Nitrogenase activity (acetylene reduction) associated with leaves of different cultivars of paddy (Oryza sativa L.)

An investigation was conducted to study the levels of nitrogen fixation on the leaf or sheath surfaces of four cultivars of paddy plants by using acetylene reduction technique. Varying levels of positive nitrogenase activity were observed on all the leaf surfaces. Sheath of IET 1991 cultivar showed a higher rate of fixation than the leaf surface. All the nitrogen-fixing organisms on the leaf or sheath surfaces belonged to the genus Beijerinckia. There was no correlation between the bacterial density and the level of fixation. Scanning electron microscopic data revealed that the upper surface of IET 1991 leaf was highly silicified and the microflora was either scanty or nil while the lower surface appeared quite different and harboured more micro-organisms. Similarly, the inner surface of sheath was devoid of silicification and showed the presence of micro-organisms.

Water activity of poultry litter: Relationship to moisture content during a grow-out

Poultry grown on litter floors are in contact with their own waste products. The waste material needs to be carefully managed to reduce food safety risks and to provide conditions that are comfortable and safe for the birds. Water activity (Aw) is an important thermodynamic property that has been shown to be more closely related to microbial, chemical and physical properties of natural products than moisture content. In poultry litter, Aw is relevant for understanding microbial activity; litter handling and rheological properties; and relationships between in-shed relative humidity and litter moisture content. We measured the Aw of poultry litter collected throughout a meat chicken grow-out (from fresh pine shavings bedding material to day 52) and over a range of litter moisture content (10–60%). The Aw increased non-linearly from 0.71 to 1.0, and reached a value of 0.95 when litter moisture content was only 22–33%. Accumulation of manure during the grow-out reduced Aw for the same moisture content. These results are relevant for making decisions regarding litter re-use in multiple grow-outs as well as setting targets for litter moisture content to minimise odour, microbial risks and to ensure necessary litter physical conditions are maintained during a grow-out. Methods to predict Aw in poultry litter from moisture content are proposed.

Bringing nature to schools to promote children’s physical activity

Physical activity (PA) is essential for human health and wellbeing across all age, socioeconomic and ethnic groups. Engagement with the natural world is a new defining criterion for enhancing the benefits of PA particularly for children and young people. Interacting with nature benefits children’s social and emotional wellbeing, develops resilience and reduces the risk of obesity and type 2 diabetes across all population groups. Governments around the world are now recognising the importance of children spending more active time outdoors. However, children’s outdoor activities, free play and nature-related exploration are often structured and supervised by adults due to safety concerns and risks. In this context schools become more accessible and safe options for children to engage in PA outdoors with the presence of nature features. Research on school designs involving young children has revealed that children prefer nature-related features in school environments. Affordances in nature may increase children’s interest in physically active behaviours. Given that present school campuses are designed for operational efficiency and economic reasons there is a need to re-design schools responding to the positive role of nature on human health. If schools were re-designed to incorporate diverse natural features children’s PA and consequent health and wellbeing would likely improve markedly.

Effect of clofibrate on the adenosine triphosphatase activity of rat liver mitochondria

The antihypercholesterolemic drug clofibrate (ethyl-α-p-chlorophenoxyisobutyrate) stimulated the latent ATPase activity and “superstimulated” the uncoupler-induced ATPase activity of rat-liver mitochondria. Addition of clofibrate decreased the turbidity of mitochondrial suspensions and released considerable amount of mitochondrial protein into solution. In these properties it closely resembled detergents like Triton X-100 and deoxycholate. However, unlike the detergents, clofibrate required the presence of a permeant cation for its disruptive action. Also, it was without any such effect on sonic submitochondrial particles. The drug enhanced the uptake of both Mg2 and Cl− by mitochondria suggesting that osmotic swelling precedes lysis. Sonic submitochondrial particles prepared in the presence of clofibrate showed a greater yield and comparable ATPase activity.

Learning style and digital activity: An ecological study

In order to understand student engagement in higher education through the use of digital technologies, it is necessary to appreciate the broader use of differing technologies. Forty-eight first-year university students completed an online survey that queried patterns of digital activity across home, school and community contexts and that included rating scale items that measured learning style (i.e., active-reflective, sensing-intuitive, visual-verbal, sequential-global). Results suggest that students vary widely in digital activities and that such variation is related to differences in learning style. For example, active learners were more likely than reflective learners to engage in digital activities in the community and users of some specific application, as opposed to non-users, were more likely to be verbal than visual learners. Implications for instructional applications of digital technology in higher education are presented.

Photocytotoxic 3d-Metal Scorpionates with a 1,8-Naphthalimide Chromophore Showing Photoinduced DNA and Protein Cleavage Activity

Ternary 3d-metal complexes of formulation [M(Tp(Ph))(py-nap)](ClO4)(1-3), where M is Co(II) (1), Cu(II) (2), and Zn(II) (3); Tp(Ph) is anionic tris (3-phenylpyrazolyl)borate; and py-nap is a pyridyl ligand with a conjugated 1,8-naphthalimide moiety, have been prepared from the reaction of metal perchlorate with KTp(Ph) and py-nap in CH2Cl2. The complexes have been characterized from analytical and physicochemical data. The complexes are stable in solution as evidenced from the electrospray ionization mass spectrometry data. The complexes show good binding propensity with calf thymus (CT) DNA, giving binding constant (K-b) values of similar to 10(5) M-1 and a molecular ``light-switch'' effect that results in an enhancement of the emission intensity of the naphthalimide chromophore on binding to CT DNA. The complexes do not show any hydrolytic cleavage of DNA. They show poor chemical nuclease activity in the presence of 3-mercaptopropionic acid or hydrogen peroxide (H2O2). The Co(II) and Cu(II) complexes exhibit oxidative pUC19 DNA cleavage activity in UV-A light of 365 rim. The Zn(II) complex shows moderate DNA photocleavage activity at 365 nm. The Cu(II)complex 2 displays photoinduced DNA cleavage activity in red light of 647.1 nm and 676 rim and near-IR light of >750 rim. A mechanistic studyin UV-A and visible light suggests the involvement of the hydroxyl radical as the reactive species in the DNA photocleavage reactions. The complexes also show good bovine serum albumin (BSA) protein binding propensity, giving K-BSA values of similar to 10(5) M-1. Complexes 1 and 2 display significant photoinduced BSA cleavage activity in UV-A light. The Co(II) complex 1 shows a significant photocytotoxic effect in HeLa cervical cancer cells on exposure to UV-A light of 365 nm, giving an IC50 value of 32 mu M. The IC50 value for the py-nap ligand alone is 41.42 mu m in UV-A light. The IC50 value is >200 mu M in the dark, indicating poor dark toxicity of 1. The Cu(II) complex 2 exhibits moderate photocytotoxicity and significant dark toxicity, giving IC50 values of 18.6 mu m and 29.7 mu m in UV-A light and in the dark, respectively.

Rhythmic activity of utilization of mevalonate for biogenesis of cholesterol

The utilization of mevalonate for biogenesis of cholesterol shows rhythmic activity with a peak at midnight and the step responsible is likely to be between mevalonate and isopentenyl pyrophosphate.

Synthetic polypeptide with antifreeze activity

MUCH information has been gathered in recent years on the so-called 'antifreeze' proteins which lower the freezing point of the serum of certain marine fishes living in sub-zero water temperatures1−4. The proteins from the Antarctic fish Trematomus borchgrevinki are glycoproteins with a repeating alanyl-alanyl-threonyl tripeptide sequence, the threonyl residue being linked to a disaccharide1,2. In contrast, the antifreeze protein from the winter flounder Pseudopleuronectus americanus in the North American Atlantic coastal region is made up of eight ammo acids with no apparent repeating sequence of the residues and no sugar moiety (ref. 4 and unpublished work of C. L. Hew, C. C. Yip & G. Fletcher). The antifreeze activity of these proteins is not compatible with the known colligative properties of solutes in solution and the mechanism of their action is not yet fully understood. But a common feature of both types of the antifreeze proteins is the preponderance of alanine which accounts for over 60% of the total amino residues. This fact, together with the absence of the carbohydrate in the protein from the winter flounder, prompted us to attempt the synthesis of polypeptide analogues having comparable proportions of alanine in them along with suitable other amino acids. As a first step, we made use of the lack of any obvious periodicity in the distribution of the alanyl residues in the flounder's protein and attempted the synthesis of a random copolypeptide containing about 65 mol % of alanine and 35 mol % of aspartic acid. The choice of aspartic acid was made on the basis of its being the next major amino acid in the flounder's protein3,4 and on the expectation that its polar character will help the water-solubility of the alanine-rich copolypeptide, as in other studies on alanine-containing random copolymers. In addition, Duman and DeVries4 have earlier indicated the involvement of carboxyl groups on the antifreeze activity by chemical modification studies. We report here the synthesis of this polypeptide and show that it possesses antifreeze activity.

Role of Temperature in the Biological Activity of a Boreal Forest

In northern latitudes, temperature is the key factor driving the temporal scales of biological activity, namely the length of the growing season and the seasonal efficiency of photosynthesis. The formation of atmospheric concentrations of biogenic volatile organic compounds (BVOCs) are linked to the intensity of biological activity. However, interdisciplinary knowledge of the role of temperature in the biological processes related to the annual cycle and photosynthesis and atmospheric chemistry is not fully understood. The aim of this study was to improve understanding of the role of temperature in these three interlinked areas: 1) onset of growing season, 2) photosynthetic efficiency and 3) BVOC air concentrations in a boreal forest. The results present a cross-section of the role of temperature on different spatial (southern northern boreal), structural (tree forest stand - forest) and temporal (day-season- year) scales. The fundamental status of the Thermal Time model in predicting the onset of spring recovery was confirmed. However, it was recommended that sequential models would be more appropriate tools when the onset of the growing season is estimated under a warmer climate. A similar type of relationship between photosynthetic efficiency and temperature history was found in both southern and northern boreal forest stands. This result draws attention to the critical question of the seasonal efficiency of coniferous species to emit organic compounds under a warmer climate. New knowledge about the temperature dependence of the concentrations of biogenic volatile organic compounds in a boreal forest stand was obtained. The seasonal progress and the inter-correlation of BVOC concentrations in ambient air indicated a link to biological activity. Temperature was found to be the main driving factor for the concentrations. However, in addition to temperature, other factors may play a significant role here, especially when the peak concentrations are studied. There is strong evidence that the spring recovery and phenological events of many plant species have already advanced in Europe. This study does not fully support this observation. In a boreal forest, changes in the annual cycle, especially the temperature requirement in winter, would have an impact on the atmospheric BVOC composition. According to this study, more joint phenological and BVOC field observations and laboratory experiments are still needed to improve these scenarios.

N-syndecan and HB-GAM in neural migration and differentiation : Modulation of growth factor activity in brain

The juvenile sea squirt wanders through the sea searching for a suitable rock or hunk of coral to cling to and make its home for life. For this task it has a rudimentary nervous system. When it finds its spot and takes root, it doesn't need its brain any more so it eats it. It's rather like getting tenure. Daniel C. Dennett (from Consciousness Explained, 1991) The little sea squirt needs its brain for a task that is very simple and short. When the task is completed, the sea squirt starts a new life in a vegetative state, after having a nourishing meal. The little brain is more tightly structured than our massive primate brains. The number of neurons is exact, no leeway in neural proliferation is tolerated. Each neuroblast migrates exactly to the correct position, and only a certain number of connections with the right companions is allowed. In comparison, growth of a mammalian brain is a merry mess. The reason is obvious: Squirt brain needs to perform only a few, predictable functions, before becoming waste. The more mobile and complex mammals engage their brains in tasks requiring quick adaptation and plasticity in a constantly changing environment. Although the regulation of nervous system development varies between species, many regulatory elements remain the same. For example, all multicellular animals possess a collection of proteoglycans (PG); proteins with attached, complex sugar chains called glycosaminoglycans (GAG). In development, PGs participate in the organization of the animal body, like in the construction of parts of the nervous system. The PGs capture water with their GAG chains, forming a biochemically active gel at the surface of the cell, and in the extracellular matrix (ECM). In the nervous system, this gel traps inside it different molecules: growth factors and ECM-associated proteins. They regulate the proliferation of neural stem cells (NSC), guide the migration of neurons, and coordinate the formation of neuronal connections. In this work I have followed the role of two molecules contributing to the complexity of mammalian brain development. N-syndecan is a transmembrane heparan sulfate proteoglycan (HSPG) with cell signaling functions. Heparin-binding growth-associated molecule (HB-GAM) is an ECM-associated protein with high expression in the perinatal nervous system, and high affinity to HS and heparin. N-syndecan is a receptor for several growth factors and for HB-GAM. HB-GAM induces specific signaling via N-syndecan, activating c-Src, calcium/calmodulin-dependent serine protein kinase (CASK) and cortactin. By studying the gene knockouts of HB-GAM and N-syndecan in mice, I have found that HB-GAM and N-syndecan are involved as a receptor-ligand-pair in neural migration and differentiation. HB-GAM competes with the growth factors fibriblast growth factor (FGF)-2 and heparin-binding epidermal growth factor (HB-EGF) in HS-binding, causing NSCs to stop proliferation and to differentiate, and affects HB-EGF-induced EGF receptor (EGFR) signaling in neural cells during migration. N-syndecan signaling affects the motility of young neurons, by boosting EGFR-mediated cell migration. In addition, these two receptors form a complex at the surface of the neurons, probably creating a motility-regulating structure.

Heparin-binding growth-associated molecule (HB-GAM) in activity-dependent neuronal plasticity in hippocampus

Cell adhesion and extracellular matrix (ECM) molecules play a significant role in neuronal plasticity both during development and in the adult. Plastic changes in which ECM components are implicated may underlie important nervous system functions, such as memory formation and learning. Heparin-binding growthassociated molecule (HB-GAM, also known as pleiotrophin), is an ECM protein involved in neurite outgrowth, axonal guidance and synaptogenesis during perinatal period. In the adult brain HB-GAM expression is restricted to the regions which display pronounced synaptic plasticity (e.g., hippocampal CA3-CA1 areas, cerebral cortex laminae II-IV, olfactory bulb). Expression of HB-GAM is regulated in an activity-dependent manner and is also induced in response to neuronal injury. In this work mutant mice were used to study the in vivo function of HB-GAM and its receptor syndecan-3 in hippocampal synaptic plasticity and in hippocampus-dependent behavioral tasks. Phenotypic analysis of HBGAM null mutants and mice overexpressing HB-GAM revealed that opposite genetic manipulations result in reverse changes in synaptic plasticity as well as behavior in the mutants. Electrophysiological recordings showed that mice lacking HB-GAM have an increased level of long-term potentiation (LTP) in the area CA1 of hippocampus and impaired spatial learning, whereas animals with enhanced level of HB-GAM expression have attenuated LTP, but outperformed their wild-type controls in spatial learning. It was also found that GABA(A) receptor-mediated synaptic transmission is altered in the transgenic mice overexpressing HB-GAM. The results suggest that these animals have accentuated hippocampal GABAergic inhibition, which may contribute to the altered glutamatergic synaptic plasticity. Structural studies of HB-GAM demonstrated that this protein belongs to the thrombospondin type I repeat (TSR) superfamily and contains two β-sheet domains connected by a flexible linker. It was found that didomain structure is necessary for biological activity of HB-GAM and electrophysiological phenotype displayed by the HB-GAM mutants. The individual domains displayed weaker binding to heparan sulfate and failed to promote neurite outgrowth as well as affect hippocampal LTP. Effects of HB-GAM on hippocampal synaptic plasticity are believed to be mediated by one of its (co-)receptor molecules, namely syndecan-3. In support of that, HB-GAM did not attenuate LTP in mice deficient in syndecan-3 as it did in wild-type controls. In addition, syndecan-3 knockout mice displayed electrophysiological and behavioral phenotype similar to that of HB-GAM knockouts (i.e. enhanced LTP and impaired learning in Morris water-maze). Thus HB-GAM and syndecan-3 are important modulators of synaptic plasticity in hippocampus and play a role in regulation of learning-related behavior.

New ternary copper(II) complexes of L-alanine and heterocyclic bases: DNA binding and oxidative DNA cleavage activity

Four new ternary copper(II) complexes of alpha-amino acid having polypyridyl bases of general formulation [Cu(L-ala)(B)(H2O)](X)(1-4), where L-ala is L-alanine, B is an N,N-donor heterocyclic base, viz. 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2) and 5,6-phenanthroline dione (dione, 3), dipyrido[3,2:2',3'-f] quinoxaline (dpq, 4), and X = ClO4-/NO3- are synthesized, characterized by various spectroscopic and X-ray crystallographic methods. The complexes show a distorted square-pyramidal (4 + 1) CuN3O2 coordination geometry. The one-electron paramagnetic complexes (1-4) display a low energy d-d band near 600 nm in aqueous medium and show a quasi-reversible cyclic voltammetric response due to one-electron Cu(II)/Cu(I) reduction near - 100 mV (versus SCE) in DMF-0.1 M TBAP. Binding interactions of the complexes with calf thymus DNA (CT-DNA) were investigated by UV-Vis absorption titration, ethidium bromide displacement assay, viscometric titration experiment and DNA melting studies. All the complexes barring the complexes 1 and 3 are avid binder to the CT-DNA in the DNA minor groove giving an order: 4 > 2 >>>1, 3. The complexes 2 and 4 show appreciable chemical nuclease activity in the presence of 3-mercaptopropionic acid (MPA) as a reducing agent. Hydroxyl radical was investigated to be the DNA cleavage active species. Control experiments in the presence of distamycin-A show primarily minor groove-binding propensity for the complexes 2 and 4 to the DNA.

Synthesis and Structure-Activity Correlation Studies of Secondary- and Tertiary-Amine-Based Glutathione Peroxidase Mimics

In this study, a series of seeondary- and tertiary-amino-substituted diaryl diselenides were synthesized and studied for their glutathione peroxidase (GPx) like antioxidant activities with H2O2, cumene hydroperoxide, or tBuOOH as substrates and with PhSH or glutathione (GSH) as thiol cosubstrates. This study reveals that replacement of the tert-amino groups in benzylamine-based diselenides by sec-amino moieties drastically enhances the catalytic activities in both the aromatic thiol (PhSH) and GSH assay systems. Particularly, the N-propyl- and N-isopropylamino-substituted diselenides are 8-18 times more active than the corresponding N,N-dipropyl- and N,N-diisopropylamine-based compounds in all three peroxide systems when GSH is used as the thiol cosubstrate. Although the catalytic mechanism of sec-amino-substituted disclenides is similar to that of the tert-amine-based compounds, differences in the stability and reactivity of some of the key intermediates account for the differences in the GPx-like activities. it is observed that the sec-amino groups are better than the tert-amino moieties for generating the catalytically active selenols. This is due to the absence of any significant thiol-exchange reactions in the selenenyl sulfides derived from sec-amine-based diselenides. Furthermore, the seleninic acids (RSeO2H) derived from the sec-amine-based compounds are more stable toward further reactions with peroxides than their tert-amine-based analogues.