Early gene expression in the rat brain following administration of corticoliberin in the neostriatum

Using in situ hybridisation with oligonucleotide probes, an expression of immediate early genes c-fos, jun B, c-jun, and NGFIA in the rat brain was studied following intrastriatal microinjection of corticotropin-releasing hormone (CRH). The hormone induced expression of c-fos, jun B, and NGFIA mRNAs in the neostriatum as well as in its target brain areas, including nucleus accumbens and different cortical areas. The expression of c-jun mRNAs was unaffected. The findings indicate that neuronal activation of the neostriatum and its target brain areas provides one possible mechanism for mediating adaptive CRH actions in stress.     

Distribution of 125I-labeled rat growth hormone in regional brain areas and peripheral tissue of the rat.

The uptake of intraperitoneally injected 125I-labeled rat growth hormone into brain and peripheral tissues was measured in normal and hypophysectomized adult rats. A significant level of radioactivity was observed in the seven brain regions examined -- the telencephalon, diencephalon, midbrain, pons-medulla, cerebellum, pineal and pituitary glands. The pineal and pituitary glands, which are outside the blood-brain barrier, contained three to four times the concentration of radioactivity of the other brain regions. Compared to brain, the level of radioactivity was much higher in peripheral tissues (the diaphragm, kidney, serum and liver). For example, the serum contained ten times the level of radioactivity of most brain regions. For a given tissue, however, the normal and hypophysectomized rats showed a comparable amount of 125I-growth hormone. Trichloroacetic acid precipitates from each tissue sample showed that peripheral tissues had a higher proportion of radioactivity (35-48% of total tissue radioactivity) than the brain samples (13-26%). The data support the view that growth hormone, or a metabolite can enter the central nervous system and may directly affect on-going metabolic processes.     

The effect of growth hormone on the metabolism of a tryptophan load in the liver and brain of hypophysectomized rats.

Growth hormone antagonizes the induction of tryptophan pyrrolase and tyrosine amino-transferase by cortisol. We have shown that contrary to previous reports, growth hormone is also capable of antagonizing the induction of these enzymes by tryptophan and alpha-methyl tryptophan. As alpha-methyl tryptophan is not metabolized appreciably in the rat, our data show that growth hormone does not act indirectly through changes in the liver tryptophan content as was suggested previously. Growth hormone decreases the rate of tryptophan catabolism in vivo after induction of tryptophan pyrrolase by tryptophan and alpha-methyl tryptophan. Because the rate of catabolism of a tryptophan is slower in animals treated with growth hormone, tissue tryptophan levels and the rate of synthesis of 5-hydroxyltryptamine in the brain are higher in these animals than in those receiving tryptophan alone. Thus, although tryptophan administration raises brain 5-hydroxytryptamine levels, induction of tryptophan pyrrolase in the liver, by the load, limits the extent and duration of the rise in brain 5-hydroxytryptamine synthesis. This has important implications for the clinical use of tryptophan in psychiatric disorders, where tryptophan is given to produce long-lasting elevations of brain 5-hydroxytryptamine.     

Delineation of a Particulate Thyrotropin-Releasing Hormone-Degrading Enzyme in Rat Brain by the Use of Specific Inhibitors of Prolyl Endopeptidase and Pyroglutamyl Peptide Hydrolase

The degradation of thyrotropin-releasing hormone in rat brain homogenates was studied in the presence of N-benzyloxycarbonyl-prolyl-prolinal and pyroglutamyl diazomethyl ketone, specific and potent active-site-directed inhibitors of prolyl endopeptidase and pyroglutamyl peptide hydrolase, respectively. Substantial TRH degradation was observed, suggesting the presence of another thyrotropin-releasing hormone-degrading enzyme(s). Reports of a thyrotropin-releasing hormone-degrading enzyme with narrow specificity that cleaves the pGlu-His bond of this tripeptide led us to develop a coupled assay using pGlu-His-Pro-2NA as the substrate to measure this activity. Cleavage of the pGlu-His bond of this substrate under conditions in which pyroglutamyl peptide hydrolase is not expressed occurred in the particulate fraction of a rat brain homogenate. This particulate pyroglutamyl-peptide cleaving enzyme was not inhibited by pyroglutamyl diazomethyl ketone but was inhibited by metal chelators such as EDTA and o-phenanthroline. The particulate pyroglutamyl-peptide cleaving enzyme was found predominantly in the brain. Activity in brain regions varied widely with highest levels present in cortex and hippocampus and very low levels in pituitary. The data suggest that degradation of thyrotropin-releasing hormone by the particulate fraction of a brain homogenate is catalyzed mainly by an enzyme that cleaves the pGlu-His bond of thyrotropin-releasing hormone but is distinct from pyroglutamyl peptide hydrolase.     

Effect of chromatin associated factors on the activity of thyroid hormone receptors in rat liver and brain

Receptors for thyroid hormones were extracted by 0.4 M KCl from the nuclei of rat liver and brain, and their binding properties compared to the properties of these receptors in unextracted nuclear suspensions. The inhibititory effect of a non-iodinated thyroid hormone analogue, 3,5,dimethyl-3′-isopropyl-l-thyronine (DIMIT) on [¹²⁵I]-T₃ binding was observed in the nuclear suspension of brain, but absent when the solubilized receptors of the same organ were tested. The initial properties of the receptor could be restored in a system containing the receptor and the extracted chromatin. Moreover, when the liver solubilized receptor was supplemented with the brain chromatin extract, the hepatic receptor acquired the binding ability of the brain receptors. The data suggest that chromatin associated components may confer organ specificity in thyroid hormone effects, and play a role in the selectivity of the recognition of thyroid hormone analogues by the receptor.     

Na, K-ATPase activity of the microsomal fraction of the rat brain exposed to insulin

The effect of insulin on the activity of Na, K-ATPase was studied in rat brain microsomes. Addition of insulin to the incubation medium in a dose of 0.18 U/ml coupled with strophanthine did not change the enzyme activity. The raising of the hormone dose to 0.36 U/ml was accompanied by inhibition of the enzyme activity. The incubation duration (10 and 30 min) did not influence the Na-pump. Preincubation of brain microsomes with insulin for 5 min significantly activated Na, K-ATPase. It has been thus demonstrated that insulin is capable of influencing the activity of Na, K-ATPase of rat brain microsomes in vitro. The effect obtained depends both on the dose of the hormone introduced into the incubation medium and the experimental conditions.     

An analogue of thyrotropin-releasing hormone, DN1417, decreases naloxone binding in the rat brain

We explored whether thyrotropin-releasing hormone may affect opioid receptors in the rat brain. Adult male rats were intraperitoneally injected twice a day with varying doses of DN1417, a potent analogue of thyrotropin-releasing hormone, for 2 days, and opioid receptors of the brain (hypothalamus, striatum, hippocampus, midbrain, ponsmedulla, and cortex) homogenates were determined using [3H]naloxone. Intraperitoneal injection of DN1417 in a dose of 0.3 mg/100 g body wt resulted in a significant reduction in naloxone binding of the striatum as compared with the saline-injected group, whereas naloxone binding of other brain regions was not affected by DN1417. DN1417 produced a dose-dependent decrease in naloxone binding of the striatum. The affinity constant of naloxone binding was similar between the saline- and DN1417-injected groups. In vitro addition of DN1417 did not interfere with the brain naloxone binding. The distribution of 3H-labeled DN1417 injected peritoneally did not differ among the brain regions. The present data imply that the opioid antagonistic action of thyrotropin-releasing hormone may be due, at least in part, to the significant decrease in the striatal opioid binding in the rat brain.     

In vivo autoradiographic analysis of prolactin binding in brain and choroid plexus of the domestic ring dove

Summary The binding of intravenously administered prolactin to choroid plexus and brain tissue was determined radioautographically in the ring dove, a species that exhibits prolactin-induced alterations in brain function. An intense autoradiographic reaction was detected over the epithelial cells of the choroid plexus 5 min after the intravenous injection of ¹²⁵I-ovine prolactin. A significant reaction was also observed over the infundibulum but no significant uptake of prolactin occurred in other brain areas. The binding of radiolabelled prolactin to infundibulum appeared to be non-specific, since excess unlabelled hormone did not reduce silver grain density. In contrast, ¹²⁵I-ovine prolactin binding in choroid plexus was significantly reduced by excess unlabelled ovine prolactin or human growth hormone, but not by ovine luteinizing hormone. Specific binding to choroid plexus was also detected in vitro. The lack of significant brain uptake of prolactin in vivo is discussed in relation to recent in vitro evidence for specific binding sites for prolactin in several dove brain regions. Similarities between the binding results obtained in this avian species and those reported previously in mammals suggest that the two vertebrate groups exhibit similar patterns of prolactin interaction with neural target tissues.     

Cloning of corticotropin-releasing hormone (CRH) precursor cDNA and immunohistochemical detection of CRH peptide in the brain of the Japanese eel,paying special attention to gonadotropin-releasing hormone

The stress-related corticotropin-releasing hormone (CRH) was first identified by isolation of its cDNA from the brain of the Japanese eel Anguilla japonica. CRH cDNA encodes a signal peptide, a cryptic peptide and CRH (41 amino acids). The sequence homology to mammalian CRH is high. Next, the distribution of CRH-immunoreactive (ir) cell bodies and fibers in the brain and pituitary were examined by immunohistochemistry. CRH-ir cell bodies were detected in several brain regions, e.g., nucleus preopticus pars magnocellularis, nucleus preopticus pars gigantocellularis and formatio reticularis superius. In the brain, CRH-ir fibers were distributed not only in the hypothalamus but also in various regions. Some CRH-ir fibers projected to adrenocorticotropic hormone (ACTH) cells in the rostral pars distalis of the pituitary and also the α-melanocyte-stimulating hormone (α-MSH) cells in the pars intermedia of the pituitary. Finally, the neuroanatomical relationship between the CRH neurons and gonadotropin-releasing hormone (GnRH) neurons was examined by dual-label immunohistochemistry. CRH-ir fibers were found to be in close contact with GnRH-ir cell bodies in the hypothalamus and in the midbrain tegmentum and GnRH-ir fibers were in close contact with CRH-ir cell bodies in the nucleus preopticus pars magnocellularis. These results suggest that CRH has some physiological functions other than the stimulation of ACTH and α-MSH secretion and that reciprocal connections may exist between the CRH neurons and GnRH neurons in the brain of the Japanese eel.     

Antagonism of ethanol-induced decrease in rat brain cGMP concentration by histidyl-proline diketopiperazine, a thyrotropin releasing hormone metabolite.

Intraperitoneal administration of thyrotropin releasing hormone (50 μmol/kg) produced an approximately 2-fold increase in rat brain cGMP concentration within 15 min. Histidyl-proline diketopiperazine, a metabolite of thyrotropin releasing hormone, produced a similar effect, but the response was faster and shorter-lasting. Intraperitoneal administration of ethanol (1.5 g/kg) decreased brain cGMP concentration approximately 50% within 10–15 min; thyrotropin releasing hormone or histidyl-proline diketopiperazine, injected 5 min after ethanol, antagonized the ethanol-induced decrease in cGMP. Antagonism of the ethanol-induced decrease in the cGMP level required 10 μmol/kg of thyrotropin releasing hormone but was observed with 5 μmol/kg of histidyl-proline diketopiperazine. These data suggest that the metabolic conversion of thyrotropin releasing hormone to histidylproline diketopiperazine might explain the previous observation that thyrotropin releasing hormone elevated the level of brain cGMP and antagonized the ethanolinduced decrease in brain cGMP concentration.     

Growth hormone and tumour recurrence.

OBJECTIVE--To determine whether using growth hormone to treat radiation induced growth hormone deficiency causes tumour recurrence. DESIGN--Comparison of tumour recurrence rates in children treated with growth hormone for radiation induced deficiency and an untreated population. Computed tomograms from children with brain tumours were reviewed when starting growth hormone and subsequently. SETTING--North West region. PATIENTS--207 children treated for brain tumour, 47 of whom received growth hormone and 161 children with acute lymphoblastic leukaemia 15 of whom received growth hormone. MAIN OUTCOME MEASURES--Tumour recurrence and changes in appearances on computed tomography. RESULTS--Among children with brain tumour, five (11%) who received growth hormone had recurrences compared with 42 (26%) who did not receive growth hormone. Also adjusting for other variables that might affect tumour recurrence the estimated relative risk of recurrence was 0.82 (95% confidence interval 0.28 to 2.37). The only child with acute lymphoblastic leukaemia who relapsed while taking growth hormone had relapsed previously before starting treatment. Two of the five children with brain tumours who relapsed had abnormal appearances on computed tomography when growth hormone was started. 14 other children who remained relapse free and had follow up computed tomography showed no deterioration in radiological appearance during treatment. CONCLUSIONS--In this population growth hormone did not increase the risk of tumour recurrence but continued surveillance is essential. Abnormal results on computed tomography are not a contraindication to treatment with growth hormone.     

Endocrine regulation of spermatogenesis in Nereis diversicolor (annelida polychaeta): experimental study of the control of meiotic differentiation

In Nereidae, spermatogenesis is regulated by a hormone secreted by the supraesophageal ganglion (brain hormone). The hormonal concentration decreases with worm age. Spermatogonial proliferation in young worms proceeds under a high hormonal level whereas differentiation of spermatozoa in aged worms occurs in the absence of brain hormone. Spermatogonia were removed from the endocrine influence of the brain in vitro by the organ culture method. Isolated parapodia produced spermatozoa after 13 days. Control cultures were obtained by associating a parapodium with the prostomium of a young worm. It seems that the brain hormone inhibits the spermatocyte differentiation since removal of the brain results in increased RNA synthesis, followed by DNA replication, meiosis, and spermiogenesis (Bertout, '83). Modalities of the hormonal control of meiosis, especially at the level of the RNA syntheses related to meiotic differentiation, were investigated. Effects of reintroducing the hormonal influence during meiotic differentiation were studied through parapodium-prostomium associations at various time after the brain inhibition has been lifted. Effects or RNA inhibitors (actinomycin D, alpha-amanitin, cordycepin) were also tested. The results lead us to propose a hypothesis according to which brain hormone would interfere with molecular events related to the transition from the stage of spermatogonial proliferation (mitotic behavior) to the stage of meiotic differentiation (meiotic behavior).     

Hormonal basis of adult eclosion in the gypsy moth (Lepidoptera: Lymantriidae)

Eclosion hormone was found to control the stereotypic adult eclosion behaviour of Lymantria dispar, the gypsy moth. A bioassay for hormonal activity was developed utilizing pharate adult females, and comparisons were made with the Manduca wing assay. The distribution of eclosion hormone activity was confined to the central nervous system tissues including the protocerebrum, corpora allata/corpora cardiaca complex, thoracic and the last abdominal ganglion. Haemolymph ecdysteroid titres were determined daily throughout pupal-adult development, and the peak activity period was found in 3–4 day pupae. Eclosion hormone activity in the brain and corpora allata/corpora cardiaca complex started to increase when the ecdysteroid titre dropped to background levels. Eclosion hormone in the brain peaked in the pharate adult stage, was released in the haemolymph 1 h prior to eclosion, which coincides with the depletion of activity in the retrocerebral complex, and fell to undetectable levels after the adult emerged.     

Changes in the ganglioside composition of various rat organs under the action of thyroid hormones

The ganglioside content in various organs of the rat were studied under normal conditions and under deficiency of thyroid hormones. The minimal ganglioside content was observed in skeletal muscles, the maximal one--in the brain. Using thin-layer chromatography, it was demonstrated that these organs possess a complex ganglioside composition which differs both qualitatively and quantitatively. Under thyroid hormone excess, the total ganglioside content shows a tendency to increase, while under hormone deficiency--to decrease. The nature of changes in individual ganglioside fractions in various tissues depends on the thyroid hormone content in the organism.     

In vitro bioassay for the brain allatotropic hormone of Galleria mellonella (Lepidoptera).

An in vitro sensitive bioassay for the Galleria mellonella brain allatotropic hormone (ATTH) was developed. This assay measures the rate of juvenile hormone (JH) synthesis in corpora cardiacacorpora allata complex (CC-CA) stimulated in vitro by ATTH released from the brain during short-term in vitro incubation, or by ATTH extracted from the tissue with methanol. CC-CA of the late VIth instar (VI3) larvae were used for assessment of ATTH. The maximum activation of test CC-CA by ATTH occurred at a concentration of 2 brain equivalents (per 100 ul medium). The highest ATTH activity was exhibited by the brains of chilled VII1 larvae: ATTH extracted from freshly dissected brains, or ATTH released from these brains during 6 h in vitro incubation, activated JH synthesis in the CC-CA nearly five or four times, respectively. The brain of VII1 hydroprenetreated larvae were ATTH inactive.     

The influence of maternal somatostatin administration on fetal brain cell proliferation and its relationship to serum gorwth hormone and brain trophin activity.

The effect of maternal somatostatin administration from days 14 to 20 of gestation was examined. Fetal body growth was unchanged but brain cell DNA synthesis per gram of tissue decreased. Maternal serum levels of growth hormone and brain trophin were elevated following treatment conclusion. It was suggested that this was a rebound phenomenon and that short term blockade of pituitary growth hormone release during somatostatin treatment had impaired fetal brain cell DNA synthesis.     

Neuromodulator mechanism of the inhibitory effect of deoxycorticosterone on the aggressive-defensive behavior of the rat

DOCA (0.3 mg/kg i.p.) inhibited the shock-induced aggression in male rats. This behavioural reaction was also inhibited by activation of brain beta-adrenergic and nicotinic receptors. The inhibitory hormone effect was potentiated to a considerable extent (p less than 0.05-0.001) by central beta-adrenergic stimulation but was blocked by beta-antagonist administration. However, it was independent of facilitatory and inhibitory actions on the brain nicotinic receptors. It is concluded that the DOCA inhibitory effect on the shock-induced defensive fighting involved the facilitation of the brain beta-adrenergic receptor activation.     

Corticotropin-releasing hormone-like immunoreactivity in the brain of the snake Bothrops jararaca

The distribution of corticotropin-releasing hormone in the brain of the snake Bothrops jararaca was studied immunohistochemically. Immunoreactive neurons were detected in telencephalic, diencephalic and mesencephalic areas such as dorsal cortex, subfornical organ, paraventricular nucleus, recessus infundibular nucleus, nucleus of the oculomotor nerve and nucleus of the trigeminal nerve. Immunoreactive fibres ran along the hypothalamo-hypophysial tract to end in the outer layer of the median eminence and the neural lobe of the hypophysis. In general, immunoreactive fibres occurred in the same places of immunoreactive neurons. In addition, immunoreactive fibres were observed in the septum, amygdala, lamina terminalis, supraoptic nucleus, nucleus of the paraventricular organ, ventromedial hypothalamic nucleus and interpeduncular nucleus. These results indicate that, as for other vertebrates, corticotropin-releasing hormone in B. jararaca brain, besides being a releasing hormone, may also act as a central neurotransmitter and/or neuromodulator.     

Brain serotonin turnover and plasma prolactin and growth hormone concentrations during changes in osmotic balance in the domestic fowl

Summary Young cockerels injected 24 h earlier with 0.9% saline,para-chorophenylalanine (pCPA, brain serotonin depletor) or alpha-methylpara-tyrosine (AMPT, brain catecholamine depletor) were deprived of access to water for 24 h. Plasma prolactin concentrations were markedly elevated by water deprivation and returned to normal on rehydration. pCPA, but not AMPT, significantly reduced the increase in prolactin. Concentrations of growth hormone were not affected by water deprivation. Brain serotonin concentrations were reduced by treatment with pCPA. Groups of cockerels were maintained under normal conditions or without access to drinking water for 12 h or 24h. Some were injected with the monoamine oxidase inhibitor pargyline, which increased the prolactin and decreased the growth hormone concentration in the plasma of the hydrated birds. The inhibitory effect of pargyline on growth hormone was augmented following water deprivation. Serotonin levels were not significantly affected by water deprivation but turnover (defined as accumulation of serotonin after pargyline treatment) was increased in the hypothalamus but not in remaining tissue. Injecting 30% saline solution intravenously markedly increased plasma prolactin whilst growth hormone concentrations were decreased. Serotonin turnover was increased in the hypothalamus but not in other brain regions. The results show that secretion of prolactin and growth hormone by the pituitary gland during osmotic imbalance in the fowl may be mediated by changes in hypothalamic scrotonin turnover.