Environmentally constrained mutation and adaptive evolution in Salmonella

The relationship between environment and mutation is complex [1]. Claims of Lamarkian mutation [2] have proved unfounded [3], [4] and [5]; it is apparent, however, that the external environment can influence the generation of heritable variation, through either direct effects on DNA sequence [6] or DNA maintenance and copying mechanisms [7], [8], [9] and [10], or as a consequence of evolutionary processes [11], [12], [13], [14], [15] and [16]. The spectrum of mutational events subject to environmental influence is unknown [6] and precisely how environmental signals modulate mutation is unclear. Evidence from bacteria suggests that a transient recombination-dependent hypermutational state can be induced by starvation [5]. It is also apparent that chnages in the mutability of specific loci can be influenced by alterations in DNA topology [10] and [17]. Here we describe a remarkable instance of adaptive evolution in Salmonella which is caused by a mutation that occurs in intermediate-strength osmotic environments. We show that the mutation is not ‘directed’ and describe its genetic basis. We also present compelling evidence in support of the hypothesis that the mutational event is constrained by signals transmitted from the external environment via changes in the activity of DNA gyrase.     

The diameter and mean sarcomere length of individual muscle fibres.

Studies of the coefficients of variation and the repeatibility of the measurements indicate that a sample of 25 fibres is sufficient to provide an accurate estimate of the mean fibre diameter and sarcomere length of a muscle. There is a significant negative correlation (−0.55) between the diameter and mean sarcomere length of an individual muscle fibre. Because they affect sarcomere length postmortem mechanical influences must be strictly standardised if fibre diameter is to be a reliable parameter of muscle growth.     

An independent validation study of loci associated with nematode resistance in sheep

Gastrointestinal nematode infection is a constraint on sheep production worldwide. Selective breeding programmes to enhance resistance to nematode infection are currently being implemented in a number of countries. Identification of loci associated with resistance to infection or causative mutations for resistance would enable more effective selection. Loci associated with indicator traits for nematode resistance has been identified in previous studies. In this study, Scottish Blackface, Texel and Suffolk lambs were used to validate the effects at eight genomic regions previously associated with nematode resistance (OAR3, 4, 5, 7, 12, 13, 14, 21). No SNP was significantly associated with nematode resistance at the region‐wide level but seven SNPs in three of the regions (OAR4, 12, 14) were nominally associated with trichostrongyle egg count in this study and six of these were also significant when fitted as single SNP effects. Nematodirus egg count was nominally associated with SNPs on OAR3, 4, 7 and 12.     

Anaplastic thyroid cancer: outcomes of trimodal therapy

BackroundThe purpose of this study is to assess the impact of trimodal therapy [surgery, chemotherapy and external beam radiotherapy (EBRT)] in patients with anaplastic thyroid cancer (ATC) treated with curative intent.Materials and methodsRetrospective review of patients with ATC treated at a tertiary referral centre between January 2009 and June 2020. Data were collected regarding demographics, histology, staging, treatment and outcomes.ResultsSeven patients (4 female) were identified. Median age was 58 years (range 52–83 years). All patients received EBRT with concurrent doxorubicin. Six patients received surgery followed by chemoradiotherapy (CRT), and one underwent neoadjuvant CRT followed by surgery. Median radiological tumour size was 50mm (range 40–90 mm). Six patients had gross extrathyroidal extension and three had N1b disease. Prescribed radiotherapy schedules were 46.4 Gy in 29 bidaily fractions (n = 2, treated 2010), 60 Gy in 30 daily fractions (n = 2), 66 Gy in 30 fractions (n = 2) and 70 Gy in 35 fractions (n = 1; patient received neoadjuvant CRT). CRT was discontinued early for two patients due to toxicities. At median follow up of 5.8 months, 42.9% (3/7) patients were alive and disease-free. Only one patient developed a local failure. Three patients died from distant metastases without locoregional recurrence.ConclusionsDespite poor prognosis of ATC, selected patients with operable tumours may achieve high locoregional control rates with trimodal therapy, with possibility of long-term survival in select cases.     

Identification of blottin: a novel gastric trefoil factor family-2 binding protein

The trefoil factor family (TFF) peptides are important in gastro-intestinal mucosal protection and repair. Their mechanism of action remains unclear and receptors are sought. We aimed to identify and characterise proteins binding to TFF2. A fusion protein of mouse TFF2 with alkaline phosphatase was generated and used to probe 2-D protein blots of mouse stomach. The resulting spots were analysed by MS. The protein identified was characterised by bioinformatics, rapid amplification of cDNA ends, in situ hybridisation (ISH) and immunohistochemistry (IHC). Functional assays were performed in gastrointestinal cell lines. A single major murine protein was identified and named blottin. It was previously unknown as a translated product. Blottin is also present in rat and human; the latter gene is also known as GDDR. The predicted full-length proteins are 184 amino acids long (20 kDa), reducing to 164 amino acids (18 kDa) after signal peptide cleavage. ISH of gastrointestinal tissues shows abundant blottin mRNA in gastric surface and foveolar epithelium. IHC shows cytoplasmic staining for blottin protein, and by immunoelectron microscopy in mucus granules and Golgi stacks. Previous work showed that blottin is down-regulated in gastric cancers. Blottin contains a BRICHOS domain, and has 56% similarity with gastrokine-1. Cultured HT-29 cells express blottin and show increased DNA synthesis with antiblottin antibody; however, this effect is reversed by the immunising peptide. We have identified and characterised a TFF2-binding protein produced by gastric epithelium. Blottin may play a role in gastrointestinal mucosal protection and modulate gut epithelial cell proliferation.     

A meta-analysis of elevated [CO2] effects on soybean (Glycine max) physiology, growth and yield

The effects of elevated [CO₂] on 25 variables describing soybean physiology, growth and yield are reviewed using meta‐analytic techniques. This is the first meta‐analysis to our knowledge performed on a single crop species and summarizes the effects of 111 studies. These primary studies include numerous soybean growth forms, various stress and experimental treatments, and a range of elevated [CO₂] levels (from 450 to 1250 p.p.m.), with a mean of 689 p.p.m. across all studies. Stimulation of soybean leaf CO₂ assimilation rate with growth at elevated [CO₂] was 39%, despite a 40% decrease in stomatal conductance and a 11% decrease in Rubisco activity. Increased leaf CO₂ uptake combined with an 18% stimulation in leaf area to provide a 59% increase in canopy photosynthetic rate. The increase in total dry weight was lower at 37%, and seed yield still lower at 24%. This shows that even in an agronomic species selected for maximum investment in seed, several plant level feedbacks prevent additional investment in reproduction, such that yield fails to reflect fully the increase in whole plant carbon uptake. Large soil containers (> 9 L) have been considered adequate for assessing plant responses to elevated [CO₂]. However, in open‐top chamber experiments, soybeans grown in large pots showed a significant threefold smaller stimulation in yield than soybeans grown in the ground. This suggests that conclusions about plant yield based on pot studies, even when using very large containers, are a poor reflection of performance in the absence of any physical restriction on root growth. This review supports a number of current paradigms of plant responses to elevated [CO₂]. Namely, stimulation of photosynthesis is greater in plants that fix N and have additional carbohydrate sinks in nodules. This supports the notion that photosynthetic capacity decreases when plants are N‐limited, but not when plants have adequate N and sink strength. The root : shoot ratio did not change with growth at elevated [CO₂], sustaining the charge that biomass allocation is unaffected by growth at elevated [CO₂] when plant size and ontogeny are considered.     

Markers of follicle function in Belclare-cross ewes differing widely in ovulation rate.

High prolificacy due to a gene that has a large effect on ovulation rate has been noted in Booroola and Inverdale ewes. High prolificacy in the Belclare breed (a composite developed from stocks selected for very large litter size or high ovulation rate) may be related to the segregation of two genes. The aims of this study were (i) to compare the morphological and functional features of ovulatory follicles from carriers (which could only be heterozygous for the genes of interest) and non-carriers, and (ii) to identify markers of the Belclare genes among secreted or cellular ovarian proteins. Belclare carrier ewes had more ovulatory follicles (4.9 +/- 0.4) than did non-carrier ewes (2.0 +/- 0.2) (P < 0.001). Ovulatory follicles from carriers were also smaller (4.4 +/- 0.1 mm versus 5.7 +/- 0.2 mm, P < 0.001) and contained a significantly reduced number of granulosa cells (P < 0.001). However, the proportion of proliferating granulosa cells in ovulatory follicles was similar in both groups. The in vitro secretion of steroids per follicle was only marginally lower in follicles from Belclare carriers compared with non-carriers. Furthermore, similar concentrations of steroidogenic enzymes were present in both groups, indicating that steroidogenic potential per granulosa cell is similar between carriers and non-carriers. Possible markers of the Belclare genes were identified among cellular proteins of follicular walls by two-dimensional PAGE and image analysis. Two spots at 78 and 49 kDa were always absent in samples from non-carriers. When secreted proteins in follicles from carriers were compared with those from non-carriers, two spots at 53 and 41 kDa were restricted to samples from carriers and three spots at 97, 91 and 45 kDa were unique to samples from non-carriers. Interestingly, the spot at 91 kDa is also affected by the Booroola gene.     

Unmodified calcium concentrations in tumour necrosis factor receptor subtype-mediated apoptotic cell death

Partial bladder outlet obstruction of the rabbit bladder results in a rapid increase in mass characterized by remodeling of the bladder wall.In this study we investigated the effect of partial outlet obstruction on microvessel density and distribution in the bladder wall immunohistochemically using CD31 as a marker for vascular endothelium, and on blood flow using a fluorescent microsphere technique. Transverse sections of bladder wall were examined after 0 (unobstructed), 1, 3, 5, 7, and 14 days of obstruction. The microvasculature of obstructed rabbit bladder mucosa and detrusor smooth muscle apparently increased relative to augmentation of these compartments, while new vessels appeared in the thickening serosa. These vascular changes correlated with results showing that, at 1 week after obstruction, blood flow (ml/min/g tissue) to the mucosa and detrusor was unchanged.Thickening of the serosa, apparent after 1 day of obstruction, began before its vascularization. Then, 1 week post-obstruction, there was significant microvessel formation in the transition region between the detrusor smooth muscle and the increasing serosa; after 2 weeks, the entire serosa was vascularized. The vascularization of the muscle-serosal transition region and then the remaining serosa apparently precedes fibroblast differentiation, providing blood supply and thus metabolic support for this process.All obstructed rabbit bladders in this study were in a state of compensated function based on their weights. Our working hypothesis is that blood flow per unit tissue mass is normal in compensated obstructed bladders, thus allowing for normal contractile function and cellular metabolism. The results of this study indicate the presence of an augmented microvasculature in compensated obstructed rabbit bladders that provides adequate blood perfusion for normal function.