Starch retrogradation in tuber : mechanisms and its implications on microstructure and glycaemic features of potatoes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in School of Food and Advanced Technology at Massey University, Palmerston North, Manawatū, New Zealand

Figures are re-used under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence, or with the publisher's permission.An increase in the occurrence of diabetes mellitus, cardiovascular disease and obesity in recent years led to the project “Starch retrogradation in tuber: mechanisms and its implications on microstructure and glycaemic features of potatoes”. Potato products can play a role in mitigating these hyperglycaemic events, if starch in these processed products is slowly digested and/or starch-derived glucose is released into the circulation in a slower and more attenuated manner. Three stages were envisaged for the project with an aim to create slowly digestible starch in whole potato tuber (in tuber) through starch retrogradation. Plant-based whole food systems, such as potato tubers encompass different cell compartments, (e.g. cell wall, vacuole, cytoplasm and intracellular spaces) within which starch gelatinisation and retrogradation occur, subject to local interactions of other cell components and water availability. Structural changes of potato starch during retrogradation in tuber and its resulting digestibility were studied. Different water pools in a cooked whole tuber were discerned by the low-field NMR (LF-NMR), having relaxation times T20 at 400 ms. A significant reduction in eGI was observed after cooling and storage compared to freshly cooked tubers. Reheating of retrograded tuber restored some of the susceptibility to enzymatic hydrolysis and internal water mobility. Longer chilled storage (7 days) yet improved the stability of retrograded tuber against reheating effects (at 90 °C). Realignment of the gelatinised amylose and amylopectin changed the distribution of crystalline and amorphous regions during refrigerated storage and subsequent reheating, resulting in starch digestibility varying with treatment combination. Several, but not all, of time-temperature cycle processes were observed to induce stepwise nucleation and propagation, facilitating starch retrogradation in tuber more than did storage fixed at 4 °C. Sous vide processing (at 55 and 65°C), akin to annealing, combined with starch retrogradation in tuber, resulted in potatoes with intermediate eGI (40-72). After reheating at 60°C, the eGI of sous vide cooked-chill potatoes increased moderately, displaying a mixture of partially gelatinised starch and swollen granules. Food processing, i.e. optimum TTC process or sous vide process might facilitate the formation of retrograded starch in tuber, resulting in a reduced eGI (than freshly cooked tubers). To retain the resistance to digestive enzymes in retrograded starch in tuber, reheating at low temperatures (50-60°C) were needed

Co-Emergence of Specialized Endothelial Cells from Embryonic Stem Cells.

A well-formed and robust vasculature is critical to the health of most organ systems in the body. However, the endothelial cells (ECs) forming the vasculature can exhibit a number of distinct functional subphenotypes like arterial or venous ECs, as well as angiogenic tip and stalk ECs. In this study, we investigate the in vitro differentiation of EC subphenotypes from embryonic stem cells (ESCs). Using our staged induction methods and chemically defined mediums, highly angiogenic EC subpopulations, as well as less proliferative and less migratory EC subpopulations, are derived. Furthermore, the EC subphenotypes exhibit distinct surface markers, gene expression profiles, and positional affinities during sprouting. While both subpopulations contained greater than 80% VE-cad+/CD31+ cells, the tip/stalk-like EC contained predominantly Flt4+/Dll4+/CXCR4+/Flt-1- cells, while the phalanx-like EC was composed of higher numbers of Flt-1+ cells. These studies suggest that the tip-specific EC can be derived in vitro from stem cells as a distinct and relatively stable EC subphenotype without the benefit of its morphological positioning in the sprouting vessel

Finding Cliques in Social Networks: A New Distribution-Free Model

We propose a new distribution-free model of social networks. Our definitions are motivated by one of the most universal signatures of social networks, triadic closure - the property that pairs of vertices with common neighbors tend to be adjacent. Our most basic definition is that of a c-closed graph, where for every pair of vertices u,v with at least c common neighbors, u and v are adjacent. We study the classic problem of enumerating all maximal cliques, an important task in social network analysis. We prove that this problem is fixed-parameter tractable with respect to c on c-closed graphs. Our results carry over to weakly c-closed graphs, which only require a vertex deletion ordering that avoids pairs of non-adjacent vertices with c common neighbors. Numerical experiments show that well-studied social networks tend to be weakly c-closed for modest values of c

Alterations to the Gastrointestinal Microbiome Associated with Methamphetamine Use among Young Men who have Sex with Men.

Methamphetamine (MA) use is a major public health problem in the United States, especially among people living with HIV (PLWH). Many MA-induced neurotoxic effects are mediated by inflammation and gut microbiota may play a role in this process, yet the effects of MA on the microbiome have not been adequately explored. Therefore, we performed 16S rRNA gene sequencing on rectal swab samples from 381 men who have sex with men, 48% of whom were PLWH and 41% of whom used MA. We compared microbiome composition between MA users and non-users while testing for potential interactions with HIV and controlling for numerous confounders using inverse probability of treatment weighting. We found that MA use explained significant variation in overall composition (R2 = 0.005, p = 0.008) and was associated with elevated Finegoldia, Parvimonas, Peptoniphilus, and Porphyromonas and reduced Butyricicoccus and Faecalibacterium, among others. Genera including Actinomyces and Streptobacillus interacted with HIV status, such that they were increased in HIV+ MA users. Finegoldia and Peptoniphilus increased with increasing frequency of MA use, among others. In summary, MA use was associated with a microbial imbalance favoring pro-inflammatory bacteria, including some with neuroactive potential and others that have previously been associated with poor HIV outcomes

High-resolution 3D refractive index microscopy of multiple-scattering samples from intensity images

Optical diffraction tomography (ODT) reconstructs a samples volumetric refractive index (RI) to create high-contrast, quantitative 3D visualizations of biological samples. However, standard implementations of ODT use interferometric systems, and so are sensitive to phase instabilities, complex mechanical design, and coherent noise. Furthermore, their reconstruction framework is typically limited to weakly-scattering samples, and thus excludes a whole class of multiple-scattering samples. Here, we implement a new 3D RI microscopy technique that utilizes a computational multi-slice beam propagation method to invert the optical scattering process and reconstruct high-resolution (NA>1.0) 3D RI distributions of multiple-scattering samples. The method acquires intensity-only measurements from different illumination angles, and then solves a non-linear optimization problem to recover the sample 3D RI distribution. We experimentally demonstrate reconstruction of samples with varying amounts of multiple scattering: a 3T3 fibroblast cell, a cluster of C. elegans embryos, and a whole C. elegans worm, with lateral and axial resolutions of 250 nm and 900 nm, respectively.Comment: 24 pages, 8 figure

An Ontology-Based Collaborative Interorganizational Knowledge Management Network

Web contents can be represented in a structural form by a finite list of vocabularies and their relationships using ontologies. The concept of ontology and its related mediation methods is capable of enhancing the collaboration among Knowledge Management (KM) approaches that only focus on managing organizational knowledge. Those KM approaches are developed in accordance with organizational KM strategies and business requirements without the concern of system interoperation. In this research, an ontology-based collaborative inter-organizational KM network is proposed to provide a platform for organizations to access and retrieve inter-organizational knowledge in a similar domain

Influences of Neural Pathway Integrity on Children's Response to Reading Instruction

As the education field moves toward using responsiveness to intervention to identify students with disabilities, an important question is the degree to which this classification can be connected to a student's neurobiological characteristics. A few functional neuroimaging studies have reported a relationship between activation and response to instruction; however, whether a similar correlation exists with white matter (WM) is not clear. To investigate this issue, we acquired high angular resolution diffusion images from a group of first grade children who differed in their levels of responsiveness to a year-long reading intervention. Using probabilistic tractography, we calculated the strength of WM connections among nine cortical regions of interest and correlated these estimates with participants’ scores on four standardized reading measures. We found eight significant correlations, four of which were connections between the insular cortex and angular gyrus. In each of the correlations, a relationship with children's response to intervention was evident

Sex differences in protein excretion in mice consuming high protein diet

Background: Normally, the renal excretion of protein (or proteinuria) is absent or very small. Ingesting high-protein diets can elevate proteinuria and in the long term, increase the work on the kidney by increasing glomerular filtration and higher energy requirement to handle the protein. Sex differences in renal function are well known and thus, differences in proteinuria may exist. The purpose of this study was to determine if sex differences exist in proteinuria in mice consuming high protein diet and investigate the potential roles of the sex steroids 17beta-estrogen (E2) and testosterone.Methods: Healthy 3-4-week-old male and female intact and gonadectomized mice were used. Mice were placed in individual metabolic cages where the urine of each mouse could be collected and measured for protein concentration. Mice consumed a 40% casein protein diet for 25 days (normal protein = 20% protein). Some gonadectomized female mice received exogenous E2 and gonadectomized male mice received exogenous testosterone. Proteinuria was measured via dipstick measurement and protein excretion (mg/day) i.e., urine flow rate (ml/day) x urine protein concentration(mg/day).Results: Intact male mice had significantly higher proteinuria compared to intact female mice (5-10 mg/day vs 25-30 mg/day, p<0.001). Gonadectomized male and female mice had very low proteinuria (3- 5 mg/day). Gonadectomized testosterone-treated male mice had high proteinuria not different from the intact male mice. Gonadectomized E2-treated female mice had similar proteinuria compared to intact female mice and slightly though not significantly higher than gonadectomized placebo-treated female mice.Conclusion: The results of this study suggest that the male sex steroid induces high proteinuria in mice consuming high protein levels. The female sex steroid plays no role or only a minor role in proteinuria under these experimental conditions. Our results suggest that androgens may account for the higher incidence of kidney disease in males compared to age-matched pre-menopausal females