Canine lymphoma-associated antigens defined by murine monoclonal antibodies

Summary Lymphoma in dogs resembles human non-Hodgkin's lymphoma in pathological presentation, immunophenotype, and response to therapy, thus representing a good model for comparative studies with human disease. Monoclonal antibodies (MAbs) were derived from mice immunized with a dog lymphoma cell line. Three MAbs were selected for further application in immunophenotyping and immunotherapy. The binding specificities, antigen characterization, and isotypes for these MAbs are described.Supported by NCI grant CA-10815     

Monoclonal antibody-defined antigens of human prostate cancer cell line PC3

Summary Over 600 hybridomas were derived from the immunization of mice with live cells and aqueous extracts of the human prostatic carcinoma cell line PC3. A total of 26 hybridomas with restricted reactivities were selected, subcloned and antibodies tested on a variety of tumor and normal cells. Seven monoclonal antibodies showed reactivity for prostate cancer and other tumor cell lines, including breast carcinomas. Three of the antibodies obtained after immunization with live cells reacted with live cells only and three of the four antibodies obtained after immunization with cell extract reacted with cell extracts and spent culture media. The fourth antibody in the latter group was reactive only in the immunoperoxidase staining assay. Antibody PrS5 recognized a 90,000 molecular weight molecule from ¹²⁵I-surface-labeled cells in immunoprecipitation analysis. Antibodies PrE3 and PrD8 detected a nonacid glycolipid pentasaccharide from PC3 cells and meconium, and a glycoprotein of 115,000 molecular weight from ¹²⁵I-surface-labeled red blood cells. The similar patterns of reactivity in RIAs and antigen analysis suggest that antibodies PrE3 and PrD8 recognize the same molecule. The results emphasize the usefulness of immunohistochemistry in the testing of monoclonal antibodies and the impact of the form in which the antigen is presented on the resultant antibody specificity     

The nature of the trifluoperazine binding sites on calmodulin and troponin-C

We have employed 1H-nuclear magnetic resonance spectroscopy to study the interaction of the drug trifluoperazine with calmodulin and troponin-C. Distinct trifluoperazine-binding sites exist in the N- and C-terminal halves of both proteins. Each site consists of a group of hydrophobic side-chains brought into proximity by the Ca2+-dependent juxtaposition of two alpha-helical segments of the protein, each, in turn, belonging to a different Ca2+-binding site in the protein half. The trifluoperazine-induced inhibition of the biological activating ability of calmodulin appears to result from conformational restrictions conferred upon the protein by the bound drug.     

Monoclonal antibodies directed against the sugar sequence of lacto-N-fucopentaose III are obtained from mice immunized with human tumors

Four hybridomas obtained from mice immunized with human adenocarcinomas of colon or stomach produce antibodies that bind specifically in solid-phase radioimmunoassay to the ceramide pentasaccharide that contains the lacto-N-fucopentaose III sequence of sugars. Binding of the antibodies to the glycolipid is inhibited by lacto-N-fucopentaose III,

but not by structurally related oligosaccharides. The antibodies bind to glycolipids of erythrocytes, granulocytes, and certain normal and malignant tissues.     

Stabilization by a disulfide bond of the N-terminal domain of a mutant troponin C (TnC48/82)

The regulatory activity of troponin C is reversibly inhibited by a disulfide bridge between cysteine residues introduced by site-directed mutagenesis in positions 48 and 82 (TnC48/82) in the N-terminal domain of rabbit skeletal troponin C (sTnC; Grabarek, Z., Tan, R.-Y., Tao, T., and Gergely, J. (1990) Nature 345, 132-135). In the present work we have investigated the effects of the disulfide on structural properties of TnC48/82 monitored by CD spectroscopy and limited trypsinolysis. The CD spectra of the mutant protein in the oxidized form (oxTnC48/82) with and without Ca2+ are similar to the corresponding ones of the reduced and carboxamidomethylated form (CAMTnC48/82), indicating that the disulfide has essentially no effect on the overall secondary structure. The N-terminal domain of oxTnC48/82 is resistant to thermal unfolding, but that of CAMTnC48/82 is only slightly more stable than the corresponding domain of sTnC. In the presence of Ca2+ oxTnC48/82 is more resistant to trypsinolysis than sTnC whereas the rate of tryptic digestion of CAMTnC48/82 is the same as that of sTnC, indicating that peptide bonds adjacent to lysine residues at position 84 and 88, the sites of tryptic attack, are protected by the disulfide. The disulfide cross-linked N-terminal peptide of TnC48/82 does not bind TnI, unlike its reduced or carboxamidomethylated forms. Our data indicate that the disulfide between Cys48 and Cys82 stabilizes the structure of the N-terminal domain of TnC and blocks its ability to interact with TnI. The effects of the disulfide appear to be restricted to the N-terminal domain of TnC.     

Endotoxic lipid A interaction with human platelets. Structure-function analysis of lipid A homologs obtained from Salmonella minnesota Re595 lipopolysaccharide

We previously reported that human blood platelets are directly stimulated by endotoxic Lipid A via the protein kinase C pathway (Grabarek, J., Timmons, S., and Hawiger, J. (1988) J. Clin. Invest. 82, 964-971). To study the relationship between the molecular structure of Lipid A and its ability to activate human platelets, we used Lipid A homologs derived from Salmonella minnesota Re595 lipopolysaccharide. Preparations of Lipid A are heterogeneous in regard to the degree of substitution of fatty acids which result in multiple homologs. These were separated by thin-layer chromatography and characterized by fast atom bombardment spectroscopy and related techniques (Johnson R. S., Her, G.-R., Grabarek, J., Hawiger, J., and Reinhold, V. N. (1990) J. Biol. Chem. 265, 8108-8116). The homologs of monophosphoryl Lipid A (MLA) present in fractions TLC-8 (heptaacyl MLA ion, m/z 1953), TLC-7 (three hexaacyl species with predominant MLA ion m/z 1715), and TLC-6 (four pentaacyl homologs with predominant MLA ion, m/z 1505) induced secretion of [14C]serotonin and aggregation of platelets. Lipid A homologs in fractions TLC-5 (three tetraacyl MLA ions, m/z 1323, 1307, and 1279), TLC-4 (one major triacyl MLA ion, m/z 1097), TLC-3 (tetraacyl MLA ion, m/z 1278), TLC-2 (a diphosphoryl hexaacyl Lipid A ion, m/z 1795, and several ions of low abundance), and TLC-1 (two ions, m/z 1097 and 666) were not active in regard to human platelet aggregation and [14C]serotonin secretion. The most active homolog was heptaacyl MLA ion, m/z 1953, present in TLC-8, while homologs present in TLC-7 and TLC-6 were 5 and 10 times less active, respectively. Rapid phosphorylation of a human platelet protein of Mr 40,000-47,000 (P47), a substrate for protein kinase C activation, preceded secretion of serotonin when platelets were triggered by the most active heptaacyl MLA ion, m/z 1953. These events were time-dependent, with half-maximal response of phosphorylation of P47 at 30 s and [14C]serotonin secretion at 45 s. A marked difference in the degree of phosphorylation of P47 was observed with heptaacyl MLA homolog present in TLC-8 inducing complete phosphorylation (97%), whereas less acylated Lipid A homologs present in TLC-1 caused marginal phosphorylation (20%). These results indicate that the degree of acylation of monophosphoryl Lipid A determines its functional properties toward human platelets in regard to secretion of [14C]serotonin, aggregation, and activation of protein kinase C.(ABSTRACT TRUNCATED AT 400 WORDS)     

Characterization of zero-length cross-links between rabbit skeletal muscle troponin C and troponin I: evidence for direct interaction between the inhibitory region of troponin I and the NH2-terminal, regulatory domain of troponin C

Interactions between troponin C (TnC) and troponin I (TnI) play an important role in the Ca2(+)-dependent regulation of vertebrate striated muscle contraction. Previous attempts to elucidate the molecular details of TnC-TnI interactions, mainly involving chemically modified proteins or fragments thereof, have led to the widely accepted idea that the "inhibitory region" (residues 96-116) of TnI binds to an alpha-helical segment of TnC comprising residues 89-100 in the nonregulatory, COOH-terminal domain. In an attempt to identify other possible physiologically important interactions between these proteins, 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) was used to produce zero-length cross-links in the complex of rabbit skeletal muscle TnC and TnI. TnC was activated with EDC and N-hydroxysuccinimide (NHS) and then mixed with an equimolar amount of TnI [Grabarek, Z., & Gergely, J. (1988) Biophys. J. 53, 392a]. The resulting cross-linked TnCXI was cleaved with cyanogen bromide, trypsin, and Staphylococcus aureus V8 protease (SAP). Cross-linked peptides were purified by reverse-phase HPLC and characterized by sequence analysis. The results indicated that residues from the regulatory Ca2(+)-binding site II in the NH2-terminal domain of TnC (residues 46-78) formed cross-links with TnI segments spanning residues 92-167. The most highly cross-linked residues in TnI were Lys-105 and Lys-107, located in the inhibitory region. These results yield the first evidence for an interaction between the N-terminal domain of TnC and the inhibitory region of TnI.     

Epstein-Barr virus in nontumorigenic and tumorigenic nasopharyngeal carcinoma (NPC) somatic cell hybrids

Somatic cell hybrids between mouse fibroblasts and human cells derived from nasopharyngeal carcinoma (NPC) biopsies or NPC tumors propagated in nude mice were examined for the expression of the Epstein-Barr nuclear antigen (EBNA), retention of Epstein-Barr viral (EBV) DNA, and tumorigenicity in nude mice. In all hybrids the expression of EBNA correlated with the detection of EBV-DNA. After more than 2 years in culture, the hybrids examined retained similar amounts of EBV-DNA when compared to previously published data. Retention of EBV-DNA did not correlate with the presence of any particular human chromosome. Use of either rodent cell lines, clone 1D or IT-22, did not affect the retention nor loss of EBV-DNA. For tumorigenicity studies, NPC cells were fused with IT-22 cells and injected into nude mice. Tumor formation did not depend on the presence or absence of EBNA and detectable EBV-DNA sequences; tumorigenicity in these studies could not be correlated with the presence of any particular human chromosome or the origin of the NPC biopsy.     

Early‐Life Exposure to Pulsed LTE Radiofrequency Fields Causes Persistent Changes in Activity and Behavior in C57BL/6 J Mice

Despite much research, gaps remain in knowledge about the potential health effects of exposure to radiofrequency (RF) fields. This study investigated the effects of early‐life exposure to pulsed long term evolution (LTE) 1,846 MHz downlink signals on innate mouse behavior. Animals were exposed for 30 min/day, 5 days/week at a whole‐body average specific energy absorption rate (SAR) of 0.5 or 1 W/kg from late pregnancy (gestation day 13.5) to weaning (postnatal day 21). A behavioral tracking system measured locomotor, drinking, and feeding behavior in the home cage from 12 to 28 weeks of age. The exposure caused significant effects on both appetitive behaviors and activity of offspring that depended on the SAR. Compared with sham‐exposed controls, exposure at 0.5 W/kg significantly decreased drinking frequency (P ≤ 0.000) and significantly decreased distance moved (P ≤ 0.001). In contrast, exposure at 1 W/kg significantly increased drinking frequency (P ≤ 0.001) and significantly increased moving duration (P ≤ 0.005). In the absence of other plausible explanations, it is concluded that repeated exposure to low‐level RF fields in early life may have a persistent and long‐term effect on adult behavior. Bioelectromagnetics. 2019;40:498–511. © 2019 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.