The Celtic fringe of Britain: insights from small mammal phylogeography

Recent genetic studies have challenged the traditional view that the ancestors of British Celtic people spread from central Europe during the Iron Age and have suggested a much earlier origin for them as part of the human recolonization of Britain at the end of the last glaciation. Here we propose that small mammals provide an analogue to help resolve this controversy. Previous studies have shown that common shrews (Sorex araneus) with particular chromosomal characteristics and water voles (Arvicola terrestris) of a specific mitochondrial (mt) DNA lineage have peripheral western/northern distributions with striking similarities to that of Celtic people. We show that mtDNA lineages of three other small mammal species (bank vole Myodes glareolus, field vole Microtus agrestis and pygmy shrew Sorex minutus) also form a ‘Celtic fringe’. We argue that these small mammals most reasonably colonized Britain in a two-phase process following the last glacial maximum (LGM), with climatically driven partial replacement of the first colonists by the second colonists, leaving a peripheral geographical distribution for the first colonists. We suggest that these natural Celtic fringes provide insight into the same phenomenon in humans and support its origin in processes following the end of the LGM.     

Landscape features and helminth co-infection shape bank vole immunoheterogeneity,with consequences for Puumala virus epidemiology

Heterogeneity in environmental conditions helps to maintain genetic and phenotypic diversity in ecosystems. As such, it may explain why the capacity of animals to mount immune responses is highly variable. The quality of habitat patches, in terms of resources, parasitism, predation and habitat fragmentation may, for example, trigger trade-offs ultimately affecting the investment of individuals in various immunological pathways. We described spatial immunoheterogeneity in bank vole populations with respect to landscape features and co-infection. We focused on the consequences of this heterogeneity for the risk of Puumala hantavirus (PUUV) infection. We assessed the expression of the Tnf-α and Mx2 genes and demonstrated a negative correlation between PUUV load and the expression of these immune genes in bank voles. Habitat heterogeneity was partly associated with differences in the expression of these genes. Levels of Mx2 were lower in large forests than in fragmented forests, possibly due to differences in parasite communities. We previously highlighted the positive association between infection with Heligmosomum mixtum and infection with PUUV. We found that Tnf-α was more strongly expressed in voles infected with PUUV than in uninfected voles or in voles co-infected with the nematode H. mixtum and PUUV. H. mixtum may limit the capacity of the vole to develop proinflammatory responses. This effect may increase the risk of PUUV infection and replication in host cells. Overall, our results suggest that close interactions between landscape features, co-infection and immune gene expression may shape PUUV epidemiology.     

Conserved roles of ems/Emx and otd/Otx genes in olfactory and visual system development in Drosophila and mouse

The regional specialization of brain function has been well documented in the mouse and fruitfly. The expression of regulatory factors in specific regions of the brain during development suggests that they function to establish or maintain this specialization. Here, we focus on two such factors—the Drosophila cephalic gap genes empty spiracles (ems) and orthodenticle (otd), and their vertebrate homologues Emx1/2 and Otx1/2—and review novel insight into their multiple crucial roles in the formation of complex sensory systems. While the early requirement of these genes in specification of the neuroectoderm has been discussed previously, here we consider more recent studies that elucidate the later functions of these genes in sensory system formation in vertebrates and invertebrates. These new studies show that the ems and Emx genes in both flies and mice are essential for the development of the peripheral and central neurons of their respective olfactory systems. Moreover, they demonstrate that the otd and Otx genes in both flies and mice are essential for the development of the peripheral and central neurons of their respective visual systems. Based on these recent experimental findings, we discuss the possibility that the olfactory and visual systems of flies and mice share a common evolutionary origin, in that the conserved visual and olfactory circuit elements derive from conserved domains of otd/Otx and ems/Emx action in the urbilaterian ancestor.     

Expression of a GABAB - Receptor in Olfactory Sensory Neurons of Sensilla trichodea on the Male Antenna of the Moth Heliothis virescens

In the olfactory pathway of Drosophila, a GABA_B receptor mediated presynaptic gain control mechanism at the first synapse between olfactory sensory neurons (OSNs) and projection neurons has been suggested to play a critical role in setting the sensitivity and detection range of the sensory system. To approach the question if such a mechanism may be realized in the pheromone recognition system of male moths in this study attempts were made to explore if moth''s pheromone-responsive cells express a GABA_B- receptor. Employing a combination of genome analysis, RT-PCR experiments and screening of an antennal cDNA library we have identified a cDNA which encodes the GABA_B-R1 receptor of Heliothis virescens. Moreover, based on the HvirGABA_B-R1 sequence we could predict a GABA_B-R1 protein from genome sequences of the silkmoth Bombyx mori. To assess whether HvirGABA_B-R1 is expressed in OSNs of male antenna we performed whole-mount in situ hybridization (WM-ISH) experiments. Several HvirGABA_B-R1 positive cells were visualized under long sensilla trichodea, known to contain pheromone-responsive OSNs. In parallel it was shown that cells under long trichoid hairs were labelled with pheromone receptor specific probes. In addition, the HvirGABA_B-R1 specific probe also labelled several cells under shorter olfactory sensilla, but never stained cells under mechanosensory/gustatory sensilla chaetica. Together, the results indicate that a GABA_B receptor is expressed in pheromone-responsive OSNs of H. virescens and suggest a presynaptic gain control mechanism in the axon terminals of these cells.     

Sex differences and effects of neonatal aromatase inhibition on masculine and feminine copulatory potentials in prairie voles

Copulatory behaviors in most rodents are highly sexually dimorphic, even when circulating hormones are equated between the sexes. Prairie voles (Microtus ochrogaster) are monomorphic in their display of some social behaviors, including partner preferences and parenting, but differences between the sexes in their masculine and feminine copulatory behavior potentials have not been studied in detail. Furthermore, the role of neonatal aromatization of testosterone to estradiol on the development of prairie vole sexual behavior potentials or their brain is unknown. To address these issues, prairie vole pups were injected daily for the first week after birth with 0.5 mg of the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD) or oil. Masculine and feminine copulatory behaviors in response to testosterone or estradiol were later examined in both sexes. Males and females showed high mounting and thrusting in response to testosterone, but only males reliably showed ejaculatory behavior. Conversely, males never showed feminine copulatory behaviors in response to estradiol. Sex differences in these behaviors were not affected by neonatal ATD, but ATD-treated females received fewer mounts and thrusts than controls, possibly indicating reduced attractiveness to males. In other groups of subjects, neonatal ATD demasculinized males' tyrosine hydroxylase expression in the anteroventral periventricular preoptic area, and estrogen receptor alpha expression in the medial preoptic area. Thus, although sexual behavior in both sexes of prairie voles is highly masculinized, aromatase during neonatal life is necessary only for females' femininity. Furthermore, copulatory behavior potentials and at least some aspects of brain development in male prairie voles are dissociable by their requirement for neonatal aromatase.     

Anatomical and functional analysis of domestication effects on the olfactory system of the silkmoth Bombyx mori

The silkmoth Bombyx mori is the main producer of silk worldwide and has furthermore become a model organism in biological research, especially concerning chemical communication. However, the impact domestication might have had on the silkmoth''s olfactory sense has not yet been investigated. Here, we show that the pheromone detection system in B. mori males when compared with their wild ancestors Bombyx mandarina seems to have been preserved, while the perception of environmental odorants in both sexes of domesticated silkmoths has been degraded. In females, this physiological impairment was mirrored by a clear reduction in olfactory sensillum numbers. Neurophysiological experiments with hybrids between wild and domesticated silkmoths suggest that the female W sex chromosome, so far known to have the sole function of determining femaleness, might be involved in the detection of environmental odorants. Moreover, the coding of odorants in the brain, which is usually similar among closely related moths, differs strikingly between B. mori and B. mandarina females. These results indicate that domestication has had a strong impact on odour detection and processing in the olfactory model species B. mori.     

Capacity of Spirulina platensis to accumulate manganese and its distribution in cell

Effects of manganese salt (MnCl₂) on growth of Spirulina platensis and capacity of the cyanobacteria to accumulate the metal in various cell components were studied. S. platensis cells were shown to tolerate high concentrations of manganese and preserve, although strongly suppressed, the capacity to grow in the medium containing 5.1 mM MnCl₂. The concentrations of manganese that did not inhibit growth considerably altered cell ultrastructure and changed the protein profile. The accumulation of manganese in S. platensis cells was proportional to the period of culturing and manganese concentration in the medium, reaching a plateau at about 2.5 mM. A threshold intracellular concentration of this metal is estimated as 28 ± 3 μmol/g dry wt. The fractionation of the manganese-enriched biomass demonstrated that the major portion of intracellular manganese (over 90%) was found in the total protein fraction. The chromatographic separation of the soluble protein fraction showed that manganese was incorporated into proteins with molecular weight of 5 to 15 kD. Dry biomass adsorbed manganese cations; this evidence seems to indicate a considerable contribution of biosorption to manganese accumulation by S. platensis cells.     

Polymorphisms at the innate immune receptor TLR2 are associated with Borrelia infection in a wild rodent population

The discovery of the key role of Toll-like receptors (TLRs) in initiating innate immune responses and modulating adaptive immunity has revolutionized our understanding of vertebrate defence against pathogens. Yet, despite their central role in pathogen recognition and defence initiation, there is little information on how variation in TLRs influences disease susceptibility in natural populations. Here, we assessed the extent of naturally occurring polymorphisms at TLR2 in wild bank voles (Myodes glareolus) and tested for associations between TLR2 variants and infection with Borrelia afzelii, a common tick-transmitted pathogen in rodents and one of the causative agents of human Lyme disease. Bank voles in our population had 15 different TLR2 haplotypes (10 different haplotypes at the amino acid level), which grouped in three well-separated clusters. In a large-scale capture–mark–recapture study, we show that voles carrying TLR2 haplotypes of one particular cluster (TLR2_c2) were almost three times less likely to be Borrelia infected than animals carrying other haplotypes. Moreover, neutrality tests suggested that TLR2 has been under positive selection. This is, to our knowledge, the first demonstration of an association between TLR polymorphism and parasitism in wildlife, and a striking example that genetic variation at innate immune receptors can have a large impact on host resistance.     

Preparation and properties of 5′-nucleotidases from bovine milk fat globule membranes

The 5′-nucleotidase (5′-ribonucleoside phosphohydrolase, EC 3.1.3.5) from bovine milk fat globule membranes was partially purified. Two separate peaks of activity were obtained from a Sepharose column and the two fractions, designated V and VI in order of elution, were collected and characterized separately. Both V and VI exhibited pH optima between 7.0 and 7.5 for AMP, GMP and CMP in the absence of metal ions. In the presence of Mg²⁺, a second pH optimum at 10.0 was observed with both fractions. Low concentrations of MnCl₂ activated Fraction V but not Fraction VI. HgCl₂ was a potent inhibitor of both fractions. The relative rates of hydrolysis of various 5′-mononucleotides differed comparing the two fractions. Optimum temperature for P_i release was 69 °C for both fractions. Activation energies were 10 400 cal/mole and 9600 cal/mole for Fractions V and VI, respectively. For V, calculated K_m values for AMP, GMP and CMP were 0.94, 2.5 and 1.16 mM, respectively. Calculated K_m values for Fraction VI for AMP, GMP and CMP were 5.0, 3.95 and 1.73 mM, respectively. ATP was a competitive inhibitor of AMP hydrolysis by Fraction V and a noncompetitive inhibitor of AMP hydrolysis by Fraction VI. Both fractions contained chloroform-methanol-extractable phospholipid. The phospholipid distribution pattern of Fraction VI was similar to that of milk fat globule membranes. Fraction V contained only sphingomyelin and phosphatidylcholine. It is proposed that milk fat globule membranes contain two separate 5′-nucleotidases.     

Are silica defences in grasses driving vole population cycles?

Understanding the factors that drive species population dynamics is fundamental to biology. Cyclic populations of microtine rodents have been the most intensively studied to date, yet there remains great uncertainty over the mechanisms determining the dynamics of most of these populations. For one such population, we present preliminary evidence for a novel mechanism by which herbivore-induced reductions in plant quality alter herbivore life-history parameters and subsequent population growth. We tested the effect of high silica levels on the population growth and individual performance of voles (Microtus agrestis) reared on their winter food plant (Deschampsia caespitosa). In sites where the vole population density was high, silica levels in D. caespitosa leaves collected several months later were also high and vole populations subsequently declined; in sites where the vole densities were low, levels of silica were low and population density increased. High silica levels in their food reduced vole body mass by 0.5% a day. We argue that silica-based defences in grasses may play a key role in driving vole population cycles.     

Delayed dispersal in the Zaisan mole vole (Ellobius tancrei): helping or extended parental investment?

The highly social subterranean voles of genus Ellobius (mole vole) represent a unique model to compare with both social bathyergids and surface-dwelling voles. Unlike most arvicolines, mole voles display the prolonged obligatory delay of dispersal. In subterranean rodents, this delay may be associated with benefits of cooperation (weaned offspring help their parents), an extended parental investment (parents care for weaned offspring), or both. To identify the role offspring aged <3 months play in mole vole families, we estimated their contribution to important group activities. We found that juveniles contributed very little to daily living activities up to the age of approximately 2 months. The older offspring carried objects at least as frequently as breeders, but they engaged in gnawing obstacles less frequently than their fathers. Male breeders and non-breeders engaged in gnawing more than the respective categories of females. Although young mole voles clearly did not surpass their parents in performing the more energetically costly activities, they gained body mass by 26 g (130 %) between days 30 and 90, often surpassing their parents in weight. Based on our results, in E. tancrei an extremely prolonged infancy is followed by intensive building of body reserves. This ontogenetic trajectory appears to be distinct from the patterns described for social bathyergids and for most voles.     

The Olfactory System as a Model to Study Axonal Growth Patterns and Morphology In Vivo

The olfactory system has the unusual capacity to generate new neurons throughout the lifetime of an organism. Olfactory stem cells in the basal portion of the olfactory epithelium continuously give rise to new sensory neurons that extend their axons into the olfactory bulb, where they face the challenge to integrate into existing circuitry. Because of this particular feature, the olfactory system represents a unique opportunity to monitor axonal wiring and guidance, and to investigate synapse formation. Here we describe a procedure for in vivo labeling of sensory neurons and subsequent visualization of axons in the olfactory system of larvae of the amphibian Xenopus laevis. To stain sensory neurons in the olfactory organ we adopt the electroporation technique. In vivo electroporation is an established technique for delivering fluorophore-coupled dextrans or other macromolecules into living cells. Stained sensory neurons and their axonal processes can then be monitored in the living animal either using confocal laser-scanning or multiphoton microscopy. By reducing the number of labeled cells to few or single cells per animal, single axons can be tracked into the olfactory bulb and their morphological changes can be monitored over weeks by conducting series of in vivo time lapse imaging experiments. While the described protocol exemplifies the labeling and monitoring of olfactory sensory neurons, it can also be adopted to other cell types within the olfactory and other systems.     

Six1 is essential for early neurogenesis in the development of olfactory epithelium

The olfactory epithelium (OE) is derived from the olfactory placode (OP) during mouse development. At embryonic day (E) 10.0-E10.5, “early neurogenesis” occurs in the OE, which includes production of pioneer neurons that emigrate out of the OE and other early-differentiated neurons. Around E12.5, the OE becomes organized into mature pseudostratified epithelium and shows “established neurogenesis,” in which olfactory receptor neurons (ORNs) are differentiated from basal progenitors. Little is known about the molecular pathway of early neurogenesis. The homeodomain protein Six1 is expressed in all OP cells and neurogenic precursors in the OE. Here we show that early neurogenesis is severely disturbed despite the unaltered expression of Mash1 at E10.5 in the Six1-deficient mice (Six1^−/−). Expression levels of neurogenin1 (Ngn1) and NeuroD are reduced and those of Hes1 and Hes5 are augmented in the OE of Six1^−/− at E10.5. Pioneer neurons and cellular aggregates, which are derived from the OP/OE and situated in the mesenchyme between the OE and forebrain, are completely absent in Six1^−/−. Moreover, ORN axons and the gonadotropin-releasing hormone-positive neurons fail to extend and migrate to the forebrain, respectively. Our study indicates that Six1 plays critical roles in early neurogenesis by regulating Ngn1, NeuroD, Hes1, and Hes5.     

Distribution and parameters of genetic polymorphism in northern red-backed vole (<Emphasis Type="Italic">Clethrionomys rutilus</Emphasis>) and bank vole (<Emphasis Type="Italic">Clethrionomys glareolus</Emphasis>) in West Siberia

This article presents data on the genetic variability of the northern red-backed vole and the bank vole that live sympatrically in West Siberia. The two species of voles have comparable, relatively high indices of genetic variability of inter simple sequences repeats DNA. The proportion of polymorphic DNA markers is 95–98%, and the Nei’s genetic diversity index is 0.33–0.35. A total of 47–58% of allozyme loci in the voles are polymorphic, and the average heterozygosity per locus is 0.058 in the northern red-backed vole and 0.054 in the bank vole. Interpopulation differentiation is less pronounced in the red-backed vole (F _ST 0.293) compared to the bank vole (F _ST 0.475). Individuals of the hybrid line of the bank vole with the mitochondrial haplotype of the red-backed vole have been found by PCR typing of cytochrome b gene fragment of mtDNA. The distribution boundary of the hybrid line of bank voles goes farther to the northeast than was shown in earlier works. The proportion of hybrid specimens range from 2 to 34%. The indices of genetic variability in the hybrid line of the bank vole are lower than those of the parental species.     

A Single-fly Assay for Foraging Behavior in Drosophila

For many animals, hunger promotes changes in the olfactory system in a manner that facilitates the search for appropriate food sources. In this video article, we describe an automated assay to measure the effect of hunger or satiety on olfactory dependent food search behavior in the adult fruit fly Drosophila melanogaster. In a light-tight box illuminated by red light that is invisible to fruit flies, a camera linked to custom data acquisition software monitors the position of six flies simultaneously. Each fly is confined to walk in individual arenas containing a food odor at the center. The testing arenas rest on a porous floor that functions to prevent odor accumulation. Latency to locate the odor source, a metric that reflects olfactory sensitivity under different physiological states, is determined by software analysis. Here, we discuss the critical mechanics of running this behavioral paradigm and cover specific issues regarding fly loading, odor contamination, assay temperature, data quality, and statistical analysis.     

Trichosomoides nasalis (Nematoda: Trichinelloidea) in the murid host Arvicanthis niloticus: Migration to the epithelium of the nasal mucosa after intramuscular development

Knowledge of the biology of the trichinelloid subfamily Trichosomoidinae is poor. Trichosomoides nasalis is a common parasite of Arvicanthis niloticus (Muridae) in Senegal, and a procedure for experimental infections has been established. It has been demonstrated that larvae develop in striated muscle fibres, similar to Trichinella spp., but they are not arrested in the first stage, and they reach the adult stage within three weeks. In the present histological study it is shown that T. nasalis females and dwarf males migrate from the abdomen and thorax to the host’s muzzle, moving through connective tissues and between muscles. A few migrating specimens were also found in the blood vessels of the nasal mucosa. While sexes were still separated in the lamina propria of the mucosa, females recovered from the epithelium contained intra-uterine males. Worms were found between the incisors in the mucosa of the anterior and median conchae which are rich in mucous cells. Only the pseudostratified epithelium was parasitized. Under natural conditions, the inflammation of the nasal mucosa that is induced by the parasites might reduce the competitiveness of infected rodents when foraging or looking for potential mates.     

Regulation of Notch signaling and endocytosis by the Lgl neoplastic tumor suppressor

The evolutionarily conserved neoplastic tumor suppressor protein, Lethal (2) giant larvae (Lgl), plays roles in cell polarity and tissue growth via regulation of the Hippo pathway. In our recent study, we showed that in the developing Drosophila eye epithelium, depletion of Lgl leads to increased ligand-dependent Notch signaling. lgl mutant tissue also exhibits an accumulation of early endosomes, recycling endosomes, early-multivesicular body markers and acidic vesicles. We showed that elevated Notch signaling in lgl⁻ tissue can be rescued by feeding larvae the vesicle de-acidifying drug chloroquine, revealing that Lgl attenuates Notch signaling by limiting vesicle acidification. Strikingly, chloroquine also rescued the lgl⁻ overgrowth phenotype, suggesting that the Hippo pathway defects were also rescued. In this extraview, we provide additional data on the regulation of Notch signaling and endocytosis by Lgl, and discuss possible mechanisms by which Lgl depletion contributes to signaling pathway defects and tumorigenesis.     

黑斑蛙嗅器和犁鼻器的组化及超微结构特征

嗅感受器主要感知外界环境中化学信号分子.本文采用银染、NADPH-组化染色和电镜技术来观察黑斑侧褶蛙(Petophylax nigromaculatus)的嗅器和犁鼻器的功能差异及细胞组成.银染法可对嗅上皮和犁鼻上皮的细胞进行分类及区分.其中,支持细胞胞核深染成黑色,嗅细胞胞核银染为花斑状.细胞计数显示,犁鼻上皮的嗅神经细胞含量百分比显著高于嗅上皮.组化结果显示,黑斑侧褶蛙嗅上皮和犁鼻上皮对NADPH-d表达模式差异显著,前者表达明显高于后者.电镜结果显示,黑斑侧褶蛙嗅上皮和犁鼻上皮的支持细胞由两种类型的细胞组成,分别为纤毛型和颗粒型支持细胞.