Load-dependent electrophysiological and structural cardiac remodelling studied in ultrathin myocardial slices.

Introduction: Myocardial slices are becoming an established system to study cardiac electrophysiology and pharmacological research and development. Unlike other preparations, cardiac slices are a multicellular preparation that has an intermediate, adequate complexity required for this research. Previous studies have successfully obtained slices from human biopsies and animal models, where the electrical and structural parameters could be maintained for several hours – a process which is comparable to other preparation types. Therefore, we aimed to use left ventricular myocardial slices obtained from rat models of mechanical unloading (HAHLT) and from two models of overload (TAC and SHR), to investigate electrophysiological and structural alterations in these models. Methods: Mechanical unloading was achieved by heterotopic abdominal heart and lung transplantation (HAHLT, 8 weeks) and overload was induced by thoracic aortic constriction (TAC, 10 and 20 weeks) in male Lewis rats. Spontaneous hypertensive rats (SHR) were also used as a second model of overload and were primarily induced by hypertension (3, 12 and 20 months). Brown Norway and Wistar Kyoto rats were used as the control groups for SHR. Myocardial slices from the left ventricle (LV) free wall were cut (300-350 µm thick) tangentially to the epicardial surface using a high-precision slow-advancing Vibratome and were point-stimulated using a multi-electrode array system (MEA), therefore, acquiring field potentials (FPs). Field potential duration (FPD) and conduction velocity (CV) were analysed locally and transmurally across the LV free wall. In addition, FPD heterogeneity within each slice was calculated. For the SHR group, the same slices used for the MEA recording were preserved and used subsequently to measure Cx43, Nav1.5 protein levels and fibrosis. Results: Slices obtained from normal rat hearts that are chronically unloaded were found to develop atrophy at a whole heart level. They showed an increase in FPD and its heterogeneity with preserved conduction properties when compared to controls. In TACs, an in vivo whole heart function assessment confirmed hypertrophy with no signs of cardiac dysfunction. Slices from TAC rats showed an increase in FPD at both 10 and 20 weeks after banding. FPD heterogeneity was increased at 10 weeks but normalised at 20 weeks. Changes in CV properties were observed in this group, showing a faster CV and longitudinal conduction velocity (CVL) at 10 weeks and no change at 20 weeks. Transverse conduction velocity (CVT) was unchanged in the TAC group. In SHRs, however, hypertrophy was confirmed and signs of dysfunction in the aged group (20 months) were observed due to the decrease in EF by 18%, especially when compared to the 12 months group. FPD and its heterogeneity was unchanged in SHR when compared to controls. Disease and age-related abnormalities in CV properties were observed in SHR and these were associated with changes in Cx43, Nav1.5 protein level and fibrosis. Conclusion: Myocardial slices are a suitable multicellular preparation to study electrophysiological remodelling obtained from different rat models of cardiovascular disease. In addition, it was possible to investigate the changes in CV and FPD transmurally in rats using this type of preparation method. Thus, this study supports the use of this multicellular preparation in understanding the mechanisms of cardiac disease and the testing of new treatments and therapeutic targets.Open Acces

Strong-field ionization and AC-Stark shifted Rydberg states in OCS

We present theoretical results for intensity-dependent above-threshold ionization (ATI) spectra from oriented OCS molecules probed by intense femtosecond laser pulses with wavelengths of 800 and 400 nm. The calculations were performed using the time-dependent Schroodinger equation within the single-active-electron approximation and including multielectron polarization effects. The results are in qualitative agreement with experimental data [Yu et al., J. Phys. B: At. Mol. Opt. Phys. 50, 235602 (2017)]. In particular, characteristic features in the ATI spectra which correspond to resonant multiphoton ionization via highly-excited Rydberg states are captured by the theory.Comment: 3 figure

The Influence of Different Light Wavelengths on Growth, Enzymes Activity and Photosynthesis of the Marine Microalga Dunaliella parva W.Lerche 1937

يعتبر الضوء عاملاً هامًا يؤثر على نمو الطحالب الدقيقة وكفاءة التمثيل الضوئي لها ؛ ومع ذلك ، لا يُعرف الكثير عن كيفية تأثير شدة الضوء مع الطول الموجي على قدرة التمثيل الضوئي ونمو الطحالب البحرية الدقيقة. في هذه الدراسة ، تمت دراسة نمو الطحالب البحرية الخضراء الدقيقة ديوناليلا بارفا  واقلمته تحت شدة الضوء المختلفة (25 ~ 70 μmol m-2 s-1) ونوعية الضوء (الأزرق والأخضر والأحمر) مقارنة بالضوء الأبيض عند 40 μmol m-2 s-1  كتجربة ضابطة (كنترول). تمت مراقبة النمو عن طريق حساب عدد الخلايا ومحتوى الصبغة وتراكيز Chl a و Chl b والكاروتينات. تم تسجيل النمو الأمثل وأعلى كفاءة التمثيل الضوئي (Fv / Fm) بكثافة ضوء 40 μmol m-2 s-1 ، ضوء أبيض ، و 1.25 مولار كلوريد الصوديوم (. 1.47 and 0.678×106 cell mL-1، على التوالي). أظهر نشاط إنزيمات مضادات الأكسدة ، بما في ذلك الكاتلاز والبيروكسيديز وكذلك محتوى الأسكوربات ، أعلى قيم بلغت 0.190 µM/min.mg Chl, 0.434 and 13.3 mg/g f.wt.  على التوالي ، تحت تأثير  الضوء الأخضر ، الذي أكد وجود ضغوط بيئية.Light is an important factor that influences the growth and photosynthetic efficiency of microalgae; however, little is known about how light intensity together with the wavelength affect the photosynthetic capacity and growth of marine microalgae. In the present study, the growth of the marine green microalga Dunaliella parva was studied and optimized under different light intensities (25 ~ 70 μmol m-2 s-1) and qualities (blue, green, and red) in comparison with white light at 40 μmol m-2 s-1 as a control. The growth was monitored by counting the cell number, pigment content, Chl a, Chl b, and carotenoids concentrations. The optimal growth and highest photosynthetic efficiency (Fv/Fm) were recorded at a light intensity of 40 μ mol m-2 s-1, white light, and 1.25 M NaCl (1.47 and 0.678×106 cell mL-1, respectively). The activity of antioxidant enzymes, including catalase and peroxidase, as well as ascorbate content, showed the highest values of 0.190 µM/min.mg Chl, 0.434 and 13.3 mg/g f.wt. respectively, under the green light, which confirmed the presence of environmental stresses

High-order harmonic generation from polyatomic molecules including nuclear motion and a nuclear modes analysis

We present a generic approach for treating the effect of nuclear motion in the high-order harmonic generation from polyatomic molecules. Our procedure relies on a separation of nuclear and electron dynamics where we account for the electronic part using the Lewenstein model and nuclear motion enters as a nuclear correlation function. We express the nuclear correlation function in terms of Franck-Condon factors which allows us to decompose nuclear motion into modes and identify the modes that are dominant in the high-order harmonic generation process. We show results for the isotopes CH$_4$ and CD$_4$ and thereby provide direct theoretical support for a recent experiment [Baker {\it et al.}, Science {\bf 312}, 424 (2006)] that uses high-order harmonic generation to probe the ultra-fast structural nuclear rearrangement of ionized methane.Comment: 6 pages, 6 figure