Sast1-mediated manifold effects inhibit Plutella xylostella fertility

BACKGROUND

Plutella xylostella (Linnaeus) is a destructive pest of cruciferous crops due to its strong reproductive capacity and extensive resistance to pesticides. Seminal fluid proteins (SFPs) are the main effective factors that determine the reproductive physiology and behaviour of both sexes. Although an increasing number of SFPs have been identified, the effects of astacins in SFPs on agricultural pests have not yet been reported. Here, we elucidated the mechanisms by which Sast1 (seminal astacin 1) regulates the fertility of Plutella xylostella (L.).

RESULTS

PxSast1 was specifically expressed in the testis and accesssory gland. CRISPR/Cas9-induced PxSast1 knockout successfully constructed two homozygous mutant strains. Sast1 impaired the fertility of P. xylostella by separately regulating the reproductive capacity of males and females. Loss of PxSast1, on the one hand, significantly decreased the ability of males to mate and fertilize, mainly manifested as shortened mating duration, reduced mating competitiveness and decreased eupyrene sperm production; on the other hand, it significantly inhibited the expression of chorion genes in females, resulting in oogenesis deficits. Simultaneously, for mated females, the differentially expressed genes in signalling pathways related to oogenesis and chorion formation were significantly enriched after PxSast1 knockout.

CONCLUSION

These analyses of the functions of PxSast1 as the regulator of spermatogenesis and oogenesis establish its importance in the fertility process of P. xylostella, as well as its potential as a promising target for genetic regulation-based pest control. © 2024 Society of Chemical Industry.

Heterozygous CAPZA2 mutations cause global developmental delay, hypotonia with epilepsy: a case report and the literature review

CAPZA2 encodes the α2 subunit of CAPZA, which is vital for actin polymerization and depolymerization in humans. However, understanding of diseases associated with CAPZA2 remains limited. To date, only three cases have been documented with neurodevelopmental abnormalities such as delayed motor development, speech delay, intellectual disability, hypotonia, and a history of seizures. In this study, we document a patient who exhibited seizures, mild intellectual disability, and impaired motor development yet did not demonstrate speech delay or hypotonia. The patient also suffered from recurrent instances of respiratory infections, gastrointestinal and allergic diseases. A novel de novo splicing variant c.219+1 G > A was detected in the CAPZA2 gene through whole-exome sequencing. This variant led to exon 4 skipping in mRNA splicing, confirmed by RT-PCR and Sanger sequencing. To our knowledge, this is the third study on human CAPZA2 defects, documenting the fourth unambiguously diagnosed case. Furthermore, this splicing mutation type is reported here for the first time. Our research offers additional support for the existence of a CAPZA2-related non-syndromic neurodevelopmental disorder. Our findings augment our understanding of the phenotypic range associated with CAPZA2 deficiency and enrich the knowledge of the mutational spectrum of the CAPZA2 gene.

[Antimicrobial resistance and plasmid-mediated colistin resistance mechanism of diarrheagenic Escherichia coli recovered from foods in parts of China in 2020]

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.

The invasion status of lymphovascular space and lymph nodes in cervical cancer assessed by mono-exponential and bi-exponential DWI-related parameters

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 (__whole) and tumour margin (__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__margin and D∗__whole showed significant differences in differentiating LVSI(+) from LVSI(-) tumours (p=0.002, 0.008, respectively), while LNM(+) tumours presented with significantly higher ADC__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__margin combined with D∗__whole in discriminating LVSI(+) from LVSI(-) was 0.826 (95% confidence interval [CI]: 0.691-0.961), while ADC__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__margin and D∗__whole) and LNM (ADC__margin).

CRISPR/Cas9-Mediated Vitellogenin Receptor Knockout Leads to Functional Deficiency in the Reproductive Development of Plutella xylostella

The vitellogenin receptor (VgR) belongs to the low-density lipoprotein receptor (LDLR) gene superfamily and plays an indispensable role in Vg transport, yolk deposition, and oocyte development. For this reason, it has become a promising target for pest control. The involvement of VgR in Vg transport and reproductive functions remains unclear in diamondback moths, Plutella xylostella (L.), a destructive pest of cruciferous crops. Here, we cloned and identified the complete cDNA sequence of P. xylostella VgR, which encoded 1805 amino acid residues and contained four conserved domains of LDLR superfamily. PxVgR was mainly expressed in female adults, more specifically in the ovary. PxVgR protein also showed the similar expression profile with the PxVgR transcript. CRISPR/Cas9-mediated PxVgR knockout created a homozygous mutant of P. xylostella with 5-bp-nucleotide deletion in the PxVgR. The expression deficiency of PxVgR protein was detected in the ovaries and eggs of mutant individuals. Vg protein was still detected in the eggs of the mutant individuals, but with a decreased expression level. However, PxVg transcripts were not significantly affected by the PxVgR knockout. Knockout of PxVgR resulted in shorter ovarioles of newly emerged females. No significant difference was detected between wild and mutant individuals in terms of the number of eggs laid in the first 3 days after mating. The loss of PxVgR gene resulted in smaller and whiter eggs and lower egg hatching rate. This study represents the first report on the functions of VgR in Vg transport, ovary development, oviposition, and embryonic development of P. xylostella using CRISPR/Cas9 technology. This study lays the foundation for understanding molecular mechanisms of P. xylostella reproduction, and for making use of VgR as a potential genetic-based molecular target for better control of the P. xylostella.

A comprehensive review of microRNA-related polymorphisms in gastric cancer

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.

Specific PCR-based assays for the identification of Fasciola species: their development, evaluation and potential usefulness in prevalence surveys

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.

Sequence analysis of the first internal transcribed spacer of rDNA supports the existence of the intermediate Fasciola between F. hepatica and F. gigantica in mainland China

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.

MRI assessment of LV relaxation by untwisting rate: a new isovolumic phase measure of tau

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.

Chiral symmetry, quark mass, and scaling of the overlap fermions

The chiral symmetry relation and scaling of the overlap fermions are studied numerically on the quenched lattices at 3 couplings with about the same physical volume. We find that the generalized Gell-Mann-Oakes-Renner relation is satisfied to better than 1% down to the smallest quark mass at m(0)a = 0.006. We also obtain the quark mass from the PCAC relation and the pseudoscalar masses. The renormalization group invariant quark mass is shown to be fairly independent of scale. The pi and rho masses at a fixed m(pi)/m(rho) ratio indicate small O(a(2)) corrections. It is found that the critical slowing down sets in abruptly at a very small quark mass close to those of the physical u and d quarks.

Independent effects of preload, afterload, and contractility on left ventricular torsion

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.

Regional differences in shape and load in normal and diseased hearts studied by three dimensional tagged magnetic resonance imaging

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.

Effect of saponins of Panax notoginseng on synaptosomal 45Ca uptake

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.

Regional left ventricular systolic function in relation to the cavity geometry in patients with chronic right ventricular pressure overload. A three-dimensional tagged magnetic resonance imaging study

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.

Left ventricular wall thickness and regional systolic function in patients with hypertrophic cardiomyopathy. A three-dimensional tagged magnetic resonance imaging study

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.

Ventricular interaction and septal deformation: a model compared with experimental data

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.

Determinants of midwall circumferential segmental length of the canine ventricular septum at end diastole

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)

Changes in the radius of curvature of the ventricular septum at end diastole during pulmonary arterial and aortic constrictions in the dog

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.

Differences in distensibility between the anterior and posterior walls of the left ventricle in dogs

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.

Heterogeneous electron transfer of cytochrome c facilitated by polypyrrole and methylene blue polypyrrole film modified electrodes

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).