ABSTRACT
The body temperatures of teleost species fluctuate following changes in the aquatic environment. As such, decreased water temperature lowers the rates of biochemical reactions and affects many physiological processes, including active transport-dependent ion absorption. Previous studies have focused on the impacts of low temperature on the plasma ion concentrations or membrane transporters in fishes. However, very few in vivo or organism-level studies have been performed to more thoroughly elucidate the process of acclimation to low temperatures. In the present study, we compared the strategies for cold acclimation between stenothermic tilapia and eurythermic goldfish. Whole-body calcium content was more prominently diminished in tilapia than in goldfish after long-term cold exposure. This difference can be attributed to alterations in the transportation parameters for Ca2+ influx, i.e., maximum velocity (Vmax ) and binding affinity (1/Km ). There was also a significant difference in the regulation of Ca2+ efflux between the two fishes. Transcript levels for Ca2+ related transporters, including the Na+/Ca2+ exchanger and epithelial Ca2+ channel, were similarly regulated in both fishes. However, upregulation of plasma membrane Ca2+ATPase expression was more pronounced in goldfish than in tilapia. In addition, enhanced Na+/K+-ATPase abundance, which provides the major driving force for ion absorption, was only detected in tilapia, while upregulated Na+/K+-ATPase activity was only detected in goldfish. Based on the results of the present study, we have found that goldfish and tilapia differentially regulate gill epithelial plasma membrane Ca2+-ATPase (PMCA) expression and Na+/K+-ATPase activity in response to cold environments. These regulatory differences are potentially linked to more effective regulation of Ca2+ influx kinetics and better maintenance of whole body calcium content in goldfish than in tilapia.
ABSTRACT
Influenza viruses are some of the most active pathogens in Taiwan. The monitoring influenza activity has been coordinated by the Centers for Diseases Control, Taiwan, and the surveillance is based on integrated clinical and virological surveillance components. Data from sentinel physician networks and other sources, mainly hospitals were collected. During 2006-07 season, a total of 1724 cases of laboratory-confirmed influenza were reported by collaborating laboratories and sentinels, which was five fold higher than during the corresponding part of the 2005-06 season. Of the Taiwan isolates analyzed using post-infection ferret antisera, 1.5% were H1N1 (A/Hi), 21.5% H3N2 (A/H3), and 77.0% influenza B viruses. This reflects the predominance of influenza B viruses during 2006-07 season. In addition, continued antigenic drift was seen with the A/I-B viruses compared with the previous season's reference strains. However, an increasing number of recent A/H3 isolates characterized in our report were amantadine sensitive. Preparation for an influenza pandemic is presently a high priority in Taiwan. Laboratory-based surveillance systems must be timely in order to be effective. The data presented here highlights the need to characterize the circulating strains both antigenically and genetically during regular surveillance. Any contribution of individual genes or gene combinations to usual or unusual epidemic characteristics might thus be identified ensuring that virus strains can be selected for vaccine formulation that will most closely match the circulating viruses.
