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PubMed2006

High efficiency and throughput system in directed evolution in vitro of reporter gene.

In vitro directed evolution, especially with DNA shuffling, is a powerful means in biological studies of protein structure and function, and consequently for industrial applications. Escherichia coli beta-glucuronidase (gusA) gene, a versatile and efficient reporter gene, was the model for studying in vitro directed evolution because of its stability, easy analysis of the enzyme properties and conveniently visible phenotype. We developed a high efficiency, throughput system for in vitro directed evolution using gusA reporter gene as the model. The system consisted mainly of three aspects: a prokaryotic expression vector pYPX251, an easy method for obtaining the mutated gene from DNA shuffling and a suitable selected strategy. The vector pYPX251 carried the moderately strong aacC1 gene promoter and T1T2 transcription terminator that allowed expression in E. coli. Over 10,000 individuals could be selected individually in a 9 cm Petri dish after colonies were absorbed on a nitrocellulose filter. A library, which contained 100,000 individuals was screened by incubating ten filter papers with X-Glu. The polymerase chain reaction products of the gusA gene, the fragments of 50-100 bp, with high mutation rates were purified using a dialysis bag from 10% PAGE after electrophoresis. The possibility of obtaining desirable mutations was increased dramatically as the size of the library expanded. A GUS variant, named GUS-TR, was obtained through this system, which is significantly more resistant to high temperature than the wild type enzyme. GUS-TR maintained its high activity even when the nitrocellulose filter containing the variant colony was heated at 100 degrees C for 30 min.

Biotechnology↗
PubMed2000

Time-dependency of the prognostic effect of carcinoembryonic antigen and p53 protein in colorectal adenocarcinoma.

BACKGROUND: This study examined the prognostic information regarding the risk of postoperative tumor recurrence obtained by simultaneous determination of preoperative serum carcinoembryonic antigen (CEA) and immunohistochemical expression of p53 protein in tumor tissue from patients with colorectal carcinoma. METHODS: A retrospective study of 174 patients (AJCC/UICC Stages I, II and III) was conducted. Serum CEA levels were determined by an enzyme-linked immunoadsorbent assay. Immunohistochemical expression of nuclear p53 protein was assessed in formalin fixed, paraffin embedded archival tumor tissue. The results of both factors were categorized by clinical and histopathologic variables. The relative prognostic significance of all factors with regard to disease free survival was assessed by Cox proportional hazards regression analysis. The stability of the predictive value of both markers was assessed: 1) by splitting the follow-up into three intervals and performing separate analyses for each period and 2) graphically by plotting the corresponding cumulative hazards ratio along the follow-up. RESULTS: Eighty-two (47%) tumors manifested overexpression of p53 protein and 60 tumors (34.4%) exhibited elevated serum CEA levels (cutoff value of 5 ng/mL). p53 positive immunostaining and elevated CEA levels were associated with low cumulative disease free survival at 60 months' of follow-up, and proved to have independent prognostic significance. Analysis performed in different time periods of follow-up showed that the prognostic effect of both markers was not stable over time. The predictive significance of CEA and p53 changed along the study periods. An elevated preoperative CEA level was an indicator of a high risk of recurrence only during the first 2 years after surgery (hazards ratio, 3.26; 95% confidence interval 95% CI, 1.65-6.42). The presence of p53 immunoreactivity in the primary tumor was an indicator of a high risk of recurrence only after the first year of follow-up (hazards ratio, 4.02; 95% CI, 1.68-9.6). CONCLUSIONS: The serum CEA level and expression of p53 protein provide complementary prognostic information. Time-dependency of the prognostic influence of both parameters should be taken into consideration when establishing postoperative predictive estimations.

Adenocarcinoma↗
PubMed1989

Electromyographic analysis of hip abductor musculature in healthy right-handed persons.

The right hip abductor (HA) musculature has been reported to demonstrate stretch weakness attributable to chronic elongation imposed by standing posture common to right-handed healthy individuals. Research has shown side-specific differences in maximal isometric torque-hip abduction angle curves for the HA muscles in a similar population. The purposes of this study were to assess isometric hip abduction torque in a sample of 40 healthy right-handed persons and to compare side differences in the HA muscles' neural drive index across a wide range of hip abduction angles. The neural drive index was defined as the magnitude of the normalized surface electromyographic activity divided by the absolute magnitude of a submaximal (20% of maximal) isometric HA muscle torque. Data were collected while subjects were positioned supine with trunk and pelvis stabilized. Statistical analysis of the data did not support earlier research on right HA muscle stretch-weakness; however, trends in the data suggest the need for further research. We also discuss the functional role of the passive noncontractile elements of the HA musculature.

Adult↗
PubMed1993

Long-term stability and prediction of soft tissue changes after LeFort I surgery.

Many evaluations of soft tissue changes after orthognathic surgery have been undertaken, and many correlations of soft tissue to hard tissue movements have been established. These studies have not, however, specifically discussed the long-term stability or characteristics of the soft tissue changes. The objectives of this study were (1) to determine the long term stability of soft tissue changes 5 years after LeFort I osteotomy, (2) to determine reliable correlations, if any, of soft tissue changes to bony movements effected in surgery, and (3) to determine the predictability of soft tissue changes as an aid to orthodontic treatment planning. Cephalometric data from 25 patients who were treated with LeFort I osteotomy with or without a concurrent mandibular procedure were analyzed retrospectively. Cases were selected from the patient records of the Department of Oral Surgery of the Vrije Universiteit in Amsterdam, the Netherlands. These patients were followed up at four time points, the last being a mean of 6.1 years after surgery. Analysis of stability data revealed that most horizontal and vertical soft tissue change after LeFort I surgery occurred in the first year after surgery. Significant (> 10%) change continued to occur for subnasale, labrale inferius, upper lip protrusion, lower lip protrusion, and soft tissue convexity during the subsequent 5 years. Hard tissue to soft tissue correlations were calculated and ratios of soft tissue to hard tissue movement were determined for appropriate hard and soft tissue landmarks at four time intervals. Reliable correlations of hard tissue change at surgery to 5-year soft tissue change could be made for 10 variables, which was considerably less frequently than for 1-year soft tissue change. The relatively low reliability of long-term prediction correlations suggests that soft tissue movements may be more independent of hard tissue over time. One-year prediction values were similar to 5-year values and thus could be used for prediction purposes in orthodontic treatment planning. Most short-term hard to soft tissue correlations found in the present study were in the range of those established by previous authors. Long-term hard tissue to soft tissue correlations gave higher ratios of soft tissue movement secondary to maxillary surgery, approaching ratios of 1.0:1.0 for some variables. This finding, as well as the long-term stability data, suggest that soft tissue settling or equilibrium after surgery may take several years to complete.

Adolescent↗
PubMed2000

Compact stellarators with modular coils.

Compact stellarator designs with modular coils and only two or three field periods are now available; these designs have both good stability and quasiaxial symmetry providing adequate transport for a magnetic fusion reactor. If the bootstrap current assumes theoretically predicted values a three field period configuration is optimal, but if that net current turns out to be lower, a device with two periods and just 12 modular coils might be better. There are also attractive designs with quasihelical symmetry and four or five periods whose properties depend less on the bootstrap current. Good performance requires that there be a satisfactory magnetic well in the vacuum field, which is a property lacking in a stellarator-tokamak hybrid that has been proposed for a proof of principle experiment. In this paper, we present an analysis of stability for these configurations that is based on a mountain pass theorem asserting that, if two solutions of the problem of magnetohydrodynamic equilibrium can be found, then there has to be an unstable solution. We compare results of our theory of equilibrium, stability, and transport with recently announced measurements from the large LHD experiment in Japan.

Journal Article↗
PubMed2004

A multilocus analysis of intraspecific competition and stabilizing selection on a quantitative trait.

The equilibrium structure of an additive, diallelic multilocus model of a quantitative trait under frequency- and density-dependent selection is derived. The trait is under stabilizing selection and mediates intraspecific competition as induced, for instance, by differential resource utilization. It is assumed that stabilizing selection is weak, but the strength of competition may be arbitrary relative to it. Density dependence is caused by population regulation, which may be of a very general kind. The number and effects of loci are arbitrary, and stabilizing selection is not necessarily symmetric with respect to the range of phenotypic values. All previously studied models of intraspecific competition for a continuum of resources known to the author reduce to a special case of the present model if overall selection is weak. Therefore, in this case our results are applicable as approximations to all these models. Our central result is the (nearly) complete characterization of the equilibrium and stability structure in terms of all parameters. It is derived under the sole assumption that selection is weak enough relative to recombination to ignore linkage disequilibrium. In particular, necessary and sufficient conditions on the strength of competition relative to stabilizing selection are found that ensure the maintenance of multilocus polymorphism and the occurrence of disruptive selection. In this case, explicit formulas for the number of polymorphic loci at equilibrium, the allele frequencies, the genetic variance, and the strength of disruptive selection are obtained. For two loci, the effects of linkage are investigated analytically; for several loci, they are studied numerically.

Alleles↗
PubMed1976

Delayed skin reactor from streptokinase-streptodornase: stability studies and amino acid analysis.

Delayed skin reactor (DSR), the material in streptokinase-streptodornase responsible for eliciting delayed hypersensitivity reactions in man, is stable as a lyophilized powder or when stored at -70 degrees C. Storage at a pH above or below 6.0 leads to a decrease in the ability of DSR to stimulate lymphocyte proliferation in vitro. Its molecular weight is 30,000 as estimated by sodium dodecyl sulfate gel electrophoresis and it is composed of approximately 260 amino acid residues without apparent sulfhydryl-bridged subunits. The extinction coefficient of DSR (A 1% 280 nm) is 2.6.

Amino Acids↗
PubMedDate not supplied

Dynamic stability of the elbow: electromyographic analysis of the flexor pronator group and the extensor group in pitchers with valgus instability.

The medical collateral ligament is a common site of injury in baseball pitchers, causing substantial morbidity and loss of pitching time. Twenty-six skilled baseball pitchers with medial collateral ligament insufficiency were studied before surgery with high-speed cinematography and fine-wire electromyography of eight muscles around the elbow. Data from the pitchers with injured elbows were compared with data obtained from uninjured pitchers. The flexor carpi radialis muscle in the pitchers with medial collateral ligament deficiencies revealed significantly decreased firing during the acceleration and deceleration phase of the fastball when compared with that of the pitchers with normal elbows, and the flexor carpi radialis muscle was significantly depressed during the early cocking and deceleration phases. The extensor muscles revealed slightly increased activity in the injured elbows; however, this was not statistically significant. Although the muscles of the flexor pronator group (especially the flexor carpi ulnaris muscle and the flexor digitorum superficialis muscles) are anatomically positioned to provide dynamic stability of the elbow, they did not demonstrate increased electrical activity in pitchers with medial collateral ligament deficiencies. This finding suggests that the muscles on the medial side of the elbow do not supplant the role of the medial collateral ligament during the fastball pitch.

Baseball↗
PubMed1998

The cox2 locus of the primitive angiosperm plant Acorus calamus: molecular structure, transcript processing and RNA editing.

Acorus calamus, or sweet flag, is a semiaquatic plant of uncertain taxonomic position. Molecular phylogenetic analysis using plastid rbcL sequences have suggested that Acorus calamus might be the most ancient surviving representative of the ancestral monocotyledonous plants. In order to provide molecular and phylogenetic data for the mitochondrial genetic system of Acorus, we have determined the structure of a mitochondrial locus, the cytochrome oxidase subunit II gene cox2. The Acorus cox2 gene harbors an unusually small group II intron, the smallest plant mitochondrial intron known to date. The transcript undergoes C-to-U RNA editing at eight sites. One of these sites is likely to play a dual functional role in both intron splicing and protein function. The 3' end of the mature transcript folds into a characteristic stem-loop structure that is presumably required for mitochondrial mRNA stability. Phylogenetic analysis of the cox2 sequence data, as well as the unusual intron structure, all support an evolutionarily isolated position for Acorus calamus.

Base Sequence↗
PubMed2006

Nonmyeloablative hematopoietic stem cell transplantation for systemic lupus erythematosus.

CONTEXT: Manifestations of systemic lupus erythematosus (SLE) may in most patients be ameliorated with medications that suppress the immune system. Nevertheless, there remains a subset of SLE patients for whom current strategies are insufficient to control disease. OBJECTIVE: To assess the safety of intense immunosuppression and autologous hematopoietic stem cell support in patients with severe and treatment-refractory SLE. DESIGN, SETTING, AND PARTICIPANTS: A single-arm trial of 50 patients with SLE refractory to standard immunosuppressive therapies and either organ- or life-threatening visceral involvement. Patients were enrolled from April 1997 through January 2005 in an autologous nonmyeloablative hematopoietic stem cell transplantation (HSCT) study at a single US medical center. INTERVENTIONS: Peripheral blood stem cells were mobilized with cyclophosphamide (2.0 g/m2) and granulocyte colony-stimulating factor (5 microg/kg per day), enriched ex vivo by CD34+ immunoselection, cryopreserved, and reinfused after treatment with cyclophosphamide (200 mg/kg) and equine antithymocyte globulin (90 mg/kg). MAIN OUTCOME MEASURES: The primary end point was survival, both overall and disease-free. Secondary end points included SLE Disease Activity Index (SLEDAI), serology (antinuclear antibody [ANA] and anti-double-stranded (ds) DNA), complement C3 and C4, and changes in renal and pulmonary organ function assessed before treatment and at 6 months, 12 months, and then yearly for 5 years. RESULTS: Fifty patients were enrolled and underwent stem cell mobilization. Two patients died after mobilization, one from disseminated mucormycosis and another from active lupus after postponing the transplantation for 4 months. Forty-eight patients underwent nonmyeloablative HSCT. Treatment-related mortality was 2% (1/50). By intention to treat, treatment-related mortality was 4% (2/50). With a mean follow-up of 29 months (range, 6 months to 7.5 years) for patients undergoing HSCT, overall 5-year survival was 84%, and probability of disease-free survival at 5 years following HSCT was 50%. Secondary analysis demonstrated stabilization of renal function and significant improvement in SLEDAI score, ANA, anti-ds DNA, complement, and carbon monoxide diffusion lung capacity adjusted for hemoglobin. CONCLUSIONS: In treatment-refractory SLE, autologous nonmyeloablative HSCT results in amelioration of disease activity, improvement in serologic markers, and either stabilization or reversal of organ dysfunction. These data are nonrandomized and thus preliminary, providing the foundation and justification for a definitive randomized trial. Clinical Trial Registration ClinicalTrials.gov Identifier: NCT00271934.

Adult↗
PubMed1996

Engineered disulfide bonds in recombinant human interferon-gamma: the impact of the N-terminal helix A and the AB-loop on protein stability.

Insertion sites for cysteines with optimal stereochemistry for the formation of unstrained disulfide bridges were identified in recombinant human interferon-gamma (rhu-IFN-gamma) by computer modelling. We have engineered two different disulfide cross-linked mutants, containing a pair of symmetry-related disulfide bonds, which stabilize the N-termini of both monomers of the homodimeric protein. Mutations E7C and S69C allow the formation of an intramonomer disulfide bond between helices A and D. In contrast, the A17C and H111C mutations lead to a covalent cross-link between both monomers. The AB-loop is linked to helix F. The fluorescence properties of native and disulfide cross-linked proteins were studied as a function of guanidine hydrochloride concentration. Melting temperatures (Tm) were calculated from the decrease in CD ellipticity at 220 nm. The induction of the antiviral effect was measured using A549 fibroblast cells infected with encephalomyocarditis virus. The ability to induce the expression of the HLA-DR antigen in Colo 205 cells was determined by fluorescence-activated cell scanning analysis. The stability of both mutants was strongly enhanced against temperature- and cosolvent-induced unfolding. The delta Tm of mutant IFN-gamma E7C/S69C was 15 degrees C. All measured biological activities of this mutant were equal to wild type. In the case of the other mutant IFN-gamma A17C/H111C, the delta Tm value was 25 degrees C. This mutation abolishes nearly the entire biological activity (< 1%) with no detectable changes of secondary structure in the CD spectrum. Our results illustrate the importance of the N-terminal helix A and the AB-loop for the unfolding pathway and thermodynamic stability of rhu-IFN-gamma.

Circular Dichroism↗
PubMed2004

Five amino acid residues responsible for the high stability of Hydrogenobacter thermophilus cytochrome c552: reciprocal mutation analysis.

Five amino acid residues responsible for extreme stability have been identified in cytochrome c(552) (HT c(552)) from a thermophilic bacterium, Hydrogenobacter thermophilus. The five residues, which are spatially distributed in three regions of HT c(552), were replaced with the corresponding residues in the homologous but less stable cytochrome c(551) (PA c(551)) from Pseudomonas aeruginosa. The quintuple HT c(552) variant (A7F/M13V/Y34F/Y43E/I78V) showed the same stability against guanidine hydrochloride denaturation as that of PA c(551), suggesting that the five residues in HT c(552) necessarily and sufficiently contribute to the overall stability. In the three HT c(552) variants carrying mutations in each of the three regions, the Y34F/Y43E mutations resulted in the greatest destabilization, by -13.3 kJ mol(-1), followed by A7F/M13V (-3.3 kJ mol(-1)) and then I78V (-1.5 kJ mol(-1)). The order of destabilization in HT c(552) was the same as that of stabilization in PA c(551) with reverse mutations such as F34Y/E43Y, F7A/V13M, and V78I (13.4, 10.3, and 0.3 kJ mol(-1), respectively). The results of guanidine hydrochloride denaturation were consistent with those of thermal denaturation for the same variants. The present study established a method for reciprocal mutation analysis. The effects of side-chain contacts were experimentally evaluated by swapping the residues between the two homologous proteins that differ in stability. A comparative study of the two proteins was a useful tool for assessing the amino acid contribution to the overall stability.

Amino Acids↗
PubMed2004

Pharmacokinetic properties and stability of continuous-infusion meropenem in adults with cystic fibrosis.

BACKGROUND: Meropenem is commonly used to treat lung infections in adults with cystic fibrosis (CF). Although continuous infusion is the ideal method to maximize the pharmacodynamic properties of this betalactam antibiotic, meropenem is stable for only approximately 4 to 6 hours at room temperature, and its pharmacokinetic (PK) properties, when administered by continuous infusion to patients with CF, are largely unknown. OBJECTIVE: This study was undertaken to determine the PK properties and stability of meropenem when administered to adults with CF by a continuous ambulatory drug-delivery infusion pump stored in a cold pouch between 2 freezer packs. METHODS: This open-label, multidose, randomized, crossover PK study was conducted at the Clinical Research Center at Hartford Hospital (Hartford, Connecticut). Adults aged > or = 18 years with CF were eligible. Study participants were randomized to receive meropenem 125 mg/h or 250 mg/h (equivalent to 3 g and 6 g, respectively, over 24 hours) by continuous IV infusion for 12 hours. Serum samples were collected throughout the infusion and then for 6 hours after infusion to determine the PK properties (volume of distribution [V(d)], elimination rate constant, total body clearance [CL], terminal half-life [t 1/2], and steady-state concentration [C(ss)]). Serum meropenem concentrations were assayed using high-performance liquid chromatography, and PK profiles were determined using compartmental analysis. Meropenem stability was ascertained by sampling the drug directly from the infusion pump at prespecified time points. Meropenem tolerability was assessed throughout the study by questioning subjects on how they felt. In addition, laboratory values of serum chemistries and liver enzymes were compared with baseline values. RESULTS: Seven adult volunteers with CF (4 women, 3 men; mean [SD] age, 27 [10] years [range, 19-46 years]) participated in the study. Mean (SD) C(ss) values were 8.31 (0.68) mg/L and 18.50 (3.31) mg/L for the 125-mg/h and 250-mg/h infusion rates, respectively. V(d), CL, and t 1/2 were dose independent and similar between the 2 infusion rates. Meropenem stability was maintained over 12 and 24 hours. Meropenem by continuous infusion was well tolerated. One patient complained of a headache during the study. CONCLUSIONS: In this study of adults with CF, meropenem infusion rates of 125 mg/h and 250 mg/h provided serum drug concentrations greater than the minimum inhibitory concentration for pathogens considered meropenem susceptible (< or =4 microg/mL) and intermediately resistant (8 microg/mL), respectively.

Adult↗
PubMed2000

Thermal unfolding of an intermediate is associated with non-Arrhenius kinetics in the folding of hen lysozyme.

A variety of techniques, including quenched-flow hydrogen exchange labelling monitored by electrospray ionization mass spectrometry, and stopped-flow absorbance, fluorescence and circular dichroism spectroscopy, has been used to investigate the refolding kinetics of hen lysozyme over a temperature range from 2 degrees C to 50 degrees C. Simple Arrhenius behaviour is not observed, and although the overall rate of folding increases from 2 to 40 degrees C, it decreases above 40 degrees C. In addition, the transient intermediate on the major folding pathway at 20 degrees C, in which the alpha-domain is persistently structured in the absence of a stable beta-domain, is thermally unfolded in a sigmoidal transition (T(m) approximately 40 degrees C) indicative of a cooperatively folded state. At all temperatures, however, there is evidence for fast ( approximately 25 %) and slow ( approximately 75 %) populations of refolding molecules. By using transition state theory, the kinetic data from various experiments were jointly fitted to a sequential three-state model for the slow folding pathway. Together with previous findings, these results indicate that the alpha-domain intermediate is a productive species on the folding route between the denatured and native states, and which accumulates as a consequence of its intrinsic stability. Our analysis suggests that the temperature dependence of the rate constant for lysozyme folding depends on both the total change in the heat capacity between the ground and transition states (the dominant factor at low temperatures) and the heat-induced destabilization of the alpha-domain intermediate (the dominant factor at high temperatures). Destabilization of such kinetically competent intermediate species is likely to be a determining factor in the non-Arrhenius temperature dependence of the folding rate of those proteins for which one or more intermediates are populated.

Allosteric Regulation↗
PubMed1981

Evidence for two forms of reverse transcriptase in human placenta of a patient with breast cancer. Purification and biochemical characterization of the enzymes.

Two DNA polymerases with properties of viral RNA-directed DNA polymerase were found in the placenta of a patient with breast cancer. Both enzyme activities were purified by column-chromatographic procedures or by preparative isoelectric focusing. The most distinguishing feature of the two enzymes is their specificity to transcribe (rA)n . (dT)12 or (rC)n . (dG)18. The two enzymes differ with respect to their elution profiles from the phosphocellulose column, isoelectric point, molecular weight, bivalent-cation requirements and thermal stability. Serological analysis of the (rA)n . (dT)12-activated enzyme showed that this enzyme is immunologically not related to DNA polymerase-gamma, or to any of the reverse transcriptases purified from retroviruses of avian, murine and subprimate origin. However, the activity of this enzyme was neutralized by antibodies to reverse transcriptase purified from human spleen of a patient with myelofibrosis [Chandra & Steel (1977) Biochem. J. 167, 513-524]. Attempts to purify reverse transcriptase of normal human placenta were repeatedly unsuccessful. Once the crude homogenate of normal placenta was freed from endogenous nucleic acids, no (rC)n . (dG)18-dependent activity cold be detected.U

Breast Neoplasms↗
PubMed2002

Replacement of His12 or His119 of bovine pancreatic ribonuclease A with acidic amino acid residues for the modification of activity and stability.

In an attempt to produce a bovine pancreatic ribonuclease A (RNase A) with increased activity and stability, the catalytic pair of His12 and His119 was substituted with aspartic acid or glutamic acid, and aspartic acid, respectively, to evaluate the role of the two histidine residues in the activity and stability. Kinetic analysis revealed that k(cat)/K(m) values were significantly reduced for all mutant enzymes due to a decreased k(cat) rather than an increased K(m): the k(cat) values for both CpA and C>p of H12D and H12E decreased to about 1/1000; the k(cat) values of H119D decreased by 1/3300 for CpA and 1/80 for C>p. Thus, neither Asp nor Glu is able to act solely as an efficient catalytic residue of RNase A. Alkylation with iodoacetic acid (IAA) revealed that mutant enzymes had reduced reaction rates and that no modification was evident at Glu12 and Asp12 of H12E and H12D, respectively. This indicates that the low catalytic activity of mutant enzymes could be due to low basicity of Asp12 and Glu12. While the T(m) of H119D was almost the same as that of the wild-type enzyme, the T(m) of both H12D and H12E markedly decreased. It became apparent that His12 located at the bottom of the active site cleft contributes significantly to the structural stability of RNase A.

Journal Article↗
PubMed2001

Efficient transformation of the yellow fever mosquito Aedes aegypti using the piggyBac transposable element vector pBac[3xP3-EGFP afm].

We report efficient germ-line transformation in the yellow fever mosquito Aedes aegypti accomplished using the piggyBac transposable element vector pBac[3xP3-EGFP afm]. Two transgenic lines were established and characterized; each contained the Vg-Defensin A transgene with strong eye-specific expression of the enhanced green fluorescent protein (EGFP) marker gene regulated by the artificial 3xP3 promoter. Southern blot hybridization and inverse PCR analyses of genomic DNA demonstrated a precise piggyBac-mediated, single copy insertion of the pBac[3xP3-EGFP afm,Vg-DefA] transposon in each transgenic line. For each line, genetic analysis confirmed stability and integrity of the entire transposon construct in the mosquito genome through the G2-G6 generations. Successful establishment of homozygous transgenic lines indicated that in both cases a non-lethal integration of the transposon into the mosquito genome had occurred. The 3xP3-EGFP marker was tested in mosquitoes with different genetic backgrounds. In white-eyed transgenic mosquitoes, the strong eye-specific expression of GFP was observed throughout all stages of development, starting from newly hatched first instar larvae to adults. A similar level and pattern of fluorescence was observed in red-eyed mosquitoes that were generated by crossing the 3xP3-EGFP transformants with the kh(w) white-eye mosquitoes transformed with the Drosophila cinnabar gene. Importantly, the utility of the 3xP3-EGFP, as marker gene for transformation of wild type mosquitoes, was demonstrated by strong eye-specific GFP expression in larval and pupal stages of black-eyed hybrids of the 3xP3-EGFP white-eye transformants and the wild type Rockefeller/UGAL strain. Finally, analysis of the Vg-DefA transgene expression in transformants from two established lines demonstrated strong blood-meal activation and fat-body-specific expression regulated by the Vg 1.8-kb 5' upstream region.

Aedes↗
PubMed2006

Parametric analysis of a predator-prey system stabilized by a top predator.

We present a complete parametric analysis of a predator-prey system influenced by a top predator. We study ecosystems with abundant nutrient supply for the prey where the prey multiplication can be considered as proportional to its density. The main questions we examine are the following: (1) Can the top predator stabilize such a system at low densities of prey? (2) What possible dynamic behaviors can occur? (3) Under which conditions can the top predation result in the system stabilization? We use a system of two nonlinear ordinary differential equations with the density of the top predator as a parameter. The model is investigated with methods of qualitative theory of ODEs and the theory of bifurcations. The existence of 12 qualitatively different types of dynamics and complex structure of the parametric space are demonstrated. Our studies of phase portraits and parametric diagrams show that a top predator can be an important factor leading to stabilization of the predator-prey system with abundant nutrient supply. Although the model here is applied to the plankton communities with fish (or carnivorous zooplankton) as the top trophic level, the general form of the equations allows applications of our results to other ecological systems.

Algorithms↗