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Background: Mexican schools closed down in-person operations due to COVID-19 from March 2020 to February 2021. According to World Bank models, this implies a loss of 0.9 years of schooling. We set forth to design a COVID-19 safe return to school program specially adapted for both low national SARS-CoV-2 testing levels and a virtually non-existent school children vaccination scheme. Methods: The Community Program for a Safe Return encompassed five strategies: i) Community Surveillance (SARS-CoV-2 RT-qPCR testing of a community); ii) COVID-19 Education; iii) Hybrid Learning Strategy (dividing a classroom into two weekly-alternating groups of in-person schooling; iv) Layered Protection (health-status questionnaire, body-temperature control, mandatory facemasks, increased classroom ventilation, physical distancing and routine disinfection of classrooms) and; v) Virus Surveillance (weekly RT-qPCR testing of students and staff). Findings: A pilot program was implemented in a community of San Luis Potosi having a SARS-CoV-2 positivity rate below 5%. Negative SARS-CoV-2 test results were maintained in both children and staff throughout the study period. Interpretation Both WHO and CDC have emphasized the priority of in-person learning for students. Our program proved capable of providing a COVID-19 safe return to school and had an additional, unexpected, benefit of increasing community awareness and increased suspect-case surveillance. Such community involvement allowed for tailored adaptations of school attendance to be made, a strategy that proved to be both economically and epidemiologically feasible for resource limited settings. Funding: This study was supported by COPOCYT-CEEPAC/CTF/136/2020, FID 18397 Declaration of Interest: We declare no competing interests. Ethical Approval: Our study was reviewed and authorized by the State Health Ministry Committee of Bioethics (SLP/07/2020).

Background Preeclampsia is a syndrome that affects 2-8 % of pregnancies worldwide and is the leading cause of maternal death. Therefore, early detection is crucial to identify women who require clinical monitoring during pregnancy and to evaluate new preventive therapies before clinical symptoms occur. Methods The chemical fingerprints of the urine from three study groups pregnant with Preeclampsia, Healthy Pregnant (HP) and pregnant at High Risk of Preeclampsia (HRP) were evaluated using an electronic nose and the data obtained were subjected to principal component analysis (PCA), Canonical Analysis of Principal Coordinates (CAP), Partial Least Squares - Discriminant Analysis (PLS-DA) and ROC curves to determine the diagnostic power of the test. Results A separation was found between the patients with preeclampsia and HP explaining 99% of the variability of the data. Subsequently, a CAP was obtained with a correct classification of 100%, and the PLS-DA was obtained an accuracy of 88%. With the results of axis CAP1, a ROC curve was performed resulting in a sensitivity of 100% and a specificity of 95.5%. Based on the CAP model it was found that 36% (n=9) of the HRP patients would develop preeclampsia based on the metabolites found in urine. Conclusion metabolomics can be used as a tool for early detection of preeclampsia in high-risk pregnant women, using portable olfactory technology.

Metabolomics is a potential tool for the discovery of new biomarkers in the early diagnosis of diseases. An ultra-fast gas chromatography system equipped to an electronic nose detector (FGC eNose) was used to identify the metabolomic profile of Volatile Organic Compounds (VOCs) in type 2 diabetes (T2D) urine from Mexican population. A cross-sectional, comparative, and clinical study with translational approach was performed. We recruited twenty T2D patients and twenty-one healthy subjects. Urine samples were taken and analyzed by FGC eNose. Eighty-eight compounds were identified through Kovats's indexes. A natural variation of 30% between the metabolites, expressed by study groups, was observed in Principal Component 1 and 2 with a significant difference (p < 0.001). The model, performed through a Canonical Analysis of Principal coordinated (CAP), allowed a correct classification of 84.6% between healthy and T2D patients, with a 15.4% error. The metabolites 2-propenal, 2-propanol, butane- 2,3-dione and 2-methylpropanal, were increased in patients with T2D, and they were strongly correlated with discrimination between clinically healthy people and T2D patients. This study identified metabolites in urine through FGC eNose that can be used as biomarkers in the identification of T2D patients. However, more studies are needed for its implementation in clinical practice.

Opuntia megarrhiza is an endemic plant used in Mexican traditional medicine for the treatment of bones fractures in humans and domestic animals. One of the most used technique for the detection and characterization of the structure of phytochemical compounds is the Gas Chromatography Coupled to Mass Spectrometry. The goals of the present study were to identify and characterize the phytochemical compounds present in wild individuals of O. megarrhiza using this analysis. We used chloroform and methanol extracts from cladodes, and they were analyzed by gas chromatography-electron impact-mass spectrometry. We obtained 53 phytochemical compounds, 19 have been previously identified with some biological activity. Most of these compounds are alkanes, alkenes, aromatic hydrocarbons, fatty acids, and ketones. We detected some fragmentation patterns that are described for the first time for this species. The variety of metabolites presents in O. megarrhiza justifies the medicinal use of this plant in traditional medicine and highlight it as a source of phytochemical compounds with potential in medicine and biotechnology.