1,655 research outputs found
The Effects of Cocaine on Different Redox Forms of Cysteine and Homocysteine, and on Labile, Reduced Sulfur in the Rat Plasma Following Active versus Passive Drug Injections
Received: 28 November 2012 / Revised: 19 April 2013 / Accepted: 6 May 2013 / Published online: 16 May 2013
The Author(s) 2013. This article is published with open access at Springerlink.comThe aim of the present studies was to evaluate
cocaine-induced changes in the concentrations of different
redox forms of cysteine (Cys) and homocysteine (Hcy),
and products of anaerobic Cys metabolism, i.e., labile,
reduced sulfur (LS) in the rat plasma. The above-mentioned
parameters were determined after i.p. acute and
subchronic cocaine treatment as well as following i.v.
cocaine self-administration using the yoked procedure.
Additionally, Cys, Hcy, and LS levels were measured
during the 10-day extinction training in rats that underwent
i.v. cocaine administration. Acute i.p. cocaine treatment
increased the total and protein-bound Hcy contents,
decreased LS, and did not change the concentrations of Cys
fractions in the rat plasma. In turn, subchronic i.p. cocaine administration significantly increased free Hcy and lowered
the total and protein-bound Cys concentrations while
LS level was unchanged. Cocaine self-administration
enhanced the total and protein-bound Hcy levels, decreased
LS content, and did not affect the Cys fractions. On the
other hand, yoked cocaine infusions did not alter the concentration
of Hcy fractions while decreased the total and
protein-bound Cys and LS content. This extinction training
resulted in the lack of changes in the examined parameters
in rats with a history of cocaine self-administration while in
the yoked cocaine group an increase in the plasma free Cys
fraction and LS was seen. Our results demonstrate for the
first time that cocaine does evoke significant changes in
homeostasis of thiol amino acids Cys and Hcy, and in some
products of anaerobic Cys metabolism, which are dependent
on the way of cocaine administration
Complex Adaptations Can Drive the Evolution of the Capacitor [PSI+], Even with Realistic Rates of Yeast Sex
The [PSI+] prion may enhance evolvability by revealing previously cryptic genetic variation, but it is unclear whether such evolvability properties could be favored by natural selection. Sex inhibits the evolution of other putative evolvability mechanisms, such as mutator alleles. This paper explores whether sex also prevents natural selection from favoring modifier alleles that facilitate [PSI+] formation. Sex may permit the spread of âcheaterâ alleles that acquire the benefits of [PSI+] through mating without incurring the cost of producing [PSI+] at times when it is not adaptive. Using recent quantitative estimates of the frequency of sex in Saccharomyces paradoxus, we calculate that natural selection for evolvability can drive the evolution of the [PSI+] system, so long as yeast populations occasionally require complex adaptations involving synergistic epistasis between two loci. If adaptations are always simple and require substitution at only a single locus, then the [PSI+] system is not favored by natural selection. Obligate sex might inhibit the evolution of [PSI+]-like systems in other species
Amino Acid Similarity Accounts for T Cell Cross-Reactivity and for âHolesâ in the T Cell Repertoire
Background: Cytotoxic T cell (CTL) cross-reactivity is believed to play a pivotal role in generating immune responses but the extent and mechanisms of CTL cross-reactivity remain largely unknown. Several studies suggest that CTL clones can recognize highly diverse peptides, some sharing no obvious sequence identity. The emerging realization in the field is that T cell receptors (TcR) recognize multiple distinct ligands. Principal Findings: First, we analyzed peptide scans of the HIV epitope SLFNTVATL (SFL9) and found that TCR specificity is position dependent and that biochemically similar amino acid substitutions do not drastically affect recognition. Inspired by this, we developed a general model of TCR peptide recognition using amino acid similarity matrices and found that such a model was able to predict the cross-reactivity of a diverse set of CTL epitopes. With this model, we were able to demonstrate that seemingly distinct T cell epitopes, i.e., ones with low sequence identity, are in fact more biochemically similar than expected. Additionally, an analysis of HIV immunogenicity data with our model showed that CTLs have the tendency to respond mostly to peptides that do not resemble self-antigens. Conclusions: T cell cross-reactivity can thus, to an extent greater than earlier appreciated, be explained by amino acid similarity. The results presented in this paper will help resolving some of the long-lasting discussions in the field of T cel
Trabecular bone volume and osteoprotegerin expression in uremic rats given high calcium
Calcium (Ca)-containing phosphate binders have been recommended for the treatment of hyperphosphatemia in children with chronic kidney disease. To study the effects of high Ca levels on trabecular bone volume (BV) and osteoprotegerin (OPG) expression in uremic young rats, a model of marked overcorrection of secondary hyperparathyroidism was created by providing a diet of high Ca to 5/6 nephrectomized young rats (Nx-Ca) for 4Â weeks. The results of chondrocyte proliferation and apoptosis, osteoclastic activity, OPG expression and BV were compared among intact rats given the control diet, intact rats given a high Ca diet and 5/6 nephrectomized rats given the control diet (Nx-Control) and the high Ca diet (Nx-Ca). Ionized Ca levels were higher and parathyroid hormone levels were lower in Nx-Ca rats than in the other groups. Final weight, final length and final tibial length of Nx-Ca rats were significantly less than those of the other groups, although the length gain did not differ among the groups. The hypertrophic zone width was markedly enlarged in Nx-Ca rats. Chondrocyte proliferation rates did not differ among the groups, whereas osteoclastic activity was decreased in Nx-Ca rats compared with the Nx-Control animals. The OPG expression and BV were increased in Nx-Ca rats compared with the Nx-Control rats. Increased BV should improve bone strength, whereas disturbance of osteoclastogenesis interferes with bone remodeling. Bone quality has yet to be determined in high Ca-fed uremic young rats
A search for the decay modes B+/- to h+/- tau l
We present a search for the lepton flavor violating decay modes B+/- to h+/-
tau l (h= K,pi; l= e,mu) using the BaBar data sample, which corresponds to 472
million BBbar pairs. The search uses events where one B meson is fully
reconstructed in one of several hadronic final states. Using the momenta of the
reconstructed B, h, and l candidates, we are able to fully determine the tau
four-momentum. The resulting tau candidate mass is our main discriminant
against combinatorial background. We see no evidence for B+/- to h+/- tau l
decays and set a 90% confidence level upper limit on each branching fraction at
the level of a few times 10^-5.Comment: 15 pages, 7 figures, submitted to Phys. Rev.
Observation and study of baryonic B decays: B -> D(*) p pbar, D(*) p pbar pi, and D(*) p pbar pi pi
We present a study of ten B-meson decays to a D(*), a proton-antiproton pair,
and a system of up to two pions using BaBar's data set of 455x10^6 BBbar pairs.
Four of the modes (B0bar -> D0 p anti-p, B0bar -> D*0 p anti-p, B0bar -> D+ p
anti-p pi-, B0bar -> D*+ p anti-p pi-) are studied with improved statistics
compared to previous measurements; six of the modes (B- -> D0 p anti-p pi-, B-
-> D*0 p anti-p pi-, B0bar -> D0 p anti-p pi- pi+, B0bar -> D*0 p anti-p pi-
pi+, B- -> D+ p anti-p pi- pi-, B- -> D*+ p anti-p pi- pi-) are first
observations. The branching fractions for 3- and 5-body decays are suppressed
compared to 4-body decays. Kinematic distributions for 3-body decays show
non-overlapping threshold enhancements in m(p anti-p) and m(D(*)0 p) in the
Dalitz plots. For 4-body decays, m(p pi-) mass projections show a narrow peak
with mass and full width of (1497.4 +- 3.0 +- 0.9) MeV/c2, and (47 +- 12 +- 4)
MeV/c2, respectively, where the first (second) errors are statistical
(systematic). For 5-body decays, mass projections are similar to phase space
expectations. All results are preliminary.Comment: 28 pages, 90 postscript figures, submitted to LP0
Evidence for an excess of B -> D(*) Tau Nu decays
Based on the full BaBar data sample, we report improved measurements of the
ratios R(D(*)) = B(B -> D(*) Tau Nu)/B(B -> D(*) l Nu), where l is either e or
mu. These ratios are sensitive to new physics contributions in the form of a
charged Higgs boson. We measure R(D) = 0.440 +- 0.058 +- 0.042 and R(D*) =
0.332 +- 0.024 +- 0.018, which exceed the Standard Model expectations by 2.0
sigma and 2.7 sigma, respectively. Taken together, our results disagree with
these expectations at the 3.4 sigma level. This excess cannot be explained by a
charged Higgs boson in the type II two-Higgs-doublet model. We also report the
observation of the decay B -> D Tau Nu, with a significance of 6.8 sigma.Comment: Expanded section on systematics, text corrections, improved the
format of Figure 2 and included the effect of the change of the Tau
polarization due to the charged Higg
Search for the decay modes D^0 â e^+e^-, D^0 â ÎŒ^+ÎŒ^-, and D^0 â e^±Όâ
We present searches for the rare decay modes D^0âe^+e^-, D^0âÎŒ^+ÎŒ^-, and D^0âe^±Ό^â in continuum e^+e^-âcc events recorded by the BABAR detector in a data sample that corresponds to an integrated luminosity of 468ââfb^(-1). These decays are highly GlashowâIliopoulosâMaiani suppressed but may be enhanced in several extensions of the standard model. Our observed event yields are consistent with the expected backgrounds. An excess is seen in the D^0âÎŒ^+ÎŒ^- channel, although the observed yield is consistent with an upward background fluctuation at the 5% level. Using the FeldmanâCousins method, we set the following 90% confidence level intervals on the branching fractions: B(D^0âe^+e^-)<1.7Ă10^(-7), B(D^0âÎŒ^+ÎŒ^-) within [0.6,8.1]Ă10^(-7), and B(D^0âe^±Ό^â)<3.3Ă10^(-7)
Study of the reaction e^{+}e^{-} -->J/psi\pi^{+}\pi^{-} via initial-state radiation at BaBar
We study the process with
initial-state-radiation events produced at the PEP-II asymmetric-energy
collider. The data were recorded with the BaBar detector at center-of-mass
energies 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454
. We investigate the mass
distribution in the region from 3.5 to 5.5 . Below 3.7
the signal dominates, and above 4
there is a significant peak due to the Y(4260). A fit to
the data in the range 3.74 -- 5.50 yields a mass value
(stat) (syst) and a width value (stat)(syst) for this state. We do not
confirm the report from the Belle collaboration of a broad structure at 4.01
. In addition, we investigate the system
which results from Y(4260) decay
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