Low rates of iridoid glycoside hydrolysis in two Longitarsus leaf beetles with different feeding specialization confer tolerance to iridoid glycoside containing host plants

Iridoid glycosides are plant defence compounds that are deterrent and/or toxic for unadapted herbivores but are readily sequestered by dietary specialists of different insect orders. Hydrolysis of iridoid glycosides by β‐glucosidase leads to protein denaturation. Insect digestive β‐glucosidases thus have the potential to mediate plant–insect interactions. In the present study, mechanisms associated with iridoid glycoside tolerance are investigated in two closely‐related leaf beetle species (Coleoptera: Chrysomelidae) that feed on iridoid glycoside containing host plants. The polyphagous Longitarsus luridus Scopoli does not sequester iridoid glycosides, whereas the specialist Longitarsus tabidus Fabricius sequesters these compounds from its host plants. To study whether the biochemical properties of their β‐glucosidases correspond to the differences in feeding specialization, the number of β‐glucosidase isoforms and their kinetic properties are compared between the two beetle species. To examine the impact of iridoid glycosides on the β‐glucosidase activity of the generalist, L. luridus beetles are kept on host plants with or without iridoid glycosides. Furthermore, β‐glucosidase activities of both species are examined using an artificial β‐glucosidase substrate and the iridoid glycoside aucubin present in their host plants. Both species have one or two β‐glucosidases with different substrate affinities. Interestingly, host plant use does not influence the specific β‐glucosidase activities of the generalist. Both species hydrolyse aucubin with a much lower affinity than the standard substrate. The neutral pH reduces the β‐glucosidase activity of the specialist beetles by approximately 60% relative to its pH optimum. These low rates of aucubin hydrolysis suggest that the ability to sequester iridoid glycosides has evolved as a key to potentially preventing iridoid glycoside hydrolysis by plant‐derived β‐glucosidases.     

HOST-PLANT SWITCHES AND THE EVOLUTION OF CHEMICAL DEFENSE AND LIFE HISTORY IN THE LEAF BEETLE GENUS OREINA

Insect-plant interactions have played a prominent role in investigating phylogenetic constraints in the evolution of ecological traits. The patterns of host association among specialized insects have often been described as highly conservative, yet not all specialized herbivorous insect lineages display the same degree of fidelity to their host plants. In this paper, we present an estimate of the evolutionary history of the leaf beetle genus Oreina. This genus displays an amazing flexibility in several aspects of its ecology and life history: (1) host plant switches in Oreina occurred between plant families or distantly related tribes within families and thereby to more distantly related plants than in several model systems that have contributed to the idea of parallel cladogenesis; (2) all species of the genus are chemically defended, but within the genus a transition between autogenous production of defensive toxins and sequestration of secondary plant compounds has occurred; and (3) reproductive strategies in the genus range from oviparity to viviparity including all intermediates that could allow the gradual evolution of viviparity. Cladistic analysis of 18 allozyme loci found two most parsimonious trees that differ only in the branching of one species. According to this phylogeny estimate, Oreina species were originally associated with Asteraceae, with an inclusion of Apiaceae in the diet of one oligophagous species and an independent switch to Apiaceae in a derived clade. The original mode of defense appears to be the autogenous production of cardenolides as previously postulated; the additional sequestration of pyrrolizidine alkaloids could have either originated at the base of the genus or have arisen three times independently in all species that switched to plants containing these compounds. Viviparity apparently evolved twice in the genus, once without matrotrophy, through a retention of the eggs inside the female's oviducts, and once in combination with matrotrophy. We hypothesize that the combination of autogenous defense and a life history that involves mobile externally feeding larvae allowed these beetles to switch host plants more readily than has been reported for highly conservative systems.     

F?nge von Habichten (Accipiter gentilis) im Wurzacher Ried: Kritische Fragen zu einem beh?rdlich genehmigten Wiedereinbürgerungsprojekt

Zusammenfassung Während des unter der Trägerschaft des Landesjagdverbandes Baden-Württemberg e. V. seit 1978 laufenden Projektes zur Wiedereinbürgerung des Birkhuhnes im Wurzacher Ried wurde behördlicherseits der Wegfang von Habichten unter bestimmten Auflagen genehmigt. Nach Beringung mußten die Vögel wieder freigelassen werden. Eine vergleichende Untersuchung der von den Projektbetreibern veröffentlichten Berichte und der Beringungsdokumente ergab erhebliche Ungereimtheiten. Die aus den Berichten der Projektbetreiber zu entnehmende Zahl von 168 gefangenen, angeblich beringten und angeblich wieder freigelassenen Habichten steht der Zahl von 98 in den Beringungslisten dokumentierten Vögel gegenüber. Bereits ein Vergleich zwischen der Wiederfundrate der dokumentierten Vögel (1 %) mit der Fänglingfundrate der Vogelwarte Radolfzell (13 %) ergab einen hochsignifikanten Unterschied. Auch der Vergleich mit der Fundrate (15 %) einer anderen, parallel laufenden Verfrachtungsstudie zeigte, daß die Wiederfundrate der Wurzacher Habichte hochsignifikant geringer ist. Die Darstellung der Projektbetreiber, wonach 1978–1981 insgesamt 90 Habichte durch die Landesanstalt für Umweltschutz verfrachtet worden sein sollen, wurde durch die Landesanstalt nicht bestätigt. Die Landesanstalt bestätigte nur fünf verfrachtete Habichte aus dem Wurzacher Projekt. Obwohl der Habichtfang im März nicht erlaubt war, haben die Projektbetreiber insgesamt vier Habichte im März gefangen und zumindest einen (nach eigenen Angaben jedoch alle!) auch noch verfrachtet. Vermutlich im Auftrag von Geflügelzüchtern wurden sieben Habichte, darunter vier Altvögel, innerhalb eines kleinen Gebietes in einer Entfernung von 13–18,5 km vom Wurzacher Ried gefangen. So besteht begründeter Verdacht, daß ein beträchtlicher Teil der im oder um das Wurzacher Ried gefangenen Habichte nicht wieder freigelassen, sondern getötet wurde. Eine Reihe der in den Projektberichten enthaltenen Angaben lassen zudem ganz erhebliche Zweifel an der Fachkompetenz der Projektbetreiber aufkommen.

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Goshawk (Accipiter gentilis) trapping in the nature reserve Wurzacher Ried: critical questions on a Black Grouse (Tetrao tetrix) reintroduction project

Summary A Black Grouse reintroduction project was established in 1978 in the nature reserve Wurzacher Ried in southwestern Germany. Since the beginning of this project the staff had a licence to catch, ring and to release but not to kill goshawks. A comparison of the very low Euring-recovery-rate of 1 percent from this project with the Euring-recovery-rate of the Vogelwarte Radolfzell (13 %) showed a significant difference (p=0.00017). In contrast, we found no difference between the recovery-rate (15 %) of a study with almost similar design conducted by the University of Tübingen (Schmidt-Koenig 1982) only 100 km apart from the Wurzacher Ried and the Euring-recovery-rate of the Vogelwarte Radolfzell (p=0.624). The recovery-rate of the reintroduction project differed, however, significantly from the recovery-rate ofSchmidt-Koenig (p=0.006). Furthermore, we found serious inconsistencies between the project reports and the ringing documents concerning this project. Our results indicate, that most of the goshawks caught in the project Wurzacher Ried may not have been released but illegally killed by the project staff.

     

Exercise training in childhood-onset systemic lupus erythematosus: a controlled randomized trial

Introduction

Exercise training has emerged as a promising therapeutic strategy to counteract physical dysfunction in adult systemic lupus erythematosus. However, no longitudinal studies have evaluated the effects of an exercise training program in childhood-onset systemic lupus erythematosus (C-SLE) patients. The objective was to evaluate the safety and the efficacy of a supervised aerobic training program in improving the cardiorespiratory capacity in C-SLE patients.

Methods

Nineteen physically inactive C-SLE patients were randomly assigned into two groups: trained (TR, n = 10, supervised moderate-intensity aerobic exercise program) and non-trained (NT, n = 9). Gender-, body mass index (BMI)- and age-matched healthy children were recruited as controls (C, n = 10) for baseline (PRE) measurements only. C-SLE patients were assessed at PRE and after 12 weeks of training (POST). Main measurements included exercise tolerance and cardiorespiratory measurements in response to a maximal exercise (that is, peak VO₂, chronotropic reserve (CR), and the heart rate recovery (ΔHRR) (that is, the difference between HR at peak exercise and at both the first (ΔHRR1) and second (ΔHRR2) minutes of recovery after exercise).

Results

The C-SLE NT patients did not present changes in any of the cardiorespiratory parameters at POST (P > 0.05). In contrast, the exercise training program was effective in promoting significant increases in time-to-exhaustion (P = 0.01; ES = 1.07), peak speed (P = 0.01; ES = 1.08), peak VO₂ (P = 0.04; ES = 0.86), CR (P = 0.06; ES = 0.83), and in ΔHRR1 and ΔHRR2 (P = 0.003; ES = 1.29 and P = 0.0008; ES = 1.36, respectively) in the C-SLE TR when compared with the NT group. Moreover, cardiorespiratory parameters were comparable between C-SLE TR patients and C subjects after the exercise training intervention, as evidenced by the ANOVA analysis (P > 0.05, TR vs. C). SLEDAI-2K scores remained stable throughout the study.

Conclusion

A 3-month aerobic exercise training was safe and capable of ameliorating the cardiorespiratory capacity and the autonomic function in C-SLE patients.

Trial registration

NCT01515163.     

STEPWISE EVOLUTION OF RESISTANCE TO TOXIC CARDENOLIDES VIA GENETIC SUBSTITUTIONS IN THE NA+/K+‐ATPASE OF MILKWEED BUTTERFLIES (LEPIDOPTERA: DANAINI)

Despite the monarch butterfly (Danaus plexippus) being famous for its adaptations to the defensive traits of its milkweed host plants, little is known about the macroevolution of these traits. Unlike most other animal species, monarchs are largely insensitive to cardenolides, because their target site, the sodium pump (Na⁺/K⁺‐ATPase), has evolved amino acid substitutions that reduce cardenolide binding (so‐called target site insensitivity, TSI). Because many, but not all, species of milkweed butterflies (Danaini) are associated with cardenolide‐containing host plants, we analyzed 16 species, representing all phylogenetic lineages of milkweed butterflies, for the occurrence of TSI by sequence analyses of the Na⁺/K⁺‐ATPase gene and by enzymatic assays with extracted Na⁺/K⁺‐ATPase. Here we report that sensitivity to cardenolides was reduced in a stepwise manner during the macroevolution of milkweed butterflies. Strikingly, not all Danaini typically consuming cardenolides showed TSI, but rather TSI was more strongly associated with sequestration of toxic cardenolides. Thus, the interplay between bottom‐up selection by plant compounds and top‐down selection by natural enemies can explain the evolutionary sequence of adaptations to these toxins.     

Automated Entire Thrombus Density Measurements for Robust and Comprehensive Thrombus Characterization in Patients with Acute Ischemic Stroke

Background and Purpose

In acute ischemic stroke (AIS) management, CT-based thrombus density has been associated with treatment success. However, currently used thrombus measurements are prone to inter-observer variability and oversimplify the heterogeneous thrombus composition. Our aim was first to introduce an automated method to assess the entire thrombus density and then to compare the measured entire thrombus density with respect to current standard manual measurements.

Materials and Method

In 135 AIS patients, the density distribution of the entire thrombus was determined. Density distributions were described using medians, interquartile ranges (IQR), kurtosis, and skewedness. Differences between the median of entire thrombus measurements and commonly applied manual measurements using 3 regions of interest were determined using linear regression.

Results

Density distributions varied considerably with medians ranging from 20.0 to 62.8 HU and IQRs ranging from 9.3 to 55.8 HU. The average median of the thrombus density distributions (43.5 ± 10.2 HU) was lower than the manual assessment (49.6 ± 8.0 HU) (p<0.05). The difference between manual measurements and median density of entire thrombus decreased with increasing density (r = 0.64; p<0.05), revealing relatively higher manual measurements for low density thrombi such that manual density measurement tend overestimates the real thrombus density.

Conclusions

Automatic measurements of the full thrombus expose a wide variety of thrombi density distribution, which is not grasped with currently used manual measurement. Furthermore, discrimination of low and high density thrombi is improved with the automated method.