Nonlinear Frequency Mixing Ultrasound Imaging of Nanoscale Contrast Agents.

OBJECTIVE: Nanoscale ultrasound contrast agents show promise as alternatives for diagnostics and therapies due to their enhanced stability and ability to traverse blood vessels. Nonetheless, their reduced size limits echogenicity. This study introduces an enhanced nanobubble frequency mixing ultrasound imaging method, by capitalizing on their nonlinear acoustic response to dual-frequency excitation. METHODS: A single broadband transducer (L12-3v) controlled by a programmable ultrasound system was used to transmit a dual-frequency single-cycle wavefront. The frequency mixing effect enabled simultaneous transducer capture of nanobubble-generated sum and difference frequencies in real time without the need for additional hardware or post-processing, by substituting the single-frequency wavefront in a standard contrast harmonic pulse inversion imaging protocol, with the dual-frequency wavefront. RESULTS: Optimization experiments were conducted in tissue mimicking phantoms. Among the dual-frequency combinations that were tested, the highest contrast was obtained using 4&8 MHz. The nanobubble contrast improved with increased mechanical index, and achieved a maximal contrast improvement of 8.4 ± 0.5 dB compared to 4 MHz pulse inversion imaging. In imaging of a breast cancer tumor mouse model, after a systemic nanobubble injection, the contrast was improved by 3.4 ± 1.7, 4.8 ± 1.8, and 6.3 ± 1.6 dB for mechanical indices of 0.04, 0.08, and 0.1, respectively. CONCLUSION: Nonlinear frequency mixing significantly improved the nanobubble contrast, which facilitated their imaging in-vivo. SIGNIFICANCE: This study offers a new avenue to enhance ultrasound imaging utilizing nanobubbles, potentially leading to advancements in other diagnostic applications.

Ultrasound Frequency Mixing for Enhanced Contrast Harmonic Imaging of Microbubbles.

Microbubbles (MBs) serve as contrast agents in diagnostic ultrasound (US) imaging. Contrast harmonic imaging (CHI) of MBs takes advantage of their nonlinear properties that generate additional harmonic frequencies in the received spectrum. However, CHI suffers from limitations in terms of contrast, the signal-to-noise ratio, and artifacts. This article presents an enhanced, real-time, nonlinear imaging technique based on the excitation of MBs with a dual frequency waveform. The MBs trigger a frequency mixing effect that generates additional frequency components in the received spectrum; i.e., difference and sum frequencies, in addition to the standard harmonics, thus amplifying the MB's nonlinear response and enhancing image contrast. In this real-time approach, two single frequency waveforms are superpositioned into a dual frequency transmission. The dual frequency waveform is incorporated into a standard pulse-inversion (PI) sequence and is transmitted by an array transducer using an arbitrary waveform generator (AWG) in a programmable US system. Upon receive, standard dynamic receive beamforming is used, without additional post processing. Numerical simulations using the Marmottant model are used to confirm the generation of the difference frequency in the MB's backscattered echoes. The resulting image quality enhancement is demonstrated in a tissue-mimicking phantom containing MBs' suspension. A maximal contrast improvement of 3.43 dB compared to standard PI was achieved, along with a reduction by 4.5 fold in the mechanical index (MI).

Thumb carpometacarpal joint soft-tissue lesions in an asymptomatic population. An MRI study.

The purpose of this study was to evaluate the prevalence of ligament pathology around the first carpometacarpal joint in an asymptomatic population. We used a compact office-based MRI system and examined the hands of 117 healthy volunteers. We checked the competence of the anterior oblique ligament and of the posterior ligament complex on the MRI images. Our results showed that, in 82% of the study population, both ligaments could be perfectly visualized, with consistent signal from origin to insertion. Examination found signal changes indicating a damaged or torn ligament in the other cases. This study suggests that ligament pathology seen on MRI should be interpreted with caution. In symptomatic patients, pathologic images are to be interpreted in the light of the relevant clinical context. LEVEL OF EVIDENCE: III.

Mechanisms explaining nursery habitat association: how do juvenile snapper (Chrysophrys auratus) benefit from their nursery habitat?

Nursery habitats provide elevated survival and growth to the organisms that associate with them, and as such are a crucial early life-stage component for many fishes and invertebrates. The exact mechanisms by which these benefits are afforded to associated organisms, however, are often unclear. Here we assessed potential explanations of the nursery function of structurally complex habitats for post-settlement snapper, Chrysophrys auratus, in New Zealand. Specifically, we deployed Artificial Seagrass Units (ASUs) and used a combination of video observation, netting and diet analysis of associated post-settlement snapper as well describing potential prey within the micro-habitats surrounding ASUs. We did not observe any predation attempts and few potential predators, suggesting that for snapper the nursery value of structurally complex habitats is not as a predation refuge. The diet of post-settlement snapper mostly consisted of calanoid and cyclopoid copepods, which were most commonly sampled from within the water column. Nearly all suspected feeding events were also observed within the water column. When considering the velocity of water flow at each ASU, plankton sampling revealed a greater availability of copepods with increasing current strength, while netting and video observation demonstrated that the abundance of snapper was highest at sites with intermediate water velocity. This study highlights that the interaction between water flow and food availability may represent an important trade-off between energy expenditure and food intake for post-settlement snapper. Structurally complex habitats may mediate this relationship, allowing snapper to access sites with higher food availability while reducing swimming costs. This mechanism may have broader relevance, potentially explaining the importance of estuarine nursery habitats for other species.

Response of catatonia to risperidone: two case reports.

The present study describes two patients, both of Yemenite origin, with catatonic schizophrenia who responded to treatment with risperidone. One had a long history of psychiatric disorder, whereas the other was a first-episode, drug-naive patient. Our observation agrees with previous reports on the use of risperidone and other novel neuroleptic agents in the treatment of catatonia of different etiologies.

Pseudotumor cerebri as a presenting symptom of acute sinusitis in a child.

Pseudotumor cerebri is a clinical syndrome characterized by increased intracranial pressure in the absence of an intracranial tumor. It is most frequently diagnosed in obese young women, but it is also reported in children of all age groups, including infants. A variety of medical conditions have been suggested as possible etiologic factors, including several infectious diseases. This study presents a child with pseudotumor cerebri as the only presenting symptom of acute frontal sinusitis. The possible association between these two conditions should be investigated in cases of pseudotumor cerebri to enable the appropriate treatment.

Early and late postoperative application of 5-fluorouracil following trabeculectomy in refractory glaucoma.

Intraocular pressure (IOP) control was studied retrospectively in two groups of 14 consecutive patients following trabeculectomy with adjunctive postoperative 5-fluorouracil (5-FU) treatment. In one of the groups (the early-treatment group), 5-FU injections were started 2.4 +/- 0.6 days postoperatively; in the other group (the delayed-treatment group), they were started only when clinical signs suggested impending bleb failure (12.6 +/- 5.4 days postsurgery). The patients in the two groups were age-matched and had a similar history of previous failed glaucoma operations or diabetes, both of which are considered indications for postoperative 5-FU injections. The mean number of 5-FU injections and the total dose in the two groups did not differ significantly (5.3 +/- 0.8 and 5.5 +/- 1.1 injections, respectively; 26.4 +/- 3.9 and 27.5 +/- 5.3 mg 5-FU total dose, respectively). The average follow up for the two groups was 16.7 +/- 2.5 and 16.9 +/- 2.7 months, respectively. With an IOP of 18 mm Hg or less with or without medications considered a success, 42.8% of the delayed-treatment and 71.4% of the early-treatment cases were successful. More medications were required in the early-treatment group. Postoperative transient corneal epithelial defects occurred in 71.4% and 78.4% of the eyes in the late- and early-treatment groups, respectively, an insignificant difference. Conjunctival wound leak occurred in one patient (in the delayed-treatment group).(ABSTRACT TRUNCATED AT 250 WORDS)

Does an impacted tooth cause root resorption of the adjacent one?

External root resorption caused by an adjacent impacted tooth was studied radiographically in 199 cases. Resorption of the root had occurred in fifteen instances (7.5 per cent), the cervical region being least affected. The incidence was highest in the 21 to 30-year-old group and mainly involved male patients. Resorption of the periodontium alone was found in sixteen additional patients; of these, five were followed for 1 year after extraction of the impacted tooth. During this period, the damaged periodontium was completely re-established.

Internalization-competent influenza hemagglutinin mutants form complexes with clathrin-deficient multivalent AP-2 oligomers in live cells.

Most membrane proteins are endocytosed through clathrin-coated pits via AP-2 adaptor complexes. However, little is known about the interaction of internalization signals with AP-2 in live cells in the absence of clathrin lattices. To investigate this issue, we employed cells cotransfected with pairs of antigenically distinct influenza hemagglutinin (HA) mutants containing different internalization signals of the YXXZ family. To enable studies on the possible association of the naturally trimeric HAs into higher order complexes via binding to AP-2, we exploited the inability of HAs from different influenza strains to form mutual trimers. Thus, we coexpressed HA pairs from different strains (Japan and X:31) bearing similar cytoplasmic tails mutated to include internalization signals. Using antibody-mediated immunofluorescence co-patching on live cells, we demonstrate that internalization-competent HA mutants form higher order complexes and that this clustering depends on the strength of the internalization signal. The clustering persisted in cells treated with hypertonic medium to disperse the clathrin lattices, as validated by co-immunoprecipitation experiments. The clustering of HAs bearing strong internalization signals appears to be mediated via binding to AP-2, as indicated by (i) the coprecipitation of alpha-adaptin with these HAs, even in hypertonically treated cells; (ii) the co-localization (after hypertonic treatment) of AP-2 with antibody-mediated patches of these mutants; and (iii) the dispersal of the higher order HA complexes following chlorpromazine treatment, which removes AP-2 from the plasma membrane. These results suggest that even in the absence of clathrin lattices, AP-2 exists in multivalent complexes capable of simultaneously binding several internalization signals from the same family.

Regulation of RCK1 currents with a cAMP analog via enhanced protein synthesis and direct channel phosphorylation.

We have recently shown that the rat brain Kv1.1 (RCK1) voltage-gated K+ channel is partially phosphorylated in its basal state in Xenopus oocytes and can be further phosphorylated upon treatment for a short time with a cAMP analog (Ivanina, T., Perts, T., Thornhill, W. B., Levin, G., Dascal, N., and Lotan, I. (1994) Biochemistry 33, 8786-8792). In this study, we show, by two-electrode voltage clamp analysis, that whereas treatments for a short time with various cAMP analogs do not affect the channel function, prolonged treatment with 8-bromoadenosine 3',5'-cyclic monophosphorothioate ((Sp)-8-Br-cAMPS), a membrane-permeant cAMP analog, enhances the current amplitude. It also enhances the current amplitude through a mutant channel that cannot be phosphorylated by protein kinase A activation. The enhancement is inhibited in the presence of (Rp)-8-Br-cAMPS, a membrane-permeant protein kinase A inhibitor. Concomitant SDS-polyacrylamide gel electrophoresis analysis reveals that this treatment not only brings about phosphorylation of the wild-type channel, but also increases the amounts of both wild-type and mutant channel proteins; the latter effect can be inhibited by cycloheximide, a protein synthesis inhibitor. In the presence of cycloheximide, the (Sp)-8-Br-cAMPS treatment enhances only the wild-type current amplitudes and induces accumulation of wild-type channels in the plasma membrane of the oocyte. In summary, prolonged treatment with (Sp)-8-Br-cAMPS regulates RCK1 function via two pathways, a pathway leading to enhanced channel synthesis and a pathway involving channel phosphorylation that directs channels to the plasma membrane.

Ligand-independent oligomerization of cell-surface erythropoietin receptor is mediated by the transmembrane domain.

Binding of erythropoietin (Epo) to the Epo receptor (EpoR) is crucial for production of mature red cells. Although it is well established that the Epo-bound EpoR is a dimer, it is not clear whether, in the absence of ligand, the intact EpoR is a monomer or oligomer. Using antibody-mediated immunofluorescence copatching (oligomerizing) of epitope-tagged receptors at the surface of live cells, we show herein that a major fraction of the full-length murine EpoR exists as preformed dimers/oligomers in BOSC cells, which are human embryo kidney 293T-derived cells. This observed oligomerization is specific because, under the same conditions, epitope-tagged EpoR did not oligomerize with several other tagged receptors (thrombopoietin receptor, transforming growth factor beta receptor type II, or prolactin receptor). Strikingly, the EpoR transmembrane (TM) domain but not the extracellular or intracellular domains enabled the prolactin receptor to copatch with EpoR. Preformed EpoR oligomers are not constitutively active and Epo binding was required to induce signaling. In contrast to tyrosine kinase receptors (e.g., insulin receptor), which cannot signal when their TM domain is replaced by the strongly dimerizing TM domain of glycophorin A, the EpoR could tolerate the replacement of its TM domain with that of glycophorin A and retained signaling. We propose a model in which TM domain-induced dimerization maintains unliganded EpoR in an inactive state that can readily be switched to an active state by physiologic levels of Epo.