25 research outputs found
Morphology of the petrosal and stapes of Borealestes (Mammaliaformes, Docodonta) from the Middle Jurassic of Skye, Scotland
We describe, in unprecedented detail, the petros-als
and stapes of the docodont Borealestes from the Middle
Jurassic of Scotland, using high resolution lCT and phase-
contrast synchrotron imaging.
We describe the inner ear endocast and the vascularized interior structure of the pet-rosal, and provide the first endocranial view of a docodontan petrosal.
Our study confirms some similarities in petrosal and stapedial morphology with the better known Haldan-odon of the Late Jurassic of Portugal, including: (1) the degree of curvature of the cochlea;
(2) multiple features related to the highly pneumatized paroccipital region;
(3) the shape of lateral trough, the fossa of the M. tensor tym-pani, and the ridge on the promontorium;
(4) the round shape of the fenestra vestibuli; and
(5) overall morphology of the stapes. But Borealestes differs from Haldanodon in having a bony ridge that separates the tympanic opening of the prootic canal, the secondary facial foramen and the hia-tus Fallopii, from the fenestra vestibuli.
We identify two new vascular structures: the anterior and posterior trans-cochlear sinuses, which traverse the pars cochlearis around the cochlear nerve (VIII). These trans-cochlear sinuses have not been observed in previous docodont specimens, and could be an autapomorphy of Borealestes, or apomorphic for this clade.
We also establish the anatomical relationship of the
circum-promontorium plexus to the inner endocast. The
high quality of our scans has made these structures visible
for the first time
The mandible and dentition of Borealestes serendipitus (Docodonta) from the Middle Jurassic of Skye, Scotland
The Middle Jurassic docodont Borealestes serendipitus was the first Mesozoic mammal found in Scotland over 40 years ago. Its affinities and morphology have remained poorly understood. Although multiple dentary fragments and isolated teeth have been recovered from Scotland and England, they have not yet been described in sufficient detail. We report new, more complete specimens collected during recent field work on Skye, Scotland, combined with previously collected material. This includes upper and lower dentition and an almost complete right dentary. We present an updated description and diagnosis of the genus Borealestes, based on high-resolution micro-computed tomography (micro-CT) and synchrotron scans. We identify seven key features that distinguish Borealestes from other docodonts, including a pronounced aâc crest, absence of the aâg crest on cusp a, an anterior fovea at the buccolingual midpoint of the upper molar, and the convergence of the Meckelâs groove with the ventral margin of the mandible. We also present a revised diagnosis for the second species, B. mussettae. Our phylogenetic analysis supports a clade formed by Borealestes, Haldanodon, Docofossor, and Docodon. Ontogenetic variation in the mandibular morphology of Borealestes is similar to that seen in Docodon and Haldanodon, with the delayed emergence of the ultimate lower molar, the shift of the last molar to the front of the coronoid process, and a posterior shift of the Meckelâs sulcus in successively older individuals. This supports a distinctive growth pattern in the clade including Borealestes and Docodon, one that may be present in Docodonta as a whole
An Amino Acid Substitution in the Coding Region of the E2 Glycoprotein Adapts Ross River Virus To Utilize Heparan Sulfate as an Attachment Moiety
Passage of Ross River virus strain NB5092 in avian cells has been previously shown to select for virus variants that have enhanced replication in these cells. Sequencing of these variants identified two independent sites that might be responsible for the phenotype. We now demonstrate, using a molecular cDNA clone of the wild-type T48 strain, that an amino acid substitution at residue 218 in the E2 glycoprotein can account for the phenotype. Substitutions that replaced the wild-type asparagine with basic residues had enhanced replication in avian cells while acidic or neutral residues had little or no observable effect. Ross River virus mutants that had increased replication in avian cells also grew better in BHK cells than the wild-type virus, whereas the remaining mutants were unaffected in growth. Replication in both BHK and avian cells of Ross River virus mutants N218K and N218R was inhibited by the presence of heparin or by the pretreatment of the cells with heparinase. Binding of the mutants, but not of the wild type, to a heparin-Sepharose column produced binding comparable to that of Sindbis virus, which has previously been shown to bind heparin. Replication of these mutants was also adversely affected when they were grown in a CHO cell line that was deficient in heparan sulfate production. These results demonstrate that amino acid 218 of the E2 glycoprotein can be modified to create an heparan sulfate binding site and this modification expands the host range of Ross River virus in cultured cells to cells of avian origin
Coulonia parva n. sp., a new species of Astropectinidae (Asteroidea; Echinodermata) from the Santonian (Upper Cretaceous) of Sierra de Montsech (southern Pyrenees, Spain)
Human Herpesvirus 8 Envelope Glycoprotein K8.1A Interaction with the Target Cells Involves Heparan Sulfate
Human herpesvirus-8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus K8.1 gene encodes for two immunogenic glycoproteins, gpK8.1A and gpK8.1B, originating from spliced messages. The 228-amino-acid (aa) gpK8.1A is the predominant form associated with the virion envelope, consisting of a 167-aa region identical to gpK8.1B and a 61-aa unique region (L. Zhu, V. Puri, and B. Chandran, Virology 262:237â249, 1999). HHV-8 has a broad in vivo and in vitro cellular tropism, and our studies showed that this may be in part due to HHV-8's interaction with the ubiquitous host cell surface molecule, heparan sulfate (HS). Since HHV-8 K8.1 gene is positionally colinear to the Epstein-Barr virus (EBV) gene encoding the gp350/gp220 protein involved in EBV binding to the target cells, gpK8.1A's ability to interact with the target cells was examined. The gpK8.1A without the transmembrane and carboxyl domains (ÎTMgpK8.1A) was expressed in a baculovirus system and purified. Radiolabeled purified ÎTMgpK8.1A protein bound to the target cells, which was blocked by unlabeled ÎTMgpK8.1A. Unlabeled ÎTMgpK8.1A blocked the binding of [(3)H]thymidine-labeled purified HHV-8 to the target cells. Binding of radiolabeled ÎTMgpK8.1A to the target cells was inhibited in a dose-dependent manner by soluble heparin, a glycosaminoglycan (GAG) closely related to HS, but not by other GAGs such as chondroitin sulfate A and C, N-acetyl heparin and de-N-sulfated heparin. Cell surface absorbed ÎTMgpK8.1A was displaced by soluble heparin. Radiolabeled ÎTMgpK8.1A also bound to HS expressing Chinese hamster ovary (CHO-K1) cells, and binding to mutant CHO cell lines deficient in HS was significantly reduced. The ÎTMgpK8.1A specifically bound to heparin-agarose beads, which was inhibited by HS and heparin, but not by other GAGs. Virion envelope-associated gpK8.1A was specifically precipitated by heparin-agarose beads. These findings suggest that gpK8.1A interaction with target cells involves cell surface HS-like moieties, and HHV-8 interaction with HS could be in part mediated by virion envelope-associated gpK8.1A
Mammalian postcranial bones from the Late Jurassic of Portugal and their implications for forelimb evolution
Identification of a Putative Coreceptor on Vero Cells That Participates in Dengue 4 Virus Infection
Dengue virus infects target cells by attaching to a cell surface receptor through the envelope (E) glycoprotein, located on the surface of the viral membrane. On Vero and BHK cells, heparan sulfate (HS) moieties of proteoglycans are the receptors for dengue virus; however, additional proteins have also been described as putative dengue virus receptors on C6/36, HL60, and BM cells. HS can also act as a receptor for other types of viruses or as an attachment molecule for viruses that require additional host cell molecules to allow viral penetration. In this study we searched for molecules other than HS that could participate in dengue virus infection of Vero cells. Labeled dengue 4 virus bound with high affinity to two molecules of 74 and 44 kDa. Binding of dengue virus to the 74-kDa molecule was susceptible to protease and sodium periodate treatment and resistant to heparinase treatments. Lectins such as concanavalin A and wheat germ agglutinin prevented dengue virus binding to both the 74- and the 44-kDa protein in overlay assays, while phytohemagglutinin P did not affect binding, suggesting that carbohydrate residues (α-mannose or N-acetylglucosamine) are important in virus binding to host cells. Protease susceptibility, biotin labeling, and immunofluorescence with a polyclonal antibody raised against the 74-kDa protein consistently identified the protein on the surfaces of Vero cells. Moreover, the antibody against the 74-kDa protein was able to inhibit dengue virus infection. These data suggest that HS might serve as a primary receptor, probably concentrating virus particles on the surfaces of Vero cells, and then other molecules, such as the 74-kDa protein, might participate as coreceptors in viral penetration. The 74-kDa protein possibly constitutes part of a putative receptor complex for dengue virus infection of Vero cells