Tissue-specific distribution of amylase in the mosquitofish (Gambusia affinis holbrooki)

Nongenetic variation, genetic-environmental interactions and altered gene expression. I. Temperature, photoperiod, diet, pH and sex-related effects

The use of protein electrophoretic data for determining the relationships among species or populations is widespread and generally accepted. However, many confounding factors may alter the results of an electrophoretic study in such a way as to allow erroneous conclusions to be drawn in taxonomic, systematic or population studies. Such variables as temperature, photoperiod, salinity, pH and diet have been shown to influence enzymes and proteins both quantitatively and qualitatively. Production of distinct "cold" and "warm" isozymes or "seasonal" isozymes have been found in a variety of organisms. The factors that are or may be responsible for the appearance of these isozymes is discussed. Most studies that have demonstrated some apparent form of environmentally induced genetic expression have not determined that mechanisms responsible. However, proteolytic modification has been shown to produce seasonal isozymes of fructose 1,6-bisphosphatase in rabbit liver and may account for other seasonal isozymes. Acclimating organisms to various conditions may actually allow detection of cryptic genetic variation and provide valuable data. There are many aspects to consider in designing acclimation experiments, and the conditions used will vary according to the aim of the research. Polyploidy may contribute to the genesis of environmentally regulated isozymes. A review of this literature follows with additional hypotheses and conclusions. Recommendations are given for the resolution of real and potential problems.

Effects of diet on amylase expression in the mosquitofish

Diets high in various carbohydrates were fed to mosquitofish,Gambusia affinis holbrooki, to determine the effects on amylase expression. Both amylase activity and amount of amylase protein were used as measures of amylase expression. Fish were fed for 21 days in one experiment, seven days in a second experiment and 24 h in a third. The first experiment compared responses of fish fed on a high-starch diet relative to a control diet. The second and third experiments compared responses on four diets relative to the control diet: maltose, starch, glucose, and glucose + cyclic adenosine monophosphate (cAMP). In the first two experiments whole visceral extracts were used. In the third experiment, gut and hepatopancreatic extracts were examined separately. Diet had a significant affect on the amount of amylase in all three experiments but affected amylase activity only in the 24 h experiment. Generally, glucose decreased amylase expression while maltose or cAMP + glucose increased it. Length of feeding period and tissue type also had significant effects on amylase expression.