Biomedical subjects

E Unger

Publications and source records attributed to E Unger.

At least 19 recordsLinked to original sources

PubMed2003

Role of cytokines in photodynamic therapy-induced local and systemic inflammation.

Photodynamic therapy (PDT) of tumour results in the rapid induction of an inflammatory response that is considered important for the activation of antitumour immunity, but may be detrimental if excessive. The response is characterised by the infiltration of leucocytes, predominantly neutrophils, into the treated tumour. Several preclinical studies have suggested that suppression of long-term tumour growth following PDT using Photofrin((R)) is dependent upon the presence of neutrophils. The inflammatory pathways leading to the PDT-induced neutrophil migration into the treated tumour are unknown. In the following study, we examined, in mice, the ability of PDT using the second-generation photosensitiser 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) to induce proinflammatory cytokines and chemokines, as well as adhesion molecules, known to be involved in neutrophil migration. We also examined the role that these mediators play in PDT-induced neutrophil migration. Our studies show that HPPH-PDT induced neutrophil migration into the treated tumour, which was associated with a transient, local increase in the expression of the chemokines macrophage inflammatory protein (MIP)-2 and KC. A similar increase was detected in functional expression of adhesion molecules, that is, E-selectin and intracellular adhesion molecule (ICAM)-1, and both local and systemic expression of interleukin (IL)-6 was detected. The kinetics of neutrophil immigration mirrored those observed for the enhanced production of chemokines, IL-6 and adhesion molecules. Subsequent studies showed that PDT-induced neutrophil recruitment is dependent upon the presence of MIP-2 and E-selectin, but not on IL-6 or KC. These results demonstrate a PDT-induced inflammatory response similar to, but less severe than obtained with Photofrin((R)) PDT. They also lay the mechanistic groundwork for further ongoing studies that attempt to optimise PDT through the modulation of the critical inflammatory mediators.

Animals↗

PubMed2003

Interaction of metal salts with cytoskeletal motor protein systems.

Interactions of chemicals with the microtubular network of cells may lead to genotoxicity. Micronuclei (MN) might be caused by interaction of metals with tubulin and/or kinesin. The genotoxic effects of inorganic lead and mercury salts were studied using the MN assay and the CREST analysis in V79 Chinese hamster fibroblasts. Effects on the functional activity of motor protein systems were examined by measurement of tubulin assembly and kinesin-driven motility. Lead and mercury salts induced MN dose-dependently. The no-effect-concentration for MN induction was 1.1 microM PbCl(2), 0.05 microM Pb(OAc)(2) and 0.01 microM HgCl(2). The in vitro results obtained for PbCl(2) correspond to reported MN induction in workers occupationally exposed to lead, starting at 1.2 microM Hg(II) (Vaglenov et al., 2001, Environ. Health Perspect. 109, 295-298). The CREST Analysis indicate aneugenic effects of Pb(II) and aneugenic and additionally clastogenic effects of Hg(II). Lead (chloride, acetate, and nitrate) and mercury (chloride and nitrate) interfered dose-dependently with tubulin assembly in vitro. The no-effect-concentration for lead salts in this assay was 10 microM. Inhibition of tubulin assembly by mercury started at 2 microM. The gliding velocity of microtubules along immobilised kinesin molecules was affected by 25 microM Pb(NO(3))(2) and 0.1 microM HgCl(2) in a dose-dependent manner. Our data support the hypothesis that lead and mercury genotoxicity may result, at least in part, via disturbance of chromosome segregation via interaction with cytoskeletal proteins.

Animals↗

PubMed2002

Analysis of the migration behaviour of single microtubules in electric fields.

By video contrast microscopy, individual microtubules formed from pure tubulin in the presence of taxol were studied in constant electric fields. At nearly physiological conditions, i.e., in a buffer at pH 6.8 and 120 mM ionic strength, suspended microtubules moved towards the anode with an electrophoretic mobility of approximately 2.6 x 10(-4) cm(2)/V s, corresponding to an unbalanced negative charge of 0.19 electron charges per tubulin dimer. Strikingly, this value is lower by a factor of at least 50 than that calculated from crystallographic data for the non-assembled tubulin dimer. Moreover, the taxol-stabilized microtubules had an isoelectric point of about pH 4.2 which is significantly lower than that known for the tubulin monomers. This indicates that microtubule formation is accompanied by substantial changes of charge distribution within the tubulin subunits. Constant electric fields were shown to affect also the orientation of microtubules gliding across a kinesin-coated surface at pH 6.8.

Animals↗

PubMed2001

Basic design and construction of the Vienna FES implants: existing solutions and prospects for new generations of implants.

We can distinguish 3 generations of FES implants for activation of neural structures: 1. RF-powered implants with antenna displacement dependent stimulation amplitude; 2. RF-powered implants with stabilised stimulation amplitude; and 3. battery powered implants. In Vienna an 8-channel version of the second generation type has been applied clinically to mobilisation of paraplegics and phrenic pacing. A 20-channel implant of the second generation type for mobilisation of paraplegics and an 8-channel implant of the third generation type for cardiac assist have been tested in animal studies. A device of completely new design for direct stimulation of denervated muscles is being tested in animal studies. There is a limited choice of technologically suitable biocompatible and bioresistant materials for implants. The physical design has to be anatomically shaped without corners or edges. Electrical conductors carrying direct current (D.C.) have to be placed inside a hermetic metal case. The established sealing materials, silicone rubber and epoxy resin, do not provide hermeticity and should only embed DC-free components. For electrical connections outside the hermetic metal case welding is preferable to soldering; conductive adhesives should be avoided. It is advisable to use a hydrophobic oxide ceramic core for telemetry antenna coils embedded in sealing polymer. Cleaning of all components before sealing in resin is of the utmost importance as well as avoidance of rapid temperature changes during the curing process.

Animals↗

PubMed2001

Selection and orientation of adjacent genes influences DAM-mediated male sterility in transformed maize.

Anther-targeted expression of E. coli DNA (Adenosine-N6-)-Methyltransferase (DAM) in maize was tested as a means to produce male-sterile plants. A high frequency of male-sterile plants with reduced anther size was observed when DAM was regulated by the maize anther-specific promoter 5126 (5126:DAM) and placed upstream of the herbicide resistance gene, pat, regulated by the cauliflower mosaic virus (CaMV) 35S promoter (35S:PAT). In contrast, placement of 5126:DAM upstream of a pat gene regulated by either the maize ubiquitin (UBI:PAT) or rice actin (rACTIN:PAT) promoters resulted in male-fertile plants. Based on these observed differences, DAM-mediated sterility was used as a phenotypic marker to assess the contribution of factors affecting gene expression such as orientation of the transcription units, choice of regulatory sequences mediating expression of adjacent genes, and effects of varying the anther-specific promoter regulating DAM. Constructs that place a portion of the CaMV 35S promoter, including the native AS-1 sequences, between 5126:DAM and UBI:PAT yielded a high frequency of male-sterile plants with reduced anther size. Significant differences in the frequency of male-sterile events and the associated anther size were also observed when the position of 35S:PAT was changed relative to 5126:DAM. These data provide evidence that gene expression in transformed maize plants can be impacted by simply altering the order, orientation or regulatory sequences of adjacent genes.

Acetyltransferases↗

PubMed2001

Functional and biological test of a 20 channel implantable stimulator in sheep in view of functional electrical stimulation walking for spinal cord injured persons.

A newly developed implantable stimulator with 20 output channels, mainly intended for the stimulation of lower extremities in paraplegics, was implanted in 6 sheep over a time period of 26 weeks. Five epineural electrodes each were used to contact various nerves at different locations to elicit hip and knee extension and flexion and to make carrousel and selective stimulation possible. Different electrode application strategies in view of paraplegic standing and walking were investigated. Additional implanted electrodes allowed M-wave monitoring for selectivity investigations in 3 sheep. Stimulator, electrode leads, and electrodes proved to be reliable. Selective stimulation with electrodes placed on the trunk of the sciatic nerve could be demonstrated but with bad reproducibility. Histological investigation of the tissues surrounding electrodes and leads showed the expected stable foreign body response. Strong hip and knee extension could be gained in all cases while only weak flexion forces could be elicited in most cases. Muscle biopsies showed that daily stimulation for 8 h at threshold level caused an increase in muscle Type I fibers and a decrease in Type IIc fibers. Implants and electrodes fulfill the most important functional and biological criteria for their clinical application for paraplegic walking. The intention to provide selective flexion functions via epineural stimulation could not be demonstrated sufficiently in this animal model.

Animals↗

PubMed2001

Video-EEG monitoring in respiratory chain disorders.

Subclinical epileptiform activity in patients with respiratory chain disorders (RCDs) has not been previously investigated by video-EEG monitoring. The purpose of this study was to look for the type and frequency of epileptiform activity during a 24 h-video-EEG recording in RCD patients. Eleven patients with RCD, 7 women and 4 men, aged 24-72 years, underwent a clinical neurologic examination, blood tests, CT/MRI scans of the brain, routine scalp EEG and continuous video-EEG monitoring over 24 consecutive hours. Ten patients had normal 24 h-video-EEG recordings. One of these patients had no CNS involvement; her resting EEGs showed diffuse background slowing. In one patient, automatic spike detection revealed 12 spikes during a 6 hour period. Resting scalp EEG in this patient showed extensive, bilaterally synchronous, pseudoperiodic polyspike-waves. In conclusion, subclinical epileptiform activity could be recorded by 24 h-video-EEG monitoring in only 1 of 11 RCD patients. The single patient with subclinical epileptiform activity presented with intermittent myoclonic jerks.

Adult↗

PubMed2001

Determination of the net exchange rate of tubulin dimer in steady-state microtubules by fluorescence correlation spectroscopy.

The microtubule cytoskeleton plays an important role in eukaryotic cells, e. g., in cell movement or morphogenesis. Microtubules, formed by assembly of tubulin dimers, are dynamic polymers changing randomly between periods of growing and shortening, a property known as dynamic instability. Another process characterizing the dynamic behaviour is the so-called treadmilling due to different binding constants of tubulin at both microtubule ends. In this study, we used tetramethylrhodamine (TMR)-labeled tubulin added to microtubule suspensions to determine the net exchange rate (NER) of tubulin dimers by fluorescence correlation spectroscopy (FCS) as a measure for microtubule dynamics. This approach, which seems to be suitable as a screening system to detect compounds influencing the NER of tubulin dimers into microtubules at steady-state, showed that taxol, nocodazole, colchicine, and vinblastine affect microtubule dynamics at concentrations as low as 10(-9)-10(-10) M.

Animals↗

PubMed2001

Pruritometer 2: portable recording system for the quantification of scratching as objective criterion for the pruritus.

Studies to evaluate therapies for itching (pruritus) related diseases often require the quantification of the itch sensation. Like all subjective symptoms the evaluation of itching is difficult and can only be done indirectly. With the Pruritometer 2 a measuring system is introduced that evaluates itching by detecting scratching movements. Based on the Pruritometer 1, that processes the signals of a piezoelectric vibration sensor, fixed on the midfinger of the patients dominant hand, and triggers a simple counter, the Pruritometer 2 allows to store the scratch activity during a 24 hours period. For each adjustable time slice of this time period, the amount of scratches and the scratch intensity are recorded. All data can be transferred to a PC via infrared link for further processing with a standard software package. An additional PC-software allows to set various parameters for optimal scratch detection and to test the patient attached system, also via the infrared link. All electronic components are shockproof encapsulated in a milled housing and are attached to a textile watchstrap that is worn by the patient like a wristwatch.

Equipment Design↗

PubMed2000

Effect of temperature on kinesin-driven microtubule gliding and kinesin ATPase activity.

DeCuevas et al. [J. Cell Biol. 116 (1992) 957-965] demonstrated by circular dichroism spectroscopy for the kinesin stalk fragment that shifting temperature from 25 to 30 degrees C caused a conformational transition. To gain insight into functional consequences of such a transition, we studied the temperature dependence of a full-length kinesin by measuring both the velocity of microtubule gliding across kinesin-coated surfaces and microtubule-promoted kinesin ATPase activity in solution. The corresponding Arrhenius plots revealed distinct breaks at 27 degrees C, corroborating the temperature-dependent conformational transition for a motility-competent full-length kinesin. Microtubules were found to glide up to 45 degrees C; at higher temperatures, kinesin was irreversibly damaged.

Animals↗

PubMed2000

Speeding up kinesin-driven microtubule gliding in vitro by variation of cofactor composition and physicochemical parameters.

So far, there has been a discrepancy between the velocities of kinesin-dependent microtubule motility measured in vitro and within cells. By changing ATP, Mg(2+), and kinesin concentrations, pH and ionic strength, we tried to find conditions that favour microtubule gliding across kinesin-covered glass surfaces. For porcine brain kinesin, we found that raising the molar Mg(2+)/ATP ratio can substantially elevate gliding velocity. Gliding became also faster after temperature elevation or lowering the number of kinesin molecules bound to the glass surface. The highest mean gliding velocity (1.8 microm/s+/-0.09 microm/s), approaching velocities measured for anterograde transport in vivo, was achieved by combination of favourable factors (2.5 m m ATP, 12.5 m m Mg(2+), 37 degrees C, 450 kinesin molecules/microm(2)).

Adenosine Diphosphate↗

PubMed2000

Ultrasound enhancement of cationic lipid-mediated gene transfer to primary tumors following systemic administration.

The impact of a localized application of ultrasound on gene transfer to primary tumors following systemic administration of cationic lipid based transfection complexes was investigated. We have previously shown that systemic administration of DOTMA (N-[(1-(2-3-dioleyloxy) propyl)]-N-N-N-trimethylammonium chloride):cholesterol-based transfection complexes to tumor-bearing mice resulted in expression in the tumor and other tissues, primarily the lungs. Application of ultrasound to the tumor before or after the injection resulted in a significant increase in gene transfer to the tumor with no increase observed in other tissues. The magnitude of increased expression ranged from three- to 270-fold depending upon the DNA dose. The following parameters were optimized for maximal increase: duration of ultrasound application, the time interval between plasmid injection and sonoporation, and plasmid dose. A combination of plasmid quantitation and fluorescence microscopy showed that ultrasound increased tumor uptake of the plasmid and that uptake was limited to the tumor vasculature. Using an IL- 12 expression plasmid, the combination of a single plasmid dose (10 microg) and ultrasound treatment produced significantly higher levels of IL-12 in tumor. This increased expression was sufficient to inhibit tumor growth compared with the control conditions. These data demonstrate the potential application of sonoporation as an effective method for enhancing the expression of systemically administered genes in tumor endothelium for cancer gene therapy.

Animals↗

PubMed2000

The use of a thrombus-specific ultrasound contrast agent to detect thrombus in arteriovenous fistulae.

RATIONALE AND OBJECTIVES: To evaluate the use of a new thrombus-specific ultrasound contrast agent, MRX-408, in the ultrasonic detection of thrombus in arteriovenous (AV) fistulae. METHODS: Six purpose-bred mongrels with two AV fistulae each were imaged with gray-scale ultrasound 7 weeks after graft implantation before and after the intravenous bolus injection of MRX-408 (a GPIIb receptor-targeted ultrasound contrast agent). Pre- and postcontrast videotaped segments were randomized and reviewed by four radiologists blinded to the presence of thrombus in the grafts. RESULTS: After the use of MRX-408, there was improved visualization of thrombus within the grafts (P < 0.0001). This was due to the enhancement of the thrombus (P < 0.0001). The improved visualization and contrast enhancement were more marked in the grafts that contained thrombus nonhyperechoic to surrounding soft tissues. CONCLUSIONS: MRX-408 demonstrated better visualization of thrombus within AV fistulae. This was shown in both patent and occluded grafts. These results are encouraging and suggest that this contrast agent merits further development.

Animals↗

PubMed1999

Microtubule formation and kinesin-driven microtubule gliding in vitro in the presence of lipopolysaccharide.

Lipopolysaccharide (LPS) is a main trigger substance for the development of septic shock and multiple organ failure. We showed by turbidity measurements that LPS inhibits microtubule formation in a pH-dependent manner. Inhibition was found to be not only due to sequestration of MAP2 by LPS, but also of MAP1 and tau MAPs, indicating that LPS is able to react with a broad variety of MAPs. LPS-induced inhibition of microtubule formation could be compensated by additional tau or by addition of taxol. Dot blots revealed that LPS binds directly to tau, but seems not to bind to tubulin. As tau is expressed in various tissue types involved in multiorgan failure, it might be regarded as a further target for LPS action. In contrast, kinesin-dependent microtubule gliding was not affected by LPS. The toxin neither blocked the cargo (vesicle) nor the microtubule binding site of kinesin, suggesting a certain specificity of LPS-MAP interaction.

Animals↗

PubMed1999

[Distraction osteogenesis with a fully implantable system. Experimental study].

Distraction osteogenesis using external or intraoral devices is an established method for lengthening the human mandible. In this preliminary study on sheep, a completely implanted device for mandibular lengthening is presented. After osteotomy of the mandible, the electromechanical device was fixed to the mandible and the power and control unit were inserted subcutaneously in the neck region. After a healing period of 5 days, the device was activated magnetically and allowed calibrated distraction steps of 0.04 mm/h, achieving a total of 1.0 mm per day. With this method, it was possible to lengthen the mandible automatically over a period of 14 days without transmucosal activation. In our study, this newly designed internal device was successfully used for distraction osteogenesis, and a maximum mandibular lengthening of 13.6 mm was achieved. Further research is necessary to achieve progression to human clinical application in the near future.

Animals↗

PubMed1999

Multifunctional implantable nerve stimulator for cardiac assistance by skeletal muscle.

Different methods are used, clinically and experimentally, to assist severely impaired heart function by means of skeletal muscle. The efficiency of these methods is restricted by skeletal muscle losing strength after transpositioning and during conditioning and not being sufficiently resistant to fatigue. This is mainly due to the nonphysiological activation of the nerves by electrical stimulation. We have developed a battery operated, ECG triggered multichannel implant that is capable of implementing various advanced stimulation techniques. The stimulator can activate 2 skeletal muscles via the motor nerves. It allows for application of multichannel stimulation methods, i.e., carousel stimulation and sequential stimulation, as well as the programming of optimized pulse trains. Synchronization delay and burst duration can be automatically and dynamically adapted to the heart rate. The multichannel stimulator is hermetically sealed in a titanium case. Its calculated life span on the basis of the integrated battery is 3-5 years, depending on the programmed stimulation parameters. The implant dimensions are 65 x 17 mm (diameter x height), and it weighs 93 g. The implant has been tested in vitro as well as in vivo.

Animals↗

PubMed1999

Long-term electromyogram recording from the posterior cricoarytenoid muscle as a potential biological trigger for phrenic pacing: results of an animal study.

Diaphragm pacing has been used to restore respiration in approximately 1,000 patients worldwide suffering from high quadriplegia or from central alveolar hypoventilation syndrome. Compared with conventional mechanical ventilation, electrophrenic respiration (EPR) reduces the risk of pulmonary infections and increases the mobility of patients. Voluntary activation of the pacemaker during speech would improve patients' quality of life and allow application of EPR in a more physiological way. An animal study was performed to investigate the electromyogram (EMG) of the posterior cricoarytenoid (PCA) muscle and the movement of the glottis via impedance measurement (electroglottography) with the aim to examine reproducibility and stability of the recordings from the PCA muscle as a potential biological trigger for a phrenic pacemaker. The EMG of the PCA muscle was recorded via implanted electrodes for a 200 day period. The EMG signal proved stable for that period, artifacts caused by movements can be suppressed, and swallowing can be detected. In contrast, impedance measurement to detect movement of the glottis proved not useful. Based on the results of this study, the use of the PCA EMG as a biological trigger for a phrenic pacemaker has to be considered a realistic option.

Animals↗

PubMed1999

Battery-powered implantable nerve stimulator for chronic activation of two skeletal muscles using multichannel techniques.

Chronic activation of skeletal muscle is used clinically in representative numbers for diaphragm pacing to restore breathing and for dynamic graciloplasty to achieve fecal continence. The 3 different stimulation techniques currently used for electrophrenic respiration (EPR) all apply high frequency powered implants. It was our goal to make these stimulation methods applicable for EPR by a battery-powered nerve stimulator that would maximize the patient's freedom of movement. Additionally, the system should allow the implementation of multichannel techniques and alternating stimulation of 2 skeletal muscles as a further improvement in graciloplasty. Generally, the developed implantable nerve stimulator can be used for simultaneous and alternating activation of 2 skeletal muscles. Stimulation of the motor nerve is achieved by either single channel or multichannel methods. Carousel stimulation and sequential stimulation can be used for graciloplasty as well as for EPR. For EPR we calculated an operating time of the implant battery of 4.1 years based on the clinically used stimulation parameters with carousel stimulation. The multichannel pulse generator is hermetically sealed in a titanium case sized 65 x 17 mm (diameter x height) and weighs 88 g.

Diaphragm↗