Carnitine revisited: potential use as adjunctive treatment in diabetes

AIMS/HYPOTHESIS

This study examined the efficacy of supplemental L: -carnitine as an adjunctive diabetes therapy in mouse models of metabolic disease. We hypothesised that carnitine would facilitate fatty acid export from tissues in the form of acyl-carnitines, thereby alleviating lipid-induced insulin resistance.

MATERIALS AND METHODS

Obese mice with genetic or diet-induced forms of insulin resistance were fed rodent chow +/- 0.5% L: -carnitine for a period of 1-8 weeks. Metabolic outcomes included insulin tolerance tests, indirect calorimetry and mass spectrometry-based profiling of acyl-carnitine esters in tissues and plasma.

RESULTS

Carnitine supplementation improved insulin-stimulated glucose disposal in genetically diabetic mice and wild-type mice fed a high-fat diet, without altering body weight or food intake. In severely diabetic mice, carnitine supplementation increased average daily respiratory exchange ratio from 0.886 +/- 0.01 to 0.914 +/- 0.01 (p < 0.01), reflecting a marked increase in systemic carbohydrate oxidation. Similarly, under insulin-stimulated conditions, carbohydrate oxidation was higher and total energy expenditure increased from 172 +/- 10 to 210 +/- 9 kJ kg fat-free mass(-1) h(-1) in the carnitine-supplemented compared with control animals. These metabolic improvements corresponded with a 2.3-fold rise in circulating levels of acetyl-carnitine, which accounts for 86 and 88% of the total acyl-carnitine pool in plasma and skeletal muscle, respectively. Carnitine supplementation also increased several medium- and long-chain acyl-carnitine species in both plasma and tissues.

CONCLUSIONS/INTERPRETATION

These findings suggest that carnitine supplementation relieves lipid overload and glucose intolerance in obese rodents by enhancing mitochondrial efflux of excess acyl groups from insulin-responsive tissues. Carefully controlled clinical trials should be considered.

Cryosurgery for resectable and unresectable hepatic metastases from colorectal cancer

AIMS

Hepatic cryosurgery is useful for patients with hepatic metastases from colorectal cancer confined to the liver but considered unresectables because of the number and location of lesions. While encouraging results were reported following cryosurgery for unresectable liver metastases we considered particularly valuable to examine the safety and effectiveness of cryosurgery in patients with resectable and unresectable metastases from colorectal cancer.

METHODS

Between January 1997 and September 2005, 53 patients with liver metastases from colorectal cancer underwent hepatic cryosurgery at our institution. Hepatic metastases were resectable in 31 (58.5%) patients and unresectable in 22 (41.5%).

RESULTS

A total of 136 liver metastases were treated in 53 patients. The size of treated lesions ranged from 0.5 to 10 cm (mean 2.7). There were 2 postoperative deaths (3.8%) from massive bleeding and from cryoshock. The overall morbidity rate was 66%. The median follow-up was 24.8 months. The overall survival rate at 12 months was 86.1%, at 48 months it was 27%. No significant difference was found between survival rates in patients with resectable or unresectable metastases. Among 31 patients with resectable liver metastases 7 (22.6%) patients developed recurrence at the site of cryosurgery.

CONCLUSION

Survival rates were comparables between patients with resectable and unresectable metastases but a high complication rate and a substantial rate of local recurrence following cryosurgery should caution against its use to treat resectable disease.

Real-time MR diffusion tensor and Q-ball imaging using Kalman filtering

Magnetic resonance diffusion imaging (dMRI) has become an established research tool for the investigation of tissue structure and orientation. In this paper, we present a method for real time processing of diffusion tensor and Q-ball imaging. The basic idea is to use Kalman filtering framework to fit either the linear tensor or Q-ball model. Because the Kalman filter is designed to be an incremental algorithm, it naturally enables updating the model estimate after the acquisition of any new diffusion-weighted volume. Processing diffusion models and maps during ongoing scans provides a new useful tool for clinicians, especially when it is not possible to predict how long a subject may remain still in the magnet.

Optimized diffusion gradient orientation schemes for corrupted clinical DTI data sets

OBJECT

A method is proposed for generating schemes of diffusion gradient orientations which allow the diffusion tensor to be reconstructed from partial data sets in clinical DT-MRI, should the acquisition be corrupted or terminated before completion because of patient motion.

MATERIALS AND METHODS

A general energy-minimization electrostatic model was developed in which the interactions between orientations are weighted according to their temporal order during acquisition. In this report, two corruption scenarios were specifically considered for generating relatively uniform schemes of 18 and 60 orientations, with useful subsets of 6 and 15 orientations. The sets and subsets were compared to conventional sets through their energy, condition number and rotational invariance. Schemes of 18 orientations were tested on a volunteer.

RESULTS

The optimized sets were similar to uniform sets in terms of energy, condition number and rotational invariance, whether the complete set or only a subset was considered. Diffusion maps obtained in vivo were close to those for uniform sets whatever the acquisition time was. This was not the case with conventional schemes, whose subset uniformity was insufficient.

CONCLUSION

With the proposed approach, sets of orientations responding to several corruption scenarios can be generated, which is potentially useful for imaging uncooperative patients or infants.

[Systemic learning planification for residents during the 6-month pediatric radiology training]

Diagnostic Radiology and Medical Imaging residents of French University Hospitals benefit from a wide array of learning tools. However, the professors' clinical workload, lack of sufficient proper formal training, lack of practical applicability of existing standards, and absence of rigorous assessment during the specialized training, reduce their very good quality formation to the level of accidental learning. This study originates from the need to apply a systemic planification of learning activities to the French residents' formal training curriculum, such as the one originally designed and applied within the Quebec educational system. This presentation also benefits from the recent introduction of the CanMEDS 2000 objectives by the Royal College of Physicians and Surgeons of Canada, in order to design an adapted version for the professional and academic activities of French radiologists. Needless to say this work will respect the outlined systematic planning of any learning activity: learning requirements, definition of learning objectives, selection of learning methods, assessment of the participants' achievement of these objectives, and evaluation of the learning activity itself.

Assessment of the early organization and maturation of infants' cerebral white matter fiber bundles: A feasibility study using quantitative diffusion tensor imaging and tractography

The human infant is particularly immature at birth and brain maturation, with the myelination of white matter fibers, is protracted until adulthood. Diffusion tensor imaging offers the possibility to describe non invasively the fascicles spatial organization at an early stage and to follow the cerebral maturation with quantitative parameters that might be correlated with behavioral development. Here, we assessed the feasibility to study the organization and maturation of major white matter bundles in eighteen 1- to 4-month-old healthy infants, using a specific acquisition protocol customized to the immature brain (with 15 orientations of the diffusion gradients and a 700 s mm(-2)b factor). We were able to track most of the main fascicles described at later ages despite the low anisotropy of the infant white matter, using the FACT algorithm. This mapping allows us to propose a new method of quantification based on reconstructed tracts, split between specific regions, which should be more sensitive to specific changes in a bundle than the conventional approach, based on regions-of-interest. We observed variations in fractional anisotropy and mean diffusivity over the considered developmental period in most bundles (corpus callosum, cerebellar peduncles, cortico-spinal tract, spino-thalamic tract, capsules, radiations, longitudinal and uncinate fascicles, cingulum). The results are in good agreement with the known stages of white matter maturation and myelination, and the proposed approach might provide important insights on brain development.

Detection and identification of bacteria in a juice matrix with Fourier transform-near infrared spectroscopy and multivariiate analysis

The use of Fourier transform-near infrared (FT-NIR) spectroscopy combined with multivariate pattern recognition techniques was evaluated to address the need for a fast and senisitive method for the detection of bacterial contamination in liquids. The complex cellular composition of bacteria produces FT-NIR vibrational transitions (overtone and combination bands), forming the basis for identification and subtyping. A database including strains of Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Bacillus cereus, and Bacillus thuringiensis was built, with special care taken to optimize sample preparation. The bacterial cells were treated with 70% (vol/vol) ethanolto enhance safe handling of pathogenic strains and then concentrated on an aluminum oxide membrane to obtain a thin bacterial film. This simple membrane filtration procedure generated reproducible FT-NIR spectra that allowed for the rapid discrimination among closely related strains. Principal component analysis and soft independent modeling of class analogy of transformed spectra in the region 5,100 to 4,400 cm(-1) were able to discriminate between bacterial species. Spectroscopic analysis of apple juices inoculated with different strains of E. coli at approximately 10(5) CFU/ml showed that FT-NIR spectralfeatures are consistent with bacterial contamination and soft independent modeling of class analogy correctly predicted the identity of the contaminant as strains of E. coli. FT-NIR in conjunction with multivariate techniques can be used for the rapid and accurate evaluation of potential bacterial contamination in liquids with minimal sample manipulation, and hence limited exposure of the laboratory worker to the agents.

Cysteine but not Glutathione Modulates the Radiosensitivity of Human Melanoma Cells by Affecting Both Survival and DNA Damage

Glutathione (GSH) and its precursor cysteine (Cys) are both known to react within any cells with oxidative species and thus play an important role in cellular defense mechanisms against oxidative stress. In melanocytes, these are also important precursors of melanogenesis by reacting non-enzymatically with l-dopaquinone to form the sulfur-containing pheomelanin. Our aim was to assess pigment role in the cellular radioprotection mechanism using a human melanoma cell model of mixed-type melanin under GSH depletion to obtain a radiosensitizing effect. The latter has been achieved either by Cys deprivation or GSH specific depletion. We first compared cell survival of Cys-deprived and GSH-depleted cells vs. control cells. Cys deprivation was achieved by decreasing Cys concentration in the culture medium for 24 h. In this condition, no toxicity was observed, Cys and GSH levels decreased, melanogenesis switched to a higher eumelanin synthesis and cells were significantly more resistant to 10-Gy dose of ionizing radiations than untreated cells. Glutathione depletion was achieved with the gamma-glutamylcysteine synthetase inhibitor buthionine-S-sulfoximine (BSO) for 24 h at 50 microM, a concentration yielding no toxicity. In this condition, intracellular GSH level decreased but no change in pigmentation was observed and cells were slightly but significantly more sensitive to radiation than the control. We then compared DNA radio-induced damages by Comet assay in control cells, cells treated as above and cells with stimulated pigmentation by increasing Tyr concentration in the medium. Our results showed that, when intracellular eumelanin content increased, DNA damage decreased. By contrast, DNA damage increased in cells treated with BSO alone. It is concluded that increasing the intracellular eumelanin content by the melanin precursor Tyr or by favoring the Pheo- to Eumelanin switch, compensates for the loss of the two intracellular radioprotectors that are GSH and Cys.

Rhinitis/Bronchopneumonia Syndrome in Irish Wolfhounds

This study describes the clinical, immunologic, genetic, and pathologic features of Irish Wolfhounds with rhinitis/bronchopneumonia syndrome. The dogs examined were from Belgium, The Netherlands, UK, Canada, Germany, and Switzerland. Signs included transient to persistent mucoid or mucopurulent rhinorrhea, cough, and respiratory dyspnea. Radiographic, rhinoscopic, and bronchoscopic findings were variable. Analysis of ciliary ultrastructure was performed in 5 affected dogs, but no characteristic primary ciliary defects (primary ciliary dyskinesia) were detected. Serum and bronchoalveolar lavage fluid (BALF) concentrations of IgA, IgG, and IgM were determined in some affected dogs and clinically normal Irish Wolfhounds. Serum IgA concentration was below the reference range in 5 of 8 affected dogs tested, whereas BALF IgA concentration was above the normal range in 2 affected adult dogs. The CD4 to CD8 lymphocyte subset ratio (CD4:CD8) in peripheral blood was tested in 3 affected dogs and was within the normal range. BALF CD4:CD8 was tested in 1 affected dog and was higher than the normal range. Decreased neutrophil phagocytosis was observed in 1 of the 4 dogs tested. Analysis of pedigrees of the Belgian, Canadian, German, and Swiss dogs revealed common ancestry, suggesting a heritable syndrome.

A pancreatic-induced intramural duodenal hematoma: a case report and literature review

Spontaneous intramural duodenal hematomas are not frequent and generally are related with an anticoagulant treatment. Pancreatic origin has seldom been described and the treatment is always controversial. We report a new case of a pancreatitis-induced intramural duodenal hematoma that was conservatively managed and we review the literature.

Correlation between culture testing of swabs and ligase chain reaction of first void urine from patients recently treated for Chlamydia trachomatis

We assessed the correlation between ligase chain reaction (LCR) on first void urine (FVU) and cultures of urethral and cervical swabs to detect chlamydia during three post-treatment follow up visits for 10 men and 19 women with genital chlamydial infections who had been treated with azithromycin or doxcycline.

Statistics of the Comet assay: a key to discriminate between genotoxic effects

The alkaline Comet assay is a widely used single cell gel electrophoresis technique for the quantification of DNA strand breaks, crosslinks and alkali-labile sites induced by a series of physical and chemical agents. DNA migration in an electric field, supposed proportional to strand breakage, is a proposed estimation of genotoxicity. Breaks are quantified from geometric and fluorescence measurements by image analysis of comet-shaped DNA, often reported parameters being tail DNA and tail moment. Although a variety of statistical approaches have been used in the literature, most of these do not take into account the distribution patterns of comet data. In order to investigate a methodology for statistically demonstrating a comet effect, two different experiments, a reproducibility study and a trend analysis, were undertaken on a murine lymphoma cell line (P388D1) photodynamically stressed after induction of porphyrins with delta-aminolaevulinic acid. This treatment results in significant heterogeneity of DNA damage, producing values ranging from 0 to 100% tail DNA in the same sample. The comparison of distribution curves for stressed and non-stressed samples shows that none of the application conditions are verified, either for parametric tests (which require normal distributions), or non-parametric tests (which assume essentially similar distributions). Meaningful statistics (median and 75th percentile) were consequently extracted from repeated experiments and found suitable for comparing stress conditions in an ANOVA and in a trend analysis; the 75th percentile is theoretically more sensitive but tends to more rapidly saturate at extensive stress levels. We conclude that a trend analysis of median comet metrics from repeated experiments at different stress levels is certainly an efficient way to statistically demonstrate a genotoxic effect. Whether the considered comet parameter is tail DNA or tail moment had no influence on the conclusions of our experiments, which were carried up to stress levels leading to a median 70% tail DNA.

[Ultrasonography of twin pregnancies]

Sonographers must be familiar with the diagnostic tools available to them for determining twin pregnancy type. During the first trimester, these tools include the number of chorionic sacs, the number of yolk sacs, and the presence of an inter-twin membrane. During the second trimester, sonographers must look for a difference in sex, the presence of two separate placentas, and a thick vs. thin membrane, or the absence of a membrane. Complications are frequent in twin pregnancies and may be maternal or fetal. Measuring cervical length is the only way for sonographers to predict pre-term labour. A cervical length of< or =2.5 cm before 23 weeks is significant. Some fetal anomalies are more frequent in twin pregnancy than in single pregnancy. The more frequent are: esophageal atresia, omphalocele and cardiac anomalies. Some fetal anomalies are peculiar to twin pregnancy: Siamese twins, digestive atresia, craniofacial deformation and club-foot. A significant growth asymmetry is defined as a CRL of 3 or more millimetres and a difference of 20% in weight. The poly-oligo sequence represents a severe level asymmetry of amniotic fluid in monodiamniotic twins where survival rate without sequelae is 13.6%. The twin-twin transfusion syndrome is an event occurring after the apparition of the poly-oligo sequence, which manifests by discordances in weight and hemodynamic changes leading to myocardial repercussion. Twin embolization syndrome follows the in utero death of a co-twin in a monochorionic twin pregnancy; ischemic events must be monitored in such cases. Cord entanglement is unpredictable and is specific to monochorionic monoamniotic twin pregnancies. Finally, an acardius is a parasitic twin that feeds on its co-twin, resulting in the viable twin's death in 50% of cases.

Acute toxicity of conventional radiation therapy for high-risk prostate cancer in EORTC trial 22863

OBJECTIVES

We analysed the acute toxicity observed in the European Organisation for Research and Treatment of Cancer (EORTC) randomised trial 22863 comparing conventional external irradiation with or without an agonist analogue of gonadotropin-releasing hormone in high-risk prostate cancer patients.

METHODS

Four hundred five patients that received a dose of at least 30 Gy were considered evaluable for acute toxicity assessment. Toxicity was grouped in a few categories: general, genito-urinary, and lower gastro-intestinal. Univariate and multivariate analyses were performed using the World Health Organisation (WHO) toxicity score and grouping together toxicity scores in different bimodal and trimodal groups.

RESULTS

Overall, our data show that age, previous surgery and irradiation dose are important predictive factors for acute toxicity, but not the use of combined hormone therapy. Fifteen percent of patients suffered of moderate to severe acute toxicity (WHO G3-G4). Life threatening toxicity was observed in six cases (1.5%).

CONCLUSIONS

The assessment of toxicity combining in different groups the original five scores scale produced conflicting results similar to those commonly reported in literature. Interpretation of the role of pre-treatment factors with uneven distribution in the study requires careful evaluation. These data obtained with conventional curative irradiation of high-risk prostate cancer patients are proposed for comparison with results achieved using modern state-of-the-art irradiation techniques.

Association of the ADAM33 gene with asthma and bronchial hyperresponsiveness

Asthma is a common respiratory disorder characterized by recurrent episodes of coughing, wheezing and breathlessness. Although environmental factors such as allergen exposure are risk factors in the development of asthma, both twin and family studies point to a strong genetic component. To date, linkage studies have identified more than a dozen genomic regions linked to asthma. In this study, we performed a genome-wide scan on 460 Caucasian families and identified a locus on chromosome 20p13 that was linked to asthma (log(10) of the likelihood ratio (LOD), 2.94) and bronchial hyperresponsiveness (LOD, 3.93). A survey of 135 polymorphisms in 23 genes identified the ADAM33 gene as being significantly associated with asthma using case-control, transmission disequilibrium and haplotype analyses (P = 0.04 0.000003). ADAM proteins are membrane-anchored metalloproteases with diverse functions, which include the shedding of cell-surface proteins such as cytokines and cytokine receptors. The identification and characterization of ADAM33, a putative asthma susceptibility gene identified by positional cloning in an outbred population, should provide insights into the pathogenesis and natural history of this common disease.

Soft-tissue venous malformations in adult patients: imaging and therapeutic issues

Venous malformations are the most common vascular malformations. However, confusion with respect to terminology and imaging guidelines continues to result in improper diagnosis and treatment. An appropriate classification scheme for vascular anomalies is important to avoid the use of false generic terms. Adequate imaging in association with clinical findings is crucial to establishing the correct diagnosis. Doppler ultrasonography should be the initial imaging modality and demonstrates absence of flow or low-velocity venous flow. Computed tomography and magnetic resonance (MR) imaging are used primarily for pretreatment evaluation of lesion extension. These lesions are usually hypointense on T1-weighted MR images and markedly hyperintense on T2-weighted images with variable gadolinium enhancement. Direct phlebography helps confirm the diagnosis and exclude other soft-tissue tumors. Three distinct phlebographic patterns (cavitary, spongy, dysmorphic) have been identified. In most cases, conservative treatment is recommended. Sclerotherapy with or without surgery is useful in cases of functional impairment or significant aesthetic prejudice, even if recurrences are frequent. Direct phlebography is performed when a more detailed assessment of the vascular pattern is needed or as part of sclerotherapy. Use of the appropriate imaging technique is critical in establishing the diagnosis, evaluating extension, and planning appropriate treatment.

[Isolated pancreatic neck rupture]

AIM OF THE STUDY

Through four cases of pancreatic neck rupture, the study aim was to emphasize the advantages of an early laparotomy when there is a doubt about a canal disruption and the risks of a later surgical management.

PATIENTS AND RESULTS

Four patients were operated on for a neck disruption of the pancreas due to blunt trauma. Two patients underwent laparotomy in the first 48 hours after a radiological exploration and underwent a left pancreatectomy with spleen preservation. There were no associated injuries, no lesions of acute pancreatitis. The two other patients were, at first, medically treated and developed an acute pancreatitis with pseudocyst. They underwent laparotomy, 7 and 10 days after the trauma because of pain and hyperthermia, and a conservative treatment by cystojejunostomy was performed in difficult conditions because of the acute pancreatitis. A late pancreatic pseudocyst (4 and 6 months) occurred in two patients.

CONCLUSION

When pancreatic trauma occurs, an exploration with echography, scanner, endoscopic retrograde cholangiopancreatography or magnetic resonance cholangiopancreatography can suggest a neck disruption and a canal rupture. When the canal is safe, a drainage close to the pancreas is sufficient. When the rupture of the canal is suspected or proved, an early laparotomy is necessary in order to investigate the pancreas and to perform the appropriate procedure. This surgery is easier before the occurrence of pseudocyst and acute pancreatitis.

Stability parameter estimation at ambient temperature from studies at elevated temperatures

The determination of specific kinetic constants k(i) in pH-profile studies is often undertaken at ambient temperature. However, when dealing with a drug substance that is stable at ambient temperature, the pH-profile study is conducted at a chosen elevated temperature and the kinetic parameters are given at this particular elevated temperature. But in stability studies we generally need kinetic constants at ambient or storage temperature for practical reasons (information and storage conditions of formulation). To assess this ambient kinetic information from studies at elevated temperatures, cumulative sequential steps are usually employed with very few statistical concerns on the final estimates. The statistical problems on these final estimates in cumulative procedures are highlighted in many papers. Because these stability parameters are useful for drug formulation and storage conditions, good practical decisions have to be made on the basis of statistically unbiased identified parameters. We propose in this paper a nonlinear model that allows the direct determination of specific activation energies E(ai) that are linked to the specific kinetic constants k(i). Hence, a mathematical relationship between drug concentration C, pH, temperature T, and time t is obtained. Kinetic data from acetylsalicylic acid (ASA) hydrolysis (first-order kinetics) are used to validate the model. The results show that it is possible to obtain directly, by an extrapolation procedure, the kinetic parameters (specific kinetic constants k(i), specific activation energies E(ai), and dissociation constant pK(a)) at low temperature from data gathered at elevated temperatures using more meaningful statistics.

US of the pediatric female pelvis: a clinical perspective

When investigating pelvic pathologic conditions in female pediatric patients, one needs to be aware of the developmental changes that take place around puberty. The prepubertal uterus is thin, with a fundus equal in size to the cervix. Owing to the hormonal stimulation of puberty, the uterus enlarges and the fundus becomes prominent. The ovaries are demonstrated with ultrasonography (US) at all ages. Ovarian volume increases after 6 years of age. Microcystic follicles are normally seen throughout childhood. US is the modality of choice for imaging the pediatric female pelvis. The main indications for pelvic US in the pediatric age group are pubertal precocity or pubertal delay, pelvic pain or pelvic masses, and ambiguous genitalia. Vaginal bleeding in the prepubertal child can be due to a vaginal foreign body, vaginal rhabdomyosarcoma, or precocious puberty. Common causes of primary amenorrhea in teenagers include gonadal dysgenesis (Turner syndrome) and müllerian (uterovaginal) anomalies. Pelvic pain or pelvic masses in pediatric patients can be due to ovarian torsion, hemorrhagic ovarian cyst, pelvic inflammatory disease, or ectopic pregnancy.

The catalytic role of tyrosine 254 in flavocytochrome b2 (L-lactate dehydrogenase from baker's yeast). Comparison between the Y254F and Y254L mutant proteins

Flavocytochrome b2 catalyses the oxidation of L-lactate to pyruvate in yeast mitochondrial intermembrane space. Its flavoprotein domain is a member of a family of FMN-dependent 2-hydroxy-acid-oxidizing enzymes. Numerous solution studies suggest that the first step of the reaction consists of proton abstraction from lactate C2, leading to a carbanion that subsequently yields electrons to FMN. The crystal structure suggests that the enzyme base is His373, and that Tyr254 may be hydrogen bonded to the substrate hydroxyl. Studies carried out with the Y254F mutant [Dubois, J., Chapman, S.K., Mathews, F.S., Reid, G.A. & Lederer, F. (1990) Biochemistry 29, 6393-6400] showed that Tyr254 does not act as a base but stabilizes the transition state. As the mutation did not induce any change in substrate affinity, the question of the existence of the hydrogen bond in the Michaelis complex remained open. Similar results with glycolate oxidase, mutated at the same position, led to the suggestion that these enzymes actually operate via a hydride transfer mechanism [Macheroux, P., Kieweg, V., Massey, V., Soderlind, E., Stenberg, K. & Lindqvist, Y. (1993) Eur. J. Biochem. 213, 1047-1054]. In the present work, we have re-investigated the matter by analysing the properties of a Y254L mutant flavocytochrome b2, as well as the behaviour of the Y254F enzyme with two substrates other than lactate, and a series of inhibitors. The Y254L protein is less efficient with L-lactate than the wild-type enzyme by a factor of 500, but the substrate affinity is unchanged. In contrast, L-phenyllactate and mandelate, poor substrates (the latter acting more as an inhibitor), exhibit an increased affinity. In addition, the Y254L mutant enzyme is more efficient with phenyllactate than lactate as a substrate. In order to rationalize these observations, we have modelled phenyllactate and mandelate in the active site, using previously described modelling experiments with lactate as a starting point. The results indicate that mandelate cannot bind in an orientation allowing proton abstraction by His373, due to steric interference by the side chains of Ala198 and Leu230. It might possibly adopt a binding mode as proposed previously for lactate, which leads to a hydride transfer and with which the 198 and 230 side chains do not interfere. However, other researchers [Sinclair, R., Reid, G.A. & Chapman, S.K. (1998) Biochem. J. 333, 117-120] showed that A198G, L230A and A198G/L230A mutant enzymes exhibit a strongly improved mandelate dehydrogenase activity. These results indicate that relief of the steric crowding facilitates catalysis by enabling a better mandelate orientation at the active site, suggesting that its productive binding mode is similar to that proposed for lactate in the carbanion mechanism. The modelling studies therefore support the hypothesis of a carbanion mechanism for all substrates. In addition, we present the effect of the two mutations at position 254 on the binding of a number of competitive inhibitors (such as sulfite, D-lactate, propionate) and of inhibitors that are known to bind at the active site both when the flavin is oxidized and when it is in the semiquinone state (propionate, oxalate and L-lactate at high concentrations). Unexpectedly, the results indicate that the integrity of Tyr254 is necessary for the binding of these inhibitors at the semiquinone stage.

In vitro susceptibility study of BMS-284756 against Legionella species

Legionella organisms are often associated with respiratory infections, and Legionella pneumonia results in significant mortality unless it is promptly and effectively treated. The present study was undertaken to compare the in vitro activity of BMS-284756 (T-3811ME), a novel des-F(6)-quinolone, against Legionella species versus the activity of other fluoroquinolones (levofloxacin, moxifloxacin, and ciprofloxacin) and of the macrolides erythromycin, clarithromycin, and azithromycin. The most potent agents tested against Legionella pneumophila serogroup 1, the largest group tested, were BMS-284756, moxifloxacin, and levofloxacin (MIC(90) = 0.016 mg/L). The MIC(90) range for BMS-284756 was 0.008-0.03 mg/L against the total panel of L pneumophila serogroups 1-9 and 12, with the lowest MIC(90) observed for serogroup 7 and the highest for serogroup 2. BMS-284756 was one of the most potent agents tested against isolates of L micdadei, L longbeachae, and other Legionella species (MIC(90) range: 0.008-0.06 mg/L). These results and the high intrinsic activity of BMS-284756 against other respiratory pathogens support its use as empiric monotherapy for a wide range of respiratory infections.

Genome sequence and comparative analysis of the solvent-producing bacterium Clostridium acetobutylicum

The genome sequence of the solvent-producing bacterium Clostridium acetobutylicum ATCC 824 has been determined by the shotgun approach. The genome consists of a 3.94-Mb chromosome and a 192-kb megaplasmid that contains the majority of genes responsible for solvent production. Comparison of C. acetobutylicum to Bacillus subtilis reveals significant local conservation of gene order, which has not been seen in comparisons of other genomes with similar, or, in some cases closer, phylogenetic proximity. This conservation allows the prediction of many previously undetected operons in both bacteria. However, the C. acetobutylicum genome also contains a significant number of predicted operons that are shared with distantly related bacteria and archaea but not with B. subtilis. Phylogenetic analysis is compatible with the dissemination of such operons by horizontal transfer. The enzymes of the solventogenesis pathway and of the cellulosome of C. acetobutylicum comprise a new set of metabolic capacities not previously represented in the collection of complete genomes. These enzymes show a complex pattern of evolutionary affinities, emphasizing the role of lateral gene exchange in the evolution of the unique metabolic profile of the bacterium. Many of the sporulation genes identified in B. subtilis are missing in C. acetobutylicum, which suggests major differences in the sporulation process. Thus, comparative analysis reveals both significant conservation of the genome organization and pronounced differences in many systems that reflect unique adaptive strategies of the two gram-positive bacteria.

Pediatric hepatic vascular anomalies

The typical vascular anomalies (tumors and vascular malformations) that involve the liver in infants and children are summarized. Many of these lesions are complex and require multiple imaging modalities, often including angiography, for precise diagnosis.

Semisynthesis of D-ring modified taxoids: novel thia derivatives of docetaxel

Two novel 5(20)-thia analogues of docetaxel have been synthesized from 10-deacetylbaccatin III or taxine B and isotaxine B. The key step of these syntheses is the concomitant thietane ring formation and acetylation of the tertiary alcohol at C-4. Both compounds are less cytotoxic than docetaxel but have divergent activity on microtubule disassembly.

Semisynthesis of D-ring modified taxoids: novel thia derivatives of docetaxel

Two novel 5(20)-thia analogues of docetaxel have been synthesized from 10-deacetylbaccatin III or taxine B and isotaxine B. The key step of these syntheses is the concomitant thietane ring formation and acetylation of the tertiary alcohol at C-4. Both compounds are less cytotoxic than docetaxel but have divergent activity on microtubule disassembly.

In vitro activity of ABT-773 versus macrolides and quinolones against resistant respiratory tract pathogens

ABT-773, a novel ketolide, was compared to erythromycin, azithromycin, clarithromycin, ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin, gatifloxacin, and gemifloxacin against antibiotic-resistant strains recently isolated from patients with respiratory tract infections. MICs were determined by agar dilution using standard NCCLS methodology. ABT-773 (MIC(90) 0.06 mg/L) was more active than the macrolides (MIC(90) > or = 2 mg/L) and fluoroquinolones (MIC(90) > or = 0.5 mg/L) against penicillin-resistant Streptococcus pneumoniae. The fluoroquinolones were the most active agents tested against beta-lactamase-positive Haemophilus influenzae (MIC(90) < or = 0.01-0.06 mg/L), against which ABT-773 (MIC(90) 4 mg/L) was comparable to azithromycin and two- and four-fold more active than erythromycin and clarithromycin, respectively. Against beta-lactamase positive Moraxella catarrhalis, the activity of ABT-773 (MIC(90) 0.06 mg/L) was comparable to gemifloxacin, trovafloxacin, levofloxacin, and ciprofloxacin (MIC(90) 0.03-0.06 mg/L) and 4- to eightfold greater than that of clarithromycin, gatifloxacin, and erythromycin. These data suggest ABT-773 could be a valuable compound for the treatment of respiratory tract infections, including those resistant to usual oral therapy.

Photodynamic DNA damage mediated by delta-aminolevulinic acid-induced porphyrins

The mutagenic properties of UVA are thought to be predominantly radical-mediated, which supposes endogenous sensitizers. In order to investigate a possible role of porphyrins, their synthesis was induced in a murine leukemia P388D1 cell model by treatment with delta-aminolevulinic acid (delta-ala). Intra-cellular protoporphyrin IX reached a plateau after about 2 h, whereas soluble porphyrins, probably the photostable uro- and/or coproporphyrins, were excreted. Irradiation of treated cells by UVA (tanning lamp) but also by visible light was found to generate in DNA a significant increase of 8-oxo-7,8-dihydro-2'-deoxyguanosine, a mutagenic marker of oxidative damage. The different parameters involved in this photodynamic effect are reported, namely delta-ala concentration and loading time, light dosage and the influence of intracellular and medium-excreted porphyrins. These results point to an implication of porphyrins in solar-induced carcinogenicity but also in possible adverse effects of the medical applications of photodynamic therapy and diagnosis.

Gastroschisis and Hirschsprung's disease: a rare combination

The authors report on a neonate with gastroschisis repaired at birth who later had abdominal distension, emesis, feeding intolerance, and an abnormal stooling pattern. Total colon and partial small bowel aganglionosis (TCAS), or Hirschsprung's disease, was diagnosed subsequently. This is the first report of this combination of gastrointestinal anomalies. J Pediatr Surg 36:638-640.

Initial sequencing and analysis of the human genome

The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

Doppler US in patients with crohn disease: vessel density in the diseased bowel reflects disease activity

PURPOSE

To determine if neovascularization associated with Crohn disease, as detected with Doppler ultrasonography (US), reflects clinical disease activity.

MATERIALS AND METHODS

A devised measurement, vessel density, was estimated with color Doppler US. Patients with Crohn disease underwent clinical and laboratory assessment in which the Crohn disease activity index was measured; patients underwent abdominal US the same week. Color Doppler US was performed by using a 7.5-10.0- or 8.0-12.0-MHz transducer, the lowest possible pulse repetition frequency without aliasing, a low wall filter, and high Doppler gain settings. The length and thickness of the affected loops were measured, and the number of color Doppler signals per square centimeter in the bowel loop was counted. Pulsed Doppler US was used to confirm that the signals originated from arteries or veins and not from movement artifacts.

RESULTS

Ninety-two patients (aged 7-20 years; mean, 14.85 years; 44 female, 48 male) underwent 119 examinations; 85 were performed in patients with active disease. Affected loops were thicker (10.6 vs 4. 6 mm; P: <.001) and had a higher vessel density with disease (69 of 119 examinations) than during remission (two of 34 examinations; P: <.001).

CONCLUSION

Vessel density in affected bowel loops, as estimated with Doppler US, and bowel wall thickness (>5 mm) reflect disease activity in patients with Crohn disease.

[Reactive hemaphagocytic syndrome in a patient with midline NK-cell lymphoma]

Different etiologies have been shown to underly lethal midline granuloma. Evidence of natural killer cell lymphoma is obtained by immunolabeling and molecular biology studies. The tumor has a characteristic immunophenotype and genotype. This clinicopathological entity is highly associated with Epstein-Barr virus (EBV). We present the case of a patient with EBV associated with nasal-type natural-killer cell lymphoma and a coexisting hemophagocytic syndrome.

Chromatographic determination of 8-oxo-7,8-dihydro-2'-deoxyguanosine in cellular DNA: a validation study

Although a series of biomarkers are widely used for the estimation of oxidative damage to biomolecules, validations of the analytical methods have seldom been presented. Formal validation, that is the study of the analytical performances of a method, is however recognized as the best safeguard against the generation and publication of data with low reliability. Classical validation parameters were investigated for the determination of an oxidative stress biomarker, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) in cellular DNA, by high-performance liquid chromatography coupled to amperometric detection (HPLC-EC); this modified base is increasingly considered as a marker of oxidative damage to DNA, but many questions are still raised on the analytical methods in use. Upon a rigorous statistical evaluation of the quality criteria currently required for assays in biological media, including selectivity, linearity, accuracy, repeatability, sensitivity, limits of detection and quantification, ruggedness and storage at different stop points in the procedure, the HPLC-EC assay method is found mostly reliable. The present validation attempt demonstrates that (i) the HPLC-EC assay of 8-oxo-dG provides consistent data allowing to reliably detect an increase of this biomarker in cellular DNA; (ii) a harsh oxidative stress does not hinder the enzymatic digestion of DNA by nuclease P1; and (iii) the analytical results must be expressed relative to the internal standard dG which significantly improves both repeatability and sensitivity. Whereas the described assay minimizes the artifactual production of the analyte from processing and storage, this cannot be totally ruled out; the true 8-oxo-dG base levels still lack a definitive assay method, which remains a considerable analytical challenge and the object of controversy.

In vitro study of the post-antibiotic effect and the bactericidal activity of Cefditoren and ten other oral antimicrobial agents against upper and lower respiratory tract pathogens

The in vitro post-antibiotic effect (PAE) and batericidal activity of cefditoren was compared to that of cefixime, cefuroxime, loracarbef, cefaclor, amoxicillin, amoxicillin/clavulanate, clarithromycin, azithromycin, erythromycin, and ciprofloxacin against ATCC culture strains and clinical respiratory isolates. A PAE > 1 h was observed for cefditoren and generally for the macrolides against Streptococcus pneumoniae, beta-lactamase-negative Moraxella catarrhalis, and Streptococcus pyogenes, whereas the other beta-lactams showed mixed results. Cefditoren was the only beta-lactam showing significant bactericidal activity (>3 log reduction of viable cells) within 4 h against penicillin-resistant S. pneumoniae. Only cefditoren and ciprofloxacin showed significant bactericidal activity against beta-lactamase-negative (after 24 h) and beta-lactamase-positive strains of H. influenzae (after 12 h). Against beta-lactamase-positive strains of M. catarrhalis, cefditoren was the only agent to show significant bactericidal activity at 6 h (versus cefuroxime and ciprofloxacin at 12 h).

Comparative in vitro activity and post-antibiotic effect of gemifloxacin against Legionella spp

The comparative in vitro potency and post-antibiotic effect (PAE) of gemifloxacin (SB-265805), moxifloxacin, trovafloxacin, grepafloxacin, levofloxacin, ofloxacin, ciprofloxacin, azithromycin, clarithromycin, erythromycin and rifampicin were evaluated against Legionella pneumophila serogroups 1-9 and 12 (n = 204) and other Legionella spp. (n = 34). MICs were determined by standard two-fold agar dilution. PAE was determined by exposing the isolates to the test agents at 4 x MIC for 1 h. Trovafloxacin was the most potent agent overall (MIC range < or =0.004-0.016 mg/L, MIC(90) < or =0.008 mg/L). Of the other quinolones tested, gemifloxacin, moxifloxacin, grepafloxacin and levofloxacin were more potent (MIC(90) 0.016 mg/L) against L. pneumophila than ciprofloxacin and ofloxacin (MIC(90) 0. 03 mg/L). Against Legionella spp., the test quinolones were more potent (MIC range < or =0.004-0.06 mg/L) than either erythromycin or azithromycin (MIC(90) 0.5 and 0.25 mg/L, respectively). Gemifloxacin had the longest PAE (4.65 h) of the agents tested against erythromycin-resistant L. pneumophila. Of the quinolones, only gemifloxacin, grepafloxacin, levofloxacin and ofloxacin had PAEs of >3 h against erythromycin-resistant Legionella spp. Azithromycin, erythromycin and clarithromycin had PAEs of <3 h against all erythromycin-resistant strains. Against erythromycin-susceptible L. pneumophila, only gemifloxacin, moxifloxacin, ofloxacin and ciprofloxacin had PAEs of >3 h, and only rifampicin, ofloxacin, gemifloxacin and erythromycin had PAEs of >2 h against erythromycin-susceptible Legionella spp. The superior potency of gemifloxacin compared with erythromycin indicates that it may be of use in the treatment of legionellosis. The significant PAE described here, combined with favourable pharmacokinetics, supports once-daily dosing for gemifloxacin in the treatment of legionella infections.

Improvement of disseminated lymphangiomatosis with recombinant interferon therapy

Disseminated lymphangiomatosis is a rare disorder with a poor prognosis. We present a case involving a 3-year-old boy who presented with pulmonary infiltrates, multiple lytic lesions of the ribcage, and small cystic lesions in the spleen. Open-lung and bone biopsies revealed disseminated lymphangiomatosis. Significant clinical and radiologic improvement were observed and persisted after 28 months of treatment with recombinant interferon alpha-2b (IFN alpha-2b). No significant toxicity has been observed.

Improved kinetic parameter estimation in pH-profile data treatment

Statistical problems in temperature stability parameter estimation have been the subject of many papers whereas statistics in, pH-profile parameter estimation have focused little attention. However, the conventional two step method used in data treatment in both cases leads to identical statistical problems. The aim of this study is then to introduce a method that improves statistics in pH-profile parameter estimation. A one step non-linear method that takes into account the errors in drug content determination is proposed. A mathematical relationship between drug content C, pH and time t is tested. The proposed method allows the estimation of the specific kinetic constants and the dissociation constant (pK(a)) in a single run. The most likely experimental initial drug contents C(0j),. where j is the index of a given experiment, are also determined. This approach that takes into account all relevant experimental information for the estimation of kinetic parameters is more rigorous from a statistical viewpoint than the classical two step methods. Kinetic data from acetylsalicylic acid (ASA) hydrolysis was used for the tests.

Doppler sonography of head and neck masses in children

This article presents a clinical approach to the investigation of a child with a mass of the head or neck. The anatomy of the head and neck region is reviewed, and the technique of Doppler sonography in children is outlined. The pathology and the sonographic appearance of common head and neck masses specific to children are described.

Effects of the hydrophobicity of taxoids on their interaction with tubulin

Modifications of the hydrophobic character at the 7 and 10 positions of the taxoids greatly modified the effect of these drugs on the tubulin microtubule system. The presence of an alkyl chain at these positions decreased the activity while their corresponding more polar analogues restored the activity of these molecules. It appears that the recognition of taxoids by tubulin depends on the location of the most important hydrophobic area.

Preoperative manual detorsion of the spermatic cord with Doppler ultrasound monitoring in patients with intravaginal acute testicular torsion

OBJECTIVE

To assess the effectiveness of preoperative manual detorsion in acute testicular torsion.

MATERIALS AND METHODS

Between June 1998 and March 1999, seven patients presenting with testicular torsion underwent manual manipulation under US monitoring in order to restore the flow to the testis prior to surgery (orchidopexy). All detorsions were lateral in direction. The success of the manoeuvre was assessed both clinically and sonographically and confirmed at surgery.

RESULTS

Six manoeuvres were successful in restoring flow to the testis. The failed attempt in the seventh patient was due to failure to manipulate beyond an initial 1 1/2 rotations (540 degrees).

CONCLUSIONS

Preoperative detorsion is the fastest way to relieve testicular ischaemia. However, manual detorsion of the spermatic cord is not a substitute for surgical exploration and bilateral orchidopexy is still necessary.

Imaging and therapeutic approach of hemangiomas and vascular malformations in the pediatric age group

Terminology regarding the vascular lesions of the soft tissues remains confusing. A single classification is necessary in order to decide on the proper investigation and the best treatment. At the Workshop on Vascular Anomalies in Rome in June 1996, the membership accepted the Mulliken and Glowacki classification, which differentiates vascular lesions into vascular tumors, including hemangiomas and vascular malformations. At Sainte-Justine, we have set up a multidisciplinary clinic for the discussion of problem patients with vascular anomalies, both in terms of diagnosis and treatment. In this review, we present our experience regarding the classification, the imaging modalities and the treatment of vascular anomalies. In our experience, Doppler ultrasound should be the initial imaging modality for recognizing vascular tumors from vascular malformations. CT scan or magnetic resonance imaging is best to evaluate the extent of the lesions prior to treatment. A multidisciplinary approach is essential to establish a correct diagnosis and define accordingly the appropriate treatment and follow-up.

Toxicity profile of interferon alfa-2b in children: A prospective evaluation

The toxicity of interferon (IFN) alfa-2b therapy was prospectively evaluated in 53 children treated from 1991 to 1996 in 2 successive studies of IFN alfa therapy for severe hemangiomas at Sainte-Justine Hospital. Toxicity was generally mild and transient, with grade 1 toxicity occurring in 100% of patients, grade 2 toxicity in 89%, grade 3 toxicity in 58%, and grade 4 toxicity in 17%. Ten of 43 patients available for evaluation had an abnormal neurologic examination. Severe neurotoxicity in the form of spastic diplegia occurred in one patient. In conclusion, IFN alfa therapy is generally well tolerated in children. However, it may rarely be associated with severe toxicity and must be used with caution.

Soft-tissue venous malformations in pediatric and young adult patients: diagnosis with Doppler US

PURPOSE

To describe the diagnostic features, appearance, and vascularization pattern of venous malformations (VMs) at Doppler ultrasonography (US).

MATERIALS AND METHODS

Between February 1991 and May 1997, 51 soft-tissue VMs were studied with Doppler US in patients between 1 day and 21 years of age (mean age, 9 years). These VMs were located in the maxillofacial region (n = 19), trunk (n = 5), and upper (n = 10) and lower (n = 17) extremities. Twenty-three VMs had venographic confirmation, seven had only histologic confirmation, and 21 had both venographic and histologic confirmation. US was performed with 7.5- or 7-10-MHz linear transducers, a low pulse repetition frequency (mean, 1,680 Hz), and the lowest wall filter (25-50 Hz).

RESULTS

At gray-scale US, VMs appeared as hypoechoic, heterogeneous lesions in 82% of cases. All lesions displayed compressibility. In eight lesions (16%), phleboliths were identified, thus confirming the diagnosis of VM. Analysis of vascular flow revealed monophasic, low-velocity flow in 40 VMs (78%), with an average flow velocity of 0.22 kHz. Biphasic flow was noted at the periphery of three lesions, which is indicative of a mixed capillary-venous malformation. The remaining eight lesions did not display any flow.

CONCLUSION

In pediatric patients, Doppler US is a noninvasive, easily available, and rapid mode of investigation of vascular lesions and can help confirm the diagnosis of VM when it shows a characteristic flow pattern.

Incorporating batch effects in the estimation of drug stability parameters using an Arrhenius model

The nonlinear estimation of drug stability parameters (energy of activation Ea and shelf-life tY) by conventional approaches employs equations relating drug content determination C at time t and temperature T. The identification procedures lead to the determination of only one initial drug content C0 for several different experiments. However, it is well known that because of experimental concentration variation or of intentional modification of the experimental schedule, there are as many initial drug contents as experiments. For these reasons, a method which takes into account batch effects is proposed to determine stability parameters and also all initial drug contents C0j where j is the index of experiment in one step. This method is more accurate from a statistical viewpoint and is suitable for data treatment in pharmaceutical industries where the initial drug content of each batch entering the stability program can be checked a posteriori. The application of this method is shown on real kinetic data from the hydrolysis of acetylsalicylic acid (ASA).

Treatment of community-acquired pneumonia in the elderly: the role of cefepime, a fourth-generation cephalosporin

In a prospective, multicentre double-blind trial, 151 patients over the age of 65 years were randomly assigned to receive either cefepime 2 g every 12 h for a minimum of 3 days and up to 14 days or ceftriaxone 1 g every 12 h for a minimum of 3 days and up to 14 days. Antibiotics were maintained until 48 h after fever had resolved; no other antibiotics were permitted. The average age in each group exceeded 77 years and significant co-morbidity was found in the majority of patients. The mean total duration of therapy was 5.8+/-2.4 days for the cefepime group and 6.7+/-2.7 days for the ceftriaxone group (P = 0.06). The clinical success rate at the end of therapy was 79.1% with cefepime and 75.4% with ceftriaxone (P = 0.62). At the end of follow-up, 91.7% of the cefepime-treated patients and 86.5% of the ceftriaxone patients had a satisfactory clinical response (P = 0.38). In 35 bacteriological evaluable patients, potential pathogens were eradicated in all but one patient receiving cefepime. Seven patients in each group died during the study period but in each case the death was unrelated to study drug. The commonest side-effect was diarrhoea (cefepime, five patients; ceftriaxone, two patients). The clinical and microbiological efficacy of cefepime is similar to that of ceftriaxone in elderly patients with community-acquired pneumonia requiring hospitalization. Cefepime is an appropriate choice for the treatment of community-acquired respiratory tract infections in the elderly.

Fourier transform infrared spectroscopic investigation of temperature- and pressure-induced disaggregation of amyloid A

The conformation-sensitive amide I band in the Fourier transform infrared (FTIR) spectra of amyloid A suspensions in D2O was examined as a function of temperature (25-95 degrees C) and applied hydrostatic pressure (1-12 kbar) to assess the stability of the peptide. The principal changes observed upon heating were a significant loss of intermolecular beta-sheet structure, and an increase in the broad band centred at 1644 cm(-1) assigned to unordered structure and alpha-helices of the dissociated species. Application of hydrostatic pressure at ambient temperature resulted in a limited degree of aggregate dissociation. These structural changes were partially reversible with cooling or release of the applied pressure. Dissolving the aggregated peptide in alkaline solution (pH 12) also resulted in disaggregation. Dissociation of organ-deposited amyloid substance bears clinical relevance. The present data indicate that residual amounts of undissociated amyloid in the milieu at physiological and acidic pH may act as nucleating foci rendering dissociated amyloid to reaggregate into organized amyloid.

In vitro activity of gatifloxacin, compared with ciprofloxacin, clarithromycin, erythromycin, and rifampin, against Legionella species

Gatifloxacin, a new advanced-generation, 8-methoxy fluoroquinolone, has shown efficacy against a broad spectrum of microorganisms. In this study, the in vitro activity of gatifloxacin was compared with that of ciprofloxacin, clarithromycin, erythromycin, and rifampin against 214 Legionella spp. Species tested in order of frequency were: L. pneumophila serogroups 1 to 9 (181 strains); L. dumoffii (10 strains); L. micdadei (9 strains); L. longbeachae (7 strains); and other Legionella spp. (7 strains). MICs were determined by a standard dilution procedure using buffered yeast extract agar. Gatifloxacin and rifampin were the most active agents against all strains of Legionella tested. Moreover, against L. pneumophila strains tested, gatifloxacin was found to be more active (highest MIC90 = 0.03 mg/L) than ciprofloxacin (highest MIC90 = 0.06 mg/L) and clarithromycin (highest MIC90 = 0.12 mg/L). L. pneumophila serogroups 1 to 4 and 6 to 9 (MIC90 = 0.016 mg/L) were more susceptible to gatifloxacinthan L. pneumophila serogroup 5 (MIC90 = 0.03 mg/L). The activity of gatifloxacin against L. micdadei was equal to that of ciprofloxacin (MIC90 = 0.016 mg/L) and greater than that of erythromycin (MIC90 = 1.0 mg/L). The activity of gatifloxacin against L. dumoffii and L. longbeachae was equal to that of ciprofloxacin (MIC90 = 0.03 mg/L). The activity of gatifloxacin was similar against isolates obtained from both patients and environmental sources.

Multidrug resistance modifies polyamines uptake in P388 murine lymphoma cells: experimental and modeling approach

Polyamines (putrescine, spermidine and spermine) are ubiquitous compounds, essential for cell growth. This paper compares the polyamine transport between sensitive P388 murine lymphoma cells and two multidrug resistant P388 sublines with the assistance of an experimental model. This new model allows the characterisation of the whole polyamines uptake and efflux. Three parameters are identified by the model: two rate constants (K+ for the uptake and K- for the efflux) which are considered as physical constants specific to the transport of one polyamine in one cell type, and Ci(o) which represents the initial intracellular concentration. This model well describes our experimental results of polyamine transport across the P388 cell plasma membrane. Multidrug resistant P388 cells exhibit spermine uptake significantly higher than that of sensitive cells when on the opposite, putrescine enters more rapidly into the sensitive P388 cells. In conclusion, comparison of polyamine transport between sensitive and multidrug resistant P388 phenotypes shows large and significant differences.