Parker B Antin
Publications
Abstract:
Network elucidation is the problem of inferring all parameters of a network from a subset of those parameters. We introduce the Network Elucidation Template (NET), which provides a framework upon which algorithms for such problems can be built. NET algorithms take advantage of novel methods for collaboration between human operators and computers. They use visualizations of the peculiar structures that appear in optimal solutions to aid the parameter search. By design, NET is at a high enough level of abstraction to describe a class of algorithms, as opposed to a single algorithm. Given a problem, and the structure of that problem, an effective instantiation of the template into an algorithm can be created. We describe one such instantiation: using a network flow framework to implement a NET algorithm for uncovering smuggling networks; as well as the general template. © 2010 Elsevier Ltd. All rights reserved.
PMID: 11357194;Abstract:
De novo cardiac myofibril assembly has been difficult to study due to the lack of available cell culture models that clearly and accurately reflect heart muscle development in vivo. However, within precardiac chick embryo ex-plants, premyocardial cells differentiate and commence beating in a temporal pattern that corresponds closely with myocyte differentiation in the embryo. Immunofluorescence staining of explants followed by confocal microscopy revealed that distinct stages of cardiac myofibril assembly, ranging from the earliest detection of sarcomeric proteins to the late appearance of mature myofibrils, were consistently recognized in precardiac cultures. Assembly events involved in the early formation of sarcomeres were clearly visualized and accurately reflected observations described by others during chick heart muscle development. Specifically, the early colocalization of α-actinin and titin dots was observed near the cell periphery representing I-Z -I-like complex formation. Myosin-containing thick filaments assembled independently of actin-containing thin filaments and appeared centered within sarcomeres when titin was also linearly aligned at or near cell borders. An N-terminal epitope of titin was detected earlier than a C-terminal epitope; however, both epitopes were observed to alternate near the cell periphery concomitant with the earliest formation of myofibrils. Although vascular actin was detected within cells during early assembly stages, cardiac actin predominated as the major actin isoform in mature thin filaments. Well-aligned thin filaments were also observed in the absence of organized staining for tropomodulin at thin filament pointed ends, suggesting that tropomodulin is not required to define thin filament lengths. Based on these findings, we conclude that the use of the avian precardiac explant system accurately allows for direct investigation of the mechanisms regulating de novo cardiac myofibrillogenesis. © 2001 Wiley-Liss, Inc.
PMID: 11404090;Abstract:
The expression pattern of the receptor tyrosine kinase gene EphB3 was examined during the early stages of chick embryogenesis, and is described in this report. In the gastrula, EphB3 is expressed in epiblast cells adjacent to and entering the anterior portion of the primitive streak; expression is extinguished once cells have ingressed. At headfold stages, EphB3 is strongly transcribed in the floor of the foregut and in anterior lateral endoderm, and is expressed in the subjacent cardiogenic mesoderm. EphB3 is transiently expressed in the lateral ectoderm, neural tube, and neural crest during these stages. Later neural expression is localized to the mesencephalon. In the somitic mesoderm, EphB3 is initially expressed in the sclerotome, but later is expressed predominantly in the dermatome. Prominent expression is also detected in the developing heart, liver, posterior ventral limb bud mesenchyme, pharyngeal arches, and head mesenchyme. Copyright © 2001 Elsevier Science Ireland Ltd.
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