Silk Reconstitution Disrupts Fibroin Self-Assembly.

Using atomic force microscopy, we present the first molecular-scale comparison of two of the most important silk dopes, native (NSF) and reconstituted (RSF) silkworm fibroin. We found that both systems depended on shear to show self-assembly. Significant differences in the nature of self-assembly between NSF and RSF were shown. In the highest studied concentration of 1000 mg/L, NSF exhibited assembly into 20-30 nm-wide nanofibrils closely resembling the surface structures found in natural silk fibers. RSF, in contrast, showed no self-assembly whatsoever at the same concentration, which suggests that the reconstitution process significantly disrupts silk's inherent self-assembly capability. At lower concentrations, both RSF and NSF formed fibrils under shear, apparently denatured by the substrate. Using image analysis, we quantified the properties of these self-assembled fibrils as a function of concentration and found low-concentration fibrils of NSF to form larger continuous structures than those of RSF, further supporting NSF's superior self-assembly capabilities.

Alterations in GLP-1 and PYY release with aging and body mass in the human gut.

The lining of our intestinal surface contains an array of hormone-producing cells that are collectively our bodies' largest endocrine cell reservoir. These "enteroendocrine" (EE) cells reside amongst the billions of absorptive epithelial and other cell types that line our gastrointestinal tract and can sense and respond to the ever-changing internal environment in our gut. EE cells release an array of important signalling molecules that can act as hormones, including glucagon-like peptide (GLP-1) and peptide YY (PYY) which are co-secreted from L cells. While much is known about the effects of these hormones on metabolism, insulin secretion and food intake, less is understood about their secretion from human intestinal tissue. In this study we assess whether GLP-1 and PYY release differs across human small and large intestinal tissue locations within the gastrointestinal tract, and/or by sex, body weight and the age of an individual. We identify that the release of both hormones is greater in more distal regions of the human colon, but is not different between sexes. We observe a negative correlation of GLP-1 and BMI in the small, but not large, intestine. Increased aging correlates with declining secretion of both GLP-1 and PYY in human large, but not small, intestine. When the data for large intestine is isolated by region, this relationship with age remains significant for GLP-1 in the ascending and descending colon and in the descending colon for PYY. This is the first demonstration that site-specific differences in GLP-1 and PYY release occur in human gut, as do site-specific relationships of L cell secretion with aging and body mass.

Genetic variation and variation in aggressiveness to native and exotic hosts among Brazilian populations of Ceratocystis fimbriata.

Ceratocystis fimbriata is a complex of many species that cause wilt and cankers on woody plants and rot of storage roots or corms of many economically important crops worldwide. In Brazil, C. fimbriata infects different cultivated crop plants that are not native to Brazil, including Gmelina arborea, Eucalyptus spp., Mangifera indica (mango), Ficus carica (fig), and Colocasia esculenta (inhame). Phylogenetic analyses and inoculation studies were performed to test the hypothesis that there are host-specialized lineages of C. fimbriata in Brazil. The internal transcribed spacer region ribosomal DNA sequences varied greatly but there was little resolution of lineages based on these sequences. A portion of the MAT1-2 mating type gene showed less variation, and this variation corresponded more closely with host of origin. However, mango isolates were found scattered throughout the tree. Inoculation experiments on the five exotic hosts showed substantial variation in aggressiveness within and among pathogen populations. Native hosts from the same families as the exotic hosts tended to be less susceptible than the cultivated hosts, but there was little correlation between aggressiveness to the cultivated and native hosts of the same family. Cultivation and vegetative propagation of exotic crops may select for strains that are particularly aggressive on those crops.

Enteroendocrine cells sense bacterial tryptophan catabolites to activate enteric and vagal neuronal pathways.

The intestinal epithelium senses nutritional and microbial stimuli using epithelial sensory enteroendocrine cells (EEC). EECs communicate nutritional information to the nervous system, but whether they also relay signals from intestinal microbes remains unknown. Using in vivo real-time measurements of EEC and nervous system activity in zebrafish, we discovered that the bacteria Edwardsiella tarda activate EECs through the receptor transient receptor potential ankyrin A1 (Trpa1) and increase intestinal motility. Microbial, pharmacological, or optogenetic activation of Trpa1+EECs directly stimulates vagal sensory ganglia and activates cholinergic enteric neurons by secreting the neurotransmitter 5-hydroxytryptamine (5-HT). A subset of indole derivatives of tryptophan catabolism produced by E. tarda and other gut microbes activates zebrafish EEC Trpa1 signaling. These catabolites also directly stimulate human and mouse Trpa1 and intestinal 5-HT secretion. These results establish a molecular pathway by which EECs regulate enteric and vagal neuronal pathways in response to microbial signals.

Irinotecan-Induced Mucositis Is Associated with Goblet Cell Dysregulation and Neural Cell Damage in a Tumour Bearing DA Rat Model.

Irinotecan-induced mucositis is a major oncological problem. Goblet cells secrete mucus, protecting the intestinal mucosa, with secretion altered during mucositis. The enteric nervous system is involved in regulating gut motility and secretion. The aim of this study was to determine whether enteric neural cells and goblet cells are altered following irinotecan treatment. Tumour-bearing Dark Agouti rats were administered a single dose of 175 mg/kg of irinotecan intraperitoneally and 0.01 mg/kg atropine subcutaneously. Experimental and untreated control rats were killed at times 6, 24, 48, 72, 96 and 120 h after treatment. Jejunum and colon samples were formalin fixed. Haematoxylin and eosin staining, Alcian Blue-PAS staining, and immunohistochemistry with S-100 antibody (neural cell marker) were carried out. Statistical analyses were carried out using Kruskal-Wallis test with Dunns post test, Mann Whitney U test and nonlinear regression. Total goblet cells decreased at 72 h compared with controls in the colon (p < 0.05). The percentage of cavitated goblet cells decreased compared to all other time points at 120 h in the colon. The number of S-100 positive cells in the submucosal plexus decreased in the colon (p = 0.0046) and in the myenteric plexus of the jejunum and colon (p = 0.0058 and p = 0.0022, respectively), when comparing treated with control. Enteric ganglia in the myenteric plexus of the jejunum decreased at 24 h and 96 h. Irinotecan-induced mucositis is associated with increases in mucus secretion, and enteric neural cell change. These changes may contribute to the pathophysiology of mucositis through the dysregulation of neural signalling.

The GLP-2 analogue elsiglutide reduces diarrhoea caused by the tyrosine kinase inhibitor lapatinib in rats.

PURPOSE: Lapatinib is a small molecule tyrosine kinase inhibitor used to treat breast cancer, often in combination with chemotherapy. Diarrhoea commonly occurs in up to 78% of patients undertaking lapatinib treatment. The mechanism of this diarrhoea is currently unknown. Elsiglutide is a GLP-2 analogue known to increase cell proliferation and reduce apoptosis in the intestine. METHODS: We used a previously developed rat model of lapatinib-induced diarrhoea to determine if co-treatment with elsiglutide was able to reduce diarrhoea caused by lapatinib. Additionally, we analysed the caecal microbiome of these rats to assess changes in the microbiome due to lapatinib. RESULTS: Rats treated with lapatinib and elsiglutide had less severe diarrhoea than rats treated with lapatinib alone. Serum lapatinib levels, blood biochemistry, myeloperoxidase levels and serum limulus amebocyte lysate levels were not significantly different between groups. Rats treated with lapatinib alone had significantly higher histopathological damage in the ileum than vehicle controls. This increase was not seen in rats also receiving elsiglutide. Rats receiving lapatinib alone had lower microbial diversity than rats who also received elsiglutide. CONCLUSIONS: Elsiglutide was able to reduce diarrhoea from lapatinib treatment. This does not appear to be via reduction in inflammation or barrier permeability, and may be due to thickening of mucosa, leading to increased surface area for fluid absorption in the distal small intestine. Microbial changes seen in this study require further research to fully elucidate their role in the development of diarrhoea.

The role of mucins in mucositis.

PURPOSE OF REVIEW: Alimentary mucositis is a severe dose limiting side effect of chemotherapy and radiotherapy. Mucin expression and secretion are associated with mucositis. This article aims to review current studies involving mucin and mucositis. RECENT FINDINGS: Mucins have been shown to alter mucositis severity and key targets associated with mucositis. First, interventions increasing mucin content has been associated with reduce damage associated with mucositis. Second, mucins have also been shown to protect microbiota from radiation-induced damage. Finally, mucins have also been shown to be involved in lumen epithelial barrier interactions altering signalling for cell proliferation, motility, and the inhibition of apoptosis. SUMMARY: The current studies suggest that mucin expression prior to and during mucositis may be very important in reducing the severity of mucositis and further research into the area is warranted.

Irinotecan induces enterocyte cell death and changes to muc2 and muc4 composition during mucositis in a tumour-bearing DA rat model.

Irinotecan-induced mucositis is a major oncological problem. Goblet cells secrete mucus, protecting the intestinal mucosa, with secretion altered during mucositis. The enteric nervous system is involved in regulating gut motility and secretion. The aim of this study was to determine whether enteric neural cells and goblet cells are altered following irinotecan treatment. Tumour-bearing Dark Agouti rats were administered a single dose of 175 mg/kg of irinotecan intraperitoneally and 0.01 mg/kg atropine subcutaneously. Experimental and untreated control rats were killed at times 6, 24, 48, 72, 96 and 120 h after treatment. Jejunum and colon samples were formalin fixed. Haematoxylin and eosin staining, Alcian Blue-PAS staining, and immunohistochemistry with S-100 antibody (neural cell marker) were carried out. Statistical analyses were carried out using Kruskal-Wallis test with Dunns post test, Mann Whitney U test, and nonlinear regression. Total goblet cells decreased at 72 h compared with controls in the colon (p < 0.05). The percentage of cavitated goblet cells decreased compared to all other time points at 120 h in the colon. The number of S-100-positive cells in the submucosal plexus decreased in the colon (p = 0.0046) and in the myenteric plexus of the jejunum and colon (p = 0.0058 and p = 0.0022, respectively), on comparing treated with control. Enteric ganglia in the myenteric plexus of the jejunum decreased at 24 h and 96 h. Irinotecan-induced mucositis is associated with increases in mucus secretion and enteric neural cell change. These changes may contribute to the pathophysiology of mucositis through the dysregulation of neural signalling.

Pathogenicity, Internal Transcribed Spacer-rDNA Variation, and Human Dispersal of Ceratocystis fimbriata on the Family Araceae.

ABSTRACT Ceratocystis fimbriata is a complex of many cryptic, host-specialized species that causes wilt and canker of woody species and rot diseases of storage roots and corms of many economically important plants worldwide. With the exception of the family Araceae, all confirmed hosts of C. fimbriata are dicotyledonous plants. We hypothesized that the isolates from members of the family Araceae would form a monophyletic lineage specialized to infect these unique hosts. Analyses of sequences of the internal transcribed spacer (ITS) region of nuclear rDNA indicate that isolates and herbarium specimens of C. fimbriata from the family Araceae represent three different groups: an Xanthosoma/Syngonium group on corms of Xanthosoma spp. from the Caribbean region and on ornamental S. podophyllum from greenhouses in Florida, Hawaii, Australia, and Brazil; an inhame group on corms of Colocasia esculenta in Brazil; and a distantly related taro group on Colocasia esculenta in Hawaii and China and on X. sagittifolium in Fiji. Inoculations of three species of Araceae (Caladium bicolor, S. podophyllum, and Colocasia esculenta) showed that isolates from all three groups are pathogenic to these three hosts. Brazilian isolates from Mangifera indica and Ficus carica were only weakly pathogenic to Caladium and Syngonium sp. and were not pathogenic to Colocasia sp. Syngonium plants appeared to be most susceptible to isolates of the Xanthosoma/Syngonium group, and Colocasia plants were least susceptible to isolates from Syngonium spp. Thus, it appears that adaptations to the family Araceae have evolved more than once in the C. fimbriata complex. It is hypothesized that the three groups of C. fimbriata on the family Araceae are native to the Caribbean, Brazil, and Asia, respectively, but they have been spread elsewhere by humans.

Dark Agouti rat model of chemotherapy-induced mucositis: establishment and current state of the art.

Mucositis is a major oncological problem. The entire gastrointestinal and genitourinary tract and also other mucosal surfaces can be affected in recipients of radiotherapy, and/or chemotherapy. Major progress has been made in recent years in understanding the mechanisms of oral and small intestinal mucositis, which appears to be more prominent than colonic damage. This progress is largely due to the development of representative laboratory animal models of mucositis. This review focuses on the development and establishment of the Dark Agouti rat mammary adenocarcinoma model by the Mucositis Research Group of the University of Adelaide over the past 20 years to characterize the mechanisms underlying methotrexate-, 5-fluorouracil-, and irinotecan-induced mucositis. It also aims to summarize the results from studies using different animal model systems to identify new molecular and cellular markers of mucositis.

Chemotherapy-induced mucositis: the role of mucin secretion and regulation, and the enteric nervous system.

Alimentary mucositis is a severe, dose-limiting, toxic side effect of cytotoxic chemotherapy and radiotherapy. Patients with mucositis often have reductions or breaks imposed on cytotoxic therapy, which may lead to reduced survival. Furthermore, there is an increased risk of infection and hospitalization, compounding the cost of treatment. There are currently limited therapeutic options for mucositis, and no effective prevention available. Mucin expression and secretion have been shown to be associated with mucositis. Furthermore, mucins exhibit protective effects on the alimentary tract through reducing mechanical and chemical stress, preventing bacterial overgrowth and penetration, and digestion of the mucosa. Additionally, a number of studies have implicated some key neurotransmitters in both mucositis and mucin secretion, suggesting that the enteric nervous system may also play a key role in the development of mucositis.

Chemotherapy-induced mucositis: the role of the gastrointestinal microbiome and toll-like receptors.

Alimentary mucositis is a major clinical problem. Patients with mucositis are at significantly increased risk of infection and are often hospitalized for prolonged periods. More importantly, these patients often have to undergo reductions in their cytotoxic therapy, which may lead to reduced survival. Unfortunately, there are very limited therapeutic options for mucositis and no effective prevention. The human gut microbiome is receiving increased attention as a key player in the pathogenesis of alimentary mucositis with recent literature suggesting that changes in bacteria lead to mucositis. The bacteria which are found throughout the gut are tightly regulated by the toll-like receptor (TLR) family which currently has 13 known members. TLRs play a critical role in gut homeostasis and bacterial regulation. Furthermore, TLRs play a critical role in the regulation of nuclear factor kappa B, a key regulator of alimentary mucositis. However to date, no research has clearly identified a link between TLRs and alimentary mucositis. This critical literature review seeks to correct this.