The evolution of collective restraint: policing and obedience among non-conjugative plasmids.

The repression of competition by mechanisms of policing is now recognized as a major force in the maintenance of cooperation. General models on the evolution of policing have focused on the interplay between individual competitiveness and mutual policing, demonstrating a positive relationship between within-group diversity and levels of policing. We expand this perspective by investigating what is possibly the simplest example of reproductive policing: copy number control (CNC) among non-conjugative plasmids, a class of extra-chromosomal vertically transmitted molecular symbionts of bacteria. Through the formulation and analysis of a multi-scale dynamical model, we show that the establishment of stable reproductive restraint among plasmids requires the co-evolution of two fundamental plasmid traits: policing, through the production of plasmid-coded trans-acting replication inhibitors, and obedience, expressed as the binding affinity of plasmid-specific targets to those inhibitors. We explain the intrinsic replication instabilities that arise in the absence of policing and we show how these instabilities are resolved by the evolution of copy number control. Increasing levels of policing and obedience lead to improvements in group performance due to tighter control of local population size (plasmid copy number), delivering benefits both to plasmids, by reducing the risk of segregational loss and to the plasmid-host partnership, by increasing the rate of cell reproduction, and therefore plasmid vertical transmission.

The mode of host-parasite interaction shapes coevolutionary dynamics and the fate of host cooperation.

Antagonistic coevolution between hosts and parasites can have a major impact on host population structures, and hence on the evolution of social traits. Using stochastic modelling techniques in the context of bacteria-virus interactions, we investigate the impact of coevolution across a continuum of host-parasite genetic specificity (specifically, where genotypes have the same infectivity/resistance ranges (matching alleles, MA) to highly variable ranges (gene-for-gene, GFG)) on population genetic structure, and on the social behaviour of the host. We find that host cooperation is more likely to be maintained towards the MA end of the continuum, as the more frequent bottlenecks associated with an MA-like interaction can prevent defector invasion, and can even allow migrant cooperators to invade populations of defectors.

Refractive status of patients attending eye clinics of the Public Health System from Aguascalientes, Mexico.

PURPOSE: This paper aims to evaluate the prevalence of REs in a clinic from Aguascalientes, Mexico by analysing clinical records from the local public health system. Refractive errors (REs) are quite common globally, but no data have been published regarding their frequency in clinics from Mexico. A priori, the frequency of ametropias should be high as admixture ancestry from this region is mainly European and Amerindian, the regions with high prevalence worldwide. METHODS: This cross-sectional study was conducted on 2195 subjects from records of public optometry services during the year 2018. Information obtained included age, gender, sphere, cylinder and axis. The prevalence of myopia, hyperopia and astigmatism was determined by gender and age groups in paediatric and adult patients. Chi-square testing was applied to determine significant differences in prevalence across age groups and gender. A p-value <0.05 was considered significant. RESULTS: In subjects under 18 years of age, the prevalence of emmetropia, astigmatism, myopia and hyperopia was 20.1%, 51.1%, 7.0% and 11.8%, respectively. In adults, emmetropia was present at a frequency of 20.1%, while 57.1% presented astigmatism, 12.4% hyperopia and 8.6% presented myopia. A significant association was observed between the presence of REs and age and gender. CONCLUSIONS: In this first report of prevalence of REs from western Mexico, astigmatism was the most prevalent RE in children, adolescents and adults while the least common was myopia. Important differences were found in prevalence in comparison to national and international reports.

Brain Metastases in Havana Cancer Patients.

INTRODUCTION: Cancer is a major public health problem worldwide and in Cuba. Approximately one third of cancer patients develop a brain metastasis. Despite this, epidemiological studies are scarce, internationally and in Cuba; published research is mainly limited to autopsy studies and hospital case series. OBJECTIVE: Characterize patients with brain metastases residing in Habana del Este Municipality, Havana, Cuba, with respect to demographics, metastasis location and primary tumor site. METHODS: A retrospective descriptive study was carried out with data for all patients with histologically confirmed cancer diagnosed in 2014 and registered in primary health care in Habana del Este Municipality. Diagnostic reports from computed tomography and/or magnetic resonance imaging were used to identify patients with brain metastases. Study variables were age, sex, skin color, number and location of brain metastases, control of primary tumor, and presence of extracranial metastases. Percentages were calculated and presented in tables. RESULTS: We identified 832 cancer patients in the Habana del Este population of 181,473 (prevalence 458.5 per 100,000 population). Among patients with cancer, 27.6% (230/832) had brain tumors, among which 83% (191/230) were brain metastases and 17% (39/230) primary tumors, a ratio of 4.9:1. Brain metastases appeared in 23% (191/832) of cancer patients (prevalence 105.2 per 100,000 population). Among patients with brain metastases, 48.2% (92/191) were aged 41-60 years and 61.3% (117/191) were female sex. The majority, 59.7% (114/191) had multiple metastases. The most frequent primary tumor location was the breast (40.8%, 78/191), followed by the lung (31.9%; 61/191); 46.8% (211/451) of brain metastases were in the parietal lobe. CONCLUSIONS: Brain metastases are more prevalent in this Cuban municipality than reported in other countries, but they constitute a higher proportion of cancer cases than seen in other population-based studies. The study's results underline the importance of detecting brain metastasis early, to permit timely interventions to improve quality of life and survival. CONTRIBUTION OF THIS RESEARCH: This is the first epidemiological study of brain metastases in Cuba and one of the few carried out internationally.