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At least 1,153 records · Page 64Linked to original sources
PubMed1990

Droperidol-fentanyl inhibits mast cell histamine release in rat synovium, but not skin, after immunologic activation: evidence for mast cell heterogeneity.

The characteristics of mast cell heterogeneity include differences in mast cell staining, cellular structure, content of proteoglycans and vasoactive amines, and in vitro responses to secretagogues. We have found that the anesthetic agent, droperidol-fentanyl, significantly decreased rat synovial vascular permeability after selective synovial mast cell degranulation. In contrast, there was no effect on skin mast cell-induced vascular permeability. To address the possibility that this difference in response represents mast cell heterogeneity and uniqueness of synovial mast cells, we investigated the effects of three different anesthetic agents on synovial mast cells. In these studies we examined whether (1) the drugs affect synovial mast cells and (2) whether the drugs affect synovial mast cells differently from mast cells in skin. Our data indicate that, compared to inhaled methoxyflurane and ethyl ether, subcutaneous droperidol-fentanyl had a significant inhibitory effect on synovial, but not skin, mast cell-mediated vascular permeability, which was associated with a significant inhibition of synovial mast cell histamine release. Thus, the permeability differences were not due only to effects on histamine receptors. Our data suggest the possibility that there are significant functional differences between synovial and skin mast cells, a phenomenon that may have important therapeutic implications for treatment of mast cell-mediated synovial inflammation.

Animals↗
PubMed1980

The spatial distribution of polyribosomes in 3T3 cells and the associated assembly of proteins into the skeletal framework.

Acridine fluorescence reveals polyribosomes in fibroblasts and Triton-extracted skeletal frameworks; simultaneous phase-contrast images show cellular structure. Polyribosomes appear near nuclei of both intact fibroblasts and skeletal frameworks. Simultaneous autoradiography of cells so examined locates radioactive proteins. After synthesis, most proteins diffuse rapidly through the cytoplasm; intact cells autoradiographed afer a 35S pulse show grains throughout. In sharp contrast, extraction with Triton leaves only radioactive skeletal proteins, which, although released from ribosomes, are near polyribosomes after a pulse. After a chase, skeletal-associated radioactivity is found throughout the framework structure. However, skeletal proteins migrate only if protein synthesis continues. Emetine administered following a pulse block protein migration; skeletal framework radioactivity remains near polyribosomes. This also indicates limited exchange between skeletal framework and soluble cytoplasmic proteins. The fact that proteins insert themselves into the skeletal framework at or near their synthesis site, with limited subsequent exchange, appears to contradict current view of protein self-assembly.

Actins↗
PubMed1981

Nerve-specific enolase and creatine phosphokinase in axonal transport: soluble proteins and the axoplasmic matrix.

The axonal transport of two soluble enzymes of intermediary metabolism was evaluated: the nerve-specific form of the glycolytic enzyme enolase (NSE) and the brain isozyme of creatine phosphokinase (CPK). Previously, little was known about the intracellular movements of the soluble proteins of the cell. Although the soluble enzymes of glycolysis and other pathways of intermediary metabolism have been thought to be freely diffusing in the cytosol, many are required in the axonal extremities of the neuron and must be transported to the sites of utilization. Comigration of purified enzymes with radioactive polypeptides associated with specific rate components of axonal transport in two-dimensional gel electrophoresis indicates that both NSE and CPK move in the axon solely as part of the group of proteins known as slow component b (SCb) at a rate of 2 mm/day. Peptide mapping following limited proteolysis confirmed identification of NSE and CPK in SCb. Materials associated with SCb have been shown to move coherently along the axon and to behave as a discrete cellular structure, the axoplasmic matrix. Association of two soluble enzymes, NSE and CPK, with the SCb complex of proteins requires a reevaluation of the assumption that these and other soluble proteins of the axon are freely diffusible.

Animals↗
PubMed1986

Caldesmon: a calmodulin-binding actin-regulatory protein.

The protein caldesmon, originally isolated from smooth muscle tissue where it is the most abundant calmodulin-binding protein, has since been shown to have a wide distribution in actin- and myosin- containing cells where it is localized in sub-cellular structures concerned with motility, shape changes and exo- or endo-cytosis. Caldesmon is believed to be an actin- regulatory protein, and binds with high affinity to actin or actin-tropomyosin. Caldesmon inhibits the activation by actin-tropomyosin of myosin MgATPase activity, and the inhibition can be reversed by Ca2+.calmodulin. The binding of caldesmon to smooth muscle proteins has been studied in detail, enabling a model to be constructed which could account for the observed Ca2+ regulation of smooth muscle thin filaments. The abundance of caldesmon, and the Ca2+-regulation of its activity via calmodulin, mean that it is potentially an important intracellular regulator of processes such as smooth muscle contraction, cell motility and secretion.

Actins↗
PubMed1985

Monocytic differentiation induced by 1,25 dihydroxyvitamin D3 in myeloid cells: an ultrastructural immunocytochemical study.

We have studied, by ultrastructural morphology and immunocytochemistry, the alterations that occur in cells from the HL60 leukaemia cell line and from patients with CGL following incubation in vitro with 1,25(OH)2D3 for 2-5 days. The main morphological changes observed were in the nuclear shape, the development of autophagic vacuoles and the appearance of a population of small granules in the cytoplasm. These changes were associated with a significant reduction in MPO activity and increased expression of membrane antigens detected by the monocyte-specific McAb FMC17 and FMC32, as shown by the IGM at EM level, and a decrease in granulocyte-specific antigens demonstrated by the McAb FMC10. These observations suggest that promyelocytes and myelocytes could transform into monocyte-like cells and that this remodelling of cells was associated with autophagic digestion of cellular structures.

Antibodies, Monoclonal↗
PubMedDate not supplied

Comparative genotoxic effects of the cooked-food-related mutagens Trp-P-2 and IQ in bacteria and cultured mammalian cells.

As part of a major study to evaluate the mutagenicity of chemicals produced during the cooking of foods, we examined the responses of bacteria and cultured Chinese hamster cells to the compounds Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole) and IQ (2-amino-3-methylimidazo[4,5-f]quinoline), constituents identified in cooked beef and fish. In the Ames/Salmonella tester strain TA1538, both compounds were confirmed to be extremely potent mutagens that were active at levels below 1 ng/plate in the presence of hamster-liver S9 microsomal fraction. 50-fold higher doses of both compounds were required for mutagenicity in the uvr+ tester strain TA1978. Trp-P-2 also behaved as a strong mutagen in CHO cells using the standard exogenous activation with hamster-liver S9 fraction. At concentrations below 1 microgram/ml it produced dose-dependent increases in cell killing, mutations at the hprt and aprt loci, sister-chromatid exchanges, and chromosomal aberrations. An excision-repair-deficient strain was about 2-fold more sensitive than the normal CHO cells with respect to these genotoxic effects of Trp-P-2. IQ had unexpectedly weak activity for all genetic endpoints in the CHO cells, and it produced clear-cut responses only in the repair-deficient cells and only above a concentration of 10 micrograms/ml. The toxicity that was observed with IQ was not affected by the repair capacity of the cells and was not associated with chromosomal aberrations, indicating that damage to cellular structures other than nuclear DNA was likely the predominant pathway for cell killing. Because the culture conditions normally used for CHO cell exposure were shown to be competent in producing bacterial mutagenicity with IQ, it was concluded that the active metabolite of IQ was present in the medium but was somehow ineffective in reaching the DNA of CHO cells and/or reacting with it. These results suggest that the relative mutagenic potency of compounds in Salmonella may bear no direct relationship to relative mutagenicity in CHO cells, emphasizing precaution in attempting to extrapolate microbial data to mammalian somatic cells. This study illustrates the use and merits of a multi-endpoint assay for genetic damage in CHO cells, the utility of using CHO cells that are defective in excision repair of DNA, and the importance of comparative testing between bacterial and mammalian systems.

Animals↗
PubMed1989

A new neuronal intermediate filament protein.

It would be an understatement to say that the vertebrate nervous system appears complex. The characterization and classification of its components rely, in addition to its gross anatomy, on analyses of the differential expression of cytoskeletal and other cellular structures and products. In this brief review Lloyd Greene describes the discovery of a novel intermediate filament protein.

Amino Acid Sequence↗
PubMed1991

A class of amphipathic proteins associated with lipid storage bodies in plants. Possible similarities with animal serum apolipoproteins.

The lipid-storing tissues of plants contain many small (0.2-1 microns) lipid (normally triacylglycerol) droplets which are surrounded and stabilized by a mixed phospholipid and protein annulus. The proteinaceous components of the lipid storage bodies are termed oleosins and are not associated with any other cellular structures. The major oleosins of rapeseed and radish have been isolated by preparative SDS-PAGE and are respectively classes of 19 kDa and 20 kDa proteins. Both protein classes were N-terminally blocked for direct sequencing, but were partially sequenced following limited proteolytic digestion. The major rapeseed oleosin was made up of at least two 19 kDa polypeptides, termed nap-I and nap-II, which have closely related but different amino acid sequences. A single 20 kDa oleosin, termed rad-I, was found in radish. A near full length cDNA clone for a major rapeseed oleosin was sequenced and found to correspond almost exactly to the sequence of nap-II. The sequences of nap-I and rad-I show very close similarity to one another, as do the sequences of nap-II and the previously determined sequence for the major oleosin from maize. All four oleosins have a large central hydrophobic domain flanked by polar N- and C-terminal domains. Secondary structure predictions for the four oleosins are similar and a novel model is proposed based on a central hydrophobic beta-strand region flanked by an N-terminal polar alpha-helix and a C-terminal amphipathic alpha-helix. The possibility that oleosins exhibit structural and functional similarities with some animal apolipoproteins is discussed.

Amino Acid Sequence↗
PubMedDate not supplied

On the role of intracellular physicochemistry in quantitative gene expression during aging and the effect of centrophenoxine. A review.

The turnover of proteins in biological systems is due mostly to an ever-occurring damaging (cross-linking) effect of the OH. free radicals. The replacement of the damaged proteins requires a continuous gene expression. A key issue of experimental gerontology is why the gene expression maintains the fidelity but loses the speed during aging. The membrane hypothesis of aging (MHA) proposes a cellular mechanism based on the fact that the more compact cellular structures (e.g., membranes) are damaged faster than the more diluted ones (e.g., cytosol). In addition, the cell membrane is exposed also to the residual heat-induced damage deriving from a frequent discharge of its electric polarity. Therefore, one can assume that even an extremely small incompleteness of the replacement of the damaged membrane components per turnover cycle may result in an error accumulation, which may be responsible first for the inhibition of growth, then for aging of cells. In agreement with this hypothesis, neurons display a life-long, gradual loss of the passive potassium permeability of the cell membrane, resulting in a continuous dehydration of the intracellular mass, i.e., an increase of physical density. Theory and experimental models show that this latter process causes a slowing down of all enzyme functions including those realizing the gene expression and the elimination of the damaged components. Increase of the dry mass content of cells and tissues is an obligatory process for maturation; however, later on it leads to aging. The known nootropic effects of centrophenoxine (CPH) can be interpreted on the basis of the OH. radical scavenger properties of dimethylaminoethanol (DMAE) which is incorporated in the neuronal membranes of the brain in form of phosphatidyl-DMAE. The protective effects of CPH (and of similar, newly synthesized other drugs) on the membrane components can slow down the age-dependent deteriorations of the intracellular physicochemistry, in agreement with the predictions of the MHA.

Aging↗
PubMed1985

Rabies virus binding at neuromuscular junctions.

Morphological, immunocytochemical, biochemical, and immunological techniques have been used to describe rabies virus binding to a sub-cellular unit and molecular complex at the neuromuscular junction (NMJ). Early after infection in vivo, virus antigen and virus particles were found by immunofluorescence, electron microscopy and immunoelectron microscopy in regions of high density acetylcholine receptors (AChR) at NMJs. One monoclonal antibody (alpha-Mab) to the alpha subunit of the AChR blocked attachment of radio-labeled rabies virus to cultured muscle cells bearing high density patches of AChR. A sub-cellular structure, resembling an array of AChR monomers, bound both rabies virus antigens and alpha-Mab. By immunoblotting with electrophoretically transferred motor endplate proteins, rabies virus proteins and alpha-Mab bound to two proteins of 43 000 and 110 000 daltons. A rabies virus glycoprotein antibody detected virus antigen bound to the 110 000 dalton protein. An auto-immune (anti-idiotypic) response followed immunization of mice with rabies virus glycoprotein antigen; the antibody was directed to the 110 000 dalton protein. This auto-antibody altered the kinetics of neutralization by rabies virus antibody and induced the formation of rabies virus antibody after inoculation of mice. These results define, at the neuromuscular junction, a rabies virus receptor which may be part of the acetylcholine receptor complex.

Animals↗
PubMed1992

Confocal microscopy in microgravity research.

We have studied the application and the feasibility of confocal scanning laser microscopy (CSLM) in microgravity research. Its superior spatial resolution and 3D imaging capabilities and its use of light as a probe, render this instrument ideally suited for the study of living biological material on a (sub-)cellular level. In this paper a number of pertinent biological microgravity experiments is listed, concentrating on the direct observation of developing cells and cellular structures under microgravity condition. A conceptual instrument design is also presented, aimed at sounding rocket application followed by Biorack/Biolab application at a later stage.

Animals↗
PubMed1988

Cardiotoxicity of Kenyan green mamba (Dendroaspis angusticeps) venom and its fractionated components in primary cultures of rat myocardial cells.

The cardiotoxic actions of Kenyan green mamba (Dendroaspis angusticeps) venom have been investigated using primary myocardial cell cultures isolated from neonatal rat hearts. The cardiotoxic actions of the whole venom and its fractionated components were evaluated on the basis of leakage of lactate dehydrogenase (LDH), changes in morphology, cell membrane lysis, decreases in viability and inhibition of spontaneous beating activity. The whole venom caused time- and concentration-dependent arrest of myocardial contraction, leakage of LDH, extensive disruption of cell monolayer, and decreases in viability. The venom was separated into 6 (DaI to DaVI) fractions by gel permeation chromatography on Sephadex G-50. Spontaneous beating activity was abolished by DaI to DaVI at high concentrations, while at lower doses they induced progressive depression of beating frequency after a 3-h treatment period. DaI to DaIV caused significant leakage of LDH, morphological damage, and decreases in viability after a 6-h incubation period. The most cardiotoxic fraction (DaIV), which also contains about 54% of the total protein of the whole venom, was fractionated into 18 polypeptides (Da1 to Da18) by ion exchange chromatography on Bio-Rex 70. On the basis of their ability to abolish myocardial contractility, release LDH, alter cellular structure, lyse cell membranes and reduce viability, the 18 fractions have been divided into 4 arbitrary subgroups of cytotoxins: cardiotoxins, Da1 to Da3; cardiotoxin-like polypeptides, Da4 to Da12, Da14; less active membrane lytic polypeptides, Da13, Da15 to Da17; and membrane lytic polypeptide, Da18. Marked synergistic cell membrane lysis occurred in myocardial cell cultures treated simultaneously with 2 cardiotoxin-like polypeptides, Da7 and Da11. It is suggested that the additive and synergistic cardiotoxic effects of high molecular weight cytotoxic proteins (DaI to DaIII), very low molecular weight cholinomimetic substances (DaV to DaVI) and the 4 subgroups of cardiotoxins may directly contribute to the pronounced cardiovascular problems observed in victims of green mamba bites.

Animals↗
PubMed1986

Kinetics of unidirectional transport in multimembrane systems as influenced by binding to macromolecules.

The distribution of externally added low-molecular-weight solutes in systems comprising alternating membraneous and aqueous compartments with binding capacity is described for special conditions of unidirectional transport and linear (i.e., far from saturation) binding. The kinetics of the process valid for a certain time period is expressed as the sum of exponential functions of time, their number being equal to the number of compartments investigated. The coefficients of the equation involve the rate and equilibrium parameters of the process as well as the volumes and the connecting areas of individual compartments. The degenerated case resulting from the cellular structure of biosystems is also considered. The description is shown to agree well with the results of drug potency testing, bioactivity being used to monitor concentration of an effector in the receptor region.

Analgesia↗
PubMed1988

Ultrastructure of the photosynthetic ciliate Mesodinium rubrum.

New cellular structures, bifurcated oral tentacles, were observed in many specimens of the photosynthetic ciliate Mesodinium rubrum from the northern Baltic Sea. Cross-sections of tentacles revealed rings (cylinders) of 14 microtubules with spokes. The number of microtubules per ring decreased from 14 to 12 or 11 inside the cell but no true kinetosomes were detected. These "micro-rings" were often associated with extrusomes and the tentacle tips consisted of extrusomes. A nucleus of a symbiotic alga was present, surrounded by algal cytoplasm containing plastids and delimited from the ciliate cytoplasm by two membranes. Each plastid was bounded by four membranes and was associated with one nucleomorph, suggesting a symbiotic origin as a cryptophyte. The unique symbiotic organization and the organelles of 14 microtubules make Mesodinium rubrum an organism of unusual evolutionary interest.

Animals↗
PubMed1990

Berberine-induced morphologic differentiation and down-regulation of c-Ki-ras2 protooncogene expression in human teratocarcinoma cells.

A pluripotent human teratocarcinoma cell clone, NT2/D1, which was derived from the Tera-2 cell line, was induced to differentiate into cells with neuronal cell morphology by treatment with berberine. As early as 1 day after a 24-h treatment of cells with berberine at a non-toxic dose of 0.1 mg/ml in culture medium, the cells started to show morphologic changes, developing into terminally differentiated neuronal cells with long, inter-connecting network-like cellular structures. This process is much faster as compared with that induced by treatment with retinoic acid (RA), which took at least several days to develop. Unlike RA, berberine could not induce murine teratocarcinoma cell line, F9, to differentiate into endodermal cells. It was also found that, although the NT2/D1 cell clone exhibited amplification and enhanced mRNA expression of c-Ki-ras2 gene as did the parent cell line, a marked down-regulation of c-Ki-ras2 mRNA expression was observed. However, there was no change in actin mRNA expression even after differentiation had occurred. Thus, morphologic differentiation of teratocarcinoma cells into neuronal cells is found to be associated with down-regulation of a protooncogene which plays some definite role in oncogenesis. The mechanism by which berberine induces differentiation in these cells needs further investigation.

Animals↗
PubMed1993

Prospects for using an IVEM with a FEG for imaging macromolecules towards atomic resolution.

Specimen preparation and imaging techniques for biological macromolecules have been improved to the point where attention to the electron-optical imaging conditions becomes a significant factor for achieving high resolution. A field emission gun (FEG) can provide an illumination source with a better spatial and temporal coherence suitable for imaging near atomic resolution. Our computational analysis of carbon film images taken between Scherzer focus and 1.1 microns underfocus (20x Scherzer focus) with the Hitachi 200 kV microscope with a cold field emission gun shows detectable contrast beyond 3.5 A resolution. In biological imaging, a large defocus is often used to optimize the low-resolution contrast in order to facilitate the subsequent steps in computer reconstruction. An intermediate-voltage electron microscope (IVEM) would optimize the contrast at high resolution by reducing the temporal coherent effects. In theory, the IVEM would give a greater depth of field so that large macromolecular assemblies such as viruses and cellular structures can be interpreted and reconstructed reliably using the projection approximation. These experimental and theoretical considerations provide a rationale for designing a future IVEM with a FEG suitable for biological macromolecule imaging close to atomic resolution.

Fourier Analysis↗
PubMed1979

Responses of nuclear glucose-6-phosphatase to diabetes and to hydrocortisone administered to normal and diabetic rats differ from those of the microsomal enzyme.

The effect of alloxan-diabetes, and of pharmacological doses of hydrocortisone administered to normal and diabetic rats, on carbamyl phosphate:glucose phosphotransferase and D-glucose-6-phosphate phosphohydrolase (EC 3.1.3.9) activities of isolated hepatic nuclei and microsomes were studied by assay at pH 7 in the absence and presence of deoxycholate. Hormonally related alterations both in activity levels and in the activation by the detergent (i.e. latency) of activities of the two cellular structural elements differed significantly. Most strikingly, (a) a 3--4-fold increase in the levels of activities of nuclei was seen in response either to diabetes or to hydrocortisone administered to normal rats whether or not detergent was added to preparations prior to assay; (b) the normally low degree of stimulation by detergent of activities of nuclei was unaltered in diabetes, and (c) administration of the glucocorticoid to diabetic rats decreased activity levels and increased their activation by detergent. Directly contrasting responses were noted with isolated microsomal preparations. Fundamental differences in the enzymes in these two organelle preparations are thus demonstrated. It appears that both synthetic and hydrolytic activities of this enzyme of nuclei may be manifest in the presence of requisite substrates, and that activities of this organelle may become increasingly prominent under certain hormonally perturbed conditions.

Animals↗
PubMed1994

The distribution of calmodulin/calmodulin binding proteins in the rat tapeworm, Hymenolepis diminuta.

Live tapeworms have been fixed to retain antigenicity of their proteins, and subsequently prepared for electron microscopy. Thin sections of tapeworms were prepared from resin blocks. Sections were immunocytochemically labelled using a colloidal gold probe and viewed using transmission electron microscopy. Calmodulin was detected associated with cellular structures to which calmodulin has previously been linked in other higher eukaryotes. Calmodulin would appear to have a similar role of importance in tapeworms, as it does in higher eukaryotes although tapeworms are prevalently a syncitium.

Animals↗