Chitosan/Alginate Dialdehyde Multilayer Films with Modulated pH‐Responsiveness and Swelling

Oxidation of alginate is a promising method that creates aldehyde groups, which can form stable cross‐links with amine groups on chitosan. In this work, it is shown that a systematic variation in the oxidation degree of alginate dialdehyde allows for effective tuning of the swelling capacity of chitosan/alginate dialdehyde multilayer films. Furthermore, it is demonstrated that the pH‐responsiveness of the multilayer films can be regulated by the choice of pH at which the layer‐by‐layer assembly is conducted. The combination of these two parameters allows for the designing polysaccharide multilayer films with a tunable degree of swelling and stimuli‐responsiveness.     

Reactive Coatings in Glass Capillaries: Preparation of Temperature‐ and Light‐Responsive Surfaces and Accurate Determination of Wettability Switching

The inner walls of thin glass capillaries are coated with a reactive precursor coating that can be converted into different temperature‐ and light‐responsive coatings. The switching range of wettability can be determined by measuring the meniscus height of water inside these capillaries at different temperatures and upon UV‐light irradiation. In comparison with the sessile drop measurement, very accurate equilibrium contact angles are obtained by this method.

     

Preparation of a Noncytotoxic Hemocompatible Ion Gel by Self‐Polymerization of HEMA in a Green Deep Eutectic Solvent

Self‐polymerization of optimized amount of 2‐hydroxyethylmethacrylate (HEMA) in a natural deep eutectic solvent (NADES) is obtained by the complexation between choline chloride and fructose (ChCl:Fruc. 2:1) in the presence of indomethacin, an anti‐inflammatory drug resulted formation of a drug‐immobilized ion gel. The ion gel thus obtained is found to be stable in gastrointestinal fluid pH (GIF) and sustained release in simulated lower intestinal fluid for 20 h (88% release) at pH 6.8 and 96% release at pH 7.4 for 15 h (colon & blood pH) at physiological human body temperature (37 °C) of the drug is recorded. The drug can be stored in the gel matrices at room temperature for long durations such as 6 months without any degradation. The ion gel of poly‐HEMA obtained in the NADES does not appear to inhibit the growth of mammalian cells in vitro and is found to be compatible to human blood thus implying toward their potential for therapeutic applications as pH‐sensitive hydrophobic drug carrier for oral application as well as in tissue engineering.

     

化学刺激诱发的人嗅觉相关电位

选取 2 0例主观嗅觉正常的健康青年人 ,将 0 3mL醋酸异戊酯饱和气在吸气早期释放入右侧鼻腔 ,反复刺激16次 ,刺激间隔约 6 0s,在头皮中央点 (Cz)处记录到稳定的相关电位。刺激前应用洁净空气做对照试验 ,无可辩波形引出。证明该相关电位系由醋酸异戊酯刺激嗅觉系统而产生。嗅觉相关电位波形主要由P1 、N1 、P2 、N2 、P3五个波组成 ,各波的潜伏期 (ms) :P1 :2 2 2± 2 5 ,N1 :2 6 5± 31,P2 :36 4± 4 0 ,N2 :4 90± 4 7,P3:5 77± 71;振幅 (μV) :P1 :0 5 1±4 5 1,N1 :- 5 2 3± 4 18,P2 :6 83± 3 78,N2 :- 7 35± 4 18,P3:- 2 82± 4 2 5。N1 P2 的峰 -峰振幅 (μV) :12 99± 5 6 2。     

Interaction of sensory and cognitive processes during visual recognition: The role of the associative areas of the cerebral cortex

The first part of the present study used a model of Alzheimers disease in two groups of animals (three monkeys in each), given injections of neurotoxins (monkeys of group I) and physiological saline (monkeys of group II). Before injections, all monkeys were trained to discriminate stimuli containing different types of information (spatial frequency grids and geometrical figures of different colors and with different spatial relationships between objects) and to perform spatial selection. The dynamics of impairments in the characteristics of working memory were identified using delayed differentiation tasks in monkeys of both groups before injections and every two months after injections. Quantitative measures of impairments were made using the entropy of visual recognition, which characterizes uncertainty in decision-taking. The development of Alzheimers disease in rhesus macaques was characterized by a deficit of working memory, resulting from lesions to the two component processes of memory. Impairments of the first of these in monkeys of group I were manifest as a significant increase in entropy, which is associated with correct decision-taking. The magnitude of the increase depended on the type of visual information. Impairments of the second component were characterized by increases in entropy associated with refusals to take decisions and were independent of the delay duration and the type of visual information. Monkeys given injections of physiological saline showed no significant changes in these characteristics. The features of working memory were also studied in the second part of the investigation, using four groups of Rhesus macaques: intact, those with bilateral extirpation of the sulcus principalis or field 7 or both: degradation again identified two components. Entropy associated with this was increased significantly for most of the stimuli tested on monkeys of all extirpation groups as compared with intact animals. Significant differences were found in these characteristics for a number of stimuli, which depended on the location of the structures removed. The characteristics of impairments of the components of working memory resulting in the development of Alzheimers disease showed that the cholinergic mechanisms responsible for sensory processing differ from those involved in decision-taking. The structural-functional organization of the interaction of sensory and cognitive processes controlled by the motivation and attention systems is discussed, as is the role of the associative areas of the cortex.Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 89, No. 10, pp. 1226–1239, October, 2003.     

The expression and role of c-Myc in mouse hair follicle morphogenesis and cycling

Although the function of c-Myc has been clarified in many tissues, until now its expression and role in hair follicle morphogenesis and the hair cycle remains unknown. In this study we detected c-Myc expression pattern in the process of mouse hair follicle development and normal cycle. We found that during hair follicle morphogenesis, the stage-specific expression of c-Myc was detected in mouse skin and was predominantly localized to the hair follicle epithelium. c-Myc expression was also consistently found in mouse skin throughout the hair follicle cycle. Through the in vivo injection of c-Myc inhibitory peptide and c-Myc expression plasmid, we also investigated the direct effects of c-Myc on the hair follicle structures during the hair follicle cycle. Our results showed that c-Myc inhibitory peptide significantly restrained the development of anagen hair follicles, while the injection of plasmid DNA encoding c-Myc in vivo clearly promoted anagen development. Our data indicate that c-Myc may play an important role in the proliferation and differentiation of the hair follicle keratinocytes during hair follicle development. c-Myc also was shown to participate in the regulation of the mouse hair growth cycle and could promote the proliferation of the hair matrix keratinocytes as well as the differentiation of the inner root sheath.     

No erasure effect of retrieval–extinction trial on fear memory in the hippocampus-independent and dependent paradigms

Recently, Monfils et al. [9] and Clem and Huganir [3] have shown that an isolated retrieval trial before the extinction sessions (retrieval–extinction) in mice and rats prevented the renewal and spontaneous recovery of the original fear memory by inhibiting reconsolidation in a hippocampus-independent manner. In contrast, Chan et al. [2], using the same paradigm, reported that retrieval extinction in rats augmented the renewal and reinstatement of extinguished fear. However, it remains unclear whether or not retrieval extinction in a hippocampus-independent paradigm erases the original fear memory by inhibiting reconsolidation. We therefore conducted three experiments to investigate whether or not retrieval extinction erases the original fear memory by inhibiting reconsolidation in mice. Our major findings were as follows. (1) Retrieval–extinction in mice did not suppress spontaneous recovery and fear renewal in a hippocampus-independent paradigm. (2) Fear renewal was observed when retrieval–strong extinction in a hippocampus-independent paradigm was performed. (3) Retrieval extinction in a hippocampus-dependent paradigm did not erase the original fear memory. These results suggested that fear extinction after retrieval in mice does not inhibit reconsolidation of previously consolidated fear memory in either a hippocampus-independent or -dependent paradigm.     

Finite-Element Modelling of the Response of the Gerbil Middle Ear to Sound

We present a finite-element model of the gerbil middle ear that, using a set of baseline parameters based primarily on a priori estimates from the literature, generates responses that are comparable with responses we measured in vivo using multi-point vibrometry and with those measured by other groups. We investigated the similarity of numerous features (umbo, pars-flaccida and pars-tensa displacement magnitudes, the resonance frequency and break-up frequency, etc.) in the experimental responses with corresponding ones in the model responses, as opposed to simply computing frequency-by-frequency differences between experimental and model responses. The umbo response of the model is within the range of variability seen in the experimental data in terms of the low-frequency (i.e., well below the middle-ear resonance) magnitude and phase, the main resonance frequency and magnitude, and the roll-off slope and irregularities in the response above the resonance frequency, but is somewhat high for frequencies above the resonance frequency. At low frequencies, the ossicular axis of rotation of the model appears to correspond to the anatomical axis but the behaviour is more complex at high frequencies (i.e., above the pars-tensa break-up). The behaviour of the pars tensa in the model is similar to what is observed experimentally in terms of magnitudes, phases, the break-up frequency of the spatial vibration pattern, and the bandwidths of the high-frequency response features. A sensitivity analysis showed that the parameters that have the strongest effects on the model results are the Young’s modulus, thickness and density of the pars tensa; the Young’s modulus of the stapedial annular ligament; and the Young’s modulus and density of the malleus. Displacements of the tympanic membrane and manubrium and the low-frequency displacement of the stapes did not show large changes when the material properties of the incus, stapes, incudomallear joint, incudostapedial joint, and posterior incudal ligament were changed by ±10 % from their values in the baseline parameter set.     

Attention and memory in aged rats: Impact of lifelong environmental enrichment

Aged rodents exhibit memory and attention dysfunctions. Environmental enrichment (EE) attenuates memory impairments. Whether it may reduce attention deficits is not known. At the age of 1 month, Long-Evans female rats were placed in standard or EE conditions and tested after 3 (young), 12 (middle-aged) or 24 (aged) months of differential housing. Spatial reference memory was assessed in a water-maze task. Attention performance was evaluated in the five-choice serial reaction time (5-CSRT) task. EE improved spatial memory at all ages, but did not ameliorate 5-CSRT performance in young and middle-aged rats; it prevented, however, the degradation of attention performances detected in aged rats. The number of ChAT (+30 to +64%)- and p75^NTR-positive (+35 to +44%) neurons was higher in the basal forebrain of aged enriched vs. standard rats, suggesting their EE-mediated protection. The weaker deficit of attention found in aged EE rats might be linked to a better survival in the very long term of neurons in the basalo-cortical system.     

Coassembly Modulated pH‐Responsive Hydrogel for Dye Absorption and Release

Hydrogel as a carrier for drug delivery system has been developed, but it is hard to change the load and release of drugs through a simple way. Herein, the authors report a novel pH‐sensitive supramolecular binary hydrogel based on Phe‐Gly derivative gelator (LPPG) and 4,4′‐dipyridine disulfide (DPDS). Fourier transform infrared spectroscopy, circular dichroism, and ¹H NMR confirm that the driving force for the coassembly process is intermolecular hydrogen bonds. The composite hydrogel can improve the dye adsorption capacity relative to LPPG hydrogel. Moreover, the controllable absorption of the dyes is studied by varying the pH and concentration of dye solutions. LPPG‐DPDS hydrogel can also release of entrapped dyes at physiological pH. The two‐component hydrogel should be a promising system for controllable drug delivery.