White-opaque flowable composite liner as a depth marker in composite restorations prevents tooth substance loss in filling removal: a randomized double-blinded in vitro study

Clinical Oral Investigations - Removal of esthetic restorations leads to loss of tooth structure and the extent of the loss is difficult to estimate due to exact-shade matching. This randomized...     

Tissue resistivities determine the current flow in the cochlea

PURPOSE OF REVIEW: In individuals with severe to profound hearing loss, cochlear implants bypass normal inner ear function by applying electrical current directly into the cochlea, thereby stimulating cochlear nerve fibers. Stimulating discrete populations of spiral ganglion cells in cochlear implant users' ears is similar to the encoding of small acoustic frequency bands in a normal-hearing person's ear. Thus, spiral ganglion cells stimulated by an electrode convey the information contained by a small acoustic frequency band. Problems that refer to the current spread and subsequent nonselective stimulation of spiral ganglion cells in the cochlea are reviewed. RECENT FINDINGS: Cochlear anatomy and tissue properties determine the current path in the cochlea. Current spreads largely via scala tympani and across turns. While most of the current leaves the cochlea via the modiolus, the facial canal and the round window constitute additional natural escape paths for the current from the cochlea. Moreover, degenerative processes change tissue resistivities and thus may affect current spread in the cochlea. SUMMARY: Electrode design and coding strategies may result in more spatial stimulation of spiral ganglion cells, resulting in a better performance of the electrode-tissue interface.     

Cytosol mediated metabolism of the experimental antitumor agent acridine carboxamide to the 9-acridone derivative.

The acridine antitumor agent N-[2'-(dimethylamino)ethyl]acridine-4-carboxamide (AC; NSC 601316; acridine carboxamide) is oxidized efficiently in vitro by rat and mouse hepatic cytosolic fractions. Under these conditions the oxidase activity has an apparent Km of 11 microM towards AC. A single product is formed which has been identified as the corresponding 9(10H)-acridone carboxamide by 1H-NMR and mass spectrometry. Inhibition with menadione and amsacrine, but not allopurinol, indicates that this reaction is most likely to be catalysed by aldehyde oxidase (EC 1.2.3.1). Several AC analogues with modifications to the side chain (the N-oxide, N-monomethyl-, and amino-derivatives) are also metabolized to the equivalent acridone product but the 7-hydroxylated and 4-carboxylic acid acridine derivatives are not.     

Die Beteiligung endogener Katecholamine an den pharmakologischen Wirkungen von Theophyllin und Coffein

Ohne Zusammenfassung     

Developmental Changes of Mechanics Measured in the Gerbil Cochlea

This report describes stiffness and best frequency measurements obtained in vitro from the basilar membrane of the gerbil cochlea at the onset of hearing, during hearing maturation, and after hearing has matured. Our stiffness data constitute the first direct experimental evidence of developmental stiffness changes in the basal and middle turns. Stiffness changes by a factor of 5.5 in the basal turn between postnatal day 11 and adult, and the difference from adult is statistically significant for all ages measured up to postnatal day 16. For the middle turn, stiffness changes by a factor of 1.6 between postnatal day 11 and adult. Whereas for postnatal day 12 and beyond there is no statistically significant difference from adult, our data suggest that there may be a significant difference of stiffness between day 11 and adult in the middle turn. For the basal turn, our motion measurements confirm a passive component to the developmental best frequency shift. For the middle turn, changes in best frequency are not statistically significant. Best frequency was determined by stimulating the tissue at audio frequencies with a glass paddle and measuring motion with a computer-based imaging system. Tissue stiffness was measured with a piezoelectric-based sensor system. Tissue stiffness changes have previously been postulated to contribute to the best frequency shift observed in the cochlear base. Incorporating our data into a simple spring-mass resonance model demonstrates that our experimentally measured stiffness change can account for the change of best frequency. These results suggest that a stiffness change is, in fact, a critical component of the best frequency shift observed in the basal turn of the gerbil cochlea after the onset of hearing.     

The antihepatotoxic activity of dithiocarb as compared with six other thio compounds in mice

In mice, diethyldithiocarbamate (dithiocarb, 100 mg/kg i.p.) completely prevented the increments of serum enzyme activities (GOT, GPT, SDH) induced by oral administration of carbon tetrachloride (0.1 ml/kg), allyl alcohol (0.05 ml/kg), bromobenzene (0.25 ml/kg), and thioacetamide (50 mg/kg). In this respect, cysteine (200 mg/kg i.p.) was active against CCl₄ and bromobenzene, cysteamine (100 mg/kg i.p.) against CCl₄ and allyl alcohol, penicillamine (100 mg/kg i.p.) against allyl alcohol, thiazolidine carbonic acid (100 mg/kg i.p.) against bromobenzene, and thioctic acid (100 mg/kg i.p.) against allyl alcohol and thioacetamide. Dimercaprol (100 mg/kg i.p.) had a weak antidotal effect only against allyl alcohol poisoning. None of the tested antidotes inhibited serum enzyme elevations evoked by dimethyl nitrosamine (100 mg/kg p.o.). These findings prove the antihepatotoxic activity of diethyldithiocarbamate to be superior to that of all other thio compounds under observation.The lowest dose of dithiocarb active against carbon tetrachloride was 25 mg/kg i.p. The dose-response curves for serum-enzyme elevations induced by carbon tetrachloride (0.1–4 ml/kg p.o.) were shifted to the right under the influence of dithiocarb indicating a competitive antagonism. Dithiocarb (100 mg/kg i.p.) depressed the p-hydroxylation of aniline in the 9000 x g liver homogenate supernatant of mice by about 55%. Thus, the antihepatotoxic activity of dithiocarb seems to be the consequence of a decreased oxidase activity.     

Transitional and marginal zone B cells have a high proportion of unmasked CD22: implications for BCR signaling

CD22, a B cell-specific member of the Siglec family, is an important inhibitor of B cell signaling. The first Ig-like domain of CD22 specifically binds to alpha2,6-linked sialic acids. Through these interactions CD22 can mediate adhesion to other cells in trans, but can also bind endogenous ligands on the B cell surface in cis. Cis binding of CD22 to sialylated ligands enhances the efficiency of inhibition and thereby reduces the BCR signaling strength. In this study we used a newly developed oligomeric streptavidin-based sialylated probe as an artificial CD22 ligand. We found that CD22 is bound to ligands in cis on most B cells. However, there is a proportion of B cells with unbound (unmasked) CD22. The subpopulation with unmasked CD22 is 2-fold increased in transitional and marginal zone B cells in the spleen and on B1 cells in the peritoneum, when compared to mature B cells. Also, B cells with unmasked CD22 have an activated phenotype. Unmasking of CD22 could be functionally involved in lowering the signaling threshold on developmental checkpoints such as transitional B cells and during B cell activation or could be a consequence of such activation processes.     

Stiffness of the gerbil basilar membrane: radial and longitudinal variations

Experimental data on the mechanical properties of the tissues of the mammalian cochlea are essential for understanding the frequency- and location-dependent motion patterns that result in response to incoming sound waves. Within the cochlea, sound-induced vibrations are transduced into neural activity by the organ of Corti, the gross motion of which is dependent on the motion of the underlying basilar membrane. In this study we present data on stiffness of the gerbil basilar membrane measured at multiple positions within a cochlear cross section and at multiple locations along the length of the cochlea. A basic analysis of these data using relatively simple models of cochlear mechanics reveals our most important result: the experimentally measured longitudinal stiffness gradient at the middle of the pectinate zone of the basilar membrane (4.43 dB/mm) can account for changes of best frequency along the length of the cochlea. Furthermore, our results indicate qualitative changes of stiffness-deflection curves as a function of radial position; in particular, there are differences in the rate of stiffness growth with increasing tissue deflection. Longitudinal coupling within the basilar membrane/organ of Corti complex is determined to have a space constant of 21 microm in the middle turn of the cochlea. The bulk of our data was obtained in the hemicochlea preparation, and we include a comparison of this set of data to data obtained in vivo.