Prediction of high risk of thrombus by haemodynamics changes in left atrial appendage using transesophageal echocardiography / 中华超声影像学杂志

Objective To study the left atrial appendage (LAA) function and haemodynamics by transesophageal echocardiography,and predict high risk of thrombosis.Methods Eighty-nine consecutive patients were studied using transesophageal echocardiography.According to with spontaneous echo contrast (SEC) or not,all patients were divided into SEC group (n =17) and non-SEC group (n-=72).LAA emptying peak flow velocity (LAA-EV),filling peak flow velocity (LAA-FV) were measured by pulsed Doppler.The middle segment of the LAA medial wall systolic peak velocity (LAA-TSV) and diastolic peak velocity (LAA-TDV) were obtained by tissue Doppler imaging.LAA color Doppler and M-mode color Doppler images were acquired and derived the LAA emptying flow propagation velocity (LAA-EPV).Results LAA-EV,LAA-FV,LAA-TSV,LAA-TDV,LAA-EPV of SEC group were lower than those of non-SEC group (P ＜0.05).LAA M-mode color Doppler had four characteristic patterns,N pattern (normal pattern) which flow eject from LAA apical to LAA orifice,R pattern (reverse pattern) which flow eject from LAA orifice to LAA apical,V pattern (vertical pattern) vertical signals seen in systole and without efficient flow,S pattern (stasis pattern) almost no flow signal.V,R and S patterns may indicate high risk of SEC and thrombosis.LAA-EPV had strong correlation with LAA-EV (r =0.742,P ＜0.001),and moderate correlation with LAA-TSV (r =0.462,P ＜0.01),LAA-EV had strong correlation with LAA-TSV (r =0.600,P ＜0.01).Conclusions LAA dysfunction would result in hypokinetic LAA wall motion and reduced blood flow velocity.Emptying abnormalities of LAA might be the important reasons for blood stasis and thrombus formation.Emptying characteristic low patterns of V,R and S might be novel methods to predict high risk of thrombus.

Conserved arginine residue in the membrane-spanning domain of HIV-1 gp41 is required for efficient membrane fusion

Despite the high mutation rate of HIV-1, the amino acid sequences of the membrane-spanning domain (MSD) of HIV-1 gp41 are well conserved. Arginine residues are rarely found in single membrane-spanning domains, yet an arginine residue, R(696) (the numbering is based on that of HXB2), is highly conserved in HIV-1 gp41. To examine the role of R(696), it was mutated to K, A, I, L, D, E, N, and Q. Most of these substitutions did not affect the expression, processing or surface distribution of the envelope protein (Env). However, a syncytia formation assay showed that the substitution of R(696) with amino acid residues other than K, a naturally observed mutation in the gp41 MSD, decreased fusion activity. Substitution with hydrophobic amino acid residues (A, I, and L) resulted in a modest decrease, while substitution with D or E, potentially negatively-charged residues, almost abolished the syncytia formation. All the fusion-defective mutants showed slower kinetics with the cell-based dual split protein (DSP) assay that scores the degree of membrane fusion based on pore formation between fusing cells. Interestingly, the D and E substitutions did show some fusion activity in the DSP assays, suggesting that proteins containing D or E substitutions retained some fusion pore-forming capability. However, nascent pores failed to develop, due probably to impaired activity in the pore enlargement process. Our data show the importance of this conserved arginine residue for efficient membrane fusion.

Preliminary application of diastolic inflow inside left ventricle using color singular value / 中华超声影像学杂志

Objective To develop a new method for describe features of inflow of left ventricle(LV) from color Doppler image by color singular value,and evaluat the value of color singular value in assessment of diastolic dysfunction. Methods Patients with diastolic dysfunction of LV including myocardial infarction (n = 37), angina( n = 35), cardiomyopathy( n = 45) and hypertension ( n =46) were selected and 30 healthy cases as control. CV and AV from color singular value of LV inflow was displayed and calculated automatically by an analyzing system developed in our laboratory. Results Compared with that of control (CV:2.40 0.22 and AV: -0.25 0.05), the absolute value of CV(1.67-1.90 in average)and AV( - 0. 11～-0. 20 in average) from color singular value were decreased significantly( P <0. 001) in groupsof myocardial infarction, angina, cardiomyopathy and hypertension. Conclusions Singular value can be applied to detect color differences in LV inflow from color Doppler signals. Changes of singular value within the diastolic inflow under pathological conditions may reflect the diastolic dysfunction of LV.