OT-CLL: a human T cell chronic lymphocytic leukemia that produces IL 2 in high titer

This report identifies and describes a human T cell chronic lymphocytic leukemia, OT-CLL, which can be triggered by selected mitogens (either PHA or Con A) to produce IL 2 in high titer. Optimal IL 2 production requires culturing OT-CLL cells at 2 to 5 X 10(6)/ml for 24 hr in the presence of 1 to 2% PHA-M. Under these conditions, the titer of IL 2 generated is greater than 20-fold that obtained from conventional sources, e.g., from mitogen-activated tonsillar lymphocytes. Two lines of experimental evidence suggest that the tumor cell product(s) is IL 2. First, in functional assays, suprenatants derived from cultures of PHA-activated OT-CLL cells trigger the proliferation and long-term growth of IL 2-dependent human TCL cells. Second, a partial biochemical purification of the active moiety(ies) derived from OT-CLL demonstrates marked similarity to conventional human IL 2. Thus, the biologically active material(s) precipitates in 50 to 70% saturated (NH4)2 SO4 solutions; elutes from DEAE-Sepharose in the presence of 0.04-0.08 M NaCl; and has an apparent m.w. of approximately 14,000, as determined by Sephadex G-100 gel filtration. In addition, analysis of OT-CLL cells by indirect immunofluorescence, utilizing a panel of monoclonal antibodies, confirms not only that these tumor cells are of T cell lineage but that they display surface antigens that define the normal human peripheral T cell subset subserving helper or inducer function: OKT3+, OKT4+ , OKT8-.     

Cyanide degradation by immobilised fungi

Summary Cyanide hydratase, which converts cyanide to formamide, was induced in mycelia of Stemphylium loti by growth in the presence of low concentrations of cyanide. Mycelia were immobilised by several methods. The most useful system was found to be treatment with flocculating agents. This technique is applicable to a wide range of easily isolated fungi that contain cyanide hydratase.     

Affinity chromatography of aminoacyl-transfer ribonucleic acid synthetases. Cognate transfer ribonucleic acid as a ligand.

The use of tRNA affinity columns for the purification of aminoacyl-tRNA synthetases was investigated. A purification method for valyl-tRNA synthetase from Bacillus stearothermophilus is described that uses two affinity columns, one containing the pure cognate tRNA, and the other containing all tRNA species except the cognate tRNA. A method for the rapid preparation of the two columns was developed, which does not require prior isolation of cognate tRNA but makes use of the ability of the target synthetase to select its cognate tRNA. The usefulness of tRNA columns is compared with that of affinity columns derived from the aminoalkyladenylate reported in the preceding paper [Clarke & Knowles (1977) Biochem J. 167, 405-417].     

Murine embryonic antigen (SSEA-1) is expressed on human cells and structurally related human blood group antigen I is expressed on mouse embryos

The stage-specific embryonic antigen (SSEA-1), present on embryonal carcinoma cells and on murine preimplantation embryos, is defined by a monoclonal antibody. The antigenic determinant of SSEA-1 is a carbohydrate structurally related to the human blood group antigen I. Since it has been suggested that the I antigen might represent a precursor or SSEA-1, we used antibodies to SSEA-1 and to I to analyze their expression on mouse preimplantation embryos. Both are expressed on mouse embryos; moreover, I is expressed on earlier embryos than SSEA-1. The I antigen is defined by its expression on human erythrocytes; accordingly, we examined expression of I and SSEA-1 on human peripheral blood elements. We find SSEA-1 to be expressed exclusively on human granulocytes while I is found only on erythrocytes. These results suggest that these closely related antigens can be independently expressed. Analysis of the expression of I and SSEA-1 was then extended to a series of mouse and human cell lines; some express both, some express only one, and some express neither of these antigens. The activation of specific glycosyltransferases and/or glycosidases during development and differentiation appears to be the biochemical mechanism regulating expression of these antigens.     

Retinol-induced modification of the extracellular matrix of endothelial cells: Its role in growth control

Summary The growth of the endothelial cell (EC) is tightly regulated throughout the body. Many factors have been implicated in modulating EC growth including diffusible compounds, cell-to-cell interactions, and the extracellular matrix (ECM). Retinol, or vitamin A alcohol, has recently been shown to inhibit the growth of bovine capillary ECs, in vitro. Retinoids are known to modify ECM in other cell systems, and pure ECM components have been shown to effect EC growth rates. We, therefore, examined the role of the matrix in the retinol-induced inhibition of ECs. Cell-free matrices from control and vitamin A-treated ECs were prepared by removing cells with EGTA treatment after 7 d of culture. Matrix proteins were analyzed by solubilizing the matrices in 5M quanidine-HCl and performing Western blot analysis using specific antibodies to matrix proteins. In isolating the ECM, we observed that retinol-treated cultures of ECs were resistant to EGTA removal; retinol-treated ECs required twice the exposure time to EGTA to detach from their matrix than did controls cells. Western blot analysis of matrix proteins derived from control and retinol-treated EC cultures demonstrated a 1.6-fold increase in lamininβ chains and a 2.5-fold increase in fibronectin in the ECM of retinol-treated EC compared to control cell matrix. Functional properties of these matrices were assessed by plating control and Day 6 retinol-treated ECs onto the matrices and measuring attachment and growth by determining cell numbers at 24, 72, and 144 h. These studies revealed that control cells attached in greatest numbers to a control matrix whereas retinol-treated ECs preferentially attached to a matrix derived from retinol-treated cells. Furthermore, control ECs which grew rapidly on a control matrix were growth inhibited on a retinol-derived matrix. These data indicate that vitamin A treatment of ECs effects both their phenotype and influences the composition and the functional properties of their underlying ECM. These studies also demonstrate that alterations of the matrix are at least in part responsible for the growth inhibition of EC by retinol.     

Cloning, overexpression and mechanistic studies of carboxyphosphonoenolpyruvate mutase from Streptomyces hygroscopicus.

The enzyme carboxyphosphonoenolpyruvate mutase catalyses the formation of one of the two C-P bonds in bialaphos, a potent herbicide isolated from Streptomyces hygroscopicus. The gene encoding the enzyme has been cloned from a subgenomic library from S. hygroscopicus by colony hybridisation using an exact nucleotide probe. An open reading frame has been identified that encodes a protein of molecular mass 32700 Da, in good agreement with the subunit molecular mass of the carboxyphosphonoenolpyruvate mutase recently isolated from this source [Hidaka, T., Imai, S., Hara, O., Anzai, H., Murakami, T., Nagaoka, K. & Seto, H. (1990) J. Bacteriol. 172, 3066-3072]. The gene shares significant sequence similarity with that of phosphoenolpyruvate mutase, an enzyme that catalyses the related interconversion of phosphoenolpyruvate and phosphonopyruvate. When the carboxyphosphonoenolpyruvate-mutase gene was subcloned into the vector pET11a, the mutase was expressed as about 20% of the total soluble cellular protein in Escherichia coli. The mutase has been purified to homogeneity in three steps in 40% yield. With malate dehydrogenase/NADH, (hydroxyphosphinyl)pyruvate gives (hydroxyphosphinyl)lactate (kcat 164 s-1 and Km 680 microM) and this spectrophotometric assay for the product of the mutase reaction has been employed in the mechanistic studies. The kinetics for the mutase reaction have been evaluated for the substrate, carboxyphosphonoenolpyruvate, and for the putative reaction intermediate carboxyphosphinopyruvate, both of which have been prepared by chemical synthesis. Carboxyphosphonoenolpyruvate is converted to (hydroxyphosphinyl)pyruvate with a kcat of 0.020 s-1 and a Km of 270 microM, and carboxyphosphinopyruvate is converted to (hydroxyphosphinyl)pyruvate with a kcat of 7.6 x 10(-4) s-1 and a Km of 2.2 microM. Although the exogenously added intermediate is not kinetically competent, these results suggest that the mechanism for the mutase reaction involves an initial rearrangement to the intermediate carboxyphosphinopyruvate, followed by decarboxylation to yield the product (hydroxyphosphinyl)pyruvate.     

Simultaneous localization and quantification of relative G and F actin content: optimization of fluorescence labeling methods.

Previous studies of fluorescence probes for labeling the monomeric actin pool have demonstrated lack of specificity. We have used quantitative analytical methods to assess the sensitivity and specificity of rhodamine DNAse I as a probe for monomeric (G) actin. The G-actin pool of attached or suspended fibroblasts was stabilized by ice-cold glycerol and MgCl2. Formaldehyde fixation was used to clamp the filamentous (F) actin pool. G- and F-actins were stained by rhodamine DNAse I and FITC-phalloidin, respectively. Confocal microscopy indicated that the G- and F-actins were spatially separate in substrate-attached cells. Flow cytometry and fluorescence spectrophotometry demonstrated low co-labeling of the separate actin pools, although measureable background binding of rhodamine DNAse I was detectable. Estimates of the extent of actin polymerization after trypsinization demonstrated reciprocal changes of monomeric and filamentous actins, consistent with the formation of a perinuclear array of F-actin. The labeling and quantitation methods were also sufficiently sensitive to detect cell type-dependent variations in actin content. Dual labeling of cells with rhodamine DNAse I and FITC-phalloidin may provide a simple and direct method to image and quantify actin rearrangement in individual cells.     

Inwardly rectifying potassium current in rabbit osteoclasts: A whole-cell and single-channel study

Summary Ionic conductances of rabbit osteoclasts were investigated using both whole-cell and cell-attached configurations of the patch-clamp recording technique. The predominant conductance found in these cells was an inwardly rectifying K⁺ conductance. Whole-cell currents showed an N-shaped current-voltage (I–13;V) relation with inward current activated at potentials negative to E_K. When external K⁺ was varied, I-V curves shifted 53 mV/10-fold change in [K⁺]_out, as predicted for a K⁺-selective channel. Inward current was blocked by Ba²⁺ and showed a time-dependent decline at negative potentials, which was reduced in Na⁺-free external solution. Inward single-channel currents were recorded in the cell-attached configuration. Single-channel currents were identified as inward-rectifier K⁺ channels based on the following observations: (i) Unitary I-V relations rectified, with only inward current resolved. (ii) Unitary conductance () was 31 pS when recorded in the cell-attached configuration with 140 mm K⁺ in the pipette and was found to be dependent on [K⁺]. (iii) Addition of Ba²⁺ to the pipette solution abolished single-channel events. We conclude that rabbit osteoclasts possess inwardly rectifying K⁺ channels which give rise to the inward current recorded at negative potentials in the whole-cell configuration. This inwardly rectifying K⁺ current may be responsible for setting the resting membrane potential and for dissipating electrical potential differences which arise from electrogenic transport of protons across the osteoclast ruffled border.This work was supported by The Arthritis Society and the Medical Research Council of Canada. M.E.M.K. was supported by a fellowship, S.J.D. a development Grant and S.M.S. a scholarship from the Medical Research Council. We thank Dr. Zu Gang Zheng for help with scanning microscopy.