Lateral Habenula contribution in Nicotine addiction : focus on Dopamine, GABA and Serotonin Interactions

Compelling evidence has shown a pivotal role of dopaminergic function in drug addiction. Recently, the Habenula (Hb) has attracted a great deal of attention as another target for nicotine in the brain because of its role in regulating dopamine (DA), gamma-aminobutyric acid (GABA) and serotonin (5-HT) systems. Nicotine acts binding to acetylcholine receptors that are widely distributed in the brain. Interestingly, the receptor subtypes that mediate nicotine withdrawal responses are highly expressed in the Hb. Moreover, the block of habenular nicotinic receptors in animals chronically treated with nicotine enhances withdrawal responses once nicotine is discontinued. Furthermore, it has been shown how a high dose of nicotine can cause massive degeneration almost exclusively in the medial habenula (MHb) and its output tract, the fasciculus retroflexus. Thus, symptoms associated with nicotine withdrawal may be caused by dysfunctions of the Hb output. Therefore, Hb might be of fundamental importance in the expression of nicotine reinforcing properties and withdrawal. Here, we will focus on the role of the lateral habenula (LHb) on nicotine modulation of DA function and we will evaluate LHb interaction with the rostromedial tegmental nucleus (RMTg), a GABAergic area, and the serotonergic raphé nuclei. Furthermore, as LHb has high density expression of 5-HT2C receptors, these subtypes might be important in the control of its neuronal activity and output to the midbrain monoaminergic and GABAergic systems.peer-reviewe

Vulnerability of white matter to ischemia varies during development

Stroke is the one of the leading causes of mortality and morbidity in developed countries. The central role of injury to white matter in the pathophysiology of stroke has been recognised over the recent years. Stroke can affect a wide range of the population (from the premature infant to the elderly) and therefore the mechanism of injury of central white matter may vary with age. The main aim of this review paper is to shed some light on the difference in maturation of injury to the axon-oligodendrocyte unit following an ischemic insult between different developmental stages. Both components of this unit exhibit varying degrees of susceptibility to ischemia throughout their development. Axons are particularly resistant to ischemia in the neonatal stage. However, they show a marked decreased in tolerance to ischemia during the period of myelination. Late oligodendrocyte progenitor cells (OPC) are the most sensitive type of oligodendrocyte, and their role in periventricular leukomalacia (PVL) is well known. On the other hand, early OPC are particularly resistant to ischemia. Studying the effect of ischemia on white matter in the brain during the different developmental stages will lead to a better understanding of the pathophysiology of white matter injury and hopefully, in the future, to the development of new therapeutic strategies of the various white matter diseases.peer-reviewe

The quasi-free-standing nature of graphene on H-saturated SiC(0001)

We report on an investigation of quasi-free-standing graphene on 6H-SiC(0001) which was prepared by intercalation of hydrogen under the buffer layer. Using infrared absorption spectroscopy we prove that the SiC(0001) surface is saturated with hydrogen. Raman spectra demonstrate the conversion of the buffer layer into graphene which exhibits a slight tensile strain and short range defects. The layers are hole doped (p = 5.0-6.5 x 10^12 cm^(-2)) with a carrier mobility of 3,100 cm^2/Vs at room temperature. Compared to graphene on the buffer layer a strongly reduced temperature dependence of the mobility is observed for graphene on H-terminated SiC(0001)which justifies the term "quasi-free-standing".Comment: 3 pages, 3 figures, accepted for publication in Applied Physics Letter

A Red Tide Monitoring Program for Texas Coastal Waters

This is the final report for the red tide monitoring project conducted at The University of Texas at Austin Marine Science Institute (UTMSI) and covers the period from 1 Nov. 1998 to 10 April 2000. The study was designed to examine the seasonal dynamics of the toxic red tide dinoflagellate Karenia brevis (Davis) G. Hansen and Moestrup at 5 locations off the Texas coast. The work was conducted in collaboration with the Texas Parks and Wildlife Department (TPWD) utilizing bimonthly finfish surveys (Coastal Fisheries Division) to collect samples. The samples were shipped to UTMSI for chl a, nutrient, and cell count analyses. Significant interannual variability occurred in the temperature and salinity fields. Temperature was lowest in Jan.-Feb. of each year and increased. In general, the 5 stations showed little concordance with each other. There was no annual pattern in nutrient distributions. Individual stations appeared to reflect local inputs, rather than coast wide events. The only exception was a generalized silicate increase noted in Feb-April 2001 at all stations except Brazos Santiago near Brownsville. Karenia brevis was observed sporadically along the coast during the winter and most observations were limited to the summer/fall months. The sporadic occurrences and numerous "no cells" observations do not support the hypothesis that a year round resident red tide population exists in the Texas coastal zone. It appears that are transported into the area by large scale oceanographic features. The mechanism for this remains unknown. A minor red tide occurred along South Padre Island in Oct./Nov 1999. The bloom advected south into Mexico, and no further fish kills were noted in 1999. However, K. brevis occurred sporadically along the coast during this time. These events suggest that K. brevis may be seeded into the area from further offshore regularly at very low levels. Until fish-killing populations develop, it likely remains undetected. One major red tide event occurred during 2000 that affected the entire Texas coast. A small red tide occurred along South Padre Island in July, 2000 but disappeared after moving north to Padre Island National Seashore. Fish-killing concentrations of K. brevis were first detected in mid August off Sabine Pass in the north and moved south along the coast over the following months. However, low level occurrences of K. brevis were found at intermediate stations well before the main red tide advected into the region, and were nearly coincident with the initial observations off Sabine Pass. It is impossible from this data to determine if the July bloom in south Texas was related to the events off Sabine, but there is a possibility that offshore continental shelf currents may well be transporting cells north from Mexico into northern Texas waters. Another toxic species closely related to K. brevis has been seen at reasonably high abundance. This species, Karenia mikimotoi, is toxic to fish and has been reported to co-occur with K. brevis in blooms. Maximum abundance of this species was 6000 cells L-1, and appeared to exhibit a distinct increase and decline in population levels at 3 different stations.Marine Scienc

Ultrafast Wiggling and Jiggling: Ir_2(1,8-diisocyanomenthane)_4^(2+)

Binuclear complexes of d^8 metals (Pt^(II), Ir^I, Rh^I,) exhibit diverse photonic behavior, including dual emission from relatively long-lived singlet and triplet excited states, as well as photochemical energy, electron, and atom transfer. Time-resolved optical spectroscopic and X-ray studies have revealed the behavior of the dimetallic core, confirming that M–M bonding is strengthened upon dσ* → pσ excitation. We report the bridging ligand dynamics of Ir2(1,8-diisocyanomenthane)_4^(2+)(Ir(dimen)), investigated by fs–ns time-resolved IR spectroscopy (TRIR) in the region of C≡N stretching vibrations, ν(C≡N), 2000–2300 cm^(–1). The ν(C≡N) IR band of the singlet and triplet dσ*pσ excited states is shifted by −22 and −16 cm^(–1) relative to the ground state due to delocalization of the pσ LUMO over the bridging ligands. Ultrafast relaxation dynamics of the ^1dσ*pσ state depend on the initially excited Franck–Condon molecular geometry, whereby the same relaxed singlet excited state is populated by two different pathways depending on the starting point at the excited-state potential energy surface. Exciting the long/eclipsed isomer triggers two-stage structural relaxation: 0.5 ps large-scale Ir–Ir contraction and 5 ps Ir–Ir contraction/intramolecular rotation. Exciting the short/twisted isomer induces a ∼5 ps bond shortening combined with vibrational cooling. Intersystem crossing (70 ps) follows, populating a ^3dσ*pσ state that lives for hundreds of nanoseconds. During the first 2 ps, the ν(C≡N) IR bandwidth oscillates with the frequency of the ν(Ir–Ir) wave packet, ca. 80 cm^(–1), indicating that the dephasing time of the high-frequency (16 fs)^(−1) C≡N stretch responds to much slower (∼400 fs)^(−1)Ir–Ir coherent oscillations. We conclude that the bonding and dynamics of bridging di-isocyanide ligands are coupled to the dynamics of the metal–metal unit and that the coherent Ir–Ir motion induced by ultrafast excitation drives vibrational dephasing processes over the entire binuclear cation

Heavy-ion total and absorption cross sections above 25 MeV/nucleon

Within the context of a double-folding optical potential approximation to the exact nucleus-nucleus multiple-scattering series, eikonal scattering theory is used to generate tables of heavy ion total and absorption cross sections at incident kinetic energies above 25 MeV/nucleon for use in cosmic ray high-energy heavy ion transport and shielding studies. Comparisons of predictions with nucleus-nucleus experimental data show excellent agreement except at the lowest energies, where the eikonal approximation may not be completely valid. Even at the lowest energies, however, agreement is typically within 20 percent

Optimal B-spline bases for the numerical solution of fractional differential problems

Efficient numerical methods to solve fractional differential problems are particularly required in order to approximate accurately the nonlocal behavior of the fractional derivative. The aim of the paper is to show how optimal B-spline bases allow us to construct accurate numerical methods that have a low computational cost. First of all, we describe in detail how to construct optimal B-spline bases on bounded intervals and recall their main properties. Then, we give the analytical expression of their derivatives of fractional order and use these bases in the numerical solution of fractional differential problems. Some numerical tests showing the good performances of the bases in solving a time-fractional diffusion problem by a collocation-Galerkin method are also displayed