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Dive into the research topics where T. Mesud Yelbuz is active.

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Featured researches published by T. Mesud Yelbuz.


Circulation | 2002

Optical Coherence Tomography A New High-Resolution Imaging Technology to Study Cardiac Development in Chick Embryos

T. Mesud Yelbuz; Michael A. Choma; Lars Thrane; Margaret L. Kirby; Joseph A. Izatt

Background—Optical coherence tomography (OCT) is a depth-resolved, noninvasive, non-destructive imaging modality, the use of which has yet to be fully realized in developmental biology. Methods and Results—We visualized embryonic chick hearts at looping stages using an OCT system with a 22 &mgr;m axial and 27 &mgr;m lateral resolution and an acquisition rate of 4000 A-scans per second. Normal chick embryos from stages 14 to 22 and sham-operated and cardiac neural crest-ablated embryos from stages 15 and 18 were scanned by OCT. Three-dimensional data sets were acquired and processed to create volumetric reconstructions and short video clips. The OCT-scanned embryos (2 in each group) were photographed after histological sectioning in comparable planes to those visualized by OCT. The optical and histological results showing cardiovascular microstructures such as myocardium, the cardiac jelly, and endocardium are presented. Conclusions—OCT is a powerful imaging modality which can provide new insight in assessing and understanding normal and abnormal cardiac development in a variety of animal models.


Developmental Dynamics | 2008

High-resolution in vivo imaging of the cross-sectional deformations of contracting embryonic heart loops using optical coherence tomography

Jörg Männer; Lars Thrane; Kambiz Norozi; T. Mesud Yelbuz

The embryonic heart tube consists of an outer myocardial tube, a middle layer of cardiac jelly, and an inner endocardial tube. It is said that tubular hearts pump the blood by peristaltoid contractions. The traditional concept of cardiac peristalsis sees the cyclic deformations of pulsating heart tubes as concentric narrowing and widening of tubes of circular cross‐section. We have visualized the cross‐sectional deformations of contracting embryonic hearts in chick embryos (HH‐stages 9–17) using real‐time high‐resolution optical coherence tomography. Cardiac contractions are detected from HH‐stage 10 onward. During the cardiac cycle, the myocardial tube undergoes concentric narrowing and widening while the endocardial tube undergoes eccentric narrowing and widening, having an elliptic cross‐section at end‐diastole and a slit‐shaped cross‐section at end‐systole. The eccentric deformation of the endocardial tube is the consequence of an uneven distribution of the cardiac jelly. Our data show that the cyclic deformations of pulsating embryonic heart tubes run other than originally thought. There is evidence that heart tubes of elliptic cross‐section might pump blood with a higher mechanical efficiency than those of circular‐cross section. The uneven distribution of cardiac jelly seems to prefigure the future AV and cono‐truncal endocardial cushions. Developmental Dynamics 237:953–961, 2008.


Developmental Dynamics | 2010

How does the tubular embryonic heart work? Looking for the physical mechanism generating unidirectional blood flow in the valveless embryonic heart tube.

Jörg Männer; Armin Wessel; T. Mesud Yelbuz

The heart is the first organ to function in vertebrate embryos. The human heart, for example, starts beating around the 21st embryonic day. During the initial phase of its pumping action, the embryonic heart is seen as a pulsating blood vessel that is built up by (1) an inner endothelial tube lacking valves, (2) a middle layer of extracellular matrix, and (3) an outer myocardial tube. Despite the absence of valves, this tubular heart generates unidirectional blood flow. This fact poses the question how it works. Visual examination of the pulsating embryonic heart tube shows that its pumping action is characterized by traveling mechanical waves sweeping from its venous to its arterial end. These traveling waves were traditionally described as myocardial peristaltic waves. It has, therefore, been speculated that the tubular embryonic heart works as a technical peristaltic pump. Recent hemodynamic data from living embryos, however, have shown that the pumping function of the embryonic heart tube differs in several respects from that of a technical peristaltic pump. Some of these data suggest that embryonic heart tubes work as valveless “Liebau pumps.” In the present study, a review is given on the evolution of the two above‐mentioned theories of early cardiac pumping mechanics. We discuss pros and cons for both of these theories. We show that the tubular embryonic heart works neither as a technical peristaltic pump nor as a classic Liebau pump. The question regarding how the embryonic heart tube works still awaits an answer. Developmental Dynamics 239:1035–1046, 2010.


Developmental Dynamics | 2003

Myocardial volume and organization are changed by failure of addition of secondary heart field myocardium to the cardiac outflow tract

T. Mesud Yelbuz; Karen L. Waldo; Xiaowei Zhang; Marzena Zdanowicz; Jeremy Parker; Tony L. Creazzo; G. Allan Johnson; Margaret L. Kirby

Cardiac neural crest ablation results in primary myocardial dysfunction and failure of the secondary heart field to add the definitive myocardium to the cardiac outflow tract. The current study was undertaken to understand the changes in myocardial characteristics in the heart tube, including volume, proliferation, and cell size when the myocardium from the secondary heart field fails to be added to the primary heart tube. We used magnetic resonance and confocal microscopy to determine that the volume of myocardium in the looped heart was dramatically reduced and the compact layer of myocardium was thinner after neural crest ablation, especially in the outflow tract and ventricular regions. Proliferation measured by 5‐bromo‐2′‐deoxyuridine incorporation was elevated at only one stage during looping, cell death was normal and myocardial cell size was increased. Taken together, these results indicate that there are fewer myocytes in the heart. By incubation day 8 when the heart would have normally completed septation, the anterior (ventral) wall of the right ventricle and right ventricular outflow tract was significantly thinner in the neural crest‐ablated embryos than normal, but the thickness of the compact myocardium was normal in all other regions of the heart. The decreased volume and number of myocardial cells in the heart tube after neural crest ablation most likely reflects the amount of myocardium added by the secondary heart field. Development Dynamics 228:152–160, 2003.


Developmental Dynamics | 2009

In vivo imaging of the cyclic changes in cross‐sectional shape of the ventricular segment of pulsating embryonic chick hearts at stages 14 to 17: A contribution to the understanding of the ontogenesis of cardiac pumping function

Jörg Männer; Lars Thrane; Kambiz Norozi; T. Mesud Yelbuz

The cardiac cycle‐related deformations of tubular embryonic hearts were traditionally described as concentric narrowing and widening of a tube of circular cross‐section. Using optical coherence tomography (OCT), we have recently shown that, during the cardiac cycle, only the myocardial tube undergoes concentric narrowing and widening while the endocardial tube undergoes eccentric narrowing and widening, having an elliptic cross‐section at end‐diastole and a slit‐shaped cross‐section at end‐systole. Due to technical limitations, these analyses were confined to early stages of ventricular development (chick embryos, stages 10–13). Using a modified OCT‐system, we now document, for the first time, the cyclic changes in cross‐sectional shape of beating embryonic ventricles at stages 14 to 17. We show that during these stages (1) a large area of diminished cardiac jelly appears at the outer curvature of the ventricular region associated with formation of endocardial pouches; (2) the ventricular endocardial lumen acquires a bell‐shaped cross‐section at end‐diastole and becomes compressed like a fireplace bellows during systole; (3) the contracting portions of the embryonic ventricles display stretching along its baso‐apical axis at end‐systole. The functional significance of our data is discussed with respect to early cardiac pumping function. Developmental Dynamics 238:3273–3284, 2009.


Magnetic Resonance in Medicine | 2003

Improved preparation of chick embryonic samples for magnetic resonance microscopy.

Xiaowei Zhang; T. Mesud Yelbuz; Gary P. Cofer; Michael A. Choma; Margaret L. Kirby; G. Allan Johnson

Previous work demonstrated the power of three‐dimensional (3D) magnetic resonance microscopy (MRM) to follow complicated morphologic development in the embryonic cardiovascular system. In this study we describe a new dual‐contrast method for specimen preparation that combines perfusion fixation and immersion in fixative with macro‐ and small molecular gadolinium agents to provide enhanced definition of both the heart wall and chamber. MRM was performed at 9.4 T with image resolutions of 25, 31, and 50 μm isotropic voxels for three stages of chick embryos (day 4, day 5.5, and day 9), and compared to histological sections of the same embryos. The results show considerable improvement of image quality over previous efforts, with better signal‐to‐noise ratio (SNR) and contrast between the cardiac chamber and myocardial wall. Excellent correlation was shown between the MRM images and histological sections. Thus, 3D high‐resolution MRM in combination with the dual‐contrast technique is useful for acquiring quantitative 3D morphologic data regarding heart development. Magn Reson Med 49:1192–1195, 2003.


Journal of the American College of Cardiology | 2010

Takotsubo Cardiomyopathy in a 2-Year-Old Girl: 3-Dimensional Visualization of Reversible Left Ventricular Dysfunction

Stephan Schoof; Harald Bertram; Dagmar Hohmann; Thomas Jack; Armin Wessel; T. Mesud Yelbuz

![Figure][1] ![Figure][1] [Video 1][2] Video 1 Transthoracic 2-dimensional electrocardiography of the patient in apical 4-chamber view by admission to the intensive care unit after surgery during circulatory depression with left ventricular dysfunction. Study is consistent with


Circulation | 2003

Approaching Cardiac Development in Three Dimensions by Magnetic Resonance Microscopy

T. Mesud Yelbuz; Xiaowei Zhang; Michael A. Choma; Harriett A. Stadt; Marzena Zdanowicz; G. Allan Johnson; Margaret L. Kirby

Cardiac neural crest (CNC) ablation in embryonic chicks leads to conotruncal anomalies of the heart as a result of altered cardiac looping. Altered looping results from failure of the myocardium from the secondary heart field to be added to the outflow tract. Various imaging techniques have been applied to visualize embryonic heart development. However, morphological abnormalities frequently cannot clearly be identified or appreciated in 2 dimensions, particularly those involving misorientation of cardiovascular structures and changes of myocardial volume. We present here 3-dimensional (3D) reconstructions of the embryonic chick heart at looping stages in sham-operated and CNC-ablated embryos acquired by magnetic resonance microscopy (MRM) using a new dual-contrast method for specimen preparation that combines perfusion fixation and immersion in fixative with a macro-molecular gadolinium-based contrast agent. In contrast to previous techniques, this method provides imaging not only of the cardiac chambers and vessel lumens but also of internal and external cardiac structures, such as the ventricular wall, myocardial trabeculations, cardiac jelly, and endocardial cushions. Furthermore, it allows morphovolumetric analysis of hearts at different stages. There is an excellent correlation between images obtained from MRM and those obtained by routine …


Annals of Anatomy-anatomischer Anzeiger | 2013

A detailed atlas of chick heart development in vivo.

Sarah Al Naieb; Christoph M. Happel; T. Mesud Yelbuz

Various model organisms such as mouse, xenopus, or zebrafish embryos have been studied in the past to gain insight into the complex processes driving normal and abnormal development of the vertebrate heart. Despite the fact that the chicken embryo has been a favored classic model system used by embryologists and cardiovascular scientists for centuries to illustrate the principles of basic vertebrate embryology and cardiovascular development, so far, no one has provided a thorough documentation of heart development in this model from early visual stages to the stage of a completely formed heart with (a) images and (b) video recordings of beating hearts. However, in vivo documentation of heart development stages is indispensable because the initially tubular embryonic heart not only undergoes dramatic morphological changes, but also intriguing functional changes during cardiogenesis, which, only if they follow and remain within the normal developmental pathway, lead to the establishment of the normal four-chambered heart. In this work we present the first reference catalogue of cardiac development in vivo with (1) 25 plates of high resolution colour images in different views from Hamburger-Hamilton (HH)-stage 12 (day 2, relatively straight heart tube, early myocardial contractions) through HH-stage 35 (day 9, four-chambered heart) in end-diastole and end-systole, including a plate with an overview of all these stages; (2) collection of 82 video recordings of beating hearts in different views corresponding to the stages shown in the plates.


Annals of Anatomy-anatomischer Anzeiger | 2011

Integration of an optical coherence tomography (OCT) system into an examination incubator to facilitate in vivo imaging of cardiovascular development in higher vertebrate embryos under stable physiological conditions

Christoph M. Happel; Lars Thrane; Jan Thommes; Jörg Männer; T. Mesud Yelbuz

High-resolution in vivo imaging of higher vertebrate embryos over short or long time periods under constant physiological conditions is a technically challenging task for researchers working on cardiovascular development. In chick embryos, for example, various studies have shown that without appropriate maintenance of temperature, as one of the main environmental factors, the embryonic heart rate drops rapidly and often results in an increase in regurgitant flow. Hemodynamic parameters are critical stimuli for cardiovascular development that, for a correct evaluation of their developmental significance, should be documented under physiological conditions. However, previous studies were mostly carried out outside of an incubator or under suboptimal environmental conditions. Here we present, to the best of our knowledge, the first detailed description of an optical coherence tomography (OCT) system integrated into an examination incubator to facilitate real-time in vivo imaging of cardiovascular development under physiological environmental conditions. We demonstrate the suitability of this OCT examination incubator unit for use in cardiovascular development studies by examples of proof of principle experiments. We, furthermore, point out the need for use of examination incubators for physiological OCT examinations by documenting the effects of room climate (22°C) on the performance of the cardiovascular system of chick embryos (HH-stages 16/17). Upon exposure to room climate, chick embryos showed a fast drop in the heart rate and striking changes in the cardiac contraction behaviour and the blood flow through the vitelline circulation. We have documented these changes for the first time by M-mode OCT and Doppler M-mode OCT.

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Armin Wessel

Hannover Medical School

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Jörg Männer

University of Göttingen

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Lars Thrane

Technical University of Denmark

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