Cytotoxicity of aged cadmium-telluride quantum dots to rainbow trout hepatocytes

The purpose of this study was to examine the lethal and sublethal toxicity of cadmium telluride (CdTe) quantum dots (Q-dots) in primary cultures of rainbow trout hepatocytes. Hepatocytes were exposed to concentrations of positively coated and aged (2 months and 2 years) Q-dots for 48 h at 15°C. Post treatment, cellular analysis was done of cell viability, lipid peroxidation (LPO), DNA damage, metallothioneins (MT), labile zinc/cadmium and heat shock proteins (chaperones). Q-dots were found to be toxic to fish hepatocytes at a threshold concentration of 0.1 mg/l. These nanoparticles increased the levels of MT, labile zinc, DNA strand breaks and heat shock proteins of the 70 kDa family. The strongest response was observed with the molecular chaperone of the 70 kDa family, reaching a 7-fold induction in exposed cells. Overall, the assessment of multiple biomarkers in trout hepatocytes exposed to differently ‘aged’ Q-dots suggests that the cytotoxic responses to two-year-old positively coated CdTe Q-dots were largely due to the liberation of Cd²⁺.     

A rapid tube ELISA for human IgG in body fluids using Staphylococcus aureus

An ELISA was designed for measurement of human IgG in urine and CSF using protein A containing Staphylococcus aureus as sorbent. This assay was performed in test tubes. An OD difference of approximately 1.0 was developed between non-specific binding and 10 μg/ml IgG solution. The method has a sensitivity of 70 ng IgG/ml. The test is simple and rapid and does not require concentration of samples. Once prepared S. aureus reagent is stable for at least one year. The merits of this method in comparison to radial immunodiffusion (RID) are discussed.     

Effects of atrazine on hepatic metabolism and endocrine homeostasis in rainbow trout (Oncorhynchus mykiss)

The herbicide atrazine (ATZ) is one of the most widely used pesticides in the world and is now under scrutiny for its alleged capacity to disrupt the endocrine system. Exhibiting negligible interaction with the estrogen receptor (ER), ATZ's mode of action remains to be elucidated. ATZ may act as an inducer of the enzyme aromatase, which converts androgens to estrogens, although other mechanisms should also be taken into consideration such as impairment of hepatic metabolism. Therefore we administered juvenile rainbow trout (Oncorhynchus mykiss) a dose of either 2 or 200 μg ATZ/kg, or of carrier control phosphate buffered saline (PBS) and we measured plasma concentrations of testosterone (T), 17beta-estradiol (E2) and vitellogenin (Vtg) 6 days after exposure. Simultaneously we analyzed hepatic gene expression of cytochrome P450 (CYP) 1A and pi-class glutathione S-transferase (GST-P), and catalase (CAT) activity. Although sex steroid levels showed no significant alterations, we found a dose-dependent increase in Vtg and a concomitant decrease in CYP1A. There was no effect of ATZ on GST-P mRNA levels but GST-P was positively correlated with CYP1A. Also, CYP1A was negatively correlated with liver CAT and E2, and varied with T concentrations in a hormetic manner. The results showed that ATZ can alter hepatic metabolism, induce estrogenic effects and oxidative stress in vivo, and that these effects are linked.     

Resolving the growth-promoting and metabolic effects of growth hormone: Differential regulation of GH-IGF-I system components

Growth hormone regulates numerous processes in vertebrates including growth promotion and lipid mobilization. During periods of food deprivation, growth is arrested yet lipid depletion is promoted. In this study, we used rainbow trout on different nutritional regimens to examine the regulation of growth hormone (GH)-insulin-like growth factor-I (IGF-I) system elements in order to resolve the growth-promoting and lipid catabolic actions of GH. Fish fasted for 2 or 6 weeks displayed significantly reduced growth compared to their fed counterparts despite elevated plasma GH, while refeeding for 2 weeks following 4 weeks of fasting partially restored growth and lowered plasma GH. Fish fasted for 6 weeks also exhausted their mesenteric adipose tissue reserves. Sensitivity to GH in the liver was reduced in fasting fish as evidenced by reduced expression of GH receptor type 1 (GHR 1) and GHR 2 mRNAs and by reduced (125)I-GH binding capacity. Expression of GHR 1 and GHR 2 mRNAs also was reduced in the gill of fasted fish. In adipose tissue, however, sensitivity to GH, as indicated by GHR 1 expression and by (125)I-GH binding capacity, increased after 6 weeks of fasting in concert with the observed lipid depletion. Fasting-associated growth retardation was accompanied by reduced expression of total IGF-I mRNA in the liver, adipose and gill, and by reduced plasma levels of IGF-I. Sensitivity to IGF-I was reduced in the gill of fasted fish as indicated by reduced expression of type 1 IGF-I receptor (IGFR 1A and IGFR 1B) mRNAs. By contrast, fasting did not affect expression of IGFR 1 mRNAs or (125)I-IGF-I binding in skeletal muscle and increased expression of IGFR 1 mRNAs and (125)I-IGF-I binding in cardiac muscle. These results indicate that nutritional state differentially regulates GH-IGF-I system components in a tissue-specific manner and that such alterations disable the growth-promoting actions of GH and promote the lipid-mobilizing actions of the hormone.     

Corticotropin releasing factor influences aggression and monoamines: modulation of attacks and retreats

Salmonids establish social hierarchies as a result of aggressive social interactions. The establishment of dominant or subordinate status is strongly linked to neuroendocrine responses mediated through the stress axis. In this study, we tested the effects of introcerebroventricular (icv) corticotropin releasing factor (CRF) on the behavioral outcome, plasma cortisol and monoamine function in trout subjected to a socially aggressive encounter. Rainbow trout were treated with an icv injection of artificial cerebrospinal fluid (aCSF), 500 or 2000 ng ovine CRF, or not injected. Fish were allowed to interact with a similarly sized conspecific for 15 min. Following the behavioral interaction, plasma cortisol and central monoamine concentrations were analyzed. Trout treated with CRF were victorious in approximately 66% of the aggressive encounters against aCSF-treated opponents. Trout injected with CRF exhibited a reduction in the total number of attacks and decreased latency to attack. When trout were divided into winners and losers, only victorious CRF-treated fish exhibited a reduced latency to attack and fewer retreats. Social stress increased cortisol levels in both winners and losers of aggressive interaction. This effect was enhanced with the additional stress incurred from icv injection of aCSF. However, icv CRF in addition to social stress decreased plasma cortisol in both winners and losers. While aggression stimulated significant changes in serotonergic and dopaminergic activity, the magnitude and direction were dependent on limbic brain region, CRF dose, and outcome of social aggression. With broad effects on aggressive behavior, anxiety, stress responsiveness, and central monoaminergic activity, CRF plays an important role in modulating the behavioral components of social interaction.     

甘肃金鳟肌肉脂肪酸组成及营养价值分析

<正>甘肃金鳟是甘肃省渔业技术推广总站以虹鳟(Oncorhynchus mykiss Walbaum)的红色突变体为材料,历经15年选育成的虹鳟新品种[1],甘肃金鳟与虹鳟属于同一物种,在鱼类分类上属于鲑     

Fasting metabolism in infants: II. The effect of severe undernutrition and infusion of alanine on glucose production estimated with U-13C-glucose

Gluconeogenesis was estimated in fasting infants by dilution of stable isotopic glucose after completion of glycogen oxidation. The effect of availability of gluconeogenic substrates was compared before and after dietary treatment of severe malnutrition and after infusion of excess alanine. Five infants were each studied in two nutritional states. Total glucose production was measured by constant i.v. infusion of uniformly labeled ¹³C-glucose and determination of the ¹³C content of plasma glucose isolated as gluconic acid. A comparison was made with possible sources of net glucose production calculated from simultaneous determinations of respiratory oxygen consumption and carbon dioxide production and urinary nitrogen excretion. Observed average rates of total fasting glucose production under these conditions were 2.8 mg/kg min (range 1.9–4.1) in the malnourished infants, and 2.7 mg/kg min (range 2.4–3.1) in the recovered infants. Average glucose concentration at the same time was $\text{37 mg}\text{100 ml}$ and $\text{42 mg}\text{100 ml}$, respectively. Oxidation of glycogen could have accounted for 7% of total glucose production in either case. Available glycerol from fat oxidation could have accounted for 18% of glucose production in the malnourished subjects and 22% after recovery. Available gluconeogenic amino acids from protein could have contributed 9% and 21% of total glucose production, respectively. The remaining major source of glucose unaccounted for in both cases is attributed to lactate, pyruvate, and alanine recycled via the Cori cycle with loss of ¹³C. It can be calculated that about 90% of carbon flux through oxaloacetate under these conditions was derived from fatty acids, accounting for the lose of ¹³C.Following measurement of endogenous glucose production, alanine was infused intravenously, 4 mg/kg min, for an additional 3 hr, resulting in a 15-fold increase in plasma alanine. There was an initial increase in glucose concentration, with an estimated initial rate of increase of the glucose pool of approximately 1 mg/kg min due to both increased inflow and decreased outflow, the proportions of which were quite variable in different subjects. Final average increase in glucose concentration was $\text{30 mg}\text{100 ml}$, and both inflow and outflow finally increased approximately 1 mg/kg min. The increase in glucose production was half as great as would have been possible from the increased rate of urea production. There were no significant differences between the malnourished and recovered children. It is concluded that following glycogenolysis the major source of gluconeogenesis in these fasting infants was recycled products of glycolysis. The large decrease in availability of gluconeogenic amino acids associated with severe undernutrition did not result in significantly decreased glucose production or hypoglycemia, because amino acids accounted for a relatively small fraction of total gluconeogenesis. The initial increase in glucose concentration after infusion of alanine was not consistently due to increased gluconeogenesis. The relatively small increase in rate of glucose production after increasing alanine and the similarity between the two groups indicates that the maximum possible rate of gluconeogenesis was not much greater than availability of endogenous substrates.     

Expression of an erythropoietin-like gene in the trout

Cross-species Northern blot hybridization and radioimmunoassay have provided evidence for the expression of an erythropoietin (EPO)-like gene in the rainbow trout. The principal site of EPO-like mRNA and antigen expression in the adult trout appears to be the kidney which also acts as the major erythropoietic organ. The data suggest that a locally produced EPO-like factor may regulate renal erythropoiesis in bony fish and, furthermore, they identify a possible evolutionary origin for renal EPO production in mammals.