Details of the kinematics of free flight are very important to understanding insect flight mechanics. Important data for aerodynamic analysis and modeling include flight trajectory, body attitude and wing kinematics for individuals flying over a diverse array of behaviors, such as hovering, climbing and turning.A number of recent studies have focused on the kinematics of hovering and forward flight, using a variety of techniques. Azuma and Watanabe (1988) changed the velocity of the wind tunnel in their measurements. Dudley and Ellington (1990) calculated angles of attack in the free forward flight of bumblebees. Willmott and Ellington (1997) employed a variable-speed wind tunnel associated with the optomotor response to investigate wing and body kinematics during free forward flight of a hawkmoth over a range of speeds from hovering to 5 m s -1 . Wakeling and Ellington (1997) filmed the free flights of dragonflies and damselflies flying over the pond in the greenhouse at the University of Cambridge. The individuals were not restrained by either tethers or wind tunnels, but were free to vary the velocity and acceleration and could perform any flight action. In their analyses of forward flight, the stroke plane was constructed based on the assumption of bilateral wing symmetry, and variations in roll, yaw and pitch angles of the body through each flapping cycle were neglected. To date no detailed information on wing orientation or shape during free flight has been acquired.All kinds of flight behaviors are important for studying the aerodynamics and the control of flight. In turning maneuvers, the wings move asymmetrically, and the change in attitude is obvious even during one flapping cycle. We have also found that dragonflies exhibit substantial chordwise deformation and changes in camber during free flight, which might be important for aerodynamic models of flight performance.To study turning maneuvers involving obvious changing of the insect attitude, the description of wing kinematics should be based on a local body-centered coordinate system, together with the body attitude and flight trajectory. We have developed a method utilizing a Projected, Comb-Fringe technique combined with the Landmarks procedure (PCFL), in which a comb-fringe pattern with high intensity and sharpness was projected onto the transparent wing of a dragonfly in free flight. Images of the wings with distorted fringes were then recorded by a high-speed camera. Based on the distorted fringe pattern and the natural landmarks on the dragonfly wings, we reconstructed wing shape and established the body-centered coordinate system. This method allowed us to derive kinematic parameters without assumptions of rigid chords or kinematic symmetry, except for the assumption of rigid leading edges. The instantaneous attitude of the body was also measured simultaneously. We measured dragonflies in two flight behaviors: forward flight and turning maneuvers, and compared the kinematics results obtained for each of them. A robust technique for determinin...
The NS5A protein of hepatitis C virus (HCV) plays roles in both virus genome replication and assembly. NS5A comprises three domains, of these domain I is believed to be involved exclusively in genome replication. In contrast, domains II and III are required for the production of infectious virus particles and are largely dispensable for genome replication. Domain I is highly conserved between HCV and related hepaciviruses, and is highly structured, exhibiting different dimeric conformations. To investigate the functions of domain I in more detail, we conducted a mutagenic study of 12 absolutely conserved and surface-exposed residues within the context of a JFH-1-derived sub-genomic replicon and infectious virus. Whilst most of these abrogated genome replication, three mutants (P35A, V67A and P145A) retained the ability to replicate but showed defects in virus assembly. P35A exhibited a modest reduction in infectivity, however V67A and P145A produced no infectious virus. Using a combination of density gradient fractionation, biochemical analysis and high resolution confocal microscopy we demonstrate that V67A and P145A disrupted the localisation of NS5A to lipid droplets. In addition, the localisation and size of lipid droplets in cells infected with these two mutants were perturbed compared to wildtype HCV. Biophysical analysis revealed that V67A and P145A abrogated the ability of purified domain I to dimerize and resulted in an increased affinity of binding to HCV 3’UTR RNA. Taken together, we propose that domain I of NS5A plays multiple roles in assembly, binding nascent genomic RNA and transporting it to lipid droplets where it is transferred to Core. Domain I also contributes to a change in lipid droplet morphology, increasing their size. This study reveals novel functions of NS5A domain I in assembly of infectious HCV and provides new perspectives on the virus lifecycle.
Subgroup J avian leukosis virus (ALV-J) is an avian retrovirus that causes severe economic losses in the poultry industry. The early identification and removal of virus-shedding birds are important to reduce the spread of congenital and contact infections. In this study, a TaqMan-based real-time PCR method for the rapid detection and quantification of ALV-J with proviral DNA was developed. This method exhibited a high specificity for ALV-J. Moreover, the detection limit was as low as 10 viral DNA copies. The coefficients of variation (CVs) of both interassay and intra-assay reproducibility were less than 1%. The growth curves of ALV-J in DF-1 cells were measured by real-time PCR, yielding a trend line similar to those determined by 50% tissue culture infective dose (TCID 50 ) and p27 antigen detection. Tissue samples suspected of ALV infection were evaluated using real-time PCR, virus isolation, and routine PCR, and the positivity rates were 60.1%, 41.6% and 44.5%, respectively. Our data indicated that the real-time PCR method provides a sensitive, specific, and reproducible diagnostic tool for the identification and quantification of ALV-J for clinical diagnosis and in laboratory research. Avian leukosis viruses (ALVs) are members of the Alpharetrovirus genus of the family Retroviridae that are associated with a variety of neoplasms, including lymphoid and myeloid leukoses. ALVs are prevalent in poultry flocks worldwide and cause serious economic losses due to decreased egg production and quality, tumor mortality, and low growth rate. ALV isolates from chickens are classified into subgroups A, B, C, D, and E and the recently identified subgroup J according to host range, viral envelope glycoprotein properties, and cross-neutralization patterns (1). Subgroup A and B ALVs occur as common pathogenic exogenous viruses, and subgroup C and D ALVs have been rarely reported in the field. Subgroup E viruses are endogenous leukosis viruses with low pathogenicity. Subgroup J ALV (ALV-J) is an exogenous virus that causes myeloid leukosis (ML) in chickens. ALV-J was first isolated from meat-type chickens and was designated subgroup J due to its distinct envelope characteristics (2). The env gene sequence of the ALV-J prototype (HPRS-103 strain) is considerably different from those of other subgroups. However, it shares high identities (75 to 97%) with env-like sequences from the endogenous avian retrovirus (EAV) family members, suggesting that it evolved by recombination with the env-like sequences of this family (3, 4).ALV-J was first isolated from broiler chickens with myeloid leukosis in the United Kingdom. Since its first report, ALV-J infection has been widely detected in multiple countries in the Americas, Asia, and Oceania (5-7). Although the virus has a broad host range and all chicken lines tested have been susceptible to infection (2, 8), no field cases of ALV-J infection and tumors in layer chickens were reported until 2004 (9). In recent years, cases of ALV-J infection and tumors have been widely reported for co...
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