Wolbachia in the Culex pipiens group mosquitoes: introgression and superinfection

Wolbachia bacteria in mosquitoes induce cytoplasmic incompatibility (CI), where sperm from Wolbachia-infected males can produce inviable progeny. The wPip strain in the Culex pipiens group of mosquitoes produces a complexity of CI crossing types. Several factors are thought to be capable of influencing the expression of CI including Wolbachia strain type and host genotype. In this study, the unidirectional CI that occurs between 2 C. pipiens complex laboratory strains, Col and Mol, was further investigated by nuclear genotype introgression. The unidirectional CI between Col and Mol was not found to be influenced by host genetic background, in contrast to a previous introgression study carried out using bidirectionally incompatible C. pipiens group strains. A line containing both wPip strain variants superinfection was also generated by embryonic cytoplasmic transfer. The same crossing type as the parental Col strain was observed in the superinfected line. Quantitative polymerase chain reaction demonstrated a low density of the injected wPipMol variant in the superinfected line after 18 generations, which was considered likely to be responsible for the crossing patterns observed. The Wolbachia density was also shown to be lower in the parental Mol strain males compared with Col strain males, and no inverse relationship between WO phage and Wolbachia density could be detected.

Cervical smear adequacy: cellularity references were found to increase both interobserver agreement and unsatisfactory rate

OBJECTIVES

To determine the degree of interobserver variation in the assessment of conventional cervical smear adequacy as defined by The Bethesda System (TBS) 2001, and to determine the effect of using reference images of known squamous cellularity when performing squamous adequacy assessments.

METHODS

Experimental pre-test/post-test design utilizing 70 conventionally prepared cervical smears. Sample smears containing scant squamous cellularity were independently rated on two occasions by six cytotechnologists. Time 1 was without the use of reference images, and Time 2 was aided by cellularity reference images. The kappa statistic was used to compare rater agreement.

RESULTS

The level of agreement increased from an average kappa of 0.26 (SD 0.10) for Time 1, to an average kappa of 0.40 (SD 0.15) for Time 2. The difference in mean kappa values at the two assessments was statistically significant (t = 3.71; P = 0.002). Unanimous agreement among the raters was observed for 15 samples (21.42%) at Time 1 (only one of which was classified as unsatisfactory) and 21 samples (30.00%) at Time 2 (12 of which were classified as unsatisfactory).

CONCLUSION

Interobserver agreement increased after cellularity reference images were implemented. Using TBS 2001 squamous adequacy criteria and images of known squamous cellularity as references resulted in a decreased number of smears reported as satisfactory.

Imported typhoid fever in Switzerland, 1993 to 2004

BACKGROUND

In industrialized countries, typhoid fever occurs mainly in returned travelers. To determine the need for preventive strategies, eg, for vaccination, continuous monitoring is needed to assess where the risk for travelers is highest.

METHODS

To investigate where the risk for travelers to acquire typhoid fever is highest, 208 patients with typhoid fever and recent travel were matched with travelers' statistics collected by the Swiss Federal Office of Statistics.

RESULTS

At the beginning of the study period, up to 30 infections with Salmonella typhi were recorded per year in Switzerland. Since 2001, less than 15 confirmed cases per year occurred. A majority of the 208 (88.5%) typhoid cases were associated with recent travel. Countries with highest risk were Pakistan (24 per 100,000), Cambodia (20 per 100,000), Nepal (14 per 100,000), India (12 per 100,000), and Sri Lanka (9 per 100,000).

CONCLUSIONS

We found that over a 12-year period (1993-2004), the travel-associated risk of typhoid fever is highest for destinations in the Indian subcontinent. All other regions showed a decline, most markedly in southern Europe. Our results suggest that typhoid fever vaccination should be recommended for all travelers to countries in South Asia. Otherwise, vaccination of tourists to frequently visited low- and intermediate-risk areas is not necessary, unless there are behavioral risk factors.

Genome evolution of Wolbachia strain wPip from the Culex pipiens group

The obligate intracellular bacterium Wolbachia pipientis strain wPip induces cytoplasmic incompatibility (CI), patterns of crossing sterility, in the Culex pipiens group of mosquitoes. The complete sequence is presented of the 1.48-Mbp genome of wPip which encodes 1386 coding sequences (CDSs), representing the first genome sequence of a B-supergroup Wolbachia. Comparisons were made with the smaller genomes of Wolbachia strains wMel of Drosophila melanogaster, an A-supergroup Wolbachia that is also a CI inducer, and wBm, a mutualist of Brugia malayi nematodes that belongs to the D-supergroup of Wolbachia. Despite extensive gene order rearrangement, a core set of Wolbachia genes shared between the 3 genomes can be identified and contrasts with a flexible gene pool where rapid evolution has taken place. There are much more extensive prophage and ankyrin repeat encoding (ANK) gene components of the wPip genome compared with wMel and wBm, and both are likely to be of considerable importance in wPip biology. Five WO-B-like prophage regions are present and contain some genes that are identical or highly similar in multiple prophage copies, whereas other genes are unique, and it is likely that extensive recombination, duplication, and insertion have occurred between copies. A much larger number of genes encode ankyrin repeat (ANK) proteins in wPip, with 60 present compared with 23 in wMel, many of which are within or close to the prophage regions. It is likely that this pattern is partly a result of expansions in the wPip lineage, due for example to gene duplication, but their presence is in some cases more ancient. The wPip genome underlines the considerable evolutionary flexibility of Wolbachia, providing clear evidence for the rapid evolution of ANK-encoding genes and of prophage regions. This host-Wolbachia system, with its complex patterns of sterility induced between populations, now provides an excellent model for unraveling the molecular systems underlying host reproductive manipulation.

Aptamer-based isolation and subsequent imaging of mesenchymal stem cells in ischemic myocard by magnetic resonance imaging

PURPOSE

Mesenchymal stem cells (MSC) seem to be a promising cell source for cellular cardiomyoplasty. We recently developed a new aptamer-based specific selection of MSC to provide "ready to transplant" cells directly after isolation. We evaluated MRI tracking of newly isolated and freshly transplanted MSC in the heart using one short ex vivo selection step combining specific aptamer-based isolation and labeling of the cells.

MATERIALS AND METHODS

Bone marrow (BM) was collected from healthy pigs. The animals were euthanized and the heart was placed in a perfusion model. During cold ischemia, immunomagnetic isolation of MSC from the BM by MSC-specific aptamers labeled with Dynabeads was performed within 2 h. For histological identification the cells were additionally stained with PKH26. Approx. 3 x 10(6) of the freshly aptamer-isolated cells were injected into the ramus interventricularis anterior (RIVA) and 5 x 10(5) cells were injected directly into myocardial tissue after damaging the respective area by freezing (cryo-scar). 3 x 10(6) of the aptamer-isolated cells were kept for further characterization (FACS and differentiation assays). 20 h after cell transplantation, MRI of the heart using a clinical 3.0 Tesla whole body scanner (Magnetom Trio, Siemens, Germany) was performed followed by histological examinations.

RESULTS

The average yield of sorted cells from 120 ml BM was 7 x 10(6) cells. The cells were cultured and showed MSC-like properties. MRI showed reproducible artifacts within the RIVA-perfusion area and the cryo-scar with surprisingly excellent quality. The histological examination of the biopsies showed PKH26-positive cells within the areas which were positive in the MRI in contrast to the control biopsies.

CONCLUSION

Immunomagnetic separation of MSC by specific aptamers linked to magnetic particles is feasible, effective and combines a specific separation and labeling technique to a "one stop shop" strategy.

Ankyrin repeat domain-encoding genes in the wPip strain of Wolbachia from the Culex pipiens group

BACKGROUND

Wolbachia are obligate endosymbiotic bacteria maternally transmitted through the egg cytoplasm that are responsible for several reproductive disorders in their insect hosts, such as cytoplasmic incompatibility (CI) in infected mosquitoes. Species in the Culex pipiens complex display an unusually high number of Wolbachia-induced crossing types, and based on present data, only the wPip strain is present.

RESULTS

The sequencing of the wPip strain of Wolbachia revealed the presence of 60 ankyrin repeat domain (ANK) encoding genes and expression studies of these genes were carried out in adult mosquitoes. One of these ANK genes, pk2, is shown to be part of an operon of three prophage-associated genes with sex-specific expression, and is present in two identical copies in the genome. Another homolog of pk2 is also present that is differentially expressed in different Cx. pipiens group strains. A further two ANK genes showed sex-specific regulation in wPip-infected Cx. pipiens group adults.

CONCLUSION

The high number, variability and differential expression of ANK genes in wPip suggest an important role in Wolbachia biology, and the gene family provides both markers and promising candidates for the study of reproductive manipulation.

Challenging the advanced: cardiac surgery without awareness of a pheochromocytoma

We report the case of a 75-year-old male patient who underwent bypass surgery. Intraoperatively unstable hemodynamics with excessive arterial blood pressure was observed. This resulted in the tearing of an anastomosis, which subsequently required hemostasis for repeated bleeding. Postoperatively, laboratory findings and diagnostic imaging confirmed the diagnosis made intraoperatively of a pheochromocytoma. Any surgery without awareness of the possibility of a pheochromocytoma will dramatically increase intraoperative and postoperative morbidity and mortality, especially in cardiac surgery. The uncontrolled release of catecholamines raises arterial blood pressure which can become life-threatening and lead to serious intraoperative complications, as well as cerebrovascular and cardiac comorbidity.

Sino-nasal assessment questionnaire: a specific outcome measure for rhinosinusitis, but what is the range in the asymptomatic population?

The sino-nasal assessment questionnaire is a system used for scoring the symptoms of chronic rhinosinusitis. However, the range of scores for this questionnaire in the healthy adult population is unknown. We aimed to establish this by recruiting 100 healthy volunteers and comparing their sino-nasal assessment questionnaire scores with those of 100 individuals who had undergone sinus surgery for rhinosinusitis. The difference in mean scores in the symptomatic group (44.62) and the asymptomatic group (8.46) was statistically significant. However, there was substantial overlap between the scores of the two groups. Factors such as age, gender and smoking did not have a statistically significant impact on the eventual score in the asymptomatic group. We believe that symptom scores can only be used effectively when the range in the asymptomatic population is known. This is so that disease severity can be gauged in the context of the normal population and post-operative improvements can be forecast.