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PubMed2006

Vacillating breathing and tumbling of vesicles under shear flow.

The dynamics of vesicles under a shear flow are analyzed analytically in the small deformation regime. We derive two coupled nonlinear equations which describe the vesicle orientation in the flow and its shape evolution. A new type of motion is found, namely, a "vacillating-breathing" mode: the vesicle orientation undergoes an oscillation around the flow direction, while the shape executes breathing dynamics. This solution coexists with tumbling. Moreover, we provide an explicit expression for the tumbling threshold. A rheological law for a dilute vesicle suspension is outlined.

Cell Physiological Phenomena↗
PubMed2005

Perforin and Fas cytolytic pathways coordinately shape the selection and diversity of CD8+-T-cell escape variants of influenza virus.

Antigenic variation is a viral strategy exploited to promote survival in the face of the host immune response and represents a major challenge for efficient vaccine development. Influenza viruses are pathogens with high transmissibility and mutation rates, enabling viral escape from immunity induced by prior infection or vaccination. Intense selection from neutralizing antibody drives antigenic changes in the surface glycoproteins, resulting in emergence of new strains able to reinfect hosts immune to previously circulating viruses. CD8+ cytotoxic T cells (CTLs) also provide protective immunity from influenza virus infection and may contribute to the antigenic evolution of influenza viruses. Utilizing mice transgenic for an influenza virus NP366-374 peptide-specific T-cell receptor, we demonstrated that the respiratory tract is a suitable site for generation of escape variants of influenza virus selected by CTL in vivo. In this report the contributions of the perforin and Fas pathways utilized by influenza virus-specific CTLs in viral clearance and selection of CTL escape variants have been evaluated. While transgenic CTLs deficient in either perforin- or Fas-mediated pathways are efficient in initial pulmonary viral control, variant virus emergence was observed in all the mice studied, although the spectrum of viral CTL escape variants selected varied profoundly. Thus, a less-restricted repertoire of escape variants was observed in mice with an intact perforin cytotoxic pathway compared with a limited variant diversity in perforin pathway-deficient mice, although maximal variant diversity was observed in mice having both Fas and perforin pathways intact. We conclude that selection of viral CTL escape variants reflects coordinate action between the tightly controlled perforin/granzyme pathway and the more promiscuous Fas/FasL pathway.

Animals↗
PubMed2002

Mycoplasmosis and immunity of fish and reptiles.

Advances in molecular phylogenetics have enabled reconstruction of the most likely chronology of events in prokaryotic evolution and correlation with the paleontologic record with increasing precision. Mycoplasmas probably evolved from clostridial ancestors by genome reduction leading to obligate parasitism of host cells. The vertebrate hosts present at the time of the origin of mycoplasmas about 400 million years ago were fish, and later amphibians and reptiles, whose descendants possess most elements of vertebrate innate and adaptive immunity. Successful colonization of those poikilothermous ("cold-blooded") hosts must have involved adaptation to those defenses, shaping mycoplasma-host interactions for more than 125 million years before the earliest emergence of mammals. That history illuminates one aspect of the potential significance of mycoplasmosis of poikilothermous vertebrates to health and disease of other hosts including humans.

Animals↗
PubMedDate not supplied

[Multiple myeloma and acute leukemia. Simultaneous evolution of plasmacyte and myelomonocytic clones].

The authors report two cases of acute myelo-monocytic leukemia occuring during the course of multiple myeloma treated by local radiotherapy and melphalan. Both patients underwent a complete remission of their myeloma for 27 and 78 months. The myeloma relapsed suddenly in the form of an acute leukemia. In one case, the onset of acute leukemia was preceded by a syndrome of marrow failure with numerous crown-shaped sideroblasts and an excess of myeloblasts in the marrow. This stage lasted two years. The biochemical abnormalities of the red cells usually associated with refractory anemia and preleukemic conditions were present in the other case.

Aged↗
PubMed1994

Dyskeratosis congenita is a chromosomal instability disorder.

Dyskeratosis congenita (DC) is a rare inherited disorder characterized by dystrophic changes in the skin and mucous membranes, bone marrow failure, and a predisposition to malignancy. In the majority of families the pattern of inheritance of DC has been compatible with X-linkage, the most likely location being Xq28. The primary defect responsible for this disease remains unknown. As DC shares many features (congenital abnormalities, bone marrow failure) with the chromosomal instability disorder. Fanconi's anaemia (FA), several studies have focused on cytogenetic features in DC. Unlike in FA, cytogenetic studies on peripheral blood lymphocytes have shown no significant difference between DC and normal lymphocytes with or without prior incubation with clastogens (bleomycin, diepoxybutane, mitomycin-c, 4-nitroquinoline-1-oxide). However, studies on DC fibroblasts have shown abnormalities in both morphology (polygonal cell shape, ballooning, dendritic-like projections) and growth rate (doubling time about twice normal), as well as numerous unbalanced chromosomal rearrangements (dicentrics, tricentrics, translocations) in the absence of any clastogenic agents. Bone marrow metaphases from one out of three patients studied (the eldest of the three) also showed unbalanced chromosomal rearrangements in the absence of any clastogens. Cell-specific difference and a higher rate of chromosomal rearrangements in the older patients appear to correlate with the clinical evolution of the disease. These findings suggest that the DC defect predisposes DC cells to developing chromosomal rearrangements.

Adolescent↗
PubMed1991

Cytoskeletal origins in sulfur-metabolizing archaebacteria.

Several of the thermophilic acidopholic sulfur-metabolizing archaebacteria lack rigid cell walls. Their irregular shapes were maintained by an internal mechanism, presumably a cytoskeleton. Apparently this is an adaptation for respiration upon elemental sulfur, which requires cell contact since sulfur is insoluble in water. Also, we speculate that there could be additional functions of the cytoskeleton, such as prevention of osmotic cell lysis, thermal stabilization of enzymes, and improvements in metabolic efficiency through specific enzyme positioning. Such a well-developed cytoskeleton, evolving first in thermophilic archaebacteria, could have been a preadaptation for the evolution of eukaryotic cells.

Archaea↗
PubMed2000

The rice R gene family: two distinct subfamilies containing several miniature inverted-repeat transposable elements.

The R and B genes of maize regulate the anthocyanin biosynthetic pathway and constitute a small gene family whose evolution has been shaped by polyploidization and transposable element activity. To compare the evolution of regulatory genes in the distinct but related genomes of rice and maize, we previously isolated two R homologues from rice (Oryza sativa). The Ra1 gene on chromosome 4 can activate the anthocyanin pathway, whereas the Rb gene, of undetermined function, maps to chromosome 1. In this study, rice R genes have been further characterized. First, we found that an Rb cDNA can induce pigmentation in maize suspension cells. Second, another rice R homologue (Ra2) was identified that is more closely related to Ra1 than to Rb. Domesticated rice and its wild relatives harbor multiple Ra-like and Rb-like genes despite the fact that rice is a true diploid with the smallest genome of all the grass species analyzed to date. Finally, several miniature inverted-repeat transposable elements (MITEs) were found in R family members. Their possible role in hastening the divergence of R genes is discussed.

Amino Acid Sequence↗
PubMed1996

Morphological stages of pilomatricoma.

In 1983, Ackerman proposed that pilomatricoma represents an infundibular-matrix cyst in its early stages. To study the evolution of this cystic neoplasm, we examined 118 lesions from 116 patients with pilomatricoma histopathologically and categorized the lesions into four distinct and chronological stages: early, fully developed, early regressive, and late regressive. Early lesions (eight cases) were small cystic structures lined by squamoid and basaloid epithelium containing keratin filaments and faulty hair matrix material composed of shadow cells. Fully developed lesions (27 cases) were large neoplasms lined by basaloid epithelium at their periphery, and within, composed of irregularly shaped, densely packed zones of cornified masses containing shadow cells. Early regressive lesions (37 cases) had no apparent epithelial lining but did have basaloid cell foci at the periphery; within, they were composed of pink hair matrix material with shadow cells surrounded by granulation tissue with inflammatory infiltrate and multinucleated histiocytic giant cells. Late regressive lesions (42 cases) had no epithelial component and were composed of irregularly shaped, partially confluent masses of faulty hair material, and calcified (and sometimes metaplastically ossified) shadow cells embedded in a desmoplastic stroma, with little or no inflammatory infiltrate. In four cases, there was a relatively large dermal nodule composed of several interconnected lobules that consisted largely of basaloid cells with only a few areas of shadow cells. We interpreted these lesions as proliferating pilomatricomas. Based upon our histopathologic findings, we propose that pilomatricomas may be categorized into four distinct morphological stages and that these stages reflect the "life" of a pilomatricoma. Thus, the lesion begins as an infundibular matrix cyst and ends up as a calcified and ossified nodule with no visible epithelial component.

Adolescent↗
PubMed2006

General model, based on two mixed weibull distributions of bacterial resistance, for describing various shapes of inactivation curves.

Cells of Listeria monocytogenes or Salmonella enterica serovar Typhimurium taken from six characteristic stages of growth were subjected to an acidic stress (pH 3.3). As expected, the bacterial resistance increased from the end of the exponential phase to the late stationary phase. Moreover, the shapes of the survival curves gradually evolved as the physiological states of the cells changed. A new primary model, based on two mixed Weibull distributions of cell resistance, is proposed to describe the survival curves and the change in the pattern with the modifications of resistance of two assumed subpopulations. This model resulted from simplification of the first model proposed. These models were compared to the Whiting's model. The parameters of the proposed model were stable and showed consistent evolution according to the initial physiological state of the bacterial population. Compared to the Whiting's model, the proposed model allowed a better fit and more accurate estimation of the parameters. Finally, the parameters of the simplified model had biological significance, which facilitated their interpretation.

Acids↗
PubMed2005

Primary malignant lymphoma of the testis.

UNLABELLED: Primary testicular lymphomas are rare entities representing 1-2% of non-Hodgkin lymphoma (NHML) and 1-7% of malignant testicular tumors and they are the most common testicular tumors in men older than 50 years of age. This study included 8 cases of inpatients diagnosed by echography and NMR with testicular tumors. The age of patients was between 46 and 81 (with a mean of 52). The tumors were unilateral, with disease limited to testicle and accompanied by pain except 1 case with bone involvement. Orchectomy was performed as first therapeutic and diagnostic purpose. All patients were clinically staged according to the Ann Arbor criteria in IE and IIID stage and received a doxorubicin based chemotherapy regimen (CHOP, MTX, CVP, and Leukeran). A standard chemotherapy protocol has not been used because of reduced number of patients. Tumor fragments were fixed in 10% formallin, paraffin embedded, sectioned and standard H.E. stained. Immunohistochemistry for L26, Alphafetoprotein, NK1, CD30, and CLA was performed. Microscopy revealed in all cases a stromal proliferation with medium size cells, monomorphic shape and prominent nucleoli. Alphafetoprotein was positive in seminal tubes and negative in tumor, NK1 in small lymphocyte and negative in tumor and L26 diffuse positive in tumor. CLA diffuse positive in tumor. We were able to follow up only four patients. CONCLUSIONS: The diagnosis was of NHML in 6 cases and for 2 secondary involvement of hematopoietic malignancy (myeloid sarcoma and leukemia). Lymphoma cases were typed using REAL classification as small and large B-cell lymphoma. Unfavorable evolution with 6 months relapse and one death prove a more aggressive evolution of primitive testicular lymphoma.

Humans↗
PubMed1985

The sonographic aspects of haemobilia. Clinical and experimental study.

The sonographic aspect of the gallbladder in seven cases of haemobilia is analysed. The changes include a diffuse echogenic gallbladder content during the initial stage. Later, irregular shaped inhomogeneous non shadowing masses are seen in the dependent parts of the lumen. This variable aspect was studied in an experimental model by percutaneous injection of blood in the gallbladder of Guinea pigs. The hyperechoic gallbladder content, seen early after injection is a transitory phenomenon which seems related to red cell aggregation before coagulation occurs. During the later stage the intraluminal masses were shown by histology to represent bloodclots. In a patient the observation of such a rapid evolution from diffuse hyper-reflectivity to less reflective masses is strongly suggestive of haemobilia.

Animals↗
PubMedDate not supplied

Cultivation of microplantlets derived from the marine red alga Agardhiella subulata in a stirred tank photobioreactor.

Macrophytic marine red algae are a diverse source of bioactive natural compounds. "Microplantlet" suspension cultures established from red algae are potential platforms for biosynthesis of these compounds, provided suitable bioreactor configurations for mass culture can be identified. The stirred tank bioreactor offers high rates of gas-liquid mass transfer, which may facilitate the delivery of the CO(2) in the aeration gas to the phototrophic microplantlet suspension culture. Therefore, the effects of impeller speed and CO(2) delivery on the long-term production of microplantlet biomass of the model red alga Agardhiella subulata was studied within a stirred tank photobioreactor equipped with a paddle blade impeller (D(i)/D(T) = 0.5). Nutrient medium replacement was required for sustained biomass production, and the biomass yield coefficient based on nitrate consumption was 1.08 +/- 0.09 g dry biomass per mmol N consumed. Biomass production went through two exponential phases of growth, followed by a CO(2) delivery limited growth phase. The CO(2)-limited growth phase was observed only if the specific growth rate in the second exponential phase of growth was at least 0.03 day(-)(1), the CO(2) delivery rate was less than 0.258 mmol CO(2) L(-)(1) culture h(-)(1), and the plantlet density was at least 10 g fresh mass L(-)(1). Increasing the aeration gas CO(2) partial pressure from 0.00035 to 0.0072 atm decreased the cultivation pH from 8.8 to 7.8, prolonged the second exponential phase of growth by increasing the CO(2) delivery rate, and also increased the photosynthetic oxygen evolution rate. Impeller speeds ranging from 60 to 250 rpm, which generated average shear rates of 2-10 s(-)(1), did not have a significant effect on biomass production rate. However, microplantlets cultivated in a stirred tank bioreactor ultimately assumed compact spherical shape, presumably to minimize exposure to hydrodynamic stress.

Bioreactors↗
PubMed1994

Properties and biogenesis of peroxisomes.

Many species of monocellular eukaryots as well as the majority of animal cell and plant tissues show the presence of peroxisomes or microperoxisomes. Their size, shape and internal organization may differ in various cellular types significantly. Typical components of animal cell peroxisomes are the membrane, matrix, low density compartment enriched in lipids, and the compartment containing D-amino acid oxidase. The group of four enzymes (catalase, D-amino acid oxidase, L-alpha-OH-acid oxidase) the location of which had been originally discovered in peroxisomes of hepatocytes of rodents was later widened by approximately forty further enzymes. It is though probable that evolution brought along a reduction and loss of various metabolic functions of peroxisomes and a decrease in the number of enzymes. Peroxisomes are characterized by high variability of the enzymatic content in dependence on the nutritional conditions and the effect of xenobiotics. Fasting, diabetes mellitus, high-lipid diet, peroxisome proliferators induce several peroxisomal enzymes, especially fatty acids beta-oxidation. The mechanism of the impact of heterogeneous substances on the gene transcription has been clarified recently. Substances as fibrates, retinoic acid, polyunsaturated fatty acids activate specific types of receptors-PPAR (peroxisome proliferators activated receptors) belonging to the superfamily of receptors activated by steroid hormones, thyroid hormones, and D-vitamins. A simultaneous induction of several peroxisomal enzymes can be achieved by the linkage between PPAR and specific areas of promotors of particular genes. Such areas-PPREs (peroxisomal proliferator response elements) with five repeated TGA(A/C/T)CT hexanucleotide sequences separated by one nucleotide were discovered in several peroxisomal genes. It is assumed that the stimulation of transcription can be achieved by the linkage between homodimers, and heterodimers of nuclear receptors on these DNA sections. The majority of peroxisomal proteins is synthesised in the cytoplasm, namely on polysomes being in matured forms. Unimpaired biogenesis of peroxisomes requires membrane transport proteins and presence of signal in polypeptide chain of imported proteins (PTS-peroxisomal targeting signal). The function of PTS in many peroxisomal proteins is fulfilled by the C-terminal tripeptide which is composed of amino acids, namely serine, lysine, and leucine (SKL-tripeptide), respectively by a tripeptide with a very similar composition in amino acids. Aside from this signal, still another signal exists, which is located at the N-end of peroxisomal proteins. The role of membrane proteins 70, 35, 256, 22, 15 kDa, is being discussed in relationship to the functions and diseases caused by impaired biogenesis of peroxisomes. (Fig. 4, Ref. 128.)

Animals↗
PubMed1999

Microtubules: strange polymers inside the cell.

This paper provides a consistent approach (within a one-dimensional approximation) to the description of the evolution of the microtubule length at both low- and high-density concentrations. We derive general master-type equations which are based on the key chemical reactions involved in the assembly and disassembly of microtubules. The processes included are: polymerization and depolymerization of a single protein dimer, catastrophic disassembly affecting an a piori arbitrary number of dimers, and a rescue event. Solutions of the derived equations are compared with the existing experimental data. Important conclusions linking the emergence of bell-shaped histograms with the nature of catastrophe and rescue phenomena are drawn. Finally, we briefly discuss the emergence of coherent phenomena in microtubule polymerization, i.e., a transition to collective oscillations in the assembly and disassembly effects.

Biopolymers↗
PubMed2003

Eyes covered by mitochondrial lenses in Petaliella spiracauda and Ptychopera purasjokii (Plathelminthes, Rhabdocoela, Trigonostominae). Ultrastructural features and phylogenetic implications.

The submicroscopic anatomy of the eyes in Petaliella spiracauda and Ptychopera purasjokii is described. These eyes correspond in general to the basic pattern of rhabdomeric pigment-cup ocelli. This, however, does not apply to modifications of the cup cell such as the differentiation of mitochondrial lenses. Corresponding with two sensory cells two extensions of the cup cell capping the eye aperture are crowded with small unmodified mitochondria in the eyes of P. spiracauda. The eyes of P. purasjokii have three sensory cells and the lenticular element is formed by a trifoil-shaped differentiation of three giant mitochondrial derivatives. These derivatives show peripheral appendages of various configurations, all of which resemble the profiles of small mitochondria. The implication of the existence of such appendages is that the lenses in P. purasjokii are derived from many fused mitochondria, rather than from a single enlarged one. It is concluded that the unmodified or modified mitochondrial differentiations in proliferations of the pigment cell capping the opening of the eye cup serve to focalize incoming light. The evolution of mitochondrial lenses in Plathelminthes is considered.

Animals↗
PubMed2004

Invertebrate humoral factors: cytokines as mediators of cell survival.

The presence and the different functional aspects of cytokine-related molecules in invertebrates are described. Cytokine-like factors affect immune functions, such as cell motility, chemotaxis, phagocytosis and cytotoxicity. In particular, cell migration shows a species-specific effect for IL-1alpha and TNF-alpha and a dose-correlated effect for IL-8, PDGF-AB and TGF-beta1. Apart from some exceptions, the phagocytic effect increases significantly at all the concentrations tested and with all the species used. PDGF-AB, TGF-beta1 and IL-8 provoke conformational changes in mollusk immunocytes, involving the signaling transduction pathways of phosphatidylinositol and cAMP. PDGF-AB and TGF-beta1 partially inhibit the induced programmed cell death in an insect cell line, and the survival effect is mediated by the activation of phosphatidylinositol 3-kinase, PKA and PKC. The exogenous administration of these growth factors in an invertebrate wound repair model showed that they are able to control the wound environment and promote the repair process by accelerating the coordinated activities involved. Moreover, IL-1alpha, IL-2 and TNF-alpha are able to induce nitric oxide synthase. PDGF-AB and TGF-beta1 provoke an increase in neutral endopeptidase-24.11 (NEP)-like activity in membrane preparations from mollusk immunocytes, while NEP deactivates the PDGF-AB- and TGF-beta1-induced cell shape changes. Cytokines are also involved in invertebrate stress response in a manner extremely similar to that in vertebrates. Several studies suggest the existence on the mollusk immunocyte membrane of an ancestral receptor capable of binding both IL-2 and CRH. Furthermore, the competition found between CRH and a large number of cytokines supports the idea that invertebrate cytokine receptors show a certain degree of promiscuity. The multiple functions of cytokines detected in invertebrates underline another characteristic of mammalian cytokines, i.e. their great pleiotropicity. Altogether, the studies on the function of the invertebrate humoral factors show a close overlapping with those found in vertebrates, and the hypothesized missing correlation between invertebrate and vertebrate cytokine genes that is emerging from the limited molecular biology data present in literature might represent a very peculiar strategy followed by Nature in the evolution of cytokines.

Animals↗
PubMed1987

Effect of tetraploidy on dendritic branching in neurons and glial cells of the frog, Xenopus laevis.

Morphological aspects of four different groups of Golgi impregnated brain cells from a tetraploid strain of Xenopus laevis frogs were compared to analogous cells in comparably sized diploid frogs. The cells examined included neurons from the telencephalon, caudal hypothalamus, and optic tectum, and radial glial cells from the optic tectum. The brains of tetraploid frogs appeared grossly normal and were the same size and contained similar cell types as diploid brains. As observed in previous studies on polyploid amphibia, somal diameters increased significantly in tetraploid cells for each of the four groups of cells examined. Also, the total length of the dendritic arbors in tetraploid brain cells increased significantly by factors ranging from 1.4 to 2.4 times the total length of the analogous processes in diploid cells. Tetraploid neurons in the telencephalon and hypothalamus increased their arbor lengths predominantly by increasing the number of dendritic branches, while maintaining the average distance between branch points in the dendritic segments. In contrast, the tetraploid large pear-shaped neurons in the optic tectum had significantly longer terminal dendritic segments than the analogous diploid neurons, although these tetraploid neurons maintained their average number of dendritic segments per cell. Tetraploid tectal radial glial cells appeared to increase both their number of branches and the lengths of their terminal segments. Thus, the mode by which tetraploid brain cells achieved longer dendritic arbors varied from cell type to cell type. These results suggest a hypothetical basis for possible effects of genomic size on vertebrate brain structure and evolution at the cellular level.

Animals↗
PubMed1983

Fine structure of the sensory receptors of Aglantha digitale (Hydromedusae: Trachylina).

Fine-structure studies of the sensory receptors of Aglantha digitale have been done by transmission- and scanning-electron microscopy. Aglantha has 8 club-shaped statocysts and three types of ciliated sensory receptors: ciliated comb pads, ciliated sensory cells with microvilli, and ciliated sensory cells without microvilli. The epithelium covering the statocyst has both ciliated sensory cells and epitheliomuscular cells. The ciliated comb pads are formed by a group of ciliated sensory cells, each having an apical kinocilium surrounded by a ring of microvilli. These microvilli show an increase in length towards the velum. The axons from the comb pad cells enter the inner nerve ring. The structure, function and the evolution of the statocysts and the possible role of the ciliated comb pads and other sensory receptors are discussed.

Animals↗