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Search Results: 1 - 10 of 208365 matches for " Richard G Harrison "
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A Δ11 desaturase gene genealogy reveals two divergent allelic classes within the European corn borer (Ostrinia nubilalis)
Kerry A Geiler, Richard G Harrison
BMC Evolutionary Biology , 2010, DOI: 10.1186/1471-2148-10-112
Abstract: The Δ11 desaturase gene genealogy does not differentiate O. nubilalis pheromone strains. However, we find two distinct clades, separated by 2.9% sequence divergence, that do not sort with pheromone strain, geographic origin, or emergence time. We demonstrate that these clades do not represent gene duplicates, but rather allelic variation at a single gene locus.Analyses of patterns of variation at the Δ11 desaturase gene in ECB suggest that this enzyme does not contribute to reproductive isolation between pheromone strains (E and Z). However, our genealogy reveals two deeply divergent allelic classes. Standing variation at loci that contribute to mate choice phenotypes may permit novel pheromone mating systems to arise in the presence of strong stabilizing selection.The origin of novel sex pheromone signaling systems may play an important role in insect speciation. Insect sex pheromones are volatile compounds or mixtures of such compounds, used in many species for mate location, species recognition, and mate choice [1]. In many moths, females produce species-specific chemical cues, and males exhibit species-specific responses (both physiological and behavioral) that are important in mate finding. Males may also produce pheromones that are used by females in exercising mate choice (e.g., [2]). These chemical cues are often blends of long-chain hydrocarbons with acetate, alcohol, or aldehyde functional groups. Because pheromone biosynthetic pathways have been well characterized [3,4], it is now possible to examine how changes at the level of protein sequence or gene expression affect pheromone phenotype, patterns of mating, and ultimately, the nature and origin of barriers to gene exchange.Pheromone signaling systems are described as "highly canalized" because changes in production or response are opposed by strong selection against novel phenotypes [5,6]. Only if the same genes control signal and response (pleiotropy), or if the genes controlling these traits are tigh
Reproductive protein evolution in two cryptic species of marine chordate
Marie L Nydam, Richard G Harrison
BMC Evolutionary Biology , 2011, DOI: 10.1186/1471-2148-11-18
Abstract: Candidate gamete recognition proteins from two lineages of C. intestinalis (Type A and B) are evolving more rapidly than control proteins, consistent with patterns seen in insects and mammals. However, ω (dN/dS) is not significantly different between the sympatric and allopatric populations, and none of the polymorphism statistics show significant differences between sympatric and allopatric populations.Enhanced prezygotic isolation in sympatry has become a well-known feature of gamete recognition proteins in marine broadcast spawners. But in most cases the evolutionary process or processes responsible for this pattern have not been identified. Although gamete recognition proteins in C. intestinalis do appear to evolve more rapidly, on average, than proteins with other functions, rates of evolution are not different in allopatric and sympatric populations of the two reproductively isolated forms. That sympatry is probably human-mediated, and therefore recent, may explain the absence of RCD.Reproductive isolation between incipient species is of particular relevance to the process of speciation. Reproductive character displacement - 'the pattern of greater divergence of a (prezygotic) isolating trait in areas of sympatry between closely related taxa than in areas of allopatry' [1,2] is a common and taxonomically widespread pattern which is of great interest when studying reproductive isolation [3]. Evidence for RCD comes from groups as diverse as fungi [4,5], plants [6], insects [7,8] mollusks [9], fish [10,11] and amphibians [12]. However, the majority of RCD examples come from the Drosophila literature [13-17].The study of RCD has historically been tied to the process of reinforcement, the evolution of prezygotic isolation resulting from selection against hybrid individuals [13-15]. More recently, however, workers have emphasized that RCD can be caused by other factors, including ecological variables [18,19]. But even where selection has been shown to play a role in
EST analysis of male accessory glands from Heliconius butterflies with divergent mating systems
James R Walters, Richard G Harrison
BMC Genomics , 2008, DOI: 10.1186/1471-2164-9-592
Abstract: We successfully sequenced 933 ESTs clustering into 371 unigenes from H. erato and 1033 ESTs clustering into 340 unigenes from H. melpomene. Results from the two species were very similar. Approximately a third of the unigenes showed no significant BLAST similarity (E-value <10-5) to sequences in GenBank's non-redundant databases, indicating that a large proportion of novel genes are expressed in Heliconius male accessory glands. In both species only a third of accessory gland unigenes were also found among genes expressed in wing tissue. About 25% of unigenes from both species encoded secreted proteins. This includes three groups of highly abundant unigenes encoding repetitive proteins considered to be candidate seminal fluid proteins; proteins encoded by one of these groups were detected in H. erato spermatophores.This collection of ESTs will serve as the foundation for the future identification and evolutionary analysis of male reproductive proteins in Heliconius butterflies. These data also represent a significant advance in the rapidly growing collection of genomic resources available in Heliconius butterflies. As such, they substantially enhance this taxon as a model system for investigating questions of ecological, phenotypic, and genomic diversity.One of the most promising and productive research approaches in contemporary biology involves deploying modern genomic methods to investigate the origin, maintenance, and function of biological diversity present in natural populations. Research efforts in this nascent field of evolutionary and ecological functional genomics (EEFG) generally can be split into two categories [1,2]. One approach studies natural populations of the few taxa (or their close relatives) that are already well-established laboratory model systems, making use of the extensive molecular genetic and genomic resources available for such organisms (e.g. Drosophila and Arabidopsis) [3,4]. The alternative approach focuses on taxa which may be less t
Influence of the Male Ejaculate on Post-Mating Prezygotic Barriers in Field Crickets
Erica L. Larson, Jose A. Andrés, Richard G. Harrison
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046202
Abstract: Post-copulatory interactions between males and females involve highly coordinated, complex traits that are often rapidly evolving and divergent between species. Failure to produce and deposit eggs may be a common post-mating prezygotic barrier, yet little is known about what prevents the induction of egg-laying between species. The field crickets, Gryllus firmus and G. pennsylvanicus are isolated by a one-way reproductive incompatibility; G. pennsylvanicus males fail to fertilize G. firmus eggs or to induce normal egg-laying in G. firmus females. We use experimental crosses to elucidate the role of accessory gland-derived vs. testis-derived components of the G. firmus male ejaculate on egg-laying in conspecific and heterospecific crosses. Using surgical castrations to create ‘spermless’ males that transfer only seminal fluid proteins (SFPs) we test whether G. firmus male SFPs can induce egg-laying in conspecific crosses and rescue egg-laying in crosses between G. pennsylvanicus males and G. firmus females. We find G. firmus SFPs induce only a small short-term egg-laying response and that SFPs alone cannot explain the normal induction of egg-laying. Gryllus firmus SFPs also do not rescue the heterospecific cross. Testis-derived components, such as sperm or prostaglandins, most likely stimulate egg-laying or act as transporters for SFPs to targets in the female reproductive tract. These results highlight the utility of experimental approaches for investigating the phenotypes that act as barriers between species and suggest that future work on the molecular basis of the one-way incompatibility between G. firmus and G. pennsylvanicus should focus on divergent testis-derived compounds or proteins in addition to SFPs.
Immunohistochemical evidence for an endocrine/paracrine role for ghrelin in the reproductive tissues of sheep
David W Miller, Joanne L Harrison, Yvonne A Brown, Una Doyle, Alanna Lindsay, Clare L Adam, Richard G Lea
Reproductive Biology and Endocrinology , 2005, DOI: 10.1186/1477-7827-3-60
Abstract: Antibodies raised against ghrelin and its functional receptor, GHSR-type 1a, were used in standard immunohistochemical protocols on various reproductive tissues collected from adult and fetal sheep. GHSR-1a mRNA presence was also confirmed by in situ hybridisation. SCF and PCNA immunoexpression was investigated in fetal testicular samples. Adult and fetal testicular immunostaining for ghrelin, GHSR-1a, SCF and PCNA was analysed using computer-aided image analysis. Image analysis data were subjected to one-way ANOVA, with differences in immunostaining between time-points determined by Fisher's least significant difference.In adult sheep tissue, ghrelin and GHSR-1a immunostaining was detected in the stomach (abomasum), anterior pituitary gland, testis, ovary, and hypothalamic and hindbrain regions of the brain. In the adult testis, there was a significant effect of season (photoperiod) on the level of immunostaining for ghrelin (p < 0.01) and GHSR-1a (p < 0.05). In the fetal sheep testis, there was a significant effect of gestational age on the level of immunostaining for ghrelin (p < 0.001), GHSR-1a (p < 0.05), SCF (p < 0.05) and PCNA (p < 0.01).Evidence is presented for the presence of ghrelin and its receptor in various reproductive tissues of the adult and fetal sheep. In addition, the data indicate that testicular expression of ghrelin and its receptor is physiologically regulated in the adult and developmentally regulated in the fetus. Therefore, the ghrelin ligand/receptor system may have a role (endocrine and/or paracrine) in the development (cellular proliferation) and function of the reproductive axis of the sheep.Ghrelin is an acylated polypeptide hormone secreted predominantly by endocrine cells of the stomach [1,2]. Several lines of evidence implicate ghrelin in the regulation of growth hormone (GH) release, energy balance, food intake and body weight [3-6], with the effects mediated via a 7-transmembrane G protein-coupled receptor, the GH secretagogue re
The NR4A2 Nuclear Receptor Is Recruited to Novel Nuclear Foci in Response to UV Irradiation and Participates in Nucleotide Excision Repair
Kasturee Jagirdar, Kelvin Yin, Matthew Harrison, Wen Lim, George E. O. Muscat, Richard A. Sturm, Aaron G. Smith
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078075
Abstract: Ultraviolet radiation (UVR) is one of the most common mutagens encountered by humans and induces the formation of cyclobutane pyrimidine dimers (CPDs) and pyrimidine-(6-4)-pyrimidone photoproduct (6-4PP) lesions in the genomic DNA. To prevent the accumulation of deleterious mutations these lesions must be efficiently repaired, primarily by nucleotide excision repair. We have previously demonstrated that the NR4A family of nuclear receptors are crucial mediators of the DNA repair function of the MC1R signalling pathway in melanocytes. Here we explore the role of the NR4A2 protein in the DNA repair process further. Using EYFP tagged-NR4A2 we have demonstrated a UVR induced recruitment to distinct nuclear foci where they co-localise with known DNA repair proteins. We reveal that the N-terminal domain of the receptor is required for this translocation and identify a role for p38 and PARP signalling in this process. Moreover disruption of the functional integrity of the Ligand Binding Domain of the receptor by deleting the terminal helix 12 effectively blocks co-localisation of the receptor with DNA repair factors. Restored co-localisation of the mutant receptor with DNA repair proteins in the presence of a Histone Deacetylase Inhibitor suggests that impaired chromatin accessibility underpins the mis-localisation observed. Finally NR4A2 over-expression facilitated a more efficient clearance of UVR induced CPD and 6-4PP lesions. Taken together these data uncover a novel role for the NR4A nuclear receptors as direct facilitators of nucleotide excision repair.
Magnetization Degree of Gamma-Ray Burst Fireballs: Numerical Study
Richard Harrison,Shiho Kobayashi
Physics , 2012, DOI: 10.1088/0004-637X/772/2/101
Abstract: The relative strength between forward and reverse shock emission in early gamma-ray burst afterglow reflects that of magnetic energy densities in the two shock regions. We numerically show that with the current standard treatment, the fireball magnetization is underestimated by up to two orders of magnitude. This discrepancy is especially large in the sub-relativistic reverse shock regime (i.e. the thin shell and intermediate regime) where most optical flashes were detected. We provide new analytic estimates of the reverse shock emission based on a better shock approximation, which well describe numerical results in the intermediate regime. We show that the reverse shock temperature at the onset of afterglow is constant, $(\bar{\Gamma}_d-1)\sim 8\times10^{-2}$, when the dimensionless parameter $\xi_{0}$ is more than several. Our approach is applied to case studies of GRB 990123 and 090102, and we find that magnetic fields in the fireballs are even stronger than previously believed.
An Unusual Zoonosis: Liver Abscess Secondary to Asymptomatic Colonic Foreign Body
Justin S. Gundara,Richard Harrison
HPB Surgery , 2010, DOI: 10.1155/2010/794271
Abstract: A liver abscess may arise following any insult to gut integrity allowing portal drainage of bacteria to hepatocytes. Foreign bodies such as bones, toothpicks and items of stationery have previously been implicated in compromising gut epithelium. Here we present the case of a 57 year old man suffering from a left liver abscess. This was defined on CT which incidentally also identified a chicken bone protruding through the wall of the distal sigmoid colon. Whilst unwell with upper abdominal pain and sepsis, the presumed source of portal sepsis within the colon remained asymptomatic throughout. Following percutaneous drainage, the liver abscess resolved but the chicken bone had not passed at two months, necessitating atraumatic removal at colonoscopy. A high rate of incidental diagnoses suggests that unidentified foreign bodies may be vastly under recognised in cases of hepatic sepsis. Thus, identification of the precise mechanism of the liver insult demands thorough consideration; foreign body should be considered in all cases. A liver abscess may arise following any insult to gut integrity that allows portal drainage of large bacterial showers to susceptible hepatocytes. Foreign bodies such as bones, toothpicks, and items of stationery have been implicated in compromising gut epithelium and may be encountered through unknowing ingestion or even psychiatric pica [1–7]. This case involved a 57-year-old Caucasian male presenting with a five-day history of progressive epigastric abdominal pain. This was punctuated by 48 hours of nausea, vomiting, and fever. Past medical history was significant only for an electively repaired left inguinal hernia. He had not undergone any recent travel, exposure to sick contacts or animals, and there was no history of trauma. Upon examination, the patient appeared unwell and diaphoretic, with a fever of 38.7°C. Abdominal examination revealed generalised tenderness and focal epigastric peritonism. Blood tests were significant for a white cell count of (neutrophils: 11.1) and deranged liver function tests (bilirubin: 30; GGT: 311; ALP: 418; AST: 45; ALT: 58 units resp.). Computed tomography (CT) of the abdomen and pelvis showed a ?cm irregular mass within liver segment III. The lesion possessed ill-defined margins and a partially cystic character, appearances consistent with liver abscess (Figure 1). Figure 1: CT demonstrating left liver abscess. Incidentally, within the pelvis, a linear density was also seen to be traversing the lumen of the mid sigmoid colon and extending into the presacral soft tissues at the S1 level. This
An immunohistochemical study of the localization and developmental expression of ghrelin and its functional receptor in the ovine placenta
Joanne L Harrison, Clare L Adam, Yvonne A Brown, Jacqueline M Wallace, Raymond P Aitken, Richard G Lea, David W Miller
Reproductive Biology and Endocrinology , 2007, DOI: 10.1186/1477-7827-5-25
Abstract: Antibodies raised against ghrelin and GHSR-1a were used in standard immunohistochemical protocols on placental tissues collected from pregnant ewes (n = 6 per gestational time point) at days 50, 80, 100, 128 and 135 of gestation (term ≈ day 145). Immunostaining for ghrelin and GHSR-1a was quantified using computer-aided image analysis. Image analysis data were subjected to one-way ANOVA, with differences in immunostaining between time-points determined by Fisher's least significant difference.Positive immunostaining for ghrelin was detected in ovine placentae at all gestational time points, with staining localized to the maternal epithelium, caruncle and trophectoderm. There was a significant effect of gestational age (p < 0.001) on the placental expression of ghrelin, with maximal levels at gestational day 80. GHSR-1a immunostaining was detected in the fetal trophectoderm at all time points. In contrast to the gestational pattern of ghrelin expression, there was no effect of gestational age on placental GHSR-1a immunoexpression.Ghrelin and GHSR-1a are both present in the ovine placenta, and ghrelin displays a developmentally-related pattern of expression. Therefore, these data strongly suggest that the ghrelin system may have a role in feto-placental development in sheep.Recent studies have indicated a role for the orexigenic hormone, ghrelin, in the regulation of energy balance, food intake and body weight in monogastric species [1-4]. Ghrelin is also involved in the regulation of growth hormone (GH) secretion, being identified in 1999 as the endogenous ligand for the GH secretagogue receptor (GHSR-1a), a 7-transmembrane G protein coupled receptor [5]. In addition to its primary origin in the stomach [5,6], ghrelin and GHSR-1a have been found, in humans and rats, to have a wide distribution in other tissues, including the bowel, heart, kidney, liver, lung, pancreas, brain, gonads and placenta [7-9]. The significance of this wide tissue distribution has yet to be d
Astrometry with the Hubble Space Telescope: Trigonometric Parallaxes of Planetary Nebula Nuclei: NGC 6853, NGC 7293, Abell 31, and DeHt 5
G. Fritz Benedict,Barbara E. McArthur,Ralf Napiwotzki,Thomas E. Harrison,Hugh C. Harris,Edmund Nelan,Howard E. Bond,Richard J. Patterson,Robin Ciardullo
Physics , 2009, DOI: 10.1088/0004-6256/138/6/1969
Abstract: We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi) parallaxes with astrometric data from Fine Guidance Sensors FGS 1R and FGS 3, white-light interferometers on the Hubble Space Telescope (HST). Proper motions, spectral classifications and VJHKT_2M and DDO51 photometry of the stars comprising the astrometric reference frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each PNN. Weighted averaging with previous independent parallax measurements yields an average parallax precision, \sigma_{\pi}/\pi = 5 %. Derived distances are: d_{NGC 6853}=405^{+28}_{-25}pc, d_{NGC 7293}=216^{+14}_{-12} pc, d_{Abell 31} = 621^{+91}_{-70} pc, and d_{DeHt 5} = 345^{+19}_{-17} pc. These PNNi distances are all smaller than previously derived from spectroscopic analyses of the central stars. Derived absolute magnitudes and previously measured effective temperatures permit estimates of PNNi radii, through both the Stefan-Boltzmann relation and Eddington fluxes. Comparing absolute magnitudes with post-AGB models provides mass estimates. Masses cluster around 0.57 M(sun), close to the peak of the white dwarf mass distribution. Adding a few more PNNi with well-determined distances and masses, we compare all the PNNi with cooler white dwarfs of similar mass, and confirm, as expected, that PNNi have larger radii than white dwarfs that have reached their final cooling tracks. (Abridged)
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