Regulation of fructosyltransferase activity by carbohydrates, in solution and immobilized on hydroxyapatite surfaces

We tested the effect of several carbohydrates on the activity of cell-free fructosyltransferases (FTF) in solution and immobilized onto hydroxyapatite (HA) and found an inhibitory dose-dependent effect of glucose on FTF activity, both on the surface and in solution. Glucose at 160 mM inhibits FTF activity by 75% both on HA and in solution. Fructose at 160 mM inhibited FTF activity by 25% in solution and by 15% on HA. Levan inhibited FTF activity by 30% in solution, while dextrans and inulin had a limited effect on FTF activity. Circular dichroism and infrared analysis demonstrated no major changes in the chemical structure of fructans synthesized by cell-free FTF on HA and in solution, in the presence or absence of glucose. However, as verified by size-exclusion chromatography, glucose inhibited the synthesis of high molecular-weight fructans. The results indicate that glucose, a byproduct of the FTF enzymatic reaction, is the main carbohydrate affecting FTF activity. Selective inhibition of high molecular-weight fructan production by glucose, may indicate that two mechanisms are involved in the synthesis of fructans, both in solution and on the surface.     

Selective inhibition of Klebsiella aerogenes growth on pentoses by pentitols.

Selective inhibition of growth by pentitols was observed when Klebsiella aerogenes M-7 which could not utilize pentitols was grown on pentoses. D-Arabitol inhibited the growth on D-arabinose as a sole carbon source, but had no effect on the growth on L-arabinose, D-xylose, and D-ribose. Similarly, L-arabitol inhibited the growth on D-arabinose and L-arabinose, ribitol inhibited the growth on D-arabinose and L-arabinose, and xylitol inhibited the growth on D-xylose. From the following reasons, we postulated that the selective growth inhibition by pentitols was due to the competitive inhibition of pentose isomerase reaction by the cell by pentitols. (i) D-Arabinose transport activity was not inhibited by pentitols. (ii) Induction of D-arabinose and L-arabinose isomerases was not inhibited by D- and L-arabitol, respectively. (iii) The specificity of growth inhibition by pentitols was the same as that of competitive inhibition of pentose isomerases by pentitols.     

Can fish survive by filter-feeding on microparticles? Energy balance in tilapia grazing on algal suspensions

Data on dietary preferences, filter-feeding mechanisms and ingestion rates of algae by tilapias are outlined and discussed. Quantitative data on algal ingestion by filter-feeding are incorporated into a bioenergetic model, demonstrating that under most conditions tilapias are unable to fulfil basic maintenance requirements and hence lose weight. It is concluded that the apparently high volumes of algae ingested by tilapias must be achieved by other means, by particulate feeding on aggregations of algae in the water column or flocculent surface scums of cyanobacteria or by grazing on periphytic mats.     

Camera traps and guard observations as an alternative to researcher observation for studying anthropogenic foraging

Foraging by wildlife on anthropogenic foods can have negative impacts on both humans and wildlife. Addressing this issue requires reliable data on the patterns of anthropogenic foraging by wild animals, but while direct observation by researchers can be highly accurate, this method is also costly and labor‐intensive, making it impractical in the long‐term or over large spatial areas. Camera traps and observations by guards employed to deter animals from fields could be efficient alternative methods of data collection for understanding patterns of foraging by wildlife in crop fields. Here, we investigated how data on crop‐foraging by chacma baboons and vervet monkeys collected by camera traps and crop guards predicted data collected by researchers, on a commercial farm in South Africa. We found that data from camera traps and field guard observations predicted crop loss and the frequency of crop‐foraging events from researcher observations for crop‐foraging by baboons and to a lesser extent for vervets. The effectiveness of cameras at capturing crop‐foraging events was dependent on their position on the field edge. We believe that these alternatives to direct observation by researchers represent an efficient and low‐cost method for long‐term and large‐scale monitoring of foraging by wildlife on crops.     

葡萄籽中原花青素对实验动物主动脉收缩和血小板聚集的影响

目的:研究葡萄籽中原花青素(PA)对大鼠离体主动脉平滑肌收缩活动和兔血小板聚集的影响.方法:采用大鼠离体主动脉环灌流方法,记录主动脉环张力变化,观察PA对去甲肾上腺素(NA)和KCl预收缩大鼠离体主动脉平滑肌收缩反应的舒张作用以及对NA量效曲线的影响.比浊法测定兔血小板聚集.结果:PA能明显抑制NA(10-6mol/L)预收缩大鼠离体主动脉环的反应,使NA量效曲线压低,最大反应降低,此作用无内皮依赖性,但对KCl预收缩主动脉环的舒张作用无明显影响,也不影响花生四烯酸(AA),ADP和胶原(collagen)蛋白诱导的兔血小板聚集.结论:PA能对抗NA而不影响KCl诱导的大鼠离体主动脉平滑肌的收缩,不影响兔血小板聚集.     

Iron-phosphorus relationship in the nutrition of tomato seedlings grown on alluvial and calcareous soils

Summary In typical alluvial and calcareous soils of Egypt 5 levels of each of P and Fe were added to study their effect on the dry matter and on their uptake by tomato seedlings in greenhouse. Application of phosphorus significantly increased the dry matter yields and both P and Fe uptake by tomatoes grown on both soils. However, application of Fe had no significant effect on the dry matter and P-uptake by tomatoes grown on alluvial soil while they were significantly increased on the calcareous one.     

激光辐照微生物的研究概况

应用激光辐照微生物的研究非常广泛。本文概述了激光辐照微生物的刺激效应的一些最新进展,同时,也就其可能机制进行了探讨。此外,还提出了在激光辐照微生物研究中的几个问题,旨在促进对激光诱变效应机制的深入和全面的了解,并进一步扩大其在生产实践中的应用。     

Vector status of three leafhopper species for Australian lucerne yellows phytoplasma

Abstract   The leafhoppers Orosius argentatus (Evans), Austroagallia torrida (Evans) and Batracomorphus angustatus (Osborn) were used in transmission tests to determine their vector status for the phytoplasma associated with Australian lucerne yellows (ALuY). Caged, seed-grown lucerne plants were monitored for foliar symptom expression after feeding by leafhoppers transferred from ALuY symptomatic lucerne plants. Twelve of 25 plants developed phytoplasma disease-like symptoms including stunting and yellowing. The most pronounced foliar symptoms were displayed by five plants that had been fed on by O. argentatus and four plants that had been fed on by A. torrida. One plant, fed on by O. argentatus , showed the distinctive root symptoms of ALuY . A phytoplasma was identified by electron microscopy in two plants fed on by O. argentatus and one by A. torrida. For each group of plants that had been fed on by a single leafhopper species, one plant was phytoplasma positive as determined by the polymerase chain reaction (PCR) using universal primers. The phytoplasma detected by PCR in the plant fed on by A. torrida was identified by restriction fragment length polymorphism (RFLP) analysis as the tomato big bud (TBB) phytoplasma. The PCR product from two plants fed on by B. angustatus and O. argentatus were too faint for RFLP analysis. PCR assays were conducted on DNA extracted from the head and thorax of each leafhopper species from transmission tests and from field-collected insects, but no phytoplasma DNA was detected. These findings suggest O. argentatus is a vector of the ALuY pathogen and A. torrida is a vector of the TBB phytoplasma.     

Impact of DNA gyrase inhibition by antisense ribozymes on rec A in <Emphasis Type="Italic">E. coli</Emphasis>

The chromosome of E. coli is maintained in a negatively supercoiled state, and supercoiling levels are affected by growth phase and a variety of environmental stimuli. Regulation of DNA supercoiling yields a complex spectrum of effects on the E. coli recA system. Previous studies indicated that inhibition of DNA gyrase by antibiotics that act on the DNA gyrase A subunit results in turning on the recA system. Here we show that antisense ribozymes that act on the DNA gyrase A subunit can also induce recA. We used real time PCR and immunoblot to analyze the impact of DNA gyrase A inhibition by antisense ribozymes on recA expression. When gyrase A was inhibited by the RNase P mediated antisense ribozymes the expression of recA was induced around 130-fold as seen by real time PCR analysis. This suggests that repair pathway is induced by antisense ribozymes against DNA gyrase A and the damage produced by these ribozymes may be similar to that produced by fluroquinolones.     

Pedilanthus diazlunanus (Euphorbiaceae): pollination by hymenopterans in a bird-pollinated genus

Pollination in the genus Pedilanthus is commonly effected by hummingbirds. Pollination by vespid wasps in Pedilanthus is documented for the first time based on observations of Pachodynerus nasidens and Eumenes americanus pollinating Pedilanthus diazlunanus. An hypothesis concerning the mechanism by which hummingbird pollination was replaced by insect pollination in Pedilanthus is advanced based on observations of insects on P. bracteatus.     

Inhibition of platelet aggregation by primary amines. Evidence for a possible role of membrane-associated calcium

The aggregation of human blood platelets by thrombin, adenosine diphosphate, wheat germ agglutinin or ristocetin was inhibited by primary amines. In general, thrombin-induced platelet aggregation was strongly affected by the amines while the effect was weak on cell aggregation by ristocetin. Usually, the diamines were stronger inhibitors of aggregation than the monoamines with cadaverine as the strongest and ethylamine as the weakest inhibitor. At concentration where platelet aggregation was inhibited, the amines neither displaced serotonin from serotinin-loaded platelets nor caused lysis of human red cells. The lectin activity of wheat germ agglutinin on human red cells was not affected by the amines indicating that the amines probably acted on platelets and not on the agglutinin. The clotting activity of thrombin on fibrinogen was partially inhibited by the amines while its esterolytic activity remained unaltered. The inhibitory action of the amines on platelet aggregation could be overcome with small amounts of calcium while other divalent cations tested had little effect. It is suggested that the amines affect platelet aggregation by interfering with the actions of membrane-associated calcium.     

Associational resistance mediated by natural enemies

Abstract.  1. Associational resistance theory suggests that the association of herbivore-susceptible plant species with herbivore-resistant plant species can reduce herbivore density on the susceptible plant species. Several casual mechanisms are possible but none has so far invoked natural enemies. Associational resistance mediated by natural enemies was tested for by examining densities of a gall fly, Asphondylia borrichiae (Diptera: Cecidomyiidae), and levels of parasitism on two closely related seaside plants, Borrichia frutescens and Iva frutescens , when alone and when co-occurring.
2. Both Borrichia and Iva grow alone or together on small offshore islands in Florida. Each host plant species has its own associated race of fly, but both races of fly are attacked by the same four species of parasitoids. Borrichia normally has a higher density of galls than Iva , and galls are larger on Borrichia than on Iva .
3. Gall size, gall abundance, parasitism levels, and parasitoid community composition were quantified on both Borrichia and Iva on islands where each species grew alone or together. Some islands were then manipulated by adding Borrichia to islands supporting only Iva , and by adding Iva to islands supporting only Borrichia . Subsequent gall densities and gall parasitism levels on the original native species were then examined.
4. On both natural and experimentally manipulated islands, gall densities on Iva were significantly lowered by the presence of Borrichia . This is because bigger parasitoid species that were common on Borrichia galls, which are bigger, spilled over and attacked the smaller Iva galls. Thus, parasitism rates on Iva were higher on islands where Borrichia co-occurred than on islands where Borrichia were absent. Most parasitoids from Iva were too small to successfully attack the large Borrichia galls and so gall density on Borrichia was unaffected by the presence of Iva .     

TV is Moving in

Visual arts teachers engage in complex work on a daily basis. This work is informed by practical knowledge that is rarely examined or drawn on in research or in the development of policy. Focusing on the work of secondary visual arts teachers, this article reports on a research program conducted in a regional area of New South Wales, Australia. The research engages in a collaborative process of educational connoisseurship and educational criticism to examine and discuss classroom practice. The process is underpinned by a belief in research as an act of discovery and is guided by a framework that provides a language and grammar of practice. Drawing on qualitative data, discussion focuses on how the collaborative process enables the mobilization and generation of new knowledge. The article concludes by considering the relationship between teaching practice, research, and policy development and by recommending support for collaborative research-based initiatives that foreground the knowledge of teachers.     

Feeding by geese on the Filsø Farmland, Denmark, and the effect of grazing on yield structure of spring barley

From the end of August to early May on average 506400 goose days were spent on the farmland of Filsø, 92% by pink-footed geese, 7% by greylag geese and 1% by bean geese. 36% of the goose days were spent on stubbles (autumn), 38% on stubbles with undersown seed grass (autumn-spring), and 21% on new-sown barley fields (spring).
Geese feeding on spring barley consume kernels left on the surface or in the upper surface layers. In 1982 and 1983 trials were set up to quantify the effect of grazing. The effect on yield and plant structure was measured by comparing ungrazed (exclosures) and grazed plots. Grazing by geese significantly reduced the grain yield (7-20%), but the reduction was not proportional to goose usage. The maximum reduction in sprout density was observed in 1982 in an area with heavy goose usage; sprout density was reduced by 72%, but the subsequent yield in the same area was only reduced by 8%. Plants on grazed plots compensated for the reduced sprout density by having more tillers with ears and grains of higher weight. The effect of grazing on stubble, seed grass, and winter cereals on Filsø is discussed.     

硝酸银对常见呼吸道病原体的抑制作用

目的证实硝酸银对常见呼吸道病原体具有抑制作用。方法采用血凝试验和鸡胚培养法观察硝酸银对副流感病毒的抑制作用;采用细胞培养法观察硝酸银对腺病毒的抑制作用;采用细菌培养法观察硝酸银对肺炎链球菌和乙型溶血型链球菌的抑制作用。结果硝酸银对副流感病毒和腺病毒有明显的抑制作用,对肺炎链球菌和乙型溶血型链球菌有极强的杀菌作用。结论硝酸银对常见呼吸道病原体有明显的抑制作用。     

Vanadate-Stimulated Nadh Oxidation Requires Polymeric Vanadate,Phosphate and Superoxide

NADH oxidation. catalyzed by the microsomal enzyme system is stimulated on addition of polymeric vanitdate Maximum stimulation by polymeric vanadnte was obtained in the presence of phosphate buffer. The small stimulation obtained by metavanadat (500μM) increased on aciditication followed by neutralization. or on adding a trace amount of polymeric vanadate (1 μM).     

Toxic action of etoposide on mouse peritoneal macrophages and its modulation by interleukin 3

In the present work, we have studied the toxic action of etoposide on mouse peritoneal macrophages. First, we have determined the induction of DNA fragmentation by this antitumour compound. To study the possible influence of interleukin 3 on the effects of etoposide on mouse macrophages, we studied intracellular protein phosphorylation induced by interleukin 3. After incubation of the cells in the presence of interleukin 3, increased phosphorylation levels of proteins of estimated molecular weights of around 29,000, 34,000, 50,000 and 61,000 daltons were observed. We have also investigated a possible influence of interleukin 3 on DNA degradation induced by etoposide. The changes of Bax levels induced by etoposide that we have observed seemed to be modulated by this cytokine. From these results, a possible role of interleukin 3 can be suggested in the attenuation of some toxic effects produced by etoposide in mouse peritoneal macrophages. Thus, a therapeutic application of interleukin 3 on antitumour treatments in cells from the mononuclear phagocytic system might be proposed.     

Effects of land preparation and maize cultivar on efficiency of N-fertilizer applied at different times and by different methods in maize—mungbean association using15N

Summary A field experiment was conducted using¹⁵N-labelled urea on a Reddish Brown Lateritic (Peleustult) soil. Growing two crops on flat land and on soil ridges of 15 cm height produced similar comparative effects from fertilizer on maize. However, fertilizer applied by broadcasting on maize with a 50 cm effective band followed by incorporating was more useful to mungbean than that applied by banding below the cereal seed rows when crops were grown on flat land. The reverse was observed when crops were grown on ridges. It was deduced that the maize cultivar was not likely to affect comparative efficiencies of fertilizer. For fertilizer application at sowing, broadcasting in 50 cm maize effective band followed by incorporating was slightly superior to banding below maize seed rows. Side-dressing of fertilizer to maize at 4 weeks after sowing was superior to application at sowing. Evenly-split application, at sowing and at 4 weeks after sowing, was either only slightly superior or comparable to non-split application by banding below maize seed rows at sowing, depending on placement method of the first application. Soil moisture status as a possible factor rendering discrepancy in the comparative efficiencies obtained by different authors is discussed.     

Radioactive analogs of neurotensin. I. Solid phase synthesis and biological characterization of Trp 11-neurotensin, a precursor of an iodized ligand

In order to generate highly labelled neurotensin analogues, synthesis has been performed of two types of precursors, one for iodination and one for tritiation. Iodination of native neurotensin occurs on both tyrosines in position 3 and 11 and thus affects greatly its binding capacities. In this article, synthesis and chemical characterization of [Trp11]-neurotensin are described which can be iodinated without loss of activity. Synthesis was by solid phase procedure on an experimental support, Pab-resin, alpha-(4-chloromethylphenylacetamido)-benzyl copoly (styrene 1 per cent divinylbenzene). After esterification of Boc-Leu by its cesium salt on the Pab-resin, each amino acid was incorporated by a double coupling with dicyclohexylcarbodiimide on a Beckman 990 synthesizer. The trifunctionnal amino acids were protected as follows : Tyr as the 2,6-dichlorobenzyl ether, Glu as benzyl ester, Lys by the benzyloxycarbonyl group, Arg by the tosyl group, and Trp by the formyl group. Boc-Asn was incorporated by the HOBt procedure. The cleavage of peptide-resin bond and the removal of lateral chain protecting groups was realized by hydrofluoric acid with 10 per cent anisol for 1 h at 0 degrees C. The peptide obtained was then treated by NH4HCO3 1 M, pH 9, for 24 h for the removal of tryptophan formyl protecting group. Purification of the crude peptide on Bio-Gel P2 followed by ion exchange chromatography on carboxymethylcellulose (CM 52) and a final desalting on Bio-Gel P2 proved very efficient in removing several shorter contaminants.(ABSTRACT TRUNCATED AT 250 WORDS)     

Habitat associations of parrots on the Wallacean islands of Buru, Seram and Sumba

Aim To investigate patterns of habitat use in nineteen populations of parrots on three Wallacean islands, and examine the degree to which habitats used by a species can be predicted across islands. Location The Wallacean islands on Buru, Seram and Sumba. Methods A logistic regression method was used to relate the presence/absence of parrot species at census plots to vegetation axes derived from ‘gross’ habitat parameters such as altitude, tree sizes, and percentages of vegetation coverage at different strata. Receiver Operating Characteristic Plots were then used to test predictions of habitat use by conspecific populations on the nearby and distant islands, and by different parrot species on the same island. Results Parrots on Buru and nearby Seram tended to be associated with open-canopied lowland forests, while on the distant and low-lying island of Sumba, the preference was for closed-canopy forests at higher altitudes. There were usually close affinities in habitat usage by conspecific populations on the two nearby islands. One exception was where the species occurred on the two islands as separate subspecies. Habitat preferences on Sumba, however, were so distinct that paradigms developed for Buru and Seram failed to predict distributions on this distant island. Main conclusions For populations on more distant islands, it will usually be better to predict habitat use by considering the habitat used by other parrot species occurring on that island, than a conspecific population from another region. Conservation research programmes which concentrate parrot study on just one or two islands in every region of Wallacea may be more successful than those which ‘run through’ several islands in a group, but which miss out whole regions.