Biology subjects

Lawrence, P.

Publications and source records attributed to Lawrence, P..

4 recordsLinked to original sources

bioRxiv2022

Determining the toxicity and potential for environmental transport of pyridine using the brown crab Cancer pagurus (L.)

1A series of mass mortalities (wash-ups) of marine life were documented along Englands north east coastline with peaks in September and October 2021, coincident with a programme of intensified maintenance dredging of the River Tees. Decapod crustaceans were the worst affected fauna, with brown crab (Cancer pagurus), European lobster (Homarus gammarus, L.), green shore crab (Carcinus maenas, L.) and velvet swimming crab (Necora puber, L.) populations severely affected. Moribund animals presented with twitching behaviours and paralysis. A potential release of the industrial pollutant pyridine was forwarded as one explanation; however, toxicology data for pyridine in decapods is lacking. In this study, we address this knowledge gap by executing a programme of immersion exposure experiments (pyridine at 2 - 100 mg L-1) using C. pagurus, measuring toxicity effects at the individual (survival) and cellular levels (cellular, mitochondrial, and lipid peroxidation reactive oxygen species (ROS) formation in the gills, hepatopancreas and claw muscle). Highest mortality rates were seen after 72 hours of exposure, returning an LC50 value of 2.75 mg L-1. Exposed crabs presented with patterns of convulsions, limb twitching, paralysis, and death. Crabs exposed to the lowest pyridine dose (2 mg L-1) were noticeably more docile than controls. Concentration was a significant factor influencing mitochondrial ROS formation at low concentrations, with tissue type, time, and their interaction all significant at 100 mg L-1. Computer simulations were used to model the transport of any pyridine released from the dredging work, demonstrating the potential for a pyridine plume to extend from Seaham to the north of the Tees to Whitby and Robin Hoods Bay to the south. This range corresponds well with the reported wash-ups and subsequent declines in catch rates.

pharmacology and toxicology↗

bioRxiv2020

The microbiome affects liver sphingolipids and plasma fatty acids in a murine model of the Western diet based on soybean oil

Studies in mice using germfree animals as controls for microbial colonization have shown that the gut microbiome mediates diet-induced obesity. Such studies use diets rich in saturated fat, however, Western diets in the USA are enriched in soybean oil, composed of unsaturated fatty acids (FAs), either linoleic or oleic acid. Here we addressed whether the microbiome is a variable in fat metabolism in mice on a soybean oil diet. We used conventionally-raised, low-germ, and germfree mice fed for 10 weeks diets either high (HF) or low (LF) in high-linoleic-acid soybean oil as the sole source of fat. All mice, including germfree, gained relative fat weight and consumed more calories on the HF versus LF soybean oil diet. Plasma fatty acid levels were generally dependent on diet, with microbial colonization status affecting iso-C18:0, C20:3n-6, C14:0, and C15:0 levels. Colonization status, but not diet, impacted levels of liver sphingolipids including ceramides, sphingomyelins, and sphinganine. Our results confirm that absorbed fatty acids are mainly a reflection of the diet, and show that microbial colonization influences liver sphingolipid pools.

systems biology↗

bioRxiv2017

Resilience mechanisms of small intestinal lactobacilli to the toxicity of soybean oil fatty acids

Over the past century, soybean oil (SBO) consumption in the United States increased dramatically. The main SBO fatty acid, linoleic acid (18:2), inhibits in vitro the growth of lactobacilli, beneficial members of the small intestinal microbiota. Human-associated lactobacilli have declined in prevalence in Western microbiomes, but how dietary changes may have impacted their ecology is unclear. Here, we compared the in vitro and in vivo effects of 18:2 on Lactobacillus reuteri and L. johnsonii. Directed evolution in vitro in both species led to strong 18:2 resistance with mutations in genes for lipid biosynthesis, acid stress, and the cell membrane or wall. Small-intestinal Lactobacillus populations in mice were unaffected by chronic and acute 18:2 exposure, yet harbored both 18:2- sensitive and resistant strains. This work shows that extant small intestinal lactobacilli are protected from toxic dietary components via the gut environment as well as their own capacity to evolve resistance.

microbiology↗

bioRxiv2017

Taking the short- or long-chain route: conversion efficiency of alpha linolenic acid to long-chain omega-3 fatty acids in aerial insectivore chicks

Food availability and quality are both critical for growing young animals. In nature, swallows (Tachycineta bicolor) and other aerial insectivores feed on both aquatic insects, which are rich in omega-3 long-chain polyunsaturated fatty acid (LCPUFA) and terrestrial insects, which contain considerably less LCPUFA. Carnivorous mammals and fishes must obtain LCPUFA from diet, as they have lost the capacity to convert the precursor omega-3 ALA into LCPUFA. Thus, the relative value of aquatic versus terrestrial insects depends not only on the fatty acid composition of the prey, but also upon the capacity of consumers to convert ALA into LCPUFA. We used a combination of stable-isotope-labeled fatty acid tracers to ask if, and how efficiently, Tree Swallows can deposit newly synthesized LCPUFA into tissue. Our data show for the first time that Tree Swallows can convert ALA into LCPUFA deposited in liver and skeletal muscle. However, high Tree Swallow demand for LCPUFA combined with low ALA availability in natural terrestrial foods may strain their modest conversion ability. This suggests that while Tree Swallows can synthesize LCPUFA de novo, LCPUFA are ecologically essential nutrients in natural systems. Our findings thus provide mechanistic support for our previous findings and the importance of LCPUFA-rich aquatic insects for Tree Swallows and most likely other aerial insectivores with similar niches.\n\nSummary StatementA stable-isotope-labeled tracer reveals the mechanism for omega-3 long-chain polyunsaturated fatty acid (LCPUFA) limitation in a wild avian insectivore, showing that LCPUFA are an ecologically essential nutrient.

ecology↗