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K Tezuka

Publications and source records attributed to K Tezuka.

At least 55 records · Page 3Linked to original sources
PubMed1992

Identification of osteopontin in isolated rabbit osteoclasts.

Bone remodeling is a complex process coupling bone formation and resorption. Osteoblasts, the bone-forming cells, are known to produce various bone matrix proteins and cytokines; however, little is known about protein factors produced by osteoclasts or bone-resorbing cells. A method utilizing the high affinity of osteoclasts for tissue culture dishes was developed to isolate a large number of pure osteoclasts from rabbit long bones. A cDNA library was then constructed from these isolated osteoclasts, and differential cDNA screening was performed between osteoclasts and spleen cells. Two clones representing osteoclast-specific clones, named OC-1 and OC-2, were isolated. By Northern blot analysis, OC-1 was expressed in osteoclasts and in kidneys, whereas OC-2 was specific for osteoclasts. OC-1 was found to encode osteopontin from its nucleotide sequence, and therefore, osteopontin may have other functions for osteoclastic bone resorption besides osteoclast attachment to bone.

Amino Acid Sequence↗
PubMed1992

Studies on synthetic pathway of xylose-containing N-linked oligosaccharides deduced from substrate specificities of the processing enzymes in sycamore cells (Acer pseudoplatanus L.).

We measured the activities of alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase, alpha-1,6-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase, beta-1,4-mannosyl-glycoprotein beta-1,2-xylosyltransferase and glycoprotein 3-alpha-L-fucosyltransferase in the Golgi fraction of suspension-cultured cells of sycamore (Acer pseudoplatanus L.) using fluorescence-labelled oligosaccharides as acceptor substrates for these transferase reactions. The structures of the pyridylaminated oligosaccharides produced by these reactions were analyzed by two-dimensional sugar mapping using high-performance liquid chromatography. We demonstrated that (formula; see text) was processed to produce by these in vitro reactions. On the basis of these results, we discuss a biosynthetic pathway for xylose containing N-linked oligosaccharides in plant glycoproteins.

Carbohydrate Sequence↗
PubMed1991

Prostaglandin F2 alpha stimulates proliferation of clonal osteoblastic MC3T3-E1 cells by up-regulation of insulin-like growth factor I receptors.

Prostaglandin F2 alpha (PGF2 alpha) stimulates proliferation of clonal osteoblastic MC3T3-E1 cells mainly via the stimulation of phospholipase C. These cells constitutively produced and secreted insulin-like growth factor I (IGF-I). In addition, a neutralizing anti-IGF-I antibody completely abolished DNA synthesis stimulated by PGF2 alpha in MC3T3-E1 cells, suggesting that IGF-I indeed mediates the PGF2 alpha effect. However, PGF2 alpha decreased the expression of IGF-I mRNA and the secretion of immunoreactive IGF-I into the medium, whereas progression activity in the conditioned medium was not affected by PGF2 alpha. Although IGF-I alone did not stimulate DNA synthesis in MC3T3-E1 cells, when PGF2 alpha was added to the cultures, IGF-I stimulated their proliferation. Thus, PGF2 alpha may potentiate the action of IGF-I. At the same time, PGF2 alpha increased the number of high affinity binding sites (molecular mass of 130 kDa) for IGF-I in a dose-dependent manner. The increase in IGF-I-binding site number preceded the elevation of DNA synthesis by approximately 3 h. Furthermore, MC3T3-E1 cells secreted at least three species of IGF-binding proteins (IGFBPs) with molecular masses of 24, 30, and 34 kDa. In the early period of PGF2 alpha exposure, PGF2 alpha attenuated the secretion of all of these IGFBPs, whereas thereafter, it markedly increased their secretion, especially that of the 34-kDa IGFBP, suggesting a modulation of metabolism and action of IGF-I. These effects of PGF2 alpha on IGF-I receptor number and IGFBP secretion may play a role in the synergism between PGF2 alpha and IGF-I that results in the stimulation of DNA synthesis in MC3T3-E1 cells.

Amanitins↗
PubMed1990

Isolation of mouse and human cDNA clones encoding a protein expressed specifically in osteoblasts and brain tissues.

Using the differential hybridization screening method between osteoblastic and fibroblastic cells, a cDNA clone coding for an osteoblast specific protein, named OSF-1, consisting of 168 amino acid residues including a possible 32 amino acid long leader sequence, was isolated from murine osteoblastic cell line MC3T3-E1. The OSF-1 gene was shown by Northern blotting analysis to be expressed in mouse calvarial osteoblast-enriched cells and in mouse brain tissues, but not in thymus, spleen, kidney, liver, lung, testis or heart. The human counterpart was also found in cDNA libraries from human osteosarcoma cell line MG63 and normal brain tissues. DNA sequence analysis revealed four amino acid sequence differences between the mouse and human, of which only one is located in the mature protein. This extremely high sequence conservation suggests that OSF-1 plays a fundamental role in bone and brain functions.

Animals↗
PubMed1990

Interstitial class II-positive cell depletion by donor pretreatment with gamma irradiation. Evidence of differential immunogenicity between vascularized cardiac allografts and islets.

We used an allograft pretreatment regimen involving lethal total-body gamma irradiation of donor rats eight days prior to transplantation to compare directly the immunogenicty of immediately-vascularized heart allografts with isolated, neovascularized pancreatic islet allografts. TBI pretreatment of heart donors (IHT) caused a modest prolongation in cardiac allograft survival compared with controls in a low-responding fully-allogeneic strain combination, Lewis-to-ACI. The addition of 10(5) donor-type dendritic cells (DCs) at the time of transplantation reversed the prolongation of IHT in this strain combination. Donor pretreatment with TBI did not lead to prolonged cardiac allograft survival in either a high-responding combination, ACI-to-Lewis, or in an MHC class II-compatible strain combination, F344-to-Lewis. In contrast, islets from irradiated donors (IIT) showed markedly prolonged survival in both low-responding (Lewis-to-ACI) and high-responding (W/F-to-Lewis) strain combinations. The addition of 10(5) donor-type DCs to the islets at the time of transplantation caused the rejection of only two of six IIT in the Lewis-to-ACI combination. Combined pretreatment regimens involving TBI-pretreated cardiac allografts--such as recipient immunosuppression with peritransplant cyclosporine (10 mg/kg on days 0, 1, and 2) or the combination of TBI (1000 cGy on day -3) and cyclophosphamide (300 mg/kg on day -5) in a pretreatment regimen--did not lead to synergistic graft prolongation in the low-responding Lewis-to-ACI combination. Immunohistologic studies showed that eight days after TBI rat hearts and islet were both greater than 90% depleted of class II (0X6+) interstitial dendritic cells while class I (0X18+) expression was unchanged. IIT are able to increase class II expression when donors are treated with recombinant gamma interferon (4000 U/day on days -3, -2, and -1). MLR data showed that ACI recipients of Lewis IIT reacted normally to donor (Lewis) and third-party (W/F) stimulator cells greater than 100 days after transplantation. The apparent greater immunogenicity of heart allografts as compared with islets in this model could be due to (1) a quantitative difference between the number of residual class II-positive cells in hearts and islets or a greater nnon-MHC antigenic load in the heart grafts given its larger size, or (2) a quanlitative difference between hearts and islets due to the presence of a vascular endothelium in the immediately vascularized heart that can present alloantigen and provide a major stimulus to rejection.

Animals↗
PubMed1990

The role of MHC compatibility in recurrence of autoimmune type I diabetes mellitus: comparison of the immune response of BB/W rats to pancreatic islet and heart allografts.

Human type I diabetes mellitus has been shown to be an autoimmune disease. The BioBreeding/Worcester (BB/W) rat is an excellent model of insulin dependent diabetes mellitus (IDDM). Using the spontaneous diabetic BB/W rats, autoimmune recurrence of diabetes mellitus was evaluated. To prevent allorejection of islets, a combination of ultraviolet B (UVB) donor islet pretreatment and brief peritransplant host immunosuppression with cyclosporine was utilized. Such combination led frequently to indefinite survival of MHC mismatched islets in the chronically diabetic BB/W recipients more than 15 days after onset of hyperglycemia, while MHC matched islets survived only briefly. The most likely reason for the relatively rapid loss of graft function of MHC matched islets is the autoimmune destruction by previously primed cells. The result of this study, together with the previous report of CHABOT et al that both MHC matched and MHC mismatched islets are destroyed in acutely diabetic BB/W rats (less than 15 days after onset) despite the use of UVB irradiation and cyclosporine, demonstrates that the initiation of autoimmune response toward islets is most likely MHC restricted. These results led to the conclusion that MHC matching may be contraindicated in future human pancreatic islet transplantation to avoid reactivation of the original autoimmune disease.

Animals↗
PubMed1989

Humoral immunity in allograft rejection. The role of cytotoxic alloantibody in hyperacute rejection and enhancement of rat cardiac allografts.

The role of humoral immunity in graft rejection in the rat model remains controversial. Passive transfer of cytotoxic alloantibody (CAA) has resulted either in hyperacute rejection or in graft enhancement. This study examines the effect of transfer of CAA on cardiac allograft survival in three rat strain combinations that are fully mismatched at the major histocompatibility (MHC) loci. Strain-specific immune responsiveness in donor-recipient pairs varied from low (Lewis-to-ACI) to high (ACI-to-Lewis) as measured by mixed lymphocyte reactions. CAA was obtained from rats sensitized by three successive skin grafts at weekly intervals. Group 1 (high responder recipients), which consisted of Lewis rats presensitized to ACI and had a lymphocytotoxicity titer of 1:512 to 1:2048, rejected ACI cardiac allografts in 10.8 +/- 7.2 hr compared with 6.5 +/- 0.5 days in naive controls (p less than 0.001). Injection of 1 ml of high-titer CAA into naive Lewis rats immediately after ACI cardiac grafting led to hyperacute rejection of ACI hears in 2.1 +/- 0.8 hr while 1 ml of CAA followed by 2 ml of guinea pig complement (GPC) resulted in even faster rejection (mean survival time (MST) of 23.8 +/- 4.7 min). Injection of 2 ml GPC alone or in combination with 1 ml naive Lewis serum had no effect on graft survival. Multiple pretransplant injections of 1 ml of CAA on days -3, -2,-1, and 0 relative to transplantation resulted in significant prolongation of allograft survival (MST of 10.3 +/- 0.3 days; P less than 0.01). In group 2 (intermediate responder recipients), where Lewis rats were presensitized to WF strain and where cytotoxicity titer was 1:16 to 1:256, the recipients rejected WF hearts in 23.8 +/- 5.8 hr compared with 6.8 +/- 0.8 days in unsensitized control recipients (P less than 0.001). Injection of 1 ml of Lewis anti-WF CAA resulted in prolonged graft survival of 9.7 +/- 3.5 days, while injection of 1 ml of CAA followed by 2 ml of GPC caused hyperacute rejection in 104 +/- 61.7 min. Pretransplant injections of CAA on days -3, -2, -1, and 0 resulted in enhancement, with an MST of 16.3 +/- 1.3 days (P less than 0.001). In group 3 (low responder recipients), ACI presensitized to Lewis developed a cytotoxicity titer of 1:2 to 1:32 and rejected Lewis hearts in 5.3 +/- 0.4 days compared with 10.6 +/- 1.0 days in naive recipients.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Tandem gene amplification in vitro for rapid and efficient expression in animal cells.

Plasmid vectors pHSG293 and pHSG747, suitable for in vitro gene amplification for subsequent animal-cell expression, were developed. A cosmid vector pHSG293 confers Km resistance to Escherichia coli host cells and G418 resistance to animal cells and contains a single BstXI recognition/cleavage site, CCACGGGG/CTGG, near the cos site (the recognition site is underlined). The cassette vector plasmid pHSG747 contains a multiple cloning site (MCS) between the simian virus 40 early promoter and the poly(A) signal sequence flanked by the same BstXI sites and confers Cm resistance to E. coli host cells. After inserting a coding fragment for human protein C or its derivative in the appropriate orientation in the MCS of pHSG747, the BstXI expression unit fragment was purified, mixed with BstXI-digested pHSG293 DNA at a molecular ratio of 20 to 40:1 and ligated. This allowed for tandem gene amplification due to asymmetric cohesive ends. Ligation products were packaged in lambda phage particles, amplified in E. coli cells as large cosmid molecules, and then introduced into CHO cells. G418R transformants were found to produce and secrete recombinant protein molecules at a high level. The plasmid vectors developed in this work will provide a rapid screening system useful for protein engineering in animal cells.

Animals↗
PubMed1988

Structure of extrachromosomal circular DNAs excised from T-cell antigen receptor alpha and delta-chain loci.

Small polydisperse circular (spc) DNA was isolated from mouse thymocytes, fragmented by HindIII digestion and cloned into the vector. Sixty DNA clones were randomly selected from the 10,400 phage library. The average size of insert was one-fifth of the original circular molecule. Twenty spc-DNA clones were homologous to DNA probes derived from T-cell antigen receptor (TCR) alpha-chain loci. We have characterized nine clones by DNA sequencing; they contain new germline sequences of the TCR alpha-chain variable (V alpha) and joining (J alpha) gene segments and the products out of the recombination of a V alpha with a J alpha gene segment. An additional four spc-DNA clones carried a new rearranging gene of the TCR delta-chain that is located between V alpha and J alpha genes. At least nine of 60 DNA clones carried the recombination junction of a heptamer-heptamer head-to-head structure expected from an excised product of V-J joining. This shows that most extrachromosomal circular DNAs in the thymus are formed by a sequence-dependent recombination mechanism. We suggest that a functional T-cell receptor V alpha gene can be constructed by somatic random rearrangements through successive looping-out, excision and deletion.

Animals↗
PubMed1988

[Studies of ceftizoxime in perinatal period].

Bacteriological studies and clinical evaluations of ceftizoxime (CZX) in perinatal period were carried out, and results are summarised as follows: Antibacterial activities of CZX in amniotic fluid were determined using the broth dilution method, and bactericidal effect on Streptococcus agalactiae, Staphylococcus aureus and Escherichia coli were demonstrated. The bactericidal effect of CZX increased in amniotic fluid and remarkable increases of activities against resistant strains were demonstrated. The penetration of CZX into mother's milk was low, and it was speculated that the drug transfer to the newborn through breast feeding was very little. Clinically, CZX was effective in the treatment of perinatal infections without any side effect. The above results has demonstrated that CZX is a clinically useful antibiotic for the prophylaxis and the treatment of perinatal infections.

Adult↗
PubMed1988

[Studies on imipenem/cilastatin sodium in the perinatal period].

Pharmacokinetic, bacteriological and clinical studies of imipenem/cilastatin sodium (IPM/CS) were carried out in the perinatal period, and the results obtained are summarized as follows: Effects of IPM on bacterial growth curves of Staphylococcus aureus (sensitive and resistant strains) and Escherichia coli (sensitive strains) in amniotic fluid were determined. The bactericidal effects of IPM increased in amniotic fluid and remarkable increases against resistant strains were demonstrated. IPM and CS were detected promptly after intravenous drip infusion to pregnant women, and reached peak levels shortly after administration in maternal plasma. Placental penetration of IPM and CS to the fetus was favorable. After intravenous drip infusion of 500 mg/500 mg of IPM/CS, drug concentrations in the umbilical cord plasma and the amniotic fluid exceeded MICs against main pathogenic organisms. Clinically, IPM/CS was effective in the treatment of perinatal infections without any side effect. The above results demonstrated that IPM/CS is a clinically useful antibiotic for the prophylaxis and the treatment of perinatal infections.

Adult↗