Biology subjects

Abdul Halim, M.

Publications and source records attributed to Abdul Halim, M..

6 recordsLinked to original sources

bioRxiv2020

Transcriptomic response of Caenorhabditis elegans expressing human Aβ42 gene treated with Salvianolic acid A

Alzheimers disease (AD) is a brain disease attributed to the accumulation of extracellular senile plaques comprising {beta}-amyloid peptide (A{beta}). In this study, a global transcriptomic analysis of the response of transgenic Caenorhabditis elegans worms expressing full length human A{beta}42 gene towards Salvianolic acid A (Sal A) was analysed. Antioxidant response genes, namely gst-4, gst-10, spr-1 and trxr-2, were upregulated. The production of A{beta}42 caused oxidative stress and the antioxidant response genes possibly provide defence to the strain. The gene product of trxr-2 also functionally interacts with the defence system and has a role in life span. Genes involved in replication, reproduction, immune response to microbes and antimicrobial activities were also upregulated. Exposure to Sal A also increased the rate of reproduction of nematodes, and heightened its immunological protection system towards microorganisms. In contrast, genes responsible for locomotion, ligand-gated cation channel, embryonic and postembryonic development, and neuromodulation of chemosensory neurons were significantly down-regulated. As an effector, Sal A might conceivably reduce the movement of the worm by interfering with neuronal transmission and embryonic and post-embryonic development.

bioinformatics↗

bioRxiv2020

Transcriptomic response of an Antarctic yeast Rhodotorula sp. USM-PSY62 to temperature changes

Rhodotorula sp. (USM-PSY62) is a psychrophilic yeast isolated from Antarctic sea ice and it grows optimally at 15 {degrees}C. This study was set up to observe how USM-PSY62 adapted to fluctuations in temperature. During cold adaptation, an elevated transcription of the CorA magnesium transporter gene in USM-PSY62 indicated a higher requirement for magnesium ions in order to gain additional enzyme cofactors or maintain cytoplasmic fluidity. The HepA homologue coding for DNA/RNA helicase was also over-expressed in cold condition possibly to reorganize secondary structures of DNA and RNA. An up-regulation of the catalase gene was also observed reflecting an increment in the concentration of reactive oxygen species and fluctuations in the associated antioxidant system. The YOP1 gene, which encodes a membrane protein associated with protein transport and membrane traffic, was the most down-regulated under cold shock condition. The genes responsible for the structural maintenance of chromosome (SMC) were also down-regulated when the temperature was shifted to 0 {degrees}C. Upon cold shock, the gene for heat shock factor protein 1 (HSF1) was also down-regulated. Hsf1 is a transcriptional regulator which regulate the heat shock responses. Although USM-PSY62 showed some common adaptive strategies as in several other psychrophilic organisms, new mechanisms were also uncovered.

bioinformatics↗

bioRxiv2020

Withania somnifera showed neuroprotective effect and increase longevity in Drosophila Alzheimer's disease model

Alzheimers disease is a complex neurodegenerative disease and is only unique to human. The disease is defined in human brain by the accumulation of amyloid beta in the parenchyma of the brain. Withania somnifera, commonly known as Ashwagandha is an Indian Ayurvedic medicine that has been used for centuries to treat countless range of human health problem. The active compound of Ashwagandha was shown to be beneficial in treating many neurodegenerative diseases including Alzheimers disease (AD). In this study, Drosophila melanogaster AD model was used to study the effect of Ashwagandha on the toxicity of beta amyloid and also the longevity effect of the compound. We found that 20 mg/mL of Ashwagandha was shown to be effective in rescuing the "rough eye phenotype" of AD Drosophila. Furthermore, Ashwagandha also promotes longevity in AD as well as wild-type Drosophila. The results above showed that Ashwagandha could potentially be a potent drug to treat AD as well as maintaining the wellbeing of cells.

pharmacology and toxicology↗

bioRxiv2020

Tocotrienol decreases β-amyloid mediated toxicity in Caenorhabditis elegans model of Alzheimer's disease

Alzheimers disease (AD) is a neurological disease caused by the accumulation of extracellular senile plaques consisting of {beta}-amyloid peptide (A{beta}) in the brain. A transgenic Caenorhabditis elegans which demonstrated paralysis due to the expression of human beta amyloid A{beta}42 gene was used to study the anti-paralysis effect of mixed tocotrienols. The content of the mixed tocotrienols were 12.1% -, 2.7% {beta}-, 18.6% {gamma}-, and 8.1% {delta}-tocotrienols. Mixed tocotrienols significantly delayed the A{beta}-induced paralysis in the transgenic nematode and exhibited anti-oxidant properties towards A{beta}-generated oxidative stress. The mixture also presented potent inhibitory activities against A{beta} aggregation with an IC50 value of 600 ng/ml. It is concluded that mixed tocotrienols could potentially serve as a new therapeutic candidate for AD.

pharmacology and toxicology↗

bioRxiv2020

Effects of salvianolic acid A on β-amyloid mediated toxicity in Caenorhabditis elegans model of Alzheimer's disease

Alzheimers disease (AD) is a brain disease attributed to the accumulation of extracellular senile plaques comprising {beta}-amyloid peptide (A{beta}). In this study, a transgenic Caenorhabditis elegans containing the human beta amyloid A{beta}42 gene which exhibited paralysis when expressed, was used to study the anti-paralysis effect of salvianolic acid A. Various concentrations ranging from 1 g/ml to 100 g/ml of salvianolic acid A were tested and exhibited the highest effect on the worm at the concentration of 100 g/ml. For anti-aggregation effect, 14 g/ml salvianolic acid A (within 4 mg/ml of Danshen) showed a significant level of inhibition of the formation of A{beta} fibrils. An amount of 100 g/ml of salvianolic acid A had the potential in reducing the ROS but did not totally obliterate the ROS production in the worms. Salvianolic acid A was found to delay the paralysis of the transgenic C. elegans, decrease A{beta}42 aggregation and decreased A{beta}-induced oxidative stress.

pharmacology and toxicology↗

bioRxiv2020

Transcriptional analysis of nitrogen fixation in Paenibacillus durus during growth in nitrogen-enriched medium

Paenibacillus durus strain ATCC 35681T is a Gram-positive diazotroph that displayed capability of fixing nitrogen even in the presence of nitrate or ammonium. However, the nitrogen fixation activity was detected only at day 1 of growth when cultured in liquid nitrogen-enriched medium. The transcripts of all the nifH homologues were present throughout the 9-day study. When grown in nitrogen-deficient medium, nitrogenase activities occurred from day 1 until day 6 and the nifH transcripts were also present during the course of the study albeit at different levels. In both studies, the absence of nitrogen fixation activity regardless of the presence of the nifH transcripts raised the possibility of a post-transcriptional or post-translational regulation of the system. A putative SigA box sequence was found upstream of the transcription start site of nifB1, the first gene in the major nitrogen fixation cluster. The upstream region of nifB2 showed a promoter recognisable by SigE, a sigma factor normally involved in sporulation. Significance and Impact of the StudyPaenibacillus durus strain ATCC 35681T is a nitrogen fixing Gram positive bacterium with an unconventional physiological characteristic of being able to fix nitrogen even in the presence of either nitrate or ammonium. It has a total of 6 nifH homologues in its genome. In this study, we analysed the transcriptional levels of the nifH homologues when grown under nitrogen-enriched and nitrogen-depleted medium. Under nitrogen-enriched condition, the nitrogen fixation activity was detected only at day 1 of growth but the transcripts of all the nifH homologues were detected during the course of the study from day 1 until day 9. In nitrogen-deficient condition, nitrogen fixation activities were recorded from day 1 until day 6 and the nifH transcripts were present throughout the study. The absence of nitrogen fixation activity even in the presence of the nifH transcripts raised the possibility of a post-transcriptional or post-translational regulation of the system.

genetics↗