Differential host utilisation by different life history stages of the fish ectoparasite Argulus foliaceus (Crustacea: Branchiura)

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\u3b12-Adrenergic stimulation enhances growth hormone secretion in the dog: a presynaptic mechanism?

ntravenous administration of clonidine (CLO), (2,4 and 8 ug/kg), a predominantly \u3b12-adrenergic receptor agonist, induced in unanesthetized dogs clear-cut and dose -related rises in plasma GH (cGH) levels. Pretreatment with the selective antagonist of \u3b11-adrenergic receptors prazosin (0.1 mg/Kg iv) left unaltered the cGH rise inducedby 4 ug/Kg of CLO whilst blockade of \u3b12-adrenergic receptors by yohimbine (2.5 mg/Kg iv) completely prevented it. In dogs treated 24 h previously with reserpine (0.5 mg/Kg iv), a depletor of brain catecholamine stores, CLO was ineffective to stimulate cGH release. These data indicate that in the dog the GH-releasing effect of CLO occurs via stimulation of \u3b12-adrenergic receptors and suggest that the latter are located presynaptically in relation to norepinephrine neurons

Prolactin lowering effect of amphetamine in normoprolactinemic subjects and in physiological and pathological hyperprolactinemia

The effect on plasma prolactin (PRL) of d-amphetamine (Amph) was studied in normo- and hyperprolactinemic subjects. In normoprolactinemic women Amph failed to lower plasma PRl levels when infused intravenously over 1 h at the dose of 7.5 mg, but induced at the dose of 15.0 mg a modest inhibition of plasma PRL (maximum PRL inhibition 20 \ub1 4.5% at 45 min). Likewise, in puerperal women Amph at the dose of 7.5 mg did not decrease significantly plasma PRL levels but it was active in this respect (maximum inhibition 37 \ub1 10% at 120 min) at the dose of 15.0 mg. In subjects with presumptive evidence of a PRL-secreting adenoma, Amph at either the 7.5 mg or the 15.0 mg dose failed to alter baseline PRL levels. These results indicate that Amph is a poor PRl suppressor in either normo- or hyperprolactinemic subjects. It is proposed that this may be due to the drug's ability to effect release of dopamine mainly from a non-granular pool of the amine

A follow-up of GH-dependent biomarkers during a 6-month period of the sporting season of male and female athletes

In order to verify the effects of the sporting season (entailing periods of training, competition, recovery, resting) on GH-dependent parameters in male and female athletes from different sporting disciplines, 47 male and female athletes (3 rowers, 5 swimmers, 7 alpine skiers, 3 soccer players, 7 middle distance runners, 14 sprinters, 4 triathletes, 1 road walker, 3 cyclists) were followed-up for a period of 6 months. Blood samples were taken every two months for the evaluation of IGF-I, N-terminal propeptide of type III procoliagen (PIIINP) and C-terminal cross-linked telopeptide of type I collagen (ICTP). Abnormal IGF-I, PIIINP and ICTP levels were observed during the follow-up period in 7/100 (7%), 9/100 (9.0%) and 8/100 (8%) samples of the male group, respectively, and in 9/88 (10.2%), 1/88 (1.1%) and 0/88 (0%) samples of the female group, respectively. Abnormal levels appeared to be randomly distributed over the different periods of the sporting season and within male and female subjects, with the large majority of abnormal values being found in the younger athletes. Taking into account all the tests done during the 6-month period (no. 564), individual markers failing outside the normal range (for age) were observed in a small number of instances (34/564 tests done, 24/300 for males and 10/264 for females). When our method for the detection of exogenous recombinant GH (rhGH) administration, based on the concomitant determination of these three peripheral GH-dependent markers and on the attribution of specific scores, was applied in the same athlete at a given time point of the 6-month period, the prevalence of a positive score was extremely low (ie, 3/188 samples or 1.6%). Total positive scores were actually recorded in only three male athletes (2 swimmers and 1 skier, aged <21 yr) at one occasion during the 6-month period considered. In contrast, no total positive scores were found in female athletes (ie, 0/88 samples). In conclusion, the concentrations of IGF-1, PIIINP and ICTP were stable and not significantly modified during 6 months of a sporting season (entailing periods of training, competition, recovery, resting) in athletes from different sporting disciplines. Therefore our method, based on the concomitant determination of three peripheral GH-dependent biomarkers appears safe, acceptable, relatively inexpensive and repeatable (in case of positive or suspected values) immediately or at different intervals of the sporting season. Further additional studies are requested to precise the cut-off values for narrower age-class subdivisions in both genders in order to improve the proposed method

Influence of growth hormone on the immunosuppressive effect of prednisolone in mice

Growth hormone can be used to counteract some catabolic effects of long-term administration of glucocorticoids, such as impairment of growth in children and osteoporosis. However, owing to its immunostimulatory properties the hormone may counteract the effect of glucocorticoids on the immune system. To investigate this question we administered different doses of hGH (4, 8, 40 IU/kg) to C57/Bl/6J mice treated for two days with prednisolone, and evaluated thymus and spleen parameters and natural killer activity. Growth hormone at the dose of 4 and 8 IU/kg reversed prednisolone-induced reduction of spleen and thymus weight and cellularity, whereas the highest dose showed to be immunosuppressive in itself. Two days after treatment withdrawal, a recovery of spleen parameters was evident, whereas the thymus was still suppressed by preceding prednisolone or hGH (40 IU/kg) treatments. The pattern of natural killer activity displayed by the splenocytes resembled that present under treatment. In a second experiment prednisolone, administered for 10 days, drastically reduced the number of viable spleen and thymus cells as well as the relative spleen and thymus weights, an effect reversed by concomitant administration of hGH (0.8, 4, 8 IU/kg). Natural killer activity, which was significantly depressed by prednisolone, was restored by the intermediate GH dose only. The 8 IU/kg GH dose was immunosuppressive in itself