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Biomedical subjects

G Costa

Publications and source records attributed to G Costa.

At least 199 records · Page 11Linked to original sources
PubMed1991

Calcium dependence of contractile activation of isolated sheep urethra. II: Responses to exogenous noradrenaline.

Isolated smooth muscle of sheep urethra responded to exogenous noradrenaline (NA) with a concentration-dependent contraction. After exposing the preparations for 30 min. to calcium-free medium, NA in a submaximal concentration was still able to produce a contractile response amounting to 36% of control value in calcium-containing solution. Readmission of calcium (administered cumulatively) restored the response in a concentration-related fashion to 85% (at 5 mM calcium) of control level. Nifedipine and verapamil failed to inhibit these graded calcium contractions in the presence of NA. Verapamil and diltiazem also failed to significantly prevent contraction induced by NA in a submaximum concentration, but nifedipine showed a concentration-dependent inhibitory effect, with a potency 1000 times lower than that observed on K+ (124 mM) induced contractions. In calcium-free medium, repeated applications of NA at 30 min. intervals, induced a progressive reduction in contractile amplitude. Nifedipine or verapamil did not affect the time course for recovery of NA-induced contraction when the preparations were returned to calcium containing medium, but the recovery was blocked almost completely by lanthanum. Furthermore, lanthanum abolished the remaining NA contraction in calcium-free medium. The results suggest that NA-induced contraction in isolated sheep urethra is dependent on both influx of extracellular calcium and on release of intracellular calcium. Calcium influx for contractile activation and refilling of intracellular stores seem to occur through membrane channels that can only partly be blocked with calcium antagonists.

Animals↗
PubMed1991

The role of a stress-response protein in Salmonella typhimurium virulence.

We recently described the use of selective transposon mutagenesis to generate a series of avirulent mutants of a pathogenic strain of Salmonella typhimurium. Cloning and sequencing of the insertion sites from two of these mutants reveals that both have identical locations within an open reading frame that is highly homologous to a gene, htrA, encoding a heat-shock protein in Escherichia coli. DNA sequence analysis of S. typhimurium htrA reveals the presence of a gene capable of encoding a protein with a calculated Mr of 49316 that has 88.7% protein:protein homology with its E. coli counterpart. In E. coli, lesions in this gene, also known as degP, reduce proteolytic degradation of aberrant periplasmic proteins. Characteristics of the S. typhimurium htrA mutants, 046 and 014, in vivo and in vitro suggested that they are avirulent because of impaired ability to survive and/or replicate in host tissues. In vitro, the S. typhimurium htrA mutants 046 and 014 are not temperature-sensitive but were found to be more susceptible to oxidative stress than the parent, suggesting that they may be less able to withstand oxidative killing within macrophages.

Alkaline Phosphatase↗
PubMed1991

Relaxation of sheep urethral muscle induced by electrical stimulation of nerves: involvement of nitric oxide.

Isolated smooth muscle preparations from the sheep urethra responded to electrical field stimulation with contraction when basal tension was low (5-6 mN), but with relaxation when the preparations were contracted with noradrenaline (NA), clonidine, or prostaglandin F2a. No relaxant response could be elicited in high K+ (124 mM) contracted preparations. Electrically induced relaxations had a threshold of less than 1 Hz and a maximum at 8 Hz. Both contractant and relaxant responses were abolished by tetrodotoxin, indicating that they were caused by transmitters released from nerves. The amplitude of the relaxant responses showed a highly significant correlation to the tension induced by noradrenaline. A coefficient (R/T) was calculated relating relaxation to noradrenaline-induced tension. In this way it is possible to separate the effect of drugs on muscle tension (non-specific effect) from their action on the electrically induced relaxation (specific effect). Chemical sympathectomy with 6-OHDA did not significantly modify the relaxant response to 6 Hz in noradrenaline contracted strips, as evaluated by the R/T coefficient. The electrically induced relaxation was not affected by hexamethonium, propranolol, phentolamine, muscarinic receptor blockade, cocaine, indomethacin, or methysergide. Both nifedipine and Bay K 8644 inhibited significantly the response induced by electrical stimulation, decreasing its maximum. Nifedipine, but not Bay K 8644, significantly reduced the level of tension induced by noradrenaline, and its effect, evaluated by the R/T coefficient, was an increase in the electrically induced relaxation, whereas Bay K 8644 had a significant inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Potassium-induced contraction in the lamb proximal urethra: involvement of norepinephrine and different calcium entry pathways.

The purpose of this work was to investigate the mechanisms involved in the peculiar biphasic response of the lamb urethral smooth muscle to high K+ solutions. The relative amplitude of the phasic and tonic components of the contraction and its reproducibility were dependent on the concentration of K+ used. Only concentrations higher than 80 mM (i.e., 120 mM) showed a tonic component greater in amplitude than the phasic one and manifested a tachyphylactic effect. Phentolamine (10(-6) M), prazosin (10(-6) M) and chemical denervation with 6-hydroxydopamine significantly inhibited the tonic component of the K+ (120 mM)-induced contraction, modifying its morphology. Reproducible contractions to K+ (120 mM) could be obtained in the presence of prazosin (10(-6) M) or cocaine (10(-6) M). The preparations were also shown to accumulate [3H]noradrenaline and release it upon depolarization with K+ (60 and 120 mM). Calcium removal inhibited the K+ (120 mM)-induced contraction. After addition of calcium (0.5-5 mM) the contractile activity was restored. Nifedipine (10(-6) M) and verapamil (10(-6) M) but not sodium nitroprusside (10(-6) M) significantly blocked the contractile response for calcium as well as the phasic component of the K+ contraction in calcium-containing medium. In preparations treated with prazosin (10(-6) M) the tonic component of the K+ (120 mM) contraction was more sensitive to nifedipine and removal of extracellular calcium than the phasic one.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1991

[Evaluation of the kinetics of MB creatine kinase in patients undergoing systemic thrombolytic therapy].

This study was aimed to evaluate if the time-course of creatinkinase MB in acute myocardial infarction (AMI) is influenced by therapy and which index, derived from the enzymatic curve, is the most reliable marker of successful coronary artery recanalization. We studied the enzymatic curves in 38 patients with transmural myocardial infarction, 19 treated with streptokinase (SK) and 19 with tissue plasminogen activator (rtPA). Blood samples were obtained every 2 hours for the first 12 hours and every 6 hours until the level of serum CK returned to baseline. Three indexes were calculated: peak serum enzyme level, time to peak enzyme level and maximal enzyme rise velocity. Time to peak did not differ significantly between SK and rtPA groups. Peak levels were significantly higher (414 +/- 40 vs 249 +/- 33; p = 0.004) in rtPA groups, as well as maximal enzyme rise velocity (1.7 +/- 0.4 vs 0.8 +/- 0.1; p = 0.02). However, infarct size evaluated by the total release of CK-MB in 28 patients was greater in rtPA group (10949 +/- 1097 vs 6346 +/- 869; p = 0.002). These findings suggest that differences in peak level and in maximal velocity of rise observed between SK and rtPA are due to differences in infarct size and not to a different recanalization rate. Thus, enzymatic estimate of infarct size significantly correlates to peak enzyme (r = 0.894, p less than 0.001), and to maximal rise velocity (r = 0.518, p = 0.007) but not to time to peak (r = 0.208, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Creatine Kinase↗
PubMed1991

New host and locality records for two protozoan (Myxosporea, Coccidia) parasites of marine fishes.

This is the first report of the myxosporean Ortholinea orientalis from Atlantic herring Clupea harrengus. It infects the kidney tubules and previously was known from Pacific herring Clupea pallasii and navaga Eleginus navaga in the White Sea and North Pacific Ocean. This is also the first report of the coccidian Eimeria raibauti from Norway pout Trisopterus esmarkii. It infects the epithelium of the pyloric ceca and previously was known only from poorcod Trisopterus minutus in the Mediterranean Sea. The new records are both from the northern North Sea.

Animals↗
PubMed1990

Alpha 2-mediated effect of dopamine on the motility of the chicken esophagus.

Dopamine (DA), apomorphine and B-HT 933 produced dose related contractions on isolated longitudinal strips of chicken esophagus, whereas phenylephrine elicited no effect. DA induced contractions of myogenic origin, these contractions were insensitive to DA antagonists and were partially suppressed by yohimbine, which suggested an alpha 2-adrenergic implication in this DA effect. This hypothesis was further investigated by performing binding experiments, in which B-HT 933 displaced the binding of [3H]DA to esophageal homogenates. The results suggest the participation of an alpha 2-adrenergic receptor in the contractile response elicited by DA in the isolated chicken esophagus.

Adrenergic alpha-Agonists↗
PubMed1990

Aging and sex influence the permeability of the blood-brain barrier in the rat.

The aim of the present study was to investigate the existence of aging- and sex-related alterations in the permeability of the blood-brain barrier (BBB) in the rat, by calculating a unidirectional blood-to-brain transfer constant (Ki) for the circulating tracer [14C]-alpha-aminoisobutyric acid. We observed that: a) the permeability of the BBB significantly increased within the frontal and temporo-parietal cortex, hypothalamus and cerebellum in 28-30 week old rats, in comparison with younger animals; b) in several brain areas of female intact rats higher Ki values (even though not significantly different) were calculated at oestrus than at proestrus; c) in 1-week ovariectomized rats there was a marked increase of Ki values at the level of the frontal, temporo-parietal and occipital cortex, cerebellum and brain-stem. One can speculate that aging- and sex-related alterations in the permeability of the BBB reflect respectively changes in brain neurochemical system activity and in plasma steroid hormone levels.

Aging↗
PubMed1990

Effect of experimental subarachnoid hemorrhage on CSF eicosanoids in the rat.

A simple and inexpensive experimental model of subarachnoid hemorrhage (SAH) was developed in the rat. Based on accumulating data indicating the important role of arachidonic acid metabolites in the etiology of delayed cerebral vasospasm, we investigated changes induced by SAH on cerebrospinal fluid (CSF) levels of prostaglandin E2 (PGE2), F2 alpha (PGF2 alpha), and thromboxane B2 (TXB2). SAH was produced by the cisternal injection of blood via percutaneous suboccipital puncture. SAH rats (n = 200) were injected with 300 microliters of fresh autologous arterial blood; Control rats (n = 100) received the same volume of mock CSF. In 60 additional animals, no injections were made. To follow the changes induced by SAH on both the spectrum and time course of CSF eicosanoids, cisternal CSF samples were collected under basal conditions, 6, 12, and 36 after cisternal injection. PGE2, PGF2 alpha, and TXB2 were assayed in aliquots of CSF obtained by pooling samples from each experimental group. Eicosanoids were assayed using radioimmunoassay techniques. Arterial spasm was verified in parallel groups of SAH and control rats by comparison of the angiographic diameters of the basilar arteries (BA) and middle cerebral arteries (MCA) to that of the stapedial artery. CSF levels of all three eicosanoids were significantly higher in the SAH groups compared to both noninjected and mock-CSF injected control rats. These increases in concentrations of eicosanoids were accompanied by a decrease in the mean vascular diameter (77.5-82.0% of control) on day 2 following cisternal injection. We conclude that marked elevations of spasmogenic eicosanoids in the CSF are associated with experimental SAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Arecoline, but not haloperidol, induces changes in the permeability of the blood-brain barrier in the rat.

The aim of the present study was to investigate the existence of alterations of the blood-brain barrier (BBB) permeability in rats injected with centrally acting drugs, by calculating a unidirectional blood-to-brain transfer constant (Ki) for the circulating tracer [14C]-alpha-aminoisobutyric acid. The intraperitoneal (i.p.) injection of the dopaminergic antagonist haloperidol (1 mg kg-1) did not modify the regional BBB permeability. When the cholinomimetic agent arecoline hydrobromide (6.25 mg kg-1) was injected i.p. into methylatropine-pretreated rats, it induced a significant decrease of Ki values within the frontal cortex, parietal cortex, striatum and brain-stem. Our findings emphasize two concepts: (1) centrally acting drugs, such as arecoline, can induce changes in the BBB permeability, through several mechanisms; (2) there is no predictable correlation of drug stimulation of specific brain neuronal pathways and changes in the permeability of the BBB.

Aminoisobutyric Acids↗
PubMed1990

[Bone transplants in prosthetic knee surgery].

The authors refer on their experience using bone grafting of tibial defects in total knee arthroplasty. The advantages, the technique, the casuistry and the results of this method are illustrated.

Bone Cements↗
PubMed1990

[Mortality according to the birthplace in a Turin longitudinal study].

Mortality 1981-85 in the Turin Longitudinal Study population, 25-74 years old, was analyzed according to selected geographic areas of birth and socioeconomic status. People born in the Southern Regions and in the Isles, when compared with people ever resident in Turin, have low mortality from malignancies and accidents and in general from all causes of death but respiratory diseases. People born in the North-Eastern Regions have high mortality, mainly due to malignancies, and respiratory and digestive diseases. Such differences are stronger among men in low socio-economic status and tend to weaken with time from migration.

Adult↗
PubMed1990

[Manual versus mechanical sutures in gastric surgery in cancer].

The Authors, on the basis of their experience in San Camillo Hospital of Rome, compare the results between manual and mechanical sutures in 597 gastric cancers operated in the last 12 years. They confirm that at present staplers are of great reliability.

Adolescent↗
PubMed1989

Vasopressin release induced by intracranial injection of tachykinins is due to activation of central neurokinin-3 receptors.

The present study investigated the effect on vasopressin release of the intracerebroventricular injection of tachykinins in rats. The selective neurokinin (NK)-3 receptor agonists [MePhe7]neurokinin B and [Asp5,6MePhe8]substance P(5-11) evoked vasopressin release. Also eledoisin, physalaemin and kassinin, which show good affinity for central NK-3 receptors, released vasopressin. On the other hand, neurokinin A, substance P and the selective NK-1 agonist [Pro9,Met(O2)11]substance P were devoid of activity. At doses releasing vasopressin, central injection of NK-3 selective agonists and of the natural tachykinins never produced hypotension. Present results indicate that activation of central NK-3 receptors is involved in vasopressin release induced by tachykinins, and rule out the possibility that the effect might be consequent to hypotension due to passage of tachykinins into the peripheral circulation.

Animals↗