Time filter

Source Type

Jeffery W.R.,Eugene Bell Center for Regenerative Biology and Tissue Engineering | Jeffery W.R.,University of Maryland University College
Genesis | Year: 2015

Summary: This year marks the 125th anniversary of the beginning of regeneration research in the ascidian Ciona intestinalis. A brief note was published in 1891, reporting the regeneration of the Ciona neural complex and siphons. This launched an active period of Ciona regeneration research culminating in the demonstration of partial body regeneration: the ability of proximal body parts to regenerate distal ones, but not vice versa. In a process resembling regeneration, wounds in the siphon tube were discovered to result in the formation of an ectopic siphon. Ciona regeneration research then lapsed into a period of relative inactivity after the purported demonstration of the inheritance of acquired characters using siphon regeneration as a model. Around the turn of the present century, Ciona regeneration research experienced a new blossoming. The current studies established the morphological and physiological integrity of the regeneration process and its resemblance to ontogeny. They also determined some of the cell types responsible for tissue and organ replacement and their sources in the body. Finally, they showed that regenerative capacity is reduced with age. Many other aspects of regeneration now can be studied at the mechanistic level because of the extensive molecular tools available in Ciona. genesis 53:48-65, 2015. © 2014 Wiley Periodicals, Inc. Source

Jeffery W.R.,Eugene Bell Center for Regenerative Biology and Tissue Engineering | Jeffery W.R.,University of Maryland University College
Invertebrate Reproduction and Development | Year: 2015

The use of the tunicate Ciona intestinalis as a model system to study the relationship between regeneration and aging is reviewed. Ciona has powerful regeneration capacities, which fade with age. Some additional benefits are a relatively short life span, the ability to study regeneration in vitro, the close phylogenetic relationship between tunicates and vertebrates, and the host of molecular tools already established in this system. The neural complex (NC), the oral siphon (OS), and the oral siphon pigment organs (OPO) have high capacities for regeneration. However, these organs show an inverse relationship between rate of regeneration and age. The ability to regenerate a complete OS disappears in the oldest animals of a natural population, probably due to the inability to form a blastema at the wound site. Effects on blastema formation could also be involved in the reduction of NC regeneration capacity. The fidelity of OPO restoration is also compromised by excess differentiation of precursor cells in local siphon niches in the oldest animals. The Ciona model provides a pathway to understand the molecular basis of these phenomena. © 2014 © 2014 The Author(s). Published by Taylor & Francis. Source

Jeffery W.R.,Eugene Bell Center for Regenerative Biology and Tissue Engineering
Mechanisms of Ageing and Development | Year: 2012

The ascidian Ciona intestinalis has a short life span and powerful regeneration capacities. The regeneration of the oral siphon (OS) involves wound healing, blastema formation, cell proliferation, and replacement of 8 oral pigment organs (OPO), the latter via differentiation and migration of stem/precursor cells from localized niches in the siphon. The restoration of OPO pattern during OS regeneration occurs with a high degree of accuracy through three successive cycles of amputation. It is shown here that oral siphons of the largest and oldest members of a wild Ciona population do not completely regenerate their siphons after amputation. The loss of regeneration capacity was accompanied by reduced cell proliferation. In contrast to arrested OS outgrowth, the stem/precursor cells responsible for OPO replacement " over-differentiate" after OS amputation in the oldest animals, the typical number of OPO is increased from 8 to 12-16, and malformed OPO are produced. Also in contrast to younger animals, the oldest animals of the population show arrested OPO development after two consecutive cycles of amputation and regeneration. We conclude that there is a size and age threshold in Ciona after which the regenerative capacity of the OS is compromised due to effects of aging on cell proliferation. © 2012 Elsevier Ireland Ltd. Source

Mehta S.B.,Eugene Bell Center for Regenerative Biology and Tissue Engineering | Sheppard C.J.R.,Italian Institute of Technology
Optica | Year: 2015

Angularly diverse or partially coherent illumination is widely used for optical, x-ray, and electron microscopy. A longstanding challenge in developing new partially coherent approaches is that the nonlinear image formation model does not allow physical intuition into how the imaging and illumination pupils impact contrast and resolution. We report a phase-space model, the phase-space imaging kernel, for partially coherent systems that describes image formation in terms of a convolution and is analogous to the point spread function model for coherent imaging. We simulate phase-space imaging kernels for brightfield and differential interference contrast (DIC) microscopes to explain a seemingly paradoxical experimental result that the DIC image of a point depends on the coherence of the illumination. We discuss interpretation of the spatial and spatial-frequency marginals of the kernel. We expect this intuitive model and simulations to facilitate design of novel computational schemes for phase imaging and optical lithography. © 2015 Optical Society of America. Source

Morgan J.R.,Eugene Bell Center for Regenerative Biology and Tissue Engineering | Skye Comstra H.,Emory University | Cohen M.,Emory University | Faundez V.,Emory University
Cold Spring Harbor Perspectives in Biology | Year: 2013

The release and uptake of neurotransmitters by synaptic vesicles is a tightly controlled process that occurs in response to diverse stimuli at morphologically disparate synapses. To meet these architectural and functional synaptic demands, it follows that there should be diversity in the mechanisms that control their secretion and retrieval and possibly in the composition of synaptic vesicles within the same terminal. Here we pay particular attention to areas where such diversity is generated, such as the variance in exocytosis/endocytosis coupling, SNAREs defining functionally diverse synaptic vesicle populations and the adaptor-dependent sorting machineries capable of generating vesicle diversity. We argue that there are various synaptic vesicle recycling pathways at any given synapse and discuss several lines of evidence that support the role of the endosome in synaptic vesicle recycling. © 2013 Cold Spring Harbor Laboratory Press; all rights reserved. Source

Discover hidden collaborations