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D J Scott

Publications and source records attributed to D J Scott.

At least 19 recordsLinked to original sources
PubMed2001

The dimerization interface of the metastasis-associated protein S100A4 (Mts1): in vivo and in vitro studies.

The S100 calcium-binding proteins are implicated in signal transduction, motility, and cytoskeletal dynamics. The three-dimensional structure of several S100 proteins revealed that the proteins form non-covalent dimers. However, the mechanism of the S100 dimerization is still obscure. In this study we characterized the dimerization of S100A4 (also named Mts1) in vitro and in vivo. Analytical ultracentrifugation revealed that apoS100A4 was present in solution as a mixture of monomers and dimers in a rapidly reversible equilibrium (K(d) = 4 +/- 2 microm). The binding of calcium promoted dimerization. Replacement of Tyr-75 by Phe resulted in the stabilization of the dimer. Helix IV is known to form the major part of the dimerization interface in homologous S100 proteins. By using the yeast two-hybrid system we showed that only a few residues of helix IV, namely Phe-72, Tyr-75, Phe-78, and Leu-79, are essential for dimerization in vivo. A homology model demonstrated that these residues form a hydrophobic cluster on helix IV. Their role is to stabilize the structure of individual subunits rather than provide specific interactions across the dimerization surface. Our mutation data showed that the specificity at the dimerization surface is not particularly stringent, which is consistent with recent data indicating that S100 proteins can form heterodimers.

Amino Acid Sequence↗
PubMed2001

The physical maps for sequencing human chromosomes 1, 6, 9, 10, 13, 20 and X.

We constructed maps for eight chromosomes (1, 6, 9, 10, 13, 20, X and (previously) 22), representing one-third of the genome, by building landmark maps, isolating bacterial clones and assembling contigs. By this approach, we could establish the long-range organization of the maps early in the project, and all contig extension, gap closure and problem-solving was simplified by containment within local regions. The maps currently represent more than 94% of the euchromatic (gene-containing) regions of these chromosomes in 176 contigs, and contain 96% of the chromosome-specific markers in the human gene map. By measuring the remaining gaps, we can assess chromosome length and coverage in sequenced clones.

Chromosomes, Human, Pair 1↗
PubMed2001

Accuracy and effectiveness of laparoscopic vs open hepatic radiofrequency ablation.

BACKGROUND: The purpose of this study was to compare the accuracy (in terms of ultrasound-guided probe placement) and the effectiveness (in terms of pathologic tumor-free margin) of laparoscopic vs open radiofrequency (RF) ablation. METHODS: Using a previously validated tissue-mimic model, 1-cm simulated hepatic tumors were ablated in 10 pigs randomized to open or laparoscopic techniques. Energy was applied until tissue temperature reached 100 degrees C (warm-up) and thereafter for 8 min. A pathologist blinded to technique examined all specimens immediately after treatment. Analysis was by Fisher's exact test and the Mann-Whitney U test; p < 0.05 was considered significant. RESULTS: Off-center distance (3.5 +/- 1.6 vs 4.2 +/- 1.4 mm), size (24.7 +/- 3.1 vs 25.6 +/- 3.8 mm), symmetry (40% vs 73%), margin positivity (33% vs 9%), and margin distance (1.1 +/- 1.2 vs 2.2 +/- 1.6 mm) were not significantly different between laparoscopic (n = 15) and open (n = 11) ablations, respectively. The proportion of round/ovoid lesions (20% vs 64%) was lower (p = 0.043), and warm-up time (20.2 +/- 14.0 vs 10.7 +/- 7.5) was longer (p = 0.049) for the laparoscopic than for the open groups, respectively. CONCLUSION: Accurate probe placement can be achieved using laparoscopic and open RF ablation techniques. The physiologic effects of laparoscopy may alter ablation shape and warm-up time. Additional studies are needed to establish effective ways of achieving complete tumor destruction.

Animals↗
PubMed2001

Laparoscopic skills training.

BACKGROUND: The purpose of this study was to quantify the learning curve of a previously validated laparoscopic skills curriculum. METHODS: Second-year medical students (MS2, n = 11) and second (PGY2, n = 11) and third (PGY3, n = 6) year surgery residents were enrolled into a curriculum using five video-trainer tasks. All subjects underwent baseline testing, training (30 minutes per day for 10 days), and final testing. Scores were based on completion time. The relationship between task completion time and the number of practice repetitions was examined. Improvement (the difference in baseline and final performance) amongst groups was compared by one-way analysis of variance using the baseline score as a covariate; P <0.05 indicated significance. RESULTS: Baseline scores were not significantly different. Final scores were significantly better for MS2s versus PGY3s. Adjusted-improvement was significantly larger for the MS2s compared with PGY2s and PGY3s, and for PGY2s compared with PGY3s. The mean number of repetitions corresponding to a predicted 90th percentile score was 32. CONCLUSION: Inexperienced subjects benefit the most from skills training. For maximal benefit, we recommend that each task be practiced for at least 30 to 35 repetitions.

Adult↗
PubMed2001

Dual phase helical CT versus portal venous phase CT for the detection of colorectal liver metastases: correlation with intra-operative sonography, surgical and pathological findings.

AIM: To assess whether dual phase helical computed tomography (DPCT) of the liver improves the detection of colorectal liver metastases compared with portal venous phase (PVP) imaging alone. MATERIALS AND METHODS: DPCT was performed in 33 consecutive patients before laparotomy for resection of colorectal liver metastases. CT comprised 8-mm slice collimation with a pitch of 1 to 1.25; imaging was commenced 20-25 and 65-70 s after the start of injection of 150 ml of contrast medium at 5 ml/s to coincide with hepatic arterial phase (HAP) and PVP contrast enhancement, respectively. Four blinded observers independently reviewed the HAP, PVP and DPCT images recording the site and size of all lesions. Alternative-free response receiver operating characteristic (AFROC) methodology was used to analyse the results, which were correlated with surgery, intra-operative ultrasound and histology. RESULTS: The mean observer sensitivities for malignant lesion detection were 75.3% for DPCT, 69.7% for PVP imaging and 66.7% for HAP imaging alone. There was a statistically significant improvement in malignant lesion detection using DPCT when compared with PVP imaging alone (P < 0.05). The mean areas under the AFROC curves were 0.84 for DPCT and 0.82 for PVP (P < 0.03) imaging alone. CONCLUSION: The detection of colorectal liver metastases was marginally better with DPCT than with PVP imaging alone, but the discovery of additional lesions did not affect the management of any of the patients in this study.

Aged↗
PubMed2001

Do patients with critical limb ischaemia undergo multiple amputations after infrainguinal bypass surgery?

BACKGROUND: it has been suggested that an aggressive policy of bypass for limb salvage in critical ischaemia may result in patients subsequently undergoing multiple amputations. The aim of this study was to test this suggestion in the context of a dedicated Vascular Surgical Unit in a U.K. teaching hospital. METHODS: three hundred and sixty-eight patients undergoing lower limb bypass operations for critical limb ischaemia between April 1991 and March 1999 were studied retrospectively. Their median age was 69 years (IQR 64--75) and 243 (66%) were men. RESULTS: seventy-five operations were followed by one or more amputation (20%). Only 2% were multiple amputations. Age and sex had no effect on amputation rates, but emergency bypass operations led to a higher rate of amputation in those with critical limb ischaemia. CONCLUSION: patients with critical limb ischaemia who undergo lower limb bypass surgery rarely have subsequent multiple amputation.

Aged↗
PubMed2001

Long saphenous vein stripping and quality of life--a randomised trial.

OBJECTIVES: To assess the quality of life of patients undergoing sapheno-femoral junction (SFJ) ligation and long saphenous vein stripping (LSV), using two different techniques. DESIGN: Prospective, randomised trial. MATERIALS AND METHODS: Eighty patients were recruited and randomised to either Perforate Invagination (PIN) stripping (43) or Conventional stripping (37). Patients completed the Short Form 36 (SF-36) and EuroQol (EQ) questionnaires preoperatively, and postoperatively at 6 weeks and 6 months. RESULTS: Bodily pain, role function and physical summary were significantly improved at 6 months in the PIN stripping group. In the Conventional group, bodily pain and physical function were similarly improved, but not role function. EQ global quality of life was significantly and progressively improved at 6 weeks and 6 months in the PIN group (global score p<0.003; self-rated score p <0.001). In the Conventional group there was no overall improvement in global score or self-rated health. CONCLUSIONS: Primary varicose vein surgery is associated with significant and progressive improvements in quality of life scores. Whilst overall quality of health does improve in the Conventional group, this appears to be to a lesser extent than in the PIN group.

Adult↗
PubMed2001

Lack of inducible nitric oxide synthase promotes intestinal tumorigenesis in the Apc(Min/+) mouse.

BACKGROUND & AIMS: The role of the inducible isoform of nitric oxide synthase (Nos2 or iNOS) in intestinal tumorigenesis is unclear. Conflicting data also exist regarding the ability of Nos2 to modulate expression and/or activity of cyclooxygenase 2 (Cox-2), which promotes intestinal tumorigenesis. Therefore, we determined the effect of a null Nos2 genotype on intestinal tumorigenesis and Cox-2 expression/activity in the Apc(Min/+) mouse model of familial adenomatous polyposis. METHODS: Apc(Min/+)Nos2(-/-) mice were generated by successive crosses between C57BL/6-Apc(Min/+) and C57BL/6-Nos2(tm1Lau) mice. Adenoma characteristics of age-matched Apc(Min/+)Nos2(+/+) and Apc(Min/+)Nos2(-/-) mice were compared. The level and cellular localization of Nos2 messenger RNA (mRNA) expression in Apc(Min/+)Nos2(+/+) mouse intestine was determined. Cox-2 expression and activity were measured in both intestinal tissue and bone marrow-derived macrophages in vitro. RESULTS: Apc(Min/+)Nos2(-/-) mice developed significantly more intestinal adenomas than Apc(Min/+)Nos2(+/+) littermates. Epithelial cell Nos2 mRNA expression was decreased in adenomas compared with histologically normal Apc(Min/+)Nos2(+/+) intestine. There was no significant difference in Cox-2 expression or activity in either intestine or bone marrow-derived macrophages from Apc(Min/+)Nos2(+/+) and Apc(Min/+)Nos2(-/-) animals. CONCLUSIONS: Nos2 plays an antineoplastic role in the Apc(Min/+) mouse model of familial adenomatous polyposis. Nos2 does not modulate Cox-2 expression or activity in the Apc(Min/+) mouse.

Adenomatous Polyposis Coli Protein↗
PubMed2001

Endovascular repair of an inflammatory abdominal aortic aneurysm complicated by aortoduodenal fistulation with an unusual presentation.

Aortoenteric fistulation (AEF) is a well-documented late complication of open abdominal aortic aneurysm (AAA) repair, occurring in between 0.4% and 4% of cases. In the absence of an anastomosis, AEF is likely to be rare after endovascular aneurysm repair (EVAR) and has only recently been described in the literature as a result of mechanical stent failure or migration. We present the case of a 61-year-old man who underwent EVAR for an AAA with a "nonspecific" periaortic inflammatory mass. Six months postoperatively, an AEF developed, presenting with metastatic sepsis followed by septic infective thromboembolization to his right leg, and amputation was necessary. His stent was well positioned and mechanically intact. We emphasize the need for vigilance about the risk of AEF when adopting an endovascular approach to repair the AAA with a nonspecific periaortic inflammatory mass and highlight the need for awareness about the unusual septic manifestations of AEF.

Aortic Aneurysm, Abdominal↗
PubMed2001

Laparoscopic marsupialization and hemisplenectomy for splenic cysts.

BACKGROUND: Splenic cysts are a rare clinical entity in the United States, and historically, management has consisted of either partial or total splenectomy via an open approach. Laparoscopic treatment of splenic cysts with preservation of splenic parenchyma offers several advantages. Compared with the open approach, a laparoscopic approach may result in less postoperative pain and a more rapid return to full activity. Compared with total splenectomy, splenic preservation eliminates the risk of overwhelming postsplenectomy infection. PATIENTS AND METHODS: We present two patients with splenic cysts. One patient was treated with laparoscopic marsupialization of the cyst and the other with laparoscopic hemisplenectomy. RESULTS: Both patients are without further symptoms at 26 and 5 months' follow-up, respectively. CONCLUSIONS: Laparoscopic marsupialization and hemisplenectomy are appropriate treatment options for patients with splenic cysts.

Adult↗
PubMed2001

The use of a standard proforma in breast cancer reporting.

AIM: To determine whether the introduction of a standard reporting proforma has led to an improvement in the completeness of histopathology reports for breast cancer excision specimens. METHODS: A standard reporting proforma was designed using the Royal College of Pathologists' minimum dataset for breast cancer histopathology reports and the national histopathology reporting form of the National Health Service (NHS) breast screening programme. This was introduced into our department in June 1999, with reports generated from the proforma replacing the standard text reports. The pathological information contained in 50 text reports issued before the introduction of the proforma and 50 reports generated using the proforma was compared with the minimum dataset and NHS breast screening programme guidelines. RESULTS: A general improvement in documentation of individual pathological features was noted after introduction of the proforma. This was most significant in relation to documentation of features, such as microcalcification and ductal carcinoma in situ. In addition, important features such as tumour grade, tumour size, and hormone receptor status were documented more frequently in the proforma group. There was an overall increase in the number of reports regarded as complete after introduction of the proforma. CONCLUSIONS: The introduction of a standard proforma led to a significant improvement in the completeness of breast cancer histopathology reports in this centre, but continued vigilance is needed to ensure that standards continue to improve.

Breast Neoplasms↗
PubMed2001

Laparoscopic Roux-en-Y gastric bypass using the porcine model.

BACKGROUND: The laparoscopic Roux-en-Y gastric bypass (LRYGBP) may be performed using a variety of methods. The purpose of this study was to learn how to perform the Roux-en-Y gastric bypass operation laparoscopically, using a porcine model. MATERIALS AND METHODS: 11 domestic pigs (mean weight 47 kg) underwent LRYGBP. In 8 animals, a completely laparoscopic approach was attempted, while in 3 animals a hand-assist device was used. Techniques for anvil placement, pouch calibration, and limb-length measurement were evaluated. Animals were sacrificed at the end of the procedure, and operative results were recorded. RESULTS: The hand-assist device restored tactile feedback but obscured visualization. The gastrojejunostomy leak rate was 64%, and the jejunojejunostomy leak rate was 73%. Anvil placement using transgastric and transoral methods was feasible. Calibrating the pouch with a Baker's tube was more accurate than using anatomical landmarks. Measuring limb-lengths using Babcock clamps was reliable with practice. CONCLUSION: The frailty of the porcine small intestine may limit one's ability to achieve intact anastomoses. Despite the anatomic limitations, the porcine model was well-suited for skill development and evaluation of techniques for performing the LRYGBP operation.

Anastomosis, Roux-en-Y↗
PubMed2001

The impact of intense laparoscopic skills training on the operative performance of urology residents.

PURPOSE: As laparoscopy has become more commonplace in urology, increased emphasis has been placed on laparoscopic education. We assessed the impact of laparoscopic skills training on the operative performance of urological surgeons inexperienced with laparoscopy. MATERIALS AND METHODS: Urology residents were prospectively randomized to undergo laparoscopic skills training (6) or no training (6). Baseline assessment of operative performance (scale 0 to 35) during porcine laparoscopic nephrectomy was completed by all subjects. Cumulative time to complete laparoscopic tasks using an inanimate trainer was also recorded. The skills training group then practiced inanimate trainer tasks for 30 minutes daily for 10 days. The 2 groups then repeated the timed inanimate trainer tasks and underwent repeat assessment of the ability to perform porcine laparoscopic nephrectomy. RESULTS: At baseline no statistical difference was noted in laparoscopic experience, inanimate trainer time or overall operative assessment in the 2 groups. In the skills training group mean cumulative time to complete inanimate trainer tasks decreased from 341 to 176 seconds (p = 0.003), while in the control group it decreased from 365 to 301 (p = 0.15). Operative assessment improved from initial to repeat porcine laparoscopic nephrectomy regardless of the trained versus control randomization grouping (22.0 to 27.8, p = 0.0008 and 20.8 to 26.5, p = 0.00007, respectively). CONCLUSIONS: In vivo experience enables urological surgeons inexperienced with laparoscopy to improve significantly in all aspects of complex laparoscopic procedures. In this pilot study the magnitude of improvement was independent of additional training in laparoscopic skills. Educational curriculum should include in vivo practice in addition to skills training.

Animals↗
PubMed2000

Metastasis-associated protein Mts1 (S100A4) inhibits CK2-mediated phosphorylation and self-assembly of the heavy chain of nonmuscle myosin.

A role for EF-hand calcium-binding protein Mts1 (S100A4) in the phosphorylation and the assembly of myosin filaments was studied. The nonmuscle myosin molecules form bipolar filaments, which interact with actin filaments to produce a contractile force. Phosphorylation of the myosin plays a regulatory role in the myosin assembly. In the presence of calcium, Mts1 binds at the C-terminal end of the myosin heavy chain close to the site of phosphorylation by protein kinase CK2 (Ser1944). In the present study, we have shown that interaction of Mts1 with the human platelet myosin or C-terminal fragment of the myosin heavy chain inhibits phosphorylation of the myosin heavy chain by protein kinase CK2 in vitro. Mts1 might also bind directly the beta subunit of protein kinase CK2, thereby modifying the enzyme activity. Our results indicate that myosin oligomers were disassembled in the presence of Mts1. The short C-terminal fragment of the myosin heavy chain was totally soluble in the presence of an equimolar amount of Mts1 at low ionic conditions (50 mM NaCl). Depolymerization was found to be calcium-dependent and could be blocked by EGTA. Our data suggest that Mts1 can increase myosin solubility and therefore suppress its assembly.

Blood Platelets↗
PubMed2000

Interaction of sigma factor sigmaN with Escherichia coli RNA polymerase core enzyme.

The equilibrium binding and kinetics of assembly of the DNA-dependent RNA polymerase (RNAP) sigma(N)-holoenzyme has been investigated using biosynthetically labelled 7-azatryptophyl- (7AW)sigma(N). The spectroscopic properties of such 7AW proteins allows their absorbance and fluorescence to be monitored selectively, even in the presence of high concentrations of other tryptophan-containing proteins. The 7AWsigma(N) retained its biological activity in stimulating transcription from sigma(N)-specific promoters, and in in vitro gel electrophoresis assays of binding to core RNAP from Escherichia coli. Furthermore, five Trp-->Ala single mutants of sigma(N) were shown to support growth under conditions of nitrogen limitation, and showed comparable efficiency in activating the sigma(N)-dependent nifH promoter in vivo, indicating that none of the tryptophan residues were essential for activity. The equilibrium binding of 7AWsigma(N) to core RNAP was examined by analytical ultracentrifugation. In sedimentation equilibrium experiments, absorbance data at 315 nm (which reports selectively on the distribution of free and bound 7AWsigma(N)) established that a 1:1 complex was formed, with a dissociation constant lower than 2 microM. The kinetics of the interaction between 7AWsigma(N) and core RNAP was investigated using stopped-flow spectrofluorimetry. A biphasic decrease in fluorescence intensity was observed when samples were excited at 280 nm, whereas only the slower of the two phases was observed at 315 nm. The kinetic data were analysed in terms of a mechanism in which a fast bimolecular association of sigma(N) with core RNAP is followed by a relatively slow isomerization step. The consequences of these findings on the competition between sigma(N) and the major sigma factor, sigma(70), in Escherichia coli are discussed.

DNA-Directed RNA Polymerases↗
PubMed2000

Interaction of sigma 70 with Escherichia coli RNA polymerase core enzyme studied by surface plasmon resonance.

The interaction between the core form of bacterial RNA polymerases and sigma factors is essential for specific promoter recognition, and for coordinating the expression of different sets of genes in response to varying cellular needs. The interaction between Escherichia coli core RNA polymerase and sigma 70 has been investigated by surface plasmon resonance. The His-tagged form of sigma 70 factor was immobilised on a Ni2+-NTA chip for monitoring its interaction with core polymerase. The binding constant for the interaction was found to be 1.9x10(-7) M, and the dissociation rate constant for release of sigma from core, in the absence of DNA or transcription, was 4x10(-3) s(-1), corresponding to a half-life of about 200 s.

Bacterial Proteins↗