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Biomedical subjects

G Frigo

Publications and source records attributed to G Frigo.

49 records · Page 3Linked to original sources
PubMed1993

Calcium-channel blockers and gastrointestinal motility: basic and clinical aspects.

Several calcium-channel blockers currently in use for the treatment of cardiovascular disorders have recently been tested for their effects on gastrointestinal motility. The rationale for this approach centers on the concept that calcium-channel blockers are at least as potent in inhibiting intestinal smooth muscle as in relaxing vascular smooth muscle. This review will give an outline of the most recent findings on the role of calcium and calcium channels in smooth muscle and neuronal function in the digestive system. It will also consider the mechanisms by which calcium-channel blockers may affect gastrointestinal motility and assess potential clinical applications in gastroenterology. The main goal for researchers in this field will be the development of gut-selective agents, with no cardiovascular side effects.

Animals↗
PubMed1989

Liquid chromatographic analysis of amino and imino acids in protein hydrolysates by post-column derivatization with o-phthalaldehyde and 3-mercaptopropionic acid.

A method for the simultaneous determination of imino and amino acids is reported. The method, based on the derivatization of amino acids, separated by ion-exchange chromatography, by reaction with alkaline hypochlorite and o-phthalaldehyde-3-mercaptopropionic acid, increases the sensitivity towards imino acids to the picomole level. The use of 3-mercaptopropionic acid gives intensely fluorescent derivatives and improves the stability of primary and secondary amino acid fluorophores towards oxidation. The accuracy and reproducibility of the method are increased by using three internal standards. The determination of all amino and imino acids present in protein hydrolysates, including tryptophan, in a single run is demonstrated.

3-Mercaptopropionic Acid↗
PubMed1982

Mode of action of ATP on propulsive activity in rabbit colon.

ATP induced a concentration-dependent reduction of the velocity of propulsion in isolated segments of rabbit colon as assessed by the aboral displacement of an intraluminal rubber balloon, and delayed the onset of the propulsive wave. ATP depressed both the reflex contraction of the circular coat above the distended balloon and the response of the circular muscle to transmural (cholinergic) stimulation. On the contrary, ATP (up to 200 muM), while causing relaxation of the circular muscle, had no effect on either the muscular contractile response induced by carbachol and histamine or the non-adrenergic inhibitory responses elicited by electrical stimulation and by radial distension of the gut wall. Within the concentration range used (10-200 muM), ATP concentration-depression curves for propulsion and transmural excitatory stimulation were shifted to the right in the presence of theophylline (10 muM). Theophylline, however, had no influence on either the direct inhibitory action of ATP on circular smooth muscle or the non-adrenergic relaxation in response to electrical stimulation. These data are consistent with the concept that at least two populations of purinergic receptors are present in intestinal tissue. Those populations located presynaptically, unlike those located postsynaptically, are blocked by theophylline. Since the contractile machinery does not appear to be affected by ATP concentrations up to 200 muM, the mechanism by which ATP impairs propulsive activity is probably dependent on activation of presynaptic purinergic receptors located on the nervous pathways subserving the wave of contraction, without having any appreciable influence on descending inhibition.

Adenosine Triphosphate↗
PubMed1981

Hyoscine-resistant peristalsis in guinea-pig ileum.

The effect of hyoscine on the peristaltic activity of the proximal and distal ileum of the guinea-pig was studied. Hyoscine strongly impaired peristalsis as indicated by the elevation of the threshold pressure and by the increased number of incomplete peristalses and blockades. Functional activity of the circular musculature was more markedly impaired. However, particularly in the distal ileum, complete peristalses occurred even after 70 min exposure to hyoscine at a concentration of 10(-6) g/ml. A tenfold increase in hyoscine concentration failed to produce further impairment of peristaltic activity and of the oral reflex contraction. The activity which remained in the presence of hyoscine was blocked by methysergide and by d-tubocurarine. The hypothesis is advanced that once the muscarinic receptors have been blocked, increased radial stretch of the circular coat results in activation of a separate, tetrodotoxin sensitive, excitatory nervous pathway, which is sufficient to maintain a discrete degree of peristaltic activity.

Animals↗
PubMedDate not supplied

Measurement of catecholamines in mouse bone marrow by means of HPLC with electrochemical detection.

BACKGROUND AND OBJECTIVE: Noradrenergic innervation is present in the bone marrow and adrenergic agents can modulate hematopoiesis. However, since no data are available concerning endogenous catecholamines at this level, we investigated their presence and origin. METHODS: Using a high performance liquid chromatographic method, we have and measured endogenous catecholamines in bone marrow from normal, 6-OHDA-treated and pargyline-treated mice. RESULTS: Noradrenaline, adrenaline and dopamine levels were, respectively, 2806.74 +/- 408.85, 803.37 +/- 87.66 and 274.47 +/- 51.54 pg/g of tissue. Noradrenaline levels were lower after 6-OHDA (1130.47 +/- 142.73 pg/g of tissue, p < 0.01 vs. control values) and higher after pargyline (4122.62 +/- 509.54 pg/g of tissue, p < 0.05). None of these treatments significantly affected adrenaline or dopamine content. INTERPRETATION AND CONCLUSIONS: Noradrenaline in the bone marrow originates mainly from sympathetic nerve endings and is metabolized through specific enzymatic pathways. Adrenaline and dopamine may originate from other sources, such as the systemic circulation.

Adrenergic Agents↗