Sonographic staging of the developmental status of mouse embryos in utero

In mouse developmental studies it is frequently desirable to isolate embryos of a specific age. However, the traditional staging of embryonic development based on postcoital dates often erroneously predicts the embryonic age, resulting in unwarranted sacrifice of the pregnant mother. Here we report a noninvasive way of staging embryonic development in utero. A clinical 14 MHz ultrasound system was employed to assess the morphology and size of developing embryos from embryonic day 7.5 to 18.5. We demonstrate that the developmental age of the mouse embryos can be accurately determined based on the sonographic morphology and size of the embryos. This noninvasive ultrasound application requires no anesthesia of the mice and the entire process of staging can be completed within 5-10 min. Empirically, this approach is applicable to mice of various genetic backgrounds and significantly enhances the efficiency of studying murine embryogenesis.     

An induced blood pressure rise does not alter upper airway resistance in sleeping humans

Wilson, Christine R., Shalini Manchanda, David Crabtree,James B. Skatrud, and Jerome A. Dempsey. An induced blood pressurerise does not alter upper airway resistance in sleeping humans.J. Appl. Physiol. 84(1): 269-276, 1998.Sleep apnea is associated with episodic increases in systemicblood pressure. We investigated whether transient increases in arterialpressure altered upper airway resistance and/or breathingpattern in nine sleeping humans (snorers and nonsnorers). Apressure-tipped catheter was placed below the base of the tongue, andflow was measured from a nose or face mask. Duringnon-rapid-eye-movement sleep, we injected 40- to 200-µg iv boluses ofphenylephrine. Parasympathetic blockade was used if bradycardia wasexcessive. Mean arterial pressure (MAP) rose by 20 ± 5 (mean ± SD) mmHg (range 12-37 mmHg) within 12 s and remained elevated for105 s. There were no significant changes in inspiratory or expiratorypharyngeal resistance (measured at peak flow, peak pressure, 0.2 l/s orby evaluating the dynamic pressure-flow relationship). Atpeak MAP, end-tidal CO₂ pressure fell by 1.5 Torr and remained low for 20-25 s. At 26 s after peak MAP, tidal volume fell by 19%, consistent with hypocapnic ventilatory inhibition. We conclude that transient increases in MAP of a magnitude commonly observed during non-rapid-eye-movement sleep-disordered breathing do not increase upper airway resistance and, therefore, willnot perpetuate subsequent obstructive events.

     

Comparative analysis of the zeta-crystallin/quinone reductase gene in guinea pig and mouse

zeta-Crystallin is a novel nicotinamide adenine dinucleotide phosphate:quinone reductase, present at enzymatic levels in various tissues of different species, which is highly expressed in the lens of some hystricomorph rodents and camelids. We report here the complementary DNA (cDNA) cloning of zeta-crystallin from liver libraries in guinea pig (Cavia porcellus), where zeta-crystallin is highly expressed in the lens, and in the laboratory mouse (Mus musculus), where expression in the lens occurs only at enzymatic levels. A 5' untranslated sequence different from the one previously reported for the guinea pig lens cDNA was found in these clones. We also report the isolation of genomic clones including the complete guinea pig zeta-crystallin gene and the 5' region of this gene in mouse. These results show the presence of two promoters in the guinea pig zeta-crystallin gene, one responsible for expression at enzymatic levels and the other responsible for the high expression in the lens. The guinea pig lens promoter is not present in the mouse gene. This is the first example in which the recruitment of an enzyme as a lens crystallin can be explained by the acquisition of an alternative lens- specific promoter.      

Helicobacter pylori-induced epithelial cell signalling in gastric carcinogenesis

Helicobacter pylori represents a highly successful human microbial pathogen that infects the stomach of more than half of the world's population. H. pylori induces gastric inflammation, and the diseases that can follow such infection include chronic gastritis, peptic ulcers and, more rarely, gastric cancer. The reasons why a minority of patients with H. pylori develops gastric cancer could be related to differences in host susceptibility, environmental factors and the genetic diversity of the organism. This review examines the features of H. pylori-induced epithelial cell signalling in gastric diseases. Clinical studies and animal models, and also evidence for H. pylori strain-related differences in gastric epithelial cell proliferation in vivo are discussed. In addition, the mechanisms by which H. pylori triggers hyperproliferative processes and takes direct command of epithelial cell signalling, including activation of tyrosine kinase receptors, cell-cell interactions and cell motility are reviewed.     

Whole-genome sequence analysis of Pseudomonas syringae pv. phaseolicola 1448A reveals divergence among pathovars in genes involved in virulence and transposition

Pseudomonas syringae pv. phaseolicola, a gram-negative bacterial plant pathogen, is the causal agent of halo blight of bean. In this study, we report on the genome sequence of P. syringae pv. phaseolicola isolate 1448A, which encodes 5,353 open reading frames (ORFs) on one circular chromosome (5,928,787 bp) and two plasmids (131,950 bp and 51,711 bp). Comparative analyses with a phylogenetically divergent pathovar, P. syringae pv. tomato DC3000, revealed a strong degree of conservation at the gene and genome levels. In total, 4,133 ORFs were identified as putative orthologs in these two pathovars using a reciprocal best-hit method, with 3,941 ORFs present in conserved, syntenic blocks. Although these two pathovars are highly similar at the physiological level, they have distinct host ranges; 1448A causes disease in beans, and DC3000 is pathogenic on tomato and Arabidopsis. Examination of the complement of ORFs encoding virulence, fitness, and survival factors revealed a substantial, but not complete, overlap between these two pathovars. Another distinguishing feature between the two pathovars is their distinctive sets of transposable elements. With access to a fifth complete pseudomonad genome sequence, we were able to identify 3,567 ORFs that likely comprise the core Pseudomonas genome and 365 ORFs that are P. syringae specific.     

[(C5H4MeEt)Ir(PPh3)2]: an agostic C-C bond or a close metal-ligand contact?

DFT calculations and orbital arguments show that the short M?C distances in the title 1,1-methylethylcyclopentadiene complex are best explained as short nonbonding contacts rather than as examples of C-C agostic bonding, as previously suggested.