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Biomedical subjects

D Scott

Publications and source records attributed to D Scott.

At least 163 records · Page 9Linked to original sources
PubMed1997

Reference curves of radiographic damage in patients with rheumatoid arthritis: application of quantile regression and fractional polynomials.

OBJECTIVE: To (1) introduce the methodology of quantile regression and fractional polynomials; (2) test the application of this methodology to develop, conditional on disease duration, preliminary reference curves of radiographic damage in patients with rheumatoid arthritis (RA); and (3) prove the importance of the definition and selection of the reference group when developing reference curves. METHODS: The study design was cross sectional. The main study factors were disease duration and radiographic damage using the Larsen score. The 2 study samples were 98 patients from a multicenter trial of cyclosporine and 203 patients with RA from a teaching hospital clinic. RESULTS: Using disease duration as the time dependent covariate we constructed quantile regression reference curves of radiographic damage. The reference curves for the 2 samples differed in shape, location, and slope. CONCLUSION: Quantile regression and fractional polynomials simplify the construction of reference curves when data cannot be easily modified to meet assumptions of normality, linearity, and constant variance. Quantile reference curves provide clinicians with a useful clinical tool to measure outcome at arbitrary timepoints, to interpret change, and to set treatment objectives. However, the definition and selection of the reference used to construct the reference curves is of critical importance.

Adult↗
PubMed1996

Methylprednisolone and cyclophosphamide, alone or in combination, in patients with lupus nephritis. A randomized, controlled trial.

BACKGROUND: Uncertainty exists about the efficacy and toxicity of bolus therapy with methylprednisolone or of the combination of methylprednisolone and cyclophosphamide in the treatment of lupus nephritis. OBJECTIVE: To determine 1) whether intensive bolus therapy with methylprednisolone is an adequate substitute for bolus therapy with cyclophosphamide and 2) whether the combination of methylprednisolone and cyclophosphamide is superior to bolus therapy with methylprednisolone or cyclophosphamide alone. DESIGN: Randomized, controlled trial with at least 5 years of follow-up. SETTING: Government referral-based research hospital. PATIENTS: 82 patients with lupus nephritis who had 10 or more erythrocytes per high-power field, cellular casts, proteinuria (> 1 g of protein per day), and a renal biopsy specimen that showed proliferative nephritis. INTERVENTIONS: Bolus therapy with methylprednisolone (1 g/m2 body surface area), given monthly for at least 1 year; bolus therapy with cyclophosphamide (0.5 to 1.0 g/m2 body surface area), given monthly for 6 months and then quarterly; or bolus therapy with both methylprednisolone and cyclophosphamide. MEASUREMENTS: 1) Renal remission (defined as < 10 dysmorphic erythrocytes per high-power field, the absence of cellular casts, and excretion of < 1 g of protein per day without doubling of the serum creatinine level), 2) prevention of doubling of the serum creatinine level, and 3) prevention of renal failure requiring dialysis. RESULTS: Renal remission occurred in 17 of 20 patients in the combination therapy group (85%), 13 of 21 patients in the cyclophosphamide group (62%), and 7 of 24 patients in the methylprednisolone group (29%) (P < 0.001). Twenty-eight patients (43%) did not achieve renal remission. By life-table analysis, the likelihood of remission during the study period was greater in the combination therapy group than in the methylprednisolone group (P = 0.028). Combination therapy and cyclophosphamide therapy were not statistically different. Adverse events were amenorrhea (seen in 41% of the cyclophosphamide group, 43% of the combination therapy group, and 7.4% of the methylprednisolone group), cervical dysplasia (seen in 11% of the cyclophosphamide group. 7.1% of the combination therapy group, and 0% of the methylprednisolone group), avascular necrosis (seen in 11% of the cyclophosphamide group, 18% of the combination therapy group, and 22% of the methylprednisolone group), herpes zoster (seen in 15% of the cyclophosphamide group, 21% of the combination therapy group, and 3.7% of the methylprednisolone group) and at least one infection (seen in 26% of the cyclophosphamide group. 32% of the combination therapy group, and 7.4% of the methylprednisolone group). CONCLUSIONS: Monthly bolus therapy with methylprednisolone was less effective than monthly bolus therapy with cyclophosphamide. A trend toward greater efficacy with combination therapy was seen.

Adult↗
PubMed1996

A simple algorithm to predict the development of radiological erosions in patients with early rheumatoid arthritis: prospective cohort study.

OBJECTIVE: To produce a practical algorithm to predict which patients with early rheumatoid arthritis will develop radiological erosions. DESIGN: Primary care based prospective cohort study. SETTING: All general practices in the Norwich Health Authority, Norfolk. SUBJECTS: 175 patients notified to the Norfolk Arthritis Register were visited by a metrologist soon after they had presented to their general practitioners with inflammatory polyarthritis, and again after a further 12 months. All the patients satisfied the American Rheumatism Association's 1987 criteria for rheumatoid arthritis and were seen by a metrologist within six months of the onset of symptoms. The study population was randomly split into a prediction sample (n = 105) for generating the algorithm and a validation sample (n = 70) for testing it. MAIN OUTCOME MEASURES: Predictor variables measured at baseline included rheumatoid factor status, swelling of specific joint areas, duration of morning stiffness, nodules, disability score, age, sex, and disease duration when the patient first presented. The outcome variable was the presence of radiological erosions in the hands or feet, or both, after 12 months. RESULTS: A simple algorithm based on a combination of three variables--a positive rheumatoid factor test, swelling of at least two large joints, and a disease duration of more than three months--was best able to predict erosions. When the accuracy of this algorithm was tested with the validation sample, the erosion status of 79% of patients was predicted correctly. CONCLUSIONS: A simple algorithm based on three easily measured items of information can predict which patients are at high risk and which are at low risk of developing radiological erosions.

Adult↗
PubMed1996

Single amino acid residues in the E- and P-selectin epidermal growth factor domains can determine carbohydrate binding specificity.

E-selectin and P-selectin are two closely related vascular cell adhesion proteins. Each selectin has an amino-terminal C-type lectin domain that is thought to possess the carbohydrate binding site that binds the sialylated Lewisx antigen (sLex or CD15s) (Neu5Acalpha2-3Galbeta1-4(Fucalpha1-3)GlcNAc). In addition to the sLex carbohydrate, P-selectin binds sulfated proteoglycan, 3-sulfated galactosyl ceramide (sulfatide), and heparin. Both E- and P-selectin have an EGF-like (EGF) domain that is immediately adjacent to and COOH-terminal to the lectin domain. We report that mutagenic substitution of single amino acid residues in either the P- or E-selectin EGF domain can dramatically alter selectin binding to sLex, heparin, or sulfatide. Substitution of E- and P-selectin EGF domain residue Ser128 with an arginine results in E- and P-selectin proteins that have lost the requirement for alpha1-3-linked fucose and are thus able to bind to sialyllactosamine. A similar phenotype is reported for an E-selectin mutation within the lectin domain. Additionally, we have determined that conservative substitution of EGF domain residues 124 and 128 can alter E-selectin binding such that it is able to adhere to heparin or sulfatide and can reduce P-selectin adherence to these ligands. The distance between the substituted EGF domain amino acid residues and the primary carbohydrate binding site within the lectin domain and their relative positioning as determined by the three-dimensional crystal structure of the E-selectin lectin and EGF domains (Graves, B. J., Crowther, R. L., Chandran, C., Rumberger, J. B., Li, S., Huang, D.-S., Presky, D. H., Familletti, P. C., Wolitzky, B. A., and Burns, D. K. (1994) Nature 367, 532-538) suggest that there is little direct contact between the two domains. However, we report mutant binding characteristics which indicate that selectin oligosaccharide binding may be modulated by both domains and that wild-type E- and P-selectin/sLex binding interactions may be significantly different from those previously hypothesized.

Amino Acid Sequence↗
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

T cell tolerance and activation to a transgene-encoded tumor antigen.

Much has been learned in recent years concerning the nature of tumor antigens recognized by T cells. To apply this knowledge clinically, the nature of the host response to individual and multiple tumor antigens has to be characterized. This will help to define the efficacy of immune surveillance and the immune status of the host following exposure to tumor antigens expressed on pre-neoplastic tissue. To approach these questions, we have developed a transgenic mouse which expresses the tumor-specific antigen P91A. The single amino acid substitution in P91A results in the expression of a new MHC class I (H-2Ld)-binding peptide. In transgenic tissue, the H-2Ld/P91A complex is expressed in isolation from other tumor-associated antigens, allowing definition of the immune response to a single defined tumor antigen, a situation closely analogous to events during tumorigenesis. We show that CD8+ T cell immune surveillance of P91A is ineffective without the introduction of a helper determinant operating through stimulation of CD4+ T cells. Recognition of the isolated P91A tumor antigen on normal tissue by CD8+ T cells is a tolerogenic process. Induction of T cell tolerance suggests tumor antigen-T cell interactions occurring during tumorigenesis may elicit T cell tolerance and hence confound some immunotherapeutic approaches.

Animals↗
PubMed1996

Opposing effects of CTLA4-Ig and anti-CD80 (B7-1) plus anti-CD86 (B7-2) on experimental allergic encephalomyelitis.

The roles of the B7 receptors, CD80 and CD86, during actively induced experimental allergic encephalomyelitis were examined with specific monoclonal antibodies and CTLA4-Ig. Injection of CTLA4-Ig on day 2 post-immunization resulted in decreased incidence and severity of resultant disease. Anti-CD80 injection on day 2 blocked development of the first disease episode. Subsequent relapses were unaffected. In contrast, injection of anti-CD86 alone had no effect. Surprisingly, combined anti-CD80 + anti-CD86 monoclonal antibody injection on day 2 resulted in marked exacerbation of disease. Examination of cytokine production in the draining lymph node cells demonstrated a reduction in both interferon (IFN)-gamma and interleukin (IL)-2 producing cells, but a dramatic increase in tumor necrosis factor (TNF)-alpha secretion in animals receiving both monoclonal antibodies. These results suggest distinct roles for CD80 and CD86 in the initiation of EAE, resulting in the diverse clinical outcomes observed in this model of EAE.

Abatacept↗
PubMed1996

Clinical evaluation in prosthodontics: practical methods to improve validity and reliability at the undergraduate level.

The potential causes of reliability and validity problems with traditional methods of evaluating a student's clinical prosthodontic skills are reviewed. Practical methods of evaluating critical skills in a reliable and valid way are presented. These methods include clinical tests using written criteria and anonymous examiners, skills assessment by faculty members, patient-based written examinations, and bell ringer examinations.

Clinical Competence↗
PubMed1996

Use of sheep maintained by intragastric infusion as a model for studying the endogenous loss of phosphorus in ruminants.

Mature sheep fitted with a rumen cannula and an abomasal catheter were used to evaluate whether sheep maintained by intragastric infusion could be used as a model for studying minimum endogenous phosporus loss in ruminants. In control periods the sheep received 1.29 g phosphorus day-1 by infusion and maintained phosphorus balance. The withdrawal of phosphorus from the infusate led to a reduction in the excretion of phosphorus to 6.4 mg kg liveweight-1 day-1, a level lower than that currently used to estimate maintenance phosphorus requirements. However, salivary phosphorus secretion, based on rumen phosphorus outflow, averaged only about 1.2 g day-1, a level which would be considered insufficient to meet rumen microbial requirements in a normally fed animal. Allowing the sheep access to a small amount of roughage, although contributing little additional phosphorus, greatly increased salivary phosphorus flow and increased their endogenous excretion of phosphorus to levels close to those used to estimate maintenance requirements. These results suggest that this technique may offer an alternative way of measuring minimum endogenous mineral loss to those currently in use.

Abomasum↗
PubMed1996

Tumour bed biopsy detects the presence of multifocal disease in patients undergoing breast conservation therapy for primary breast carcinoma.

This study prospectively examined tumour bed biopsies in 135 consecutive patients undergoing conservative surgery for breast carcinoma. All had wide resection of the primary tumour and histologically clear margins. Twelve patients (9%) had positive tumour bed biopsies. Two subgroups of patients had positive bed biopsies; those with ductal carcinoma in situ, and a second group with more aggressive disease characterized by lymph node involvement, vascular invasion and a higher grade and mitotic count. As the majority of recurrences from breast carcinoma occur in the region of the primary tumour, bed biopsy may aid in the identification of a group of patients with multifocal or aggressive disease who are at increased risk of local recurrence.

Biopsy↗
PubMed1996

Planning and assessing a cross-training initiative with multi-skilled employees.

BACKGROUND: An improvement initiative begun by nurses at Parkview Episcopal Medical Center (Pueblo, Colo) to develop patient-focused care delivered by multiskilled workers followed a quality improvement methodology. Implementation of the new care delivery system on a model unit--2 South--provided the opportunity to plan, analyze data, and make changes as appropriate. Parkview's indoctrination of the teachings of W. Edwards Deming has helped leaders and staff realize the integral role of training in improvement activities. In his 14 points, Deming emphasizes the importance of employee education and of the employee having a clear understanding of his or her job. The time and money put into up-front education should help ensure the long-term success of this initiative. DEFINING THE CAREPARTNER: Three new multi-skilled positions were developed on 2 South--a Personal CarePartner, a Business CarePartner, and a Clinical CarePartner. By cross-training each of these roles to perform duties formerly done by centralized departments, 2 South was able to cut costs and time while ensuring quality care. TRAINING THE CAREPARTNER: An internally developed training program provided the new CarePartners with up-front education to prepare them to deliver patient-centered care. RESULTS: 2 South has experienced drops in patient falls and medication errors--areas that are often negatively affected when multi-skilled programs are instituted. Patient and physician surveys have shown increased satisfaction with care provided on the unit. The increased efficiency of the model unit has produced these outcomes while cutting costs substantially. LESSONS LEARNED: The interdisciplinary team coordinating the improvement project learned many lessons in the process, including the importance of communication, education, and a sense of humor.

Clinical Competence↗
PubMed1996

No defect in G1/S cell cycle arrest in irradiated Li-Fraumeni lymphoblastoid cell lines.

The radiation response of Epstein-Barr virus (EBV)-immortalised lymphoblastoid cell lines derive from Li-Fraumeni syndrome (LFS) and LFS-like individuals was investigated. Cells from all LFS and LFS-like cases showed an accumulation of p53 protein following 137Cs gamma-irradiation, which was associated with cell cycle arrest at the G1/S border. This response was indistinguishable from that seen in cells derived from normal individuals, and occurred in cases with missense mutations in the TP53 gene at codons 175, 180, 220 and 248 and also in two LFS-like individuals with no TP53 mutation. Previous studies using lymphocytes and fibroblasts from LFS individuals have demonstrated abnormal radiation responses in these cells. This suggest cell type specificity in the contribution of a mutant p53 protein to phenotype.

Burkitt Lymphoma↗
PubMed1996

An H-YDb epitope is encoded by a novel mouse Y chromosome gene.

Rejection of male tissue grafts by genotypically identical female mice has been explained by the existence of a male-specific transplantation antigen, H-Y (ref. 1), but the molecular nature of H-Y antigen has remained obscure. Hya, the murine locus controlling H-Y expression, has been localized to delta Sxrb, a deletion interval of the short arm of the Y chromosome. In mice, H-Y antigen comprises at least four distinct epitopes, each recognized by a specific T lymphocyte clone. It has recently been shown that one of these epitopes, H-YKk, is a peptide encoded by the Y-linked Smcy gene, presented at the cell surface with the H-2Kk major histocompatibility complex (MHC) molecule. However, deletion mapping and the analysis of variable inactivation of H-Y epitopes has suggested that the Hya locus may be genetically complex. Here we describe a novel mouse Y chromosome gene which we call Uty (ubiquitously transcribed tetratricopeptide repeat gene on the Y chromosome). We identify the peptide WMHHNMDLI derived from the UTY protein as an H-Y epitope, H-YDb. Our data formally demonstrate that H-Y antigen is the product of more than one gene on the Y chromosome.

Amino Acid Sequence↗
PubMed1996

Dose-rate sparing for micronucleus induction in lymphocytes of controls and ataxia-telangiectasia heterozygotes exposed to 60Co gamma-irradiation in vitro.

We investigated the reproducibility of the cytochalasin B micronucleus (MN) assay in irradiated human lymphocytes to assess its suitability in predicting cancer predisposition and response to radiotherapy by virtue of defects in the processing of clastogenic lesions. G0 lymphocytes were exposed to 3.0 Gy 60Co gamma-rays at high (HDR) or low dose-rate (LDR). Six healthy donors were assayed three times each in nine experiments and compared with six ataxia-telangiectasia (A-T) heterozygotes. In controls, significant interexperiment variability in MN yields was observed at HDR and LDR, also in dose-rate sparing (i.e. reduction in MN yield at LDR compared with HDR). Significant inter-individual variability was seen at HDR, but not at LDR or for sparing. Average sparing was 66.4 +/- 4.8%. In spite of the experimental variability, a significant difference between controls and A-T heterozygotes was detected at LDR, and 5/6 heterozygotes had sparing values below the control range. This gives encouragement for the use of this assay in predictive testing if sources of experimental variability can be identified so as to improve discrimination between individuals. HDR and to a lesser extent LDR irradiation induced significant mitotic inhibition, seen as a reduction in binucleate cells after cytocholasin treatment. A positive correlation between mitotic inhibition and MN frequency suggests that similar lesions may be involved in these effects.

Adult↗
PubMed1996

Fibroblasts from Li-Fraumeni patients are resistant to low dose-rate irradiation.

A group of adult skin fibroblast cultures from four individuals representing Li-Fraumeni families with different mutations in the p53 gene were found to be resistant to low dose-rate (0.011 Gy per min) 60Co radiation when compared with a control group of four cultures from normal individuals. The Li-Fraumeni fibroblasts, which could not be distinguished from controls after high dose rate (1.07 Gy per min) irradiation, were shown to be heterozygous (+/mut) at the p53 locus at the time of irradiation.

Adolescent↗