Circular polarization of transmitted light by sapphirinidae copepods.

Circularly polarized light, rare in the animal kingdom, has thus far been documented in only a handful of animals. Using a rotating circular polarization (CP) analyzer we detected CP in linearly polarized light transmitted through epipelagic free living Sapphirina metallina copepods. Both left and right handedness of CP was detected, generated from specific organs of the animal's body, especially on the dorsal cephalosome and prosome. Such CP transmittance may be generated by phase retardance either in the muscle fibers or in the multilayer membrane structure found underneath the cuticle. Although the role, if any, played by circularly polarized light in Sapphirinidae has yet to be clarified, in other animals it was suggested to take part in mate choice, species recognition, and other forms of communication.Planktonic Sapphirinidae copepods were found to circularly polarize the light passing through them. Circular polarization may be created by unique, multilayered features of the membrane structure found under their cuticle or by organized muscle fibers

Maps of the modulation depth of the signals through a <i>Sapphirina</i> copepod, when incoming light is linearly polarized, as detected by a CP detector.

<p>A modulation depth of 1.0 indicates that all measured light is CP, whereas 0 signifies no CP. <b><u>A</u></b>: Each image is for a different orientation of the entrance polarizer, and therefore, of the illuminating beam, in 20° steps. The orientation for 0° was arbitrarily set. Note that CP handedness is not recorded. Locations of CP activity correspond with both muscles fibers as illuminated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086131#pone-0086131-g001" target="_blank">Fig 1C</a> and areas of CP created under depolarized illumination as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086131#pone-0086131-g001" target="_blank">Fig 1D</a>. <b><u>B</u></b>: The modulation depth as a function of the input polarization orientation at six locations on the animal is indicated in the figure inset.</p

Outline of the system used to detect transmitted CP.

<p>Illuminating light passed first through a depolarizer, and then, if needed, it was linearly polarized. After passing through the specimen, depending on handedness, the light was or was not filtered through a rotating 1/2 λ retarder that covered half of the field of view. The circularly polarized light was then linearized by a 1/4 λ retarder and an analyzer was used to examine it.</p

A <i>Sapphirina metallina</i> copepod under a dissecting microscope and transmitted illumination.

<p><b><u>A</u></b>: With a depolarizing light and no polarizing filter. <b><u>B</u></b>: Between two linearly polarizers at 45° to each other, showing body structure and polarization active (depolarizing, phase retardance, or birefringence<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086131#pone.0086131-Sabbah2" target="_blank">[24]</a>) structures. <b><u>C</u></b>: The animal between crossed linear polarizers showing only linearly polarization-active structures. Such linear polarization activity can arise from change in orientation of polarization, depolarization, or the creation of CP. <b><u>D</u></b>: Circularly polarized light passing through a copepod, according to its left or right handedness. Incoming light was depolarized. Arrows indicate areas of relatively strong CP, though not more than 30%; dark and bright areas indicate right and left CP, respectively. Note that most of these areas, such as eye tubes or posterior parts of carapace, do not show up when placed between crossed linear polarizers (insert C) suggesting that the process causing the CP under depolarized illumination, is not mere retardance such as by muscle fibers.</p

Assessment of Intra-Abdominal Pressure with a Novel Continuous Bladder Pressure Monitor—A Clinical Validation Study

Introduction: Intra-abdominal hypertension and the resulting abdominal compartment syndrome are serious complications of severely ill patients. Diagnosis requires an intra-abdominal pressure (IAP) measurement, which is currently cumbersome and underused. We aimed to test the accuracy of a novel continuous IAP monitor. Methods: Adults having laparoscopic surgery and requiring urinary catheter intra-operatively were recruited to this single-arm validation study. IAP measurements using the novel monitor and a gold-standard foley manometer were compared. After anesthesia induction, a pneumoperitoneum was induced through a laparoscopic insufflator, and five randomly pre-defined pressures (between 5 and 25 mmHg) were achieved and simultaneously measured via both methods in each participant. Measurements were compared using Bland–Altman analysis. Results: In total, 29 participants completed the study and provided 144 distinct pairs of pressure measurements that were analyzed. A positive correlation between the two methods was found (R2 = 0.93). There was good agreement between the methods, with a mean bias (95% CI) of −0.4 (−0.6, −0.1) mmHg and a standard deviation of 1.3 mmHg, which was statistically significant but of no clinical importance. The limits of agreement (where 95% of the differences are expected to fall) were −2.9 and 2.2 mmHg. The proportional error was statistically insignificant (p = 0.85), suggesting a constant agreement between the methods across the range of values tested. The percentage error was 10.7%. Conclusions: Continuous IAP measurements using the novel monitor performed well in the clinical setup of controlled intra-abdominal hypertension across the evaluated range of pressures. Further studies should expand the range to more pathological values