Naoyuki Kamatani

Hypouricaemic effect after oral administration in chickens of polyethylene glycol-modified uricase entrapped in liposomes

Liposomal‐entrapped methoxypolyethyleneglycol (PEG) modified uricase was used to study the plasma urate lowering effect after its oral administration to chickens. Plasma uric acid concentrations fell gradually and were accompanied by a rise in plasma uricolytic activity. Serum from chickens given PEG‐modified uricase liposomes did not react with native uricase in immunodiffusion plates. These results suggested the clinical usefulness of liposome‐entrapped PEG modified uricase in the treatment of hyperuricaemia.

Human anticentriole autoantibody in patients with scleroderma and Raynaud's phenomenon.

Unique autoantibody was found in sera from two different patients that reacted with centrioles of both cultured mammalian cells and human peripheral leukocytes as detected by the indirect immunofluorescent method. Sera from the same individuals, one with scleroderma and the other suffering from Raynauds phenomenon, also stained the basal bodies of rat tracheal ciliated cells by the identical technique. Data from subsequent investigations have suggested that the antigen(s) involved in the reaction are water-insoluble protein(s) or polypeptide(s) associated with centrioles and are distinct from microtubular proteins or purine nucleoside phosphorylase.

Theophylline increases serum uric acid levels

The present study was undertaken to investigate the effect of theophylline on serum uric acid and then to elucidate the mechanisms of action of theophylline as a cause of hyperuricemia. There was a significant increase of serum uric acid levels in male asthmatic patients who received theophylline compared to male control subjects without theophylline (6.3 +/- 0.4 mg/ml, mean +/- SEM, versus 4.3 +/- 0.2 mg/ml, p less than 0.01). A significant correlation of serum levels of uric acid and theophylline was demonstrated in asthmatic patients who received 200 to 400 mg sustained-release theophylline (male group, r = 0.480, p less than 0.001; female group, r = 0.398, p less than 0.01). Intravenous administration of aminophylline in three healthy adult male patients did not inhibit uric acid clearance, suggesting that inhibition of excretion of uric acid by theophylline is unlikely. Theophylline slightly inhibited hypoxanthine guanine phosphoribosyltransferase activity in human erythrocyte lysates at concentrations over 5 mM that is considerably more than therapeutic concentrations of theophylline as determined by the conversion of [14C]hypoxanthine to [14C]inosinic acid. Theophylline caused a moderate inhibition of [14C]hypoxanthine uptake by K-562 cells (approximately 50%) at 10mM that is over 100 times as high as those achieved clinically. Further studies remain to be performed to elucidate the exact mechanisms of theophylline-induced hyperuricemia.

Japanese single nucleotide polymorphism database for 267 possible drug‐related genes

To establish ‘personalized medicines’ that can provide the right drug at the appropriate dose for each individual patient on the basis of genetic background, we have been building the infrastructure for a Japanese single nucleotide polymorphism (SNP) database of the genes encoding various enzymes, transporters and receptors that are involved in the metabolism, transportation and action of drugs. We have so far screened a genomic region of 4068.3 kb, and identified a total of 7552 genetic variations, including 6733 SNP and 819 genetic variations of other types among 267 genes in Japanese populations. Interestingly, among the 212 non‐synonymous substitutions we found, six would be considered to be nonsense mutations. In this review, we focused on the molecular features of the non‐synonymous substitutions and insertion/deletion polymorphisms within coding regions detected in drug‐related gene loci. The database established in this study makes us confident of achieving one of our goals, which is establishment of personalized medicine. (Cancer Sci 2006; 97: 16–24)

Inhibition of purine nucleoside phosphorylase activity and of T-cell function with allopurinol-riboside

Allopurinol-riboside competitively inhibits the action of purine nucleoside phosphorylase on inosine in vitro with aKi of 277 μmol. After simple incubation of allopurinol-riboside with PNP, allopurinol was not formed. Lymphocyte blastogenesis induced by PHA and Con A was significantly suppressed by allopurinol-riboside in a concentration-dependent manner. When LPS was used as a mitogen, the inhibition of allopurinol-riboside on lymphocyte proliferation was less marked. Humoral immunity was not suppressed by allopurinol-riboside. In contrast, cellular immunity was significantly suppressed by allopurinol-riboside in vivo. These results suggested that allopurinol-riboside is a drug which produces a model of PNP deficiency, and that it may be a useful inhibitor of cellular immunity.

Differential inhibition of lymphocyte function by 2-chloroadenosine

The effects of 2-chloroadenosine, a poorly metabolized adenosine analogue, on some human lymphocyte functions were studied. Mixed lymphocyte responses were strongly inhibited by very low concentrations of 2-chloroadenosine. The mitogen-induced proliferation of human lymphocytes was also generally suppressed by 2-chloroadenosine in a dose dependent manner. Blastogenesis induced by Con A and PWM was severely inhibited by low doses of 2-chloroadenosine while its inhibition of that induced by PHA was less marked. Natural killer cell activity was inhibited only about 55% by high concentrations of 2-chloroadenosine. These results suggested that many subsets of human lymphocytes are controlled by adenosine receptor.

Influences of ethanol on 5-phosphoribosyl-1-pyrophosphate concentration and purine-metabolizing enzyme activities in the mouse liver

Abstract The incubation of isolated mouse hepatic cells with ethanol led to increase the 5-phosphoribosyl-1-pyrophosphate contents. The 5-phosphoribosyl-1-pyrophosphate contents, glucose-6-phosphate dehydrogenase, and purine nucleoside phosphorylase activities in the mouse liver were not changed with the low doses of ethanol treatment, but were significantly elevated with higher dosage. The hepatic hypoxanthine-guanine phosphoribosyl transferase activity was not changed with the low and high doses of ethanol treatment. These results suggested that excessive amount of alcohol intake may accerate the de novo purine synthesis and may result in overproduction of uric acid.

Tubular Function Impairment in Patients with Asymptomatic Hyperuricemia

Renal function studies were done on asymptomatic hyperuricemic subjects and normouricemic controls matched as to age, sex and blood pressure. Abnormal urinary sediments and proteinuria were found more frequently in asymptomatic hyperuricemic subjects than in the controls. In addition, the maximal osmolar concentrating ability of urine was markedly reduced in the asymptomatic hyperuricemic subjects. There was no difference in renal function measured by phenolsulfonphthalein excretion between the groups. Our results suggest that hyperuricemia alone may contribute to renal tubular impairment.

Accurate automated clustering of two-dimensional data for single-nucleotide polymorphism genotyping by a combination of clustering methods: evaluation by large-scale real data

MOTIVATIONnThe Invader assay is a fluorescence-based high-throughput genotyping technology. If the output data from the Invader assay were classified automatically, then genotypes for individuals would be determined efficiently. However, existing classification methods do not necessarily yield results with the same accuracy as can be achieved by technicians. Our clustering algorithm, Genocluster, is intended to increase the proportion of data points that need not be manually corrected by technicians.nnnRESULTSnGenocluster worked well even when the number of clusters was unknown in advance and when there were only a few points in a cluster. The use of Genocluster enabled us to achieve an acceptance rate (proportion of assay results that did not need to be corrected by expert technicians) of 84.4% and a proportion of uncorrected points of 95.8%, as determined using the data from over 31 million points.nnnAVAILABILITYnInformation for obtaining the executable code, example data and example analysis are available at http://www.genstat.net/genocluster.

Suppression of Cellular Immunity due to Inhibition of Purine Nucleoside Phosphorylase by Allopurinol-Riboside

Recently, children with purine nucleoside Phosphorylase (PNP) deficiency have been reported to show defective T cell immunity but intact B cell immunity (1). These findings suggest that inhibition of PNP may result in suppression of T cell functions and an inhibitor of PNP may also be a useful immunosuppressive agent.