Reassessment of requirements for anaerobic xylose fermentation by engineered, non-evolved Saccharomyces cerevisiae strains.

Expression of a heterologous xylose isomerase, deletion of the GRE3 aldose-reductase gene and overexpression of genes encoding xylulokinase (XKS1) and non-oxidative pentose-phosphate-pathway enzymes (RKI1, RPE1, TAL1, TKL1) enables aerobic growth of Saccharomyces cerevisiae on d-xylose. However, literature reports differ on whether anaerobic growth on d-xylose requires additional mutations. Here, CRISPR-Cas9-assisted reconstruction and physiological analysis confirmed an early report that this basic set of genetic modifications suffices to enable anaerobic growth on d-xylose in the CEN.PK genetic background. Strains that additionally carried overexpression cassettes for the transaldolase and transketolase paralogs NQM1 and TKL2 only exhibited anaerobic growth on d-xylose after a 7-10 day lag phase. This extended lag phase was eliminated by increasing inoculum concentrations from 0.02 to 0.2 g biomass L-1. Alternatively, a long lag phase could be prevented by sparging low-inoculum-density bioreactor cultures with a CO2/N2-mixture, thus mimicking initial CO2 concentrations in high-inoculum-density, nitrogen-sparged cultures, or by using l-aspartate instead of ammonium as nitrogen source. This study resolves apparent contradictions in the literature on the genetic interventions required for anaerobic growth of CEN.PK-derived strains on d-xylose. Additionally, it indicates the potential relevance of CO2 availability and anaplerotic carboxylation reactions for anaerobic growth of engineered S. cerevisiae strains on d-xylose.

Heterotrophic growth of microalgae: metabolic aspects.

Microalgae are considered photoautotrophic organisms, however several species have been found living in environments where autotrophic metabolism is not viable. Heterotrophic cultivation, i.e. cell growth and propagation with the use of an external carbon source under dark conditions, can be used to study the metabolic aspects of microalgae that are not strictly related to photoautotrophic growth and to obtain high value products. This manuscript reviews studies related to the metabolic aspects of heterotrophic grow of microalga. From the physiological and metabolic perspective, the screening of microalgal strains in different environments and the development of molecular and metabolic engineering tools, will lead to an increase in the number of known microalgae species that growth under strict heterotrophic conditions and the variety of carbon sources used by these microorganisms.

[Variability of the menstrual cycle in Mexican women according to the weight and the distribution of the adipose fabric]. / Variabilidad del ciclo menstrual en mujeres mexicanas según el peso y la distribución del tejido adiposo.

BACKGROUND: Menstrual cycle characteristics have been studied throughout the world in several populations. OBJECTIVE: To analyze the frequency of occurrence of menstruation, duration and volume loss during it and its relationship with age, weight and body fat distribution in Mexican women. MATERIAL AND METHODS: prospective, cross-sectional and descriptive study conduced in women which accompanied patients to hospital consultation, with menstrual cycles considered normal by them, age was documented; body mass index (BMI) and waist hip ratio (WHR) were calculated. They were questioned about: periodicity of the cycle, duration, number and type of pads used per day, and the quantity of menstrual bleeding was calculated. STATISTICAL ANALYSIS: Central tendency and dispersion measurements, as well as percentages were calculated. For the comparison between the groups ANOVA was used and Pearson correlation analysis was done. RESULTS: 161 women were studied. Average age was 23.9 +/- 6.1 years, BMI 26.1 +/- 4.3 and WHR 0.9 +/- 0.1. The cycle periodicity was 29.3 +/- 3.1 days, being 86.4% between 28 and 30 days. The periodicity of menstrual bleeding was affected neither by age nor by BMI and WHR. Bleeding duration was 4.9 +/- 1.6 days, and the most common was from 4-7 days, only in those older than 35 years was from 1-3 days. The calculated average volume was 151.5 +/- 81.0 mL. In those with BMI < 20 loses were between 81and 120 ml, and in those with BMI > 35 from 121-160 ml; 85.5% of women with WHR < or = 0.85 had loses between 81 and 160 ml and 39.3% of those with WHR > 0.85. CONCLUSION: BMI greater than 35 is associated with more abundant bleeding, and android distribution of body fat with smaller bleeding.

[Motives for abandoning the healthcare process for precancerous lesions of the uterine cervix]. / Motivos de abandono en el proceso de atención médica de lesiones precursoras de cáncer cervicouterino.

OBJECTIVE: To determine factors associated with medical care abandon of women with CIN. MATERIAL AND METHODS: A nested case-control study in a cohort was done. Patients referred to clinical Dysplasia of Gyneco-Obstetrician Services in third level Hospitals were considered. CASES: Patients who abandoned medical care. CONTROLS: women who attend their medical appointments during follow-up. All subjects underwent structured interviews focused on social, clinical and health services factors in two different times, applied at the beginning of study and the end of follow-up. Clinical records were reviewed to obtain clinical information. ANALYSIS: Descriptive and inferential statistical was done. Non conditional Logistic Regression analysis was done to obtain adjusted association. RESULTS: Abandon cumulative incidence rate was 108/525 = 20.7% (I.C. 95% = 17.2-24.3); 60.2% happened in diagnosis phase, 17.7% ocured during therapeutic phase and 23.1% happened in surveillance phase. We studied 108 cases and 417 controls to analysis. Next adjusted risk factors were obtained: Afraid to death (ORa = 4.2, IC.95% = 1.8-9.5), long appointments (ORa = 6.6, I.C.95% = 3.4-13.0), lack of privacity (ORa = 12.5, I.C.95% = 2.6-59.8), reject to treatment (ORa = 40.4, I.C.95% = 2.1-785.4), lack of information (ORa = 41.9, I.C.95% =14.2-124.1) and other factors. CONCLUSIONS: Patient perception, access and barriers in health services were the most important factors associated with medical care abandon.