Activation of C-myc, C-Neu and int-2 oncogenes in the transformation of the human breast epithelial-cell line mcf-10f treated with chemical carcinogens in-vitro

Genetic alterations of the c-myc, c-neu and int-2 oncogenes have been reported in human breast cancer. In order to determine if these oncogenes are activated at different stages of breast cancer progression, we are using an in vitro system in which human breast epithelial cells (MCF-10F) have been transformed with benzo(a)pyrene(BP) or dimethylbenz(a)anthracene (DMBA). DMBA-treated cells gave rise to clones D3 and D3-1, BP-treated cells gave rise to clones BP1 and BP1-E. BP1-E cell line, derived from BP1 cell line, was tumorigenic in SCID mice. Southern blot analysis detected gene amplification and rearrangement of the int-2 oncogene in BP1 and BP1-E cells, but no changes were detected in D3 and D3-1 cells. Amplification of c-neu gene was only observed in BP1 and BP1-E cell lines. Neither amplification nor rearrangement was detected for the c-myc gene. At the transcriptional level, Northern blot analysis showed that int-2 mRNA was increased 1.5, 1.8, 1.3 and 2.0-fold in the BP1, BP1-E, D3 and D3-1 cell lines respectively. c-neu mRNA was increased 8.0-fold in BP1 and BP-1E cells and c-myc mRNA was increased 1.5-fold in D3 cells, but no changes were detected in the other cell lines. The data indicate that BP treatment induces changes both at the genomic and transcriptional level. However, none of the differences explain the tumorigenic properties of the BP1-E cell line. DMBA treatment induces changes that are only reflected at transcriptional level for the two oncogenes studied. Whereas none of these oncogenes can be considered the driving force in the expression of the tumorigenic phenotype, the interaction among them or with other oncogenes in the expression of the transformation phenotype cannot be ruled out.

Specific transforming growth factor-beta subtypes regulate embryonic mouse Meckel's cartilage and tooth development

Members of the transforming growth factor-beta (TGF-beta) superfamily have emerged as critical regulators for cell growth and differentiation. Whereas the different TGF-beta subtypes are equipotent in the majority of biological assays using cell lines cultured in vitro, there are indications that in more complex systems involving epithelial-mesenchymal interactions, the TGF-beta subtypes differ in their biological activities. To test the hypothesis that TGF-beta subtypes specifically regulate either Meckel's cartilage or tooth morphogenesis, we designed experiments to compare loss of function effects of TGF-beta 1, TGF-beta 2, and TGF-beta 3 subtypes using a serumless, chemically defined medium to culture embryonic mouse E10 (42-44 somite pairs) mandibular explants. The major effect of loss of function resulting from abrogation of TGF-beta 1 using antisense treatment resulted in a 20% increase (P < 0.05) in chondrocyte number, a decrease in extracellular matrix, and dysmorphology of the rostral region of Meckel's cartilage. Exogenous TGF-beta 1 provided indistinguishable recovery to the normal phenotype. TGF-beta 2 antisense treatment produced a threefold enlargement (P < 0.05) of tooth organs and advanced their development to the cap stage. TGF-beta 2 provided recovery to the normal phenotype (e.g., reduced tooth size and development to the bud stage), whereas TGF-beta 1 or TGF-beta 3 polypeptides had no effect. TGF-beta 3 antisense treatment resulted in a reduction of approximately 15% in the length of Meckel's cartilage. We interpret these results to suggest that TGF-beta 1 functions to regulate the number of chondrogenic cells, the amount of extracellular matrix, and the rate of developmental assembly of the rostral to posterior segments in forming Meckel's cartilage. TGF-beta 2 appears to regulate tooth size and stage of development without affecting cartilage. TGF-beta 3 appears to regulate Meckel's cartilage size without altering tooth size or shape. The results are discussed in terms of the regulatory functions of the TGF-beta subtypes during embryonic craniofacial morphogenesis.

DNA synthesis and development strategies with possible consequences on sexual dimorphism in adult mouse submandibular glands

This article summarizes a series of recent studies that broaden the criteria for sexual dimorphism in adult mouse submandibular gland. From these observations, a hypothesis is presented, suggesting that the gross histological differences that are characteristic of adult sexual dimorphism in the gland secondarily result from differences in the activities of three fundamental cellular processes, that is, rates of cell proliferation, cell sizes, and ongoing patterns of differentiation.

Parenchymal cell proliferation and mechanisms for maintenance of granular duct and acinar cell populations in adult male mouse submandibular gland

To evaluate proliferation as a factor in maintenance of parenchymal cell populations in adult male mouse submandibular glands, a variety of surveys were conducted following a pulse with 3H-thymidine. Striated granular duct (SGD) cells had the highest labeling index, followed by intercalated duct (ID) cells, then acinar (AC) cells, and granular duct (GD) cells had the lowest. These cell types showed from 30% to 60% completion of mitosis by 24 hr, with SGD, AC, and GD showing a likely second wave of mitosis sometime between 2 and 7 days after the pulse. About 40% of the pulse-labeled cells still remained as single cells at 42 days after the pulse. Repeat divisions in daughter cells of the primary labeled cells were very rare. A shift in the pattern of labeled cells at the ID-GD junction indicates that ID and SGD cells in this compartment are differentiating to GD cells. Further comparison of the magnitude of this conversion with the amount of noncompartmental GD cell proliferation provided a basis for calculating that approximately 70% of GD cell population maintenance occurs by self-proliferation, and the remaining 30% is contributed by differentiation from ID and SGD cells. A similar survey at the ID-acinus junction showed no evidence of conversion of ID cells to AC cells indicating that most, if not all, proliferative activity leading to AC cell population maintenance occurs by self-proliferation. Finally, based in part on structural changes at the ID-GD junction during the survey period, a pattern of cell conversion described as "in situ differentiation" is proposed. When this pattern is carried to fruition, this explains several structural features of the secretory complex typical to the male pattern submandibular gland. The proposed mechanism is supported by a three-dimensionally reconstructed sequence of likely intermediate structures.

Proliferative and structural differences between male and female mouse submandibular glands

Sexual dimorphism has been observed in salivary glands of many species. In this study, evidence for sexual differences in adult mouse submandibular gland is extended beyond parenchymal cell composition, size, and volumes to include patterns of DNA synthesis and complexity of ductal branching. Computer-assisted three-dimensional reconstructions also revealed differences in overall organization of secretory complexes. Consistent with observations by others, granular intercalated duct cells were absent, while striated granular duct cells were low in proportion in the male glands relative to female glands. When the mean of average cell volumes were compared, acinar (AC) cells were smaller than granular duct (GD) cells in the male, but in the female the reverse was true. Furthermore, in addition to differences in average volumes of GD cells, the average volume of AC cells was significantly greater in females than males. The most dramatic evidence for sexual dimorphism was observed following a 90-min labeling with 3H-thymidine. Though all cell types showed DNA replication activity, the intercalated duct (ID) cells were substantially more active than AC and GD cells in the female, while in the male the GD cells, ID cells, and AC cells all showed approximately equal activity. Three-dimensional reconstructions indicated that the female possessed a more highly branched intercalated duct system and that the GD usually terminated within a secretory complex, whereas in males the GD typically passes through a secretory complex and forms a prominent cap-like structure on the opposite side.

Gene expression, signal transduction and tissue-specific biomineralization during mammalian tooth development

Tooth development provides a paradigm for intrinsic molecular controls for cell- and extracellular matrix (ECM)-mediated biomineralization. The intent of this review is to evaluate the sequential timing and positional information prerequisite for tissue-specific biomineralization. Recent investigations suggest that 1,25-dihydroxyvitamin D3 functions to up-regulate VDR (vitamin D receptor) that in turn could induce structural gene products, including calcium-binding proteins and several ECM proteins (e.g., enamelins, amelogenins, dentine sialoglycoproteins (DSP) and dentine phosphoproteins (DPP)), resulting in dentine and enamel formation. Inhibition of regulatory gene products and/or their receptors likely results in hypoplastic and/or hypomineralized ECM as a direct consequence of down-regulated (1) transcription and/or translation of structural and regulatory genes, (2) posttranslational modifications, (3) and/or decreased calcium transport to the forming dentine and enamel matrices. Advances in serumless in vitro culture methodology; computer-assisted access to nucleic acid sequences for probes to define when, where, and how many specific regulatory and structural gene products are expressed; antisense oligodeoxynucleotides to inhibit specific translation; and microtechniques to analyze biomineralization all provide additional avenues to investigate tissue-specific biomineralization.

Three-dimensional localization of DNA synthesis in secretory elements of adult female mouse submandibular gland

A system based in part on three-dimensional structural relationships is described for precisely characterizing the location of cells within secretory complexes of the adult female mouse submandibular gland. The pattern of DNA synthesis during a 90-minute pulse with 3H-thymidine was characterized based upon the above system. Seventy-eight percent of all radiolabeled nuclei were found in the intercalated duct system. One-half of these were in second-order intercalated ducts. DNA synthesis was also observed in acinar cells, granular intercalated duct cells, striated granular duct cells, and granular duct cells. Some secretory complexes contained multiple radiolabeled nuclei, with some of these nuclei in a side-by-side configuration. Approximately one-half of all secretory complexes contained radiolabeled nuclei. A second survey of the frequency of complexes containing radiolabeled nuclei was conducted following four pulses at eight-hour intervals over a 26-hour period. Only about 30% of all complexes contained radiolabeled nuclei. This reduction in the frequency of radiolabeled nuclei when compared with the single pulse suggests the possibility of individual variation. However, a more prolonged period of daily injections for nine days with 3H-thymidine resulted in all but one of the secretory complexes containing radiolabeled nuclei. This latter observation suggests that cell addition in adult submandibular glands is widespread.

Three-dimensional reconstruction of adult female mouse submandibular gland secretory structures

Computer-assisted reconstructions of adult female mouse submandibular gland have been used to positionally characterize within the three-dimensional structure likely intermediates in secretory cell replacement. The locations of striated granular duct cells and granular intercalated duct cells are consistent with a role as intermediates between intercalated duct cells and granular duct cells or acinar cells, respectively. Average volumes of the two putative intermediate cell types are also consistent with this role. The reconstructions suggest that, in addition to a "streaming" mechanism for secretory cell replacement, formation of new secretory structures composed of multiple acini and second-order intercalated ducts may also contribute to the cell replacement process.

Appearance of acinar-cell-specific mucin in prenatal mouse submandibular glands

The appearance of an acinar-cell-specific mucin was studied during fetal mouse submandibular gland development. The mucin was first detected in stage 23 and was quantitated through birth by radioimmunoassay (RIA). Quantitation results showed that the mucin accumulation was biphasic. Results from Western blotting and radioimmunoassay indicated that the mucin from the prenatal glands was similar both antigenically and in size to the mucin isolated from adult mice. Observations from light microscopy revealed a continuing progression of complexity throughout prenatal development, indicative of morphogenesis characteristic of differentiating exocrine tissues. When sections from various stages were compared morphometrically, it became clear that the overall ratio of epithelial cells to mesenchymal cells increased nearly 6-fold throughout the prenatal stages observed. The study suggests that acinar cell development in the mouse submandibular gland passes through a protodifferentiated stage. The proportions of epithelial and mesenchymal cells in the submandibular gland and the sensitivity of the RIA indicate that the mucin per cell actually increased to detectable levels at the onset of protodifferentiation, and this increase does not reflect a change in the relative proportions of epithelial and mesenchymal cells.

Three-dimensional movement analysis of lateral pterygoid electromyographic activity during mastication in the rat

Simultaneous recordings of mandibular movement in three dimensions (frontal, horizontal and sagittal plane), and lateral pterygoid electromyographic (EMG) data during mastication of pellets and slurry, were collected from 5 rats by the opto-electronic mandibular tracking (OMT) method and computerized digital-processing of the EMG wave-forms. The microcomputer analyses allowed determination of frontal-, horizontal- and sagittal-plane movement displacements and velocities for whole chew cycles and, during lateral pterygoid activity, opening burst (OB) and closing burst (CB) latencies. There were significant (p less than or equal to 0.01) differences between duration, displacement and velocity data from slurry and pellet chew cycles. OB latencies were significantly (p less than or equal to 0.01) longer than CB, and OB displacements started significantly (p less than or equal to 0.01) farther from minimal gape than CB ones. Working-side OB activity occurred as the mandible moved inferiorly, laterally and posteriorly; working-side CB activity occurred as the mandible moved superiorly, medially and anteriorly. A secondary peak of OB activity, coinciding with anterior sagittal translation during the last third of mandibular depression, was detected; this may represent independent activity of the rat superior lateral pterygoid effecting anterior translation of the mandibular-joint disc and capsule. Rat lateral pterygoid activity has the same basic, bimodal pattern (active during both mandibular depression and elevation) as is found in humans.

Role of extracellular iron in the action of the quinone antibiotic streptonigrin: mechanisms of killing and resistance of Neisseria gonorrhoeae

The quinone antibiotic streptonigrin is believed to kill bacteria by promoting formation of oxygen radicals. This antibiotic has also been used to select resistant bacterial mutants, some of which vary in iron utilization. We examined the effects of streptonigrin on Neisseria gonorrhoeae and several types of gonococcal mutants. Streptonigrin (0.025 microgram/ml) efficiently killed gonococcal strain FA1090, and this effect depended on iron. Streptonigrin-resistant mutant FA6271 had normal iron uptake but was moderately deficient in total iron. Resistance most likely resulted from failure of FA6271 to divert electrons to streptonigrin, as demonstrated by a reduction in KCN-insensitive respiration (a hallmark of the action of quinones) and superoxide formation. Other mutants selected for inability to use human iron-binding proteins (strains FA6273 and FA6275) had no increase in streptonigrin MIC and no decrease in KCN-insensitive respiration. Mutants did not demonstrate an increase in superoxide dismutase or catalase. Streptonigrin killing of gonococci depended on a reaction(s) in which extracellular iron was important, presumably because iron was required for catalysis of hydroxyl radical. The results suggest that a membrane component may be a target for the actions of streptonigrin.

Stimulated human neutrophils limit iron-catalyzed hydroxyl radical formation as detected by spin-trapping techniques

Neutrophils stimulated with phorbol myristate acetate (PMA) in the presence of the spin trap 5,5-dimethyl-1-pyrroline 1-oxide (DMPO), dimethyl sulfoxide, and diethylenetriaminepentaacetic acid (DETAPAC) fail to generate hydroxyl radical (.OH), detected as the methyl spin-trapped adduct of DMPO (2,2,5-trimethyl-1-pyrrolidinyloxyl, DMPO-CH3), unless ferric salts (Fe3+) are also added (Britigan, B. E., Rosen, G. M., Chai, Y., and Cohen, M. S. (1986) J. Biol. Chem. 261, 4426-4431). Even then, .OH formation wanes in spite of ongoing superoxide (O2-.) production. In contrast, ferric salt supplementation of a hypoxanthine/xanthine oxidase O2-. generating system containing DETAPAC produces continual .OH, suggesting that neutrophils limit the formation of this free radical. To evaluate this hypothesis, neutrophil cytoplasts (largely devoid of granules but able to generate O2-.) were stimulated with PMA in the presence of Fe3+, DETAPAC, dimethyl sulfoxide, and DMPO. This resulted in continual production of DMPO-CH3. In the presence of dimethyl sulfoxide, HL-60 (promyelocytic) cells differentiate into cells similar in morphology and O2-. generating capacity to neutrophils. However, their granules lack the iron-binding protein lactoferrin (LF). Ferric salt supplementation of HL-60 cells stimulated with PMA yielded an EPR spectrum similar to cytoplasts. Supernatant obtained following PMA-induced neutrophil degranulation (which releases LF extracellularly) suppressed DMPO-CH3 formation by the hypoxanthine/xanthine oxidase/Fe3+/DETAPAC system. Anti-LF antibody, but not anti-transferrin antibody, prevented stimulated neutrophil supernatant inhibition of hypoxanthine/xanthine oxidase/Fe3+/DETAPAC-mediated .OH formation. Similarly, neutrophils stimulated with PMA in the presence of Fe3+, DETAPAC, and anti-LF antibody (but not anti-transferrin antibody) demonstrated continual formation of .OH. Neutrophil degranulation of LF limits Fe3+-catalyzed .OH formation which in vivo could protect tissue from possible .OH-mediated injury.

Do human neutrophils make hydroxyl radical? Determination of free radicals generated by human neutrophils activated with a soluble or particulate stimulus using electron paramagnetic resonance spectrometry

Using electron paramagnetic resonance spectrometry and the spin trap 5,5-dimethyl-1-oxide (DMPO), neutrophil free radical production in response to phorbol myristate acetate and opsonized zymosan was investigated. Using phorbol myristate acetate and zymosan (3 mg/ml), the superoxide spin-trapped adduct 2-2-dimethyl-5-hydroperoxy-1-pyrrolidinyloxyl (DMPO-OOH) and the hydroxyl spin-trapped adduct 2-2-dimethyl-5-hydroxy-1-pyrrolidinyloxyl (DMPO-OH) were detected. Only DMPO-OH was observed with zymosan (0.5 mg/ml). Hydroxyl radical production in the presence of dimethylsulfoxide (Me2SO) and DMPO yields 2,2,5-trimethyl-1-pyrrolidinyloxyl. The only 2,2-trimethyl-1-pyrrolidinyloxyl detected following neutrophil stimulation was that expected from DMPO-OOH degradation. Superoxide dismutase but not catalase inhibited generation of all three spin-trapped adducts. These data indicate that DMPO-OH arose from DMPO-OOH degradation and does not represent hydroxyl radical production. Under certain conditions DMPO-OH is the predominant spin-trapped adduct resulting from neutrophil superoxide production, perhaps due to cellular bioreduction of DMPO-OOH to DMPO-OH. Cytochalasin B, which prevents phagosome closure, inhibited zymosan-stimulated neutrophil oxygen consumption and electron paramagnetic resonance superoxide detection. No hydroxyl radical was detected. Spin trapping with DMPO appears to detect intraphagosomal free-radical formation.

Effects of human serum on the growth and metabolism of Neisseria gonorrhoeae: an alternative view of serum

Humans are the sole reservoir of Neisseria gonorrhoeae, an organism which undergoes a marked increase in metabolic rate after exposure to a low-molecular-weight, heat-stable component(s) of human serum. Further studies on the effect of serum on gonococcal metabolism were undertaken. Gonococcal broth (GCB) is commonly used for in vitro cultivation of gonococci. Gonococci suspended in GCB plus 10% serum exhibited oxygen consumption rates of 139% (P less than 0.01) and 456% (P less than 0.01) of those suspended in GCB or Hanks balanced salt solution, respectively. A twofold increase in growth rate also resulted from the addition of 10% serum to GCB. Gonococcal 14C-labeled adenine incorporation increased threefold with 10% serum supplementation of Hanks balanced salt solution. Dialysis of serum in 1,000-molecular-weight exclusion tubing removed the stimulatory factor(s). Neither correction of anion-cation concentrations altered by dialysis nor addition of substances of known importance to the metabolism of gonococci (i.e., lactate, pyruvate, cysteine, ATP, AMP, NADPH, amino acids, malate, and glutathione) to dialyzed serum reconstituted stimulatory capacity. The effect of serum on gonococcal glucose-catabolic pathways was measured by modified radiospirometry. An apparent threefold increase in Entner-Doudoroff and pentose phosphate pathway activities was induced by 10% serum, as was the increased shunting of glucose-derived glyceraldehyde-3-phosphate into these pathways. These metabolic changes did not allow specific identification of the serum stimulatory factor(s). Acetate, the major by-product of gonococcal glucose catabolism, inhibited gonococcal oxygen consumption as previously reported. A high-molecular-weight serum component, probably albumin, reversed acetate-mediated inhibition of gonococcal oxygen consumption, identifying a second mechanism by which serum increases gonococcal metabolism. These results suggest that supplementation of growth media with serum should be considered to provide N. gonorrhoeae with conditions more consistent with its normal environment.