Comprehensive lung injury pathology induced by mTOR inhibitors

Interstitial lung disease is a rare side effect of temsirolimus treatment in renal cancer patients. Pulmonary fibrosis is characterised by the accumulation of extracellular matrix collagen, fibroblast proliferation and migration, and loss of alveolar gas exchange units. Previous studies of pulmonary fibrosis have mainly focused on the fibroproliferative process in the lungs. However, the molecular mechanism by which sirolimus promotes lung fibrosis remains elusive. Here, we propose an overall cascade hypothesis of interstitial lung diseases that represents a common, partly underlying synergism among them as well as the lung pathogenesis side effects of mammalian target of rapamycin inhibitors (AU)

Wnt signalling and cancer stem cells

Intracellular signalling mediated by secreted Wnt proteins is essential for the establishment of cell fates and proper tissue patterning during embryo development and for the regulation of tissue homeostasis and stem cell function in adult tissues. Aberrant activation of Wnt signalling pathways has been directly linked to the genesis of different tumours. Here, the components and molecular mechanisms implicated in the transduction of Wnt signal, along with important results supporting a central role for this signalling pathway in stem cell function regulation and carcinogenesis will be briefl y reviewed (AU)

Hedgehog signalling as a target in cancer stem cells

Hedgehog (Hh) is one of the most important signalling pathways. Together with the Wnt, TGF-Beta/BMP and Notch pathways, it is involved in both embryonic development and adult tissue homeostasis. This is because Hh plays a central role in the proliferative control and differentiation of both embryonic stem cells and adult stem cells. In this way, an alteration in the Hh pathway, either by misexpression of components of that pathway or by changes in the expression of other cellular components that interfere with the Hh signalling system, may trigger the development of several types of cancer. This occurs because normal stem cells or their intermediaries toward differentiated mature cells are not part of the normal proliferative/ differentiation balance and begin to expand without control, triggering the generation of the so-called cancer stem cells. In this review, we will focus on the molecular aspects and the role of Hh signalling in normal tissues and in tumour development (AU)

Influence of hepatic regeneration after partial hepatectomy on theophylline pharmacokinetics in rats.

The influence of hepatic regeneration after partial hepatectomy on theophylline pharmacokinetics has been studied on the rat. At different times after partial hepatectomy, theophylline was administered intravenously as a single dose of 6 mg/Kg. Drug plasma levels were determined by HPLC and pharmacokinetic parameters were obtained. Physiological parameters were also measured. Following hepatectomy, an increase in mass liver was observed and 15 days after surgery, liver mass was 78% of nonhepatectomized rats. Initial theophylline concentrations varied during the regeneration period, as well as the distribution volume at steady-estate (Vss). Elimination half-life (t 1/2), notably increased after hepatectomy (7.27+/-1.38 h), decreased with time (6.70+/-1.18 h, 6.47+/-0.69 and 5.17+/-0.87 h after 24 h, 3 days and 15 days post-hepatectomy, respectively) to reach a value close to that of the control group (4.30+/-1.37 h). The increase in elimination half-life led to a decrease in the mean residence time during the period of liver regeneration. However, the intrinsic clearance hardly varied during regeneration period. We could establish the following relationship between liver weight (LW) and the elimination half-life: t 1/2 (h)=-0.358*LW (g)+8.6168 (R2=0.9906). For the mean residence time (MRT) this relationship was: MRT (h) =-0.5173*LW (g)+12.433 (R2=0.991).

Effect of aging on the release of salbutamol sulfate from lipid matrices.

The aim of the present work was to evaluate the influence of aging that might condition the release of salbutamol sulfate from oral formulations (lipid matrices) using Gelucire as lipid excipients. Gelucires are essentially characterized by their melting point and their hydrophilic-lipophilic balance. The release profiles of salbutamol sulfate from the capsules elaborated were dependent on the type of Gelucires, fast release, in the case of Gelucire 35/10, a slower release for Gelucire 48/09 and a slow release for Gelucire 46/07. Differential scanning calorimetry was used to study the physical state of drugs in the matrices. Gelucires may exhibit aging effects, whereby a range of physical properties may change upon storage. In the case of Gelucire 35/10, which presents a fast release of salbutamol sulfate, storage produces a decrease in the values of dissolution constant for all capsule sizes. Gelucire 48/09 showed a slower release rate than Gelucire 35/10, and after 1 year of storage, a decrease in the salbutamol dissolution rate for capsule number 3 and 4 was observed. Gelucire 46/07 presented the slowest dissolution rate, but there were not statistically significant differences. These results show that the faster the dissolution rate, and the larger the capsule size, the higher is the influence of storage.

Enhanced immune response after subcutaneous and oral immunization with biodegradable PLGA microspheres.

PLGA microspheres containing bovine serum albumin (BSA) as a model antigen, were prepared by a double emulsion/solvent extraction method and their in vitro characterization was performed. The same microspheres were used in a series of in vivo studies to evaluate the immune response induced after subcutaneous or oral inoculation following different immunization protocols. The in vivo data confirm that the immunogenicity of the albumin is not affected by the encapsulation procedure. The subcutaneous administration of microspheres showed an immune response (serum IgG levels by ELISA) statistically above BSA solution, even when the dose administered was 10 times lower. The adjuvanticity of the microspheres was found to be comparable to that of Freund's complete adjuvant (FCA), but in contrast to FCA they are biocompatible and did not induce any adverse reaction at the site of injection. A single oral administration of the microspheres was not a successful strategy for the induction of a reproducible response. Therefore, microspheres of 1 and 5 micrometer were orally administered on 3 consecutive days and the response obtained showed that the use of a boosting dose was not necessary for the 1 micrometer particles. These results suggest the possibility of simplifying the immunization schedule to a primary immunization if 1 micrometer particles are administered.

Influence of shaking and surfactants on the release of bsa from plga microspheres.

The aim of the present work was to study the release of a model protein, bovine serum albumin (BSA) encapsulated within biodegradable poly (D,L-lactide-co-glycolide) (PLGA) microspheres prepared by a modified solvent evaporation method using a double emulsion. These microspheres were characterized for size, morphology, surface adsorbed protein, encapsulation efficiency and release kinetics. Two types of in vitro assays were developed to evaluate the influence of shaking and the addition of surfactants on the release profile of encapsulated protein. Scanning electron microscopy (SEM) observation showed spherical and smooth surface particles, with a mean particle size of 20 microm and an encapsulation efficiency of 81%. Surface associated protein was about 25%. The in vitro release profile showed a biphasic pattern described by means of a biexponential equation. There was an initial burst effect due to the release of the protein adsorbed on the microsphere surface and a sustained release phase due to protein diffusion through the channels or pores formed in the polymer coat. The release obtained profiles in static and dynamic assays showed statistically significant differences in the amount of the released protein, whereas the release rate was not affected. The burst effect was 28.30+/-1.63% and 35.20+/-1.50% of the total encapsulated protein for the static and dynamic assays respectively. The addition of surfactants (SDS) to the release medium increased the rate and the amount of drug released. In both assays the value of the slow release rate constant, beta, was 0.029+/-0.002 days(-1) when the surfactant was added, and 0.017+/-0.0014 days(-1) in the samples without surfactant. It is believed that the surfactant leads to an increase in the microsphere surface polarity which allows channel and pore formation inside the polymer through which the protein diffuses easily.

Influence of formulation variables on the in-vitro release of albumin from biodegradable microparticulate systems.

Poly(D,L-lactide-co-glycolide) microspheres containing BSA were prepared by a modified solvent evaporation method using a double emulsion. These microspheres were characterized for size, morphology, surface absorbed protein, encapsulation efficiency and release kinetics. The influence of two formulation variables (the procedure to obtain the first emulsions and the lyophilization of the microspheres once obtained) on the physical characteristics and release behaviour of the microspheres was also investigated. Sonicated microspheres were smooth and spherical, with a mean particle size of 20 microns and an encapsulation efficiency of 81%. When the first emulsion was prepared by vortex mixing the particles were irregular and porous, with a mean size of 31 microns and a lower encapsulation efficiency (56%). The sonication allows a more homogeneous emulsion as well as a lower percentage of albumin adsorbed on the surface. The in vitro release profile was described as a biexponential process with an initial burst effect due to the release of the protein adsorbed on the microsphere surface and a second sustained release phase due to protein diffusion through the channels or pores formed in the polymer coat. The release of BSA was dependent on the preparation method. The greatest burst release was found for microspheres formulated using the vortex mixer, 58% of the encapsulated protein was released during the first 24 h, whereas sonicated microspheres released 32.2%. This burst effect could be reduced by lyophilizing the microspheres following their preparation. The amount of protein released decreased to 28.3% and 51.6% in sonicated and non-sonicated microspheres respectively, when they were lyophilized.

Influence of route of administration and dosage form in the pharmacokinetics and bioavailability of salbutamol.

The present study was carried out to define the pharmacokinetics of salbutamol sulfate administered to mongrel dogs in five pharmaceutical forms via two routes of administration. One pharmaceutical form was administered intravenously (Ventolin i.v.) while the other four were administered orally (Ventolin: immediate-release formulation, Volmax: commercial osmotic pump, SG7 and SG14: sustained-release hydrophilic matrices developed in our laboratory). We obtained a first-order release kinetic of the salbutamol from Ventolin and SG7, whereas a zero-order release kinetic was observed for SG14 and Volmax formulations. Oral bioavailability was 80% and there were neither significant differences (P > 0.05) in terms of the calculation method used (relation of the areas under the plasma level curve Loo-Riegelman, deconvolution) nor in terms of the dosage form (Ventolin Volmax, SG7 and SG14). The elimination half-life value of salbutamol was 1.2 h when administered intravenously; this parameter had a value of 3.0 h for the immediate-release formulation and ranged between 5.4 and 7.2 h in the sustained-release formulations when administered orally. These changes in the half-life value of the sustained-release formulations will allow us to modify the frequency of administration in relation to immediate-release formulations.

Influence of partial hepatectomy in rats on the activity of hepatic microsomal enzymatic systems.

The influence of partial hepatectomy on the activity of the hepatic microsomal enzymatic systems was determined in rats. Cytochrome P-450, cytochrome b5, four mixed functional oxidase (MFO) activities (microsomal aniline hydroxylase, p-nitroanisole O-demethylase, aminopyrine N-demethylase and NADPH cytochrome c reductase) and glutathione levels were measured in unhepatectomized rats (control group) and in hepatectomized rats 12 h, 24 h, 3 days and 6 days after 70% hepatectomy. Following surgery the remaining lobes of the liver grow rapidly in order to restore the original liver mass. Partial hepatectomy significantly reduces cytochrome P-450 and b5 content in the remaining liver as well as the four MFO activities studied. But when the enzymatic systems are expressed as nmoles/mg microsomal protein, only cytochrome P-450 shows statistical differences. The hepatic biotransformation capacity of drugs and xenobiotics decreases during the regeneration period due to the reduction of hepatic mass rather than because of a reduction of their metabolic capacity. Glutathione levels are increased after partial hepatectomy but increased glutathione-dependent protector mechanisms are not expected.

Influence of partial hepatectomy on theophylline pharmacokinetics in rats.

The influence of partial hepatectomy on the pharmacokinetics of theophylline was determined in rats. The pharmacokinetics of intravenous theophylline was studied in unhepatectomized rats (control group: CG) and in hepatectomized rats (HG) 12 h after 70% hepatectomy. Liver function was monitored in both groups by measurements of total and direct bilirubin, transaminases GOT and GPT, and plasma protein. Seventy per cent hepatectomy caused significant liver dysfunction: transaminase levels (GOT and GPT) increased by 118 and 683%, respectively, and the total and direct bilirubin levels increased by 28.6 and 9.1%, respectively. At the same time, plasma concentrations of theophylline decreased significantly and half-life increased from 4.16 +/- 0.57 h (CG) to 7.08 +/- 0.69 h (HG), as did the distribution volumes values of central (Vc) and peripheral (Vp) compartments (Vc: CG, 0.18 +/- 0.03 L; HG, 0.24 +/- 0.03 L) (Vp: CG, 0.08 +/- 0.05 L; HG, 0.13 +/- 0.05 L). The percentage of theophylline binding to plasma proteins decreased from 44.3% in CG to 33.8% in HG. The theophylline intrinsic clearance (CLint) dropped from 1.35 +/- 0.43 mL/min (CG) to 0.93 +/- 0.10 mL/min (HG)1, which can be attributed to a significant fall in the quantity of hepatic microsomal enzymes. These modifications on the pharmacokinetics of drugs with low hepatic extraction coefficients, such as theophylline, should be considered when dosage regimens during the posthepatectomy hepatic regeneration period are planned.

Pharmacokinetics and distribution of ketamine after extradural administration to dogs.

We have studied the pharmacokinetics and distribution of ketamine and its biotransformation products in dogs after extradural administration of ketamine at L4-5. The mean apparent uptake rate constants of ketamine for plasma and CSF were 4.17 (SD 1.84) and 5.15 (2.50) h-1, respectively. The concentrations of ketamine in CSF were greater than those found in plasma. The elimination half-life values of the parent drug for both biological fluids were similar (4.3 (2.96) h and 4.6 (3.31) h for plasma and CSF, respectively). The apparent formation rate constant of norketamine was greater than that of dehydronorketamine. However, the concentrations of the biotransformation products in CSF were smaller than those of the parent drug. These results are similar to the distribution of ketamine and its metabolites in different cerebral structures and tissues. The concentrations decreased in concert with the increase in polarity of the metabolites. A specific distribution for all compounds was observed. Ketamine showed a greater affinity for brainstem, while norketamine and dehydronorketamine were distributed mostly in cerebellum and kidney, respectively.

Pharmacokinetics of dibenzylamine administered in a sustained drug delivery system with cefazolin.

The pharmacokinetics of dibenzylamine administered in a sustained drug delivery system with cefazolin was studied after i.m. administration of a dose of 1250 mg to healthy volunteers. The serum and urine levels of dibenzylamine were determined by a GLC technique using a specific nitrogen-phosphorus detector. Characterization of the kinetic parameters was performed by applying compartmental and non-compartmental analysis. Dibenzylamine was found to reach concentrations close to 300 ng ml-1 approximately 5 h after administration. The elimination constant had a value of 0.832 +/- 0.821 h-1 (mean +/- S.D.), which is higher than the release constant of the derivative (0.109 +/- 0.072 h-1) (mean +/- S.D.). These results show that release of dibenzylamine may be considered the limiting kinetic process, which governs the elimination of the product from the organism. Only a small amount of dibenzylamine is excreted in urine unchanged 3.43 +/- 3.28 per cent (mean +/- S.D.). Using the pharmacokinetic parameters calculated for dibenzylamine, a prediction has been made of the concentrations reached in a multiple dosage regimen after administration of a dose of 1250 mg every 24 h. The accumulation factor was 1.09.

Pharmacokinetics of rectal ketamine in children.

We have studied the pharmacokinetics of ketamine administered rectally in a dose of 10 mg kg-1 to five children aged 6-9 yr and mean weight 28.80 (SD 6.55) kg. An acceptable level of anaesthesia was not obtained in any patient. Despite this, the degree of analgesia obtained was good and no child required further administration of analgesics during the postoperative period. Tolerance to the suppositories was excellent. The absorption of ketamine was found to be relatively fast, with a median peak concentration of 160 ng ml-1 (range 96-250 ng ml-1) at 0.75 h (range 0.50-1.00 h) after administration. The plasma concentrations of norketamine were greater than those of the parent drug, with a maximum of 510 ng ml-1 (range 450-810 ng ml-1) at 0.81 h (range 0.50-1.00 h) after administration. The medians of the half-lives of ketamine and norketamine were 3.15 h and 2.56 h, respectively (range 1.57-4.95 h and 1.47-5.30 h, respectively).

Choice of optimum pharmacokinetic model of orally administered paracetamol.

The present work studies the characterization of the pharmacokinetic profile of paracetamol following oral administration of DUOROL tablets containing 500 mg of the active compound. Analysis is made of the influence of statistical weighting on the selection of the pharmacokinetic model chosen. In the model proposed, the uptake of the drug into the systemic circulation is described by two first-order sequential kinetic processes. The values of the first order rate constants that define the absorption process have values of 4.79 and 9.73 h-1. Validation of the absorption model proposed was performed by applying the Wagner-Nelson method, according to which values of 4.63 and 10.95 h-1 were obtained for each of the constants defining the uptake of the drug into the systemic circulation.

Bioequivalence study of two oral formulations of paracetamol.

The pharmaceutical preparations of paracetamol Duorol and Termalgin, both containing 500 mg of active compound, were studied to test their bioequivalence. The results obtained showed that absorption of the drug follows two sequential kinetic processes by their corresponding first order rate constants (K1 and K2) with values of 0.31, 5.69 and 0.30, 5.71 h-1 for Duorol and Termalgin, respectively. Analysis of variance showed that there were no statistically significant differences (p greater than 0.5) in the absorption, biotransformation and excretion processes between the two preparations assayed. Finally, the use of symmetric confidence intervals by the Westlake test, showed that both preparations are bioequivalent.

Pharmacokinetic and clinical evaluation of ketamine administered by i.v. and epidural routes.

The evolution of the plasma levels of ketamine and its two biotransformation products, norketamine (metabolite I) and dehydronorketamine (metabolite II) was studied after i.v. and epidural administration at doses of 2 and 5 mg/kg, respectively. The results show a good access capacity of ketamine from the epidural space to the systemic circulation as reflected in the high value of its apparent incorporation constant (ka = 5.54 +/- 2.33 h-1) and its good bioavailability (F = 0.77 +/- 0.22). The evaluation of clinical parameters points to a more attenuated cardiovascular and respiratory response after administration of the anesthetic by the epidural route.