Thermosensitive System Research Articles

Perspective on NO in brain function

The ability to sense and respond appropriately to increases in ambient and body temperatures is critical for the survival of all animals. Although evidence suggests that brain serotonergic systems play a role in thermoregulation, including thermoregulatory cooling, evidence for activation of brainstem serotonergic neurons in vivo, in unanesthetized animals, during heat exposure is lacking. In this experiment we tested the hypothesis that populations of serotonergic neurons in the midbrain and medullary raphe complex are activated following exposure to warm ambient temperature. Rats were exposed to an incubation chamber at either warm ambient temperature (37 °C) or room temperature (RT; 23 °C) for 105 min. Brains then were removed and processed for immunohistochemical detection of the protein product of the immediate-early gene c-fos (as a marker of neuronal activation) and tryptophan hydroxylase (as a marker of serotonergic neurons). Exposure to warm ambient temperature increased body temperature and c-Fos expression in topographically organized populations of serotonergic neurons in the dorsal raphe nucleus. Activation of the dorsal raphe nucleus serotonergic system was positively correlated with body temperature following exposure to the incubation chamber. In the medulla, exposure to warm ambient temperature, compared with exposure to RT, decreased c-Fos expression in serotonergic neurons in the raphe pallidus nucleus and in non-serotonergic cells in the rostral ventrolateral medulla. Together, these results provide evidence for multiple but anatomically discrete thermosensitive serotonergic systems that may have implications for the regulation of body temperature, as well as, via projections to forebrain targets, cognitive and affective functions.

A diffusion-reaction model for ?-chymotrypsin carrying uniform thermosensitive gel beads

In this study, the kinetic behavior of α-chymotrypsin-immobilized, uniform poly(isopropylacrylamide) gel beads was investigated. The kinetic study was performed by using a continuous reactor operated at steady-state conditions. In the experiments, substrate feed concentration, residence time, and reactor temperature were changed. The results were explained by a diffusion-reaction model developed for steady-state conditions. The effectiveness factor and Thiele modulus values of the thermosensitive enzyme-gel system were estimated at different temperatures by using an iterative procedure based on fourth order Runge-Kutta algorithm. The results indicated that the overall hydrolysis rate was controlled by the substrate diffusion through the gel matrix. A bending point was detected for the Thiele modulus at the lower critical solution temperature (LCST) of the thermosensitive gel. The effective diffusion coefficient of substrate and effectiveness factor decreased suddenly at LCST. The mass transfer process within the thermosensitive carrier could be described in detail by the proposed model. The results of our numerical procedure were also compared with an analytical approximate solution available in the literature. The consistency between two different model was reasonably good.

A new hydrogel system undergoing a volume phase transition upon heating

A new hydrogel system capable of a thermotropic collapse at about 47°C is the complex poly-(diallyldimethylammonium chloride)/sodium dodecyl sulfate (PDADMA-Cl/SDS). It was found that the stoichiometric complex of PDADMA-Cl/SDS being highly ordered in the collapsed state is capable of swelling strongly in the presence of excess SDS. Upon swelling the gel loses its ordered structure and becomes transparent. The hydrogel shrinks upon heating approaching its initial volume. However, in the newly achieved collapsed state the gel has no ordered structure and the volume phase transition is associated with drastic changes in the heat capacity typical of co-operative conformational and phase transitions. It is reasonable to suggest that this hydrogel system is only an example of a wide group of thermosensitive polymer systems which may undergo conformational and phase transitions.

The Relationship between the Steric Hindrance and Absorption Spectrum of Fluoran Dyes. Part I

Fluoran compounds used for the thermosensitive data-recording systems usually have substituted amino groups at the 2-position of the fluoran ring. Their absorption spectra are significantly affected by the electron-donative ability of the 2-amino groups. We investigated the relationship between the steric effects around the 2-amino groups and the absorption spectra of fluoran dyes.

Stress-strain state of a thermosensitive bimetallic system

We study the influence of various conditions of heating of a thermosensitive bimetallic plate made of an ordinary structural material and alloy with shape-memory effect on stresses and displacements formed in the plate and establish the optimal ratio of the thicknesses of constituent materials which guarantces the maximum possible susceptibility of the system to displacements in the temperature range of the martensitic phase transformation.

Preparation of polyacrylamide derivatives showing thermo-reversible coacervate formation and their potential application to two-phase separation processes

A synthetic polymer forming a thermo-reversible coacervate in aqueous milieu was prepared in this study by radical copolymerization of N,N-dimethylacrylamide (DMAA) with N-phenylacrylamide (PA). Increased content of PA in the copolymer (DPA) led to an abrupt decrease in its cloud point (lower critical solution temperature, LCST) owing to an increase in hydrophobicity. The heat of transition ( ΔH) for a 1.0wt% aqueous solution of the copolymer at the LCST was determined to be in the range of 3–4 cal g −1 by differential scanning calorimetry, considerably smaller than that obtained for a neutral amphiphilic polymer, such as poly( N-isopropylacrylamide), undergoing a steep dehydration at the LCST. This small value of ΔH suggests the incomplete dehydration of the polymer chain at the LCST. Indeed, microscopic observation revealed the formation of coacervate droplets in the aqueous solution of the copolymer, which is clear evidence of liquid—liquid phase separation. The concentration of the copolymer in the coacervate phase formed from 1.0wt% aqueous solution of the copolymer at 37°C is approximately 20 wt%. It is of interest that the formation and disappearance of the coacervate are completely thermo-reversible. To estimate the feasibility of applying this thermo-sensitive coacervate system to thermo-modulated aqueous two-phase separation, partitioning of model solutes from aqueous milieu to the coacervate was carried out. By increasing the temperature, preferential partitioning of Trypan Blue (3,3′-[(3,3′-dimethyl[1,1′-biphenyl] 4,4′-diyl)bis(azo)]bis(5-amino-4-hydroxy-2,7-naphthalenedisulfonic acid) tetrasodium salt) from aqueous phase to coacervate phase was observed, whereas no partitioning of vitamin B 12 to coacervate phase took place. Consequently, the separation of Trypan Blue from the mixed solution of vitamin B 12 and Trypan Blue was achieved solely through the change in the environmental temperature. It may be feasible to apply such copolymers showing liquid—liquid phase separation that responds to temperature as the stationary phase in thermo-regulated liquid chromatography for the separation of water-soluble drugs and dyestuffs.

ジアゾ系感熱記録媒体における熱増感剤と熱発色特性

Color development characteristics of diazonium thermo-sensitive systems were investigated using phase diagrams of coupler and thermo-sensitizer systems. Benzil, Phenyl-1-hydroxy-2naphthoate, and Benzoin were used as the thermo-sensitizer. Density versus temperature curves were characterized by three factors: color initiation temperature (Tin), color development temperature (Tcd), and tangent of the color development curve (γ). The γ was largest at the eutectic composition since the amount of molten coupler increases as the composition approaches the eutectic point. The Tcd and Tin were dependent on the eutedtic temperature.

フロログルシノール，フロログルシドを用いたジアゾ系感熱記録材料

In the diazonium thermosensitive systems, phloroglucinol and phlorogrucide were investigated as black developing couplers. Black-like dye images could be obtained by using either of them and a basic compound as a catalyst. The color development occurs via the evolution of water of crystallization of couplers. Phloroglucide, which has lower solubility in water than phloroglucinol, showed better shelf-life characteristics.