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Biomedical subjects

G Gatti

Publications and source records attributed to G Gatti.

At least 145 records · Page 8Linked to original sources
PubMed1988

Second-messenger control of catecholamine release from PC12 cells. Role of muscarinic receptors and nerve-growth-factor-induced cell differentiation.

The role of various intracellular signals and of their possible interactions in the control of neurotransmitter release was investigated in PC12 cells. To this purpose, agents that affect primarily the cytosolic concentration of Ca2+, [Ca2+]i (ionomycin, high K+), agents that affect cyclic AMP concentrations (forskolin; the adenosine analogue phenylisopropyladenosine; clonidine) and activators of protein kinase C (phorbol esters) were applied alone or in combination to either growing chromaffin-like PC12-cells, or to neuron-like PC12+ cells differentiated by treatment with NGF (nerve growth factor). In addition, the release effects of muscarinic-receptor stimulation (which causes increase in [Ca2+]i, activation of protein kinase C and decrease in cyclic AMP) were investigated. Two techniques were employed to measure catecholamine release: static incubation of [3H]dopamine-loaded cells, and perfusion incubation of unlabelled cells coupled to highly sensitive electrochemical detection of released catecholamines. The results obtained demonstrate that: (1) release from PC12 cells can be elicited by both raising [Ca2+]i and activating protein kinases (protein kinase C and, although to a much smaller extent, cyclic AMP-dependent protein kinase); and (2) these various control pathways interact extensively. Activation of muscarinic receptors by carbachol induced appreciable release responses, which appeared to be due to a synergistic interplay between [Ca2+]i and protein kinase C activation. The muscarinic-induced release responses tended to become inactivated rapidly, possibly by feedback desensitization of the receptor mediated by protein kinase C. Muscarinic inactivation was prevented (or reversed) by agents that increase, and accelerated by agents that decrease, cyclic AMP. Agents that stimulate release primarily through the Ca2+ pathway (ionomycin and high K+) were found to be equipotent in both PC12- and PC12+ cells, whereas the protein kinase C activator 12-O-tetradecanoyl-phorbol 13-acetate was approx. 10-fold less potent in PC12+ cells, when administered either alone or in combination with ionomycin. In contrast, the cell binding of phorbol esters was not greatly modified by NGF treatment. Thus control of neurotransmitter release from PC12 cells is changed by differentiation, with a diminished role of the mechanism mediated by protein kinase C.

Adrenal Gland Neoplasms↗
PubMed1988

Reassessment of copper stoichiometry in ascorbate oxidase.

A very pure ascorbate oxidase solution was obtained by dissolving a crystalline sample of the enzyme. The ratio between 280 and 610 nm absorbancies was 22.5. It contained 8.0 +/- 0.2 Cu ions, 50% EPR detectable, per dimeric molecule (140,000 M.W.) with a molar extinction coefficient of 10,000 cm-1 at 610 nm. Two Cu ions were removed by treatment with N,N-diethyldithiocarbamate. The optical blue absorption band was unaffected, while two EPR detectable Cu ions were lost, with disappearance of the type 2 Cu signal. It is concluded that native ascorbate oxidase contains two type 1, two type 2, and four type 3 Cu ions.

Ascorbate Oxidase↗
PubMed1988

Circadian variations of interferon-induced enhancement of human natural killer (NK) cell activity.

We searched for circadian changes in the enhancement of the NK activity after exposure to IFN-gamma of peripheral blood mononuclear (PBM) cells obtained serially throughout the 24-h cycle. In August-October 1986, blood was drawn from 7 healthy, diurnally active and nocturnally resting male volunteers (22-34 yr) at 4-h intervals for 24 h starting at 08:00. PBM cells were immediately separated and assayed for NK cell activity, using K 562 cultured cells as a target in a 4-h 51Cr release assay after prior incubation for 20 h with buffer or 300 IU rIFN-gamma. Circadian variations of the spontaneous NK cell cytotoxicity were apparent; the activity was at its maximum at the end of the night or in the early morning and then declined in the afternoon. The 24-h rhythmic pattern was validated with statistical significance by the Cosinor method (p less than 0.02; acrophase 04:22). Maximum enhancement by IFN-gamma was attained in the second part of the night or in the early morning, i.e. in phase with the peak of the spontaneous NK cell activity. A significant circadian rhythm of the percent increase above control levels was validated by the Cosinor method (p less than 0.01; acrophase 04:03). Our findings may be of relevance to a better understanding of the mechanisms of control of human NK activity and warrant consideration as an approach to improve the effectiveness of time-qualified immunotherapy.

Adult↗
PubMed1988

Effect of flurithromycin, a new macrolide antibiotic, on carbamazepine disposition in normal subjects.

The effects of flurithromycin, a new macrolide antibiotic, on the disposition of a single oral dose of carbamazepine (CBZ) (400 mg) were investigated in seven normal subjects. Flurithromycin (2 x 250 mg thrice daily for 10 days) caused a slight increase in the CBZ area under the serum concentration curve and a moderate reduction in carbamazepine-10, 11-epoxide (CBZ-E) levels. These results suggest that flurithromycin can inhibit the conversion of CBZ to CBZ-E, although, at the dosage tested, the magnitude of this effect was significantly smaller than that observed after administration of erythromycin in the same subjects.

Adult↗
PubMed1987

Inhibition by cortisol of human natural killer (NK) cell activity.

The effects of cortisol on the natural killer (NK) activity of human peripheral blood mononuclear (PBM) cells were studied in vitro using a direct 4-h 51Cr-release assay and K 562 cell line as a target. Preincubation for 20 h of PBM cells drawn from healthy donors with 1 X 10(-8) to 1 X 10(-5) M cortisol resulted in a significant decrease of NK cell activity. The magnitude of the suppression was directly related to the steroid concentration and inversely related to the number of effector cells. Cortisol was able to minimize the enhancement of NK cytotoxicity obtainable in the presence of immune interferon (IFN-gamma). A significantly higher suppression was achieved after sequential exposure of PBM cells to cortisol and equimolar levels of prostaglandin E2 (PgE2). The concomitant incubation with theophylline and isobutyl-methylxanthine failed to enhance the cortisol-induced suppression, whereas PgE2-dependent inhibition significantly increased after exposure of PBM cells to methyl-xanthines. The inhibitory effect of cortisol was partially or totally prevented by the concomitant incubation with equimolar amounts of 11-deoxycortisol and RU 486 but not of progesterone. Treatment of NK effectors with a monoclonal anti-human corticosteroid-binding globulin (CBG) antibody produced an enhancement of the spontaneous NK activity and a partial suppression of cortisol-mediated effects. Our results suggest that endogenous glucocorticoids play a role in the regulation of NK cell-mediated cytotoxicity. Since the effect of cortisol was additive to that of PgE2 and was not changed by phosphodiesterase inhibitors, it is conceivable that the hormone acts at a level different from the adenylate cyclase-phosphodiesterase system. Data obtained with the use of antiglucocorticoids and the anti-CBG antibody are compatible with a role both of high-affinity glucocorticoid receptors and of CBG in mediating cortisol action on the human NK cell activity.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Studies on the mechanism of cortisol inhibition of human natural killer cell activity: effects of calcium entry blockers and calmodulin antagonists.

The role of Ca2+ in mediating the inhibition by glucocorticoids of human natural killer (NK) activity was investigated using Ca2+ entry blockers (verapamil and its desmethoxy-derivatives LU46973 and LU47093) and calmodulin antagonists (pimozide and two naphthalenesulfopamide derivatives, W-7 and W-13). Peripheral blood mononuclear (PBM) cell preparations were incubated for 20 h with 1 x 10(-6) M cortisol and these agents in various combinations (concentration range: 1 x 10(-7) - 1 x 10(-5) M) and then assayed in a direct 4-h cytolytic assay using 51Cr-labeled K 562 target cells. Exposure to cortisol led to a significant reduction of NK cell activity (about 50% with respect to the spontaneous activity). Ca2+ entry blockers displayed per se a dose-dependent depressive effect on cytotoxicity and gave significant enhancement of cortisol-dependent inhibition. Calmodulin antagonists were per se minimally effective but clearly amplified the cortisol-mediated inhibition. Raising extracellular Ca2+ by CaCl2 or intracellular Ca2+ by the ionophore A23187 yelded an appreciable reduction of these effects. Our data are compatible with the view that extracellular and intracellular Ca2+ play a role in the control of human NK cell activity. Moreover, it is conceivable that the mechanisms involved in glucocorticoid inhibition of NK cell activity involve Ca2+-dependent pathways.

Adult↗
PubMed1987

Serum protein binding of phenytoin and valproic acid in insulin-dependent diabetes mellitus.

The serum protein binding of valproic acid (VPA) and phenytoin (PHT) was determined in spiked serum samples collected from 17 patients with insulin-dependent diabetes mellitus and 16 healthy control subjects. The free fraction of VPA was significantly greater in patients than in controls (7.6 +/- 1.6% vs. 6.2 +/- 1.2%, p less than 0.01); for PHT, free fraction values were similar in the two groups (8.2 +/- 1.1% vs. 8.4 +/- 1.2%). The free fraction of VPA in diabetic patients was positively correlated with free fatty acid (FFA) concentration (r = 0.79, p less than 0.01). No significant relationships could be found between free drug fraction and either serum albumin or glycosylated protein concentration.

Adolescent↗
PubMed1987

Inhibition by erythromycin of the conversion of carbamazepine to its active 10,11-epoxide metabolite.

The serum levels of carbamazepine (CBZ) and its 10,11-epoxide metabolite (CBZ-E) were determined in seven subjects after a single dose of CBZ (400 mg) in the control state and during co-administration of erythromycin (500 mg three times daily for 10 days). Erythromycin treatment was associated with a decrease in CBZ clearance and a prolongation of CBZ half-life, while CBZ-E levels were markedly reduced. These data provide evidence that erythromycin inhibits the conversion of CBZ to its epoxide metabolite.

Adult↗
PubMed1987

Circadian changes in human natural killer-cell activity.

The circadian changes in natural killer (NK) activity of peripheral blood mononuclear cells (PDM) were studied in five clinically healthy, diurnally active, nocturnally resting women. Data on spontaneous NK-cell activity were complemented by data on the chronosusceptibility to in vitro inhibition by 1 X 10(-6) M cortisol and by the rhythmometric evaluation of rectal temperature and plasma cortisol as potential circadian markers. In April-July, 1985, blood was drawn at 4-hr intervals for 24 hr starting at 0800 hr. Cells were immediately separated and assayed for NK activity using K 562 cultured cells as a target and a 4-hr 51Cr-release assay. Circadian variations of the spontaneous NK activity were apparent; the maximum of the activity occurred in the morning or in the early afternoon. In individual subjects, peak-to-through differences were 50% or more of the 24-hr mean. Chronosusceptibility to cortisol (20 hr incubation prior to the cytotoxic assay) was ecphasic with respect to the spontaneous NK-cell activity, with a maximum in the evening or night. Data obtained by immunofluorescence using specific anti-NK cell monoclonal antibodies confirm the occurrence of a higher number of phenotypically identifiable NK effectors in the morning vs. other circadian stages. Our data confirm previous findings and extend their scope to immunopharmacology emphasizing the need for time-qualified investigations on immune coordination in vivo.

Adult↗
PubMed1986

Short term ethanol ingestion can affect the testicular response to single-dose human chorionic gonadotropin in normal subjects.

Ten sober adult male subjects, with normal sexual development and function, were examined under basal conditions and after a short-term period (7 days) of alcohol ingestion (200 g/daily). Plasma concentrations of testosterone (T), 17 beta estradiol (E2), progesterone (P) and 17-hydroxyprogesterone (17-OH P) were measured on blood samples drawn before and then every 24 h until the 96th h following a single dose of human chorionic gonadotropin (hCG, 2,000 IU im). Basal plasma T was significantly decreased after short-term ethanol ingestion (p less than 0.01) whereas E2, P and 17-OH P were comparable in both conditions. The magnitude of the T response to hCG injection was significantly lower after ethanol ingestion but still significantly higher than the corresponding one obtainable in chronic alcoholics. At the 7th day of ethanol ingestion plasma LH levels were higher than controls (p less than 0.05). These results demonstrate that short-term ingestion of 200 g ethanol daily can lead to altered testicular response to hCG in normal adult males and corroborate the view that ethanol is a gonadal toxin.

17-alpha-Hydroxyprogesterone↗
PubMed1986

Cortisol at physiological concentrations and prostaglandin E2 are additive inhibitors of human natural killer cell activity.

The effects of cortisol and prostaglandin E2 on preparations of human peripheral blood mononuclear cells that mediate natural killer cytotoxicity were evaluated. Natural killer cell activity was measured using 51Cr-labelled K562 target cells and effector to target cell (E:T) ratios of 50:1, 25:1, 12.5:1 and 6:1. In vitro preincubation of mononuclear cell preparations for 20 h with 1 X 10(-8) to 1 X 10(-5) M cortisol resulted in a significant decrease of natural killer cell activity. The magnitude of the suppression was directly related to the steroid concentration and inversely related to the E:T ratio. Exposure of cortisol-treated mononuclear cells to 1 X 10(-6) M prostaglandin E2 resulted in a significantly higher level of inhibition than after treatment with the two agents singularly. In contrast, the concomitant incubation with 1 X 10(-5) to 1 X 10(-4) M theophylline, or with 1 X 10(-6) to 1 X 10(-5) M isobutyl-methylxanthine, two widely used phosphodiesterase inhibitors, failed to demonstrate a significant enhancement of cortisol-induced suppression. Prostaglandin E2-dependent inhibition, on the other hand, was more intense after the inhibition of phosphodiesterase activity. Taken together, these results show that cortisol at physiological concentrations has the property of depressing human natural killer cell activity in vitro and suggest that endogenous glucocorticoids play a role in the in vivo regulation of this natural cytotoxicity. Additionally, cortisol and prostaglandin E2 are additive inhibitors of natural killer cell activity. Since the effect of cortisol in our experiments was not changed by theophylline or isobutyl-methylxanthine it is conceivable that the hormone acts at a level different from the adenylate cyclase/phosphodiesterase system.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Assessment of polymorphonucleate leucocyte functions in adult epileptic patients undergoing long-term phenytoin treatment.

Twelve patients given more than 1 year phenytoin monotherapy and 12 healthy control subjects taking no drugs and matched for sex and age were examined for polymorphonucleate (PMN) functions. To assess PMN activity, cell locomotion and directed migration, phagocytosing ability and bactericidal activity were investigated. No change either in the absolute or relative counts of PMN leucocytes was found in the patients. However, a significant impairment of both PMN chemotaxis and stimulated Nitro Blue Tetrazolium reduction or superoxide anion generation was observed in the patients as compared with the control group of subjects.

Adult↗
PubMed1986

Comparison between pituitary computed tomographic findings and tests of hypothalamo-pituitary function in 72 patients with hyperprolactinaemia.

To verify the diagnostic capacity of some dynamic tests of the prolactin (Prl) secretion, the findings obtained by high-resolution computed tomography (CT) were compared with results obtained from tests using nomifensine (NOM) domperidone (DOM) and thyrotrophin-releasing hormone (TRH) in 72 patients with pathological hyperprolactinaemia. None of the patients with tumours had a positive Prl response to NOM or to DOM administration; however, a positive response to these tests was present in only 24 and 41%, respectively, of the patients with normal CT picture. The results of TRH testing were similar to those obtained with DOM. Different neuroendocrine patterns were disclosed by comparing pituitary Prl and thyrotrophin (TSH) responses to DOM: 1) some subjects had a reduced Prl response together with an exaggerated or normal TSH response to DOM; they comprised patients with tumour, empty sella, and normal CT picture; 2) other patients with normal CT picture had a positive Prl and a normal TSH response to DOM. These results demonstrate that a negative Prl response to NOM and DOM characterizes all patients with adenoma; however, the tumour-like responses in patients with no visible tumours seem to reduce the diagnostic value of these tests, unless the latter may predate the radiological appearance of an adenoma. On the other hand, a positive Prl and a normal TSH response to DOM exclude the presence of a pituitary tumour. This diagnostic finding is strengthened by the positive response also to NOM. Whatever may be the diagnostic validity of dynamic tests, they provide sound information on the functional state of dopamine neurotransmission.

Adenoma↗
PubMed1985

Crystallization of an odorant-binding protein from cow nasal mucosa.

The first odorant-binding protein isolated from mammalian nasal mucosa is a dimer of subunits of identical molecular weight (19,000) that specifically binds bell pepper odorants, "green" smelling compounds. The protein can be purified in milligram quantities from tissue extractions by sequential use of a silica based anion exchange column and Mono-P chromatofocussing column. In the presence of the binding compound 2-isobutyl-3-methoxypyrazine and of the organic solvent 2-methyl-2,4-pentanediol (17%, v/v), the protein crystallizes in the monoclinic space group P2(1), with unit cell constants a = 54.3 A, b = 66.7 A, c = 41.5 A, beta = 97.2 degrees. From consideration of the crystal packing densities compatible with its unit cell, it can be concluded that two subunits of 19,000 Mr each are present in the asymmetric unit. The diffraction pattern on still photographs of this crystal form of the protein extends to 2.5 A resolution and allows for a detailed crystallographic investigation.

Animals↗