The effects of environmental stress on the physiology of growth in rainbow trout, Salmo gairderi Richardson

There is little doubt that both mammalian and teleost growth hormones can accelerate growth and increase food conversion efficiency in all commonly-reared species of salmonid fish. In those vertebrates that have been closely studied (predominantly mammals), the pituitary hormone somatotropin (GH or growth hormone) is a prime determinant of somatic growth. The hormone stimulates protein biosynthesis and tissue growth, enhances lipid utilization and lipid release from the adipose tissues (a protein-sparing effect) and suppresses the peripheral utilization of glucose. The present study is a prerequisite for future work on growth hormone physiology in salmonids and should contribute to our understanding of the mechanisms of growth suppression in stressed fish. Plasma growth hormone (GH) levels were measured in rainbow trout using a radioimmunoassay developed against chinook salmon growth hormone

Overwinter fasting and re-feeding in rainbow trout: plasma growth hormone and cortisol levels in relation to energy mobilization

This study investigated the roles of cortisol and growth hormone during a period of fasting in overwintering salmonid fish. Indices of carbohydrate (plasma glucose, liver glycogen), lipid (plasma free fatty acids) and protein metabolism (plasma protein, total plasma amino acids) were determined, together with plasma growth hormone (GH), cortisol and somatolactin levels (SL) at intervals in three groups of rainbow trout (continuously fed; fasted for 9 weeks then fed; fasted for 17 weeks). In fasted fish, a decline in body weight and condition factor was accompanied by reduced plasma glucose and hepatic glycogen and increased plasma FFA. No consistent elevation of plasma GH occurred until after 8 weeks of fasting when plasma GH levels increased nine-fold. No changes were observed in plasma total protein and AA until between weeks 13 and 17 when both were reduced significantly. When previously fasted fish resumed feeding, plasma glucose and FFA, and hepatic glycogen levels rapidly returned to control values and weight gain resumed. No significant changes in plasma cortisol levels, related to feeding regime, were evident at any point during the study and there was no evidence that SL played an active role in the response to fasting. The results suggest that overwinter fasting may not represent a significant nutritional stressor to rainbow trout and that energy mobilisation during fasting may be achieved without the involvement of GH, cortisol or SL

Directional bias of illusory stream caused by relative motion adaptation

AbstractEnigma is an op-art painting that elicits an illusion of rotational streaming motion. In the present study, we tested whether adaptation to various motion configurations that included relative motion components could be reflected in the directional bias of the illusory stream. First, participants viewed the center of a rotating Enigma stimulus for adaptation. There was no physical motion on the ring area. During the adaptation period, the illusory stream on the ring was mainly seen in the direction opposite to that of the physical rotation. After the physical rotation stopped, the illusory stream on the ring was mainly seen in the same direction as that of the preceding physical rotation. Moreover, adapting to strong relative motion induced a strong bias in the illusory motion direction in the subsequently presented static Enigma stimulus. The results suggest that relative motion detectors corresponding to the ring area may produce the illusory stream of Enigma

Predicting concentrations of human pharmaceuticals throughout the river systems of Europe

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Active Brownian Particles. From Individual to Collective Stochastic Dynamics

We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework of statistical mechanics. Examples of such active units in complex physico-chemical and biological systems are chemically powered nano-rods, localized patterns in reaction-diffusion system, motile cells or macroscopic animals. Based on the description of individual motion of point-like active particles by stochastic differential equations, we discuss different velocity-dependent friction functions, the impact of various types of fluctuations and calculate characteristic observables such as stationary velocity distributions or diffusion coefficients. Finally, we consider not only the free and confined individual active dynamics but also different types of interaction between active particles. The resulting collective dynamical behavior of large assemblies and aggregates of active units is discussed and an overview over some recent results on spatiotemporal pattern formation in such systems is given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte

Accuracy of methods of sex steroid determination

Reproductive hormones (estrogenic and androgenic steroids) enter natural water bodies from various sources, e.g. human sewage, farmed livestock and vertebrate wildlife. A previous Defra research study (SF0241 Impacts of intensive in-river aquaculture on wild salmonids) reported very high concentrations of such steroids in two UK rivers (the River Test and R. Avon in Hampshire/Wiltshire) in the vicinity of trout farms. The mean reported concentrations of the natural steroids 11-ketotestosterone (11-KT), testosterone (T) and oestradiol (E2) ranged from 4 to 79 ng/L. The maximum level observed in an individual sample was 145 ng/L for 11-KT. Furthermore, the subject brown trout and rainbow trout farms were implicated as a source of the steroids, as mean levels reported “downstream” of the trout farms were 1.3 to 6 fold higher than those “upstream”. Nevertheless, the steroid concentrations reported both upstream and downstream of the trout farms would be of great concern for wild fish in these rivers due to potential for endocrine disruption, i.e. when exogenous substances negatively impact the endogenous hormone systems and reproductive function of the organism. The synthetic sex steroid ethinyl-estradiol (EE2) was also measured in the SF0241 study. EE2 originates from human prescription medicine (the contraceptive pill) via sewage treatment works, and has been studied in rivers due to its endocrine disruptive activity. Levels of EE2 reported in SF0241 were one to two orders of magnitude lower than the natural steroids. Mean values were in the range of 0.13 – 0.30 ng/L, and were not found to be elevated downstream of the trout farms. The very high levels of the natural sex steroids that were reported were not only of concern because of potential adverse effects on resident fish, but were also surprisingly high. In the SF0241 study, all steroid levels in acquired water samples had been measured using commercial Enzyme-ImmunoAssay (EIA) kits (also referred to as Enzyme-Linked Immuno-Sorbent Assay, ELISA kits). However, the kits used to measure the natural steroids used a different enzyme component in the assay to the EE2 kits. Environmental water samples are typically concentrated before assay, and it was speculated that other compounds in the river water may have interfered with the enzyme stage in the kits for the natural steroids. It was therefore hypothesised that the very high concentrations of the natural steroids reported in SF0241 were false positives due to interference in the EIAs. Due to concern over the possible inaccuracy of the EIA kits (and trout farms as a source of endocrine disrupting compounds), Defra’s Chemicals and Nanotechnology Division funded this project (CB0427) to examine the “Accuracy of methods of sex steroid determination”. The aim of the project was to test the above hypothesis by repeating the sampling and sample processing, and then assaying for the steroids using the EIA kits and an additional method – radioimmunoassay (RIA) - expected to be less susceptible to interference. Water samples were collected from the two trout farm sites, one on the R. Test and one on the R. Avon, between January and June 2010 and extracted (C18 solid phase extraction (SPE) followed by extract clean-up with aminopropyl SPE). Additional “spiked” and “blank” water samples were also prepared and processed. Four independent laboratories conducted EIAs and RIAs (3 laboratories per assay technique) for the four steroids (11-KT, T, E2, EE2) using replicate aliquots of the same 44 samples, each aliquot representing ca 1 L of river water. Participating laboratories (other than the lead laboratory) conducted the assays blind (i.e. were unaware of the sample details) and returned the calculated steroid concentrations to the project leaders for collation. A few anomalous results were questioned and, upon investigation, were found to be due to human errors and were subsequently corrected. There was broad agreement between the EIA and RIA measurements for all four steroids showing that the EIA kits did not generate erroneously high values. The base hypothesis for the project, i.e. that some EIA kits generate erroneously high values, was therefore rejected. The two assay methods were comparable for accuracy and precision. Recovery of steroids using the SPE methodology was examined using water samples spiked with known amounts of steroids. It was found that the recovery efficiency varied between samples and steroids. Higher recoveries were evident for the oestrogens (mean recovery 69% and 67% for E2 and EE2 respectively) than for the androgenic compounds (mean recovery 29% and 46% for 11KT and T respectively). Measured steroid concentrations in river water samples were all <0.6 ng/L. The measured concentrations cannot be considered definitive, as they are uncorrected for recovery efficiency. Nevertheless, they are considered low, unlikely to be of concern for endocrine disruption, and demonstrate that the water steroid levels reported in SF0241 were not typical of river steroid concentrations in 2010. The levels of 11KT, T, E2 and EE2 in the rivers were respectively 1300, 70, 90 and 3 times lower than reported in SF0241. In addition to the major difference in measured levels between the two studies: • the relative concentrations also differed, with 11KT being the lowest rather than highest as reported in SF0241. • river steroid levels were higher in Spring rather than the Winter period, being opposite to the seasonal effect reported in SF0241 • river EE2 levels in 2010 were too low to be detectable by EIA (equivalent to <0.05 ng/L). • the clear elevation in river water concentrations of the natural steroids associated with the fish farms reported in SF0241 was not evident in the present study. It was not possible to provide a definitive explanation for the differences found between the present results and those reported within SF0241. Eleven alternate hypotheses are discussed that could have contributed to the divergent results. The available evidence points towards miscalculation and assaying errors within SF0241 as the probable cause of differences. However, this hypothesis could not be definitively accepted because the raw assay data and the calculations from which the SF0241 results derived had not been retained. Published information on steroid output from fish farms is presented. It is suggested that there is no urgent requirement to further examine the steroid output from UK fish farms. Although the current research did indicate a possible 0.13 ng/L increase in testosterone in the immediate outflow of one farm, this was questionable and, if real, is below concentrations that cause endocrine disruption and would be further diluted in the receiving channel and then main river. During this project, a number of potential sources of error associated with the measurement of steroids from samples were identified and are discussed. It is suggested that guidance for quality control could be developed. Future research into river water steroids could also include: • comparisons of the recovery efficiencies of different steroids from water samples, and a full optimisation and validation of the most appropriate extraction methodology for the different steroids • a comparison of ‘modelled’ versus ‘measured’ river water steroid levels to examine whether the exclusion of other sources of steroids, e.g. agricultural livestock, is an important omission