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PubMed2001

Accessing molecular dynamics in cells by fluorescence correlation spectroscopy.

Fluorescence correlation spectroscopy (FCS) analyzes spontaneous fluctuations in the fluorescence emission of small molecular ensembles, thus providing information about a multitude of parameters, such as concentrations, molecular mobility and dynamics of fluorescently labeled molecules. Performed within diffraction-limited confocal volume elements, FCS provides an attractive alternative to photobleaching recovery methods for determining intracellular mobility parameters of very low quantities of fluorophores. Due to its high sensitivity sufficient for single molecule detection, the method is subject to certain artifact hazards that must be carefully controlled, such as photobleaching and intramolecular dynamics, which introduce fluorescence flickering. Furthermore, if molecular mobility is to be probed, nonspecific interactions of the labeling dye with cellular structures can introduce systematic errors. In cytosolic measurements, lipophilic dyes, such as certain rhodamines that bind to intracellular membranes, should be avoided. To study free diffusion, genetically encoded fluorescent labels such as green fluorescent protein (GFP) or DsRed are preferable since they are less likely to nonspecifically interact with cellular substructures.

Carbocyanines↗
PubMedDate not supplied

[Reflection of local inflammatory activity in rheumatic diseases in synovial imprint cytology].

Cytological signs of the synovial imprint preparation have been correlated with findings of systemic, histomorphologic and arthroscopic inflammatory symptoms in 123 patients with rheumatic arthropathies. Out of the observed cellular and non-cellular structures of the synovial imprint cytology, fibrin, fibrinous necroses and relations of neutrophil polymorphs, as well as synovial phagocytes, reflect the acute inflammatory activity of the joint examined. The content in synovial imprint preparation of cells and cell groups are manners of expression both of the acute and proliferative activity as well as basic activity, respectively, of the synovial membrane. The synovial imprint cytogram's number of giant cells correlates with the histomorphologic degree of severity of the local proliferative inflammatory activity. Correlations between the level of the 1-h-value of the erythrocyte sedimentation rate (ESR) and the imprintocytological finding cellular distribution density, as well as relations between synoviocytes and neutrophil polymorphs, had to be demonstrated statistically. No correlations, however, were found between cytologic structures of inflammatory activities of the synovial imprint cytogram and the differential cell picture of the associated serosynovitis.

Arthritis, Infectious↗
PubMed1989

[Early development of cerebral blood vessels: on the morphological changes in endothelial cells during the fetal period in the rat brain].

Developmental changes of cerebral blood vessels in the rat fetal brain from the embryonic day 11 (E 11) to E 21 were chronologically observed with light and electron microscopes. Based on the fine structures the development of the blood vessels was divided into three successive stages: Stage I (from E 11 to E 21). The neural groove fused at the dorsal portion and transferred to the neural tube. Endothelial cells located only around the neural tissue, and showed a primitive nature in their cellular structures, such as immature nucleus and intracytoplasmic organelles. There were many pores at the thin portion of the cytoplasmic processes. Stage II (from E 13 to E 16). Matrix cells in the neural tube began to produce neuroblasts. These neuroblasts migrated from the matrix layer and were recognized as the migrating zone just outside the matrix layer. The formation of the migrating zone started at the ventrolateral portion and successively spread to the lateral neopallium and then to the medial one of the cerebrum. Perineural vessels invaded into the neural tissue at the ventrolateral portion and were distributed in the migrating zone and the matrix layer. It was the first appearance of the intraneural blood vessels, and the next invading seemed to follow the area which formed the migrating zone. The endothelial cells at this stage became to increase their cytoplasmic thickness and simultaneously to protrude many cell processes to the luminal and abluminal sides. Numerous large vesicles in the cytoplasm were also observed. Being associated with the vesicle formation the pores in the cytoplasm were rapidly decreased. Pericytes were recognized around the endothelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

[Cytophysiology of the absorption cycle of enterocytes].

The protein absorption (albumin and gamma-globulin) by epithelial cells of small intestine of neonatal rats was studied in order to define the duration of its stages, the role of intracellular structures in trensport of the absorbed substances, and the cyclic activity of enterocytes. The volume of the absorbed substances depends on the number and size of pynocytotic formations at the cell apex. The protein transport via cells into interstitia is an active process involving the Golgi complex, mitochondria, and other cellular structures. Due to be intracellular regeneration, the restoration of enterocytes begins from gradual protein unloading and is over when the product has been transported to the lymphatic capillary lumen from interstitia. As a result, the continuous absorption is possible in the mucous layer of small intestine although the villi enterocytes activity is of a cyclic character.

Animals↗
PubMed2001

Glutamine protects mitochondrial structure and function in oxygen toxicity.

Glutamine is an important mitochondrial substrate implicated in the protection of cells from oxidant injury, but the mechanisms of its action are incompletely understood. Human pulmonary epithelial-like (A549) cells were exposed to 95% O2 for 4 days in the absence and presence of glutamine. Cell proliferation in normoxia was dependent on glutamine, and glutamine deprivation markedly accelerated cell death in hyperoxia. Glutamine significantly increased cellular ATP levels in normoxia and prevented the loss of ATP in hyperoxia seen in glutamine-deprived cells. Mitochondrial membrane potential as assessed by flow cytometry with chloromethyltetramethylrosamine was increased by glutamine in hyperoxia-exposed A549 cells, and a glutamine dose-dependent increase in mitochondrial membrane potential was detected. Glutamine-supplemented, hyperoxia-exposed cells had a higher O2 consumption rate and GSH content. Electron and fluorescence microscopy revealed that, in hyperoxia, glutamine protected cellular structures, especially mitochondria, from damage. In hyperoxia, activity of the tricarboxylic acid cycle enzyme alpha-ketoglutarate dehydrogenase was partially protected by its indirect substrate, glutamine, indicating a mechanism of mitochondrial protection.

Adenosine Triphosphate↗
PubMed1977

The structure of the cells lining the stomach of the tammar wallaby (Macropus eugenii).

The stomach of the tammar may be divided into cardiac, "oesophageal", fundic and pyloric regions. In the cells of the cardiac region (which occupy 65% of the stomach) at least three types of mucous droplet are present. The stratified squamous "oesophageal" region occupies 20% of the stomach and the fundic and pyloric regions make up the remaining 15%. The cellular structure of the three last named regions seems to be similar to that described for other monogastric mammals. Endocrine cells were found in all glandular regions.

Animals↗
PubMed2001

Myosins in protists.

This review focuses on selected papers that illustrate an historical perspective and the current knowledge of myosin structure and function in protists. The review contains a general description of myosin structure, a phylogenetic tree of the myosin classes, and descriptions of myosin isoforms identified in protists. Each myosin is discussed within the context of the taxonomic group of the organism in which the myosin has been identified. Domain structure, cellular location, function, and regulation are described for each myosin.

Adenosine Triphosphate↗
PubMed1976

The kinetics of biological phase transitions manifested by sigmoid time curves: a review of approaches.

Experimental biological data showing a time course of sigmoid shape are customarily interpreted in terms of mass-action chemical kinetic theory of reactions in free solution. But the reactive sites in biological systems are often located in solid or structured cellular components through which cooperative interactions may occur, resulting in phase transitions. In inorganic systems, the time course of phase transitions often shows experimental curves of sigmoid shape, and this may be predicted theoretically. Therefore it is suggested that when sigmoid time curves are observed in biological systems containing solid or structured components, mathematical analysis based on cooperative interactions and phase transitions is more likely to be valid than analysis based on mass-action concepts.

Animals↗
PubMed2006

ARP2 and ARP3 are localized to sites of actin filament nucleation in tobacco BY-2 cells.

Complete depolymerization of actin filaments (AFs) at low temperature (0 degrees C) is followed by the formation of transient actin structures at 25 degrees C in tobacco BY-2 cells (Nicotiana tabacum L.). Using antibodies against fission yeast actin-related proteins (ARP2 and ARP3), we show here that transient actin structures (dots, dotted filaments, rods) colocalize with epitopes stained by these antibodies and thus are likely to represent sites of actin filament nucleation (SANs). In contrast to the cold-induced disassembly of AFs, no transient actin structures were detectable during recovery of AFs from latrunculin B-induced depolymerization. However, the staining pattern obtained with ARP antibodies in latrunculin B-treated cells was similar to that in controls and cold-treated cells. This suggests that, in addition to the complete depolymerization of AFs, disruption of other cellular structures is needed for the formation of transient actin structures during the early phase of recovery from cold treatment.

Actin Cytoskeleton↗
PubMed2002

The Hook1 gene is non-functional in the abnormal spermatozoon head shape (azh) mutant mouse.

In mice carrying the autosomal recessive mutation 'abnormal spermatozoon head shape' (azh) all spermatozoa display a highly abnormal head morphology that differs drastically from the compact and hook-shaped head of the normal murine sperm. Moreover, the azh mutation causes tail abnormalities often resulting in coiled sperm tails or in the decapitation of the sperm head from the flagellum. We have isolated and characterized murine Hook1 cDNA and analyzed the corresponding genomic structure. Furthermore, the Hook1 gene was mapped to the same region on chromosome 4 to which the azh locus was previously linked. The Hook1 gene is predominantly expressed in haploid male germ cells, and immunohistochemical analysis revealed that Hook1 is responsible for the linkage of the microtubular manchette and the flagellum to cellular structures. Here, we report that the azh mutation is due to a deletion of exons 10 and 11 in the murine Hook1 gene leading to a non-functional protein. Our results indicate that loss of Hook1 function results in ectopic positioning of microtubular structures within the spermatid and causes the azh phenotype. Therefore, the human HOOK1 gene could serve as a candidate gene for male infertility due to teratozoospermia or decapitation defects.

Alternative Splicing↗
PubMed1986

Visualization of the living cytoskeleton by video-enhanced microscopy and digital image processing.

Two steps led to our present-day view of the cytoskeleton as a highly dynamic structure that is actively involved in force generation for various kinds of cell motility and, as a result, is itself often actively moving. The first step was the introduction of video microscopy, especially of the Allen Video Enhanced Contrast-Differential Interference Contrast Microscopy (AVEC-DIC), which allows the visualization of cellular structures in the light microscope that are up to 10 times smaller than the limit of resolution. This enables one to see images of unfixed, unstained, native or purified microtubules and actin bundles, and their interaction with membrane-bound organelles. The second step was the discovery of a system exceptionally well-suited to study microtubule and organelle movements, namely, the extruded axoplasm of the squid giant axon. From this axon the cytoplasm can be extruded free from surrounding plasma membrane, and individual microtubules and organelles can be separated from the bulk axoplasm. The study of these native microtubules by AVEC-DIC microscopy yielded a great number of quite unexpected details of the dynamic behaviour of both the microtubules themselves and the motility associated with them.

Animals↗
PubMedDate not supplied

[Changes in the pool of polyamines [correction of polyvitamins] during transition from anaerobic to aerobic conditions and localization of enzymes for their synthesis in Escherichia coli cells].

The content of intra- and extracellular polyamines and the activity of enzymes mediating their synthesis change depending on the regime of cell aeration. The pool of putrescine rises abruptly upon the transition from anaerobic to aerobic conditions owing to its liberation from the bound state as well as due to an increase in the activity of ornithine decarboxylase; as a result, the structural-functional organisation of membranes is restored. The free pool of cadaverine appears because, presumably, its binding to membranes is upset and the activity of lysine decarboxylase rises. The localisation of the enzymes for polyamine synthesis in the cell seems to be determined by the specific action of their products on particular cellular structures and metabolic processes in Escherichia coli cells.

Aerobiosis↗
PubMedDate not supplied

Membrane and network theta-rhythm generation in hippocampal slices.

The hippocampal rhythms observed in vivo are the result of a complex interplay between cellular and synaptic properties within the hippocampus, and extra-hippocampal tonic as well as periodic inputs. For the stable rhythm to occur, the hippocampal circuitry should have the potential to oscillate at the specific frequencies. The in vitro studies revealed multiple mechanisms supporting the generation of the theta rhythm, which is the main operational mode of the hippocampus. In the hippocampus and related structures cellular membranes can oscillate at theta rhythm when they are depolarized to near-threshold membrane potentials; membranes are also adjusted to resonate with the external signal applied at theta frequency. Synaptically connected hippocampal network alone can generate theta rhythm when a necessary tonic excitation is provided. Finally, rhythmic inputs in theta range from the septum and entorhinal cortex have a propensity to synchronize oscillations in the whole hippocampal formation and associated structures to operate in a unified mode of activity. Based on the results obtained in slices and slice cultures, the present review shows this multilevel hierarchy, which serves to guarantee easy occurrence and reliable maintenance of the theta rhythm in the hippocampus.

Cell Membrane↗
PubMed2003

Modeling of microstructural kinematics during simple elongation of central nervous system tissue.

Damage to axons and glial cells in the central nervous system (CNS) white matter is a nearly universal feature of traumatic brain injury, yet it is not clear how the tissue mechanical deformations are transferred to the cellular components of the CNS. Defining how cellular deformations relate to the applied tissue deformation field can both highlight cellular populations at risk for mechanical injury, and define the fraction of cells in a specific population that will exhibit damage. In this investigation, microstructurally based models of CNS white matter were developed and tested against measured transformations of the CNS tissue microstructure under simple elongation. Results show that axons in the unstretched optic nerves were significantly wavy or undulated, where the measured axonal path length was greater than the end-to-end distance of the axon. The average undulation parameter--defined as the true axonal length divided by the end-to-end length--was 1.13. In stretched nerves, mean axonal undulations decreased with increasing applied stretch ratio (lambda)--the mean undulation values decreased to 1.06 at lambda = 1.06, 1.04 at lambda = 1.12, and 1.02 at lambda = 1.25. A model describing the gradual coupling, or tethering, of the axons to the surrounding glial cells best fit the experimental data. These modeling efforts indicate the fraction of the axonal and glial populations experiencing deformation increases with applied elongation, consistent with the observation that both axonal and glial cell injury increases at higher levels of white matter injury. Ultimately, these results can be used in conjunction with computational simulations of traumatic brain injury to aid in establishing the relative risk of cellular structures in the CNS white matter to mechanical injury.

Animals↗
PubMed1970

Intracellular development of bacteriophage phi-R. II. Fractionation of replicative form deoxyribonucleic acid associated with rapidly sedimenting host cell components.

When Escherichia coli is infected with bacteriophage phiR, parental deoxyribonucleic acid (the single- or double-stranded DNA containing the isotopic label of the infecting phage) becomes firmly attached to a cellular structure and can be isolated as a rapidly sedimenting component as described earlier for phiX174. If this component is centrifuged to equilibrium, two peaks of infective DNA are observed at densities of 1.30 and 1.15 g/ml. At low multiplicities of infection, (32)P-labeled parental DNA is found associated with only the cellular components in the dense band; as the multiplicities of infection are increased, the dense band becomes saturated and parental DNA molecules are then found at the light density as well. Actively replicating host DNA is found only in the dense band, whereas progeny DNA, which does not replicate semiconservatively, can become associated with cellular components in the light band. This fractionation of cellular components on the basis of their buoyant density separates primary sites of DNA replication associated with the dense band from nonfunctional binding sites in the light band.

Carbon Isotopes↗
PubMed2005

Cell type-specific response to growth on soft materials.

Many cell types respond to forces as acutely as they do to chemical stimuli, but the mechanisms by which cells sense mechanical stimuli and how these factors alter cellular structure and function in vivo are far less explored than those triggered by chemical ligands. Forces arise both from effects outside the cell and from mechanochemical reactions within the cell that generate stresses on the surface to which the cells adhere. Several recent reviews have summarized how externally applied forces may trigger a cellular response (Silver FH and Siperko LM. Crit Rev Biomed Eng 31: 255-331, 2003; Estes BT, Gimble JM, and Guilak F. Curr Top Dev Biol 60: 91-126, 2004; Janmey PA and Weitz DA. Trends Biochem Sci 29: 364-370, 2004). The purpose of this review is to examine the information available in the current literature describing the relationship between a cell and the rigidity of the matrix on which it resides. We will review recent studies and techniques that focus on substrate compliance as a major variable in cell culture studies. We will discuss the specificity of cell response to stiffness and discuss how this may be important in particular tissue systems. We will attempt to link the mechanoresponse to real pathological states and speculate on the possible biological significance of mechanosensing.

Animals↗
PubMed2000

Mechanism for uptake of silica particles by monocytic U937 cells.

We examined the mechanism for uptake by monocytic cells of particles found in the atmosphere of some industrial work places. As a model system, irregular crystalline silica particles (SPs), sphere-like cryptocrystalline microsilica particles (MPs) and carbon particles (CPs) were exposed to pro-monocytic U937 cells. Plasma-treated SP and MP, but not CP, activated the alternative complement pathway, but bound little C3b. However, all particles adsorbed serum IgG, IgA and IgM unspecifically. Phenotyping of U937 cells for complement receptors (CRs) and Fcgamma receptors (FcgammaRs) showed that interferon gamma (INFgamma) increased expression of FcgammaRI, CR3 (CD11b/CD18) and CR4 (CD11c/CD18) and that phorbol-12-myristate-13-acetate (PMA) increased expression of CR4. Scanning electron microscopy (SEM) demonstrated higher phagocytosis of plasma-treated SP than native SP by both PMA- and INFgamma-stimulated, but not unstimulated, cells. MP and CP could not be distinguished from cellular structures. Inhibition experiments in SEM revealed uptake of heparin-plasma-treated SP via FcgammaRI on INFgamma-stimulated U937 cells, but could not exclude possible participation of CR3. The results indicate that plasma-treated SPs bind Ig and are internalized by differentiated monocytic cells via FcgammaRI, which is known to trigger cellular production of toxic oxygen species that may induce pulmonary inflammation in vivo.

Complement Activation↗
PubMed2006

[Chemical structure of Mycobacterium tuberculosis. Part I--lipids].

Tuberculosis is a burning health issue in the contemporary world. Recognition of mechanisms by means of which pathogenic bacilli affect host cells and their virulence factors is indispensable to developing and synthesis of new drugs and vaccines. The authors discuss groups of the most important chemical compounds from the pathological point of view, which are responsible for morbidity and virulence of tubercle bacillus. They also point out the construction of cellular structures with reference to their functions. High content of lipid compounds especially in bacterial cell wall is a specific feature of tubercle bacillus. These molecules play different and very important roles both in growth and virulence of Mycobacterium tuberculosis.

Antigens, Bacterial↗