Effects of Mutations Within Surface-Exposed Loops in the Pore-Forming Domain of the Cry9Ca Insecticidal Toxin of Bacillus thuringiensis

The pore-forming domain of Bacillus thuringiensis insecticidal Cry toxins is formed of seven amphipathic α-helices. Because pore formation is thought to involve conformational changes within this domain, the possible role of its interhelical loops in this crucial step was investigated with Cry9Ca double mutants, which all share the previously characterized R164A mutation, using a combination of homology modeling, bioassays and electrophysiological measurements. The mutations either introduced, neutralized or reversed an electrical charge carried by a single residue of one of the domain I loops. The ability of the 28 Cry9Ca double mutants to depolarize the apical membrane of freshly isolated Manduca sexta larval midguts was tested in the presence of either midgut juice or a cocktail of protease inhibitors because these conditions had been shown earlier to greatly enhance pore formation by Cry9Ca and its R164A single-site mutant. Most mutants retained toxicity toward neonate larvae and a pore-forming ability in the electrophysiological assay, which were comparable to those of their parental toxin. In contrast, mutants F130D, L186D and V189D were very poorly toxic and practically inactive in vitro. On the other hand, mutant E129A depolarized the midgut membrane efficiently despite a considerably reduced toxicity, and mutant Q192E displayed a reduced depolarizing ability while conserving a near wild-type toxicity. These results suggest that the conditions found in the insect midgut, including high ionic strength, contribute to minimizing the influence of surface charges on the ability of Cry9Ca and probably other B. thuringiensis toxins to form pores within their target membrane.     

Quorum sensing by 2-alkyl-4-quinolones in Pseudomonas aeruginosa and other bacterial species

Pseudomonas aeruginosa produces the cell-to-cell signal molecule 2-heptyl-3-hydroxy-4-quinolone (The Pseudomonas quinolone signal; PQS), which is integrated within a complicated quorum sensing signaling system. PQS belongs to the family of 2-alkyl-4-quinolones (AQs), which have been previously described for their antimicrobial activities. PQS is synthesized via the pqsABCDE operon which is responsible for generating multiple AQs including 2-heptyl-4-quinolone (HHQ), the immediate PQS precursor. In addition, PQS signaling plays an important role in P. aeruginosa pathogenesis because it regulates the production of diverse virulence factors including elastase, pyocyanin and LecA lectin in addition to affecting biofilm formation. Here, we summarize the most recent findings on the biosynthesis and regulation of PQS and other AQs including the discovery of AQs in other bacterial species.     

Lactobacillus acidophilus modulates intestinal pain and induces opioid and cannabinoid receptors

Abdominal pain is common in the general population and, in patients with irritable bowel syndrome, is attributed to visceral hypersensitivity. We found that oral administration of specific Lactobacillus strains induced the expression of mu-opioid and cannabinoid receptors in intestinal epithelial cells, and mediated analgesic functions in the gut-similar to the effects of morphine. These results suggest that the microbiology of the intestinal tract influences our visceral perception, and suggest new approaches for the treatment of abdominal pain and irritable bowel syndrome.     

Assessment of single-dose benzodiazepines on insulin secretion,insulin sensitivity and glucose effectiveness in healthy volunteers: a double-blind,placebo-controlled,randomized cross-over trial [ISRCTN08745124]

Background  

The present study aimed at investigating in healthy volunteers the effects of diazepam and clonazepam on beta-cell function, insulin sensitivity and glucose effectiveness based on the frequently sampled intravenous (0.5 gkg^-1) glucose tolerance test with minimal-model analysis.     

Effects of zamic as a means for zinc supplementation in growing children

We investigated the effects of zinc supplementation in cases of moderate growth retardation in which GH treatment could not be used. Zamic (ZA, an association containing arginine, L-methionine, and zinc; from Aguettant pharmaceuticals) was compared with arginine aspartate (AA) (5 g) in a crossover randomized trial (6 mo of each treatment at random order over 1 yr). We present preliminary results of 24 children who completed the study (3 girls, 21 boys, age 9–13 yr). Subjects had to be prepubertal, with no GH deficiency diagnosed. In 15 subjects growth velocity was lower than 5 mm/mo: In this case ZA improved growth velocity (rising from 3.105 ± 0.229 to 5.4 ± 0.69 mm/mop < 0.01), whereas the effect of AA was not significant. The increase in growth velocity was higher with ZA (+2.44 ±0.657 mm/mo) than AA (+0.438 ± 0.450 mm/mo)p < 0.05. These results suggest that ZA is more efficient than AA, consistent with the hypothesis that zinc needs are increased in those children in this period of life.     

Factors predicting patient use of the emergency department: a retrospective cohort study

Background:

Many studies have shown the tendency for people without a regular care provider or primary physician to make greater use of emergency departments. We sought to determine the effects of three aspects of care provided by primary physicians (physician specialty, continuity of care and comprehensiveness of care) on their patients’ use of the emergency department.

Methods:

Using provincial administrative databases, we created a cohort of 367 315 adults aged 18 years and older. Participants were residents of urban areas of Quebec. Affiliation with a primary physician, the specialty of this physician (i.e., family physician v. specialist), continuity of care (as measured using the Usual Provider Continuity index) and comprehensiveness of care (i.e., number of complete annual examinations) were measured among participants (n = 311 701) who had visited a physician three or more times during a two-year baseline period. We used multivariable negative binomial regression to investigate the relationships between measures of care and the number of visits to emergency departments during a 12-month follow-up period.

Results:

Among participants under 65 years of age, emergency department use was higher for those not affiliated than for those affiliated with a family physician (incidence rate ratio [IRR] 1.11, 95% confidence interval [CI] 1.05–1.16) or a specialist (IRR 1.10, 95% CI 1.04–1.17). Among patients aged 65 years and older, having a specialist primary physician, as opposed to a family physician, predicted increased use of the emergency department (IRR 1.13, 95% CI 1.09–1.17). Greater continuity of care with a family physician predicted less use of the emergency department only among participants who made 25 or more visits to a physician during the baseline period. Greater continuity of care with a specialist predicted less use of the emergency department overall, particularly among participants with intermediate numbers of multimorbidities and admissions to hospital. Greater comprehensiveness of care by family physicians predicted less use of the emergency department.

Interpretation:

Efforts to increase the proportion of adults affiliated with a family physician should target older adults, people who visit physicians more frequently and people with multiple comorbidities and admissions to hospital.Reforming primary care in Canada has been stimulated in part by increased crowding of emergency departments and evidence that their use, particularly for nonurgent care, may be related to inadequate primary care in the community.^1,2 Restructuring efforts, such as encouraging family physicians to work in multidisciplinary group practices with 24-hour access, are challenged by a relative shortage of family physicians.³ These issues are of particular importance in Quebec; despite relatively high numbers of family physicians per capita, in comparison with other provinces, residents of Quebec have the lowest rates of affiliation with a family physician and have one of the highest rates of seeing specialists.^4,5 In addition, residents of Quebec have among the highest rates of visits to emergency departments in international comparative studies.^6–8Research is needed into the effect that affiliation with a specialist rather than a family physician has on patients’ use of the emergency department, as is research into the continuity and comprehensiveness of care provided by the primary physician, regardless of specialty.Many studies have shown the tendency for people without a regular care provider to use the emergency department more often than people who have a primary physician.^1,9,10 Greater continuity of care with a primary physician has also been associated with fewer visits to the emergency department, but much of this research is cross-sectional, making causal interpretation difficult.¹¹ Furthermore, the distinction between continuity with a family physician versus a specialist primary physician has not been made, although one American study reported that having a specialist primary physician was associated with increased use of emergency departments.⁹We sought to determine whether certain factors predicted patients’ subsequent use of emergency departments, such as the specialty of their primary physician, the continuity of care with that physician and the comprehensiveness of care provided by that physician. To determine whether certain subgroups of the population may derive greater benefit from a particular type of care, we examined the potentially modifying effects of demographic factors, health status and previous use of health services. We restricted our study to residents of urban areas of Quebec for three reasons: rural residents visit the emergency department for primary care more often than residents of urban areas;¹² most specialist care is provided in urban areas; and primary care services in rural areas are more likely to be provided by salaried physicians, whose information is not available in the billing database.     

A new classification of HLA-DRB1 alleles differentiates predisposing and protective alleles for autoantibody production in rheumatoid arthritis

The HLA-DRB1 gene was reported to be associated with anticitrullinated protein/peptide autoantibody (ACPA) production in rheumatoid arthritis (RA) patients. A new classification of HLA-DRB1 alleles, reshaping the shared epitope (SE) hypothesis, was recently found relevant in terms of RA susceptibility and structural severity.     

Aphid clonal resistance to a parasitoid fails under heat stress

Parasitoid virulence and host resistance are complex interactions depending on metabolic rate and cellular activity, which in aphids additionally implicate heritable secondary symbionts among the Enterobacteriaceae. As performance of the parasitoid, the aphid host and its symbionts may differentially respond to temperature, the success or failure of aphid parasitism is difficult to predict when temperature varies. We tested the hypothesis that resistance of the pea aphid Acyrthosiphon pisum to the parasitoid Aphidius ervi, which is linked to aphid secondary symbionts, may depend on temperature in several resistant and non-resistant aphid clonal lineages of different geographic origin and of known bacterial symbiosis, using experiments in controlled environments. Complete immunity to A. ervi at 20 degrees C in three different aphid clones whose symbiosis is characterized by the possession of Hamiltonella defensa reversed to high susceptibility at 25 degrees C and especially 30 degrees C, suggesting that the aphid's immune responses to the establishment and early development of the parasitoid is strongly reduced at moderately high temperatures. There was no evidence that a pea aphid control genotype that was susceptible to A. ervi at 20 degrees C could become more resistant as temperature increases, as has been suggested for insect fungal pathogens. By contrast, our results suggest that aphid clonal resistance to A. ervi and related parasitoids is characteristic of cool temperature conditions, similar to various other fitness attributes of aphids. Based on evidence that H. defensa symbionts characterized all three A. ervi resistant pea aphid clones studied, but was absent in control aphids that remained susceptible at all temperatures, we suggest that secondary symbiosis plays a key role in the heat sensitivity of aphid clonal resistance. Our study may also indicate that aphid natural control of variably susceptible host populations by aphid parasitoids is more likely at moderate to high temperatures.     

Fire and Pinus mugo Turra communities in the western Alps (Susa Valley, Italy) during the Lateglacial-Holocene transition: an evidence of refugia area

In western Italian Alps, small distinct populations of Pinus mugo Turra raise some questions concerning its ecological status and dynamics in the occidental Alps. This note present new palaeobotanical data based on cone imprints of Pinus mugo, identified in travertine systems located in the Val di Susa and dated back to the Late Dryas (11506+/-66 BP) and the Early Holocene (10145+/-225 et 9475+/-670 BP). Heliophilous species and charcoal fragments were also identified, testifying to the oldness of wildfires in this region. The data support the hypothesis that this zone was a refuge area of this pine during the last glaciation. Here we discuss about the postglacial dynamics of the Pinus mugo in the occidental Alps.