Differential proto-oncogene mRNA induction from rats treated with peroxisome proliferators

After experimental treatment of rats with clofibrate or ciprofibrate, two peroxisomes proliferators with hypolipidemic activity, RNAs were prepared from liver, kidney, heart and brain; hybridization was done with DNA probes for c-myc and c-Ha-ras oncogenes and for cyanide insensitive Acyl CoA oxidase, a peroxisomal protein. c-myc mRNA is highly abundant in liver and at a lower extent in kidney, especially after treatment with ciprofibrate; clofibrate also allows a c-myc mRNA increase, but at a lower extent. c-Ha-ras, which is already expressed in all tested tissues from control animals, is stimulated by clofibrate and ciprofibrate treatments. Comparatively these compounds stimulate the cyanide insensitive Acyl CoA oxidase expression as well as they increase the somatic index of liver and kidney. From these experiments we suggest that hepatocarcinogenesis triggered by some hypolipidemic agents could be mediated by proto-oncogene mRNA level increase.     

Macro-Climatic Distribution Limits Show Both Niche Expansion and Niche Specialization among C4 Panicoids

Grasses are ancestrally tropical understory species whose current dominance in warm open habitats is linked to the evolution of C₄ photosynthesis. C₄ grasses maintain high rates of photosynthesis in warm and water stressed environments, and the syndrome is considered to induce niche shifts into these habitats while adaptation to cold ones may be compromised. Global biogeographic analyses of C₄ grasses have, however, concentrated on diversity patterns, while paying little attention to distributional limits. Using phylogenetic contrast analyses, we compared macro-climatic distribution limits among ~1300 grasses from the subfamily Panicoideae, which includes 4/5 of the known photosynthetic transitions in grasses. We explored whether evolution of C₄ photosynthesis correlates with niche expansions, niche changes, or stasis at subfamily level and within the two tribes Paniceae and Paspaleae. We compared the climatic extremes of growing season temperatures, aridity, and mean temperatures of the coldest months. We found support for all the known biogeographic distribution patterns of C₄ species, these patterns were, however, formed both by niche expansion and niche changes. The only ubiquitous response to a change in the photosynthetic pathway within Panicoideae was a niche expansion of the C₄ species into regions with higher growing season temperatures, but without a withdrawal from the inherited climate niche. Other patterns varied among the tribes, as macro-climatic niche evolution in the American tribe Paspaleae differed from the pattern supported in the globally distributed tribe Paniceae and at family level.     

Different contributions of HtrA protease and chaperone activities to Campylobacter jejuni stress tolerance and physiology

The microaerophilic bacterium Campylobacter jejuni is the most common cause of bacterial food-borne infections in the developed world. Tolerance to environmental stress relies on proteases and chaperones in the cell envelope, such as HtrA and SurA. HtrA displays both chaperone and protease activities, but little is known about how each of these activities contributes to stress tolerance in bacteria. In vitro experiments showed temperature-dependent protease and chaperone activities of C. jejuni HtrA. A C. jejuni mutant lacking only the protease activity of HtrA was used to show that the HtrA chaperone activity is sufficient for growth at high temperature or under oxidative stress, whereas the HtrA protease activity is essential only under conditions close to the growth limit for C. jejuni. However, the protease activity was required to prevent induction of the cytoplasmic heat shock response even under optimal growth conditions. Interestingly, the requirement of HtrA at high temperatures was found to depend on the oxygen level, and our data suggest that HtrA may protect oxidatively damaged proteins. Finally, protease activity stimulates HtrA production and oligomer formation, suggesting that a regulatory role depends on the protease activity of HtrA. Studying a microaerophilic organism encoding only two known periplasmic chaperones (HtrA and SurA) revealed an efficient HtrA chaperone activity and proposed multiple roles of the protease activity, increasing our understanding of HtrA in bacterial physiology.     

Response of Listeria monocytogenes to Disinfection Stress at the Single-Cell and Population Levels as Monitored by Intracellular pH Measurements and Viable-Cell Counts

Listeria monocytogenes has a remarkable ability to survive and persist in food production environments. The purpose of the present study was to determine if cells in a population of L. monocytogenes differ in sensitivity to disinfection agents as this could be a factor explaining persistence of the bacterium. In situ analyses of Listeria monocytogenes single cells were performed during exposure to different concentrations of the disinfectant Incimaxx DES to study a possible population subdivision. Bacterial survival was quantified with plate counting and disinfection stress at the single-cell level by measuring intracellular pH (pH_i) over time by fluorescence ratio imaging microscopy. pH_i values were initially 7 to 7.5 and decreased in both attached and planktonic L. monocytogenes cells during exposure to sublethal and lethal concentrations of Incimaxx DES. The response of the bacterial population was homogenous; hence, subpopulations were not detected. However, pregrowth with NaCl protected the planktonic bacterial cells during disinfection with Incimaxx (0.0015%) since pH_i was higher (6 to 6.5) for the bacterial population pregrown with NaCl than for cells grown without NaCl (pH_i 5 to 5.5) (P < 0.05). The protective effect of NaCl was reflected by viable-cell counts at a higher concentration of Incimaxx (0.0031%), where the salt-grown population survived better than the population grown without NaCl (P < 0.05). NaCl protected attached cells through drying but not during disinfection. This study indicates that a population of L. monocytogenes cells, whether planktonic or attached, is homogenous with respect to sensitivity to an acidic disinfectant studied on the single-cell level. Hence a major subpopulation more tolerant to disinfectants, and hence more persistent, does not appear to be present.Listeria monocytogenes is a food-borne, human pathogen that has a remarkable ability to colonize food-processing environments (5, 16, 20, 21, 26, 29). Some L. monocytogenes strains can persist for years in food-processing plants (11, 14, 20, 27), and specific molecular subtypes can repeatedly be isolated from the processing environment (29) despite being very infrequent in the outdoor environment (9). This ability to persist has, hitherto, not been linked to any specific genetic or phenotypic trait.It has been suggested that persistent L. monocytogenes strains may be more tolerant or resistant to cleaning and especially disinfectants used in the food industry. Aase et al. (1) found increased tolerance to both benzalkonium chloride and ethidium bromide in L. monocytogenes isolates that had persisted for more than 4 years; however, other studies have not been able to link persistence and tolerance to disinfectants (6, 10, 11, 13). We recently compared disinfection sensitivities of persistent and presumed nonpersistent L. monocytogenes strains using viable-cell counts and did not find the latter group more sensitive to the two disinfectants Triquart SUPER and Incimaxx DES than persistent strains (13). However, we found that for all subtypes of L. monocytogenes, growth with NaCl increased the tolerance of planktonic L. monocytogenes cells to Incimaxx DES, whereas spot-inoculated, dried L. monocytogenes cells were not protected by NaCl against disinfection.There is no doubt that L. monocytogenes will be completely inactivated at the disinfectant concentrations recommended for use in the food industry; however, the efficiency of the disinfectant is very much influenced by the presence of organic material being inactivated by the presence of food debris. Hence, it is likely that the bacterial cell in a food production environment may be exposed to concentrations at a sublethal level. It is currently not known if treatment with a sublethal concentration of disinfectant affects the entire bacterial population or only attacks a fraction of the cell population, leaving another fraction of cells unaffected. In case of the latter, some bacterial cells may be able to survive the disinfection treatment. The potential presence of such tolerant subpopulations could, ultimately, ensure that the genome is propagated, leading to persistence.The presence of a more tolerant subpopulation can be determined on the single-cell level. Flow cytometry is a rapid method useable for measurements at the single-cell resolution (22); however, it cannot monitor the same single cells over time. Optical microscopy combined with microfluidic devices that allow measurement of growth of single cells is a useful technique (2), and in situ analyses of the physiological condition of single cells by the fluorescence ratio imaging microscopy (FRIM) technique represents another elegant approach (25). FRIM enables studies of dynamic changes with high sensitivity and on the single-cell level in important physiological parameters: e.g., intracellular pH (pH_i). Listeria maintains its pH_i within a narrow range of 7.6 to 8 at extracellular pH (pH_ex) values of 5.0 to 8.0 (4, 25) and at pH_ex 4.0 with the presence of glucose (23). It is believed that viable cells need to maintain a transmembrane pH gradient with their pH_i above the pH_ex, and failure to maintain pH_i homeostasis indicates that the bacterial cell is severely stressed and ultimately leads to loss of cell viability. FRIM has been used to determine the pH_i of L. monocytogenes after exposure to osmotic and acid stress (7, 23). Also, the dissipation of the pH gradient in L. monocytogenes after exposure to different bacteriocins has been determined with FRIM (4, 12). Hornbæk et al. (12) found that treatment with subinhibitory concentrations of leucocin and nisin gave rise to two subpopulations: one consisting of cells with a dissipated pH gradient (ΔpH) and the other consisting of cells that maintained ΔpH, which could indicate phenotypic heterogeneity.The aim of the present study was to investigate the physiological effects of the disinfectant Incimaxx DES at sublethal and lethal concentrations on single cells and the population level of a persistent L. monocytogenes strain to study a possible subdivision of sensitivity in the population. We also addressed the potential protective effect of NaCl against disinfection and compared sensitivities in a population of planktonic and attached bacteria. We applied the in situ technique FRIM and compared the pH_i measurements with the traditional viable-cell-count method.(Part of the results have been presented at a poster session at the 95th International Association for Food Protection annual meeting in Columbus, OH, 3 to 6 August 2008.)     

Modulation of chloride secretory responses and barrier function of intestinal epithelial cells by the Salmonella effector protein SigD

The Salmonella effector protein SigD is an inositol phosphate phosphatase that inhibits phosphatidylinositol 3-kinase-dependent signaling. Because epidermal growth factor (EGF) inhibits chloride secretion via phosphatidylinositol 3-kinase, we explored whether Salmonella infection might modify the inhibitory effect of EGF. As expected, EGF inhibited chloride secretion induced by carbachol in T₈₄ epithelial cells. Infection with wild-type (WT) but not sigD^– mutant S. typhimurium SL1344 decreased CCh-stimulated chloride secretion. Moreover, WT but not sigD^– Salmonella reduced the inhibitory effect of EGF on carbachol-stimulated chloride secretion. Complementation of sigD restored the ability of mutant Salmonella to reverse the inhibitory effect of EGF. EGF-induced EGF receptor phosphorylation was similar in cells infected with either WT or mutant Salmonella, and neither WT nor sigD^– Salmonella altered recruitment of the p85 subunit of phosphatidylinositol 3-kinase to EGF receptor, implying that SigD acts downstream of these signaling events. Furthermore, transepithelial resistance fell more rapidly in cells infected with WT vs. sigD^– Salmonella, indicating an early role for SigD in reducing barrier function, perhaps via activation of protein kinase C. We conclude that the Salmonella bacterial effector protein SigD may play critical roles in the pathogenesis of disease caused by this microorganism. chloride secretion; Salmonella typhimurium; epidermal growth factor     

Pharmacological undertreatment of coronary risk factors in patients with psoriasis: observational study of the Danish nationwide registries

Background

Patients with psoriasis have increased prevalence of coronary risk factors and limited recent results have suggested that these risk factors are undertreated in patients with psoriasis. This may contribute to the increased risk of cardiovascular diseases observed in patients with psoriasis.

Objective

To examine the pharmacological treatment of coronary risk factors in patients with severe psoriasis treated with biologic agents in a real-world setting.

Methods and Findings

Medical history of patients with severe psoriasis treated with biologic agents in the time period 2007–09 was retrieved from a Danish nationwide registry (DERMBIO). Individual-level linkage of nationwide administrative registries of hospitalizations, concomitant medications, and socioeconomic status was performed to gain insights into the use of pharmacological treatment. A total of 693 patients (mean age 46.1±12.7 years, 65.7% male) with severe psoriasis treated with biologic agents were identified. Hypertension, hypercholesterolemia, and diabetes mellitus were identified in 16.6%, 9.2%, and 6.7% of cases, respectively. Patients with severe psoriasis were significantly less likely to receive cardiovascular pharmacotherapy compared to age, sex, and coronary risk factor matched controls. In psoriatic patients with hypertension 27.7% received no antihypertensive pharmacotherapy. Patients with dyslipidemia received cholesterol-lowering medications in 55.8% of cases and patients with diabetes mellitus received angiotensin converting enzyme inhibitors/angiotensin II receptor blockers and cholesterol-lowering medications in 42.1% and 23.7% of cases, respectively. Similar results were found for the subset of patients with >1 coronary risk factor and for high risk patients with established atherosclerotic disease.

Conclusion

This nationwide study of patients with severe psoriasis demonstrated substantial undertreatment of coronary risk factors. Increased focus on identifying cardiovascular risk factors and initiation of preventive cardiovascular pharmacotherapy in patients with psoriasis is warranted.     

Analysis of the collar-whisker structure of temperate lactococcal bacteriophage TP901-1

Proteins homologous to the protein NPS (neck passage structure) are widespread among lactococcal phages. We investigated the hypothesis that NPS is involved in the infection of phage TP901-1 by analysis of an NPS- mutant. NPS was determined to form a collar-whisker complex but was shown to be nonessential for infection, phage assembly, and stability.