Kinetics of phytoremediation of petroleum hydrocarbon contaminated soil

Earthmaster and the University of Waterloo have successfully developed plant growth promoting rhizobacteria (PGPR) - Enhanced Phytoremediation Systems (PEPSystems™) which have been deployed across Canada for the treatment of soil contaminated with petroleum hydrocarbons (PHCs), including CCME fractions F2 and F3. A challenge with phytoremediation is to predict the length of time to remediate a site so that site owners will be inclined to use the technology. In previous field trials of PEPSystems, it was determined that PHC was mostly degraded by microbes in the rhizosphere, following first-order exponential decay kinetics. Using new PEPSystems data collected from multiple commercial remediation sites across Western Canada, the kinetic equations of PHC decay were tested to determine if remediation time was accurately predicted. In general, when compared to the predicted time to remediation endpoint, data from recent commercial field applications showed that 35% and 20% less time was needed to reach remediation endpoints for fractions F2 and F3, respectively. As a result, the predictive kinetic equation for fraction F2 degradation was updated to reflect current remediation outcomes. Insufficient data were available to update the F3 equation. Being able to more accurately predict remediation timelines will enhance the value and utilization of PEPSystems.

Expression and recovery of biologically active recombinant Apolipoprotein AI(Milano) from transgenic safflower (Carthamus tinctorius) seeds

Apolipoprotein AI Milano (ApoAI(Milano) ) was expressed as a fusion protein in transgenic safflower seeds. High levels of expression corresponding to 7 g of ApoAI(Milano) per kilogram of seed have been identified in a line selected for commercialization. The ApoAI(Milano) fusion protein was extracted from seed using an oilbody-based process and matured in vitro prior to final purification. This yielded a Des-1,2-ApoAI(Milano) product which was confirmed by biochemical characterization including immunoreactivity against ApoAI antibodies, isoelectric point, N-terminal sequencing and electrospray mass spectrometry. Purified Des-1,2-ApoAI(Milano) readily associated with dimyristoylphosphatidylcholine in clearance assays comparable to Human ApoAI. Its biological activity was assessed by cholesterol efflux assays using Des-1,2-ApoAI(Milano) :1-palmitoyl-2-oleoyl phosphatidylcholine complexes in vitro and in vivo. This study has established that high levels of biologically functional ApoAI(Milano) can be produced using a plant-based expression system.

Transgenic expression and recovery of biologically active recombinant human insulin from Arabidopsis thaliana seeds

The increased incidence of diabetes, coupled with the introduction of alternative delivery methods that rely on higher doses, is expected to result in a substantial escalation in the demand for affordable insulin in the future. Limitations in the capacity and economics of production will make it difficult for current manufacturing technologies to meet this demand. We have developed a novel expression and recovery technology for the economical manufacture of biopharmaceuticals from oilseeds. Using this technology, recombinant human precursor insulin was expressed in transgenic plants. Plant-derived insulin accumulates to significant levels in transgenic seed (0.13% total seed protein) and can be enzymatically treated in vitro to generate a product with a mass identical to that of the predicted product, DesB(30)-insulin. The biological activity of this product in vivo and in vitro was demonstrated using an insulin tolerance test in mice and phosphorylation assay performed in a mammalian cell culture system, respectively.

Compartmentalized signaling by GPI-anchored ephrin-A5 requires the Fyn tyrosine kinase to regulate cellular adhesion

Eph receptor tyrosine kinases and their corresponding surface-bound ligands, the ephrins, provide cues to the migration of cells and growth cones during embryonic development. Here we show that ephrin-A5, which is attached to the outer leaflet of the plasma membrane by a glycosyl-phosphatidylinositol-anchor, induces compartmentalized signaling within a caveolae-like membrane microdomain when bound to the extracellular domain of its cognate Eph receptor. The physiological response induced by this signaling event is concomitant with a change in the cellular architecture and adhesion of the ephrin-A5-expressing cells and requires the activity of the Fyn protein tyrosine kinase. This study stresses the relevance of bidirectional signaling involving the ephrins and Eph receptors during brain development.

The soluble granulocyte-macrophage colony-stimulating factor receptor's carboxyl-terminal domain mediates retention of the soluble receptor on the cell surface through interaction with the granulocyte-macrophage colony-stimulating factor receptor beta-subunit

The hematopoietic cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) mediates its activity through binding to cell-surface receptors. The high-affinity GM-CSF receptor (GMR) consists of two transmembrane-anchored subunits: a ligand-specific, low-affinity subunit (GMRalpha); and a signal-transducing beta-subunit (GMRbeta). The human GMRalpha subunit also exists in a soluble isoform (SOLalpha) which antagonizes GM-CSF activity in vitro. Previous studies by us have shown that coexpression of SOLalpha and a mutated GMRbeta in BHK cells results in retention of SOLalpha on the cell surface and the formation of an intermediate affinity binding complex (Kd approximately 300 pM). This paper investigates the mechanism of the retention of SOLalpha on the cell surface. The data demonstrate that SOLalpha is anchored by a direct, ligand-independent interaction with GMRbeta which also occurs when SOLalpha is coexpressed with wild-type GMRbeta. However, SOLalpha and wild-type GMRbeta form a complex which binds GM-CSF with high affinity (Kd = 39 pM), indistinguishable from the binding characteristics of the TMalpha/GMRbeta complex. The experiments further reveal that the interaction between SOLalpha and GMRbeta is abrogated by removal of the unique 16 amino acid carboxyl-terminal domain of SOLalpha. Specific mutation of cysteine 323 in this carboxyl-domain to alanine also eliminates the cell-surface retention of SOLalpha identifying this residue as being necessary for the formation of the SOLalpha/GMRbeta complex.

Antibody cross-linking of the glycosylphosphatidylinositol-linked protein CD59 on hematopoietic cells induces signaling pathways resembling activation by complement

CD59 is a glycosylphosphatidylinositol-anchored cell surface glycoprotein involved in protecting cells from host-mediated complement attack. Studies have shown that antibody cross-linking of CD59 induces a series of intracellular signaling events including the activation of protein-tyrosine kinases (PTK). To further characterize these events, antibodies and complement 8, one of the natural ligands of CD59, were used to activate CD59. Antibody-induced cross-linking of CD59 on the surface of THP-1 and U937 hematopoietic cell lines as well as exposure to complement 8 induces a rapid increase in the tyrosine phosphorylation of several proteins within the cell. Consistent with an early role for the Src family PTKs in these signaling events, we found that transient activation of Hck- and CD59-mediated signaling was abrogated in the presence of the Src family PTK-selective inhibitor PP1. Although the molecular mechanism by which CD59 communicates to Hck is unknown, cellular fractionation studies indicated that both CD59 and Hck are compartmentalized in plasma membrane microdomains. We also detected tyrosine phosphorylation of the adaptor proteins p120 and Shc, and the cytoplasmic nonreceptor tyrosine kinase Syk. The identification of CD59-mediated signaling events may help explain why paroxysmal nocturnal hemoglobinuria patients, who are deficient in glycosylphosphatidylinositol-linked proteins including CD59, are susceptible to proliferative disorders.

Oligomerization of the soluble granulocyte-macrophage colony-stimulating factor receptor: identification of the functional ligand-binding species

The ligand-specific alpha subunit of the dimeric human GM-CSF receptor exists in both transmembrane anchored (tmGM-CSFR alpha) and soluble (sGM-CSFR alpha) isoforms. sGM-CSFR alpha binds to GM-CSF in solution and antagonizes GM-CSF biological activity in vitro. In an effort to better understand the biological properties of sGM-CSFR alpha the authors have attempted to define the exact stoichiometry of the interaction between GM-CSF and sGM-CSFR alpha. Size separation of sGM-CSFR alpha by polyacrylamide gel electrophoresis (PAGE) under non-reducing conditions demonstrated that sGM-CSFR alpha can exist in solution not only in a monomeric state but also in higher order oligomers. FPLC analysis of ligand/sGM-CSFR alpha complexes suggested that only one of these sGM-CSFR alpha species could functionally bind GM-CSF. PAGE analysis of FPLC fractions demonstrated that the peak of GM-CSF binding activity corresponded to the presence of a monomeric form of sGM-CSFR alpha. The experiments demonstrate that while sGM-CSFR alpha can adopt oligomeric forms in solution, the binding of GM-CSF to sGM-CSFR alpha most likely occurs in a (GM-CSF)1 (sGM-CSFR alpha)1 configuration.

Ligand-independent cell surface expression of the human soluble granulocyte-macrophage colony-stimulating factor receptor alpha subunit depends on co-expression of the membrane-associated receptor beta subunit

The hematopoietic cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) mediates its activity through binding to cell surface receptors. The receptor for GM-CSF belongs to a superfamily of cytokine receptors characterized by a conserved extracellular motif. The high affinity GM-CSF receptor (GMR) consists of two transmembrane anchored subunits; a ligand binding alpha subunit (transmembrane GMRalpha) and a signal transducing beta subunit (GMRbeta), both of which belong to the cytokine receptor superfamily. The human GM-CSF receptor alpha subunit also exists in a soluble form (solGMRalpha), which antagonizes GM-CSF activity in vitro. We directly tested the potential for solGMRalpha to interact with GMRbeta in vitro. Our experiments demonstrated that exogenous solGMRalpha, even in the presence of GM-CSF, does not interact with GMRbeta on the cell surface. However, when solGMRalpha and GMRbeta are co-expressed in baby hamster kidney cells, solGMRalpha is retained on the cell surface and forms a functional intermediate affinity GM-CSF binding complex (Kd = 331 pM). In addition, the cell surface expression of solGMRalpha is independent of the presence of GM-CSF as demonstrated using flow cytometry. Cells expressing only solGMRalpha do not show cell surface retention or form functional GM-CSF cell surface binding complexes. Sequencing of our GMRbeta clone revealed a nucleotide substitution (A --> C) resulting in the substitution of Ala for Glu at position 9 from the amino terminus of the mature GMRbeta peptide. Because the GMRbeta (A --> C) clone is capable of forming functional high affinity receptors with transmembrane GMRalpha (Kd = 64 pM), we feel that the cell surface retention of solGMRalpha is independent of the GMRbeta mutation. We suggest that the co-expression and interaction of solGMRalpha and GMRbeta represents a previously unrecognized GM-CSF receptor complex and a novel, ligand-independent mechanism of cytokine receptor assembly.

Rapid genotype analysis in type 2B von Willebrand's disease using a universal heteroduplex generator

A new diagnostic technique based on DNA heteroduplex analysis has been used to identify specific point mutations in the von Willebrand's factor (vWF) gene of patients with von Willebrand's disease type 2B. Molecular analysis in these patients has shown previously that their mutations are clustered in a short region of sequence in exon 28 of the vWF gene. The principle of the method involves heteroduplex formation between amplified genomic sequence containing the defect and an exon 28 vWF gene universal heteroduplex generator (UHG). The UHG is a synthetic vWF gene exon 28 homologue which contains a number of sequence mismatches designed to generate allele specific heteroduplexes for each type 2B mutation. Individual mutant genotypes are identified by characteristic banding patterns following polyacrylamide minigel electrophoresis. The technique is rapid, simple, inexpensive, and is ideally suited for adoption by non-specialist haematology laboratories for screening purposes.

Enterococcal meningitis: report of four cases and review

Enterococci, a significant cause of human infections outside of the CNS, have only rarely been documented to cause meningitis. To add to our understanding of this uncommon infectious process, we report our experience with four patients with enterococcal meningitis and summarize findings associated with 28 additional cases found in the medical literature. The majority of the adult patients with this condition had coexistent chronic underlying illnesses and were frequently exposed to immunosuppressive therapy. In addition, more than one-third of these patients had experienced CNS trauma or surgery, and 31% had an infection with enterococci at a site other than the CNS. Pediatric patients predominantly had underlying CNS pathology primarily consisting of neural tube defects or hydrocephalus. Primary meningitis occurred in 25% of pediatric patients, with most of these episodes occurring in neonates. Most patients presented with expected signs, symptoms, and physical features of acute bacterial meningitis and had typical CSF abnormalities, including leukocytic pleocytosis, elevated protein levels, and hypoglycorrhachia. The overall mortality rate among patients with enterococcal meningitis was 13%. The small number of patients in this review failed to demonstrate a definite difference in mortality among patients treated with cell wall-active agents alone vs. those treated with combination therapy with an aminoglycoside, although studies of patients with other complicated enterococcal infections suggest that combination therapy would be preferable.

Germ-line mosaicism for a valine-to-methionine substitution at residue 553 in the glycoprotein Ib-binding domain of von Willebrand factor, causing type IIB von Willebrand disease

The origin of new single-gene mutations resulting in inherited disease is an issue which may be at least partially resolved by our enhanced ability to detect these changes. In this report we describe the identification of a missense mutation at codon 553 (guanine to adenine) in the von Willebrand factor (vWf) gene in affected members of a family with type IIB von Willebrand's disease (vWd). We found no evidence for this substitution in 190 normal vWf genes. The encoded substitution of a methionine for a valine at this residue is nonconservative in nature and has affected a vWf protein region which has been shown to facilitate binding to the platelet receptor glycoprotein Ib. In patients with type IIB vWd this interaction is characteristically increased in affinity. This mutation has also recently been recorded in four other type IIB vWd families. Thus, there is strong circumstantial evidence to incriminate this substitution as the disease causing mutation in this family. As further supporting evidence for this claim, we have shown by vWf polymorphism analysis that the mutation originated in a vWf gene transmitted from a phenotypically normal grandfather. Analysis of the sperm from this individual showed that approximately 5% of the germ line contained the mutant 553 sequence. These results confirm (1) that the candidate type IIB vWd mutation in this family occurred at some time during the development of the germ line of the grandfather and presumably was related to a mitotic cell division and (2) that, as a result, he is a low-level germ-line mosaic for the mutation.

Recurring mutations at CpG dinucleotides in the region of the von Willebrand factor gene encoding the glycoprotein Ib binding domain, in patients with type IIB von Willebrand's disease

The mutant von Willebrand factor (vWf) molecule in type IIB von Willebrand's disease (vWd) has an increased binding affinity for the platelet receptor glycoprotein Ib (GpIb). In previous studies we have confirmed genetic linkage of this phenotype to the vWf gene and in this report we document three recurring missense mutations in the region of the gene that encodes the GpIb binding domain. Two families with type IIB vWd were found to have an arginine to tryptophan substitution at residue 543, three families had a valine to methionine substitution at residue 553, and one kindred had an arginine to glutamine change at amino acid 578. None of these sequence changes were found in 200 normal vWf genes and within each of the six families the mutations were only found in affected subjects. This is strong circumstantial evidence in support of these substitutions representing the disease causing mutations in these families. All three of these substitutions have occurred at CpG dinucleotide sequences, and their polymorphic associations indicate that they represent recurring new mutations. Missense mutations at these sites may represent the underlying genetic pathology in a large number of type IIB vWd families.

Cosegregation of von Willebrand factor gene polymorphisms and possible germinal mosaicism in type IIB von Willebrand disease

Recent reports of the mutations resulting in von Willebrand disease (vWD) have indicated that some cases of type IIA vWD are caused by single nucleotide substitutions in the gene encoding von Willebrand factor (vWF). However, the molecular pathogenesis of type IIB vWD remains unresolved and, with the complex posttranslational processing required for fully functional vWF, the mutations responsible for this phenotype may occur at loci other than the vWF gene. This study has used six intragenic vWF polymorphisms to assess the linkage of type IIB vWD to this gene in three families (48 individuals). The results of these studies indicate that there is significant linkage between the vWF gene and the type IIB phenotype (logarithm of the odds ratio of 7.2 at theta = 0), suggesting that the mutations responsible for this disorder frequently occur at this locus. Results from one of these families indicates that the disorder has been transmitted from an unaffected parent to two children who have inherited the same vWF gene as seven unaffected siblings. This finding is suggestive of the presence of germinal mosaicism for the mutation in the father.