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W Li

Publications and source records attributed to W Li.

At least 1,207 records · Page 67Linked to original sources
PubMed1993

CD4-positive helper T lymphocytes mediate mouse cardiac allograft rejection independent of donor alloantigen specific cytotoxic T lymphocytes.

Mouse heterotopic cardiac allograft recipients were depleted of CD4+ or CD8+ T lymphocytes in vivo to assess cellular requirements for graft infiltration, tissue damage, and acute allograft rejection. Modified limiting dilution analysis was employed to quantitate IL-2-producing Th lymphocytes (HTL) and CTL infiltrating the graft. Results were correlated with graft function and histologic evidence of tissue damage. In unmodified recipients, large numbers of donor alloantigen-specific CTL infiltrated the graft, overshadowing a modest number of HTL. CTL infiltration coincided with tissue damage and loss of graft function, suggesting a key role for CTL in rejection. In vivo treatment with anti-CD4 mAb inhibited both HTL and CTL infiltration, and no histologic evidence of tissue damage was observed. This observation suggested that HTL, although few in number, regulated the development of effector CTL and/or entry of these CTL into the graft. Reconstitution of HTL-depleted recipients with IL-2 resulted in graft infiltration by stimulated CTL, as assessed by modified limiting dilution analysis. However, these stimulated CTL failed to mediate tissue damage, and graft survival was prolonged. Unlike CTL obtained from unmodified recipients, graft-infiltrating CTL of IL-2-reconstituted mice were incapable of directly lysing donor cells in a 51Cr release assay. Hence, while IL-2 facilitated partial CTL differentiation and mobilization to the graft, additional signals appear necessary for maturation into lytic CTL. Furthermore, in recipients depleted of CTL by treatment with anti-CD8 mAb, HTL infiltrating the allograft, though few in number, were associated with extensive tissue damage and loss of graft function. These data suggest a less important role for CTL in the rejection process, and indicate that graft-infiltrating CTL are insufficient as sole mediators of cardiac allograft rejection. Potential mechanisms by which CD4+ HTL mediate cardiac allograft rejection independent of CTL are discussed.

Animals↗
PubMed1993

Molecular characterization of the her-1 gene suggests a direct role in cell signaling during Caenorhabditis elegans sex determination.

We have characterized two transcripts from the male-determining her-1 locus in Caenorhabditis elegans. The larger transcript, which appears more important for male development, is predicted to encode a novel 175-amino-acid, cysteine-rich polypeptide with an apparent amino-terminal signal sequence and potential cleavage and glycosylation sites. Expression of a full-length cDNA construct for the larger transcript driven by a body-wall-myosin promoter causes extensive masculinization of all sexually dimorphic tissues in XX (normally hermaphrodite) animals. This activity is dependent on the presence of the her-1 signal sequence or a substitute synthetic signal sequence in the encoded polypeptide. These results suggest that a secreted product of the her-1 gene dictates male development.

Amino Acid Sequence↗
PubMed1993

Two signaling molecules share a phosphotyrosine-containing binding site in the platelet-derived growth factor receptor.

Autophosphorylation sites of growth factor receptors with tyrosine kinase activity function as specific binding sites for Src homology 2 (SH2) domains of signaling molecules. This interaction appears to be a crucial step in a mechanism by which receptor tyrosine kinases relay signals to downstream signaling pathways. Nck is a widely expressed protein consisting exclusively of SH2 and SH3 domains, the overexpression of which causes cell transformation. It has been shown that various growth factors stimulate the phosphorylation of Nck and its association with autophosphorylated growth factor receptors. A panel of platelet-derived growth factor (PDGF) receptor mutations at tyrosine residues has been used to identify the Nck binding site. Here we show that mutation at Tyr-751 of the PDGF beta-receptor eliminates Nck binding both in vitro and in living cells. Moreover, the Y751F PDGF receptor mutant failed to mediate PDGF-stimulated phosphorylation of Nck in intact cells. A phosphorylated Tyr-751 is also required for binding of phosphatidylinositol-3 kinase to the PDGF receptor. Hence, the SH2 domains of p85 and Nck share a binding site in the PDGF receptor. Competition experiments with different phosphopeptides derived from the PDGF receptor suggest that binding of Nck and p85 is influenced by different residues around Tyr-751. Thus, a single tyrosine autophosphorylation site is able to link the PDGF receptor to two distinct SH2 domain-containing signaling molecules.

Amino Acid Sequence↗
PubMed1993

Human coronary arteries: projection angiograms reconstructed from breath-hold two-dimensional MR images.

The authors sought to render projection magnetic resonance (MR) angiograms depicting a substantial length of human coronary arteries from sequential breath-hold two-dimensional MR images. Tomographic images of the right and left anterior descending coronary arteries were collected with use of a segmented gradient-recalled sequence that incorporated fat suppression and prone positioning of the patient over a surface coil. After editing the images to eliminate overlapping chamber signals and after realigning the images, a maximum-intensity-projection algorithm was applied to create projection angiograms. For the 10 coronary arteries without severe narrowing, visualized length with projection MR angiography was 109 mm +/- 29 (mean +/- standard error of estimate) versus 121 mm +/- 29 with conventional coronary angiography (ranges, 62-147 mm and 70-180 mm, respectively). At conventional angiography linear regression indicated vessel length to be 1.03 times the length depicted at MR angiography with good correlation (r = .8). Results indicate good correlation between measurements of vessel length with both conventional and MR angiography.

Adult↗
PubMed1993

Fat-suppressed breath-hold magnetic resonance coronary angiography.

BACKGROUND: The ability to image the coronary arteries noninvasively would represent an advance in patient care. We have developed a magnetic resonance (MR) angiographic technique that allows the acquisition of complete images of coronary flow within a single breath-hold. By this method, the feasibility of noninvasive MR coronary angiography was evaluated in 25 subjects, including 19 healthy adult volunteers and six patients after diagnostic coronary angiography. METHODS AND RESULTS: Noninvasive MR coronary angiography was performed with a fat-suppressed ECG-gated gradient-echo sequence with k-space segmentation. Overlapping transverse sections were initially used to image coronary flow, with oblique images obtained after identification of proximal anatomy. The left main coronary artery was seen in 24 subjects (96%), with a mean diameter of 4.8 mm (range, 3.4-6.2 mm) and average length of 10 mm (range, 8-14 mm). The left anterior descending coronary artery was seen in 100% of subjects, with a mean proximal diameter of 3.6 mm (range, 2.6-4.3 mm) and for an average length of 44 mm (range, 28-93 mm). The left circumflex coronary artery was seen in 76% of subjects, with a mean proximal diameter of 3.5 mm (range, 2.6-4.3 mm) and for an average length of 25 mm (range, 9-42 mm). The right coronary artery was also identified in 100% of subjects, with a mean proximal diameter of 3.7 mm (range, 2.7-5.1 mm) and for an average length of 58 mm (range, 24-122 mm). Quantitative angiography of normal proximal segments demonstrated a good correlation with MR-determined lumen diameters (r = 0.86, p < 0.002). Occluded vessels in patients with coronary artery disease displayed an absence of flow signal distal to the occlusion, whereas vessels with significant angiographic stenoses demonstrated signal loss corresponding to the area of the stenosis, with visualization of the more distal vessel. CONCLUSIONS: Breath-hold MR coronary angiography provides visualization of the major epicardial vessels. In the future, MR coronary angiography may provide a noninvasive means for the evaluation of patients with known or suspected coronary artery disease.

Adult↗
PubMed1993

Chemical modification of biopolymers--mechanism of model graft copolymerization of chitosan.

Mechanism of graft copolymerization of vinyl monomers onto chitosan initiated by Ce(IV) ion, one of the important ways of chemical modification of chitosan, has been investigated by means of kinetics measurement and polymer chain structure analysis. It is found that when Ce(IV) ions reacts with adjacent hydroxylamine structure in chitosan, a chelate complex is first formed and then it disproportionates to radical for initiation of graft copolymerization. There exist two ways for such initiation depending upon the reaction temperature. For a reaction temperature lower than 40 degrees C, a -CHO group and a -C = NH group are introduced, and the aldehyde group reacts with Ce(IV) ions to form an acyl radical which initiates a graft polymer chain in this saccharide unit. For temperatures higher than 90 degrees C, the -C = NH group hydrolyzes to form an amine and an aldehyde group which also reacts with Ce(IV) ions. In this case there should be two aldehyde groups, i.e. two initiation sites, in one adjacent hydroxyl-amine structure. That means that the initial radical in the chitosan/Ce(IV) system is similar to that in the cellulose/Ce(IV) one, but the former usually gives a lower grafting reactivity than the latter due to the higher stability of the chelate.

Biopolymers↗
PubMed1993

Tyrosyl radical generated by myeloperoxidase catalyzes the oxidative cross-linking of proteins.

Phagocytes generate H2O2 for use by a secreted heme enzyme, myeloperoxidase, to kill invading bacteria, viruses, and fungi. We have explored the possibility that myeloperoxidase might also convert L-tyrosine to a radical catalyst that cross-links proteins. Protein-bound tyrosyl residues exposed to myeloperoxidase, H2O2, and L-tyrosine were oxidized to o,o'-dityrosine, a stable product of the tyrosyl radical. The cross-linking reaction required L-tyrosine but was independent of halide and free transition metal ions; the heme poisons azide and aminotriazole were inhibitory. Activated neutrophils likewise converted polypeptide tyrosines to dityrosine. The pathway for oxidation of peptide tyrosyl residues was dependent upon L-tyrosine and was inhibited by heme poisons and catalase. Dityrosine synthesis was little affected by plasma concentrations of Cl- and amino acids, suggesting that the reaction pathway might be physiologically relevant. The requirement for free L-tyrosine and H2O2 for dityrosine formation and the inhibition by heme poisons support the hypothesis that myeloperoxidase catalyzes the cross-linking of proteins by a peroxidative mechanism involving tyrosyl radical. In striking contrast to the pathways generally used to study protein oxidation in vitro, the reaction does not require free metal ions. We speculate that protein dityrosine cross-linking by myeloperoxidase may play a role in bacterial killing or injuring normal tissue. The intense fluorescence and stability of biphenolic compounds may allow dityrosine to act as a marker for proteins oxidatively damaged by myeloperoxidase in phagocyte-rich inflammatory lesions.

Amino Acid Sequence↗
PubMed1993

Stimulation of progesterone secretion by recombinant follistatin-288 in human granulosa cells.

The effects of recombinant human follistatin (follistatin-288) on basal and hCG-stimulated progesterone secretion were examined in cultured human granulosa cells. Follistatin increased progesterone secretion in a dose-dependent manner. However, follistatin did not augment hCG- or cAMP-stimulated progesterone secretion. Time-course analysis revealed that follistatin increased progesterone secretion after 24 h of incubation. Follistatin also enhanced basal, but not hCG-stimulated, 20 alpha-hydroxyprogesterone accumulation, indicating that the increase in progesterone accumulation was not due to a blockade of the 20 alpha-hydroxylase metabolic pathway. In the presence of the phosphodiesterase inhibitor isobutylmethylxanthine, follistatin significantly increased intracellular cAMP accumulation to levels comparable to those induced by 1 IU/ml hCG. These results provide the first evidence of a stimulatory action of follistatin on progestin secretion in the human ovary, which is accompanied by an increased accumulation of intracellular cAMP levels. Follistatin may well be another potential regulator of steroid hormone production in human granulosa cells during the periovulatory period.

20-alpha-Dihydroprogesterone↗
PubMed1993

Racial differences in aldosterone excretion: a longitudinal study in children.

Aldosterone production, estimated from urinary excretion of aldosterone and the plasma aldosterone level, was found in a previous cross-sectional study to be lower in black children than white children. The present study examined aldosterone excretion longitudinally to determine whether the aldosterone excretion rate changed with time and if the racial difference in aldosterone excretion persisted. Urine samples were collected every 6 months for up to 5.5 yr in 351 white and 170 black children for measurements of aldosterone, sodium (Na+), and potassium (K+) excretion. Results were expressed per mumol urinary creatinine. Mean values for excretion rates for the total longitudinal period were determined. Na+ excretion was not significantly different in the two groups, whereas K+ excretion was 18% lower in blacks than whites (P = 0.0001). Body weight and urinary Na+ and K+ excretion were significantly related to aldosterone excretion. After adjusting for these variables, the aldosterone excretion rate was 35% lower in blacks than whites (P = 0.0001), a racial difference that did not change with age. Aldosterone excretion rates showed no longitudinal trend to either increase or decrease. The physiological relevance of the lower aldosterone excretion rate in black children remains unknown.

Adolescent↗
PubMed1993

Secretion of epidermal growth factor-like molecular species by lung parenchymal macrophages: induction by interferon-gamma.

A population of cells enriched for pulmonary interstitial macrophages was obtained by differential adherence of lung parenchymal cells released by dissociation with trypsin. These cells secreted a molecule or molecules that bound to epidermal growth factor (EGF) receptors expressed on pulmonary fibroblasts. Secretion was reproducibly stimulated by exposure of the macrophages to interferon-gamma. Binding to EGF receptors could be blocked by a polyclonal antibody to EGF. It could also be partially blocked by incubation with heparin, suggesting that at least a component of the activity might be due to a member of the heparin-binding subgroup of the EGF family of growth factors. Because pulmonary fibrosis is consistently associated with inflammatory accumulation of activated T-lymphocytes, induction by interferon-gamma of growth factor secretion by macrophages could have pathogenetic importance. We speculate that similar cellular interactions may play a role in the progression of other chronic inflammatory lesions to fibrosis.

Animals↗
PubMed1993

[Relationship between the presynaptic depolarization effect of acupuncture and r-aminobutyric acid, opioid peptide and substance P].

The present study was performed on 22 cats to explore whether r-aminobutyric acid (GABA), endogenous opioid peptide and substance P (SP) were involved in the regulation of presynaptic inhibition in acupuncture analgesia. The size of the antidromic compound C action potentials of the sural nerve evoked by the testing stimulation in spinal cord was measured as an indicator of C-afferent terminal excitability. It was found that the electro-acupuncture (EA) at "Huantiao" (GB30) and "Yang lingquan" (GB34) points induced significant enlargement of the antidromic C-waves, showing the depolarization of presynaptic terminals of primary C-afferents was enhanced. The depolarization effect of EA was significantly reduced by bicuculline, naloxone and the antiserum of SP locally applied to the surface of spinal cord respectively. It is supposed that GABA, endogenous opioid peptide and SP may be involved in the regulation of presynaptic inhibition in acupuncture analgesia.

Action Potentials↗
PubMed1993

State of the foreign gene and of the genome in transgenic rice (Oryza sativa L.).

PCR with random primers (RAPD analysis) performed on the DNA of embryogenic and non-embryogenic suspension cultured rice and of transformed rice plants allows the evaluation of the extent of DNA changes in the different biological materials. This is thus suggested as a convenient approach, in combination with restriction analysis and Southerns blotting, to evaluate the integrity of the foreign gene, the stability of the insertion site and the stability of the whole genome.

Base Sequence↗
PubMed1993

[The role of OLS in peripheral acupuncture analgesia in arthritic rats].

Our previous work has shown that opiate-like substance (OLS) is involved in the central mechanism of acupuncture analgesia (AA) in the arthritic rats. In this paper, the role of OLS in peripheral mechanism of AA is further studied. Twenty four hours after a subcutaneous injection of Freund's adjuvant into the right ankles, acute arthritis with typical symptoms developed in all the rats. Following needling at Huantiao points for 10 minutes, the pain threshold (PT) was raised by 42.3% (P < 0.05) in the inflamed ankles and by 5.6% in the non-inflamed ones. When systemically administered a dose of 250 and 100 micrograms, naloxone (Nx) could completely and partially (49.6%) block AA respectively. While locally injected a dose of 100 micrograms even 20 micrograms, Nx could completely antagonize AA. After systemic administration of morphine (10, 5.0, 2.5, 1.25 mg/kg), PT rise was dose-related, and PT was raised by 86.5 +/- 22.7% in the affected ankles and by 32.9 +/- 14.9% in the normal ankles at 5 mg/kg in dose. It is evident that the opiate receptors in the inflamed area should by sensitized. These results demonstrate that activation of endogenous opiate system may also be involved in the peripheral AA. Acupuncture may enhance the release of peripheral OLS which can act at the sensitized opiate receptors, leading to more potent analgesic effect in the inflamed area.

Acupuncture Analgesia↗
PubMed1993

[Experimental research of acupuncture manipulation of reinforcing and reducing by lifting and thrusting needle on the animal].

The experiment were performed on model rabbits injected with large dosage of Dexamethasone (DXM) for 5 days. Reinforcing manipulation (RIM), reducing manipulation (RDM), and electric stimulation (ES) were respectively used to puncture Zusanli (ST 36) points for 5 days to observe the change on temperature, body weight, corticosterone assay, testosterone assay, and the amplitude of the plethysmogram. The result showed that there was a similar syndrome of the kidney deficiency after injecting DXM. The body weight was increased in the DXM control group, decreased in the RDM group and had no significant influence in the other groups. The body weights between the reinforcing manipulation and the reducing manipulation groups had obvious difference. But the other indices of observation had no significant influence among the different groups. So there wasn't significant difference on most of observed signs among the RIM group, the RDM group and ES group. The study of acupuncture manipulation will have yet to be further done.

Acupuncture Therapy↗
PubMed1993

[Localization of the meridian track over body surface by the method of blocking the acupuncture effect with mechanical pressure].

Plotting out the meridian course with objective methods is one of the important projects in the research of meridian at present. Therefore, selecting a proper indication to plot out the meridian track over the body surface during acupuncture is significant for elucidating the essence of meridian. The purpose of this paper was to plot out the Large Intestine Meridian track by blocking the acupuncture effect with mechanical pressure, when electroretinogram (ERG) was taken as a responsive indication. The plotting out the track was carried out on 5 subjects with marked propagated sensation along meridians (PSM) and 5 without PSM. The pressure was applied on Wenliu (LI 7), Shoushanli (LI 10), Quchi (LI 11), Binao (LI 14) and Jianyu (LI 15) respectively, when Hegu (LI 4) was punctured. Under such condition the variation of ERG amplitude decreased markedly or even disappeared. But the variation rate of ERG amplitude was still distinctly increased when the pressure was applied on both sides of any above points. The difference is highly significant (P < 0.01). The results revealed that the meridian track over the body surface during acupuncture could be plotted out not only in the subjects with marked PSM, but also in those without PSM, when the proper objective indication was used. Its course basically coincided with that of the meridian described in the books of traditional Chinese medicine. Now it is safe to say the meridian track over the body surface is existed in human in common. It provides a new approach to plot out the meridian course with objective methods and opens up broad prospects for further application.

Acupuncture Points↗
PubMed1993

[The influence of pressing the meridian course on electroretinogram during acupuncture].

Observation was performed on 23 subjects with marked propagated sensation along meridians (PSM) and 30 without PSM. The electroretinogram (ERG) was recorded with surface electrode and added by an averager. The b wave of ERG evoked by flash stimulation was positive with a latent period about 60 ms and amplitude of 22 +/- 1.66 muv (n = 53). There were 2 types of ERG response during puncturing Hegu (LI 4). The amplitude of ERG b wave increased in 33 subjects and decreased in 20 subjects. However, the acupuncture effect was kept relatively stable in each subject. The spontaneous variation of ERG amplitude was about 10%. In contrast, it changed by 26.5 +/- 2.43% (n = 20) when Hegu (LI 4) was acupunctured alone. It is particularly to be noted that the amplitude of b wave almost remained unchanged, with in the range of 10.08 +/- 2.42% (n = 20), as the pressure was applied on Shousanli (LI 10) during acupuncture, no matter whether the subjects with or without PSM. However, the variation rate of b wave increased by 24.83 +/- 3.74% (n = 15) once again, if the pressure was applied on both side of Shousanli (LI 10), it was nearly equal to the value caused by acupuncture Hegu (LI 4) alone. The contrast between the two is striking. The result revealed again that there may be a certain substantial process advancing along the channel during acupuncture. It is the blockade of this process by mechanical pressure which leads to the decrease of the acupuncture effect.

Acupuncture Therapy↗
PubMed1993

[Observation on the relation between propagated sensation along meridians and the therapeutic effect of acupuncture on myopia of youngsters].

Nine hundred and ninety two eyes suffering from various degrees of myopia in 536 youngsters were treated with acupuncture. A method of exciting propagated sensation along meridians (PSM) and making it travel toward the affected region was employed in treatment. Bilateral Hegu (LI4) and Taichong (LR3); and bilateral Waiguan (ST5) and Guangming (GB37) were punctured on alternate days. The results showed that after 1-3 periods of treatment, the vision of 868 eyes (87.5%) were improved in various extent. Among them, the vision completely recovered in 131 eyes (13.31%), and the diopter decreased-0.75 to -1.00 D.S. in 13 eyes after acupuncture treatment. The therapeutic effect of acupuncture seemed to be considerably satisfactory and stable in two years following up. The extent of distinctness of PSM raised markedly with the increase of times of acupuncture. There was a close relation between the extent of distinctness of PSM and effectiveness of acupuncture. The more striking the centripetal PSM, the better was therapeutic effect of acupuncture. The excellent effect was always achieved when PSM arrived at the affected eye. Since PSM arrived at a large number of eyes in the subjects in younger year and so the better therapeutic effect was also achieved.

Acupuncture Therapy↗