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1.
Summary. Positron emission tomography (PET) is a 3-dimensional imaging technique that has undergone tremendous developments during
the last decade. Non-invasive tracing of molecular pathways in vivo is the key capability of PET. It has become an important tool in the diagnosis of human diseases as well as in biomedical
and pharmaceutical research. In contrast to other imaging modalities, radiotracer concentrations can be determined quantitatively.
By application of appropriate tracer kinetic models, the rate constants of numerous different biological processes can be
determined. Rapid progress in PET radiochemistry has significantly increased the number of biologically important molecules
labelled with PET nuclides to target a broader range of physiologic, metabolic, and molecular pathways. Progress in PET physics
and technology strongly contributed to better scanners and image processing. In this context, dedicated high resolution scanners
for dynamic PET studies in small laboratory animals are now available. These developments represent the driving force for
the expansion of PET methodology into new areas of life sciences including food sciences. Small animal PET has a high potential
to depict physiologic processes like absorption, distribution, metabolism, elimination and interactions of biologically significant
substances, including nutrients, ‘nutriceuticals’, functional food ingredients, and foodborne toxicants. Based on present
data, potential applications of small animal PET in food sciences are discussed. 相似文献
2.
Pawelke B 《Amino acids》2005,29(4):377-388
Summary. Substances of various chemical structures can be labelled with appropriate positron emitting isotopes and applied as tracer
compounds in PET examinations. Using dynamic data acquisition protocols, time-activity curves of radioactivity uptake in organs
can be derived and the measurements of tissue tracer concentrations can be translated into quantitative values of tissue function.
However, analysis of metabolites of these tracers regarding their nature and distribution in the living organism is an essential
need for the quantitative analysis of PET measurements. In addition, metabolite analysis contributes to the interpretation
of the images obtained as well as to the identification of pathological changes in metabolic pathways. This paper reports
on representative examples of radiolabelled compounds which might be of importance in food science (e.g., amino acids, polyphenols,
and model compounds for advanced glycation end products (AGEs)). Typical procedures of analysis (radio-HPLC, radio-TLC) including
pre-analytical sample preparation are described. Specific challenges of the method, e.g., trace amounts of radiolabelled compounds
and the influence of the often very short half-lives of positron-emitting nuclides used are highlighted. Representative results
of analyses of plasma, urine, and tissue samples are presented and discussed in terms of the metabolic fate of the tracers. 相似文献
3.
Summary. Resveratrol (3,4′,5-trihydroxy-trans-stilbene) is a naturally occurring phytoalexin and polyphenol existing in grapes and various other plants, and one of the
best known ‘nutriceuticals’. It shows a multiplicity of beneficial biological effects, particularly, by attenuating atherogenic,
inflammatory, and carcinogenic processes. However, despite convincing evidence from experimental and clinical studies, data
concerning the role of resveratrol and other members of the large polyphenols family for human health is still a matter of
debate. One reason for this is the lack of suitable sensitive and specific methods, which would allow direct assessment of
biodistribution, biokinetics, and the metabolic fate of these compounds in vivo. The unique features of positron emission tomography (PET) as a non-invasive in vivo imaging methodology in combination with suitable PET radiotracers have great promise to assess quantitative information on
physiological effects of polyphenols in vivo. Herein we describe the radiosynthesis of an 18F-labelled resveratrol derivative, 3,5-dihydroxy-4′-[18F]fluoro-trans-stilbene ([18F]-1), using the Horner-Wadsworth-Emmons reaction as a novel radiolabelling technique in PET radiochemistry for subsequent functional
imaging of polyphenol metabolism in vivo. In a typical “three-step/one-pot” reaction, 18F-labelled resveratrol derivative [18F]-1 could be synthesized within 120–130 min including HPLC separation at a specific radioactivity of about 90 GBq/μmol. The radiochemical
yield was about 9% (decay-corrected) related to [18F]fluoride and the radiochemical purity exceeded 97%. First radiopharmacological evaluation included measurement of biodistribution
ex vivo and positron emission tomography (PET) studies in vivo after intravenous application of [18F]-1 in male Wistar rats using a dedicated small animal PET camera with very high spatial resolution. Concordantly with data on
bioavailability and metabolism of native resveratrol from the literature, these investigations revealed an extensive uptake
and metabolism in the liver and kidney, respectively, of [18F]-1. This study represents the first investigation of polyphenols in vivo by means of PET. 相似文献
4.
Summary. Lipid-protein adducts are formed during oxidative and nitrative stress conditions associated with increasing lipid and protein
oxidation and nitration. The focus of this review is the analysis of interactions between oxidative-modified lipids and proteins
and how lipid nitration can modulate lipid-protein adducts formation. For this, two biologically-relevant models will be analysed:
a) human low density lipoprotein, whose oxidation is involved in the early steps of atherogenesis, and b) α-synuclein/lipid
membranes system, where lipid-protein adducts are being associated with the develop of Parkinson disease and other synucleinopathies. 相似文献
5.
R. M. L. McKAY † G. R. PALMER X. P. MA D. B. LAYZELL B. T. A. McKEE 《Plant, cell & environment》1988,11(9):851-861
Abstract. Positron emission tomography (PET) has been utilized to obtain dynamic images of long distance nutrient translocation in plants. Positron emitting 18 F, produced by a Van de Graaff accelerator using the reaction 18 O(p,n)18 F, was fed in solution to excised stems of Glycine max positioned vertically in a large-aperture PET detector system. Images of tracer activity were recorded with a time resolution of 0.5 min and a spatial resolution of 4 mm. Maximum tracer activities at stem sites were obtained within 3 min of the pulse feed. A model is presented enabling evaluation of regional values for tracer flow, tracer binding, flow speed and flow volume. Analysis of data for one stem position yielded a flow volume of 2.1mm3 min−1 and a flow speed of 36cm min−1 . Comparison with the distribution of 14 C-inulin, which was simultaneously fed to the cut stems, indicates the 18 F is suitable for use as an apoplastic tracer; 92% of the tracer activity accumulated in the leaves. The fraction of 18 F that remained bound was most concentrated at stem nodal regions, an observation consistent with the existence of transfer cells at these sites. Advantages and limitations of PET applied to plant physiological investigations are discussed. 相似文献