38,109 research outputs found
Cloning and expression of porcine Ī²1,4 N-acetylgalactosaminyl transferase encoding a new xenoreactive antigen
Xenograft rejection of pigs organs with an engineered mutation in the GGTA-1 gene (GTKO) remains a predominantly antibody mediated process which is directed to a variety of non-Gal protein and carbohydrate antigens. We previously used an expression library screening strategy to identify six porcine endothelial cell cDNAs which encode pig antigens that bind to IgG induced after pig-to-primate cardiac xenotransplantation. One of these gene products was a glycosyltransferase with homology to the bovine Ī²1,4 N-acetylgalactosaminyltransferase (B4GALNT2). We now characterize the porcine B4GALNT2 gene sequence, genomic organization, expression, and functional significance
Improvements in the preparation of heterologous antilymphocyte globulin with special reference to absorption and diethylaminoethyl cellulose batch production
Antilymphocyte gamma-G globulin (ALGG) was produced from the serum of immunized horses. Modifications of the preliminary absorption techniques permitted the removal of undesirable, extraneous antibodies. With the use of a batch technique, pure gamma-G globulin could then be removed in bulk quantities. The resulting product was first confirmed to have immunosuppressive qualities in dogs and then given a clinical trial. In patients, its administration occasionally caused low-grade fever and thrombocytopenia. Pain at the injection site was not eliminated. Precipitin antibody responses have apparently been prevented in the patients but not a host response to Forssman antigens. Ā© 1969
Structure and dielectric properties of polar fluids with extended dipoles: results from numerical simulations
The strengths and short-comings of the point-dipole model for polar fluids of
spherical molecules are illustrated by considering the physically more relevant
case of extended dipoles formed by two opposite charges separated by a
distance (dipole moment ). Extensive Molecular Dynamics
simulations on a high density dipolar fluid are used to analyse the dependence
of the pair structure, dielectric constant \eps and dynamics as a function of
the ratio (\sig is the molecular diameter), for a fixed dipole
moment . The point dipole model is found to agree well with the extended
dipole model up to d/\sig \simeq 0.3. Beyond that ratio, \eps shows a
non-trivial variation with d/\sig. When d/\sig>0.6, a transition is
observed towards a hexagonal columnar phase; the corresponding value of the
dipole moment, \mu^2/\sig^3 k T=3, is found to be substantially lower than
the value of the point dipole required to drive a similar transition.Comment: 10 pages, 11 figures; Paper submitted to Molecular Physic
Low-Lying Dirac Eigenmodes, Topological Charge Fluctuations and the Instanton Liquid Model
The local structure of low-lying eigenmodes of the overlap Dirac operator is
studied. It is found that these modes cannot be described as linear
combinations of 't Hooft "would-be" zeromodes associated with instanton
excitations that underly the Instanton Liquid Model. This implies that the
instanton liquid scenario for spontaneous chiral symmetry breaking in QCD is
not accurate. More generally, our data suggests that the vacuum fluctuations of
topological charge are not effectively dominated by localized lumps of unit
charge with which the topological "would-be" zeromodes could be associated.Comment: Presented by I. Horvath at the NATO Advanced Research Workshop
"Confinement, Topology, and other Non-Perturbative Aspects of QCD", January
21-27, 2002, Stara Lesna, Slovakia. 12 pages, 6 figures, uses crckapb.st
Digging for answers: contributions of density- and frequency-dependent factors on ectoparasite burden in a social mammal
Due to the density-dependent nature of parasite transmission parasites are generally assumed to constrain the evolution of sociality. However, evidence for a correlation between group size and parasite burden is equivocal, particularly for mammals. Host contact rates may be modified by mobility of the host and parasite as well as social barriers. In the current study, we used the common mole-rat (Cryptomys hottentotus hottentotus), a social subterranean rodent, as a model system to investigate the effect of host density and frequency of contact rates on ectoparasite burdens. To address these factors we used a study species that naturally varies in population densities and intergroup contact rates across its geographic range. We found that ectoparasite prevalence, abundance and species richness decreased with increasing host density at a regional scale. At the same time, measures of parasite burden increased with intergroup contact rates. Ectoparasite burdens decreased with colony size at the group level possibly as a result of increased grooming rates. Equating group size with population density might be too simplistic an approach when assessing parasite distributions in social mammals. Our data suggest that frequency-dependent mechanisms may play a much greater role at a population level than density-dependent mechanisms in determining parasite distributions in social species. We suggest that future studies should explicitly consider behavioural mechanisms that may affect parasite distributionNational Research Foundation (South Africa
Automatic, fast and robust characterization of noise distributions for diffusion MRI
Knowledge of the noise distribution in magnitude diffusion MRI images is the
centerpiece to quantify uncertainties arising from the acquisition process. The
use of parallel imaging methods, the number of receiver coils and imaging
filters applied by the scanner, amongst other factors, dictate the resulting
signal distribution. Accurate estimation beyond textbook Rician or noncentral
chi distributions often requires information about the acquisition process
(e.g. coils sensitivity maps or reconstruction coefficients), which is not
usually available. We introduce a new method where a change of variable
naturally gives rise to a particular form of the gamma distribution for
background signals. The first moments and maximum likelihood estimators of this
gamma distribution explicitly depend on the number of coils, making it possible
to estimate all unknown parameters using only the magnitude data. A rejection
step is used to make the method automatic and robust to artifacts. Experiments
on synthetic datasets show that the proposed method can reliably estimate both
the degrees of freedom and the standard deviation. The worst case errors range
from below 2% (spatially uniform noise) to approximately 10% (spatially
variable noise). Repeated acquisitions of in vivo datasets show that the
estimated parameters are stable and have lower variances than compared methods.Comment: v2: added publisher DOI statement, fixed text typo in appendix A
Holographic Penta and Hepta Quark State in Confining Gauge Theories
We study a new embedding solutions of D5 brane in an asymptotic
AdS space-time, which is dual to a confining gauge
theory. The D5 brane is wrapped on as in the case of the vertex of
holographic baryon. However, the solution given here is different from the
usual baryon vertex in the point that it couples to -anti-quarks and
quarks on the opposite two points of , the north and south poles,
respectively. The total quark number of this state is preserved as when
minus one is assigned to anti-quark, then it forms a color singlet like the
baryon. However, this includes anti-quarks and quarks, whose number is larger
than that of the baryon. When we set as , we find the so called penta
and hepta-quark states. We study the dynamical properties of these states by
solving the vertex and string configurations for such states. The mass spectra
of these states and the tension of the stretched vertex are estimated, and they
are compared with that of the baryon.Comment: 24 pages, 6 figure
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