Plant coloration undermines herbivorous insect camouflage

The main point of our hypothesis "coloration undermines camouflage" is that many color patterns in plants undermine the camouflage of invertebrate herbivores, especially insects, thus exposing them to predation and causing them to avoid plant organs with unsuitable coloration, to the benefit of the plants. This is a common case of "the enemy of my enemy is my friend" and a visual parallel of the chemical signals that plants emit to call wasps when attacked by caterpillars. Moreover, this is also a common natural version of the well-known case of industrial melanism, which illustrates the great importance of plant-based camouflage for herbivorous insects and can serve as an independent test for our hypothesis. We claim that the enormous variations in coloration of leaves, petioles and stems as well as of flowers and fruits undermine the camouflage of invertebrate herbivores, especially insects. We assume that the same principle might operate in certain animal-parasite interactions. Our hypothesis, however, does not contrast or exclude other previous or future explanations of specific types of plant coloration. Traits such as coloration that have more than one type of benefit may be selected for by several agents and evolve more rapidly than ones with a single type of advantage.     

Isolation and characterization of the tobramycin biosynthetic gene cluster from Streptomyces tenebrarius

The biosynthetic gene cluster for tobramycin, a 2-deoxystreptamine-containing aminoglycoside antibiotic, was isolated from Streptomyces tenebrarius ATCC 17920. A genomic library of S. tenebrarius was constructed, and a cosmid, pST51, was isolated by the probes based on the core regions of 2-deoxy-scyllo-inosose (DOI) synthase, and L-glutamine:DOI aminotransferase and L-glutamine:scyllo-inosose aminotransferase. Sequencing of 33.9 kb revealed 24 open reading frames (ORFs) including putative tobramycin biosynthetic genes. We demonstrated that one of these ORFs, tbmA, encodes DOI synthase by in vitro enzyme assay of the purified protein. The catalytic residues of TbmA and dehydroquinate synthase were studied by homology modeling. The gene cluster found is likely to be involved in the biosynthesis of tobramycin.     

Swim exercise training and adaptations in the antioxidant defense system of myocardium of old rats: relationship to swim intensity and duration

We examined a suitable swim program of different intensities and durations that could evoke changes in the myocardial antioxidant capacity in 22-month-old rats. Male rats (Rattus norvegicus) were assigned to either a sedentary control (SE-C) group or one of six trainee groups. Animals were swim-exercised for 4 weeks with either 20 min or 40 min/day, and three intensities, low, moderate and high. Low-intensity at 20 min/day elicited maximum swim velocity (Sv) and endurance capacity (P<0.05). While serum total cholesterol, triglyceride and low-density lipoprotein (LDL-C) levels were significantly reduced, high-density lipoprotein (HDL-C) showed an increase (P<0.05) in low-intensity trained rats (20 min/day) over SE-C. Notable reduction in blood lactate was also evident. Exercise training significantly increased superoxide dismutase (Mn-SOD), decreased lipid peroxidation products, malondialdehyde and lipofuscin in the left and right ventricles. Increased Mn-SOD with concomitant decrease in lipofuscin in left ventricle was significantly greater than in right ventricle. Moderate- to high-intensity exercise was not effective in either reducing lipid peroxidation products or elevating Mn-SOD activity. These data suggest that swim training at low-intensity of 20 min/day is beneficial as a major protective adaptation against oxidative stress in old myocardium.     

Sexual selection, natural selection and the evolution of dimorphic coloration and ornamentation in agamid lizards

Both sexual selection and natural selection can influence the form of dimorphism in secondary sexual traits. Here, we used a comparative approach to examine the relative roles of sexual selection and natural selection in the evolution of sexually dimorphic coloration (dichromatism) and ornamentation in agamid lizards. Sexual dimorphism in head and body size were used as indirect indicators of sexual selection, and habitat type (openness) as an index of natural selection. We examined separately the dichromatism of body regions "exposed to" and "concealed from" visual predators, because these body regions are likely to be subject to different selection pressures. Dichromatism of "exposed" body regions was significantly associated with habitat type: males were typically more conspicuously coloured than females in closed habitats. By contrast, dichromatism of "concealed" body regions and ornament dimorphism were positively associated with sexual size dimorphism (SSD). When we examined male and female ornamentation separately, however, both were positively associated with habitat openness in addition to snout-vent length and head SSD. These results suggest that natural selection constrains the evolution of elaborate ornamentation in both sexes as well as sexual dichromatism of body regions exposed to visual predators. By contrast, dichromatism of "concealed" body regions and degree of ornament dimorphism appear to be driven to a greater degree by sexual selection.     

Synthesis and antihyperglycemic activity profiles of novel thiazolidinedione derivatives

A number of thiazolidine-2,4-diones derivatives having carboxylic ester appendage at N-3 were synthesized and their antihyperglycemic activity was evaluated. Many of these derivatives as well as their corresponding carboxylic acid showed significant improvement on post-prandial hyperglycemia in normal rats, in contrast to their poor agonist activity at PPARgamma.     

RNA polyadenylation and degradation in cyanobacteria are similar to the chloroplast but different from Escherichia coli

The mechanism of RNA degradation in Escherichia coli involves endonucleolytic cleavage, polyadenylation of the cleavage product by poly(A) polymerase, and exonucleolytic degradation by the exoribonucleases, polynucleotide phosphorylase (PNPase) and RNase II. The poly(A) tails are homogenous, containing only adenosines in most of the growth conditions. In the chloroplast, however, the same enzyme, PNPase, polyadenylates and degrades the RNA molecule; there is no equivalent for the E. coli poly(A) polymerase enzyme. Because cyanobacteria is a prokaryote believed to be related to the evolutionary ancestor of the chloroplast, we asked whether the molecular mechanism of RNA polyadenylation in the Synechocystis PCC6803 cyanobacteria is similar to that in E. coli or the chloroplast. We found that RNA polyadenylation in Synechocystis is similar to that in the chloroplast but different from E. coli. No poly(A) polymerase enzyme exists, and polyadenylation is performed by PNPase, resulting in heterogeneous poly(A)-rich tails. These heterogeneous tails were found in the amino acid coding region, the 5' and 3' untranslated regions of mRNAs, as well as in rRNA and the single intron located at the tRNA(fmet). Furthermore, unlike E. coli, the inactivation of PNPase or RNase II genes caused lethality. Together, our results show that the RNA polyadenylation and degradation mechanisms in cyanobacteria and chloroplast are very similar to each other but different from E. coli.     

Conspicuous males suffer higher predation risk: visual modelling and experimental evidence from lizards

Colour pattern variation is a striking and widespread phenomenon. Differential predation risk between individuals is often invoked to explain colour variation, but empirical support for this hypothesis is equivocal. We investigated differential conspicuousness and predation risk in two species of Australian rock dragons, Ctenophorus decresii andC. vadnappa . To humans, the coloration of males of these species varies between ‘bright’ and ‘dull’. Visual modelling based on objective colour measurements and the spectral sensitivities of avian visual pigments showed that dragon colour variants are differentially conspicuous to the visual system of avian predators when viewed against the natural background. We conducted field experiments to test for differential predation risk, using plaster models of ‘bright’ and ‘dull’ males. ‘Bright’ models were attacked significantly more often than ‘dull’ models suggesting that differential conspicuousness translates to differential predation risk in the wild. We also examined the influence of natural geographical range on predation risk. Results from 22 localities suggest that predation rates vary according to whether predators are familiar with the prey species. This study is among the first to demonstrate both differential conspicuousness and differential predation risk in the wild using an experimental protocol. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

Effect of a polyherbal formulation, Ambrex, on butylated hydroxy toluene (BHT) induced toxicity in rats

Effect of polyherbal formulation Ambrex was evaluated in butylated hydroxytoluene (BHT) induced toxicity of lungs and liver in rats. Toxicity was produced by administering BHT (500 mg/kg/day) for 3 days. Lung damage was evidenced by elevated levels of broncho alveolar lavage fluid (BAL) parameters such as protein, lactate, lactate dehydrogenase (LDH), alkaline phosphatase (ALP), acid phosphatase (ACP) and glucose-6-phosphate dehydrogenase (G6PDH). Liver damage was proved by elevated levels of serum protein and markers such as LDH, ALP, aspartate amino transferase (AST), alanine amino transferase (ALT), decreased level of lipid peroxides (LPO) in serum and glutathione (GSH) in liver. Administration of aqueous suspension of Ambrex (50 mg/kg orally) retained these elevated levels of BAL-protein, lactate, LDH, ALP, ACP, G6PDH and serum-protein, LDH, ALP, AST and ALT at near normal values. Decreased level of liver GSH was retained at near normalcy in Ambrex pretreated BHT-administered animals. There was no change in liver LPO in all the four groups.     

Effect of fish oil on mitochondrial respiration in isoproterenol induced myocardial infarction in rats

Following isoproterenol treatment mitochondrial lipid peroxidation, phosphoslipase activity, lactate and calcium increased significantly, while activities of tricarboxylic acid cycle enzymes, enzymes of respiratory chain and ATP production showed decline. Oxidative phosphorylation was also affected on isoproterenol treatment with significant reduction in all the variables. Fish oil pretreatment in isoproterenol treated rats showed improved mitochondrial energy metabolism. The results suggest cardioprotective effect of fish oil.     

Prevention of HCl-ethanol induced gastric mucosal injury in rats by Garcinia cambogia extract and its possible mechanism of action

Oral pretreatment of rats with G. cambogia fruit extract (1 g/kg body weight/day at interval of 7 and 15 days) protected gastric mucosa against HCl-ethanol induced damage by decreasing the volume and acidity of gastric juice. Increased lipid peroxidation, decreased activity of antioxidant enzymes, altered levels of protein and glycoproteins in the ulcerated mucosa, and gastric juice were maintained at near normal levels in G. cambogia pretreated rats. The results suggest the anti-ulcer activity of G. cambogia by virtue of its ability to decrease acidity and increase mucosal defense.