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1.
J Fish Biol ; 95(6): 1471-1479, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31621087

RESUMO

This study used 3 H-L -alanyl-L -alanine to demonstrate dipeptide uptake using in vitro gut sacs prepared from the hindgut of the Pacific hagfish Eptatretus stoutii. Concentration-dependent kinetic analysis resulted in a sigmoidal distribution with a maximal (± SE) uptake rate (Jmax -like) of 70 ± 3 nmol cm-2 h-1 and an affinity constant (Km -like) of 1072 ± 81 µM. Addition of high alanine concentrations to transport assays did not change dipeptide transport rates, indicating that hydrolysis of the dipeptide in mucosal solutions and subsequent uptake via apical amino acid transporters was not occurring, which was further supported by a Km distinct from that of amino acid transport. Transport occurred independent of mucosal pH, but uptake was reduced by 42% in low mucosal sodium. This may implicate cooperation between peptide transporters and sodium-proton exchangers, previously demonstrated in several mammalian and teleost species. Finally, apical L -alanyl-L -alanine uptake rates (i.e., mucosal disappearance) were significantly increased following a meal, demonstrating regulation of uptake. Overall, this examination of dipeptide acquisition in the earliest extant Agnathan suggests evolutionarily conserved mechanisms of transport between hagfish and later-diverging vertebrates such as teleosts and mammals.


Assuntos
Alanina/metabolismo , Sistema Digestório/metabolismo , Dipeptídeos/metabolismo , Feiticeiras (Peixe)/metabolismo , Animais , Concentração de Íons de Hidrogênio , Cinética , Sódio/química
2.
Soft Matter ; 15(42): 8627-8637, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31631202

RESUMO

The defense mechanism of hagfish against predators is based on its ability to form slime within a few milliseconds. Hagfish slime consists of two main components, namely mucin-like glycoproteins and long protein threads, which together entrap vast amounts of water and thus form a highly dilute hydrogel. Here, we investigate the mucin part of this hydrogel, in particular the role of the saline marine environment on the viscoelasticity and structure. By means of dynamic light scattering (DLS), shear and extensional rheology we probe the diffusion dynamics, the flow behavior, and the longest filament breaking time of hagfish mucin solutions. Using DLS we find a concentration-independent diffusion coefficient - characteristic for polyelectrolytes - up to the entanglement regime of 0.2 mg ml-1, which is about ten times higher than the natural concentration of hagfish mucin in hagfish slime. We also observe a slow relaxation process associated with clustering, probably due to electrostatic interactions. Shear rheology further revealed that hagfish mucin possesses pronounced viscoelastic properties at high concentrations (3 mg ml-1), showing that mucin alone achieves mechanical properties similar to those of natural hagfish slime (mucins and protein threads). The main effects of added seawater salts, and predominantly CaCl2 is to reduce the intensity of the slow relaxation process, which suggests that calcium ions lead to an ionotropic gelation of hagfish mucins.


Assuntos
Feiticeiras (Peixe)/química , Hidrogéis/química , Mucinas/química , Animais , Citoesqueleto/química , Cinética , Conformação Proteica , Multimerização Proteica
3.
Okajimas Folia Anat Jpn ; 96(1): 1-11, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31462619

RESUMO

The liver architecture of vertebrates can be classified into two types, the portal triad type (having periportal bile ducts) and the non-portal triad type (having non-periportal bile ducts). The former is detectable in the tetrapod liver whereas the lungfish liver has the latter. It remains to be revealed which type of hepatic architecture the coelacanth, which together with the lungfish belongs to the Sarcopterygii, possesses. The present study was undertaken to determine the histological characteristics of the coelacanth liver, and to compare with those of other vertebrates. The coelacanth liver had periportal bile ducts and ductules as detected in mammalian livers. The hepatic artery was found around large portal veins. Hagfish, shark, bichir, sturgeon, bowfin and frog livers had periportal bile ducts and bile ductules, whereas most intrahepatic bile ducts of the lungfish were independent of the distribution of the portal veins as seen in the Otocephala and Euteleostei. The lungfish liver developed duct and ductule structures in the parenchyma. These data indicate that the coelacanth liver had a mammalian-type hepatic architecture with a portal triad, and that the ancestors of tetrapods may have had a portal triad-type liver architecture.


Assuntos
Fígado/irrigação sanguínea , Fígado/citologia , Sistema Porta , Animais , Feiticeiras (Peixe)
4.
PLoS One ; 14(4): e0215027, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30951564

RESUMO

Hagfishes are living representatives of the earliest-diverging vertebrates and are thus useful for the study of early vertebrate physiology. It has been previously postulated that digestive enzymes account for the majority of digestion because hagfish are agastric with notable zymogen granules in specialized cells of the hindgut. While the presence of some digestive enzymes (amylase, lipase and leucinaminopeptidase) have been confirmed with histochemistry, quantification of enzymatic activity is limited. This study sought to biochemically quantify the tissue activity of six digestive enzymes (α-amylase, maltase, lipase, trypsin, aminopeptidase and alkaline phosphatase) along the length of the Pacific hagfish (Eptatretus stoutii) alimentary canal. In addition, the effect of feeding on the rate of enzyme activity was examined. Overall, maltase and trypsin activities were unchanging with respect to location or feeding status, while the activities of α-amylase and alkaline phosphatase decreased substantially following feeding, but were consistent along the length. Lipase and aminopeptidase activities were elevated in the anterior region of the alimentary canal in comparison to the more posterior regions, but were not altered with feeding. This study indicates hagfish have an assortment of digestive enzymes that likely are the result of a varied diet. The differential expression of these enzymes along the tract and in regards to feeding may be indications of early compartmentalization of digestive function.


Assuntos
Fosfatase Alcalina/metabolismo , Aminopeptidases/metabolismo , Amilases/metabolismo , Sistema Digestório/enzimologia , Feiticeiras (Peixe)/enzimologia , Lipase/metabolismo , Tripsina/metabolismo , alfa-Glucosidases/metabolismo , Animais , Feiticeiras (Peixe)/fisiologia , Período Pós-Prandial
5.
J R Soc Interface ; 16(150): 20180710, 2019 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-30958163

RESUMO

Hagfish slime is a unique predator defence material containing a network of long fibrous threads each ∼10 cm in length. Hagfish release the threads in a condensed coiled state known as skeins (∼100 µm), which must unravel within a fraction of a second to thwart a predator attack. Here we consider the hypothesis that viscous hydrodynamics can be responsible for this rapid unravelling, as opposed to chemical reaction kinetics alone. Our main conclusion is that, under reasonable physiological conditions, unravelling due to viscous drag can occur within a few hundred milliseconds, and is accelerated if the skein is pinned at a surface such as the mouth of a predator. We model a single skein unspooling as the fibre peels away due to viscous drag. We capture essential features by considering simplified cases of physiologically relevant flows and one-dimensional scenarios where the fibre is aligned with streamlines in either uniform or uniaxial extensional flow. The peeling resistance is modelled with a power-law dependence on peeling velocity. A dimensionless ratio of viscous drag to peeling resistance appears in the dynamical equations and determines the unraveling time scale. Our modelling approach is general and can be refined with future experimental measurements of peel strength for skein unravelling. It provides key insights into the unravelling process, offers potential answers to lingering questions about slime formation from threads and mucous vesicles, and will aid the growing interest in engineering similar bioinspired material systems.


Assuntos
Feiticeiras (Peixe) , Hidrodinâmica , Modelos Biológicos , Muco , Comportamento Predatório/fisiologia , Natação/fisiologia , Animais , Feiticeiras (Peixe)/química , Feiticeiras (Peixe)/fisiologia , Muco/química , Muco/metabolismo , Água do Mar , Viscosidade
6.
J Morphol ; 280(6): 827-840, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30927384

RESUMO

Hagfish use forceful retractions of a dental plate to shear and ingest food. Retractile force is generated by the retractor muscle complex of the posterior hagfish feeding apparatus (HFA). While gross morphological descriptions exist, the organization of muscle and connective tissue fibers that form the soft tissue retractor complex do not. In this study, we used paraffin histology to prepare serial sections of Pacific (Eptatretus stoutii, Lockington, 1879) and Atlantic (Myxine glutinosa, Linnaeus, 1758) hagfishes in order to describe constituent soft tissue anatomy and fiber orientations. We generated 3D reconstructions in which digitized sections were segmented and fitted to volumetric scans of retractor complexes taken prior to microtomy. These models confirmed that the retractor complex is composed of a perpendicularis muscle that fits within the eye of a needle-shaped clavatus muscle, which anteriorly bears the dental plate tendon, and in turn fits within a sleeve-like tubulatus muscle. Analysis of fiber orientations within these muscles resulted in novel functional hypotheses: (a) The tubulatus muscle represents a novel tubular bipennate muscle with a considerable physiological cross-sectional area. Its activation may indirectly create tension in the dental plate tendon: as the tubulatus muscle forcefully extends, it displaces the terminal bulb and the clavatus muscle posteriorly. (b) Within the HFA terminal bulb, the muscle fibers of the clavatus and perpendicularis muscles are mutually perpendicular and may cocontract to form a swelling stopper knot-like muscular complex that resists being pulled through the tubulatus muscle. (c) While overall feeding apparatus muscle morphology is conserved, the physiological cross-sectional area of the tubulatus muscle in E. stoutii, is relatively larger than that of M. glutinosa, suggesting a more forceful retraction. The tubular bipennate construction of the tubulatus may represent a novel soft robotic actuator design.


Assuntos
Força de Mordida , Feiticeiras (Peixe)/anatomia & histologia , Mastigação , Boca/anatomia & histologia , Músculos/anatomia & histologia , Animais , Oclusão Dentária , Ingestão de Alimentos , Comportamento Alimentar , Feiticeiras (Peixe)/fisiologia , Boca/fisiologia , Músculos/fisiologia
7.
Artigo em Inglês | MEDLINE | ID: mdl-30878760

RESUMO

Hagfishes (Class: Myxini) are marine jawless craniate fishes that are widely considered to be osmoconformers whose plasma [Na+], [Cl-] and osmolality closely resemble that of sea water, although they have the ability to regulate plasma [Ca2+] and [Mg2+] below seawater levels. We investigated the responses of Pacific hagfish to changes in respiratory and ionoregulatory demands imposed by a 48-h exposure to altered salinity (25 ppt, 30 ppt (control) and 35 ppt) and by an acute hypoxia exposure (30 Torr; 4 kPa). When hagfish were exposed to 25 ppt, oxygen consumption rate (MO2), ammonia excretion rate (Jamm) and unidirectional diffusive water flux rate (JH2O, measured with 3H2O) were all reduced, pointing to an interaction between ionoregulation and gas exchange. At 35 ppt, JH2O was reduced, though MO2 and Jamm did not change. As salinity increased, so did the difference between plasma and external water [Ca2+] and [Mg2+]. Notably, the same pattern was seen for plasma Cl-, which was kept below seawater [Cl-] at all salinities, while plasma [Na+] was regulated well above seawater [Na+], but plasma osmolality matched seawater values. MO2 was reduced by 49% and JH2O by 36% during hypoxia, despite a small elevation in overall ventilation. Our results depart from the "classical" osmorespiratory compromise but are in accord with responses in other hypoxia-tolerant fish; instead of an exacerbation of gill fluxes when gas transfer is upregulated, the opposite happens.


Assuntos
Feiticeiras (Peixe)/fisiologia , Hipóxia , Osmorregulação , Consumo de Oxigênio , Salinidade , Água do Mar , Água/metabolismo , Animais , Difusão
8.
J Immunol Methods ; 466: 24-31, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30611766

RESUMO

The variable lymphocyte receptor B (VLRB) of jawless vertebrates has a similar function to the antibodies produced by jawed vertebrates, and has been considered as an alternative source to mammalian antibodies for use in biological research. We developed a modified yeast display vector system (pYD8) to display recombinant hagfish VLRB proteins on the extracellular surface of yeast for the isolation of antigen-specific VLRBs. After observing an up-regulation in the VLRB response in hagfish immunized with hemagglutinin 1 of avian influenza virus H9N2 subtype (H9N2-HA1), the antigen-specific VLRBs decorated on the yeast's surface were selected by quantitative library screening through magnetic-activated cell sorting (MACS) and fluorescent-activated cell sorting (FACS). We also demonstrated a strong specificity of the antigen-specific VLRBs, when expressed as a secreted protein using a mammalian expression system. Together, our findings suggest that the pYD8 vector system could be useful for screening antigen-specific hagfish VLRBs, and the specificity of secreted VLRB may have potential for a variety of biological applications.


Assuntos
Antígenos/imunologia , Receptores de Antígenos de Linfócitos B/imunologia , Saccharomyces cerevisiae/imunologia , Animais , Linfócitos B/imunologia , Feiticeiras (Peixe) , Receptores de Antígenos de Linfócitos B/genética
9.
Proc Natl Acad Sci U S A ; 116(6): 2146-2151, 2019 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-30670644

RESUMO

Hagfish depart so much from other fishes anatomically that they were sometimes considered not fully vertebrate. They may represent: (i) an anatomically primitive outgroup of vertebrates (the morphology-based craniate hypothesis); or (ii) an anatomically degenerate vertebrate lineage sister to lampreys (the molecular-based cyclostome hypothesis). This systematic conundrum has become a prominent case of conflict between morphology- and molecular-based phylogenies. To date, the fossil record has offered few insights to this long-branch problem or the evolutionary history of hagfish in general, because unequivocal fossil members of the group are unknown. Here, we report an unequivocal fossil hagfish from the early Late Cretaceous of Lebanon. The soft tissue anatomy includes key attributes of living hagfish: cartilages of barbels, postcranial position of branchial apparatus, and chemical traces of slime glands. This indicates that the suite of characters unique to living hagfish appeared well before Cretaceous times. This new hagfish prompted a reevaluation of morphological characters for interrelationships among jawless vertebrates. By addressing nonindependence of characters, our phylogenetic analyses recovered hagfish and lampreys in a clade of cyclostomes (congruent with the cyclostome hypothesis) using only morphological data. This new phylogeny places the fossil taxon within the hagfish crown group, and resolved other putative fossil cyclostomes to the stem of either hagfish or lamprey crown groups. These results potentially resolve the morphological-molecular conflict at the base of the Vertebrata. Thus, assessment of character nonindependence may help reconcile morphological and molecular inferences for other major discords in animal phylogeny.


Assuntos
Feiticeiras (Peixe)/anatomia & histologia , Feiticeiras (Peixe)/classificação , Feiticeiras (Peixe)/genética , Paleontologia , Filogenia , Vertebrados/classificação , Vertebrados/genética , Animais , Líbano
10.
Artigo em Inglês | MEDLINE | ID: mdl-30529394

RESUMO

Hagfishes are characterised by feeding behaviours that may include long intervals between meals, and a hypoxic feeding environment inside decaying carrion. The effects of feeding on metabolism (oxygen consumption rate), gut mass and morphology (gut somatic index, gut epithelium mucosal thickness), and digestive function (maltase and peptidase activity) were examined in the New Zealand hagfish, Eptatretus cirrhatus. The influence of post-prandial hypoxia on oxygen consumption rate was also investigated to replicate the immersive feeding environment. Fed hagfish displayed a 1.9-fold increase in peak oxygen consumption relative to sham controls. This elevation in post-prandial oxygen consumption continued for 72 h, during which the energy cost of digesting the meal (specific dynamic action; SDA) was 2.1 kJ. Oxygen consumption rate increased when the post-prandial environment was hypoxic, a response suggesting a lack of hypoxia tolerance in this species. Feeding did not alter gut somatic index (percentage of digesta-free gut mass to whole body mass), but there was an increase in the mucosal thickness of the gut epithelium. Maltase activity in the gut was unchanged by feeding, but the activity of gut peptidases was increased significantly, consistent with a protein-based diet. These data indicate that some postprandial responses of New Zealand hagfish are similar in nature to those seen in other animals, but this species does not exhibit the extreme post-prandial physiological and biochemical changes that are observed in other intermittently-feeding vertebrates.


Assuntos
Digestão , Comportamento Alimentar , Feiticeiras (Peixe)/fisiologia , Intestinos/anatomia & histologia , Período Pós-Prandial , Animais , Feiticeiras (Peixe)/metabolismo , Consumo de Oxigênio
11.
J Comp Physiol B ; 189(1): 37-45, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30488102

RESUMO

Hagfishes are ancient vertebrates, which have the ability to tolerate nearly a year of food deprivation with energy during fasting maintained using lipid stores. While lipid transporters are evolutionarily conserved, there are relatively few studies examining mechanisms of lipid acquisition in teleosts and no reports in the primitive and evolutionarily important agnathans. We examined tissue lipid droplet distribution and used gut sac preparations to characterize uptake mechanisms of the monounsaturated fatty acid, oleic acid (OA; 18:1 cis-9), in the Pacific hagfish. OA absorption was carrier-mediated and demonstrated saturable concentration-dependent uptake with an affinity constant of 55 ± 7 µM, and a maximal rate of uptake of 1311 ± 97 pmol cm- 2 h- 1. Additionally, regulation of intestinal transport was demonstrated as feeding significantly increased uptake. To further examine post-prandial effects on fatty acid transport, hagfish were dosed with bovine insulin, which had no effect on OA intestinal acquisition, but did lower plasma glucose. Overall, this is the first evidence for intestinal fatty acid acquisition in an agnathan, which are ideal models for understanding the evolution of nutrient transport processes in vertebrates, and are particularly suited to lipid research owing to their dependence upon this energy source during prolonged periods of fasting.


Assuntos
Feiticeiras (Peixe)/metabolismo , Mucosa Intestinal/metabolismo , Gotículas Lipídicas/metabolismo , Ácido Oleico/metabolismo , Animais , Transporte Biológico/efeitos dos fármacos , Glicemia/análise , Insulina/farmacologia
12.
J Comp Physiol B ; 189(1): 17-35, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30483931

RESUMO

The Pacific hagfish (Eptatretus stoutii) is a representative of the most basal extant craniates, and is a marine osmoconformer with an extremely low metabolic rate (MO2 = 475 µmol O2/kg/h at 12 °C). We investigated potential physiological trade-offs associated with compensatory changes in gill ventilation and perfusion when 12 °C-acclimated hagfish were acutely exposed to 7 °C or 17 °C, as reflected in diffusive unidirectional water flux ([Formula: see text], measured with tritiated water: 3H2O), net ammonia flux (Jamm), and plasma ion and acid-base status. [Formula: see text] was high (~ 1.4 L/kg/h at 12 °C) in comparison to marine teleosts and elasmobranchs. MO2 increased linearly with temperature (R2 = 0.991), and was more sensitive (Q10 = 3.22) in the 12-7 °C range than either Jamm (1.86) or [Formula: see text] (1.35), but the pattern reversed from 12 to 17 °C (Q10s: MO2 = 2.77, Jamm = 2.88, [Formula: see text] = 4.01). Heart rate, ventilatory index (a proxy for total ventilation), and coughing frequency also increased but with different patterns. At 17 °C, plasma [Ca2+] and [Mg2+] decreased, although osmolality increased, associated with elevations in plasma [Na+] and [Cl-]. Blood pH and PCO2 were unaffected by acute temperature changes while [HCO3-] increased. Hyperoxia (PO2 > 300 Torr) attenuated the increase in [Formula: see text] at 17 °C, did not affect Jamm, and had diverse effects on plasma ion and acid-base status. Our results suggest a clear osmorespiratory compromise occurring for the diffusive water fluxes as a result of acute temperature changes in this osmoconformer.


Assuntos
Feiticeiras (Peixe)/fisiologia , Temperatura , Equilíbrio Ácido-Base , Adaptação Fisiológica , Animais , Metabolismo Basal , Brânquias/fisiologia , Frequência Cardíaca , Osmorregulação , Oxigênio/metabolismo , Respiração
13.
Nature ; 565(7739): 347-350, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30518864

RESUMO

Jawed vertebrates have inner ears with three semicircular canals, the presence of which has been used as a key to understanding evolutionary relationships. Ostracoderms, the jawless stem gnathostomes, had only two canals and lacked the lateral canal1-3. Lampreys, which are modern cyclostomes, are generally thought to possess two semicircular canals whereas the hagfishes-which are also cyclostomes-have only a single canal, which used to be regarded as a more primitive trait1,4. However, recent molecular and developmental analyses have strongly supported the monophyly of cyclostomes5-7, which has left the evolutionary trajectory of the vertebrate inner ear unclear8. Here we show the differentiation of the otic vesicle of the lamprey Lethenteron camtschaticum and inshore hagfish Eptatretus burgeri. This is the first time, to our knowledge, that the development of the hagfish inner ear is reported. We found that canal development in the lamprey starts with two depressions-which is reminiscent of the early developmental pattern of the inner ear in modern gnathostomes. These cyclostome otic vesicles show a pattern of expression of regulatory genes, including OTX genes, that is comparable to that of gnathosomes. Although two depressions appear in the lamprey vesicle, they subsequently fuse to form a single canal that is similar to that of hagfishes. Complete separation of the depressions results in anterior and posterior canals in gnathostomes. The single depression of the vesicle in hagfishes thus appears to be a secondarily derived trait. Furthermore, the lateral canal in crown gnathostomes was acquired secondarily-not by de novo acquisition of an OTX expression domain, but by the evolution of a developmental program downstream of the OTX genes.


Assuntos
Feiticeiras (Peixe)/anatomia & histologia , Lampreias/anatomia & histologia , Organogênese , Filogenia , Canais Semicirculares/anatomia & histologia , Canais Semicirculares/embriologia , Vertebrados/anatomia & histologia , Vertebrados/embriologia , Animais , Regulação da Expressão Gênica no Desenvolvimento , Feiticeiras (Peixe)/embriologia , Feiticeiras (Peixe)/genética , Lampreias/embriologia , Lampreias/genética , Camundongos/anatomia & histologia , Camundongos/embriologia , Organogênese/genética , Tubarões/anatomia & histologia , Tubarões/embriologia , Vertebrados/genética , Peixe-Zebra/anatomia & histologia , Peixe-Zebra/embriologia
14.
J Fish Biol ; 94(2): 261-276, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30549032

RESUMO

We made anatomical and physiological observations of the breathing mechanisms in Pacific hagfish Eptatretus stoutii, with measurements of nostril flow and pressure, mouth and pharyngo-cutaneous duct (PCD) pressure and velum and heart impedance and observations of dye flow patterns. Resting animals frequently exhibit spontaneous apnea. During normal breathing, water flow is continuous at a high rate (~125 ml kg-1 min-1 at 12°C) powered by a two-phase unidirectional pumping system with a fast suction pump (the velum, ~22 min-1 ) for inhalation through the single nostril and a much slower force pump (gill pouches and PCD ~4.4 min-1 ) for exhalation. The mouth joins the pharynx posterior to the velum and plays no role in ventilation at rest or during swimming. Increases in flow up to >400 ml kg-1 min-1 can be achieved by increases in both velum frequency and stroke volume and the ventilatory index (product of frequency x nostril pressure amplitude) provides a useful proxy for ventilatory flow rate. Two types of coughing (flow reversals) are described. During spontaneous swimming, ventilatory pressure and flow pulsatility becomes synchronised with rhythmic body undulations.


Assuntos
Brânquias/fisiologia , Feiticeiras (Peixe)/fisiologia , Respiração , Animais , Feiticeiras (Peixe)/anatomia & histologia , Pressão , Sistema Respiratório/anatomia & histologia , Natação
15.
Gen Comp Endocrinol ; 274: 1-7, 2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-30571962

RESUMO

Prolactin-releasing peptide2 (PrRP2) belongs to the RFamide peptide group and is a paralog of prolactin-releasing peptide (PrRP). Recent studies demonstrated that PrRP2, but not PrRP, regulates prolactin release in teleosts. The evolutionary origin of PrRP and PrRP2 dates back to at least early vertebrates because homologs of PrRP/PrRP2 were identified in lampreys, one of the earliest branch of vertebrates class Agnatha. However, PrRP/PrRP2 remains to be identified in hagfish, another representative species of class Agnatha. Here, we examined the distribution of PrRP2 in the brain and pituitary of the inshore hagfish Eptatretus burgeri to obtain further understanding of the neuroendocrine system of PrRP2. PrRP2-immunoreactive (ir) cell bodies were detected in the infundibular nucleus of hypothalamus (HYinf). PrRP2-ir fibers were restricted around PrRP2-ir cell bodies and were not detected in the dorsal wall of the neurohypophysis compared to the abundant PrRP2-ir fiber distribution in the brain and innervation to the pituitary in other vertebrates. To examine possible reciprocal connections of PrRP2 and other neuropeptides, we further conducted dual-label immunohistochemistry of PrRP2 and the PQRFamide (PQRFa) peptide or corticotropin-releasing hormone (CRH). Reciprocal connections are suggested between PrRP2 and PQRFa neurons as well as between PrRP2 and CRH neurons. The present study demonstrates, for the first time, that PrRP2 is expressed in the brain of inshore hagfish. The restricted distribution of PrRP2-ir fibers in the HYinf suggests that PrRP2 does not directly regulate the pituitary gland, but regulates the function of the HYinf where PQRFa and CRH are expressed.


Assuntos
Encéfalo/metabolismo , Feiticeiras (Peixe)/metabolismo , Imuno-Histoquímica/métodos , Hormônio Liberador de Prolactina/metabolismo , Animais , Especificidade de Anticorpos , Hormônio Liberador da Corticotropina/metabolismo , Feminino , Hipotálamo/metabolismo , Masculino , Hipófise/metabolismo
16.
J Exp Biol ; 221(Pt 24)2018 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-30541919

RESUMO

Hagfishes defend themselves from fish predators by producing defensive slime consisting of mucous and thread components that interact synergistically with seawater to pose a suffocation risk to their attackers. Deployment of the slime occurs in a fraction of a second and involves hydration of mucous vesicles as well as unraveling of the coiled threads to their full length of ∼150 mm. Previous work showed that unraveling of coiled threads (or 'skeins') in Atlantic hagfish requires vigorous mixing with seawater as well as the presence of mucus, whereas skeins from Pacific hagfish tend to unravel spontaneously in seawater. Here, we explored the mechanisms that underlie these different unraveling modes, and focused on the molecules that make up the skein glue, a material that must be disrupted for unraveling to proceed. We found that Atlantic hagfish skeins are also held together with a protein glue, but compared with Pacific hagfish glue, it is less soluble in seawater. Using SDS-PAGE, we identified several soluble proteins and glycoproteins that are liberated from skeins under conditions that drive unraveling in vitro Peptides generated by mass spectrometry of five of these proteins and glycoproteins mapped strongly to 14 sequences assembled from Pacific hagfish slime gland transcriptomes, with all but one of these sequences possessing homologs in the Atlantic hagfish. Two of these sequences encode unusual acidic proteins that we propose are the structural glycoproteins that make up the skein glue. These sequences have no known homologs in other species and are likely to be unique to hagfishes. Although the ecological significance of the two modes of skein unraveling described here are unknown, they may reflect differences in predation pressure, with selection for faster skein unraveling in the Eptatretus lineage leading to the evolution of a glue that is more soluble.


Assuntos
Feiticeiras (Peixe)/fisiologia , Muco/química , Água do Mar/química , Animais , Feiticeiras (Peixe)/química , Solubilidade , Especificidade da Espécie
17.
J Immunol ; 201(10): 3119-3128, 2018 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-30333123

RESUMO

The variable lymphocyte receptor (VLR) B of jawless vertebrates functions as a secreted Ab of jawed vertebrates and has emerged as an alternative Ab with a single polypeptide chain. After observing an upregulated VLRB response in hagfish immunized with avian influenza virus (AIV) subtype H9N2, we screened AIV H9N2-specific VLRB using a mammalian expression system. To improve the binding avidity of the Ag-specific VLRB to the Ag, we enabled multimerization of the VLRB by conjugating it with C-terminal domain of human C4b-binding protein. To dramatically enhance the expression and secretion of the Ag-specific VLRB, we introduced a glycine-serine linker and the murine Ig κ leader sequence. The practical use of the Ag-specific VLRB was also demonstrated through various immunoassays, detected by anti-VLRB Ab (11G5). Finally, we found that the Ag-specific VLRB decreased the infectivity of AIV H9N2. Together, our findings suggest that the generated Ag-specific VLRB could be used for various immunoapplications.


Assuntos
Técnicas Imunológicas , Vírus da Influenza A Subtipo H9N2/imunologia , Engenharia de Proteínas/métodos , Receptores de Antígenos/genética , Receptores de Antígenos/imunologia , Animais , Proteínas de Peixes/genética , Proteínas de Peixes/imunologia , Feiticeiras (Peixe) , Humanos , Camundongos
18.
ACS Appl Mater Interfaces ; 10(47): 40460-40473, 2018 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-30371056

RESUMO

Intermediate filaments (IFs) are known for their extensibility, flexibility, toughness, and their ability to hydrate. Using keratin-like IFs obtained from slime fibers from the invertebrate Atlantic hagfish ( Myxine glutinosa), films were produced by drop-casting and coagulation on the surface of a MgCl2 buffer. Drop-casting produced self-supporting, smooth, and dense films rich in ß-sheets (61%), whereas coagulation formed thin, porous films with a nanorough surface and a lower ß-sheet content (51%). The films hydrated and swelled immediately when immersed in water and did not dissolve. X-ray diffraction showed that the ß-crystallites remained stable upon hydration, that swelling presumably happens in the amorphous C-terminal tail-domains of the IFs, and that high salt conditions caused a denser network mesh size, suggesting polyelectrolyte behavior. Hydration resulted in a roughly 1000-fold decrease in apparent Young's modulus from 109 to 106 Pa as revealed by atomic force microscopy nanoindentation. Nanoindentation-based power-law rheology and stress-relaxation measurements indicated viscoelasticity and a soft-solid hydrogel character for hydrated films, where roughly 80% of energy is elastically stored and 20% is dissipated. By pulling coagulation films from the buffer interface, macroscopic fibers with highly aligned IF ß-crystals similar to natural hagfish fibers were produced. We propose that viscoelasticity and strong hydrogen bonding interactions with the buffer interface are crucial for the production of such long biomimetic fibers with aligned ß-sheets. This study demonstrates that hagfish fiber IFs can be reconstituted into functional biomimetic materials that are stiff when dry and retain the ability to hydrate to become soft and viscoelastic when in water.


Assuntos
Feiticeiras (Peixe)/química , Filamentos Intermediários/metabolismo , Nanopartículas/química , Animais , Materiais Biomiméticos/química , Módulo de Elasticidade , Filamentos Intermediários/química , Mucinas/metabolismo , Estrutura Secundária de Proteína , Viscosidade , Água/química
19.
Acta Biomater ; 79: 123-134, 2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-30170194

RESUMO

The defense mechanism of hagfish slime is remarkable considering that hagfish cannot control the concentration of the resulting gel directly; they simply exude a concentrated material into a comparably "infinite" sea of water to form a dilute, sticky, cohesive elastic gel. This raises questions about the robustness of gel formation and rheological properties across a range of concentrations, which we study here for the first time. Across a nearly 100-fold change in concentration, we discover that the gel has similar viscoelastic time-dependent properties with constant power-law exponent (α=0.18±0.01), constant relative damping tanδ=G''/G'≈0.2-0.3, and varying overall stiffness that scales linearly with the concentration (∼c0.99±0.05). The power-law viscoelasticity (fit by a fractional Kelvin-Voigt model) is persistent at all concentrations with nearly constant fractal dimension. This is unlike other materials and suggests that the underlying material structure of slime remains self-similar irrespective of concentration. This interpretation is consistent with our microscopy studies of the fiber network. We derive a structure-rheology model to test the hypothesis that the origins of ultra-soft elasticity are based on bending of the fibers. The model predictions show an excellent agreement with the experiments. Our findings illustrate the unusual and robust properties of slime which may be vital in its physiological use and provide inspiration for the design of new engineered materials. STATEMENT OF SIGNIFICANCE: Hagfish produce a unique gel-like material to defend themselves against predator attacks. The successful use of the defense gel is remarkable considering that hagfish cannot control the concentration of the resulting gel directly; they simply exude a small quantity of biomaterial which then expands by a factor of 10,000 (by volume) into an "infinite" sea of water. This raises questions about the robustness of gel formation and properties across a range of concentrations. This study provides the first ever understanding of the mechanics of hagfish slime over a very wide range of concentration. We discover that some viscoelastic properties of slime are remarkably constant regardless of its concentration. Such a characteristic is uncommon in most known materials.


Assuntos
Feiticeiras (Peixe)/química , Muco/química , Animais , Materiais Biocompatíveis/química , Fenômenos Biomecânicos , Elasticidade , Humanos , Modelos Biológicos , Dinâmica não Linear , Fatores de Tempo , Viscosidade
20.
Genesis ; 56(6-7): e23213, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-30134067

RESUMO

Cranium of jawed vertebrates is composed of dorsal moiety that encapsulates the brain, or the neurocranium, and the is called the neurocranium, and the ventral moiety, the viscerocranium, that supports the pharynx. In modern jawed vertebrates (crown gnathostomes), the viscerocranium is predominantly of neural crest origin, and for the neurocranium, the rostral part is derived from neural crest cells, whereas the posterior part from the mesoderm. In the cyclostome cranium, the mesoderm/neural crest boundary of the neurocranium used to be enigmatic, let alone the morphological comparison of neurocranial between two cyclostome groups, lampreys and hagfishes. By examining the hagfish development it has become clear that cyclostomes share a common craniofacial embryonic pattern that is not shared by modern gnathostomes, and cyclostome cranium can be compared among the group as developmental modular units with comparable mesoderm/neural crest boundary within the neuroranium. Also, the dual origin of the jawed vertebrate neurocranium has now turned out to represent a derived condition, and ancestrally, the neurocranium would likely have been predominantly of mesodermal origin. Enlargement of the forebrain and reorganization of the oral apparatus seem to have led to the involvement of the neural crest in the rostral neurocranium.


Assuntos
Crista Neural/embriologia , Crânio/embriologia , Animais , Evolução Biológica , Endoderma , Feiticeiras (Peixe)/embriologia , Humanos , Arcada Osseodentária/embriologia , Lampreias/embriologia , Mesoderma , Crista Neural/fisiologia , Crânio/fisiologia , Vertebrados/embriologia
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