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At least 919 records · Page 51Linked to original sources
PubMed2026

Wound healing in Atlantic spiny dogfish sharks.

Field observations and limited experimental studies indicate that elasmobranchs can repair substantial skin injuries, but the temporal course and cellular composition of wound healing in Atlantic spiny dogfish remain poorly characterized. We conducted an exploratory laboratory study in 20 female Atlantic spiny dogfish (Squalus acanthias) using standardized full-thickness skin wounds monitored by serial photography for 35 days, histological analysis at defined post-injury time points, and pooled single-nucleus RNA sequencing of intact and wounded skin. A continuous neoepithelial layer covered all examined wound beds by Day 1, whereas macroscopic wound area decreased progressively over 35 days and dermal denticles remained absent from the repaired surface. Histological examination showed progressive neoepidermal maturation, basement-membrane reformation, collagen deposition, and granulation-tissue organization, indicating that epithelial coverage preceded restoration of normal skin architecture. Single-nucleus RNA sequencing identified epithelial, stromal, vascular, pigment, neural, and immune-cell populations. T and B cells were detected in intact skin, and their relative abundance, together with that of several other leukocyte populations, increased at Day 1 and generally declined by Day 14. Because samples were pooled by time point, these transcriptomic changes are descriptive. These findings characterize rapid early reepithelialization followed by slower tissue remodeling in Atlantic spiny dogfish and provide a foundation for future comparative studies of elasmobranch skin repair.

Animals↗
PubMed1981

Studies on carbon monoxide binding by shark haemoglobin.

The kinetics of the reactions of Pacific-porbeagle haemoglobin with CO were studied by flash-photolysis and stopped-flow methods, and the equilibrium binding curves for CO were measured in spectrophotometric titrations. Measurements were made in the pH range 6-8 and in the temperature range 0-40 degrees C. The results are discussed in terms of the allosteric model proposed by Monod, Wyman & Changeux [(1965) J. Mol. Biol. 12, 88-118]. Within this framework the results indicate that in the R-state the haem groups fall into two classes of different reactivity with different spectral characteristics, but that in the T-state the groups may be essentially equivalent. The physiological importance of the temperature-insensitivity of the equilibrium ligand-binding curves for porbeagle haemoglobin is discussed.

Animals↗
PubMed1985

Shark myoglobins. II. Isolation, characterization and amino acid sequence of myoglobin from Galeorhinus japonicus.

Native oxymyoglobin (MbO2) was isolated from red muscle of G. japonicus by chromatographic separation from metmyoglobin (metMb) on DEAE-cellulose and the amino acid sequence of the major chain was determined with the aid of sequence homology with that of G. australis. It was shown to differ in amino acid sequence from that of G. australis by 10 replacements, to be acetylated at the amino terminus and to contain glutamine at the distal (E7) residue. It was also shown to have a spectrum very similar to that of mammalian MbO2. However, the pH-dependence for the autoxidation of MbO2 was seen to be quite different from that of sperm whale (Physeter catodon) MbO2. Although the sequence homology between sperm whale and G. japonicus myoglobins is about 40%, their hydropathy profiles were very similar, indicating that they have a similar geometry in their globin folding.

Amino Acid Sequence↗
PubMed2006

An evolutionarily mobile antigen receptor variable region gene: doubly rearranging NAR-TcR genes in sharks.

Distinctive Ig and T cell receptor (TcR) chains define the two major lineages of vertebrate lymphocyte yet similarly recognize antigen with a single, membrane-distal variable (V) domain. Here we describe the first antigen receptor chain that employs two V domains, which are generated by separate VDJ gene rearrangement events. These molecules have specialized "supportive" TcRdeltaV domains membrane-proximal to domains with most similarity to IgNAR V. The ancestral NAR V gene encoding this domain is hypothesized to have recombined with the TRD locus in a cartilaginous fish ancestor >200 million years ago and encodes the first V domain shown to be used in both Igs and TcRs. Furthermore, these data support the view that gamma/delta TcRs have for long used structural conformations recognizing free antigen.

Amino Acid Sequence↗
PubMed2000

Rearrangement of immunoglobulin genes in shark germ cells.

The variable (V), (diversity [D]), and joining (J) region recombinases (recombination activating genes [RAGs]) can perform like transposases and are thought to have initiated development of the adaptive immune system in early vertebrates by splitting archaic V genes with transposable elements. In cartilaginous fishes, the immunoglobulin (Ig) light chain genes are organized as multiple VJ-constant (C) clusters; some loci are capable of rearrangement while others contain fused VJ. The latter may be key to understanding the evolutionary role of RAG. Are they relics of the archaic genes, or are they results of rearrangement in germ cells? Our data suggest that some fused VJ genes are not only recently rearranged, but also resulted from RAG-like activity involving hairpin intermediates. Expression studies show that these, like some other germline-joined Ig sequences, are expressed at significant levels only early in ontogeny. We suggest that a rejoined Ig gene may not merely be a sequence restricting antibody diversity, but is potentially a novel receptor no longer tied to somatic RAG expression and rearrangement. From the combined data, we arrived at the unexpected conclusion that, in some vertebrates, RAG is still an active force in changing the genome.

Amino Acid Sequence↗