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Y Liu

Publications and source records attributed to Y Liu.

At least 955 records · Page 53Linked to original sources
PubMed2000

Cloning, characterization, and expression analysis of mouse enamelysin.

Enamelysin is a recently isolated member of the matrix metalloproteinase (MMP) family of extracellular matrix (ECM)-degrading enzymes. Here we describe the isolation and characterization of the mouse enamelysin cDNA. Expression of mouse enamelysin was detectable only in ameloblasts and odontoblasts of developing teeth. Characterization of mouse enamelysin demonstrated that it is highly conserved in both its sequence content and pattern of expression relative to the porcine, human, and bovine homologues previously described.

Amino Acid Sequence↗
PubMed2000

Distribution of H type 1-4 chains of the ABO(H) system in different cell types of human respiratory epithelium.

We used three anti-H monoclonal antibodies (MAbs) specific for H Type 1, H Type 2, and H Type 3/4 antigens to investigate the distribution of H Type 1-H Type 4 chains of the ABO(H) histo-blood group in the human respiratory system. Strong staining of H Type 1 chain and weak staining of H Type 2 chain were observed in mucous cells of submucosal glands of bronchial epithelium, which were dependent on the secretor status. No H Type 3/4 chains were detected in mucous cells. Serous cells of submucosal glands of respiratory system showed no staining by three anti-H antibodies. H Type 1 and H Type 3/4 antigens were detected heterogeneously in apical surfaces of bronchial epithelium from secretors but not from nonsecretors. In contrast, basal cells of bronchial epithelium expressed H Type 2 irrespective of the secretor status, probably regulated by the H gene. Some alveolar Type II cells contained only H Types 3/4, which were dependent on the secretor status, whereas alveolar Type I cells had no H antigens. Our results indicated that different cell types in respiratory epithelium expressed different types of carbohydrate chains of histo-blood group antigens under the control of the H or the Se gene.

ABO Blood-Group System↗
PubMed2000

Long-term consequences of early linear growth retardation (stunting) in Swedish children.

Linear growth retardation (stunting) is prevalent (10-80%) in developing countries. It takes place between 6 and 18 mo of age and can be characterized by the delayed onset of the childhood phase of growth. The objective of this work was to study the existence of stunting in early life and, when present, its lifelong effects on final height in a normal healthy population in a developed country. A total of 2432 children with longitudinal height data from birth to adulthood were analyzed. The series represents a normal healthy population-based sample of full-term children born around 1974 in Göteborg, Sweden. We found the incidence of stunting to be about 10% as indicated by delayed onset of the childhood phase of growth (>12 mo of age): 14% in boys and 8% in girls. In a multiple linear regression model, final height was described by length at 6 mo of age, age at onset of the childhood phase of growth, and age at peak height velocity during puberty. All three measures contributed significantly (p < 0.05) to final height with a total R2 of 0.33. A final height difference of 5.0 cm could be explained by abnormal onset of the childhood phase of growth in this normal population. The timing of the childhood onset of growth did not correlate with the timing of puberty. For the first time, we can conclude that stunting in early life is not only a problem in developing countries. Its importance on final height achieved is clearly shown, even after controlling for the timing of puberty.

Body Height↗
PubMed2000

TRH-R2 exhibits similar binding and acute signaling but distinct regulation and anatomic distribution compared with TRH-R1.

TRH (thyroliberin) is a tripeptide (pGlu-His-ProNH2) that signals via G protein-coupled receptors. Until recently, only a single receptor for TRH was known (TRH-R1), but two groups identified a second receptor, TRH-R2. We independently discovered TRH-R2. Using an extensive set of TRH analogs, we found no differences in TRH-R1 and TRH-R2 binding or in acute stimulation of signaling. TRH-R2 was more rapidly internalized upon binding TRH and exhibited a greater level of TRH-induced down-regulation than TRH-R1. During prolonged exposure to TRH, cells expressing TRH-R2 exhibited a lower level of gene induction than cells expressing TRH-R1. TRH-R2 receptor mRNA was present in very discrete nuclei and regions of rat brain. A major mRNA transcript for TRH-R2 was seen in the cerebral cortex, pons, thalamus, hypothalamus, and midbrain with faint bands found in the striatum and pituitary. The extensive distribution of TRH-R2 in the brain suggests that it mediates many of the known functions of TRH that are not transduced by TRH-R1. The variations in agonist-induced internalization and down-regulation/desensitization, and anatomic distribution of TRH-R2 compared with TRH-R1, suggest important functional differences between the two receptors.

Amino Acid Sequence↗
PubMed2000

Human junction adhesion molecule regulates tight junction resealing in epithelia.

Epithelial cells form a highly selective barrier and line many organs. The epithelial barrier is maintained by closely apposed cell-cell contacts containing tight junctions, the regulation of which is incompletely understood. Here we report the cloning, tissue localization and evidence for a role in epithelial barrier regulation of an immunoglobulin superfamily member that likely represents the human homolog of murine junction adhesion molecule (JAM). Analysis of the primary structure of human JAM, cloned from T84 epithelial cells, predicts a transmembrane protein with an extracellular domain that contains two IgV loops. Monoclonal antibodies generated against the putative extracellular domain were reactive with a 35-39 kDa protein from both T84 epithelial cells and human neutrophils. By immunofluorescence, JAM mAbs labeled epithelial cells from intestine, lung, and kidney, prominently in the region of tight junctions (co-localization with occludin) and also along lateral cell membranes below the tight junctions. Flow cytometric studies confirmed predominant JAM expression in epithelial cells but also revealed expression on endothelial and hematopoietic cells of all lineages. Functional studies demonstrated that JAM specific mAbs markedly inhibited transepithelial resistance recovery of T84 monolayers after disruption of intercellular junctions (including tight junctions) by transient calcium depletion. Morphologic analysis revealed that, after disassembly of cell-cell junctions, anti-JAM inhibition of barrier function recovery correlated with a loss of both occludin and JAM, but not ZO-1, in reassembling tight junction structure. Reassembly of the major adherens junction component E-cadherin was not affected by JAM specific mAbs. Our findings suggest that JAM plays an important role in the regulation of tight junction assembly in epithelia. Furthermore, these JAM-mediated effects may occur by either direct, or indirect interactions with occludin.

Amino Acid Sequence↗
PubMed2000

Role of the ribosome in sequence-specific regulation of membrane targeting and translocation of P-glycoprotein signal-anchor transmembrane segments.

It is thought that the topology of a polytopic protein is generated by sequential translocation and membrane integration of independent signal-anchor and stop-transfer sequences. Two well-characterized cell-free systems (rabbit reticulocyte lysate and wheat germ extract) have been widely used to study the biogenesis of secretory and membrane proteins, but different results have been observed with proteins expressed in these two different systems. For example, different topologies of P-glycoprotein (Pgp) were observed in the two systems and the cause was thought to be the source of ribosomes. To understand how the ribosome is involved in dictating membrane translocation and orientation of polytopic proteins, individual signal-anchor sequences of Pgp were dissected and examined for their membrane targeting and translocation in a combined system of wheat germ ribosomes (WGR) and rabbit reticulocyte lysate (RRL). Addition of wheat germ ribosomes to the rabbit reticulocyte lysate translation system can enhance, reduce, or have no effect on the membrane targeting and translocation of individual Pgp signal-anchor sequences, and these effects appear to be determined by the amino acid residues flanking each signal-anchor. Ribosomes regulate the membrane targeting and translocation of Pgp signal-anchors in a polytopic form differently from the same signal-anchors in isolation. Furthermore, we demonstrated that ribosomes regulate the membrane targeting and translocation of each signal-anchor cotranslationally and that this activity of ribosomes is associated with the 60S subunit. Based on this and previous studies, we propose a mechanism by which ribosomes dynamically dictate the membrane targeting and translocation of nascent polytopic membrane proteins.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Cancer mortality in the high background radiation areas of Yangjiang, China during the period between 1979 and 1995.

The objective of the present study was to estimate cancer risk associated with the low-level radiation exposure of an average annual effective dose of 6.4 mSv (including internal exposure) in the high background-radiation areas (HBRA) in Yangjiang, China. The mortality survey consisted of two steps, i.e., the follow-up of cohort members and the ascertainment of causes of death. The cohort members in HBRA were divided into three dose-groups on the basis of environmental dose-rates per year. The mortality experiences of those three dose groups were compared with those in the residents of control areas by means of relative risk (RR). During the period 1987-1995, we observed 926,226 person-years by following up 106,517 subjects in the cohort study, and accumulated 5,161 deaths, among which 557 were from cancers. We did not observe an increase in cancer mortality in HBRA (RR = 0.96, 96% CI, 0.80 to 1.15). The combined data for the period 1979-95 included 125,079 subjects and accumulated 1,698,316 person-years, observed 10,415 total deaths and 1,003 cancer deaths. The relative risk of all cancers for whole HBRA as compared with the control area was estimated to be 0.99 (95% CI, 0.87 to 1.14). The relative risks of cancers of the stomach, colon, liver, lung, bone, female breast and thyroid within whole HBRA were less than one, while the risks for leukemia, cancers of the nasopharynx, esophagus, rectum, pancreas, skin, cervix uteri, brain and central nervous system, and malignant lymphoma were larger than one. None of them were significantly different from RR = 1. Neither homogeneity tests nor trend tests revealed any statistically significant relationship between cancer risk and radiation dose. We did not find any increased cancer risk associated with the high levels of natural radiation in HBRA. On the contrary, the mortality of all cancers in HBRA was generally lower than that in the control area, but not statistically significant.

Adolescent↗
PubMed2000

Effect of C:N molar ratio on monomer composition of polyhydroxyalkanoates produced by Pseudomonas mendocina 0806 and Pseudomonas pseudoalkaligenus YS1.

Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by bacteria. In this study, the effect of C:N molar ratio on the monomer composition of PHAs was investigated, including medium chain length PHA produced by Pseudomonas mendocina 0806 and PHA blends consisting of monomers of 3-hydroxybutyrate and medium chain length hydroxyalkanoate produced by Pseudomonas pseudoalkaligenus YS1. It was observed that there were some fixed ranges of C:N molar ratio that affect the monomer composition of PHA independently of the substrate. For strain 0806, the ranges were C:N < 20, 20 < C:N < 200, and C:N > 200. The monomer composition was constant among these ranges when using glucose and octanoate as the sole substrate. For strain YS1, the ranges were C:N < 20, 20 < C:N < 45, and C:N > 45. These results are useful for controlling monomer composition in PHA production.

3-Hydroxybutyric Acid↗
PubMed2000

Microcalorimetric study of Escherichia coli growth inhibited by the selenomorpholine complexes.

The inhibitory or antibiotic action of four kinds of the selenomorpholine complex on a strain of Escherichia coli was studied by microcalorimetry. Differences in their capacities to inhibit the metabolism of this bacterium were observed. The extent and duration of the inhibitory effect on the metabolism as judged from the rate constant, k, and the half-inhibitory concentration, IC50, varied with the different drugs. The rate constant (k) of Escherichia coli (in the log phase) in the presence of the drugs decreased with increasing concentrations of the drugs (C). The relationship of k and C is nearly linear for (1) selenomorpholine and (2) selenomorpholine hydrochloride, but for (3) N,N'-methylene bisselenomorpholine and (4) N-dodecyl selenomorpholine, it is not linear. The experimental results reveal that the sequence of antibiotic activity of selenomorpholines is (3) and (4) > (1) > (2).

Calorimetry↗
PubMed2000

Microcalorimetric study of the toxic effect of sodium selenite on the mitochondria metabolism of Carassius auratus liver.

The fundamental thermogenesis curves of the metabolic process of liver mitochondria from Carassius auratus and the toxic effect of Na2SeO3 on it were studied by using an LKB-2277 bioactivity monitor, ampoule method, at 28 degrees C. From the thermogenesis curves, the thermokinetic equations were established under different conditions. The kinetics show that a low concentration of Na2SeO3 (1-4 mg/L) had promoting action on the metabolism process of Carassius aurantus liver mitochondria, but that a high concentration of Na2SeO3 (8-16 mg/L) inhibited the mitochondria metabolism.

Animals↗
PubMed2000

P-glycoprotein and bioavailability-implication of polymorphism.

P-Glycoprotein (P-gp) may have a significant impact on systemic and tissue/cellular bioavailability of drugs because it functions as an "anti-absorption" mechanism that effluxes drug molecules out of the lipid bilayer and cytoplasm. The ability to reduce bioavailability at the tissue/cellular level was first discovered during the investigation of the causes of multidrug resistance (MDR) in cancer chemotherapy. Initially, it was thought that MDR is only caused by P-gp. Recently, many other transporters such as multidrug resistance-related protein (MRP) have also been identified. The ability of P-gp to impact systemic drug bioavailability was only recently recognized. Dr. Alfred Schinkel's group was first to show a significant improvement in the systemic bioavailability of several drugs in the MDR1 knockout mice. The same group also discovered that the blood-brain barrier (BBB) has a very high expression level of P-gp, and that this protein is necessary to restrict the entrance of various drug molecules into the central nervous system (CNS). Polymorphism in the normal human cells has not been reported, but it has been discovered in human cancer cells. Functional implication of P-gp polymorphism in changing the tissue bioavailability has been studied in rodents. These studies strongly support the role of P-gp in restricting tissue bioavailability of anticancer drugs. These studies also support the effectiveness of P-gp in limiting CNS toxicity of the cytotoxic drugs. The functional implication of P-gp on systemic bioavailability is much less well defined in humans, although it appears to be quite obvious in MDR1 knockout mice. Pharmacokinetic models clearly suggest that a change in the absorption rate will have a significant impact on systemic blood level of a drug. However, whether functionally significant polymorphisms of P-gp exist in humans has not been determined. If they do exist, they will surely impact on both systemic bioavailability and drug interaction potentials of many drugs. In the drug development process, several models may be used to select a lead compound that may or may not interact with P-gp, depending on whether the interaction is desirable. Several inhibitors of P-gp are currently on the clinical trial stage. Natural inhibitors of P-gp have also been discovered. There is no doubt that these new developments will have significant impact on the bioavailability of a variety of anticancer and CNS drugs in the next decades.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Descriptive epidemiology of nonsyndromic cleft lip with or without cleft palate in Shanghai, China, from 1980 to 1989.

OBJECTIVE: The purpose of this study was to characterize nonsyndromic cleft lip with or without cleft palate (CL+/- CP) in an Asian population. DESIGN: Birth prevalence was assessed in a large birth series in Shanghai, China. A 1:3 sex-age-hospital matched case-control design was used to assess the effects of parental ages and pregnancy history on risk of CL+/- CP. PARTICIPANTS: Records of live births from 1980 to 1989 in 22 hospitals in Shanghai, China, were reviewed, comprising 541,504 consecutive births, which is by far the largest such Chinese sample ever investigated. The case-control study included 528 (308 male, 220 female) nonsyndromic CL+/- CP cases and 1,563 (912 male, 651 female) controls. RESULTS: From 1980 to 1989, the overall birth prevalence was 1.2 per 1,000 live births with statistically significant seasonal variation (more CL+/- CP births in January to July). The overall male:female ratio was 1.40:1. For males, statistically significant associations were identified with maternal age for the most severe clefts (bilateral overall, and also bilateral CL+CP subgroup). For females, statistically significant association was shown for pregnancy age with birth order (overall and in most subgroups). CONCLUSIONS: The birth prevalence of CL+/- CP in this Asian population was similar to published Caucasian rates. The observed seasonal variation would be consistent with possible environmental factors. Significant associations with maternal age, pregnancy age, and birth order warrant additional study of pregnancy history in Asian CL+/- CP.

Birth Order↗
PubMed2000

Porcine fetal enamel matrix derivative stimulates proliferation but not differentiation of pre-osteoblastic 2T9 cells, inhibits proliferation and stimulates differentiation of osteoblast-like MG63 cells, and increases proliferation and differentiation of normal human osteoblast NHOst cells.

BACKGROUND: Embryonic enamel matrix proteins are hypothesized to be involved in the formation of acellular cementum during tooth development, suggesting that these proteins can be used to regenerate periodontal tissues. Enamel matrix protein derived from embryonic porcine tooth germs is used clinically, but the mechanisms by which it promotes the formation of cementum, periodontal ligament, and bone are not well understood. METHODS: This study examined the response of osteoblasts at 3 stages of osteogenic maturation to porcine fetal enamel matrix derivative (EMD). Proliferation (cell number and [3H]-thymidine incorporation), differentiation (alkaline phosphatase and osteocalcin), matrix synthesis ([35S]-sulfate incorporation; percentage of collagen production), and local factor production (prostaglandin E2 [PGE2] and transforming growth factor-beta 1 [TGF-beta1]) were measured in cultures of 2T9 cells (pre-osteoblasts which exhibit osteogenesis in response to bone morphogenetic protein-2 [BMP-2]), MG63 human osteoblast-like osteosarcoma cells, and normal human osteoblasts (NHOst cells). RESULTS: EMD regulated osteoblast proliferation and differentiation, but the effects were cell-specific. In 2T9 cell cultures, EMD increased proliferation but had no effect on alkaline phosphatase-specific activity. EMD decreased proliferation of MG63 cells and increased cellular alkaline phosphatase and osteocalcin production. There was no effect on collagen synthesis, proteoglycan sulfation, or PGE2 production; however, TGF-beta1 content of the conditioned media was increased. There was a 60-fold increase in cell number in third passage NHOst cells cultured for 35 days in the presence of EMD. EMD also caused a biphasic increase in alkaline phosphatase that was maximal at day 14. CONCLUSIONS: EMD affects early states of osteoblastic maturation by stimulating proliferation, but as cells mature in the lineage, EMD enhances differentiation.

Alkaline Phosphatase↗
PubMed2000

Time-of-day effects of ethanol consumption on EEG topography and cognitive event-related potential in adult males.

Time-of-day effects of ethanol consumption on EEG topography and cognitive event-related potential in adult males were studied. Ethanol (0.5 g/kg) or control drink was orally administered to nine healthy males at 10:00 and 18:00. The alpha 2 amplitude was significantly lower than that of the control at 0.5, 2.5 and 4.5 hours after ethanol consumption in the morning. These effects were observed in the left hemisphere and were only found after consumption in the morning. The subjectively rated attention was significantly lower than that of the control at 0.5 and 2.5 hours after ethanol consumption in the morning and at 0.5 hours after ethanol consumption in the evening. In contrast, the search speed of serial search task and P300 amplitude was significantly lower than that of the control at 2.5 hours after ethanol consumption in the evening. These results demonstrate that effects of ethanol are dependent on time-of-day of consumption. Ethanol consumption significantly lowered the alpha 2 amplitude when consumed in the morning, and lowered P300 amplitude when consumed in the evening.

Adult↗
PubMed2000

[Loss of imprinting of insulin-like growth factor II gene in acute myeloid leukemia].

OBJECTIVE: To investigate the status of insulin- like growth factor-2(IGF-2) gene imprinting in acute myeloid leukemia(AML). METHODS: Selection of heterozygous cases for Apa I polymorphism within exon 9 of IGF-2 gene and further analysis of loss of imprinting(LOI) were done in 26 AML patients by polymerase chain reaction(PCR), reverse transcription PCR (RT-PCR) and restriction fragment length polymorphism(RFLP) technique. RESULTS: Eleven cases of AML patients were identified as heterozygous for IGF-2(11/26); 8 heterozygous patients showed biallelic expression of IGF-2, indicating loss of IGF-2 imprinting. CONCLUSION: The frequent LOI of IGF-2 may play a role in the development of acute myeloid leukemia.

Adolescent↗
PubMed2000

Overexpression of MMP-1 and MMP-3 by cultured conjunctivochalasis fibroblasts.

PURPOSE: To determine whether conjunctivochalasis, denoting redundant, loose, nonedematous inferior bulbar conjunctiva, is associated with increased expression and activity of matrix metalloproteinases (MMPS) over their tissue inhibitors (TIMPs). METHODS: Expression of transcripts and proteins of MMPs, TIMPs, and urokinase plasminogen activator (uPA) by cultured normal human conjunctival and conjunctivochalasis fibroblasts was determined by Northern hybridization, enzyme-linked immunosorbent assay (ELISA), and Western blot analysis, respectively. Gelatin and casein zymography and quantitative collagenase activity assay were performed in the serum-free conditioned media. RESULTS: Compared with normal conjunctival fibroblasts from six subjects, conjunctivochalasis fibroblasts from eight patients showed markedly increased transcript expression of MMP-1 (5- to 32-fold) and MMP-3 (4 to 30-fold), whereas that of MMP-2, TIMP-1, TIMP-2, and uPA was similar between the two groups. Protein levels were increased in the serum-free conditioned media of conjunctivochalasis fibroblasts for MMP-1 (3.5- to 7.6-fold) and MMP-3 (2.3- to 13-fold), determined by ELISA and Western blot analysis. There was increased caseinolytic activity of MMP-3 and collagenolytic activity of MMP-1 (2.2-fold) by conjunctivochalasis fibroblasts, whereas no difference was noted between these two types of fibroblasts in the protein and gelatinolytic activity of MMP-2 or expression of TIMP-1 and TIMP-2 proteins, although that of TIMP-1 transcript was slightly higher in some conjunctivochalasis fibroblasts. No expression of MMP-9 was detected. CONCLUSIONS: Overexpression of MMP-1 and MMP-3 mRNA by conjunctivochalasis fibroblasts is correlated with their increased protein levels and proteolytic activities. Collectively, these data help explain how conjunctivochalasis manifests excessive degradation of the conjunctival matrix and Tenon's capsule.

Blotting, Northern↗