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Distinct Populations (distinct + population)
Terms modified by Distinct Populations Selected AbstractsTwo Genetically Distinct Populations of Colletotrichum gloeosporioides Penz.JOURNAL OF PHYTOPATHOLOGY, Issue 3 2005Causing Anthracnose Disease of Yam (Dioscorea spp.) Abstract Variation within Colletotrichum gloeosporioides, the causal agent of yam anthracnose disease, is still poorly defined and this hinders breeding for resistance. Two morphotypes of C. gloeosporioides, designated slow-growing grey (SGG) and fast-growing salmon (FGS), are associated with anthracnose disease of yam in Nigeria. The morphotypes are distinguishable based on colony and conidial morphology, growth rate, virulence, as well as vegetative compatibility, but molecular differentiation of SGG and FGS strains is needed to facilitate epidemiological studies. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified small subunit (18S) rDNA fragments, and microsatellite-primed PCR (MP-PCR) genomic fingerprinting were employed to provide a basis for molecular differentiation of the morphotypes. DGGE analysis revealed patterns that clearly differentiated isolates of the aggressive defoliating SGG from the moderately virulent non-defoliating FGS strains. Genetic analysis based on 52 MP-PCR markers revealed highly significant differentiation between the SGG and FGS populations on yam (GST = 0.22; Nei's genetic identity = 0.85; , = 0.28, P < 0.001), indicating that the SGG and FGS morphotypes represent genetically differentiated populations. The results of the molecular typing using DGGE and MP-PCR analyses were consistent with the disease phenotype caused by the two morphotypes. Consequently, these molecular techniques might be used, at least partly, to replace time-consuming virulence studies on yam. [source] Bacterial diversity in the bacterioneuston (sea surface microlayer): the bacterioneuston through the looking glassENVIRONMENTAL MICROBIOLOGY, Issue 5 2005Mark P. Franklin Summary The bacterioneuston is defined as the community of bacteria present within the neuston or sea surface microlayer. Bacteria within this layer were sampled using a membrane filter technique and bacterial diversity was compared with that in the underlying pelagic coastal seawater using molecular ecological techniques. 16S rRNA gene libraries of , 500 clones were constructed from both bacterioneuston and the pelagic water samples and representative clones from each library were sequenced for comparison of bacterial diversity. The bacterioneuston was found to have a significantly lower bacterial diversity than the pelagic seawater, with only nine clone types (ecotaxa) as opposed to 46 ecotaxa in the pelagic seawater library. Surprisingly, the bacterioneuston clone library was dominated by 16S rRNA gene sequences affiliated to two groups of organisms, Vibrio spp. which accounted for over 68% of clones and Pseudoalteromonas spp. accounting for 21% of the library. The dominance of these two 16S rRNA gene sequence types within the bacterioneuston clone library was confirmed in a subsequent gene probing experiment. 16S rRNA gene probes specific for these groups of bacteria were designed and used to probe new libraries of 1000 clones from both the bacterioneuston and pelagic seawater DNA samples. This revealed that 57% of clones from the bacterioneuston library hybridized to a Vibrio sp.-specific 16S rRNA gene probe and 32% hybridized to a Pseudoalteromonas sp.-specific 16S rRNA gene probe. In contrast, the pelagic seawater library resulted in only 13% and 8% of 16S rRNA gene clones hybridizing to the Vibrio sp. and Pseudoalteromonas sp. probes respectively. Results from this study suggest that the bacterioneuston contains a distinct population of bacteria and warrants further detailed study at the molecular level. [source] Human Th17 cells: Are they different from murine Th17 cells?EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2009Francesco Annunziato Abstract Type 17 Th (Th17) cells have been identified as a distinct population of CD4+ effector T cells different from Th1 and Th2 cells. While the pre-eminent cytokine of Th1 cells is IFN-, and that of Th2 cells is IL-4, the distinctive cytokine of Th17 cells is IL-17A. However, although murine and human Th1 and Th2 cells exhibit strong similarities, human and murine Th17 cells seem to differ in several aspects. [source] A novel brain receptor is expressed in a distinct population of olfactory sensory neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2000Sidonie Conzelmann Abstract Three novel G-protein-coupled receptor genes related to the previously described RA1c gene have been isolated from the mouse genome. Expression of these genes has been detected in distinct areas of the brain and also in the olfactory epithelium of the nose. Developmental studies revealed a differential onset of expression: in the brain at embryonic stage 17, in the olfactory system at stage E12. In order to determine which cell type in the olfactory epithelium expresses this unique receptor type, a transgenic approach was employed which allowed a coexpression of histological markers together with the receptor and thus visualization of the appropriate cell population. It was found that the receptor-expressing cells were located very close to the basal membrane of the epithelium; however, the cells extended a dendritic process to the epithelial surface and their axons projected into the main olfactory bulb where they converged onto two or three glomeruli in the dorsal and posterior region of the bulb. Thus, these data provide evidence that this unique type of receptor is expressed in mature olfactory neurons and suggests that it may be involved in the detection of special odour molecules. [source] Impact of rifting and hydrography on the genetic structure of Clarias gariepinus in eastern AfricaJOURNAL OF FISH BIOLOGY, Issue 5 2002C.S. Giddelo In a study of the genetic structure of Clarias gariepinus at the ND5 and ND6 loci of mitochondrial DNA using RFLP,PCR in 16 populations (267 fish), a total of 18 haplotypes was detected. The most common haplotype was EA1 and represented 46% of all genotypes. Three phylogenetic groups characterized the region, with the East African clade occurring between the western rift in the west, Lake Baringo in the north, the Indian Ocean in the east and the Rufiji River in the south. The Lower Tana River (unlike the Upper Tana River) and Lake Kamnarok grouped with the North clade, while the Ruaha River (tributary of the Rufiji River) represented a contact zone between the East and the South-central African clade. Genetic structure was distinct (FST=0·66), with the Lower Tana River and Lake Mtera forming specific units. Within the East clade, the Oloibortoto River, Upper Tana River and Lake Victoria each formed a distinct population. Lake Baringo grouped either with the eastern rift or the western rift depending on the analysis. Lake Jipe, the Pangani River, Rusizi River, Lake Edward, Nyabugogo River and the Luiche River clustered together. Among group variance explained 66·8% of the total variance; the impact of vicariance (rifting and uplifting) on the phylogeography was considerable. A distribution model of the catfish is proposed which combines the separation by rifting several million years ago with a high gene flow in the western rift due to historical connectivity among lakes and rivers. [source] MHC haplotype frequencies in a UK breeding colony of Mauritian cynomolgus macaques mirror those found in a distinct population from the same geographic originJOURNAL OF MEDICAL PRIMATOLOGY, Issue 1 2009Edward T. Mee Abstract Background, Mauritian cynomolgus macaques have greatly restricted genetic diversity in the MHC region compared to other non-human primates; however, the frequency of common MHC haplotypes among captive-bred populations has not been reported. Methods, Microsatellite PCR was used to determine MHC haplotype frequencies among captive macaques at a UK breeding facility. Allele-specific PCR and reference strand conformational analysis were used to determine the allele expression profile of a subset of animals. Results, Haplotypes H3 (21%) and H1 (19%) were most common in the captive population of Mauritian cynomolgus macaques. Predicted alleles were detected by allele-specific PCR-SSP in 98% of animals. Allele expression profiles were similar in animals with identical haplotypes. Conclusions, Mauritian cynomolgus macaques in the UK breeding facility have restricted MHC diversity comparable to a previously described population. Microsatellite-derived haplotypes are highly predictive of allele expression. A selective breeding program has been established to produce MHC-identical animals for biomedical research. [source] Nuclear and mitochondrial markers reveal distinctiveness of a small population of bottlenose whales (Hyperoodon ampullatus) in the western North AtlanticMOLECULAR ECOLOGY, Issue 11 2006MEREL L. DALEBOUT Abstract Small populations at the edge of a species' distribution can represent evolutionary relics left behind after range contractions due to climate change or human exploitation. The distinctiveness and genetic diversity of a small population of bottlenose whales in the Gully, a submarine canyon off Nova Scotia, was quantified by comparison to other North Atlantic populations using 10 microsatellites and mitrochondrial DNA (mtDNA) control region sequences (434 bp). Both markers confirmed the distinctiveness of the Gully (n = 34) from the next nearest population, off Labrador (n = 127; microsatellites ,FST= 0.0243, P < 0.0001; mtDNA ,,ST = 0.0456, P < 0.05). Maximum likelihood microsatellite estimates suggest that less than two individuals per generation move between these areas, refuting the hypothesis of population links through seasonal migration. Both males and females appear to be philopatric, based on significant differentiation at both genomes and similar levels of structuring among the sexes for microsatellites. mtDNA diversity was very low in all populations (h = 0.51, , = 0.14%), a pattern which may be due to selective sweeps associated with this species' extreme deep-diving ecology. Whaling had a substantial impact on bottlenose whale abundance, with over 65 000 animals killed before the hunt ceased in the early 1970s. Genetic diversity was similar among all populations, however, and no signal for bottlenecks was detected, suggesting that the Gully is not a relic of a historically wider distribution. Instead, this unique ecosystem appears to have long provided a stable year-round habitat for a distinct population of bottlenose whales. [source] Crystallization of the , form in random propylene-ethylene copolymersPOLYMER INTERNATIONAL, Issue 12 2004Antonio Marigo Abstract Wide-angle X-ray scattering and differential scanning calorimetry measurements have been conducted on seven random copolymers of propylene with ethylene in order to study the , phase formation as a function of the comonomer content. The lamellar morphology of the samples was also investigated by small-angle X-ray scattering. The content of the , phase was found to go through a maximum with crystallization temperature and to increase with comonomer concentration, up to a point (ethylene ,6.5 wt%) where the latter parameter became less influential. The multiple melting endotherms behaviour of the samples was studied by DSC and temperature-controlled diffractometric techniques. The attribution of the DSC peaks to the different isotactic polypropylene polymorphs that form in these conditions was confirmed. The results obtained permitted us to ascertain that, in the experimental conditions chosen, some further formation of crystallites takes place during the quenching to room temperature after the crystallization isotherm. In this phase, the chains organize themselves in stacks with thin lamellae, forming a distinct population with respect to those formed on isothermal crystallization. The melting of the thinner lamellae determines a convergence of the two populations into just one, still retaining an organization in stacks, that gradually disappears until complete melting of the material. Copyright © 2004 Society of Chemical Industry [source] Hypothalamic input is required for development of normal numbers of thyrotrophs and gonadotrophs, but not other anterior pituitary cells in late gestation sheepTHE JOURNAL OF PHYSIOLOGY, Issue 4 2008Eva Szarek To evaluate the hypothalamic contribution to the development of anterior pituitary (AP) cells we surgically disconnected the hypothalamus from the pituitary (hypothalamo-pituitary disconnection, HPD) in fetal sheep and collected pituitaries 31 days later. Pituitaries (n= 6 per group) were obtained from fetal sheep (term = 147 ± 3 days) at 110 days (unoperated group) of gestation and at 141 days from animals that had undergone HPD or sham surgery at 110 days. Cells were identified by labelling pituitary sections with antisera against the six AP hormones. Additionally, we investigated the colocalization of glycoprotein hormones. The proportions of somatotrophs and corticotrophs were unchanged by age or HPD. Lactotrophs increased 80% over time, but the proportion was unaffected by HPD. Thyrotrophs, which were unaffected by age, increased 70% following HPD. Gonadotrophs increased with gestational age (LH+ cells 55%; FSH+ cells 19-fold), but this was severely attenuated by HPD. We investigated the possible existence of a reciprocal effect of HPD on multipotential glycoprotein-expressing cells. Co-expression of LH and TSH was extremely rare (< 1%) and unchanged over the last month of gestation or HPD. The increase of gonadotrophs expressing FSH only or LH and FSH was attenuated by HPD. Therefore, the proportions of somatotrophs, lactotrophs and corticotrophs are regulated independently of hypothalamic input in the late gestation fetal pituitary. In marked contrast, the determination of the thyrotroph and gonadotroph lineages over the same time period is subject to complex mechanisms involving hypothalamic factors, which inhibit differentiation and/or proliferation of thyrotrophs, but stimulate gonadotrophs down the FSH lineage. Development of a distinct population of gonadotrophs, expressing only LH, appears to be subject to alternative mechanisms. [source] Temporal genetic heterogeneity of juvenile orange-spotted grouper (Epinephelus coioides, Pisces: Serranidae)AQUACULTURE RESEARCH, Issue 10 2009Panuwat Pumitinsee Abstract Juveniles of orange-spotted grouper (Epinephelus coioides), a tropical serranid species, are heavily harvested for aquaculture seeds from nursing grounds in several Southeast Asian countries. Because juveniles of similar sizes are present in a nursery area throughout the year, we aimed to determine whether more than one genetically distinct population contributes to juvenile aggregations. We examined the temporal genetic heterogeneity of juvenile aggregations collected at four different times of the year at a nursery area in coastal waters of the Andaman Sea in Trang province, Thailand. Also, we examined the differences between these temporal samples and an outgroup collected from the Gulf of Thailand (Chantaburi). The genetic variation at six polymorphic microsatellite loci within each sample was moderate, with observed heterozygosities across all loci ranging from 0.551 to 0.629 and number of alleles per locus ranging from 7.0 to 8.33. Results indicated substantial genetic differences between the two geographically distant samples, Trang and Chantaburi (Fst=0.040,0.050, P<0.005), and between the July sample and the remaining samples from Trang (Fst=0.096,0.106, P<0.005). The observed temporal genetic heterogeneity of E. coioides juveniles may reflect high variability in the reproductive success of each spawning event and the existence of spatially isolated groups of spawners. [source] Atypical glandular cells of undetermined significance (AGUS): Clinical considerations and cytohistologic correlationDIAGNOSTIC CYTOPATHOLOGY, Issue 3 2002Joseph F. Nasuti M.D. Abstract The diagnoses of atypical glandular cells of undetermined significance (AGUS) made upon evaluation of cervical/vaginal (Pap) smears is examined to ascertain salient clinical and cytologic features that may lead to better characterization of the true nature of these lesions. Prior history of squamous dysplasia, age of the patient, and the occurrence of abnormal microbiopsy tissue fragments are investigated to determine their value in the proper evaluation of AGUS specimens. Of the 86,234 Pap smears submitted to our laboratory during a period of 2 yr, 187 (0.2%) were diagnosed as AGUS. Available follow-up in 128 (69%) cases revealed 54 (42%) significant tissue proven abnormalities, the majority (55%, 30 patients) of which were diagnosed as squamous intraepithelial lesions (SIL). Squamous dysplasia is significantly more common in women younger than 40 (15/18, 83%) and in patients with prior history of SIL (29/30, 97%). In addition, all nine patients diagnosed with endometrial lesions on subsequent histology were older than 40. Age, however, was not a discriminating factor in women proven to have endocervical glandular lesions. Additionally, certain tissue fragment cytomorphologic features were significantly more often observed on follow-up in specific histologic diagnostic categories. The Pap smears of patients diagnosed with SIL were noted to contain tissue fragments composed of both dysplastic squamous and benign glandular cells in 29 of 30 (97%). The presence of two distinct populations of glandular tissue fragments (typical and atypical) was found in the Pap smears of all nine women with endometrial abnormalities and in the smears of most women subsequently diagnosed with endocervical glandular lesions (87%, 13/15). These observations suggest that a more specific and clinically useful Pap smear interpretation other than AGUS is often possible by consideration of the patient's age and prior history along with the correct identification of the type of atypical cells observed in abnormal tissue fragments. Diagn. Cytopathol. 2002;26:186,190; DOI 10.1002/dc.10070 © 2002 Wiley-Liss, Inc. [source] Multi-phase evolution of gnammas (weathering pits) in a Holocene deglacial granite landscape, Minnesota (USA)EARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2008David Domínguez-Villar Abstract The morphometry of 85 gnammas (weathering pits) from Big Stone County in western Minnesota allows the assessment of the relative ages of the gnamma population. The ratio between maximum and minimum depths is independent of the initial size of the cavity and only depends on the weathering evolution. Therefore, the distribution of depth ratios can be used to assess the gnamma population age and the history of weathering. The asymmetrical distribution of depth ratios measured in Big Stone County forms three distinct populations. When these sets are analyzed independently, the correlation (r2) between maximum and minimum depths is greater than 0·95. Each single population has a normal distribution of depth ratios and the average depth ratios (, -value) for each population are ,1 = 1·60 ± 0·05, ,2 = 2·09 ± 0·04 and ,3 = 2·42 ± 0·08. The initiation of gnamma formation followed the exhumation of the granite in the region. This granite was till and saprolite covered upon retreat of the ice from the Last Glacial Maximum. Nearby outcrops are striated, but the study site remained buried until it was exhumed by paleofloods issuing from a proglacial lake. These Holocene-aged gnammas in western Minnesota were compared with gnammas of other ages from around the world. Our new results are in accordance with the hypothesis that , -values represent the evolution of gnammas with time under temperate- to cold-climate dynamics. Phases of the formation of new gnammas may result from changes in weathering processes related to climate changes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Patterns of phenotypic and genetic variability show hidden diversity in Scottish Arctic charrECOLOGY OF FRESHWATER FISH, Issue 1 2007C. E. Adams Abstract,,, This study examined the degree and pattern of variability in trophic morphology in Arctic charr (Salvelinus alpinus L.) at three spatial scales: across 22 populations from Scotland and between and within two adjacent catchments (Laxford and Shin) in northern Scotland. In addition, the variability at six microsatellite loci between and within the Laxford and Shin systems was determined. Habitat use by charr differed significantly between populations. The pattern of variability in trophic morphology, known to influence foraging ability in charr, showed a very high degree of between-population variation with at least 52% of population pairs showing significant differences in head shape. Trophic morphology and genetic variation was also high over small geographical scales; variation being as high between charr from lakes within the same catchment, as between adjacent catchments. The pattern of both phenotypic and genotypic variation suggests a mosaic of variation across populations with geographically close populations often as distinct from each other as populations with much greater separation. Very low levels of effective migrants between populations, even within the same catchment, suggest that this variation is being maintained by very low straying rates between phenotypically and genetically distinct populations, even when there is no apparent barrier to movement. We conclude that the genetic and phenotypic integrity of charr populations across Scotland is high and that this adaptive radiation constitutes a ,hidden' element of diversity in northern freshwater systems. Two consequences of this are that the population (rather than the species) makes a more rational unit for the consideration of conservation strategies and that the habitat requirements and therefore management needs may differ significantly between populations. [source] In situ substrate conversion and assimilation by nitrifying bacteria in a model biofilmENVIRONMENTAL MICROBIOLOGY, Issue 9 2005Armin Gieseke Summary Local nitrification and carbon assimilation activities were studied in situ in a model biofilm to investigate carbon yields and contribution of distinct populations to these activities. Immobilized microcolonies (related to Nitrosomonas europaea/eutropha, Nitrosomonas oligotropha, Nitrospira sp., and to other Bacteria) were incubated with [14C]-bicarbonate under different experimental conditions. Nitrifying activity was measured concomitantly with microsensors (oxygen, ammonium, nitrite, nitrate). Biofilm thin sections were subjected to fluorescence in situ hybridization (FISH), microautoradiography (MAR), and local quantification of [14C]-bicarbonate uptake (beta microimaging). Nitrifying activity and tracer assimilation were restricted to a surface layer of different thickness in the various experiments (substrate or oxygen limitation). Excess oxygen uptake under all conditions revealed heterotrophic activity fuelled by decay or excretion products during active nitrification. Depth limits and intensity of tracer incorporation profiles were in agreement with ammonia-oxidation activity (measured with microsensors), and distribution of incorporated tracer (detected with MAR). Microautoradiography revealed a sharp individual response of distinct populations in terms of in-/activity depending on the (local) environmental conditions within the biofilm. Net in situ carbon yields on N, expressed as e, equivalent ratios, varied between 0.005 and 0.018, and, thus, were in the lower range of data reported for pure cultures of nitrifiers. [source] Female Choice by Scent Recognition in the Spotted Cucumber BeetleETHOLOGY, Issue 3 2006Jeremy F. Brodt In species that demonstrate female choice, geographically distinct populations can vary in their signal-response behaviors as a result of environmental differences or genetic drift. Observing whether or not females discriminate against males from allopatric populations can establish such signal deviations. Here we compare mating success within and between populations of the spotted cucumber beetle (Diabrotica undecimpunctata howardi) collected from Delaware, Tennessee, Missouri, and New Mexico, USA. A no-choice cross-mating experiment was employed to measure female preference for sympatric and allopatric males. While only two of the populations (Tennessee and Missouri) demonstrated statistically significant female preference for sympatric males, this trend was observed in all populations tested. Further, we show that (i) males from Tennessee, Missouri, and New Mexico differ in their scent, (ii) females may use population-specific scents to discriminate among males, and (iii) females whose antennae have been surgically removed are unable to recognize acceptable mates. New Mexico males, which were never accepted by either Tennessee or Missouri females, became acceptable mates when crowded with Tennessee or Missouri males prior to copulation. We infer that male odor may be an important factor in determining cucumber beetle mating success. [source] Effects of nicotine in the dopaminergic system of mice lacking the alpha4 subunit of neuronal nicotinic acetylcholine receptorsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2003L. M. Marubio Abstract The mesostriatal dopaminergic system influences locomotor activity and the reinforcing properties of many drugs of abuse including nicotine. Here we investigate the role of the ,4 nicotinic acetylcholine receptor (nAChR) subunit in mediating the effects of nicotine in the mesolimbic dopamine system in mice lacking the ,4 subunit. We show that there are two distinct populations of receptors in the substantia nigra and striatum by using autoradiographic labelling with 125I ,-conotoxin MII. These receptors are comprised of the ,4, ,2 and ,6 nAChR subunits and non-,4, ,2, and ,6 nAChR subunits. Non-,4 subunit-containing nAChRs are located on dopaminergic neurons, are functional and respond to nicotine as demonstrated by patch clamp recordings. In vivo microdialysis performed in awake, freely moving mice reveal that mutant mice have basal striatal dopamine levels which are twice as high as those observed in wild-type mice. Despite the fact that both wild-type and ,4 null mutant mice show a similar increase in dopamine release in response to intrastriatal KCl perfusion, a nicotine-elicited increase in dopamine levels is not observed in mutant mice. Locomotor activity experiments show that there is no difference between wild-type and mutant mice in basal activity in both habituated and non-habituated environments. Interestingly, mutant mice sustain an increase in cocaine-elicited locomotor activity longer than wild-type mice. In addition, mutant mice recover from depressant locomotor activity in response to nicotine at a faster rate. Our results indicate that ,4-containing nAChRs exert a tonic control on striatal basal dopamine release, which is mediated by a heterogeneous population of nAChRs. [source] EVOLUTION OF INTRINSIC GROWTH RATE: METABOLIC COSTS DRIVE TRADE-OFFS BETWEEN GROWTH AND SWIMMING PERFORMANCE IN MENIDIA MENIDIAEVOLUTION, Issue 6 2006Stephen A. Arnott Abstract There is strong evidence that genetic capacity for growth evolves toward an optimum rather than an absolute maximum. This implies that fast growth has a cost and that trade-offs occur between growth and other life-history traits, but the fundamental mechanisms are poorly understood. Previous work on the Atlantic silverside fish Menidia menidia has demonstrated a trade-off between growth and swimming performance. We hypothesize that the trade-off derives from the competing metabolic demands associated with growth and swimming activity. We tested this by measuring standard metabolic rate (MSTD), maximum sustainable metabolic rate (MACT) and metabolic scope of laboratory-reared silversides originating from two geographically distinct populations with well-documented differences in genetic capacity for growth. The fast-growth genotype had a significantly greater MSTD than the slow-growth genotype, but a similar MACT when swum to near exhaustion. The scope for activity of the fast-growth genotype was lower than that of the slow-growth genotype. Furthermore, the fast-growth genotype eats larger meals, thereby incurring a greater postprandial oxygen demand. We conclude that a metabolic trade-off occurs between growth and other metabolic demands and that this trade-off provides a general mechanism underlying the evolution of growth rate. [source] Genetic population structure of marine fish: mismatch between biological and fisheries management unitsFISH AND FISHERIES, Issue 4 2009Henning Reiss Abstract An essential prerequisite of a sustainable fisheries management is the matching of biologically relevant processes and management action. In fisheries management and assessment, fish stocks are the fundamental biological unit, but the reasoning for the operational management unit is often indistinct and mismatches between the biology and the management action frequently occur. Despite the plethora of population genetic data on marine fishes, to date little or no use is made of the information, despite the fact that the detection of genetic differentiation may indicate reproductively distinct populations. Here, we discuss key aspects of genetic population differentiation in the context of their importance for fisheries management. Furthermore, we evaluate the population structure of all 32 managed marine fish species in the north-east Atlantic and relate this structure to current management units and practice. Although a large number of studies on genetic population structure have been published in the last decades, data are still rare for most exploited species. The mismatch between genetic population structure and the current management units found for six species (Gadus morhua, Melanogrammus aeglefinus, Merlangius merlangus, Micromesistius poutassou, Merluccius merluccius and Clupea harengus), emphasizes the need for a revision of these units and questions the appropriateness of current management measures. The implementation of complex and dynamic population structures into novel and less static management procedures should be a primary task for future fisheries management approaches. [source] TATA Box-Binding Protein gene is associated with risk for schizophrenia, age at onset and prefrontal functionGENES, BRAIN AND BEHAVIOR, Issue 4 2009K. Ohi Schizophrenia is a common polygenic disease in distinct populations, while spinocerebellar ataxia type 17 (SCA17) is a rare autosomal dominant neurodegenerative disorder. Both diseases involve psychotic symptoms. SCA17 is caused by an expanded polyglutamine tract in the TATA box-binding protein (TBP) gene. In the present study, we investigated the association between schizophrenia and CAG repeat length in common TBP alleles with fewer than 42 CAG repeats in a Japanese population (326 patients with schizophrenia and 116 healthy controls). We found that higher frequency of alleles with greater than 35 CAG repeats in patients with schizophrenia compared with that in controls (p = 0.042). We also examined the correlation between CAG repeats length and age at onset of schizophrenia. We observed a negative correlation between the number of CAG repeats in the chromosome with longer CAG repeats out of two chromosomes and age at onset of schizophrenia (p = 0.020). We further provided evidence that TBP genotypes with greater than 35 CAG repeats, which were enriched in patients with schizophrenia, were significantly associated with hypoactivation of the prefrontal cortex measured by near-infrared spectroscopy during the tower of Hanoi, a task of executive function (right PFC; p = 0.015, left PFC; p = 0.010). These findings suggest possible associations of the genetic variations of the TBP gene with risk for schizophrenia, age at onset and prefrontal function. [source] Expression of CD8, identifies a distinct subset of effector memory CD4+ T lymphocytesIMMUNOLOGY, Issue 2 2006Iole Macchia Summary Circulating CD4+ CD8+ T lymphocytes have been described in the peripheral blood of humans and several animal species. However, the origin and functional properties of these cells remain poorly understood. In the present study, we evaluated the frequency, phenotype and function of peripheral CD4+ CD8+ T cells in rhesus macaques. Two distinct populations of CD4+ CD8+ T cells were identified: the dominant one was CD4hi CD8lo and expressed the CD8,, homodimer, while the minor population was CD4lo CD8hi and expressed the CD8,, heterodimer. The majority of CD4hi CD8,lo T cells exhibited an activated effector/memory phenotype (CCR5lo CD7, CD28, HLA-DR+) and expressed relatively high levels of granzyme B. Intracellular cytokine staining assays demonstrated that the frequency of cytomegalovirus-specific T cells was enriched five-fold in CD4hi CD8,lo T cells compared to single-positive CD4+ T cells, whereas no consistent enrichment was observed for simian immunodeficiency virus (SIV)-specific T cells. Cross-sectional studies of SIV-infected animals demonstrated that the frequency of CD4hi CD8,lo T cells was lower in wild-type SIV-infected animals compared to uninfected controls, although prospective studies of SIV-infected animals demonstrated depletion of CD4hi CD8,lo lymphocytes only in a subset of animals. Taken together, these data suggest that CD4+ T cells expressing CD8, represent an effector/memory subset of CD4+ T cells and that this cell population can be depleted during the course of SIV infection. [source] Haplotype Frequency Distribution in Northeastern European Saduria entomon (Crustacea: Isopoda) Populations.INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 6 2003A Phylogeographic Approach Abstract The distribution pattern of mtDNA haplotypes in distinct populations of the glacial relict crustacean Saduria entomon was examined to assess phylogeographic relationships among them. Populations from the Baltic, the White Sea and the Barents Sea were screened for mtDNA variation using PCR-based RFLP analysis of a 1150 bp fragment containing part of the CO I and CO II genes. Five mtDNA haplotypes were recorded. An analysis of geographical heterogeneity in haplotype frequency distributions revealed significant differences among populations. The isolated populations of S. entomon have diverged since the retreat of the last glaciation. The geographical pattern of variation is most likely the result of stochastic (founder effect, genetic drift) mechanisms and suggests that the haplotype differentiation observed is probably older than the isolation of the Baltic and Arctic seas. [source] Can low densities of carnivores result in genetic depletion?JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 3 2006An investigation within French polecat populations Summary Carnivores as top predators are commonly found in relatively low densities even in optimal habitats. Despite a lack of empirical studies, it could be suspected that long-term low density could result in genetic depletion. The genetic structure of European polecat Mustela putorius natural populations was investigated by allozyme electrophoresis in five distinct areas. Density estimates significantly differed among sites from 0.17 to 0.83 individuals/km2 with an average of 0.56 individuals per km2, resulting in a scattered distribution. Genetic structure varied among distinct populations both in number of polymorphic loci and heterozygosity. Polecats from Brittany revealed a very low observed heterozygosity (HO = 0.028) whereas mean heterozygosity reached HO = 0.072 in Brière. That the lowest heterozygosity levels and highest inbreeding coefficient FIS were significantly associated with the lowest densities suggests that low densities may affect populations of carnivores. Both the loss of polymorphic loci and the reduction in heterozygosity rates suggest a density-dependent effect and population density can be arguably regarded as a factor affecting genetic diversity in top carnivores. [source] Determination of baseline susceptibility to Cry1Ab protein for Asian corn borer (Lep., Crambidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2005K. He Abstract:, Although transgenic Bacillus thuringiensis (Bt) corn can provide a new tool for control of the Asian corn borer (ACB), Ostrinia furnacalis (Guenée), concern has been raised regarding the possibility of the target insect evolving resistance to the Bt protein under intensive selection pressure from Bt corn. Therefore, it is necessary to establish baseline data to enable detection of changes in susceptibility in field populations after prolonged exposure to Bt corn. Susceptibility to purified Cry1Ab protein from Bt was determined for 10 populations of ACB from the major corn-growing regions of China, ranging geographically from Heilongjiang Province in the northeast to Shaanxi Province in the east-central part. Neonate ACB were exposed to semi-artificial diet incorporated with increasing Cry1Ab protein concentrations, and mortality and growth inhibition were evaluated after 7 days. The range of LC50 (50% lethal concentration) among the populations was 0.10 to 0.81 ,g/g (Cry1Ab protein/diet). Differences (P < 0.05) in susceptibility among the populations were significant. LC50s generated from the Huanghuaihai Summer Corn Region were higher than those from the Spring Corn Regions. Bt was one of the significant natural biomortality factors of overwintering generation ACB. There was a significant correlation between percentage of the larvae infected with Bt and their LC50 values to Cry1Ab protein in geographic distinct populations (r = 0.7350*, d.f. = 8, r0.05 = 0.632). Based on the background of Bt formulations used for corn insect pests control in these areas, these differences were not caused by prior exposure to Bt insecticides. Instead, the small differences likely reflect natural Bt selection pressure. Because the variation in susceptibility to Cry1Ab was small (<10-fold), the ACB apparently is susceptible to Cry1Ab across its range within China. [source] Evidence for selection on coloration in a Panamanian poison frog: a coalescent-based approachJOURNAL OF BIOGEOGRAPHY, Issue 5 2010Jason L. Brown Abstract Aim, The strawberry poison frog, Oophaga pumilio, has undergone a remarkable radiation of colour morphs in the Bocas del Toro archipelago in Panama. This species shows extreme variation in colour and pattern between populations that have been geographically isolated for < 10,000 years. While previous research has suggested the involvement of divergent selection, to date no quantitative test has examined this hypothesis. Location, Bocas del Toro archipelago, Panama. Methods, We use a combination of population genetics, phylogeography and phenotypic analyses to test for divergent selection in coloration in O. pumilio. Tissue samples of 88 individuals from 15 distinct populations were collected. Using these data, we developed a gene tree using the mitochondrial DNA (mtDNA) d-loop region. Using parameters derived from our mtDNA phylogeny, we predicted the coalescence of a hypothetical nuclear gene underlying coloration. We collected spectral reflectance and body size measurements on 94 individuals from four of the populations and performed a quantitative analysis of phenotypic divergence. Results, The mtDNA d-loop tree revealed considerable polyphyly across populations. Coalescent reconstructions of gene trees within population trees revealed incomplete genotypic sorting among populations. The quantitative analysis of phenotypic divergence revealed complete lineage sorting by colour, but not by body size: populations showed non-overlapping variation in spectral reflectance measures of body coloration, while variation in body size did not separate populations. Simulations of the coalescent using parameter values derived from our empirical analyses demonstrated that the level of sorting among populations seen in colour cannot reasonably be attributed to drift. Main conclusions, These results imply that divergence in colour, but not body size, is occurring at a faster rate than expected under neutral processes. Our study provides the first quantitative support for the claim that strong diversifying selection underlies colour variation in the strawberry poison frog. [source] Current and historical factors influencing patterns of species richness and turnover of birds in the Gulf of Guinea highlandsJOURNAL OF BIOGEOGRAPHY, Issue 8 2005Catherine H. Graham Abstract Aim, The aims of this paper are to: examine how current and historical ecological factors affect patterns of species richness, endemism and turnover in the Gulf of Guinea highlands, test theoretical biogeographical predictions and provide information for making informed conservation decisions. Location, The Gulf of Guinea highlands in West Africa. Methods, We used multivariate and matrix regression models, and cluster analyses to assess the influence of current climate and current and historical isolation on patterns of richness and turnover for montane birds across the highlands. We examined three groups of birds: montane species (including widespread species), montane endemics and endemic subspecies. We applied a complementarity-based reserve selection algorithm using species richness with irreplaceability measures to identify areas of high conservation concern. Results, Environmental factors influenced richness for all groups of birds (species, endemic species and subspecies). Areas with high and consistent annual rainfall showed the highest species and endemic richness. Species clusters for all groups of birds generally differentiated three major montane regions, which are topographically isolated. Multiple mantel tests identified these same regions for endemic species and subspecies. The influence of historical isolation varied by species group; distributions of endemic montane species and subspecies were more associated with historical breaks than were all montane species, which included widespread non-endemic species. Main conclusions, Our analyses indicated important geographical structure amongst the bird assemblages in the highlands and, therefore, conservation prioritization should include mountains from within the geographical subregions identified in these analyses because these regions may harbour evolutionarily distinct populations of birds. [source] Genetic structure of two populations of the Namibian giraffe, Giraffa camelopardalis angolensisAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Rick A. Brenneman Abstract Two geographically distinct populations of giraffe (Giraffa camelopardalis) were sampled for this study, the northern Namib Desert and Etosha National Park. Population genetic parameters and relationships within subpopulations were estimated to better understand the genetic architecture of this isolated subspecies. Gene flow between the geographically separated populations can be attributed to recent translocation of giraffe between the two populations. Inbreeding estimates in the six subpopulations studied were low though we found evidence that genetic drift may be affecting the genetic diversity of the isolated populations in northern Namibia. Population dynamics of the sampling locations was inferred with relationship coefficient analyses. Recent molecular systematics of the Namibian giraffe populations indicates that they are distinct from the subspecies Giraffa camelopardalis giraffa and classified as G. c. angolensis. Based on genetic analyses, these giraffe populations of northern Namibia, the desert-dwelling giraffe and those protected in Etosha National Park, are a distinct subspecies from that previously assumed; thus we add data on G. c. angolensis to our scientific knowledge of this giraffe of southern Africa. Résumé Deux populations de girafes (Giraffa camelopardalis) distinctes sur le plan géographique ont servi d'échantillons pour cette étude, celle du nord du Désert du Namib et celle du Parc National d'Etosha. Nous avons estimé les paramètres génétiques des populations et les relations au sein des sous-populations pour mieux comprendre l'architecture génétique de cette sous-espèce isolée. Les flux génétiques entre les populations séparées géographiquement peuvent être attribués à la récente translocation de girafes entre ces deux populations. L'inbreeding estimé dans les six sous-populations étudiées était faible, encore que nous ayons découvert des preuves que la dérive génétique pourrait bien affecter la diversité génétique des populations isolées dans le nord de la Namibie. La dynamique des populations des endroits où furent faits les échantillonnages fut déduite en fonction de l'analyse des coefficients. La nouvelle systématique moléculaire des populations de girafes de Namibie indique qu'elles sont distinctes de la sous-espèce Giraffa camelopardalis giraffa et classées comme G.c. angolensis. Selon les analyses génétiques, ces populations de girafes du nord de la Namibie, les girafes qui vivent dans le désert et celles qui sont protégées dans le Parc National d'Etosha sont une sous-espèce distincte de celle que l'on croyait auparavant, et nous ajoutons ainsi des données sur G.c. angolensisà la connaissance scientifique de cette girafe d'Afrique australe. [source] Sexual selection on phenotypic traits in a hybrid zone of Littorina saxatilis (Olivi)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2001R. Cruz Step clinal transitions in inherited character(s) between genetically distinct populations are usually referred to as hybrid zones. An example is found in the population of the intertidal snail Littorina saxatilis in Galicia (NW Spain). We studied the shape of the overall fitness surface for sexual selection in this hybrid zone, and the position of hybrids and pure morphs on this surface. We found that sexual divergent selection acted on a combination of phenotypic traits separating the pure morphs, and therefore that sexual selection contributed to morph differentiation. The average fitness of hybrids as a group was not significantly different from that of the pure morphs, but they did show divergent sexual selection in some traits. These results are in agreement with a model of divergent selection favouring both the pure morph as well as those hybrids most resembling each morph. The finding of divergent selection is remarkable because quadratic selection gradients are usually weak in nature. [source] A new species and geographical variation in the Telmatochromis temporalis complex (Teleostei, Cichlidae) from Lake TanganyikaJOURNAL OF FISH BIOLOGY, Issue 3 2003M. Hanssens Telmatochromis brachygnathus sp.n. is described from the southern and central parts of Lake Tanganyika. It can be distinguished from the similar T. temporalis mainly by its smaller mouth. Morphological distinct populations were found in both species. [source] Skin-type antifreeze protein expression in integumental cells of larval winter flounderJOURNAL OF FISH BIOLOGY, Issue 6 2002H. M. Murray Wholemount in situ hybridization using an antisense riboprobe complementary to a winter flounder Pleuronectes americanus skin-type antifreeze protein mRNA (WFp9) and immuno histochemistry using polyclonal antibodies to the corresponding protein detected cells expressing this gene in larval winter flounder integument. Immunohistochemistry revealed two distinct populations of cells. One population extended laterally along the length of the fish and was detectable using in situ hybridization. Staining in these cells declined following yolk-sac absorption suggesting that expression was only important here during early larval development. The polyclonal antibody for skin-type antifreeze protein also reacted with another population of cells scattered throughout the integument. These cells stained with alcian blue suggesting that they were integumental mucous cells. In situ hybridization using the above probe was not able to detect the corresponding transcript within the same cells. This suggests that another gene may be involved in the production of a similar protein in this case. These data suggest that two distinct populations of cells within the larval integument are involved in skin-type antifreeze protein expression and possibly involve the activity of at least two different genes. [source] Concordance between semen-derived HIV-1 proviral DNA and viral RNA hypervariable region 3 (V3) envelope sequences in cases where semen populations are distinct from those present in bloodJOURNAL OF MEDICAL VIROLOGY, Issue 1 2002Rebecca Curran Abstract Sequence analysis of the third hypervariable region (V3) of the envelope gene of the HIV-1 was carried out on HIV proviral and viral populations present in blood and semen. Phylogenetically distinct populations of virus were observed in three of the 10 patients analysed. Although the majority of the viruses were predicted to have an R5 phenotype, amino acid differences between blood and semen-derived virus and provirus sequences were observed at sites previously shown to affect cell tropism. Importantly, the semen proviral population was representative of that observed for cell-free virus. This indicates that seminal fluid mononuclear cells are possible sources for the cell-free virus in found in semen. J. Med. Virol. 67:9,19, 2002. © 2002 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||||||||||||||