arXiv subjects

Jose L. Toca-Herrera

Publications and source records attributed to Jose L. Toca-Herrera.

3 recordsLinked to original sources

arXiv2026

Mechanical Softening of Vero Cells Induced by an Attenuated Measles Vaccine Virus

Quantitative characterization of biophysical alterations caused by viral infection remains at an early stage. In this study, we examined the mechanical response of Vero cells after exposure to an attenuated Measles Vaccine Virus using atomic force microscopy (AFM) in combination with confocal microscopy. AFM force distance measurements were conducted in the perinuclear region to evaluate changes in elastic and viscoelastic properties. Within 24 hours post infection, cells infected at a multiplicity of infection of 0.5 exhibited an approximately thirty five percent decrease in median of the Young modulus relative to uninfected controls, indicating substantial cellular softening. Corresponding shifts in viscoelastic behavior were observed, including reductions in the relaxed modulus and in viscosities (effects comparable to those induced by cytochalasin D mediated actin depolymerization). Confocal microscopy further revealed a dependent reorganization of the cytoskeleton upon infection, marked by altered F actin distribution and changes in filament architecture. These findings suggest that actin remodeling contributes to the altered viscoelastic properties observed during infection. This work proposes a straightforward and complementary approach for characterizing virus cell interactions by integrating AFM with confocal imaging.

physics.bio-ph↗

arXiv2022

The stiffness of elastomeric surfaces influences the mechanical properties of endothelial cells

Optimal characterization of the mechanical properties of both cells and their surrounding is an issue of major interest. Indeed, cell function and development are strongly influenced by external stimuli. Furthermore, a change in cell mechanics might, in some cases, associate with diseases or malfunctioning. In this work, atomic force microscopy (AFM) was applied to examine the mechanical properties of the silicone elastomer polydimethylsiloxane (PDMS) a common substrate in cell culture. Force spectroscopy analysis was done over different specimens of this elastomeric material containing varying ratios of resin to cross-linker in its structure (5:1, 10:1, 20:1, 30:1 and 50:1), which impacts the final material properties (e.g., stiffness, elasticity). To quantify the mechanical properties of the PDMS, factors as the modulus of Young, the maximum adhesive forces as well as both relaxation amplitudes and times upon constant height contact of the tip (dwell time different of zero) were calculated from the different segments forming the force curves. It is demonstrated that the material stiffness is increased by prior oxygen plasma treatment of the sample, required for hydrophilic switching, contrarily to what observed for its adhesiveness. Subsequent incubation of endothelial HUVEC cells on top of these plasma treated PDMS systems yields minor variation in cell mechanics in comparison to those obtained on a glass reference, on which cells show much higher spreading tendency and, by extension, a remarkable membrane hardening. Thus, surface wettability turns a factor of higher relevance than substrate stiffness inducing variations in the cell mechanics.

physics.bio-ph↗

arXiv2008

Strength stimuli on the quadriceps femoris influences the physiological tremor of the index finger

The influence of fatiguing stimuli applied to the quadriceps femoris on the tremor of the index finger on sixteen healthy subjects has been investigated, by measuring the acceleration and the electromyography activity of the extensor digitorum at two different speeds. No significant changes in the basal condition could be measured at 0.52 rad/s. However, at 1.05 rad/s the tremor amplitude (12.23%, p<0.05) and the electromyography activity (20.19%, p<0.05) increased in the time domain. In the frequential domain, the peak associated to the acceleration increased in 26.30% (p<0.05), while the electromiography activity experienced an increase of 81.34% (p<0.05). The largest change in frequency took place in the range 7-17 Hz. The discussion of the results leads to the conclusion that the supraespinal mechanism is responsible for the measured effect.

physics.med-ph↗