Biomedical subjects

S Liu

Publications and source records attributed to S Liu.

At least 433 records · Page 24Linked to original sources

PubMed1999

The role of protein phosphatases in the expression of inducible nitric oxide synthase in the rat hepatocyte.

Previously, we demonstrated that nuclear factor-kappaB (NF-kappaB) mediates cytokine-induced hepatic inducible nitric oxide synthase (iNOS) expression. NF-kappaB activation is regulated by kinases and phosphatases whose function is only beginning to be understood. Therefore, experiments were performed to determine the role of protein phosphatases (PPase) in cytokine-induced iNOS expression. Hepatocytes were stimulated with cytokines in the presence or absence of tyrosine phosphatase inhibitors (pervanadate [PV], phenylarsine oxide [PAO]) and a serine-threonine phosphatase inhibitor (okadaic acid [OA]). Cytokines induced hepatocyte iNOS mRNA, protein, and NO2- production that was substantially decreased by the addition of the tyrosine phosphatase inhibitors (PAO and PV). The serine-threonine phosphatase inhibitor (OA) decreased NO release and protein levels in a concentration-dependent fashion; however, iNOS mRNA levels were not significantly reduced. Nuclear run-on experiments demonstrated that protein tyrosine phosphatases (PTPases) are required for iNOS transcription, while the serine-threonine phosphatase inhibitor (OA) had no effect on iNOS transcription. Electromobility shift assays (EMSAs) revealed that the tyrosine-phosphatase inhibitors blocked cytokine-induced NF-kappaB activation, while OA did not have a significant effect on NF-kappaB DNA binding activity. Therefore, tyrosine phosphatases are involved in the regulation of cytokine-induced activation of NF-kappaB, while serine-threonine phosphatases posttranscriptionally regulate iNOS translation. These results identify the regulatory role of specific protein phosphatases (PPases) in hepatic iNOS expression.

Animals↗

PubMed1999

Bacterial expression and characterization of functional recombinant triosephosphate isomerase from Schistosoma japonicum.

The dimeric enzyme triosephosphate isomerase (TPI) converts glyceraldehyde-3-phosphate to dehydroxyacetone phosphate, a key reaction in glycolysis. Previous studies of the native enzyme in the human blood-flukes belonging to the genus Schistosoma have indicated that TPI is a promising anti-schistosome vaccine antigen. However, a recombinant form of the enzyme is required as an alternative to the impractical option of using biochemically purified TPI obtained from worm tissue for large-scale vaccine use. We previously cloned and sequenced a full-length cDNA encoding the TPI of the Asian (Chinese strain) schistosome Schistosoma japonicum (SjcTPI). We now report very high level bacterial expression of this cDNA and the subsequent purification of the recombinant protein to >98% homogeneity under nondenaturing conditions. The recombinant SjcTPI (re-SjcTPI) was shown to be enzymatically active with a specific activity of 7687 units/mg protein, an activity higher than that of commercially obtained porcine TPI tested concurrently under the same assay conditions. The K(m) value for the re-SjcTPI using glyceraldehyde-3-phosphate as substrate was 406.7 microM, which is similar to the K(m) values reported for the yeast enzyme and various mammalian TPIs. With the availability of substantial amounts of enzymatically active and readily purified re-SjcTPI made in bacteria we can now test whether the recombinant protein can induce a similar level of protection in vaccination/challenge experiments as the native, biochemically purified enzyme.

Animals↗

PubMed1999

Immunohistochemical study of T lymphocyte subsets on frozen substituted plastic embedding section of the bone marrow from patients with myelodysplastic syndrome and its clinical implication.

An immunohistochemical study of T lymphocyte subsets on frozen substituted plastic embedding bone marrow sections obtained from 10 patients with myelodysplastic syndrome (MDS) was presented. The results of qualitative and quantitative immunohistochemical analysis are as follows: (1) Labile antigens of T lymphocytes were well preserved, thus allowing analysis of distribution of T lymphocyte subsets in situ: (2) the average number of T3, T4 and T8 lymphocyte of the diffuse infiltrate was about 2%, 0.4%, 0.5%, respectively, of all nucleated cells in bone marrow, and T4/T8 of T cells were below 1.0 in patients with MDS; (3) there were cases of RAS showing T lymphocyte aggregation in bone marrow, but no patient exhibited progressive refractory anemia with excess of blasts (RAEB) and RAEB in transformation (RAEBT). These findings indicated that the immunological abnormalities are of importance in the evaluation of pathogenesis and prognosis of MDS.

Aged↗

PubMed1999

Intrauterine infusion of bacterial lipopolysaccharide (LPS) prior to mating has no adverse effect on fertility, fetal survival and fetal development.

Lipopolysaccharide (LPS, endotoxin) is a component of the cell wall of gram-negative bacteria and a potent inducer of severe inflammatory reactions. In mice, systemically administered LPS induces fetal resorption and increases fetal mortality. However, effects of intrauterine LPS on fertility, fetal survival and development have not been reported. In the present study, pigs were used to determine the effect of intrauterine infused LPS on fertility, fetal survival and development. Prior to mating, gilts received intrauterine infusion of either a single dose of saline or increasing doses of LPS in saline using an insemination catheter. On day 30 of pregnancy, gilts were hysterectomized and litter size, fetal length, number of corpora lutea (CL), ovarian and placental weights, and allantoic and amniotic fluid volumes were recorded. Blood progesterone levels from days 10-30 of pregnancy were also determined. Results indicated that intrauterine infusion of LPS had no adverse effects on blood progesterone levels, fertility, fetal survival or fetal development. Intrauterine injection of LPS did cause an increase in fetal weight and amniotic fluid volume (P < 0.05). These results suggest that sperm, oocytes and gametes are tolerant of local LPS challenge and, to some extent, this mechanism protects gametes and conceptuses from maternal response to mating introduced bacteria and their potential endotoxins.

Amniotic Fluid↗

PubMed1999

Ribozyme-mediated specific gene replacement of the alpha1-antitrypsin gene in human hepatoma cells.

BACKGROUND/AIMS: Some of the mutant forms of cellular proteins not only lose their function, but also cause diseases by their toxic effects. One of the challenging tasks in the field of gene therapy will be "gene replacement" accomplished by inhibiting mutant gene expression and providing normal function of the same gene, simultaneously. Although lung involvement in alpha1-antrypsin (alpha1-AT) deficiency is caused by the lack of alpha1-AT function, the liver involvement is due to the accumulation of the mutated alpha1-AT protein. Therefore, one possible approach to prevent and treat the disease manifestations of alpha1-AT deficiency is to inhibit the expression of the mutated gene and replace it with normally functioning alpha1-AT protein in the liver. METHODS: For the inhibition of alpha1-AT gene expression, panels of alpha1-AT-specific hammerhead ribozymes designed to target different GUC sites in the alpha1-AT mRNA were evaluated in a human hepatoma cell-line, transduced with retroviral vectors which express ribozymes under the control of a human tRNA promoter. A bi-functional vector was also constructed, which contained a functional alpha1-AT ribozyme and was combined with a modified alpha1-AT gene, whose product was engineered to be resistant to the specific alpha1-AT ribozyme. This construct was transduced into target hepatoma cells. RESULTS: The transduced hepatoma cells showed the effective expression of modified alpha1-AT, under the conditions where the endogenous alpha1-AT gene expression was inhibited. CONCLUSION: This ribozyme-mediated, specific gene replacement is a first step in the gene therapy of alpha1-AT deficiency.

Base Sequence↗

PubMed1999

The experience in the treatment of patients with extensive full-thickness burns.

The aim of the present study is to analyze the changes of cure rate and the main causes of death in the last 40 years, and to summarize our experience in the treatment of extensive full-thickness burn patients. The clinical characteristics, cure rate and main causes of death of 73 cases with total burned area more than 90% TBSA and full-thickness burn area more than 70% TBSA were analyzed retrospectively. Among them, 21 cases (28.8%) were cured and 52 cases (71.2%) died. The cure rate increased significantly in the recent years, and the main causes of death changed from shock and sepsis in the time period 1959-1978 to sepsis and MODS in the past two decades. Due to the improvement of early comprehensive management of burn shock, aggressive surgical approach to full-thickness burn wound and potent systemic supporting measures, the survival rate increased significantly.

Adult↗

PubMed1999

An age-related decline in striatal taurine is correlated with a loss of dopaminergic markers.

Taurine is present in high concentration in the mammalian brain and is known to decline with aging. The present studies examined the relationship between the loss of striatal neurotransmitters and spatial learning ability in aged male Long-Evans rats. The effects of intrahippocampal infusions of neurotrophic factors-nerve growth factor (NGF) and brain-derived neurotrophic factor-were also examined for their ability to ameliorate the age-related decline in brain amino acid content. Taurine content was found to be significantly reduced in the striatum of aged rats (26 months old) that were impaired in spatial learning performance when compared to young unimpaired rats (5 months old). Aged rats that were behaviorally unimpaired had more modest reductions in taurine. Striatal dopamine content was also significantly reduced in aged learning-impaired rats. There was a significant (p < 0.001) correlation (r=0.61) between the striatal content of taurine and dopamine, but no such correlation was found for other striatal transmitters (glutamate, serotonin, norepinephrine). Treatment with neurotrophins had little effect on the age-related decline in striatal amino acids, although NGF treatment did improve spatial learning. These studies suggest (1) a link between age-related declines in striatal dopamine and taurine and (2) that NGF-induced improvement in spatial learning is not related to mechanisms involving changes in taurine or glutamate content.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1999

Identification of genes directly and indirectly involved in the insect transmission of African cassava mosaic geminivirus by Bemisia tabaci.

The inability to transmit progeny virus resulting from the cloned components of an isolate of African cassava mosaic virus originating from Kenya (ACMV-K) has been shown to be due to defects in both genomic components. This was achieved by the production of infectious pseudorecombinants between ACMV-K and the cloned components of a whitefly-transmissible ACMV isolate originating from Nigeria (ACMV-NOg). The exchange of gene fragments between ACMV-K and ACMV-NOg has been used to demonstrate that the defects responsible for lack of transmissibility reside on the coat protein and DNA B C1 gene of ACMV-K. The significance of these finding with respect to the present understanding of the function of these gene products are discussed.

Animals↗

PubMed1999

Transplanted embryonic stem cells survive, differentiate and promote recovery in injured rat spinal cord.

Transplantation approaches using cellular bridges, fetal central nervous system cells, fibroblasts expressing neurotrophin-3 (ref. 6), hybridoma cells expressing inhibitory protein-blocking antibodies, or olfactory nerves ensheathing glial cells transplanted into the acutely injured spinal cord have produced axonal regrowth or functional benefits. Transplants of rat or cat fetal spinal cord tissue into the chronically injured cord survive and integrate with the host cord, and may be associated with some functional improvements. In addition, rats transplanted with fetal spinal cord cells have shown improvements in some gait parameters, and the delayed transplantation of fetal raphe cells can enhance reflexes. We transplanted neural differentiated mouse embryonic stem cells into a rat spinal cord 9 days after traumatic injury. Histological analysis 2-5 weeks later showed that transplant-derived cells survived and differentiated into astrocytes, oligodendrocytes and neurons, and migrated as far as 8 mm away from the lesion edge. Furthermore, gait analysis demonstrated that transplanted rats showed hindlimb weight support and partial hindlimb coordination not found in 'sham-operated' controls or control rats transplanted with adult mouse neocortical cells.

Animals↗

PubMed1999

Functional group I metabotropic glutamate receptors in submucous plexus of guinea-pig ileum.

Intracellular recording methods and immunostaining revealed the existence of functional group I metabotropic glutamate receptors (mGluRs) in submucous plexus neurons of guinea-pig ileum. Selective group I, but not groups II or III metabotropic glutamate receptor agonists induced concentration-dependent, slowly-activating depolarizing responses. Group I metabotropic glutamate receptor antagonism observed with (S)-4-carboxyphenylglycine (S-4-CPG) (100 - 600 microM) was competitive as determined by Schild analysis (pA(2)=3.81+/-0.02). Neither the group II and III metabotropic nor ionotropic glutamate receptor antagonists altered responses evoked by group I receptor agonists. Immunoreactivities for metabotropic glutamate 1alpha and 5 receptors were found to locate exclusively in neurons in the submucous plexus of guinea-pig ileum with the highest density around the cell bodies. The results suggest that group I metabotropic glutamate receptors are functionally expressed in the submucous plexus of guinea-pig small intestine.

Animals↗

PubMed1999

A double blind, placebo controlled study of intracavernosal vasoactive intestinal polypeptide and phenotolamine mesylate in a novel auto-injector for the treatment of non-psychogenic erectile dysfunction.

Three hundred and four patients with non-psychogenic erectile dysfunction (ED) completed a dose assessment phase with intracavernosal injection utilizing 25 micrograms vasoactive intestinal polypeptide (VIP) combined with phentolamine mesylate 1.0 mg (VIP/P-1) or 2.0 mg (VIP/P-2) in an auto-injector for a response rate of 83.9%. In a sub-group of 183 patients who withdrew from one or more previous ED therapies, 82% responded with an erection suitable for intercourse. One hundred and ninety-five patients were subsequently treated in a placebo controlled phase. 75.1% responded to VIP/P-1, 12% to placebo (P < 0.001); 66.5% responded to VIP/P-2, 10.3% to placebo (P < 0.001), with the median duration of erection of 54 min. The principal adverse event was transient facial flushing in 2770 injections (33.9%). There was no pain post injection and two episodes of priapism (0.05%). Only nine patients withdrew because of adverse events. Over 85% and 95% of patients were satisfied with the drug and auto-injector, respectively. Over 81% of patients and 76% of partners reported an improved quality of life.

Adult↗

PubMed1999

Resolution beyond the rayleigh limit using beam displacement

Two fluorescence microscope systems which claim to achieve resolution beyond the Rayleigh limit have recently been described. These systems operate using two displaced beams focused on the sample and produce the image from the region of overlap. We describe an analogous system, which performs in a similar manner but does not rely on fluorescence. The imaging performance of these systems is analysed and we show that they all give improved resolution although, crucially, the optical bandwidth is not increased. These systems merely attenuate the lower spatial frequencies and, although such systems can be useful and operate in a manner analogous to pupil plane filters, it is important to appreciate that they do not offer true superresolution, contrary to the impression given in previous papers.

Journal Article↗

PubMed1999

Transplantation of neural progenitor and stem cells: developmental insights may suggest new therapies for spinal cord and other CNS dysfunction.

Multipotent neural progenitors and stem cells may integrate appropriately into the developing and degenerating central nervous system. They may also be effective in the replacement of genes, cells, and nondiffusible factors in either a widespread or a more circumscribed manner, depending on the therapeutic demands of the clinical situation. In addition, they may be uniquely responsive to some types of neurodegenerative conditions. We believe that these various appealing capabilities are the normal expression of basic biologic properties and attributes of a stem cell. The therapeutic utility of some of those properties is illustrated in this review of ongoing work in our laboratory, particularly with regard to spinal dysfunction. In these examples, we believe we have tapped into a mechanism that underlies a remarkable degree of natural plasticity programmed into the nervous system at the cellular level, and we have now exploited those properties for therapeutic ends.

Animals↗

PubMed1999

Whole-grain consumption and risk of coronary heart disease: results from the Nurses' Health Study.

BACKGROUND: Although current dietary guidelines for Americans recommend increased intake of grain products to prevent coronary heart disease (CHD), epidemiologic data relating whole-grain intake to the risk of CHD are sparse. OBJECTIVE: Our objective was to evaluate whether high whole-grain intake reduces risk of CHD in women. DESIGN: In 1984, 75521 women aged 38-63 y with no previous history of cardiovascular disease or diabetes completed a detailed, semiquantitative food-frequency questionnaire (SFFQ) and were followed for 10 y, completing SFFQs in 1986 and 1990. We used pooled logistic regression with 2-y intervals to model the incidence of CHD in relation to the cumulative average diet from all 3 cycles of SFFQs. RESULTS: During 729472 person-years of follow-up, we documented 761 cases of CHD (208 of fatal CHD and 553 of nonfatal myocardial infarction). After adjustment for age and smoking, increased whole-grain intake was associated with decreased risk of CHD. For increasing quintiles of intake, the corresponding relative risks (RRs) were 1.0 (reference), 0.86, 0.82, 0.72, and 0.67 (95% CI comparing 2 extreme quintiles: 0.54, 0.84; P for trend < 0.001). After additional adjustment for body mass index, postmenopausal hormone use, alcohol intake, multivitamin use, vitamin E supplement use, aspirin use, physical activity, and types of fat intake, these RRs were 1.0, 0.92, 0.93, 0.83, and 0.75 (95% CI: 0.59, 0.95; P for trend = 0.01). The inverse relation between whole-grain intake and CHD risk was even stronger in the subgroup of never smokers (RR = 0. 49 for extreme quintiles; 95% CI: 0.30, 0.79; P for trend = 0.003). The lower risk associated with higher whole-grain intake was not fully explained by its contribution to intakes of dietary fiber, folate, vitamin B-6, and vitamin E. CONCLUSIONS: Increased intake of whole grains may protect against CHD.

Adult↗

PubMed1999

Quantitative determination of LSD and a major metabolite, 2-oxo-3-hydroxy-LSD, in human urine by solid-phase extraction and gas chromatography-tandem mass spectrometry.

An assay has been developed for quantitative determination of lysergic acid diethylamide (LSD) and a major metabolite of LSD in human urine at concentrations as low as 10 pg/mL. In most LSD-positive urine samples the metabolite, 2-oxo-3-hydroxy-LSD, is present at higher concentrations than LSD and can be detected for a longer time than LSD after ingestion of the drug. Urine samples are extracted using Varian Bond Elut Certify extraction cartridges. Confirmatory identification is accomplished by trimethylsilylation of LSD and 2-oxo-3-hydroxy-LSD, followed by gas chromatography-tandem mass spectrometry analysis using positive ion chemical ionization and selected reaction monitoring. Commercially available lysergic acid methylpropylamide and 2-oxo-3-hydroxy-LAMPA are used as internal standards. With selected reaction monitoring, both compounds gave linear calibration curves from 10 pg/mL to 5000 pg/mL. Forty-nine human urine samples that had previously been shown to contain LSD were reanalyzed by the new method. These samples showed an average LSD concentration of 357 pg/mL and an average 2-oxo-3-hydroxy-LSD concentration of 3470 pg/mL. Additional experiments using clinical samples in which two subjects were dosed with LSD support the conclusion that analysis for 2-oxo-3-hydroxy-LSD can permit identification of LSD users for a longer period following ingestion than analysis for the parent drug.

Forensic Medicine↗

PubMed1999

Identification of a receptor-binding region within domain 4 of the protective antigen component of anthrax toxin.

Anthrax toxin from Bacillus anthracis is a three-component toxin consisting of lethal factor (LF), edema factor (EF), and protective antigen (PA). LF and EF are the catalytic components of the toxin, whereas PA is the receptor-binding component. To identify residues of PA that are involved in interaction with the cellular receptor, two solvent-exposed loops of domain 4 of PA (amino acids [aa] 679 to 693 and 704 to 723) were mutagenized, and the altered proteins purified and tested for toxicity in the presence of LF. In addition to the intended substitutions, novel mutations were introduced by errors that occurred during PCR. Substitutions within the large loop (aa 704 to 723) had no effect on PA activity. A mutated protein, LST-35, with three substitutions in the small loop (aa 679 to 693), bound weakly to the receptor and was nontoxic. A mutated protein, LST-8, with changes in three separate regions did not bind to receptor and was nontoxic. Toxicity was greatly decreased by truncation of the C-terminal 3 to 5 aa, but not by their substitution with nonnative residues or the extension of the terminus with nonnative sequences. Comparison of the 28 mutant proteins described here showed that the large loop (aa 704 to 722) is not involved in receptor binding, whereas residues in and near the small loop (aa 679 to 693) play an important role in receptor interaction. Other regions of domain 4, in particular residues at the extreme C terminus, appear to play a role in stabilizing a conformation needed for receptor-binding activity.

Amino Acid Sequence↗

PubMed1999

A case of jejunal intussusception with gastrointestinal bleeding caused by metastatic testicular germ cell cancer.

BACKGROUND/AIM: We report an unusual case of metastatic testicular germ cell tumor with its unusual presentation. METHOD: A patient presented to the San Joaquin General Hospital with gastrointestinal bleeding and obstruction and a testicular mass is described. The patient's clinical course is followed and the literature reviewed. RESULTS: The patient presented with jejunal intussusception due to metastatic testicular cancer. He was treated with orchiectomy and bowel resection followed by postoperative chemotherapy. CONCLUSION: This case illustrates the need to consider metastatic small-bowel obstruction and/or intussusception in patients presenting with testicular mass and abdominal pain.

Adult↗

PubMed1999

Hypoglycemia and impaired hepatic glucose production in mice with a deletion of the C/EBPbeta gene.

The transcription factor CCAAT/enhancer-binding protein beta (C/EBPbeta) is enriched in liver and adipose tissue and controls the expression of a wide variety of genes coding for important metabolic pathways, including gluconeogenesis and lipid synthesis. To investigate the role of C/EBPbeta on glucose homeostasis, we studied mice with a targeted deletion of the gene for C/EBPbeta-/- mice. Adult C/EBPbeta-/- mice have hypoglycemia after an 18-hour fast, accompanied by lower hepatic glucose production (40% of that of wild-type mice), with no change in plasma insulin and a lower concentration of plasma free fatty acids (FFA). Glucagon infusion during a pancreatic clamp acutely stimulated hepatic glucose production by 38% in wild-type animals, with no change detected in C/EBPbeta-/- mice. Unexpectedly, both the basal and glucagon-stimulated hepatic cyclic adenosine monophosphate (cAMP) levels were lower in C/EBPbeta-/- mice, indicating an essential role for C/EBPbeta in controlling proximal signal transduction. Fasting hypoglycemia was associated with normal levels of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) gene expression, however net liver glycogenolysis was impaired in C/EBPbeta-/- mice. FFA release from isolated adipose tissue in response to epinephrine was 68% lower in C/EBPbeta-/- mice than in control animals; however, N6,O2'-dibutyryladenosine (Bt2) cAMP stimulated a twofold increase in FFA release in C/EBPbeta-/- compared with no further increase in wild-type mice. Because a deletion in the gene for C/EBPbeta reduces blood glucose and circulating FFA, it could be an important therapeutic target for the treatment of non-insulin-dependent diabetes and possibly obesity, based on designing antagonists that decrease C/EBPbeta activity.

Animals↗