Carie M. Frantz

Grain trapping by filamentous cyanobacterial and algal mats: implications for stromatolite microfabrics through time.

Archean and Proterozoic stromatolites are sparry or fine-grained and finely laminated; coarse-grained stromatolites, such as many found in modern marine systems, do not appear until quite late in the fossil record. The cause of this textural change and its relevance to understanding the evolutionary history of stromatolites is unclear. Cyanobacteria are typically considered the dominant stromatolite builders through time, but studies demonstrating the trapping and binding abilities of cyanobacterial mats are limited. With this in mind, we conducted experiments to test the grain trapping and binding capabilities of filamentous cyanobacterial mats and trapping in larger filamentous algal mats in order to better understand grain size trends in stromatolites. Mats were cut into squares, inclined in saltwater tanks at angles from 0 to 75° (approximating the angle of lamina in typical stromatolites), and grains of various sizes (fine sand, coarse sand, and fine pebbles) were delivered to their surface. Trapping of grains by the cyanobacterial mats depended strongly on (i) how far filaments protruded from the sediment surface, (ii) grain size, and (iii) the mats incline angle. The cyanobacterial mats were much more effective at trapping fine grains beyond the abiotic slide angle than larger grains. In addition, the cyanobacterial mats actively bound grains of all sizes over time. In contrast, the much larger algal mats trapped medium and coarse grains at all angles. Our experiments suggest that (i) the presence of detrital grains beyond the abiotic slide angle can be considered a biosignature in ancient stromatolites where biogenicity is in question, and, (ii) where coarse grains are present within stromatolite laminae at angles beyond the abiotic angle of slide (e.g., most modern marine stromatolites), typical cyanobacterial-type mats are probably not solely responsible for the construction, giving insight into the evolution of stromatolite microfabrics through time.

Ultrasound-guided HIFU neurolysis of peripheral nerves to treat spasticity and pain

Spasticity, a major complication of disorders of the central nervous system (CNS) signified by uncontrollable muscle contractions, is difficult to treat effectively. We report on the use of ultrasound image-guided high-intensity focused ultrasound (HIFU) to target and suppress the function of the sciatic nerve of rabbits in vivo as a possible treatment of spasticity and pain. The image-guided HIFU device included a 3.2 MHz spherically curved transducer (focal dimensions of 5.1 mm/spl times/0.76 mm) integrated with an intraoperative imaging probe (CL10-5, Philips HDI-1000), such that the HIFU focus was within the image plane. The sciatic nerve was imaged in cross-section and identified between two muscle planes, and the HIFU treatment was directed to the nerve and monitored in real time. In situ focal acoustic intensity of 1480-1850 W/cm/sup 2/ was applied using a scanning method (scan rate of 0.5-0.6 mm/s). The force response of the plantarflexion muscles in the rabbit foot to electrical stimulation of the sciatic nerve was measured both before and after HIFU treatment using a force gauge perpendicularly coupled to the metatarsal joint of the rabbit foot. The force response was approximately 0.55 N before HIFU treatment, and complete suppression of this force was achieved after HIFU treatment, indicating complete conduction block. HIFU treatment time of 36/spl plusmn/14 s (mean /spl plusmn/ standard deviation) was effective in achieving complete conduction block in 100% of the 22 nerves treated (11 rabbits). Gross examination showed blanching of the nerves at the HIFU treatment site and lesion volumes of 2.8/spl plusmn/1.4 cm/sup 2/ encompassing the nerves. Histologic results indicated axonal demyelination and necrosis of Schwann cells as probable mechanisms of nerve block. With accurate localization and targeting of peripheral nerves using ultrasound imaging, HIFU could become a promising tool for the suppression of spasticity and pain.

Ultrasound‐guided high frequency focused ultrasound neurolysis of peripheral nerves to treat spasticity and pain

Spasticity, a complication of central nervous system disorders, signified by uncontrollable muscle contractions, is difficult to treat effectively. The use of ultrasound image‐guided high‐intensity focused ultrasound (HIFU) to target and suppress the function of the sciatic nerve of rabbits in vivo, as a possible treatment of spasticity and pain, will be presented. The image‐guided HIFU device included a 3.2‐MHz spherically‐curved transducer and an intraoperative imaging probe. A focal intensity of 1480−1850 W/cm2 was effective in achieving complete conduction block in 100% of 22 nerves with HIFU treatment times of 36±14 s (mean±SD). Gross examination showed blanching of the nerve at the treatment site and lesion volumes of 2.8±1.4 cm3 encompassing the nerve. Histological examination indicated axonal demyelination and necrosis of Schwann cells as probable mechanisms of nerve block. Long‐term studies showed that HIFU intensity of 1930 W/cm2, applied to 12 nerves for an average time of 10.5±4.9 s, enabled n...

Ultrasound‐Guided HIFU Neurolysis Of Peripheral Nerves to Treat Spasticity and Pain

Spasticity, a major complication of disorders of the central nervous system (CNS) signified by uncontrollable muscle contractions, is difficult to treat effectively. We report on the use of ultrasound image-guided high-intensity focused ultrasound (HIFU) to target and suppress the function of the sciatic nerve of rabbits in vivo as a possible treatment of spasticity and pain. The image-guided HIFU device included a 3.2 MHz spherically curved transducer (focal dimensions of 5.1 mm/spl times/0.76 mm) integrated with an intraoperative imaging probe (CL10-5, Philips HDI-1000), such that the HIFU focus was within the image plane. The sciatic nerve was imaged in cross-section and identified between two muscle planes, and the HIFU treatment was directed to the nerve and monitored in real time. In situ focal acoustic intensity of 1480-1850 W/cm/sup 2/ was applied using a scanning method (scan rate of 0.5-0.6 mm/s). The force response of the plantarflexion muscles in the rabbit foot to electrical stimulation of the sciatic nerve was measured both before and after HIFU treatment using a force gauge perpendicularly coupled to the metatarsal joint of the rabbit foot. The force response was approximately 0.55 N before HIFU treatment, and complete suppression of this force was achieved after HIFU treatment, indicating complete conduction block. HIFU treatment time of 36/spl plusmn/14 s (mean /spl plusmn/ standard deviation) was effective in achieving complete conduction block in 100% of the 22 nerves treated (11 rabbits). Gross examination showed blanching of the nerves at the HIFU treatment site and lesion volumes of 2.8/spl plusmn/1.4 cm/sup 2/ encompassing the nerves. Histologic results indicated axonal demyelination and necrosis of Schwann cells as probable mechanisms of nerve block. With accurate localization and targeting of peripheral nerves using ultrasound imaging, HIFU could become a promising tool for the suppression of spasticity and pain.