Intercellular Bridges in Vertebrate Gastrulation

The developing zebrafish embryo has been the subject of many studies of regional patterning, stereotypical cell movements and changes in cell shape. To better study the morphological features of cells during gastrulation, we generated mosaic embryos expressing membrane attached Dendra2 to highlight cellular boundaries. We find that intercellular bridges join a significant fraction of epiblast cells in the zebrafish embryo, reaching several cell diameters in length and spanning across different regions of the developing embryos. These intercellular bridges are distinct from the cellular protrusions previously reported as extending from hypoblast cells (1–2 cellular diameters in length) or epiblast cells (which were shorter). Most of the intercellular bridges were formed at pre-gastrula stages by the daughters of a dividing cell maintaining a membrane tether as they move apart after mitosis. These intercellular bridges persist during gastrulation and can mediate the transfer of proteins between distant cells. These findings reveal a surprising feature of the cellular landscape in zebrafish embryos and open new possibilities for cell-cell communication during gastrulation, with implications for modeling, cellular mechanics, and morphogenetic signaling

The utilization of neural nets in populating an object-oriented database

Existing NASA supported scientific data bases are usually developed, managed and populated in a tedious, error prone and self-limiting way in terms of what can be described in a relational Data Base Management System (DBMS). The next generation Earth remote sensing platforms (i.e., Earth Observation System, (EOS), will be capable of generating data at a rate of over 300 Mbs per second from a suite of instruments designed for different applications. What is needed is an innovative approach that creates object-oriented databases that segment, characterize, catalog and are manageable in a domain-specific context and whose contents are available interactively and in near-real-time to the user community. Described here is work in progress that utilizes an artificial neural net approach to characterize satellite imagery of undefined objects into high-level data objects. The characterized data is then dynamically allocated to an object-oriented data base where it can be reviewed and assessed by a user. The definition, development, and evolution of the overall data system model are steps in the creation of an application-driven knowledge-based scientific information system

Reexamining the Racial Record of Abraham Lincoln

Since his death in 1865 Abraham Lincoln has been universally honored in black America. In many black homes and businesses, his photograph often hangs in honor next to the one of Martin Luther King Jr. But a new book by Ebony editor Lerone Bennett Jr. contends that Lincoln was a crude bigot who told demeaning darky jokes, had an unquenchable thirst for minstrel shows, consistently used the word nigger, and supported efforts to ship Negroes back to Africa. As Jack E. White pointed out in a recent Time magazine article, this book largely has been ignored by the mainstream press. The book was not reviewed in The Washington Post, The New Yorker, The Chicago Tribune, or USA Today. JBHE [Journal of Blacks in Higher Education] asked a group of leading Lincoln scholars for their opinions of the Bennett book and the controversy surrounding its publication. Here are the replies

Bromostibine complexes of iron(II): hypervalency and reactivity

The halostibine complexes [CpFe(CO)2(SbMe2Br)][CF3SO3] and [CpFe(CO)2(SbMe2Br)][BF4] both contain significant interactions between the anion and the formally neutral Sb(III) ligand, which simultaneously displays Lewis acidic and Lewis basic properties. The unexpected secondary product [CpFe(CO)(Me2BrSb-?-Br-SbBrMe2)] is formed in the presence of excess ligand, the strongly associated Br– anion bridging the two Sb donors to form a four-membered FeSb2Br ring.<br/

Biochemical and Molecular Aspects of Vascular Adrenergic Regulation of Blood Pressure in the Elderly

Hypertension, orthostatic hypotension, arterial insufficiency, and atherosclerosis are common disorders in the elderly that lead to significant morbidity and mortality. One common factor to these conditions is an age-related decline in vascular beta-adrenergic receptor-mediated function and subsequent cAMP generation. Presently, there is no single cellular factor that can explain this age-related decline, and thus, the primary cause of this homeostatic imbalance is yet to be identified. However, the etiology is clearly associated with an age-related change in the ability of beta-adrenergic receptor to respond to agonist at the cellular level in the vasculature. This paper will review what is presently understood regarding the molecular and biochemical basis of age-impaired beta-adrenergic receptor-mediated signaling. A fundamental understanding of why β-AR-mediated vasorelaxation is impaired with age will provide new insights and innovative strategies for the management of multiple clinical disorders

Plea Bargaining as Contract

Most criminal prosecutions are settled without a trial. The parties to these settlements trade various risks and entitlements: the defendant relinquishes the right to go to trial (along with any chance of acquittal), while the prosecutor gives up the entitlement to seek the highest sentence or pursue the most serious charges possible. The resulting bargains differ predictably from what would have happened had the same cases been taken to trial. Defendants who bargain for a plea serve lower sentences than those who do not. On the other hand, everyone who pleads guilty is, by definition, convicted, while a substantial minority of those who go to trial are acquitted. There is something puzzling about the polarity of contemporary reactions to this practice. Most legal scholars oppose plea bargaining, finding it both inefficient and unjust. Nevertheless, most participants in the plea bargaining process, including (perhaps especially) the courts, seem remarkably untroubled by it. Not only is the practice widespread, but participants generally approve of it. Why is plea bargaining at once so widely condemned and so widely tolerated? One place to look for an answer is in the law and literature of plea bargaining as contract. Plea bargains are, as the name suggests, bargains; it seems natural to argue that they should be regulated and evaluated accordingly. But while that argument is common, there is little agreement on where it leads. Two of the harshest and most influential critics of plea bargaining, Albert Alschuler and Stephen Schulhofer, maintain that contract theory supports prohibiting any bargained-for allocation of criminal punishment. The courts, on the other hand, have proceeded to construct a body of contract-based law to regulate the plea bargaining process, taking for granted the efficiency and decency of the process being regulated. The many academic arguments for abolishing (or at least severely restricting) plea bargaining have thus been largely ignored. It is tempting to explain this reaction as a product of the chasm between an overly fastidious academic world and the unpleasant realities of modem criminal processes. But the intuition that plea bargaining is fundamentally flawed is too strong and too widespread to be so casually dismissed