Induction of a novel epidermal growth factor-secreting cell lineage by mucosal ulceration in human gastrointestinal stem cells

Epidermal growth factor, and its human homologue urogastrone (EGF/URO), are secreted by the gut-associated salivary and Brunner's glands. Recombinant EGF/URO is a powerful stimulator of cell proliferation and differentiation in the rodent and neonatal human intestine. But EGF/URO is not absorbed from the adult gut and has no action when given through the gut lumen; thus the role of secreted EGF/URO is unknown. We now report that ulceration of the epithelium anywhere in the human gastrointestinal tract induces the development of a novel cell lineage from gastrointestinal stem cells. This lineage initially appears as a bud from the base of intestinal crypts, adjacent to the ulcer, and grows locally as a tubule, ramifying to form a new small gland, and ultimately emerges onto the mucosal surface. The lineage produces neutral mucin, shows a unique lectin-binding profile and immunophenotype, is nonproliferative, and contains and secretes abundant immunoreactive EGF/URO. We propose that all gastrointestinal stem cells can produce this cell lineage after mucosal ulceration, secreting EGF/URO to stimulate cell proliferation, regeneration and ulcer healing. This cell lineage is very commonly associated with gastrointestinal mucosal ulceration, and we conclude that a principal in vivo role for EGF/URO is to stimulate ulcer healing throughout the gut through induction of this cell lineage in the adjacent mucosa.     

The genome of the choanoflagellate Monosiga brevicollis and the origin of metazoans

Choanoflagellates are the closest known relatives of metazoans. To discover potential molecular mechanisms underlying the evolution of metazoan multicellularity, we sequenced and analysed the genome of the unicellular choanoflagellate Monosiga brevicollis. The genome contains approximately 9,200 intron-rich genes, including a number that encode cell adhesion and signalling protein domains that are otherwise restricted to metazoans. Here we show that the physical linkages among protein domains often differ between M. brevicollis and metazoans, suggesting that abundant domain shuffling followed the separation of the choanoflagellate and metazoan lineages. The completion of the M. brevicollis genome allows us to reconstruct with increasing resolution the genomic changes that accompanied the origin of metazoans.     

Charge order and three-site distortions in the Verwey structure of magnetite

The mineral magnetite (Fe(3)O(4)) undergoes a complex structural distortion and becomes electrically insulating at temperatures less than 125 kelvin. Verwey proposed in 1939 that this transition is driven by a charge ordering of Fe(2+) and Fe(3+) ions, but the ground state of the low-temperature phase has remained contentious because twinning of crystal domains hampers diffraction studies of the structure. Recent powder diffraction refinements and resonant X-ray studies have led to proposals of a variety of charge-ordered and bond-dimerized ground-state models. Here we report the full low-temperature superstructure of magnetite, determined by high-energy X-ray diffraction from an almost single-domain, 40-micrometre grain, and identify the emergent order. The acentric structure is described by a superposition of 168 atomic displacement waves (frozen phonon modes), all with amplitudes of less than 0.24 ?ngstr?ms. Distortions of the FeO(6) octahedra show that Verwey's hypothesis is correct to a first approximation and that the charge and Fe(2+) orbital order are consistent with a recent prediction. However, anomalous shortening of some Fe-Fe distances suggests that the localized electrons are distributed over linear three-Fe-site units, which we call 'trimerons'. The charge order and three-site distortions induce substantial off-centre atomic displacements and couple the resulting large electrical polarization to the magnetization. Trimerons may be important quasiparticles in magnetite above the Verwey transition and in other transition metal oxides.     

Effect of niacin/nicotinamide deficiency on the diabetogenic effect of streptozotocin

Weanling CD-1 mice were fed either a control diet or a diet deficient in niacin/nicotinamide for one month and then injected i.v. with 60, 80, 100, 120, 140, or 160 mg/kg streptozotocin. Mice on the deficient diet developed a higher incidence of diabetes and more severe hyperglycemia than those on the control diet.     

3-Ethyl-2,5-dimethylpyrazine,a component of the trail pheromone of the antMessor bouvieri

Summary 3-Ethyl-2,5-dimethylpyrazine, found in the poison gland of workers, induces trail following in the Mediterranean harvester antMessor bouvieri. The poison gland contains on average 9 ng of this trail pheromone component. The alkaloids anabasine and anabaseine are also present in this gland, but induce no reaction in workers. Trail following is also induced by substances present in the Dufour gland, but the combined effect of both glands shows no synergism.