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Search Results: 1 - 10 of 417748 matches for " James M Cook "
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Effects of a sex-ratio distorting endosymbiont on mtDNA variation in a global insect pest
Ana M Delgado, James M Cook
BMC Evolutionary Biology , 2009, DOI: 10.1186/1471-2148-9-49
Abstract: The mtDNA phylogeny of 95 individuals sampled from 10 countries on four continents revealed two major clades. One contained only Wolbachia-infected individuals from Malaysia and Kenya, while the other contained only uninfected individuals, from all countries including Malaysia and Kenya. Within the uninfected group was a further clade containing all individuals from Australasia and displaying very limited sequence variation. In contrast, a biparental nuclear gene phylogeny did not have infected and uninfected clades, supporting the notion that maternally-inherited Wolbachia are responsible for the mtDNA pattern. Only about 5% (15/306) of our global sample of individuals was infected with the plutWB1 isolate and even within infected local populations, many insects were uninfected. Comparisons of infected and uninfected isofemale lines revealed that plutWB1 is associated with sex ratio distortion. Uninfected lines have a 1:1 sex ratio, while infected ones show a 2:1 female bias.The main correlate of mtDNA variation in P. xylostella is presence or absence of the plutWB1 infection. This is associated with substantial sex ratio distortion and the underlying mechanisms deserve further study. In contrast, geographic origin is a poor predictor of moth mtDNA sequences, reflecting human activity in moving the insects around the globe. The exception is a clade of Australasian individuals, which may reflect a bottleneck during their recent introduction to this region.Patterns of within-species variation in animal mtDNA are influenced by various factors, including mutation, selection, demography and geography, and analysis of haplotype diversity patterns can provide information on population structure and gene flow. In addition, mtDNA sequences are often used to investigate the evolutionary history of a species, by combining geographic and phylogenetic information in phylogeographic studies [1]. However, theory predicts that mtDNA variation and evolution may also be influenced s
Ant Larval Demand Reduces Aphid Colony Growth Rates in an Ant-Aphid Interaction
Tom H. Oliver,Simon R. Leather,James M. Cook
Insects , 2012, DOI: 10.3390/insects3010120
Abstract: Ants often form mutualistic interactions with aphids, soliciting honeydew in return for protective services. Under certain circumstances, however, ants will prey upon aphids. In addition, in the presence of ants aphids may increase the quantity or quality of honeydew produced, which is costly. Through these mechanisms, ant attendance can reduce aphid colony growth rates. However, it is unknown whether demand from within the ant colony can affect the ant-aphid interaction. In a factorial experiment, we tested whether the presence of larvae in Lasius niger ant colonies affected the growth rate of Aphis fabae colonies. Other explanatory variables tested were the origin of ant colonies (two separate colonies were used) and previous diet (sugar only or sugar and protein). We found that the presence of larvae in the ant colony significantly reduced the growth rate of aphid colonies. Previous diet and colony origin did not affect aphid colony growth rates. Our results suggest that ant colonies balance the flow of two separate resources from aphid colonies- renewable sugars or a protein-rich meal, depending on demand from ant larvae within the nest. Aphid payoffs from the ant-aphid interaction may change on a seasonal basis, as the demand from larvae within the ant colony waxes and wanes.
Deep mtDNA divergences indicate cryptic species in a fig-pollinating wasp
Eleanor R Haine, Joanne Martin, James M Cook
BMC Evolutionary Biology , 2006, DOI: 10.1186/1471-2148-6-83
Abstract: We studied variation in 71 fig-pollinating wasps from across the large geographic range of Ficus rubiginosa in Australia. All wasps sampled belong to one morphological species (Pleistodontes imperialis), but we found four deep mtDNA clades that differed from each other by 9–17% nucleotides. As these genetic distances exceed those normally found within species and overlap those (10–26%) found between morphologically distinct Pleistodontes species, they strongly suggest cryptic fig wasp species. mtDNA clade diversity declines from all four present in Northern Queensland to just one in Sydney, near the southern range limit. However, at most sites multiple clades coexist and can be found in the same tree or even the same fig fruit and there is no evidence for parallel sub-division of the host fig species. Both mtDNA data and sequences from two nuclear genes support the monophyly of the "P. imperialis complex" relative to other Pleistodontes species, suggesting that fig wasp divergence has occurred without any host plant shift. Wasps in clade 3 were infected by a single strain (W1) of Wolbachia bacteria, while those in other clades carried a double infection (W2+W3) of two other strains.Our study indicates that cryptic fig-pollinating wasp species have developed on a single host plant species, without the involvement of host plant shifts, or parallel host plant divergence. Despite extensive evidence for coevolution between figs and fig wasps, wasp speciation may not always be linked strongly with fig speciation.Hosts and their symbionts often have major effects on each other's evolution. Indeed, many symbioses show coevolution of key traits, such as parasite virulence and host resistance and, in some cases, may also manifest cospeciation. A classic example of a coevolved mutualism is provided by the obligate relationship between fig trees (Ficus species) and fig-pollinating wasps (Hymenoptera:Agaonidae). Female wasps enter receptive fig syconia (inflorescences) via a nar
Spatial Stratification of Internally and Externally Non-Pollinating Fig Wasps and Their Effects on Pollinator and Seed Abundance in Ficus burkei
Sarah Al-Beidh,Derek W. Dunn,James M. Cook
ISRN Zoology , 2012, DOI: 10.5402/2012/908560
Abstract: Fig trees (Ficus spp.) are pollinated by tiny wasps that enter their enclosed inflorescences (syconia). The wasp larvae also consume some fig ovules, which negatively affects seed production. Within syconia, pollinator larvae mature mostly in the inner ovules whereas seeds develop mostly in outer ovules—a stratification pattern that enables mutualism persistence. Pollinators may prefer inner ovules because they provide enemy-free space from externally ovipositing parasitic wasps. In some Australasian Ficus, this results in spatial segregation of pollinator and parasite offspring within syconia, with parasites occurring in shorter ovules than pollinators. Australian figs lack non-pollinating fig wasps (NPFW) that enter syconia to oviposit, but these occur in Africa and Asia, and may affect mutualist reproduction via parasitism or seed predation. We studied the African fig, F. burkei, and found a similar general spatial pattern of pollinators and NPFWs within syconia as in Australasian figs. However, larvae of the NPFW Philocaenus barbarus, which enters syconia, occurred in inner ovules. Philocaenus barbarus reduced pollinator abundance but not seed production, because its larvae replaced pollinators in their favoured inner ovules. Our data support a widespread role for NPFWs in contributing to factors preventing host overexploitation in fig-pollinator mutualisms. 1. Introduction Mutualisms are reciprocally beneficial interspecific interactions [1, 2], and a well-known system is that between fig trees (Ficus spp.) and their agaonid wasp pollinators [3–6]. In return for pollination, the wasps gall some fig ovules, which are then eaten by the larvae. About half (300+) of Ficus species are monoecious, where both male flowers and ovules are present in the same syconium (enclosed inflorescence or “fig”). Within monoecious syconia, ovules are highly variable in length [7–10]. Long (inner) ovules have short styles and mature near the centre of the syconium, whereas short (outer), long-styled ovules mature nearer the outer wall (see Figure 1). Female pollinating wasps (foundresses) lay their eggs by inserting their ovipositors down the flower styles. At maturation, wasp galls are clustered at the syconium’s centre [4, 6, 9–13] with seeds at the outer wall. This spatial stratification of pollinating wasps and seeds enables mutualism stability, although the mechanisms preventing the wasps from galling all ovules are unclear. Figure 1: Variation in style and pedicel length in female flowers of monoecious Ficus (adapted from Dunn et al. [ 13]). Mechanisms proposed to
Opposing Effects of Omega-3 and Omega-6 Long Chain Polyunsaturated Fatty Acids on the Expression of Lipogenic Genes in Omental and Retroperitoneal Adipose Depots in the Rat
B. S. Muhlhausler,R. Cook-Johnson,M. James,D. Miljkovic,E. Duthoit,R. Gibson
Journal of Nutrition and Metabolism , 2010, DOI: 10.1155/2010/927836
Abstract: This study aimed to determine the effect of varying dietary intake of the major n-3 PUFA in human diets, -linolenic acid (ALA; 18 : 3n-3), on expression of lipogenic genes in adipose tissue. Rats were fed diets containing from 0.095%en to 6.3%en ALA and a constant n-6 PUFA level for 3 weeks. Samples from distinct adipose depots (omental and retroperitoneal) were collected and mRNA expression of the pro-lipogenic transcription factors Sterol-Retinoid-Element-Binding-Protein1c (SREBP1c) and Peroxisome Proliferator Activated Receptor- (PPAR), lipogenic enzymes Sterol-coenzyme Desaturase1 (SCD-1), Fatty Acid Synthase (FAS), lipoprotein lipase (LPL) and glycerol-3-phosphate dehydrogenase (G3PDH) and adipokines leptin and adiponectin determined by qRT-PCR. Increasing dietary ALA content resulted in altered expression of SREBP1c, FAS and G3PDH mRNA in both adipose depots. SREBP1c mRNA expression was related directly to n-6 PUFA concentrations (omental, 2=.71; <.001; Retroperitoneal, 2=.20; <.002), and inversely to n-3 PUFA concentrations (omental, 2=.59; <.001; Retroperitoneal, 2=.19; <.005) independent of diet. The relationship between total n-6 PUFA and SREBP1c mRNA expression persisted when the effects of n-3 PUFA were controlled for. Altering red blood cell concentrations of n-3 PUFA is thus associated with altered expression of lipogenic genes in a depot-specific manner and this effect is modulated by prevailing n-6 PUFA concentrations.
Methods underpinning national clinical guidelines for hypertension: describing the evidence shortfall
Fiona Campbell, Heather O Dickinson, Julia VF Cook, Fiona R Beyer, Martin Eccles, James M Mason
BMC Health Services Research , 2006, DOI: 10.1186/1472-6963-6-47
Abstract: This paper compares the methods used in gathering, analysing and linking of evidence to guideline recommendations in ten current hypertension guidelines.It found several guidelines had failed to implement methods of searching for the relevant literature, critical analysis and linking to recommendations that minimise the risk of bias in the interpretation of research evidence. The more rigorous guidelines showed discrepancies in recommendations and grading that reflected different approaches to the use of evidence in guideline development.Clinical practice guidelines as a methodology are clearly still an evolving health care technology.Clinical practice guidelines can provide building blocks for changing and improving health care [1] and are a useful means of bridging the gap between scientific research evidence and usual practice [2]. They are defined as 'systematically developed statements to assist physicians and patients about appropriate health care for specific clinical circumstances' [3]. To achieve their potential as effective tools for improving health care they need to maximise their validity, a feature related to the use of evidence within a guideline and development using a multidisciplinary process [4]. However, despite an apparently explicit methodology there are variations in what guidelines say and how they relate this to underlying evidence [3,5,6]. There is also concern that guideline development may be subject to external influence [7,8].Like many other conditions hypertension has been the subject of many different international guidelines. The World Health Organisation (WHO) have described hypertension – defined as a blood pressure of greater than 140/90 mmHg – as one of the ten leading risk factors influencing the global burden of disease [9]. It is a contributory factor in ischaemic heart disease and cerebrovascular disease accounting for 20% and 10% of all deaths in England and Wales respectively [10]. Reducing blood pressure levels leads to si
Site-specific analysis of gene expression in early osteoarthritis using the Pond-Nuki model in dogs
Aaron M Stoker, James L Cook, Keiichi Kuroki, Derek B Fox
Journal of Orthopaedic Surgery and Research , 2006, DOI: 10.1186/1749-799x-1-8
Abstract: The ACL of four dogs was completely transected arthroscopically, and the contralateral limb was used as the non-operated control. After two weeks the dogs were euthanatized and tissues harvested from the tibial plateau and femoral condyles of both limbs. Two dogs were used for histologic analysis and Mankin scoring. From the other two dogs the surface of the femoral condyle and tibial plateau were divided into four regions each, and tissues were harvested from each region for biochemical (GAG and HP) and gene expression analysis. Significant changes in gene expression were determined using REST-XL, and Mann-Whitney rank sum test was used to analyze biochemical data. Significance was set at (p < 0.05).Significant differences were not observed between ACL-X and control limbs for Mankin scores or GAG and HP tissue content. Further, damage to the tissue was not observed grossly by India ink staining. However, significant changes in gene expression were observed between ACL-X and control tissues from each region analyzed, and indicate that a unique regional gene expression profile for impending ACL-X induced joint pathology may be identified in future studies.The data obtained from this study lend credence to the research approach and model for the characterization of OA, and the identification and validation of future diagnostic modalities. Further, the changes observed in this study may reflect the earliest changes in AC reported during the development of OA, and may signify pathologic changes within a stage of disease that is potentially reversible.Osteoarthritis (OA) is a progressive and debilitating disease that may take years to clinically manifest in affected individuals [1,2]. OA often progresses from a focal loss of articular cartilage integrity to a complete loss of joint structure and function. Currently, there is not a cure for OA, and available treatments only slow the progression of disease. Early diagnosis with initiation of treatment may dramatically impr
A Review of Translational Animal Models for Knee Osteoarthritis
Martin H. Gregory,Nicholas Capito,Keiichi Kuroki,Aaron M. Stoker,James L. Cook,Seth L. Sherman
Arthritis , 2012, DOI: 10.1155/2012/764621
Abstract: Knee osteoarthritis remains a tremendous public health concern, both in terms of health-related quality of life and financial burden of disease. Translational research is a critical step towards understanding and mitigating the long-term effects of this disease process. Animal models provide practical and clinically relevant ways to study both the natural history and response to treatment of knee osteoarthritis. Many factors including size, cost, and method of inducing osteoarthritis are important considerations for choosing an appropriate animal model. Smaller animals are useful because of their ease of use and cost, while larger animals are advantageous because of their anatomical similarity to humans. This evidence-based review will compare and contrast several different animal models for knee osteoarthritis. Our goal is to inform the clinician about current research models, in order to facilitate the transfer of knowledge from the “bench” to the “bedside.” 1. Introduction Knee osteoarthritis (OA) affects an estimated 27 million Americans [1]. Despite extensive research seeking therapeutic interventions for this disease, there are still no proven disease-modifying treatments for osteoarthritis. With the number of total knee arthroplasties growing each year, this is a rapidly expanding public health epidemic, both in terms of health-related quality of life and financial expenditure [2]. The major hurdles in osteoarthritis research include elucidating the mechanisms of disease, determining methods for early detection, and developing strategies for intervention and disease modification. Translational research is a critical step towards understanding and mitigating the long-term effects of this disease process. Animal models provide practical and clinically relevant ways to study both the natural history and response to treatment of knee osteoarthritis. A translational animal model is one that facilitates the translation of findings from basic science to practical applications that enhance human health and well-being. The other types of animal models would include veterinary clinical (an animal model of an animal disease), comparative, discovery, and mechanistic, among others. This evidence-based review will compare and contrast several different animal models for knee (stifle) osteoarthritis. Our goal is to provide an outline of the factors that are important in choosing an appropriate animal model and to provide illustrative examples that demonstrate how each animal model has aided our understanding of OA. The OARSI histopathology initiative brought
Opposing Effects of Omega-3 and Omega-6 Long Chain Polyunsaturated Fatty Acids on the Expression of Lipogenic Genes in Omental and Retroperitoneal Adipose Depots in the Rat
B. S. Muhlhausler,R. Cook-Johnson,M. James,D. Miljkovic,E. Duthoit,R. Gibson
Journal of Nutrition and Metabolism , 2010, DOI: 10.1155/2010/927836
Abstract: This study aimed to determine the effect of varying dietary intake of the major n-3 PUFA in human diets, -linolenic acid (ALA; 18?:?3n-3), on expression of lipogenic genes in adipose tissue. Rats were fed diets containing from 0.095%en to 6.3%en ALA and a constant n-6 PUFA level for 3 weeks. Samples from distinct adipose depots (omental and retroperitoneal) were collected and mRNA expression of the pro-lipogenic transcription factors Sterol-Retinoid-Element-Binding-Protein1c (SREBP1c) and Peroxisome Proliferator Activated Receptor- (PPAR ), lipogenic enzymes Sterol-coenzyme Desaturase1 (SCD-1), Fatty Acid Synthase (FAS), lipoprotein lipase (LPL) and glycerol-3-phosphate dehydrogenase (G3PDH) and adipokines leptin and adiponectin determined by qRT-PCR. Increasing dietary ALA content resulted in altered expression of SREBP1c, FAS and G3PDH mRNA in both adipose depots. SREBP1c mRNA expression was related directly to n-6 PUFA concentrations (omental, ; ; Retroperitoneal, ; ), and inversely to n-3 PUFA concentrations (omental, ; ; Retroperitoneal, ; ) independent of diet. The relationship between total n-6 PUFA and SREBP1c mRNA expression persisted when the effects of n-3 PUFA were controlled for. Altering red blood cell concentrations of n-3 PUFA is thus associated with altered expression of lipogenic genes in a depot-specific manner and this effect is modulated by prevailing n-6 PUFA concentrations. 1. Introduction In adults, changes in the patterns of expression of key regulatory and functional genes within adipose tissue are important determinants of fat accumulation and can profoundly influence the ability of an individual to maintain energy balance and resist weight gain [1–4]. The transcription factors Sterol Retinoid Binding Protein-1c (SREBP1c) and Peroxisome Proliferator Activated Receptor- (PPAR ) regulate lipid storage and adipose tissue mass by regulating the expression of genes in the lipogenic pathway. Specifically, activation of SREBP1c and PPAR increases the expression of a series of enzymes which increase the synthesis and storage of triglycerides in adipose tissue, including lipoprotein lipase (LPL), which increases uptake of fatty acids from the circulation, and Fatty Acid Synthase (FAS) and glycerol-3-phosphate dehydrogenase (G3PDH), which both promote triglyceride synthesis [5]. While the cause of the current global obesity epidemic includes excessive food consumption and reduced exercise, there is increasing evidence that both the quantity and the type of fats in the diet have a major role in defining the propensity of an individual to
α4-Containing GABAA Receptors are Required for Antagonism of Ethanol-Induced Motor Incoordination and Hypnosis by the Imidazobenzodiazepine Ro15-4513
Sangeetha V. Iyer,James M. Cook,Harry L. June,Gregg E. Homanics
Frontiers in Pharmacology , 2011, DOI: 10.3389/fphar.2011.00018
Abstract: Alcohol (ethanol) is widely consumed for its desirable effects but unfortunately has strong addiction potential. Some imidazobenzodiazepines such as Ro15-4513 are able to antagonize many ethanol-induced behaviors. Controversial biochemical and pharmacological evidence suggest that the effects of these ethanol antagonists and ethanol are mediated specifically via overlapping binding sites on α4/δ-containing GABAA-Rs. To investigate the requirement of α4-containing GABAA-Rs in the mechanism of action of Ro15-4513 on behavior, wildtype (WT) and α4 knockout (KO) mice were compared for antagonism of ethanol-induced motor incoordination and hypnosis. Motor effects of ethanol were tested in two different fixed speed rotarod assays. In the first experiment, mice were injected with 2.0 g/kg ethanol followed 5 min later by 10 mg/kg Ro15-4513 (or vehicle) and tested on a rotarod at 8 rpm. In the second experiment, mice received a single injection of 1.5 g/kg ethanol ± 3 mg/kg Ro15-4513 and were tested on a rotarod at 12 rpm. In both experiments, the robust Ro15-4513 antagonism of ethanol-induced motor ataxia that was observed in WT mice was absent in KO mice. A loss of righting reflex (LORR) assay was used to test Ro15-4513 (20 mg/kg) antagonism of ethanol (3.5 g/kg)-induced hypnosis. An effect of sex was observed on the LORR assay, so males and females were analyzed separately. In male mice, Ro15-4513 markedly reduced ethanol-induced LORR in WT controls, but α4 KO mice were insensitive to this effect of Ro15-4513. In contrast, female KO mice did not differ from WT controls in the antagonistic effects of Ro15-4513 on ethanol-induced LORR. We conclude that Ro15-4513 requires α4-containing receptors for antagonism of ethanol-induced LORR (in males) and motor ataxia.
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