For a few years more: reductions in plant diversity 70 years after the last fire in Mediterranean forests

Plant Ecology - Changes in community diversity and dynamics after fires in Mediterranean ecosystems are rarely investigated more than a few years after the fire even though pronounced changes can...     

Conjugation of a new two-photon fluorophore to poly(ethylenimine) for gene delivery imaging

We report herein the molecular engineering of an efficient two-photon absorbing (TPA) chromophore based on a donor-donor bis-stilbenyl entity to allow conjugation with biologically relevant molecules. The dye has been functionalized using an isothiocyanate moiety to conjugate it with the amine functions of poly(ethylenimine) (PEI), which is a cationic polymer commonly used for nonviral gene delivery. Upon conjugation, the basic architecture and photophysical properties of the active TPA chromophore remain unchanged. At the usual N/P ratio (ratio of the PEI positive charges to the DNA negative charges) of 10 used for transfection, the transfection efficiency and cytotoxicity of the labeled PEI/DNA complexes were found to be comparable to those of the unlabeled PEI/DNA complexes. Moreover, when used in combination with unlabeled PEI (at a ratio of 1 labeled PEI to 3 unlabeled PEI), the labeled PEI does not affect the size of the complexes with DNA. The labeled PEI was successfully used in two-photon fluorescence correlation spectroscopy measurements, showing that at N/P = 10 most PEI molecules are free and the diffusion coefficient of the complexes is consistent with the 360 nm size measured by quasielastic light scattering. Finally, two-photon images of the labeled PEI/DNA complexes confirmed that the complexes enter into the cytoplasm of HeLa cells by endocytosis and hardly escape from the endosomes. As a consequence, the functionalized TPA chromophore appears to be an adequate tool to label the numerous polyamines used in nonviral gene delivery and characterize their complexes with DNA in two-photon applications.     

L-phenylalanine binding and domain organization in human phenylalanine hydroxylase: a differential scanning calorimetry study

Human phenylalanine hydroxylase (hPAH) is a tetrameric enzyme that catalyzes the hydroxylation of L-phenylalanine (L-Phe) to L-tyrosine; a dysfunction of this enzyme causes phenylketonuria. Each subunit in hPAH contains an N-terminal regulatory domain (Ser2-Ser110), a catalytic domain (Asp112-Arg410), and an oligomerization domain (Ser411-Lys452) including dimerization and tetramerization motifs. Two partially overlapping transitions are seen in differential scanning calorimetry (DSC) thermograms for wild-type hPAH in 0.1 M Na-Hepes buffer, 0.1 M NaCl, pH 7.0. Although these transitions are irreversible, studies on their scan-rate dependence support that the equilibrium thermodynamics analysis is permissible in this case. Comparison with the DSC thermograms for truncated forms of the enzyme, studies on the protein and L-Phe concentration effects on the transitions, and structure-energetic calculations based on a modeled structure support that the thermal denaturation of hPAH occurs in three stages: (i) unfolding of the four regulatory domains, which is responsible for the low-temperature calorimetric transition; (ii) unfolding of two (out of the four) catalytic domains, which is responsible for the high-temperature transition; and (iii) irreversible protein denaturation, which is likely responsible for the observed exothermic distortion in the high-temperature side of the high-temperature transition. Stages 1 and 2 do not appear to be two-state processes. We present an approach to the analysis of ligand effects on DSC transition temperatures, which is based on the general binding polynomial formalism and is not restricted to two-state transitions. Application of this approach to the L-Phe effect on the DSC thermograms for hPAH suggests that (i) there are no binding sites for L-Phe in the regulatory domains; therefore, contrary to the common belief, the activation of PAH by L-Phe seems to be the result of its homotropic cooperative binding to the active sites. (ii) The regulatory domain appears to be involved in cooperativity through its interactions with the catalytic and oligomerization domains; thus, upon regulatory domain unfolding, the cooperativity in the binding of L-Phe to the catalytic domains seems to be lost and the value of the L-Phe concentration corresponding to half-saturation is increased. Overall, our results contribute to the understanding of the conformational stability and the substrate-induced cooperative activation of this important enzyme.     

Experience with using Ellenberg’s <Emphasis Type=Italic>R</Emphasis> indicator values in Slovakia: Oligotrophic and mesotrophic submontane broad-leaved forests

Ellenberg’s indicator values have been suggested as useful method of estimating site conditions using plants. We examined whether Ellenberg’s R values are suitable for indicating soil reaction and if calibration to physical pH measurements can improve bioindication in oligotrophic and mesotrophic submontane broad-leaved forests in Slovakia. Vegetation relevés and pH-H₂O and pH-CaCl₂ soil reaction were recorded for this purpose. Ellenberg’s R values (R _e) were compared to Jurko’s indicator values (R _j) and a set of species R values and tolerances (T), which were calibrated with physical pH data using the weighted averaging (R _w, T _w) and Huisman-Olff-Fresco modelling (R _h, T _h). Original R _e values were then recalibrated with measured pH data to establish new, adjusted set of scores (R _c, T _c) at Ellenberg’s scale. The Re values are significantly correlated with the other R values, and they demonstrate similar frequency distribution to R _j and R _w values for the studied species pool. The frequency distribution becomes similar across all the R values when indifferent species were excluded. The performance of all the indicator values in terms of bioindication was tested. Relevé means of the R values were regressed on the field pH measurements. The performance of bioindication varied from 36% to 49% of the explained variance for pH-CaCl₂, with the R _e and R _c values yielding 46% and 49% respectively. The bioindication slightly improved for all calibrated methods (R _w, R _h and R _c) when species were weighted inversely with their tolerances — the performance varied from 42% to 51%, and the R _c values performed most effectively. We concluded that Ellenberg’s R values represent a powerful system for bioindicating soil acidity when compared to the other alternatives, with pH-CaCl₂ showing better results than pH-H₂O. Recalibration of Ellenberg’s values to the measured data improved the indicator system.     

A new species of Onychopterochelius Blüthgen (Hymenoptera: Vespidae: Eumeninae) from Turkey

Onychopterocheilus sarikamisensis sp. n. is described and illustrated from eastern Turkey. The species is related to O. hellenicus (Morawitz, 1885) but differs by the shape of the clypeus and antennae, and by the pale colouration of the maculations.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:A3E75353-EC16-458F-908FAB9240E8016B     

Between- and within-host species selection on cytoplasmic incompatibility-inducing Wolbachia in haplodiploids

Abstract The most common effect of the endosymbiont Wolbachia is cytoplasmic incompatibility (CI), a form of postzygotic reproductive isolation that occurs in crosses where the male is infected by at least one Wolbachia strain that the female lacks. We revisited two puzzling features of Wolbachia biology: how Wolbachia can invade a new species and spread among populations, and how the association, once established in a host species, can evolve, with emphasis on the possible process of infection loss. These questions are particularly relevant in haplodiploid species, where males develop from unfertilized eggs, and females from fertilized eggs. When CI occurs in such species, fertilized eggs either die (female mortality type: FM), or develop into males (male development type: MD), raising one more question: how transition among CI types is possible. We reached the following conclusions: (1) the FM type is a better invader and should be retained preferentially after a new host is captured; (2) given the assumptions of the models, FM and MD types are selected on neither the bacterial side nor the host side; (3) selective pressures acting on both partners are more or less congruent in the FM type, but divergent in the MD type; (4) host and symbiont evolution can drive infection to extinction for all CI types, but the MD type is more susceptible to the phenomenon; and (5) under realistic conditions, transition from MD to FM type is possible. Finally, all these results suggest that the FM type should be more frequent than the MD type, which is consistent with the results obtained so far in haplodiploids.     

Prebiotic processes in planetary atmospheres

Within 40 years of experimental studies in prebiotic chemistry, most of the building blocks of the living systems have been synthesized in plausible conditions of the primitive Earth. The starting ingredients correspond to two complementary classes: volatile organics, and their non volatile oligomers. They may have been formed in the atmosphere on the primitive Earth and/or imported by extra-terrestrial sources. Organic chemistry is involved in meteorites, comets, in the giant planets and several of their satellites. Again this chemistry presents the two complementary aspects. In particular, with a dense reduced atmosphere rich in organic compounds in gas and aerosol phases, Titan appears as a natural laboratory for studying prebiotic chemistry at a planetary scale.     

A clinical return-to-work rule for patients with back pain

Background

Tools for early identification of workers with back pain who are at high risk of adverse occupational outcome would help concentrate clinical attention on the patients who need it most, while helping reduce unnecessary interventions (and costs) among the others. This study was conducted to develop and validate clinical rules to predict the 2-year work disability status of people consulting for nonspecific back pain in primary care settings.

Methods

This was a 2-year prospective cohort study conducted in 7 primary care settings in the Quebec City area. The study enrolled 1007 workers (participation, 68.4% of potential participants expected to be eligible) aged 18–64 years who consulted for nonspecific back pain associated with at least 1 day''s absence from work. The majority (86%) completed 5 telephone interviews documenting a large array of variables. Clinical information was abstracted from the medical files. The outcome measure was “return to work in good health” at 2 years, a variable that combined patients'' occupational status, functional limitations and recurrences of work absence. Predictive models of 2-year outcome were developed with a recursive partitioning approach on a 40% random sample of our study subjects, then validated on the rest.

Results

The best predictive model included 7 baseline variables (patient''s recovery expectations, radiating pain, previous back surgery, pain intensity, frequent change of position because of back pain, irritability and bad temper, and difficulty sleeping) and was particularly efficient at identifying patients with no adverse occupational outcome (negative predictive value 78%– 94%).

Interpretation

A clinical prediction rule accurately identified a large proportion of workers with back pain consulting in a primary care setting who were at a low risk of an adverse occupational outcome.Since the 1950s, back pain has taken on the proportions of a veritable epidemic, counting now among the 5 most frequent reasons for visits to physicians'' offices in North America^1,2,3 and ranking sixth among health problems generating the highest direct medical costs.⁴ Because of its high incidence and associated expense, effective intervention for back pain has great potential for improving population health and for freeing up extensive societal resources.So-called red flags to identify pain that is specific (i.e., pain in the back originating from tumours, fractures, infections, cauda equina syndrome, visceral pain and systemic disease)⁵ account for about 3% of all cases of back pain.⁶ The overwhelming majority of back-pain problems are thus nonspecific. One important feature of nonspecific back pain among workers is that a small proportion of cases (< 10%) accounts for most of the costs (> 70%).^{7,8,9,10,11,12,13,14} This fact has led investigators to focus on the early identification of patients who are at higher risk of disability, so that specialized interventions can be provided earlier, whereas other patients can be expected to recover with conservative care.^{9,15,16,17,18,19,20,21,22,23,24,25} Although this goal has become much sought-after in back-pain research, most available studies in this area have 3 methodological problems:

• Potential predictors are often limited to administrative or clinical data, whereas it is clear that back pain is a multidimensional health problem.
• The outcome variable is most often a 1-point dichotomous measure of return to work, time off work or duration of compensation, although some authors have warned against the use of first return to work as a measure of recovery. Baldwin and colleagues,²⁶ for instance, point out that first return to work is frequently followed by recurrences of work absence.
• Most published prediction rules developed for back pain have not been successfully validated on any additional samples of patients.

Our study aimed to build a simple predictive tool that could be used by primary care physicians to identify workers with nonspecific back pain who are at higher risk of long-term adverse occupational outcomes, and then to validate this tool on a fresh sample of subjects.     

The first report of autochthonous non-vector-borne transmission of canine leishmaniosis in the Nordic countries

Background

Leishmania spp. are zoonotic protozoans that infect humans and other mammals such as dogs. The most significant causative species in dogs is L. infantum. In dogs, leishmaniosis is a potentially progressive, chronic disease with varying clinical outcomes. Autochthonous cases of canine leishmaniosis have not previously been reported in the Nordic countries.

Results

In this report we describe the first diagnosed autochthonous cases of canine leishmaniosis in Finland, in which transmission via a suitable arthropod vector was absent. Two Finnish boxers that had never been in endemic areas of Leishmania spp., had never received blood transfusions, nor were infested by ectoparasites were diagnosed with leishmaniosis. Another dog was found with elevated Leishmania antibodies. A fourth boxer dog that had been in Spain was considered to be the source of these infections. Transmission occurred through biting wounds and semen, however, transplacental infection in one of the dogs could not be ruled out.Two of the infected dogs developed a serious disease and were euthanized and sent for necropsy. The first one suffered from membranoproliferative glomerulonephritis and the second one had a chronic systemic disease. Leishmania sp. was detected from tissues by PCR and/or IHC in both dogs. The third infected dog was serologically positive for Leishmania sp. but remained free of clinical signs.

Conclusions

This case report shows that imported Leishmania-infected dogs may pose a risk for domestic dogs, even without suitable local arthropod vectors.