Direct Outgrowth Research Articles

Some remarks on the history of Ricci’s absolute differential calculus

The article offers a general account of the genesis of the absolute differential calculus (ADC), paying special attention to its links with the history of differential geometry. In relatively recent times, several historians have described the development of the ADC as a direct outgrowth either of the theory of algebraic and differential invariants or as a product of analytical investigations, thus minimizing the role of Riemann’s geometry in the process leading to its discovery. Our principal aim consists in challenging this historiographical tenet and analyzing the intimate connection between the development of Riemannian geometry and the birth of tensor calculus.

Chicana/o Movement Politics, the Cold War, and the White Racial Frame: The Case of El Colegio Jacinto Treviño

Abstract This article examines resistance to the establishment and operations of El Colegio Jacinto Treviño in the early 1970s. El Colegio, a direct outgrowth of Chicana/o movement activism as it gained notable traction across the United States in the late 1960s, was founded in the small border town of Mercedes, Texas, and, despite its short history (1970–76), is remembered as the first “Chicano” college in the United States. Yet, from its inception, it was mired in controversy as one local citizen, the Reverend Oliver W. Sumerlin, led what one local newspaper described as a “one-man war against Jacinto Trevino College.” Drawing on archival research, this examination of Sumerlin’s and others’ resistance to the establishment of El Colegio reveals how, in the wake of the “counterframe” offered in and through El Colegio, the White racial frame was defended and bolstered in the Rio Grande valley.

Synergy of Nanotopography and Electrical Conductivity of PEDOT/PSS for Enhanced Neuronal Development.

Biomaterials able to promote neuronal development and neurite outgrowth are highly desired in neural tissue engineering for the repair of damaged or disrupted neural tissue and restoring the axonal connection. For this purpose, the use of either electroactive or micro- and nanostructured materials has been separately investigated. Here, the use of a nanomodulated conductive poly(3,4-ethylendioxithiophene) poly(styrenesulfonate) (PEDOT/PSS) substrate that exhibits instructive topographical and electrical cues at the same time was investigated for the first time. In particular, thin films featuring grooves with sizes comparable with those of neuronal neurites (NanoPEDOT) were fabricated by electrochemical polymerization of PEDOT/PSS on a nanomodulated polycarbonate template. The ability of NanoPEDOT to support neuronal development and direct neurite outgrowth was demonstrated by assessing cell viability and proliferation, expression of neuronal markers, average neurite length, and direction of neuroblastoma N2A cells induced to differentiate on this novel support. In addition to the beneficial effect of the nanogrooved topography, a 30% increase was shown in the average length of neurites when differentiating cells were subjected to an electrical stimulation of a few microamperes for 6 h. The results reported here suggest a favorable effect on the neuronal development of the synergistic combination of nanotopography and electrical stimulation, supporting the use of NanoPEDOT in neural tissue engineering to promote physical and functional reconnection of impaired neural networks.

The development of thoracic and abdominal muscle depends on SDF1 and CXCR4

In vertebrates, the lateral body wall muscle formation is thought to be initiated by direct outgrowth of the dermomyotomes resulting in the elongation of the hypaxial myotomes. This contrasts with the formation of the muscles of the girdle, limbs and intrinsic tongue muscles, which originate from long-range migrating progenitors. Previous work shows that the migration of these progenitors requires CXCR4 which is specifically expressed in the migrating cells, but not in the dermomyotome. Here, we show that cells in the ventrolateral-lip (VLL) of the dermomyotome at the flank level express CXCR4 in a pattern consistent with that of Pax3 and MyoR. In ovo gain-of-function experiments using electroporation of SDF-1 constructs into the VLL resulted in increased expression of c-Met, Pax3 and MyoD. In contrast, a loss-of-function approach by implantation of CXCR4-inhibitor beads into the VLL of the flank region caused a reduction in the expression of these markers. These data show that CXCR4 is expressed in the VLL, and by experimentally manipulating the CXCR4/SDF-1 signaling, we demonstrate the importance of this axis in body wall muscle development.

Pyramid Schemes: Resurrecting Tikal through the Military-Industrial-Academic Complex

ABSTRACT Carved out of the jungle by American big business, Penn Museum’s project at Tikal to restore massive pyramids and showcase Maya civilization was a direct outgrowth of government, military, and corporate connections. The story of Pennsylvania in the Petén is about American involvement in developing tourism, infrastructure, research stations, training, and the making of Guatemalan heritage citizens. It is also about increasing US government vigilance south of the border after the 1954 CIA-backed coup, whether in forging anti-communist alliances or commercial concessions. Philanthropists supporting Tikal were themselves representatives from US banking, oil, agriculture, aviation, and tourism sectors, making it impossible to disentangle archaeology from industrial and political adventurism. Extractive economies involving archaeology, oil, chicle, and bananas all ferried equipment and products back and forth to the Petén via American boats and planes, along dirt roads and airstrips built by American firms. Sold as the first great city of the Americas and costing almost a million dollars, the resurrection of Tikal underlines the ineluctable dependencies between security, espionage, international politics, corporations, conservation, and donor economies.

Regulation of LIM homeodomain 2 (Lhx2) in the distal limb bud during patterning and development

During limb morphogenesis, fibroblast growth factors (Fgfs) secreted from the apical ectodermal ridge (AER) direct proximodistal outgrowth of the limb, while sonic hedgehog (Shh) released from the zone of polarizing activity modulate anteroposterior expansion of the limb. Fgfs and Shh maintain each other’s expression through an autoregulatory loop. The transcription factor LIM homeodomain 2 (Lhx2) is expressed in the distal sub‐AER mesoderm and is important for Shh expression. We have identified a chicken enhancer upstream of the LHX2 promoter that is active in the distal sub‐AER LHX2 expression domain that contains putative transcription factor binding sites for known downstream targets of FGF signaling that are critical for activity. Therefore, we hypothesized that LASARM1 interacts with the LHX2 promoter and that FGF works through LASARM1 to regulate LHX2 expression. To determine this, we performed chromosome conformation capture (3C) on cells isolated from distal chicken limb buds and compared them to non‐LHX2 expressing tail cells. Promoter and enhancer specific primers were used to isolate ligated promoter‐enhancer fragments by end‐point PCR. Amplified sequences were then sequence validated. A 3C ligation product library was used as a control. We also evaluated the role of FGF to regulate LASARM1 activity in subAER mesoderm by analyzing LASARM1 activity following inhibition of FGF signaling by an FGF‐receptor inhibitor. End‐point PCR revealed promoter‐enhancer ligated amplicons in distal limb bud cells, but not in tail cells. DNA sequencing of enhancer‐ligated fragments confirmed LHX2‐LASARM1 fusion fragments for distal limb bud cells. Interestingly, disruption of FGF signaling via a specific FGF receptor inhibitor did not alter LASARM1 activity, although LHX2 expression was markedly reduced. These findings suggest that LASARM1 interacts with the LHX2 promoter during limb patterning, but additional enhancers are required to mediate the FGF‐mediated up‐regulation of LHX2. Evaluation of additional LHX2 enhancers is underway. Investigations regarding the relationship between FGF and LHX2 will provide important insights into the mechanisms underlying LHX2 regulation and the FGF‐to‐SHH reciprocal loop.

In the Struggle: Scholars and the Fight Against Industrial Agribusiness in California

In the Struggle: Scholars and the Fight Against Industrial Agribusiness in California

Screening of Biocatalysts for Synthesis of the Wieland–Miescher Ketone

Lipases, a versatile class of biocatalysts, have been shown to function in non-aqueous media/organic solvents and to possess “promiscuous” catalytic activity for a wide range of organic transformations. In this study, we explored the biocatalytic properties of a library of commercially available lipases by screening them for catalysis of a one-pot synthesis of Wieland–Miescher ketone, an important intermediate in the synthesis of biologically active compounds such as steroids and terpenoids, from methyl vinyl ketone and 2-methyl-1,3-cyclohexanedione. As a direct outgrowth of this screen, we created an optimized procedure for Wieland–Miescher ketone (WMK) synthesis using crude lipase preparations, characterizing both reaction yield and enantiomeric excess. We also identified principal components of the crude lipase mixture through proteomics and present evidence for a non-lipolytic origin of the observed catalysis. Finally, using the optimized conditions developed in this study, we propose a general absorbance-based screening methodology for assessing biocatalytic potential of crude enzyme preparations for synthesis of WMK.

Magnetic Organization of Neural Networks via Micro‐Patterned Devices

AbstractGuiding neuronal migration and outgrowth has great importance for therapeutic applications and for bioelectronics interfaces. Many efforts have been devoted to the development of tools to form predesigned structured neuronal networks. Here, a unique approach to localize cell bodies and direct neurite outgrowth is described based on local magnetic manipulations. Inspired by spintronic devices, a multi‐layer deposition process is developed to generate nanometric‐thick films with perpendicular magnetization that provide stable attraction forces toward the entire magnetic pads. PC12 cells, a common neuronal model, are transformed to magnetic units by incubation with superparamagnetic nanoparticles, which are then plated and differentiated atop the substrates. The vast majority of MNPs‐loaded cells adhere to the magnetic pads, showing high affinity to the magnetic patterns in correlation with numerical simulations of the magnetic force strength. Additionally, neuronal growth analysis shows that the magnetic substrate is effective in directing the extending neurites, which tend to remain atop the magnetic pads, and even follow complex patterns such as hexagons. This suggests that the MNPs diffuse into the neuronal processes throughout network formation. The ability to remotely control neuronal motility together with network design via smart magnetic materials opens possibilities for new neuronal interfaces and implantable therapeutic devices.

The Unitary Executive: Past, Present, Future

Under the U.S. Constitution, is the executive branch unitary, and if so, in what sense? For many decades, there has been a sharp dispute between those who believe in a strongly unitary presidency, in accordance with the idea that the president must have unrestricted removal power over high-level officials entrusted with implementation of federal law, and those who believe in a weakly unitary presidency, in accordance with the view that Congress may, under the Necessary and Proper Clause, restrict the president’s removal power, so long as the restriction does not prevent the president from carrying out his constitutionally specified functions. Both positions can claim support from the original understanding of relevant clauses; both can claim to keep faith with constitutional commitments in light of dramatically changed circumstances, above all the rise of the modern administrative state. In Seila Law v. Consumer Financial Protection Bureau, a sharply divided Court enthusiastically embraced the strongly unitary position, in an ambiguous opinion that might be read to preserve the constitutionality of independent multimember commissions, but that also left a great deal of room for constitutional challenges to such commissions in their present form. The Court’s analysis purports to be rooted in the original understanding of the constitution, and not implausibly so; but the Court relies so heavily on abstract principles, such as “liberty” and “accountability,” that its analysis is not easily distinguishable from a dynamic constitutionalism suffused with political morality. The Court’s holding and analysis can thus be seen as a direct outgrowth of modern anxiety, rooted in structural concerns, about the threats posed by a powerful, discretion-wielding administrative apparatus, and a belief that presidential control is an essential safeguard.

Low-income Families Guide Innovation: Application of Human-Centered Design

The Prosperity Agenda (TPA) is a nonprofit organization whose human-centered design process centers on the belief that all people are resilient and resourceful. From 2016 to 2019, with support from the W.K. Kellogg Foundation, they collaborated with the Washington State Department of Commerce to design and implement a new program to encourage two-generational savings among families receiving social welfare assistance. Innovative classroom events focused on savings were a direct outgrowth of TPA’s work with families experiencing poverty. The positive results of the yearlong pilot confirmed the idea that an intervention rooted in human-centered design and guided by both the experiential wisdom of low-income families and the deep expertise of event facilitators would help families build financial resilience.

Determining Neurotrophin Gradients in Vitro To Direct Axonal Outgrowth Following Spinal Cord Injury.

A spinal cord injury can damage neuronal connections required for both motor and sensory function. Barriers to regeneration within the central nervous system, including an absence of neurotrophic stimulation, impair the ability of injured neurons to reestablish their original circuitry. Exogenous neurotrophin administration has been shown to promote axonal regeneration and outgrowth following injury. The neurotrophins possess chemotrophic properties that guide axons toward the region of highest concentration. These growth factors have demonstrated potential to be used as a therapeutic intervention for orienting axonal growth beyond the injury lesion, toward denervated targets. However, the success of this approach is dependent on the appropriate spatiotemporal distribution of these molecules to ensure detection and navigation by the axonal growth cone. A number of in vitro gradient-based assays have been employed to investigate axonal response to neurotrophic gradients. Such platforms have helped elucidate the potential of applying a concentration gradient of neurotrophins to promote directed axonal regeneration toward a functionally significant target. Here, we review these techniques and the principles of gradient detection in axonal guidance, with particular focus on the use of neurotrophins to orient the trajectory of regenerating axons.

A Collaborative Response to Provocative Comments in a Medical School

This article was migrated. The article was marked as recommended. In 2018, anonymous online provocative comments were submitted to student leaders of a Syrian Refugee Initiative (SRI) at the Penn State College of Medicine. This triggered a series of actions with students and medical school leaders aimed at identifying the person who submitted the comments, trying to understand mutual perspectives, and managing the impact of the event on the student body.We describe the history of our college's commitment to humanism and how the SRI was a direct outgrowth of that culture. Voices of the student leaders who were directly impacted by the provocative comments and educational leaders who worked to resolve the crisis are presented. We also describe a collaborative process that involved engaging cybersecurity experts to identify the perpetrator, and share how the students and educational leaders were able to develop trust despite initial skepticism by students over the leadership's avowed commitment to taking the hate speech seriously.While the perpetrator was never identified and opportunities for improvement were identified along the way, by including student leaders in the process, students and administrators were able to develop trust and reach reasonable closure on this disturbing event. Take home messages are presented to guide other institutions in navigating instances of provocative comments or speech.

The ubiquitin ligase PHR promotes directional regrowth of spinal zebrafish axons

To reconnect with their synaptic targets, severed axons need to regrow robustly and directionally along the pre-lesional trajectory. While mechanisms directing axonal regrowth are poorly understood, several proteins direct developmental axon outgrowth, including the ubiquitin ligase PHR (Mycbp2). Invertebrate PHR also limits regrowth of injured axons, whereas its role in vertebrate axonal regrowth remains elusive. Here we took advantage of the high regrowth capacity of spinal zebrafish axons and observed robust and directional regrowth following laser transection of spinal Mauthner axons. We found that PHR directs regrowing axons along the pre-lesional trajectory and across the transection site. At the transection site, initial regrowth of wild-type axons was multidirectional. Over time, misdirected sprouts were corrected in a PHR-dependent manner. Ablation of cyfip2, known to promote F-actin-polymerization and pharmacological inhibition of JNK reduced misdirected regrowth of PHR-deficient axons, suggesting that PHR controls directional Mauthner axonal regrowth through cyfip2- and JNK-dependent pathways.

Electromigration of Cell Surface Macromolecules during Galvanotaxis

Weak, DC electric fields (EFs) direct cellular polarity, migration and outgrowth. They are used to induce polarity during tissue engineering and direct migration to promote epidermal wound repair. Fields as weak as 10 mV/mm, are sufficient to direct migration, although the mechanisms used by cells to sense such weak fields are still debated as weaknesses exist in the competing models. We hypothesize that cellular polarization is achieved by the redistribution of a cell surface, electric field receptor (EFR) in the presence of an applied EF. We are investigating the electromigration model that depends on electrically generated forces in the plane of the plasma membrane and parallel to the electric field vector, specifically, electrophoretic and electro-osmotic forces. Electrophoretic force drives net negatively charged macromolecules to the anode while electro-osmotic flow of water, in the boundary layer, drives macromolecules with large extracellular domains to the cathode. We have derived a model based on these opposing forces, to predict the relative concentration of surface proteins over space and time, allowing us to test the redistribution of known plasma membrane surface macromolecules in applied EFs and under controlled conditions. The model closely describes accumulation of a net negatively charged, GPI-anchored, fluorescent protein to the cathode under different field strengths, showing that redistribution reaches steady-state within minutes, significantly faster than cathodally migrating cells turn toward the cathode. The model is useful for determining the most likely candidates for the EFR on many different cell types.

Automation and assessment of de novo modeling with Pathwalking in near atomic resolution cryoEM density maps.

With the rapidly growing number of macromolecular structures solved to near-atomic resolution using electron cryomicroscopy (cryoEM), map interpretation and model building directly from the density without the use of structural templates has become increasingly important. As part of the 2015/2016 Map and Model Challenge, we attempted to assess our latest de novo modeling tool, Pathwalking, in terms of performance and usability, as well as identify areas for future improvements. In total, we applied Pathwalking to six density maps between 3 and 4.5 Å resolution selected from the challenge data sets. In five of the six cases, Pathwalking was able to accurately determine the protein fold and in three of these cases, the final all atom model had less than 1.6 Å RMSD when compared to the known structure. Model building and refinement was nearly completely automated, used default parameters and took less than 30 min to complete a refined all atom model. A direct outgrowth of this work was a more streamlined automated command line Pathwalking utility, as well as a novel sequence assignment and optimization routine, which attempts to register sidechain density with expected side chain volume. In total, Pathwalking offers a nearly complete, robust and efficient method for constructing atomistic protein structures directly from a density map without the aid of a template.

The Fundamental and Ornamental Use of Scripture in Two Dominican Procedurals on Confession from the Early Thirteenth Century: Cum ad sacerdotes and Confessio debet

Abstract Although the expansion of jurisprudence in the twelfth century was a direct outgrowth of theological scholasticism, several historians of law such as Richard Helmholz have noted that the use of sacred scripture as a basis for jurisprudence steadily declined in the thirteenth and fourteenth centuries. He identified the increasing relegation of biblical references to an ornamental, rather than a fundamental, mode of citation beginning with the earliest post-Gratian glosses and treatises. Because the Dominican Order of Preachers, renowned for their biblical preaching, also produced many great canonists and legal texts, the question of whether their legal writings experienced a similar decline is of particular interest. In the present study, a close reading of two Dominican procedurals for confessors and penitents will conclude that the Dominicans themselves recognized the difference between fundamental and ornamental citation and that they began to streamline their biblical references, removing ornamental and leaving only fundamental citations.

Mechanism of Fgf‐Mediated Lhx2 Upregulation

IntroductionDuring development, fibroblast growth factors (FGFs) secreted from the apical ectodermal ridge (AER) direct limb outgrowth. FGFs also coordinate limb patterning through cross‐talk with other signaling molecules. The LIM homeobox transcription factor LHX2 is a suspected regulator of patterning cross‐talk, is expressed at the distal tip of the limb bud subjacent to the AER, and is a primary response target of FGF (Figure 1). However, the mechanism by which FGFs upregulate LHX2 is unknown. There are four major FGF signaling pathways through which regulation may occur: Jak/Stat, PLCγ, AKT, and Ras‐related (Figure 2). Based on the suspected roles of each signaling pathway, we hypothesize that FGF mediates LHX2 upregulation through the Ras‐related pathway.MethodsTo determine whether FGFs regulate LHX2 through the Ras‐related pathway, we injected the chemical inhibitor Salirasib (2.5 mM) into the anterior, posterior, and distal tips of the right limb of chick embryos at Hamburger‐Hamilton stage 21–22 (Figure 3). We also examined the potential function of the other Fgf pathways using pathway‐specific inhibitors. The embryos were harvested 24 hours after treatment and assessed for morphology. Whole mount in situ hybridization for LHX2 was then performed (Figure 4).ResultsPreliminary results indicate that inhibition of the Ras‐related pathway caused growth inhibition of the treated limbs in all embryos. In addition, LHX2 expression was markedly decreased in the these limbs. Treatment with a PLCγ‐specific inhibitor did not alter limb growth, while an AKT‐specific inhibitor impaired limb growth and LHX2 expression.ConclusionThese results suggest that the Ras‐related and AKT pathways control Fgf‐mediated LHX2 upregulation, whereas PLCγ does not. Further studies are needed to confirm these findings and to evaluate the Jak/Stat pathway.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Disaggregating LWOP: Life Without Parole, Capital Punishment, and Mass Incarceration in Florida, 1972–1995

Over the past 40 years, life imprisonment without the possibility of parole (LWOP) has been transformed from a rare sanction and marginal practice of last resort into a routine punishment in the United States. Two general theses—one depicting LWOP as a direct outgrowth of death penalty abolition; another collapsing LWOP into the tough-on-crime sentencing policy of the mass incarceration era—serve as working explanations for this phenomenon. In the absence of in-depth studies, however, there has been little evidence for carefully evaluating these narratives. This article provides a state-level historical analytic account of LWOP's rise by looking to Florida—the state that uses LWOP more than any other—to explicate LWOP's specific processes and forms. Recounting LWOP's history in a series of critical junctures, the article identifies a different stimulus, showing how LWOP precipitated as Florida translated major structural upheavals that broke open traditional ways of doing and thinking about punishment. In doing so, the article reveals LWOP to be a multilayered product of incremental change, of many, sometimes disjointed and indirectly conversant, pieces. Presenting LWOP as the product of a variety of penal logics, including those prioritizing fairness and efficiency, the article more generally illustrates how very severe punishments can arise from reforms without primarily punitive purposes and in ways that were not necessarily planned.

An Ichor-dependent apical extracellular matrix regulates seamless tube shape and integrity.

During sprouting angiogenesis in the vertebrate vascular system, and primary branching in the Drosophila tracheal system, specialized tip cells direct branch outgrowth and network formation. When tip cells lumenize, they form subcellular (seamless) tubes. How these seamless tubes are made, shaped and maintained remains poorly understood. Here we characterize a Drosophila mutant called ichor (ich), and show that ich is essential for the integrity and shape of seamless tubes in tracheal terminal cells. We find that Ich regulates seamless tubulogenesis via its role in promoting the formation of a mature apical extracellular matrix (aECM) lining the lumen of the seamless tubes. We determined that ich encodes a zinc finger protein (CG11966) that acts, as a transcriptional activator required for the expression of multiple aECM factors, including a novel membrane-anchored trypsin protease (CG8213). Thus, the integrity and shape of seamless tubes are regulated by the aECM that lines their lumens.