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The prevalance of dens invaginatus in maxillary incisors

Kong YW

Dent J Malaysia Singapore, 1972 May;12(1):9-14.
PMID: 4507360
Fulltext Explicit nonlinear finite element geometric analysis of parabolic leaf springs under various loads

Kong YS, Omar MZ, Chua LB, Abdullah S

ScientificWorldJournal, 2013;2013:261926.
PMID: 24298209 DOI: 10.1155/2013/261926

This study describes the effects of bounce, brake, and roll behavior of a bus toward its leaf spring suspension systems. Parabolic leaf springs are designed based on vertical deflection and stress; however, loads are practically derived from various modes especially under harsh road drives or emergency braking. Parabolic leaf springs must sustain these loads without failing to ensure bus and passenger safety. In this study, the explicit nonlinear dynamic finite element (FE) method is implemented because of the complexity of experimental testing A series of load cases; namely, vertical push, wind-up, and suspension roll are introduced for the simulations. The vertical stiffness of the parabolic leaf springs is related to the vehicle load-carrying capability, whereas the wind-up stiffness is associated with vehicle braking. The roll stiffness of the parabolic leaf springs is correlated with the vehicle roll stability. To obtain a better bus performance, two new parabolic leaf spring designs are proposed and simulated. The stress level during the loadings is observed and compared with its design limit. Results indicate that the newly designed high vertical stiffness parabolic spring provides the bus a greater roll stability and a lower stress value compared with the original design. Bus safety and stability is promoted, as well as the load carrying capability.
Fulltext Effect of Cadmium and Copper Exposure on Growth, Secondary Metabolites and Antioxidant Activity in the Medicinal Plant Sambung Nyawa (Gynura procumbens (Lour.) Merr)

Ibrahim MH, Chee Kong Y, Mohd Zain NA

Molecules, 2017 Oct 12;22(10).
PMID: 29023367 DOI: 10.3390/molecules22101623

A randomized complete block (RCBD) study was designed to investigate the effects of cadmium (Cd) and copper (Cu) on the growth, bioaccumulation of the two heavy metals, metabolite content and antibacterial activities in Gyanura procumbens (Lour.) Merr. Nine treatments including (1) control (no Cd and Cu); (2) Cd 2 = cadmium 2 mg/L; (3) Cd 4 = cadmium 4 mg/L; (4) Cu 70 = copper 70 mg/L; (5) Cu 140 = copper 140 mg/L); (6) Cd 2 + Cu 70 = cadmium 2 mg/L + copper 70 mg/L); (7) Cd 2 + Cu 140 = cadmium 2 mg/L + copper 70 mg/L); (8) Cd 4 + Cu 70 = cadmium 4 mg/L+ copper 70 mg/L and (9) Cd 4 + Cu 140 = cadmium 4 mg/L + copper 140 mg/L) were evaluated in this experiment. It was found that the growth parameters (plant dry weight, total leaf area and basal diameter) were reduced with the exposure to increased concentrations of Cd and Cu and further decreased under interaction between Cd and Cu. Production of total phenolics, flavonoids and saponin was observed to be reduced under combined Cd and Cu treatment. The reduction in the production of plant secondary metabolites might be due to lower phenyl alanine lyase (PAL) activity under these conditions. Due to that, the 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant potential (FRAP) and antibacterial activities was also found to be reduced by the combined treatments. The current experiments show that the medicinal properties of G. procumbens are reduced by cadmium and copper contamination. The accumulation of heavy metal also was found to be higher than the safety level recommended by the WHO in the single and combined treatments of Cd and Cu. These results indicate that exposure of G. procumbens to Cd and Cu contaminated soil may potentially harm consumers due to bioaccumulation of metals and reduced efficacy of the herbal product.
Therapeutic potential of human umbilical cord-derived mesenchymal stem cells transplantation in rats with optic nerve injury

Looi SY, Bastion MC, Leow SN, Luu CD, Hairul NMH, Ruhaslizan R, et al.

Indian J Ophthalmol, 2022 Jan;70(1):201-209.
PMID: 34937239 DOI: 10.4103/ijo.IJO_473_21

Purpose: There are no effective treatments currently available for optic nerve transection injuries. Stem cell therapy represents a feasible future treatment option. This study investigated the therapeutic potential of human umbilical cord-derived mesenchymal stem cell (hUC-MSC) transplantation in rats with optic nerve injury.
Methods: Sprague-Dawley (SD) rats were divided into three groups: a no-treatment control group (n = 6), balanced salt solution (BSS) treatment group (n = 6), and hUC-MSCs treatment group (n = 6). Visual functions were assessed by flash visual evoked potential (fVEP) at baseline, Week 3, and Week 6 after optic nerve crush injury. Right eyes were enucleated after 6 weeks for histology.
Results: The fVEP showed shortened latency delay and increased amplitude in the hUC-MSCs treated group compared with control and BSS groups. Higher cellular density was detected in the hUC-MSC treated group compared with the BSS and control groups. Co-localized expression of STEM 121 and anti-S100B antibody was observed in areas of higher nuclear density, both in the central and peripheral regions.
Conclusion: Peribulbar transplantation of hUC-MSCs demonstrated cellular integration that can potentially preserve the optic nerve function with a significant shorter latency delay in fVEP and higher nuclear density on histology, and immunohistochemical studies observed cell migration particularly to the peripheral regions of the optic nerve.
Examining CO2 and N2O pollution and reduction from forestry application of pure and mixture forest

Kong Y, Ma NL, Yang X, Lai Y, Feng Z, Shao X, et al.

Environ Pollut, 2020 Oct;265(Pt A):114951.
PMID: 32554093 DOI: 10.1016/j.envpol.2020.114951

Greenhouse gases (GHGs) carbon dioxide (CO2) and nitrous oxide (N2O), contribute significantly to global warming, and they have increased substantially over the years. Reforestation is considered as an important forestry application for carbon sequestration and GHGs emission reduction, however, it remains unknown whether reforestation may instead produce too much CO2 and N2O contibuting to GHGs pollution. This study was performed to characterize and examine the CO2 and N2O emissions and their controlling factors in different species and types of pure and mixture forest used for reforestation. Five soil layers from pure forest Platycladus orientalis (PO), Robinia pseudoacacia (RP), and their mixed forest P-R in the Taihang mountains of central China were sampled and incubated aerobically for 11 days. The P-R soil showed lower CO2 and N2O production potentials than those of the PO soils (P
Psychological impact amongst patients with COVID-19 in Perak state

Loo TH, Arvinder-Singh HS, Ang YC, Kong YH, Vikram Suarn S, Rakesh S

Med J Malaysia, 2022 Nov;77(6):643-649.
PMID: 36448379

INTRODUCTION: Psychological distress had been documented since the beginning of the COVID-19 outbreak in 2019. The aim of the study is to describe the psychological impact among those who were hospitalized for COVID-19 infection within 6 months after being discharged from the hospital. The psychological impact in this study is defined as depression, anxiety, and stress.
MATERIALS AND METHODS: This was a cross-sectional study conducted from July 2020 till August 2021 in a regional state hospital, north of Malaysia. All patients requiring hospitalization for COVID-19 were approached within the first 2 weeks after admission to administer the Depression, Anxiety and Stress Scale - 21 Items (DASS-21) scale. Follow-up phone calls were made within 3 months of discharged to enquire about the DASS-21 items as well as the Impact of Event Scale-Revised (IES-R) scale items. Participants above the age of 18 and technology savvy to answer an online questionnaire were recruited for the study. We excluded participants with a known history of psychotic disorder from the study. We utilised the DASS-21 to screen for depression, anxiety, and stress, as well as the IES-R to identify symptoms of post-traumatic stress disorder. Participants could answer the questionnaires in either English or Bahasa Malaysia. For comparison of two categorical data, a chi-square was applied. A univariate analysis was first conducted and all variables with a p ≤0.3 was then entered into the multivariate analysis for the final output. Other than the univariate analysis, all other p values <0.05 were considered to be statistically significant. All data collected were tabulated and analysed in the SPSS v21.0 system.
RESULTS: A total of 306 out of 696 COVID-19 patients responded. The mean age for the participants was 31.69 (SD:11.19) years old. From the total, 54.2% were ladies, 78.8% were Malay, 50.7% were unmarried, 55.2% had higher education, and 67.6% were employed at the time of the survey. We found 20.5% of the participants were depressed, 38.9% had moderate anxiety, and 17.3% were stressed. From the total, 31.7% of the participants were deemed to have had some symptoms of post-traumatic stress disorder (PTSD) ranging from mild to severe. From the final multivariate analysis, it was found that depression (p=0.02) had a 2.78 times likeliness of having PTSD, anxiety (p<0.001) had a 3.35 times likeliness of having PTSD and stressed patients (p=0.02) 2.86 times likeliness of having PTSD when compared to those without PTSD.
CONCLUSION: Patients reported to suffer from symptoms of PTSD and might benefit from psychological interventions to mitigate the impact in the long run.
Current advances of nanocellulose application in biomedical field

Leong MY, Kong YL, Harun MY, Looi CY, Wong WF

Carbohydr Res, 2023 Oct;532:108899.
PMID: 37478689 DOI: 10.1016/j.carres.2023.108899

Nanocellulose (NC) is a natural fiber that can be extracted in fibrils or crystals form from different natural sources, including plants, bacteria, and algae. In recent years, nanocellulose has emerged as a sustainable biomaterial for various medicinal applications including drug delivery systems, wound healing, tissue engineering, and antimicrobial treatment due to its biocompatibility, low cytotoxicity, and exceptional water holding capacity for cell immobilization. Many antimicrobial products can be produced due to the chemical functionality of nanocellulose, such disposable antibacterial smart masks for healthcare use. This article discusses comprehensively three types of nanocellulose: cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), and bacterial nanocellulose (BNC) in view of their structural and functional properties, extraction methods, and the distinctive biomedical applications based on the recently published work. On top of that, the biosafety profile and the future perspectives of nanocellulose-based biomaterials have been further discussed in this review.
A scaffoldless technique for self-generation of three-dimensional keratinospheroids on liquid crystal surfaces

Soon CF, Thong KT, Tee KS, Ismail AB, Denyer M, Ahmad MK, et al.

Biotech Histochem, 2016 May;91(4):283-95.
PMID: 27008034 DOI: 10.3109/10520295.2016.1158865

We describe a new scaffold-free three-dimensional (3D) cell culture model using cholesteryl ester based lyotropic liquid crystal (LC) substrates. Keratinocytes were deposited randomly on the LC surface where they self-assembled into 3D microtissues or keratinospheroids. The cell density required to form spheroids was optimized. We investigated cell viability using dead/live cell assays. The adhesion characteristics of cells within the microtissues were determined using histological sectioning and immunofluorescence staining. Fourier transform infrared spectroscopy (FTIR) was used to characterize the biochemistry of the keratinospheroids. We found that both cells and microtissues could migrate on the LC surface. The viability study indicated approximately 80% viability of cells in the microtissues up to 20 days of culture. Strong intercellular adhesion was observed in the stratification of the multi-layered microspheroids using field emission-scanning electron microscopy (FE-SEM) and histochemical staining. The cytoskeleton and vinculins of the cells in the microtissues were expressed diffusely, but the microtissues were enriched with lipids and nucleic acids, which indicates close resemblance to the conditions in vivo. The basic 3D culture model based on LC may be used for cell and microtissue migration studies in response to cytochemical treatment.
Targeting neutrophils using novel drug delivery systems in chronic respiratory diseases

Chellappan DK, Yee LW, Xuan KY, Kunalan K, Rou LC, Jean LS, et al.

Drug Dev Res, 2020 06;81(4):419-436.
PMID: 32048757 DOI: 10.1002/ddr.21648

Neutrophils are essential effector cells of immune system for clearing the extracellular pathogens during inflammation and immune reactions. Neutrophils play a major role in chronic respiratory diseases. In respiratory diseases such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, lung cancer and others, there occurs extreme infiltration and activation of neutrophils followed by a cascade of events like oxidative stress and dysregulated cellular proteins that eventually result in apoptosis and tissue damage. Dysregulation of neutrophil effector functions including delayed neutropil apoptosis, increased neutrophil extracellular traps in the pathogenesis of asthma, and chronic obstructive pulmonary disease enable neutrophils as a potential therapeutic target. Accounting to their role in pathogenesis, neutrophils present as an excellent therapeutic target for the treatment of chronic respiratory diseases. This review highlights the current status and the emerging trends in novel drug delivery systems such as nanoparticles, liposomes, microspheres, and other newer nanosystems that can target neutrophils and their molecular pathways, in the airways against infections, inflammation, and cancer. These drug delivery systems are promising in providing sustained drug delivery, reduced therapeutic dose, improved patient compliance, and reduced drug toxicity. In addition, the review also discusses emerging strategies and the future perspectives in neutrophil-based therapy.