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1.
Photochem Photobiol ; 96(1): 37-45, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31441051

RESUMO

Among Etmopteridae and Dalatiidae, luminous species use hormonal control to regulate bioluminescence. Melatonin (MT) triggers light emission and, conversely, alpha melanocyte-stimulating hormone (α-MSH) actively reduces ongoing luminescence. Prolactin (PRL) acts differentially, triggering light emission in Etmopteridae and inhibiting it in Dalatiidae. Interestingly, these hormones are also known as regulators of skin pigment movements in vertebrates. One other hormone, the adrenocorticotropic hormone (ACTH), also members of the skin pigmentation regulators, is here pharmacologically tested on the light emission. Results show that ACTH inhibits luminescence in both families. Moreover, as MT and α-MSH/ACTH receptors are members of the G-protein coupled receptor (GPCR) family, we investigated the effect of hormonal treatments on the cAMP level of photophores through specific cAMP assays. Our results highlight the involvement of ACTH and cAMP in the control of light emission in sharks and suggest a functional similarity between skin pigment migration and luminescence control, this latter being mediated by pigment movements in the light organ-associated iris-like structure cells.

2.
Zoological Lett ; 5: 9, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30873292

RESUMO

Background: In the darkness of the ocean, an impressive number of taxa have evolved the capability to emit light. Many mesopelagic organisms emit a dim ventral glow that matches with the residual environmental light in order to camouflage themselves (counterillumination function). Sharks use their luminescence mainly for this purpose. Specific lateral marks have been observed in Etmopteridae sharks (one of the two known luminous shark families) suggesting an inter/intraspecific recognition. Conversely, dorsal luminescence patterns are rare within these deep-sea organisms. Results: Here we report evidence that Etmopterus spinax, Etmopterus molleri and Etmopterus splendidus have dorsal luminescence patterns. These dorsal patterns consist of specific lines of luminous organs, called photophores, on the rostrum, dorsal area and at periphery of the spine. This dorsal light seems to be in contrast with the counterilluminating role of ventral photophores. However, skin photophores surrounding the defensive dorsal spines show a precise pattern supporting an aposematism function for this bioluminescence. Using in situ imaging, morphological and histological analysis, we reconstructed the dorsal light emission pattern on these species, with an emphasis on the photogenic skin associated with the spine. Analyses of video footage validated, for the first time, the defensive function of the dorsal spines. Finally, we did not find evidence that Etmopteridae possess venomous spine-associated glands, present in Squalidae and Heterondontidae, via MRI and CT scans. Conclusion: This work highlights for the first time a species-specific luminous dorsal pattern in three deep-sea lanternsharks. We suggest an aposematic use of luminescence to reveal the presence of the dorsal spines. Despite the absence of venom apparatus, the defensive use of spines is documented for the first time in situ by video recordings.

3.
Sci Rep ; 9(1): 3581, 2019 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-30837589

RESUMO

Environmental DNA (eDNA) metabarcoding is a recently developed method to assess biodiversity based on a high-throughput parallel DNA sequencing applied to DNA present in the ecosystem. Although eDNA metabarcoding enables a rapid assessment of biodiversity, it is prone to species detection errors that may occur at sequential steps in field sampling, laboratory experiments, and bioinformatics. In this study, we illustrate how the error rates in the eDNA metabarcoding-based species detection can be accounted for by applying the multispecies occupancy modelling framework. We report a case study with the eDNA sample from an aquarium tank in which the detection probabilities of species in the two major steps of eDNA metabarcoding, filtration and PCR, across a range of PCR annealing temperatures, were examined. We also show that the results can be used to examine the efficiency of species detection under a given experimental design and setting, in terms of the efficiency of species detection, highlighting the usefulness of the multispecies site occupancy modelling framework to study the optimum conditions for molecular experiments.

4.
Sci Rep ; 9(1): 953, 2019 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-30700755

RESUMO

The profound changes in global SO2 emissions over the last decades have affected atmospheric composition on a regional and global scale with large impact on air quality, atmospheric deposition and the radiative forcing of sulfate aerosols. Reproduction of historical atmospheric pollution levels based on global aerosol models and emission changes is crucial to prove that such models are able to predict future scenarios. Here, we analyze consistency of trends in observations of sulfur components in air and precipitation from major regional networks and estimates from six different global aerosol models from 1990 until 2015. There are large interregional differences in the sulfur trends consistently captured by the models and observations, especially for North America and Europe. Europe had the largest reductions in sulfur emissions in the first part of the period while the highest reduction came later in North America and East Asia. The uncertainties in both the emissions and the representativity of the observations are larger in Asia. However, emissions from East Asia clearly increased from 2000 to 2005 followed by a decrease, while in India a steady increase over the whole period has been observed and modelled. The agreement between a bottom-up approach, which uses emissions and process-based chemical transport models, with independent observations gives an improved confidence in the understanding of the atmospheric sulfur budget.

5.
Placenta ; 84: 4-8, 2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-30772008

RESUMO

Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialized topics. At IFPA meeting 2018 there were nine themed workshops, four of which are summarized in this report. These workshops discussed new knowledge and technological innovations in the following areas of research: 1) viviparity in ocean-living species; 2) placental imaging; 3) epigenetics; and 4) extracellular vesicles in pregnancy.

6.
Anat Rec (Hoboken) ; 301(11): 1801-1808, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30288958

RESUMO

In this study, we examined the structure of the heart of the whale shark, Rhincodon typus, using a plastination technique and three-dimensional X-ray computer tomography (3DCT). Inspection of the atrium revealed a symmetric distribution of the pectinate muscles attached to the commissures of the sino-atrial valve, suggesting some functional advantages. The majority of the ventricular wall comprised spongiosa, and compacta accounted for only ~3% of the entire thickness. There were three major fiber orientations in the spongiosa: the fibers on the endocardial side formed trabeculae that were aligned with the blood flow tract, whereas those on the epicardial side formed a circular pattern around the flow tract. Transmural myofibers connected the inner and outer layers in the spongiosa, which may serve as an intraventricular conduction pathway. Plastination and 3DCT is a powerful combination that allowed for multifaceted visualization of the internal structure of rare heart specimens in a nondestructive manner. Anat Rec, 301:1801-1808, 2018. © 2018 Wiley Periodicals, Inc.


Assuntos
Coração/anatomia & histologia , Coração/diagnóstico por imagem , Imagem Tridimensional/métodos , Plastinação/métodos , Tomografia Computadorizada por Raios X/métodos , Animais , Tubarões
7.
Nat Ecol Evol ; 2(11): 1761-1771, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30297745

RESUMO

Modern cartilaginous fishes are divided into elasmobranchs (sharks, rays and skates) and chimaeras, and the lack of established whole-genome sequences for the former has prevented our understanding of early vertebrate evolution and the unique phenotypes of elasmobranchs. Here we present de novo whole-genome assemblies of brownbanded bamboo shark and cloudy catshark and an improved assembly of the whale shark genome. These relatively large genomes (3.8-6.7 Gbp) contain sparse distributions of coding genes and regulatory elements and exhibit reduced molecular evolutionary rates. Our thorough genome annotation revealed Hox C genes previously hypothesized to have been lost, as well as distinct gene repertories of opsins and olfactory receptors that would be associated with adaptation to unique underwater niches. We also show the early establishment of the genetic machinery governing mammalian homoeostasis and reproduction at the jawed vertebrate ancestor. This study, supported by genomic, transcriptomic and epigenomic resources, provides a foundation for the comprehensive, molecular exploration of phenotypes unique to sharks and insights into the evolutionary origins of vertebrates.


Assuntos
Evolução Biológica , Genoma , Tubarões/genética , Animais , Elasmobrânquios/genética , Vertebrados/genética
8.
Stud Health Technol Inform ; 249: 151-157, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29866972

RESUMO

The widespread adoption of smartphones creates an enormous potential to improve healthcare services. Numerous apps, sensors, and devices are developed for health self-management purposes. However, adoption rates remain low and long-term user engagement is a major issue. The goal of this study is to identify major motivational factors that can facilitate prolonged use of mobile health systems. To this end, we conducted 16 interviews with representatives of various cultural backgrounds, disease history, age, and gender. Participants' experiences indicated that existing systems were unable to answer their self-management needs properly. People with a disease history favored learning from data, as well as from others via social media integration. People without chronic disease felt more reserved about social media integration. In conclusion, systems that collect and share personal data should have a clear opt-in or opt-out option to motivate usage. Additionally, researchers and mobile health system developers could achieve long-term adoption by giving clear answers to privacy and trust issues, while offering people strong added value according to their individual needs.


Assuntos
Motivação , Preferência do Paciente , Smartphone , Telemedicina , Doença Crônica , Humanos , Mídias Sociais , Interface Usuário-Computador
9.
Gen Comp Endocrinol ; 265: 174-179, 2018 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-29510152

RESUMO

Captive breeding in aquaria is a useful means for ex situ preservation of threatened elasmobranch species. To promote captive breeding, it is important to determine the female reproductive status. However, information regarding reproductive status in female elasmobranchs is limited. Here, we used zebra sharks, Stegostoma fasciatum, as a model for elasmobranch reproduction in captivity. We investigated the relationships among changes in the sex steroid hormone levels, follicle size, and egg-laying period to develop indicators for the female reproductive status. We confirmed that mature female zebra sharks undergo an annual reproductive cycle. Additionally, we showed that the variations in sex steroid hormone levels correlated with reproductive status in mature female zebra sharks. Plasma estradiol-17ß (E2) concentrations increased two months before ovarian follicle development and decreased along with follicle regression. Interestingly, E2 levels were inversely correlated with water temperature (R = -0.901). Moreover, high levels of testosterone (T) correlated well with the laying period. These results strongly suggest that E2 is an indicator for ovarian follicle development, and that T is a useful indicator for both the onset and end of the egg-laying period in captive zebra sharks.


Assuntos
Hormônios Esteroides Gonadais/sangue , Reprodução , Tubarões/sangue , Tubarões/fisiologia , Animais , Estradiol/sangue , Feminino , Masculino , Folículo Ovariano/anatomia & histologia , Oviductos/metabolismo , Óvulo/metabolismo , Temperatura Ambiente , Testosterona/sangue
10.
Anat Rec (Hoboken) ; 301(6): 1068-1073, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29316367

RESUMO

The lunate-shaped caudal fin in lamnid sharks is a morphological specialization for their thunniform mode of locomotion, but its developmental process during gestation has been poorly investigated. Observations of 21 embryonic specimens of the white shark (Carcharodon carcharias) revealed that their caudal fin morphology drastically changes from strongly heterocercal to lunate-shaped through ontogeny. This morphological change involves (1) rapid elongation of the ventral lobe, (2) increased upward curvature of the vertebra within the caudal fin, and (3) formation of keels at both lateral sides of the caudal fin base. These morphological changes are probably shared among the members of the family Lamnidae and are in contrast with the developmental process of the heterocercal tail in the lamniform Carcharias taurus, in which the caudal fin morphology is almost unchanged through the late gestation period. Anat Rec, 301:1068-1073, 2018. © 2018 Wiley Periodicals, Inc.


Assuntos
Nadadeiras de Animais/embriologia , Morfogênese/fisiologia , Tubarões/embriologia , Animais
11.
J Biomed Inform ; 74: 104-122, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28893671

RESUMO

Symptom checkers are software tools that allow users to submit a set of symptoms and receive advice related to them in the form of a diagnosis list, health information or triage. The heterogeneity of their potential users and the number of different components in their user interfaces can make testing with end-users unaffordable. We designed and executed a two-phase method to test the respiratory diseases module of the symptom checker Erdusyk. Phase I consisted of an online test with a large sample of users (n=53). In Phase I, users evaluated the system remotely and completed a questionnaire based on the Technology Acceptance Model. Principal Component Analysis was used to correlate each section of the interface with the questionnaire responses, thus identifying which areas of the user interface presented significant contributions to the technology acceptance. In the second phase, the think-aloud procedure was executed with a small number of samples (n=15), focusing on the areas with significant contributions to analyze the reasons for such contributions. Our method was used effectively to optimize the testing of symptom checker user interfaces. The method allowed kept the cost of testing at reasonable levels by restricting the use of the think-aloud procedure while still assuring a high amount of coverage. The main barriers detected in Erdusyk were related to problems understanding time repetition patterns, the selection of levels in scales to record intensities, navigation, the quantification of some symptom attributes, and the characteristics of the symptoms.


Assuntos
Sistemas Homem-Máquina , Sistemas de Apoio a Decisões Clínicas , Humanos , Análise Multivariada , Análise de Componente Principal
12.
Sci Rep ; 7(1): 11744, 2017 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-28924159

RESUMO

One of the mysteries of shark aplacental viviparity is the ability of the embryos to acquire oxygen from their mothers without a placental connection. It has been assumed that embryonic respiration in aplacental viviparous shark depends on oxygen from the uterine wall, although this hypothesis has not been confirmed quantitatively. Morphological observations of the uterine wall of white shark (Carcharodon carcharias) provided the first quantitative evidence to support the ability of the uterus to supply ample oxygen to the embryo of viviparous elasmobranchs. The uterine surface of the white shark is characterized by (1) uterine lamellae that develop perpendicular to the uterine wall, (2) uterine lamellae folded in an accordion-like fashion, and (3) numerous micro-ridges on the lamellar surface. These modifications result in increased uterine surface are to up to 56 folds compared to the uterus with a smooth surface. Histological observations revealed that the diffusion barrier of the uterine wall is approximately 12 µm. By using these values, the oxygen-diffusion capacity of 1 cm2 of the uterine wall of white shark was estimated to be 63.6 nmol·min-1·torr-1. This value is 250-400 times greater than that observed in other aplacental viviparous sharks (Squalus spp.) and is comparable with that of fish gills.


Assuntos
Embrião não Mamífero/metabolismo , Embrião não Mamífero/fisiologia , Oxigênio/metabolismo , Tubarões/embriologia , Útero/metabolismo , Animais , Desenvolvimento Embrionário , Feminino
13.
Environ Sci Technol ; 51(14): 7972-7981, 2017 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-28686425

RESUMO

The source-receptor relationship analysis of PAH deposition in Northeast Asia was investigated using an Eulerian regional-scale aerosol chemical transport model. Dry deposition (DD) of PAH was controlled by wind flow patterns, whereas wet deposition (WD) depended on precipitation in addition to wind flow patterns. The contribution of WD was approximately 50-90% of the total deposition, except during winter in Northern China (NCHN) and Eastern Russia (ERUS) because of the low amount of precipitation. The amount of PAH deposition showed clear seasonal variation and was high in winter and low in summer in downwind (South Korea, Japan) and oceanic-receptor regions. In the downwind region, the contributions from NCHN (WD 28-52%; DD 54-55%) and Central China (CCHN) (WD 43-65%; DD 33-38%) were large in winter, whereas self-contributions (WD 20-51%; DD 79-81%) were relatively high in summer. In the oceanic-receptor region, the deposition amount decreased with distance from the Asian continent. The amount of DD was strongly influenced by emissions from neighboring domains. The contributions of WD from NCHN (16-20%) and CCHN (28-35%) were large. The large contributions from China in summer to the downwind region were linked to vertical transport of PAHs over the Asian continent associated with convection.


Assuntos
Poluentes Atmosféricos , Monitoramento Ambiental , Ásia , China , Japão , República da Coreia , Federação Russa , Estações do Ano
14.
Mol Ecol Resour ; 17(6): e63-e75, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28603873

RESUMO

Terrestrial animals must have frequent contact with water to survive, implying that environmental DNA (eDNA) originating from those animals should be detectable from places containing water in terrestrial ecosystems. Aiming to detect the presence of terrestrial mammals using forest water samples, we applied a set of universal PCR primers (MiMammal, a modified version of fish universal primers) for metabarcoding mammalian eDNA. The versatility of MiMammal primers was tested in silico and by amplifying DNAs extracted from tissues. The results suggested that MiMammal primers are capable of amplifying and distinguishing a diverse group of mammalian species. In addition, analyses of water samples from zoo cages of mammals with known species composition suggested that MiMammal primers could successfully detect mammalian species from water samples in the field. Then, we performed an experiment to detect mammals from natural ecosystems by collecting five 500-ml water samples from ponds in two cool-temperate forests in Hokkaido, northern Japan. MiMammal amplicon libraries were constructed using eDNA extracted from water samples, and sequences generated by Illumina MiSeq were subjected to data processing and taxonomic assignment. We thereby detected multiple species of mammals common to the sampling areas, including deer (Cervus nippon), mouse (Mus musculus), vole (Myodes rufocanus), raccoon (Procyon lotor), rat (Rattus norvegicus) and shrew (Sorex unguiculatus). Many previous applications of the eDNA metabarcoding approach have been limited to aquatic/semiaquatic systems, but the results presented here show that the approach is also promising even for forest mammal biodiversity surveys.


Assuntos
Código de Barras de DNA Taxonômico/métodos , DNA/isolamento & purificação , Florestas , Mamíferos/classificação , Metagenômica/métodos , Tanques , Água/análise , Animais , DNA/genética , Primers do DNA/genética , Japão , Mamíferos/genética
15.
J Morphol ; 278(2): 215-227, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27889924

RESUMO

Unlike most viviparous vertebrates, lamniform sharks develop functional teeth during early gestation. This feature is considered to be related to their unique reproductive mode where the embryo grows to a large size via feeding on nutritive eggs in utero. However, the developmental process of embryonic teeth is largely uninvestigated. We conducted X-ray microcomputed tomography to observe the dentitions of early-, mid-, and full-term embryos of the white shark Carcharodon carcharias (Lamniformes, Lamnidae). These data reveal the ontogenetic change of embryonic dentition of the species for the first time. Dentition of the early-term embryos (∼45 cm precaudal length, PCL) is distinguished from adult dentition by 1) the presence of microscopic teeth in the distalmost region of the paratoquadrate, 2) a fang-like crown morphology, and 3) a lack of basal concavity of the tooth root. The "intermediate tooth" of early-term embryos is almost the same size as the adjacent teeth, suggesting that lamnoid-type heterodonty (lamnoid tooth pattern) has not yet been established. We also discovered that mid-term embryos (∼80 cm PCL) lack functional dentition. Previous studies have shown that the maternal supply of nutritive eggs in lamnoid sharks ceases during mid- to late-gestation. Thus, discontinuation of functional tooth development is likely associated with the completion of the oophagous (egg-eating) phase. Replacement teeth in mid-term embryos include both embryonic and adult-type teeth, suggesting that the embryo to adult transition in dental morphology occurs during this period. J. Morphol. 278:215-227, 2017. © 2016 Wiley Periodicals,Inc.


Assuntos
Dentição , Tubarões/embriologia , Dente/embriologia , Animais , Microtomografia por Raio-X
16.
J Vis Exp ; (117)2016 11 25.
Artigo em Inglês | MEDLINE | ID: mdl-27911387

RESUMO

Recent studies demonstrated the use of environmental DNA (eDNA) from fishes to be appropriate as a non-invasive monitoring tool. Most of these studies employed disk fiber filters to collect eDNA from water samples, although a number of microbial studies in aquatic environments have employed filter cartridges, because the cartridge has the advantage of accommodating large water volumes and of overall ease of use. Here we provide a protocol for filtration of water samples using the filter cartridge and extraction of eDNA from the filter without having to cut open the housing. The main portions of this protocol consists of 1) filtration of water samples (water volumes ≤4 L or >4 L); (2) extraction of DNA on the filter using a roller shaker placed in a preheated incubator; and (3) purification of DNA using a commercial kit. With the use of this and previously-used protocols, we perform metabarcoding analysis of eDNA taken from a huge aquarium tank (7,500 m3) with known species composition, and show the number of detected species per library from the two protocols as the representative results. This protocol has been developed for metabarcoding eDNA from fishes, but is also applicable to eDNA from other organisms.


Assuntos
DNA , Peixes , Animais , Meio Ambiente , Filtração , Água
17.
Vet J ; 216: 183-8, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27687950

RESUMO

The aim of this study was to isolate mesenchymal stem cells (MSCs) from feline peripheral blood (fPB-MSCs) and to characterise the cells' in vitro properties. The mononuclear cell fractions were isolated from venous blood of cats by density gradient centrifugation and cultured on plastic dishes under various culture conditions to isolate MSCs. When these cells were cultured with 5% autologous plasma (AP) and 10% foetal bovine serum (FBS), adherent spindle shaped fibroblast-like cells (fPB-MSCs) were obtained from 15/22 (68%) cats. These cells were isolated only from medium containing both AP and FBS. The morphology of these MSCs was similar to those isolated from other species and from other feline tissues. fPB-MSCs expanded steadily up to 5-6 passages, but had increased population doubling time during passaging and almost all cells stopped proliferation at passages 7-9. These cells expressed CD44 and CD90, and were mostly negative for major histocompatibility class II and CD4. The cells could be induced to differentiate into adipogenic, osteogenic and chondrogenic cell lineages. These findings indicate that fPB-MSCs can be generated but appear to require specific culture conditions.


Assuntos
Gatos/sangue , Técnicas de Cultura de Células/veterinária , Diferenciação Celular , Células-Tronco Mesenquimais/citologia , Adipogenia , Animais , Gatos/metabolismo , Células Cultivadas , Condrogênese , Células-Tronco Mesenquimais/metabolismo , Osteogênese
18.
BMC Res Notes ; 9(1): 428, 2016 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-27581739

RESUMO

BACKGROUND: In recent years, measurement of cerebral regional oxygen saturation (rSO2) has attracted attention during resuscitation. However, serial changes of cerebral rSO2 in pre-hospital settings are unclear. The objective of this study was to clarify serial changes in cerebral rSO2 of patients with out-of-hospital cardiac arrest (OHCA) in the pre-hospital setting. METHODS: We recently developed a portable rSO2 monitor that is small (170 × 100 × 50 mm in size and 600 g in weight) enough to carry in pre-hospital settings. The sensor is attached to the patient's forehead by the ELT (Emergency Life-saving Technician), and it monitors rSO2 continuously. RESULTS: From June 2013 through August 2014, serial changes in cerebral rSO2 in seven patients were evaluated. According to the results of the serial changes in rSO2, four patterns of rSO2 change were found, as follows. Type 1: High rSO2 (around about 60 %) type (n = 1). Initial electrocardiogram was ventricular fibrillation and ROSC (return of spontaneous circulation) could be diagnosed in pre-hospital setting. Her outcome at discharge was Good Recovery (GR). Type 2: Low rSO2 (around about 45-50 %) type (n = 3). They did not get ROSC even once. Type 3: Gradually decreasing rSO2 type (n = 2): ROSC could be diagnosed in hospital, but not in pre-hospital setting. Their outcomes at discharge were not GR. Type 4: other type (n = 1). In this patient with ROSC when ELT started cerebral rSO2 measurement, cerebral rSO2 was 67.3 % at measurement start, it dropped gradually to 54.5 %, and then rose to 74.3 %. The cerebral oxygenation was impaired due to possible cardiac arrest again, and after that, ROSC led to the recovery of cerebral blood flow. CONCLUSION: We could measure serial changes in cerebral rSO2 in seven patients with OHCA in the pre-hospital setting. Our data suggest that pre-hospital monitoring of cerebral rSO2 might lead to a new resuscitation strategy.


Assuntos
Encéfalo/metabolismo , Monitorização Fisiológica/métodos , Parada Cardíaca Extra-Hospitalar/metabolismo , Oxigênio/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Auxiliares de Emergência , Feminino , Hospitalização , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do Tratamento
19.
Biol Open ; 5(9): 1211-5, 2016 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-27635035

RESUMO

The great white shark (Carcharodon carcharias) exhibits viviparous and oophagous reproduction. A 4950 mm total length (TL) gravid female accidentally caught by fishermen in the Okinawa Prefecture, Southern Japan carried six embryos (543-624 mm TL, three in each uterus). Both uteri contained copious amounts of yellowish viscous uterine fluid (over 79.2 litres in the left uterus), nutrient eggs and broken egg cases. The embryos had yolk stomachs that had ruptured, the mean volume of which was approximately 197.9 ml. Embryos had about 20 rows of potentially functional teeth in the upper and lower jaws. Periodic acid Schiff (PAS)-positive substances were observed on the surface and in the cytoplasm of the epithelial cells, and large, secretory, OsO4-oxidized lipid droplets of various sizes were distributed on the surface of the villous string epithelium on the uterine wall. Histological examination of the uterine wall showed it to consist of villi, similar to the trophonemata of Dasyatidae rays, suggesting that the large amount of fluid found in the uterus of the white shark was likely required for embryo nutrition. We conclude that: (1) the lipid-rich fluid is secreted from the uterine epithelium only in early gestation before the onset of oophagy, (2) the embryos probably use the abundant uterine fluid and encased nutrient eggs for nutrition at this stage of their development, and (3) the uterine fluid is the major source of embryonic nutrition before oophagy onset. This is the first record of the lipid histotrophy of reproduction among all shark species.

20.
Sci Rep ; 6: 27786, 2016 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-27282933

RESUMO

Five striking and prey capture events of two goblin sharks were videotaped at sea for the first time, showing their extraordinary biting process. The goblin sharks swung their lower jaw downward and backward to attain a huge gape and then rapidly protruded the jaws forward a considerable distance. The jaws were projected at a maximum velocity of 3.1 m/s to 8.6-9.4% of the total length of the shark, which is by far the fastest and greatest jaw protrusion among sharks. While the jaws were being retracted, the mouth opened and closed again, which was considered a novel feeding event for sharks. Phylogenetic evidence suggested that their feeding behavior has evolved as an adaptation to food-poor deep-sea environments, possibly as a trade-off for the loss of strong swimming ability.


Assuntos
Comportamento Alimentar/fisiologia , Tubarões/fisiologia , Animais , Fenômenos Biomecânicos , Força de Mordida , Força Compressiva , Movimentos da Cabeça/fisiologia , Arcada Osseodentária/fisiologia , Comportamento Predatório/fisiologia , Fatores de Tempo
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