2,213 research outputs found
Gli2a protein localization reveals a role for Iguana/DZIP1 in primary ciliogenesis and a dependence of Hedgehog signal transduction on primary cilia in the zebrafish
Background: In mammalian cells, the integrity of the primary cilium is critical for proper regulation of the Hedgehog (Hh) signal transduction pathway. Whether or not this dependence on the primary cilium is a universal feature of vertebrate Hedgehog signalling has remained contentious due, in part, to the apparent divergence of the intracellular transduction pathway between mammals and teleost fish.
Results: Here, using a functional Gli2-GFP fusion protein, we show that, as in mammals, the Gli2 transcription factor localizes to the primary cilia of cells in the zebrafish embryo and that this localization is modulated by the activity of the Hh pathway. Moreover, we show that the Igu/DZIP1 protein, previously implicated in the modulation of Gli activity in zebrafish, also localizes to the primary cilium and is required for its proper formation.
Conclusion: Our findings demonstrate a conserved role of the primary cilium in mediating Hedgehog signalling activity across the vertebrate phylum and validate the use of the zebrafish as a representative model for the in vivo analysis of vertebrate Hedgehog signalling
Laparoscopy-Assisted Resection of Tailgut Cysts: Report of a Case
Tailgut cysts, or retrorectal cystic hamartomas, are rare congenital developmental lesions, most commonly located in the retrorectal space, and are more common in women. We present a case of retrorectal tailgut cyst managed using a laparoscopic approach. A 36-year-old woman presented with incidentally detected retrorectal tumors during evaluation for a gallbladder polyp. Her past medical history revealed that she had undergone cesarean section twice. The tumor marker CA 19-9 level was 42.52 U/ml. CT of the pelvis with contrast and pelvic MRI revealed a 3.9 × 3.3 cm well-defined, homogeneous cystic mass in the right presacral area, and a 2.5 × 1.5 cm cystic mass in the precoccygeal space. The patient underwent laparoscopic exploration with a preoperative diagnosis of tailgut cysts based on radiological findings. The operative time was 90 min including 30 min of subsequent laparoscopic cholecystectomy without placement of additional trocars. The surgical specimens consisted of two fragments of fibrofatty tissues, unilocular cystic masses. The final pathologic diagnosis was tailgut cysts with no evidence of malignancy. Postoperative recovery was uneventful, and the patient was discharged after 3 days. In conclusion, surgical resection is recommended in the management of retrorectal tailgut cyst to establish a definite diagnosis and to rule out malignancy. The laparoscopic approach is a feasible and safe option
Exact quantum states of a general time-dependent quadratic system from classical action
A generalization of driven harmonic oscillator with time-dependent mass and
frequency, by adding total time-derivative terms to the Lagrangian, is
considered. The generalization which gives a general quadratic Hamiltonian
system does not change the classical equation of motion. Based on the
observation by Feynman and Hibbs, the propagators (kernels) of the systems are
calculated from the classical action, in terms of solutions of the classical
equation of motion: two homogeneous and one particular solutions. The kernels
are then used to find wave functions which satisfy the Schr\"{o}dinger
equation. One of the wave functions is shown to be that of a Gaussian pure
state. In every case considered, we prove that the kernel does not depend on
the way of choosing the classical solutions, while the wave functions depend on
the choice. The generalization which gives a rather complicated quadratic
Hamiltonian is simply interpreted as acting an unitary transformation to the
driven harmonic oscillator system in the Hamiltonian formulation.Comment: Submitted to Phys. Rev.
Age-related Changes in the Cellular Level of Amylase and Protein Synthesis in the Rat Parotid Gland
Age-related changes in the cellular content of secretory proteins and protein synthesis were studied in parotid glands of rats of various ages. The secretory protein content (determined by measuring the level of α-amylase activity) and the synthesis of proteins (assayed by the rate of incorporation of 3H-leucine into acid-insoluble proteins) decline with increasing age. Morphological and radioautographic studies of the gland indicate that the decline in protein synthesis is due to the reduction in the ability of secretory cells to synthesize proteins.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67245/2/10.1177_00220345810600031401.pd
Temperature dependence of the upper critical field of high-Tc superconductors from isothermal magnetization data. Influence of a temperature dependent Ginzburg-Landau parameter
We show that the scaling procedure, recently proposed for the evaluation of
the temperature variation of the normalized upper critical field of type-II
superconductors, may easily be modified in order to take into account a
possible temperature dependence of the Ginzburg-Landau parameter kappa. As an
example, we consider kappa (T) as it follows from the microscopic theory of
superconductivity.Comment: 7 pages, 4 figur
On the interpretation of the equilibrium magnetization in the mixed state of high-Tc superconductors
We apply a recently developed scaling procedure to the analysis of
equilibrium magnetization M(H) data that were obtained for T-2212 and
Bi-2212single crystals and were reported in the literature. The temperature
dependencies of the upper critical field and the magnetic field penetration
depth resulting from our analysis are distinctly different from those obtained
in the original publications. We argue that theoretical models, which are
usually employed for analyses of the equilibrium magnetization in the mixed
state of type-II superconductors are not adequate for a quantitative
description of high-Tc superconductors. In addition, we demonstrate that the
scaled equilibrium magnetization M(H) curve for a Tl-2212 sample reveals a
pronounced kink, suggesting a phase transition in the mixed state.Comment: 9 pages, 5figure
Inactivation of dispatched 1 by the chameleon mutation disrupts Hedgehog signalling in the zebrafish embryo
AbstractSearches of zebrafish EST and whole genome shotgun sequence databases for sequences encoding the sterol-sensing domain (SSD) protein motif identified two sets of DNA sequences with significant homology to the Drosophila dispatched gene required for release of secreted Hedgehog protein. Using morpholino antisense oligonucleotides, we found that inhibition of one of these genes, designated Disp1, results in a phenotype similar to that of the “you-type” mutants, previously implicated in signalling by Hedgehog proteins in the zebrafish embryo. Injection of disp1 mRNA into embryos homozygous for one such mutation, chameleon (con) results in rescue of the mutant phenotype. Radiation hybrid mapping localised disp1 to the same region of LG20 to which the con mutation was mapped by meiotic recombination analysis. Sequence analysis of disp1 cDNA derived from homozygous con mutant embryos revealed that both mutant alleles are associated with premature termination codons in the disp1 coding sequence. By analysing the expression of markers of specific cell types in the neural tube, pancreas and myotome of con mutant and Disp1 morphant embryos, we conclude that Disp1 activity is essential for the secretion of lipid-modified Hh proteins from midline structures
Determination of the threshold of the break-up of invariant tori in a class of three frequency Hamiltonian systems
We consider a class of Hamiltonians with three degrees of freedom that can be
mapped into quasi-periodically driven pendulums. The purpose of this paper is
to determine the threshold of the break-up of invariant tori with a specific
frequency vector. We apply two techniques: the frequency map analysis and
renormalization-group methods. The renormalization transformation acting on a
Hamiltonian is a canonical change of coordinates which is a combination of a
partial elimination of the irrelevant modes of the Hamiltonian and a rescaling
of phase space around the considered torus. We give numerical evidence that the
critical coupling at which the renormalization transformation starts to diverge
is the same as the value given by the frequency map analysis for the break-up
of invariant tori. Furthermore, we obtain by these methods numerical values of
the threshold of the break-up of the last invariant torus.Comment: 18 pages, 4 figure
A new non-Fermi liquid fixed point
We study a new exchange interaction in which the conduction electrons with
pseudo spin interact with the impurity spin . Due to the
overscreening of the impurity spin by higher conduction electron spin, a new
non-trivial intermediate coupling strength fixed point is realized. Using the
numerical renormalization group (NRG), we show that the low-energy spectra are
described by a non-Fermi liquid excitation spectrum. A conformal field theory
analysis is compared with NRG results and excellent agreement is obtained.
Using the double fusion rule to generate the operator spectrum with the
conformal theory, we find that the specific heat coefficient and magnetic
susceptibility will diverge as , that the scaling dimension of an
applied magnetic field is , and that exchange anisotropy is always
relevant. We discuss the possible relevance of our work to two-level system
Kondo materials and dilute cerium alloys, and we point out a paradox in
understanding the Bethe-Ansatz solutions to the multichannel Kondo model.Comment: Revised. 20 page
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