碩士 / 國立臺灣大學 / 漁業科學研究所 / 86 / Freshwater giant prawns, Macrobrachium rosenbergii, atropical decapods. is a commercially important culture species in Taiwan. Mass mortality of this species has often occurred in the winter season, because of their intolerability to cold temperatures. The main objectives of this study is aimed to document hyperglycemic responses and activity changes of the enzymes relevant to glucose metabolism under cold shock, and to monitor the dominance of energy metabolic pathways determined by the shifts in the activity ratio of lactate dehydrogenase (LDH), citrate synthase (CS) and pyruvate kinase (PK).
Crustacean hyperglycemic hormone (CHH) synthesized and released from Xorgan sinus gland complex, induces hyperglycemia of the prawns. Catecholamines mediate the release of CHH under stress or acts directly on target tissues, and is consequence, blood glucose in eventually elevated. The increase in the blood glucose of the prawns under cold shock is primarily resulted from the activation of gluconeogenesis and glycogenolysis pathways, and glucose in utilized as the energy source in muscular tissues.
The prawns acclimated under 23℃ was better tolerant to cold shock at 13℃ than those acclimated under 28℃. When the prawns was transferred directly from 28℃ to 18℃ or 13℃, the blood glucose increased notably but in the process of recovery after 4 hr, the glucose coulent showed to decline gradually down to the original level. The physiological compensation to the cold stress is reflected in the changes of hemolymph glucose over the cold exposure, and sustained elevation of glucose accumulation in the hemolymph would be indicative of possible physiological disorder, exhaustion leading towards the death.
In glycolysis process, the enzyme activities of LDH, CS and PK in the muscular and hepatopancreatic tissues were monitored under 13℃ cold shock. Significant fluctuation of the CS/PK activity ratio was observed in the hepatipancreatic tissues under the cold shock, but the ratio maintained rather constant in the recovery period. It might suggest that great fluctuations in the enzyme activity ratio well indicate the exhaustion state of physiological acclimation to the cold stress.
The hemolymph glucose peaked at 65.62±5.93 mg/dl in 1 hr after the prawns received an injection of norepinephrine at the dose of 10 nM/prawn, followed by glucose decline to 19.87±4.06 mg/dl within an hour, at which the hemolymph glucose content is insignificantly different from those in control. The hyperglycemic response of the prawns in this case is mainly resulted from the enhancement of glycogenolysis, rather than gluconeogenesis. Furthermore, norepinephrine was found effective to stimulate the release of glucose in vitro from the hepatopancrease, which is considered one of important source of glucose in this species. Release of glucose from the muscular tissue in vitro was also observed, but the quantity released was not as much as those from the hepatopancreatic tissues. However, importance of the muscles as the source of glucose can not be ignored. The glucose accumulation in the culture media under in vitro stimulation at 16℃ was much less than those at 26℃, and the effectiveness of the norepinephrine on the glucose release via a chain of glucose metabolism is certainly related to the temperatures employed.
| Identifer | oai:union.ndltd.org:TW/086NTU03451001 |
| Date | January 1998 |
| Creators | Kuo, Ming-Youn, 郭銘元 |
| Contributors | Kuo, Ching-Ming, 郭欽明 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 87 |
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