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Biomedical subjects

D Scott

Publications and source records attributed to D Scott.

At least 91 records · Page 5Linked to original sources
PubMed1999

Characterization of the effect of high molecular weight hyaluronan on trans-synovial flow in rabbit knees.

1. The effect of a rooster comb hyaluronan (3.6-4.0 g l-1) of similar chain length to rabbit synovial fluid hyaluronan, on the trans-synovial escape of fluid from the joint cavity in the steady state ( 8d s) was studied in 29 rabbit knees at controlled intra-articular pressures (Pj). 2. Rooster hyaluronan caused the pressure-flow relation to flatten out as pressure was raised. At 10-20 cmH2O the slope of the quasi-plateau, 0.05 +/- 0.01 microliter min-1 cmH2O-1 (mean +/- s.e.m.), was 1/39th that for Ringer solution (1.94 +/- 0.01 microliter 2O-1 ). 3. Bovine synovial fluid had a similar effect to hyaluronan in Ringer solution. 4. The quasi-plateau was caused by increasing opposition to outflow; the pressure required to drive unit outflow increased 4.4-fold between 5 and 20 cmH2O. The increased opposition to outflow at 20 cmH2O was equivalent to an effective osmotic pressure of 13-17 cmH2O at the interface. Since the infusate's osmotic pressure was only 0.9 cmH2O, this implied concentration polarization to 15-18 g l-1 hyaluronan at the interface. 5. Mechanical perforation of the lining, or enzymatic degradation of the interstitial matrix by chymopapain, abolished the quasi-plateau. Hydrational expansion of the matrix by approximately 2-fold did not. The increased opposition to outflow was reversible by washing out the hyaluronan, or by reducing Pj. It was unaffected by interruption of tissue blood flow or synoviocyte oxidative metabolism. These properties are compatible with a concentration polarization mechanism, i.e. flow-induced concentration of hyaluronan at the synovial interface due to molecular reflection. 6. A concentration polarization theory was developed for a partially reflected solute. Numerical solutions supported the feasibility of this osmotic explanation of the quasi-plateau. Additional mechanisms may also be involved. 7. It is concluded that native-size hyaluronan helps to retain synovial fluid in the joint cavity when pressure is raised and acts, at least in part, by exerting osmotic pressure at the interface between synovial matrix and a concentration polarization layer.

Animals↗
PubMed1999

The effect of surface roughness on the stress adaptation of trabecular architecture around a cylindrical implant.

The effect of implant-bone bonding and the effect of implant surface roughness on bone remodeling near the bone-implant interface were studied by using a surface remodeling theory and the boundary element method. The study has shown that implant attachment plays an important role in bone remodeling near the implant. It has been observed in animal experiments and in clinical situations that the remodeled trabecular bone architecture around a cylindrical implant could vary, on one hand, from a hub surrounding the implant with a set of external spokes to, on the other hand, a hubless situation in which a set of spokes attach directly to the implant. It is shown here that the difference in these structures may be attributed to differences in implant attachment. The results show that the bone with perfect bonding or roller boundary condition without a gap remodeled to a hubless spoke trabecular bone architecture. On the other hand, the roller boundary condition with a specified gap yielded a spoke trabecular architecture with a hub or ring surrounding the implant. These quantitative results mirror the experimental and clinical observations. It is concluded that the hub is a consequence of the gap and not a consequence of the lack of friction between the implant and the bone.

Humans↗
PubMed1999

Expression of oestrogen and progesterone receptors in gastric cancer: a flow cytometric study.

Increased expression of oestrogen (ER) and progesterone (PR) receptors have been reported in gastric adenocarcinoma, although results have been variable. Immunohistochemical staining methodologies, in particular in the detection of ER, have been inconsistent with many tumours being classified ER-negative. In this study we have used flow cytometry to quantify expression of ER and PR in gastric adenocarcinoma and examine their relationships with established prognostic indicators. Cytokeratin-positive cells obtained from tumour biopsies of 50 patients with gastric cancer and ten control patients were labelled with biotinylated ER or PR antibodies followed by streptavidin PE. Flow cytometry was seen to increase the detection of ER levels in gastric cancer with more receptor-positive patients in this study than in results published to date. We believe this is related to the sensitivity of the flow cytometric assay with the detection of small shifts in ER level detected using cytokeratin gating. On analysis, the data showed no significant correlations with tumour stage and grade, and no differences were seen between normal mucosa and gastric cancer samples.

Adenocarcinoma↗
PubMed1999

Troglitazone exhibits immunomodulatory activity on the cytokine production of activated human lymphocytes.

Troglitazone (TGL), a thiazolidinedione compound that improves the response of peripheral target tissue to insulin, also has anti-inflammatory properties, a potential means of protection from Type 1 (insulin dependent) diabetes. In order to test the ability of TGL to affect cytokine production, peripheral blood mononuclear cells from healthy donors were exposed to TGL in the presence or absence of a polyclonal activator (PHA) and the production of cytokines assayed. TGL enhanced PHA response, promoted secretion of the cytokines granulocyte and macrophage colony-stimulating factor and leukaemia inhibitory factor and inhibited tumour necrosis factor-alpha secretion, consistent with causing Th-2 differentiation in T-cells. These results suggest that TGL is capable of modulating cytokine production and could therefore influence Th1/Th2 differentiation.

Chromans↗
PubMed1999

Increased chromosomal radiosensitivity in breast cancer patients: a comparison of two assays.

PURPOSE: It has been shown previously that sensitivity to the induction of chromosome damage by ionizing radiation is, on average, higher in G2 or G0 lymphocytes of breast cancer patients than of normal healthy controls. The authors suggested that elevated chromosomal radiosensitivity may be a marker for breast cancer predisposition. To investigate whether the G0 micronucleus assay is a true surrogate for the more demanding G2 metaphase assay, both tests have now been performed on the same blood samples from 80 patients. METHODS: For the G0 micronucleus assay, cells were exposed to 3.5 Gy 137Cs gamma-rays 6 h before mitogenic stimulation, treated with cytochalasin B at 24 h post-stimulation and harvested at 90 h. For the G2 assay, at 72 h after stimulation cells were given 0.5 Gy X-rays and harvested 90 min later. RESULTS: Previous observations were confirmed, now with much larger numbers of donors, in that approximately 40% of breast cancer patients showed elevated sensitivity in the G2 assay (135 patients, 105 normals) and 25% in the G0 assay (130 patients, 68 normals). However, there was no correlation between G2 and G0 sensitivity for the 80 patients tested (r = -0.001, p = 0.99). Most of the sensitive patients were either G2 or G0 sensitive, with only 4% sensitive in both assays. CONCLUSIONS: The results suggest that different mechanisms of chromosomal radiosensitivity operate in G2 and G0 cells and that, in general, each chromosomally radiosensitive patient is defective in only one such mechanism, possibly via mutation (or polymorphism) of a single gene. Such mutations may confer cancer predisposition, of low penetrance, in a substantial proportion of patients.

Adult↗
PubMed1999

Heritability of cellular radiosensitivity: a marker of low-penetrance predisposition genes in breast cancer?

Many inherited cancer-prone conditions show an elevated sensitivity to the induction of chromosome damage in cells exposed to ionizing radiation, indicative of defects in the processing of DNA damage. We earlier found that 40% of patients with breast cancer and 5%-10% of controls showed evidence of enhanced chromosomal radiosensitivity and that this sensitivity was not age related. We suggested that this could be a marker of cancer-predisposing genes of low penetrance. To further test this hypothesis, we have studied the heritability of radiosensitivity in families of patients with breast cancer. Of 37 first-degree relatives of 16 sensitive patients, 23 (62%) were themselves sensitive, compared with 1 (7%) of 15 first-degree relatives of four patients with normal responses. The distribution of radiosensitivities among the family members showed a trimodal distribution, suggesting the presence of a limited number of major genes determining radiosensitivity. Segregation analysis of 95 family members showed clear evidence of heritability of radiosensitivity, with a single major gene accounting for 82% of the variance between family members. The two alleles combine in an additive (codominant) manner, giving complete heterozygote expression. A better fit was obtained to a model that includes a second, rarer gene with a similar, additive effect on radiosensitivity, but the data are clearly consistent with a range of models. Novel genes involved in predisposition to breast cancer can now be sought through linkage studies using this quantitative trait.

Alleles↗
PubMed1999

Family functioning, neurocognitive functioning, and behavior problems in children with sickle cell disease.

OBJECTIVE: To investigate the independent and combined contributions of neurocognitive and family functioning to mother-reported behavior problems in children with sickle cell disease (SCD) and evaluate the factor structure of the Family Environment Scale (FES) with African American families. METHOD: The study sample included 289 children enrolled in the multisite Cooperative Study of Sickle Cell Disease. The study protocol included neuropsychological evaluation and brain magnetic resonance imaging (MRI) of the children, and mothers completed the Child Behavior Checklist and Family Environment Scale. RESULTS: With child and maternal demographic parameters controlled, conflicted family functioning, but not neurocognitive functioning, accounted for a significant portion of the variance in mother-reported behavior problems. The factor structure of the FES for families of children with SCD was found to be similar to that for other families. CONCLUSIONS: Family functioning may be a salient target for fostering adaptation to chronic childhood illness.

Adaptation, Psychological↗
PubMed1999

High prevalence of NSAID enteropathy as shown by a simple faecal test.

BACKGROUND: The diagnosis of non-steroidal anti-inflammatory drug (NSAID) induced enteropathy is difficult, requiring enteroscopy or the use of four day faecal excretion of (111)In labelled white cells. AIMS: To assess faecal calprotectin (a non-degraded neutrophil cytosolic protein) as a method for diagnosing NSAID enteropathy. METHODS: Single stool faecal calprotectin concentrations were compared with the four day faecal excretion of (111)In labelled white cells in 47 patients taking NSAIDs. The prevalence and severity of NSAID enteropathy was assessed using this method in 312 patients (192 with rheumatoid arthritis, 65 with osteoarthritis, 55 with other conditions) taking 18 different NSAIDs. RESULTS: The four day faecal excretion of (111)In white cells correlated significantly with faecal calprotectin concentrations. In the group of 312 patients on NSAIDs faecal calprotectin concentrations were significantly higher than in controls, the prevalence of NSAID enteropathy being 44%. The prevalence and severity of NSAID enteropathy was independent of the particular type or dose of NSAID being taken or other patient variables. CONCLUSIONS: Assay of faecal calprotectin provides a simple practical method for diagnosing NSAID enteropathy in man. Forty four per cent of patients receiving these drugs had NSAID induced enteropathy when assessed by this technique; 20% of these had comparable levels of inflammation to that previously reported in patients with inflammatory bowel disease.

Adolescent↗
PubMed1999

Introduction to reading radiographs by the Scott modification of the Larsen method.

To examine its ability to evaluate progressive radiological damage, the Scott modification of the Larsen score was used for the hands, wrists, and feet (metatarsophalangeal joints) at time zero and at 12 months in 52 patients with early rheumatoid arthritis taking part in a therapeutic intervention study. The major practical difficulty was the technical discrepancy between initial and followup films in some patients. The metrological problems are discussed in the analysis, which compares the score on the same films using the Sharp score.

Arthritis, Rheumatoid↗
PubMed1999

Imaging in rheumatoid arthritis: results of group discussions.

None of the current scoring methods for radiological damage in rheumatoid arthritis (RA) is ideal. The objective for RA imaging at OMERACT IV was to start discussion about the problems and applicability of the current scoring methods for radiological damage and to start discussion on the challenge of new imaging techniques. The RA imaging module comprised preconference reading material, plenary sessions, small group discussions, and a plenary report of the group sessions, combined with interactive voting. The OMERACT filter guided the discussions. Priorities for further research in imaging studies were: (1) pathologies versus features on radiographs; (2) relation with longterm outcome; and (3) definition of minimum clinically important difference.

Arthritis, Rheumatoid↗
PubMed1999

Effects of variations in live weight gain on bone growth and composition and on markers of bone turnover in lambs.

Growing lambs were fed the same diet at intakes supporting mean live weight gains of 0.1, 0.2 and 0.3 kg day-1, representing slow, intermediate and fast growth groups, respectively. The effects on bone growth and composition, and on blood and urinary bone marker concentrations or excretion rates were monitored. Compared with the slow-growing lambs, the higher intake group grew twice as fast, had higher rates of bone growth (indicated by external metatarsal length), and larger and heavier bones at slaughter. Bones from fast-growing animals had higher collagen and deoxypyridinoline concentrations, and lower Ca:collagen, Ca :P and pyridinoline : deoxypyridinoline ratios, indicating a less mature bone compared with the slow-growing lambs. Bone growth rate had no effect on plasma osteocalcin, bone-specific alkaline phosphatase or growth hormone concentrations, nor on the urinary excretion of pyridinoline and deoxypyridinoline. The results for plasma markers may be explained by an increase in blood volume linked with increased body weight.

Alkaline Phosphatase↗
PubMed1999

Differences in Ki67 and c-erbB2 expression between screen-detected and true interval breast cancers.

Breast cancer screening facilitates the early detection of breast cancer, although a significant number of tumors still arise in the interval between screening. The objective of this study was to measure the expression of five markers of proven prognostic significance in symptomatic breast cancer (estrogen receptor, progesterone receptor, p53, Ki67, and c-erbB2) in screen-detected and interval breast cancers to identify biological markers that may be associated with the emergence of symptomatic breast cancer in the screening interval. The expression of estrogen receptor, progesterone receptor, p53, Ki67, and c-erbB2 was assessed in a series of 51 true interval and 84 screened-detected invasive tumors by immunohistochemistry. Interval cancers tended to be of higher histological grade and were of larger pathological size than screen-detected cancers. Expression of estrogen receptor was 1.7-fold lower (P<0.001), whereas expression of p53 was 2.5-fold (P<0.01), Ki67 2.4-fold (P<0.001), and c-erbB2 3.6-fold higher (P<0.01) in true interval cancers compared with screen-detected invasive cancers. There was no significant difference in progesterone receptor expression. The most important differences identified by multiple logistic regression analysis were in the expression of Ki67 and c-erbB2. The differences in the expression of these markers were more important than clinical features such as pathological grade and size. Using the logistic regression model, 83% of the tumors analyzed in this study could be correctly assigned as interval or screen-detected tumors on the basis of Ki67 and c-erbB2 expression. The importance of high expression of Ki67 in interval cancers compared with screen-detected cancers suggests that tumors may become symptomatic in the screening interval as a result of increased levels of cell proliferation. The inclusion of c-erbB2 in the regression equation suggests that this growth factor receptor may play a significant role in stimulating the rapid growth of interval cancers.

Aged↗
PubMed1999

Reduced cadherin/catenin complex expression in celiac disease can be reproduced in vitro by cytokine stimulation.

Celiac disease is characterized by a chronic immune response to dietary gluten, in which T cell responses result in elevated mucosal levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, interferon (IFN)-gamma, and transforming growth factor (TGF)-beta, which induce profound mucosal remodeling associated with increased enterocyte proliferation, apoptosis, and migration. Reduced intestinal expression of the morphoregulatory cell adhesion molecule E-cadherin, which forms complexes with beta-catenin, can increase enterocyte proliferation and migration. However, its mechanism of action in gastrointestinal inflammatory conditions and any involvement in celiac disease is unknown. In this study, we describe changes in E-cadherin and beta-catenin expression in celiac disease tissue and determine the effect of cytokines on their expression in an in vitro model. We assessed E-cadherin and beta-catenin expression in intestinal biopsies from 24 patients with celiac disease, 12 patients with treated celiac disease, and 10 healthy patients by immunohistochemistry, Western blotting, and confocal microscopy. Using Caco-2 cells, we examined the effect of TNF-alpha, IL-1, IFN-gamma, and TGF-beta on E-cadherin expression. E-cadherin transcription was assessed in both intestinal biopsies and Caco-2 cells by in situ hybridization and RT-PCR, respectively. A marked reduction in protein expression of E-cadherin and beta-catenin that returns to normal levels after treatment was observed in celiac disease; this reduction was associated with reduced levels of E-cadherin mRNA. E-cadherin expression in Caco-2 cells was significantly reduced after TNF-alpha, IL-1, and IFN-gamma stimulation. The effect of TNF-alpha on E-cadherin expression was maximal after stimulation for 48 hours and also induced modest reductions in beta-catenin expression. The action of TNF-alpha on E-cadherin was reversible and was shown to act at the transcriptional level. These results demonstrate the novel findings that E-cadherin and beta-catenin expression are reversibly down-regulated in celiac disease and that such changes in epithelial cadherin/catenin complexes may be mediated by cytokines acting on cadherin transcription.

Base Sequence↗
PubMed1999

Stent design favorably influences the vascular response in normal porcine coronary arteries.

OBJECTIVES: The purpose of this study was to compare the arterial response following implantation of a stainless-steel, balloon-expandable, tubular slotted stent with that of a novel computer-designed, multi-cellular stent in normal porcine coronary arteries. BACKGROUND: Intracoronary stent placement has evolved into the primary strategy for percutaneous revascularization of symptomatic coronary arterial lesions. Presently there is intense interest in developing new stent designs to improve stent delivery and biocompatability. METHODS: Computer-assisted design was utilized to develop a balloon-expandable stent with symmetric expansion properties, uniform arterial wall coverage, longitudinal flexibility and radial strength. Quantitative coronary angiography and histological assessment of the stented arteries was used to evaluate the acute and chronic vascular responses to a stainless-steel, balloon-expandable, tubular slotted stent as compared to the computer-designed BX stent in the normolipemic swine. RESULTS: Forty stents (24 BX, 16 tubular slotted) were implanted in 19 miniature swine at a mean inflation pressure of 9 atm using identical delivery systems. Eight of the BX and none of the tubular slotted stents were post-dilated with a non-compliant balloon at 12-14 atm. The mean stent-to-artery ratio was similar for the BX (1.03 +/- 0.06) and tubular slotted (1.04 +/- 0.11; p = 0.59) designs. Protrusion or asymmetric radial flaring of a strut at the stent margin was present in 1 of 23 BX stents (4.3%) and 10 of 15 tubular slotted stents (66.7%; p < 0.0001). The mean arterial injury score was significantly less for the BX stent (0.2 +/- 0.2) as compared with the tubular slotted stents (0.4 +/- 0.4; p = 0.025). At 3 days, thrombus area was similar for the BX and tubular slotted designs (0.42 +/- 0.16 mm2 versus 0.44 +/- 0.18 mm2, respectively; p = 0.88). The mean neointimal area was significantly less for the BX at 2 months (1.09 +/- 0.25 mm2 versus 2.93 +/- 2.26 mm2 in the tubular slotted stent) and at 6 months (1.10 +/- 0.26 mm2 versus 2.07 +/- 0.65 mm2 in the tubular slotted stent; p = 0.01), resulting in approximately 50% less in-stent stenosis. CONCLUSIONS: The arterial response to a balloon-expandable stent can be favorably influenced by computer-assisted modification of design in an experimental model. Further study is warranted to determine the impact of stent design upon clinical in-stent restenosis.

Angioplasty, Balloon, Coronary↗
PubMed1998

Two functional states of the CD11b A-domain: correlations with key features of two Mn2+-complexed crystal structures.

In the presence of bound Mn2+, the three- dimensional structure of the ligand-binding A-domain from the integrin CR3 (CD11b/CD18) is shown to exist in the "open" conformation previously described only for a crystalline Mg2+ complex. The open conformation is distinguished from the "closed" form by the solvent exposure of F302, a direct T209-Mn2+ bond, and the presence of a glutamate side chain in the MIDAS site. Approximately 10% of wild-type CD11b A-domain is present in an "active" state (binds to activation-dependent ligands, e.g., iC3b and the mAb 7E3). In the isolated domain and in the holoreceptor, the percentage of the active form can be quantitatively increased or abolished in F302W and T209A mutants, respectively. The iC3b-binding site is located on the MIDAS face and includes conformationally sensitive residues that undergo significant shifts in the open versus closed structures. We suggest that stabilization of the open structure is independent of the nature of the metal ligand and that the open conformation may represent the physiologically active form.

Amino Acid Substitution↗
PubMed1998

Effect of depletion of glycosaminoglycans and non-collagenous proteins on interstitial hydraulic permeability in rabbit synovium.

1. The hydraulic resistance of synovial interstitium helps to retain a lubricating fluid within the joint cavity. The contributions of sulphated glycosaminoglycans to resistance were assessed by selective depletion by chondroitinase ABC, keratanase and heparinases I, II and III in vivo. Also, since glycosaminoglycans do not account fully for the resistance, the contribution of non-collagenous, structural proteins in interstitium was assessed by treatment with chymopapain, a collagen-sparing protease. 2. Ringer solution containing enzyme was injected into the synovial cavity of the knee in anaesthetized rabbits. After >= 30 min the intra-articular pressure was raised and the relation between pressure (Pj) and trans-synovial outflow (Qs) determined. The slope dQs/dPj at low pressures, i.e. below yield pressure, represents the hydraulic conductance of the lining, i.e. 1/resistance. The contralateral joint received Ringer solution without enzyme as a control. Action of enzymes on the tissue was confirmed by histochemical and immunohistochemical studies. 3. Treatment with chondroitinase ABC (5 joints) increased the hydraulic conductance of the lining by 2.3 times (control, 1.34 +/- 0.22 microliter l min-1 cmH2O-1; post-enzyme, 3.11 +/- 0.45 microliter l min-1 cmH2O-1). This was significantly less than the effects of leech, Streptomyces and testicular hyaluronidases, which caused an average 4.7 times increase (P < 0.001, ANOVA). Analogous findings were made above yield pressure. 4. Treatment with keratanase (3 joints) or heparinases I, II and III (3 joints) caused no significant increase in trans-synovial flows or conductance, even though the concentration of heparan sulphate in synovium is higher than that of chondroitin sulphates or hyaluronan. 5. Treatment with chymopapain (7 joints) caused the greatest increases in trans-synovial flow, which exceeded control flow by an order of magnitude in one case. After 0.1 U chymopapain the average conductance was 6.6 times the control conductance below yield pressure. Immunohistochemical studies confirmed that chymopapain treatment removed the synovial proteoglycans. 6. It is concluded that, despite their similar resistivities in vitro, the different glycosaminoglycans do not contribute equally, weight for weight, to interstitial resistance in vivo. Hyaluronan is the dominant glycosaminoglycan governing synovial interstitial resistance. In addition, non-collagenous structural proteins contribute significantly to interstitial resistance.

Animals↗
PubMed1998

Genetic and functional studies of a germline TP53 splicing mutation in a Li-Fraumeni-like family.

We report an extensive Li-Fraumeni-like family in which there is an unusual spectrum of tumours at relatively late onset. A germline TP53 splice donor mutation in exon 4 is present in all affected family members available for testing. The mutation abolishes correct splicing of intron 4 and techniques of RT-PCR have identified three different aberrant transcripts from the mutant TP53 allele. Using the yeast functional assay to analyse transcripts in cells from a number of family members with the mutant allele, TP53 appears wild-type. Functional studies have been carried out on cells from patients with and without cancer who carry the germline mutation, and on cells from unaffected individuals from the same family who do not carry the mutation. Using a number of functional endpoints known to distinguish between cells carrying mutant or wild-type TP53 alleles, we were unable to discriminate normal (wt/wt) from heterozygous (wt/mut) cells by lymphocyte apoptosis and fibroblast survival following low dose rate ionising radiation exposure. However germline mutation carriers show increased sensitivity to radiation-induced chromosome damage in the G2 phase of the cell cycle, and decreased transient and permanent G1 arrest. These studies demonstrate the importance of fully characterising the effects of TP53 germline mutations, and may explain some of the phenotypic features of this family.

Adult↗