Conditional expression of vaccinia virus genes in mammalian cell lines expressing the tetracycline repressor

A new system was developed for producing conditional-lethal vaccinia virus mutants using the tetracycline controlled gene expression system from bacteria. The tetracycline resistance operon (tetO) sequence was placed between the promoter and coding sequence of the target gene of the virus. To regulate the expression of the target gene, the tetO-containing virus was used to infect a tetracycline repressor (TetR) expressing cell line. This method allowed isolation of a tetO-containing virus in the absence of the TetR thereby eliminating the risk of selecting for an inactivated viral tetR gene caused by recombination of the virus genome and improving the stability of the engineered mutants.     

Sociability trait and serotonin metabolism in the rat social interaction test

Social behaviour is the basis of one of the most generally accepted independent dimensions of personality. The purpose of the present study was to find out whether the social activity of individual rats, expressed in the social interaction test of anxiety, is consistent, and associated with monoamine levels. Four social interaction tests with 10 days intervals were carried out in 20 rats, and the animals were decapitated 4 days after the last test. There was no consistent correlation between performances in single tests, but the social interaction time in each test correlated strongly with the mean values of social activity in all or the other three tests. Social interaction time of rats correlated moderately but significantly with their partner's social activity in the test. The average social interaction time correlated strongly with 5-HIAA levels in the frontal cortex (r = -0.67, P < 0.01). Neither exposure of rats singly to the social interaction test box nor the test procedure had any effect on monoamine levels. When animals were decapitated immediately after a single social interaction test, there was a negative correlation between the social interaction time and 5-HIAA and 5-HT levels in the septum, but not in the frontal cortex or hippocampus. Thus, social behaviour is a stable trait, expression of which depends in part upon the partner's social behaviour. This trait is negatively associated with 5-HT metabolism in the frontal cortex. Social activity of rats in a particular test situation may rather be related to 5-HT metabolism in the septum.     

Mondini dysplasia and recurrent bacterial meningitis in a girl with relapsing Langerhans cell histiocytosis

We report a case of a girl with Langerhans cell histiocytosis (LCH) of multifocal bone disease, who developed recurrent bacterial meningitis and unilateral sensorineural hearing loss during the relapsing course of the disease. Mondini dysplasia, a congenital inner ear anomaly, was suspected by high resolution computed tomographic scan and the dysplasia with cerebrospinal fluid leakage was confirmed by surgery in the ipsilateral ear showing hearing loss. Although rare, congenital inner ear anomalies such as Mondini dysplasia should be kept in mind in pediatric patients with hearing impairment and/or recurrent bacterial meningitis during chemotherapy for various types of neoplasms including LCH.     

Ciprofloxacin greatly increases concentrations and hypotensive effect of tizanidine by inhibiting its cytochrome P450 1A2-mediated presystemic metabolism

BACKGROUND AND OBJECTIVE: Tizanidine, a centrally acting skeletal muscle relaxant, is metabolized mainly by cytochrome P450 (CYP) 1A2 and has a low oral bioavailability. The fluoroquinolone antibiotic ciprofloxacin is only a moderately potent inhibitor of CYP1A2. Our objective was to study the extent and mechanism of a possible interaction of ciprofloxacin with tizanidine. METHODS: In a double-blind, randomized, 2-phase crossover study, 10 healthy volunteers ingested 500 mg ciprofloxacin or placebo twice daily for 3 days. On day 3, a single dose of 4 mg tizanidine was ingested 1 hour after the morning dose of ciprofloxacin. Plasma concentrations of tizanidine and ciprofloxacin and pharmacodynamic variables were measured. A caffeine test was used as a marker for CYP1A2 activity. RESULTS: Ciprofloxacin increased the area under the plasma concentration-time curve from time 0 to infinity [AUC(0-infinity)] of tizanidine by 10-fold (range, 6-fold to 24-fold; P < .001) and its peak concentration by 7-fold (range, 4-fold to 21-fold; P < .001), whereas its elimination half-life was only prolonged from 1.5 to 1.8 hours (P = .007). The pharmacodynamic effects of tizanidine were much stronger during the ciprofloxacin phase than during the placebo phase with regard to changes in systolic blood pressure (-35 mm Hg versus -15 mm Hg, P = .001), diastolic blood pressure (-24 mm Hg versus -11 mm Hg, P < .001), Digit Symbol Substitution Test (P = .02), subjective drug effect (P = .002), and subjective drowsiness (P = .009). The AUC(0-infinity) of tizanidine and its change correlated (P < .01) with the caffeine/paraxanthine ratio and its change. CONCLUSIONS: Ciprofloxacin greatly elevates plasma concentrations of tizanidine and dangerously potentiates its hypotensive and sedative effects, mainly by inhibiting its CYP1A2-mediated metabolism, at least when administered 1 hour before tizanidine. Tizanidine seems to be a useful probe drug for measuring presystemic metabolism by CYP1A2. Care should be exercised when tizanidine is used concomitantly with ciprofloxacin.     

Neural retina limits the nonviral gene transfer to retinal pigment epithelium in an in vitro bovine eye model

We investigated the permeation of liposomal and polymeric gene delivery systems through neural retina into retinal pigment epithelium (RPE) and determined the roles of various factors in permeation and subsequent uptake of the delivery systems by RPE. Anterior parts and vitreous of fresh bovine eyes were removed. Retina was left intact or peeled away. Complexes of ethidium monoazide (EMA)-labeled plasmid DNA and cationic carriers (polyethyleneimine, poly-L-lysine, DOTAP liposomes) were pipetted on the retina or RPE. Two hours later the neural retina was removed, if present, and the RPE cells were detached. Contaminants were removed by sucrose centrifugation, and the RPE cells were analyzed for DNA uptake by flow cytometry. Cellular uptake of FITC-dextrans (molecular weight [mw] 20,000, 500,000 and 2,000,000), FITC-poly-L-lysine (mw 20,000), FITC-labeled oligonucleotide (15-mer), and naked EMA-labeled plasmid DNA was determined after pipetting the solutions on the RPE or neural retina. Location of the fluorescent materials in the retina was visualized with fluorescence microscopy. Neural retina decreased the cellular uptake of DNA complexes by an order of magnitude, the uptake of FITC-dextrans slightly, whereas delivery of polycationic FITC-poly-L-lysine to RPE was almost completely inhibited. Neural retina decreased the cellular uptake of FITC-oligonucleotides, while the uptake of uncomplexed plasmid was always negligible. Conclusions from FACS and fluorescence microscopy were similar: delivery of polymeric and liposomal DNA complexes into RPE are limited by the neural retina. This is due to the size and positive charge of the complexes.     

Phenotypic expression of the targeted null-mutation in the dopamine transporter gene varies as a function of the genetic background

The dopamine transporter (DAT) plays a critical role in calibrating the duration and intensity of dopamine (DA) neurotransmission. Mice in which the DAT gene has been genetically deleted exhibit constitutively high levels of extrasynaptic DA and spontaneous hyperactivity. Numerous studies have characterized the adaptive molecular, physiological, and behavioural consequences of abnormal DA neurotransmission in these mice. In order to determine the genetic background contribution to these phenotypes, the DAT mutation was transferred on C57BL/6JOrl (B6) or DBA/2JOrl (D2) inbred backgrounds for more than ten generations of back-crossing to derive three B6-, D2-, and B6xD2(F(1))-DAT strains. We observed that the genetic background dramatically affects phenotypes previously reported on DAT knockout (KO) mice. Depending on the genetic background, it was possible to restore survival, growth rate and ability to lactate. Interactions with the genetic background were found to modulate both quantitative and qualitative patterns of novelty-driven spontaneous hyperactivity. The paradoxical calming effect of cocaine was observed for all DAT-KO mice. However, the genetic background influenced individual threshold responses to both locomotor and rewarding effects of cocaine. These findings reveal the extent of phenotypic variation associated with the DAT mutation. They also provide concrete arguments against the assumption that the normal function of a gene can be inferred directly from its mutant phenotype.     

Dynamic magnetic resonance tomography and proton magnetic resonance spectroscopy of prostate cancers in rats treated by radiotherapy

RATIONALE AND OBJECTIVES: To establish an experimental setting for monitoring perfusion and metabolism in orthotopic prostate cancer at 1.5 T using dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) and 1H-MR spectroscopy (MRS). METHODS: Dunning rat prostate cancer cells were injected into the prostate by open surgery. Twelve tumor-bearing rats (5 of these irradiated) and 6 healthy controls were followed up using gadolinium-diethylenetriaminepentaacetic acid -enhanced dynamic MRI and 1H-MRS. Amplitude and the exchange rate constant kep were calculated (2-compartment model). From 1H-MR spectra, ratios of choline (Cho) and creatine (tCr) were calculated. All tumors were examined histologically. RESULTS: On DCE MRI parameter maps, tumors showed increased vascularization. kep and microvessel density were correlated (r = 0.97). Tumors showed elevated Cho/tCr and an unexpected lipid fraction (2.0-2.2 parts per million). Irradiation slowed tumor growth significantly. Changes of perfusion and metabolism could be detected in all tumors during follow up. CONCLUSION: DCE MRI and 1H-MRS has potential to characterize orthotopic Dunning prostate cancer in rats, which is a promising model similar to human prostate carcinomas.