Evidence for a direct inhibitory effect of morphine on the secretion of posterior pituitary hormones

The effect of morphine and naloxone on vasopressin and oxytocin release from incubated neurointermediate lobe and pars nervosa of rat pituitaries were investigated. It was shown that morphine and endorphins blocked hormonal output and that this inhibitory action was reversed by naloxone. It is concluded that opiates exert a direct inhibitory influence on vasopressin and oxytocin secretions from the neurohypophysis.

[Specificity of the effect of vasopressin at the anterior pituitary level (author's transl)]

The present investigation was conducted in order to get more insight into the mechanism of action of vasopressin (VP) on ACTH secretion and characterize VP interaction with putative receptor sites at the level of the anterior pituitary gland. The experimental procedure consisted of increasing ACTH release from incubated pituitary fragments as induced by VP in the presence or absence of oxytocin (OT) and various releasing factors. Our results show that, whereas OT was able to depress VP-induced release of ACTH (Fig. 2), TRF (Fig. 3), LH-RH (Fig. 4) and crude "CRF" extract (Fig. 1) it did not exhibit any significant inhibitory effect. This provides indirect evidence for the presence of specific pituitary sites for VP and related peptides such as OT. The latter, however, was devoided of corticotrophic releasing properties.

In vitro regulation of ACTH release from neurointermediate lobe of rat hypophysis. III. Effect of potassium (K+), calcium (Ca++) and dibutyryl cyclic 3',5'-adenosine monophosphate (dbc-AMP)

Alterations in the ionic composition of the medium and different secretagogues have been used in order to study the mechanism of release of ACTH from superfused neurointermediate lobes (NIL) of rat hypophysis. We showed that: (a) a tenfold increase of K+ in the medium caused a reversible and repeatable stimulation of the ACTH release; (b) removal of Ca++ reversibly abolished the stimulating effect of high K+; (c) removal of Ca++ had no effect on the stimulating effect of a hypothalamic extract (HE); (d) in the latter case, a reversible significant weakening was obtained by the addition of EDTA in the Ca++-free medium; (e) dbc-AMP caused a reversible and repeatable stimulation of the ACTH release; (f) comparable results were obtained for anterior lobes (AL) superfused in the same conditions. From these data we can conclude that Ca++ is necessary for the stimulation of the hormonal release and that factors such as K+ or dbc-AMP can mimic the in vitro stimulating effect of a HE. Similarities, which appear in this study, between the modulation of the ACTH release from NIL and AL, led us to support the idea that, in vivo, a release of ACTH from the NIL, may occur in physiological conditions.

Comparative studies of ventricular ejection phase parameters for the detection of impaired cardiac function

Experimental studies were carried out in 11 anesthetized pigs in order to compare the sensitivity of left ventricular ejection phase parameters as determined by quantitative angiocardiographic methods, for detection of mild or moderate ventricular dysfunction. The experimental setup implied various degrees of nonadequate muscular hypertrophy in relation to chronic volume overload by aortic insufficiency. Left ventricular stroke volume, flow, ejection fraction and mean circumferential fiber shortening did not demonstrate impairment of ventricular function reserve when studied in the resting state of the circulation, but became indicative to some degree by their abnormal pattern of response to acute afterload stress (angiotensin infusion). Mean normalized systolic ejection rate as well as normalized values of systolic ejection time were found to be the most sensitive indices of ventricular function in this study.

Involvement of vasopressin in corticotropin-releasing effect of hypothalamic median eminence extract

Incubation of anterior pituitary (AP) fragments of rats was used to determine the specific role played by vasopressin (VP) in the overall effect of crude hypothalamic median eminence (HME) extract on ACTH release. Using the property of an AVP antiserum (AS) to completely abolish the CRF-like effect of hypothalamic VP without apparently affecting the effect of CRF, we show that under specific incubation conditions, the effect of the two secretagogues are additive at the pituitary level. ACTH secretion of pituitaries was enhanced when incubation was carried out in the presence of VP together with a maximum effective dose of VP-free HME extract (from Brattleboro rats). These observations favor the hypothesis that VP and CRF have different receptor sites in the anterior pituitary.

[Goitres with "cold" nodules in an endemic goitre area (author's transl)]

Of 339 goitres with "cold" nodules 17.7% were histologically malignant. Related to all cold nodules which were examined, this suggest a "true" malignancy rate of nodules of about 0.4%. The risk of malignancy is highest in patients over 60 years of age. The malignancy rate was high, at 23%, in cold nodules of recurrent goitres. Fine-needle aspiration biopsy pre-operatively will correctly diagnose over 90% of malignant nodules.

Renal transplantation in insulin-treated diabetics

In our view, renal transplantation in the uremic diabetic patient is justified. Recipients should be selected with caution. Patients with both loss of vision and heart disease will only rarely benefit from renal transplantation. Living related donor should be preferred if possible.

Effects of adrenalectomy and hypercorticism on the ACTH content of the anterior and posterior pituitary in rats with inherited diabetes insipidus (Brattleboro strain)

The effects of adrenalectomy (Adx) and hypercorticism on the ACTH content in the anterior (AH) and the neurointermediate lobe (NIL) of the pituitary in Long Evans (+/+), heterozygous (+/DI) and homozygous (DI/DI) Brattleboro rats were determined using dispersed adrenal cells bioassay. Adx decreased the NIL-ACTH content in +/DI and DI/DI rats and left it unchanged in the +/+ rats. Adx increased the AH-ACTH content in the three groups. Hypercorticism had a delayed decreasing effect both in the AH and in the NIL in all rats, with one exception for the NIL in DI/DI rats. Conversely to what appeared in Wistar rats, in Long Evans and Brattleboro rats the corticosterone administered in drinking water was unable to reduce the increase in AH-ACTH activity. These data suggest that Brattleboro, and, to a lesser extent, Long Evans rats from which the former are derived present some particularities in the regulation of their corticotropic function at the AH and the NIL level. We also observed that NaCl (0.9%) added to drinking water and hypercorticism are two factors able to increase diabetes insipidus in homozygous rats without modifying the water intake in Long Evans and heterozygous rats.

Relationship between ACTH secretion and corticoid binding to specific receptors in perifused adenohypophyses

This study reports on the kinetics of glucocorticoid-induced inhibition of ACTH release, together with steroid binding to specific pituitary receptors. It was shown that corticosterone (CORT) inhibited ACTH output provoked by either corticotropin-releasing factor (CRF) extracts or dbcAMP, in a manner which was both dose- and time-dependent. A close correlation appeared to exist between the degree of ACTH blockade and the percentage of filled steroid-binding sites. However, exposure of hypophyses to CORT for a critical period of time was a prerequisite for such a relationship to develop. Furthermore, it was found that dexamethasone (DEX) was more potent than CORT in inhibiting ACTH secretion and, in addition, bound to a greater extent to nuclei of pituitary cells. These data suggest the existence of a close correlation between occupancy of pituitary glucocorticoid receptors and modulation of ACTH secretion.

In vitro regulation of ACTH release from neurointermediate lobe of rat hypophysis. II. Effect of neurotransmitters

The effect of various neurotransmitters on adrenocorticitropic hormone (ACTH) release from superfused neurointermediate lobes of rat hypophysis (NIL) was investigated. Acetylcholine, serotonin, and histamine were shown to have no significant effect on the spontaneous release of ACTH. In contrast, dopamine (DA) and noradrenaline (NA) stimulated NIL ACTH release in a dose-dependent manner. The stimulating effect of DA was mimicked by apomorphine and inhibited by haloperidol, whereas that of NA was abolished by phentolamine. In a comparative study, none of these neurotransmitters is shown to have any significant stimulating effect on ACTH release from superfused anterior lobes. It is concluded that the ACTH release from NIL might be controlled, at least in part, by catecholaminergic innervation.

Specific interaction of corticosteroids with binding sites in the plasma membranes of the rat anterior pituitary gland

The binding of glucocorticoids to a crude fraction of rat pituitary plasma membranes and to solubilized membrane proteins was measured. The binding characteristics were similar to those exhibited by transcortin: radioactive corticosterone was bound to a greater extent than radioactive dexamethasone and labelled corticosterone, but not labelled dexamethasone, was displaced by unlabelled corticosterone, deoxycorticosterone and progesterone. A Scatchard plot of the binding data revealed the presence of a binding material with a dissociation constant of about 3.2 nmol/l, which sedimented at 4S after sucrose density-gradient centrifugation. It was found that the number of binding sites was inversely related to the concentration of corticosterone in the circulation and was increased after long-term adrenalectomy. These data suggest that a material similar to transcortin is complexed to the plasma membrane of rat pituitary cells.

Brachial plexus palsy in neonates and children

In 135 children with obstetrical palsy, clinical and electrodiagnostic studies on inital and serial evaluation aided in designing a conservative treatment program. Prevention of contractures, maintenance of muscle strength and reinforcing the child's awareness of the affected limb were predicated on the limiting factors of permanent denervation and agnosia. Instability of the scapula, scapulohumeral adhesions and elbow flexion with loss of active supination defy conventional range of motion exercises. Forced passive supination of the elbow may actually compound the problem of radial head dislocation and ulnar bowing. Because of the young age of most of the patients, only 7 have had orthopedic intervention. Rotational osteotomy of the humerus and transfer of intact muscles seem to improve function. Prior to selection of muscles for transfer, electromyography is advised. Later surgical treatment of the shoulder and elbow seems to improve cosmesis but not function. Of the 135 children, 70% had mild residua, 22% showed moderate impairment and 8% had severe deficit.

Inverse effects of corticosterone and thyroxine on glucocorticoid binding sites in the anterior pituitary gland

The aim of this study was to determine whether pituitary glucocorticoid binding sites are under hormonal control. It was shown that corticosterone and thyroxine exerted antagonistic effects on both the transcortin-like component and true receptor present in the hypophysis: thyroid hormones, in contrast to glucocorticoids which exhibited opposite influence, increased maximum binding without affecting significantly the apparent association constant. Thus, it seems that the concentration of glucocorticoid binding sites is regulated by the glucocorticoid ligands, as well as by a different hormone. Moreover, a striking parallelism was found between plasma transcortin and pituitary transcotin-like capacity, argueing in favour of a plasma origin for this pituitary binder.

In vitro regulation of ACTH release from neurointermediate lobe of rat hypophysis. I. Effect of crude hypothalamic extracts

Using incubated glands, we showed that cerebral cortex and liver extracts (CCE and LE) stimulated ACTH release from neurointermediate lobe (NIL) of hypophysis as well as hypothalmus extract (HE) did. Moreover, the HE-induced ACTH release was much smaller for the NIL (1.9 X basal level) than for the anterior lobe (AL; 13.7 x basal level). Thus, under these conditions, HE seemed to have no specific effect on NIL ACTH release. Using superfused glands, we showed: (a) that both spontaneous and HE-induced ACTH release decreased during superfusion; (b) that using this system, a specific stimulatory effect on HE on NIL was observed. In contrast to HE, CCE and LE had only a small effect on NIL ACTH release (always less than 20% of that caused by HE) which could be considered as a nonspecific response; (c) that trypsin suppressed the stimulating effect on HE as well on NIL as on AL; and (d) that arginine antidiuretic hormone (ADH) was not responsible for the stimulating effect of HE on NIL ACTH release, because synthetic ADH had no effect and HE containing ADH (from normal rats) or HE containing no ADH (from Brattleboro rats or from immunoneutralization of ADH in normal HE) had the same effect. From these results, we can conclude that HE contain a peptidic factor different from ADH which is able to stimulate in vitro release of ACTH from the NIL.

[Reduced radiation sensitivity of hyperthyroid goiter with endocrine ophthalmopathy (author's transl)]

The therapeutic success of fractionated radioiodine treatment of hyperthyroid patients with and without endocrine ophthalmopathy is examined. To achieve a stable euthyroid metabolism, patients with endocrine ophthalmopathy generally need a greater number of treatments with a necessarily higher total dose of radioiodine and longer duration of treatment than hyperthyroid patients without endocrine ophthalmopathy. The average age, the average uptake of 131l and the serum concentration of free T4 were comparable in both groups of patients. A struma nodosa was more frequently found in the group of hyperthyroid patients with endocrine ophthalmopathy than in hyperthyroid patients without exophthalmus.

Comparative in vitro studies on corticotropin releasing activity of vasopressin and hypothalamic median eminence extract

The in vitro corticotropic releasing effects of vasopressin (VP) and hypothalamic median eminence (HME) extract were compared as a function of their concentration and preincubation and incubation times. Whereas HME extract augmented the ACTH secretion from non-preincubated adenohypophyses, VP released corticotropin from the pituitaries only after a 2 h preincubation period. The disappearance of endogenous VP during the preincubation time rendered the gland responsive. The maximal stimulation of ACTH secretion by VP was markedly less than that induced by HME extract. The results suggest the presence of VP receptor sites in the anterior pituitary (AP) which are probably different from the receptor sites of the hypothalamic corticotropin releasing factor (CRF).

Heterogeneity of pituitary glucocorticoid binding evidence for a transcortin-like compound

Scatchard analysis, as well as sucrose gradient centrifugation demonstrate that at least two classes of specific glucocorticoid binding sites occur in the adenohypophysis. One, exhibited high affinity for both corticosterone and dexamethasone (receptor D), while the other bound only corticosterone. The latter binder revealed physico-chemical properties closely similar to those of plasma transcortin, but was shown not to be due to simple blood contamination of cytosol. This transcortin-like (TL) component, however, seemed to be carried over from plasma, since the concentration of pituitary binding sites strikingly paralleled physiological variations of plasma transcortin. Furthermore, experiments carried out with isolated pituitary cells suggested an intracellular location of that binder, although sticking to the cell membrane cannot be excluded. Finally, it was shown that the TL compound was unable, unlike the receptor D, to transfer glucocorticoids into the nuclei. One of its possible roles could be to modulate the interaction between steroids and compound D.