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Biomedical subjects

Y Shi

Publications and source records attributed to Y Shi.

At least 541 records · Page 30Linked to original sources
PubMed1995

Cellodextrin efflux by the cellulolytic ruminal bacterium Fibrobacter succinogenes and its potential role in the growth of nonadherent bacteria.

When glucose or cellobiose was provided as an energy source for Fibrobacter succinogenes, there was a transient accumulation (as much as 0.4 mM hexose equivalent) of cellobiose or cellotriose, respectively, in the growth medium. Nongrowing cell suspensions converted cellobiose to cellotriose and longer-chain cellodextrins, and in this case the total cellodextrin concentration was as much as 20 mM (hexose equivalent). Because cell extracts of glucose- or cellobiose-grown cells cleaved cellobioise and cellotriose by phosphate-dependent reactions and glucose 1-phosphate was an end product, it appeared that cellodextrins were being produced by a reversible phosphorylase reaction. This conclusion was supported by the observation that the ratio of cellodextrins to cellodextrins with one greater hexose [n/(n + 1)] was approximately 4, a value similar to the equilibrium constant (Keq) of cellobiose phosphorylase (J. K. Alexander, J. Bacteriol. 81:903-910, 1961). When F. succinogenes was grown in a cellobiose-limited chemostat, cellobiose and cellotriose could both be detected, and the ratio of cellotriose to cellobiose was approximately 1 to 4. On the basis of these results, cellodextrin production is an equilibrium (mass action) function and not just an artifact of energy-rich cultural conditions. Cellodextrins could not be detected in low-dilution-rate, cellulose-limited continuous cultures, but these cultures had a large number of nonadherent cells. Because the nonadherent cells had a large reserve of polysaccharide and were observed at all stages of cell division, it appeared that they were utilizing cellodextrins as an energy source for growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

A switch region determines the cell type-specific positive or negative action of YY1 on the activity of the human papillomavirus type 18 promoter.

YY1 is a zinc finger transcription factor which acts as either a repressor or an activator dependent on the promoter context. YY1 is a potent activator of the genuine human papillomavirus type 18 (HPV-18) upstream regulatory region (URR) in HeLa cells, which are known for high-level expression of the HPV-18 early genes. The activating activity of YY1 is dependent on the presence of a newly identified switch region located upstream of the YY1 binding site. Deletion of this region causes YY1 to act as a repressor of HPV-18 promoter activity. In vivo footprinting of the HPV-18 URR and an in vitro electrophoretic mobility shift assay identified proteins binding to the switch region. Site-directed mutagenesis of the switch region and YY1 binding sites suggests that these two regions work in concert to yield high-level HPV-18 URR activity in HeLa cells but not in HepG2 cells, where HPV-18 is almost inactive. These data identified a novel mode of cell type-specific regulation of HPV-18 promoter activity by positive or negative action of YY1, determined by the switch region binding factor(s).

Base Sequence↗
PubMed1995

The carboxyl-terminal transactivation domain of heat shock factor 1 is negatively regulated and stress responsive.

We have characterized a stress-responsive transcriptional activation domain of mouse heat shock factor 1 (HSF1) by using chimeric GAL4-HSF1 fusion proteins. Fusion of the GAL4 DNA-binding domain to residues 124 to 503 of HSF1 results in a chimeric factor that binds DNA yet lacks any transcriptional activity. Transactivation is acquired upon exposure to heat shock or by deletion of a negative regulatory domain including part of the DNA-binding-domain-proximal leucine zippers. Analysis of a collection of GAL4-HSF1 deletion mutants revealed the minimal region for the constitutive transcriptional activator to map within the extreme carboxyl-terminal 108 amino acids, corresponding to a region rich in acidic and hydrophobic residues. Loss of residues 395 to 425 or 451 to 503, which are located at either end of this activation domain, severely diminished activity, indicating that the entire domain is required for transactivation. The minimal activation domain of HSF1 also confers enhanced transcriptional response to heat shock or cadmium treatment. These results demonstrate that the transcriptional activation domain of HSF1 is negatively regulated and that the signal for stress induction is mediated by interactions between the amino-terminal negative regulator and the carboxyl-terminal transcriptional activation domain.

3T3 Cells↗
PubMed1995

[An experimental study on the integrated effects of heat-cleaning and detoxifying drugs and fire-purging drugs used in combination].

Heat-cleaning and detoxifying drugs and fire-purging drugs used in combination have been proved able to restore the endotoxin-induced deviant of HCT, blood viscositites, PTT and fibrinolytic activity, and reduce the blood content of both endotoxin and PGE2 in rabbits. In addition, the combination can also decrease the pes swelling percentage in rats as well as evans blue extravasation volume in mice. In practice, however, it should be noted that the bitter and cold qualities of these two kinds of drugs may be harmful to health.

Albumins↗
PubMed1995

[The regulation of estradiol and progesterone in tumor necrosis factor production in vitro].

The production of tumor necrosis factor (TNF) induced by lipopolysaccharide (LPS) in peripheral blood mononuclear cells (PBMC) from normal woman were determined. The study investigated the role of regulation of estradiol (E2) and progesterone (P) in the production of TNF in-vitro. The results showed that PBMC would produce TNF when stimulated by E2 or P in culture in-vitro. The appropriate dosages were 125 pmol/L in E2 and 10-20 nmol/L in P. The findings suggested that some sex hormones could play a regulating role in the production of TNF by PBMC. E2 and P may be endogenous substances capable of inducing TNF production. The results revealed a beneficial aspect of sex hormones in anti-cancer treatment.

Adult↗
PubMed1995

[Report of a case of glucagonoma misdiagnosed as "eczema" and "hepatic angioma" for three years and review of literature].

Glucagonoma is a rare pancreatic tumor, necrolytic migratory erythema is its distinctive feature and it is often associated with diabetes mellitus, weight loss, anemia, hypoaminoacidemia, glossitis and stomatitis. We reported a case of glucagonoma misdiagnosed as "eczema" and "benign hepatic anginoma" for 3 years. His blood glucagon level was 1,758 ng/L. The results of abdominal B-mode ultrasonography and CT scan were negative, but selected arteriogram showed a tumor mass between the pancreatic body and tail. Before operation, treatment with octreotide and supply of amino acids were given with improvement of the skin lesion. After resection of the tumor from pancreas, necrolytic migratory erythema disapeared, but his blood level of glucagon and amino acids did not improve. It is suggested that any diabetic patient with chronic skin damage should be checked for blood glucagon level. In suspected cases, selected arteriogram will be helpful for location of the tumor. Vigorous resection of the pancreatic tumor should be done as soon as possible, even though there is already metastases.

Diagnostic Errors↗
PubMed1995

[Antitumor activities of 8-chloroadenosine in vivo and in vitro].

8-chloroadenosine showed marked activity against mice solid tumor hepatoma 22 (H22) and ascitic leukemia L-1210. At 100mg. Kg-1. /d x 7, the inhibition rate of H22 was 71.7 +/- 13.3% (P < 0.01) and 66.1 +/- 4.46% (P < 0.01), i.p. and i.v., respectively; at the same dose, the life-prolonging rate of mice bearing L-1210 was 124.0 +/- 22.1% (P < 0.01) and 104.2 +/- 20.1% (P < 0.01), i.p. and i.v., respectively. 8-chloroadenosine also showed activity against 3 human cancer cell lines in vitro. The IC50 values were determined by measuring cell growth using trypan blue dye exclusion. The results showed that HL-60 and K562, and human gastric cancer cell line MGc80-3 and IC50 values of 1. 8 mumol/L, 4.2 mumol/L and 1.56 mumol/L, respectively. The toxicity of 8-chloroadenosine was low, with LD50 of 1025.0 +/- 52.4 mg/kg for mice and 793.4 +/- 70.1 mg/kg for rats by single i.p. injection.

2-Chloroadenosine↗
PubMed1995

[Preliminary study on the anti-tubercular effect of Ottelia alismoides (L.) Pers].

In clinical trials, the extract of Ottelia alismoides cured two cases of bilateral tuberculosis of cervical lymph gland within 3 months. The result of drug sensitive test showed that water extract of this herb could kill or inhibit human tubercular bacteria effectively, which suggests that Ottelia alismoides is a promising medicinal herb with anti-tubercular effect.

Antitubercular Agents↗
PubMed1995

A pilot study of zileuton, a novel selective 5-lipoxygenase inhibitor, in patients with systemic lupus erythematosus.

OBJECTIVE: This is a pilot study of zileuton, a selective 5-lipoxygenase inhibitor in systemic lupus erythematosus (SLE). METHODS: Forty patients with SLE received zileuton 600 mg qid or placebo in an 8 week, randomized prospective, double blind trial. Disease activity was manifested largely by constitutional, articular, and skin manifestations with no evidence of active renal, cardiac, or neurologic involvement. Concomitant administration of nonsteroidal antiinflammatories, corticosteroids, or antimalarials was not permitted. Disease activity was determined at baseline and at Days 15 and 57 by assessment of arthritis severity, the Systemic Lupus Activity Measure (SLAM), investigator and patient global ratings, hematologic indices, and serologic measures including autoantibody titers, complement levels, and interleukin 2 receptors (IL-2R). Total body sulfidopeptide leukotriene synthesis was measured by urinary leukotriene E4 (LTE4) concentrations. RESULTS: Overall SLAM (the primary measure of efficacy in this study) was significantly improved with zileuton compared with placebo (-2.1 +/- 1.3, compared with an increase of 2.3 +/- 1.3 with placebo by Day 57, p = 0.048). Changes in individual SLAM subscores, arthritis severity, global ratings, and IL-2R levels compared with baseline did not achieve statistical significance, but were generally decreased from baseline with zileuton (indicating trends towards improvement) and increased from baseline with placebo (indicating trends towards clinical worsening). Urine LTE4 levels at Day 57 had increased from baseline in the placebo group (indicating worsening) and decreased in the zileuton group (indicating improvement). CONCLUSION: Selective 5-lipoxygenase inhibition may be beneficial in mild SLE.

Adult↗
PubMed1995

[Two case of androgen-secreting ovary tumor].

Two cases of androgen-secreting ovary tumor were reported. patients' chief complaints were menoxemia and hirsutism; clitorism was found by physical examination. Their serum testosterone (T) were high (10.2-6.7nmol/L) and could not be suppressed to normal range by middle-dose dexamethasone inhibiting test. ACTH stimulating test could not stimulate the high serum T to raise futher, but HCG stimulating test could increase serum T to higher level. Pelvic examination, type B ultrasonic and CT scan confirmed a mass on one of the ovaries. Sertoli-Leydig cell tumor and gynandroblastoma were proved respectively by pathology. After removing the tumor, their serum T were returned to normal level.

Adult↗
PubMed1995

Changes of nitric oxide and protective effects of nitric oxide inhibitors in newborn rats with sepsis.

In a newborn rat model of sepsis, the changes of nitric oxide and the protective effects of methylene blue or/and dexamethason were investigated. The results revealed that plasma nitric oxide levels were elevated at 6 h and peaked at 12 h after bacterial challenge. The treatment with methylene or/and dexamethasone was found to blunt hypoglycemia and hyperlacticemia, to reduce the occurrence rate of loss of response to pain, and to prolong the survival time. Moreover, therapy by dexamethasone was shown to decrease the 24 h mortality. The results suggested that nitric oxide play an important role during the course of fatal P. aeruginosa sepsis, but it is clear that the clinical value of nitric oxide and its inhibitors need to be further studied.

Animals↗
PubMed1995

Genetics of follicular thyroid cancer.

Cancer is a multistep phenomenon, and multiple cellular genetic lesions are involved in the emergence of the malignant neoplasm. Several early events, including ras mutations in follicular thyroid carcinoma and RET gene rearrangement in papillary tumors, have been implicated in the neoplastic transformation of thyrocytes. The stepwise array of mutations or deletions described to date in candidate oncogenes and tumor suppressor genes that are necessary for the advance to malignancy and for tumor progression await further investigation. The identification of additional, thyroid-cancer-specific lesions in these pathways is being further studied also.

Adenocarcinoma, Follicular↗
PubMed1995

[Chemical constituents of Hemsleya pengxianensis W.J. Chang].

Six compounds were isolated from the tubers of Hemsleya pengxianensis and identified as chikuset-susaponin IV a, hemslosides Ma1, G1, H1, dihydrocucurbitacin F-25-O-acetate and dihydrocucurbitacin F on the basis of chemical and physical properties and spectral data. They were all isolated from this plant for the first time.

Drugs, Chinese Herbal↗
PubMed1994

Higher autoantibody levels and recognition of a linear NH2-terminal epitope in the autoantigen GAD65, distinguish stiff-man syndrome from insulin-dependent diabetes mellitus.

The smaller form of the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD65) is a major autoantigen in two human diseases that affect its principal sites of expression. Thus, destruction of pancreatic beta cells, which results in insulin-dependent diabetes mellitus (IDDM), and impairment of GABA-ergic synaptic transmission in Stiff-Man syndrome (SMS) are both characterized by circulating autoantibodies to GAD65. Anti-GAD65 autoantibodies in IDDM are predominantly directed to conformational epitopes. Here we report the characterization of humoral autoimmune responses to GAD65 in 35 SMS patients, of whom 13 (37%) also had IDDM. All SMS patients immunoprecipitated native GAD65 and the main titers were orders of magnitude higher than in IDDM patients. Furthermore, in contrast to the situation in IDDM, autoantibodies in 35 of 35 (100%) of SMS patients recognized denatured GAD65 on Western blots. Two major patterns of epitope specificity were identified on Western blots. The first pattern, detected in 25 of 35 SMS patients (71%), of whom 11 had IDDM (44%), was predominantly reactive with a linear NH2-terminal epitope residing in the first eight amino acids of GAD65. Nine of nine individuals who were HLA-haplotyped in this group carried an IDDM susceptibility haplotype and HLA-DR3, DQw2 was particularly abundant. The second pattern, detected in 10 of 35 patients (29%) of whom two had IDDM (20%), included reactivity with the NH2-terminal epitope plus strong reactivity with one or more additional epitope(s) residing COOH-terminal to amino acid 101. The second epitope pattern may represent epitope spreading in the GAD65 molecule, but may also include some cases of epitope recognition associated with IDDM resistant HLA-haplotypes. The principal NH2-terminal linear epitope in GAD65 distinguishes the reactivity of SMS and IDDM autoantibodies and may be a determinant of pathogenicity for GABA-ergic neurons. The greater magnitude and distinct specificity of the humoral response to GAD65 in SMS may reflect a biased involvement of the T helper cell type 2 (Th2) subset of CD4+ T cells and antibody responses, whereas IDDM is likely mediated by the Th1 subset of CD4+ T cells and cytotoxic T cell responses.

Adult↗
PubMed1994

Defective production of anti-inflammatory cytokine, TGF-beta by T cell lines of patients with active multiple sclerosis.

Activated T lymphocytes play an important role in the pathogenesis of multiple sclerosis (MS). These T cells secrete both pro- and anti-inflammatory cytokines. We have studied the production of these two kinds of cytokines by PBL of patients with MS and compared it with normal controls and other autoimmune diseases (OAD). PBL of 29 patients with MS, 14 patients with OAD, and 14 healthy normal controls were cultured for 5 wk. PBL of MS patients produced more pro-inflammatory cytokines, IL-2, IFN-gamma and TNF/lymphotoxin, and less anti-inflammatory cytokine, TGF-beta, during wk 2 to 4 in culture than PBL of normal controls. PBL of MS patients also produced more IL-2 and TNF/lymphotoxin than PBL of OAD patients. Decreased TGF-beta production by lymphocytes of patients with MS correlated directly with disease activity. MS patients with active disease produced less TGF-beta than MS patients with stable disease. The cells producing TGF-beta were primarily CD8+ T cells and CD45RA+T cells. These findings emphasize the complexity of immune response in MS patients and suggest that the increased production of pro-inflammatory cytokines by lymphocytes of patients with MS, combined with the decreased production of TGF-beta (anti-inflammatory cytokine), may play an important role in the mechanisms and manifestations of MS.

Adult↗
PubMed1994

The mutant Escherichia coli F112W cyclophilin binds cyclosporin A in nearly identical conformation as human cyclophilin.

The periplasmic Escherichia coli cyclophilin is distantly related to human cyclophilin (34% sequence identity). Peptidyl-prolyl isomerase activity, cyclosporin A binding, and inhibition of the calcium-dependent phosphatase calcineurin are compared for human and E. coli wild-type and mutant proteins. Like human cyclophilin, the E. coli protein is a cis-trans peptidyl-prolyl isomerase. However, while the human protein binds cyclosporin A tightly (Kd = 17 nM), the E. coli protein does not (Kd = 3.4 microM). The mutant F112W E. coli cyclophilin has enhanced cyclosporin binding (Kd = 170 nM). As for the human protein, the complex of the E. coli mutant with cyclosporin A inhibits calcineurin. Here we describe the structure at pH 6.2 of cyclosporin A bound to the mutant E. coli cyclophilin as solved with solution NMR methods. Despite the low overall sequence identity, the structure of the bound cyclosporin A is virtually identical in both proteins. To assess differences of the cyclosporin binding site, the solution structure of wild-type E. coli cyclophilin was compared with structures of uncomplexed human cyclophilin A and with cyclosporin bound. Despite the structural similarity of bound cyclosporin A, the architecture of the binding site in the E. coli protein is substantially different at the site most distant to tryptophan 121 (human sequence). This site is constructed by a five-residue insertion in a loop of the E. coli protein, replacing another loop in the human protein.

Amino Acid Isomerases↗