Improving medication administration through an enhanced occurrence reporting system

Accurate data about medication errors are essential to prevention efforts. A multidisciplinary team at Bon Secours Hospital trialed an innovative method of reporting medication errors. It increased the number of reported medication errors six times compared with the same time period for the previous year on the pilot unit. It also saved time for the person reporting the error. The continuous quality improvement methodology was used to implement the new process.

High level arsenite resistance in Leishmania tarentolae is mediated by an active extrusion system

Leishmania tarentolae cells selected for resistance to the oxyanions pentavalent or trivalent antimonials or to trivalent arsenicals exhibited cross-resistance to the other oxyanions. The basis for resistance in these mutants was studied by transport experiments using radioactive arsenite. All mutants exhibiting high level resistance to arsenite showed a marked decrease in the steady-state accumulation of arsenite. Decreased accumulation was also observed in antimonials-resistant mutants cross-resistant to various concentrations of arsenite. Cells depleted of endogenous energy reserves with metabolic inhibitors were loaded with radioactive arsenite; following addition of glucose, rapid efflux of arsenite was observed from arsenite mutant cells. Mutants resistant to high levels of arsenicals exhibited amplification of the P-glycoprotein related gene ltpgpA or of a linear amplicon of unknown function. However, the efflux-mediated arsenite resistance did not correlate with the amplification of the ltpgpA gene or with the presence of the linear amplicon. The calcium channel blocker verapamil and arsenite act in synergy in cells exhibiting the efflux system. Overall the oxyanion efflux system in Leishmania shares several properties with other resistance efflux systems mediated by transporters.

Nuclear localization of the PEP protein tyrosine phosphatase

PEP is an intracellular protein tyrosine phosphatase expressed primarily by cells of hematopoietic origin that can be divided structurally into a catalytic domain and a large carboxy-terminal domain. The carboxy-terminal domain is enriched in proline, glutamic acid, serine, and threonine residues (PEST sequences) and contains a nonperfect tandem repeat sequence enriched in proline residues and a carboxy terminus enriched in basic amino acids. Here we show that PEP is diffusely expressed in lymphoid tissues, consistent with expression by many different cell types. Analysis of the PEP protein identifies a nuclear localization sequence within the extreme carboxy terminus. Transfer of 18 amino acids from the carboxy terminus of PEP to beta-galactosidase conferred nuclear localization, indicating that this sequence was sufficient for nuclear localization. Proteins enriched in PEST sequences are often rapidly degraded. However, pulse-chase analysis indicates that PEP has a half-life of greater than 5 h.

Autonomous replication of bacterial DNA plasmid oligomers in Leishmania

Extrachromosomal amplicons are frequently observed in drug-resistant Leishmania. A dominant selectable marker, the neomycin phosphotransferase gene, was introduced by gene targeting in a circular amplicon derived from the H locus of Leishmania in a mutant cell. This recombinant amplicon was isolated and transfected in a wild-type cell. The amplicon was kept in the wild-type cells, provided the selective pressure was maintained, suggesting that it was capable of autonomous replication. Novel Leishmania expression vectors suited for stable transfections were made to isolate, by a high transformation assay, the putative origin of replication in the amplicons. However, these plasmids, which did not contain a single Leishmania nucleotide, were found as extrachromosomal circular oligomers in Leishmania transfectants. Their relative stability, in addition to changes in their methylation pattern, indicated that these plasmids were most likely replicating. No specific sequences seem to be required for replication (and expression) in Leishmania, therefore precluding the isolation of origins of replication by genetic transformation.

Contribution of the Leishmania P-glycoprotein-related gene ltpgpA to oxyanion resistance

Oxyanions in the form of pentavalent antimony compounds are currently the drug of choice for treating leishmaniasis. Leishmania mutants resistant to high concentrations of the oxyanion arsenite were obtained in a stepwise selection procedure. Amplification of the H locus P-glycoprotein-related gene ltpgpA, as part of extrachromosomal circles, is a frequent event in arsenite-resistant cells, but was observed only in cells resistant to high concentrations of the metalloid salts. Revertants grown in the absence of the drug lost their ltpgpA-containing amplicon and part of their resistance. The results of previous transfection experiments in Leishmania had suggested that ltpgpA is only involved in low level resistance to arsenite and antimonite. The results of this study using transfection of ltpgpA alleles isolated from arsenite-resistant mutants or of whole circular amplicons containing ltpgpA demonstrate clearly that this P-glycoprotein-related gene is involved in low level resistance to oxyanions, including the pentavalent antimony-containing drug Pentostam. By site-directed mutagenesis, the LtpgpA protein was shown to require an intact nucleotide-binding site to confer arsenite resistance. Under the experimental conditions used, decreased accumulation of the 73AsO2- drug was not observed in the ltpgpA transfectants. One possibility is that LtpgpA-mediated arsenite resistance could result from sequestration of the toxic anion in an intracellular compartment. The results indicate that despite the fact that ltpgpA amplification is a frequent event in oxyanion-resistant mutants, it contributes only slightly to the overall resistance.

Changes in folate and pterin metabolism after disruption of the Leishmania H locus short chain dehydrogenase gene

The short chain dehydrogenase gene ltdh, which is derived from the H locus of Leishmania, confers high level resistance to the dihydrofolate reductase inhibitor methotrexate via a novel mechanism. Resistance is correlated with LTDH overproduction. High level resistance of ltdh transfectants was observed even in poor media where reduced folates are essential for the synthesis of thymidylate precursors. The ltdh transfectants were also capable of growing for several passages, at slightly reduced rates, in unsupplemented folate-deficient medium (fdDME-L), unlike the wild-type cells that could grow only in fdDME-L if supplemented with various folates or pterins. An homozygous ltdh mutant was obtained by gene targeting. This mutant became hypersensitive to methotrexate, but unlike wild-type cells, methotrexate toxicity could not be circumvented by the addition of thymidine. Although the homozygous mutant was capable of growing in fdDME-L supplemented with folate derivatives, it lost its ability to thrive in fdDME-L supplemented with pterins. Our results support the model in which LTDH is a key enzyme responsible for the conversion of a pterin derivative into an essential cofactor. This essential cofactor can also be converted into reduced folates at sufficient levels for growth when LTDH is overproduced, rendering dihydrofolate reductase dispensable. The novelty and uniqueness of LTDH opens the possibility of developing parasite-specific inhibitors.

Easy adaptation of protein structure to sequence

An investigation into the conservation of coarse, medium and fine grain structural properties has been performed over a data set of 175 protein tertiary structures in 34 different families, each characterized by a common core fold and a library of conserved sites formed for each family. It is shown that, while the conservation of coarse and medium grain properties correlates to the structural deviation between the proteins, fine grain properties are poorly conserved except in functional sites. This flexibility in fine grain properties suggests that folding can be viewed as an optimization process whereby side chains have freedom to position themselves as best as possible given environmental conformational constraints and that given a basic framework, the local structure is able to adapt easily to sequence variation. The conserved cores of the 34 families are used to estimate a minimal core size of 35% of the fold, consistent with buried residue considerations. Finally, conservation in side chain chi 1 torsion angles is combined with structural deviation, sequence deviation and resolution to suggest a set of example structure pairs suitable for testing automatic homology modelling programs.

Channels for ions and amino acids in kidney cultured cells (MDCK) during volume regulation

A cell line from canine kidney (MDCK) was studied in hypotonic conditions to determine the transport mechanisms involved during regulatory volume decrease (RVD). It was found that RVD was related to a loss of K+, Cl- and amino acids. Membrane potential measurements during RVD have shown a hyperpolarization followed by a depolarization, implying that ion fluxes were probably occurring through channels. Quinine was found to inhibit RVD, the ion fluxes and the amino acid losses. A long preincubation in Ca(++)-free EGTA medium had no effect on RVD in cells exposed to the hypotonic medium. Single channel experiments with the patch clamp technique have shown that cell swelling rapidly activates K+ channels and, after a 30 sec delay, Cl- channels. The K+ channel was highly selective and had a linear I-V curve with a conductance of 25 pS. The Cl- channel was an outward rectifier with conductances of 63 and 26 pS. It was not very selective; replacing Cl- with NO3- did not change the I-V curve and did not affect RVD. The amino acid losses during RVD were studied with HPLC. It was found that three of them, glutamate, taurine and glycine, had large concentrations and were lost at different rates. Their fluxes during RVD depended linearly on their external concentrations, meaning that the transport process was diffusional. Single channel measurements with glutamate, aspartate or taurine in place of Cl- have shown that these amino acid losses occurred through the Cl- channel.

Channels for amino acids and metabolites activated by cell volume regulation

Cell volume regulation after swelling has been widely demonstrated and attributed to a loss of KCl in the external medium. But it was also shown in a few cell types that organic cell osmolytes, particularly amino acids, were contributing to volume regulation. These effluxes occurred through a diffusional type of transport. Electrophysiological experiments with patch-clamp electrodes have demonstrated the activation of selective K+ channels in parallel with chloride channels during volume regulation. These chloride channels appear much less selective for a large variety of anions. Many cell osmolytes, not only negatively charged but also neutral ones, are permeable through these channels. When the cells swell in hypotonic media, they loose amino acids and other neutral and negative osmolytes through these channels. It is possible that these channels in astrocytes play an important role in pathological conditions, e.g. brain ischemia, by releasing glutamate in the external medium and contributing to the damaging effect of glutamate in ischemia.

Lidar-inversion technique based on total integrated backscatter calibrated curves

The integrated backscatter signal from a smoke cloud contained in a chamber is studied as function of the measured concentration. An analysis based on the total backscattered signal leads to the determination of calibration curves specific to the material and to the lidar system. This procedure leads to a lidar inversion technique based on a calibrated total integrated backscatter curve. The limitation of the technique is discussed in terms of the maximum optical depth permitted for acceptable results.

Frequent amplification of a short chain dehydrogenase gene as part of circular and linear amplicons in methotrexate resistant Leishmania

The H locus of Leishmania codes for a short chain dehydrogenase gene (ltdh) that is involved in antifolate resistance. Leishmania tarentolae cells, selected in a step by step fashion for resistance to the antifolate methotrexate (MTX), frequently amplified ltdh in response to drug selection. Both circular and linear extrachromosomal amplicons were generated de novo from the chromosomal H locus and several contained inverted duplications. At least four different rearrangement points were used during the formation of amplicons, with one of them used preferentially. All mutants highly resistant to MTX, whether or not they have the H locus amplified, showed a decreased steady-state accumulation of MTX. Nevertheless, two types of transport mutants were clearly discernable. In the first type, accumulation was reduced four to five-fold, whereas in the second class of mutants, accumulation was reduced more than 50-fold. The ltdh gene was amplified in all the mutants with the transport mutation of the first type, but not in all the mutants with a more pronounced decrease in the steady-state accumulation of MTX. Both types of transport mutation, leading to the reduction in MTX accumulation, arose early during the selection process and were stable even when cells were grown in absence of the drug for prolonged period.

[Are day care children often absent because of illness?]

Over an 18-month period, we observed 759 children attending eight day care centres in the Quebec City area to determine the rate of absenteeism due to illness in day care centres. 481 children were absent for a mean duration of 4.1 days. The absenteeism rate was 5.6 days out of a possible 1 000 days of attendance and did not vary with day care centre or age.

Frusemide-induced diabetes mellitus in insulin pretreated rabbits as an experimental model

Single dose of frusemide 0.1 mg/kg orally was administered in 10 rabbits pretreated with soluble insulin 4 IU intravenously. Induction of diabetes after 24 h was confirmed by an increase in blood sugar and glucosylated haemoglobin and a decrease in serum insulin levels. Ten diabetic rabbits which received only frusemide without insulin pretreatment were used as controls, whereas equal number of insulin-pretreated rabbits receiving hydrochlorothiazide 250 mg/kg orally served as the positive control group. All biochemical parameters remained unaltered in the frusemide-treated test group as well as the positive control group after two weeks. The pancreatotoxic effect of frusemide may induce a stable hyperglycaemic state in rabbits which could lead to a useful diabetic model.

Ocimum sanctum Linn--a study on gastric ulceration and gastric secretion in rats

The antiulcerogenic property of Ocimum sanctum Linn (Tulsi) was studied in pyloric ligated and pyloric ligated & aspirin treated rats. The extract of OSL reduced the ulcer index, free & total acidity on acute and chronic administration. Seven days pretreatment with the drug increased the mucous secretion also. It may be concluded that OSL extract has antiulcerogenic property against experimental ulcers, and it is due to its ability to reduce acid secretion and increase mucous secretion.

Anion channels for amino acids in MDCK cells

Large losses of amino acids by diffusion were previously observed in Madin-Darby canine kidney (MDCK) cells during volume regulation. Also, an outward rectifying anion channel was activated. Because this channel was not selective among anions, it was suggested that it could be permeable to amino acids. Its permeability to aspartate, glutamate, and taurine was studied using the patch-clamp technique in the inside-out configuration. Solutions containing 500 mM aspartate or glutamate were used on the cytoplasmic side of excised patches to detect single-channel currents carried by these anions. Permeability ratios were estimated in two different ways: 1) from the shift in reversal potential of current-voltage curves after anion replacement in the bath solution and 2) from comparisons of amplitudes of single-channel currents carried by tested anions and chloride, respectively. The values of aspartate-to-chloride and glutamate-to-chloride permeability ratios obtained with both methods were quite consistent and were of the order of 0.2 for both amino acids. Taurine in solutions at physiological pH 7.3 is a zwitterionic molecule and bears no net charge. To detect single-channel currents carried by taurine, solutions containing 500 mM taurine at pH 8.2 were used in inside-out experiments. Under these conditions 120 mM of negatively charged taurine was present in the solutions bathing the cytoplasmic side of excised patches. The permeability ratio estimated from the shift in reversal potential was 0.75. These results showed that some of the organic compounds released by cells during regulatory volume decrease could diffuse through this outwardly rectifying anionic channel.

Activation of amino acid diffusion by a volume increase in cultured kidney (MDCK) cells

When MDCK cells are cultured in MEM, they maintain a high concentration of three amino acids: glutamate (25 mM), taurine (19 mM) and glycine (9 mM). With incubation of the cells in hypotonic media, the contents of these amino acids measured by HPLC are reduced in different time courses: taurine decreases most rapidly, followed by glutamate and glycine. All these losses are Na+ independent. To determine the transport mechanism activated by the hypotonic media, increasing external concentrations reaching 60 mM for nine different amino acids in Na(+)-free media were tested separately. For the five neutral (zwitterionic) amino acids, taurine, glycine, alanine, phenylalanine and tryptophan, cell contents increased linearly with external concentrations in hypotonic media, whereas in isotonic media only a slight rise was observed. The two anionic amino acids, glutamate and aspartate, were also increased linearly with their external concentrations in hypotonic media, but the changes were lower than those found for neutral amino acids. The presence of a negative membrane potential was responsible for this behavior since, using a K+ hypotonic medium which clamps the potential to zero, the glutamate content was found to increase linearly with an amplitude similar to the one observed for neutral amino acid. When external concentrations of two cationic amino acids, arginine and lysine, were increased in hypotonic media, only a small change, similar to that in isotonic media, was observed. These results indicate that a diffusion process for neutral and anionic amino acids is activated by a volume increase and it is suggested that an anion channel is involved.

A novel antifolate resistance gene on the amplified H circle of Leishmania

In several Leishmania spp., resistance to methotrexate and other drugs is often associated with amplification of the chromosomal H region in the form of extrachromosomal H circles. We report here that the H circle of Leishmania tarentolae contains an 867 bp open reading frame, ltdh, which mediates high levels of resistance to methotrexate and other antifolates, after transfection. The predicted amino acid sequence of the ltdh gene product has significant similarities to a family of short-chain dehydrogenases, enzymes that are involved in several oxido-reduction reactions in a wide range of organisms. To resist antifolates, Leishmania amplifies the ltdh gene as part of the H circle. We propose that LTDH might be involved in an alternative pathway for the synthesis of reduced folates and that ltdh overproduction represents a novel mechanism for resistance to antifolates. Our results support the hypothesis that the H region of the Leishmania genome contains several drug resistance genes and that preferential amplification of this region has evolved as a defense mechanism against cytotoxic drugs.

Coinduction of hsp27 phosphorylation and drug-resistance in chinese-hamster cells

Treatments of Chinese hamster fibroblasts with A23187, 2-deoxyglucose, tunicamycin, beta-mercaptoethanol or glucosamine induce an increase in cell resistance to doxorubicin and VM-26 that attains a maximum after 8 h of treatment. We tested the possibility that HSP27, a heat shock protein whose overexpression in cells was shown to confer thermoresistance and chemoresistance, might also be associated with this acquisition of drug resistance. [H-3]leucine incorporation and immunoblot analyses showed that the increased resistance was not accompanied by the synthesis or accumulation of HSP27 or other heat shock proteins. However, drug resistance promoting agents all stimulated protein kinase activities that phosphorylated HSP27 in vitro and stimulated incorporation of P-32 into HSP27 in vivo. HSP27 is thought to exert in unstressed cells functions linked with growth signal pathways. It is suggested that stimulation of HSP27 phosphorylation may modulate a protective function associated with the maintenance of signal transduction homeostasis.

Remote biodetection performance of a pulsed monostatic lidar system

A monostatic pulsed lidar system called the laser cloud mapper was operated at the lidar range facility at the Defence Research Establishment Valcartier for 2 weeks during the autumn of 1990 to determine and assess its sensitivity for the remote detection of airborne biological organisms. The methodology called for the measurement of the depolarization of the lidar return signals that were backscattered from a biological aerosol cloud introduced into a large outdoor aerosol chamber. The test aerosol was produced by aerosolization of bacterial spores suspended in tap water; the relative concentration (by volume) of the bacterial material in tap water was varied from 1.0 to 0.001%. The detection performance of the laser cloud mapper is characterized through the ordered statistics of the depolarization ratio (e.g., sample distribution functions, quantile-quantile plots, and shift functions). In addition, a robust detection statistic based on the a-trimmed mean has been considered and the bootstrap-resampling method has been utilized to estimate uncertainties or confidence limits for this statistic. The receiver-operating characteristic curves of the laser cloud mapper (i.e., the probability of detection, <p>P</p>(D), versus the probability of false alarm, P(FA)) for both the empirical distribution function and the linearly thresholded, trimmed mean-level detectors are presented as a function of the source concentration of the test aerosol.

Carboxylic acid replacement structure-activity relationships in suosan type sweeteners. A sweet taste antagonist. 1

N-(4-Cyanophenyl)-N'-(2-carboxyethyl)urea (2), an analogue of suosan [1,N-(4-nitrophenyl)-N'-(2-carboxyethyl)urea], is a known high-potency sweetener derived from beta-alanine. Sulfonic and phosphonic acid analogues of 2 were prepared to develop structure-activity relationships through modification of the carboxylic acid region of this family of sweeteners. Neither of the carboxylic acid replacements resulted in sweet analogues. However, we found that N-(4-cyanophenyl)-N'-[(sodiosulfo)methyl]urea (7) is an antagonist of the sweet taste response. The bitter taste response to caffeine, quinine, and naringin was also antagonized. Antagonist 7 was found to inhibit the sweet taste perception of a variety of sweeteners. Antagonist 7 had no effect on the sour or salty taste response.