Methodology approaches and challenges in population-based longitudinal study of a neuroprotective model for healthy longevity.

AIM: The 36-month Long-Term Research Grant Scheme project: Towards Usual Aging - Neuroprotective Model for Healthy Longevity among Malaysian Elderly was designed to address multidimensional aspects including psychosocial, biophysical health, nutrition and dietary pattern, and auditory and visual function to highlight the magnitude of these associations in a single study. METHODS: A total of 2322 respondents aged ≥60 years were recruited at baseline using the multistage sampling method, followed up at 18 months and 36 months. RESULTS: Response rates at baseline, 18 months and 36 months were 87.8%, 77.3% and 67.1%, respectively. At baseline, the prevalence of successful aging, usual aging and mild cognitive impairment was 11%, 73% and 16%, respectively. The prevalence of single and multimorbidity at baseline were 25.9% and 50.3%, respectively. The incidence rates of mild cognitive impairment at 18 months and 36 months were 6.5 and 5.6 per 100 person-years. The incidence rates of multimorbidity at 18 months and 36 months were 23.7 and 21.5 per 100 person-years, respectively. CONCLUSIONS: The Long-Term Research Grant Scheme project: Towards Usual Aging study provides an opportunity to investigate the interactions between wide ranges of aspects of the older population in a nationally representative sample of the older population. Geriatr Gerontol Int 2019; 19: 233-239.

Prediction of radiosensitivity in human bladder cell lines using nuclear chromatin phenotype.

BACKGROUND: Nuclear texture analysis measures phenotypic changes in chromatin distribution within a cell nucleus, while the alkaline Comet assay is a sensitive method for measuring the extent of DNA breakage in individual cells. The authors aim to use both methods to provide information about the sensitivity of cells to ionizing radiation. METHODS: The alkaline Comet assay was performed on six human bladder carcinoma cell lines and one human urothelial cell line exposed to gamma-radiation doses from 0 to 10 Gy. Nuclear chromatin texture analysis of 40 features was then performed in the same cell lines exposed to 0, 2, and 6 Gy to explore if nuclear phenotype was related to radiation sensitivity. RESULTS: Comet assay results demonstrated that the cell lines exhibited different levels of radiosensitivity and could be divided into a radiosensitive and a radioresistant group at >6 Gy. Using stepwise discriminant analysis, a subset of important nuclear texture features that best discriminated between sensitive and resistant cell lines were identified A classification function, defined using these features, correctly classified 81.75% of all cells into their radiosensitive or radioresistant groups based on their pretreatment chromatin phenotype. Posttreatment chromatin changes also varied between cell lines, with sensitive cell lines showing a relaxed chromatin conformation following radiation, whereas resistant cell lines exhibited chromatin condensation. CONCLUSIONS: The authors conclude that the alkaline Comet assay and nuclear texture methodologies may prove to be valuable aids in predicting the response of tumor cells to radiotherapy.

Use of the comet-FISH assay to demonstrate repair of the TP53 gene region in two human bladder carcinoma cell lines.

The alkaline single-cell gel electrophoresis (comet) assay can be combined with fluorescence in situ hybridization (FISH) methodology to investigate the localization of specific gene domains within an individual cell. The position of the fluorescent hybridization spots in the comet head or tail indicates whether the sequence of interest lies within or in the vicinity of a damaged region of DNA. In this study, we used the comet-FISH assay to examine initial DNA damage and subsequent repair in the TP53 gene region of RT4 and RT112 bladder carcinoma cells after 5 Gy gamma irradiation. In addition to standard comet parameter measurements, the number and location of TP53 hybridization spots within each comet was recorded at each repair time. The results indicate that the rate of repair of the TP53 gene region was fastest during the first 15 min after damage in both cell lines. When compared to overall genomic repair, the repair of the TP53 gene region was observed to be significantly faster during the first 15 min and thereafter followed a rate similar to that for the overall genome. The data indicate that the TP53 domain in RT4 and RT112 cells is repaired rapidly after gamma irradiation. Furthermore, this repair may be preferential compared to the repair of overall genomic DNA, which gives a measure of the average DNA repair response of the whole genome. We suggest that the comet-FISH assay has considerable potential in the study of gene-specific repair after DNA damage.