Effets du chlorhydrate d'heptaminol sur la transmission neuromusculaire

1988 ◽  
Vol 66 (11) ◽  
pp. 1442-1449 ◽  
Author(s):  
Jean Vautrin ◽  
Jean Mambrini ◽  
Nicole Mauro ◽  
Caroline Quillent
Keyword(s):  
Neuromuscular Transmission ◽  
Synaptic Delay ◽  
Quantal Content ◽  
Quantal Size ◽  
Motor End Plate ◽  
Diaphragm In Vitro ◽  
Dose Dependent ◽  
Indirect Stimulation ◽  
Stimulation Of

6-Amino-2-methyl-2-heptanol chlorhydrate, heptaminol chlorhydrate, blocks the response to indirect stimulation of the mouse diaphragm in vitro. This effect is due to a dose-dependent pre- and post-synaptic block of neuromuscular transmission starting at 1 mM heptaminol (HEPT). The complete block of neuromuscular transmission occurs at 10 mM. At 2 mM, the decrease in quantal size is more significant in the presence of d-tubocurarine than when the extracellular calcium is lowered. At this concentration, heptaminol also prolongs the depolarization time of the motor end plate potential. Slightly higher concentrations of heptaminol produce a decrease in quantal content. This latter effect is associated with an increase in synaptic delay.

Antral gland cell column: a method for studying release of gastric hormones

1983 ◽  
Vol 245 (4) ◽  
pp. G463-G469
Author(s):  
B. Richelsen ◽  
J. F. Rehfeld ◽  
L. I. Larsson
Keyword(s):  
In Vitro Release ◽  
Dependent Manner ◽  
Gastrin Release ◽  
Cell Column ◽  
Independent Manner ◽  
Response Characteristics ◽  
Dose Dependent ◽  
Vitro Release ◽  
Stimulation Of

A technique for studying in vitro release of gastric hormones has been developed. The system utilizes nonenzymatically isolated antropyloric glands from humans or rats, which are perifused in a Bio-Gel P-2 column. The system permits the study of kinetics and dose-response characteristics using the glands as their own control. The glands were stimulated with carbachol and bombesin, and the antral peptides gastrin and somatostatin were measured. Bombesin and carbachol both evoked a dose-dependent stimulation of gastrin release, beginning at below 10(-10) M (bombesin) and 10(-7) M (carbachol). Carbachol inhibited the release of somatostatin in a dose-dependent manner, being maximally effective at 10(-6) M and then producing 60% inhibition of somatostatin release. Bombesin was without effect on antropyloric somatostatin release. These data suggest that the gastrin-stimulating effect of carbachol is partially or totally due to inhibition of somatostatin release, whereas bombesinergic stimulation of gastrin release must work in an independent manner. In addition, data on the effects of these substances on the release of gastrin and ACTH-like peptides from human antropyloric glands are presented. Due to the absence of local neural reflexes, this system is a useful supplement to the isolated perfused stomach model.

Two Neuropeptides Colocalized in a Command-Like Neuron Use Distinct Mechanisms to Enhance Its Fast Synaptic Connection

2003 ◽  
Vol 90 (3) ◽  
pp. 2074-2079 ◽  
Author(s):  
H.-Y. Koh ◽  
F. S. Vilim ◽  
J. Jing ◽  
K. R. Weiss
Keyword(s):  
High Frequency ◽  
Synaptic Connection ◽  
Quantal Content ◽  
Functional Consequence ◽  
Functional Implication ◽  
Quantal Size ◽  
Quantal Analysis ◽  
Cholinergic Interneuron ◽  
Single Synapse ◽  
Stimulation Of

In many neurons more than one peptide is colocalized with a classical neurotransmitter. The functional consequence of such an arrangement has been rarely investigated. Here, within the feeding circuit of Aplysia, we investigate at a single synapse the actions of two modulatory neuropeptides that are present in a cholinergic interneuron. In combination with previous work, our study shows that the command-like neuron for feeding, CBI-2, contains two neuropeptides, feeding circuit activating peptide (FCAP) and cerebral peptide 2 (CP2). Previous studies showed that high-frequency prestimulation or repeated stimulation of CBI-2 increases the size of CBI-2 to B61/62 excitatory postsynaptic potentials (EPSPs) and shortens the latency of firing of neuron B61/62 in response to CBI-2 stimulation. We find that both FCAP and CP2 mimic these two effects. The variance method of quantal analysis indicates that FCAP increases the calculated quantal size ( q) and CP2 increases the calculated quantal content ( m) of EPSPs. Since the PSP amplitude represents the product of q and m, the joint action of the two peptides is expected to be cooperative. This observation suggests a possible functional implication for multiple neuropeptides colocalized with a classical neurotransmitter in one neuron.

scholarly journals Lithium stimulation of granulopoiesis in diffusion chambers--a model of a humoral, indirect stimulation of stem cell proliferation

Blood ◽  
1985 ◽  
Vol 65 (1) ◽  
pp. 163-168 ◽  
Author(s):  
MA Doukas ◽  
EO Niskanen ◽  
PJ Quesenberry
Keyword(s):  
Progenitor Cell ◽  
Rest Period ◽  
Direct Effects ◽  
Diffusion Chambers ◽  
Macrophage Colony ◽  
Chamber Fluid ◽  
Indirect Stimulation ◽  
Stimulation Of

Abstract Lithium has been recognized as a stimulator of granulopoiesis both in vivo and in vitro. The mechanism by which lithium provokes this stimulation is unclear, with previous data focusing on such divergent causes as direct effects on progenitor cells v elevations in granulocyte macrophage colony-stimulating activity (GM-CSA) production. In the present study, we used a model system of granulopoiesis in diffusion chambers to study this stimulation of granulopoiesis. Lithium pretreatment of mice followed by a rest period to allow for excretion of the lithium (confirmed by serum assays) revealed a stimulation of progenitor cell growth within the diffusion chambers. No changes in the serum and chamber fluid GM-CSA levels were discernible between the control host mice and the lithium-pretreated mice. These data indicate that lithium stimulates granulopoiesis by an indirect mechanism that does not appear to involve GM-CSA.

Secretory patterns of 1α-hydroxycorticosterone in the isolated perifused interrenal gland of the dogfish, Scyliorhinus canicula

1990 ◽  
Vol 5 (1) ◽  
pp. 55-60 ◽  
Author(s):  
L. B. O'Toole ◽  
K.J. Armour ◽  
C. Decourt ◽  
N. Hazon ◽  
B. Lahlou ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Significant Rise ◽  
Dependent Manner ◽  
Steroid Production ◽  
Secretory Rate ◽  
Scyliorhinus Canicula ◽  
Interrenal Gland ◽  
Dose Dependent ◽  
Stimulation Of

ABSTRACT An isolated in-vitro perifused interrenal gland preparation from the dogfish Scyliorhinus canicula was used to study production of quantitatively the major corticosteroid 1α-hydroxycorticosterone (1α-OH-B), measured by radioimmunoassay. Basal secretory rates were 877·1 ± 145 (s.e.m.) fmol/mg per 15 min (n=14) and the preparation remained viable for up to 22 h, as reflected in a brisk response to 10 μm cyclic AMP (cAMP) after this time. Steroid production responded in a dose-dependent manner to porcine ACTH, with 10 μm producing a maximum stimulation of 225% above the basal secretory rate. cAMP (10 μm) produced an increase of 278% above basal, while 1 μm forskolin increased basal secretory rates by 127%. [Val5]- and [Ile5]-angiotensin II (0·1 μm) increased 1α-OH-B production by 120 and 372% respectively over basal secretory rates. Increasing the concentration of K+ in the perfusate from 8 mm to 12, 18, 28 and 40 mm produced a significant rise only at 28 mm. Alterations in the concentration of Na+ and osmolarity of the perifusion medium had inconsistent effects on steroid production. Increased concentrations of urea (from 360 to 720 mm) increased the basal secretory rate by 121%, whilst reducing the concentration of urea (from 360 to 90 mm) had no effect.

Stimulation of HCO3- transport in isolated proximal bullfrog duodenum by prostaglandins

1980 ◽  
Vol 239 (3) ◽  
pp. G198-G203 ◽  
Author(s):  
G. Flemstrom
Keyword(s):  
Electrical Potential ◽  
Potential Difference ◽  
Electrical Potential Difference ◽  
Morphological Examination ◽  
Minimal Concentration ◽  
Dependent Transport ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Stimulation Of

An in vitro preparation of proximal duodenum from the bullfrog transported alkali into the luminal solution (approximately 1 mueq x h-1 x cm-2) and generated a transepithelial electrical potential difference (5-10 mV, lumen negative). Transport was inhibited by 2,4-dinitrophenol (10(-5) M), CN- (5 X 10(-3) M), indomethacin (5 X 10(-5) M), and acetazolamide (5 X 10(-3) M) indicating that metabolism is required. Both alkali transport and the electrical potential difference showed a dose-dependent increase on administration of the prostaglandins E2, 16,16-dimethyl E2, and F2 alpha. The minimal concentration stimulating transport was lower with the E-type prostaglandins (10(-8) M than with F2 alpha (10(-6) M), and the former also produced greater maximal responses. In addition to metabolic-dependent transport of alkali, there was passive transmucosal migration of HCO3-, amounting to approximately 40% of basal (unstimulated) transport and sensitive to variation of the transmucosal hydrostatic pressure. Morphological examination showed that the preparation is devoid of Brunner glands. Stimulation of duodenal epithelial HCO3- transport by prostaglandins may contribute to their previously demonstrated ability to prevent duodenal ulceration.

Platyhelminth FMRFamide-related peptides (FaRPs) contract Schistosoma mansoni (Trematoda: Digenea) muscle fibres in vitro

Parasitology ◽  
1994 ◽  
Vol 109 (4) ◽  
pp. 455-459 ◽  
Author(s):  
T. A. Day ◽  
A. G. Maule ◽  
C. Shaw ◽  
D. W. Halton ◽  
S. Moore ◽  
...  
Keyword(s):  
Schistosoma Mansoni ◽  
Neuromuscular Transmission ◽  
Free Acid ◽  
Muscle Fibres ◽  
Channel Blockers ◽  
Excitatory Effect ◽  
Extracellular Medium ◽  
High K ◽  
Dose Dependent

SUMMARYMolluscan FMRFamide and two recently discovered platyhelminth FMRFamide-related peptides (FaRPs), GNFFRFamide from the cestode Moniezia expansa and RYIRFamide from the terrestrial turbellarian Artioposthia triangulata, cause dose-dependent contractions of individual muscle fibres from Schistosoma mansoni in vitro. The most potent FaRP tested was the turbellarian peptide RYIRFamide, which produced a concentration-dependent effect between 10−9 and 10−7 M. FMRFamide and GNFFRFamide were less potent, inducing contractions between 10−8–10−6 M and 10−7–10−5 M respectively. The contractile effect of each of these peptides was blocked by the presence of 1 µM FMR-DFamide. FMRF free acid did not elicit contraction of the muscle fibres. The FaRP-induced contractions did not occur if the Ca2+ was omitted and 0·5 µM EGTA was added to the extracellular medium. The FaRP-induced contractions were not blocked by the Ca2+ channel blockers nicardipine, verapamil or diltiazem, although high K+-induced contractions of these fibres were blocked by nicardipine. These data indicate the presence of FaRP receptors on schistosome muscle fibres and demonstrate their ability to mediate muscle contraction. The action of these endogenous flatworm peptides on schistosome muscle is the first demonstration of a direct excitatory effect of any putative neurotransmitter on the muscle of a flatworm, and establishes a role for FaRPs in neuromuscular transmission in trematodes. In addition, it provides the first evidence that the peptidergic nervous system is a rational target for chemotherapeutic attack in parasitic platyhelmiths.

THE EFFECTS OF TESTOSTERONE AND ITS 5α-REDUCED METABOLITES ON PITUITARY RESPONSIVENESS TO GONADOTROPHIN-RELEASING HORMONE (Gn-RH)

1977 ◽  
Vol 86 (4) ◽  
pp. 728-732 ◽  
Author(s):  
Y. Epstein ◽  
B. Lunenfeld ◽  
Z. Kraiem
Keyword(s):  
Pituitary Gland ◽  
Mature Male ◽  
Male Rats ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone ◽  
Low Levels ◽  
High Doses ◽  
Dose Dependent ◽  
Stimulation Of

ABSTRACT The aim of this study was to investigate effects of androgens on gonadotrophin release in response to gonadotrophin-releasing hormone (Gn-RH) stimulation in vitro. Hemipituitaries of mature male rats were pre-incubated for 90 min with T, DHT, 3α- or 3β-diol (4 ng or 4 μg/ml medium), and the incubation continued for 240 min after adding Gn-RH (1 ng/ml medium). Gn-RH caused a 4-5-fold rise in the secretion of LH and a 2-fold rise in FSH secretion. The effect of the androgens was dose-dependent. At low levels, T and DHT exerted no effect on Gn-RH-stimulated gonadotrophin release, whereas the two androstanediols (3α- and 3β-diol) augmented the Gn-RH stimulation of both gonadotrophins, though preferentially LH. With high doses of androgens, the results obtained showed: a) no effect of T; b) DHT suppression of the Gn-RH-stimulated FSH release; c) suppression of Gn-RH stimulation by 3α- and 3β-diol regarding both LH and FSH. It is concluded that T exerts through its reduced metabolites a feedback effect on the pituitary gland responsiveness to Gn-RH stimulation.

Actions of somatotrophin on oxytocin and progesterone release from the microdialysed bovine corpus luteum in vitro

1994 ◽  
Vol 143 (2) ◽  
pp. 243-250 ◽  
Author(s):  
J Liebermann ◽  
D Schams
Keyword(s):  
Early Pregnancy ◽  
Oestrous Cycle ◽  
Luteal Function ◽  
Bovine Corpus Luteum ◽  
Oxytocin Release ◽  
Dose Levels ◽  
Dose Dependent ◽  
Bovine Somatotrophin ◽  
Stimulation Of

Abstract In the present investigation, the effect of recombinant (BST) and pituitary-derived (bGH) bovine somatotrophin on progesterone and oxytocin release was examined. Individual copora lutea (CL) were obtained from cows at different stages of the oestrous cycle (days 5–7, 8–12 and 15–18) and also from early pregnancy (days 60–120) and were implanted with an in vitro microdialysis system (MDS). Perfusion with BST for 60 min (005, 0·5 and 5 μmol/l) induced a dose-dependent stimulation of progesterone release. Release of oxytocin from CL was significantly stimulated by BST at all dose levels. BST (0·5 μmol/l) stimulated progesterone release most during the early and mid-luteal phases and oxytocin release especially during the early luteal stage (days 5–7) of the oestrous cycle. CL from early pregnancy (days 60–120) treated with BST showed a significant response in progesterone and oxytocin release. bGH showed comparable effects. Our results suggest that somatotrophin acts directly on the secretory function of bovine CL in the MDS, specifically during the early luteal stage (days 5–7) of the oestrous cycle and early pregnancy (days 60–120). Somatotrophin may therefore have physiologically relevant effects associated with the development and maintenance of luteal function. Journal of Endocrinology (1994) 143, 243–250

Heparin Induces Synthesis and Secretion of Tissue Factor Pathway Inhibitor from Endothelial Cells In Vitro

2000 ◽  
Vol 83 (06) ◽  
pp. 937-943 ◽  
Author(s):  
Birgit Svensson ◽  
Randi Olsen ◽  
Mirella Ezban ◽  
Bjarne Østerud ◽  
Ruth Paulssen ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Surface Membrane ◽  
Molecular Size ◽  
Fold Increase ◽  
Coagulation System ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Stimulation Of

SummaryTFPI is a potent inhibitor of the extrinsic coagulation system constitutively synthesized by endothelial cells. A major portion of intravascular TFPI is stored associated with endothelial cells, and administration of unfractionated heparin (UFH) in vivo causes a prompt mobilization of TFPI into the circulation. The present study was conducted to investigate how UFH affected the synthesis, secretion and anticoagulant potency of TFPI in endothelial cells in vitro. A spontaneously transformed immortal endothelial cell line was used (ECV304). Stimulation of ECV304 cells with UFH caused a prompt dose-dependent (0-5 IU UFH/ml) release of TFPI to the medium accompanied by no change of TFPI at the surface membrane assessed by immunocytochemical methods. Northern blot analysis revealed two mRNA transcripts for TFPI with a molecular size of 1.4 kb and 4.4 kb, respectively. Stimulation of ECV304 cells for 24 hrs with various concentrations of UFH caused a dose-dependent increase of TFPI in the medium (6.2-29.6 ng/106 cells within the concentration range 0-10 IU/ml). A similar dose-dependent increase in the expression of both TFPI mRNA species was observed. Long-term incubation of ECV304 cells with 5.0 IU/ml UFH caused a 5-10 fold increase in the TFPI concentration accumulated in the medium over 48 hrs. The increased TFPI mRNA expression induced by UFH appeared already after 10 min, peaked after 2-4 hrs, remained augmented throughout the entire period of UFH exposure, and preceeded the synthesis-dependent increase in TFPI release by 2-4 hrs. The procoagulant activity of the cells was downregulated by 36 % and the contribution of TFPI to the anticoagulant potency of ECV304 cells was moderately increased after 24 hrs heparin stimulation. It is suggested that these mechanisms are of major importance for the anticoagulant function of heparins.

Cholera toxin stimulates secretion of immunoreactive intestinal mucin

1981 ◽  
Vol 240 (1) ◽  
pp. G10-G16 ◽  
Author(s):  
J. F. Forstner ◽  
N. W. Roomi ◽  
R. E. Fahim ◽  
G. G. Forstner
Keyword(s):  
Cholera Toxin ◽  
Mucin Secretion ◽  
Glycoprotein Synthesis ◽  
Intestinal Mucin ◽  
Storage Granules ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Stimulation Of

In vitro secretion of goblet cell mucin from rat small intestine was measured using a double-antibody radioimmunoassay for mucin. Cholera toxin (12.5-50 mg crude filtrate/ml) added to incubations of intestinal slices caused a dose-dependent increase in mucin secretion. By 90 min there was a four- to fivefold enhancement in secretion over noncholera-treated controls. Crude filtrate (dialyzed or nondialyzed) was a more effective mucin secretogogue than purified enterotoxin. Secretion was also assessed by administering [1-14C]glucosamine intraperitoneally to rats in vivo and 3 h later monitoring in vitro secretion of radioactive glycoprotein from intestinal slices. Cholera filtrate (12.5-50 mg/ml) caused a 1.5- to 2.0-fold enhancement in secretion after 90 min. The radioactivity data, however, underestimated total mucin secretion and the dependency of secretion on the dose of cholera filtrate. Cholera preparations also caused an enhancement (20-30% over controls) in the incorporation of [3H]glucosamine into tissue acid-precipitable glycoprotein, indicating a stimulation of glycoprotein synthesis. In the same experiments it was noted that the secretion of 3H-labeled (i.e., newly glycosylated) glycoprotein was increased 2.5- to 3.0-fold over untreated controls. Assuming that radioactivity partially reflects mucin synthetic and secretory events, it is possible, therefore, that cholera toxin promotes the release of both "old" mucin from storage granules as well as the synthesis and secretion of "new" mucin formed in goblet cells during incubation.

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