529 research outputs found
First report of lesions resembling red mark syndrome observed in wild-caught common dab (Limanda limanda)
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Workshop on exploration for hot dry rock geothermal systems
Separate abstracts were prepared for fifteen papers. (MHR
Gene flow at the leading range edge: the long-term consequences of isolation in European Beech (Fagus sylvatica L. Kuhn)
Aim Isolation is expected to lead to negative impacts on populations due to a reduction in effective population size and gene flow, exacerbating the effects of genetic drift, which might be stronger in peripheral and fragmented populations. Fagus sylvatica (European beech) in southern Sweden presents a gradient of isolation towards the leading range edge of the species. We sought to determine the impact of longâterm isolation on genetic diversity and population genetic structure within populations of this species. Location Samples were obtained from 14 sites towards the northern edge of the native range of beech in Sweden. Taxon Fagaceae. Methods Using historical sources, we obtained areaâ and distanceâbased measures of isolation. We measured genetic diversity and structure by using nuclear microsatellite marker data, and performed parentage analysis to estimate external pollenâmediated gene flow. We implemented a partial least squares regression to determine the effects of isolation on each of the genetic diversity estimators and the measures of external pollenâmediated gene flow. Results Longâterm isolation generally had a negative impact on genetic diversity, which is exacerbated over time, further affecting progeny and suggesting that isolated populations are subject to strong genetic drift, possibly due to the combination of founder events and persistent small population sizes. Bayesian cluster analysis revealed that isolation was also acting as a barrier to gene flow in the northâeastern distribution of beech. Main conclusions Isolation at the leading range edge of beech in Sweden has created gradients of contemporary gene flow within the species. The longâterm cumulative effects of isolation on this windâpollinated tree species and its negative impacts on genetic diversity and gene flow, could lead to inbreeding depression and higher extinction risk where populations remain small and isolated
Structural basis for HCMV Pentamer receptor recognition and antibody neutralization
Human cytomegalovirus (HCMV) represents the viral leading cause of congenital birth defects and uses the gH/
gL/UL128-130-131A complex (Pentamer) to enter different cell types, including epithelial and endothelial cells.
Upon infection, Pentamer elicits the most potent neutralizing response against HCMV, representing a key vaccine
candidate. Despite its relevance, the structural basis for Pentamer receptor recognition and antibody neutralization
is largely unknown. Here, we determine the structures of Pentamer bound to neuropilin 2 (NRP2) and a set of
potent neutralizing antibodies against HCMV. Moreover, we identify thrombomodulin (THBD) as a functional
HCMV receptor and determine the structures of the Pentamer-THBD complex. Unexpectedly, both NRP2 and
THBD also promote dimerization of Pentamer. Our results provide a framework for understanding HCMV receptor
engagement, cell entry, antibody neutralization, and outline strategies for antiviral therapies against HCMV
Genetic differentiation among host-associated Alebra leafhoppers (Hemiptera: Cicadellidae)
The limited importance ascribed to sympatric speciation pro cesses via host race formation is partially due to the few
cases of host races that have been reported among host
populations. This work sheds light on the taxonomy of Alebra
leafhoppers and examines the possible existence of host
races among host-associated populations. The species of
this genus show varying degrees of host association with
deciduous trees and shrubs and, frequently, host popu lations of uncertain taxonomic status coexist and occasion ally become pests. Allozyme electrophoresis of 21 Greek
populations including sympatric, local and geographically
distant samples collected on 13 different plant species, show
that they represent at least five species: A. albostriella
Falle´n, A. viridis (Rey) (sensu Gillham), A. wahlbergi Bo Keywords: host races; leafhoppers; sympatric speciation; sibling species; allozymes; Alebra
Introduction
Sympatric speciation is a controversial subject in evol utionary biology (see Mayr, 1963; Futuyma and Mayer,
1980; Paterson, 1981; Via, 2001). One of the reasons for
this controversy is that sympatric speciation seems to be
an extremely rare phenomenon occurring only in very
few groups of taxa, represented chiefly by phytophagous
insects (Tauber and Tauber, 1977; Menken, 1981; Wood,
1993; Emelianov et al, 1995; Via, 1999; Finchak et al, 2000;
Craig et al, 2001). The limited number of reported cases
among organisms with sexual reproduction can be at
least partially attributed to the fact that taxa undergoing
sympatric speciation events must fulfill very restrictive
biological and ecological requirements.
Most sympatric speciation models demand that there is
intraspecific genetic variation in traits that differentially
affect the fitness of individuals that colonise new habitats
or hosts (Dieckman and Doebeli, 1999; Hawthorne and
Via, 2001 but see Higashi et al, 1999 and Takimoto et al,
2000). They assume that selection acting on these traits
can prevent genetic exchange between populations
(Bush, 1975; Tauber and Tauber, 1977; Diehl and Bush,
1989). In phytophagous insects, this means that host pref erences must be genetically determined and mating
should occur on the host (Bush, 1975; Diehl and Bush,
Correspondence: D Aguin-Pombo, Department of Biology, University of
Madeira, Campus Universitario da Penteada, 9000 Funchal, Madeira,
Portugal. E-mail: aguin uma.pt
Received 12 December 2000; accepted 13 December 2001
heman and two new species. Of these, one is associated
to Quercus frainetto and other is specific to Crataegus spp.
Significant genetic differences among sympatric and local
host populations were found only in A. albostriella, between
populations on Turkey oak, beech and common alder. It is
suggested that the last two of these host populations may
represent different host races. The results show that both
the host plant and geographical distance affect the patterns
of differentiation in the genus. The formation of some spec ies seems to have been the result of allopatric speciation
events while, for others, their origin can be equally explained
either by sympatric or allopatric speciation.info:eu-repo/semantics/publishedVersio
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1984 Bibliography of atomic and molecular processes
This annotated bibliography includes papers on atomic and molecular processes published during 1984. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory
Recommended from our members
1985 bibliography of atomic and molecular processes
This annotated bibliography includes papers on atomic and molecular processes published during 1985. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory
Circadian-Related Heteromerization of Adrenergic and Dopamine D4 Receptors Modulates Melatonin Synthesis and Release in the Pineal Gland
Dopamine and adrenergic receptor complexes form under a circadian-regulated cycle and directly modulate melatonin synthesis and release from the pineal gland
Circadian-Related Heteromerization of Adrenergic and Dopamine D4 Receptors Modulates Melatonin Synthesis and Release in the Pineal Gland
Dopamine and adrenergic receptor complexes form under a circadian-regulated cycle and directly modulate melatonin synthesis and release from the pineal gland
DNA Fingerprinting of Pearls to Determine Their Origins
We report the first successful extraction of oyster DNA from a pearl and use it to identify the source oyster species for the three major pearl-producing oyster species Pinctada margaritifera, P. maxima and P. radiata. Both mitochondrial and nuclear gene fragments could be PCR-amplified and sequenced. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in the internal transcribed spacer (ITS) region was developed and used to identify 18 pearls of unknown origin. A micro-drilling technique was developed to obtain small amounts of DNA while maintaining the commercial value of the pearls. This DNA fingerprinting method could be used to document the source of historic pearls and will provide more transparency for traders and consumers within the pearl industry
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