95 research outputs found
Bronchial carcinoid in children
Bronchial carcinoids (BCs) are uncommon, slow growing, low-grade malignant neoplasm comprising 0.5-2.5% of all primary lung cancers. Although BC’s in childhood often have an endobronchial location causing airway obstruction, they are frequently misdiagnosed as benign conditions, resulting in a delay in definitive diagnosis and treatment. Lung sparing surgery should be done whenever possible, more so in children, for better quality of life and minimizing skeletal abnormality which follows pneumonectomy. We present two cases of bronchial carcinoid in young children
Large asymmetric Stark shift in GaxIn1–xAs/InP/InAsyP1–y composite quantum wells
Strong asymmetric Stark shift in excess of 115 meV of the lowest energy transition has been experimentally observed in composite Ga/sub x/In/sub 1-x/As/InP/InAs/sub y/P/sub 1-y/ quantum-well system. In this structure, we can independently control the confinement of electrons and holes by controlling the strain. The photoexcited electrons and holes are confined in spatially separated regions without the application of an electric field. Due to the large asymmetry in the structure, we observed large blueshifts and redshifts of the absorption edge with an applied electric field. All our measurements agree with the calculations within the framework of the Bir-Pikus strain Hamiltonia
Ameliorative effect of ethanolic extract of roots of Tetracera akara (Burm. f.) Merr. on D-galactosamine induced hepatotoxicity in Wistar rats by downregulation of inflammatory mediators like TNFα, COX-2 and iNOS
161-171Tetracera akara, a climbing shrub locally called Nennalvalli or Pattuvalli, is an ethnomedicinal plant used by Kani tribe of Kerala to treat chronic liver disorders and inflammatory conditions. The present study was aimed to evaluate the hepatoprotective activity of ethanolic extract of roots of Tetracera akara root on D-Galactosamine induced hepatotoxicity in Wistar rats. Hepatotoxicity was induced in Wistar rats by intraperitoneal injection of D-GalN (400 mg/kg in saline) in Wistar rats. Ethanolic extract of T. akara root (TA ETH) was administered to the experimental rats in varying doses of (50, 150 and 300 mg/kg/day), p. o. for 7 days. The hepatoprotective effect was evaluated by the estimation of biochemical markers of hepatic injury, anti-oxidant status of the liver by estimating hepatic catalase, superoxide dismutase, glutathione and malondialdehyde, gene and protein expression level of inflammatory marker genes and histopathological evaluation of experimental animals. Administration of TA ETH (150 and 300 mg/kg) significantly (P ≤0.05) restored the levels of serum bilirubin, protein and other hepatic enzymes almost comparable to the standard drug Silymarin-treated groups. The levels of antioxidant enzymes like SOD and CAT were elevated and lipid peroxidation was inhibited as evident from the reduced levels of MDA. The gene expression studies by quantitative PCR method showed that TA ETH significantly (P ≤0.05) downregulated pro inflammatory cytokines, inflammatory COX-2 genes and upregulated IL 10 gene levels in D-GalN induced liver tissue, which was further confirmed in protein estimation by ELISA method. The histopathological observations were in correlation with the biochemical findings showing the presence of normal hepatic architecture, which further evidenced the hepatoprotective effect of TA ETH. Ethanolic extract of the root of T. akara possesses significant hepatoprotective activity mainly by scavenging reactive free radicals, boosting the endogenous antioxidant system in liver and inhibiting pro-inflammatory mediator like TNF α, COX-2, iNOS and promoting the anti-inflammatory IL 10, thus substantiating the tribal claim
Host microbiome in tuberculosis: disease, treatment, and immunity perspectives
Tuberculosis (TB), an airborne pulmonary disease caused by Mycobacterium tuberculosis (M. tb), poses an unprecedented health and economic burden to most of the developing countries. Treatment of TB requires prolonged use of a cocktail of antibiotics, which often manifest several side effects, including stomach upset, nausea, and loss of appetite spurring on treatment non-compliance and the emergence of antibiotic resistant M. tb. The anti-TB treatment regimen causes imbalances in the composition of autochthonous microbiota associated with the human body, which also contributes to major side effects. The microbiota residing in the gastrointestinal tract play an important role in various physiological processes, including resistance against colonization by pathogens, boosting host immunity, and providing key metabolic functions. In TB patients, due to prolonged exposure to anti-tuberculosis drugs, the gut microbiota significantly loses its diversity and several keystone bacterial taxa. This loss may result in a significant reduction in the functional potency of the microbiota, which is a probable reason for poor treatment outcomes. In this review, we discuss the structural and functional changes of the gut microbiota during TB and its treatment. A major focus of the review is oriented to the gut microbial association with micronutrient profiles and immune cell dynamics during TB infection. Furthermore, we summarize the acquisition of anti-microbial resistance in M. tb along with the microbiome-based therapeutics to cure the infections. Understanding the relationship between these components and host susceptibility to TB disease is important to finding potential targets that may be used in TB prevention, progression, and cure
Differential Regulation of Two Arms of mTORC1 Pathway Fine-Tunes Global Protein Synthesis in Resting B Lymphocytes
Protein synthesis is tightly regulated by both gene-specific and global mechanisms to match the metabolic and proliferative demands of the cell. While the regulation of global protein synthesis in response to mitogen or stress signals is relatively well understood in multiple experimental systems, how different cell types fine-tune their basal protein synthesis rate is not known. In a previous study, we showed that resting B and T lymphocytes exhibit dramatic differences in their metabolic profile, with implications for their post-activation function. Here, we show that resting B cells, despite being quiescent, exhibit increased protein synthesis in vivo as well as ex vivo. The increased protein synthesis in B cells is driven by mTORC1, which exhibits an intermediate level of activation in these cells when compared with resting T cells and activated B cells. A comparative analysis of the transcriptome and translatome of these cells indicates that the genes encoding the MHC Class II molecules and their chaperone CD74 are highly translated in B cells. These data suggest that the translatome of B cells shows enrichment for genes associated with antigen processing and presentation. Even though the B cells exhibit higher mTORC1 levels, they prevent the translational activation of TOP mRNAs, which are mostly constituted by ribosomal proteins and other translation factors, by upregulating 4EBP1 levels. This mechanism may keep the protein synthesis machinery under check while enabling higher levels of translation in B cells
Observed anomalous upwelling in the Lakshadweep Sea during the summer monsoon season of 2005
Repeat near-fortnightly expendable bathythermograph (XBT) transects made along Kochi-Kavaratti (KK) shipping lane in the Lakshadweep Sea (LS) during 2002–2006 are examined to describe the observed year-to-year variability of upwelling during summer monsoon season (SMS). Among all the years, the upwelling characterized by up-sloping of 25°C isotherm is relatively weaker and persisted until November during SMS of 2005 and is stronger during the SMS of 2002. As a result of prolonged upwelling, the sea surface temperature has shown cooling extending into the postmonsoon season. The estimated marine pelagic fish landings along the southwest coast of India (SWCI) have also shown increase until December. The governing mechanisms both in terms of local and remote forcings are examined to explain the observed anomalous upwelling during SMS of 2005. The equatorward alongshore wind stress (WS) along the KK XBT transect persisted in a transient manner beyond September only during SMS of 2005. The westerly wind bursts over the equator during the winter of 2004–2005 are both short-lived and relatively weaker triggering weaker upwelling Kelvin waves that propagated into LS in the following SMS of 2005. The observed distribution of negative sea surface height anomaly in the LS is relatively weaker during the SMS of 2005 and lasted longer. The correlation analysis suggests that the local alongshore WS off the SWCI and the remote forcing from the southern coast of Sri Lanka has greater influence on the observed interannual variability of upwelling in the LS when compared to the remote forcing from the equator
Independent control of valence- and conduction-band states in composite quantum wells
The driving force for the rapid development of two-dimensional semiconductor structures, such as quantum wells, is their potential for various electronic and opto-electronic applications. The advent of modern epitaxial techniques allows the growth of semiconductors with a precision down to a single atomic layer. Due to the intense research in epitaxial growth, it is even possible to fabricate the quantum well structures for lattice mismatched materials as well, as long as the critical thickness is not exceeded. Under such circumstances, strain becomes an important design tool to tune the band-structure in a quantum well. This thesis focuses on type-II asymmetric composite quantum well structures in which the valence and conduction bands can be tuned independently by engineering the strain. The composite well region consists of GaxIn1-xAs and InAsyP1-y layers. These materials are chosen because of the different conduction and valence band offsets with respect to InP barrier material. The resulting potential profile is highly asymmetric and it leads to real space separation of electrons and holes in these structures even without the application of an external electric field. The electrons are confined in the InAsyP1-y part of the composite well while the holes are confined in the GaxIn1-xAs well. We have shown that adjusting the strain in the structure can control the zero field separation of electrons and holes. The strain can also modify the valence band ground-state. By putting more tension on the GaxIn1-xAs part of the composite well the valence band ground-state changes from heavy-hole to light-hole character. In a conventional type-I quantum well, the application of an external electric field pulls the electrons and holes to the opposite sides of the quantum well. This results in a red shift of the transition energy together with a decrease in absorption (Quantum confined Stark effect). However, a blue shift of the transition energy is observed, if the electric field pushes the electrons and holes close to one another. This results in an enhancement of the electron-hole overlap which leads to an increase in oscillator strength. Due to the initial electron-hole separation in our composite quantum well structures, an applied electric field can either push the carriers close to one another or pull them further away. So, depending on the direction of the applied electric field either a blue or a red Stark shift of the transition energy is observed. The blue shifting quantum well structures offer potential advantages for advanced opto-electronic systems such as self-electro-optic effect devices (SEEDs). The photocurrent measurements carried out on our composite quantum wells at 100 K shows a large asymmetric Stark shift (blue and red) of the ground-state transition energy. Due to the non-zero dipole moment present in the system, the observed Stark shift is quite linear at lower electric fields, which changes to quadratic field dependence at higher fields. A blue shift of 35 meV together with an enhancement in oscillator strength has been achieved in a "strain balanced" structure (GaxIn1-xAs under 1.3 % tension and InAsyP1-y under 1.3% compression) at an applied electric field of 106 kV/cm. We have been the first to demonstrate that a blue shift of this magnitude can be realised in III/V composite quantum wells. Such systems clearly have attractive possibilities for advanced optoelectronic devices based on the blue shifted quantum confined Stark effect. By varying the width and composition of the GaxIn1-xAs and InAsyP1-y layers, the energy of the groundstate and the degree of separation of electron and hole wave functions can be controlled. This can be used to optimise both operating wavelength and the magnitude of the blue shift for practical devices. All the measurements agree with our theoretical calculations. Our results show that one can choose material combinations with optimum confinement characteristics for the electrons and holes individually. In addition to the electric field induced blue shift, these composite wells (undoped and unbiased) also exhibit a blue shift of the transition energy with optical excitation. When the structure is illuminated the photo-created electrons and holes are accumulated in spatially separated regions. Electrons are captured in the InAsyP1-y well and holes are trapped in the GaxIn1-xAs part of the composite well. The observed blue shift of the transition energy with increase in optical excitation density is related to the build-up of photogenerated carriers causing band-structure modifications. These results were compared with the selfconsistent calculations of the band-structure incorporating the contribution of the exchange and correlation effects. This reveals that the dominant mechanism causing the optically induced blue shift is the change of the electrostatic potential due to the build-up of spatially separated electrons and holes. We have also shown that one can control over the maximum achievable blue shift by controlling the strain in the structure. The observed effect has great promise for all-optical switching applications. We have already seen that by controlling the strain one can change the character of the valence band in these composite wells. Polarisation of the luminescence collected from the cleaved side of the samples gives valuable information on the character of the valence band ground-states. Information on excited-states is also extracted by polarisation dependent photoluminescence excitation (PLE) measurements at low temperatures. These results agree with our model calculations. The low temperature photoluminescence spectrum from the "strain balanced" sample shows a side-band on the low energy side of the exciton peak. This is a longitudinal-optical (LO) phonon side-band. The presence of the LO-phonon peak in the photoluminescence spectrum suggests that the excitons are localised in the alloy fluctuations. The PLE from this sample also shows a large Stokes shift of 13.5 meV. The presence of the LO-phonon peak together with the large Stokes shift is a clear indication of exciton localisation at the quantum well plane at low temperatures. In order to probe the extent of localisation we have performed photoluminescence measurements in magnetic fields. The intensity of the photoluminescence from the "strain balanced" sample decreases up to 4 T and then saturates. The transition energy shows a quadratic diamagnetic shift. Both are indications of localisation. We have extracted the extent of localisation from the best fit to the quadratic variation of the transition energy, and found that it is approximately 7 nm. For both the lattice matched (GaxIn1-xAs lattice matched to InP) and "strain balanced" structure, the InAs0.42P0.58 part of the composite well is always under 1.3 % compression. The difference arises from the GaxIn1-xAs part of the composite well. As we change the Ga content from 0.47 to 0.67, the diamagnetic shift changes from linear to a quadratic behaviour. This clearly indicates the localisation caused in the GaxIn1-xAs part of the composite well and it increases with increase in the Ga content. For the "strain balanced" structure, the photoluminescence line shape at low temperature and excitation intensity as well as the evolution of its peak energy with temperature are characteristics of the localised excitons induced by potential fluctuations. The peak energy of the photoluminescence spectrum of this sample shows a deviation from the temperature induced bandgap modification of the quantum well materials. It shows an S-shaped temperature dependence with a blue shift of 13 meV at low temperatures. The full width at half maximum of the photoluminescence peak from this sample shows an inverted S-shaped dependence with increase in temperature. This anomalous behaviour toget with the dependence of line shape with temperature clearly indicates the presence of localised states in this structure. The estimated localisation energy is 13 meV. This value of the localisation energy is comparable to the Stokes shift of 13.5 meV observed in this sample. These results strongly support the results on localised states by PLE and magnetooptic measurements done on this system. However, this localisation does not affect the device operation at room temperature. The temperature dependent photoluminescence of the "strain balanced" sample shows that the phonon side-band is completely washed away at temperature above 100 K. This shows that there is no in-plane localisation above 100
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