bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and validation of a melatonin radioimmunoassay using radioiodinated melatonin as tracer
Authors: Vakkuri Olli , Leppäluoto Juhani , Vuolteenaho Olli
Published: December 2008

Abstract. A new radioimmunoassay (RIA) using [125I]melatonin as tracer for determination of melatonin in biological fluids has been developed. Melatonin antisera were raised in rabbits by immunization with bovine thyroglobulin conjugate of n-acetyl-5-methoxytryptophan. Two high-affinity and specific antisera were obtained. Unlike in previous studies melatonin was radioiodinated directly. Iodo-Gen was used as the oxidant. Radioiodinated melatonin was purified by TLC for use in RIA. Melatonin was extracted from plasma, serum and urine samples (1 ml) with chloroform. Using the extraction the sensitivity of the RIA method was 18 fmol/ml of original sample. Plasma, serum and urine extracts diluted parallelly with synthetic melatonin in RIA. HPLC analysis of plasma and serum extracts showed only one immunoreactive peak co-eluting with synthetic melatonin. Majority of urine immunoreactivity co-eluted with synthetic melatonin, but 7–23% contaminating immunoreactivity was also observed. Daytime values for rat plasma, human serum and urine melatonin were 30–60, 20–40 and 50–130 fmol/ml and the respective night values were 160–300, 180–370 and 230–470 fmol/ml. Thus a characteristic diurnal rhythm of melatonin was observed in all cases. The urinary excretion of immunoreactive melatonin during the day was 3–9 and during the night 11–28 pmol/h. Thus we have developed a specific and valid RIA method for the determination of plasma and serum melatonin. Despite the incomplete specificity of the RIA for urine determinations, a clear diurnal rhythm for urine melatonin was observed. The distinct advantage of the utilization of [125I]melatonin as tracer is that the costly and cumbersome scintillation counting can be avoided.
Growth hormone increases neonatal mouse urine epidermal growth factor
Authors: Perheentupa J. , Lakshmanan J. , Macaso T. , Fisher D. A.
Published: December 2008

Abstract. The effects of bovine growth hormone (bGH) and triiodothyronine (T3), alone and in combination, were studied on urinary-EGF (U-EGF) in newborn mice. All three treatments significantly augmented the concentration of U-EGF. The effect was far greater for T3 than for bGH. No EGF response was seen in submandibular gland or kidney tissues suggesting that, in newborn animals, these hormones selectively modulate U-EGF.
Effects of hypo- and hyperthyroidism on pancreatic TRH-degrading activity and TRH concentrations in developing rat pancreas
Authors: Aratan-Spire Sonia , Wolf Bryan , Czernichow Paul
Published: December 2008

Abstract. High concentrations of thyrotrophin-releasing hormone (TRH) in the rat pancreas were detected during the first few days of life decreasing thereafter while pancreatic TRH-degrading activity (TRH-DA) absent at birth appeared on day 14 and increased to reach adult values by day 21. This period of life is also remarkable by the low level of circulating thyroid hormones. Since TRH-degrading activity may be thyroid hormone dependent it was of interest to study the effects of thyroid status fluctuations both on TRH-DA and TRH content during the neonatal period.

In this study, hypo- and hyperthyroidism were induced by 6-n-propyl-2-thiouracil (PTU) and triiodothyronine (T3) respectively. Pancreatic TRH-DA and TRH concentrations were measured at different ages from birth until day 29, in treated animals and results compared to control age-matched rats.

In hypothyroid rats, pancreatic TRH concentrations remained significantly higher after day 16 while TRH-DA was lower during the whole period studied. Following T3 treatment, pancreatic TRH concentrations decreased significantly from day 3 onwards. However, no significant changes were found for TRH-DA except a two-fold increase on day 28.

These results suggest that two different mechanisms may account for thyroid hormones action: 1) a direct effect on pancreatic TRH 2) an inductive saturable effect on TRH-DA. Furthermore a fine tuner modulatory role of TRH-DA on TRH concentrations cannot be excluded.
A comparison of the effects of semisynthetic human insulin and porcine insulin on transmembrane ion shifts and glucose metabolism during euglycaemic clamping
Authors: Heine R.J. , Ponchner M. , Hanning I. , Home P. D. , Brown M. , Williams D. , Alberti K. G. M. M.
Published: December 2008

Abstract. Disturbances of potassium, calcium, phosphate and magnesium homeostasis in diabetes mellitus are well documented. We have compared the effects of semisynthetic human and pancreatic porcine insulin on transmembrane shifts of these ions, and on glucose metabolism, at two insulin infusion rates, 20 and 50 mU/kg/h, during euglycaemic clamping for 2 h in 6 normal volunteers. The glucose requirements and the changes in blood metabolite concentrations were not significantly different during the porcine and human insulin infusions.

Serum potassium levels, however, showed a significant greater decline with infusions of porcine insulin (4.2 ± 0.1 to 3.5 ± 0.1 mmol/l compared with human insulin (4.2 ± 0.1 to 3.7 ± 0.1 mmol/l) 50 mU/kg/h (P < 0.05). Potasssium levels were significantly lower during the porcine insulin infusion at 105 and 120 min and at 15 and 30 min after stopping the infusion.

Electrocardiographic T-wave voltage decreased during the porcine and human insulin infusion by 0.13 ± 0.02 and 0.10 ± 0.01 mV, respectively (P < 0.02). Changes in serum levels of magnesium, calcium, phosphate, and red blood cell concentrations of magnesium and 2,3-DPG, were not significantly different between the insulins.

Thus a small but significant greater decline in potassium levels with similar glucose requirements was found during iv administration of porcine insulin compared with human insulin.
Effects of increase of brain GABA levels on the hypothalamic-pituitary-luteinizing hormone axis in rats
Authors: Donoso Alfredo O. , Banzan Arturo M.
Published: December 2008

Abstract. The effects of increasing brain GABA levels by administration of aminooxyacetic acid (AOAA), a GABA-transaminase inhibitor, on tonic and induced LH release were evaluated in ovariectomized rats.

Pulsatile LH release was clearly inhibited by AOAA. Mean plasma LH levels fell, the frequently of pulses decreased, and the intervals between pulses increased. An absence of LH pulses was seen in some animals. Administration of the GABA antagonist, bicuculline, prevented these modifications. In addition, it enhanced mean plasma LH levels.

AOAA blunted the rise of plasma LH levels produced by either oestradiol or progesterone in oestradiol-primed ovariectomized rats. In contrast, the AOAA treatment apparently facilitated the inhibitory feedback of oestradiol on LH release. The acute release of LH produced by LRH injection was not altered by AOAA.

The results support the view that brain GABA exerts an inhibitory action on LH release in the rat.
Local anaesthesia and immunomodulatory effects of antithyroid drugs
Authors: Hallengren Bengt , Melander Arne , Thesleff Stephen
Published: December 2008

Abstract. Propylthiouracil (PTU) and propranolol can suppress, while methimazole (MMI) can enhance, mitogenie activation of lymphocytes. The present study investigated whether this effect of PTU, as has been shown for propranolol, relates to local anaesthetic activity. MMI (1 mm) but not PTU (1 mm) reduced the action potential in rat skeletal muscle. Thus, PTU seems to lack local anaesthetic activity. Moreover, the recorded local anaesthetic capacity of MMI hardly explains the stimulatory influence of MMI on lymphocyte activation. Apparently, the interference of MMI and PTU with lymphocyte activation seems to be due to another mechanism than local anaesthetic activity.
Effects of sodium ipodate and propylthiouracil in athyreotic human subjects, role of triiodothyronine and pituitary thyroxine monodeiodination in thyrotrophin regulation
Authors: Schaison G. , Thomopoulos P. , Leguillouzic D. , Thomas G. , Moatti M.
Published: December 2008

Abstract. To investigate the respective role of triiodothyronine (T3) and thyroxine (T4) in the regulation of TSH secretion, we studied the action of sodium ipodate and propylthiouracil (PTU) in 11 athyreotic patients. The lT4 replacement dose was adjusted to obtain, in each patient, a normal basal TSH level and a normal TSH response to TRH. In the 5 ipodate-treated patients (single 6 g oral dose), the mean serum T3 level fell by 64% below the baseline value and serum rT3 rose 180% above the baseline. The free T4 index (FT4I) did not change whereas the mean serum TSH concentration increased 280% above baseline values. In the 6 PTU-treated patients (250 mg orally every 6 h for 10 days), serum T3 levels fell 33%, serum rT3 increased up to 82% and the FT4I did not change. The mean serum TSH concentration increased 68% above the baseline value. Thus, the mean percentage increase in serum TSH was less in PTU- than in ipodate-treated patients (68% vs 280%). Statistical analysis of the correlation between the serum T3 decrease (ΔT3) and the serum TSH (ΔTSH) increase demonstrated that for the same T3 diminution, the ipodate-treated group displayed higher increase of TSH than the PTU-treated patients. In the rat, PTU interferes with the 5'-deiodination of T4 in the liver and kidney but not in the pituitary, while ipodate appears to have the same effect in all tissues. If this holds true for human subjects, our data strongly suggest that circulating T4 (through its intrapituitary conversion to T3) shares with serum T3 the capacity to regulate TSH secretion in man.
Conjugated oestrogen during the menstrual cycle measured by a direct radioimmunoassay with an antiserum prepared against oestradiol-17-glucosiduronate-[C-6]-BSA conjugate
Authors: Honjo Hideo , Otsubo Kazuo , Yasuda Jinsuke , Kitawaki Jo , Okada Hiroji , Ohkubo Tadashi , Nambara Toshio
Published: December 2008

Abstract. Early morning and 24 h urine samples and serum were collected daily throughout the menstrual cycle in women. Urinary oestradiol-17-glucosiduronate (E2-17-G) was measured with a direct radioimmunoassay whose antiserum had been prepared against E2-17-G-[C-6]-bovine serum albumin conjugate and was very specific. On the average, E2-17-G in early morning and 24 h urine samples showed a prominent peak one day before the peak of urinary LH. The time relationship between these urinary E2-17-G and serum E2 levels and peaks was also investigated.
Effects of chronic luteinizing hormone-releasing hormone agonist treatment on dysfunctional uterine bleeding in the stumptailed macaque
Authors: Fraser Hamish M. , Shaw Robert W.
Published: December 2008

Abstract. Dysfunctional uterine bleeding is a disorder which presents problems for effective treatment and management. We have utilized the ability of chronic LRH agonist treatment to suppress ovarian steroid production to examine its effects on stumptailed macaques with a detailed history of excessive days of menstrual bleeding. Five monkeys were treated for 6 months with daily injections of D-Ser[But]6 LRH (1–9) nonapeptideethylamide. This was successful in suppressing ovarian steroid production in all monkeys as indicated by the maintenance of serum concentrations of oestradiol at < 100 pg/ml and progesterone at < 1 ng/ml. All monkeys menstruated for their typical time period during the first treatment cycle, but thereafter bleeding stopped in 2 monkeys and was considerably reduced in a further 2. In the remaining monkey, no significant improvement occurred. The results indicate that suppression of ovarian function in this way may have a significant role to play in the treatment of dysfunctional uterine bleeding.
The dependence of human decidual prolactin production and secretion on the osmotic environment in vitro
Authors: Andersen Jesper Rye , Borggaard Birgit , Schroeder Erik , Olsen Elith Bjarne , Stimpel Hans , Nyholm Henrik Christian
Published: December 2008

Abstract. Human decidual tissue from uncomplicated term pregnancies was incubated in vitro using a cross-over design of incubation lasting for 72 h. The decidual tissue of each membrane was added sequentially to media with the osmolalities 252, 315 and 387 mmol/kg, and the different osmolalities were in 33 experiments induced by changing the concentration either of sodium chloride, potassium chloride, mannitol, sucrose, or choline chloride.

At 387 mmol/kg all substances elicited a significant increase in Prl secretion compared with the 315 mmol/kg media (14–27%) or the 252 mmol/kg media (26–46%). When the sodium chloride, potassium chloride, sucrose, and choline chloride media at 387 mmol/kg were compared in another 7 experiments, potassium chloride increased Prl secretion more effectively than the others (10%, P < 0.05).

The incubation cross-over design did not permit determination of the decidual Prl content after incubation in each of the various media, but in 28 experiments the mean decidual Prl content was 12.7 mIU per 100 mg dry tissue (range 4–30) before and 8.7 mIU per 100 mg dry tissue (1–17) after the experiments. The mean amount of Prl secreted during the successive incubations was 152.2 mIU per 100 mg dry tissue (19–672) which showed the secretion to be a result of continued Prl production. The effect of osmolality was independent of the basal production rate. These results indicate that the intracellular ionic concentrations, probably of potassium ion or of chloride ion, are of importance in the regulation of the synthesis and secretion of decidual Prl in vitro.
Changes in nephrogenous cyclic AMP excretion and plasma cyclic AMP following treatment of hyperthyroidism
Authors: Naafs M. A. B. , van der Velden P. C. , Fischer H. R. A. , Koorevaar G. , van Duin S. , Hackeng W. H. L. , Schopman W. , Silberbusch J.
Published: December 2008

Abstract. Plasma cyclic AMP (PcAMP) concentration and the excretion of cyclic AMP dl GF were estimated in 11 thyrotoxic patients before and after medical treatment.

PcAMP concentrations were significantly higher during hyperthyroidism (2.30 ± 0.69 vs 1.88 ± 0.71 nmoldl; P < 0.05), and total urinary cyclic AMP (TcAMP) excretion showed no significant changes (3.24 ± 0.64 vs 3.44 ± 1.77 nmol/dl GF). Nephrogenous (NcAMP) excretion rose significantly (1.00 ±0.82 vs 1.68 ±1.31 mmol/dl GF; P < 0.025). The increase in NcAMP excretion correlated significantly with the decrease in serum T3 levels (r = -0.46; P < 0.05). Serum iPTH levels showed no significant change. Both the serum Ca, corrected for serum total protein and TmPO4 GFR declined after treatment (respectively 2.44 ± 0.13 vs 2.33 ± 0.08 mmol l; P <0.05 and 1.18 ± 0.29 vs 1.05 ±0.22 mmol/l; P < 0.05). It is concluded that the rise in NcAMP excretion corroborates the concept of increasing parathyroid activity following the treatment of hyperthyroidism.
The distribution of immunoglobulin-containing cells in human autoimmune thyroiditis
Authors: Wilkin T. J. , Casey C.
Published: December 2008

Abstract. The peroxidase-antiperoxidase (PAP) staining method was used to identify immunoglobulin-containing cells in the lvmphoid infiltrates of thyroids removed from patients with Hashimoto's autoimmune thyroiditis. A composite picture of the distribution of such cells in the thyroid infiltrate was obtained by carefully superimposing cell-distribution maps from serial histological sections, each stained for a different immunoglobulin class.

Ig-containing cells were present to varying extents in all areas of the gland, but were most dense in areas of epithelial 'invasion'. IgG was the commonest immunoglobulin, but there were more cells containing IgD and IgE than IgA or IgM. Both λ and K light chains were identified in cells occupying the follicle centres.

Lymphoid follicle structure was strikingly similar to that described previously for gut-associated lymphoid tissue (GALT), and the theory is advanced that autoimmune thyroiditis represents a form of ectopic GALT in which B-cells, which normally home on markers in the gut, are attracted instead to antigenically active sites in the thyroid.
Factors influencing beta-cell function and insulin sensitivity in patients with type 2 (non-insulin-dependent) diabetes
Authors: Groop Leif , Tolppanen Esa-Matti
Published: December 2008

Abstract. This study was designed to evaluate the influence of age, duration of diabetes, relative body weight and glycaemic control on beta-cell function and insulin sensitivity in 250 patients with onset of nonketotic diabetes between the age of 35 and 70 years (Type 2 diabetes). Beta-cell function was assessed by measuring serum C-peptide concentrations after I mg of glucagon iv. It was not influenced by age, age at onset of diabetes nor by the duration of the disease. This suggests that progressive deterioration of beta-cell function with time is not a consistent finding in Type 2 diabetes. Insulin sensitivity, measured as the glucose disappearance rate, KITT, in response to iv-insulin, was not significantly influenced by age or age at onset, but decreased consistently with the duration of the disease (P < 0.001). Beta-cell function was not correlated to fasting blood glucose and HbA1 concentrations. In contrast, there was a strong inverse relationship between glycaemic control and insulin sensitivity (P < 0.001) indicating that decreased insulin sensitivity contributes to poor glycaemic control in these patients. Attempts to improve glycaemic control in patients with Type 2 diabetes should therefore include means to improve insulin sensitivity.
Evaluation of treated acromegalic patients with normal growth hormone levels during oral glucose load
Authors: Rieu Max , Kuhn Jean-Marc , Bricaire Henri , Luton Jean-Pierre
Published: December 2008

Abstract. Twenty-one treated acromegalics with plasma GH levels ≤ 5 ng/ml were evaluated during an oral glucose tolerance test (OGTT). Serum insulin-like growth factor (IGF) levels, measured by a competitive binding assay, were high in 10, normal in 8 and low in 3 patients. Urinary calcium excretion (Ca U), measured over 24 h, was elevated in 9 of the 10 patients whose IGF levels were high, whereas only 1 of the patients with normal or low IGF levels was hypercalciuric. A paradoxical rise in GH following TRH injection was observed in 5 of the 10 patients whose IGF levels were high, whereas all patients with normal or low IGF levels showed no GH response to TRH. GH levels ≥ 10 ng/ml occurred during ornithine (ORN) administration in 6 of the 18 patients with normal or high IGF levels. The remaining 12 patients with no GH rise during ORN included 2 cases in which IGF levels were high and GH rose following TRH, and 2 cases in which IGF levels were normal and GH levels were ≥ 10 ng/ml during insulin-induced hypoglycaemia (IIH), thus excluding a GH deficiency.

These results show that acromegaly is not cured in certain treated patients with normal GH levels during OGTT. It seems that IGF and Ca U determinations are valuable indices of activity, in contrast to GH response to ORN. The GH response to TRH is also relatively useful.
Direct visualization of binding, aggregation and internalization of human growth hormone in cultured human lymphocytes
Authors: Eshet Rina , Peleg Shulamit , Laron Zvi
Published: December 2008

Abstract. The distribution of human growth hormone (hGH) receptor complexes on IM-9 cultured lymphocytes was studied using fluorescein and 125I-labelled hGH (F-hGH and [125I]hGH). The cells labelled with F-hGH were visualized with a sensitive video intensification microscopic system which permitted direct observation of the location of the fluorescent hormone on the surface of the living lymphocytes. At 4°C F-hGH bound diffusely to the cell surface and remained dispersed but following incubation for 30 min at 37°C the hormone receptor complexes aggregated into patches on the cell surface and formed a single cap on one pole of the cell. Progressive internalization into the cell was demonstrated at 37°C with [125I]hGH. It is hypothesized that the aggregation and internalization of the hGH receptor complexes are associated with the action and degradation of the hormone and probably also with the mechanism of down-regulation of the receptors.
Maintenance of differentiated sheep thyroid cells in primary culture for three months
Authors: Mothersill Carmel , Seymour C. , Malone J. F.
Published: December 2008

Abstract. A method is described which permits culture of primary thyroid cells without subculture for at least 100 days. Cultures are maintained without medium changes for the entire period, and concentrated glucose is added to replenish energy supplies at carefully defined intervals. The cells retain morphological and functional differentiation shown by light and electron microscopy, PAS positive histochemistry, iodine uptake and T4 production for at least 100 days. After this time fairly sudden death of the cultures occurs. Possible mechanisms for the effect are postulated. The technique should make it possible to study long-term effects of drugs/radiation on differentiated cultures without the need for continuous subculture.
Failure of chronic experimental hyperinsulinism to alter insulin binding to hypothalamic receptors in the rat
Authors: Melnyk Roman B. , Martin J. M.
Published: December 2008

Abstract. We have previously shown that [125I]insulin binding to medial hypothalamic receptors is attenuated following 14 days of food restriction. Such rats are characterized by considerably reduced circulating insulin levels with unchanged hypothalamic insulin concentration. The present data demonstrate that, in contrast to the effects of starvation, [125I]insulin binding to hypothalamic receptors from rats made hyperinsulinaemic by daily injections of protamine zinc insulin (4–6 U/rat/day for 14 days) is unaffected by this manipulation, even though hypothalamic insulin concentration in insulininjected animals was significantly higher than in salineinjected controls. Insulin binding to partially purified membranes from the medial hypothalamic region was significantly greater than that from the lateral area, confirming a finding in our earlier study. Insulin treatment was associated with slight reductions in maximal insulin-binding capacity of medial hypothalamic receptors, a tendency which appeared to be compensated by reciprocal changes in receptor affinity for this hormone. The data indicate that hypothalamic insulin receptors are not regulated by peripheral or even central insulin levels per se; it appears, rather, that some other, as yet unidentified, correlate(s) of significantly altered food intake and/or body weight can modify hypothalamic insulin receptor function. Perhaps such modifications could, in turn, participate in the activation of regulatory mechanisms involved in correcting energy imbalance.
Hydrocortisone elicits the effect of clomiphene citrate on luteinizing hormone-releasing hormone release in vitro
Authors: Miyake Akira , Tasaka Keiichi , Sakumoto Tetsuro , Nagahara Yasuhito , Aono Toshihiro
Published: December 2008

Abstract. The effect of hydrocortisone on the release of luteinizing hormone (LH) and LH-releasing hormone (LRH) in response to clomiphene citrate (clomiphene) were examined in a sequential double chamber perifusion system by perifusing the mediobasal hypothalami (MBH) and/or pituitaries excised from normal female rats in dioestrus. When the MBH and the pituitary were perifused in sequence with medium containing 5 × 10−6 m hydrocortisone, a significant release in LH (100– 150% increase, P < 0.01–P < 0.05) was observed 40 min after the administration of 3 × 10−8 mol clomiphene. Clomiphene had no effect on LH release from the pituitary when perifused in series with the MBH without basal hydrocortisone infusion. Administration of clomiphene did not cause a significant increase in LH from the pituitary perifused alone, with or without medium containing hydrocortisone. The concentration of LRH in the efflux was significantly increased 40 min after clomiphene administration when MBH was perifused with medium containing hydrocortisone, whereas clomiphene had no effect when perifused with medium only. These data indicate that hydrocortisone stimulates the effect of clomiphene on LRH release from the hypothalamus, which in turn induces LH release from the pituitary.
Immunoreactive IGF-II in serum of healthy subjects and patients with growth hormone disturbances and uraemia
Authors: Enberg Gösta , Hall Kerstin
Published: December 2008

Abstract. A radioimmunoassay has been developed for IGF-II, using Sepharose-coupled antibodies. Porcine insulin, human insulin and human proinsulin showed no cross-reaction, whereas the cross-reaction for IGF-I was 10%. To minimize the influence of the binding protein(s), all serum samples were extracted with acid ethanol before assay.

The mean serum level of immunoreactive IGF-II and 95% confidence limit in 46 healthy adults were 587 ng/ml and 354–974 ng/ml, respectively. In contrast to the declining levels of IGF-I with increasing age, no such age-dependent decrease was found for IGF-II levels between 20 to 70 years. No difference in IGF-II levels was found between patients with acromegaly and healthy adult controls. In cord serum and serum from adult patients with GH deficiency the levels were significantly lower (P < 0.001) compared to controls. In diabetic patients with uraemia the mean level and 95% confidence limit were 1222 ng/ml and 532–2808 ng/ml, respectively. Thus, significantly increased serum levels of immunoreactive IGF-II have only been found in serum from patients with uraemia. Whether this is due to an increased production of IGF-II, or secondary to other factors such as the binding protein(s), will require further investigation.
Hormonal control of protein synthesis in chick chondrocytes: a comparison of effects of insulin, somatomedin C and triiodothyronine
Authors: Kemp Stephen F. , Mutchnick Murry , Hintz Raymond L.
Published: December 2008

Abstract. Somatomedin C (SM-C), insulin, and triiodothyronine (T3) each result in a 2-fold stimulation of incorporation of [125I]leucine into protein by cultured chick sternal chondrocytes. Maximal stimulation occurred at concentrations of 12.5 × 10−9 m SM-C, 11 × 10−9 m insulin, and 1.5 × 10−9 m T3. Submaximal concentrations of SM-C and T3 were additive in their effect, and together stimulated [125I]leucine incorporated to a level greater than that achieved by either alone. Submaximal concentrations of SM-C and insulin were also additive in their stimulatory effect, but only to the level achieved by either alone. It was possible to demonstrate specific binding of [14C]SM-C to chondrocytes, and bound SM-C could be displaced by either unlabelled SM-C or insulin at concentrations similar to concentrations that stimulated protein synthesis. Actinomycin D abolished stimulation by T3, but not by insulin or SM-C. Thus, it appears that SM-C and insulin increase protein synthesis by stimlating the translational process after binding to the same receptor. T3 appears to act through a different mechanism, which requires stimulation of transcription.
Effect of phorbol esters on the release of growth hormone and prolactin from rat pituitary cells cultured in monolayer
Authors: Ohmura Eiji , Tsushima Toshio , Murakami Hitomi , Wakai Kae , Shizume Kazuo
Published: December 2008

Abstract. The effect of phorbol diester tumour promoters on the release of growth hormone (GH) and prolactin (Prl) was studied in rat pituitary cells cultured in monolayer. 12-O-tetradecanoyl phorbol-13-acetate (TPA), the most potent phorbol ester, stimulated GH accumulation in the cultured medium in a dose-dependent manner. TPA also stimulated Prl accumulation. A time course study indicated that TPA mainly stimulates release of GH. The maximal stimulation of GH release by TPA (100 ng/ml) was 3–4-fold over control. Phorbol-12,13-dibutyrate (PDB), another tumour-promoting phorbol ester, stimulated GH release to an extent similar to that of TPA, while a biologically inactive compound, phorbol-12,13-diacetate (PDA), had no effect. TPA-stimulated GH release was not affected by the presence of indomethacin, an inhibitor of prostaglandin (PG) synthesis, indicating that PG is not involved in the process of TPA-stimulated GH release. Co++, a competitive antagonist of Ca++, at 2.0 mm completely suppressed the GH release induced by TPA, and this inhibition was partially reversed by the addition of 2.0 mm Ca++. Verapamil, a Ca++ channel blocker, reduced TPA-stimulated GH release, and trifluoperazine, an inhibitor of Ca-calmodulin formation, had a similar effect. Somatostatin (SRIF) also inhibited the GH release by TPA. These observations are compatible with the idea that Ca++ may be involved in the process of TPA-stimulated GH release. Since TPA has been reported to activate a Ca++- and phospholipiddependent protein kinase (protein kinase C), it is possible that TPA stimulate GH release by activating the enzyme. Further studies are required to clarify this point.
Involvement of norepinephrine in pituitary LH release induced by oestradiol in vitro
Authors: Miyake A. , Tasaka K. , Aono T.
Published: December 2008

Abstract. The direct effects of oestradiol-17β (E2) on pituitary luteinizing hormone (LH) release and the role of norepinephrine (NE) in E2-induced gonadtrophin release were examined in a sequential double chamber perifusion system by perifusing the mediobasal hypothalami (MBH) and/or pituitaries excised from normally cycling female rats. Administration of E2 induced significant release (70–160% increase, P < 0.05) of LH from the pituitary of rats in pro-oestrus, but not in other stages of the oestrous cycle. When the MBH and the pituitary were perifused in sequence, E2 induced significant release of LH in all stages of the oestrous cycle except oestrus. When the pituitary from rats in dioestrus II was perifused alone with medium containing 200 ng/ml NE, significant release of LH (80–170% increase, P < 0.05) was observed after the administration of E2. The E2-induced LH release in pro-oestrus was completely abolished by perifusion with medium containing diethyldithiocarbamate, an inhibitor of NE synthesis. These findings suggest that NE may be involved in changes of pituitary responsiveness in LH secretion to oestrogen during the rat oestrous cycle.
Forskolin perturbs cGMP as well as cAMP levels in human thyroid cells
Authors: Brandi Maria Luisa , Rotella Carlo M. , Lopponi Andrea , Kohn Leonard D. , Aloj Salvatore M. , Toccafondi Roberto
Published: December 2008

Abstract. Forskolin, at 10−11 m, stimulates guanylate cyclase activity in primary human thyroid cell cultures, but does not modify cAMP accumulation. At a 10-fold higher concentration it still stimulates guanylate cyclase activity and becomes an inhibitor of cAMP production. Above 10−9 m, forskolin stimulation of cGMP decreases, while it also becomes a stimulator of cAMP production. There is an additive effect of TSH and forskolin on cAMP production at concentrations of the diterpene which are stimulatory. Concentrations of forskolin which are inhibitory for cAMP, but stimulatory for cGMP, are inhibitory for TSH stimulation of cAMP. The addition of 8-bromo-cGMP duplicates the forskolin effect at low concentrations.
A stimulation test with calcitonin for differential diagnosis of hypercalcaemia
Authors: Benson Lars , Wide Leif , Åkerström Göran , Ljunghall Sverker
Published: December 2008

Abstract. Experimental studies have suggested that in primary hyperparathyroidism (HPT) the cells of the hyperfunctioning parathyroid tissue retain some capacity for stimulation and that an increase in secretion of parathyroid hormone (PTH) can occur when the extracellular calcium concentration is lowered within the hypercalcaemic range.

We have tested this hypothesis in 23 patients with HPT, 10 patients with hypercalcaemia of other origin (7 of whom had disseminated malignant disease) and 17 normal subjects.

In all three groups a single injection of 100 MRC units of salmon calcitonin caused a reduction in serum calcium of approximately 3 to 5%. In the hypercalcaemic patients this reduction was correlated to the basal calcium level (r = −0.57, P < 0.01). In the patients with HPT, although they all remained hypercalcaemic, the decrease in serum calcium was associated with a mean increase in serum PTH of 10%. Only in 2 patients did such an increase fail to occur despite an adequate decrease in serum calcium. These 2 patients had high basal PTH levels and the lack of response might have been due to a high degree of autonomous parathyroid function. Calcitonin also reduced serum calcium and increased serum PTH in normal subjects.

None of the patients with hypercalcaemia of other origin than primary HPT displayed a secretory PTH response to serum calcium reduction.

Thus, this test could be of practical clinical value, particularly in patients with borderline PTH values. A calcitonin-induced rise in PTH while serum calcium is lowered within the hypercalcaemic range strongly suggests primary HPT.
X-chromatin in congenital virilizing adrenal hyperplasia
Authors: Mendonça B. B. , Zogno M. A. , Wajchenberg B. L. , Giannella-Neto D. , Toledo S. P. A.
Published: December 2008

Abstract. X-chromatin body (XCB) frequencies in oral mucosa were investigated in 14 female patients with the simple non-salt-losing form of congenital virilizing adrenal hyperplasia (CVAH) due to 'partial' 21-hydroxylase deficiency (CVAH-type I), using toluidine blue (TBS) and Feulgen's stains (FS).

They were found to be lower than normal controls by both TBS (12.6 ± 1.73 vs 18.38 ± 0.41) and FS (13.60 ± 2.16 vs 17.94 ± 0.76) methods. After 4–5 weeks on glucocorticoid therapy, XCB frequencies overlapped with those of normal controls using both TBS (16.54 ± 1.76) and FS (17.09 ± 1.98). Karyotypes performed in 8 of the 14 cases showed a normal female pattern.

Two possible interpretations are proposed: First, variations of XCB counts may reflect the average nuclear size of the cell populations studied. Second, high androgen levels found in untreated cases with CVAH-type I might lead to partial chromosome depiralization and increasing euchromatic areas. At present the first possibility appears more likely.
Hormonal, metabolic, and neuroradiologic abnormalities associated with septo-optic dysplasia
Authors: Arslanian S. A. , Rothfus W. E. , Foley T. P. , Becker D. J.
Published: December 2008

Abstract. The clinical, neuroradiologic, and endocrine features in 16 patients with septo-optic dysplasia are reviewed. All of the patients had clinical optic nerve hypoplasia with varying degrees of nystagmus and visual impairment. Only one-half of the patients had absence of the septum pellucidum. Fourteen children were growth hormone deficient, 9 were adrenocorticotrophic hormone deficient, 3 were thyroid-stimulating hormone deficient, and 4 had diabetes insipidus. In most instances, the diagnosis of septo-optic dysplasia can be established by physical examination and neuroradiologic findings, at which point a thorough evaluation of the hypothalamicpituitary endocrine function is indicated because of the high incidence of hypopituitarism with this syndrome.
Biphasic modulation of pituitary sensitivity to GnRH by oestrogens: the effects of A- and D-ring substitution on LH release in cultured pituitary cells
Authors: Emons G. , Knuppen R. , Ball P. , Catt K.J.
Published: December 2008

Abstract. The sensitizing effect of oestrogens on GnRH-stimulated LH release was evaluated in pituitary cells from adult female rats, cultured for 2 days in the presence of 10−13 to 10−6 m concentrations of oestradiol and selected A- and D-ring modified oestrogens. With almost all steroids tested, bell-shaped dose-response curves with comparable LH-maxima but different EDmax values were obtained for the LH response to a submaximal GnRH stimulus (5 × 10−10 m). Maximal LH response to 5 × 10−10 m GnRH were found at the following oestrogen concentrations: oestradiol and 4-hydroxyoestradiol = 10−11 m; 2-methyloestradiol = 10−9 m; 2-hydroxyoestradiol = 10−8 m; with 4-methyloestradiol no significant maximum was observed. When cells were pretreated with 10−13, 10−11 and 10−9 m oestradiol, or 4-hydroxyoestradiol, or 2-hydroxyoestradiol, and exposed to increasing concentrations of GnRH (10−11 to 10−7 m), an almost 10-fold decrease in the ED50 for GnRH was observed after pretreatment with 10−11 m oestradiol and 4-hydroxyoestradiol. With 2-hydroxyoestradiol at this concentration, the sensitizing effect was much less pronounced. Increasing the steroid concentration to 10−9 m slightly decreased the effect of oestradiol and 4-hydroxyoestradiol, whereas it increased the effect of 2-hydroxyoestradiol. Thus, at the target cell 4-hydroxyoestradiol has the same potency as oestradiol, while 2-hydroxyoestradiol is significantly less active. The sensitizing effect of oestradiol is only slightly decreased by the presence of a methyl group in position 2, but is markedly reduced by a methyl group in position 4. Our results also demonstrate the high sensitivity of the pituitary to oestrogen-induced enhancement of GnRH-stimulated gonadotrophin release, as well as the decrease of the positive effect at high oestrogen concentrations. The bell-shaped dose-response curves for oestrogen action should be taken into account when evaluating the effects of oestrogens and their derivatives upon gonadotrophin release from the pituitary gland.
Effects of continuous infusions of 4-hydroxyoestradiol and oestradiol on plasma LH-levels in the ovariectomized ewe
Authors: Emons G. , Brack C. , Chatelain R. , Abel H. H. , Isedor S. , Ball P.
Published: December 2008

Abstract. Ovariectomized ewes were infused over a period of 12 h at constant rates with different doses of the catecholoestrogen 4-hydroxyoestradiol (4-OHE2) or the primary oestrogen oestradiol (E2) via a catheter placed in the right atrium. Blood samples were drawn every hour for a total period of 48 h starting 1 h before the beginning of the steroid infusion. Luteinizing hormone (LH), 4-OHE2 and E2 concentrations were measured in these samples by specific radioimmunoassays. Infusions of low doses E2 (0.5 μg/h) or 4-OHE2 (2 μg/h) caused only a suppression of LH-secretion. At doses of 1 μg E2/h or 5 μg 4-OHE2/h this negative effect was followed by inconsistent elevations of plasma LH. Beyond this threshold dose, E2 at infusion rates of 2, 5 and 10 μg/h and 4-OHE2 at infusion rates of 10, 25 and 50 μg/h produced the negative effect and massive LH-surges. At still higher infusion rates (E2: 20 μg/h, 4-OHE2: 100 μg/h) lower elevations of plasma LH levels were observed. 4-OHE2 had to be infused at 4–5 times higher rates than E2 to obtain comparable plasma concentrations of either oestrogen. Under this condition the effects of 4-OHE2 and E2 were similar indicating that 4-OHE2 has the same potency as E2 at central target sites.
The accumulation of [35S]methimazole by monocytes and macrophages
Authors: Weetman A. P. , Gunn Catherine , Hall R. , McGregor A. M.
Published: December 2008

Abstract. We have used an automatic cell harvester and micro culture techniques to examine the accumulation of [35S]methimazole by monocytes, macrophages and lymphocytes. Significant temperature-dependent accumulation of the drug was found in resting monocytes and macrophages; this was increased up to 4-fold by phagocytosis. Lymphocytes accumulated little or no drug and myeloma and leukaemic cell lines accumulated none. These results show that two interrelated cells with endogenous peroxidatic activity take up the antithyroid drug methimazole providing further support for the concept that immunosuppression by this drug in Graves' disease is mediated via an action on antigen-presenting cells.
Differential calcium response of normal and adenomatous parathyroid glands
Authors: Diete Manfred , Hölzel Fritz , Arps Hartmut , Bressel Max
Published: December 2008

Abstract. In vitro parathyroid hormone secretion of normal (n = 10) and adenomatous (n = 20) human parathyroid glands was compared in response to different calcium (Ca++) concentrations. The glands, prepared for tissue culture immediately after surgical removal, were incubated under identical conditions for 6 h. The medium was changed hourly and analyzed for PTH and cAMP using radioimmunoassay. During the first 2 h of the experiment, the Ca++ concentrations of all preparations was kept constant at 1.2 mm equivalent to the normal Ca++ level of the intercellular space. The PTH level of the 2nd h was defined as reference value corresponding to 100%. After the 2nd h of incubation the Ca++ concentration in the medium was shifted either to low (0.9 or 0.6 mm) or to high (1.9 or 2.6 mm) values. In low Ca++ concentrations (0.6 mm) the normal parathyroid glands responded by stimulation of the PTH release up to 310% in relation to the reference value, whereas the adenomas enhanced the PTH release to 160% only. The incubations in 0.9 mm Ca++ resulted in a slightly lower degree of stimulation. During the incubation in high Ca++ the PTH secretion was reduced to 28% by normal glands and to 52% by adenomatous parathyroid glands. Movements of cAMP measurements paralleled PTH values. The study provides evidence for an abnormally low responsiveness of parathyroid adenomas to Ca++ when compared with normal glands. The reduction in Ca++ responsiveness of adenomatous cells appears to have a fundamental role in primary hyperparathyroidism since the tumour cells may obviously recognize normal Ca++ levels as 'hypocalcaemic' and react by a stimulated PTH secretion.
Effect of ACTH on endogenous steroid biosynthesis in long-term primary cultures from newborn rat adrenal cells
Authors: Ramirez Leyla C. , Millot Claire , Maume Bernard F.
Published: December 2008

Abstract. Normal newborn rat adrenal cells kept in primary culture up to 2½ months respond to ACTH stimulation and produced corticosteroid hormones and smaller amounts of 20α-reduced progesterone metabolites. Cholesterol from the serum complemented culture medium serves as precursor without further addition of exogenous steroid substrates. A long-term qualitative and quantitative study of individual steroid production under the influence of ACTH was performed.

ACTH treatment produced a triphasic effect on steroid production: an induction period (up to 3 days), an acute maximum production period (3rd to 6th day) and a chronic production period (to the end of the treatment). The increase in total steroid production resulted from the increase in the production of corticosteroids only. This indicated an increase of cholesterol side-chain cleavage and of the 21- and 11β/18-steroid hydroxylations. Removal of ACTH led to a reversible drop in total steroid production. The response to ACTH was dose dependent, so that a 2.2 mU/ml dose elicited lower steroid production than the 6.6 or 22 mU/ml doses. Increasing the lower dose after a week of treatment to a higher dose brought total steroid production and 1 1β/18-steroid hydroxylation up to the corresponding chronic production levels. The 20α-steroid reduction system was not affected by ACTH.

ACTH changes the importance of the two main steroidogenic pathways. With no ACTH there is approximately a 1:1 ratio between corticosteroid synthesis and progesterone reductive metabolism; a low dose of ACTH increases the total steroid production, but since corticosteroid production and 20α-reduced metabolites both increase, the ratio changes little; a high dose of ACTH increases the ratio to more than 30:1.

Refractoriness or desensitization to ACTH is postulated to occur through the control of cholesterol availability inside the cell possibly combined with a control of its utilization for steroidogenesis.
Growth and bone haemodynamic responses to castration in male rats. Reversibility by testosterone
Authors: Schoutens A. , Verhas M. , L'Hermite-Baleriaux M. , L'Hermite M. , Verschaeren A. , Dourov N. , Mone M. , Heilporn A. , Tricot A.
Published: December 2008

Abstract. Orchidectomy in postpubertal 55 day old rats, compared to sham-operated controls, led beyond 2 months to a decrease in body weight (87% of controls by 120 d), tibial length (97% of controls) and in tibial calcium content (85% of controls). Bone plasma flow increased three times to reach a peak at 31 days; it was decreased but no significantly at 86 and 120 days. The number of oosteoclasts was maximal at 51 days (X 2.3) and was still elevated at 120 days. The calcium accretion rate increased briefly at 31 days (110% of controls) and was diminished at 86 and 120 days (78% of controls). The initial 'physiological' changes in the tibia occurred before any weight change and might be directly due to the lack of androgens. They can be interpreted as inducing the conditions for enhanced bone resorption. Testosterone replacement therapy, initiated after the initial haemodynamic response, inhibited the negative effect of castration on bone growth.
Restoration of LH pulsatility in patients with prolactinomas after trans-sphenoidal surgery
Authors: Koizumi Kiyoshi , Aono Toshihiro , Koike Koji , Kurachi Keiichi
Published: December 2008

Abstract. In hyperprolactinaemic patients with amenorrhoea, pulsatile secretion of LH is reported to be infrequent or absent. For further assessment of the effect of prolactin (Prl) on LH pulsatility, the serum gonadotrophin concentration was determined at 15 min intervals for 180 min in 12 patients with prolactinomas before treatment and in 6 patients who showed normalization of the Prl level after trans-sphenoidal surgery.

Surgical treatment caused a significant reduction (P < 0.05) of the mean (± se) serum Prl level from 519 ± 152 to 9.2 ± 1.4 ng/ml. The mean LH level (7.3 ± 1.2 mIU/ml) before treatment was significantly increased (P < 0.05) after trans-sphenoidal surgery (12.7 ± 2.4 mIU/ml). An LH spike was defined as an LH concentration that exceeded the mean LH level over the study period by 2 sd of the intra-assay variation, achieving a level of above 10 mIU/ml. LH spikes were observed in 2 of 12 patients (16.7%) before treatment, and in 5 of 6 patients (83.3%) after trans-sphenoidal surgery, the difference being significant (P < 0.05).

These results suggest that hyperprolactinaemia in prolactinoma patients may cause impaired LH pulsatile secretion and that this derangement can be reversed by reduction of the Prl level by adenomectomy.
The effects of progesterone on gonadotrophin release in hypogonadal women
Authors: Minakami H. , Kimura K. , Yano H. , Kanazawa T. , Tamada T.
Published: December 2008

Abstract. The effect of progesterone on pulsatile and basal release of gonadotrophins was studied in 10 hypogonadal women. The day before progesterone treatment, control blood samples were obtained at 15 min intervals between 15.00 and 20.00 h. The next day, 50 mg of progesterone was administered im at 06.00 h and blood samples again were obtained at 15 min intervals between 15.00 and 20.00 h. Serum progesterone levels were 28.4 ± 4.4 ng/ml at 15.00 h, 24.2 ± 3.9 ng/ml at 17.30 h and 20.7 ± 2.5 ng/ml (mean ± sd) at 20.00 h. Progesterone prolonged the interval between LH pulses from 85 ± 27 to 155 ± 55 min (mean ± sd), augmented their amplitude 2-fold, and caused average declines in LH and FSH concentrations of 27 and 15%, respectively. The results suggest that progesterone suppresses the mean levels of LH and FSH concentrations by acting in the brain to decrease the pulse frequency of gonadotrophin-releasing hormone.