Biology subjects

Nguyen, A. H.

Publications and source records attributed to Nguyen, A. H..

4 recordsLinked to original sources

bioRxiv2021

Cardiotoxic effects of methamphetamine associated with electrophysiological and epigenetic aberrations in Zebrafish

Long-term methamphetamine (Meth) abuse damages functional and molecular changes in the brain that causes chronic and relapsing disease. In this study, we sought to investigate a relationship between cardiotoxicity and arrhythmia with associated Meth abuse in zebrafish to identify and to understand the adverse cardiac symptoms associated with Meth as well as to assess the applicability of zebrafish as an appropriate model for cardiac-related drug screening studies. Over a two-week duration, zebrafish were first treated with various concentrations of Meth, ranging from 0 to 50 M. Immediately after treatment, zebrafish underwent electrocardiogram (ECG) measurement for electrophysiological analysis. Results show that a higher incidence of increased heart rate over the duration of the experiment, corroborating with results from previous human case studies involving Meth users. However, abnormalities commonly cited in those same case studies, such as prolongation of QTc, were not significantly presented in obtained ECG recordings. We have also conducted genetic, epigenetic, and histochemical analysis in an attempt to understand the cardiotoxic effects of Meth on zebrafish cardiac function. These results suggested myocardial damage and decrease in gene expression associated with normal physiological function. Finally, this paper provides insights into potential reasons for the apparent discrepancies in our data with prior research as well as an outlook of zebrafish cardiotoxic drug screening studies.

physiology↗

bioRxiv2021

Simultaneous Cardiac and Neurological Monitoring to Assess Chemical Exposures and Drug Toxicity in Xenopus Laevis

Simultaneous monitoring of electrocardiogram (ECG) and electroencephalogram (EEG) under chemical exposure requires innovative engineering techniques that can capture minute physiological changes in studied animal models. However, this is often administered with a bulky system that may cause signal distortions and discomfort for animals. We develop an integrated bioelectronic sensing system to provide simultaneous ECG and EEG assessment in real-time under chemical exposure for Xenopus laevis. The microelectrode array (MEA) membrane with integrated ECG and EEG sensing offers an opportunity to achieve multichannel noninvasive electrophysiological monitoring with favorable dimensions and spatial resolution. To validate the performance of our system, we assessed the ECG and EEG of Xenopus under exposure of Pentylenetetrazol (PTZ), an epilepsy-inducing drug. Effects of PTZ were detected with clear ECG and EEG alterations, including frequent ictal and interictal EEG events, 30 dB average EEG amplitude elevations, abnormal ECG morphology, and heart rate changes. Overall, our Xenopus-based real-time electrophysiology monitoring system holds high potential for many applications in drug screening and remote environmental toxicity monitoring.

physiology↗

bioRxiv2021

A Novel Art of Electrocardiogram Assessment in Zebrafish for Cardiovascular Disease Studies and Drug Screening

The zebrafish (Dario rerio) has proven to be an excellent animal model for biological research owing to its small size, low cost for maintenance, short generation time, amenable genetics, and optical transparency. Zebrafish have been extensively used in cardiovascular studies in which mutant lines with cardiovascular defects were introduced and analyzed. Despite the small size, technological advances have paved the way to effectively assess cardiac functions of zebrafish. Here, we present a novel art for long-term simultaneous monitoring and analysis of electrocardiogram (ECG) in multiple zebrafish with controlled environment. The system helps minimize the effect of anesthetic drug and temperature to cardiac rhythm side effects as well as save time and efforts by 40-50 fold compared with the conventional approach. We further employed the system to study the Na+ sensitivity in the development of sinus arrest in Tg(SCN5A-D1275N) fish, a study model of the sick sinus syndrome, as well as the relationship between this variant and drug administration. The novel ECG system developed in this study holds promise to greatly accelerate other cardiovascular studies and drug screening using zebrafish.

bioengineering↗

bioRxiv2020

Toxic Y chromosome: increased repeat expression and age-associated heterochromatin loss in male Drosophila with a young Y chromosome

Sex-specific differences in lifespan are prevalent across the tree of life and influenced by heteromorphic sex chromosomes. In species with XY sex chromosomes, females often outlive males. Males and females can differ in their overall repeat content due to the repetitive Y chromosome, and repeats on the Y might lower survival of the heterogametic sex (toxic Y effect). Here, we take advantage of the well-assembled young Y chromosome of Drosophila miranda to study the sex-specific dynamics of chromatin structure and repeat expression during aging in male and female flies. Male D. miranda have about twice as much repetitive DNA compared to females, and live shorter than females. Heterochromatin is crucial for silencing of repetitive elements, yet old D. miranda flies lose H3K9me3 modifications in their pericentromere, with heterochromatin loss being more severe during aging in males than females. Satellite DNA becomes de-repressed more rapidly in old vs. young male flies relative to females. In contrast to what is observed in D. melanogaster, we find that transposable elements (TEs) are expressed at higher levels in male D. miranda throughout their life. We show that epigenetic silencing via heterochromatin formation is ineffective on the large TE- rich neo-Y chromosome, resulting in up-regulation of Y-linked TEs already in young males. This is consistent with an interaction between the age of the Y chromosome and the genomic effects of aging. Our data support growing evidence that "toxic Y chromosomes" can diminish male fitness and a reduction in heterochromatin can contribute to sex-specific aging.

evolutionary biology↗