A high resolution reaction microscope with universal two-region time-focusing method

This paper presents a novel reaction microscope designed for ion-atom collision investigations, established at the Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China. Its time-of-flight (TOF) spectrometer employs an innovative flight-time focusing method consisting of two acceleration regions, providing optimal time focusing conditions for charged fragments with diverse initial velocities. The TOF spectrometer's axis intentionally tilts by 12° relative to the ion beam direction, preventing potential obstructions from the TOF grid electrodes. The introduced focusing method allows for a flexible time-focusing TOF spectrometer design without restricting the length ratio of the two regions. In addition, this configuration in our case significantly suppresses noise on the recoil ion detector produced by residual gas in the ion beam trajectory, which is a considerable challenge in longitudinal spectrometers. In a test experiment on the single electron capture reaction involving 62.5 keV/u He2+ ions and a helium atomic beam, the recoil longitudinal momentum resolution achieved 0.068 atomic units. This novel configuration and successful test run show excellent precision for ion-atom collision studies.

Dose-response relationship between risk factors and incidence of COVID-19 in 325 hospitalized patients: A multicenter retrospective cohort study

BACKGROUND

The epidemiological and clinical characteristics of coronavirus disease 2019 (COVID-19) patients have been widely reported, but the assessment of dose-response relationships and risk factors for mortality and severe cases and clinical outcomes remain unclear.

AIM

To determine the dose-response relationship between risk factors and incidence of COVID-19.

METHODS

In this retrospective, multicenter cohort study, we included patients with confirmed COVID-19 infection who had been discharged or had died by February 6, 2020. We used multivariable logistic regression and Cox proportional hazard models to determine the dose-response relationship between risk factors and incidence of COVID-19.

RESULTS

It clarified that increasing risk of in-hospital death were associated with older age (HR: 1.04, 95%CI: 1.01-1.09), higher lactate dehydrogenase [HR: 1.04, 95% confidence interval (CI): 1.01-1.10], C-reactive protein (HR: 1.10, 95%CI: 1.01-1.23), and procalcitonin (natural log-transformed HR: 1.88, 95%CI: 1.22-2.88), and D-dimer greater than 1 μg/mL at admission (natural log transformed HR: 1.63, 95%CI: 1.03-2.58) by multivariable regression. D-dimer and procalcitonin were logarithmically correlated with COVID-19 mortality risk, while there was a linear dose-response correlation between age, lactate dehydrogenase, D-dimer and procalcitonin, independent of established risk factors.

CONCLUSION

Higher lactate dehydrogenase, D-dimer, and procalcitonin levels were independently associated with a dose-response increased risk of COVID-19 mortality.

[Establishment of human colon cancer transplantation tumor model in normal immune mice]

Objective: Establishment of a new model of human primary colon cancer transplantation tumor in normal immune mice and to provide a reliable experimental animal model for studying the pathogenesis of colon cancer under normal immunity. Methods: Human colon cancer cells come from colon cancer patients who underwent surgery in the Affiliated Hospital of Jining Medical College in 2017. The mice in the cell control group were inoculated with phosphate buffered solution (PBS) containing colon cancer cells, the microcarrier control group was inoculated with PBS containing microcarrier 6, and the cell-microcarrier complex group was inoculated with the PBS containing colon cancer cell-microcarrier complex. The cells of each group were inoculated under the skin of the right axilla of mice by subcutaneous injection, and the time, size, tumor formation rate and pathological changes under microscope were recorded. The transplanted tumor tissue was immunohistochemically stained with the EnVisiion two-step method, and the tumor formation rate of the transplanted tumor was judged according to the proportion of positive cells in the visual field. The polymerase chain reaction (PCR) method was used to detect the expression of human-specific Alu sequence in mice tumor tissue. Results: After inoculation with tumor cells, the mice in the cell control group and the microcarrier control group did not die and did not form tumors; the mice in the cell-microcarrier complex group had palpable subcutaneous tumors in the right axillary subcutaneously on the 5th to 7th days after inoculation, and tumor formation rate is 67% (10/15), and the tumor volume can reach about 500 mm(3) 2 to 3 weeks after vaccination. The immunohistochemistry results showed that CK20, CDX-2 and carcinoembryonic antigen were all positively expressed. The PCR results showed that the expression of human-specific Alu sequence can be detected in the transplanted tumor tissue of tumor-bearing mice. Conclusion: Human primary colon cancer cells used microcarrier 6 as a carrier to form tumors in normal immunized mice, and successfully established a new model of human colon cancer transplantation tumor in normal immune mice.

Microvascular invasion and positive HB e antigen are associated with poorer survival after hepatectomy of early hepatocellular carcinoma: A retrospective cohort study

BACKGROUND

We aimed to identify the independent predictive factors of microvascular invasion (MVI) for curative resection of HCC and to investigate the impacts of MVI and HBeAg on long-term recurrence and survival after resection.

METHODS

The clinicopathological parameters of 237 patients with HCC with MVI who underwent hepatic resection from April 2005 to November 2010 were investigated. Clinical features and factors associated with the clinical outcomes of 386 patients with HCC without MVI were used for comparison.

RESULTS

Multivariate stepwise logistic regression analysis revealed that alpha-fetoprotein level>100μg/L, positive HBeAg, and tumour size were independent prognostic factors in patients with HCC with MVI. The overall survival (OS) of patients in the HCC with MVI group was significantly poorer compared with the HCC without MVI group (P<0.001). However, patients with HCC without MVI group exhibited a significantly better recurrence-free survival rate (RFS) (P<0.001). While the HCC with positive HBeAg group exhibited significantly lower OS compared with the HCC with negative HBeAg group (P=0.007).

CONCLUSIONS

AFP level>100μg/L, positive HBeAg, and tumour size>2cm are independent indicators of poorer prognosis for HCC with MVI. The present study confirmed that microvascular invasion itself had a negative impact on patient survival; moreover, HBeAg was an independent risk factor influencing OS, while not RFS of patients with HCC underwent hepatectomy. It is important to predict the presence of MVI before hepatic resection to determine treatment strategies.

MeCP2 level is associated with hepatocellular carcinoma development in chronic hepatitis B patients under antiviral therapy

AIM

Hepatocellular carcinoma (HCC) is a common and aggressive malignant tumor with especially high prevalence in Asia. This present study aimed to investigate the association of MeCP2 with HCC development in patients with undetectable HBV DNA by antiviral therapy.

METHODS

We retrospectively reviewed the 258 patients that were recruited into the present study. The control patients were matched with the HCC patients by age, gender, hepatitis e antigen (HBeAg) status, and duration of NA therapy in a 1:1:1 ratio. Area under ROC curve (AUC) was also used to compare diagnostic significance of MeCP2 using the Hanley and McNeil method.

RESULTS

For the entire cohort of 258 patients, MeCP2 was overexpressed in HCC tissues, which was significantly higher than that in cirrhosis and non-cirrhosis tissues (P<0.001). MeCP2 significantly increased in HCC cell lines compared with the control group of THLE-2 including SMMC-7721 (P<0.001), Huh-7 (P<0.001), and Hep3B (P<0.001). Overexpression of MeCP2 was closely related to liver cirrhosis (P=0.001) and TNM stage (P=0.017). The AUROC for the entire cohort, cirrhotic patients and non-cirrhotic patients, was 0.741 (95% CI: 0.629-0.804), 0.682 (95% CI: 0.526-0.782), and 0.776 (95% CI: 0.646-0.903), respectively. The predictive accuracies of MeCP2 in different groups of patients were further compared. For the whole cohort, this test had a high specificity in identifying patients without HCC development (85%). Among patients without cirrhosis, this test had a high sensitivity in identifying patients with future HCC development (83%).

CONCLUSIONS

We found that MeCP2 was expressed significantly higher in HCC tissues compared with cirrhosis and non-cirrhosis tissues. MeCP2 could be a novel risk marker to predict HCC development in CHB patients with profound viral suppression under NA therapy. MeCP2 measurement may serve as a useful strategy for risk stratification in terms of follow up interval and HCC surveillance.

Overexpression of long non-coding RNAs DUXAP9 and DUXAP10 is associated with prognosis in patients with hepatocellular carcinoma after hepatectomy

AIM

Hepatocellular carcinoma (HCC) is a common and aggressive malignant tumor with an especially high prevalence in Asian populations. This study aimed to identify differentially expressed lncRNAs using expression microarray and to explore the association between differential expression of lncRNAs and prognosis of HCC.

METHODS

We retrospectively reviewed 63 patients with primary HCC that underwent a curative liver resection at the Department of General Surgery, Jingmen First People's Hospital. The expression level of lncRNAs DUXAP9 and DUXAP10 were detected by real-time PCR. Prognostic factors were evaluated using Kaplan-Meier curves and Cox proportional hazards models.

RESULTS

By microarray profiling of lncRNAs, 256 were found to be differentially expressed, including 162 upregulated and 94 downregulated (P<0.05, fold change >2). Two candidate lncRNAs were determined as targets in this study, including DUXAP9 (upregulated by 6.35 fold) and DUXAP10 (upregulated by 4.53 fold). DUXAP9 and DUXAP10 were downregulated in the normal liver cell lines Chang liver, HL7702, THLE-2, THLE-3, FL62891, and AML12, which were significantly lower than HCC cell lines SMMC-7721, Hep3B, HuH7, MHCC-97H, HCC-LM, and SK-Hep-1 (P<0.05). Overexpression of lncRNAs DUXAP9 and DUXAP10 were associated with decreasing OS rates, respectively (P=0.0263 and P=0.0285). Meanwhile, Overexpression of DUXAP9 and DUXAP10 was associated with decreasing PFS rates, respectively (P=0.0174 and P=0.0041). After adjusting for competing risk factors, we identified microvascular invasion (P=0.014), tumor size (P=0.026), and lncRNAs DUXAP9 (P=0.001) and DUXAP10 (P=0.036) expression levels as independent prognostic factors associated with prognosis of patients with HCC.

CONCLUSIONS

We found that lncRNAs DUXAP9 and DUXAP10 are expressed significantly higher in HCC tissues compared with non-tumorous tissues. Overexpression of DUXAP9 and DUXAP10 were independent risk factors associated with prognosis of patients with HCC.

Partial hepatectomy for spontaneous tumor rupture in patients with hepatocellular carcinoma: a retrospective cohort study

BACKGROUND

The impact of ruptured hepatocellular carcinoma (HCC) on a patients outcome after hepatic resection remains insufficient. We aimed to identify the independent predictive factors of spontaneous tumor rupture (STR) for curative resection of HCC and to investigate the impact of STR of HCC on long-term survival after resection.

PATIENTS AND METHODS

The clinicopathological parameters of 106 patients with ruptured HCC and 201 patients with non-ruptured HCC who underwent hepatic resection from 2007 to 2011 were investigated. Clinical features and factors associated with the clinical outcomes were compared between both groups.

RESULTS

Of 774 HCC patients who underwent surgical resection, 106 (13.7%) had tumor rupture. Multivariate stepwise logistic regression analysis revealed hypertension, liver cirrhosis, total bilirubin (TB), tumor size and ascites to be independent prognostic factors for patients with ruptured HCC. The overall survival (OS) of patients in the ruptured HCC group was significantly poorer compared with those in the non-ruptured HCC group. The 1-, 3- and 5-year OS rates were 77.7%, 56.9% and 41.6%, respectively, in the non-ruptured HCC group and 37.7%, 19.7%, 14.%, respectively, in the ruptured HCC group (P<0.001). Similar OS rates were found in patients with non-ruptured and ruptured HCC; patients in the non-ruptured HCC group had a significantly better recurrence-free survival (RFS) rate compared with those in the ruptured group (P=0.016).

CONCLUSION

The presence of hypertension, liver cirrhosis, higher TB levels, tumor size >5 cm and ascites are the independent indicators of poorer prognosis for patients undergoing hepatic resection after ruptured HCC. The present study confirmed that tumor rupture itself had a negative impact on patient survival, but hepatic resection, when technically feasible, is safe and appropriate in selected patients and can result in OS and RFS rates comparable to that of patients with non-ruptured HCC.

Exosomal miR-9-3p suppresses HBGF-5 expression and is a functional biomarker in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer-related death worldwide. Exosomes are secreted membrane vesicles that play important roles in various diseases by transporting proteins and RNAs, including microRNAs, between cells. However, the function of exosomal miRNA in HCC has not been fully investigated.

METHODS

Exosomes were obtained from the sera by ultracentrifugation and were processed for transmission electron microscopy (TEM). Real time PCR were revealed changes of miRNA between patients and normal donors. Predicted targets of miRNA were described by bioinformatics analysis, luciferase reporter assay was used to confirmed whether miR-9-3p regulates target expression. And then miRNA were over-expressed in HCC cell line to study its function, western blotting were used to test expression of miRNA targets, Cell viability and proliferation were analyzed after over-expressed miR-9-3p using MTT and BrdU assay.

RESULTS

Serum exosomes from patients with HCC contained significantly lower levels of the miR-9-3p than did serum exosomes from normal donors, suggesting a potential role for this microRNA in HCC. Bioinformatics analysis identified fibroblast growth factor 5 (HBGF-5), which plays an important role in cell proliferation, as a potential miR-9-3p target mRNA. Luciferase reporter assay confirming that miR-9-3p can directly regulate HBGF-5 expression. Consistent with this finding, overexpression of miR-9-3p in three HCC cell lines significantly downregulated HBGF-5 expression at both the mRNA and protein levels. Finally, overexpression of miR-9-3p reduced HCC cell viability and proliferation, and additionally reduced ERK1/2 expression, suggesting a potential mechanism by which miR-9-3p acts.

CONCLUSIONS

These results provide new insight into the functions of miR-9-3p and HBGF-5 in HCC and identify miR-9-3p as a potential therapeutic target for HCC.

[Role of cytokine-matrix metalloproteinase axis on promoting vascular neointima hyperplasia in mice]

Objective: To observe the effects of tumor necrosis factor-α (TNF-α) and platelet derived growth factor (PDGF) on vascular neointimal hyperplasia on matrix metalloproteinase 9/2 gene knockout (MMP9/2^-/-) mice and explore related mechanisms. Methods: Mice of control group, MMP9^-/- group, MMP2^-/- group and MMP9/2^-/- group were studied. Femoral artery was injured by transluminal wire, the mRNA expression levels of TNF-α and PDGF on femoral artery were detected by RT-PCR; the protein expression of MMP9 and MMP2 were assessed by Western blot on day 0, 1, 3, 7, 14 and 28 post injury. Mice in control group received TNF-α(5 ng/ml, 0.10 ml), TNF-α(0.05 ml)+ MMP inhibitor SB-3CT(0.50 ng/ml, 0.05 ml) injection, or PDGF-bb (10 ng/ml, 0.10 ml)and PDGF-bb(0.05 ml)+ SB-3CT(0.05 ml)injection around injured artery, intimal hyperplasia at 2 and 4 weeks after injury was observed. Intimal hyperplasia at 2 and 4 weeks after injury was also observed in MMP9/2^-/- mice. TNF-α(5 ng/ml, 0.10 ml)was injected to MMP2^-/- mice, PDGF-bb (0.1 ml) was injected to MMP9^-/- mice around injured artery, intimal hyperplasia at 2 and 4 weeks after injury was observed. The degree of neointimal hyperplasia were observed by the Elastica-van Gieson staining and the area of neointima and media of the arteries were measured by SigmaPlot and intima ratio was calculated. Vascular smooth muscle cell (VSMC) mediums of MMP9^-/- and MMP2^-/- mice were stimulated by TNF-α and PDGF-bb, respectively, and migration assay, and proliferation assay were performed, relative migration and proliferation cells numbers were counted. Results: (1) mRNA expression of TNF-α (235.33±23.68) and PDGF-bb (3.30±0.56) in femoral arteries peaked at 1 day after injury, while MMP9 or MMP2 protein expression peaked at 7 or 28 days after injury. (2)In control mice, TNF-α intervention significantly enhanced intimal hyperplasia at 2 weeks after injury (2.21±0.05 vs. 1.55±0.03 in blank control group, P<0.05), while PDGF-bb intervention significantly enhanced intimal hyperplasia at 4 weeks after injury (2.60±0.07 vs. 1.89±0.04, P=0.03). (3) Intima hyperplasia was significantly higher in control group than in MMP9/2^-/- group at 2 weeks (1.63±0.05 vs. 0.46±0.01, P=0.008) and 4 weeks (2.24±0.06 vs. 0.51±0.01) after injury(P=0.005). (4) TNF-α intervention stimulated intimal hyperplasia in MMP2^-/-mice (intimal ratio at 2 weeks after injury: 1.73±0.05 vs.1.23±0.03, P=0.02)and PDGF-bb intervention stimulated intimal hyperplasia in MMP9^-/-mice(intimal ratio at 4 weeks after injury: 2.32±0.06 vs.1.35±0.03, P=0.03). (5) Reduced VSMC migration was evidenced in MMP9^-/- mice post TNF-α stimulation (1.45±0.03 vs. 2.16±0.04 in control group, P=0.03), while reduced VSMC proliferation post PDGF was seen in MMP2^-/- group (1.15±0.02 vs.1.82±0.04 in control group, P=0.03). Conclusions: TNF-α induced MMP9 activation plays a major role on promoting VSMC migration at the first 2 weeks after vascular injury, while PDGF induced MMP2 activation plays a crucial role on VSMC proliferation on the following 2 weeks after vascular injury in this mice model. Thus, the axis of TNF-α-MMP9-VSMC migration axis and PDGF-MMP2-VSMC proliferation axis are the two major working mechanisms responsible for intimal hyperplasia post vascular injury.

Genetic diversity analysis of tree peony germplasm using iPBS markers

We examined the genetic diversity of 10 wild species (populations) and 55 varieties of tree peony using inter-primer binding site (iPBS) markers. From a total of 36 iPBS primers, 16 were selected based on polymorphic amplification. The number of bands amplified by each primer ranged from 9 to 19, with an average of 12.88 bands per primer. The length of bands ranged from 100 to 2000 bp, concentrated at 200 to 1800 bp. Sixteen primers amplified 206 bands in total, of which 173 bands were polymorphic with a polymorphism ratio of 83.98%. Each primer amplified 10.81 polymorphic bands on average. The data were then used to construct a phylogenetic tree using unweighted pair group method with arithmetic mean methods. Clustering analysis showed that the genetic relationships among the varieties were not only related to the genetic background or geographic origin, but also to the flowering phase, flower color, and flower type. Our data also indicated that iPBS markers were useful tools for classifying tree peony germplasms and for tree peony breeding, and the specific bands were helpful for molecular identification of tree peony varieties.

[Scale-dependency of spatial variability of surface soil moisture under different land use types in Heihe Oasis, China]

To study the surface soil moisture spatial variability and its scale effect is of significance to understand the real variability of soil moisture and to objectively provide a reference for constructing a logical sampling scheme. By using "re-sampling" method, this paper studied the scale-dependency of the spatial variability of soil surface moisture in the woodland and farmland in the oasis ecological system in the middle reaches of Heihe River. The results showed that the variation degree of the surface soil moisture in the test woodland and farmland increased with increasing soil moisture content, and the coefficient of variation (CV) became closer to the true value when the sampling scale increased. Under both dry and moist conditions, and when the sampling amplitude increased within a definite range, the CV, Moran's I index, nugget, and sill of soil moisture in the woodland and farmland as well as the variation range in the woodland all increased, while the variation range in the farmland under arid condition did not show a stable regular pattern. When the sampling density increased within a definite range, the nugget and variation range increased, but the CV, Moran's I index, and sill showed less change.

Genetic relationships of the Japanese persimmon Diospyros kaki (Ebenaceae) and related species revealed by SSR analysis

Simple sequence repeat (SSR) molecular markers based on 18 primers were employed to study the genetic relationship of Japanese persimmon (Diospyros kaki) specimens. Two hundred and sixty-two bands were detected in 30 Japanese persimmon samples, including 14 Japanese and 10 Chinese genotypes of Japanese persimmon (Diospyros kaki) and six related species, D. lotus, D. glaucifolia, D. oleifera, D. rhombifolia, D. virginiana, and Jinzaoshi (unclassified - previously indicated to be D. kaki). All SSR primers developed from D. kaki were successfully employed to reveal the polymorphism in other species of Diospyros. Most of the primers were highly polymorphic, with a degree of polymorphism equal to or higher than 0.66. The results from the neighbor-joining dendrogram and the principal coordinate analysis diagram were the same; i.e., the Chinese and Japanese genotypes and related species were separated and the relationships revealed were consistent with the known pedigrees. We also concluded that 'Xiangxitianshi' from Xiangxi municipality, Hunan Province, China, is actually a sport or somaclonal variant of 'Maekawa-Jirou', and that 'Jinzaoshi' should be classified as a distinct species of Diospyros. We found that SSR markers are a valuable tool for the estimation of genetic diversity and divergence in Diospyros.

[Anatomical study and clinical applications of flaps based on cutaneous branches arising from posterior tibial vessels]

OBJECTIVE

To provide an anatomical basis for the clinical applications of the medial fascinocutaneous flap of calf and to verify its clinical value.

METHODS

In 20 lower limb specimens of adult human cadavers, the number, course, size, position and distribution of septocutaneous branches of the posterior tibial vessels are marked by means of red latex and black ink irrigations through femur artery and septocutaneous branches of the posterior tibial artery respectively.

RESULTS

The posterior tibial artery gives off several septocutaneous branches at the upper, middle and lower one-third of the leg respectively. Each septocutaneous artery has one or sometimes two concomitant veins. Based on this result, anterograde or reverse pedicled fasciocutaneous flap can be performed for the purpose of repairing soft tissue defects of leg and foot. The flap was clinically applied to treat leg and foot soft tissue defects in 12 cases with satisfactory results.

CONCLUSION

The flap is easy to dissect, the posterior tibial artery can be preserved with high successful rate. Therefore, it offers an useful alternative in the repairing and reconstruction of nonextensive soft tissue defects in the leg and foot.

Inhibitory effects of dauricine on potassium currents in guinea pig ventricular myocytes

AIM

To study the effects of dauricine(Dau) on the rapidly activating component (IKr), the slowly activating component (IKs) of the delayed rectifier potassium current, and the inward rectifier potassium current (IKl) in guinea pig ventricular myocytes.

METHODS

Single myocytes were dissociated by enzymatic dissociation method. The currents were recorded with the whole-cell configuration of the patch-clamp technique.

RESULTS

(1) Dau 1, 3, 10, 30, and 100 mumol.L-1 blocked IKr and tail current (IKr-tail) in a concentration-dependent manner. The IC50 for block of IKr-tail was 16 (95% confidence limits: 13-22) mumol.L-1. The time constant of IKr-tail deactivation was (140 +/- 38) ms in the control and (130 +/- 26) ms in the presence of Dau 30 mumol.L-1 (n = 6 cells from 3 animals, P > 0.05). (2) Dau 1-100 mumol.L-1 produced concentration-dependent blocks of IKs and tail current (IKs-tail). The IC50 value for block of IKs-tail was 33 (95% confidence limits: 24-46) mumol.L-1. The time constant of IKs-tail deactivation was (92 +/- 18) ms in the control and (84 +/- 16) ms in the presence of Dau 30 mumol.L-1 (n = 8 cells from 4 animals, P > 0.05). (3) Addition of Dau 30 mumol.L-1 induced block of IKs and IKs-tail (n = 7 cells from 3 animals). The degree of block of IKs and IKs-tail depended on test potentials, increasing with more positive depolarizations. (4) Dau 20 mumol.L-1 blocked mainly inward component of IKl and reduced the reversal potential from -72 mV (control) to -78 mV (n = 6 cells from 3 animals).

CONCLUSION

(1) Dau inhibited IKs, but not the process of IKs deactivation. (2) Dau blocked IKr, but not the process of deactivation. (3) Dau had a blocking effect on IKl.

Dauricine inhibited L-type calcium current in single cardiomyocyte of guinea pig

AIM

To study the effect of dauricine (Dau) on L-type calcium current in guinea pig ventricular myocytes.

METHODS

Using whole-cell recording method to record L-type calcium current (ICa) in single ventricular cell of guinea pig.

RESULTS

Dau 1, 10, and 100 mumol.L-1 markedly reduced ICa by 15.2% +/- 2.2%, 41% +/- 5%, and 82% +/- 8%, respectively. After washing out, ICa partially recovered. Dau inhibited ICa at 3 Hz and 1 Hz to a similar extent, its effect on ICa appeared to be not frequency-dependent.

CONCLUSION

Dau had a calcium channel blocking effect.

Effects of dauricine, quinidine, and sotalol on action potential duration of papillary muscles in vitro

AIM

To compare the characteristics of dauricine, sotalol, and quinidine on action potential duration (APD).

METHODS

Using intracellular microelectrode method to record APD in guinea pig papillary muscles.

RESULTS

Dauricine 20 mumol.L-1 prolonged action potential at 90% repolarization, the percent of APD prolongation were 22 +/- 8, 11 +/- 6, 9 +/- 5, 7 +/- 5, 6 +/- 3, 4.3 +/- 2.8, 4.5 +/- 2.8 at the cycle lengths of 200-2000 ms, dauricine became more effective in lengthening APD at short cycle lengths. The effect of dauricine on prolonging APD exhibited normal use-dependence, whereas quinidine 1 mumol.L-1 and sotalol 10 mumol.L-1 were less effective in lengthening APD at short cycle lengths. The effect of quinidine and sotalol on APD exhibited reverse use-dependence.

CONCLUSION

[corrected] The effect of dauricine on APD depends on activation frequency.