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Biomedical subjects

C A Smith

Publications and source records attributed to C A Smith.

At least 109 records · Page 6Linked to original sources
PubMed1999

Microsomal epoxide hydrolase gene polymorphism and susceptibility to colon cancer.

We examined polymorphisms in exons 3 and 4 of microsomal epoxide hydrolase in 101 patients with colon cancer and compared the results with 203 control samples. The frequency of the exon 3 T to C mutation was higher in cancer patients than in controls (odds ratio 3.8; 95% confidence intervals 1.8-8.0). This sequence alteration changes tyrosine residue 113 to histidine and is associated with lower enzyme activity when expressed in vitro. This suggests that putative slow epoxide hydrolase activity may be a risk factor for colon cancer. This appears to be true for both right- and left-sided tumours, but was more apparent for tumours arising distally (odds ratio 4.1; 95% confidence limits 1.9-9.2). By contrast, there was no difference in prevalence of exon 4 A to G transition mutation in cancer vs controls. This mutation changes histidine residue 139 to arginine and produces increased enzyme activity. There was no association between epoxide hydrolase genotype and abnormalities of p53 or Ki-Ras.

Adolescent↗
PubMed1999

Functional disability in adolescents and young adults with symptoms of irritable bowel syndrome: the role of academic, social, and athletic competence.

OBJECTIVE: To examine perceived academic, social, and athletic competence as potential moderators of the relation between symptoms of irritable bowel syndrome (IBS) and functional disability in adolescents and young adults with a history of recurrent abdominal pain (RAP). METHODS: We assessed IBS symptoms, competence, and disability by telephone interview in RAP patients five years following their medical evaluation. RESULTS: For both male and female subjects, the relation between symptoms and disability was stronger at lower levels of perceived academic competence. Furthermore, among females, the relation between symptoms and disability was stronger at lower levels of perceived social competence; among males, the relation was stronger at lower levels of perceived athletic competence. CONCLUSIONS: Perceived competence moderated the relation between IBS symptoms and functional disability. Interventions designed to enhance patient competence in various roles may be useful in reducing disability among adolescents and young adults with symptoms of IBS.

Adolescent↗
PubMed1999

Dual pH probe monitoring versus single pH probe monitoring in infants on milk feeds: the impact on diagnosis.

OBJECTIVES: Oesophageal pH monitoring is the gold standard technique for the detection of gastro-oesophageal reflux in adults and children. A standard parameter used to define "abnormal" reflux is the percentage of recording time for which the gastric pH is < 4. This study investigated the relevance of this measure in infants on regular milk feeds whose gastric contents and refluxate will be neutral for most of the recording time. METHODS: Simultaneous oesophageal and gastric pH monitoring was carried out on all infants who were milk fed exclusively and admitted to hospital for suspected gastro-oesophageal reflux. In vitro studies were performed to establish the buffering capacities of the fruit juice, Dioralyte (a glucose electrolyte solution), breast milk, and milk formula feeds available on the paediatric wards. RESULTS: Complete sets of data were obtained from 30 babies with a mean age of 4 months. Gastric pH was </= 4 for a mean (SEM) of 42.4 (4.9)% of the recording time. The mean (SEM) percentage time that oesophageal pH was < 4 for the total recording period was 6.89 (0.92)%. Recalculation of the percentage of time that the gastric pH was > 4 increased this value to 17.81 (2. 46)%. Using a cut off point of 10%, 11 of the 30 babies would have been diagnosed positive for reflux using the conventional method; however, recalculation by ignoring the time for which gastric pH was high doubled this to 22 positive for reflux. CONCLUSION: Combined oesophageal and gastric pH monitoring greatly increases the number of positive results from tests in infants on regular milk feeds.

Animals↗
PubMed1999

The importance of an extra hour of cycler therapy to obtain better adequacy.

As continuous ambulatory peritoneal dialysis (CAPD) patients lose residual renal function, it frequently becomes impossible from them to obtain adequate dialysis unless the dialysis prescription is changed. Increasing the dwell volumes, increasing the frequency of exchanges, and using a night-exchange device or a cycler are the means available to improve adequacy. In an effort to obtain dialysis adequacy, we studied how an extra hour on cycler therapy can contribute to improving dialysis adequacy. Over 18 months, we optimized solute clearance using the PD Adequest program (Baxter Healthcare Corporation, Chicago, Illinois, U.S.A.) in 70 patients. After finding the best total cycler volume, we compared the weekly creatinine clearance and weekly Kt/V from 8-hour cycler therapy to that from 9-hour cycler therapy for the four types of membrane transport. Adding one extra hour on cycler therapy improved weekly creatinine clearance by 3-6.5 L and the weekly Kt/V by 0.16-0.20. When patients are marginally approaching the required weekly Kt/V or creatinine clearance, an extra hour on the cycler may help to achieve the desired adequacy.

Humans↗
PubMed1999

Evaluating clinical decision-making skills of nurse practitioner students.

The evaluation of clinical competencies of nurse practitioner (NP) students has traditionally been accomplished by direct observation of student-patient interactions. Adult and family NP faculty at the Medical University of South Carolina directly observe students at their clinical site at least twice each semester. Recently, faculty recognized the need for additional validation of clinical decision-making skill development and added the Clinical Competency Evaluation (CCE), a standardized simulated patient encounter, to the evaluation process. The purpose of the CCE is to (a) maximize use of available evaluation technology, (b) evaluate student clinical skills in a controlled, standardized environment using a criterion-referenced format, (c) give students an additional performance feedback mechanism, and (d) identify benchmarks to validate student advancement and completion of the NP program. This article discusses how the CCE process was developed, current methods of conducting and grading the examination, faculty and student evaluation of the outcomes, and recommendations.

Adult↗
PubMed1999

Automated semantic indexing of imaging reports to support retrieval of medical images in the multimedia electronic medical record.

This paper describes preliminary work evaluating automated semantic indexing of radiology imaging reports to represent images stored in the Image Engine multimedia medical record system at the University of Pittsburgh Medical Center. The authors used the SAPHIRE indexing system to automatically identify important biomedical concepts within radiology reports and represent these concepts with terms from the 1998 edition of the U.S. National Library of Medicine's Unified Medical Language System (UMLS) Metathesaurus. This automated UMLS indexing was then compared with manual UMLS indexing of the same reports. Human indexing identified appropriate UMLS Metathesaurus descriptors for 81% of the important biomedical concepts contained in the report set. SAPHIRE automatically identified UMLS Metathesaurus descriptors for 64% of the important biomedical concepts contained in the report set. The overall conclusions of this pilot study were that the UMLS metathesaurus provided adequate coverage of the majority of the important concepts contained within the radiology report test set and that SAPHIRE could automatically identify and translate almost two thirds of these concepts into appropriate UMLS descriptors. Further work is required to improve both the recall and precision of this automated concept extraction process.

Abstracting and Indexing↗
PubMed1999

Bridging the Quantum gap: attaining adequacy utilizing the Quantum night-time exchange device.

BACKGROUND: The advent of night-time exchange devices (NXDs), such as the Quantum, gives the client on home peritoneal dialysis the option of five exchanges well spaced in a day or, for those who need only four exchanges a day, the ability to change their long dwell to the daytime. PURPOSE: To ascertain whether we were able to attain the NKF-DOQI recommended Kt/V of 2.0 for CAPD clients by adding a fifth exchange utilizing the Quantum NXD or by introducing a long daytime dwell for clients who only needed four exchanges per day. We also looked at alternative uses for a NXD. METHOD: As part of our CQI process for all clients on home peritoneal dialysis, dialysis adequacy testing is performed two weeks after the start of full prescription and biannually thereafter. In this study, the first group of clients, the "lifestyle group", changed to using the NXD to allow more daytime freedom. This first group had repeated 24 hour dialysate collections to ensure they maintained adequate Kt/Vs. The second group of clients, the "adequacy group", had Kt/Vs falling below the NKF-DOQI recommendation of 2.0. This second group had their peritoneal dialysis prescription optimized utilizing a computer modeling program. Their prescription was then changed accordingly Two weeks after the change in prescription, 24 hour dialysate collections were repeated for each client to ensure the new Kt/Vs were within the predicted parameters. RESULTS CONCLUSIONS: We were able to attain the NKF-DOQI recommended Kt/V, utilizing the CANUSA recommended fill volumes, for all clients underdialyzed on CAPD through the addition of a fifth exchange using the NXD. Other clients who may benefit from the use of NXDs are those who need more daytime freedom.

Adult↗
PubMed1998

Infusion of cytotoxic T cells for the prevention and treatment of Epstein-Barr virus-induced lymphoma in allogeneic transplant recipients.

Epstein-Barr virus (EBV) causes potentially lethal immunoblastic lymphoma in up to 25% of children receiving bone marrow transplants from unrelated or HLA-mismatched donors. Because this complication appears to stem from a deficiency of EBV-specific cytotoxic T cells, we assessed the safety and efficacy of donor-derived polyclonal (CD4(+) and CD8(+)) T-cell lines as immunoprophylaxis and treatment for EBV-related lymphoma. Thirty-nine patients considered to be at high risk for EBV-induced lymphoma each received 2 to 4 intravenous infusions of donor-derived EBV-specific T lymphocytes, after they had received T-cell-depleted bone marrow from HLA-matched unrelated donors (n = 33) or mismatched family members (n = 6). The immunologic effects of this therapy were monitored during and after the infusions. Infused cells were identified by detection of the neo marker gene. EBV-specific T cells bearing the neo marker were identified in all but 1 of the patients. Serial analysis of DNA detected the marker gene for as long as 18 weeks in unmanipulated peripheral blood mononuclear cells and for as long as 38 months in regenerated lines of EBV-specific cytotoxic T cells. Six patients (15.5%) had greatly increased amounts of EBV-DNA on study entry (>2, 000 genome copies/10(6) mononuclear cells), indicating uncontrolled EBV replication, a complication that has had a high correlation with subsequent development of overt lymphoma. All of these patients showed 2 to 4 log decreases in viral DNA levels within 2 to 3 weeks after infusion and none developed lymphoma, confirming the antiviral activity of the donor-derived cells. There were no toxic effects that could be attributed to prophylactic T-cell therapy. Two additional patients who did not receive prophylaxis and developed overt immunoblastic lymphoma responded fully to T-cell infusion. Polyclonal donor-derived T-cell lines specific for EBV proteins can thus be used safely to prevent EBV-related immunoblastic lymphoma after allogeneic marrow transplantation and may also be effective in the treatment of established disease.

Adolescent↗
PubMed1998

The ability of a variety of polymerases to synthesize past site-specific cis-syn, trans-syn-II, (6-4), and Dewar photoproducts of thymidylyl-(3'-->5')-thymidine.

The role of photoproduct structure, 3' --> 5' exonuclease activity, and processivity on polynucleotide synthesis past photoproducts of thymidylyl-(3' --> 5')-thymidine was investigated. Both Moloney murine leukemia virus reverse transcriptase and 3' --> 5' exonuclease-deficient (exo-) Vent polymerase were blocked by all photoproducts, whereas Taq polymerase could slowly bypass the cis-syn dimer. T7 RNA polymerase was able to bypass all the photoproducts in the order cis-syn > Dewar > (6-4) > trans-syn-II. Klenow fragment could not bypass any of the photoproducts, but an exo- mutant could bypass the cis-syn dimer to a greater extent than the others. Likewise T7 DNA polymerase, composed of the T7 gene 5 protein and Escherichia coli thioredoxin, was blocked by all the photoproducts, but the exo- mutant Sequenase 2.0 was able to bypass them all in the order cis-syn > Dewar > trans-syn-II > (6-4). No bypass occurred with an exo- gene 5 protein in the absence of the thioredoxin processivity factor. Bypass of the cis-syn and trans-syn-II products by Sequenase 2.0 was essentially non-mutagenic, whereas about 20% dTMP was inserted opposite the 5'-T of the Dewar photoproduct. A mechanism involving a transient abasic site is proposed to account for the preferential incorporation of dAMP opposite the 3'-T of the photoproducts.

Base Sequence↗
PubMed1998

Novel diversity in Th1, Th2 type differentiation of hemagglutinin-specific T cell clones elicited by natural influenza virus infection in three major haplotypes (H-2b,d,k).

We report novel diversity in the lymphokine (LK) secretion profile of hemagglutinin-specific, CD4+ T cell clones elicited by influenza virus infection in three major haplotypes: I-Ad- or I-Ed-restricted T cell clones obtained from individual BALB/c donors, and specific for three distinct antigenic peptides (p56-76, or p186-205 or p177-199), were uniformly Th1 type, releasing only IFN-gamma on activation. In contrast, extensive diversity was evident for the C57BL/10 or CBA/Ca repertoire. Sibling T cell clones, established from the same C57BL/10 donor and expressing identical TCR beta-chains in their recognition of p186-205, released either (IFN-gamma and IL-5) or (IFN-gamma and IL-4 and IL-5) or (IL-4 and IL-5 and IL-10) following Ag-specific or nonspecific stimulation. Similarly, I-Ak-restricted T cell clones, specific for p120-139 secreted either (IFN-gamma only) or (IFN-gamma and IL-5) or (IFN-gamma and IL-2 and IL-5) on activation. Despite such phenotypic diversity within the individual's repertoire, all clones had been maintained under identical in vitro culture conditions. Moreover, sequence analyses of TCR beta gene usage indicated that in most instances clones from the same donor expressed identical (VDJ)beta rearrangements, indicative of a common progenitor cell. FACS analysis of cytoplasmic cytokine production confirmed that for the novel phenotype (IFN-gamma and IL-5), both LKs were synthesized at the single cell level. Sibling families of T cell clones, established from a common donor following viral infection but differing in LK secretion, may offer a suitable model system for further studies of signal transduction mechanisms that discriminate between Th1- and Th2-specific responses to a well defined protective Ag.

Animals↗
PubMed1998

Altering the context of an RNA bulge switches the binding specificities of two viral Tat proteins.

The bovine immunodeficiency virus (BIV) Tat protein binds with high affinity to its TAR RNA site through a large set of specific RNA-protein contacts whereas human immunodeficiency virus (HIV) Tat makes relatively few contacts to HIV TAR and requires the assistance of a cellular protein to bind with high affinity. The two TAR sites are structurally very similar, but BIV Tat appears unable to make the same set of high-affinity contacts to HIV TAR. To determine the basis of this discrimination, we examined BIV Tat binding to a series of hybrid TARs both in vivo and in vitro. We expected that differences in the architectures of the bulges might account for the binding specificity; however, the results show that flanking base pairs provide the key determinants. Based on these data, we designed a novel TAR that is recognized by both BIV Tat and HIV Tat. This RNA may be viewed as a primordial TAR from which two distinct recognition strategies can be evolved.

Animals↗
PubMed1998

Extensive cross-reactivity of adenovirus-specific cytotoxic T cells.

Although adenovirus is a major source of morbidity for immunocompromised individuals and a popular vector for gene therapy, little is known about the cellular immune responses it evokes in humans. Initial trials using adenovirus vectors have been disappointing, probably owing both to a preexisting immune response to Ad2 and Ad5, the most commonly used vector backbones, and to a response to the transgene. The former problem might be overcome by switching from the common type C adenoviruses, of which Ad2 and Ad5 are members, to other less common serotypes. Evidence for the feasibility of this approach has been provided by a rat model system. However, its success in humans depends on there being no immunological cross-reactivity between groups at the humoral or cellular level. Here, we examine the cross-reactivity of the cellular immune response to adenovirus in a human system, and find that human cytotoxic T lymphocytes (CTLs) prepared in vitro against an adenovirus from two of the six subgroups can lyse cells infected with adenoviruses from the other subgroups. Hence, the proposed use of adenovirus vectors from uncommon subgroups to evade memory immune response to subgroup C adenoviruses may not be successful. However, this same cross-reactivity indicates that adoptive transfer of CTLs generated in vitro against one adenovirus serotype may protect immunocompromised patients from infections by adenoviruses of all serotypes.

Adenoviridae↗
PubMed1998

Structural homologies with ATP- and folate-binding enzymes in the crystal structure of folylpolyglutamate synthetase.

Folylpolyglutamate synthetase, which is responsible for the addition of a polyglutamate tail to folate and folate derivatives, is an ATP-dependent enzyme isolated from eukaryotic and bacterial sources, where it plays a key role in the retention of the intracellular folate pool. Here, we report the 2.4-A resolution crystal structure of the MgATP complex of the enzyme from Lactobacillus casei. The structural analysis reveals that folylpolyglutamate synthetase is a modular protein consisting of two domains, one with a typical mononucleotide-binding fold and the other strikingly similar to the folate-binding enzyme dihydrofolate reductase. We have located the active site of the enzyme in a large interdomain cleft adjacent to an ATP-binding P-loop motif. Opposite this site, in the C domain, a cavity likely to be the folate binding site has been identified, and inspection of this cavity and the surrounding protein structure suggests that the glutamate tail of the substrate may project into the active site. A further feature of the structure is a well defined Omega loop, which contributes both to the active site and to interdomain interactions. The determination of the structure of this enzyme represents the first step toward the elucidation of the molecular mechanism of polyglutamylation of folates and antifolates.

Adenosine Triphosphate↗
PubMed1998

Ribozyme-mediated repair of sickle beta-globin mRNAs in erythrocyte precursors.

Sickle cell anemia is the most common heritable hematological disease, yet no curative treatment exists for this disorder. Moreover, the intricacies of globin gene expression have made the development of treatments for hemoglobinopathies based on gene therapy difficult. An alternative genetic approach to sickle cell therapy is based on RNA repair. A trans-splicing group I ribozyme was used to alter mutant beta-globin transcripts in erythrocyte precursors derived from peripheral blood from individuals with sickle cell disease. Sickle beta-globin transcripts were converted into messenger RNAs encoding the anti-sickling protein gamma-globin. These results suggest that RNA repair may become a useful approach in the treatment of genetic disorders.

Anemia, Sickle Cell↗
PubMed1998

Two high-resolution crystal structures of the recombinant N-lobe of human transferrin reveal a structural change implicated in iron release.

The N-lobe of human serum transferrin (hTF/2N) has been expressed in baby hamster kidney cells and crystallized in both orthorhombic (P212121) and tetragonal (P41212) space groups. Both crystal forms diffract to high resolution (1.6 and 1.8 A, respectively) and have been solved by molecular replacement. Subsequent refinement resulted in final models for the structure of hTF/2N that had crystallographic R-factors of 18.1 and 19.7% for the two crystal forms, respectively; these models represent the highest-resolution transferrin structures determined to date. The hTF/2N polypeptide has a folding pattern similar to those of other transferrins, including the presence of a deep cleft that contains the metal-binding site. In contrast to other transferrins, both crystal forms of hTF/2N display disorder at the iron-binding site; model building suggests that this disorder consists of alternative conformations of the synergistically bound carbonate anion, the side chain for Arg-124, and several solvent molecules. Subsequent refinement revealed that conformation A has an occupancy of 0.63-0. 65 and corresponds to the structure of the iron-binding site found in other transferrins. The alternative conformation B has an occupancy of 0.35-0.37; in this structure, the carbonate has rotated 30 degrees relative to the iron and the side chain for Arg-124 has moved to accommodate the new carbonate position. Several water molecules appear to stabilize the carbonate anion in the two conformations. These structures are consistent with the protonation of the carbonate and resulting partial removal of the anion from the metal; these events would occur prior to cleft opening and metal release.

Animals↗
PubMed1998

Characterisation of gamma-glutamylcysteine synthetase-heavy subunit promoter: a critical role for AP-1.

The 5'-flanking region of human gamma-glutamylcysteine synthetase-heavy subunit (gamma-GCS-HS) was characterised by creating a series of chloramphenicol acetyl transferase (CAT) reporter deletion constructs. Analysis of various deleted CAT constructs revealed that a putative AP-1 consensus sequence is required to direct the constitutive and oxidant-mediated promoter activity. Gel mobility shift and mutation analysis of the sequence (-269 to -263 bp), showed binding of AP-1 is involved in the oxidant-mediated regulation of gamma-GCS-HS promoter activity.

Cells, Cultured↗
PubMed1998

CD34+CD38-lin- cord blood cells develop into dendritic cells in human thymic stromal monolayers and thymic nodules.

Thymic dendritic cells (DCs) appear to have distinct biologic and functional properties compared with DCs in other tissues. Currently, little is known about human thymic DCs because they have been difficult to isolate and culture in vitro. Here, we report that human thymic stroma can support the development of primitive human hemopoietic stem cells into mature DCs without cytokine or serum supplementation. Coculture of CD34+CD38-lineage (lin)- and CD34+CD38+lin- umbilical cord blood cells with thymic stromal monolayers induced 43 +/- 17-fold and 32 +/- 16-fold expansions, respectively, of umbilical cord blood progenitors and also generated large numbers of cells with the morphologic, phenotypic, and functional characteristics of mature DCs. These cells expressed class I and class II MHC, CD1a, CD2, CD4, CD11c, CD40, CD45, CD80, CD83, and CD86 and were potent stimulators of allogeneic T cell activation. Primitive hemopoietic progenitors also developed into mature DCs in a novel tissue culture system of thymic nodules wherein thymic epithelial cells and fibroblasts were grown in nodular aggregates in vitro. These results demonstrate that human thymic stroma efficiently supports the development of CD34+CD38-lin- cord blood cells into mature DCs. In addition, the culture conditions described in this report are useful systems for studying the ontogeny of human DCs in thymic microenvironments.

ADP-ribosyl Cyclase↗