Tau-dependent microtubule disassembly initiated by prefibrillar β-amyloid

Alzheimer's Disease (AD) is defined histopathologically by extracellular β-amyloid (Aβ) fibrils plus intraneuronal tau filaments. Studies of transgenic mice and cultured cells indicate that AD is caused by a pathological cascade in which Aβ lies upstream of tau, but the steps that connect Aβ to tau have remained undefined. We demonstrate that tau confers acute hypersensitivity of microtubules to prefibrillar, extracellular Aβ in nonneuronal cells that express transfected tau and in cultured neurons that express endogenous tau. Prefibrillar Aβ42 was active at submicromolar concentrations, several-fold below those required for equivalent effects of prefibrillar Aβ40, and microtubules were insensitive to fibrillar Aβ. The active region of tau was localized to an N-terminal domain that does not bind microtubules and is not part of the region of tau that assembles into filaments. These results suggest that a seminal cell biological event in AD pathogenesis is acute, tau-dependent loss of microtubule integrity caused by exposure of neurons to readily diffusible Aβ

The pedunculopontine tegmental nucleus and the nucleus basalis magnocellularis: Do both have a role in sustained attention?

It is well established that nucleus basalis magnocellularis (NbM) lesions impair performance on tests of sustained attention. Previous work from this laboratory has also demonstrated that pedunculopontine tegmental nucleus (PPTg) lesioned rats make more omissions on a test of sustained attention, suggesting that it might also play a role in mediating this function. However, the results of the PPTg study were open to alternative interpretation. We aimed to resolve this by conducting a detailed analysis of the effects of damage to each brain region in the same sustained attention task used in our previous work. Rats were trained in the task before surgery and post-surgical testing examined performance in response to unpredictable light signals of 1500 ms and 4000 ms duration. Data for PPTg lesioned rats were compared to control rats, and rats with 192 IgG saporin infusions centred on the NbM. In addition to operant data, video data of rats' performance during the task were also analysed

Biophysical Basis for Three Distinct Dynamical Mechanisms of Action Potential Initiation

Transduction of graded synaptic input into trains of all-or-none action potentials (spikes) is a crucial step in neural coding. Hodgkin identified three classes of neurons with qualitatively different analog-to-digital transduction properties. Despite widespread use of this classification scheme, a generalizable explanation of its biophysical basis has not been described. We recorded from spinal sensory neurons representing each class and reproduced their transduction properties in a minimal model. With phase plane and bifurcation analysis, each class of excitability was shown to derive from distinct spike initiating dynamics. Excitability could be converted between all three classes by varying single parameters; moreover, several parameters, when varied one at a time, had functionally equivalent effects on excitability. From this, we conclude that the spike-initiating dynamics associated with each of Hodgkin's classes represent different outcomes in a nonlinear competition between oppositely directed, kinetically mismatched currents. Class 1 excitability occurs through a saddle node on invariant circle bifurcation when net current at perithreshold potentials is inward (depolarizing) at steady state. Class 2 excitability occurs through a Hopf bifurcation when, despite net current being outward (hyperpolarizing) at steady state, spike initiation occurs because inward current activates faster than outward current. Class 3 excitability occurs through a quasi-separatrix crossing when fast-activating inward current overpowers slow-activating outward current during a stimulus transient, although slow-activating outward current dominates during constant stimulation. Experiments confirmed that different classes of spinal lamina I neurons express the subthreshold currents predicted by our simulations and, further, that those currents are necessary for the excitability in each cell class. Thus, our results demonstrate that all three classes of excitability arise from a continuum in the direction and magnitude of subthreshold currents. Through detailed analysis of the spike-initiating process, we have explained a fundamental link between biophysical properties and qualitative differences in how neurons encode sensory input

The Changes of the Body Weight and Some Blood Parameters of Pekin Ducklings Dependent on Transportation Duration

Onbasilar, Ebru/0000-0002-1321-0280; ERISIR, Zeki/0000-0003-0420-023X; Erisir, Mine/0000-0001-6209-4792WOS: 000262562100003The effect of transportation on body weight and some blood parameters of hatching Pekin ducklings were investigated. A total of 500 (250 male, 250 female) 1 day-old ducklings (Star 52-Grimaud Freres) were obtained from a commercial hatchery. Upon hatching and on the 4, 8 and 12 h of the transportation, each duckling was weighed to determine their body weights. Before transportation and on the 4, 8 and 12 h of the transportation, necks of 10 male and 10 female ducklings were broken and blood samples were taken. Plasma corticosterone, glucose, cholesterol, triglyceride, AST (Aspartate transaminase), CK (Creatine kinase), total protein, albumin levels and blood H/L (heterophile/lymphocyte) ratios were determined. The body weights, which were 46.1 and 45.7 g for hatching male and female ducklings, fell down to 41.3 and 41.5 g at the end of transportation. During transportation, a total of 4 ducklings died; 1 male and 1 female on the 8 h, 1 male and 1 female on the 12 h. Plasma glucose levels of ducklings decreased up to 8 h of transportation, but increased at 12 h. Plasma corticosterone, cholesterol, triglyceride, AST, total protein, albumin levels and blood H/L ratios increased in transported ducklings due to increasing transportation time

Alkaline sulphite anthraquinone pulping of caucasian spruce (Picea orientalis L.) chips with added sodium borohydride and ethanol

The study determined and compared the yield, viscosity, and chemical and physical properties of the pulps obtained as a result of Alkaline Sulfite–Anthraquinone(AS-AQ) pulping of Caucasian spruce wood with and without the addition of sodium borohydride (ASAB process) and ethanol (ASAE). It was found that the addition of ethanol to the AS-AQ pulping had a favourable influence on the screened yield and kappa number of the pulps. The addition of NaBH4 to the AS-AQ pulping in general also had a favourable influence on these pulps’ indices, provided that the amount added was not higher than 1–2% and the time of pulping was 180 mins. The higher yield of the ASAE pulps resulted from the higher retention of both cellulose and hemicelluloses, while the higher yield of ASAB pulps resulted from the higher retention of hemicelluloses and lignin. Regarding the AS-AQ pulping conditions,a distinct negative effect of modification on the viscosity of the pulps was observed in the case of the NaBH4 a additions to this pulping process. The viscosity reduction was, however, lower with extended pulping time. The static strength properties (tensile index and burst index) of the ASAB and ASAE pulps were in general lower than the AS-AQ pulps. In the case of the tear index, the tendency was similar.The addition of ethanol and especially NaBH4 to the AS-AQ pulping had a distinctly unfavourable influence on the whiteness and brightness of the pulps

Effect of Different Housing Systems on Growth and Welfare of Pekin Ducks

Onbasilar, Ebru/0000-0002-1321-0280; ERISIR, Zeki/0000-0003-0420-023XWOS: 000264104700007The aim of this study was to investigate the effect of different housing systems on growth and welfare of Pekin ducks. A total of 420 (212 male, 208 female) one-day-old ducklings were used in this study. The ducklings were randomly divided into 4 treatment groups; 2 Intensive Systems (IS) (one without pool and the other with swimming pool) and 2 intensive systems with outside activity (IOS) (one with swimming pool and the other without pool). The IOS with swimming pool was found to influence the body weight at 6 weeks of age. Body weight at 6 weeks of age was lower in ducks reared in IOS with pool than those reared in IOS without pool. Feed consumption was the highest and also feed efficiency was the lowest in ducks reared in IS without pool. The differences between the groups in terms of values for immune response, H-L ratio, plasma corticosterone, cholesterol, glucose and triglyceride levels were not statistically significant. It is concluded that although, the most common system used for duck rearing worldwide is IS without pool, the findings of the present study indicate that IOS with swimming pool is the best system in terms of duck welfare and growth

Effects of Housing System, Swimming Pool and Slaughter Age on Duck Performance, Carcass and Meat Characteristics

Onbasilar, Ebru/0000-0002-1321-0280; ERISIR, Zeki/0000-0003-0420-023X; OKSUZTEPE, Gulsum/0000-0003-3267-6841WOS: 000268160300037The aim of this study was to determine the effects of different housing systems, swimming pool and slaughter age on performance, carcass and meat characteristics of ducks. A total of 420 (212 male, 208 female) one day old ducklings (Star 52-Grimaud Freres) were obtained from a commercial hatchery. The ducklings were randomly divided into four treatment groups; two Intensive Systems (IS) (one without pool and the other with swimming pool) and two intensive systems with outside activity (IOS) (one with swimming pool and the other without pool). Each group included 105 (53 male and 52 female) ducklings. European Efficiency Factor (EEF), feed efficiency and livability rate were affected by the housing system, swimming pool and age. Housing system and slaughter age significantly affected the slaughter weight and cold carcass yield. Breast, legs and wings percentages were significantly affected by slaughter age. PH(24), cooking loss, ash, protein and lipid contents of leg muscle were significantly altered by age. PH(24), ash, protein and lipid contents increased while, the cooking loss decreased with age. Housing system had no effect on the carcass chemical composition. From the point of EEF the market age of Pekin ducks at 6 weeks is more beneficial due to the better feed efficiency, lower feed intake and lower feed cost. Open sided area and swimming pool enhanced the EEF.FUBAP (Management Office of Scientific Research Projects of Firat University)Firat University [1333]This study was partially supported with a grant by FUBAP (Management Office of Scientific Research Projects of Firat University) (Project No: 1333; Project coordinator: Dr. Z. Erisir). We are grateful to FUVEM (Research and Practice Directorship of Farm of Firat University) for their cooperation

Experience-dependent synaptic plasticity in V1 occurs without microglial CX3CR1

Brief monocular deprivation (MD) shifts ocular dominance and reduces the density of thalamic synapses in layer 4 of the mouse primary visual cortex (V1). We found that microglial lysosome content is also increased as a result of MD. Previous studies have shown that the microglial fractalkine receptor CX3CR1 is involved in synaptic development and hippocampal plasticity.Wetherefore tested the hypothesis that neuron-to-microglial communication via CX3CR1 is an essential component of visual cortical development and plasticity in male mice. Our data show that CX3CR1 is not required for normal development of V1 responses to visual stimulation, multiple forms of experience-dependent plasticity, or the synapse loss that accompanies MD in layer 4. By ruling out an essential role for fractalkine signaling, our study narrows the search for understanding how microglia respond to active synapse modification in the visual cortex. Keywords: microglia; ocular dominance plasticity; stimulus-selective response potentiation; synaptic plasticity; visual cortexNational Institutes of Health (U.S.) (Grant R01-EY012309)National Institutes of Health (U.S.) (Grant R01-EY0237

Rapid Structural Remodeling of Thalamocortical Synapses Parallels Experience-Dependent Functional Plasticity in Mouse Primary Visual Cortex

Monocular lid closure (MC) causes a profound shift in the ocular dominance (OD) of neurons in primary visual cortex (V1). Anatomical studies in both cat and mouse V1 suggest that large-scale structural rearrangements of eye-specific thalamocortical (TC) axons in response to MC occur much more slowly than the shift in OD. Consequently, there has been considerable debate as to whether the plasticity of TC synapses, which transmit competing visual information from each eye to V1, contributes to the early functional consequences of MC or is simply a feature of long-term deprivation. Here, we used quantitative immuno-electron microscopy to examine the possibility that alterations of TC synapses occur rapidly enough to impact OD after brief MC. The effect of short-term deprivation on TC synaptic structure was examined in male C57BL/6 mice that underwent 3 and 7 d of MC or monocular retinal inactivation (MI) with tetrodotoxin. The data show that 3 d of MC is sufficient to induce substantial remodeling of TC synapses. In contrast, 3 d of MI, which alters TC activity but does not shift OD, does not significantly affect the structure of TC synapses. Our results support the hypothesis that the rapid plasticity of TC synapses is a key step in the sequence of events that shift OD in visual cortex.National Institutes of Health (U.S.) (F31NS059189)National Institutes of Health (U.S.) (K25NS052422)National Institutes of Health (U.S.) (RO1EY12138)National Institutes of Health (U.S.) (RO1EYO12309