Evolutionary divergence of anaphase spindle mechanics in nematode embryos constrained by antagonistic pulling and viscous forces

Cellular functions such as cell division are remarkably conserved across phyla. However, the evolutionary principles of cellular organization that drive them are less well explored. Thus, an essential question remains: to what extent do cellular parameters evolve without altering the basic functions they sustain? Here we have observed six different nematode species for which the mitotic spindle is positioned asymmetrically during the first embryonic division. Whereas the C. elegans spindle undergoes oscillations during its displacement, the spindle elongates without oscillations in other species. We asked which evolutionary changes in biophysical parameters could explain differences in spindle motion while maintaining a constant output. Using laser microsurgery of the spindle, we revealed that all species are subjected to cortical pulling forces of varying magnitudes. Using a viscoelastic model to fit the recoil trajectories and with an independent measurement of cytoplasmic viscosity, we extracted the values of cytoplasmic drag, cortical pulling forces, and spindle elasticity for all species. We found large variations in cytoplasmic viscosity, whereas cortical pulling forces and elasticity were often more constrained. In agreement with previous simulations, we found that increased viscosity correlates with decreased oscillation speeds across species. However, the absence of oscillations in some species despite low viscosity can only be explained by smaller pulling forces. Consequently, we find that spindle mobility across the species analyzed here is characterized by a tradeoff between cytoplasmic viscosity and pulling forces normalized by the size of the embryo. Our work provides a framework for understanding mechanical constraints on evolutionary diversification of spindle mobility.     

Functional and phylogenetic diversity of an agricultural matrix avifauna: The role of habitat heterogeneity in Afrotropical farmland

Varied strategies to alleviate the loss of farmland biodiversity have been tested, yet there is still insufficient evidence supporting their effectiveness, especially when considering phylogenetic and functional diversity alongside traditional taxonomic diversity metrics. This conservation challenge is accentuated in the Afrotropics by the rapid agricultural expansion and intensification for the production of cash crops and by a comparative lack of research. In this study, we assessed how farming practices influence avian phylogenetic and functional diversity. We conducted point‐count surveys to assess avian diversity in monocultures of tea and mixed crop farming systems surrounding the Nyungwe rainforest in south‐west Rwanda, allowing us to investigate the drivers of avian diversity at farm level. Species composition was found to be moderately different between farm types, with mixed crop farms supporting higher phylogenetic diversity than tea plantations. There were no significant seasonal differences in species composition, functional or phylogenetic diversity. Overall, functional diversity did not differ between farm types, but the dispersion of trophic‐related traits was significantly higher in mixed crop farms. Both functional and phylogenetic diversity were influenced by floristic diversity, vegetation height, tree number, and elevation to varying degrees. Our results also (i) highlight the role of farmland heterogeneity (e.g., crop species composition, height, and tree cover extent) in encouraging avian functional and phylogenetic diversity in the Afrotropics and (ii) indicate that the generally negative biodiversity impacts of monoculture agriculture can be partially alleviated by extensive agroforestry with an emphasis on indigenous tree species.     

Mucopolysaccharide histochemistry of rat tooth germs

Summary The histochemical distribution and localization of acid mucopolysaccharides and glycoproteins have been studied in rat tooth germs and lower joints. After fixation, sections were stained with PAS, alcian blue-PAS, colloidal iron, colloidal iron-PAS, colloidal iron-Feulgen, azure A and safranin O. Prior to staining, sections were incubated in hyaluronidase, pepsin and papain. A 2 hour incubation in pepsin greatly enhanced AB or CI basophilia in the stellate reticulum and the enamel-dentinal junction. These findings demonstrated that some acidic radicals of the polysaccharides are partially blocked by basic proteins. Hyaluronidase did not completely destroy the alcian blue or colloidal iron positive material whereas azure A metachromasia was completely removed. These results indicated that AB and/or CI stained substrates different from those revealed by azure A.With 10 Figures in colourThis work was supported by Grant No. D-1325 of the National Institutes of Health, Bethesda, Maryland.On leave of absence at the University of Rome Medical School, Viale Regina Elena 287-A, Rome, Italy.     

Probiotic strain <Emphasis Type="Italic">Bacillus subtilis</Emphasis> CU1 stimulates immune system of elderly during common infectious disease period: a randomized,double-blind placebo-controlled study

Background

Bacillus probiotics health benefits have been until now quite poorly studied in the elderly population. This study aimed to assess the effects of Bacillus subtilis CU1 consumption on immune stimulation and resistance to common infectious disease (CID) episodes in healthy free-living seniors.

Results

One hundred subjects aged 60–74 were included in this randomized, double-blind, placebo-controlled, parallel-arms study. Subjects consumed either the placebo or the probiotic (2.10⁹ B. subtilis CU1 spores daily) by short periodical courses of 10 days intermittently, alternating 18-day course of break. This scheme was repeated 4 times during the study. Symptoms of gastrointestinal and upper/lower respiratory tract infections were recorded daily by the subjects throughout the study (4 months). Blood, saliva and stool samples were collected in a predefined subset of the first forty-four subjects enrolled in the study. B. subtilis CU1 supplementation did not statistically significantly decrease the mean number of days of reported CID symptoms over the 4-month of study (probiotic group: 5.1 (7.0) d, placebo group: 6.6 (7.3) d, P?=?0.2015). However, in the subset of forty-four randomized subjects providing biological samples, we showed that consumption of B. subtilis CU1 significantly increased fecal and salivary secretory IgA concentrations compared to the placebo. A post-hoc analysis on this subset showed a decreased frequency of respiratory infections in the probiotc group compared to the placebo group.

Conclusion

Taken together, our study provides evidence that B. subtilis CU1 supplementation during the winter period may be a safe effective way to stimulate immune responses in elderly subjects.