Biomedical subjects

K Nishikawa

Publications and source records attributed to K Nishikawa.

At least 19 recordsLinked to original sources

PubMed1995

Mutation in aspartic acid residues modifies catalytic and haemolytic activities of Bacillus cereus sphingomyelinase.

Four aspartic acid residues (Asp126, Asp156, Asp233 and Asp295) of Bacillus cereus sphingomyelinase (SMase) in the conservative regions were changed to glycine by in vitro mutagenesis, and the mutant SMases [D126G (Asp126-->Gly etc.), D156G, D233G and D295G] were produced in Bacillus brevis 47, a protein-producing strain. The sphingomyelin (SM)-hydrolysing activity of D295G was completely abolished and those of D126G and D156G were reduced by more than 80%, whereas that of D233G was not so profoundly affected. Two mutant enzymes (D126G and D156G) were purified and characterized further. The hydrolytic activities of D126G and D156G toward four phosphocholine-containing substrates with different hydrophobicities, SM, 2-hexadecanoylamino-4-nitrophenylphosphocholine(HNP), lysophosphatidylcholine (lysoPC) and p-nitro-phenylphosphocholine (p-NPPC), were compared with those of the wild-type. The activity of D126G toward water-soluble p-NPPC was comparable with that of the wild-type. On the other hand, D156G catalysed the hydrolysis of hydrophilic substrates such as HNP and p-NPPC more efficiently (> 4-fold) than the wild-type. These results suggested that Asp126 and Asp156, located in the highly conserved region, may well be involved in a substrate recognition process rather than catalytic action. Haemolytic activities of the mutant enzymes were found to be parallel with their SM-hydrolysing activities. Two regions, including the C-terminal region containing Asp295, were found to show considerable sequence identity with the corresponding regions of bovine pancreatic DNase I. Structural predictions indicated structural similarity between SMase and DNase I. An evolutionary relationship based on the catalytic function was suggested between the structures of these two phosphodiesterases.

Amino Acid Sequence↗

PubMed1995

Influence of spontaneous portosystemic collateral pathways on portal hemodynamics in living-related liver transplantation in children. Doppler ultrasonographic study.

We investigated the influence of spontaneous portosystemic collateral pathways on the portal hemodynamics and examined the necessity for ligating these vessels in pediatric liver transplantation from living donors. We assessed portal blood flow before, during, and after surgery in 82 pediatric recipients (mean age, 4.2 years), using Doppler ultrasonography. When blood flow in the reconstructed portal vein was decreased (< 10 ml/min/kg body weight) and portosystemic collaterals persisted during surgery, those vessels were ligated and Doppler flowmetry was examined again. Spontaneous portosystemic collaterals were detected at one or more sites in 67 patients before transplantation. These collaterals had been ligated in 17 patients before intraoperative flowmetry. Among the remaining 50 patients, initial Doppler studies revealed a decrease in portal blood flow in 22 patients. Nine patients had hepatofugal splenic venous flow and 6 had no significant flow signals from the intrahepatic portal vein. Ligation of collaterals resulted in a remarkable increase in portal blood flow in 20 patients, all of whom are alive. The remaining 2 patients died of graft failure due in part to portal hypoperfusion. On the other hand, the collaterals were not ligated in 24 patients because adequate portal blood flow was confirmed by intraoperative flowmetry. Postoperatively, flow signals from the unligated collateral vessels gradually diminished, but they still persisted in 3 patients at 12 months after transplantation. Hepatofugal blood flow through the portosystemic collateral pathways may persist after implantation of a normal graft. If the patent collaterals significantly reduce the effective portal blood flow, these vessels should be ligated in order to avoid graft failure.

Adolescent↗

PubMed1995

Beneficial effect of CV-4151 (Isbogrel), a thromboxane A2 synthase inhibitor, in a rat middle cerebral artery thrombosis model.

Effects of thromboxane A2 (TXA2) synthase inhibitors (CV-4151 and ozagrel) on cerebral thrombosis and cerebral damage were examined in a rat middle cerebral artery (MCA) thrombosis model and their potencies were compared with the conventional antithrombotic agents, aspirin and ticlopidine. CV-4151 significantly inhibited photochemically induced MCA thrombosis by oral (1 and 10 mg/kg) and intravenous (1 mg/kg) administration. Ozagrel (10 mg/kg, p.o.) also inhibited it. The potency of CV-4151 was about 10 times stronger than that of ozagrel, being comparable with the inhibition of blood TXA2 generation. Aspirin (100 mg/kg, p.o.) and ticlopidine (300 mg/kg, p.o.) showed an inhibitory tendency on MCA thrombosis. Twenty-four h after photochemical stimulation, cerebral edema and cerebral infarction were observed, and the lactate content in the brain increased. CV-4151 and ozagrel prevented this edema, and the antiedema effects of the drugs were correlated with the antithrombotic effect on thrombotic MCA occlusion. CV-4151 (10 mg/kg, p.o.), furthermore, significantly reduced the infarct size and inhibited the increase in lactate content. These results indicate that TXA2 synthase inhibitors inhibit cerebral damage by inhibition of MCA occlusion with thrombosis, probably resulting from the inhibition of TXA2 generation, and their effects are superior to those of aspirin and ticlopidine. TXA2 might play an important role in cerebral damage in the MCA thrombosis model. CV-4151 might be a useful drug for the treatment of cerebral thrombosis and for the prevention of cerebral infarction.

Animals↗

PubMed1995

Side-chain structure is critical for the transport of sterols from lysosomes to cytoplasm.

Macrophages take up and metabolize negatively charged liposomes containing free cholesterol efficiently, resulting in a massive accumulation of cholesteryl esters and triacylglycerols in their cytoplasm (Nishikawa, K., Arai, H. and Inoue, K. (1990) J. Biol. Chem. 265, 5226-5231). This system was used to assess the effects of structural variation of sterol on the intracellular transport and the metabolism of endocytosed sterols by the cells. Liposomes containing phytosterols with an extra one (campesterol) or two (beta-sitosterol, stigmasterol, fucosterol) carbons at the C-24 position of the cholesterol side-chain were endocytosed as efficiently as those containing cholesterol without exhibiting any apparent toxicity on the cells. Esterification of endocyotosed phytosterols was, however, extremely low; campesterol esterification was only 20% that of cholesterol and either beta-sitosterol or stigmasterol was not esterified appreciably. A morphological study showed that the endocytosed phytosterols were accumulated in the phagolysosomes of the cells. Blocking of esterification of endocytosed cholesterol by an acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor did not lead to cholesterol accumulation in the phagolysosomes. These data suggest that accumulation of endocytosed phytosterols in phagolysosomes is not a consequence of the inability of the cell to esterify sterols in the endoplasmic reticulum. In the light of these observations, we conclude that cultured macrophages can discriminate between sterols that differ only by a methyl or ethyl group at the C-24 position at their lysosomal compartment.

Animals↗

PubMed1995

Desk-top analysis of the structural stability of various point mutations introduced into ribonuclease H.

The structural stability of Escherichia coli ribonuclease HI mutants was analyzed by a pseudo-energy potential developed for evaluating structure-sequence compatibility. From the structure profile, the energy changes of the folding of mutant proteins relative to that of the wild-type, which correspond to the changes of free energy differences, were estimated. They are weakly but significantly correlated with the experimentally determined changes in the melting temperature between the mutant proteins and the wild-type. The correlation coefficient between the experimental data and the computation, estimated for all the known data (96 point mutations) and for the buried site data (32 point mutations), are -0.51 and -0.68, respectively. Experimentally known mechanisms to increase the structural stability are explained by the method: the main contributor to the stability in mutations of Val74 to either Ile or Leu is the side-chain packing energy, and that of Lys95 to Gly is the local conformational energy. This analysis is easy to do on a desk-top computer, and allows one to consider all the sites of possible candidates for point mutations. From the profile, new promising sites to increase the structural stability are suggested.

Computer Simulation↗

PubMed1995

Highly specific and efficient cleavage of squid tRNA(Lys) catalyzed by magnesium ions.

Two lysine isoacceptor tRNAs corresponding to the codons AAA and AAG, respectively, were isolated from squid (Loligo bleekeri), and their nucleotide sequences were determined. During this analysis, we discovered that the tRNA with the anticodon CUU was efficiently cleaved at a specific site in the presence of magnesium ions, whereas the tRNA with the anticodon UUU was not. Cleavage occurred almost exclusively at the phosphodiester linkage between G15 and D16 (p16). The most remarkable feature of this cleavage reaction is that the end product was not a 2',3'-cyclic phosphate but was mainly a 3'-phosphate. Thus, this reaction was distinct from the well characterized cleavage of yeast tRNA(Phe) by lead and from reactions catalyzed by various other metalloribozymes. The presence of a cytidine residue at position 60 was required for efficient cleavage but was not crucial for the reaction, and the entire tRNA molecule had to be intact for this specific and efficient cleavage reaction. The present study provides evidence that there exists a new catalytic mechanism for cleavage of tRNA that exploits biologically ubiquitous ions rather than toxic, nonessential ions such as lead.

Animals↗

PubMed1995

Exclusive expression of C. elegans osm-3 kinesin gene in chemosensory neurons open to the external environment.

In Caenorhabditis elegans three genetic loci osm-3, unc-104 and unc-116 have been identified, which encode anterograde motor kinesin. Here we show that osm-3 encodes a 672 amino acid long kinesin-like protein (KLP) that contains all three functional domains similar to the kinesin heavy chain, including a globular motor region, an alpha-helical coiled-coil rod, and a globular tail region. OSM-3 shows homology in both the motor and rod domains with kinesins from divergent species such as mouse KIF3, and sea urchin KRP95, and also with the rod domains of several non-kinesin proteins, such as myosin, ezrin, outer membrane proteins alpha precursor OMPA, yeast intracellular protein transport USO1, and the rat neurofilament NF-H. Temporal and spatial expression of the osm-3::lacZ fusion gene during development is limited to an exclusive set of 26 chemosensory neurons whose dendritic endings are exposed to the external environment, including six IL2 neurons of the inner labial sensilla, eight pairs of amphid neurons (ADF, ADL, ASE, ASG, ASH, ASI, ASJ, ASK) in the head, and two pairs of phasmid neurons (PHA and PHB) in the tail. Our data are consistent with the known structural defects in the amphid and phasmid sensilla in osm-3 mutants and also show the expression of the gene in IL2 neurons. Temporally, the gene is differentially expressed in all three types of chemosensory sensilla. Further work on osm-3, unc-104 and unc-116 mutants should give insight into the in vivo functions of the kinesin family during C. elegans neurogenesis.

Amino Acid Sequence↗

PubMed1995

Effects of thromboxane A2 synthase inhibitors (CV-4151 and ozagrel), aspirin, and ticlopidine on the thrombosis caused by endothelial cell injury.

The antiplatelet and antithrombotic effects of CV-4151 (isbogrel), a potent selective thromboxane A2 (TXA2) synthase inhibitor, were compared with those of ozagrel (OKY-046), aspirin, and ticlopidine in rats. Two hours after oral administration, CV-4151, ozagrel and aspirin inhibited blood TXA2 generation with ID50 values of 0.04, 0.3 and 6.4 mg/kg, respectively. These values were similar to the oral ID50 values of CV-4151 (0.06 mg/kg), ozagrel (0.92 mg/kg) and aspirin (7.0 mg/kg) for arachidonic acid (AA)-induced platelet aggregation ex vivo. Two hours after p.o. administration, CV-4151 and ozagrel inhibited femoral vein platelet-rich thrombosis caused by endothelial injury with ID50 values of 2.46 and 13.7 mg/kg, respectively. However, aspirin (100 mg/kg, p.o.) only slightly inhibited the thrombosis. Ticlopidine (300 mg/kg, p.o.) slightly but significantly inhibited AA-induced and ADP-induced platelet aggregation, however, it potently inhibited the thrombosis. CV-4151 and ozagrel given by i.v. injection showed therapeutic effects on the thrombosis with ED50 values of 0.026 and 0.066 mg/kg, respectively. These values were similar to the i.v. ED50 values of CV-4151 (0.0056 mg/kg) and ozagrel (0.042 mg/kg) for blood TXA2 generation. However, aspirin (30 mg/kg, i.v.) only moderately reduced the thrombosis. CV-4151 (> 0.3 mg/kg, p.o.), ozagrel (> 3 mg/kg, p.o.) and ticlopidine (300 mg/kg, p.o.) all significantly prolonged tail bleeding time. Aspirin (100 mg/kg, p.o.) tended to prolong the bleeding time. The antiplatelet and antithrombotic effects of CV-4151 are more potent than those of ozagrel, aspirin and ticlopidine in rats. CV-4151 may therefore be a useful drug for the treatment of thrombotic diseases.

Animals↗

PubMed1995

Trifluoroethanol-induced stabilization of the alpha-helical structure of beta-lactoglobulin: implication for non-hierarchical protein folding.

Trifluoroethanol (TFE) is known to stabilize the alpha-helical structure in proteins and their fragments. However, the relationship between the TFE-induced structures and the native structure is not clear. Here we show that beta-lactoglobulin, which consists predominantly of beta-sheets, exhibited a markedly high propensity to form an alpha-helical structure in the presence of TFE, as measured by far-UV circular dichroism. A cooperative transformation from the beta-sheet structure to an alpha-helical structure occurred at a TFE concentration between 10% and 20%. These results were in contrast to a gradual beta-sheet to alpha-helix transition of the constant fragment of the immunoglobulin light chain, which is also a beta-sheet protein. To understand the significance of the high helical propensity of beta-lactoglobulin, we measured the TFE-induced conformational transition of more than 20 proteins of various secondary structural types. Whereas the alpha-helical proteins showed a propensity to form an extensive helical structure in TFE, the helical propensity of proteins with a low helical content in the native state varied. The helical content in TFE was correlated more with the helical content predicted by a secondary structure prediction than with the helical content of the native structure, suggesting that the stability of the helical structure in TFE is determined by local interactions between nearby amino acid residues. Our results suggest that an alpha-helical intermediate can accumulate during the refolding process of beta-lactoglobulin and that a hierarchical model of protein folding is not necessarily true for some beta-sheet proteins including beta-lactoglobulin.

Animals↗

PubMed1995

Evaluation of protective effects of prostaglandin E1 on ischemic liver damage with in vivo 31P-MR spectroscopy.

The cytoprotective effect of prostaglandins (PG) was evaluated by in vivo 31P MR spectroscopy. Twenty rabbits were divided into two groups; the control group given physiological saline, and the PG group given prostaglandin E1 (0.5 microgram/kg/min). Each solution was infused for 8 min, after which complete hepatic ischemia was induced for 20 min, followed by reperfusion for 40 min. During ischemia, beta-ATP decreased to 23.6% and 42.3%, phosphomonoester increased to 260% and 200% of their initial values in the control and the PG groups, respectively. Inorganic phosphate also increased. After reperfusion, beta-ATP recovered to 65.2% and 96.5%, phosphomonoester to 130% and 110%, inorganic phosphate to 140% and 120% in the control and PG groups, respectively. The changes during ischemia were significantly smaller and the recoveries during reperfusion were more complete in the PG group. These results may confirm the cytoprotective effect of prostaglandins by in vivo 31P-MR spectroscopy.

Adenosine Triphosphate↗

PubMed1995

Mechanisms of biliary excretion of lithocholate-3-sulfate in Eisai hyperbilirubinemic rats (EHBR).

Biliary excretion of lithocholate-3-sulfate is markedly impaired in EHBR. To examine the mechanism of biliary lithocholate-3-sulfate excretion in EHBR, the effects of colchicine treatment, a vesicular transport inhibitor, and infusion of taurocholate and organic anions were studied in EHBR and Sprague-Dawley rats. Colchicine treatment and taurocholate infusion had no effect of biliary lithocholate-3-sulfate excretion in EHBR, suggesting that biliary lithocholate-3-sulfate excretion is not mediated by the vesicular transport or by the bile acid excretory pathway. In control Sprague-Dawley rats, both sulfobromophthalein and dibromosulfophthalein infusion inhibited biliary lithocholate-3-sulfate excretion. In contrast, in EHBR dibromosulfophthalein infusion inhibited biliary lithocholate-3-sulfate excretion but BSP infusion did not. Indocyanine green and pravastatin infusion did not affect biliary lithocholate-3-sulfate excretion but pravastatin infusion had no effect in EHBR. These findings indicate that, whether physiologically important or not, two of more excretory pathways for organic anions exist at the canalicular membrane other than the ATP-dependent one.

Animals↗

PubMed1995

Two flavone 2'-glucosides from Scutellaria baicalensis.

Two new flavone glucosides, 5,2',6'-trihydroxy-6,7,8-trimethoxyflavone 2'-O-glucoside and 5,2',6'-trihydroxy-6,7-dimethoxyflavone 2'-O-glucoside were isolated from the aqueous methanol extract of the roots of Scutellaria baicalensis. From the extract, seven phenolics, 5,7,2',6'-terahydroxyflavone, 5,7,2',5'-tetrahydroxy-8,6'-dimethoxyflavone, skullcapflavone II, baicalin, baicalin methyl ester, wogonin 7-glucuronide and 3,5,7,2',6'-pentahydroxyflavanone were also isolated.

Flavonoids↗

PubMed1995

Vascular complications in living related liver transplantation detected with intraoperative and postoperative Doppler US.

BACKGROUND/AIMS: The purpose of this study was to clarify changes in the graft hemodynamics induced by vascular complications in living related liver transplantation. METHODS: This study included 46 pediatric recipients who underwent partial liver transplantation from living related donors. The blood flow was evaluated in the portal system, the hepatic artery and the hepatic vein with serial intra- and post-operative Doppler ultrasound (US). RESULTS: In 12 patients, intraoperative Doppler US showed a decrease in portal venous inflow (< 9 ml.min-1.kg-1) toward the liver graft and could act as a guide for ligation of collaterals in seven patients, portal re-construction in two, thrombectomy in one and relief of hepatic venous outflow obstruction in two for increasing the portal venous inflow. In five patients, intraoperative Doppler US showed poor arterial inflow, i.e. dampened arterial waveforms which involved both low pulsatility index (< 0.90) and low peak-systolic velocity (< 31 cm/s). In three of them, the waveform was more pulsatile after re-anastomosis or relief from stretching of the hepatic artery. The remaining two patients developed hepatic artery thrombosis. Most of the hepatic venous outflow obstruction (four of five patients) had flat waveforms, low flow velocity (< 10 cm/s) of the hepatic vein, and poor portal inflow (flow velocity < 14 cm/s). Postoperative Doppler US showed hepatic venous outflow obstruction in three patients, hepatic artery thrombosis in three (twice in one patient), portal vein stenosis in two and portal vein thrombosis in one. These complications were successfully managed with surgical procedures in three patients, transhepatic angioplasty in three and conservative treatments in four. Six patients died of non-vascular complications. CONCLUSIONS: Serial intra- and post-operative Doppler US was a useful technique for making an early diagnosis of abnormal hemodynamics of the graft circulation. Furthermore, intraoperative Doppler US could assess reconstructed vessels objectively and would reduce the incidence of vascular complications following transplantation.

Adolescent↗

PubMed1995

The ability of bovine mitochondrial transfer RNAMet to decode AUG and AUA codons.

The ability of bovine mitochondrial tRNA(Met) with the anticodon f5CAU (where f5C is 5-formylcytidine) to decode AUG and AUA codons was examined in a codon-dependent ribosomal binding assay. The AUG codon stimulated the binding of Met-tRNA(Met) to mitochondrial ribosomes in the presence of EF-Tu/TSmt. In contrast, the AUA codon did not promote the binding to mitochondrial Met-tRNA to the ribosome. To investigate the translation of the AUG and AUA codons more fully, an in vitro translation system from bovine liver mitochondria was developed. The activity of this system was greatly enhanced by the addition of 1 mM spermine and reached about half the activity observed with a comparable translational system from E coli. Two types of mRNA containing either AUG or AUA codons were synthesized using T7 RNA polymerase to transcribe their chemically synthesized genes. In the E coli system, the AUG-containing mRNA was translated as Met and the AUA-containing mRNA was translated as Ile. The AUG-containing mRNA but not the AUA-containing mRNA was translated as Met by the mitochondrial translational system. The process by which the AUA codon is translated as Met in the mitochondrial system remains to be clarified.

Animals↗

PubMed1995

Sens-A-Ray characteristics with variations in beam quality.

This study examined the relationship between x-ray beam quality and image characteristics with the use of the Sens-A-Ray (Regam Medical Systems, Sundsvall, Sweden). To evaluate the x-ray response, properties of the image sensor, dark current and statistical noise, sensitivity, and contrast resolution were measured. Tube voltage, tube current, and exposure time were varied. Exposures were determined with the use of an ionization chamber. Pixel values beneath a lead strip were used to calculate dark current effects. Contrast was measured with pixel values from the images of a step-wedge. Dark current noise increased in proportion to exposure time. Although the sensitivity at each tube voltage was linear and proportional to the exposure, the gradient was inversely proportional to increased tube voltage. After subtraction of the dark current and statistical noise, the gradient of the sensitivity at low tube voltage remained steeper than at high tube voltages. Hence, sensitivity decreased with increased tube voltage. Sensitivity gradients at each different tube current were similar. Irrespective of exposure, contrast resolution between adjoining step-wedge steps > or = 9 mm were too small to distinguish at 50 kVp. The gray levels for each step below 12 mm in thickness were distinguishable with 90 kVp. Increased dark current noise consequent to long exposure times narrowed the available gray scale range. Lower tube voltage resulted in higher sensitivity with larger gradients than higher tube voltages.

Analog-Digital Conversion↗

PubMed1995

Expression of basic fibroblast growth factor and its receptor in human pancreatic carcinomas.

We examined the expression of basic fibroblast growth factor (FGF) and FGF receptor by immunohistochemistry in 32 human pancreatic ductal adenocarcinomas. Mild to marked basic FGF immunoreactivity was noted in 19 (59.4%) of the 32 tumours examined, and 30 (93.3%) of the tumours exhibited a cytoplasmic staining pattern against FGF receptor. The tumours were divided into two groups according to the proportion of positively stained tumour cells: a low expression group (positive cells < 25%) and a high expression group (positive cells > or = 25%). No statistically significant difference in tumour size, differentiation, metastases or stage was found between the low and high basic FGF expression groups. However, a significant correlation was found between FGF receptor expression level and the presence of retroperitoneal invasion, lymph node metastasis, and tumour stage. In addition, low FGF receptor expression was significantly associated with a longer post-operative survival as compared with high FGF receptor expression, whereas there was no significant difference in post-operative survival between the low and high basic FGF expression groups. Increased expression of FGF receptor is correlated with the extent of malignancy and post-operative survival in human pancreatic ductal adenocarcinomas. Thus, overexpression of FGF receptor may prove to be a more useful prognostic marker than basic FGF expression level in pancreatic cancer patients.

Adult↗

PubMed1995

Characterization of vitelline membrane outer layer protein I, VMO-I: amino acid sequence and structural stability.

Vitelline membrane outer layer protein I (VMO-I) tightly bound to ovomucin fibrils of hen's egg yolk membrane was characterized in terms of its amino acid sequence and structural stability. The deduced sequence of VMO-I using the conventional sequencing method is: RTREYTSVITVPNGGHWGKWGIRQFCHSGYANGFALKVEPSQFGRDDTALNGIRLRCLD- GSVIESLVGKWGTWTSFLVCPTGYLVSFSLRSEKSQGGGDDTAANNIQFRCSDEAVLVGD- DLSWGRFGPWSKRCKICGLQTKVESPQGLRDDTALNNVRFFCCK. Thus, VMO-I is composed of 163 amino acid residues with a calculated molecular weight of 17,979. The sequence confirms the cDNA sequence of VMO-I we recently determined and does not show any significant similarity to proteins compiled in the NBRF database. Two of the four disulfide bonds found in VMO-I were estimated to lie between Cys26 and Cys57 and between Cys79 and Cys110. The sequence analyses show that VMO-I contains three 53-residue internal repeats that contain distinctive regions of turns flanked by beta-sheets consistent with the recent finding that the molecule contains a new beta-fold motif, the beta-prism. The molecular characteristics of VMO-I in solution were examined by CD spectroscopy in the far and near ultraviolet regions, NMR spectroscopy, and high sensitive differential scanning calorimetry (DSC). CD spectra in the far UV region at room temperature were similar to that assigned to a random coil, while in the near UV region, small positive peaks were observed. The ellipticity in both regions decreased on raising the temperature. Proton NMR experiments showed the native structure unfolds to unordered conformations at 70 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1995

Impaired high-shear-stress-induced platelet aggregation in patients with chronic renal failure undergoing haemodialysis.

We investigated shear-induced platelet aggregation (SIPA) in 30 patients with chronic renal failure (CRF) undergoing haemodialysis. 26 patients showed a significant decrease in SIPA at high shear stress but no change in SIPA at low shear stress. The former reaction reflects the interaction between plasma von Willebrand factor (vWF) and its platelet receptors, glycoprotein (GP) Ib-IX and IIb/IIIa complex, whereas the latter is assumed to involve the binding of plasma fibrinogen to GP IIb/IIIa complex. These SIPA profiles in CRF patients after haemodialysis showed almost no change compared to those before haemodialysis. The ratio of ristocetin cofactor/vWF antigen in plasma was slightly lower in CRF patients than in controls (P < 0.01). However, the level of GPIb antigen in the platelets of these patients was significantly reduced (42.1 +/- 20.3% of normal platelets), with partial destruction of GPIb antigen. The number of vWF receptors on the GPIb molecule was quantitated using the GPIb-binding protein alboaggregin-B (AL-B), purified from the snake venom of Trimeresurus albolabris. AL-B bound to GPIb at a total of 48,760 +/- 9944 molecules per normal platelet and a Kd of 85.44 +/- 15.70 nM at saturation. In contrast, binding in CRF platelets was 22,980 +/- 6395 molecules per platelet and Kd was 50.08 +/- 13.83 nM. Taking these results together, we conclude that the impaired SIPA found in CRF patients is due to both abnormalities in plasma vWF and in its platelet GPIb receptor.

Adult↗