RESUMEN
Sharp wave-ripple complexes (SPW-Rs) are spontaneous oscillatory events that characterize hippocampal activity during resting periods and slow-wave sleep. SPW-Rs are related to memory consolidation - the process during which newly acquired memories are transformed into long-lasting memory traces. To test the involvement of SPW-Rs in this process, it is crucial to understand how SPW-Rs originate and propagate throughout the hippocampus. SPW-Rs can originate in CA3, and they typically spread from CA3 to CA1, but little is known about their formation within CA3. To investigate the generation and propagation of SPW-Rs in CA3, we recorded from mouse hippocampal slices using multi-electrode arrays and patch-clamp electrodes. We characterized extracellular and intracellular correlates of SPW-Rs and quantified their propagation along the pyramidal cell layer of CA3. We found that a hippocampal slice can be described by a speed and a direction of propagation of SPW-Rs. The preferred propagation direction was from CA3c (the subfield closer to the dentate gyrus) toward CA3a (the subfield at the boundary to CA2). In patch-clamp recordings from CA3 pyramidal neurons, propagation was estimated separately for excitatory and inhibitory currents associated with SPW-Rs. We found that propagation speed and direction of excitatory and inhibitory currents were correlated. The magnitude of the speed of propagation of SPW-Rs within CA3 was consistent with the speed of propagation of action potentials in axons of CA3 principal cells. KEY POINTS: Hippocampal sharp waves are considered important for memory consolidation; therefore, it is of interest to understand the mechanisms of their generation and propagation. Here, we used two different approaches to study the propagation of sharp waves in mouse CA3 in vitro: multi-electrode arrays and multiple single-cell recordings. We find a preferred direction of propagation of sharp waves from CA3c toward CA3a - both in the local field potential and in sharp wave-associated excitatory and inhibitory synaptic activity. The speed of sharp wave propagation is consistent with the speed of action potential propagation along the axons of CA3 pyramidal neurons. These new insights into the dynamics of sharp waves in the CA3 network will inform future experiments and theoretical models of sharp-wave generation mechanisms.
RESUMEN
Resumen OBJETIVO: Exponer los desenlaces de dos técnicas de sutura hemostática uterina para controlar la hemorragia obstétrica. MATERIALES Y MÉTODOS: Estudio prospectivo, observacional y longitudinal, llevado a cabo en tres unidades hospitalarias de Guanajuato, México, del 1 de enero al 30 de noviembre de 2018. Se incluyeron pacientes con hemorragia transcesárea y posparto. En las primeras se aplicó la técnica de B-Lynch y en las segundas la de Hayman. Se analizaron las variables: 1) cantidad de hemorragia antes y después de aplicar la sutura, 2) tiempo del procedimiento, 3) concentración de hemoglobina al ingreso a la unidad de atención, 1 hora después de la hemorragia y 24 horas posteriores a la intervención quirúrgica, 4) desenlace de las técnicas y 5) complicaciones. Para el análisis de los datos se utilizó el programa SPSS versión 22 para Windows. RESULTADOS: Se registraron 34 pacientes: 26 con aplicación de la técnica de sutura B-Lynch y 8 con la técnica de Hayman. La pérdida sanguínea después de la aplicación de las técnicas fue menor (p < 0.001). El tiempo entre el diagnóstico de hemorragia y la aplicación de la sutura fue de 11.5 ± 5.9 minutos. La concentración de hemoglobina al ingreso al hospital y 1 h posterior a la hemorragia fue significativamente menor (p < 0.01) versus 24 h después (p < 0.05) 30 de 34 pacientes tuvieron reacción favorable al tratamiento quirúrgico. Cuatro mujeres requirieron procedimientos adicionales para el control de la hemorragia. No se reportaron complicaciones ni muertes maternas asociadas con las técnicas de sutura. CONCLUSIONES: Las técnicas de sutura uterina representan un procedimiento útil, rápido y sin complicaciones para el control de la hemorragia obstétrica.
Abstract OBJECTIVE: To present the results obtained with two techniques of uterine hemostatic sutures for the control of obstetric hemorrhage. MATERIALS AND METHODS: Prospective, observational, longitudinal study in three hospital units of the 1st. from January to November 30, 2018. Thirty-four patients with postpartum and transcesarean hemorrhage were included. The postpartum patients underwent Hayman technique and the B-Lynch technique. The following were analyzed: 1) amount of hemorrhage before and after the sutures, 2) time between diagnosis and placement, 3) hemoglobin levels at admission to the care unit, 1 hour after the hemorrhage and 24 hours after treatment, 4) results with the two techniques and 5) complications. Statistical analysis of all these variables was performed with SPSS, 22 version. RESULTS: A total of 34 patients were registered: 26 sutures performed with B-Lynch technique and 8 with Hayman technique. The amount of bleeding after the application was lower (p <0.001). The time between diagnosis of bleeding and placement was 11.5 + 5.9 minutes. The hemoglobin levels at admission to the hospital and one hour after the hemorrhage were significantly lower (p <0.01) and 24 hours later (p <0.05). In 30/34 of cases, a favorable response to surgical treatment was achieved. In four cases, another procedure was required to control bleeding. There were no complications with the use of sutures or maternal deaths. CONCLUSIONS: The use of uterine sutures was a useful, fast and uncomplicated therapy for the control of obstetric hemorrhage.
RESUMEN
The clam Lucina pectinata inhabits the sulfide-rich west coast of the island of Puerto Rico. It contains three different hemoglobins. Hemoglobin I (HbI), which is monomeric at all concentrations, carries H2S in its ferric state. Overexpression of recombinant HbI from Lucina pectinata in BL21STAR(DE3) Escherichia coli cells was performed in the presence of delta-aminolevulinic acid (delta-ALA). Purification of the protein was achieved using FPLC anion exchange and size exclusion chromatography. Functional characterization of the recombinant holo-protein was assessed by detection of the protein heme O2, CO, and H2S derivatives by UV-Vis spectroscopy, with Soret maxima at 416, 421, and 425 nm, respectively. The results indicated that the recombinant HbI binds H2S and forms a heme sulfide complex like the HbI wild-type hemoglobin. Kinetic measurements were performed to determine the H2S affinity of the recombinant HbI. The H2S dissociation and association rate constants were 0.055 x 10(-3)s(-1) and 0.068 x 10(5) M(-1)s(-1), respectively. The H2S affinity constant of the recombinant HbI (0.124 x 10(9) M(-1)) is eightfold lower than that of the native clam HbI reported earlier. This effect is attributed mostly to the first of two missense mutations [Met 61 (E4)-->Val 61 and Ile101 (FG4)-->Val 101] and additional amino acids present in our construct as demonstrated by measurements of the association rate with a new construct lacking most of the additional residues and the missense mutations. The elimination of these residues restores the similarity between the expressed and wild-type hemoglobins, as evidenced by H2S association kinetics. A pH dependence on the H2S association rate was also contributing to the overall affinity constant and was taken into account in the measurements of the functional properties of the new HbI construct.