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Segmental Differences (segmental + difference)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

Segmental Differences of Impaired Diastolic Relaxation Following Cardiopulmonary Bypass Surgery in Children: A Tissue Doppler Study

ARTIFICIAL ORGANS, Issue 11 2009
Linda B. Pauliks
Abstract Impaired myocardial relaxation is an important aftereffect of cardiopulmonary bypass (CPB). Infants with their immature calcium metabolism may be particularly vulnerable. However, it has been difficult to quantitate diastolic dysfunction clinically. This study used tissue Doppler to measure regional diastolic myocardial velocities in 31 pediatric patients undergoing open heart surgery. Color tissue Doppler images were acquired in the operating room before and 8 and 24 h post CPB surgery. Early (E) and atrial (A) diastolic velocities were determined. Long axis motion was assessed from apical views near the mitral and tricuspid rings and radial wall motion from the parasternal view. The study included 31 children aged 3.6 ± 4.4 years (6 days to 16 years), with a mean weight of 14.7 ± 13.7 kg and body surface area of 0.59 ± 0.35 m2. Tissue Doppler analysis of regional wall motion revealed abnormal left ventricle (LV) and right ventricle (RV) diastolic relaxation in the early postoperative phase after CPB. Initially, all segments were significantly altered, but by 24 h, regional differences became apparent: LV radial wall motion was recovered, while longitudinal fibers in LV and RV appeared to be less resilient. RV myocardial mechanics were most abnormal. Tissue Doppler analysis may deepen our understanding of myocardial recovery and offers a sensitive tool to compare different cardioprotective strategies. [source]

Rapid Vasodilation in Isolated Skeletal Muscle Arterioles: Impact of Branch Order

MICROCIRCULATION, Issue 2 2010
BRUNO T. ROSEGUINI
Microcirculation (2010) 17, 1,11. doi: 10.1111/j.1549-8719.2009.00005.x Abstract We tested the hypothesis that segmental differences in the responsiveness and time course of vasodilation to metabolic signals putatively involved in rapid onset vasodilation (ROV) at the start of exercise exist within the skeletal muscle vasculature. Cannulated first-order (1As) and third-order arterioles (3As) of the rat gastrocnemius (G) muscle were exposed to cumulative doses of KCl, acetylcholine (Ach), or adenosine (Ado). In addition, time course and magnitude of vasodilation to localized application of these agonists were determined. 1As and 3As dilated similarly to incremental doses of the agonists. Continuous monitoring of internal diameter revealed a fast and transient dilatory response to microinjections of the agonists, with an average time delay (TD) before the onset of vasodilation of 2.8 ± 0.2 seconds (1As: 3.0 ± 0.3 seconds and 3As: 2.6 ± 0.3 seconds) and time-to-peak (TP) of 8.2 ± 0.7 seconds (1As: 10.3 ± 1 seconds and 3As:5.7 ± 0.5 seconds). No significant differences were detected for all parameters between 1As and 3As for KCl or Ado application, while 1As had a significantly longer TP and greater peak dilation than 3As to Ach. These findings demonstrate that 1As and 3As from the rat G muscle appear to have similar responsiveness to vasoactive agonists. Furthermore, the average TD before vasodilation supports a role for metabolic signals as contributors to the ROV. [source]

Some Segmental Features on the Structure of the Aortic Wall of the Dog

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 3 2004
A. M. Orsi
Summary Structural features of segmental parts of the aorta of the dog were studied by light microscopy (LM) and scanning electron microscopy (SEM). The variability in the wall architecture composition and vascular thickness of the ascending (T2-3 level), thoracic (T7-8 level) and abdominal (L6-7 infrarenal level) segments of the aorta was analysed. Morphological features such as presence of intimal folds, pattern of the medial myoconnective components with segmental variations in the number of elastic lamellae, whose relative number was higher in the thoracic aorta (ascending and descending parts), compared with the abdominal aorta, and a network of connective (stromal) elements formed by elastic and collagen lamellae and fibres in the adventitia were observed. The results were discussed on a histophysiological basis, because small but significant segmental differences had been characterized in the aortic wall structure of the dog. [source]

In situ kinetic modelling of intestinal efflux in rats: functional characterization of segmental differences and correlation with in vitro results

BIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 5 2007
Isabel González-Alvarez
Abstract The objective was to devise and apply a novel modelling approach to combine segmental in situ rat perfusion data and in vitro cell culture data, in order to elucidate the contribution of efflux in drug absorption kinetics. The fluoroquinolone CNV97100 was used as a model P-gp substrate. In situ intestinal perfusion was performed in rat duodenum, jejunum, ileum and colon to measure the influence of P-gp expression on efflux. Inhibition studies of CNV97100 were performed in the presence of verapamil, quinidine, cyclosporin A and p -aminohippuric acid. Absorption/efflux parameters were modelled simultaneously, using data from both in situ studies as well as in vitro studies. The maximal efflux velocity was modelled as a baseline value, corrected for each segment based on the expression level. CNV97100 passive diffusional permeability (Pdiff) and its affinity for the efflux carrier (Km) were assumed to be the same in all segments. The results indicate the new approach to combine in situ data and in vitro data succeed in yielding a unified, quantitative model for absorption/efflux. The model incorporated a quantitative relationship between P-gp expression level and the efflux functionality, both across in situ and in vitro systems, as well across different intestinal segments in the in situ studies. Permeability values decreased from duodenum to ileum in accordance with the increasing P-gp expression levels in rat intestine. The developed model reflects a strong correlation between in vitro and in situ results, including intrinsic differences in surface area. The successful application of a model approach to combine absorption data from two different experimental systems holds promise for future efforts to predict absorption results from one system to a second system. Copyright © 2007 John Wiley & Sons, Ltd. [source]