Chemogenetic silencing of spinal cord-projecting cortical neurons attenuates Aß fiber-derived neuropathic allodynia in mice.

Mechanical allodynia (pain caused by innocuous mechanical stimulation) is a hallmark symptom of neuropathic pain occurring following peripheral nerve injury (PNI). Using a transgenic mouse line, in which myelinated primary afferents, including Aß fibers, express channelrhodopsin-2, we found that illumination of the plantar skin of mice following PNI produced an Aß fiber-mediated pain-like withdrawal behavior and increased c-FOS+ neurons in the superficial spinal dorsal horn (SDH). These two responses were attenuated by chemogenetic silencing of primary sensory cortex (S1) neurons projecting directly to the SDH. These findings indicate that spinally projecting cortical S1 neurons contribute to Aß fiber-derived neuropathic allodynia.

Properties of ultrasonic waves in bovine bone marrow.

We investigated the properties of ultrasonic waves in bovine bone marrow. Six bone marrow samples were obtained from different parts (proximal, middle and distal) of the shafts of two bovine femora without destruction. The measured frequency range was 3 to 10 MHz, and the temperature range was 15 to 40°C. Both wave velocity and attenuation coefficient in bone marrow always decreased as temperature increased. The velocity ranged from 1400 to 1610 m/s and attenuation coefficient ranged from 4 to 16 dB/cm. Wave velocities in bone marrow were similar to those in water, whereas the temperature dependences were different, and the wave attenuation coefficients were much higher than those in water. The dependence of velocity on temperature changed slightly around 23-24°C, where a transition from soft gel to oily liquid occurred. The transition temperature was confirmed by differential scanning calorimetry (DSC). Below this transition temperature, positive velocity dispersion was observed.