Degradation of cholecystokinin octapeptide,related fragments and analogs by human and rat plasma in vitro

The rate of degradation of cholecystokinin octapeptide, related fragments and analogs by human and rat plasma was investigated, using high pressure liquid chromatography for the separation and identification of the degradation products.CCK tetrapeptide showed a half-life of 13 min in human plasma while its cleavage in rat plasma occurred at a very high rate (half-life of less than 1 min).The kinetics of disappearance of both sulphated and unsulphated CCK-8 indicated more than a single rate of degradation; the faster degrading system showed a half-life of 18 min for unsulphated CCK-8 and of 50 min for the sulphated peptide in human plasma as compared respectively with 5 and 17 min in rat plasma. The cleavage of CCK-8 was inhibited by bestatin and puromycin, suggesting that aminopeptidases play a major role in the breakdown of this peptide.CCK-9 analogs were rapidly converted into their corresponding octapeptides (half-life of 2.7 min in human plasma). This conversion was inhibited by puromycin and bestatin, suggesting the participation of aminopeptidase(s) probably specific for basic amino acids.CCK decapeptide exhibited a greater stability than the nonapeptides (half-life of 30 and 45 min in human and rat plasma respectively) and also gave rise to CCK-8 as degradation product. This cleavage was not affected by aminopeptidase inhibitors but was decreased by aprotinin (Trasylol®), suggesting that trypsin-like and/or kallikrein-like enzyme(s) were involved in the plasma metabolism of this peptide.     

Effect of Tylenchorhynchus robustoides on Growth of Buffalo Grass and Western Wheatgrass

Tylenchorhynchus robustoides reduced (P = 0.05) growth of Agropyron smithii (western wheatgrass) at soil temperatures of 20, 25, 30, and 35 C. Growth reduction increased with increasing soil temperatures. Highest populations of T. robustoides were recovered at 25 and 30 C. Clipping weights of Buchloe dactyloides (buffalo grass) were reduced at 25 and 30 C; however, root/crown weights were reduced at 15, 20, 30, and 35 C in nematode infested vs. noninfested soil. Reproduction of T. robustoides was greater at 25, 30, and 35 C than at 20 C on B. dactyloides. In a greenhouse study, T. robustoides reduced clipping and root/crown weights of both grasses 24-64%.     

Ladies last: diel rhythmicity of adult emergence in a parasitoid with complementary sex determination

Protandry, the earlier adult emergence of males, is explained as either an adaptive strategy maximizing male mating opportunities at the same time as minimizing female pre‐reproductive mortality, or as an incidental by‐product of sexual dimorphism fuelled by selection for other life‐history traits. Adult emergence sequences are monitored of broods of the gregarious larval endoparasitoid Cotesia glomerata L. (Hymenoptera: Braconidae) undergoing pupal development under different temperature regimes. As a haplodiploid species with single‐locus complementary sex determination, gender in C. glomerata is determined by the genotype at one sex locus. Haploids are always male, whereas diploids are female when heterozygous but male when homozygous at the sex locus. Sibling mating promotes homozygosity and thus the production of diploid males. Diploid males are produced at the expense of females, and impose a genetic burden on individuals and populations, despite their exceptional fertility in C. glomerata. Emergence of broods is typically completed within 2 days. Irrespective of temperature, males emerge earlier and within a shorter time interval than females, and a majority of the males in a cluster emerge before the first female. The implications of an incomplete temporal segregation of the sexes on the incidence of inbreeding in C. glomerata are discussed in the light of its sex determination mechanism and its patterns of mating, host exploitation and natal dispersal.     

Effects of temperature, photoperiod, and light intensity on the calling rhythm in Arctiid moths

Mean times of onset for calling in Haploa clymene (Brown), Spilosoma virginica (Fabricius), Pareuchaetes insulata (Walker), Cycnia tenera (Hübner), and Euchaetes egle (Drury) advance to earlier times in the photoperiod at lower temperatures. Temperature has no apparent effect on the calling period in Pyrrharctia isabella (J. E. Smith), Spilosoma congrua Walker, and Apantesis nais (Drury). The relationship between the temperatures experienced by each of these species as adults and the response of their calling rhythms to temperature is discussed. Lights-on can elicit calling behaviour in C. tenera, although it is not an absolute requirement because calling eventually begins when lights-on is delayed 4 h and calling also begins prior to lights-on at lower temperatures. Calling periods lengthen in C. tenera and S. congrua when the scotophase is prolonged and in S. congrua after the onset of a lower photophase light intensity (40 lux), suggesting that a higher photophase light intensity (450 lux) inhibits calling and thus causes its termination.

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Résumé Aux faibles températures le moment moyen de déclenchement de l'appel apparaît plus tôt au cours de la photopériode chez Haploa clymene Brown, Spilosoma virginica Fab., Pareuchaetes insulata Walk., Cycnia tenera Hübn. et Euchaetes egle Drury. La température n'a apparemment pas d'effet sur le moment où l'appel débute chez Pyrrharctica isabella J.E. Smith, S. congrua Walk. et Apantesis nais Drury.L'analyse porte sur les relations entre les températures subies par les adultes de ces espèces et leurs réactions d'appel aux différentes températures. L'apparition de la lumière peut induire le comportement d'appel chez C. tenera, bien que ce ne soit pas indispensable puisqu'il peut éventuellement commencer à des températures plus basses avant l'illumination quand celle-ci est retardée de 4 heures. Les périodes d'appel sont prolongées avec la scotophase chez C. tenera et S. congrua, et même après l'apparition d'une photophase à faible intensité lumineuse (40 lux), l'appel de S. congrua se poursuit, ce qui suggère que les photophases à intensité lumineuse plus élevée (450 lux) inhibent l'appel et ainsi en provoquent la fin.

     

Metabarcoding for the parallel identification of several hundred predators and their prey: Application to bat species diet analysis

Assessing diet variability is of main importance to better understand the biology of bats and design conservation strategies. Although the advent of metabarcoding has facilitated such analyses, this approach does not come without challenges. Biases may occur throughout the whole experiment, from fieldwork to biostatistics, resulting in the detection of false negatives, false positives or low taxonomic resolution. We detail a rigorous metabarcoding approach based on a short COI minibarcode and two‐step PCR protocol enabling the “all at once” taxonomic identification of bats and their arthropod prey for several hundreds of samples. Our study includes faecal pellets collected in France from 357 bats representing 16 species, as well as insect mock communities that mimic bat meals of known composition, negative and positive controls. All samples were analysed using three replicates. We compare the efficiency of DNA extraction methods, and we evaluate the effectiveness of our protocol using identification success, taxonomic resolution, sensitivity and amplification biases. Our parallel identification strategy of predators and prey reduces the risk of mis‐assigning prey to wrong predators and decreases the number of molecular steps. Controls and replicates enable to filter the data and limit the risk of false positives, hence guaranteeing high confidence results for both prey occurrence and bat species identification. We validate 551 COI variants from arthropod including 18 orders, 117 family, 282 genus and 290 species. Our method therefore provides a rapid, resolutive and cost‐effective screening tool for addressing evolutionary ecological issues or developing “chirosurveillance” and conservation strategies.     

Athenolide A,a New Steroidal Lactone from the Leaves of Athenaea martiana (Solanaceae) Determined by Means of HPLC‐HR‐MS‐SPE‐NMR Analysis

Athenaea (Solanaceae) is an endemic genus belonging to the Brazilian Atlantic Rainforest. Recently, botanical investigations suggested the re‐evaluation of the generic status of the genus Athenaea as a synonym of Aureliana. In this study, the first investigation of the Athenaea genus performed on Athenaea martiana by means of HPLC‐HR‐MS‐SPE‐NMR combined with high‐resolution radical scavenging profile led to identification of several phenolic acids as radical scavengers: protocatechuic acid ( 1 ), 4‐hydroxybenzoic acid ( 2 ), caffeic acid ( 3 ), vanillic acid ( 4 ), and ferulic acid ( 6 ). Additional analysis revealed a new steroidal lactone, named athenolide A ( 9 ). Their structures were elucidated by extensive use of NMR spectroscopy as well as HR‐MS. Chemotaxonomic considerations based on these results supported the chemical relationships between the Athenaea and Aureliana genera, in agreement with the recent botanical findings.     

Effects on temperature on spontaneous and thyroxine-stimulated locomotor activity of Atlantic cod

Spontaneous locomotor activity of cod Gadus morhua maintained at 6° C tripled from February to May. In contrast, locomotor activity of cod held at 2° C was significantly lower than at 6° C (between 25 and 65% lower) and the seasonal increase was smaller. Plasma levels of both thyroxine (T₄) and triiodothyronine (T₃) did not differ between 2 and 6° C. T₄ injection increased locomotor activity by 10% for both temperature regimes. These data indicate that low water temperature reduces locomotor activity associated with migration in cod and that thyroid hormones are not involved in this decrease. This study provides a possible mechanism through which cold waters may affects migration and distribution of cod via its Effects on locomotor activity and swimming speed.     

Heat stress in the presence of low RNA polymerase activity increases chromosome copy number of Escherichia coli

Summary A temperature shift-up accompanied by a reduction in RNA polymerase activity in Escherichia coli causes an increased rate of initiation leading to a 1.7- to 2.2-fold increase in chromosome copy number. A temperature shift-up without a reduction in polymerase activity induces only a transient non-scheduled initiation of chromosome replication caused by heat shock with no detectable effect on chromosome copy number.     

Bacterial peptidoglycan muropeptides benefit mitochondrial homeostasis and animal physiology by acting as ATP synthase agonists

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