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Biomedical subjects

J Takagi

Publications and source records attributed to J Takagi.

At least 91 records · Page 5Linked to original sources
PubMed1990

Feedback regulation of platelet function by 12S-hydroxyeicosatetraenoic acid: inhibition of arachidonic acid liberation from phospholipids.

We have proposed a mechanism that platelet aggregation is regulated by its 12-lipoxygenase product, 12S-hydroxyeicosatetraenoic acid (12-HETE) (Sekiya, F., Takagi, J. and Saito, Y. (1989) Thrombos. Res. 56, 407-415). Inhibition of endogenous 12-HETE production by 15-HETE, a specific inhibitor of 12-lipoxygenase, accelerated aggregation of bovine platelets in response to collagen and arachidonic acid liberation from phospholipids was enhanced. Exogenously added 12-HETE suppressed collagen-induced liberation of arachidonic acid and the aggregation was also inhibited. On the other hand, 12-HETE did not interfere with thromboxane synthesis from free arachidonic acid in a cell-free system. These observations suggest that 12-HETE exerts a negative feedback to prevent excess aggregation through interference with arachidonic acid liberation from membrane phospholipids.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1989

Elucidation of a role of plasma albumin during collagen-induced aggregation of bovine platelets.

Bovine platelets of which phospholipids were labeled with [14C] arachidonate were stimulated by collagen. Omitting albumin in suspending medium suppressed aggregation and arachidonate liberation from phospholipids. Analysis of [14C] arachidonate metabolites released into medium revealed that release of 12S-hydroxyeicosatetraenoic acid (12-HETE) from stimulated platelets was dependent on the existence of albumin, while thromboxane B2 release was not. Moreover, exogenously added 12-HETE inhibited collagen-induced aggregation. These observations suggest that albumin potentiates aggregation by preventing intracellular accumulation of 12-HETE, and strengthen our previous finding that albumin in plasma is very essential for collagen-induced aggregation of platelets (Sekiya, F., Takagi, J., Kasahara, K., Inada, Y. and Saito, Y. (1988) Thrombos. Res. 50, 837-846.).

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1989

A collagen-binding glycoprotein from bovine platelets is identical to propolypeptide of von Willebrand factor.

Several proteins from bovine platelet lysate bound to type I collagen immobilized to the beads of formyl derivatives of cellulose. Among these proteins, a protein of about 100,000 daltons was purified to homogeneity by two additional affinity chromatographies, an organomercurial-agarose and a lentil lectin-agarose. This protein consisted of a single polypeptide chain which contains carbohydrate moiety and many intrapolypeptide disulfide bridges. In addition to platelets, this protein was present in plasma and cultured endothelial cells but not in red blood cells, leukocytes, and smooth muscle cells. Furthermore, it was released from platelets upon stimulation by various agonists. The purified 100-kDa protein was labeled with 125I to quantitate its binding to fibrillar type I collagen. The protein specifically bound to fibrillar collagen with the apparent dissociation constant of 5.6 x 10(-8) M for the high affinity site and 5.5 x 10(-7) M for the low affinity site. Analyses of amino acid sequences of both intact and tryptic fragments of this protein revealed that it had strong homology to the propolypeptide of human von Willebrand factor, which is also known as von Willebrand antigen II. Various properties of this protein listed above also strongly suggest that it was indeed the propolypeptide of bovine von Willebrand factor.

Amino Acid Sequence↗
PubMed1989

Inhibition of platelet-collagen interaction by propolypeptide of von Willebrand factor.

A collagen-binding glycoprotein was isolated from human platelets using affinity chromatography of immobilized collagen. Based upon characterizations of this protein we confirmed that it was identical to the propolypeptide of von Willebrand factor (pp-vWF), which is also called von Willebrand antigen II. The characteristics we have investigated are molecular weight, existence of carbohydrate chains, and the NH2-terminal amino acid sequence. pp-vWF has strong affinity to collagen and inhibits collagen-induced aggregation of human platelets at a concentration as low as 2 micrograms/ml even in the presence of plasma. This inhibitory effect is specific for collagen-induced aggregation since it does not inhibit aggregation of platelets induced by other agonists such as ADP, arachidonic acid, platelet-activating factor, ionophore A23187, and ristocetin. As pp-vWF is quickly released from platelets upon activation by various agonists, it is possible that pp-vWF functions as a repressor for excess platelet aggregation induced by collagen and constitutes a negative feed-back mechanism. Considering the fact that mature vWF supports platelet adhesion to subendothelium, present observations suggest that the propeptide portion and the mature protein could have opposing effects on hemostasis.

Amino Acid Sequence↗
PubMed1989

The development of porcine zona pellucida using monoclonal antibodies: I. Immunochemistry and light microscopy.

We established three monoclonal antibodies (Mabs) against the zonae pellucidae (ZP) of porcine oocytes, named STA-1, STA-2, and STA-3, and eventually we determined that they all reacted with the isolated ZP. Based on Western blotting without 2-mercaptoethanol (2-ME), STA-1 reacted with the 80,000-110,000 Mr component, STA-2 with the 42,000-63,000 Mr component, and STA-3 with the 40,000-80,000 Mr component of ZP. We immunohistochemically specified the components of porcine ZP reactive with the three Mabs during the course of follicular development. Each Mab reacted with both the ZP and the interfollicular cell space (IFCS). One ZP component, reactive with STA-2 and STA-3, was first produced in the primordial follicle and was not found at the cumulus follicle stage, which corresponds to the stage of large antral follicles more than 5 mm in diameter. Another ZP component, reactive with STA-1, was not produced until the secondary follicle stage, and was never found at the antral follicle stage. These results suggest that each ZP component is produced and secreted at a specific stage or stages of folliculogenesis.

Animals↗
PubMed1989

The development of porcine zona pellucida using monoclonal antibodies: II. Electron microscopy.

Following our previous study on the immunohistochemistry of porcine zonae pellucidae (ZP), we undertook the present study to localize the components of the ZP with immunoelectron microscopy, using three types of anti-porcine-ZP monoclonal antibodies (Mabs), named STA-1, STA-2, and STA-3. Some organelles of the oocyte were seen to react with STA-2 and STA-3 prior to ZP formation. As soon as a follicle began to mature, STA-2 and STA-3 reacted with the perinuclear space and the endoplasmic reticular membrane of the oocyte. The follicle first reacted with STA-1 at the secondary follicle stage. At this stage, the positive reaction involved the follicular cell layer as well as the oocyte and ZP. Positive reaction was scattered within and limited to the interfollicular cell space and was never found in the cytoplasm of follicular cells. At the antral follicle stage, the oocyte was surrounded by a thick, electron-dense ZP. A strong reaction was observed in the outer layer, but no significant reaction occurred in the inner layer. The convex and ragged outer margin of the ZP was characterized by the strongest reaction.

Animals↗
PubMed1989

Hemodynamic evaluation and morphological changes of right ventricular out-flow tract and pulmonary valve after balloon pulmonary valvuloplasty.

Balloon pulmonary valvuloplasty (BPV) was attempted in 38 cases of congenital pulmonary valve stenosis. It was effective and was done without complication in 36 cases, however it was not effective in two cases of pulmonary valve dysplasia. The balloon used was 20-50% larger in diameter than the pulmonary valve annulus. In the seven cases in which the transvalvular pressure gradient was above 100 mmHg on cardiac catheterization, right ventriculography demonstrated that the functional obstruction of the right ventricular outflow tract increased immediately after BPV, however it subsequently improved at one year after the procedure. At between one and three months after BPV, two-dimensional echocardiography demonstrated that the morphological obstruction to the right ventricular outflow tract had diminished. In two cases, localized right ventricular septal hypertrophy with severe pulmonary valve stenosis was observed by two-dimensional echocardiography and right ventriculography, and persisted at one year. In all cases, two-dimensional echocardiography and angiography demonstrated doming pulmonary valves with valve stenosis, which was diminished by BPV. The pulmonary valve morphology was observed by two-dimensional echocardiography in three cases following BPV. In one case, partial relief of pulmonary valve obstruction was seen to be due to commissural splitting and in the other two, to tearing of cusp tissue. Inspection of the pulmonary valve at operation was made in one case who underwent elective surgery for repair of an atrial septal defect which was associated with pulmonary valve stenosis. It demonstrated partial relief of pulmonary valve stenosis by tearing of cusp tissue. In conclusion, BPV is as effective a treatment for congenital pulmonary valve stenosis as open valvulotomy. In our follow-up study, it has shown no apparent complications. The transient obstruction in the right ventricular outflow tract immediately after BPV improved within one month and improved further after three months and one year. However, in the more long-standing cases the localized right ventricular septal hypertrophy persisted and these cases will require, a long term follow-up.

Blood Pressure↗
PubMed1989

Sterility of total parenteral nutrient solutions stored at room temperature for seven days.

The sterility of total parenteral nutrient (TPN) solutions stored at room temperature for up to seven days after preparation was studied. The study was conducted in two parts. In part 1, a positive control phase was conducted to validate that the filter set would capture bacteria or fungi in the TPN solutions. In part 2,300 unused TPN solutions were retrieved from patient-care areas within 24 hours of preparation. These solutions were randomized into three study groups of 24, 72, or 168 hours after preparation. Each TPN solution was filtered aseptically using an inline 0.22-micron filter. The filters were suspended in brain-heart infusion broth and incubated at 35 degrees C. Filters were visually evaluated for turbidity as an indicator of microbial contamination. Microbial growth was reported in 2 of 100 samples filtered 24 hours after preparation (group 1) and in 1 of 100 samples filtered 72 hours after preparation (group 2). No growth was detected in TPN solutions filtered 168 hours after preparation (group 3). Turbid samples were subcultured, and contaminants were identified as coagulase-negative Staphylococcus species and gram-positive bacilli in the group 1 samples and coagulase-negative Staphylococcus species in the group 2 samples. The difference in contamination rates among the three groups was not significant. TPN solutions may be stored after preparation at room temperature for an extended time (up to 168 hours) without increasing the risk to patient safety. However, at this institution, expiration dates are extended only to the time that supports practical recycling of standard TPN solutions (72 hours).

Drug Storage↗
PubMed1988

Subunit B of factor XIII is present in bovine platelets.

Distribution of B subunit of coagulation factor XIII(FXIII B) in bovine platelets was determined. Intracellular location of FXIII B in platelets was confirmed by fluorescent antibody technique. Positive staining of FXIII B was observed with Triton-permeabilized platelets but not with non-permeabilized platelets. Immunoblots of plasma and platelet lysate revealed that the antibody was specific for FXIII B and this antigen existed in the supernatant of sonication-solubilized platelets. The amount of FXIII B in platelets was determined to be 17.3 +/- 6.7 ng/10(8) platelets by radioimmunoassay. This is the first visual and quantitative demonstration of intracellular FXIII B.

Animals↗
PubMed1988

Plasma albumin is essential for collagen-induced platelet aggregation.

We found that platelets must have albumin on the surface to respond to collagen and aggregate. Albumin, however, was not absolutely necessary for ADP-, platelet activating factor-, serotonin- or thrombin-induced aggregation, while fibrinogen was required for ADP- or serotonin-induced aggregation. Immunofluorescent microscopy revealed that albumin was retained on gel-filtrated platelets but not on washed platelets. Albumin was not required for platelet adhesion to immobilized collagen. Without albumin thromboxane formation upon collagen-stimulation was diminished. These data suggest that albumin is essential in some step(s) that results in production of thromboxane A2.

Animals↗
PubMed1988

"A" subunit of factor XIII is present on bovine platelet membrane and mediates collagen-induced platelet activation.

The Fab fragment of a polyclonal antibody against platelet factor XIII inhibited the collagen-induced platelet aggregation in a dose-dependent manner. This inhibitory effect was specific for collagen, and it had no effect on arachidonic acid-, ADP-, and serotonin-induced aggregations. This finding strengthens our notion that platelet factor XIII is involved in collagen-induced platelet aggregation. (Saito, Y., Imada, T., Takagi, J., Kikuchi, T. and Inada, Y. J. Biol. Chem. 261, 1355-1358, 1986). We have investigated membrane localization of bovine platelet factor XIII using immunological techniques. Immunofluorescent visualization revealed that the factor XIII was expressed on the surface of non-permeabilized bovine platelets, where we detected neither lactate dehydrogenase, a cytoplasmic enzyme marker, nor B subunit of factor XIII, which is present in plasma. Cell surface iodination and immunoprecipitation also confirmed that it existed on the surface of platelets.

Animals↗
PubMed1988

Venom from southern copperhead snake (Agkistrodon contortrix contortrix). II. A unique phospholipase A2 that induces platelet aggregation.

A platelet aggregation factor was purified from the venom of southern copperhead snake (Agkistrodon contortrix contortrix) by DEAE-cellulose ion-exchange chromatography, precipitation with ammonium sulfate, affinity chromatography using bovine serum albumin as ligand, and gel filtration on Cellulofine GCL-2000. It had molecular weights of 11,000 and 14,000, as determined by gel filtration chromatography and sodium dodecyl sulfate--polyacrylamide gel electrophoresis (SDS-PAGE), respectively. It consists of a single polypeptide, and was identified as a phospholipase A2. It was quite resistant to heat and various denaturing reagents including urea and SDS. It lost both phospholipase A2 activity and platelet aggregating activity upon modification of histidine residue(s) with p-bromophenacyl bromide. Its specificity towards the beta-position of phospholipid in esterolytic reaction was confirmed by gas-liquid chromatography using a pure synthetic phosphatidylcholine. Platelet aggregation by this phospholipase A2 was completely inhibited by prostacyclin, but was little inhibited by aspirin which indicates almost no direct participation of released arachidonic acid in the aggregation mechanism.

Animals↗
PubMed1987

Analysis of distribution of receptors among platelets by flow cytometry.

We have investigated the binding of fluorescein isothiocyanate (FITC)-labeled fibrinogen to platelets using a fluorescence spectrophotometer and a flow cytometer. The amount of fibrinogen bound by stimulation of adenosine diphosphate (ADP) and 5-hydroxytryptamine (5HT) increased in a dose-dependent manner. Stimulation of one agonist was independent of that of another agonist. Fibrinogen could bind to platelets in response to ADP, regardless of whether they were desensitized by 5HT, and vice versa. It was found by flow cytometric analysis that individual platelets responded uniformly to both ADP and 5HT, indicating that individual platelets have receptors for both ADP and 5HT on their surfaces.

Adenosine Diphosphate↗