Reactivity and binding of benzo(a)pyrene diol epoxide to poly(dG-dC).(dG-dC) and poly(dG-m5dC).(dG-m5dC) in the B and Z forms

The physical and covalent binding of the carcinogen benzo(a)pyrene-7,8-diol-9,10-oxide (BaPDE) to poly(dG-dC).(dG-dC) and poly(dG-m5dC).(dG-m5dC) in the B and Z forms were studied utilizing absorbance, fluorescence and linear dichroism techniques. In the case of poly(dG-dC).(dG-dC) the decrease in the covalent binding of BaPDE with increasing NaCl concentration (0.1-4 M) as the B form is transformed to the Z form is attributed to the effects of high ionic strengths on the reactivity and physical binding of BaPDE to the polynucleotides; these effects tend to obscure differences in reactivities with the B and Z forms of the nucleic acids. In the case of poly(dG-m5dC).(dG-m5dC) the B-to-Z transition is induced at low ionic strength (2 mM NaCl + 10 microM Co(NH3)6Cl3) and the covalent binding is found to be 2-3-times lower to the Z form than to the B form. Physical binding of BaPDE by intercalation, which precedes the covalent binding reaction, is significantly lower in the Z form than in the B form, thus accounting, in part, for the lower covalent binding. The linear dichroism characteristics of BaPDE covalently bound to the Z and B forms of poly(dG-m5dC).(dG-m5dC) are consistent with nonintercalative, probably external conformations of the aromatic pyrenyl residues.     

Changes in protein phosphorylation during the cell cycle of Chinese hamster ovary cells

The phosphorylation patterns of proteins were examined during the cell cycle of Chinese hamster ovary cells. This was accomplished by labeling synchronized cells at various times with [32P]orthophosphate and separating the proteins by both isoelectric focusing and nonequilibrium pH gradient two-dimensional gel electrophoresis. The most dramatic changes occurred during late G2/M when approximately eight proteins (including vimentin, lamin B, and histones 1 and 3) showed increased phosphorylation. Ten other proteins appeared to be uniquely phosphorylated during late G2/M. Of these 10 proteins, seven were no longer phosphorylated shortly after mitosis. There is also at least one protein which showed a relative decrease in phosphorylation during late G2/M.     

Characteristics of different cytoplasmic and nuclear estrogen receptors appearing with continuous hormonal exposure

Biochemical properties of cytosol estrogen receptor (ERC) and nuclear estrogen receptor (ERN) from rat uteri continuously exposed in vivo to 17 beta-[2,4,6,7-3H] estradiol ( [3H]E2) for 6 h have been studied on the basis of immunological recognition and chromatographic elution patterns. Overall concentrations of ERC and ERN did not change during this time period when receptor-saturating concentrations of [3H]E2 were maintained (Jakesz, R., Kasid, A., and Lippman, M. E. (1983) J. Biol. Chem. 258, 11798-11806); however, biochemical characteristics were different in ERC and ERN after short or long term hormonal exposure. When ERC from rats treated with estradiol for 30 min was applied to HAP or DEAE columns, two different ER binding components were seen. DNA binding in a cell-free system revealed that these binding components represented an activated and a nonactivated ERC population. After long term hormonal exposure (6 h), only one component of ERC with low DNA binding could be shown despite the preservation of an equivalent quantity of cytoplasmic binding activity. This binder does not react with a monoclonal antibody directed against extranuclear estrogen receptor species. These data suggest disappearance of the activated ERC population, with appearance of a new, immunologically nonrecognizable ERC species with 6 h of continuous hormonal exposure. Elution profiles of ERN on HAP chromatography reveal 2 different binding components at 30 min and at 6 h of continuous [3H]E2 exposure. There is an increase of the population eluted at higher molarity after 6 h of in vivo treatment. This later eluting binding component is the major DNA binder in vitro. ERN from both time points are recognized immunologically by monoclonal antibody. After reaction with the antibody, the sedimentation coefficient shifted to 8-9 S on sucrose gradients, but the previously described faster sedimentation of ERN extracted 6 h after injection persisted. We conclude that ER in both cellular compartments undergoes time-dependent alterations, which may be involved in the initiation of hormone action.     

The Role of Surface Water and Light on Differentiation in the Cellular Slime Molds

A key environmental factor in inducing final fruiting body differentiation in the migrating slugs of cellular slime molds is loss of contact with a surface film of water. If the slug tip reaches above the water film, fruiting tends to occur, but if it stays in contact with the surface water, continued migration is favored. Light is effective in promoting fruiting only if the phototactic slugs orient away from surface (as with overhead light) and therefore, only indirectly affects differentiation.     

The Plastids and Pigments of Fresh and Dried Chinese Gooseberries (Actinidia chinensis)

The pericarp of Chinese gooseberries is green due to the presenceof low concentrations of chlorophylls. On a f. wt basis thereis about 1.5 times more tetrapyrollic pigments (chlorophyllsand related compounds) in the outer pericarp than in the innerpericarp, whereas the carotenoid pigment values only showed1.25 times more in the outer than in the inner part of the fruit.The drying of Chinese gooseberries at 40 °C for 40 h resultedin the loss of at least half the tetrapyrollic pigments andof carotenoids. Chlorophylls a and b were converted to chlorophyllides,pheophytins and pheophorbides. Chloroplasts in the outer pericarp are clustered closely aroundthe nucleus and have a well-defined grana and inter-granal membranesystem. In the inner pericarp the chloroplasts are again clusteredaround the nucleus and there is a proliferation of inter-granalmembranes. In dried tissue the limiting membrane of chloroplastswas completely dispersed whereas some of the internal membranesremained intact. Actinidia chinensis Planch., Chinese gooseberry, Kiwi fruit, pigments, chloroplast structure     

Influence of prey species and stages on predatory efficiency and development of two phytoseiid mites

The effect of prey species and the different stages of prey on the predatory efficiency and biology of the phytoseiid mites,Amblyseius gossipi Elbadry andTyphlodromus mangiferus sp. n. was studied. It was found that feeding either predator onTetranychus cucurbitacearum (Sayed) promoted faster development and a higher rate of oviposition than rearing on the twospotted spider mite,T. urticae (Koch). Different stages of both prey species also produced different responses in the biological activities of these predaceous mites.

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Résumé On a étudié l'effet de l'espèce de la proie et de ses différents stades sur l'efficacité et la biologie des acariens phytoseiides,Amblyseius gossipi Elbadry etTyphlodromus mangiferus sp. n. Il a été constaté que l'alimentation des 2 prédateurs avecTetranychus cucurbitacearus (Sayed) assure un dévelopment plus rapide et une fécondité plus élevée que leur élevage surT. urticae (Koch). Les différents stades de ces 2 proies produisent des réponses différentes dans les activités biologiques des 2 acariens prédateurs.

     

The distribution and abundance of species of Danthonia DC on the New England Tablelands (Australia)

The distribution and percent frequency of the 13 species and one variety of Danthonia recorded on the New England Tablelands were examined in a survey of 110 predominantly pastoral sites. The relationships between site factors and the presence and percent frequency of the different Danthonia species were subjected to canonical correlation analysis. Individual species were found to have particular sets of environmental factors associated with their distribution and percent frequency; a fact not well recognized in the past. The most common factor associated with the abundance of Danthonia was either a long time since the last cultivation or no cultivation at all. Other factors such as altitude, drainage, soil parent material, soil texture and total soil phosphorus status were also of some importance. The six species most commonly recorded throughout the New England Tablelands were D. racemosa RBr, D. pilosa RBr, D. laevis J. Vickery, D. linkii Kunth., D. richardsonii Cashmore and D. tenuior (Steud.) Conert. Of these the first three are ecologically wide species. The first two can coexist with other naturalized species under grazing while D. laevis tends to disappear with disturbance. D. linkii and D. richardsonii require fairly narrow habitat conditions but these conditions and consequently these species are common. Both species respond positively to disturbance. Danthonia linkii increases with cultivation and D. richardsonii colonizes eroded soil surfaces. Danthonia tenuior has more restricted requirements and is not so frequent The other seven species and one variety did not occur often enough for detailed study and the occurrence of two of these species, D. carphoides and D. caespitosa must be considered as rare.     

Isozymes of Ipomoea batatas catechol oxidase differ in catalase-like activity.

The amino acid sequences of two isozymes of catechol oxidase from sweet potatoes (Ipomoea batatas) were determined by Edman degradation of BrCN cleavage fragments of the native protein and by sequencing of amplified cDNA fragments. Sequence alignment and phylogenetic analysis of plant catechol oxidases revealed about 80% equidistance between the two I. batatas catechol oxidases and approximately 40--60% to catechol oxidases of other plants. When H(2)O(2) was applied as substrate the 39 kDa isozyme, but not the 40 kDa isozyme, showed catalase-like activity. The structure of the 40 kDa isozyme was modeled on the basis of the published crystal structure of the 39 kDa isozyme [T. Klabunde et al., Nat. Struct. Biol. 5 (1998) 1084]. The active site model closely resembled that of the 39 kDa isozyme determined by crystallography, except for a mutation of Thr243 (40 kDa isozyme) to Ile241 (39 kDa isozyme) close to the dimetal center. This residue difference affects the orientation of the Glu238/236 residue, which is thought to be responsible for the catalase-like activity of the 39 kDa isozyme for which a catalytic mechanism is proposed.