Extremely low frequency (ELF) pulsed-gradient magnetic fields inhibit malignant tumour growth at different biological levels

Extremely low frequency (ELF) pulsed-gradient magnetic field (with the maximum intensity of 0.6-2.0 T, gradient of 10-100 T.M(-1), pulse width of 20-200 ms and frequency of 0.16-1.34 Hz treatment of mice can inhibit murine malignant tumour growth, as seen from analyses at different hierarchical levels, from organism, organ, to tissue, and down to cell and macromolecules. Such magnetic fields induce apoptosis of cancer cells, and arrest neoangiogenesis, preventing a supply developing to the tumour. The growth of sarcomas might be amenable to such new method of treatment.

[Diethylstilbestrol-induced uterine sarcoma in mice]

Female mice of CBA strain received diethylstilbestrol (DES) 1 g body weight intraperitoneally. High incidence of histiocytic uterine sarcoma was observed in parents (25%), first generation (F1), descendants (10.9%), and generation F2m (through F1 males mated with females in control) (17.8%). Morphologically, tumor cells examined through light and electron microscopy were referred to as histiocyte-like elements. Half of the animals had metastases in the liver, kidneys, lungs, spleen, pineal and adrenal glands and stomach. The development of tumors in generation F2m, which was not exposed to DES, might be accounted for by "transgeneration" carcinogenesis, i.e. passage of carcinogenic effect through a generation.

Spontaneously formed tumorigenic hybrids of Meth A sarcoma cells and macrophages in vivo

We have recently demonstrated that malignant cells can hybridize with tissue macrophages in vitro, giving rise to tumorigenic hybrids. We now demonstrate that this can occur spontaneously in vivo as a result of fusion between inoculated Meth A sarcoma cells and host cells, presumably macrophages. Thus, from tumor cell suspensions prepared by collagenase perfusion and density centrifugation, hybrid cells could be isolated that were neoplastic but in contrast to Meth A expressed macrophage markers and had phagocytic capacity. Their morphologic features were intermediate between Meth A and macrophages. By taking advantage of a semiallogeneic experimental system by inoculation of Meth A cells from BALB/c (H-2 K(d)) into (BALB.K x BALB/c) F(1) (H-2(k/d)), hybrid cells from these tumors could be shown to express MHC antigens of both the Meth A and the host haplotypes. Hybrid cells grew faster than Meth A cells in vivo, indicating acquisition of growth-promoting properties through heterotypic cell fusion.

Spontaneous hybridization of macrophages and Meth A sarcoma cells

We present evidence of hybridization between Meth A sarcoma cells and syngeneic as well as semigeneic peritoneal macrophages. The resultant hybrids are characterized by morphology, membrane markers, ploidy, chromosomal content and functional features. Briefly, after a few days of coculture, cells appeared with morphology intermediate between the 2 original cell types. Typical macrophage surface molecules appeared in the hybrids. Meth A cells were labeled with red fluorescence and macrophages with green fluorescence. After 4 days in vitro, hybrids with yellow fluorescence appeared. Macrophages from BALB.K mice (H-2 K(k)) were cocultivated with Meth A cells from BALB/c mice (H-2 K(d)). The semigeneic hybrids displayed both specificities, as demonstrated by flow cytometry. The hybrids appeared moderately phagocytic, less so than the macrophages and markedly more so than the essentially nonphagocytic Meth A cells. The hybrids had a mean number of 76 chromosomes, as opposed to 53 in the Meth A cells and 40 in the macrophages. The macrophage DNA index was set at 1; Meth A cells were found to have an index of 1.6 in G1 phase, and the hybrids had a 2.6 index. The hybrids grew more slowly in vitro than Meth A cells, but grew faster in vivo.

Evidence for characteristic vascular patterns in solid tumours: quantitative studies using corrosion casts

The vascular architecture of four different tumour cell lines (CaX, CaNT, SaS, HEC-1B) transplanted subcutaneously in mice was examined by means of microvascular corrosion casting in order to determine whether there is a characteristic vascular pattern for different tumour types and whether it differs significantly from two normal tissues, muscle and gut. Three-dimensional reconstructed scanning electron microscope images were used for quantitative measurements. Vessel diameters, intervessel and interbranch distances showed large differences between tumour types, whereas the branching angles were similar. In all tumours, the variability of the vessel diameters was significantly higher than in normal tissue. The quantitative data provide strong evidence for a characteristic vascular network determined by the tumour cells themselves.

Morphological and biological characterization of two mesenchymal murine tumors and the modulation of their growth parameters by n-3 and n-6 polyunsaturated fatty acids

Certain tumor growth parameters (GP) of two mesenchymal transplantable tumors maintained on C57BL/6J mice were characterized. Considering that many experimental, clinical and epidemiologic data have indicated that n-3 and n-6 essential fatty acids are nutrients which may delay the development as well as improve the course of cancer, GPs were evaluated on hosts fed on a semisynthetic formula containing 5% of corn oil (CO) or cod liver oil (CLO) and stock diet (C group). Although survival and latency time of tumor-bearing mice were shortened, other GP as percentage of successful implants were improved by both oils in sarcoma-bearing hosts, suggesting that n-3 and n-6 fatty acids might play a modulating role for the development of these tumors.

Video rate confocal laser scanning reflection microscopy in the investigation of normal and neoplastic living cell dynamics

The introduction of video rate confocal laser scanning microscopes (VRCLSM) used in reflection mode with high magnification, high aperture objective lenses and with further magnification by a zoom facility allowed the first detailed observations of the activity of living cytoplasm and offered a new tool for investigation of the structural transition from the living state to the specimen fixed for electron microscopy (EM). We used a Noran Odyssey VRCLSM in reflection (backscattered) mode. A greater degree of oversampling and more comfortable viewing of the liver or taped video image was achieved at zoom factor 5, giving a display monitor field width of 10 microns. A series of mesenchyme derived cell lines--from normal cells to sarcoma cells of different malignancy--was used to compare behaviour of the observed intracellular structures and results of fixation. We contrasted the dynamic behaviour of fine features in the cytoplasm of normal and neoplastic living cells and changes induced by various treatments. The tubulomembraneous 3D structure of cytoplasm in living cells is dynamic with motion observable at the new limits of resolution provided by VRCLSM. All organelles appear integrated into one functional compartment supporting the continuous 3D trafficking of small particles (vesicles). This integrated dynamic spatial network (IDSN) was found to be largest in neoplastic cells.

Lewis lung carcinoma and two transplantable sarcomas in mice as experimental therapy models: biological characteristics and cell population kinetics

The biological characteristics of three transplantable tumours: two sarcomas (SaL, MCA) and Lewis lung carcinoma (LLC) have been studied. We investigated histology, DNA ploidy and cell kinetics parameters of the tumours. All examined tumours were aneuploid and rapidly proliferating, with the hyperdiploid fraction greater than 60%. The SaL tumour was found to have the lowest mean aneuploid bromodeoxyuridine labelling index (LI) equal to 21%, while the highest LI of 35.8% was measured for the LLC tumour. The mean S-phase time was short, lasting 8.5 - 10.9 hrs. The potential doubling time (T(pot)) assessed by BrdUrd staining and flow cytometry were as follows: 37.1 hours for SaL, 22.7 hours for MCA and 21.4 hours for LLC tumour. The MCA had the shortest volume doubling time (T(d)) equal to 1.7 days and the longest one, equal to 4.7 days, was found for the LLC. The lowest cell loss was found in the MCA tumour (44%), while the highest in the LLC tumour (81%). As all the examined tumours proliferate rapidly, there is a capacity for accelerated repopulation and therefore the tumours seem to be good models for experimental radiotherapy.

Macrophage cytotoxicity against murine meth A sarcoma involves nitric oxide-mediated apoptosis

We have studied the cytotoxic effect of stimulated macrophages on Meth A tumor cells in vitro. When stimulated with interferon-gamma and soluble beta-1,3-D-glucan, macrophages exerted cytotoxicity towards syngeneic Meth A tumor cells. This cytotoxicity was associated with a high level of nitric oxide production. Both cell death and nitric oxide production were significantly inhibited by the addition of aminoguanidine, a specific inhibitor of inducible nitric oxide synthase (iNOS), to the culture medium. The cytotoxic effect was accompanied by internucleosomal cleavage of DNA as shown by electrophoresis and DNA fragmentation assay.

Variability of differentiation patterns in xenotransplanted spindle cell sarcomas: a histomorphological, immunohistochemical, and ultrastructural study

Three leiomyosarcomas, 3 nerve sheath sarcomas, 1 rhabdomyosarcoma, and 1 sarcoma not otherwise classifiable with 17 of their xenografts, grown on nude mice, were analyzed to assess the degree of concordance between histomorphology, immunohistochemistry, and ultrastructure in spindle cell sarcoma xenograft differentiation. Histomorphology was inconclusive or misleading in 4/8 sarcoma strains and immunohistochemistry in 4/8 originals and in 10/17 xenografts, although specific patterns had been identified ultrastructurally. Electron microscopy was superior to immunohistochemistry and histomorphology in spindle cell sarcoma differential diagnosis. A further purpose of this study was to clarify whether spindle cell sarcoma xenografts retain the morphological characteristics of their primaries. Histomorphological features of the primaries were preserved over all passages, whereas the immunohistochemical marker profiles as well as the ultrastructural phenotypes changed in 14/17 xenografts and in 8/17 xenografts, respectively. Moreover, unusual bidirectional or tridirectional patterns of differentiation were identified ultrastructurally with leiomyomatous as well as Schwann cells occurring side by side and with MFH-like areas in 5/17 xenotransplants. These findings suggest genetic instability of tumor cells and may be important in the consideration of mesenchymal differentiation pathways.

A simple and accurate method for 3-D measurements in microcorrosion casts illustrated with tumour vascularization

Microvascular corrosion casting is an established method to investigate vascular patterns of nearly all organs. Trying to evaluate these specimens quantitatively using native scanning electron microscope (SEM) pictures always implied a big error, because the information of depth cannot be taken into account. However, SEM stereo pairs allow for exact measurements. Tumour microcorrosion casts were used to demonstrate the feasibility of this 3-D quantification method. The information of depth was calculated for each measuring point using the parallax. From the resulting coordinates the intervascular distances, the interbranching distances as well as the interbranching angles were determined. We found significant differences between all investigated tumours. Reproducibility tests and tests for the greatest error possibilities resulted in a maximum deviation of 2.5% to be expected. Consequently this method is suitable for all application ranges of microvascular corrosion casting as a quantitative determination method.

Expression of manganese superoxide dismutase reduces tumor control radiation dose: gene-radiotherapy

This study investigated the in vitro and in vivo radiation response of tumor cells transfected with human manganese superoxide dismutase (MnSOD) cDNA. A major objective was to test the potential tumor suppressive effect of MnSOD in vivo. Tumor cells studied were an in vitro line derived from a murine spontaneous fibrosarcoma, FSa-II, which expressed an undetectable MnSOD activity. These cells were transfected with pSV2-NEO plasmid (NEO line) or cotransfected with MnSOD plasmid plus pSV2-NEO plasmid (SOD lines) as described previously. The cell lines used were SOD-L and SOD-H, which expressed, respectively, low and high MnSOD activities after transfection, and NEO and parental FSa-II controls. Both SOD-L and SOD-H cell lines were slightly more resistant to ionizing radiation than were the two control cell lines when irradiated in vitro in the presence of oxygen. The dose-modifying factors calculated at the survival level of 0.01 were 1.13 and 1.15 for the SOD-L and SOD-H cells, respectively. To investigate potential tumor suppressive effects, animal tumors of 4 mm diameter were irradiated in vivo under hypoxic conditions, and the radiation dose to control one-half of the irradiated tumors (TCD50) was determined for each tumor. The TCD50S obtained on the basis of the tumor control rate in 120 days after irradiation were substantially lower for the SOD-H and SOD-L tumors compared to the NEO tumors. They were 22.9, 28.6, and 47.5 Gy for SOD-H, SOD-L and NEO tumors, respectively. To analyze these data, survival curves were obtained for hypoxic cells by irradiating NEO and SOD-H tumors under hypoxic conditions in vivo and assaying in vitro. Analysis of these curves suggests that the decrease in the TCD50S of SOD tumors is attributable to the reduced tumorigenicity in these tumors. The hypoxic cell survival curves also showed that SOD did not protect cells from radiation in the absence of oxygen. Electron microscopy showed no morphological differences between these cells. These results suggest that the fraction of tumorigenic cells could be reduced by expression of MnSOD, resulting in a substantial decrease in the TCD50.

Fiber matrix descriptors from permeability data without requiring membrane thickness: theory, results, and optimization

OBJECTIVE

Permeability of basement membrane and all other barriers contains a term for membrane thickness (delta x). This naturally leads to development of methods for measuring delta x that are imprecise, inaccurate, expensive, subject to preparation artifact, and inattentive to variability. Although height and shape of permeability (P) vs. probe radius (aE) curves are sensitive to delta x, In(P) or In (P/free diffusivity or D0) curves have shapes independent of delta x. It should, thus, be possible using such characteristics to determine fiber radius (rf) and void volume ratio (epsilon) without delta x. We developed such a method to derive membrane structure by the standard model of Ogston and present its experimental evaluation.

METHODS

Basement membranes were self-assembled using 1:1 Matrigel: 0.01 M Tris/150 mM NaCl/1.0 mM CaCl2 buffer on 0.4-mu polycarbonate supports with transport measured in diffusion chambers using FITC-labeled hydroxyethyl starch probes from 25 to 102 A in radius. Sampling was at 0.5 hr and then for each hour up to 5. Other membranes were measured 7 days after formation.

RESULTS

The best fit of the new technique occurred at 3 hr with R2 = 0.949 +/- 0.003 SEM, rf = 36.8 = 2.4 A, and epsilon = 0.87 +/- 0.02. Membranes studied for 7 days showed more variability but essentially the same characteristics.

CONCLUSIONS

Membrane thickness is not necessary to reduce permeability of basement membrane to structure, and optimum sampling time is 3 hr.

Effects of vinblastine on cell membrane fluidity and the growth of SA-1 tumor in mice

Cell membranes can be targets of some anti-cancer drugs. Therefore, the purpose of this study was to determine whether vinblastine (VLB) can also affect the tumor cell membrane. On the in vivo SA-1 tumor model, alteration of cell membrane fluidity (measured by electron paramagnetic resonance, EPR), cytotoxicity and morphological changes of the SA-1 tumor cells after VLB treatment were studied. The cytotoxic effect of VLB was biphasic, with an initial fast increase in cytotoxicity followed by a plateau. The surviving cells had increased membrane fluidity and were morphologically changed. The dose-response curve of VLB on membrane fluidity was also biphasic with an initial fast increase in membrane fluidity followed by a plateau. Since dose-response curves of VLB cytotoxicity and its effect on membrane fluidity were similar, there was a high correlation between both effects. The effect of VLB on membrane fluidity was the most pronounced at 24 h and 48 h after treatment. The results of this study indicate that VLB affects cell membrane by increasing the membrane fluidity of SA-1 tumor cells in vivo in a dose-and time-dependent manner. Therefore, this finding may be beneficially implemented also in priming cells for other cytotoxic drugs and for appropriate timing of drug sequence in combined schedules.

A temporal study of the lesions induced by MoMuSV-349

We used time point studies to document the progression of neoplasms, haematologic abnormalities and associated lesions induced by Moloney murine sarcoma virus-349 (MoMuSV-349). BALB/c mice inoculated intraperitoneally with MoMuSV-349 first developed histologically discernible lesions at 14 days post-inoculation (d.p.i.). The initial neoplasms were characterized by whorls of fusiform or spindle-shaped cells enmeshing dense infiltrates of neutrophils and macrophages. By 21 d.p.i., clinical signs associated with MoMuSV-349 infection were evident. The distribution of the neoplasms was more widespread, although the histologic appearance of the tumours was very similar to that found at 14 d.p.i. All mice sacrificed at 28 d.p.i. exhibited characteristic clinical signs associated with MoMuSV-349, including moderate cachexia. Histologically, neoplasms observed at 28 d.p.i. contained a significant vascular component. By 35 d.p.i., all mice exhibited severe clinical signs (e.g. cachexia, dull hair coat, uneven gait). Histologically, all the neoplasms had a predominant vascular component. Non-neoplastic lesions, such as severe thymic atrophy and multifocal pulmonary haemorrhage, were commonly present. Mice sacrificed 42 d.p.i. were clinically, grossly and histologically similar to those sacrificed at 35 d.p.i. However, one difference found in the 42 d.p.i. group was the presence of rare rhabdomyosarcomas infiltrating the skeletal muscles. Mice inoculated with MoMuSV-349 developed severe neutrophilia and lymphopenia, and moderate anaemia. This study demonstrates that MoMuSV-349 induced angiosarcomatous neoplasms are characterized by stage development and severe haematologic and non-neoplastic abnormalities.

The "bystander effect": tumor regression when a fraction of the tumor mass is genetically modified

Tumor cells expressing the herpes simplex virus thymidine kinase (HSV-TK) gene are sensitive to the drug ganciclovir (GCV). We demonstrate here that HSV-TK-positive cells exposed to GCV were lethal to HSV-TK-negative cells as a result of a "bystander effect." HSV-TK-negative cells were killed in vitro when the population of cultured cells contained only 10% HSV-TK-positive cells. The mechanism of this "bystander effect" on HSV-TK-negative cells appeared to be related to the process of apoptotic cell death when HSV-TK-positive cells were exposed to GCV. Flow cytometric and electron microscopic analyses suggested that apoptotic vesicles generated from the dying gene-modified cells were phagocytized by nearby, unmodified tumor cells. Prevention of apoptotic vesicle transfer prevented the bystander effect. The toxic effect of HSV-TK-positive cells on HSV-TK-negative cells was reproduced in an in vivo model. A mixed population of tumor cells consisting of HSV-TK-positive and HSV-TK-negative cells was inoculated s.c. into mice. Regression of the tumor mass occurred when the inoculum consisted of as few as 10% HSV-TK-expressing tumor cells. The bystander effect was also demonstrated in i.p. tumor studies. Initial experiments demonstrated that prolonged survival (> 70 days) occurred when a mixture containing 50% HSV-TK-positive and 50% HSV-TK-negative cells was injected i.p. followed by GCV treatment. Further, survival was prolonged for mice with a preexisting HSV-TK-negative i.p. tumor burden by injecting HSV-TK-positive cells and GCV. These results suggest that genetic modification of tumor cells may be useful for developing cancer therapies.

Ultrastructural localization of lectin-binding sites in different basement membranes

In the present work we localized binding sites for the lectins WGA, RCA I, con A and SBA at the ultrastructural levels in morphologically different basement membranes. These different basement membranes included (a) thin ones, for example, tubular basement membrane of the mouse kidney which separates epithelial cell layers from mesenchymal cells and glomerular basement membrane which separates epithelial cells from other epithelial cells, (b) thick multilayered ones, for example. Reichert's membrane which is built up during the embryonic development of rodents and as an example of a pathologically thickened basement membrane, the basement membrane of the Engelbreth-Holm-Swarm (EHS) sarcoma. We were able to show that, in contrast to the thick multilayered basement membranes, the thin ones showed a strong positive SBA-binding pattern. Thick basement membranes otherwise revealed very strong labelling with the lectins WGA and RCA I. Our findings lead us to conclude that thin and thick basement membranes differ markedly in the quality and quantity of the carbohydrates which they contain.

Uterine sarcomas in CBA mice induced by combined treatment with 1,2-dimethylhydrazine and estradiol dipropionate. Light and electron microscopy

Three uterine sarcomas induced by combined treatment (1,2-dimethylhydrazine and estradiol dipropionate) in CBA mice were examined by light and electron microscopy. Histologically the tumours consisted either of loose areas with stellate cells or of solid cellular areas. These were formed of elongated cells of the fibroblastic type and rounded cells with clear nuclei and abundant cytoplasm without clearly discernible bodies. Ultrastructurally, undifferentiated mesenchymal cells and cells with the features of fibroblasts and myofibroblasts were distinguished. The tumours described bear resemblance to human endometrial stromal sarcomas and are interpreted as sarcomas originating from immature mesenchymal cells differentiating mainly in the direction of cells of the fibroblastic type. Certain similarities with fibrous histiocytomas are noted.

Cryofixation of basement membranes followed by freeze substitution or freeze drying demonstrates that they are composed of a tridimensional network of irregular cords

Since conventional chemical fixation may extract tissue components and thus alter structural organization, cryofixation was used to reexamine the ultrastructure of three thick basement membranes: lens capsule, Reichert's membrane, and Engelbreth-Holm-Swarm (EHS) tumor matrix, and two thin basement membranes, those of epididymis and semi-niferous tubules. Cryofixation was achieved by slam freezing followed by either freeze substitution in dry acetone containing 1% osmium tetroxide and 0.05% uranyl acetate or freeze drying in a molecular distillation dryer. The results by both procedures demonstrate that thick basement membranes and the lamina densa of thin basement membranes are composed of a network of anastomosing strands referred to as cords. The cords vary in density and distinctiveness, but their thickness averages 3 to 5 nm in every tissue examined. The spaces separating the cords vary within wide limits, but their mean diameter is approximately 15 nm in every case. Two other common features are 1) the presence within the network of a few 1.5-3.0-nm-thick filaments and 2) 4.5-nm-wide sets of parallel lines referred to as double tracks. When these results are compared with those previously described after conventional fixation, no significant difference is observed in either the cord network or the associated filaments and "double tracks." However, in the thin basement membranes processed by cryofixation, the lamina densa is in direct contact with epithelial cells, whereas, after conventional fixation, the lamina densa is separated from the epithelial cells by a pale layer referred to as lamina lucida or lamina rara. Immunogold labeling of three basement membranes after cryofixation and freeze substitution in acetone containing 0.3% glutaraldehyde yields strong reactions for laminin, type IV collagen, and heparan sulfate proteoglycan. Comparison with previous results indicates that conventional formaldehyde fixation adequately preserves laminin and type IV collagen but causes the loss of some proteoglycan. It is concluded that, except for this loss and the absence of lamina lucida in cryofixed thin basement membranes, the morphological and antigenic features obtained after cryofixation are similar to those observed in the past after conventional fixation.

Metabolism of the malignant cell, in vivo, is anaerobic and significantly plays a factor in the pathway to carcinogenesis

The malignant cell, in vivo, metabolizes and respires anaerobically. For a good many years scientists have been aware of anaerobia being present in malignant growths. The prevailing opinion is that the malignant cell is able to remain viable in an anaerobic medium. This assumption is incorrect and is actually misleading. My investigative studies indicates that the malignant cell metabolizes and respires intracellularly so that the consequence of such a physiology is anaerobic and the basis for such anaerobia is a metabolic phenomenon. There is a reason for this anaerobiosis. Studies demonstrated the fact that there are present within the malignant cell and in the immediate area bacterial spores arising from one of several varieties of plant bacteria. And with an adequate circulating flow of blood, by the animal (human) host, to that particular site, provides the metabolites, enzymes, and the exchange of gases to enhance this abnormal physiopathological anaerobiosis. It is this intracellular anaerobic metabolism within an animal cell that becomes the basis for its malignant transformation.

[Ultrastructural changes in tumor cell nuclei during spontaneous regression of induced mouse sarcoma virus tumors]

Experimental induction of tumours by mouse sarcoma virus inoculation into the Balb/c mice is a suitable model for following up the mechanisms involved in the regression processes, that is, degradation of tumour cells. Using the electron microscope the analysis of the nucleus of tumour cells in different phases of regression (from 8 to 23 day after inoculation) was performed in order to observe the mechanisms of degradation of tumour cells. It has been concluded that the changes of apoptosis of tumour cells occurred most frequently.

Variations in the occurrence of silver-staining nucleolar organizer regions (AgNORs) in non-proliferating and proliferating tissues

Previous studies on the subject of silver-staining nucleolar organizer regions (AgNORs) as indicators of precise proliferative status of tissues have sometimes resulted in ambiguity. The studies, however, have most frequently addressed themselves to the prognosis of neoplasias, with the aim of using AgNORs principally to distinguish between benign and malignant tumours. This investigation was to determine a base-line relationship of AgNOR clusters to proliferation and thus concentrated on normally proliferative tissues and conditionally renewing tissues after appropriate stimulation. Two murine transplantable tumours were also examined as examples of frank malignancy. As an example of the former, variations in AgNOR clusters were noted in the small intestine of man, mouse, and rat. The conditionally renewing systems of liver, prostate, and salivary glands were stimulated into proliferation by two-thirds partial hepatectomy, castration followed by treatment with testosterone, and isoproterenol treatment, respectively, in rat models; the murine sarcoma SaF and carcinoma CaNT provided relatively simple malignant tumours for AgNOR investigation. Proliferation was monitored by noting labelling indices after injection with bromodeoxyuridine (BrdUrd) in vivo followed by immunocytochemical visualization of S-phase cells. In all tissues, an increase in the size of AgNOR clusters rather than their number correlated positively with elevated labelling, particularly with the emergence of silver-staining regions of 2-3 microns visible diameter. Thus, increased AgNOR cluster size (diameter) as representative of AgNOR cluster/nucleolus volume was found to be dependent on proliferative activity in a range of normal and neoplastic tissues.

Deformation-driven, lethal damage to cancer cells. Its contribution to metastatic inefficiency

Direct and indirect, in vivo and in vitro observations are in accord with the hypothesis that as a consequence of their deformation within capillaries, cancer cells undergo sphere-to-cylinder shape-transformations that create a demand for increased surface area. When this demand cannot be met by apparent increases in surface area accomplished by nonlethal, surface "unfolding," the cell surface membrane is stretched; if expansion results in more than a 4% increase in true surface area, the membrane ruptures, resulting in cancer cell death. It is suggested that this deformation-driven process is an important factor in accounting for the rapid death of circulating cancer cells that have been trapped in the microvasculature. Therefore, this mechanism is thought to make a significant contribution to metastatic inefficiency by acting as a potent rate-regulator for hematogenous metastasis.

Adhesion of Kirsten-ras+ tumor-progressing and Kirsten-ras- revertant 3T3 cells on fibronectin proteolytic fragments

Adhesion has been evaluated for tumor cell populations derived from Kirsten murine sarcoma virus (KiMSV)-transformed BALB/c 3T3 cells responding to substrata coated with intact plasma fibronectin (pFN), a family of related proteolytic fragments from pFN or cellular fibronectins (FNs), and the heparan sulfate-binding platelet factor-4 (PF4). Both early-passage KiMSV cells, harboring the viral Kirsten ras oncogene (v-Ki-ras+), and late-passage KiMSV cells, in which most cells have lost the oncogene (v-Ki-ras-), are compared with primary tumor and lung metastatic tumor cells after three routes of injection into nude mice; nontumorigenic v-Ki-ras- revertant cells have been cloned from the late-passage KiMSV population. Attachment of early-passage KiMSV, primary tumor, and lung metastatic tumor cells was optimal and resistant to soluble RGDS peptide in the medium on intact pFN, on fragment F-155 from pFN containing the RGDS cell-binding domain and the heparinII domain, and on PF4 but decreased for metastatic cells on F110 containing only the RGDS domain (and sensitive to RGDS peptide). Cytoplasmic spreading of early-passage KiMSV and all tumor cells was good to excellent in polygonal patterns on pFN and on F155, while most cells remained round on F110. Responses for KiMSV and tumor cells varied on different heparin-binding proteins; cells remained rounded or detached on F38 derived from pFN or on PF4 but spread effectively with long linear process extension on cellular FN-derived fragments F44 + 47 harboring the extra domaina sequence. That F44 + 47 may contain a new cell-binding site for v-Ki-ras+ cells was also indicated by resistance to bacterial heparitanase in cell responses on F44 + 47 but not on PF4 and extensive catabolism of proteoglycans in the substratum-attached material of these cells. v-Ki-ras- revertant cells, nontumorigenic in nude mice, have reacquired 3T3-like responses to proteolytic fragments, including much more effective spreading on PF4 or on F38 substrata, and have reverted in generating microfilament stress fibers on pFN, a competence lacking in all v-Ki-ras+ cells. These results indicate that (a) v-Ki-ras+ primary and metastatic tumor cells respond similarly to most proteolytic fragments of FNs harboring known binding domains, with a few exceptions; (b) v-Ki-ras gene expression correlates with a new cell surface receptor activity recognized by extra domaina-containing fragments from cellular FNs; and (c) loss of the viral oncogene to generate v-Ki-ras- revertant cells reverts their FN-mediated adhesion responses.

Growth-associated shedding of a tumor antigen (CE7) detected by a monoclonal antibody

A monoclonal antibody was developed against an antigen, termed CE7, which was highly expressed on the surface of rat fibrosarcoma KMT-17 cells (clone A3) cultured in low serum medium (A3-1% FCS). The CE7 antigen was not detectable on A3 cells cultured in ordinary high serum medium (A3-10% FCS), on in vivo passaged A3 cells, or on parental in vivo KMT-17 cell line. However, immunoelectron microscopy and Western blot analyses indicated that CE7 antigen was produced by these tumor cells in all circumstances but was shed from their surfaces in vesicular form into the surrounding tissue culture medium or ascites, unless low serum concentration prevailed and disappeared from their cell surfaces. We have previously reported that the immunogenicity of A3 cells was increased when the serum concentration was lowered from 10% to 1% and the phenomenon paralleled the CE7 antigen expression on the A3 cells. These results suggest that the CE7 antigen could be a tumor-associated rejection antigen and that the expression of the CE7 antigen on A3-1% FCS cells (which is shed by high serum culture or in vivo transplantation and disappears from the cell surface) may play a role in immunological responses against the tumor cells.

A dihydropyridine-sensitive calcium channel in rodent osteoblastic cells

Rat osteogenic sarcoma cells (UMR 106-01) and normal rat trabecular bone osteoblasts (ROB) were studied using the whole cell version of the patch clamp technique to determine the existence of calcium (Ca2+) channels. Pipette and bath solutions were designed to separate Ca2+ channel currents from other voltage-dependent currents, and Ba2+ was used as the charge carrier. In both UMR 106-01 and ROB cells, a Ba2+ current was measured, which expressed the characteristics of an L-channel, such as activation range, dihydropyridine sensitivity, and little or no inactivation. In some cases, this channel was detectable only with BAY-K-8644 in the bath solution. The dihydropyridine agonist increased the current intensity and shifted the peak inward current to more negative potentials. This study, confirming previous observations, demonstrates the existence of a Ca2+ channel in both transformed and normal osteoblastic cells.

The flavonoid tangeretin inhibits invasion of MO4 mouse cells into embryonic chick heart in vitro

Tangeretin, a flavonoid from citrus plants, was found to inhibit the invasion of MO4 cells (Kirsten murine sarcoma virus transformed fetal mouse cells) into embryonic chick heart fragments in vitro. The flavonoid appeared to be chemically stable in tissue culture medium, and the anti-invasive effect was reversible on omission of the molecule from the medium. Unlike (+)-catechin, another anti-invasive flavonoid, tangeretin bound poorly to extracellular matrix. It did not alter fucosylated surface glycopeptides of MO4 cells. Tangeretin seemed not to act as a microtubule inhibitor, as immunocytochemistry revealed no disturbance of the cytoplasmic microtubule complex. However, at anti-invasive concentrations of tangeretin, cell proliferation and thymidine incorporation appeared to be inhibited. When cultured on an artificial substrate, treated MO4 cells were less elongated, covered a larger surface area and exhibited a slower directional migration than untreated cells. From the decrease in ATP content in MO4 cells after tangeretin treatment, we deduce that this flavonoid inhibits a number of intracellular processes, which leads to an inhibition of cell motility and hence of invasion.

The use of electron microscopy and immunocytochemistry to characterise spontaneously-arising, transplantable rat tumors

When examined by light microscopy, transplanted animal tumors frequently bear little resemblance to the original neoplasm. If such tumors are to be used as models of human cancer they should be characterised as regards extant rather than historical features. Consequently, we have examined, by electron microscopy and immunocytochemistry, five spontaneously arising tumors transplantable in the WAB/Not rat that are currently diagnosed on the basis of historical features only. A typical sarcoma was used for comparison. Of four spontaneously arising tumors previously classified as carcinoma, Sp4 possessed epithelial features on both ultrastructural and immunocytochemical analysis, Sp107 on ultrastructural analysis only and Sp15 and Sp22 by neither technique. Expression of vimentin was most marked with Sp15 and Sp107. The putative sarcoma, Sp24, showed clear evidence of epithelial differentiation but no evidence of vimentin expression. This study (a) records the phenotypic drift of experimental tumors on transplantation (most clearly with Sp107) and the co-expression of cytokeratins and vimentin in putative carcinomas, (b) confirms the inadequacy of routine histology for accurate characterisation of such tumors and (c) details techniques for a more thorough assessment of state of differentiation that should guide the choice of experimental model.

Neural crest origin of clear cell sarcoma of tendons and aponeuroses. Ultrastructural and enzyme cytochemical study of human and nude mouse-transplanted tumours

In order to clarify the histogenesis of clear cell sarcoma of tendons and aponeuroses (CCS), two cases of human and one nude mouse-transplanted CCS line were studied using an ultrastructural and enzyme cytochemical approach. Most of the tumour cells obtained from the primary and transplanted CCS demonstrated melanosomes in various stages of development within the cytoplasm, whereas no melanosomes could be identified in the metastatic CCS. However, cholinesterase and tyrosinase activities could be demonstrated not only in the melanotic primary and transplanted CCS but also in the amelanotic metastatic CCS. The results therefore support the hypothesis that CCS is a soft tissue tumour derived from the neural crest.

Antitumor effects of endotoxin against solid murine Meth A tumors of different ages. Quantitative histology of the tumors and regional lymph nodes

Mice with 3-, 6-, 9- and 15-day Meth A tumors in the skin were injected intravenously with endotoxin to study age-dependent induction of tumor necrosis and reactive changes in draining lymph nodes. By 24 h after treatment with endotoxin, macroscopic necrosis was seen in 9-day, and to an even greater extent in 15-day tumors; microscopy showed extensive necrosis in 9-day tumors and some necrosis in 6-day tumors. The necrosis was predominantly coagulative, but the 9- and 15-day tumors showed a rim of hemorrhagic necrosis near the skin with surviving tumor tissue located at the lateral and basal margins. All the tumors showed about equal hyperemia by 4 h and mitotic arrest by 4 and 24 h. Depletion of mast cells, which were most numerous in the 9-day tumors, was seen on the dermal aspects by 24 h. Endotoxin did not change the morphology of the lymph nodes and disseminated tumor cells within 24 h. Endotoxin is known to cure 9-day Meth A tumors, and the extent of the rapid necrosis induced is clearly the crucial factor. Necrosis, however, is not a direct consequence of early hyperemia or mitotic arrest and other factors related to the age and site of the tumor, apparently affect whether or not necrosis ensues.

PC12 cell aggregation and dopamine production on EHS-derived extracellular matrix

PC12 cells on plastic grow as a single-layered lawn of cells which synthesize, store and secrete dopamine. In contrast, PC12 cells cultured on Englebreth-Holm-Swarm (EHS) tumor-derived extracellular matrix grow into multicellular aggregates. Matrix dissolution and cell migration appear to follow aggregate formation. PC12 cell plating efficiency is decreased on EHS-matrix but the doubling time of cells on EHS-matrix is comparable to plastic. Dopamine secretion and cellular content determined with a radioenzymatic assay as well as dopamine synthesis determined with cation-exchange chromatography are similar on a per cell basis in cultures of PC12 cells on plastic and EHS-matrix.

Characterization of human soft tissue sarcomas in nude mice. Evidence for histogenic properties of malignant fibrous histiocytomas

Twenty-two human sarcomas were grafted subcutaneously into nude mice. Twelve tumors grew successfully. Nine of these 12 tumors had an aneuploid DNA content, whereas only 1 of 10 nonsuccessful tumors was aneuploid. The 12 sarcomas included two leiomyosarcomas, two malignant schwannomas, one synovial sarcoma, and seven malignant fibrous histiocytomas (MFHs). With light and electron microscopic and immunolabeling studies the original and xenografted tumors (the latter for at least two generations) were histopathologically compared. The xenografted leiomyosarcomas showed ultrastructurally a more pronounced leiomyodifferentiation, and one of the malignant schwannomas a more pronounced schwannian differentiation. The second malignant schwannoma and the synovial sarcoma, however, remained unchanged. Five storiform pleomorphic MFHs expressed features that were not observed in the original tumors. Tumor cells of three of these xenografted sarcomas showed leiomyogenic differentiation (filamentous densities, pinocytotic vescicles, and desmin immunoreactivity), whereas cells of the two others demonstrated schwannian differentiation (long cytoplasmic processes, basal lamina). A xenografted myxoid MFH and a pleomorphic MFH gave rise to pleomorphic sarcomas composed of undifferentiated cells. It appeared that under transplantation conditions tumor cells of storiform pleomorphic MFH can differentiate into various directions.

Two human tumors with high basement-membrane-producing potential

Two human tumors, an adenoid cystic carcinoma and a yolk sac tumor, were found by immunocytochemical, ultrastructural, and biochemical studies to contain abundant basement membrane matrix in contrast to the vast majority of human tumors which contained either an absent or scant basement membrane matrix. These tumors were established as xenografts in athymic (nude) mice. Both xenografts maintained characteristic histologic features, immunocytochemical localization of basement membrane components, and reasonable yields of native laminin and Type IV collagen throughout three successive transplant generations. Although only a small fraction of the yield of that of the murine Engelbreth-Holm, Swarm (EHS) sarcoma, the yield of the human basement membrane-producing tumors could be increased by rendering the mice lathyritic. The human basement membrane proteins so extracted were identical on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to their murine counterparts. These human tumors then represent a potential source of human basement membrane proteins.

Morphological and biological characteristics of mammary tumours induced by the direct application of DMBA powder to rat mammary glands

Mammary tumours were induced by the direct dusting of 1 mg, 7,12-dimethylbenz(a)anthracene (DMBA) powder onto the mammary gland of both 30-day-old female and male Sprague-Dawley rats, and the tumours were examined histologically. Mammary tumours developed in 43/43 (100%) of the females 11 to 20 weeks after DMBA dusting and 16/23 (70%) of the males 18 to 28 weeks after dusting, while non-mammary spindle cell sarcomas occurred in 5/23 (22%) of the males 15 to 24 weeks after dusting. A variety of benign and malignant mammary tumours of epithelial and/or mesenchymal origin were induced, which are comparable to human mammary tumours. Different histological patterns were observed in different areas of the same tumours. Ovariectomy revealed hormone (ovary)-dependency in 10/17 (59%) of the tumours, revealing regressing epithelial and proliferating mesenchymal tumour elements on histological examination.

Self-assembly of a high molecular weight basement membrane heparan sulfate proteoglycan into dimers and oligomers

A high molecular weight basement membrane heparan sulfate proteoglycan, isolated from murine Englebreth-Holm-Swarm tumor, is seen in platinum replicas as an elongated flexible core (Mr = 450,000) consisting of a series of tandem globular domains from which extend, at one end, two to three heparan sulfate chains (average Mr = 80,000 each). This macromolecule will self-assemble into dimers and lesser amounts of oligomers when incubated in neutral isotonic buffer. These molecular species can be separated by zonal velocity sedimentation and assembly is seen to be time- and concentration-dependent. In rotary-shadowed platinum replicas the binding region is found at or near the end of the core at the pole opposite the origin of the heparan sulfate chains. Dimers are double-length structures and oligomers are seen as stellate clusters: in both, the heparan sulfate chains appear peripherally oriented. While isolated cores self-assemble, isolated heparan sulfate chains do not bind intact proteoglycans. Furthermore, proteolytic removal of a non-heparan sulfate containing core moiety destroys the ability of the proteoglycan monomer to form larger species or bind intact proteoglycan, further supporting the binding topography determined morphologically. These negatively charged macromolecular complexes may be important contributors to basement membrane structure and function.

Modifications of tumor histology by point mutations in the v-fps oncogene: possible role of extracellular matrix

Fujinami sarcoma virus (FSV) encodes a protein-tyrosine kinase, p130gag-fps, whose enzymatic activity and ability to transform cultured cells to a neoplastic phenotype are reduced by substitution of the major autophosphorylation site tyrosine-1073 with other amino acids. We compared the histopathology of tumors formed in syngeneic immunocompetent rats by Rat-2 cells and by Rat-2 cells transformed in culture with (a) wild type (wt) FSV, (b) mutant FSV where the codon for tyrosine-1073 of p130gag-fps had been changed to codons for phenylalanine or serine, and (c) a revertant FSV, genotypically identical to wt FSV, in which the codon for tyrosine-1073 had been restored. Latency periods from cell inoculation to tumor formation were 12-29 weeks with Rat-2 cells, 6-8 weeks with mutant-transformed Rat-2 cells, and 2-4 weeks with wt FSV- and revertant FSV-transformed Rat-2 cells. Untransfected Rat-2 cells formed tumors that histologically resembled low grade fibrosarcomas or fibromas and were characterized by uniform fusiform cells in parallel arrays with a prominent collagenous stroma. The growth pattern of tumors produced by mutant FSV-transformed cells was generally similar, although cellular forms and intercellular organization were less uniform. In contrast, Rat-2 cells transformed with either wt FSV or revertant FSV produced tumors that resembled highly malignant sarcomas and were composed of diffuse sheets of pleomorphic, disorganized cells and stroma rich in hyaluronate but poor in fibrous components. Local invasion occurred in 25% of tumors produced by Rat-2 cells and in 53 and 36% of tumors formed by mutant FSV- and wt FSV-transformed cells, respectively. In culture, Rat-2 cells and mutant FSV-transformed cells produced fibrillar pericellular matrices of collagen I and fibronectin. From 5 to 15% of protein secreted by these cells was collagen. Cultures of wt FSV- and revertant FSV-transformed cells lacked collagen and fibronectin matrices and collagen secretion was reduced to 0-2%. These results show that clinically relevant histological characteristics of malignant tumors can correlate with single amino acid substitutions previously shown to affect the enzymatic activity and transforming ability of an oncogenic protein tyrosine kinase. The mechanisms underlying some of the histological differences in this system may be related to differences in the production of extracellular matrix components among the transformed cells.

Structure and affinity for antithrombin of heparan sulfate chains derived from basement membrane proteoglycans

Metabolically 35S- or 3H-labeled heparan sulfate was isolated from murine Reichert's membrane, an extraembryonic basement membrane produced by parietal endoderm cells, and from the basement membrane-producing Engelbreth-Holm-Swarm mouse tumor. The polysaccharides were subjected to structural analysis involving identification of products formed on deamination of the polysaccharides with nitrous acid. The polysaccharide from Reichert's membrane contained N- and O-sulfate groups in approximately equal proportions. It bound almost quantitatively and with high affinity to antithrombin. A high proportion of antithrombin-binding sequence was also indicated by the finding that 3-O-sulfated glucosamine residues accounted for about 10% of the total O-sulfate groups. In contrast, at least 80% of the sulfate residues in the heparan sulfate isolated from the mouse tumor were N-substituents. Only a minor proportion of this polysaccharide bound with high affinity to antithrombin, and no 3-O-sulfated glucosamine residues were detected. These results are discussed in relation to the possible functional role of heparan sulfate in basement membranes.

Basement membrane complexes with biological activity

We have studied the reconstitution of basement membrane molecules from extracts prepared from the basement membrane of the EHS tumor. Under physiological conditions and in the presence of added type IV collagen and heparan sulfate proteoglycan, gellike structures form whose ultrastructure appears as interconnected thin sheets resembling the lamina dense zone of basement membrane. The major components of the reconstituted structures include laminin, type IV collagen, heparan sulfate proteoglycan, entactin, and nidogen. These components polymerize in constant proportions on reconstitution, suggesting that they interact in defined proportions. Molecular sieve studies on the soluble extract demonstrate that laminin, entactin, and nidogen are associated in large but dissociable complexes which may be a necessary intermediate in the deposition of basement membrane. The reconstituted matrix was biologically active and stimulated the growth and differentiation of certain cells.

Studies on the mechanism of macrophage cytotoxicity

The interactions with tumor target cells of resident and BCG-activated murine peritoneal macrophages (M phi) as well as of BCG-activated M phi additionally stimulated by a lymphokine-like factor were investigated in order to get some insight into the cytolytic process mediated by activated M phi. The lymphokine-like factor enhancing the cytotoxicity of BCG-activated M phi (MCF) was isolated and partially purified from cell-free fluid of rat Zajdela ascites hepatoma. M phi cytotoxicity was determined by a modified 51Cr release assay. Scanning and transmission electron microscopic findings suggested a two-step mechanism of target cell lysis: a first step of specific attachment of processes of M phi on the target cell surface and a second step with transport of lysosome-like vesicles to the target cells obviously with liberation of these vesicles in the immediate vicinity of target cells resulting in a local accumulation of cytolytic substances. This interpretation was supported by findings after treatment of interacting effector and target cells with amphotericin B and bestatin which substances were modifying M phi cytotoxicity. MCF caused only an augmentation of M phi cytotoxicity without qualitative differences to the cytolytic action of merely BCG-activated M phi.

Properties and functions of a nucleolus-specific phosphoprotein of mouse ascites sarcoma cells

A 110K-dalton phosphoprotein previously was isolated from the nucleoli of mouse ascites sarcoma cells. The localization of this phosphoprotein in the nucleoli was confirmed by an indirect immunofluorescence assay with rabbit antisera to the phosphoprotein. This phosphoprotein formed a complex of 280K daltons with a nonphosphoprotein of 32K daltons in a molar ratio of 1 to 1. The protein complex dissociated in the presence of 6 M guanidine hydrochloride or 1% sodium dodecylsulphate. The nucleolus-specific phosphoprotein complex bound preferentially to nucleolar DNAs other than the ribosomal RNA gene in vitro and located in nucleosomes prepared from the nucleoli. The major phosphoamino acid in the phosphoprotein was phosphoserine, and slight though significant amounts of phosphotyrosine and phosphothreonine also were detected. These phosphorylated amino acids were concentrated in a specific polypeptide fragment of about 30K daltons obtained by partial digestion with V8 protease. The phosphoprotein was phosphorylated in vitro by the protein kinase activity presented in the complex itself.

Dihydrofolate reductase gene expression in cultured mouse cells is regulated by transcript stabilization in the nucleus

Methotrexate-resistant cells, which contain a 500-fold amplification of dihydrofolate reductase (DHFR) genes, were used as a model system for studying the regulation of DHFR gene expression during growth stimulation. We have shown that a threefold increase in DHFR mRNA levels following growth stimulation results from a corresponding increase in DHFR mRNA production (i.e., delivery to the cytoplasm) and is not the result of a change in DHFR mRNA half-life. We previously showed that the increase in DHFR mRNA production during growth stimulation is not accompanied by an increase in the relative rate of transcription of the DHFR gene. This suggested that changes in DHFR mRNA production during growth stimulation are due to changes in the stability of DHFR transcripts in the nucleus. Using continuous labeling experiments in vivo comparing the stability of DHFR RNA with specific reference sequences, we show that in growing cells most DHFR transcripts were converted to mRNA, whereas in resting cells the majority of DHFR transcripts were rapidly degraded in the nucleus. There was no significant difference in the rate of processing and transport of stable DHFR transcripts. Therefore, changes in the stability of DHFR RNA in the nucleus control the amount of mRNA available for translation in the cytoplasm.

Analysis of methylglyoxal bis(guanylhydrazone)-induced alterations of hamster tumor mitochondria by correlated studies of selective rhodamine binding, ultrastructural damage, DNA replication, and reversibility

Because of the renewed importance of methylglyoxal bis(guanylhydrazone) (MGBG) in recent clinical trials for a variety of cancers, and because the antiproliferative activity of MGBG cannot be accounted for exclusively by the known inhibition by the drug of polyamine biosynthesis, but is thought to involve an alternative action in which the mitochondria are implicated, we have investigated several new aspects of the nature and reversibility of this mitochondrial damage. Using Rous sarcoma hamster tumor cells as a model, treatment of monolayer cultures during exponential growth with 10, 25, and 50 microM MGBG (up to 48 hr) resulted in dose-dependent (reversible) growth inhibition and selective ultrastructural damage to the mitochondria (e.g., extreme swelling, loss of cristae and matrix components, and dense inclusions) in up to 96% of cells, while nuclei appeared normal, corroborating and extending findings by others in mouse, rat, and human cells. Mitochondria in 3 to 5% of cells failed to swell, even at highest drug dosage, but were of unusual structure. After removal of MGBG, damaged mitochondria in 90 to 95% of cells recovered near-normal ultrastructure within 1 to 2 days; in some cells, mitochondrial recovery from severe damage could be monitored following a lag period of up to 5 days. The potential-dependent, supravital fluorescent probe rhodamine 123 (RH 123) selectively and relatively uniformly stained the grossly enlarged mitochondria, strikingly delineating residual organelle membranes. Quantitative assays of the uptake and retention of RH 123/10(6) cells demonstrated the maintenance of mitochondrial membrane potential in both control and MGBG-treated cell populations. These data also support the concept of mitochondrial fusion in MGBG-treated cells. The fate of mitochondrial DNA (mtDNA) both during (24 to 48 hr) and following (7 hr to 7 days) MGBG treatment was monitored by ultrastructural, electron autoradiographic, pulse-labeling, gradient centrifugation, restriction cleavage, and electrophoretic methods. MGBG treatment (50 microM; 7 and 16 hr) selectively inhibited mtDNA replication (73% at 16 hr) prior to significant inhibition of nuclear DNA synthesis (19% at 16 hr); the drug induced structural alterations, without substantial degradation, of the closed circular (major form) of mtDNA, and cessation of D-loop strand (7S) initiation within the replication origin. Upon return to drug-free medium, mtDNA resumed replicative activity, and mtDNA fibrils appeared to be associated with regenerating cristae, as assessed by electron microscopy. The combined results demonstrate mitochondria to be a selective target of MGBG action, and define structu

Nude mice as models for human leukemia studies

Human leukemic promyelocytes of the HL-60 line were grown as tumors in nude mice and studied. A single nonmetastatic granulocytic sarcoma developed after subcutaneous inoculation with HL-60 cells. Some exceeded 5 cm in size. Almost all mice developed tumors after initial priming with cyclophosphamide. Older sarcomas showed viable tumor islands in necrotic and fibrotic tissue. Some tumors appeared greenish. Histologic and electron-microscopic analysis demonstrated large, vaguely outlined cells in poorly vascularized sheets. The cells displayed high nucleocytoplasmic ratios, basophilic granular cytoplasms lacking Auer rods, and enzymes characteristic of cultured HL-60 promyelocytes. Some tumor cells also demonstrated monocyte/macrophage enzymes, such as butyrate esterase. Induced HL-60 tumors also corresponded morphologically to a human subcutaneous promyelocytic tumor specimen. Comparative cytologic studies of induced HL-60 tumors in nude mice and cultured HL-60 cells revealed virtual identity, suggesting the nude mouse tumor as a useful model for in vivo studies of human leukemic cells.

Unphosphorylated gelsolin is localized in regions of cell-substratum contact or attachment in Rous sarcoma virus-transformed rat cells

Regions associated with cell-substratum contact or attachment in Rous sarcoma virus (RSV)-transformed rat fibroblasts (RR1022 cells) were identified by reflection-interference microscopy. Electron microscopy of such regions revealed the presence of discrete membrane-associated structures composed of a paracrystalline lattice of hexagons and pentagons to which actin filaments appear to be attached. Staining of actin by biotin-labeled heavy meromyosin showed that transformed cells, unlike normal fibroblasts, lack prominent actin fibers, and that, instead, much of the fluorescence is concentrated in loci corresponding to locations of transient association between the cell and the substratum. In stationary cells, such loci were found in rosette formation, predominantly in the region beneath the nucleus. In cells engaged in active movement, such as during migration into a wound, the actin-containing spots were concentrated in the region of the leading edge. A similar pattern of staining was observed with antibody to gelsolin, a 91,000-dalton Ca2+-dependent actin filament-shortening protein. Since the action of gelsolin on actin is reversible and dependent on physiologically relevant changes in calcium concentration, the localization of gelsolin, together with actin-bundling proteins such as alpha-actinin, in the regions containing many small microfilament bundles on the ventral side of cytoplasm suggests that gelsolin may be a component of the mechanism for the disassembly and assembly of actin during the dissolution and reformation of structures for cell-substratum contact during cell locomotion. Regulation of gelsolin activity was not dependent on protein phosphorylation, as shown by lack of 32P-incorporation into gelsolin in either transformed or normal fibroblasts.

Demonstration of virus particles in Moloney murine sarcoma virus-induced periosteal bone in mice

Balb/c mice were inoculated intramuscularly with Moloney murine sarcoma virus in one of the hind legs. This led to the rapid development of a regressive sarcoma and also to the proliferation and osteogenic differentiation of cells in the adjacent periosteum. Examination of the tissues by transmission electron microscopy revealed the presence of type A and C virus particles within the sarcoma cells as well as within the cells of the newly formed bone. Extracellular type C virus particles were formed by budding from the cell surface and by release from disintegrating cells. No virus particles were found in the bone or the surrounding soft tissues of the contralateral, noninfected leg. These observations suggest that viral infection of periosteal cells are at least partly responsible for the osteogenic response associated with the virus-induced sarcoma. Production of growth factors by the sarcoma cells could also contribute to this process.