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In combined orthodontic-orthognathic treatment, the maxillary palatine suture is closed in most patients with insufficient maxillary width, and bony expansion of the maxilla cannot be achieved by dental expansion or rapid palatal expansion (RPE) which causes buccal inclination of the maxillary posterior teeth leading to unstable results. Therefore, segmental LeFort Ⅰ osteotomy and surgically assisted RPE are often used in clinical practice. In recent years, with the application of implant anchorage technology, implant anchorage assisted RPE has been gradually applied in orthognathic treatment. This article reviewed the indications, contraindications, complications, efficacy and long-term stability in different treatment approaches including segmental LeFort Ⅰ osteotomy, surgically assisted RPE and implant-supported maxillary skeletal expansion.

Objective: To investigate the antimicrobial resistance of food-borne diarrheagenic Escherichia coli (DEC) and the prevalence of mcr genes that mediates mobile colistin resistance in parts of China, 2020. Methods: For 91 DEC isolates recovered from food sources collected from Fujian province, Hebei province, Inner Mongolia Autonomous Region and Shanghai city in 2020, Vitek2 Compact biochemical identification and antimicrobial susceptibility testing platform was used for the detection of antimicrobial susceptibility testing (AST) against to 18 kinds of antimicrobial compounds belonging to 9 categories, and multi-polymerase chain reaction (mPCR) was used to detect the mcr-1 - mcr-9 genes, then a further AST, whole genome sequencing (WGS) and bioinformatics analysis were platformed for these DEC isolates which were PCR positive for mcr genes. Results: Seventy in 91 isolates showed different antimicrobial resistance levels to the drugs tested with a resistance rate of 76.92%. The isolates showed the highest antimicrobial resistance rates to ampicillin (69.23%, 63/91) and trimethoprim-sulfamethoxazole (59.34%, 54/91), respectively. The multiple drug-resistant rate was 47.25% (43/91). Two mcr-1 gene and ESBL (extended-spectrum beta-lactamase) positive EAEC (enteroaggregative Escherichia coli ) strains were detected. One of them was identified as serotype of O11:H6, which showed a resistance profile to 25 tested drugs referring to 10 classes, and 38 drug resistance genes were predicted by genome analysis. The other one was O16:H48 serotype, which was resistant to 21 tested drugs belonging to 7 classes and carried a new variant of mcr-1 gene ( mcr-1.35 ). Conclusion: An overall high-level antimicrobial resistance was found among foodborne DEC isolates recovered from parts of China in 2020, and so was the MDR (multi-drug resistance) condition. MDR strains carrying multiple resistance genes such as mcr-1 gene were detected, and a new variant of mcr-1 gene was also found. It is necessary to continue with a dynamic monitoring on DEC contamination and an ongoing research into antimicrobial resistance mechanisms.

Objective: To investigate the knowledge, use and barriers when prescribing GLP-1RA and SGLT2i among cardiologists, endocrinologists and general practitioners, and explore the influencing factors that hinder the use of these medications. Methods: A questionnaire was conducted among physicians in the above departments in Peking University Third Hospital and health service institutions at all levels in its medical consortium. A total of 342 physicians were involved. Among them, 40.6% (139) were cardiologists, 28.9% (99) were endocrinologists and 30.4% (104) were general practitioners; 66.7% (270) came from Beijing while 33.3% (72) from other provinces. The survey included clinicians' knowledge and current use of GLP-1RA and SGLT2i, and the possible reasons that influenced the prescription of these medications. Medical therapies of physicians were investigated by simulating different clinical scenarios. The difference of measures among physicians in different departments was compared. Results: A total of 342 physicians were involved, with the average age of 40 (35, 46) years old and the average working time of 13 (7, 20) years. Among them, 40.6% (139) were male. 77.5% (265) physicians had comprehensive knowledge of SGLT2i and prescribed it, which was higher than that for GLP-1RA (70.5%, 241) ( P <0.001). 21.1% (72) physicians prescribed SGLT2i more than 20 times per month, which was higher than that for GLP-1RA (8.2%, 28) ( P <0.001). Endocrinologists had more knowledge and prescribed more GLP-1RA and SGLT2i compared with other physicians (both P values < 0.001). 38.1% (53) cardiologists, 22.2% (22) endocrinologists, and 30.8% (32) general practitioners believed patients needed an endocrinologist to evaluate and adjust GLP-1RA, which was the primary barrier for the use of medications ( P= 0.042). 27.4% (38) cardiologists, 14.1% (14) endocrinologists, and 30.8% (32) general practitioners believed patients needed an endocrinologist to evaluate and adjust SGLT2i, which was the primary barrier for the use of medications ( P= 0.018). 21.6% (30) cardiologists, 45.5% (45) endocrinologists, and 31.7% (33) general practitioners believed side effects of SGLT2i was the primary barrier for the use of medications ( P< 0.001). For patients with unqualified glycemic control and cardiovascular complications, 65.4% (75) cardiologists, 69.7% (69) endocrinologists, and 43.3% (45) general practitioners chose the above medications ( P <0.001). For patients with qualified glycemic control, combined with cardiovascular complications and diabetic organ damage, 35.3% (49) cardiologists, 52.5% (52) endocrinologists, and 25.0% (26) general practitioners chose the above medications ( P< 0.001). Conclusions: Physicians had more knowledge and prescription of SGLT2i than that of GLP-1RA. Endocrinologists had more knowledge and prescription of the above medications than other physicians. The side effect of medications was potential primary barrier for the use of the novel hypoglycemic agent with cardiovascular benefits. In clinical practice, most of physicians considered that high-risk patients with cardiovascular comorbidities need to be referred to cardiologist or endocrinologist to adjust clinical therapies.

Aim: To investigate whether mono-exponential and bi-exponential diffusion-weighted imaging (DWI)-related parameters of the primary tumour can evaluate the status of lymphovascular space invasion (LVSI) and lymph node metastasis (LNM) in patients with cervical carcinoma preoperatively., Materials and Methods: Eighty patients with cervical carcinoma were enrolled, who underwent preoperative multi b-value DWI and radical hysterectomy. They were classified into LVSI(+) versus LVSI(-) and LNM(+) versus LNM(-) according to postoperative pathology. The apparent diffusion coefficient (ADC), pure molecular diffusion (D), pseudo-diffusion coefficient (D∗), and perfusion fraction (f) were calculated from the whole tumour (&#95; whole ) and tumour margin (&#95; margin ). All parameters were compared between LVSI(+) and LVSI(-) and between LNM(+) and LNM(-). Logistic regression analysis and receiver operating characteristic (ROC) curve analysis were performed to evaluate the diagnostic performance of these parameters., Results: f&#95; margin and D∗&#95; whole showed significant differences in differentiating LVSI(+) from LVSI(-) tumours (p=0.002, 0.008, respectively), while LNM(+) tumours presented with significantly higher ADC&#95; margin than that of LNM(-) tumours (p=0.009). The other parameters were not independent related factors with the status of LVSI or LNM according to logistic regression analysis (p>0.05). The area under the ROC curve of f&#95; margin combined with D∗&#95; whole in discriminating LVSI(+) from LVSI(-) was 0.826 (95% confidence interval [CI]: 0.691-0.961), while ADC&#95; margin in differentiating LNM(+) from LNM(-) was 0.788 (95% CI: 0.648-0.928)., Conclusions: The parameters generated from mono-exponential and bi-exponential DWI of the primary cervical carcinoma could help discriminate its status regarding LVSI (f&#95; margin and D∗&#95; whole ) and LNM (ADC&#95; margin )., (Copyright © 2020 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Objective: The purpose of this study was to investigate role of inhibition of microRNA-34a (miR-34a) in neural damage and repair after spinal cord injury, and to explore the underlying mechanism., Materials and Methods: In BV2 microglia, we conducted classical activation using lipopolysaccharide (LPS) and pre-treatment using miR-34a mimics. The expressions of miR-34a, Notch 1, and Jagged 1 were detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Moreover, the protein expressions of inflammatory microglia markers were evaluated by Western blotting. In vivo, SCI model was successfully established in rats. Subsequently, the expression levels of miR-34a, Notch 1, and Jagged 1 levels within 1 week were measured by qRT-PCR. Meanwhile, protein expressions of inflammatory mediators were determined by enzyme-linked immunosorbent assay (ELISA) assay. Immunofluorescence was conducted to display the activation degree of microglia and residual neural structure. Furthermore, locomotor function recovery was estimated using BBB rating scale., Results: Compared with the only LPS-activated group, pre-treatment of miR-34a mimics significantly decreased the expressions of Notch 1 and Jagged 1. Similarly, the protein expressions of CD11b and iNOS were significantly down-regulated. In vivo, the levels of Notch 1 and Jagged 1 within 1 week increased significantly, while miR-34a was negatively regulated following spinal cord injury (SCI). Furthermore, the contents of interleukin-1 beta (IL-1β) and IL-6 were reduced with the treatment of miR-34a mimics when compared with SCI group. With the treatment of miR-34a, the number of inflammatory microglia decreased significantly, and the remaining neural structure was similarly improved. In addition, locomotor function recovery of hindlimbs in rats was significantly ameliorated after the administration of miR-34a mimics., Conclusions: Increase of miR-34a suppresses neuronal apoptosis and alleviates microglia inflammation by negatively targeting the Notch pathway, thereby improving neural recovery and locomotor function.

Objective: To evaluate the Treatment effect of geriatric ankle osteoarthritis by arthrodesis with screw fixation through lateral malleolus osteotomy. Methods: Thirty-three patients with severe osteoarthritis according to the classification of Takakura-Tanakawere treated by ankle arthrodesis through lateral malleolus osteotomy with screw fixation from January 2010 to June 2015. Twenty-five patients were combined with more than 1 internal diseases. Twenty-six patients owned ankle injury history. Clinical and radiologic evaluations were performed before surgery and at the most recent follow-up. Results: The American Orthopaedic Foot and Ankle Society scale was (50.9±12.0) points beforesurgery and (78.8±9.6) points at the most recent follow-up ( P <0.01). The visual analogue scalein last follow up was significantly decreased to (1.7±1.1), compared with (6.1±1.7)preoperatively.Seven patients were accompanied with incision complications. 27 patients(81.8 percent) reached complete solid fusion , which was confirmed by CT. 4 patients was partially bony fused, which could also perform weight-bearing walk. The other 2 patients with nonunion were reoperated lastly. Conclusions: Ankle arthrodesis by screw fixation through lateral malleolus osteotomy is the preferable surgical treatment option in patients with end-stage geriatric ankle arthritis, showing high reliability and effectivity in pain relieving and function improvement. Incision and bony healing complications should draw attention especially in patients combined with internal disease.

Matrix proteins that either weakly acidic or unusually highly acidic have important roles in shell biomineralization. In this study, we have identified and characterized hic22, a weakly acidic matrix protein, from the nacreous layer of Hyriopsis cumingii. Total protein was extracted from the nacre using 5 M EDTA and hic22 was purified using a DEAE-sepharose column. The N-terminal amino acid sequence of hic22 was determined and the complete cDNA encoding hic22 was cloned and sequenced by rapid amplification of cDNA ends-polymerase chain reaction. Finally, the localization and distribution of hic22 was determined by in situ hybridization. Our results revealed that hic22 encodes a 22-kDa protein composed of 185 amino acids. Tissue expression analysis and in situ hybridization indicated that hic22 is expressed in the dorsal epithelial cells of the mantle pallial; moreover, significant expression levels of hic22 were observed after the early formation of the pearl sac (days 19-77), implying that hic22 may play an important role in biomineralization of the nacreous layer., Competing Interests: The authors declare no conflict of interest.

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules of about 22 nucleotides in length. miRNAs are highly conserved in both plants and animals, and function as gene regulators by binding to the 3'-untranslated region of target mRNAs for cleavage and/or translational repression. miRNA biogenesis, stability, and regulation of expression are strongly sequence dependent. Sequence variants, such as single nucleotide polymorphisms (SNPs) in pri-miRNA, pre-miRNA, promoter regions, or miRNA-target sites, can influence miRNA function, thereby contributing to the pathological features of human disease. In this review, we focus on miRNA-related SNPs in gastric cancer and comprehensively analyze some commonly studied SNPs.

Antimicrobial peptides (AMPs), of which big defensins are examples, are an important component of the natural defenses of most living organisms, and possess remarkable microbicidal activities. In the present study, using expressed-sequence tag sequences from a cDNA library and RACE, the full-length cDNA sequence of the big defensin gene from the triangle-shell pearl mussel, Hyriopsis cumingii, (HcBD), was cloned. The gene consists of a 5'-untranslated region (UTR) of 166 bp, a 3'-UTR region of 96 bp, and an open reading frame of 342 bp that encodes 113 amino acids, consisting of a 23 amino acid signal peptide and a mature peptide of 90 amino acids with a molecular mass of 12.5 kDa. Amino acid sequence analysis showed that the sequence contained a transmembrane domain and a hydrophobic region. The full-length amino acid sequence showed the highest similarity to an amphioxus (Branchiostoma floridae) sequence (64%), and lower similarities to other known defensins (α-, β-, and θ-defensins, and insect defensins). Expression of HcBD was relatively high in the mantle and blood, lower in other tested tissues, and absent in gill and foot tissues. Real-time quantitative PCR was used to investigate HcBD expression in various tissues at different time points after injection of Aeromonas hydrophila. At 4 h post-inoculation, HcBD expression in the mantle, liver, intestine, gill, and foot was greater than in the control, with the greatest expression at 72 h, while at 24 h, expression in the liver, intestine, gill, and foot were at their lowest levels. These results suggest that HcBD might play an important role in the host immune response. This study enriches the basic research on the big defensin family of antimicrobial peptides and lays foundations for further research on antimicrobial peptide expression and relevance to disease defense.

Among the helminths infecting ruminants in China are three taxa belonging to the genus Fasciola: F. hepatica, F. gigantica and the so-called 'intermediate form' that appears to lie between these two species. Based on the sequences of the second internal-transcribed spacers (ITS-2) within the parasites' nuclear ribosomal DNA (rDNA), a pair of primers (DSJf/DSJ3) specific for F. hepatica and a pair (DSJf/DSJ4) specific for F. gigantica were designed and used to develop PCR-based assays. These assays allowed the identification and differentiation of F. hepatica, F. gigantica and the 'intermediate' Fasciola, with no amplicons produced from heterologous DNA samples. The results of sequencing confirmed the species-specific identity of the amplified products. The assays showed good sensitivity, giving positive results with as little as 0.11 ng of F. hepatica DNA and 0.35 ng of F. gigantica DNA. This meant that the DNA from a single Fasciola egg or a single infected snail was sufficient for identification of the Fasciola taxon. The developed PCR assays could provide useful tools for the detection, identification and epidemiological investigation of Fasciola infection in humans, other mammals and snails.

In the present study, a polymerase chain reaction-linked single-strand conformation polymorphism (PCR-SSCP) approach combined with DNA sequencing was used to characterise samples of Fasciola spp. from different host species and geographical locations in mainland China. The first internal transcribed spacer (ITS-1) of ribosomal DNA (rDNA) was amplified by PCR from individual Fasciola and analysed by SSCP. SSCP analyses displayed three different banding profiles that allowed the identification of all Fasciola samples examined into three groups: Fasciola hepatica, F. gigantica and the "intermediate" Fasciola. Then, the ITS-1 rDNA was sequenced from representative Fasciola samples, and analysis of the complete ITS-1 sequences supported the identification of all Fasciola samples by SSCP approach. The length of the ITS-1 sequences was 422 bp for all Fasciola samples sequenced. Although there was no variation in length or composition of the ITS-1 sequences among multiple specimens within each of the taxa, F. hepatica and F. gigantica differed by 1.2% in their ITS-1 sequences, whereas the "intermediate" Fasciola was unique, in which two different ITS-1 sequences exist in the rDNA array within a single Fasciola worm. One of the sequences is identical to that of F. hepatica, and the other is identical to that of F. gigantica. This study demonstrated that PCR-SSCP analysis of the ITS-1 rDNA followed by selective sequencing provides a reliable approach for the accurate identification of Fasciola spp., and also supports the existence of the "intermediate" Fasciola between F. hepatica and F. gigantica in mainland China.

Most noninvasive measures of diastolic function are made during left ventricular (LV) filling and are therefore subject to "pseudonormalization," because variation in left atrial (LA) pressure may confound the estimation of relaxation rate. Counterclockwise twist of the LV develops during ejection, but untwisting occurs rapidly during isovolumic relaxation, before mitral opening. We hypothesized that the rate of untwisting might reflect the process of relaxation independent of LA pressure. Recoil rate (RR), the velocity of LV untwisting, was measured by tagged magnetic resonance imaging and regressed against the relaxation time constant (tau), recorded by catheterization, in 10 dogs at baseline and after dobutamine, saline, esmolol, and methoxamine treatment. RR correlated closely (average r = -0.86) with tau and was unaffected by elevated LA pressure. Multiple regression showed that tau, but not LA or aortic pressure, was an independent predictor of RR (P < 0.0001, P = 0.99, and P = 0.18, respectively). The rate of recoil of torsion, determined wholly noninvasively, provides an isovolumic phase, preload-independent assessment of LV relaxation. Use of this novel parameter should allow the detailed study of diastolic function in states known to affect filling rates, such as aging, hypertension, and congestive heart failure.

Shortening of oblique left ventricular (LV) fibers results in torsion. A unique relationship between volume and torsion is therefore expected, and the effects of load and contractility on torsion should be predictable. However, volume-independent behavior of torsion has been observed, and the effects of load on this deformation remain controversial. We used magnetic resonance imaging (MRI) with tagging to study the relationships between load and contractility, and torsion. In ten isolated, blood-perfused canine hearts, ejection was controlled by a servopump: end-diastolic volume (EDV) was controlled by manipulating preload parameters and end-systolic volume (ESV) by manipulating afterload using a three-element windkessel model. MRI was obtained at baseline, two levels of preload alteration, two levels of afterload alteration, and dobutamine infusion. An increase in EDV resulted in an increase in torsion at constant ESV (preload effect), whereas an increase in ESV resulted in a decrease in torsion at constant EDV (afterload effect). Dobutamine infusion increased torsion in association with an increase in LV peak-systolic pressure (PSP), even at identical EDV and ESV. Multiple regression showed correlation of torsion with preload (EDV), afterload (ESV), and contractility (PSP; r = 0.67). Furthermore, there was a close linear relationship between torsion and stroke volume (SV) and ejection fraction (EF) during load alteration, but torsion during dobutamine infusion was greater than expected for the extent of ejection. Preload and afterload influence torsion through their effects on SV and EF, and there is an additional direct inotropic effect on torsion that is independent of changes in volume but rather is force dependent. There is therefore potential for the torsion-volume relation to provide a load-independent measure of contractility that could be measured noninvasively.

Objectives: We aimed to characterize regional geometry in relation to load in two groups of patients with hypertrophic cardiomyopathy (HCM) and right ventricular pressure overload (RVPO) in relation to a group of subjects with normal left ventricular (LV) function., Background: Both these diseases are associated with marked changes in LV shape and function, which have not been studied with detailed three dimensional tools., Methods: Three dimensional (3D) tagged magnetic resonance imaging (MRI) was used to characterize the 3D geometry and regional stresses of the left ventricles in patients with HCM and RVPO. Curvatures, stresses, wall thickness, and endocardial motion were calculated from surface and volume elements., Results: Hearts with RVPO exhibited more circumferential and meridional flattening of the septum than normal and HCM hearts. The stress indices were lowest in the HCM hearts, compared to normal and RVPO hearts, due to the larger thicknesses. There was a more significant difference between lateral wall motion and other regional wall motions in the HCM and RVPO hearts as compared to normal hearts., Conclusions: It is suggested that curvature and stress mapping by 3D tagged MRI can be used as an important clinical tool for characterizing and distinguishing between healthy and diseased hearts. The results provided here validated previous knowledge on HCM and RVPO known from planary imaging methods.

Aim: To explore the calcium uptake antagonism of saponins of Panax notoginseng (PNS)., Methods: Synaptosomes were prepared from rat cerebral cortex by using differential Ficoll gradients. The effects of PNS on synaptosomal 45Ca uptake were measured in vitro or after acute treatment., Results: PNS 50-800 mg.L-1 produced a concentration-rated inhibition of Ca2+ uptake [IC50 = 111 (46-176) mg.L-1]. Both initial and maximal uptake were inhibited. Similar effect was obtained after acute PNS treatment with 200 mg.kg-1 i.p. The blocking effect of PNS was reversed by calcium in media., Conclusion: PNS is a calcium channel blocker in neurons.

Background: Distortion of the left ventricular (LV) cavity in patients with right ventricular pressure overload (RVPO) is well known. However, no direct measurements of regional myocardial function in terms of myocardial shortening and wall thickening are available; therefore, exactly how RVPO disturbs LV regional performance remains unclear. By using three-dimensional (3D) tagged magnetic resonance imaging, we were able to measure regional systolic function directly. Our objective was to study the relation between the distortion of the LV circular shape and regional LV function., Methods and Results: In nine patients with RVPO and six healthy volunteers, four parallel short-axis images (with 12 radial tags) and two mutually orthogonal long-axis images (with four parallel tags) were generated, and endocardial and epicardial borders were manually traced. By integration of the short- and long-axis images, 3D reconstruction of the LV tracking points from end diastole to end systole was obtained. Data from the midventricular two short-axis image slices were analyzed. These were then divided into anterior, lateral, posterior, and septal regions. Circumferential and longitudinal shortening were then calculated from the endocardial and epicardial tag intersection points. Wall thickness and thickening were calculated by the 3D volume-element approach. An eccentricity index (EI), the ratio of septum-to-free-wall to anteroposterior diameters, was used to describe the shape of the LV cavity. The regional curvature was also measured. The RVPO group was characterized by flattening of the septum and LV lateral wall, decreased EI reflecting the distorted LV shape, altered distribution of endocardial circumferential shortening, and preserved ejection fraction. Changes in EI closely correlated with the septal curvature. The EI was smaller at end systole, reflecting further shape distortion relative to end diastole. Reduced myocardial performance, as measured by wall thickening and circumferential and longitudinal shortening fractions, was observed for the septum. A reduction in endocardial circumferential shortening of the septal and lateral walls was directly related to the end-systolic EI. In addition, whereas for healthy subjects a linear relation between area ejection fraction and endocardial circumferential shortening was observed, in RVPO patients a curvilinear (quadratic) relation was observed., Conclusions: In patients with RVPO, compared with healthy subjects, the septal function was reduced, as evidenced by reduced thickening and shortening fractions. The distortion in LV cavity at end systole due to the flattening of the septum contributes to preserved systolic ventricular function and nonuniform distribution in endocardial circumferential shortening.

Background: Regional performance of the hypertrophied left ventricle (LV) in hypertrophic cardiomyopathy (HCM) is still incompletely characterized with studies variably reporting that the hypertrophied myocardium is hypokinetic, akinetic, or has normal function. Different imaging modalities (M-mode or two-dimensional echocardiography) and methods of analysis (fixed or floating frame of reference for wall motion analysis) yield different results. We assessed regional function in terms of systolic wall thickening and shortening and related these parameters to end-diastolic thickness using tagged magnetic resonance imaging and the three-dimensional volume-element approach., Methods and Results: In 17 patients with HCM and 6 healthy volunteers, four parallel short-axis images with 12 radial tags and two mutually orthogonal long-axis images with four parallel tags were obtained at end diastole and end systole. After the LV endocardial and epicardial borders were traced, three-dimensional volume elements were constructed by connecting two matched planar segments in two adjacent short-axis image planes, accounting for translation, twist, and long-axis shortening. A total of 72 such volume elements encompassed the entire LV. From each of these elements, end-diastolic thickness and systolic function (fractional thickening and circumferential shortening) were calculated. The average end-diastolic thickness was 15.8 +/- 4.2 mm in patients with HCM, which was significantly greater than that in healthy subjects (8.6 +/- 2.1 mm, P < .001). Fractional thickening was significantly less in patients with HCM than in healthy subjects (0.31 +/- 0.22 versus 0.56 +/- 0.23, P < .001). There was a highly significant inverse correlation between fractional thickening and end-diastolic thickness that was independent of the type of hypertrophy or age group. Similar inverse relations were observed between circumferential shortening and end-diastolic wall thickness., Conclusions: The myocardium in patients with HCM is heterogeneously thickened and the fractional thickening and circumferential shortening of the abnormally thickened myocardium are reduced compared with healthy subjects. The decrease in fractional thickening and shortening is inversely related to the local thickness.

Diastolic ventricular interaction is associated with septal shift and deformation, the consequences of which have not been fully assessed. A model was therefore developed to describe the mechanisms involved in interaction between the ventricles under different loading conditions. We assumed a circular cardiac minor-axis geometry surrounded by a pericardial membrane with the left ventricle (LV) and septum described by three layers. To define the equilibrium condition, we required the net force-balance at the right ventricular (RV)-LV intersection points to equal zero. The model was tested with and without consideration of bending forces associated with a change of curvature of a thick-walled structure. Model results were compared with data from animal experiments subjected to aortic and pulmonary constriction. LV and RV end-diastolic pressures as well as pericardial pressure were measured. In six dogs, septal segment length was measured using sonomicrometry, and in seven dogs, endocardial curvature was measured using echocardiography. Model and experimental results show that 1) with severe RV loading, septal inversion occurs at a negative transseptal gradient, and 2) the end-diastolic septal segment length continues to shorten after septal inversion during pulmonary constriction. Model simulation suggests that bending moments account for the septal curvature at zero transseptal pressure. In addition, the model predicts the shift in the pressure-area relationship of each ventricle by a change in loading of the opposite ventricle and predicts that large transmural gradients in stress and strain are associated with septal inversion. Thus the model and the experimental data agree and describe the important factors that modulate diastolic septal mechanics during acute differential ventricular loading.

The ventricular septum attaches to the insertion points of the ventricular free walls, separates, and is shared by both the left (LV) and right (RV) ventricles. Changes in the transseptal pressure gradient (PTS, the difference between LV and RV pressures) will change the stress in the septum and, therefore, the length of the septal segment (Ls). However, since most of the septal myocardial fibers are continuous with those of LV free wall and the septum appears to be an integral part of LV, one might also expect that if the LV transmural pressure (Plvtm; the difference between LV and pericardial pressure) is raised, Ls would increase even in the absence of any change in PTS. Therefore, we hypothesized that at end diastole, Ls depends on both Plvtm and PTS. To test this hypothesis, we measured Ls (sonomicrometry), LV and RV pressures (micromanometers), and pericardial pressure (flat liquid-containing balloon) in seven anesthetized open-chest dogs. Plvtm was increased through volume loading, whereas PTS was maintained constant at 10, 5, 0, -5, -10, and -15 mmHg by adjusting the degree of constriction of the pulmonary artery or aorta. These procedures were performed first with pericardium reapproximated and then after the pericardium had been opened widely. At each controlled PTS level, Ls increased linearly with the increase in Plvtm. Both the slope and the intercept of this Ls-Plvtm relation were affected by PTS in a nonlinear fashion. (ABSTRACT TRUNCATED AT 250 WORDS)

Background: At end diastole, the position and shape of the ventricular septum depend on the transseptal pressure gradient. It is not clear, however, how the septal radius of curvature changes in response to the gradual change in transseptal pressure gradient during progressive pulmonary arterial constriction (PAC) and aortic constriction (AC)., Methods and Results: In 11 anesthetized open-chest dogs, the septal radius of curvature was measured from the short-axis two-dimensional echocardiogram, and the transseptal pressure gradient (left ventricular [LV] pressure minus right ventricular [RV] pressure) was calculated from ventricular pressures measured with micromanometers. Seven dogs were studied with both PAC and AC (group 1) and four dogs only with PAC, which was initiated before and after volume loading (group 2). The transseptal pressure gradient decreased during PAC. As the transseptal pressure gradient decreased, the septum shifted continuously leftward with decreases in the LV septum-free wall diameter and in LV cross-sectional area. The septal radius of curvature (Rs) increased until the septum became flat. The flat septum (i.e., Rs = infinity) occurred at a relatively constant value of transseptal pressure gradient (-4.6 +/- 1.4 mm Hg) independently of the absolute values of LV pressures when between 2 and 9 mm Hg, although necessarily a greater RV pressure was needed to make the septum flat when LV pressure was higher. After inversion, the septum again became curved, with a decrease in the absolute value of septal radius of curvature as the transseptal pressure gradient became increasingly negative. The septum was still concave to the LV cavity at zero transseptal pressure gradient, and its curvature decreased (i.e., its radius of curvature increased) with increases in ventricular pressures. During AC, the septal radius of curvature also increased, but with an increase in transseptal pressure gradient accompanied by increases in LV septum-free wall diameter and in LV area. In group 2 animals, at zero transseptal pressure gradient, the normalized septal radius of curvature was greater (p less than 0.005) at high LV pressure than at low LV pressure. The transseptal pressure gradient required to make the septum flat was not significantly different between low and high LV pressure, which confirmed the results of group 1., Conclusions: The results of the present study show that the shape and position of the ventricular septum are determined by the transseptal pressure gradient but that the shape of the septum is also affected by the ventricular pressures. The septum was not flat but rather still concave to the LV cavity at zero transseptal pressure gradient. Approximately 5 mm Hg of negative transseptal pressure gradient was required to displace the septum farther leftward and make it flat. The septal radius of curvature increased during both PAC (which decreased transseptal pressure gradient) and AC (which increased transseptal pressure gradient), indicating that the mechanisms involved in changing septal radius of curvature are different during PAC and AC.

Nonuniformity of myocardial systolic and diastolic performance in the normal left ventricle has been recognized by a number of investigators. Lack of homogeneity in diastolic properties might be caused by or related to differences in the distensibility of different regions of the left ventricular (LV) wall. Thus, we compared the end-diastolic transmural pressure-strain relations in both the anterior and posterior LV walls in seven anesthetized dogs during two interventions (pulmonary artery constriction and aortic constriction). Transmural pressure was defined as the difference between LV intracavitary pressure and local pericardial pressure. LV pressure was measured using a micromanometer; pericardial pressures over the LV anterior and posterior walls were measured with balloon transducers. Circumferentially oriented pairs of sonomicrometer crystals were implanted in the midwall of the anterior and posterior walls of the LV to measure segment lengths. Strains were calculated as (L-L0)/L0, where L was the instantaneous segment length and L0 was the segment length when transmural pressure was zero. The pattern of end-diastolic transmural pressure--strain relations was similar in all dogs. The change in strain in the posterior wall was always greater than that in the anterior wall. Opening the pericardium did not affect the difference in distensibility of the anterior and posterior walls. The results suggest that the posterior wall is more compliant than the anterior wall (that is, for a given difference in transmural pressure, the local segment length change of the posterior wall was greater). This seems consistent with other observations, which suggest that the posterior wall might make a greater contribution to diastolic filling.

Polypyrrole and methylene blue incorporated polypyrrole thin-film modified electrodes were prepared by the electrochemical polymerization method. These modified electrodes may facilitate heterogeneous electron transfer of cytochrome c with high electrocatalytic activity and good stability. Optical thin-layer spectroelectrochemical techniques were used to determine the characteristics of these electrochemical processes such as formal redox potential (E0), electron transfer number (n), and the apparent rate constant (ks.h0).