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D R Soll

Publications and source records attributed to D R Soll.

At least 91 records · Page 5Linked to original sources
PubMed1993

Coordinate regulation of two opaque-phase-specific genes during white-opaque switching in Candida albicans.

Cells of Candida albicans WO-1 switch spontaneously and frequently between a white and an opaque CFU. Recently, an opaque-phase-specific cDNA, PEP1, was cloned and was demonstrated to code for a pepsinogen. By using a differential hybridization screen, a second opaque-phase-specific cDNA, Op4, has been isolated and its corresponding gene has been cloned. Op4 is coordinately regulated with PEP1 but resides on a different chromosome. During temperature-induced mass conversion from opaque to white, transcription of PEP1 and Op4 is immediately inhibited by the increase in temperature, but transcription of both genes can be rapidly reestablished by a downshift in temperature prior to phenotypic commitment. However, the capacity to rapidly induce both PEP1 and Op4 is lost coincidentally with the second semisynchronous round of cell division and phenotypic commitment during mass conversion. Op4 shows no significant base or amino acid sequence homology with a known gene or protein, respectively. However, the deduced Op4 protein exhibits several interesting characteristics, including a hydrophobic amino terminus with 26 amino acids, a pI of 10.73 for the last 100 amino acids, two serine repeats adjacent to alanine repeats, and the potential for alpha-helical conformation within the alanine-rich sequences. No genomic reorganization was evident in the proximity of Op4 during transcriptional activation and deactivation accompanying the white-opaque transition.

Amino Acid Sequence↗
PubMed1993

Genetic similarity of Candida albicans strains from vaginitis patients and their partners.

The moderately repetitive sequence Ca3 was used to fingerprint strains of Candida albicans isolated from vulvovaginal infections of 10 women and strains isolated from their male partners. The Dendron software package was then used to compare the DNA fingerprints of these strains with those of vaginal commensals from women from the same geographical locale, vaginal commensals from women from a different geographical locale, and commensals from male partners of asymptomatic women from the same geographical locale. The results demonstrate that, in the majority of cases (8 of 10), strains from symptomatic patients and their partners are either identical or more similar to each other than to other strains, infecting strains do not represent a group genetically distinguishable from vaginal commensal isolates from women from the same geographical locale, and both infecting strains and commensals from individuals in the test locale can be distinguished from commensals obtained in another geographical locale. The results also suggest that women with vaginal infections are responsible for strain replacement in their male partners.

Adult↗
PubMed1993

Genetic similarity and phenotypic diversity of commensal and pathogenic strains of Candida albicans isolated from the oral cavity.

Colony phenotype and genetic similarity were assessed within and between groups of commensal and pathogenic strains of Candida albicans collected from the oral cavities of individuals in a single geographical locale. Thirty-eight percent of pathogenic isolates contained predominant or minor variant colony morphologies (other than smooth) when samples from the sites of infection were cultured on plates, while 16% of commensal isolates contained minor variant colony morphologies when samples from the sites of carriage were cultured. The genetic similarities of isolates within and between groups were assessed by DNA fingerprinting by using Southern blot hybridization with the fingerprinting probe Ca3 and analysis with the computer-assisted, automated Dendron system. Both the commensal and the pathogenic groups contained a major cluster of genetically similar C. albicans isolates representing 31 and 33% of the strains in the respective groups. When a combined dendrogram of both commensal and pathogenic isolates was generated, the major clusters of genetically similar isolates in each group mixed into one large cluster. Minor clusters in the individual dendrograms also mixed. These results suggest common clonal origins for commensal and pathogenic strains in the same geographical locale.

Adult↗
PubMed1993

Characterization and partial nucleotide sequence of the DNA fingerprinting probe Ca3 of Candida albicans.

The moderately repetitive Ca3 fragment of Candida albicans has been used as an effective DNA fingerprinting probe in epidemiological studies. EcoRI digestion of Ca3 DNA results in seven fragments of 4.2 kb (A), 2.98 kb (B), 2.85 kb (C), 0.77 kb (D1), 0.77 kb (D2), 0.38 kb (E), and 0.30 kb (F). Five of these EcoRI fragments have been mapped in the 5'-3' order C B D1 A D2. The intact Ca3 probe and the three largest EcoRI fragments, A, B, and C, were individually used to probe Southern blots of EcoRI-digested DNA of a set of test strains, transverse alternating field electrophoresis-separated chromosomes of strain 3153A, and Northern (RNA) blots of test strain 3153A. Fragments, A, B, and C each generate a different Southern blot hybridization pattern with EcoRI-digested whole-cell DNA; Ca3 sequences are present in at least five of seven separable chromosomes and a minichromosome of strain 3153A; fragments A, B, and C are distributed differently on chromosomes; and fragments A, B, and C do not cross-hybridize. Ca3 hybridizes to three major transcripts of 2.8, 2.3, and 1.5 kb. Fragment A hybridizes intensely to the 1.5-kb transcript, while fragments B and C both hybridize intensely to the 2.8- and 2.3-kb transcripts. The B fragment, which contains 2,980 bp and contributes to the major portion of the Ca3 pattern, was sequenced. Both direct and inverted repeat sequence motifs were identified. These results provide us with initial insights into the evolution of the Ca3 pattern and the nature of the probe.

Base Sequence↗
PubMed1993

Development of DNA probes for fingerprinting Aspergillus fumigatus.

Several different DNA fragments containing nonribosomal repetitive sequences have been isolated from the genome of Aspergillus fumigatus and tested as potential DNA fingerprinting probes. Eight of these clones generate 19 or more bands when hybridized to EcoRI-digested DNA of a reference strain in Southern blots, and they fall into four families. Individual clones from two families were tested and were found to generate complex Southern blot hybridization patterns which are stable within a single strain over many generations, which vary among unrelated strains, and which are amenable to computer-assisted analyses involving large numbers of strains in epidemiological studies. Clones from three of the families clustered a majority of test strains in a similar fashion in individual dendrograms based on similarity coefficients computed from band positions in Southern blot hybridization patterns. These clones therefore fulfill the major requisites for effective DNA fingerprinting probes.

Aspergillosis↗
PubMed1993

HIV-induced syncytia of a T cell line form single giant pseudopods and are motile.

The human immunodeficiency virus, HIV, induces syncytium formation in cultures of many T cell lines. These syncytia have previously been viewed as disorganized fusion products in the throes of death. Evidence is presented that in HIV1-infected SupT1 cultures, syncytia five times to over one hundred times larger than single cells organize their many nuclei into blastula-like balls, reorganize their cytoskeleton to mimic that of a single cell, and extend single, giant pseudopods in a polar fashion. Medium-sized syncytia are capable of translocation through extension of these giant pseudopods. The rate of translocation of syncytia is comparable to that of single cells. Single cell motility, syncytium motility and pseudopod extension also appear to play roles in the recruitment of cells into syncytia. Finally, condensation of F-actin at cell-syncytium and syncytium-syncytium adhesion sites suggests the involvement of the cytoskeleton in the adhesion and/or subsequent fusion event. These results suggest that the fusion events involved in HIV-induced syncytia formation involve both cell motility and reorganization of the cytoskeleton, and demonstrate that syncytia are highly organized, motile entities.

Actins↗
PubMed1992

Three-dimensional motility cycle in leukocytes.

A 3-dimensional dynamic image analyzing system (3D-DIAS) has been developed in which a translocating cell is optically sectioned in the z-axis within a 2 sec period; the perimeter of the cell in each section is digitized into the 3D-DIAS data file, and the digitized perimeters are wrapped in order to reconstruct the cell image in three dimensions. Using 3D-DIAS, we have obtained the first dynamic 3-dimensional description of human polymorphonuclear leukocytes (PMN) translocating on a glass surface. A general behavior cycle has emerged which includes two phases. In the first, an ellipsoidal PMN with significant z-axis extends anteriorly and descends to the substratum. When the ventral surface of the anterior end contacts the substratum, there is rapid anterior expansion, which correlates with velocity peaks. In the second phase, the elongate PMN stops translocating along the substratum, the anterior end lifts off of the substratum, sometimes to heights greater than the length of the PMN at the substratum, and finally the PMN retracts into an ellipsoidal morphology still capable of random protrusions. During this second phase, which correlates with velocity troughs, turning usually occurs. The degree of turning is restricted by the continuous integrity of the posterior uropod. The period of the behavior cycle varies from roughly 0.5 to 2 min between PMNs, but is relatively constant within each individual PMN.

Cell Movement↗
PubMed1992

Behavior of Dictyostelium amoebae is regulated primarily by the temporal dynamic of the natural cAMP wave.

The instantaneous velocity plots of Dictyostelium discoideum amoebae responding to natural waves and simulated temporal waves of cAMP with periods of 7 min are highly similar. This similarity has been used to deduce the dynamics of a natural wave crossing an amoeba, and the behavior of amoebae has been characterized during the different phases of a natural wave with a computer-assisted dynamic image analyzing system. During the first approximately 150 sec of the front of a natural wave, cells move persistently toward the aggregation center, with high instantaneous velocity and a decreased frequency of lateral pseudopod formation. During the last 30 sec of the front of the wave and the first 30 sec of the back of the wave, there is a "freeze" in cell shape and a dramatic depression in cell motility, pseudopod formation, and intracellular particle movement. During the last 180 sec of the back of the wave, there is a rebound in pseudopod formation, but it is random in direction and leads to no net cellular translocation. The data suggest that all of the behavior of a cell but orientation during the translocation phase is mediated by the temporal dynamics of the wave. The data also suggest that orientation toward the aggregation center occurs early in the front of the wave and that, once oriented, cells move in a blind fashion during the translocation phase.

Animals↗
PubMed1992

Discoidin proteins of Dictyostelium are necessary for normal cytoskeletal organization and cellular morphology during aggregation.

The onset of aggregation of bacterially-grown Dictyostelium discoideum amoebae is accompanied by the accumulation of the discoidin proteins. An immunofluorescent analysis demonstrates that discoidin is distributed throughout the cytoplasm, but is excluded from vesicles and nucleoli. There is no indication of either extracellular or membrane localization. Translocating amoebae of mutants lacking discoidin form more dispersed pseudopodial regions at the cell periphery, possess an abnormally centered microtubule organizing center, are blunt rather than elongate, and lack the tapered posterior uropod characteristic of translocating wild-type cells. However, in spite of the loss of the normal elongate morphology, discoidinless mutants translocate with instantaneous velocities and directional persistence comparable to wild-type cells, and they respond normally to the rapid addition of cAMP. These results demonstrate that the discoidin proteins are cytoplasmic components essential for the maintenance of the elongate cell morphology, cytoskeletal organization and the ability to align with other cells during aggregation. However, the elongate morphology is not a requisite for rapid and persistent single cell translocation.

Actins↗
PubMed1992

High-frequency switching in Candida albicans.

Most strains of Candida albicans are capable of switching frequently and reversibly between a number of phenotypes distinguishable by colony morphology. A number of different switching systems have been defined according to the limited set of phenotypes in each switching repertoire, and each strain appears to possess a single system. Switching can affect many aspects of cellular physiology and morphology and appears to be a second level of phenotypic variability superimposed upon the bud-hypha transition. The most dramatic switching system so far identified is the "white-opaque transition." This system dramatizes the extraordinary effects switching can have on the budding cell phenotype, including the synthesis of opaque-specific antigens, the expression of white-specific and opaque-specific genes, and the genesis of unique cell wall structures. Switching has been demonstrated to occur at sites of infection and between episodes of recurrent vaginitis, and it may function to generate variability in commensal and infecting populations for adaptive reasons. Although the molecular mechanisms involved in the switch event are not understood, recent approaches to its elucidation are discussed and an epigenetic mechanism is proposed.

Adaptation, Physiological↗
PubMed1992

Genetic similarity and maintenance of Candida albicans strains from a group of AIDS patients, demonstrated by DNA fingerprinting.

By using the computer-assisted Dendron system to analyze the patterns of Southern blots probed with the repetitive sequence Ca3, we have compared oral isolates of Candida spp. from a group of 11 nonhospitalized patients with AIDS suffering from recurrent episodes of oral thrush in Leicester, England, with oral isolates from a group of control individuals. Genetic diversity among the AIDS strains was significantly reduced compared with that of control strains. In addition, the same strains persisted through recurrent infections in patients with AIDS. Although AIDS strains were genetically less diverse than either control strains or oral commensal strains analyzed in previous studies, the majority did not form a genetically distinct group. The results of this study suggest that in the majority of patients with AIDS in this group from Leicester, original commensal strains were replaced, replacement occurred early in the manifestation of AIDS, and replacement occurred only once.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Transcription of the gene for a pepsinogen, PEP1, is regulated by white-opaque switching in Candida albicans.

Cells of Candida albicans WO-1 spontaneously switch between a white and opaque CFU, and this phase transition involves a dramatic change in cellular phenotype. By using a differential hybridization screen, an opaque-specific cDNA, Op1a, which represents the transcript of a gene regulated by switching, has been isolated. The gene for Op1a is transcribed by opaque but not by white cells. The nucleotide sequence of the Op1a cDNA reveals over 99% base homology with an acid protease gene of C. albicans, and the predicted amino acid sequence demonstrates that the product of this gene is a member of the family of pepsinogens, which possess a hydrophobic leader sequence for secretion and two catalytic aspartate domains. Southern blots of both genomic DNA digested with 14 different endonucleases and electrophoretically separated chromosomes were probed with the Op1a cDNA. No polymorphisms were detected in either case between white and opaque cells, suggesting that no genomic reorganization occurs in the proximity of the gene during the white-opaque transition. Although transcription of Op1a correlates with the high levels of extracellular protease activity in opaque cell cultures and the absence of activity in white cell cultures, stimulation of extracellular protease activity by addition of serum albumin is not accompanied by Op1a transcription in cultures of WO-1 white cells or cultures of two additional clinical isolates of C. albicans, suggesting that expression of one or more other protease genes is stimulated in these cases. The results demonstrate that transcription of the Op1a gene is under the rigid control of switching in strain WO-1.

Amino Acid Sequence↗
PubMed1992

Biological and molecular correlates between induced dedifferentiation and spore germination in Dictyostelium.

When developing cultures of Dictyostelium discoideum are disaggregated at any time prior to cell wall formation and challenged to reinitiate development, amoebae will progress through the original sequence of morphogenetic stages, but the second time through they will do so in roughly one-tenth the original time, a process known as 'rapid recapitulation'. However, if disaggregated cells are suspended in nutrient medium, they enter a program of dedifferentiation during which they lose the capacity to rapidly recapitulate after an 80 minute lag period in a process known as 'erasure'. Here we show that cells that have completed the morphogenetic program and emerge from spore coats in the process of germination have also erased. In addition, the germination-specific 270 gene family is expressed during induced dedifferentiation in a unique fashion, and a germination-defective mutant exhibits a dramatic delay in erasure without concomitant defects in the program of gene regulation accompanying induced dedifferentiation. These results suggest for the first time that induced dedifferentiation and spore germination share some common processes in converting cells from a developmental to vegetative state.

Animals↗
PubMed1991

Invasion by WC5 rat cerebellar cells is independent of RSV-induced changes in growth and adhesion.

The WC5 rat cerebellar cell line, which is infected with a Rous sarcoma virus that is temperature-sensitive for pp60src transformation, shows temperature-dependent expression of the neural-cell-adhesion molecule (N-CAM) and glial fibrillary acidic protein (GFAP). We found that WC5 cells maintained at the non-permissive temperature in both monolayer cultures and spheroids are subject to density-dependent inhibition of growth, whereas cells maintained at the permissive temperature continued to grow. The movement of isolated WC5 cells at both temperatures was similar, while the migration of WC5 cells out of 3-dimensional aggregates was faster at the non-permissive temperature. We tested whether the RSV-induced changes affect the invasion of the WC5 cells in 2 in vitro assays: the chorio-allantoic-membrane assay and the chick-heart-fragment assay. In both assays, WC5 cells grown at either temperature were invasive. These results indicate that growth rate is unrelated to invasion and that loss of N-CAM-mediated cell-cell adhesion is not necessary for invasion.

Animals↗
PubMed1991

Invasion of Rous sarcoma virus-transformed retinal cells: role of cell motility.

Transformation of retinal neuro-epithelial cells by Rous sarcoma virus (RSV) leads to many alterations in cell phenotype, including changes in cell movement, cell-cell adhesion and protease secretion. To define and quantitate the alterations in cell movement, we analyzed video recordings of cultured cells using the computer-assisted Dynamic Morphology System (DMS). Control neuro-epithelial cells showed very low levels of translocation and membrane activity. After transformation, neuro-epithelial cells exhibited increased membrane activity, although directed cell translocation remained low. Developing retinas also contain a small proportion of Müller glial cells, which were purified by repeated passaging of control cultures. In contrast to neuro-epithelial cells, both control and RSV-transformed glial cells showed high levels of translocation and membrane activity. To analyze how different kinds of cell movement affect invasive behavior, we compared the ability of control and RSV-transformed cells to invade the chorio-allantoic membrane of developing chicken embryos. Control neuro-epithelial cells were not invasive. RSV-transformed neuro-epithelial cells, which showed low levels of translocation as revealed by DMS, were invasive. Similarly, RSV-transformed glial cells were invasive while control glial cells, which translocated, were not invasive. These results suggest that high levels of cell translocation are not necessary for invasion. In addition, the results suggest that elevated membrane activity in neuro-epithelial cells may be important for their invasion.

Allantois↗