Shallow slow earthquakes to decipher future catastrophic earthquakes in the Guerrero seismic gap.

The Guerrero seismic gap is presumed to be a major source of seismic and tsunami hazard along the Mexican subduction zone. Until recently, there were limited observations at the shallow portion of the plate interface offshore Guerrero, so we deployed instruments there to better characterize the extent of the seismogenic zone. Here we report the discovery of episodic shallow tremors and potential slow slip events in Guerrero offshore. Their distribution, together with that of repeating earthquakes, seismicity, residual gravity and bathymetry, suggest that a portion of the shallow plate interface in the gap undergoes stable slip. This mechanical condition may not only explain the long return period of large earthquakes inside the gap, but also reveals why the rupture from past M < 8 earthquakes on adjacent megathrust segments did not propagate into the gap to result in much larger events. However, dynamic rupture effects could drive one of these nearby earthquakes to break through the entire Guerrero seismic gap.

Short-term interaction between silent and devastating earthquakes in Mexico.

Either the triggering of large earthquakes on a fault hosting aseismic slip or the triggering of slow slip events (SSE) by passing seismic waves involve seismological questions with important hazard implications. Just a few observations plausibly suggest that such interactions actually happen in nature. In this study we show that three recent devastating earthquakes in Mexico are likely related to SSEs, describing a cascade of events interacting with each other on a regional scale via quasi-static and/or dynamic perturbations across the states of Guerrero and Oaxaca. Such interaction seems to be conditioned by the transient memory of Earth materials subject to the "traumatic" stress produced by seismic waves of the great 2017 (Mw8.2) Tehuantepec earthquake, which strongly disturbed the SSE cycles over a 650 km long segment of the subduction plate interface. Our results imply that seismic hazard in large populated areas is a short-term evolving function of seismotectonic processes that are often observable.

[Use of an external fixator in open tibial shaft fractures as definitive treatment]. / Uso de fijador externo en fracturas diafisarias de tibia expuestas como tratamiento definitivo.

BACKGROUND: We conducted a study evaluating the clinical and radiologic results of the open tibial shaft fractures using an external fixator as definitive treatment. METHODS: Clinical, observational, descriptive, prospective and longitudinal study. Forty-six patients were included, 40 males (87%) and 6 females (13%), whose age was 31.02 +/- 14.62 years; the time elapsed from the accident to admission in the Emergency Room was 1-16 hours, with a mean of 5.1 +/- 3.35 hours. Ten patients (21.74%) had a Gustilo grade I open fracture, and 36 patients (78.26%) a Gustilo grade II fracture. They were also classified according to the AO classification, with the following resulting groups: 13 (28.9%) patients were A3, 12 (26.1%) were B3, 8 (17.4%) B1, 8 (17.4%) were B2, and 5 (10.9%) were A2. The dynamization of the fixator was done at a mean of 11.56 +/- 1.10 weeks. RESULTS: Forty-three patients had healing at 23.51 +/- 3.62 weeks; Gustilo I fractures healed at 22.8 +/- 3.5 weeks; Gustilo II fractures at 23.7 +/- 3.7 weeks, with a P value of 0.48. In 3 patients (6.53%), due to absence of healing, the external fixator was exchanged for an intramedullary nail with a bone graft, with healing occurring at 18 weeks. Six infections (13%) were reported at the nail insertion site; angulations ranged from 0 degrees to 8 degrees, which is tolerable. CONCLUSIONS: This fixator is safe in properly selected patients, since the few complications that occurred are similar to other reports using different internal fixation methods.

[Cognitive deterioration after consumption of cannabis]. / Deterioro cognitivo tras consumo de cannabis.

OBJECTIVES: The use of cannabis in humans causes several malfunctions in the cognitive performance, but it remains unclear if these alterations are reversible after the abstinence. DEVELOPMENT: The author carries out a wide bibliographical review from the first studies including a large number of subjects, which results are not reliable due to methodological defects. Recent researches, using more strict criteria and modern techniques of neuroimaging, show a subtle and permanent fail in several cognitive functions. CONCLUSIONS: We consider that long term cannabis use (more than 15 years) would lead to a subtle and permanent impairment in cognitive performance, mainly in the capacity of retain new information (probably due to inability to filter tangential information).

Detection of the mouse acrosome reaction by acid phosphatase. Comparison with chlortetracycline and electron microscopy.

The sperm acrosome is a uniquely regulated secretory vesicle containing several hydrolase enzymes, including acid phosphatase (AP). The exocytotic event that releases these enzymes, the acrosome reaction, is required for fertilization in mammals. Different methods have been described in the scientific literature for detection of the acrosome reaction: double and triple stains, fluorescent-lectin stains, monoclonal antibodies against acrosomal antigens (immunodetection techniques), Coomassie blue, differential interference contrast or phase contrast, flow cytometry, and chlortetracycline (CTC). In contrast, only 1 method to detect AP released by live and reacted sperm has been described in the literature thus far. In this work we compare 2 classical methods, CTC and transmission electron microscopy (TEM), with the assay of AP released from the acrosome. AP released during the acrosome reaction was measured in the culture medium. Enzyme remaining in nonreacted sperm cells was released by Triton X-100 treatment. This enzyme-based methodology shows an increase of AP in the culture media after the acrosome reaction and a corresponding decrease in the detergent-releasable enzyme. The AP assay thus permits the detection of the mouse acrosome reaction and compares well with the CTC and TEM methods. This method is performed on the whole sperm population and so avoids the observer error that is inherent in light microscopic methods.

Morphometrical comparison of human spermatozoa obtained from semen and swim-up methodology.

Because morphology is regularly established in semen smears, but not in swim-up spermatozoa, we were interested in comparing some morphological parameters of semen and swim-up spermatozoa to establish if the cells selected by the swim-up method were morphologically similar to those considered normal in semen. Normal human semen samples were divided into two aliquots. One of these aliquots was washed by centrifugation with B2 medium and sperm smears were prepared with the resulting pellet as a control. The other aliquot was used to perform swim-up separation and the spermatozoa from the supernatant were used as experimental smears. Both groups were stained according to the triple stain technique and spontaneous acrosome reaction and viability were determined. Video microscopy and computer-assisted image processing of live and non-reacted sperm cells were used to establish morphometrical parameters of the sperm head in both populations. The following set of morphometrical parameters were considered: width, length, width/length ratio, acrosome area, head area, and acrosome area/head area ratio. An increase in head width, a decrease in head length and a subsequent increase of width/length ratio were found in swim-up cells compared with the control group. A slight increase in acrosome area/head area ratio was also observed in swim-up supermatozoa. Through the swim-up methodology we were able to select a subpopulation of oval shaped heads with spermatozoa having a bigger acrosome area in comparison to semen.