Adenosine analogue–oligo-arginine conjugates (ARCs) serve as high-affinity inhibitors and fluorescence probes of type I cGMP-dependent protein kinase (PKGIα)

Introduction

Type I cGMP-dependent protein kinase (PKGIα) belongs to the family of cyclic nucleotide-dependent protein kinases and is one of the main effectors of cGMP. PKGIα is involved in regulation of cardiac contractility, vasorelaxation, and blood pressure; hence, the development of potent modulators of PKGIα would lead to advances in the treatment of a variety of cardiovascular diseases. Aim: Representatives of ARC-type compounds previously characterized as potent inhibitors and high-affinity fluorescent probes of PKA catalytic subunit (PKAc) were tested towards PKGIα to determine that ARCs could serve as activity regulators and sensors for the latter protein kinase both in vitro and in complex biological systems. Results: Structure–activity profiling of ARCs with PKGIα in vitro demonstrated both similarities as well as differences to corresponding profiling with PKAc, whereas ARC-903 and ARC-668 revealed low nanomolar displacement constants and inhibition IC₅₀ values with both cyclic nucleotide-dependent kinases. The ability of ARC-based fluorescent probes to penetrate cell plasma membrane was demonstrated in the smooth muscle tissue of rat cerebellum isolated arteries, and the compound with the highest affinity in vitro (ARC-903) showed also potential for in vivo applications, fully abolishing the PKG1α-induced vasodilation.     

Feeding through artificial membranes reduces fecundity for females of the blood‐feeding insect,Rhodnius prolixus

The blood‐feeding insect, Rhodnius prolixus, has been raised in the laboratory for close to 100 years. Various feeding techniques have been employed ranging from the use of warm‐blooded hosts, to the use of previously collected blood offered through artificial membranes. This study compared the fecundity in mated and unmated females fed rabbit blood directly from the shaved belly of a rabbit to that of females fed defibrinated rabbit blood through an artificial membrane. These results confirm previous reports that this insect's feeding efficacy is reduced using an artificial membrane. It also demonstrates for the first time that the fecundity index, which measures the efficiency of turning the blood meal into eggs, is significantly reduced. We suggest that the natural feeding on a warm‐blooded host may provide cues that have the short‐term effect of enhancing the act of feeding and the long‐term effect of increasing egg production efficiency. Until an artificial feeding method that does not interfere with feeding and fecundity is devised, experiments on reproduction in R. prolixus warrant the use of a warm‐blooded host to emulate feeding in its natural setting. © 2010 Wiley Periodicals, Inc.     

Some New Aryl-5′-fluoro-2′-meth-oxyphenyl Ketones and Their Thiosemicarbazones as Possible Fungicides

Feeding studies on rice genetically modified with soybean glycinin were performed on rats for four weeks. The rats were divided into three groups, each being fed on (I) only a commercial diet, (II) this diet plus control rice and (III) this diet plus rice genetically modified with glycinin. The rats were fed with 10 g/kg-weight of rice every day by oral administration. During the test period, the rats in every group grew well without marked differences in appearance, food intake, body weight, or cumulative body weight gain. There were also no significant differences in the blood count, blood composition or internal organ weights among the rats. Necropsy at the end of the experiment indicated neither pathological symptoms nor histopathological abnormalities in the liver and kidney. Judging from these results, the rice genetically modified with glycinin is considered to have been essentially the same in nutritional and biochemical characteristics as the control rice.     

Enzymatic Synthesis of Dehydro Cyclo(His–Phe)s,Analogs of the Potent Cell Cycle Inhibitor,Dehydrophenylahistin, and Their Inhibitory Activities toward Cell Division

Cyclo(His–Phe) was effectively converted to its dehydro derivatives by the enzyme of Streptomyces albulus KO-23, an albonoursin-producing actinomycete. Two types of dehydro derivatives were isolated from the reaction mixture and identified as cyclo(ΔHis–ΔPhe) and cyclo(His–ΔPhe). This is the first report on cyclo(His–ΔPhe) and the enzymatic preparation of both compounds. Cyclo(ΔHis–ΔPhe), a tetradehydro cyclic dipeptide, exhibited a minimum inhibitory concentration of 0.78 μmol/ml inhibitory activity toward the first cleavage of sea urchin embryos, in contrast to cyclo(His–ΔPhe) that had no activity. The finding that the isoprenylated derivative of cyclo(ΔHis–ΔPhe), dehydrophyenylahistin, had 2,000 times higher activity than cyclo(ΔHis–ΔPhe) indicates that an isoprenyl group attached to an imidazole ring of the compound was essential for the inhibitory activity.     

Does the energy equivalence rule apply to intertidal macrobenthic communities?

Energy equivalence assumes equal contribution of large and small species to production and energy flow in communities. As in a double logarithmic plot, physiological rates decline with body weight by –0.25, log biomass should increase by 0.25 and log abundance decline by –0.75 with log species weight, when this concept is valid. This was tested with annual data sets of the macrobenthos of 4 intertidal sites in the German Wadden Sea (Königshafen) and 3 sites in a south Portuguese lagoon (Ria Formosa). Only abundance data from two of these sites displayed significantly negative slopes with mean body size of the species. Biomass and secondary production data were significantly positively correlated with mean body size for all Ria Formosa sites and also for the biomass of a mussel bed in Königshafen. However, high variation in body size of the individuals of a species limits interpretation of these plots.It is preferable to test this concept by body weight classes regardless of its species composition. At Königshafen, biomass and production displayed two distinct peaks. One peak at small body size was caused by browsing species. The other peak at larger body size was caused by animals which potentially extract their food from the water column. This bimodality was only vaguely reflected at one station in the Ria Formosa, possibly because of a dominance of detritus feeding species. In a normalized form (log biomass or production / width of size classvs. log size class), these spectra imply a dominance of small individuals in biomass and production at all sites (except for a mussel bank at Königshafen). This is interpreted as a consequence of permanent disturbances.     

In silico and empirical evaluation of twelve metabarcoding primer sets for insectivorous diet analyses

During the most recent decade, environmental DNA metabarcoding approaches have been both developed and improved to minimize the biological and technical biases in these protocols. However, challenges remain, notably those relating to primer design. In the current study, we comprehensively assessed the performance of ten COI and two 16S primer pairs for eDNA metabarcoding, including novel and previously published primers. We used a combined approach of in silico, in vivo‐mock community (33 arthropod taxa from 16 orders), and guano‐based analyses to identify primer sets that would maximize arthropod detection and taxonomic identification, successfully identify the predator (bat) species, and minimize the time and financial costs of the experiment. We focused on two insectivorous bat species that live together in mixed colonies: the greater horseshoe bat (Rhinolophus ferrumequinum) and Geoffroy's bat (Myotis emarginatus). We found that primer degeneracy is the main factor that influences arthropod detection in silico and mock community analyses, while amplicon length is critical for the detection of arthropods from degraded DNA samples. Our guano‐based results highlight the importance of detecting and identifying both predator and prey, as guano samples can be contaminated by other insectivorous species. Moreover, we demonstrate that amplifying bat DNA does not reduce the primers' capacity to detect arthropods. We therefore recommend the simultaneous identification of predator and prey. Finally, our results suggest that up to one‐third of prey occurrences may be unreliable and are probably not of primary interest in diet studies, which may decrease the relevance of combining several primer sets instead of using a single efficient one. In conclusion, this study provides a pragmatic framework for eDNA primer selection with respect to scientific and methodological constraints.     

Inspection and feeding of larvae by worker honey bees (Hymenoptera: Apidae): Effect of starvation and food quantity

Honey bee larvae are frequently inspected and, sometimes, provided with food by adult workers, but the stimuli that elicit the important task of food provisioning have never been investigated. Larvae with their food experimentally deprived received more frequent inspection and feeding visits from nurse bees than normally fed larvae, suggesting that there could be a hunger signal. Food-deprived larvae with artificially supplied larval food received the same rate of feeding visits from nurse bees as did normally fed larvae but still received more inspection visits. These results suggest that stimuli eliciting feeding are different from those for inspection. They also support the hypothesis that worker bees deposit food in a larval cell only when the quantity of food is below a certain minimum threshold that is perceived during larval inspections. A model is presented regarding the stimuli from larvae that result in worker feeding behavior.     

Insights into the evolution of lanthipeptide biosynthesis

Lanthipeptides are a group of posttranslationally modified peptide natural products that contain multiple thioether crosslinks. These crosslinks are formed by dehydration of Ser/Thr residues followed by addition of the thiols of Cys residues to the resulting dehydroamino acids. At least four different pathways to these polycyclic natural products have evolved, reflecting the high efficiency and evolvability of a posttranslational modification route to generate conformationally constrained peptides. The wealth of genomic information that has been made available in recent years has started to provide insights into how these remarkable pathways and their posttranslational modification machineries may have evolved. In this review, we discuss a model for the evolution of the lanthipeptide biosynthetic enzymes that has recently been developed based on the currently available data.     

Description of the digestive tract and feeding habits of the king angelfish and the Cortes angelfish

Morphologically, the digestive tracts of the king angelfish Holacunthus passer and the Cortes angelfish Pomacanthus zonipectus are similar, yet the king angelfish intestine is almost 30% longer than that of the Cortes angelfish. Both pomacanthids have a small mouth with villiform teeth, a short oesophagus, a well-defined stomach, and a terminal sac at the end of the digestive tract. The terminal sac, the acid pH in the stomach, and the long intestine may facilitate efficient use of seaweed nutrients. Stomach contents were analysed to determine diets and interspecific overlap. Seventy-one species were found in the stomachs of the king angelfish and 53 in the stomachs of the Cortes angelfish. Because of the wide range of species in their diets, both angelfish must be regarded as omnivorous. The most frequent foods were seaweed and sponges, but for the king angelfish, crustaceans were also important. A cluster analysis was done to determine whether the diets of these fish were similar by sex, size, or season. No similarities were found. Dietary overlap is high in relation to other pomacanthids.     

Perils of ingesting harmful prey by advanced snakes

The advanced snakes (Alethinophidia) include the extant snakes with a highly evolved head morphology providing increased gape and jaw flexibility. Along with other physiological and morphological adaptations, this allows them to immobilize, ingest, and transport prey that may be disproportionately large or presents danger to the predator from bites, teeth, horns, or spines. Reported incidents of snakes failing to consume prey and being injured or killed during feeding mostly reflect information in the form of natural-history notes. Here we provide the first extensive review of such incidents, including 101 publications describing at least 143 cases of mortality (including six of ‘multiple individuals’) caused by ingestion or attempted consumption of injurious prey. We also report on 15 previously unpublished injurious feeding incidents from the USA, Austria, and Bulgaria, including mortality of five juvenile piscivorous dice snakes (Natrix tessellata) from a single location. Occurrences are spread across taxa, with mortality documented for at least 73 species from eight families and 45 genera. Incidents were generally well represented within each of three major categories: oversized prey (40.6%), potentially harmful prey (40.6%), and predator's behavioural/mechanical errors (18.9%). Reptile (33%) and fish (26%) prey caused disproportionately high mortality compared to mammals (16%). Feeding can be dangerous throughout a snake's life, with the later stages of feeding likely being more perilous. The number of reports has increased over time, and the data seem biased towards localities with a higher number of field-working herpetologists. We propose a standardized framework, comprising a set of basic information that should ideally be collected and published, and which could be useful as a template for future data collection, reporting, and analyses. We conclude that incidents of mortality during feeding are likely to be more common than previously assumed, and this hypothesis has implications for the ecology of persistence where populations are impacted by changing trophic environments.