Search

We measured force–distance curves of polystyrene (PS)/poly (vinyl methyl ether) (PVME) blend thin films using atomic force microscopy (AFM) in order to pursue the possible usage of AFM as a tool for detecting viscoelastic properties of polymeric materials from a nanoscopic point of view. In quasi-static measurements of force–distance curves for a sample whose PS content equals 100%, both adhesive force and capillary force were measured separately. A phenomenon possibly assigned to pulling off of polymer chains by an AFM tip could also be observed for a sample whose PS content equals 60%. By changing the velocity of the AFM tip acting on a blend sample whose PS content equals 40%, we confirmed that the law of time–temperature reducibility holds even on such a nanoscopic scale. This blend sample behaved as a viscous fluid at room temperature, while its behavior became glassy when faster movements of the AFM tip were applied. A discussion on the future development of a new field of research which should be called “nanorheology" was also presented.

The cross-linked polyacrylamide films containing covalently-bonded N'-4- (2-acryloyloxyethyl)phenyl-N5-4-chlorophenylbiguanide hydrochloride (CPF-2) exhibit antibacterial activity at their surfaces and successfully act as self- sterilizing materials. Scanning electron microscopy studies indicate that inoc ulated cells of E. coli and S. aureus onto CPF-2 films undergo morphological changes, such as shrinkage and deformation, while those inoculated on blank cross-linked films remain intact. These morphological changes were ascribed to the collapse of the bacterial cells due to the action of released N1-4-(2-hydroxy ethyl)phenyl-N5-4-chlorophenylbiguanide hydrochloride from CPF-2 by hy drolysis.

Sensitive and selective high-performance liquid chromatographic determination of catecholamines by pre-column solid-phase dansylation is described. After catecholamines are adsorbed on alumina, the amino groups not responsible for adsorption are dansylated by a solid-phase reaction. The excess reagent and fluorescent contaminants are washed out, and the dansylated catecholamines are eluted and separated by reversed-phase high-performance liquid chromatography. The four catecholamine derivatives can be separated within 10 min and no major interfering peak is observed on chromatograms. The response of each catecholamine is linear from 10 to 500 pmol per sample and the detection limit is 0.5 pmol. This method was applied to determination of catecholamines in human urine.

Polyesters and polyamides with pendant N-alkylpyridinio-4-ylmethyl groups and definite spacer length between the pyridinio groups were prepared. It was found that the polyesters generally exhibit higher antibacterial activity than the corresponding monomers. Furthermore, the longer the alkyl chain length attached to the nitrogen of the pyridine ring, the higher is the antimicrobial activity. Polyamides with various spacer length were fractionated by gel filtration chromatography to obtain samples with comparable average molecular weights. Antimicrobial assessment of the fractionated polyamide samples demonstrated the existence of an optimum spacer length for lethal action.

Thirty patients with post operative paranasal cysts and ophthalmological symptoms were treated at Tokyo Medical College Hospital from January, 1984 to December, 1987, 18 males and 12 females. They were classified into four groups according to the location of the cyst: 1) maxillary type, 14 cases, 2) maxillary-ethmoidal type, 6 cases, 3) ethmoidal type, 5 cases, 4) frontal-ethmoidal type, 5 cases. The average interval between the first sinus operation and the second operation for the cyst was 26.1 years. This was longer than the interval in patients with the usual form of postoperative cyst.Exophthalmos was the most prominent eye disorder. The literature is reviewed briefly.

Induced circular dichroism (ICD) in the mixed bilayer of azobenzene amphiphiles with dipalmitoyl-L-α-phosphatidylcholine was closely related to membrane fluidity controlled by trans–cis photoisomerization of the chromophore. Degree of the photochemical perturbation on membrane properties was the strongest when the azobenzene moiety was located in the middle of the long alkyl chain.

An acrylate monomer with a pendant biguanide, N'-4-(2-acryloyl- oxyethyl)phenyl-N5-4-chlorophenylbiguanide hydrochloride (2), when incor porated covalently into cross-linked polyacrylamide matrices was found to hydrolyzed in water to release N1-4-(2-hydroxyethyl)phenyl-N5-chlorophenylbi guanide hydrochloride (1). When the degree of cross-linking was high, the release was approximately zero-order at least over a period of one week. In con trast to 2, methacrylate and acrylamide monomers with pendant biguanide groups were strongly resistant to hydrolysis. Detailed release profiles from various cross-linked polyacrylamide films containing covalently or non- covalently bound biguanide compounds indicate that the rate of release can be tailored to specific delivery needs.

Cell migration is crucial for many biological and pathological processes such as chemotaxis of immune cells, fibroblast migration during wound healing, and tumor cell invasion and metastasis. Cells migrate forward by extending membrane protrusions. The formation of these protrusions is driven by assembly of actin filaments at the leading edge [1]. Neural Wiskott-Aldrich syndrome protein (N-WASP), a ubiquitous member of the WASP family, induces actin polymerization by activating Arp2/3 complex and is thought to regulate the formation of membrane protrusions [2, 3]. However, it is totally unclear how N-WASP activity is spatially and temporally regulated inside migrating cells. To detect and image sites of N-WASP activity during cell motility and invasion in carcinoma cells, we designed an N-WASP fluorescence resonance energy transfer (FRET) biosensor that distinguishes between the active and inactive conformations and mimics the function of endogenous N-WASP. Our data show that N-WASP is involved in lamellipodia extension, where it is activated at the leading edge, as well as in invadopodia formation of invasive carcinoma cells, where it is activated at the base. This is the first time that the activity of full-length N-WASP has been visualized in vivo, and this has lead to new insights for N-WASP function.

MIKAMYCIN, an antibiotic belonging to the group of PA114, streptogramin, staphylomycin and ostreogrycin, is composed of two main active principles—mikamycin A and mikamycin B—both of which have been demonstrated to be potent inhibitors of protein synthesis in a certain species of bacteria1–4. The inhibition of protein synthesis by streptogramin has been observed by Vazquez5 in the intact cells of Staphyloccus aureus. The site of action of mikamycins appears to be located in the process in which amino-acid bound to sRNA is transferred to protein on the ribosomes, as is the case with chloramphenicol6–9 or puromycin9–14.

The release rate of indomethacin from chitosan granules was compared with that of conventional commercial indomethacin capsules and a sustained-release capsule. In contrast with the rapid release of a commercial conventional capsule form, sustained release from the chitosan granules was observed. Furthermore, the release rate could be controlled by changing the mixing ratio of drug and chitosan.The potential of chitosan granules as an oral sustained-release dosage form of indomethacin was investigated in rabbits. When a conventional commercial capsule was administered orally to rabbits, the plasma concentration reached the maximum level 1 h after administration. In the case of the granules with a 1: 2 mixture of drug and chitosan, the chitosan granules did not give a sharp peak of plasma concentration, but produced a sustained plateau level of indomethacin. The area under the plasma concentration curve (AUC)(0-8 h) value of chitosan granules showed a slightly higher value than that of commercial capsules. This may be due to the slow rate of release from the chitosan granules and the longer residence time in the stomach.Thus, in terms of decrease in the peak of plasma concentration and maintenance of indomethacin concentration in plasma, the chitosan granules were superior to the conventional commercial capsules. Indomethacin granule preparations using chitosan may be practically useful as oral preparations with reduced side effects and with prolonged action.

The potential of chitosan granules as an oral sustained-release dosage form of indomethacin has been compared with conventional capsules in beagle dogs. When a commercial capsule was administered orally, the plasma concentrations reached the maximum level in 30 min. The granules did not give a sharp peak to the plasma concentration, but produced a sustained plateau of the drug. This may be due to the slow rate of release and a longer residence time in the stomach. Thus, in terms of reducing the peak in plasma concentration and maintenance of drug concentration in plasma, the chitosan granules were superior to conventional capsules.

As a clinical test, direct observation of the middle ear should be ideally performed without any surgical intervention such as myringotomy. This paper reports a newly invented superfine fiberscope which makes it possible to insert through the eustachian tube, and direct views of the middle ear structures on normal subjects and patients. The patients were of a small cholesteatoma and traumatic dislocation of the ossicular chain. All of them were tested with local anesthesia in outpatient clinic. This superfine fiberscope was of great value in observing of middle ear structures as a diagnostic instruments, as that no surgical intervention was necessary in the procedure.

Neural Wiskott-Aldrich syndrome protein (N-WASP)1 functions in several intracellular events including filopodium formation2, vesicle transport3 and movement of Shigella frexneri4,5 and vaccinia virus6, by stimulating rapid actin polymerization through the Arp2/3 complex. N-WASP is regulated by the direct binding of Cdc42 (refs 7, 8 ), which exposes the domain in N-WASP that activates the Arp2/3 complex2,9. A WASP-related protein, WAVE/Scar, functions in Rac-induced membrane ruffling10,11; however, Rac does not bind directly to WAVE10, raising the question of how WAVE is regulated by Rac. Here we demonstrate that IRSp53, a substrate for insulin receptor12 with unknown function, is the ‘missing link’ between Rac and WAVE. Activated Rac binds to the amino terminus of IRSp53, and carboxy-terminal Src-homology-3 domain of IRSp53 binds to WAVE to form a trimolecular complex. From studies of ectopic expression, we found that IRSp53 is essential for Rac to induce membrane ruffling, probably because it recruits WAVE, which stimulates actin polymerization mediated by the Arp2/3 complex.