An updated model of hydrocephalus in sheep to evaluate the performance of a device for ambulatory wireless monitoring of cerebral pressure through shunts.

BACKGROUND: Cerebrospinal fluid (CSF) diversion by shunts is the most common surgical treatment for hydrocephalus. Though effective, shunts are associated with risk of dysfunction leading to multiple surgical revisions, affecting patient quality-of-life and incurring high healthcare costs. There is a need for ambulatory monitoring systems for life-long assessment of shunt status. The present study aimed to develop a preclinical model assessing the feasibility of our wireless device for continuous monitoring of cerebral pressure in shunts. METHODS: We first adapted a previous hydrocephalus model in sheep, which used an intracisternal kaolin injection. Seven animals were used to establish the model, and 1 sheep with naturally dilated ventricles was used as control. Hydrocephalus was confirmed by clinical examination and brain imaging before inserting the ventriculoperitoneal shunts and the monitoring device allowing continuous measurement of the pressure through the shunt for a few days in 3 sheep. An external ventricular drain was used as gold standard. RESULTS: Our results showed that a reduction in kaolin dose associated to postoperative management was crucial to reduce morbidity and mortality rates in the model. Ventriculomegaly was confirmed by imaging 4 days after injection of 75mg kaolin into the cisterna magna. For the implanted sheep, recordings revealed high sensitivity of our sensor in detecting fluctuations in cerebral pressure compared to conventional measurements. CONCLUSIONS: This proof-of-concept study highlights the potential of this preclinical model for testing new shunt devices.

Towards a laser neutron driver.

During the last few years, important experimental investigations have been made concerning the possibility of induced nuclear fission of high-Z elements by electromagnetic interaction (photofission, electron fission, neutron fission). Fast ions, neutrons and fission fragments from such interactions can be used to pump a laser medium, to produce energy from the (232)Th-(233)U nuclear fission cycle. The main aim of the present work is to study a three-step process, in a relatively new experimental scheme, in order to improve the number of both neutrons and fast ions. In the proposed scheme, high-energy particles and photons are produced by high-intensity laser beam interaction with a solid or gas target, which are utilized later on to trigger the nuclear reactions for the production of (photo) neutrons. These neutrons can give rise to fission of (232)Th that leads through a cascade of decays to (233)U --a highly fissionable material. Such a process will enhance, by an important factor, the final neutron flux and the energetic fission fragments. The use of a high intensity pulsed laser beam will control the turn-on and turn-off of the nuclear reactions and allow one to ensure the security of the whole operation. Finally, the produced neutrons are used to accomplish a major population inversion in an appropriate gas medium for the last stage of amplification of a high-contrast ultra-short laser seed pulse.

Study of substrate specificity of human aromatase by site directed mutagenesis.

Human aromatase is responsible for estrogen biosynthesis and is implicated, in particular, in reproduction and estrogen-dependent tumor proliferation. The molecular structure model is largely derived from the X-ray structure of bacterial cytochromes sharing only 15-20% identities with hP-450arom. In the present study, site directed mutagenesis experiments were performed to examine the role of K119, C124, I125, K130, E302, F320, D309, H475, D476, S470, I471 and I474 of aromatase in catalysis and for substrate binding. The catalytic properties of mutants, transfected in 293 cells, were evaluated using androstenedione, testosterone or nor-testosterone as substrates. In addition, inhibition profiles for these mutants with indane or indolizinone derivatives were obtained. Our results, together with computer modeling, show that catalytic properties of mutants vary in accordance with the substrate used, suggesting possible differences in substrates positioning within the active site. In this respect, importance of residues H475, D476 and K130 was discussed. These results allow us to hypothesize that E302 could be involved in the aromatization mechanism with nor-androgens, whereas D309 remains involved in androgen aromatization. This study highlights the flexibility of the substrate-enzyme complex conformation, and thus sheds new light on residues that may be responsible for substrate specificity between species or aromatase isoforms.

New aromatase inhibitors. Synthesis and biological activity of aryl-substituted pyrrolizine and indolizine derivatives.

We report herein the design and the synthesis of some aryl-substituted pyrrolizine and indolizine derivatives, on the basis of a hypothetical pharmacophore structure designed to fit the catalytic site of the human cytochrome P450 aromatase. The in vitro biological evaluation of these compounds allowed us to point out two new potent non-steroidal aromatase inhibitors, MR 20494 and MR 20492, with IC50 values in the range of 0.1 microM.

[Preclinical evaluation of aromatase inhibitors antitumor activity]. / Evaluation préclinique del'activité antitumorale des inhibiteurs de l'aromatase.

Aromatase is an enzymatic complex responsible for the conversion of androgens into estrogens; these hormones are important in development, reproduction, but also in the growth of estrogen-dependent cancer. This enzyme is present in 60-70% of the breast cancer. The aromatase inhibitors are important drugs in the breast cancer treatment of postmenopausal women. In order to study their in vivo activity, animal models have been developed, e.g. rat with tumour induced by 7,12-dimethylbenz[a]anthracene, PMSG-primed immature rat or athymic nude mice with aromatase transfected MCF-7 xenograft. In this review, we were interested in preclinical results obtained with both classes: steroidal and nonsteroidal inhibitors. The former group, as substrate analogs formestane or exemestane, are irreversible, selective and long-lasting inhibitors of aromatase. The nonsteroidal molecules, such as letrozole or anastrozole, are reversible inhibitors with high affinity. Finally, knowledge of the enzyme active site, with molecular modeling and site-directed mutagenesis, could be useful to develop new inhibitor families, more specific and potent in vivo.

MR 20492 and MR 20494: two indolizinone derivatives that strongly inhibit human aromatase.

In this study, we describe the synthesis of a new family of indolizinone derivatives designed to fit an extrahydrophobic pocket within the active site of aromatase and to strongly inhibit human aromatase. This could help improve the specificity of the inhibitors. Equine aromatase, very well characterized biochemically, is used as a comparative model. Indeed, in a previous comparison between both human and equine aromatases, we described the importance of the interaction between the inhibitor and this pocket for the indane derivative MR 20814. MR 20492 and MR 20494 are more potent inhibitors of human aromatase (Ki/Km: 1.0+/-0.3 and 0.5+/-0.3, respectively). The Ki/Km for MR 20494 is slightly higher than that obtained for fadrozole (0.1+/-0.0) and Ki/Km for both indolizinone derivatives are lower than those obtained for 4-hydroxyandrostenedione (1.9+/-0.8) and MR 20814 (8.1+/-.7). These new compounds are not enzyme inactivators. Moreover, as indicated by the higher Ki/Km values obtained with equine enzyme (9.0+/-0.6 and 6.1+/-1.6 for MR 20492 and MR 20494, respectively), both human and equine aromatase active sites appear to be structurally different. Difference absorption spectra study (350-500 nm) revealed that MR20492 and MR20494 were characterized by a combination of type-I and -II spectra with both enzymes. This result could be due to the isomerization of the molecule in polar solvent (Z and E forms). The evaluation of these new molecules, as well as 4-hydroxyandrostenedione and fadrozole, on aromatase activity in transfected 293 cell cultures evidenced a strong inhibition (IC50: 0.20+/-0.03 microM, 0.20+/-0.02 microM and 0.50+/-0.40 microM for MR 20494, fadrozole and 4-OHA, respectively) except for MR 20492 (3.9+/-0.9 microM) and MR 20814 (10.5+/-0.6 microM). These results proved that these molecules formed part of a promising family of potent inhibitors and that they penetrate 293 cells, without evidencing any cytotoxicity in Hela cells with MTT assay. This is thus encouraging for the development of new drugs for the treatment of estrogen-dependent cancers, these molecules also constitute new tools for understanding the aromatase active site.

PAAn-1b and PAAn-E: two phosphorothioate antisense oligodeoxynucleotides inhibit human aromatase gene expression.

Estrogen-dependent diseases, especially breast cancers, are frequently treated with aromatase inhibitors. Another more recent strategy is the antisense technology. In this study, after predicting aromatase mRNA secondary structure, we describe the design, the efficiency, and the toxicity of two antisense phosphorothioate oligodeoxynucleotides (PAAn-1b and PAAn-E) directed toward aromatase mRNA. Indeed, 2 microM PAAn-1b and PAAn-E encapsulated with 54 microM polyethylenimine inhibit aromatase activity by 71 and 79%, respectively, in transfected 293 cells, with IC50 values of 0.2 and 0.6 microM. The mechanism of inhibition appears to be specific after using sense and scramble oligodeoxynucleotides as controls and largely decreases aromatase mRNA and protein amounts. Moreover, PAAn-1b and PAAn-E are not cytotoxic for 293 cells. This study finally provides a new strategy for aromatase inhibition. It offers new tools for studying aromatase gene expression and its role in cancer for instance, and this could be of help for the therapy of estrogen-dependent diseases.

Design and synthesis of a new type of non steroidal human aromatase inhibitors.

The structure-activity relationship study of one of recently described aromatase inhibitors, compound 1 (MR20814), allowed us to design some related derivatives as potential new inhibitors. Among those we synthesized, chlorophenylpyridylmethylenetetrahydroindolizinone 5 (MR20492) exhibited in vitro a ten-fold higher inhibition of the enzyme (IC50 = 0.2 +/- 0.0 microM and Ki = 10.3 +/- 3.3 nM).

[Prostate hypertrophy. Surgical experience in Belgium. Multi-center study of 1,140 patients of 80 years and older]. / Prostaathypertrofie. Chirurgische ervaring in België. Multicenter studie over 1.140 patiënten 80 jaar en ouder.

An inquiry organized by the Belgian Society of Surgery brought data on the mortality and morbidity of surgery on patients of 80 years and older for benign prostatic hypertrophy in a total number of 1,140 operations. Consensus exist to see this surgery as planned surgery. The mortality was 73 (6.3%) without statistical difference between endoscopic and open surgery. The morbidity of 824 patients was 165. This last figure relates to the big series in the literature. The mortality is in direct relation to the age of the patients. Evaluation of cardio-pulmonary risk (70.8% of the mortality), operation on indication at earlier diagnosis and prospective studies on the risk of operation in this population group are indicated.