Electrical high frequency stimulation of the caudate nucleus induces local GABA outflow in freely moving rats

Electrical high frequency stimulation of the globus pallidus internus or the subthalamic nucleus has beneficial motor effects in advanced Parkinson's disease. The mechanisms underlying these clinical results remain, however, unclear. From previous in vitro studies it is proposed that the gamma-aminobutyric acid (GABA) system is involved in the effectiveness of electrical high frequency stimulation (HFS). In these experiments, we developed an in vivo model that allows for simultaneous and collocated microdialysis and HFS by electrical pulses of 124 Hz in the caudate nucleus of freely moving rats. GABA and glutamate outflow were sampled by microdialysis technique and quantified after pre-column o-phthaldialdehyde sulphite derivatization using HPLC with electrochemical detection. As the most outstanding result, we could demonstrate that high frequency stimulation significantly increased basal GABA outflow without affecting glutamate levels in freely moving rats.

A systemic route for drug loading to lymphatic phagocytes

Lymph nodes are primary germination and proliferation sites for many types of pathogens. Maintaining therapeutic levels of appropriate chemotherapeutic agents in the lymph node tissue is critical for the treatment of both infection and cancer. This study was intended to develop a systemic route for loading lymph node phagocytes with drugs, using a lymph node specific nanocarrier. The latter is assembled as a 10-15 nm particle with a drug-carrying core and a phagocyte-homing poly(1-->6)-alpha-d-glucose based interface. Biokinetics and microdistribution of the model carrier were investigated in vivo. Nanocarrier accumulation in lymph nodes reached 30-35% dose/g in central lymph nodes, with deposition in various phagocytic cell populations. The latter included cells harboring inhaled microparticles translocated to lymph nodes from the lungs. In view of the nanocarrier ability to transport and release significant amounts of various drug substances, the data suggests feasibility of systemic drug loading to lymphatic phagocytes and, through drug release, to the neighboring cells.

Propacetamol and diclofenac alone and in combination for analgesia after elective tonsillectomy

BACKGROUND

Diclofenac and paracetamol have different mechanisms and sites of action. Therefore, we tested if their combination is more effective for analgesia after tonsillectomy than either drug alone with respect to rescue analgesic consumption and visual analog scale values.

METHODS

The analgesic effects of intravenously administered propacetamol (injectable pro-drug of paracetamol) and diclofenac or a combination on postoperative pain were compared in 71 adult elective tonsillectomy patients in a randomized, double-blind study. After induction of anesthesia the patients received monotherapy with 2 g propacetamol (n = 25) or 75 mg diclofenac (n = 25), or a combined treatment with 2 g propacetamol and 75 mg diclofenac (n = 21) in physiologic saline as an infusion. Postoperatively the propacetamol dosage was repeated twice and diclofenac once on the ward. Oxycodone (0.03 mg kg(-1)) was used as a rescue analgesic by patient-controlled analgesia.

RESULTS

On average the patients needed oxycodone 15.3, 13.2 and 10.6 times in the propacetamol, diclofenac and combination groups, respectively (NS). A verbal rating scale and a visual analog scale were employed for assessing post-tonsillectomy pain, nausea and patient satisfaction in all groups. No statistically significant differences were found between the groups. Twelve of the 25 (48%) patients having received propacetamol complained of pain at the cannulation site.

CONCLUSION

Combined treatment with propacetamol and diclofenac with the dosages used provided clinically only a minor advantage over monotherapy with propacetamol or diclofenac with respect to postoperative analgesia or the incidence of side-effects in adult tonsillectomy patients.

Synthesis of a Macromolecular Camptothecin Conjugate with Dual Phase Drug Release

A water soluble macromolecular conjugate of camptothecin (CPT) with a new, dual phase hydrolytic drug release mechanism was prepared on the basis of a 60 kDa biodegradable hydrophilic "stealth" polyacetal, poly(1-hydroxymethylethylene hydroxy-methyl formal). Succinamido-glycinate was used as a prodrug releasing group. A model preparation with 7.5% CPT content w/w was water soluble. The lipophilic camptothecin prodrug, camptothecin-(O20)-succinimidoglycinate, was released from the conjugate with t(1/2) = 2.2 +/- 0.1 h in rodent plasma. The blood clearance in a rodent model as measured by CPT was release limited, t(1/2) = 2.1 +/- 0.2 h, while the conjugate half-life was 14.2 +/- 1.7 h. In a xenograft tumor model, the conjugate demonstrated higher antineoplastic efficacy than CPT at a less than equitoxic dose. This improved therapeutic window is in line with the modified drug pharmacokinetics and with camptothecin release in a stabilized lipophilic prodrug form. Regulation of prodrug release and hydrolysis rates through linker structure modification will open the way to further improve both pharmacokinetics and pharmacodynamics.

New genes encoding subunits of a cytochrome bc1-analogous complex in the respiratory chain of the hyperthermoacidophilic crenarchaeon Sulfolobus acidocaldarius

The soxL gene from Sulfolobus acidocaldarius (DSM 639) encodes a Rieske iron-sulfur protein. In this study we report the identification of two open reading frames in its downstream region. The first one, named soxN, codes for a membrane protein bearing a resemblance to the b-type cytochromes of the cytochrome bc1 and b6f complexes. The protein is predicted to contain at least 10 transmembrane helices and features the two conserved histidine pairs coordinating the heme groups of these cytochromes. The second open reading frame, named odsN, encodes a soluble protein of unknown function. The genomic region displays a complex transcription pattern. Northern blot and RT-PCR analyses revealed the presence of mono- and bi-cistronic transcripts as well as a tri-cistronic transcript of soxL and cbsAB, encoding the mono-heme cytochrome b558/566. Phylogenetic analyses of the genes of the soxLN pair and of other archaeal gene pairs encoding Rieske iron-sulfur proteins and b-type cytochromes revealed an identical branching patterns for both protein families, suggesting an evolutionary link of these genes provided by the functional interaction of the proteins. On the basis of the findings of this study and the previously studied properties of the soxL and cbsA proteins, we propose the occurrence of a novel cytochrome bc1-analogous complex in the membranes of Sulfolobus, consisting of the cytochrome b homolog soxN, the Rieske protein soxL, the high potential cytochrome cbsA, as well as the non-redox-active subunits cbsB and odsN.

[Applications for a robot in the lateral skull base. Evaluation of robot-assisted mastoidectomy in an anatomic specimen]

In the past decade, a great variety of robot systems have been applied in numerous areas of life. In the public health system, robots are increasingly used in the operating theater. The potential for reproducibility and predictability was one of the main arguments for the use of robots in orthopedic treatment of bones, especially the implantation of a cementless total hip replacement. In otorhinolaryngological surgery (ENT), different hearing aids were developed: the cochlea implant for the deaf or the totally implantable hearing aid for the hearing impaired. Their site of implantation is localized in the lateral skull base. Removal of the bone mass with the reamer requires both great precision and considerable physical effort on the part of the surgeon, which does not result in an ergonomic operating technique. The following project describes the evaluation of processing parameters for a robot-assisted mastoidectomy to expose an implantation bed. The goal was to establish different parameters for robot-controlled reaming in the calotte or mastoid. In addition, several parameters were tested for their influence on surface structure, procedure reliability, and quality as well as the ability of the Mayfield clip to stabilize the head during the operation.

Synthesis of novel 2-azabicyclo[2.2.0]- and [2.1.1]hexanols

Methyl- and phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6 were reacted with NBS in wet DMSO to afford bromohydrins. Mixtures of unrearranged 6-exo-bromo-5-endo-hydroxy-2-azabicyclo[2.2.0]hexanes 7a,b and rearranged 5-anti-bromo-6-anti-hydroxy-2-azabicyclo[2.1.1]hexanes 8a,b were formed stereoselectively from the parent alkene 6a and 4-methyl alkene 6b. The 5-methyl alkene 6c affords only unrearranged bromohydrin 7c and dibromohydrin 9. By contrast, solely rearranged 3-endo-substituted-2-azabicyclo[2.1.1]hexane bromohydrins 8d-f result from additions to 3-endo-methyl alkene 6d, 3-endo-4-dimethyl alkene 6e, and 3-endo-phenyl alkene 6f. As an alternative route to bromohydrins, the parent 5,6-exo-epoxide 10a and 5-endo-methyl-5,6-exo-epoxide 10b were ring opened with bromine/triphenylphosphine to afford unrearranged 5-endo-bromo-6-exo-hydroxy-2-azabicyclo[2.2.0]hexanes 11a,b, while the 3-endo-methyl epoxide 10c afforded solely the rearranged 5-anti-bromo-6-anti-hydroxy-3-exo-methyl-2-azabicyclo[2.1.1]hexane isomer 8g. Tributyltin hydride reduction of bromohydrins 7a,b and 11a afforded novel 2-azabicyclo[2.2.0]hexan-5-ols 13a,b and -6-ol 14, and bromohydrins 8a,b, 8d-g afforded new 2-azabicyclo[2.1.1]-hexan-5-ols 15a,b and 15d-g.

Tracheal intubation after induction of anesthesia in children with propofol--remifentanil or propofol-rocuronium

PURPOSE

To compare the intubating conditions after remifentanil-propofol with those after propofol-rocuronium combination with the aim of determining the optimal dose of remifentanil.

METHODS

In a randomized, double-blind study 80 healthy children aged three to nine years were assigned to one of four groups (n=20): 2 or 4 microgxkg(-1) remifentanil (Re2 or Re4); 2 microgxkg(-1) remifentanil and 0.2 mgxkg(-1) rocuronium (Re2-Ro0.2); 0.4 mgxkg(-1) rocuronium (Ro0.4). After atropine, remifentanil was injected over 30 sec followed by 3.5 mgxkg(-1) propofol and rocuronium. After 60 sec, laryngoscopy and intubation were attempted. Intubating conditions were assessed as excellent, good or poor based on ease of ventilation, jaw relaxation, position of the vocal cords, and coughing to intubation.

RESULTS

In all children intubation was successful. Overall intubating conditions were better (P < 0.01), and the frequency of excellent conditions, 85%, was higher (P < 0.01) in the Re4 group than in the Ro0.4 group. No child manifested signs of muscular rigidity. In the remifentanil groups, arterial pressure decreased 11-13% and heart rate 6-9% after anesthetic induction, and remained at that level throughout the study.

CONCLUSION

The best intubating conditions were produced by the combination of 4 microgxkg(-1) remifentanil and 3.5 mgxkg(-1) propofol. It provided excellent or good intubating conditions in all children without causing undue cardiovascular depression.

Robot-assisted surgery system with kinesthetic feedback

The better understanding of the systems of the human body and their specific functions has led to minimally invasive and microsurgical procedures being carried out on an ever smaller scale. New therapies will require precision of 10 microm or better, which will only be achievable with robotic teleoperators. Experience with existing robot-assisted surgery systems shows that the human-machine interface is a critical component for acceptance of this technology, but no universally satisfactory interface has yet been found. Therefore, this article investigates a new concept based on kinesthetic motion feedback and presents details of the implementation of a first prototype.

A voice-controlled robotic assistant for neuroendoscopy

This paper describes experiments with a voice-controlled robot system to be used in endoscopic neurosurgery. The robot was a modified version of the robot described in previous publications of the group at Fraunhofer IPA and HSK. To control the robot a voice-controlled user interface was developed. The experiments were conducted on cadavers for three standard approaches in neuroendoscopy. The goal was to gain experience with a voice-controlled user interface and also with the set-up and use of the robotic system under clinical conditions. The results indicate that modifications to the robot and user interface are necessary. However the overall feasibility of the application was demonstrated.