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D R Soll

Publications and source records attributed to D R Soll.

At least 73 records · Page 4Linked to original sources
PubMed1995

HIV-induced syncytia in peripheral blood cell cultures crawl by extending giant pseudopods.

It was previously demonstrated that HIV-induced syncytia of the immortalized T cell line SupT1 reorganize their cytoskeleton and form a spherical supernuclear complex, thus mimicking the organization, polarity, and morphology of a single SupT1 cell. Then, through extension of a single, giant pseudopod, these syncytia, which grow to more than 100 times the volume of a single SupT1 cell, translocate along a substratum. To verify that syncytium motility is not peculiar to the SupT1 cell line, we have analyzed the cytoskeletal organization and motile capabilities of HIV-induced syncytia formed in peripheral blood cell cultures containing more than 90% CD4-positive cells. The results demonstrate that although peripheral blood T cells differ from SupT1 cells in size and morphology, they are continuously motile and translocate along a substratum in a manner quite similar to that of SupT1 cells, and peripheral blood T cell syncytia induced by HIV-1LAI as well as two additional clinical isolates translocate by the extension of a giant anterior pseudopod in a fashion indistinguishable from that of HIV-induced SupT1 syncytia. Together, these results support the generalization that HIV-induced T cell syncytia are motile.

Adult↗
PubMed1995

A mutation that depresses cGMP phosphodiesterase activity in Dictyostelium affects cell motility through an altered chemotactic signal.

The streamer F (StmF) mutant of Dictyostelium discoideum is defective in cGMP-phosphodiesterase activity. In early aggregation territories, when individual cells chemotax toward aggregation centers prior to streaming, the average periodicity of surging of StmF cells is half that of wild-type cells. In addition, in the period between surges, which has been interpreted to include the peak and back of the wave, StmF cells abnormally remain nonmotile and retain their elongate shape. In contrast, in the period between surges wild-type cells form pseudopods randomly around their cell perimeter and take on an amorphous shape. Using a newly developed protocol for vitally staining and tracking individual mutant cells in unstained wild-type aggregation territories and individual wild-type cells in unstained StmF aggregation territories, we have found that mutant cells behave normally (i.e., like their predominant wild-type neighbors) in the deduced back of waves generated by wild-type cells. Conversely, wild-type cells behave aberrantly (i.e., like their predominant StmF neighbors) in the deduced back of waves generated by mutant cells. These results suggest that the defective behavior of StmF cells in early StmF aggregation territories is not due to a single cell defect in responsiveness, but, rather, is due either to the genesis of an aberrant cAMP wave or to the accumulation of a molecule which interferes with normal behavior in the back of the wave.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1995

Ponticulin plays a role in the positional stabilization of pseudopods.

Ponticulin is a 17-kD glycoprotein that represents a major high affinity link between the plasma membrane and the cortical actin network of Dictyostelium. To assess the role of ponticulin in pseudopod extension and retraction, the motile behavior of two independently generated mutants lacking ponticulin was analyzed using computer-assisted two- and three-dimensional motion analysis systems. More than half of the lateral pseudopods formed off the substratum by ponticulin-minus cells slipped relative to the substratum during extension and retraction. In contrast, all pseudopods formed off the substratum by wild-type cells were positionally fixed in relation to the substratum. Ponticulin-minus cells also formed a greater proportion of both anterior and lateral pseudopods off the substratum and absorbed a greater proportion of lateral pseudopods into the uropod than wild-type cells. In a spatial gradient of cAMP, ponticulin-minus cells were less efficient in tracking the source of chemoattractant. Since ponticulin-minus cells extend and retract pseudopods with the same time course as wild-type cells, these behavioral defects in ponticulin-minus cells appear to be the consequence of pseudopod slippage. These results demonstrate that pseudopods formed off the substratum by wild-type cells are positionally fixed in relation to the substratum, that ponticulin is required for positional stabilization, and that the loss of ponticulin and the concomitant loss of positional stability of pseudopods correlate with a decrease in the efficiency of chemotaxis.

Actins↗
PubMed1995

Phagocytosis of individual CD4+ T cells by HIV-induced T cell syncytia.

Transmission electron microscopic analysis of HIV-induced syncytia of the CD4+ SupT1 cell line has revealed profiles of whole T cells in the syncytium cytoplasm. Serial sections demonstrate that these T cells are completely enveloped by a second membrane in the syncytium cytoplasm and represent phagosomes. Pycnosis of engulfed T cell nuclei, vacuolation of the cytoplasm of engulfed T cells, and the association of engulfed T cells with dense vesicular clusters in the syncytium cytoplasm support the conclusion that they represent phagosomes. In addition, transmission electron micrographs of the syncytium surface reveal giant pseudopodial extensions wrapping around T cells, in a fashion similar to bacterial and yeast phagocytosis by professional phagocytes. These results suggest that phagocytosis is a characteristic acquired during HIV-induced syncytium formation, and that it may represent an avenue of T cell death in addition to fusion in HIV-infected SupT1 cell cultures.

CD4-Positive T-Lymphocytes↗
PubMed1995

Colonizing populations of Candida albicans are clonal in origin but undergo microevolution through C1 fragment reorganization as demonstrated by DNA fingerprinting and C1 sequencing.

The genetic homogeneity of nine commensal and infecting populations of Candida albicans has been assessed by fingerprinting multiple isolates from each population by Southern blot hybridization first with the Ca3 probe and then with the 0.98-kb C1 fragment of the Ca3 probe. The isolates from each population were highly related, demonstrating the clonal origin of each population, but each population contained minor variants, demonstrating microevolution. Variation in each case was limited to bands of the Ca3 fingerprint pattern which hybridized with the 0.98-kb C1 fragment. The C1 fragment was therefore sequenced and demonstrated to contain an RPS repetitive element. The C1 fragment also contained part or all of a true end of the RPS element. These results, therefore, demonstrate that most colonizing C. albicans populations in nonimmuno-suppressed patients are clonal, that microevolution can be detected in every colonizing population by C1 hybridization, and that C1 contains the repeat RPS element.

Base Sequence↗
PubMed1995

Functional analysis of the promoter of the phase-specific WH11 gene of Candida albicans.

Candida albicans WO-1 switches spontaneously, frequently, and reversibly between a hemispherical white and a flat gray (opaque) colony-forming phenotype. This transition affects a number of morphological and physiological parameters and involves the activation and deactivation of phase-specific genes. The WH11 gene is transcribed in the white but not the opaque phase. A chimeric WH11-firefly luciferase gene containing the 5' upstream region of WH11 was demonstrated to be under phase regulation regardless of the site of integration, and a series of promoter deletion constructs was used to delineate two white-phase-specific transcription activation domains. Gel retardation experiments with the individual distal or proximal domain and white-phase or opaque-phase protein extract demonstrated the formation of one distal white-phase-specific complex and two proximal white-phase-specific complexes. Specific subfragments were tested for their ability to compete with the entire domain in the formation of complexes with white-phase protein extract in order to map the proximal domain sequence involved in white-phase-specific complex formation. Our results indicate that white-phase-specific transcription of WH11 is positively regulated by trans-acting factors interacting with two cis-acting activation sequences in the WH11 promoter.

Animals↗
PubMed1995

The use of computers in understanding how animal cells crawl.

Amoeboid cell motility is a complex three-dimensional process which involves pseudopod expansion, cellular translocation, and, in some cases, pseudopod retraction and complex interactions between the ventral surface of the pseudopod and substratum. In order to quantify the basic behavior of amoeboid cells and the dynamics of pseudopod extension and retraction, sophisticated two-dimensional and three-dimensional computer-assisted motion analysis systems have been developed which reconstruct digitized images and compute motility and dynamics morphology parameters. These systems provide a wealth of information of how amoeboid cells crawl and they have begun to be utilized (1) to elucidate the basic rules of amoeboid movement, (2) to identify the behavioral defects of cytoskeletal mutants, and (3) to elucidate the mechanism of chemotaxis. In addition, these systems represent powerful tools for analyzing the effects of drugs on cell behavior, most notably that of white blood cells and neoplastic cells. Since computer-assisted motion analysis is a relatively young field, the technologies are still evolving and have been underutilized in most areas involving cell motility. This review, which includes a description of these technologies and examples of their application, will hopefully serve as an impetus for expanded use.

Animals↗
PubMed1994

Three-dimensional dynamics of pseudopod formation and the regulation of turning during the motility cycle of Dictyostelium.

Employing a newly developed computer-assisted system for visualizing and quantitating cell motility in three dimensions, we have examined the 3-dimensional changes in cell shape and the dynamics of pseudopod extension during translocation of Dictyostelium amoebae. Amoebae exhibit a 3-dimensional behavior cycle with an average period of 1.5 min. The cycle includes a transient pseudopod extension phase in the x,y axis followed by a z-axis expansion phase. Anterior pseudopod extension in the x,y axis is accompanied by a decrease in height, not by uropod retraction. The increase in height is accompanied by uropod retraction. In the pseudopod extension phase in the x,y axes, pseudopods form either anteriorly or laterally, and either on or above the substratum. Pseudopods which initially form on the substratum in almost all cases continue to expand as the anterior end of the cell. In the case of lateral pseudopods, anteriorization leads to a turn. Approximately half of anterior pseudopod and two-thirds of lateral pseudopods which initially form above the substratum are retracted. These results suggest that pseudopod-substratum interaction plays a fundamental role in the regulation of directionality and turning in the translocation phase of the 3-dimensional behavior cycle.

Animals↗
PubMed1994

Partial nucleotide sequence of a single ribosomal RNA coding region and secondary structure of the large subunit 25 s rRNA of Candida albicans.

A rDNA cistron of Candida albicans strain WO-1 was cloned and the ITS1, ITS2, 5.8 s rDNA and 25 s rDNA coding regions sequenced in their entirety. These sequences were compared to those of three related yeast species (Saccharomyces cerevisiae, Saccharomyces carlsbergensis, and Thermomyces lanuginosus), and the 5.8 s rDNA was compared to seven additional 5.8 s rDNAs from organisms ranging in complexity from D. discoideum to H. sapiens. The C. albicans ITS regions are shorter than those of most other eukaryotes. The 25 s and 5.8 s rDNA sequences were folded into a secondary structure model based on comparative methods. In a comparison of regional similarities between the large subunit rDNAs of C. albicans, the three related yeasts and other eukaryotes, it is demonstrated that the additional sequences not present in the E. coli 23 s rDNA are more variable than the regions present in both prokaryotes and eukaryotes.

Animals↗
PubMed1994

Developmental and molecular biology of switching in Candida albicans.

Candida albicans and related species switch frequently and reversibly between a number of general phenotypes usually discriminated by colony morphology and in some cases by cellular morphology. Switching has been demonstrated to affect a number of physiologic and architectural characteristics of single cells including most of the putative virulence factors of C.albicans. In the past few years, we have cloned several genes regulated by switching in the white-opaque transition of C.albicans strain WO-1. Two of the genes, PEP1 and Op4, are transcribed only in the opaque phase, and one of the genes, Wh11, is transcribed only in the white phase. These coordinately regulated genes are unlinked in the genome and do not undergo sequence reorganization in switching. With the identification of a cis-acting regulatory sequence in the five-prime flanking sequence of Wh11, we now believe that phase-specific genes are regulated by transacting factors and that these factors may be coded for or under the direct regulation of a single master regulatory gene at which site the basic switch event occurs.

Base Sequence↗
PubMed1994

Regulation of phase-specific genes in the more general switching system of Candida albicans strain 3153A.

It was previously demonstrated that the genes PEP1 and Op4 are selectively transcribed in the opaque phase of the white-opaque transition in Candida albicans strain WO-1, and that the gene Wh11 is selectively transcribed in the white phase. However, the white-opaque transition occurs in only a minority of C. albicans strains and the opaque cell phenotype is highly specialized. To test whether these genes are regulated in more mainstream switching systems in C. albicans, their expression was analysed in the switching system of the laboratory strain 3153A. Both PEP1 and Op4 are not expressed in the basic smooth phenotype of 3153A, but they are expressed in switch phenotypes. However, expression is dissociated. Op4 is expressed in irregular wrinkle, star and revertant-smooth cells, while PEP1 is expressed only in star cells. Wh11 is expressed in the basic smooth and three tested variant phenotypes and is again associated with growth in a round budding form. The results support the general conclusion that PEP1 and Op4 are under the strict regulation of switching in C. albicans.

Blotting, Northern↗
PubMed1994

An increase in switching frequency correlates with an increase in recombination of the ribosomal chromosomes of Candida albicans strain 3153A.

When cells of Candida albicans strain 3153A are treated with a low dose of ultraviolet irradiation, they switch at high frequency (10(-2)) between a number of switch phenotypes discriminated by colony morphology. Clones from switching lineages exhibit continuous reorganization of their ribosomal chromosomes (R chromosomes), while clones from lineages maintaining the original smooth phenotype exhibit no reorganization. R chromosome reorganization results in decreases as well as increases in size of the chromosomes, but changes are not reciprocal between R chromosome homologues.

Artifacts↗
PubMed1994

Differences in adhesion of Candida albicans 3153A cells exhibiting switch phenotypes to buccal epithelium and stratum corneum.

Cells of the laboratory strain 3153A of Candida albicans can be stimulated to undergo high-frequency phenotypic switching by a low dose of UV. We have compared the adhesive properties of cells exhibiting the basic original smooth (o-smooth) phenotype and three switch phenotypes (star, irregular wrinkle, and revertant smooth) to buccal epithelium and stratum corneum. The generalized hierarchy of adhesion is as follows: o-smooth > irregular wrinkle > revertant smooth > star. This is the inverse of the hierarchy of the proportions of elongate hyphae formed by these phenotypes in culture. These results suggest that the differences in adhesion between o-smooth and the three switch phenotypes of strain 3153A reflect, at least in part, the level of interference due to the formation of elongate hyphae, which tend to cause clumping in suspension. No major differences in the levels of adhesion of cells of the different phenotypes between buccal epithelium and stratum corneum were observed. Results which demonstrate that buccal epithelium induces germination (hypha formation) by conditioning the medium are also presented.

Adhesiveness↗
PubMed1994

Evolution and replacement of Candida albicans strains during recurrent vaginitis demonstrated by DNA fingerprinting.

Southern blot hybridization with the Ca3 probe and the C fragment of the Ca3 probe was used to assess the genetic relatedness of Candida albicans strains from one patient with recurrent C. albicans infection in whom the same strain was maintained, one patient in whom the infecting strain was replaced, and their male sexual partners. In the patient in whom the infecting strain was maintained, the infecting strain exhibited a minor genetic change in each successive episode of Candida vaginitis. These genetic changes occurred in the C-fragment bands of the Ca3 hybridization pattern. In the patient in whom the infecting strain was replaced by another infecting strain, a transition infection involved a genetically mixed infecting population, and the replacement strain appeared to have originated from the oral cavity of the male partner. The results demonstrate that the infecting strains of recurrent Candida vaginitis are not genetically stable, that drug treatment can result in the selection of variants of the previously infecting strain or replacement by a genetically unrelated strain, and that the male partner can be the source of a replacement strain.

Adult↗
PubMed1993

A white-specific gene in the white-opaque switching system of Candida albicans.

The Candida albicans strain WO-1 cells switch spontaneously, frequently, and reversibly between white and opaque colony-forming units which differ dramatically in their budding phenotypes. By screening a subtracted white cDNA library, the first white-specific cDNA, cWh11, was isolated and sequenced. This, in turn, was used to clone the Wh11 gene. Wh11 shows significant homology to the glucose/lipid-regulated GLP1 gene of Saccharomyces cerevisiae. Upon temperature-induced mass conversion from opaque to white colonies, transcription of Wh11 is abruptly activated at the second cell doubling, concomitant with commitment to the white phenotype. Wh11 exhibits the unique characteristics of being regulated not only by switching, but also by the bud-hypha transition.

Amino Acid Sequence↗
PubMed1993

High-frequency phenotypic switching in Candida albicans.

Most strains of Candida albicans are capable of switching spontaneously and at high frequencies between a number of phenotypes distinguished by colony morphology. Unlike switching in many other microbial pathogens, switching in C. albicans is pleiotropic, affecting several morphological and physiological parameters. Recently, the first phase-specific genes were identified and shown to be regulated at the level of gene transcription.

Antigenic Variation↗