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Biomedical subjects

M Bergamaschi

Publications and source records attributed to M Bergamaschi.

At least 37 records · Page 2Linked to original sources
PubMed1983

The tripeptide ZAMI-420 inhibits thromboxane-induced gastric vasoconstriction and ischaemia.

The tripeptide ZAMI-420 has been shown by Gervasi et al. (4) to be able to prevent experimentally-induced gastric damage, possibly by interfering with the synthesis and the action of thromboxane A2 (TXA2), a potent vasoconstrictor and platelet aggregator. Further studies on a canine stomach wedge preparation, supplied with a fixed flow of 10 ml/min-1 of arterial blood from the same dog have been designed to investigate this hypothesis. Bolus injection of arachidonic acid (AA) through a 30-sec incubation coil that allows the production of TXA2 resulted in a dose-related increase in resistance to flow in the stomach wedge vasculature and blanching of the gastric mucosa. This was progressively inhibited by ZAMI-420 perfused through the delay coil. Similar results were obtained with 1-benzylimidazole (BI). ZAMI-420, but not BI, produced a partial inhibition of TXA2-induced vasoconstriction when infused close to the stomach. Investigations of the antagonistic action of ZAMI-420 on the pharmacological effect of the formed TXA2 were carried out using strips of celiac and mesenteric artery from rabbits and gastric artery from dogs. Preincubation of these vascular preparations with ZAMI-420 led to progressive inhibition of the contraction induced either by the stable endoperoxide U-46619 or by CaCl2. Whittle et al. (3) reported that TXA2 may be involved in the pathogenesis of ulcerative disorders of the stomach; if so, both the inhibition of the synthesis and the antagonism of TXA2-induced effects could be of value in the prevention of experimentally-induced gastric disorders.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1982

A positive feedback sympathetic pressor reflex during stretch of the thoracic aorta in conscious dogs.

The role of pressor sympathetic reflexes in circulatory control was investigated in conscious dogs. Animals were previously instrumented with a 6- to 8-cm rigid core cannula covered by an inflatable rubber cylinder in the thoracic aorta, a pressure catheter implanted in the aorta above the cannula, and a second catheter inserted into the aorta below the cannula through a femoral artery. Two piezoelectric crystals were positioned at opposing adventitial sites to measure aortic distension with ultrasound techniques. After recovery from surgery, the diameter of the aortic segment surrounding the cannula was increased by 9.6 +/- 0.4% from 16 +/- 1 mm by inflating the rubber cylinder, without obstructing blood flow. Mean aortic pressure rose 31 +/- 3% from 100 +/- 3 mm Hg and heart rate 20 +/- 3% from 91 +/- 3 beats/min (P less than 0.01). The pressor response was abolished by alpha-adrenergic blockade (phentolamine 1 mg/kg, iv). The heart rate response was reduced either by beta-blockade (propranolol 1 mg/kg, iv) or muscarinic blockade (atropine 0.2 mg/kg, iv) and abolished by their combination. During aortic stretch, the sensitivity of the baroreflex was reduced 57 +/- 7% from 18 +/- 2 msec/mm Hg (P less than 0.01). The pressor response was increased by 49 +/- 8% after bilateral carotid sinus nerve section and vagotomy. These excitatory reflex responses were obtained in absence of any pain reaction. Thus, in the conscious dog, aortic distension within physiological ranges induces a potent pressor sympathetic reflex with positive feedback characteristics. Such a pressor reflex not only occurs in the presence of functioning baroreflexes, but is also capable of reducing their sensitivity.

Adrenergic alpha-Antagonists↗
PubMed1979

Positive feedback sympathetic reflexes and hypertension.

A pressor reflex that can be elicited from the thoracic aorta in conscious dogs is described. Distension of the aorta excites sympathetic afferent fibers and results in an increase in arterial blood pressure because of increased sympathetic outflow to the heart and blood vessels. The reflex center for this positive feedback mechanism is located in the spinal cord and, when the reflex is activated, it can modulate other negative feedback control systems.

Animals↗
PubMed1979

A sympathetic pressor reflex in the conscious dog.

1. The effects of mechanical activation of aortic sympathetic sensory fibres have been studied in conscious dogs. 2. A cannula covered by an inflatable rubber balloon, previously implanted in the descending thoracic aorta, was used to stretch the aortic walls without obstructing blood flow. 3. Aortic stretch significantly increased mean arterial blood pressure and heart rate from control values in the absence of pseudo-affective reactions. 4. This response indicates that positive feedback sympathetic reflexes are operative in the conscious, fully innervated animal.

Animals↗
PubMed1975

PGE2:PGE-2:.

The biological activities of 8,12-diiso-PGE2 (ent-11,15-epi-PGE2), PGE2 and PGF2alpha have been compared in a series of pharmacological preparations intended to differentiate between F and E type of activity. Similar to PGF2alpha but unlike PGE2, 8,12-diiso-PGE2 increased the tone of isolated smooth muscle preparations of guinea pig trachea, guinea pig colonic circular layer, rabbit Fallopian tubes. The stimulation effect of 8,12-diiso-PGE2 and PGF2alpha on visceral smooth muscle was also shown in vivo: the two drugs were in all instances able to increase the miogenic activity and tone of rabbit uterus in situ, while these were depressed by PGE2. 8,12-diiso-PGE2 decreased pulmonary compliance and increased pulmonary vascular resistance in the anaesthetized cat; PGE2 always decreased pulmonary vascular resistance, while leaving pulmonary compliance unaltered. The possibility is suggested that 8,12-diiso-PGE2 acts on PGF receptor in different tissues.

Animals↗