The murine IgM secretory poly(A) site contains dual upstream and downstream elements which affect polyadenylation.

Regulation of polyadenylation efficiency at the secretory poly(A) site plays an essential role in gene expression at the immunoglobulin (IgM) locus. At this poly(A) site the consensus AAUAAA hexanucleotide sequence is embedded in an extended AU-rich region and there are two downstream GU-rich regions which are suboptimally placed. As these sequences are involved in formation of the polyadenylation pre-initiation complex, we examined their function in vivo and in vitro . We show that the upstream AU-rich region can function in the absence of the consensus hexanucleotide sequence both in vivo and in vitro and that both GU-rich regions are necessary for full polyadenylation activity in vivo and for formation of polyadenylation-specific complexes in vitro . Sequence comparisons reveal that: (i) the dual structure is distinct for the IgM secretory poly(A) site compared with other immunoglobulin isotype secretory poly(A) sites; (ii) the presence of an AU-rich region close to the consensus hexanucleotide is evolutionarily conserved for IgM secretory poly(A) sites. We propose that the dual structure of the IgM secretory poly(A) site provides a flexibility to accommodate changes in polyadenylation complex components during regulation of polyadenylation efficiency.     

Micropropagation of flowering dogwood (Cornus florida) from seedlings

A method for regenerating whole plants from nodal (axillary bud) cultures of seedlings was developed for flowering dogwood (Cornus florida L.). The seed source significantly influenced the rate of proliferation, although cultures initiated from each of the seven mother trees produced some shoots. Woody plant medium (WPM) was superior to either Murashige and Skoog or Schenk and Hildebrandt basal medium. 6-Benzyladenine (BA) at 2.2 or 4.4 m stimulated the generation of significantly more useable shoots (1 cm) compared to all other concentrations (0.5–22.5 m tested. Thidiazuron (TDZ) at 0.6 and 1.1 m supported proliferation, but strongly inhibited shoot elongation. TDZ initiated cultures transferred to medium containing 4.4 m BA produced usable shoots after five additional subcultures. Shoots generated adventitious roots when exposed to either a 12-h pulse of relatively high concentrations (246–1230 m or continuous lower concentrations (0.5–49.0 m of indolebutyric acid (IBA) for longer periods. Microshoots produced the significantly greatest number of roots when subjected to 4.9 m IBA in WPM over a 4-week period. Whole plants were acclimatized to the laboratory conditions and subsequently to the greenhouse. The methodology described here should be useful in a breeding program by supplying multiple copies of unique, recombinant genotypes.     

The Dark Side of Humanity: The Work of Robert Herte and Its Legacy

The Dark Side of Humanity: The Work of Robert Herte and Its Legacy, Robert Parkin. Amsterdam: Harwood Academic Publishers, 1996. 226 pp.     

Molecular characterisation of gibberellin 20-oxidases. Structure-function studies on recombinant enzymes and chimaeric proteins

Gibberellin (GA) 20-oxidases are multifunctional enzymes that catalyse reactions at an important branch point in the GA biosynthetic pathway. These enzymes oxidise the C-20 methyl group of a diterpene carboxylic acid precursor (e.g. GA₁₂) to form an alcohol (in our case GA₁₅-open lactone) and an aldehyde (GA₂₄). The aldehyde is either oxidised to a tricarboxylic acid (GA₂₅) or, with loss of carbon-20 and lactonisation, to a C₁₉-GA (GA₉). This branching is interesting to study, because C₁₉-GA derivatives function as plant hormones in different tissues, whereas the C₂₀-GA tricarboxylic acids have no known function. We have constructed chimaeric proteins by combining a GA 20-oxidase from immature seeds of Cucurbita maxima L., which produces mainly C-20 carboxylic acids, with a 20-oxidase from Marah macrocarpus immature seeds, which forms predominantly CC₁₉-GAs. The cDNAs encoding these two very similar 20-oxidases were digested with restriction endonucleases Van 911. Bcl 1, and Bsa WI, and six chimaeric sequences were produced by recombination of the DNA fragments. The pCM1 -construct was obtained by exchanging nt 303–809 of the Cucurbita cDNA with the homologous DNA from the March 20-oxidase. In pCM2, pCM3, pCM4, pCM5 and pCM6, nt 810–992, nt 993–end, nt 303–992, nt 810–end, and nt 311–end were exchanged, respectively. All constructs were cloned in a pUC18 vector and functionally expressed in E. coli NM522 cells. GA 20-oxidase activity was detectable in cell-lysates from the transformed E. coli, but the extent and kind of conversion depended on the construct. Highest conversion of GA₁₂was found with pCM1 and pCM3, one-tenth of this conversion was observed with pCM5 and pCM6, and one-hundredth was obtained with the hybrid proteins from pCM2 and pCM4. With pCM2 and pCM4, neither the C₁₉-end product, GA₉, nor the C₂₀-end product, GA₂₅-was formed. However, after transformation with constructs pCM1, pCM3, pCM5 or pCM6. GA₉accounted for 30, 40, 60 and 90%, respectively, of the end products formed. Thus, the segments originating from M. macrocarpus conferred upon the chimaeric proteins an increasing ability to direct the biosynthetic flow into C₁₉-GAs in this order. Although GA₂₄is the immediate precursor, much less end products were formed by using this substrate.     

ETHYL ALCOHOL REDUCTION OF SALMONELLA TYPHIMURIUM IN POULTRY FEED

This study was designed to evaluate the effect of ethyl alcohol as a potential treatment for reduction of Salmonella populations in poultry feed. Growth rate of S. typhimurium in tryptic soy broth was significantly reduced by addition of greater than 0.3% volume/volume of ethyl alcohol and growth was completely inhibited by addition of 5% ethyl alcohol. Ethyl alcohol concentrations of 20% volume/weight and greater significantly reduced initial S.typhimurium populations in poultry feed (for 20% treated, 2.31 ± 0.31 vs 3.39 ± 0.29 for untreated; P < 0.05). When feed treatment was administered either before or after inoculation of S. typhimurium with 60% ethyl alcohol or 0.04% buffered propionic acid, populations in feeds treated after inoculation were decreased to a nondetection level (< 1.0 log₁₀ CFU/g) by ethyl alcohol treatment but not by other treatments. Ethyl alcohol treatment may have the potential for reducing Salmonella spp. contamination in poultry feed.     

Biomarkers of marine pollution observed in species of mullet living in two eastern Mediterranean harbours

The activities of enzymes associated with xenobiotic metabolism and or oxidative processes, and the levels of aromatic DNA adducts, have been determined in the livers of grey mullet Oedalechilus labeo and Lisa ramada living in two eastern Mediterranean harbours. Glutathione peroxidase GSH P activity was 2.5 times higher 9 IU g-1 liver and glutathione reductase GSSG R activity was twice as high 2.5 IU g-1 liver in fish from the more polluted harbour at Mersin than in the harbour near Erdemli. Superoxide dismutase SOD activity was 25 lower 4.3 IU g-1 liver in the more polluted harbour. The concentrations of glutathione and malondialdehyde varied both with species and environment by a factor of 2.5-3. DNA adducts in liver were determined by 32P postlabelling. In Oedalechilus labeo in the more polluted harbour, adduct levels were 258 21 adducts per 108 nucleotides mean SE ; two groups of Lisa ramada were distinguished having 261 48 and 30 6 adducts per 108 nucleotides, respectively. The average adduct level in a group of mullet of mixed species in the less polluted harbour was 3.3 2.3 adducts per 108 nucleotides. The results illuminate the ability of mullet to live in contaminated marine environments, and show that enzyme activities and liver DNA adduct levels can serve as indicators of marine pollution.     

Effects of aerial spray volume, coverage, and abamectin on Scirtothrips perseae (Thysanoptera: Thripidae).

Helicopter applications using abamectin in different spray volumes were made against Scirtothrips perseae Nakahara in Ventura County, CA. On small (2.2 m tall) trees, spray coverage on water-sensitive papers was 24-48% and 43-97% for 468 and 935 liter/ha volume treatments, respectively. On large (6.2-8.1 m tall) trees, spray coverage was lower and quite variable, from 1 to 28% and 10 to 70% for 468 and 935 liter/ha treatments, respectively. On small trees, 468, 701, and 935 liter/ha with a high abamectin rate (26 g [AI]/ha) were equally effective against larvae from 13 to 27 d after treatment (DAT). On medium (4.2 m tall) trees, 468 and 935 liter/ha with the high rate were equally effective from 23 to 113 DAT. On large (6.5-8.1 m tall) trees, 468 and 935 liter/ha with a low abamectin rate (13 g [AI]/ha) were ineffective in three tests. In a fourth large (6.8 m tall) tree test, 468 and 935 liter/ha with the high rate were effective at 3 and 37 DAT. In a fifth large (6.2 m tall) tree test, 468-1,403 liter/ha with the high and 935 liter/ha with the low rate were equally effective 2-22 DAT. After all effective treatments, thrips numbers were lower than in controls for 1-3 mo. However, stable and highest reductions in populations were sometimes delayed until 20-23 DAT even when coverage was high. The variability in spray coverage on the lower levels of large trees and the delayed effect may explain inconsistencies in the reporting of or in actual aerial application results.     

El Nuevo Mundo: The Landscape of Latino Los Angeles

El Nuevo Mundo: The Landscape of Latino Los Angeles. Photographs by Camilo José Vergara. National Building Museum, Washington, D.C., December 3, 1998-March 19, 1999; Cooper-Hewitt National Design Museum, New York City, June 25-September 5, 1999; Natural History Museum of Los Angeles County, Los Angeles, January 29–July 16, 2000 (review venue); Graham Foundation, Chicago, November 15,2000–January 25,2001.
ElNuevo Mundo: The Landscape of Latino Los Angeles. Photographs by Camilo José Vergara. Gustavo Leclerc. Michael J. Dear. and J. Dallas Dishman. eds. Los Angeles: Southern California Studies Center, 2000.48 pp.     

KINETICS OF NITRATE,AMMONIUM, AND UREA UPTAKE BY FOUR INTERTIDAL SEAWEEDS FROM NEW ZEALAND1

The competitive ability for N uptake by four intertidal seaweeds, Stictosiphonia arbuscula (Harvey) King et Puttock, Apophlaea lyallii Hook. f. et Harvey, Scytothamnus australis Hook. f. et Harvey, and Xiphophora gladiata (Labillardière) Montagne ex Harvey, from New Zealand is described by the uptake kinetics for NO₃^?, NH₄⁺, and urea. This is the first study to report uptake kinetics for N uptake by a range of southern hemisphere intertidal seaweeds in relation to season and zonation. Species growing at the highest shore positions had higher NO₃^? and urea uptake at both high and low concentrations and had unsaturable NH₄⁺ uptake in both summer and winter. Although there was evidence of some feedback inhibition of V_max for NO₃^? uptake by Stictosiphonia arbuscula growing at the lower vertical limits of its range, rates were high compared with species growing lower on the shore. Our results highlight the superior competitive ability for N uptake of certain high intertidal seaweeds, and consistent with our previous findings we can conclude that intertidal seaweeds in southeast New Zealand are adapted to maximizing N acquisition in a potentially N‐limiting environment.