757 research outputs found
Gyrification in relation to cortical thickness in the congenitally blind
Greater cortical gyrification (GY) is linked with enhanced cognitive abilities and is also negatively related to cortical thickness (CT). Individuals who are congenitally blind (CB) exhibits remarkable functional brain plasticity which enables them to perform certain non-visual and cognitive tasks with supranormal abilities. For instance, extensive training using touch and audition enables CB people to develop impressive skills and there is evidence linking these skills to cross-modal activations of primary visual areas. There is a cascade of anatomical, morphometric and functional-connectivity changes in non-visual structures, volumetric reductions in several components of the visual system, and CT is also increased in CB. No study to date has explored GY changes in this population, and no study has explored how variations in CT are related to GY changes in CB. T1-weighted 3D structural magnetic resonance imaging scans were acquired to examine the effects of congenital visual deprivation in cortical structures in a healthy sample of 11 CB individuals (6 male) and 16 age-matched sighted controls (SC) (10 male). In this report, we show for the first time an increase in GY in several brain areas of CB individuals compared to SC, and a negative relationship between GY and CT in the CB brain in several different cortical areas. We discuss the implications of our findings and the contributions of developmental factors and synaptogenesis to the relationship between CT and GY in CB individuals compared to SC. F
ΠΡΠ΅Π½ΠΊΠ° ΠΏΡΠΎΡΠ½ΠΎΡΡΠ½ΡΡ Ρ Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊ Π·Π°ΡΡΠ±Π΅ΠΆΠ½ΠΎΠ³ΠΎ ΠΈ ΠΎΡΠ΅ΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎΠ³ΠΎ ΡΠ΅Π½ΡΡΠ°ΡΠΎΡΠΎΠ²
Π ΡΡΠ°ΡΡΠ΅ ΠΏΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½ ΡΡΠ°Π²Π½ΠΈΡΠ΅Π»ΡΠ½ΡΠΉ Π°Π½Π°Π»ΠΈΠ· Π΄Π²ΡΡ
ΠΈΡΠΏΠΎΠ»Π½Π΅Π½ΠΈΠΉ ΡΠ΅Π½ΡΡΠ°ΡΠΎΡΠΎΠ²-ΡΡΡΠ±ΡΠ»ΠΈΠ·Π°ΡΠΎΡΠΎΠ² ΡΠ°Π·Π½ΡΡ
ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈΡΠ΅Π»Π΅ΠΉ ΠΏΡΡΠ΅ΠΌ ΠΎΡΠ΅Π½ΠΈΠ²Π°Π½ΠΈΡ Π½Π°ΠΏΡΡΠΆΠ΅Π½Π½ΠΎ-Π΄Π΅ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ ΡΠΎΡΡΠΎΡΠ½ΠΈΡ ΠΏΡΠΎΠ΅ΠΊΡΠ½ΡΡ
ΠΌΠΎΠ΄Π΅Π»Π΅ΠΉ ΡΠ΅Π½ΡΡΠ°ΡΠΎΡΠΎΠ² ΡΠΈΡΠΌ "Matrix" ΠΈ "ΠΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΈΠΉ Π·Π°Π²ΠΎΠ΄" ΠΏΡΠΈ ΡΠΊΡΠΏΠ»ΡΠ°ΡΠ°ΡΠΈΠΎΠ½Π½ΡΡ
Π½Π°Π³ΡΡΠ·ΠΊΠ°Ρ
Seasonal and interannual effects of hypoxia on fish habitat quality in central Lake Erie
1. Hypoxia occurs seasonally in many stratified coastal marine and freshwater ecosystems when bottom dissolved oxygen (DO) concentrations are depleted below 2β3 mg O2 L-1.
2. We evaluated the effects of hypoxia on fish habitat quality in the central basin of Lake Erie from 1987 to 2005, using bioenergetic growth rate potential (GRP) as a proxy for habitat quality. We compared the effect of hypoxia on habitat quality of (i) rainbow smelt, Osmerus mordax mordax Mitchill (young-of-year, YOY, and adult), a cold-water planktivore, (ii) emerald shiner, Notropis atherinoides Rafinesque (adult), a warm-water planktivore, (iii) yellow perch, Perca flavescens Mitchill (YOY and adult), a cool-water benthopelagic omnivore and (iv) round goby Neogobius melanostomus Pallas (adult) a eurythermal benthivore. Annual thermal and DO profiles were generated from 1D thermal and DO hydrodynamics models developed for Lake Erieβs central basin.
3. Hypoxia occurred annually, typically from mid-July to mid-October, which spatially and temporally overlaps with otherwise high benthic habitat quality. Hypoxia reduced the habitat quality across fish species and life stages, but the magnitude of the reduction varied both among and within species because of the differences in tolerance to low DO levels and warm-water temperatures.
4. Across years, trends in habitat quality mirrored trends in phosphorus concentration and water column oxygen demand in central Lake Erie. The per cent reduction in habitat quality owing to hypoxia was greatest for adult rainbow smelt and round goby (mean: -35%), followed by adult emerald shiner (mean: -12%), YOY rainbow smelt (mean: -10%) and YOY and adult yellow perch (mean: -8.5%).
5. Our results highlight the importance of differential spatiotemporally interactive effects of DO and temperature on relative fish habitat quality and quantity. These effects have the potential to influence the performance of individual fish species as well as population dynamics, trophic interactions and fish community structure
Laser treatment in diabetic retinopathy
Diabetic retinopathy is a leading cause of visual impairment and blindness in developed countries due to macular edema and proliferative diabetic retinopathy (PDR). For both complications laser treatment may offer proven therapy: the Diabetic Retinopathy Study demonstrated that panretinal scatter photocoagulation reduces the risk of severe visual loss by >= 50% in eyes with high-risk characteristics. Pan-retinal scatter coagulation may also be beneficial in other PDR and severe nonproliferative diabetic retinopathy (NPDR) under certain conditions. For clinically significant macular edema the Early Treatment of Diabetic Retinopathy Study could show that immediate focal laser photocoagulation reduces the risk of moderate visual loss by at least 50%. When and how to perform laser treatment is described in detail, offering a proven treatment for many problems associated with diabetic retinopathy based on a high evidence level. Copyright (c) 2007 S. Karger AG, Basel
Intramolecular additions of various Ο-nucleophiles to chemoselectively activated amides and application to the synthesis of (Β±)-tashiromine
Abstract: Vilsmeier-Haack type cyclizations proved to be particularly efficient for generating parts of the polycyclic
cores of many alkaloids, although only monocyclizations have so far been reported. With the goal of
rapidly and efficiently constructing polycyclic alkaloids, we decided to exploit the Vilsmeier-Haack
reaction by utilizing iminium ions successively generated and trapped with tethered nucleophiles. To
develop such a strategy, we had to set the first cyclization. This constitutes a great challenge in itself
because amide activation conditions are usually not compatible with tethered nucleophiles, except for
indoles and aromatic rings which have already been reported. This paper describes the comprehensive
study of intramolecular addition of silyl enol ethers, allylsilanes, and enamines to chemoselectively activated
formamides, aliphatic amides, and lactams. Good to excellent yields were obtained for the 5-exo, 6-exo,
and 6-endo modes of cyclization. Moreover, we demonstrated that the species in solution after the
cyclization are iminium ions. This is highly encouraging for the development of bis-cyclization strategies.
An expeditious total synthesis of (()-tashiromine is also reported
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