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Allied Health Personnel↗
Biomedical subjects
D E Muller
Publications and source records attributed to D E Muller.
Butyrate-induced cell differentiation of cell-cycle mutants and 'wild-type' mastocytoma cells: histamine, 5-hydroxytryptamine and metachromatic granules as independently regulated differentiation markers.
In cultures of heat-sensitive (hs; arrested at 39.5 degrees C, multiplying at 33 degrees C) and cold-sensitive (cs; arrested at 33 degrees C, multiplying at 39.5 degrees C) cell-cycle mutants that had been isolated from the same subclone (K21) of the murine P-815-X2 mastocytoma line, the degree of cell differentiation was assessed by determining the cellular histamine and 5-hydroxytryptamine (5-HT) content as well as the number of metachromatic granules per cell. The findings were compared with those obtained for 'wild-type' K21 and P-815-X2 cells. The addition of butyrate to 'wild-type' cells or to mutant cells maintained at the respective permissive temperature resulted in a relative increase in the level of all three differentiation markers. In cs mutant cells, essentially the same pronounced increase in granule numbers was observed during butyrate treatment at 39.5 degrees C and during incubation at 33 degrees C without butyrate, thereby suggesting that butyrate induces morphological cell differentiation in cs mutants via the same mechanisms as exposure to the nonpermissive temperature. In contrast, the histamine and 5-HT levels reached in hs and cs mutant cells in the presence of butyrate were higher than those observed during incubation at the nonpermissive temperature. Large quantitative differences were detected with respect to the potential of individual cell lines to express the three differentiation parameters. High levels of histamine were characteristic of 'wild-type' P-815-X2 cells treated at 33 degrees C with butyrate, while low amine levels and small numbers of granules were observed in K21 cells (i.e., the parent line of hs and cs mutants.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Formation of mast cell granules in cell cycle mutants of an undifferentiated mastocytoma line: evidence for two different states of reversible proliferative quiescence.
A heat-sensitive (hs, arrested at 39.5 degrees C, multiplying at 33 degrees C) and a cold-sensitive (cs, arrested at 33 degrees C, multiplying at 39.5 degrees C) cell cycle variant were isolated from an undifferentiated P-815 murine mastocytoma line. At the respective nonpermissive temperature, both the hs and the cs variant cells were reversibly arrested with a DNA content, typical of G1 phase. The cells of two cs variant subclones, when exposed to the nonpermissive temperature of 33 degrees C, formed metachromatically staining granules with an ultrastructure resembling that of mature mast cells. In addition, the cellular 5-hydroxytryptamine content underwent a marked increase, and the cells responded to compound 48/80 by degranulation as described for normal mast cells. On the other hand, in cells of two hs variant subclones, essentially no mast cell granules were detectable at either 33 or 39.5 degrees C. As previously reported, the cs cell cycle variant phenotype is expressed dominantly in heterokaryons obtained by fusing cs with wild-type cells, whereas hs cell cycle variant cells, similar to other hs mutants, were found to behave recessively under these conditions. Thus the state of proliferative quiescence induced in the cs cells at 33 degrees C is qualitatively different from the state of cell cycle arrest observed in hs cells at 39.5 degrees C and may represent a model for proliferative quiescence of differentiated cells in the intact organism.
Animals↗
Maturation of parvovirus LuIII in a subcellular system. I. Optimal conditions for in vitro synthesis and encapsidation of viral DNA.
The development of an in vitro system prepared by lysis of LuIII virus-infected cells with Brij-58 has enabled the study of the assembly pathway of a parvovirus. Under optimal conditions, radioactive precursors are incorporated both into viral replicative form double-stranded DNA and into progeny viral DNA (vDNA) during pulses as short as 30 s. Labelled 110S particles can be isolated at the end of such pulses. Therefore, synthesis and encapsidation of progeny viral DNA into pre-existing empty viral capsids appear to be closely related processes. Up to about 10 min after incorporation of vDNA, the 110S particles band at 1.44 g/ml and are relatively unstable in 3.5 M-CsCl. Moreover, newly synthesized vDNA molecules show an abnormal electrophoretic behaviour probably due to the presence of a covalently linked terminal protein. This so far uncharacterized alkali-stable polypeptide is lost (cleaved off?) concomitant with the maturation of the 110S virus particles. Maturation is reflected by a change in the virus stability in CsCl and a shift in density from 1.44 to 1.41 g/ml around 10 to 15 min after encapsidation of progeny vDNA.
Capsid↗
Maturation of parvovirus LuIII in a subcellular system. II. Isolation and characterization of nucleoprotein intermediates.
Nucleoprotein (NP) intermediates in the assembly pathway of parvovirus LuIII were isolated. These structures consist of replicating viral DNA and of preformed viral capsids into which progeny viral DNA is encapsidated concomitant with synthesis. The NP complexes sediment at between 70S and 100S. They are unstable in CsCl and dissociate in the presence of 1 M-NaCl. After fixation with glutaraldehyde, however, they accumulate at a density of 1.37 g/ml in CsCl gradients. Electron microscopy of fixed complexes revealed structures consisting of DNA threads associated with capsid-like particles. A considerable proportion of the DNA labelled during short pulses in such complexes, in a subcellular in vitro system derived from infected nuclei, can be effectively chased into 110S virions. The resulting 110S particles apparently have to undergo a sequence of morphogenic events to acquire the physicochemical properties of the mature infectious parvovirus.
Cells, Cultured↗