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C W Stackpole

Publications and source records attributed to C W Stackpole.

52 records · Page 3Linked to original sources
PubMed1974

Hybrid antibody-induced topographical redistribution of surface immunoglobulins, alloantigens, and concanavalin A receptors on mouse lymphoid cells.

Redistribution of surface immunoglobulins, H-2(b), Thy-1.2, and TL.1,2,3 alloantigens, and concanavalin A receptors on mouse lymphoid cells induced by hybrid rabbit F(ab')(2) antibody (anti-mouse immunoglobulin/anti-visual marker or anti-concanavalin A/anti-visual marker) was studied by immunofluorescence. When used directly to label surface immunoglobulin, and indirectly to label alloantigens and concanavalin A receptors, hybrid antibodies induced similar displacement of all surface components from a uniform distribution into "patches" and "caps" at 37 degrees . One hybrid antibody preparation, antimouse immunoglobulin/anti-ferritin, contained negligible amounts of bivalent anti-mouse immunoglobulin antibody, and was therefore "monovalent" for the antimouse immunoglobulin specificity. This observation suggests that factors other than multivalent crosslinking are responsible for hybrid antibody-induced redistribution of cell-surface components. Cap formation induced by hybrid antibody was enhanced markedly by attachment of the visual marker, either ferritin or southern bean mosaic virus, at 37 degrees . At -5 degrees , hybrid antibody does not displace uniformly distributed H-2(b) alloantigen-alloantibody complexes, but patches of label develop when ferritin attaches to the hybrid antibody. These results explain the patchy distribution of cell-surface components, which is a temperature-independent characteristic of labeling with hybrid antibodies and visual markers for electron microscopy.

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PubMed1973

Topographical location of H-Y antigen on mouse spermatozoa by immunoelectronmicroscopy.

H-Y (male) antigen was visually located on mouse sperm by electron microscopy, by use of the indirect hybrid antibody method and tobacco mosaic virus as the visual marker. Labeling was achieved by centrifugation of the sperm through a discontinuous gradient consisting of alternating layers of immune reagents and wash solutions. Treated sperm were examined topographically by preparation of platinum-carbon replicas. Antigen was located mainly on the acrosomal cap of the sperm head.

Animals↗
PubMed1972

Hapten-conjugated antibodies and visual markers used to label cell-surface antigens for electron microscopy: an approach to double labeling.

Haptens can be coupled to mouse immunoglobulin with retention of antibody specificity. Such hapten-coupled alloantibody, when bound to cells, can be bridged to an electron microscopic marker in two ways: (i) by a hybrid antibody, i.e., anti-hapten:anti-marker, and (ii) by untreated bivalent anti-hapten antibody if the marker is also haptenized. Through the use of immunologically non-crossreactive haptens and markers it should be possible to localize multiple, different antigens on the surface of an individual cell. Double labeling has been achieved with the first method.

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PubMed1971

Cell surface antigens: serial sectioning of single cells as an approach to topographical analysis.

The topographical distribution of H-2 antigens on the surfaces of C57BL/6 mouse thymocytes and lymph-node lymphocytes was investigated by a new technique. Single cells were reacted with visually labeled antibody directed against H-2 antigen. Each cell was processed for electron microscopy individually and was serially sectioned. Models constructed from serial electron micrographs provided detailed views of the entire cell surface and showed that H-2 antigen occurs on thymocytes in small isolated regions and on lymphocytes in large interconnected regions.

Animals↗
PubMed1969

Herpes-type virus of the frog renal adenocarcinoma. I. Virus development in tumor transplants maintained at low temperature.

Development of the herpes-type virus of the frog kidney tumor was investigated by electron microscopy and high-resolution autoradiography in eyechamber transplants of tumor maintained at 7.5 C for up to 27 weeks. Virus particles were first detected at 10 weeks in nuclei containing aggregates of dense granular material. The initial incorporation of a pulse of (3)H-thymidine into these aggregates indicated that they contained newly synthesized viral deoxyribonucleic acid. Capsids enclosing doubleshelled cores were labeled with (3)H-thymidine before capsids with dense cores, and intermediate core forms were observed, suggesting that the double-shelled core transforms into the dense core. Particles with dense cores were observed while being enveloped by budding through the inner membrane of the nuclear envelope, and subsequently while being unenveloped in passing through the outer membrane into the cytoplasm. Virus particles within the cytoplasm acquired fibrillar coats and budded into vesicles, from which they were released, in enveloped form, at the cell surface. Tubular forms and particles considerably smaller than virus particles were regularly encountered in infected nuclei, and the relationship of these forms to virus replication is discussed.

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PubMedDate not supplied

Failure of orally administered RA233 to influence B16 melanoma growth or metastasis.

Possible prophylactic antitumor and/or antimetastatic effects of long-term oral administration of a potent inhibitor of platelet aggregation, the pyrimido-pyrimidine derivative RA233, were assessed using four phenotypically distinct clones of the mouse B16 melanoma. The clones tested included: a poorly tumorigenic, very slowly growing and poorly metastatic population (G3.15); a moderately tumorigenic and slowly growing population that frequently metastasizes to the lungs (G3.5); a highly tumorigenic, moderately growing and highly metastatic population (G3.12); and a highly tumorigenic and rapidly growing population that is generally nonmetastatic but can be slightly metastatic when tumors are initiated by very small numbers of cells (G3.26). Addition of 0.5 mg/ml RA233 to the drinking water continuously from the time of subcutaneous injection of cultured tumor cells until death from tumor growth, which resulted in a daily uptake of 80-100 mg/kg of drug per mouse, failed to significantly influence the tumorigenicities, tumor growth rates, metastatic incidences, or metastatic burdens of any of these clones. RA233 at doses equivalent to those delivered daily to experimental animals strongly inhibited ADP-induced aggregation of homologous C57BL/6 mouse platelets and exhibited selective anti-proliferative effects on cultured cells. Although RA233 prolonged bleeding times, pharmacokinetic analysis indicated that clearance of RA233 from mice was so rapid that achievement of sustained circulating levels sufficient to influence tumor cells or platelet-tumor cell interactions by oral administration was unlikely.

Administration, Oral↗
PubMedDate not supplied

Differences in organization of metastatic and nonmetastatic tumors initiated by the same B16 melanoma clone in mature and young mice.

Subcutaneous transplants of mouse B16 melanoma clone G3.26 grow more slowly, and are markedly more metastatic to the lungs, in mature (greater than 12-month-old) mice than in young (2-month-old) mice. Previous studies suggested that tumors in young mice fail to disseminate viable tumor cells into the hematogenous circulation. To determine if changes in intratumor organization might accompany this altered tumor behavior, G3.26 tumors growing in young and mature mice were examined comparatively at progressive sizes relative to the onset of metastatic dissemination in the older mice. Although the degree of necrosis was comparable in both groups of tumors, vascular density, measured morphometrically in histological sections, was significantly lower in tumors from mature mice at a size when dissemination would be occurring. With the onset of reduced vascular density in tumors in mature mice, there was a substantial increase in the proportion of viable tumor cells that was hypoxic, based on radioresistance and incorporation of the hypoxic cell sensitizer, misonidazole. Quiescent tumor cells, identified by flow cytometry, were also more numerous in tumors from mature mice than in tumors from young mice. Although the importance of these differences in tumor organization to enhanced metastatic behavior is unclear, increased intratumor hypoxia might promote generation of metastatic variants. Alternately, dissemination of tumor cells might be facilitated through a reduced and possibly defective vasculature.

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PubMedDate not supplied

Host immunity to mycoplasma antigens introduced into B16 melanoma cells: effect on tumor growth rate and metastasis.

Immunization of syngeneic C57BL/6 mice with X-irradiated B16 melanoma cells was previously shown to elicit antibodies specific to viral antigens on the melanoma cells. When immunized mice were challenged with viable subcutaneous transplants of B16 melanoma cells that formed non-metastatic tumors in normal mice, tumors failed to develop in some mice, but there was a high incidence of lung metastasis in mice with progressively growing tumors. To determine whether protective immunity and/or enhanced metastasis were the consequences of immune responses specific for inherent tumor-associated viral antigens, non-metastatic B16 melanoma cells were deliberately infected with Mycoplasma arginini. The result was incorporation of perpetuating antigens that elicited, in mycoplasma-immunized mice, humoral and cell-mediated immune responses to infected (B16-M+) but not uninfected (B16-M-) cells. When mycoplasma-immunized mice were challenged with B16-M+ and B-16M- subcutaneous transplants, only B16-M+ tumors were rendered slower-growing and appreciably more metastatic. By contrast, in mice immunized against uninfected B16 melanoma cells, both B16-M+ and B16-M- tumors grew more slowly, and metastasized to a greater extent, than corresponding tumors in unimmunized mice. Enhanced metastasis was not experimentally separable from reduced tumor growth rate and was not simply the consequence of a longer period of tumor growth. Evidence suggests that host immunity does not directly promote metastasis, but that reduced tumor growth rates resulting from protective immunity are more conducive to successful dissemination of metastases.

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PubMedDate not supplied

B16 melanoma variants selected by one or more cycles of spontaneous metastasis to the same organ fail to exhibit organ specificity.

Metastatic clones of the mouse B16 melanoma spontaneously disseminate from subcutaneous tumors throughout the body in two stages, initially to the lungs and secondarily from established lung metastases to systemic sites. From the heterogeneous 'parent' B16 melanoma cell line and from two representative clones, G3.5 and G3.12, cell populations were selected after one or more cycles of tumor growth or metastasis to a particular site, to determine whether metastatic variants with greater organ preference or specificity could be generated. Variants with enhanced secondary metastatic activity were obtained only from G3.12 tumor-disseminated metastases growing in the lungs or in systemic organs. Regardless of the organ of selection or the number of selection cycles, all variants exhibited an overall increase in secondary metastasis incidence and burden in the brain, adrenals, kidneys and ovaries, but no organ preference or specificity was obtained. Populations that grew especially well in the brain, ovaries or liver following intravascular injection were either non-metastatic or exhibited no organ preference during spontaneous metastasis. The increased secondary metastatic activity of G3.12 variants was apparently not due to either longer host survival or to tumor-disseminated cells bypassing the lungs, but may result from enhanced growth potential or greater secondary dissemination capability imparted during growth as lung metastases.

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PubMedDate not supplied

B16 melanoma spontaneous brain metastasis: occurrence and development within leptomeninges blood vessels.

Subcutaneous tumors initiated with mouse B16 melanoma clones G3.5 and G3.12 disseminated visible spontaneous brain metastases in 67 per cent and 32 per cent, respectively, of mice with extensive lung metastasis. Most brain metastases appeared as pigmented emboli within blood vessels of the leptomeninges overlying the cerebral cortex. Intravascular metastases consisted of tumor cell aggregates surrounded by fibrous material and generally contained viable cells that proliferated in culture. Some metastatic emboli apparently proliferated intravascularly to such an extent as to cause vessel disruption, permitting tumor invasion into the adjacent cerebral cortex. Cultured cells from G3.12 leptomenings metastases produced tumors that metastasized to a much greater extent than unselected G3.12 tumors, but brain metastasis still occurred only secondarily, after initial dissemination to the lungs. In contrast, G3.5 brain metastasis-derived populations formed tumors that ultimately metastasized to the brain to lesser extents than did unselected G3.5 tumors. One selected variant, G3.12/BM2, reproducibly formed visible and viable brain metastases in more than 80 per cent of tumor-bearing mice, and lethal or potentially lethal brain metastases in 10-15 per cent of mice. This variant may serve as a model for clinical brain metastasis.

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PubMedDate not supplied

Cytotoxic effect of RA233 on hypoxic B16 melanoma cells in vitro.

The pyrimido-pyrimidine derivative RA233 was found to selectively kill cultured mouse B16 melanoma cells after prolonged hypoxia. At the optimum cytotoxic concentration (100 microM), RA233 reduced cell clonogenicity by about 80% when administered during long-term hypoxia of 4 days. Comparable cytotoxicity was also evident when RA233 was present only during re-oxygenation following 4 days of hypoxia. RA233 treatment during both hypoxia and re-oxygenation resulted in the greatest cytotoxicity, with only about 1% of cells surviving such treatment. By contrast, the hypoxic cell sensitizer misonidazole was cytotoxic only when administered during hypoxia. RA233 appears to be a unique hypoxic cell sensitizer that kills long-term hypoxic tumor cells principally during re-oxygenation.

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