The growth, reproduction and survival of 'Cascabela thevetia' seedlings under two levels of canopy cover

The ornamental tree 'Cascabela thevetia', from tropical America, has naturalised and formed large infestations at several locations in northern Australia. Some understanding of its ecology and invasiveness was gleaned from a field experiment undertaken in North Queensland. The experiment quantified the growth, time to seed formation and survival of seedlings of the peach biotype growing under light and dense canopy cover within a riparian habitat. Growth, reproduction and survival of young plants varied. Growth was most rapid for seedlings away from, or on the edge of infestations because they were constrained by parent plants. The findings also suggested that land managers have at least 12 months following control to detect new plants, or regrowth, before plants set seed and replenish soil seed banks.

Studies on Aspergillus niger glutamine synthetase: Regulation of enzyme levels by nitrogen sources and identification of active site residues

The specific activity of glutamine synthetase (L-glutamate: ammonia ligase, EC 6.3.1.2) in surface grown Aspergillus niger was increased 3-5 fold when grown on L-glutamate or potassium nitrate, compared to the activity obtained on ammonium chloride. The levels of glutamine synthetase was regulated by the availability of nitrogen source like NH4 + , and further, the enzyme is repressed by increasing concentrations of NH4 +. In contrast to other micro-organisms, the Aspergillus niger enzyme was neither specifically inactivated by NH4+ or L-glutamine nor regulated by covalent modification.Glutamine synthetase from Aspergillus niger was purified to homogenity. The native enzyme is octameric with a molecular weight of 385,000±25,000. The enzyme also catalyses Mn2+ or Mg2+-dependent synthetase and Mn2+-dependent transferase activity.Aspergillus niger glutamine synthetase was completely inactivated by two mol of phenylglyoxal and one mol of N-ethylmaleimide with second order rate constants of 3·8 M–1 min–1 and 760 M–1 min–1 respectively. Ligands like Mg. ATP, Mg. ADP, Mg. AMP, L-glutamate NH4+, Mn2+ protected the enzyme against inactivation. The pattern of inactivation and protection afforded by different ligands against N-ethylamaleimide and phenylglyoxal was remarkably similar. These results suggest that metal ATP complex acts as a substrate and interacts with an arginine ressidue at the active site. Further, the metal ion and the free nucleotide probably interact at other sites on the enzyme affecting the catalytic activity.

Effect of human chorionic gonadotropin on serum levels of progesterone and estrogens in the pregnant bonnet monkev (Macaca radiata)

Administration of human chorionic gonadotropin to pregnant bonnet monkeys (Macaca radiata) at 55-60 days and 130-140 days of pregnancy resulted in a significant increase in serum progesterone levels. This effect could be observed even in lutectomized monkeys.However, no significant change in the serum estrogen level was noticed. These results suggest that although no chorionic gonadotropin is detectable in the serum after 35 days of pregnancy, the foetoplacental steroidogenic system is still responsive to exogenous gonadotropic stimulation.

Concentration levels of heavy metals and polycyclic aromatic hydrocarbons in car parks at Queensland University of Technology

This study investigates the level of pollutants (polycyclic aromatic hydrocarbons (PAHs) and heavy metals) in three car parks at QUT, one at Kelvin Grove campus and two at the Gardens Point campus. In addition, comparisons between site designs were assessed to identify the possible sources of heavy metals and PAHs. The main contributing source for heavy metals was identified to be from vehicle debris and emissions, while the source of PAHs was identified to be from petrol and diesel engine vehicle emissions. The highest concentration of pollutants was typically found for the 63 micro meter dust samples, proposed to be due to increased surface areas and thus available adsorption sites.

On-farm Campylobacter and Escherichia coli in commercial broiler chickens: Re-used bedding does not influence Campylobacter emergence and levels across sequential farming cycles

Limitations in quality bedding material have resulted in the growing need to re-use litter during broiler farming in some countries, which can be of concern from a food-safety perspective. The aim of this study was to compare the Campylobacter levels in ceca and litter across three litter treatments under commercial farming conditions. The litter treatments were (a) the use of new litter after each farming cycle; (b) an Australian partial litter re-use practice; and (c) a full litter re-use practice. The study was carried out on two farms over two years (Farm 1, from 2009–2010 and Farm 2, from 2010–2011), across three sheds (35,000 to 40,000 chickens/shed) on each farm, adopting three different litter treatments across six commercial cycles. A random sampling design was adopted to test litter and ceca for Campylobacter and Escherichia coli, prior to commercial first thin-out and final pick-up. Campylobacter levels varied little across litter practices and farming cycles on each farm and were in the range of log 8.0–9.0 CFU/g in ceca and log 4.0–6.0 MPN/g for litter. Similarly the E. coli in ceca were ∼log 7.0 CFU/g. At first thin-out and final pick-up, the statistical analysis for both litter and ceca showed that the three-way interaction (treatments by farms by times) was highly significant (P < 0.01), indicating that the patterns of Campylobacter emergence/presence across time vary between the farms, cycles and pickups. The emergence and levels of both organisms were not influenced by litter treatments across the six farming cycles on both farms. Either C. jejuni or C. coli could be the dominant species across litter and ceca, and this phenomenon could not be attributed to specific litter treatments. Irrespective of the litter treatments in place, cycle 2 on Farm 2 remained campylobacter-free. These outcomes suggest that litter treatments did not directly influence the time of emergence and levels of Campylobacter and E. coli during commercial farming.

Regulation of arginine decarboxylase and putrescine levels in Cucumis sativus cotyledons

Arginine decarboxylase (arginine carboxy-lyase EC 4.1.1.19) of Cucumis sativus cotyledons, has a pH optimum of 8.3 and a temperature optimum of 40°. Among the various plant hormones administered to excised cotyledons in culture, benzyladenine and its riboside were most effective in increasing the arginine decarboxylase activity and putrescine content. The enzyme activity and putrescine content were significantly increased on acid feeding of the cotyledons and decreased by KCl treatment. The KCl effect could be only partially reversed by benzyladenine. Abscisic acid inhibited cotyledon growth and also reduced arginine decarboxylase and putrescine levels. This effect was overcome by cytokinins. The half life of the enzyme using cycloheximide was 3.7 hr. Dibutyryl cyclic AMP and 5′-AMP also marginally stimulated the enzyme and putrescine levels. Mixing experiments indicate that there is neither a non-dialysable activator nor inhibitor of the enzyme.

Amine levels in Lathyrus sativus seedlings during development

In growing Lathyrus sativus seedlings, the levels of DNA, RNA and protein markedly decreased in the cotyledons and progressively increased in the embryo-axis. In cotyledons, spermidine and spermine contents were substantially reduced while those of agmatine and putrescine were sharply increased. By contrast the embryo-axis progressively accumulated relatively larger amounts of agmatine, homoagmatine. putrescine, cadaverine, spermidine and spermine in parallel with similar changes in its DNA, RNA and protein content. While the cotyledons contained ca 50% of the total agmatine and putrescine present in the plant embryo by day 10, the embryo-axis, though representing less than 20% of the dry wt, contained 90 and 75% of total cadaverine and homoagmatine respectively of the seedlings. Spermidine and spermine levels of this tissue were also comparatively higher, being of the order of 80 and 50% respectively of the total. The root and shoot portions of the embryo-axis also exhibited a similar relationship between changes in DNA, RNA and protein and all the above amines during development. However, the polyamine content of the shoots was relatively higher than those of the roots during the growth period.

Light- and cytokinin-induced changes in the levels of leucine and tyrosine isoaccepting tRNA species and modified nucleotide contents of total tRNA in cucumber seedlings

We have determined relative levels of chloroplast leucine and tyrosine isoaccepting tRNAs and modified nucleotide contents from total tRNAs isolated from dark-grown, light-grown, N6-isopentenyladenine (i6A)-treated dark-grown and i6A-treated light-grown cucumber seedlings. Significant increases in the relative amounts of tRNA(Leu)2 and tRNA(Leu)3 were observed in the i6A-treated dark-grown seedlings compared to dark-grown, light-grown and i6A-treated light-grown seedlings. On the other hand, i6A-treated light-grown seedlings tRNA(Tyr)1 increased to 85% of total tRNAs(Tyr) from about 9% in light-grown seedlings and tRNA(Tyr)2 decreased to 15% compared with 91% in light-grown seedlings. Analysis of modified nucleotide of total tRNAs indicated that pT, pI, pm1A, pm5C, pGm, pm1G, pm2G and pm7G contents were significantly higher in the total tRNA of i6A-treated dark-grown seedlings than those from untreated dark-grown seedlings. Illumination of 8-day-old dark-grown seedlings for 12 h increased the contents of pT, pI, pGm and pm1G when compared to 8-day-old dark-grown seedlings with extended growth for 12 h in dark. On the contrary, i6A had no stimulatory effect in the contents of modified nucleotide in the light-grown seedlings.

Associations of serum perfluoroalkyl acid levels with T-helper cell-specific cytokines in children: By gender and asthma status

Perfluoroalkyl acids (PFAAs) are a group of common chemicals that ubiquitously exist in wildlife and humans. Experimental data suggest that they may alter T-lymphocyte functioning in situ by preferentially enhancing the development of T-helper 2 (TH2)- and inhibiting TH1-lymphocyte development and might increase allergic inflammation, but few human studies have been conducted. To evaluate the association between serum PFAAs concentrations and T-lymphocyte-related immunological markers of asthma in children, and further to assess whether gender modified this association, 231 asthmatic children and 225 non-asthmatic control children from Northern Taiwan were recruited into the Genetic and Biomarker study for Childhood Asthma. Serum concentrations of ten PFAAs and levels of TH1 [interferon (IFN)-γ, interleukin (IL)-2] and TH2 (IL-4 and IL-5) cytokines were measured. The results showed that asthmatics had significantly higher serum PFAAs concentrations compared with the healthy controls. When stratified by gender, a greater number of significant associations between PFAAs and asthma outcomeswere found in males than in females. Among males, adjusted odds ratios for asthma among those with the highest versus lowest quartile of PFAAs exposure ranged from 2.59 (95% CI: 1.14, 5.87) for the perfluorobutanesulfonate (PFBS) to 4.38 (95% CI: 2.02, 9.50) for perfluorooctanesulfonate (PFOS); and serum PFAAs were associated positively with TH2 cytokines and inversely with TH1 cytokines among male asthmatics. Among females, no significant associations between PFAAs and TH2 cytokines could be detected. In conclusion, increased serum PFAAs levels may promote TH cell dysregulation and alter the availability of key TH1 and TH2 cytokines, ultimately contributing to the development of asthma that may differentially impact males to a greater degree than females. These results have potential relevance in asthma prevention.

Differences in the levels of aminoacylation and contents of modified nucleotides between total tRNAs from N2- and NH4+-grown Azospirillum lipoferum cells

Total tRNAs isolated from N2- and NH4(+)-grown Azospirillum lipoferum cells were compared with respect to amino acid acceptance, isoacceptor tRNA species levels and extent of nucleotide modifications. Amino-acylation of these two tRNA preparations with ten different amino acids indicated differences in the relative acceptor activities. Comparison of aminoacyl-tRNA patterns by RPC-5 column chromatography revealed no qualitative differences in the elution profiles. However, quantitative differences in the relative amounts of some isoacceptors were observed. These results indicate that alterations of relative amounts of functional tRNA species occur to match cellular requirements of the bacterial cells using N2 or NH4+ as nitrogen source. In addition, the content of modified nucleotides in total tRNAs of N2- and NH4(+)-grown cells was determined. In the NH4(+)-grown cells, content of most of the modified nucleotides decreased significantly. Based upon these results, the relationship of chargeability of tRNAs to base modifications is discussed.

Variations in the Levels of Chloroplast tRNAs and Aminoacyl-tRNA Synthetases in Senescing Leaves of Phaseolus vulgaris

The relative amounts of chloroplast tRNAs(Leu), tRNA(Glu), tRNA(Phe), tRNAs(Thr), and tRNA(Tyr) and of chloroplastic and cytoplasmic aminoacyl-tRNA synthetases were compared in green leaves, yellowing senescing leaves, and N(6)-benzyladenine-treated senescing leaves from bean (Phaseolus vulgaris, var Contender). Aminoacylation of the tRNAs using Escherichia coli aminoacyl-tRNA synthetases indicated that in senescing leaves the relative amount of chloroplast tRNA(Phe) was significantly lower than in green leaves. Senescing leaves treated with N(6)-benzyladenine contained higher levels of this tRNA than untreated senescing leaves. No significant change in the relative amounts of chloroplast tRNAs(Leu), tRNAs(Thr), and tRNA(Tyr) was detected in green, yellow senescing, or N(6)-benzyladine-treated senescing leaves. Relative levels of chloroplast tRNAs were also estimated by hybridization of tRNAs to DNA blots of gene specific probes. These experiments confirmed the results obtained by aminoacylation and revealed in addition that the relative level of chloroplast tRNA(Glu) is higher in senescing leaves than in green leaves. Transcription run-on assays indicated that these changes in tRNA levels are likely to be due to a differential rate of degradation rather than to a differential rate of transcription of the tRNA genes. Chloroplastic and cytoplasmic leucyl-, phenylalanyl-, and tyrosyl-tRNA synthetase activities were greatly reduced in senescing leaves as compared to green leaves, whereas N(6)-benzyladenine-treated senescing leaves contained higher enzyme activities than untreated senescing leaves. These results suggest that during senescence, as well as during senescence-retardation by cytokinins, changes in enzyme activities, such as aminoacyl-tRNA synthetases, rather than reduced levels of tRNAs, affect the translational capacity of chloroplasts.

Limiting the Extent of the RDN1 Heterochromatin Domain by a Silencing Barrier and Sir2 Protein Levels in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, transcriptional silencing occurs at the cryptic mating-type loci (HML and HMR), telomeres, and ribosomal DNA ( rDNA; RDN1). Silencing in the rDNA is unusual in that polymerase II (Pol II) promoters within RDN1 are repressed by Sir2 but not Sir3 or Sir4. rDNA silencing unidirectionally spreads leftward, but the mechanism of limiting its spreading is unclear. We searched for silencing barriers flanking the left end of RDN1 by using an established assay for detecting barriers to HMR silencing. Unexpectedly, the unique sequence immediately adjacent to RDN1, which overlaps a prominent cohesin binding site (CARL2), did not have appreciable barrier activity. Instead, a fragment located 2.4 kb to the left, containing a tRNA(Gln) gene and the Ty1 long terminal repeat, had robust barrier activity. The barrier activity was dependent on Pol III transcription of tRNA(Gln), the cohesin protein Smc1, and the SAS1 and Gcn5 histone acetyltransferases. The location of the barrier correlates with the detectable limit of rDNA silencing when SIR2 is overexpressed, where it blocks the spreading of rDNA heterochromatin. We propose a model in which normal Sir2 activity results in termination of silencing near the physical rDNA boundary, while tRNA(Gln) blocks silencing from spreading too far when nucleolar Sir2 pools become elevated.

Role of information and communication in redefining unmanned aerial vehicle autonomous control levels

Autonomous mission control, unlike automatic mission control which is generally pre-programmed to execute an intended mission, is guided by the philosophy of carrying out a complete mission on its own through online sensing, information processing, and control reconfiguration. A crucial cornerstone of this philosophy is the capability of intelligence and of information sharing between unmanned aerial vehicles (UAVs) or with a central controller through secured communication links. Though several mission control algorithms, for single and multiple UAVs, have been discussed in the literature, they lack a clear definition of the various autonomous mission control levels. In the conventional system, the ground pilot issues the flight and mission control command to a UAV through a command data link and the UAV transmits intelligence information, back to the ground pilot through a communication link. Thus, the success of the mission depends entirely on the information flow through a secured communication link between ground pilot and the UAV In the past, mission success depended on the continuous interaction of ground pilot with a single UAV, while present day applications are attempting to define mission success through efficient interaction of ground pilot with multiple UAVs. However, the current trend in UAV applications is expected to lead to a futuristic scenario where mission success would depend only on interaction among UAV groups with no interaction with any ground entity. However, to reach this capability level, it is necessary to first understand the various levels of autonomy and the crucial role that information and communication plays in making these autonomy levels possible. This article presents a detailed framework of UAV autonomous mission control levels in the context of information flow and communication between UAVs and UAV groups for each level of autonomy.