Genetic diversity of cultured Penaeus vannamei shrimp using three molecular genetic techniques.

Three molecular genetic techniques, restriction fragment length polymorphisms (RFLPs), random amplification of polymorphic DNA (RAPD), and allozyme variability, were used to evaluate the genetic diversity of two specific-pathogen-free (SPF) populations (numbers 1 and 2) and one candidate SPF population (number 4) of Penaeus vannamei developed and maintained by the U.S. Marine Shrimp Farming Program. A total of 114 individuals were tested, which included 30 each from families 1.5 and 1.6 of population 1 and from population 2, and 24 from population 4. Two HhaI mitochondrial DNA polymorphisms (A and B) were found in all the animals examined, with family 1.5 and population 2 showing type A and family 1.6 showing type B. After scoring 73 bands obtained with six different RAPD primers, the percentage of polymorphic bands was: 55% for families 1.5 and 1.6 of population 1, 48% for population 2, and 77% for population 4, suggesting that population 4 is the most polymorphic of all three populations. The allozymic variation at 30 loci showed no fixed differences in isozyme genotypes between families 1.5 and 1.6. The percentage of polymorphic loci, under the criterion that the frequency of the most common allele was less than 0.95 in each population, was 6.67%, 3.33% and 16.67% for family 1.5 of population 1, family 1.6 of population 1, and population 2, respectively. Mean heterozygosities (+/- SE) were 0.023 +/- 0.017, 0.018 +/- 0.016, and 0.064 +/- 0.026, respectively. The low levels of allozyme polymorphisms indicate that mitochondrial DNA and nuclear DNA techniques are more useful for examining genetic diversity in order to follow individual stocks within a breeding program and to correlate genotypes with desirable growth and reproductive performance of SPF P. vannamei stocks.

Soluble peptidase isozymes of the Japanese Medaka (Oryzias latipes): tissue distributions and substrate specificities.

Peptidases catalyze the hydrolysis of di- and tripeptidases to their constituent amino acids. Five isozymes (PEP A, B, C, D, and S) were shown to be the products of independent genetic loci by several criteria including distinct adult tissue and substrate specificities, non-cross-reacting immunochemical properties, and independent genetic variation at three of the loci. Four of the peptidases had at least one substrate against which they contributed over 95% of the activity. These substrates were used for isozyme-specific assays. In adult tissues, three of the peptidases had higher activities in liver and intestine than in other tissues (PEP A, B, and S). PEP C had a 10-fold higher specific activity in brain than in other tissues.

Effects of organic solutes on transmural PD and Na transport in freshwater prawn intestine.

Addition of 1 mM L-alanine or 0.5 mM D-glucose to the mucosal surface of freshwater prawn (Macrobrachium rosenbergii) intestine rapidly increased transmural potential difference (PD) (serosa became more positive). Luminal perfusion with 1 mM D-alanine did not affect the spontaneous PD. Addition of 10 mM serosal L-alanine induced a slow elevation in PD with the same polarity as shown with luminal alanine. The alanine-evoked PD was a hyperbolic function of luminal alanine concentration and was reduced to zero with 0.5 mM serosal ouabain. Luminal 1 mM L-alanine stimulated JNanet from mucosa to serosa from 1.29 +/- 0.45 to 2.83 +/- 0.66 mu mol . cm-2 . h-1. Extensive metabolic breakdown of L-alanine and D-glucose occurred during intestinal transit resulting in a small, but significant, net flux of unaltered sugar from lumen to blood (103.9 +/- 23.1 nmol . cm-2 . h-1) and an absence of net amino acid flow. While 1 mM alanine influx into the epithelium was largely Na dependent, quantitatively insigificant amounts of Na were cotransported into the cell with amino acid (approx 52 nmol . cm-2 . h-1) to account for increased JNanet observed in the presence of this organic solute. Electrogenic effects of luminal nutrients result from their catabolism to fuels for the basolateral Na pump, Increased Na-pump activity stimulates Na entry into the cell by allosteric apical carrier proteins and enhances transmural PD by accelerating net movement of cation across the tissue.