Ultrasound Localization of Nitinol Wire of Sub-Wavelength Dimension.

Goal: To enhance endovascular navigation using surgical guidewires and the use of ionizing radiation, we demonstrate a method for ultrasonic localization of wires with diameters less than the wavelength of ultrasound in the medium. Methods: Nitinol wires with diameters ranging from 50 µm to 250 µm were imaged ultrasonically in a 0.25-in-diameter water-filled tube in a gelatin medium. Imaging frequencies were 5 MHz, 7.5 MHZ, and 10 MHz. Results: For the full range of diameters traversing the phantom, the wires were localized successfully via visual inspection of both regular and difference ultrasound images. Similarly, two convolutional neural networks were trained, and both achieved an accuracy of over 95%. Conclusions: Wires with diameters as small as 50 µm were localized successfully in a water-based gelatin phantom, indicating the potential use of ultrasound to enhance endovascular navigation and surgical treatment.

Imipramine treatment increases cell proliferation following fluid percussion brain injury in rats.

OBJECTIVE: Researchers have observed unsustainable neurogenesis of the dentate gyrus of the hippocampus, as well as cognitive improvements in short-term imipramine-treated mice following a controlled cortical impact (CCI) model of traumatic brain injury (TBI). But they have yet to investigate the effects of a longer-duration imipramine treatment. In this study, we investigated the effects of a longer treatment regimen on rats following a fluid percussion injury (FPI) model, which creates a brain injury that more closely resembles those incurred by human patients. METHODS: We administered imipramine to rats for 8 weeks following FPI. Brain histology was performed to measure neurogenesis and cognitive recovery was evaluated using the Morris water maze (MWM). RESULTS: The Injury+imipramine group demonstrated 172% neurogenesis relative to the injury alone group at 9+ weeks in the dentate gyrus of the hippocampus. Neurogenesis observed here involved both the injured and the uninjured sides of the brain. All four groups (FPI+imipramine, FPI, sham, sham+imipramine) showed a similar performance in the MWM task. DISCUSSION: Longer duration of treatment with imipramine promotes sustained increase in hippocampal cell proliferation and survival. Global neurogenesis corresponds to the diffuse nature of FPI injury. Cognitive outcome can be due to a delay in our behavior testing as much as an absence of cognitive benefit of imipramine at this stage of neurogenesis. Nevertheless, exploring the potential benefits of prophylactic antidepressant treatment in human TBI patients is worthwhile.

Parabrachial and hypothalamic interaction in sodium appetite.

Rats with bilateral lesions of the lateral hypothalamus (LH) fail to exhibit sodium appetite. Lesions of the parabrachial nuclei (PBN) also block salt appetite. The PBN projection to the LH is largely ipsilateral. If these deficits are functionally dependent, damaging the PBN on one side and the LH on the other should also block Na appetite. First, bilateral ibotenic acid lesions of the LH were needed because the electrolytic damage used previously destroyed both cells and axons. The ibotenic LH lesions produced substantial weight loss and eliminated Na appetite. Controls with ipsilateral PBN and LH lesions gained weight and displayed robust sodium appetite. The rats with asymmetric PBN-LH lesions also gained weight, but after sodium depletion consistently failed to increase intake of 0.5 M NaCl. These results dissociate loss of sodium appetite from the classic weight loss after LH damage and prove that Na appetite requires communication between neurons in the LH and the PBN.

Conjunctive effects of reward and behavioral episodes on hippocampal place-differential neurons of rats on a mobile treadmill.

Previous studies reported context (or behavior)-dependent activities of hippocampal place cells, which are suggested to be the neural basis of episodic memory. However, it remains unclear what distinctive items these context-dependent activities encode. We investigated separately the effects of space, locomotion, and episodes with positive/negative reinforcements on activity of place-differential neurons in the hippocampal CA1 area. Rats were placed on a treadmill affixed to a motion stage translocated along a figure 8-shaped track. The track could be navigated by two different routes that shared a common central stem. The stage was paused at the start and end of the routes, where conditioned response tasks with different reinforcements were imposed. As the rats passed the common central stem, some neurons fired differently depending on the route. Comparison of hippocampal spatial firing patterns across different conditions with and without treadmill operation and/or the tasks indicated that these route-dependent spatial firing patterns were sensitive to locomotion, the tasks, and vestibular sensation or visual cues such as optic flow. The results suggest that external sensory inputs, path integration, and reinforcement context are all integrated in the hippocampus, which might provide the neural basis of episodic memory.