium flavoviride, on feeding by the tropical grasshopper pest , Zonocerus variegatus, was investigated in field - cage studies . A significant reduction in feeding , as indicated by faecal production , was recorded 2 - 3 days after inoculation for a range of spore doses (104 , 105 and 5 105 spores per insect) . This was before any mortality was recorded due to infection . All infected individuals died by day 7 . At this time , faecal production of the treated grasshoppers was equivalent to less than 2 days faecal production by grasshoppers untreated with spores . This reduction in feeding (69 , 71 and 74% total reduction by day 7 in the 104 , 105 and 5 105 doses respectively in comparison to controls) is a substantial contribution to the overall effects of the slow acting pathogen . Furthermore , the rapid reduction in feeding indicated that this effect was not simply due to invasion of the host tissues by the pathogen or production of secondary metabolites . The possibility that reduction in feeding is associated with a behavioural response in which there is a trade - off between host defence and feeding during early stages of infection is discussed     

Degradation of bisphenol A by the lignin-degrading enzyme, manganese peroxidase, produced by the white-rot basidiomycete, Pleurotus ostreatus

Degradation of 2,2-Bis(4-hydroxyphenyl)propane (bisphenol A, BPA), an endocrine-disturbing chemical, by the growing mycelia of the white-rot basidiomycete, Pleurotus ostreatus, was examined. About 80% of BPA initially present decreased in 12 days of culture with this fungus. By in vitro experiments using the lignin-degrading enzyme manganese peroxidase (MnP), BPA was metabolized to phenol, 4-isopropenylphenol, 4-isopropylphenol, and hexestrol. The degradation products of BPA were assumed to be formed by the one-electron oxidation of the substrate.     

Chemical modification of the calmodulin-stimulated phosphatase, calcineurin, by phenylglyoxal

Chemical modification of calcineurin by phenylglyoxal was used to probe for the presence of arginine at, or in close proximity to, the catalytic site of this phosphatase. Phenylglyoxal inactivated calcineurin with a second-order rate constant of 1.5 M-1 min-1 at pH 7.5 and 30 degrees C. The inactivation reaction was extremely sensitive to Ca2+-induced conformational changes on calcineurin; removal of this metal ion from the reaction medium increased the rate of inactivation by almost 1 order of magnitude. Furthermore, significant protection of calcineurin by ADP was observed only in the presence of Ca2+, which suggests either that distinct sites are modified by phenylglyoxal in the absence and presence of Ca2+ or that the metal ion promotes binding of ADP to calcineurin. Inactivation of calcineurin by phenyl[2-14C]glyoxal resulted in the incorporation of more than 12 eq of the reagent. However, a kinetic analysis of the order of the inactivation reaction and complete protection of calcineurin by p-nitrophenyl phosphate suggest that only one of the modified residues is responsible for the loss of enzymatic activity. Protection of calcineurin by ADP was enhanced severalfold by calmodulin, which correlated well with a calmodulin-stimulated decrease in the Ki for this ligand. Protection of calcineurin from inactivation by phenylglyoxal was also observed in the presence of various other nucleotides; half-maximal protection by these poor substrates and competitive inhibitors was observed at concentrations near their respective inhibition constants. Thus, the results of this modification study indicate that at least 1 arginine residue is essential for the expression of catalytic activity of the calmodulin-regulated phosphatase.     

Biosynthesis of the beta-lactam antibiotic, thienamycin, by Streptomyces cattleya

Radioactive- and stable isotope-containing substrates were used to identify the biosynthetic precursors of the beta-lactam antibiotic, thienamycin, in Streptomyces cattleya. Acetate is utilized by the organism to form C(6) and C(7) of the beta-lactam ring. The two carbons of the hydroxyethyl group attached to C(6) are both derived from the methyl of methionine. The cysteaminyl side chain attached to C(2) is derived from cysteine. Selective inhibition of thienamycin and cephamycin C biosynthesis has been achieved either through the addition of metabolic inhibitors or through manipulation of the growth medium. These results suggest that the two beta-lactam antibiotics, thienamycin and cephamycin C, are formed by different biosynthetic pathways.     

Promotion of capacitation of guinea pig spermatozoa by the membrane mobility agent,A2C,and inhibition by the disulfide-reducing agent,DTT

The membrane mobility agent A₂C accelerates the onset of the acrosome reaction of guinea pig spermatozoa by promoting capacitation. Spermatozoa incubated in a suspension of A₂C particles in Ca²⁺-free medium for one hour undergo a synchronous, rapid acrosome reaction upon the addition of Ca²⁺. These acrosome-reacted spermatozoa are capable of fertilization as assessed by their ability to penetrate (fuse with) zona-free hamster eggs. The disulfide-reducing agent, dithiothreitol (DTT) inhibits A₂C-mediated capacitation. It also blocks fertilization of zone-free eggs by acrosome-reacted spermatozoa by preventing attachment of the spermatozoa to the egg plasma membrane. The mode of A₂C action on spermatozoa is compared to that of A₂C-induced fusion in somatic cells. The similarity of the molecular events in the sperm membrane during capacitation and the acrosome reaction to these in other fusion events is pointed out. Inhibition of capacitation by DTT points to the importance of membrane and/or submembrane proteins and thiol groups in this process. Oxidation of sperm membrane SH groups may play an important role in in vivo capacitation.     

Structural heterogeneity of the plasmalemma of the yeast,Schwanniomyces occidentalis,induced by substrate

The growth of the yeast Schwanniomyces occidentalis on hydrocarbons (C₁₂?C₂₀) is followed by the formation of spherical invaginations. They are inwardly directed and border the ‘canals’ of the cell wall forming with them a single complex. The invaginations differ from the rest (smooth) part of the plasmalemma in the density of intramembrane particles. There is also a significant difference in the distribution of intramembrane particles in the plasmalemma of S. occidentalis grown on hydrocarbons and glucose. Invaginations and ‘canals’ are considered as a manifestation of the structural heterogeneity of the yeast cell envelope induced by a hydrocarbon substrate and, evidently, conditioned by adaptive processes.     

Inhibition by maltose, isomaltose, and nigerose of the synthesis of high-molecular-weight D-glucans by the D-glucosyltransferases of Streptococcus sobrinus

Two D-glucosyltransferases are produced by Streptococcus sobrinus C211. One (GTF-S) catalyzes the conversion of sucrose into soluble alpha-(1----6)-linked alpha-(1----3)-branched D-glucans, and the other (GTF-I), of sucrose into alpha-(1----3)-linked alpha-(1----6)-branched D-glucans. These enzymes were studied by using maltose, isomaltose, and nigerose as inhibitors. Maltose and isomaltose were found to be competitive inhibitors of GTF-S, whereas nigerose has no effect on GTF-S activity. The Ki values for maltose and isomaltose were determined to be 11 and 15mM, respectively. Maltose, isomaltose, and nigerose competitively inhibit GTF-I. The Ki values for these inhibitors were found to be approximately 0.8, 2.5, and 15mM, respectively. The inhibitory properties of each disaccharide are interpreted in terms of conformational comparisons with sucrose.     

Modulation of eosinophil recruitment in the rat by the platelet-activating factor (PAF) antagonist, BN 52021, the somatostatin analog, BIM 23014, and by cyclosporin A

The factors responsible for in vivo eosinophil recruitment are poorly defined, although T-lymphocytes appear to be involved in the etiology of eosinophilia. In order to clarify this relationship, we studied the modulation of eosinophil mobilization in the rat after immune challenge, by chronic treatment with the PAF-antagonist, BN 52021, the somatostatin analog, BIM 23014 and with Cyclosporin A (CsA). In rats made hypereosinophilic by pretreatment with cyclophosphamide or sephadex, a significant increase of the eosinophil count in blood and peritoneal fluid was induced by anaphylactic reaction. CsA totally abolished both hypereosinophilia and peritoneal eosinophil infiltration. BIM 23014 also, significantly reduced the circulating eosinophils (-68%, p less than 0.001) and cell infiltration (-86%, p less than 0.05). In contrast, BN 52021 decreased peritoneal eosinophil recruitment, while having relatively little effect on circulating cells. CsA and somatostatin are known to affect T-cell proliferation, and as T-cells are involved in the differentiation of hematopoietic cells into eosinophils, these drugs could decrease eosinophil availability for recruitment. In contrast, the PAF antagonist may act by inhibiting PAF-induced eosinophil chemotaxis, providing a more specific inhibition of this process than that exerted by CsA, BIM 23014 and other immunosuppressive agents.     

Inhibition, by an amphiphilic substance, niflumic acid, of the inward rectification of the crustacean muscle fiber

Agents such as TEA+ or CS+ ions, these last ions instead of K+ ions in poor K extracellular solution, known to reduce or abolish the inwardly rectifying channel in many preparations produced no effect in crayfish muscle membrane By contrast, poor Cl extracellular solution (Cl- ions were replaced by CH3OSO3- ions) blocked the inward current activated by hyperpolarizing pulses and produced an increase of the resting potential. Niflumic acid is a agent which inhibited the inward going rectification of the crayfish muscle membrane. Apparent dissociation constant of niflumic acid with membrane sites was equal to about 6 X 10(-8) M; this value corresponds to that given by Cousin & Motais (1979) concerning translocation of Cl- ions in the membrane of red cells. Activation of the inward going rectification in the crayfish membrane is responsible of an inward current carried by Cl- ions.     

Seed dispersal of the Korean pine,Pinus koraiensis,by the red squirrel,Sciurus vulgaris

Seed hoarding behavior of the red squirrel,Sciurus vulgaris, was studied in relation to the amount of dispersed seeds of the Korean pine,Pinus koraiensis, and the distribution of its seedlings. After removing a cone from a tree, squirrels sat on the ground and ripped off its cone scales before transporting it. A mean of 3.2 seeds were scatter-hoarded per hole. Of 7.7×10⁴ mature seeds produced in a 0.21 ha planted Korean pine forest, 22% were estimated to be directly eaten by four squirrels, 9% were hoarded by them in the pine forest and 65% were cached outside the forest. Squirrels rediscovered hoarded seeds frequently, until the ground was covered with snow, during the period from snow fall until seed germination the next spring, few hoarded seeds were utilized. Korean pine seedlings were found up to 600 m from their mother trees. Scatter-hoarding by squirrels extensively contributes to seed dispersal to places suitable for the regeneration of the Korean pine. The large size of the cone, the absciss-layer at the cone penduncle, the infrequent dehiscence of cone scales, the large and wingless seeds, and the thick seed-coats have probably all been specialized to facilitate utilization by GenusSciurus.     

Determination of the triterpenoid,betulinic acid,in Doliocarpus schottianus by HPLC

The isolation, detection and quantification of betulinic acid in Doliocarpus schottianus are described. The isolation from the plant extract was made by column chromatography and centrifugal TLC, and betulinic acid was characterized by spectrometric methods. The detection and quantification were made by HPLC using a C18 column eluted with acetonitrile: water and detected at 210 nm. The results showed that the metabolite accumulates in the bark of the plant, but very small concentrations were also found in the leaves and wood.     

Antibody-independent activation of C1, the first component of complement, by cardiolipin

Lipid vesicles containing phospholipids known to be present in substantial amounts in mitochondrial membranes were tested for their capacity to activate C1. Among them, only cardiolipin (CL) was highly efficient in C1 activation; no such effect was observed with phosphatidylcholine, phosphatidylethanolamine, or phosphatidylinositol. CL was shown to bind specifically C1q, because only unlabeled C1q competed with 125I-C1q for binding to CL. The requirement for C1q was confirmed by the finding that only fully reconstituted macromolecular C1, containing C1q, was activated by CL. The specificity of CL-induced activation of C1 was also demonstrated by introducing adriamycin, an agent known to interact with CL. Whereas adriamycin did not decrease C1 activation induced by immune complexes, it abrogated C1 activation by CL. The latter was shown to be a strong nonimmune activator of C1, because C1-INH did not inhibit CL-induced activation. When the concentration of CL in vesicles was decreased in the presence of phosphatidylcholine, C1 activation was detected only above a critical level of 35 mol% CL, compatible with a minimal density or clustering of CL molecules in the plane of the membrane. Moreover, C1 activation by CL was modulated by the addition of cholesterol. The threshold of CL required for C1 activation was lowered by the incorporation of more than 35 mol% cholesterol into the vesicles. These results show that CL incorporated into liposomes can be a potent nonimmune activator of C1. The negatively charged phosphate groups in CL are likely candidates for Clq-binding.     

Rescue of light responses in the Drosophila "null" phospholipase C mutant,norpAP24, by the diacylglycerol kinase mutant,rdgA, and by metabolic inhibition

Light responses in Drosophila are reportedly abolished in severe mutants of the phospholipase C (PLC) gene, norpA. However, on establishing the whole-cell recording configuration in photoreceptors of the supposedly null allele, norpAP24, we detected a small ( approximately 15 pA) inward current that represented spontaneous light channel activity. The current decayed during approximately 20 min, after which tiny residual responses (<2 pA) were elicited by intense flashes. Both spontaneous currents and light responses appeared to be mediated by residual PLC activity, because they were enhanced by impairing diacylglycerol (DAG) kinase function by mutation (rdgA) or by restricting ATP but were reduced or abolished by a mutation of the PLC-specific Gq alpha subunit. It was reported recently that metabolic inhibition activated the light-sensitive transient receptor potential and transient receptor potential-like channels, even in norpAP24, leading to the conclusion that this action was independent of PLC (Agam, K., von Campenhausen, M., Levy, S., Ben-Ami, H. C., Cook, B., Kirschfeld, K., and Minke, B. (2000) J. Neurosci. 20, 5748-5755). However, we found that channel activation by metabolic inhibitors in norpAP24 was strictly dependent on the residual PLC activity underlying the spontaneous current, because the inhibitors failed to activate any channels after the spontaneous current had decayed. By contrast, polyunsaturated fatty acids invariably activated the channels independently of PLC. The results strongly support the obligatory requirement for PLC and DAG in Drosophila phototransduction, suggest that activation by metabolic inhibition is primarily because of the failure of diacylglycerol kinase, and are consistent with the proposal that polyunsaturated fatty acids, which are potential DAG metabolites, act directly on the channels.     

The hierarchical genetic structure of an urban town, Kidlington, Oxfordshire, examined by the coefficient of relationship by isonymy.

The surnames of the 3443 males registered to vote in Kidlington in 1977 yield a Coefficient of Relationship by Isonymy of 0.000564 {Ri = sigma(n(n-1))/2 N(N-1), in which n = the number of men of each surname and N = sigma n}. Those of the four wards separately average 0.000722. However, if one includes only one male of any one surname in each residence, the values are, respectively, 0.000534 and 0.000535. That is, the only structure seen between the two levels is in the influence of men of the same surname resident in the same house. An analysis of relationship by residence on the same street yields a value of Ri somewhat higher than that for the ward as a whole, however, suggesting that even within a ward there may be a tendency for the house of relatives occasionally to lie close together.     

应用DGGE法对青海相邻两盐湖中细菌多样性的快速检测

分别对青海相邻两盐湖柯柯盐湖、茶卡盐湖土样、泥样进行富集培养后,从中提取的DNA用两套不同的细菌通用引物进行扩增,分别得到包含V8和V9高变区的16SrDNA片断。经变性梯度凝胶电泳(DGGE)分析,结果显示这两个盐湖富集样品中细菌多样性具有较大的差异,而且同一盐湖不同性质样品中的细菌多样性差异也较大,两湖的泥样富集样品中均表现出了稍丰富的多样性。     

Cloning, production, and functional expression of the bacteriocin enterocin A, produced by Enterococcus faecium T136, by the yeasts Pichia pastoris, Kluyveromyces lactis, Hansenula polymorpha, and Arxula adeninivorans

The bacteriocin enterocin A (EntA) produced by Enterococcus faecium T136 has been successfully cloned and produced by the yeasts Pichia pastoris X-33EA, Kluyveromyces lactis GG799EA, Hansenula polymorpha KL8-1EA, and Arxula adeninivorans G1212EA. Moreover, P. pastoris X-33EA and K. lactis GG799EA produced EntA in larger amounts and with higher antimicrobial and specific antimicrobial activities than the EntA produced by E. faecium T136.     

Suppression of the growth of the basidiomycete yeast, Rhodotorula minuta, by cinnamic acid

Rhodotorula minuta, a basidiomycete fungus, prefers neutral pH for growth and its growth inhibition by food preservatives such as benzoic acid and cinnamic acid has not been reported. Cinnamic acid at 1 g l^–1 arrested the growth and decreased the respiration of Rhodotorula but did not kill the yeast. The inhibitory effect was stronger in a mutant strain, 5-286, deficient in the -ketoadipate pathway than in the wild, suggesting that -ketoadipate pathway functions to detoxify this acid by restoring the decreased respiration.     

Activation of the Na,K-pump by isoproterenol, methylxanthines, and iodoacetate in erythrocytes of the frogRana temporaria

Our preliminary studies have shown that the Na,K-pump in frog erythrocytes is activated by isoproterenol (ISP), phosphodiesterase blocker (3-isobutyl-methylxantine, IBMX), and by iodoacetate (MIA). The aim of the present study was to determine a mechanism responsible for the effect of MIA on the Na,K-pump activity in frog red blood cells as well as the role of G proteins and intracellular messengers in modulation of active K⁺ transport induced by ISP. An additive stimulation of active K⁺ (⁸⁶Rb) transport in frog erythrocytes was found after exposure of the cells to MIA in a combination with ISP or IBMX. The treatment of the red blood cells with 1 mM MIA for 1 or 2 h was associated with a significant decrease in intracellular Na⁺ concentration, on average, by 13 and 20%, respectively, suggesting a direct action of MIA on the Na,K-pump. Incubation of cells in the presence of dibutyryl-cAMP (1 mM) or adenylate cyclase activator forskolin (0.1 mM) caused stimulation of the active K⁺ influx by 21.8 and 27.9%, respectively. AlF ₄ ^- and cholera toxin able to increase cell cAMP levels via G protein interactions had no effect on the total and IPS-induced K⁺ influx in frog erythrocytes. The treatment of the red blood cells with sodium nitroprusside that increases cGMP concentration in cells also had no effect on the K⁺ influx. The stimulatory influence of ISP on the Na,K-pump was reduced with increase of the intracellular Na⁺ concentration. ISP increased affinity of the Na,K-pump to Na⁺ (the Mihaelis constant K_M = 34.4 ± 5.1 in control and 25.3 ± 2.8 mM in the presence of ISP,p < 0.01), but did not change maximal velocity (8.1 ± 0.6 and 7.7 ± 0.3 mmol/1/h in the control and ISP-treated cells, respectively). The results obtained indicate the presence of several different signal pathways involved in regulation of the Na,K-pump activity in frog erythrocytes.