Study on the process of cardiomyocyte apoptosis after pulsed field ablation.

Background: The development of pulsed field ablation (PFA) as a new technique for pulmonary vein isolation (PVI) has been advancing rapidly in recent years. My team's previous work has shown the safety and long-term efficacy of bipolar asymmetric pulses in animal experiments. However, in ongoing clinical trials, we have observed that atrial fibrillation (AF) recurs in some patients after surgery, but the rhythm returns to normal without surgical intervention after seven days, and there is no recurrence in the follow-up.Based on this observation, we have proposed the hypothesis that myocardial cell apoptosis may play a role in AF recurrence after PFA. Our team has designed animal experiments to verify this hypothesis and further investigate the process of PFA-induced cardiomyocyte apoptosis. Methods: Pulse field ablation was performed on 15 dogs and the animals were dissected at various time points after the operation (immediately, 3 days, 7 days, 30 days, and 150 days). To obtain ablation voltage maps, electroanatomic mapping was performed before and after ablation and before dissection. The ablation area was also subjected to HE and TUNEL staining to analyze apoptosis and pathological results. Results: The edge area of the ablation in the pulmonary vein (PV) demonstrated continuous dynamic changes from 0 to 2 h after the operation and a slight expansion of the ablation range was observed in the long-term follow-up. Myocardial intima hyperplasia was observed from 0 to 7 days. Local apoptosis was detected from 0 to 2 h and massive, concentrated apoptosis was observed at 3 days. No recurrence of apoptosis was seen at 7 days, 30 days, and 150 days. Conclusions: The results of this study showed that after pulse field ablation (PFA), the central ablation area of the canine heart experienced immediate cardiomyocyte death. Meanwhile, cardiomyocytes in the edge ablation area underwent apoptosis, which began from 0 to 2 h post-operation and ended between 3 and 7 days. This process occurred simultaneously with intimal thickening.In the long-term follow-up group, there was no recovery of isolation and no recurrence of cardiomyocyte apoptosis, and no change was observed in the endomyocardial intima.

More direction but less freedom? How task rules affect intrinsic motivation.

Task rules restrict freedom by definition, but do they necessarily harm intrinsic motivation? We examine how task rules for an open-ended writing activity affect intrinsic motivation, or enjoyment, with one's sense of direction and psychological freedom as potential mechanisms. Results from three online experiments (Experiment 1, Experiments 3a and 3b; N = 1,176), conducted with both undergraduate student and adult (Amazon MTurk and Prolific) samples, suggest that task rules may indirectly increase enjoyment by enhancing direction (indirect effect: ß's range [0.09, 0.17], p's < .05), yet at the same time, indirectly decrease enjoyment by reducing freedom (indirect effect: ß's range [-0.31, -0.07], p's < .05). Results from a fourth online experiment (Experiment 2; student sample; N = 121) address a potential alternative explanation, finding that only the task rules, not mere examples, were sufficient to increase direction (rules present: d = 0.55, p = .04; examples: d = 0.25, p = .48) and reduce freedom (rules present: d = 0.78, p < .001; examples: d = 0.22, p = .31). Theoretical and empirical connections are made to self-determination theory and flow theory. Further research is needed to delineate situational and personal factors that may moderate these effects. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Effects of M currents on the persistent activity of pyramidal neurons in mouse primary auditory cortex.

Neuronal persistent activity (PA) is a common phenomenon observed in many types of neurons. PA can be induced in neurons in the mouse auditory nucleus by activating cholinergic receptors with carbachol (CCh), a dual muscarinic and nicotinic receptor agonist. PA is presumed to be associated with learning-related auditory plasticity at the cellular level. However, the mechanism is not clearly understood. Many studies have reported that muscarinic receptor agonists inhibit muscarinic-sensitive potassium channels (M channels). Potassium efflux through M channels produces potassium currents, called M currents, that play an essential role in regulating neural excitability and synaptic plasticity. Further study is needed to determine whether M currents affect the PA of auditory central neurons and provide additional analysis of the variations in electrophysiological properties. We used in vitro whole cell patch-clamp recordings in isolated mouse brain slices to investigate the effects of M currents on the PA in pyramidal neurons in layer V of the primary auditory cortex (AI-L5). We found that blocking M currents with XE991 depolarized the AI-L5 pyramidal neurons, which significantly increased the input resistance. The active threshold and threshold intensity were significantly reduced, indicating that intrinsic excitability was enhanced. Our results also showed that blocking M currents with XE991 switched the neuronal firing patterns in the AI-L5 pyramidal neurons from regular spiking to intrinsic bursting. Blocking M currents facilitated PA by increasing the plateau potential and enhancing intrinsic excitability. Our results suggested that blocking M currents might facilitate the PA in AI-L5 pyramidal neurons, which underlies auditory plasticity.NEW & NOTEWORTHY Persistent activity (PA) in AI-L5 pyramidal neurons plays an essential role in acoustic information processing. We used in vitro whole cell patch-clamp recordings to investigate the effects of M currents on the PA in AI-L5 pyramidal neurons. Blocking M currents with XE991 facilitated PA by increasing the plateau potential and enhancing intrinsic excitability, causing the firing patterns of AI-L5 pyramidal neurons to become more bursting. These results provide new insight into our understanding of the cellular mechanisms that govern learning-induced auditory plasticity.

Isoalantolactone Inhibits Esophageal Squamous Cell Carcinoma Growth Through Downregulation of MicroRNA-21 and Derepression of PDCD4.

BACKGROUND: This study was designed to explore the anticancer potential of isoalantolactone, a sesquiterpene lactone, on esophageal squamous cell carcinoma (ESCC) cells and associated molecular mechanisms. METHODS: ESCC cell lines were treated with isoalantolactone or vehicle and tested for viability, proliferation, cell cycle distribution, and apoptosis. Xenograft tumor studies in nude mice were done to examine the in vivo anticancer effect of isoalantolactone. RESULTS: Isoalantolactone treatment reduced ESCC cell viability and proliferation in vitro, which was coupled with induction of G0/G1 cell cycle arrest and apoptosis. In vivo studies confirmed the growth-suppressive effect of isoalantolactone on ESCC cells. Mechanistically, isoalantolactone reversed microRNA-21-mediated repression of programmed cell death 4 (PDCD4). Overexpression of microRNA-21 and knockdown of PDCD4 blocked the growth suppression and apoptosis induction by isoalantolactone in ESCC cells. CONCLUSIONS: Isoalantolactone shows growth-suppressive activity against ESCC cells, which is ascribed to upregulation of PDCD4 via downregulation of microRNA-21.

Using aptamers to elucidate esophageal cancer clinical samples.

The epithelial cell adhesion molecule (EpCAM) is closely correlated with the occurrence and development of various cancers of epithelial origin. This study tested, for the first time, the ability of EpCAM aptamer SYL3C to detect EpCAM expression in 170 cases of esophageal cancer (EC) and precancerous lesions, as well as 20 cases of EC series samples, using immunofluorescence imaging analysis. Corresponding antibodies were used as control. EpCAM overexpression was 98% in both esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EACA) and 100% in metastasis, but no EpCAM overexpression was detected in undifferentiated EC (UEC). Significant differences were noted among various stages of differentiation (p < 0.05) with the degree of differentiation inversely correlated with the expression of EpCAM. Overexpressed EpCAM was detected in severe dysplasia, but negative in mild to moderate dysplasia and benign esophageal lesions. In a competitive binding experiment, EpCAM aptamer generated a staining pattern similar to that of antibody, but the binding sites with EpCAM were different. Based on these results, it can be concluded that EpCAM is suitable for use as an EC biomarker, therapeutic target, and effective parameter for tumor transfer and prognosis evaluation by aptamer SYL3C staining.

Using DNA aptamer probe for immunostaining of cancer frozen tissues.

Tissue immunostaining is critically important in clinical applications, and antibodies have been used extensively as the molecular probes. Recently, aptamer, as a new class of probes, have attracted much attention for their potential clinical and research value. Epithelial cell adhesion molecule (EpCAM) is a specific biomarker which is overexpressed in many cancers of epithelial origin. Here, a DNA-based EpCAM aptamer SYL3C is reported as a probe for the immunostaining of frozen and paraffin-embedded sections of colorectal cancer tissues. Commercialized EpCAM antibodies were also used as a standard control. EpCAM aptamer SYL3C specifically recognized and immunostained cancer nests of colorectal tumor sections, but it neither reacted with background cells within tumor sites nor exhibited cross-reaction to the benign lesions or inflammation of colorectal tissues. No cross-linking to EpCAM-negative malignant tumor sections occurred. Compared with standard antibody staining, our EpCAM aptamer SYL3C protocol is simpler to implement with a shorter reaction time. Moreover, SYL3C can specifically bind with either frozen or paraffin-embedded tissue sections. Since the histopathology of frozen tissue is closer to that of fresh tissue and since frozen sections can be produced more quickly than paraffin-embedded sections, SYL3C immunostaining of frozen sections is a quick protocol that is easy to implement.

Aptamer-functionalized nanoparticles for drug delivery.

Aptamers are artificial single-stranded DNA or RNA sequences, usually 20-60 bases long, that fold into secondary and tertiary structures, which enables their binding to a wide range of targets, including amino acids, drugs, proteins or even entire cells, with high affinity and specificity. Generally synthesized through an in vitro selection and amplification process known as the SELEX (systematic evolution of ligands by exponential enrichment), selected aptamers have dissociation constants ranging from nanomolar to picomolar level. Nanotechnology is the manipulation of matter on an atomic and molecular scale, generally in the 1-100 nm dimension range. The many unique physicochemical properties of nanoparticles include their ultra-small size, large surface area-to-mass ratio, and high reactivity, making them different from bulk materials and overcoming some of the limitations found in traditional therapeutic and diagnostic agents. By combining both technologies, aptamer-conjugated nanoparticles offer new opportunities for applications in biomedicine, including early diagnosis and drug delivery. This review summarizes the recent developments in aptamer-mediated drug delivery for therapeutics based on aptamer conjugation with a variety of nanoparticles.