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At least 487 records · Page 27Linked to original sources
PubMed1994

Biotransformation of the naturally occurring lignan (-)-arctigenin in mammalian cell lines genetically engineered for expression of single cytochrome P450 isoforms.

V79 Chinese hamster cells genetically engineered for stable expression of single forms of rat cytochromes P450 1A1, P450 1A2, and P450 2B1, and human P450 1A2 were used to analyse the metabolism of (-)-arctigenin. Concentrations of metabolites formed in the medium were determined by TLC, HPLC, GC, and GC-MS. Only in the cell line expressing rat P450 2B1 was (-)-arctigenin metabolized to a significant extent. The lignan was converted by O-demethylation to (-)-3'-O-demethylarctigenin.

Animals↗
PubMed2006

Phenotyping of genetically engineered mice: humane, ethical, environmental, and husbandry issues.

The growing use of genetically engineered (GE) mice in scientific research has raised many concerns about the animal welfare of such mice. The types of welfare concerns may differ within the three stages that comprise the establishment of GE animal models: development, production, and research use. The role and impact of the members of the research team on these concerns may also vary with each stage. To make both scientific and animal welfare decisions at each stage, it is necessary to have a thorough knowledge of the animal model-in this case, the phenotypic expression of the GE animal. Phenotype screening is the analysis of visible or measurable characteristics of an animal that result from the genotype and its interaction with the environment. Phenotypes expressed that are relevant to the research program are usually carefully investigated; however, those that may have an impact on the animal's welfare but have little or no impact on the disease process under study are often less carefully studied. Thorough analysis and documentation of the animal welfare aspects of phenotype provide the research team with the information they need to control the environment to minimize negative animal welfare effects. Such information is also essential to allow members of the institutional animal care and use committee to perform necessary cost:benefit ethical review of proposed GE animal studies. Investigators who submit information about models for publication should document all aspects of a phenotype, including the area of scientific interest as well as those areas that affect animal welfare, for clarity and for subsequent research with the respective models.

Animal Experimentation↗
PubMed1998

A genetically engineered strain of Saccharopolyspora erythraea that produces 6,12-dideoxyerythromycin A as the major fermentation product.

The erythromycin producer, Saccharopolyspora erythraea ER720, was genetically engineered to produce 6,12-dideoxyerythromycin A, a novel erythromycin derivative, as the major macrolide in the fermentation broth. Inspection of the biosynthetic pathway for erythromycin would suggest that production of this compound could be achieved simply through the disruption of two genes, that encoding the erythromycin C-6 hydroxylase (eryF) and that encoding the erythromycin C-12 hydroxylase (eryK). The double mutant, however, was found to produce a mixture of 6,12-dideoxyerythromycin A and the precursor, 6-deoxyerythromycin D. Complete conversion to the desired product (to the limit of detection by TLC) was achieved by inserting an additional copy of the eryG gene, encoding the erythromycin 3"-O-methyltransferase and driven by the ermE* promoter, into the S. erythraea chromosome.

Bacterial Proteins↗
PubMed1995

Experimental quantification of transmission of genetically engineered pseudorabies virus.

There is concern that live pseudorabies virus (PRV) vaccine or PRV vector vaccine strains may spread from vaccinated to unvaccinated pigs. Moreover, it is feared that recombining PRV vaccine strains with related vaccine or wild-type strains may lead to spread and survival of recombinant PRV. To learn more about to what extent different PRV vaccine strains could spread we used a previously described experimental model to study the transmission of intranasally inoculated PRV mutant strains under experimental conditions. We used PRV strains that lacked glycoprotein E (gE) or thymidine kinase (TK), and a PRV vector vaccine (gE-, TK-, gG-) that expresses the glycoprotein E1 (E1) of hog cholera virus. In addition, we investigated whether intranasally co-inoculated gE-negative and gE-positive PRV strains competed in transmission among pigs. The extent of transmission was estimated using the reproduction ratio R. This ratio has a threshold property; when R1, the infection can spread; when R < 1, the infection will disappear. We found that R for a gE-negative strain was 10.1, and R for a TK-negative strain was 5. Furthermore, the R for the vector vaccine (gE-, TK-, gG-) expressing E1 was 0.18, and did not differ significantly from the R for the control strain without E1. The R of gE-negative strain was significantly 1 (P = 0.0005). Co-inoculation with a gE-positive field strain did not prevent the transmission of a gE-negative strain. This study shows that a small-scale experiment can be used to estimate the transmission of genetically engineered organisms in their host species. The results of this study indicate that the deletion of gE alone or TK alone is not enough to prevent spread of PRV among susceptible pigs, and that transmission of gE-negative PRV is not firmly limited by co-presence of a gE-positive strain.

Administration, Intranasal↗
PubMed1992

Tracking genetically engineered bacteria: monoclonal antibodies against surface determinants of the soil bacterium Pseudomonas putida 2440.

Assessment of potential risks involved in the release of genetically engineered microorganisms is facilitated by the availability of monoclonal antibodies (MAbs), a tool potentially able to monitor specific organisms. We raised a bank of MAbs against the soil bacterium Pseudomonas putida 2440, which is a host for modified TOL plasmids and other recombinant plasmids. Three MAbs, 7.3B, 7.4D, and 7.5D, were highly specific and recognized only P. putida bacteria. Furthermore, we developed a semiquantitative dot blot assay that allowed us to detect as few as 100 cells per spot. A 40-kDa cell surface protein was the target for MAbs 7.4D and 7.5D. Detection of the cell antigen depended on the bacterial growth phase and culture medium. The O antigen of lipopolysaccharide seems to be the target for MAb 7.3B, and its in vivo detection was independent of the bacterial growth phase and culture medium. MAb 7.3B was used successfully to track P. putida (pWW0) released in unsterile lake mesocosms.

Antibodies, Monoclonal↗
PubMed2004

Real-time PCR quantification of a green fluorescent protein-labeled, genetically engineered Pseudomonas putida strain during 2-chlorobenzoate degradation in soil.

The potential for real-time PCR (RTm-PCR) detection of the genetically engineered strain Pseudomonas putida GN2 was studied during 2-chlorobenzoate (2-CB) degradation in three different soils. The strain contained the constructed plasmid pGN2 which encoded genes for 2-CB oxidation (cbdA) and the green fluorescent protein (gfp). P. putida GN2 numbers were assessed by plating onto 2-CB minimal media and also by RTm-PCR detection of cbdA and gfp. Addition of P. putida GN2 decreased the time required to degrade 2-CB in all tested soils by more than 7 days. The RTm-PCR estimations of P. putida GN2 numbers strongly correlated with those obtained from plate count methods during active 2-CB degradation. However, after 2-CB degradation in the soils had ceased, RTm-PCR estimations of cbdA and gfp genes were generally one order of magnitude lower than those from plate counts. These results indicate the potential for RTm-PCR to rapidly determine degrader numbers in soil following bioaugmentation but also the need to exercise caution when attempting to determine cell numbers of degraders from the RTm-PCR quantification of plasmid encoded genes after substrate is depleted.

Chlorobenzoates↗
PubMed1985

Monoclonal antibodies to human growth hormone can distinguish between pituitary and genetically engineered forms.

Monoclonal antibodies (MABs) prepared against human pituitary growth hormone (hGH) have been compared for their binding to pituitary-derived and genetically engineered methionyl growth hormone (met-hGH). The antibodies bind to four non-overlapping epitopes of which two are completely shared with human choronic somatomammotropin (hCS). The determinant defined by MAB NA27 was expressed on met-hGH to a lesser degree than on hGH of pituitary origin. However, another antibody, QA68, which binds to a determinant closely related to NA27, failed to discriminate between hGH and met-hGH. A further two MABs (EB1 and NA71) were similarly ineffective in distinguishing between the two forms of the hormone. The determinant recognized by antibody EB2 was equally represented on hGH and met-hGH when assessed by a liquid-phase radioimmunoassay: however, measurement of the binding in a solid-phase assay resulted in a two-four-fold lower binding to met-hGH. Bioactivity assessed by both an in vitro cell proliferation assay and an in vivo cartilage sulphation bioassay failed to distinguish between the two hormones. It is therefore concluded that the NH2-terminal methionine on bacterially derived growth hormone results in altered antigenicity of the hormone without any measurable effect on bioactivity.

Animals↗
PubMedDate not supplied

Alginate encapsulation of genetically engineered mammalian cells: comparison of production devices, methods and microcapsule characteristics.

PRIMARY OBJECTIVE: Microencapsulation is a novel method for in vivo immunoprotection of genetically engineered mammalian cells. This study aimed at optimizing alginate/poly-l-lysine/alginate (APA) microencapsulation of mammalian cells in small size (< 300 microm) hollow core microcapsules and at evaluating some of the physical characteristics of APA microcapsules produced by different devices and with different alginate preparations. METHODS AND PROCEDURES: Alginate preparations with higher or lower viscosity were used with three different methods: (i) vibrating nozzle, (ii) coaxial gas flow extrusion (AirJet) and (iii) laminar jet break-up (JetCutter). Parameters and device settings for the production of microcapsules with specific characteristics were defined for all three methods. Mechanical stability of APA microcapsules and cell viability of encapsulated cells were investigated in long-term culture and in an animal model. MAIN RESULTS: Uniform spherical beads with a mean diameter < 300 microm could be produced by all three encapsulation methods. For the production of uniform microcapsules with a small diameter (< 300 microm) the vibrating nozzle technique required a relatively low viscosity of alginate (< 0.2 Pa/s), while the AirJet and JetCutter devices performed equally well with alginate of higher viscosity. In all cases, alginate with a lower molar mass was inferior to higher molar mass alginate in terms of mechanical stability of the microcapsules. Microcapsules with optimized mechanical properties were injected intravascularly in rats and shown to maintain their shape and the viability of encapsulated cells. CONCLUSIONS: The described methods and devices are able to produce APA microcapsules of small size and uniform shape which are mechanically stable in culture and may maintain the viability of the enclosed cells over extended periods of time. These microcapsules seem to be suitable for further therapeutic studies in an animal model of human disease.

Alginates↗
PubMed2001

Genetically engineered peptide fusions for improved protein partitioning in aqueous two-phase systems. Effect of fusion localization on endoglucanase I of Trichoderma reesei.

Genetic engineering has been used for fusion of the peptide tag, Trp-Pro-Trp-Pro, on a protein to study the effect on partitioning in aqueous two-phase systems. As target protein for the fusions the cellulase, endoglucanase I (endo-1,4-beta-Dglucan-4-glucanohydrolase, EC 3.2.1.4, EGI, Cel7B) of Trichoderma reesei was used. For the first time a glycosylated two-domain enzyme has been utilized for addition of peptide tags to change partitioning in aqueous two-phase systems. The aim was to find an optimal fusion localization for EGI. The peptide was (1) attached to the C-terminus end of the cellulose binding domain (CBD), (2) inserted in the glycosylated linker region, (3) added after a truncated form of EGI lacking the CBD and a small part of the linker. The different constructs were expressed in the filamentous fungus T. reesei under the gpdA promoter from Aspergillus nidulans. The expression levels were between 60 and 100 mg/l. The partitioning behavior of the fusion proteins was studied in an aqueous two-phase model system composed of the thermoseparating ethylene oxide (EO)-propylene oxide (PO) random copolymer EO-PO (50:50) (EO50PO50) and dextran. The Trp-Pro-Trp-Pro tag was found to direct the fusion protein to the top EO50PO50 phase. The partition coefficient of a fusion protein can be predicted with an empirical correlation based on independent contributions from partitioning of unmodified protein and peptide tag in this model system. The fusion position at the end of the CBD, with the spacer Pro-Gly, was shown to be optimal with respect to partitioning and tag efficiency factor (TEF) was 0.87, where a fully exposed tag would have a TEF of 1.0. Hence, this position can further be utilized for fusion with longer tags. For the other constructs the TEF was only 0.43 and 0.10, for the tag fused to the truncated EGI and in the linker region of the full length EGI, respectively.

Amino Acid Sequence↗
PubMed2005

Long-term therapeutic effects on parkinsonian rats of intrastriatal co-grafts with genetically engineered fibroblasts expressing tyrosine hydroxylase and glial cell line-derived neurotrophic factor.

The long-term improvement of intrastriatal co-grafts with genetically engineered fibroblasts expressing tyrosine hydroxylase (TH) and glial cell line-derived neurotrophic factor (GDNF) was investigated in the present study. Two recombinant vectors, pCMV-TH and pCI-neo-GDNF, were transfected respectively into the primary fibroblasts, and their expression was further identified by in situ hybridization and immunocytochemistry. The engineered fibroblasts expressing TH, GDNF, or both were transplanted into the striatum of parkinsonian rats, and the therapeutic effects were observed for 20 weeks. Data revealed that only animals with fibroblasts expressing both TH and GDNF exhibited a stable and significant behavioral and biochemical recovery. Moreover, persistence of both TH and GDNF expression in grafts was demonstrated 20 weeks after transplantation. These results suggest that combined transplantation of fibroblasts expressing TH and GDNF can lead to long-term and remarkable therapeutic effects on parkinsonian rat model.

Animals↗
PubMed1991

Assay for detection and enumeration of genetically engineered microorganisms which is based on the activity of a deregulated 2,4-dichlorophenoxyacetate monooxygenase.

An assay system was developed for the enumeration of genetically engineered microorganisms expressing a deregulated 2,4-dichlorophenoxyacetate (TFD) monooxygenase, which converts phenoxyacetate (PAA) to phenol. In PAA-amended cultures of Pseudomonas aeruginosa PAO1C(pRO103) and Pseudomonas putida PPO301(pRO103), strains which express a deregulated TFD monooxygenase, phenol production was proportional to cell number. Phenol was reacted, under specific conditions, with a 4-aminoantipyrine dye to form an intensely colored dye-phenol complex (AAPPC), which when measured spectrophotometrically could detect as few as 10(3) cells per ml. This assay was corroborated by monitoring the disappearance of PAA and the accumulation of phenol by high-performance liquid chromatography and gas chromatography. The AAPPC assay was modified for use with plate cultures and clearly distinguished colonies of PPO301(pRO103) and PAO1C(pRO103) from a strain expressing a regulated TFD monooxygenase. Colonies of P. putida PPO301(pRO101) remained cream colored, while colonies of PPO301(pRO103) and PAO1C(pRO103) turned a distinct red.

Ampyrone↗
PubMed2005

[Construction of multifunctional genetically engineered pesticides-degrading bacteria by homologous recombination].

Construction of multifunctional pesticides-degrading genetically engineered microorganisms (GEMs) is increasing important in the bioremediation of various pesticides contaminants in environment. However, construction of genetically stable GEMs without any exogenous antibiotic resistance is thought to be one of the bottlenecks in GEMs construction. In this article, homologous recombination vectors with the recipient's 16S rDNA as homologous recombination directing sequence (HRDS) and sacB gene as double crossover recombinants positive selective marker were firstly constructed. The methyl parathion hydroalse gene (mpd) was inserted into the 16S rDNA site of the carbofuran degrading strain Sphingomonas sp. CDS-1 by homologous recombination single crossover in the level of about 3.7 x 10-(7) - 6.8 x 10(-7). Multifunctional pesticides-degrading GEMs with one or two mpd genes inserted into the chromosome without any antibiotic marker were successfully constructed. The homologous recombination events were confirmed by PCR and southern blot methods. The obtained GEMs were genetically stable and could degrade methyl parathion and carbofuran simultaneously. The insertion of mpd gene into rrn site did not have any significant effect on recipient' s physiological and original degrading characteristics. The methyl parathion hydrolase (MPH) was expressed at a relatively high level in the recombinants and the recombinant MPH specific activity in cell lysate was higher than that of original bacterium (DLL-1) in every growth phase tested. The highest recombinant MPH specific activity was 6.22 mu/tg. In this article, we describe a first attempt to use rRNA-encoding regions of Sphingomonas strains as target site for expression of exogenous MPH, and constructed multifunctional pesticides degrading GEMs, which are genetically stable and promising for developing bioremediation strategies for the decontamination of pesticides polluted soils.

Biodegradation, Environmental↗
PubMed2006

[The genetic engineering animal models of retinoblastoma].

The article summarized the latest progress of retinoblastoma animal models using transgenetic engineering technology, and discussed the mechanism of Rb production. According to the the established animal models using current genetic engineering, the dysfunction of Rb1 gene is not the only gene in response to the development of Rb, multiple genes abnormal are required.

Animals↗