Electron microscopic visualization of DNA single strand breaks

DNA single strand breaks (ssb) have been induced in FLC/C cells in culture. They have been visualized in the electron microscope after decoration with biotin-avidin-ferritin complexes and spreading as monomolecular mixed films. This allowed one to determine the average number of decorated ssbs per unit of DNA length applying straight-forward and simple evaluation methods. This method has been used to investigate the DNA alterations by benzo[a]pyrene (B[a]P) on FLC/C culture cells. Thus a B[a]P-DNA damage curve can be constructed as a regression with a correlation coefficient of r = 0.97, while its isomer benzo[e]pyrene (B[e]P) known to have only low mutagenicity under the same experimental conditions is virtually without effect. The method has further informational potential regarding damage distribution and repair of DNA.     

Protein-to-wet weight relationships in supragingival plaques from caries-prone tooth surfaces.

The ratio of protein to wet weight in unpooled samples of supragingival plaques from sound and carious tooth surfaces was studied. Protein was assayed by a procedure developed for the study, in order to achieve a sensitivity of 1 microgram with minimum effects upon quantitation from protein composition and nonprotein components. Ratios of protein to wet weight in plaque specimens from caries-free surfaces were almost equally distributed into two main categories of 9.4% and 6.5%. Corresponding values for specimens from carious surfaces were 9.1% and 5.0%. The occurrence of high and of low values among samples from each type of surface indicated that the plaques differed quantitatively in protein, water, or a nonprotein component, possibly extracellular polysaccharide. Although compositional differences between plaques from the two types of surfaces were indicated by the lower ratios of 6.5% from noncarious and 5.0% from carious surfaces, they were not indicated by the higher ratio values, which were similar. These results suggest either that protein-to-wet weight ratios are not related to caries, or that the ratio values are related to caries for some but not all types of plaques.     

Über den Geruchssinn einiger Vögel

Zusammenfassung Bei Haustauben, Eichelhäher und Star spricht sich ein Dressurerfolg nicht in den positiven Wahlakten aus. Tauben zeigen indes durch ihr Zögern vor einer falschen Wahl, daß sie die gebotenen Duftstoffe (Nelkenöl, Anisöl, Rosenöl, Cumarin) riechen.Stockenten, Blaumeise, Amsel, Grünfink, Rotkehlchen und Grasmücken lassen sich dressieren auf Rosenöl (Enten, Amsel, Grünfink, Rotkehlchen, Grasmücken), Nelkenöl (Amsel, Grünfink), Skatol (Blaumeise), Benzaldehyd (Rotkehlchen, Grasmücken), Amylacetat (Grasmücken).Das minimum perceptibile der Blaumeise für Skatol ist ähnlich- wie beim Menschen.Rotkehlchen und Grasmücken vermögen nicht zu unterscheiden zwischen den Riechstoffpaaren Benzaldehyd gegen Nitrobenzol und Amylacetat gegen Methylheptenon, die auch für den Menschen ähnlich riechen.Rotkehlchen und Grasmücken sind nicht zu dressieren auf Regenwurmsaft.     

Efficient synthesis of N alpha-acetylarginine methylamide

A simple preparation of Ac-Arg-(p-TosH or HCl)-NHMe is described. The NG-protonated Z-Arg was coupled with methylamine by the mixed anhydride method. Z-Arg-NHMe was purified as a NG-p-toluene sulfonate salt by crystallization from water. After removal of the Z group by catalytic hydrogenation and acetylation Ac-Arg(p-TosH)-NHMe was obtained. Ac-Arg(HCl)-NHMe was prepared by chromatography of the NG-TosH derivative on Dowex 44 (in Cl- form).     

Aggregation of sponge cells. Isolation and characterization of an inhibitor of aggregation receptor from the cell surface.

From the cell membranes of the sponge Geodia cydonium a component was isolated and purified which inhibits the aggregation factor isolated from the same source; the component was termed anti-aggregation receptor. This molecule was characterized as a glycoprotein (54% neutral carbohydrate) and its molecular weight is in the range of 180,000 One biological site of the anti-aggregation receptor was determined to be D-galactose. Indirect evidence presented seems to indicate that this molecule is present in an active form in aggregation-deficient cells and absent in aggregation-susceptible cells.     

Genetic and phenotypic analysis of Tcm, a mutation affecting early eye development

Tcm (total cataract with microphthalmia) is an autosomal dominant mouse eye mutation. Heterozygous Tcm/+ mice are born with several eye malformations including microphthalmia, retinal and iris dysplasia, total lens cataract, and ventral coloboma. The Tcm mutation was previously mapped to a 26-Mb region on Chr 4 between D4Mit235 and D4Mit106. In this study, we characterize the Tcm/Tcm homozygous mutant and find they are viable but severely microphthalmic. The developing eye in the Tcm/Tcm homozygote shows defects during early eye development, before formation of the optic cup. Further genetic mapping reduced the Tcm critical region to a 1.3-Mb region bordered by SNPs rs3666764 and rs3713818. This critical region contains two known genes (Asph and Gfd6) and three predicted genes, all of which are positional candidates for Tcm. Sequence analysis of Tcm genomic DNA revealed no mutations in the coding regions and splice site junctions of the five candidate genes. These results indicate that the causitive Tcm mutation falls within a noncoding regulatory region of one of the five candidate genes or in an undescribed gene.     

Partial purification and properties of a chromatin bound endonuclease from the marine sponge Geodia cydonium

A chromatin bound endonuclease (Mr:107,000) has been extracted and partially purified from the siliceous sponge Geodia cydonium. Disc gel electrophoresis showed that only one enzyme was present in the partially purified preparation which was able to degrade DNA and poly(A). The enzyme liberates oligonucleotides on incubation with poly(A), which are further degraded to yield the 5'-mononucleotide, which has a pI of 6.5 and a pH optimum of 7.5-8.0. Cations are not required for enzymic activity and EDTA does not inhibit the enzyme. Only iodosobenzoic acid was found to completely inhibit the enzyme. The enzyme hydrolysed poly(A), poly(U), poly(C), DNA, poly[d(A-T)], poly[d(G-C)], but not poly (dA) or poly(G).