Biomedical subjects

W K Liu

Publications and source records attributed to W K Liu.

At least 55 records · Page 3Linked to original sources

PubMed1995

Isolation and characterization of two distinct lectins with antiproliferative activity from the cultured mycelium of the edible mushroom Tricholoma mongolicum.

Two lectins, TML-1 and TML-2, were isolated from Tricholoma mongolicum by ion-exchange chromatography and gel filtration. They are dimers with molecular weight near 37000. The hemagglutinating activities of TML-1 and TML-2 are sensitive to lactose inhibition and are stable between 10 and 80 degrees C. They exhibit antiproliferative activities against mouse monocyte-macrophage PU5-1.8 cells and mouse mastocytoma P815 cells in vitro. The two lectins differ in the content of proline and tyrosine residues. Both are non-glycoproteins and have hydroxyproline residues.

Basidiomycota↗

PubMed1995

Effects of decoctions prepared from Aconitum carmichaeli, Aconitum kusnezoffii and Tripterygium wilfordii on serum lactate dehydrogenase activity and histology of liver, kidney, heart and gonad in mice.

Mature ICR mice were randomly divided into groups and treated with various doses (1 mg, 5 mg or 10 mg herb/25 g body weight) of a decoction of one of three following Chinese medicinal herbs: Aconitum carmichaeli, Aconitum kusnezoffi and Tripterygium wilfordii, once daily for 4 days. Twenty four hours after the last injection the animals were bled and the blood samples were stored at -20 degrees C until assay for liver lactate dehydrogenase (LDH) isozyme activity. The livers, kidneys, hearts and gonads were dissected out, immediately fixed in Bouin's fluid, and subsequently processed for histological examination. It was found that the gonads and hearts of the drug-treated mice were histologically similar to those of control animals. After treatment with the lowest dose of the herbs i.e. 1 mg/25 body weight, the liver and kidney did not undergo observable changes. However, the herbs at the doses of 5 mg and 10 mg/25 g body weight produced damaging effects on the liver and kidney, the effects produced by the higher dose being more dramatic. The tissue damage was accompanied by elevations of liver LDH isozyme activity in the serum.

Animals↗

PubMed1995

The effects of methimazole on haematopoiesis in mice.

The effects of anti-thyroid drug, methimazole (MMI), on haematopoiesis in inbred C57BL/6 mice were studied. The in vitro proliferative response of bone marrow (BM) cells to interleukin-3 (IL-3) was significantly increased when mice were provided with 0.1% MMI in water (w/v) ad librium for 4 to 6 weeks. Using soft agar agar colony assay, the numbers of myeloid cell colonies were also significantly increased in mice treated with MMI. However, the proliferative response of BM cells to IL-3 was found to be greatly reduced 10 weeks after MMI treatment. In vitro studies showed that MMI alone at the concentrations of 500 microM or above inhibited both the growth of normal BM cells in liquid culture and the formation of macrophage (M)-/granulocyte (G)-colonies in soft agar culture in a dose dependent manner. Direct cytotoxic effect of MMI (0 - 1250 microM) to normal BM cells was not observed. Results from this study suggested that MMI can modulate the development of myeloid haematopoietic cells.

Animals↗

PubMed1995

Detection of a Cdc2-related kinase associated with Alzheimer paired helical filaments.

By immunocytochemical staining and Western blotting, we detected a Cdc2-related kinase in human brains. The kinase is recognized by antibodies against the carboxyl and the amino termini of p34Cdc2 but is not recognized by antibodies against the PSTAIRE motif. It is slightly smaller than p34Cdc2 in molecular mass (approximately 33 kd). This 33-kd Cdc2-related kinase is present in intracellular neurofibrillary tangles in neurons of elderly humans and in Alzheimer's disease, and it is associated with paired helical filaments (PHF) from Alzheimer's disease brains. Unlike the antibodies to the carboxyl and amino termini of p34Cdc2, antibodies to an abundant brain Cdc2-related kinase PSSLARE/Cdk5 did not immunolabel Alzheimer's disease neurofibrillary lesions. PHF preparations were demonstrated to contain kinases capable of phosphorylating histone H1, PHF-Tau, and a synthetic peptide (VAVVRTPPKSPSSAK). By virtue of its physical association with PHF, the 33-kd Cdc2-related kinase may play a role in transforming normal Tau proteins to PHF-Tau characteristic of Alzheimer's disease.

Alzheimer Disease↗

PubMed1994

Effect of trichosanthin and momorcharins on isolated rat hepatocytes.

alpha-Momorcharin, beta-momorcharin and trichosanthin increased the secretion of glutamate-pyruvate transaminase, lactate dehydrogenase and isocitrate dehydrogenase by isolated rat hepatocytes into the culture medium. This hepatotoxic effect of the proteins appeared to be concentration-dependent. The plant proteins induced morphological changes in hepatocytes including increased formation of cytoplasmic blebs and a reduction of microvilli on plasma membrane.

Alanine Transaminase↗

PubMed1994

Expression of tau exon 8 in different species.

A synthetic peptide corresponding to a region encoded by tau gene exon 8 was used to raise an antibody. The antibody, E8, was used to probe normal tau from different species and abnormal tau proteins from subjects with Alzheimer's disease. Immunoblotting and enzyme-linked immunosorbent assays demonstrated that only bovine tau reacted with the E8 antibody. The E8 immunoreactive tau isoform was estimated to represent less than 2% of the bovine tau. Our results indicate that bovine tau is unique in containing isoforms positive with E8, and that PHF formation does not require the presence of PHF-tau with exon 8.

Amino Acid Sequence↗

PubMed1994

Action of alpha-momorcharin, a ribosome inactivating protein, on cultured tumor cell lines.

1. alpha-Momorcharin, a glycoprotein isolated from seeds of the bitter gourd, Momordica charantia inhibited incorporation of [3H]thymidine, [3H]leucine and [3H]uridine into P388 (mouse monocyte-macrophage), J774 (Balb/c macrophage), JAR (human placental choriocarcinoma) and sarcoma S180 cell lines. 2. The most potent inhibitory effect was exerted on P388 cells and the smallest effect on sarcoma cells. 3. alpha-Momorcharin also enhanced the tumoricidal effect of mouse macrophages on mouse mastocytomal (P815) cells.

Animals↗

PubMed1994

Amino acid residues 226-240 of tau, which encompass the first Lys-Ser-Pro site of tau, are partially phosphorylated in Alzheimer paired helical filament-tau.

A synthetic peptide corresponding to residues 226-240 (E9 peptide) of human tau, which contains an Lys-Ser-Pro motif, was used to raise a polyclonal antibody. The antibody, E9, was 10-fold less reactive with phospho-E9 peptide than with native E9 peptide. E9 antibody was used to study the extent of phosphorylation in a modified form of tau (PHF-tau) that is found in Alzheimer's disease brain and is incorporated into paired helical filaments (PHFs). E9 immunolabeled Alzheimer's disease neurofibrillary tangles and abnormal neurites in brain sections intensely, with increased immunoreactivity detected after pretreatment of sections with phosphatase. On immunoblots and ELISA, E9 reacted with PHF-tau and recombinant human tau but not with the high and middle molecular weight neurofilament proteins. Phosphatase treatment of PHF-tau improved the E9 immunoreactivity by 30-50%. Dephosphorylated high but not middle molecular weight neurofilament protein became reactive with E9. These results indicate that < 50% of the PHF-tau is phosphorylated in the subregion corresponding to residues 226-240 of tau and suggest that the phosphorylation of this region may not be essential for PHF formation.

Alzheimer Disease↗

PubMed1994

Ultrastructure and biochemical composition of paired helical filaments in corticobasal degeneration.

Corticobasal degeneration (CBD) is a neurodegenerative disorder associated with extensive cytoskeletal abnormalities. These include tau-positive neuropil threads and grains, ballooned or swollen neurons, neurofibrillary tangles, and glial inclusions. Given the presence of tau-positive structures in CBD, we investigated whether abnormalities in tau proteins associated with CBD were similar to those in Alzheimer's disease (AD). Fractions of abnormal tau proteins were isolated as Sarkosyl-insoluble pellets. By electron microscopic examination, the fraction from CBD contained twisted filaments that differed from paired helical filaments of AD. In CBD, filaments were shorter in length, rarely longer than 400 nm, 10 to 20% wider in the maximum and minimum widths (26 to 28 nm and 13 to 14 nm, respectively), and the periodic twist (169 to 202 nm) was twice as long as that in AD. Immunogold labeling with a panel of tau-reactive antibodies (Alz 50, Tau 14, AH-1, E-11, PHF-1, and Tau 46) showed no apparent differences in the pattern of tau immunoreactivity between filaments of CBD and AD. Western blots revealed that polypeptides of abnormal tau were present in both fractions; however, only two polypeptides (68 and 64 kd) were present in CBD as compared with three (68, 64, and 60 kd) in AD. Both of these polypeptides were reactive with additional antibodies (E-9, Tau-1 after dephosphorylation, AT8, and NP8). Only one polypeptide (68 kd) bound an antibody to adult-specific tau sequence encoded by exon 2, but neither was reactive with antibodies to adult-specific sequences encoded by exons 3 and 10. The results suggest that abnormalities in the number and heterogeneity of isoforms of tau may be one of the factors contributing to ultrastructural differences in pathological filaments of CBD and AD.

Aged↗

PubMed1993

Synergistic control mechanism for abnormal site phosphorylation of Alzheimer's diseased brain tau by kinase FA/GSK-3 alpha.

When a synthetic peptide fragment (VAVVRTPPKSPSSAK) which corresponds to amino acid residues 226-240 from brain microtubule-associated protein tau was used as a testing substrate, we found that protein kinase FA/GSK-3 alpha was almost inactive towards this substrate. In sharp contrast, when Ser-10 of this peptide was replaced by a phosphoserine, the phosphopeptide fragment (VAVVRTPPKS(p)PSSAK) became an excellent substrate for kinase FA/GSK-3 alpha. Sequential manual Edman degradation together with phosphoamino acid analysis and protein sequencing further revealed that Thr-6 of the peptide fragment which corresponds to an important abnormal phosphorylation site Thr-231 in Alzheimer's diseased brain tau was the only site that was greatly phosphorylated, demonstrating that a pre-phosphorylation becomes a prerequisite and is essential for promoting phosphorylation of Thr-231. Taken together, the results provide initial evidence that kinase FA/GSK-3 alpha mediates a synergistic phosphorylation control mechanism involved in the abnormal site phosphorylation of Alzheimer's diseased brain tau.

Alzheimer Disease↗

PubMed1993

Application of synthetic phospho- and unphospho- peptides to identify phosphorylation sites in a subregion of the tau molecule, which is modified in Alzheimer's disease.

Phospho- and unphospho- peptides were used to define the essential sequence for a tau epitope, which is recognized by Tau-1 antibody and phosphorylated in Alzheimer's disease (AD). The epitope was mapped within the amino acid residues 192-199 of tau and was phosphorylated by the p34cdc2/p58cyclin A proline directed kinase (PDPK), but not by purified mitogen activated protein kinase (p42mapk). Addition of phosphate to the last serine of the epitope was the most effective in abolishing the reactivity of the epitope to Tau-1 antibody. Our results suggest that one and possibly more members of the PDPK family may play a role in the pathogenesis of AD.

Alzheimer Disease↗

PubMed1993

Phosphorylated tau immunoreactivity of granulovacuolar bodies (GVB) of Alzheimer's disease: localization of two amino terminal tau epitopes in GVB.

An immunocytochemical study of Alzheimer's disease hippocampus with a panel of anti-tau antibodies revealed two antibodies that stained granulovacuolar bodies (GVB) in pyramidal neurons of Ammon's horn. These two affinity-purified anti-tau antibodies were raised in rabbits against synthetic peptides homologous to sequences (amino acids 44-55 and 75-87) in the 58 amino acid insert in the amino terminus of the longest form of human tau. This region is homologous to exons 2 and exon 3 of bovine tau. The exon 2 peptide contains a serine (amino acid residue 46), which has been shown to be a phosphorylated site in paired helical filaments. Antibodies to a nonphosphorylated exon 2 peptide failed to immunostain GVB, but those to the phosphopeptide consistently stained GVB. Staining, however, was most consistent with the antibody to the exon 3 sequence. As in previous studies, GVB were also stained by RT97, a neurofilament antibody whose epitope in tau appears to be a phosphorylated site in or near exon 2, perhaps at serine residue 46 (Brion et al. 1992). Antibodies to epitopes in the amino terminus, mid-region and carboxy terminus of tau failed to consistently stain GVB. More often they produced staining around the periphery of the GVB, giving the appearance of an "empty vacuole." Most GVB were also immunoreactive with an antibody to ubiquitin. The results are consistent with the hypothesis that GVB are derived from sequestered altered tau possibly mediated by ubiquitin. The failure to detect most regions of tau in GVB is consistent with the idea that tau is partially degraded or highly modified in GVB.

Aged↗

PubMed1993

Expression of tumor necrosis factor and c-fos genes in peritoneal macrophages of hypothyroid mice.

It is well documented that hypothyroid patients are more susceptible to microbial infections. In order to study whether this impaired response is due to a decrease in production of antitumor molecules or an impaired ability to transmit information in the macrophage, a hypothyroid animal model was used to study the expression of both tumor necrosis factor gene and c-fos protooncogene in peritoneal macrophages. Inbred mice were rendered hypothyroid by an antithyroid drug, methimazole, and the expression of tumor necrosis factor gene and c-fos protooncogene in peritoneal macrophages were studied. Impairment of c-fos and TNF genes were at both transcriptional and translational levels using northern blot analysis, bioassays, and immunocytochemical staining methods. These results indicate that the reduction in signal transduction and in the production of antitumor molecules may cause the poor defense ability of hypothyroid animals.

Animals↗

PubMed1993

Stimulation of murine splenocytes by melatonin and methoxytryptamine.

Male C57 mice kept under a 14:10 (L:D) photoperiod received vehicle (VEH), melatonin (MEL) and methoxytryptamine (MTA) in the drinking water for 2 weeks. Splenocytes from MEL-treated mice showed an augmented mitogenic response to concanavalin A and lipopolysaccharide (LPS) while splenocytes from MTA-treated mice demonstrated an enhanced mitogenic response to LPS when compared to the VEH-treated control. Splenocytes from MEL-treated and MTA-treated mice also produced higher levels of gamma interferon and interleukin-2. Lymphokines prepared from splenocytes of MEL-treated mice stimulated peritoneal macrophages to produce more nitrite than those from splenocytes of MTA-treated and control mice, suggesting that MEL had a stronger stimulating effect on the lymphocytes than MTA. Understimulation of lymphokines from MEL-treated mice, peritoneal macrophages from MTA-treated mice produced a greater inhibition of the growth of murine mastocytoma P815 cells than that produced by macrophages from control and MEL-treated mice, suggesting that MTA was more potent than MEL in rendering the macrophages responsive to lymphokines. The results point to immunostimulatory actions of the pineal indoles MEL and MTA.

5-Methoxytryptamine↗

PubMed1993

Repressed activity of peritoneal macrophages in methimazole-induced hypothyroid mice.

In this study we compared the functions of normal peritoneal macrophages with those from methimazole-induced hypothyroid C57BL/6 mice. Methimazole (MMI) suppressed the expression of the tumor necrosis factor (TNF) gene in peritoneal macrophages (MAM) at both transcriptional and translational levels. The kinetics of TNF synthesis by MAM following in vivo and in vitro lipopolysaccharide (LPS) challenge were different, but both treatments resulted in significant decreases (P < 0.05) in TNF mRNA and protein after 60 min. Similarly, the production of reactive nitrogen and oxygen intermediates by MAM were significantly (P < 0.05) lower compared with control macrophages (CAM). In addition, the serum TNF protein was significantly lower (P < 0.05) in MMI-treated mice following intravenous LPS challenge for 90 min. These data suggested that peritoneal macrophages were inactivated in MMI-induced hypothyroid mice.

Animals↗

PubMed1993

The effects of electric current on bacteria colonising intravenous catheters.

The effect of a direct electric current (10 microA) on the growth of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis was investigated. When the ends of negatively-charged intravascular catheters were placed in nutrient agar seeded with bacteria, circular zones of inhibition of bacterial growth were observed around the catheters. The zones ranged from 6 to 16 mm in diameter according to the organism under test. Zones of inhibition were not produced around positively-charged catheters. Bacteria colonising the surfaces of catheters were similarly affected by the application of a 10 microA electric current. A negative electric current applied to colonised catheters for 4 to 24 h significantly reduced the number of adherent viable organisms as compared to controls. The results demonstrated that a constant electric current of low amperage might be used to reduce bacterial colonisation of intravascular catheters. This may offer a novel means of protecting catheters and other prosthetic devices from associated sepsis in vivo.

Bacterial Adhesion↗

PubMed1993

Monitoring of hospital water supplies for Legionella.

In order to determine the value of regular surveillance for Legionella in the prevention of hospital-acquired (nosocomial) legionellosis, water samples were obtained over a three-year period from 17 hospitals located in England and Scotland. Prior to the study, all of the hospitals had in operation defined protocols and maintenance schedules which followed national guidelines for the prevention of legionellosis in health care premises. Six samples, from key locations in the water system of each hospital, were taken at six-monthly intervals. Total viable bacterial count (TVC), coliform count and legionella cultures were performed on all the samples. No coliforms were detected in any of the samples, whereas the TVC was variable. Legionella pneumophila was isolated from both the hot and cold water supplies of two hospitals. The TVC was not related to the isolation of Legionella. Confirmation of the presence of Legionella was subsequently attributed to defects in the equipment and water maintenance programmes. It was concluded that the microbiological examination of water is an effective approach to the audit of the maintenance of hospital water systems in order to prevent legionellosis.

Colony Count, Microbial↗

PubMed1993

Antiproliferative effect of pineal indoles on cultured tumor cell lines.

The in vitro antiproliferative action of pineal indoles on several tumor cell lines including melanoma (B16), sarcoma (S180), macrophage-like cell line (PU5), fibroblasts (3T3), and choriocarcinoma (JAr) was examined by measuring the incorporation of 3H-thymidine by the tumor cells, and, in the case of melanoma cells, by also measuring the incorporation of 3H-leucine and 3H-uridine. Uptake of crystal violet was used to assess the viability of the tumor cells. The order of inhibitory potency of the indoles was found to be methoxytryptamine > melatonin, methoxytryptophol, hydroxytryptophol, and methoxyindoleacetic acid > serotonin and hydroxyindoleacetic acid. The possibility of an adverse effect of the indoles on the viability of normal cells was also investigated by employing a primary culture of rat hepatocytes. The release of glutamate-oxaloacetate transaminase by hepatocytes was not affected by the indoles, although the release of glutamate-pyruvate transaminase was increased to a small extent and the uptake of crystal violet was slightly inhibited.

3T3 Cells↗