Algorithms and Bounds for Drawing Directed Graphs

In this paper we present a new approach to visualize directed graphs and their hierarchies that completely departs from the classical four-phase framework of Sugiyama and computes readable hierarchical visualizations that contain the complete reachability information of a graph. Additionally, our approach has the advantage that only the necessary edges are drawn in the drawing, thus reducing the visual complexity of the resulting drawing. Furthermore, most problems involved in our framework require only polynomial time. Our framework offers a suite of solutions depending upon the requirements, and it consists of only two steps: (a) the cycle removal step (if the graph contains cycles) and (b) the channel decomposition and hierarchical drawing step. Our framework does not introduce any dummy vertices and it keeps the vertices of a channel vertically aligned. The time complexity of the main drawing algorithms of our framework is $O(kn)$, where $k$ is the number of channels, typically much smaller than $n$ (the number of vertices).Comment: Appears in the Proceedings of the 26th International Symposium on Graph Drawing and Network Visualization (GD 2018

The pancreatic beta cell surface proteome

The pancreatic beta cell is responsible for maintaining normoglycaemia by secreting an appropriate amount of insulin according to blood glucose levels. The accurate sensing of the beta cell extracellular environment is therefore crucial to this endocrine function and is transmitted via its cell surface proteome. Various surface proteins that mediate or affect beta cell endocrine function have been identified, including growth factor and cytokine receptors, transporters, ion channels and proteases, attributing important roles to surface proteins in the adaptive behaviour of beta cells in response to acute and chronic environmental changes. However, the largely unknown composition of the beta cell surface proteome is likely to harbour yet more information about these mechanisms and provide novel points of therapeutic intervention and diagnostic tools. This article will provide an overview of the functional complexity of the beta cell surface proteome and selected surface proteins, outline the mechanisms by which their activity may be modulated, discuss the methods and challenges of comprehensively mapping and studying the beta cell surface proteome, and address the potential of this interesting subproteome for diagnostic and therapeutic applications in human disease

Beyond equilibrium climate sensitivity

ISSN:1752-0908ISSN:1752-089

Revascularization and remodelling of pancreatic islets grafted under the kidney capsule

The revascularization and the structural changes resulting from interactions between the graft and the host were investigated in transplanted pancreatic islets under the kidney capsule. Islets were isolated from mice pancreata and transplanted in syngeneic diabetic animals. Graft-bearing kidneys were collected on different days post-transplant and processed for light microscopy, immunohistochemistry and transmission electron microscopy. A numerical analysis was performed in order to compare the percentage number of the different types of cells in native islets and at different time points after the transplant. Recipient animals reversed diabetes within 4 days. An intraperitoneal glucose tolerance test was performed to determine islet functionality under stressful conditions. During the initial few days post-transplant, the islets showed peculiar shapes and the graft tended to aggregate along the vessels. Starting at days 4–7 post-transplant, islets were revascularized from vessels connected to both the cortical and the capsular vascular network of the kidney. From day 7–14 post-transplant, the vessels progressively appeared more similar in features and size to those of in situ pancreatic islets. Both the percentage number of the different cell types and the distribution of Alpha, Beta and Delta cells inside the graft were significantly different as compared with intact islets, demonstrating quantitative and structural changes after the engraftment. No concomitant proliferation of Beta cells was detected using a bromodeoxyuridin staining method. Despite the fact that quick revascularization preserved a large mass of tissue, the remodelling process of the graft and the newly formed vascularization led to a different organization of the endocrine tissue as compared with intact in situ islets. This constitutes the morphological basis for alterations of the normal intercellular interactions and may explain the altered secretory cell function often observed in transplant

The Reproductive Ecology of Industrial Societies, Part II : The Association between Wealth and Fertility.

Studies of the association between wealth and fertility in industrial populations have a rich history in the evolutionary literature, and they have been used to argue both for and against a behavioral ecological approach to explaining human variability. We consider that there are strong arguments in favor of measuring fertility (and proxies thereof) in industrial populations, not least because of the wide availability of large-scale secondary databases. Such data sources bring challenges as well as advantages, however. The purpose of this article is to illustrate these by examining the association between wealth and reproductive success in the United States, using the National Longitudinal Study of Youth 1979. We conduct a broad-based exploratory analysis of the relationship between wealth and fertility, employing both cross-sectional and longitudinal approaches, and multiple measures of both wealth (income and net worth) and fertility (lifetime reproductive success and transitions to first, second and third births). We highlight the kinds of decisions that have to be made regarding sample selection, along with the selection and construction of explanatory variables and control measures. Based on our analyses, we find a positive effect of both income and net worth on fertility for men, which is more pronounced for white men and for transitions to first and second births. Income tends to have a negative effect on fertility for women, while net worth is more likely to positively predict fertility. Different reproductive strategies among different groups within the same population highlight the complexity of the reproductive ecology of industrial societies. These results differ in a number of respects from other analyses using the same database. We suggest this reflects the impossibility of producing a definitive analysis, rather than a failure to identify the "correct" analytical strategy. Finally, we discuss how these findings inform us about (mal)adaptive decision-making

Morphological changes of isolated rat pancreatic islets: a structural, ultrastructural and morphometric study

Improved techniques for pancreatic islet extraction can yield a reasonable number of transplantable cells. However, the isolation and purification process may damage the islets and impair their physiological functions. The aim of this study was to determine the effect of the isolation procedure on the structure of isolated islets and to correlate this with their functionality. Islets were isolated from rat pancreata and purified by Eurocollins-Ficoll discontinuous density gradient processing, and then processed for light microscopy, and scanning and transmission electron microscopy. Morphometric analysis was also performed. Islet functionality was determined by reversal of streptozotocin-induced diabetes and the intraperitoneal glucose tolerance test in a syngeneic rat model of pancreatic islet transplantation. Fragments of variable size and shape comprised a relatively large proportion (26%) of the isolated endocrine tissue. Isolated islets showed slight alterations of cell ultrastructure. Major damage (including breakage of the plasma membrane) and loss of cells were observed in the peripheral cells of the isolated islets. An equal mass of islet equivalent (IEq, islets with an average diameter of 150 µm), but with a different islet equivalent/islet number ratio, was transplanted in diabetic animals. When larger and more complete islets were transplanted (higher ratio), better function of the graft was observed by reversal of hyperglycaemia and response to the glucose tolerance test as compared with the functionality and response of smaller (fragmented) islets transplanted (lower ratio). Digestion, trauma and hypoxia during isolation are responsible for qualitative and quantitative changes of isolated islets. Alterations in normal secretory function after the transplant were related to lower islet equivalent/islet number ratio. The incomplete integrity of the islets may explain the failure of the fine glycaemic metabolic regulation