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At least 217 records · Page 12Linked to original sources
PubMed1999

Raman Spectra of Porous beta-TCP Bioceramics Implanted into Rabbit Femur.

The Raman spectra of porous beta-TCP(beta-tricalcium phosphate)bioceramics implanted into rabbits femur the boundary and rabbit femur were studied using Raman spectroscopy(excited with 514.5nm and 623.8nm laser)and near-infrared FT-Raman spectroscopy. The Raman characteristic frequencies were assigned. The advantages and disadvantages of visible and near IR excitation are described. The Raman characteristic frequencies of calcium phosphate collagen protein and lipid(or phospholipid)were shown in the Raman spectra. These results demonstrated that besides calcium phosphate collagen protein and lipids also existed in the implants and the boundary forming components of organic bone tissues. Results indicated that the beta-TCP bioceramic when implanted into rabbit femur was partly dissolved and degraded the new bone tissues were formed on the surface and in pores of implanted bioceramics.

Journal Article↗
PubMed2003

[In vitro release of tetracycline hydrochloride from alpha-TCP cement].

Drug release from alpha-TCP cement containing tetracycline hydrochloride (TTCH) was studied in vitro. Results from X-ray diffraction study indicated that TTCH did not prevent the hydration of alpha-TCP. In vitro drug release study showed that TTCH release could sustain over 1200 h, and the release was controlled by two mechanisms: (1) diffusion of free TTCH molecules through the porous cement (square-root-of-time kinetics); (2) dissociation of TTCH from the apatite-TTCH complex (zero-order kinetics). The mechanism controlling release would changed with the variety of the antibiotic content of cement pellets, as a result of TTCH adsorption and bonding on calcium phosphates. The first mechanism was predominantly for low concentration system TTCH-loaded apatite cement systems at the initial release period, and for high concentration TTCH-loaded apatite cement systems. As for low concentration TTCH-loaded apatite cement systems at later release stage, drug release was controlled by the coupling of the two mechanisms.

Anti-Bacterial Agents↗
PubMed2003

[Preparation of a biphasic calcined bone of beta-TCP/HAP and its application in BMP-2 gene medicine].

In this study, we produced a biphasic absorbable calcined bone (CB) of beta-TCP/HAP, and evaluated its function as a carrier of bone marrow derived mesenchymal stem cells(BMSCs) in BMP-2 gene medicine. Biphasic CB was manufactured and its surface was coated by collagen. X-ray diffraction analysis, scanning electron microscopy and biomechanical measurement were performed on the product. Heterotopic bone induction of product as carrier of BMP-2 gene transferred BMSCs and its biodegradability were tested in nude mice and goats. X-ray diffraction analysis showed biphasic patterns of HAP and beta-TCP. Scanning electron microscopy showed the porosity were similar to those of the cancellous bone, and the adhesion of cells on the CB surface were better after surface-coating with collagen. It had certain biomechanical strength and appropriate biodegradability. Biphasic CB loaded with Adv-hBMP-2 transduced BMSCs could induce much bony callus at the subcutaneous site of nude mice and the tibial bone defects of goats. The results showed biphasic CB is a superior carrier of cells in BMP-2 gene medicine.

Animals↗
PubMedDate not supplied

TCP and NTCP in preclinical and clinical research in Europe.

European research in radiation oncology has a long and successful tradition. The aim of this research is to increase the therapeutic window of radiotherapy by increasing the tumor control probability (TCP) and/or by decreasing the normal tissue complication probability (NTCP). This paper summarizes the basic radiobiological concept underlying treatment optimization by TCP-NTCP data and discusses some of the limitations of currently used models. These are controversial in many aspects and cannot be recommended for clinical routine practice but should rather be considered as a research tool.

Animals↗
PubMed1989

Autogenous, allogenic, and beta-TCP grafts: comparative effectiveness in experimental bone furcation defects in dogs.

The healing responses of three implant materials--fresh autogenous bone, allogenic decalcified freeze-dried bone, and alloplastic implant, beta-tricalcium phosphate (beta-TCP)--were evaluated and compared. Through-and-through furcational defects were surgically created in the third and fourth mandibular premolars of three dogs. Implant material was then placed individually in the surgical defects. All defects without grafting served as controls. Following grafting (ten weeks into the healing period), individual dogs were killed and prepared for light microscopy. The following results were recorded: (1) All materials were well-tolerated. No post-surgical complications occurred. (2) Graft sites showed more pronounced regeneration and the possibility of higher periodontal attachment than did control sites. (3) The defects filled with autogenous bone showed slightly more pronounced regeneration than in allogenic freeze-dried bone and beta-TCP.

Alveolar Bone Loss↗
PubMed1988

Anatomic correlation of NMDA and 3H-TCP-labeled receptors in rat brain.

Using quantitative autoradiography, we have compared the regional distribution of N-methyl-D-aspartate (NMDA) receptors labeled with 3H-glutamate and dissociative anesthetic binding sites labeled with 3H-N-(1-[2-thienyl]cyclohexyl)3,4-piperidine (3H-TCP). Binding of both ligands was highest in the hippocampal formation, with high concentrations in a number of cortical and olfactory regions. Intermediate amounts of binding for both ligands were measured in several thalamic and basal telencephalic structures. Very little binding was observed in the hypothalamus, some deep forebrain regions, and most brain-stem structures. Linear-regression analysis comparing the binding at both sites revealed a marked concordance (R = 0.95; p less than 0.001; Pearson product-moment). The granule cell layer of the cerebellum was the only region in which this concordance was not observed. Scatchard analysis of 3H-glutamate binding to NMDA receptors in stratum radiatum of hippocampal formation revealed an apparent single binding site with a Bmax of 9.78 +/- 0.84 pmol/mg protein and KD of 158 +/- 37 nM. 3H-TCP also bound to an apparent single site with a Bmax of 2.07 +/- 0.16 pmol/mg protein and KD of 127 +/- 30 nM. Our results are consistent with the hypothesis that the dissociative anesthetic binding site is linked to the NMDA receptor, and the data suggest that there are approximately 4-5 NMDA binding sites for each dissociative anesthetic binding site.

Animals↗
PubMed1980

[Principles of the TCP-implantation system after 2 years of clinical experience].

The TCP implantation system is based on absorbable tricalcium phosphate ceramics which is used in different ways as porcelain-fused-to-metal material. The strict and complex application of preimplantologic and peri-implantologic principles, particularly the cleansing and preparation of the implant bed and of the bone tissue, as well as newly developed, internally cooled cutting and self-cleaning instructions are of special importance. The shape of the implant and the operative technique also play an important role in achieving a successful oral implant. The nonmetalic surface of the TCP implant has proved to be an important advantage. Since these implants induce a fusion with the bone tissue which does not include connective tissue, the use of elastic coupling elements that functionally imitate the periodontal tissue have proved to be an important factor in the primary and long-term success of the implant. The gnathologic formation of the chewing surfaces is just as important as the need for proper information, training, and supervision of the dentists as well as control of implants.

Blade Implantation↗
PubMed1997

A comparison of fibrous tissue formation surrounding intraperitoneal and subcutaneous implantation of ALCAP, HA, and TCP ceramic devices.

It is well demonstrated in the literature that ceramic drug delivery systems are highly compatible and non-immunogenic. Recent studies in our laboratory have documented the need of an experiment comparing foreign body reactions of several different types of ceramics used for implantation and/or drug delivery. The specific objective of this study was to compare the subcutaneous (s.c.) and intraperitoneal (i.p.) foreign body reactions and biocompatibility of the following implantable materials presently used in orthopedics: ALCAP (aluminum calcium phosphate), HA (hydroxyapatite), and TCP (tricalcium phosphate). The rats were divided into four groups: Group I consisted of 10 rats implanted with ALCAP i.p. and s.c., Group II (n = 10) animals were implanted i.p. and s.c. with HA, Group III consisted of 10 rats implanted i.p. and s.c. with TCP, and Group IV consisted of 10 control animals that were housed under the same environmental conditions as the three experimental groups. At 90 days post-implantation, rats in all four groups were euthanized. The microscopic evaluation of the fibrous tissue surrounding i.p. and s.c. implants revealed the following: 1) all of the ceramic devices had varying degrees of fibrous capsule formation at the time of sacrifice, 2) the thickness of the fibrous tissue capsule was dependent on the type of ceramic used, and 3) the thickness of the fibrous tissue capsules around the subcutaneous devices differed remarkably from implants placed intraperitoneally. The data from this study indicates that capsule formation is dependent upon factors such as ceramic composition and surgical implantation site.

Aluminum Compounds↗
PubMed1997

Subunit characterization of the Caenorhabditis elegans chaperonin containing TCP-1 and expression pattern of the gene encoding CCT-1.

The chaperonin containing TCP-1 (CCT) from the free-living nematode Caenorhabditis elegans was purified and shown to contain at least seven subunit species ranging from 52-65 kDa. SDS-gel electrophoresis and Western blot analyses with antibodies against C. elegans CCT-1 and CCT-5 and an antibody which recognizes a conserved region in vertebrate CCT subunits confirm that the subunit compositions of CCTs from distantly related organisms (C. elegans and bovine species) are remarkably similar. Surprisingly, the co-purified HSP60 chaperonin present in the C. elegans CCT preparation has the greatest binding activity for denatured actin. Expression of a reporter gene under the control of the C. elegans cct-1 promoter is found to be mainly restricted to neuronal and muscle tissues, an observation which is consistent with the participation of CCT in actin and tubulin folding.

Amino Acid Sequence↗
PubMed1996

Chromosomal assignment and imprinting tests for the mouse delta subunit of the cytosolic chaperonin containing TCP-1 (Cct4) gene to proximal chromosome 11.

The CCT (chaperonin containing TCP-1) complex functions as a molecular chaperone in the eukaryotic cytosol. This complex consists of several species of related polypeptides. The chromosomal localization of the mouse Cct4 gene encoding the delta subunit of CCT was assigned in this study to proximal chromosome 11 by genetic mapping. Restriction mapping analysis using YAC and pulse-field gel electrophoresis showed that Cct4 is located within a region about 300 kb from the imprinted gene U2af1-rs1. Expression of Cct4 was biallelic, and therefore Cct4 is not imprinted in neonatal mice. The localization of the human homologue of Cct4 on chromosome 2 corresponds well with the fact that homologues of other genes in the proximal region of mouse chromosome 11 also map to the region of conserved synteny in human chromosome 2.

Alleles↗
PubMed2006

Characterization of the cytoplasmic chaperonin containing TCP-1 from the Antarctic fish Notothenia coriiceps.

The cytoplasmic chaperonin containing TCP-1 (CCT) plays a critically important role in the folding and biogenesis of many cytoskeletal proteins, including tubulin and actin. For marine ectotherms, the chronically cold Southern Ocean (-2 to +2 degrees C) poses energetic challenges to protein folding, both at the level of substrate proteins and with respect to the chaperonin/chaperone folding system. Here we report the partial functional and structural characterization of CCT from an Antarctic notothenioid fish, Notothenia coriiceps. We find that the mechanism of folding by the Antarctic fish CCT differed from that of mammalian CCT: (1) the former complex was able to bind denatured beta-tubulin but (2) when reconstituted with rabbit Cofactor A, failed to release the protein to yield the tubulin/cofactor intermediate. Moreover, the amino acid sequences of the N. coriiceps CCT beta and theta chains contained residue substitutions in the equatorial, apical, and intermediate domains that would be expected to increase the flexibility of the subunits, thus facilitating function of the chaperonin in an energy poor environment. Our work contributes to the growing realization that protein function in cold-adapted organisms reflects a delicate balance between the necessity of structural flexibility for catalytic activity and the concomitant hazard of cold-induced denaturation.

Adaptation, Physiological↗
PubMed2006

Affinity purification reveals the association of WD40 protein constitutive photomorphogenic 1 with the hetero-oligomeric TCP-1 chaperonin complex in mammalian cells.

Constitutive photomorphogenic 1 (COP1), a protein composed of a RING finger, a coiled-coil domain and seven WD40 repeats, functions as an E3 ubiquitin ligase that targets key transcription factors for ubiquitination and degradation in both higher plants and mammalian cells. While COP1 is required for light-mediated development in plants, its mammalian counterpart has been implicated in tumorigenesis. We previously showed that COP1 forms high-molecular-weight complexes in mammalian cells. Here we report our attempts in characterizing the components of the mammalian COP1 complexes by affinity purification combined with mass spectral analysis. We find that both transiently and stably expressed COP1 associates with the hetero-oligomeric TCP-1 chaperonin complex (TRiC), heat shock protein 70 (Hsp70) and BAG-family molecular chaperone regulator-2 (BAG2). In addition, stably expressed COP1 binds to major vault protein (MVP) and translocated promoter region (Tpr). The TRiC/Hsp70 complex is known to interact with and assist in the folding of a number of WD40 proteins in Saccharomyces cerevisiae. The association of WD40 protein COP1 with TRiC/Hsp70 in mammalian cells suggests that facilitating the folding of WD40 proteins may be a conserved function for TRiC/Hsp70 from yeast to mammals.

Animals↗
PubMed2003

Transient kinetic analysis of ATP-induced allosteric transitions in the eukaryotic chaperonin containing TCP-1.

The chaperonin CCT (chaperonin containing t-complex polypeptide 1 (TCP-1)) from bovine testis was mixed rapidly with different concentrations of ATP and the time-resolved change in fluorescence emission, upon excitation at 280 nm, was followed. Two kinetic phases were observed and assigned by (i) analyzing the dependence of the corresponding observed rate constants on ATP concentration; and (ii) by carrying out mixing experiments also with ADP, ATPgammaS and ATP without K(+). The values of the observed rate constants corresponding to both phases are found to be dependent on ATP concentration. The observed rate constant corresponding to the fast phase displays a bi-sigmoidal dependence on ATP concentration with Hill coefficients that are similar to those determined in steady-state ATPase experiments. This phase most likely reflects ATP binding-induced conformational changes. The rate constant of the conformational change in the presence of excess ATP is about 17s(-1) (at 25 degrees C) and is tenfold slower than the corresponding rate constant of GroEL. The observed rate constant corresponding to the second slower phase displays a hyperbolic dependence on ATP concentration. This phase is not observed in mixing experiments of CCT with ADP, ATPgammaS or ATP without K(+) and it, therefore, reflects a conformational change associated with ATP hydrolysis. Taken together, our results indicate that the kinetic mechanism of the allosteric transitions of CCT differs considerably from that of GroEL.

Adenosine Triphosphate↗
PubMed2001

Microtubule cytoskeleton perturbation induced by taxol and colchicine affects chaperonin containing TCP-1 (CCT) subunit gene expression in Tetrahymena cells.

We report the existence of a CCT epsilon subunit gene that encodes subunit epsilon of the chaperonin CCT (chaperonin containing TCP-1) in Tetrahymena pyriformis. This work focuses on the study of the effects of the microtubule polymerizing agent taxol and the depolymerizing agent colchicine on microtubule dynamics and their role in the regulation of tubulin and CCT subunit genes. Under taxol treatment some TpCCT and tubulin genes are distinctly expressed until 30 min of treatment. Cytoplasmic TpCCT mRNA levels slightly decrease while tubulin transcripts are increasing. In colchicine treated cells TpCCT and tubulin transcripts decrease in the initial 30 min of treatment and then start to increase. However, both antimitotic agents induce TpCCT and tubulin gene transcription. This induction does not correlate with increased steady-state levels of TpCCT proteins and seems to be necessary to replete cytoplasmic TpCCT mRNAs. Moreover, we found that TpCCT epsilon and TpCCT alpha but not TpCCT eta are present in the insoluble fraction after a postmitochondrial fractionation that contains components of the ciliate cortex structure, basal bodies and cilia. This suggests that some TpCCT subunits may be associated with these structures. The association of TpCCT epsilon subunit is stimulated either by taxol or colchicine treatment. These observations support the idea that CCT subunits could have additional roles in vivo.

Actins↗
PubMed1997

Cytoplasmic chaperonin containing TCP-1: structural and functional characterization.

Actin and tubulin polypeptide chains acquire their native conformation in the presence of the cytoplasmic chaperonin containing TCP-1 (CCT, also called TRiC) and, in the case of alpha- and beta-tubulin, additional protein cofactors. It has been previously demonstrated that nucleotide exchange and ATP hydrolysis act to switch CCT between conformations that interact either strongly or weakly with unfolded substrates [Melki, R., & Cowan, N.J. (1994) Mol. Cell. Biol. 14, 2895-2904]. The present study further documents the conformational changes and function of CCT. It is first shown, by the use of a range of labeled denatured substrate proteins and a radiolabeled total soluble HeLa cell extract, that CCT in the absence of nucleotides can bind any of a large number of proteins in vitro with high affinity. Second, by the use of denatured labeled beta-actin and beta-tubulin as model substrates for binding to CCT, we demonstrate that the CCT particle can contain two substrate protein chains simultaneously. Third, by electron microscopy, sedimentation velocity, and intrinsic fluorescence measurements, we document the conformational difference between CCT in its ATP- and ADP-bound forms, as well as the change that results from binding of substrate protein. A model summarizes substrate association with CCT and the role of the nucleotide in regulating the affinity of CCT for target proteins.

Actins↗
PubMed2005

Sequential ATP-induced allosteric transitions of the cytoplasmic chaperonin containing TCP-1 revealed by EM analysis.

The eukaryotic cytoplasmic chaperonin containing TCP-1 (CCT) is a hetero-oligomeric complex that assists the folding of actins, tubulins and other proteins in an ATP-dependent manner. To understand the allosteric transitions that occur during the functional cycle of CCT, we imaged the chaperonin complex in the presence of different ATP concentrations. Labeling by monoclonal antibodies that bind specifically to the CCTalpha and CCTdelta subunits enabled alignment of all the CCT subunits of a given type in different particles. The analysis shows that the apo state of CCT has considerable apparent conformational heterogeneity that decreases with increasing ATP concentration. In contrast with the concerted allosteric switch of GroEL, ATP-induced conformational changes in CCT are found to spread around the ring in a sequential fashion that may facilitate domain-by-domain substrate folding. The approach described here can be used to unravel the allosteric mechanisms of other ring-shaped molecular machines.

Adenosine Triphosphate↗
PubMed1997

Developmental and light-dependent changes of the cytosolic chaperonin containing TCP-1 (CCT) subunits in maize seedlings, and the localization in coleoptiles.

The cytosolic chaperonin containing TCP-1 (CCT) is known to keep fold cytoskeletal proteins and is involved in the proper organization of the cytoskeleton. These studies are based on the assumption that growth responses linked to structural rearrangement of the plant cytoskeleton include the action of CCT and the need for newly synthesized tubulin. The presence of the alpha- and epsilon-subunits of CCT was investigated in soluble fractions of protein extracts from maize mesocotyls and coleoptiles at distinct growth stages. The CCT-subunits, tubulins and actin decreased in the coleoptile in response to far-red light. In addition, independent from light treatment, the amount of CCT epsilon abundance declined with age in coleoptiles and mesocotyls between 2 and 4.5 days after sowing. In contrast to CCT epsilon, no significant light regulation of CCT alpha was found in the mesocotyl. In two day old, light-grown rapidly elongating coleoptiles part of the CCT alpha subunit and the bulk of actin and tubulin was found shifted into fractions of high molecular weight complexes when compared to slowly elongating, dark grown coleoptiles. In 4.5 day old, etiolated and elongating coleoptiles, part of both CCT-subunits and cytoskeleton proteins were found in fractions of high molecular weight. A complete disappearance of these polypeptides was observed in old far-red irradiated growth-arrested coleoptiles. CCT epsilon was found to be colocalized to microtubular structures and to the nucleus. We conclude from our data that abundance of CCT-subunits in soluble extracts is dependent on age and light treatment, but independent from the growth stage of mesocotyl and coleoptile.

Base Sequence↗