The genus sidastrum E. G. Baker (Malvaceae): A correction

Examination of a Jacquin type reveals an incorrect interpretation in a recent treatment ofSidastrum and requires the publication of the new combinationSidastrum multiflorum as the correct name for the species previously calledS. acuminatum.     

Acid-catalyzed and almond β-d-glucosidase-catalyzed hydrolysis of purin-6-yl 2-deoxy-1-thio-β-d-arabino-hexopyranoside

Hydrolysis of purin-6-yl 2-deoxy-1-thio-β-d-arabino-hexopyranoside (2) to 6-mercaptopurine and 2-deoxy-d-glucose is catalyzed by hydronium ion and almond β-d-glucosidase. The dependence of rate on acidity in water and deuterium oxide indicates that 2 and its conjugate acid undergo hydrolysis via a mechanism that involves a partially rate-limiting proton transfer. Although 2 is ≈103 more reactive than 6-purinyl β-d-glucothiopyranoside (1) in dilute aqueous acid, 1 is a better substrate for almond β-d-glucosidase.     

B chromosome variation in Euphydryas colon (Lepidoptera: Nymphalidae)

Cytogenetic analysis of an Idaho population of the checkerspot butterfly, Euphydryas colon, has revealed considerable inter- and intra-individual variation in chromosome number which turns out to be a classic case of B chromosome variation. The basic chromosome complement of the species is n (, )=31. The A chromosomes were aligned equatorially at mitotic metaphase and metaphase II, and axially at metaphase I, indicating a restriction of centric activity at the first meiotic division. No failure of pairing between homologous A chromosomes was observed and, although a marked asynchrony of chromatid separation was found to be characteristic of mitotic telophase and telophase II, the frequency of macrospermatid formation was low. The B chromosomes were at least partly heterochromatic but exhibited some variation in both pycnosity and size. Mitotically stable B-containing individuals showed a preponderance of unpaired Bs at first metaphase and these divided at either first or second anaphase. The presence of Bs was associated with a heightened production of abnormal spermatids particularly in individuals with high numbers of B chromosomes. Among the 25 individuals sampled, 21 carried from 1–6 B chromosomes, and of these 14 were mitotically stable. In all 7 unstable individuals the mean number of B chromosomes per cell exceeded the modal number. Assuming that the modal number represents the zygotic number, these results suggest that a mechanism to boost the number of B chromosomes exists in males of E. colon.     

Affinity chromatography of tryptophan synthase from Escherichia coli. Systematic studies with immobilized tryptophanol phosphate.

Inhibition studies and affinity chromatography indicate that derivatives of tryptophanol phosphate are suitable ligands for the affinity chromatography of tryptophan synthase. A phenyl group on the spacer arm strengthens the interaction of immobilized tryptophanol phosphate with the enzyme. The alpha 2 beta 2 complex specifically requires the presence of 0.3--0.5 M phosphate ions for binding. The alpha subunit binds in dilute Tris buffer, but its binding is also enhanced by the presence of phosphate ions. The beta 2 subunit binds unspecifically but strongly to the affinity material and to a variety of other immobilized hydrophobic ligands. Binding studies with suspensions of affinity material show that the alpha subunit interacts rapidly and reversibly. Indoleglycerol phosphate and indolepropanol phosphate release bound alpha 2 beta 2 complex and alpha subunit in a competitive manner, indicating that the interaction occurs biospecifically, i.e. via the active site of alpha subunit. L-Serine is a non-competitive inhibitor of binding. These results are discussed with regard to the composite-active-site hypothesis [T. E. Creighton (1970) Eur. J. Biochem, 13, 1--10]. Both the alpha subunit and the alpha 2 beta 2 complex of tryptophan synthase from Escherichia coli can be obtained with high yields and in homogenous form by absorption to the affinity material from partially purified preparations. Elution is achieved with linear gradients either of indolepropanol phosphate or of indoleglycerol phosphate or, in the case of the complex, of L-serine. At the low concentrations of the complex found in crude extracts of wild-type E. coli cells, the unexpectedly high affinity of the beta 2 subunit for hydrophobic ligands leads to partial dissociation of the complex.     

R Plasmids R91 and R91a from Pseudomonas aeruginosa Share Only the Gene for Carbenicillin Resistance

Plasmid R91a of Pseudomonas aeruginosa strain 9169 is homologous with RP1. Plasmid R91 carried by the same strain is related in the Tn1 region but is otherwise unrelated to R91a.     

ULTRASTRUCTURAL DEVELOPMENT OF CAPITATE GLANDULAR HAIRS OF CANNABIS SATIVA L. (CANNABACEAE)

The capitate-sessile and capitate-stalked glands of the glandular secretory system in Cannabis, which are interpreted as lipophilic type glandular hairs, were studied from floral bracts of pistillate plants. These glands develop a flattened multicellular disc of secretory cells, which with the extruded secretory product forms the gland head and the auxiliary cells which support the gland head. The secretory product accumulates beneath a sheath derived from separation of the outer wall surface of the cellular disc. The ultrastructure of secretory cells in pre-secretory stages is characterized by a dense ground plasm, transitory lipid bodies and fibrillar material, and well developed endoplasmic reticulum. Dictyosomes and dictyosome-derived secretory vesicles are present, but never abundant. Secretory stages of gland development are characterized by abundant mitochondria and leucoplasts and by a large vacuolar system. Production of the secretory product is associated with plastids which increase in number and structural complexity. The plastids develop a paracrystalline body which nearly fills the mature plastid. Material interpreted as a secretion appears at the surface of plastids, migrates, and accumulates along the cell surface adjoining the secretory cavity. Extrusion of the material into the secretory cavity occurs directly through the plasma membrane-cell wall barrier.