Jonathan Sg | Universidad Veracruzana (original) (raw)

Papers by Jonathan Sg

Journal of Trauma-injury Infection and Critical Care, 2008

The purpose of this American Association for the Surgery of Trauma multicenter study is to assess... more The purpose of this American Association for the Surgery of Trauma multicenter study is to assess the early efficacy and safety of endovascular stent grafts (SGs) in traumatic thoracic aortic injuries and compare outcomes with the standard operative repair (OR). Prospective, multicenter study. Data for the following were collected: age, blood pressure, and Glasgow Coma Scale (GCS) at admission, type of aortic injury, injury severity score, abbreviate injury scale (AIS), transfusions, survival, ventilator days, complications, and intensive care unit and hospital days. The outcomes between the two groups (open repair or SG) were compared, adjusting for presence of critical extrathoracic trauma (head, abdomen, or extremity AIS >3), GCS score </=8, systolic blood pressure <90 mm Hg, and age…

Bulletin of The Royal College of Surgeons of England, 2006

Experimental Eye Research, 2004

A disulfide bond between key redox-sensitive cysteine residues and glutathione is one mechanism b... more A disulfide bond between key redox-sensitive cysteine residues and glutathione is one mechanism by which redox related allosteric effectors can regulate protein structure and function. Here we test the hypothesis that glutaredoxin-1 (Grx-1), a member of the oxidoreductase family of enzymes, may be a critical component of redox-sensitive molecular switches by mediating reversible protein S-glutathionylation and enzymatic catalysis of thiol/disulfide exchange. Deglutathionylation of a 70 kDa protein by Grx-1 was detected using a monoclonal antibody specific to protein S-glutathionylation. Heat shock cognate protein 70 (Hsc70) was identified as a substrate of Grx-1 through mass spectrometry. Recombinant Hsc70 was glutathionylated in vitro, and protein S-glutathionylation reversed by Grx-1. Glutathionylated Hsc70 was more effective in preventing luciferase aggregation at 438C than reduced Hsc70 in a dose dependent fashion. ATP did not effect the chaperone activity of Hsc70-SG but did increase the activity of reduced Hsc70-SG. Reversible glutathionylation of Hsc70 may provide a mechanism for post-translation regulation of chaperone activity. q

Atmospheric Environment, 1996

Model uncertainty is a major issue concerning regional-scale air quality simulation. One major so... more Model uncertainty is a major issue concerning regional-scale air quality simulation. One major source of uncertainty in regional Eulerian models is due to sub-grid-scale (SGS) effects related to anthropogenic emissions. Regional models typically have horizontal grid resolution (A) of 20-80 km. Since NO~ chemistry in plumes is nonlinear and often diffusion-limited, the sudden dilution of plumes over regional grid dimensions, as in current models, can lead to a fundamental distortion of their chemistry, resulting in over-production of ozone, peroxides, sulfates and nitrates in the source region, and a related over-depletion of NOx. The corresponding model uncertainty over the whole regional domain remains unquantified. In this paper, we use high-resolution information from urban and regional emission inventories and plume field studies to examine SGS features of the emissions of anthropogenic NOx and VOC (volatile organic compounds), and of their mesoscale dispersion and chemistry. Such examination provides useful insight into some of the main sources of SGS uncertainty, as well as guidance for reducing it. The mesoscale chemistry of power plant plumes is very diffusion-limited, being controlled by VOC entrainment from the background. The crosswind spread of large point-source plumes typically takes 4-6 h to reach 30 km in convective conditions, and at least a full diurnal cycle to reach 80 km. For A much larger than 20--30 km, regional models will not be able to capture the essence of the behavior of rural point-source plumes even with plume-in-grid treatment, or to resolve the NOx emissions from many large power plants in urban peripheries from the urban VOC emissions. Within urban areas, there is progressive improvement in the resolution of the important ratio VOC/NOx as A is decreased below 20 km. The nature of these emissions-related SGS features suggests that significant gain in regional model accuracy should result by limiting A to 20-30 km in the regional domain, by the use of finer nested gridding in metropolitan sub-domains, and by a reactive plume-in-grid treatment of major point-source emissions. Copyright

Although the use of business simulation games as a means of active learning has been widely debat... more Although the use of business simulation games as a means of active learning has been widely debated, there is continuing interest in how students learn from and respond to them. This paper presents a quantitative exploration of students' perceptions of a business simulation game. Four factors are extracted that reflect students' perceptions of the learning- gaming experience and the effects

Journal of Investigative Dermatology, 1988

Obesity Surgery, 2007

Background Sleeve gastrectomy (SG) has been used for the surgical treatment of morbid obesity, as... more Background Sleeve gastrectomy (SG) has been used for the surgical treatment of morbid obesity, as a first step or as a definitive treatment.The objective of this pilot study was to establish an animal model for SG in Wistar rats. Methods 12 male Wistar rats were operated on. 8 of them underwent a SG, with a hand-sewn invaginating suture, and 4 underwent a laparotomy and stomach manipulation (control group). Sterilized materials, prophylactic antibiotics and nutritional supplementation were used. The animals’ weight was checked on the operation day and on a weekly basis, for 7 weeks. Results The experimental SG model was possible due to careful procedures in the pre- and postoperative period. The average weight loss in the sleeve gastrectomy group was 49.6 g (43 to 60 g) until the 4th week, whereas in the control group average weight loss was 15 g (10 to 25 g) but the weight loss was achieved in the 1st week. After the 7th week, there was weight gain in both groups. However, in the SG group, this gain was significantly lower than in the control group. Conclusion It has been possible to obtain a SG experimental model. The effects of this SG appear to be beneficial in weight loss. Biochemical and molecular mechanisms may also be investigated based on this model.

Gene, 1996

Previous studies have suggested that inducible erythromycin (Er) resistance in staphylococci medi... more Previous studies have suggested that inducible erythromycin (Er) resistance in staphylococci mediated by the plasmid-borne ABC-transporter msrA is dependent on additional unidentified chromosomally encoded transmembrane (TM) domains. The requirement for two S. aureus candidate sequences, stpC and smpC, highly similar to sequences adjacent to msrA on the original S. epidermidis plasmid was investigated. Deletion of the sequences by allelic replacement was accomplished by electroporation of S. aureus RN4220 with a nonreplicating suicide vector. S. aureus strains carrying a delta(stpC-smpC) mutation showed an identical ErR phenotype to those arising from single crossover events and unmutated RN4220 containing msrA. This proves that neither stpC nor smpC is required for ErR. To further define the minimal functional unit required for MSR, the control region within the leader sequence of msrA was deleted. This resulted in constitutive resistance to Er and type B streptogramins (Sg), proving that SgR does not require the presence of Er. Deletion constructs containing the N- or C-terminal ABC regions of MsrA did not confer ErR in RN4220 singly or in combination.

Archives of Biochemistry and Biophysics, 2003

4-Hydroxynonenal (4HNE) is a major product of peroxidative membrane lipid destruction and exerts ... more 4-Hydroxynonenal (4HNE) is a major product of peroxidative membrane lipid destruction and exerts a variety of deleterious actions through formation of covalent adducts with cellular nucleophiles. Consequently, a number of cellular enzyme systems exist that are capable of detoxifying this reactive aldehyde by oxidation, reduction, or conjugation with glutathione. In this investigation we characterize the multidrug resistance-associated protein 2 (MRP2) as the primary transmembrane transport protein in hepatocytes responsible for extracellular export of 4HNE-glutathione conjugate (HNE-SG) from the intracellular site of its formation. Suspensions of freshly isolated hepatocytes (10 6 cells/ml) prepared from either wild-type (WT) Wistar rats or TR À rats possessing a mutated Mrp2 gene were incubated with 4HNE (50 nmol/10 6 cells). The formation of 4HNE metabolites, 4-hydroxynonenoic acid (HNA) and HNE-SG, was quantified in the intracellular and extracellular fractions. These studies demonstrated that freshly isolated hepatocytes from both WT and TR À rats formed and exported the oxidized metabolite (HNA) to similar extents. Likewise, both populations of hepatocytes displayed nearly identical rates of glutathione conjugation with 4HNE. However, the rate of HNE-SG export from TR À hepatocytes was approximately fourfold less than that of WT hepatocytes. In TR À hepatocytes, HNE-SG accumulated and remained predominantly intracellular throughout the time course, suggesting an absence of compensatory export by other hepatocellular transporters. In conclusion, these data demonstrate that although WT and TR À hepatocytes are similar in their conjugative and oxidative metabolism of 4HNE, export of 4HNE-SG is mediated by the MRP2 transporter, a transport system distinct from that involved in HNA efflux.

We determine how the differences in the treatment of the sub-filter-scale physics affect the prop... more We determine how the differences in the treatment of the sub-filter-scale physics affect the properties of the flow for three closely related regularizations of Navier-Stokes. The consequences on the applicability of the regularizations as sub-grid-scale (SGS) models are also shown by examining their effects on super-filter-scale properties. Numerical solutions of the Clark−α model are compared to two previously employed regularizations, the Lagrangian-Averaged Navier-Stokes α−model (LANS−α) and Leray−α albeit at significantly higher Reynolds number than previous studies, namely Re ≈ 3300, Taylor Reynolds number of R λ ≈ 790, and to a direct numerical simulation (DNS) of the Navier-Stokes equations. We derive the Kármán-Howarth equation for both the Clark−α and Leray−α models. We confirm one of two possible scalings resulting from this equation for Clark−α as well as its associated k −1 energy spectrum. At sub-filter scales, Clark−α possesses similar total dissipation and characteristic time to reach a statistical turbulent steady-state as Navier-Stokes, but exhibits greater intermittency. As a SGS model, Clark−α reproduces the large-scale energy spectrum and intermittency properties of the DNS. For the Leray−α model, increasing the filter width, α, decreases the nonlinearity and, hence, the effective Reynolds number is substantially decreased. Therefore even for the smallest value of α studied Leray−α was inadequate as a SGS model. The LANS−α energy spectrum ∼ k 1 , consistent with its so-called "rigid bodies," precludes a reproduction of the large-scale energy spectrum of the DNS at high Re while achieving a large reduction in numerical resolution. We find, however, that this same feature reduces its intermittency compared to Clark−α (which shares a similar Kármán-Howarth equation). Clark−α is found to be the best approximation for reproducing the total dissipation rate and the energy spectrum at scales larger than α, whereas high-order intermittency properties for larger values of α are best reproduced by LANS−α.

Analysis of energy transfers in turbulent channel flow at Re_τ=180, 300 has been carried out usin... more Analysis of energy transfers in turbulent channel flow at Re_τ=180, 300 has been carried out using an orthogonal wavelet decomposition of DNS data. This representation is a function of discrete scale, r_m, and spatial position and is therefore suited to studying correlations between energetic turbulent events and coherent structures in the flow, these structures also being `local' in both Fourier and physical space. In the context of modelling energy transfer between the resolved, grid-scale motions and the unresolved, subgrid-scale motions in Large Eddy Simulation (LES), an important quantity is π_sg^(m)[ x], which represents the flux of energy through scale rm at location x, due only to scales smaller than r_m. In the linear sublayer π_sg^(m) is positive (i.e. flux is from the large scales to the small scales), in the mean, consistent with unsteady Couette flow, and is attributable to vortex stretching. In the buffer region π_sg^(m) is negative (`backscatter'), the opposite sense to the conventional cascade. Also π_sg^(m) is not positive over any significant portion of the channel at any scale. This deficiency is accounted for in the term ν^(m)[ x], which represents the viscous dissipation at the scale rm and raises some concerns regarding the usefulness of DNS data at these Reynolds numbers in educing structures responsible for inertial transfer. In previous studies as well as our own, it has been shown that backscatter in the buffer region is associated with sweep events (u>0, v<0) which in turn are dynamically related to quasi-streamwise vortices. We are currently using the cubic discriminant scheme of Cantwell phet. al to isolate the contribution of specific features of the near-wall flow to π_sg.

Molecular Brain, 2010

Background A central feature of Alzheimer's disease is the cleavage of the amyloid precursor prot... more Background A central feature of Alzheimer's disease is the cleavage of the amyloid precursor protein (APP) to form beta-amyloid peptide (Aβ) by the β-secretase and γ-secretase enzymes. Although this has been shown to occur after endocytosis of APP from the cell surface, the exact compartments of APP processing are not well defined. We have previously demonstrated that APP and γ-secretase proteins and activity are highly enriched in purified rat liver lysosomes. In order to examine the lysosomal distribution and trafficking of APP in cultured cells, we generated constructs containing APP fused to a C-terminal fluorescent protein tag and N-terminal HA-epitope tag. These were co-transfected with a panel of fluorescent-protein tagged compartment markers. Results Here we demonstrate using laser-scanning confocal microscopy that although APP is present throughout the endosomal/lysosomal system in transfected Cos7 and neuronal SN56 cell lines as well as in immunostained cultured mouse neurons, it is enriched in the lysosome. We also show that the Swedish and London mutations reduce the amount of APP in the lysosome. Surprisingly, in addition to its expected trafficking from the cell surface to the early and then late endosomes, we find that cell-surface labelled APP is transported rapidly and directly from the cell surface to lysosomes in both Cos7 and SN56 cells. This rapid transit to the lysosome is blocked by the presence of either the London or Swedish mutations. Conclusions These results demonstrate the presence of a novel, rapid and specific transport pathway from the cell surface to the lysosomes. This suggests that regulation of lysosomal traffic could regulate APP processing and that the lysosome could play a central role in the pathophysiology of Alzheimer's disease.

Pediatric Nephrology, 2009

Albuminuria predicts cardiovascular and end-stage kidney disease in indigenous populations. Early... more Albuminuria predicts cardiovascular and end-stage kidney disease in indigenous populations. Early detection in indigenous children may identify those who could benefit from early treatment. Community-based detection of albuminuria needs to be performed using a reliable, inexpensive, and widely available test, such as a proteinuria dipstick. Dipstick accuracy for detecting albuminuria in a community setting has not been evaluated. We assessed the accuracy of Multistix 10 SG dipsticks to detect baseline albuminuria and predict for persistent albuminuria at a 2-year follow-up in a population-based cohort of Australian Aboriginal and non-Aboriginal elementary-school-aged children. Variability in the accuracy of dipsticks in subgroups of higher risk children was analyzed using the relative diagnostic odds ratio (RDOR). Using Multistix 10 SG dipsticks, index-test-positive cases were defined as ≥0.30 g/L (1+) proteinuria and index-test-negative cases as Referent-test-positive cases were defined as spot albumin:creatinine (ACR) ≥3.4 mg/mmol, and referent-test-negative cases as ACR

Time series of MODIS vegetation indices are widely used to map vegetation. However, some noise ca... more Time series of MODIS vegetation indices are widely used to map vegetation. However, some noise can affect the temporal profiles. Thus, many techniques have been developed to smooth them. Four algorithms are applied on crop pixels in the Brazilian Amazonian State of Mato Grosso. Comparisons led to the selection of the Weighted Least Squares (WLS) algorithm and the Savitzky-Golay (SG) filter. Those techniques were computed on MODIS data in order to detect six crop classes. Tests of separability show that the smoothed data improved the potential of separability at each MODIS sub-period. Moreover, supervised classifications were then realized. The WLS data refined efficiently the classification result when using C4.5 decision tree. When using the Maximum Likelihood and Spectral Angle Mapper classifiers, the smoothed data did not improve the classification results as compared with those obtained through original MODIS data. However, it required fewer input MODIS images to reach good results. The SG filter led to better results than the WLS algorithm when using those classifiers.

Artificial Intelligence, 2002

This paper provides algorithms that use an information-theoretic analysis to learn Bayesian netwo... more This paper provides algorithms that use an information-theoretic analysis to learn Bayesian network structures from data. Based on our three-phase learning framework, we develop efficient algorithms that can effectively learn Bayesian networks, requiring only polynomial numbers of conditional independence (CI) tests in typical cases. We provide precise conditions that specify when these algorithms are guaranteed to be correct as well as empirical evidence (from real world applications and simulation tests) that demonstrates that these systems work efficiently and reliably in practice. 

Polymer, 2000

In this paper I describe the computer simulations that I have performed to critically examine the... more In this paper I describe the computer simulations that I have performed to critically examine the Lauritzen-Hoffman and the Sadler-Gilmer theories of polymer crystallization. In particular, I have computed the free energy profile for nucleation of a new crystalline layer on the growth face to compare with that assumed by the Lauritzen-Hoffman theory, I have analysed the mechanism of thickness selection in a multi-pathway model in which some of the constraints in the Lauritzen-Hoffman theory are relaxed, and I have re-examined the model used by Sadler-Gilmer. These investigations have lead to a mechanism of thickness selection of lamellar polymer crystals that differs from the two theories that I set out to examine.

Discrete Mathematics, 1995

Journal of Trauma-injury Infection and Critical Care, 2008

The purpose of this American Association for the Surgery of Trauma multicenter study is to assess... more The purpose of this American Association for the Surgery of Trauma multicenter study is to assess the early efficacy and safety of endovascular stent grafts (SGs) in traumatic thoracic aortic injuries and compare outcomes with the standard operative repair (OR). Prospective, multicenter study. Data for the following were collected: age, blood pressure, and Glasgow Coma Scale (GCS) at admission, type of aortic injury, injury severity score, abbreviate injury scale (AIS), transfusions, survival, ventilator days, complications, and intensive care unit and hospital days. The outcomes between the two groups (open repair or SG) were compared, adjusting for presence of critical extrathoracic trauma (head, abdomen, or extremity AIS &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;3), GCS score &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/=8, systolic blood pressure &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;90 mm Hg, and age…

Bulletin of The Royal College of Surgeons of England, 2006

Experimental Eye Research, 2004

A disulfide bond between key redox-sensitive cysteine residues and glutathione is one mechanism b... more A disulfide bond between key redox-sensitive cysteine residues and glutathione is one mechanism by which redox related allosteric effectors can regulate protein structure and function. Here we test the hypothesis that glutaredoxin-1 (Grx-1), a member of the oxidoreductase family of enzymes, may be a critical component of redox-sensitive molecular switches by mediating reversible protein S-glutathionylation and enzymatic catalysis of thiol/disulfide exchange. Deglutathionylation of a 70 kDa protein by Grx-1 was detected using a monoclonal antibody specific to protein S-glutathionylation. Heat shock cognate protein 70 (Hsc70) was identified as a substrate of Grx-1 through mass spectrometry. Recombinant Hsc70 was glutathionylated in vitro, and protein S-glutathionylation reversed by Grx-1. Glutathionylated Hsc70 was more effective in preventing luciferase aggregation at 438C than reduced Hsc70 in a dose dependent fashion. ATP did not effect the chaperone activity of Hsc70-SG but did increase the activity of reduced Hsc70-SG. Reversible glutathionylation of Hsc70 may provide a mechanism for post-translation regulation of chaperone activity. q

Atmospheric Environment, 1996

Model uncertainty is a major issue concerning regional-scale air quality simulation. One major so... more Model uncertainty is a major issue concerning regional-scale air quality simulation. One major source of uncertainty in regional Eulerian models is due to sub-grid-scale (SGS) effects related to anthropogenic emissions. Regional models typically have horizontal grid resolution (A) of 20-80 km. Since NO~ chemistry in plumes is nonlinear and often diffusion-limited, the sudden dilution of plumes over regional grid dimensions, as in current models, can lead to a fundamental distortion of their chemistry, resulting in over-production of ozone, peroxides, sulfates and nitrates in the source region, and a related over-depletion of NOx. The corresponding model uncertainty over the whole regional domain remains unquantified. In this paper, we use high-resolution information from urban and regional emission inventories and plume field studies to examine SGS features of the emissions of anthropogenic NOx and VOC (volatile organic compounds), and of their mesoscale dispersion and chemistry. Such examination provides useful insight into some of the main sources of SGS uncertainty, as well as guidance for reducing it. The mesoscale chemistry of power plant plumes is very diffusion-limited, being controlled by VOC entrainment from the background. The crosswind spread of large point-source plumes typically takes 4-6 h to reach 30 km in convective conditions, and at least a full diurnal cycle to reach 80 km. For A much larger than 20--30 km, regional models will not be able to capture the essence of the behavior of rural point-source plumes even with plume-in-grid treatment, or to resolve the NOx emissions from many large power plants in urban peripheries from the urban VOC emissions. Within urban areas, there is progressive improvement in the resolution of the important ratio VOC/NOx as A is decreased below 20 km. The nature of these emissions-related SGS features suggests that significant gain in regional model accuracy should result by limiting A to 20-30 km in the regional domain, by the use of finer nested gridding in metropolitan sub-domains, and by a reactive plume-in-grid treatment of major point-source emissions. Copyright

Although the use of business simulation games as a means of active learning has been widely debat... more Although the use of business simulation games as a means of active learning has been widely debated, there is continuing interest in how students learn from and respond to them. This paper presents a quantitative exploration of students&amp;amp;amp;#39; perceptions of a business simulation game. Four factors are extracted that reflect students&amp;amp;amp;#39; perceptions of the learning- gaming experience and the effects

Journal of Investigative Dermatology, 1988

Obesity Surgery, 2007

Background Sleeve gastrectomy (SG) has been used for the surgical treatment of morbid obesity, as... more Background Sleeve gastrectomy (SG) has been used for the surgical treatment of morbid obesity, as a first step or as a definitive treatment.The objective of this pilot study was to establish an animal model for SG in Wistar rats. Methods 12 male Wistar rats were operated on. 8 of them underwent a SG, with a hand-sewn invaginating suture, and 4 underwent a laparotomy and stomach manipulation (control group). Sterilized materials, prophylactic antibiotics and nutritional supplementation were used. The animals’ weight was checked on the operation day and on a weekly basis, for 7 weeks. Results The experimental SG model was possible due to careful procedures in the pre- and postoperative period. The average weight loss in the sleeve gastrectomy group was 49.6 g (43 to 60 g) until the 4th week, whereas in the control group average weight loss was 15 g (10 to 25 g) but the weight loss was achieved in the 1st week. After the 7th week, there was weight gain in both groups. However, in the SG group, this gain was significantly lower than in the control group. Conclusion It has been possible to obtain a SG experimental model. The effects of this SG appear to be beneficial in weight loss. Biochemical and molecular mechanisms may also be investigated based on this model.

Gene, 1996

Previous studies have suggested that inducible erythromycin (Er) resistance in staphylococci medi... more Previous studies have suggested that inducible erythromycin (Er) resistance in staphylococci mediated by the plasmid-borne ABC-transporter msrA is dependent on additional unidentified chromosomally encoded transmembrane (TM) domains. The requirement for two S. aureus candidate sequences, stpC and smpC, highly similar to sequences adjacent to msrA on the original S. epidermidis plasmid was investigated. Deletion of the sequences by allelic replacement was accomplished by electroporation of S. aureus RN4220 with a nonreplicating suicide vector. S. aureus strains carrying a delta(stpC-smpC) mutation showed an identical ErR phenotype to those arising from single crossover events and unmutated RN4220 containing msrA. This proves that neither stpC nor smpC is required for ErR. To further define the minimal functional unit required for MSR, the control region within the leader sequence of msrA was deleted. This resulted in constitutive resistance to Er and type B streptogramins (Sg), proving that SgR does not require the presence of Er. Deletion constructs containing the N- or C-terminal ABC regions of MsrA did not confer ErR in RN4220 singly or in combination.

Archives of Biochemistry and Biophysics, 2003

4-Hydroxynonenal (4HNE) is a major product of peroxidative membrane lipid destruction and exerts ... more 4-Hydroxynonenal (4HNE) is a major product of peroxidative membrane lipid destruction and exerts a variety of deleterious actions through formation of covalent adducts with cellular nucleophiles. Consequently, a number of cellular enzyme systems exist that are capable of detoxifying this reactive aldehyde by oxidation, reduction, or conjugation with glutathione. In this investigation we characterize the multidrug resistance-associated protein 2 (MRP2) as the primary transmembrane transport protein in hepatocytes responsible for extracellular export of 4HNE-glutathione conjugate (HNE-SG) from the intracellular site of its formation. Suspensions of freshly isolated hepatocytes (10 6 cells/ml) prepared from either wild-type (WT) Wistar rats or TR À rats possessing a mutated Mrp2 gene were incubated with 4HNE (50 nmol/10 6 cells). The formation of 4HNE metabolites, 4-hydroxynonenoic acid (HNA) and HNE-SG, was quantified in the intracellular and extracellular fractions. These studies demonstrated that freshly isolated hepatocytes from both WT and TR À rats formed and exported the oxidized metabolite (HNA) to similar extents. Likewise, both populations of hepatocytes displayed nearly identical rates of glutathione conjugation with 4HNE. However, the rate of HNE-SG export from TR À hepatocytes was approximately fourfold less than that of WT hepatocytes. In TR À hepatocytes, HNE-SG accumulated and remained predominantly intracellular throughout the time course, suggesting an absence of compensatory export by other hepatocellular transporters. In conclusion, these data demonstrate that although WT and TR À hepatocytes are similar in their conjugative and oxidative metabolism of 4HNE, export of 4HNE-SG is mediated by the MRP2 transporter, a transport system distinct from that involved in HNA efflux.

We determine how the differences in the treatment of the sub-filter-scale physics affect the prop... more We determine how the differences in the treatment of the sub-filter-scale physics affect the properties of the flow for three closely related regularizations of Navier-Stokes. The consequences on the applicability of the regularizations as sub-grid-scale (SGS) models are also shown by examining their effects on super-filter-scale properties. Numerical solutions of the Clark−α model are compared to two previously employed regularizations, the Lagrangian-Averaged Navier-Stokes α−model (LANS−α) and Leray−α albeit at significantly higher Reynolds number than previous studies, namely Re ≈ 3300, Taylor Reynolds number of R λ ≈ 790, and to a direct numerical simulation (DNS) of the Navier-Stokes equations. We derive the Kármán-Howarth equation for both the Clark−α and Leray−α models. We confirm one of two possible scalings resulting from this equation for Clark−α as well as its associated k −1 energy spectrum. At sub-filter scales, Clark−α possesses similar total dissipation and characteristic time to reach a statistical turbulent steady-state as Navier-Stokes, but exhibits greater intermittency. As a SGS model, Clark−α reproduces the large-scale energy spectrum and intermittency properties of the DNS. For the Leray−α model, increasing the filter width, α, decreases the nonlinearity and, hence, the effective Reynolds number is substantially decreased. Therefore even for the smallest value of α studied Leray−α was inadequate as a SGS model. The LANS−α energy spectrum ∼ k 1 , consistent with its so-called "rigid bodies," precludes a reproduction of the large-scale energy spectrum of the DNS at high Re while achieving a large reduction in numerical resolution. We find, however, that this same feature reduces its intermittency compared to Clark−α (which shares a similar Kármán-Howarth equation). Clark−α is found to be the best approximation for reproducing the total dissipation rate and the energy spectrum at scales larger than α, whereas high-order intermittency properties for larger values of α are best reproduced by LANS−α.

Analysis of energy transfers in turbulent channel flow at Re_τ=180, 300 has been carried out usin... more Analysis of energy transfers in turbulent channel flow at Re_τ=180, 300 has been carried out using an orthogonal wavelet decomposition of DNS data. This representation is a function of discrete scale, r_m, and spatial position and is therefore suited to studying correlations between energetic turbulent events and coherent structures in the flow, these structures also being `local' in both Fourier and physical space. In the context of modelling energy transfer between the resolved, grid-scale motions and the unresolved, subgrid-scale motions in Large Eddy Simulation (LES), an important quantity is π_sg^(m)[ x], which represents the flux of energy through scale rm at location x, due only to scales smaller than r_m. In the linear sublayer π_sg^(m) is positive (i.e. flux is from the large scales to the small scales), in the mean, consistent with unsteady Couette flow, and is attributable to vortex stretching. In the buffer region π_sg^(m) is negative (`backscatter'), the opposite sense to the conventional cascade. Also π_sg^(m) is not positive over any significant portion of the channel at any scale. This deficiency is accounted for in the term ν^(m)[ x], which represents the viscous dissipation at the scale rm and raises some concerns regarding the usefulness of DNS data at these Reynolds numbers in educing structures responsible for inertial transfer. In previous studies as well as our own, it has been shown that backscatter in the buffer region is associated with sweep events (u>0, v<0) which in turn are dynamically related to quasi-streamwise vortices. We are currently using the cubic discriminant scheme of Cantwell phet. al to isolate the contribution of specific features of the near-wall flow to π_sg.

Molecular Brain, 2010

Background A central feature of Alzheimer's disease is the cleavage of the amyloid precursor prot... more Background A central feature of Alzheimer's disease is the cleavage of the amyloid precursor protein (APP) to form beta-amyloid peptide (Aβ) by the β-secretase and γ-secretase enzymes. Although this has been shown to occur after endocytosis of APP from the cell surface, the exact compartments of APP processing are not well defined. We have previously demonstrated that APP and γ-secretase proteins and activity are highly enriched in purified rat liver lysosomes. In order to examine the lysosomal distribution and trafficking of APP in cultured cells, we generated constructs containing APP fused to a C-terminal fluorescent protein tag and N-terminal HA-epitope tag. These were co-transfected with a panel of fluorescent-protein tagged compartment markers. Results Here we demonstrate using laser-scanning confocal microscopy that although APP is present throughout the endosomal/lysosomal system in transfected Cos7 and neuronal SN56 cell lines as well as in immunostained cultured mouse neurons, it is enriched in the lysosome. We also show that the Swedish and London mutations reduce the amount of APP in the lysosome. Surprisingly, in addition to its expected trafficking from the cell surface to the early and then late endosomes, we find that cell-surface labelled APP is transported rapidly and directly from the cell surface to lysosomes in both Cos7 and SN56 cells. This rapid transit to the lysosome is blocked by the presence of either the London or Swedish mutations. Conclusions These results demonstrate the presence of a novel, rapid and specific transport pathway from the cell surface to the lysosomes. This suggests that regulation of lysosomal traffic could regulate APP processing and that the lysosome could play a central role in the pathophysiology of Alzheimer's disease.

Pediatric Nephrology, 2009

Albuminuria predicts cardiovascular and end-stage kidney disease in indigenous populations. Early... more Albuminuria predicts cardiovascular and end-stage kidney disease in indigenous populations. Early detection in indigenous children may identify those who could benefit from early treatment. Community-based detection of albuminuria needs to be performed using a reliable, inexpensive, and widely available test, such as a proteinuria dipstick. Dipstick accuracy for detecting albuminuria in a community setting has not been evaluated. We assessed the accuracy of Multistix 10 SG dipsticks to detect baseline albuminuria and predict for persistent albuminuria at a 2-year follow-up in a population-based cohort of Australian Aboriginal and non-Aboriginal elementary-school-aged children. Variability in the accuracy of dipsticks in subgroups of higher risk children was analyzed using the relative diagnostic odds ratio (RDOR). Using Multistix 10 SG dipsticks, index-test-positive cases were defined as ≥0.30 g/L (1+) proteinuria and index-test-negative cases as Referent-test-positive cases were defined as spot albumin:creatinine (ACR) ≥3.4 mg/mmol, and referent-test-negative cases as ACR

Time series of MODIS vegetation indices are widely used to map vegetation. However, some noise ca... more Time series of MODIS vegetation indices are widely used to map vegetation. However, some noise can affect the temporal profiles. Thus, many techniques have been developed to smooth them. Four algorithms are applied on crop pixels in the Brazilian Amazonian State of Mato Grosso. Comparisons led to the selection of the Weighted Least Squares (WLS) algorithm and the Savitzky-Golay (SG) filter. Those techniques were computed on MODIS data in order to detect six crop classes. Tests of separability show that the smoothed data improved the potential of separability at each MODIS sub-period. Moreover, supervised classifications were then realized. The WLS data refined efficiently the classification result when using C4.5 decision tree. When using the Maximum Likelihood and Spectral Angle Mapper classifiers, the smoothed data did not improve the classification results as compared with those obtained through original MODIS data. However, it required fewer input MODIS images to reach good results. The SG filter led to better results than the WLS algorithm when using those classifiers.

Artificial Intelligence, 2002

This paper provides algorithms that use an information-theoretic analysis to learn Bayesian netwo... more This paper provides algorithms that use an information-theoretic analysis to learn Bayesian network structures from data. Based on our three-phase learning framework, we develop efficient algorithms that can effectively learn Bayesian networks, requiring only polynomial numbers of conditional independence (CI) tests in typical cases. We provide precise conditions that specify when these algorithms are guaranteed to be correct as well as empirical evidence (from real world applications and simulation tests) that demonstrates that these systems work efficiently and reliably in practice. 

Polymer, 2000

In this paper I describe the computer simulations that I have performed to critically examine the... more In this paper I describe the computer simulations that I have performed to critically examine the Lauritzen-Hoffman and the Sadler-Gilmer theories of polymer crystallization. In particular, I have computed the free energy profile for nucleation of a new crystalline layer on the growth face to compare with that assumed by the Lauritzen-Hoffman theory, I have analysed the mechanism of thickness selection in a multi-pathway model in which some of the constraints in the Lauritzen-Hoffman theory are relaxed, and I have re-examined the model used by Sadler-Gilmer. These investigations have lead to a mechanism of thickness selection of lamellar polymer crystals that differs from the two theories that I set out to examine.

Discrete Mathematics, 1995