Effect of Salmonella assay negative and positive carcinogens on intrachromosomal recombination in S-phase 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 Saccharomyces cerevisiae. We have shown previously 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, induced DEL recombination in growing, in G1 and in G2 arrested yeast cells. Since we found interesting differences in response between dividing and arrested cells, we wanted to find out whether these differences were due to the difference between cell division versus cell cycle arrest or to any particular cell cycle phase. In the present paper we incubated cells in the presence of hydroxyurea (HU) for cell cycle arrest in S-phase and exposed them to the above carcinogens, and plated them onto selective medium to determine DEL and interchromosomal recombination (ICR) frequencies. It was surprising that carbon tetrachloride had no effect on DEL recombination or ICR in HU treated cells even though it induced DEL recombination in G1 and G2 arrested as well as dividing cells. Further experiments are in agreement with the interpretation that carbon tetrachloride was responsible for prematurely pushing G1 cells into S-phase. The consequence of this may be replication on a damaged template which may be responsible for the action of carbon tetrachloride. EMS, MMS, 4-NQO and urethane were more recombinagenic in HU treated cells than in previous experiments with G2 arrested cells. None of the carcinogens appeared to be activated by S9 for either DEL recombination or ICR induction. Furthermore, we only detect cytochrome P-450 in dividing but not in arrested cells, arguing that possible differences in the ability to metabolize the compounds does not explain the observed differences for DEL recombination induction in the different cell cycle phases. We discuss these data in terms of the mechanism of induced DEL recombination and the possible biological activities of these carcinogens.

[Potential of ultrasonography and ultrasonography-guided biopsy in the diagnosis of local recurrence following radical prostatectomy]

INTRODUCTION

[corrected] We investigated the diagnostic role of combined transrectal US (TRUS) and biopsy to detect recurrent cancer after radical prostatectomy, in patients with negative bone scintigraphy and elevated prostate specific antigen (PSA) levels.

MATERIALS AND METHODS

From March, 1997, to May, 1998, we examined 12 patients with persistently detectable serum PSA levels and negative bone scintigraphy. At the time of diagnosis, an average 36 months had elapsed since prostatectomy. Digital rectal examination (DRE) and disease stage at the time of surgery were also considered. Patients age ranged 47 to 83 years (mean: 65). All patients underwent TRUS with a 7.5 MHz biplane probe; biopsy was performed with a 16 G cutting needle. TRUS findings were considered suspicious if the scan showed any unusual hypoechoic tissue adjacent to the bladder neck, in retrotrigone or peri-retroanastomotic site. In these cases a transperineal US-guided biopsy was performed.

RESULTS

The biopsy proved cancer in 10/12 cases (in 12 cases after two biopsies), showing a better diagnostic accuracy than DRE, which poorly distinguished postoperative changes from recurrent or residual cancer.

CONCLUSIONS

The early detection of recurrences after radical prostatectomy in patients with negative bone scintigraphy is feasible when the above examinations are performed in the same order as described: PSA levels, if altered, indicate the patients to be submitted to TRUS. The latter may be falsely negative in some cases because small recurrences may exhibit no findings at US, and therefore US-guided biopsy of peri-retro-anastomotic regions should be always performed too. The recurrence must be confirmed at histology because histologic findings help choose adjuvant treatment and/or radical irradiation.

Acute regulation of norepinephrine transport: I. protein kinase C-linked muscarinic receptors influence transport capacity and transporter density in SK-N-SH cells

Using SK-N-SH cells, we observe that muscarinic acetylcholine receptor activation by methacholine (MCh) rapidly and selectively diminishes l-NE transport capacity (Vmax) with little or no change in norepinephrine (NE) Km and without apparent effects on membrane potential monitored directly under current clamp. Over the same time frame, MCh exposure reduces the density of [3H]nisoxetine binding sites (Bmax) in intact cells but not in total membrane fractions, consistent with a loss of transport capacity mediated by sequestration of transporters rather than changes in intrinsic transport activity or protein degradation. Similar changes in NE transport and [3H]nisoxetine binding capacity are observed after phorbol ester (beta-PMA) treatment. Inhibition of PKC by antagonists and downregulation of PKC by chronic treatment with phorbol esters abolishes beta-PMA-mediated effects but produce only a partial blockade of MCh-induced effects. Neither muscarinic acetylcholine receptor nor PKC activation require extracellular Ca++ to diminish NET activity. In contrast, treatment of cells with the Ca++/ATPase antagonist, thapsigargin in Ca++-free medium, eliminates the staurosporine-insensitive component of MCh regulation. These findings were further corroborated by the ability of [1, 2-bis(o-amino-phenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)ester application in Ca++-free medium to abolish NET regulation by MCh. Although they may contribute to basal NET expression, we could not implicate CaMKII-, PKA- or nitric oxide-linked pathways in MCh regulation. Together, these findings 1) provide evidence in support of G-protein coupled receptor-mediated regulation of catecholamine transport, 2) reveal intracellular Ca++-sensitive, PKC-dependent and -independent pathways that serve to regulate NET expression and 3) indicate that the diminished capacity for NE transport evident after mAChR and PKC activation involves a redistribution of NET protein.

Patch-clamp and amperometric recordings from norepinephrine transporters: channel activity and voltage-dependent uptake

Transporters for the biogenic amines dopamine, norepinephrine, epinephrine and serotonin are largely responsible for transmitter inactivation after release. They also serve as high-affinity targets for a number of clinically relevant psychoactive agents, including antidepressants, cocaine, and amphetamines. Despite their prominent role in neurotransmitter inactivation and drug responses, we lack a clear understanding of the permeation pathway or regulation mechanisms at the single transporter level. The resolution of radiotracer-based flux techniques limits the opportunities to dissect these problems. Here we combine patch-clamp recording techniques with microamperometry to record the transporter-mediated flux of norepinephrine across isolated membrane patches. These data reveal voltage-dependent norepinephrine flux that correlates temporally with antidepressant-sensitive transporter currents in the same patch. Furthermore, we resolve unitary flux events linked with bursts of transporter channel openings. These findings indicate that norepinephrine transporters are capable of transporting neurotransmitter across the membrane in discrete shots containing hundreds of molecules. Amperometry is used widely to study neurotransmitter distribution and kinetics in the nervous system and to detect transmitter release during vesicular exocytosis. Of interest regarding the present application is the use of amperometry on inside-out patches with synchronous recording of flux and current. Thus, our results further demonstrate a powerful method to assess transporter function and regulation.

Fluctuation analysis of norepinephrine and serotonin transporter currents

Findings from an electrophysiological analysis of neurotransmitter transporters show that transmitter-induced currents are associated with these transporters: For charged transmitters, such as NE and 5-HT, a fraction of the total current is carried by the transmitter itself; however, the transmitter also induces an extra current in analogy to an ligand-gated ion channel. An additional conductance not discussed in this article is the so-called leak, in which neurotransmitter transporters generate an ionic current in the absence of transmitter. Using a combination of flux measurements, voltage clamp, and fluctuation analysis has shown that, for norepinephrine and serotonin transporters, the transmitter-induced current greatly exceeds the transmitter current. Such data can provide an exact measure of the ratio of these charge movements to transmitter translocation at the molecular level, suggesting new strategies to understand neurotransmitter transporters.

Relationship between chronic nasal obstruction and craniofacial growth: an experimental model

The aim of this paper was to verify if the growth of the nasomaxillary complex can be influenced by a purely functional alteration such as nasal obstruction, which was induced experimentally in a genetically controlled animal model. Sixty albino rats were employed. Twenty of them had the right nostril occluded by a synthetic resin; another twenty had both nostrils occluded; the other 20 were taken as control group. When the growth was completed, the rats were sacrificed and cephalometric analysis was carried out. Both treated groups showed a statistically significant reduction in overall weight and height, in the vertical development of the nasomaxillary complex and in the skullbase longitudinal axis. After discussing the literature on the subject, the authors conclude that normal craniofacial growth in the rat must somehow depend on physiological nasal breathing, which should therefore be considered of crucial importance.

Neuro- and ototoxicity of high-dose carboplatin treatment in poor prognosis ovarian cancer patients

BACKGROUND

Hematopoietic toxicity of high-dose carboplatin (HD-CBDCA) chemotherapy can be managed effectively with autologous blood cell support, but no conclusive data are available on its neuro- and ototoxicity.

PATIENTS AND METHODS

We determined the neuro- and ototoxicity of HD-CBDCA in 10 patients affected by advanced ovarian cancer. HD-CBDCA was delivered as 24-hour continuous infusion or as 5-day schedules. Each patient underwent an extended clinical and instrumental neurological and otological evaluation before, during and after treatment.

RESULTS

After HD-CBDCA only 1 patient had a clinically-evident peripheral neuropathy, while 3 additional patients had only distal paresthesias. Neurophysiological examination evidenced mild, although diffuse, sensory nerve impairment. Motor nerve impairment was also occasionally observed. All the sensory and motor pathological changes had a favorable course during the follow-up period. Ototoxicity was more severe than neurotoxicity and, in one case it was dose-limiting and audiologic impairment tended to remain constant also in the follow-up period.

CONCLUSIONS

HD-CBDCA treatment can be tolerated by most of the patients, but careful monitoring of neuro- and, especially, ototoxicity should be planned.

Regulated phosphorylation and trafficking of antidepressant-sensitive serotonin transporter proteins

Presynaptic serotonin (5-hydroxytryptamine, 5-HT) transporters (SERTs) mediate antidepressant-sensitive clearance of 5-HT following release. Although we have been aware for decades that SERT-mediated 5-HT clearance can be modulated by exogenous agents including serotonin-selective reuptake inhibitors, amphetamines, and cocaine, we have had little reason to speculate that SERT activity was actively controlled through endogenous pathways. Recent studies indicate that SERTs are likely to be trafficked to specific plasma membrane subdomains to achieve localized clearance of 5-HT, and that the number of SERTs resident in the plasma membrane is controlled through kinase- and phosphatase-linked pathways. In particular, roles for protein kinase C and phosphatase 2A become apparent through studies with enzyme activators and inhibitors in SERT-transfected cells, where SERT proteins are rapidly phosphorylated in parallel with transporter redistribution and loss of functional uptake capacity. Based on our findings, and the studies of others in native tissues and transfected cells, we propose a model whereby SERTs are organized in a macromolecular complex in the plasma membrane that may serve to locate reuptake activity near release sites. Although many elements of this model remain hypothetical, our findings suggest a much more dynamic picture of transporter-mediated 5-HT reuptake than typically described and suggest opportunities both for the development of new SERT regulatory agents and for the identification of regulatory pathways that may be compromised in mental illness.

Effects of DNA double-strand and single-strand breaks on intrachromosomal recombination events in cell-cycle-arrested yeast cells

Intrachromosomal recombination between repeated elements can result in deletion (DEL recombination) events. We investigated the inducibility of such intrachromosomal recombination events at different stages of the cell cycle and the nature of the primary DNA lesions capable of initiating these events. Two genetic systems were constructed in Saccharomyces cerevisiae that select for DEL recombination events between duplicated alleles of CDC28 and TUB2. We determined effects of double-strand breaks (DSBs) and single-strand breaks (SSBs) between the duplicated alleles on DEL recombination when induced in dividing cells or cells arrested in G1 or G2. Site-specific DSBs and SSBs were produced by overexpression of the I-Sce I endonuclease and the gene II protein (gIIp), respectively. I-Sce I-induced DSBs caused an increase in DEL recombination frequencies in both dividing and cell-cycle-arrested cells, indicating that G1- and G2-arrested cells are capable of completing DSB repair. In contrast, gIIp-induced SSBs caused an increase in DEL recombination frequency only in dividing cells. To further examine these phenomena we used both gamma-irradiation, inducing DSBs as its most relevant lesion, and UV, inducing other forms of DNA damage. UV irradiation did not increase DEL recombination frequencies in G1 or G2, whereas gamma-rays increased DEL recombination frequencies in both phases. Both forms of radiation, however, induced DEL recombination in dividing cells. The results suggest that DSBs but not SSBs induce DEL recombination, probably via the single-strand annealing pathway. Further, DSBs in dividing cells may result from the replication of a UV or SSB-damaged template. Alternatively, UV induced events may occur by replication slippage after DNA polymerase pausing in front of the damage.

High-level expression of RXRalpha and the presence of endogenous ligands contribute to expression of a peroxisome proliferator-activated receptor-responsive gene in hepatoma cells

Genes containing peroxisome proliferator-activated receptor (PPAR) binding sites are both inducible by peroxisome proliferators and expressed in a tissue-specific fashion. A PPAR-responsive reporter gene cotransfected with a PPARalpha expression vector was highly expressed in H4IIEC3 hepatoma cells. Addition of clofibrate resulted in a modest further induction of the reporter gene. In CV-1 cells, high expression of the reporter required the addition of clofibrate. H4IIEC3 cells had higher levels of retinoid X receptor (RXRalpha) than CV-1 cells; cotransfection of CV-1 cells with PPARalpha plus RXRalpha expression plasmids abolished the cell line difference in basal and clofibrate-stimulated expression of the reporter. Lipid extracts of hepatoma cells or of liver or kidney stimulated expression of the reporter; extracts of CV-1 cells were far less effective. Chromatographic analysis of these extracts revealed high levels of three fractions of lipid in liver and H4IIEC3 cells that were lower in CV-1 cells. We conclude that (1) in cells expressing high levels of both RXRs and PPARalpha, such as hepatocytes and kidney cells, these factors are constitutively active; (2) activators of PPARalpha may increase its ability to form heterodimers with RXRs when the latter are limiting; and (3) hepatoma cells, liver, and kidney contain lipid-extractable compounds capable of activating PPARalpha.

A countrywide programme of continuing professional development in Argentina. Argentine Society of Paediatrics, Subcommittee of Continuing Paediatric Education

The Argentinean Society of Paediatrics introduced in 1993 a continuing professional development (CPD) programme to raise standards of clinical practice. The aims of the project were to introduce a structured, distance learning programme accessible to all paediatricians in the country, but especially for those working far from centres of paediatric excellence. The programme is planned on an annual basis. It includes four activities: a written manual designed by a team of medical experts and educationalists comprising 12 topics; field work for participants; annual meetings in several locations in the country for discussion of the subjects; and an evaluation based on centrally designed multiple choice questions distributed by mail. In spite of a registration free of 90 Pounds a year, participation in the programme increased from 3357 in 1993 to 4126 in 1996, from a membership of 10 216 paediatricians in Argentina. The popularity of the programme may result from an appropriate interpretation of professional needs of paediatricians in Argentina, adequate organisational arrangements that reach all colleagues, including those working in remote areas, and a genuine motivation of paediatricians for participating in a learning process.

Bactericidal activity of chlorine dioxide against Escherichia coli in water and on hard surfaces

The efficacy of chlorine dioxide as a disinfectant was evaluated against cells of Escherichia coli ATCC 11229 in aqueous suspension and adhering to the surfaces of stainless steel AISI 304 and PVC. The concentrations tested ranged from 0.7 to 14 mg/liter; the exposure times investigated were 30 s and 1, 2, 4, and 8 min. When the bacteria were suspended in water with 1.4 mg/liter of chlorine dioxide, a 10(5)-fold reduction of the initial viable count occurred within 30 s; when cells were attached to the steel surface, the same rate of inactivation took place only after 6 min with 7 mg/liter or 4 min with 14 mg/liter of chlorine dioxide. A 5-log reduction was not obtained when organisms were adhered to polyvinyl chloride (PVC). Scanning electron microscope micrographs of contaminated surfaces revealed that the PVC was very rough with pores much larger in diameter than the cells. Time values determining a 90% reduction of the E. coli population (90% killing time) were calculated for each concentration of disinfectant tested in suspension and on the steel surface. If the same experimental conditions were strictly adopted, linear functions of the log of bacterial inactivation could be plotted (log 90% killing time versus log concentration of disinfectant). This work showed that results obtained with suspension tests could not be used to estimate disinfection of hard surfaces.

Inhibition of cholinesterase-associated aryl acylamidase activity by anticholinesterase agents: focus on drugs potentially effective in Alzheimer's disease

The potency of a series of anticholinesterase (anti-ChE) agents and serotonin-related amines as inhibitors of the aryl acylamidase (AAA) activity associated with electric eel acetylcholinesterase (AChE) (EC 3.1.1.7) and horse serum butyrylcholinesterase (BuChE) (EC 3.1.1.8) was examined and compared with the potency of the same compounds as ChE inhibitors. Neostigmine, physostigmine, BW 284C51, (+/-)-huperzine A, E2020, tacrine, edrophonium and heptyl-physostigmine were, in that order, the most potent in inhibiting eel AChE-associated AAA activity, their inhibitor constant (Ki) values being in the range 0.02-0.37 microM. The rank order of the same compounds as AChE inhibitors basically paralleled that of AAA, although they were in general stronger on AChE (Ki = 0.001-0.05). The peripheral anionic site inhibitors propidium and gallamine were inactive on AChE-associated AAA. Serotonin and its derivatives were slightly stronger on AAA (Ki = 7.5-30 microM) than on AChE (Ki = 20-140 microM). Tacrine (IC50 = 0.03 microM), diisopropylfluorophosphate (IC50 = 0.04 microM), heptyl-physostigmine (IC50 = 0.11 microM), physostigmine (IC50 = 0.15 microM) and tetra-iso-propylpyrophosphoramide (iso-OMPA) (IC50 = 0.75 microM) were the most potent in inhibiting horse serum BuChE-associated AAA activity. Serotonin and related amines were very weak on BuChE-associated AAA activity. These results indicate that the inhibitory potencies of the active site anti-ChE agents on the AAA activity associated with eel AChE and horse serum BuChE are closely correlated with their action on the respective ChE. In addition, the efficacy of tacrine, E2020, heptyl-physostigmine and (+/-)-huperzine A in the treatment of Alzheimer's disease is unlikely to be related to the action of these drugs on ChE-associated AAA.

Tricyclic heteroaromatic systems. Pyrazolo[3,4-c]quinolin-4-ones and pyrazolo[3,4-c]quinoline-1,4-diones: synthesis and benzodiazepine receptor activity

Some pyrazolo[3,4-c]quinoline-4-ones 1-14 and pyrazolo[3,4-c]-quinoline-1,4-diones 15-17 were prepared and biologically evaluated for their binding at the benzodiazepine receptor (BZR) in rat cortical membranes. The moderate binding activity of 1-5, 7, 9-10, 13 is attributable to the lack of the optional proton acceptor at position-1, while the inactivity of the 1,4-dione derivatives 15-17 is due to the lack of the essential proton acceptor at position-3. These conclusions confirm the validity of our proposed pharmacophoric model.

Tricyclic heteroaromatic systems. 1,2,4-triazolo[4,3-a]quinoxalines and 1,2,4-Triazino[4,3-a]quinoxalines: synthesis and central benzodiazepine receptor activity

Some 1,2,4-triazolo[4,3-a]quinoxalines 1-10, and 1,2,4-triazino[4,3-a]quinoxalines 11-12 were prepared and biologically evaluated for their binding at the benzodiazepine receptor (BZR) in rat cortical membranes. The BZR affinity of 1-10 demonstrates that the presence of a proton acceptor at position-1 is important for the potency of a BZR ligand. On the other hand, the BZR inactivity of the 1,2,5-trione derivatives 11-12 shows that the right collocation of the essential L2 lipophilic substituent is of paramount importance for receptor-ligand interaction.

Salivary nitrate, nitrite and N-nitroso compounds in patients with cancer of the upper aerodigestive tract

N-nitroso compounds are carcinogens that can be ingested directly or synthesized from nitrites and nitrates. The possible role of N-nitroso compounds in the induction of upper aerodigestive tract tumours was considered in a case-control study conducted in the Valle d'Aosta, an Italian region with a high incidence of these neoplasms. Nitrate, nitrite, labile and stable N-nitroso compounds were analysed in the saliva of 36 patients with cancers of the upper aerodigestive tract and 23 healthy individuals. After allowing for tobacco, salivary nitrate, nitrite and N-nitroso compounds were not associated with an increased risk of upper aerodigestive tract cancers. The odds ratio for continuous units of total N-nitros compounds was 0.99 (95% confidence interval 0.9-1.1). Thus, salivary nitrate, nitrite and N-nitroso compounds might not be suitable markers for the assessment of the risk of cancer of the upper aerodigestive tract, although a role for N-nitroso compounds cannot be excluded.

Antinociceptive profile of 3-alpha-tropanyl 2-(4-Cl-phenoxy)butyrate (SM-21) [corrected]: a novel analgesic with a presynaptic cholinergic mechanism of action

The antinociceptive effect of (+/-)-3-alpha-tropanyl 2-(4-Cl-phenoxy)butyrate [corrected] (SM-21) (10-40 mg kg(-1) s.c., 10-30 mg kg(-1) i.p., 20-60 mg kg(-1) p.o., 3-20 mg kg(-1) i.v. and 5-20 microg per mouse i.c.v.) was examined in rodents and guinea pigs by using the hot-plate, abdominal constriction, tail-flick and paw-pressure tests. The antinociception produced by (+/-)-SM-21 was prevented by atropine, pirenzepine and hemicholinium-3 but not by quinpirole, R-(alpha)-methylhistamine, [1-[2(methylsufonyl)amino]ethyl]-4-piperidinyl]methyl-5-floro++ +-2-methoxy-1H-indole-3-carboxylate hydrochloride, N6-cyclopentyladenosine, 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine hydrobromide, naloxone, 3-aminopropyl-diethoxy-methyl-phosphinic acid or reserpine. On the basis of the above data, it can be postulated that (+/-)-SM-21 exerted an antinociceptive effect mediated by a central potentiation of cholinergic transmission. Affinity profiles of (+/-)-SM-21 for muscarinic receptor subtypes, determined by functional studies (rabbit vas deferens for M1, guinea pig atrium for M2, guinea pig ileum for M3 and immature guinea pig uterus for putative M4) have shown a selectivity ratio M2/M1 of 4.6 that, although very low, might be responsible for the antinociception induced by (+/-)-SM-21 through an increase in ACh extracellular levels. In the antinociceptive dose range, (+/-)-SM-21 did not impair mouse performance evaluated by the rota-rod and hole-board tests.

Drosophila serotonin transporters have voltage-dependent uptake coupled to a serotonin-gated ion channel

Serotonin (5HT) transporters (SERTs) couple to existing ion gradients to transport 5HT into presynaptic terminals. In mammalian SERTs, the transport cycle is reported as electroneutral, with a translocation of zero net charge, and 5HT uptake is independent of membrane voltage. Yet mammalian SERTs exhibit 5HT-induced currents, and Drosophila SERTs (dSERTs) show voltage-dependent uptake. Thus, the relationship between uptake and current remains controversial; furthermore, the number of 5HT molecules translocated per ion channel event is unknown. To investigate this, we have used heterologous expression of cloned dSERTs to measure 5HT flux and dSERT currents concurrently under voltage clamp, and we have used fluctuation analysis to measure the size of the elementary ionic events in the same cells. RNA-injected Xenopus oocytes accumulate 5HT, and paroxetine or desipramine inhibit this uptake. RNA-injected oocytes also display paroxetine-sensitive 5HT-induced currents and 5HT-independent leak currents. Na replacement decreases the uptake and the induced currents. 5HT-induced current and 5HT uptake both increase at negative potentials, where 5HT carries approximately 5% of the induced current. Recently, several groups have reported similar phenomena for other transporters, in which transmitter-induced currents exceed the predictions of coupled transport. We now provide evidence that in dSERT, approximately 500 5HT molecules are translocated per channel opening, which, at -20 mV, carries approximately 10,000 electronic charges. These data support a model in which 500 SERT cycles occur for each 5HT-induced channel opening or a model in which 500 5HT molecules and 10,000 electronic charges pass through a common pore.