Effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on corticotropin-releasing hormone (CRH) gene expression in the rat hypothalamic paraventricular nucleus

Pituitary adenylate cyclase-activating peptide (PACAP) is a 38-amino-acid polypeptide, first isolated from hypothalamus, which directly stimulates in vitro the production of cAMP as well as the release of several pituitary hormones, such as growth hormone and luteinizing hormone. In vivo, PACAP has been shown to stimulate ACTH release. The presence of PACAP receptors in several brain areas, including the hypothalamus, suggests that this peptide might play a role as a neurotransmitter/neuromodulator and might be involved in the regulation of hypophysiotropic neurohormones. In order to study the role of PACAP on corticotropin-releasing hormone (CRH) neuron, we have investigated the effects of intracerebroventricular (i.c.v.) and intravenous (i.v.) injections of PACAP and the potent PACAP antagonist PACAP(6–38) on CRH gene expression in the hypothalamic paraventricular nucleus (PVN) in the male rat. The levels of CRH mRNA were evaluated by quantitative in situ hybridization. The i.c.v. injection of PACAP (4 μg/kg b.wt.) produced a 22% increase in the hybridization signal, an effect which was completely prevented by the concomitant injection of the PACAP antagonist (4 μg/kg b.wt.). On the other hand, the administration of the PACAP antagonist induced by itself a 40% decrease in the amounts of CRH mRNA. The i.v. injection of the same peptides (100 μg/kg. b.wt.) produced very similar results. These data strongly suggest that PACAP is involved in the positive regulation of CRH gene expression via specific central receptors and then can play a role as a neurotransmitter/neuromodulator. The effect observed after i.v. injection of PACAP also suggests that the circulating levels of PACAP can play a role in the modulation of CRH gene expression. PACAP might then be involved in the regulation of the HPA axis by a double mechanism: stimulation of CRH gene expression at the central level and direct effect on pituitary corticotrophs.     

Melatonin, Thymic Serum Factor, and Cortisol Levels in Healthy Subjects of Different Age and Patients With Skin Melanoma

Results are given of daily excretion levels of 6-oxymelatonin, thymic serum factor (FTS), and cortisol in the blood of 140 healthy subjects and 90 patients with skin melanoma, ranging from 20 to 49 years of age. Correlation factor (eta) was used for evaluating the correlation between the indices examined. Daily excretion of 6-oxymelatonin was found to decrease considerably in healthy men over 30 years of age, the extent of such reduction correlating with age (eta = 0.48 +/- 0.19, P less than 0.02). Similar correlation is absent in healthy women. There is an age-related reduction in FTS in both healthy women (eta = 0.63 +/- 0.13, P less than 0.001) and men (eta = 0.57 +/- 0.12 P less than 0.001), although in the latter this reduction occurs 10 years earlier (beginning at 30 years) and is more pronounced. Blood cortisol levels in healthy subjects increase with age, more notably in men than in women. Age-related changes in the content of the hormones under study are still more pronounced when patients of corresponding age groups develop neoplasms. Male patients from 20 to 29 and 30 to 49 years of age with melanoma show daily levels of 6-oxymelatonin excretion of 10.13 +/- 0.71 micrograms/24 hr and 11.70 +/- 1.26 micrograms/24 hr, respectively, while healthy men of the same age show much higher melatonin levels, i.e., 18.98 +/- 1.36 micrograms/24 hr and 15.46 +/- 1.13 micrograms/24 hr, respectively. Male melanoma patients aged 30 to 49 years have reduced log2 of FTS titers (as little as 1.44 +/- 0.23) compared to that of healthy, age-matched males (3.40 +/- 0.23, P less than 0.05). In female patients aged 20-39 years and 40-49 years, the log2 of FTS titers was 1.96 +/- 0.37 and 1.62 +/- 0.25, respectively, which is significantly lower (P less than 0.05) than values for healthy women of the same age (5.60 +/- 0.17 and 3.60 +/- 0.41). In melanoma male and female patients from 20 to 49 years of age, cortisol levels are significantly higher than the mean values for this hormone in age-matched healthy subjects, being 193.18 +/- 19.67 ng/ml and 135.43 +/- 14.36 ng/ml, respectively (with normal levels of 140.60 +/- 9.62 ng/ml and 101.03 +/- 8.61 ng/ml). The results of correlation analysis indicate that daily excretion values for 6-oxymelatonin in healthy subjects correlate with both FTS titers and cortisol content, while the latter two correlate with each other (P less than 0.05). Statistically significant correlation between the levels of all examined hormones was found in melanoma patients as well (P less than 0.05).     

Immunochemical studies of antisera to human fibrinopeptide-B

The immunochemical specificity of rabbit antisera to human fibrinopeptide-B (FPB) has been studied by comparing the relative abilities of FPB and of various proteins and peptides containing the NH2-terminal segment of the B beta-chain of human fibrinogen to inhibit the binding of a radioiodinated FPB derivative by each of seven anti- FPB sera. Anti-FBP sera varied in the extent to which they cross- reacted with fibrinogen, the NH2-terminal disulfide knot of fibrinogen (N-DSK), B beta 1(Pyr)-118(Met), B beta 1(Pyr)-42(Arg), and desarginyl- FPB. Anti-FPB sera have been identified that discriminate effectively between FPB and larger FBP-containing peptides; such antisera can be used to measure FPB in the absence of the larger peptides or to demonstrate the presence of larger peptides such as B beta 1(Pyr)- 42(Arg) in extracts of clinical plasma samples by means of an increase in FPB immunoreactivity following thrombin treatment. One anti-FPB serum has been identified that is capable of detecting desarginyl-FPB, and this antiserum has been used in the development of a radioimmunoassay for desarginyl-FPB. Thus, by precisely defining the specificity of anti-FPB sera, it has been possible to identify antisera that are useful, not only in the measurement of FPB, but also in the detection of other important related molecules, such as B beta 1(Pyr)- 42(Arg) and desarginyl-FPB. The immunochemical detection of these FPB- related peptides should provide useful information concerning the action of proteolytic enzymes, such as plasmin on the NH2-terminal segment of the B beta-chain of fibrinogen, and of carboxypeptidase-B on free FPB, in human plasma.