Amphiphilic derivatives of dextran: Adsorption at air/water and oil/water interfaces

Ionic amphiphilic dextran derivatives were synthesized by the attachment of sodium sulfopropyl and phenoxy groups on the native polysaccharide. A family of dextran derivatives was thus obtained with varying hydrophobic content and charge density in the polymer chains. The surface-active properties of polymers were studied at the air-water and dodecane-water interfaces using dynamic surface/interfacial tension measurements. The adsorption was shown to begin in a diffusion-limited regime at low polymer concentrations, that is to say, with the diffusion of macromolecules in the bulk solution. In contrast, at long times the interfacial adsorption is limited by interfacial phenomena: adsorption kinetics or transfer into the adsorbed layer. A semiempirical equation developed by Filippov was shown to correctly fit the experimental curves over the whole time range. The presence of ionic groups in the chains strongly lowers the adsorption kinetics. This effect can be interpreted by electrostatic interactions between the free molecules and the already adsorbed ones. The adsorption kinetics at air-water and oil-water interfaces are compared.

Amphiphilic polysaccharides: useful tools for the preparation of nanoparticles with controlled surface characteristics

Polymeric surfactants obtained by hydrophobic modification of dextran are used as stabilizers for oil-in-water emulsions. The kinetics of interfacial tension decrease is studied as a function of polymer structural characteristics (degree of hydrophobic substitution) and at various polymer concentrations. Several hydrocarbon oils, either aliphatic (octane, decane, dodecane, and hexadecane) or aromatic (styrene), are tested. Kinetics exhibits the same general trends no matter which oil or polymer is considered. The emulsifying properties of the polymeric surfactants are illustrated by the preparation of oil-in-water emulsions. The droplet size at the preparation is correlated to the amount of oil and to the polymer concentration in the aqueous phase. For low polymer/oil ratios, it is shown that the droplet size is limited by the initial amount of polymer. On the contrary, for high polymer/oil ratios, the droplet size seems to level down, indicating that other parameters become predominant. Emulsion aging occurs by Ostwald ripening, and it is demonstrated that the theoretical equation of Lifshitz, Slyozov, and Wagner (LSW) correctly describes the experimental results. The nature of the oil has important effects on emulsion aging, as described by the LSW equation. The aging of emulsions containing oil mixtures is quantitatively described on the basis of the results with pure oils. The influence of polymer chemical structure can be conveniently correlated to interfacial tension results through the LSW equation. On the contrary, the influence of oil volume fraction seems to be overestimated by the usual correction factor, k(phi). The effect of temperature on emulsion aging is finally examined. Miniemulsions stabilized with dextran derivatives are used for the radical polymerization of styrene. Following this procedure, polysaccharide-covered polystyrene nanoparticles are prepared and characterized (size and surface coverage). The size of the particles is directly correlated to that of the initial droplets for styrene volume fractions around 10%. On the contrary, for initial styrene volume fractions around 20%, particles exhibit a larger size than the initial droplets, indicating that coalescence processes take place during polymerization. The amount of dextran at the surface of the particles is determined and compared to the adsorbed amounts resulting from emulsion preparation.

A simple and rapid high-performance liquid chromatographic (HPLC) method for 5-fluorouracil (5-FU) assay in plasma and possible detection of patients with impaired dihydropyrimidine dehydrogenase (DPD) activity

BACKGROUND

Dihydropyrimidine dehydrogenase (DPD) gene polymorphism may lead to severe toxicity with 5-fluorouracil (5-FU), a major anticancer drug extensively used in clinical oncology. Drug monitoring combined with early detection of patients at risk would enable timely dose adaptation so as to maintain drug concentrations within a therapeutic window. However, the best method to identify such patients remains to be determined.

OBJECTIVE

The aim of this study was to develop a rapid and simple high-performance liquid chromatographic (HPLC) method for estimating uracil/dihydrouracil (U/UH2) ratio in plasma, as an index of DPD status, and for assaying 5-FU as part of drug level monitoring.

METHOD

Assay of 5-FU, and U/UH2 detection were performed on a HPLC system equipped with UV detector. Analytes were separated at room temperature using a 5 microm particles, 25 cm RP-18 X-Terra column. The mobile-phase consisted of a KH(2)PO(4) salt solution (0.05 m) + 0.1% triethylamine (TEA) pumped at 0.4 mL/min. Detection of 5-FU and 5-bromouracil were performed at 254 nm; U and UH2 elution was monitored at 210 nm.

RESULTS

The method was sensitive and specific for assaying 5-FU within the 5-500 ng/mL concentration range, which covers exposure levels currently met in clinical practice. The method was simple, and relatively cheap, and rapid, with an analytical run time of about 30 min. Data from a patient with 5-FU toxicity suggest that the method was capable of identifying DPD metabolic phenotype in cancer patients, based on measurement of plasma U/UH2 ratio.

CONCLUSION

The method described should be suitable both for detecting patients at high risk of 5-FU toxicity, and for drug level monitoring during chemotherapy.

[Botulism toxin in practice]

Botulinum toxins (A and B) are neurotoxins derived from Clostridium botulinum. Clostridium are anaerobic bacteria. C. botulinum produces exotoxins (A to G) with distinct antigenicities. The neurotoxins inhibit the release of the neurotransmitter acetylcholine from the axon terminals of motor neurons. Botulinum toxin is officially used in clinic for the treatment of muscular hyperactivity (strabismus, blepharospam, cervical dystonia). Botulinum toxins are also used in non recognized clinical applications: neurogenic incontinence, palmar and axillary hyperhidrosis, chronic anal fissure. The respective formulations of Botox, Dysport and Neurobloc are described. Special considerations for administration are introduced.

Population pharmacokinetics of cisplatin after 120-h infusion: application to routine adaptive control with feedback

OBJECTIVE

A Bayesian population pharmacokinetics study of data from routine therapeutic drug monitoring cisplatin during a 5-day infusion of cisplatin.

METHODS

A total of 95 kinetics data sets (58 patients) were available to perform this study. Individual pharmacokinetic parameters, estimated from 20 courses of treatment in 18 patients, were used to calculate the population parameters (cl: 0.175 +/- 0.034 L/h; t(1/2): 327 +/- 91 h). The accuracy of Bayesian forecasting was tested by comparing in 40 other patients the clearance values calculated either from a complete kinetics profile (eight sampling times) or from three early samples and the new population parameters. Finally, drug monitoring efficacy was assessed by comparing the target Cmax values with the Cmax obtained after dose adjustment based upon early Bayesian estimation of the individual pharmacokinetic parameters.

RESULTS

: No significant difference was found between Bayesian and experimental clearances. Besides, dose-individualization proved to successfully adjust Cmax values around their respective target.

CONCLUSION

The new reference pharmacokinetic population parameters lead to accurate estimation of individual pharmacokinetic parameters from a limited number of samples, thus allowing efficient therapeutic drug monitoring during 5-day infusion regimens of cisplatin.

alpha4 integrins and L-selectin differently orchestrate T-cell activity during diabetes prevention following oral administration of CTB-insulin

Oral administration of insulin conjugated to the B chain of cholera toxin (CTB-insulin) in non-obese diabetic (NOD) mice results in diabetes prevention. We investigated the respective contributions of L-selectin (CD62L) and alpha4-integrin pathways during CTB-driven tolerance. Purified CD62L+CD4+ cells from CTB-insulin fed mice significantly reduced the capacity of diabetogenic T cells to transfer diabetes in syngeneic recipients. In vivo antibody blockade of fed animals during adoptive co-transfer experiments indicated that both CD62L and alpha4-integrins pathways were necessary to develop a protective response after oral tolerance induction. In contrast, when antibodies were given to recipient mice, only CD62L was critical for the protection. In vitro stimulated CD62L+CD4+ cells from the spleen of fed animals secreted lower amounts of IL-4 and IL-10 but comparable levels of TGFbeta than CD62L-cells. A reduced IFN-gamma production between the two cell subsets was specifically observed in CTB-insulin fed mice. Furthermore, antibody treatments induced changes in T-cell migration to the spleen, mesenteric and pancreatic lymph nodes. The protective effect was also associated with migration of regulatory T cells into pancreatic islets. Taken together, our results suggest that L-selectin and alpha4-integrin have distinct but complementary roles in the generation and function of regulatory CD4+ T cells following CTB-insulin administration.

Experience of a combination including indinavir 400 mg plus ritonavir 200 mg twice daily in HIV-infected patients: pharmacokinetic data

Low doses of ritonavir, a strong inhibitor of cytochrome P450 3A4, enhances the pharmacokinetic profile of indinavir with increased serum levels. We assessed the indinavir-ritonavir 400/200 twice daily combination in 17 HIV-infected patients focusing on the pharmacokinetic data and the tolerance of this regimen. IDV trough and peak concentrations were measured by high-performance liquid chromatography. Median indinavir trough and peak concentrations were 553 ng/ml and 3626 ng/ml, respectively. A good tolerance was observed except for three patients who experienced a major toxicity. Only one dose adjustment was related to indinavir toxicity. Considering the fact that Cmax is mainly responsible of the adverse effects, particularly renal stones, the indinavir-ritonavir 400/200 mg twice daily regimen offers a well-tolerated combination with an increased Cmin but a lower Cmax compared with both the standard tid regimen and higher dose of IDV-RTV regimens.

Surface Activity and Emulsification Properties of Hydrophobically Modified Dextrans

Neutral polymeric surfactants were synthesized by covalent attachment of hydrophobic groups (aromatic rings) onto a polysaccharide backbone (dextran). By changing the conditions of the modification reaction, the number of grafted hydrophobic groups per 100 glucopyranose units (substitution ratio) was varied between 7 and 22. In aqueous solution, these polymers behaved like classical associative polymers as demonstrated by viscometric measurements. The associative behavior was more pronounced when the substitution ratio increased. The surface-active properties of the modified dextrans were evidenced by surface tension (air/water) and interfacial tension (dodecane/water) measurements. In each case the surface or interfacial tension leveled down above a critical polymer concentration, which was attributed to the formation of a dense polymer layer at the liquid-air or liquid-liquid interface. Dodecane-in-water emulsions were prepared using the polymeric surfactants as stabilizers, with oil volume fractions ranging between 5 and 20%. The oil droplet size (measured by dynamic light scattering) was correlated to the amount of polymer in the aqueous phase and to the volume of emulsified oil. The thickness of the adsorbed polymer layer was estimated thanks to zeta potential measurements coupled with size measurements. This thickness increased with the amount of polymer available for adsorption at the interface. The dextran-based surfactants were also applied to emulsion polymerization of styrene and stable polystyrene particles were obtained with a permanent adsorbed dextran layer at their surface. The comparison with the use of an unmodified dextran indicated that the polymeric surfactants were densely packed at the surface of the particles. The colloidal stability of the suspensions of polystyrene particles as well as their protection against protein adsorption (bovine serum albumin, BSA, used as a test protein) were also examined.

Bayesian population model of methotrexate to guide dosage adjustments for folate rescue in patients with breast cancer

BACKGROUND

Methotrexate (MTX) infusions may induce severe side-effects, and alkaline hydration along with folinic acid rescue is a common way to reduce such toxic risks. The purpose of this study was to develop an adaptive rescue strategy based upon the early detection of patients with impaired MTX elimination.

METHODS AND RESULTS

In this study, we propose a simple population-based Bayesian approach for predicting MTX plasma concentration from a limited number of samples, so as to adapt both duration and dosage of the rescue agent to be used next. Ten kinetic profiles obtained after 10 courses of MTX (1.5 g/m2) in seven patients with inflammatory breast cancer were used to establish the population pharmacokinetic parameters (Cl, 8.16 L/h; t1/2, 12.7 h). This population was next involved in the Bayesian estimation of MTX individual pharmacokinetic parameters from only two blood samples (T24 and T36 h), thus allowing one to forecast the elimination of this drug by predicting MTX levels at 48 h. According to the MTX concentrations predicted during the elimination phase, folinic acid rescue was then prolonged in patients likely to be overexposed.

CONCLUSION

The Bayesian estimation presented in this study was an easy and convenient method to efficiently detect patients with impaired MTX elimination in routine clinical practice. This information enabled the introduction of strategies for minimizing the risk of severe drug toxicity.

Rapid high-performance liquid chromatographic determination of docetaxel (Taxotere) in plasma using liquid-liquid extraction

A new rapid and sensitive high-performance liquid chromatographic method for analysis of docetaxel (Taxotere) in human plasma was developed and validated. After adding an internal standard (paclitaxel, Taxol), plasma was extracted following a simple liquid-liquid extraction with diethyl ether. Extraction efficiency averaged 95% for docetaxel. Separation was performed using a Nucleosil (C18) 5 microm column, monitored at 227 nm. The isocratic mobile phase consisted of acetonitrile-acetate buffer, pH 5-tetrahydrofuran (45:50:5, v/v) pumped at a flow-rate of 1.8 ml/min. The limit of quantification for docetaxel in plasma was 12.5 ng/ml. Retention times for docetaxel and paclitaxel were 7.7 and 9 min, respectively. Standard curves were linear over a range of 25-1,000 ng/ml. This new method is rapid since it does not require time-consuming extraction procedures, or complex chromatographic conditions. This rapidity, along with the lack of chromatographic interferences with various other drugs likely to be administered to the cancer patients (pain killers, corticoids, antiemetics drugs) make this method suitable for daily routine analysis of Taxotere, a major anticancer drug extensively used in clinical oncology.

The fungal biocontrol agent Coniothyrium minitans: production by solid-state fermentation, application and marketing

Biological control agents (BCAs) are potential alternatives for the chemical fungicides presently used in agriculture to fight plant diseases. Coniothyrium minitans is an example of a promising fungal BCA. It is a naturally occurring parasite of the fungus Sclerotinia sclerotiorum, a wide-spread pathogen which substantially reduces the yield of many crops. This review describes, exemplified by C. minitans, the studies that need to be carried out before a fungal BCA is successfully introduced into the market. The main aspects considered are the biology of C. minitans, the development of a product by mass production of spores using solid-state fermentation technology, its biocontrol activity and marketing of the final product.

Pharmacokinetic and pharmacodynamic analysis of sedative and amnesic effects of lorazepam in healthy volunteers

This study describes for the first time the pharmacokinetic and pharmacodynamic modeling of the psychomotor and amnesic effects of a single 2-mg oral dose of lorazepam in healthy volunteers. Twelve healthy volunteers were included in this randomized, double-blinded, placebo-controlled two-way crossover study. The effect of lorazepam was examined for a battery of tests that explored mood, vigilance, psychomotor performance, and memory. The pharmacokinetic and pharmacodynamic modeling of these tests was performed using the indirect response model. Vigilance and psychomotor performance were significantly impaired. Short-term memory was not affected, but a paradoxical tendency to improvement of the score was observed 0.4 hours after drug intake. Significant impairment was observed for immediate and delayed cued verbal recall, for immediate and delayed free recall, and for picture recognition as well as for visual-verbal recall, but not for cued visual-spatial recall or priming. Globally, the different effects were greatest between 0.4 to 3 hours after dosing. However, the time course profile of the recovery period suggests a possible dissociation between the kinetics of the effects of lorazepam on vigilance, psychomotor performance, and visual episodic memory, on the one hand, and on verbal episodic memory, on the other. The pharmacokinetic and pharmacodynamic model used two compartments with first-order absorption to describe the lorazepam concentrations and an indirect response model with inhibition or stimulation of Kin to describe the effects. The mean values for calculated median effective concentration (EC50) derived from the pharmacokinetic and pharmacodynamic modeling of the different tests ranged from 11.3 to 39.8 ng/mL. According to these EC50 values, lorazepam seemed to be more potent on the delayed-recall trials than on the immediate-recall trials; similar observations were made concerning the free-recall versus cued-recall trials. The previously stated results suggest that the tests performed in this study represent sensitive measurements of the effects of lorazepam on the central nervous system. Moreover, the parameter values derived from pharmacokinetic and pharmacodynamic modeling, especially, the EC50 values, may provide sensitive indices that can be used to compare the central nervous system effects of benzodiazepines.

Phase II study of a combination of cisplatin, all-trans-retinoic acid and interferon-alpha in squamous cell carcinoma: clinical results and pharmacokinetics

Preclinical and clinical data suggest a certain antitumor efficacy for combination of retinoids, cytokines and cytotoxic compounds.

PATIENTS AND METHODS

Between November 1994 and October 1996, 38 patients with advanced squamous cell carcinoma were enrolled in a phase II study to investigate an association of low-dose all-trans-retinoic acid (tRA) (40 mg/m2/day, 84 days), interferon-alpha (IFN-alpha) (6.10(6) UI/day, 84 days s.c.) and cisplatin (40 mg/m2/day, day 1, 28 and 56, i.v.). A Pharmacokinetic evaluation was performed on 12 patients.

RESULTS

The incidence of grade 3/4 hematologic toxicities was moderate (< 20%). Extra hematological toxicities were frequent but easily manageable and not life threatening. However, treatment delivery was poor since only 6 patients (16%) received full therapy. Seven objective responses were observed (21%), suggesting some degree of synergism between tRA, IFN-alpha and cisplatin. Interestingly, continuous tRA treatment in combination with IFN-alpha and cisplatin did not induce a significant decrease in plasma levels, as had been previously described.

CONCLUSIONS

Regarding the short median response duration and the frequency of toxic events, this regimen should no longer be recommended in pretreated patients with advanced disease. However, the consistent response rate reported here may warrant further investigation in an early setting.

Panax vietnamensis protects mice against carbon tetrachloride-induced hepatotoxicity without any modification of CYP2E1 gene expression

In order to explore the effect of Panax vietnamensis on carbon tetrachloride-induced hepatotoxicity, mice were pretreated for 7 days with either crude extract or total saponins. Crude extract and total saponins dramatically decreased carbon tetrachloride-induced increase of serum GST alpha level (-50.0%, -49.5% respectively). Serum AST level was significantly decreased only with total saponins (-52.2%) and ALT level was slightly modified. In vitro experiments shown that both preparations at high concentrations (> 2000 micrograms/ml) are able to inhibit CYP2E1 enzymatic activity in mouse and human microsomes. However, we did not observe any modification of Cyp2e1 gene expression (enzymatic activity, protein and mRNA levels) in mice treated with either crude extract or total saponins. Taken together, these data demonstrated that Panax vietnamensis could be used as an hepatoprotectant. However, the mechanism of action is not associated with CYP2E1 expression, as previously suggested in vitro in rat for total saponins from Panax ginseng.

Plasma, urine and skin pharmacokinetics of cefepime in burns patients

We studied the pharmacokinetics of cefepime (2 g bd) in six burns patients. Blood, urine and skin samples were collected to measure cefepime concentrations. A two-compartment model was fitted to the data. At day 1, t(1/2beta) was 2.45 +/- 0.56 h, V(ss) 0.36 +/- 0.1 L/kg, total clearance 152 +/- 25.2 mL/min, and AUC 217 +/- 34 mg*h/L. There was no statistical difference between day 1 and day 3 for any of the pharmacokinetic parameters. We demonstrated good penetration of cefepime in skin. These results show that it is not necessary to change the standard dosage of cefepime in burns patients.

Relationship between efficacy, tolerance, and plasma drug concentration of ritonavir in children with advanced HIV infection

The relationship between ritonavir plasma concentration, efficacy, and tolerance was evaluated in 31 children with advanced HIV infection who were receiving a triple therapy with ritonavir as protease inhibitor. Median CD4+ lymphocyte count and median viral load before the initiation of ritonavir-containing combination therapy were 1320 cells/mL and 5 log10 copies/mL, respectively. Ritonavir was given at a dose ranging from 300 to 450 mg/m2 twice daily. The median follow-up of triple therapy was 19 months. Response was defined as a drop of viremia of more than 1 log. Plasma drug levels were determined twice during the observation period: after at least 4 weeks and after 3 months of combined treatment. Samples were collected before (residual) and 2 hours (T2) after drug intake. Cholesterol, triglycerides, alanine transaminase, aspartate transaminase, and gamma-glutamyl transpeptidase were assessed at the same time. The median values of ritonavir residual and T2 levels were 1.64 mg/L and 5.9 mg/L at observation 1 and 3.35 mg/L and 6.29 mg/L at observation 2, respectively. According to virologic response, median residual concentrations of ritonavir were 3.17, 2.52, and 1.04 mg/L for the complete, the partial, and the no-response groups. The authors observed a wide intersubject variability of ritonavir concentrations with an increase in residual levels between the two observation periods. Residual levels were correlated with virologic response whereas there was no direct association between T2 levels and long-term response. Patients with complete or partial response displayed statistically significantly higher residual concentrations than the no-response group. No correlation could be demonstrated between elevated plasma drug concentrations and abnormal cholesterol or triglycerides values. These results emphasize the importance of a sustained high ritonavir concentration to achieve optimal treatment efficacy. Furthermore, these results prove the clinical benefit of therapeutic drug monitoring and could potentially improve patient evaluation in terms of treatment efficacy, compliance, and viral resistance.

[Treatments with alpha-stimulants in urology]

Neuropharmacology is a rapidly expanding field due to the regular discovery of new neurotransmitters or neuroreceptors. Hopes have now been raised for the treatment of vesicosphincteric disorders by developing molecules with a potential selective clinical action on the detrusor or the urethra. After a brief review of the neuroanatomy and general neuropharmacology of the sympathetic nervous system, the current indications for alpha agonists are reviewed and discussed. These indications include the treatment of priapism, retrograde ejaculation, and incontinence due to sphincter incompetence. The more recent use of agents with a central mechanism of action is also discussed (detrusor hyperactivity of spinal cord injury patients). The authors review the current indications and note that, although the use of these drugs is very specific and limited in the field of urology, it is nevertheless based on an interesting concept. Like molecules at the stage of clinical trials for peripheral or central targets, the mechanism of action of these molecules on the sympathetic adrenergic system needs to be more fully elucidated. Their adverse effects remain the limiting factor for use on peripheral targets.

Oxidative metabolism of bupivacaine into pipecolylxylidine in humans is mainly catalyzed by CYP3A

Bupivacaine is used to provide prolonged anesthesia and postoperative analgesia. The human cytochrome P450 (CYP) involved in bupivacaine degradation into pipecolylxylidine (PPX), its major metabolite, has, to our knowledge, never been described. Microsome samples were prepared from six human livers and incubated in the presence of bupivacaine. The concentrations of PPX in the microsomal suspensions were assessed, and K(m) and V(max) values were calculated. Bupivacaine incubations were then performed with specific CYP substrates and inhibitors. For each sample of hepatic microsomes, the correlation between the rate of PPX formation and the corresponding erythromycin N-demethylase activity was analyzed. Finally, an immunoinhibition study using an anti-rabbit CYP3A6 antibody and assays with cDNA-expressed human CYP were conducted. The apparent K(m) and V(max) values of bupivacaine were, respectively, 125 microM and 4.78 nmol/min/mg of microsomal protein. The strongest inhibition of bupivacaine metabolism was obtained for troleandomycin (-95% at 50 microM), a specific CYP3A inhibitor. The correlation between PPX formation and erythromycin N-demethylase activity showed an R value of 0.99 whereas anti-rabbit CYP3A6 antibody inhibited the degradation of bupivacaine into PPX by 99%. Finally, CYP1A2 and CYP2E1 cDNA-expressed forms of human CYP did not allow PPX formation, CYP2C19 and CYP2D6 produced only small amounts whereas CYP3A4 most efficiently metabolized bupivacaine into PPX. These results demonstrated that bupivacaine degradation into PPX was mediated in humans by CYP3A.

Pharmacokinetics of intrapleural cisplatin for the treatment of malignant pleural effusions

We determined the toxicity and pharmacokinetics of high-dose intrapleural cisplatin (CDDP) as a treatment of malignant pleural effusions (MPE). Fourteen patients with MPE were enrolled in this study. After complete drainage of the fluid, a catheter was inserted into the pleural cavity during a thoracoscopy. CDDP (300 mg) was administered via the catheter in a 6-h infusion. Peak levels, the areas under the concentration curve (AUC), and drug half-lives were measured in pleural fluid and plasma samples collected at 0 (baseline), 6, and 24 h as well as 4, 14, and 21 days after intrapleural administration. The dosage of CDDP ranged from 153 to 203 mg/m2. The time interval between infusion was prolonged until a maximum of 109 days. Only 7/40 infusions were associated with adverse effects in 4 patients (18%). Residual concentrations in pleural fluid (0.66+/-0.07 microgram /ml) were three-fold higher than in plasma (0.13+/-0.07 microgram/ml). In pleural fluid, maximal concentration (Cmax) varied from 19 to 900 microgram/ml and in plasma from 0.34 to 3.65 microgram/ml. AUC in plasma during the three courses was 112+/-49 microgram/ml/d. The T1/2 was 31+/-33 days higher than that previously reported after intravenous administration (8-15 days). Although intrapleural CDDP has the potential advantage of treating the underlying malignancy in addition to controlling the malignant effusion with a good tolerance, it cannot be recommended for the standard control of malignant pleural effusion. Indeed we observed a great variability of intrapleural CDDP concentration depending on the extent of pleural invasion and plasma diffusion. Further studies are needed to determine the value of high-dose intrapleural CDDP for the treatment of MPE.

Kinetics of plasma and tissue distribution of 9-cis-retinoic acid in rat

The biotransformation and tissue distribution of 9-cis-retinoic acid was investigated in hairless rats. Indeed, only limited information is available about the pharmacokinetics of 9-cis-retinoic acid. Assuming that the target site for retinoids is the skin, tissue distribution study is therefore particularly justified. Following single oral administration of 30 mg/kg of 9-cis-retinoic acid, the parent drug and five metabolites were detected in plasma. Additionally, concentrations of 9-cis-retinoic acid and metabolites were determined in the skin and seven other tissues. The distribution of 9-cis-retinoic acid was rapid in all of the organs studied (T(max) </=2 h). In skin, unchanged 9-cis-retinoic acid was still measurable up to 168 h after administration and was undetectable in other organs and plasma after 48 h.

Oral administration of cholera toxin B-insulin conjugates protects NOD mice from autoimmune diabetes by inducing CD4+ regulatory T-cells

Restoration of peripheral tolerance to target autoantigens during autoimmune diseases has met with several limitations because of the limited efficacy of this approach in an already immune host. To optimize the induction of tolerance, we have shown that feeding insulin conjugated to cholera toxin B-subunit (CTB), a potent mucosal adjuvant, reduced by 5,000 the amounts of antigen necessary for delaying diabetes onset in NOD mice. To analyze these protective mechanisms, we have performed cotransfer experiments using splenocytes from young females fed once with 10 microg of CTB-insulin, mixed with diabetogenic T-cells, and intravenously injected into irradiated syngeneic male recipients. We demonstrated that the delayed onset of diabetes relied on CD4+ T-cells. We studied the cytokine production from plate-bound anti-CD3-stimulated cells. Higher interleukin (IL)-4 amounts were observed in both splenocytes and pancreatic lymph node (PLN) cell cultures from CTB-insulin-fed mice as soon as 4 h after the feeding. An increase in the levels of transforming growth factor-beta was seen after 24 h only in the mesenteric lymph nodes (MLN). In both of these organs, a reduction of gamma-interferon (IFN-gamma) production occurred after CTB-insulin treatment, at 24 h in the PLN and at 7 days in the MLN. Reverse transcription-polymerase chain reaction analysis indicated an increase in the level of IL-4 and a reduction in IFN-gamma transcripts in the PLN of mice treated orally with CTB-insulin and of the recipients of regulatory T-cells. Using different strains of congenic NOD mice at the Thy1 locus, we showed that protection was associated with the accumulation of T-cells from CTB-insulin-fed mice in the lymph nodes from draining sites containing functional islets, i.e., the PLN in normal mice and the renal lymph nodes after a syngeneic islet graft under the kidney capsule of streptozotocin-treated mice. Taken together, our results clearly indicate that oral administration of CTB-insulin conjugates in NOD mice produced a shift from a T-helper type 1 to a type 2 profile with the induction of antigen-specific regulatory CD4+ T-cells in the vicinity of the mucosal barrier and close to the inflamed islets.

Pharmacokinetic-pharmacodynamic analysis of mnesic effects of lorazepam in healthy volunteers

AIMS

To describe the pharmacokinetic-pharmacodynamic modelling of the psychomotor and mnesic effects of a single 2 mg oral dose of lorazepam in healthy volunteers.

METHODS

This was a randomized double-blind, placebo-controlled two-way cross-over study. The effect of lorazepam was examined with the following tasks: choice reaction time, immediate and delayed cued recall of paired words and immediate and delayed free recall and recognition of pictures.

RESULTS

The mean calculated EC50 values derived from the PK/PD modelling of the different tests ranged from 12.2 to 15.3 ng ml-1. On the basis of the statistical comparison of the EC50 values, the delayed recall trials seemed to be more impaired than the immediate recall trials; similar observations were made concerning the recognition vs recall tasks.

CONCLUSIONS

The parameter values derived from PK/PD modelling, and especially the EC50 values, may provide sensitive indices that can be used, rather than the raw data derived from pharmacodynamic measurements, to compare CNS effects of benzodiazepines.

CYP2E1 and CYP3A1/2 gene expression is not associated with the ursodeoxycholate effect on ethanol-induced lipoperoxidation

Ethanol is a well-known hepatotoxicant inducing steatosis and membrane lipoperoxidation. The aim of the present study was to investigate in rats, whether the protective effect of UDC on ethanol-induced lipid peroxidation may be related with CYP2E1 and CYP3A1/2 gene expression. We showed that UDC treatment in ethanol-fed rats induced a significant decrease in liver triglyceride concentration which was closely correlated with a reduction in malondialdehyde and hydroxyalkenal levels. In chronically ethanol-fed rats, CYP2E1 and CYP3A1/2 gene expressions were increased by a post-transcriptional mechanism. These inductions, mainly of CYP2E1, could take part in alcohol-induced hepatic lipoperoxidation. UDC modified neither the specific activity, nor the protein level, nor the mRNA level of CYP2E1 when compared with control. UDC supplementation to alcohol diet did not prevent the increase in CYP2E1 expression of ethanol-fed rats. Furthermore, CYP3A1/2 protein levels were similarly increased by ethanol and ethanol plus UDC treatment. Therefore, UDC protective effect against ethanol-induced lipoperoxidation was not associated with a modification of CYP2E1 and CYP3A1/2 expression.

Histamine H3-receptor stimulation is unable to modulate noradrenaline release by the isolated rat heart during ischaemia-reperfusion

The aim of this study was to evaluate the ability of H3-histaminergic prejunctional receptors to modulate the noradrenaline release induced by myocardial ischaemia in the rat, and the effects of an eventual modulation on haemodynamic, biochemical and electrophysiological parameters. Isolated rat hearts were perfused according to the Langendorff technique. Control hearts (n = 13) were not treated; two groups were treated with the H3-agonist R-alpha-methyl-histamine at 0.3 microM (n = 14) and 1 microM (n = 11) and one group, used as positive control, was treated with the selective alpha 2-agonist Mivazerol at 0.5 microM (n = 14) added to the perfusion medium. Noradrenaline, lactate and transaminase output in the coronary effluent, as well as various haemodynamic and electrophysiological parameters, were measured during global and total ischaemia (30 min) and reperfusion (30 min). alpha 2-receptor stimulation increased ischaemia-induced noradrenaline release during reperfusion (195 +/- 13 vs. 145 +/- 12 pmol.g-1 in control group, P < 0.05). In contrast, R-alpha-methyl-histamine, at both doses, did not significantly modify these parameters. Both treatments did not affect ischaemia- and reperfusion-induced haemodynamic (decrease in heart rate or in left ventricular developed pressure), biochemical (lactate and GOT release) and electrophysiological (arrhythmias or increase in action potential duration) alterations. Unlike other species, the rat appears to be insensitive to H3-histaminergic receptor modulation of ischaemia-induced noradrenaline release, although a modulation can be seen with other prejunctional receptor agonists.

Sensitivity of three recent questionnaires to mild traumatic brain injury-related effects

OBJECTIVE

To evaluate the sensitivity of three recently developed questionnaires to mild traumatic brain injury (MTBI)-related effects.

DESIGN

Comparison of an MTBI group, within 3 weeks of injury, to a normal control group.

SETTING

Outpatient rehabilitation clinic.

SUBJECTS

120 MTBI patients and 120 age, education, sex, and preinjury socioeconomic status-matched normal control subjects.

MAIN OUTCOME MEASURES

The Problem Checklist (PCL) from the New York Head Injury Family Interview to assess MTBI symptoms, the Short Form-36 Health Survey (SF-36) to assess functional burden associated with health problems, and the Community Integration Questionnaire (CIQ) to assess home, social, and productive activities.

RESULTS

Patients' self-ratings on the PCL and SF-36, but not the CIQ, were generally worse than those of the normal controls. The largest differences were obtained on SF-36 measures that appear to assess musculoskeletal injury effects.

CONCLUSIONS

The PCL and SF-36 show promise as sensitive measures of MTBI-related effects. The SF-36 may be particularly useful in evaluating associated musculoskeletal injuries, which might otherwise be overlooked by MTBI health care providers.

Myocardial meta-[125l]iodobenzylguanidine uptake in awake genetically hypertensive rats at different ages: an autoradiographic study

The purpose of this work was to evaluate changes in myocardial meta-[125I]iodobenzylguanidine ([125I]MIBG) uptake and distribution with age in awake spontaneously hypertensive rats (SHR) with respect to Wistar-Kyoto (WKY) rats. Rats were randomly divided into two groups, one for measuring myocardial [125I]MIBG uptake and distribution 4 h after its injection and the second for evaluating myocardial catecholamine concentrations. Mean arterial blood pressure, cardiac hypertrophy index (heart/body weight ratio), and heart rate were significantly higher with increasing age in SHR compared with matched WKY rats. Myocardial catecholamine concentrations and turnover did not differ between the two strains and were significantly decreased with increasing age. Myocardial [125I]MIBG uptake determined by gamma counting was similar in WKY rats and SHR and did not vary significantly with age when expressed as uptake density. However, in both strains of rats, [125I]MIBG uptake determined by autoradiography was significantly greater at the base of the heart than at the apex and midventricular levels, and the uptake values of young rats were significantly higher than those of older rats. In 21-week-old WKY rats and SHR, the highest [125I]MIBG uptake values were found in the right ventricle. Thus, quantitative autoradiography allowed detection of significant changes in myocardial [125I]MIBG uptake and showed its heterogeneous distribution in the rat heart.

In vivo demonstration of H3-histaminergic inhibition of cardiac sympathetic stimulation by R-alpha-methyl-histamine and its prodrug BP 2.94 in the dog

1. The aim of this study was to investigate whether histamine H3-receptor agonists could inhibit the effects of cardiac sympathetic nerve stimulation in the dog. 2. Catecholamine release by the heart and the associated variation of haemodynamic parameters were measured after electrical stimulation of the right cardiac sympathetic nerves (1-4 Hz, 10 V, 10 ms) in the anaesthetized dog treated with R-alpha-methyl-histamine (R-HA) and its prodrug BP 2.94 (BP). 3. Cardiac sympathetic stimulation induced a noradrenaline release into the coronary sinus along with a tachycardia and an increase in left ventricular pressure and contractility without changes in mean arterial pressure. Intravenous administration of H3-receptor agonists significantly decreased noradrenaline release by the heart (R-HA at 2 micromol kg(-1) h(-1): +77 +/- 25 vs +405 +/- 82; BP 2.94 at 1 mg kg(-1): +12 +/- 11 vs +330 +/- 100 pg ml(-1) in control conditions, P < or = 0.05), and increases in heart rate (R-HA at 2 micromol kg(-1) h(-1): +26 +/- 8 vs +65 +/- 10 and BP 2.94 at 1 mg kg(-1): +30 +/- 8 vs 75 +/- 6 beats min(-1), in control conditions P < or = 0.05), left ventricular pressure, and contractility. Treatment with SC 359 (1 mg kg(-1)) a selective H3-antagonist, reversed the effects of H3-receptor agonists. Treatment with R-HA at 2 micromol kg(-1) h(-1) and BP 2.94 at 1 mg kg(-1) tended to decrease, while that with SC 359 significantly increased basal heart rate (from 111 +/- 3 to 130 +/- 5 beats min(-1), P < or = 0.001). 4. Functional H3-receptors are present on sympathetic nerve endings in the dog heart. Their stimulation by R-alpha-methyl-histamine or BP 2.94 can inhibit noradrenaline release by the heart and its associated haemodynamic effects.

A randomized trial of two treatments for mild traumatic brain injury

The purpose of this study was to compare an education-oriented single session treatment (SS) for mild traumatic brain injury (MTBI) to a more extensive assessment, education, and treatment-as-needed intervention (TAN). Participants were 111 adults with MTBI who were recruited from consecutive admissions to two hospital emergency wards. They were randomly assigned to either the SS or TAN modality. The groups did not differ on any demographic, injury-related, or questionnaire variable when first seen within 3 weeks of injury. The groups generally improved a similar amount and did not differ from each other on any symptom-related, functional, or vocational variables 3-4 months after their baseline session. Patient satisfaction ratings with services provided were also similar for the two groups. Brief educational intervention given soon after MTBI appears to be adequate for most MTBI survivors.

A preliminary normative profile of mild traumatic brain injury diagnostic criteria

This study investigated how mild traumatic brain injury (MTBI) diagnostic and related variables present in a large, nonreferred MTBI sample. Participants were 119 adults with MTBI, drawn from consecutive admissions to two hospital emergency wards. Within 3 weeks of injury, they were asked how the 1993 American Congress of Rehabilitation Medicine MTBI diagnostic criteria and related phenomena presented in their particular cases. Results showed that retrograde amnesia was not reported or was generally very brief; retrograde amnesia was not reported unless posttraumatic amnesia was also reported; and the median ratio of posttraumatic amnesia to retrograde amnesia duration, when both were reported, was 300:1. These and other data provide a preliminary normative profile of such MTBI phenomena, and can help with differential diagnosis of MTBI in individual cases.

Myocardial beta-adrenergic reactivity in pressure overload-induced cardiac hypertrophy in the rat

The purpose of this study was to evaluate the changes in myocardial beta-adrenergic reactivity in animals undergoing a 4 week cardiac pressure-overload. Abdominal aortic constriction (AAC) or sham operation (sham) were performed in male Wistar rats, and 4 weeks later, isoprenaline dose-effects (chronotropic, inotropic and lusitropic properties) were studied after pithing. Noradrenaline (NA) and adrenaline (A) concentrations and NA turn-over index (DHPG /NE ratio) were evaluated in heart ventricles, while beta-adrenoceptor characteristics in ventricle homogenates and slices with [125I]iodocyanopindolol and the beta (1)/beta (2)-adrenoceptor ratio were estimated. Four weeks of cardiac pressure overload resulted in a 70% increase in ventricle weight/body weight ratio (from 2.5 +/- 0.1 to 4.2 +/- 0.3 mg/g in sham and AAC rats, respectively) and a 24% increase in protein contents (from 11.3 +/- 0.7 to 14.0 +/- 1.1 mg/100 mg ventricle in sham and AAC rats respectively). The ventricle NA content was similar in AAC and sham, while the ventricle A content and NA turn-over index were significantly increased in AAC rats (35 and 80% vs sham, respectively). Dose response of isoprenaline was significantly shifted to the right for all studied effects in AAC rats. However, maximal response (in relative values) was similar in AAC and sham rats only for heart rate but not for parameters depending on left ventricle contractile response. The beta-adrenoceptor density was significantly decreased in AAC by 30% without apparent affinity change and due to decreases in beta (1)-sites in septum and to beta (1)- and beta (2)-adrenoceptors in left ventricle endocardium. Decreases in isoprenaline-induced cardiac responses in AAC rats are associated with beta (1)-adrenoceptor density reduction and modification of beta (1)- and beta (2)-adrenoceptor ratio. These modifications are not the only reason for such dose response changes, at least for contractile response.

Myocardial beta-adrenergic reactivity in volume overload-induced cardiac hypertrophy in the rat

The purpose of this study was to evaluate the changes in myocardial beta-adrenergic reactivity in animals undergoing a 4 week cardiac volume overload. Aortocaval shunt (ACS) or sham operation (sham) were performed in male Wistar rats, and 4 weeks later, isoproterenol dose-effects (chronotropic, inotropic and lusitropic properties) were studied after pithing. Noradrenaline (NA) and adrenaline (A) concentrations and NA turn-over index were evaluated in plasma and heart ventricles, while beta-adrenoceptor characteristics in ventricle homogenates and slices with [125I]iodocyanopindolol, and the beta(1)/beta(2)-adrenoceptor ratio were estimated. Four weeks of cardiac volume overload resulted in a 55% increase in ventricle weight/body weight ratio (from 2.5 +/- 0.1 to 3.9 +/- 0.1 mg/g in sham and ACS rats, respectively) and a 20% increase in protein contents (from 11.3 +/- 0.7 to 13.8 +/- 1.1 mg/100 mg ventricles in sham and ACS rats, respectively). Furthermore, NA and A concentrations and NA turn-over index were increased in ACS rats (14, 40 and 80% versus sham, respectively). A shift to the right of the responses in heart rate, left ventricular systolic pressure, +dP/dtmax and -dP/dtmax responses following increasing doses of isoproterenol was observed, without change in the dose inducing maximum effect. Total beta-adrenoceptor characteristics and beta(1)/beta(2) ratio were unchanged. However, beta(1)-adrenoceptor density increased in epicardium while decreasing in endocardium of left ventricle from ACS rats. Rightward shift at lower doses of isoproterenol-induced cardiac responses in volume-overloaded rats are not likely due to overall beta-adrenoceptor density changes.

Bayesian calculation of methotrexate clearance after low dose intramuscular administration in patients with rheumatoid arthritis

OBJECTIVE

To determine a pharmacokinetic procedure (Bayesian method) for estimation of methotrexate (MTX) clearance, using only 2 blood samples, in outpatients with rheumatoid arthritis treated with low dose intramuscular (i.m.) MTX.

METHODS

Population pharmacokinetic parameters were obtained by the weighted least squares (WLSQ) method in plasma samples from 14 patients with rheumatoid arthritis (RA). In each patient, 11 samples were measured by fluorescence polarization immunoassay, at Time 0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, and 24 h after i.m. administration. These measures were validated by pharmacokinetic studies in 20 other patients with RA. Individual total body clearance of MTX was calculated using only 2 plasma samples (at 0.5 and 2 h after i.m. injection) by the Bayesian method using the population pharmacokinetic parameters. The clearance measures obtained by the Bayesian method were compared with those obtained by the WLSQ method.

RESULTS

The pharmacokinetic variables (clearance, half-life, area under the curve) of 14 patients were determined, as well as the covariance and the mean values necessary to apply the Bayesian method. No significant difference was found between clearance values obtained by the Bayesian method compared to the WLSQ method, confirming the validity of the Bayesian values.

CONCLUSION

The present population pharmacokinetic parameters allowed the determination of individual clearance of MTX with only 2 plasma samples (0.5 and 2 h after administration) in patients treated with low dose im MTX. Individual clearance is used to modulate MTX administration in patients presenting adverse reactions in spite of good clinical response. Individual determination of MTX pharmacokinetics in patients at risk for adverse MTX reactions could be useful for adjustment of the drug regimen.

Assay of paclitaxel (Taxol) in plasma and urine by high-performance liquid chromatography

A new, rapid and sensitive high-performance liquid chromatographic method for the analysis of paclitaxel (Taxol) in human plasma and urine was developed and validated. After addition of an internal standard, paclitaxel was extracted from plasma or urine by a liquid-liquid extraction using diethyl ether. Extraction efficiency averaged 90%. Chromatography was performed isocratically on a reversed-phase column monitored at 227 nm. Retention times were 7.7 and 6.7 min for paclitaxel and docetaxel, respectively, and the assay was linear in the range 25-1000 ng/ml. The limits of quantification for paclitaxel were 25 and 40 ng/ml in plasma and urine, respectively. The assay was shown to be suitable for pharmacokinetic studies of children involved in a phase I clinical trial.

Effects of tobacco smoke on the gene expression of the Cyp1a, Cyp2b, Cyp2e, and Cyp3a subfamilies in mouse liver and lung: relation to single strand breaks of DNA

Cigarette smoking is a worldwide health problem and is the greatest risk factor for lung cancer. By activating procarcinogens, hepatic and extrahepatic cytochromes P450 can participate in lung carcinogenesis. Tobacco smoke contains numerous cytochrome P450 inducers, substrates, and inhibitors. In the present study we investigated, in male NMRI mice, the effects of cigarette smoke on hepatic and pulmonary cytochrome P450 expression and their possible role in the induction of DNA lesions such as DNA single strand breaks (SSB). Hepatic and pulmonary mouse cytochrome P450 isozymes involved in carcinogenesis (Cyp1a, 2b, 2e, 3a) were differently induced by cigarette smoke. Cyp2e1 mRNA was dramatically enhanced (12.7-fold increase) while Cyp2b10 mRNA remained unchanged and Cyp1a1 was decreased or not detected. Cyp3a protein and mRNA were not detected in lung, suggesting that this isozyme is not expressed in mouse pulmonary tissue. The SSB of DNA increased in lung and liver treated mice. In contrast no modification was observed in lymphocytes that barely expressed cytochromes P450. Cimetidine and propylene glycol reduced SSB of DNA induced by smoking in liver and lung cells. The inhibition (-70%) observed in lung following treatment by propylene glycol, a CYP2E1 inhibitor, suggested that this isozyme is at least in part involved in pulmonary DNA damage induced by tobacco smoke. The high concentration of CYP2E1 function and regulation in mammals suggests that this protein could be involved in pulmonary carcinogenesis in human smokers.

In vitro antiarrhythmic effect of prior whole body hyperthermia: implication of catalase

The protective effect of heat stress against mechanical dysfunction and myocardial necrosis after prolonged ischemia is well known. We have investigated whether the protective effect of heat stress extends to reperfusion arrhythmias in the isolated perfused rat heart. Rats were exposed to 20 min of 42 degrees C hyperthermia. Twenty-four h later their hearts were isolated, perfused and subjected to a 5-min period of occlusion of the left coronary artery. The incidence and duration of reperfusion arrhythmias were assessed in the 30-min reperfusion period. Prior heat stress led to a reduction in the incidence (from 100 to 60%, P</=0.05) and duration (from 611+/-251 to 62+/-51 s, P</=0.05) of ventricular tachycardia and/or fibrillation, upon reperfusion following a 5-min ischemic period. This prevention of reperfusion arrhythmias was associated with a two-fold increase in endogenous catalase activity and an enhanced heat stress protein hsp 72 and 27 expression. Catalase inhibition by 3-amino triazole (AT) abolished the antiarrhythmic effect of heat stress. The incidence (80 v 100%) and duration (691+/-238 v 989+/-242 s) of reperfusion arrhythmias were not different between the group heat shocked + AT and the group treated only with AT. On the other hand, in the presence of AT, myocardial noradrenaline release was attenuated by prior heat stress (upon stabilization: 3.9+/-0.8 compared to 9.4+/-2.1 pg/ml/g tissue, P</=0.05; upon reperfusion: 42.7+/-7.3 compared to 69.8+/-9.5 pg/ml/g tissue, P</=0.05). In conclusion, heat stress leads to protection against reperfusion arrhythmias occurring after a short ischemic insult, in the isolated rat heart. Heat stress proteins and catalase seem to be implicated in this protective effect. Finally, we have shown that in presence of AT, heat stress decreases myocardial noradrenaline release.

Fetal heart modelling based on a pressure-volume relationship

Study of the cardiovascular system of the human fetus is based on non-invasive measurement methods such as Doppler echography systems. The circulation conditions in fetal vessels are usually evaluated by resistance indices, giving limited physiological information on distal territories such as the placenta or the brain. To enhance the understanding of human fetal haemodynamics, a numerical model of the fetal heart has been developed, using the hydraulic-electric analogy. The model is based on a mechanical hypothesis of parallel functioning of the right and left ventricles, considered to have analogue elastance properties. Their behaviour is equivalent to that of a single ventricle ejecting an equivalent blood volume of 7 ml in the aorta. The characterisation of the equivalent ventricle is based on the determination of a set of four parameters (Emax, Vo, kv and Po) representing the maximum ventricle contractility, a reference volume, and volume and pressure constants, respectively. The model proposed is validated by studying the effects of preload and afterload variations on the fetal heart work, and by comparing the numerical results with literature and measured data. The model constitutes the first step towards a global model of the cardiovascular system of the human fetus.