The influence of glutathione upon light-induced high-amplitude swelling and lipid peroxideformation of spinach chloroplasts

Light-induced high-amplitude swelling and lipid peroxide formationof isolated spinach chloroplasts were studied with regard tothe supposed analogy to lipid peroxide dependent disintegrationof mitochondria. Addition of glutathione to chloroplasts exposedto light results in excessive stimulation of swelling, whereasthe rate of lipid peroxide accumulation is significantly decreased.In the dark, glutathione does not show any substantial effect.Glutathione apparently serves as a donor substrate for the reductionof lipid peroxides in chloroplasts. The increased water uptakeof chloroplasts in the presence of glutathione cannot be conditionedby peroxidation of membrane lipids, as could be demonstratedfor mitochondria in similar experiments. Evidence is presentedthat a glutathione peroxidase activity is present in spinachhomogenate. The enzyme system, however, behaves quite differentlyfrom glutathione peroxidase of animal sources in respect tostability and pH dependency of the reaction rate (Received October 24, 1970; )     

Enzymes of de novo Pyrimidine Biosynthesis in Babesia rodhaini1

ABSTRACT. The pathway of de novo pyrimidine biosynthesis in the rodent parasitic protozoa Babesia rodhaini has been investigated. Specific activities of five of the six enzymes of the pathway were determined: aspartate transcarbamylase (ATCase: E.C. 2.1.3.2): dihydroorotase (DHOase: E.C. 3.5.2.3): dihydroorotate dehydrogenase (DHO-DHase: E.C. 1.3.3.1); orotate phosphoribosyltransferase (OPRTase: E.C. 2.4.2.10); and orotidine-5′-phosphate decarboxylase (ODCase: E.C. 4.1.1.23). Michaelis constants for ATCase, DHO-DHasc. OPRTase, and ODCase were determined in whole homogenates. Several substrate analogs were also investigated as inhibitors and inhibitor constants determined. N-(phosphonacetyl)-L-aspartate was shown to be an inhibitor of the ATCase with an apparent K, of 7μM. Dihydro-5-azaorotate inhibited the DHO-DHase (K, 16 μM) and 5-azaorotate (K_i, 21 μM) was an inhibitor of the OPRTase. The UMP analog, 6-aza-UMP (K_i, 0.3 μM) was a potent inhibitor of ODCase, while lower levels of inhibition were found with the product. UMP (K_i, 120 μM) and the purine nucleotide, XMP (K₁, 95 μM). Additionally, menoctone, a ubiquinone analog, was shown to inhibit DHO-DHase.     

The genus Rhanterium (Asteraceae: Inuleae)

WIKLUND, A., 1986. The genus Rhanterium (Aateraceae: Inuleae) . This revision of the genus Rhanterium Desf. of the /nu/a-group in the Asteraceae: Inuleae, subtribe Inulinae, is based on studies of herbarium material. The genus is distributed over western North Africa, the Arabian peninsula, Iraq and Iran. Three species are recognized: R. adpressum Coss. & Durieu, R. epapposum Oliver and R. suaveolens Desf. A fourth previously accepted species, R. intermedium Coss. & Durieu ex Pomel, is here considered to be composed of hybrids between R. adpressum and R. suaveolens. A laxonomical recognition of these hybrids is not found to be justified. The morphology, phylogeny and phytogeography of the species are discussed and a cladogram of the genus is proposed.     

Determination of Affinity and Activity of Ligands at the Human Neuropeptide Y Y4 Receptor by Flow Cytometry and Aequorin Luminescence

Fluorescence-labeled neuropeptide Y (NPY) has been used in flow cytometric binding assays for the determination of affinity constants of NPY Y₁, Y₂, and Y₅ receptor ligands. Because the binding of fluorescent NPY is insufficient for competition studies at the human Y₄ receptor (hY₄R), we replaced Glu-4 in hPP with Lys for the derivatization with cyanine-5. Because cy5-[K⁴]hPP has high affinity (K_d 5.6 nM) to the hY₄R, it was used as a probe in a flow cytometric binding assay. Specific binding of cy5-[K⁴]hPP to hY₄R was visualized by confocal microscopy. The hY₄R, the chimeric G protein G_qi5 and mitochondrially targeted apoaequorin were stably coexpressed in CHO cells. Aequorin luminescence was quantified in a microplate reader and by a CCD camera. By application of these methods 3-cyclohexyl-N-[(3-1H-imidazol-4-ylpropylamino)(imino)methyl]propanamide (UR-AK49) was discovered as the first nonpeptidic Y₄R antagonist (pK_i 4.17), a lead to be optimized in terms of potency and selectivity.     

The genus Rhanteriopsis (Asteraceae–Inuleae)

The genus Rhanteriopsis Rauschert, belonging to the f/iula–group of the Asteraceae–Inuleae, is monographed in a study based on herbarium material. Rhanteriopsis has a disjunct distribution with a westerly occurrence in Lebanon and Syria and an easterly distribution in Iran and Iraq along the Iranian border. Eour species are recognized: R. hombvcina (Boiss. & Hausskn.) Rauschert, R. lanuginosa (DC.) Rauschert, R. microcephala (Boiss.) Rauschert and R. puberula (Boiss. & Hausskn.) Rauschert. The morphology and phytogeography of the genus are discussed, a cladogram is proposed and a taxonomic treatment is provided.     

The Effect of 3-Aminobenzamide on Thymidine Incorporation in Ultra-Violet Irradiated Chick Pigment Epithelium Cells

The addition of 3-aminobenzamide (3-AB) to cultures of chick embryo pigmented epithelium rescues these cells after high doses of ultraviolet treatment. The addition of 3-AB prevents cells from losing pre-formed protein and DNA and stimulates thymidine incorporation by the cells after ultraviolet irradiation. Since 3-AB is an inhibitor of poly (ADP) ribosylation, these observations support the conclusion that death of these cells after ultra-violet irradiation depends upon poly (ADP) ribosylation and may be an apoptotic response.