The use of percentages and size-specific indices to normalize physiological data for variation in body size: wasted time, wasted effort?

Packard, Gary C.; Boardman, Thomas J.

doi:10.1016/s1095-6433(98)10170-8

Cited by 410 publications

(301 citation statements)

References 23 publications

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“…When VTG was not detected in male fish, we used the detection limit as the VTG value. To avoid biases associated with size-specific indices (Packard and Boardman, 1999;Kang et al, 2002), analysis of covariance (ANCOVA) with the body weight of the medaka as a covariate was used to compare the GSI and HSI values among all experimental groups. The data pertaining to sex ratios were assessed by 2 analysis.…”

Section: Discussionmentioning

confidence: 99%

Effects of binary mixtures of estrogen and antiestrogens on Japanese medaka (Oryzias latipes)

2009

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a b s t r a c tIt is supposed that the estrogenic effects of estrogenic chemicals will be balanced by the presence of other endocrine-disrupting chemicals (EDCs) with different properties. However, little convincing research into this issue has been carried out to date. In the present study, the combined effects of EDCs with estrogenic and antiestrogenic activities were assessed using a 21-day reproduction assay with the Japanese medaka (Oryzias latipes) as an in vivo model. Natural estrogen (17␤-estradiol, E2) and the pharmaceutical substances letrozole and tamoxifen, which are both model antiestrogens, were tested as reference compounds individually and in combination. Exposure to E2 (200 ng/L) alone resulted in significant biological changes in paired fish, including impaired reproductive capacity and plasma vitellogenin induction. Upon coexposure with tamoxifen or letrozole (10, 50 and 250 g/L), the effects of estrogen on some biomarkers (e.g., plasma vitellogenin concentration) could be neutralized to some extent, but the impairments in reproductive performance were hardly ameliorated or even became more severe. Since reproductive performance is a more holistic parameter with population-level relevance, the possibility that the effects of estrogenic chemicals can be cancelled out by the presence of antiestrogens in aquatic organisms should be questioned. Our observations also illustrate the importance of considering multiple endpoints at different biological levels of organisms for accurate and adequate assessment of the integrated effects of EDCs, especially in environmentally relevant exposure situations.

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Section: Discussionmentioning

confidence: 99%

Effects of binary mixtures of estrogen and antiestrogens on Japanese medaka (Oryzias latipes)

2009

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“…Typical indexes attempt to control for body size by taking simple ratios (mass divided by the cube of body size), slope-adjusted ratios (slope of log(body mass) on log(body size)) or residuals (Jakob et al 1996). All of these indexes have been criticized, largely because the true relationship between the two variables is unknown a priori, and each method introduces assumptions that may not be biologically or statistically justified (see Jakob et al 1996;Kotiaho 1999;Packard & Boardman 1999;Green 2000;Darlington & Smulders 2001;García-Bertou 2001). To confound matters, there is no assurance that fresh weight is always a good indicator of fat reserves, or that fat reserves are a good indicator of fitness.…”

Section: What Is Condition?mentioning

confidence: 99%

Do sexual ornaments demonstrate heightened condition-dependent expression as predicted by the handicap hypothesis?

Cotton

Fowler

Pomiankowski

2004

Proc. R. Soc. Lond. B

574

681

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The handicap hypothesis of sexual selection predicts that sexual ornaments have evolved heightened condition-dependent expression. The prediction has only recently been subject to experimental investigation. Many of the experiments are of limited value as they: (i) fail to compare condition dependence in sexual ornaments with suitable non-sexual trait controls; (ii) do not adequately account for body size variation; and (iii) typically consider no stress and extreme stress manipulations rather than a range of stresses similar to those experienced in nature. There is also a dearth of experimental studies investigating the genetic basis of condition dependence. Despite the common claim that sexual ornaments are conditiondependent, the unexpected conclusion from our literature review is that there is little support from welldesigned experiments.

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“…0.05). The common regression coefficient was computed (see the electronic supplementary data S2), and in the case where this was significantly different from 0, it was used to standardize all data for the covariate [40] following log 10 -transformation of the data. Corrections for the covariate are normally made to the grand mean, but given that the data have been log transformed, proportionality across the covariate is maintained and adjustment of BMR and leak rates were therefore made to a standard value.…”

Section: (G) Statistical Analysismentioning

confidence: 99%

Phylogenetic differences of mammalian basal metabolic rate are not explained by mitochondrial basal proton leak

et al. 2011

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Metabolic rates of mammals presumably increased during the evolution of endothermy, but molecular and cellular mechanisms underlying basal metabolic rate (BMR) are still not understood. It has been established that mitochondrial basal proton leak contributes significantly to BMR. Comparative studies among a diversity of eutherian mammals showed that BMR correlates with body mass and proton leak. Here, we studied BMR and mitochondrial basal proton leak in liver of various marsupial species. Surprisingly, we found that the mitochondrial proton leak was greater in marsupials than in eutherians, although marsupials have lower BMRs. To verify our finding, we kept similar-sized individuals of a marsupial opossum (Monodelphis domestica) and a eutherian rodent (Mesocricetus auratus) species under identical conditions, and directly compared BMR and basal proton leak. We confirmed an approximately 40 per cent lower mass specific BMR in the opossum although its proton leak was significantly higher (approx. 60%). We demonstrate that the increase in BMR during eutherian evolution is not based on a general increase in the mitochondrial proton leak, although there is a similar allometric relationship of proton leak and BMR within mammalian groups. The difference in proton leak between endothermic groups may assist in elucidating distinct metabolic and habitat requirements that have evolved during mammalian divergence.

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The use of percentages and size-specific indices to normalize physiological data for variation in body size: wasted time, wasted effort?

Cited by 410 publications

References 23 publications

Effects of binary mixtures of estrogen and antiestrogens on Japanese medaka (Oryzias latipes)

Effects of binary mixtures of estrogen and antiestrogens on Japanese medaka (Oryzias latipes)

Do sexual ornaments demonstrate heightened condition-dependent expression as predicted by the handicap hypothesis?

Phylogenetic differences of mammalian basal metabolic rate are not explained by mitochondrial basal proton leak

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