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Biomedical subjects

D Horn

Publications and source records attributed to D Horn.

At least 91 records · Page 5Linked to original sources
PubMed1991

Suppression of tumor cell susceptibility to monocyte-induced cell death by growth-inhibitory signals generated during monocyte/tumor cell interaction.

In a recently established serum-free in vitro system it has been demonstrated that the susceptibility of various human tumor cells to the induction of cell death by elutriated human monocytes is critically dependent on tumor cell density and growth state. In the present work it is shown by flow cytofluorometric analysis of bromodeoxyuridine incorporation rates and of expression of the proliferation-associated nuclear antigen Ki-67, that tumor cells forced out of the cell cycle into the quiescent state (G0), which can be accomplished by treatment with supernatant from monocyte/tumor cell interaction cultures, are no longer susceptible to the induction of cell death by monocytes. This suggests that processes essential for the lytic pathway cannot take place in quiescent cells. It is furthermore demonstrated that tumor cells are driven into G0 during interaction with monocytes and that the rate of transit from G1 to G0 increases with increasing monocyte dosage. This explains our earlier finding that maximum rates of tumor cell death are induced at rather low monocyte:tumor cell ratios of around 1:2 and that lysis is suppressed at higher monocyte dosages (van der Bosch et al.:Exp Cell Res 187:185-192, 1990). The potential significance of these findings for the supposed function of mononuclear phagocytes in tumor defense lies in the notion that tumor cells driven into G0 might escape this control and that signals involved in monocyte/tumor cell-interaction contribute to the accumulation of tumor cells in G0.

Cell Communication↗
PubMed1991

Monocyte-mediated growth control and the induction of tumor cell death.

In the present article a hypothesis is put forward and supporting data are referred that explain the elimination of tumorigenic cells as a consequence of their failure to comply with the rules of ubiquitous negative growth control mechanisms involving among others also mononuclear phagocytes as effector cells. This hypothesis does not invoke the recognition of altered cell surface structures on tumorigenic cells as the basis for discriminating them from normal cells and thus avoids one of the most irritating problems of hypothetical tumor defense mechanisms involving the recognition of spontaneously arising tumor cells as 'non-self' by immunologic effector cells.

Animals↗
PubMed1990

Density-dependent tumor cell death and reversible cell cycle arrest: mutually exclusive modes of monocyte-mediated growth control.

The population development of five human tumor cell lines is examined under the influence of elutriator-prepared human monocytes in a serum-free hormone- and growth factor-supplemented medium. Analysis was performed by electronic counting and sizing of tumor cell nuclei and flow cytometric detection of cell cycle phases. Tumor cell death is triggered at rather low monocyte:tumor cell ratios (1:2 to 1:4) whereas it is strongly reduced at high monocyte densities. Furthermore, it is shown that confluence of the target cell population is a necessary prerequisite for lysis. The data suggest that in monocyte/tumor cell cocultures the decision on target cell lysis is not made by the effector cell, but rather by the target cell and that the criterion for this decision is the target cell's ability or inability to respond to a monocyte challenge by arresting the cell cycle in G1. Interactions between target cells play an important role in determining the result of this decision process. A common basis is suggested for this kind of density-dependent monocyte-triggered lysis and density-dependent cell death in 3T3 cell cultures as described previously.

Cell Cycle↗
PubMed1990

Distribution, metabolism, and excretion of [14C] glutaraldehyde.

Radiolabeled glutaraldehyde (GA) was infused into rats in order to determine its distribution between cellular and humoral fractions of the blood, its potential metabolism by RBC's, its rate of excretion, and the nature of its urinary products. This study demonstrated that [14C]GA was distributed between the RBC's and plasma at a ratio greater than 1. Although the absolute counts of both fractions dropped 80% over 3 days, the percentage bound or incorporated increased over time. Despite the extensive uptake by RBC's these cells were unable to metabolize GA to CO2. Urinary excretion of the radiolabel was rapid; the predominant form in the urine was less than 1 kDa in size. All evidence suggested that it was not native GA. We conclude that the RBC's can incorporate GA, but can not metabolize it completely to CO2. Nevertheless, much of the infused GA was rapidly converted to nonreactive metabolites and eliminated by the kidney.

Aldehydes↗
PubMed1990

Subcellular localization of glutaraldehyde.

Glutaraldehyde (GA) has been proposed as an alternative to formocresol for pulpotomies in primary teeth and as an irrigant in root canal therapy. These studies were undertaken to determine if GA can associate with the nucleus of living cells, thereby posing a mutagenic threat. Rats were infused IV with 14C-GA and killed 5 min and 1 h later. The cystolic, membrane, and nuclear fractions of harvested liver cells were separated and analyzed for radioactivity. We determined that significant radioactivity was located in the cytosol and membrane fractions, but not in the nuclear fraction. In an in vitro experiment, liver slices were incubated with 14C-GA in sealed vials in which 14C-CO2 was captured. After 1 h the nucleic acids of the liver slices were isolated and counted. In vitro the liver cells incorporated and metabolized GA to CO2 but no significant label could be detected in the isolated nucleic acids. We concluded from these experiments that GA which was incorporated into liver cells did not reach the nucleus to a significant extent, and that its potential for mutagenicity in the context of pulp treatment was nil.

Animals↗
PubMed1990

Regulation of cell growth by recombinant oncostatin M.

Oncostatin M is a novel growth regulator originally isolated from differentiated human histiocytic lymphoma cells and activated T-lymphocytes based on its ability to inhibit the growth of A375 melanoma cells. We report here that oncostatin M is a widely acting regulator which alters the growth and/or morphology of cells derived from a variety of cancer cell types. At picomolar concentrations, recombinant oncostatin M inhibited the growth of 13/24 tumor cell lines. Six out of 7 lung cancer cell lines were inhibited by oncostatin M, but none of 6 colon cancer cell lines were affected. Oncostatin M also stimulated the growth of some normal cells (3/6), indicating that it, like many growth regulators, is bifunctional. Oncostatin M receptors appear necessary but not sufficient for a growth response to oncostatin M, since none of the cell lines lacking receptor responded to oncostatin M, whereas many but not all cell lines with receptor responded to oncostatin M. Receptor size (Mr congruent to 150,000) was similar for cells in which growth was inhibited, stimulated, or unaffected by oncostatin M.

Animals↗
PubMed1989

Identification and characterization of cellular receptors for the growth regulator, oncostatin M.

Oncostatin M is a polypeptide growth regulator produced by activated T cells and phorbol ester-treated U937 cells. To identify specific cellular receptors for this factor, we have characterized the binding of 125I-labeled oncostatin M to a variety of normal and malignant mammalian cells. Recombinant oncostatin M was labeled with 125I with full retention of growth inhibitory activity on A375 melanoma cells. 125I-Oncostatin M bound to sensitive cells in a time- and temperature-dependent fashion. Binding was specifically inhibited by unlabeled native or recombinant oncostatin M, but not by other polypeptide growth factors tested. Binding to human leukemic and normal blood cells was generally less than to nonhematopoietic cells. With four different cell lines, maximal growth inhibition by oncostatin M was achieved at less than maximal binding site occupancy. Scatchard graphs of direct binding data were curvilinear and indicated that 125I-oncostatin M bound with higher apparent affinity at lower 125I-oncostatin M concentrations. Using a two binding site model, affinity constants of Kd1 = 11 +/- 11 pM and Kd2 = 1000 +/- 380 pM were extrapolated from binding data with A375 cells, and values of Kd1 = 3 +/- 2 pM and Kd2 = 400 +/- 44 pM from A549 cells. The major 125I-oncostatin M binding species in a number of mammalian cell lines was identified by chemical cross-linking as a specific protein(s) of Mr = 150,000-160,000. 125I-Oncostatin M was internalized (t1/2 = 30 min) and degraded subsequent to binding to a responsive cell line.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Assessment of the systemic distribution and toxicity of glutaraldehyde as a pulpotomy agent.

The systemic distribution of glutaraldehyde (GA) from a pulpotomized tooth of a rat was estimated to be 40 nanomoles or 25% of the applied dose. Metabolic studies disclosed that GA was eliminated in urine and expired gases; 90% was cleared from body tissues in 3 days. To evaluate the toxicity of GA, doses 500x greater than that systemically distributed from a pulpotomy site were infused into the jugular veins of rats. Twenty-four hours postinfusion the rats were evaluated in vivo for physiologic changes or sacrificed for biochemical and histologic evaluation of harvested tissues. Only one of the assays, a physiologic parameter, was altered by the 500x dose. Considering the relatively large dose administered and the limited effects, we conclude that GA would not be toxic when used as a pulpotomy agent.

Aldehydes↗
PubMed1988

Biosynthesis of high molecular weight breast carcinoma associated mucin glycoproteins.

We have studied the biosynthesis of mucin glycoproteins recognized by monoclonal antibody W1 in MCF7 cells. Proteins of Mr 170,000, 185,000, 260,000, and 275,000 were immunoprecipitated from cells pulse-labeled with [3H]threonine and [3H]proline. Evidence suggesting that these proteins were precursors of high molecular weight mucin(s) included: 1) their kinetics of disappearance corresponded with appearance of mature mucin(s) (t1/2 = 30 min); 2) their processing into mature mucin(s) was not blocked by cycloheximide, but was disrupted by monensin, which impairs glycoprotein processing in the Golgi; 3) they were inaccessible to antibody added outside the cells, whereas mature mucin(s) was accessible and appeared at the cell surface with a t1/2 = 45 min; and 4) their mobilities of precursors varied between different cell lines, but generally correlated with mobilities of mature mucin(s). The precursors were sensitive to endoglycosidase H, indicating that they contained high mannose N-linked oligosaccharides. Less than 3% of threonine residues in the precursors, but more than 75% in mature mucin(s), were substituted with O-linked oligosaccharides. Therefore, initiation of N-linked oligosaccharides occurred soon after initiation of core protein synthesis, but initiation of O-linked oligosaccharides occurred much later, just prior to appearance of mature mucin(s) at the cell surface.

Antibodies, Monoclonal↗
PubMed1988

Monoclonal antibodies reactive with mucin glycoproteins found in sera from breast cancer patients.

Monoclonal antibodies to mucin glycoproteins have previously been shown to detect elevated antigen levels in sera from breast cancer patients. To determine whether different mucin epitopes represent better targets for serum assays, we have produced and characterized 14 new monoclonal antibodies directed against the mucin glycoproteins detected by antibody W1. Many of the new antibodies differed from each other in their ability to bind to mucins from various sources. Cross-competition analyses of antibody binding indicated that while epitopes for some antibodies were distinct, most epitopes showed complex structural or steric relationships with those for other antibodies. Antibody M26 bound glycolipids from meconium and kidney, indicating that it recognized a carbohydrate epitope. Antibodies M15, M22, M23, and M27 bound to structurally or sterically related epitopes on deglycosylated milk-derived mucin, suggesting that they recognized core protein epitopes. Enzyme immunoassays were developed with the new antibodies and evaluated for their ability to discriminate between sera from breast cancer patients and from controls with benign breast disease. The best single test in terms of sensitivity and specificity used a combination of two antibodies, antibody M29 for antigen capture and antibody M38 for antigen detection. A second test using antibody M26 for antigen capture and antibody M38 for antigen detection detected elevated antigen levels in sera from some patients which were in the control range of the M29/M38 test. By combining results from these tests, significantly more cancer patients were detected than with the W1 and CA 15.3 tests.

Animals↗