Nitric oxide induces an increased Na+ conductance in identified neurons of Aplysia

The ionic mechanism of the effects of micropressure ejections of hydroxylamine (HOA) and sodium nitroprusside (SNP), nitric oxide (NO) generators, on the membrane of identified neurons (R9-R12) of Aplysia kurodai was investigated with conventional voltage-clamp, micropressure ejection, and ion-substitution techniques. Micropressure ejection of HOA and SNP onto the neurons caused a marked depolarization in the unclamped neurons. Clamping the same neurons at their resting potential level (-60 mV) and reejecting HOA and SNP with the same dose produced a slow inward current (Ii(HOA) and Ii(SNP), 3-7 nA in amplitude, 15-60 s in duration) associated with an increase in input membrane conductance. Bath-applied hemoglobin (50 microM), a nitric oxide scavenger, almost completely blocked Ii(HOA) and Ii(SNP), and 3-isobutyl-1-methylxanthine (IBMX, 50 microM) prolonged and enhanced both Ii(HOA) and Ii(SNP). An intracellular injection of cyclic guanosine 3',5'-monophosphate (cGMP) into the same neurons produced a slow inward current (Ii(cGMP)) which resembled the responses to HOA and SNP, and this current was enhanced in IBMX. Bath-applied methylene blue (10 microM), an inhibitor of guanylate cyclase, significantly reduced Ii(HOA) and Ii(SNP). The inward currents induced by HOA, SNP and cGMP were sensitive to changes in the external Na+ concentration. These results suggest that extracellular NO can induce a slow inward current associated with an increase in Na+ conductance, mediated by an increase in intracellular cGMP.

Toxic and nontoxic effects of ouabain on the transmitter release from frog motor nerve terminals

Toxic and nontoxic effects of ouabain were investigated on frog neuromuscular preparation by measuring the mean quantal content of endplate potentials elicited during repetitive nerve stimulation. In the untreated normal muscles, application of 10 microM ouabain gave rise to a slow exponential increase in the transmitter release (toxic ouabain effect) with a certain delay. This delay was increased with either 100 microM amiloride, a Na(+)-Ca2+ exchange blocker, or the intracellular loading of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), a specific intracellular Ca2+ chelator. Measurements of frequency augmentation-potentiation (FAP) revealed a specific nontoxic effect of ouabain: 1 microM ouabain pivoted the long-linear FAP relation counter-clockwise without altering the intercept on the ordinate. Contrary to their action in the toxic effect, both 100 microM amiloride and the intracellular loading of BAPTA failed to counteract the nontoxic effect of 1 microM ouabain. The present results suggest that the toxic and nontoxic effects of ouabain are of different entities. The ouabain-sensitive subtype of Na+,K(+)-ATPase, which is abundant in neural tissues, seems to play a specific role in the process of nontoxic potentiation of transmitter release.

Clonal determination of uterine leiomyomas by analyzing differential inactivation of the X-chromosome-linked phosphoglycerokinase gene

To investigate the clonality of uterine leiomyomas, we developed a PCR-based method involving the differential inactivation of the X-chromosome-linked phosphoglycerokinase (PGK) gene. Small DNA samples of 22 leiomyomas from 9 Japanese patients, showing heterozygosity at the BstXI site of the PGK gene, were digested with the methylation-sensitive restriction enzyme HpaII. Only the inactive (methylated) PGK gene allele was selectively amplified by PCR followed by digestion with BstXI and electrophoresis. All leiomyoma samples consisted of a single type of inactive allele, even though alleles were detected that were specific to each nodule. The results indicated that all leiomyoma nodules were unicellular in origin but independently generated in the uterus.

Cytokine network in the central nervous system and its roles in growth and differentiation of glial and neuronal cells

Cells resident within the central nervous system (CNS) can synthesize, secrete and respond to inflammatory cytokines not only contributing to the responses to injury or immunological challenge within the CNS, but also regulating their own growth and differentiation potential. The actions and cell communication via cytokines in the CNS are designated as the CNS cytokine network, in which microglia and astrocytes play the central roles. To further characterize the CNS cytokine network we investigated the differences in roles of these cells, and found that microglia might contribute to the early phase of cytokine production reaction and that astrocytes might contribute the late phase of the reaction. We also investigated roles of inhibitory cytokines such as TGF beta, IL-4, and IL-10, and showed that each might play a distinct role in the inhibitory regulation in the CNS. We summarized our previous report about cellular distribution of cytokine receptors in the CNS cells and discussed their roles in the CNS cytokine network. Finally, we investigated that expression of IL-6 and IL-2 receptors in neuronal and oligodendrocytic differentiation, respectively. From these results, we discussed the features of the CNS cytokine network.

Effects of inhibitors of ouabain-sensitive Na+, K(+)-ATPase and Li+ ions on the neuromuscular transmission of the frog

The effect of blockade of ouabain-sensitive alpha 2 and alpha 3 (neural type) isozymes of Na+, K(+)-ATPase was investigated on frog neuromuscular preparations by recording the frequency augmentation-potentiation (FAP) of the endplate potential, an electrophysiological and neuropharmacological technique to analyze the drug actions on the release process of the readily releasable transmitter quanta. Erythrosin B, which was thought to selectively inhibit the neural type Na+, K(+)-ATPase, pivoted the log-linear FAP relation counterclockwise without altering the intercept on the ordinate. Chlormadinone had a similar action. An increase in the concentration of extracellular K+ ions pivoted the FAP relation clockwise with a concomitant upward shift of the intercept on the ordinate, and low K+ Ringer's solution produced an inverse effect. In contrast, Li+ ions shifted the FAP relation upwards dose-dependently leaving its slope unchanged. Cinnarizine, a blocker for inositol-1,4,5-trisphosphate-induced Ca2+ release, and 5,5'-dimethyl-1,2-bis(2-amino-phenoxy)ethane-N,N,N',N'-tetraacetic acid, a specific intracellular Ca2+ chelator, significantly antagonized the potentiating action of Li+. The ouabain-sensitive neural type Na+, K(+)-ATPase isozyme, which is abundant in neural tissues, seems to play an important role in stimulation frequency-dependent modulation of the quantal transmitter release such as FAP.

Production of interleukin-10 by mouse glial cells in culture

In this study, we examined the production of IL-10 by glial cells in vitro. IL-10 was detected in the culture supernatants of microglia and in the cell lysate of astrocytes by enzyme-linked immunosorbent assay. We also detected IL-10 mRNA and IL-10 receptor mRNA in both microglia and astrocytes. The expression of IL-10 mRNA, as well as the production of IL-10 protein, was enhanced by the stimulation of these cells with lipopolysaccharide(LPS). Recombinant IL-10 effectively suppressed both LPS-induced cytokine production and IFN-gamma-induced class II major histocompatibility complex antigen expression by microglia. These results suggest that IL-10 is produced in the CNS and plays a role as an inhibitory regulator in the CNS cytokine network.

Inhibitory effect of vasoactive intestinal peptide (VIP) on phagocytosis in mouse peritoneal macrophages

The effect of VIP on phagocytosis in peritoneal macrophages was examined by means of flow cytometry (FCM). This assay revealed that VIP suppressed phagocytosis in a dose-dependent manner. VIP(1-12) did not suppress phagocytosis. VIP(10-28) was more suppressive than VIP(1-28). A known VIP-antagonist (N-Ac-Tyr1,D-Phe2)-growth hormone-releasing factor (GRF) (1-29)-NH2 suppressed phagocytosis less than VIP. Control phagocytosis was partially suppressed in Ca(2+)-free solution. Phagocytosis was suppressed by VIP further in Ca(2+)-free solution than in the normal solution. Phagocytosis was suppressed in a known phosphodiesterase inhibitor IBMX-containing solution. The degree of suppression by VIP was the same in the presence or the absence of IBMX. These results suggest that VIP suppresses extracellular Ca(2+)-dependent and -independent phagocytosis, that the C-terminal fragment of VIP is essential for VIP action, that the suppression is mediated by cAMP and that the inhibition of macrophage phagocytosis by VIP is one of the mechanisms which modulates immune responses by the nervous system.

Molecular cloning and functional expression of a mouse cytochrome P-450 (Cyp3a-13): examination of Cyp3a-13 enzyme to activate aflatoxin B1 (AFB1)

A cDNA encoding a novel member of the cytochrome P-450 superfamily, Cyp3a-13, has been isolated from mouse liver cDNA library by hybridization screening. The Cyp3a-13 encoded 503 amino acid residues and shared 71% amino acid identity with Cyp3a-11. When Cyp3a-13 cDNA was expressed in CR119 cells which had been established as a cell line stably expressing NADPH-cytochrome P-450 reductase cDNA of guinea pigs, aflatoxin B1-dependent cytotoxicity was observed. This cytotoxicity was enhanced by alpha-naphthoflavone (7,8-benzoflavone), which is known to augment the CYP3A enzymatic activity. The results indicate that CYP3A in mice, which are relatively insensitive to aflatoxin B1, can activate aflatoxin B1 to a genotoxic product.

Induction of MHC class II antigen expression on murine microglia by interleukin-3

The effects of various cytokines on MHC class II antigen expression were examined in murine microglia. Interleukin-3 (IL-3), as well as interferon-gamma (IFN-gamma), induced MHC class II antigen expression on these cells. IL-3 additionally enhanced MHC class II antigen expression induced by IFN-gamma. The induction of MHC class II antigen expression by IL-3 was not mediated via IFN-gamma production, because the effect was not blocked by antibodies to IFN-gamma. In contrast, granulocyte-macrophage colony-stimulating factor (GM-CSF) did not affect the expression of MHC class II antigen on naive cells and down-regulated IFN-gamma-mediated induction of MHC class II antigen expression on microglia. Because IL-3 and GM-CSF are apparently produced in the central nervous system, MHC class II antigen expression on microglia may be regulated by these cytokines synthesized in the central nervous system.

Implantation and growth of epidermal growth factor (EGF) receptor expressing human ovarian cancer xenografts in nude mice is dependent on EGF

BACKGROUND

The importance of epidermal growth factor (EGF) receptor-dependent growth has not been clarified for in vivo growth of primary human ovarian cancers.

METHODS

Seventeen primary human ovarian cancer tissue samples were examined for the presence of EGF receptors by a 125I-EGF-binding study. Three groups of mice were inoculated with EGF receptor expressing and not-expressing cancer tissues. The groups were as follows: control group, Sx group (mice that underwent sialoadenectomy; EGF depleted mice), and Sx+EGF (EGF-replaced) group. The ability of the inoculated tissues to implant and grow then was studied.

RESULTS

Of the 17 primary ovarian cancers, 12 expressed EGF receptors and 5 did not. Eight of 12 EGF-receptor expressing cancer tissues implanted and formed growing tumors in control animals. None implanted in the Sx animals. Epidermal growth factor receptor-expressing cancers implanted in Sx animals that received EGF administration. Two of five EGF receptor-negative ovarian cancers implanted and grew in both control and Sx animals.

CONCLUSION

Growth of EGF receptor-expressing primary human ovarian cancers may be dependent on EGF in vivo.

Developmentally regulated expression of a murine receptor-type protein tyrosine phosphatase in the thymus

Reversible phosphorylation of tyrosine residues plays a crucial regulatory role in various cellular events, including differentiation and proliferation of lymphocytes. Here, we report the isolation of a murine receptor-type protein tyrosine phosphatase (PTP), mRPTP-sigma, which is expressed in both immature thymocytes and stroma cells. At least two alternatively spliced transcripts of mRPTP-sigma (T and B) were observed. mRPTP-sigma T was the dominant form in the thymus and had three Ig-like and eight fibronectin type III-like domains in the extracellular portion. mRPTP-sigma T was almost identical with RPTP-sigma/PTP NE-3/PTP-P1/CPTP1, a PTP recently cloned from rat brain, except that RPTP-sigma/PTP NE-3/PTP-P1 was about 400 amino acids shorter than mRPTP-sigma T. mRPTP-sigma B, the second form of mRPTP-sigma, was dominant in the brain and was most likely the murine counterpart of RPTP-sigma/PTP NE-3/PTP-P1. In the developing thymocytes, the expression of mRPTP-sigma was high in double negative (CD4-CD8-), low in double positive (CD4+CD8+), and marginal in single positive (SP; CD4+CD8- or CD4-CD8+) subpopulations. No upregulation of mRPTP-sigma was observed in the spleen cells stimulated with Con A. Developmental regulation of mRPTP-sigma expression suggests its involvement in the control of T lymphocyte differentiation.

Developmentally regulated expression of a murine receptor-type protein tyrosine phosphatase in the thymus

Reversible phosphorylation of tyrosine residues plays a crucial regulatory role in various cellular events, including differentiation and proliferation of lymphocytes. Here, we report the isolation of a murine receptor-type protein tyrosine phosphatase (PTP), mRPTP-sigma, which is expressed in both immature thymocytes and stroma cells. At least two alternatively spliced transcripts of mRPTP-sigma (T and B) were observed. mRPTP-sigma T was the dominant form in the thymus and had three Ig-like and eight fibronectin type III-like domains in the extracellular portion. mRPTP-sigma T was almost identical with RPTP-sigma/PTP NE-3/PTP-P1/CPTP1, a PTP recently cloned from rat brain, except that RPTP-sigma/PTP NE-3/PTP-P1 was about 400 amino acids shorter than mRPTP-sigma T. mRPTP-sigma B, the second form of mRPTP-sigma, was dominant in the brain and was most likely the murine counterpart of RPTP-sigma/PTP NE-3/PTP-P1. In the developing thymocytes, the expression of mRPTP-sigma was high in double negative (CD4-CD8-), low in double positive (CD4+CD8+), and marginal in single positive (SP; CD4+CD8- or CD4-CD8+) subpopulations. No upregulation of mRPTP-sigma was observed in the spleen cells stimulated with Con A. Developmental regulation of mRPTP-sigma expression suggests its involvement in the control of T lymphocyte differentiation.

Symptomatic middle cerebral artery stenosis and occlusion: comparison of three-dimensional time-of-flight magnetic resonance angiography with conventional angiography

The usefulness of magnetic resonance (MR) angiography using the three-dimensional time-of-flight method for the characterization of symptomatic middle cerebral artery (MCA) occlusive lesions was evaluated in 10 patients with MCA occlusion and 10 with MCA stenosis. All lesions were symptomatic and documented by conventional angiography. There was no false-negative MR angiogram that failed to demonstrate the MCA occlusive lesion. MR angiography correctly evaluated the location of lesions and the difference between stenosis and occlusion. Stenosis appeared as a focal signal loss (< 1.0 cm) of the MCA at the site of stenosis, and occlusion as a complete signal loss of the MCA distal to the site of occlusion. However, MR angiography could not distinguish diffuse stenosis and one point stenosis demonstrated by conventional angiography. MR angiography is a useful noninvasive diagnostic method for evaluating occlusive lesions of the MCA in symptomatic patients.

Studies on the mechanism controlling generation of superoxide radical in luteinized rat ovaries during regression

The mechanism regulating the luteolytic release of superoxide radical (SOR) was examined in prostaglandin F2 alpha (PGF2 alpha)-treated rats. Tail vein injection of PGF2 alpha caused a rapid increase in SOR in mitochondria and plasma membrane samples prepared from luteinized rat ovaries. The peak in the mitochondria preceded that in the plasma membrane, and both occurred before progesterone concentrations decreased in the blood. The amount of SOR produced was greater when samples from the plasma membrane, mitochondria, and cytosol were combined. In plasma membrane samples, SOR generation was lowered by inhibitors of intracellular signaling pathways, but not by cyanide, which blocks electron transport in respiratory enzymes. In mitochondria samples, however, SOR was blocked by cyanide, but not by inhibitors of intracellular signaling enzymes. The addition of phospholipase-A2, phorbol myristate acetate (protein kinase-C activator), or arachidonic acid stimulated SOR production in plasma membrane samples from ovaries of control rats, and phorbol myristate acetate and arachidonic acid inhibited LH-stimulated progesterone secretion in dispersed rat luteal cells. Also, when mitochondria prepared from ovaries of PGF2 alpha-treated rats were added to dispersed corpus luteum cells, there was an increase in SOR generation and an inhibition of LH-stimulated cAMP formation and progesterone secretion. These results indicate that SOR production in the corpus luteum after PGF2 alpha treatment is generated by several subcellular components. Formation in the plasma membrane may be initiated by SOR generation from the mitochondria and regulated by intracellular signaling pathways. Our results indicate that formation of SOR may lead to the disruption of LH stimulation of progesterone secretion.

Suppression of phagocytosis by adrenocorticotropic hormone in murine peritoneal macrophages

Phagocytosis of latex beads by peritoneal macrophages was examined by means of flow cytometry (FCM). This assay revealed that adrenocorticotropic hormone (ACTH) suppressed phagocytosis in a dose-dependent manner. ACTH (1-24) was more suppressive than ACTH (1-39). Control phagocytosis was partially suppressed in Ca(2+)-free solution. Phagocytosis was suppressed by ACTH in this solution to the same degree as in the normal solution. Suppression by ACTH was reduced in phosphodiesterase inhibitor-containing solution. These results suggest that (1) ACTH suppresses extracellular Ca(2+)-dependent and -independent phagocytosis, (2) the suppression is not mediated by cAMP and (3) the inhibition of macrophage phagocytosis by ACTH is one of the mechanisms that modulate immune responses in stressful situations.

Expression of cytokines during glial differentiation

Astrocytes and microglia produce a variety of cytokines, some of which may have roles in the proliferation and differentiation of glial cells during development in the central nervous system. Cytokine mRNAs and activities were therefore assayed during glial development in mixed glial cell cultures from newborn mouse brain. Cytokine mRNAs were also measured in mouse brain during postnatal development in vivo. Macrophage colony-stimulating factor(M-CSF) mRNA, interleukin-1 beta (IL-1 beta) mRNA and tumor necrosis factor alpha (TNF alpha) mRNA were all detected on the in vitro cultures and each showed a distinct time course of expression. IL-6 and granulocyte-macrophage colony-stimulating factor(GM-CSF) mRNAs were not detected in the cultured cells. Measurements of cytokine activity in culture supernatants as well as cytokine mRNAs in vivo gave similar results. The data suggest that IL-1, TNF alpha and M-CSF are produced in the period of gliogenesis, and that M-CSF rather than GM-CSF may promote the generation and proliferation of microglia. Although IL-6 and GM-CSF exhibit neurotrophic effects, these cytokines may not function as neurotrophic factors during early postnatal development.

[Metastasis of an adenocarcinoma of unknown origin to mediastinal lymph nodes, and transient regression]

A 67-year-old woman was admitted to our hospital because of fever. Chest roentgenogram showed an enlargement of mediastinal lymph nodes. Despite thorough examination, no definite diagnosis could be made. The mediastinal lymph nodes got smaller over the next 3 weeks and a chest roentgenogram taken 4 months later showed no mediastinal lymphadenopathy. The mediastinal lymphadenopathy and fever recurred 5 months later. She underwent thoracotomy and the mediastinal lymph nodes were excised. Microscopic examination of pretracheal lymph node specimens showed invasion of poorly differentiated adenocarcinoma associated with abundant tumor-infiltrating lymphocytes. The other lymph nodes showed sarcoid reaction. Although she has been followed for one year and 11 months, no primary site of the cancer has been found. Metastasis of cancer of unknown origin to mediastinal lymph nodes is extremely rare. It is also interesting that the lymph node swelling diminished spontaneously. The tumor-infiltrating lymphocytes and sarcoid reactions may have been immunological responses to the cancer and may have caused the transient regression.

Interleukin-4 induces proliferation and activation of microglia but suppresses their induction of class II major histocompatibility complex antigen expression

We recently found that microglia, brain macrophages, express interleukin-4 (IL-4) receptor mRNA in vitro. Since IL-4 exhibits a variety of functions on the cells of monocyte-macrophage lineage, we examined the effects of IL-4 on the functions of microglia. Recombinant IL-4 induced the proliferation of microglia in a dose- and time-dependent manner as determined by MTT colorimetric assay, [3H]thymidine uptake and bromodeoxyuridine (BrdU) incorporation. IL-4 also synergistically enhanced the proliferation of microglia with such colony-stimulating factors as IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF). It also increased acid phosphatase activity and superoxide anion formation by these cells. Despite these positive effects on proliferation and activation, IL-4 suppressed the IFN gamma-induced class II MHC antigen expression in these cells. Since these effects of recombinant IL-4 were inhibited by the addition of monoclonal antibody against IL-4 receptors, the effects of IL-4 on microglia appear to be a specific function via IL-4 receptors. Although microglia and astrocytes produce a variety of immunoregulatory cytokines, neither cell produced IL-4 as determined by bioassay or detection of IL-4 mRNA by RT-PCR method. Thus, the exogenous IL-4 may contribute to the accumulation of microglia in or around inflammatory lesions in the central nervous system, and may be involved in the regulatory mechanisms of microglia.

Alterations in free radical activity in aging Drosophila

Drosophila were examined to see if there is an increase in damage associated with free radical activity in older flies. The levels of superoxide radical and of lipid peroxides were higher in membrane samples from older flies. Also, in older Drosophila there was a significant decrease in membrane fluidity, as determined by fluorescence polarization, and an increase in ATP-dependent calcium uptake. In homogenates from whole flies, the concentration of inorganic peroxides and activity of the proteolytic enzyme, cathepsin B, increased with age. During their lifetime, vestigial wing Drosophila displayed a greater level of free radical activity than wild-type flies and a significantly shorter life span (26.7 +/- 0.7 days vs. 34.4 +/- 1.0, p < 0.01). These results indicate that the level of oxidative stress is closely coupled to cellular damage and to life span, and they indicate that free radicals may play a central role in the aging process in Drosophila.

cDNA cloning of a novel protein tyrosine phosphatase with homology to cytoskeletal protein 4.1 and its expression in T-lineage cells

Reversible tyrosine phosphorylation plays important regulatory roles in various cellular events including the differentiation and function of lymphocytes. Here we report the cDNA cloning of a non-receptor type protein tyrosine phosphatase, PTP36, which is expressed in murine thymus. PTP36 was a new member of a tyrosine phosphatase subfamily defined by MEG-01 and PTPH1, which had a C-terminal phosphatase domain as well as an N-terminal domain with homology to cytoskeletal-associated proteins like band 4.1, ezrin, and talin. In addition, we found a putative SH3-binding motif in PTP36 but not in MEG-01 or PTPH1. PTP36 was expressed in cells of both hematopoietic and non-hematopoietic origins. In thymocytes subpopulations, PTP36 was preferentially expressed in double positive stage cells. The change of PTP36 expression level along with T cell maturation suggests its involvement in the regulation of T cell development.

Clonal analysis of human gynecologic cancers by means of the polymerase chain reaction

Clonality of human gynecologic cancers was analyzed in small DNA samples prepared from cryostat sections, by means of the polymerase chain reaction (PCR). The method used for clonal analysis was based on restriction fragment length polymorphism of the X-chromosome-linked phosphoglycerokinase (PGK) gene and on the differential methylation of the PGK gene due to random inactivation of 1 of 2 X-chromosomes by methylation in females. Among 52 gynecologic cancers tested, 25 were found to be heterozygous for the BstXI polymorphism of the PGK gene. All the 25 gynecologic cancers (4 cervix, 11 endometrium, 7 ovary and 3 fallopian tube) analyzed by the PCR-based method were monoclonal in origin while adjacent normal tissues were polyclonal. When DNA samples were prepared from widely separated sites of tumors and/or metastatic lesions, every sample was found to be monoclonal, and the same allele of the PGK gene was inactivated in each case. These results demonstrate that clonal analysis by PCR offers a good method for studying clonality in small DNA samples prepared from cryostat sections of tumors. This method could be applied to distinguish between benign and malignant gynecologic lesions.

Stable expression of human CYP1A2 and N-acetyltransferases in Chinese hamster CHL cells: mutagenic activation of 2-amino-3-methylimidazo[4,5-f]quinoline and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline

In order to investigate the metabolic activation pathway of food-derived heterocyclic amines, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), cultured cell lines which stably expressed human cytochrome P4501A2 (CYP1A2) and N-acetyltransferases (NATs) were developed by the method of complementary DNA (cDNA) transfection. First, a cell line expressing CYP1A2, designated A2R-5, was established from the cell line CR-68, which was previously established by introducing NADPH-cytochrome P-450 reductase cDNA into Chinese hamster CHL cells. The expression of CYP1A2 in the transfected cells was confirmed by determining sensitivity to aflatoxin B1. As the next step, the A2R-5 as well as CR-68 cells were further transfected with human monomorphic NAT (NAT1) or polymorphic NAT (NAT2) cDNAs. The expression of NAT in the transfected cells was confirmed using p-aminobenzoic acid and sulfamethazine as substrates, while no activity was seen in parental CR-68 and A2R-5 cells. The cell line, ANP-25, which expressed both CYP1A2 and NAT2, was approximately 370- and 100-fold more sensitive to IQ and MeIQx, respectively, than parental CR-68 cells in cytotoxicity assays. There were no clear differences in sensitivity to both compounds among CR-68, A2R-5, and the cell lines which expressed NAT1 alone, NAT2 alone, and CYP1A2 plus NAT1. Mutagenicity of IQ and MeIQx at the hypoxanthine-guanine phosphoribosyltransferase locus was also detectable only in ANP-25 cells but not in A2R-5 or the cell line expressing CYP1A2 plus NAT1. From these results, it is proposed that both CYP1A2 and NAT2 (but not NAT1) are required for mutagenic activation of these compounds, implying that acetylator polymorphism may be an important risk factor in the carcinogenicity of these compounds.

Establishment and characterization of human vaginal malignant melanoma xenotransplants

Human vaginal malignant melanoma represents rare gynecological malignancies of poor prognosis. We have established a melanoma tumor line in nude mice, designated Mela-1, and have examined the histological and biological characteristics of this tumor. The Mela-1 tumor has preserved the histological, histochemical and biological characteristics of malignant melanoma even after 20 passages. Tumor cells are of epitheloid shape varying in size. An ultrastructural study revealed that the tumor cells were characterized by the presence of cells with deeply indented nuclei, and both types of melanosomes, eumelanosomes and pheomelanosomes, in various stages of maturation with vesiculo-globular bodies in the cytoplasm. Melanin analysis of the tumor indicated the Mela-1 tumor to be pheomelanic. Immunohistochemical examinations revealed that the Mela-1 cells were stained positively by melanoma-associated antibody (NKI/C3) and by antibodies for S-100 protein and vimentin, and negatively for keratin and CEA. The levels of AFP, CA125 and CEA in sera of tumor-bearing mice were within normal range. The 5-S-cysteinyldopa level in sera of tumor-bearing mice correlated well with the size of the tumor. Chromosomal analysis showed the human karyotype with great heterogeneity and a modal number of 102 chromosomes. Thus the Mela-1 tumor will be useful in establishing the biological characteristics in the search for an effective treatment of human malignant melanoma of the vagina.