VITAMIN AND GROWTH FACTOR RESEARCH 



in 1941 (43) will serve to illustrate the outstanding role played by 

 investigations with microorganisms. 



A tabulation of vitamins and growth factors discovered, 

 isolated, or synthesized since 1942, together with the test organ- 

 isms employed during their isolation or characterization, is given 

 in Table I. The difficulties in assigning individual names and 

 dates to the discovery of vitamins is obvious especially where, as 

 with folic acid and vitamin B12, approaches from several different 

 directions with different test organisms have been made, and 

 where the specificity of assay procedures has been improved over 

 a period of years by several different investigators. The popular 

 tendency to assign a given scientific advance to a specific individ- 

 ual, although sometimes justified (depending upon the magni- 

 tude of the advance), more often represents an injustice to other 

 workers whose important contributions remain thereby un- 

 acknowledged. So it is with discovery, isolation, and character- 

 ization of the vitamins — never yet a one-man job ! The names 

 associated with the assay methods of Table I, therefore, represent 

 not necessarily the original discoverers of the growth factor but 

 rather the devisers of the first reasonably specific assay pro- 

 cedures that permitted real progress toward isolation and char- 

 acterization of that growth factor. 



PYRIDOXAL AND PYRIDOXAMINE 



Discovery of these two forms of vitamin Be resulted from an 

 attempt to devise a quantitative microbiological method for the 

 determination of pyridoxine, which at that time was considered 

 synonymous with vitamin Be. When lactic acid bacteria were 

 the test organisms and pyridoxine the reference standard, 

 impossibly high values for the "pyridoxine" content of natural 

 materials were obtained (73). Obviously, substances other 

 than pyridoxine were promoting growth in the vitamin Bg- 

 deficient medium. The observation (61) that the growth- 

 promoting activity of pyridoxine increased upon heating with 

 the growth medium and that pyridoxine itself was essentially in- 

 active in promoting growth (61,73) suggested that closely related 



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