Phylogeography and Sexual Macrocyst Formation in the Social Amoeba DictyosteliumGiganteumDictyostelium Giganteum

Background: Microorganisms are ubiquitous, yet we are only beginning to understand their diversity and population structure. Social amoebae (Dictyostelia) are a diverse group of unicellular eukaryotic microbes that display a unique social behaviour upon starvation in which cells congregate and then some die to help others survive and disperse. The genetic relationships among co-occurring cells have a major influence on the evolution of social traits and recent population genetic analysis found extensive genetic variation and possible cryptic speciation in one dictyostelid species $(Dictyostelium purpureum)$. To further characterize the interplay among genetic variation, species boundaries, social behaviour, and reproductive isolation in the Dictyostelia, we conducted phylogenetic analyses and mating experiments with the geographically widespread social amoeba $Dictyostelium giganteum$. Results: We sequenced approximately 4,000 basepairs of the nuclear ribosomal DNA from 24 isolates collected from Texas, Michigan, Massachusetts, Virginia, and Wisconsin and identified 16 unique haplotypes. Analyses of the sequence data revealed very little genetic differentiation among isolates and no clear evidence of phylogenetic structure, although there was evidence for some genetic differentiation between the Massachusetts and Texas populations. These results suggest that sexual mating (macrocyst formation) is not likely to correlate with either genetic or geographical distance. To test this prediction, we performed 108 mating experiments and found no association between mating probability and genetic or geographical distance. Conclusions: $D. giganteum$ isolates from across North America display little genetic variation, phylogeographic structure, and genetic differentiation among populations relative to the cryptic species observed within $D. purpureum$. Furthermore, variation that does exist does not predict the probability of mating among clones. These results have important implications for our understanding of speciation and social evolution in microbes.Other Research Uni

Phylogeography and sexual macrocyst formation in the social amoeba Dictyostelium giganteum

<p>Abstract</p> <p>Background</p> <p>Microorganisms are ubiquitous, yet we are only beginning to understand their diversity and population structure. Social amoebae (Dictyostelia) are a diverse group of unicellular eukaryotic microbes that display a unique social behaviour upon starvation in which cells congregate and then some die to help others survive and disperse. The genetic relationships among co-occurring cells have a major influence on the evolution of social traits and recent population genetic analysis found extensive genetic variation and possible cryptic speciation in one dictyostelid species (<it>Dictyostelium purpureum</it>). To further characterize the interplay among genetic variation, species boundaries, social behaviour, and reproductive isolation in the Dictyostelia, we conducted phylogenetic analyses and mating experiments with the geographically widespread social amoeba <it>Dictyostelium giganteum</it>.</p> <p>Results</p> <p>We sequenced approximately 4,000 basepairs of the nuclear ribosomal DNA from 24 isolates collected from Texas, Michigan, Massachusetts, Virginia, and Wisconsin and identified 16 unique haplotypes. Analyses of the sequence data revealed very little genetic differentiation among isolates and no clear evidence of phylogenetic structure, although there was evidence for some genetic differentiation between the Massachusetts and Texas populations. These results suggest that sexual mating (macrocyst formation) is not likely to correlate with either genetic or geographical distance. To test this prediction, we performed 108 mating experiments and found no association between mating probability and genetic or geographical distance.</p> <p>Conclusions</p> <p><it>D. giganteum </it>isolates from across North America display little genetic variation, phylogeographic structure, and genetic differentiation among populations relative to the cryptic species observed within <it>D. purpureum</it>. Furthermore, variation that does exist does not predict the probability of mating among clones. These results have important implications for our understanding of speciation and social evolution in microbes.</p

Mind the gap: a comparative study of migratory behavior in social amoebae

Social amoebae aggregate to form a multicellular slug that migrates some distance. Most species produce a stalk during migration, but some do not. We show that Dictyostelium giganteum, a species that produces stalk during migration, is able to traverse small gaps and utilize bacterial resources following gap traversal by shedding live cells. In contrast, we found that Dictyostelium discoideum, a species that does not produce stalk during migration, can traverse gaps only when in the presence of other species’ stalks or other thin filaments. These findings suggest that production of stalk during migration allows traversal of gaps that commonly occurs in soil and leaf litter. Considering the functional consequences of a stalked migration may be important for explaining the evolutionary maintenance or loss of a stalked migration

The Rate and Effects of Spontaneous Mutation on Fitness Traits in the Social Amoeba, Dictyostelium discoideum

We performed a mutation accumulation (MA) experiment in the social amoeba Dictyostelium discoideum to estimate the rate and distribution of effects of spontaneous mutations affecting eight putative fitness traits. We found that the per-generation mutation rate for most fitness components is 0.0019 mutations per haploid genome per generation or larger. This rate is an order of magnitude higher than estimates for fitness components in the unicellular eukaryote Saccharomyces cerevisiae, even though the base-pair substitution rate is two orders of magnitude lower. The high rate of fitness-altering mutations observed in this species may be partially explained by a large mutational target relative to S. cerevisiae. Fitness-altering mutations also may occur primarily at simple sequence repeats, which are common throughout the genome, including in coding regions, and may represent a target that is particularly likely to give fitness effects upon mutation. The majority of mutations had deleterious effects on fitness, but there was evidence for a substantial fraction, up to 40%, being beneficial for some of the putative fitness traits. Competitive ability within the multicellular slug appears to be under weak directional selection, perhaps reflecting the fact that slugs are sometimes, but not often, comprised of multiple clones in nature. Evidence for pleiotropy among fitness components across MA lines was absent, suggesting that mutations tend to act on single fitness components

The role of ureteric indocyanine green fluorescence in colorectal surgery: a retrospective cohort study.

BACKGROUND Ureteric injury (UI) is an infrequent but serious complication of colorectal surgery. Prophylactic ureteric stenting is employed to avoid UI, yet its efficacy remains debated. Intraoperative indocyanine green fluorescence imaging (ICG-FI) has been used to facilitate ureter detection. This study aimed to investigate the role of ICG-FI in identification of ureters during colorectal surgery and its impact on the incidence of UI. METHODS A retrospective cohort study involving 556 consecutive patients who underwent colorectal surgery between 2018 and 2023 assessed the utility of routine prophylactic ureteric stenting with adjunctive ICG-FI. Patients with ICG-FI were compared to those without ICG-FI. Demographic data, operative details, and postoperative morbidity were analyzed. Statistical analysis included univariable regression. RESULTS Ureteric ICG-FI was used in 312 (56.1%) patients, whereas 43.9% were controls. Both groups were comparable in terms of demographics except for a higher prevalence of prior abdominal surgeries in the ICG-FI group. Although intraoperative visualization was significantly higher in the ICG-FI group (95.3% vs 89.1%; p = 0.011), the incidence of UI was similar between groups (0.3% vs 0.8%; p = 0.585). Postoperative complications were similar between the two groups. Median stent insertion time was longer in the ICG-FI group (32 vs 25 min; p = 0.001). CONCLUSION Ureteric ICG-FI improved intraoperative visualization of the ureters but was not associated with a reduced UI rate. Median stent insertion time increased with use of ureteric ICG-FI, but total operative time did not. Despite its limitations, this study is the largest of its kind suggesting that ureteric ICG-FI may be a valuable adjunct to facilitate  ureteric visualization during colorectal surgery

Segregate or cooperate- a study of the interaction between two species of Dictyostelium

<p>Abstract</p> <p>Background</p> <p>A major challenge for evolutionary biology is explaining altruism, particularly when it involves death of one party and occurs across species. Chimeric fruiting bodies of <it>Dictyostelium discoideum </it>and <it>Dictyostelium purpureum </it>develop from formerly independent amoebae, and some die to help others. Here we examine co-aggregation between <it>D. discoideum </it>and <it>D. purpureum</it>, determine its frequency and which party benefits, and the extent of fair play in contribution to the altruistic caste.</p> <p>Results</p> <p>We mixed cells from both species in equal proportions, and then we analyzed 198 individual fruiting bodies, which always had either a <it>D. discoideum </it>or <it>D. purpureum </it>phenotype (<it>D. discoideum</it>- 98, <it>D. purpureum</it>- 100). Fifty percent of the fruiting bodies that looked like <it>D. discoideum </it>and 22% of the fruiting bodies that looked like <it>D. purpureum </it>were chimeric, though the majority of spores in any given fruiting body belonged to one species (<it>D. discoideum </it>fruiting bodies- 0.85 ± 0.03, <it>D. purpureum </it>fruiting bodies- 0.94 ± 0.02). Clearly, there is species level recognition occurring that keeps the cells mostly separate. The number of fruiting bodies produced with the <it>D. discoideum </it>phenotype increased from 225 ± 32 fruiting bodies when <it>D. discoideum </it>was alone to 486 ± 61 in the mix treatments. However, the number of <it>D. discoideum </it>spores decreased, although not significantly, from 2.75e⁷± 1.29e⁷spores in the controls to 2.06e⁷± 8.33e⁶spores in the mix treatments. <it>D. purpureum </it>fruiting body and spore production decreased from 719 ± 111 fruiting bodies and 5.81e⁷± 1.26e⁷spores in the controls to 394 ± 111 fruiting bodies and 9.75e⁶± 2.25e⁶spores in the mix treatments.</p> <p>Conclusion</p> <p>Both species appear to favor clonality but can cooperate with each other to produce fruiting bodies. Cooperating amoebae are able to make larger fruiting bodies, which are advantageous for migration and dispersal, but both species here suffer a cost in producing fewer spores per fruiting body.</p

Amino Acid Repeats Cause Extraordinary Coding Sequence Variation in the Social Amoeba Dictyostelium discoideum

Protein sequences are normally the most conserved elements of genomes owing to purifying selection to maintain their functions. We document an extraordinary amount of within-species protein sequence variation in the model eukaryote Dictyostelium discoideum stemming from triplet DNA repeats coding for long strings of single amino acids. D. discoideum has a very large number of such strings, many of which are polyglutamine repeats, the same sequence that causes various human neurological disorders in humans, like Huntington's disease. We show here that D. discoideum coding repeat loci are highly variable among individuals, making D. discoideum a candidate for the most variable proteome. The coding repeat loci are not significantly less variable than similar non-coding triplet repeats. This pattern is consistent with these amino-acid repeats being largely non-functional sequences evolving primarily by mutation and drift

Fatal pulmonary thromboembolism in gastrectomy intraoperative procedures by gastric adenocarcinoma: case report

The case of a patient with gastric adenocarcinoma with indication for gastrectomy is reported. The surgery took place without complications. A palliative, subtotal gastrectomy was performed after para-aortic lymph nodes compromised by neoplasm were found, which was confirmed by pathological exam of frozen sections carried out during the intervention. At the end of the gastroenteroanastomosis procedure, the patient began to show intense bradycardia: 38 beats per minute (bpm), arterial hypotension, changes in the electrocardiogram's waveform (upper unlevelling of segment ST), and cardiac arrest. Resuscitation maneuvers were performed with temporary success. Subsequently, the patient had another circulatory breakdown and again was recovered. Finally, the third cardiac arrest proved to be irreversible, and the intra-operative death occurred. Necropsy showed massive pulmonary embolism. The medical literature has recommended heparinization of patients, in an attempt to avoid pulmonary thromboembolism following major surgical interventions. However, in the present case, heparinization would have been insufficient to prevent death. This case indicates that it is necessary to develop preoperative propedeutics for diagnosing the presence of venous thrombi with potential to migrate, causing pulmonary thromboembolism (PTE). If such thrombi could be detected, preventative measures, such as filter installation in the Cava vein could be undertaken.Relata-se um caso de paciente com adenocarcinoma gástrico com indicação de gastrectomia. O ato operatório transcorreu sem anormalidades. Foi realizada gastrectomia subtotal paliativa, pois encontrou-se linfonodos para-aórticos comprometidos pela neoplasia, confirmado por exame anátomo-patológico de congelação realizado no decorrer da intervenção. Ao fim da confecção da gastroêntero-anastomose o paciente passou a apresentar bradicardia intensa: 38 batimentos por minuto (bpm), hipotensão arterial, alterações do traçado do eletrocardiograma (Supra-desnivelamento do segmento ST) e parada cardíaca. Realizadas as manobras de ressucitação com sucesso temporário, já que a seguir o paciente apresentou novo colapso circulatório, sendo novamente recuperado, finalmente a 3a parada cardíaca foi irreversível e constatou-se o óbito intra-operatório

Nationwide implementation of the self-management program "Living well with COPD": Process and effectiveness evaluation using a mixed-methods approach.

To evaluate the nationwide implementation of the "Living well with COPD" program by the Swiss Lung Association in various cantons in Switzerland. For the process evaluation, we used qualitative (interview, focus group) and quantitative (questionnaires, documentation analysis) methods to assess the implementation outcomes reach, dose, fidelity and acceptability. For the effectiveness, we performed a pre-post analysis of patient data collected at baseline and program end (after 14 months). Seven Cantonal Lung Associations implemented the program into their services according to plan, conducted it 13 times and included 122 COPD patients. Patients' attendance rate was 81% and coaches' fidelity to protocol 94%. Acceptance and satisfaction of all involved persons was high. Integration of the coaches' additional workload, uncertainties regarding roles and responsibilities and sustainable reimbursement were major challenges. Patients significantly improved in COPD specific quality of life and increased exercise capacity with on average 3.2 more repetitions in the 1-minute sit-to-stand test. The program was successfully implemented throughout Switzerland with high acceptability and positive association with patients' quality of life. Our findings support the broader multiplication throughout Switzerland and serves the international community since it is one of the first nationwide implementations beyond study settings

Review of Studies Evaluating Effectiveness of Risk Minimization Measures Assessed by the European Medicines Agency Between 2016 and 2021

The European Medicines Agency (EMA) supervises medicines' safe and effective use throughout the product's life cycle by, for example, monitoring the implementation of risk minimization measures (RMMs). Limited information is available on factors associated with effectiveness of RMMs. This study reviews post-authorization safety studies (PASS) evaluating the effectiveness of RMMs assessed by the Pharmacovigilance Risk Assessment Committee (PRAC) between 2016 and 2021. PASS assessment reports finalized by PRAC between January 1, 2016, and December 31, 2021, were compiled from non-public EMA databases and PASS characteristics were extracted. Of the 93 PASS included, 62.4% aimed to measure healthcare professionals' awareness, knowledge, and behavior regarding RMMs. There were 67.7% of the 93 PASS that used primary data, 24.7% used secondary data sources, and 7.5% used both. A cross-sectional study design was most frequently applied (77.4%), followed by a cohort study design (29.0%). Nearly 40% of the included PASS did not render a conclusion on RMM effectiveness. Of the 60% that did render a conclusion, 82.1% were deemed effective. Only minor differences in characteristics were found when stratified by outcome (i.e., effective RMM, ineffective RMM, and no conclusion on RMM effectiveness). To conclude, 4 out of 10 PASS assessing impact of RMMs did not render a conclusion on RMM effectiveness. No clear differences in PASS characteristics were found in relation to their outcomes, indicating that additional research is needed to understand better the underlying reasons for PASS being inconclusive