Validation of an arterial tortuosity measure with application to hypertension collection of clinical hypertensive patients

<p>Abstract</p> <p>Background</p> <p>Hypertension may increase tortuosity or twistedness of arteries. We applied a centerline extraction algorithm and tortuosity metric to magnetic resonance angiography (MRA) brain images to quantitatively measure the tortuosity of arterial vessel centerlines. The most commonly used arterial tortuosity measure is the distance factor metric (DFM). This study tested a DFM based measurement’s ability to detect increases in arterial tortuosity of hypertensives using existing images. Existing images presented challenges such as different resolutions which may affect the tortuosity measurement, different depths of the area imaged, and different artifacts of imaging that require filtering.</p> <p>Methods</p> <p>The stability and accuracy of alternative centerline algorithms was validated in numerically generated models and test brain MRA data. Existing images were gathered from previous studies and clinical medical systems by manually reading electronic medical records to identify hypertensives and negatives. Images of different resolutions were interpolated to similar resolutions. Arterial tortuosity in MRA images was measured from a DFM curve and tested on numerically generated models as well as MRA images from two hypertensive and three negative control populations. Comparisons were made between different resolutions, different filters, hypertensives versus negatives, and different negative controls.</p> <p>Results</p> <p>In tests using numerical models of a simple helix, the measured tortuosity increased as expected with more tightly coiled helices. Interpolation reduced resolution-dependent differences in measured tortuosity. The Korean hypertensive population had significantly higher arterial tortuosity than its corresponding negative control population across multiple arteries. In addition one negative control population of different ethnicity had significantly less arterial tortuosity than the other two.</p> <p>Conclusions</p> <p>Tortuosity can be compared between images of different resolutions by interpolating from lower to higher resolutions. Use of a universal negative control was not possible in this study. The method described here detected elevated arterial tortuosity in a hypertensive population compared to the negative control population and can be used to study this relation in other populations.</p

Effect of Grain Size and Shape on Undrained Behaviour of Sands

The stress–strain and stress path characteristics of sands are influenced by their grain size, shape, and packing. Morphological characteristics and size of particles play important role on the undrained shear strength of sands. Often, effects of these parameters are complex and cannot be easily distinguished. This study advances the knowledge of the role of particle size and shape on the undrained shear strength of sands. To eliminate the consequence of morphological characteristics, two sands with different particle sizes but similar angularity, and another sand with different roundness were selected for the study. These morphological characteristics for all three sands were determined from the analysis of scanning electron microscope images. F131 sand with higher median grain size and lower shape factors (rᵣ and rₛ) had highest undrained peak shear strength and phase transformation value. Undrained strength (qₚₜ) and effective principal stress (P′ₚₜ) in phase transformation point had direct relationship with grain median grain size (D₅₀) and inversely effect of shape factor (rᵣ and rₛ). F131 and F161 sands represented highest peak and ultimate steady-state strengths, respectively. Flow potential appeared to be directly proportional with (rᵣ and rₛ) and inversely with D₅₀. The peak index decreased with increasing shape factors (rᵣ and rₛ)

Platelets generated from human embryonic stem cells are functional in vitro and in the microcirculation of living mice

Platelets play an essential role in hemostasis and atherothrombosis. Owing to their short storage time, there is constant demand for this life-saving blood component. In this study, we report that it is feasible to generate functional megakaryocytes and platelets from human embryonic stem cells (hESCs) on a large scale. Differential-interference contrast and electron microscopy analyses showed that ultrastructural and morphological features of hESC-derived platelets were indistinguishable from those of normal blood platelets. In functional assays, hESC-derived platelets responded to thrombin stimulation, formed microaggregates, and facilitated clot formation/retraction in vitro. Live cell microscopy demonstrated that hESC-platelets formed lamellipodia and filopodia in response to thrombin activation, and tethered to each other as observed in normal blood. Using real-time intravital imaging with high-speed video microscopy, we have also shown that hESC-derived platelets contribute to developing thrombi at sites of laser-induced vascular injury in mice, providing the first evidence for in vivo functionality of hESC-derived platelets. These results represent an important step toward generating an unlimited supply of platelets for transfusion. Since platelets contain no genetic material, they are ideal candidates for early clinical translation involving human pluripotent stem cells

An outbreak of post-acupuncture cutaneous infection due to Mycobacterium abscessus

BACKGROUND: Despite the increasing popularity of acupuncture, the importance of infection control is not adequately emphasized in Oriental medicine. In December 2001, an Oriental medical doctor in Seoul, South Korea, encountered several patients with persistent, culture-negative skin lesions on the trunk and extremities at the sites of prior acupuncture treatment. We identified and investigated an outbreak of Mycobacterium abscessus cutaneous infection among the patients who attended this Oriental medicine clinic. METHODS: Patients were defined as clinic patients with persistent cutaneous infections at the acupuncture sites. Medical records for the previous 7 months were reviewed. Clinical specimens were obtained from the patients and an environmental investigation was performed. M. abscessus isolates, cultured from patients, were compared by pulsed-field gel electrophoresis (PFGE). RESULTS: Forty patients who attended the Oriental medicine clinic and experienced persistent cutaneous wound infections were identified. Cultures from five of these patients proved positive, and all other diagnoses were based on clinical and histopathologic examinations. All environmental objects tested were negative for M. abscessus, however, most were contaminated by various nosocomial pathogens. Molecular analysis using PFGE found all wound isolates to be identical. CONCLUSION: We have identified a large outbreak of rapidly growing mycobacterial infection among patients who received acupuncture at a single Oriental medicine clinic. Physicians should suspect mycobacterial infections in patients with persistent cutaneous infections following acupuncture, and infection control education including hygienic practice, should be emphasized for Oriental medical doctors practicing acupuncture