The Effects Of Short Time Right Ventricular Pacing On Left Atrial Mechanical Functions

Objectives

Left atrium (LA) plays an important role in left ventricular filling. It is well known that right ventricular apical pacing has unfavorable effects on ventricular systolic and diastolic performance. The aim of this study is to evaluate the LA mechanical functions with 2D echocardiography in patients with a permanent pacemaker after short time ventricular pacing.

Design

Echocardiographic examination was performed in 38 patients (mean age 63.0± 10.9, 18 female) with dual chamber pacemakers or defibrillators (< 20% ventricular pacing within previous 6 months, all of them on sinus rhythm) before and after 4 hours > 90% ventricular pacing at 70 beats per minute in DDD mode with an optimal AV interval. Left atrial volumes (LAV) including at the time of mitral valve opening (Vmax), at closure (Vmin), and at the onset of atrial systole (Volp) were measured. The passive emptying, conduit, active emptying and total emptying volume, stroke volumes were also calculated.

Results

No significant differences were noted at baseline and after pacing for absolute Vmax, Volp, passive emptying, conduit, active emptying, total emptying volumes as well as the volumes indexed to body surface area (p >0.05).

Conclusions

Short - time RV pacing seems to have no acute effects on left atrial mechanical functions.     

Two-dimensional intraventricular flow pattern visualization using the image-based computational fluid dynamics

The image-based computational fluid dynamics (IB-CFD) technique, as the combination of medical images and the CFD method, is utilized in this research to analyze the left ventricle (LV) hemodynamics. The research primarily aims to propose a semi-automated technique utilizing some freely available and commercial software packages in order to simulate the LV hemodynamics using the IB-CFD technique. In this research, moreover, two different physiological time-resolved 2D models of a patient-specific LV with two different types of aortic and mitral valves, including the orifice-type valves and integrated with rigid leaflets, are adopted to visualize the process of developing intraventricular vortex formation and propagation. The blood flow pattern over the whole cardiac cycle of two models is also compared to investigate the effect of utilizing different valve types in the process of the intraventricular vortex formation. Numerical findings indicate that the model with integrated valves can predict more complex intraventricular flow that can match better the physiological flow pattern in comparison to the orifice-type model.     

Constructions of expression vectors of polyhydroxybutyrate-co-hydroxyvalerate (PHBV) and transient expression of transgenes in immature oil palm embryos

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is a polyhydroxyalkanoate (PHA) bioplastic group with thermoplastic properties is thus high in quality and can be degradable. PHBV can be produced by bacteria, but the process is not economically competitive with polymers produced from petrochemicals. To overcome this problem, research on transgenic plants has been carried out as one of the solutions to produce PHBV in economically sound alternative manner. Four different genes encoded with the enzymes necessary to catalyze PHBV are bktB, phaB, phaC and tdcB. All the genes came with modified CaMV 35S promoters (except for the tdcB gene, which was promoted by the native CaMV 35S promoter), nos terminator sequences and plastid sequences in order to target the genes into the plastids. Subcloning resulted in the generation of two different orientations of the tdcB, pLMIN (left) and pRMIN (right), both 17.557 and 19.967 kb in sizes. Both plasmids were transformed in immature embryos (IE) of oil palm via Agrobacterium tumefaciens. Assays of GUS were performed on one-week-old calli and 90% of the calli turned completely blue. This preliminary test showed positive results of integration. Six-months-old calli were harvested and RNA of the calli were isolated. RT-PCR was used to confirm the transient expression of PHBV transgenes in the calli. The bands were 258, 260, 315 and 200 bp in size for bktB, phaB, phaC and tdcB transgenes respectively. The data obtained showed that the bktB, phaB, phaC and tdcB genes were successfully integrated and expressed in the oil palm genome.     

Monoamine oxidases (MAO) in the pathogenesis of heart failure and ischemia/reperfusion injury

Recent evidence highlights monoamine oxidases (MAO) as another prominent source of oxidative stress. MAO are a class of enzymes located in the outer mitochondrial membrane, deputed to the oxidative breakdown of key neurotransmitters such as norepinephrine, epinephrine and dopamine, and in the process generate H₂O₂. All these monoamines are endowed with potent modulatory effects on myocardial function. Thus, when the heart is subjected to chronic neuro-hormonal and/or peripheral hemodynamic stress, the abundance of circulating/tissue monoamines can make MAO-derived H₂O₂ production particularly prominent. This is the case of acute cardiac damage due to ischemia/reperfusion injury or, on a more chronic stand, of the transition from compensated hypertrophy to overt ventricular dilation/pump failure. Here, we will first briefly discuss mitochondrial status and contribution to acute and chronic cardiac disorders. We will illustrate possible mechanisms by which MAO activity affects cardiac biology and function, along with a discussion as to their role as a prominent source of reactive oxygen species. Finally, we will speculate on why MAO inhibition might have a therapeutic value for treating cardiac affections of ischemic and non-ischemic origin. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.     

Structure of the hypothetical protein Ton 1535 from Thermococcus onnurineus NA1 reveals unique structural properties by a left‐handed helical turn in normal α‐solenoid protein

The crystal structure of Ton1535, a hypothetical protein from Thermococcus onnurineus NA1, was determined at 2.3 Å resolution. With two antiparallel α‐helices in a helix‐turn‐helix motif as a repeating unit, Ton1535 consists of right‐handed coiled N‐ and C‐terminal regions that are stacked together using helix bundles containing a left‐handed helical turn. One left‐handed helical turn in the right‐handed coiled structure produces two unique structural properties. One is the presence of separated concave grooves rather than one continuous concave groove, and the other is the contribution of α‐helices on the convex surfaces of the N‐terminal region to the extended surface of the concave groove of the C‐terminal region and vice versa. Proteins 2014; 82:1072–1078. © 2013 Wiley Periodicals, Inc.     

High prevalence of cerebral venous sinus thrombosis (CVST) as presentation of cystathionine beta-synthase deficiency in childhood: Molecular and clinical findings of Turkish probands

Classical homocystinuria is the most commonly inherited disorder of sulfur metabolism, caused by the genetic alterations in human cystathionine beta-synthase (CBS) gene. In this study, we present comprehensive clinical findings and the genetic basis of homocystinuria in a cohort of Turkish patients. Excluding some CBS mutations, detailed genotype–phenotype correlation for different CBS mutations has not been established in literature. We aimed to make clinical subgroups according to main clinical symptoms and discussed these data together with mutational analysis results from our patients. Totally, 16 different mutations were identified; twelve of which had already been reported, and four are novel (p.N93Y, p.L251P, p.D281V and c.829−2A>T). The probands were classified into three major groups according to the clinical symptoms caused by these mutations. A psychomotor delay was the most common diagnostic symptom (n = 12, 46.2% neurological presentation), followed by thromboembolic events (n = 6, 23.1% vascular presentation) and lens ectopia, myopia or marfanoid features (n = 5, 19.2% connective tissue presentation). Pyridoxine responsiveness was 7.7%; however, with partial responsive probands, the ratio was 53.9%.     

依那普利叶酸片对高血压伴高同型半胱氨酸血症大鼠左室肥厚干预的研究

目的:观察高同型半胱氨酸对高血压大鼠心肌内质网应激相关因子GRP94、caspase12表达的影响,及依那普利叶酸片(简称依叶片)对其表达的干预作用。方法:30只雄性成年自发性高血压大鼠(SHR),随机分为对照组、模型组和依叶片组,每组10只。对照组给予普通颗粒饲料喂养同时给予双蒸水灌胃,模型组给予含3%蛋氨酸的颗粒饲料喂养同时给予双蒸水灌胃,依叶片组给予含3%蛋氨酸的颗粒饲料喂养同时给予依叶片粉剂20 mg/kg/d灌胃。实验第8周末,用颈动脉插管法测各组大鼠平均动脉压(MAP),同型半胱氨酸检测仪检测血清同型半胱氨酸(homocystein,Hcy)浓度,称取体质量、全心质量及左心室质量计算大鼠心肌肥厚指数HWI及LVEI,通过HE染色观察心肌细胞形态学改变,免疫组化检测大鼠心肌组织中GRP94及caspase12表达水平。结果:①大鼠血清Hcy水平的变化。对照组大鼠血清Hcy值在正常值范围。与对照组相比,模型组大鼠血清Hcy值显著增高(P0.01);与模型组相比,依叶片组大鼠血清Hcy值明显降低(P0.01)。②大鼠HWI、LVEI及MAP的变化。模型组大鼠的HWI及LVEI均明显高于对照组(P0.05);依叶片干预后大鼠的HWI及LVEI均明显降低(P0.05)。对照组与模型组大鼠的MAP均明显增高,但两组大鼠的MAP差异无统计学意义(P0.05);与模型组相比,依叶片干预后大鼠的MAP明显降低(P0.01)。③大鼠心肌细胞内质网应激(endoplasmic reticulum stress,ERS)相关因子GRP94及caspase12表达。对照组及模型组大鼠心肌细胞GRP94及caspase12表达均增高。与对照组相比,模型组大鼠心肌细胞GRP94、caspase12表达增高更为明显(P0.05)。依叶片干预后大鼠心肌细胞GRP94、caspase12表达明显降低(P0.05)。结论:高Hcy通过ERS途径使高血压大鼠左室肥厚程度加重;依叶片可有效降低血清Hcy及血压水平,抑制心肌细胞ERS,从而有效逆转左室肥厚,其对左室肥厚干预的分子机制为"H型"高血压的预防及治疗提供了新的理论依据。     

Msd1/SSX2IP‐dependent microtubule anchorage ensures spindle orientation and primary cilia formation

Anchoring microtubules to the centrosome is critical for cell geometry and polarity, yet the molecular mechanism remains unknown. Here we show that the conserved human Msd1/SSX2IP is required for microtubule anchoring. hMsd1/SSX2IP is delivered to the centrosome in a centriolar satellite‐dependent manner and binds the microtubule‐nucleator γ‐tubulin complex. hMsd1/SSX2IP depletion leads to disorganised interphase microtubules and misoriented mitotic spindles with reduced length and intensity. Furthermore, hMsd1/SSX2IP is essential for ciliogenesis, and during zebrafish embryogenesis, knockdown of its orthologue results in ciliary defects and disturbs left‐right asymmetry. We propose that the Msd1 family comprises conserved microtubule‐anchoring proteins.     

Numerical simulation of blood flow in the left ventricle and aortic sinus using magnetic resonance imaging and computational fluid dynamics

Understanding cardiac blood flow patterns has many applications in analysing haemodynamics and for the clinical assessment of heart function. In this study, numerical simulations of blood flow in a patient-specific anatomical model of the left ventricle (LV) and the aortic sinus are presented. The realistic 3D geometry of both LV and aortic sinus is extracted from the processing of magnetic resonance imaging (MRI). Furthermore, motion of inner walls of LV and aortic sinus is obtained from cine-MR image analysis and is used as a constraint to a numerical computational fluid dynamics (CFD) model based on the moving boundary approach. Arbitrary Lagrangian–Eulerian finite element method formulation is used for the numerical solution of the transient dynamic equations of the fluid domain. Simulation results include detailed flow characteristics such as velocity, pressure and wall shear stress for the whole domain. The aortic outflow is compared with data obtained by phase-contrast MRI. Good agreement was found between simulation results and these measurements.