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Biomedical subjects

T Mukai

Publications and source records attributed to T Mukai.

At least 91 records · Page 5Linked to original sources
PubMed1999

Species difference in radioactivity elimination from liver parenchymal cells after injection of radiolabeled proteins.

To elucidate the cause for the different levels of hepatic radioactivity among mammals after injection of protein radiopharmaceuticals, the metabolism of radiolabeled proteins and the fate of their radiometabolites in the parenchymal cells of rat liver were investigated and compared with those of mice. We used galactosyl-neoglycoalbumin (NGA) as a carrier protein, and NGA was labeled with 111In via 1-(4-isothiocyanatobenzyl)ethylenediaminetetraacetic acid (SCN-Bz-EDTA) or 1-[p-(5-maleimidopentyl)aminobenzyl]ethylenediaminetetraacetic acid (EMCS-Bz-EDTA) and with 125I via direct iodination. All radiolabeled NGAs exhibited rapid accumulation in liver parenchymal cells after intravenous injection into rats. Radioactivity was eliminated following NGA-125I injection at similar rates from rat and mouse liver. In contrast, both 111In-labeled NGAs demonstrated much slower elimination of radioactivity in rat when compared with mouse liver. Analyses of radioactivity in bile and liver indicated that both SCN-Bz-EDTA and EMCS-Bz-EDTA rendered mono-amino acid adducts as the final radiometabolites, which were generated in rat liver within 1 h postinjection. Subcellular distribution studies suggested that these radiometabolites were copurified with lysosome in rat liver. Because similar results were observed in mice previously, the difference between rats and mice in radioactivity elimination from liver parenchymal cells would be predominantly attributable to the different efflux rate of the 111In-labeled metabolites from the lysosome between these species. Such differences in the efflux rates of radiometabolites from the lysosome among mammals may also account for the different hepatic radioactivity levels of radiolabeled proteins between animal and clinical studies.

Albumins↗
PubMed1999

Sleeping environments as risk factors of sudden infant death syndrome in Japan.

For the purpose of assessing the risk factors of the sleeping environment in SIDS, we performed a population-based, case-control study. Index cases comprised 56 SIDS cases which were diagnosed on the basis of autopsies during a period of 11 years at the Department of Legal Medicine, Faculty of Medicine, University of the Ryukyus. Control cases comprised infants who were examined at regional health centers for Infant Health Screening. The incidence of SIDS obtained was 0.25 per 1000 live births, which was comparable to that obtained in other districts having the established medical examiner's system. The proportion of prone sleeping was 81.0% and 38.3% in the SIDS and control groups, respectively, and an odds ratio was calculated as 10.4 (99% confidence interval, 3.9 to 37.6). This indicates that prone sleeping is a risk factor of SIDS, in Japan, as reported in various countries. Various kinds of bedclothes were used in this country, and our survey of bedclothes in the control revealed their improper use for infants to sleep, particularly with the prone position. In addition, the co-sleeping habit, which was not uncommon in Japan, seems to contribute to certain deaths of infants whose causes of death were controversial. In the investigation of SIDS, therefore, the sleeping environments, such as bedclothes and the co-sleeping habit, as well as the sleeping position should be taken into consideration as risk factors.

Journal Article↗
PubMed1999

Physiological and chemotaxonomical studies on microflora within a composter operated at high temperature.

Physiological and chemotaxonomical studies were carried out on microorganisms isolated from a composter operated at around 50 to 60 degrees C. Only gram-positive rods were isolated and the microbial counts on agar plates were relatively low (10(3) to 10(5) cfu/g-sample). The chemotaxonomic properties of the ten isolates revealed that they were typical of the genus Bacillus. Identification by the Biolog system concurred with the chemotaxonomy; all the strains were determined to be Bacillus. 16S rDNA analysis closely identified five of the isolates as B. licheniformis, one as B. subtilis, and two as B. thermoamylovorans, while the remaining two strains seemed to belong to a new species. However, in several cases 16S rDNA analysis and the Biolog system gave different results at the species level. The stability of microflora within the composter was also investigated using the Biolog system. Analysis of colonies obtained during three sampling periods--December 1997, April 1998, and June 1998--showed that the microflora in the composter remained fairly stable.

Journal Article↗
PubMed1999

Characterization of ocular pharmacokinetics of beta-blockers using a diffusion model after instillation.

PURPOSE: To characterize the ocular pharmacokinetics of beta-blockers (timolol and tilisolol) after instillation in the albino rabbit using a mathematical model that includes a diffusion process. METHODS: The disposition of fluorescein isothiocyanate-dextran (FITC-dextran, molecular weight 4400), timolol, and tilisolol was determined in tear fluid and aqueous humor after instillation or ocular injection in rabbits. The in vivo penetration parameters were estimated by fitting the concentration-time profiles to the Laplace equations based on a diffusion model using MULTI(FILT) program. The in vitro permeability of drugs was measured across cornea using a two-chamber diffusion cell. RESULTS: Concentration-time profiles of drugs in the tear fluid after instillation showed a monoexponential curve. Although a monoexponential curve was observed in the aqueous humor concentration of FITC-dextran after injection into the aqueous chamber, timolol and tilisolol showed a biexponential curve. On the basis of these results, an in vivo pharmacokinetic model was developed for estimation of penetration parameters. The in vitro partition parameters were higher than those of the in vivo parameters. CONCLUSIONS: The ocular absorption of timolol and tilisolol was characterized using an in vivo pharmacokinetic model and in vivo penetration parameters.

Absorption↗
PubMed1999

Short communication: emission of nitrous oxide (N2O) from transgenic tobacco expressing antisense NiR mRNA

The emission of N2 and N2O from intact transgenic tobacco (clone 271) expressing antisense nitrite reductase (NiR) mRNA, and wild-type plants grown aseptically, on NO3-, NO2- or NH4+ -containing medium was investigated. 15N contents of gas sampled from gas-sealed pots, in which the plants were grown on 15N-containing medium, were analyzed by gas chromato- graphy and mass spectrometry (GC-MS). No emission of N2 was detected in either of the gas samples from plant clone 271 or the wild-type grown on NO3--containing medium. N2O emission from clone 271 grown on NO3--containing medium was detected, but not from the wild-type plants. The N2O emission rate of clone 271 was 106 ng N2O mg-1 incorporated N week-1 and the N2O emission was inhibited by tungstate (a nitrate reductase inhibitor). No emission of N2O was found from clone 271 or wild-type plants grown on medium containing NH4+. Emission of N2O also was detected from clone 271 grown on NO2--containing medium and its emission rate increased with increasing NO2- levels in plants. We speculate that NO3- is reduced to NO2- and that a part of NO2- is metabolized to N2O in clone 271.

Journal Article↗
PubMed1999

Psychiatric disorders among Japanese children.

OBJECTIVE: To generate current data on the prevalence of psychiatric disorders among Japanese children, using DSM-III-R criteria. METHOD: As part of an ongoing longitudinal study in a Japanese community sample, 114 mother-child dyads were interviewed when the children were approximately 8 years old. DSM-III-R disorders of the children were diagnosed through the administration of a structured diagnostic instrument, the parent and child versions of the Child Assessment Schedule, to both the children and their mothers. RESULTS: The prevalence rate for any diagnosis was 49.1%, which is similar to that of U.S. children and adolescents. CONCLUSION: The Child Assessment Schedule is an appropriate scale for assessing the psychopathology of Japanese children, which is as prevalent as in a U.S. sample.

Adolescent↗
PubMed1999

Comparison of the complete DNA sequences of human herpesvirus 6 variants A and B.

Human herpesvirus 6 (HHV-6), which belongs to the betaherpesvirus subfamily and infects mainly T cells in vitro, causes acute and latent infections. Two variants of HHV-6 have been distinguished on the basis of differences in several properties. We have determined the complete DNA sequence of HHV-6 variant B (HHV-6B) strain HST, the causative agent of exanthem subitum, and compared the sequence with that of variant A strain U1102. A total of 115 potential open reading frames (ORFs) were identified within the 161,573-bp contiguous sequence of the entire HHV-6 genome, including some genes with remarkable differences in amino acid identity. All genes with <70% identity between the two variants were found to contain deleted regions when ORFs that could not be expressed were excluded from the comparison. Except in the case of U47, these differences were found in immediate-early/regulatory genes, DR2, DR7, U86/90, U89/90, and U95, which may represent characteristic differences of variants A and B. Also, we have successfully typed 14 different strains belonging to variant A or B by PCR using variant-specific primers; the results suggest that the remarkable differences observed were conserved evolutionarily as variant-specific divergence.

DNA, Viral↗
PubMed1999

In-vivo evaluation of indium-111-diethylenetriaminepentaacetic acid-labelling for determining the sites and rates of protein catabolism in mice.

Pharmacokinetic analyses of protein pharmaceuticals are of prime importance for their clinical application. Because many proteins have pharmacological activity at low concentrations, radiolabelling of proteins is widely used to identify the sites and determine the rates of protein catabolism in-vivo due to the high sensitivity of detection of radioactivity. Recently, a metallic radionuclide, (111)In, has been used to trace the pharmacokinetics of proteins of interest after conjugation of the proteins with diethylenetriaminepentaacetic acid (DTPA). In this study, galactosyl-neoglycoalbumin (NGA) was reacted with the cyclic dianhydride of DTPA and labelled with (111)In to estimate the validity of this radiolabelling procedure for pharmacokinetic analyses. For comparison, we also evaluated direct radioiodination, because directly-radioiodinated proteins are widely used to assess the pharmacokinetics of proteins of interest. The hepatic radioactivity profile after intravenous injection of [131I]NGA or [(111)In]DTPA-NGA into mice was analysed pharmacokinetically, and the first-order rate constant representing the elimination of the respective radiometabolite from hepatic parenchymal cells was determined. The results indicated that direct radioiodination is inappropriate for pursuing the pharmacokinetics of the proteins, because of rapid elimination of the radioactivity from the sites of protein catabolism. These findings also implied that the [(111)In]DTPA label could be used to identify the catabolic sites and determine the rates of catabolism of proteins with relatively short biological half-lives, although characterization of radiolabelled species at the sites of accumulation would be required for accurate determination of the catabolic sites of proteins.

Albumins↗
PubMed1999

Characterization of ocular pharmacokinetics of tilisolol after instillation into anesthetized rabbits.

The purpose of this study was to characterize the ocular pharmacokinetics of a beta-blocker, tilisolol, after instillation into anesthetized rabbits using a mathematical model including a diffusion process. The samples were analyzed by HPLC. Anesthetized rabbit was used as a model of tear secretion deficiency. Anesthetized rabbits showed higher drug concentration in the tear fluid and aqueous humor after instillation than unanesthetized rabbits. A mathematical model including a diffusion process and in vivo penetration parameters well described the concentrations of tilisolol in the aqueous humor after instillation in anesthetized rabbits.

Administration, Topical↗
PubMed1999

Continuous microinstillation of phenol red on liver surface for liver site-selective delivery.

We report a very promising approach for liver site-selective drug delivery through drug instillation on liver surface. Phenol red, which was selected as a model drug, was accumulated in the instillation site after instillation on the rat liver surface. The site-selective localization was enhanced by gradually and continuously instilling a small amount of drug solution on the liver surface.

Animals↗
PubMed1999

Drug absorption behavior after periocular injections.

The purpose of this study was to investigate the absorption behavior of an ophthalmic drug injected in rabbit periocular tissues. After intracapsular, retrobulbar and palpebral conjunctival injections of 150 microl and 50 microl fluorescein isothiocyanate dextran (FITC-dextran, average molecular weight 11000), leakage of the dye into the tear fluid was dependent on the injection route and volume. After periocular injections (50 microl) of tilisolol, as a model beta-blocker, the concentrations in the tear fluid, blood, aqueous humor and vitreous body were determined by HPLC. Slight drug leakage was observed in the tear fluid after injections. The periocular injections showed a faster absorption and a higher area under the concentration-time curve (AUC) in the plasma and a lower AUC in the aqueous humor than those observed in instillation. They also showed a higher ratio of AUC of tilisolol in the vitreous body to AUC in the aqueous humor than that observed in the instillation. Among the periocular injections, retrobulbar injection showed the highest concentrations in the plasma and the lowest in the aqueous humor and vitreous body, while intracapsular injection showed the lowest in the plasma and the highest in the aqueous humor and vitreous body. Although the periocular injections showed a rapid systemic absorption of drug by a rich topical vasculature, it might be an effective approach to deliver the drug to the periocular tissues and vitreous body.

Absorption↗
PubMed1999

Topical delivery system of ophthalmic drugs by periocular injection with viscous solution.

The purpose of this study is to evaluate periocular injections with viscous solution as a topical delivery system of ophthalmic drugs. Tilisolol and carboxymethylcellulose (CMC) were used as a model beta-blocker and a viscous polymer, respectively. After intracapsular, retrobulbar and palpebral conjunctival injections (50 microl) of tilisolol with 3% CMC into rabbits, drug concentrations in the tear fluid, blood, aqueous humor and vitreous body were determined by HPLC. Periocular injection (50 microl) of tilisolol with 3% CMC showed slight leakage of the drug in the tear fluid from the injection site. The viscous vehicle decreased the absorption rate constant of the drug from the injection site to systemic circulation compared with the buffer solution. It suggests that the viscous solution improved the retention of drug at both the injection site and in periocular tissues. Although the periocular injections with viscous vehicle (3% CMC) showed lower AUC in the aqueous humor than that observed in instillation, they showed comparable AUC in the vitreous humor. Compared to the results after the periocular injections with buffer solution, CMC increased the AUCs in the vitreous body 3.1-fold with retrobulbar injection and 1.4-fold with palpebral conjunctival injection, respectively. As a result, periocular injections with 3% CMC showed higher delivery of tilisolol to the vitreous body against the aqueous humor than the instillation and periocular injections with buffer solution.

Absorption↗
PubMed1999

Expression of MEF2 genes during human cardiac development.

To better understand the regulatory mechanisms in gene expression of human cardiomyocytes, we studied the expression of MEF2 genes encoding transcription factors during the course of cardiac development. Expression of all four MEF2 transcripts (MEF2A, MEF2B, MEF2C, and MEF2D) were detected in all developmental stage of the human heart, while Mef2b transcripts were down-regulated in mouse heart development. Although none of the MEF2 genes, besides mouse Mef2b, exhibited any remarkable quantitative change in their transcripts, qualitative changes in MEF2 transcripts were found during the course of cardiac development. In particular, MEF2D transcripts showed prominent changes by alternative splicing in the perinatal period. MEF2D transcripts containing the 21-base exon (exon b) were predominantly expressed after birth. At the same time, transcripts of the alpha myosin heavy chain (alphaMHC) gene increased after birth, as the splicing pattern in transcripts of the cardiac troponin T (cTnT) gene changed to decrease the transcripts of cTnT1 after birth. These changes seemed to be correlated with the alternative splicing changes of MEF2 genes, especially MEF2D. The alternative splicing as well as transcriptional regulation in MEF2 genes might be important for regulating the alphaMHC gene and the maturation of cardiomyocytes.

Animals↗
PubMed1999

Enhancement of ocular drug penetration.

Although new drugs have recently been developed within the field of ophthalmology, the eye's various defense mechanisms make it difficult to achieve an effective concentration of these drugs within the eye. Drugs administered systemically have poor access to the inside of the eye because of the blood-aqueous and blood-retinal barriers. And although topical instillation of drugs is very popular in ophthalmology, topically applied drugs are rapidly eliminated from the precorneal area. In addition, the cornea, considered a major pathway for ocular penetration of topically applied drugs, is an effective barrier to drug penetration, since the corneal epithelium has annular tight junctions (zonula occludens), which completely surround and effectively seal the superficial epithelial cells. Various drug-delivery systems have been developed to increase the topical bioavailability of ophthalmic drugs by enhancement of the ocular drug penetration. The first approach is to modify the physicochemical property of drugs by chemical and pharmaceutical means. An optimum promoiety can be covalently bound to a drug molecule to obtain a prodrug that can chemically or enzymatically be converted to the active parent drug, either within the cornea or after the corneal penetration. Along these same lines, the transient formation of a lipophilic ion pair by ionic bonding is also useful for improving ocular drug penetration. The second approach is to modify the integrity of the corneal epithelium transiently by coadministration of an amphiphilic substance or by chelating agents that act as drug-penetration enhancers. The third approach modifies the integrity of the corneal epithelium transiently by physical techniques including iontophoresis and phonophoresis. This paper reviews the absorption behavior and ocular membranes penetration of topically applied drugs, and the various approaches for enhancement of ocular drug penetration in the eye.

Drug Carriers↗
PubMed1999

Analysis of germline CDKN1C (p57KIP2) mutations in familial and sporadic Beckwith-Wiedemann syndrome (BWS) provides a novel genotype-phenotype correlation.

Beckwith-Wiedemann syndrome (BWS) is a human imprinting disorder with a variable phenotype. The major features are anterior abdominal wall defects including exomphalos (omphalocele), pre- and postnatal overgrowth, and macroglossia. Additional less frequent complications include specific developmental defects and a predisposition to embryonal tumours. BWS is genetically heterogeneous and epigenetic changes in the IGF2/H19 genes resulting in overexpression of IGF2 have been implicated in many cases. Recently germline mutations in the cyclin dependent kinase inhibitor gene CDKN1C (p57KIP2) have been reported in a variable minority of BWS patients. We have investigated a large series of familial and sporadic BWS patients for evidence of CDKN1C mutations by direct gene sequencing. A total of 70 patients with classical BWS were investigated; 54 were sporadic with no evidence of UPD and 16 were familial from seven kindreds. Novel germline CDKN1C mutations were identified in five probands, 3/7 (43%) familial cases and 2/54 (4%) sporadic cases. There was no association between germline CDKN1C mutations and IGF2 or H19 epigenotype abnormalities. The clinical phenotype of 13 BWS patients with germline CDKN1C mutations was compared to that of BWS patients with other defined types of molecular pathology. This showed a significantly higher frequency of exomphalos in the CDKN1C mutation cases (11/13) than in patients with an imprinting centre defect (associated with biallelic IGF2 expression and H19 silencing) (0/5, p<0.005) or patients with uniparental disomy (0/9, p<0.005). However, there was no association between germline CDKN1C mutations and risk of embryonal tumours. No CDKN1C mutations were identified in six non-BWS patients with overgrowth and Wilms tumour. These findings (1) show that germline CDKN1C mutations are a frequent cause of familial but not sporadic BWS, (2) suggest that CDKN1C mutations probably cause BWS independently of changes in IGF2/H19 imprinting, (3) provide evidence that aspects of the BWS phenotype may be correlated with the involvement of specific imprinted genes, and (4) link genotype-phenotype relationships in BWS and the results of murine experimental models of BWS.

Beckwith-Wiedemann Syndrome↗
PubMed1998

Cloning of the Xenopus laevis aldolase C gene and analysis of its promoter function in developing Xenopus embryos and A6 cells.

A Xenopus aldolase C gene (XAClambda3-1), much longer (9.6 kb) than human and rat genes (3.7-3.6 kb), was isolated and characterized, and expression studies were performed using Xenopus embryos and A6 cells, a kidney cell line constitutively expressing aldolase C gene. The Xenopus gene contained nine exons, and in its proximal 5'-upstream region a GC box and a 16 bp long aldolase C-specific element (ACSE), and in addition, a CCAAT box and a TATA-like element, both missing in mammalian genes. The lacZ gene connected to the 5'-upstream region (1.6 kb) of the aldolase gene containing many potentially regulative sequence elements was expressed in embryos temporally and spatially like the endogenous aldolase C gene. Deletion experiments using embryos and A6 cells suggested that this 5'-upstream DNA contained in its distal part a region which negatively affected on its expression in embryos, but not in A6 cells. The proximal-most region contained a basal promoter (68 bp) essential for expression in both embryos and A6 cells. Deletion experiments using A6 cells failed to detect such regulative regions within the first intron (spanning ca. 4 kb). Analyses with mutated promoters in A6 cells revealed that the GC box was the crucial element in the basal promoter, although the TATA-like element appeared to have a slightly stimulative effect on the GC box functioning. Gel retardation and foot-printing assays revealed the occurrence in A6 cells of a nuclear factor(s) that binds specifically to the GC box. Since Xenopus aldolase C gene has several unique structural features, we expect that it will provide an interesting material for studying the evolution and developmental control of the aldolase C gene.

Amino Acid Sequence↗