Author Index Volume 71 2004

Authors Index

Author Index Volume 71 2004     

Base Cation and Nitrogen Budgets for a Mixed Hardwood Catchment in South-central Ontario

There is growing concern that available base cation pools in soil are declining in eastern North America and that some forests are approaching nitrogen (N) saturation due to the combined effects of acid deposition and harvesting. To assess these concerns, elemental mass balances for calcium (Ca), magnesium (Mg), potassium (K), and N were conducted over a 17-year period in a representative mixed hardwood forest (HP4) in the Muskoka-Haliburton region in central Ontario, Canada. On average, 76% of the N measured in bulk deposition, which is a conservative estimate of total N deposition, was retained in HP4, with tree uptake accounting for over half of the retained N. Year-to-year variations in annual NO₃ export were affected by climate variations, although the low annual NO₃-N concentrations (80–156 g/L) suggest that HP4 is not approaching N saturation. Losses of Ca, Mg, and K in stream export plus accumulation in trees (more than 12 cm in diameter at breast height) exceeded inputs in deposition by 296, 76.2, and 53.6 kg/ha, respectively, over the 17-year period. Inclusion of mineral weathering estimates obtained using PROFILE, zirconium (Zr) depletion, and total analysis correlation failed to balance Ca losses from HP4, and calculations indicate that between 98 and 145 kg/ha (depending on mineral weathering estimate) was lost from the soil exchangeable pool between 1983 and 1999. These losses were supported by repeated field measurements, which showed that the exchangeable Ca concentrations and soil pH decreased over the 17-year period, particularly in the upper soil horizons. When mineral weathering estimates are included, mass balance calculations generally indicated that there was no net loss of Mg and K from HP4, which was confirmed by our soil measurements. At present, there is sufficient Ca in the soil exchangeable pool to sustain forest growth at HP4; however, continued losses of Ca due to leaching and harvesting at the present rate may ultimately threaten the health and productivity of the forest within just a few decades.     

Non-geographically based population structure of South Pacific sperm whales: dialects, fluke-markings and genetics

1. This study addresses the issue of structure in sperm whale ( Physeter macrocephalus Linnaeus) populations and whether it is geographically based.
2. During a survey around the South Pacific Ocean, we collected sloughed skin for genetic analyses, recorded coda vocalizations, and photographed fluke markings.
3. Groups of female and immature sperm whales had characteristic mitochondrial haplotypes, coda repertoires, and fluke-mark patterns, but there was no clear geographical structure in any of these attributes.
4. However, similarities of coda repertoire and mitochondrial haplotype distribution were significantly correlated among pairs of groups in a manner that was not geographically based. There was also a significant canonical correlation coefficient between coda repertoire and fluke-mark patterns.
5. These results suggest that attributes (such as vocal repertoire and techniques of predator defence) which are acquired matrilineally, and probably culturally, are conserved during the fission and dispersal of groups.     

Variations in Red Snapper oocyte development and spawning in relation to environmental and habitat parameters

Environmental Biology of Fishes - The reproductive biology of Red Snapper, Lutjanus campechanus, is well understood, but there is little information on the impact of environmental, climatic, and...     

The mtDNA mutation spectrum of the progeroid Polg mutator mouse includes abundant control region multimers

Polg mtDNA mutator mice are important models for investigating the role of acquired mtDNA mutations in aging. Despite extensive study, there remains little consensus on either the etiology of the progeroid phenotype or the mtDNA mutation spectrum induced by disrupted polymerase-γ function. To investigate the latter, we have developed a novel, pragmatic approach we term "Mito-seq," applying next-generation sequencing to enriched, native mtDNA. Regardless of detection parameters we observed an increase of at least two orders of magnitude in the number of mtDNA single nucleotide variants in Polg mutator mice compared to controls. We found no evidence for the accumulation of canonical mtDNA deletions but multimers of the mtDNA control region were identified in brain and heart. These control region multimers (CRMs) contained heterogeneous breakpoints and formed species that excluded the majority of mtDNA genes. CRMs demonstrate that polymerase-γ 3'-5' exonuclease activity is required for preserving mtDNA integrity.     

Construction of miniplasmids from the 7.2-kb and 5.1-kb penicillinase-producing plasmids of Neisseria gonorrhoeae reveals two replication regions

Two replication regions have been identified on a 7.2-kb penicillinase-producing plasmid (pJD4) of Neisseria gonorrhoeae. Through construction of mini-plasmids, one replication region of pJD4 was located on a 1.5-kb fragment, designated region "a," that included the unique HindIII site of this plasmid. This region is absent from the 5.1-kb naturally occurring gonococcal penicillinase-producing plasmid (pJD5) which is considered to be a deletion-derivative of the 7.2-kb plasmid. A 1.5-kb fragment (region "b"), part of a 2.5-kb fragment essential for the replication of the 5.1-kb plasmid (pJD5), was found to be responsible for incompatibility. Incompatibility studies showed that in vitro-derived deletion-derivatives from pJD4 and pJD5 containing either region "a" or region "b" were compatible. The DNA sequence of part of region "a" showed that this region was A-T rich. It contained seven sets of A-T rich multiple direct repeats and two putative dnaA boxes, suggesting that the mechanism of replication of region "a" was similar to that of OriC in Escherichia coli.     

Production,purification and characterisation of genetically derived scFv and bifunctional antibody fragments capable of detecting illicit drug residues

We have generated a single chain antigen binding protein (scFv) recognising morphine. Variable regions of heavy (V(H)) and light (V(L)) chain antibody genes isolated from a murine immune repertoire were connected via a glycine-serine linker and cloned into the expression vector pAK 400. The scFv was produced in Escherichia coli JM83 yielding a functional protein of approximately M(r) 30000. Immunoaffinity chromatography using M3G-BSA-Sepharose column proved most effective for scFv purification. Purity was monitored by SDS-PAGE and Western blotting and the scFv characterised using ELISA and BIAcore. The scFv was capable of specifically binding free morphine in solution and was applicable to real sample analysis in saliva. In order to express a bivalent "minibody" the scFv gene was recloned into a vector containing a gene encoding a helix for dimerisation. The scFv was expressed as a protein of M(r) 75000 and retained its antibody binding capabilities. Cloning the scFv gene into a vector containing the bacterial alkaline phosphatase gene produced a bifunctional molecule, which retained the binding activity of the parental scFv along with the enzymatic activity of alkaline phosphatase.     

Multiple Origins and Replication Proteins Influence Biological Properties of β-Lactamase-Producing Plasmids from Neisseria gonorrhoeae

The beta-lactamase-producing Asia-type plasmid pJD4 of Neisseria gonorrhoeae is a 7.4-kb, broad-host-range plasmid. It is part of a family of plasmids which are structurally related yet vary in size, found in both N. gonorrhoeae and Haemophilus ducreyi. Branch-point analysis by electron microscopy indicates that pJD4 carries three clustered but distinguishable origins of replication, which we named ori1, ori2, and ori3. Although pJD4 belongs to incompatibility (Inc) group W, it also carries a silent IncFII determinant which is expressed when ori2 and ori3 are absent. The Africa-type plasmid pJD5, a naturally occurring deletion derivative of pJD4, carries only ori1, belongs to the IncFII group, and, in contrast to pJD4, requires DNA polymerase I (Pol I) for replication. Plasmids constructed from pJD4 which lack ori1 but carry ori2 and ori3 do not require Pol I and are incompatible with IncW plasmids, suggesting that the ori2 or ori3 region contains the IncW determinant. We have cloned a replication initiation protein (RepB) that is necessary for ori2 and ori3 to function. This Rep protein is distinct from RepA, which is necessary for ori1. Thus, pJD4 is unique because it is the smallest plasmid characterized containing three origins of replication and two unique Rep proteins.