Search PubMed⌕ Search

Biomedical subjects

A E Adams

Publications and source records attributed to A E Adams.

At least 37 records · Page 2Linked to original sources
PubMed1993

Unexpected combinations of null mutations in genes encoding the actin cytoskeleton are lethal in yeast.

To understand the role of the actin cytoskeleton in cell physiology, and how actin-binding proteins regulate the actin cytoskeleton in vivo, we and others previously identified actin-binding proteins in Saccharomyces cerevisiae and studied the effect of null mutations in the genes for these proteins. A null mutation of the actin gene (ACT1) is lethal, but null mutations in the tropomyosin (TPM1), fimbrin (SAC6), Abp1p (ABP1), and capping protein (CAP1 and CAP2) genes have relatively mild or no effects. We have now constructed double and triple mutants lacking 2 or 3 of these actin-binding proteins, and studied the effect of the combined mutations on cell growth, morphology, and organization of the actin cytoskeleton. Double mutants lacking fimbrin and either Abp1p or capping protein show negative synthetic effects on growth, in the most extreme case resulting in lethality. All other combinations of double mutations and the triple mutant lacking tropomyosin, Abp1p, and capping protein, are viable and their phenotypes are similar to or only slightly more severe than those of the single mutants. Therefore, the synthetic phenotypes are highly specific. We confirmed this specificity by overexpression of capping protein and Abp1p in strains lacking fimbrin. Thus, while overexpression of these proteins has deleterious effects on actin organization in wild-type strains, no synthetic phenotype was observed in the absence of fimbrin. We draw two important conclusions from these results. First, since mutations in pairs of actin-binding protein genes cause inviability, the actin cytoskeleton of yeast does not contain a high degree of redundancy. Second, the lack of structural and functional homology among these genetically redundant proteins (fimbrin and capping protein or Abp1p) indicates that they regulate the actin cytoskeleton by different mechanisms. Determination of the molecular basis for this surprising conclusion will provide unique insights into the essential mechanisms that regulate the actin cytoskeleton.

Actin Depolymerizing Factors↗
PubMed1993

Discriminant analysis for classification of murine melanomas and human cervical epithelial cells.

Computer analysis of cell images offers many advantages over routine visual examination. It leads to quantitative and accurate detection of subvisual information and provides reproducible measures so that objective decisions in cancer diagnosis become possible. Such diagnostic decisions usually follow partly from a classification process. In this paper two multivariate discriminant analysis methods--namely, linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA)--are presented. LDA and QDA were used to classify cytologic data based on some morphodensitometric measurements. The cytologic data constituted two samples, one representing B16 cell lines and the other including three types of normal human cervical epithelial cells. LDA and QDA were assessed both individually and in comparison to each other, mainly on the basis of the rate of correct classification and robustness. The measurements extracted from the cytologic data employed were shown to be stable and consistent. The statistical results obtained from experiments on cervical cells look particularly promising and encouraging for future work. It has also been shown in this study that the classification techniques employed are valid and that LDA performed almost as well as QDA.

Animals↗
PubMed1992

Image processing for cell cycle analysis and discrimination in metastatic variant cell lines of the B16 murine melanoma.

Computer-based image analysis offers a wide range of techniques which can be used to make objective and reproducible detection and measurement of subvisual features of microscopic images of cells. We describe here a prototype imaging system for specimen analysis. Using this system, studies have been carried out on the low metastasis variant F1 and high metastasis variant BL6 of the B16 murine melanoma. Cell cycle analyses have been carried out based on the measurement of integrated nuclear density, nuclear area and nucleocytoplasmic ratio of cells stained using standard procedures. It has been possible to discriminate between the two cell populations on the basis of ploidy. The two cell lines had a similar proportion of cells in the S-phase.

Animals↗
PubMed1991

Requirement of yeast fimbrin for actin organization and morphogenesis in vivo.

The SAC6 gene was found by suppression of a yeast actin mutation. Its protein product, Sac6p (previously referred to as ABP67), was independently isolated by actin-filament affinity chromatography and colocalizes with actin in vivo. Thus Sac6p binds to actin in vitro, and functionally associates with actin structures involved in the development and maintenance of cell polarity in vivo. We report here that Sac6p is an actin-filament bundling protein 43% identical in amino-acid sequence to the vertebrate bundling protein fimbrin. This yeast fimbrin homologue contains two putative actin-binding regions homologous to domains of dystrophin, beta-spectrin, filamin, actin-gelation protein and alpha-actinin. Mutants lacking Sac6p do not form normal actin structures and are defective in morphogenesis. These findings demonstrate an in vivo role for the well-documented biochemical interaction between fimbrin and actin.

Actin Cytoskeleton↗
PubMed1990

Purification of profilin from Saccharomyces cerevisiae and analysis of profilin-deficient cells.

We have isolated profilin from yeast (Saccharomyces cerevisiae) and have microsequenced a portion of the protein to confirm its identity; the region microsequenced agrees with the predicted amino acid sequence from a profilin gene recently isolated from S. cerevisiae (Magdolen, V., U. Oechsner, G. Müller, and W. Bandlow. 1988. Mol. Cell. Biol. 8:5108-5115). Yeast profilin resembles profilins from other organisms in molecular mass and in the ability to bind to polyproline, retard the rate of actin polymerization, and inhibit hydrolysis of ATP by monomeric actin. Using strains that carry disruptions or deletions of the profilin gene, we have found that, under appropriate conditions, cells can survive without detectable profilin. Such cells grow slowly, are temperature sensitive, lose the normal ellipsoidal shape of yeast cells, often become multinucleate, and generally grow much larger than wild-type cells. In addition, these cells exhibit delocalized deposition of cell wall chitin and have dramatically altered actin distributions.

Actins↗
PubMed1990

CDC42 and CDC43, two additional genes involved in budding and the establishment of cell polarity in the yeast Saccharomyces cerevisiae.

Budding in the yeast Saccharomyces cerevisiae involves a polarized deposition of new cell surface material that is associated with a highly asymmetric disposition of the actin cytoskeleton. Mutants defective in gene CDC24, which are unable to bud or establish cell polarity, have been of great interest with regard to both the mechanisms of cellular morphogenesis and the mechanisms that coordinate cell-cycle events. To gain further insights into these problems, we sought additional mutants with defects in budding. We report here that temperature-sensitive mutants defective in genes CDC42 and CDC43, like cdc24 mutants, fail to bud but continue growth at restrictive temperature, and thus arrest as large unbudded cells. Nearly all of the arrested cells appear to begin nuclear cycles (as judged by the occurrence of DNA replication and the formation and elongation of mitotic spindles), and many go on to complete nuclear division, supporting the hypothesis that the events associated with budding and those of the nuclear cycle represent two independent pathways within the cell cycle. The arrested mutant cells display delocalized cell-surface deposition associated with a loss of asymmetry of the actin cytoskeleton. CDC42 maps distal to the rDNA on chromosome XII and CDC43 maps near lys5 on chromosome VII.

Cell Cycle↗
PubMed1989

A yeast actin-binding protein is encoded by SAC6, a gene found by suppression of an actin mutation.

The protein encoded by SAC6, a gene that can mutate to suppress a temperature-sensitive defect in the yeast actin gene, has been identified as a 67-kilodalton actin-binding protein (ABP 67) that associates with all identifiable actin structures. This finding demonstrates the in vivo functional importance of the actin-ABP 67 interaction previously established in vitro and illustrates the use of suppressor analysis to identify physically interacting proteins.

Actins↗
PubMed1989

Dominant suppressors of yeast actin mutations that are reciprocally suppressed.

A gene whose product is likely to interact with yeast actin was identified by the isolation of pseudorevertants carrying dominant suppressors of the temperature-sensitive (Ts) act1-1 mutation. Of 30 independent revertants analyzed, 29 were found to carry extragenic suppressor mutations and of these, 24/24 tested were found to be linked to each other. This linkage group identifies a new gene SAC6, whose product, by several genetic criteria, is likely to interact intimately with actin. First, although act1-1 sac6 strains are temperature-independent (Ts+), 4/17 sac6 mutant alleles tested are Ts in an ACT1+ background. Moreover, four Ts+ pseudorevertants of these ACT1+ sac6 mutants carry suppressor mutations in ACT1; significantly, three of these are again Ts in a SAC6+ background, and are most likely new act1 mutant alleles. Thus, mutations in ACT1 and SAC6 can suppress each other's defects. Second, sac6 mutations can suppress the Ts defects of the act1-1 and act1-2, but not act1-4, mutations. This allele specificity indicates the sac6 mutations do not suppress by simply bypassing the function of actin at high temperature. Third, act1-4 sac6 strains have a growth defect greater than that due to either of the single mutations alone, again suggesting an interaction between the two proteins. The mutant sac6 gene was cloned on the basis of dominant suppression from an act1-1 sac6 mutant library, and was then mapped to chromosome IV, less than 2 cM from ARO1.

Actins↗
PubMed1988

Functions of microtubules in the Saccharomyces cerevisiae cell cycle.

We used the inhibitor nocodazole in conjunction with immunofluorescence and electron microscopy to investigate microtubule function in the yeast cell cycle. Under appropriate conditions, this drug produced a rapid and essentially complete disassembly of cytoplasmic and intranuclear microtubules, accompanied by a rapid and essentially complete block of cellular and nuclear division. These effects were similar to, but more profound than, the effects of the related drug methyl benzimidazole carbamate (MBC). In the nocodazole-treated cells, the selection of nonrandom budding sites, the formation of chitin rings and rings of 10-nm filaments at those sites, bud emergence, differential bud enlargement, and apical bud growth appeared to proceed normally, and the intracellular distribution of actin was not detectably perturbed. Thus, the cytoplasmic microtubules are apparently not essential for the establishment of cell polarity and the localization of cell-surface growth. In contrast, nocodazole profoundly affected the behavior of the nucleus. Although spindle-pole bodies (SPBs) could duplicate in the absence of microtubules, SPB separation was blocked. Moreover, complete spindles present at the beginning of drug treatment appeared to collapse, drawing the opposed SPBs and associated nuclear envelope close together. Nuclei did not migrate to the mother-bud necks in nocodazole-treated cells, although nuclei that had reached the necks before drug treatment remained there. Moreover, the double SPBs in arrested cells were often not oriented toward the budding sites, in contrast to the situation in normal cells. Thus, microtubules (cytoplasmic, intranuclear, or both) appear to be necessary for the migration and proper orientation of the nucleus, as well as for SPB separation, spindle function, and nuclear division.

Actins↗
PubMed1985

Chronic pain: electromechanical recording device for measuring patients' activity patterns.

Many authors have recommended the development and use of automated recording devices as alternatives to self-report measures of activity patterns in chronic pain patients. An electromechanical device is described that can be used to measure downtime or uptime in chronic pain patients. This monitor has several advantages over mercury tilt-switch devices including freedom from plane dependence, resistance to artifact associated with rapid or vigorous movements, and the flexibility to permit conceptualization of sitting time as either uptime or downtime, depending upon placement of the position switch. The monitor consists of a miniature electronic timer, a switching delay circuit and battery pack, an electromechanical position switch, a belt with carrying cases, and a battery recharger. The device has high reliability (agreement coefficients of 1.0) and concurrent validity (r = 0.99) for both downtime and uptime assessments. Research applications and clinical use of this device are discussed as well as directions for the further development of automated recording devices.

Chronic Disease↗
PubMed1984

Structural rearrangements of tubulin and actin during the cell cycle of the yeast Saccharomyces.

The distribution of actin and tubulin during the cell cycle of the budding yeast Saccharomyces was mapped by immunofluorescence using fixed cells from which the walls had been removed by digestion. The intranuclear mitotic spindle was shown clearly by staining with a monoclonal antitubulin; the presence of extensive bundles of cytoplasmic microtubules is reported. In cells containing short spindles still entirely within the mother cells, one of the bundles of cytoplasmic microtubules nearly always extended to (or into) the bud. Two independent reagents (anti-yeast actin and fluorescent phalloidin) revealed an unusual distribution of actin: it was present as a set of cortical dots or patches and also as distinct fibers that were presumably bundles of actin filaments. Double labeling showed that at no stage in the cell cycle do the distributions of actin and tubulin coincide for any significant length, and, in particular, that the mitotic spindle did not stain detectably for actin. However, both microtubule and actin staining patterns change in a characteristic way during the cell cycle. In particular, the actin dots clustered in rings about the bases of very small buds and at the sites on unbudded cells at which bud emergence was apparently imminent. Later in the budding cycle, the actin dots were present largely in the buds and, in many strains, primarily at the tips of these buds. At about the time of cytokinesis the actin dots clustered in the neck region between the separating cells. These aspects of actin distribution suggest that it may have a role in the localized deposition of new cell wall material.

Actins↗
PubMed1984

Relationship of actin and tubulin distribution to bud growth in wild-type and morphogenetic-mutant Saccharomyces cerevisiae.

The distribution of actin in wild-type cells and in morphogenetic mutants of the budding yeast Saccharomyces cerevisiae was explored by staining cells with fluorochrome-labeled phallotoxins after fixing and permeabilizing the cells by several methods. The actin appeared to be localized in a set of cortical spots or patches, as well as in a network of cytoplasmic fibers. Bundles of filaments that may possibly correspond to the fibers visualized by fluorescence were observed with the electron microscope. The putative actin spots were concentrated in small and medium-sized buds and at what were apparently the sites of incipient bud formation on unbudded cells, whereas the putative actin fibers were generally oriented along the long axes of the mother-bud pairs. In several morphogenetic mutants that form multiple, abnormally elongated buds, the actin patches were conspicuously clustered at the tips of most buds, and actin fibers were clearly oriented along the long axes of the buds. There was a strong correlation between the occurrence of active growth at particular bud tips and clustering of actin spots at those same tips. Near the end of the cell cycle in wild-type cells, actin appeared to concentrate (as a cluster of spots or a band) in the neck region connecting the mother cell to its bud. Observations made using indirect immunofluorescence with a monoclonal anti-yeast-tubulin antibody on the morphogenetic mutant cdc4 (which forms multiple, abnormally elongated buds while the nuclear cycle is arrested) revealed the surprising occurrence of multiple bundles of cytoplasmic microtubules emanating from the one duplicated spindle-pole body per cell. It seems that most or all of the buds contain one or more of these bundles of microtubules, which often can be seen to extend to the very tips of the buds. These observations are consistent with the hypotheses that actin, tubulin, or both may be involved in the polarization of growth and localization of cell-wall deposition that occurs during the yeast cell cycle.

Actins↗
PubMed1983

[Dual organization of sensorimotor activity].

An anatomical symmetry of the bilateral organism and the functional assignment of brain hemispheres each to one side of the body are preconditions for sensorimotor brain localization. The invariant system elements necessary for this consist of "modules". These are associations of about 2 500 cortical cells in each case. When we refer to duality, we do not mean dualistically separated, but mutually assigned or mutually coordinated half-systems. The mainly decussated sensory and nervous systems of the vertebrates probably give rise to their rhythmic gait coordinated in relation to the axis of the body. Compared to such vital movements, human motor activity varies between voluntary action and involuntary expression. Cortical projection duplicates in the form of secondary or supplementary sensorimotor areas are ascribed hypothetically to an identifiable somatosensory sensation. A development leading to man is likely to have commenced as the brain halves of a pithecanthropus gained asymmetric degrees of freedom in relation to their somatotopic binding to the body. This phylogenetic differentiation led to a dual disjunction of the cerebral hemispheres which enabled a side-different "either/or" in human actions. Speech and thought as transitive order forms are also based on functional asymmetries of the human cerebrum.

Cerebral Cortex↗