Pseudomonas aeruginosa PAO1 kills Caenorhabditis elegans by cyanide poisoning.

In this report we describe experiments to investigate a simple virulence model in which Pseudomonas aeruginosa PAO1 rapidly paralyzes and kills the nematode Caenorhabditis elegans. Our results imply that hydrogen cyanide is the sole or primary toxic factor produced by P. aeruginosa that is responsible for killing of the nematode. Four lines of evidence support this conclusion. First, a transposon insertion mutation in a gene encoding a subunit of hydrogen cyanide synthase (hcnC) eliminated nematode killing. Second, the 17 avirulent mutants examined all exhibited reduced cyanide synthesis, and the residual production levels correlated with killing efficiency. Third, exposure to exogenous cyanide alone at levels comparable to the level produced by PAO1 killed nematodes with kinetics similar to those observed with bacteria. The killing was not enhanced if hcnC mutant bacteria were present during cyanide exposure. And fourth, a nematode mutant (egl-9) resistant to P. aeruginosa was also resistant to killing by exogenous cyanide in the absence of bacteria. A model for nematode killing based on inhibition of mitochondrial cytochrome oxidase is presented. The action of cyanide helps account for the unusually broad host range of virulence of P. aeruginosa and may contribute to the pathogenesis in opportunistic human infections due to the bacterium.

Surface control of oxidation by an adsorbed Ru(IV)-oxo complex.

When adsorbed to optically transparent, thin films of TiO(2) nanoparticles on glass, the aqua complex [Ru(II)(tpy)(bpy(PO(3)H(2))(2))(OH(2))](2+) (bpy(PO(3)H(2))(2) is 2,2'-bipyridyl-4,4'-diphosphonic acid; tpy is 2,2':6',2' '-terpyridine) is oxidized by Ce(IV)(NH(4))(2)(NO(3))(6) in 0.1 M HClO(4) to its Ru(IV)=O(2+) form as shown by UV-visible measurements and analysis of oxidative equivalents by oxidation of hydroquinone to quinone. Kinetic studies on the oxidations of cyclohexene, benzyl alcohol, phenol, and trans-stilbene by surface-bound Ru(IV)=O(2+) by UV-visible monitoring reveal direct evidence for initial 2-electron steps to give Ru(II) intermediates in all four cases. These steps are masked in solution where Ru(IV) --> Ru(II) reduction is followed by rapid reactions between Ru(II) intermediates and Ru(IV)=O(2+) to give Ru(III). Reactions between Ru(II) and Ru(IV)=O(2+) on the surface are inhibited by binding to the surface, which restricts translational mobility. Rate constants on the surface and in solution are comparable, pointing to comparable reactivities. The surface experiments give unprecedented insight into oxidation mechanism with important implications for achieving product selectivity in synthesis by limiting oxidation to two electrons.

Drosophila as a model host for Pseudomonas aeruginosa infection.

Using the fruit fly Drosophila melanogaster as model host, we have identified mutants of the bacterium Pseudomonas aeruginosa with reduced virulence. Strikingly, all strains strongly impaired in fly killing also lacked twitching motility; most such strains had a mutation in pilGHIJKL chpABCDE, a gene cluster known to be required for twitching motility and potentially encoding a signal transduction system. The pil chp genes appear to control the expression of additional virulence factors, however, since the wild-type fly-killing phenotype of a subset of mutants isolated on the basis of their compact colony morphology indicated that twitching motility itself was not required for full virulence in the fly.

Stop-and-go movements of plant Golgi stacks are mediated by the acto-myosin system.

The Golgi apparatus in plant cells consists of a large number of independent Golgi stack/trans-Golgi network/Golgi matrix units that appear to be randomly distributed throughout the cytoplasm. To study the dynamic behavior of these Golgi units in living plant cells, we have cloned a cDNA from soybean (Glycine max), GmMan1, encoding the resident Golgi protein alpha-1,2 mannosidase I. The predicted protein of approximately 65 kD shows similarity of general structure and sequence (45% identity) to class I animal and fungal alpha-1,2 mannosidases. Expression of a GmMan1::green fluorescent protein fusion construct in tobacco (Nicotiana tabacum) Bright Yellow 2 suspension-cultured cells revealed the presence of several hundred to thousands of fluorescent spots. Immuno-electron microscopy demonstrates that these spots correspond to individual Golgi stacks and that the fusion protein is largely confined to the cis-side of the stacks. In living cells, the stacks carry out stop-and-go movements, oscillating rapidly between directed movement and random "wiggling." Directed movement (maximal velocity 4.2 microm/s) is related to cytoplasmic streaming, occurs along straight trajectories, and is dependent upon intact actin microfilaments and myosin motors, since treatment with cytochalasin D or butanedione monoxime blocks the streaming motion. In contrast, microtubule-disrupting drugs appear to have a small but reproducible stimulatory effect on streaming behavior. We present a model that postulates that the stop-and-go motion of Golgi-trans-Golgi network units is regulated by "stop signals" produced by endoplasmic reticulum export sites and locally expanding cell wall domains to optimize endoplasmic reticulum to Golgi and Golgi to cell wall trafficking.

What the hand surgeon should know about workers' compensation.

It is important for surgeons treating work-related conditions to be knowledgeable of workers' compensation laws in their states. They should also work closely with the designated provider and/or employer to effect speedy recovery and return to work.

Influence of a combination of ritodrine and nifedipine on the isolated rat uterus.

Studies were undertaken to evaluate the efficacy of the beta 2-adrenergic agonist ritodrine and the calcium channel blocker nifedipine, alone and in combination, for inhibition of contraction in isolated rat uterine strips. Both compounds produced a dose-dependent reduction of area under the curve. When contractions were produced by oxytocin, a 26% reduction was observed with 0.144mcg of ritodrine and a significant 68.1% decrease was produced with 1.44mcg of ritodrine. Contraction frequency (contractions per ten minutes) was not significantly affected. Prostaglandin F2 alpha-induced contractions were significantly inhibited 27.1% and 62.2% by 1.44mcg and 14.4mcg of ritodrine, respectively. Also, contraction frequency was significantly affected by both concentrations. Inhibition of area under the curve of oxytocin-induced contractions produced by nifedipine was 39.3% for 0.05mcg and 78.4% (P less than 0.05) for 0.50mcg. Contraction frequency was unaffected. Prostaglandin F2 alpha-induced contractions were significantly attenuated by 60% and 86% with nifedipine (0.50mcg and 5.02mcg, respectively); contraction frequency was significantly reduced from 15 to 2 contractions per ten minutes by 5.02mcg. Oxytocin-induced contraction was attenuated 39.8% by a combination of ritodrine 0.144mcg and nifedipine 0.05mcg; contraction frequency was unaffected. Area under the curve and contraction frequency of oxytocin-induced contractions were significantly decreased by a combination of ritodrine 0.144mcg and nifedipine 0.50mcg (89.8% reduction; decrease in frequency from 12 contractions in control to 4 contractions post-inhibitory agent). Significant attenuation of prostaglandin F2 alpha-induced contractions was produced by ritodrine 1.44mcg and nifedipine 0.50mcg. Area under the curve decreased by 73.2% and frequency was reduced from 13 to 8 contractions. A combination of ritodrine 1.44mcg and nifedipine 5.02mcg also produced significant decreases in area under the curve (85.3%) and frequency (13 contractions in control to 1 contraction after compounds were added). Because the mechanisms of action of these two agents are different, it is reasonable to suggest that they be used in combination to control premature labor. The results of this study suggest they may provide inhibition of contraction superior to either agent alone, and could therefore provide more effective inhibition and possibly reduce untoward side effects common to ritodrine therapy.

Effects of tetracycline hydrochloride on pleurae in dogs with induced pleural effusion.

Pleural effusion was induced in 12 dogs by ligation of the cranial vena cava. Pleurodesis was attempted by injecting a solution of tetracycline hydrochloride into the pleural space of 8 dogs (4 dogs, 25 mg/kg of body weight; 4 dogs, 50 mg/kg) via bilateral thoracostomy tubes. In both groups, tetracycline was diluted in 40 ml of normal saline solution and 10 ml of 1% lidocaine before injection. Half of the solution (25 ml) was instilled in each hemithorax. Four control dogs were treated in the same manner with a solution of normal saline and lidocaine. Daily pleural fluid production was measured after the attempted pleurodesis. Thirty days after administration of the solution, each dog was euthanatized and necropsied. Surface area of pleural adhesions was measured. Tissues from regions of pleural adhesions and areas of parietal and visceral pleura not involved in adhesions were analyzed histologically. Formation of pleural fluid stopped in all but 1 control dog within 48 hours after injection of solution. This dog effused throughout the study. The resolution of effusion was not significantly (P less than 0.05) different between the tetracycline-treated dogs and the control group. Although diffuse pleural adhesions were not induced in any of the dogs, significantly (P less than 0.0027) more surface area of lung was adhered in dogs treated with the higher dose of tetracycline.