Intrinsic optical properties, such as optical birefringence, may serve as a tool for minimally invasive neuroimaging methods with high spatiotemporal resolution to aid in the study of neuronal activation patterns. To facilitate imaging neuronal activity by sensing dynamic birefringence, temporal characteristics behind the signal must be better understood. We have developed a novel nerve chamber to investigate changes in birefringence at the stimulation site, and at distances ~4-28 mm from that site. Using crustacean nerves with either heterogeneous or homogeneous size distributions of axon diameters, we found that the gradual (slow) recovery of the crossed-polarized signal is not explained by the arrival times of action potentials in smaller axons. Through studying the effects of stimulating current and voltage pulses, we hypothesize that the recovery may be caused by a capacitive-like coupling between firing axons and adjacent tissue structures, and we report data consistent with this hypothesis. This study will aid in the utilization of action-potential-related changes in birefringence to study fast changes in neuronal network activity.

Polarized light can be used to measure the electrical activity associated with action potential propagation in nerves, as manifested in simultaneous dynamic changes in their intrinsic optical birefringence. These signals may serve as a tool for minimally invasive neuroimaging in various types of neuroscience research, including the study of neuronal activation patterns with high spatiotemporal resolution. A fast linear photodiode array was used to image propagating action potentials in an excised portion of the lobster walking leg nerve. We show that the crossed-polarized signal (XPS) can be reliably imaged over a ≥2 cm span in our custom nerve chamber, by averaging multiple-stimulation signals, and also in single-scan real-time “movies”. This demonstration paves the way toward utilizing changes in the optical birefringence to image more complex neuronal activity in nerve fibers and other organized neuronal tissue.

Background and Objective: In vitro studies were conducted to evaluate the use of an automated system for highspeed scanning of single 9.3 µm CO 2 laser pulses in the inhibition of caries-like lesion formation in the enamel of extracted human molars. The effect of the laser in generating an acid-resistant layer and the effect of the layer on inhibiting surface mineral loss during pH cycling was explored. Study Design/Materials and Methods: Laser irradiation was performed with fluences of 0.6, 0.8, and 1.0 J/cm 2 for single pulses of 1 mm diameter (1/e 2 ), with pulse durations of 17, 22, and 27 microseconds, respectively. The laser was scanned at a 750 Hz pulse repetition rate in an automated pattern covering an area of 7 mm 2 in 0.3 sec. Six treatment groups were investigated: three groups for each fluence for laser-only and three for laser irradiation with additional fluoride from a toothpaste slurry (sodium fluoride at 1100 ppm). Each group used non-irradiated areas, which included untreated controls for the laser-only groups and a fluoride-only treatment for the groups with additional fluoride. pH cycling was performed on both groups, followed by microhardness testing to determine the relative mineral loss (ΔZ) from a caries-like formation and surface mineral loss (ΔS). Results: Laser irradiation with the 9.3 µm CO 2 laser generated an acid-resistant layer of about 15 µm in depth. For the laser-irradiated samples with additional fluoride application, the relative mineral loss (ΔZ) was 113 ± 63 vol%-µm, while for those with only fluoride application ΔZ was 572 ± 172 vol%-µm. At the highest fluence (1.0 J/cm 2 ) used, an 80.2% inhibition of caries-like lesion was measured by ΔZ. Using only laser irradiation at the highest fluence resulted in an inhibition of caries-like lesion of 79.5% for the irradiated samples (ΔZ = 374 ± 149 vol%-µm) relative to the control (ΔZ = 1826 ± 325 vol%-µm).Surface microhardness tests resulted in an inhibition of surface softening, as measured by the Knoop Hardness Value (KHN) (108 ± 33 KHN for laser irradiated with additional fluoride, for nonirradiated controls with fluoride only 52 ± 16 KHN). Inhibition of surface loss was observed for all laser fluences, but the maximum surface loss for the untreated control group was only 2.2 ± 0.49 µm. Conclusions:The results demonstrate a significant benefit of the 9.3 µm CO 2 laser at fluences of 0.6, 0.8, and 1.0 J/cm 2 in caries-like lesion inhibition as measured by the relative mineral loss in depth and surface mineral loss, without significant damage to the enamel. Additionally, inhibition of surface softening and surface loss during pH cycling was observed. The surface loss was small compared with the overall lesion depth and thickness of the generated acid-resistant layer. Lasers Surg. Med.

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The loggerhead sea turtle (Caretta caretta), has the broadest distribution among sea turtle species in the Mediterranean and requires regional and international collaborations in addition to local efforts to better inform conservation actions. Molecular techniques are powerful tools to assess population dynamics at large scales, especially by determining the connectivity among different nesting and foraging sites, and genetic diversity. In this study, a large sample was collected synchronously in the nesting areas located in the north, south and east of the Mediterranean. Recently described nesting sites from Albania and other nesting sites represented by lower sample size were also included in order to fully assess the genetic composition of the region's rookeries. Samples from 710 individuals were collected and the longer (815 bp) mtDNA D-loop fragment of these samples was ampli ed. We recorded 15 haplotypes, three of which were novel. In addition, our results show that some haplotypes, considered of Atlantic origin, have a wider dispersal in the Mediterranean than previously thought, albeit with low levels of representation. Our results, which also contribute to determining the likely origin of haplotypes that were previously known only from foraging sites, highlight the utility of broad-scale sampling, with increased sample number and longer mtDNA sequence to determine genetic diversity and connectivity. This study also demonstrates that it is important to continue to monitor the contribution of Atlantic origin haplotypes to the Mediterranean population, and the resident Mediterranean population, which is expected to expand its geographical range for reproduction with the effect of climate change and climate change in the long term. This work is important for, among other things, mixed stock analyses (MSA) that seek to localize the origin of stranded or accidentally caught sea turtles or those purposefully obtained from foraging sites to better understand the migratory distribution for conservation purposes.