Cell motility driving mediolateral intercalation in explants of Xenopus laevis

In Xenopus, convergence and extension are produced by active intercalation of the deep mesodermal cells between one another along the mediolateral axis (mediolateral cell intercalation), to form a narrower, longer array. The cell motility driving this intercalation is poorly understood. A companion paper shows that the endodermal epithelium organizes the outermost mesodermal cells immediately beneath it to undergo convergence and extension, and other evidence suggests that these deep cells are the most active participants in mediolateral intercalation (Shih, J. and Keller, R. (1992) Development 116, 887–899). In this paper, we shave off the deeper layers of mesodermal cells, which allows us to observe the protrusive activity of the mesodermal cells next to the organizing epithelium with high resolution video microscopy. These mesodermal cells divide in the early gastrula and show rapid, randomly directed protrusive activity. At the early midgastrula stage, they begin to express a characteristic sequence of behaviors, called mediolateral intercalation behavior (MIB): (1) large, stable, filiform and lamelliform protrusions form in the lateral and medial directions, thus making the cells bipolar; (2) these protrusions are applied directly to adjacent cell surfaces and exert traction on them, without contact inhibition; (3) as a result, the cells elongate and align parallel to the mediolateral axis and perpendicular to the axis of extension; (4) the elongate, aligned cells intercalate between one another along the mediolateral axis, thus producing a longer, narrower array. Explants of essentially a single layer of deep mesodermal cells, made at stage 10.5, converge and extend by mediolateral intercalation. Thus by stage 10.5 (early midgastrula), expression of MIB among deep mesodermal cells is physiologically and mechanically independent of the organizing influence of the endodermal epithelium, described previously (Shih, J. and Keller, R. (1992) Development 116 887–899), and is the fundamental cell motility underlying mediolateral intercalation and convergence and extension of the body axis

The epithelium of the dorsal marginal zone of Xenopus has organizer properties

We have investigated the properties of the epithelial layer of the dorsal marginal zone (DMZ) of the Xenopus laevis early gastrula and found that it has inductive properties similar to those of the entire Spemann organizer. When grafts of the epithelial layer of the DMZ of early gastrulae labelled with fluorescein dextran were transplanted to the ventral sides of unlabelled host embryos, they induced secondary axes composed of notochord, somites and posterior neural tube. The organizer epithelium rescued embryos ventralized by UV irradiation, inducing notochord, somites and posterior neural tube in these embryos, while over 90% of ventralized controls showed no such structures. Combinations of organizer epithelium and ventral marginal zone (VMZ) in explants of the early gastrula resulted in convergence, extension and differentiation of dorsal mesodermal tissues, whereas similar recombinants of nonorganizer epithelium and the VMZ did none of these things. In all cases, the axial structures forming in response to epithelial grafts were composed of labelled graft and unlabelled host cells, indicating an induction by the organizer epithelium of dorsal, axial morphogenesis and tissue differentiation among mesodermal cells that otherwise showed non-axial development. Serial sectioning and scanning electron microscopy of control grafts shows that the epithelial organizer effect occurs in the absence of contaminating deep cells adhering to the epithelial grafts. However, labelled organizer epithelium grafted to the superficial cell layer contributed cells to deep mesodermal tissues, and organizer epithelium developed into mesodermal tissues when deliberately grafted into the deep region. This shows that these prospective endodermal epithelial cells are able to contribute to mesodermal, mesenchymal tissues when they move or are moved into the deep environment. These results suggest that in normal development, the endodermal epithelium may influence some aspects of the cell motility underlying the mediolateral intercalation (see Shih, J. and Keller, R. (1992) Development 116, 901–914), as well as the tissue differentiation of mesodermal cells. These results have implications for the analysis of mesoderm induction and for analysis of variations in the differentiation and morphogenetic function of the marginal zone in different species of amphibians

The patterning and functioning of protrusive activity during convergence and extension of the Xenopus organiser

We discuss the cellular basis and tissue interactions regulating convergence and extension of the vertebrate body axis in early embryogenesls of Xenopus. Convergence and extension occur in the dorsal mesoderm (prospective notochord and somite) and in the posterior nervous system (prospective hindbrain and spinal cord) by sequential cell intercalations. Several layers of cells intercalate to form a thinner, longer array (radial intercalation) and then cells intercalate in the mediolateral orientation to form a longer, narrower array (mediolateral intercalation). Fluorescence microscopy of labeled mesodermal cells in explants shows that protrusive activity is rapid and randomly directed until the midgastrula stage, when it slows and is restricted to the medial and lateral ends of the cells. This bipolar protrusive activity results in elongation, alignment and mediolateral intercalation of the cells. Mediolateral intercalation behavior (MIB) is expressed in an anterior- posterior and lateral-medial progression in the mesoderm. MIB is first expressed laterally in both somitic and notochordal mesoderm. From its lateral origins in each tissue, MIB progresses medially. If convergence does not bring the lateral boundaries of the tissues closer to the medial cells in the notochordal and somitic territories, these cells do not express MIB. Expression of tissue-specific markers follows and parallels the expression of MIB. These facts argue that MIB and some aspects of tissue differentiation are induced by signals emanating from the lateral boundaries of the tissue territories and that convergence must bring medial cells and boundaries closer together for these signals to be effective. Grafts of dorsal marginal zone epithelium to the ventral sides of other embryos, to ventral explants and to UV-ventralized embryos show that it has a role in organising convergence and extension, and dorsal tissue differentiation among deep mesodermal cells. Grafts of involuting marginal zone to animal cap tissue of the early gastrula shows that convergence and extension of the hindbrain-spinal cord are induced by planar signals from the involuting marginal zone

A Targeted Therapeutic Rescues Botulinum Toxin-A Poisoned Neurons

Botulinum neurotoxin (BoNT), a Category A biothreat agent, is the most potent poison known to mankind. Currently no antidote is available to rescue poisoned synapses. BoNT acts specifically by blocking neurotransmission primarily at peripheral nerve-muscle junctions causing severe flaccid muscle paralysis, which is fatal if proper medical care is not provided. The neurotoxin acts by specifically entering the presynaptic nerve endings where it interferes with the biochemical machinery involved in the process of neurotransmitter release, i.e., neuroexocytosis. Most serotypes of BoNT are known to remain active for weeks to months after entering the nerves, but BoNT/A is the most potent and long lasting in causing muscle paralysis. An effective medical countermeasure strategy requires developing a drug that could rescue poisoned neuromuscular synapses, and would include its efficient delivery specifically to presynaptic nerve terminals. Here we report rescuing of botulinum poisoned nerve cells by Mastoparan-7 (Mas-7), a peptide constituent of bee venom, that was delivered through a drug delivery vehicle (DDV) constructed from the non-toxic fragment of botulinum neurotoxin itself. We found that Mas-7 that was delivered into BoNT/A intoxicated cultured mouse spinal cord cells restored over 40% of stimulated neurotransmitter release. The rescue of the cell poisoning did not occur from inhibition of the endopeptidase activity of BoNT/A against its well known substrate, SNAP-25 that is mechanistically involved in the exocytosis process. Rather, Mas-7 induced a physiological host response apparently unrelated to SNAP-25, but linked to the phospholipase signal transduction pathway. In addition to providing the first effective antidote against botulism, our results open new avenues to study the mechanism of exocytosis, and also to examine an alternative cellular mechanism of botulinum neurotoxin action. An effective BoNT-based DDV can also be utilized for drug delivery against many neuronal and neuromuscular disorders

Properties of nonaqueous electrolytes Quarterly report, 20 Sep. - 19 Dec. 1966

Vapor phase chromatographic analysis of dimethyl formamide, and physical properties of electrolytes containing lithium chloride and/or aluminum chlorid

Early development of Ensatina eschscholtzii: an amphibian with a large, yolky egg

<p>Abstract</p> <p>Background</p> <p>Comparative analyses between amphibians, concentrating on the cellular mechanisms of morphogenesis, reveal a large variability in the early developmental processes that were thought to be conserved during evolution. Increased egg size is one factor that could have a strong effect on early developmental processes such as cleavage pattern and gastrulation. Salamanders of the family Plethodontidae are particularly appropriate for such comparative studies because the species have eggs of varying size, including very large yolky eggs.</p> <p>Results</p> <p>In this paper, we describe for the first time the early development (from fertilization through neurulation) of the plethodontid salamander <it>Ensatina eschscholtzii</it>. This species has one of the largest eggs known for an amphibian, with a mean ± SD diameter of 6 ± 0.43 mm (range 5.3-6.9; n = 17 eggs). Cleavage is meroblastic until approximately the 16-cell stage (fourth or fifth cleavage). At the beginning of gastrulation, the blastocoel roof is one cell thick, and the dorsal lip of the blastopore forms below the equator of the embryo. The ventral lip of the blastopore forms closer to the vegetal pole, and relatively little involution occurs during gastrulation. Cell migration is visible through the transparent blastocoel roof of the gastrula. At the end of gastrulation, a small archenteron spreading dorsally from the blastopore represents the relatively small and superficial area of the egg where early embryonic axis formation occurs. The resulting pattern is similar to the embryonic disk described for one species of anuran.</p> <p>Conclusions</p> <p>Comparisons with the early development of other species of amphibians suggest that an evolutionary increase in egg size can result in predictable changes in the patterns and rate of early development, but mainly within an evolutionary lineage.</p

PNE – Lots of Talk, Superficial Results

Objective: A narrative review (NR) of meta-analyses (MA) and systematic reviews (SR) that assess the effectiveness or efficacy of pain neuroscience education (PNE) on various outcome measures in individuals with chronic musculoskeletal (MSK) pain. Methods: This was a mixed methodology review involving systematic searches across 4 databases (PubMed, ScienceDirect, CENTRAL (Cochrane), and Google Scholar). Inclusion criteria stipulated MAs and SRs that assessed the effectiveness or efficacy of PNE on CP population. Quantitative eligibility criteria included randomized controlled trials (RCTs), adults (18+ years of age), English or Spanish speaking individuals, and reporting of chronic pain (persistent or recurrent pain lasting ≥ 3 months). Qualitative eligibility criteria included individuals reporting chronic pain and experienced a PNE intervention. Two reviewers screened 9,760 articles via COVIDENCE. 11 reviews met inclusion criteria and underwent full text review, specifically examining methodology and outcomes. Conclusions: This narrative review, including 11 reviews, emphasizes the need for further research pertaining to the efficacy and effectiveness of PNE utilization in healthcare. Each of these reviews are laced with varying levels of heterogeneity or low-quality evidence. Additionally, it remains unknown which information is pertinent to be included with PNE to achieve desired outcomes and belief reconceptualization. This is the result of a lack of thorough research and evaluation of PNE due to its recent establishment within healthcare. An updated systematic review should be performed that includes recently published literature with broad inclusion criteria to obtain a full-picture perspective of PNE

Phytosciology of the Cox woods: A remnant of forest primeval in Orange county, Indiana

Today Indiana forests are primarily in a stage of secondary succession, and small tracts, comparatively little disturbed by cultural influences, with tree giants which have ahsorbed for centuries the radiant energy of light, and stored it in their massive trunks, have become so large that they arouse interest and curiosity of the public at large

The role of trained champions in sustaining and spreading nutrition care improvements in hospital: qualitative interviews following an implementation study.

BACKGROUND: Many patients are already malnourished when admitted to hospital. Barriers and facilitators to nutrition care in hospital have been identified and successful interventions developed; however, few studies have explored how to sustain and spread improvements. The More-2-Eat phase 1 study involved five hospitals across Canada implementing nutrition care improvements, while phase 2 implemented a scalable model using trained champions, audit and feedback, a community of practice with external mentorship and an implementation toolkit in 10 hospitals (four continuing from phase 1). Process measures showed that screening and assessment from phase 1 were sustained for at least 4 years. The objective of this study was to help explain how these nutrition care improvements were sustained and spread by understanding the role of the trained champions, and to confirm and expand on themes identified in phase 1. METHODS: Semistructured telephone interviews were conducted with champions from each phase 2 hospital and recordings transcribed verbatim. To explore the champion role, transcripts were deductively coded to the 3C model of Concept, Competence and Capacity. Phase 2 transcripts were also deductively coded to themes identified in phase 1 interviews and focus groups. RESULTS: Ten interviews (n=14 champions) were conducted. To sustain and spread nutrition care improvements, champions needed to understand the Concepts of change management, implementation, adaptation, sustainability and spread in order to embed changes into routine practice. Champions also needed the Competence, including the skills to identify, support and empower new champions, thus sharing the responsibility. Capacity, including time, resources and leadership support, was the most important facilitator for staying engaged, and the most challenging. All themes identified in qualitative interviews in phase 1 were applicable 4 years later and were mentioned by new phase 2 hospitals. There was increased emphasis on audit and feedback, and the need for standardisation to support embedding into current practice. CONCLUSION: Trained local champions were required for implementation. By understanding key concepts, with appropriate and evolving competence and capacity, champions supported sustainability and spread of nutrition care improvements. Understanding the role of champions in supporting implementation, spread and sustainability of nutrition care improvements can help other hospitals when planning for and implementing these improvements. TRIAL REGISTRATION NUMBER: NCT02800304, NCT03391752