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Biomedical subjects

L Negri

Publications and source records attributed to L Negri.

At least 127 records · Page 7Linked to original sources
PubMed1975

Uperolein and other active peptides in the skin of the Australian leptodactylid frogs Uperoleia and Taudactylus.

Methanol extracts of the skin of the Australian leptodactylid frogs Uperoleia rugosa, Uperoleia marmorata and Taudactylus acutirostris contain several highly active polypeptides belonging to different peptide families. The most abundant peptide was uperolein, a tachykinin closely related to physalaemin and possessing the same spectrum of biological activity. Uperolein was present in the three species examined. Other tachykinins were represented by Rugosa-uperolein II and Marmorata-uperolein II, the structures of which still await full elucidation. Another peptide family represented in both Uperleia and Taudactylus was that of bombesin-like peptides. They were abundant in Uperoleia rugosa and scarce in Uperoleia marmorata and in Taudactylus. These bombesins are possibly similar to the bombesins, among which is litorin, present in the skin of other Australian leptodactylid frogs. Finally, Taudactylus contained a bradykinin-like peptide and both the Uperoleia species an hitherto unclassified peptide. These new findings have further enriched the already considerable list of active peptides and biogenic amines occurring in the amphibian skin.

Animals↗
PubMed1975

Parallel bioassay of bombesin and litorin, a bombesin-like peptide from the skin of Litoria aurea.

The spectrum of biological activity exhibited by litorin, a bombesin-like nonapeptide found in extracts of the skin of the Australian leptodactylid frog Litoria aurea was compared with that exhibited by the tetradecapeptide bombesin. 2 Litorin proved to be more potent than bombesin on isolated smooth muscle preparations and on the urinary bladder in situ. However, it was less potent on dog systemic blood pressure and kidney vasculature activation of the renen-angiotensin system being slight or lacking. 3 Gastrin release and acid secretion produced by litorin was more rapid in onset but less intense and less sustained than that elicited by bombesin. The same could be observed for pancreatic secretion. 4 Gall bladder contraction stimulated by litorin was probably caused by a double action of the peptide, directly on the bladder smooth muscle, and indirectly by cholecystokinin release. 5 In its effects on the myo-electric activity of the dog duodenum (inhibition of spikes and increase in frequency of pacesetter potentials leading to the appearance of a sequence of slow and small potentials) litorin possessed approximately 50 to 70% of the activity of bombesin.

Action Potentials↗
PubMed1975

Relative potency of bombesin-like peptides.

The pharmacological activity of two natural bombesin-like peptides, alytesin and litorin, and 25 related synthetic peptides has been compared to that of bombesin. 2 The minimum length of the amino acid chain required for the first appearance of bombesin-like effects was represented by the C-terminal heptapeptide, and the minimum length for maximal effects by the C-terminal nonapeptide. The latter possessed approximately the same activity as bombesin and may be considered a good substitute. 3 Both the tryptophan and histidine residues seemed to be essential for bombesin-like activity. 4 The C-terminal octapeptide was less active than either bombesin or the C-terminal nonapeptide and its action was more rapid in onset and less sustained. 5 Litorin apparently has an intermediate position between bombesin octapeptide and bombesin nonapeptide in the speed and duration of its effects. The relationship between structure and activity is discussed.

Animals↗
PubMed1972

Occurrence of bombesin and alytesin in extracts of the skin of three European discoglossid frogs and pharmacological actions of bombesin on extravascular smooth muscle.

1. Methanol extracts of the skin of Bombina bombina and Bombina variegata variegata, two European discoglossid frogs, contain an active tetradecapeptide, bombesin. Alytesin, a tetradecapeptide strictly related to bombesin is present in extracts of the skin of Alytes obstetricans, another European discoglossid frog. The American frog Rana pipiens, contains in its skin ranatensin, an endecapeptide related to bombesin and alytesin.2. Passage of crude skin extracts of Bombina through a column of alumina yields eluates which may be considered free of other peptide contaminants and are suitable for the isolation of bombesin in a pure form.3. Bombesin has a stimulant action on several preparations of intestinal, uterine and urinary tract smooth muscle. Sometimes the effect is easily repeatable and shows a fair proportionality to the dose, but at other times a prompt and intense tachyphylaxis is observed. Other smooth muscle preparations are poorly sensitive or insensitive to bombesin. The rat uterus, the kitten small intestine, the guinea-pig colon and the rat urinary bladder may be used for the quantitative bioassay of bombesin.4. Bombesin-like peptides may easily be distinguished from all other naturally occurring peptides by parallel assay. They constitute a new group of active peptides possessing a peculiar spectrum of activity.

Amino Acid Sequence↗
PubMedDate not supplied

Feprazone: absence of hemolytic effects in glucose-6-phosphate dehydrogenase-deficient subjects.

Some drugs, including nonsteroidal antiinflammatory compounds, can be hemolytic in glucose-6-phosphate dehydrogenase-deficient patients. We have studied the potential hemolytic activity of feprazone, a nonsteroidal antiinflammatory compound in vitro and in vivo. Agents that may be hemolytic for glucose-6-phosphate dehydrogenase-deficient erythrocytes will stimulate the hexose monophosphate shunt in normal erythrocytes. Eleven normal subjects were treated with feprazone and their erythrocytes were incubated in their own sera (containing active feprazone metabolites) and [1-14C]-glucose. Because no statistically significant increase in 14CO2 evolution was observed, 15 pediatric male patients with glucose-6-phosphate dehydrogenase deficiency who required antiinflammatory treatment were treated with feprazone. No hemolytic crises and no statistically significant changes of hematologic tests were observed.

Adolescent↗