Biomedical subjects

L Y Lin

Publications and source records attributed to L Y Lin.

At least 37 records · Page 2Linked to original sources

PubMed1998

A SAS macro for a simulation study of imputation methods for missing values--an application of Bebbington's algorithm.

This paper presents a SAS macro for a simulation study of comparing a new variant of hot-deck imputation with mean imputation for missing values, in which a simple algorithm proposed by Bebbington (Applied Statistics, 1975) for carrying out simple random sampling without replacement was employed to draw repeated random samples efficiently. A simulated example of drawing repeated random samples from a regional survey of obesity in school children was used to demonstrate the SAS macro.

Algorithms↗

PubMed1998

Dynamic displacement changes of the bladder neck with the patient supine and standing.

PURPOSE: With the patient standing and supine we determine the differences in dynamic changes of the bladder neck and directions of dynamic bladder neck displacement. MATERIALS AND METHODS: To evaluate the dynamic movement of the bladder neck we recruited into the study 78 consecutive women 27 to 69 years old with various urogynecological complaints. The anatomical changes of the bladder neck from rest to maximal straining and from rest to holding were evaluated and compared with the patients supine and standing. RESULTS: Except for bladder neck rotational angle with the patient standing, all parameters were significantly different from corresponding measurements with the patient supine. Mean rotational angle of rest to maximal straining plus or minus standard deviation was 39.4 +/- 18.9 degrees when standing versus 39.8 +/- 23.4 degrees when supine (p > 0.05). The distances between the bladder neck and symphysis pubis at rest, and during maximal straining and holding the bladder neck in the supine position were significantly longer than those in the standing position. The direction of bladder neck displacement from rest to maximal straining was more caudad and ventral when standing. The bladder neck moved cephalad and ventral when the patient was standing, and cephalad and dorsal with the patient supine and holding the bladder neck. CONCLUSIONS: The anatomical locations and dynamic displacements of the bladder neck at rest, and during maximal straining and holding were significantly different in the supine and standing positions. While evaluating the dynamic motion of the bladder neck to determine bladder neck mobility, patient position must be considered and specified in accordance with diagnostic standards.

Adult↗

PubMed1997

Metal-induced metallothionein gene expression can be inactivated by protein kinase C inhibitor.

The effects of protein kinase C (PKC) inhibitors on the metallothionein (MT) gene expression induced by metals were investigated. When PKC inhibitor (H7 or chelerythrine) was administered to Cd resistant, MT gene-amplified Chinese hamster ovary (CdR) cells, the induction of MT mRNA by Cd or Zn was blocked. Treating the CdR cells with a PKA-specific inhibitor, HA1004, did not cause an inhibition of metal-induced MT gene transcription. The inhibitory effect was effectuated by adding inhibitors within 40 min of exposing the cells to Cd. Apparently, AP1 was not involved in this down-regulatory effect of PKC inhibitor on MT gene expression since the inducibility of MT promoter was blocked by H7 even in the absence of the AP1-binding sequence. For Cd-treated cells, Cd accumulation in the cell was similar with or without H7 treatment. However, H7 markedly reduced cellular Zn accumulation when the cells were treated with Zn. Cycloheximide treatment increased the level of MT mRNA. This elevation can also be blocked by treating the cell with PKC inhibitor. Results in this study suggest that PKC participates in the process of metal-induced MT gene expression.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1997

Cloning of porcine neuron growth inhibitory factor (metallothionein III) cDNA and expression of the gene in Saccharomyces cerevisiae.

Growth inhibitory factor (GIF), a member of the metallothionein (MT) family, is also known as MTIII. This protein distinguishes itself from other MT isoforms by exerting an inhibitory effect on cortical neuron growth instead of metal ion buffering. In this work, we cloned MTIII genes from a porcine brain cDNA library. Two species of clones were isolated that vary with respect to one nt in the coding sequence. This discrepancy results in the translation of two MTIII primary structures having a different amino acid at residue 46. Herein, both MTIII cDNAs were constructed into an expression vector and transformed into yeast cells, respectively. The yeast carrying either MTIII gene displayed a similar metal tolerance when cultured in a medium containing metal. The resistance to metal toxicity was attributed to the expression of MTIII gene which was confirmed by RNA and protein analyses. The characteristics of the protein stability, metal binding affinity and ultraviolet absorption spectrum of the yeast produced MTIII are also compared with those of MTII. The comparison reveals that both MTs have similar physical characteristics. Moreover, circular dichroism spectrum of Cd saturated MTIII was analyzed as well. Typical Cys-Cd bands for MTII appear in the spectrum, indicating similar metal-thiol interactions for MTIII to those for other MT isoforms.

Alzheimer Disease↗

PubMed1997

Applicability of perineal sonography in anatomical evaluation of bladder neck in women with and without genuine stress incontinence.

Thirty-seven patients with proven genuine stress incontinence (GSI) underwent ultrasound study to evaluate the bladder neck position relative to the symphysis pubis. Sixty-five continent women including 40 parous and 25 nulliparous women were recruited as a control group. Several parameters were found to be statistically different between incontinent and control groups (P < 0.01). If 28 degrees or 13 mm were used as the cut-off point for rotational angle (RA) and descent of bladder neck (DBN), the sensitivity, specificity, and positive and negative predictive values were 78.0%, 76.9%, 64.3%, and 33.3%, respectively. The specificity and positive predictive value for GSI increased to 83.1% and 67.6% if these two parameters were used together. Perineal sonography is valuable in assessing anatomic change of the bladder neck, but it is not a sensitive tool for predicting GSI.

Adult↗

PubMed1997

The results of laparoscopic adhesiolysis for intractable urinary frequency.

PURPOSE: We evaluated urinary frequency related to pelvic adhesions around the bladder serosa and the result of laparoscopic adhesiolysis on intractable urinary frequency caused by adhesions that did not respond to conservative treatment. MATERIALS AND METHODS: Laparoscopic adhesiolysis was performed for the diagnosis and treatment of 10 referred patients with a history of pelvic surgery in whom conservative treatment had failed. Urinary symptoms and signs, a urinary diary and cystometry were followed before and after surgery. RESULTS: In all cases there were various degrees of pelvic adhesion, mainly around the bladder. Frequency and urgency were improved in 9 of 10 patients. Urinary diary and cystometry parameters showed improvement at followup. CONCLUSIONS: Adhesions involving the bladder wall may restrict bladder distension in most of these patients. Laparoscopic adhesiolysis is beneficial in the diagnosis and treatment of this subgroup of patients.

Adult↗

PubMed1997

Consequences of analysing complex survey data using inappropriate analysis and software computing packages.

In the analysis of complex survey data such as stratified multi-stage cluster samples, ignoring the design effects such as clustering and stratification usually will lead to erroneous conclusions. In this paper, we will demonstrate the consequences in the estimation of means and proportions by two examples from a stratified two-stage cluster sample. A brief review of methodology will be presented, and some suggestions on computational issues will be provided.

Adult↗

PubMed1997

Oxidation of methamphetamine and methylenedioxymethamphetamine by CYP2D6.

Methamphetamine (MeAmp) abuse has recently experienced a resurgence and approaches to the treatment of its addiction similar to those used with cocaine have been considered. As the treatment regimes are likely to use drugs whose metabolism is related to that of MeAmp, studies were initiated to establish the enzymology of the fate of MeAmp. This report describes investigations of the role of CYP2D6, the human isoform of the enzyme that catalyzes debrisoquine hydroxylation, in the 4-hydroxylation and N-demethylation of MeAmp. The results of studies with human liver microsomes including those from a genetically poor metabolizer with respect to CYP2D6, showing correlation between MeAmp and metoprolol hydroxylation and MDMA demethylenation, were consistent with a major involvement of CYP2D6 in the aromatic 4-hydroxylation of MeAmp. This was confirmed by studies with recombinant CYP2D6 expressed in yeast, which was also shown to effect the N-demethylation of MeAmp. The rate of the 4-hydroxylation reaction was substantially slower than the demethylenation of MDMA. In contrast to MeAmp, MDMA was not N-demethylated by CYP2D6. Since CYP2D6 participates in the major steps of MeAmp metabolism, pharmacokinetic interactions are likely with other drug substrates proposed for the treatment of MeAmp addiction. Furthermore, the genetic polymorphism associated with the enzyme could manifest itself in abnormal responses to MeAmp.

Cytochrome P-450 CYP2D6↗

PubMed1996

Structure and expression of metallothionein gene in ducks.

Metallothionein (MT) cDNAs were cloned and sequenced from two genera of ducks, Muscovy (Cairina muschata) and Tsai ya (Anas platyrhynchos). The two cDNAs show an extremely high sequence homology and contain an open reading frame encoding 63 amino acids. MT mRNA expressions were studied after metal induction using the cloned cDNA as a probe. Cadmium and copper induced MT gene efficiently, whereas zinc showed a markedly less effect. In addition, the MT mRNA accumulations in various developmental stages were also investigated. The result reveals a different pattern of expression from that of mammals. The discrepancy in MT gene between Tsai ya and Muscovy was further explored by examining genomic DNA structures. The duck MT showed three exons and two introns. The most significant variation of the genes occurs at intron II in which Tsai ya MT has 24 bases more than Muscovy MT. Moreover, MT expressions in the hybrids of Muscovy and Tsai ya were investigated using a reverse transcriptase-polymerase chain reaction. Those results demonstrated that parental MT genes are expressed in the hybrids after metal induction.

Amino Acid Sequence↗

PubMed1996

Prenatal diagnosis in a Chinese family with type Ia glycogen storage disease by PCR-based genetic analysis.

Type Ia glycogen storage disease (GSD), an autosomal recessive metabolic disorder, is caused by a deficiency in glucose-6-phosphatase (G6Pase). We had previously identified the nature of the causative mutations in a Chinese family whose first two children were affected with type Ia GSD. Two different point mutations in the G6Pase gene, a guanine to adenine substitution at base position 327 in exon 2 and a thymine to adenine substitution at base position 1101 in exon 5, change the restriction sites for the enzymes Fok I and Hinc II. Family study revealed that both parents were heterozygous carriers: the father with a mutant G6Pase allele at exon 2 and the mother with another mutant G6Pase allele at exon 5. This paper deals with a prenatal diagnosis on the fetus of this family who is at risk of type Ia GSD. Genomic DNA was extracted from a chorionic villus biopsy sampled at the tenth week of gestation. Exons 2 and 5 of the G6Pase gene were amplified by the polymerase chain reaction (PCR) followed by restriction enzyme digestion and direct sequence analysis. DNA analysis indicated that the fetus was a heterozygous carrier of type Ia GSD with a mutant G6Pase allele at exon 2 and a normal G6Pase allele at exon 5. The diagnosis was further confirmed by the same method with cultured amniocytes and with a blood sample after the baby was born. This is the first report of prenatal carrier detection of type Ia GSD at the gene level.

Chorionic Villi Sampling↗

PubMed1996

Identification and characterization of metallothionein III (growth inhibitory factor) from porcine brain.

Porcine metallothionein III (MTIII) was isolated from brain tissue by the combination of gel filtration and anion-exchange chromatographies. The identity of MTIII was confirmed by comparing the chromatographic characteristics to other MT isoforms isolated from porcine liver. Porcine MTIII has a low molecular weight and a pl of 4.1. This protein contains both zinc and copper, and the zinc can be replaced by cadmium. Using reverse transcriptase-polymerase chain reaction, a 0.2 kb DNA fragment can be amplified from the porcine brain mRNA. This DNA fragment was demonstrated to contain MTIII coding region after cloning and sequencing. The revealed DNA sequence can be translated into 68 amino acids and shows a common structural characteristic of MTIII from other species. Northern blot analysis indicated that MTIII and mRNA is expressed in every specified region of the porcine brain examined here.

Amino Acid Sequence↗

PubMed1996

Sequences and comparisons of duck mitochondrial DNA control regions.

In this study, the nucleotide sequences of the displacement loop (D-loop) and the ribosomal RNA genes of mitochondrial DNA (mtDNA) were determined from a representative each of two genera of ducks, Cainina muschata and Anas platyrhynchos. The duck mtDNA shows a specific gene order at 5' upstream of D-loop (5'ND6-tRNA(Glu)-D-loop3') that is identical to chick mtDNA but is different from that of mammalian or amphibian (5' cytochrome b-tRNA(Thr)-tRNA(Pro)-D-loop3'). Nucleotide diversity is greatest in the D-loop while being most conserved in the 12S rRNA gene, as indicated from a sequence comparison between duck and chick mtDNA. A consensus sequence in the D-loop region, which may play influential roles in the regulation of transcription and replication of mtDNA, was found in both CSB-1 and repeated sequences of birds. Sequences of four tRNA genes in this region are also reported. Among them, tRNA(Glu) shows the greatest sequence divergence when different order of birds are compared.

Animals↗

PubMed1996

Genetic analysis of the glucose-6-phosphatase mutation of type 1a glycogen storage disease in a Chinese family.

Type 1a glycogen storage disease (GSD) is an autosomal recessive metabolic disorder caused by a deficiency in glucose-6-phosphatase (G6Pase). Polymerase chain reaction (PCR) and nucleotide sequence analysis were used to identify the location and nature of mutations at the G6Pase locus in two siblings affected with type 1a GSD. Both patients are compound heterozygotes with two different single nucleotide substitutions in the two G6Pase alleles. A guanine to adenine transition was identified at base position 327 in the exon 2, converting an arginine to a histidine at codon 83. The second substitution was a thymine to adenine transversion at base position 1101 in the exon 5, converting an isoleucine to an asparagine at codon 341. Family study reveals that both parents are heterozygous carriers: the father with a mutant G6Pase allele at exon 2, the mother with another mutant G6Pase allele at exon 5. This is the first family study in Taiwan on type 1a GSD identified by molecular analysis. The mutations identified herein are novel substitutions in the G6Pase gene. In addition, an adenine to guanine substitution was observed at base position 653 in the exon 5 of G6Pase gene in both sibling patients and their parents, as well as in 15 normal Chinese subjects and three normal Caucasian subjects.

Child, Preschool↗

PubMed1996

Selective mechanism-based inactivation of rat CYP2D by 4-allyloxymethamphetamine.

The high selectivity of amphetamine and its derivatives for CYP2D-mediated oxidations suggested the use of the phenylisopropylamine skeleton as a template for a selective inhibitor of this important enzyme. Accordingly, 4-allyloxymethamphetamine-amine (ALLMA) was synthesized and its ability to selectively inactivate CYP2D was investigated both in in vitro and in vivo experiments. Incubation studies with rat liver microsomes demonstrated that this compound suppressed the CYP2D-mediated methylenedioxymethamphetamine (MDMA) demethylation in time- and dose-dependent manner and that the inhibition required the presence of NADPH. The development of irreversible inhibition was associated with oxidation at position 4 of the aromatic ring, the common site of CYP2D-mediated oxidation of this group of compounds. In in vivo studies doses of ALLMA (1-10 mg/kg) were administered to adult male Sprague-Dawley rats and liver microsomes were obtained 3 hr later. Methamphetamine p-hydroxylation and low Km MDMA demethylation activities, both mediated by CYP2D, were reduced by more than 80% after a dose of 10 mg/kg. Cytochrome P-450 reactions attributed to P-450s other than CYP2D, such as aniline p-hydroxylation, the high Km system of MDMA demethylation and the N-demethylation of methamphetamine, benzphetamine, aminopyrine and erythromycin, all appeared to be minimally affected. The importance of aromatic ring oxidation in the metabolism is such that inhibition of CYP2D would be expected to cause a significant change in the pharmacokinetics of these compounds. The kinetics of MDMA metabolic activity in microsomes from ALLMA-pretreated rats were comparable to those from female Dark-Agouti rats, an animal model for CYP2D1 deficiency.

Animals↗

PubMed1995

Cloning and characterization of the 5'-flanking region of metallothionein-I gene from Chinese hamster ovary cells.

The 5'-flanking region of the Chinese hamster ovary metallothionein-I gene (MT-I) was isolated and sequenced. This region contains several cis-regulatory sequences, including metal-responsive element (MRE), AP1-binding site, Sp1-binding site and glucocorticoid-responsive element (GRE). These elements are located within 250 bases upstream of the transcription initiation site, as determined by primer extension. This region was fused with a reporter gene that could be activated by the challenge of cadmium only when the MREs were present. Thus, the isolated DNA is the promoter region of the CHO MT-I gene.

Animals↗

PubMed1995

Cytochrome P4502D isozymes catalyze the 4-hydroxylation of methamphetamine enantiomers.

The 4-hydroxylation of S(+)- and R(-)-methamphetamine by rat liver microsomes was examined in Sprague-Dawley and Dark Agouti strains to determine the role of cytochrome P4502D (CYP2D) subfamily isozymes in catalyzing the reaction. In the study, anti-P450-BTL IgG, bufuralol, and quinine, a substrate and inhibitors of CYP2D isozymes, respectively, were found to block approximately 90% of the reaction as catalyzed by microsomes from Sprague-Dawley rats. Reconstituted systems of CYP2D isozymes purified from rat liver microsomes also mediated the reaction. These observations and the minimal activity found in microsomes from Dark Agouti rats support the notion that methamphetamine, like other phenylisopropylamine compounds, is oxidized on the 4-position of the aromatic ring by CYP2D isozymes.

Animals↗

PubMed1995

Inactivation of constitutive hepatic cytochromes P450 by phencyclidine in the rat.

The purpose of this study was to determine whether phencyclidine (PCP) inhibits constitutive hepatic cytochrome P450 (CYP) isozymes when administered to naive adult male Sprague-Dawley rats. Animals were pretreated with PCP (25 mg/kg/day for 2 days), killed 3 and 16 hr after the last dose, and liver microsomes prepared. The washed microsomes were then assayed for benzphetamine, methamphetamine (MA), and methylenedioxymethamphetamine (MDMA) N-demethylation together with MDMA demethylenation and MA 4-hydroxylation activities. MDMA demethylenation (low substrate concentration), MA 4-hydroxylation, and metoprolol alpha-hydroxylation reactions, which are catalyzed by CYP2D isozymes, were reduced > 74% 3 hr after the last PCP dose and were only partially restored 13 hr later. Benzphetamine and (-)-MDMA N-demethylation activities were restored to control values 16 hr after the last dose. These results indicate that PCP suppresses constitutive isozymes, including CYP2C11 and members of the CYP2D subfamily. The suppression of cytochromes P450 activity by PCP in vivo is consistent with its in vitro actions found in this and other studies, and demonstrates that alteration of CYP activity is another pharmacological effect of this compound.

Amphetamines↗

PubMed1994

The demethylenation of methylenedioxymethamphetamine ("ecstasy") by debrisoquine hydroxylase (CYP2D6).

The metabolism of methylenedioxymethamphetamine (MDMA, "ecstasy") was examined in a microsomal preparation of the yeast Saccharomyces cerevisiae expressing human debrisoquine hydroxylase, CYP2D6. Only one product, dihydroxymethylamphetamine (DHMA), was detected in the incubation mixture, and this product accounted for all of the substrate consumption at low concentration (10 microM). Mean +/- SD values of apparent Km(microM) and Vmax (nmol/min per nmol P450) for the demethylenation of (+) and (-)-MDMA at low concentrations (1-100 microM) were 1.72, 0.12 and 6.45, 0.10 and 2.90, 0.10 and 7.61, 0.06, respectively. At high concentrations (> 1000 microM) substrate inhibition was noted, with Ki values of 14.2 and 28.2 mM, respectively, for the (+) and (-) enantiomers. Incubation of MDMA isomers with human liver microsomes indicated that their demethylenation is deficient in the poor metabolizer phenotype. Thus, MDMA is converted to the catecholamine DHMA by CYP2D6, and this may give rise to genetically-determined differences in toxicity.

3,4-Methylenedioxyamphetamine↗