Effects of Early Strabismus On The Development of Binocular Response Properties of Neurons In Visual Area 2 (V2) Of Rhesus Monkeys

Purpose:Although alterations of the binocular response properties of neurons in the primary visual cortex (V1) of monkeys reared with experimentally imposed strabismus have been well characterized, very little is known about the effects of early abnormal visual experience on the development of extrastriate neurons. In this study, we investigated the binocular response properties of V2 neurons in monkeys reared with early surgical strabismus. Methods:A small convergent misalignment was surgically induced in five infant monkeys at 4 weeks of age. Behavioral testing to measure their monocular and binocular visual capacities with respect to amblyopia, stereodeficiencies and residual strabismus were conducted between 2 and 4 years of age. Upon completion of the behavioral testing, extracellular single-unit recording experiments were conducted under anesthesia and paralysis. The binocular response properties of V2 neurons were quantitatively assessed. The data obtained in V2 were compared to those in V1 of the same monkeys. Results:The ocular dominance tests revealed that a relative reduction of binocularly balanced units in V1 was significantly greater than that in V2. However, the sensitivity of V2 units to relative interocular spatial phase disparity was significantly reduced in both V1 and V2. There was an increase in the proportion of units exhibiting interocular suppression in V2 relative to V1 in strabismic monkeys. The observed binocular suppression in V2 units of strabismic monkeys was more pronounced for higher spatial frequency gratings. This spatial frequency dependent increase in the prevalence of binocularly suppressive units was much less clear in V1. Conclusion:Alterations in how binocular signals are combined in V2 neurons of strabismic monkeys are generally more extensive and more complex than those in V1. The results suggest that these deficits in V2 are not a mere reflection of anomalies in V1 but may include a consequence of active competitive processes in V2

BiodosEPR-2006 Meeting: Acute dosimetry consensus committee recommendations on biodosimetry applications in events involving uses of radiation by terrorists and radiation accidents

In the aftermath of a radiological terrorism incident or mass-casualty radiation accident, first responders and receivers require prior guidance and pre-positioned resources for assessment, triage and medical management of affected individuals [NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA]. Several recent articles [Dainiak, N., Waselenko, J.K., Armitage, J.O., MacVittie, T.J., Farese, A.M., 2003. The hematologist and radiation casualties. Hematology (Am. Soc. Hematol. Educ. Program) 473-496; Waselenko, J.K., MacVittie, T.J., Blakely, W.F., Pesik, N., Wiley, A.L., Dickerson, W.E., Tsu, H., Confer, D.L., Coleman, C.N., Seed, T., Lowry, P., Armitage, J.O., Dainiak, N., Strategic National Stockpile Radiation Working Group, 2004. Medical management of the acute radiation syndrome: recommendations of the Strategic National Stockpile Radiation Working Group. Ann. Intern. Med. 140(12), 1037-1051; Blakely, W.F., Salter, C.A., Prasanna, P.G., 2005. Early-response biological dosimetry-recommended countermeasure enhancements for mass-casualty radiological incidents and terrorism. Health Phys. 89(5), 494-504; Goans, R.E., Waselenko, J.K., 2005. Medical management of radiation casualties. Health Phys. 89(5), 505-512; Swartz, H.M., Iwasaki, A., Walczak, T., Demidenko, E., Salikhov, I., Lesniewski, P., Starewicz, P., Schauer, D., Romanyukha, A., 2005. Measurements of clinically significant doses of ionizing radiation using non-invasive in vivo EPR spectroscopy of teeth in situ. Appl. Radiat. Isot. 62, 293-299; Weisdorf, D., Chao, N., Waselenko, J.K., Dainiak, N., Armitage, J.O., McNiece, I., Confer, D., 2006. Acute radiation injury: contingency planning for triage, supportive care, and transplantation. Biol. Blood Marrow Transplant. 12(6), 672-682], national [National Council of Radiation Protection and Measurements (NCRP), 1994. Management of persons accidentally contaminated with radionuclides. NCRP Report No. 65, Bethesda, Maryland, USA; NCR-P, 2001. Management of terrorist events involving radioactive material. NCRP Report No. 138, Bethesda, Maryland, USA; NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA] and international [IAEA, 2005. Generic procedures for medical response during a nuclear or radiological emergency. EPR-Medical 2005, IAEA, Vienna, Austria] agencies have reviewed strategies for acute-phase biodosimetry. Consensus biodosimetric guidelines include: (a) clinical signs and symptoms, including peripheral blood counts, time to onset of nausea and vomiting and presence of impaired cognition and neurological deficits, (b) radioactivity assessment, (c) personal and area dosimetry, (d) cytogenetics, (e) in vivo electron paramagnetic resonance (EPR) and (f) other dosimetry approaches (i.e. blood protein assays, etc.). Emerging biodosimetric technologies may further refine triage and dose assessment strategies. However, guidance is needed regarding which biodosimetry techniques are most useful for different radiological scenarios and consensus protocols must be developed. The Local Organizing Committee for the Second International Conference on Biodosimetry and Seventh International Symposium on EPR Dosimetry and Applications (BiodosEPR-2006 Meeting) convened an Acute Dosimetry Consensus Committee composed of national and international experts to: (a) review the current literature for biodosimetry applications for acute-phase applications in raiological emergencies, (b) describe the strengths and weaknesses of each technique, (c) provide recommendations for the use of biodosimetry assays for selected defined radiation scenarios, and (d) develop protocols to apply these recommended biological dosimetry techniques with currently available supplies and equipment for first responders. The Acute Dosimetry Consensus Committee developed recommendations for use of a prioritized multiple-assay biodosimetric-based strategy, concluding that no single assay is sufficiently robust to address all of the potential radiation scenarios including management of mass casualties and diagnosis for early medical treatment. These recommendations may be used by first responders/first receivers that span time-windows of (i.e. 0-5 days) after the radiological incident for three radiological scenarios including: (a) radiation exposure device (RED), (b) radiological dispersal device (RDD), and (c) an improvised (or otherwise acquired) nuclear device (IND). Consensus protocols for various bioassays (i.e. signs and symptoms recording, bioassay sampling for radioactivity analysis, nail-clipping sampling for EPR analysis and blood collection for hematology, cytogenetics, and blood chemistry analyses) are presented as Appendix materials. As stated in NCRP Commentary No. 19 [NCRP, 2005. Key elements of preparing emergency responders for nuclear and radiological terrorism. NCRP Commentary No. 19, Bethesda, Maryland, USA], multi-parameter triage (i.e. time to vomiting, lymphocyte kinetics, and other biodosimetry indicators) offers the current best strategy for early assessment of absorbed dose. (c) 2007 Elsevier Ltd. All rights reserved