The role of somatostatin and/or dopamine in basal and TRH-stimulated TSH release in food-restricted rats

1991 ◽  
Vol 125 (2) ◽  
pp. 186-191 ◽  
Author(s):  
Felipe Rodriguez ◽  
Trinidad Jolin
Keyword(s):  
Rabbit Serum ◽  
Dopamine Antagonists ◽  
Normal Rabbit Serum ◽  
Restricted Feeding ◽  
Gh Secretion ◽  
Endogenous Dopamine ◽  
Tsh Secretion ◽  
Anterior Pituitary Function ◽  
Plasma Gh

Abstract. The present study was carried out to examine the role of endogenous dopamine and somatostatin in the mechanisms involved in the restricted feeding-induced inhibition of TSH secretion in rats. GH secretion was examined in parallel. Restricted feeding by 50% or 75% was associated with a decrease in the pituitary and circulating levels of TSH and GH in both untreated and TRH-treated groups (p<0.001), the changes being proportional to the feeding level. Intravenous injections of the dopamine antagonists, domperidone or haloperidol, failed to affect the magnitude of the differences in plasma TSH and GH levels among control and food-restricted groups, indicating that dopaminergic mechanisms had little effect on the regulation of TSH and GH secretion during restricted feeding in rats. Cerebroventricular injection of somatostatin anti-serum resulted in a marked increase in plasma TSH and GH levels in all the experimental groups (p<0.001). The increase in plasma GH and TSH induced by somatostatin anti-serum was greater in rats fed a 25% diet than in either controls or rats fed 50% of the diet; the values for the latter two groups were also different (p<0.001). The decreased TSH and GH values in somatostatin anti-serum-treated food restricted rats as compared with those in control animals on somatostatin anti-serum or normal rabbit serum can probably be attributed to the decreased available pituitary TSH and GH pools. The data indicate that long-term restricted feeding affects anterior pituitary function in rats, presumably reflecting alterations in the secretion of an inhibiting hormone, somatostatin.

Central administration of alpha-MSH antiserum augments fever in the rabbit

1986 ◽  
Vol 250 (5) ◽  
pp. R803-R806 ◽  
Author(s):  
S. T. Shih ◽  
O. Khorram ◽  
J. M. Lipton ◽  
S. M. McCann
Keyword(s):  
Interleukin 1 ◽  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
Central Administration ◽  
Normal Body Temperature ◽  
Melanocyte Stimulating Hormone ◽  
Average Rise ◽  
The Brain ◽  
Antipyretic Action

alpha-Melanocyte-stimulating hormone (alpha-MSH) has a marked antipyretic action when given centrally or peripherally, and the concentration of this peptide within the septal region of the brain increases during fever. To assess the significance of endogenous central alpha-MSH in fever, antiserum was given to rabbits via a cannula implanted in the third cerebral ventricle. Each day for 3 days, the animals received 50 microliters of normal rabbit serum (NRS) or an equal volume of antiserum raised against alpha-MSH. Interleukin 1 (IL 1) was then injected intravenously to determine the effect of central immunoneutralization of alpha-MSH on the febrile response. Immunoneutralization markedly prolonged fever. The average rise in temperature and the area under the fever curve after IL 1 injection were also significantly increased. Antiserum treatment did not alter normal body temperature, and NRS had no effect on IL 1-induced fever. These results indicate that endogenous central alpha-MSH contributes to physiological limitation of fever and that the role of this peptide in temperature regulation is relevant to the febrile state but not to normothermia.

Inactivation of White Spot Syndrome Virus (WSSV) by normal rabbit serum: Implications for the role of the envelope protein VP28 in WSSV infection of shrimp

2006 ◽  
Vol 118 (1-2) ◽  
pp. 55-61 ◽  
Author(s):  
Javier Robalino ◽  
Caroline Payne ◽  
Pamela Parnell ◽  
Eleanor Shepard ◽  
Adrian C. Grimes ◽  
...  
Keyword(s):  
Envelope Protein ◽  
White Spot Syndrome Virus ◽  
White Spot ◽  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
White Spot Syndrome

Effect of actively immunizing sheep against growth hormone-releasing hormone or somatostatin on spontaneous pulsatile and neostigmine-induced growth hormone secretion

1995 ◽  
Vol 144 (1) ◽  
pp. 83-90 ◽  
Author(s):  
E Magnan ◽  
L Mazzocchi ◽  
M Cataldi ◽  
V Guillaume ◽  
A Dutour ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Body Weight ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Physiological Role ◽  
Gh Secretion ◽  
Igf I ◽  
Plasma Gh ◽  
Hypophysial Portal

Abstract The physiological role of endogenous circulating GHreleasing hormone (GHRH) and somatostatin (SRIH) on spontaneous pulsatile and neostigmine-induced secretion of GH was investigated in adult rams actively immunized against each neuropeptide. All animals developed antibodies at concentrations sufficient for immunoneutralization of GHRH and SRIH levels in hypophysial portal blood. In the anti GHRH group, plasma GH levels were very low; the amplitude of GH pulses was strikingly reduced, although their number was unchanged. No stimulation of GH release was observed after neostigmine administration. The reduction of GH secretion was associated with a decreased body weight and a significant reduction in plasma IGF-I concentration. In the antiSRIH group, no changes in basal and pulsatile GH secretion or the GH response to neostigmine were observed as compared to controls. Body weight was not significantly altered and plasma IGF-I levels were reduced in these animals. These results suggest that in sheep, circulating SRIH (in the systemic and hypophysial portal vasculature) does not play a significant role in pulsatile and neostigmine-induced secretion of GH. The mechanisms of its influence on body weight and production of IGF-I remain to be determined. Journal of Endocrinology (1995) 144, 83–90

Secretion of growth hormone-releasing hormone in patients with idiopathic pituitary dwarfism and acromegaly

1988 ◽  
Vol 117 (2) ◽  
pp. 273-281 ◽  
Author(s):  
Ryuichi Yamasaki ◽  
Haruhiko Saito ◽  
Kazuhito Kameyama ◽  
Eiji Hosoi ◽  
Shiro Saito
Keyword(s):  
Type I ◽  
Normal Children ◽  
Pituitary Dwarfism ◽  
Gh Secretion ◽  
Fasting Plasma ◽  
Pathophysiological Role ◽  
Plasma Gh ◽  
High Level ◽  
Normal Adults

Abstract. The plasma levels of immunoreactive-GHRH in patients with idiopathic pituitary dwarfism and acromegaly were studied in the basal state and during various tests by a sensitive and specific RIA. The fasting plasma GHRH level in 22 patients with idiopathic pituitary dwarfism was 6.3 ± 2.3 ng/l (mean ± sd), which was significantly lower than that in normal children (9.8 ± 2.8 ng/l, N = 21), and eight of them had undetectable concentrations (less than 4.0 ng/l). Little or no response of plasma GHRH to oral administration of L-dopa was observed in 7 of 10 pituitary dwarfs, and 3 of the 7 patients showed a response of plasma GH to iv administration of GHRH (1 μg/kg). These findings suggest that one of the causes of idiopathic pituitary dwarfism is insufficient GHRH release from the hypothalamus. The fasting plasma GHRH level in 14 patients with acromegaly and one patient with gigantism was 8.0 ± 3.9 ng/l, which was slightly lower than that in normal adults (10.4 ± 4.1 ng/l, N = 72). One acromegalic patient with multiple endocrine neoplasia type I had a high level of plasma GHRH (270 ng/l) with no change in response to L-dopa and TRH test. In 3 untreated patients with acromegaly L-dopa did not induce any response of plasma GHRH in spite of inconsistent GH release, and in 4 patients with acromegaly, TRH evoked no response of plasma GHRH in spite of a marked GH release, suggesting that the GH responses are not mediated by hypothalamic GHRH. These findings suggest that the measurement of plasma GHRH in response to L-dopa with a sensitive and specific RIA could be of use in clarifying the pathophysiological role of endogenous GHRH in patients with GH secretion disorders.

Antiserum against tumor necrosis factor enhances lipopolysaccharide fever in rats

1990 ◽  
Vol 258 (2) ◽  
pp. R332-R337 ◽  
Author(s):  
N. C. Long ◽  
S. L. Kunkel ◽  
A. J. Vander ◽  
M. J. Kluger
Keyword(s):  
Tumor Necrosis Factor ◽  
Intramuscular Injection ◽  
Tumor Necrosis ◽  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Control Serum ◽  
Necrosis Factor

The role of tumor necrosis factor (TNF, cachectin), a putative endogenous pyrogen, was investigated by comparing fever and plasma TNF levels after the intraperitoneal and intramuscular injection of 10 micrograms/kg lipopolysaccharide (LPS) into male Sprague-Dawley rats and by neutralization of endogenous TNF using TNF antiserum. An intraperitoneal injection of LPS caused a biphasic fever that lasted approximately 6.5 h. TNF levels in these rats peaked at 657 +/- 222 U/ml at 1 h then declined to virtually undetectable levels by the fourth hour. The intramuscularly injected animals showed a lower monophasic fever and low sustained TNF levels (40 +/- 10 U/ml at 1 h, 18 +/- 11 U/ml at 4 h). In a second study, an antiserum that had been shown to neutralize rat TNF was injected intraperitoneally 2 h before the intramuscular injection of 10 micrograms/kg LPS. Control rats were injected with normal rabbit serum before LPS. During the second hour after the injection of LPS, the animals that received the antiserum developed fevers that tended to be lower than those seen in the rats that were injected with control serum (0.33 +/- 0.06 vs. 0.58 +/- 0.1), although this difference was not significant. However, during the third through eighth hours after LPS, the antiserum-injected rats had mean body temperatures that were significantly higher than those of the control rats (1.62 +/- 0.11 vs. 1.07 +/- 0.09; P = 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Cryptic peptides of prepro-TRH antagonize TRH-induced GH secretion in chickens at extrapituitary sites

1996 ◽  
Vol 151 (3) ◽  
pp. 359-364 ◽  
Author(s):  
S Harvey ◽  
L A Cogburn
Keyword(s):  
Amino Acids ◽  
Pituitary Function ◽  
Gh Secretion ◽  
Rat Pituitary ◽  
Basal Plasma ◽  
Anterior Pituitary Function ◽  
Pituitary Glands ◽  
Plasma Gh ◽  
Sites Of Action

Abstract Complete processing of the TRH precursor in the rat hypothalamus generates TRH and a number of other 'cryptic' peptides that flank the TRH progenitor sequences. Two of these peptides, P4 (Ser-Phe-Pro-Trp-Met-Glu-Ser-Asp-Val-Thr; present between amino acids 160 and 169 of rat prepro-TRH) and P5 (Phe-Ile-Asp-Pro-Gly-Leu-Gln-Arg-Ser-Trp-Glu-Glu-Lys-Glu-Gly-Glu-Gly-Val-Leu-Met-Pro-Glu; present between amino acids 178 and 199 of rat prepro-TRH), have recently been shown to modulate TRH-induced GH and thyrotrophin release from rat pituitary glands. The possibility that these peptides might modulate GH secretion in chickens was examined, since TRH is a physiological GH-releasing factor in birds. The administration of P4 and P5 (at doses of 10 and 100 μg/kg) consistently lowered basal plasma GH concentrations 30 and 60 min after a bolus i.v. injection. Pretreatment with P4 and P5 similarly suppressed the GH response to systemic TRH challenge. The GH-releasing activity of maximally stimulatory doses of TRH was also reduced by concomitant injections of either P4 (100 μg/kg) or P5 (100 μg/kg), which blocked the GH-releasing activity of submaximally effective doses of TRH. In marked contrast, neither P4 nor P5 significantly affected basal or TRH-induced GH release from chicken pituitary glands incubated in vitro. These results demonstrate novel actions of P4 and P5 on hypothalamic–pituitary function and, for the first time, indicate extrapituitary sites of action for these cryptic peptides in modulating anterior pituitary function. Journal of Endocrinology (1996) 151, 359–364

The role of prolactin in the inhibitory action of bromocriptine on growth hormone secretion in acromegaly

1983 ◽  
Vol 103 (4) ◽  
pp. 446-450 ◽  
Author(s):  
S. W. J. Lamberts ◽  
J. G. M. Klijn ◽  
C. C. J. van Vroonhoven ◽  
S. Z. Stefanko ◽  
A. Liuzzi
Keyword(s):  
Pituitary Adenomas ◽  
Inhibitory Action ◽  
Growth Hormone Secretion ◽  
Pituitary Tumour ◽  
Tumour Tissue ◽  
Simultaneous Presence ◽  
Gh Secretion ◽  
Plasma Gh ◽  
Plasma Prl

Abstract. Bromocriptine treatment results in clinical improvement and inhibition of plasma GH levels in only part of the acromegalic patients. The possible role of the simultaneous presence of Prl and GH in GH-secreting pituitary adenomas was investigated with regard to the inhibitory action of bromocriptine on GH secretion and the paradoxical increase of GH release in reaction to TRH. Surgically obtained pituitary tumour tissue from 35 consecutive acromegalic patients was studied immunohistochemically. In 21 patients no Prl was present in the tumour tissue. These patients had normal plasma Prl levels. In the other 14 patients Prl was present in the tumour tissue. Hyperprolactinaemia was found in 10 of these 14 patients. Plasma GH levels from 2 till 10 h after the administration of 2.5 mg bromocriptine measured before operation were significantly more suppressed in the patients with mixed GH/Prl-containing than in those with pure GH-containing pituitary adenomas, being 38 ± 4% and 65 ± 4% of basal values, respectively (P< 0.01). The response of GH to TRH, however, did not differ significantly between the two groups. Conclusions: 1. In about 70% of patients with 'mixed' GH/Prl containing adenomas, hyperprolactinaemia is present. 2. The simultaneous presence of Prl and GH in a GH-secreting pituitary tumour increases the sensitivity of GH secretion to bromocriptine. 3. The plasma Prl level is of value to predict which patients with acromegaly are likely to respond to bromocriptine with an inhibition of GH secretion.

scholarly journals Role of laminin in epithelium formation by F9 aggregates.

1983 ◽  
Vol 97 (1) ◽  
pp. 137-144 ◽  
Author(s):  
A Grover ◽  
G Andrews ◽  
E D Adamson
Keyword(s):  
Basement Membrane ◽  
Morphological Changes ◽  
Embryoid Bodies ◽  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
Type I ◽  
Mrna Levels ◽  
Epithelial Layer ◽  
Afp Production

The formation and maturation of the outer epithelial layer is essential for maximal alphafetoprotein (AFP) production during differentiation of F9 embryoid bodies in the presence of 5 X 10(-8) M retinoic acid (Grover et al., 1983. J. Cell Biol. 96:1690-1696). The critical phase is between the third and the fourth day when the components of the extracellular matrix organize into a basement membrane. The role of some of these components in the process of epithelium formation and maturation is analyzed in this paper. The role of laminin was investigated by testing the effect of exogenous laminin and antilaminin in cultures of differentiating F9 aggregates. Tests included growth rates, morphological changes, AFP production, determination of AFP mRNA levels, and fluorescent staining for basement membrane components and for epithelial markers. At concentrations greater than 5 micrograms/ml, exogenous laminin inhibited the production of AFP and prevented AFP gene transcription. On the basis of immunofluorescence tests, exogenous laminin appeared to act by preventing the accumulation of a basement membrane and by disrupting the organization of the outer layer into an epithelium. No such effects were produced by fibronectin or collagens type I or IV. Aggregates cultured in the presence of antilaminin also failed to organize an epithelium and did not produce AFP, whereas those in normal rabbit serum differentiated normally. Therefore, endogenous laminin plays a key role not only as a basement membrane structural component but also in organizing the epithelial layer of endoderm cells and hence (indirectly) in gene expression.

Diurnal Variations of Plasma Growth Hormone and Brain Monoamines in Adult Male Rats

1973 ◽  
Vol 51 (12) ◽  
pp. 890-892 ◽  
Author(s):  
R. Collu ◽  
J. C. Jéquier ◽  
J. Letarte ◽  
G. Leboeuf ◽  
J. R. Ducharme
Keyword(s):  
Growth Hormone ◽  
Adult Male ◽  
Physiological Role ◽  
Male Rats ◽  
Male Rat ◽  
Plasma Growth Hormone ◽  
Gh Secretion ◽  
Adult Male Rat ◽  
Plasma Gh

Brain levels of monoamines (MA) in the adult male rat show a diurnal pattern of secretion with noradrenaline (NA) and serotonin (5-HT) reaching a peak at 1300 and 1800, respectively, and dopamine (DA) showing a bimodal pattern with peaks at 0500 and 1800. Plasma growth hormone (GH) values fluctuate widely during the nycthemeral period. Statistically significant correlations between plasma GH and brain MA levels, confirming the existence of a physiological role of MA in the control of GH secretion, could not be demonstrated in the present study.

Cocaine- and amphetamine-regulated transcript peptide attenuates phenylephrine-induced bradycardia in anesthetized rats

2003 ◽  
Vol 285 (6) ◽  
pp. R1496-R1503 ◽  
Author(s):  
Phouangmala Scruggs ◽  
Siok L. Dun ◽  
Nae J. Dun
Keyword(s):  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
Solitary Tract ◽  
Peptide Fragment ◽  
Tract Tracing ◽  
Anesthetized Rats ◽  
Nodose Ganglia ◽  
Cart Peptide ◽  
Resting Blood Pressure

The present study was undertaken to investigate the origin of cocaine- and amphetamine-regulated transcript (CART) peptide immunoreactive (irCART) fibers observed in the nucleus of the solitary tract (NTS) and assess the role of CART peptide on phenylephrine (PE)-induced baroreflex. Immunohistochemical and retrograde tract-tracing studies showed that some of the irCART fibers observed in the NTS may have their cell bodies in the nodose ganglia. In urethane-anesthetized rats, intracisternal or bilateral intra-NTS microinjection of the CART peptide fragment 55-102 (0.1-3 nmol), referred to herein as CARTp, consistently and dose dependently attenuated PE-induced bradycardia. CARTp, in the doses used here, caused no significant changes of resting blood pressure or heart rate. Bilateral intra-NTS injections of CART antibody (1:500) potentiated PE-induced bradycardia. Injections of saline, normal rabbit serum, or concomitant injection of CARTp and CART antiserum into the NTS caused no significant changes of PE-induced baroreflex. The result suggests that endogenously released CARTp from primary afferents or exogenously administered CARTp modulates PE-induced baroreflex.

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