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Biomedical subjects

L Bogorad

Publications and source records attributed to L Bogorad.

158 records · Page 9Linked to original sources
PubMed1970

Evidence for variation in the quantity of DNA among plastids of Acetabularia.

The DNA content of individual plastids of the giant unicellular algae Acetabularia mediterranea, and Polyphysa cliftoni was studied. Four methods were used for localizing DNA: acridine orange staining, radioautography following actinomycin D-(3)H treatment, electron microscopy of thin tissue sections, and electron microscopy of osomotically disrupted plastids. With each method, DNA was readily detected in 20-35% of plastids, but no DNA was observed in the remaining 65-80%. The results further showed that in those plastids with detectable DNA the amount of DNA present was variable. The sensitivity and reliability of the localization methods are discussed, and the possible implications of these findings are considered.

Autoradiography↗
PubMed1968

Inhibition of the formation of photosynthetic enzymes by inhibitors of photosynthesis.

It has been shown previously that an increase in ribulose diphosphate carboxylase activity occurs upon brief illumination of leaves of dark-grown Zea mays plants; an increase in ribose 5-phosphate isomerase occurs after prolonged illumination. Both of these responses to illumination are inhibited by chloramphenicol.The administration of p-chlorophenyldimethylurea, an inhibitor of photosynthesis, to etiolated maize does not affect the normal early rise in ribulose diphosphate carboxylase activity when the leaves are illuminated but does block the increase in ribose 5-phosphate isomerase. This pattern of response suggests that photosynthetic activity is required for the increase in isomerase-perhaps products of photosynthesis induce isomerase synthesis-but that the level of ribulose diphosphate carboxylase is controlled by other processes. Chlorophyll formation (as has been shown by others) is slightly suppressed by the inhibitor; levels of total soluble leaf protein appear to be unaffected.Salicylaldoxime, which is a more general inhibitor of metabolism than p-chlorophenyldimethylurea, arrests the normally observed increases of ribulose diphosphate carboxylase, ribose 5-phosphate isomerase, and chlorophyll during illumination of dark-grown maize. The level of soluble leaf protein is also lower in leaves treated with this compound.

Journal Article↗
PubMed1968

delta-Aminolevulinic Acid Transaminase in Chlorella vulgaris.

An enzyme catalyzing the formation of delta-aminolevulinic acid by transamination of gamma,delta-dioxovaleric acid with l-alpha-alanine, l-glutamic acid, or l-phenylalanine has been detected in extracts of Chlorella vulgaris. The activity of this enzyme does not appear to parallel changes in chlorophyll content in a Chlorella mutant which requires light for chlorophyll production. The role of this enzyme in delta-aminolevulinic acid metabolism in plants is not clearly understood.

Journal Article↗
PubMed1967

Early effects of illumination on the activity of some photosynthetic enzymes.

Leaves of dark-grown corn (Zea mays) were illuminated for periods ranging from 3 minutes to 12 hours. The changes in the activities of ribose-5-phosphate isomerase, ribulose-5-phosphate kinase, and ribulose-1,5-diphosphate carboxylase were followed.The activity of ribose-5-phosphate isomerase did not change significantly until between 12 and 24 hours of illumination. An increase in ribulose-5-phosphate kinase activity occurred after a lag of about 6 hours. The increase in carboxylase activity began after 3 minutes of illumination and increased until after 3 to 6 hours in the light, after which it began to decline. The increases in these enzymes appear to be the result of protein synthesis.

Journal Article↗
PubMed1967

(Minus) S-adenosyl-L-methionine-magnesium protoporphyrin methyltransferase, an enzyme in the biosynthetic pathway of chlorophyll in Zea mays.

The enzyme (-) S-adenosyl-L-methionine-magnesium protoporphyrin methyltransferase, which catalyzes the transfer of the methyl group from (-) S-adenosyl-L-methionine to magnesium protoporphyrin to form magnesium protoporphyrin monomethyl ester, has been detected in chloroplasts isolated from Zea mays. Zinc protoporphyrin and free protoporphyrin also act as substrates in the system, although neither one is as active as magnesium protoporphyrin. THE FOLLOWING SCHEME OF CHLOROPHYLL SYNTHESIS IN HIGHER PLANTS IS PROPOSED: delta-aminolevulinic acid --> --> --> protoporphyrin --> magnesium protoporphyrin --> magnesium protoporphyrin monomethyl ester --> --> --> chlorophyll a.

Alkylation↗
PubMed1967

Control of chlorophyll production in rapidly greening bean leaves.

The possible involvement of nucleic acid and protein synthesis in light-regulated chlorophyll formation by rapidly greening leaves has been studied.Removing leaves from illumination during the phase of rapid greening results in a reduction in the rate of pigment synthesis; cessation occurs within 2 to 4 hours. Etiolated leaves which exhibit a lag in pigment synthesis when first placed in the light do not show another lag after a 4 hour interruption of illumination during the phase of rapid greening.Actinomycin D, chloramphenicol, and puromycin inhibit chlorophyll synthesis when applied before or during the phase of rapid greening. Application of delta-amino-levulinic acid partially relieves the inhibition by chloramphenicol.It is suggested that light regulates chlorophyll synthesis by controlling the availability of delta-aminolevulinic acid, possibly by mediating the formation of an enzyme of delta-aminolevulinate synthesis. This process may result from gene activation or derepression; the involvement of RNA synthesis of some sort is suggested by the inhibitory effect of actinomycin D on chlorophyll production by rapidly greening leaves.

Journal Article↗
PubMed1967

Studies on the regeneration of protochlorophyllide after brief illumination of etiolated bean leaves.

The effects of various inhibitors of nucleic acid and protein synthesis on protochlorophyllide synthesis in dark-grown Phaseolus vulgaris var. Red Kidney have been studied. Actinomycin D, chloramphenicol, and puromycin inhibit the regeneration of protochlorophyllide holochrome (detected as a 650 mmu absorption peak) in vivo in darkness after photoconversion of endogenous protochlorophyllide a to chlorophyllide a; this inhibition does not occur in similarly treated leaves supplied with delta-aminolevulinic acid.These data suggest that the regeneration of protochlorophyllide results from the synthesis of RNA and enzymes required for the production of delta-aminolevulinate.

Journal Article↗
PubMed1966

Studies on the formation of phycocyanin, porphyrins, and a blue phycobilin by wild-type and mutant strains of Cyanidium caldarium.

The synthesis of chlorophyll a and the bile-pigment and protein moieties of phycocyanin were arrested in illuminated cells of Cyanidium caldarium, strain III-D-2, incubated with chloramphenicol, ethionine, p-fluorophenylalanine, and p-chloromercuribenzoate. Pigment synthesis was similarly retarded in illuminated cells provided with nutrient medium lacking nitrogen.Porphobilinogen, porphyrins, and a blue phycobilin were excreted into the nutrient medium by illuminated and unilluminated cells of wild-type and mutant C. caldarium strains incubated with delta-aminolevulinic acid in darkness. Pigment production from delta-aminolevulinic acid was sensitive to treatment with chloramphenicol and ethionine. Cells of C. caldarium excreted 7 red-fluorescing porphyrins into the suspending medium during incubation with delta-aminolevulinic acid. Three of these porphyrins were identified as uroporphyrin III, coproporphyrin III, and protoporphyrin on the basis of their spectral properties and by paper chromatogaphy with standards. The blue phycobilin was characterized spectrally and compared with biliverdin. The algal phycobilin displayed properties of a pigment with a violin-type structure. The phycobilin may be an immediate precursor of phycocyanobilin, the phycocyanin chromophore, or identical to it.

Eukaryota↗