Unusual weak and delayed GTPase activity of FtsZ from human pathogenic bacteria Helicobacter pylori

Actively treadmilling FtsZ acts as the pivotal scaffold for bacterial cell divisome components providing them with a circumferential ride along the site of future division. FtsZ from slow growing Helicobacter pylori (HpFtsZ), a class I carcinogen which thrives abundantly in the acidic environment is poorly understood. We studied HpFtsZ as a function of pH, cations and time and compared it with well-studied E. coli FtsZ (EcFtsZ). HpFtsZ shows pH dependent GTPase activity which is inhibited under acidic conditions. Mg+2 ions play an indispensable role in its GTPase activity, however, higher Mg+2 levels negatively affect its activity. As compared to EcFtsZ, HpFtsZ exhibits lower and slower nucleotide hydrolyzing activity. Molecular Dynamics Simulation studies of FtsZ reveal that GTP binding induces a rewiring of the hydrogen bond network which results in reduction of the binding cleft volume leading to the spontaneous release of GTP. The GTPase activity is linked to the extent of reduction in the binding cleft volume, which is also supported by the binding free energy analysis. Evidently, HpFtsZ is a pH sensitive GTPase with low efficiency that may reflect on the overall slow growth rate of H. pylori.

Genome-wide binding sites of Plasmodium falciparum mini chromosome maintenance protein MCM6 show new insights into parasite DNA replication

Multiple rounds of DNA replication take place in various stages of the life cycle in the human malaria parasite Plasmodium falciparum. Previous bioinformatics analysis has shown the presence of putative Autonomously Replicating Sequence (ARS) like sequences in the Plasmodium genome. However, the actual sites and frequency of replication origins in the P. falciparum genome based on experimental data still remain elusive. Minichromosome maintenance (MCM) proteins are recruited by the Origin recognition complex (ORC) to the origins of replication in eukaryotes including P. falciparum. We used PfMCM6 for chromatin immunoprecipitation followed by sequencing (ChIP-seq) in the quest for identification of putative replication origins in the parasite. PfMCM6 DNA binding sites annotation revealed high enrichment at exon regions. This is contrary to higher eukaryotes that show an inclination of origin sites towards transcriptional start sites. ChIP-seq results were further validated by ChIP-qPCR results as well as nascent strand abundance assay at the selected PfMCM6 enriched sites that also showed preferential binding of PfORC1 suggesting potential of these sites as origin sites. Further, PfMCM6 ChIP-seq data showed a positive correlation with previously published histone H4K8Ac genome-wide binding sites but not with H3K9Ac sites suggesting epigenetic control of replication initiation sites in the parasites. Overall, our data show the genome-wide distribution of PfMCM6 binding sites with their potential as replication origins in this deadly human pathogen that not only broadens our knowledge of parasite DNA replication and its unique biology, it may help to find new avenues for intervention processes.

Relationship between Clinical Profile, Severity and Outcome of Community Acquired Pneumonia with Hyponatremia in Children Aged 2-60 Months

Hyponatremia is the most common electrolyte imbalance seen in clinical practice and a common laboratory findings in children with community acquired pneumonia. This study aimed to find out relationship between clinical profile, severity and outcome of community acquired pneumonia with hyponatremia in children aged 2-60 months. This descriptive cross-sectional study was done in pediatrics department of Mymensingh Medical College Hospital, Bangladesh. Study period was 6 month from November 2016 to April 2017. Data were collected from 2 months to 60 months old children who fulfill the selection criteria. In this study sampling technique was purposive. Detailed history was taken, and meticulous examinations and relevant investigations were performed. 100 patients with community acquired pneumonia were enrolled, 34.0% patient had hyponatremia and 66.0% patients had no hyponatremia. Hyponatremia is more marked (45.5%) in severe pneumonia followed by moderate pneumonia (33.3%) and no hyponatremia found in mild pneumonia. Mean temperature, respiratory rate, heart rate, head nodding, nasal flaring, grunting, stridor, cyanosis, convulsion, feeding problem, Poor air entry were significantly higher in patient of pneumonia with hyponatremia when compared to patient of pneumonia without hyponatremia. Mean duration of symptoms and mean duration of hospital stay were also significantly higher in patient of pneumonia with hyponatremia. The mean serum sodium concentration was 132.18±1.51mmol/L in hyponatremic patients and 137.91±1.94mmol/L in normonatremic patients. Mean values of total leucocyte count, ESR, and C-reactive protein were significantly higher in patient of pneumonia with hyponatremia. Serum hemoglobin was significantly lower in hyponatremic patients than normonatremic patients. Maximum (55.9%) patients of community acquired pneumonia (CAP) with hyponatremia had patchy opacity, 26.5% had consolidation, 11.8% had interstitial opacity and 5.9% had pneumatocele. All the patients were treated with appropriate antibiotics and fluid and discharged after complete recovery without any complication. There was no death in the study population. From this study we can conclude that, hyponatremia is directly related with the severity of community acquired pneumonia (CAP). The intensity of clinical profile and investigation findings are also directly related with the severity of pneumonia.

Study on Blood Pressure Profile in School Children of Mymensingh City

High blood pressure and its related problems are progressively assuming public health dimensions in developing countries like Bangladesh. There was a suggestion that hypertensive process can be aborted in its early stages. But it is poorly understood in its early stages. So, early natural history of hypertension and its evolution from the youth needs to be investigated. Objective of this study was to determine blood pressure distribution in school children aged 6-15 years. This descriptive cross-sectional study was conducted in the Department of Paediatrics, Mymensingh Medical College, Mymensingh, Bangladesh from November 2014 to October 2015. The sample was collected by simple random sampling from five different schools of Mymensingh after applying inclusion and exclusion criteria. After taking proper history and doing relevant examination, both systolic and diastolic BP was recorded by auscultatory method. Out of 994 children, 480(48.29%) were boys and 514(51.71%) were girls. In boys, the mean±SD of systolic and diastolic blood pressure (BP) were 105.9±10.8 mm of Hg and 67.4±6.7 mm of Hg and in girls it was 106.1±11.8 and 67.5±6.9 mm of Hg respectively. Systolic BP was found higher in girls belongs to 10-13 years. The study has shown that BP rises linearly with age and both systolic and diastolic BP has a significant positive correlation with age, sex, height and BMI in both sexes. This study also showed, 46(4.6%) children were hypertensive and 89(8.9%) were pre-hypertensive. Hypertension was found more in girls but there was no significant difference between two sexes. Hypertension was found more in relation to overweight, obesity and family history of hypertension. Hypertension is not uncommon in children. Routine blood pressure measurement should be conducted in all children.

Comparison of Growth of School Children in Mymensingh City Area, Bangladesh Using the 2000 CDC Standards and 2007 WHO Standards

Growth assessment is an essential component of child health surveillance. The most influential tool in the growth assessment is the growth chart. Growth parameters of children are usually interpreted in relation to international standards like the NCHS/1977, CDC/2000 and WHO/2007 growth charts. This comparative study was carried out in the Department of Paediatrics, Mymensingh Medical College, Mymensingh, Bangladesh from November 2014 to October 2015 to compare the growth parameters of children using 2000 CDC standards and 2007 WHO standards. A total of five hundred healthy school children, aged 6 to 10 years were randomly selected proportionately from each class of five government primary schools from Mymensingh city area. Children with physical deformities and acutely ill and those with chronic debilitating diseases were excluded from the study. The mean and median weight, height and BMI were calculated for each age and sex. The median weight, height and BMI were then standardized by converting them to Z-scores (SD) for comparing against known reference values of 2000 CDC and 2007 WHO charts. Among 500 children, 252(50.4%) were boys and 248(49.6%) were girls. The mean age was found 8.0±1.42 years in boys and 8.04±1.42 years in girls. The mean weight was found 24.4±6.36kg in boys and 24.08±6.35kg in girls. The mean height was 125.90±10.16cm in boys and 125.38±10.74cm in girls. The mean weight, height and BMI of boys and girls were found to be lower in all age groups with compared to 2000 CDC standard and 2007 WHO standard but were closer to the WHO standards compared to the CDC standards. According to CDC and WHO in the study it was observed that underweight was found 16.3% and 14.7%, stunting 7.1% and 6.7%, overweight 6.7% and 8.7%, and obese 2.8% and 4.0% respectively in male subjects. On the other hand, in female subjects it was observed that according to CDC chart and WHO chart underweight was found 19.4% and 13.3%, stunting 6.0% and 4.8%, overweight 7.3% and 8.1% and obese 2.0% and 2.0% respectively. The findings in this study imply that growth pattern of Bangladeshi school children is closer with WHO standards and wider from CDC standards.

Efficacy of Nebulized Hypertonic Saline (3%) Versus Normal Saline and Salbutamol in Treating Acute Bronchiolitis in A Tertiary Hospital: A Randomized Controlled Trial

Acute bronchiolitis is a viral respiratory illness of infants and young children that occurs in the first two years of life. It is a major cause of hospital admissions in Bangladesh. Management of bronchiolitis is a great challenge for the pediatrician both in the outpatient and inpatient department. Because mainstay of treatment options are usually supportive like cool humidified oxygen, fluids, bronchodilators, epinephrine and corticosteroids. A number of agents have been proposed as adjunctive therapies, but their effects are controversial. Nebulized hypertonic saline (3%) has been reported to have some benefit in recent studies. So the objective of this study was to compare the efficacy of nebulized 3% hypertonic saline (HS) with salbutamol and normal saline (0.9%) nebulization in children with acute bronchiolitis. A double-blind randomized controlled trial was conducted in the Department of Paediatrics, Mymensingh Medical College Hospital, Bangladesh from November 2015 to October 2016. A total of 100 children aged one month to two years with acute bronchiolitis admitted in the Pediatric wards of MMCH were included in the study and were randomly assigned to either 3% nebulized hypertonic saline (n=50) or to 0.9% nebulized isotonic saline with salbutamol solution (n=50). The main outcome variables were clinical severity score, length of hospital stay, duration of oxygen therapy and oxygen saturation (SpO2). The therapy was repeated three times on every hospitalization day and the outcome was evaluated two times daily (12 hourly) for 60 hours. Mean duration of oxygen therapy in study group was 33.6±21.7 hours and in control group was 36.8±22.5 hours. But their difference was not statistically significant (p>0.05). The mean clinical severity score and mean oxygen saturation of the entire study patients in both groups decreased and increased respectively during hospital stay. There was significant difference of mean clinical severity score and oxygen saturation between admission and follow up-5 in each group (p<0.001). But their difference between two groups was not statistically significant (p>0.05). Mean duration of hospital stay was 2.91±1.54 days in study group and 3.09±1.85 days in control group. But their difference between two groups was not statistically significant (p>0.05). So in acute bronchiolitis nebulized hypertonic saline (3%) is as effective as normal saline (0.9%) and salbutamol nebulization.

The tetrameric structure of Plasmodium falciparum phosphoglycerate mutase is critical for optimal enzymatic activity

The glycolytic enzyme phosphoglycerate mutase (PGM) is of utmost importance for overall cellular metabolism and has emerged as a novel therapeutic target in cancer cells. This enzyme is also conserved in the rapidly proliferating malarial parasite Plasmodium falciparum, which have a similar metabolic framework as cancer cells and rely on glycolysis as the sole energy-yielding process during intraerythrocytic development. There is no redundancy among the annotated PGM enzymes in Plasmodium, and PfPGM1 is absolutely required for the parasite survival as evidenced by conditional knockdown in our study. A detailed comparison of PfPGM1 with its counterparts followed by in-depth structure-function analysis revealed unique attributes of this parasitic protein. Here, we report for the first time the importance of oligomerization for the optimal functioning of the enzyme in vivo, as earlier studies in eukaryotes only focused on the effects in vitro. We show that single point mutation of the amino acid residue W68 led to complete loss of tetramerization and diminished catalytic activity in vitro. Additionally, ectopic expression of the WT PfPGM1 protein enhanced parasite growth, whereas the monomeric form of PfPGM1 failed to provide growth advantage. Furthermore, mutation of the evolutionarily conserved residue K100 led to a drastic reduction in enzymatic activity. The indispensable nature of this parasite enzyme highlights the potential of PfPGM1 as a therapeutic target against malaria, and targeting the interfacial residues critical for oligomerization can serve as a focal point for promising drug development strategies that may not be restricted to malaria only.

Role of unique loops in oligomerization and ATPase function of Plasmodium falciparum gyrase B

DNA gyrase is an ATP dependent Type IIA topoisomerase that is unique to prokaryotes. Interestingly DNA gyrase has also been found in the apicoplasts of apicomplexan parasites like Plasmodium falciparum (Pf) the causative agent of Malaria. Gyrase B (GyrB), a subunit of gyrase A₂ B₂ complex has an N-terminal domain (GyrBN) which is endowed with ATPase activity. We reported earlier that PfGyrB exhibits ATP-independent dimerization unlike its bacterial counterparts. Here we report the role of two unique regions (L1 and L2) identified in PfGyrBN. Deletions of L1 alone (PfGyrBNΔL1), or L1 and L2 together (PfGyrBNΔL1ΔL2) have indicated that these regions may play an important role in ATPase activity and the oligomeric state of PfGyrBN. Our experiments show that the deletion of L1 region disrupts the dimer interface of PfGyrBN and reduces its ATPase activity. Further through ITC experiments we show that the binding affinity of ATP to PfGyrBN is reduced upon the deletion of L1 region. We have observed a reduction in ATPase activity for of all three proteins PfGyrBN, PfGyrBNΔL1, and PfGyrBNΔL1ΔL2 in presence of coumermycin. Our results suggests that L1 region of PfGyrBN is likely to be functionally important and may provide a unique dimer interface that affects its enzymatic activity. Since deletion of L1 region decreases the affinity of ATP to the protein, this region can be targeted toward designing novel inhibitors of ATP hydrolysis.

Magnetic ground states of Ce3TiSb5, Pr3TiSb5and Nd3TiSb5determined by neutron powder diffraction and magnetic measurements

TheR₃TiSb₅ternary compounds, withRa light rare earth (La to Sm) have been reported to crystallize with the anti-Hf₅CuSn₃-type hexagonal structure (Pearson's symbolhP18; space-groupP6₃/mcm, N. 193). An early article that reported possible superconductivity in some of these intermetallic phases (namely those withR= La, Ce, and Nd) caught our attention. In this work, we have now refined the crystal structure of theR₃TiSb₅compounds withR= Ce, Pr and Nd by Rietveld methods using high-resolution neutron powder diffraction data. The magnetic ground states of these intermetallics have been investigated by low-temperature magnetization and high-intensity neutron diffraction. We find two different magnetic transitions corresponding to two related magnetic structures atT_N1= 4.8 K (k₁= [0, 1/2, 1/8]) andT_N2= 3.4 K (k₂= [0, 0, 1/8]), respectively for Ce₃TiSb₅. However, the magnetic ordering appears to occur following a peculiar hysteresis: thek₂-type magnetic structure develops only after thek₁-type phase fraction has first slowly ordered with time and the size of the ordered Ce³⁺magnetic moment has become large enough to induce the second magnetic transition. AtT= 1.5 K the maximum amplitude of the Ce moment in the coexisting phases amounts toμ_Ce= 2.15 μ_B. For Nd₃TiSb₅an antiferromagnetic ordering belowT_N= 5.2 K into a relatively simpler commensurate magnetic structure with a magnetic moment ofμ_Nd= 2.14(3)μ_Band magnetic propagation vector ofk= [0, 0, 0], was determined. No evidence of superconductivity has been found in Nd₃TiSb₅. Finally, Pr₃TiSb₅does not show any ordering down to 1.5 K in neutron diffraction while an antiferromagnetic ground state is detected in magnetization measurements. There is no sign of magnetic contribution from Ti atoms found in any of the studied compounds.

Antibacterial action of acriflavine hydrochloride for eradication of the gastric pathogen Helicobacter pylori

Helicobacter pylori, a type 1 carcinogen, accounts for numerous gastric cancer-related deaths worldwide. Repurposing existing drugs or developing new ones for a combinatorial approach against increasing antimicrobial resistance is the need of the hour. This study highlights the efficacy of acriflavine hydrochloride (ACF-HCl) in inhibiting the growth of H. pylori reference strain and antibiotic-resistant clinical isolates at low concentrations. ACF-HCl inhibits H. pylori growth at MIC value 10 times less than that in Escherichia coli, another Gram-negative bacteria. Furthermore, ACF-HCl demonstrates synergistic effect with clarithromycin, a commonly used antibiotic against H. pylori. ACF-HCl treatment also eradicates H. pylori infection in the mice model efficiently. Our in vitro data indicate that bacterial membrane is the prime target. The novel action of ACF-HCl against antibiotic-resistant clinical isolates, synergistic effect with the conventional antibiotic clarithromycin and eradication of H. pylori from infected mice highlight the potential of ACF-HCl as a promising therapeutic agent against H. pylori by itself as well as for combinatorial therapy.

Potent in vivo antimalarial activity of water-soluble artemisinin nano-preparations

Artemisinin is a remarkable compound whose derivatives and combinations with multiple drugs have been utilized at the forefront of malaria treatment. However, the inherent issues of the parent compound such as poor bioavailability, short serum half-life, and high first-pass metabolism partially limit further applications of this drug. In this study, we enhanced the aqueous phase solubility of artemisinin by encapsulating it in two nanocarriers based on the polymer polycaprolactone (ART-PCL) and lipid-based Large Unilamellar Vesicles (ART-LIPO) respectively. Both nanoformulations exhibit in vitro parasite killing activity against Plasmodium falciparum with the ART-LIPO performing at comparable efficacy to the control drug solubilized in ethanol. These water-soluble formulations showed potent in vivo antimalarial activity as well in the mouse model of malaria at equivalent doses of the parent drug. Additionally, the artemisinin-PCL nanoformulation used in combination with either pyrimethamine or chloroquine increased the survival of the Plasmodium berghei infected mice for more than 34 days and effectively cured the mice of the infection. We highlight the potential for polymer and liposome-based nanocarriers in improving not only the aqueous phase solubility of artemisinin but also concomitantly retaining its therapeutic efficacy in vivo as well.

Synthesis of Novel Ciprofloxacin-Based Hybrid Molecules toward Potent Antimalarial Activity

Antimalarial drug resistance is a serious obstacle in the persistent quest to eradicate malaria. There is a need for potent chemical agents that are able to act on drug-resistant Plasmodium falciparum populations at reasonable concentrations without any related toxicity to the host. By rational drug design, we envisaged to address this issue by generating a novel hybrid drug possessing two pharmacophores that can act on two unique and independent targets within the cell. We synthesized a new class of ciprofloxacin-based hybrid molecules, which have been integrated with acridine, quinolone, sulphonamide, and cinnamoyl pharmacophores (1-4). We realized a potent chloroquinolone-ciprofloxacin-based antimalarial hybrid (2, CQ-CFX) whose mechanism of action is unlike that of its parent molecules indicating a unique biological target. CQ-CFX is not only potent against CQ-resistant and susceptible strains of Plasmodium falciparum at low nanomolar concentrations (IC₅₀ values are 63.17 ± 1.2 nM and 25.52 ± 4.45 nM, respectively) but is also not toxic to mammalian and bacterial systems up to 20 μM and 1 μM, respectively.

Anisotropic magnetic properties of trigonal ErAl2Ge2 single crystal

We report the anisotropic magnetic properties of the ternary compound ErAl₂Ge₂. Single crystals of this compound were grown by high temperature solution growth technique,using Al:Ge eutectic composition as flux. From the powder x-ray diffraction we confirmed that ErAl₂Ge₂ crystallizes in the trigonal CaAl₂Si₂-type crystal structure. The anisotropic magnetic properties of a single crystal were investigated by measuring the magnetic susceptibility, magnetization, heat capacity and electrical resistivity. A bulk antiferromagnetic ordering occurs around 4 K as inferred from the magnetic susceptibility and the heat capacity. The susceptibility is larger along the ab-plane and flattens out below the magnetic transition temperature ([Formula: see text]) and the magnetization in the ordered state increases more rapidly along the ab-plane than along the c-axis suggesting that the moments are inclined more towards the ab-plane. The magnetic susceptibility, magnetization and the 4f -derived part of the heat capacity in the paramagnetic regime analysed based on the point charge model of the crystalline electric field (CEF) indicate a relatively low CEF energy level splitting.

Plasmodium falciparum GCN5 acetyltransferase follows a novel proteolytic processing pathway that is essential for its function

The pathogenesis of human malarial parasite Plasmodium falciparum is interlinked with its timely control of gene expression during its complex life cycle. In this organism, gene expression is partially controlled through epigenetic mechanisms, the regulation of which is, hence, of paramount importance to the parasite. The P. falciparum (Pf)-GCN5 histone acetyltransferase (HAT), an essential enzyme, acetylates histone 3 and regulates global gene expression in the parasite. Here, we show the existence of a novel proteolytic processing for PfGCN5 that is crucial for its activity in vivo We find that a cysteine protease-like enzyme is required for the processing of PfGCN5 protein. Immunofluorescence and immuno-electron microscopy analysis suggest that the processing event occurs in the vicinity of the digestive vacuole of the parasite following its trafficking through the classical ER-Golgi secretory pathway, before it subsequently reaches the nucleus. Furthermore, blocking of PfGCN5 processing leads to the concomitant reduction of its occupancy at the gene promoters and a reduced H3K9 acetylation level at these promoters, highlighting the important correlation between the processing event and PfGCN5 activity. Altogether, our study reveals a unique processing event for a nuclear protein PfGCN5 with unforeseen role of a food vacuolar cysteine protease. This leads to a possibility of the development of new antimalarials against these targets.This article has an associated First Person interview with the first author of the paper.

Magnetostructural behavior in the non-centrosymmetric compound Nd7Pd3

A systematic study of the physical properties and microscopic magnetism of Nd₇Pd₃ compound, which in the paramagnetic state crystallizes in the non-centrosymmetric hexagonal Th₇Fe₃-type structure (hP20-P6₃ mc; with a  =  10.1367(1) Å and c  =  6.3847(1) Å at 300 K), confirms multiple magnetic ordering transitions that occur upon cooling. Antiferromagnetic transition is observed at T _N  =  37 K, which is followed by ferromagnetic transformation at T _C  =  33 K. The first-order magnetic transition at T _C is magnetoelastic: it involves a change of crystal symmetry from P6₃ mc to Cmc2₁ and leads to anisotropic changes of the unit cell parameters. While the antiferromagnetic structure is symmetry allowed in P6₃ mc, the ferromagnetic structure with magnetic moments along the a-direction of the original hexagonal unit cell induces the first order transition to Cmc2₁. Density functional theory calculations confirm the experimentally observed ground state with the a-axis as the easy magnetization direction.

Role of tyrosine residue (Y213) in nuclear retention of PCNA1 in human malaria parasite Plasmodium falciparum

Proliferating Cell Nuclear Antigen (PCNA) undergoes several post-translational modifications including phosphorylation leading to its regulation in mammalian and yeast systems. Plasmodium falciparum possesses two PCNAs (PCNA1 & PCNA2) with an edge of PfPCNA1 over PfPCNA2 for DNA replication. Recent phospho-proteome data report phosphorylation of S191 residue without its functional implication. In mammalian cells, phosphorylation of HsPCNA at Y211 stabilizes chromatin bound PCNA. We find tyrosine (but not S191) to be conserved in PfPCNAs and it is important for its nuclear localization and foci formation of PfPCNA1. Further, a Y213F mutation in PfPCNA1 leads to its functional loss both in yeast and parasite. We highlight the importance of evolutionarily conserved tyrosine in PCNA from parasite to mammal linked with DNA replication and cell proliferation.

In silico identification of inhibitors against Plasmodium falciparum histone deacetylase 1 (PfHDAC-1)

In erythrocytes, actively multiplying Plasmodium falciparum parasites exhibit a unique signature of virulence associated histone modifications, thereby epigenetically regulating the expression of the majority of genes. Histone acetylation is one such modification, effectuated and maintained by the dynamic interplay of two functionally antagonist enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). Their inhibition leads to hypo/hyperacetylation and is known to be deleterious for P. falciparum, and hence they have become attractive molecular targets to design novel antimalarials. Many compounds, including four Food and Drug Administration (FDA) approved drugs, have been developed so far to inhibit HDAC activity but are not suitable to treat malaria as they lack selectivity and cause cytotoxicity in mammalian cells. In this study, we used comparative modeling and molecular docking to establish different binding modes of nonselective and selective compounds in the PfHDAC-1 (a class I HDAC protein in P. falciparum) active site and identified the involvement of active site nonidentical residues in binding of selective compounds. Further, we have applied virtual screening with precise selection criteria and molecular dynamics simulation to identify novel potential inhibitors against PfHDAC-1. We report 20 compounds (10 from ChEMBL and 10 from analogues compound library) bearing seven scaffolds having better affinity toward PfHDAC-1. Sixteen of these compounds are known antimalarials with 14 having activity in the nanomolar range against various drug resistant and sensitive strains of P. falciparum. The cytotoxicity of these compounds against various human cell lines are reported at relatively higher concentration and hence can be used as potential PfHDAC-1 inhibitors in P. falciparum. These findings indeed show great potential for using the above molecules as prospective antimalarials.

Identification of a novel trafficking pathway exporting a replication protein, Orc2 to nucleus via classical secretory pathway in Plasmodium falciparum

Malaria parasites use an extensive secretory pathway to traffic a number of proteins within itself and beyond. In higher eukaryotes, Endoplasmic Reticulum (ER) membrane bound transcription factors such as SREBP are reported to get processed en route and migrate to nucleus under the influence of specific cues. However, a protein constitutively trafficked to the nucleus via classical secretory pathway has not been reported. Herein, we report the presence of a novel trafficking pathway in an apicomplexan, Plasmodium falciparum where a homologue of an Origin Recognition Complex 2 (Orc2) goes to the nucleus following its association with the ER. Our work highlights the unconventional role of ER in protein trafficking and reports for the first time an ORC homologue getting trafficked through such a pathway to the nucleus where it may be involved in DNA replication and other ancillary functions. Such trafficking pathways may have a profound impact on the cell biology of a malaria parasite and have significant implications in strategizing new antimalarials.

Observation of pseudogap in MgB2

We investigate the electronic structure of a specially prepared highly dense conventional high temperature superconductor, MgB₂, employing high resolution photoemission spectroscopy. The spectral evolution close to the Fermi energy is commensurate to BCS descriptions as expected. However, the spectra in the wider energy range reveal the emergence of a pseudogap much above the superconducting transition temperature indicating an apparent departure from the BCS scenario. The energy scale of the pseudogap is comparable to the energy of the [Formula: see text] phonon mode responsible for superconductivity in MgB₂ and the pseudogap can be attributed to the effect of electron-phonon coupling on the electronic structure. These results reveal a scenario of the emergence of the superconducting gap within an electron-phonon coupling induced pseudogap and have significant implications in the study of high temperature superconductors.

Identification and characterization of ARS-like sequences as putative origin(s) of replication in human malaria parasite Plasmodium falciparum

DNA replication is a fundamental process in genome maintenance, and initiates from several genomic sites (origins) in eukaryotes. In Saccharomyces cerevisiae, conserved sequences known as autonomously replicating sequences (ARSs) provide a landing pad for the origin recognition complex (ORC), leading to replication initiation. Although origins from higher eukaryotes share some common sequence features, the definitive genomic organization of these sites remains elusive. The human malaria parasite Plasmodium falciparum undergoes multiple rounds of DNA replication; therefore, control of initiation events is crucial to ensure proper replication. However, the sites of DNA replication initiation and the mechanism by which replication is initiated are poorly understood. Here, we have identified and characterized putative origins in P. falciparum by bioinformatics analyses and experimental approaches. An autocorrelation measure method was initially used to search for regions with marked fluctuation (dips) in the chromosome, which we hypothesized might contain potential origins. Indeed, S. cerevisiae ARS consensus sequences were found in dip regions. Several of these P. falciparum sequences were validated with chromatin immunoprecipitation-quantitative PCR, nascent strand abundance and a plasmid stability assay. Subsequently, the same sequences were used in yeast to confirm their potential as origins in vivo. Our results identify the presence of functional ARSs in P. falciparum and provide meaningful insights into replication origins in these deadly parasites. These data could be useful in designing transgenic vectors with improved stability for transfection in P. falciparum.

Targeting the β-clamp in Helicobacter pylori with FDA-approved drugs reveals micromolar inhibition by diflunisal

The β-clamp is the processivity-promoting factor for most of the enzymes in prokaryotic DNA replication; hence, it is a crucial drug target. In the present study, we investigated the β-clamp from Helicobacter pylori, aiming to seek potential drug molecules against this gastric-cancer-causing bacterium. An in silico screening of Food and Drug Administration (FDA) approved drugs against the H. pylori β-clamp, followed by its in vitro inhibition using a surface competition approach, yielded the drug diflunisal as a positive initial hit. Diflunisal inhibits the growth of H. pylori in the micromolar range. We determined the structure of diflunisal in complex with the β-clamp to show that the drug binds at subsite I, which is a protein-protein interaction site. Successful identification of FDA-approved molecules against H. pylori may lead to better and faster drug development.

Superconducting and charge density wave transition in single crystalline LaPt2Si2

We present results of our comprehensive studies on single crystalline LaPt₂Si₂. Pronounced anomaly in electrical resistivity and heat capacity confirms the bulk nature of superconductivity (SC) and charge density wave (CDW) transition in the single crystals. While the charge density wave transition temperature is lower, the superconducting transition temperature is higher in single crystal compared to the polycrystalline sample. This result confirms the competing nature of CDW and SC. Another important finding is the anomalous temperature dependence of upper critical field H _C2(T). We also report the anisotropy in the transport and magnetic measurements of the single crystal.

Designing novel inhibitors against histone acetyltransferase (HAT: GCN5) of Plasmodium falciparum

During active proliferation phase of intra-erythrocytic cycle, the genome of P. falciparum is regulated epigenetically and evolutionary conserved parasite-specific histone proteins are extensively acetylated. The reversible process of lysine acetylation, causing transcriptional activation and its deacetylation, causing transcriptional repression is regulated by balanced activities of HATs and HDACs. They are also known to regulate antigenic variations and gametocytic conversion in P. falciparum. These histone modifying enzymes have been identified as potential targets for development of anitmalarials in literature. PfGCN5, a HAT family member of P. falciparum is predominantly involved in H3K9 acetylation. In this study, through comparative structure and sequence analysis, we elucidate differences in the catalytic pocket of PfGCN5 which can be exploited to design selective inhibitors. Through virtual screening of known antimalarials from ChEMBL bioassay database, we mapped 10 compounds with better affinity towards PfGCN5. Further, we identified 10 more novel compounds which showed remarkably better affinity towards the Plasmodium target from analogues of mapped inhibitors from ZINC database of commercially available compounds. Comparative molecular dynamics simulation study of one of the compounds (C14) complex with PfGCN5 and HsGCN5 suggested the possible reason for its selectivity. In vitro parasite growth assay in the presence of C14 showed IC50 value at lower nanomolar range (∼ 225 nM). However, no effect in mammalian fibroblast cells was observed for C14 (up to 20 μM). Further, reduced level of HAT activity of recombinant GCN5 and H3K9Ac was observed in the parasites treated with C14. Overall, this study reports 20 potential inhibitors of PfGCN5 and experimental validation of one molecule (C14) with antimalarial activity at low nanomolar range.

Probing the magnetic ground state of single crystalline Ce3TiSb5

Motivated by the report of superconductivity in R₃TiSb₅ (R  =  La and Ce) and possibly Nd₃TiSb₅ at  ∼4 K, we grew single crystals of La₃TiSb₅ and Ce₃TiSb₅ by the high-temperature solution method using Sn as a flux. While in both compounds we observed a superconducting transition at 3.7 K for resistivity and low-field magnetization, our data conclusively show that it arose from residual Sn flux present in the single crystals. In particular, the heat capacity data do not present any of the anomalies expected from a bulk superconducting transition. The anisotropic magnetic properties of Ce₃TiSb₅, crystallizing in a hexagonal P6₃/mcm structure, were studied in detail. We find that the Ce ions in Ce₃TiSb₅ form a Kondo lattice and exhibited antiferromagnetic ordering at 5.5 K with a reduced moment and a moderately normalized Sommerfeld coefficient of 598 mJ/mol K². The characteristic single-ion Kondo energy scale was found to be  ∼8 K. The magnetization data were subjected to a crystal electric field (CEF) analysis. The experimentally observed Schottky peak in the 4f-electron heat capacity of Ce₃TiSb₅ was reproduced fairly well by the energy levels derived from the CEF analysis.

Design, Synthesis and Evaluation of Bifunctional Acridinine-Naphthalenediimide Redox-Active Conjugates as Antimalarials

A novel class of bifunctional molecules was synthesized integrating acridine (Ac) and redox-active naphthalenediimide (NDI) scaffolds directly and through a flexible linker (en). We evaluated in vitro antiplasmodial activity, physicochemical properties, and a possible mode of action. Theoretical studies suggested electronic segmentation between the electron-rich Ac and electron-deficient NDI scaffolds. Orthogonal Ac-NDI molecules showed activities in the micromolar to submicromolar range against a chloroquine (CQ)-sensitive strain of human malaria pathogen Plasmodium falciparum (maximum activity, IC₅₀: 0.419 μM). The flexible Ac-en-NDI molecules were most potent and showed activity in the nanomolar range against both CQ-sensitive (with most effective compounds, IC₅₀: 3.65 and 4.33 nM) as well as CQ-resistant (with most effective compounds, IC₅₀: 52.20 and 28.53 nM) strains of P. falciparum. Significantly, with CQ-resistant strains, the activity of the most effective compounds was 1 order of magnitude better than that of standard drug CQ. Ac-en-NDI-conjugated molecules were significantly more potent than the individual NDI and Ac-based molecules. The structure-activity relationship (SAR) suggests that the flexible spacer (en) linking the Ac and NDI scaffolds plays a vital role in exhibiting improved potency. None of the molecules triggered hemolysis in culture, and the most potent compounds did not show cytotoxicity in vitro against mammalian fibroblast NIH3T3 cells at their respective IC₅₀ values. The other significant outcome of this work is that some of the investigated molecules have the potential to affect multiple processes in the parasite including the hemozoin formation in digestive vacuoles (DVs), mitochondrial membrane potential, and the redox homeostasis of the parasite.

Posterior polar cataract: Minimizing risks

BACKGROUND

Comparing surgical outcomes of management of posterior polar cataract, a congenital cataract, which is difficult to manage surgically and has been associated with poor surgical outcomes.

METHODS

46 eyes of 38 patients with posterior polar cataract underwent phacoemulsification and PCIOL implantation.

RESULTS

In a prospective analytical study, 46 eyes of 38 patients with posterior polar cataracts underwent surgery at a zonal hospital of the armed forces. The posterior polar cataract incidence was 1.23 per 1000 with confidence interval (CI) of 0.0012. Of the 46 eyes operated, 6 had a posterior capsular rupture (PCR) (13.04%). The PCR incidence in normal cataracts is reported at approx. 1.1%, whereas, various studies have reported incidence of 6-36% in posterior polar cataracts. 41 eyes achieved a visual acuity of 6/12 or better (89.13%) and 39 eyes of 6/9 or better (84.78%). 4 patients had amblyopia (8.6%), Two patients developed macular edema (4.34%). Mean follow-up was 7 months (range 3-11 months). There was no case of nucleus drop or retinal detachment.

CONCLUSION

Posterior polar cataracts are a surgical challenge. With controlled surgery, well defined techniques, a good surgical outcome can be achieved with reduced incidence of PCR.

'Modulation of the enzymatic activities of replicative helicase (DnaB) by interaction with Hp0897: a possible mechanism for helicase loading in Helicobacter pylori'

DNA replication in Helicobacter pylori is initiated from a unique site (oriC) on its chromosome where several proteins assemble to form a functional replisome. The assembly of H. pylori replication machinery is similar to that of the model gram negative bacterium Escherichia coli except for the absence of DnaC needed to recruit the hexameric DnaB helicase at the replisome assembly site. In the absence of an obvious DnaC homologue in H. pylori, the question arises as to whether HpDnaB helicase is loaded at the Hp-replication origin by itself or is assisted by other unidentified protein(s). A high-throughput yeast two-hybrid study has revealed two proteins of unknown functions (Hp0897 and Hp0340) that interact with HpDnaB. Here we demonstrate that Hp0897 interacts with HpDnaB helicase in vitro as well as in vivo. Furthermore, the interaction stimulates the DNA binding activity of HpDnaB and modulates its adenosine triphosphate hydrolysis and helicase activities significantly. Prior complex formation of Hp0897 and HpDnaB enhances the binding/loading of DnaB onto DNA. Hp0897, along with HpDnaB, colocalizes with replication complex at initiation but does not move with the replisome during elongation. Together, these results suggest a possible role of Hp0897 in loading of HpDnaB at oriC.

Regulation of DNA replication proteins in parasitic protozoans: possible role of CDK-like kinases

Regulatory roles of CDKs in fundamental processes including cell cycle progression and transcription are well conserved in metazoans. This family of proteins has undergone significant evolutionary divergence and specialization. Several CDK-like kinases have been identified and characterized in parasitic protozoans. However, clear functional role and physiological relevance of these proteins in protozoans still remain elusive. In continuation with the recent finding that CDK-like protein PfPK5 regulates important DNA replication protein like origin recognition complex subunit 1 in Plasmodium falciparum, here we have discussed the emerging significance of CDK1/2 homologs in DNA replication of parasitic protozoans. In fact, involvement of these proteins in crucial cellular processes projects them as potential drug targets. The possibilities that CDKs offer as potential therapeutic targets in controlling parasite progression have also been explored.

Magnetic structures of R5Ni2In4 and R11Ni4In9 (R = Tb and Ho): strong hierarchy in the temperature dependence of the magnetic ordering in the multiple rare-earth sublattices

The magnetic properties and magnetic structures of the R 5Ni2In4 and the microfibrous R 11Ni4In9 compounds with R  =  Tb and Ho have been examined using magnetization, heat capacity, and neutron diffraction data. Rare earth atoms occupy three and five symmetrically inequivalent rare earth sites in R 5Ni2In4 and R 11Ni4In9 compounds, respectively. As a result of the intra- and inter-magnetic sublattice interactions, the magnetic exchange interactions are different for various rare earth sites; this leads to a cascade of magnetic transitions with a strong hierarchy in the temperature dependence of the magnetic orderings. A transition at T C  =  125 K in Tb5Ni2In4 [κ 1  =  (0, 0, 0)] leads to a ferro/ferrimagnetic order where the magnetic ordering in one of the three R-sublattices leads to the ordering of another one; the third sublattice stays non-magnetic. New magnetic Bragg peaks appearing below T N  =  20 K can be indexed with the incommensurate magnetic propagation vector κ 2  =  (0, 0.636, ½); at T N  =  20 K a cycloidal spin order, which acts mostly upon the third R-sublattice, occurs. Ho5Ni2In4 establishes first antiferromagnetism [κ  =  (0, 0, 0)] at T N  =  31 K on two R-sublattices; then the system becomes ferro/ferrimagnetic at T C  =  25 K with the third sublattice ordering as well. Tb11Ni4In9 has three magnetic transitions at T C  =  135 K, T N1  =  35 K and at T N2  =  20 K; they are respectively coupled to the appearance of different propagation vectors [κ 1  =  (0, 0, 0), κ 2  =  (0, 0, ½), κ 3  =  (0, 1, ½)], which themselves are operating differently on the five different R-sublattices. Two sublattices remain mostly ferromagnetic down to lowest temperature while the three others are predominantly coupled antiferromagnetically. In Ho11Ni4In9 a purely antiferromagnetic order, described by four different magnetic propagation vectors [κ 1  =  (0, 0.62, 0), κ 2  =  (0, 1, 0), κ 3  =  (0, 0, ½), κ 4  =  (0, 1, ½)], succeedingly includes all five different sublattices on cooling through transitions at T N1  =  22 K, T N2  =  12 K, T N3  =  8 K and T N4  =  7 K. The strength of the magnetic interactions of the different sublattices can be linked to structural details for both R 5Ni2In4 and R 11Ni4In9 compounds.

Enhanced conduction band density of states in intermetallic EuTSi3 (T = Rh, Ir)

We report on the physical properties of single crystalline EuRhSi3 and polycrystalline EuIrSi3, inferred from magnetization, electrical transport, heat capacity and (151)Eu Mössbauer spectroscopy. These previously known compounds crystallise in the tetragonal BaNiSn3-type structure. The single crystal magnetization in EuRhSi3 has a strongly anisotropic behaviour at 2 K with a spin-flop field of 13 T, and we present a model of these magnetic properties which allows the exchange constants to be determined. In both compounds, specific heat shows the presence of a cascade of two close transitions near 50 K, and the (151)Eu Mössbauer spectra demonstrate that the intermediate phase has an incommensurate amplitude modulated structure. We find anomalously large values, with respect to other members of the series, for the RKKY Néel temperature, for the spin-flop field (13 T), for the spin-wave gap (≃20-25 K) inferred from both resistivity and specific heat data, for the spin-disorder resistivity in EuIrSi3 (≃240 μΩ cm) and for the saturated hyperfine field (52 T). The enhanced values of the quantities that depend on the electronic density of states at the Fermi level, imply that the latter must be strongly enhanced in these two materials. EuIrSi3 exhibits a giant magnetoresistance ratio, with values exceeding 600% at 2 K in a field of 14 T.

Regulation of Plasmodium falciparum Origin Recognition Complex subunit 1 (PfORC1) function through phosphorylation mediated by CDK-like kinase PK5

Plasmodium falciparum Origin Recognition Complex subunit 1 (PfORC1) has been implicated in DNA replication and var gene regulation. While the C-terminus is involved in DNA replication, the specific role of N-terminus has been suggested in var gene regulation in a Sir2-dependent manner. PfORC1 is localized at the nuclear periphery, where the clustering of chromosomal ends at the early stage of parasite development may be crucial for the regulation of subtelomeric var gene expression. Upon disassembly of telomeric clusters at later stages of parasite development, ORC1 is distributed in the nucleus and parasite cytoplasm where it may be required for its other cellular functions including DNA replication. The level of ORC1 decreases dramatically at the late schizont stage. The mechanisms that mediate regulation of PfORC1 function are largely unknown. Here we show, by the use of recombinant proteins and of transgenic parasites expressing wild type or mutant forms of ORC1, that phosphorylation of the PfORC1-N terminal domain by the cyclin-dependent kinase (CDK) PfPK5 abolishes DNA-binding activity and leads to changes in subcellular localization and proteasome-mediated degradation of the protein in schizonts. These results reveal that PfORC1 phosphorylation by a CDK is central to the regulation of important biological functions like DNA replication and var gene silencing.

Attitude and Practices of Mothers on Breastfeeding Attended at a Tertiary Hospital in Bangladesh

This descriptive cross sectional study was conducted in Pediatric Out Patient Department (OPD) of Mymensingh Medical College Hospital (MMCH) from November 2013 to April 2014 to assess the knowledge and practices of the mothers about breastfeeding. Four hundred mothers having children 6 months to 2 years of age attended at OPD of MMCH for any cause were included in the study by systematic random sampling. A structured, pre-tested, interview schedule was used to collect data from mothers. All mothers were continuing to breastfeed their children. Two hundred and seventy-two (68.00%) infants received breast feeding within 1 hour after birth, while 128(32.00%) infants received breast feeding after 1 hour of birth. Of 128, in 48(37.50%) cases, mother's illness was the reason for delay in initiation of breast feeding, whereas in 70(54.69%) cases, it was due to reduced milk production on mother's statement. Pre-lacteal feeding was given in 96(24.00%) children. Among them honey was given in 24(25.00%) cases, cow's milk was given in 14(14.58%) cases, sugar water was given in 18(18.75%) cases and formula milk was given in 40(41.67%) cases. One hundred and twenty-eight (32.00%) mothers started to give their child food other than breast milk before 3 months of age and 148(37.00) mothers started to give their child food other than breast milk before 6 months of age. The reason for starting to give their child food other than breast milk before 6 months of age was mother's assumption of milk insufficiency in 166(60.14%) cases and baby's cry for hunger in 110(39.86%) cases. Formula milk was given in 120(30.00%) infants before 6 months of age. Among them 96(80.00%) mothers prepared it with larger amount of water. Plain water was given in 240(60.00%) children before the age of 6 months. One hundred and twenty-four (31.00%) children were exclusively breastfeed for first 6 months of age. Breastfeeding is almost universal in Bangladesh but the exclusive breastfeeding rate is alarmingly very low. Great emphasis is needed to educate mothers about benefits of colostrum, exclusive breastfeeding, and the harmful effects of pre-lacteal feeding.

Knowledge and practices of mothers on childhood diarrhoea and its management attended at a tertiary hospital in bangladesh

This descriptive cross sectional study was conducted in Pediatric out Patient Department (OPD) of Mymensingh Medical College Hospital (MMCH) from March 2014 to August 2014 to assess the knowledge and practices of the mothers in acute diarrhoeal diseases in children under-five years of age regarding use of oral rehydration solution (ORS), zinc, other drugs and feeding practices. Four hundred children under-five years of age having acute diarrhoea were included in the study by systematic random sampling. A structured, pretested, interviewer-administered questionnaire was used to collect data from mothers of children having diarrhoeal diseases. ORS was offered by 360(90.00%) of the mothers. Out of which 279(77.50%) used it by their own knowledge. One hundred and ninety-one (53.06%) mothers prepared it correctly, while 169(46.94%) prepared it incorrectly. Of 169, 129(35.83%) mothers used less amount of water, while 40(11.11%) mothers used much amount of water to prepare ORS. Of 360 mothers, 89(24.72%) mixed part of the content of ORS sachet at a time. Of 360 mothers, only 55(15.28%) offered correct amount of ORS after each purging. Zinc was offered in 142(35.50%) children. Of 400, only 13(3.25%) mothers used recommended home-based fluid, while 70(17.50%) mothers offered increased amount of fluid to their child. Drugs other than zinc and ORS were used in 247(61.75%) children. Among drugs, other than zinc and ORS, antibiotics was used in 109(44.13%) cases, whereas antiprotozoal in 97(39.27%) cases. Amount of liquid given was more than usual in 70(17.50%) children, same as usual in 57(14.25%) children and less than usual in 273(68.25%) children. Amount of food given was same as usual in 59(14.75%) children, while less than usual in 341(85.25%) children. Control of diarrhoeal diseases programme is successful in introducing ORS at mass level. Great emphasis is needed to educate mothers about preparation and quantity of ORS to be given to children with diarrhoeal diseases.

Potent antimalarial activity of acriflavine in vitro and in vivo

Malaria continues to be a major health problem globally. There is an urgent need to find new antimalarials. Acriflavine (ACF) is known as an antibacterial agent and more recently as an anticancer agent. Here, we report that ACF inhibits the growth of asexual stages of both chloroquine (CQ) sensitive and resistant strains of human malarial parasite, Plasmodium falciparum in vitro at nanomolar concentration. ACF clears the malaria infection in vivo from the bloodstreams of mice infected with Plasmodium berghei. Interestingly, ACF is accumulated only in the parasitized red blood cells (RBCs) and parasite specific transporters may have role in this specific drug accumulation. We further show that ACF impairs DNA replication foci formation in the parasites and affects the enzymatic activities of apicoplast specific Gyrase protein. We thus establish ACF as a potential antimalarial amidst the widespread incidences of drug resistant Plasmodium strains.

Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds: a neutron diffraction, magnetization and heat capacity study

The synthesis of the new equiatomic RScSb (R = La-Nd, Sm, Gd-Tm, Lu, Y) compounds has been recently reported. These rare earth compounds crystallize in two different crystal structures, adopting the CeScSi-type (I4/mmm) for the lighter R (La-Nd, Sm) and the CeFeSi-type (P4/nmm) structure for the heavier R (R = Gd-Tm, Lu, Y). Here we report the results of neutron diffraction, magnetization and heat capacity measurements on some of these compounds (R = Ce, Pr, Nd, Gd and Tb). Band structure calculations have also been performed on CeScSb and GdScGe (CeScSi-type), and on GdScSb and TbScSb (CeFeSi-type) to compare and understand the exchange interactions in CeScSi and CeFeSi structure types. The neutron diffraction investigation shows that all five compounds order magnetically, with the highest transition temperature of 66 K in TbScSb and the lowest of about 9 K in CeScSb. The magnetic ground state is simple ferromagnetic (τ = [0 0 0]) in CeScSb, as well in NdScSb for 32 > T > 22 K. Below 22 K a second magnetic transition, with propagation vector τ = [¼ ¼ 0], appears in NdScSb. PrScSb has a magnetic structure within, determined by mostly ferromagnetic interactions and antiferromagnetic alignment of the Pr-sites connected through the I-centering (τ = [1 0 0]). A cycloidal spiral structure with a temperature dependent propagation vector τ = [δ δ ½] is found in TbScSb. The results of magnetization and heat capacity lend support to the main conclusions derived from neutron diffraction. As inferred from a sharp peak in magnetization, GdScSb orders antiferromagnetically at 56 K. First principles calculations show lateral shift of spin split bands towards lower energy from the Fermi level as the CeScSi-type structure changes to the CeFeSi-type structure. This rigid shift may force the system to transform from exchange split ferromagnetic state to the antiferromagnetic state in RScSb compounds (as seen for example in GdScSb and TbScSb) and is proposed to explain the change-over from a ferromagnetic structure as found in the CeScSi-type compounds CeScSb and NdScSb to the antiferromagnetic state as found in TbScSb and GdScSb.

Estimate of the Coulomb correlation energy in CeAg2Ge2 from inverse photoemission and high resolution photoemission spectroscopy

The occupied and the unoccupied electronic structure of CeAg2Ge2 single crystal has been studied using high resolution photoemission and inverse photoemission spectroscopy, respectively. High resolution photoemission reveals the clear signature of Ce 4f states in the occupied electronic structure which was not observed clearly in our earlier studies. The Coulomb correlation energy in this system has been determined experimentally from the position of the 4f states above and below the Fermi level. Theoretically, the correlation energy has been determined by using the first principles density functional calculations within the generalized gradient approximations taking into account the strong intra-atomic (on-site) interaction Hubbard Ueff term. The calculated valence band shows minor changes in the spectral shape with increasing Ueff due to the fact that the density of Ce 4f state is narrow in the occupied part and is hybridized with the Ce 5d, Ag 4d and Ge 4p states. On the other hand, substantial changes are observed in the spectral shape of the calculated conduction band with increasing Ueff since the density of Ce 4f state is very large in the unoccupied part, compared to other states. The estimated value of correlation energy for CeAg2Ge2 from the experiment and the theory is ≈ 4.2 eV. The resonant photoemission data are analyzed in the framework of the single-impurity Anderson model which further confirms the presence of the Coulomb correlation energy and small hybridization in this system.

Anisotropic magnetic behavior of single crystalline CeTiGe3 and CeVGe3

We have grown the single crystals of iso-structural CeTiGe3 and CeVGe3 compounds by using Ce-Ge eutectic as flux. Using the techniques of magnetization, electrical resistivity and heat capacity, our data on single crystals reveal pronounced magnetic anisotropies in these compounds with hexagonal symmetry. The c-axis is the easy axis of magnetization in CeTiGe3 which orders ferromagnetically at 14 K, and a gap in the magnon excitation spectra of ∼ 28 K is inferred from both electrical resistivity and heat capacity. The electrical resistivity of CeTiGe3 shows anisotropic Kondo behavior and the heat capacity indicates the existence of the first excited crystal electric field split doublet lying at about ∼ 50 K. The nature of magnetic ordering changes to antiferromagnetic in CeVGe3, which undergoes a magnetic transition at TN ∼ 6 K with the a - b plane as the easy plane of magnetization. Below TN, the electrical resistivity of CeVGe3 along the c axis shows an upturn due to the opening of a gap. The 4f contribution to the resistivity ρ4f establishes that CeVGe3, like the Ti analog, is also a Kondo lattice compound. The present work on single crystals further advances our understanding of these materials based on polycrystalline samples which have been studied earlier in the literature.

Redox proteomic identification of HNE-bound mitochondrial proteins in cardiac tissues reveals a systemic effect on energy metabolism after doxorubicin treatment

Doxorubicin (DOX), one of the most effective anticancer drugs, is known to generate progressive cardiac damage, which is due, in part, to DOX-induced reactive oxygen species (ROS). The elevated ROS often induce oxidative protein modifications that result in alteration of protein functions. This study demonstrates that the level of proteins adducted by 4-hydroxy-2-nonenal (HNE), a lipid peroxidation product, is significantly increased in mouse heart mitochondria after DOX treatment. A redox proteomics method involving two-dimensional electrophoresis followed by mass spectrometry and investigation of protein databases identified several HNE-modified mitochondrial proteins, which were verified by HNE-specific immunoprecipitation in cardiac mitochondria from the DOX-treated mice. The majority of the identified proteins are related to mitochondrial energy metabolism. These include proteins in the citric acid cycle and electron transport chain. The enzymatic activities of the HNE-adducted proteins were significantly reduced in DOX-treated mice. Consistent with the decline in the function of the HNE-adducted proteins, the respiratory function of cardiac mitochondria as determined by oxygen consumption rate was also significantly reduced after DOX treatment. Treatment with Mn(III) meso-tetrakis(N-n-butoxyethylpyridinium-2-yl)porphyrin, an SOD mimic, averted the doxorubicin-induced mitochondrial dysfunctions as well as the HNE-protein adductions. Together, the results demonstrate that free radical-mediated alteration of energy metabolism is an important mechanism mediating DOX-induced cardiac injury, suggesting that metabolic intervention may represent a novel approach to preventing cardiac injury after chemotherapy.

Effects of nebulized budesonide as an adjunct to standard treatment of asthma exacerbations: a randomized, double-blind, placebo-controlled trial

This study was done to determine the effects and outcome of inhaled budesonide in addition to standard management of asthma exacerbations in pediatric age groups. A randomized, double-blind, placebo controlled trial was done in a tertiary care urban hospital. Sixty six children aged 5 to 15 years with moderate to severe asthma exacerbations were eligible. All patients received a single dose of prednisolone 1mg/kg orally as first dose of systemic corticosteroids and then salbutamol (0.15mg/kg) and ipratropium bromide (500mcg) was nebulized every 20 minutes for 3 doses and then hourly for 2 hours as a part of standard treatment of asthma exacerbations. The intervention was 2mg (4mL) of budesonide or 4mL of normal saline which was nebulized immediately after the 1st dose of nebulized salbutamol and ipratropium bromide. The baseline characteristics of the budesonide group (n=33) and placebo group (n=33) were similar, but at 1 hour, 2 hour and 3 hour PEFR, respiratory rate, pulse rate, SaO2 and asthma score were significantly improved in the budesonide group compared to placebo group (p<0.01). The positive immediate effect of nebulized budesonide added to standard treatment of asthma exacerbations is an encouraging finding for further investigations of its routine use in the treatment of asthma exacerbations in children.

EuNiGe₃, an anisotropic antiferromagnet

Single crystals of EuNiGe3, crystallizing in the non-centrosymmetric BaNiSn3-type structure, were grown using In flux, enabling us to explore the anisotropic magnetic properties, which was not possible with previously reported polycrystalline samples. The EuNiGe3 single crystalline sample is found to order antiferromagnetically at 13.2 K, as revealed from the magnetic susceptibility, heat capacity and electrical resistivity data. The low temperature magnetization M (H) is distinctly different for the field parallel to the ab-plane and c-axis; the ab-plane magnetization varies almost linearly with the field before the occurrence of an induced ferromagnetic (FM) phase (spin-flip) at 6.2 Tesla. On the other hand M (H) along the c-axis is accompanied by two metamagnetic transitions followed by a spin-flip at 4.1 T. A model including anisotropic exchange and dipole-dipole interactions reproduces the main features of magnetization plots but falls short of full representation. (H,T) phase diagrams have been constructed for the field applied along the principal directions. From the (151)Eu Mössbauer spectra, we determine that the 13.2 K transition leads to an incommensurate antiferromagnetic (AFM) intermediate phase followed by a transition near 10.5 K to a commensurate AFM configuration.

Anisotropic magnetic properties and crystal electric field studies on CePd2Ge2 single crystal

The anisotropic magnetic properties of the antiferromagnetic compound CePd2Ge2, crystallizing in the tetragonal crystal structure have been investigated in detail on a single crystal grown by the Czochralski method. From the electrical transport, magnetization and heat capacity data, the Néel temperature is confirmed to be 5.1 K. Anisotropic behaviour of the magnetization and resistivity is observed along the two principal crystallographic directions-namely, [100] and [001]. The isothermal magnetization measured in the magnetically ordered state at 2 K exhibits a spin reorientation at 13.5 T for the field applied along the [100] direction, whereas the magnetization is linear along the [001] direction attaining a value of 0.94 μ(B)/Ce at 14 T. The reduced value of the magnetization is attributed to the crystalline electric field (CEF) effects. A sharp jump in the specific heat at the magnetic ordering temperature is observed. After subtracting the phononic contribution, the jump in the heat capacity amounts to 12.5 J K(-1)mol(-1) which is the expected value for a spin ½ system. From the CEF analysis of the magnetization data the excited crystal field split energy levels were estimated to be at 120 K and 230 K respectively, which quantitatively explains the observed Schottky anomaly in the heat capacity. A magnetic phase diagram has been constructed based on the field dependence of magnetic susceptibility and the heat capacity data.

Electronic structure of EuFe2As2

Employing high resolution photoemission spectroscopy, we studied the temperature evolution of the electronic structure of EuFe2As2, a unique pnictide, where antiferromagnetism of the Eu layer survives within the superconducting phase due to 'FeAs' layers, achieved via substitution and/or pressure. High energy and angle resolution helped to reveal the signature of peak-dip features, having significant p orbital character and spin density wave transition induced band folding in the electronic structure. A significant spectral weight redistribution is observed below 20 K manifesting the influence of antiferromagnetic order on the conduction electrons.

Plasmodium falciparum: epigenetic control of var gene regulation and disease

Plasmodium falciparum, one of the deadliest parasites on earth causes human malaria resulting one million deaths annually. Central to the parasite pathogenicity and morbidity is the switching of parasite virulence (var) gene expression causing host immune evasion. The regulation of Plasmodium var gene expression is poorly understood. The complex life cycle of Plasmodium and mutually exclusive expression pattern of var genes make this disease difficult to control. Recent studies have demonstrated the pivotal role of epigenetic mechanism for control of coordinated expression of var genes, important for various clinical manifestations of malaria. In this review, we discuss about different Plasmodium histones and their various modifications important for gene expression and gene repression.Contribution of epigenetic mechanism to understand the var gene expression is also highlighted. We also describe in details P. falciparum nuclear architecture including heterochromatin, euchromatin and telomeric regions and their importance in subtelomeric and centrally located var gene expression. Finally, we explore the possibility of using Histone Acetyl Transferase (HAT) and Histone Deacetylase (HDAC)inhibitors against multi-drug resistance malaria parasites to provide another line of treatment for malaria.

Antiferro- and ferromagnetic ordering in a PrGe single crystal

An equiatomic PrGe single crystal was grown by the Czochralski pulling method. The grown single crystal was found to have CrB-type orthorhombic crystal structure with the space group Cmcm (no. 63). Transport and magnetization data reveal large anisotropy in the electrical resistivity, magnetic susceptibility and magnetization. PrGe was found to exhibit two consecutive magnetic orderings at 44 K and 41.5 K, respectively. The magnetic susceptibility measurement along the three principal directions in low applied fields revealed a cusp-like behaviour at 44 K while at 41.5 K a ferromagnetic-like increase was observed. The hysteretic behaviour in the magnetization measurement at 1.8 K confirmed the ferromagnetic nature of PrGe at low temperatures. The heat capacity data clearly revealed the bulk nature of two magnetic transitions by the presence of two sharp peaks attaining values exceeding 40 J K(-1) mol(-1) at the respective temperatures. The absence of a Schottky contribution in the magnetic part of the heat capacity indicates a quasi-ninefold degenerate J = 4 magnetic ground state in this system. The low temperature data of electrical resistivity and the magnetic part of the heat capacity show the existence of a gap in the spin-wave spectrum.

Anisotropic magnetic properties and superzone gap formation in CeGe single crystal

Single crystals of CeGe and its non-magnetic analog LaGe have been grown by the Czochralski method. The CeGe compound crystallizes in the orthorhombic FeB-type crystal structure with the space group Pnma (#62). The anisotropic magnetic properties have been investigated for well oriented single crystals by measuring the magnetic susceptibility, electrical resistivity and heat capacity. It has been found that CeGe orders antiferromagnetically at 10.5 K. Both transport and magnetic studies have revealed large anisotropy, reflecting the orthorhombic crystal structure. The magnetization data at 1.8 K reveal metamagnetic transitions along the [010] direction at 4.8 and 6.4 T and along the [100] direction at a critical field of 10.7 T, while the magnetization along the [001] direction increases linearly without any anomaly up to a field of 16 T. From the magnetic susceptibility and the magnetization measurements it has been found that the [010] direction is the easy axis of magnetization. The electrical resistivity along the three crystallographic directions exhibits an upturn at T(N), indicating superzone gap formation below T(N) in this compound. We have performed crystal electric field analysis on the magnetic susceptibility and the heat capacity data and found that the ground state is a doublet, and the energies of splitting from the ground state to the first and second excited doublet states were estimated to be 39 and 111 K, respectively.

The role of N-terminus of Plasmodium falciparum ORC1 in telomeric localization and var gene silencing

Plasmodium falciparum origin recognition complex 1 (ORC1) protein has been implicated in DNA replication and silencing var gene family. However, the mechanism and the domain structure of ORC1 related to the regulation of var gene family are unknown. Here we show that the unique N-terminus of PfORC1 (PfORC1N_1–238) is targeted to the nuclear periphery in vivo and this region binds to the telomeric DNA in vitro due to the presence of a leucine heptad repeats. Like PfORC1N_1–238, endogenous full length ORC1, was found to be associated with sub telomeric repeat regions and promoters of various var genes. Additionally, binding and propagation of ORC1 to telomeric and subtelomeric regions was severely compromised in PfSir2 deficient parasites suggesting the dependence of endogenous ORC1 on Sir2 for var gene regulation. This feature is not previously described for Plasmodium ORC1 and contrary to yeast Saccharomyces cerevisiae where ORC function as a landing pad for Sir proteins. Interestingly, the overexpression of ORC1N_1–238 compromises the binding of Sir2 at the subtelomeric loci and var gene promoters consistent with de-repression of some var genes. These results establish role of the N-terminus of PfORC1 in heterochromatin formation and regulation of var gene expression in co-ordination with Sir2 in P. falciparum.

Antiferromagnetic ordering in EuPtGe3

The magnetic properties of single crystalline EuPtGe(3), crystallizing in the non-centrosymmetric BaNiSn(3)-type crystal structure, have been studied by means of magnetization, electrical resistivity, heat capacity and (151)Eu Mössbauer spectroscopy. The susceptibility and heat capacity data indicate a magnetic transition at T(N) = 11 K. The Mössbauer data confirm this conclusion, but evidence a slight first-order character of the transition. Analysing the magnetization data using a mean field model with two antiferromagnetically coupled sublattices allows us to explain some aspects of the magnetic behaviour, and to derive the first- and second-neighbour exchange integrals in EuPtGe(3).

Manganese superoxide dismutase is a mitochondrial fidelity protein that protects Polγ against UV-induced inactivation

Manganese superoxide dismutase is a nuclear encoded primary antioxidant enzyme localized exclusively in the mitochondrial matrix. Genotoxic agents, such as ultraviolet (UV) radiation, generates oxidative stress and cause mitochondrial DNA (mtDNA) damage. The mtDNA polymerase (Polγ), a major constituent of nucleoids, is responsible for the replication and repair of the mitochondrial genome. Recent studies suggest that the mitochondria contain fidelity proteins and MnSOD constitutes an integral part of the nucleoid complex. However, it is not known whether or how MnSOD participates in the mitochondrial repair processes. Using skin tissue from C57BL/6 mice exposed to UVB radiation, we demonstrate that MnSOD has a critical role in preventing mtDNA damage by protecting the function of Polγ. Quantitative-PCR analysis shows an increase in mtDNA damage after UVB exposure. Immunofluorescence and immunoblotting studies demonstrate p53 translocation to the mitochondria and interaction with Polγ after UVB exposure. The mtDNA immunoprecipitation assay with Polγ and p53 antibodies in p53(+/+) and p53(-/-) mice demonstrates an interaction between MnSOD, p53 and Polγ. The results suggest that these proteins form a complex for the repair of UVB-associated mtDNA damage. The data also demonstrate that UVB exposure injures the mtDNA D-loop in a p53-dependent manner. Using MnSOD-deficient mice we demonstrate that UVB-induced mtDNA damage is MnSOD dependent. Exposure to UVB results in nitration and inactivation of Polγ, which is prevented by addition of the MnSOD mimetic Mn(III)TE-2-PyP(5+). These results demonstrate for the first time that MnSOD is a fidelity protein that maintains the activity of Polγ by preventing UVB-induced nitration and inactivation of Polγ. The data also demonstrate that MnSOD has a role along with p53 to prevent mtDNA damage.