Search PubMed⌕ Search

Biomedical subjects

G Costa

Publications and source records attributed to G Costa.

At least 181 records · Page 10Linked to original sources
PubMed1992

Characterization of postsynaptic alpha-adrenoceptors in the arteries supplying the oviduct.

1. In vitro experiments were designed to characterize postjunctional alpha-adrenoceptor subtypes in ring segments (1 mm length; outer diameter 300-500 microns) from arteries supplying the oviduct of the heifer. 2. Noradrenaline, adrenaline and phenylephrine evoked concentration-dependent contractile responses. The pD2 values were 5.67, 5.89 and 5.93, respectively. Medetomidine clonidine and B-HT 920 (2-amino-6-allyl-5,6,7,8-tetra-hydro-4H-(thiazo)-4,5-d-azepoine ) were ineffective. 3. The alpha-adrenoceptor selective antagonists, prazosin (1 nM-0.1 microM) and rauwolscine (0.1-10 microM) competitively antagonized the response to noradrenaline. The pA2 values were 9.38 and 6.83, respectively. 4. The dissociation constant (KD) for noradrenaline calculated by use of the irreversible antagonist, dibenamine, was 3.95 (2.09-5.81) microM. The occupancy-response relationship was non-linear. Half-maximal response to noradrenaline was obtained with 22% receptor occupancy while maximal response required 100% occupancy. 5. B-HT 920 evoked a biphasic contractile concentration-dependent response in preparations incubated in a physiological solution containing 20 mM K+, 0.1 microM prazosin and 1 microM propranolol. Rauwolscine 0.1 microM significantly (P less than 0.01) blocked the first component of the B-HT 920 concentration-response curve with an apparent pA2 value of 8.52 (7.86-9.18). 6. These results strongly suggest that alpha-adrenoceptors in oviductal arteries are mainly of the alpha 1 subtype, although a possible role for alpha 2-adrenoceptors cannot be excluded.

Acetylcholine↗
PubMed1992

Ageing influences haloperidol-induced changes in the permeability of the blood-brain barrier in the rat.

The effect of the dopaminergic antagonist haloperidol on the permeability of the blood-brain barrier (BBB) to [14C]alpha-aminoisobutyric acid was studied in 10-12- and 28-30-week old rats. Following the intraperitoneal injection of haloperidol (1 mg kg-1), an increase in the permeability of the BBB, with respect to younger animals, was observed within the occipital cortex, striatum, hippocampus and hypothalamus in the older rats. No correlation was found between haloperidol-induced changes and age-related differences in the permeability of the BBB. Such age-associated increase in the vulnerability of the BBB when challenged with haloperidol might be related to a deterioration of the dopaminergic control of cerebrovascular permeability.

Aging↗
PubMed1992

Cancer risk among Danish and Italian farmers.

Cancer risk for farmers in Denmark and Italy was studied by linking occupational census data with incidence of cancer in Denmark and with cancer mortality in Italy. Farmers in the two countries had a consistent risk reduction for cancer of the lung, bladder, small intestine, colon, rectum, and prostate. No excess of stomach cancer was found among farmers in the two countries, which is in agreement with the most recent data from other surveys. The risk of oesophageal cancer was reduced among the Danish and increased among the Italian male farmers. This can probably be explained by differences in alcohol consumption between the Danish and Italian farmers compared with the general population. The risk of brain cancer was significantly reduced among Italian farmers. There was a significant risk reduction for Hodgkin's disease and no excess for non-Hodgkin's lymphoma in Denmark, whereas in Italy a statistically significant excess risk was found for the first and a slight excess risk for the second of these diseases. The per capita consumption of phenoxy-herbicides between 1950 and 1970 was lower in Italy than in Denmark but treatments were performed mainly by professional applicators in Denmark and by the farmers themselves in Italy. Risk of leukaemia among Italian female farmers was increased. In Denmark, this increase was limited to women who were themselves owners of a farm. Specific occupations in agriculture showing a high risk for cancers of the lymphopoietic system in Denmark mostly entailed contact with animals.

Adolescent↗
PubMed1992

Focal xanthogranulomatous pyelonephritis: diagnostic and therapeutic aspects.

The authors report 2 cases of localized xanthogranulomatous pyelonephritis (XGP) in which computed tomography (CT) permitted to raise a motivated clinical suspicion of inflammatory disease: the surgical exploration documented absence of neoplasm and allowed a conservative therapy implying only the removal of the mass. A literature review confirms that some CT signs in XGP permit differentiation from carcinoma. If they are present, in unifocal cases of disease, the authors suggest a limited surgical approach and a therapeutic strategy as conservative as possible.

Female↗
PubMed1992

HLA-DQB1 genotype in Sardinian multiple sclerosis: evidence for a key role of DQB1 *0201 and *0302 alleles.

We studied HLA-DQB1 haplotypes in 103 unrelated multiple sclerosis (UMS) patients and in 26 related (RMS) patients from 12 families from Sardinia, Italy, where the disease was associated with the HLA-DR4 allele. Using polymerase chain reaction and allele-specific oligonucleotide probes, we found in UMS an increased frequency of the DQB1 *0201 (p = 0.010) and DQB1 *0302 (p = 0.025) alleles, whereas the DQB1 *0301 allele was significantly decreased (p = 0.027). In RMS, only the DQB1 *0302 allele was increased (p = 0.047), and no difference was found in the DQB1 *0301 allele. For DQB haplotypes, an increased frequency of DQB1 *0302/*0502 (p = 0.026) and a decreased frequency of DQB1 *0201/*0601 (p = 0.009) and DQB1 *0502/*0502 (p = 0.025) was found in UMS patients, whereas RMS patients showed an increased frequency of DQB1 *0301/*0302 (p = 0.005). Because DQB1 *0201 and *0302 alleles are increased in Caucasian MS patients, where the disease is related to HLA-DR2 and where a primary association with the HLA-DR2, DQB1 *0602 allele has been reported, we conclude that Caucasian and Sardinian populations share HLA-DQB1 *0201 and *0302 alleles in genetic susceptibility to MS.

Alleles↗
PubMed1992

Danazol. A new perspective in the treatment of HTLV-1 associated myelopathy (preliminary report).

We investigated the efficacy of danazol treatment in eight patients with HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). Treatment with danazol yielded clinical improvement of urinary control and gait disturbances in 7 out of the 8 patients. The improvement was noted within 15 days of danazol administration. Analysis of factors of relevance to the clinical improvement with danazol showed that the beneficial response was preferentially found in females.

Adult↗
PubMed1992

[Social differences in infant mortality in a longitudinal Turin study].

The Turin longitudinal study enables to study the one-year survival of children born to any member of the study population and to relate the still-born and infant mortality to the parents' census characteristics. In this paper 25,108 children, born between 1981 and 1985 of parents residents in Turin at the 1981 population census, were followed up with respect to one-year survival. The numbers of infant deaths have been observed according to parents' education, housing ownership, occupational status and professional position. Only parents' education showed consistent differential in the still-born and infant mortality risks, adjusted for maternal age.

Confidence Intervals↗
PubMed1992

[The frequency of early coronary reperfusion assessed by electrocardiographic criteria in relation to the timing of thrombolytic therapy in acute myocardial infarct].

This study was aimed at assessing coronary reperfusion in patients with acute myocardial infarction (AMI) undergoing systemic thrombolysis with SK and rtPA. The occurrence of reperfusion was related to the time of treatment. The evaluation of reperfusion was performed by monitoring ST segment changes. 56 patients with AMI were studied. 22 out of these (39.2%) showed a significant decrease (greater than 50%) in ST segment sum (sigma ST) at 100 minutes from the beginning of the treatment. Analysis of the relationship between reperfusion and elapsed time between the onset of symptoms and the treatment, reveals that the reperfusion is less frequent (p less than 0.05) in patients treated at 180 minutes or later. The standard electrocardiogram appears as the most useful method to evaluate indirectly coronary reperfusion in acute myocardial infarction. A further refinement of this method is desirable to recommend its widespread clinical use. The assessment of reperfusion by means of ECG in large series of patients will permit the evaluation of the benefits of reperfusion, in terms of survival, complications and incidence of ventricular dysfunction.

Adult↗
PubMed1991

Characterization of alpha-adrenoceptors in the preprostatic urethra of sexually immature male lambs.

Strips of preprostatic urethra from immature male lambs (3-4 months old) were used to study alpha-adrenoceptor-mediated contractions in vitro. The rank order of potency of the agonists was noradrenaline = phenylephrine greater than adrenaline. B-HT 920 was ineffective and clonidine behaved as a weak partial agonist. The rank order of efficacy was found to be noradrenaline greater than phenylephrine greater than adrenaline. Prazosin (10(-9)-10(-6) M) and rauwolscine (10(-6)-10(-4) M) antagonized noradrenaline-induced contractions. The pA2 values were 7.89 and 5.38 for prazosin and rauwolscine, respectively. Phenoxybenzamine reduced the maximal response to noradrenaline and shifted the concentration-response curve to the right. The dissociation constant (KA) of noradrenaline was calculated to be 4.05 +/- 0.21 x 10(-6) M and the occupancy-response plot for noradrenaline showed a linear relationship. It is concluded that alpha-adrenergic contraction of the preprostatic urethra from immature lambs are mediated by alpha 1-adrenoceptors. It is also suggested that the lack of a receptor reserve may affect the degree of urethral constriction and could be related to hormonal status.

Adrenergic alpha-Agonists↗
PubMed1991

The release of atrial natriuretic factor induced by central carbachol injection may be mediated by muscarinic M1 receptors.

We investigated the effect of selective muscarinic antagonists on atrial natriuretic factor (ANF) release induced by intracerebroventricular (i.c.v) injection of carbachol in the rat. The muscarinic antagonists were given by i.c.v. injection 1 min before carbachol, 1 micrograms/rat. 4-Diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), a rather selective M1 and M3 receptor antagonist, was the most potent inhibitor of carbachol-induced ANF release, its ID50 being 0.18 nmol/rat. Pirenzepine, a selective M1 antagonist, also potently inhibited the effect of carbachol, its ID50 being 2.74 nmol/rat. The M3-selective antagonist, p-fluoro-hexahydro-sila-diphenidol, was much weaker than pirenzepine, with an ID50 of 57.52 nmol/rat. The selective M2 receptor antagonist, methoctramine, on the other hand, was a very weak inhibitor of carbachol-induced ANF release. The rank order of potency as well as the - log ID50 of the antagonists tested were consistent with their pA2 values for muscarinic M1 receptors, suggesting that this receptor subtype may mediate the central effect of cholinergic mechanisms in the control of ANF release.

Animals↗
PubMed1991

Patch clamp analysis of a partially purified ion channel from rat liver mitochondria.

A protein fraction isolated from detergent-solubilized mitochondrial membranes by affinity chromatography on immobilized quinine was reconstituted into phospholipid vesicles by detergent dialysis. Vesicles were fused to a diameter of 10 microns or larger by dehydration and rehydration. Patch clamp recordings carried out in detached mode with a symmetrical solution of 150 mM KCl, 5 mM HEPES, and 0.1 mM CaCl2 revealed conductance increments of 140 pS. Transitions of 40 pS were less frequently observed. Control vesicles which lacked protein showed no channel activity. The probability for the 140 pS channel to be open increased with increasing voltage in the range from 20 to 80 mV (positive potentials relative to what was the vesicle interior prior to excision), while the single channel conductance remained essentially constant. The 140 pS channel did not open at negative voltages. The voltage dependence suggests asymmetric incorporation of the 140 pS channel into vesicle membranes during reconstitution.

Animals↗
PubMed1991

The hypothalamic paraventricular nucleus is a site of action for the central effect of tachykinins on plasma vasopressin.

The intracerebroventricular injection of eledoisin (ELE), or of other tachykinins with potent agonist activity at neurokinin B (NK-3) receptors, increases plasma vasopressin in the rat. The effect is antagonized by saralasin pretreatment, thus suggesting that it is mediated by angiotensin receptor activation. Since the magnocellular part of the hypothalamic paraventricular nucleus (PVN) is very rich in NK-3 receptors, the present study was aimed at investigating the role of this nucleus in the effect of ELE on plasma vasopressin. Direct injection of ELE into the PVN increased plasma vasopressin levels more potently than the injection of the same doses into the lateral ventricle. Lesioning of the magnocellular part of the PVN completely abolished the increase in plasma vasopressin induced by the injection of ELE 100 ng/rat into the lateral ventricle. Pretreatment into the PVN either with saralasin or with captopril resulted in a marked suppression of the effect of ELE on plasma vasopressin. These findings indicate the PVN as a site of action for the central effect of tachykinins on plasma vasopressin and suggest that the angiotensin mediation of the effect might take place in the same nucleus.

Amino Acid Sequence↗
PubMed1991

Mechanisms implicated in the histamine response of the sheep ureterovesical junction.

The isotonic response of the sheep ureterovesical junction to histamine receptor agonists and antagonists was studied in vitro. Histamine (10(-7)-10(-4) M) produced a concentration-dependent contraction which was dependent on the extracellular calcium concentrations. Nifedipine (10(-9)-10(-6) M) partially inhibited the contractile response to histamine. 2-Methylhistamine and 2-pyridylethylamine elicited contractile effect in a concentration-related manner. The order of potency was histamine greater than 2-methylhistamine greater than 2-pyridylethylamine. Dimaprit and 4-methylhistamine produced no response in this tissue. The histamine contraction was antagonized by mepyramine, the pA2 value being 8.41, but not by cimetidine (10(-4) M). Scopolamine (10(-5) M) and indomethacin (10(-6) M) had an inhibitory effect. Phentolamine (10(-5) M), propranolol (10(-7)) and hexamethonium (10(-6) M) did not alter the histamine-induced contractions. The present results indicate that the response to histamine in sheep ureterovesical junction is mediated mainly by a direct action on the smooth muscle through excitatory histamine H1-receptors and partly by an indirect action via the stimulation of intramural cholinergic nerves.

Animals↗
PubMed1991

Ectomycorrhizin Synthesis and Polypeptide Changes during the Early Stage of Eucalypt Mycorrhiza Development.

In functioning eucalypt ectomycorrhizas, biochemical alterations are accompanied by a differential accumulation of polypeptides including the synthesis of symbiosis-related proteins (JL Hilbert, Martin FM [1988] New Phytol 110: 339-346). In the present study, protein biosynthesis in the early stages of ectomycorrhiza formation on Eucalyptus globulus subsp. bicostata Kirkp. was examined using compatible and incompatible isolates of the basidiomycete Pisolithus tinctorius (Coker & Couch). Changes in polypeptide composition were observed within hours following contact of the compatible mycelium with the roots, well before the differentiation of typical symbiotic tissues. At this stage, at least seven symbiosis-related proteins (ectomycorrhizins) accumulated in root tissues. In vivo incorporation of [(35)S]methionine by ectomycorrhizas followed by electrophoresis of the labeled proteins revealed that most of these differences in polypeptide concentrations, including the ectomycorrhizin accumulation, are the result of differential protein biosynthesis rather than posttranslational modifications of the polypeptides. The initial development of eucalypt ectomycorrhizas, therefore, coincides with the synthesis of symbiosis-related proteins and the data presented here provide essential evidence to ascribe a functional developmental role to these proteins.

Journal Article↗
PubMed1991

Calcium dependence of contractile activation of isolated sheep urethra. I: Responses to electrical stimulation.

In isolated sheep urethral smooth muscle at resting tension, responses elicited by electrical stimulation of nerves were either contraction (40%), or contraction preceded by relaxation (60%). All responses were suppressed by tetrodotoxin (TTX), but at stimulation frequencies exceeding 16 Hz, there was a small TTX resistant contraction, which at the highest frequency used (50 Hz) amounted to about 15% of the total response. alpha-Adrenoceptor blockade suppressed the contractions, as did chemical sympathectomy with 6-hydroxydopamine. In calcium-free medium all electrically induced contractions were abolished. Nifedipine, verapamil, and lanthanum had concentration-dependent depressant actions, whereas Bay K 8644 (10(-6) M) significantly increased the responses. In preparations prelabelled with 3H-noradrenaline, electrical stimulation caused a release of 3H that could be blocked by TTX, and effectively reduced by calcium-free medium and lanthanum. However, the release was unaffected by nifedipine, and moderately reduced by high concentrations of verapamil (10(-5) M). It is suggested that contractile responses to electrical stimulation in isolated sheep urethral smooth muscle are mediated by the sympathetic nervous system, mainly through release of noradrenaline stimulating postjunctional alpha 1-adrenoceptors. The release of noradrenaline, as well as the action of released noradrenaline on postjunctional membranes are calcium-dependent. However, the calcium entry pathways used are partly different from those inhibited by organic calcium antagonists.

Animals↗