Differentiation of cloned populations of immature B cells after transformation with Abelson murine leukemia virus

The nature of the target cell for Abelson virus transformation and the effect of transformation on B cell differentiation were studied with six cloned lines of nontransformed immature B lymphocytes. Three clones were at the pre-B cell stage of maturation prior to A-MuLV infection; two were at the B cell stage, and one appeared to represent a stage prior to rearrangement of the mu heavy chain gene. All six cloned lines could be transformed by Abelson virus. Many of the transformants of the pre-B cell clones underwent kappa light chain gene rearrangement and expression following viral infection. Distinct light chain gene rearrangements were segregated by further subcloning these transformed lines. Abelson virus infection of one cloned cell line believed to represent a stage of maturation prior to the pre-B cell stage produced pre-B cell transformants with a variety of heavy chain gene rearrangements. Thus B lymphoid target cells for Abelson virus are not restricted to a single developmental stage, and some transformed subclones can undergo extensive immunoglobulin gene rearrangements shortly after viral infection.     

Progression of the transformed phenotype in clonal lines of Abelson virus-infected lymphocytes.

Some molecular changes which correlate with the tumorigenic progression of neoplastic cells can best be studied with in vitro cell lines that represent each stage in the progression. Lymphoid cells infected by Abelson murine leukemia virus exhibit a wide range of growth potential in vitro and in vivo. Uncloned populations that are poorly oncogenic early after infection become progressively more oncogenic with successive passages of the cells in culture. In such mass cultures, it is difficult to evaluate whether a rare subpopulation of highly oncogenic cells becomes dominant in the culture or whether the individual cells progress in oncogenic phenotype. To examine this latter possibility, Abelson virus-infected lymphoid cells were cloned by limiting-dilution culture 10 days postinfection. We isolated two clones that grew poorly in agar, required feeder layers of adherent bone marrow cells for growth in liquid culture, and were extremely slow to form tumors in syngeneic animals. Both clones, after passage in the presence of adherent feeder layers for 3 months, grew well in liquid and agar-containing cultures in the absence of feeder layers and formed tumors in animals at a rapid rate. The progression of these clonal cell lines to a more malignant growth phenotype occurred in the absence of detectable changes in the concentration, half-life, phosphorylation, in vitro kinase activity, or cell localization of the Abelson virus-encoded transforming protein. No change in the concentration or arrangement of integrated Abelson viral DNA sequences was detected in either clone. Thus, perhaps changes in the expression of cellular genes would appear to alter the growth properties of lymphoid cells after their initial transformation by Abelson virus. Such cellular changes could complement the activity of the Abelson virus transforming protein in producing the fully malignant growth phenotype.     

Microsomal-catalyzed hydroperoxide-dependent C-oxidation of amines

Organic hydroperoxides are capable of supporting the C-oxidation of several different amines in the presence of hepatic microsomes. Evidence is presented that indicates that microsomal cytochrome P-450 acts as the catalyst. Removal of the NADPH-cytochrome $\text{c}$ oxidoreductase or essential phospholipid from microsomes does not significantly affect the peroxidase activity. Of the amine substrates C-oxidized by organic hydroperoxides in the presence of microsomes, only aminopyrine and dimethylaniline are rapidly oxidized by hydroperoxides in the presence of catalase. The catalase-mediated reaction can also be distinguished from the microsomal-catalyzed reaction by the use of differential inhibitors.     

Enzyme des Stärkeumsatzes in Bündelscheiden- und Palisadenchloroplasten von Zea mays

Summary Isolated chloroplasts from the bundle sheath cells show considerable activity of the ADPG- and UDPG-pyrophosphorylase (EC 2.7.7.9), ADPG- and UDPG-transglucosylase (EC 2.4.1.21), and the starch phosphorylase (EC 2.4.1.1). In chloroplasts of the palisade cells, on the other hand, only the UDPG-pyrophosphorylase is remarkably active.     

Immunological studies in tropical splenomegaly syndrome in Uganda

An immunological evaluation carried out in eight patients with the tropical splenomegaly syndrome showed no evidence of impairment in cellular or humoral immunity, though raised levels of macroglobulins were noted in four patients. Hence gross immunological deficiency cannot be associated with the intense lymphoreticular proliferation observed in this disorder.     

Micro Radiometric Method for Study of Acid-insoluble Materials in Monolayer Cell Cultures

A simple radiometric procedure for study of acid-insoluble products synthesized in monolayer cell cultures is described. Cell cultures were produced directly on the bottom surface of scintillation vials or on glass cover slips (8 X 30 mm). The cells were labeled and extracted; the radioactivity was determined while the cells remained affixed to the glass surface upon which they were grown. This procedure enabled rapid investigations of certain biosynthetic processes to be carried out by using many individual cell cultures. The method was applied to an investigation of (3)H-thymidine incorporation induced by vaccinia virus in a 5-bromodeoxyuridine-resistant cell line. (14)C-labeling was evaluated as an alternate procedure for cell quantitation.     

Vaccinia Neutralization Test Using a Radioisotope Assay for Virus-induced Enzyme Activity

Vaccinia virus induction of a metabolic activity in host cell cultures forms the basis of a new assay for neutralizing antibodies. A direct relationship between the amount of vaccinia virus infecting cell cultures and the induced incorporation of tritium-labeled thymidine into the acid-insoluble fraction of the cells provided an indicator system. A liquid scintillation spectrometer was used to determine radioactivity associated with cell materials, and it provided a method for partial automation of an immunological procedure. Reproducibility of the method was satisfactory, and agreement with conventional vaccinia serum neutralization tests was demonstrated.     

Uraninschwellen des Protoplasmas der BraunalgeStypocaulon scoparium

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