The effects of varying the timing of inputs on a neural oscillator

The gastric mill network of the stomatogastric ganglion of the crab Cancer borealis is comprised of a set of neurons that require modulatory input from outside the stomatogastric ganglion and input from the pyloric network of the animal in order to oscillate. Here we study how the frequency of the gastric mill network is determined when it receives rhythmic input from two different sources but where the timing of these inputs may differ. We find that over a certain range of the time difference one of the two rhythmic inputs plays no role what so ever in determining the network frequency, while in another range, both inputs work together to determine the frequency. The existence and stability of periodic solutions to model sets of equations are obtained analytically using geometric singular perturbation theory. The results are validated through numerical simulations. Comparisons to experiments are also presented

A model of hematopoietic bone marrow apoptosis during growth factor deprivation in combination with a cytokine

Abstract Background The process by which blood cells are formed is referred to as hematopoiesis. This process involves a complex sequence of phases that blood cells must complete. During hematopoiesis, a small fraction of cells undergo cell death. Causes of cell death are dependent upon various factors; one such factor being growth factor deprivation. Methods In this paper, a mathematical model of hematopoiesis during growth factor deprivation is presented. The model consists of a set of three coupled differential delay equations. Phase plane and linear stability analysis are performed in order to locate and determine stability of fixed points. Numerical simulations of the governing equations are run and provide a visual display of the behavior of the stem cell population undergoing growth factor deprivation. In addition, the effect of cytokine administration is incorporated in the model in an effort to understand how cytokine administration can offset the negative effects of apoptosis caused by growth factor deprivation. Conclusions The model produces qualitatively similar results to that observed during serum deprivation. The model captures apoptosis levels of cells at different time points. Additionally, it is shown that cytokine administration stabilizes the stem cell count

Assessment of Information on Concussion Available to Adolescents on Social Media

Background: Considering how many people obtain information about their health online, the aim of this study was to describe the content of the currently most widely viewed YouTube videos related to concussions and to test the hypothesis that consumer videos would be anecdotal, while other sources would be more informational. Methods: The term “concussion” was used to search for videos with 100,000 or more views on YouTube that were posted in English or Spanish. Descriptive information about each video was recorded, as was information on whether certain content was conveyed during the video. The main outcome measures are sources of upload and content of videos. Results: Consumer videos accounted for 48% of the videos, television based accounted for 50% of the videos, and internet based accounted for only 2% of the videos. None of the videos viewed fell into the professional category. Television based videos were viewed significantly more than consumer or internet based videos. Consumer and television based videos were equally anecdotal. Many of the videos focused on adolescents and were related to sports injuries. The majority of the videos (70.4%) addressed concussion causes, with 48% stating sports. Few videos discussed symptoms of concussion and prevention. Conclusions: The potential for widespread misinformation necessitates caution when obtaining information on concussion on a freely accessible and editable medium, such as YouTube

A model of hematopoietic stem cell proliferation under the influence of a chemotherapeutic agent in combination with a hematopoietic inducing agent

Background: Hematopoiesis is a complex process that encompasses both pro-mitotic and anti-mitotic stimuli. Pharmacological agents used in chemotherapy have a prominent anti-mitotic effect. The approach of inhibiting cell proliferation is rational with respect to the rapidly dividing malignant cells. However, it poses a serious problem with respect to cell proliferation of cell types required for the \u27house-keeping\u27 operations of the human body. One such affected system is hematopoiesis. Chemotherapy induced anemia is an undesired side effect of chemotherapy that can lead to serious complications. Patients exhibiting anemia or leukopenia during chemotherapy are frequently administered a hematopoietic inducing agent that enhances hematopoiesis. Methods. In previous work, we derived a mathematical model consisting of a set of delay differential equations that was dependent on the effect of a hematopoietic inducing agent. The aim of the current work was to formulate a mathematical model that captures both the effect of a chemotherapeutic agent in combination with a hematopoietic inducing agent. Steady state solutions and stability analysis of the system of equations is performed and numerical simulations of the stem cell population are provided. Results: Numerical simulations confirm that our mathematical model captures the desired result which is that the use of hematopoietic agents in conjunction with chemotherapeutic agents can decrease the negative secondary effects often experienced by patients. Conclusions: The proposed model indicates that the introduction of hematopoietic inducing agents have clinical potential to offset the deleterious effects of chemotherapy treatment. Furthermore, the proposed model is relevant in that it enhances the understanding of stem cell dynamics and provides insight on the stem cell kinetics. © 2014 Mouser et al.; licensee BioMed Central Ltd

Hematopoietic stem cell proliferation modeling under the influence of hematopoietic-inducing agent

The process by which hematopoietic stem cells (HSCs) residing in the bone marrow differentiate into blood cells is known as hematopoiesis. In the event of hemorrhagic shock, it is crucial for the HSC to rapidly differentiate into new committed erythroid progenitor cells that will give rise to erythrocytes. Growth factors and cytokines enhance the self-renewing process of HSC and are therefore crucial to restoring normal levels of blood cells in the body. Hematopoietic-inducing agents (HIAs) such as the cytokine erythropoietin and granulocyte-colony-stimulating factor play a vital role in hematopoiesis because they are capable of inducing the proliferation of stem cells. The aim of the current study is to mathematically model the effect of HIA on the proliferation rate of hematopoietic stem cells at varying levels of oxygenation. The role of HIA was analyzed by constructing a set of coupled ordinary differential equations upon which mathematical analysis was performed. The model makes predictions of hematopoietic activity during low oxygen levels (ranging from 3% to 15%) similar to conditions ranging from acute blood loss to normal conditions. © 2009 by the Shock Society