Scallop Theorem and Swimming at the Mesoscale.

By comparing theoretical modeling, simulations, and experiments, we show that there exists a swimming regime at low Reynolds numbers solely driven by the inertia of the swimmer itself. This is demonstrated by considering a dumbbell with an asymmetry in coasting time in its two spheres. Despite deforming in a reciprocal fashion, the dumbbell swims by generating a nonreciprocal Stokesian flow, which arises from the asymmetry in coasting times. This asymmetry acts as a second degree of freedom, which allows the scallop theorem to be fulfilled at the mesoscopic scale.

Effects of pair bonding on parental behavior and dopamine activity in the nucleus accumbens in male prairie voles.

Male parental care is a vital behavior for the development as well as the physical and mental well-being of the young. However, little is known about the neurochemical regulation of male parental behavior, mainly due to the lack of appropriate animal models. In this study, we used the socially monogamous male prairie vole (Microtus ochrogaster) to investigate the effect of pair-bonding experience on paternal behavior and dopamine (DA) signaling in the nucleus accumbens (NAcc) in the brain. We compared sexually naïve males with males that were pair bonded with a female for two weeks. Our data showed that pair-bonded males displayed enhanced paternal behavior, particularly in pup licking/grooming, associated with increased DA type-1 receptor (D1R) protein expression in the NAcc, compared to sexually naïve males. Site-specific brain microdialysis revealed a significant, but transient, increase in DA release in the NAcc associated with pup exposure in both groups of the males. Further, pharmacological blockade of D1R in the NAcc decreased pup licking/grooming in the pair-bonded males. Together, our data demonstrate that pair-bonding experience with a female facilitated male parental behavior via NAcc D1R mediation in male prairie voles.

Targeted activation of the hippocampal CA2 area strongly enhances social memory.

Social cognition enables individuals to understand others' intentions. Social memory is a necessary component of this process, for without it, subsequent encounters are devoid of any historical information. The CA2 area of the hippocampus, particularly the vasopressin 1b receptor (Avpr1b) expressed there, is necessary for memory formation. We used optogenetics to excite vasopressin terminals, originating from the hypothalamic paraventricular nucleus, in the CA2 of mice. This markedly enhanced their social memory if the stimulation occurred during memory acquisition, but not retrieval. This effect was blocked by an Avpr1b antagonist. Finally, this enhanced memory is resistant to the social distraction of an introduced second mouse, important for socially navigating populations of individuals. Our results indicate the CA2 can increase the salience of social signals. Targeted pharmacotherapy with Avpr1b agonists or deep brain stimulation of the CA2 are potential avenues of treatment for those with declining social memory as in various dementias.

Characterization and optimization of a simple, repeatable system for the long term in vitro culture of aligned myotubes in 3D.

Increased recent research activity in exercise physiology has dramatically improved our understanding of skeletal muscle development and physiology in both health and disease. Advances in bioengineering have enabled the development of biomimetic 3D in vitro models of skeletal muscle which have the potential to further advance our understanding of the fundamental processes that underpin muscle physiology. As the principle structural protein of the extracellular matrix, collagen-based matrices are popular tools for the creation of such 3D models but the custom nature of many reported systems has precluded their more widespread adoption. Here we present a simple, reproducible iteration of an established 3D in vitro model of skeletal muscle, demonstrating both the high levels of reproducibility possible in this system and the improved cellular architecture of such constructs over standard 2D cell culture techniques. We have used primary rat muscle cells to validate this simple model and generate comparable data to conventional established cell culture techniques. We have optimized culture parameters for these cells which should provide a template in this 3D system for using muscle cells derived from other donor species and cell lines.

The effect of cell density on the maturation and contractile ability of muscle derived cells in a 3D tissue-engineered skeletal muscle model and determination of the cellular and mechanical stimuli required for the synthesis of a postural phenotype.

The successful engineering of a truly biomimetic model of skeletal muscle could have a significant impact on a number of biomedical disciplines. Although a variety of techniques are currently being developed, there is, as of yet, no widely available and easily reproducible culture system for the synthesis of 3D artificial muscle tissues. In attempting to generate such a model it is essential to optimise any protocol in order to generate a tissue that best represents the in vivo environment. Since the maturation of muscle derived cells in culture is critically dependent on density, a major factor to be addressed in the development of these models is the ideal concentration at which to seed cells in order to generate an optimal response. In studying the effect of cell density on the performance of cells in an established 3D collagen based model of skeletal muscle, we demonstrate that an optimum density does exist in terms of peak force generation and myogenic gene expression data. Greater densities however, lead to the formation of a more physiologically relevant tissue with a phenotype characteristic of slow, postural muscle.

A randomised controlled trial of subcutaneous sodium salicylate therapy for osteoarthritis of the thumb.

BACKGROUND: Current treatment for osteoarthritis (OA) is limited. Many patients with OA of the hand have areas of tender subcutaneous thickening in the forearm and upper scapular region. A pilot study showed an improvement in pain from OA at the first carpometacarpal joint after injection of such areas with 0.5% sodium salicylate or saline, an inexpensive treatment that can be administered by general practitioners and nurses. The study indicated that a randomised, sham-controlled trial was justified. METHODS: 40 patients with OA of the first carpometacarpal joint were randomised to receive either injections of sodium salicylate into tender, thickened areas of subcutaneous tissue on the forearm (baseline) and upper scapular region (week 1) or sham injections consisting of pressure without skin penetration. Blinded assessments were made at weeks 3, 7 and 13 after baseline. RESULTS: Pain and tenderness during follow-up were both significantly lower in the active treatment group compared with the sham group: 19% and 14% greater reduction in mean visual analogue scale (VAS) score, respectively (p=0.007 and 0.02, baseline mean 5.65 and 5.35 cm, average difference in change from baseline VAS 1.9 and 1.4 cm, 95% CI 0.6 to 3.2 and 0.2 to 2.5). Active and sham injections were painful, the former significantly more so; however, there was no significant correlation between the pain of active injections and response. CONCLUSION: The data show that subcutaneous sodium salicylate injections are an effective symptomatic treatment for OA of the thumb. The results provide a basis for further physiological and therapeutic research in this area.

The Impact of Rate Formulations on Stochastic Molecular Motor Dynamics.

Cells are complex structures which require considerable amounts of organization via transport of large intracellular cargo. While passive diffusion is often sufficiently fast for the transport of smaller cargo, active transport is necessary to organize large structures on the short timescales necessary for biological function. The main mechanism of this transport is by cargo attachment to motors which walk in a directed fashion along intracellular filaments. There are a number of models which seek to describe the motion of motors with attached cargo, from detailed microscopic to coarse phenomenological descriptions. We focus on the intermediate-detailed discrete stochastic hopping models, and explore how cargo transport changes depending on the number of motors, motor interaction, system constraints and rate formulations, which are derived from common thermodynamic assumptions. We find that, despite obeying the same detailed balance constraint, the choice of rate formulation considerably affects the characteristics of the overall motion of the system, with one rate formulation exhibiting novel behavior of loaded motor groups moving faster than a single unloaded motor.

Richter transformation of chronic lymphocytic leukemia presenting as a dural-based non-hodgkin lymphoma mass.

Richter transformation is defined as a diffuse large cell lymphoma, occurring by transformation of chronic lymphocytic leukemia (CLL). We present a 64-year-old man with a history of CLL and a left parieto-occipital transtentorial extra-axial mass. The patient underwent CT and MR imaging, demonstrating a large dural-based mass with extracranial extension, which occluded the left transverse sinus. Biopsy of the mass proved a pathologic diagnosis of diffuse large cell non-Hodgkin lymphoma, consistent with Richter transformation of CLL.

Aerogel Cherenkov detector for characterizing the intense flash x-ray source, Cygnus, spectrum.

An aerogel Cherenkov detector is proposed to measure the X-ray energy spectrum from the Cygnus-intense flash X-ray source operated at the Nevada National Security Site. An array of aerogels set at a variety of thresholds between 1 and 3 MeV will be adequate to map out the bremsstrahlung X-ray production of the Cygnus, where the maximum energy of the spectrum is normally around 2.5 MeV. In addition to the Cherenkov radiation from aerogels, one possible competing light-production mechanism is optical transition radiation (OTR), which may be significant in aerogels due to the large number of transitions from SiO2 clusters to vacuum voids. To examine whether OTR is a problem, four aerogel samples were tested using a mono-energetic electron beam (varied in the range of 1-3 MeV) at NSTec Los Alamos Operations. It was demonstrated that aerogels can be used as a Cherenkov medium, where the rate of the light production is about two orders magnitude higher when the electron beam energy is above threshold.

Measuring fast stochastic displacements of bio-membranes with dynamic optical displacement spectroscopy.

Stochastic displacements or fluctuations of biological membranes are increasingly recognized as an important aspect of many physiological processes, but hitherto their precise quantification in living cells was limited due to a lack of tools to accurately record them. Here we introduce a novel technique--dynamic optical displacement spectroscopy (DODS), to measure stochastic displacements of membranes with unprecedented combined spatiotemporal resolution of 20 nm and 10 µs. The technique was validated by measuring bending fluctuations of model membranes. DODS was then used to explore the fluctuations in human red blood cells, which showed an ATP-induced enhancement of non-Gaussian behaviour. Plasma membrane fluctuations of human macrophages were quantified to this accuracy for the first time. Stimulation with a cytokine enhanced non-Gaussian contributions to these fluctuations. Simplicity of implementation, and high accuracy make DODS a promising tool for comprehensive understanding of stochastic membrane processes.

Parallel and spiral flow patterns of vertebral artery contributions to the basilar artery.

PURPOSE: To demonstrate that the in vivo flow from individual vertebral arteries can be imaged and tracked in the basilar artery by use of saturation planes with three-dimensional time of flight MR angiography. METHODS: Twenty volunteers were studied with intracranial three-dimensional time of flight angiography MR. The MR angiography was repeated with saturation of the individual vertebral arteries. Flow voids and signal intensity within the basilar and posterior cerebral arteries were evaluated for flow patterns. RESULTS: Of 15 volunteers with a "normal" vertebrobasilar anatomy, 80% demonstrated a pattern of flow within the basilar artery in which the contributing vertebral components remained ipisilateral. This pattern was called "parallel." A "spiral" pattern of rotation of the contributing vertebral components was found in 20% of studies. The inflow to the posterior cerebral arteries could be identified from specific vertebral contributions and was related to the size-dominance of the vertebral artery. CONCLUSION: There is nonadmixture of vertebral artery flows of variable duration within the basilar artery; at least two patterns of flow can be described within the basilar artery. The method presented is a simple technique for determining vertebral artery flow components with routine software and without secondary data manipulation.

MRA detection of vascular occlusion in a child with progeria.

We report a case of progeria and the utility of visualizing the cerebrovascular anatomy by using MR angiography. A 4-year-old child with Hutchinson-Guilford syndrome developed symptoms of ischemia and MR angiography showed bilateral occlusion of internal carotid and vertebral artery origins; the anterior spinal artery was prominent.

Time-of-flight intracranial MR venography: evaluation of the sequential oblique section technique.

PURPOSE: To implement a time-of-flight MR angiographic technique using the oblique acquisition of thin gradient-echo sections to evaluate the intracranial venous system, and to assess the feasibility of application of this technique in a routine clinical setting. METHODS: The MR angiographic technique consisted of a two-dimensional gradient-echo technique with sequential overlapped sections obtained with an oblique orientation, angled from the sagittal toward the coronal plane. Parameters were evaluated during 41 measurements in 21 healthy volunteers with the section orientation varying from direct sagittal to direct coronal, followed by 64 examinations in 53 patients with an angle of obliquity of 15 degrees to 20 degrees from the sagittal toward the coronal plane. Confirmation of MR venographic findings was through correlation with clinical data and imaging studies. RESULTS: The volunteer data demonstrated optimal visibility of the smaller midline structures with an angle of obliquity of 15 degrees or greater. Patient examinations with this angle demonstrated sinus obstruction or thrombosis (n = 11), sinus compression (n = 2), and apparent sinus stenosis (n = 1). CONCLUSIONS: Oblique-acquisition time-of-flight MR venography seems to provide a rapid, robust technique for intracranial venous examination and can be applied as a useful adjunct to parenchymal MR in the evaluation of suspected venoocclusive disease. This oblique technique demonstrated improved vessel contrast over direct sagittal acquisition, required significantly fewer sections and thus a shorter acquisition time than direct coronal acquisition, and was applied without difficulty in the vast majority of patients in the clinical setting.

Short versus long echo time for cranial MR angiography in children and adults.

PURPOSE: To evaluate the ability of short-echo-time (TE) versus long-TE three-dimensional time-of-flight MR angiography sequences to decrease phase-related signal loss and refocus signal from blood in intracranial MR angiography of adults and children. METHODS: We evaluated 3-D time-of-flight cranial MR angiography in 33 cases (18 children and 15 adults) using two sequences. The longer-echo reference sequence had a TE of 8.0 milliseconds and a field echo of 6.5 milliseconds; the shorter-echo sequence had a TE of 5.1 and a field echo of 4.2 milliseconds. Repetition time, flip angle, and matrix were constant. The bandwidth for the longer-echo sequence was 130 Hz, 195 Hz for the shorter-echo sequence. RESULTS: The greatest improvement in diagnostic images was for children; significant and mildly improved signal recovery was demonstrated in 15 and 2 cases, respectively, of a total of 18 studies. This allowed improved diagnostic assessment. However, in the adult group significantly and mildly improved signal recovery were present in only 2 and 6 cases, respectively, of a total of 15 studies. In the group of children and adults combined, decreased lumen definition and peripheral vessel visibility were present in 24 and 30 of 33 cases, respectively, because of higher signal from background tissue when the shorter-TE field-echo sequence was used and, hence, reduced vascular contrast. CONCLUSION: The use of a short-field-echo/TE sequence is therefore recommended as the initial study in children but as a secondary examination in areas of abnormality in adults. This study illustrates the improved signal recovery from phase-related sources and improved visibility of intracranial stenosis in children with the use of a short-echo sequence. In adults, the short-echo sequence should not be used for the initial screening but reserved for secondary evaluation.

Menkes kinky hair disease: characteristic MR angiographic findings.

We report two cases of Menkes kinky hair disease in which MR and MR angiography were performed. The clinical and imaging features are reviewed. MR demonstrated characteristic cerebrovascular tortuousity and thus may be a valuable aid in diagnosis and follow-up.

MR of ballistic materials: imaging artifacts and potential hazards.

The most common ballistic materials available in the urban setting were studied for their MR effects on deflection force, rotation, heating, and imaging artifacts at 1.5 T to determine the potential efficacy and safety for imaging patients with ballistic injuries. The 28 missiles tested covered the range of bullet types and materials suggested by the Cleveland Police Department. The deflection force was measured by the New method. Rotation was evaluated 30 min after bullets had been placed in a 10% (weight per weight) ballistic gelatin designed to simulate brain tissue, with the long axis of the bullet placed parallel and perpendicular to the Z axis of the magnet. Heating was measured with alcohol thermometers by imaging for 1 hr alternatively with gradient-echo and spin-echo sequences (RF absorption = 0.033 and 0.326 w/kg respectively). Image artifacts on routine sequences were evaluated. All the steel-containing bullets except for the Winchester armor-piercing 38 caliber exhibited deflection. A nonsteel 7.38-mm Mauser also deflected. Deflection range was 514 to 15,504 dynes. Rotation occurred when the bullets were not parallel to the Z axis. Temperature changes were not significant. Deflecting projectiles resulted in obliteration of the image. The artifacts from other projectiles were small but varied by content. The artifact of the Winchester armor-piercing 38-caliber bullet was similar to those without steel. Bullets that contain steel or ferromagnetic contaminates such as nickel can be rotated within the MR unit.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of the delayed mask for improved demonstration of aneurysms on intraarterial DSA.

PURPOSE: We retrospectively explored the use of the delayed mask technique for intraarterial digital subtraction angiography (IADSA) to demonstrate the anatomy of aneurysm necks. METHODS: The delayed mask technique was utilized in 22 patients who had craniotomies for aneurysms demonstrated at angiography. The operative notes were compared to the angiographic findings of both the traditionally masked IADSA and the delayed mask IADSA. In addition, an in vitro model was constructed to examine the relationship between the size of the aneurysm neck and the ability to indirectly define its anatomy by demonstrating the flow jet. RESULTS: In 12 of 22 cases, the delayed mask technique demonstrated a systolic jet that was not demonstrated by traditional subtraction techniques. In nine of 12 cases, the delayed mask technique gave more specific information regarding the size, location, and orientation of the aneurysm neck. CONCLUSION: The delayed mask technique can add important information regarding the anatomy of aneurysm without adding time or risk to the procedure.

The significance of asymmetry of the foramen of Vesalius.

The foramen of Vesalius is a small, variable but consistently symmetrical structure located anteromedial to the foramen ovale and lateral to the foramen rotundum and vidian canal. It transmits an emissary vein through which the cavernous sinus and pterygoid plexus communicate. Fifty high-resolution CT scans of the skull base and two three-dimensional (Cemax) reconstructions were reviewed to determine criteria for defining the normal appearance of the foramen of Vesalius. Three normal types were classified: (1) a well-formed foramen, 1-2 mm in size (n = 32); (2) lack of visualization of the foramen (n = 11); and (3) partial assimilation of the foramen with the foramen ovale (n = 7). The foramen was remarkably symmetric in a large number of cases (n = 48). Asymmetry signified abnormality in four of the six cases. Abnormal causes of asymmetry included invasion by nasopharyngeal melanoma, angiofibroma, carotid cavernous fistula with drainage through the emissary vein, and neurofibromatosis. Thus, for these usually symmetric foramina of Vesalius, asymmetry is more likely the result of a pathologic process than a normal variant.

Diagnosis of ruptured intracranial dermoid cyst: value MR over CT.

The CT and MR findings of seven patients with pathologically proved ruptured dermoid cysts were reviewed to analyze the MR characteristics and to see if MR evaluation had significant advantages over CT. In six cases, both CT and MR identified fatty material in the CSF spaces. Hemorrhage complicated preoperative diagnosis in one case. Patterns of extraaxial fat distribution were as follows: intraventricular fat/CSF levels (three patients), generalized subarachnoid spread (six patients), and localized subarachnoid spread with sulcal widening (one patient). There was no correlation between fat distribution and clinical symptoms. MR showed the vascular involvement better than CT did in five of seven cases, and showed extension of the cysts into the skull base in two cases. Signal intensity of the solid mass was low on T1-weighted MR images and inhomogeneously high on T2-weighted images, which correlated pathologically with the presence of crystal cholesterol, hair, sebaceous glands, and epithelial cells in all cases. On MR, brain parenchyma showed little edema or other reaction to the masses, which were typically large. The value of MR over CT in the examination of ruptured dermoid cysts is the conspicuity of the extent of subarachnoid spread, involvement of the extraaxial structures, and evidence of vascular compromise, which can obviate angiography. MR had no advantage over CT in making the initial diagnosis of ruptured dermoid, but it would be the preferred preoperative study.