Cholecystokinin and Panic Disorder: Reflections on the History and Some Unsolved Questions

The classic gut hormone cholecystokinin (CCK) and its CCK₂-receptor are expressed in almost all regions of the brain. This widespread expression makes CCK by far the most abundant peptidergic transmitter system in the brain. This CNS-ubiquity has, however, complicated the delineation of the roles of CCK peptides in normal brain functions and neuropsychiatric diseases. Nevertheless, the common panic disorder disease is apparently associated with CCK in the brain. Thus, the C-terminal tetrapeptide fragment of CCK (CCK-4) induces, by intravenous administration in a dose-related manner, panic attacks that are similar to the endogenous attacks in panic disorder patients. This review describes the history behind the discovery of the panicogenic effect of CCK-4. Subsequently, the review discusses three unsettled questions about the involvement of cerebral CCK in the pathogenesis of anxiety and panic disorder, including therapeutic attempts with CCK₂-receptor antagonists.     

Dissymetrization of molecular crystals: a driving force for property formation

Phenomena of dissymetrization of molecular crystals are reviewed which lead to sector wise polar properties. Orientational disorder of prolate‐type dipolar molecules taking place at attachment sites can produce partial polar alignment of dipoles in corresponding growth sectors of molecular crystals nucleating into topologically centric packings. As a result bi‐polar crystals are obtained. In case of native polar groups, Monte Carlo simulations predict a basic behaviour for pyroelectric molecular crystals: the dipoles belonging to sectors of either the plus or minus direction of the unique axis show a non‐vanishing probability to be gradually reversed. Domain reversal may start upon a single orientational defect developing into complete sector reversal. Basic features of growth induced stochastic polarity formation are confirmed by scanning pyroelectric microscopy, phase sensitive second harmonic generation microscopy and x‐ray scattering. Real systems comprise channel‐type inclusion compounds, single component molecular crystals, solid solutions and long chain proteins in natural tissues. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Correlation between the residual resistivity ratio and the power‐law of the normal‐state resistivity in MgB2

MgB₂ polycrystalline superconducting specimens were irradiated with several doses of γ‐rays up to 100 MR. An increase in the normal state resistivity and a broadening of the resistive transition to the superconducting state were observed with increasing γ‐irradiation dose. Although very small changes to the superconducting transition temperature were obtained after γ‐irradiation, different temperature dependence of normal‐state resistivity and different residual resistivity ratios, RRR were obtained for different doses. We have found a correlation between RRR and the power law dependence of resistivity, n as the irradiation dose increases. This correlation may be an indication that the electron‐phonon interaction is important in these samples. These results are attributed to the disorder caused by γ‐rays. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of structure disorders and temperaturesof systems on the bio-energy transport in proteinmolecules (Ⅱ)

The influence of molecular structure disorders and physiological temperature on the states and properties of solitons as transporters of bio-energy are numerically studied through the fourth-order Runge-Kutta method and a new theory based on my paper [Front. Phys. China, 2007, 2(4): 469]. The structure disorders include fluctuations in the characteristic parameters of the spring constant, dipole-dipole interaction constant and exciton-phonon coupling constant, as well as the chain-chain interaction coefficient among the three channels and ground state energy resulting from the disorder distributions of masses of amino acid residues and impurities. In this paper, we investigate the behaviors and states of solitons in a single protein molecular chain, and in α-Helix protein molecules with three channels. In the former we prove first that the new solitons can move without dispersion, retaining its shape, velocity and energy in a uniform and periodic protein molecule. In this case of structure disorder, the fluctuations of the spring constant, dipole-dipole interaction constant and exciton-phonon coupling constant, as well as the ground state energy and the disorder distributions of masses of amino acid residues of the proteins influence the states and properties of motion of solitons. However, they are still quite stable and are very robust against these structure disorders, even in the presence of larger disorders in the sequence of masses, spring constants and coupling constants. Still, the solitons may disperse or be destroyed when the disorder distribution of the masses and fluctuations of structure parameters are quite great. If the effect of thermal perturbation of the environment on the soliton in nonuniform proteins is considered again, it is still thermally stable at the biological temperature of 300 K, and at the longer time period of 300 ps and larger spacing of 400 amino acids. The new soliton is also thermally stable in the case of motion over a long time period of 300 ps in the region of 300–320 K under the influence of the above structure disorders. However, the soliton disperses in the case of a higher temperature of 325 K and in larger structure disorders. Thus, we determine that the soliton’s lifetime and critical temperature are 300 ps and 300–320 K, respectively. These results are also consistent with analytical data obtained via quantum perturbed theory. In α-Helix protein molecules with three channels, results obtained show that these structure disorders and quantum fluctuations can change the states and features of solitons, decrease their amplitudes, energies and velocities, but they still cannot destroy the solitons, which can still transport steadily along the molecular chains while retaining energy and momentum when the quantum fluctuations are small, such as in structure disorders and quantum fluctuations of and and . Therefore, the solitons in the improved model are quite robust against these disorder effects. However, the solitons may be dispersed or disrupted in cases of very large structure disorders. When the influence of temperature on solitons is considered, we find that the new solitons can transport steadily over 333 amino acid residues in the case of motion over a long time period of 120 ps, and can retain their shapes and energies to travel forward along protein molecules after mutual collision of the solitons at the biological temperature of 300 K. Therefore, the soliton is also very robust against thermal perturbation of the α-helix protein molecules at 300 K. However, the soliton disperses in cases of higher temperatures at 325 K and in larger structure disorders. Thus, their critical temperature is about 320 K. When the effects of structure disorder and temperature are considered simultaneously, the soliton has high thermal stability and can transport for a long time along the protein molecular chains while retaining its amplitude, energy and velocity, even though the fluctuations of the structure parameters and temperature of the medium increase continually. However, the soliton disperses in the larger fluctuations of and at T=300 K, and at temperatures higher than 315 K when the fluctuations are and . This means that the critical temperature of the soliton is only 315 K in this condition. In a word, we can conclude from the above investigations that the soliton in the improved model is very robust against the structure disorders and thermal perturbation of proteins at the biological temperature of 300 K in α-helix protein molecules, and is a possible bio-energy transport carrier; the improved model is a possible candidate for the mechanism of this transport.      

Temperature dependence of optical absorption in In1‐xGaxAs solid solutions

Absorption spectra near the fundamental absoption edge of n‐type of In_1‐xGa_xAs are studied. The temperature coefficient of the In_1‐xGa_xAs energy gap, dE_g/dT, has been obtained and compared with calculated data. An exponential dependence of the absorption coefficient on photon energy has been found. The slope of the exponential absorption curve is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Reordering kinetics of ion-disordered Ni Al

A study of the reordering kinetics of ion-irradiated Ni₃Al is presented. The development of long-range order during annealing treatments is measured by quantitative electron diffractometry. According to the temperature dependence of the observed kinetics, the reaction is dominated by non-equilibrium vacancies. As a consequence, the kinetics can be calibrated versus the absolute number of atomic jumps necessary to establish the observed degree of order. In order to analyse the experimental data, Monte Carlo simulations are performed. It is shown that, beside the temperature dependence of the driving force, the ordering efficiency of the vacancy jumps itself is temperature dependent due to different mobilities of the atomic species. Received 6 December 1999 and Received in final form 23 June 2000     

‘Pseudo-proper’ ferroelectric phase transitions in oxyfluoride K3WO3F3

Based on the structural data on the phases of cryolite (ordered perovskite) K₃WO₃F₃, we develop a statistical model, which allows to describe the sequence of phase transitions observed in this compound using a unified approach. According to the model, the crystal possesses two structural subsystems: the K cations located in the octahedral positions and the WO₃F₃ octahedra in positions alternating with K cations. In the symmetric (cubic) phase, each subsystem can be found in one of the eight states. At decreasing temperature, an orientational phase transition in the subsystem of octahedra occurs first, followed by a phase transition to the low-temperature phase, caused by the loss of stability with respect to the ordering in the K cation subsystem. We find that the electric polarization occurs as pseudoproper and discuss the mechanisms of formation of the phase states.     

Raman scattering in TlInS2xSe2(1−x) layered mixed crystals (0.25≤x≤1): Compositional dependence of the mode frequencies and line widths

The Raman spectra of TlInS_2xSe_2(1−x) layered mixed crystals were studied for a wide composition range (0.25≤x≤1) in the frequency region 10-360 cm⁻¹ at room temperature. The shift of Raman-active phonon frequencies versus mixed crystals composition x were established. The effect of crystal disorder on the line width broadening of three high-frequency Raman-active modes is reported.