65 research outputs found
Salivary steroid profiles in the assessment of adrenocortical function in childhood cancer survivors
A new mutation in the promoter region of the PAX8 gene causes true congenital hypothyroidism with thyroid hypoplasia in a girl with Down's syndrome
<b>Background:</b> Thyroid dysfunction is common in newborn infants with Down's syndrome (DS), but defects causing classic thyroid dysgenesis (TD) with permanent congenital hypothyroidism (CH) have not been described.<p></p>
<b>Objective:</b> We studied a girl with DS and CH who had a mutation in the promoter sequence of the PAX8 gene.<p></p>
<b>Results:</b> A female infant was found to have trisomy 21 and CH, with a venous thyrotropin (TSH) of >150 mU/L and a free thyroxine (fT4) of 15.1 pmol/L (day 12). Thyroid peroxidase antibodies and thyroglobulin antibodies were elevated. Scintigraphy showed normal uptake, but ultrasound identified a small gland with heterogenous echotexture and cystic changes. Sequence analysis of the PAX8 gene revealed a new heterozygous maternally inherited mutation (−3C>T) close to the transcription initiation site. Electromobility shift assay studies of the wild type and the mutant PAX8 sequence incubated with nuclear extracts from PCCL3 cells exhibited that the sequence at position −3 is not involved in specific protein binding. However, the mutant PAX8 promoter showed a significantly reduced transcriptional activation of a luciferase reporter gene in vitro tested in HEK, PCCL3, as well as in HeLa cells, indicating that this mutation is very likely to lead to reduced PAX8 expression.<p></p>
<b>Conclusions:</b> The persistent CH in this patient with DS is likely to be attributable to the diminished PAX8 expression due to a new heterozygous mutation in the PAX8 promoter sequence. Our case shows that true CH may occur in DS, as in the general population. Furthermore, it is possible that the trisomy 21 itself may have resulted in a more severe phenotypic expression of the PAX8 mutation in the child than the mother
Selfconsistent gauge-invariant theory of in-plane infrared response of high-Tc cuprate superconductors involving spin fluctuations
We report on results of our theoretical study of the in-plane infrared
conductivity of the high-Tc cuprate superconductors using the model where
charged planar quasiparticles are coupled to spin fluctuations. The
computations include both the renormalization of the quasiparticles and the
corresponding modification of the current-current vertex function (vertex
correction), which ensures gauge invariance of the theory and local charge
conservation in the system. The incorporation of the vertex corrections leads
to an increase of the total intraband optical spectral weight (SW) at finite
frequencies, a SW transfer from far infrared to mid infrared, a significant
reduction of the SW of the superconducting condensate, and an amplification of
characteristic features in the superconducting state spectra of the inverse
scattering rate 1/tau. We also discuss the role of selfconsistency and propose
a new interpretation of a kink occurring in the experimental low temperature
spectra of 1/tau around 1000cm^{-1}.Comment: 9 pages with 6 figures, submitted to Physical Review
Interpretation of the in-plane infrared response of the high-Tc cuprate superconductors involving spin fluctuations revisited
The in-plane infrared response of the high-Tc cuprate superconductors was
studied using the spin-fermion model, where charged quasiparticles of the
copper-oxygen planes are coupled to spin fluctuations. First, we analyzed
structures of the superconducting-state conductivity reflecting the coupling of
the quasiparticles to the resonance mode observed by neutron scattering. The
conductivity computed with the input spin susceptibility in the simple form of
the mode exhibits two prominent features: an onset of the real part of the
conductivity starting around the frequency of the mode omega_{0} and a maximum
of a related function W(omega), roughly proportional to the second derivative
of the scattering rate, centered approximately at
omega=omega_{0}+Delta_{0}/hbar, where Delta_{0} is the maximum value of the
superconducting gap. The two structures are well known from earlier studies.
Their physical meaning, however, has not been sufficiently elucidated thus far.
Our analysis involving quasiparticle spectral functions provides a clear
interpretation. Second, we explored the role played by the spin-fluctuation
continuum. Third, we investigated the temperature dependence of the
conductivity, of the intraband spectral weight, and of the effective kinetic
energy. The changes of the latter two quantities below Tc are determined by the
formation of the gap, by a feedback effect of the spin fluctuations on the
quasiparticles, and by a significant shift of the chemical potential.Comment: 20 pages, 18 figures, submitted to Physical Review
Barnase as a New Therapeutic Agent Triggering Apoptosis in Human Cancer Cells
RNases are currently studied as non-mutagenic alternatives to the harmful DNA-damaging anticancer drugs commonly used in clinical practice. Many mammalian RNases are not potent toxins due to the strong inhibition by ribonuclease inhibitor (RI) presented in the cytoplasm of mammalian cells.In search of new effective anticancer RNases we studied the effects of barnase, a ribonuclease from Bacillus amyloliquefaciens, on human cancer cells. We found that barnase is resistant to RI. In MTT cell viability assay, barnase was cytotoxic to human carcinoma cell lines with half-inhibitory concentrations (IC(50)) ranging from 0.2 to 13 microM and to leukemia cell lines with IC(50) values ranging from 2.4 to 82 microM. Also, we characterized the cytotoxic effects of barnase-based immunoRNase scFv 4D5-dibarnase, which consists of two barnase molecules serially fused to the single-chain variable fragment (scFv) of humanized antibody 4D5 that recognizes the extracellular domain of cancer marker HER2. The scFv 4D5-dibarnase specifically bound to HER2-positive cells and was internalized via receptor-mediated endocytosis. The intracellular localization of internalized scFv 4D5-dibarnase was determined by electronic microscopy. The cytotoxic effect of scFv 4D5-dibarnase on HER2-positive human ovarian carcinoma SKOV-3 cells (IC(50) = 1.8 nM) was three orders of magnitude greater than that of barnase alone. Both barnase and scFv 4D5-dibarnase induced apoptosis in SKOV-3 cells accompanied by internucleosomal chromatin fragmentation, membrane blebbing, the appearance of phosphatidylserine on the outer leaflet of the plasma membrane, and the activation of caspase-3.These results demonstrate that barnase is a potent toxic agent for targeting to cancer cells
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