John L. Martin

Immunologic responses of mice fed diets supplemented with selenite selenium.

Summary These experiments indicate that dietary Se at levels above that generally accepted as nutritionally adequate (0.1 ppm) enhances the primary immune response in mice as measured by the PFC test and by hemagglutination.

Injectable Selenium: Effect on the Primary Immune Response of Mice

Summary Sodium selenite administered to mice ip (ca. 5 μg Se) enhances the primary immune response to the sheep red blood cell antigen. Enhancement of the primary immune response is greatest when Se is administered prior to or simultaneously with the sheep red blood cell antigen.

Separate elution by ion-exchange chromatography of some biologically important selenoamino acids☆

Abstract Ion-exchange chromatographic procedures have been described which permit the separate elution of selenocystine, selenomethionine, selenocystathionine, Se -methylselenocysteine and selenohomocystine from their sulfur analogs and from other amino acids in a mixture. These procedures have been used to characterize the selenoamino acids present in the seeds of certain selenium accumulator plants.

Use of 75Se-selenite for the study of selenium metabolism in Astragalus

Abstract Selenium metabolism in Se-accumulating species of Astragalus and in related nonaccumulators was studied by supplying 75Se-labeled selenite directly to leaves and racemes excised from plants growing in their natural habitat. Analysis of the ethanol extracts by ion-exchange chromatography gave results comparable to earlier work with species of these plants grown from seed in the laboratory. Scans of the column effluents from accumulators showed radioactive peaks at the position of Se-methylselenocystein; for several of the species, peaks were noted at the position of selenocystathionine. Nonaccumulators showed either very little or no radioactivity associated with these compounds. Where nonradioactive selenocystathionine was present, its sulfur analog, cystathionine, could not be detected. Field use of 75Se-selenite offers a convenient biochemical method for a widespread metabolic and taxonomic survey of this large genus of plants.

TISSUE SELENIUM LEVELS AND GROWTH RESPONSES OF MICE FED SELENOMETHIONINE, SE-METHYLSELENOCYSTEINE OR SODIUM SELENITE

Abstract Mice fed diets containing selenomethionine at a level of 20 ppm selenium and raised to 30 ppm selenium at 3 weeks on experiment showed (1) delayed response to selenium toxicity, (2) slow recovery from the toxicity after removal of selenium from the diet and (3) relatively high deposition and retention of tissue selenium. These data suggest that selenomethonine initially becomes incorporated in to the primary structure of proteins and as such is not particularly toxic. However, upon its slow removal from protein, selenomethionine becomes toxic by forming selenium IV compounds through a pathway similar to that followed by methionine. Mice fed diets containing sodium selenite or Se-methylselenocysteine at the same level of selenium as the selenomethionine diet showed (1) immediate response to selenium toxicity (2) rapid recovery from the toxicity after removal of selenium from the diet and (3) relatively low deposition and relatively rapid depletion of tissue selenium. These data suggest that sodium...

ASSIMILATION, DISTRIBUTION, AND METABOLISM OF (75Se)-SELENITE, SELENATE, AND SELENOAMINO ACIDS BY ESCHERICHIA COLI

Abstract Assimilation of selenium (Se) by Escherichia coli as (75Se)-selenite, selenate, selenomethionine, selenocystine and Se‒CH3-selenocystine revealed that (a) selenoamino acids from a culture media are more completely assimilated than selenite or selenate and (b) that the amount of selenite is assimilated three to four times selenate. Most (>95%) of the Se assimilated by E. coli could not be solubilized by sonication and ethanol extraction but much (28% to 70%) of the Se, except Se from selenomethionine, was removed by alkaline dialysis. Se from selenocystine and from Se‒CH3-selenocystine dialyzed from intact cells, whereas Se from selenite and selenate did not. Dialyzable Se is that Se probably present in selenotrisulfide (R‒S‒Se‒S‒R) bonds or bound nonspecifically. Analysis of the soluble Se metabolites from selenite, selenate, selenomethionine and selenocystine showed that E. coli produces at least one major metabolic product common to all substrates which upon chromatography appeared to be seleno...