Low-temperature Fourier transform infrared spectroscopy of photoactive yellow protein.

The photocycle intermediates of photoactive yellow protein (PYP) were characterized by low-temperature Fourier transform infrared spectroscopy. The difference FTIR spectra of PYP(B), PYP(H), PYP(L), and PYP(M) minus PYP were measured under the irradiation condition determined by UV-visible spectroscopy. Although the chromophore bands of PYP(B) were weak, intense sharp bands complementary to the 1163-cm(-1) band of PYP, which show the chromophore is deprotonated, were observed at 1168-1169 cm(-1) for PYP(H) and PYP(L), indicating that the proton at Glu46 is not transferred before formation of PYP(M). Free trans-p-coumaric acid had a 1294-cm(-1) band, which was shifted to 1288 cm(-1) in the cis form. All the difference FTIR spectra obtained had the pair of bands corresponding to them, indicating that all the intermediates have the chromophore in the cis configuration. The characteristic vibrational modes at 1020-960 cm(-1) distinguished the intermediates. Because these modes were shifted by deuterium-labeling at the ethylene bond of the chromophore while labeling at the phenol part had no effect, they were attributed to the ethylene bond region. Hence, structural differences among the intermediates are present in this region. Bands at about 1730 cm(-1), which show that Glu46 is protonated, were observed for all intermediates except for PYP(M). Because the frequency of this mode was constant in PYP(B), PYP(H), and PYP(L), the environment of Glu46 is conserved in these intermediates. The photocycle of PYP would therefore proceed by changing the structure of the twisted ethylene bond of the chromophore.

Childhood thyroid cancer: comparison of Japan and Belarus.

The high incidence of childhood thyroid cancer in Belarus is suspected to be due to radiation exposure after the Chernobyl reactor accident. To clarify the clinical and histological characteristics of childhood thyroid cancer in Belarus, we therefore compared these patients to a radiation non-exposed control series in Japan. In Belarus, 26 thyroid cancers in subjects aged 15 or younger were diagnosed among 25,000 screened between 1991 and 1995 by Chernobyl-Sasakawa Health and Medical Cooperation Project. The clinical and morphologic features of these 26 cases were compared to 37 childhood thyroid cancers in Japan diagnosed between 1962 and 1995. The age distribution at operation in Belarus showed a peak at 10 years old, with a subsequent fall in numbers. In contrast, the age distribution at operation in Japan showed a smooth increase between the ages of 8 and 14. The mean tumor diameter was smaller in Belarus than that in Japan (1.4 +/- 0.7 vs. 4.1 +/- 1.7 cm, P < 0.001). The sex ratio, regional lymph node metastasis, extension to surrounding tissues or lung metastasis did not differ significantly. Histologically, all cases in Belarus were papillary and in Japan 33 cases were papillary and 4 cases were follicular carcinomas. Among papillary carcinomas, the frequency of a solid growth pattern, a criteria for classifying a tumor as poorly differentiated, was higher in Belarus than that in Japan (61.5 vs. 18.2%, P < 0.001). The difference between the features of childhood thyroid cancer in Japan and Belarus may be due to the difference in the process of carcinogenesis, but more direct evidence and further analysis by molecular epidemiology are needed in Belarussian cases.

Immunohistochemical detection of nm23-H1/NDP kinase in childhood thyroid carcinoma.

Childhood thyroid cancer is known to be aggressive. High incidence of lymph node and distant metastasis are characteristic features of these cases. In adult, reduced expression of nm23-H1/nucleoside diphosphate (NDP) kinase has been correlated with cancer invasion and metastasis in some tumor types. Therefore, we examined the expression of nm23-H1 gene product in childhood thyroid carcinomas in Japan. 27 primary thyroid carcinomas and 8 metastatic lymph nodes were analyzed by immunohistochemistry using monoclonal antibody H1-229. 21 out of 23 cases (91%) of papillary carcinomas were positively immunostained, whereas none of the 4 follicular carcinomas showed any immunoreactivity. No correlation was found between the nm23-H1/NDP kinase antigen expression and nodal involvement or distant metastasis in primary tumors. However, only 50% (4 out of 8) of metastatic lymph nodes from papillary carcinoma were positively stained, demonstrating a significant decrease comparing to those of primary sites. These data indicate that the expression of nm23-H1/NDP kinase cannot predict tumor metastatic potential in childhood thyroid cancer.

Inhibitory effect of bombesin/gastrin-releasing peptide (GRP) antagonists RC-3950-II and RC-3095 on MCF-7 MIII human breast cancer xenografts in nude mice.

Bombesin/gastrin-releasing peptide (GRP) may be involved in the growth of human breast cancers. Nude mice bearing xenografts of MCF-7 MIII human breast cancer cell line were treated for 7 weeks with bombesin/GRP antagonists RC-3950-II and RC-3095. RC-3950-II, administered sc twice daily at a dose of 10 micrograms, produced significant inhibitory effects on tumor growth after 2 weeks of administration. RC-3095 acetate (D 22213), injected sc twice daily at the same dose of 10 micrograms, suppressed tumor growth after 4 weeks. Both RC-3950-II and RC-3095 significantly decreased the final tumor volume and tumor weights. RC-3950-II appeared to be somewhat more efficacious than RC-3095 in inhibiting the growth of MCF-7 MIII breast cancers. Chronic treatment with either bombesin/GRP antagonist caused down-regulation of receptors for epidermal growth factor (EGF) in tumor cell membranes, which might be related to inhibition of tumor growth. These findings suggest that bombesin/GRP antagonists should be considered for a new endocrine therapy of breast cancer.

Treatment with luteinizing-hormone-releasing hormone antagonist sb-75 decreases levels of epidermal growth-factor receptor and its messenger-RNA in ov-1063 human epithelial ovarian-cancer xenografts in nude-mice.

The aim of this study was to investigate the effect of administration of LH-RH antagonist SB-75 and agonist [D-Trp(6)]LH-RH on receptors for epidermal growth factor (EGF) in OV-1063 human epithelial ovarian cancer. Female athymic nude mice bearing xenografts of OV-1063 human epithelial ovarian cancer were treated for 3 weeks with the modern LH-releasing hormone (LH-RH) antagonist [Ac-DNal(2)(1), D-Phe(4Cl)(2), D-Pal(3)(3), D-Cit(6), D-Ala(10)] LH-RH (SB-75, Cetrorelix), the agonist [D-Trp(6)]LH-RH, or bombesin/gastrin-releasing peptide antagonist RC-3095. SB-75 and [D-Trp(6)] LH-RH were injected s.c. at doses of 100 mu g/day, and RC-3095 was injected at a dose of 40 mu g/day. Tumor growth, as measured by percentage change in tumor volume, was significantly inhibited by the treatment with SB-75, but not by [D-Trp(6)] LH-RH or RC-3095. Treatment with SB-75 greatly decreased the levels of mRNA for EGF receptor and reduced the number of EGF binding sites on tumor membranes. Effects of SB-75 on EGF receptors might be related to inhibition of tumor growth. Our findings support the view that LH-RH antagonists such as SB-75 could be considered for possible hormonal therapy of epithelial ovarian cancer.

Inhibition of growth of the human malignant glioma cell line (U87MG) by the steroid hormone antagonist RU486.

Treatment of nude mice bearing xenografts of the human malignant glioma U87MG cell line with the steroid hormone antagonist RU486 for 4 weeks resulted in a significant and dose-dependent suppression of tumor volume and weight. Receptor analyses of tumor cytosol preparations demonstrated a single class of high affinity binding sites for dexamethasone, but the absence of receptors for progesterone. RU486 also nullified the stimulatory effect of dexamethasone on proliferation of U87MG cells in vitro. These results indicate that the growth of U87MG human malignant glioma is dependent on corticoids. The antiproliferative effect of RU486 appears to be due to the inhibition of binding of glucocorticoid hormones to their receptor proteins. Our results suggest a new therapy for some brain tumors, such as malignant gliomas based on the steroid hormone antagonist RU486.

Regulation of cystathionine gamma-lyase in Saccharomyces cerevisiae.

Regulation of the two enzymes in reverse trans-sulfuration was investigated in Saccharomyces cerevisiae. In wild-type strains, cystathionine gamma-lyase, but not cystathionine beta-synthase, was depressed nearly 15-fold if cells were starved for both inorganic and organic sulfur compounds. In a met17 strain which is defective of O-acetylserine and O-acetylhomoserine sulfhydrylase, the same enzyme was derepressed if organic sulfur compounds were limited; the repressive effect was in the order of glutathione greater than methionine greater than cysteine. The repressive effect of methionine was not observed, however, in a cys2 cys4 strain which is deficient of serine O-acetyltransferase and cystathionine beta-synthase, indicating that methionine itself is not the effector. The weak repressive effect of cysteine was attributed to inefficient uptake of this amino acid. Our observations indicate that cystathionine gamma-lyase is the target of regulation in reverse trans-sulfuration and that cysteine is very likely to be the effector of this regulation.

A case of cervical carcinoma of the uterus presenting with hyperosmolar non-ketotic coma as a manifestation of ectopic adrenocorticotropic hormone syndrome.

A case of advanced cervical carcinoma of the uterus with ectopic adrenocorticotrophic hormone (ACTH) syndrome is described. The patient was seen for general malaise 21 months after surgical treatment of the primary lesion whose histology was undifferentiated small cell carcinoma of the uterine cervix. She had extensive metastases in the liver and the abdominal wall. In addition to the typical clinical manifestations of Cushing's syndrome such as moon face, central obesity and acne vulgaris, hyperglycemia was so severe that she was in a hyperosmolar non-ketotic coma. Endocrinological examinations revealed elevated plasma ACTH and cortisol, and urinary excretion of 17-hydroxycorticosteroids and 17-ketosteroids, which were not suppressed by high-dose dexamethasone administration. Based on these clinical and laboratory findings, a diagnosis of ectopic ACTH syndrome was made. Among the results of other endocrinological examinations conducted to find the etiological cause of the hyperglycemic coma, which seemed to be unusual for ectopic ACTH syndrome, the plasma somatostatin level was abnormally high. Metastatic tumors in the liver obtained at the time of autopsy contained large amounts of both ACTH and somatostatin, and gel filtration studies revealed that the peptides produced by the tumor had the molecular sizes of the biologically active forms of the respective peptides. These observations suggest possible involvement of the somatostatin in deteriorating glucose intolerance to develop hyperglycemic hyperosmolar non-ketotic coma as a drastic disturbance of metabolism.

Cysteine biosynthesis in Saccharomyces cerevisiae: mutation that confers cystathionine beta-synthase deficiency.

The cys2-1 mutation of Saccharomyces cerevisiae was originally thought to confer cysteine dependence through a serine O-acetyltransferase deficiency. In this study, we show that cys2-1 strains lack not only serine O-acetyltransferase but also cystathionine beta-synthase. However, a prototrophic strain was found to be serine O-acetyltransferase deficient because of a mutation allelic to cys2-1. Moreover, revertants obtained from cys2-1 strains had serine O-acetyltransferase but not cystathionine beta-synthase, whereas transformants obtained by treating a cys2-1 strain with an S. cerevisiae genomic library had cystathionine beta-synthase but not serine O-acetyltransferase. From these observations, we conclude that cys2-1 (serine O-acetyltransferase deficiency) accompanies a very closely linked mutation that causes cystathionine beta-synthase deficiency and that these mutations together confer cysteine dependence. This newly identified mutation is named cys4-1. These results not only support our previous hypothesis that S. cerevisiae has two functional cysteine biosynthetic pathways but also reveal an interesting gene arrangement of the cysteine biosynthetic system.