Structural and dielectric studies of ferroelectric Nd2Ti2O7 for high temperature pyro sensor application

High temperature pyroelectric sensing technology is important in materials processing as well as in automotive and aerospace engineering. In aerospace it can be used as Exhaust Gas Temperature Sensor (EGTS) for hot chamber of jet engine as EGTS measures engine’s health and other sensing application. The primary requirement from the material perspective is it must be stable in high temperature range (600 to 1000° C). Ferroelectric material with high Tc (>1000°C) can be used in temperature sensing technology due to its pyroelectric properties. Neodymium Titanate (Nd2Ti2O7) is a promising candidate for this application as it has curie temperature of ~ 1480°C. NTO is a member of layered perovskite ferroelectric material. High Tc of NTO is due to the presence of dominant 180° ferroelectric domains and ferroelectric to paraelectric phase transition contains displacement of the whole sub lattice of TiO6 octahedron. In this thesis, we report the studies on synthesis of material, FullProf refinement and high temperature dielectric and pyroelectric properties of Neodymium Titanate material. Synthesis of NTO material is done by solid state reaction method. Neodymium oxide and titanium oxide is taken as primary materials in 1:2 molar ratios and the mixture is grinded with mortar and pestle for 4 hours. Phase purity is obtained by calcination of powder sample at 1250°C for 4 hours. XRD studies confirm the phase purity of neodymium titanate material. After ball milling powder is pressed to make pellet. Green pellets were sintered at 1400°C for 5 hours with a heating and cooling rates of 5°C/min. Detailed study of structural refinement was carried out by FullProf Suite software with CIF file taken from COD data base. SEM images of pellet shows densely packing of particles. Finally, dielectric property study is done by impedance analyzer instrument and furnace that goes up to 800°C. First experiment is done with applied voltage 0.8 V and data is taken during cooling from 750°C-50°C which shows the variation of dielectric constant and dielectric loss with temperature and frequency. Good curve is obtained with increasing temperature for higher frequency like 100kHz or 1kHz. For higher frequency almost no variation of dielectric viii constant and dielectric constant with temperature and that is expected as temperature range is low. Low dielectric loss for higher frequencies will be good for application. For temperature sensing application it is very important to show pyroelectricity. NTO is a ferroelectric material, so it’s must have pyroelectric property. To know its temperature sensitivity pyrocurrent measurement is done. Pellets connected with platinum wires using silver paste kept inside the furnace and wires connected to source meter unit (Keithley-2401). Current vs time data is taken with temperature ramping between 600°C to 500°C which shows exponentially increasing or decreasing current w.r.t to temperature ramping. This is called pyrocurrent. This is the evidence of pyroelectricity in NTO material for temperature sensing application

Revisiting steroidogenesis and its role in immune regulation with the advanced tools and technologies.

Historically tools and technologies facilitated scientific discoveries. Steroid hormone research is not an exception. Unfortunately, the dramatic advancement of the field faded this research area and flagged it as a solved topic. However, it should have been the opposite. The area should glitter with its strong foundation and attract next-generation scientists. Over the past century, a myriad of new facts on biochemistry, molecular biology, cell biology, physiology and pathology of the steroid hormones was discovered. Several innovations were made and translated into life-saving treatment strategies such as synthetic steroids, and inhibitors of steroidogenesis and steroid signaling. Steroid molecules exhibit their diverse effects on cell metabolism, salt and water balance, development and function of the reproductive system, pregnancy, and immune-cell function. Despite vigorous research, the molecular basis of the immunomodulatory effect of steroids is still mysterious. The recent excitement on local extra-glandular steroidogenesis in regulating inflammation and immunity is revitalizing the topic with a new perspective. Therefore, here we review the role of steroidogenesis in regulating inflammation and immunity, discuss the unresolved questions, and how this area can bring another golden age of steroid hormone research with the development of new tools and technologies and advancement of the scientific methods

Targeted mRNA degradation by complex-mediated delivery of antisense RNAs to intracellular human mitochondria

Mitochondrial dysfunction underlies a large number of acute or progressive diseases, as well as aging. However, proposed therapies for mitochondrial mutations suffer from poor transformation of mitochondria with exogenous DNA, or lack of functionality of the transferred nucleic acid within the organelle. We show that a transfer RNA import complex (RIC) from the parasitic protozoon Leishmania tropica rapidly and efficiently delivered signal-tagged antisense (STAS) RNA or DNA to mitochondria of cultured human cells. STAS-induced specific degradation of the targeted mitochondrial mRNA, with downstream effects on respiration. These results reveal the existence of a novel small RNA-mediated mRNA degradation pathway in mammalian mitochondria, and suggest that RIC-mediated delivery could be used to target therapeutic RNAs to the organelle within intact cells

An atlas of mouse CD4(+) T cell transcriptomes.

BACKGROUND: CD4(+) T cells are key regulators of the adaptive immune system and can be divided into T helper (Th) cells and regulatory T (Treg) cells. During an immune response Th cells mature from a naive state into one of several effector subtypes that exhibit distinct functions. The transcriptional mechanisms that underlie the specific functional identity of CD4(+) T cells are not fully understood. RESULTS: To assist investigations into the transcriptional identity and regulatory processes of these cells we performed mRNA-sequencing on three murine T helper subtypes (Th1, Th2 and Th17) as well as on splenic Treg cells and induced Treg (iTreg) cells. Our integrated analysis of this dataset revealed the gene expression changes associated with these related but distinct cellular identities. Each cell subtype differentially expresses a wealth of 'subtype upregulated' genes, some of which are well known whilst others promise new insights into signalling processes and transcriptional regulation. We show that hundreds of genes are regulated purely by alternative splicing to extend our knowledge of the role of post-transcriptional regulation in cell differentiation. CONCLUSIONS: This CD4(+) transcriptome atlas provides a valuable resource for the study of CD4(+) T cell populations. To facilitate its use by others, we have made the data available in an easily accessible online resource at www.th-express.org

Single-Cell RNA Sequencing Reveals a Dynamic Stromal Niche That Supports Tumor Growth

Here, using single-cell RNA sequencing, we examine the stromal compartment in murine melanoma and draining lymph nodes (LNs) at points across tumor development, providing data at http://www.teichlab.org/data/. Naive lymphocytes from LNs undergo activation and clonal expansion within the tumor, before PD1 and Lag3 expression, while tumor-associated myeloid cells promote the formation of a suppressive niche. We identify three temporally distinct stromal populations displaying unique functional signatures, conserved across mouse and human tumors. Whereas "immune" stromal cells are observed in early tumors, "contractile" cells become more prevalent at later time points. Complement component C3 is specifically expressed in the immune population. Its cleavage product C3a supports the recruitment of C3aR(+) macrophages, and perturbation of C3a and C3aR disrupts immune infiltration, slowing tumor growth. Our results highlight the power of scRNA-seq to identify complex interplays and increase stromal diversity as a tumor develops, revealing that stromal cells acquire the capacity to modulate immune landscapes from early disease.Peer reviewe

CLICK-chemoproteomics and molecular dynamics simulation reveals pregnenolone targets and their binding conformations in Th2 cells

Pregnenolone (P5) is synthesized as the first bioactive steroid in the mitochondria from cholesterol. Clusters of differentiation 4 (CD4+) and Clusters of differentiation 8 (CD8+) immune cells synthesize P5 de novo; P5, in turn, play important role in immune homeostasis and regulation. However, P5’s biochemical mode of action in immune cells is still emerging. We envisage that revealing the complete spectrum of P5 target proteins in immune cells would have multifold applications, not only in basic understanding of steroids biochemistry in immune cells but also in developing new therapeutic applications. We employed a CLICK-enabled probe to capture P5-binding proteins in live T helper cell type 2 (Th2) cells. Subsequently, using high-throughput quantitative proteomics, we identified the P5 interactome in CD4+ Th2 cells. Our study revealed P5’s mode of action in CD4+ immune cells. We identified novel proteins from mitochondrial and endoplasmic reticulum membranes to be the primary mediators of P5’s biochemistry in CD4+ and to concur with our earlier finding in CD8+ immune cells. Applying advanced computational algorithms and molecular simulations, we were able to generate near-native maps of P5–protein key molecular interactions. We showed bonds and interactions between key amino acids and P5, which revealed the importance of ionic bond, hydrophobic interactions, and water channels. We point out that our results can lead to designing of novel molecular therapeutics strategies

Induction of Transfer RNA Import Into Human Mitochondria : Implications for Correction of Genetic Disorders

A variety of clinical disorders resulted from translation defects due to the mutations in mitochondrial tRNA genes. Till date there is no therapy for these diseases. Here we tried to develop an alternative strategy for such disorders by exploiting RNA import machinery of Leishmania. Our main aim was to pool the cytocolic tRNA to the mitochondrial matrix, of which the mitochondrial cognate is mutated , by introducing RIC into the mitochondrial membrane. Here we have used MERRF (due to A8344G point mutation on mitochondrial tRNALys gene) and Kearns Sayre syndrome( due to deletion of tRNALys along with some other protein coding genes) as model disease and tested our hypothesis on patient derived cybrids homoplasmic for particular mutation. We have shown here that RIC induces import of human cytoplasmic tRNALys into human isolated mitochondria. The imported tRNA undergoes efficient aminoacylation within the organelle and supports protein synthesis. Mitochondrial translation in MERRF and KSS mitochondria , containing mutant tRNALys genes, is stimulated significantly to near wild type levels and the formation of disease specific aberrant polypeptides suppressed by RIC mediated import of human cytoplasmic tRNALys. When RIC comes in contact with the cells ,it internalized by CAV-1 dependent pathway and targeted to mitochondria. Internalisation process completed within 24 hour of RIC treatment to the cells. We found RIC treated cells import specific tRNAs which contain the import signal including tRNALys from cytosol. Such RIC induced import is able restore the lost mitochondrial membrane potential,depleted mitochondrial translation and lost Complex IV activity in MERRF cells .RIC treated MERRF cells grows normally in galactose containing media indicating restoration of lost respiratory chain. Moreover oxygen consumption rateof RIC treated MERRF cells reaches near wild type level. In KSS cell the treatment of RIC has no effect on mitochondrial function as along with tRNALys , the COII, COIII, A6 and A8 gene are also deleted. But expession of all the existing protein coding genes increases due to import of cytosolic tRNAs. We did not found any cytotoxic/apoptotic effect of RIC in cultured cells and grows normally in presence of RIC. These results suggest a novel way to introduce a heterologous tRNA import machinery for correction of disorders due to mitochondrial tRNA mutations. Here we have shown that in case of tRNALys point mutation it is effective in vitro / in live cells.. We demonstrated here that besides tRNALys some other tRNAs containing signal motif were imported, among them some are disease causing when mutated. So this approach could also be applied to other disease causing mitochondrial tRNA mutations

Editorial: Organs integrative endocrinology - the interplay between the pathways regulating endocrine organs

Peer reviewed: Tru

CLICK-chemoproteomics and molecular dynamics simulation reveals pregnenolone targets and their binding conformations in Th2 cells

Peer reviewed: TruePregnenolone (P5) is synthesized as the first bioactive steroid in the mitochondria from cholesterol. Clusters of differentiation 4 (CD4+) and Clusters of differentiation 8 (CD8+) immune cells synthesize P5 de novo; P5, in turn, play important role in immune homeostasis and regulation. However, P5’s biochemical mode of action in immune cells is still emerging. We envisage that revealing the complete spectrum of P5 target proteins in immune cells would have multifold applications, not only in basic understanding of steroids biochemistry in immune cells but also in developing new therapeutic applications. We employed a CLICK-enabled probe to capture P5-binding proteins in live T helper cell type 2 (Th2) cells. Subsequently, using high-throughput quantitative proteomics, we identified the P5 interactome in CD4+ Th2 cells. Our study revealed P5’s mode of action in CD4+ immune cells. We identified novel proteins from mitochondrial and endoplasmic reticulum membranes to be the primary mediators of P5’s biochemistry in CD4+ and to concur with our earlier finding in CD8+ immune cells. Applying advanced computational algorithms and molecular simulations, we were able to generate near-native maps of P5–protein key molecular interactions. We showed bonds and interactions between key amino acids and P5, which revealed the importance of ionic bond, hydrophobic interactions, and water channels. We point out that our results can lead to designing of novel molecular therapeutics strategies.</jats:p