The effect of different preparative procedures for electron microscopy on the size and shape of murine oncornaviruses has been studied. With conventional negative staining procedures using neutral sodium phosphotungstate, both murine mammary tumor virus and murine leukemia virus appeared in head-and-tail forms, with a peak head diameter of 122 and 130 nm, respectively. Negative staining with ur...

Adult Sprague-Dawley rats were perfused through the left ventricle first with balanced salt (10) to remove the blood. They were then fixed by perfusion with a mixture of 6.5 per cent glutaraldehyde and 2 per cent acrolein in a phosphate buffer (pH 7.5) (11). After 15 minutes, the duodenum was removed, fixed for an additional hour in the same aldehyde mixture, and rinsed in Veronal-acetate buffe...

Once embryonic cells have begun a course of somatic differentiation, they are characterized by a remarkable degree of adhesiveness which can be disrupted by trypsin in calcium-poor solutions (1-3) and which seems attributable in part to desmosomelike specializations, the zonula ad-haerens and macula adhaerens (4-5). Another cell contact specialization, one which has received little attention fr...

Density functional theory is employed to investigate uranyl dihydroxide, UO2(OH)2, isomerization reaction energy barriers, including those occurring via proton shuttles. The ground-state structure of a uranyl dihydroxide complex containing a uranyl moiety with a near 90 degrees O=U=O bond angle is reported for the first time. Furthermore, we predict the vibrational spectra of these compounds. S...

We have evaluated the quality of ultrastructural preservation of erythrocyte ghosts achieved under various electron microscopic preparative conditions. Initially, negative staining was used to monitor gross morphology of the ghosts. Of several negative stains used (phosphotungstate, silicotungstate, ammonium molybdate, and uranyl acetate), all but uranyl acetate resulted in fragmentation of mem...

Five canine cutaneous histiocytomas were studied by electron microscopy and esterase cytochemistry. The tumor cells contained irregular nuclei, characteristic lysosomal granules, and perinuclear microfilaments. The cells showed activity with anaphthyl acetate esterase stains. These characteristics are evidence that this tumor originates from the mononuclear phagocyte system. Canine cutaneous hi...