Low dispersing species : population genetic processes in space and time : the genus "Trochulus" (Gastropoda: Hygromiidae) as a case study

RÉSUMÉ Une espèce est rarement composée d'une population unique. Parce que les individus ont des capacités de dispersion limitées et que les paysages sont des mosaïques d'habitats, la plupart des espèces sont plutôt composées de sous-populations connectées par la migration. Cette variation spatiale influence directement la distribution de la variabilité génétique dans et entre les populations. Durant ce travail, nous avons abordé certains des processus populationnels qui ont joué un rôle supposé dans l'apparition de nouvelles espèces au sein du genre Trochulus. Plus précisément, nous avons tenté d'évaluer les impacts respectifs de l'isolement passé (facteurs historiques) et présent (facteurs locaux). Nous avons d'abord pu montrer que les faibles capacités de dispersion des escargots terrestres ont directement influencé leur histoire évolutive à toutes les échelles spatiales et temporelles. En réduisant l'effet homogénéisant de la migration, une faible dispersion maintient dans les populations les traces génétiques d'évènements passés. A l'échelle de la distribution globale de Trochulus villosus, ces traces ont permis de reconstruire une histoire faite d'isolements et d'expansions de populations. En combinant des données génétiques avec une modélisation de la niche climatique passée, il a été possible de proposer un scénario significativement meilleur que toutes les hypothèses alternatives que nous avons testées. A l'échelle locale par contre, l'héritage historique est difficile à distinguer de la dynamique actuelle. Ce fut le cas des lignées mitochondriales du complexe sericeus-hispidus : les deux principales lignées étaient phylogénétiquement éloignées, avaient eu des démographies passées différentes et corrélaient avec des différences morphologiques. D'un autre côté, le flux de gène nucléaire était fort, contredisant l'idée de deux espèces cryptiques isolées reproductivement. Pour pouvoir conclure à la présence ou non de deux espèces, il nous a manqué des informations locales sur la dynamique des populations et les conditions écologiques que l'on trouve dans la région d'étude. Enfin, nous avons pu souligner que la connectivité entre populations d'escargots est soumise à la qualité des habitats et à leur organisation spatiale. Les escargots sont dépendants d'un habitat et s'y adaptent, comme l'indiquent la présence de «poils » uniquement sur la coquille d'espèces vivant dans des habitats humides ou la corrélation entre morphologie et habitat au sein du complexe sericeus-hispidus. Logiquement donc, les escargots migrent préférentiellement au travers d'habitats favorables comme l'a montré la réduction de flux de gènes au travers des prairies chez T. villosus (une espèce forestière). De ces données, nous pouvons supposer que les populations d'escargots en particulier, et des espèces à faible dispersion en général, ont de fortes chances d'être affectées par les changements climatiques, avec de probables implications pour leurs histoires évolutives. SUMMARY : Species rarely consists in a single population. Because individuals have limited dispersal abilities, because landscapes are habitat patchworks, most species are made of several subpopulations connected by migration. This spatial variation has consequences on the distribution of genetic diversity within and between populations, creating a structure among the populations. During the present work, we investigated some of the population processes assumed to have played an important role on the speciation within the genus Trochulus. More specifically, we questioned the respective impacts of past (historical factors) or present (local factors) population isolations. We first could show that the poor dispersal abilities of land snails have had profound impacts on their evolutionary histories at all spatial and temporal scales. Low dispersal maintains a strong signature of past events in the populations by minimising the homogenising effects of geneflow. At the scale of Trochulus villosus global distribution, they allowed to retrieve the detailed history of this species population isolations and expansions. Combining a large genetic dataset with paleo-climatic niche modelling ended up with a historical scenario significantly better than all traditional alternatives we tested. At local scale on the contrary, past events become difficult to tease apart from ongoing processes. This was the case for the divergent mitochondria) lineages within the sericeus-hispidus complex: the two principal lineages appeared to be phylogenetically distant, to have experienced different demographic histories and to correlate with morphological differences. On the other hand, nuclear (present day) geneflow was high, contradicting the idea of two reproductively isolated cryptic species. Information on the local population dynamics and environmental conditions are lacking to be able to decide whether past isolation has indeed resulted here in new species. Finally, we emphasised the importance of the habitat types present in a landscape as well as their spatial organisation for the population connectivity of land snails. These species are tightly dependent on a habitat and adapt to it as shown by thé occurrence of hair-like structures only in species living in humid environments or by the correlation between shell morphology and habitat in the sericeus-hispidus complex. As a result, land snails preferentially migrate through favourable habitats: Trochulus villosus, a forest species, had its geneflow significantly reduced across meadows. From these data, we can hypothesise that the populations of land snails in particular and of low dispersing species in general are likely to be strongly affected by the ongoing climate changes, with potential major consequences on their evolutionary histories.

The human Ia-associated invariant chain is synthesized in Ia-negative B cell variants and is not expressed on the cell surface of both Ia-negative and Ia-positive parental cells.

The expression of Ia-associated human Invariant (In) chain glycoproteins was studied in the Raji B cells as well as in their RJ 2.2.5 Ia-negative derived variant cells by using a specific rabbit anti-human In chain antiserum. Two-dimensional gel electrophoresis of immunoprecipitates from either biosynthetically labeled or surface labeled cells were analyzed. In addition, flow microfluorometric analysis of stained cells was performed. The results indicate that the In chain is constitutively produced in the Ia-negative B cell variant. Moreover, it appears that several forms of In chain-related molecules, with different charges and distinct m.w. are equally expressed in Ia-positive and Ia-negative B cells. Finally, no evidence could be obtained that the In molecular family was expressed on the cell surface of Ia-positive Raji and Ia-negative RJ 2.2.5 cells.

Altered growth in male peroxisome proliferator-activated receptor gamma (PPARgamma) heterozygous mice: involvement of PPARgamma in a negative feedback regulation of growth hormone action.

The peroxisome proliferator-activated receptor gamma (PPARgamma) plays a major role in fat tissue development and physiology. Mutations in the gene encoding this receptor have been associated to disorders in lipid metabolism. A thorough investigation of mice in which one PPARgamma allele has been mutated reveals that male PPARgamma heterozygous (PPARgamma +/-) mice exhibit a reduced body size associated with decreased body weight, reflecting lean mass reduction. This phenotype is reproduced when treating the mice with a PPARgamma- specific antagonist. Monosodium glutamate treatment, which induces weight gain and alters body growth in wild-type mice, further aggravates the growth defect of PPARgamma +/- mice. The levels of circulating GH and that of its downstream effector, IGF-I, are not altered in mutant mice. However, the IGF-I mRNA level is decreased in white adipose tissue (WAT) of PPARgamma +/- mice and is not changed by acute administration of recombinant human GH, suggesting an altered GH action in the mutant animals. Importantly, expression of the gene encoding the suppressor of cytokine signaling-2, which is an essential negative regulator of GH signaling, is strongly increased in the WAT of PPARgamma +/- mice. Although the relationship between the altered GH signaling in WAT and reduced body size remains unclear, our results suggest a novel role of PPARgamma in GH signaling, which might contribute to the metabolic disorder affecting insulin signaling in PPARgamma mutant mice.

Combined impact of negative lifestyle factors on cardiovascular risk in children: a randomized prospective study.

PURPOSE: Negative lifestyle factors are known to be associated with increased cardiovascular risk (CVR) in children, but research on their combined impact on a general population of children is sparse. Therefore, we aimed to quantify the combined impact of easily assessable negative lifestyle factors on the CVR scores of randomly selected children after 4 years. METHODS: Of the 540 randomly selected 6- to 13-year-old children, 502 children participated in a baseline health assessment, and 64% were assessed again after 4 years. Measures included anthropometry, fasting blood samples, and a health assessment questionnaire. Participants scored one point for each negative lifestyle factor at baseline: overweight; physical inactivity; high media consumption; little outdoor time; skipping breakfast; and having a parent who has ever smoked, is inactive, or overweight. A CVR score at follow-up was constructed by averaging sex- and age-related z-scores of waist circumference, blood pressure, glucose, inverted high-density lipoprotein, and triglycerides. RESULTS: The age-, sex-, pubertal stage-, and social class-adjusted probabilities (95% confidence interval) for being in the highest CVR score tertile at follow-up for children who had at most one (n = 48), two (n = 64), three (n = 56), four (n = 41), or five or more (n = 14) risky lifestyle factors were 15.4% (8.9-25.3), 24.3% (17.4-32.8), 36.0% (28.6-44.2), 49.8% (38.6-61.0), and 63.5% (47.2-77.2), respectively. CONCLUSIONS: Even in childhood, an accumulation of negative lifestyle factors is associated with higher CVR scores after 4 years. These negative lifestyle factors are easy to assess in clinical practice and allow early detection and prevention of CVR in childhood.

Age above 60 years is not a negative predictive factor for combined antiviral therapy with pegylated interferon alpha and ribavirin in hepatitis C patients

Background: Age is frequently discussed as negative host factor to achieve a sustained virological response (SVR) to antiviral hepatitis C therapy. However, elderly patients often show relevant fibrosis or cirrhosis which is a known negative predictive factor, making it difficult to interpret age as an independent predictive factor. Methods: From the framework of the Swiss hepatitis C cohort (SCCS), we collected data from 545 antiviral hepatitis C therapies, including data from 67 hepatitis C patients ≥ 60 y who had been treated with PEG-interferon and ribavirin. We analyzed host factors (age, gender, fibrosis, haemoglobin, depression, earlier hepatitis C treatment), viral factors (genotype, viral load) and treatment course (early virological response, end of treatment response, SVR). Generalised estimating equations (GEE) regression modelling was used for the primary end point (SVR), with age ≥ 60 y and < 60 y as independent variable and gender, presence of cirrhosis, genotype, earlier treatment and viral load as confounders. SVR was analysed in young and elderly patients after matching for these confounders. Additionally, classification tree analysis was done in elderly patients using these confounders. Results: SVR analyzed in 545 patients was 55%. In genotype 1/4, SVR was 42.9% in 259 patients < 60 y and 26.1% in 46 patients ≥ 60 y. In genotype 2/3, SVR was 74.4% in 215 patients < 60 y and 84% in 25 patients ≥ 60 y. However, GEE model showed that age had no influence on achieving SVR (Odds ratio 0.91). Confounders influenced SVR as known from previous studies (cirrhosis, genotype 1/4, previous treatment and viral load >600'000 IE/ml as negative predictive factors). When young and elderly patients were matched (analysis in 59 elderly patients), SVR was not different in these patient groups (54.2% and 55.9%, resp.; p=0.795 in binomial test). The classification tree-derived best criterion for SVR in elderly patients was genotype, with no further criteria relevant for predicting SVR in genotype 2/3. In patients with genotype 1/4, further criteria were presence of cirrhosis and low viral load <600'000 IE/ml in non-cirrhotic patients. Conclusions: Age is not a relevant predictive factor for achieving SVR, when confounders were taken into account. In terms of effectiveness of antiviral therapy, age does not play a major role and should not be regarded as relevant negative predictive factor. Since life expectancy in Switzerland at age 60 is more than 22 y, hepatitis C therapy is reasonable in elderly patients with known relevant fibrosis or cirrhosis, because interferon-based hepatitis C therapy improves survival and reduces carcinogenesis.

β-Glucan Antigenemia Anticipates Diagnosis of Blood Culture-Negative Intraabdominal Candidiasis.

Rationale: Life-threatening intraabdominal candidiasis (IAC) occurs in 30 to 40% of high-risk surgical intensive care unit (ICU) patients. Although early IAC diagnosis is crucial, blood cultures are negative, and the role of Candida score/colonization indexes is not established. Objectives: The aim of this prospective Fungal Infection Network of Switzerland (FUNGINOS) cohort study was to assess accuracy of 1,3-β-d-glucan (BG) antigenemia for diagnosis of IAC. Methods: Four hundred thirty-four consecutive adults with abdominal surgery or acute pancreatitis and ICU stay 72 hours or longer were screened: 89 (20.5%) at high risk for IAC were studied (68 recurrent gastrointestinal tract perforation, 21 acute necrotizing pancreatitis). Diagnostic accuracy of serum BG (Fungitell), Candida score, and colonization indexes was compared. Measurements and Main Results: Fifty-eight of 89 (65%) patients were colonized by Candida; 29 of 89 (33%) presented IAC (27 of 29 with negative blood cultures). Nine hundred twenty-one sera were analyzed (9/patient): median BG was 253 pg/ml (46-9,557) in IAC versus 99 pg/ml (8-440) in colonization (P < 0.01). Sensitivity and specificity of two consecutive BG measurements greater than or equal to 80 pg/ml were 65 and 78%, respectively. In recurrent gastrointestinal tract perforation it was 75 and 77% versus 90 and 38% (Candida score ≥ 3), 79 and 34% (colonization index ≥ 0.5), and 54 and 63% (corrected colonization index ≥ 0.4), respectively. BG positivity anticipated IAC diagnosis (5 d) and antifungal therapy (6 d). Severe sepsis/septic shock and death occurred in 10 of 11 (91%) and 4 of 11 (36%) patients with BG 400 pg/ml or more versus 5 of 18 (28%, P = 0.002) and 1 of 18 (6%, P = 0.05) with BG measurement less than 400 pg/ml. β-Glucan decreased in IAC responding to therapy and increased in nonresponse. Conclusions: BG antigenemia is superior to Candida score and colonization indexes and anticipates diagnosis of blood culture-negative IAC. This proof-of-concept observation in strictly selected high-risk surgical ICU patients deserves investigation of BG-driven preemptive therapy.

Delayed referral and gram-negative organisms increase the conversion thoracotomy rate in patients undergoing video-assisted thoracoscopic surgery for empyema

BACKGROUND: The role of video-assisted thoracoscopic surgery in the treatment of pleural empyema was assessed in a consecutive series of 328 patients between 1992 and 2002. An analysis of the predicting factors for conversion thoracotomy in presumed stage II empyema was performed. METHODS: Empyema stage III with pleural thickening and signs of restriction on computer tomography imaging was treated by open decortication, whereas a thoracoscopic debridement was attempted in presumed stage II disease. Conversion thoracotomy was liberally used during thoracoscopy if stage III disease was found at surgery. Predictive factors for conversion thoracotomy were calculated in a multivariate analysis among several variables such as age, sex, time interval between onset of symptoms and surgery, involved microorganisms, and underlying cause of empyema. RESULTS: Of the 328 patients surgically treated for stage II and III empyema, 150 underwent primary open decortication for presumed stage III disease. One hundred seventy-eight patients with presumed stage II empyema underwent a video-assisted thoracoscopic approach. Of these 178 patients, thoracoscopic debridement was successful in 99 of 178 patients (56%), and conversion thoracotomy and open decortication was judged necessary in 79 of 178 patients (44%). The conversion thoracotomy rate was higher in parapneumonic empyema (55%) as compared with posttraumatic (32%) or postoperative (29%) empyema; however, delayed referral (p < 0.0001) and gram-negative microorganisms (p < 0.01) were the only significant predictors for conversion thoracotomy in a multivariate analysis. CONCLUSIONS: Video-assisted thoracoscopic debridement offers an elegant, minimally invasive approach in a number of patients with presumed stage II empyema. However, to achieve a high success rate with the video-assisted thoracoscopic approach, early referral of the patients to surgery is required. Conversion thoracotomy should be liberally used in case of chronicity, especially after delayed referral (> 2 weeks) and in the presence of gram-negative organisms.

Right coronary artery flow velocity and volume assessment with spiral K-space sampled breathhold velocity-encoded MRI at 3 tesla: accuracy and reproducibility.

PURPOSE: To evaluate accuracy and reproducibility of flow velocity and volume measurements in a phantom and in human coronary arteries using breathhold velocity-encoded (VE) MRI with spiral k-space sampling at 3 Tesla. MATERIALS AND METHODS: Flow velocity assessment was performed using VE MRI with spiral k-space sampling. Accuracy of VE MRI was tested in vitro at five constant flow rates. Reproducibility was investigated in 19 healthy subjects (mean age 25.4 +/- 1.2 years, 11 men) by repeated acquisition in the right coronary artery (RCA). RESULTS: MRI-measured flow rates correlated strongly with volumetric collection (Pearson correlation r = 0.99; P < 0.01). Due to limited sample resolution, VE MRI overestimated the flow rate by 47% on average when nonconstricted region-of-interest segmentation was used. Using constricted region-of-interest segmentation with lumen size equal to ground-truth luminal size, less than 13% error in flow rate was found. In vivo RCA flow velocity assessment was successful in 82% of the applied studies. High interscan, intra- and inter-observer agreement was found for almost all indices describing coronary flow velocity. Reproducibility for repeated acquisitions varied by less than 16% for peak velocity values and by less than 24% for flow volumes. CONCLUSION: 3T breathhold VE MRI with spiral k-space sampling enables accurate and reproducible assessment of RCA flow velocity.

Asymmetry of Functional Connectivity in Schizophrenia at Different Spatial Scales

Introduction: The interhemispheric asymmetries that originate from connectivity-related structuring of the cerebral cortex are compromised in schizophrenia (SZ). Recently, we have revealed the whole-head topography of EEG synchronization in SZ (Jalili et al. 2007; Knyazeva et al. 2008). Here we extended the analysis to assess the abnormality in the asymmetry of synchronization, which is further motivated by the evidence that the interhemispheric asymmetries suspected to be abnormal in SZ originate from the connectivity-related structuring of the cortex. Methods: Thirteen right-handed SZ patients and thirteen matched controls, participated in this study and the multichannel (128) EEGs were recorded for 3-5 minutes at rest. Then, Laplacian EEG (LEEG) were calculated using a 2-D spline. The LEEGs were analysis through calculating the power spectral density using Welch's average periodogram method. Furthermore, using a state-space based multivariate synchronization measure, S-estimator, we analyzed the correlate of the functional cortico-cortical connectivity in SZ patients compared to the controls. The values of S-estimator were obtained at three different special scales: first-order neighbors for each sensor location, second-order neighbors, and the whole hemisphere. The synchronization measures based on LEEG of alpha and beta bands were applied and tuned to various spatial scales including local, intraregional, and long-distance levels. To assess the between-group differences, we used a permutation version of Hotelling's T2 test. For correlation analysis, Spearman Rank Correlation was calculated. Results: Compared to the controls, who had rightward asymmetry at a local level (LEEG power), rightward anterior and leftward posterior asymmetries at an intraregional level (first- and second-order S-estimator), and rightward global asymmetry (hemispheric S-estimator), SZ patients showed generally attenuated asymmetry, the effect being strongest for intraregional synchronization. This deviation in asymmetry across the anterior-to-posterior axis is consistent with the cerebral form of the so-called Yakovlevian or anticlockwise cerebral torque. Moreover, the negative occipital and positive frontal asymmetry values suggest higher regional synchronization among the left occipital and the right frontal locations relative to their symmetrical counterparts. Correlation analysis linked the posterior intraregional and hemispheric abnormalities to the negative SZ symptoms, whereas the asymmetry of LEEG power appeared to be weakly coupled to clinical ratings. The posterior intraregional abnormalities of asymmetry were shown to increase with the duration of the disease. The tentative links between these findings and gross anatomical asymmetries, including the cerebral torque and gyrification pattern in normal subjects and SZ patients, are discussed. Conclusions: Overall, our findings reveal the abnormalities in the synchronization asymmetry in SZ patients and heavy involvement of the right hemisphere in these abnormalities. These results indicate that anomalous asymmetry of cortico-cortical connections in schizophrenia is amenable to electrophysiological analysis.

Node-negative T1-T2 anal cancer: radiotherapy alone or concomitant chemoradiotherapy?

PURPOSE: To evaluate the influence of concomitant chemotherapy on loco-regional control (LRC) and cancer-specific survival (CSS) in patients with T1-T2 N0 M0 anal cancer treated conservatively by primary radiotherapy (RT). MATERIALS AND METHODS: Between 1976 and 2008, 146 patients with T1 (n=29) or T2 (n=117) N0 M0 anal cancer were treated curatively by RT alone (n=71) or by combined chemoradiotherapy (CRT) (n=75) consisting of mitomycin C±5-fluorouracil. Univariate and multivariate analyses were performed to assess patient-, tumor- and treatment-related factors influencing LRC and CSS. RESULTS: With a median follow-up of 62.5 months (interquartilerange, 26-113 months), 122 (84%) patients were locally controlled. The five-year actuarial LRC, CSS and overall survival for the population were 81.4%±3.6%, 91.9%±2.6%, and 75.4%±3.9%, respectively. The five-year LRC and CSS for patients treated with RT alone and with CRT were 75.5%±6.0% vs. 86.8%±4.1% (p=0.155) and 88.5%±4.5% vs. 94.9%±2.9% (p=0.161), respectively. In the multivariate analysis, no clinical or therapeutic factors were found to significantly influence the LRC and CSS, while the addition of chemotherapy was of borderline significance (p=0.065 and p=0.107, respectively). CONCLUSIONS: In the management of node negative T1-T2 anal cancer, LRC and CSS tend to be superior in patients treated by combined CRT, even though the difference was not significant. Randomized studies are warranted to assess definitively the role of combined treatment in early-stage anal carcinoma.

False-negative PCR result due to gene polymorphism: the example of Neisseria meningitidis.

Early treatment of meningococcal meningitis is mandatory but may negate the cerebrospinal fluid culture. Etiological diagnosis then mainly relies on PCR. Here, we report a case of false-negative results for real-time PCR for a Neisseria meningitidis serogroup B isolate with a polymorphism in the ctrA gene.

Renal and neurohormonal responses to increasing levels of lower body negative pressure in men.

BACKGROUND: The stimulation of efferent renal sympathetic nerve activity induces sequential changes in renin secretion, sodium excretion, and renal hemodynamics that are proportional to the magnitude of the stimulation of sympathetic nerves. This study in men investigated the sequence of the changes in proximal and distal renal sodium handling, renal and systemic hemodynamics, as well as the hormonal profile occurring during a sustained activation of the sympathetic nervous system induced by various levels of lower body negative pressure (LBNP). METHODS: Ten healthy subjects were submitted to three levels of LBNP ranging between 0 and -22.5 mm Hg for one hour according to a triple crossover design, with a minimum of five days between each level of LBNP. Systemic and renal hemodynamics, renal water and sodium handling (using the endogenous lithium clearance technique), and the neurohormonal profile were measured before, during, and after LBNP. RESULTS: LBNP (0 to -22.5 mm Hg) induced an important hormonal response characterized by a significant stimulation of the sympathetic nervous system and gradual activations of the vasopressin and the renin-angiotensin systems. LBNP also gradually reduced water excretion and increased urinary osmolality. A significant decrease in sodium excretion was apparent only at -22.5 mm Hg. It was independent of any change in the glomerular filtration rate and was mediated essentially by an increased sodium reabsorption in the proximal tubule (a significant decrease in lithium clearance, P < 0.05). No significant change in renal hemodynamics was found at the tested levels of LBNP. As observed experimentally, there appeared to be a clear sequence of responses to LBNP, the neurohormonal response occurring before the changes in water and sodium excretion, these latter preceding any change in renal hemodynamics. CONCLUSIONS: These data show that the renal sodium retention developing during LBNP, and thus sympathetic nervous stimulation, is due mainly to an increase in sodium reabsorption by the proximal segments of the nephron. Our results in humans also confirm that, depending on its magnitude, LBNP leads to a step-by-step activation of neurohormonal, renal tubular, and renal hemodynamic responses.

Calcineurin signaling as a negative determinant of keratinocyte cancer stem cell potential and carcinogenesis.

Calcineurin is the only known serine-threonine phosphatase under calcium-calmodulin control and key regulator of the immune system. Treatment of patients with calcineurin-inhibitory drugs like cyclosporin A and FK506 to prevent graft rejection dramatically increases the risk of cutaneous squamous cell carcinoma, which is a major cause of death after organ transplants. Recent evidence indicates that suppression of calcineurin signaling, together with its impact on the immune system, exerts direct tumor-promoting effects in keratinocytes, enhancing cancer stem cell potential. The underlying mechanism involves interruption of a double negative regulatory axis, whereby calcineurin and nuclear factors of activated T-cell signaling inhibits expression of ATF3, a negative regulator of p53. The resulting suppression of keratinocyte cancer cell senescence is of likely clinical significance for the many patients under treatment with calcineurin inhibitors and may be of relevance for other cancer types in which altered calcium-calcineurin signaling plays a role.