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Biomedical subjects

E E Conn

Publications and source records attributed to E E Conn.

At least 55 records · Page 3Linked to original sources
PubMed1978

Laetrile toxicity studies in dogs.

Dogs were fed laetrile and fresh, sweet almonds under various conditions. The doses of laetrile were similar to those prescribed for patients with cancer and ranged on a basis of gram to square meter from an equivalent of the oral dose for man to five times this dose. Six of the ten dogs died of cyanide poisoning. One dog recovered, and three dogs, at the time of sacrifice, demonstrated various levels of neurologic impairment, ranging from difficulty in walking to coma. These studies demonstrate that oral laetrile is highly toxic when taken with some common table foods. We predict that there will be an increased incidence of cyanide poisoning in man as laetrile becomes more readily available.

Administration, Oral↗
PubMed1978

Presence of the cyanogenic glucoside dhurrin in isolated vacuoles from sorghum.

Large numbers of vacuoles (10(6)-10(7)) have been isolated from Sorghum bicolor protoplasts and analyzed for the cyanogenic glucoside dhurrin. Leaves from light-grown seedlings were incubated for 4 hours in 1.5% cellulysin and 0.5% macerase to yield mesophyll protoplasts which then were recovered by centrifugation, quantitated by a hemocytometer, and assayed for cyanogenic glucosides. Mature vacuoles, released from the protoplasts by osmotic shock, were purified on a discontinuous Ficoll gradient and monitored for intactness by their ability to maintain a slightly acid interior while suspended in an alkaline buffer as indicated by neutral red stain. Cyanide analysis of the protoplasts and the vacuoles obtained there from yielded equivalent values of 11 mumoles of cyanogenic glucoside dhurrin per 10(7) protoplasts or 10(7) vacuoles. This work supports an earlier study from this laboratory which demonstrated that the vacuole is the site of accumulation of the cyanogenic glucoside in Sorghum.

Journal Article↗
PubMed1977

Subcellular localization of the cyanogenic glucoside of sorghum by autoradiography.

The use of microautoradiography at the electron microscopic level indicates that the vacuole is the site of accumulation of the cyanogenic glucoside of Sorghum bicolor. When a specific biosynthetic precursor of dhurrin, p-hydroxy[3,5-(3)H]phenylacetaldoxime, was used, 90% of the tritium label was recovered in the vacuoles of tissue prepared for microautoradiography. l-[3,5-(3)H]Tyrosine and d-[1-(3)H(N)]glucose, nonspecific precursors of dhurrin, of differing solubilities and biosynthetic capacity, were also fed to the shoots. The data obtained from these controls indicated that the high recovery of label in the vacuole of aldoxime-fed shoots was not indicative simply of the size of the vacuole, nor was it a result of movement of labeled compounds during preparation of the tissue for electron microscopy. The problem of movement of these labeled compounds during dehydration of tissue was dramatically reduced by chemical dehydration in 2,2-dimethoxypropane in less than 30 minutes rather than with routine dehydration in acetone or alcohol series for 24 hours.

Journal Article↗
PubMed1977

Localization of Cinnamic Acid 4-Monooxygenase and the Membrane-bound Enzyme System for Dhurrin Biosynthesis in Sorghum Seedlings.

The localization of three monooxygenase (hydroxylase) enzyme systems which occur in dark-grown seedlings of Sorghum bicolor has been studied. Cinnamic acid 4-hydroxylase (CAH) (trans-cinnamate 4-monooxygenase, EC 1.14.13.11), which has been increasingly utilized in plants as a marker for the endoplasmic reticulum, migrated with that fraction in continuous and discontinuous sucrose gradients. When 10 mm MgCl(2) was used to shift the density banding of the marker enzyme, NADPH cytochrome c reductase, from 1.12 to 1.17 g/cm(3), the CAH activity was displaced as well.The membrane-bound enzyme system involved in the biosynthesis of the cyanogenic glucoside dhurrin was also shown to be closely associated with the endoplasmic reticulum. This system contains hydroxylases capable of hydroxylating tyrosine to form N-hydroxytyrosine and hydroxylating p-hydroxyphenylacetonitrile to form p-hydroxy-(S)-mandelonitrile.

Journal Article↗
PubMed1975

Stereochemical aspects of the biosynthesis of the epimeric cyanogenic glucosides dhurrin and taxiphyllin.

Dhurrin, I ((S)-p-hydroxymandelonitrile-beta-D-glucopyranoside), and taxiphyllin, II (the (R) epimer), occur in the genera Sorghum and Taxus, respectively. Both derive biosynthetically from L-tyrosine via the hydroxylation of p-hydroxyphenylacetonitrile, III. (3R)- and (3S)-L-[3-3H1]tyrosine, prepared by enzymic hydroxylation of the corresponding phenylalanines, were fed separately to shoots from sorghum seedlings (Sorghum bicolor (Linn) Moench) and cuttings from Japanese Yew (Taxus cuspidata Sieb. and Zucc.) and the appropriate cyanogenic glycoside was isolated (I or II). The fraction of the 3H conserved in I and II was calculated from both parallel feeding and 3H:14C double labeling experiments. The results for II were the reverse of I. Both hydroxylations of III, which give rise to the enantiomeric products (S)- and (R)-p-hydroxymandelonitrile, occurred with retention of configuration. The retention mode is characteristic of hydroxylations at aliphatic carbons catalyzed by mixed function oxidases.

Cyanosis↗
PubMed1975

The in vitro biosynthesis of dhurrin, the cyanogenic glycoside of Sorghum bicolor.

A microsomal fraction from seedlings of Sorghum bicolor (Linn) Moench has been shown to catalyze the conversion of L-tyrosine to p-hydroxymandelonitrile via p-hydroxyphenylacetaldoxime. This transformation is consistent with the general pathway for cyanogenic glycoside biosynthesis proposed on the basis of in vivo experiments. When the microsomal fraction was combined with a protein fraction from the soluble portion of the cell and uridine diphosphate glucose, it was possible to demonstrate the synthesis of the cyanogenic glycoside dhurrin from L-tyrosine.

Aerobiosis↗
PubMed1971

Formation of -cyanoalanine by O-acetylserine sulfhydrylase.

Cell-free extracts of Bacillus megaterium form beta-cyanoalanine (beta-CNA)-(14)C from Na(14)CN and l-cysteine, O-acetyl-l-serine or, to a lesser extent, l-serine. However, the presence of cyanide in the growth medium does not increase the capacity of cell extracts to catalyze the formation of beta-CNA from cysteine and cyanide. The formation of beta-CNA is readily detected in extracts of cells grown in synthetic media with sulfate or l-djenkolic acid as sulfur sources; such cells also exhibit an increased ability to form cysteine when compared with cells grown on cysteine as the sulfur source. beta-CNA formation could not be detected in extracts of cells grown on cysteine as the sulfur source. A 40-fold purification of the O-acetyl-serine sulfhydrylase resulted in the co-purification of the beta-CNA-forming activity. The sulfhydrylase and the beta-CNA-forming activity co-chromatographed on diethyl-aminoethyl cellulose and Sephadex G-100.

Acetates↗