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Power Et Al. (power + et_al)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Application of the New Keystone-Species Concept to Prairie Dogs: How Well Does It Work?

CONSERVATION BIOLOGY, Issue 6 2000
Natasha B. Kotliar
This prompted Power et al. (1996) to refine the definition: keystone species have large effects on community structure or ecosystem function (i.e., high overall importance), and this effect should be large relative to abundance (i.e., high community importance). Using prairie dogs (Cynomys spp.) as an example, I review operational and conceptual difficulties encountered in applying this definition. As applied to prairie dogs, the implicit assumption that overall importance is a linear function of abundance is invalid. In addition, community importance is sensitive to abundance levels, the definition of community, and sampling scale. These problems arise largely from the equation for community importance, as used in conjunction with removal experiments at single abundance levels. I suggest that we shift from the current emphasis on the dualism between keystone and nonkeystone species and instead examine how overall and community importance vary (1) with abundance, (2) across spatial and temporal scales, and (3) under diverse ecological conditions. In addition, I propose that a third criterion be incorporated into the definition: keystone species perform roles not performed by other species or processes. Examination of how these factors vary among populations of keystone species should help identify the factors contributing to, or limiting, keystone-level functions, thereby increasing the usefulness of the keystone-species concept in ecology and conservation. Although the quantitative framework of Power et al. falls short of being fully operational, my conceptual guidelines may improve the usefulness of the keystone-species concept. Careful attention to the factors that limit keystone function will help avoid misplaced emphasis on keystone species at the expense of other species. Resumen: Se ha sugerido que el concepto de especie pilar no sea usado más en ecología y conservación, principalmente debido a que el concepto ha sido pobremente definido. Esto instigó a Power et al. (1996) a refinar la definición: las especies pilar tienen grandes efectos en la estructura de una comunidad o la función de un ecosistema (alta importancia en lo general), y este efecto debe ser grande en relación con la abundancia (alta importancia en la comunidad). Usando los perros de pradera (Cynomys spp) como ejemplo, revisé las dificultades operativas y conceptuales encontradas durante la aplicación de esta definición. Al aplicarse a perros de pradera, la suposición implícita de que la importancia en lo general es una función lineal de la abundancia es inválida. Además, la importancia en la comunidad es sensible a los niveles de abundancia, a la definición de comunidad y a la escala de muestreo. Estos problemas surgen, en gran medida, de la ecuación para la importancia en la comunidad, al ser usada conjuntamente con experimentos de remoción a un solo nivel de abundancia. Sugiero que el énfasis actual en la dualidad sobre especies pilares/no pilares cambie para examinar cómo varía la importancia en lo general y en la comunidad; (1) con la abundancia, (2) a lo largo de escalas espaciales y temporales, y (3) bajo diversas condiciones ecológicas. Además, propongo que sea incorporado un tercer criterio en la definición: las especies pilar llevan a cabo funciones no llevadas a cabo por otras especies o procesos. El análisis de cómo varían estos factores entre poblaciones de especies pilar ayudará a identificar los factores que contribuyen, o limitan las funciones a nivel pilar, incrementando con ello la utilidad del concepto de especie pilar en ecología y conservación. Aunque el marco de trabajo cuantitativo de Power et al. no llega a ser completamente operacional, mis guías conceptuales pueden mejorar la utilidad de este concepto. Una atención especial a los factores que limitan el funcionamiento pilar ayudaría a evitar un énfasis mal ubicado en especies pilar a costa de otras especies. [source]

Microarray analysis of retinoid-dependent gene activity during rat embryogenesis: Increased collagen fibril production in a model of retinoid insufficiency

DEVELOPMENTAL DYNAMICS, Issue 4 2004
George R. Flentke
Abstract Retinoic acid (RA) is an essential mediator of embryogenesis. Some, but not all, of its targets have been identified. We previously developed a rat model of gestational retinoid deficiency (RAD; Power et al. [1999] Dev. Dyn. 216:469,480) and generated embryos with developmental impairments that closely resemble genetic and dietary models of retinoid insufficiency. Here, we used microarray analysis and expression profiling to identify 88 transcripts whose abundance was altered under conditions of retinoid insufficiency, as compared with normal embryos. Among these, the induction by RAD of genes involved in collagen I synthesis (COL1A1, IA2 and VA2, prolyl-4-hydroxylase-,1) and protein galactosylation (galactokinase, ABO galactosyltransferase, UDP-galactose transporter-related protein) was especially noteworthy because extracellular matrix regulates many developmental events. We also identified several genes involved with stress responses (cathepsin H, UBC2E, IGFBP3, smoothelin). Real-time polymerase chain reaction analysis of selected candidates revealed excellent agreement with the array findings. Further validation came from the demonstration that these genes were similarly dysregulated in two genetic models of retinoid insufficiency, the retinol binding protein null-mutant embryo and the Raldh2 null-mutant embryo. In situ hybridization of RAD embryos found increased collagen IA1 and IGFBP3 mRNA within the connective mesenchyme and vasculature, respectively, and a failure to repress the growth factor midkine within the RAD neural tube. Many of the identified genes were not known previously to respond to retinoid status and will provide new insights to retinoid roles and to the consequences of retinoid insufficiency. Developmental Dynamics 229:886,898, 2004. © 2004 Wiley-Liss, Inc. [source]

A service evaluation to determine the effectiveness of current dietary advice in treating human immunodeficiency virus-associated weight loss and to highlight potential service improvements

JOURNAL OF HUMAN NUTRITION & DIETETICS, Issue 4 2008
C.A. Hunt
Background:, Weight loss and muscle wasting are experienced by many patients with human immunodeficiency virus (HIV) (Grinspoon et al., 2003). Malnutrition is an important predicator of morbidity and mortality; people who are malnourished who received antiretroviral treatment are six times more likely to die than those who are adequately nourished (Paton et al., 2006). The physical manifestations of muscle wasting can have significant psychosocial implications for HIV patients (Power et al., 2003; Sattler, 2003). The aim of this study to evaluate provision of dietetic care to patients referred for acute weight loss advice and identify areas for potential service improvement. Methods:, The data were gathered from the departmental dietetic activity statistics in 2007, diagnosis code ,HIV , acute weight loss'. Fifty-nine cards were located and baseline weight, height and body mass index (BMI) were recorded (two female, 57 male). Qualitative data on dietetic intervention were extracted from record cards , little and often eating approach, food fortification (FF), high energy high protein oral nutritional supplement (ONS) prescribed. Data were collected on body image, exercise and weight at follow-up visits during 2007. Results:, Forty-three percent of the patients referred for ,HIV-acute weight loss' were lost to follow-up. Forty-seven percent of the remaining patients had a BMI <20 kg m,2. Following their initial dietetic intervention, 81% of these patients had gained weight at the first follow-up. All had received nutritional counselling on little and often eating approach and FF; 75% had ONS prescribed. Average weight gain with nutritional counselling alone was 1.3 kg (2.1 kg) and for nutritional counselling plus supplementation was 2.1 kg (1.8 kg). This represented 2.5% (4.1%) and 3.9% (3.4%) weight gain, respectively. Discussion:, This evaluation has highlighted that patient follow-up frequency is an area for service improvement. Fifty-three per cent of patients (excluding those lost to follow up) had a BMI ,20 kg m,2 and were inaccurately recorded in the statistics as being referred for ,HIV-acute weight loss'. Fifty-two percent of these patients reported lipodystrophy and body image concerns, similar to findings of other studies. Fifty-six percent reported weight improvements following dietetic consultation. Body image is a frequent referral trigger, therefore improvements should be made to identify and treat patients with body shape issues. Conclusions:, Dietitians are effective at achieving weight gain in HIV positive patients with a BMI <20 kg m,2 using nutritional counselling methods with or without oral nutritional supplementation; these patients experienced a 3.3% weight gain. Strategies need to be implemented to reduce the number of patients lost to follow-up, as weight loss is a key morbidity and mortality indicator in HIV. References, Grinspoon, S. & Mulligan, K. (2003) Weight loss and wasting in patients infected with HIV. Clin. Infect. Dis.36 (Suppl. 2): 69,78. Nerad, J., Romeyn, M., Silverman, E., Allen-Reid, J., Dieterich, D., Merchant, J., Pelletier, V., Tinnerello, D. & Fenton, M. (2003) General nutritional management in patients infected with HIV. Clin. Infect. Dis.36 (Suppl. 2): 52,62. Ockenga, J., Grimble, R., Jonkers-Schuitema, C., Macallan, D., Melchior, J.C., Sauerwein, H.P., Schwenk, A. & Suttmann, U. (2006) ESPEN guidelines on enteral nutrition: wasting in HIV and other chronic infectious diseases. Clin. Nutr.25, 319,329. Paton, N.I., Sangeetha, S., Earnest, A. & Bellamy, R. (2006) The impact of malnutrition on survival and the CD4 count response in HIV-infected patients starting antiretroviral therapy. HIV Med.7, 232,330. Power, R., Tate, H.L., McGill, S.M. & Taylor, C. (2003) A qualitative study of the psychosocial implications of lipodystrophy syndrome on HIV positive individuals. Sex. Transm. Infect.79, 137,141. Sattler, F. (2003) Body habitus changes related to lipodystrophy. Clin. Infect. Dis36 (Suppl. 2): 84,90. [source]