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Biomedical subjects

Yuji Imafuku

Publications and source records attributed to Yuji Imafuku.

10 recordsLinked to original sources
PubMed2006

[Standardization and issues of rheumatoid factor measurement].

OBJECTIVES: To disclose the current situation of rheumatoid factor (RF) measurement in Japan. METHOD: A small-scale survey was performed among members of the committee for the improvement of RF measurement in 2003 using manufacturers' RF reference materials valued based on WHO RF reference and pooled sera. A nationwide questionnaire survey was also performed. Questionnaires were sent to 356 educational institutes certified by the Japan College of Rheumatology in December 2004. RESULTS: The small-scale survey showed inter-laboratory differences of measured RF values, especially using RF references, and less in pooled sera. In the questionnaire survey (187 responses, recovery, 53%), qualitative or semi-quantitative RF measurement methods were used in a small number of institutes and quantitative methods were used in large numbers of institutes, the latex immunoassay (turbidimetric or nepherometric) was predominantly employed. The measuring instruments were various. The upper limit of the reference interval was distributed widely from 5 IU/ml to 40 IU/ml, indicating obvious inter-laboratory differences in RF measurement. Many institutes used the reference intervals recommended by the manufacturers. CONCLUSION: There are remarkable inter-laboratory differences in RF measurement. Clearly, one of the major issues is the lack of reference materials. We therefore need to establish a reference material of RF, even if it is a temporary one. Scientific societies (Japan College of Rheumatology and Japanese Society of Laboratory Medicine) and manufacturers providing RF measurement reagents should work together for the improvement of RF measurement.

Arthritis, Rheumatoid↗
PubMed2005

Serum amyloid A (SAA) concentration varies among rheumatoid arthritis patients estimated by SAA/CRP ratio.

BACKGROUND: C reactive protein (CRP) and serum amyloid A (SAA) are similarly sensitive indicators of inflammation, but discrepancies are recognized in several disease conditions. SAA levels are generally higher and vary more among individuals. The significance of the SAA/CRP ratio was evaluated in the estimation of SAA. METHODS: Sera of out-patients with rheumatoid arthritis (RA) and healthy subjects were measured for CRP and SAA cross-sectionally and longitudinally by a highly sensitive latex agglutination turbidimetric immunoassay. The results were classified into four groups according to the CRP concentration, and the SAA/CRP ratios were calculated and evaluated. RESULTS: In the cross-sectional study, CRP and SAA were shown to correlate significantly in sera of patients with RA, but not in healthy subjects. The SAA/CRP ratios were wide RA patients and tended to decrease in the range and mean values were observed depending on the concentration of CRP. In the longitudinal study, variations of the ratio among individuals were wide, but smaller and similar within individuals. The difference in magnitude of the ratios is due to the difference in SAA concentration. CONCLUSION: Variations of SAA/CRP ratios were affected by SAA concentrations. The ratio should be checked in the evaluation of SAA.

Arthritis, Rheumatoid↗
PubMed2004

Potassium flux of erythrocytes in chronic hemodialysis patients.

BACKGROUND: In chronic hemodialysis patients, hyperkalemia is frequently observed. In these patients, erythrocytes were examined to know whether they participate in the regulation of K(+) or not. METHODS: Erythrocyte K(+) release (DeltaKr) was induced by the incubation of erythrocyte suspension at 4 degrees C for 24 h and the K(+) influx followed at 37 degrees C for 3 h. K(+) flux of erythrocytes or DeltaKi/DeltaKr ratio, which was reflected by Na(+)/K(+)-exchanging ATPase, was measured in chronic hemodialysis patients. K(+) concentration was measured by ion-selective electrode method. RESULTS: Non-diabetic hemodialysis patients classified into three groups according to their serum levels were compared for various factors. Among them, the DeltaKi/DeltaKr ratios in medium- and high-serum K(+) groups were significantly lower than those in the low serum K(+) group. The effect of hemodialysis on erythrocyte K(+) flux was examined. After hemodialysis, the mean DeltaKi/DeltaKr ratio increased significantly compared with that before the treatment. Erythrocyte K(+) concentrations converted into a narrower range after hemodialysis. CONCLUSION: The reduced K(+) flux in erythrocyte may play a part in the development of hyperkalemia in non-diabetic chronic hemodialysis patients.

Adult↗
PubMed2004

Proteomics approaches to identify tumor antigen directed autoantibodies as cancer biomarkers.

The identification of autoantibodies to tumor cell proteins by proteomics approaches has great potential impact on cancer biomarker discovery. The humoral immune response represents a form of biological amplification of signals that are otherwise weak due to very low concentrations of antigen, especially in the early stages of cancers. In addition, proteomics can detect immunoreactivity directed against protein post-translational modifications. Two-dimensional gel based Western blots, protein antigen microarrays, and multiplex ELISA reactions have been applied by our group to antigen based biomarker detection and validation. The latter two are based on liquid-phase separations that are suitable for automation. This work has resulted in the identification of numerous cancer biomarker candidates. Large clinical studies are currently planned to establish their value in early cancer diagnosis.

Antibodies, Neoplasm↗
PubMed2004

Matrix effects in clinical immunoassays and the effect of preheating and cooling analytical samples.

Immunological reactions are influenced by various factors including antigens, antibodies and other variables. We focused on two items: i) matrix effects, especially of detergents and ii) temperature effects: preheating sera, especially effects on rheumatoid factor (RF) measurement and false-positive reactions in ELISAs, and cold storage of sera, especially effects on complement. Among various additives, detergents affected the agglutination reaction for fecal hemoglobin and hepatitis B surface (HBs) antigen. Some of the detergents examined abolished these antigenicities, however, polyethylenglycols enhanced the reactions. Heat-inactivation of sera at 56 degrees C for 30 min was employed in serological testing. However, in RF measurement, 10 min of preheating was sufficient to abolish C1q (subcomponent of C1), which could participate in the agglutination reaction. In ELISA for antibodies, false-positive reactions were caused by preheating sera. By the analyses of assays for antibodies to hepatitis C virus (HCV) and cardiolipin, it was found that they were induced by immunoglobulin G (IgG) modified by preheating. Cold storage induced activation of complement (cold activation) in anti-HCV antibody positive sera. CH50 titers in the sera were lowered by one cycle of freezing at -20 degrees C and thawing, and the decrease was affected by the containers.

Autoantibodies↗
PubMed2003

Reactivity of agalactosyl IgG with rheumatoid factor.

BACKGROUND: The difference in the reactivity of rheumatoid factor (RF) with agalactosyl IgG and galactosyl or intact IgG is controversial. METHODS: ELISAs for IgM-RF, using agalactosyl IgG and galactosyl IgG as a coated antigen, were developed. The sera of patients with RA, systemic lupus erythematosus (SLE), chronic liver diseases (CLD) and healthy subjects were measured for IgM-RF. An absorption test was performed using these IgGs with or without heat-pretreatment to determine any differences in the antigenicity between agalactosyl IgG and intact IgG. RESULTS: IgM-RF titers were higher against agalactosyl IgG than those against both heated-intact and intact IgG in three of nine RA patients' sera. Three other serum samples showed similar titers against all three forms of IgG and the remaining three serum samples showed varied results. IgM-RF titers were higher in sera of RA patients than those of SLE, CLD and healthy subjects. Absorptions of RA sera showed that RF was completely absorbed by 5x of absorptions with agalactosyl IgG as well as intact IgG. CONCLUSIONS: The reactivity of IgM-RF is higher with agalactosyl IgG than with heated-intact or intact IgG. The antigenic epitopes of agalactosyl and intact IgG were shown to be closely similar by the absorption test.

Absorption↗
PubMed2002

The effect of EDTA contaminated in sera on laboratory data.

BACKGROUND: We report two cases in which the data marked by low levels of serum iron (Fe) (negative value), low levels of serum calcium (Ca) and high levels of serum potassium (K) were inconsistent with their clinical states. Re-examination within 1 day showed that all the data were within or close to the reference intervals. These results could suggest contamination of ethylene diamine tetraacetate-dipotassium salt (K(2)EDTA) used in the blood collection tube for peripheral blood cell count in the tube for the serum. One of the mechanisms was suspected to be due to the backflow of evacuated blood mixed with K(2)EDTA into serum tube. MATERIALS AND METHODS: To analyze the influence of EDTA on routine and nonroutine laboratory tests, we performed routine examination using serum and EDTA plasma from healthy volunteers. RESULTS: We found a definite effect on iron, calcium and potassium and alkaline phosphatase, zinc sulfate turbidity test, ammonia, leucine aminopeptidase and CH50. We also found a definite effects on copper, angiotensin-converting enzyme (ACE), matrix metalloproteinase (MMP)-1, -3 and -9, tissue inhibitor of matrix metalloproteinase (TIMP)-1, hepatocyte growth factor (HGF), monoamine oxidase (MAO), vitamin B(12), ACTH and IL-6, though the mechanisms were not clear. CONCLUSIONS: Inappropriate blood collection can induced false biochemical data due to the contamination of EDTA.

Adult↗
PubMed2002

Identification of a dysfibrinogenemia of gammaR275C (Fibrinogen Fukushima).

BACKGROUND: Various dysfibrinogenemias have been identified worldwide. This paper describes a case of dysfibrinogenemia recently identified in our laboratory. PATIENT: A 34-year-old pregnant woman without any clinical complaints was admitted to our hospital for delivery. She had an extremely low fibrinogen concentration as determined by the thrombin time method though immunoassay showed a titer within the reference range. Dysfibrinogenemia was suspected and further analyses were performed including on her family. Thrombin time was measured using human and bovine thrombin with and without calcium ion. Reptilase time was also measured. To identify the genetic mutation responsible for this dysfibrinogen, genomic DNA extracted from the blood was analyzed for mutation-rich regions in the fibrinogen gene. RESULTS: The subject, her mother and her two infants showed the same pattern of results while her father showed a regular pattern. Thrombin time calculated using both human and bovine thrombin and reptilase time was elongated in the propositus. The extent of the elongation was decreased in the presence of calcium ion. DNA sequencing showed heterogeneous fibrinogen gammaR275C mutations in the propositus, mother and two children. The father showed no mutation. CONCLUSIONS: A case of dysfibrinogenemia gammaR275C without any clinical symptoms was found by routine coagulation testing and was genetically identified.

Adult↗
PubMed2002

[Microbiology--laboratory examinations for bacterias].

As it has been required to identify pathogenic microbes in shorter times, simple and rapid methods have been developed and used. Here, we summarized the present situation of rapid diagnostic testing in clinical microbiology in Japan, and also presented our results on PBP2' detection. The rapid test kits available in Japan for E. coli, Helicobacter pylori, Salmonella, Streptococcus and Staphylococcus aureus were described. Rapid examination methods are based mainly on immunologic reactions, which included slide agglutination using latex particle, immunochromatography and ELISA. Times required for the identification are 10 to 15 minutes. Moreover, rapid test kits employing PCR are also marketed. Further, we evaluated MRSA-LA "Seiken" which is a rapid detection kit for PBP2' produced by MRSA. The test was shown to be highly sensitive and specific. For the rapid identification of pathogenic microbes, simple and rapid test kits described here will be used more in clinical diagnosis.

Bacteria↗