Modern Bony Fish Research Articles

Proceedings from the International Symposium on Primordial Prevention of Cardiovascular Disease Risk Factors: Introduction

A signature feature of tetrapod pro-opiomelanocortin (POMC) is the presence of three melantropin (MSH) coding regions (α-MSH, β-MSH, γ-MSH). The MSH duplication events occurred early during the radiation of the jawed vertebrates well over 400 million years ago. However, in at least one order of modern bony fish (subdivision Teleostei; order Salmoniformes; i.e. salmon and trout) the γ-MSH sequence has been deleted from POMC. To determine whether the γ-MSH deletion has occurred in other teleost orders, a POMC cDNA was cloned from the pituitary of the neoteleost Oreochromis mossambicus (order Perciformes). In O. mossambicus POMC, the deletion is more extensive and includes the γ-MSH sequence and most of the joining peptide region. Because the salmoniform and perciform teleosts do not share a direct common ancestor, the γ-MSH deletion event must have occurred early in the evolution of the neoteleost fishes. The post-translational processing of O. mossambicus POMC occurs despite the fact that the proteolytic recognition sequence, (R/K)-Xn-(R/K) where n can be 0, 2, 4, or 6, a common feature in mammalian neuropeptide and polypeptide hormone precursors, is not present at several cleavage sites in O. mossambicus POMC. These observations would indicate that either the prohormone convertases in teleost fish use distinct recognition sequences or vertebrate prohormone convertases are capable of recognizing a greater number of primary sequence motifs around proteolytic cleavage sites.

Cloning of a neoteleost ( Oreochromis mossambicus) pro-opiomelanocortin (POMC) cDNA reveals a deletion of the γ-melanotropin region and most of the joining peptide region: implications for POMC processing☆

A signature feature of tetrapod pro-opiomelanocortin (POMC) is the presence of three melantropin (MSH) coding regions (α-MSH, β-MSH, γ-MSH). The MSH duplication events occurred early during the radiation of the jawed vertebrates well over 400 million years ago. However, in at least one order of modern bony fish (subdivision Teleostei; order Salmoniformes; i.e. salmon and trout) the γ-MSH sequence has been deleted from POMC. To determine whether the γ-MSH deletion has occurred in other teleost orders, a POMC cDNA was cloned from the pituitary of the neoteleost Oreochromis mossambicus (order Perciformes). In O. mossambicus POMC, the deletion is more extensive and includes the γ-MSH sequence and most of the joining peptide region. Because the salmoniform and perciform teleosts do not share a direct common ancestor, the γ-MSH deletion event must have occurred early in the evolution of the neoteleost fishes. The post-translational processing of O. mossambicus POMC occurs despite the fact that the proteolytic recognition sequence, (R/K)-X n-(R/K) where n can be 0, 2, 4, or 6, a common feature in mammalian neuropeptide and polypeptide hormone precursors, is not present at several cleavage sites in O. mossambicus POMC. These observations would indicate that either the prohormone convertases in teleost fish use distinct recognition sequences or vertebrate prohormone convertases are capable of recognizing a greater number of primary sequence motifs around proteolytic cleavage sites.

Immunoreactivity of the corpuscles of Stannius of the garpike, Lepisosteus osseus, to antisera against salmon and trout stanniocalcins

Stanniocalcin-immunoreactive cells were localized in the corpuscles of Stannius of a holostean fish, the garpike (Lepisosteus osseus), using antisera against salmon and trout stanniocalcins and the peroxidase-antiperoxidase and protein A-gold immunohistochemical methods. The stanniocalcin-immunoreactive cells were periodic acid-Schiff-positive, and antibody staining was abolished if the antiserum was preabsorbed with corpuscle homogenate. Immunocytochemistry revealed two reactive cell types in the glandular parenchyma, and immunoreactivity was confined to the secretory granules. Staining of the granules was also abolished when the antisera were blocked with crude corpuscle homogenate. When corpuscle extracts from garpike were subjected to sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blot analysis, a single dense band was evident with a molecular weight of ∼68 kDa under non-reducing conditions, whereas three bands were observed (∼29, ∼31, and ∼34 kDa) under reducing conditions. Staining of all bands disappeared following preabsorption of the antiserum with salmon stanniocalcin, trout stanniocalcin, or garpike corpuscle extract. The results are compared with stanniocalcins from another extant holostean, the bowfin (Amia calva), and from more modern bony fishes, the teleosts.

Primitive actimoterigian fishes can synthesize ascorbic acid

Amphibians and reptiles evolved with the capacity to synthesize ascorbic acid. Some higher vertebrates, like bats, guinea pigs, primates, and humans have lost the microsomal enzyme gulonolactone oxidase, and in cases of ascorbic acid deficiency suffer from symptoms of scurvy. The question of whether the capacity to synthesize ascorbate is also present in lower vertebrates could throw light on the evolution of this pathway. In order to find out whether ascorbic acid synthesis took place in two primitive Actinopterigian fish, the paddlefish (Polydon spathula) and the white sturgeon (Acipenser transmontanus) were fed with a scorbutogenic diet or diet(s) supplemented with a graded level of ascorbic acid. We found no growth depression nor external symptoms of scurvy, which would be pronounced in modern bony fishes (Teleostei) under similar conditions. The tissue level of ascorbate in both these primitive species indicated that vitamin C in intestine and liver is not depleted when fed a scorbutogenic diet. Gulonolactone oxidase activity was found in the kineys of the Actinopterigian fishes. Thus, I question the accepted evolutionary pathway for ascorbic acid biosynthesis in lower vertebrates and suggest that the modern bony fishes,Teleostei, lost their ability to express the gulonolactone oxidase genes after they had separated during the Silurian from their common ancestor with the coelacanths (Latimeria) and Dipnoi.

Sequence analysis of 12 structural genes and a novel non-coding region from mitochondrial DNA of Atlantic cod, Gadus morhua

We have determined the nucleotide sequences of 12 structural genes from the mitochondrial DNA of Atlantic cod, Gadus morhua. These genes encode the proteins NADH dehydrogenase subunit 2, cytochrome c oxidase subunit I, cytochrome c oxidase subunit II, and apocytochrome b, as well as the transfer RNAs tRNA Ile tRNA Gln, tRNA Met, tRNA Ser (UCN), tRNA Asp, tRNA Glu, tRNA Thr and tRNA Pro. The apocytochrome b sequences were used to construct a phylogenetic tree revealing the evolutionary divergence between modern bony fishes, sturgeon and sharks. We found that bony fishes display the same slow amino acid substitution rates in the mitochondrial encoded proteins as cartilaginous fishes (sharks). A novel non-coding region of 74 base pairs not found in other fishes where sequence data are available is located between the genes encoding tRNA Thr and tRNA Pro. This region contains both direct and inverted repeat motifs that may function in termination of the H-strand transcript.

Lungfish prolactin exhibits close tetrapod relationships

This paper describes the isolation and the complete amino-acid sequence of prolactin (PRL) from the pituitary glands of African lungfish, Protoputerus aethiopicus. We purified the hormone from an alkaline extract of the pituitaries using a two-step chromatographic procedure by detecting specific immunoblot reactivity with rabbit antisera against salmon PRL. The lungfish PRL consists of 200 amino-acid residues. Sequence comparison revealed that the PRL shows 66% identities with amphibian, reptilian and bird PRLs, 57% with mammalian PRLs, and 38% with teleost (modern bony fish) PRLs. Moreover, the PRL contains three disulfide bonds homologous to those of tetrapod PRLs and differs from teleost PRLs which lack the amino-terminal disulfide bond. Thus, the structural features of lungfish PRL indicate a closer relationship to tetrapod PRLs than to teleost PRLs. All PRLs sequenced to date share 22 common amino acids, which may be important for the activities common to all PRLs.

The complete amino acid sequence of growth hormone of an elasmobranch, the blue shark ( Prionace glauca)

The complete amino acid sequence of growth hormone (GH) from a phylogenetically ancient fish, the blue shark ( Prionace glauca), was determined. The shark GH isolated from pituitary glands by U. J. Lewis, R. N. P. Singh, B. K. Seavey, R. Lasker, and G. E. Pickford (1972, Fish. Bull. 70, 933–939) was purified by reversed-phase high-performance liquid chromatography. The hormone was reduced, carboxymethylated, and subsequently cleaved in turn with cyanogen bromide and Staphylococcus aureus protease. The intact protein was also cleaved with lysyl endopeptidase and o-iodosobenzoic acid. The resulting peptide fragments were separated by rpHPLC and submitted to sequence analysis by automated and manual Edman methods. The shark GH consists of 183 amino acid residues with a calculated molecular weight of 21,081. Sequence comparisons revealed that the elasmobranch GH is considerably more similar to tetrapod GHs (e.g., 68% identity with sea turtle GH, 63% with chicken GH, and 58% with ovine GH) than teleostean GHs (e.g., 38% identities with salmon GH and 42% with bonito GH) except for eel GH (61% identity), and substantiates the earlier finding derived from the immunochemical and biological studies ( Hayashida and Lewis, 1978) that the primitive fish are less diverged from the main line of vertebrate evolution leading to the tetrapod than are the modern bony fish.

Immunochemical and biological studies with antiserum to shark growth hormone

A comparative immunochemical study was conducted with an antiserum prepared for the first time against growth hormone (GH) from a phylogenetically ancient fish, the blue shark ( Prionace glauca). The result of immunodiffusion studies revealed extensive immunochemical relatedness of GHs from species representing each of the major vertebrate classes. The findings obtained with a homologous radioimmunoassay (RIA) system did not show good correlation with those obtained by immunodiffusion. However, a heterologous system employing the same antiserum and a purified rat GH for standards and for the tracer, gave results that were in good agreement with the findings based on immunodiffusion. Interestingly, in the heterologous RIA, the purified GH of a modern bony fish ( Tilapia) as well as the presumptive GH in pituitary extracts of several other modern bony fishes (teleosts), showed significant relatedness to shark GH only when employed at very high concentrations. The rat tibial plate-stimulating activity shown by a shark pituitary extract was completely blocked with injections of antisera to purified shark or turtle GH. Furthermore, purified shark GH showed a very significant stimulation in the rat tibia assay, in contrast to the lack of stimulation reported earlier by several investigators using pituitary extracts of teleostean species and the relatively low degree of stimulation shown recently with a highly purified GH from a teleost ( Tilapia). The data obtained thus far based on immunochemical and biological studies suggest that there must be some significant differences in the structure of shark GH compared to the structure of GH from modern bony fishes, in spite of the existence of substantial similarities.

Fine Structure of the Adrenocortical Homolog and the Corpuscles of Stannius ofAmia calva L.

A comparison is made between the fine structure of yellow corpuscles and white corpuscles located within the kidneys of the holostean fish, Amia calva L. The yellow corpuscles are composed of epithelial cells possessing all the features of steroid-producing tissues, namely an abundance of vacuoles, tubular smooth endoplasmic reticulum, and mitochondria with tubular cristae. The Golgi apparatus is also a conspicuous component of their cytoplasm. These cells are homologous to adrenocortical cells of higher vertebrates and they have cytoplasmic projections which extend into the lumina of surrounding sinusoids. The white corpuscles possess epithelial cells of variable appearance but all cells contain secretory granules and an extensive rough endoplasmic reticulum. The secretory granules appear to originate at the Golgi apparatus and occasionally are observed intact in the intercellular space. However the method of release of these granules was not clearly defined. These corpuscles are similar to the corpuscles of Stannius which have been described in modern bony fish. The presence of multivesicular bodies and smooth endoplasmic reticulum in some cells may reflect the origin of the corpuscles of Stannius from the tubular nephron. A. calva appears to be a suitable organism for comparative studies into the function of the adrenocortical homolog and corpuscles of Stannius in “primitive” fish.

A genetic model for the evolution of the glycosphingolipids.

The glycosphingolipids have been found in many animal tissues, but the complexity of their molecular structure varies considerably among the different phyla. Relatively simple structures have been found in invertebrate species, while the most complex have been demonstrated in brain tissue of modern fishes and amphibians. The data on the phylogenetic distribution of the glycosphingolipids has been interpreted to indicate that a significant number of gene duplications, involving many different structural genes, may have occurred during a few specific periods of vertebrate evolution. The transition from invertebrate to jawless vertebrate, the divergence of rays and skates from true sharks, the advent of modern bony fishes and the transition from aquatic to terrestrial vertebrates, each could have veen accompained by duplications of genes involved in the synthesis and degradation of glycosphingolipids. The evolutionary study of such a multi-enzyme system may be one means to detect alterations in the genome as a whole. The apparent correspondence in time of these gene duplications involved in glycosphingolipid metabolism and periods of rapid vertebrate evolution which may have been accompanied by significant increases in the amount of cellular DNA suggests that such changes may have occurred via the mechanism of tetraploidization.

Biological and immunochemical studies with growth hormone in pituitary extracts of holostean and chondrostean fishes

The results of the present investigation suggest that growth hormone (GH) in extracts of pituitaries from representatives of the two existing genera of holostean fish, the bowfin ( Amia) and the gar ( Lepisosteus), and in an extract of pituitaries of a chondrostean fish ( Polypterus), shows significant immunochemical relatedness to mammalian (rat) GH and appears to be capable of stimulating growth in the mammal on the basis of the tibia test in the rat. These findings are analogous to those previously reported for GH in pituitary extracts of two other chondrostean fish, the sturgeon and the paddlefish, but are in direct contrast to the negative results obtained with pituitary extracts of modern bony fish (teleostean). The findings to date indicate that a general correlation appears to exist between the immunochemical relatedness of fish GH with respect to mammalian (rat) GH, the ability of that fish GH to stimulate growth in the mammal (rat tibia test) and the general degree of development of the median eminence in the particular species from which the GH originates.

Fish growth hormone: A biological, immunochemical, and ultrastructural study of sturgeon and paddlefish pituitaries

In contrast to pituitary growth hormone (GH) of modern bony fish (teleosts), the hormone in pituitary extracts of two primitive bony fish (chondrosteans)—the Pacific white sturgeon and the paddlefish—stimulated growth of the hypophysectomized rat as demonstrated by the tibia assay and immunochemically cross-reacted with monkey antiserum to rat GH, as shown by radioimmunoassay. In addition, electron microscopic studies revealed that these primitive fish, unlike the teleosts, possess a median eminence, with morphological features similar to those of tetrapods.

Calcium metabolism of teleosts.

The osseous tissues of modern bony fishes are usually classified as cellular or acellular bone. The latter lacks osteocytes; the former is restricted to individual families within the Clupeiformes and Scopeliformes. Many fishes can take up calcium actively from their environment and apparently can store considerable amounts of calcium in sites other than bone. The question asto the degree that fishes can or do utilize a closed-cycle, bone—body fluid continum is a subject of controversy; those fishes that have abandoned apatites must operate as an open-cycle system. Data from several laboratories have shown that hypophysectomy does affect calcium homeostasis, at least at the serum and kidney levels. There is no evidence that the observed alterations involve metabolism of bone. The idea that the ultimobranchial body has a parathyroid-like function is an attractive one, but the evidence in favor of this view is based entirely on histological grounds and is far from decisive. Studies using extracts of this gland, and purified mammalian parathyroid hormone, are needed.