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Effects of blocking developmental cell death on sexually dimorphic calbindin cell groups in the preoptic area and bed nucleus of the stria terminalis
Background: Calbindin-D28 has been used as a marker for the sexually dimorphic nucleus of the preoptic area (SDN-POA). Males have a distinct cluster of calbindin-immunoreactive (ir) cells in the medial preoptic area (CALB-SDN) that is reduced or absent in females. However, it is not clear whether the sex difference is due to the absolute number of calbindin-ir cells or to cell position (that is, spread), and the cellular mechanisms underlying the sex difference are not known. We examined the number of cells in the CALB-SDN and surrounding regions of C57Bl/6 mice and used mice lacking the pro-death gene, Bax, to test the hypothesis that observed sex differences are due to cell death. Methods: Experiment 1 compared the number of cells in the CALB-SDN and surrounding regions in adult males, females, and females injected with estradiol benzoate on the day of birth. In experiment 2, cell number in the CALB-SDN and adjacent regions were compared in wild-type and Bax knockout mice of both sexes. In addition, calbindin-ir cells were quantified within the principal nucleus of the bed nucleus of the stria terminalis (BNSTp), a nearby region that is larger in males due to Bax-dependent cell death. Results: Males had more cells in the CALB-SDN as well as in surrounding regions than did females, and estradiol treatment of females at birth masculinized both measures. Bax deletion had no effect on cell number in the CALB-SDN or surrounding regions but increased calbindin-ir cell number in the BNSTp. Conclusions: The sex difference in the CALB-SDN of mice results from an estrogen-dependent difference in cell number with no evidence found for greater spread of cells in females. Blocking Bax-dependent cell death does not prevent sex differences in calbindin-ir cell number in the BNST or CALB-SDN but increases calbindin-ir cell number in the BNSTp of both sexes
Symmetry Scheme for Amino Acid Codons
Group theoretical concepts are invoked in a specific model to explain how
only twenty amino acids occur in nature out of a possible sixty four. The
methods we use enable us to justify the occurrence of the recently discovered
twenty first amino acid selenocysteine, and also enables us to predict the
possible existence of two more, as yet undiscovered amino acids.Comment: 18 pages which include 4 figures & 3 table
The non-dynamical r-matrices of the degenerate Calogero-Moser models
A complete description of the non-dynamical r-matrices of the degenerate
Calogero-Moser models based on is presented. First the most general
momentum independent r-matrices are given for the standard Lax representation
of these systems and those r-matrices whose coordinate dependence can be gauged
away are selected. Then the constant r-matrices resulting from gauge
transformation are determined and are related to well-known r-matrices. In the
hyperbolic/trigonometric case a non-dynamical r-matrix equivalent to a
real/imaginary multiple of the Cremmer-Gervais classical r-matrix is found. In
the rational case the constant r-matrix corresponds to the antisymmetric
solution of the classical Yang-Baxter equation associated with the Frobenius
subalgebra of consisting of the matrices with vanishing last row. These
claims are consistent with previous results of Hasegawa and others, which imply
that Belavin's elliptic r-matrix and its degenerations appear in the
Calogero-Moser models. The advantages of our analysis are that it is elementary
and also clarifies the extent to which the constant r-matrix is unique in the
degenerate cases.Comment: 25 pages, LaTeX; expanded by an appendix detailing the proof of
Theorem 1 and a concluding section in version
Duality in String Cosmology
Scale factor duality, a truncated form of time dependent T-duality, is a
symmetry of string effective action in cosmological backgrounds interchanging
small and large scale factors. The symmetry suggests a cosmological scenario
("pre-big-bang") in which two duality related branches, an inflationary branch
and a decelerated branch are smoothly joined into one non-singular cosmology.
The use of scale factor duality in the analysis of the higher derivative
corrections to the effective action, and consequences for the nature of exit
transition, between the inflationary and decelerated branches, are outlined. A
new duality symmetry is obeyed by the lowest order equations for inhomogeneity
perturbations which always exist on top of the homogeneous and isotropic
background. In some cases it corresponds to a time dependent version of
S-duality, interchanging weak and strong coupling and electric and magnetic
degrees of freedom, and in most cases it corresponds to a time dependent
mixture of both S-, and T-duality.
The energy spectra obtained by using the new symmetry reproduce known results
of produced particle spectra, and can provide a useful lower bound on particle
production when our knowledge of the detailed dynamical history of the
background is approximate or incomplete.Comment: 6 pages, no figures, latex2e using ltwol2e.sty. Based on talks at the
44'th annual meeting of the Israel Physical Society, Apr 8, 1998, Rehovot,
Israel, and ICHEP98, 23-29 July, Vancouver, BC, Canada, and second conf. on
Quantum Aspects of Gauge Theories, Supersymmetry and Unification, Sept 21-26,
1998, Corfu, Greece. To be published in the proceeding
Towards a Stringy Resolution of the Cosmological Singularity
We study cosmological solutions to the low-energy effective action of
heterotic string theory including possible leading order corrections
and a potential for the dilaton. We consider the possibility that including
such stringy corrections can resolve the initial cosmological singularity.
Since the exact form of these corrections is not known the higher-derivative
terms are constructed so that they vanish when the metric is de Sitter
spacetime. The constructed terms are compatible with known restrictions from
scattering amplitude and string worldsheet beta-function calculations. Analytic
and numerical techniques are used to construct a singularity-free cosmological
solution. At late times and low-curvatures the metric is asymptotically
Minkowski and the dilaton is frozen. In the high-curvature regime the universe
enters a de Sitter phase.Comment: 6 pages, 2 Figures; minor revisions; references added; REVTeX 4;
version to appear in Phys. Rev.
Robustness of circadian clocks to daylight fluctuations: hints from the picoeucaryote Ostreococcus tauri
The development of systemic approaches in biology has put emphasis on
identifying genetic modules whose behavior can be modeled accurately so as to
gain insight into their structure and function. However most gene circuits in a
cell are under control of external signals and thus quantitative agreement
between experimental data and a mathematical model is difficult. Circadian
biology has been one notable exception: quantitative models of the internal
clock that orchestrates biological processes over the 24-hour diurnal cycle
have been constructed for a few organisms, from cyanobacteria to plants and
mammals. In most cases, a complex architecture with interlocked feedback loops
has been evidenced. Here we present first modeling results for the circadian
clock of the green unicellular alga Ostreococcus tauri. Two plant-like clock
genes have been shown to play a central role in Ostreococcus clock. We find
that their expression time profiles can be accurately reproduced by a minimal
model of a two-gene transcriptional feedback loop. Remarkably, best adjustment
of data recorded under light/dark alternation is obtained when assuming that
the oscillator is not coupled to the diurnal cycle. This suggests that coupling
to light is confined to specific time intervals and has no dynamical effect
when the oscillator is entrained by the diurnal cycle. This intringuing
property may reflect a strategy to minimize the impact of fluctuations in
daylight intensity on the core circadian oscillator, a type of perturbation
that has been rarely considered when assessing the robustness of circadian
clocks
EULAR recommendations for women's health and the management of family planning, assisted reproduction, pregnancy and menopause in patients with systemic lupus erythematosus and/or antiphospholipid syndrome.
OBJECTIVES: Develop recommendations for women's health issues and family planning in systemic lupus erythematosus (SLE) and/or antiphospholipid syndrome (APS). METHODS: Systematic review of evidence followed by modified Delphi method to compile questions, elicit expert opinions and reach consensus. RESULTS: Family planning should be discussed as early as possible after diagnosis. Most women can have successful pregnancies and measures can be taken to reduce the risks of adverse maternal or fetal outcomes. Risk stratification includes disease activity, autoantibody profile, previous vascular and pregnancy morbidity, hypertension and the use of drugs (emphasis on benefits from hydroxychloroquine and antiplatelets/anticoagulants). Hormonal contraception and menopause replacement therapy can be used in patients with stable/inactive disease and low risk of thrombosis. Fertility preservation with gonadotropin-releasing hormone analogues should be considered prior to the use of alkylating agents. Assisted reproduction techniques can be safely used in patients with stable/inactive disease; patients with positive antiphospholipid antibodies/APS should receive anticoagulation and/or low-dose aspirin. Assessment of disease activity, renal function and serological markers is important for diagnosing disease flares and monitoring for obstetrical adverse outcomes. Fetal monitoring includes Doppler ultrasonography and fetal biometry, particularly in the third trimester, to screen for placental insufficiency and small for gestational age fetuses. Screening for gynaecological malignancies is similar to the general population, with increased vigilance for cervical premalignant lesions if exposed to immunosuppressive drugs. Human papillomavirus immunisation can be used in women with stable/inactive disease. CONCLUSIONS: Recommendations for women's health issues in SLE and/or APS were developed using an evidence-based approach followed by expert consensus
Emergence of Noise-Induced Oscillations in the Central Circadian Pacemaker
Computational modeling and experimentation explain how intercellular coupling and intracellular noise can generate oscillations in a mammalian neuronal network even in the absence of cell-autonomous oscillators
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