bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variance in isotopic signatures as a descriptor of tissue turnover and degree of omnivory
Authors: SWEETING C. J. , JENNINGS S. , POLUNIN N. V. C. 
Published: October 2005

Summary

Diet analyses using C and N stable isotopes commonly focus on mean isotopic signatures; however, isotopic variance among individuals is likely to also contain useful information including details of omnivory.
Changes in isotopic signature as a result of dietary shifts are not instantly manifest in the isotopic signature of consumer tissues, but lagged over a period of time required for equilibration. Tissue turnover times have not previously been described in terms of variance in isotopic signature among individuals, and variance among individuals following equilibration with a constant diet is limited.
Temporal changes in δ15N and δ13C variance in juvenile European Sea Bass (Dicentrarchus labrax) muscle, heart and liver were monitored following a shift from a wild diet to two single‐source diets administered under seminatural conditions in captivity. Exponential decay functions of the standard deviation of δ15N and δ13C among individuals were used to model changes in variance over time.
All tissues exhibited a similar rate of tissue turnover using variance. However, variance among individuals within tissue types differed once fishes were equilibrated with the laboratory diet. The coefficients of variation of δ13C and δ15N were smallest in muscle and greatest in liver and greater among sampling dates than within.
Analysis of δ15N and δ13C in different tissues will not therefore provide equivalent power to detect differences in diet or to track changes in patterns of omnivory. Analysis of omnivory should be restricted to variance from a single tissue type. Of the tissues considered here, white muscle is most appropriate for this purpose.
Variance estimates derived here provide minimum values expected for a highly specialist feeding population. Departure from these values can be used to describe the degree of omnivory within a population.
Defects in ProTaper S1 instruments after clinical use: fractographic examination
Authors: Cheung G. S. P. , Peng B. , Bian Z. , Shen Y. , Darvell B. W. 
Published: October 2005

AbstractAim  To investigate the mode of failure of a brand of nickel‐titanium instruments separated during clinical use, by detailed examination of the fracture surface.Methodology  A total of 122 ProTaper S1 instruments were discarded from an endodontic clinic at a stomatological school in China over a period of 17 months; 28 had fractured. These fractured instruments were ultrasonically cleaned, autoclaved and then examined under a scanning electron microscope. From the lateral view the fracture was classified into ‘torsional’ or ‘flexural’. The specimens were then re‐mounted and the presence of characteristics of shear failure and fatigue striations was recorded under high‐power view of the fracture surface. The difference in the mean lengths of fractured segment between the shear and fatigue groups was compared using Student's t‐test.Results  Twenty‐seven separated instruments were available for analysis. Under low‐power magnification, only two fell into the category of ‘torsional’ failure when examined laterally; the others appeared to be ‘flexural’. Close examination of the fracture surface revealed the presence of fatigue striations in 18 specimens. Nine instruments (including the two putative ‘torsional’ failures above) fell into the shear fracture group, in which fatigue striations were absent or characteristics of shear failure of the material were found. The mean length of fractured segments resulting from fatigue failure (4.3 ± 1.9 mm) was significantly greater than that for shear failure (2.5 ± 0.8 mm) (P < 0.001, two‐sample t‐test).Conclusions  Examination of the fracture surface at high magnification is essential to reveal features that may indicate the possible origin of cracks and the mode of material failure. Macroscopic or lateral examination of separated instruments would fail to reveal the true mechanism of failure. Fatigue seems to be an important reason for the separation of rotary instruments during clinical use.
Reduction of osteocalcin expression in aged human dental pulp
Authors: Muramatsu T. , Hamano H. , Ogami K. , Ohta K. , Inoue T. , Shimono M. 
Published: October 2005

AbstractAim  To investigate the expression of osteocalcin mRNA in young and in aged human dental pulp tissue to determine the characteristics of osteocalcin expression.Methodology  Human dental pulp tissues of the third molars were obtained from healthy young (17–23 years) and aged (>50 years) subjects, and total RNA was extracted. Osteocalcin mRNA expression was determined by RT‐PCR and by quantitative real‐time RT‐PCR (QRT‐PCR). The threshold cycle (Ct) value, which reflects the amount of PCR, was calculated and the difference between the value in young and aged pulp was statistically analysed.Results  Osteocalcin mRNA was detected in all samples of human dental pulp tissue homogenates by RT‐PCR analysis. Osteocalcin mRNA was expressed in young adult dental pulp but was decreased in aged human dental pulp. QRT‐PCR analysis also showed a reduced expression of osteocalcin mRNA in aged human pulp. Expression of osteocalcin in young human pulp was significantly higher (about sixfold) than in aged pulp (P < 0.01, Mann–Whitney U‐test).Conclusion  Reduction of osteocalcin expression may be associated with the loss of viability in human dental pulp tissue, and may be a characteristic of aged human dental pulps.
Ultrastructural alterations of frozen‐thawed Asian elephant (Elephas maximus) spermatozoa
Authors: SA‐ARDRIT M. , SAIKHUN J. , THONGTIP N. , DAMYANG M. , MAHASAWANGKUL S. , ANGKAWANISH T. , JANSITTIWATE S. , FAISAIKARM T. , KITIYANANT Y. , PAVASUTHIPAISIT K. , PINYOPUMMIN A. 
Published: October 2005

SummaryIntact plasma and acrosome membranes and functional mitochondria following cryopreservation are important attributes for the fertilizing ability of spermatozoa. In the present study, functional and ultrastructural changes of Asian elephant spermatozoa after cryopreservation either in TEST + glycerol or HEPT + dimethyl sulphoxide (DMSO) were evaluated by fluorescent techniques and electron microscopy. Sperm frozen in TEST + glycerol had higher proportion of sperm with intact plasma (49.1 ± 9.2% vs. 30.9 ± 3.9%) and acrosomal (53.7 ± 4.9% vs. 35.8 ± 6.1%) membranes, as well as active mitochondria (57.0 ± 7.2% vs. 42.0 ± 5.0%) than those cryopreserved in HEPT + DMSO. The results obtained from electron microscopy were similar to those obtained by fluorescence microscopy. The percentage of normal spermatozoa was higher when spermatozoa were frozen in TEST + glycerol than those frozen in HEPT + DMSO (31.8 ± 5.6 vs. 28.5 ± 6.4). The ultrastructural alterations revealed by transmission electron microscopy could be classified as (i) distension of plasma membrane, while the acrosome was swollen; (ii) disruption or loss of plasma membrane, while acrosome was swollen with distended outer acrosomal membrane; (iii) disruption or loss of plasma and outer acrosomal membrane with leakage of acrosome content; (iv) extensive vesiculation of plasma and outer acrosomal membrane and leakage of acrosome content; (v) a complete loss of both plasma membrane and outer acrosomal membrane; and (vi) swelling of mitochondria. These findings suggest that the freezing and thawing procedure caused structural damage to elephant spermatozoa, especially in the plasma membrane, acrosome and mitochondria. Fluorescence and electron microscopic evaluations are potentially a powerful tool in the analysis of elephant spermatozoa after freezing and thawing.
Reduced foraging efficiency of a parasitoid under habitat complexity: implications for population stability and species coexistence
Authors: GOLS R. , BUKOVINSZKY T. , HEMERIK L. , HARVEY J. A. , VAN LENTEREN J. C. , VET L. E. M. 
Published: October 2005

SummaryHabitat complexity may stabilize interactions among species of different trophic levels by providing refuges to organisms of lower trophic levels.Searching behaviour of the parasitoid,Diadegma semiclausum, was followed in different semifield set‐ups, a low and high‐density monoculture ofBrassica oleraceaand two intercrops,B. oleraceawithSinapis alba(also a member of the Brassicaceae) andB. oleraceawithHordeum vulgare(Poaceae).When a low‐density monocrop ofB. oleraceawas compared with a high‐density monocrop, no differences were found in the ability of the female wasps to locate a host‐infested plant,B. oleracea, infested withPlutella xylostellathat was placed in the centre of the set‐up.The efficiency of the parasitoid to locate the host‐infested plant was differentially affected by the species composition of the vegetation. Wasps entered theSinapis‐Brassicaset‐up faster, but took more time to find the host‐infested plant than in theHordeum‐Brassicaset‐up.The horizontal arrangement, i.e. by mixingS. albaorH. vulgarewith, or placing them as rows betweenB. oleracea, did not affect host‐finding efficiency.Plant height did influence host finding. Wasps found the host‐infested plants earlier in the set‐up with shortSinapisplants compared with tallSinapisplants.Once the wasps had landed on the host‐infested plant, the surrounding vegetation did not affect time needed to parasitize five consecutive hosts on the same infested plant, regardless of the composition or horizontal/vertical arrangement of the set‐up.Chemical and structural refuges in complex landscapes may play an important role in the persistence of this system through dampening oscillations of parasitoid and host populations.
Vole cycles and predation in temperate and boreal zones of Europe
Authors: KORPIMÄKI ERKKI , OKSANEN LAURI , OKSANEN TARJA , KLEMOLA TERO , NORRDAHL KAI , BANKS PETER B. 
Published: October 2005

Summary

Graham & Lambin (2002) have reported on a weasel‐reduction experiment, concluding that the impact of weasel predation on field vole survival was neither sufficient nor necessary to initiate and drive the cyclic decline of field vole populations in Kielder Forest, northern England. They also stated that their findings contradict conclusively the specialist predator hypothesis put forward to explain population cycles of voles in North Europe.
Straightforward inferences from Kielder Forest to the northern boreal zone are misleading, because the population cycles of voles in Kielder Forest differ essentially from North European vole cycles. The low amplitude of the vole cycles in Kielder Forest, their restricted spatial synchrony in comparison to northern Europe and the virtual lack of interspecific synchrony in Kielder Forest suggest that there are essential differences between the mechanisms responsible for the two types of cyclic fluctuations of voles.
The weasel‐reduction experiment may provide a misleading picture on the role of predators, even in the Kielder Forest cycle. The experimental reduction of weasels alone may not stop the population decline of voles, because competing larger predators are expected to increase their hunting in the weasel‐reduction areas. The small spatial scale of the experiment, which produced only slight, short‐term differences in weasel densities between reduction and control areas, also suggests that other predators could have compensated easily for the weasels that were removed.
We propose a new version of the predation hypothesis to explain low‐amplitude population cycles of voles in temperate Europe, including the Kielder Forest. The interaction between generalist predators and vole populations might account for these cycles because generalists can have a functional response that is destabilizing in the neighbourhood of the equilibrium point. As most generalists are orders of magnitude larger than weasels, and thus need much more food for survival, generalist‐driven cycles should be characterized by high prey minima, as observed in Kielder Forest.
Using historical ecology to understand patterns of biodiversity in fragmented agricultural landscapes
Authors: Lunt Ian D. , Spooner Peter G. 
Published: October 2005

AbstractAim  To enhance current attempts to understand biodiversity patterns by using an historical ecology approach to highlight the over‐riding influence of land‐use history in creating past, current and future patterns of biodiversity in fragmented agricultural landscapes.Methods  We develop an integrative conceptual framework for understanding spatial and temporal variations in landscape patterns in fragmented agricultural landscapes by presenting five postulates (hypotheses) which highlight the important role of historical, anthropogenic disturbance regimes. We then illustrate each of these postulates with examples drawn from fragmented woodlands in agricultural areas of south‐eastern Australia, and discuss these findings in an international context. Location examples are drawn from agricultural areas in south‐eastern Australia.Results  We conclude that there is limited potential to refine our understanding of patterns of biodiversity in human‐modified landscapes based on traditional concepts of island biogeography, or simple assumptions of ongoing destruction and degradation. Instead, we propose that in agricultural landscapes that were largely cleared over a century ago: (1) present‐day remnant vegetation patterns are not accidental, but are logically arrayed due to historic land‐use decisions, (2) historic anthropogenic disturbances have a major influence on current ecosystem conditions and diversity patterns, and (3) the condition of remnant ecosystems is not necessarily deteriorating rapidly.Main conclusions  An historical ecology approach can enhance our understanding of why different species and ecosystem states occur where they do, and can explain internal variations in ecological conditions within remnant ecosystems, too often casually attributed to the ‘mess of history’. This framework emphasizes temporal changes (both past and future) in biotic patterns and processes in fragmented agricultural landscapes. Integration of spatially and temporally explicit historical land‐use information into ecological studies can prove extremely useful to test hypotheses of the effects of changes in landscape processes, and to enhance future research, restoration and conservation management activities.
Inter‐ and intraspecific phylogeography of small mammals in the Atacama Desert and adjacent areas of northern Chile
Authors: Eduardo Palma R. , Marquet Pablo A. , Boric‐Bargetto Dusan 
Published: October 2005

AbstractAim  We evaluated the phylogeography of sigmodontine taxa of the genera Phyllotis and Abrothrix at the intra and interspecific level, in the Atacama desert and adjacent Andean and Puna regions of northern Chile. The major goal was to test the hypothesis that sigmodontine mice differentiated in the lowlands, most likely via peripatric speciation, dispersing from highland to lowland areas across the desert vegetated canyons, thus reaching the Pacific coast. Dispersing individuals may have found favourable habitats along these valleys, in northern Chile, which connect the high altitude Puna region with the lowlands.Location  The study was conducted in northern Chile (18–22° S), in coastal pre‐Puna and Puna regions.Methods  For phylogeographic analyses we analysed cytochrome b mitochondrial sequences for 29 specimens of the genera Abrothrix and Phyllotis, from the region of study. All results were analysed phylogenetically using maximum‐likelihood, Bayesian, and uncorrected median‐joining network methodology.Results  In Phyllotis we recognized two major clusters of taxa: one restricted to the Puna region identified as Phyllotis xanthopygus chilensis, in close association to a pre‐Punean and lowland clade constituted by Phyllotis limatus, on the western slopes of the Andes. A similar pattern was distinguished for Abrothrix, where Abrothrix andinus was recognized in the Andean Altiplano‐pre‐Puna region and Abrothrix olivaceus in the lowlands of northern Chile.Main conclusions  We found that the radiation of sigmodontine mice in the central Andes may have been facilitated by the historical events that affected high Andean elevations during Pleistocene times, as well as changes in the vegetation composition and climate that started to prevail during that time. Our results also support previous hypotheses that the major mode of evolution for small mammals in the Andes region has been based on the founder effect or the peripheral isolates model, from a central range located in the Andes.
Patterns of hybridization and population genetic structure in the terrestrial orchids Liparis kumokiri and Liparis makinoana (Orchidaceae) in sympatric populations
Authors: CHUNG MI YOON , NASON JOHN D. , CHUNG MYONG GI 
Published: October 2005

AbstractWe investigated the potential for gene flow and genetic assimilation via hybridization between common and rare species of the terrestrial orchid genus Liparis, focusing specifically on sympatric and allopatric populations of the common Liparis kumokiri and the rare Liparis makinoana. We utilized analyses of genetic diversity, morphology, and the spatial distributions of individuals and genotypes to quantify the dynamics of interspecific gene flow at within‐ and among‐population scales. High levels of allozyme genetic diversity (HE) were found in populations of the rare L. makinoana (0.317), whereas the common L. kumokiri (N = 1744 from 14 populations) revealed a complete lack of variation. This contrast may reflect different breeding systems and associated rates of genetic drift (L. makinoana is self‐incompatible, whereas L. kumokiri is self‐compatible). At the two known sympatric sites, individuals were found that recombined parental phenotypes, possessing floral characteristics of L. kumokiri and vegetative characteristics of L. makinoana. These putative hybrids were the only individuals found segregating alleles diagnostic of both parental species. Analysis of these individuals indicated that hybrid genotypes were skewed towards L. kumokiri and later generation recombinants of L. kumokiri at both sympatric sites. Furthermore, Ripley's bivariate L(r) statistics revealed that at one site these hybrids are strongly spatially clustered with L. kumokiri. Nonetheless, the relatively low frequency of hybrids, absence of ongoing hybridization (no F1s or first generation backcrossess), and strong genetic differentiation between morphologically ‘pure’ parental populations at sympatric sites (FST = 0.708–0.816) indicates that hybridization was not an important bridge for gene flow. The results from these two species suggest that natural hybridization has not played an important role in the diversification of Liparis, but instead support the view that genetic drift and limited gene flow are primarily responsible for speciation in Liparis. Based on genetic data and current status of the species, implications of the research for conservation are considered to provide guidelines for appropriate conservation and management strategies.
The voyage of an invasive species across continents: genetic diversity of North American and European Colorado potato beetle populations
Authors: GRAPPUTO ALESSANDRO , BOMAN SANNA , LINDSTRÖM LEENA , LYYTINEN ANNE , MAPPES JOHANNA 
Published: October 2005

AbstractThe paradox of successful invading species is that they are likely to be genetically depauperate compared to their source population. This study on Colorado potato beetles is one of the few studies of the genetic consequences of continent‐scale invasion in an insect pest. Understanding gene flow, population structure and the potential for rapid evolution in native and invasive populations offers insights both into the dynamics of small populations that become successful invaders and for their management as pests. We used this approach to investigate the invasion of the Colorado potato beetle (Leptinotarsa decemlineata) from North America to Europe. The beetles invaded Europe at the beginning of the 20th century and expanded almost throughout the continent in about 30 years. From the analysis of mitochondrial DNA (mtDNA) and amplified fragment length polymorphism (AFLP) markers, we found the highest genetic diversity in beetle populations from the central United States. The European populations clearly contained only a fraction of the genetic variability observed in North American populations. European populations show a significant reduction at nuclear markers (AFLPs) and are fixed for one mitochondrial haplotype, suggesting a single successful founder event. Despite the high vagility of the species and the reduction of genetic diversity in Europe, we found a similar, high level of population structure and low gene flow among populations on both continents. Founder events during range expansion, agricultural management with crop rotation, and selection due to insecticide applications are most likely the causes partitioning genetic diversity in this species.
Identification and molecular characterization of an N‐acetylmuramyl‐l‐alanine amidase Sle1 involved in cell separation of Staphylococcus aureus
Authors: Kajimura Junko , Fujiwara Tamaki , Yamada Sakuo , Suzawa Yoshika , Nishida Tetsuya , Oyamada Yoshihiro , Hayashi Ikue , Yamagishi Jun–ichi , Komatsuzawa Hitoshi , Sugai Motoyuki 
Published: October 2005

SummaryWe purified a peptidoglycan hydrolase involved in cell separation from a Staphylococcus aureus atl null mutant and identified its gene. Characterization of the gene product shows a 32 kDa N‐acetylmuramyl‐l‐alanine amidase that we designated Sle1. Analysis of peptidoglycan digests showed Sle1 preferentially cleaved N‐acetylmuramyl‐l‐Ala bonds in dimeric cross‐bridges that interlink the two murein strands in the peptidoglycan. An insertion mutation of sle1 impaired cell separation and induced S. aureus to form clusters suggesting Sle1 is involved in cell separation of S. aureus. The Sle1 mutant revealed a significant decrease in pathogenesis using an acute infection mouse model. Atl is the major autolysin of S. aureus, which has been implicated in cell separation of S. aureus. Generation of an atl/sle1 double mutant revealed that the mutant cell separation was heavily impaired suggesting that S. aureus uses two peptidoglycan hydrolases, Atl and Sle1, for cell separation. Unlike Atl, Sle1 is not directly involved in autolysis of S. aureus.