Radioactive Isotopes in Soils and Their Impact on Plant Growth

Mechanisms of ethylene biosynthesis and response in plants

Essays in Biochemistry ◽

10.1042/bse0580061 ◽

2015 ◽

Vol 58 ◽

pp. 61-70 ◽

Cited By ~ 11

Author(s):

Paul B. Larsen

Keyword(s):

Plant Growth ◽

Growth And Development ◽

Ethylene Biosynthesis ◽

Unsaturated Hydrocarbon ◽

Flower Senescence ◽

Detailed Knowledge ◽

Plant Growth And Development ◽

Step Process ◽

Ethylene Response ◽

Ethylene Signalling

Ethylene is the simplest unsaturated hydrocarbon, yet it has profound effects on plant growth and development, including many agriculturally important phenomena. Analysis of the mechanisms underlying ethylene biosynthesis and signalling have resulted in the elucidation of multistep mechanisms which at first glance appear simple, but in fact represent several levels of control to tightly regulate the level of production and response. Ethylene biosynthesis represents a two-step process that is regulated at both the transcriptional and post-translational levels, thus enabling plants to control the amount of ethylene produced with regard to promotion of responses such as climacteric flower senescence and fruit ripening. Ethylene production subsequently results in activation of the ethylene response, as ethylene accumulation will trigger the ethylene signalling pathway to activate ethylene-dependent transcription for promotion of the response and for resetting the pathway. A more detailed knowledge of the mechanisms underlying biosynthesis and the ethylene response will ultimately enable new approaches to be developed for control of the initiation and progression of ethylene-dependent developmental processes, many of which are of horticultural significance.

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Bioavailability of Vitamin B12

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000041 ◽

2010 ◽

Vol 80 (45) ◽

pp. 330-335 ◽

Cited By ~ 28

Author(s):

Lindsay Helen Allen

Keyword(s):

Vitamin B12 ◽

Vitamin B12 Deficiency ◽

The Elderly ◽

Radioactive Isotopes ◽

Animal Source Foods ◽

Dietary Requirements ◽

In Vivo Labeling ◽

B12 Deficiency ◽

Vitamin B12 Malabsorption

Vitamin B12 deficiency is common in people of all ages who consume a low intake of animal-source foods, including populations in developing countries. It is also prevalent among the elderly, even in wealthier countries, due to their malabsorption of B12 from food. Several methods have been applied to diagnose vitamin B12 malabsorption, including Schillings test, which is now used rarely, but these do not quantify percent bioavailability. Most of the information on B12 bioavailability from foods was collected 40 to 50 years ago, using radioactive isotopes of cobalt to label the corrinoid ring. The data are sparse, and the level of radioactivity required for in vivo labeling of animal tissues can be prohibitive. A newer method under development uses a low dose of radioactivity as 14C-labeled B12, with measurement of the isotope excreted in urine and feces by accelerator mass spectrometry. This test has revealed that the unabsorbed vitamin is degraded in the intestine. The percent bioavailability is inversely proportional to the dose consumed due to saturation of the active absorption process, even within the range of usual intake from foods. This has important implications for the assessment and interpretation of bioavailability values, setting dietary requirements, and interpreting relationships between intake and status of the vitamin.

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