Definition of the specific roles of lysolecithin and palmitic acid in altering the susceptibility of dipalmitoylphosphatidylcholine bilayers to phospholipase A2

Bilayers composed of phosphatidylcholine initially resist catalysis by phospholipase A2. However, after a latency period, they become susceptible when sufficient reaction products (lysolecithin and fatty acid) accumulate in the membrane. Temperature near the main bilayer phase transition and calcium concentration modulate the effectiveness of the reaction products. The purpose of this study was to examine the individual contributions of lysolecithin and palmitic acid to the susceptibility of dipalmitoylphosphatidylcholine vesicles and to rationalize the effects of temperature and calcium. Various fluorescent probes (Prodan, Laurdan, pyrene-labeled fatty acid, and dansyl-labeled phospholipid) were used to assess changes in the ability of the reaction products to perturb the bilayer and to affect the interactions with the enzyme. Un-ionized palmitic acid decreased bilayer polarity and perturbed the membrane surface exposing some of the Prodan to bulk water. Lysolecithin increased bilayer polarity and the rate of dipolar relaxation in response to the excited states of Laurdan and Prodan. A combination of the individual contributions of each product was observed when palmitic acid and lysolecithin were present together at low calcium, and the effects of lysolecithin dominated at high calcium. Palmitic acid, but not lysolecithin, promoted the binding of phospholipase A2 to the bilayer surface in the absence of calcium. Lysolecithin reduced the ability of fatty acid to enhance binding apparently by altering the structure of fatty acid domains in the membrane. Furthermore, increased temperature and ionization of the fatty acid tended to cause segregation of bound phospholipase A2 into domains poor in phospholipid content which presumably impeded bilayer hydrolysis. In contrast, un-ionized palmitic acid and lysolecithin promoted hydrolysis by augmenting a step distal to the adsorption of enzyme to the bilayer. This kinetic response to lysolecithin was calcium-dependent. A model accounting for these varied influences of the reaction products is presented.     

The simplified two-pipette technique is more efficient than the conventional three-pipette method for blastomere biopsy in human embryos

Kell and Kx are two quantitatively minor proteins from the human erythrocyte membrane which carry blood groups antigens and are thought to be a metalloprotease and a membrane transporter, respectively. In the red cell membrane, these proteins form a complex stabilized by disulfide bond(s). Phosphorylation status of these proteins was studied, in the presence or absence of effectors of several kinases, either on intact cells incubated with [32P]-orthophosphate or on ghosts incubated with [gamma-32P]ATP. Purification of Kell-Kx complex, by immunochromatography on an immobilized human monoclonal antibody of Kell blood group specificity allowed to establish that (i) neither protein is phosphorylated on tyrosine; (ii) the Kell protein is a putative substrate for Casein Kinase II (CKII) and Casein Kinase I (CKI) but not for protein kinase C (PKC), whereas Kx protein is phosphorylated by CKII and PKC but not by CKI; (iii) Protein Kinase A neither phosphorylates the Kell nor the Kx proteins.     

Point mutations in human GLI3 cause Greig syndrome

Greig cephalopolysyndactyly syndrome (GCPS, MIM 175700) is a rare autosomal dominant developmental disorder characterized by craniofacial abnormalities and post-axial and pre-axial polydactyly as well as syndactyly of hands and feet. Human GLI3, located on chromosome 7p13, is a candidate gene for the syndrome because it is interrupted by translocation breakpoints associated with GCPS. Since hemizygosity of 7p13 resulting in complete loss of one copy of GLI3 causes GCPS as well, haploinsufficiency of this gene was implicated as a mechanism to cause this developmental malformation. To determine if point mutations within GLI3 could be responsible for GCPS we describe the genomic sequences at the boundaries of the 15 exons and primer pair sequences for mutation analysis with polymerase chain reaction-based assays of the entire GLI3 coding sequences. In two GCPS cases, both of which did not exhibit obvious cytogenetic rearrangements, point mutations were identified in different domains of the protein, showing for the first time that Greig syndrome can be caused by GLI3 point mutations. In one case a nonsense mutation in exon X generates a stop codon truncating the protein in the C-H link of the first zinc finger. In the second case a missense mutation in exon XIV causes a Pro-->Ser replacement at a position that is conserved among GLI genes from several species altering a potential phosphorylation site.     

Susceptibility of penicillin-susceptible and -resistant pneumococci to CFC-222, a new fluoroquinolone

Rotavirus (RV) strains infecting newborns often have unique neutralization antigens (P serotypes) on their outer capsids that are distinct from those found on RV strains that cause diarrhea in older children. We examined the hypothesis that unusual RV strains preferentially infect newborns because the newborns lack maternal neutralizing antibodies to these strains. To test this hypothesis, sera and saliva samples collected from neonates infected with 116E-like (P[11]G9) strains in the maternity ward of the All India Institute of Medical Sciences (AIIMS) hospital in New Delhi were tested for neutralizing antibodies against common RV strains and those infecting newborns and these titers were compared with those of newborns who did not become infected (controls). The infected neonates had significantly lower levels of cord blood neutralizing antibodies to 116E than the controls, suggesting that immunity to neonatal RV infection is acquired transplacentally through maternal antibodies. Further, this study confirmed the immunogenicity of the AIIMS neonatal strain 116E, a vaccine candidate, in its ability to evoke a potent RV-specific immunoglobulin A and neutralizing antibody response in serum and saliva among the infected babies. Our findings have important implications for the development of an effective RV vaccine. In India, where G9 strains are common in the community, the use of 116E as a vaccine, together with the rhesus tetravalent vaccine, may provide a broader protection against all the circulating RV serotypes, including serotype G9, which is not represented in the current rhesus RV tetravalent vaccine (G1-G4).     

A review on improving the autonomy of unmanned surface vehicles through intelligent collision avoidance manoeuvres

In recent years unmanned vehicles have grown in popularity, with an ever increasing number of applications in industry, the military and research within air, ground and marine domains. In particular, the challenges posed by unmanned marine vehicles in order to increase the level of autonomy include automatic obstacle avoidance and conformance with the Rules of the Road when navigating in the presence of other maritime traffic. The USV Master Plan which has been established for the US Navy outlines a list of objectives for improving autonomy in order to increase mission diversity and reduce the amount of supervisory intervention. This paper addresses the specific development needs based on notable research carried out to date, primarily with regard to navigation, guidance, control and motion planning. The integration of the International Regulations for Avoiding Collisions at Sea within the obstacle avoidance protocols seeks to prevent maritime accidents attributed to human error. The addition of these critical safety measures may be key to a future growth in demand for USVs, as they serve to pave the way for establishing legal policies for unmanned vessels.     

Posterior representation with a multi‐modal likelihood using the gaussian sum filter for localization in a known map

A Gaussian sum filter (GSF) with component extended Kalman filters (EKF) is proposed as an approach to localizing an autonomous vehicle in an urban environment with limited GPS availability. The GSF uses vehicle‐relative vision‐based measurements of known map features coupled with inertial navigation solutions to accomplish localization in the absence of GPS. The vision‐based measurements have multimodal measurement likelihood functions that are well represented as weighted sums of Gaussian densities. The GSF is used because of its ability to represent the posterior distribution of the vehicle pose with better efficiency (fewer terms, less computational complexity) than a corresponding bootstrap particle filter with various numbers of particles because of the interaction with measurement hypothesis tests. The expectation‐maximization algorithm is used off line to determine the representational efficiency of the particle filter in terms of an effective number of Gaussian densities. In comparison, the GSF, which uses an iterative condensation procedure after each iteration of the filter to maintain real‐time capabilities, is shown through a series of in‐depth empirical studies to more accurately maintain a representation of the posterior distribution than the particle filter using 37 min of recorded data from Cornell University's autonomous vehicle driven in an urban environment, including a 32 min GPS blackout. © 2012 Wiley Periodicals, Inc.     

A theoretical and experimental study of low-loss SAW filters with interdigitated interdigital transducers

A study of low-loss surface-acoustic-wave (SAW) interdigitated interdigital transducer (IIDT) structures is presented. A model based on mixed scattering matrices was used in the analysis. It is shown that the inherent comb frequency response of the IIDT can be smoothed by slanting the transducers in the structure. Alternatively, the combs can be enhanced to produce a compact low-loss feedback element for potential application in multimode oscillators. Experimental verification of the analysis is provided by a 3:2 slanted-finger IIDT filter with a 10% relative bandwidth of 5.9-dB insertion loss, and a comb filter with 13.4-dB insertion loss and comb spacing of about 3 MHz. The measured responses agree quite well with the theory.