Biomedical subjects

P S Thong

Publications and source records attributed to P S Thong.

5 recordsLinked to original sources

PubMed1999

The onset of atherosclerotic lesion formation in hypercholesterolemic rabbits is delayed by iron depletion.

The theory that iron may play a significant role in atherogenesis by promoting the formation of free radicals is controversial. Previous results using the new technique of nuclear microscopy showed a seven-fold increase in iron concentrations within newly formed atherosclerotic lesions in hypercholesterolemic rabbits compared to healthy artery tissue. In a follow-up time sequence study described here, we show that iron accumulation occurs at the onset of lesion formation. In addition, weekly bleeding decreases the iron uptake into the artery wall and delays the onset of atherogenesis. These results provide direct evidence for a key role of iron in initiating atherogenesis.

Animals↗

PubMed1999

Nuclear microscopy in the life sciences at the National University of Singapore. A review.

The nuclear microscope is now gaining popularity in the field of life sciences. In particular, the combination of proton-induced X-ray emission to measure the elemental concentrations of inorganic elements, Rutherford backscattering spectrometry to characterize the organic matrix, and scanning transmission ion microscopy to provide information on the density and structure of the sample represents a powerful set of techniques that can be applied simultaneously to the specimen under investigation. These techniques are extremely useful for measuring any imbalances in trace elements in localized regions of biological tissue and, as such, can provide unique information on many diseases. In this article, we describe the nuclear microscope and its related ion-beam techniques, and we review the biomedical work carried out using the nuclear microscope in the National University of Singapore.

Animals↗

PubMed1996

Increased iron in the substantia nigra of 6-OHDA induced parkinsonian rats: a nuclear microscopy study.

The trace elemental concentrations, including iron, in the substantia nigra (SN) of a 6-OHDA induced rat model of Parkinson's disease were measured using nuclear microscopy. Only rats that exhibited amphetamine induced rotation of more than 7 turns/min were used. The results showed that the iron levels were significantly increased in the 6-OHDA lesioned SN, compared with the intact contralateral SN, and the SN of normal control rats injected with ascorbic acid, which showed no significant difference in iron levels between injected and non-injected sides. In both 6-OHDA lesioned and ascorbic acid injected SN, there were no alterations in the levels of calcium, magnesium, copper and zinc. In the 6-OHDA lesioned SN there was an almost complete loss of tyrosine hydroxylase positive cells in the SN. These results suggested that the 6-OHDA induced dopaminergic cell death may be related to the increased iron.

Animals↗

PubMed1996

Elemental changes in atherosclerotic lesions using nuclear microscopy.

The roles of iron and other trace metals in the aetiology of heart and brain diseases has been a subject of keen research because of the ability of metal ions to participate in reactions involving free radicals, which have been implicated in many of these diseases. Unstained freeze dried tissue sections from the aorta of New Zealand white rabbits fed with a 1% cholesterol diet for 12 weeks were scanned with a 2 MeV proton beam using the National University of Singapore nuclear microscope facility. Results from 6 test and 4 control rabbits show that there is an average of seven-fold increase in iron and an average of nearly two-fold increase in phosphorus in the atherosclerotic lesion compared with healthy tissue. The increase in iron adds weight to the hypothesis that iron-catalyzed free radical reactions may be associated with the development of atherosclerosis. A depletion of other elements analyzed was seen in the lesion. Elemental mapping also showed the occurrence of granules rich in sodium, chlorine and potassium at the interface between lesioned and non-lesioned tissue.

Animals↗

PubMed1996

A review of nuclear microscopy and applications in medicine.

Nuclear Microscopy, the extraction of analytical information from microscopic regions of a sample using a scanning focused high energy ion beam, has been increasing in popularity recently, despite its technical complexity. The three ion beam related techniques Particle Induced X-ray Emission (PIXE), Rutherford Backscattering Spectrometry (RBS) and Scanning Transmission Ion Microscopy (STIM) can be carried out simultaneously at sub-micron spatial resolutions, and provide structural and quantitative elemental analysis down to the parts per million levels of analytical sensitivity. These techniques are extremely useful for measuring any imbalances in trace elements, including metal ions, in localised regions of biological tissue, and as such can provide unique information on many diseases. In this paper we briefly describe the nuclear microscope and its related ion beam techniques, and briefly review recent work carried out using the nuclear microscope into the degenerative diseases Alzheimer's disease, Parkinson's disease and atherosclerosis.

Alzheimer Disease↗