Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cellular Structures”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,243 records · Page 69Linked to original sources
PubMed2005

Overcoming limitations of natural anticancer drugs by combining with artificial agents.

During a billion years of evolution, living creatures have perfected cytotoxic agents to kill other organisms without killing themselves, thus providing us with antibiotics to kill bacteria without killing eukaryotic (e.g. human) cells. Some natural agents inhibit specifically most vital cellular structures and functions in cancer cells. However, nature was not creating antibiotics for cancer, and natural agents kill cancer cells precisely because they share targets with normal cells. To discriminate between particular cancer cells and normal cells, we can design or select artificial agents that are not necessarily lethal but are aimed either at cancer-specific targets or at dispensable and even unavailable (in cancer cells) targets. Using rational drug combinations, such selective agents can assist natural agents to eradicate cancer cells selectively.

Antineoplastic Agents, Alkylating↗
PubMed2005

Identification and treatment of scurvy: a case report.

Scurvy is a nondiscriminatory disease process resulting from a nutritional deficiency of ascorbic acid (vitamin C). The severe vitamin deficiency produces a breakdown in the cellular structure of the body. This case report describes a middle-age woman with a history of edema, bruising of the lower extremities, anemia, and severe periodontal disease. Her presentation and medical history are classic for the signs of scurvy. Scurvy is now only uncommonly seen in developed countries, but there are still vulnerable populations whose nutritional status can lead to scurvy. The aim of this report is to help the clinician identify and treat scurvy, a disease that was once feared for its high mortality but is now easily treatable, even in cases that have progressed to multiple organ dysfunction and failure.

Adult↗
PubMed2004

Identification of hibernating myocardium by acoustic microscopy.

Hibernating myocardium is viable myocardium that recovers after revascularization. The observation of loss of contractile proteins (myofibrils) and accumulation of glycogen in hibernating cardiomyocytes provide the basis for diagnosing hibernating myocardium. In this pilot study, acoustic microscopy was used to identify the cellular structure of normal vs. hibernating myocardium. Sections cut at 5-microm of archival paraffin blocks on glass slides were used for this study. Acoustic microscopy of normal cardiomyocytes showed intracellular linear echoes suggestive of myofibrils, and cardiomyocytes of hibernating myocardium revealed absence of myofibrils and dense intracellular echoes that corresponded to glycogen accumulation on optical microscopy. This modality of visualization allows a definitive diagnosis of hibernating myocardium.

Glycogen↗
PubMed2005

Pneumatic foam generation in the presence of a high-intensity ultrasound field.

Designer foams find applications in a wide range of industries. Foam quality is mostly determined by its complex cellular structure which defines its texture, rheology and stability. In addition to formulation design, the formation process is crucial to the development of a foam with an optimum structure. There is, therefore, a need for techniques that can assist in the generation of controlled foam structures. The work described in this paper demonstrates the potential of using high-intensity ultrasound to control foam structure during production. Foam generated in the presence of ultrasound usually exhibits a narrower bubble size distribution, i.e. a more uniform texture. Such enhanced homogeneity in texture is desirable to reduce the presence of aesthetically unattractive large cavities, and to reduce the destabilising effects of foam coarsening. In addition, a smaller mean bubble size and a slower rate of foam collapse usually result when ultrasound is applied. The work shows the effects on foams stabilised with different surfactants.

Journal Article↗
PubMed2004

Fc receptors in livestock species.

Many of the receptors for the Fc domain of immunoglobulins in cattle, sheep, pigs and horses have been cloned and characterized recently. This review summarises recent developments and relates them to the current understanding of the primary structure, cellular specificity and binding properties of Fc receptors (FcRs). Although there is an obvious overall similarity to their human and mouse counterparts, some Fc receptors in domestic animals are unusual, perhaps most notably the bovine Fcgamma2R, which although related to other mammalian FcgammaRs, belongs to a novel gene family and the porcine FcgammaRIIIA, which associates with a molecule that contains significant homology to the cathelin family of antimicrobial proteins. Accumulating data suggest the possibility of a different role for the FcRn in ruminants, which may secrete IgG onto the mucosal surfaces, rather than absorbing it, as was suggested by mouse studies. These differences may be linked to the diversity of immunoglobulin classes in different mammalian species, and may contribute to different immune functions. The observations made so far emphasize the importance of elucidating and analyzing the roles of these molecules within the immune system of each host animal, rather than inferring roles from conclusions made in human and mouse studies. A better understanding of Fc receptor expression on immune effector cells should help in developing new immunization protocols, while knowledge of the Fc receptors involved in immunoglobulin transport, especially in the mammary gland, may help to develop new products which could be used not only for veterinary purposes but perhaps also for human therapy.

Animals↗
PubMed2006

Vitellogenesis in the tick Amblyomma triste (Koch, 1844) (Acari: Ixodidae) Role for pedicel cells.

This study presents new information on the vitellogenesis of the tick Amblyomma triste. In this species, the ovary consists of a layer of epithelial cells, which form the ovarian wall, oogonia and developing oocytes; and the pedicel, a cellular structure that synthesizes and provides yolk precursors for developing oocytes. The pedicel also attaches oocytes to the external surface of the epithelial wall. In this study, evidence is provided in support of pedicel cells in providing compounds for oocytes during vitellogenesis.

Animals↗
PubMed2005

Caspase-3 is required in the apoptotic disintegration of the nuclear matrix.

Apoptotic breakdown of cellular structures is largely mediated by caspases. One target of degradation is a proteinaceous framework of the nucleus termed the nuclear matrix. We compared the apoptotic changes of the nuclear matrix in staurosporine-treated caspase-3-deficient MCF-7 cells transfected with intact CASP-3 gene (MCF-7c3) or an empty vector (MCF-7v) as a control. Nuclear Mitotic Apparatus protein (NuMA), lamin A/C and lamin B were used as markers for internal nuclear matrix and peripheral nuclear lamina, respectively. In both cell lines, staurosporine induced rapid cytoplasmic shrinkage and partial chromatin condensation. MCF-7c3 cells formed apoptotic bodies, whereas MCF-7v cells did not. NuMA and lamins were actively cleaved in MCF-7c3 cells following caspase-3 activation, but only minimal or no cleavage was detected in MCF-7v cells. Interestingly, lamin B but not lamin A/C was relocated into cytoplasmic granules in apoptotic MCF-7v cells. Pancaspase inhibitor, z-VAD-fmk, prevented the apoptotic changes, while caspase-3 inhibitor, z-DEVD-fmk, induced lamin B granules in both cell lines. These results show that caspase-3 is involved in the cleavage of NuMA and lamins either directly or by activating other proteases. This may be essential for disintegration of the nuclear structure during apoptosis.

Amino Acid Chloromethyl Ketones↗
PubMed2005

Deficient innervation characterizes intestinal strictures in a rat model of colitis.

Intestinal strictures are a common complication of Crohn's disease leading to serious consequences. With unknown etiology and cellular composition, strictures can be neither prevented nor reversed by current therapeutic strategies, and research has been limited by the lack of a well-developed animal model. We observed the sporadic occurrence of intestinal strictures at Day 35 in the TNBS rat model of colitis, which persisted beyond Day 90. Strictured tissue showed fusion, thickening, and disorganization of the smooth muscle layers. Immunocytochemistry revealed that all strictures were characterized by deficient innervation with a complete loss of intrinsic neurons, and a 92% loss of total axons per area. The number of alpha-smooth muscle actin-positive smooth muscle cells (SMC) increased in strictures, but immunolabeling showed phenotypic modulation of these cells, with the SMC phenotype (desmin-positive, vimentin-negative) entirely replaced by a myofibroblast phenotype (desmin-negative, vimentin-positive). Although cellular structure still predominated in the strictured regions, histochemistry showed increased extracellular matrix collagen, from 6 +/- 0.9% to 22 +/- 4% of total area. With previous evidence for neural loss in colitis, and in vitro studies showing neural regulation of smooth muscle cell (SMC) growth, we conclude that the regional loss of innervation may initiate tissue re-modeling that is characteristic of stricture formation.

Animals↗
PubMed2000

Cell volume measurement using scanning ion conductance microscopy.

We report a novel scanning ion conductance microscopy (SICM) technique for assessing the volume of living cells, which allows quantitative, high-resolution characterization of dynamic changes in cell volume while retaining the cell functionality. The technique can measure a wide range of volumes from 10(-19) to 10(-9) liter. The cell volume, as well as the volume of small cellular structures such as lamelopodia, dendrites, processes, or microvilli, can be measured with the 2.5 x 10(-20) liter resolution. The sample does not require any preliminary preparation before cell volume measurement. Both cell volume and surface characteristics can be simultaneously and continuously assessed during relatively long experiments. The SICM method can also be used for rapid estimation of the changes in cell volume. These are important when monitoring the cell responses to different physiological stimuli.

Animals↗
PubMed2003

Regulation of protein mobility via thermal membrane undulations.

The in-plane diffusivelike motion of membrane bound proteins on the surface of cells is considered. We suggest, on the basis of theoretical arguments and simulation, that thermally excited undulations of the lipid bilayer may serve as a mechanism for proteins to hop between adjacent regions on the cell surface separated by barriers composed of internal cellular structure (e.g., the cytoskeleton). We specifically investigate the mobility of band 3 dimer on the surface of red blood cells where the spectrin cytoskeletal meshwork defines a series of "corrals" on the cell surface known to hinder protein motion. Previous models of this system have postulated that the cytoskeleton must deform to allow passage of membrane bound proteins out of these corral regions and have ignored fluctuations of the bilayer. Our model provides a complementary mechanism and we posit that the mobility of real proteins in real cells is likely the result of several mechanisms acting in parallel.

Algorithms↗
PubMed1997

The renewal of the epidermis: a topological mechanism.

Using a topological approach, we study the dynamics of the basement membrane of the mammalian epidermis when basal cells detach or divide. A theoretical characterization of the steady state of the tissue, in very good agreement with experimental data, includes for the first time the division and the disappearance of cells in a two-dimensional random cellular structure. We predict a strong correlation between the size of the attachment of basal cells to the basement membrane and their biological behavior (division or detachment). This suggests that the main factor determining the fate of basal cells, and thus controlling the renewal of the epidermis, is the cells' surface tension and adhesion.

Animals↗
PubMed1997

Localization and molecular interactions of mitoxantrone within living K562 cells as probed by confocal spectral imaging analysis.

Studying mechanisms of drug antitumor action is complicated by the lack of noninvasive methods enabling direct monitoring of the state and interactions of the drugs within intact viable cells. Here we present a confocal spectral imaging (CSI) technique as a method of overcoming this problem. We applied this method to the examination of localization and interactions of mitoxantrone (1, 4-dihydroxy-5, 8-bis-[([2-(2-hydroxyethyl)-amino]ethyl)amino]-9,10-anthracenedione dihydrochloride), a potent antitumor drug, in living K562 cells. A two-dimensional set of fluorescence spectra of mitoxantrone (MITOX) recorded with micron resolution within a drug-treated cell was analyzed to reveal formation of drug-target complexes and to create the maps of their intracellular distribution. The analysis was based on detailed in vitro modeling of drug-target (DNA, RNA, DNA topoisomerase II) interactions and environmental effects affecting drug fluorescence. MITOX exposed to aqueous intracellular environment, MITOX bound to hydrophobic cellular structures, complexes of MITOX with nucleic acids, as well as the naphtoquinoxaline metabolite of MITOX were simultaneously detected and mapped in K562 cells. These states and complexes are known to be immediately related to the antitumor action of the drug. The results obtained present a basis for the subsequent quantitative analysis of concentration and time-dependent accumulation of free and bound MITOX within different compartments of living cancer cells.

Antineoplastic Agents↗
PubMed1997

Quantitative confocal spectral imaging analysis of mitoxantrone within living K562 cells: intracellular accumulation and distribution of monomers, aggregates, naphtoquinoxaline metabolite, and drug-target complexes.

Confocal spectral imaging (CSI) technique was used for quantitative analysis of the uptake, subcellular localization, and characteristics of localized binding and retention of anticancer agent mitoxantrone (MITOX) within human K562 erythroleukemia cells. The CSI technique enables identification of the state and interactions of the drug within the living cells. Utilizing this unique property of the method, intracellular distributions were examined for monomeric MITOX in polar environment, MITOX bound with hydrophobic cellular structures, naphthoquinoxaline metabolite, and nucleic acid-related complexes of MITOX. The features revealed were compared for the cells treated with 2 microM or 10 microM of MITOX for 1 h and correlated to the known data on antitumor action of the drug. MITOX was found to exhibit high tendency to self-aggregation within intracellular media. The aggregates are concluded to be a determinant of long-term intracellular retention of the drug and a source of persistent intracellular binding of MITOX. Considerable penetration of MITOX in the hydrophobic cytoskeleton structures as well as growing accumulation of MITOX bound to nucleic acids within the nucleus were found to occur in the cells treated with a high concentration of the drug. These effects may be among the factors stimulating and/or accompanying high-dose mitoxantrone-induced programmed cell death or apoptosis.

Antineoplastic Agents↗
PubMedDate not supplied

Bioelectrorheological model of the cell. 8. Cellular deformation under prolonged and recurrent shear stress.

The influence of a prolonged and recurrent shear stress created by a periodic electric field on the mechanical properties of Neurospora crassa cells was investigated. Conditions were found under which modifications of cellular structures responding to stress become irreversible, and plastic flow of the viscoelastic structural elements is observed. The symmetry of the response of the cell under stress application and relaxation was lost, when compared to the reference conditions. To interpret the results a general rheological model was proposed. As previously described (Pawłowski et al., 1997), the existence of the three hypothetical supramolecular regions of the membrane (F, S and O) was suggested. Rheological parameters for the above regions were calculated. Theoretical functions were satisfactorily fitted to the experimental results.

Cell Physiological Phenomena↗
PubMed1998

Axonal elongation through acellular nerve segments of the cat tibial nerve: importance of the near-nerve environment.

Peripheral nerve regeneration is considered to be influenced by structural, cellular and humoral factors in the distal nerve stump. Axonal elongation was, however, not affected by the presence of a 20 mm acellular nerve segment (ANS) distal to a crush lesion in a cat tibial nerve which was shielded from the environment by a silicone cuff [K. Fugleholm, H. Schmalbruch, C. Krarup, Early peripheral nerve regeneration after crushing, sectioning, and freeze studied by implanted electrodes in the cat, J. Neurosci., 14 (1994) 2659-2673]. In the present study axons were challenged to regenerate through crush lesions combined with 30-, 40-, 50-, 60- and 70-mm ANSs. For 30- and 40-mm ANSs, the nerves were shielded by impermeable silicone cuffs containing electrodes for electrophysiological evaluation of axonal elongation. All nerves were examined histologically by light microscopy 9 weeks after the lesion. The elongation through the shielded 30-mm ANS was slower than through a shielded nerve segment with viable cells. In the isolated 40-mm ANS, incomplete Wallerian degeneration and lack of blood vessels were observed, and axonal elongation was severely impaired. Regeneration across 40-70 mm non-shielded ANSs was intact and there was no relation between the number of regenerated fibers and the length of the ANS. There was no reduction in the number of blood vessels in the non-isolated ANSs. The results suggest that regeneration through an isolated acellular nerve segment exceeding 30 mm depends on cellular and humoral support from the near-nerve environment. Thus, the near-nerve environment is crucial for regeneration through long ANSs, and the importance of humoral, cellular and vascular support is discussed.

Action Potentials↗
PubMed1998

Sulfotransferase-mediated activation of mutagens studied using heterologous expression systems.

Sulfation is a common final step in the biotransformation of xenobiotics and is traditionally associated with inactivation. However, the sulfate group is electron-withdrawing and may be cleaved off heterolytically in some molecules leading to electrophilic cations which may form adducts with DNA and other important cellular structures. Since endogenous sulfotransferases do not appear to be expressed in indicator cells of standard mutagenicity tests, rat and human sulfotransferases have been stably expressed in his- Salmonella typhimurium strain TA1538 and Chinese hamster V79 cells. Using these recombinant indicator cells, sulfotransferase-dependent genotoxic activities were detected with N-hydroxy-2-acetylaminofluorene, 2-acetylaminofluorene (in the presence of co-expressed rat cytochrome P450 1A2), hycanthone, 1'-hydroxysafrole, alpha-hydroxytamoxifen and various benzylic alcohols derived from polycyclic aromatic hydrocarbons. In several cases, it was critical that the reactive sulfuric acid conjugates were formed directly within the indicator cells, owing to the inefficient penetration of cell membranes. In other cases, spontaneous benzylic substitution reactions with medium components, such as halogenide ions or amino acids, led to secondary, membrane-penetrating reactive species. Different sulfotransferases, including related forms from rat and human, substantially differed in their substrate specificity towards the investigated promutagens. It is known that some sulfotransferases are expressed with high tissue and cell type specificities. This site-dependent expression together with the limitations in the distribution of reactive sulfuric acid conjugates may explain organotropic effects of compounds activated by this metabolic pathway.

Animals↗
PubMed1987

In vitro interactions between pulmonary macrophages and respirable particles.

Pulmonary alveolar macrophage cells (PAM) are an important component of the pulmonary response to particles deposited in the deep lung. To more fully characterize the interactions between macrophages and particulate materials, a correlative light and electron microscopic technique was developed that allowed light microscopic identification of individual cell viability after in vitro particle exposure, followed by scanning and transmission electron microscopic analyses of specific PAM, including surface morphology, X-ray microanalytic evaluation of particle content, and internal cellular structure. Individual cell viability, particle content, and morphologic alterations were evaluated for three particle types: Ni3S2, TiO2, and glass beads. Cell death and stages of cell disruption including bleb cluster formation, loss of surface features, formation of membrane tears and holes, and cell degranulation correlated with Ni3S2 and TiO2 content. Glass beads were not associated with cell disruption or viability reduction. Correlative microscopic techniques were essential in describing particle-dependent effects on an individual cell basis.

Animals↗
PubMed1997

Lack of vacuolar proton ATPase association with the cytoskeleton in osteoclasts of osteosclerotic (oc/oc) mice.

We examined the pathogenetic mechanism underlying the lack of bone resorption in osteosclerotic oc/oc mice. An immunoelectron microscopic analysis revealed that in the osteoclasts of these mice, no ruffled borders formed, and that vacuolar H+-ATPase (V-ATPase) was present throughout the cytoplasm but not on the apical membranes. The activity of V-ATPase in oc/oc mice was similar to that in normal mice. In normal spleen cell-derived osteoclast-like cells (OCLs), immunoreactivity for V-ATPase was detected in association with Triton X-100-insoluble cellular structure, but not in oc/oc spleen cell-derived OCLs. Moreover, in renal proximal convoluted tubules of oc/oc mice, the basal striation did not form. These results suggest that osteosclerosis in oc/oc mice is possibly due to the dissociation of V-ATPase and cytoskeleton in osteoclasts.

Adenosine Triphosphatases↗