Tree resistance to Lymantria dispar caterpillars: importance and limitations of foliar tannin composition

The ability of foliar tannins to increase plant resistance to herbivores is potentially determined by the composition of the tannins; hydrolyzable tannins are much more active as prooxidants in the guts of caterpillars than are condensed tannins. By manipulating the tannin compositions of two contrasting tree species, this work examined: (1) whether increased levels of hydrolyzable tannins increase the resistance of red oak (Quercus rubra L.), a tree with low resistance that produces mainly condensed tannins, and (2) whether increased levels of condensed tannins decrease the resistance of sugar maple (Acer saccharum Marsh.), a tree with relatively high resistance that produces high levels of hydrolyzable tannins. As expected, when Lymantria dispar L. caterpillars ingested oak leaves coated with hydrolyzable tannins, levels of hydrolyzable tannin oxidation increased in their midgut contents. However, increased tannin oxidation had no significant impact on oxidative stress in the surrounding midgut tissues. Although growth efficiencies were decreased by hydrolyzable tannins, growth rates remained unchanged, suggesting that additional hydrolyzable tannins are not sufficient to increase the resistance of oak. In larvae on condensed tannin-coated maple, no antioxidant effects were observed in the midgut, and levels of tannin oxidation remained high. Consequently, neither oxidative stress in midgut tissues nor larval performance were significantly affected by high levels of condensed tannins. Post hoc comparisons of physiological mechanisms related to tree resistance revealed that maple produced not only higher levels of oxidative stress in the midgut lumen and midgut tissues of L. dispar, but also decreased protein utilization efficiency compared with oak. Our results suggest that high levels of hydrolyzable tannins are important for producing oxidative stress, but increased tree resistance to caterpillars may require additional factors, such as those that produce nutritional stress.     

Specificity of Developmental Resistance in Gypsy Moth （Lymantria dispar） to two DNA-Insect Viruses

Gypsy moth (Lymantria dispar) larvae displayed marked developmental resistance within an instar to L. dispar M nucleopolyhedrovirus (LdMNPV) regardless of the route of infection (oral or intrahemocoelic) in a previous study, indicating that in gypsy moth, this resistance has a systemic component. In this study, gypsy moth larvae challenged with the Amsacta moorei entomopoxvirus (AMEV) showed developmental resistance within the fourth instar to oral, but not intrahemocoelic, inoculation. In general, gypsy moth is considered refractory to oral challenge with AMEV, but in this study, 43% mortality occurred in newly molted fourth instars fed a dose of 5×10⁶ large spheroids of AMEV; large spheroids were found to be more infectious than small spheroids when separated by a sucrose gradient. Developmental resistance within the fourth instar was reflected by a 2-fold reduction in mortality (18%–21%) with 5×10⁶ large spheroids in larvae orally challenged at 24, 48 or 72 h post-molt. Fourth instars were highly sensitive to intrahemocoelic challenge with AMEV; 1PFU produced approximately 80% mortality regardless of age within the instar. These results indicate that in gypsy moth, systemic developmental resistance may be specific to LdMNPV, reflecting a co-evolutionary relationship between the baculovirus and its host.     

FAK and paxillin: regulators of N-cadherin adhesion and inhibitors of cell migration?

FAK and paxillin are important components in integrin-regulated signaling. New evidence suggests that these two proteins function in crosstalk between cell-matrix and cell-cell adhesions. Further, new insight suggests that under some conditions these proteins inhibit cell migration, in contrast to their established roles in several cell systems as positive regulators of cell adhesion and migration.     

Removal of H₂O₂ and generation of superoxide radical: role of cytochrome c and NADH

In cells, mitochondria, endoplasmic reticulum, and peroxisomes are the major sources of reactive oxygen species (ROS) under physiological and pathophysiological conditions. Cytochrome c (cyt c) is known to participate in mitochondrial electron transport and has antioxidant and peroxidase activities. Under oxidative or nitrative stress, the peroxidase activity of Fe³⁺cyt c is increased. The level of NADH is also increased under pathophysiological conditions such as ischemia and diabetes and a concurrent increase in hydrogen peroxide (H₂O₂) production occurs. Studies were performed to understand the related mechanisms of radical generation and NADH oxidation by Fe³⁺cyt c in the presence of H₂O₂. Electron paramagnetic resonance (EPR) spin trapping studies using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were performed with NADH, Fe³⁺cyt c, and H₂O₂ in the presence of methyl-β-cyclodextrin. An EPR spectrum corresponding to the superoxide radical adduct of DMPO encapsulated in methyl-β-cyclodextrin was obtained. This EPR signal was quenched by the addition of the superoxide scavenging enzyme Cu,Zn-superoxide dismutase (SOD1). The amount of superoxide radical adduct formed from the oxidation of NADH by the peroxidase activity of Fe³⁺cyt c increased with NADH and H₂O₂ concentration. From these results, we propose a mechanism in which the peroxidase activity of Fe³⁺cyt c oxidizes NADH to NAD^•, which in turn donates an electron to O₂, resulting in superoxide radical formation. A UV-visible spectroscopic study shows that Fe³⁺cyt c is reduced in the presence of both NADH and H₂O₂. Our results suggest that Fe³⁺cyt c could have a novel role in the deleterious effects of ischemia/reperfusion and diabetes due to increased production of superoxide radical. In addition, Fe³⁺cyt c may play a key role in the mitochondrial “ROS-induced ROS-release” signaling and in mitochondrial and cellular injury/death. The increased oxidation of NADH and generation of superoxide radical by this mechanism may have implications for the regulation of apoptotic cell death, endothelial dysfunction, and neurological diseases. We also propose an alternative electron transfer pathway, which may protect mitochondria and mitochondrial proteins from oxidative damage.     

Genome size and DNA base composition of geophytes: the mirror of phenology and ecology?

Background and Aims

Genome size is known to affect various plant traits such as stomatal size, seed mass, and flower or shoot phenology. However, these associations are not well understood for species with very large genomes, which are laregly represented by geophytic plants. No detailed associations are known between DNA base composition and genome size or species ecology.

Methods

Genome sizes and GC contents were measured in 219 geophytes together with tentative morpho-anatomical and ecological traits.

Key Results

Increased genome size was associated with earliness of flowering and tendency to grow in humid conditions, and there was a positive correlation between an increase in stomatal size in species with extremely large genomes. Seed mass of geophytes was closely related to their ecology, but not to genomic parameters. Genomic DNA GC content showed a unimodal relationship with genome size but no relationship with species ecology.

Conclusions

Evolution of genome size in geophytes is closely related to their ecology and phenology and is also associated with remarkable changes in DNA base composition. Although geophytism together with producing larger cells appears to be an advantageous strategy for fast development of an organism in seasonal habitats, the drought sensitivity of large stomata may restrict the occurrence of geophytes with very large genomes to regions not subject to water stress.     

Evaluation of RbCl and CrCl₃ as markers of Triatoma brasiliensis (Hemiptera: Reduviidae) nymphs: persistence and influence of Rb and Cr on triatomine biology

In order to mark Triatoma brasiliensis, the vector of Chagas disease in Brazil, two chemical compounds, rubidium chloride (RbCl) and chromium chloride (CrCl?), were tested. First, 199 N2-N5 nymphs were fed on blood with 0.025M RbCl. Rb marker positivity ranged from 2.5% (N3)-70% (N2), with a maximum persistence of 98 days. Second, 265 N2-N5 nymphs were fed on blood containing 0.0015M CrCl?. Cr marker positivity ranged up to 93% (N5), with a maximum persistence of 119 days. Finally, we blood fed 213 T. brasiliensis to investigate whether CrCl? altered the biology of this insect. The developmental time of T. brasiliensis was unaltered, but the survival of the Cr-marked group was lower than that of the control group. Differences in the mean fecundity of the control (mean of 156.1) and experimental (mean of 135.6) groups were not statistically significant and 100% of the egg batches of females Cr-marked as nymphs were positive. In conclusion, CrCl? is a useful tool for marking T. brasiliensis nymphs due to its high positivity and persistence.     

The acceptance of scientific theories and images of masculinity and femininity: 1959–±1985

The acceptance of scientific theories and images of masculinity and femininity: 1959–±1985     

Thermodynamic and structural analysis of homodimeric proteins: Model of β-lactoglobulin

The energetics of protein homo-oligomerization was analyzed in detail with the application of a general thermodynamic model. We have studied the thermodynamic aspects of protein-protein interaction employing β-lactoglobulin A from bovine milk at pH = 6.7 where the protein is mainly in its dimeric form. We performed differential calorimetric scans at different total protein concentration and the resulting thermograms were analyzed with the thermodynamic model for oligomeric proteins previously developed. The thermodynamic model employed, allowed the prediction of the sign of the enthalpy of dimerization, the analysis of complex calorimetric profiles without transitions baselines subtraction and the obtainment of the thermodynamic parameters from the unfolding and the association processes and the compared with association parameters obtained with Isothermal Titration Calorimetry performed at different temperatures. The dissociation and unfolding reactions were also monitored by Fourier-transform infrared spectroscopy and the results indicated that the dimer of β-lactoglobulin (N₂) reversibly dissociates into monomeric units (N) which are structurally distinguishable by changes in their infrared absorbance spectra upon heating. Hence, it is proposed that β-lactoglobulin follows the conformational path induced by temperature:N₂ ? 2N ? 2D. The general model was validated with these results indicating that it can be employed in the study of the thermodynamics of other homo-oligomeric protein systems.     

Volatilisation of metals and metalloids: An inherent feature of methanoarchaea?

As shown by recent studies, anaerobic members of Archaea and Bacteria are involved in processes that transform ionic species of metals and metalloids (arsenic, antimony, bismuth, selenium, tellurium and mercury) into volatile and mostly toxic derivatives (mainly methyl derivatives or hydrides). Since the fact that these transformations proceed in both environmental settings and in parts of the human body, we have to consider that these processes also interfere directly with human health. The diversity of the volatile derivatives produced and their emission rates were significantly higher in methanoarchaeal than in bacterial strains, which supports the pivotal role of methanoarchaea in transforming metals and metalloids (metal(loid)s) into their volatile derivatives. Compared with methanoarchaea, 14 anaerobic bacterial strains showed a significantly restricted spectrum of volatilised derivatives and mostly lower production rates of volatile bismuth and selenium derivatives. Since methanoarchaea isolated from the human gut (Methanosphaera stadtmanae, Methanobrevibacter smithii) showed a higher potential for metal(loid) derivatisation compared to bacterial gut isolates, we assume that methanoarchaea in the human gut are mainly responsible for the production of these volatile derivatives. The observation that trimethylbismuth ((CH(3))(3)Bi), the main volatile derivative of bismuth produced in human feces, inhibited growing cultures of Bacteroides thetaiotaomicron, a representative member of the human physiological gut flora, suggests that these volatiles exert their toxic effects on human health not only by direct interaction with host cells but also by disturbing the physiological gut microflora.     

Structure-Activity Relationships of Tiazofurin Analogs: Synthesis and Computational Studies of 4′-Thio Derivatives of Thiophenfurin and Furanfurin

Abstract

The synthesis and computational studies of 5-(4-thio-β-D-ribofuranosyl)-furan-3-carboxamide (furanthiofurin) and 5-(4-thio-β-D-ribofuranosyl)thiophene-3-carboxamide (thiophenthiofurin) are reported.     

The cost of disturbance: a waste of time and energy?

Quantifying the effect of disturbance is a central issue in conservation. Using time and energy budgets, we obtain a range of ways to assess the importance of disturbance. One measure is the time that must be spent foraging in order to balance the energy budget. From this we derive critical levels of wastage (rate of disturbance multiplied by duration of disturbance) at which the animal runs out of time or reaches a limit on energy expenditure. In the case of the time constraint, the critical wastage is the net rate of energetic gain while foraging divided by the rate of energetic expenditure during a disturbance. The associated critical rate of disturbance is the net rate of energetic gain while foraging divided by the energy spent during a disturbance. The model is illustrated using data from the African wild dog, which suffers disturbance from lions and kleptoparasitism from hyenas. Findings suggest that disturbance imposes significant costs on wild dog time and energy budgets. We show how alternative environments can be evaluated in terms of their effective rate of gain, which is the net rate of gain from foraging minus the rate of energy expenditure as a result of disturbance.     

Prothoracicotropic hormone — like activity in the embryonated eggs of gypsy moth,Lymantria dispar (L.)

Summary Prothoracicotropic hormone (PTTH)-like activity was obtained from embryonated eggs of the gypsy moth, Lymantria dispar. Activity was detected using an in vitro prothoracic gland stimulation bioassay. Doseresponse kinetics of crude extract revealed a 4-fold activation range with a maximum activation of 35-fold. Nearly 70% of the activity was sensitive to denaturation by heat or organic solvent extraction. Heat and organic solvent-stable activity is due to a protein. Dose-response kinetics suggest the presence of a small molecular weight PTTH with pre-hatch eggs providing a rich source of the hormone.Abbreviations Ar activation ratio - ED ₅₀ 50 percent effective dose - eq equivalent - HPLC high performance liquid chromatography - PC prothoracic gland - PTTH prothoracicotropic hormone - RIA radioimmuno assay - TFA trifluoroacetic acid     

Thermodynamic and structural analysis of homodimeric proteins: model of β-lactoglobulin

The energetics of protein homo-oligomerization was analyzed in detail with the application of a general thermodynamic model. We have studied the thermodynamic aspects of protein-protein interaction employing β-lactoglobulin A from bovine milk at pH=6.7 where the protein is mainly in its dimeric form. We performed differential calorimetric scans at different total protein concentration and the resulting thermograms were analyzed with the thermodynamic model for oligomeric proteins previously developed. The thermodynamic model employed, allowed the prediction of the sign of the enthalpy of dimerization, the analysis of complex calorimetric profiles without transitions baselines subtraction and the obtainment of the thermodynamic parameters from the unfolding and the association processes and the compared with association parameters obtained with Isothermal Titration Calorimetry performed at different temperatures. The dissociation and unfolding reactions were also monitored by Fourier-transform infrared spectroscopy and the results indicated that the dimer of β-lactoglobulin (N(2)) reversibly dissociates into monomeric units (N) which are structurally distinguishable by changes in their infrared absorbance spectra upon heating. Hence, it is proposed that β-lactoglobulin follows the conformational path induced by temperature:N(2)?2N?2D. The general model was validated with these results indicating that it can be employed in the study of the thermodynamics of other homo-oligomeric protein systems.     

Categories of race: technologies of knowing and governing Australian aborigines†

This article documents the first decades of the work of the Aboriginal Protection Board in Victoria, Australia in the mid-nineteenth century, as it oversees the establishment of mission stations to gather up Aboriginal peoples and provide protection from settler violence. It augments existing accounts of white settler governance of Aboriginal peoples by examining the social and historical conditions for the emergence of separations and distinctions between Aboriginal peoples through shifting governmental versions of the ‘Aboriginal problem’. The production of race-based categories of persons is highlighted in the State's management of the Aboriginal children through the mission systems and their effects on Aboriginal ties to community and identity.     

Consolidation and reconsolidation: two lives of memories?

Most studies on memory consolidation consider the new information as if it were imposed on a tabula rasa, but considerable evidence indicates that new memories must be interleaved within a large network of relevant pre-existing knowledge. Early studies on reconsolidation highlighted that a newly consolidated memory could be erased after reactivation, but new evidence has shown that an effective reactivation experience must also involve memory reorganization to incorporate new learning. The combination of these observations on consolidation and reconsolidation highlights the fundamental similarities of both phenomena as the integration of new information and old, and it suggests reconsolidation = consolidation as a neverending process of schema modification.     

The mechanism of C-banding: depurination and β-elimination

C-banding of chromosomes involves the differential solubilization of fragmented DNA from euchromatin by three sequential treatments: 1. Acid, 2. Mild base, 3. Hot salt. The data indicate solubilization is effected by 1) depurination, 2) DNA denaturation, 3) chain breakage of the depurinated sites respectively in the three treatments. Conditions were found wherein each treatment in proper sequence was necessary for C-banding and the appropriate chemical reactions were measured in these treatment conditions. The acid treatment (0.2 N HCl) depurinates chromosomal DNA at the rate of 0.26×10^–6 purines/dalton min to an alkaline molecular weight of 10⁵ daltons but does not break the depurinated sites. Bleomycin can substitute for acid as a base removing agent. Sodium borohydride, by reducing the depurinated sugar's aldehyde thereby preventing chain breakage by the -elimination reaction, reversibly inhibits DNA-extraction. Chain breakage at the DNA's apurinic sites occurs not in the 2 min mild alkali treatment where the half-life for breakage is 26 min but in the 18 h hot salt treatment where the half-life for chain breakage is 1–2 h. Most of the DNA extraction occurs in the hot salt as 10⁵ dalton fragments as measured in formamide gradients. Bleomycin is introduced as a substitute for HCl; it removes nitrogenous bases from DNA in situ while better preserving the morphology of the final C-banded chromosomes.     

Inhibitors of Adenosine Deaminase: Synthesis of Coformycin and 3′-Deoxycoformycin

Abstract

Glycosylation of the heterocycle, 6,7-dihydro-imidazo [4,5-d] [1,3] diazepin-8(3H)-one, with suitably protected sugars under the influence of Lewis acid catalysts gave the β-D-ribo- and 3′-deoxy-β-D-erythropento-furanosyl nucleosides. Deprotection and reduction of the keto nucleosides with sodium borohydride gave the (8R)- and (8S)-3-β-D-glycofuranosyl-3,6,7,8-tetrahydroimidazo [4,5-d]-[1,3] diazepin-8-ols, the (8R)-isomers of which are potent inhibitors of adenosine deaminase.