scholarly journals Metabolism of [14C]adenine and derivatives by cerebral tissues, superfused and electrically stimulated

1972 ◽  
Vol 126 (4) ◽  
pp. 965-973 ◽  
Author(s):  
I. Pull ◽  
H. McIlwain
Keyword(s):  
Electrical Stimulation ◽  
Guinea Pig ◽  
Main Product ◽  
Electrical Excitation ◽  
Cerebral Tissue ◽  
Low Concentrations ◽  
Adenosine Derivatives

1. Uptake of [14C]adenine and [14C]adenosine from surrounding fluids to guinea-pig cerebral tissues was measured during incubation in vitro. Output of 14C-labelled compounds from the loaded tissues to superfusion fluids occurred on continued incubation, at about 0.2% of the tissue's content/min, and this rate was increased about fourfold by electrical excitation of the tissue. 2. The compounds released from the tissue to superfusion fluids included adenine, adenosine, inosine and hypoxanthine with small amounts of nucleotides. Output of all these compounds, except adenine, increased on excitation. Media depleted of oxygen or glucose also increased the output of 14C-labelled derivatives from [14C]adenine-loaded tissues, and this augmented output was further increased by electrical stimulation. 3. [14C]Adenosine was found as the main product from [14C]ATP when this was added at low concentrations to fluids superfusing cerebral tissue. Metabolic and neurohumoural explanations of the liberation and action of adenosine derivatives in the tissue are discussed.

scholarly journals Adenosine as a constituent of the brain and of isolated cerebral tissues, and its relationship to the generation of adenosine 3′:5′-cyclic monophosphate

1977 ◽  
Vol 164 (1) ◽  
pp. 131-137 ◽  
Author(s):  
Michael Newman ◽  
Henry McIlwain
Keyword(s):  
Electrical Stimulation ◽  
Cyclic Amp ◽  
Guinea Pig ◽  
Room Temperature ◽  
Fold Increase ◽  
Electrical Excitation ◽  
Adenosine Concentration ◽  
The Brain ◽  
Guinea Pig Brain

1. Adenosine was determined in rapidly frozen rat and guinea-pig brain and in guinea-pig cerebral tissues after incubation in vitro. Adenosine concentrations were approx. 2nmol/g wet wt. in frozen tissue, diminished at room temperature, and returned to 2nmol/g on incubation in oxygenated glucose/salines. 2. Superfusion with noradrenaline then increased the tissue's adenosine concentration 2.5-fold, and hypoxia caused an 8-fold increase. 3. Electrical stimulation alone or in the presence of noradrenaline or histamine increased the tissue's adenosine and cyclic AMP, but adenosine concentrations reached their peak later and were maintained for longer than those of cyclic AMP. 4. Superfusion with l-glutamate with and without electrical excitation raised adenosine concentrations to 15–34nmol/g. The increases in cyclic AMP on electrical stimulation, superfusion with glutamate or a combination of these treatments were diminished by addition of adenosine deaminase or theophylline. 5. It is concluded that adenosine can be produced endogenously in cerebral systems, in sufficient concentrations to accelerate an adenosine-activated adenylate cyclase, and by this route can contribute to the cerebral actions of electrical stimulation and of the neurohumoral agents. In certain instances cyclic AMP as substrate contributes to an increase in adenosine.

Nuclear Fos immunoreactivity in guinea pig myenteric neurons following activation of motor activity

1997 ◽  
Vol 273 (2) ◽  
pp. G498-G507 ◽  
Author(s):  
R. C. Ritter ◽  
M. Costa ◽  
S. H. Brookes
Keyword(s):  
Electrical Stimulation ◽  
Guinea Pig ◽  
Motor Activity ◽  
Muscle Tone ◽  
Smooth Muscle Contraction ◽  
Early Gene ◽  
Enteric Neurons ◽  
Experimental Conditions ◽  
Fos Expression

To identify enteric neurons activated during intestinal motor activity, we examined myenteric plexus of guinea pig small intestinal segments for expression of the immediate early gene product, Fos. Fos immunoreactivity was detected immunohistochemically following in vitro manipulations, which included distension, electrical stimulation, exposure to forskolin, and peristalsis. All of these manipulations induced neuronal Fos expression, which was prevented by tetrodotoxin, indicating that expression depended on nerve activity. Distension-induced Fos expression was blocked by omega-conotoxin and significantly reduced by hexamethonium, indicating that neurons expressing Fos immunoreactivity were activated synaptically. Blocking smooth muscle contraction with nicardipine reduced expression of neuronal Fos, suggesting that muscle tone influences neuronal activity. Calbindin-immunoreactive putative sensory neurons did not express Fos during distension, peristalsis, or exposure to forskolin and expressed Fos only weakly after strong electrical stimulation. Conversely, calretinin-immunoreactive ascending excitatory interneurons and longitudinal muscle motoneurons exhibited Fos immunoreactivity after all experimental manipulations. These results indicate that Fos expression can, with some caution, be used to identify classes of enteric neurons activated by different stimuli under various experimental conditions.

EFFECTS OF LOW CONCENTRATIONS OF THYROID STIMULATING HORMONE: PHARMACOLOGICAL EXPERIMENTS IN VITRO

1970 ◽  
Vol 64 (1) ◽  
pp. 133-149 ◽  
Author(s):  
M.-L. Desbarats-Schönbaum ◽  
E. A. Sellers ◽  
Malle Laansoo ◽  
Eva Koves ◽  
E. Schönbaum
Keyword(s):  
Guinea Pig ◽  
Thyroid Tissue ◽  
Phosphodiesterase Inhibitor ◽  
Thyroid Stimulating Hormone ◽  
Low Concentration ◽  
Low Concentrations ◽  
Stimulating Hormone

ABSTRACT In guinea pig thyroid tissue incubated at 25°C for forty hours the binding (organification) of iodide appears to be the step most sensitive to TSH. Binding is independent of uptake in this system and physiological doses of TSH can stimulate binding while uptake is partially inhibited. At a suitably low concentration of PTU, the addition of TSH can counteract the effect of this drug. At less than maximal concentrations, the effects of TSH and theophylline (a phosphodiesterase inhibitor) are additive, which supports the hypothesis that TSH acts by stimulating the production of cyclic 3′,5′-AMP. The effect of TSH appears to be exerted equally on any iodide present in the thyroid at the beginning of, or taken up during, incubation in vitro. In this system deiodination has been excluded as a major complicating factor.

Respiration and oxidation of various substrates by ileum in vitro

1965 ◽  
Vol 209 (2) ◽  
pp. 329-332 ◽  
Author(s):  
Edgar M. Neptune
Keyword(s):  
Guinea Pig ◽  
Full Thickness ◽  
Rabbit Ileum ◽  
Rat Ileum ◽  
Low Concentrations ◽  
Mucosal Cells

The respiration of ileum from the rabbit, monkey, hamster, guinea pig, and rat in vitro was studied. Measurements were also made of the rate of oxidation of labeled glucose, glutamine, acetate, and palmitate to C14O2 by ileum in these species. Added glutamine and acetate are oxidized at a faster rate than added glucose by rabbit ileum. The guinea pig and monkey ileum gave values similar to the rabbit except that the guinea pig tissue had a higher rate of respiration. The hamster and rat ileum both oxidized glutamine and glucose at nearly the same rate. All species oxidized acetate vigorously. All species oxidized labeled palmitate which was added at low concentrations. Mucosal cells of rabbit ileum oxidized the various substrates at rates that were proportional to full-thickness ileum. It is concluded that ileum from various species of animals can oxidize a number of different substrates in vitro. There are differences in rates of oxidation by various species.

Pharmacological modulation of cholinergic neurotransmission in guinea pig trachea in vitro

1980 ◽  
Vol 58 (7) ◽  
pp. 810-822 ◽  
Author(s):  
Thomas R. Jones ◽  
John T. Hamilton ◽  
Neville M. Lefcoe
Keyword(s):  
Electrical Stimulation ◽  
Guinea Pig ◽  
Low Frequency ◽  
Electrical Field Stimulation ◽  
Prostaglandin E ◽  
Cholinergic Nerves ◽  
Experimental Conditions ◽  
Cholinergic Neurotransmission ◽  
Stimulation Of

Electrical (field) stimulation of the isolated guinea pig trachea with normal intrinsic tone produced a biphasic response which consisted of an initial (cholinergic) contraction followed by (adrenergic and nonadrenergic) relaxation. Treatment of the tissue with the prostaglandin synthetase inhibitor indomethacin (2.8–5.6 μM) removed intrinsic tone and increased the responsiveness of the tissue to stimulation of cholinergic nerves and to exogenous acetylcholine. Indomethacin-relaxed tracheae were subsequently used to study cholinergic neurotransmission because under these experimental conditions only the contractile component of the response to electrical stimulation was observed. The β adrenoceptor blocking agents dl-propranolol and sotalol and the adrenergic neuron blocking agent guanethidine produced further enhancement of the contraction to electrical stimulation at low frequency (1–10 Hz). Prostaglandin E1, l-noradrenaline, l-adrenaline, salbutamol, phenylephrine, and phentolamine selectively attenuated the contractions to electrical stimulation in concentrations which did not significantly alter the matched responses to exogenous acetylcholine. The selective depressant effect of l-noradrenaline, l-adrenaline, salbutamol, phenylephrine, and phentolamine but not prostaglandin E1 were blocked by dl-propranolol or sotalol. The present results demonstrate that responses to stimulation of cholinergic nerves were altered by (1) prostaglandins and inhibitors of their synthesis, (2) neurally released adrenergic transmitter, and (3) exogenously added β adrenoceptor agonists. The possibility that prostaglandins and adrenergic neurotransmitter may modulate cholinergic neurotransmission at both pre- and post-junctional sites is hypothesized. It is proposed that more attention should be paid to the role of cholinergic transmission and its modulation in the studies of airway smooth muscle.

Effects of immunological sensitization on the responses and sensitivity of guinea pig airways to bronchoconstrictors. Modulation by selective inhibition of arachidonic acid metabolism

1983 ◽  
Vol 61 (8) ◽  
pp. 876-887 ◽  
Author(s):  
Maan H. Saad ◽  
John F. Burka
Keyword(s):  
Guinea Pig ◽  
Contractile Activity ◽  
Nordihydroguaiaretic Acid ◽  
Selective Inhibition ◽  
Arachidonic Acid Metabolism ◽  
Resting Tension ◽  
Low Concentrations ◽  
High Concentrations ◽  
Inhibitor Treatment

The force generated by tracheal spirals and lung parenchymal strips from normal and ovalbumin-sensitized guinea pigs was measured in vitro, after challenge with histamine, carbachol, leukotriene (LT) C4, LTD4, or a prostaglandin endoperoxide analog (U-44069). The responses and sensitivity of airway tissues to the above agonists were identical in normal and sensitized animals. Treatment of tracheal spirals with indomethacin (8.5 μM), phenidone (185 μM), and nordihydroguaiaretic acid (NDGA: 30 μM) reduced resting tension (tone) equally in both normal and sensitized trachea, but did not affect lung parenchymal strips from either group. The responses of tracheal spirals from normal and sensitized animals to low concentrations of histamine, carbachol, LTC4, and LTD4 were reduced or abolished by treatment with the above inhibitors. Responses to higher concentrations of the same agonists were significantly enhanced. In contrast, treatment of normal and sensitized trachea with indomethacin (2.8 and 8.5 μM) did not abolish or reduce the effects of low concentrations of U-44069. However, an enhancement of the effect of high concentrations occurred only on normal tracheal spirals, even though the control tissues from each group responded identically with U-44069 in the absence of any inhibitor. Parenchymal strips increased in sensitivity to histamine, but not carbachol, as a result of time, vehicle, or prior exposure to the drug. Inhibitor treatment did not affect sensitivity or responsiveness of parenchyma to histamine, carbachol, and U-44069, but the contractile activity of LTD4 on both normal and sensitized lung parenchymal strips was reduced by indomethacin, NDGA, and phenidone. We conclude that ovalbumin sensitization does not induce hyperreactivity of guinea pig airways.

EFFECTS OF OXYTOCIN ON THE UTERINE RESPONSE TO ELECTRICAL STIMULATION

1962 ◽  
Vol 41 (2) ◽  
pp. 161-169 ◽  
Author(s):  
N. Wiqvist ◽  
I. Wiqvist ◽  
C. A. Fielitz ◽  
R. Caldeyro-Barcia
Keyword(s):  
Electrical Stimulation ◽  
Dose Response ◽  
Response Relationship ◽  
Dose Response Relationship ◽  
Rat Uterus ◽  
Experimental Conditions ◽  
Minimum Effective Concentration ◽  
Low Concentrations ◽  
Tenfold Increase

ABSTRACT The enhancing effect of low concentrations of oxytocin on the uterine response to electrical stimulation was measured »in vitro« on the superfused rat uterus. In order to reduce the incidence of spontaneous motility, the pacemaker areas were excised from the uterine strip and the calcium concentration was lowered to 1/5th of that of a normal Krebs solution. Under these experimental conditions, it was found that the minimum effective concentration of oxytocin was generally between 5 and 20 μU/ml. A graded dose-response relationship was obtained within a range of concentrations from 5 to 50 μU/ml; within this range, a tenfold increase of the oxytocin concentration caused a five-fold augmentation of the uterine response. The possible use of this method for the bioassay of oxytocin is discussed. Both the range of oxytocin concentrations employed as well as the dose-response relationship found in this investigation for the superfused rat uterus bear a suggestive resemblance to the results published by others for the response of the pregnant human uterus »in situ« to the intravenous infusion of oxytocin.

scholarly journals Neural pathways regulating Brunner's gland secretion in guinea pig duodenum in vitro

2000 ◽  
Vol 279 (5) ◽  
pp. G910-G917 ◽  
Author(s):  
Beverley A. Moore ◽  
David Kim ◽  
Stephen Vanner
Keyword(s):  
Electrical Stimulation ◽  
Guinea Pig ◽  
Nerve Fibers ◽  
Neural Pathways ◽  
Brunner's Glands ◽  
Brunner’S Glands ◽  
Perivascular Nerves ◽  
Acinar Lumen ◽  
Stimulation Of

This study examined the neural pathways innervating Brunner's glands using a novel in vitro model of acinar secretion from Brunner's glands in submucosal preparations from the guinea pig duodenum. Neural pathways were activated by focal electrical stimulation and excitatory agonists, and videomicroscopy was used to monitor dilation of acinar lumen. Electrical stimulation of perivascular nerves evoked large dilations that were blocked by TTX (1 μM) or the muscarinic receptor antagonist 4-diphenylacetoxy- N-(2-chloroethyl)-piperidine hydrochloride (1 μM). The nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium iodide (100 μM) had no effect, and the nerve-evoked responses were not inhibited by hexamethonium (200 μM). Dilations were abolished in preparations from chronically vagotomized animals. Activation of submucosal ganglia significantly dilated submucosal arterioles but not Brunner's glands. Effects of electrical stimulation of perivascular and submucosal nerves were not altered by guanethidine. Capsaicin and substance P also dilated arterioles but had no effect on Brunner's glands. Cholinergic (choline acetyltransferase-immunoreactive) nerve fibers were found in Brunner's glands. These findings demonstrate that Brunner's glands are innervated by cholinergic vagal fibers but not by capsaicin-sensitive or intrinsic enteric nerves.

The effects of vasoactive intestinal polypeptide on the motility of human and guinea pig gallbladder

1984 ◽  
Vol 62 (4) ◽  
pp. 356-359 ◽  
Author(s):  
Thomas M. Feeley ◽  
Alexander S. Clanachan ◽  
Gerald W. Scott
Keyword(s):  
Guinea Pig ◽  
Spontaneous Activity ◽  
Vasoactive Intestinal Polypeptide ◽  
Human Gallbladder ◽  
Cholecystokinin Octapeptide ◽  
Low Concentrations ◽  
Resting Tone ◽  
Intestinal Polypeptide

The effects of several preparations of vasoactive intestinal polypeptide (VIP) on the motility of strips of human and guinea pig gallbladder were investigated in vitro. VIP (10−12 to 10−6 M) had no measurable effects on the spontaneous activity, resting tone or cholecystokinin-octapeptide induced tone of human gallbladder strips. However, VIP (10−12 to 10−6 M) caused biphasic effects on the tone of guinea pig gallbladder strips. At low concentrations (10−12 to 10−10 M) contractions were observed that became smaller at higher concentrations (10−9 to 10−8 M). At still higher concentrations (10−7 to 10−6 M) relaxations were elicited. It appears that VIP is not as potent a relaxant of gallbladder muscle as first described. Human gallbladder tissue was totally unresponsive to the VIP preparations tested.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

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