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objective: To analyse the role of recombinant HIV-1 protein p17 in the modulation of cell activity. Methods: Peripheral blood mononuclear cells (PBMC) obtained from healthy donors were cultured in the presence or absence of p17 with mitogens such as phytohaemagglutinin or interleukin-2 and their response assayed by cell proliferation. Cross-linking experiments were employed to investigate the presence of a binding between p17 and factor(s) present in human serum. An immunoenzymatic assay for p24 antigen detection was used to analyse the effect of the addition of exogenous p17 to cultures of PBMC infected with HIV-1 in vitro. Results: Purified recombinant p17 protein at a concentration of 0.25 μg/ml significantly increased the proliferation of preactivated PBMC obtained from healthy donors. This effect was obtained by binding p17 to factor(s) present in human serum and observed on both CD4 + and CD8 + T cells. Recombinant p17 also induced an increased rate of HIV-1 replication, probably due to enhanced T-cell proliferation. The activity of p17 protein was inhibited by anti-p17 antibodies generated by injecting recombinant p17 in rabbits, but not by human antibodies generated during the natural course of HIV infection. Conclusion: Characterization of the human factor(s) and identification of the interacting p17 epitope(s) will improve our understanding of the mechanisms used by HIV to efficiently replicate in our organisms.

To study the onset of the action of gonadal sex steroids on the GH axis in spontaneous puberty, which is prolonged and sparingly predictable, we present a clinical investigative paradigm in which six previously untreated boys with isolated hypogonadotropic hypogonadism were exposed to progressively higher testosterone levels designed to mimic the androgen environment recognized during the early stages of puberty. We administered three incremental doses of testosterone (25-, 50-, and 100-mg im injections), each over a period of 4 weeks. Studies of overnight pulsatile GH secretion and GH responses to GHRH alone or combined with L-arginine (a functional somatostatin antagonist) were performed before testosterone administration and after each dose of testosterone. Serum testosterone, but not estrogen, levels increased progressively in all subjects during therapy. Deconvolution analysis of GH release profiles disclosed that GH secretory burst mass was stimulated significantly even by 25 mg testosterone. This parameter was not altered further by higher doses of testosterone. Spontaneous GH secretory burst number and amplitude increased significantly only after the 50- and 100-mg testosterone treatments, after which the serum GH response to GHRH and arginine also rose significantly. In contrast, the GH response to GHRH alone was not significantly affected by any dose of testosterone. Serum testosterone levels correlated significantly with the primary parameters of nocturnal GH secretion. In summary, our experimental model suggests that in males even very small increases in circulating testosterone occurring during the earliest stages of puberty are able to amplify pulsatile GH secretion. Our concomitant secretagogue data further suggest that testosterone exerts its action at different sites in the hypothalamo-somatotropic axis, i.e. directly at the pituitary level, and also at hypothalamic loci, possibly increasing both GHRH and somatostatin release.

The possible involvement of peripheral dopaminergic mechanisms in the action of atrial natriuretic peptides was investigated in 10 subjects by administering 200 micrograms h-ANP 99-126 intravenously for 30 min during treatment with 50 mg carbidopa, a peripheral inhibitor of dopamine synthesis, every 8 h, or during placebo. Atrial natriuretic peptide (ANP) infusion during placebo was associated with a significant increase of diuresis, natriuresis, kaliuresis, urinary noradrenaline, and dopamine excretion. Plasma aldosterone significantly decreased. Blood pressure was slightly reduced. The administration of carbidopa significantly reduced urinary dopamine excretion but did not modify natriuresis, diuresis, indexes of adrenergic and renin-aldosterone system activity, blood pressure, or heart rate, both in basal conditions and in response to ANP infusion. We conclude that the effects of exogenous ANP administration are independent from dopaminergic mechanisms that involve the synthesis of dopamine outside the central nervous system, particularly in the kidney.

Sex steroids play an important role in modulating pulsatile growth hormone (GH) release, acting at both hypothalamic and pituitary level in both humans and experimental animals. Selective estrogen receptor modulators (SERMs) act as either estrogen receptor agonists or antagonists in a tissue-selective manner. In postmenopausal women, serum GH levels correlate positively with endogenous estradiol levels and insulin-like grwoth factor-I (IGF-I) is positively related to bone mineral density (BMD) at the spine and hip. The aim of the present study was to evaluate, for the first time, the direct effect of LY117018, an analog of raloxifene, on GH secretion from both human and rodent pituitary cells in vitro. Our results demonstrated that pharmacological concentrations of the raloxifene analog LY117018 can stimulate GH secretion through a direct action on the pituitary. LY117018 also showed an estrogen-like activity, inducing the proliferation of rat pituitary GH-secreting adenomatous cells (GH1).

In this work we have studied the kinetic parameters of oligomeric tumour necrosis factor alpha (TNF-alpha) dissociation using biospecific interaction analysis (BIA), based on surface plasmon resonance (SPR) of TNF-alpha immobilized on a sensor chip, and by an ELISA technique able to detect TNF-alpha oligomers in solution. Validation studies, carried out with sensor chips bearing TNF-alpha oligomers or bovine albumin monomers, verified that: (a) TNF-alpha can be immobilized in the oligomeric form onto sensor chips; (b) the covalent linkage between TNF-alpha and sensor chips is stable under the experimental conditions; (c) TNF-alpha monomers are present on the sensor chips after dissociation; (d) immobilization and dissociation rate constant (kdiss) measurements are reproducible. The kdiss of recombinant TNF-alpha, measured under non denaturing conditions at pH 7.4 by BIA and ELISA were in good agreement, being 0.92 x 10(-5)/s and 1.1 x 10(-5)/s respectively (corresponding to a half life of about 20.9 h and 17.5 h, respectively). The dissociation rate was found to be significantly affected by the presence of detergents and by the pH of the solution, suggesting that TNF-alpha, at low concentrations, exists in solution with different molecular forms depending on the time of storage and buffer composition. Real-time BIA is rapid and does not require particular antibodies or reagents. Thus, the stability of the quaternary structure of natural or recombinant TNF-alpha from human or animal species as well as that of other oligomeric cytokines can probably be studied using this method.

Background The aim of our study was to assess whether there could be any clinical and/or endocrine (spontaneous growth hormone [GH] secretion rate, baseline insulin-like growth factor-1 [IGF-1]) predictors and/or determinants of the acute effects of continuous intravenous infusion of recombinant human GH on hemodynamic parameters in 12 patients with dilated cardiomyopathy and congestive heart failure (CHF). Methods And Results The study involved 12 male patients with chronic CHF (ischemic in 8 patients and idiopathic in 4). Ten patients were in New York Heart Association functional class III or IV and 2 in class II. The first 24 hours were considered the control period; in fact, during the following 24 hours, all the patients underwent intravenous constant pump infusion of recombinant human GH. Blood samples for GH assay were taken every 20 minutes during the first night of the study (from 10 PM to 6 AM). Moreover, blood samples for GH assay were also taken during exogenous GH infusion. Blood samples for IGF-1 assays were taken at 8 AM of each of the 3 days of the study. Pulmonary artery pressure (PAP) and capillary wedge (PCWP) pressure, cardiac index, and arterial blood pressure were measured 30 minutes after right heart catheterization (baseline 1), at the end of the control period (baseline 2), and every 4 hours during GH infusion. A negative correlation has been found between mean nocturnal GH levels and baseline IGF-1 levels (r = –0.47, P = .124) and between mean nocturnal GH levels and both postinfusion absolute (r = –0.67, P < .05) and delta (postinfusion–preinfusion) (r = –0.58; P < 005) IGF-1 levels. No significant correlations have been found between several parameters of liver function (albumin, bilirubin, and pseudocholinesterase) and mean nocturnal GH. However, baseline IGF-1 levels showed a negative significant correlation (r = –0.76, P < .01) with total bilirubin and a positive correlation (r = 0.72, P < .01) with pseudocholinesterase. Baseline IGF-1 levels showed a significant negative correlation with baseline mean PAP (r = –0.68, P < .05) and PCWP (r = –0.70, P < .05) and a positive correlation with baseline cardiac index (r = 0.71, P < .05). Baseline IGF-1 levels also showed a significant negative correlation with absolute mean PAP (r = –0.63, P < .05) and mean PCWP (r = –0.67, P < .05) after GH infusion. After GH infusion, IGF-1 levels also negatively correlated with post–GH infusion mean PAP (r = –0.50, P = .09) and mean PCWP (r = –0.66, P < .05). The positive correlation between either baseline or postinfusion IGF-1 and the postinfusion cardiac index (r = 0.40 and 0.43, respectively) did not reach statistical significance. Conclusions GH has acute functional effects on the heart in patients with CHF, including both an increase in myocardial contractility and a decrease in vascular resistances, and among patients with CHF, those with low baseline IGF-1 are likely to have fewer beneficial effects from GH infusion. (Am Heart J 1999;137:1035-43.)

The aim of the present study was to characterize in a large series (N = 12) of cultured somatotrope adenomas the in vitro effects of the neuropeptide galanin on growth hormone (GH) secretion. This was contrasted with two peptides known to be GH secretagogues (GH-releasing hormone [GHRH] and thyrotropin-releasing hormone [TRH]) and a peptide with a known GH-inhibitory effect (the somatostatin analog octreotide). Groups of three wells were incubated for 4 hours with growth medium alone (control incubation), galanin, GHRH(1–29)NH 2 , TRH, or octreotide. Galanin and octreotide were applied at concentrations of 0.1, 1, and 10 μmol/L, and GHRH and TRH at concentrations of 0.01, 0.1, and 1 μmol/L. Galanin was able to inhibit GH release in nine of 12 cultured somatotrope adenoma cells. This inhibitory effect was clearly dose-dependent in five adenomas. Overall, the mean GH nadir after galanin was −36.1% in nine responder adenoma cultures versus control wells. Octreotide inhibited GH release in five of eight cultured somatotrope adenoma cells. The mean GH nadir after octreotide was −32.7% in five responder adenoma cultures compared with control wells. GHRH and TRH were able to stimulate GH release, respectively, in seven of 11 and in six of seven cultured somatotrope adenoma cells. The mean GH peaks after either GHRH or TRH in responder adenoma cultures were, respectively, +71.5% and +143.7% compared with levels in the control wells. In conclusion, the consistency and potency of the in vitro GH-inhibitory effect of galanin in a large series of somatotrope adenomas are at least similar to those of the most effective available GH-lowering agent, the somatostatin analog octreotide.

The aim of our study was to investigate the effect of hexarelin, a novel GH-releasing peptide-6 analog, and GH-releasing hormone (GHRH) (alone or in combination) on GH secretion in adult patients with increased somatostatin tone due to chronic glucocorticoid excess. We studied seven adult patients undergoing long-term (no less than 6 months) immunosuppressive glucocorticoid treatment for non-endocrine diseases (six females and one male, age range 42–68 years) and one subject (female, age 31 years) with endogenous hypercortisolism due to adrenal adenoma. Six normal subjects (four females and two males) matched for sex and age with the patients and not undergoing any therapy served as controls. All the subjects underwent the following three tests in random order: (1) human GHRH (1–29)NH2 (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min, (2) hexarelin (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min and (3) hexarelin (100 μg in 1 ml of saline) plus GHRH (100 μg in 1 ml saline) injected as an i.v. bolus at 0 min. After GHRH alone the patients with glucocorticoid excess showed a blunted GH response as compared with normal subjects (median delta GH: 0·9, range 0–5·6 μg/l vs 7·1, range 0·3–14·9 μg/l). No significant differences were observed in the steroid-treated group with respect to normal subjects after hexarelin alone (median delta GH: 15·5, range 1·9–45·2 μg/l vs 17·9, range 5·5–53·9 μg/l). The GH responses after the combined stimuli were significantly decreased in the patients with glucocorticoid excess as compared with normal subjects (median delta GH: 43·5, range 21–56·9 μg/l vs 73·7, range 19·6-116·8 μg/l). The two stimuli acted in a synergistic fashion in both groups of subjects. It may be hypothesized that hexarelin influences the GH inhibitory effect of glucocorticoids in humans, acting at the hypothalamic somatostatin level. Journal of Endocrinology (1995) 146, 227–232

It has been previously reported that different quantitative results can be obtained when TNF alpha is measured in biological fluids by bioassay and immunoassay. This is thought to be related to the presence of antigenic forms of TNF alpha that cannot be detected by bioassay, such as complexes with soluble receptors (sTNF-R) or TNF alpha monomers. In this work we have observed discrepancies between antigenic and bioactive TNF alpha even when we used a sandwich-ELISA, unable to detect TNF alpha monomers, based on antibodies that bind epitopes overlapping with the soluble-receptor binding site of TNF alpha. Moreover, we found that antigenic TNF alpha levels in the presence of p55-sTNF-R (sTNF-R1) measured by different immunoassays were variable, depending on the immunoreagents and incubation time. To investigate whether TNF alpha-soluble receptor complex dissociation occurring during assay incubations contributes to the variability of results, we studied the kinetics of TNF alpha-soluble receptor interactions and examined the effect of complex dissociation using different analytical systems. TNF alpha association (k(on)) and dissociation (k(off)) rate constants with sTNF-R1, measured by real-time biospecific interaction analysis, were 5.01 x 10(5) s(-1) M(-1) and 2.8 x 10(-4) s(-1), corresponding to an equilibrium constant (K-d) of 0.59 nM and to a half life for these complexes of 38 min. Complex dissociation and differential changes in the TNF alpha-sTNF-R1 bound:free ratio, in different analytical systems, markedly affects TNF alpha quantification.