Biology subjects

SINGH, R.

Publications and source records attributed to SINGH, R..

4 recordsLinked to original sources

bioRxiv2025

Role of zinc in growth, stress response and virulence gene expression of pathogenic Mucorale Rhizopus arrhizus

During COVID-19 pandemic, the cases of mucormycosis increased substantially, with rhino-orbito-cerebral form linked to uncontrolled diabetes being the predominant manifestation. Some clinical and epidemiological studies associated the usage of zinc supplements with the occurrence of COVID-19 associated mucormycosis, but experimental evidence remains limited. This study aimed to elucidate the impact of zinc enrichment on Rhizopus arrhizus, the predominant causative agent of mucormycosis. The effect of zinc supplementation (5 to 150 {micro}M) on fungal growth, metabolic activity, antifungal susceptibility and biofilm formation, along with cell-wall (Congo red), oxidative (hydrogen peroxide) and osmotic (sodium chloride) stress was evaluated in RPMI-1640. Morphological changes were visualized by scanning electron microscopy. Gene expression was monitored by RNA sequencing. Zinc supplementation promoted R. arrhizus growth in a concentration-dependent manner, with the effect being particularly pronounced under less-favorable conditions, such as alkaline conditions resembling the nasal pH of diabetics. Exposure to zinc enhanced the metabolic activity, and partly alleviated the cell-wall and oxidative stress. Susceptibility to amphotericin B and posaconazole was unchanged. Zinc-supplemented cultures over-expressed multiple genes, notably those associated with respiratory electron transport chain, ergosterol biosynthesis, chitosan production, oxidative stress response, mucoricin, high-affinity iron permease, iron transport multi-copper oxidase and ferric-reductase-like protein. Zinc also augmented the growth/metabolism of several other Mucorales but not Aspergillus fumigatus and Candida albicans. The findings suggest that zinc supplementation supports mucoralean growth and enhances the expression of key virulence factors, implying that excessive intake of zinc supplements during COVID-19 pandemic likely contributed to the emergence of mucormycosis. IMPORTANCEMucormycosis remains a highly devastating fungal infection that presented additional challenges during the COVID-19 pandemic. Several risk factors were implicated in the emergence of COVID-19 associated mucormycosis (CAM), including inappropriate corticosteroid usage and COVID-19 associated glycemic imbalance. The excessive intake of nutritional supplements, especially that of zinc, owing to self-medication and over-prescription, was also proposed as a plausible factor in the rise of CAM in many clinical/epidemiological studies. This study experimentally evaluated the potential impact of zinc enrichment on pathogenic Mucorales. The work demonstrates that zinc supplementation supports Rhizopus arrhizus growth, metabolism and stress response, and enhances the expression of key virulence factors, including mucoricin and iron transporters. Notably, the augmentation was specifically observed in pathogenic Mucorales but not Aspergillus fumigatus and Candida albicans. The work provides experimental evidence for the potential association of zinc over-availability with the occurrence of CAM, and strengthens evidence-based therapeutic practices in clinical settings.

microbiology↗

bioRxiv2025

Development of a Human iPSC-Derived "Corticospinal Tract-on-a-Chip" for Neurodegenerative Disease Research

Degeneration of the corticospinal tract is a central feature in a number of neurodegenerative disorders and leads to significant disability. However, modeling corticospinal neuron (CSN) pathology and corticospinal connectivity in neurological disorders is particularly challenging. While rodent models are important for understanding early degeneration of CSN, interspecies differences in corticospinal connectivity and challenges of in vivo study suggest that human in vitro models of corticospinal biology may be ripe for development. Human induced pluripotent stem cells (hiPSC) are promising tools for overcoming intrinsic limitations that arise from physiological differences between rodents and humans. We have developed an innovative hiPSC-based microfluidic platform for modeling human CSN and spinal motor neuron (SpMN) connectivity. The incorporation of regionally specific astrocyte subtypes (cortical and spinal) in addition to CSNs and SpMNs in this newly designed system allows for the modeling of both regional and neural cell-subtype interactions. Using this model, multielectrode array electrophysiology reveals the maturation of both cortical and spinal motor neurons over the time course of 12 weeks. Retrograde labeling methods demonstrate synaptic connectivity between corticospinal and spinal motor neurons. Optogenetic strategies to selectively activate excitatory CNs attenuated by glutamate receptor antagonism confirms the functional relevance of the model. Incorporating morphological, electrophysiological and physiological measures of corticospinal connectivity, this platform is a versatile model for use in neurodegenerative disease research and for the future development of targeted CSN therapies. Significance StatementDegeneration of the corticospinal tract is a key feature of numerous neurodegenerative diseases, yet current in vitro models lack the anatomical and functional fidelity to study this system. We developed a human iPSC-derived "Corticospinal Tract-on-a-Chip" using a multielectrode array platform that incorporates regionally patterned cortical and spinal neurons and astrocytes. This model demonstrates structural and functional synaptic connectivity and enables longitudinal electrophysiological recordings. Critically, it supports compartment-specific manipulation and real-time analysis of CST network dynamics, capabilities lacking in existing systems. By mimicking human corticospinal physiology in vitro, this platform offers a novel tool for mechanistic investigation and preclinical testing of CST-targeted therapies. It holds broad relevance for studying disorders such as ALS, hereditary spastic paraplegia, and primary lateral sclerosis.

neuroscience↗

bioRxiv2020

Quantitative assessment of morphology and sub-cellular changes in macrophages and trophoblasts during inflammation

During inflammatory condition in pregnancy, the macrophages present at the feto-maternal junction release an increased amount of NO and pro-inflammatory cytokines such as TNF- and INF-{gamma}, which can disturb the trophoblast functions and thereby the pregnancy outcome. Measurement of the cellular and sub-cellular morphological modifications associated with inflammatory responses are important in order to quantify the extent of trophoblast dysfunction for clinical implication. With this motivation, we investigated morphological, cellular and sub-cellular changes in externally inflamed RAW264.7 (macrophage) and HTR-8/SVneo (trophoblast) using structured illumination microscopy (SIM) and quantitative phase microscopy (QPM). We monitored the production of nitric oxide (NO), changes in cell membrane and mitochondrial structure of macrophages and trophoblasts when exposed to different concentration of pro-inflammatory agents (LPS and TNF-). In vitro NO production by LPS-induced macrophages increased 22-folds as compared to controls, whereas no significant NO production was seen after TNF- challenge. Under similar conditions as with macrophages, trophoblasts did not produce NO following either LPS or TNF- challenge. Super-resolution SIM imaging showed changes in the morphology of mitochondria and plasma membrane in macrophages following LPS challenge and in trophoblasts following TNF- challenge. Label-free QPM showed a decrease in the optical thickness of the LPS-challenged macrophages while TNF- having no effect. The vice-versa is observed for the trophoblasts. We further exploited machine learning approaches on QPM dataset to detect and to classify the inflammation with an accuracy of 99.9% for LPS-challenged macrophages and 98.3% for TNF--challenged trophoblasts. We believe that the multi-modal advanced microscopy methodologies coupled with machine learning approach could be an alternative way for early detection of pregnancy related inflammation after clinical studies.

cell biology↗

bioRxiv2019

The bacterial endosymbiont Wolbachia increases reproductive investment and accelerates the life cycle of ant colonies

Wolbachia is a widespread group of maternally-transmitted endosymbiotic bacteria that often manipulates the reproductive strategy and life history of its solitary hosts to enhance its own transmission. Wolbachia also commonly infects eusocial insects such as ants, although the effects of infection on social organisms remain largely unknown. We tested the effects of infection on colony-level reproduction and life history traits in the invasive pharaoh ant, Monomorium pharaonis. First we compared the reproductive investment of infected and uninfected colonies with queens of three discrete ages, and we found that infected colonies had increased reproductive investment. Next, we compared the long-term growth and reproduction of infected and uninfected colonies across their life cycle, and we found that infected colonies had increased colony-level growth and early colony reproduction. These colony-level effects of Wolbachia infection seem to result because of a live fast, die young life history strategy of infected queens. Such accelerated colony life cycle is likely beneficial for both the host and the symbiont and may have contributed to success of the highly invasive pharaoh ant.

evolutionary biology↗