Biomedical subjects

Yu-Qing Zhou

Publications and source records attributed to Yu-Qing Zhou.

9 recordsLinked to original sources

PubMed2006

Integrin-linked kinase expression is elevated in human cardiac hypertrophy and induces hypertrophy in transgenic mice.

BACKGROUND: Although numerous signaling pathways are known to be activated in experimental cardiac hypertrophy, the molecular basis of the hypertrophic response inherent in human heart diseases remains largely unknown. Integrin-linked kinase (ILK) is a multifunctional protein kinase that physically links beta-integrins with the actin cytoskeleton, suggesting a potential mechanoreceptor role. METHODS AND RESULTS: Here, we show a marked increase in ILK protein levels in hypertrophic ventricles of patients with congenital and acquired outflow tract obstruction. This increase in ILK was associated with activation of the Rho family guanine triphosphatases, Rac1 and Cdc42, and known hypertrophic signaling kinases, including extracellular signal-related kinases (ERK1/2) and p70 S6 kinase. Transgenic mice with cardiac-specific expression of a constitutively active ILK (ILK(S343D)) or wild-type ILK (ILK(WT)) exhibited a compensated ventricular hypertrophic phenotype and displayed an activation profile of guanine triphosphatases and downstream protein kinases concordant with that seen in human hypertrophy. In contrast, transgenic mice with cardiomyocyte-restricted expression of a kinase-inactive ILK (ILK(R211A)) were unable to mount a compensatory hypertrophic response to angiotensin II in vivo. CONCLUSIONS: Taken together, these results identify ILK-regulated signaling as a broadly adaptive hypertrophic response mechanism relevant to a wide range of clinical heart disease.

Alanine↗

PubMed2006

Hemodynamics in the mouse aortic arch as assessed by MRI, ultrasound, and numerical modeling.

Mice are widely used to study arterial disease in humans, and the pathogenesis of arterial diseases is known to be strongly influenced by hemodynamic factors. It is, therefore, of interest to characterize the hemodynamic environment in the mouse arterial tree. Previous measurements have suggested that many relevant hemodynamic variables are similar between the mouse and the human. Here we use a combination of Doppler ultrasound and MRI measurements, coupled with numerical modeling techniques, to characterize the hemodynamic environment in the mouse aortic arch at high spatial resolution. We find that the hemodynamically induced stresses on arterial endothelial cells are much larger in magnitude and more spatially uniform in the mouse than in the human, an effect that can be explained by fluid mechanical scaling principles. This surprising finding seems to be at variance with currently accepted models of the role of hemodynamics in atherogenesis and the known distribution of atheromatous lesions in mice.

Animals↗

PubMed2006

Ultrahigh frame rate retrospective ultrasound microimaging and blood flow visualization in mice in vivo.

To overcome frame rate limitations in high-frequency ultrasound microimaging, new data acquisition techniques have been implemented for 2-D (B-scan) and color flow visualization. These techniques, referred to as retrospective B-scan imaging (RBI) and retrospective color flow imaging (RCFI) are based on the use of the electrocardiogram (ECG) to trigger signal acquisitions. B-scan and color flow images are reconstructed by retrospectively assembling the processed data on a line-by-line basis. Retrospective techniques are used to produce the first in vivo B-scan and color flow images of mouse carotid arteries at frame rates up to 10,000 fps. Retrospective B-scan images of mouse heart were also produced at frame rates of 1000 fps using a version of RBI implemented on a commercial imaging system (Vevo660, VisualSonics, Toronto, ON, Canada). This technology enables detailed in vivo biomechanical studies of dynamic tissues such as the myocardium of the mouse heart with high temporal resolution.

Animals↗

PubMed2005

Abnormal cardiac inflow patterns during postnatal development in a mouse model of Holt-Oram syndrome.

Tbx5(del/+) mice provide a model of human Holt-Oram syndrome. In this study, the cardiac functional phenotypes of this mouse model were investigated with 30-MHz ultrasound by comparing 12 Tbx5(del/+) mice with 12 wild-type littermates at 1, 2, 4, and 8 wk of age. Cardiac dimensions were measured with two-dimensional and M-mode imaging. The flow patterns in the left and right ventricular inflow channels were evaluated with Doppler flow sampling. Compared with wild-type littermates, Tbx5(del/+) mice showed significant changes in the mitral flow pattern, including decreased peak velocity of the left ventricular (LV) early filling wave (E wave), increased peak velocity of the late filling wave (A wave), and decreased or even reversed peak E-to-A ratio. The prolongation of LV isovolumic relaxation time was detected in Tbx5(del/+) neonates as early as 1 wk of age. In Tbx5(del/+) mice, LV wall thickness appeared normal but LV chamber dimension was significantly reduced. LV systolic function did not differ from that in wild-type littermates. In contrast, the Doppler flow spectrum in the enlarged tricuspid orifice of Tbx5(del/+) mice demonstrated increased peak velocities of both E and A waves and increased total time-velocity integral but unchanged peak E/A. In another 13 mice (7 Tbx5(del/+), 6 wild-type) at 2 wk of age, significant correlation was found between Tbx5 gene expression level in ventricular myocardium and LV filling parameters. In conclusion, the LV diastolic function of Tbx5(del/+) mice is significantly deteriorated, whereas the systolic function remains normal.

Animals↗

PubMed2004

Comprehensive transthoracic cardiac imaging in mice using ultrasound biomicroscopy with anatomical confirmation by magnetic resonance imaging.

High-frequency ultrasound biomicroscopy (UBM) has recently emerged as a high-resolution means of phenotyping genetically altered mice and has great potential to evaluate the cardiac morphology and hemodynamics of mouse mutants. However, there is no standard procedure of in vivo transthoracic cardiac imaging using UBM to comprehensively phenotype the adult mice. In this paper, the characteristic mouse thoracic anatomy is elucidated using magnetic resonance (MR) imaging on fixed mice. Besides the left parasternal and apical windows commonly used for transthoracic ultrasound cardiac imaging, a very useful right parasternal window is found. We present strategies for optimal visualization using UBM of key cardiac structures including: 1) the right atrial inflow channels such as the right superior vena cava; 2) the right ventricular inflow tract via the tricuspid orifice; 3) the right ventricular outflow tract to the main pulmonary artery; 4) the left atrial inflow channel, e.g., pulmonary vein; 5) the left ventricular inflow tract via the mitral orifice; 6) the left ventricular outflow tract to the ascending aorta; 7) the left coronary artery; and 8) the aortic arch and associated branches. Two-dimensional ultrasound images of these cardiac regions are correlated to similar sections in the three-dimensional MR data set to verify anatomical details of the in vivo UBM imaging. Dimensions of the left ventricle and ascending aorta are measured by M-mode. Flow velocities are recorded using Doppler at six representative intracardiac locations: right superior vena cava, tricuspid orifice, main pulmonary artery, pulmonary vein, mitral orifice, and ascending aorta. The methodologies and baseline measurements of inbred mice provide a useful guide for investigators applying the high-frequency ultrasound imaging to mouse cardiac phenotyping.

Animals↗

PubMed2004

Ultrasound-guided left-ventricular catheterization: a novel method of whole mouse perfusion for microimaging.

We describe a novel technique to perform whole-body perfusion fixation in mice with specific relevance to micro-imaging. With the guidance of high-frequency ultrasound imaging, we were able to perfuse fixative and contrast agents via a catheter inserted into the left ventricle, and therefore preserved the integrity of the chest and abdominal cavity. In this preliminary study, our success rate over 15 animals was 73%. We demonstrate applications of this technique for magnetic resonance imaging and micro-CT, but we expect that this method can be generally applied to whole-body perfusions of other small animals in which the intact body is necessary.

Animals↗

PubMed2004

Superstructure in SmCo7 phase.

We have performed a systematic investigation on the microstructural features of SmCo(7-x)Cu(x) (x = 0, 3.5) alloys. Transmission electron microscopy observations suggest that the SmCo7 is essentially a superstructure phase with a modulation wave vector q = (a* + b*)/3 + c*/2. The superstructure can be well interpreted by the partial ordered substitution of Co-pairs for Sm atoms within the basic structure of SmCo5. In situ cooling and heating observations indicated that the superstructure phase is stable below 670 K. Additional substitution of Cu for Co in SmCo3.5Cu3.5 does not result in evident changes of crystal structure, but makes the superstructure phase unstable at temperatures >480 K.

Alloys↗

PubMed2003

Developmental changes in left and right ventricular diastolic filling patterns in mice.

Developmental changes in left and right ventricular diastolic filling patterns were determined noninvasively in isoflurane-anesthetized outbred ICR mice. Blood velocities in the mitral and tricuspid orifices were recorded in 16 embryos at days 14.5 (E14.5) and 17.5 of gestation (E17.5) using an ultrasound biomicroscope and also serially in three groups of postnatal mice aged 1-7 days (n = 23), 1-4 wk (n = 18), and 4-12 wk (n = 27) using 20-MHz pulsed Doppler. Postnatal body weight increased rapidly to 8 wk. Heart rate increased rapidly from approximately 180 beats/min at E14.5 to approximately 380 beats/min at 1 wk after birth and then more gradually to plateau at approximately 450 beats/min after 4 wk. Ventricular filling was quantified using the ratio of peak velocity of early ventricular filling due to active relaxation (E wave) to that of the late ventricular filling caused by atrial contraction (A wave) (peak E/A ratio) and the ratio of the peak E velocity to total time-velocity integral of E and A waves (peak E/total TVI ratio). Both ventricles had similar diastolic filling patterns in embryos (peak E/A ratio of 0.28 +/- 0.02 for mitral flow and 0.27 +/- 0.02 for tricuspid flow at E14.5). After birth, mitral peak E/A increased to >1 between the third and fifth day, continued to increase to 2.25 +/- 0.25 at approximately 3 wk, and then remained stable. The tricuspid peak E/A ratio increased much less but stabilized at the same age (increased to 0.79 +/- 0.03 at 3 wk). The peak E/total TVI ratio showed similar left-right differences and changes with development. Age-related changes were largely due to increases in peak E velocity. The results suggest that diastolic function matures approximately 3 wk postnatally, presumably in association with maturation of ventricular recoil and relaxation mechanisms.

Anesthesia↗

PubMed2002

Three-dimensional gray scale volume rendering of the liver: preliminary clinical experience.

OBJECTIVE: To investigate the potential clinical usefulness of three-dimensional gray scale volume rendering in the liver. METHODS: Sixty-two patients were enrolled in the study and categorized into 2 groups: group I with ascites and group II without. Two types of volume-rendering modes, i.e., surface and transparent, were used to obtain the three-dimensional images. The data were reviewed to identify the differences between two- and three-dimensional images of the liver in each subject. RESULTS: In group I, three-dimensional sonography was superior to two-dimensional sonography in terms of surface features, edges, overall three-dimensional impression, image clarity, and structural relationships. However, it seemed that three-dimensional sonography in the surface mode was inferior to two-dimensional sonography in showing intrahepatic structures, because it had decreased resolution. In group II, three-dimensional sonography was superior to two-dimensional sonography with respect to the continuity of intrahepatic vessels, overall three-dimensional impression of the vessels, image clarity, and the relationship between lesions and neighboring vessels. However, the resolution of the lesions was decreased in 7 cases of hepatocellular carcinoma. CONCLUSIONS: Our experience suggests that three-dimensional gray scale volume rendering of the liver provides more diagnostic information than two-dimensional sonography; however, further studies are needed to evaluate its clinical importance.

Adolescent↗