Biology subjects

Guevara, M.

Publications and source records attributed to Guevara, M..

3 recordsLinked to original sources

bioRxiv2025

Human Stress Response Specificity through Bioresonance Selectivity

Bold First ParagraphIn eukaryotes, the mitogen activated protein kinase (MAPK) cascade, a multilayered interconnected network of enzymes, connects external stimuli to gene regulation, determining cellular fate 1. Environmental stress sensed by a cell starts a complex chain of reactions between MAPK enzymes that ultimately activates the master stress response regulator protein p38 MAPK 2,3. Thus activated, p38 must then selectively activate targets from a pool of hundreds to initiate appropriate cellular responses 3. Mechanisms for how p38 performs this selection remain unclear 4,5. Here we show that human p38 target selectivity is based on the same principles as modern electronic telecommunications systems, except using waves of chemicals rather than electromagnetic fields or electric currents. p38 encodes information about stimuli as different frequency oscillations of its activation state, and targets are selected through frequency-dependent resonance of oscillating biochemical reactions between p38 and its targets. We demonstrate this mechanism by activating various genetic responses in human cells by applying only sugar at different frequencies. These results unify observations of oscillating signaling components and altered responses 6-19 into a coherent framework to understand and control human gene expression. As failures of this mechanism may contribute to some p38-associated diseases 2,20-28, these findings may have implications for pharmaceutical development and therapeutic strategies.

biophysics↗

bioRxiv2019

Downscaling Satellite Soil Moisture using Geomorphometry and Machine Learning

Annual soil moisture estimates are useful to characterize trends in the climate system, in the capacity of soils to retain water and for predicting land and atmosphere interactions. The main source of soil moisture spatial information across large areas (e.g., continents) is satellite-based microwave remote sensing. However, satellite soil moisture datasets have coarse spatial resolution (e.g., 25-50 km grids); and large areas from regional-to-global scales have spatial information gaps. We provide an alternative approach to predict soil moisture spatial patterns (and associated uncertainty) with higher spatial resolution across areas where no information is otherwise available. This approach relies on geomorphometry derived terrain parameters and machine learning models to improve the statistical accuracy and the spatial resolution (from 27km to 1km grids) of satellite soil moisture information across the conterminous United States on an annual basis (1991-2016). We derived 15 primary and secondary terrain parameters from a digital elevation model. We trained a machine learning algorithm (i.e., kernel weighted nearest neighbors) for each year. Terrain parameters were used as predictors and annual satellite soil moisture estimates were used to train the models. The explained variance for all models-years was >70% (10-fold cross-validation). The 1km soil moisture grids (compared to the original satellite soil moisture estimates) had higher correlations with field soil moisture observations from the North American Soil Moisture Database (n=668 locations with available data between 1991-2013; 0-5cm depth) than the original product. We conclude that the fusion of geomorphometry methods and satellite soil moisture estimates is useful to increase the spatial resolution and accuracy of satellite-derived soil moisture. This approach can be applied to other satellite-derived soil moisture estimates and regions across the world.

ecology↗

bioRxiv2018

Increased and decreased superficial white matter structural connectivity in schizophrenia and bipolar disorder

Schizophrenia (SZ) and bipolar disorder (BD) are often conceptualized as \"disconnection syndromes\", with substantial evidence of abnormalities in deep white matter tracts, forming the substrates of long-range connectivity, seen in both disorders. However, the study of superficial white matter (SWM) U-shaped short-range tracts remained challenging until recently, although findings from post-mortem studies suggest they are likely integral components of SZ and BD neuropathology. This diffusion weighted imaging (DWI) study aimed to investigate SWM microstructure in vivo in both SZ and BD for the first time. We performed whole brain tractography in 31 people with SZ, 32 people with BD and 54 controls using BrainVISA and Connectomist 2.0. Segmentation and labelling of SWM tracts were performed using a novel, comprehensive U-fiber atlas. Analysis of covariances yielded significant generalized fractional anisotropy (gFA) differences for 17 SWM bundles in frontal, parietal and temporal cortices. Post hoc analyses showed gFA reductions in both patient groups as compared with controls in bundles connecting regions involved in language processing, mood regulation, working memory and motor function (pars opercularis, insula, anterior cingulate, precentral gyrus). We also found increased gFA in SZ patients in areas overlapping the default mode network (inferior parietal, middle temporal, precuneus), supporting functional hyperconnectivity of this network evidenced in SZ. We thus illustrate that short U-fibers are vulnerable to the pathological processes in major psychiatric illnesses, encouraging improved understanding of their anatomy and function.

neuroscience↗