Restricted dispersal in a long-distance migrant bird with patchy distribution,the great reed warbler

In patchily distributed species dispersal connects local populations into metapopulations. Reliable quantifications of dispersal are therefore crucial to understanding the population dynamics and genetic structure of such metapopulation systems. The great reed warbler (Acrocephalus arundinaceus) inhabits eutrophic lakes and has a patchy breeding distribution. In this study we investigated the dispersal pattern of the great reed warbler based on an extensive capture-recapture effort covering a large census area (22,500 km²). At two adjacent breeding sites (10 km apart) in southern Central Sweden, the "main study area", we ringed the majority of adult and nestling great reed warblers between 1992 and 1999. In 1998 and 1999, we opportunistically searched for territorial males at the majority of the Swedish breeding sites, and were able to examine about 56% of all males in the region. Analyses of recaptured males demonstrated that philopatry predominated. Sixty-nine percent of the recruiting nestlings returned to breed in the main study area (their natal area), and 92% of the resighted adults were found at the same breeding locality in both study years. Breeding dispersal was significantly more restricted than natal dispersal. Additional data on natal and breeding dispersal within the main study area in 1992-1999 suggested that females were as philopatric as males. The overall high level of philopatry, with only occasional longer dispersal distances documented, yielded a root-mean-square dispersal distance of 33 km per generation. High philopatry, short dispersal distances and similar dispersal patterns of male and female great reed warblers contrast the findings among birds in general, but conform to data of species having patchy breeding habitat and isolated populations. Restricted dispersal suggests limited gene flow even among several Swedish populations, which is in line with some previous findings of the population ecology of the great reed warbler: (1) structured mtDNA lineages among European populations; (2) small-scale population differences in song patterns; and (3) low genetic variation and occurrence of inbreeding depression in our main study population.     

Gender differences in inflammatory proteins and pathways in seasonal allergic rhinitis

In model organisms, thousands of genes differ in expression between females and males. It is not known if differences on a similar scale are found in humans nor how this relates to disease. However, in allergic disease gender differences in the levels of both inflammatory cells and proteins have been shown. In this study, we found lower nasal fluid allergen-specific IgE in women than men with seasonal allergic rhinitis (SAR). This led to genome-wide analyses of gene expression in allergen-challenged CD4⁺ cells from patients with SAR before and after treatment with cortisone. Before treatment, 975 genes differed in expression between women and men: 337 were higher in women. After treatment only 428 genes and one pathway differed in expression. The genes that differed in expression between women and men were over-represented in 10 pathways. Five of the pathways regulated chemotaxis. All five were less active in women. One of the pathways was induced by the eosinophilic chemokine CCL4. Analysis of nasal fluid CCL4 protein confirmed lower levels in women with seasonal allergic rhinitis, before and during the pollen season. By contrast, nasal fluid CCL3 levels did not differ between the genders. In summary, this study shows gender differences in specific inflammatory pathways and proteins in patients with seasonal allergic rhinitis. Further studies are warranted to examine if such differences have diagnostic and therapeutic implications in allergic diseases.     

Equilibration of [3H]glucosamine and [35S]sulfate with intracellular pools of UDP-N-acetylhexosamine and 3′-phosphoadenosine-5′-phosphosulfate (PAPS) in cultured fibroblasts

Nucleotides and sugar nucleotides were extracted from cultures of human fibroblasts with perchloric acid, separated by isotachophoresis, and quantified by uv absorption analysis at 254 nm. ATP (936 pmol/μg DNA) was, as expected, the dominating nucleotide pool. The energy charge was estimated to 0.9. The UDP-N-acetylhexosamine pool was also a very prominent compound (596 pmol/μg DNA). After incubation of fibroblasts with [³H]glucosamine, more than 95% of the acid-soluble radioactivity was found in the UDP-N-acetylhexosamine pool. Incubation with [³⁵S]sulfate resulted in the incorporation of [³⁵S]sulfate into 3′-phosphoadenosine-5′-phosphosulfate (PAPS). The latter could, however, only be measured as radioactivity, as the amount was too small to be quantified as total mass. Pulse-labeling of fibroblasts with [³⁵S]sulfate and [³H]glucosamine from 5 min to 16 h showed that [³⁵S]PAPS was equilibrated in less than 10 min, while [³H]glucosamine required a longer time, 2–4 h, to attain a steady state with UDP-N-acetylhexosamine. [¹⁴C]Glucose required approximately the same time as [³H]glucosamine to reach steady state with UDP-acetylhexosamine, which suggests that the reason for the long equilibration time is the slow turnover of this pool.     

The effects of 884 MHz GSM wireless communication signals on headache and other symptoms: an experimental provocation study

Findings from prior studies of possible health and physiological effects from mobile phone use have been inconsistent. Exposure periods in provocation studies have been rather short and personal characteristics of the participants poorly defined. We studied the effect of radiofrequency field (RF) on self-reported symptoms and detection of fields after a prolonged exposure time and with a well defined study group including subjects reporting symptoms attributed to mobile phone use. The design was a double blind, cross-over provocation study testing a 3-h long GSM handset exposure versus sham. The study group was 71 subjects age 18-45, including 38 subjects reporting headache or vertigo in relation to mobile phone use (symptom group) and 33 non-symptomatic subjects. Symptoms were scored on a 7-point Likert scale before, after 1(1/2) and 2(3/4) h of exposure. Subjects reported their belief of actual exposure status. The results showed that headache was more commonly reported after RF exposure than sham, mainly due to an increase in the non-symptom group. Neither group could detect RF exposure better than by chance. A belief that the RF exposure had been active was associated with skin symptoms. The higher prevalence of headache in the non-symptom group towards the end of RF exposure justifies further investigation of possible physiological correlates. The current study indicates a need to better characterize study participants in mobile phone exposure studies and differences between symptom and non-symptom groups.     

Lactate and epinephrine during exercise in altitude natives

Kayser, Bengt, Roland Favier, Guido Ferretti, DominiqueDesplanches, Hilde Spielvogel, Harry Koubi, Brigitte Sempore, and HansHoppeler. Lactate and epinephrine during exercise in altitudenatives. J. Appl. Physiol. 81(6):2488-2494, 1996.We tested the hypothesis that the reported lowblood lactate accumulation ([La]) during exercise inaltitude-native humans is refractory to hypoxia-normoxia transitions byinvestigating whether acute changes in inspiredO₂ fraction(FI_O2) affect the[La] vs. power output ()relationship or, alternatively, as reported for lowlanders, whetherchanges in [La] vs. on changes inFI_O2 are related tochanges in blood epinephrine concentration ([Epi]). Altitude natives [n = 8, age 24 ± 1 (SE) yr, body mass 62 ± 3 kg, height 167 ± 2 cm]in La Paz, Bolivia (3,600 m) performed incremental exercise with twolegs and one leg in chronic hypoxia and acute normoxia (AN). Submaximalone- and two-leg O₂ uptake (O₂) vs. relationships were not altered byFI_O2. AN increased two-legpeak O₂ by 10% and peak by 7%. AN paradoxically decreasedone-leg peak O₂ by 7%,whereas peak remained the same. The[La] vs. relationships were similar tothose reported in unacclimatized lowlanders. There was a shift to theright on AN, and maximum [La] was reduced by 7 and 8% forone- and two-leg exercises, respectively. [Epi] and[La] were tightly related (mean r = 0.81) independently ofFI_O2. Thus normoxiaattenuated the increment in both [La] and [Epi]as a function of , whereas the correlation between[La] and [Epi] was unaffected. These data suggest loose linkage of glycolysis to oxidative phosphorylation under influence from [Epi]. In conclusion, high-altitudenatives appear to be not fundamentally different from lowlanders with regard to the effect of acute changes inFI_O2 on [La] during exercise.

     

Structural studies of the manganese stabilizing subunit in photosystem II

Photosystem II (PSII) is the plant photosynthetic reaction center that carries out the light driven oxidation of water. The water splitting reactions are catalyzed at a tetranuclear manganese cluster. The manganese stabilizing protein (MSP) of PSII stabilizes the manganese cluster and accelerates the rate of oxygen evolution. MSP can be removed from PSII, with an accompanying decrease in activity. Either an Escherichia coli expressed version of MSP or native, plant MSP can be rebound to the PSII reaction center; MSP reconstitution reverses the deleterious effects associated with MSP removal. We have employed Fourier transform infrared (FTIR) spectroscopy and solution small angle x-ray scattering (SAXS) techniques to investigate the structure of MSP in solution and to define the structural changes that occur before and after reconstitution to PSII. FTIR and SAXS are complementary, because FTIR spectroscopy detects changes in MSP secondary structure and SAXS detects changes in MSP size/shape. From the SAXS data, we conclude that the size/shape and domain structure of MSP do not change when MSP binds to PSII. From FTIR data acquired before and after reconstitution, we conclude that the reconstitution-induced increase in beta-sheet content, which was previously reported, persists after MSP is removed from the PSII reaction center. However, the secondary structural change in MSP is metastable after removal from PSII, which indicates that this form of MSP is not the lowest energy conformation in solution.     

New aspects on phosphate sensing and signalling in Saccharomyces cerevisiae

The mechanism involved in the cellular phosphate response of Saccharomyces cerevisiae forms part of the PHO pathway, which upon expression allows a co-ordinated cellular response and adaptation to changes in availability of external phosphate. Although genetic studies and analyses of the S. cerevisiae genome have produced much information on the components of the PHO pathway, little is known about how cells sense the environmental phosphate level and the mechanistic regulation of phosphate acquisition. Recent studies emphasize different levels in phosphate sensing and signalling in response to external phosphate fluctuations. This review integrates all these findings into a model involving rapid and long-term effects of phosphate sensing and signalling in S. cerevisiae. The model describes in particular how yeast cells are able to adjust phosphate acquisition by integrating the status of the intracellular phosphate pools together with the extracellular phosphate concentration.     

Activated platelet-derived growth factor autocrine pathway drives the transformed phenotype of a human glioblastoma cell line

Human glioblastoma cells (A172) were found to concomitantly express PDGF-BB and PDGF β-receptors. The receptors were constitutively autophosphorylated in the absence of exogenous ligand, suggesting the presence of an autocrine PDGF pathway. Neutralizing PDGF antibodies as well as suramin inhibited the autonomous PDGF receptor tyrosine kinase activity and resulted in up-regulation of receptor protein. The interruption of the autocrine loop by the PDGF antibodies reversed the transformed phenotype of the glioblastoma cell, as determined by (1) diminished DNA synthesis, (2) inhibition of tumor colony growth, and (3) reversion of the transformed morphology of the tumor cells. The PDGF antibodies showed no effect on the DNA synthesis of another glioblastoma cells line (U343MGa 31L) or on Ki-ras-transformed fibroblasts. The present study demonstrates an endogenously activated PDGF pathway in a spontaneous human glioblastoma cell line. Furthermore, we provide evidence that the autocrine PDGF pathway drives the transtormed phenotype of the tumor cells, a process that can be blocked by extracellular antagonists. © 1994 Wiley-Liss, Inc.     

A new approach to study dispersal: immigration of novel alleles reveals female-biased dispersal in great reed warblers

We use the assignment technique and a new approach, the 'novel allele technique', to detect sex-biased dispersal in great reed warblers Acrocephalus arundinaceus. The data set consisted of immigrants and philopatric birds in a semi-isolated population in Sweden scored at 21 microsatellite loci. Fourteen cohorts were represented of which the four earliest were used to define a reference population. Female immigrants had lower assignment probability than males (i.e. were less likely to have been sampled in the reference population), and carried the majority of 'novel alleles' (i.e. alleles observed in the population for the first time). The difference in number of novel alleles between sexes was caused by a strong over-representation of females among the few individuals that carried several novel alleles, and there was a tendency for a corresponding female bias among individuals with low assignment probabilities. Immigrant males had similar or lower reproductive success than females. These results lead us to conclude that important interregional gene flow in great reed warblers depends on relatively few dispersing females, and that the novel allele technique may be a useful complement to the assignment technique when evaluating dispersal patterns from temporally structured data.