TX-1877: design, synthesis, and biological activities as a BRM-functional hypoxic cell radiosensitizer

PURPOSE

2-Nitroimidazole acetamide TX-1877 and its derivatives (TX-1877 analogs) were designed, synthesized, and evaluated by their in vitro and in vivo radiosensitization, tumor growth control, suppression of lung metastasis, and immunopotentiation, as biological response modifier (BRM)-functional hypoxic cell radiosensitizers.

MATERIALS AND METHODS

TX-1877 analogs were designed and synthesized in our laboratory. In vitro radiosensitizing ability was estimated using EMT6/KU cells under hypoxic conditions. In vivo radiosensitization, antimetastasis, and immunopotentiation were evaluated using female C3H/He mice bearing the SCCVII tumor. Days (15 or 10) after the inoculation of 10(5) SCCVII tumor cells into the hinder thigh, a drug (0.4 mg/g) was administered i.p. and local irradiation of 30 Gy was given at 30 min after its administration. Tumor growth was observed for 20 days and mice were euthanized to count the number of metastatic nodules on the surface of the lungs. Tumor tissues were extirpated and stained by the ABC method at 1, 2, and 3 weeks after treatment for immunological evaluation.

RESULTS

Novel types of bifunctional radiosensitizers, TX-1877 and its analogs possessing BRM-functions (i.e., antimetastatic and immunopotentiation effects) were developed. In vitro radiosensitizing abilities of TX-1877 and its analogs, with their partition coefficient values of more than 0.050, were comparable to misonidazole (MISO) at their doses of 1 mM. Tumor regrowth was suppressed evidently 20 days after the treatment in the irradiated group with TX-1877 (TX-1877 plus R) and with KIN-806 (KIN-806 plus R). The former group reduced markedly the mean number of metastatic lung nodules regardless of radiation therapy. TX-1877 and KIN-806 plus R induced helper T lymphocytes. The TX-1877, TX-1877 plus R, KIN-806, and KIN-806 plus R enhanced macrophage infiltration for 3 weeks after treatment.

CONCLUSION

TX-1877 is an excellent BRM-functional hypoxic cell radiosensitizer, expected to be useful for clinical use.

Substrate recognition of tRNA (Guanosine-2'-)-methyltransferase from Thermus thermophilus HB27

Transfer RNA (guanosine-2'-)-methyltransferase (Gm-methylase, EC 2.1. 1.32) from Thermus thermophilus HB27 is one of the tRNA ribose modification enzymes. The broad substrate specificity of Gm-methylase has so far been elucidated using various species of tRNAs from native sources, suggesting that the common structures in tRNAs are recognized by the enzyme. In this study, by using 28 yeast tRNAPhe variants obtained by transcription with T7 RNA polymerase, it was revealed that the nucleotide residues G18 and G19 and the D-stem structure are essentially required for Gm-methylase recognition, and that the key sequence for the substrate is pyrimidine (Py)17G18G19. The other conserved sequences were found not to be essential, but U8, G15, G26, G46, U54, U55, and C56 considerably affected the methylation efficiency. These residues are located within a limited space embedded in the L-shaped three-dimensional structure of tRNA. Therefore, disruption of the three-dimensional structure of the substrate tRNA is necessary for the catalytic center of Gm-methylase to be able to access the target site in the tRNA, suggesting that the interaction of Gm-methylase with tRNA consists of multiple steps. This postulation was confirmed by inhibition experiments using nonsubstrate tRNA variants which functioned as competitive inhibitors against usual substrate tRNAs.

The tyrosinase gene from medakafish: transgenic expression rescues albino mutation

We have determined the 9.8 kb genomic nucleotide sequence of the tyrosinase gene and its 5 upstream region from a teleost, medakafish (Oryzias latipes), and shown that the coding region is composed of five exons and four introns, spanning 4.7 kb. While the number and sizes of the exons were found to be similar to those of mammalian tyrosinase genes, however, the total size of the coding region (4.7 kb) was demonstrated to be less than one tenth those of mouse (ca. 70 kb) and human (> 70 kb) genes. Primer extension analysis revealed that the transcription initiation site starts with a long untranslated leader sequence (340 nucleotide long) from the AUG start codon. A characteristic CATGTG sequence known as a putative regulatory motif in melanocyte-specific genes was present in the 131st base upstream from the initiation site, while other typical regulatory elements such as the TATA-box or M-box common to terrestrial vertebrates were lacking. Transgenic experiments were carried out by microinjecting two kinds of plasmid clones into fertilized eggs of the albino i(l) mutant: one consisting of the genomic tyrosinase gene with the 10 kb 5 upstream region and the other the tyrosinase cDNA with the 3 kb 5 upstream region. The results showed that 53 and 45 of 114 and 118 transgenic eggs, respectively, developed normally beyond hatching and 15 and 10 exhibited a mosaic pattern of pigmentation. Despite the absence of typical regulatory elements like a TATA-box in both cases correct melanin pigmentation was obtained without ectopic expression. Thus, transgenic expression rescued from the albino-i(l) mutation, and the i locus of the medaka genome can be concluded to encode the tyrosinase gene.

Failure in detection of Epstein-Barr virus and cytomegalovirus in specimen obtained by fine needle aspiration biopsy of thyroid in patients with subacute thyroiditis

To study the possible role of viral infection in the etiology of subacute thyroiditis (SAT), we measured serum virus-specific antibodies to measles, rubella, mumps, type I herpes, chicken pox, human parvovirus B19 and cytomegalovirus (CMV) in 10 patients with SAT during the course of illness. In spite of the presence of IgG to each virus in more than 70% of patients, no significant changes in the IgG titers were observed except those to measles, rubella, chicken pox or CMV in only 10% of patients, respectively. Then we examined the presence of virus DNA in specimens of 9 patients with SAT obtained by fine-needle aspiration biopsy (FNAB) of the thyroid. DNA was amplified to detect that of Epstein-Barr virus and CMV by polymerase chain reaction. However, none of them were detected in all the specimens. Whereas previous studies suggest the involvement of viral infection in the pathogenesis of SAT, we failed to demonstrate significant changes in serum antiviral antibody titers or to detect viral DNA in the specimens obtained by FNAB of the thyroid. Thus further studies are clearly required to establish the definite role of viral infection in the pathogenesis of SAT.

Applicability of combination with tirapazamine in boron neutron capture therapy

SCC VII tumor-bearing mice were continuously given 5-bromo-2'-deoxyuridine (BrdU) to label all proliferating cells. After injection of tirapazamine (TPZ), a bioreductive agent, combined with sodium borocaptate-10B (BSH) or dl-p-boronophenylalanine-10B (BPA) administration, the tumors were irradiated with thermal neutrons, and then isolated and incubated with cytochalasin-B (a cytokinesis blocker). The micronucleus (MN) frequency in cells without BrdU labeling (quiescent (Q) cells) was determined by means of immunofluorescence staining for BrdU, and that for total cells was obtained from tumors not pretreated with BrdU. Even when no 10B-compound was administered, TPZ increased the MN frequency of tumor cells including Q cells, resulting in reduction of the difference in MN frequency between total and Q cells, mainly by increasing the MN frequency of Q cells. TPZ increased the MN frequency of Q cells when combined with BPA administration, but TPZ showed no apparent effect on each cell population when combined with BSH. Namely, TPZ reduced the difference in MN frequency between total and Q cells caused by 10B-compound administration, especially when BPA was administered. From the viewpoint of the overall cell killing effect in boron neutron capture therapy (BNCT), combination with TPZ appeared to be useful in BPA-BNCT, but not in BSH-BNCT.

Lymph node metastasis and lymphadenectomy for carcinoma in the gastric cardia: clinical experience

METHOD AND MATERIALS

To suggest improved guidelines for treating lymphatic spread and to understand the results of extended lymphadenectomy. A total of 141 cases of cardia carcinoma admitted to our hospital during 1980 to 1993 were analyzed.

RESULTS

123 of 141 cases underwent resection. The incidence of mediastinal lymph node involvement rose from 8.7% in cases with 1-2 cm invasion to 52.9% in cases with more than 4 cm invasion into the esophagus. The incidence of abdominal lymph node involvement also rose with increasing esophageal invasion. Paraaortic lymph node metastasis was frequently observed in cases of more than 1 cm esophageal invasion. D4 lymphadenectomy (extended lymphadenectomy) revealed better results for the cases with lymph node involvement (P<0.05). There was no difference in the incidence of postoperative complication or in operative death, between the abdominal approach and the thoracoabdominal approach, or between the D4 lymphadenectomy and D2 lymphadenectomy.

CONCLUSION

Sufficient mediastinal and abdominal lymphadenectomy under a clear wide surgical field achieved through the thoracoabdominal approach appeared to bring better results.

Effects of (+)-8',8',8'-trifluoroabscisic acid on alpha-amylase expression and sugar accumulation in rice cells

The effects of (+)-8',8',8'-trifluoroabscisic acid (trifluoro-ABA) on alpha-amylase expression were studied in rice embryoless half-seeds, scutella, and suspension-cultured cells derived from the embryo, and the effects of the analog on sugar accumulation were also studied in scutella and suspension-cultured cells. Treatment with (+)-trifluoro-ABA strongly inhibited the gibberellic acid-inducible expression of alpha-amylase I-1 encoded by RAmy1A in the aleurone layers of embryoless half-seeds at the levels of transcription, protein synthesis, and enzyme activity. It was also found that (+)-trifluoro-ABA stimulated (i) the uptake of glucose from the incubation medium and (ii) the synthesis of sucrose in scutellar tissues and suspension-cultured cells of rice. The biological activity of (+)-trifluoro-ABA was found to be more potent and persistent than that of natural ABA. We further examined the effects of trifluoro-ABA on the expression of alpha-amylase I-1 in scutellar tissues and suspension-cultured cells. It was found that (+)-trifluoro-ABA did not inhibit the formation of alpha-amylase I-1 in the absence of external glucose. However, glucose and (+)-trifluoro-ABA cooperatively suppressed the formation of alpha-amylase I-1. Judging from these results, we conclude that the regulatory mechanism for the expression of alpha-amylase I-1 in the scutellar epithelium is distinguishable from that operating in the aleurone layer.

Detection of a tryptophan radical as an intermediate species in the reaction of horseradish peroxidase mutant (Phe-221 --> Trp) and hydrogen peroxide

The crucial reaction intermediate in the reaction of peroxidase with hydrogen peroxide (H2O2), compound I, contains a porphyrin pi-cation radical in horseradish peroxidase (HRP), which catalyzes oxidation of small organic and inorganic compounds, whereas cytochrome c peroxidase (CcP) has a radical center on the tryptophan residue (Trp-191) and oxidizes the redox partner, cytochrome c. To investigate the roles of the amino acid residue near the heme active center in discriminating the function of the peroxidases in these two enzymes, we prepared a CcP-like HRP mutant, F221W (Phe-221 --> Trp). Although the rapid spectral scanning and stopped-flow experiments confirmed that the F221W mutant reacts with H2O2 to form the porphyrin pi-cation radical at the same rate as for the wild-type enzyme, the characteristic spectral features of the porphyrin pi-cation radical disappeared rapidly, and were converted to the compound II-type spectrum. The EPR spectrum of the resultant species produced by reduction of the porphyrin pi-cation radical, however, was quite different from that of compound II in HRP, showing typical signals from a Trp radical as found for CcP. The sequential radical formation from the porphyrin ring to the Trp residue implies that the proximal Trp is a key residue in the process of the radical transfer from the porphyrin ring, which differentiates the function of peroxidases.

Effects of thyroid hormone on carbonic anhydrase I gene expression in human erythroid cells

Individuals with hyperthyroidism exhibit concentrations of carbonic anhydrase I (CAI) in red blood cells that reflect the integrated serum thyroid hormone concentration over the preceding few months. Furthermore, triiodothyronine T3, at a physiological free concentration, decreases the CAI concentration in both human erythroleukemic YN-1 cells and burst-forming unit-erythroid (BFU-E)-derived cells. In the present study, the effect of T3 on CAI mRNA levels in various human erythroleukemic cell lines (YN-1, HEL and KU-812) and BFU-E-derived cells was studied. Northern analysis of RNA extracted from erythroid cells revealed a CAI mRNA of 1.5 kilobases. T3 significantly decreased the levels of CAI mRNA in YN-1 and BFU-E-derived cells in a dose-dependent manner. Incubation of T3-stimulated cells with actinomycin D prevented the decrease in CAI mRNA levels. By contrast, T3 had no effect on either the concentrations of CAI or the levels of CAI mRNA in HEL and KU-812 cells. These results suggest that YN-1 and BFU-E-derived cells may be useful models for investigating T3 actions on CAI mRNA in human cells.

Essentially minimal sequence for substrate recognition by tRNA (guanosine-2')-methyltransferase from Thermus thermophilus HB27

Transfer RNA (guanosine-2'-)-methyltransferase (Gm-methylase, EC.2.1.1.32) from extreme thermophile, Thermus thermophilus HB27 is one of the tRNA-ribose modification enzymes; this enzyme specifically catalyze the transfer of a methyl group from S-adenosyl-L-methionine to 2'-OH of the ribose of the guanosine at position 18 in tRNA. A broad substrate specificity of Gm-methylase was observed using natural tRNAs as methyl group acceptors, which suggests that some local stractures common in tRNAs are recognized by the enzyme. By using yeast tRNA(Phe) variants obtained by transcription of their genes with T7 RNA polymerase, it was revealed that the residues G18 and G19, as well as the D-stem structure were primarily required for the methylation reaction and that the essentially minimal sequence for the substrate was Pyrimidine17-G18-G19. The other conserved sequences and the tertiary base-pairs were not essential, but G15, G46, U55 and C56 strongly affected the methylation efficiency.

Expression of Xenopus laevis translation initiation factor 4E (eIF-4E) by baculovirus-insect cell system

A gene encoding Xenopus laevis eIF-4E was cloned into a transfer vector, and its gene expression was attempted in cells of E. coli, yeast and insect. Effective expression of the active eIF-4E was achieved in the soluble fraction of the insect cell Sf9, which was infected with the recombinant baculovirus. Overexpression of the eIF-4E protein caused remarkable change in the shape of the cells.

Signal transduction inhibitors, hibarimicins A, B, C, D and G produced by Microbispora. II. Structural studies

The structure of hibarimicins A, B, C, D and G which are inhibitors for tyrosine specific protein kinase are determined using spectroscopic techniques. Hibarimicins described in this report consist of a common aglycon and six deoxyhexoses. The aglycon contains a highly oxidized naphtylnaphthoquinone as a chromophore. Among them, hibarimicin B was identical with angelmicin B.

The complete cDNA coding sequence for the bovine proalpha2(I) chain of type I procollagen

The complete sequence of the cDNA for the pro alpha2(I) chain of bovine type I procollagen is presented. The encoded amino acid sequence shows 92.0% identity to the human pro alpha2(I) collagen chain.

Signal transduction inhibitors, hibarimicins, A, B, C, D and G produced by Microbispora. I. Taxonomy, fermentation, isolation and physico-chemical and biological properties

Strain TP-AO121 which produces a complex of novel tyrosine kinase inhibitors designated hibarimicins A, B, C, D and G was considered to be a new subspecies of Microbispora rosea, and the name, Microbispora rosea subsp. hibaria, was proposed. Hibarimicins A, B, C and D specifically inhibited the src tyrosine kinase activity without affecting protein kinase A or protein kinase C. They also showed in vitro anti-Gram-positive bacterial and antitumor activities. The molecular formulae of hibarimicins A, B, C, D and G were assigned to be C85H112O37, C85H112O37, C83H110O36, C85H112O38, and C85H112O39 respectively.

Effects of GnRH on protein kinase C activity, Ca2+ mobilization and steroidogenesis of human granulosa cells

Gonadotropin-releasing hormone (GnRH) and its agonists have been known to directly affect steroid hormone production in human granulosa cells. In this study, we examined effects of GnRH on Ca2+ mobilization, protein kinase C activity and steroidogenesis of human granulosa cells. Human granulosa cells were harvested by aspiration of follicles during oocyte retrieval for IVF. Test substances, that is, GnRH agonist ([D-Ser(TBu)6]-LHRH-EA), 12-O-tetradecanoyl-phorbol-13-acetate (TPA), A23187, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) and nordihydroguaiaretic acid (NDGA) were added to HTF medium with human granulosa cells. At the end of a 5-h incubation period, progesterone and estradiol in the medium were extracted and measured. GnRH agonist (10(-9)M and 10(-8)M) significantly stimulated (P < 0.05) progesterone and estradiol accumulation in the medium. TPA (10(-7)M, 10(-8)M and 10(-9)M) also significantly stimulated (P < 0.05) progesterone accumulation. A23187 (10(-6)M) significantly stimulated progesterone accumulation (P < 0.05) and significantly enhanced (P < 0.05) the stimulatory effect of TPA on progesterone production. H-7 (10(-3)M, 10(-4)M and 10(-5)M) and NDGA (10(-3)M, 10(-4)M and 10(-5)M) significantly inhibited (P < 0.05) the effect of GnRH agonist on progesterone and estradiol production by the granulosa cells. The granulosa cells were loaded with 4 microM Fura 2-AM, and the ratio of the intensities of fluorescent emission at 510 nm with excitation at 340 and 380 nm was calculated at 100-ms intervals. GnRH agonist (10(-7)M and 10(-6)M) increased (P < 0.05) [Ca2+]i significantly as compared with the control. These results suggested that the effects of GnRH on progesterone and estradiol production in human granulosa cells were mediated partially by calcium mobilization and partially by C-kinase activity, and protein kinase C, [Ca2+]i and lipoxygenase were suspected of being important intracellular messages for GnRH in human granulosa cells.

20beta-hydroxy-C21-steroid 20beta-oxidase activity of cytochrome P450c21 purified from bovine adrenocortical microsomes

We showed previously that cytochrome P450c21 (CYP21A1) from bovine adrenocortical microsomes has a putative 20beta-oxidase activity for 20beta-hydroxyprogesterone leading to a conversion to progesterone [M. Tsubaki, K. Morimoto, S. Tomita, S. Miura, Y. Ichikawa, A. Miyatake, F. Masuya, H. Hori, Biochim. Biophys. Acta 1259 (1995) 89-98]. We have extended the investigation on the 20beta-oxidase activity of cytochrome P450c21. Combination of 17alpha, 20beta-dihydroxyprogesterone with purified cytochrome P450c21 in oxidized form caused an induction of a typical type I difference spectrum (a peak at 390 nm and a trough at 420 nm) with a spectral dissociation constant of 2.3 microM. EPR spectrum at low temperature (15 K) exhibited an appearance of a new low-spin signal at gz=2.42, gy=2.21, and gx=1.966 and an increase in intensity of the high-spin signal (g=8.06, 3.54) upon formation of the enzyme-steroid complex, as previously found for 17alpha-hydroxyprogesterone and 20beta-hydroxyprogesterone. The enzymatic activity for 17alpha, 20beta-dihydroxyprogesterone was confirmed in a reconstituted system consisting of cytochrome P450c21 and NADPH-cytochrome P450 reductase. 17alpha,20beta-Dihydroxyprogesterone was converted to 17alpha-hydroxyprogesterone via the 20beta-oxidase reaction. The high turnover numbers of the 20beta-oxidase activity for 20beta-hydroxy-c21-steroids suggests that this activity is likely to have some physiological roles. Cytochrome P450c21 and 20beta-hydroxysteroid dehydrogenase may regulate the androgen biosynthesis catalyzed by cytochrome P450c17alpha with controlling the concentration of 20beta-hydroxy-C21-steroids.

Substitutions of conserved aromatic amino acid residues in subunit I perturb the metal centers of the Escherichia coli bo-type ubiquinol oxidase

Cytochrome bo is a four-subunit quinol oxidase in the aerobic respiratory chain of Escherichia coli and functions as a redox-coupled proton pump. Subunit I binds all the redox metal centers, low-spin heme b, high-spin heme o, and CuB, whose axial ligands have been identified to be six invariant histidines. This work explored the possible roles of the aromatic amino acid residues conserved in the putative transmembrane helices (or at the boundary of the membrane) of subunit I. Sixteen aromatic amino acid residues were individually substituted by Leu, except for Tyr61 and Trp282 by Phe and Phe415 by Trp. Leu substitutions of Trp280 and Tyr288 in helix VI, Trp331 in loop VII-VIII, and Phe348 in helix VIII reduced the catalytic activity, whereas all other mutations did not affect the in vivo activity. Spectroscopic analyses of the purified mutant enzymes revealed that the defects were attributable to perturbations of the binuclear center. On the basis of these findings and recent crystallographic studies on cytochrome c oxidases, we discuss the possible roles of the conserved aromatic amino acid residues in subunit I of the heme-copper terminal oxidases.

Changes in circulating LH, sex steroid hormones, thyroid hormones and corticosterone in relation to breeding and molting in captive humboldt penguins (Spheniscus Humboldti) kept in an outdoor open display

Penguins are highly adapted to marine life. Their hydrodynamic efficiency depends on feathers which wear with age and need to be replaced regularly. During molting, penguins can not enter the sea to forage and are forced to fast. Therefore the duration of molting is necessarily brief. To better understand molting in penguins, we collected plasma samples from 16 (8 pairs) Humboldt penguins kept in an open display pen at Tokyo Sea Life Park from May to September, 1994 and estimated circulating concentrations of LH, testosterone, estradiol, thyroxine (T4), triiodothyronine (T3) and corticosterone. Body mass was also measured at each blood sampling. Throughout the year, reproductive activities (egg laying, incubation, hatching and rearing) and molting were observed and recorded. Humboldt penguins maintained reproductive activity from January to December except during molting. Each pair started molting between the end of July and early August; usually males started earlier. The duration of molting was 13.4 +/- 0.8 days for males and 12.9 +/- 0.3 days for females. Body masses were highest just before the start of molting in both sexes. Plasma concentrations of LH were high, (> 2 ng/ml) in May in both sexes, then gradually decreased, to 0.53 +/- 0.38 ng/ml in males and 0.72 +/- 0.11 ng/ml in females by the end of July. Testosterone and estradiol concentrations in plasma decreased and were lowest during molting. On the other hand, plasma concentrations of T4 were low until early July (ca. 20 ng/ml) and then doubled within 10 days; the high levels were maintained for one month and then decreased greatly in males and slightly in females. When the plasma concentrations of T4 started to decrease, plasma concentrations of LH increased. Changes in plasma T3 were not consistent with molting. These results indicate that the decrease of plasma levels of sex steroid hormones and the sharp increase of T4 induced molting, which lasted only for a short period.

Hyperthyroid Graves' disease and primary hypothyroidism caused by TSH receptor antibodies in monozygotic twins: case reports

A 33-year-old woman with signs and symptoms of hypothyroidism, including increased thyroid stimulating blocking antibody (TSBAb) activity, was referred for treatment by her local physician. Her monozygote twin was treated for hyperthyroid Graves' disease 10 years earlier. This case of hyperthyroidism and hypothyroidism in identical twins suggests the involvement of environmental factors in the pathogenesis of autoimmune thyroid diseases.

The methylthioadenosine phosphorylase gene is frequently co-deleted with the p16INK4a gene in acute type adult T-cell leukemia

Adult T-cell leukemia (ATL) is a retrovirus-associated leukemia with poor prognosis and often has deletions of the p16INK4a and p15INK4b genes on chromosome 9p21. The gene for methylthioadenosine phosphorylase (MTAP), a purine and methionine metabolic enzyme, resides approximately 100 Kb telomeric to the p16INK4a gene and is frequently co-deleted with the tumor suppressor gene in a variety of cancers. This enzyme deficiency can be exploited for selective chemotherapy with de novo purine synthesis inhibitors and/or methionine depletion. To determine whether ATL can be a candidate for selective chemotherapy based on genetic alterations on chromosome 9p21, we analyzed the MTAP gene in 41 samples from ATL patients (27 acute type and 14 chronic type ATL) and 3 cell lines established from ATL patients. Five samples from the acute type had deletions of the MTAP gene (4 total deletions and 1 partial deletion of exons 6-8). The MTAP gene was always co-deleted with p16INK4a. No deletion of the MTAP gene was detected in samples from the chronic type. Of 3 cell lines, 2 showed partial deletions of exons 5-8 of the MTAP gene, and 1 lost all exons. The p16INK4a gene was deleted in all cell lines. In conclusion, deletions of the MTAP gene were found in 5 of 27 acute type ATL samples. Acute type ATL with MTAP deficiency can be a good candidate for selective chemotherapy by depleting purines and/or methionine.

Role of thyroid-stimulating blocking antibody in patients who developed hypothyroidism within one year after 131I treatment for Graves' disease

OBJECTIVE

We recently reported that thyroid-stimulating blocking antibody (TSBAb) may not contribute to the development of hypothyroidism more than six years after 131I treatment. In the present study, we attempted to determine whether hypothyroidism that develops within a shorter period of time following 131I therapy is associated with TSBAb.

DESIGN

Retrospective study.

PATIENTS

Sera were obtained from 8 patients who developed hypothyroidism within 6 months after 131I therapy (Group 1), 8 patients who became euthyroid one year after 131I therapy (Group 2), and 7 patients who developed transient hypothyroidism (Group 3).

MEASUREMENTS

Thyroid stimulating antibody (TSAb) activity was measured as the amount of cyclic adenosine monophosphate (cAMP) produced by cultured FRTL-5 cells, and TSBAb activity as the inhibition of cAMP produced in response to 100 mU/l bovine TSH.

RESULTS

At about 3 months after 131I treatment, TSAb activity increased significantly in Groups 2 and 3, but did not change in Group 1. In contrast, TSBAb activity in Group 1 increased significantly and was positive in 6 patients at that time. At 12-18 months after 131I treatment, TSBAb activity tended to decrease and remained positive in 3 patients but became negative in 3 patients. It did not change in the patients in Groups 2 and 3. The patients in Group 1 were treated with levothyroxine, 75-125 micrograms/day. Levothyroxine was discontinued in the 3 patients whose TSBAb activity disappeared. Two of them remained euthyroid, and 1 became hypothyroid.

CONCLUSION

Results indicate that the hypothyroidism that develops within a short time after 131I treatment may be caused by TSBAb activity. Thyroid function may be recovered when TSBAb activity disappears.

Effect of extracellular calcium on the intracellular calcium level of newborn rat skin basal cells

The effect of extracellular calcium on the intracellular calcium level of newborn rat skin basal cells was examined. The intracellular calcium level of basal cells was affected by the extracellular calcium concentration on culture of the cells on a collagen-coated filter, but not on a plate. The intracellular calcium ion concentration ([Ca2+]i) of cells on a collagen-coated filter with 0.05 mM external CaCl2 was 15 nM and increased to 20-22 nM on culture with 2.0 mM extracellular CaCl2. From these results we concluded that the culture matrix (e.g. culture plates, or collagen-coated filters) affects the response of the basal cells to changes in the extracellular calcium content. The intracellular calcium level of Swiss 3T3 cells cultured both on plates and collagen-coated filters were affected by the extracellular calcium concentration. Their [Ca2+]i was determined as 49-50 nM in the presence of 0.05 mM external CaCl2, and 54-56 nM in the presence of 2.0 mM CaCl2. These different responses to extracellular Ca2+ may be due to differences in the proliferative profiles of basal cells and fibroblasts.

Albinism due to transposable element insertion in fish

The i locus of the medaka fish, Oryzias latipes, is responsible for tyrosinase expression, and several mutant alleles have been identified. The genotype i1/i1 exhibits a complete albino phenotype, having pale orange-red skin and red eyes. This mutant lacks in vivo tyrosinase activity. The genotype i4/i4, on the other hand, shows a quasi-albino phenotype with skin as bright as that of i1/i1 but with red-wine-colored eyes. At the light microscope level, reduced pigmentation is observed both in the skin and eyes of this mutant. The tyrosinase genes for the i1 and the i4 alleles were cloned and sequenced, and compared with that of the wild-type tyrosinase gene. The i1 allele was found to contain a 1.9-kb transposable element in the 1st exon, and the i4 allele was found to contain a 4.7-kb transposable element in the 5th exon. Both i1 and i4 are alleles that were found in a commercial breeding population. The insertion of a transposable element thus appears to constitute a natural cause of mutations that cause albinism in this organism.

FK506 inhibits anti-IgM antibody-induced apoptosis and 17 kD endonuclease activity in the human B-cell line, MBC-1, established from Burkitt's lymphoma

The endonuclease which causes antibody-induced apoptotic cell death in B cells is not completely understood. We previously established a B-cell line (MBC-1) from a patient with Burkitt's lymphoma at the leukaemic stage which demonstrated the typical morphology and internucleosomal DNA fragmentation of apoptotic cell death when treated with anti-IgM antibody. FK506, an immunosuppressive agent and calcineurin inhibitor, partially rescued the anti-IgM antibody-induced cell death in these MBC-1 cells. DNA SDS-PAGE nuclease activity assay demonstrated that a 17 kD protein exhibited endonuclease activity. Active gel assay showed nuclease activity in the cellular nuclear extract not treated with anti-IgM antibody. This nuclease activity was inhibited by FK506 at concentrations of 10-200 ng/ml in the active gel assay. These results raise the possibility that the 17 kD endonuclease is one of the nuclear members of the immunophilin family, which may function as an endogenous endonuclease in MBC-1 cells.

Genetic polymorphisms of tobacco- and alcohol-related metabolizing enzymes and human esophageal squamous cell carcinoma susceptibility

Many human cancers are caused by synthetic or natural chemical compounds in the environment. Esophageal squamous cell carcinoma has been reported to be epidemiologically associated with tobacco and alcohol consumption. We studied the association between genetic polymorphisms of tobacco- and alcohol-related metabolizing enzymes and esophageal squamous cell carcinoma susceptibility. We examined genetic polymorphisms of the CYPIA1, GSTM1, CYPIIE1, ADH2, and ALDH2 genes in 94 Japanese patients with esophageal squamous cell carcinoma and 70 unrelated healthy Japanese persons. There were no significant differences between healthy controls and patients with esophageal cancer in the polymorphisms of the CYPIA1, GSTM1, and CYPIIE1 genes. On the other hand, there were significant differences in the ADH2 and ALDH2 polymorphisms between healthy controls and esophageal cancer patients. The ADH2(1)/ADH2(1) and ALDH2(1)/ALDH2(2) genotypes were independently and significantly higher in esophageal cancer patients than in healthy controls. Furthermore, persons with the combined genotypes ADH2(1)/ADH2(1) and ALDH2(1)/ALDH2(2) were at extraordinarily high risk for esophageal squamous cell carcinoma, with an odds ratio of 17.9 (p < 0.001). Thus polymorphisms of alcohol-metabolizing enzymes, that is, ADH2 and ALDH2, may be useful for screening patients at high risk for esophageal cancer, which might facilitate clarification of esophageal tumorigenesis and prevention of esophageal cancer.

Glutamate-286 mutants of cytochrome bo-type ubiquinol oxidase from Escherichia coli: influence of mutations on the binuclear center structure revealed by FT-IR and EPR spectroscopies

Glutamate-286 mutants of cytochrome bo-type ubiquinol oxidase from Escherichia coli were examined by EPR and FT-IR spectroscopies. We confirmed a very low enzymatic activity for E286Q. However, E286D retained one-third of the wild-type activity, probably due to the presence of the carboxylic group on the side-chain. The effect of the mutations at position 286 on the binuclear site was observed clearly in the EPR spectral change for the air-oxidized state. The effect was more significantly manifested in the presence of cyanide or azide in the oxidized state. In contrast, the mutations only slightly perturbed the binuclear center of the CO-reduced enzymes. These results indicate the importance of a direct through-bond connectivity between CuB and Glu286 via Pro285 and His284.

Resonance Raman, infrared, and EPR investigation on the binuclear site structure of the heme-copper ubiquinol oxidases from Acetobacter aceti: effect of the heme peripheral formyl group substitution

Acetobacter aceti produces two different terminal ubiquinol oxidases (cytochromes a1 and o) depending on the culture conditions. Two types of oxidases share a common protein moiety but with different heme components at the binuclear center (heme A for cytochrome a1 and heme O for cytochrome o). We investigated the structure of the binuclear site of the two oxidases using resonance Raman, Fourier transform-infrared (FT-IR), and EPR spectroscopies to clarify the interactions of heme A formyl group with protein moiety. We found that the overall architecture and the electronic configuration at the binuclear center in the oxidized state seem to be well conserved irrespective of the heme peripheral group at position 8, except for the azide-inhibited state. In contrast, we observed great variations in the C-N stretching frequency and cyanide-binding affinity in the CN-reduced state, in addition to multiple C-O stretching bands in the CO-reduced state. Present and previous studies suggest that the conformational flexibility of the binuclear center in the reduced ligand-bound state may be a common feature among the heme-copper oxidase superfamily. In the CN-reduced state, a hydrogen bond network may be formed among the formyl group, water molecule(s), and the surrounding amino acid residue(s). This network may be very important to maintain proper orientations of the distal amino acid residues and/or the CuB1+ ion relative to the cyanide ion bound to the ferrous heme iron and could play a critical role for the high affinity in cyanide binding.

Characterization of a 30-kDa peripheral nerve glycoprotein that binds laminin and heparin

We have shown previously that a bovine peripheral nerve protein with a molecular mass of about 30 kDa binds laminin in blot overlay assay. In this paper, we have characterized this 30-kDa laminin-binding protein (LBP30). LBP30 was extracted from the crude bovine peripheral nerve membranes at pH 12 or by 0.5 M NaCl but not by 2% Triton X-100. LBP30 bound to heparin-Sepharose in the presence of 0.5 M NaCl. The results of lectin staining indicated that LBP30 contained both terminally sialylated and nonsialylated Ser/Thr-linked oligosaccharides. LBP30 bound laminin-2 as well as laminin-1 but not fibronectin or collagen type IV. When immobilized LBP30 was incubated with the crude peripheral nerve membrane extracts, all of the endogenous peripheral nerve laminin chain isoforms, the alpha1, alpha2, beta1, beta2, and gamma1 chains, were detected bound to LBP30. The binding of LBP30 to laminin was inhibited by heparin, heparan sulfate, dextran sulfate, or NaCl but was not affected significantly by chondroitin sulfate, dextran, or EDTA. Although LBP30 bound to laminin-1 denatured with SDS in a nonreducing condition, the binding was reduced drastically when laminin-1 was denatured with SDS in a reducing condition, suggesting that the binding of LBP30 is somewhat dependent on the high order structure of laminin-1. Immunohistochemical analysis demonstrated the broad distribution of LBP30 in the perineurium and endoneurium of bovine peripheral nerve. These results indicate that LBP30 is a laminin- and heparin-binding glycoprotein localized in the perineurium and endoneurium of bovine peripheral nerve.

Existence of two heme B centers in cytochrome b561 from bovine adrenal chromaffin vesicles as revealed by a new purification procedure and EPR spectroscopy

We have established a new purification procedure of cytochrome b561 from bovine adrenomedullary chromaffin vesicles. The heme content analysis of the purified sample indicated the presence of 1.7 molecules of heme B/cytochrome b561 molecule. EPR spectroscopy of the purified enzyme in oxidized state showed that there were three types of low spin heme species. Two of them showed usual EPR signals at gz = 3.14 and gz = 2.84 arising from the same heme and were interconvertible depending on pH. The other species showed a highly anisotropic low spin signal at gz = 3.70, with a lower redox potential than the others, and a temperature-sensitive character. These properties are very similar to low potential cytochrome b (bL or b566) of the mitochondrial complex III, indicating that the gz = 3.70 species is derived from a heme component different from the one that shows the usual low spin EPR signals. Based on our new structural model, these two heme B prosthetic groups are likely to be located on both sides of the membranes in close contact with the ascorbic acid- and semidehydroascorbic acid-binding sites, respectively, to facilitate the electron transfer across the membranes. This molecular architecture may provide a structural basis for the transmembrane electron transfer catalyzed by this hemoprotein.

Effects of bioreductive agents, tirapazamine and mitomycin C, on quiescent cell populations in solid tumors, evaluated by micronucleus assay

Mice bearing transplantable solid tumors received 10 intraperitoneal administrations of 5-bromo-2'-deoxyuridine (BrdU) to label the proliferating (P) tumor cells, and were then irradiated with 60Co gamma-rays or injected with cis-diamminedichloroplatinum (II) (cisplatin). The tumor cells were isolated and incubated with cytochalasin-B (a cytokinesis blocker). The micronucleus (MN) frequency in the cells without BrdU labeling, which were regarded as quiescent (Q) cells in the tumor, was determined using immunofluorescence staining for BrdU. The MN frequency in the total (P + Q) tumor cell population was determined from tumors that were not pretreated with BrdU. Pretreatment with tirapazamine, a bioreductive agent, could enhance the sensitivity of tumor cells, including Q cells, to radiation more markedly than mitomycin C pretreatment as judged from an in vivo assay immediately after irradiation. Post-irradiation administration of tirapazamine produced a large post-irradiation radiosensitizing effect on both the total and Q tumor cell populations in vivo. Cisplatin treatment combined with tirapazamine demonstrated that tirapazamine also has a chemosensitizing potential for both the total and Q tumor cell populations. We confirmed that the sensitivity of Q cell populations to radiation and chemotherapy using cisplatin can be enhanced by combined treatment with tirapazamine.

Effects of mineral fibers on the expression of genes whose product may play a role in fiber pathogenesis

To determine which factors are useful for the risk assessment of man-made fibers, we examined the gene expression of proinflammatory cytokines, growth factors, manganese superoxide dismutase (MnSOD), and inducible nitric oxide synthase (iNOS) in mineral fiber-exposed rats by means of reverse transcription-polymerase chain reaction (RT-PCR). Male Wistar rats received a single intratracheal instillation of either saline (control) or two types of fibers (2 mg of Union Internationale Centre le Cancer (UICC) chrysotile or alumina silicate refractory ceramic fiber [RCF]). Expression of interleukin-1 alpha (IL-1 alpha), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), platelet-deriving growth factor-A, (PDGF-A), platelet-deriving growth factor-B (PDGF-B), transforming growth factor beta 1 (TGF-beta 1), basic fibroblast growth factor (bFGF), MnSOD, and iNOS mRNA from lung and lipopolysaccharide (LPS)-stimulated alveolar macrophages (AM) were assessed by RT-PCR. Among these factors, IL-1 alpha, TNF-alpha, IL-6, bFGF, and iNOS would be the possible parameters for the risk assessment of fibers. In a follow-up study, we investigated the time course (3 days, 1 week, 1 month, and 3 months) of expression of IL-1 alpha and TNF-alpha by LPS-stimulated AM exposed to mineral fibers in vivo. Male Wistar rats were instilled intratracheally with saline or fibers (2 mg of Union Internationale Contre le Cancer UICC crocidolite or potassium octatitanate whisker [TW]). The expression of IL-1 alpha mRNA by fibers was greatest in TW, crocidolite, chrysotile, and RCF-instilled rat AM, in that order. The increase of IL-1 alpha and TNF-alpha mRNA in AM peaked at 1 month and 3 days after exposure to crocidolite or TW, respectively. The expression of IL-1 alpha by fibers (crocidolite, chrysotile, TW, and RCF) may be a good indicator of the pathologic potential of fibers.

Expression of matrix metalloproteinases, tissue inhibitors of metalloproteinases, and extracellular matrix mRNA following exposure to mineral fibers and cigarette smoke in vivo

To determine the effect of mineral fibers and cigarette smoke on remodeling of lung tissues, we examined matrix metalloproteinase-1 (MMP-1), MMP-2, tissue inhibitors of metalloproteinase-1 (TIMP-1), TIMP-2, and types I and IV collagen mRNA levels from rat lungs exposed to mineral fibers and/or cigarette smoke in vivo. Male Wistar rats (10 weeks of age) were given a single intratracheal instillation of 2 mg of chrysotile or alumina silicate ceramic fibers (RCF). Animals were then exposed to cigarette smoke (side stream) 5 days per week for 4 weeks. Transcriptional levels of mRNA extracted from the lungs were assessed by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Exposure to cigarette smoke induced increases in MMP-1 and TIMP-1 mRNA levels and decreased TIMP-2 and type I collagen mRNA levels in lung. Chrysotile or RCF stimulated the expression of MMP-1 mRNA in the lung. The mineral fibers and cigarette smoke had more than additive effects on the expression of MMP-2 and TIMP-1 in the lung. These data suggest that the imbalance of the expression of MMPs, TIMPs, and extracellular matrix may be associated with the remodeling of lung tissues induced by mineral fibers and/or cigarette smoke.

A novel action of collapsin: collapsin-1 increases antero- and retrograde axoplasmic transport independently of growth cone collapse

Chick collapsin-1, a member of the semaphorin family, has been implicated in axonal pathfinding as a repulsive guidance cue. Collapsin-1 induces growth cone collapse via a pathway which may include CRMP-62 and heterotrimeric G proteins. CRMP-62 protein is related to UNC-33, a nematode neuronal protein required for appropriately directed axonal extension. Mutations in unc-33 affect neural microtubules, the basic cytoskeletal elements for axoplasmic transport. Using computer-assisted video-enhanced differential interference contrast microscopy, we now demonstrate that collapsin-1 potently promotes axoplasmic transport. Collapsin-1 doubles the number of antero- and retrograde-transported organelles but not their velocity. Collapsin-1 decreases the number of stationary organelles, suggesting that the fraction of time during which a particle is moving is increased. Collapsin-1-stimulated transport occurs by a mechanism distinct from that causing growth cone collapse. Pertussis toxin (PTX) but not its B oligomer blocks collapsin-induced growth cone collapse. The holotoxin does not affect collapsin-stimulated axoplasmic transport. Mastoparan and a myelin protein NI-35 induce PTX-sensitive growth cone collapse but do not stimulate axoplasmic transport. These results provide evidence that collapsin has a unique property to activate axonal vesicular transport systems. There are at least two distinct pathways through which collapsin exerts its actions in developing neurons.

Differential distribution and expressions of collagens in the cerebral aneurysmal wall

To investigate the role of collagens in the formation and rupture of cerebral aneurysms, we examined the distribution and synthesis of vascular collagens in the wall of normal human cerebral main trunks and of cerebral aneurysms using immunohistochemistry and in situ hybridization techniques. Fifteen cerebral aneurysmal walls were resected at operation; control cerebral main trunks were obtained from seven autopsy cases. Semiserial sections from the specimens were subjected to immunofluorescence and immunohistochemical staining with antibodies to collagen types I, III, IV, V, VI, desmin and alpha-smooth muscle actin. In addition, type III collagen mRNA was examined by in situ hybridization. Immunohistochemical study showed that all collagen types were grossly preserved in the aneurysmal wall, although the distribution patterns were different for each collagen. The distribution of major fibrillar collagen types I and III was more diffuse and homogeneous in the luminal layer of the aneurysmal wall than the media of the control artery, although the intensity of immunohistochemical staining was weaker in the abluminal layer of the aneurysmal wall than the adventitia of the control artery. Collagen types IV and V were distributed more sparsely in the luminal layer of the aneurysmal wall than the media of the control artery. Collagen type VI was noted in the luminal as well as the abluminal layer of the aneurysmal wall, whereas it was located exclusively in the adventitia of the control artery. In situ hybridization showed that the signal for collagen type III mRNA on fibroblastic and smooth muscle cells was higher in the aneurysmal walls than the control arteries, suggesting up-regulation of type III collagen transcription in the cerebral aneurysmal wall. The study of the distribution and synthetic regulation of various types of collagen in the aneurysmal wall may be essential for understanding the formation of the aneurysmal wall and its protection against enlargement or rupture.

Salvage therapy for relapsed or refractory childhood acute lymphocytic leukemia by alternative administration a lymphoid- and myeloid-directed chemotherapeutic regimen consisting of dual modulation of ara-C, hydroxyurea, and etoposide

Risk-directed chemotherapeutic regimens in recent use have improved the prognosis of children with acute lymphocytic leukemia (ALL). However, many patients relapse during or shortly after cessation of the initial continuation chemotherapy. Since achievement of a second complete remission (CR) is the initial step in successful retreatment effort, it is important to develop salvage protocols for children with relapsed or refractory ALL. In the present study, we developed a new salvage protocol (MLL-93) and applied the concept of dual chemical modulation of cytarabine, hydroxyurea, and etoposide with the alternative administration of high doses of myeloid- and lymphoid-directed agents. We also planned to perform allogeneic bone marrow transplantation (BMT) following a CR if patients had HLA-identical donor(s). The six patients treated with the MLL-93 protocol achieved a second CR. One patients in CR died of interstitial pneumonia after an unrelated allogeneic BMT. The other five patients have been in CR for 12-41 months. We suggest that the concepts of alternative administration of lymphoid- and myeloid-directed drugs and biochemical modulation are useful in the treatment of children with relapsed or refractory ALL.

A novel chloride-binding site modulates the heme-copper binuclear center of the Escherichia coli bo-type ubiquinol oxidase

Cytochrome bo-type ubiquinol oxidase in Escherichia coli belongs to a superfamily of the heme-copper respiratory oxidases and catalyzes the redox-coupled proton pumping. Previous studies [Y. Orii, T. Mogi, M. Sato-Watanabe, T. Hirano, and Y. Anraku (1995) Biochemistry 34, 1127-1132] suggest that it requires chloride ions for the facilitated heme b-to-heme o intramolecular electron transfer. To extend our previous studies on chloride binding by bo-type ubiquinol oxidase, we prepared two kinds of chloride-bound enzymes, UQO-412 and UQO-409, and a chloride-depleted enzyme, UQO-407, and examined their spectroscopic and enzymatic properties. UQO-412, which exhibits the Soret peak at 412 nm in the air-oxidized state, was obtained by purification with anion-exchange liquid chromatography, and UQO-409 was derived from UQO-412 by extensive washing and showed a 3-nm blue shift. UQO-407 was obtained from UQO-409 by omitting chloride ions from buffers throughout purification and showed a further blue shift in the Soret peak and the pronounced chloride-sensitive EPR signals at g=6 and g=3.15, which are attributable to spin-spin exchange interaction at the binuclear center. Kinetic studies on chloride binding by UQO-407 revealed the presence of a chloride-binding site with a K(d) value of 3.5 mM. Flow-flash experiments demonstrated that the heme b-to-heme o electron transfer was perturbed in both UQO-409 and UQO-407, although steady state enzyme activities of three UQOs were indistinguishable. The present studies demonstrated that the E. coli bo-type ubiquinol oxidase is endowed with a novel chloride-binding site which controls the electromagnetic state of the heme-copper binuclear center. Further, we suggest that the intramolecular electron transfer in the enzyme requires diffusible molecules other than the bound chloride ion.

[Isolation of Legionella pneumophila from 24 hr-home bath water and an eradication trial of the bacteria from the bath]

Contamination of 24 hr home bath with Legionella pneumophila is recently well recognized. Eradication of the water-bath contamination from L. pneumophila and other bacteria is an important matter to prevent the infection because the 24 hr-bathing facility is widely accepted in Japanese houses. Among the 16 bathing water samples we tested, Legionella pneumophia was isolated from 6 cases (37.5%) when the bathing water was not treated with disinfectants. Number of L. pneumophila increased up to 10(3) cfu/ml and total culturable bacterial counts reached to 10(5) cfu/ml within 5 days when the water was not treated. We selected 5 water baths among 6 positive cases to study the bactericidal effect of chlorine. As a result we concluded that the growth of L. pneumophila in 24 hr-water bath could be stopped by the 2 ppm chlorination program every day.

Crystallization, preliminary diffraction and electron paramagnetic resonance studies of a single crystal of cytochrome P450nor

Cytochrome P450nor (P450nor) is a heme-containing nitric oxide reductase from the denitrifying fungus, Fusarium oxysporum. This enzyme catalyzes the reduction of NO to N2O. In the present study, we report results from preliminary crystallographic and electron paramagnetic resonance (EPR) analysis of a single crystal of P450nor. The crystal was grown in 100 mM MES buffer at pH 5.6 using PEG 4000 as a precipitant. It belongs to the orthorhombic system with cell dimensions of a = 54.99 A, b = 82.66 A, c = 87.21 A, and the space group is P2(1)2(1)2(1). The crystal diffracts synchrotron radiation at higher than 2.0 A resolution, and therefore it is suitable for X-ray crystal structure analysis at atomic resolution. Bijvoet and dispersive anomalous difference Patterson maps show a clear peak corresponding to the heme iron. The structure solution is currently underway by means of MIR and MAD techniques. EPR analysis determined the orientation of the heme within the P450nor crystal.

Exploring subunit-subunit interactions in the Escherichia coli bo-type ubiquinol oxidase by extragenic suppressor mutation analysis

Cytochrome bo-type ubiquinol oxidase is a four-subunit heme-copper terminal oxidase and functions as a redox-coupled proton pump in the aerobic respiratory chain of Escherichia coli. On the basis of deletion and chemical cross-linking analyses on subunit IV, we proposed that subunit IV is essential for CuB binding to subunit I and that it is present in a cleft between subunits I and III (Saiki, K., Nakamura, H., Mogi, T., and Anraku, Y. (1996) J. Biol. Chem. 271, 15336-15340). To extend previous studies, we carried out alanine-scanning mutagenesis for selected 16-amino acid residues in subunit IV to explore subunit-subunit interactions in bo-type ubiquinol oxidase. We found that only the replacement of Phe83 in helix III resulted in the reduction of the catalytic activity but that this did not significantly affect the UV-visible spectroscopic properties and the copper content. This suggests that individual amino acid substitutions, including the six invariant residues, are not enough to alter such properties of the metal centers. Extragenic suppressor mutations were isolated for the Phe83 --> Ala mutation of subunit IV and identified as missense mutations in helices VII and VIII in subunit I. These observations provide further support for specific interactions of subunit IV with helix VII and/or VIII, the CuB binding domain, of subunit I and suggest that subunit IV functions as a domain-specific molecular chaperon in the oxidase complex.

Optical and electron paramagnetic resonance absorption spectra of complexes of nitric oxide synthase I with isocyanides

Neuronal nitric oxide synthase (NOS I) was purified from porcine brains, and optical and EPR spectra of the complexes of NOS I with isocyanides were investigated. The complex of oxidized NOS I with tert-butylisocyanide exhibited optical absorption peaks at 437 and 560 nm in the difference spectrum, whereas with tert-butylisocyanide and phenylisocyanide, optically reduced NOS I-isocyanide complexes with absorbance maxima at 433, 451, 541 and 573 nm were produced. The dissociation constants of the NOS I-isocyanide complexes were optically determined, the constants being significantly larger than those of microsomal cytochromes P-450. Phenylisocyanide did not affect the optical spectrum of oxidized NOS I. A high concentration of phenylisocyanide also had no effect on the EPR spectrum of oxidized NOS I. The optical spectra of the reduced NOS I-isocyanide complexes were pH-dependent. With increasing pH, the intensity of the absorbance at 451 nm of the complexes increased and that of the absorbance at 433 nm decreased in parallel. Upon the addition of a saturating concentration of L-arginine, the difference spectra of the reduced NOS I-phenylisocyanides complex showed a drastic change, i.e., an increase in optical intensity at 433 nm and a concomitant decrease in the intensity at 451 nm. In titration experiments with L-arginine, spectral binding, Ks = 2.5 microM, was determined from the absorbance increase at 433 nm. No spectral change was observed on the addition of the same concentration of D-arginine. N(omega)-nitro-L-arginine methyl ester (NAME), a potent inhibitor of NOS I, had a similar effect to L-arginine, but the time course of the spectral change was very slow. These results suggest that: (1) the heme-iron pocket of NOS I will be narrower than those of the microsomal and mitochondrial cytochromes P-450; and (2) the binding of L-arginine and its analogue to their binding sites caused conformational changes around the ferrous heme moiety of NOS I.

Calcium-dependent inactivation of neuronal nitric oxide synthase: evidence for the existence of stabilization / activation factor

Neuronal nitric oxide synthase (nNOS; EC 1.14.13.39) activity in supernatant of rat cerebellum homogenate was unstable and chelating reagent protected the activity from the rapid decrease. The main target ion of the chelating reagent was found to be Ca2+. Although the enzyme was very unstable after purification by the procedures including DEAE-cellulose chromatography and ammonium sulfate precipitation, the inactivation was neither accelerated by addition of Ca2+ nor protected by EGTA. Upon addition of boiled supernatant of rat cerebellum homogenate, this purified enzyme became more active and stable, but rapid inactivation occurred again by addition of Ca2+, suggesting the existence of previously unreported Ca2(+)-dependent stabilizer / activator in the boiled supernatant. This factor was concentrated by organic solvent and the effects on the enzyme were completely canceled by addition of Ca2+ or phospholipase C treatment.

Effect of dibutyryl cyclic AMP on axoplasmic transport in the hippocampus

The effect of dibutyryl cyclic AMP (dbcAMP) on axoplasmic transport of cultured hippocampal neuron cells from postnatal 1-day mice was analyzed with a computer-assisted video-enhanced differential interference contrast microscope system. Dibutyryl cyclic AMP increased the axoplasmic transport in both anterograde and retrograde directions. The number of particles flowing in the neurites was increased by 0.5 mM dbcAMP. The peak reached about 160% of the initial value. The instantaneous velocity of axoplasmic transport was also increased by 0.5 mM dbcAMP. The average velocity of anterograde and retrograde direction changed respectively from 1.95 +/- 1.01 microm/s (n = 55) to 2.66 +/- 1.26 microm/s (n = 58) and from 1.94 +/- 0.85 (n = 57) to 2.39 +/- 0.93 (n = 57). Rates were 136.1 and 123.1%, respectively. Previously, we have found that acetylcholine suppressed and adrenaline increased the axoplasmic transport in superior cervical ganglion cells. These effects are related to the amount of endogeneous cAMP. The results of the present report suggest that endogeneous cAMP is also related to hippocampal axoplasmic transport.

Remarkable functional aspects of myoglobin induced by diazaheme prosthetic group

The iron complex of beta,delta-diazamesoporphyrin III, a molecular hybrid of porphyrin and phthalocyanine, was incorporated into apomyoglobin to investigate novel biological aspects of myoglobin. The reconstituted ferric protein forms an internal hemichrome with the iron-bound distal histidine. The reduced ferrous protein has extraordinarily high affinities for O2 and CO. The ferrous myoglobin is capable of strong binding with pyridine, imidazole, cyanide, and azide, and reacts moderately with ammonia. The NO complex exhibited 5-coordinate to 6-coordinate transition over 150 min. The instability of 5-coordinate NO heme is consistent with a high affinity of imidazole to the ferrous heme. The kinetic analyses of the ferrous derivatives suggest the importance of the pi orbitals in neutral ligands as well as the negative charges in anionic ligands. A high affinity of imidazole to ferrous diazaheme accounts for the internal hemochrome formation in ferrous myoglobin containing phthalocyanines.

Design, synthesis, and biological activity of anti-angiogenic hypoxic cell radiosensitizer haloacetylcarbamoyl-2-nitroimidazoles

We designed, synthesized, and evaluated haloacetylcarbamoyl-2-nitroimidazoles, including chloro (KIN-1800, TX-1835, and TX-1836) and bromo derivatives (TX-1844, TX-1845, and TX-1846), as potential hypoxic cell radiosensitizers with antiangiogenic activities. To establish biological function owing to the haloacetylcarbamoyl group in the side-chain, we compared their in vitro radiosensitizing activities with those of their parent 2-nitroimidazoles without haloacetylcarbamoyl groups: misonidazole (MISO), TX-1831, and TX-1832, respectively. Both tert-butoxy substituted derivatives. TX-1835 and TX-1845, were more potent radiosensitizers than TX-1831. The p-tert-butylphenoxy-substituted derivatives, TX-1836 and TX-1846, and the methoxysubstituted derivatives, KIN-1800 and TX-1844, were stronger radiosensitizers than TX-1832 and MISO. We examined the anti-angiogenic activities of these 2-nitroimidazole derivatives containing haloacetylcarbamoyl group by the rat lung endothelial (RLE) cell proliferation assay and chick embryo chorioallantoic membrane (chick CAM) angiogenesis assay and showed that haloacetylcarbamoyl-2-nitroimidazoles were more potent angiogenic inhibitors than the corresponding desacetylcarbamoyl-2-nitroimidazoles. The in vivo chick CAM angiogenesis assay showed that the strong bromoacetylcarbamoyl-2-nitroimidazole radiosensitizers, such as TX-1845 and TX-1846, were the strongest angiogenic inhibitors among them. We concluded that the bromoacetylcarbamoyl-2-nitroimidazole radiosensitizers, such as TX-1845 and TX-1846, are promising as anti-angiogenic hypoxic cell radiosensitizers.

Molecular cloning of the human methylthioadenosine phosphorylase processed pseudogene and localization to 3q28

Human methylthioadenosine phosphorylase (MTAP) is a purine and methionine metabolic enzyme present ubiquitously in all normal tissues, but often deleted in many types of cancer. The gene for this enzyme maps to chromosome 9 at band p21 where the cyclin-dependent kinase inhibitor genes for p16 and p15 also reside. During our efforts to clone this gene we also isolated a phage clone containing a processed pseudogene of MTAP. The sequence is 92% homologous to the MTAP cDNA, is flanked at its 3' end by a repetitive element, but does not possess a poly(A) stretch. We localized this processed pseudogene to band 28 on the long arm of chromosome 3 by fluorescence in situ hybridization. All 22 malignant cell lines with deletions at 9p21 screened possessed the pseudogene.