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Y Ma

Publications and source records attributed to Y Ma.

At least 91 records · Page 5Linked to original sources
PubMed2001

Ontogeny of REM rebound in postnatal rats.

STUDY OBJECTIVES: The aim of this study was to determine developmental changes (ontogeny) of REM rebound in postnatal rats. DESIGN: Different groups of 2, 3, and 4-week-old experimental rats were instrumentally REM sleep deprived (RSD rats) for 33-48 hours and their sleep was monitored polysomnographically for 48 hours after the REM sleep deprivation (RSD). Age-matched control (RSC) rats also had polysomnographic recordings. SETTINGS: N/A. PARTICIPANTS: Subjects were 18 male Long-Evans RSD rats (5 age 2 weeks, 5 age 3 weeks, and 8 age 4 weeks); and 17 age-matched male Long Evans RSC rats (5 age 2 weeks, 5 age 3 weeks, and 7 age 4 weeks). INTERVENTIONS: Implants for the polysomnographic recordings of the RSD and RSC rats were made by the soft head plug method which permitted continuous, 24 hour/day records during the REM deprivation and post deprivation periods. RSD rats had instrumental RSD by the shaking platform method. RSC rats remained in stationary cages. MEASUREMENTS AND RESULTS: At age 2 weeks, compared with age-matched RSC rats, RSD rats had no REM rebound. At age 3 weeks, compared with age-matched RSC rats, RSD rats had a small but significant REM rebound limited to the first 6 hours after RSD. At age 4 weeks, compared with RSC rats, RSD rats had a larger REM rebound that extended for 18 hours after RSD. The size and duration of REM rebound at the different ages was significantly different. Total sleep lost during the RSD process at each age was made up. CONCLUSIONS: The findings possibly indicate that in rats a REM sleep homeostatic process develops between ages 2 and 4 weeks and that a total sleep homeostatic process is already developed by age 2 weeks.

Animals↗
PubMed2001

Separation and purification of isoflavones from a crude soybean extract by high-speed counter-current chromatography.

A set of isoflavones with a broad range of polarity including daidzin, glycitin, genistin, acetyldaidzin, glycitein, acetylgenistin and daidzein was separated from a crude soybean extract by high-speed counter-current chromatography using a two-step operation. Three solvent systems were used: chloroform-methanol-water (4:3:2, v/v); chloroform-methanol-n-butanol-water (4:3:0.5:2, v/v); and methyl tert.-butyl ether-tetrahydrofuran-0.5% aqueous trifluoroacetic acid (2:2:0.15:4, v/v). The first solvent system was used for separating less polar isoflavones and the second for more polar isoflavones by eluting the lower organic phase. Genistin and glycitin, which were only partially resolved in the chloroform system, were separated by the third solvent system. Each isolated component showed 98-99% purity as determined by high-performance liquid chromatography analysis. Their structures were identified by LC-MS.

Chromatography, High Pressure Liquid↗
PubMed2001

Definitive identification of mammalian 5-hydroxymethyluracil DNA N-glycosylase activity as SMUG1.

Purification from calf thymus of a DNA N-glycosylase activity (HMUDG) that released 5-hydroxymethyluracil (5hmUra) from the DNA of Bacillus subtilis phage SPO1 was undertaken. Analysis of the most purified fraction by SDS-polyacrylamide gel electrophoresis revealed a multiplicity of protein species making it impossible to identify HMUDG by inspection. Therefore, we renatured the enzyme after SDS-polyacrylamide gel electrophoresis and assayed slices of the gel for DNA N-glycosylase activity directed against 5hmUra. Maximum enzymatic activity was identified between molecular mass markers 30 and 34 kDa. Protein was extracted from gel slices and subjected to tryptic digestion and analysis by mass spectrometry. Analysis revealed the presence of 11 peptides that were homologous or identical to the sequence of the recently characterized human single-stranded monofunctional uracil DNA N-glycosylase (hSMUG1). The cDNA of hSMUG1 was isolated and expressed as a recombinant glutathione S-transferase fusion protein that was shown to release 5hmUra with 20x the specific activity of the most purified bovine fraction. We conclude that hSMUG1 and HMUDG are the same protein.

Amino Acid Sequence↗
PubMed2001

Synthesis of bicyclic pyrimidine derivatives as ATP analogues.

A highly efficient and general solid-phase synthesis of bicyclic pyrimidine derivatives that target purine dependent proteins is reported. The synthesis of the key intermediate, 4,6-disubstituted-5-amino-pyrimidine, involved reduction of the corresponding nitro derivatives using 1,1'-dioctyl-viologen in a triphasic milieu. The mild reduction conditions enable the use of any acid labile solid support as well as a wide range of combinatorial substituents, thus enabling the synthesis of large libraries of highly diverse bicyclic pyrimidines. Alternative reduction conditions with tin(II) chloride and structure-reactivity studies are discussed as well.

Adenosine Triphosphate↗
PubMed2001

Molecular mechanisms for aberrant expression of the human breast cancer specific gene 1 in breast cancer cells: control of transcription by DNA methylation and intronic sequences.

Breast cancer specific gene 1 (BCSG1), also referred as synuclein gamma, is the third member of a neuronal protein family synuclein. BCSG1 is not expressed in normal breast tissues but highly expressed in advanced infiltrating breast carcinomas. When over expressed, BCSG1 significantly stimulates breast cancer metastasis. To elucidate the molecular mechanisms underlying the abnormal transcription of BCSG1 in breast cancer cells, in this study, we isolated a 2195 base pair fragment of human BCSG1 gene. This fragment includes 1 kb 5'-flanking region, exon 1, and intron 1. By analysing the promoter activity and the methylation status of the exon 1 region, we show that (1) Intron 1 plays critical roles in the control of BCSG1 gene transcription through cis-regulatory sequences that affect BCSG1 transcription in cell type-specific and cell type-nonspecific manners. (2) The activator protein-1 (AP-1) is functionally involved in BCSG1 transcription in breast cancer cells through its binding to an AP-1 motif located in the intron 1. (3) The exon 1 region of BCSG1 gene contains a CpG island that is unmethylated in BCSG1-positive SKBR-3 and T47D cells but densely methylated in BCSG1-negative MCF-7 cells. (4) Treating MCF-7 cells with a demethylating agent 5-Aza-2'-deoxycytidine specifically activated BCSG1 transcription. Thus, our results suggest that while the cellular content of transcription activators and repressors that interact with the cis-regulatory sequences present in the intron 1 contribute prominently to the tissue-specific expression of BCSG1, demethylation of exon 1 is an important factor responsible for the aberrant expression of BCSG1 in breast carcinomas.

Amino Acid Motifs↗
PubMed2001

DNA length-dependent cooperative interactions in the binding of Ku to DNA.

Despite its central role in the nonhomologous DNA end joining process, we still have an incomplete picture of the interaction between Ku and DNA. Here we describe both kinetic (surface plasmon resonance or SPR) and equilibrium (electrophoretic mobility shift assay or EMSA) studies of Ku binding to linear double-stranded DNA. Ku interaction with 1-site DNA is noncooperative, as expected. Electrophoretic mobility shift assays indicate cooperativity in the binding of Ku molecules to DNA long enough for two Ku molecules to bind (2-site DNA). For the kinetic studies, we use surface plasmon resonance in which one end of the DNA molecules is linked to a surface while the other end is free to interact with Ku. We find that one Ku molecule dissociates from 1-site DNA with simple Langmuir (i.e., independent) kinetics. However, two Ku molecules associate and dissociate from 2-site DNA with a time course that cannot be described as a simple Langmuir interaction. On 3- and 4-site DNA, EMSA and SPR studies do not reveal any cooperativity, suggesting that the middle Ku does not exhibit cooperative interaction with the two Ku molecules bound at the DNA ends. These results indicate that Ku molecules can demonstrate cooperative interaction, and this is influenced by their positions along the DNA.

Antigens, Nuclear↗
PubMed2001

The critical window of brain development from susceptive to insusceptive. Effects of clomipramine neonatal treatment on sexual behavior.

The immature brain is much more sensitive to abnormal experience, particularly sleep deprivation, drug exposure, and maternal separation. The critical time period during which features in the brain's susceptibility to such experience change, however, has not yet been determined. In previous studies on rats, we found that neonatal treatment with clomipramine (CLI) during postnatal days 8--21 (P8-21) produced behavioral and physiological abnormalities in adult rats that resembled the abnormalities found in human endogenous depression. The objective of the present study is to determine (1) the critical (more specifically, the latest) time frame in which CLI treatment will produce adult depression and (2) the shortest treatment window during which CLI can induce adult depression. Male rats were neonatally treated with CLI (20 mg/kg, sc) twice daily or with an equivolume of saline. The treatment windows were P12--17, P14--20, P16--22, and P12--15. Six variables, including number of mounts, intromission, ejaculation, mount latency, ejaculation latency, and post-ejaculation interval, were measured visually between the ages of 4 and 5 months. Rats treated with CLI showed significant sexual impairment in treatment windows P12--17 and P14--20 and slight sexual deficiency in the short window P12--15. No significant sexual impairment was found in window P16--22. We concluded that P14--20 was the latest window during which CLI treatment produces adult sexual deficiency and that 6 days might be the shortest treatment window to produce significant behavior abnormalities.

Animals↗
PubMed2001

Mediator proteins orchestrate enzyme-ssDNA assembly during T4 recombination-dependent DNA replication and repair.

Studies of recombination-dependent replication (RDR) in the T4 system have revealed the critical roles played by mediator proteins in the timely and productive loading of specific enzymes onto single-stranded DNA (ssDNA) during phage RDR processes. The T4 recombination mediator protein, uvsY, is necessary for the proper assembly of the T4 presynaptic filament (uvsX recombinase cooperatively bound to ssDNA), leading to the recombination-primed initiation of leading strand DNA synthesis. In the lagging strand synthesis component of RDR, replication mediator protein gp59 is required for the assembly of gp41, the DNA helicase component of the T4 primosome, onto lagging strand ssDNA. Together, uvsY and gp59 mediate the productive coupling of homologous recombination events to the initiation of T4 RDR. UvsY promotes presynaptic filament formation on 3' ssDNA-tailed chromosomes, the physiological primers for T4 RDR, and recent results suggest that uvsY also may serve as a coupling factor between presynapsis and the nucleolytic resection of double-stranded DNA ends. Other results indicate that uvsY stabilizes uvsX bound to the invading strand, effectively preventing primosome assembly there. Instead, gp59 directs primosome assembly to the displaced strand of the D loop/replication fork. This partitioning mechanism enforced by the T4 recombination/replication mediator proteins guards against antirecombination activity of the helicase component and ensures that recombination intermediates formed by uvsX/uvsY will efficiently be converted into semiconservative DNA replication forks. Although the major mode of T4 RDR is semiconservative, we present biochemical evidence that a conservative "bubble migration" mode of RDR could play a role in lesion bypass by the T4 replication machinery.

Bacteriophage T4↗
PubMed2001

Liquid chromatography-tandem mass spectrometry identification of metabolites of two 5-HT1A antagonists, N-[2-[4-(2-methoxylphenyl)piperazino]ethyl]-N-(2-pyridyl) trans- and cis-4-fluorocyclohexanecarboxamide, produced by human and rat hepatocytes.

Two 5-HT1A antagonists, t-FCWAY and c-FCWAY, were developed as imaging agents for positron emission tomography (PET). In order to evaluate these compounds, hepatocytes from both human and rat were utilized to produce metabolites and LC-MS-MS was used to identify metabolites. These in vitro metabolism studies indicate that hydrolysis of the amide linkage is the major metabolism pathway for humans, whereas aromatic ring-oxidation is the major metabolism pathway for rat. The rat hepatocyte results correlate well with in vivo rat metabolism studies. Based on the structures of the metabolites, we have developed an extraction procedure to determine the concentration of the parent compound in plasma.

Animals↗
PubMed2001

Bocdene and mocdene derivatives of catechols and catecholamines.

[reaction in text] Catechols react chemoselectively, in the presence of either alcohols, 1,2-diols, or simple phenols, with tert-butyl propynoate and with methyl propynoate to give 2-Boc-ethylidene (Bocdene) and 2-Moc-ethylidene (Mocdene) acetals, respectively, in 96-100% yields within 30 min at room temperature, provided that 150 mol % of DMAP is added. Cleavage of these acetals with pyrrolidine readily takes place (at room temperature!) in 95-100% yields. By taking advantage of the features of Bocdene acetals, novel catecholamine-related phosphate mimetics have been prepared.

Acetals↗
PubMed2001

Effect of the interaction of parathyroid hormone and cyclosporine a on bone mineral metabolism in the rat.

Cyclosporine A (CsA) induces high turnover osteopenia in the rat and there is evidence for this in humans. Recent studies suggest that increases in parathyroid hormone (PTH) may be involved in posttransplantation bone loss. However, human studies are difficult to interpret since transplant patients usually receive a cocktail of immunosuppressants and have underlying disease. Our aim was to try to resolve the influence of the absence or presence of PTH on CsA-induced bone disease. Male Sprague Dawley rats aged 7-9 months, either sham operated or parathyroidectomized (PTX), were randomly divided into vehicle and CsA groups. All PTX rats were given oral calcium supplementation ad libitum. The rats were divided into groups: basal, sham/vehicle, sham/CsA, PTX/vehicle, and PTX/CsA. Serial biochemistry was performed 0, 14, and 28 days after the start of the experimental period; bone histomorphometry was performed 28 days after the start of the experimental period. Statistical analysis consisted of group comparisons and factorial analyses. The results showed that CsA alone produced a high turnover osteopenia consistent with previous studies. In the PTX animals there was an increase in bone mass. PTX also decreased osteoblast activity and recruitment, and serum 1,25OH2D levels. Serum levels of osteocalcin (BGP) were unaffected by PTX. The combination group (PTX/CsA) did not differ statistically from the controls in most of the histomorphometric parameters measured, with the exception of reduced mineral apposition and bone formation rates, reflecting the effects of PTX. Serum BGP and 1,25OH2D levels did not differ, but PTH was reduced from the control. Explanations for these results are (1) CsA and PTX exert their effects via separate mechanisms, negating each other; (2) in the absence of PTH, CsA managed to cause bone loss, and thus PTH may not be essential for CsA-induced bone loss; or (3) the profound accelerated bone loss produced by CsA in normal rats requires PTH. These findings may help explain the discrepancies found in clinical studies where bone loss occurs with either elevated or normal PTH levels.

Animals↗
PubMed2001

An association study of DRD5 with smoking initiation and progression to nicotine dependence.

A large body of genetic epidemiological data strongly implicate genetic factors in the etiology of smoking behavior. Polymorphisms of genes in the dopaminergic system are plausible functional candidate genes and a linkage and an association study suggested that the type 5 dopamine receptor gene (DRD5) may be etiologically involved. We investigated the association of four DRD5 polymorphisms with smoking initiation and progression to nicotine dependence in a population-based sample of over 900 subjects. For smoking initiation, there was no significant association with the four DRD5 markers we studied; however, maximum likelihood analyses suggested the presence of a haplotype protective against smoking initiation. For progression to nicotine dependence, there were no strongly significant associations with the four DRD5 markers or for the estimated haplotypes. These data are not consistent with a strong etiological role for DRD5 in the etiology of these complex smoking behaviors.

Adolescent↗
PubMed2001

Analysis of epistasis in linked regions in the Irish study of high-density schizophrenia families.

Epistasis may be important in the etiology of schizophrenia. Analysis of epistasis has been important in the positional cloning of a gene involved in the etiology of type II diabetes mellitus. We investigated the importance of epistasis among six linked regions in 268 multiplex pedigrees in the Irish Study of High-Density Schizophrenia Families (ISHDSF) by computing pairwise correlations between nonparametric linkage scores for narrow, intermediate, and broad diagnostic definitions. The linked regions were on chromosomes 2, 4, 5, 6, 8, and 10. No correlation reached our a priori level of statistical significance. Using this statistical approach, we did not find evidence of important epistatic effects among these six regions in the ISHDSF.

Chromosomes, Human↗
PubMed2001

Cervical ectopy in adolescent girls with and without human immunodeficiency virus infection.

The objective of this study was to examine factors, including human immunodeficiency virus (HIV) infection, associated with ectopy among adolescent girls aged 12-20 years who were participating in an ongoing study of HIV infection in adolescents. Samples for detection of bacterial vaginosis, Chlamydia trachomatis, and Neisseria gonorrhoeae and a high-resolution photograph of the cervix for ectopy measurement were collected. Ectopy data for 189 and 92 HIV-positive and -negative adolescents, respectively, were examined. Although univariate analysis found HIV infection and oral contraceptive use to be associated with the amount of ectopy, multivariate logistic regression analysis showed that only number of lifetime sex partners was a significant predictor, with more partners associated with less ectopy (odds ratio, 0.47; 95% confidence interval, 0.22-1.00; P=.05). In summary, adolescent girls with greater numbers of lifetime sex partners were more likely to have mature cervixes (less ectopy). HIV infection was not independently associated with ectopy.

Adolescent↗
PubMed2001

Effect of low dose irradiation on estrogen receptor level in MCF-7 breast cancer cells.

Exposure of MCF-7 cells to single and/or repeated low gamma-ray doses (0.5 to 8 Gy) resulted in a decrease in the capacity of these cells to concentrate tritiated estradiol ([3H]E2) (reduction of the number of binding sites). The decrease in the [3H]E2-binding capacity was higher than the survival rate, indicating that it could not be ascribed to cell death. Moreover, such low irradiation doses failed to similarly affect the specific incorporation of [3H]ORG 2058, even when the progesterone receptor was induced by E2, a finding that rejects the hypothesis of a nonspecific effect on all steroid hormone receptors. This loss of [3H]E2 binding was reflected by the elimination of the estrogen receptor alpha (ER) when the latter was assessed by immunocytochemistry. However, additional immunochemical studies (Western blot data) performed on cell extracts under denaturing conditions failed to show any similar elimination of the ER peptide, suggesting that the loss of E2-binding capacity would be relevant to subtle changes in the ER structure and/or ER-associated proteins. The loss of binding capacity, produced by a 3-Gy irradiation, failed to decrease the sensitivity of the cells to E2, since progesterone receptor induction and growth stimulation were maintained. Insufficient ER diminution may explain this observation.

Binding Sites↗
PubMed2001

Single-molecule immunoassay and DNA diagnosis.

Many assays relevant to disease diagnosis are based on electrophoresis, where the migration velocity is used for distinguishing molecules of different size or charge. However, standard gel electrophoresis is not only slow but also insensitive. We describe a single-molecule imaging procedure to measure the electrophoretic mobilities of up to 100000 distinct molecules every second. The results correlate well with capillary electrophoresis (CE) experiments and afford confident discrimination between normal (16.5 kbp) and abnormal (6.1 kbp) mitochondrial DNA fragments, or beta-phycoerythrin-labeled digoxigenin (BP-D) and its immunocomplex (anti-D-BP-D). This demonstrates that virtually all electrophoresis diagnostic protocols from slab gels to CE should be adaptable to single-molecule detection. This opens up the prossibility of screening single copies of DNA or proteins within single biological cells for disease markers without performing polymerase chain reaction (PCR) or other biological amplification.

Antigen-Antibody Complex↗
PubMed2001

Blinded positron emission tomography study of dopamine cell implantation for Parkinson's disease.

We assessed nigrostriatal dopaminergic function in Parkinson's disease (PD) patients undergoing a double-blind, placebo-controlled surgical trial of embryonic dopamine cell implantation. Forty PD patients underwent positron emission tomography (PET) imaging with [18F]fluorodopa (FDOPA) prior to randomization to transplantation or placebo surgery. The 39 surviving patients were rescanned one year following surgery. Images were quantified by investigators blinded to treatment status and clinical outcome. Following unblinding, we determined the effects of treatment status and age on the interval changes in FDOPA/PET signal. Blinded observers detected a significant increase in FDOPA uptake in the putamen of the group receiving implants compared to the placebo surgery patients (40.3%). Increases in putamen FDOPA uptake were similar in both younger (age < or = 60 years) and older (age > 60 years) transplant recipients. Significant decrements in putamen uptake were evident in younger placebo-operated patients (-6.5%) but not in their older counterparts. Correlations between the PET changes and clinical outcome were significant only in the younger patient subgroup (r = 0.58). The findings suggest that patient age does not influence graft viability or development in the first postoperative year. However, host age may influence the time course of the downstream functional changes that are needed for clinical benefit to occur.

Adult↗