RESUMEN
This study examined the effect of substituting vegetable oil for fish oil in feed, with subsequent re-introduction of fish oil-rich feed (finishing feeding) in late stages of growth, on the fatty acids of cultivated European whitefish (Coregonus lavaretus). Restorative finishing feeding with fish oil-rich feed for 15 and 25 weeks was sufficient to change the total content of nutritionally valuable long-chain n-3 fatty acids, eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3), to correspond to that of fish fed the fish oil-rich feed throughout their lifespan. Under natural conditions, 15 and 25 weeks correspond to weight gains of 75% and 100% (i.e. doubling), respectively. Also, the fatty acid profile of the fish was restored after finishing periods of 15 and 25 weeks. Limiting the use of fish oil by lowering the overall fat content of the feed (no vegetable oil added) resulted in a decrease in the long-chain n-3 fatty acids. Based on the results, after receiving a vegetable oil-rich diet, restorative fish oil-rich feeding in the last stages of growth in European whitefish is nutritionally justified in order to balance nutritional gain for consumers with sustainable use of finite marine oils. The results encourage commercial efforts to further utilize and optimize finishing feeding practices.
Asunto(s)
Ácidos Grasos Omega-3/análisis , Aceites de Pescado/administración & dosificación , Salmonidae/crecimiento & desarrollo , Alimentación Animal/análisis , Animales , Grasas de la Dieta/administración & dosificación , Salmonidae/metabolismoRESUMEN
The effect of variation in origin and season on the lipids and sensory quality of European whitefish (Coregonus lavaretus) was studied. The proportion of docosahexaenoic acid (22:6n-3) of the total phospholipid fatty acids in fillets was considerably higher in spring compared with autumn. Farmed fish contained 3-4 times more lipids than wild fish. Combined, the fillets of farmed fish contained 2-3 times more eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid than the fillets of wild fish. Contents of vitamin D were high both in farmed and wild fish. Aroma of raw farmed whitefish was less algae-like than wild one. Raw farmed whitefish was harder, less springy, and lighter in flesh color than wild whitefish. Cooked, farmed fish had slightly stronger flavor than wild fish. There was no significant difference in pleasantness between whitefish of different origin in any of the evaluated characteristics. Both farmed and wild European whitefish caught in autumn and spring proved to have a high content of n-3 fatty acids and vitamin D, and hence they serve as a good source of nutritionally important lipids.
Asunto(s)
Ácidos Grasos , Productos Pesqueros/análisis , Calidad de los Alimentos , Salmonidae , Estaciones del Año , Animales , Vitamina DRESUMEN
Evolutionary consequences of thermally varying environments were studied in the ciliated protozoan Tetrahymena thermophila. Replicated lines were propagated for 60 days, a maximum of 500 generations, in stable, slowly fluctuating (red spectrum), and rapidly fluctuating (blue spectrum) temperatures. The red and blue fluctuations had a dominant period length of 15 days and two hours, respectively. The mean temperature of all time series was 25 degrees C and the fluctuating temperatures had the same minimum (10 degrees C), maximum (40 degrees C), and variance. During the experiment, population sizes and biomasses were monitored at three-day intervals. After the experiment, carrying capacity and maximum growth rate were measured at low (15 degrees C), intermediate (25 degrees C), and high (35 degrees C) temperatures for each experimental line. Physiological changes in the lines were assessed by measuring the expression of stress-induced heat shock protein Hsp90 at 25 degrees C, 35 degrees C, and 39 degrees C. Population sizes and biomasses showed no differences between stable, blue, or red temperature treatments during the experiment. Also, after the experiment, mean carrying capacities and maximum growth rates were comparable in the stable, blue, and red temperature treatments. The expression of Hsp90 was higher in lines from the blue environment than in lines from the stable environment. Lines from the red environment had an intermediate level of Hsp90 expression. This supports the hypothesis that inducible thermotolerance and expression of canalizing genes can evolve in response to rapidly varying environments. Furthermore, we found correlative evidence of benefits and disadvantages of high Hsp90 expression. Lines with high expression of Hsp90 had an increased growth rate at the highest temperature when food resources were not limiting growth. At low and intermediate temperatures the same lines had the lowest carrying capacities.
Asunto(s)
Evolución Biológica , Ambiente , Expresión Génica , Proteínas HSP90 de Choque Térmico/metabolismo , Temperatura , Tetrahymena thermophila/crecimiento & desarrollo , Análisis de Varianza , Animales , Proteínas HSP90 de Choque Térmico/genética , Tetrahymena thermophila/genética , Factores de TiempoRESUMEN
Elevated temperature induces a rapid heat shock transcription factor (HSFs)-mediated expression of heat shock (hsp) genes. The effect of cold exposure on hsp gene expression has hardly been investigated, although ectothermic animals experience both cold and heat stress. We have previously shown in zebrafish that the expression of hsf1a and a unique isoform hsf1b vary in a tissue-specific manner upon heat stress. In the current study, using a zebrafish (Danio rerio) embryonic cell line (ZF4), we have compared the effects of heat shock (28-->37 degrees C) vs. cold shock (28-->20 degrees C) on the expression of ahsf1a, zhsf1b and hsp70. Concomitantly, the suitability of the ZF4 cells as a model system was verified. The expression pattern of HSP70 proteins following heat or cold exposure is distinct, and the total HSP70 level is upregulated or stable, respectively. Moreover, heat exposure specifically increases the ratio of zhsf1a/b expression (10-fold), whereas cold exposure decreases it to one half. These data suggest that the zhsf1a/zhsf1b ratio is regulated in a temperature-dependent manner, and the ratio may be indicative of the stressor-specific HSP70 expression. Furthermore, the response in ZF4 cells upon heat shock resembles the response observed in zebrafish liver and thus, supports the use of this cell line in stress response studies.
Asunto(s)
Frío , Regulación de la Expresión Génica , Proteínas HSP70 de Choque Térmico/genética , Respuesta al Choque Térmico/genética , Calor , Pez Cebra/genética , Animales , Línea Celular , Factores de Transcripción del Choque Térmico , Isoformas de Proteínas/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factores de Tiempo , Factores de Transcripción/genética , Proteínas de Pez Cebra/genéticaRESUMEN
Heat shock transcription factors (HSFs) regulate expression of heat shock proteins (Hsps). We have previously shown that in zebrafish a unique isoform, zHSF1b, disappears concomitant with heat shock-induced Hsp70 expression. To characterize the role of zHSF1a and zHSF1b isoforms in the regulation of the stress response in vivo, we have carried out cadmium (10-100 microM) and copper (10-30 microM) exposures in order to specify whether the disappearance of HSF1b is specific for heat stress. After 4-h metal exposures we analyzed the expression of hsp70, zHSF1a, zHSF1b and metallothionein (MT) by reverse transcriptase polymerase chain reaction in zebrafish liver, gonads and gills. Although cadmium is a known inducer of Hsps, it did not affect hsp70 expression significantly in the studied tissues. Induction of hsp70 was observed upon copper exposure in liver and gonads, but not in gills. Neither metal affected the zHSF1a/b ratio. Both cadmium and copper exposure caused upregulation of MT, regulator of metal homeostasis and detoxification, confirming that the tissues were subjected to metal loads. Thus, hsp70 appears to be more weakly induced upon metal exposure than in response to heat shock and HSF1 isoforms may participate in stressor-specific regulation of hsp70.