Biomedical subjects

J Feng

Publications and source records attributed to J Feng.

At least 163 records · Page 9Linked to original sources

PubMed1998

Cadherin-6 mediates the heterotypic interactions between the hemopoietic osteoclast cell lineage and stromal cells in a murine model of osteoclast differentiation.

Osteoclasts are multinucleated cells of hemopoietic origin that are responsible for bone resorption during physiological bone remodeling and in a variety of bone diseases. Osteoclast development requires direct heterotypic cell-cell interactions of the hemopoietic osteoclast precursors with the neighboring osteoblast/stromal cells. However, the molecular mechanisms underlying these heterotypic interactions are poorly understood. We isolated cadherin-6 isoform, denoted cadherin-6/2 from a cDNA library of human osteoclast-like cells. The isolated cadherin-6/2 is 3,423 bp in size consisting of an open reading frame of 2,115 bp, which encodes 705 amino acids. This isoform lacks 85 amino acids between positions 333 and 418 and contains 9 different amino acids in the extracellular domain compared with the previously described cadherin-6. The human osteoclast-like cells also expressed another isoform denoted cadherin-6/1 together with the cadherin-6. Introduction of cadherin-6/2 into L-cells that showed no cell-cell contact caused evident morphological changes accompanied with tight cell-cell association, indicating the cadherin-6/2 we isolated here is functional. Moreover, expression of dominant-negative or antisense cadherin-6/2 construct in bone marrow-derived mouse stromal ST2 cells, which express only cadherin-6/2, markedly impaired their ability to support osteoclast formation in a mouse coculture model of osteoclastogenesis. Our results suggest that cadherin-6 may be a contributory molecule to the heterotypic interactions between the hemopoietic osteoclast cell lineage and osteoblast/bone marrow stromal cells required for the osteoclast differentiation. Since both osteoclasts and osteoblasts/bone marrow stromal cells are the primary cells controlling physiological bone remodeling, expression of cadherin-6 isoforms in these two cell types of different origin suggests a critical role of these molecules in the relationship of osteoclast precursors and cells of osteoblastic lineage within the bone microenvironment.

Amino Acid Sequence↗

PubMed1998

Studies on diffusion maximum in x-ray diffraction patterns of plasma-sprayed hydroxyapatite coatings.

Study of an amorphous phase in plasma-sprayed hydroxyapatite (HA) coatings is important owing to its unique characteristics and nonnegligible amount of the amorphous phase compared to crystalline HA. However, little is known about the component parts of an amorphous phase. It is known that amorphous phase usually appears as the diffusion maximum (Dmax) in X-ray diffraction (XRD) patterns. Analyzing Dmax, including the position (Pmax) and area of Dmax, we can indicate the component parts of an amorphous phase and their transitions. In this study, the variation of Dmax in XRD patterns of the coatings during plasma spraying, in postheating, and in dissolving in vitro was studied with the aid of XRD. It was found that component parts of the amorphous phase in the coating varied with increasing thickness, consisting of two part represented by Dmax1, located between 29.4 and 29.8 degrees (2 theta), and Dmax2, located between 31.0 and 31.4 degrees (2 theta). It was concluded that Dmax3, located between 32.0 and 32.4 degrees (2 theta), should be referred to as nanocrystals of HA. In addition, the particle size of the starting powder may affect the component parts of the amorphous phase in the coating in addition to thickness. With vacuum heating (650 degrees C) and water vapor treatment at a low temperature (125 degrees C) in a saturated vaporic atmosphere, transition of the amorphous components was not as efficient as that at 490 degrees C with water vapor. The reason might be that the amorphous-to-crystalline HA conversion is dependent on both temperature and water vapor pressure. It was found that amorphous components were transformed completely into crystalline HA after heating at 490 degrees C with a partial water vapor pressure of 0.01 MPa for 2 h. It was concluded that the unstable amorphous components (Dmax1, Dmax2) converted into more stable nanocrystals of HA (Dmax3). Degradation in vitro showed that Dmax3 was more stable than Dmax1 and Dmax2. It was concluded that nucleation of apatite in vitro should be attributed to nanocrystals of HA (Dmax3) except for the amorphous components. It is recommended that the optimal phasic contents of the plasma-sprayed HA coating be mainly composed of crystalline HA and nanocrystals of HA (Dmax3) in terms of the stability and biocompatibility of the coating.

Air↗

PubMed1998

IGF I induction of p53 requires activation of MAP kinase in cardiac muscle cells.

The aim of this study was to investigate whether IGF I induction of p53 expression and p21 promoter require activation of MAP kinase in cardiac muscle cells. Compared to cardiomyocytes transfected with control vector, activation of MAP kinase by IGF I was decreased by approximately 60-70% in the cells transfected with dominant negative MAP kinase Y185. Transfection with Y185 also resulted in decreased induction of p53 mRNA by IGF I (70% reduction). In the cells transfected with a wildtype p21WAF1/CIP1 promoter construct, activation of luciferase reporter gene by IGF I was decreased in the cells co-transfected with Y185. To further confirm these findings, cells were preincubated with PD98059, a specific MAP kinase kinase inhibitor. As expected, PD98059 inhibited induction of p53 mRNA and p21WAF1/CIP1 promoter by IGF I. These data indicate that transcriptional activation of p53 and p21WAF1/CIP1 by IGF I involves MAP kinase pathway in cardiomyocytes, and thus link MAP kinase to negative modulation of the cell cycle in cardiac muscle cells.

Animals↗

PubMed1998

Cytokine rescue of p53-dependent apoptosis and cell cycle arrest is mediated by distinct Jak kinase signaling pathways.

Exposure of hematopoietic progenitors to gamma-irradiation (IR) induces p53-dependent apoptosis and a p53-independent G2/M cell cycle arrest. These responses to DNA-damage can be inhibited by treatment with cytokine growth factors. Here we report that gamma-IR-induced apoptosis and cell cycle arrest are suppressed by specific cytokines (e.g., erythropoietin and interleukin-3) and that activation of the Jak kinase is necessary and sufficient for these effects. Using myleoid cells expressing a series of erythropoietin receptor (EpoR) mutants, we have demonstrated that Jak kinase-dependent signals initiated from the membrane proximal domain of EpoR were sufficient to prevent IR-induced apoptotic cell death, but failed to prevent cell cycle arrest. Cell survival by Epo did not require activation of other known signaling pathways including PI-3 kinase, PLC-gamma, Ras or Stats. Signaling targets of Jak kinase pathways included members of the Bcl-2 family of anti-apoptotic proteins, and enforced expression of Bcl-2 or Bcl-xL was as effective as cytokine treatment in blocking IR-induced apoptosis but did not prevent growth arrest. A distinct signal derived from a membrane distal domain of EpoR is required to overcome growth arrest associated with DNA damage. These findings functionally link the Jak signaling pathway to suppression of p53-mediated cell death by cytokines and demonstrate that the apoptotic and growth arrest responses to DNA damage in hematopoietic cells are modulated by distinct, cytokine specific signal transduction pathways.

Animals↗

PubMed1998

A third member of the synapsin gene family.

Synapsins are a family of neuron-specific synaptic vesicle-associated phosphoproteins that have been implicated in synaptogenesis and in the modulation of neurotransmitter release. In mammals, distinct genes for synapsins I and II have been identified, each of which gives rise to two alternatively spliced isoforms. We have now cloned and characterized a third member of the synapsin gene family, synapsin III, from human DNA. Synapsin III gives rise to at least one protein isoform, designated synapsin IIIa, in several mammalian species. Synapsin IIIa is associated with synaptic vesicles, and its expression appears to be neuron-specific. The primary structure of synapsin IIIa conforms to the domain model previously described for the synapsin family, with domains A, C, and E exhibiting the highest degree of conservation. Synapsin IIIa contains a novel domain, termed domain J, located between domains C and E. The similarities among synapsins I, II, and III in domain organization, neuron-specific expression, and subcellular localization suggest a possible role for synapsin III in the regulation of neurotransmitter release and synaptogenesis. The human synapsin III gene is located on chromosome 22q12-13, which has been identified as a possible schizophrenia susceptibility locus. On the basis of this localization and the well established neurobiological roles of the synapsins, synapsin III represents a candidate gene for schizophrenia.

Alternative Splicing↗

PubMed1998

A new isoform of human myosin phosphatase targeting/regulatory subunit (MYPT2): cDNA cloning, tissue expression, and chromosomal mapping.

Myosin phosphatase target subunit 1 (MYPT1), a subunit of myosin phosphatase, plays a pivotal role in the regulation of myosin phosphatase activity. Here we have cloned a novel isoform of MYPT1, termed MYPT2, from a human brain cDNA library screened with a cDNA fragment of rat MYPT1. Overlapping clones indicated an open reading frame of 3763 nucleotides and a predicted polypeptide of mass 110,398. Ankyrin repeats and leucine zipper motifs were identified for the sequences 57-316 and 956-982, respectively. Overall, the deduced amino acid sequence of MYPT2 was 61% identical to MYPT1. MYPT2 gene is transcribed abundantly in heart and skeletal muscle, while Western blots using an antibody specific for MYPT2 showed exclusive expression of MYPT2 in heart and brain. A recombinant of the N-terminal two-thirds of MYPT2 bound to the catalytic subunit of type 1 phosphatase (delta isoform) and increased activity toward phosphorylated myosin light chain. In situ hybridization localized the human MYPT2 gene on chromosome 1q32.1, compared to the chromosomal location 12q15-q21-2 for MYPT1. It is suggested that the products of the two gene families of myosin phosphatase target subunit may be localized differently among various tissues.

Amino Acid Sequence↗

PubMed1998

Scanning of the dopamine D1 and D5 receptor genes by REF in neuropsychiatric patients reveals a novel missense change at a highly conserved amino acid.

In previous analyses of schizophrenic patients, multiple missense changes and one nonsense change were identified in the D5 dopamine receptor (DRD5) gene, but no sequence changes of likely functional significance were identified in the D1 dopamine receptor (DRD1) gene. In the present study, we examined these genes in patients with certain other neuropsychiatric disorders that may be related to dopaminergic dysregulation. The coding regions of the DRD1 and DRD5 genes were examined in 25 and 25 autistic patients, 25 and 28 attention deficit hyperactivity disorder patients, and 51 and 43 alcoholic patients, respectively. In addition, the DRD5 gene was examined in 75 schizophrenic patients to search for additional variants affecting protein structure or expression (VAPSEs). These patients were analyzed with REF (restriction endonuclease fingerprinting), a hybrid between SSCP and restriction endonuclease digestion, which allows the entire coding sequence to be screened in one lane of a gel. Approximately 800 kb of genomic sequence were examined. No sequence changes were identified in the DRD1 gene among the 101 patient samples analyzed. Two sequence changes were identified in the DRD5 gene among the 171 patient samples. These included one previously identified silent polymorphism at base pair 978 (P326P). The change was identified in patients from all disease categories and from different ethnic backgrounds. One novel missense change, L88F, occurred in transmembrane domain II at a highly conserved amino acid in all dopamine receptors as well as in alpha1- and beta-adrenergic receptors. The mutation was identified in a Caucasian male patient with autism. Further analysis is necessary to determine if this missense change is associated with a particular neuropsychiatric phenotype.

Adult↗

PubMed1998

Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores

Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500 degrees C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35 degrees to 80 degrees C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140 degrees C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water.

Journal Article↗

PubMed1998

The mouse telomerase RNA 5"-end lies just upstream of the telomerase template sequence.

Telomerase is a ribonucleoprotein enzyme with an essential RNA component. Embedded within the telomerase RNA is a template sequence for telomere synthesis. We have characterized the structure of the 5' regions of the human and mouse telomerase-RNA genes, and have found a striking difference in the location of the template sequence: Whereas the 5'-end of the human telomerase RNA lies 45 nt from the telomerase-RNA template sequence, the 5'-end of the mouse telomerase RNA lies just 2 nt from the telomerase-RNA template sequence. Analysis of genomic sequences flanking the 5'-end of the human and mouse telomerase RNA-coding sequences reveals similar promoter-element arrangements typical of mRNA-type promoters: a TATA box-like element and an upstream region containing a consensus CCAAT box. This putative promoter structure contrasts with that of the ciliate telomerase-RNA genes whose structure resembles RNA polymerase III U6 small nuclear RNA (snRNA) promoters. These and other comparisons suggest that, during evolution, both the RNA-polymerase specificity of telomerase RNA-gene promoters and, more recently, the position of the template sequence in the telomerase RNA changed.

Animals↗

PubMed1998

Neglect and constructive disorder.

A 61 year-old right handed man, who suffered from right cerebral infarction with evidences of visual-spatial neglect and constructive disorder, was reported. When copying simple geometric designs, he omitted to copy figures on the left side of the page; he tended to bisect the line to the right of the line's real center; after memorizing the familiar pictures he mainly mentioned the pictures on the right side of the page; when copying the "Rey Complex" he also ignored the structures on the left side. The relations of the neglect and construction disorder are discussed.

Apraxias↗

PubMed1998

Impact of temporal variation and the balance between excitation and inhibition on the output of the perfect integrate-and-fire model.

We consider how the output of the perfect integrate-and-fire (I&F) model of a single neuron is affected by the properties of the input, first of all by the distribution of afferent excitatory and inhibitory postsynaptic potential (EPSP, IPSP) inter-arrival times, discriminating particularly between short- and long-tailed forms, and by the degree of balance between excitation and inhibition (as measured by the ratio, r, between the numbers of inhibitory and excitatory inputs). We find that the coefficient of variation (CV; standard deviation divided by mean) of efferent interspike interval (ISI) is an increasing function of the length of the tail of the distribution of EPSP inter-arrival times and the ratio r. There is a range of values of r in which the CV of output ISIs is between 0.5 and 1. Too tight a balance between EPSPs and IPSPs will cause the model to produce a CV outside the interval considered to correspond to the physiological range. Going to the extreme, an exact balance between EPSPs and IPSPs as considered in [24] ensures a long-tailed ISI output distribution for which the moments such as mean and variance cannot be defined. In this case it is meaningless to consider quantities like output jitter, CV, etc. of the efferent ISIs. The longer the tail of the input inter-arrival time distribution, the less is the requirement for balance between EPSPs and IPSPs in order to evoke output spike trains with a CV between 0.5 and 1. For a given short-tailed input distribution, the range of values of r in which the CV of efferent ISIs is between 0.5 and 1 is almost completely inside the range in which output jitter (standard deviation of efferent ISI) is greater than input jitter. Only when the CV is smaller than 0.5 or the input distribution is a long-tailed one is output less than input jitter [21]. The I&F model tends to enlarge low input jitter and reduce high input jitter. We also provide a novel theoretical framework, based upon extreme value theory in statistics, for estimating output jitter, CV and mean firing time.

Action Potentials↗

PubMed1998

Similar gene expression pattern in senescent and hyperoxic-treated fibroblasts.

Different DNA-damaging treatments produce a senescence-like phenotype. Young human fibroblasts are transferred to a senescence-like state after 4 to 6 weeks of culture under 40% ambient oxygen partial pressure. In order to understand the causes of senescence it would be advantageous to know how well this state equals accelerated senescence. Therefore, we measured the expression of genes with known senescence-specific expression pattern in human fibroblasts, which were irreversibly proliferation-inhibited by chronic hyperoxic treatment. A senescence-specific gene expression pattern was confirmed by semiquantitative RT-PCR for eight out of nine examined genes in BJ foreskin fibroblasts and for four out of four genes in MRC-5 lung fibroblasts. For all these cases, gene expression under hyperoxia was similar to that in senescent cells, suggesting that chronic mild hyperoxia is a valid model for accelerated senescence.

Cells, Cultured↗

PubMed1998

Source and magnitude of ammonium generation in maize roots

Studies with 15N indicate that appreciable generation of NH4+ from endogenous sources accompanies the uptake and assimilation of exogenous NH4+ by roots. To identify the source of NH4+ generation, maize (Zea mays L.) seedlings were grown on 14NH4+ and then exposed for 3 d to highly labeled 15NH4+. More of the entering 15NH4+ was incorporated into the protein-N fraction of roots in darkness (approximately 25%) than in the light (approximately 14%). Although the 14NH4+ content of roots declined rapidly to less than 1 &mgr;mol per plant, efflux of 14NH4+ continued throughout the 3-d period at an average daily rate of 14 &mgr;mol per plant. As a consequence, cumulative 14NH4+ efflux during the 3-d period accounted for 25% of the total 14N initially present in the root. Although soluble organic 14N in roots declined during the 3-d period, insoluble 14N remained relatively constant. In shoots both soluble organic 14N and 14NH4+ declined, but a comparable increase in insoluble 14N was noted. Thus, total 14N in shoots remained constant, reflecting little or no net redistribution of 14N between shoots and roots. Collectively, these observations reveal that catabolism of soluble organic N, not protein N, is the primary source of endogenous NH4+ generation in maize roots.

Journal Article↗

PubMed1998

Transmural heterogeneity of action potentials and Ito1 in myocytes isolated from the human right ventricle.

Limited information is available about transmural heterogeneity in cardiac electrophysiology in man. The present study was designed to evaluate heterogeneity of cardiac action potential (AP), transient outward K+ current (Ito1) and inwardly rectifying K+ current (IK1) in human right ventricle. AP and membrane currents were recorded using whole cell current- and voltage-clamp techniques in myocytes isolated from subepicardial, midmyocardial, and subendocardial layers of the right ventricle of explanted failing human hearts. AP morphology differed among the regional cell types. AP duration (APD) at 0.5-2 Hz was longer in midmyocardial cells (M cells) than in subepicardial and subendocardial cells. At room temperature, observed Ito1, on step to +60 mV, was significantly greater in subepicardial (6.9 +/- 0.8 pA/pF) and M cells (6.0 +/- 1.1 pA/pF) than in subendocardial cells (2.2 +/- 0.7 pA/pF, P < 0.01). Slower recovery of Ito1 was observed in subendocardial cells. The half-inactivation voltage of Ito1 was more negative in subendocardial cells than in M and subepicardial cells. At 36 degrees C, the density of Ito1 increased, the time-dependent inactivation and reactivation accelerated, and the frequency-dependent reduction attenuated in all regional cell types. No significant difference was observed in IK1 density among the regional cell types. The results indicate that M cells in humans, as in canines, show the greatest APD and that a gradient of Ito1 density is present in the transmural ventricular wall. Therefore, the human right ventricle shows significant transmural heterogeneity in AP morphology and Ito1 properties.

Action Potentials↗

PubMed1998

Ultrarapid delayed rectifier current inactivation in human atrial myocytes: properties and consequences.

The ultrarapid delayed rectifier current (IK,ur) plays a significant role in human atrial repolarization and is generally believed to show little rate dependence because of slow and partial inactivation. This study was designed to evaluate in detail the properties and consequences of IK,ur inactivation in isolated human atrial myocytes. IK,ur inactivated with a biexponential time course and a half-inactivation voltage of -7.5 +/- 0.6 mV (mean +/- SE), with complete inactivation during 50-s pulses to voltages positive to +10 mV (37 degreesC). Recovery from inactivation proceeded slowly, with time constants of 0.42 +/- 0.06 and 7.9 +/- 0.9 s at -80 mV (37 degreesC). Substantial frequency dependence was observed at 37 degreesC over a clinically relevant range of frequencies. Inactivation was faster and occurred at more positive voltages at 37 degreesC compared with room temperature. The voltage and time dependencies of Kv1.5 inactivation were studied in Xenopus oocytes to avoid overlapping currents and strongly resembled those of IK,ur in native myocytes. We conclude that, while IK,ur inactivation is slow, it is extensive, and slow recovery from inactivation confers important frequency dependence with significant consequences for understanding the role of IK,ur in human atrial repolarization.

Action Potentials↗

PubMed1998

Matrilysin activity in the rat uterus during the oestrous cycle and implantation.

The objective of this study was to follow changes in the activity of the small matrix metalloproteinase matrilysin (MMP-7) in the rat uterus during the oestrous cycle and embryo implantation. Matrilysin was extracted from rat uteri, partially purified and separated into active and latent forms. The two forms of the enzyme were quantified at all stages of the oestrous cycle and after oestradiol and progesterone treatment. The activity was also measured during the first 7 days of pregnancy. Both latent and active forms of MMP-7 reached a peak during the pro-oestrous stage of the cycle; the concentrations were three times higher than at dioestrus and metoestrus. In rats treated with 0.1 mg oestradiol at metoestrus, both latent and active forms of the enzyme increased by more than two-fold after 24 h. In rats treated at pro-oestrus with 0.4 mg progesterone, there was a 70% increase in latent MMP-7, but no change in the active form. The highest concentrations of MMP-7 were observed on the first day of pregnancy. Between days 3 and 7 of pregnancy, the concentrations were relatively constant and comparable to the low concentrations at dioestrus. Enzyme activities were not different at implantation sites compared with remote sites.

Analysis of Variance↗

PubMed1998

Mutagenicity tests on epristeride in vitro and in vivo.

AIM: To evaluate the genetic effects of epristeride (Epr), a new prospective drug for treating benign prostatic hyperplasia. METHODS: 1) Assaying reverse mutation in histidine nutritional deficiency strain of Salmonella typhimurium 2) detecting chromosome aberrations in Chinese hamster lung cells (CHL); 3) micronucleus assays of mouse bone marrow; 4) counting sperm shape abnormalities 35 d after first ig Epr. RESULTS: 1) The reverse mutation happened at almost the same rate of the negative control. Epr did not induce bacterial mutation. 2) In vitro, the rates of aberration were all below 3%, thus Epr did not induce chromosome damage in CHL. 3) Micronucleated polychromatic erythroblasts (PCE) were not apparently more than those of sovent control, Epr did not induce the formation of micronuclei in PCE. 4) With Epr 818, 682, and 341 mg.kg-1, the head abnormalities of sperms were 5.3% +/- 2.7%, 5.3% +/- 1.9%, and 5.2% +/- 1.2%, respectively. CONCLUSION: No genetic toxicity of Epr was detected.

5-alpha Reductase Inhibitors↗

PubMed1998

[Effects of early enteral feeding on nitric oxide synthase activity in small intestine in burned rat].

OBJECTIVE: Our previous studies have proved that early enteral feeding could improve intestine blood flow after burn injury. But the mechanism was far from being clarified. This study was attempted to explore the effects of early enteral feeding on nitric oxide synthase (NOS) activity in burned rat small intestine and the relationship between the intestine mucosa blood flow (IMBF) and the activity of NOS. METHODS: The rats were randomly divided into three groups: burned control (B), burned and early enteral feeding (EF), and normal control (C). The activity of NOS including constitute NOS(cNOS) and inducible NOS(iNOS), and the IMBF were determined at postburn 0, 3, 6, 12, 24, 48 hours. RESULTS: It was found that cNOS activity and IMBF were decreased markedly postburn, and there was positive correlation between cNOS and IMBF (r = 0.97, P < 0.01). But the activity of iNOS, total NOS were increased significantly postburn, they had no correlation to the IMBF. In EF group cNOS activity and the IMBF were significantly higher, the iNOS was obviously lower than that of B group and there was no significant difference of total activity of NOS between two groups. CONCLUSION: Our results suggested that NOS which is catalyzed from cNOS may play main role in adjusting IMBF. By using early enteral feeding the activity of cNOS is increased and the ischemic state in small intestine is improved after burn injury.

Animals↗