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Results for “evolution of cell shape”

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At least 55 records · Page 3Linked to original sources
PubMed1993

Quantitative pathology of the cervical intraepithelial neoplasia.

The objective of this study was to determine the efficiency of quantitative microscopy as a method of estimating the progressive cervical intraepithelial neoplasia (CIN). The research design consisted of an analytical study of cases and controls. The study took place in the Pathology Services of 4 hospitals in our region and the Image Processing and Cytometry Service of the university. Two subsequent cervical biopsies taken more than six months apart belonging to 42 patients diagnosed for CIN were studied. As a reference, 20 normal biopsies were taken. Quantitative Microscopy by Digital Image Processing was applied to each one of the three epithelial layers. Cellular orientation, shape factor, perimeter, area and nuclear diameter were taken as maturative markers and the cellularity as a marker of proliferative change. The cellularity in the middle layer of the epithelium allowed us to distinguish patients with CIN (22.9 +/- 6.9) from normal cases (4.6 +/- 2.3) in 93% of the cases. According to this variable in the middle and superficial layers, in 95.2% of the cases 4 new groups were automatically defined. The shape factor of the cells in the superficial cell layer enabled us, although with low sensitivity (45.45%), to predict evolution towards cancer in 65.5% of the cases. In conclusion the validity of Quantitative Microscopy as an objective marker of structural change in the CIN was verified although its value as a predictive marker of evolution is low.

Female↗
PubMed1981

Study of two cases of ring 13 chromosome using high-resolution banding.

The chromosomes of two patients with ring 13 (r13) were studied using high-resolution RBG banding of prometaphase cells. The rings of the two patients differ slightly in breakpoints. Cell with multiple single, double-sized rings, quadruple-sized rings, rod- and ring-shaped fragments, and fragments showing varied states of condensation were seen, as were cells monosomic for chromosome 13. The evolution of these cell lines as a result of sister chromatid exchange, nondisjunction, ring breakage, and premature chromosome condensation is discussed. Clinical features of these patients reflect the heterogeneity of phenotype for r13 patients. Each case includes a feature of trisomy 13. The significance of mosaicism of cell lines in patients bearing ring chromosomes is considered with respect to variation in clinical findings.

Abnormalities, Multiple↗
PubMed1994

The evolution of echinoderm development is driven by several distinct factors.

We analyzed a comparative data base of gene expression, cell fate specification, and morphogenetic movements from several echinoderms to determine why developmental processes do and do not evolve. Mapping this comparative data onto explicit phylogenetic frameworks revealed three distinct evolutionary patterns. First, some evolutionary differences in development correlate well with larval ecology but not with adult morphology. These associations are probably not coincidental because similar developmental changes accompany similar ecological transformations on separate occasions. This suggests that larval ecology has been a potent influence on the evolution of early development in echinoderms. Second, a few changes in early development correlate with transformations in adult morphology. Because most such changes have occurred only once, however, it is difficult to distinguish chance associations from causal relationships. And third, some changes in development have no apparent phenotypic consequences and do not correlate with obvious features of either life history or morphology. This suggests that some evolutionary changes in development may evolve in a neutral or nearly neutral mode. Importantly, these hypotheses make specific predictions that can be tested with further comparative data and by experimental manipulations. Together, our phylogenetic analyses of comparative data suggest that at least three distinct evolutionary mechanisms have shaped early development in echinoderms.

Animals↗
PubMedDate not supplied

The effects of tumor sera on cell shape and photosynthesis of Euglena gracilis.

Cells of Euglena gracilis treated with human sera show a marked change in cell shape: Fully elongated cells have nearly totally been transformed to disk-shaped cells. This serum-mediated contraction is followed by irreversible cytolysis. Disintegration of chloroplast membranes leads to decreased photosynthetic O2 evolution. Sera from humans suffering from tumors reveal higher lytic activities than sera from individuals not suffering from tumors. Heating sera at 56 degrees C for 10 min or addition of EDTA destroyed or inhibited, respectively, the lytic activities completely. Polysaccharides transformed in polyanions by sulphatisation like dextransulphates or heparin seem to protect Euglena against serum activities. The effects described for human sera are believed to display the role of the complement pathway in the cytolysis of Euglena gracilis.

Animals↗
PubMed1997

The shape of cell death.

Cell death, a scheduled event during development and tissue turnover, or the ultimate consequence of toxic or pathologic insults seems to involve a relatively limited number of execution pathways. This reflects the evolution of an organized sequence of events perhaps converging onto final common pathways that are used to dispose of unwanted or injured cells. In many cases, the ordered execution of this internal death program leads to typical morphological and biochemical changes that have been termed apoptosis. Apoptosis, often equated with developmental or programmed cell death, has been opposed to unscheduled or accidental cell lysis/necrosis. However, increasing evidence suggests that the two forms of cell demise share similar characteristics, at least in the signaling and early progression phase. Recent studies have shown that, when the intensity of the insult is very high and/or when ATP generation is deficient, cells fail to execute the ordered changes ensuing in apoptosis. Then cell lysis/necrosis supervenes before the processes leading to nuclear condensation and exposure of surface molecules can be completed. Thus, apoptosis and necrosis seem to represent only different shapes of cell demise, resulting from a more or less complete execution of the internal death program.

Animals↗
PubMed1992

Proteasomes: protein and gene structures.

Proteasomes are ring- or cylinder-shaped particles that have a sedimentation coefficient of 20S and are composed of a characteristic set of small polypeptides. These particles have a latent multicatalytic proteinase activity. Recently, proteasomes were found to combine reversibly with multiple protein components to form 26S proteolytic complexes that catalyze ATP-dependent, selective breakdown of proteins ligated with ubiquitin. This suggests that the 26S complexes are a new type of ATP-requiring protease in eukaryotic cells. We have studied the structures of various eukaryotic proteasomes at the molecular level by physicochemical and recombinant DNA techniques and have proposed that the gross structures of proteasomes, such as their size and shape, have been highly conserved during evolution. Proteasome subunits appear to be encoded by a family of homologous genes named the "proteasome gene family," which may have evolved from a common ancestral gene. Evidence obtained by genetic analyses in yeast and studies on the levels of proteasome expression in various eukaryotic cells indicates that proteasomes have essential roles in the cell. In this review, we summarize available information on the protein and gene structures of proteasomes and discuss the biological functions of proteasomes.

Amino Acid Sequence↗
PubMed1999

Hemoperitoneum due to a ruptured gastric stromal tumor.

BACKGROUND/AIMS: Gastrointestinal stromal tumors form a group of uncommon neoplasms originated from pluripotential mesenchymal cells. Many patients are asymptomatic and the tumor is discovered during an abdominal operation. Massive intraperitoneal bleeding is an exceptional complication associated with high mortality rates. Our aim is to report a case of a gastric stromal tumor in an 83-year-old patient presenting with intraperitoneal hemorrhage and hypovolemic shock, successfully operated. METHODS: Emergency laparotomy showed a hemoperitoneum caused by rupture of a large exogastric tumor attached to the greater curvature. Total gastrectomy and esophagojejunostomy was performed. RESULTS: Histological examination revealed proliferation of spindle-shaped cells but immunocytochemistry failed to identify specific markers of smooth muscle and neural cells. Diagnosis of a gastric stromal tumor was made. Postoperative evolution was uncomplicated. CONCLUSION: Gastric stromal tumor is a relatively rare neoplasm of mesenchymal origin whose nature and prognosis is unclear.

Aged↗
PubMed2025

Pleiotropic mutational effects on function and stability constrain the antigenic evolution of influenza hemagglutinin.

The evolution of human influenza virus hemagglutinin (HA) involves simultaneous selection to acquire antigenic mutations that escape population immunity while preserving protein function and stability. Epistasis shapes this evolution, as an antigenic mutation that is deleterious in one genetic background may become tolerated in another. However, the extent to which epistasis can alleviate pleiotropic conflicts between immune escape and protein function/stability is unclear. Here, we measure how all amino acid mutations in the HA of a recent human H3N2 influenza strain affect its cell entry function, acid stability, and neutralization by human serum antibodies. We find that epistasis has entrenched certain mutations so that reverting to the ancestral amino acid identity in earlier strains is no longer tolerated. Epistasis has also enabled the emergence of antigenic mutations that were detrimental to HA's cell entry function in earlier strains. However, epistasis appears insufficient to overcome the pleiotropic costs of antigenic mutations that impair HA's stability, explaining why some mutations that strongly escape human antibodies never fix in nature. Our results refine our understanding of the mutational constraints that shape recent H3N2 influenza evolution: epistasis can enable antigenic change, but pleiotropic effects can restrict its trajectory.

Journal Article↗
PubMed1996

Amyloid tumors of the lung--an immunocytoma?

Amyloid tumors are nodular amyloid depositions usually limited to one organ, which often develop without a known cause. In most cases they may be observed as being situated in the lung, the larynx, the skin, the urinary bladder and in the region of the orbita, and are restricted to these organs. In the present study, we report on two cases of pulmonal amyloid tumors which after immunohistochemical investigation revealed a clonal evolution of light chain restricted plasma cells and lymphocytes corresponding to a localized primary extranodal lymphoplasmacytic immunocytoma, with only few vital tumor cells among abundant tumor-shaped amyloid. Additionally, using polymerase chain reaction (PCR) to investigate IgH gene rearrangement, clonality of the tumor cells could be demonstrated in both cases.

Aged↗
PubMed2000

The skeletal muscle alpha-actin gene of channel catfish (Ictalurus punctatus) and its association with piscine specific SINE elements.

The alpha-actin gene of channel catfish (Ictalurus punctatus) was cloned and sequenced. The gene has a similar organization and exhibited a high level of sequence similarity to those from other vertebrate animals. The upstream region of the alpha-actin gene included a TATA box, a CAAT box, three E-boxes, and a CArG box. Nested deletion segments containing these transcriptional motifs were fused to the reporter gene chloramphenicol acetyl transferase (CAT). Transfection of the clones into C2C12 cells indicated that all these motifs are required for transcriptional activities. The channel catfish alpha-actin gene is associated with two distinct short interspersed repetitive elements (SINEs). The first SINE element showed high levels of sequence similarity to the zebrafish Mermaid element, while the second SINE element is not similar to the Mermaid element except for an 8bp sequence CCCCGTGC suggesting their evolutionary linkage. However, the second SINE element appeared to co-exist with the Mermaid element in most cases and therefore was designated as the Merman element. Approximately 9000 copies and 1200 copies of the Mermaid and Merman elements exist per haploid channel catfish genome, respectively. BLAST searches indicated that both the Mermaid and the Merman elements were frequently associated with gene sequences, mostly those of aquatic animals, suggesting their evolutionary origin in association with aquatic organisms and their function in shaping the evolution of genomes in aquatic animals.

Actins↗
PubMed1998

Mollicutes-wall-less bacteria with internal cytoskeletons.

The structure and motility of the Mollicutes (Spiroplasma, Mycoplasma, and Acholeplasma) are briefly reviewed. The data are presented from the perspective of prokaryotic and eukaryotic motors, cytoskeletons, and cell motility. The Mollicutes are eubacteria derived from Clostridia by regressive evolution and genome reduction to produce the smallest and simplest free-living and self-replicating cells. Structurally, the Mollicutes are characterized by a complete lack of a cell wall and the presence of an internal cytoskeleton. Spiroplasma, which are helical cells with a flat, ribbon-like cytoskeleton, are amenable to structural and geometrical analysis. Motility and shape changes can be explained and modeled by the cytoskeleton acting as a linear motor.

Acholeplasma↗
PubMed1998

Distribution and functional diversification of the ras superfamily in Saccharomyces cerevisiae.

The recent availability of the full Saccharomyces cerevisiae genome sequence offers a first opportunity to analyze the composition, function and evolution of GTPases in the ras-p21 superfamily. This superfamily in yeast is composed of 29 proteins divided into five families: ras with four sequences implicated in cell signalling; rho, six genes related to the cell shape machinery; ypt-rab, ten proteins with different roles in intracellular trafficking; arf-sar, seven proteins related to vesicular trafficking in secretory pathways; and ran, two proteins acting as components of the nuclear transport system. The superfamily covers a wide range of cellular functions from signalling to intracellular trafficking, while conserving the structural framework and a common mechanism of GTP hydrolysis.

Evolution, Molecular↗
PubMed1999

Molecular and evolutionary computation: the tug of war between context freedom and context sensitivity.

Proteins and nucleic acids constitute a vast potential reservoir of pattern recognizers that operate on the basis of shape complementarity. It is possible to construct models of computing in which these shape-based interactions contribute directly to recognition of signal patterns at the device (or cell) level. The input-output transform is molded by variation-selection evolution. Such models provide clues as to the organizational features that enable biomolecular matter to acquire nonevolutionary modes of problem solving through the evolutionary process. The requisite organizations are characterized by a high dimensionality that allows them to simultaneously exhibit aspects of context-sensitivity and context-independence.

Animals↗
PubMed1996

Isopycnic Focusing Study of the Transient State in the Settling of Colloidal Particles

Various effective field forces can generate the concentrating flux of the colloidal particles. Centrifugal field forces were used in this work to study the kinetics of the transport phenomena and the effect of interparticle interactions of the model silica suspension. Isopycnic focusing of the colored density marker beads was used to visualize the evolution and final quasi-equilibrium shape of the density gradient formed in silica suspension. Many operational parameters and experimental conditions (thickness of the liquid layer in measuring cells, intensity of the centrifugal forces, average concentration of the silica particles, and geometrical shape of the measuring cells) were tested to evidence their influence on the concentration and density gradient formation. The main objective was to apprehend the processes governing isoperichoric focusing in thin layers under model static conditions which is necessary for the optimization of isoperichoric focusing field-flow fractionation dynamic experiments carried out under conditions of hydrodynamical flow as an active factor of the separation by focusing effect. The experimental results were compared with the hypothetical model of noninteracting particles to demonstrate the effect of the actual interparticle interactions.

Journal Article↗
PubMed1999

A morphological study of the cochlear nuclei of the pigeon (Columba livia).

The pigeon cochlear nucleus angularis (NA) and nucleus magnocellularis (NM) were analyzed with Golgi and Nissl techniques. NA was divided into a medial NAm and NA proper, which could be subdivided further into an intermediate NAi and lateral NAl. NAm contained a mostly homogeneous population of a unique multipolar cell type with very short dendrites and large somatic spines. NA proper contained four cell types: large, medium, and small multipolars, and medium bipolar. The medium multipolar cells were most common, and resembled the multipolar cells of the mammalian ventral cochlear nucleus. NM presented a homogenous appearance with a mediolateral gradient of cell size and shape. Medially located higher best frequency NM principal cells had round cell bodies with small somatic spines and few dendrites. By comparison, laterally located low best frequency NM stellate cells had more dendrites and spindle shaped cell bodies. The similarities between the cell types of NA and the cell types in the cochlear nuclei of other amniote vertebrates may be due to homology or convergent evolution.

Animals↗
PubMed1998

Biochemistry of the extracellular matrix of Volvox.

The volvocine algae range in complexity from unicellular Chlamydomonas to multicellular organisms in the genus Volvox. The transition from unicellularity to multicellularity in the Volvocales is a recent event in evolution. Thus, these organisms provide a unique opportunity for exploring the development of a complex extracellular matrix (ECM) from the cell wall of a unicellular ancestor. The ECM of Volvox is divided into four main zones: The flagellar, boundary, cellular, and deep zones. Each zone is defined by ultrastructure and by characteristic ECM glycoproteins. Volvox ECM is modified under developmental control or in response to external stimuli, like the sex-inducing pheromone or stress factors. The structures of more than 10 ECM glycoproteins from a single species of Volvox are now known in molecular detail and are compared to other algal and plant cell wall/ECM glycoproteins. Although usually classified as hydroxyproline-rich glycoproteins, the striking feature of all algal ECM glycoproteins is a modular composition. Rod-shaped hydroxyproline-rich modules are combined with hydroxyproline-free domains that meet the multiple functional requirements of a complex ECM. The algal ECM provides another example of the combinatorial advantage of shuffling modules that is so evident in the evolution of the metazoan ECMs.

Algal Proteins↗
PubMed1994

Modulation of cardiac myocyte phenotype in vitro by the composition and orientation of the extracellular matrix.

Cellular phenotype is the result of a dynamic interaction between a cell's intrinsic genetic program and the morphogenetic signals that serve to modulate the extent to which that program is expressed. In the present study we have examined how morphogenetic information might be stored in the extracellular matrix (ECM) and communicated to the neonatal heart cell (NHC) by the cardiac alpha 1 beta 1 integrin molecule. A thin film of type I collagen (T1C) was prepared with a defined orientation. This was achieved by applying T1C to the peripheral edge of a 100 mm culture dish. The T1C was then drawn across the surface of the dish in a continuous stroke with a sterile cell scraper and allowed to polymerize. When NHCs were cultured on this substrate, they spread, as a population, along a common axis in parallel with the gel lattice and expressed an in vivo-like phenotype. Individual NHCs displayed an elongated, rod-like shape and disclosed parallel arrays of myofibrils. These phenotypic characteristics were maintained for at least 4 weeks in primary culture. The evolution of this tissue-like organizational pattern was dependent upon specific interactions between the NHCs and the collagen-based matrix that were mediated by the cardiac alpha 1 beta 1 integrin complex. This conclusion was supported by a variety of experimental results. Altering the tertiary structure of the matrix or blocking the extracellular domains of either the cardiac alpha 1 or beta 1 integrin chain inhibited the expression of the tissue-like pattern of organization. Neither cell-to-cell contact or contractile function were necessary to induce the formation of the rod-like cell shape. However, beating activity was necessary for the assembly of a well-differentiated myofibrillar apparatus. These data suggest that the cardiac alpha 1 beta 1 integrin complex serves to detect and transduce phenotypic information stored within the tertiary structure of the surrounding matrix.

Animals↗