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Biomedical subjects

K Sheldon

Publications and source records attributed to K Sheldon.

18 recordsLinked to original sources

Social roles as mechanisms for psychological need satisfaction within social groups.

The authors explored ways in which needs for autonomy and relatedness can be simultaneously met within the context of group life. Specifically, it was hypothesized that social role performances provide means of both expressing the self and connecting with group members. Consistent with the assumption that autonomy and relatedness are complementary rather than conflictual, these needs were positively correlated in all 5 studies. Consistent with the authors' assumption that these needs are both important, feelings of autonomy and relatedness in social roles independently predicted subjective well-being, as measured by concurrent (Studies I and 3), peer-report (Study 2). and longitudinal (Studies 4 and 5) methodologies. Study 5 showed that participants whose characteristics matched an assigned role experienced more autonomy and relatedness and thus more positive mood during a group task. Implications for optimal functioning in group contexts are discussed.

Adult↗

Loligomers: design of de novo peptide-based intracellular vehicles.

Defined branched peptides (loligomers) incorporating cytoplasmic translocation signals, nuclear localization sequences, and fluorescent probes were designed and synthesized to demonstrate the feasibility and simplicity of creating novel classes of intracellular vehicles. Loligomers containing all the above signals were rapidly internalized by Chinese hamster ovary (CHO) cells and accumulated in their nucleus. At 4 degrees C, the interaction of peptide constructs with CHO cells was limited to membrane association. Loligomers entered cells at higher temperatures by adsorptive endocytosis. Inhibitors of ATP synthesis affected cytoplasmic import only weakly but abolished nuclear uptake. The peptide signals guided both cytoplasmic and nuclear localization events. The properties exhibited by loligomers suggest a strategy for the facile design of "guided" classes of intracellular agents.

Amino Acid Sequence↗

Targeting of [111In]biocytin to cultured ovarian adenocarcinoma cells using covalent monoclonal antibody-streptavidin conjugates.

Three monoclonal antibodies (mAb) directed against the human ovarian adenocarcinoma cell line HEY, were substituted with maleimide and covalently bonded to thiolated streptavidin. The conjugates were separated from unreacted reagents by successive affinity chromatography on protein A-Sepharose and iminobiotin columns. Purified conjugates consisted of an immunoglobulin (Ig) monomer bound to a streptavidin tetramer through a covalent bond between the Ig molecule and one of the streptavidin subunits. The conjugates were able to specifically target [111In]biocytin to HEY cells in vitro in the presence of human serum and ascitic fluid from ovarian cancer patients.

Adenocarcinoma↗

Evaluation of reduction-mediated labelling of antibodies with technetium-99m.

Monoclonal antibodies can be labelled with technetium-99m by prereduction of the antibody with 2-mercaptoethanol, then reduction of pertechnetate with an aliquot of a stannous kit, resulting in greater than 97% labelling without the need for further purification. The present work shows that equally high labelling can be obtained with a variety of weak ligands and that the optimum quantity of stannous chloride is 2-4 micrograms. Although the label was stable to challenge with excess DTPA, cysteine was able to remove a portion of the label. We have also shown that this technique works with the IgG2a isotype in addition to the previously reported IgG1 isotype. This approach is simple, convenient and reproducible, and warrants further clinical evaluation.

Antibodies, Monoclonal↗

Imaging of human ovarian tumour xenografts in nude mice using a novel 111In-labelled monoclonal antibody (10B).

Monoclonal antibody (mAb) 10B, directed against the human ovarian adenocarcinoma cell line, HEY, was conjugated with cyclic DTPA anhydride and labelled with 111In. The biodistribution of 111In-DTPA-10B was determined in non-tumour bearing mice and mice bearing subcutaneous (s.c.) and intraperitoneal (i.p.) HEY tumours. The radiolabel was preferentially targeted to s.c. and i.p. tumours in comparison with a control mAb. 111In-DTPA-2G3, which does not bind to HEY cells. Among normal organs, the predominant uptake of radiolabel was into liver and kidney. Subcutaneous tumours were successfully imaged using external gamma scintigraphy following i.v. injection of 111-In-DTPA-10B. The results suggest that 111In-DTPA-10B may be a useful agent for the diagnostic imaging of tumour masses in patients with ovarian cancer.

Animals↗

Labelling of monoclonal antibodies 10B, 8C, and M2A with indium-111.

Monoclonal antibodies 10B, 8C and M2A were conjugated with cyclic DTPA anhydride to a substitution level of 1-2 mol DTPA/mol antibody. The DTPA-conjugated antibodies were purified by size-exclusion mini-column chromatography and labelled with [111In]In acetate to a specific activity of 37-74 kBq/micrograms (1-2 microCi/micrograms). The radiochemical purity of the antibody preparation was 76-81%. The immunoreactive fraction of the radiolabelled antibodies ranged from 0.17 to 0.31, significantly lower than that of their radioiodinated analogs.

Antibodies, Monoclonal↗

Characterization of binding of four monoclonal antibodies to the human ovarian adenocarcinoma cell line HEY.

Four mouse monoclonal antibodies (mAb) (10B, IgG1; 8C, IgG2a; M2A, IgG2a; M2D, IgG2b) were characterized with respect to their binding to the ovarian adenocarcinoma cell line HEY, using displacement assays and Scatchard plot analyses. The four mAb reacted with different antigens on the surface of HEY cells, with affinity constants ranging from 1 X 10(9) to 3 X 10(9) M-1. The number of binding sites per cell for each antibody was approximately 2 X 10(4). mAb 8C and M2D remained associated with the cell surface following binding to their respective antigens, while mAb 10B was rapidly internalized, with 50% of the bound mAb being lost from the cell surface during 4 h of incubation at 37 degrees C. These different binding characteristics of the mAb may influence their ability to target radioactivity and cytotoxic drugs to HEY cells.

Adenocarcinoma↗

Production of a monoclonal antibody specific for seminomas and dysgerminomas.

A monoclonal antibody (M2A, IgG2a) was produced against a cultured human ovarian epithelial adenocarcinoma cell line, HEY. Monoclonal antibody M2A reacted with a glycoprotein of molecular weight 40,000 on the surface of HEY cells. The affinity constant of the monoclonal antibody M2A for HEY cells was 10(9) M-1, and the number of binding sites on HEY cells was 2 X 10(4) per cell. The monoclonal antibody produced positive immunoperoxidase staining of fetal (but not adult) testis and of seminomas and dysgerminomas but did not stain various normal adult tissues or other gonadal or extragonadal tumors. Monoclonal antibody M2A may be useful for confirming a histological diagnosis of seminoma and dysgerminoma.

Antibodies, Monoclonal↗

Monoclonal antibodies to an epithelial ovarian adenocarcinoma: distinctive reactivity with xenografts of the original tumor and a cultured cell line.

Four monoclonal antibodies (mAb) (8C, 10B, M2A, and M2D) were produced against the human epithelial ovarian adenocarcinoma cell line, HEY. The affinity constants of binding of the mAb to cultured HEY cells were 8 X 10(8) M-1 (M2D) and 10(9) M-1 (8C and 10B). mAb 8C reacted with a major glycoprotein of Mr 90,000 on the surface of HEY cells. The four mAb differed from previously reported mAb to epithelial ovarian adenocarcinomas on the basis of their reactivity with cultured ovarian adenocarcinoma cell lines using a cell-binding radioimmunoassay, and their staining of cryostat sections of various human normal and tumor tissues using an immunoperoxidase reaction. All four mAb reacted with s.c. tumors derived by injecting cultured HEY cells into thymectomized CBA/CJ mice. However, only two of the four mAb (8C and 10B) also reacted with s.c. tumors of the original HEY xenograft from which the cultured cell line was derived. In addition, mAb 8C and 10B reacted by immunoperoxidase staining with 2 and 4 different cases, respectively, of 11 epithelial ovarian adenocarcinomas examined. Cultured HEY cells were adapted to grow i.p. in BALB/c-nu/nu mice and the i.p. tumors retained their reactivity with the monoclonal antibodies. These tumor-bearing mice offer a useful model system for studying the potential of mAb, especially 8C and 10B, for the diagnosis and treatment of patients with peritoneal extension of epithelial ovarian adenocarcinomas.

Adenocarcinoma↗

A new method with high sensitivity and specificity for localization of abnormal parathyroid glands.

A novel method for localization of abnormal parathyroid glands involving color-processing of nuclear scintigrams of the neck after injection of Thallium-201 and Technetium pertechnetate is presented with surgical correlation. Preoperative localization of single parathyroid adenomas was successful in 88% of previously unoperated patients and in 85.7% of those with adenomas not located at previous surgery. Eighty-three per cent of glands with secondary hyperplasia, 66% of glands with primary hyperplasia, and one carcinoma were localized. No abnormal studies were seen in non-hyperparathyroid hypercalcemia, and no false positive studies were seen. Localization appeared related to larger adenomas (300-5000 mg), although one of 60 mg was localized. Color-comparison dual-isotype scintigraphy was useful for localization of parathyroid adenomas and hyperplastic glands and exceeded the reported sensitivity of either ultrasonography or computerized tomography. It deserves wider evaluation in preoperative management of at least hyperparathyroidism of the primary or persistent types.

Adenoma↗

Contrast enhancement of thallium-201 myocardial scintigrams: improved sensitivity with diminished specificity in coronary disease detection.

Thallium-201 myocardial scintigraphy (TMS) has become an increasingly popular noninvasive technique with a high diagnostic specificity, but a somewhat lower sensitivity for coronary disease (CAD) detection. Many centers now routinely employ computer techniques to contrast enhance scintigrams, but the resulting changes in sensitivity and specificity have not been carefully evaluated. In the present study, three observers with different levels of experience blindly interpreted both unprocessed and enhanced exercise TMS from 40 patients with CAD and from 15 without significant obstructions. The sensitivity for CAD achieved by each observer was higher with the enhanced scintigrams (increase from an average of 80% to 93%), but there was concomitant loss of specificity (from 93% to 73%). Similarly, significant changes were present in the sensitivity and specificity with which ischemic regions were diagnosed. In addition, contrast enhancement facilitated interpretation of TMS studies, particularly in making comparisons between exercise scintigrams and subsequent rest or redistribution images. Contrast enhancement affected the interpretations of the inexperienced observer most significantly. We conclude that contrast enhancement improves TMS sensitivity but results in some loss of specificity. The variable effect of enhancement on observers with different levels of experience suggests that laboratories should critically evaluate their own results before routinely employing computer processing.

Computers↗

A new radioligand for the epidermal growth factor receptor: 111In labeled human epidermal growth factor derivatized with a bifunctional metal-chelating peptide.

More specific radiopharmaceuticals are currently being evaluated for the in vivo detection and therapy of breast cancer. The human epidermal growth factor (hEGF) represents a good radiopharmaceutical candidate in view of the reported overexpression of its receptor by breast cancer cells. To enhance the imaging potential of this peptide ligand, a synthetic strategy was developed to rapidly create small peptides containing a large number of metal-chelating groups that can be readily coupled to hEGF. A prototypic 15-amino acid branched peptide containing four EDTA-like chelator groups was assembled by solid phase peptide synthesis. The metal chelating peptide, abbreviated MCP-4-EDTA-SH, was selectively incorporated into hEGF(1-51) at its unique N-terminus amino group. The coupling of a single MCP-4-EDTA-SH into hEGF(1-51) was confirmed by SDS polyacrylamide gel electrophoresis, western blotting, and amino acid analysis. The protein conjugate was successfully labeled with 111In. Its specific binding to EGF receptors present on MDA-MB-468 breast cancer cells confirmed that such a construct retains the properties of the natural ligand.

Amino Acid Sequence↗

Sensitivity of multidrug resistant KB-C1 cells to an antibody-dextran-adriamycin conjugate.

Resistance to adriamycin is an important limitation to the use of the drug in cancer therapy. This resistance is often a manifestation of the multidrug resistance phenotype. Studies with multidrug resistant cell lines in vitro may be useful to design approaches for overcoming the drug resistance encountered clinically. We investigated the possibility of overcoming adriamycin resistance in vitro in a multidrug resistant subline (KB-C1) of human epidermal carcinoma (KB-3-1) cells using antibody-mediated drug targeting. Adriamycin was conjugated through a dextran bridge to a monoclonal antibody (mAb), 10B, which bound to KB-3-1 cells with a Ka of 4 x 10(8) M-1. The conjugate retained immunoreactivity with the target cells. Adriamycin (0.2 micrograms/ml) caused a 50% inhibition of DNA synthesis in KB-3-1 cells, but failed to achieve this degree of inhibition in KB-C1 cells at levels as high as 10 micrograms/ml. In contrast, the 10B-dextran-adriamycin conjugate produced 50% inhibition of DNA synthesis in KB-C1 cells at a concentration of 2.5 micrograms/ml. This was significantly more cytotoxic than adriamycin conjugated to control mAb or bovine serum albumin (BSA). Similarly, a 10B-recombinant ricin A (rRA) immunotoxin was more cytotoxic to KB-C1 cells than free rRA. These results indicate that adriamycin resistance in KB-C1 cells in vitro can be partially overcome by specifically targeting adriamycin to the cells using an 10B-dextran-adriamycin conjugate. This approach may be useful in overcoming adriamycin resistance encountered during the course of cancer therapy.

Antibodies, Monoclonal↗

Comparison of growth inhibition of a human ovarian adenocarcinoma cell line by free monoclonal antibodies and their corresponding antibody-recombinant ricin A chain immunotoxins.

Four mouse monoclonal antibodies (mAb) (8C, IgG2a; M2A, IgG2a; M2D, IgG2b; 10B, IgG1) directed against the human ovarian adenocarcinoma cell line HEY were compared for their ability in the free form and as immunotoxins made with recombinant ricin A chain (rRA) to inhibit the growth of HEY cells. For in vitro studies cultured HEY cells were assayed for protein synthesis and plated in agarose to form colonies, and for in vivo studies they were injected intraperitoneally (i.p.) into BALB/c nu/nu (nude) mice at a challenge dose (3 X 10(5) cells) which produced carcinomatosis with ascites, leading to death 30 days following injection. In the free form, mAB 8C was the most potent in inhibiting colony formation in the complement (C)-mediated and ADCC (antibody-dependent cell-mediated cytoxicity) assays in vitro. This mAb was also the only one capable of prolonging survival of mice, both in tumor cell neutralization, and tumor growth inhibition experiments. The four mAb-rRA immunotoxins were effective in inhibiting protein synthesis in vitro in the presence of 10(-7) M monensin. However, in vivo, only 8C-rRA and M2A-rRA were capable of prolonging survival of mice in tumor growth inhibition experiments. Our results suggest that mAb 8C might be useful in the free form and as an 8C-rRA immunotoxin for i.p. immunotherapy of ovarian cancer.

Adenocarcinoma↗

Damning for all.

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Crime↗

When the tables turn.

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Attitude of Health Personnel↗