Effect of rainbow trout growth hormone complementary DNA on body shape, carcass yield, and carcass composition of F1 and F2 transgenic common carp (Cyprinus carpio)

The effect of rainbow trout growth hormone complementary DNA on body shape, dress-out yield, and body composition were assessed in the F1 and F2 generations of transgenic common carp (Cyprinus carpio). All measurements were compared with those for nontransgenic full-sibling common carp in their respective families, and the fish were communally evaluated in earthen ponds. The body weight and length were highly correlated (P <0.01) in both genotypes in all the families. Head morphometrics were negatively correlated (P <0.05) to weight and length of the fish. Various head, body, and caudal traits grew disproportionately faster in transgenic fish in both generations. The altered body shape of transgenic fish resulted in improved dressing percentage in the F2 generation. The carcass composition of transgenic muscle had a lower percentage of (P <0.01) moisture and lipids and higher (P <0.01) percentage of protein in both generations. Six of the 18 amino acids analyzed in F1 transgenic common carp muscle were higher F1 (P <0.05) than the control genotype; however, amino acid ratios were minimally changed. Also, the fatty acid profiles of both genotypes were minimally altered. Higher histidine and lysine ratios in the diet are recommended for maximum growth and health of transgenic common carp in intensive culture systems on the basis of essential amino acid ratios.

Survival of F2 transgenic common carp (Cyprinus carpio) containing pRSVrtGH1 complementary DNA when subjected to low dissolved oxygen

The survival and tolerance of F2 transgenic common carp (Cyprinus carpio) containing pRSVrtGH1 complementary DNA were compared with nontransgenic (control) common carp when subjected to low dissolved oxygen. The tolerance of low oxygen was evaluated in 8 families of common carp in rectangular tanks (3 x 1 x 1 m). The absolute mean percentage of survival of transgenic common carp subjected to low oxygen (0.4 mg/L) was higher (P <0.05) than that of control carp in 2 of the 8 families of common carp tested; however, the overall means for all families of transgenic and control carp were not different (P > 0.05). When oxygen tolerance was measured in time to death rather than absolute survival or mortality, the growth hormone transgenic common carp had a longer group mean (P <0.05) than did controls. The mean survival time in minutes for the transgenic genotype was greater (P <0.05) in 5 of the 8 families assessed. Transgenic common carp in some families had higher percentage and longer times of survival than control common carp when subjected to low oxygen. The definition of tolerance of low oxygen and how it is measured is important, and can affect interpretation of results. The pleiotropic effect of pRSVrtGH1 cDNA on superior survival of low oxygen in common carp has important implications for intensive fish culture.

Adaptive variation in lactate dehydrogenase-B gene expression: role of a stress-responsive regulatory element

Although changes in gene regulation may play an important role in adaptive evolution, there have been few attempts to investigate the molecular mechanisms responsible for adaptively significant variation in gene expression. Here we describe the mechanism underlying an adaptive difference in the expression of the lactate dehydrogenase-B gene (Ldh-B) between northern and southern populations of the fish Fundulus heteroclitus. Ldh-B regulatory sequences from northern and southern individuals, coupled to a luciferase reporter gene, were introduced into the livers of live fish. Deletion studies indicated that sequence changes between 400 and 500 bp upstream of the transcription start site resulted in a 2-fold difference in reporter gene transcription. These sequence changes can account for the previously observed 2-fold difference in Ldh-B transcription between populations. Variation in transcription factors did not play an important role. Sequences within the functionally important region resemble a mammary tumor virus glucocorticoid responsive element (MTV-GRE) in southern alleles, whereas northern alleles differ from the consensus by 1 bp. To test the hypothesis that this element is involved in the variation between populations of F. heteroclitus, we exposed transiently transgenic fish containing Ldh-B regulatory sequence/reporter gene constructs to handling stress or injected cortisol. Both treatments increased reporter gene transcription driven by southern alleles but not northern alleles, as expected if an MTV-GRE sequence were involved. This finding suggests that sequence variation in a GRE is the cause of the adaptive differences in Ldh-B gene expression between populations and demonstrates that small changes in gene regulatory sequences can have important evolutionary consequences.

Predator Avoidance of Transgenic Channel Catfish Containing Salmonid Growth Hormone Genes

Transgenic channel catfish (Ictalurus punctatus) containing salmonid growth hormone genes can grow 33% faster than normal channel catfish under aquaculture conditions. However, before transgenic catfish are released and utilized by the private sector, their genetic impact on the natural environment must be examined. Predator avoidance is one of the major fitness traits determining potential environmental risk. To determine the predator avoidance ability and growth performance of transgenic catfish in a natural habitat, various densities of transgenic and nontransgenic channel catfish were communally stocked in 0.04-ha earthen ponds without supplemental feeding. Largemouth bass (Micropterus salmoides) and green sunfish (Lepomis cyanellus) were stocked as predators. Nontransgenic fry had better predator avoidance than transgenic channel catfish when data were pooled (p <.01). When data were not pooled, nontransgenic catfish had better predator avoidance in six trials and transgenic individuals had better predator avoidance in four trials. There was no difference in predator avoidance in three trials. Overall predator avoidance was also better for nontransgenic individuals (p <.01) when the fish were evaluated as 3.5-g fingerlings, more clearly than as fry, as transgenic individuals were more vulnerable in 3 of 4 trials at this life stage. There was no significant difference in growth performance between transgenic and nontransgenic channel catfish in ponds without supplemental feeding. These findings indicate that transgenic channel catfish could be used for commercial aquaculture without affecting the natural environment. Although transgenic channel catfish may be released to nature by accident, any ecological effect would be unlikely because the increased susceptibility of transgenic channel catfish to predators would most likely decrease or eliminate the transgenic genotype.

Isolation and Characterization of an Actin Promoter from the Red Abalone (Haliotis rufescens)

: We have isolated and characterized the 5'-flanking and part of the coding region of an actin gene from the red abalone Haliotis rufescens. There is high sequence homology between the abalone actin coding region and actins from other species. The sequence of this abalone actin is more closely related to vertebrate cytoplasmic actins than to muscle actins. RNase protection assays located the position of the transcription start point 66 bp upstream of the initiation codon. Promoter prediction by neural network located a TATA box 30 bp upstream of the transcription start point. A search with the SIGNAL SCAN program identified several potential transcription factor binding sites in the abalone sequence. These sites include sequences highly conserved in other actin promoters, like several putative CAAT and E boxes and a modified CArG box. Transfection assays with a construct containing the 5' flanking region of the abalone actin coupled to a luciferase reporter gene showed that the promoter is functional in mammalian and fish cell lines, as well as in abalone gonad tissue. Expression vectors constructed with the abalone actin promoter will be useful for gene transfer studies into abalone and other mollusks.

Efficient gene transfer into Xiphophorus muscle and melanoma by injection of supercoiled plasmid DNA

Muscle and melanoma tissue of fish in the genus Xiphophorus were examined for their ability to take up and express foreign DNA. Supercoiled plasmid DNA containing a firefly luciferase reporter gene with expression driven by the cytomegalovirus enhancer and thymidylate kinase promoter was directly injected into the muscle or melanoma of individual Xiphophorus. Expression levels gradually increased to a maximum at 6 days after injection in both tissues, and this level was maintained for at least 10 days after injection. In both muscle and melanoma, there was a clear relationship between dose injected and reporter gene activity, with maximal expression at a dose of 20 microg of plasmid injected. At higher doses expression levels declined, suggesting the possibility that the uptake mechanism can be inhibited by high concentrations of DNA. Histochemical localization using a beta-galactosidase construct revealed high expression of the enzyme in isolated muscle fibers. The activity of a second coinjected reporter gene, sea pansy (Renilla reniformis) luciferase, was highly correlated with the activity of the firefly luciferase reporter gene in both tissues (R2 >.940), suggesting that the majority of variation between samples results from variation in overall DNA uptake between individuals. When firefly luciferase activity is expressed as a function of activity of the coinjected reporter, the variation between samples is greatly reduced. As a result, small differences in activity between constructs can be detected. This demonstrates the usefulness of the system for gene expression analysis in vivo.

Evolutionary adaptations of gene structure and expression in natural populations in relation to a changing environment: a multidisciplinary approach to address the million-year saga of a small fish

We have used an experimentally based strategy to address molecular mechanisms underlying adaptation in Fundulus heteroclitus. In an attempt to falsify the hypothesis that selection is a major driving force in the maintenance of genetic diversity, we employed a multidisciplinary approach including allelic isozyme and mtDNA phylogeography, kinetic analyses of allelic isozymes, analysis of variation in coding and regulatory DNA sequences, metabolic biochemistry, organismal physiology, and selection experiments. Observed differences in gene structure and expression led us to make testable predictions about differences in metabolic flux, whole organism performance, and differential survival between allotypes. We have shown that variation in the lactate dehydrogenase-B (Ldh-B) protein results in differences in physiological function and is correlated with differences in survival at high temperatures. Recent work has investigated the role of variation in Ldh-B expression. There are differences in the levels of Ldh-B protein, mRNA, and transcription rate. We have addressed the mechanisms responsible for differences in transcription rate by a combination of sequence comparison, DNase I footprinting, and functional analyses both in vitro and in vivo. We have shown that variation in the regulatory sequence of Ldh-B is responsible for the differences in transcription rate between populations and that the patterns of variation are inconsistent with a neutral model of molecular evolution. This functional differentiation, coupled with departures from neutral expectations, suggests that natural selection has acted on the regulation of Ldh-B. This article illustrates the value of a multidisciplinary approach in addressing problems in gene structure, expression, and evolutionary adaptation.

A monophyletic origin of heart-predominant lactate dehydrogenase (LDH) isozymes of gnathostome vertebrates: evidence from the cDNA sequence of the spiny dogfish (Squalus acanthias) LDH-B

Duplication of a single lactate dehydrogenase locus early in vertebrate evolution has been proposed to have given rise to Ldh-A and Ldh-B, the encoded isozymes of which predominate in skeletal and heart muscle, respectively. This view has been challenged recently by phylogenetic analyses of LDH sequences. One question that has been raised is whether the heart-predominant isozyme (LDH-B) of cartilaginous fishes is orthologous to that of bony fishes and their derivatives. To address this issue, we determined the complementary DNA sequence of the LDH-B of the chondrichthyan Squalus acanthias. Phylogenetic analysis of this and other LDH isozyme sequences provided strong support for a single origin of LDH-Bs prior to the divergence of cartilaginous and bony fishes.

Binding of [3H]-SK&F 107260 and [3H]-SB 214857 to purified integrin alphaIIbbeta3: evidence for a common binding site for cyclic arginyl-glycinyl-aspartic acid peptides and nonpeptides

The aggregation of activated platelets is mediated by the binding of fibrinogen to its cell surface receptor, the integrin alphaIIbbeta3. The recognition of fibrinogen by alphaIIbbeta3 depends, in part, on the tripeptide sequence Arg-Gly-Asp (RGD) in the adhesive protein. The interactions of a cyclic RGD-containing pentapeptide, [3H]-SK&F-107260, and a 1,4-benzodiazepine-based nonpeptide [3H]-SB-214857, with purified alphaIIbbeta3 have been investigated. Both compounds potently inhibit platelet aggregation at submicromolar concentrations. Binding of both [3H]-SK&F-107260 (Kd = 1.19 nM) and [3H]-SB-214857 (Kd = 1.85 nM) to alphaIIbbeta3 is of high affinity and fully reversible. The binding is monophasic, indicating a single class of noncooperative binding sites. The two radioligands exhibited similar values in binding to alphaIIbbeta3 purified on an RGD-affinity column (Bmax = 0.2 mol/mol alphaIIbbeta3) or to alphaIIbbeta3 purified over a lentil lectin column (Bmax = 0.03 mol/mol alphaIIbbeta3), suggesting that SK&F-107260 and SB-214857 interact with the same population of receptors. Binding of [3H]-SK&F-107260 and [3H]-SB-214857 to alphaIIbbeta3 require divalent cations, Mg++, Ca++ and Mn++ are able to support binding, with Mn++ being the most effective. Thirteen alphaIIbbeta3 antagonists, including four linear and three cyclic RGD peptides, five peptidomimetics, the fibrinogen gamma-chain dodecapeptide (HHLGGAKQAGDV) and the snake venom protein, echistatin, complete for [3H]-SK&F-107260 or [3H]-SB-214857 binding to alphaIIbbeta3. The affinity constants (Ki) of these compounds, determined by the two radioligand binding assays, are similar. Furthermore, these compounds exhibit the same rank order of potency in inhibiting biotinylated-fibrinogen binding to alphaIIbbeta3. Scatchard plot analyses of the [3H]-SK&F-107260 binding isotherms in the presence of unlabeled SB-214857 and gamma-chain dodecapeptide reveal competitive-type antagonism, indicating that SB-214857, gamma-chain dodecapeptide and SK&F-107260 interact with mutually exclusive binding sites on alphaIIbbeta3.

Lactate dehydrogenase (LDH) gene duplication during chordate evolution: the cDNA sequence of the LDH of the tunicate Styela plicata

L-Lactate dehydrogenase (L-LDH, E.C. 1.1.1.27) is encoded by two or three loci in all vertebrates examined, with the exception of lampreys, which have a single LDH locus. Biochemical characterizations of LDH proteins have suggested that a gene duplication early in vertebrate evolution gave rise to Ldh-A and Ldh-B and that an additional locus, Ldh-C arose in a number of lineages more recently. Although some phylogenetic studies of LDH protein sequences have supported this pattern of gene duplication, others have contradicted it. In particular, a number of studies have suggested that Ldh-C represents the earliest divergence among vertebrate LDHs and that it may have diverged from the other loci well before the origin of vertebrates. Such hypotheses make explicit statements about the relationship of vertebrate and invertebrate LDHs, but to date, no closely related invertebrate LDH sequences have been available for comparison. We have attempted to provide further data on the timing of gene duplications leading to multiple vertebrate LDHs by determining the cDNA sequence of the LDH of the tunicate Styela plicata. Phylogenetic analyses of this and other LDH sequences provide strong support for the duplications giving rise to multiple vertebrate LDHs having occurred after vertebrates diverged from tunicates. The timing of these LDH duplications is consistent with data from a number of other gene families suggesting widespread gene duplication near the origin of vertebrates. With respect to the relationships among vertebrate LDHs, our data are not consistent with previous claims that Ldh-C represented the earliest divergence. However, the precise relationships among some of the main lineages of vertebrate LDHs were not resolved in our analyses.

Sibling models of socioeconomic effects on the timing of first premarital birth

Data on 1,000 pairs of sisters from the National Longitudinal Survey of Youth are used to estimate the effects of observed individual-level factors, common family-level variables, and shared unobserved family-level traits on the timing of premarital births. Results show a moderate correlated risk of premarital childbearing among siblings after controlling for the effects of measured covariates. The effect of older sisters' out-of-wedlock childbearing on the timing of younger sisters' premarital birth is overestimated when shared unmeasured family-level traits are ignored. Public policy measures designed to reduce premarital births have a smaller multiplier effect via reduced younger sisters' premarital births because unmeasured family-level factors are less amenable to policy measures. However, because the older-sibling effect is large when other sources of variability in premarital birth timing are controlled, interventions may be effective in reducing premarital births among young women in high-risk families.

Structural and functional differences in the promoter and 5' flanking region of Ldh-B within and between populations of the teleost Fundulus heteroclitus

We have investigated the mechanisms underlying differences in the transcriptional regulation of lactate dehydrogenase-B (Ldh-B) between northern and southern populations of a teleost fish, Fundulus heteroclitus. A 1-kb region immediately 5' of the gene was sequenced from populations throughout the species range. There were two major allele classes in the sample, one containing alleles from Maine and another containing those from Florida. Populations from intermediate localities contained both allele classes. Some individuals from Georgia had sequences intermediate between the two classes, representing either ancestral alleles or recombinants. Tests of neutrality were applied to determine whether observed variation was consistent with neutral expectations. Significant deviations from neutral expectations were detected for the 5' flanking region, but not for other loci. The functional consequences of flanking sequence variation were assessed by transfection of reporter gene constructs into cultured cells and injection into living fish. Consistent with observed variation in Ldh-B transcription rate between populations, significant differences in reporter gene activity were driven by flanking regions from northern and southern populations both in cell culture and in vivo. This functional differentiation, coupled with departures from neutral expectations, suggests that selection may have acted on the regulation of Ldh-B in F. heteroclitus.

Sequence variation of the first internal spacer (ITS-1) of ribosomal DNA in ahermatypic corals from California

Interspecific and intraspecific variation in the first internal transcribed spacer region (ITS-1) of ribosomal DNA (rDNA) was examined in two species of ahermatypic corals (lacking symbiotic algae and non-reef-building) with different dispersal characteristics, Paracyathus stearnsii (gamete-spawner with pelagic larvae) and Balanophyllia elegans (brooder with benthic larvae) from California. An approximately 300-bp region of the ITS-1 was amplified by polymerase chain reaction (PCR) and sequenced from populations at Pt. Loma, La Jolla, Monterey Bay, and Santa Catalina Island and compared for each species and compared with the same region from the hermatypic coral Favia lizardensis. There was a wide range of sequence variation in the ITS-1 region between the species, and these differences readily distinguished the taxa. Intraspecific comparisons of P. stearnsii individuals showed very little sequence variation (two polymorphisms) in the ITS-1 region. In contrast to P. stearnsii, we found 14 variable nucleotide sties in the ITS-1 region for B. elegans. Although there were no nucleotide sites that diagnostically separated central and southern populations, these findings indicate that the ITS-1 region is variable in B. elegans and a promising source for nuclear molecular markers in ahermatypic corals.

Descriptive and functional characterization of variation in the Fundulus heteroclitus Ldh-B proximal promoter

Variation in enzyme expression may be an important mechanism for physiological and evolutionary adaptation. The Ldh-B locus in the teleost fish Fundulus heteroclitus is one of a very few loci for which an evolutionary difference in transcription rate between populations has been demonstrated. To begin to understand the molecular modifications that are responsible for altering transcription, we have characterized the Ldh-B proximal promoter using a combination of sequence analysis, transient transfection, and in vivo footprinting. The Ldh-B gene has several transcription start sites and a TATA-less, Inr (initiator of transcription motif) containing promoter with multiple Sp1-like motifs. Transfection experiments reveal that Sp1 sites, TCC repeats, and Inrs are functional components of the proximal promoter. We find substantial sequence variation between populations within the proximal promoter (250 bp from the transcription start sites) and footprinting analysis indicates that some of this sequence variation is associated with differential protein binding to the apparent TFIID binding site and Sp1 sites. Together, these data suggest that variation in the Ldh-B proximal promoter may play a role in the observed difference in transcription rates between northern and southern populations of F. heteroclitus.

Electroporation as an effective means of introducing DNA into abalone (Haliotis rufescens) embryos

Recombinant plasmid containing the Drosophila beta-actin promoter coupled to a beta-galactosidase cassette was linearized and introduced in fertilized eggs of the red abalone (Haliotis rufescens) by electroporation. Fertilized abalone eggs tolerated electroporation well with larval survival rates between 70% and 84% of that for non-electroporated siblings. Dot blot and Southern blot analysis were used to detect if abalone retained the foreign gene at various developmental stages. The inserted construct was retained in 70% to 100% of all abalone sampled with an average of 72% retention in the three- to seven-month-old juveniles. Maximal DNA uptake and retention was observed in abalone electroporated at 30-40 min after fertilization. Southern hybridization analysis suggested that the inserted vector was in head-to-tail concantermers integrated in the abalone genome. This preliminary study demonstrates that electroporation is an efficient means of transferring foreign DNA into abalone embryos.

The cDNA sequence of the lactate dehydrogenase-A of the spiny dogfish (Squalus acanthias): corrections to the amino acid sequence and an analysis of the phylogeny of vertebrate lactate dehydrogenases

The cDNA sequence of the lactate dehydrogenase-A (LDH-A) of the spiny dogfish was determined. The deduced amino acid sequence differed from a previously determined protein sequence by 5%. Separate maximum parsimony analyses of the two sequences along with LDHs of other vertebrates resulted in shorter trees with the sequence presented here, as well as fewer equally parsimonious trees. The new sequence also indicates a greater conservation of length among vertebrate LDHs than was previously suspected. Analyses of the phylogeny of vertebrate LDHs resulted in a monophyletic grouping of LDH-As, from within which mammalian LDH-C is derived. The phylogeny of LDH-As did not exactly match the phylogeny of the organisms, raising the possibility of multiple origins and losses of a muscle-predominant gene. LDH-Bs appear to have shared a single origin.

Rapid in vivo footprinting method for the detection of DNA-protein interactions in isolated nuclei

Here we report a simple method of in vivo footprinting for the detection of DNA-protein interactions in the liver of a small teleost fish, Fundulus heteroclitus. This method allows the determination of these interactions in nuclei isolated from intact liver, obviating the need for cell culture. Cells in culture often do not respond to environmental cues in the same way as do tissues within the intact organism and therefore may be inappropriate for the study of certain adaptive responses. Furthermore, cell lines are available for only a small number of marine organisms. This technique may therefore be of general utility for the study of gene regulation in a wide variety of marine organisms.

Evolutionary relations among vertebrate muscle-type lactate dehydrogenases

Gene duplication has produced two lactate dehydrogenase (LDH) isozymes, LDH-A and LDH-B, that are found in essentially all vertebrates. On the basis of the biochemical properties of the LDH-A and LDH-B isozymes, it has been suggested that each locus is orthologous among all vertebrates. However, phylogenetic studies have not supported a common evolutionary history among the LDH-A isozymes, particularly when those from lower vertebrates are examined. We present here the sequence of a muscle-type LDH from Fundulus heteroclitus, a teleost fish for which the LDH-B sequence has been determined and shown to be unrelated phylogenetically to tetrapod LDH-A isozymes. Although the sequence of the teleost muscle LDH shares certain features with the LDH-A of tetrapods, phylogenetic analyses do not support an orthologous relation among the LDH-A isozymes of teleost fish and tetrapod vertebrates.

Production of a biologically active recombinant teleostean growth hormone in E. coli cells

We have isolated and characterized several recombinant lambda phage clones carrying growth hormone (GH) cDNA of striped bass (Morone saxatilis). Nucleotide sequence and the predicted amino acid sequence of sbGH was determined from a recombinant clone carrying the longest cDNA insert. The sbGH cDNA encodes a pre-hormone of 204 amino acid residues. Comparison of the predicted amino acid sequence of sbGH with those of other vertebrates revealed different degrees of sequence identity: approximately 98% with European sea bass; 90% with bluefin tuna; bonito and red seabream; 71% with winter flounder; 64% with salmonids; 55% with carp; and 38% with human. Expression of the mature sbGH cDNA (without the signal peptide sequence) in E. coli cells under regulation of the lambda phage PL promoter produced a polypeptide of 20 kDa. Following renaturation, this recombinant hormone was shown to be biologically active in a radioreceptor competition binding assay and in the induction of hepatic insulin-like growth factor I (IGF-I) mRNA synthesis in vivo.

The gene family encoding the fucoxanthin chlorophyll proteins from the brown alga Macrocystis pyrifera

Six members of a multigene family encoding polypeptide constituents of the fucoxanthin, chlorophyll a/c protein complex from female gametophytes of the brown alga Macrocystis pyrifera have been cloned and characterized. The deduced amino acid sequences are very similar to those of fucoxanthin chlorophyll binding proteins (Fcp) from the diatom Phaeodactylum tricornutum and exhibit limited homology to chlorophyll a/b binding (Cab) polypeptides from higher plants. The primary translation products from the M. pyrifera fcp genes are synthesized as higher molecular weight precursors that are processed prior to their assembly into the Fcp complex. The presumed N-terminal 40-amino acid presequence of the Fcp precursor polypeptide has features resembling that of a signal sequence. This presequence may be required for the protein to transverse the endoplasmic reticulum that surrounds the plastid in brown algae. A subsequent targeting step would be required for the protein to cross the double membrane of the plastid envelope. M. pyrifera fcp transcripts are of two sizes, 1.2 and 1.6 kb. The size difference is accounted for by the length of the 3' untranslated region, which can be up to 1000 bases. Transcript abundance's of members of the fcp gene family are dependent on light quantity, light quality, or both. Transcript levels of one gene increased approximately five- to tenfold in thalli grown in low intensity relative to high intensity white or blue light. Transcripts from this gene also significantly increase in red light relative to blue light at equivalent light intensities.

Characterization of mammalian Gs-alpha proteins expressed in yeast

The guanine nucleotide regulatory protein, GS, mediates transmembrane signaling by coupling membrane receptors to the stimulation of adenylyl cyclase activity. The full length coding sequences for the M(r) = 42-45,000, short form (S), and M(r) = 46-52,000, long form (L), of the alpha-subunits of rat GS were placed in yeast expression vectors under the regulatory control of the copper-inducible CUP1 promoter and transformed into Saccharomyces cerevisiae. In the presence of 100 microM CuSO4, the transformed yeast expressed GS-alpha mRNAs and proteins. In reconstitution experiments, rat GS-alpha(S and L), solubilized from yeast membranes with 1% cholate, conferred NaF-, (-)isoproterenol-, and guanine nucleotide-dependent sensitivity to adenylyl cyclase catalytic units in S49 lymphoma cyc- cell membranes, which are devoid of endogenous GS-alpha. GS-alpha (S) demonstrated twice the activity of GS-alpha(L) in reconstitution assays of fluoride-stimulated adenylyl cyclase activity. Comparison of GS-alpha (S) expressed in yeast with GS purified from rabbit liver or human erythrocytes showed that the crude recombinant protein was fully competent in reconstituting NaF-stimulated adenylyl cyclase activity, but was only 2-5% as potent as purified GS. Addition of bovine brain beta gamma subunits during reconstitution enhanced all parameters of adenylyl cyclase activity for GS-alpha(S and L) obtained from yeast. In contrast, transducin beta gamma only enhanced agonist-stimulated adenylyl cyclase activity for GS-alpha (S and L) following reconstitution. These results demonstrate that the expression of functional mammalian GS-alpha subunits in yeast may be useful for their biochemical characterization.

Ribosomal DNA sequences discriminate among toxic and non-toxic Pseudonitzschia species

Cultured isolates of Pseudonitzschia australis Frenguelli, P. delicatissima (Cleve) Heiden, P. americana (Hasle) Fryxell, P. pungens (Grunow) Hasle, and P. pungens f. multiseries (Hasle) Hasle from Monterey Bay, California, were compared on the basis of their large-subunit ribosomal RNA gene (LsrDNA). Pseudonitzschia australis, P. pungens f. multiseries, and P. delicatissima were previously shown to produce the neurotoxin domoic acid; the remaining isolates are considered non-toxic. For each isolate approximately 800 base pairs of LsrDNA, encompassing both evolutionarily conserved and evolutionarily variable regions of the molecule, were amplified using the polymerase chain reaction (PCR) and sequenced. Phylogenetic trees generated by parsimony analysis of aligned sequences afford a preliminary view of the organisms genetic relationships. Species defined by morphological criteria are also distinguishable by LsrDNA sequence. Organisms known or suspected to produce domoic acid cluster at different termini on the phylogenetic tree. Two genetically distinct strains of P. australis and P. pungens were identified. Development of a restriction fragment length polymorphism (RFLP) assay of the LsrDNA is described. The RFLP assay discriminates each species, including distinguished strains of P. australis and P. pungens. The restriction test provides a rapid and convenient method for screening isolates' LsrDNA, facilitating further tests of the apparent positive correlation between Pseudonitzschia species' ribosomal gene signatures, morphology, and capacity to produce domoic acid.

Concordant mitochondrial and nuclear DNA phylogenies for populations of the teleost fish Fundulus heteroclitus

Molecular phylogenies using mitochondrial DNA and nuclear alleles of the lactate dehydrogenase B locus were found to be concordant for populations of Fundulus heteroclitus ranging from Canada to Florida. Both mitochondrial DNA and lactate dehydrogenase alleles show a clear separation between the northern individuals (from Nova Scotia and Maine) and the southern ones (from Georgia and Florida), with a mixed population found in the geographic intermediate (New Jersey). An historical isolation, possibly as ancient as 0.5-1 million years old, may have played a role in shaping the situation observed today.

Structure of the channel catfish (Ictalurus punctatus) growth hormone gene and its evolutionary implications

A DNA fragment of 1.6 kilo base pairs (kb), encoding part of the channel catfish (Ictalurus punctatus) growth hormone (GH) gene, was generated by the polymerase chain reaction (PCR) using 2 degenerate synthetic oligonucleotides (30 and 33 mer) derived from the N- and C-terminal amino acid sequences of the catfish GH polypeptide as amplification primers and with catfish genomic DNA as a template. This DNA fragment was used as a probe for the isolation of a catfish GH gene from a genomic library constructed in a lambda phage cloning vector, lambda Dash II. Three positive clones were isolated, and their complete nucleotide sequences were determined. Nucleotide sequences from clones 1 and 3 were identical, whereas clone 2 had 2 base substitutions. The gene spans approximately 3 kb and is comprised of 5 exons and 4 introns. The initiation codon, the termination codon, and the canonical polyadenylation sequence were identified. The amino acid sequence deduced from the predicted coding region of the gene is in agreement with that of the native GH polypeptide sequence. A sequence (TATAAAA) matching the TATA box consensus sequence was located at nucleotide positions -30 to -23. Furthermore, 2 sequences corresponding to the mammalian Pit-1/GHF-1 binding sites (consensus sequence TT[AA]TATNCAT) were identified in the 5' flanking region starting at positions -113 and -134. Another sequence (GTACCAGTGA) conserved among the GH genes of the channel catfish and other known animal species was also identified at position -220. The biological functions of this sequence remain to be determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression and inheritance of RSVLTR-rtGH1 complementary DNA in the transgenic common carp, Cyprinus carpio

Transgenic common carp, Cyprinus carpio, possessing the long terminal repeat (LTR) sequence of avian Rous sarcoma virus (RSV) fused to the rainbow trout (rt) growth hormone (GH1) complementary DNA (cDNA) were produced by microinjection. Initial studies showed that the transgenic common carp transmitted the foreign DNA to a significant fraction of their progeny in three of four crosses of transgenic males with control females. These progeny grew 20 to 40% faster than their nontransgenic full siblings. In this study, additional experiments were conducted to evaluate inheritance and expression of the foreign GH gene in transgenic common carp, and the growth performance of these transgenic fish. Four P1 (parental generation produced by microinjection) x nontransgenic controls, four P1 x P1, and one P1 x F1 matings of transgenic carp containing RSVLTR-rtGH1 cDNA were made. The percentages of transgenic progeny resulting from these matings were: 0, 32, 42, 100 (4 progeny only), 21, 21, 31, 30, and 23%, respectively. All crosses except 1 siblot (control x P1) exhibited progeny ratios below the expected 50 or 75% transgenic. These results indicate that most of these transgenic P1 had the foreign gene in their germ line but were mosaics, and at least one transgenic individual did not have the RSVLTR-rtGH1 cDNA in the gonadal tissue. Both P1 and F1 transgenic fish produce trout growth hormone mRNA and polypeptide as determined by reverse transcription polymerase chain reaction amplification, RNA dot-blot hybridization, and radio-immunobinding assay. Growth response by families of F1 transgenic fish to the addition of rtGH1 cDNA varied widely.(ABSTRACT TRUNCATED AT 250 WORDS)

Interspecific and intrapopulation variation in mitochondrial ribosomal DNA sequences of Mytilus spp. (Bivalvia: Mollusca)

A 560-base pair portion of the mitochondrial 16S ribosomal DNA (16S rDNA) from three morphologically similar mussels, Mytilus edulis, M. galloprovincialis, and M. trossulus, was amplified with the polymerase chain reaction, and 349 base pairs were sequenced. These data showed that this gene in M. edulis and M. galloprovincialis has not diverged; however, the north Pacific mussel, M. trossulus, showed fixed differences from M. edulis and M. galloprovincialis at 5 nucleotide positions. Furthermore, the population of M. trossulus at Tillamook Bay, Oregon, was found to contain two very divergent 16S rDNA genotypes that differ at 37 nucleotide positions. Thus, intraspecific variation in this gene in M. trossulus is greater than that seen interspecifically in M. edulis and M. galloprovincialis. Despite this large difference, in the absence of evidence of genetic isolation between these groups of M. trossulus, no taxonomic changes are proposed. These data are consistent with a north Pacific origin of the genus with subsequent dispersal to the Atlantic Ocean across the Artic Sea, giving rise to M. edulis in northern Europe and subsequently M. galloprovincialis in southern Europe and the Mediterranean Sea.

Sequence analysis of teleost retina-specific lactate dehydrogenase C: evolutionary implications for the vertebrate lactate dehydrogenase gene family

At least two gene duplication events have led to the three lactate dehydrogenase (LDH; EC 1.1.1.27) isozymes (LDH-A, LDH-B, and LDH-C) of chordates. The prevailing model for the evolution of the LDH loci involves duplication of a primordial LDH locus near the origin of vertebrates, giving rise to Ldh-A and Ldh-B. A third locus, designated Ldh-C, is expressed in the spermatocytes of mammals and a single family of birds and in the eye or liver tissues of teleost fishes. Ldh-C might have arisen independently in these taxa as duplications of either Ldh-A or Ldh-B. Several authors have challenged this traditional hypothesis on the basis of amino acid sequence and immunological similarity of the three LDH isozymes. They suggest that the primordial LDH gene was duplicated to form Ldh-C and a locus that later gave rise to Ldh-A and Ldh-B. We have differentiated between these hypotheses by determining the cDNA sequence of the retina-specific LDH-C from a teleost, Fundulus heteroclitus. On the basis of amino acid sequence similarity, we conclude that the LDH-C isozymes in fish and mammals are not orthologous but derive from independent gene duplications. Furthermore, our phylogenetic analyses support previous hypotheses that teleost Ldh-C is derived from a duplication of the Ldh-B locus.

Evolutionary adaptation to different thermal environments via transcriptional regulation

Populations of the teleost fish Fundulus heteroclitus are subjected to the clinical variation in environmental temperatures that occurs along the eastern seacoast of North America. In concordance with this change in temperature is the clinal variation in the enzyme concentration of the heart-type lactate dehydrogenase (LDH-B; E.C.1.1.1.27). Previously we have shown that the compensating change in the LDH-B enzyme concentration is due to a change in the amount of LDH-B mRNA, but we did not define whether this was due to differences in mRNA stability or to differences in rate of transcription. The results presented here help clarify the molecular mechanism responsible for the variation in Ldh-B gene expression: the rate of transcription from the Ldh-B locus is significantly different between populations, and this difference is responsible for the compensatory change in LDH-B enzyme concentration.

Transfer, expression, and inheritance of salmonid growth hormone genes in channel catfish, Ictalurus punctatus, and effects on performance traits

We examined expression and inheritance of salmonid growth hormone genes RSVLTR-rtGH1 cDNA and RSVLTR-csGH cDNA, transferred to channel catfish (Ictalurus punctatus) by microinjection. One to 9 copies of the foreign DNA were inserted in either head-to-tail tandem array at single insertion sites or single copies at multiple insertion sites. All P1 transgenic catfish evaluated produced salmonid growth hormone regardless of the construct. Five P1 x P1 matings were accomplished. The spawning rate and fertility of these P1 transgenics in artificial spawning conditions were comparable to those of normal channel catfish. In two of three years, 100% spawning and 100% hatch were obtained. Percent transgenic progeny observed in the five matings were 20, 52, 7, 47, and 0%, which was lower (P < 0.001, chi 2) than the 75% inheritance expected assuming the P1 brood stock had at least one copy of the foreign gene integrated and were not mosaics in the germ line. At least 7 of 10 P1 were mosaics, and a minimum of 2 of 10 P1 did not possess the salmonid growth hormone genes in their germ line. P1 transgenics grew at the same rate as their nontransgenic full siblings, which is not surprising because the P1 were mosaics. F1 transgenic progeny in two families possessing RSVLTR-csGH cDNA grew 26% faster, to 40 to 50 gm, than their nontransgenic full siblings when evaluated communally. One F1 progeny group produced by RSVLTR-rtGH1 cDNA x RSVLTR-csGH cDNA mating and one F1 progeny group (parents either RSVLTR-rtGH1 cDNA or RSVLTR-csGH cDNA) grew at the same rate as normal full siblings when grown communally to 25 gm and 60 mg, respectively. In families where F1 progeny grew faster than controls, the range in body weight and coefficient of variation for the transgenic full siblings were less than those for controls. In families where F1 progeny grew at the same rate as controls, range in body weight and coefficient of variation were similar for transgenic and normal individuals. The percent deformities observed in P1 transgenics (13.6%) was higher (P < 0.05) than in microinjected P1 nontransgenics (5.1%). Percent deformities in transgenics and control F1 channel catfish was not different (p > 0.05; 0.5 and 2.8%, respectively).

Electroporation: a method for transferring genes into the gametes of zebrafish (Brachydanio rerio), channel catfish (Ictalurus punctatus), and common carp (Cyprinus carpio)

Recombinant plasmids containing the Rous sarcoma virus long-terminal repeat (RSVLTR) promoter linked to either rainbow trout (Oncorhyncus mykiss) growth hormone 1 (rtGH1) or growth hormone 2 (rtGH2) cDNA were linearized and introduced into the fertilized eggs of zebrafish (Brachydanio rerio), channel catfish (Ictalurus punctatus), and common carp (Cyprinus carpio) by both electroporation and microinjection. The latter two species had these rainbow trout constructs (RSVLTR-rtGH1cDNA or RSVLTR-rtGH2) electroporated into both gametes (i.e., sperm and unfertilized eggs) prior to fertilization, into eggs shortly after fertilization, and at the first cell division stage. Survival was determined just after hatching and again between 3 and 5 months after hatching. Polymerase chain reactions and Southern blot analyses were used to detect those individuals carrying the introduced foreign genes 3 to 5 months after hatching, respectively. Individuals analyzed by both methods yielded identical results in a double-blind study. The electroporation results were compared with groups that were microinjected. Although survival was similar, electroporation tended to produce a greater number of transgenic individuals than the microinjection procedure, and many more eggs could be treated per unit time by electroporation than microinjection. Survival was better for common carp when electroporation was performed shortly after fertilization, whereas channel catfish fared better at the first cell division stage. Electroporation prior to and shortly after fertilization, and at the first cell stage appeared to generate a large fraction of transgenic fish. We cautiously conclude that electroporation is an efficient method for introducing foreign DNA into fish gametes and embryos and may be an ideal method for treating large numbers of gametes in a modest period.

Molecular phylogeny of the prickly shark, Echinorhinus cookei, based on a nuclear (18S rRNA) and a mitochondrial (cytochrome b) gene

The classification of the sharks is unclear. This is particularly true for the superorder Squalomorphii. The relationships between the squalomorphs and other superorders of sharks and the relationships between the different orders within the squalomorphs are a matter of debate. Here, we report a molecular phylogeny for a little known member of this superorder, the genus Echinorhinus. Echinorhinus is most commonly classified in either the family Echinorhinidae (Squaliformes) or the family Squalidae (Squaliformes). However, some authors have suggested a closer relationship to the order Hexanchiformes. In an attempt to shed light on this controversy, we have cloned, sequenced, and compared two genes widely used in molecular phylogeny studies, the cytochrome b and the 18S rRNA from the rare prickly shark, Echinorhinus cookei, and two potential relatives, the spiny dogfish Squalus acanthias (Squaliformes), and the sevengill shark, Notorynchus cepedianus (Hexanchiformes). The sequences of these genes for the prickly shark, the dogfish, and the sevengill shark were found to be equally divergent, suggesting that the prickly shark is no closer to the order Squaliformes than to the order Hexanchiformes.

Nucleotide sequence of the 18S ribosomal ribonucleic acid gene from two teleosts and two sharks and their molecular phylogeny

The 18S rRNA sequence was determined for two teleostean fish species, Fundulus heteroclitus and Sebastolobus altivelis, and two sharks, Squalus acanthias and Echinorhinus cookei. To study the molecular phylogeny of these taxa, the sequences were compared with 18S rRNA sequences of the Coelacanth Latimeria chalumnae, the frog Xenopus laevis, and humans. Maximum parsimony analysis of the sequences resulted in a single most parsimonious tree that is in agreement with the expected phylogeny. The correct phylogenetic tree was also found when using S. altivelis alone as the teleost representative. In contrast, the most parsimonious tree found by using F. heteroclitus as the teleost representative presented anomalous groupings (the teleost branch being grouped with humans), matching results previously obtained. However, a bootstrap analysis showed that some branches containing anomalous relationships were not significantly supported. An explanation for this peculiarity, the differences between our tree and previously identified ones, and their phylogenetic implications are discussed.

Ribosomal RNA sequences and the diversity of symbiotic dinoflagellates (zooxanthellae)

Zooxanthellae are unicellular algae that occur as endosymbionts in many hundreds of common marine invertebrates. The issue of zooxanthella diversity has been difficult to address. Most zooxanthellae have been placed in the dinoflagellate genus Symbiodinium as one or several species that are not easily distinguished. We compared Symbiodinium and nonsymbiotic dinoflagellates using small ribosomal subunit RNA sequences. Surprisingly, small ribosomal subunit RNA diversity within the genus Symbiodinium is comparable to that observed among different orders of nonsymbiotic dinoflagellates. These data reinforce the conclusion that Symbiodinium-like zooxanthellae represent a collection of distinct species and provide a precedent for a molecular genetic taxonomy of the genus Symbiodinium.

Effect of hypoalbuminemia and parenteral nutrition on free water excretion and electrolyte-free water resorption

OBJECTIVE

To measure the effect of human albumin supplementation during parenteral nutrition on serum albumin concentrations, colloid oncotic pressure, free water clearance, electrolyte-free water resorption, and sodium excretion.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Tertiary care center.

PATIENTS

Thirty adult, hypoalbuminemic patients who required parenteral nutrition.

INTERVENTIONS

Parenteral nutrition (control) or parenteral nutrition plus human albumin 25 g/L as a continuous infusion (treatment) for a 5-day study period.

MEASUREMENTS

On days 1 and 5, serum albumin concentration, colloid oncotic pressure, free water clearance, electrolyte-free water resorption, and sodium excretion were measured.

RESULTS

Serum albumin concentrations increased significantly from day 1 to day 5 in both groups (control: 2.0 +/- 0.1 [mean +/- SEM] vs. 2.3 +/- 0.1 g/dL [20 +/- 1 vs. 23 +/- 1 g/L], p = .02; treatment: 2.2 +/- 0.1 vs. 3.5 +/- 0.2 g/dL [22 +/- 1 vs. 35 +/- 2 g/L], p = .0001). Day 5 serum albumin concentrations were significantly higher in the treatment group compared with control (p = .0001). Colloid oncotic pressure increased significantly from day 1 to day 5 in the treatment group (17.8 +/- 0.8 vs. 25.1 +/- 1.0 mm Hg, p = .0001), and was significantly higher than control at day 5 (p = .0001). No significant differences were found for free water clearance, electrolyte-free water resorption, or sodium excretion within or between groups.

CONCLUSIONS

In hypoalbuminemic patients, human albumin supplementation during parenteral nutrition results in significant increases in serum albumin concentrations and colloid oncotic pressure, but has no apparent effect on free water clearance, electrolyte-free water resorption, or sodium excretion.

Platelet-activating factor stimulates phosphoinositide turnover in neurohybrid NCB-20 cells: involvement of pertussis toxin-sensitive guanine nucleotide-binding proteins and inhibition by protein kinase C

Platelet-activating factor (PAF) is an unusually potent phospholipid known to be produced by neuronal cells and to modulate cerebral blood flow and metabolism. In previous studies with NCB-20 cells, we reported that PAF induced a significant mobilization of intracellular free Ca2+ ([Ca2+]i), which was inhibited by PAF antagonists. The increase was the result of release from intracellular stores and influx from extracellular sources. The present study was designed to characterize further PAF receptor-mediated cellular signal-transduction mechanisms in myo-[3H]inositol-labeled cells. PAF induced a concentration-dependent increase in phosphatidylinositol (Pl) metabolism, with EC50 values of 1.96 +/- 0.62 nM and 1.12 +/- 0.50 nM for inositol trisphosphate (IP3) and inositol monophosphate (IP1) formation, respectively (four experiments). The maximal production of IP3 and IP1 induced by 50 nM PAF was 254 +/- 34% and 178 +/- 25% over the basal, respectively (four experiments). PAF-induced Pl metabolism was concentration-dependently inhibited by the PAF antagonist BN50739, with an IC50 value of 6.48 +/- 0.52 nM (four experiments). The protein kinase C (PKC) activator phorbol 12,13-dibutyrate concentration-dependently inhibited PAF-induced Pl metabolism and [Ca2+]i mobilization in NCB-20 cells, of NCB-20 cells with pertussis toxin (PTX) resulted in a concentration-dependent inhibition of PAF-induced IP3 production and intracellular Ca2+ release, with a maximal reduction of 66.9 +/- 3.5% and 63 +/- 6.1%, respectively, at 300 ng/ml PTX. PTX in the presence of [32P]NAD specifically [32P]ADP-ribosylated a 38-kDa protein in membranes prepared from NCB-20 cells. Pretreatment of the cells with PTX resulted in a concentration-dependent inhibition of subsequent 32P-labeling of the toxin substrate in the membranes and correlated with the uncoupling of PAF-induced IP3 formation. PAF (0.01-10 nM) elicited a concentration-related stimulation in guanosine 5'-O-(3-[35S]) triphosphate ([35S]GTP gamma S) binding to G alpha i(1,2) proteins, which was inhibited by the PAF antagonist BN50739. PAF at 10 nM also increased [35S]GTP gamma S binding to G alpha s and G alpha o. PAF-evoked activation of G alpha i(1,2) and G alpha o was reduced by preincubation with PTX. Our results reveal that neuronal cells possess PAF receptors linked through guanine nucleotide-binding proteins to phospholipase C and receptor-operated Ca2+ channels that are regulated by PKC. Both PTX-sensitive and -insensitive guanine nucleotide-binding proteins appear to couple the PAF receptor to activation of phospholipase C and the increase in [Ca2+]i. These results contribute to the further understanding of the mechanisms behind PAF actions on neuronal cells.

Evidence of lactate dehydrogenase-B allozyme effects in the teleost, Fundulus heteroclitus

The evolutionary significance of protein polymorphisms has long been debated. Exponents of the balanced theory advocate that selection operates to maintain polymorphisms, whereas the neoclassical school argues that most genetic variation is neutral. Some studies have suggested that protein polymorphisms are not neutral, but their significance has been questioned because one cannot eliminate the possibility that linked loci were responsible for the observed differences. Evidence is presented that an enzymatic phenotype can affect carbon flow through a metabolic pathway. Glucose flux differences between lactate dehydrogenase-B phenotypes of Fundulus heteroclitus were reversed by substituting the Ldh-B gene product of one homozygous genotype with that of another.

Cloning and sequencing of the gilthead seabream (Sparus aurata) growth hormone-encoding cDNA

The cDNA clones encoding gilthead seabream (gsb) (Sparus aurata) growth hormone (GH) have been isolated from a cDNA library prepared from seabream pituitary gland poly(A)+ RNA. The cDNA library was screened using red seabream and rainbow trout GH cDNAs. The complete nucleotide (nt) sequence of gsbGH has been determined. The cDNA sequence codes for a polypeptide of 204 amino acids (aa), including a putative signal peptide of 17 aa. The 5'- and 3'-untranslated regions of the message are 55 and 236 nt long, respectively. The predicted aa sequence of gsbGH revealed 97% homology with red seabream GH, 95% with tuna GH, 85% with yellowtail GH, and 65% with rainbow trout GH.

A molecular genetic classification of zooxanthellae and the evolution of animal-algal symbioses

Zooxanthellae are unicellular algae that occur as endosymbionts in many hundreds of marine invertebrate species. Because zooxanthellae have traditionally been difficult to classify, little is known about the natural history of these symbioses. Zooxanthellae were isolated from 131 individuals in 22 host taxa and characterized by the use of restriction fragment length polymorphisms (RFLPs) in nuclear genes that encode small ribosomal subunit RNA (ssRNA). Six algal RFLPs, distributed host species specifically, were detected. Individual hosts contained one algal RFLP. Zooxanthella phylogenetic relationships were estimated from 22 algal ssRNA sequences-one from each host species. Closely related algae were found in dissimilar hosts, suggesting that animal and algal lineages have maintained a flexible evolutionary relation with each other.

Gene transfer, expression and inheritance of pRSV-rainbow trout-GH cDNA in the common carp, Cyprinus carpio (Linnaeus)

A recombinant plasmid containing the Rous sarcoma virus-long terminal repeat (RSV-LTR) promoter linked to rainbow trout (Salmo gairdneri) growth hormone (GH) cDNA was microinjected into fertilized carp eggs. Genomic DNA extracted from pectoral fin of individual presumptive transgenic fish was analyzed by dot blot and Southern blot hybridization, using the RSV-LTR and/or the GH cDNA sequences as probes. Out of 365 presumptive transgenic fish analyzed, 20 individuals were found to contain pRSV-rtGH-cDNA sequence in the genomic DNA. Expression of the trout GH polypeptide was detected by immunobinding assay in the red blood cells of nine transgenic fish tested. The level of expression, however, varied among the transgenics and could not be correlated with exogenous DNA copy number. Although there was considerable variation in the sizes of the transgenic fish, those microinjected during the one-cell stage were (P less than 0.05) 22% larger, on the average, than their sibling controls. A randomly selected fraction of the progeny derived from crosses between transgenic males and non-transgenic females inherited the foreign DNA. These transgenic progeny grew faster (P less than 0.05) than their non-transgenic siblings.

Transgenic fish

A range of transgenic animal species have been generated using DNA microinjection, and application of this technique to fish is now showing some degree of success. Studies to optimize microinjection techniques specifically for use with fish, and to investigate possible alternative methods for mass culture, should lead to the commercial production of transgenic fish able to transmit desirable characteristics, such as enhanced growth or disease resistance, to their progeny.

Molecular basis of evolutionary adaptation at the lactate dehydrogenase-B locus in the fish Fundulus heteroclitus

At the extremes of its natural distribution, populations of the common killifish Fundulus heteroclitus experience a difference of more than 15 degrees C in mean annual temperature. These populations are virtually fixed for two different codominant alleles at the heart-type lactate dehydrogenase locus (Ldh-B) which code for allozymes with different and adaptive kinetic responses to temperature. Two populations near the extremes of the species range (i.e., Maine and Georgia) were further studied for thermal adaptation at this locus. In the absence of any kinetic differences one would predict that to maintain a constant reaction velocity, 2 to 3 times as much enzyme would be required for each 10 degrees C decrease in environmental temperature. Consistent with this adaptive strategy and in addition to the adaptive kinetic characteristics, the LDH-B4 enzyme (EC 1.1.1.27) concentration and its mRNA concentration were approximately twice as great in the northern population as in the southern population. Acclimation experiments allow us to conclude that these differences are due to a combination of fixed genetic traits (evolutionary adaptation) and plastic responses to temperature (physiological acclimation). Furthermore, our calculations show that the LDH-B4 reaction velocities are essentially equivalent for these two populations, even though they live in significantly different thermal environments.

Fish as model systems

Fish represent the largest and most diverse group of vertebrates. Their evolutionary position relative to other vertebrates and their ability to adapt to a wide variety of environments make them ideal for studying both organismic and molecular evolution. A number of other characteristics make them excellent experimental models for studies in embryology, neurobiology, endocrinology, environmental biology, and other areas. In fact, they have played a critical role in the development of several of these disciplines. Research techniques that enable scientists to make isogenic lines in a single generation, create and maintain mutants, culture cells, and transfer cloned genes into embryos signal an increasing role for fish as experimental models.