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Bay K8644 increased unidirectional Ca2+ influx and produced tension development in rabbit aorta. Both responses could be evoked in the tissue maximally stimulated with norepinephrine. When the arterial rings were maximally activated by high K+ depolarization,Bay K8644 was without effect. The tension evoked by high K+ and Bay K8644 was more sensitive to the dihydropyridine Ca2+ antagonist PY108-068 than norepinephrine induced tension. These results indicate that Bay K8644 activates only potential operated Ca2+ channels which are opened by high K+ depolarization. View Publication

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We cultured sensory neurons from chick embryos in media containing the alkaloid taxol at concentrations from 7 X 10(-9) to 3.5 X 10(-6) M. When plated at taxol concentrations above 7 X 10(-8) M for 24 h,neurons have short broad extensions that do not elongate on the culture substratum. When actively growing neurites are exposed to these levels of taxol,neurite growth stops immediately and does not recommence. The broad processes of neurons cultured 24 h with taxol contain densely packed arrays of microtubules that loop back at the ends of the process. Neurofilaments are segregated from microtubules into bundles and tangled masses in these taxol-treated neurons. At the ends of neurites treated for 5 min with taxol,microtubules also turn and loop back abnormally toward the perikaryon. In the presence of 7 X 10(-9) M taxol neurites do grow,although they are broader and less branched than normally. The neurites of these cells appear to have normal structure except for a large number of microtubules. Taxol probably stimulates microtubule polymerization in these cultured neurons. At high levels of the drug,this action inhibits neurite initiation and outgrowth by removing free tubulin from the cytoplasm and destroying the normal control of microtubule assembly in growing neurites. The rapid inhibition suggests that microtubule assembly may occur at neurite tips. At lower concentrations,taxol may slightly enhance the mechanisms of microtubule assembly in neurons,and this alteration of normal processes changes the morphogenetic properties of the growing neurites. View Publication

Sinefungin,a naturally occurring antifungal antibiotic nucleoside containing an ornithine residue,linked by a C-C bond to C-5' of adenosine,cures mice infected with Trypanosoma brucei brucei,T. congolense,or T. vivax; the effect of the drug is more pronounced towards T. congolense. Anti-trypanosomal activity of sinefungin could be the result of the inhibition of transmethylation reactions or of polyamine biosynthesis--or both--in parasites. View Publication

A collaborative study of the second international Reference Preparation of Erythropoietin,Human,Urinary,for Bioassay was carried out in 10 laboratories. Combined potency estimates obtained by comparison with the International Reference Preparation,indicate that ampoules of the second Preparation contain 10.0 IU (weighted mean potency) or,taking the unweighted mean potency,9.8 IU,with fiducial limits (P=0.95) of 8.4-11.5 IU. The second Preparation could be used as a standard in estimating the potency of a preparation of sheep plasma erythropoietin (68/307) although,as with the International Reference Preparation,there was a tendency for the sheep plasma preparation to produce log-dose-log-response regression lines that were steeper than those produced by the second Preparation.In accelerated degradation studies of the second Preparation stored as the dry product in ampoules for up to 1 year,there was no consistent trend to indicate instability of the preparation.Following its establishment in 1971,the Second International Reference Preparation was allocated a potency of 10 IU/ampoule. View Publication

A cytotoxic common ALL antiserum (CALLA) specific for leukemic cells of most patients with non-T-cel- acute lymphoblastic leukemia (ALL) and of some patients with chronic myelogenous leukemia (CML) in blast crisis has been reproducibly prepared using cell lines for absorption. CALLA reacts with leukemic cells of 110 of 134 patients (82%) with non-T-cell ALL; 1 of 71 (1%) patients with acute myelogenous leukemia (AML); 2 of 7 patients (29%) with chronic myelogenous leukemia in blast crisis; 7 of 92 patients (8%) with other hematologic malignancies; and with the leukemic cell lines Laz 221 and NALM-1. It does not react with the normal hematopoietic cells,B- or T-cell lines,or cells from 26 patients with T-cell ALL that were tested. CALLA reactivity and periodic acid Schiff (PAS) staining correlate poorly,with CALLA reacting with cells from 86% (64 of 74) of patients with PAS-positive and 76% (29 of 38) of those with PAS-negative non-T-cell ALL. In these patients,CALLA reacts with cells from 89% of those under age 12 (78 of 88); 74% of those aged 12--20 (20 of 27); and 58% of those over 20 (11 of 19). Using only CALLA and antisera specific for Ia-like and T-cell antigens,we can now distinguish most cases of ALL from AML and other hematologic malignancies. View Publication

Monoclonal antibody HEA125 was used to study the tissue distribution of an epithelial cell surface glycoprotein of Mr 34,000 (Egp34). A large panel of normal and neoplastic tissues was examined for immunoreactivity with HEA125 by means of a sensitive immunoperoxidase technique. HEA125 labeled most epithelial cell types throughout the body but did not label any nonepithelial tissue. Major exceptions were epidermal keratinocytes,gastric parietal cells,hepatocytes,thymic cortical epithelial,and myoepithelial cells. Normal mesothelial cells were unreactive. In normal glandular epithelia and tubular adenocarcinomas exclusively the basolateral cell membranes were stained. HEA125 intensely reacted with all tested carcinoma specimens derived from colorectum,stomach,pancreas,liver,lung,mammary gland,ovary,thyroid,kidney,urinary bladder,and prostate including a number of anaplastic,diffusely infiltrating carcinomas. Metastatic lesions of these tumors were consistently positive. Generally,the staining of tumor cells was very homogeneous. The majority of squamous cell carcinomas were less strongly labeled than adenocarcinomas; keratinizing areas of the tumor masses were negative. Germ cell tumors and mesotheliomas of epithelioid type focally expressed the antigen. Egp34 was found to be absent from sarcomas,lymphomas,melanomas,and neurogenic tumors. Hence,HEA125 is a useful reagent for the distinction of carcinomas from nonepithelial neoplasms,even at very low degrees of histological differentiation. Furthermore,HEA125 allows the immunohistochemical detection of micrometastases originating from carcinomas. The antigen is detectable in formalin-fixed paraffin sections. View Publication

Plasmacytoma growth factor (PCT-GF),a putative macrophage-derived lymphokine essential for the in vitro viability and proliferation of early generation plasmacytomas,was purified from conditioned medium of the murine macrophage cell line P388D1. The purification of PCT-GF was accomplished by a batch concentration on trimethylsilyl-controlled pore glass beads,followed by: gel filtration chromatography; hydrophobic interaction HPLC; and reverse-phase HPLC. SDS-PAGE analysis of the purified PCT-GF revealed a single band of Mr 23,000. The amino terminal sequence of PCT-GF was established as NH2-Pro-Thr-Ser-Gln-Val-Arg-Arg-Gly-Asp-Phe-Thr-Glu-Asp-Thr-Thr-Pro-Asn- Arg-Pro-Val-Tyr-Thr. No significant homology was found between this sequence and proteins in the National Biomedical Research Foundation database,suggesting that PCT-GF is a new lymphokine unrelated to previously described growth and differentiation factors. View Publication

Complementary DNA clones encoding the human kidney epidermal growth factor (EGF) precursor have been isolated and sequenced. They predict the sequence of a 1,207 amino acid protein which contains EGF flanked by polypeptide segments of 970 and 184 residues at its NH2- and COOH-termini,respectively. The structural organization of the human EGF precursor is similar to that previously described for the mouse protein and there is 66% identity between the two sequences. Transfection of COS-7 cells with the human EGF precursor cDNA linked to the SV40 early promoter indicate that it can be synthesized as a membrane protein with its NH2-terminus external to the cell surface. The human EGF precursor gene is approximately 110 kilobase pairs and has 24 exons. Its exon-intron organization revealed that various domains of the EGF precursor are encoded by individual exons. Moreover,15 of the 24 exons encode protein segments that are homologous to sequences in other proteins. Exon duplication and shuffling appear to have played an important role in determining the present structure of this protein. View Publication

A cDNA clone encoding a novel hematopoietic growth factor activity produced by a gibbon T cell line has been identified using a mammalian cell expression cloning system. The sequence of this cDNA proved to have significant homology to the sequence encoding murine interleukin 3 (IL-3). The human gene,which was readily identified because of its high degree of homology to the gibbon sequence,also displayed significant homology with the murine IL-3 sequence. The recombinant gibbon IL-3 protein proved to have multipotent colony stimulating activity when tested with normal human bone marrow cells,proving that this primate hematopoietin is not only structurally but also functionally related to murine IL-3. View Publication

A simple and efficient procedure for the construction of bifunctional molecules is described and their use in a variety of applications documented. This procedure is based on our observation that mouse IgG1 monoclonal antibodies,when mixed with equimolar amounts of a high-affinity rat monoclonal antibody specific for mouse IgG1,yield uniform cyclic tetramolecular complexes each consisting of two mouse and two rat antibodies as shown by gel electrophoresis and electron microscopy. When solutions of two mouse antibodies (e.g. a and b) are mixed prior to the formation of complexes with the rat antibody,stable bispecific (a X b) complexes together with monospecific (a X a and b X b) complexes are obtained. Bispecific complexes prepared in this way were able to efficiently bind peroxidase to cell surface antigens,and to bind red blood cells to selected nucleated cell types present in heterogeneous populations. Tetrameric antibody complexes are more easily prepared than bispecific antibodies or bifunctional antibodies produced by transfection of myelomas with recombinant genes. They also have the advantage that the antigen-binding properties of the bivalent monoclonal antibodies are not compromised. Tetrameric antibody complexes thus represent a powerful new type of cross-linking reagent that may have a wide spectrum of applications in biology and medicine. View Publication

The work described in this paper demonstrates that the cellular binding of transforming growth factor beta,epidermal growth factor,platelet-derived growth factor,and fibroblast growth factor is reduced as cell density is increased. The reduction in transforming growth factor beta binding was observed in five different cell lines. Examination of several of the cell lines,under conditions where transforming growth factor beta binding is reduced,revealed that epidermal growth factor binding,platelet-derived growth factor binding,and fibroblast growth factor binding are also reduced. In the case of NRK-49F cells,the reduction in transforming growth factor beta binding results from a decrease in the number of high-affinity receptors and not from a change in receptor affinity. Similarly,it was determined that the reduction in epidermal growth factor binding is due to a selective reduction in the high-affinity receptors for epidermal growth factor. Overall,the data suggest that the effect of cell density on growth factor binding,which we refer to as density-induced down regulation of growth factor receptors,differs both from down regulation induced by a specific growth factor and from receptor transmodulation. View Publication