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Columnar cacti have been traditionally classified as crassulacean acid metabolism (CAM) plants, though recent research indicates some cactus seedlings employ the C(3) pathway. To verify this last result, we measured acidity fluctuations for five columnar and one globular cactus species in seedlings from 1 to 48 d old after experimental exposure to 60% and 30% full sunlight, and in adult plants in the field. Using light-response curves of chlorophyll fluorescence, we determined photosynthetic efficiency (ΔF/Fm'), maximum electron transport rate (ETR(max)) and saturating photosynthetically active photon flux density (PPFD(sat)). All seedlings used the CAM pathway from their first day of development, and increases in nocturnal acidity depended on species, light treatment, and age. The CAM pathway was also found in adult plants. Cactus seedlings were able to acclimatize to light conditions by making photochemical adjustments, mainly by modifying the level of light at which photosystem II is saturated (PPFD(sat)). The presence of CAM in the seedlings of columnar cacti increases water-use efficiency and reduces the risk of photoinhibition. This could favor survival in the highly variable light levels characteristic of the desert environments of columnar cacti.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the current coronavirus disease 2019 (COVID-19) pandemic, affecting more than 219 countries and causing the death of more than 5 million people worldwide. The genetic background represents a factor that predisposes the way the host responds to SARS-CoV-2 infection. In this sense, genetic variants of ACE and ACE2 could explain the observed interindividual variability to COVID-19 outcomes. In order to improve the understanding of how genetic variants of ACE and ACE2 are involved in the severity of COVID-19, we included a total of 481 individuals who showed clinical manifestations of COVID-19 and were diagnosed by reverse transcription PCR (RT-PCR). Genomic DNA was extracted from peripheral blood and saliva samples. ACE insertion/deletion polymorphism was evaluated by the high-resolution melting method; ACE single-nucleotide polymorphism (SNP) (rs4344) and ACE2 SNPs (rs2285666 and rs2074192) were genotyped using TaqMan probes. We assessed the association of ACE and ACE2 polymorphisms with disease severity using logistic regression analysis adjusted by age, sex, hypertension, type 2 diabetes, and obesity. The severity of the illness in our study population was divided as 31% mild, 26% severe, and 43% critical illness; additionally, 18% of individuals died, of whom 54% were male. Our results showed in the codominant model a contribution of ACE2 gene rs2285666 T/T genotype to critical outcome [odds ratio (OR) = 1.83; 95%CI = 1.01–3.29; p = 0.04] and to require oxygen supplementation (OR = 1.76; 95%CI = 1.01–3.04; p = 0.04), in addition to a strong association of the T allele of this variant to develop critical illness in male individuals (OR = 1.81; 95%CI = 1.10–2.98; p = 0.02). We suggest that the T allele of rs2285666 represents a risk factor for severe and critical outcomes of COVID-19, especially for men, regardless of age, hypertension, obesity, and type 2 diabetes.

Background The increasing rate of cancer cases is alarming. In 2018, 9.6 million people died of the disease (WHO 2020). Current treatments, such as chemical therapy using cisplatin (CisPt) as a basis, cause considerable collateral damage to the patient (Ahmad 2017). CisPt acts as an alkylating agent with affinity to DNA, binds to the guanine and cytosine residues, and prevents the processes of replication and transcription of the genetic material, resulting in cell death by apoptosis (Ahmad 2017). However, cisplatin is unable to differentiate between normal and cancerous cells. Moreover, cancer cells can develop

El presente estudio proporciona información del crecimiento de Brosimum alicastrum (ramón) durante sus primeros años, en una plantación comercial localizada en Yucatán, México. Las plantas fueron desarrolladas a partir de semillas y cultivadas en vivero hasta la edad de un año de edad y 65 cm de altura, momento en el cual fueron transportadas al campo en donde se plantaron a una distancia de 5 m entre ellas. Los trasplantes se realizaron en los años 2006, 2007 y 2009 y las mediciones se hicieron del 2010 al 2012, cuando contaban con 2, 4 y 5 años de edad. Se eligieron 10 árboles de cada edad, y durante 24 meses se midió la altura máxima y el diámetro del tallo a 50 cm del suelo. Se determinó que las plántulas desarrolladas en vivero, en los primeros seis meses, crecen en forma lineal a una tasa de 0.65 m año-1, posteriormente, en condiciones de campo hasta los 7 años, el crecimiento fue exponencial. La fase de endurecimiento inicia a los 6 años, con un incremento en el diámetro del tallo superior al doble. Durante la época de lluvias se registraron 65 y 69 % del crecimiento en diámetro y altura respectivamente, comparado con el crecimiento en la época de sequía. Las edades de los árboles considerados en este trabajo se consignan como primera etapa de crecimiento, ya que algunos de los individuos de siete años iniciaron el proceso de floración, lo que indica el término del periodo juvenil de la planta.

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Abstract. Tuberculous meningitis (TBM) is the most severe form of tuberculosis. It is caused by Mycobacterium tubercu losis (M. tuberculosis; MT) and it is very difficult to diagnose. The symptoms are similar to other infectious neurological diseases, such as neurocysticercosis, neuroborreliosis, or herpes viral infection. The aim of this study was to identify tuberculosis (TB) in cases of meningitis with clinical and laboratory evidence suggestive of TBM, and to confirm our findings with molecular tests for TB infection. We recruited patients with neurological symptoms who were examined at the neurology services of Hospitals of Instituto Mexicano del Seguro Social (IMSS) in Mexico City. A total of 144 consecutive patients with suggestive infectious meningitis were initially included; 94 cases of meningitis with clinical and laboratory evidence suggestive of TBM were included, but only 50 of these cases fulfilled the criteria for probable TBM. As the controls, we included 50 cases of meningitis with clinical and laboratory evidence suggestive of non-TBM. Cerebrospinal fluid (CSF) was collected from all 100 patients (cases and controls) and tested for TB by multiplex and nested PCR analyses. Nested PCR detected 0.1 fg of M. tuberculosis DNA. TB infection was confirmed with molecular tests in 49 patients from the 50 cases suggestive of TBM and in 1 of the 50 non-TBM cases. The analysis exhibited a sensitivity of 98.0%, a specificity of 92.0%, a positive predictive value of 88.0% and a negative predictive value of 98.0%. The use CSF for the analyses proved to be effective for the rapid diagnosis of TBM using a developed system of multiplex and nested PCR analyses in patients presenting neurological symptoms.

Abstract:We investigated relationships between population dynamics and microclimate, physiology, and the degree of mycorrhizal colonization, for three species (Piscidia piscipula L.(Sarg.)) (Fabaceae), Bunchosia swartziana Griseb. (Malpighiaceae) and Psidium sartorianum (Bergius) Nied. (Myrtaceae)) of a tropical sub deciduous forest in Yucatan, Mexico that were growing in plots of different successional ages. We hypothesized that abundance and persistence were related to increased plasticity in CO 2 assimilation. We found that Piscidia piscipula had greater abundance in intermediate plots (18 to 21 years), presented higher levels of plasticity in CO 2 assimilation (greater variability among individuals, plots, and seasons), presented the highest CO 2 assimilation rates, and presented greater drought resistance (higher water potentials and capacitance). Conversely, Psidium sartorianum had greater abundance in older plots (more than 50 years of secondary succession), lower assimilation rates, and low levels of plasticity in CO 2 assimilation. Bunchosia had intermediate values. Locally, the degree of mycorrhizal colonization was consistent with abundance across plots. Regionally (but not locally), plasticity in CO 2 assimilation was consistent with abundance. We found differences in microclimates among plots and within plots among species. Physiological adjustments appeared to play an important role in the capacity to regenerate and in the successional persistence of these species in this tropical dry forest.