Biology subjects

Stringer, A.

Publications and source records attributed to Stringer, A..

4 recordsLinked to original sources

bioRxiv2025

Irinotecan-induced mucositis is associated with variation in the expression of regulatory compounds associated with goblet cells

Alimentary mucositis (AM) is a common side effect of antineoplastic treatment and a key reason for cessation of treatment, compromising the chance of remission. Gastrointestinal mucin secretion is associated with regulatory compounds nitric oxide and its respective synthases inducible, epithelial and neural nitric oxide synthase (iNOS, eNOS and nNOS, respectively), vasoactive intestinal polypeptide (VIP), and prostaglandin E2 (PGE2). Changes in secretion during mucositis have been demonstrated in numerous studies, however no secretory regulatory signals have been associated in mucositis induced secretory change. The aim of this study is to investigate regulator factors in the gastrointestinal tract involved in mucin secretion, VIP, NOS, and PGE2, which are suspected of being involved in mucositis, specifically through alteration of neural or goblet cells. Tumour-bearing Dark Agouti rats received a single dose of 175 mg/kg of irinotecan (i.p.) and 0.01mg/kg atropine. (s.c.). Rats were killed post treatment at 6, 24, 48, 72, 96 and 120 hours. Samples were collected, immunohistochemistry and real time PCR were performed to analyse the expression of iNOS, eNOS, nNOS, VIP, and PGE2. Following irinotecan treatment, staining intensity for iNOS positive goblet cells in the crypts of the jejunum decreased significantly at 48 h (p < 0.05). VIP, and PGE2 positive goblet cell numbers showed no change. mRNA expression in iNOS, eNOS, and nNOS showed no change. Irinotecan-induced mucositis is associated with altered secretory regulatory compounds; this may affect mucin secretion increasing the severity of irinotecan induced mucositis.

pharmacology and toxicology↗

bioRxiv2024

Different liposomal formulations of 5-Fluorouracil result in variations to gastrointestinal toxicities

5-Fluorouracil (5FU) treatment can induce severe mucositis, gastrointestinal toxicity. New formulations of 5-FU increase cancer cytotoxicity, such as neutral liposomes (NL), cationic liposomes (CL), and polyethylenimine copper (PEI-Cu) complexes. However, gastrointestinal toxicity for these new formulations remains unclear. We aim to determine if new formulations in 5FU reduce mucositis by reducing intestinal goblet cell and nerve integrity. Sprague Dawley rats were randomly assigned to groups: saline (n=6), 5FU (n=6 ), NL-5FU (n=5), CL-5FU (n=5), PEI-CU-5FU (n=6), NL-PEI-Cu-5FU (n=5) CL-PEI-Cu-5FU (n=5) (Formulations were equivalent to 10mg/kg 5FU in saline). Treatment was administered daily for 5 days. Rats where humanely killed 2 days after treatment. Haematoxylin and Eosin staining for histological change, Alcian Blue-PAS staining for mucin composition, and immunohistochemistry with S100 antibody for nerve integrity were performed. Statistical analysis using Kruskal-Wallis test with Dunns post-test and Mann Whitney U test d were performed. Effect size was determined using Cohens D test. In the jejunum, inflammatory infiltrate increased in PEI-Cu-5FU rats compared to 5-FU controls (p=0.0011). S100 positive nerve bundles increased in NL-5FU rats compared to saline control (p<0.05). S100 positive cells increased in CL-PEI-Cu-5FU rats compared to saline controls. PEI-Cu-5FU formulation was associated with increased inflammatory infiltrate potentially in response to damage in the jejunum. However, liposomal formulations increased S100 positive neural cells, which may offer protection through increased gastrointestinal motility and contraction. While these formulations of 5FU increase cancer cytotoxicity, the gastrointestinal toxicity remains similar. However, further close monitoring of 5FU formulations for gastrointestinal toxicity is warranted.

molecular biology↗

bioRxiv2017

Determining the Specificity of Cascade Binding, Interference, and Priming in vivo

In CRISPR-Cas immunity systems, short CRISPR RNAs (crRNAs) are bound by CRISPR-associated (Cas) proteins, and these complexes target invading nucleic acid molecules for degradation in a process known as interference. In type I CRISPR-Cas systems, the Cas protein complex that binds DNA is known as Cascade. Association of Cascade with target DNA can also lead to acquisition of new immunity elements in a process known as primed adaptation. Here, we assess the specificity determinants for Cascade-DNA interaction, interference, and primed adaptation in vivo, for the type I-E system of Escherichia coli. Remarkably, as few as 5 bp of crRNA-DNA are sufficient for association of Cascade with a DNA target. Consequently, a single crRNA promotes Cascade association with numerous off-target sites, and the endogenous E. coli crRNAs direct Cascade binding to >100 chromosomal sites. In contrast to the low specificity of Cascade-DNA interactions, >18 bp are required for both interference and primed adaptation. Hence, Cascade binding to sub-optimal, off-target sites is inert. Our data support a model in which initial Cascade association with DNA targets requires only limited sequence complementarity at the crRNA 5{square} end, whereas recruitment and/or activation of the Cas3 nuclease, a prerequisite for interference and primed adaptation, requires extensive base-pairing.\n\nIMPORTANCEMany bacterial and archaeal species encode CRISPR-Cas immunity systems that protect against invasion by foreign DNA. In the Escherichia coli CRISPR-Cas system, a protein complex, Cascade, binds 61 nt CRISPR RNAs (crRNAs). The Cascade complex is directed to invading DNA molecules through base-pairing between the crRNA and target DNA. This leads to recruitment of the Cas3 nuclease that destroys the invading DNA molecule and promotes acquisition of new immunity elements. We make the first in vivo measurements of Cascade binding to DNA targets. Thus, we show that Cascade binding to DNA is highly promiscuous; endogenous E. coli crRNAs can direct Cascade binding to >100 chromosomal locations. By contrast, we show that target degradation and acquisition of new immunity elements requires highly specific association of Cascade with DNA, limiting CRISPR-Cas function to the appropriate targets.

microbiology↗

bioRxiv2016

Nus factors have a widespread regulatory function in bacteria

Nus factors are broadly conserved across bacterial species, and are often essential for viability. A complex of five Nus factors (NusB, NusE, NusA, NusG and SuhB) is considered to be a dedicated regulator of ribosomal RNA folding, and has been shown to prevent Rho-dependent transcription termination. We have established the first cellular function for the Nus factor complex beyond regulation of ribosomal assembly: repression of the Nus factor-encoding gene, suhB. This repression occurs by translation inhibition followed by Rho-dependent transcription termination. Thus, the Nus factor complex can prevent or promote Rho activity depending on the gene context. Extensive conservation of NusB/E binding sites upstream of nus factor genes suggests that Nus factor autoregulation occurs in many species. Putative NusB/E binding sites are also found upstream of many other genes in diverse species, and we demonstrate Nus factor regulation of one such gene in Citrobacter koseri. We conclude that Nus factors have an evolutionarily widespread regulatory function beyond ribosomal RNA, and that they are often autoregulatory.

microbiology↗