The midguts and associated muscle fibers of A. quadrimaculatus were dissected out in saline solution and immediately fixed in a solution of 1 % osmium tetroxide in 0.1 M potassium phosphate buffer, pH 7.2, for 5 min at room temperature. The specimens were subsequently dehydrated in ethyl alcohol for 2 hr and embedded in Epon 812 (Luft, 1961). Sections were cut on an LKB ultra microtome with gla...

Single DNA molecules can be rendered visible in the electron microscope by "staining" with water-soluble salts of heavy metals. The best results were obtained with lanthanum nitrate, uranyl acetate, and lead perchlorate. The molecules appear as filaments approximately 20 A wide. Their length was not determined, but it could be shown that it varied with the molecular weight of the DNA used. The ...

Cover photograph: Transmission electron micrographs of wild-type (top) and phoU mutant (bottom) cells of the Gram-negative alphaproteobacterium Sinorhizobium meliloti. The cells were cultured in morpholinepropanesulfonic acid-buffered minimal medium with 7.5 mM glucose and 2 mM KH2PO4. Unlike the uniform rod-shaped wild-type cells, the phoU mutant cells are enlarged and pleomorphic, accumulate ...

Fragments of 40 ovaries of various laboratory mammals, including mice, golden hamsters, rabbits and ferrets have been studied. The structures described in this paper were observed in some of the oocytes in the 14-day-old golden hamster ovary. The specimens in which they were present were obtained from 4 animals. After fixation for 60 min in chilled, buffered osmium tetroxide, the blocks were de...

Determination of terazosin hydrochloride dihydrate (TRZ) in drug substance and tablets was studied by fluorimetric techniques. The fluorimetric methods are based on: (1) measurement of the native fluorescence of the drug in water at 750 nm after excitation at 330 nm. (2) sensitizing the native fluorescence by formation a binary complex of drug with aqueous uranyl acetate (0.1% w/v) at the same ...

Frayed cilia from Tetrahymena pyriformis have been examined in the electron microscope using both uranyl acetate and phosphotungstic acid as negative stains. Observations on the central microtubules show that one member of the pair exhibits two rows of short projections. These are about 18 nm long, and are spaced longitudinally at 16-nm intervals. In many specimens the projections are separated...

For initial 3D analysis, negative-stain images of partially purified phage contrasted with 1% ammonium molybdate were taken on a Zeiss 901 operating at 80 kV and magnification of 30,000x. Micrographs were digitized at a rate of 14 μm, corresponding to 4.7 Å at the sample. Selected images were analyzed by self-common lines to generate a coarse model from a single particle that was used to begin ...

This study investigated the partitioning of uranyl within a quaternary system made up of uranyl, citrate, goethite, and the bacterium Pseudomonas fluorescens. In the absence of cells, uranyl was sorbed to goethite as a complex involving surface groups and/or citrate. Measurements of the evolution of CO2 indicated that the addition of bacterial cells lead to the gradual biodegradation of citrate...