The gut supports neurogenic differentiation of periocular mesenchyme, a chondrogenic neural crest-derived cell population

Periocular mesenchyme (PM) is a mesencephalic neural crest derived cell population which as a result of an interaction with the retinal pigment epithelium forms the scleral cartilage of the avian eye. Enteric neurons are derived from vagal crest cells which invade the gut. To study factors which regulate neuronal differentiation, we investigated whether the gut could direct neurogenesis in PM, a cell population that does not produce neurons in vivo. We report here that PM cultured in the presence of aneural chick hindgut on the chorioallantoic membrane (CAM), invaded the gut and formed large numbers of neurons. These were localized in enteric ganglia and contained neurofilament immunoreactivity, vasoactive intestinal peptide immunoreactivity, and somatostatin immunoreactivity. In the control PM cultured alone on the CAM, a small number of cells contained neurofilament immunoreactivity but lacked the appearance of mature neurons.     

Kinetics of actin-myosin binding. II. Two-variable model and actin gelation

We consider a model of actin-myosin interaction in which the sites belonging to each seven-site regulated actin unit are subdivided into two classes, "internal" and "external." The time evolution of each class of sites is considered separately, leading to a pair of coupled differential equations that may be integrated numerically. We also consider the critical sol-gel transition point for actin filaments crosslinked by two-headed heavy meromyosin (HMM). The possibility of new types of chemical oscillation and pattern formation arising from periodic sol-gel transitions is discussed.     

Comprehensive inhibitor profiling of the Proteus mirabilis metalloprotease virulence factor ZapA (mirabilysin)

In this study we report for the first time the comprehensive inhibitor profiling of the Proteus mirabilis metalloprotease virulence factor ZapA (mirabilysin) using a 160 compound focused library of N-alpha mercaptoamide dipeptides, in order to map the and binding site preferences of this important enzyme. This study has revealed a preference for the aromatic residues tyrosine and tryptophan in and aliphatic residues in . From this library, six compounds were identified which exhibited sub- to low-micromolar K_i values. The most potent inactivator, SH–CO₂–Y–V–NH₂ was capable of preventing ZapA-mediated hydrolysis of heat-denatured IgA, indicating that these inhibitors may be capable of protecting host proteins against ZapA during colonisation and infection.     

Stainless steel mesh supports high density cell growth and production of recombinant Mullerian Inhibiting Substances

Summary Stainless steel mesh supported the high density growth of anchorage dependent CHO fibroblasts without the use of a special culture system. CHO cells, designated B-9, containing an amplified genomic construct of the human gene for Mullerian Inhibiting Substance (MIS), grew to a high confluent density on stainless steel meshwork while producing substantial amounts of human recombinant MIS over a long period of time. The mesh could be easily coated with various extracellular matrix proteins, such as Laminin, Fibronectin, Collagen or Matrigel, which permitted the testing of the effects of surface modifications on cell yield and recombinant protein production. Since the amount of medium per surface area required for optimal cell growth is lower than for some large volume cell culture methods, media costs can be reduced using mesh. In addition, no special cell culture equipment or complex manipulations are required. Thus, the use of meshwork for anchorage-dependent cells can increase the efficiency of growth and decrease the cost of recombinant protein production. This work is supported by NIH grant CA 17393 and American Cancer Society grant PDT 221A to P. K. D. and NIH grant EY 06535 to J. E. Editor's Statement This approach to large scale, high density cultivation of cells, one of several which are based on increasing surface area of the cultures, allows the production of large amounts of recombinant product within a research laboratory with modest bulk culture capability.     

MicroRNA-processing enzyme Dicer is required in epicardium for coronary vasculature development

The epicardium is a sheet of epithelial cells covering the heart during early cardiac development. In recent years, the epicardium has been identified as an important contributor to cardiovascular development, and epicardium-derived cells have the potential to differentiate into multiple cardiac cell lineages. Some epicardium-derived cells that undergo epithelial-to-mesenchymal transition and delaminate from the surface of the developing heart subsequently invade the myocardium and differentiate into vascular smooth muscle of the developing coronary vasculature. MicroRNAs (miRNAs) have been implicated broadly in tissue patterning and development, including in the heart, but a role in epicardium is unknown. To examine the role of miRNAs during epicardial development, we conditionally deleted the miRNA-processing enzyme Dicer in the proepicardium using Gata5-Cre mice. Epicardial Dicer mutant mice are born in expected Mendelian ratios but die immediately after birth with profound cardiac defects, including impaired coronary vessel development. We found that loss of Dicer leads to impaired epicardial epithelial-to-mesenchymal transition and a reduction in epicardial cell proliferation and differentiation into coronary smooth muscle cells. These results demonstrate a critical role for Dicer, and by implication miRNAs, in murine epicardial development.     

Pit membranes in tracheary elements of Rosaceae and related families: new records of tori and pseudotori

The micromorphology of pits in tracheary elements was examined in 35 species representing 29 genera of Rosaceae and related families to evaluate the assumption that angiosperm pits are largely invariant. In most Rosaceae, pit membranes between fibers and tracheids frequently appear to have amorphous thickenings with an irregular distribution. Although these structures are torus-like under the light microscope, observations by electron microscopy illustrate that they represent "pseudotori" or plasmodesmata-associated thickenings. These thickenings frequently extend from the periphery of the pit membrane and form a cap-like, hollow structure. Pseudotori are occasionally found in few Elaeagnaceae and Rhamnaceae and appear to be related to species with fiber-tracheids and/or tracheids. True tori are strongly associated with round to oval pit apertures and are consistently present in narrow tracheary elements of Cercocarpus (Rosaceae), Planera (Ulmaceae), and ring-porous species of Ulmus and Zelkova (Ulmaceae). Vestured pits with homogenous pit membranes are reported for Hemiptelea (Ulmaceae). The homoplastic nature of pit membrane characteristics may be related to functional adaptations in terms of safety and efficiency of water transport or may reflect different developmental processes of xylem elements. These observations illustrate that there is more variation in angiosperm pits than previously thought.     

Marine macroalgae and their associated microbiomes as a source of antimicrobial chemical diversity

ABSTRACT

This article reviews the role of microbial biofilms in infection, and the antimicrobial chemical diversity of marine macroalgae and their associated microbiomes. Antimicrobial resistance (AMR) represents one of the major health threats faced by humanity over the next few years. To prevent a global epidemic of antimicrobial-resistant infections, the discovery of new antimicrobials and antibiotics, better anti-infection strategies and diagnostics, and changes to our current use of antibiotics have all become of paramount importance. Numerous studies investigating the bioactivities of seaweed extracts as well as their secondary and primary metabolites highlight the vast biochemical diversity of seaweeds, with new modes of action making them ideal sources for the discovery of novel antimicrobial bioactive compounds of pharmaceutical interest. In recent years, researchers have focused on characterizing the endophytic and epiphytic microbiomes of various algal species in an attempt to elucidate host-microbe interactions as well as to understand the function of microbial communities. Although environmental and host-associated factors crucially shape microbial composition, microbial mutualistic and obligate symbionts are often found to play a fundamental role in regulating many aspects of host fitness involving ecophysiology and metabolism. In particular, algal ‘core’ epiphytic bacterial communities play an important role in the protection of surfaces from biofouling, pathogens and grazers through the production of bioactive metabolites. Together, marine macroalgae and their associated microbiomes represent unique biological systems offering great potential for the isolation and identification of novel compounds and strategies to counteract the rise and dissemination of AMR.     

Cyanide-induced transition from endogenous carbohydrate to lipid oxidation as indicated by the carbon-13 content of respiratory CO2

The respiration of thin aerated discs of potato tuber tissue rises sigmoidally through 24 h. Aged disc respiration is ostensibly resistant to concentrations of cyanide which inhibit the respiration of fresh discs. It has been shown that cyanide-resistant respiration does not represent indifference to the inhibitor, but is rather due to the suppression of one respiratory carbon path and the evocation of another. The predominant respiratory carbon path of aged discs in the absence of cyanide comprises glycolysis linked to the tricarboxylic acid cycle. The carbon path mediating the cyanide-induced respiration reflects tricarboxylic acid cycle-independent lipid degradation.

The respiratory substrate at any time was deduced by comparing the ¹³C/¹²C ratio of respired CO₂, collected from discs in the presence or absence of cyanide, with the ¹³C/¹²C ratios characterizing endogenous potential metabolites. The determination of the predominant respiratory substrate in potato discs, which have an endogenous substrate reserve, proved possible because the relative concentrations of the stable carbon isotopes in endogenous compounds such as lipid and starch are widely different.