Mycobacterial glycolipids: pathways to synthesis and role in virulence

Mycobacterial diseases are responsible for numerous deaths worldwide, the major pathogens being Mycobacterium tuberculosis and Mycobacterium leprae. Also, in recent years threats from opportunistic pathogens, such as Mycobacterium marinum and Mycobacterium kansasii have been on the rise. These mycobacteria possess a unique lipid-rich cell wall with an array of mycolic acids and species-specific antigenic glycolipids, like the lipooligosaccharides. Some of these solvent extractable lipids possess immunomodulatory properties and play an important role during infection. Lipooligosaccharides (LOS) are surface exposed, polar, antigenic glycolipids that are present in several mycobacterial species. This study used the opportunistic human pathogens M. marinum and M. kansasii as a model system to unravel the genes involved in the biosynthesis of LOSs in Mycobacterium. Using directed mutagenesis and transposon mutagenesis, mutant strains defective in various parts of the LOS biosynthetic pathway were isolated. Analysis of these strains helped in further delineating the pathway and understanding the role of LOSs in virulence. A part of this thesis focussed on studying mycolic acid processing and transport using Mycobacterium smegmatis as a surrogate system. Mycolic acids are the most distinctive components of the mycobacterial cell wall. While their biosynthesis has been studied in detail, processing and transport across the membrane is not well understood. This study attempted to explore the roles of the two putative type II mycolyltransferases MSMEG3437 and MSMEG5851 in mycolic acid processing. Additionally, the role of M. tuberculosis mmpL11 gene was probed as the Mtb-mmpL11 had been reported to be involved in virulence. A null ii mutant of the M. smegmatis homologue, Ms-mmpL11 (MSMEG0241) was generated and analysed for the above study. Deletion mutant strains of the two putative mycolyltransferase II did not show any phenotype, suggesting that their roles are redundant in vivo. Although the Ms-mmpL gene was found to be non-essential, it was found to be involved in transport of free mycolic acids

Unleashing the Power of Differential Fault Attacks on QARMAv2

QARMAv2 represents a family of lightweight block ciphers introduced in ToSC 2023. This new iteration, QARMAv2, is an evolution of the original QARMA design, specifically constructed to accommodate more extended tweak values while simultaneously enhancing security measures. This family of ciphers is available in two distinct versions, referred to as QARMAv2-$b$-$s$, where ‘$b$’ signifies the block length, with options for both 64-bit and 128-bit blocks, and ‘$c$’ signifies the key length. In this paper, for the first time, we present differential fault analysis (DFA) of all the QARMAv2 variants- QARMAv2-64, and QARMAv2-128 by introducing an approach to utilize the fault propagation patterns at the nibble level, with the goal of identifying relevant faulty ciphertexts and vulnerable fault positions. This technique highlights a substantial security risk for the practical implementation of QARMAv2. By strategically introducing six random nibble faults into the input of the $(r − 1)$-th and $(r − 2)$-th backward rounds within the $r$-round QARMAv2-64, our attack achieves a significant reduction in the secret key space, diminishing it from the expansive $2^{128}$ to a significantly more smaller set of size $2^{32}$. Additionally, when targeting QARMAv2-128-128, it demands the introduction of six random nibble faults to effectively reduce the secret key space from $2^{128}$ to a remarkably reduced $2^{24}$. To conclude, we also explore the potential extension of our methods to conduct DFA on various other iterations and adaptations of the QARMAv2 cryptographic scheme. To the best of our knowledge, this marks the first instance of a differential fault attack targeting the QARMAv2 tweakable block cipher family, signifying an important direction in cryptographic analysis

Formulation Development to Enhance the Solubility of Metoclopramide Base Drug by Solid Dispersion and Evaluation of Transdermal Film

Aims & Objectives: The present work deals with the modification of controlled release dosage form of poorly water soluble drug (Metoclopramide hydrochloride) in order to improve the bioavailability and to control drug release for a longer period of time by the aid of solid dispersion. Methods: Various binary combination of MET-solid dispersion was prepared with different carriers such as HPβCD, PVP K30 and PLX-188 by solvent evaporation technique and then the aqueous solubility, dissolution study and phase solubility study was performed. DSC analysis is performed to carry out for metoclopramide loaded solid dispersion, physical mixture & also for pure drug to analyze the crystalline and amorphous nature of compounds. Results and Discussion:  The saturation solubility of Metoclopramide with various carriers at different pH was performed and found that in pH 5.5 (solubility is 5553.2µg/ml), pH 6.8 (3363.3µ/ml), pH 7.4 (1367.3µg/ml) at 37oC. In dissolution study of solid dispersion (5:1) of different carriers in DDW, the Cumulative % dissolution is found in the order of PVP K30>PLX-Met>HPβCD-Met & in pH 7.4, in the order of PLX-Met>PVP K30>HPβCD-Met. DSC thermogram of Metoclopramide base showed a sharp endothermic peak at its melting point (147oC) which exhibits in crystalline form complying with that of Metoclopramide hydrochloride form, melting point was found to be 850C.  In the ex-vivo study of several transdermal patches, patch C [SD of MET: HPβCD (1:5)] showed the controlled release and permeation of drug. Conclusion: Poor solubility of new chemical entities being a well known problem for past few decades despite the imbalance between significant research efforts & few successful marketed formulations, the solid dispersion proves to hold a key position among all the various formulation strategies to enhance the aqueous solubility & dissolution rate and thereby the bioavailability of  poorly aqueous solubility of drug. Keywords: Bioavailability,DSC, Metoclopramide hydrochloride, solid dispersion, HPβCD

Constitutively-stressed yeast strains are high-yielding for recombinant Fps1:implications for the translational regulation of an aquaporin

Background: We previously selected four strains of Saccharomyces cerevisiae for their ability to produce the aquaporin Fps1 in sufficient yield for further study. Yields from the yeast strains spt3Δ, srb5Δ, gcn5Δ and yTHCBMS1 (supplemented with 0.5 μg/mL doxycycline) that had been transformed with an expression plasmid containing 249 base pairs of 5′ untranslated region (UTR) in addition to the primary FPS1 open reading frame (ORF) were 10–80 times higher than yields from wild-type cells expressing the same plasmid. One of the strains increased recombinant yields of the G protein-coupled receptor adenosine receptor 2a (A2aR) and soluble green fluorescent protein (GFP). The specific molecular mechanisms underpinning a high-yielding Fps1 phenotype remained incompletely described. Results: Polysome profiling experiments were used to analyze the translational state of spt3Δ, srb5Δ, gcn5Δ and yTHCBMS1 (supplemented with 0.5 μg/mL doxycycline); all but gcn5Δ were found to exhibit a clear block in translation initiation. Four additional strains with known initiation blocks (rpl31aΔ, rpl22aΔ, ssf1Δ and nop1Δ) also improved the yield of recombinant Fps1 compared to wild-type. Expression of the eukaryotic transcriptional activator GCN4 was increased in spt3Δ, srb5Δ, gcn5Δ and yTHCBMS1 (supplemented with 0.5 μg/mL doxycycline); these four strains also exhibited constitutive phosphorylation of the eukaryotic initiation factor, eIF2α. Both responses are indicative of a constitutively-stressed phenotype. Investigation of the 5′UTR of FPS1 in the expression construct revealed two untranslated ORFs (uORF1 and uORF2) upstream of the primary ORF. Deletion of either uORF1 or uORF1 and uORF2 further improved recombinant yields in our four strains; the highest yields of the uORF deletions were obtained from wild-type cells. Frame-shifting the stop codon of the native uORF (uORF2) so that it extended into the FPS1 ORF did not substantially alter Fps1 yields in spt3Δ or wild-type cells, suggesting that high-yielding strains are able to bypass 5′uORFs in the FPS1 gene via leaky scanning, which is a known stress-response mechanism. Yields of recombinant A2aR, GFP and horseradish peroxidase could be improved in one or more of the yeast strains suggesting that a stressed phenotype may also be important in high-yielding cell factories. Conclusions: Regulation of Fps1 levels in yeast by translational control may be functionally important; the presence of a native uORF (uORF2) may be required to maintain low levels of Fps1 under normal conditions, but higher levels as part of a stress response. Constitutively-stressed yeast strains may be useful high-yielding microbial cell factories for recombinant protein production

Functional recombinant protein is present in the pre-induction phases of Pichia pastoris cultures when grown in bioreactors, but not shake-flasks

Background - Pichia pastoris is a widely-used host for recombinant protein production; expression is typically driven by methanol-inducible alcohol oxidase (AOX) promoters. Recently this system has become an important source of recombinant G protein-coupled receptors (GPCRs) for structural biology and drug discovery. The influence of diverse culture parameters (such as pH, dissolved oxygen concentration, medium composition, antifoam concentration and culture temperature) on productivity has been investigated for a wide range of recombinant proteins in P. pastoris. In contrast, the impact of the pre-induction phases on yield has not been as closely studied. In this study, we examined the pre-induction phases of P. pastoris bioreactor cultivations producing three different recombinant proteins: the GPCR, human A2a adenosine receptor (hA2aR), green fluorescent protein (GFP) and human calcitonin gene-related peptide receptor component protein (as a GFP fusion protein; hCGRP-RCP-GFP). Results - Functional hA2aR was detected in the pre-induction phases of a 1 L bioreactor cultivation of glycerol-grown P. pastoris. In a separate experiment, a glycerol-grown P. pastoris strain secreted soluble GFP prior to methanol addition. When glucose, which has been shown to repress AOX expression, was the pre-induction carbon source, hA2aR and GFP were still produced in the pre-induction phases. Both hA2aR and GFP were also produced in methanol-free cultivations; functional protein yields were maintained or increased after depletion of the carbon source. Analysis of the pre-induction phases of 10 L pilot scale cultivations also demonstrated that pre-induction yields were at least maintained after methanol induction, even in the presence of cytotoxic concentrations of methanol. Additional bioreactor data for hCGRP-RCP-GFP and shake-flask data for GFP, horseradish peroxidase (HRP), the human tetraspanins hCD81 and CD82, and the tight-junction protein human claudin-1, demonstrated that bioreactor but not shake flask cultivations exhibit recombinant protein production in the pre-induction phases of P. pastoris cultures. Conclusions - The production of recombinant hA2aR, GFP and hCGRP-RCP-GFP can be detected in bioreactor cultivations prior to methanol induction, while this is not the case for shake-flask cultivations of GFP, HRP, hCD81, hCD82 and human claudin-1. This confirms earlier suggestions of leaky expression from AOX promoters, which we report here for both glycerol- and glucose-grown cells in bioreactor cultivations. These findings suggest that the productivity of AOX-dependent bioprocesses is not solely dependent on induction by methanol. We conclude that in order to maximize total yields, pre-induction phase cultivation conditions should be optimized, and that increased specific productivity may result in decreased biomass yields

A potent betulinic acid analogue ascertains an antagonistic mechanism between autophagy and proteasomal degradation pathway in HT-29 cells

Betulinic acid (BA), a member of pentacyclic triterpenes has shown important biological activities like anti-bacterial, anti-malarial, anti-inflammatory and most interestingly anticancer property. To overcome its poor aqueous solubility and low bioavailability, structural modifications of its functional groups are made to generate novel lead(s) having better efficacy and less toxicity than the parent compound. BA analogue, 2c was found most potent inhibitor of colon cancer cell line, HT-29 cells with IC50 value 14.9 μM which is significantly lower than standard drug 5-fluorouracil as well as parent compound, Betulinic acid. We have studied another mode of PCD, autophagy which is one of the important constituent of cellular catabolic system as well as we also studied proteasomal degradation pathway to investigate whole catabolic pathway after exploration of 2c on HT-29 cells. Mechanism of autophagic cell death was studied using fluorescent dye like acridine orange (AO) and monodansylcadaverin (MDC) staining by using fluorescence microscopy. Various autophagic protein expression levels were determined by Western Blotting, qRT-PCR and Immunostaining. Confocal Laser Scanning Microscopy (CLSM) was used to study the colocalization of various autophagic proteins. These were accompanied by formation of autophagic vacuoles as revealed by FACS and transmission electron microscopy (TEM). Proteasomal degradation pathway was studied by proteasome-Glo™ assay systems using luminometer.The formation of autophagic vacuoles in HT-29 cells after 2c treatment was determined by fluorescence staining – confirming the occurrence of autophagy. In addition, 2c was found to alter expression levels of different autophagic proteins like Beclin-1, Atg 5, Atg 7, Atg 5-Atg 12, LC3B and autophagic adapter protein, p62. Furthermore we found the formation of autophagolysosome by colocalization of LAMP-1 with LC3B, LC3B with Lysosome, p62 with lysosome. Finally, as proteasomal degradation pathway downregulated after 2c treatment colocalization of ubiquitin with lysosome and LC3B with p62 was studied to confirm that protein degradation in autophagy induced HT-29 cells follows autolysosomal pathway. In summary, betulinic acid analogue, 2c was able to induce autophagy in HT-29 cells and as proteasomal degradation pathway downregulated after 2c treatment so protein degradation in autophagy induced HT-29 cell

Bicomplex Version of Some Well Known Results in Complex Analysis

In this paper, we explore for the bicomplex version of the wellknown Hadamard’s three circles theorem in complex analysis and also deduceits convex form. Also, the relation between zeros and poles of abicomplex valued function is established. Moreover the Jenson’s Inequalityas well as some results on univalent functions are proved here in thebicomplex context

Peripartum cardiomyopathy coexistent with human immunodeficiency virus: A substantial obstetric jeopardy

Peripartum cardiomyopathy (PPCM) is a rare cause of pregnancy-related heart failure, which affects a woman during the last months of pregnancy or first months of parturition. Its etiopathogenesis is still unclear. Coexistence of PPCM with human immunodeficiency virus (HIV) has been scarcely analyzed. A low CD4 count is proposed to be one of the predictors of dilated cardiomyopathy in HIV. Here, a pregnant woman with HIV presented with signs of congestive heart failure for the first time during her last trimester. Echocardiography revealed a dilated cardiomyopathy with ejection fraction of 34% which proved the diagnosis of PPCM. She underwent cesarean section for impending previous scar rupture. Her status deteriorated subsequently in spite of all efforts and she succumbed due to ventricular tachycardia. This case necessitates an awareness regarding coexistence of HIV with PPCM and dreaded clinical sequences. Patients suffering from HIV should be treated well and their CD4 count should be improved before conception to avoid such complications in pregnancy