Joseph V. Scaletti

Properties of DNA of bacteriophage N1, a DNA with reversible circularity☆

Abstract The DNA of N1 bacteriophage ( Naylor and Burgi, 1956 ), like that of its host, Micococcus lysodeikticus , has high guanine plus cytosine content ( Scaletti and Naylor, 1959 ). We report here the results of some further physicochemical studies of the properties of this bacteriophage DNA. The most important results are that the DNA, as prepared by lysis of the phage, is linear but cyclizes when suitably annealed, and that the circular molecules revert to a linear form on heating and quenching. Thus, the molecules contain cohesive ends just as does the DNA of bacteriophage λ. The buoyant density indicates a base composition of 64(±1)% GC. The molecular weigth, as estimated from the sedimentation velocity and by electron-microscope length measurements, is 33(±1.5) × 106. There appear to be no inherent single-strand breaks in the DNA. A method is described for positive staining with uranyl ion of DNA samples prepared for electron microscopy by the basic protein film technique ( Kleinschmidt and Zahn, 1959 ). This modification makes shadowing unnecessary.

Water and urea transport in human erythrocytes infected with the malaria parasite Plasmodium falciparum

The permeability properties of the human red cell membrane to various solutes are altered by malarial infection. In the present work we show that the permeability of the red cell membrane to water is also affected by the intraerythrocytic growth of the malaria parasite Plasmodium falciparum, whereas urea permeability appears unchanged. The data from infected cells show decreases in membrane surface area, cell volume, the osmotically active water fraction (Weff), and osmotic water permeability (Pf) as measured by stopped-flow spectroscopy. On the other hand, the data suggest an increase in diffusive water permeability (Pd) in infected cells with no change in urea permeability when measured by the continuous flow method. The decreased Pf/Pd ratio of infected cell membranes and its implications in the geometry of the red cell membrane water channel or pore are discussed.

Impact of previously frozen deglycerolized red blood cells on cytomegalovirus transmission to newborn infants

The incidence of cytomegalovirus (CMV) infection in low birth weight newborn infants was compared in infants transfused with liquid red blood cells (RBC) and previously frozen deglycerolized red blood cells (FRBC). Three of 21 transfused infants with seropositive mothers who had positive CMV titers developed positive cultures; two became clinically ill. Two of the 16 infants born to seronegative mothers developed positive cultures, one became clinically ill. There were no deaths. With FRBC, one culture was positive in the 23 babies born to seropositive mothers and one in the 26 born to seronegative mothers. This infant received a single transfusion of 28 mL FRBC from a donor with a positive titer, but his mothers serology converted while she was breast-feeding him. Neither of these two infants who received FRBC developed clinical disease. Substitution of FRBC for transfusion of the low birth weight newborns was associated with a significantly lower incidence of transfusion-associated CMV infection and clinical illness.

Radiosensitivity of defined populations of lymphocytes: VI. Functional, structural, and biochemical consequences of in vitro irradiation

Abstract Single cell suspensions of BALB/c thymocytes (T cells) and nu/nu spleen cells (B cells) were exposed to 0, 50, and 500 rads and examined for topological abnormalities and alterations in surface glycoproteins and capacity to traffic normally upon transfer to syngeneic recipients. The results show that irradiated lymphocytes from both sources undergo extensive topological alterations which become more pronounced with the passage of time and which appear to precede the loss of cell viability. Viable T and B cells irradiated in vitro also fail to recirculate normally and accumulate in abnormal proportions in the spleen at the expense of the lymph nodes and gut-associated lymphoid tissues. Similarly, after a 2-hr incubation in saline at room temperature, irradiation of both T and B cells resulted in alterations in extractable surface glycoproteins. The results are consistent with the hypothesis that alterations in the recirculation of irradiated lymphocytes are associated with alterations in the plasma membrane.

Isolation of viral RNA using cesium chloride-ethidium bromide equilibrium sedimentation

Abstract The effect of ethidium bromide (EB) on the buoyant density of reovirus RNA during equilibrium sedimentation has been investigated. The addition of the dye ethidium bromide was found to reduce the buoyant density of reovirus RNA in a Cs2SO4 gradient by a value of 0.13 to 0.15 g/cc, and provided a separation limit of 0.10 g/cc relative to the ϱ of marker DNA. Ethidium bromide was found also to reduce the ϱ of reovirus RNA to allow this RNA to band on a CsCl gradient. The separation factor between DNA and RNA on a CsCl-EB gradient was found to be 0.23 g/cc, indicating this type of gradient to be highly effective for separating the two types of polynucleotides.