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Biomedical subjects

P Carter

Publications and source records attributed to P Carter.

At least 37 records · Page 2Linked to original sources
PubMed2000

Atrial endocardial changes in mitral valve disease: a scanning electron microscopy study.

BACKGROUND: The precise contribution of left atrial appendage (LAA) endocardial damage and dysfunction to the process of thrombus formation in patients with mitral valve (MV) disease, especially in the presence of atrial fibrillation (AF), has not as yet been clearly described. This may be important because the LAA is the usual site for thrombus formation. METHODS: The purpose of this study was to describe endocardial surface changes, through the use of scanning electron microscopy, in the left and right atrial appendages of patients with MV disease and the differences, if any, between patients with mitral stenosis and mitral regurgitation as well as between those with AF and sinus rhythm. Our second objective was to relate endocardial changes to plasma levels of von Willebrand factor (vWf), an established marker for endothelial damage. LAA specimens were obtained immediately after commencement of cardiopulmonary bypass from 35 patients (18 men; mean age 65 years, range 20 to 85) during surgery for MV repair or replacement. Right atrial appendage (RAA) specimens were similarly obtained as controls for individual patients. The specimens were fixed in 2.5% glutaraldehyde solution overnight, stored in Sorensen's phosphate buffer, and examined by means of scanning electron microscopy. Two independent observers documented the most advanced lesion in each specimen as follows: (1) "minimal" changes, with minimal disruption of the endocardium; (2) "intermediate" changes or prethrombotic lesions; and (3) "advanced" changes, with endocardial disruption and thrombotic lesions. Plasma levels of vWf were also measured (enzyme-linked immunosorbent assay) in all patients, and results were compared with those of age- and sex-matched healthy control patients. RESULTS: Advanced changes were more frequently seen in the endocardium of the LAA when compared with the RAA (31% vs 6%), whereas minimal changes were more frequently seen in the RAA compared with the LAA (23% vs 6%) (P =.00167). Similarly, the LAA from patients with mitral stenosis had a higher proportion of "advanced" endocardial changes when compared with patients with mitral regurgitation (67% vs 24%; P =.0066). The LAA in patients with AF had more "advanced" changes (39% vs 27%), but this was not statistically significant. Plasma vWf levels were significantly higher in patients with MV disease compared with healthy control patients (132 +/- 33 IU/dL vs 99 +/- 37 IU/dL; P =.0004) and in patients with advanced LAA changes compared with earlier changes (149 +/- 34 IU/dL vs 121 +/- 31 IU/dL; P =.042). CONCLUSIONS: Endocardial damage occurs in the atrial appendages of patients with MV disease. Potentially thrombogenic changes are more commonly seen in the LAA compared with the RAA and in patients with mitral stenosis compared with mitral regurgitation. These anatomic appearances may contribute to the risk of intra-atrial thrombus formation in patients with mitral valve disease, especially if AF is present.

Adult↗
PubMed2000

Effective treatment of a patient with a high-grade endometrial stromal sarcoma with an accelerated regimen of carboplatin and paclitaxel.

The rarity of endometrial stromal sarcoma (ESS) and its poor response to treatment provides fertile ground for investigational therapies. An accelerated regimen of carboplatin and paclitaxel is investigated. A patient with a recent history of treated tuberculosis of the lung represented with infertility and acute abdominal pain from suspected fibroids, and underwent a laparotomy with a diagnosis of a high-grade ESS. A novel therapeutic approach using a regimen of carboplatin and paclitaxel with the reinfusion of filgrastim-mobilized peripheral blood progenitor cells is described. A partial response was observed following six cycles of chemotherapy. Grade IV thrombocytopenia occurred after the last cycle, with recovery prior to pelvic radiotherapy. The patient remained well 1 year post-diagnosis. High-grade ESS is responsive to combination chemotherapy with paclitaxel and carboplatin, and requires further evaluation. The use of an accelerated regimen may also have contributed to the response and this question awaits randomized trials.

Adult↗
PubMed2000

Substrate-assisted catalysis: molecular basis and biological significance.

Substrate-assisted catalysis (SAC) is the process by which a functional group in a substrate contributes to catalysis by an enzyme. SAC has been demonstrated for representatives of three major enzyme classes: serine proteases, GTPases, and type II restriction endonucleases, as well as lysozyme and hexose-1-phosphate uridylyltransferase. Moreover, structure-based predictions of SAC have been made for many additional enzymes. Examples of SAC include both naturally occurring enzymes such as type II restriction endonucleases as well as engineered enzymes including serine proteases. In the latter case, a functional group from a substrate can substitute for a catalytic residue replaced by site-directed mutagenesis. From a protein engineering perspective, SAC provides a strategy for drastically changing enzyme substrate specificity or even the reaction catalyzed. From a biological viewpoint, SAC contributes significantly to the activity of some enzymes and may represent a functional intermediate in the evolution of catalysis. This review focuses on advances in engineering enzyme specificity and activity by SAC, together with the biological significance of this phenomenon.

Catalysis↗
PubMed2000

Improving outcomes in rectal cancer.

Concerted efforts are being made to improve the poor surgical outcomes in rectal carcinomas and this includes the use of total mesorectal excision by specially trained colorectal surgeons, in addition to the use of pre- or postoperative radiotherapy and chemotherapy. The role of each modality should be carefully evaluated, and benefits weighed against toxicity and added costs.

Antineoplastic Agents↗
PubMed2000

Antibody engineering--IBC's Tenth International Conference. 6-9 December 1999, La Jolla, CA, USA.

This meeting covered emergent antibody technologies through preclinical and clinical development of antibodies to the latest clinical data with antibody drugs. On the technology front, human antibody phage libraries have increased in size and quality, and have been combined with high-throughput screening methods. Such phage libraries have become powerful tools for the generation of antibody therapeutics and may also prove useful in the identification of new therapeutic targets. Indeed, four high affinity human antibodies from phage libraries are currently in clinical trials. Transgenic mice containing human immunoglobulin genes have also emerged as a route to high affinity human antibodies, including two that have progressed into the clinic. Molecular evolution of scFv fragments to increase their stability has led to improved localization to tumors in animal models and to their enhanced performance as intrabodies. In clinical trials, significant efficacy with minimal or acceptable toxicities were reported for the chimeric Fab fragment, ReoPro (abciximab; Centocor Inc), in coronary artery disease; the humanized anti-HER2 antibody, Herceptin (trastuzumab; Genentech Inc), in metastatic breast cancer; and, the humanized anti-IgE antibody, E25 (Genentech Inc), in asthma and allergic rhinitis.

Journal Article↗
PubMed1999

Identification of a human anti-CD55 single-chain Fv by subtractive panning of a phage library using tumor and nontumor cell lines.

A large naive human single-chain (sc) Fv phage library was used to search for tumor-associated antigens by panning with a lung adenocarcinoma cell line, 1264, and counter-selecting with a nontumor bronchial epithelial cell line, BEAS-2B. After three rounds of subtractive panning, 239 of 673 clones analyzed bound selectively to 1264 tumor cells in a phage ELISA. Diversity analysis of these tumor-selective clones by BstNI fingerprinting and nucleotide sequencing revealed 14 distinct scFv fragments. Four clones bound selectively to 1264 over BEAS-2B cells when analyzed by a more discriminating flow cytometric assay using scFv. Moreover, these clones showed only limited cross-reactivity to several primary human cell lines. One clone, LU30, also cross-reacted strongly with the lung adenocarcinoma line, A549. The LU30 antigen was identified as decay-accelerating factor (CD55) by expression cloning from a 1264 cDNA library. The mean number of decay-accelerating factor molecules on the surface of 1264 and BEAS cells used for panning and counter-selection was estimated as 75,000 +/- 5,000 and 13,000 +/- 10,000, respectively. Thus, phage library panning combined with expression cloning permits identification of antibodies and their cognate antigens for proteins that are differentially expressed on the surface of distinct cell populations.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1999

Phage library-derived human anti-TETA and anti-DOTA ScFv for pretargeting RIT.

Pretargeting techniques have promise for radioimmunotherapy (RIT) in cancer because of the potential for markedly increasing the therapeutic ratio. Human antibody fragments can be retrieved from phage libraries and used to realize this potential. The library can be used to select the genetic material required to generate molecules with binding sites for both radiochelates and tumor antigens. In this study, human anti-chelate scFvs (single-chain fragments) for two metal chelates (Cu-TETA and Y-DOTA) were selected from a large, naive human scFv library. These anti-chelate scFvs were intended to serve as one arm of bispecific pretargeting molecules and to bind radiochelates given subsequently as Cu-67-TETA or Y-90-DOTA. Phage that displayed the anti-chelate scFv were selected by absorption to antibody (Lym-1) bound Cu-TETA or Y-DOTA. Enzyme-linked immunosorbent assays (ELISA) were performed to assess the intensity and specificity of phage binding to the specific chelate. Ninety-six clones demonstrating metal chelate binding seven times greater than to Lym-1 alone were chosen for diversity analysis. BstN I restriction digests were performed on DNA from these clones. Twenty-three and 43 different DNA fingerprint patterns were identified for anti-TETA and anti-DOTA clones, respectively. DNA sequencing of 39 anti-TETA clones for 23 different BstN I fingerprint patterns revealed 22 distinct sequences. Eleven of the anti-TETA clones were selected for further study. Five hundred to 1000 microg (100 to 320 microg per liter of culture) of purified scFv was produced from each of the 11 anti-TETA clones. Preliminary studies by BIAcore demonstrated evidence of 25- to 200-nM affinities. Comparable examination of the anti-DOTA clones is in progress. This study provides evidence that human scFv against unique synthetic targets can be readily selected from a large, naive human immunoglobulin phage library. Selections against metal chelated antibodies provided a wealth of scFvs with diverse binding affinities useful for engineering molecules for pretargeting RIT.

Antibodies, Monoclonal↗
PubMed1999

Elastase substrate specificity tailored through substrate-assisted catalysis and phage display.

The catalytic histidine of human neutrophil elastase was replaced with alanine (H57A) to determine if a substrate histidine could substitute for the missing catalytic group-'substrate-assisted catalysis'. H57A and wild-type elastase were recovered directly from Pichia pastoris following expression from a synthetic gene lacking the elastase pro sequence, thereby obviating the need for zymogen activation. Potential histidine-containing substrates for H57A elastase were identified from a phage library of randomized sequences. One such sequence, REHVVY, was cleaved by H57A elastase with a catalytic efficiency, k(cat)/K(M), of 2800 s(-1) M(-1), that is within 160-fold of wild-type elastase. In contrast, wild-type but not H57A elastase cleaved the related non-histidine containing sequence, REAVVY. Ten different histidine-containing linkers were cleaved by H57A elastase. In addition to the requirement for a P2 histidine, significant preferences were observed at other subsites including valine or threonine at P1, and methionine or arginine at P4. A designed sequence, MEHVVY, containing the preferred residues identified at each subsite proved to be a more favorable substrate than any of the phage-derived sequences. Extension of substrate-assisted catalysis to elastase suggests that this engineering strategy may be widely applicable to other serine proteases thereby creating a family of highly specific histidine-dependant proteases.

Amino Acid Sequence↗
PubMed1999

Glutamate transport asymmetry and metabolism in the functioning kidney.

Renal glutamate extraction in vivo shows a preference for the uptake of D-glutamate on the antiluminal and L-glutamate on the luminal tubule surface. To characterize this functional asymmetry, we isolated rat kidneys and perfused them with an artificial plasma solution containing either D- or L-glutamate alone or in combination with the system X-AG specific transport inhibitor, D-aspartate. To confirm that removal of glutamate represented transport into tubule cells, we monitored products formed as the result of intracellular metabolism and related these to the uptake process. Perfusion with D-glutamate alone resulted in a removal rate that equaled or exceeded the L-glutamate removal rate, with uptake predominantly across the antiluminal surface; L-glutamate uptake occurred nearly equally across both luminal and antiluminal surfaces. Thus the preferential uptake of D-glutamate at the antiluminal and L-glutamate at the luminal surface confirms the transport asymmetry observed in vivo. Equimolar D-aspartate concentration blocked most of the antiluminal D-glutamate uptake and a significant portion of the luminal L-glutamate uptake, consistent with system X-AG activity at both sites. D-Glutamate uptake was associated with 5-oxo-D-proline production, whereas L-glutamate uptake supported both glutamine and 5-oxo-L-proline formation; D-aspartate reduced production of both 5-oxoproline and glutamine. The presence of system X-AG activity on both the luminal and antiluminal tubule surfaces, exhibiting different reactivity toward L- and D-glutamate suggests that functional asymmetry may reflect two different X-AG transporter subtypes.

Animals↗
PubMed1999

Patterns of burden in wives who care for husbands with dementia.

The purpose of the study described in this article was to examine the longitudinal pattern of subjective burden in a sample of 899 wives caring for husbands with irreversible dementia. Differences in caregiver burden between those caregivers who continued home care and those who placed their relative in institutional care were also tested. For both continuing care and placement cohorts the longitudinal pattern showed increases in burden. However, significantly higher levels of burden were found in the caregivers who placed their husbands in institutional care than in those who continued care in the home. Following placement, the wives experienced a decrease in burden. Clinical and health policy implications of these findings are also addressed for nurses and other health professionals.

Adult↗
PubMed1999

Antibody phage libraries for the next generation of tumor targeting radioimmunotherapeutics.

Pretargeting techniques have shown promise for enhancement of the therapeutic index of radioimmunotherapy for cancer. However, methods to vary and compare antibody configurations and select optimal combinations have proved rather formidable. New options for the construction of pretargeting molecules are provided by sophisticated use of the diversity and malleability of antibody genes. Diverse arrays of single-chain antibody fragments (scFvs) can now be obtained reactive with virtually any target antigen by selection from human naive phage antibody libraries. ScFvs can also be cloned directly from hybridoma for construction of phage libraries that facilitate subsequent manipulation: e.g., affinity maturation and modification of specificity. ScFvs affinity selected from these sources to their specific antigen targets have demonstrated a wide spectrum of binding characteristics. ScFvs selected from a large human naive phage antibody library by binding Cu-1,4,8,11-tetra-azacyclotetradecane-N,N',N'',N'''-tetraacetic acid (TETA) or Y-1,4,7,10-tetra-azacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) have shown diversity by DNA fingerprints. DNA sequence information confirmed that the anti-TETA scFv represented diverse scFv gene families. ScFvs for Y-DOTA and those for lymphoma-associated HLA DR10 (Lym-1) were selected in a similar manner from mouse antibody gene libraries derived from hybridoma. ScFv clones for each of these antigens were chosen for further study based on the results of ELISA assays involving the respective cell membrane or metal chelate antigens. A PCR primer system built to pCANTAB 5E expression vector sequence was designed to facilitate cloning of antibody heavy (V(H)) and light (V(L)) genes from selected scFvs as cassettes into diabody modules. Thus, chosen scFvs could be expressed in the same diabody format for comparative study. Selected mouse anti-DOTA scFv and Lym-1 scFv genes were linked as V(HA) anti-DOTA-link-V(LB) Lym-1; V(HB) anti-DOTA-link-V(LA) Lym-1 and ligated into the pCANTAB 5E vector. Corresponding diabodies were expressed in Escherichia coli and purified by affinity chromatography. Here we provide a perspective on the power of antibody phage libraries and the possibilities of creating simple molecular formats that can be used en route to the development of new tumor targeting and pretargeting molecules.

Animals↗
PubMed1998

Contribution of domain interface residues to the stability of antibody CH3 domain homodimers.

Dimers of CH3 domains from human IgG1 were used to study the effect of mutations constructed at a domain-domain interface upon domain dissociation and unfolding, "complex stability". Alanine replacement mutants were constructed on one side of the interface for each of the sixteen interdomain contact residues by using a single-chain CH3 dimer in which the carboxyl terminus of one domain was joined to the amino terminus of the second domain via a (G4S)4 linker. Single-chain variants were expressed in Escherichia coli grown in a fermentor and recovered in yields of 6-90 mg L-1 by immobilized metal affinity chromatography. Guanidine hydrochloride-induced denaturation was used to follow domain dissociation and unfolding. Surprisingly, the linker did not perturb the complex stability for either the wild type or two destabilizing mutants. The CH3 domain dissociation and unfolding energetics are dominated by six contact residues where corresponding alanine mutations each destabilize the complex by >2.0 kcal mol-1. Five of these residues (T366, L368, F405, Y407, and K409) form a patch at the center of the interface and are located on the two internal antiparallel beta-strands. These energetically key residues are surrounded by 10 residues on the two external beta-strands whose contribution to complex stability is small (three have a Delta DeltaG of 1.1-1.3 kcal mol-1) or very small (seven have a Delta DeltaG of </=0.7 kcal mol-1). Thus, at the center of the CH3 structural interface there is a small "functional interface" of residues that make significant contributions to complex stability.

Alanine↗
PubMed1998

ZYG-9, a Caenorhabditis elegans protein required for microtubule organization and function, is a component of meiotic and mitotic spindle poles.

We describe the molecular characterization of zyg-9, a maternally acting gene essential for microtubule organization and function in early Caenorhabditis elegans embryos. Defects in zyg-9 mutants suggest that the zyg-9 product functions in the organization of the meiotic spindle and the formation of long microtubules. One-cell zyg-9 embryos exhibit both meiotic and mitotic spindle defects. Meiotic spindles are disorganized, pronuclear migration fails, and the mitotic apparatus forms at the posterior, orients incorrectly, and contains unusually short microtubules. We find that zyg-9 encodes a component of the meiotic and mitotic spindle poles. In addition to the strong staining of spindle poles, we consistently detect staining in the region of the kinetochore microtubules at metaphase and early anaphase in mitotic spindles. The ZYG-9 signal at the mitotic centrosomes is not reduced by nocodazole treatment, indicating that ZYG-9 localization to the mitotic centrosomes is not dependent upon long astral microtubules. Interestingly, in embryos lacking an organized meiotic spindle, produced either by nocodazole treatment or mutations in the mei-1 gene, ZYG-9 forms a halo around the meiotic chromosomes. The protein sequence shows partial similarity to a small set of proteins that also localize to spindle poles, suggesting a common activity of the proteins.

Adenosine Triphosphatases↗
PubMed1998

Antibody engineering.

Among the most important advances in antibody engineering of this past year is the advent of new tools to study the relationship between protein (including antibody) structure and function. Very rapid large-scale mutational analysis of antibodies is now possible by using in vitro transcription and translation. Ribosome display is a rapidly evolving technology for modifying antibody function that offers several potential advantages over phage display.

Animals↗
PubMed1998

An efficient route to human bispecific IgG.

Production of bispecific IgG (BsIgG) by coexpressing two different antibodies is inefficient due to unwanted pairings of the component heavy and light chains. To overcome this problem, heavy chains were remodeled for heterodimerization using engineered disulfide bonds in combination with previously identified "knobs-into-holes" mutations. One of the variants, S354C:T366W/Y349'C:T366'S:L368'A:Y407++ +'V, gave near quantitative (approximately 95%) heterodimerization. Light chain mispairing was circumvented by using an identical light chain for each arm of the BsIgG. Antibodies with identical light chains that bind to different antigens were identified from an scFv phage library with a very restricted light chain repertoire for the majority (50/55) of antigen pairs tested. A BsIgG capable of simultaneously binding to the human receptors HER3 and cMpI was prepared by coexpressing the common light chain and corresponding remodeled heavy chains followed by protein A chromatography. The engineered heavy chains retain their ability to support antibody-dependent cell-mediated cytotoxicity as demonstrated with an anti-HER2 antibody.

Antibody Specificity↗
PubMed1998

Sequential treatment including high-dose chemotherapy with peripheral blood stem cell support in patients with high-risk stage II-III breast cancer: outpatient administration in community cancer centers.

The authors determined outcomes for patients with localized high-risk breast cancer undergoing sequential outpatient treatment with conventional-dose adjuvant therapy, chemotherapy, and growth factor mobilization of peripheral blood stem cells (PBSC) and high-dose chemotherapy (HDC) with PBSC support in community cancer centers. Ninety-six patients with stage II-IIIB noninflammatory breast cancer with 10 or more positive lymph nodes and a median age of 46 years (range, 22-60 years) were treated with: 1) doxorubicin, 5-fluorouracil, and methotrexate (AFM), four courses at 2-week intervals; 2) cyclophosphamide (4 g/m2) and etoposide (600 mg/m2) (CE), followed by filgrastim (6 microg/kg per day) and PBSC harvest; and 3) cyclophosphamide (6 g/m2), thiotepa (500 mg/m2), and carboplatin (800 mg/m2) (CTCb), followed by PBSC infusion. All 96 patients received AFM, 95 (99%) received CE, and 95 (99%) received CTCb with a median hospital stay of 12 days (5-34 days) for all phases of treatment. Sixty-nine patients (72%) are alive, 55 (57%) without relapse at a median follow-up of 53 months (range, 37-77 months). One patient (1%) died of acute myeloid leukemia and all other deaths were associated with recurrent breast cancer. The probabilities of event-free survival (EFS) at 4 years for patients with or without locally advanced disease were 0.37 and 0.69, respectively (p = 0.004), and 0.71 and 0.48 for patients who were estrogen/progesterone receptor (ER/PR) positive or ER/PR negative, respectively (p = 0.016). In multivariate analyses, locally advanced disease (relative risk, 2.3; p = 0.021) and ER/PR-negative hormone receptor status (relative risk, 2.2; p = 0.014) were the only adverse risk factors for EFS identified. Patients with zero, one, or two of these adverse risk factors had 4-year EFS of 0.80, 0.56, and 0.33, respectively. The sequential administration of AFM, CE, and CTCb followed by PBSC in an outpatient community setting was well tolerated in patients with high-risk stage II-III breast cancer. More intensive or more novel treatment strategies will be required to decrease relapses in patients who have ER/PR-negative tumors and/or have locally advanced disease.

Adult↗