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M R Adelman

Publications and source records attributed to M R Adelman.

16 recordsLinked to original sources
PubMed1992

Effects of tubulozole on the amoeboflagellate transformation in Physarum polycephalum.

The Amoeboflagellate Transformation (AFT) of Physarum polycephalum involves rapid changes in the cytoskeleton, cell shape and cell motility. Use of pharmacologic agents to probe the role of cytoskeletal elements in the AFT are impeded because the transforming cells are very sensitive to such commonly-used drug solvents as DMSO. The anti-microtubule agent tubulozole is found to disrupt, rapidly and transiently, the AFT, inhibiting flagella formation, cell elongation and the arrangement of microtubules and microfilaments. Cells recover quickly, possibly due to precipitation of the drug; the reappearance of normal arrays of microfilaments and cytoplasmic microtubules lags behind flagella formation.

Animals↗
PubMed1988

Assembly, disassembly, and movements of the microfilament-rich ridge during the amoeboflagellate transformation in Physarum polycephalum.

The amoeboflagellate transformation in Physarum polycephalum involves a series of dramatic changes in cell shape and motile behavior. This report describes the morphological and behavioral changes through which a synchronously transforming population of cells passes, stressing that, although there are a series of distinguishable stages, cells at all stages display striking plasticity. Our previous studies showed that amoeboflagellates transiently display a flattened motile extension--the ridge--that projects from a specific location on the cell surface and contains a laminar core densely packed with a series of crisscrossing arrays of actin microfilaments. Details are presented here concerning the movements of the ridge as well as the dynamics of ridge formation and disassembly in relation to other morphogenetic events of the transformation. The ridge forms at about the same time as transforming cells begin to elongate, propagates undulations parallel to the long axis of the cell as the transformation proceeds, and disassembles late in the transformation. Staining of fixed cells with the fluorescent probe rhodaminephalloidin shows that the actin of amoeboid cells is strikingly redistributed as the transformation proceeds. Amoeboflagellates contain most of the stainable actin in the ridge and in a ventral-posterior spot that may be a site of cell-substratum adhesion. These results provide additional insights into the possible functions of the ridge and the roles of actin during the amoeboflagellate transformation.

Actin Cytoskeleton↗
PubMed1985

Improved negative staining of microfilament arrangements in detergent-extracted Physarum amoeboflagellates.

A motile, lamellipodium-like structure, the ridge, forms as amoeboflagellate cells of Physarum polycephalum release from a substratum and begin swimming in fluid. Actin microfilaments form a distinct laminar core within the ridge; they are seen as a sparse, disordered meshwork in cytoskeletons prepared by conventional methods using uranyl acetate negative staining [10]. Preservation and visualization of these filaments and their arrangements improved considerably when cytoskeletons were imaged with phosphotungstic acid buffered with ammonium hydroxide (PTA(NH4]. Microfilaments within ridge cytoskeletons were found to form loose bundles and criss-crossing, 'meshwork' arrays several layers deep. Differences could be detected in morphology and detailed arrangement of microfilaments within cytoskeletons prepared in the presence of phalloidin. PTA(NH4) may be useful for studies of cytoskeletal elements and their rearrangements in dynamic, motile regions of cells.

Cell Cycle↗
PubMed1984

Nucleotide specificity for reactivation of organelle movements in permeabilized axons.

In a permeabilized axon model, exogenous ATP can reactivate intraaxonal saltatory organelle movements (microscopically visible manifestations of fast axonal transport). We have studied the dependence of the reactivated movements on the ATP concentration and have also examined the nucleotide specificity of the reactivation. Organelle transport was visualized in isolated lobster giant motor axons using Nomarski optics and video microscopy. The axons were permeabilized with saponin, and movement was reactivated with ATP or other nucleotides. Some slight movement was seen with ATP concentrations as low as 10 microM. The velocity and frequency of the reactivated transport increased with increasing ATP concentrations up to about 5 mM. Movement was also reactivated by deoxyadenosine triphosphate, but not by AMP-PNP (a nonhydrolyzable ATP analogue), ADP, or AMP. Although other nucleotides (CTP, GTP, UTP, ITP) could reactivate transport, movement equivalent to that produced by 0.1 mM ATP was only seen with tenfold or greater concentrations of the other nucleotides. This pattern of specificity is consistent with the hypothesis that a dynein-like ATPase, rather than a myosin, is involved in fast axonal transport.

Adenosine Triphosphate↗
PubMed1984

Circus movements in dissociated cells from two new hybrid frog embryos.

Circus movements are a peculiar kind of cell movement, seen in many amphibian cells, that involve the formation of a hyaline protrusion from the cell surface and rotation of this blister around the circumference of the cell. Studies of cells from normal Rana pipiens embryos have shown a close correlation between circus movements in vitro and gastrulation related cell movements in vivo. Cells from two developmentally arrested hybrid embryos (R. pipiens female X R. sylvatica male and R. pipiens female X R. catesbiana male) are deficient in circus movements to an extent that corresponds to their gastrulation deficiencies. This study reports on the preparation of two new hybrids (R. pipiens female X R. temporaria male (temp) and R. pipiens female X R. clamitans male (clam)). Cells from temp embryos show some circus movements but the proportion of cells displaying such movements does not increase with increasing developmental age to the same extent as is seen in cells from normal embryos. Cells from clam embryos show very few circus movements at any developmental age. These aberrations in the onset and extent of circus movements are discussed in relation to characteristic morphogenetic events that occur in normal embryos and in these two new arrested hybrid embryos.

Animals↗
PubMed1981

Circus movements in dissociated cells in normal and hybrid frog embryos.

Circus movements, involving circumferential rotation of a hyaline cytoplasmic blister and endoplasmic flow, occur in EDTA-dissociated gastrula stage Rana pipiens embryos. Such cell movements occur in very few cells taken from pre-gastrula stage embryos. During gastrulation, there is a progressive increase in the proportion of a population of cells that is engaged in circus movements. Circus movements do not occur in dividing cells. Individual cells in culture, as well as small clusters of cells in vitro, are jostled about in an apparently aimless fashion over short distances by circus movements, although the translocation of masses of cells over long distances is substantially greater than the translocation of isolated cells. In an early gastrula stage normal embryo, cells from around the site of blastopore invagination are most active in circus movements. Cells taken from different stages of arrested hybrid embryos show variable depression in the formation of rotating hyaline blebs. Aggregates of cells from arrested hybrid embryos are also relatively immobile in culture. The morphogenetic significance of circus movements in normal embryos and gastrula-arrest hybrid embryos is discussed.

Animals↗
PubMed1977

Physarum action. Observations on its presence, stability, and assembly in plasmodial extracts and development of an improved purification procedure.

Actin is readily extracted from plasmodia of Physarum polycephalum by low ionic strength solutions which do not solubilize the plasmodial myosin. The actin in such extracts exists predominantly as a monomer which slowly denatures, apparently via removal of bound nucleotide, and is subsequently proteolyzed. However, the native monomeric actin can be induced to assemble into polymeric arrays under appropriate solvent conditions. Actin assembly is dependent on the addition of ATP and is a function of KCl and CaCl2 concentrations. These observations have allowed the development of an improved actin purification scheme which is simple, rapid, and efficient, yielding approximately 60 mg of protein from 100 g of plasmodium. The actin thus obtained is pure, stable, and comparable to that obtained by previously described procedlres. Furthermore, the observations suggest that actin polymers may be metastably assembled in vivo and raise the possibility that actin assembly, and plasmodial movements, could be regulated via alterations in intracellular concentrations of nucleotide and/or divalent cation.

Actins↗
PubMed1977

A comparison of professionally employed lesbians and heterosexual women on the MMPI.

The hypothesis tested is whether lesbianism implies psychopathology. The MMPI was given to 26 nonpatient lesbians who were professionally employed full time, and the results were compared to those for a group of 29 similarly employed heterosexual women. With the exception of the Sc scale, no difference was found on the clinical scales. The lesbian group achieved a significantly higher elevation than the nonlesbians on the Mf and Sc scales. Further analysis of the data on the Sc subscales indicated no difference on the pathological part of the scale, but rather a difference in degree of social alienation. Analysis of the data according to a second variable, living status, found significant differences and has important implications for future studies of the lesbian population. Single women, regardless of sexual orientation, scored significantly higher on scales K and Pa and on the Pa subscale naivete. A significant interaction between sexual orientation and living status was achieved on one scale, the F scale.

Female↗
PubMed1973

Ribosome-membrane interaction. Nondestructive disassembly of rat liver rough microsomes into ribosomal and membranous components.

In a medium of high ionic strength, rat liver rough microsomes can be nondestructively disassembled into ribosomes and stripped membranes if nascent polypeptides are discharged from the bound ribosomes by reaction with puromycin. At 750 mM KCl, 5 mM MgCl(2), 50 mM Tris.HCl, pH 7 5, up to 85% of all bound ribosomes are released from the membranes after incubation at room temperature with 1 mM puromycin. The ribosomes are released as subunits which are active in peptide synthesis if programmed with polyuridylic acid. The ribosome-denuded, or stripped, rough microsomes (RM) can be recovered as intact, essentially unaltered membranous vesicles Judging from the incorporation of [(3)H]puromycin into hot acid-insoluble material and from the release of [(3)H]leucine-labeled nascent polypeptide chains from bound ribosomes, puromycin coupling occurs almost as well at low (25-100 mM) as at high (500-1000 mM) KCl concentrations. Since puromycin-dependent ribosome release only occurs at high ionic strength, it appears that ribosomes are bound to membranes via two types of interactions: a direct one between the membrane and the large ribosomal subunit (labile at high KCl concentration) and an indirect one in which the nascent chain anchors the ribosome to the membrane (puromycin labile). The nascent chains of ribosomes specifically released by puromycin remain tightly associated with the stripped membranes. Some membrane-bound ribosomes (up to 40%) can be nondestructively released in high ionic strength media without puromycin; these appear to consist of a mixture of inactive ribosomes and ribosomes containing relatively short nascent chains. A fraction ( approximately 15%) of the bound ribosomes can only be released from membranes by exposure of RM to ionic conditions which cause extensive unfolding of ribosomal subunits, the nature and significance of these ribosomes is not clear.

Amino Acids↗