Toshihiko Tsukada

Anti-cachectic effect of ghrelin in nude mice bearing human melanoma cells

Ghrelin is a novel brain-gut peptide that stimulates food intake and body weight gain. We studied the anabolic effect of ghrelin in a cancer cachexia mouse model. SEKI, a human melanoma cell line, was inoculated into nude mice to examine the effects of ghrelin on food intake and body weight. The intraperitoneal administration of ghrelin twice a day (6 nmol/mice/day) for 6 days suppressed weight loss in SEKI-inoculated mice and increased the rate of weight gain in vehicle-treated nude mice. Ghrelin administration also increased food intake in both SEKI- and vehicle-treated mice. Both the weight of white adipose tissue and the plasma leptin concentration were reduced in tumor-inoculated mice compared with vehicle-treated mice; these factors increased following ghrelin administration. The levels of both ghrelin peptide and mRNA in the stomach were upregulated in tumor-inoculated mice. The anabolic effect of ghrelin efficiently reverses the cachexia in mice bearing SEKI human melanoma. Ghrelin therefore may have a therapeutic ability to ameliorate cancer cachexia.

Identification of the mRNA coding for the ACTH-β-lipotropin precursor in a human ectopic ACTH-producing tumor

Abstract The mRNA coding for the ACTH-β-lipotropin precursor from a human ectopic ACTH-producing thymic carcinoid was identified by blot hybridization analysis with the bovine cDNA as a probe. The mRNA from the tumor had the same length (approximately 1,100 nucleotides) as that from the human pituitary. An additional hybridization-positive RNA species of a larger size was found in the tumor. Cell-free translation of the mRNA from the tumor as well as from the pituitary yielded a product with an apparent molecular weight of 38,000 that was reactive both with antibody to ACTH and with antibody to β-endorphin.

Taste function in patients with anorexia nervosa and bulimia nervosa

The sensitivity to sucrose, sodium hydrochloride, tartrate, and quinine was examined by a filter paper disc method in patients with anorexia nervosa and with bulimia nervosa. There were 20 of the 23 anorexia patients and 11 of the 13 bulimic patients who showed hypogeusia. There were 12 of the 23 anorexia patients and 8 of the 13 bulimia patients who showed dysgeusia. Seven anorexia patients were restudied when the treatments produced a weight gain to more than 85% of normal body weight. Taste function had improved substantially in all but still was subnormal. Serum zinc, iron, and triiodothyronine levels in these patients were depressed; however, none of these levels correlated with the taste recognition scores or dysgeusia scores. In conclusion, patients with anorexia nervosa and bulimia nervosa showed hypogeusia and/or dysgeusia, although the etiology of the taste dysfunction in these patients remains to be determined. These findings should be considered in the implications for treating these patients.

Serotonin involvement in the inhibition of luteinizing hormone (LH) release during immobilization in castrated male rats

The involvement of serotonin in mediating the inhibitory effect of immobilization stress on LH secretion in castrated male rats was examined by employing p-chlorophenylalanine (PCPA, 320 mg/kg, ip), an inhibitor of serotonin synthesis, and 5,6-dihydroxytryptamine (5,6-DHT, 50 micrograms, icv), a drug toxic to the indoleaminergic system. Immobilization stress suppressed pulsatile LH release and decreased mean plasma LH levels. Pretreatment with PCPA or 5,6-DHT apparently eliminated the inhibitory effect of immobilization stress on LH release. These results suggest the possible involvement of a serotoninergic mechanism in mediating the suppression of LH release induced by immobilization stress in castrated male rats.

Vasoactive intestinal peptide gene expression in the rat pheochromocytoma cell line PC12

Vasoactive intestinal peptide (VIP) gene expression was analyzed in PC12 cells. VIP mRNA was detected in PC12 cells treated with VIP or forskolin whereas no VIP mRNA was detected in the untreated cells. The induction of the VIP mRNA was enhanced by the simultaneous treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA). PC12 cells stimulated with forskolin plus TPA released immunoreactive VIP. Sephadex G-50 column chromatography revealed that the immunoreactive VIP secreted from PC12 cells is comprised of multiple forms, one of which was indistinguishable from the authentic VIP. PC12 cells supported an efficient transcription from the human VIP gene promoter in a cell-specific as well as cAMP-dependent manner. These results definitely demonstrated the expression of the VIP gene in PC12 cells. VIP biosynthesis may be positively regulated by VIP in an autocrine fashion in PC12 cells.

Immunoreactive corticotropin-releasing hormone levels in the hypothalamus of female Wistar fatty rats.

We have studied immunoreactive corticotropin-releasing hormone (CRH) levels in the hypothalamus of female Wistar fatty rats, a strain with the fa gene transferred from the Zucker rat to the Wistar Kyoto rat, in an attempt to understand the role of CRH in the development of obesity. A study was conducted with 5-week- and 12-week-old female Wistar fatty rats and lean littermates. There was no significant difference in hypothalamic CRH levels between lean and obese rats at the age of 5 weeks (1887 +/- 99.6 vs. 1767 +/- 124 pg/tissue; mean +/- S.E.M.). Hypothalamic CRH immunoreactivities, however, were significantly lower in 12-week-old obese rats (2361 +/- 132 pg/tissue) than those in lean littermates (2992 +/- 118 pg/tissue; P less than 0.05). The difference of CRH contents between the lean and obese group becomes apparent as they grow up and develop obesity.

PLASMA DISAPPEARANCE OF OVINE CORTICOTROPHIN‐RELEASING FACTOR IN MAN

Disappearance of immunoreactive ovine corticotrophin‐releasing factor (IR‐oCRF) from plasma after a single intravenous injection of ovine corticotrophinreleasing factor (oCRF) was studied in man in the morning and evening. Synthetic oCRF (80 μg) was injected intravenously to four normal male volunteers at 0900 h or at 2200 h. Blood samples were drawn before and 2, 5, 10, 15, 30, 45, 60, 90 and 120 min after the oCRF injection. Plasma IR‐oCRF was measured by a specific radioimmunoassay for OCRF. Plasma concentrations of IR‐oCRF after oCRF injections in the morning and in the evening did not differ significantly (P>0·05). Disappearance of IR‐oCRF was modelled with a two‐exponent function by using a non‐linear least squares computer program. The metabolic clearance rate, the apparent initial volume of distribution, the plasma half‐life for the fast component and that for the slow component calculated from all eight tests in the morning and evening were 1·49·0±05 ml/min·kg, 44·4±1·7 ml/kg, 6·8±0·7 min and 46·2±2·3 min (mean ± SEM), respectively. This relatively long half‐life may be responsible for the prolonged biological effect of oCRF administered intravenously. There were no significant differences between parameters of IR‐oCRF disappearance curves in the morning and those in the evening (P>0·05).

Evidence for noradrenergic involvement in naloxone-induced stimulation of luteinizing hormone release in prepubertal female rats

The effects of phenoxybenzamine an alpha-adrenergic blocker, propranolol a beta-adrenergic blocker, and diethyldithiocarbamate a noradrenaline synthesis inhibitor, on the LH increase induced by naloxone an opiate antagonist, was investigated in 25 day old female rats. Pretreatment with phenoxybenzamine or diethyldithiocarbamate suppressed the LH increase induced by naloxone, whereas pretreatment with propranolol had no significant effects on the naloxone-induced LH release. These results suggest that naloxone-induced increase in LH release is mediated via a noradrenergic mechanism.

Regulation of Gene Expression of Pituitary Hormones by Hypophysiotropic Hormones

Forty years ago, Harris (1948) proposed that the secretion of anterior pituitary hormones was regulated by factors synthesized in hypothalamic neurons, released into the hypophyseal-pituitary portal circulation and carried to the anterior pituitary, where they stimulated the secretion of their specific tropic or growth-related hormones. This remarkable concept was demonstrated regarding hypothalamic regulation of pituitary hormone secretion. During the past 20 years five hypophysiotropic hormones have been isolated and definitely characterized; thyrotropin-releasing hormone (TRH); luteotropin(folliculotropin)-releasing hormone (LH(FSH)RH) or gonadotropin-releasing hormone (GnRH); growth hormone (GH) release inhibiting hormone (GHIH) or somatotropin release-inhibiting factor (SRIF; somatostatin); corticotropin-releasing hormone (CRH); and GH-releasing hormone (GHRH). The factors which stimulate or inhibit prolactin (PRL) release have not yet been definitely identified. Although these hypophysiotropic hormones are called releasing hormones because of the rapidity with which they increase plasma levels of pituitary hormones, there is evidence that they also stimulate synthesis of pituitary hormones.

Proopiomelanocortin gene expression in normal and malignant tissues

Summary (1) POMC, the precursor of ACTH, in tumors seems identical to that in the pituitary, although post-translational processing of the precursor is often different in tumors. (2) No gross abnormalities in genomic DNA and mRNA encoding POMC could be detected in tumor tissues. These results suggest that tumor cells produce hormones due to abnormalities in regulation of gene expression. (3) Tissue-specific factors seem to be important for the correct transcription and regulation of the POMC gene. These tissue specific factors may be responsible for the ectopic ACTH production in neoplasms.