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Biomedical subjects

G Jung

Publications and source records attributed to G Jung.

At least 451 records · Page 25Linked to original sources
PubMed1987

Induction of cytotoxicity in human peripheral blood mononuclear cells by monoclonal antibody OKT3.

It has been previously reported from this laboratory that incubation of PBMC with OKT3 generates potent cytotoxic lymphocytes that can be targeted by using antibody heteroconjugates consisting of anti-target cell antibody and OKT3. In the present study these conjugates were used to explore the kinetics of induction of cytotoxicity in PBMC and the subpopulations of lymphocytes involved. It was found that in addition to conjugate-dependent cytotoxicity, a considerable amount of conjugate-independent cytotoxicity was generated during OKT3 stimulation. Although the conjugate-dependent activity resided in the CD8+ population, the conjugate-independent cytotoxicity was found to be a function of CD4-/CD8- natural killer-like cells. Being largely CD3-, those cells were most likely activated by lymphokines produced by OKT3-stimulated CD3+ cells. They were capable of killing not only tumor cells but also autologous lymphocytes. The CD4+ cells of some donors were found to exhibit low but clearly demonstrable cytotoxicity. Induction of cytotoxicity was characterized as an early event in T cell activation, correlating with the kinetics of RNA synthesis. Cytotoxicity, interleukin 2 receptor expression, and DNA synthesis declined after 3 days of activation with OKT3, indicating the existence of as yet undefined regulatory mechanisms.

Antibodies, Monoclonal↗
PubMed1987

Lipopeptides of the N-terminus of Escherichia coli lipoprotein: synthesis, mitogenicity and properties in monolayer experiments.

The N-terminal part of the lipoprotein from the outer membrane of Escherichia coli, tripalmitoyl-S-glyceryl-L-Cys-Ser and analogs with longer sequences, are polyclonal activators for B-lymphocytes. Triple-chain lipopeptides also constitute efficient low-molecular-weight carrier/adjuvant systems, which can be linked to antigens to yield immunogens for antibody production without further additives. This is the first report of monolayer experiments with chemically well defined, synthetic lipopeptide mitogens with the composition of the N-terminus of an important bacterial membrane protein. Various derivatives of the lipoprotein N-terminus were synthesized. These lipopeptides differed in the length of the peptide moiety, the number of fatty acid residues, and protective groups. In order to obtain the surface areas for the lipopeptides in isotherms and hysteresis isotherms, monolayer experiments with a computer-controlled film balance were performed. To get some information about the interaction of these compounds with typical membrane lipids mixed monolayers were formed from triple-chain lipopeptides with dipalmitoylphosphatidylcholine and cholesterol. A comparison of the mitogenic response of the compounds was made in an in vitro system with B-lymphocytes from Balb/c mice.

Animals↗
PubMed1987

Depth-dependent fluorescent quenching of a tryptophan residue located at defined positions on a rigid 21-peptide helix in liposomes.

Five lipophilic 21-peptide analogs of the potential-dependent pore-former, alamethicin, were synthesized bearing tryptophan residues at the position 1, 6, 11, 16 and 21 on a long, conformationally rigid, alpha-helix. The alpha-helical conformation was induced and stabilized using the sequential oligomers (Ala-Aib-Ala-Aib-Ala)n as analyzed by CD and NMR. The partitioning of the N-t-butoxycarbonyl 21-peptide methyl esters and the N-terminally deprotected alpha-helices was followed by fluorescence enhancement in phospholipid bilayer vesicles. Quenching experiments were performed by titrating with n-doxyl stearic acids bearing the nitroxide label at positions 5, 7, 10, 12 and 16. This well-defined system revealed that the N- and C-terminal tryptophan residues become situated in the hydrophilic region. Tryptophan at position 11 was found in the lipophilic core, whereas the tryptophan at positions 6 and 16 were localized at intermediate depths of the lipid membrane. Therefore, the helices span the lipid bilayer with their long axis normal to the membrane surface.

Alamethicin↗
PubMed1987

Induction of cytotoxicity in resting human T lymphocytes bound to tumor cells by antibody heteroconjugates.

An in vitro model for peripheral human T-cell activation and resultant tumor cell killing is described. Cytotoxic T lymphocytes may be generated from resting lymphocytes by incubation of human peripheral blood mononuclear cells for 3 days with the anti-CD3 monoclonal antibody OKT3. Cytotoxicity in peripheral blood mononuclear cells can also be induced by adding an anti-target-OKT3 antibody conjugate and 10% (vol/vol) fetal calf serum to the culture medium. Conjugate activation of T cells was almost completely blocked, however, when 20% (vol/vol) human serum was added to the medium. Conjugate-mediated peripheral blood mononuclear cells activation was restored to some extent by the addition of melanoma target cells to the culture and was markedly enhanced by a second conjugate containing anti-target cell and anti-CD28 antibody. Monoclonal antibody 9.3 (anti-CD28) provides a progression signal in T-lymphocyte activation when used in combination with anti-CD3. Thus, presentation by the tumor target cells of anti-CD3 and anti-CD28 to resting human lymphocytes causes T-cell activation, which is independent of monocytes, proceeds in the presence of human serum, and results in tumor cell killing.

Antibodies, Monoclonal↗
PubMed1987

The heavy chain of Acanthamoeba myosin IB is a fusion of myosin-like and non-myosin-like sequences.

Acanthamoeba castellanii myosins IA and IB demonstrate the catalytic properties of a myosin and can support analogues of contractile and motile activity in vitro, but their single, low molecular weight heavy chains, roughly globular shapes, and inabilities to self-assemble into filaments make them structurally atypical myosins. We now present the complete amino acid sequence of the 128-kDa myosin IB heavy chain, which we deduced from the nucleotide sequence of the gene and which reveals that the polypeptide is a fusion of myosin-like and non-myosin-like sequences. Specifically, the amino-terminal approximately 76 kDa of amino acid sequence is highly similar to the globular head sequences of conventional myosins. By contrast, the remaining approximately 51 kDa of sequence shows no similarity to any portion of conventional myosin sequences, contains regions that are rich in glycine, proline, and alanine residues, and lacks the distinctive sequence characteristics of an alpha-helical, coiled-coil structure. We conclude, therefore, that the protein is composed of a myosin globular head fused not to the typical coiled-coil rod-like myosin tail structure but rather to an unusual carboxyl-terminal domain. These results support the conclusion that filamentous myosin is not required for force generation and provide a further perspective on the structural requirements for myosin function. Finally, we find a striking conservation of intron/exon structure between this gene and a vertebrate muscle myosin gene. We discuss this observation in relation to the evolutionary origin of the myosin IB gene and the antiquity of myosin gene intron/exon structure.

Acanthamoeba↗
PubMed1987

The cytolytic protein of human lymphocytes related to the ninth component (C9) of human complement: isolation from anti-CD3-activated peripheral blood mononuclear cells.

A 70-kDa channel-forming protein has recently been isolated from human large granular lymphocytes maintained in interleukin-2-dependent culture. The protein was shown to be immunochemically related to the ninth component of complement (C9) and was therefore designated C9-related protein (C9RP). Using the procedure that was developed for the isolation of C9RP from large granular lymphocytes--i.e., affinity chromatography employing anti-human C9 linked to Sepharose, a cytolytic protein has now been isolated from OKT3-activated human peripheral blood mononuclear cells. Nineteen to 40 micrograms of active protein was obtained from 1 X 10(9) human peripheral blood mononuclear cells after the cells were cultured for 3 days with OKT3 (monoclonal antibody to cell surface antigen T3). During this period, a marked increment occurred in the amount of the cytotoxic protein contained per cell, indicating that OKT3 induced de novo synthesis of the protein. By NaDodSO4/PAGE the molecular mass was determined to be 70 kDa. By ELISA the isolated protein and C9RP of large granular lymphocytes reacted to the same extent with anti-C9RP. Using K-562 or M21 human melanoma cells as targets, the cytotoxic activity of the isolated protein, in the presence of 5 mM Ca2+, was comparable to that of C9RP. The same cytolytic protein was isolated from peripheral blood mononuclear cells that were depleted of CD16+ cells prior to OKT3 activation and that consisted primarily of CD4+ and CD8+ T lymphocytes. These results suggest that the cytolytic protein of OKT3-activated cytotoxic T lymphocytes is identical with C9RP of interleukin-2-stimulated large granular lymphocytes.

Antibodies, Monoclonal↗
PubMed1987

Induction of synthesis of the cytolytic C9 (ninth component of complement)-related protein in human peripheral mononuclear cells by monoclonal antibody OKT3 or interleukin 2: correlation with cytotoxicity and lymphocyte phenotype.

Synthesis of the cytolytic C9-related protein (C9RP) was induced by activation of resting human peripheral T lymphocytes with the anti-CD3 antibody OKT3 or interleukin 2. Comparison of cellular cytotoxicity and C9RP content at various times during activation yielded a coefficient of correlation r = 0.92. During OKT3 stimulation of peripheral mononuclear cells, maximal C9RP content and cytotoxicity were observed by day 2 or 3, with subsequent decline to baseline values by day 5, whereas during interleukin 2 stimulation, both parameters reached the maximal level at days 3-5. After fluorescence-activated cell sorting, C9RP and cytotoxicity were quantitated in CD4+, CD8+, and Leu-19+ subsets. In OKT3-activated CD8+ cells, C9RP increased to approximately 3 X 10(6) molecules per cell, with a corresponding increase in lysis of human melanoma cells mediated by anti-CD3-anti-melanoma monoclonal antibody conjugates. Interleukin 2-stimulated CD8+ cells showed similar increases, but cytotoxicity was conjugate-independent. Activated CD4+ cells showed minimal increase in C9RP content. Leu-19+ cells, which exhibit natural killer cell activity, had a high C9RP content (approximately 2.5 X 10(6) molecules per cell) before stimulation.

Antibodies, Monoclonal↗
PubMed1987

Pancreatic polypeptide inhibits pancreatic enzyme secretion via a cholinergic pathway.

In rat pancreatic slices, rat pancreatic polypeptide (PP) or C-terminal hexapeptide of PP [PP-(31-36)] inhibited potassium-stimulated amylase release in a dose-dependent manner. The inhibition was unaffected by addition of hexamethonium but blocked by atropine. In contrast, PP(31-36) did not have any effect on acetylcholine- or cholecystokinin octapeptide-stimulated amylase release. In addition, when pancreatic slices were incubated with [3H] choline, PP(31-36) inhibited the potassium-evoked release of synthesized [3H] acetylcholine in a dose-dependent manner. The inhibitory action of PP was unaffected by adrenergic, dopaminergic, or opioid receptor antagonists. Thus PP inhibits pancreatic enzyme secretion via presynaptic modulation of acetylcholine release. This newly identified pathway provides a novel mechanism for hormonal inhibition of pancreatic enzyme secretion via modulation of the classic neurotransmitter function.

Acetylcholine↗
PubMed1987

Molecular mechanisms of cytotoxicity: comparison of complement and killer lymphocytes.

The membrane attack complex of complement is an amphiphilic fusion product of 5 glycoproteins, C5, C6, C7, C8 and C9. The membrane attack complex forms transmembrane channels that vary in size depending on the number of C9 molecules incorporated into the complex. The C5b-8 complex forms small channels and at high multiplicity can kill nucleated cells. At least 12 C9 molecules are required to form tubular poly C9 which evokes the ultrastructural image of the classical membrane lesion produced by complement. The membranes of erythrocytes and other blood cells contain a 70,000 dalton protein that can inhibit channel formation by the membrane attack complex. This protein is species specific and has been called homologous restriction factor. A cytotoxic protein immunochemically related to C9 was isolated from cytotoxic human large granular lymphocytes and from OKT3 activated human peripheral blood mononuclear cells. In the presence of Ca++, isolated C9 related protein (C9RP) formed circular structures that resembled poly C9. C9RP efficiently killed K562 cells, human melanoma cells, Raji cells and human large granular lymphocytes. The results suggest that the channel forming protein of cytotoxic lymphocytes and C9 of complement have a common evolutionary ancestry.

Complement C9↗
PubMed1986

A synthetic analogue of Escherichia coli lipoprotein, tripalmitoyl pentapeptide, constitutes a potent immune adjuvant.

Lipoprotein from the outer membrane of Escherichia coli and other Enterobacteriaceae constitutes a potent B lymphocyte mitogen and polyclonal activator in various species. Tripalmitoyl pentapeptide (S-(2,3-bis-(palmitoyloxy)-(2RS)-propyl)-N-palmitoyl-(R)-cysteinyl -(S)-seryl-(S)-seryl-(S)-asparaginyl-(S)-alanine) is a synthetic analogue of the N-terminal part of lipoprotein and has, in all assays tested, a biologic activity similar to native lipoprotein. It also exhibits a strong adjuvant activity in vitro: In the presence of 3.3 to 33.3 micrograms/ml of tripalmitoyl pentapeptide, the stimulation of the primary antibody response toward underivatized sheep red blood cells (SRBC) and toward trinitrophenylated (TNP-) SRBC was markedly enhanced, as measured by a direct hemolytic plaque assay. At optimal mitogen- and antigen-doses, plaque formation was increased up to 100-fold, and at suboptimal doses (0.03 to 0.3 microgram/ml) a 10- to 60-fold increase of plaque numbers was achieved. In the presence of tripalmitoyl pentapeptide, the antigen-specific IgM response was increased about sevenfold and the IgG response was augmented about 10-fold, as measured by ELISA. Similarly, in the secondary in vitro response to TNP-SRBC, a 7 to 10-fold enhancement of the antibody titer was obtained in the presence of the adjuvant. The application of tripalmitoyl pentapeptide and antigen had to occur concurrently in order to achieve a strong adjuvant effect. Addition of tripalmitoyl pentapeptide to the cell cultures 1 day after or 1 day before antigen application had no significant positive effect, and in several instances a decrease in antibody production was found. Thus, tripalmitoyl pentapeptide, a well-characterized synthetic product available in major amounts, constitutes a potent immune adjuvant for potential animal and clinical use.

Adjuvants, Immunologic↗
PubMed1986

Epidermin: sequencing of a heterodetic tetracyclic 21-peptide amide antibiotic.

Epidermin is a large peptide antibiotic, which is synthesized in the ribosome via a precursor protein, followed by enzymatic modifications. It was isolated from the culture filtrate of Staphylococcus epidermidis Tü 3298 by adsorption on Amberlite XAD-8. The basic heneicosapeptide amide was chromatographed on Sephadex LH-20 and purified to homogeneity via multiplicative counter-current distributions in one acidic and one neutral system. Tryptic digestion gave the soluble N-terminal fragment epidermin-(1-13)-peptide (P1) and the insoluble C-terminal fragment 2-oxobutyryl-epidermin-(15-21)-peptide amide (P2), each possessing two sulfide ring systems. The heterodetic rings consisted of meso-lanthionine and (2S,3S, 6R)-3-methyllanthionine (P1), meso-lanthionine and C-terminally the new amino acid S-(2-aminovinyl)-D-cysteine (P2). The complex sequence was elucidated via a combination of desulfurization with Raney nickel, enzymatic and acidolytic degradations, gas-phase sequencing, fast-atom bombardment and field-desorption mass spectrometry and NMR spectroscopy.

Amino Acid Sequence↗
PubMed1986

[Blood fibronectin changes in various neoplasms].

In 85 patients presenting with various cancers, changes in the frequencies of plasma fibronectin and of the carcino-embryonic antigen (CEA) were compared and the results were correlated with the degree of extension. Forty-six percent of patients with mammary adenocarcinoma had plasma fibronectin values higher than the age-related limit range, but only 18% had an increase in CEA. In patients with secondary metastases, the highest values were significantly different from those found in controls. In these cases, fibronectin was present in abnormal concentrations in more than 80% of the patients, and CEA in 50%. Positive fibronectin values were less frequent in other cancers, except those of the genital tract. Neither fibronectin nor CEA are organ-specific, yet these two tumoral markers differ in the frequency with which they appear, notably in patients with mammary carcinoma.

Adult↗
PubMed1986

Voltage-dependent channel formation by rods of helical polypeptides.

The voltage-dependence of channel formation by alamethicin and it natural analogues can be described by a dipole flip-flop gating model, based on electric field-induced transbilayer orientational movements of single molecules. These field-induced changes in orientation result from the large permanent dipole moment of alamethicin, which adopts alpha-helical conformation in hydrophobic medium. It was, therefore, supposed that the only structural requirement for voltage-dependent formation of alamethicin-type channels might be a rigid lipophilic helical segment of minimum length. In order to test this hypothesis we synthesized a family of lipophilic polypeptides--Boc-(Ala-Aib-Ala-Aib-Ala)n-OMe, n = 1-4--which adopt alpha-helical conformation for n = 2-4 and studied their interaction with planar lipid bilayers. Surprisingly, despite their large difference in chain length, all four polypeptides showed quantitatively similar behavior. At low field strength of the membrane electric field these polypeptides induce a significant, almost voltage-independent increase of the bilayer conductivity. At high field strength, however, a strongly voltage-dependent conductance increase occurs similar to that observed with alamethicin. It results from the opening of a multitude of ion translocating channels within the membrane phase. The steady-state voltage-dependent conductance depends on the 8th-9th power of polypeptide concentration and involves the transfer of 4-5 formal elementary charges. From the power dependences on polypeptide concentration and applied voltage of the time constants in voltage-jump current-relaxation experiments, it is concluded that channels could be formed from preexisting dodecamer aggregates by the simultaneous reorientation of six formal elementary charges. Channels exhibit large conductance values of several nS, which become larger towards shorter polypeptide chain length. A mean channel diameter of 19 A is estimated corresponding roughly to the lumen diameter of a barrel comprised of 10 alpha-helical staves. Similar to experiments with the N-terminal Boc-derivative of alamethicin we did not observe the burst sequence of nonintegral conductance steps typical of natural (N-terminal Ac-Aib)-alamethicin. Saturation in current/voltage curves as well as current inactivation in voltage-jump current-relaxation experiments are found. This may be understood by assuming that channels are generated as dodecamers but, while reaching the steady state, reduce their size to that of an octamer or nonamer. We conclude that the overall behavior of these synthetic polypeptides is very similar to that of alamethicin.(ABSTRACT TRUNCATED AT 400 WORDS)

Alamethicin↗
PubMed1986

Activation of human peripheral blood mononuclear cells by anti-T3: killing of tumor target cells coated with anti-target-anti-T3 conjugates.

Cytotoxic T-cell clones have been shown to be capable of killing unrelated target cells in the presence of heteroconjugates consisting of OKT3 (monoclonal antibody against cell surface antigen T3) and targeting antibody. In contrast, human peripheral blood T cells were not known to have this ability, although these cells have been shown to undergo proliferation in response to OKT3 and accessory signals. Here we report that OKT3-stimulated human peripheral blood mononuclear cells effectively killed human melanoma or Raji cells coated with anti-target-cell--OKT3 conjugates. The extent of target-cell killing by stimulated effector cells was much greater than that observed with unstimulated cells, in spite of down-regulation of the T3 structure on the OKT3-treated cells. Target-cell lysis occurred at physiological concentrations of effector cells and was inhibited by monomeric OKT3, indicating that killing was T-cell-mediated.

Antibodies, Monoclonal↗
PubMed1986

Genetic evidence that Acanthamoeba myosin I is a true myosin.

Acanthamoeba castellanii contains two enzymes, myosins IA and IB, that exhibit the catalytic properties of a myosin but possess very unusual physical properties, the most striking of which are their single, low molecular weight heavy chain, their globular shape, and their inability to form bipolar filaments. We have now isolated a putative myosin IB heavy chain gene from Acanthamoeba, using as a heterologous probe a portion of a sarcomeric myosin heavy chain gene from Caenorhabditis elegans. The amoeba genomic clone hybridizes to a 4250-nucleotide RNA species and hybrid-selects an mRNA encoding a 125-kDa polypeptide. This polypeptide comigrates exactly with the heavy chain of purified amoeba myosin IB and is specifically immunoprecipitated with antiserum to myosin IB. We sequenced two restriction enzyme fragments of this gene, and the deduced amino acid sequences show strong homology with the regions of muscle myosins that contain the reactive thiols and the ATP binding site. Our identification of a myosin IB heavy chain gene demonstrates that myosin IB, despite the unusually low molecular weight of its heavy chain, is a true gene product. The sequence results show that, despite its atypical physical properties, myosin IB is clearly related to conventional myosins.

Amino Acid Sequence↗
PubMed1986

Lymphokine-activated killer cells targeted by monoclonal antibodies to the disialogangliosides GD2 and GD3 specifically lyse human tumor cells of neuroectodermal origin.

Monoclonal antibodies 14.18 (IgG3) and 11C64 (IgG3) directed against disialogangliosides GD2 and GD3, respectively, when used in conjunction with human peripheral blood mononuclear cells (PBMCs) stimulated with human recombinant interleukin (rIL-2) lyse both human melanoma and neuroblastoma cells by antibody-dependent cellular cytotoxicity. Such monoclonal antibody-"armed" effector cells are specifically directed to targets expressing the given disialoganglioside without detectable cross-reactivity. In addition, antibody-dependent cellular cytotoxicity as well as the natural killing ability of human PBMCs is augmented by a brief coincubation with rIL-2. PBMCs augmented by rIL-2 and armed with monoclonal antibodies significantly suppressed tumor growth in the xenotransplant nude mouse model. Our results suggest that once a threshold level of activation of PBMCs is achieved, additional rIL-2 (over three orders of magnitude of concentration) does not significantly enhance cytolytic augmentation. Furthermore, anti-GD3 monoclonal antibody 11C64 together with rIL-2-stimulated PBMCs from melanoma patients with widely differing tumor burdens effectively lyse melanoma tumor targets in antibody-dependent cellular cytotoxicity. Our results also suggest that GD2 and GD3 represent distinct and relevant immunotherapeutic target structures on melanoma whereas GD2 does the same for neuroblastoma tumors. Our data suggest that targeting of activated human effector cells may provide a new and effective cancer immunotherapy protocol.

Animals↗
PubMed1986

Fengycin--a novel antifungal lipopeptide antibiotic produced by Bacillus subtilis F-29-3.

Fengycin is an antifungal lipopeptide complex produced by Bacillus subtilis strain F-29-3. It inhibits filamentous fungi but is ineffective against yeast and bacteria. The inhibition is antagonized by sterols, phospholipids and oleic acid, whereas two other unsaturated fatty acids increase the antifungal effect. Fengycin consists of two main components differing by one amino acid exchange. Fengycin A is composed of 1 D-Ala, 1 L-Ile, 1 L-Pro, 1 D-allo-Thr, 3 L-Glx, 1 D-Tyr, 1 L-Tyr, 1 D-Orn, whereas in fengycin B the D-Ala is replaced by D-Val. The lipid moiety of both analogs is more variable, as fatty acids have been identified as anteiso-pentadecanoic acid (ai-C15), iso-hexadecanoic acid (i-C16), n-hexadecanoic acid (n-C16), and there is evidence for further saturated and unsaturated residues up to C18.

Antifungal Agents↗