Lampbrush loop-specific protein of Drosophila hydei.

By immunofluorescence techniques and protein blotting experiments we have shown that an antiserum specifically reacts with a Mr 80,000 protein (the "Ps protein") in the lampbrush loop " pseudonucleolus " in spermatocyte nuclei of Drosophila hydei. Comparative studies of X/Y and X/0 testes indicate that the gene encoding the Ps protein is not located on the Y chromosome but on an autosome or the X chromosome. The Ps protein is tissue specific. It is likely to be a rather conserved protein since the antigenic determinant recognized by the antiserum could be detected in the spermatocyte nuclei of a number of other Drosophila species. For those species with prominent Y chromosomal lampbrush loops, it could be shown that the cross-reaction is, as in D. hydei, associated with a specific Y chromosomal loop.     

Double average parallel steady-state free precession imaging: optimized eddy current and transient oscillation compensation.

Balanced steady-state free precession (SSFP) imaging is sensitive to off-resonance effects, which can lead to considerable artifacts during a transient phase following magnetization preparation or steady-state interruption. In addition, nonlinear k-space encoding is required if contrast-relevant k-space regions need to be acquired at specific delays following magnetization preparation or for transient artifact reduction in cardiac-gated k-space segmented CINE imaging. Such trajectories are problematic for balanced SSFP imaging due to nonconstant eddy current effects and resulting disruption of the steady state.In this work, a novel acquisition strategy for balanced SSFP imaging is presented that utilizes scan time reduction by parallel imaging for optimized "double average" eddy current compensation and artifact reduction during the transient phase following steady-state storage and magnetization preparation. Double average parallel SSFP imaging was applied to k-space segmented CINE SSFP tagging as well as nongated centrically encoded SSFP imaging. Phantom and human studies exhibit substantial reduction in steady-state storage and eddy current artifacts while maintaining spatial resolution, signal-to-noise ratio, and similar total scan time of a standard SSFP acquisition. The proposed technique can easily be extended to other acquisition schemes that would benefit from nonlinear reordering schemes and/or rely on interruption of the balanced SSFP steady state.     

In vivo assessment and visualization of intracranial arterial hemodynamics with flow-sensitized 4D MR imaging at 3T

SUMMARY: We evaluated electrocardiogram-synchronized flow-sensitized 4-dimensional MR imaging at 3T in combination with advanced 3D visualization strategies to ascertain its feasibility for the assessment of local intracranial blood-flow patterns in vivo. In large arteries of healthy volunteers, the temporal and spatial evolution of blood flow was successfully visualized and revealed--for example, a helical flow pattern in the carotid siphon. In a patient with steno-occlusive neurovascular disease, stagnant and retrograde flow patterns were readily visible.     

Time-resolved 3D MR velocity mapping at 3T: improved navigator-gated assessment of vascular anatomy and blood flow

PURPOSE: To evaluate an improved image acquisition and data-processing strategy for assessing aortic vascular geometry and 3D blood flow at 3T. MATERIALS AND METHODS: In a study with five normal volunteers and seven patients with known aortic pathology, prospectively ECG-gated cine three-dimensional (3D) MR velocity mapping with improved navigator gating, real-time adaptive k-space ordering and dynamic adjustment of the navigator acceptance criteria was performed. In addition to morphological information and three-directional blood flow velocities, phase-contrast (PC)-MRA images were derived from the same data set, which permitted 3D isosurface rendering of vascular boundaries in combination with visualization of blood-flow patterns. RESULTS: Analysis of navigator performance and image quality revealed improved scan efficiencies of 63.6%+/-10.5% and temporal resolution (<50 msec) compared to previous implementations. Semiquantitative evaluation of image quality by three independent observers demonstrated excellent general image appearance with moderate blurring and minor ghosting artifacts. Results from volunteer and patient examinations illustrate the potential of the improved image acquisition and data-processing strategy for identifying normal and pathological blood-flow characteristics. CONCLUSION: Navigator-gated time-resolved 3D MR velocity mapping at 3T in combination with advanced data processing is a powerful tool for performing detailed assessments of global and local blood-flow characteristics in the aorta to describe or exclude vascular alterations.     

Reconstruction of MRI data encoded with arbitrarily shaped,curvilinear, nonbijective magnetic fields

A basic framework for image reconstruction from spatial encoding by curvilinear, nonbijective magnetic encoding fields in combination with multiple receivers is presented. The theory was developed in the context of the recently introduced parallel imaging technique using localized gradients (PatLoc) approach. In this new imaging modality, the linear gradient fields are generalized to arbitrarily shaped, nonbijective spatial encoding magnetic fields, which lead to ambiguous encoding. Ambiguities are resolved by adaptation of concepts developed for parallel imaging. Based on theoretical considerations, a practical algorithm for Cartesian trajectories is derived in the case that the conventional gradient coils are replaced by coils for PatLoc. The reconstruction method extends Cartesian sensitivity encoding (SENSE) reconstruction with an additional voxelwise intensity‐correction step. Spatially varying resolution, signal‐to‐noise ratio, and truncation artifacts are described and analyzed. Theoretical considerations are validated by two‐dimensional simulations based on multipolar encoding fields and they are confirmed by applying the reconstruction algorithm to initial experimental data. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Optimized parallel imaging for dynamic PC‐MRI with multidirectional velocity encoding

Phase contrast MRI with multidirectional velocity encoding requires multiple acquisitions of the same k‐space lines to encode the underlying velocities, which can considerably lengthen the total scan time. To reduce scan time, parallel imaging is often applied. In dynamic phase contrast MRI using standard generalized autocalibrating partially parallel acquisitions (GRAPPA), several central k‐spaces for autocalibration of the reconstruction (autocalibrating signal lines (ACS)) are typically acquired, separately for each velocity direction and each cardiac timeframe, for calculating the reconstruction weights. To further accelerate data acquisition, we developed two methods, which calculated weights with a substantially reduced number of ACSl lines. The effects on image quality and flow quantification were compared to fully sampled data, standard GRAPPA, and time‐interleaved sampling scheme in combination with generalized autocalibrating partially parallel acquisitions (TGRAPPA). The results show that the two proposed methods can clearly improve scan efficiency while maintaining image quality and accuracy of measured flow or myocardial tissue velocities. Compared to TGRAPPA, the proposed methods were more accurate in evaluating flow velocity. In conclusion, the proposed reconstruction strategies are promising for dynamic multidirectionally encoded acquisitions and can easily be implemented using the standard GRAPPA reconstruction algorithm. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Randomized clinical trial of vertical or transverse laparotomy for abdominal aortic aneurysm repair

BACKGROUND: The objective of this randomized trial was to evaluate the incidence of incisional hernia after transverse or vertical incisions for open aortic aneurysm repair. METHODS: The study group comprised 69 patients who underwent elective aneurysm repair between November 1998 and November 2000 (60 men, nine women; mean age 72.8 (range 56-95) years). Patients were randomized to a transverse (n = 32) or vertical (n = 37) incision for the procedure. Of the 42 patients who were still alive in February 2004, 37 (15 transverse, 22 vertical incisions) attended for review. Laparotomy scars were assessed both clinically and ultrasonographically by the same examiner, to look for incisional hernia. RESULTS: Mean follow-up was 4.4 years. A multivariable logistic regression analysis revealed that the type of incision was the only parameter that significantly influenced the rate of incisional hernia: six of 15 patients with a transverse laparotomy versus 20 of 22 with a vertical laparotomy (P = 0.010). CONCLUSION: The incidence of incisional hernia was high after aortic aneurysm repair, but was lower in patients who had a transverse incision.     

Mechanical heart support at the Deutsches Herzzentrum Berlin: Recent developments (2011)

Since the inception of the mechanical circulatory support (MCS) program at the Deutsches Herzzentrum Berlin (DHZB) in 1987, more than 1600 patients have received support with 18 different designs of technical blood pump systems, in accordance with the respective state of the art. At the beginning, pulsatile pneumatic extracorporeal ventricular assist devices (VAD) and implantable pneumatic total artificial hearts (TAH) were available, followed by pulsatile electromechanical implantable devices. At this time the assist program was based on three objectives: bridging to recovery, bridging to heart transplantation (HTx) and for permanent support. Very soon (in 1995) patients of advanced age – over 65 years – were included in the program. In 1998 rotary blood pumps with continuous flow entered the program, from 2006 edging out step by step the pulsatile systems. Today the implantable pulsatile systems have disappeared from the DHZB program, with the exception of the extracorporeal uni‐ or biventricular pneumatic EXCOR systems (Berlin Heart GmbH), which are the only systems available for newborns and children. The only approved total artificial heart is the CardioWest device, implanted in rare cases after explantation of the natural heart. Miniaturized rotary blood pumps, axial flow turbines or centrifugal radial flow pumps are leading today's market. The size and configuration of one of these pumps, the hydrodynamically and magnetically levitated HeartWare HVAD, allowed its application as a biventricular implantable assist device. The worldwide first clinical implantation of this system was performed at the DHZB in 2009. With the increasing number of patients needing immediate circulatory support and the stagnating or even decreasing number of donor hearts available for HTx, the extreme discrepancy means that other therapies are gaining increasing importance. The objectives of the MCS program therefore had to focus on permanent VADs, thus creating a growing population of long‐term outpatients with implanted systems, living with their families a near‐normal life. Within a quarter century VAD implantation has grown from an experimental procedure into an established and generally accepted therapy. Facing the rapidly increasing population of patients with end‐stage heart failure and the stagnating number of heart transplants, the use of VAD technology may represent the most advanced progress in cardiac care in the coming years. Further minaturization of the devices will allow the treatment of patients with a wide age spectrum, from newborn children to the elderly, even with biventricular support. The ultimate goal will be the development of a durable total artificial heart, based on the rotary blood pump technology, with transcutaneous energy transfer through the intact skin, guaranteeing the patients optimal quality of life for many years of support.     

AAV-mediated intravitreal gene therapy reduces lysosomal storage in the retinal pigmented epithelium and improves retinal function in adult MPS VII mice.

The beta-glucuronidase-deficient mucopolysaccharidosis type VII (MPS VII) mouse accumulates partially degraded glycosaminoglycans in many cell types, including retinal pigmented epithelial (RPE) cells in the eye. This lysosomal storage in RPE cells leads to progressive retinal degeneration and reduced function as measured by flash electroretinography (ERG). The impact of AAV-mediated intraocular gene therapy on pathology and retinal function was examined in normal and MPS VII mice treated at 4 weeks of age, when lysosomal storage is evident but functional impairment is minimal in affected animals. At 16 weeks, an age at which untreated MPS VII mice have advanced histologic lesions and significantly reduced ERG amplitudes, treated eyes had nearly normal levels of beta-glucuronidase activity, preservation of cells in the outer nuclear layer of the retina, and decreased lysosomal storage within the RPE. The AAV-treated MPS VII mice also had significantly increased dark-adapted ERG amplitudes compared to untreated MPS VII mice. Although retinal function was improved, the efficacy of the treatment depended heavily on parameters related to the injection procedure, such as the injection volume, injection site, and vector dose. These data suggest that intraocular AAV-mediated therapy may be efficacious for treating the retinal disease associated with certain lysosomal storage diseases.