Effect of pretreatment of long-term ovariectomized rats with an LRH antagonist on LH release in vitro by LRH, elevated K+ or N6-monobutyryl adenosine 3',5'-monophosphate (mbcAMP) plus theophylline

1985 ◽  
Vol 108 (3) ◽  
pp. 331-337 ◽  
Author(s):  
G. P. van Rees ◽  
J. A. M.J. van Dieten
Keyword(s):  
Ovariectomized Rats ◽  
Serum Lh ◽  
Low Concentrations ◽  
Pituitary Glands ◽  
Lh Release ◽  
Release In Vitro ◽  
High Concentrations ◽  
Response Line ◽  
The Right

Abstract. The effect of the LRH antagonist (Ac-D-p--Cl-Phe1,2,D-Trp3,D-Phe6-D-Ala10)-LRH (Org 30093) on pituitary LH release was studied, using pituitary glands of ovariectomized rats. In vitro, the antagonist had no detectable agonist activity in the concentration used, had no effect on the maximal LH release which can be induced by LRH and shifted the dose-response line of LRH to the right, without changing its slope. By this the antagonist fulfilled the conditions of purely competitive antagonist. Also, when present in vitro, the antagonist had no effect on LH release induced by raised K+, whether alone or in combination with mbcAMP plus theophylline. A single injection of Org 30093 decreased serum LH without inducing a change of pituitary LH content measured 24 h later. Twenty-four h after the sc injection of the agonist, LH release in vitro induced by LRH was affected differently, depending on the concentration of LRH used: the effect of low concentrations of LRH was inhibited, whereas the effect of high concentrations of LRH was augmented. Pretreatment with the agonist had no effect on LH release by raised K+ combined with mbcAMP plus theophylline, but slightly increased LH release by raised K+.

Effect of Ca2+ deprivation on release of luteinizing hormone induced by luteinizing hormone releasing hormone from female rat pituitary glands in vitro

1982 ◽  
Vol 94 (1) ◽  
pp. 11-20 ◽  
Author(s):  
J. de Koning ◽  
A. M. I. Tijssen ◽  
J. A. M. J. van Dieten ◽  
G. P. van Rees
Keyword(s):  
Protein Synthesis ◽  
Initial Phase ◽  
Phase Response ◽  
Ovariectomized Rats ◽  
Second Phase ◽  
Pituitary Glands ◽  
Lh Release ◽  
Lh Rh ◽  
Intact Rats

Continuous exposure of hemi-pituitary glands from intact female rats to LH releasing hormone (LH-RH) in vitro displayed three phases in the pattern of LH release: during the first hour release of LH was low (first phase response), then it increased to a higher level during the second hour and remained constant during the next 2 h (second phase response), after which there was a refractoriness of LH release (third phase response). The initial phase response of pituitary glands from intact rats was blocked by EGTA (a Ca2+ chelator) but there was a small but significant increase in the rate of LH release during the second phase response. This increase could be prevented by inhibition of protein synthesis by cycloheximide. Cycloheximide and EGTA did not affect basal release of LH by glands from intact rats, neither did EGTA affect the high basal release of LH by glands from ovariectomized rats. However, the LH-RH-induced release of LH from pituitary glands of ovariectomized rats, which did not show the initial phase of low LH release, was completely suppressed by EGTA throughout a 4-h incubation period. The pattern of LH release stimulated by the combination of N6-monobutyryl cyclic AMP and theophylline (mbcAMP/theophylline) showed an initial phase of low LH release lasting 4 h after which it increased. The magnitude of the effect was small compared with the action of LH-RH. As it did with LH-RH, EGTA completely blocked the initial response, but allowed a small increase in the rate of LH release thereafter; this increase could also be blocked by inhibition of protein synthesis. Addition of EGTA to media during pretreatment of pituitary glands from intact rats with either LH-RH or mbcAMP/theophylline did not impair the facilitatory effect of these secretagogues on the responsiveness of the glands to subsequent exposure to LH-RH and cycloheximide and normal Ca2+ levels. The restoration of Ca2+ levels after withdrawal neither affected basal nor LH-RH-induced release of LH. Exclusion of Ca2+ from the media during a 6-h incubation of pituitary glands from intact rats with LH-RH prevented the glands from becoming refractory to subsequent stimulation by LH-RH, which occurs when normal Ca2+ concentrations are present. The results suggested that extracellular Ca2+ is obligatory for LH release and the induction of refractoriness by LH-RH. In contrast, that part of the action of LH-RH which is cyclic AMP-mediated and protein synthesis-dependent is not affected by withdrawal of extracellular Ca2+.

Release of LH in vitro from anterior pituitary glands of ovariectomized rats by LRH or elevated potassium concentration after pre-treatment with oestradiol benzoate in vivo

1982 ◽  
Vol 99 (2) ◽  
pp. 206-210 ◽  
Author(s):  
A. M. I. Tijssen ◽  
J. de Koning ◽  
G. P. van Rees
Keyword(s):  
Ovariectomized Rats ◽  
Bicarbonate Buffer ◽  
High K ◽  
Oestradiol Benzoate ◽  
Negative Effect ◽  
Pituitary Glands ◽  
Lh Release ◽  
Pre Treatment ◽  
Positive Effect

Abstract. Pituitary glands from ovariectomized rats which had been pre-treated with oestradiol benzoate (OeB) or solvent oil were incubated in Krebs-Ringer bicarbonate buffer with glucose containing either LRH (1000 ng/ml) or a high K+ concentration (50 mM). OeB (7 μg sc) or oil was injected at 2.5 or 6.5 h before the beginning of the incubation experiment or during the three preceding days (three daily injections). Depending upon the period during which the pituitary glands had been exposed to OeB LH release induced by LRH was inhibited (negative effect of OeB) or augmented (positive effect). When the glands were incubated in medium containing high K+, only the negative effect of OeB pre-treatment was seen. It is concluded that that part of LRH-induced LH release which is mimicked by high K+ is involved in the negative effect of OeB, but not in its positive effect.

Effect of pretreatment of long-term ovariectomized (OVX) rats with a competitive LRH antagonist on FSH release in vitro

1985 ◽  
Vol 109 (4) ◽  
pp. 481-484
Author(s):  
J. A. M. J. van Dieten ◽  
G. P. van Rees
Keyword(s):  
Specific Effect ◽  
High Concentration ◽  
Ovx Rats ◽  
High K ◽  
Basal Release ◽  
Pituitary Glands ◽  
Lh Release ◽  
Release In Vitro

Abstract. The effect of a single sc injection of an LRH antagonist ((Ac - D - p - Cl - Phe1,2,D-Trp3,D-Phe6,D-Ala10)-LRH, Org 30093) into OVX rats on FSH release 24 h later was studied. Plasma FSH was decreased but pituitary FSH content was not changed. Incubation of the pituitary glands during 4 h resulted in a decreased basal release. FSH release induced by a low concentration of LRH (1 ng/ml) was depressed but that of a high concentration (10000 ng/ml) was augmented in comparison to FSH release induced in control glands. However, pretreatment with the antagonist had no specific effect on FSH release in vitro induced by high K+ or high K+ plus mbcAMP and theophylline, indicating that the changes of pituitary responsiveness to LRH are not caused by those parts of the secretory mechanism which are stimulated by these secretagogues. Moreover, it is concluded that the changes of pituitary LH release induced by administration of an LRH antagonist also concern FSH.

Effect of pre-treatment of long-term ovariectomized rats with anti-LRH on the response of the pituitary gland in vitro to the analogue of LRH D-ser-(tBu)6-des-gly10-ethylamide-LRH (Buserelin®)

1983 ◽  
Vol 104 (3) ◽  
pp. 272-278 ◽  
Author(s):  
G. P. van Rees ◽  
J. A. M. J. van Dieten ◽  
J. de Koning ◽  
A. F. P. M. de Goey
Keyword(s):  
Pituitary Gland ◽  
Ovariectomized Rats ◽  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
Basal Release ◽  
Pituitary Glands ◽  
Lh Release ◽  
Pre Treatment

Abstract. Ovariectomized rats were injected iv with an antiserum against LRH or normal rabbit serum. AntiLRH caused a decrease of plasma LH and FSH. After 24 or 48 h, the rats were decapitated and the pituitary glands incubated in the presence of an analogue of LRH which reacts minimally with anti-LRH (Buserelin). Pretreatment with anti-LRH caused an increased response of pituitary LH release to Buserelin. Similar results were obtained with regard to FSH. In this case, however, basal release of FSH was lowered by pre-treatment with antiLRH. Pituitary LH and FSH contents were not affected by anti-LRH, but synthesis of LH and FSH in vitro was smaller than in control glands obtained from rats pretreated with normal rabbit serum.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Aggregation of Cat Platelets in Vitro

1970 ◽  
Vol 23 (03) ◽  
pp. 601-620 ◽  
Author(s):  
Th. B Tschopp
Keyword(s):  
Adenosine Monophosphate ◽  
Blood Collection ◽  
Base Line ◽  
Reversible Aggregation ◽  
Low Concentrations ◽  
Irreversible Aggregation ◽  
High Concentrations ◽  
Two Phases ◽  
Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

Changes in the characteristics of pulsatile luteinizing hormone secretion during the oestrous cycle and after ovariectomy and oestrogen treatment in female rats

1982 ◽  
Vol 94 (2) ◽  
pp. 177-182 ◽  
Author(s):  
Takashi Higuchi ◽  
Masazumi Kawakami
Keyword(s):  
Hormone Secretion ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Luteinizing Hormone Secretion ◽  
Oestrogen Treatment ◽  
Serum Lh ◽  
Lh Release

Changes in the characteristics of LH secretory pulses in female rats were determined in different hormonal conditions; during the oestrous cycle and after ovariectomy and oestrogen treatment. The frequency and amplitude of the LH pulses were stable during the oestrous cycle except at oestrus when a pattern could not be discerned because of low LH concentrations. These were significantly lower than those measured during other stages of the cycle. Mean LH concentrations and LH pulse amplitudes increased with time up to 30 days after ovariectomy. The frequency of the LH pulse was unchanged 4 days after ovariectomy when mean LH levels had already increased. The frequency increased 10 days after ovariectomy and then remained stable in spite of a further increase in mean serum LH concentrations. Oestradiol-17β injected into ovariectomized rats caused a decrease in LH pulse amplitude but no change in pulse frequency. One day after treatment with oestradiol benzoate no LH pulse was detectable, probably because the amplitude was too small. A generator of pulsatile LH release is postulated and an oestrogen effect on its function is discussed.

An evaluation of potential seed treatments to control Fusarium solani f.sp. phaseoli, the cause of foot and root rot of Phaseolus vulgaris

1977 ◽  
Vol 89 (1) ◽  
pp. 235-238 ◽  
Author(s):  
P. E. Russell ◽  
A. E. A. Mussa
Keyword(s):  
Phaseolus Vulgaris ◽  
Fusarium Solani ◽  
Root Rot ◽  
Similar Pattern ◽  
Fungal Growth ◽  
Systemic Fungicide ◽  
Product Concentration ◽  
Low Concentrations ◽  
High Concentrations

SummaryTwo systemic fungicides, benomyl and thiabendazole, were more active than the non-systemic fungicide Drazoxolon in inhibiting fungal growth in vitro. A similar pattern was obtained in glasshouse trials with benomyl and thiabendazole giving adequate protection at low concentrations while Drazoxolon was ineffective unless applied at 50% the commercial product concentration. A field trial using thiabendazole, Drazoxolon and a mixture of benomyl and thiram confirmed the glasshouse results.Some phytotoxicity was noticed with high concentrations of both benomyl and thiabendazole, but satisfactory disease control was achieved using fungicide concentrations which did not induce phytotoxicity.

scholarly journals Colchicine-binding protein of the liver. Its characterization and relation to microtubules.

1975 ◽  
Vol 66 (3) ◽  
pp. 609-620 ◽  
Author(s):  
C Patzelt ◽  
A Singh ◽  
Y L Marchand ◽  
L Orci ◽  
B Jeanrenaud
Keyword(s):  
High Speed ◽  
Specific Binding ◽  
Electrophoretic Analysis ◽  
Binding Activity ◽  
Low Concentrations ◽  
Electrophoretic Behavior ◽  
High Affinity Binding Site ◽  
High Concentrations

Colchicine-binding activity of mouse liver high-speed supernate has been investigated. It has been found to be time and temperature dependent. Two binding activities with different affinities for colchicine seem to be present in this high-speed supernate, of which only the high-affinity binding site (half maximal binding at 5 x 10(-6) M colchicine) can be attributed to microtubular protein by comparison with purified tubulin. Vinblastine interacted with this binding activity by precipitating it when used at high concentrations (2 x 10(-3) M), and by stabilizing it at low concentrations (10(-5) M). Lumicolchicine was found not to compete with colchicine. The colchicine-binding activity was purified from liver and compared with that of microtubular protein from brain. The specific binding activity of the resulting preparation, its electrophoretic behavior, and the electron microscope appearance of the paracrystals obtained upon its precipitation with vinblastine permitted its identification as microtubular protein (tubulin). Electrophoretic analysis of the proteins from liver supernate that were precipitated by vinblastine indicated that this drug was not specific for liver tubulin. Preincubation of liver supernate with 5 mM EGTA resulted in a time-dependent decrease of colchicine-binding activity, which was partly reversed by the addition of Ca++. However, an in vitro formation of microtubules upon lowering the Ca++ concentration could not be detected. Finally, a method was developed enabling that portion of microtubular protein which was present as free tubulin to be measured and to be compared with the total amount of this protein in the tissue. This procedure permitted demonstration of the fact that, under normal conditions, only about 40% of the tubulin of the liver was assemled as microtubules. It is suggested that, in the liver, rapid polymerization and depolymerization of microtubules occur and may be an important facet of the functional role of the microtubular system.

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