Continuum percolation theory of epimorphic regeneration

A biophysical model of epimorphic regeneration based on a continuum percolation process of fully penetrable disks in two dimensions is proposed. All cells within a randomly chosen disk of the regenerating organism are assumed to receive a signal in the form of a circular wave as a result of the action/reconfiguration of neoblasts and neoblast-derived mesenchymal cells in the blastema. These signals trigger the growth of the organism, whose cells read, on a faster time scale, the electric polarization state responsible for their differentiation and the resulting morphology. In the long time limit, the process leads to a morphological attractor that depends on experimentally accessible control parameters governing the blockage of cellular gap junctions and, therefore, the connectivity of the multicellular ensemble. When this connectivity is weakened, positional information is degraded leading to more symmetrical structures. This general theory is applied to the specifics of planaria regeneration. Computations and asymptotic analyses made with the model show that it correctly describes a significant subset of the most prominent experimental observations, notably anterior-posterior polarization (and its loss) or the formation of four-headed planaria.Comment: This author wish to retract the paper arXiv:1705.06720 because it began as part of a collaboration that later fell apart and it was published without the consent from the collaborators. Furthermore, the collaborators have managed to provide a better solution to this proble

Behavior of Planaria in Instrumental Learning Paradigms

Worm behavior in instrumental learning paradigm

ETHANOL-INDUCED IMPACTS ON NERVOUS SYSTEM DEVELOPMENT AND DOPAMINE TRANSPORTER CHARACTERIZATION IN SCHMIDTEA MEDITERRANEA PLANARIA

Fetal alcohol spectrum disorders (FASD) are diagnosed in 2-5% of newborns, but the biology underlying FASD is poorly understood and challenging to study with existing model organisms. A new model for FASD research is Schmidtea mediterranea (Smed) planaria. Smed have a remarkable ability to regenerate their central nervous system (CNS), and possess a well-studied, simple genome. Previous studies have shown that ethanol exposure delays this regeneration, yet this relationship is not fully understood. Here, we show that alcohol exposure affects Smed in a dose-dependent manner, eliciting characteristic withdrawal-like behaviors and impacting cognitive function. Interestingly, prior exposure does not alter subsequent regenerative ability or exacerbate alcohol\u27s influence on regeneration, suggesting a direct impact of alcohol on the molecular processes occurring during regeneration and not an effect on stem cell regulation or differentiability. Additionally, it has been established that dopamine systems play a role in alcohol\u27s effects on neurons. Smed have robust dopaminergic systems that have limited characterization. Thus, we developed a new method to visualize dopamine transporters in Smed and investigate alcohol-induced changes in these systems during head regeneration. This method enables future investigation in planaria that has been inaccessible previously, suggesting even greater potential for this model organism. Taken together, this work increases the viability of the planarian model for FASD and establishes a foundation for future molecular-level characterization in planaria

Memory Acquisition by Brainless Juvenile Terrestrial Planarians (Bipalium kewense)

Learning is how organisms build and store memories in their brains to aid them in survival. This process occurs as organisms experience new stimuli. Bipalium kewense, a terrestrial planarian, has a very minimal central nervous system. The nervous system of planarians consists of only two nerve cords and two ganglion which serve as a “brain.” This species reproduces by segmenting a small piece of their posterior end as a fragment, which initially lacks most adult structures. The fragments must regenerate the head, brain, mouth, functioning digestive system, and reproductive organs. To determine where memory is stored in these terrestrial planarians, we are testing whether they can learn without a brain as fragments and retain this memory throughout adulthood. In our experiment, we will be investigating memory acquisition in headless juvenile Bipalium kewense by raising fragments on two different textured surfaces. Once the fragmented planaria begin to develop a head, one group will be placed on the treatment surface and be exposed to a negative stimulus. The planaria will be trained to avoid this surface and memory will be measured in adulthood to determine if they can distinguish between these two environments.https://digitalcommons.cortland.edu/slides/1029/thumbnail.jp

Planaria as a model for the effects of the co-use of alcohol and nicotine

Poly drug abuse is the abuse of more than one drug, often simultaneously, and is common in many drug-abusers in real-life conditions (Raffa, 2008). The co-use of alcohol and cigarettes is especially prevalent among heavy drinkers such as those diagnosed with alcoholism or alcohol abuse (Bobo & Husten, 2000). The purpose of this study is to gain further insight into the potential mechanisms involved in the poly-drug abuse of alcohol and cigarettes by observing the withdrawal effects of each individual drug versus the combined drugs in the planarian flatworm. Planarian locomotor velocity (pLMV) and atypical behaviours are the behavioural paradigms used in this experiment to quantify the withdrawal effects observed. Results reveal a complex relationship between alcohol and nicotine with interactions between concentration and exposure time to influence the poly-drug relationship.Honours Essa

Planaria: an animal model that integrates development, regeneration and pharmacology

Although planarians are established model organisms in developmental biology and regeneration studies, in the last forty years or so, they have caught the attention of pharmacologists, especially to study the pharmacology of drugs of abuse. This review covers the following topics: some fundamentals of the history of animal models and planarians in biomedical research; an abbreviated story of systematic pharmacology research using planarians as a model organism; an example of how planarians are contributing to the search for compounds against acute cocaine toxicity; an analysis of the number of papers on planarians and pharmacological topics from 1900- 2016; some perspectives on pharmacology in developmental and regeneration studies, arguing in favor of the planarian model as a leading subject for this interdisciplinary area of research, and finally some concluding thoughts

Donald Austin Olewine papers

This collection consists of Donald Austin Olewine’s research on various subjects related to medical physiology and biology. Materials span 1965-1982 and include published and unpublished articles, pamphlets, brochures, magazines, and student work. Find this collection in the University Libraries\u27 catalog.https://digitalcommons.georgiasouthern.edu/finding-aids/1063/thumbnail.jp

Retinoic acid inhibition impairs planarian eye regeneration

Retinoic acid is a known morphogen in regulating animal growth and development. Planaria are a key model system for regeneration and their eyes are a morphological marker of anterior differentiation. We explored the requirement for retinoic acid signaling in the regeneration of body parts in the planaria S. mediterranea using an inhibitor of retinoic acid synthesis, diethylaminobenzaldehyde (DEAB). Whole planaria, soaked in DEAB for three days prior to and five days following amputation, produced trunk and tail fragments with defective anterior regeneration. Following regeneration, up to 80% of posterior fragments developed abnormal eyes. The abnormalities included animals without eyes, with only a single eye, with one enlarged eye, or two eyes of different sizes. Eyes were considered to be functional because animals responded to blue laser light with turning behavior. No abnormalities in eye regeneration were observed in side by side vehicle controls. These results suggest that retinoic acid is necessary for normal eye regeneration following injury and supports a previously undocumented signaling role in planaria eye development

ENGINEERING A HIGH-THROUGHPUT SCREENING PLATFORM FOR ASSESSING DEVELOPMENTAL NEUROTOXICITY THROUGHOUT HEAD- REGENERATION IN SCHMIDTEA MEDITERRANEA

The increase in commercially used chemicals that are inadequately evaluated for safety and risk to development has created a reticent threat to human health. Addressing these deficiencies is compounded by limited methodologies to determine the etiology of exposure-related developmental neurotoxicity (DNT). Current means of assessing DNT are largely retrospective and limited by the expensive, time-consuming, and labor-intensive use of laboratory animal models, thereby motivating a global research effort to produce alternative chemical screening assays. In this work, we have developed a novel high- throughput platform that serves as a new tool to evaluate the effects of exogenous chemical exposure on developmental processes in the non-vertebrate animal model, Schmidtea mediterranea (Smed). We demonstrate that light avoidance in Smed is a robust behavior that can be assayed throughout head regeneration and is temporally correlated to the anatomical development of central nervous system structure. Thus, reacquisition of this behavior serves as a surrogate measure of neurodevelopment that can be utilized to characterize exposure-related effects in DNT. Our high-throughput screening platform enables a more sensitive classification of these responses and assesses both endpoint and temporal effects of chemical exposure in DNT, which paves the way for more exhaustive and predictive chemical assessment to minimize the impact on human health

The Effects of Fluoride Ions on Neuromuscular Activity and Regeneration in Dugesia tigrina

Fluoride ions have been implicated in numerous nervous system pathologies, though the association of these ions with these conditions has been controversial. The purpose of this research is to determine the effects that fluoride ions have on the nervous system development and function in planarians as a simple model for fluoride-nervous system interactions. In the first set of experiments, planarians were exposed to one of four concentrations of sodium fluoride: 0 mM, 1 mM, 1 mM, and 5 mM. In the second set of experiments, planarians were bisected and exposed to 1 mM of NaCl and NaF for regeneration purposes. Regenerated planarians were then stained using Luxol staining methods to determine any physical effects of fluoride on nervous system regeneration. The results showed that swimming activity decreased with increasing levels of fluoride ions, suggesting an inhibition of nervous system activity by fluoride. Additionally, planarians that regenerated in the presence of NaF lacked key structural nervous system components, suggesting a negative impact on the system. It was concluded that fluoride ions negatively impact nervous system activity and development in planarians and possibly in similar organisms