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G Coruzzi

Publications and source records attributed to G Coruzzi.

At least 127 records · Page 7Linked to original sources
PubMed1984

Tissue-specific and light-regulated expression of a pea nuclear gene encoding the small subunit of ribulose-1,5-bisphosphate carboxylase.

We have examined the expression of a member of the multigene family encoding the small subunit (rbcS) of ribulose-1,5-bisphosphate carboxylase in various tissues of pea. The rbcS gene, pPS-2.4, was characterized by DNA sequence analysis and 5' and 3' end mapping of its mRNA transcript. rbcS polypeptides were shown to be differentially present in various tissues of light- and dark-grown plants. Northern analysis shows that compared with green leaves, the level of rbcS mRNA is reduced to approximately 50% in pericarps, 8% in petals and seeds, and 1-3% in etiolated leaves, stems, and roots. 5' S1 nuclease mapping of total rbcS mRNA was used to quantitate the relative amount of pPS-2.4 gene-specific transcripts in each tissue. pPS-2.4 mRNA accounts for approximately 30-35% of total rbcS transcripts in green leaves, but only 5-10% in pericarps, 15-20% in seeds, and is below detection in petals and etiolated leaves. We conclude that the pPS-2.4 gene is expressed in a tissue-specific, light-regulated fashion and that transcriptional controls of individual rbcS genes vary.

Base Sequence↗
PubMed1984

Action of the new H2-antagonist, DA 4577, on different in vitro and in vivo preparations.

The new H2-antagonist, 4(5)-(4- isopropylaminomethyleniminophenyl )-imidazole (compound marked DA 4577), was tested for its activity on different in vitro preparations and also in the conscious cat. Its effect was compared with that of some new H2 antagonists. Two sets of experiments were performed: in the first, concerning the specific H2-receptor antagonism, DA 4577 was found to be extremely potent on the guinea-pig papillary muscle and on the human atrium stimulated by histamine (pA2 = 8.24 and 8.60 respectively). Compound DA 4577 was also found very active in inhibiting histamine-induced acid secretion from the isolated rat fundus (pA2 = 7.37) and on the dimaprit-induced gastric secretion in conscious gastric fistula cats (ID50 = 0.39 mumol kg-1 h-1). In the second set of experiments, concerning effects independent of the H2-receptor blockade (side effects of the molecule), compound DA 4577 was found to be devoid of negative inotropic effect on the human atrium in the absence of histamine stimulation; in this respect it behaved like cimetidine or ranitidine but unlike oxmetidine which showed a constant negative inotropic effect even at concentration 10 times lower than those of DA 4577. Furthermore DA 4577 was ineffective in modifying gastrointestinal motility in vitro in concentrations up to 3 X 10(-4) M, conversely from ranitidine (which stimulated motility) and oxmetidine (which inhibited motility). On the whole DA 4577 appeared to be a very potent and selective H2 antagonist which, unlike other members of the family, is devoid of non-specific effect on human atrium and on motility of the gastrointestinal tract of different animal species.

Animals↗
PubMed1984

Action of histamine and of some H2-antagonists on gastric secretion 'in vitro'.

The effect of histamine and of some H2-antagonists on isolated gastric mucosal preparation from immature (14-18 days) rats, was investigated. Basal secretion varied, in our experimental conditions, between 1.06 and 3.54 mumol cm-2 h-1, reaching higher values (approximately 4.6 mumol cm-2 h-1) only in a small percentage of animals (10%). Histamine exerted a concentration-dependent stimulation of acid secretion in concentrations varying between 2 X 10(-6) and 1.6 X 10(-4) M. The response to histamine was competitively antagonized by ranitidine (pA2 value = 6.78) and by 4(5)-(4- isopropylaminomethyleniminophenyl ) imidazole (compound marked DA 4577) (pA2 value = 7.37). Oxmetidine acted as a competitive antagonist only for concentrations as low as 10(-8) M; higher concentrations (10(-7) and 10(-6) M) determined a non-competitive inhibition. Ranitidine and compound marked DA 4577 did not affect basal secretion up to concentrations of 3 X 10(-4) M. On the contrary oxmetidine exerted a concentration-dependent inhibition starting from 10(-5) M. Since in our experimental conditions the role of calcium ions in the regulation of basal secretion could not be established, the mechanism of action of oxmetidine was not completely clarified, even if an interference in the utilization of calcium ions may be suggested. In any case it is deemed of interest that this H2-antagonist was the only compound capable of inducing a reversible complete inhibition of basal acid secretion (only KSCN, in very high concentrations, had a similar behaviour).

Animals↗
PubMed1984

Action of mifentidine and ranitidine on the isolated rat uterus.

The new H2-antagonist mifentidine (compound marked DA 4577) was tested for its inhibitory effect on the relaxation induced by histamine on the rat uterus and was compared with the well known H2-blocker ranitidine. Mifentidine was shown to be more effective than ranitidine (about 10 times). However whereas ranitidine behaved as a "classical" competitive antagonist, mifentidine at concentrations of 10(-7) M, caused a remarkable depression of the maximum response to histamine. This "unsurmountable" antagonism may connected with a tight binding of the compound to the receptor with a consequent low degree of dissociation. Ranitidine, but not mifentidine, at concentrations of 10(-5) M was able to potentiate the stimulatory effect of acetylcholine thus confirming also in the uterus its cholinergic-like effects so far observed mainly in the gastrointestinal tract.

Acetylcholine↗
PubMed1983

Nucleotide sequences of two pea cDNA clones encoding the small subunit of ribulose 1,5-bisphosphate carboxylase and the major chlorophyll a/b-binding thylakoid polypeptide.

Two major chloroplast proteins are encoded by nuclear genes and synthesized on free cytoplasmic ribosomes: the small subunit of ribulose 1,5-bisphosphate carboxylase and the apoprotein components of the chlorophyll a/b light harvesting complex. We have recently reported the isolation of two cDNA clones from pea which encode both the small subunit of ribulose 1,5-bisphosphate carboxylase (pSS15) and the polypeptide 15 (pAB96), the major chlorophyll a/b binding protein (Broglie, R., Bellemare, G., Bartlett, S., Chua, N.-H., and Cashmore, A. R. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 7304-7308). To further characterize these clones, we determined their nucleotide sequence. Clone pSS15 contains a 691-base pair cDNA insert which encodes the entire 123 amino acids of the mature small subunit protein. In addition, this clone also encodes 33 amino acids of the NH2-terminal transit peptide extension and 148 nucleotides of the 3' noncoding region preceding the poly(A)tail. A second cDNA clone (pAB96) contains an 833-nucleotide insert which encodes most of polypeptide 15. The DNA sequence of this cloned cDNA was used to deduce the previously undetermined amino acid sequence of this integral thylakoid membrane protein. The nucleotide sequence of the cDNA clone, pSS15, should provide information concerning the role of the transit sequence in the transport of cytoplasmically synthesized chloroplast proteins. Similarly, the deduced amino acid sequence of polypeptide 15 will provide information for predicting its orientation in thylakoid membranes as well as its role in binding chlorophyll.

Amino Acid Sequence↗
PubMed1983

Effect of some new H2-receptor antagonists on gastrointestinal motility.

Some new histamine H2-receptor antagonists were tested for their effects on gastrointestinal motility. Ranitidine was found to possess definite stimulatory effects which appeared to be connected with an interference with the cholinergic system and occurred, though in different degree, from the lower esophageal sphincter (LES) to the colon. Etintidine, on the contrary, showed a remarkable antimuscarinic effect on the LES of the rat and the guinea-pig. Cimetidine, SK&F 93479 and tiotidine were virtually ineffective whereas oxmetidine exerted a consistent inhibitory activity on both basal motility and on the contractions induced by a variety of stimulatory agents. This effect, which was completely independent of the autonomic nervous system appeared to be connected with an inhibition of the transport of calcium ions. All the above results suggest that the H2-antagonists so far available may not be absolutely selective for the H2-receptor but may be endowed with non-specific effects which could have an interest at least from a pharmacological viewpoint.

Animals↗
PubMed1983

Cardiac effects of the new H2-receptor antagonists.

A series of new H2-receptor antagonists were tested for their effects on different isolated heart preparations. In the guinea-pig atria and papillary muscle the inhibitory effect on histamine H2-receptors was evaluated. In the perfused rabbit heart and in strips of human atria the effect of the H2-antagonists on the spontaneous or electrically-stimulated contractions was evaluated. In the first two preparations some main quantitative differences were pointed out, tiotidine and compound SKF 93479 being the most potent antagonists, cimetidine, metiamide and ranitidine the less effective. In the rabbit heart and in human atria results were quite different: cimetidine and ranitidine were virtually ineffective up to the maximum concentration tested (3 x 10(-3) M), oxmetidine and compound SKF 93479 had a negative inotropic and chronotropic effect starting from concentrations of 3 x 10(-6)-10(-5) M. On the basis of the behaviour of other compounds endowed with negative cardiac effects (propranolol, anaesthetic-like compounds, verapamil) and of that of compounds capable of counteracting the effect of oxmetidine (increased concentration of calcium ions and isoproterenol) it was hypothesized that oxmetidine may interfere in the transport of calcium ions. Our data emphasize the importance of the different structure of the H2-antagonists in determining non-specific effects absolutely independent of the primary action that is the H2-receptor blockade.

Animals↗
PubMed1983

Action of angiotensin on vascular and intestinal smooth muscle and its antagonism by saralasin.

Angiotensin II was tested for its activity on rabbit aorta, lower esophageal sphincter (LES) from the rat, rat gastric fundus and rat colon. The peptide had a powerful stimulatory effect on vascular and extravascular smooth muscle beginning from concentrations of 10(-10) M. Its effect was antagonized by saralasin which acted in the different preparations to approximately the same extent: active concentrations of saralasin varied from 10(-8) M to 10(-7) M. The activity of angiotensin on the rabbit aorta appeared to be a direct one on its specific receptors. A mixed action connected with stimulation of adrenergic alpha receptors was observed in the rat LES, whereas an interference of the prostaglandin system was pointed out in the rat fundus and the rat colon. The circumstance of a similar sensitivity of the various tissues to the stimulatory effect of angiotensin and a similar degree of antagonism induced by saralasin tends to minimize the hypothesis of different subtypes of angiotensin receptors at least under the conditions of the present investigation.

Angiotensin II↗
PubMed1983

Extragastric H2-receptors.

The discovery of H2-receptors by Black and coworkers opened a new era in the history of histaminology. Their importance became apparent when, soon after their discovery, the physiological role of histamine in the regulation of gastric secretion was clarified. In the last decade the explosion of research in the field of histamine and its receptors has demonstrated that H2-receptors have a much wider distribution than previously suspected. H2-receptors are found in the brain, the endocrine and exocrine glands, the pulmonary system, the cardiovascular system of different species, the gastrointestinal muscle, the genitourinary system, the immunological system and in the skin. In some instances stimulation of the various H2-receptors evokes responses that are opposite to those elicited by stimulation of H1-receptors. In other cases they are quite similar. Usually, activation of H2-receptors leads to an increased activity of the adenylate cyclase system with a consequent increase in intracellular cyclic AMP. Most H2-receptors are located postsynaptically on muscle or gland surfaces. However, there is recent evidence concerning the possibility of a presynaptic localization with a modulatory function on the release of different mediators. Finally, controversy exists over the possibility that H2-receptors do not represent a homogeneous population. In fact, several observations suggest that "anomalous" H2-receptors are characterized by different sensitivity to the H2-antagonists and/or antagonists in various tissues. If this is true, exact characterization of H2-receptors will be decidedly more difficult and will require "super selective" H2-agonists and antagonists which are not currently available.

Animals↗
PubMed1983

Further observations on the motor activity of some new histamine H2-receptor antagonists on the digestive system.

Some new H2-receptor antagonists were tested for their motor effects on the rat lower oesophageal sphincter, on the guinea pig ileum and on the guinea pig gall bladder. Two of these compounds, SKF93479 and DA4577, were found to be virtually inactive despite the fact that they are the most potent antagonists of the H2-receptors so far described. Ranitidine possessed a stimulatory effect on all the preparations examined and its mechanism of action was shown to involve the cholinergic system. Conversely oxmetidine exerted an inhibitory effect on the contractions produced by a variety of spasmogenic compounds. All of these observations, together with other data from our laboratory, seem to suggest that H2-receptors do not play an important role in the regulation of the motility of the digestive system. Moreover our data emphasize the fact that the motor effects of the H2-antagonists are connected with single molecules rather than with the entire class, and therefore represent side-effects of these compounds independent of the H2-receptor blockade.

Acetylcholine↗
PubMed1983

Pirenzepine and exocrine secretions: a selective agent for gastric glands?

Nineteen healthy volunteers were studied to investigate whether or not muscarinic receptors of different exocrine glands could be distinguished from one another by the use of pirenzepine. A simultaneous evaluation of lacrimation, salivation and gastric secretion was carried out, bethanechol (80 micrograms/kg/hr) being used as a stimulant and pirenzepine (10 or 5 mg i.v.) as an inhibitor. Bethanechol increased salivation significantly and the volume of gastric juice, and non-significantly increased lacrimation and total acid output. Pirenzepine abolished the hypersecretion induced by bethanechol, and decreased the basal level of the exocrine secretions, to approximately the same extent. These experiments seem to demonstrate that if there is a difference among the muscarinic receptors of lacrimal, salivary and gastric oxyntic glands, pirenzepine is unable to discriminate them from one another, at least under the experimental conditions of this investigation.

Adult↗
PubMed1983

Effect of MDL 646, a new synthetic prostaglandin, on gastroesophageal motility of the rat.

Compound marked MDL 646, a synthetic prostaglandin belonging to the 16-methyl-16-methoxy PGE1 series was tested for its motor effects on some in vitro and in vivo preparations from the rat. The lower esophageal sphincter (LES) was contracted at threshold doses ranging from 10 to 20 ng/ml; the fundus was even more sensitive whereas the pyloric sphincter showed remarkable differences according to the in vitro or in vivo preparation. In all the different tests MDL 646 showed a high degree of tachyphylaxis. PGE1 tested for comparison, exerted a constant relaxant effect in all the preparations excepting the gastric fundus. The present data emphasize the importance of the substitutions in positions 15 and 16 in the synthetic prostaglandin for determining the peculiar biological activity: in fact both MDL 646 and the parent PGE1 inhibit gastric secretion but they have almost opposite effects on gastroesophageal motility.

Alprostadil↗
PubMed1982

Histamine receptors in the lower esophageal sphincter (LES).

The motor response of histamine on the lower esophageal sphincter and the receptors involved were investigated on isolated preparations from rats, guinea pigs and humans. Histamine exerted a spasmogenic effect through excitation of H1-receptors. H1-receptor selective agonists in the rat but not in the guinea pig seem to act through release of prostaglandin-like substances. Apparently H2-receptors, whose stimulation causes relaxation of the sphincter, do not occur in the LES of rat and human whereas they are present in the guinea pig. H2-receptor antagonists exerted different and sometimes opposite effects and this suggests that their actions depend on the specific molecules and not on the H2-receptor blockade. The significance and the importance of the above findings are discussed.

Animals↗
PubMed1982

Cholinergic-like effects of the new histamine H2-receptor antagonist ranitidine.

The new H2-receptor blocker ranitidine, together with the effect on histamine H2-receptors, possesses a series of cholinergic-like actions: it provokes atropine-sensitive contractions of several isolated smooth muscle preparations from different animal species and it potentiates the stimulant effect of acetylcholine. Moreover it contracts human lower esophageal sphincter in vivo, an effect which is completely prevented by small doses of atropine. Finally, ranitidine potentiates the stimulant effect of bethanechol and of carbachol on salivary glands of the rat while leaving unaffected the secretagogue effect of physalaemin which is known to be completely independent of the cholinergic system. In the in vivo experiments the doses of ranitidine capable of eliciting cholinergic-like effects were of the same order of magnitude as those necessary to cause the H2-receptor blockade.

Animals↗
PubMed1982

[Action of a new synthetic prostaglandin on gastroesophageal motility of the rat].

A new synthetic prostaglandin, namely the 15 alpha, 16 (R), 16-methyl-16-methoxy PGE1 (compound marked MDL 646), endowed with a potent antiulcer activity, was studied for its effects on gastroesophageal motility of the rat in comparison with natural PGE1. Surprisingly enough, the two compounds were found to differ not only from a quantitative but also from a qualitative point of view. In fact, the natural PGE1 had, as expected, a relaxant effect on all the preparations examined except the rat fundus which is known to be contracted by all the different types of prostaglandins; conversely its synthetic analogue (MDL 646) showed a remarkable stimulatory effect on both "in vitro" and "in vivo" preparations. It is obvious that if these observations will be confirmed in other animal species, they could have a remarkable practical interest.

Alprostadil↗
PubMed1982

[Pharmacological effects of the combination of a spasmolytic (otilonium) with a benzodiazepine (diazepam)].

The pharmacological effects of an association represented by a myolitic agent (otilonium bromide) and a benzodiazepine (diazepam) were investigated on different in vitro preparations and on one in vivo test. In the isolated preparations both drugs administered alone showed a remarkable inhibitory effect on the motility of different areas of the digestive system both spontaneous and evoked by different stimulatory agents. Association of the two compounds gave rise to additive effects or actually to a potentiating effect according to the different tissues and animal species. Negative interference was never observed. The same was true also in the in vivo preparation ("in situ" rat pylorus). The significance and the importance of these observations are discussed also in the light of the relevant clinical implications.

Acetylcholine↗