bluuebunny/crossref_metadata_2025 huggingface dataset:
Population subdivision in westslope cutthroat trout (Oncorhynchus clarki lewisi) at the northern periphery of its range: evolutionary inferences and conservation implications
Authors: Taylor E. B. , Stamford M. D. , Baxter J. S.
Published: September 2003

Westslope cutthroat trout (Oncorhynchus clarki lewisi, Salmonidae) are native to the upper Columbia, Missouri, and South Saskatchewan river drainages of western North America and are at the northern periphery of their range in southeastern British Columbia, Canada. We examined geographical variation in allele frequencies at eight microsatellite loci in 36 samples of westslope cutthroat trout from British Columbia to assess levels of population subdivision and to test the hypothesis that different habitat types (principally mainstem vs. above migration barrier habitats) would influence levels of genetic diversity, genetic divergence among populations, and attainment of equilibrium between gene flow and genetic drift. Across all samples, the mean number of alleles per locus was 3.9 and mean expected heterozygosity was 0.56. Population subdivision was extensive with an overallFst(θ) of 0.32. Populations sampled above migration barriers had significantly fewer alleles, lower expected heterozygosity, but greater average pairwiseFstthan populations sampled from mainstem localities. We found evidence for isolation‐by‐distance from a significant correlation between genetic distance and geographical distance (r = 0.31), but the pattern was much stronger (r = 0.51) when above barrier populations and a population that may have been involved in headwater exchanges were removed. By contrast, isolation‐by‐distance was not observed when only above barrier populations were tested among themselves. Our data support the maintenance of separate demographic management strategies for westslope cutthroat trout inhabiting different river systems and illustrate how differing habitat structure (e.g. presence of migration barriers) may influence patterns of biodiversity and gene flow‐drift equilibrium.
Colony and population genetic structure of the Formosan subterranean termite, Coptotermes formosanus, in Japan
Authors: Vargo Edward L. , Husseneder Claudia , Grace J. Kenneth
Published: September 2003

Subterranean termites have unusual plasticity in their breeding systems. As a result of their cryptic foraging and nesting habits, detailed information on the numbers and types of reproductive individuals in colonies has been difficult to obtain. In this study, we used microsatellite markers to infer the major features of the breeding system of the Formosan subterranean termite, Coptotermes formosanus, in southern Japan, where it is believed to have been introduced from China. A total of 30 colonies was sampled from two islands (Kyushu and Fukue) located 100 km apart. Twenty workers from each colony were genotyped at six microsatellite loci. Analysis of worker genotypes within colonies indicated that 27 colonies (90%) were simple (Mendelian) families. The remaining three colonies, all from Kyushu, were consistent with being extended families having begun as simple families but being currently headed by multiple neotenic (secondary) reproductives descended from the original king and queen. Workers from simple families in both populations were significantly inbred (FIT = 0.10 for Kyushu and 0.46 for Fukue) and highly related to their nestmates (coefficient of relatedness, r = 0.59 for Kyushu and 0.77 for Fukue), suggesting that many simple‐family colonies were headed by closely related reproductives, especially in the Fukue population. This conclusion is supported by the high coefficient of relatedness between nestmate reproductives in simple‐family colonies (r = 0.23 for Kyushu and 0.61 for Fukue) based on genotypes inferred from their worker offspring. There was moderate genetic differentiation (FST = 0.12) between the two populations, suggesting rather restricted gene flow between them. There was no significant isolation by distance among colonies, as might be expected given the limited dispersal of reproductives, presumably because of the frequent movement of colonies by humans. Finally, there was no evidence of a recent bottleneck, a finding possibly consistent with the more than 300‐year history of this species in Japan.
Genetic distinction of wildcat (Felis silvestris) populations in Europe, and hybridization with domestic cats in Hungary
Authors: Pierpaoli M. , Birò Z. S. , Herrmann M. , Hupe K. , Fernandes M. , Ragni B. , Szemethy L. , Randi E.
Published: September 2003

The genetic integrity and evolutionary persistence of declining wildcat populations are threatened by crossbreeding with widespread free‐living domestic cats. Here we use allelic variation at 12 microsatellite loci to describe genetic variation in 336 cats sampled from nine European countries. Cats were identified as European wildcats (Felis silvestris silvestris), Sardinian wildcats (F. s. libyca) and domestic cats (F. s. catus), according to phenotypic traits, geographical locations and independently of any genetic information. Genetic variability was significantly partitioned among taxonomic groups (FST = 0.11; RST = 0.41; P < 0.001) and sampling locations (FST = 0.07; RST = 0.06; P < 0.001), suggesting that wild and domestic cats are subdivided into distinct gene pools in Europe. Multivariate and Bayesian clustering of individual genotypes also showed evidence of distinct cat groups, congruent with current taxonomy, and suggesting geographical population structuring. Admixture analyses identified cryptic hybrids among wildcats in Portugal, Italy and Bulgaria, and evidenced instances of extensive hybridization between wild and domestic cats sampled in Hungary. Cats in Hungary include a composite assemblage of variable phenotypes and genotypes, which, as previously documented in Scotland, might originate from long lasting hybridization and introgression. A number of historical, demographic and ecological conditions can lead to extensive crossbreeding between wild and domestic cats, thus threatening the genetic integrity of wildcat populations in Europe.
Phylogeography of the coronulid barnacle, Chelonibia testudinaria, from loggerhead sea turtles, Caretta caretta
Authors: Rawson P. D. , Macnamee R. , Frick M. G. , Williams K. L.
Published: September 2003

The barnacle, Chelonibia testudinaria, is a common inhabitant of the marine turtle epibiont community and plays a key role in the development of this community. Phylogeographic analysis of 79 cytochrome c oxidase I (COX1) sequences for barnacles collected from five populations found contrasting patterns of divergence for populations in the Atlantic vs. the Pacific Ocean. Our analysis indicates that the two Pacific populations, Senri Beach, Japan and Bahia Magdalena, Mexico, were not only highly divergent from the Atlantic populations but are highly divergent from one another. We suggest that barnacles from these populations may represent cryptic species. In contrast, sequence divergence was greatly reduced among barnacles collected from Wassaw Island, GA, USA, Keewaydin, FL, USA, and Kyparissia, Pèloponnésus Island, Greece. A reduction in sequence diversity at the latter site was attributed to a recent range expansion into the Mediterranean Sea. We examined historical patterns of migration among the three Atlantic and Mediterranean populations using the program migrate. This analysis indicates a high rate of migration from Keewaydin to Wassaw Island, contrasted with a much lower rate of migration in the opposite direction. The estimated migration rate from Kyparissia to Keewaydin was also non‐negligible. We suggest that the association between C. testudinaria and loggerhead turtles and the patterns of turtle migration have played key roles in the expansion of the range of C. testudinaria into the Mediterranean Sea and the subsequent patterns of barnacle migration. We further propose that the difference between ocean basins, with respect to the impact of host migration on barnacle gene flow, probably stems from the fact that host‐mediated dispersal in the Atlantic depends on advanced stage juveniles and adults while any host‐mediated dispersal in the Pacific would have to involve early ‘pelagic’ stage juvenile loggerheads.
Cryptic species and morphological plasticity in long‐lived bivalves (Unionoida: Hyriidae) from inland Australia
Authors: Baker Andrew M. , Bartlett Chris , Bunn Stuart E. , Goudkamp Katrina , Sheldon Fran , Hughes Jane M.
Published: September 2003

Molecular (mitochondrial DNA, isozyme) and morphological diversity of freshwater mussels (Family Hyriidae) was examined at 21 sites encompassing four large river systems, across southwest Queensland, Australia. Evidence was found for two major morphological groups. One group, which occurred in every river system, closely matched a recognized species (Velesunio ambiguus) both morphologically and in a well‐supported lineage within a mitochondrial phylogeny generated from partial cytochrome c oxidase subunit I (COI) sequences. The second group most closely matched Velesunio wilsonii in shell morphology but formed three deeply divergent mitochondrial DNA lineages. All four lineages occurred sympatrically in some areas and displayed corresponding fixed differences at nuclear allozyme loci, which suggests an absence of recent hybridization and the presence of separate species.
A hybrid zone dominated by fertile F1s: maintenance of species barriers inRhododendron
Authors: Milne R. I. , Terzioglu S. , Abbott R. J.
Published: September 2003

Isolating barriers between interbreeding sympatric or parapatric interfertile species are maintained by processes that occur within their hybrid zones. Although the effects of intrinsic selection on hybrid fitness are well known, less is understood about extrinsic fitness variation. At Tiryal Dag, northeast Turkey,Rhododendron×sochadzeae(R. ponticum×caucasicum) forms large populations in which neither segregation nor backcrossing occur, in habitats intermediate between those of its parents. Using single‐copy species‐specific random amplified polymorphic DNA and inter simple sequence repeat markers, it was determined that most or allR.×sochadzeaeplants are F1s, and that there are many separate genets present. Hand pollination and germination experiments showed thatR.×sochadzeaeplants can produce viable seed of F2s or backcrosses in either direction. Furthermore, adult backcrosses have been observed in habitats atypical forR.×sochadzeae. From this, all non‐F1hybrid derivatives appear to be eliminated in the hybrid zone at Tiryal Dag as a result of postgermination selection. This absence of post‐F1hybrid derivatives apparently prevents introgression. This type of hybrid population is here termed an F1‐dominated hybrid zone (F1DZ), and also occurs inEncelia. The observed dominance of F1s within a narrow habitat range is best explained by habitat‐mediated superiority of F1s over all other genotype classes. Therefore, habitat‐mediated selection against the second hybrid generation might be preventing interspecific gene flow inR.×sochadzeae. F1DZ formation is postulated to require the formation of F1s in quantity, habitat‐mediated superiority in F1s, and highly specific habitat conditions.
Ecological and morphological differentiation among cryptic evolutionary lineages in freshwater limpets of the nominal form‐group Ancylus fluviatilis (O.F. Müller, 1774)
Authors: Pfenninger Markus , Staubach Sid , Albrecht Christian , Streit Bruno , Schwenk Klaus
Published: September 2003

The phylogeny and potential mode of speciation of the river limpet Ancylus fluviatilis (Basommatophora) was examined using mitochondrial DNA sequences from 16S ribosomal RNA, cytochrome c oxidase subunit I (COI) and nuclear DNA from internal transcribed spacer (ITS‐1) regions from 103 populations across Europe. Four highly divergent lineages were observed within Ancylus. Clade 1, representing the nominal taxon Ancylus fluviatilis (O.F. Müller, 1774), is mainly found in central and northern Europe, Clade 2 is present in a single Portuguese population, Clade 3 is distributed on the Canary islands, North Africa and the eastern Mediterranean region, whereas Clade 4 inhabits the Northern Mediterranean coasts. Phylogenetic analyses revealed an overall consistent topology of nuclear and mitochondrial gene trees. Based on a molecular clock, we estimated that the basic radiation occurred in the late Pliocene. Although clades differ significantly in size independent shell shape, morphological differentiation of lineages is not feasible without genetic data. Environmental data related to climate (precipitation, temperature, etc.) showed a significant differentiation of clades. Clade 1 dwells in relatively colder and more stable habitats than Clades 3 and 4, whose habitats in turn differ in a low or high amount of precipitation during spring and autumn, respectively. Based on the combined data sets on mitochondrial DNA, nuclear DNA, morphological and ecological differentiation, we conclude that Ancylus represents a cryptic species complex of reproductively and genetically isolated lineages. In addition, the joint analysis suggests that ecological speciation is probable to explain current patterns.
Phylogeography of shy and white‐capped albatrosses inferred from mitochondrial DNA sequences: implications for population history and taxonomy
Authors: Abbott Cathryn L. , Double Michael C.
Published: September 2003

The evolutionary relationship between shy (Thalassarche cauta) and white‐capped (T. steadi) albatrosses was examined using mitochondrial control region sequences. Results were interpreted in the context of a recent and contentious taxonomic revision that recommended full species status for shy and white‐capped albatrosses. Low sequence divergence between shy and white‐capped albatrosses (1.8%) and between their close relatives, Salvin's and Chatham albatrosses (2.9%), was observed. Much higher sequence divergence was found between the shy/white‐capped pair and the Salvin’s/Chatham pair (7.0%). Phylogenetic analyses confirmed the separation of the shy/white‐capped pair from the Salvin’s/Chatham pair but did not provide species‐level resolution. Phylogeographic analyses, including a nested clade analysis, FST estimates and an analysis of molecular variance, indicated unambiguous genetic structuring between shy and white‐capped albatrosses, thus confirming the demographic isolation of the species, but showed little to no structuring within each species. The geographical distribution of mtDNA haplotypes and other evidence suggest that shy albatrosses arose through range expansion by white‐capped albatrosses.
Genetic and behavioural estimates of reproductive skew in male fallow deer
Authors: Say L. , Naulty F. , Hayden T. J.
Published: September 2003

Populations of fallow deer, in general, have low genetic diversity. Nevertheless, we screened 39 microsatellite loci and identified 20 that were polymorphic and suitable to determine paternity of fallow deer. To date, paternity has been studied for 87, 110 and 152 fallow deer fawns born between 2000 and 2002. Our results confirm the existence of a strong polygynous mating system in our population and confirm that the number of copulations performed by males is globally a good estimator of their reproductive success: males which performed the largest proportion of matings fathered the largest proportion of fawns. Nevertheless, we report some differences between the two measurements of the males’ reproductive success: measures of copulatory success underestimated the variance of the males’ reproductive success. On average, males whose copulatory score exceeded their paternity had mated with a higher proportion of younger females. Young females may be more likely to lose the conceptus, or their offspring may suffer high postnatal mortality.
Coevolution between slave‐making ants and their hosts: host specificity and geographical variation
Authors: Blatrix R. , Herbers J. M.
Published: September 2003

We explored the impact of a slave‐making ant, Protomognathus americanus, on two of its hosts, Leptothorax longispinosus and L. ambiguus. We showed that, on average, slave‐maker colonies conduct raids on 2.7 L. longispinosus and 1.4 L. ambiguus nests in a single year. The more common host, L. longispinosus, survives raiding and colony‐founding events in a third of the cases, but the less common host rarely survives attacks from the slave‐makers. We compare our results, collected in Vermont, to a study conducted in New York where the slave‐maker pressure is much stronger. Our results suggest that in Vermont the slave‐maker has a sparing strategy when raiding L. longispinosus, but not when raiding L. ambiguus. Thus coevolution between slave‐making ants and their hosts shows host specificity and geographical variation.
Mitochondrial DNA sequences reveal extensive cryptic diversity within a western American springsnail
Authors: Liu Hsiu‐Ping , Hershler Robert , Clift Kayla
Published: September 2003

We analysed cytochrome c oxidase subunit I and NADH dehydrogenase subunit I sequence variation among 29 populations of a widely ranging southwestern springsnail (Pyrgulopsis micrococcus) and 18 regional congeners. Cladistic analyses of these sequences depict P. micrococcus as a polyphyletic composite of five well‐supported clades. Sequence divergences among these clades and subclades imply the possible occurrence of as many as seven or eight cryptic species in addition to P. micrococcus. Our finding that P. micrococcus contains multiple, genetically distinct and geographically restricted lineages suggests that diversification within this highly speciose aquatic genus has been structured in large part by the operation of terrestrial barriers to gene flow. However, these sequence data also indicate that recent dispersal among hydrographically separated areas has occurred within one of these lineages, which we attribute to passive transport on migratory waterbirds.
Cryptic population structure in a large, mobile mammalian predator: the Scandinavian lynx
Authors: Rueness E. K. , Jorde P. E. , Hellborg L. , Stenseth N. C. , Ellegren H. , Jakobsen K. S.
Published: September 2003

The Eurasian lynx (Lynx lynx) is an example of a species that has gone through a severe bottleneck, leading to near extinction in Scandinavia around 1930 — a pattern shared with several other large carnivorous mammals. Here we extend previous genetic analyses of northern European lynx, confirming that lynx from the Scandinavian Peninsula represent a distinct clade differing clearly from European conspecifics. Furthermore, and despite a recent bottleneck and subsequent range expansion, we detect marked genetic differentiation within Scandinavia. This differentiation is largely manifested as a north–south gradient, with a linear increase in the quantity FST/(1 − FST). Aided by computer simulations we find that this pattern is unlikely to have arisen by random genetic drift in the short time since lynx started to expand in the 1950s, suggesting that the spatial structure may predate the bottleneck. Individual‐based analyses indicate that, instead of a continuous gradient, Scandinavian lynx may be structured into three more or less distinct groups, possibly corresponding to northern, central and southern subpopulations. The presence of such structuring was unknown previously and was unexpected from general considerations on the mobility of the species, historical data and the absence of geographical barriers. Our study demonstrates how molecular markers may be used to detect cryptic population structure, invisible using traditional methods.
Gene flow and population history in high dispersal marine invertebrates: mitochondrial DNA analysis ofHolothuria nobilis(Echinodermata: Holothuroidea) populations from the Indo‐Pacific
Authors: Uthicke S. , Benzie J. A. H.
Published: September 2003

The sea cucumber,Holothuria nobilis, has a long‐lived planktotrophic larvae, and previous allozyme surveys have suggested that high dispersal is realized. In contrast, recent ecological studies indicate that dispersal is low. To reconcile these data, and to investigate the evolution of this Indo‐Pacific species, we screened geographical variation in 559 bp of a mitochondrial gene (COI) in 360 samples from the Australasian region and La Réunion. Sequences from La Réunion differed by > 7% from others and may constitute another species. Haplotype diversity in other samples was high (0.942, SD = 0.007), but haplotypes were closely related (mean nucleotide diversity: 0.0075, SD = 0.0041).amova, pairwiseFSTvalues and exact tests did not detect significant population structure. Nested clade analysis showed that one of two main clades was over‐represented in west Australia, whereas the other was more common in the northern Great Barrier Reef. Isolation‐by‐distance was identified as the main determinant of population structure at several clade levels. Contiguous range expansion was inferred for evolutionary older clade levels and this may correspond to a late Pleistocene (88 000–193 000 years ago) population expansion inferred from haplotype mismatch distributions. Thus, the population genetic structures detected are likely to be formed prior to the last ice age, with some indications for high dispersal on shorter time scales.
Genetics of colonization inHypochaeris tenuifolia(Asteraceae, Lactuceae) on Volcán Lonquimay, Chile
Authors: Tremetsberger K. , Stuessy T. F. , Samuel R. M. , Baeza C. M. , Fay M. F.
Published: September 2003

Understanding the genetics of colonizing populations has been, and continues to remain, an important focus in evolutionary biology. Different theoretical models predict varying levels of genetic variation in colonizing populations depending upon strength of founder effect, gene flow and rate of population growth and immigration following colonization. We analyse overall genetic variation using amplified fragment length polymorphism markers in colonizing populations ofHypochaeris tenuifolia(Asteraceae) in the southern Andes. Volcán Lonquimay newly erupted on 25 December 1988, producing a side cone, La Navidad, and sent lava and ash into surrounding areas. Many domesticated animals (estimated at 10 000) and many natural plant populations were destroyed. Into this new open habitat have come immigrant populations of several angiosperm species, most conspicuouslyH. tenuifoliathat forms leaf rosettes with flowering scapes to 15 cm and orange–yellow heads 1–2 cm in diameter. Genetic diversity in five founder populations in the eruption zone is compared with that from five nearby survivor populations, as well as with eight isolated northern and four southern populations from throughout the entire range of the species in Chile. Results from 477 individuals representing 447 different multilocus phenotypes, yielded 170 DNA fragments of which 144 (85%) were polymorphic. Genetic diversity within founder populations is neither lower than in survivor populations nor in isolated populations throughout the range of the species, but it is lower among founder populations than among other populations immediately and distantly outside the zone of disturbance. Closest genetic similarity occurs between founders and nearby survivor populations as well as those in adjacent southern regions.
Genetic analysis of spatial foraging patterns and resource sharing in bumble bee pollinators
Authors: Chapman R. E. , Wang J. , Bourke A. F. G.
Published: September 2003

Conservation biologists, evolutionary ecologists and agricultural biologists require an improved understanding of how pollinators utilize space and share resources. Using microsatellite markers, we conducted a genetic analysis of space use and resource sharing at several spatial scales among workers of two ecologically dissimilar bumble bee species (Bombus terrestris and B. pascuorum) foraging in an urban landscape (London, UK). At fine scales, the relatedness of workers visiting small patches of flowers did not differ significantly from zero. Therefore, colonies shared flower patches randomly with other colonies, suggesting that worker scent‐marks deterring visits to unrewarding flowers have not evolved as signals benefiting nestmates. To investigate space use at intermediate scales, we developed a program based on Thomas & Hill's maximum likelihood sibship reconstruction method to estimate the number of colonies utilizing single sites. The average number of colonies (95% confidence limits) sending workers to forage at sites of ≈ 1 ha in area was 96 colonies (84–118) in B. terrestris and 66 colonies (61–76) in B. pascuorum. These values are surprisingly high and suggested that workers travelled far from their colonies to visit the sites. At the landscape scale, there was little or no genetic differentiation between sites. We conclude that urban habitats support large bumble bee populations and are potentially valuable in terms of bumble bee conservation. In addition, bumble bee‐mediated gene flow in plants is likely to occur over large distances and plant–bumble bee conservation requires landscape‐scale action.
Fine‐scale phylogeographical analysis of Mediterranean Anacamptis palustris (Orchidaceae) populations based on chloroplast minisatellite and microsatellite variation
Authors: Cozzolino S. , Cafasso D. , Pellegrino G. , Musacchio A. , Widmer A.
Published: September 2003

The phylogeographical history of the rare marsh orchid Anacamptis palustris (Orchidaceae) was reconstructed using highly polymorphic chloroplast minisatellite and microsatellite loci. Allelic variation at chloroplast microsatellite loci was due to length variation in poly(A/T) repeats and was informative on a regional scale, but was not sufficient to unravel relationships among populations on a local geographical scale. The minisatellite locus, however, was found to be highly variable. Nine distinct repeat types were found and variation in repeat number occurred in five repeat types. The distribution of chloroplast haplotypes, combining microsatellite and minisatellite repeat type variation, provided a clear phylogeographical picture on a large geographical scale, whereas length variation in one highly polymorphic minisatellite repeat type provided fine‐scale phylogeographical information. Mediterranean populations could be divided into four main lineages, a western European lineage, a northern and central Italian lineage, a well‐isolated southern Italian (Apulian) lineage, and an eastern European lineage. Variation at the most variable minisatellite repeat type N revealed 19 alleles and allowed the study of seed‐mediated gene flow and an estimation of the ratio of pollen to seed flow among neighbouring populations.
Is there a common mechanism of gastrointestinal nematode expulsion?
Authors: Lawrence Catherine E.
Published: September 2003

Parasitic gastrointestinal (GI) nematodes are one of the most commonly acquired infections in the world. Although they cause relatively little mortality, infections result in high levels of morbidity that can result in developmental consequences in infected children and cause significant economic loss in infected animals. Over the last 30 years there has been extensive research into the mechanisms controlling the expulsion of gastrointestinal nematodes. Although many of the effector mechanisms that contribute to the loss of the parasite have been defined, we still appear to be some way from understanding the actual cause of parasite loss. Part of this stems from the different responses induced by different gastrointestinal parasites. It is clear that a Th2 response is essential for the expulsion of GI helminths; however, each of the characteristic immunological effector mechanisms induced following infection with these parasites may not be required or may be insufficient in isolation, but together they operate to expel GI helminths. These responses then succeed more efficiently in some cases than in others to induce parasite expulsion. The contribution made by various effector mechanisms to the expulsion of these parasites may therefore be a reflection of both the niche which the parasite inhabits as well as possible evasive/suppressive mechanisms employed by the parasites. In this review the various aspects of parasite expulsion will be described and the controversial issues in the field will be discussed.
Progress and new technologies for developing vaccines against gastrointestinal nematode parasites of sheep
Authors: Newton S. E. , Meeusen E. N. T.
Published: September 2003

Despite the identification of highly effective native antigens for vaccination against Haemonchus contortus, particularly ‘hidden’ antigens derived from the intestine of adult worms, to date similar efficacy has not been shown with recombinant antigens. In addition, progress towards identification of protective antigens from other sheep gastrointestinal (GI) nematode species is limited. Coupled with this is an incomplete understanding of the mechanism of natural immunity to GI nematodes, making selection of appropriate immunization strategies and adjuvants for evaluation of candidate ‘natural’ antigens problematic. The current explosion in new high‐throughput technologies, arising from human studies, for analysis of the genome, transcriptome, proteome and glycome offers the opportunity to gain a better understanding of the molecular pathways underlying pathogen biology, the host immune system and the host–pathogen interaction. An overview is provided on how these technologies can be applied to parasite research and how they may aid in overcoming some of the current problems in development of commercial vaccines against GI nematode parasites.
The mucosal immune system
Authors: MacDonald Thomas T.
Published: September 2003

This article outlines the lymphoid structures and cell types important in the intestinal immune response. Particular attention is paid to differences between rodents and man where there appears to be fundamental differences in the sources of the T and B cells which populate the mucosa. The majority of the data still suggest that Peyer's patches are the inductive site of mucosal immunity and the mucosa (lamina propria and epithelium) is the effector site, but there is growing realization that mucosal immune responses can occur in the absence of Peyer's patches and that antigen sampling may also occur in the lamina propria.
Mucosal defences against Giardia
Authors: Eckmann Lars
Published: September 2003

Giardia lamblia (syn. G. duodenalis or G. intestinalis), the causative agent of giardiasis, is one of the most common causes worldwide of intestinal infections in humans. Symptomatic infection is characterized by diarrhoea, epigastric pain, nausea, vomiting, and weight loss, yet many infections are asymptomatic. The protozoan, unicellular parasite resides in the lumen and attaches to the epithelium and overlying mucus layers but does not invade the mucosa and causes little or no mucosal inflammation. Giardiasis is normally transient, indicating the existence of effective host defences, although re‐infections can occur, which may be related to differences in infecting parasites and/or incomplete immune protection. Mucosal defences against Giardia must act in the small intestinal lumen in the absence of induction by classical inflammatory mediators. Secretory IgA antibodies have a central role in anti‐giardial defence. B cell‐independent mechanisms also exist and can contribute to eradication of the parasite, although their identity and physiological importance are poorly understood currently. Possible candidates are nitric oxide, antimicrobial peptides such as Paneth cell α‐defensins, and lactoferrin. Elucidation of the key anti‐giardial effector mechanisms will be important for selecting the best adjuvants in the rational development of vaccination strategies against Giardia.
The SCARECROW gene's role in asymmetric cell divisions in rice plants
Authors: Kamiya Noriko , Itoh Jun‐Ichi , Morikami Atsushi , Nagato Yasuo , Matsuoka Makoto
Published: September 2003

Asymmetric cell division is one of the most important mechanisms in the diversification of cell function and fate. In Arabidopsis, SCARECROW (SCR) is essential for the asymmetric division of the cortex/endodermis progenitor cell in the root. To learn more about how SCR is involved in asymmetric division, we analyzed the rice SCR (OsSCR) expression. In the root tip, OsSCR expression was observed in the endodermal cell layer and downregulated in the daughter cortex cell after asymmetric division, just as with Arabidopsis SCR. In leaf primordia, expression of OsSCR was observed in stomatal and ligule formation. In stomatal development, OsSCR was specifically expressed in the stomatal cell files before formation of guard mother cells (GMCs), and then, its expression was localized in GMCs, when the first asymmetric division occurred to generate the GMCs. Before the second asymmetric division of subsidiary mother cells (SMCs), localized OsSCR expression was observed in SMCs in the area close to the GMCs. Before these asymmetric divisions, the localization of OsSCR mRNA in GMC‐forming cells and SMCs was observed in the area of the daughter GMC and subsidiary cells. OsSCR expression was also observed in the initiation area of ligule formation, and its downregulation occurred in the inner L2 cells generated by asymmetric division. Based on these observations, we proposed that OsSCR is involved not only in the asymmetric division of the cortex/endodermis progenitor cell but also during stomata and ligule formation by establishing the polarization of cytoplasm.
Killing cancer cells by poly‐drug elevation of ceramide levels
Authors: Radin Norman S.
Published: September 2003

Many papers have shown that sphingolipids control the balance in cells between growth and proliferation, and cell death by apoptosis. Sphingosine‐1‐phosphate (Sph1P) and glucosylceramide (GlcCer) induce proliferation processes, and ceramide (Cer), a metabolic intermediate between the two, induces apoptosis. In cancers, the balance seems to have come undone and it should be possible to kill the cells by enhancing the processes that lead to ceramide accumulation. The two control systems are intertwined, modulated by a variety of agents affecting the activities of the enzymes in Cer‐GlcCer‐Sph1P interdependence. It is proposed that successful cancer chemotherapy requires the use of many agents to elevate ceramide levels adequately. This review updates current knowledge of sphingolipid metabolism and some of the evidence showing that ceramide plays a causal role in apoptosis induction, as well as a chemotherapeutic agent.
Characterization of a triplex DNA‐binding protein encoded by an alternative reading frame of loricrin
Authors: Ciotti Paola , Van Dyke Michael W , Bianchi‐Scarrà Giovanna , Musso Marco
Published: September 2003

In an attempt to identify genes encoding triple‐helical DNA‐binding proteins, we performed South‐Western screening of a human keratinocyte cDNA expression library using a purine (Pu)‐rich triplex DNA probe. We isolated two independent clones containing part of the loricrin gene. Both were translated with a different reading frame than that of the loricrin protein, the major component of the cell envelope during normal keratinocyte cornification. The affinity of the encoded polypeptide for Pu‐triplex DNA was confirmed by electrophoretic mobility shift assays using a bacterially expressed N‐terminal loricrin deletion fused with the maltose‐binding protein (MBP–LOR3ARF). Interactions between Pu‐triplex DNA and MBP–LOR3ARF are characterized by a distribution of four increasingly slower mobility complexes, suggesting that multiple MBP–LOR3ARF molecules can recognize a single triplex. Binding was also observed between MBP–LOR3ARF and a pyrimidine‐motif triplex DNA, although at lower affinity than Pu‐triplex DNA. No apparent binding was observed between MBP–LOR3ARF and double‐stranded DNA, suggesting that MBP–LOR3ARF is a bona fide Pu‐triplex binding protein. Finally, purified specific rabbit antibodies against LORARF detected four human proteins with apparent molecular masses of 210, 110, 68, and 66 kDa on Western blot analysis. The 210‐, 110‐, and 68‐kDa proteins also showed specific Pu‐triplex DNA binding in a South‐Western experiment, suggesting that LORARF shares common domains with other human Pu‐triplex DNA‐binding proteins.
Self‐oligomerization and protein aggregation of α‐synuclein in the presence of Coomassie Brilliant Blue
Authors: Lee Daekyun , Lee Eun‐Kyung , Lee Ju‐Hyun , Chang Chung‐Soon , Paik Seung R.
Published: September 2003

α‐Synuclein has been implicated in various neurodegenerative disorders, including Parkinson's and Alzheimer's diseases, by its participation in abnormal protein depositions. As the protein has been suggested to play a significant role in the formation of the deposits which might be responsible for neurodegeneration, there is a strong demand to screen for α‐synuclein‐interactive small molecules. In this report, Coomassie Brilliant Blue (CBB) interaction of α‐synuclein has been investigated with respect to induction of protein self‐oligomerization in the presence of the chemical coupling reagentN‐(ethoxycarbonyl)‐2‐ethoxy‐1,2‐dihydroquinoline. Both CBB‐G and CBB‐R, which differ by only two methyl groups, induced the self‐oligomerization of α‐synuclein in a biphasic manner with optimal dye concentrations of 250 µmand 150 µm, respectively. The protein aggregates of α‐synuclein induced by the dyes in the absence of the coupling reagent were analysed by electron microscopy. Whereas CBB‐G induced formation of protein aggregates with a worm‐like structure, CBB‐R induced clear fibrilization of α‐synuclein on a background of granular structures. CBB‐R interacted with α‐synuclein approximately twice as effectively as CBB‐G (dissociation constants 0.63 µmand 1.37 µm, respectively). These dye interactions were independent from the acidic C‐terminus of α‐synuclein, which was reminiscent of the Αβ25–35 interaction of α‐synuclein. However, the metal‐catalysed oxidative self‐oligomerization of α‐synuclein in the presence of Cu2+/H2O2, which was augmented synergistically by Αβ25–35, was not affected by the dyes. This indicates that the dye binding site is also distinctive from the Αβ25–35 interaction site on α‐synuclein. These biochemically specific interactions between α‐synuclein and the dyes indicate that α‐synuclein‐interactive small molecules could provide a tool with which to approach development of diagnostic, preventive, or therapeutic strategies for various α‐synuclein‐related neurodegenerative disorders.
Differential functional relevance of a plasma membrane ganglioside sialidase in cholinergic and adrenergic neuroblastoma cell lines
Authors: von Reitzenstein Carolina , Kopitz Jürgen , Schuhmann Vera , Cantz Michael
Published: September 2003

Gangliosides located in the outer leaflet of the plasma membrane are important modulators of cellular functions. Our previous work has shown that in cultured human SK‐N‐MC neuroblastoma cells a sialidase residing in the same membrane selectively desialylates gangliosides with terminal sialic acid residues, causing a shift from higher species to GM1 and a conversion of GM3 to lactosylceramide. Inhibition of this sialidase by 2‐deoxy‐2,3‐dehydro‐N‐acetylneuraminic acid (NeuAc2en) resulted in increased cell proliferation and a loss of differentiation markers. In this study, we examined the occurrence and function of this ganglioside sialidase in other neuronal cells. Subcellular fractionation showed the sialidase to be located in the plasma membrane of all cell lines studied. The presence of the inhibitor NeuAc2en led to a profound decrease in the amount of the differentiation marker 200 kDa/70 kDa neurofilaments and an increase in cell proliferation in the cholinergic SK‐N‐MC and mixed cholinergic/adrenergic SK‐N‐FI and SK‐N‐DZ neuroblastoma lines, but had little or no effect in the human adrenergic SK‐N‐SH and SK‐N‐AS and the adrenergic/cholinergic PC12 cells from rat. The influence of the inhibitor on cell behaviour was paralleled by a diminished number of cholera toxin B‐binding GM1 sites. The findings demonstrate that the plasma membrane ganglioside sialidase is an important element of proliferation and differentiation control in some, but not all, neuroblastoma cells and suggest that there might be a relationship between plasma membrane sialidase activity and cholinergic differentiation.
Mannosylerythritol lipid induces characteristics of neuronal differentiation in PC12 cells through an ERK‐related signal cascade
Authors: Wakamatsu Yoko , Zhao Xiaoxian , Jin Chuyuan , Day Noel , Shibahara Miki , Nomura Nobuhiko , Nakahara Tadaatsu , Murata Takehide , Yokoyama Kazunari K.
Published: September 2003

Rat pheochromocytoma PC12 cells undergo neuronal differentiation in response to nerve growth factor (NGF). The differentiation involves protein kinase cascades that include the kinases MEK and ERK, as well as activation of the transcription factors c‐Jun and c‐Fos. We show here, that exposure of PC12 cells to mannosylerythritol lipid (MEL), a yeast extracellular glycolipid, enhances the activity of acetylcholinesterase and interrupts the cell cycle at the G1 phase, with resulting outgrowth of neurites and partial cellular differentiation. Treatment with MEL stimulates the phosphorylation of ERK to a similar extent as treatment with NGF, although, the appearance of phosphorylated ERK is somewhat delayed. Both the MEL‐induced outgrowth of neurites and the increase in the activity of acetylcholinesterase are prevented by PD98059, a specific inhibitor of MEK. Northern blotting analysis of c‐jun transcripts and analysis of transcription in PC12 cells of a c‐jun/CAT reporter construct demonstrated a significant increase in the rate of transcription of the c‐jun gene upon treatment with MEL. The sequence elements required for the MEL‐mediated activation of transcription of the c‐jun gene are located between nucleotides −126 and −79 in the 5′ flanking region. Our results suggest that MEL induces characteristics of neuronal differentiation in PC12 cells, with transactivation of the c‐jun gene, via an ERK‐related signal cascade that is partially overlapping the pathways activated in response to NGF. These results might provide the groundwork for the use of microbial extracellular glycolipids as novel reagents for the treatment of cancer cells.
Zinc‐dependent conformational changes in domain D5 of high molecular mass kininogen modulate contact activation
Authors: Herwald Heiko , Mörgelin Matthias , Svensson Henrik G. , Sjöbring Ulf
Published: September 2003

Human high molecular mass kininogen (HK) participates as nonenzymatic cofactor in the contact system. Here, we show that recombinant domain D5 of HK (rD5) prolongs the clotting time of the intrinsic pathway of coagulation and attenuates the generation of bradykinin. Further studies indicate that a correct fold of domain D5 within HK is required for the activation of the contact system. The folding of rD5 seems to be modulated by the metal ions Zn2+, Ni2+, and Cu2+ as a specific antibody directed against the zinc‐binding site in HK binds to HK and rD5 in a metal ion concentration dependent manner. The finding that these three metal ions specifically affect contact activation suggests that they regulate the accessibility of rD5 for negatively charged surfaces. Support for the assumption that the observed phenomena are due to conformational changes was obtained by fluorescence spectroscopy of rD5, demonstrating that its fluorescence spectrum was changed in the presence of ZnCl2. Moreover, negative staining electron microscopy experiments suggest that the zinc‐induced changes in D5 also affect the conformation of the entire HK protein. The present data emphasize the role of zinc and other metal ions in the regulation of contact activation.
The heterodimeric complex of MRP‐8 (S100A8) and MRP‐14 (S100A9)
Authors: Hessian Paul A. , Fisher Lorryn
Published: September 2003

The S100 calcium‐binding proteins MRP‐8 (S100A8) and MRP‐14 (S100A9) form a heterodimeric complex in the cytosol of monocyte and neutrophil cell types circulating in peripheral blood. This complex, but not the individual subunit proteins, is specifically recognized by mAb 27E10. Domains in MRP‐8 and MRP‐14 mediating heterodimeric complex formation have not yet been identified but it is predicted that the structure of the complex will be similar to homodimeric forms of other S100 proteins. This study makes use of the specificity of mAb 27E10, and an in vitro coupled transcription/translation system to further examine the formation and maintenance of the MRP‐8/MRP‐14 complex. Truncated mutants of MRP‐14 that lack the N‐terminal residues 1–4 or the extended C‐terminal ‘tail’, both complex with MRP‐8. These deleted domains of MRP‐14 are therefore not essential for complex formation. Peptides from MRP‐8 or MRP‐14, used to induce the epitope recognized by mAb 27E10, show that a critical interaction in complex formation involves the N‐terminal of MRP‐8 interacting with MRP‐14. Phage display analysis defined composite residues of the epitope recognized by mAb 27E10. The epitope is trans‐subunit, composed of residues in the C‐terminal ends of helix IV in MRP‐14 and helix I of MRP‐8. A further complex‐specific mAb, named 5.5, recognizes the hydrophobic residues in helix IV of MRP‐8, exposed during heterodimer formation. The definition of these two epitopes indicates that helices IV of MRP‐8 and MRP‐14 are also a prominent point of interaction and suggests that the subunit proteins will assume an antiparallel alignment in the heterodimer, similar in structure to the homodimeric forms of S100 proteins.
Rules for Nest Sanitation in a Social Spider Mite, Schizotetranychus miscanthi Saito (Acari: Tetranychidae)
Authors: Sato Yukie , Saito Yutaka , Sakagami Takane
Published: September 2003

Waste management behavior is essential to achieve nest sanitation that is highly inferential on the evolution of group living because nest waste is an inevitable cost. However, how group living animals dispose of waste has not attracted much attention. Schizotetranychus miscanthi Saito is a social spider mite infesting a perennial grass (Miscanthus sinensis Anderss), in which all nest members tend to defecate at specific sites. We investigated the mechanisms by which the individuals select the site of defecation. The results show that nest members defecate at only one site inside the nest, and that waste management is maintained by two simple rules. First, mites defecate near the nest entrances if no volatile chemical cues are available, and secondly, when chemical cues are available from feces deposited previously, they defecate at this site. We discuss the adaptive significance of these mechanisms, as well as their role in the evolution of sociality in mites.