Role of Riboflavin and Certain Amino Acids in the Excystment of Schizopyrenus russelli*

SYNOPSIS. A simple medium, consisting of riboflavin and a mixture of L-glutamic acid, L-tryptophan, L-isoleucine, L-serine, and L-proline has been shown to induce rapid and mass scale excystment in Schizopyrenus russelli. Whereas percentage excystment was found to depend on the concentration of riboflavin and amino acids, more than 80% of cysts were found to excyst within 4 hr, when adequate amounts of these were supplied. Several individual amino acids, particularly L-glutamic acid, L-tryptophan, and L-proline, also supported considerable excystment, but riboflavin was always indispensable.     

Prevalence of and Risk Factors for Oral Human Papillomavirus Infection among HIV-Positive and HIV-Negative People Who Inject Drugs

Background

Human papillomavirus (HPV) causes most oropharyngeal cancers in the United States. Oral HPV prevalence is associated with immunosuppression, and drug use can be immunosuppressive, but the epidemiology of oral HPV among people who use drugs is not well described.

Methods

We enrolled men and women with a current or prior history of injection drug use in this cross-sectional sub-study within the AIDS Linked to the Intravenous Experience (ALIVE) cohort. We tested oral rinse samples for 37 types of HPV DNA and collected self-reported risk factor information. We compared oral HPV prevalence across categories using chi-squared statistics and multivariable logistic regression.

Results

Among 199 subjects, 32% were HIV-positive (median CD4 count 384 cells/μL), 90% were Black, 56% had less than a high school education, 17% had recently used injection drugs, and the median age was 54 years. Most had performed oral sex (82%) but had fewer than 5 lifetime partners (58%). The prevalence of any oral HPV was 29%, and of any oncogenic oral HPV was 13%. Oral HPV prevalence was high among both heterosexual men (30%) and women (20%). After adjustment, odds of oral HPV were increased among HIV-positive individuals with a low CD4 count (<350 cells/μl, aOR = 2.7, 95%CI = 1.2–6.4, vs. HIV-negative individuals), but not among HIV-positive individuals with a higher CD4 cell count. Odds were also elevated for those who had recently performed oral sex on a woman (aOR = 2.2, 95%CI = 1.01–4.6) and, even after this adjustment, among bisexual/lesbian females (aOR = 5.6, 95%CI = 1.4–23, vs. heterosexual females). Oral HPV prevalence was not associated with vaginal sex, performing oral sex on a man, or recent drug use.

Conclusions

Recent drug use was not associated with oral HPV prevalence in our study. However, despite modest numbers of sexual partners, the prevalence of oral HPV among this largely Black population with lower socioeconomic status was high.     

Suppression of Virulence of Toxigenic Vibrio cholerae by Anethole through the Cyclic AMP (cAMP)-cAMP Receptor Protein Signaling System

Use of natural compounds as antivirulence drugs could be an alternative therapeutic approach to modify the outcome of bacterial infections, particularly in view of growing resistance to available antimicrobials. Here, we show that sub-bactericidal concentration of anethole, a component of sweet fennel seed, could suppress virulence potential in O1 El Tor biotype strains of toxigenic Vibrio cholerae, the causative agent of the ongoing 7^th cholera pandemic. The expression of cholera toxin (CT) and toxin coregulated pilus (TCP), the major virulence factors of V. cholerae, is controlled through a regulatory cascade involving activation of ToxT with synergistic coupling interaction of ToxR/ToxS with TcpP/TcpH. We present evidence that anethole inhibits in vitro expression of CT and TCP in a toxT-dependent but toxR/toxS-independent manner and through repression of tcpP/tcpH, by using bead-ELISA, western blotting and quantitative real-time RT-PCR assays. The cyclic AMP (cAMP)-cAMP receptor protein (CRP) is a well-studied global signaling system in bacterial pathogens, and this complex is known to suppress expression of tcpP/tcpH in V. cholerae. We find that anethole influences the virulence regulatory cascade by over-expressing cyaA and crp genes. Moreover, suppression of toxigenic V. cholerae-mediated fluid accumulation in ligated ileum of rabbit by anethole demonstrates its potentiality as an antivirulence drug candidate against the diseases caused by toxigenic V. cholerae. Taken altogether, these results revealing a mechanism of virulence inhibition in V. cholerae by the natural compound anethole, may have relevance in designing antivirulence compounds, particularly against multiple antibiotic resistant bacterial pathogens.     

Cytotoxic Helix-Rich Oligomer Formation by Melittin and Pancreatic Polypeptide

Conversion of amyloid fibrils by many peptides/proteins involves cytotoxic helix-rich oligomers. However, their toxicity and biophysical studies remain largely unknown due to their highly dynamic nature. To address this, we chose two helical peptides (melittin, Mel and pancreatic polypeptide, PP) and studied their aggregation and toxicity. Mel converted its random coil structure to oligomeric helical structure upon binding to heparin; however, PP remained as helix after oligomerization. Interestingly, similar to Parkinson’s associated α-synuclein (AS) oligomers, Mel and PP also showed tinctorial properties, higher hydrophobic surface exposure, cellular toxicity and membrane pore formation after oligomerization in the presence of heparin. We suggest that helix-rich oligomers with exposed hydrophobic surface are highly cytotoxic to cells irrespective of their disease association. Moreover as Mel and PP (in the presence of heparin) instantly self-assemble into stable helix-rich amyloidogenic oligomers; they could be represented as models for understanding the biophysical and cytotoxic properties of helix-rich intermediates in detail.     

Role of salicylic acid on physiological and biochemical mechanism of salinity stress tolerance in plants

Salinity stress is one of the major abiotic stresses affecting plant growth and productivity globally. In order to improve the yields of plants growing under salt stress bear remarkable importance to supply sustainable agriculture. Acclimation of plants to salinized condition depends upon activation of cascade of molecular network involved in stress sensing/perception, signal transduction, and the expression of specific stress-related genes and metabolites. Isolation of salt overly sensitive (SOS) genes by sos mutants shed us light on the relationship between ion homeostasis and salinity tolerance. Regulation of antioxidative system to maintain a balance between the overproduction of reactive oxygen species and their scavenging to keep them at signaling level for reinstating metabolic activity has been elucidated. However, osmotic adaptation and metabolic homeostasis under abiotic stress environment is required. Recently, role of phytohormones like Abscisic acid, Jasmonic acid, and Salicylic acid in the regulation of metabolic network under osmotic stress condition has emerged through crosstalk between chemical signaling pathways. Thus, abiotic stress signaling and metabolic balance is an important area with respect to increase crop yield under suboptimal conditions. This review focuses on recent developments on improvement in salinity tolerance aiming to contribute sustainable plant yield under saline conditions in the face of climate change.     

In vitro kinetics and antifungal activity of various extracts of Terminalia chebula seeds against plant pathogenic fungi

The aim of the present study was to examine the efficacy of various seed extracts of Terminalia chebula as an antifungal potential against certain important plant pathogenic fungi. The organic extracts of methanol, ethyl acetate and chloroform at the used concentration of 1500 ppm/disc revealed remarkable antifungal effect as a fungal mycelial growth inhibitor against Fusarium oxysporum, Fusarium solani, Phytophthora capsici and Botrytis cinerea, in the range of 41.6–61.3%, along with MIC values ranging from 62.5 to 500 μg/ml. Also, the extracts had a strong detrimental effect on spore germination of all the tested plant pathogens along with concentration as well as time-dependent kinetic inhibition of B. cinerea. The results obtained from this study suggest that the natural products derived from Terminalia chebula could become an alternative to synthetic fungicides for controlling such important plant pathogenic fungi.     

Denatured State Structural Property Determines Protein Stabilization by Macromolecular Crowding: A Thermodynamic and Structural Approach

Understanding of protein structure and stability gained to date has been acquired through investigations made under dilute conditions where total macromolecular concentration never surpasses 10 g l⁻¹. However, biological macromolecules are known to evolve and function under crowded intracellular environments that comprises of proteins, nucleic acids, ribosomes and carbohydrates etc. Crowded environment is known to result in altered biological properties including thermodynamic, structural and functional aspect of macromolecules as compared to the macromolecules present in our commonly used experimental dilute buffers (for example, Tris HCl or phosphate buffer). In this study, we have investigated the thermodynamic and structural consequences of synthetic crowding agent (Ficoll 70) on three different proteins (Ribonuclease-A, lysozyme and holo α-lactalbumin) at different pH values. We report here that the effect of crowding is protein dependent in terms of protein thermal stability and structure. We also observed that the structural characteristics of the denatured state determines if crowding will have an effect or not on the protein stability.