Teruaki Oka

Bio: Teruaki Oka is an academic researcher. The author has contributed to research in topics: Xanthopterin & Neopterin. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

A comparative study of urinary xanthopterin and neopterin in liver diseases.

Abstract: By adsorption to activated charcoal, various pteridine derivatives in human urine are oxidized to xanthopterin. Following this oxidation, xanthopterin in urine from healthy subjects and from patients with liver diseases was assayed by high performance liquid chromatography. The mean values for xanthopterin in healthy subjects were 532 +/- 116 mumol/mol creatinine (mean +/- SD) in males and 585 +/- 153 mumol/mol creatinine in females; the difference was statistically significant (p < 0.01). Xanthopterin concentrations in patients with liver disease were significantly higher than those in normal subjects. When compared with urinary neopterin, which is a marker of activated cell immunity, xanthopterin was significantly increased even in fatty liver disease. These findings suggest that increased concentrations of urinary xanthopterin in liver diseases reflect not only the status of activated cell-mediated immunity, but also injury to liver cells.

Erroneous HbA1c measurements in the presence of β-thalassemia and common Chinese hemoglobin variants.

Abstract: Background HbA1c is a widely used biomarker for the management of diabetes mellitus and can be quantified from blood samples by using various methods, including ion-exchange high-performance liquid chromatography (HPLC), boronate affinity HPLC, and capillary electrophoresis (CE). Here, we evaluated the accuracy of four separation methods for determination of HbA1c values in Chinese patients with different hemoglobin disorders. Methods Blood samples from normal patients, patients with β-thalassemia, patients exhibiting heterozygosity, and patients exhibiting homozygosity were analyzed using ion-exchange HPLC (Variant II Turbo, Bio-Rad and Adams A1c HA-8160, Arkray, run in diabetes mode), boronate affinity HPLC (Ultra2, Trinity Biotech), and CE (Capillarys 2 Flex Piercing, Sebia). Results Samples from patients with β-thalassemia produced significant positive biases on the Variant II Turbo system compared to the other three systems. For heterozygous βA/βE patients, a good agreement was observed between Capillarys 2 Flex Piercing and Ultra2 systems, while a significant negative bias was observed between HA-8160 and Capillarys 2 Flex Piercing systems and between Variant II Turbo and Capillarys 2 Flex Piercing systems. For homozygous (βE/βE) patients, a clear context without HbA, all systems except the Capillarys 2 Flex Piercing system yielded random HbA1c results. Only the Capillarys 2 Flex Piercing system could detect all hemoglobin variants tested. Conclusions β-Thalassemia can cause errors in HbA1c determination using the Variant II Turbo system. HbE heterozygosity or HbE homozygosity also complicated HbA1c measurements. The Capillarys 2 Flex Piercing system detected all Hb variants and HbA1c in patients with β-thalassemia and could provide measurements with high accuracy.

Determination of pteridines in biological samples with an emphasis on their stability

Abstract: Pteridines are a group of endogenous heterocyclic compounds whose concentrations in biological fluids may be increased in some disorders, such as infections, autoimmune disorders and cancer. In particular, pteridine concentrations in urine may represent promising noninvasive markers. However, their specificity requires further investigation. Pteridines can occur in three oxidation states with different stability. In order to enable the analysis of the unstable di- and tetra-hydroforms either an oxidation (mainly with iodine) or stabilization by reducing agents is applied. Due to the high polarity of pteridines, many analytical procedures employed ion-pair, ion-exchange or hydrophilic interaction liquid chromatography using mostly fluorescence detection. In the last decade, MS was found to be applicable. The objective of this Review is to show possibilities and different approaches in pteridine analysis in biological samples.

Multicentre evaluation of the Premier Hb9210 HbA1c analyser.

Abstract: Background: The accurate and precise quantification of HbA1c is essential for the diagnosis and routine monitoring of patients with diabetes. We report an evaluation of the Trinity Biotech Premier Hb9210 analyser (Bray, Ireland/Kansas City, MO, USA), a boronate affinity chromatography-based high performance liquid chromatography (HPLC) system for the measurement of glycated haemoglobin. Methods: We evaluated the analytical performance of the Hb9210 as part of a multicentre evaluation. The effect of haemoglobin variants, other potential interferences and the performance in comparison to both the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and National Glycohemoglobin Standardization Program (NGSP) reference systems, was assessed. Most of the centres participating also act as reference laboratories for both the IFCC standardisation network for HbA1c and the NGSP. Results: The combined data from all centres showed total coefficients of variation (CV) of 2.71%, 2.32% and 2.14% at low, medium and high values, respectively, for mmol/mol (SI units) and 1.62%, 1.59% and 1.68% for % (NGSP units), which are well below the recommended upper limits of 3% CV for mmol/mol (SI units) and 2% CV for % (NGSP). The analyser showed a good correlation to HbA1c methods currently used in clinical practice and the IFCC reference method procedure. Haemoglobin variants AC, AS, AE and AD do not affect the measurement of HbA1c. Overall the Hb9210 performs well across the whole analytical range. Conclusions: The Hb9210 performs well and is suitable for clinical application in the analysis of HbA1c.

Is neopterin level a predictive and differential biomarker in patients with thyroid disorders

Abstract: Neopterin production provides information about the extent of cellular immune activation. Measurement of neopterin levels may also provide predictive and prognostic information in patients with malignant thyroid diseases. In the present study, neopterin levels were investigated in patients with thyroid disorders (no.=68). Twenty-four patients had papillary thyroid cancers and the rest of them benign thyroid disorders. Results were compared with a healthy control group (no.=30). It was observed that there was a significant difference in neopterin levels between the control group and the thyroid disorders group (p<0.05). The mean neopterin levels in malignant and benign patients were also significantly different (p<0.05). Monitoring of urinary neopterin profile may be used in early diagnosis of papillary thyroid cancer. Neopterin seems to be a differential biomarker for malignant and benign thyroid disorders.