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PubMed1999

The effect of sintered beta-dicalcium pyrophosphate particle size on newborn Wistar rat osteoblasts.

During recent years, sintered dicalcium phosphate (SDCP) has been shown to be an effective artificial bone filler for repairing bone defects. The goal of this study was to elucidate the effect of SDCP particle size on osteoblasts. Osteoblasts were mixed and cultured with various sized SDCP particles (0.5-3.0, 37-63, 177-250, and 420-841 microns) for 1 h, 3 h, 1 day, 3 days, and 7 days and then analyzed. The results show that the adding of smaller sized SDCP particles (0.5-3.0 and 37-63 microns) into osteoblast culture can significantly affect the cell counts of osteoblasts. The secretion of transforming growth factor-beta 1, alkaline phosphatase, and prostaglandin E2 in culture medium increased significantly. The changes were most significant and persisted longer in smaller particle groups. Small sintered dicalcium phosphate particles can inhibit the proliferation of the osteoblasts. The inhibitory effects of the smaller sized SDCP particles on the osteoblasts were mediated by the promotion of osteoblast differentiation and the increased synthesis of prostaglandin E2.

Alkaline Phosphatase↗
PubMed1993

Contributions of nuclear medicine to the therapy of malignant tumors.

Radionuclides are applied in oncology for diagnosis and therapy. The former demands gamma--emitting radionuclides for labeling specific substrates for localizing malignant tissue and for analyzing tumor metabolism in vivo. Here, positron emission tomography (PET) may register in vivo the metabolism, for example, of glucose, amino acids, and receptors and of potentially useful cytotoxic agents. The advantage of the positron emitting radionuclides of carbon, nitrogen and fluorine is the labeling of substrates without changing substrate specificity within the metabolic reaction chain; also, substrate concentration in situ may be quantified. With regard to therapy radionuclides that emit beta- and alpha-particles or decay by electron capture with the Auger effect, are administered in ionic form or with tumor seeking substrates. Examples are radioiodine for treating thyroid malignancy and radiophosphorus for myeloproliferative diseases. Organically bound radionuclides are given as labeled ligands for specific receptors, such as meta-iodo-benzylguanidine (MIBG) for treating the catecholamine producing tumors phaeochromocytoma and neuroblastoma and labeled monoclonal antibodies for tumors specific receptors. Highly localized energy depositions come from Auger emitters such as 125I and by the neutron capture therapy, where boron-10 in the tumor cell is exposed to thermal neutrons for initiating the B10 (n; alpha) Li7 reaction, especially for treating neuro- and glioblastoma and melanoma. Endogenous radiotherapy with radionuclides rely on the success of delivering a proper amount of energy into individual tumor cells with optimal protection of normal tissue. The inevitable heterogeneity of energy deposition events from such approaches demands careful dosimetric assessment for which the classical methods of dosimetry for percutaneous radiotherapy are not applicable.

Alpha Particles↗
PubMed1979

Nonidentity of the 48,000-dalton protein of mRNA-protein particles and the beta subunit of eukaryotic initiation factor 2.

The beta subunits of the GTP-dependent initiator methionyl-tRNA-binding protein and the 48,000-dalton protein, which is one of the two major proteins present in isolated mRNA . protein particles, have been shown to share a number of similar structural and mRNA-binding properties. The nonidentity of these two proteins is now established by documentation of differing molecular weights, isoelectric focusing points, and products of protease or cyanogen bromide cleavage.

Animals↗
PubMed2005

Imaging amyloid beta peptide oligomeric particles in solution.

While all protein misfolding diseases are characterized by fibrous amyloid deposits, the favorable free energy and strongly cooperative nature of the self-assembly have complicated the development of therapeutic strategies aimed at preventing their formation. As structural models for the amyloid fibrils approach atomic resolution, increasing evidence suggests that early folding intermediates, rather than the final structure, are more strongly associated with the loss of neuronal function. For that reason we now demonstrate the use of cryo-etch high-resolution scanning electron microscopy (cryo-HRSEM) for the direct observation of pathway intermediates in amyloid assembly. A congener of the Abeta peptide of Alzheimer's disease, Abeta(13-21), samples a variety of time-dependent self-assembles in a manner similar to those seen for larger proteins. A morphological description of these intermediates is the first step towards their structural characterization and the definition of their role in both amyloid assembly and neurotoxicity.

Amyloid beta-Peptides↗
PubMedDate not supplied

Specificity of a beta-glucan receptor on macrophages from Atlantic salmon (Salmo salar L.).

This study was undertaken to study the specificity of a beta-glucan receptor on Atlantic salmon macrophages. Previous in vitro studies have shown that Atlantic salmon macrophages express a receptor that rapidly recognizes and mediates uptake of nonopsonized beta-glucan particles. The ingestion of particles was shown to be inhibited by preincubating the macrophages with glucans containing beta-1,3-linkages, but not by glucans containing other linkages. In the present study we have shown that small oligomers from formolyzed beta-glucan particles, and linear beta-1,3-linked oligomers with a degree of polymerization (DP) > or = 3, were efficient inhibitors of uptake of glucan particles. Oligomers from beta-1,6-linked pustulan, or small size oligomers with linkages other than beta-1,3, were not able to inhibit uptake of glucan particles. The inhibitory effect of laminarin and laminariheptaose was abolished by degrading the nonreducing terminal ends by sodium periodate treatment. The inhibitory effect of laminarin was regained by a complete Smith degradation; that is, periodate oxidation followed by reduction and hydrolysis. Modification of the reducing end of laminariheptaose had no effect on its ability to inhibit uptake. Furthermore, it was shown that periodate-oxidized glucan particles were not taken up by salmon macrophages, and that the uptake was regained when the particles were hydrolyzed to recover the nonreducing terminal end. Lastly, it was shown that endo-beta-1,6-glucanase treatment of the yeast glucan particles did not reduce uptake, confirming that beta-1,6-linkages are not involved in the recognition. These results suggest that Atlantic salmon macrophages possess a receptor that may recognize even very short beta-1,3-linked glucosyl chains extending from yeast cell walls.

Animals↗
PubMed1985

SERGE, the subcellular site of initial hepatic glycogen deposition in the rat: a radioautographic and cytochemical study.

Hormonal control of hepatic glycogen and blood glucose levels is one of the major homeostatic mechanisms in mammals: glycogen is synthesized when portal glucose concentration is sufficiently elevated and degraded when glucose levels are low. We have studied initial events of hepatic glycogen synthesis by injecting the synthetic glucocorticoid dexamethasone (DEX) into adrenalectomized rats fasted overnight. Hepatic glycogen levels are very low in adrenalectomized rats, and DEX causes rapid deposition of the complex carbohydrate. Investigation of the process of glycogen deposition was performed by light and electron microscopic (EM) radioautography using [3H]galactose as a glycogen precursor. Rats injected with DEX for 2-3 h and [3H]galactose one hour before being killed displayed an increasing number of intensely labeled hepatocytes. EM radioautography revealed silver grains over small (+/- 1 micron) ovoid or round areas of the cytosome that were rich in smooth endoplasmic reticulum (SER) and contained a high concentration of small dense particles. These distinct areas or foci of SER and presumptive glycogen (SERGE) were most numerous during initial periods of glycogen synthesis. After longer exposure to DEX (4-5 h) more typical deposits of cytoplasmic glycogen were evident in the SERGE regions. Several criteria indicated that the SERGE foci contained glycogen or presumptive glycogen: resemblance of the largest dense particles to beta-glycogen particles in EM; association of 3H-carbohydrate with the foci; removal of particles and label with alpha-amylase; and positive reaction with periodic acid-chromic acid-silver methenamine. The concentration of SER in the small foci and the association of newly formed glycogen particles with elements of SER suggest a role for this organelle in the initial synthesis of glycogen.

Animals↗
PubMed2005

Yeast whole glucan particle (WGP) beta-glucan in conjunction with antitumour monoclonal antibodies to treat cancer.

Beta-glucans, biological response modifiers (BRMs) derived from the cell walls of yeast and other sources, have been demonstrated to prime leukocyte complement receptor 3 (CR3), thus enabling these cells to kill tumours opsonised with complement fragment iC3b. Many tumours activate complement via the classical pathway mediated by antitumour monoclonal antibodies (mAbs) or natural antibodies. Studies into the cellular and molecular mechanisms of action have demonstrated that orally administrated yeast beta-glucans are ingested and processed by macrophages. These macrophages secrete the active moiety that primes neutrophil CR3 to kill iC3b-opsonised tumour cells. Extensive studies in preclinical animal tumour models have demonstrated the efficacy of combined oral particulate yeast beta-glucan with antitumour mAb therapy in terms of tumour regression and long-term survival. It is proposed that the addition of beta-glucan will further improve the clinical therapeutic efficacy of antitumour mAbs in cancer patients.

Animals↗
PubMed1992

Stimulation of human monocyte beta-glucan receptors by glucan particles induces production of TNF-alpha and IL-1 beta.

beta-glucans are pharmacologic agents that rapidly enhance host resistance to a variety of biologic insults through mechanisms involving macrophage activation. To determine whether stimulation of the beta-glucan receptors on human monocytes resulted in cytokine production, monolayers of monocytes were incubated with purified yeast glucan particles and measured for tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) mRNA and protein. By Northern blot analysis, TNF-alpha mRNA was detected within 30 min of incubation with glucan particles, peaked at 2 h, and remained elevated for at least 8 h. Glucan induction of IL-1 beta mRNA followed a similar time-course of initiation and accumulation. By enzyme-linked immunosorbent assays (ELISAs), significant levels of TNF-alpha and IL-1 beta were present in supernatants of glucan-treated cells within 1 h and plateau levels of both cytokines were approached within 4 h. At particle-to-cell ratios of from 0.4 to 18, glucan particles induced dose-dependent increases in TNF-alpha and IL-1 beta mRNA and corresponding increases in TNF-alpha and IL-1 beta proteins. Exposure of monocytes to glucan particles for 0-30 min and washing before continued incubation for 4 h in particle-free buffer induced production and secretion of TNF-alpha and IL-1 beta in a time-dependent fashion compatible with phagocytosis. The pretreatment of monocyte monolayers with trypsin reduced glucan-induced production of TNF-alpha and IL-1 beta in a dose-dependent manner with 5 micrograms/ml of trypsin effecting reductions of greater than 50%. Thus, glucan particles induce human monocyte production of TNF-alpha and IL-1 beta by a mechanism that is dependent on trypsin-sensitive beta-glucan receptors.

Cells, Cultured↗
PubMed1971

Morphological and biochemical characteristics of glycogen particles isolated from rabbit polymorphonuclear leukocytes.

The fine structure of ascitic cells, consisting of 87-92% heterophil, 5-10% eosinophil leukocytes, and 3% macrophages, is well preserved by glutaraldehyde-osmium tetroxide fixation only when the osmolality of the fixative is appropriately balanced. The beta-glycogen particles, 35-45 mmicro in diameter, are found either as large accumulations in the perinuclear region or in a dispersed form in peripheral cytoplasm. In the heterophils, they are embedded in a coarse-grained ground substance. Extraction and purification of the glycogen were performed by differential precipitation-centrifugation. Yield (35% recovery), purity (4% protein contamination), and preservation of a high sedimentation coefficient (240S) represent the main advantages of the proposed procedure. The analysis of the profile of the sedimentation curve, together with an analysis of the particle size measurements and of particle fine structure, leads to the conclusion that the beta-particles form a homogeneous population with a gaussian distribution curve. Each particle consists of smaller units which increase in number with increasing size, the largest ones taking on the appearance of small rosettes. The glycogen particles of the microsomal fraction, still loaded with phosphorylase, were submitted to a synthetic activity by incubation in the presence of glucose-l-phosphate. The analysis of the particle growth shows that particles of all sizes respond equally well.

Animals↗
PubMed1987

Specificity of membrane complement receptor type three (CR3) for beta-glucans.

The binding of the iC3b receptor (CR3) to unopsonized zymosan was shown to result from CR3 attachment to cell wall beta-glucans. A specificity of neutrophil responses for beta-glucan was first suggested by a comparison of yeast (Saccharomyces cerevisiae) cell wall components for stimulation of a neutrophil superoxide burst. Neutrophils responded poorly to heat-killed yeast, but gave increasingly better responses to cell wall polysaccharides devoid of proteins (zymosan) and nearly pure beta-glucan particles derived from zymosan. Zymosan triggered a burst that was 29% as great as that stimulated by phorbol myristate acetate (PMA), and beta-glucan particles stimulated a burst that was 72% as great as that produced by PMA. Phagocytic responses to yeast were also inhibited by soluble glucans but not by soluble mannans. Three types of experiments demonstrated a role for CR3 in these responses. First, neutrophil ingestion of either yeast or yeast-derived beta-glucan particles was blocked by monoclonal anti-CR3, fluid-phase iC3b, or soluble beta-glucan from barley. Monocyte ingestion of beta-glucan particles was also blocked by anti-CR3, but not by anti-CR1 or anti-C3. Second, the neutrophil superoxide burst response to either zymosan or beta-glucan particles was blocked by anti-CR3 or fluid-phase iC3b, and was completely absent with neutrophils from 3 patients with an inherited deficiency of CR3. Third, CR3 was isolated from solubilized neutrophils by affinity chromatography on beta-glucan-Sepharose.

Glucans↗
PubMed2004

Preparation of microcapsules containing two-phase core materials.

Urea-formaldehyde (UF) microcapsules containing two-phase core materials in which phthalocyanine blue BGS (beta-CuPc) particles were homodispersed in tetrachloroethylene (TCE) were prepared by in situ polymerization. The effects of the various process parameters, including the type of surface modifier, the viscosity of UF prepolymer, the type of water-soluble surfactant, and the concentration of oil-soluble surfactant in the capsule core on the dispersity of beta-CuPc particles in TCE and the properties of the capsule wall and the adsorption of beta-CuPc particles on the internal surface of capsule wall were experimentally investigated. It was shown that using octadecylamine (ODA) to modify beta-CuPc particles resulted in a significant increase of the dispersing extent (DE) and the electrophoresis velocity of the particles in TCE (about 4 and 20 times more than that of unmodified). In addition, the optimal reaction conditions of the synthesis UF prepolymer were obtained by the orthogonal test. On the other hand, as the oil/water interfacial tension of emulsion was big enough, the microcapsule formed. The concentration of Span-80 in TCE was no less than 0.062 mM; the adsorption of beta-CuPc particles on internal surface of wall were restrained. Finally, the microcapsules in which beta-CuPc particles possess reversible response to dc electric field were obtained.

Amines↗
PubMed1980

An ultrastructural study of the craniocaudal continuation of the glycogen body.

An ultrastructural analysis of the chicken glycogen body and its craniocaudal continuation areas shows a continuum of astroglial cell types. Characteristic glycogen body astroglia are confined to the classically defined body located in the chicken lumbosacral spinal cord. These are large cells which have an eccentric dark nucleus surrounded by a rim of dense cytoplasm which contains the usual complement of organelles. The remainder of the cell volume is occupied by alpha and beta glycogen particles interspersed with a flocculo-granular material continuous with the main cytoplasmic mass. Astroglial cells of continuation areas usually have a light cytoplasm and a centrally placed nucleus. They contain beta glycogen particles of varying sizes, but like the glycogen body cells, may have beta particles as large as 48 nm. Such particles, which resemble four leaf clovers in shape, are suggestive of an ordered substructure. Gliofilaments are not always conspicuous in astroglial perikarya, but large numbers of them are present in the processes. Although the continuation areas are mostly confined to gray matter regions, the contained astroglial processes exhibit circular, triangular, or cylindrical shapes and form an unpatterned mosaic. Astrocytic processes forming the glia limitans on the anterior and posterior margins of the cord often contain conspicuous amounts of glycogen. The ultrastructural identification of such large amounts of glycogen within the chicken nervous system suggests that it plays a major role in avian neural metabolism.

Animals↗
PubMed1993

The altricial pigeon is born blind with a transient glycogen cataract.

The lens nucleus of altricial birds contains a large amount of glycogen. It is not known why glycogen in such concentration does not cause a trace of lens opalescence. Here we report that the altricial pigeon is born with a dense nuclear opacity; this opacity has practically disappeared by 4 weeks of age. Thin-section electron microscopy revealed that the opacity was specifically associated with an enormous number of large glycogen aggregates in nuclear fiber cells. These aggregates of various sizes (up to approximately 5 microns) were composed of smaller individual 35-nm beta glycogen particles. In contrast, glycogen aggregates were not seen in nuclear fiber cells of all transparent older lenses. The glycogen aggregates have gradually dissociated into a homogeneous distribution of individual beta particles in the entire cytoplasm of nuclear fibers which accompanies the development of lens transparency. This study suggests that an extensive accumulation of glycogen aggregates in the lens nucleus is the cause of light scattering and opacification. The transparency of the altricial pigeon lens during normal development is therefore regulated by two different forms of glycogen. Precocial birds such as chick have no lens glycogen, therefore never develop a glycogen cataract and have excellent visual acuity upon hatching.

Agglutination↗
PubMed1990

Evidence for the presence of glycogen in rat thymus.

Chemical and biochemical analysis of the polysaccharide, present in rat thymus, indicate that it consists of glucose units alpha-1,4 and alpha-1,6 linked. Electron microscopy reveals the presence of a polysaccharide, similar to the beta-glycogen particles observed in liver and muscle with an average diameter of 20-30 nm. They are located in the cytoplasmic area of T-cells from the cortical region of the thymus. Enzymatic analysis indicates that the beta-particles contain a highly branched glucan with short external chains. Some of the enzymes of glycogen metabolism: synthase, phosphorylase and branching were for the first time partially purified from rat thymus and some of their properties were studied. Therefore, glycogen appeared to be synthesized in rat thymus.

1,4-alpha-Glucan Branching Enzyme↗
PubMed2005

Macrophage internalization of fungal beta-glucans is not necessary for initiation of related inflammatory responses.

Cell wall beta-glucans are highly conserved structural components of fungi that potently trigger inflammatory responses in an infected host. Identification of molecular mechanisms responsible for internalization and signaling of fungal beta-glucans should enhance our understanding of innate immune responses to fungi. In this study, we demonstrated that internalization of fungal beta-glucan particles requires actin polymerization but not participation of components of caveolar uptake mechanisms. Using fluorescence microscopy, we observed that uptake of 5-([4,6-dichlorotriazin-2-yl] amino)-fluorescein hydrochloride-Celite complex-labeled Saccharomyces cerevisiae beta-glucan by RAW macrophages was substantially reduced in the presence of cytochalasin D, which antagonizes actin-mediated internalization pathways, but not by treatment with nystatin, which blocks caveolar uptake. Interestingly, beta-glucan-induced NF-kappaB translocation, which is necessary for inflammatory activation, and tumor necrosis factor alpha production were both normal in the presence of cytochalasin D, despite defective internalization of beta-glucan particles following actin disruption. Dectin-1, a major beta-glucan receptor on macrophages, colocalized to phagocytic cups on macrophages and exhibited tyrosine phosphorylation after challenge with beta-glucan particles. Dectin-1 localization and other membrane markers were not affected by treatment with cytochalasin D. Furthermore, dectin-1 receptors rather than Toll-like receptor 2 receptors were shown to be necessary for both efficient internalization of beta-glucan particles and cytokine release in response to the fungal cell wall component.

Actins↗
PubMed2003

Application of cyclam-capped beta-cyclodextrin-bonded silica particles as a chiral stationary phase in capillary electrochromatography for enantiomeric separations.

Two novel types of substituted cyclam-capped beta-cyclodextrin (beta-CD)-bonded silica particles have been prepared and used as chiral stationary phases in capillary electrochromatography (CEC). The two stationary phases have a chiral selector with three recognition sites: beta-CD, cyclam, and the latter's sidearm. They exhibit excellent enantioselectivities in CEC for a wide range of compounds as a result of the cooperative functioning of the anchored beta-CD and cyclam. After inclusion of the metal ion (Ni2+) from the running buffer into the substituted cyclams and their sidearm ligands, the bonded stationary phases become positively charged and can provide extra electrostatic interactions with ionizable solutes and enhance the dipolar interactions with some polar neutral solutes. This enhances the host-guest interaction with some solutes and improves chiral recognition and enantioselectivity. These new types of stationary phases exhibit great potential for fast chiral separations in CEC.

Chromatography↗