Effect of glucocorticoid treatment on the excitability of rat skeletal muscle

Dexamethasone treatment in the rat produced depolarization of extensor digitorum longus (EDL) muscle fibers but not soleus (SOL) fibers studies in vitro at 23° C. The depolarization of EDL fibers was most prominent after 1 day of treatment (treated–77.5±1.1 mV, control–87.2±0.8 mV; mean±S.E.), and was associated with elevation of the action potential threshold and reduction of the action potential overshoot. In vivo, or in vitro in chloride-free solution, the resting potential and action potential threshold and overshoot of EDL fibers from glucocorticoid-treated and control rats were similar. Sodium currents were studied with a patch voltage clamp. Glucocorticoid treatment did not alter the voltage dependence of sodium channel activation or inactivation currents at about –29 mV and half-maximal inward currented at about –50 mV. Sodium channels were half inactivated at about –71 mV. Glucocorticoid treatment did not alter the sarcolemmal resistance or capacitance. We conclude that glucocorticoid treatment does not produce muscle weakness or atrophy by altering the excitability of muscle fibers.     

Selection of specific gene probes by combined use of low-stringency PCR amplification and Southern-blot hybridization

We have developed a protocol to isolate a gene from which only limited (amino-acid) sequence information is available. It involves two PCR amplifications using one constant primer and a set of nested primers and subsequent crosswise Southern hybridization. The amplified DNA giving a signal in both lanes is further processed for use in gene bank screening by applying standard procedures. In this way the structural gene for a thiol protease, BLH1, the homologue of the bleomycin A (a cancerostatic drug) resistance gene of rabbit (and man), was isolated from yeast genomic DNA.     

Assessment of vascular remodeling under antiangiogenic therapy using DCE‐MRI and vessel size imaging

Purpose

To assess vascular remodeling in tumors during two different antiangiogenic therapies with dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) and vessel size imaging and to evaluate the vessel size index (VSI) as a novel biomarker of therapy response.

Materials and Methods

In two independent experiments, nude mice bearing human skin squamous cell carcinoma xenografts were treated with a vascular endothelial growth factor (VEGF) inhibitor (bevacizumab) or a multitargeted tyrosine kinase inhibitor (SU11248). Changes in tumor vascularity were assessed by DCE‐MRI and vessel size imaging. DCE‐MRI data were analyzed applying a two‐compartment model (Brix), calculating the parameters Amplitude and k_ep.

Results

For both experiments Amplitude decreased significantly in treated tumors while k_ep did not change significantly. VSI showed controversial results. VSI was significantly increased in SU11248‐treated A431 tumors, whereas no changes were found in bevacizumab‐treated HaCaT‐ras‐A‐5RT3 tumors. Immunohistology confirmed these results and suggest differences in the maturation of tumor vascularization as a possible explanation.

Conclusion

DCE‐MRI and vessel size imaging provide reliable and supplementing biomarkers of antiangiogenic therapy response. The results of both methods are in excellent agreement with histology. Nevertheless, our results also indicate that vascular remodeling is complex and that a uniform response cannot be expected for different tumors and therapies. J. Magn. Reson. Imaging 2009;29:1125–1133. © 2009 Wiley‐Liss, Inc.     

Volumetric high-frequency Doppler ultrasound enables the assessment of early antiangiogenic therapy effects on tumor xenografts in nude mice

The sensitivity of Doppler ultrasound below 10 MHz to assess antiangiogenic therapy effects in tumor xenografts has been shown to be limited. Thus, our aim was to evaluate high-frequency volumetric power-Doppler ultrasound (HF-VPDU) for monitoring antiangiogenic treatments. Squamous cell carcinoma xenografts grown in nude mice were scanned with HF-VPDU at a center frequency of 30 MHz. Images with 200-μm slice thicknesses were recorded and merged into a three-dimensional dataset, of which the relative color pixel density was determined. Animals received either VEGFR2 antibodies or 0.9% NaCl and were examined at days 0, 3 and 6 of treatment. After the last examination, tumors were resected and their vascularization characterized by immunohistology. At day 6, the volumes of treated and untreated tumors were not significantly different yet. In contrast, mean tumor vascularization in treated animals had decreased to 44%, while in the control group it had increased to 152% (P < 0.01). In correspondence, vessel density, as determined by CD31 staining, was 0.19 ± 0.10% in treated and 0.92 ± 0.41% in untreated tumors (P < 0.01). Additionally, the fraction of mature (SMA-positive) vessels increased under therapy. Thus, HF-VPDU can be considered as an easily applicable and fast method to screen high animal numbers for antiangiogenic therapy effects. M. Jugold and M. Palmowski contributed equally to this work     

Influence of different breathing maneuvers on internal and external organ motion: use of fiducial markers in dynamic MRI

PURPOSE: To investigate, with dynamic magnetic resonance imaging (dMRI) and a fiducial marker, the influence of different breathing maneuvers on internal organ and external chest wall motion. METHODS AND MATERIALS: Lung and chest wall motion of 16 healthy subjects (13 male, 3 female) were examined with real-time trueFISP (true fast imaging with steady-state precession) dMRI and a small inductively coupled marker coil on either the abdomen or thorax. Three different breathing maneuvers were performed (predominantly "abdominal breathing," "thoracic breathing," and unspecific "normal breathing"). The craniocaudal (CC), anteroposterior (AP), and mediolateral (ML) lung distances were correlated (linear regression coefficient) with marker coil position during forced and quiet breathing. RESULTS: Differences of the CC distance between maximum forced inspiration and expiration were significant between abdominal and thoracic breathing (p < 0.05). The correlation between CC distance and coil position was best for forced abdominal breathing and a marker coil in the abdominal position (r = 0.89 +/- 0.04); for AP and ML distance, forced thoracic breathing and a coil in the thoracic position was best (r = 0.84 +/- 0.03 and 0.82 +/- 0.03, respectively). In quiet breathing, a lower correlation was found. CONCLUSION: A fiducial marker coil external to the thorax in combination with dMRI is a new technique to yield quantitative information on the correlation of internal organ and external chest wall motion. Correlations are highly dependent on the breathing maneuver.     

Measurements of respiratory motion using fast magnetic resonance imaging and inductively-coupled marker coils

The respiratory motion of the thoracic wall provides indirect information about the breathing displacement of the inner organs. To analyze the correlation between thoracic wall and lung motion for applications in radiation therapy, the breathing displacement of the lung is visualized with a fast gradient echo pulse sequence (trueFISP) at a rate of 2-3 images/sec. For quantification of the motion, a small inductively-coupled marker coil is attached to the chest wall and detected with a fast projection technique. Since the marker coil generates a flip angle amplification (factor 15) in its interior, very small nominal flip angles of 2 degrees can be used during the projection measurements which do not affect the image quality of the trueFISP images. Volunteer studies with the marker coil showed a good agreement with simultaneously acquired breathing belt data and position information extracted from the MR images. Whereas the breathing belt provided reliable data only within a certain dynamic range, the marker coil could detect also extreme breathing excursions with a precision better than 2 millimeters.     

Principles of optical and fluorescence mediated tomography in turbid media

Three-dimensional, tomographic imaging of biological tissues by means of visible light is becoming increasingly important. Current progress in the mathematical-physical modelling of photon propagation in scattering media allows spatially-resolved reconstructions of optical parameters with common computing hardware. Especially in the field of molecular imaging, optical tomography promises a transfer of knowledge from successful in vitro assays (as evaluated by fluorescence microscopy) to in vivo imaging of living animals. In the latter case, spatial resolution is not as critical as the ability to quantify the concentration of fluorescence-labelled probes, a task not solvable by the use of common planar imaging techniques. In this article, the theoretical foundations of optical tomography are introduced along with some examples of applications.     

Kardiale Defibrillation durch Laien- und Ersthelfer ?First-Responder”–überlegungen zu einem neuen Rettungskonzept gegen den pl?tzlichen Herztod

Nach wie vor ist die Letalit?t des pl?tzlichen Herztodes, beim Vorliegen von Kammerflimmern oder pulsloser ventrikul?rer Tachykardie, erschreckend hoch. Neue technische M?glichkeiten und das Verst?ndnis neuzeitlicher notfallmedizinischer M?glichkeiten und Hilfeleistung erm?glichen ein optimiertes Behandlungskonzept für Notfallpatienten. Da allein die rasche kardiale Defibrillation die definitive Interventionsm?glichkeit zur Terminierung von Kammerflimmern oder pulsloser ventrikul?rer Tachykardie darstellt, sollte die Anwendung der modernen externen Defibrillationstechnik nicht erst durchgeführt werden, wenn der Notarzt oder das qualifizierte Notfallteam beim Patienten eintrifft. Auch nicht?rztliches Personal und trainierte Laien k?nnen (und dürfen!) diese lebensrettende Ma?nahmen mittels halbautomatischen Defibrillatoren durchführen. Diese M?glichkeiten sollten zu überlegungen und Empfehlungen der Fachverb?nde eingehen, die zu neuen Rettungskonzepten führen.     

Automatic slice tracking in interventional magnetic resonance imaging

Magnetic resonance imaging (MRI) is ideally suited to monitor minimally invasive operations with catheters or needles, since it offers both a superior soft-tissue contrast and the possibility to perform functional tests. In the present study, small radio-frequency coils were attached to the instruments in order to localize the MR-invisible instruments. The implementation of active instrument tracking is described on the basis of the example of active catheter tracking. In this case, the current position information of the instrument is used to automatically position the MRI slice at the catheter location. In combination with a user interface, the interventional radiologist is offered the possibility to perform vascular interventions from within the MR scanner room. At image update rates of approximately 3 Hz, tracking and placement of catheters in vascular structures are possible with interactive switching of slice orientation and image contrast. In an animal model, the technique was successfully used to selectively visualize the abdominal vessels and their branches under MRI guidance.     

A comparison of EMIT and FPIA methods for the detection of cyclosporin A blood levels: does impaired liver function make a difference?

Objective: Apparent cyclosporin A (CSA) blood levels, as determined by fluorescence polarization immunoassay (FPIA) and enzyme-multiplied immunoassay technique (EMIT), were compared in CSA-treated patients with various degrees of liver dysfunction. Methods: FPIA and EMIT were performed in parallel according to test manufacturer instructions in blood from kidney (n=82), liver (n=96) and heart transplant (n=20) patients. Results: The precision of both techniques was greatest in patients with the highest blood levels, and at each blood level greater for the FPIA than for the EMIT. Apparent CSA blood levels, as determined by EMIT, were typically approximately 70% of those determined by FPIA, indicating greater cross-reaction of the antibody in the FPIA with CSA metabolites. However, the ratio of values determined with EMIT and FPIA was very similar in kidney, liver and heart transplant patients. Among liver transplant patients it was also very similar in those without major alterations of hepatic function and in those with impaired excretory (increased bilirubin and γGT) or synthetic (i.e., reduced thromboplastin time) function. Extended storage of blood samples for up to 10 days did not affect apparent CSA blood level estimates by EMIT in a clinically relevant manner. Conclusions: We conclude that the greater specificity of the antibody in the EMIT for the CSA parent compound does not translate into a clinically relevant advantage for CSA monitoring. Received: 20 September 1996 / Accepted in revised form: 17 February 1997