A chloride channel blocker prevents the suppression by inorganic phosphate of the cytosolic calcium signals that control muscle contraction.

KEY POINTS: Accumulation of inorganic phosphate (Pi ) may contribute to muscle fatigue by precipitating calcium salts inside the sarcoplasmic reticulum (SR). Neither direct demonstration of this process nor definition of the entry pathway of Pi into SR are fully established.  We showed that Pi promoted Ca2+ release at concentrations below 10 mm and decreased it at higher concentrations. This decrease correlated well with that of [Ca2+ ]SR .  Pre-treatment of permeabilized myofibres with 2 mm Cl- channel blocker 9-anthracenecarboxylic acid (9AC) inhibited both effects of Pi .  The biphasic dependence of Ca2+ release on [Pi ] is explained by a direct effect of Pi acting on the SR Ca2+ release channel, combined with the intra-SR precipitation of Ca2+ salts. The effects of 9AC demonstrate that Pi enters the SR via a Cl- pathway of an as-yet-undefined molecular nature. ABSTRACT: Fatiguing exercise causes hydrolysis of phosphocreatine, increasing the intracellular concentration of inorganic phosphate (Pi ). Pi diffuses into the sarcoplasmic reticulum (SR) where it is believed to form insoluble Ca2+ salts, thus contributing to the impairment of Ca2+ release. Information on the Pi entrance pathway is still lacking. In amphibian muscles endowed with isoform 3 of the RyR channel, Ca2+ spark frequency is correlated with the Ca2+ load of the SR and can be used to monitor this variable. We studied the effects of Pi on Ca2+ sparks in permeabilized fibres of the frog. Relative event frequency (f/fref ) rose with increasing [Pi ], reaching 2.54 ± 1.6 at 5 mm, and then decreased monotonically, reaching 0.09 ± 0.03 at [Pi ] = 80 mm. Measurement of [Ca2+ ]SR confirmed a decrease correlated with spark frequency at high [Pi ]. A large [Ca2+ ]SR surge was observed upon Pi removal. Anion channels are a putative path for Pi into the SR. We tested the effect of the chloride channel blocker 9-anthracenecarboxylic acid (9AC) on Pi entrance. 9AC (400 µm) applied to the cytoplasm produced a non-significant increase in spark frequency and reduced the Pi effects on this parameter. Fibre treatment with 2 mm 9AC in the presence of high cytoplasmic Mg2+ suppressed the effects of Pi on [Ca2+ ]SR and spark frequency up to 55 mm [Pi ]. These results suggest that chloride channels (or transporters) provide the main pathway of inorganic phosphate into the SR and confirm that Pi impairs Ca2+ release by accumulating and precipitating with Ca2+ inside the SR, thus contributing to myogenic fatigue.

De la medicina narrativa a los cuidados humanizados: El hospital El Cruce en pandemia

Este libro intenta compartir los aportes técnicos de los enfoques con las vivencias emocionales recogidas en múltiples relatos. Contiene descripciones rigurosas de las dos disciplinas que confluyen, la medicina narrativa y los cuidados humanizados, así como de las medidas adoptadas en la organización del hospital y la asistencia. Suma a esos contenidos el relato de la experiencia en todo el enfoque humanístico de la crisis, de la reflexión grupal en los talleres, las estrategias adoptadas para la resolución de problemas complejos como las visitas, el aislamiento y los cuidados del final de la vida. En cada tema, aporta textos comprometidos y personales de los actores y diversos profesionales de la salud que comparten sus emociones y conmociones en la circunstancia extrema de la pandemia. (AU)

Abordaje transfibular modificado para fracturas del platillo tibial posterolateral. Serie de Casos / Modified transfibular approach for posterolateral tibial plateau fractures. Case Series

Introducción Las fracturas del platillo tibial posterolateral exigen un abordaje que permita una buena visualización de la superficie articular para su restitución anatómica, restablecimiento de la altura y un espacio adecuado para la aplicación del material de osteosíntesis y fijación estable. Hay diversos abordajes descritos en la literatura que no proporcionan la visualización deseada o conllevan múltiples limitaciones y/o complicaciones. El propósito de este estudio es describir una modificación a la técnica quirúrgica de la osteotomía de la fíbula para el manejo de las fracturas de platillo tibial posterolateral. Materiales y métodos Se presentan los resultados clínicos de una serie de casos retrospectiva de 15 pacientes con fracturas de platillo tibial posterolateral que al momento del estudio tenían un seguimiento promedio de 6 meses. Resultados Los resultados funcionales en escala de Lysholm fueron excelentes en 3 pacientes, buenos en 8 y regulares en 4. En todos los pacientes se logró una reducción satisfactoria de la superficie articular de la tibia, sin pérdida de altura de la misma, con alineación adecuada, sin síntomas de inestabilidad, todos con consolidación de la fíbula que no retrasó la rehabilitación, no hubo lesiones del nervio peroneal ni problemas con la piel; se presentó un caso de infección superficial que se manejó con antibióticos orales sin complicaciones. Discusión El abordaje descrito facilita una amplia exposición de la superficie articular, es técnicamente fácil y reproducible, permite la reducción y fijación necesaria, con menor riesgo de complicaciones, con la cual se conserva el aporte vascular de la tibia proximal, se evita el daño a la articulación tibiofibular proximal y se propicia una mayor área de consolidación de la osteotomía. Ésta técnica puede utilizarse sola o en combinación con otros abordajes, para fracturas agudas o crónicas con mala unión. Consideramos que el abordaje con la técnica descrita es una alternativa para el manejo de las fracturas posterolaterales, con resultados alentadores.

Background Fractures of the posterolateral tibial plateau require an approach that allows a good visualization of the articular surface for its anatomical restitution, restoration of height and an adequate space for the application of osteosynthesis material and stable fixation. There are several approaches described in the literature that do not provide the desired visualization or involve multiple limitations and / or complications. The purpose of this study is to describe a modification to the surgical technique of the fibula osteotomy for the management of posterolateral tibial plate fractures. Methods We present the clinical results of a retrospective case series of 15 patients with posterolateral tibial plate fractures that at the time of the study had an average follow-up of 6 months. Results Functional results in Lysholm scale were excellent in 3 patients, good in 8 and regular in 4. Good results were obtained in all patients with a reduction of the tibia articular surface, without loss of height of the same, with alignment adequate, without symptoms of instability, all with consolidation of the fibula that did not delay rehabilitation, there were no peroneal nerve injuries or problems with the skin; There was a case of superficial infection that was managed with oral antibiotics without complications. Discussion The described approach facilitates a broad exposure of the articular surface, is technically easy and reproducible, allows the necessary reduction and fixation, with a lower risk of complications, with which the vascular supply of the proximal tibia is conserved, the damage is avoided to the proximal tibiofibular joint and a greater area of consolidation of the osteotomy is favored. This technique can be used alone or in combination with other approaches, for acute or chronic fractures with poor union. We consider that the approach with the described technique is an alternative for the management of posterolateral fractures, with encouraging results.

The voltage sensor of excitation-contraction coupling in mammals: Inactivation and interaction with Ca2.

In skeletal muscle, the four-helix voltage-sensing modules (VSMs) of CaV1.1 calcium channels simultaneously gate two Ca2+ pathways: the CaV1.1 pore itself and the RyR1 calcium release channel in the sarcoplasmic reticulum. Here, to gain insight into the mechanism by which VSMs gate RyR1, we quantify intramembrane charge movement associated with VSM activation (sensing current) and gated Ca2+ release flux in single muscle cells of mice and rats. As found for most four-helix VSMs, upon sustained depolarization, rodent VSMs lose the ability to activate Ca2+ release channels opening; their properties change from a functionally capable mode, in which the mobile sensor charge is called charge 1, to an inactivated mode, charge 2, with a voltage dependence shifted toward more negative voltages. We find that charge 2 is promoted and Ca2+ release inactivated when resting, well-polarized muscle cells are exposed to low extracellular [Ca2+] and that the opposite occurs in high [Ca2+]. It follows that murine VSMs are partly inactivated at rest, which establishes the reduced availability of voltage sensing as a pathogenic mechanism in disorders of calcemia. We additionally find that the degree of resting inactivation is significantly different in two mouse strains, which underscores the variability of voltage sensor properties and their vulnerability to environmental conditions. Our studies reveal that the resting and activated states of VSMs are equally favored by extracellular Ca2+ Promotion by an extracellular species of two states of the VSM that differ in the conformation of the activation gate requires the existence of a second gate, inactivation, topologically extracellular and therefore accessible from outside regardless of the activation state.

The HUGE formula (hematocrit, urea, gender) for screening for chronic kidney disease in elderly patients: a study of diagnostic accuracy.

Chronically reduced glomerular filtration rate (GFR) in old people does not always mean that they suffer from chronic kidney disease (CKD) since their GFR can just be reduced by aging. The HUGE equation has been recently described and validated in Spain for screening CKD without taking into account the patient's GFR value. This equation is based on patient's hematocrit, plasma urea levels and gender. The present study documented that the HUGE equation had and acceptable performance for screening CKD in elderly Argentine patients.

Alterations in zebrafish development induced by simvastatin: Comprehensive morphological and physiological study, focusing on muscle.

The cholesterol synthesis inhibitor simvastatin, which is used to treat cardiovascular diseases, has severe collateral effects. We decided to comprehensively study the effects of simvastatin in zebrafish development and in myogenesis, because zebrafish has been used as a model to human diseases, due to its handling easiness, the optical clarity of its embryos, and the availability of physiological and structural methodologies. Furthermore, muscle is an important target of the drug. We used several simvastatin concentrations at different zebrafish developmental stages and studied survival rate, morphology, and physiology of the embryos. Our results show that high levels of simvastatin induce structural damage whereas low doses induce minor structural changes, impaired movements, and reduced heart beating. Morphological alterations include changes in embryo and somite size and septa shape. Physiological changes include movement reduction and slower heartbeat. These effects could be reversed by the addition of exogenous cholesterol. Moreover, we quantified the total cell number during zebrafish development and demonstrated a large reduction in cell number after statin treatment. Since we could classify the alterations induced by simvastatin in three distinct phenotypes, we speculate that simvastatin acts through more than one mechanism and could affect both cell replication and/or cell death and muscle function. Our data can contribute to the understanding of the molecular and cellular basis of the mechanisms of action of simvastatin.

Growth hormone receptors in zebrafish (Danio rerio): adult and embryonic expression patterns.

Growth hormone receptor (GHR) is a critical regulator of growth and metabolism. Although two GHRs have been characterized in many fish species, their functional characteristics, mechanisms of regulation and roles in embryonic development remain unclear. The zebrafish (Danio rerio) is an excellent model organism to study both developmental and physiological processes. In the present work, we characterized the complete cDNA sequences of zebrafish GHRs, ghra and ghrb, and their gene structures. We studied the expression of both receptors in adult tissues, and during embryonic development and larval stages by means of RT-PCR and whole-mount in situ hybridization. We determined that both transcripts are maternal ones, with specific expression patterns during development. Both GHR transcripts are mainly expressed in the notochord, myotomes, anterior structures and in the yolk cell. Interestingly, their expression became undetectable at 96h post-fertilization. Unlike other reports in fish, ghrs expression could not be detected in brain when adult tissues were used, and we detected ghrb but not ghra transcripts in muscle. In addition, we determined alternative transcript sequences for ghra with specific domain deletions, and alternative transcripts for ghrb that generate a premature stop codon and codify for truncated isoforms. These isoforms lack intracellular regions necessary for the activation of signal transducers and activators of transcription (STAT) family transcription factors 5.

Control of dual isoforms of Ca2+ release channels in muscle.

Here we compare excitation-contraction coupling in single muscle cells of frogs and rats. Because amphibians have isoform 3 (or 3) of the ryanodine receptor/Ca2+ release channel, in addition to 1 (alpha), which is also present in the mammal, any extra feature present in the frog may in principle be attributed to isoform 3. Ca2+ release under voltage clamp depolarization has a peak and a steady phase in both taxonomic classes, but the peak is more marked in the frog, where the ratio of amplitudes of the two phases is voltage-dependent. This dependence is a hallmark of CICR. Confocal imaging identified Ca2+ sparks in the frog, but not in the voltage-clamped rat cells. Because Ca2+ sparks involve CICR both observations indicate that the contribution of CICR is minor or null in the mammal. The "couplon" model well accounts for observations in the frog, but assumes a structure that we now know to be valid only for the rat. A revised model is proposed, whereby the isoform 3 channels, located parajunctionally, are activated by CICR and contribute its characteristic global and local features. Several issues regarding the roles of different channels remain open to further study.

Control of dual isoforms of Ca2+ release channels in muscle

Here we compare excitation-contraction coupling in single muscle cells of frogs and rats. Because amphibians have isoform 3 (or b) of the ryanodine receptor/Ca2+ release channel, in addition to 1 (a), which is also present in the mammal, any extra feature present in the frog may in principle be attributed to isoform 3. Ca2+ release under voltage clamp depolarization has a peak and a steady phase in both taxonomic classes, but the peak is more marked in the frog, where the ratio of amplitudes of the two phases is voltage-dependent. This dependence is a hallmark of CICR. Confocal imaging identified Ca2+ sparks in the frog, but not in the voltage-clamped rat cells. Because Ca2+ sparks involve CICR both observations indicate that the contribution of CICR is minor or null in the mammal. The "couplon" model well accounts for observations in the frog, but assumes a structure that we now know to be valid only for the rat. A revised model is proposed, whereby the isoform 3 channels, located parajunctionally, are activated by CICR and contribute its characteristic global and local features. Several issues regarding the roles of different channels remain open to further study.

Differential effects of voltage-dependent inactivation and local anesthetics on kinetic phases of Ca2+ release in frog skeletal muscle.

In voltage-clamped frog skeletal muscle fibers, Ca(2+) release rises rapidly to a peak, then decays to a nearly steady state. The voltage dependence of the ratio of amplitudes of these two phases (p/s) shows a maximum at low voltages and declines with further depolarization. The peak phase has been attributed to a component of Ca(2+) release induced by Ca(2+), which is proportionally greater at low voltages. We compared the effects of two interventions that inhibit Ca(2+) release: inactivation of voltage sensors, and local anesthetics reputed to block Ca(2+) release induced by Ca(2+). Holding the cells partially depolarized strongly reduced the peak and steady levels of Ca(2+) release elicited by a test pulse and suppressed the maximum of the p/s ratio at low voltages. The p/s ratio increased monotonically with test voltage, eventually reaching a value similar to the maximum found in noninactivated fibers. This implies that the marked peak of Ca(2+) release is a property of a cooperating collection of voltage sensors rather than individual ones. Local anesthetics reduced the peak of release flux at every test voltage, and the steady phase to a lesser degree. At variance with sustained depolarization, they made p/s low at all voltages. These observations were well-reproduced by the "couplon" model of dual control, which assumes that depolarization and anesthetics respectively, and selectively, disable its Ca(2+)-dependent or its voltage-operated channels. This duality of effects and their simulation under such hypotheses are consistent with the operation of a dual, two-stage control of Ca(2+) release in muscle, whereby Ca(2+) released through multiple directly voltage-activated channels builds up at junctions to secondarily open Ca(2+)-operated channels.

Two components of voltage-dependent inactivation in Ca(v)1.2 channels revealed by its gating currents.

Voltage-dependent inactivation (VDI) was studied through its effects on the voltage sensor in Ca(v)1.2 channels expressed in tsA 201 cells. Two kinetically distinct phases of VDI in onset and recovery suggest the presence of dual VDI processes. Upon increasing duration of conditioning depolarizations, the half-distribution potential (V(1/2)) of intramembranous mobile charge was negatively shifted as a sum of two exponential terms, with time constants 0.5 s and 4 s, and relative amplitudes near 50% each. This kinetics behavior was consistent with that of increment of maximal charge related to inactivation (Qn). Recovery from inactivation was also accompanied by a reduction of Qn that varied with recovery time as a sum of two exponentials. The amplitudes of corresponding exponential terms were strongly correlated in onset and recovery, indicating that channels recover rapidly from fast VDI and slowly from slow VDI. Similar to charge "immobilization," the charge moved in the repolarization (OFF) transient became slower during onset of fast VDI. Slow VDI had, instead, hallmarks of interconversion of charge. Confirming the mechanistic duality, fast VDI virtually disappeared when Li(+) carried the current. A nine-state model with parallel fast and slow inactivation pathways from the open state reproduces most of the observations.

Zapatas mecedoras para camas: profilaxis y tratamiento de las úlceras por presión / Mobile support for beds: prophylaxis and treatment of pressure ulcers

Los A.A. han ideado unas zapatas movibles que permiten transformar cualquier cama de una plaza en oscilante. Esto permite prevenir las úlceras por presión y demás complicaciones

Zapatas mecedoras para camas: profilaxis y tratamiento de las úlceras por presión / Mobile support for beds: prophylaxis and treatment of pressure ulcers

Los A.A. han ideado unas zapatas movibles que permiten transformar cualquier cama de una plaza en oscilante. Esto permite prevenir las úlceras por presión y demás complicaciones (AU)