Biomedical subjects

W K Liu

Publications and source records attributed to W K Liu.

At least 37 records · Page 2Linked to original sources

PubMed1999

Multiple system atrophy: a sporadic synucleinopathy.

Multiple system atrophy (MSA) is a sporadic neurodegenerative disease characterized clinically by varying degrees of Parkinsonism, cerebellar ataxia and autonomic dysfunction and pathologically by degeneration in the substantia nigra, putamen, olivary nucleus, pontine nuclei and cerebellum. In addition to selective neuronal loss, iron pigment accumulation and gliosis, myelin pathology is increasingly recognized. In affected white matter, myelin displays signs of degeneration and oligodendroglia contain argyrophilic inclusion bodies, so-called glial cytoplasmic inclusions (GCI). GCI are composed of 10-15-nm diameter coated filaments that are immunoreactive for ubiquitin and alpha-synuclein. Similar inclusions are occasionally found in neuronal cell bodies and cell processes in MSA. Given the presence of inclusion bodies composed of synuclein, it is reasonable to assume that biochemical alterations would be detected in synuclein in MSA and indeed this is the case. In MSA synuclein has biophysical properties that suggest increasing insolubility such as sedimentation in dense fractions in sucrose gradients and ready extraction into detergents and formic acid. Surprisingly, these biochemical modifications in synuclein are more widespread in the brain that the obvious pathology and suggest a fundamental molecular characteristic of the disorder. Similar neuronal, and less frequently glial, inclusions are detected in Lewy body disease, where there is also evidence for biophysical alterations in synuclein. Thus, MSA and LBD are both synucleinopathies, and they may comprise different poles of a disease spectrum that includes sporadic disorders as well as genetically determined disorders such as familial Lewy body Parkinsonism.

Humans↗

PubMed1998

A novel lectin with potent immunomodulatory activity isolated from both fruiting bodies and cultured mycelia of the edible mushroom Volvariella volvacea.

A novel lectin has been purified from the fruiting bodies as well as cultured mycelia of the edible mushroom Volvariella volvacea. The lectin, designated as VVL, was a homodimeric protein with a molecular weight of 32 kDa as demonstrated by gel filtration and SDS-PAGE. VVL had no carbohydrate moiety, and its hemagglutinating activity was inhibited by thyroglobulin but not by simple carbohydrates such as monomeric or dimeric sugars. The immunomodulatory activity of VVL was demonstrated by its potent stimulatory activity toward murine splenic lymphocytes. VVL was also found to markedly enhance the transcriptional expression of interleukin-2 and interferon-gamma by reverse transcriptase-polymerase chain reaction. As revealed by its N-terminal amino acid sequence, VVL possessed a molecular structure distinct from other immunomodulatory proteins previously reported in the same fungus.

Adjuvants, Immunologic↗

PubMed1997

Mechanisms of the bactericidal activity of low amperage electric current (DC).

The mechanisms whereby low amperage (10-100 microA) electric current (DC) is bactericidal were investigated with Staphylococcus epidermidis and Staphylococcus aureus. A zone of inhibition test involving the insertion of an anode and cathode into an agar plate inoculated with a lawn of bacteria was used to study the antimicrobial activity of electric current. A zone of inhibition was produced around the cathode when 10 microA (DC) was applied for 16 h. The diameter of the zone was greatly reduced in the presence of catalase. There was no zone around the cathode when the test was carried out under anaerobic conditions. H2O2 was produced at the cathode surface under aerobic conditions but not in the absence of oxygen. A salt-bridge apparatus was used to confirm that H2O2 was produced at the cathode and chlorine at the anode. The antimicrobial activity of low amperage electric current under anaerobic conditions and in the absence of chloride ions against bacteria attached to the surface of a current carrying electrode was also investigated. Antibacterial activity was reduced under anaerobic conditions, which is compatible with the role of H2O2 as a primary bactericidal agent of electricity associated with the cathode. A reduction in chloride ions did not significantly reduce the antibacterial activity suggesting that chlorine plays only a minor role in the bactericidal activity towards organisms attached to anodal electrode surfaces. The localized production of H2O2 and chlorine and the intrinsic activity due to electric current may offer a useful method for eradicating bacteria from catheter surfaces.

Catalase↗

PubMed1997

[Experimental morphological study of injection nerve injuries in rabbits].

The sciatic nerve of 16 rabbits were examined with the optical and electron microscope 2, 24, 72 hours and 7 days after injecting penicillin (200,000 U) into nerve or its peripheral in experiment group and control group. The experiment group showed successively nerve fiber tumefaction, myelin sheath lamellar separation and degeneration partly, the construction of axonal change abnormality myelin and axonal obvious degeneration from 2 hours to 7 days. The control group showed perinerve edema, hyperemia, epineurium hyperplasia, the nerve fiber of near epineurium had mild pathologic changes.

Animals↗

PubMed1996

Cytotoxic effects of sinococuline.

Three alkaloids, aknadinine, 1-nitroaknadinine and sinococuline, isolated from Stephania sutchuenensis were studied for their effects on a fibroblast cell line, eight tumor cell lines and a rat alveolar macrophage culture. Sinococuline is an effective tumor cell growth inhibitor whereas the toxicity of aknadinine and 1-nitroaknadinine towards all tested cells is low. A dose-dependent decrease in cell viability and in the uptake of tritiated-thymidine, -leucine and -uridine by these cells was observed when they were grown in the presence of sinococuline for 24 h. Exposure to sinococuline in vitro also altered the macrophage function by reducing the production of tumor necrosis factor and reactive nitrogen intermediates. Human leukaemic HL60 cells and mouse fibroblast L929 cells were used to study the underlying mechanism of cytotoxicity and apoptosis seem to be the mode of death induced by sinococuline

Animals↗

PubMed1996

Modulated induction of tau proteins in cultured human neuroblastoma cells.

Previous studies indicated that a chemically-defined, differentiation medium (DM) induces neuroblastoma cells, especially IMR32K cells, to exhibit phenotypes of mature neurons (including neurite outgrowth and synthesis of neurofilament polypeptides) and develop certain attributes of the neurons which are affected by neurofibrillary degeneration in Alzheimer's disease, such as expression of tangle-associated epitopes and accumulation of paired helical filaments-(PHF-) like fibrils. Immunocytochemical staining suggested that this cytoskeletal abnormality most likely results from altered expression of tau proteins. In the current study, we addressed this issue by analyzing tau-enriched preparations of IMR32K cells that were previously exposed to different incubation media using a panel of antibodies specific to tau and related microtubule-associated proteins. These cultured cells exhibited three groups of tau immunoreactivities which differ in molecular weight. Among them the level of high molecular weight tau (MW 90-112 kDa) was selectively augmented after DM incubation. The tau proteins produced in these neuron-like cells shared phosphorylated sites with PHF-tau and fetal tau, but differed from PHF-tau in their lack of the N-terminal insert which characterizes adult isoforms.

Brain Neoplasms↗

PubMed1996

RNA expression patterns of a type 2 metallothionein-like gene from rice.

A type 2 metallothionein-like gene from rice, OsMT-2 (Oryza sativa metallothionein-like gene-2), was isolated in its cDNA form and sequenced. By northern analyses OsMT-2 expression was shown to be induced under stress by sucrose starvation, heat shock and, to a lesser extent, abscisic acid, but not excess metals, including copper. Its response to sucrose starvation was transient and different from OsMT-1, a type 1 metallothionein-like gene of rice inducible by copper. These results suggest that while OsMT-2 is also involved in cellular response to stress, its function may be complementary to that of OsMT-1.

Abscisic Acid↗

PubMed1996

The immunomodulatory and antitumor activities of lectins from the mushroom Tricholoma mongolicum.

TML-1 and TML-2 were two lectins isolated from the mushroom Tricholoma mongolicum. They did not differ appreciably in their pH stability and cationic requirement for hemagglutinating activity. They both stimulated the production of nitrite ions and activated the macrophages in mice. The two lectins were able to inhibit the growth of implanted sarcoma 180 cells by 68.84% and 92.39% respectively. The growth of tumor cells in the mouse peritoneal cavity was also inhibited by the two lectins with TML-2 expressing a greater potency.

Adjuvants, Immunologic↗

PubMed1996

Immunomodulation and antitumor activity of polysaccharide-protein complex from the culture filtrates of a local edible mushroom, Tricholoma lobayense.

1. The polysaccharide-protein complex (PSPC) isolated from the culture filtrate of Tricholoma lobayense showed antitumor activity in mice. 2. PSPC had the ability to restore the phagocytic function of peritoneal exudate cells (PEC) and T-cell mitogenic activity of tumor-bearing mice. 3. An increase in the production of reactive nitrogen intermediates and tumor necrosis factor (TNF) was determined in PEC of mice that had received PSPC. 4. The present study showed that PSPC both induced the various immune responses in vivo and exhibited cytotoxicity against tumor cell lines in the presence of PSPC at doses of 30 and 60 micrograms/ml in vitro.

Adjuvants, Immunologic↗

PubMed1996

Polysaccharide-peptide complexes from the cultured mycelia of the mushroom Coriolus versicolor and their culture medium activate mouse lymphocytes and macrophages.

The aim of this study was to investigate the effects of the mushroom Coriolus versicolor on cells of the immune system. The cultured mycelia of the mushroom Coriolus versicolor and their culture medium were separately extracted with boiling water. The resulting polysaccharopeptide preparations were designated intramycelial (IM) and extramycelial materials (EM), and were separated by gel filtration before determining their effects on lymphocytes and macrophages in vitro and in vivo. After gel filtration on Sepharose 6B, only a single peak with a molecular weight of 13-19 KDa was obtained. Gel filtration of IM and EM on Sephadex G-50 revealed the presence of a larger peak of 28 KDa (from IM) and 15 KDa (from EM) and a smaller peak of 3.5 KDa. IM, EM and their large molecular peaks enhanced the mitogenic response of T-cells from BALB/c mice in vitro. Splenocytes from C57BL/6 mice pre-treated by force-feeding with IM and EM demonstrated an augmented mitogenic response to Con A. The macrophages of C57BL/6 mice that had been pre-treated with IM or EM showed an enhanced production of nitrite ions. The results indicate that both mouse lymphocytes and macrophages were activated by preparations of polysaccharopeptide from cultured mycelia and culture medium of C. versicolor. However, no direct cytotoxic activity against fibroblasts, hepatoma cells and choriocarcinoma cells could be demonstrated.

Animals↗

PubMed1996

The state of phosphorylation of normal adult brain tau, fetal tau, and tau from Alzheimer paired helical filaments at amino acid residue Ser262.

Antibody Ab262 was raised against a synthetic tau peptide (SKIGSTENLK, amino acids 258-267 of tau, termed Ser262 peptide). The antibody was more reactive with Ser262 peptide and unphosphorylated tau than a related phosphopeptide [SKIGS(P)TENLK, termed PSer262 peptide] and tau phosphorylated by a partially purified kinase, glycogen synthase kinase (GSK) 3 beta. AB262 reacted poorly with a peptide having the sequence DRV-QSKIGSLD (amino acids 348-358). Treatment of PSer262 peptide or GSK 3 beta phosphorylated tau with alkaline phosphatase increased Ab262 immunoreactivity, indicating that Ab262 is a reagent useful for studying tau phosphorylation at the Ser262 residue. The Ab262 immunoreactivity was detected in tau from normal brains and Alzheimer paired helical filament (PHF-tau) and in PHFs. Alkaline phosphatase treatment had no effect on the Ab262 immunoreactivity of normal tau and PHF-tau but altered the tau-1 and PHF-1 immunoreactivities, tau proteins from rat brains at 3 and 8 h postmortem exhibited 5 and 19%, respectively, more Ab262 immunoreactivity than tau from fresh tissues. In comparison, rat tau at 8 h postmortem was 40% more immunoreactive with Tau-1. The results suggest that Ser262 is not a major phosphorylation site in vivo. Moreover, there is little or no difference between PHF-tau and normal tau in the extent of phosphorylation at Ser262.

Alzheimer Disease↗

PubMed1996

A polysaccharide-peptide complex from cultured mycelia of the mushroom Tricholoma mongolicum with immunoenhancing and antitumor activities.

A polysaccharide-peptide complex with immunoenhancing and antitumor activities was obtained from the mycelial culture of Tricholoma mongolicum, an edible mushroom found in Northern China. The polysaccharide-peptide complex had a molecular mass of 15.5 kDa, as estimated by gel filtration, and a carbohydrate-protein ratio of about 8:1 and was not adsorbed on DEAE-Sepharose CL-6B. It possessed the activities of activating macrophages, stimulating macrophage antigen-presenting activity, which in turn enhanced proliferation of T-cells, and inhibiting the growth of sarcoma 180 cells that had been implanted in mice.

Adjuvants, Immunologic↗

PubMed1995

Detection of D-aspartate in tau proteins associated with Alzheimer paired helical filaments.

Paired helical filaments (PHF) characteristic of Alzheimer neurofibrillary lesions are known to contain a modified form of microtubule associated protein tau. These proteins, PHF-tau, differ from normal tau in the extent and the site of phosphorylation. To determine whether PHF-tau, tau proteins from normal adult brains (N-tau), tau proteins from Alzheimer brains not associated with PHF (A-tau), and tau proteins from fetal brains (F-tau) differ in racemization, these proteins were compared for their D-aspartate content. The results demonstrated that PHF-tau contain more D-aspartate than N-tau, A-tau and F-tau. The average percentage D-aspartate for these proteins, after a correction for background, are 4.9%, 2.8%, 1.6%, and 1% for PHF-tau, N-tau, A-tau and F-tau, respectively. It remains to be determined if the increase in D-aspartate is a consequence of PHF formation. It is also unknown if the change in D-aspartate content in PHF-tau is associated with phosphorylation, which alters the susceptibility of tau to proteolysis.

Alzheimer Disease↗

PubMed1995

A novel stress-inducible metallothionein-like gene from rice.

A novel rice genomic sequence encoding coding segments homologous to other metallothionein-like genes was isolated from Oryza sativa genomic library. This sequence, hereby designated as rgMT (rice genomic metallothionein-like gene), consists of two exons and one intron. From the coding sequence, it is predicted that rgMT encodes one protein of 74 amino acids. Differential expression of rgMT in rice plants was observed as mature transcripts were more abundant in roots than in leaves and sheaths. Under different stress conditions, such as excess heavy metals and heat shock, expression of rgMT was significantly elevated. This was especially noticeable with 250 microM CuCl2 for 16 h, 40 degrees C heat for 2 h and 0.06% DMSO for 1 h. Under sucrose starvation, rgMT transcripts also increased with time up to 72 h. During recovery from sucrose starvation, the transcripts declined slightly within 12 h of recovery. rgMT transcripts were also seen to have increased expression in senescent leaves. These results support the notion that rgMT is a stress-inducible gene in rice heretofore unreported.

Abscisic Acid↗

PubMed1995

Epitope expression and hyperphosphorylation of tau protein in corticobasal degeneration: differentiation from progressive supranuclear palsy.

Corticobasal degeneration (CBD) is a rare, progressive neurological disorder characterized by widespread neuronal and glial accumulation of abnormal tau protein. Using immunohistochemistry we analyzed tau epitope expression and phosphorylation state in CBD and compared them to cytoskeletal changes in Alzheimer's disease (AD) and progressive supranuclear palsy (PSP). Epitopes spanning the entire length of the tau protein were present in CBD inclusions. An antibody against the alternatively spliced exon 3 did not recognize cytoskeletal lesions in CBD, but did in AD and PSP. Tau epitopes from each region of the molecule were present in cytoskeletal inclusions in CBD, including gray matter astrocytic plaques, gray and white matter threads, and oligodendroglial inclusions. As in AD, tau from CBD was highly phosphorylated. Antibodies that recognized phosphorylated tau epitopes reacted with material from CBD in a highly phosphatase-dependent manner. Again, all types of inclusions contained phosphorylated epitopes. We conclude that abnormal tau protein in CBD comprises the entire tau molecule and is highly phosphorylated, but is distinguished from AD and PSP by the paucity of epitopes contained in the alternatively spliced exon 3.

Aged↗

PubMed1995

Immunomodulatory and antitumor activities of a polysaccharide-peptide complex from a mycelial culture of Tricholoma sp., a local edible mushroom.

A polysaccharide-peptide complex (PSPC) with immunomodulatory and antitumor activities was obtained from a submerged mycelial culture of Tricholoma sp., a local edible mushroom. The polysaccharide-peptide complex exhibited a molecular weight of 17 K in gel filtration and a single band after SDS-polyacrylamide gel electrophoresis. It was characterized by non-adsorption on both DEAE-Sepharose CL-6B and CM-cellulose. It could activate the macrophages, stimulate the proliferation of T-cells, and inhibit the growth of sarcoma 180 in mice. It possessed more potent immunomodulatory and antitumor activities than Coriolus versicolor polysaccharopeptide (PSP) and deserves to be studied as a potential agent for immunomodulation and cancer therapy.

Adjuvants, Immunologic↗

PubMed1995

Sister-chromatid exchanges in lymphocytes from methimazole-induced hypothyroid mice.

The inhibitory effect of an antithyroid drug on mouse T lymphocytes was investigated. Inbred C57BL/6 mice were provided with an antithyroid drug, methimazole, for 2, 4 and 6 weeks and the in vitro responses of the lymphocytes were studied. The proliferative responses of T lymphocytes from the spleen of methimazole (MMI)-treated mice significantly (p < 0.05) decreased following concanavalin A stimulation, and the inhibitory effect became prominent with the increased duration of MMI treatment. A concomitant increase in the frequency of induced sister-chromatid exchanges was also observed in these T lymphocytes. When the splenocytes were stimulated with concanavalin A for 24 h, their ability to produce interleukin-2 (IL-2) was significantly decreased (p < 0.05). The results indicated that methimazole interfered with the normal proliferation of T lymphocytes by suppressing the production of IL-2, a cytokine also known as T cell growth factor, as well as inducing a higher incidence of sister-chromatid exchange during cell division.

Animals↗

PubMed1995

Human microtubule-associated protein-2c localizes to dendrites and axons in fetal spinal motor neurons.

Microtubule-associated protein-2 (MAP-2) functions to maintain neuronal morphology by promoting the assembly of microtubules. MAP-2c is an alternately spliced form of MAP-2, containing the first 151 amino acids of high-molecular-weight (HMW) MAP-2 joined to the last 321 amino acids, eliminating 1,352 amino acids specific to HMW MAP-2. A polyclonal antibody generated to the splice site of human MAP-2c was used to determine its cellular localization. The MAP-2c antiserum was depleted of any HMW MAP-2 reactivity by absorption with HMW MAP-2 fusion protein. Western blot analysis of human fetal spinal cord homogenates demonstrated that the antibody is specific for human MAP-2c. MAP-2c immunoreactivity was found in the perinuclear cytoplasm and processes of anterior motor neurons and large processes of the posterior column in sections from 22-24-week human fetal spinal cord. Double-label confocal microscopy was performed using the MAP-2c polyclonal antibody and either a HMW MAP-2 or a neurofilament protein (highly phosphorylated 160- and 200-kDa protein) monoclonal antibody to identify these processes as dendrites or axons, respectively. HMW MAP-2 and MAP-2c colocalized in cell bodies and dendrites of anterior motor neurons, demonstrating for the first time the presence of native MAP-2c within dendrites. In addition, immunoelectron microscopy showed MAP-2c associated with microtubules in dendrites of motor neurons. MAP-2c and the neurofilament proteins were found in axons of the dorsal and ventral roots. The presence of MAP-2c within axons and dendrites suggests that MAP-2c contributes to neuronal plasticity during human fetal development.

Axons↗