Ixodes ricinus, transmitted diseases and reservoirs

The tick Ixodes ricinus has been recorded in most Italian regions especially in thermo-mesophilous woods and shrubby habitats where the relative humidity allow the tick to complete its 3 year developmental cycle, as predicted for the European climatic ranges. This tick acts both as vector and reservoir for a series of wildlife zoonotic pathogens, especially the agents of Lyme diseases, Tick borne encephalitis and Human Granulocytic Ehrlichiosis, which are emerging in most of Europe. To assess the spatial distribution of these pathogens and the infection risk for humans and animals within the territory of the Province of Trento, we carried out a long term study using a combination of eco-epidemiological surveys and mathematical modelling. An extensive tick collection with a GIS based habitat suitability analysis allowed us to identify the areas where tick occurs at various density. To identify the areas with higher infection risk, we estimated the values of R0 for Borrelia burgdorferi s.l., TBE virus and Anaplasma phagocytophila under different ecological conditions. We assessed the infection prevalence in the vector and in the wildlife reservoir species that play a central role in the persistence of these infections, ie the small mammals A. flavicollis and C. glareolus. We also considered the double effect of roe deer (Capreolus capreolus) which act as reservoir for A. phagocytophila but is an incompetent host for B. burgdorferi and TBE virus, thus reducing the infection prevalence in ticks of these last two pathogens. Infection prevalence with B. burgdorferi and A. phagocytophila in the vector was assessed by PCR screening 1212 I. ricinus nymphs collected by dragging in six main study areas during 2002. The mean infection prevalence recorded was 1.32% for B. burgdorferi s.l. and 9.84% for A. phagocytophila. Infection prevalence in nymphs with TBE virus, as assessed in a previous study was 0.03%. Infection prevalence in rodents was assessed by screening (with ELISA and PCR) tissues and blood samples collected from 367 rodent individuals trapped extensively during 2002 within 6 main study areas. A. flavicollis (N=238) was found to be infected with all three pathogens investigated, with infection prevalence ranging from 3.3% for TBE virus to 11.7% for A. phagocytophila, and 16.6% with B. burgdorferi s.l. C. glareolus (N=108) showed an infection prevalence of 6.5% with A. phagocytophila and 12.7% with B. burgdorferi s.l., while no individuals were infected with TBE virus. We also screened 98 spleen samples collected from roe deer with PCR, resulting in a mean prevalence of infection with A. phagocytophila of 19.8%. Using a deterministic model we explored the condition for diseases persistence under different rodent and roe deer densities. R0 values resulted largely above 1 for B. burgdorferi s.l. in the vast majority of the areas classified as suitable for I. ricinus occurrence in Trentino, while the condition for TBE persistence appeared to be more restricted by a combination of climatic condition and host densities.     

Phenotype–fitness relationships and pollen-transfer efficiency of five orchid species with different pollination strategies

Premise

Deceptive pollination, a fascinating mechanism that independently originated in several plant families for benefiting from pollinators without providing any reward, is particularly widespread among orchids. Pollination efficiency is crucial in orchids due to the aggregated pollen in a pollinarium, which facilitates pollen transfer and promotes cross-pollination as pollinators leave after being deceived.

Methods

In this study, we compiled data on reproductive ecology from five orchid species with different pollination strategies: three deceptive-strategy species (shelter imitation, food deception, sexual deception), one nectar-rewarding species, and one shelter-imitation but spontaneously selfing species. We aimed to compare the reproductive success (female fitness: fruit set; male fitness: pollinarium removal) and pollination efficiency of species representing these strategies. We also investigated pollen limitation and inbreeding depression among the pollination strategies.

Results

Male and female fitness were strongly correlated in all species but the spontaneously selfing species, which had high fruit set and low pollinarium removal. As expected, pollination efficiency was highest for the rewarding species and the sexually deceptive species. Rewarding species had no pollen limitation but did have high cumulative inbreeding depression; deceptive species had high pollen limitation and moderate inbreeding depression; and spontaneously selfing species did not have pollen limitation or inbreeding depression.

Conclusions

Pollinator response to deception is critical to maintain reproductive success and avoid inbreeding in orchid species with non-rewarding pollination strategies. Our findings contribute to a better understanding of the trade-offs associated with different pollination strategies in orchids and highlight the importance of pollination efficiency in orchids due to the pollinarium.

     

Elicitation of Necrosis in Vigna unguiculata Walp. by Homogeneous Aspergillus niger Endo-Polygalacturonase and by alpha-d-Galacturonate Oligomers

Endo-polygalacturonase (PG) was purified from a commercial preparation of Aspergillus niger pectinase by means of carboxymethylcellulose chromatography, preparative isoelectric focusing, and gel permeation through Sephadex G-50. The enzyme was electrophoretically homogeneous and consisted of a single polypeptide chain with a molecular weight of 33,500. The enzyme exhibited a specific activity significantly higher than those of purified polygalacturonases from phytopathogenic fungi. Galacturonate oligomers with a degree of polymerization higher than four appeared quickly as products of the enzymic hydrolysis of Napolygalacturonate. The oligomers were later degraded to di- and monogalacturonate. The homogeneous enzyme and growing mycelium of Aspergillus niger separately elicited a necrotic response in cowpea (Vigna unguiculata Walp.) pods. Heat-inactivated PG and PG inactivated with specific antibodies did not elicit necrosis, suggesting that the catalytic activity of the enzyme is necessary for its function as an elicitor. The PG-released oligosaccharides from Vigna cell wall and the galacturonides with a degree of polymerization greater than four separately elicited necrosis, whereas di- and monogalacturonate did not.     

Molecular characterization of p53 mutations in primary and secondary liver tumors: diagnostic and therapeutic perspectives

p53 is one of the most mutated genes in human cancer. We have performed the molecular characterization of p53 and have searched for correlations with etiological factors and clinical parameters in primary and secondary liver tumors. A systematic study was carried out, innovative in many respects, to determine the mutational pattern of all 11 exons of p53 and analysis was extended also to exons 1–4 and 9–11 and the exon/intron junctions. Our analyses were performed on case histories of 114 patients from the European area and highlighted p53 mutation patterns different from those reported in the literature for the same tumors. In our case history, different tumors of the same organ showed a different frequency and distribution of mutations. In analyzed tumor types, gene status was a prognostic indicator of survival because patients undergoing liver resection without mutated p53 had a more favorable prognosis than mutated patients. This suggests p53 molecular diagnosis could become a further criterion in the decision for surgery and possible therapies. We describe the ideal conditions for polymerase chain reaction (PCR), single-strand conformation polymorphism (SSCP), and direct sequencing, which we have set in order to optimize yields, sensitivity, and time of what might become a massive molecular screening.     

Mechanisms underlying the impacts of exotic plant invasions

Although the impacts of exotic plant invasions on community structure and ecosystem processes are well appreciated, the pathways or mechanisms that underlie these impacts are poorly understood. Better exploration of these processes is essential to understanding why exotic plants impact only certain systems, and why only some invaders have large impacts. Here, we review over 150 studies to evaluate the mechanisms underlying the impacts of exotic plant invasions on plant and animal community structure, nutrient cycling, hydrology and fire regimes. We find that, while numerous studies have examined the impacts of invasions on plant diversity and composition, less than 5% test whether these effects arise through competition, allelopathy, alteration of ecosystem variables or other processes. Nonetheless, competition was often hypothesized, and nearly all studies competing native and alien plants against each other found strong competitive effects of exotic species. In contrast to studies of the impacts on plant community structure and higher trophic levels, research examining impacts on nitrogen cycling, hydrology and fire regimes is generally highly mechanistic, often motivated by specific invader traits. We encourage future studies that link impacts on community structure to ecosystem processes, and relate the controls over invasibility to the controls over impact.     

Brain-derived neurotrophic factor prevents changes in Bcl-2 family members and caspase-3 activation induced by excitotoxicity in the striatum

Brain-derived neurotrophic factor (BDNF) prevents the loss of striatal neurons caused by excitotoxicity. We examined whether these neuroprotective effects are mediated by changes in the regulation of Bcl-2 family members. We first analyzed the involvement of the phosphatidylinositol 3-kinase/Akt pathway in this regulation, showing a reduction in phosphorylated Akt (p-Akt) levels after both quinolinate (QUIN, an NMDA receptor agonist) and kainate (KA, a non-NMDA receptor agonist) intrastriatal injection. Our results also show that Bcl-2, Bcl-x(L) and Bax protein levels and heterodimerization are selectively regulated by NMDA and non-NMDA receptor stimulation. Striatal cell death induced by QUIN is mediated by an increase in Bax and a decrease in Bcl-2 protein levels, leading to reduced levels of Bax:Bcl-2 heterodimers. In contrast, changes in Bax protein levels are not required for KA-induced apoptotic cell death, but decreased levels of both Bax:Bcl-2 and Bax:Bcl-x(L) heterodimer levels are necessary. Furthermore, QUIN and KA injection activated caspase-3. Intrastriatal grafting of a BDNF-secreting cell line counter-regulated p-AKT, Bcl-2, Bcl-x(L) and Bax protein levels, prevented changes in the heterodimerization between Bax and pro-survival proteins, and blocked caspase-3 activation induced by excitotoxicity. These results provide a possible mechanism to explain the anti-apoptotic effect of BDNF against to excitotoxicity in the striatum through the regulation of Bcl-2 family members, which is probably mediated by Akt activation.     

Variation in Trill Characteristics in Tree Pipit Songs: Different Trills for Different Use?

Transmitting information about singer's quality is an important function of song in many bird species, and this information should be useful in territorial interactions. Fast trills, being physically demanding song structures, are particularly suitable candidates for signalling of quality or aggressive motivation. We have evaluated trill characteristics in songs within a population of the Tree Pipit, a common European songbird with no sexual dimorphism, in which song apparently plays a key role in territory defence as well as mate choice. Two types of relatively fast trills (each of them in multiple variants differing in complexity) were commonly observed in repertoires of Tree Pipit males. Trill rates significantly differed among individuals, suggesting that these song structures may carry information about male quality in this species. We tested by playback experiments whether both trill types are used in territorial encounters. Only one of the trill types was sung by males in response to playback, regardless on the trill type played to them. In an immediate response to playback, they increased the frequency of use of this trill, and also significantly increased the trill rate in comparison with spontaneous songs. This confirmed field observations, suggesting that this trill is important in male–male interactions. On the contrary, the use of the fastest, apparently more demanding, trill type actually decreased after the simulated territorial intrusion. We hypothesize that the latter one is more directed towards females, and that while performance of both trill types may reflect male quality, they are primarily used in different contexts.