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PubMed1998

Competence for natural transformation in Neisseria gonorrhoeae: a model system for studies of horizontal gene transfer.

A combined effort integrating studies of gonococcal Tfp biogenesis, the data made available from the gonococcal genome sequence project and applied molecular genetics have been used to identify the fibrillar filaments themselves, the PilT protein and the ComP protein as essential components for the DNA uptake phase of competence for natural transformation. Our ongoing studies are focused on identifying and understanding the complex interactions which exist between these essential constituents. These studies may be relevant not only to the early steps of genetic transformation but also to the two other venues for horizontal gene transfer based on recent findings. First, the thin pili of IncI1 conjugal plasmids required for liquid mating belong to the type IV family of pili (Yoshida et al., 1998). Secondly, type IV pili are required for lysogenic conversion of Vibrio cholerae by a filamentous phage encoding cholera toxin (Waldor and Mekalanos, 1996). How these highly conserved surface organelles contribute to such diverse forms of DNA translocation across membranes remains to be seen.

Adenosine Triphosphatases↗
PubMed2006

Designing and transgenic expression of melanin gene in tobacco trichome and cotton fiber.

In Streptomyces antibioticus, there are two genes TYRA and ORF438 required for the melanin biogenesis. To investigate whether expression of these two genes in cotton can change cotton fiber colour, we modified the TYRA and ORF438 genes to make their codon usage closer to the codon preference of cotton fiber genes. The resulting versions of these two genes were referred to as DTYRA and DORF438, respectively. Vacuolar targeting signals were also added to their ends. Under the cotton fiber specific LTP3 promoter, DORF438 and DTYRA were first transformed into model plant tobacco (Nicotiana tabacum). Molecular analyses showed that both the DORF438 and DTYRA genes were successfully expressed in transgenic plants, and the melanin deposition was observed in the trichomes of transgenic tobacco. Excitedly, when the same DORF438 and DTYRA expression cassettes were transformed into cotton (Gossypium hirsutum L.) by pollen tube pathway, the colour of cotton fiber changed from white to brown. Molecular analyses confirmed that both genes were transformed into cotton and expressed successfully. All these results indicate that the synthesized DOFR438 and DTYRA genes can work well in tobacco and cotton. Our study may provide a potential method for modifying the colour of cotton fiber.

Amino Acid Sequence↗
PubMed1999

Myb-transformed hematopoietic cells as a model for monocyte differentiation into dendritic cells and macrophages.

Immune induction is effected through the interaction of antigen-presenting cells with specific receptors on the surface of thymus-derived lymphocytes. Cells most able to ingest, process, and present antigen appear to be related to the mononuclear phagocyte/neutrophil series. For example dendritic cells (DC) can be found in colonies of GM-CSF-responsive bone marrow cells, and under experimental conditions are routinely expanded as a population in vitro from GM-CSF-responsive progenitor cells. To address the question of DC lineage and to determine what genes are involved in lineage commitment, we have generated a series of GM-CSF-responsive cell lines that can be induced to differentiate in a homogeneous manner in vitro. The cloned cell lines are derived from 12-day fetal liver and are transformed with a truncated form of c-myb, which lacks the normal autoregulatory sequences. As far as we know, these myb-transformed hemopoi-etic cells (MTHC) differ from normal only in the unregulated expression of myb, a gene whose expression is obligatory for proliferation of hemopoietic cells. MTHC in the presence of TNF-alpha and IL-4 will differentiate into cells that have many of the properties of macrophages. When the same MTHC lines are exposed to TNF-alpha in combination with IFN-gamma, the cells instead become DC. The differentiated DC are potent presenters of antigen in mixed lymphocyte reactions and of soluble antigen to specific T cell lines. Thus, cells with the properties of both macrophages and DC can be derived from a single type of GM-CSF-responsive progenitor cell. We have used this MTHC system to analyze differences in gene expression as the cells mature along the DC and macrophage pathways. A distinctive pattern of differentially expressed cDNAs is evident where macrophage-specific cDNAs are homologous to genes encoding cytoskeletal and cell-surface proteins, whereas the DC-specific cDNAs are homologous to signaling, chemokine, and IFN-gamma-inducible genes. We discuss the utility of MTHC in analyzing the relationships between DC and macrophages, and suggest that DC and macrophages represent extreme phenotypes in a spectrum of antigen handling cells that are somewhat interchangeable, depending on their immediate environment.

Animals↗
PubMed2003

Cleaning up with genomics: applying molecular biology to bioremediation.

Bioremediation has the potential to restore contaminated environments inexpensively yet effectively, but a lack of information about the factors controlling the growth and metabolism of microorganisms in polluted environments often limits its implementation. However, rapid advances in the understanding of bioremediation are on the horizon. Researchers now have the ability to culture microorganisms that are important in bioremediation and can evaluate their physiology using a combination of genome-enabled experimental and modelling techniques. In addition, new environmental genomic techniques offer the possibility for similar studies on as-yet-uncultured organisms. Combining models that can predict the activity of microorganisms that are involved in bioremediation with existing geochemical and hydrological models should transform bioremediation from a largely empirical practice into a science.

Bacteria↗
PubMed2006

Activin is a neuronal survival factor that is rapidly increased after transient cerebral ischemia and hypoxia in mice.

One approach for developing targeted stroke therapies is to identify the neuronal protective and destructive signaling pathways and gene expression that follow ischemic insult. In some neural injury models, the transforming growth factor-beta family member activin can provide neuroprotective effects in vivo and promote neuronal survival. This study tests if activin supports cortical neurons after ischemic challenge in vitro and if signals after cerebral ischemia involve activin in vivo. In a defined cell culture model that uses hydrogen peroxide (H(2)O(2))-free radical stress, activin addition maintained neuronal survival. H(2)O(2) treatment increased activin mRNA twofold in surviving cortical neurons, and inhibition of activin with neutralizing antibodies caused neuronal death. These data identify activin gene changes as a rapid response to oxidative stress, and indicate that endogenous activin acts as a protective factor for cortical neurons in vitro. Similarly, after transient focal cerebral ischemia in adult mice, activin mRNA increased at 1 and 4 h ipsilateral to the infarct but returned to control values at 24 h after reperfusion. Intracellular activated smad signals were detected in neurons adjacent to the infarct. Activin was also increased after 2 h of 11% hypoxia. Activin mRNA increased at 1 h but not 4 or 24 h after hypoxia, similar to the time course of erythropoietin and vascular endothelial growth factor induction. These findings identify activin as an early-regulated gene response to transient ischemia and hypoxia, and its function in cortical neuron survival during oxidative challenge provides a basis to test activin as a potential therapeutic in stroke injury.

Activins↗
PubMed2005

Uncertainties in extreme surge level estimates from observational records.

Ensemble simulations with a total length of 7540 years are generated with a climate model, and coupled to a simple surge model to transform the wind field over the North Sea to the skew surge level at Delfzijl, The Netherlands. The 65 constructed surge records, each with a record length of 116 years, are analysed with the generalized extreme value (GEV) and the generalized Pareto distribution (GPD) to study both the model and sample uncertainty in surge level estimates with a return period of 104 years, as derived from 116-year records. The optimal choice of the threshold, needed for an unbiased GPD estimate from peak over threshold (POT) values, cannot be determined objectively from a 100-year dataset. This fact, in combination with the sensitivity of the GPD estimate to the threshold, and its tendency towards too low estimates, leaves the application of the GEV distribution to storm-season maxima as the best approach. If the GPD analysis is applied, then the exceedance rate, lambda, chosen should not be larger than 4. The climate model hints at the existence of a second population of very intense storms. As the existence of such a second population can never be excluded from a 100-year record, the estimated 104-year wind-speed from such records has always to be interpreted as a lower limit.

Computer Simulation↗
PubMed2000

A comparative study of transformational leadership in nursing development units and conventional clinical settings.

AIMS: This is a comparative study of the leadership provided by nurse managers and leaders in Nursing Development Units and conventional clinical settings in England. BACKGROUND: Nursing development units (NDUs) were originally conceived as centres of nursing excellence, innovation and leadership development. This article describes the first published use of a leadership practices inventory (LPI) explicitly based upon a model of transformational leadership. This style of leadership has been commended as highly effective and suitable for nursing. METHODS: The use of the LPI was piloted as a postal questionnaire and as a schedule for telephone interviewing, these pilots supported the use of telephone interviewing in the main study. Two matched samples of 70 nurses in total were recruited from across England, comprising 14 nurse leaders and 56 of their day to day colleagues. Data was collected by telephone interviewing over a 6-week period between February and April 1998. Six null hypotheses were developed to identify significant inter-group differences in leadership behaviour. Descriptive and inferential data analysis techniques were employed using SPSS for Windows. FINDINGS: The leadership provided by NDU leaders was evaluated more highly than non-NDU leaders. A higher level of congruence between self and observer evaluations was shown by NDU leaders. Statistically significant inter-group differences were apparent in three of the five practices of exemplary leadership and in the overall leadership behaviour. NDU leaders show greater self awareness and are more transformational than their non-NDU counterparts. The limitations of the study design are discussed. CONCLUSIONS: NDU leaders provide leadership of a more transformational nature than their counterparts working in conventional settings. This finding suggests that NDU leaders have enhanced leadership potential and that formalizing nursing development within NDUs may promote the emergence of transformational leadership and provide a microculture in which it might flourish. The LPI is regarded as a useful, adaptable tool suitable for use in UK nursing applications including research, leadership development and education.

Attitude of Health Personnel↗
PubMed2006

A risk score for predicting incident diabetes in the Thai population.

OBJECTIVE: The objective of this study was to develop and evaluate a risk score to predict people at high risk of diabetes in Thailand. RESEARCH DESIGN AND METHODS: A Thai cohort of 2,677 individuals, aged 35-55 years, without diabetes at baseline, was resurveyed after 12 years. Logistic regression models were used to identify baseline risk factors that predicted the incidence of diabetes; a simple model that included only those risk factors as significant (P < 0.05) when adjusted for each other was developed. The coefficients from this model were transformed into components of a diabetes score. This score was tested in a Thai validation cohort of a different 2,420 individuals. RESULTS: A total of 361 individuals developed type 2 diabetes in the exploratory cohort during the follow-up period. The significant predictive variables in the simple model were age, BMI, waist circumference, hypertension, and history of diabetes in parents or siblings A cutoff score of 6 of 17 produced the optimal sum of sensitivity (77%) and specificity (60%). The area under the receiver-operating characteristic curve (AUC) was 0.74. Adding impaired fasting glucose or impaired glucose tolerance status to the model slightly increased the AUC to 0.78; adding low HDL cholesterol and/or high triglycerides barely improved the model. The validation cohort demonstrated similar results. CONCLUSIONS: A simple diabetes risk score, based on a set of variables not requiring laboratory tests, can be used for early intervention to delay or prevent the disease in Thailand. Adding impaired fasting glucose or impaired glucose tolerance or triglyceride and HDL cholesterol status to this model only modestly improves the predictive ability.

Adult↗
PubMed2003

Type IV pili-related natural transformation systems: DNA transport in mesophilic and thermophilic bacteria.

Horizontal gene flow is a driving force for bacterial adaptation. Among the three distinct mechanisms of gene transfer in bacteria, conjugation, transduction, and transformation, the latter, which includes competence induction, DNA binding, and DNA uptake, is perhaps the most versatile mechanism and allows the incorporation of free DNA from diverse bacterial species. Here we review DNA transport machineries mediating uptake of naked DNA in gram-positive and gram-negative bacteria. Different putative models of transformation machineries comprising components similar to proteins of type IV pili are presented. Emphasis is placed on a comparative discussion of the underlying mechanisms of DNA transfer in mesophilic and extremely thermophilic bacteria, highlighting conserved and distinctive features of these transformation machineries.

Adaptation, Physiological↗
PubMed2003

[Study on the defluoridation of drinking water with model-La cation exchange resin].

Model-La cation exchange resin was transformed from strong acid cation exchange resin, which was used for the defluoridation of drinking water. The 001 x 7 strong acid cation exchange resin was transformed into model-La cation exchange by soaking in the La(NO3)3 solution. The F- in the water was removed by model-La cation exchange resin under the optimum condition because it was combined into fluoride with the La3+ in the model-La cation exchange resin. The used resin was regenerated with the La(NO3)3 solution and was used to defluoridate many times. The optimum conditions of transform and defluoridation and regeneration were d(rasin) = 0.315-0.600 mm, V(rasin):V(regeneration) = 1:6, t(transform) = 48 h, T = 298.16 K(25 degrees C). The defluoridation capacity was 5.60 mg/g in column test, and 4.08 mg/g in batch test. The model-La cation exchange resin could be used for defluoridation for 8 times. The results suggest that the model-La cation exchange resin is a novel material of defluoridation. This method is easy to master and the pH value of the solution doesn't need to be regenerated that the cost of defluoridation can be reduced significantly and it can be used for a long time.

Cation Exchange Resins↗
PubMed1997

[Paradigmatic changes in care caused by the experiences of pediatric nurses].

The aim of this study is revealing the work process development of nurses which works in the child care area and to understand how paradigmatical transformations of model and care occur from the daily experience. The participants were ten (10) nurses, all of them, females of long experience in the area of child care. This investigation follows the four steps indicated by Giorgi (1985) and Comiotto (1992). The results showed four phenomenological essences: building one's self; the discovery of the child care significance; the nurse as educator; the perception of the constant series of transformations. Starting from the essences, the phenomenological dimensions appear in number of fourteen (14). This work provided profound reflections about the relationship of the process and the act of care.

Adult↗
PubMed1992

Acquisition of responsiveness to chemical carcinogens by rodent embryo fibroblasts expressing high levels of the c-myc proto-oncogene.

We investigated the ability of overexpression of the c-myc proto-oncogene to potentiate in vitro transformation by model chemical carcinogens. A mouse c-myc gene was introduced to C3H 10T1/2 and Rat 6 embryo fibroblast cell lines via a retroviral vector containing the gene for neomycin resistance. Our present work extends previous findings by showing that individual vectored C3H 10T1/2 clones have enhanced (two-fold to sevenfold) sensitivity to benzo[a]pyrene (BP) and N-methyl-N-nitro-N'-nitrosoguanidine (MNNG). Rat 6 clones acquiring the c-myc gene display various degrees of altered morphology. They form orderly but densely packed cells, grow to higher saturation density, and yield microcolonies in soft agar. The degree of altered growth properties is directly correlated with the level of c-myc expression. Transient exposure of c-myc-expressing clones to BP and MNNG induced the formation of distinct, large colonies in soft agar, whereas the untreated cells formed microcolonies and the parental Rat 6 cells remained single cells in soft agar. We also demonstrated that the degree of responsiveness to chemical carcinogens of the clones correlates with their ability to form microcolonies in soft agar. These cells overexpressing c-myc may be used as a model system to study the interaction between oncogenes and chemical carcinogens in the process of multistage carcinogenesis.

Animals↗
PubMed1999

Differential contribution of the ERK and JNK mitogen-activated protein kinase cascades to Ras transformation of HT1080 fibrosarcoma and DLD-1 colon carcinoma cells.

Although an important contribution of ERK and JNK mitogen-activated protein kinase (MAPK) activation in Ras transformation of rodent fibroblasts has been determined, their role in mediating oncogenic Ras transformation of human tumor cells remains to be established. We have utilized the human HT1080 fibrosarcoma and DLD-1 colon carcinoma cell lines, which contain endogenous mutated and oncogenic N- and K-ras alleles, respectively, to address this role. Study of these cells is advantageous over Ras-transformed rodent model cell systems for two key reasons. First, the ras mutations occurred naturally in the progression of the tumors from which the cell lines were derived, rather than due to overexpression of an exogenously introduced gene. Second, although these tumor cells possess defects in multiple genetic loci, it has been established that mutated Ras contributes significantly to the transformed phenotype of these cells. Clonal variant lines of HT1080 and DLD-1 have been isolated which have lost the oncogenic ras allele and exhibit a corresponding impairment in growth transformation in vitro and in vivo. We found that upregulation of Raf/MEK/ERK and JNK correlated with expression of oncogenic Ras in HT1080, but not DLD-1 cells. Furthermore, inhibition of ERK activation in parental HT1080 cells caused the same changes in cell morphology and actin stress fiber organization seen with loss of expression of activated N-Ras(61K). Thus, we suggest that constitutive activation of the Raf/MEK/ERK and JNK pathways is necessary for Ras-induced transformation of HT1080 but not DLD-1 cells. These results emphasize that cell type differences exist in the signaling pathways by which oncogenic Ras causes transformation.

3T3 Cells↗
PubMedDate not supplied

Transforming growth factor-beta isoforms expressions in pulmonary adenocarcinomas as prognostic markers: an immunohistological study of one hundred and twenty patients.

The transforming growth factor (TGF)-beta1, TGF-beta2 and TGF-beta3 expressions were immunohistologically studied in tissues specimens from 120 patients with a pulmonary adenocarcinoma. The results of a univariate analysis indicated that the expression of each of the TGF-beta isoforms correlated with the prognosis. Of the three prognostic factors examined using Cox's stepwise regression model, the TGF-beta1 isoform was found to correlate with survival. These findings suggest that TGF-beta isoforms play an important role in tumor progression and that the TGF-beta1 isoform is a useful prognostic marker for pulmonary adenocarcinomas.

Adenocarcinoma↗
PubMed1992

[Establishment and computer drawings of a dynamic mathematical eyeball model].

A dynamic mathematic model of the eyeball is established with the computer on the basis of ocular anatomical data and equations of the axial length as the variable in relation to other parameters. With an automatic plotter, the model is transformed into 4 geometric diagrams of the frontal and lateral views, and the meridian and coronary sections. Meanwhile, a set of pictures for intraocular foreign body localization is developed.

Computer Graphics↗
PubMed1994

Expression of transforming growth factor-beta mRNAs and proteins in pulmonary vascular remodeling in the sheep air embolization model of pulmonary hypertension.

Transforming growth factor-beta (TGF-beta) has been suggested as one of the mediators of vascular remodeling in chronic pulmonary hypertension. We have previously shown a transient early increase in TGF-beta levels in lung lymph during the development of sustained pulmonary hypertension in a sheep model (12 days of air embolization). The present study examines expression and cellular localization of mRNA and protein of the three mammalian isoforms of TGF-beta in lung biopsy tissue taken during the development of pulmonary hypertension (0, 1, 4, 8, and 12 days of embolization). In control tissue, immunohistochemical techniques localized each of the TGF-beta proteins in an identical pattern in large preacinar airways--bronchial epithelium and subepithelial cells--and in the medial wall of muscular vessels; no protein was detected in intraacinar regions. Following air embolization, immunoreactivity appeared in peripheral lung. At day 1, immunoreactivity for TGF-beta 1 and TGF-beta 3 proteins was seen in edema fluid, in perivascular cells associated with nonmuscular intraacinar arteries, and in alveolar walls; no increased immunoreactivity was detected for TGF-beta 2. After 4, 8, and 12 days of embolization, immunoreactivity for all three TGF-beta proteins was associated with newly muscularized intraacinar arteries. With in situ hybridization, the three TGF-beta mRNAs co-localized in lung tissue from both control and air-embolized animals. In control tissue, hybridization was seen around preacinar airways and muscular vessels; no hybridization seen in intraacinar regions of the lung. After 1 day of embolization, the pattern of hybridization was similar to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗