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Biomedical subjects

A Galli

Publications and source records attributed to A Galli.

At least 91 records · Page 5Linked to original sources
PubMed1996

Effects of Salmonella assay negative and positive carcinogens on intrachromosomal recombination in G1-arrested yeast cells.

A wide variety of carcinogens including Ames assay (Salmonella) positive as well as Salmonella-negative carcinogens induce intrachromosomal recombination (DEL recombination) in strain RS112 of Saccharomyces cerevisiae. It has been previously shown that the Salmonella-positive carcinogens ethyl methanesulfonate (EMS), methyl methanesulfonate (MMS) and 4-nitroquinoline-N-oxide (4-NQO) and the Salmonella-negative carcinogens safrole, benzene, thiourea, carbon tetrachloride and urethane induce DEL recombination in G2-arrested yeast cells. DEL recombination is preferentially induced by safrole, benzene and carbon tetrachloride in G2-arrested cells which might be explained by preferential induction of unequal sister chromatid recombination leading to deletions. To test this, cells of strain RS112 were arrested in the G1 phase of the cell cycle, exposed to these carcinogens and the frequencies of DEL and interchromosomal recombination (ICR) were determined. EMS, MMS and 4-NQO induced DEL recombination and ICR in G1-arrested cells with a linear dose-response curve. In contrast, the Salmonella-negative carcinogens safrole, benzene, carbon tetrachloride, thiourea and urethane induced DEL recombination and ICR with a threshold below which no significant increase was seen and only at already cytotoxic doses. EMS, MMS and 4-NQO were more recombinagenic in previous experiments with growing cells than in G1-arrested cells. On the other hand, safrole, benzene and carbon tetrachloride were more recombinagenic in G1-arrested than in growing cells. Thus, inducibility of DEL recombination in G1-arrested cells parallels inducibility in G2-arrested cells making it less likely that sister chromatid recombination events might be involved. These data are discussed in terms of the mechanism of induced DEL recombination and the possible biological activities of these carcinogens.

Carcinogens↗
PubMed1996

Norepinephrine transporters have channel modes of conduction.

Neurotransmitter transporters couple to existing ion gradients to achieve reuptake of transmitter into presynaptic terminals. For coupled cotransport, substrates and ions cross the membrane in fixed stoichiometry. This is in contrast to ion channels, which carry an arbitrary number of ions depending on the channel open time. Members of the gamma-aminobutyric acid transporter gene family presumably function with fixed stoichiometry in which a set number of ions cotransport with one transmitter molecule. Here we report channel-like events from a presumably fixed stoichiometry [norepinephrine (NE)+, Na+, and Cl-], human NE (hNET) in the gamma-aminobutyric acid transporter gene family. These events are stimulated by NE and by guanethidine, an hNET substrate, and they are blocked by cocaine and the antidepressant desipramine. Voltage-clamp data combined with NE uptake data from these same cells indicate that hNETs have two functional modes of conduction: a classical transporter mode (T-mode) and a novel channel mode (C-mode). Both T-mode and C-mode are gated by the same substrates and antagonized by the same blockers. T-mode is putatively electrogenic because the transmitter and cotransported ions sum to one net charge. However, C-mode carries virtually all of the transmitter-induced current, even though it occurs with low probability. This is because each C-mode opening transports hundreds of charges per event. The existence of a channel mode of conduction in a previously established fixed-stoichiometry transporter suggests the appearance of an aqueous pore through the transporter protein during the transport cycle and may have significance for transporter regulation.

Biological Transport↗
PubMed1996

Synthesis and binding activity of some pyrazolo[1,5-c]quinazolines as tools to verify an optional binding site of a benzodiazepine receptor ligand.

The synthesis and binding activity at the benzodiazepine receptor of some 2-substituted pyrazolo[1,5-c]quinazolines are reported. The structure-activity relationships and in vitro efficacy of the title compounds, which are devoid of the proton acceptor atom at position 1, are similar to those of some previously reported tricyclic heteroaromatic compounds. This suggests that a proton acceptor at position 1 is an optional binding site of a benzodiazepine receptor ligand which only affects potency.

Animals↗
PubMed1996

Hydroxyurea induces recombination in dividing but not in G1 or G2 cell cycle arrested yeast cells.

Hydroxyurea, a chemotherapeutic and radiosensitizing agent, inhibits ribonucleotide reductase, arrests cells in the S-phase and is mutagenic and recombinagenic. In this paper we investigated whether the recombinagenic activity of hydroxyurea is due to the same activity that leads to arrest in the S-phase or to a more direct action on DNA. The effect of hydroxyurea on intrachromosomal and interchromosomal recombination was investigated in dividing and in G1 or G2 cell cycle-arrested cells of the yeast Saccharomyces cerevisiae. Treatment of dividing cells with hydroxyurea resulted in a large increase in recombination frequencies, even at low non-toxic doses. In contrast, in cells arrested in the G1 or G2 phase, hydroxyurea failed to induce recombination, even at 60-fold higher toxic doses. The presence of metabolic activation (S9 mix) did not change the effects of hydroxyurea on recombination. The data suggest that the recombinagenic activity of hydroxyurea may not be due to any direct effect of hydroxyurea on DNA, but may be linked to the inhibition of ribonucleotide reductase causing inhibition of DNA synthesis leading to S-phase arrest and possibly causing recombinagenic lesions.

Antineoplastic Agents↗
PubMed1996

Structure-activity relationship studies of novel pyrazolo[1,5-c][1,3]benzoxazines: synthesis and benzodiazepine receptor affinity.

Some 2-arylpyrazolo[1,5-c][1,3]benzoxazin-5-ones 1 and 5- oxopyrazolo[1,5-c][1,3]benzoxazin-2-carboxylates 2 were prepared and biologically evaluated for their binding at benzodiazepine receptor (BZR) in rat cortical membranes. Structure-activity relationship studies suggest that, although proton donor d and proton acceptor a1 are both optional pharmacophoric descriptors, at least one of them must be present for good BZR affinity. When the proton donor d is not present, the heteroatom acceptor a1 is necessary either in the tricyclic core or in the appended substituent at the C-2 to obtain sub-micromolar BZR affinity.

Animals↗
PubMed1996

Functional role of low-voltage-activated dihydropyridine-sensitive Ca channels during the action potential in adult rat sensory neurones.

Neuronal cell firing is crucial to nerve-nerve communication. The ability to produce consecutive action potentials is related to the activation of inward currents after each upstroke. If fast Na current is indeed responsible for the overshoot, it is still unclear which current drives membrane voltage to the Na threshold. In this study we present evidence that in adult rat sensory neurones a dihydropyridine-sensitive Ca channel exists in addition to the well characterized L-type, or high-threshold Ca channel. During stimulated action potential trains, L-type Ca channels open during the excitation wave, whereas activity of the other dihydropyridine-sensitive Ca channel was observed primarily between action potentials. This second Ca pathway shows remarkably long openings at negative potentials after a series of positive prepulses. The nerve action potential and the repetitive firing work as a physiological Ca channel facilitation mechanism. Therefore, we suggest that this novel Ca conductance provides inward current, between two consecutive action potentials, able to modulate the frequency of neuronal bursts.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1996

Combined craniofacial approach to facial tumours involving the anterior skull base.

The authors report their experience on six male patients and one female patient (age range: 58-76 years, median: 67) with facial tumours involving the anterior skull base, undergoing craniofacial resection between January 1992 and May 1994 at the Division of Surgical Oncology in the Tumor Institute, Genoa. Three patients had squamous carcinoma and adenocarcinoma of the nasal fossa; two patients had squamous carcinoma rT4NO and adenocarcinoma rT4NO1 of the maxillary sinus; one patient had squamous carcinoma of the eyelid, and another had squamous carcinoma of the internal chantus. Four patients had had previous radiotherapy, another underwent pre-operative chemoradiotherapy, and only two patients had not been treated before. A proper craniofacial tumour resection was performed in three patients; one patient had a left maxillectomy with ethmoidectomy and orbital exenteration; one patient underwent maxillectomy, resection of the medial and inferior wall of the orbit, ethmoidectomy, and orbital exenteration; one patient underwent maxillectomy, ethmoidectomy, and mucosectomy of the sphenoidal sinus, and one patient had total ethmoidectomy. As for reconstruction procedures of the anterior skull base, lyophilized dura with galeal pericranial flap was commonly used. A myocutaneous flap transposition (transverse rectus abdominis and latissimus dorsi myocutaneous flap) was used in two patients for the reconstruction of the resected tissues and bones of maxillary and orbital regions. Post-operative complications included intraoperative liquorrhea in one patient; one case of early and serious pneumocephalus; flap necrosis occurred following transposition of latissimus dorsi. Median hospital stay was 34 days. After a median follow-up of 18 months (range: 3 to 34 months) five of seven patients (71.4%) are alive and disease-free at 15, 17, 18, 30 and 34 months from surgery.

Adenocarcinoma↗
PubMed1996

Reversible inhibition of cholinesterases by opioids: possible pharmacological consequences.

The inhibitory potency of opioids belonging to different structural categories on electric eel and rat brain acetylcholinesterase (AChE) and horse serum butyrylcholinesterase (BuChE) was investigated. The phenylazepine meptazinol, the pyrrolo-[2,3-b]-indole derivative eseroline and the benzomorphan normetazocine were the most potent inhibitors of AChE among the compounds tested. These were followed by (-)-metazocine, N-allylnorcyclazocine, 3-(1,3-dimethyl-3-pyrrodinyl)-phenol, levallorphan, levorphanol and pentazocine. The opioids which inhibited horse serum BuChE were in order of potency: meptazinol, methadone, profadol, levallorphan and 1,2,3-trimethyl-3-(3-hydroxyphenyl)-piperidine. The results of this work appear consistent with the fact that the anticholinesterase activity of the opioids is not confined to specific structural categories, although conformationally constrained molecules, like those of morphinans, benzomorphans or pyrrolo-[2,3-b]-indoles, appear to favour affinity for AChE, whereas highly flexible molecules, like those of acyclic opioids, inhibit BuChE in a rather selective way. In all cases, the inhibitory action of opioids markedly differed from that of carbamates or organophosphorous compounds, in that it was time-independent and immediately reversible on dilution. In general the anticholinesterase action of opioids does not seem to influence appreciably the pharmacological properties of the drugs since it is evidenced at drug doses higher than those which are analgesic. However, in the case of mixed agonist/antagonist opioids with rather weak analgesic activity, the enzyme inhibition caused by the levels of circulating drugs can be so marked as to exert also a cholinergic component of action.

Acetylcholinesterase↗
PubMed1996

Acetylcholinesterase inhibition and protection by dizocilpine (MK-801) enantiomers.

The optical isomers of the N-methyl-D-aspartate (NMDA) receptor ion-channel blocker dizocilpine (MK-801) were shown to interact with electric eel and rat brain acetylcholinesterase (AChE) in a mixed competitive-noncompetitive way. The (-) form, pharmacologically less active, was the most potent of the two isomers as an AChE inhibitor (Ki for electric eel and rat brain AChE being 6.2 and 17.9 microM, respectively, compared with 200 and 450 microM, respectively, of the (+) form). Both enantiomers premixed with AChE preparations, dose-dependently protected the enzyme from inactivation by diisopropylfluorophosphate (DFP). The maximal protective effects against 40 and 10 microM DFP were in the ranges 10.7-23.8 and 19.5-31.4% of control enzymic activity for the (+) and (-) forms of dizocilpine, respectively. The extent of the protective effect against DFP was increased up to 80.1% of control enzymic activity for (-)-dizocilpine and to 38.4% for (+)-dizocilpine by diluting the enzymic mixtures 1000 times after treatment with the organophosphate agent. The two enantiomers added to AChE 15 min after DFP, failed to reactivate the enzyme. Finally, it was shown that (+)- and (-)-dizocilpine dose-dependently and competitively decreased the DFP bimolecular reaction constant, K(i). We conclude that dizocilpine exerts a protective action towards AChE against irreversible DFP inhibition, but the molecular mechanism of such an action is at present unclear.

Animals↗
PubMed1996

Flow cytometric analysis of bronchoalveolar lavage and venous blood lymphocyte phenotype for the diagnosis of acute graft rejection in lung transplant patients. The Lung Transplant Group, Ospedale Maggiore di Milano.

OBJECTIVE: To investigate modifications of phenotype in bronchoalveolar lavage (BAL) and venous blood lymphocytes as markers of acute organ rejection in lung transplant patients. STUDY DESIGN: Five consecutive patients receiving successful single lung transplants between March 1991 and April 1992 were followed for two years; serial bronchoscopies with BAL and transbronchial biopsies (TBBs) were performed. BAL and venous blood lymphocyte cytofluorimetry was performed at every procedure, and an index, (blood T4/T8)/(BAL T4/T8), was computed. RESULTS: The index was always > or = 3 in the two patients who did not have graft rejection and always < 3 in the two patients who had repeated episodes of acute rejection (even when no rejection was apparent). The index was frequently < 3 when cytomegalovirus infection was diagnosed. CONCLUSIONS: Since BAL is far less invasive and carries lower risks than TBB, the index might be considered, if our results are confirmed, for screening patients at high risk of acute rejection. TBB could be used as a confirmatory tool for patients who have an index < 3.

Adult↗
PubMed1995

On the mechanism of UV and gamma-ray-induced intrachromosomal recombination in yeast cells synchronized in different stages of the cell cycle.

A genetic system selecting for deletion events (DEL recombination) due to intrachromosomal recombination has previously been constructed in the yeast Saccharomyces cerevisiae. Intrachromosomal recombination is inducible by chemical and physical carcinogens. We wanted to understand better the mechanism of induced DEL recombination and to attempt to determine in which phase of the cell cycle DEL recombination is inducible. Yeast cells were arrested at specific phases of the cell cycle, irradiated with UV or gamma-rays, and assayed for DEL recombination and interchromosomal recombination. In addition, the contribution of intrachromatid crossing-over to the number of radiation induced DEL recombination events was directly investigated at different phases of the cell cycle. UV irradiation induced DEL recombination preferentially in S phase, while gamma-rays induced DEL recombination in every phase of the cell cycle including G1. UV and gamma-radiation induced intrachromatid crossing over preferentially in G1, but it accounted at the most for only 14% of the induced DEL recombination events. The possibility is discussed that single-strand annealing or one-sided invasion events, which can occur in G1 and may be induced by a double-strand break intermediate, may be responsible for a large proportion of the induced DEL recombination events.

Cell Cycle↗
PubMed1995

IL-10 up-regulates human monocyte phagocytosis in the presence of IL-4 and IFN-gamma.

Interleukin-10 (IL-10), a cytokine produced by type 2 helper T (Th2) cells, inhibits the microbicidal effector function of interferon-gamma (IFN-gamma)-activated macrophages. However, recent observations indicate that IL-10, like IFN-gamma, increases Fc gamma RI expression and Fc gamma R-mediated cytotoxic activity on human monocytes, suggesting that this cytokine cannot be classified purely as a monocyte deactivator. The present study found that incubation for 40 h of human monocytes or monocyte-derived macrophages in the presence of IL-10 caused a significant enhancement of their capacity to ingest particles coated with immunoglobulin G (Fc gamma R-mediated ingestion) or with C3b/C3bi fragments of the complement system (CR1/CR3-mediated ingestion). The number of phagocytosing cells (% phagocytosis) and the number of ingested particles per cell (phagocytic index) were both significantly higher after 40-h incubation of monocytes with IL-10 concentrations > or = 1 U/ml. This up-regulating activity on phagocytosis was completely reversed by anti-IL-10 monoclonal antibody (mAb). As previously reported, IL-10 stimulated Fc gamma RI expression on monocytes but did not induce the expression of Fc gamma RII, Fc gamma RIII, CR1, and CR3. IFN-gamma, like IL-10, up-regulated only Fc gamma RI expression but significantly reduced both Fc gamma R- and CR-mediated ingestion. IL-10 almost completely reversed the IFN-gamma-induced inhibition of both Fc gamma R- and CR-mediated phagocytosis, without concomitant changes in membrane expression of phagocytic receptors. Exposure of monocytes to IL-4 reduced the membrane expression of all three Fc gamma Rs and also inhibited Fc gamma R-mediated ingestion. On the other hand, IL-4 up-regulated both CR3 expression and CR-mediated ingestion on cultured monocytes. IL-10 not only neutralized the down-regulatory effect of IL-4 on Fc gamma R expression but also completely reversed the IL-4-induced suppression of Fc gamma R-mediated phagocytosis. Exposure of monocytes to a combination of IL-10 and IL-4 resulted in a synergistic effect on CR-mediated ingestion, even though no additive effects were observed on CR membrane expression. Finally, culture of monocytes in medium containing anti-IL-10 mAb significantly reduced their capacity to ingest IgG- or C3b/C3bi-coated particles, suggesting a role for endogenously produced IL-10 in the modulation of phagocytosis by human monocytes.(ABSTRACT TRUNCATED AT 400 WORDS)

Humans↗
PubMed1995

NMDA receptor heterogeneity in mammalian tissues: focus on two agonists, (2S,3R,4S) cyclopropylglutamate and the sulfate ester of 4-hydroxy-(S)-pipecolic acid.

Several potent and selective agonists of the glutamate (L-GLU) receptors of N-methyl-D-aspartate (NMDA) type have been tested on the L-[3H]GLU binding to rat cortical membranes, on the depolarization of mouse cortical wedges and on the contraction of guinea pig longitudinal muscle myenteric plexus preparations with the aim of comparing the NMDA receptors present in the cortex and those present in the gut. When the depolarization of the cortical wedges was evaluated, the EC50 values of the agonists were (microM): (R,S)-(tetrazol-5-yl)-glycine (TG) 0.3; trans-4-hydroxy-(S)-pipecolic acid-4-sulfate (t-HPIS) 0.7; 1-aminocyclobutane-cis-1,3-dicarboxylic acid (ACBD) 0.8; NMDA 8; (2S,3R,4S) cyclopropylglutamate (L-CGA C) 12; quinolinic acid (QUIN) 400. When the contraction of the longitudinal muscle myenteric plexus was evaluated, the EC50 values were (microM): L-CGA C 1; TG 8; ACBD 50; t-HPIS 100; QUIN 500 and NMDA 680. When the displacement of NMDA specific L-[3H]GLU binding from rat cortical membranes was evaluated, the IC50 values were (microM): L-CGA C 0.003; TG 0.005; ACBD 0.044; t-HPIS 0.062; NMDA 0.31 and QUIN 15. No significant correlation was found when the EC50 values obtained in the ileum were plotted against the EC50 values obtained in the cortex (r = 0.47). In particular it was noted that L-CGA C was approximately three orders of magnitude more potent than NMDA when tested in the ileum but had a potency not significantly different from that of NMDA when tested in the cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids, Dicarboxylic↗
PubMed1995

Salmonella test positive and negative carcinogens show different effects on intrachromosomal recombination in G2 cell cycle arrested yeast cells.

There is considerable controversy about the extrapolation of results obtained with high doses of chemicals in long-term and animal carcinogenesis studies to the low doses human beings are exposed to. In the present study, we compare the effect of Salmonella test positive carcinogens, ethyl methanesulfonate, methyl methanesulfonate, 4-nitroquinoline-1-oxide and gamma-rays versus Salmonella test negative carcinogens, benzene, safrole, urethane, thiourea and carbon tetrachloride over a dose range of 10(4)-fold on the frequency of intrachromosomal recombination in Saccharomyces cerevisiae. This short-term test is positive with both kinds of carcinogens. The Salmonella test negative carcinogens safrole, benzene and carbon tetrachloride induced intrachromosomal recombination to much higher levels in G2 arrested cells compared to growing cells; the reverse was true for the Salmonella test positive carcinogens. The Salmonella test positive carcinogens caused an almost linear dose response for induction of intrachromosomal recombination starting at a dose 100- to 1000-fold below the lowest toxic dose. In contrast, all Salmonella test negative carcinogens showed a sharp threshold below which no effect was detected, and the first effective dose for induction of intrachromosomal recombination was the first toxic dose.

Animals↗
PubMed1995

Local and systemic toxicity in 'borderline true' hyperthermic isolated perfusion for lower limb melanoma.

This paper reports clinical results of hyperthermal (41.5 degrees C) isolated perfusion of the lower limb for melanoma treatments in association with cytostatic drugs (L-PAM) in 10 consecutive patients. Attention is focussed on the toxicity effects in the search for a possible correlation between the treatment variables and toxicity. Careful heat administration techniques and thorough and accurate temperature monitoring have resulted in a uniform and closely controlled temperature distribution, allowing us to approach the limiting temperature value for possible damage both of the limb tissues and of the perfusate. Care was taken to avoid perfusate overheating (42 degrees C maximum). Local toxicity was observed between grades II and III. Systemic toxicity was of insignificant level. The clinical results show that high-temperature treatments with simultaneous administration of the cytostatic are feasible with acceptable toxicity. Further clinical investigations are recommended to ascertain the efficacy of the method.

Antineoplastic Agents, Alkylating↗
PubMed1995

Sodium-dependent norepinephrine-induced currents in norepinephrine-transporter-transfected HEK-293 cells blocked by cocaine and antidepressants.

Transport of norepinephrine (NE+) by cocaine- and antidepressant-sensitive transporters in presynaptic terminals is predicted to involve the cotransport of Na+ and Cl-, resulting in a net movement of charge per transport cycle. To explore the relationship between catecholamine transport and ion permeation through the NE transporter, we established a human norepinephrine transporter (hNET) cell line suitable for biochemical analysis and patch-clamp recording. Stable transfection of hNET cDNA into HEK-293 (human embryonic kidney) cells results in lines exhibiting (1) a high number of transporter copies per cell (10(6)), as detected by radioligand binding and hNET-specific antibodies, (2) high-affinity, Na(+)-dependent transport of NE, and (3) inhibitor sensitivities similar to those of native membranes. Whole-cell voltage-clamp of hNET-293 cells reveals NE-induced, Na(+)-dependent currents blocked by antidepressants and cocaine that are absent in parental cells. In addition to NE-dependent currents, transfected cells posses an NE-independent mode of charge movement mediated by hNET. hNET antagonists without effect in non-transfected cells abolish both NE-dependent and NE-independent modes of charge movement in transfected cells. The magnitude of NE-dependent currents in these cells exceeds the expectations of simple carrier models using previous estimates of transport rates. To explain our observations, we propose that hNETs function as ion-gated ligand channels with an indefinite stoichiometry relating ion flux to NE transport. In this view, external Na+ and NE bind to the transporter with finite affinities in a cooperative fashion. However, coupled transport may not predict the magnitude or the kinetics of the total current through the transporter. We propose instead that Na+ gates NE transport and also the parallel inward flux of an indeterminate number of ions through a channel-like pore.

Adrenergic alpha-Agonists↗