Patterns of genomic differentiation between two Lake Victoria cichlid species, Haplochromis pyrrhocephalus and H. sp. 'macula'.

Background: The molecular basis of the incipient stage of speciation is still poorly understood. Cichlid fish species in Lake Victoria are a prime example of recent speciation events and a suitable system to study the adaptation and reproductive isolation of species.

Results: Here, we report the pattern of genomic differentiation between two Lake Victoria cichlid species collected in sympatry, Haplochromis pyrrhocephalus and H.

Visual adaptation in Lake Victoria cichlid fishes: depth-related variation of color and scotopic opsins in species from sand/mud bottoms.

Background: For Lake Victoria cichlid species inhabiting rocky substrates with differing light regimes, it has been proposed that adaptation of the long-wavelength-sensitive (LWS) opsin gene triggered speciation by sensory drive through color signal divergence. The extensive and continuous sand/mud substrates are also species-rich, and a correlation between male nuptial coloration and the absorption of LWS pigments has been reported. However, the factors driving genetic and functional diversity of LWS pigments in sand/mud habitats are still unresolved.

SCPP Genes and Their Relatives in Gar: Rapid Expansion of Mineralization Genes in Osteichthyans.

Gar is an actinopterygian that has bone, dentin, enameloid, and ganoin (enamel) in teeth and/or scales. Mineralization of these tissues involves genes encoding various secretory calcium-binding phosphoproteins (SCPPs) in osteichthyans, but no SCPP genes have been identified in chondrichthyans to date. In the gar genome, we identified 38 SCPP genes, seven of which encode "acidic-residue-rich" proteins and 31 encode "Pro/Gln (P/Q) rich" proteins.

Development of the Heart Endocardium at an Early Stage of Chick Embryos Evaluated at Light- and Electron-Microscopic Levels.

Development of the endocardium in the heart of 4 to 4·1/2-day-incubated chick embryos was observed light and electron microscopically, and these results were evaluated by immunohistochemistry for desmin, FLK1 (VEGFR-2) or CD31, and by in situ hybridization assays for flk1-mRNA expression. At this developmental stage, the atrium and the ventricle were already discriminated by formation of the atrio-ventricular junction. The cardiac wall consisted of three layers; the inner endocardium, the middle myocardium, and the outer epicardium.

Organization of Mhc class II A and B genes in the tilapiine fish Oreochromis.

Perch-like fishes of the family Cichlidae are models for the study of speciation. An important tool in these studies is the major histocompatibility complex (Mhc) and its organization. The present study takes the first step toward the elucidation of the Mhc class II gene organization in the tilapiine fish Oreochromis niloticus (Orni).

Pups of dams fed low-fat diet during pregnancy and lactation showed strong preference for high-fat diet to achieve optimal growth.

To investigate the causes why pups of dams fed a low-fat high-carbohydrate diet (LFD) showed a strong preference for fat, three groups of dams were fed one of three diets during pregnancy and lactation: the LFD, a control diet (CTD) or a high-fat low-carbohydrate diet (HFD). After weaning, pups of each of the three groups were divided into two equal subgroups (Pair 1 and Pair 2), for a total of six pup subgroups. Each subgroup was placed on a two-choice diet program of the LFD and the HFD (Pair 1), or the LFD and a HFDLE (with cellulose added to maintain the same energy concentration as the LFD) (Pair 2), for 3 wk.

Rats allowed to self-select zinc-deficient lard and fish-oil diets did not develop a preference for fish-oil diet.

Zinc (Zn)-deficiency causes a reduction in food intake and alters adipose metabolism. The effect of zinc restriction in rats on the selection of fish-oil and lard was studied during a period of reduced appetite. The reduction of appetite was caused by an experimentally induced Zn-deficiency.

Spectrum of MHC class II variability in Darwin's finches and their close relatives.

The study describes >400 major histocompatibility complex (MHC) class II B exon 2 and 114 intron 2 sequences of 36 passerine bird species, 13 of which belong to the group of Darwin's finches (DFs) and the remaining 23 to close or more distant relatives of DFs in Central and South America. The data set is analyzed by a combination of judiciously selected statistical methods. The analysis reveals that reliable information concerning MHC organization, including the assignment of sequences to loci, and evolution, as well as the process of species divergence, can be obtained in the absence of genomic sequence data, if the analysis is taken several steps beyond the standard phylogenetic tree construction approach.

[Anatomists in the anatomical theater of Tartu (Dorpat) University].

In 1632, King Gustav II Adolphus of Sweden founded Academia Gustaviana,the predecessor of the present Tartu University in Estonia. After the reopening of the University in 1802, the development of the Faculty of Medicine started. The number of outstanding anatomists; Burdach, von Baer, Reichert, Bidder, Reissner, Kupffer, and Rauber made various discoveries at the Anatomical Theater (Theatrum Anatomicum).

Effect of plant- and fish-oil derived n-3 polyunsaturated fatty acids on counteraction of n-3 fatty acid shortage in adult rats fed a lard diet.

These studies aimed to compare the effects of alpha-linolenic acid (ALA)+eicosapentaenoic acid (EPA)+docosahexaenoic acid (DHA) on plasma-lipid concentrations and preferential fat intake of rats fed a lard diet (LD). Each of 2 groups of 4-wk-old male rats was used in studies 1 and 2. In studies 1 and 2, two groups of rats received the LD (LD group) and the fish-oil diet (FD; FD group), and the LD and the perilla-oil diet (PD; PD group), respectively (dietary treatment period).

Identification and characterization of integrin-binding sialoprotein (IBSP) genes in reptile and amphibian.

Integrin-binding sialoprotein (IBSP) is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family; and the whole SIBLING family is further included in a larger secretory calcium-binding phosphoprotein (SCPP) family. SIBLING proteins are known to construct a part of the non-collagenous extracellular matrices of calcified tissues, and considered to have arisen by duplication and subsequent divergent evolution of a single ancient gene. To understand the alterations of SIBLING molecules associated with the evolution of calcified tissues in vertebrates, we initiated a search for lower vertebrate orthologs of SIBLING genes.

MHC, TSP, and the origin of species: from immunogenetics to evolutionary genetics.

The acronym Mhc, major histocompatibility complex, is customarily not allied with topics in evolutionary biology. Here, however, we attempt to demonstrate that the Mhc has much to offer to this discipline and intimate that evolutionary biologists who ignore its contributions miss out on a chance of applying a new approach to vexing questions. One aspect of the Mhc in particular affords a fresh look at the population processes that transform one species into another: the trans-species polymorphism, the passage of allelic lineages from ancestral to descendant species.

Gene flow between species of Lake Victoria haplochromine fishes.

The haplochromine cichlid fishes of Lake Victoria (LV), East Africa, are a textbook example of adaptive radiation-a rapid divergence of multiple morphologically distinguishable forms from a few founding lineages. The forms are generally believed to constitute a "flock" of several hundred reproductively isolated species in a dozen or so genera. This belief has, until now, not been subjected to a test, however.

Mhc class I genes of the cichlid fish Oreochromis niloticus.

In terms of number of species, perciform (perch-like) fishes are one of the most diversified groups of modern vertebrates. Within this group, the family Cichlidae is best known for its spectacular adaptive radiation in the great lakes of East Africa. The molecular tool kit used in the study of this radiation includes the major histocompatibility complex (Mhc) genes.

Organization, alternative splicing, polymorphism, and phylogenetic position of lamprey CD45 gene.

CD45 of jawed vertebrates is a receptor-type protein tyrosine phosphatase regulating lymphocyte development and activation. To shed light on the evolution of the CD45 gene, the organization of its orthologue in the lamprey, a jawless vertebrate, was determined. Compared to its mammalian and fugu counterparts, the lamprey gene was found to be lacking several exons in the segment encoding the extracellular part of the protein.

A molecule bearing an immunoglobulin-like V region of the CTX subfamily in amphioxus.

An expressed sequence tag with significant similarity to a vertebrate T-cell receptor (Tcr) sequence was found in a cDNA library prepared from the posterior part of the adult amphioxus, Branchiostoma lanceolatum ( Brla). Characterization of the corresponding cDNA clone revealed the presence of an open reading frame encoding a 351 amino acid residue-long polypeptide. The putative protein, tentatively designated Brla-VDB for "V-domain bearing", appears to consist of two domains.

Genes encoding putative natural killer cell C-type lectin receptors in teleostean fishes.

Mammalian natural killer (NK) cells are cytotoxic lymphocytes that express receptors specific for MHC class I molecules. The NK cell receptors belong to two structurally unrelated families, the killer cell Ig-like receptors and the killer cell C-type lectin receptors. We describe a cDNA clone derived from the bony (cichlid) fish Paralabidochromis chilotes and show that it encodes a protein related to the CD94/NK cell group 2 (NKG2) subfamily of the killer cell C-type lectin receptors.

Origin and speciation of haplochromine fishes in East African crater lakes investigated by the analysis of their mtDNA, Mhc genes, and SINEs.

The Western Branch of the East African Great Rift Valley is pocketed with craters of extinct or dormant volcanoes. Many of the craters are filled with water, and the lakes are inhabited by fishes. The objective of the present study was to determine the amount and nature of genetic variation in haplochromine fishes inhabiting two of these crater lakes, Lake Lutoto and Lake Nshere, and to use this information to infer the origin and history of the two populations.

Identification and characterization of a TAP-family gene in the lamprey.

An expressed sequence tag obtained from a sea lamprey ( Petromyzon marinus) cDNA library was used to obtain a full-length coding sequence showing significant similarity to ABCB transporter proteins. The sequence is closely related to the mammalian ABCB9 protein and the TAP1 and TAP2 proteins that transport peptides for loading onto nascent Mhc class I molecules. The Pema-ABCB9 gene has an exon-intron organization similar to that of the mammalian TAP genes, with the exception of exon 2, which in the lamprey is split into two by a 949-bp long intron.

Identification of chemokines and a chemokine receptor in cichlid fish, shark, and lamprey.

Chemokines are small, inducible, structurally related proteins that guide cells expressing the right chemokine receptors to sites of immune response. They have been identified and studied extensively in mammals, but little is known about their presence in other vertebrate groups. Here we describe seven new chemokines in bony fish and one in a cartilaginous fish, as well as one chemokine receptor in a jawless vertebrate.

Macrophage migration inhibitory factor (MIF) of jawed and jawless fishes: implications for its evolutionary origin.

The macrophage migration inhibitory factor (MIF) is a cytokine produced by T lymphocytes and macrophages in response to inflammatory stimuli. We sequenced MIF cDNA clones of two jawless fishes, the sea lamprey (Petromyzon marinus) and the North Atlantic hagfish (Myxine glutinosa), as well as of the jawed (cichlid) fish Paralabidochromis chilotes. The fish MIF-encoding genes have the same exon-intron organization as the mammalian MIF genes and are present in one copy per haploid genome.

Persistence of Mhc heterozygosity in homozygous clonal killifish, Rivulus marmoratus: implications for the origin of hermaphroditism.

The mangrove killifish Rivulus marmoratus, a neotropical fish in the order Cyprinodontiformes, is the only known obligatorily selfing, synchronous hermaphroditic vertebrate. To shed light on its population structure and the origin of hermaphroditism, major histocompatibility complex (Mhc) class I genes of the killifish from seven different localities in Florida, Belize, and the Bahamas were cloned and sequenced. Thirteen loci and their alleles were identified and classified into eight groups.

Lamprey lymphocyte-like cells express homologs of genes involved in immunologically relevant activities of mammalian lymphocytes.

To shed light on the origin of adaptive immunity, a cDNA library was prepared from purified lymphocyte-like cells of a jawless vertebrate, the sea lamprey (Petromyzon marinus). Randomly selected cDNA clones were sequenced, and their homologies to proteins in the databases were determined. Of the sequences homologous to proteins involved in immune responses, five were selected for further characterization.

Identification and characterization of ameloblastin gene in a reptile.

Ameloblastin (AMBN) is one of the enamel sheath proteins which presumably has a role in determining the prismatic structure of growing enamel crystals. There may therefore be a relationship between the molecular evolution of the AMBN gene and the development of enamel prismatic structures. To investigate whether such a relationship exists, it was necessary to identify the homologues of the AMBN gene in a reptile whose teeth lack an enamel prismatic structure.