Dual Frequency Method for Simultaneous Translation and Real-Time Imaging of Ultrasound Contrast Agents Within Large Blood Vessels

A dual frequency excitation method for simultaneous translation and selective real-time imaging of microbubbles is presented. The method can distinguish signals originating from free flowing and static microbubbles. This method is implemented on a programmable scanner with a broadband linear array. The programmable interface allows for dynamic variations in the acoustic parameters and aperture attributes, enabling application of this method to large blood vessels located at varying depths. The performance of the method was evaluated in vitro (vessel diameter 2mm) by quantifying the sensitivity of the method to various acoustic, microbubble, and fluid flow parameters. It was observed that the static microbubble response maximized at the approximate resonance frequency of the microbubble population (estimated from a coulter counter measurement), thus, signifying the need for dual frequency excitation. The static microbubble signal declined from 25 to 12 dB with increasing centerline flow velocities (2.65–15.9cm/s); indicating the applicable range of flow velocities. The maximum intensity of the static microbubbles signal scaled with variations in the microbubble concentration. The rate of increment of static microbubble signal was independent of microbubble concentration. It was deduced that the rate of increment of the static microbubble signal is primarily a function of the pulse frequency, whereas the maximum static microbubble signal intensity is dependent on three parameters: (a) the pulse frequency, (b) the flow velocity and (c) the microbubble concentration. The proposed dual frequency sequence may enable the application of radiation force for optimizing the effect of targeted imaging and modulating drug delivery in large blood vessels with high flow velocities. (E-mail: avp2b@virginia.edu)     

Neurological symptoms in children with intussusception

Aim:  The classical combination of abdominal pain, vomiting, rectal blood loss and a palpable abdominal mass is only present in a minority of children with intussusception. Neurological signs and symptoms have been described, but are not a well understood phenomenon. We performed a retrospective study to ascertain the frequency and nature of these symptoms and to describe the characteristics of the patients presenting in this atypical way.
Methods:  The records of 58 children presenting with intussusception from 2003 to 2008 were reviewed for abdominal and neurological signs and symptoms, duration of symptoms and effectiveness of treatment.
Results:  In 10 out of 58 patients (17%), one or more neurological symptoms were recorded at presentation, with lethargy being the most frequent, followed by hypotonia and fluctuating consciousness. The patients with neurological abnormalities were significantly younger and presented with a shorter duration of symptoms. Therapy was more invasive, although not statistically significant, in this patient category.
Conclusion:  Intussusception should be considered in the differential diagnosis in young children presenting with lethargy, hypotonia and/or sudden alterations of consciousness even in the absence of the classical symptoms of intussusception.     

Neuraxial labor analgesia in an obese parturient with influenza A H1N1

We describe the use of epidural analgesia in a 39-year-old G2P1 parturient presenting at 38⁺⁶ weeks estimated gestation with confirmed influenza A H1N1 and superimposed bilateral pneumonia. Although the patient had an uncomplicated intra- and post-partum course, little is known about the safety of performing neuraxial analgesia or anesthesia in patients with influenza. The prevalence of viremia and possible translocation of blood-borne virus to the central nervous system are discussed.     

Interventions to reduce vasovagal reactions in blood donors: a systematic review and meta‐analysis

Vasovagal reactions (VVRs) in blood donors have significant implications for the welfare of donors, donor retention and the management of donor sessions. We present a systematic review of interventions designed to prevent or reduce VVRs in blood donors. Electronic databases were searched for eligible randomised trials to March 2015. Data on study design and outcomes were extracted and pooled using random effects meta‐analyses. Sixteen trials met the inclusion criteria: five trials (12 042 participants) of pre‐donation water, eight trials (3500 participants) of applied muscle tension (AMT) and one trial each of AMT combined with water, caffeine, audio‐visual distraction and/or social support. In donors receiving pre‐donation water, the relative risk (RR) compared with controls for VVRs was 0·79 [95% confidence interval (CI) 0·70–0·89, P < 0·0001] and the mean difference (MD) in severity of VVRs measured with the Blood Donation Reactions Inventory (BDRI) score was ?0·32 (95% CI ?0·51 to ?0·12, P < 0·0001). Excluding trials with a high risk of selection bias, the RR for VVRs was 0·70 (95% CI 0·45–1·11, P = 0·13). In donors who received AMT, there was no difference in the risk of chair recline in response to donor distress from controls (RR 0·76, 95% CI 0·53–1·10, P = 0·15), although the MD in BDRI score was ?0·07 (95% CI ?0·11 to ?0·03, P = 0·0005). There was insufficient data to perform meta‐analysis for other interventions. Current evidence on interventions to prevent or reduce VVRs in blood donors is indeed limited and does not provide strong support for the administration of pre‐donation water or AMT during donation. Further large trials are required to reliably evaluate the effect of these and other interventions in the prevention of VVRs.     

Differential quantum tunneling contributions in nitroalkane oxidase catalyzed and the uncatalyzed proton transfer reaction

The proton transfer reaction between the substrate nitroethane and Asp-402 catalyzed by nitroalkane oxidase and the uncatalyzed process in water have been investigated using a path-integral free-energy perturbation method. Although the dominating effect in rate acceleration by the enzyme is the lowering of the quasiclassical free energy barrier, nuclear quantum effects also contribute to catalysis in nitroalkane oxidase. In particular, the overall nuclear quantum effects have greater contributions to lowering the classical barrier in the enzyme, and there is a larger difference in quantum effects between proton and deuteron transfer for the enzymatic reaction than that in water. Both experiment and computation show that primary KIEs are enhanced in the enzyme, and the computed Swain-Schaad exponent for the enzymatic reaction is exacerbated relative to that in the absence of the enzyme. In addition, the computed tunneling transmission coefficient is approximately three times greater for the enzyme reaction than the uncatalyzed reaction, and the origin of the difference may be attributed to a narrowing effect in the effective potentials for tunneling in the enzyme than that in aqueous solution.     

Mechanical stress-induced sarcomere assembly for cardiac muscle growth in length and width

A ventricular myocyte experiences changes in length and load during every beat of the heart and has the ability to remodel cell shape to maintain cardiac performance. Specifically, myocytes elongate in response to increased diastolic strain by adding sarcomeres in series, and they thicken in response to continued systolic stress by adding filaments in parallel. Myocytes do this while still keeping the resting sarcomere length close to its optimal value at the peak of the length-tension curve. This review focuses on the little understood mechanisms by which direction of growth is matched in a physiologically appropriate direction. We propose that the direction of strain is detected by differential phosphorylation of proteins in the costamere, which then transmit signaling to the Z-disc for parallel or series addition of thin filaments regulated via the actin capping processes. In this review, we link mechanotransduction to the molecular mechanisms for regulation of myocyte length and width.