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Biomedical subjects

W Shi

Publications and source records attributed to W Shi.

At least 235 records · Page 13Linked to original sources
PubMed1993

Adverse conditions which cause lack of flagella in Escherichia coli.

Wild-type Escherichia coli was not motile when grown in tryptone broth under the following adverse conditions: the presence of high temperature [J. Adler and B. Templeton, J. Gen. Microbiol. 46:175-184, 1967; R. B. Morrison and J. McCapra, Nature (London) 192:774-776, 1961; K. Ogiuti, Jpn. J. Exp. Med. 14:19-28, 1936], high concentrations of salts, high concentrations of carbohydrates, high concentrations of low-molecular-weight alcohols, or the pressure of gyrase inhibitors. Under all these conditions, growth was necessary for the loss of motility. This loss of motility was correlated with a reduction in the amount of cellular flagellin. We isolated and studied mutants that are resistant to suppression of motility by some of these conditions, because of the ability to synthesize flagella under these conditions. The mutations were mapped to 42 min, a region of the chromosome where many of the flagellar genes map. We also studied the effect of a preexisting gyrA mutation which allowed flagellar formation in the presence of nalidixate.

Cell Movement↗
PubMed1993

Mechanism of adverse conditions causing lack of flagella in Escherichia coli.

Escherichia coli lacks flagella when grown in tryptone broth in the presence of various adverse conditions (C. Li, C. J. Louise, W. Shi, and J. Adler, J. Bacteriol. 175:2229-2235, 1993). Now, the synthesis, rather than the degradation, of flagellin was shown to be inhibited. Studies of transcriptional fusions of flagellar operons to the lacZ gene revealed that transcription of the flagellar genes was reduced in cells grown under these adverse conditions. Increasing gene dosage of the flhD operon by a plasmid partially suppressed the nonflagellation caused by some adverse conditions. The signal which shuts off the synthesis of flagella under adverse conditions remains to be discovered. This shutting-off process does not result from catabolite repression or from signals from the chemotaxis system.

Chemotaxis↗
PubMed1993

Role of transforming growth factor alpha (TGF-alpha) in the transformation of ras-transfected rat intestinal epithelial cells.

Most intestinal tumors express transforming growth factor alpha (TGF-alpha) while normal immature crypt cells, the targets for tumor initiation, do not. We have used a rat intestinal cell line derived from immature epithelial crypt cells (IEC-18) to investigate the role of this growth factor in intestinal tumorigenesis. ras transformation of IEC-18 cells induces expression and secretion of TGF-alpha. By studying several independently derived IEC-ras clones, we have established that the amount of TGF-alpha secreted is proportional to the level of activated ras expressed by each clone. The growth of all ras-transformed IEC clones is significantly inhibited by neutralizing antibodies against TGF-alpha and by an antisense TGF-alpha expression vector, indicating a mitogenic role for this growth factor through an autocrine loop. To determine whether TGF-alpha itself can transform intestinal cells, IEC-18 clones transfected with TGF-alpha expression vectors were isolated and characterized. None of the TGF-alpha-expressing clones show any signs of tumorigenic transformation even when they secrete as much TGF-alpha as the IEC-ras clones. It seems, therefore, that TGF-alpha per se does not have the capacity to transform rat epithelial intestinal cells and that its role is mostly related to autocrine growth stimulation.

Animals↗
PubMed1992

Mutational identification of an essential tryptophan in tryptophanyl-tRNA synthetase of Bacillus subtilis.

The strongly conserved single tryptophan residue, Trp92, in Bacillus subtilis tryptophanyl-tRNA synthetase has been mutagenized via site direction singly into Gln, Ala, and Phe. All three mutant enzymes were inactive toward the catalysis of tRNA tryptophanylation. The Trp92----Phe mutant has been subcloned into the high expression plasmid pKK223-3 to yield the recombinant plasmid pKSW-F92. Growth of bacteria carrying the latter plasmid made possible the purification of the mutant TrpRS-F92 enzyme to homogeneity. This mutant enzyme was deficient in ultraviolet absorbance and fluorescence relative to the wild type enzyme and inactive in the partial reaction of Trp-activation as well as the overall reaction of tRNA tryptophanylation. Furthermore, unlike the wild type B. subtilis trpS gene, the mutant trpS-F92 gene upon transformation into Escherichia coli trpS 10343 failed to complement the temperature sensitive trpS mutation of the host cells. Trp92 therefore represents an essential residue both in vitro and in vivo for the function of the tryptophanyl-tRNA synthetase.

Amino Acid Sequence↗
PubMed1992

DnaK, DnaJ, and GrpE are required for flagellum synthesis in Escherichia coli.

The DnaK, DnaJ, and GrpE heat shock proteins are required for motility of Escherichia coli. Cells deleted for dnaK or dnaJ, or with some mutations in the dnaK or grpE gene, are nonmotile, lack flagella, exhibit a 10- to 20-fold decrease in the rate of synthesis of flagellin, and show reduced rates of transcription of both the flhD master operon (encoding FlhD and FlhC) and the fliA operon (encoding sigma F). Genetic studies suggest that DnaK and DnaJ define a regulatory pathway affecting flhD and fliA synthesis that is independent of cyclic AMP-catabolite gene activator protein or the chemotaxis system.

Bacterial Proteins↗
PubMed1992

[Syndrome differentiation in traditional Chinese medicine in chronic aplastic anemia; T-lymphocyte subpopulation in peripheral blood and erythrocyte C3b receptors].

UNLABELLED: In this paper, the Syndrome Differentiation in TCM and the determination on T-lymphocyte subpopulation and RBC C3b receptor were carried out by using indirect SPA assay and RBC C3b receptor ring test among 51 chronic aplastic anemia patients. RESULT: The OKT3, OKT4 and OKT4/OKT8 ratio in groups of Kidney-Yin Deficiency group were lower, while the OKT8 was higher than that of controls. In the group of both Kidney-Yin and Yang Deficiency, OKT4 and OKT4/OKT8 ratio were lower. and the value of OKT8 is higher than that of controls. The OKT8 in the Kidney-Yang Deficiency group was higher. and the ratio of OKT4/OKT8 was lower than that of controls. The OKT8 in the Kidney-Yin Deficiency group among three groups increased higher than that of other two groups. while the OKT4/OKT8 ratio reduced. The OKT4/OKT8 ratio in the group of both Kidney-Yin and Yang Deficiency was higher than that of Kidney-Yang Deficiency group. Among the three groups, the rosette rates of RBC C3b receptor were lower than controls. The above-mentioned data were statistically significant. These characteristic changes could be used as a reference of microcosmic Syndrome Differentiation and also a guide for how to apply the immunosuppressant and immunopotentiator.

Adolescent↗
PubMed1992

[Expression and secretion of human interferon alpha A in yeast Kluyveromyces lactis].

The vector pE1 is derived from the plasmid pKD1 isolated from the yeast Kluyveromyces lactis. It can be maintained stably in the yeast K. lactis at high copy number. We explored the possibility of using the pKD1/K. lactis system for heterologous gene expression. The human interferon alpha A secretion cassette was inserted into pE1. The obtained plasmid, pE-IFN1, showed slightly instability when compared to pE1. The data showed that the secretion signal sequence of the alpha factor of Saccharomyces cerevisiae was functionally active in K. lactis. The K. lactis transformants carrying pE-IFN1 secreted efficiently IFN into the growth medium when they were grown in nonselective medium. The total amount of IFN released reached 1-2 mg per liter of culture supernatant.

Gene Expression↗
PubMed1990

Fragmentation of biliary stones with a 308 nm excimer laser.

The use of a XeCl excimer laser (308 nm) for biliary stone fragmentation is reported. Laser energy is delivered via UV grade fused silica fibers to the target stones immersed in normal saline solution. Sixty biliary calculi--pigment (n = 40), and cholesterol (n = 20)--were fragmented in vitro. The total energy delivered per unit mass of the stone is kept constant. Two energy fluences (80 and 110 mJ/mm2) at two repetition rates (5 and 20 Hz) delivered through fibers of two core sizes (300 and 600 microns) are utilized to study the effect of different laser parameters on the fragmentation process. Although both pigment and cholesterol stones are susceptible to excimer laser fragmentation, higher fragmentation efficiency is obtained for the pigment stones than for the cholesterol stones. Our study suggests that higher energy fluence and larger fiber core size result in higher fragmentation efficiency for pigment stones. Fragmentation thresholds at stone surface for a variety of biliary calculi of known composition were measured. The threshold energy fluence is approximately 3 mJ/mm2 and 17 mJ/mm2 for pigment and cholesterol stones, respectively. Our study indicates that the 308 nm excimer laser may be effective as a laser lithotriptor with low threshold and good efficiency for biliary stone fragmentation.

Cholelithiasis↗
PubMed1990

Prevalence of lupus anticoagulant and anticardiolipin antibodies in a healthy population.

This study was designed to explore the incidence of lupus anticoagulant (LA) and anticardiolipin antibodies (ACA) and their relationship to each other in a healthy population of 499 blood donors. Plasma samples were tested for LA activity and IgG, IgM and polyvalent ACA. Prolongation of the kaolin clotting time of a mixture of 80% normal plasma and 20% test plasma compared to the normal (dKCT) was used to detect LA activity. A normal distribution of dKCT was found with the mean 3.5 seconds +/- SD 10.6 seconds. Forty subjects (8%) were greater than 10% of the normal control; among these, 18 (3.6%) were outside the 95% confidence limits. The median age (29.3) and sex (M = 12, F = 28) of the 40 subjects with prolonged KCT were significantly different (p less than 0.001) from the group as a whole, younger females predominating. The frequency distribution of IgG, IgM and polyvalent ACA was skewed and the majority did not have detectable levels. ACA concentration falling within 95% of the population group were regarded as normal. Applying this definition, abnormal IgG ACA was greater than 4.33 U/ml, IgM ACA greater than 3.55 U/ml and polyvalent ACA greater than 4.55 U/ml with a prevalence of 4.6%, 4.6% and 5.6% respectively. Of the subjects with positive ACA of any class there was no significant association with either age or sex or the presence of LA. Only three plasma samples had both activities. Neither ACA nor LA were associated with antinuclear antibodies (ANA) or rheumatoid factor (Rh factor). Thus, in a healthy population LA is found predominantly in younger females and neither LA or ACA appear to identify subjects with other autoimmune parameters such as ANA or Rh factor or, for that matter, each other.

Adult↗
PubMed1990

High-level expression of Bacillus subtilis tryptophanyl-tRNA synthetase in Escherichia coli.

The trpS gene encoding Bacillus subtilis tryptophanyl-tRNA synthetase (TrpRS) was prepared from the pUC8-derived pTSQ2 plasmid, mutagenized to introduce an EcoRI site immediately in front of the ATG start codon, and inserted into the pKK223-3 vector downstream to the tac promoter to yield the pKSW1 plasmid. Upon induction with isopropyl-beta-D-thiogalactopyranoside, Escherichia coli JM109[pKSW1] cells synthesized TrpRS to a level corresponding to 45% of total cell proteins. This high level of gene expression facilitates large scale preparation of TrpRS for physical studies, detection of in vivo degradation of mutant forms of TrpRS, and comparative assays of TrpRS by [3H]Trp-tRNA formation and by Trp-hydroxamate formation for the purpose of mutant characterization. Finally, since pKSW1 could complement the temperature-sensitive TrpRS mutation on E. coli trpS 10343 cells, defective mutations of the trpS gene on pKSW1 would be deductible on the basis of complementation testing.

Amino Acyl-tRNA Synthetases↗
PubMed1990

[Effects of radix Salviae Miltiorrhizae on visceral pain discharges in the posterior nucleus of the thalamus in cats].

Extracellular microelectrode method and stereotaxic technique of brain were used to investigate the effects of Radix Salviae Miltiorrhizae on the discharges of visceral pain in the posterior nucleus of thalamus(po)in cats. Experiments showed that Radix Salvia Miltiorrhizae inhibited the discharges of visceral pain in po, Radix Salviae Miltiorrhizae acts directly on the peripheral nerve trunk and cannot block its exciting conduction. This suggests that the analgesic effect of Radix Salviae Miltiorrhizae is exerted via central nervous system.

Analgesics↗
PubMed1990

CT manifestations of schizencephaly.

Schizencephaly is a neuronal migration malformation characterized by a cleft traversing the cerebral hemisphere. The cleft is lined by heterotopic gray matter, and the lips of the cleft may be fused or separated. Often associated with anomalies of the septum pellucidum or corpus callosum, and polymicrogyria, schizencephaly has characteristic CT findings. Of 17 patients with this lesion detected by CT 2 had bilateral schizencephaly.

Adolescent↗
PubMed1986

[Influences of inflammatory macrophages on the proliferation of mouse tumor cells in vitro].

Augmented growth of tumor cells of both syngeneic and allogeneic origin was often observed when these cells were cocultured with the peritoneal inflammatory macrophages of C57BL/6 mouse, induced by thioglycollate in vitro. While large doses of macrophage-activating factor (MAF) were required for activating these inflammatory macrophages to exert the tumoricidal activity, and much less (suboptimal) doses of MAF were required for activating their cytostatic effect on tumor cells. Whether the macrophage inhibits or enhances the tumor cell proliferation, depends not only on the degree of the activation of macrophage, but also on the macrophage/tumor cell ratio.

Animals↗
PubMedDate not supplied

Increased reactivity to endothelin of pulmonary arteries in long-term post-obstructive pulmonary vasculopathy in rats.

Post-obstructive pulmonary vasculopathy (POPV) describes the constellation of findings following chronic ligation of one pulmonary artery, including bronchial angiogenesis, pulmonary vasculopathy and increased vasoreactivity to pharmacologic agents. Previously, we found in rats with POPV of 28 days duration that maximal responses to endothelin-1 (ET-1) and ET-3 of pulmonary arteries but not veins were increased, and that relaxation of arteries to ET-1 was reduced, attributable to an elevated proportion of ETA over ETB receptors. To determine the reactivity of pulmonary vessels and airways to ET in protracted POPV, we ligated the left main pulmonary artery of nine rats. Eleven months later, using a lung explant technique, we compared contractile responses of pulmonary vessels and airways to ET-1 and ET-3 in POPV lungs with controls. Morphometric measurements were made on the vessels, and immunoreactivity to ET-1 and endothelin converting enzyme (ECE-1) studied. We found contractile responses to ET-1 and ET-3 significantly increased in arteries, but not veins or airways. Morphometry showed arteries and veins had reduced diameters with muscle thickening only in veins. Expression of ET-1 and ET-3 in vascular endothelial cells and airway epithelial cells were not altered significantly. Our data suggest that protracted POPV selectively enhanced the contractility of pulmonary arteries to ET, and is not attributable to medial muscle thickening.

Animals↗