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Biomedical subjects

A Ambrosini

Publications and source records attributed to A Ambrosini.

At least 19 recordsLinked to original sources
PubMed1992

Purified unitary kainate/alpha-amino-3-hydroxy-5-methylisooxazole-propionate (AMPA) and kainate/AMPA/N-methyl-D-aspartate receptors with interchangeable subunits.

We have purified and characterized two vertebrate excitatory amino acid ionotropic receptors from the Xenopus central nervous system. Each is a unitary receptor (i.e., having more than one class of excitatory amino acid agonist specificity within one protein oligomer). The first is a unitary non-N-methyl-D-aspartate (non-NMDA) receptor and the second is a unitary NMDA/non-NMDA receptor. The specific agonist-activated channel activity and pharmacology of each type were recognized by patch-clamping lipid bilayers in which the isolated protein was reconstituted. In the second case, the NMDA and the non-NMDA sites could not be physically separated and exhibited functional interaction. Parallel evidence for this was obtained when poly(A) RNA from Xenopus brain was translated in oocytes: a noncompetitive inhibition of the response to L-kainate is produced by NMDA to a maximum depression of 30% at 1 mM NMDA. Each isolated oligomer contains 42-kDa subunits of the non-NMDA ligand binding type, but the second type has an additional NMDA-receptor-specific 100-kDa subunit. Thus, a subunit-exchange hypothesis can account for the known multiplicity of excitatory amino acid receptor types.

Animals↗
PubMed1992

[Role of endoscopy in the diagnosis and follow-up of bleeding lesions of the colon].

Considering the results of the centre of colonoscopy we can draw some considerations about the irreplaceable role of endoscopy in the diagnosis of bleeding colonic lesions and about its greater security in comparison with the traditional radiologic exam, about its possibilities to be sometimes resolutive even for the therapy and about its great importance in the follow-up of patients treated for lesions of this kind.

Angiodysplasia↗
PubMed1991

AMPA and kainate-operated channels reconstituted in artificial bilayers.

Cationic channels which can be activated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) and kainate play a key role in the generation of excitatory postsynaptic potentials in the brain of all vertebrates. On a protein carrying binding sites for both these ligands, affinity-purified from the Xenopus nervous system, electrical measurements have been performed to investigate its functional properties after the pure complex had been incorporated into planar lipid bilayers. Domoate, AMPA or kainate added to the reconstituted protein activated cationic channels, which were blocked by typical antagonists for this neurotransmitter system. These data suggest that the reconstituted protein is an ionotropic receptor of the unitary non-NMDA subtype.

Animals↗
PubMed1991

Effect of the fungicides tributyltin acetate and tributyltin chloride on multilamellar liposomes: fluorescence studies.

The influence of tri-n-butyltin acetate (TBTA) and tri-n-butyltin chloride (TBTC) on the physico-chemical state of charged and neutral phospholipids was investigated using multilamellar liposomes. The thermal dependence of steady state fluorescence polarization of DPH and its charged derivative TMA-DPH was recorded. The two fungicides lowered DPPC phase transition temperature and broadened the temperature range of the transition in different ways. The effects were concentration-dependent. The results show that TBTC interacts more effectively with DPPC model membranes rather than TBTA. Moreover, TBTC broadens and shifts the main phase transition (Tm) more effectively in DPPC rather than in DMPC liposomes. Below Tm, TBTC decreases fluorescence polarization (P) in all phospholipids used. Above Tm P is almost constant in phospholipids with saturated acyl chains, except for DMPG. In fact, an increase of P is detectable in this lipid as in PLs with unsaturated acyl chains. It is suggested that the effects of TBT on liposomal membranes are dependent on the anion moiety and phospholipids characteristics.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Differential scanning calorimetry characterization of oxidized egg phosphatidylcholine liposomes.

Differential scanning calorimetry has been used to characterize liposomes made from mixtures of unoxidized and singlet oxygen oxidized egg phosphatidylcholine. Cooling scans reveal that trapped water decreases when the oxidized phosphatidylcholine content is increased in the liposomes. Liposomes made from mixtures containing more than 50% by weight of oxidized phosphatidylcholine do not show trapped water.

Calorimetry↗
PubMed1990

Interaction of the herbicide atrazine with model membranes. I: Physico-chemical studies on dipalmitoyl phosphatidylcholine liposomes.

Atrazine (2-chloro-4 ethylamino-6-(isopropylamino)-s-triazine) is one of the most widely used herbicides. Fourier transform infrared spectroscopy, differential scanning calorimetry and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and of its derivative 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) were used to study the interaction of atrazine with dipalmitoyl phosphatidylcholine liposomes used as a model for biological membranes. The results show that atrazine does not perturb the hydrophobic core of the lipid bilayer and suggest that the herbicide localizes near the glycerol backbone of the lipid.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Interaction of the herbicide atrazine with model membranes. II: Effect of atrazine on fusion of phospholipid vesicles.

The effect of atrazine on Ca2+ induced fusion of cardiolipin(CL) and phosphatidylserine (PS) vesicles is studied by Tb3+/dipicolinic acid fluorescence and turbidity measurements. The interaction of herbicide with CL and PS membranes is studied by DPH fluorescence polarization. At low concentrations the pesticide partially inhibits fusion, especially in CL vesicles. Higher concentrations of atrazine decrease inhibition of fusion in CL, while fusion is slightly increased in PS. The Ca2(+)-induced increase of turbidity is not affected by atrazine in both PS and CL aggregation experiments. DPH polarization measurements show a perturbation only of the membrane hydrophobic core of PS, in presence of Ca2+. It is hypothesized that this biphasic effect shown by low and high atrazine concentrations on Ca2(+)-induced fusion of vesicles is due to a different localization of the pesticide in the membrane.

Atrazine↗
PubMed1990

Gestational trophoblastic disease in the Gynaecologic and Obstetric Institute of Sassari in the period 1976-89.

61 cases of gestational trophoblastic disease (GTD) were examined retrospectively in the period 1976-89 (60 cases of simple vesicular mole and one case of chorionepithelioma), analysing them from the epidemiologic point of view. The incidence of GTD were 3.6/1000 live births, higher than the Italian and European average, with a very low incidence, on the contrary, of chorionepithelioma (0.06/1000 live births). No significant epidemiological data emerged, with the exception of age (11 cases of over 40 years) and of ABO typing (a notable incidence of ORh + group). The gestational capacity of the patients returning for checking was 78.9%, similar to that of the general population.

Adult↗
PubMed1990

Fist line chemotherapy in advanced ovarian cancer: a comparison of three therapeutic regimes.

The first line polichemotherapeutic regimens are compared (intracavitary Cyclophosphamide + CMF, ACy and PEC) in 47 patients with advanced ovarian carcinoma. The response was 56.4% for Ex-CMF (CR 39.1%), 76.8% for ACy (CR 61.5%) and 81.8% for PEC (CR 63.6%). The three-year survival was 39.1% with Ex-CMF, 53.8% with ACy and 72.7% (follow-up not yet completed) for PEC. Toxicity was modest in all the three therapeutic regimens.

Adult↗
PubMed1990

Endometrial carcinoma in the Sardinian population.

The biological and clinical characteristics of endometrial carcinoma in Sardinia were examined, with particular regard to the very high incidence (42.7/100,000 age-selected women) of this neoplasia in this Island. The use of post-surgical Radiotherapy on the basis of the protocols of integrated therapies allowed us to reduce the incidence of relapses in these last few years, with an evident increase in survival.

Adult↗
PubMed1990

Endocavitary beta-interferon in neoplastic effusions.

Thirteen patients with malignant genital or mammary neoplasias, with endocavitary neoplastic effusion (pleural or ascitic), were examined in order to study the modifications of neoplastic effusion in endocavitary treatment (intrapleural or intraperitoneal) with Beta-Interferon. There was an overall objective response in 70% of the patients treated, with 53.8% complete responses and an average duration response of above 6 months. The best results were obtained in patients with ovarian cancer, with 75% of objective responses (50% CR), confirming the efficacy of Beta-Interferon particularly at peritoneal level, where there is higher concentration and exposure of the drug in the site of disease.

Adult↗
PubMed1990

The modifications of T-lymphocyte cell subpopulations in patients with beta-interferon intracavitary treatment.

18 patients with malignant genital or mammary neoplasia, treated with endocavitary Beta-Interferon (intrapleural or intraperitoneal), were examined in order to study the modifications of T-lymphocyte subpopulations (T3, T4, T8, T4/T8) in the peripheric blood. An improvement in the immune state in complessively 50% of the patients treated was observed, while there were no modifications in the remaining patients (in 3 patients with advanced ovarian cancer there was persistence of immunodepression preexisting to treatment). This indicates that endocavitary Beta-Interferon induced very poor immune response at peripheric level (contrary to what other Authors have described at peritoneal level), correlated to the dose used and to the extent of serous surface exposed to the drug.

Aged↗
PubMed1990

The treatment of endometrial carcinoma: our experience in the period 1983-89.

The Authors evaluated 87 cases of endometrial carcinoma, of whom 65 (74.7%) at pathological stage I. The surgical ratio was (96.5% 84/87 cases), and 31 cases were subjected to adjuvant postsurgical Radiotherapy because of the presence of risk factors. The incidence of relapses resulted complessively in 14.2%, with a NED-survival of 86.1% and an overall survival of 91.9% at the pathological stage I. The Authors emphasise particularly the importance of post-surgical Radiotherapy in the cases at risk, which allowed an important decrease of the incidence of relapses at stage I with regard to previous studies.

Aged↗
PubMed1990

Wertheim-Meigs operation in the Gynaecologic and Obstetric Institute of Sassari in the ten-year period 1980-89.

In a retrospective study we examined 42 radical hysterectomies according to Wertheim-Meigs in the ten year period 1980-89, of whom 39 for carcinoma of the cervix, two for endometrial carcinoma at stage II one for microinvasive vaginal carcinoma. The incidence of relapses was 11.9% (5 cases) globally, with 3.7% at pathologic stage I, while the actuarial survival was 95.4% at stage I. The intraoperative, perioperative and postactinic complications related to integrated treatment are described, underlining the importance of post-surgical Radiotherapy in cases at risk.

Female↗
PubMed1989

Muscarinic and quisqualate receptor-induced phosphoinositide hydrolysis in primary cultures of striatal and hippocampal neurons. Evidence for differential mechanisms of activation.

Several neurotransmitters activate polyphosphoinositide (PPI) hydrolysis in CNS neurons as the first step of a transmembrane signalling cascade that may lead to neuronal circuit modulation. Muscarinic and quisqualate receptor-triggered PPI hydrolysis was investigated in neuronal primary cultures. A clear increase in inositol phosphates (Ins-Ps) was detected as early as 15 s after the agonist addition; at this time, the increases of inositol 1,4,5-trisphosphate (measured by HPLC) were relatively larger with respect to the other Ins-Ps. Ins-P accumulation was maintained in part in a Ca2+-free medium, excluding that Ca2+ entry is the fundamental step of the receptor-induced PPI hydrolysis. Acute cell pretreatment with phorbol dibutyrate, an activator of protein kinase C, was able to inhibit 50% of the response to carbachol, and almost completely the quisqualate effect, suggesting a negative feedback modulation by the enzyme. Finally, pertussis toxin failed to inhibit muscarinic responses, whereas it blocked greater than 70% of the quisqualate stimulation. The two receptors therefore appear coupled to phosphodiesterase by two different G proteins. The comparison of the results obtained by stimulating the two receptor systems suggests that the generation of the same intracellular signal at two distinct receptor types may occur by different coupling mechanisms, and be differently regulated even in the same neuronal preparations.

Animals↗
PubMed1989

Evidence for a single glutamate receptor of the ionotropic kainate/quisqualate type.

The kainate (KA) and the quisqualate (QUIS) receptors that activate cation channels in the central nervous system have previously been defined as two of the major glutamate receptor types. In amphibian brain, an exceptionally rich source of these sites, they can be coextracted by octylglucoside and shown to behave as one entity in all analyses made in solution. When partly purified by lectin affinity, ion-exchange chromatography or by sucrose gradient centrifugation, the two activities comigrate in a 1:1 ratio. When the QUIS component is bound to an immobilized specific QUIS agonist, the KA component is extracted in parallel with it. There are equivalent numbers of the QUIS and KA sites and the two sites show a single affinity series for the binding of glutamatergic agonists. We deduce that KA or QUIS select different conformations of a single KA/QUIS receptor binding site, leading thus to the different channel-opening events that have been reported for these two agonists.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
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↗