Biochemical Identification of the Two Races of Radopholus similis by Starch Gel Electrophoresis

Analysis of genetic variation between the banana and the citrus races of Radopholus similis by starch gel eleclrophoresis demonstrated that 7 of 16 enzyme-encoding loci could be used for their diagnostic separation. The two races are closely related arid share approximately 75% of the enzymes evaluated. The level of dissimilarities o1 inherited bands indicates that no gene flow occurs between the races. Aldolase, α + β esterase, glucose-6-phosphate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase, malate dehydrogenase, and phosphoglucose isomerase are diagnostic markers of the races.     

Cellular responsiveness to growth factors correlates with a cell's ability to express the transformed phenotype

Five random subclones of the rat fibroblast line F2408 vary in their frequency of transformation by the unrelated Kirsten murine sarcoma virus and Abelson murine leukemia virus. The same pattern of sensitivity is displayed when the cells are induced to anchorage-independent growth (transformed) by epidermal, platelet-derived, and sarcoma growth factors, or by whole serum. Our results demonstrate that a growth factor's ability to render cells anchorage independent is not unique to transforming growth factors, but common to many growth factors; anchorage-independent growth is a function of the total growth factor concentration in the medium; cells vary in their inherent responsiveness to growth-factor-induced anchorage-independent growth; and cells resistant to growth-factor-induced anchorage-independent growth are also resistant to transformation by a variety of tumor viruses. We conclude that the way a cell responds to growth factors plays a central role in the expression of the transformed phenotype.     

Lambda Ig constant region genes are translocated to chromosome 8 in Burkitt''s lymphoma with t(8;22)

By in situ hybridization of normal human chromosomes with a cloned genomic probe specific for the constant region of the lambda immunoglobulin genes, band 22q11 was preferentially labelled. In two cell lines with t(8;22) derived from Burkitt's lymphoma a strong signal was noted on the 8q+ chromosome derivative, indicating that the constant region of the lambda Ig gene cluster was translocated from chromosome 22 to chromosome 8. In addition, the signal observed on the 22q- derivative chromosome was stronger than the background in one of the two cell lines tested, but not in the other. The implications are that the break point in chromosome 22 in some cases lies within the Ig gene itself or between clusters of such genes, and that different cases have different break points.     

Cellular aspects of tolerance. I. Parameters of tolerance induction in T cells of spleen and thymus

Unresponsiveness of T cells in thymus and spleen of tolerant animals was determined by reconstitution of lethally irradiated recipients. The degree of responsiveness of these animals was assessed by antigen elimination and two types of plaque assays (liquid and agar) with different sensitivity. Unresponsiveness occurred more rapidly in T spleen cells than in thymus cells. Unresponsiveness of T cells could be induced in the spleens of thymectomized animals and in T cell repopulated thymectomized lethally irradiated recipients. Induction of unresponsiveness did not depend on proliferating bone marrow cells or on accessory cells.     

Serum-dependent depression of alkaline phosphatase in HeLa cells

Reduction in alkaline phosphatase activity was observed when HeLa S3 cells were grown in Puck's medium containing high concentrations of human serum. This effect was not seen with the enzyme of Chang liver 8A cells. The induction of increased alkaline phosphatase in HeLa S3 by prednisolone or by osmolality changes was not prevented by serum. The concentration of serum in the culture medium had no influence on acid phosphatase activity.     

Formation of prototrophs in mixtures of two auxotrophic mutants of Serratia marcescens HY by a transducing bacteriophage produced by some auxotrophs

Summary Prototrophs arising in mixtures of two auxotrophs of Serratia marcescens strain HY are caused by a filtrable agent produced by one of the partners. 3. donors of this filtrable agent, HY/thyl, HY/ade11, and HY/thr2, were found among 16 auxotrophs, strain HY/thyl producing the agent of the highest activity. The prototrophic wildtype HY is not a donor. The agent does not enhance the growth of the auxotrophic recipient bacteria on minimal medium, therefore the increase in prototophs is not due to more spontaneous mutations. Dilution experiments showed that the reaction of one agent particle with a recipient-cell can cause a prototroph and that the number of recipient cells is not the limiting factor of prototroph formation.When the donor of a filtrable agent contained (besides the agent-inducing thyl-auxotrophy) a second auxotrophy of the same type as the recipient the relative frequency of prototrophs formed was much lower than that one produced by the HY/thyl filtrate. This indicates an influence of pseudoallelism of the markers on prototroph formation as would be expected by transfer of genetic material.The filtrable agent is non-dialyzable, precipitates by ammonium sulfate and is resistant to unspecific phosphodiesterase. When the filtrate was centrifuged in a CsCl density-gradient (24 hours at 35000 rpm) a band occurred at a density of 1.497 g/cm³ which contained the activities for prototroph and plaque formation. It contained also much material with an UV-absorption spectrum typical of phages. Electron micrographs revealed this material to consist of phage particles with hexagonal heads of 50 m diameter and a very short tail. These particles were named y phage.One strain, AX, of Serratia marcescens (among 47 tested) gave small, turbid plaques with filtrates from the known donors but not from other auxotrophs or HY. The plaque titer of y phage on AX was about the same as the transduction to prototrophy of HY/leu27. Phage y is a general-transducing bacteriophage of Serratia marcescens HY since 13 auxotrophic markers of strain HY and 10 of strain AX could be transduced. The low e.o.p. of y phage produced by HY/thyl, may therefore not be due to restriction by the AX cells but may indicate that this y phage is defective.