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D Scott

Publications and source records attributed to D Scott.

At least 19 recordsLinked to original sources
PubMed1996

Structure-function analysis of P-selectin-sialyl LewisX binding interactions. Mutagenic alteration of ligand binding specificity.

P-selectin is a vascular cell adhesion molecule that is expressed on the surface of platelets and endothelial cells in response to inflammatory stimuli. It is believed to aid in the binding and recruitment of leukocytes to inflamed tissue. P-selectin adhesion to leukocytes is mediated by the amino-terminal lectin domain that binds the sialyl LewisX (sLeX) carbohydrate (Neu5Acalpha2-3Galbeta1-4(Fucalpha1-3)GlcNAc). Neither the three-dimensional structure of P-selectin nor the protein-carbohydrate interactions that mediate the binding of P-selectin to the sLeX carbohydrate have been determined. The most closely related protein for which a ligand-bound three-dimensional structure has been resolved is the rat mannose-binding protein (Weis, W. I., Drickamer, K., and Hendrickson, W. A. (1992) Nature 360, 127-134). Using the known binding interactions that occur between the rat mannose-binding protein and its ligand (oligomannose) as a template, we have used site-directed mutagenesis to substitute Ala-77 with lysine. This substitution changed P-selectin-carbohydrate binding specificity from sLeX to oligomannose. Further substitution altered the binding preference from mannose to galactose in a predictable manner. These results indicate that P-selectin binds sLeX in a shallow cleft that is similar to the mannose-binding protein saccharide-binding cleft. Additionally, we present an extensive mutagenic analysis of P-selectin Lys-113, a residue that has previously been implicated in P-selectin binding to both sLeX and 3-sulfated galactosylceramide (sulfatide). Our analysis demonstrates that Lys-113 is probably not involved in P-selectin binding to either sulfatide or sLeX. Functionally, it appears that P-selectin has retained a conserved carbohydrate and calcium coordination site that enables it to bind carbohydrate in a manner that is quite similar to that which has been determined for the rat mannose-binding protein.

Alanine↗
PubMed1996

Microangiopathic haemolytic anaemia and systemic vasculitis.

Two cases of systemic vasculitis complicated by microangiopathic haemolytic anaemia (MAHA) are described: this association has not previously been reported. Both patients had atypical presentations of their primary disease, one with parotitis and one with a Guillain-Barré syndrome. Other causes of MAHA were excluded and a possible link with macromolecular von Willebrands factor is speculated upon.

Aged↗
PubMed1996

Chromosomal radiosensitivity in G2-phase lymphocytes as an indicator of cancer predisposition.

Sanford et al. (Int. J. Radiat. Biol. 55, 963-981, 1989) have reported that G2-phase cells from many heritable cancer-prone conditions exhibit higher yields of X-ray-induced chromosome damage than those found in the majority of healthy controls. We have applied their protocol to lymphocytes of a group of control and cancer-prone individuals to see if we could confirm these observations. For control donors we observed higher aberration yields, different kinetics and more interexperiment variability than found by Sanford et al. These differences could not be attributed to unavoidable minor variations in procedures (e.g. serum batches, glassware washing methods), but the difference in X-ray qualities used in the two laboratories may have made a small contribution to the discrepancies. We attribute some of our experimental variability to the fact that, to varying extents in different experiments, centrifugation of cells prior to irradiation can slow down the progression of cells into metaphase and that cells can continue to repair during the harvesting procedure (centrifugation and hypotonic treatment). We have applied the assay to cases of ataxia telangiectasia (AT, homozygotes and heterozygotes), xeroderma pigmentosum (homozygotes and heterozygotes), familial adenomatous polyposis and the syndromes Li-Fraumeni, basal cell nevus, Down's and Fanconi's but have been unable to discriminate between these groups and controls except for AT homozygotes. By including a control sample in parallel with samples from cancer-prone groups we found a significant difference in mean aberration yields between controls and AT homozygotes and heterozygotes, but not for the other groups. Since technical features could explain the discrepancies between our laboratories, we have devised our own G2-phase assay which appears to be giving promising results.

Adenomatous Polyposis Coli↗
PubMed1995

Rational design and synthesis of small molecule, non-oligosaccharide selectin inhibitors: (alpha-D-mannopyranosyloxy)biphenyl-substituted carboxylic acids.

The calcium dependent E-selectin/sialyl Lewisx (sLex) interaction plays a key role in inflammation where it mediates the rolling of leukocytes prior to firm adhesion and extravasation from the vasculature. A model of E-selectin/sLex binding, along with previously reported structure-activity relationships of sLex-related oligosaccharide, was used in the rational design of non-oligosaccharide inhibitors of this pivotal interaction. A palladium-mediated biaryl-coupling (Suzuki) reaction was used as the key step to prepare a number of substituted biphenyls which were assayed for their ability to inhibit the binding of E-, P-, and L-selectin-IgG fusion proteins to sLex expressed on the surface of HL60 cells. Some of the compounds developed had greater in vitro potency than the parent sLex tetrasaccharide and are currently being evaluated in in vivo models of inflammation to select a candidate for clinical development.

Animals↗
PubMed1995

Interleukin-11 stimulates multilineage progenitors, but not stem cells, in murine and human long-term marrow cultures.

Interleukin-11 (IL-11) is a bone marrow microenvironment-derived growth factor with pleiotropic effects on a variety of hematopoietic cells. To more accurately assess the effects of IL-11 on stem and progenitor compartments within the hematopoietic microenvironment (HM), we added recombinant human (rh) IL-11 to human and murine long-term bone marrow cultures (LTMC) and analyzed primitive (high proliferative potential-colony forming cells [HPP-CFC], long-term culture-initiating cells [LTC-IC], and long-term reconstituting stem cells) and progenitor (day 12 colony forming unit-spleen [CFU-S12], colony forming unit-megakaryocyte [CFU-Mk] and colony forming unit-granulocyte/macrophage [CFU-GM]) compartments throughout the duration of the cultures. rhIL-11 (100 ng/mL) added twice weekly resulted in significantly increased nonadherent (NA) cellularity, CFU-GM, and CFU-Mk production in human LTMC. Addition of rhIL-11 to murine LTMC was associated with a 5- to 40-fold increase in CFU-GM and a four- to 20-fold increase in day 12 CFU-S in NA cells. However, IL-11 had no significant effect on total HPP-CFC concentration and decreased the size of the more primitive stem/progenitor compartment as evidenced by both decreased LTC-IC frequency in human LTMC and decreased frequency of long-term reconstituting stem cells in murine LTMC. These data suggest that IL-11 may increase commitment of stem cells into a multipotential progenitor compartment.

Animals↗
PubMed1995

A single amino acid residue can determine the ligand specificity of E-selectin.

E-selectin (ELAM-1) is a member of the selectin family of cellular adhesion molecules. This family of proteins possesses an amino-terminal Ca(2+)-dependent lectin or carbohydrate recognition domain that is essential for ligand binding. A known E-selectin ligand is the carbohydrate antigen, sialyl Lewis(x) (sLe(x) (Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc). We have developed a model of E-selectin binding to the sLe(x) tetrasaccharide, (Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc), using the NMR-determined, E-selectin-bound solution conformation of sLe(x) (Cooke, R.M., Hale, R.S., Lister, S. G., Shah, G., and Weir, M. P. (1994) Biochemistry 33, 10591-10596) together with the x-ray crystallographic structures of E-selectin (Graves, B. J., Crowther, R. L., Chandran, C., Rumberger, J. B., Li, s., Huang, K.-S., Presky, D. H., Familletti, P. C., Wolitzky, B. A., and Burns, D. K. (1994) Nature 367, 532-538) (ligand unbound) and a related C-type animal lectin, the mannose-binding protein (Weis, W. I., Drickamer, K., and Hendrickson, A. (1992) Nature 360, 127-134) (ligand bound). Analysis of this model indicated that the alteration of one E-selectin amino acid, alanine 77, to a lysine residue might shift binding specificity from sLe(x) to mannose. The results presented here show that an E-selectin mutant protein possessing this change displays preferential binding to mannose containing oligosaccharides and that further mutagenesis of this mannose-binding selectin confers galactose recognition in a predictable manner. These mutagenesis data support the presented model of the detailed interactions between E-selectin and the sLe(x) oligosaccharide.

Amino Acid Sequence↗
PubMed1995

Foot care among diabetic patients in south Auckland.

AIM: To describe footcare among diabetic patients in south Auckland. METHOD: Direct interview of 331 European, 86 Maori and 123 Pacific Islands patients attending local diabetes services and a stratified subsample of general practitioners. Interviews included closed and open questions of diabetes knowledge, demographic and medical history and were followed by a thorough inspection of the feet. RESULTS: Major lesions (amputation, foot ulcer) and predisposing lesions (callus or fungal infection/maceration) were present in 48.5% of patients. Major lesions were particularly common among Pacific Islands patients (9.4%) vs European (3.9%), Maori (5.5%), (p < 0.05). Fungal infection/maceration was less common among Pacific Islands patients (23.0%) vs 42.3%, 42.2% respectively, (p < 0.001). Fungal infection/maceration was more common and callus formation less common among men when compared with women. Forty percent (n = 214) of patients, including eight with either an ulcer or a blister, had not had their feet examined over the preceding 12 months. Good foot care was present in 52.7% Europeans, 31.0% Maori and 26.8% Pacific Islands patients (p < 0.001). Diabetes knowledge was poorest in those with poor foot care among Europeans and Maori. CONCLUSION: While the provision of footcare advice, adherence to such advice and monitoring of footcare remain uneven, the hospital and community costs of the diabetic foot will continue to be high.

Adolescent↗
PubMed1995

Role of B7:CD28/CTLA-4 in the induction of chronic relapsing experimental allergic encephalomyelitis.

T cell activation requires both Ag/MHC recognition and costimulatory signals. The present studies were designed to test whether the loss of tolerance to myelin basic protein (MBP) requires costimulation by members of the B7 receptor family. CTLA-4Ig, a fusion protein ligand for B7-1 and B7-2, was used to assess the role of B7-mediated costimulation in chronic relapsing experimental allergic encephalomyelitis (EAE) induced by the transfer of MBP specific T cell lines. In adoptively transferred EAE, administering CTLA-4Ig to donor mice or during in vitro activation of MBP specific-T cells resulted in diminution of clinical disease. The presence of CTLA-4Ig during both the immunization and in vitro activation stages was most effective in preventing clinical signs of disease. This diminution in clinical disease was paralleled by a decreased proliferative response and reduced production of IL-2 and IL-4, but not IFN-gamma, after antigenic stimulation of encephalitogenic T cells in vitro. In contrast, CTLA-4Ig treatment of recipient animals after the transfer of MBP-activated T cells affected neither disease course nor severity. These results indicate that additional costimulatory pathways may be involved in established EAE, or that some cells are independent of costimulation or, alternatively, that CTLA-4Ig does not enter brain parenchyma in therapeutic concentrations. Thus, we conclude that costimulation provided by B7 molecules plays a major role in the development of encephalitogenic T cells and in the establishment of chronic relapsing EAE, a prototypic CD4+ T cell-mediated autoimmune disease.

Abatacept↗
PubMed1995

A probability vector and transition matrix analysis of eye movements during visual search.

This report describes a new method for analysing eye movement records during free viewing. The proposed new measures originate from a categorisation of saccade directions. The proportion of each categorised direction and the transition matrix of each two successive categorised directions are then calculated. These new measures are proposed as objective indicators of the strategies employed by an observer engaged in a visual search task. It is concluded that the probability vector and transition matrix analysis are particularly suitable as measures of observer strategies in relation to performance on VDU-based tasks. The relation between these measures and other measures related to search efficiency are also discussed.

Attention↗
PubMed1995

Turnover of the gastric H+,K(+)-adenosine triphosphatase alpha subunit and its effect on inhibition of rat gastric acid secretion.

BACKGROUND & AIMS: The rate of turnover and the effect of inhibition of acid secretion on the turnover of gastric H+,K(+)-adenosine triphosphatase (ATPase) is unknown. The aim of this study was to determine the turnover of the alpha subunit of gastric H+,K(+)-ATPase in rats under control conditions and during inhibition of acid secretion by ranitidine or omeprazole. METHODS: The turnover of the alpha subunit of the ATPase was determined by measuring the loss of incorporated 35S-methionine. This was compared with the rate of recovery of K(+)-stimulated ATPase activity in the omeprazole-treated animals. RESULTS: The half-life of the alpha subunit was 54 hours. A 1-week treatment with omeprazole had no significant effect, but the half-life increased to 125 hours (P < 0.01) after continuous ranitidine infusion. After omeprazole treatment, K(+)-stimulated ATPase activity recovered with a half-time of 15 hours. CONCLUSIONS: The turnover of the gastric ATPase subunit was independent of omeprazole inhibition but was prolonged by ranitidine. The effect of ranitidine suggests that the resting pump in tubulovesicles may turn over more slowly than the stimulated pump in the secretory canaliculus. The rapid recovery of ATPase activity compared with turnover after omeprazole is caused by both H+,K(+)-ATPase synthesis and loss of covalently bound drug.

Animals↗
PubMed1995

The effect of video games on feelings of aggression.

Fueled by the media, the controversy over whether playing popular arcade/computer games increases aggressiveness has only been compounded by inconsistencies within empirical research. This experiment, conducted with university students in Scotland, was designed to explore some of these inconsistencies. Aggressiveness was manipulated as the independent variable. As dependent variables, the Buss-Durkee Hostility Inventory (Buss & Durkee, 1957) and the Eysenck Personality Questionnaire (EPQ; Eysenck & Eysenck, 1975) were used. There was no linear pattern in aggressive affect change across three games that contained varying levels of violence. Results are discussed in terms of the general lack of support for the commonly held view that playing aggressive computer games causes an individual to feel more aggressive.

Adult↗
PubMed1995

Abnormal radiosensitivity of lymphocytes from breast cancer patients with excessive normal tissue damage after radiotherapy: chromosome aberrations after low dose-rate irradiation.

There is a need for a simple, rapid assay for predicting normal tissue reactions in radiotherapy patients to reduce morbidity in sensitive patients and to allow dose escalation in resistant cases. Towards this goal we have investigated the gamma-ray sensitivity of lymphocytes from 16 breast cancer patients who had shown an exaggerated acute or late radiation reaction ('overreaction') of normal tissues after radiotherapy, using chromosome damage (dicentrics) as the endpoint because of its close relationship with cell killing. The use of a low dose-rate (LDR; 0.31 cGy min-1) was found to be better than a high dose-rate (170 cGy min-1) in discriminating between over-reactors and controls, as predicted (and here confirmed) from previous studies on ataxia-telangiectasia (A-T) homozygotes and heterozygotes. Five of seven patients with excessive early skin reactions (e.g. erythema, moist desquamation) showed abnormal radiosensitivity, manifested either as aberration yields above the control range after LDR exposure or as less sparing than controls. The average LDR yield for early over-reactions was significantly higher than for controls (p = 0.009) and average sparing was less (p = 0.0002). Two of 10 patients with late complications (fibrosis, telangiectasia) had LDR yields above the control range, but the average yield for late over-reactors was not significantly above that of controls. Unexpectedly, two patients (one early, one late reaction) had LDR aberration yields below the control range. Quantitatively our results are consistent with the notion that over-reacting breast cancer patients are carriers of the A-T gene. Pilot studies on controls showed that the sparing effect of LDR irradiation was increased by lowering the dose-rate to 0.13 cGy min-1 and by using micronuclei rather than metaphase damage as the endpoint. These modifications to the protocol will be used in a large-scale prospective study.

Adult↗
PubMed1995

A comparison of the radiosensitivity of lymphocytes from normal donors, cancer patients, individuals with ataxia-telangiectasia (A-T) and A-T heterozygotes.

The aim was to determine whether peripheral blood lymphocytes can be used retrospectively to detect hypersensitivity to radiation in breast cancer patients who had exhibited severe reactions to radiotherapy. Blood samples were obtained from patients who developed both acute and late complications. For comparison, samples were also taken from a group of normal individuals, ataxia-telangiectasia (A-T) patients, A-T gene carriers and breast cancer patients previously treated with radiotherapy who failed to develop treatment-related complications. Radiosensitivity was assessed using a limiting dilution clonogenic assay following both high (HDR) and low (LDR) dose-rate irradiation. Following HDR irradiation, only lymphocytes from individuals with A-T were significantly more radiosensitive than those from normal donors. In contrast, at LDR, lymphocytes from A-T heterozygotes and breast cancer over reactors were also, on average, more sensitive than those from normal donors. Lymphocytes from breast cancer patients treated with radiotherapy without developing complications showed no significant differences in radiosensitivity compared with normals. This work has shown that peripheral blood lymphocytes from cancer patients who suffered severe reaction to radiotherapy are, on average, more radiosensitive than those from normal donors, and suggests that lymphocytes may be useful in the future for the development of rapid predictive assays for normal tissue tolerance to radiotherapy.

Ataxia Telangiectasia↗
PubMed1995

Fracture blister formation: a laboratory study.

A biomechanical study was performed to examine a proposed mechanism of fracture blister formation. Sixty cadaver ankle skin specimens were subjected to several levels of uniaxial strain and examined histologically. Dermal-epidermal separation patterns similar to those found histologically in previous studies of biopsied fracture blisters were seen in specimens strained 152% and greater. These findings support the hypothesis that fracture blisters can result from strain developed in the skin during initial fracture deformation.

Biomechanical Phenomena↗
PubMed1995

Retinoblastoma in association with the chromosome breakage syndromes Fanconi's anaemia and Bloom's syndrome: clinical and cytogenetic findings.

Two children presenting with sporadic unilateral retinoblastoma and exhibiting a high degree of chromosome breakage were noted to have unusual facies, microcephaly and abnormal skin pigmentation. In the first child the pattern of both spontaneous and mitomycin-C-induced chromosome breakage was characteristic of Fanconi's anaemia although the degree of breakage was extreme. She also exhibited a striking increase in X-ray-induced chromosomal damage in G0 lymphocytes as measured by dicentric formation and increase in chromatid-type aberrations. She had a number of typical clinical features, including cafe-au-lait patches and abnormalities involving the kidney; however, she demonstrated neither the hypoplasia of radius and thumb nor the typical aplastic phase of this disorder. At age 22 months the child became anaemic with trilineage myelodysplasia, which was rapidly followed by the development of acute myeloblastic leukaemia. The early onset (at age 4 months) of retinoblastoma may have been associated with the underlying genomic instability. The second child exhibited a pattern of chromosome breakage characteristic of Bloom's syndrome, in addition to a moderate increase in damage induced by mytomycin-C. She had the typical stunted growth and malar hypoplasia of Bloom's syndrome although she did not demonstrate the frequently described erythematous 'butterfly rash' Although patients with Fanconi's anaemia and Bloom's syndrome are recognised to be at an increased risk of cancer, retinoblastoma has not previously been described in patients with either condition. We suggest that underlying recessive chromosome breakage syndromes may be underdiagnosed in paediatric cancer patients, with important implications for prognosis and genetic counselling.

Bloom Syndrome↗
PubMed1995

Assessment of a specimen mount for biopsy of impalpable breast lesions.

Biopsy of the impalpable breast lesion is an increasing part of the surgical workload as a result of the National Breast Cancer Screening Programme. A specimen mount card has been described to orientate such specimens in three dimensions prior to radiological and pathological examination. Experience with 243 biopsies in this unit has shown it to be a useful aid in determining completeness of excision. It may also be used as a guide to further surgery when excision is incomplete and breast conservation is the treatment option of choice.

Biopsy↗