77 research outputs found
The Corticomedial Amygdala and Learning in an Agonistic Situation in the Rat
Social agonistic behaviour of intact male rats is strongly reduced by the experience of defeat by a dominant male conspecific. Small electrolytic lesions in the corticomedial amygdala strongly affected this behavioural change due to defeat. No effects of the lesions were observed before and during the defeat. Some learning is still possible in corticomedial amygdala lesioned animals. A comparison of the effects of lesions made before the defeat with lesions made after the defeat revealed that the lesions primarily produce a retention deficit in social learning.
Tetramer-based quantification of cytomegalovirus (CMV)-specific CD8+ T lymphocytes in T-cell-depleted stem cell grafts and after transplantation may identify patients at risk for progressive CMV infection
Recovery of cytomegalovirus (CMV)-specific T-cell-mediated immunity after
allogeneic hematopoietic stem cell transplantation (SCT) is critical for
protection against CMV disease. The study used fluorochrome-conjugated
tetrameric complexes of HLA-A2 molecules loaded with the immunodominant
NLVPMVATV (NLV) peptide derived from the CMV protein pp65 to quantify
A2-NLV-specific CD8+ T cells in partially T-cell-depleted grafts
administered to 27 HLA-A*0201+ patients and to monitor recovery of these T
cells during the first 12 months after SCT. None of the 9 CMV-seronegative
patients became infected with CMV, whereas 14 of 18 CMV-seropositive
patients developed CMV antigenemia after SCT. CMV-seropositive recipients
of grafts from CMV-seronegative donors required more preemptive treatment
with ganciclovir (GCV) than those of grafts from CMV-seropositive donors
(3 [1-6] versus 1 [0-3] courses, respectively; P =.009). The number of
A2-NLV-specific CD8+ T cells in the grafts correlated inversely with the
number of preemptive GCV courses administered (r = -0.61; P =.01). None of
the 9 CMV-seronegative patients mounted a CMV-specific immune response as
measured by monitoring A2-NLV-specific CD8+ T cells after SCT. Thirteen of
14 CMV-seropositive patients without CMV disease recovered these T cells.
In spite of preemptive GCV treatment, CMV disease developed in 4 patients,
who all failed to recover A2-NLV-specific CD8+ T cells after SCT (P
=.002). Thus, enumeration of HLA-restricted, CMV-specific CD8+ T cells in
the grafts and monitoring of these T cells after SCT may constitute a
rapid and sensitive tool to identify SCT recipients at risk for developing
CMV disease
Dietary diversity affects feeding behaviour of suckling piglets
Stimulating solid feed intake in suckling piglets is important to facilitate the weaning transition, exemplified by the positive correlation between pre- and post-weaning feed intake. The present study compared the effect of dietary diversity (i.e. offering two feeds simultaneously) and flavour novelty (i.e. regularly changing the flavour of one feed) on the feeding behaviour and performance of suckling piglets until weaning at day 22. It was hypothesized that presentation of the feed in a more diverse form, by varying multiple sensory properties of the feed, stimulates pre-weaning feed intake. Piglets received ad libitum feed from 2 days of age in two feeders per pen (choice feeding set-up). One group of piglets (dietary diversity (DD), n = 10 litters) were given feed A and feed B which differed in production method, size, flavour, ingredient composition and nutrient profile, smell, texture and colour. The other group of piglets (flavour novelty (FN), n = 9 litters) received feed A plus feed A to which one of 4 flavours were added from day 6 in a daily sequential order. Feeding behaviour was studied by weighing feed remains (d6, 12, 16, 22) and by live observations (4-min scan sampling, 6 h/d; d9, 14, 21; n = 6 litters per treatment). Observations were also used to discriminate âeatersâ from ânon-eatersâ. All piglets were weighed at d2, 6 and 22. Piglets did not prefer feed A (d2â22: 1.4 ± 0.16 kg/litter) over B (1.6 ± 0.18) within DD nor had a preference for feed A with (d6â22: 1.1 ± 0.06 kg/litter) or without additional flavours (0.9 ± 0.07) within FN. Nevertheless, DD-litters (d2â22: 3.0 ± 0.32 kg) ate significantly more than FN-litters (2.0 ± 0.12 kg; P = 0.02) and explored the feed 2.6 times more at d14 (P = 0.001). Furthermore feed A, the common feed provided in DD and FN, was more consumed in DD (d2â22: 1.4 ± 0.16 kg) compared to FN (1.0 ± 0.07 kg; P = 0.04). The percentage of eaters within a litter did not differ over time between DD (d9: 26%, d14: 78%, d21: 94%) and FN (20%, 71% and 97%) and no effect was found on pre-weaning weight gain. In conclusion, this study showed that provision of dietary diversity to suckling piglets stimulated their feed exploration and intake more than dietary flavour novelty only, but did not enhance the percentage of piglets within a litter that consume the feed or their growth performance. These data suggest that dietary diversity could be an innovative feeding strategy to stimulate solid feed intake in suckling piglets.</p
Polydisperse star polymer solutions
We analyze the effect of polydispersity in the arm number on the effective
interactions, structural correlations and the phase behavior of star polymers
in a good solvent. The effective interaction potential between two star
polymers with different arm numbers is derived using scaling theory. The
resulting expression is tested against monomer-resolved molecular dynamics
simulations. We find that the theoretical pair potential is in agreement with
the simulation data in a much wider polydispersity range than other proposed
potentials. We then use this pair potential as an input in a many-body theory
to investigate polydispersity effects on the structural correlations and the
phase diagram of dense star polymer solutions. In particular we find that a
polydispersity of 10%, which is typical in experimental samples, does not
significantly alter previous findings for the phase diagram of monodisperse
solutions.Comment: 14 pages, 7 figure
Effective interaction between helical bio-molecules
The effective interaction between two parallel strands of helical
bio-molecules, such as deoxyribose nucleic acids (DNA), is calculated using
computer simulations of the "primitive" model of electrolytes. In particular we
study a simple model for B-DNA incorporating explicitly its charge pattern as a
double-helix structure. The effective force and the effective torque exerted
onto the molecules depend on the central distance and on the relative
orientation. The contributions of nonlinear screening by monovalent counterions
to these forces and torques are analyzed and calculated for different salt
concentrations. As a result, we find that the sign of the force depends
sensitively on the relative orientation. For intermolecular distances smaller
than it can be both attractive and repulsive. Furthermore we report a
nonmonotonic behaviour of the effective force for increasing salt
concentration. Both features cannot be described within linear screening
theories. For large distances, on the other hand, the results agree with linear
screening theories provided the charge of the bio-molecules is suitably
renormalized.Comment: 18 pages, 18 figures included in text, 100 bibliog
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