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Biomedical subjects

W Shi

Publications and source records attributed to W Shi.

At least 163 records · Page 9Linked to original sources
PubMed1998

[Congenital cataract extraction with intraocular lens implantation in children].

OBJECTIVE: To evaluate the results of cataract extraction with intraocular lens (IOL) implantation in children. METHODS: Cataract extracapsular extraction with anterior vitrectomy and IOL implantation was performed on 104 eyes of 64 children with congenital cataract aged 1.5 - 14 years old. The visual acuity and possible complications were followed up for a mean period of 22 months. RESULTS: After operation 86.4% patients were relieved from blindness, 62.7% obtained corrected vision >or= 0.3, binocular vision and stereopsis were restored in 41.8% and 30.6% respectively. In 3 eyes secondary cataract developed and in 5 eyes slight iris capture occurred. CONCLUSIONS: Cataract extraction with anterior vitrectomy and IOL implantation is effective in pediatric cataract treatment. Most patients get remarkable improvement in visual acuity and visual function with minimal complications after surgery. The influence factors on the postoperative visual function need further study.

Adolescent↗
PubMed1998

[Treatment of intraocular fibrinous membrane by anterior chamber injection of tissue plasminogen activator after IOL implantation].

OBJECTIVE: To investigate the method of treatment of intraocular fibrinous membrane by tissue plasminogen activator (t-PA) after intraocular lens (IOL) implantation and evaluate its clinical results. METHODS: 58 eyes of 43 patients after cataract surgery were divided into three groups, and received t-PA anterior chamber (AC) injection or combined with YAG laser therapy at different times after the operation. Group 1 included 26 eyes which received 4 microg t-PA AC injection at the end of operation. In group 2, 22 eyes whose fibrinous membrane was formed 5 - 7 days after the operation were injected with 4 microg t-PA at that time. In group 3, 10 eyes with thicker membrane were given YAG laser treatment at postoperative 5 - 9 days and then 4 microg t-PA was injected into the AC. RESULTS: In group 1, hyphema occurred in 4 eyes, in 8 eyes at the pupillary region the fibrinous membrane was formed which was completely lysed after t-PA AC injection at postoperative 3 - 5 days. In group 2, the membrane was lysed within 24 hours in 20 of 22 eyes and no hyphema was found. In group 3, the membrane was lysed within 4 - 24 hours after t-PA injection in all cases, and no hyphema occurred. CONCLUSION: It is very effective to treat fibrinous membrane formation after IOL implantation by t-PA AC injection at postoperative 1 week when the AC inflammation is well controlled. The combined use of YAG laser with t-PA AC injection is much more effective for the treatment of such a membrane.

Adolescent↗
PubMed1998

[The choice of intraocular lens before cataract extraction for cases with high myopia].

OBJECTIVE: To study the choice of diopter and size of optical portion of intraocular lens (IOL) before cataract extraction for cases with high myopia. METHODS: Extracapsular cataract extraction (ECCE) or phacoemulsification with IOL implantation was performed on 60 cases (94 eyes) with high myopia (axial length > 26mm). The posterior chamber IOL selected and inserted was the one with the diopter and size of the optical portion suitable for the recipient to have a postoperative low myopia and easy to be examined with an ophthalmoscope. RESULTS: The postoperative eyes were of low myopia, -2.07 +/- 1.95 D. The larger size of optical portion was more suitable for ocular fundus examination. Great care was taken for phacoemulsification for cataractous nucleus below III grade. CONCLUSIONS: For patients with axial myopia, the IOL implanted should create low myopia postoperatively. Larger optic size is better for fundus examination. Phacoemulsification can produce less astigmatism and damage, but the indication must be controlled strictly.

Adolescent↗
PubMed1998

[Enrichment with polyamide and dual-wavelength spectrophotometric determination of gold and silver].

The absorbent performance of polyamide resin has been studied. Au(III) and Ag(I) easily react with [SCN]- to form complex anions in dilute nitric acid medium, and be adsorbed on the polyamide resin to enrich, and be separated from many other base metals. When Na2SO3 and NH3 x H2O is used as eluating agent, Au and Ag can be recovered quantitatively. Therein can be retreated and reused easily. In addition, we established a dual-wavelength spectrophotometric method which has been applied to the determination of Au(III) and Ag(I) in standard samples with relative standard deviation of less than 5.1%.

English Abstract↗
PubMed1997

Identification of two nervous system-specific members of the erg potassium channel gene family.

Two new potassium channel genes, erg2 and erg3, that are expressed in the nervous system of the rat were identified. These two genes form a small gene family with the previously described erg1 (HERG) gene. The erg2 and erg3 genes are expressed exclusively in the nervous system, in marked contrast to erg1, which is expressed in both neural and non-neural tissues. All three genes are expressed in peripheral sympathetic ganglia. The erg3 channel produces a current that has a large transient component at positive potentials, whereas the other two channels are slowly activating delayed rectifiers. Expression of the erg1 gene in the sympathetic nervous system has potential implications for the etiology of the LQT2 form of the human genetic disease long QT syndrome.

Animals↗
PubMed1997

Sensing antimonite and arsenite at the subattomole level with genetically engineered bioluminescent bacteria.

A highly sensitive and selective optical sensing system for antimonite has been developed using genetically engineered bacteria. The basis of this system is the ability of certain bacteria to survive in environments that are contaminated with antimonite, arsenite, and arsenate. The survival is conferred to the bacteria by the ars operon, which consists of five genes that code for three structural proteins, ArsA, ArsB, and ArsC, and two regulatory proteins, ArsD and ArsR. ArsA, ArsB, and ArsC form a protein pump system that extrudes antimonite, arsenite, and arsenate once these anions reach the cytoplasm of the bacterium. A method was developed for monitoring antimonite and arsenite by using a single plasmid that incorporates the regulatory gene of the extrusion system, arsR, and the genes of bacterial luciferase, luxA and luxB. In the designed plasmid, ArsR regulates the expression of bacterial luciferase in a manner that is dependent on the concentration of antimonite and arsenite in the sample. Thus, the bioluminescence emitted by luciferase can be related to the concentration of antimonite and arsenite in the sample. Concentrations for antimonite and arsenite in the order of 10(-5) M, which corresponds to subattomole levels, can be detected. This bacterial-based sensing system is highly selective for antimonite and arsenite.

Adenosine Triphosphatases↗
PubMed1997

The structure of L-aspartate ammonia-lyase from Escherichia coli.

The X-ray crystal structure of l-aspartate ammonia-lyase has been determined to 2.8 A resolution. The enzyme contains three domains, and each domain is composed almost completely of alpha helices. The central domain is composed of five long helices. In the tetramer, these five helices form a 20-helix cluster. Such clusters have also been seen in delta-crystallin and in fumarase. The active site of aspartase has been located in a region that contains side chains from three different subunits. The structure of the apoenzyme has made it possible to identify some of the residues that are involved in binding the substrate. These residues have been examined by site-directed mutagenesis, and their putative roles have been assigned [Jayasekera, M. M. K., Shi, W., Farber, G. K., & Viola, R. E. (1997) Biochemistry 36, 9145-9150].

Aspartate Ammonia-Lyase↗
PubMed1997

Evaluation of functionally important amino acids in L-aspartate ammonia-lyase from Escherichia coli.

The high-resolution structure of l-aspartate ammonia-lyase from Escherichia coli has recently been determined [Shi, W., Dunbar, J., Jayasekera, M. M. K., Viola, R. E., & Farber, G. K. (1997) Biochemistry 36, 9136-9144]. An examination of the putative active site has been carried out, with the active site located in a cleft that contains the functionally significant lysine 327. A list of potential active site residues has been generated based on their proximity to this active site lysine, sequence homology comparisons with other members of the aspartase-fumarase enzyme family, and the necessity for chemically reasonable functionalities for the proposed roles. The five most likely candidates in the putative active site cleft have been examined by site-directed mutagenesis to test their feasibility for either substrate binding or acid-base catalytic roles. Arginine and lysine residues have been identified that appear to function in the orientation and binding of aspartic acid at the enzyme active site. Some tentative assignments have also been made of the acid and base catalytic groups that are proposed to be involved in the deamination reaction.

Amino Acids↗
PubMed1997

STAT3 as an adapter to couple phosphatidylinositol 3-kinase to the IFNAR1 chain of the type I interferon receptor.

STAT (signal transducers and activators of transcription) proteins undergo cytokine-dependent phosphorylation on serine and tyrosine. STAT3, a transcription factor for acute phase response genes, was found to act as an adapter molecule in signal transduction from the type I interferon receptor. STAT3 bound to a conserved sequence in the cytoplasmic tail of the IFNAR1 chain of the receptor and underwent interferon-dependent tyrosine phosphorylation. The p85 regulatory subunit of phosphatidylinositol 3-kinase, which activates a series of serine kinases, bound to phosphorylated STAT3 and subsequently underwent tyrosine phosphorylation. Thus, STAT3 acts as an adapter to couple another signaling pathway to the interferon receptor.

Acute-Phase Proteins↗
PubMed1997

Targeted disruption of the mouse Stat3 gene leads to early embryonic lethality.

Signal transducer and activator of transcription (STAT) proteins have been shown to mediate biological actions in response to cytokines. Stat3, a member of the STAT family, is activated by a variety of cytokines, including the interleukin 6 family of cytokines, leptin, granulocyte colony-stimulating factor, and epidermal growth factor. To address the biological function of Stat3, we generated mice deficient in Stat3 by gene targeting. No viable Stat3-deficient mice could be obtained from heterozygote intercross. Analysis of embryos at several gestation times revealed that Stat3-deficient embryos showed a rapid degeneration between embryonic days 6.5 and 7.5, although they developed into the egg cylinder stage until embryonic day 6.0. These results demonstrate that Stat3 is essential for the early development of mouse embryos.

Animals↗
PubMed1997

OCI-5/rat glypican-3 binds to fibroblast growth factor-2 but not to insulin-like growth factor-2.

OCI-5 encodes the rat homologue of glypican-3, a membrane-bound heparan sulfate proteoglycan that is mutated in the Simpson-Golabi-Behmel overgrowth syndrome. OCI-5 and glypican-3 are 95% identical. It has been recently suggested that glypican-3 interacts with insulin-like growth factor-2 (IGF-2) and that this interaction regulates IGF-2 activity. We report here that we have transfected OCI-5 into two different cell lines, and we have not been able to detect an interaction between the OCI-5 proteoglycan produced by the transfected cells and IGF-2. On the other hand, we have found that OCI-5 interacts with FGF-2, as has already been shown for glypican-1. This interaction is mediated by the heparan sulfate chains of OCI-5 because it can be inhibited by heparin or by heparitinase.

Animals↗
PubMed1997

Aspartate-407 in Rhodobacter sphaeroides cytochrome c oxidase is not required for proton pumping or manganese binding.

Several pathways for proton transport in cytochrome c oxidase have been proposed on the basis of mutational analysis and X-ray structure: at least one for moving "pumped" protons from the interior to exterior of the membrane and a separate route for transporting "substrate" protons from the interior to the binuclear metal center to combine with oxygen to make H2O. According to the crystal structures of cytochrome c oxidase, Asp407 (Rhodobacter sphaeroides numbering) is at the interface of subunit I and subunit II of the oxidase, in a negative patch proposed to be the proton exit site in a pumping pathway, as well as a possible ligand to Mg [Iwata et al. (1995) Nature 376, 660-669]. Three mutants at the Asp407 position of R. sphaeroides cytochrome oxidase, Asp407Ala, Asp407Asn, and Asp407Cys, have been purified and characterized. All showed electron transfer activity, and pH dependence of activity, similar to that of the wild type enzyme and no major structural changes, as evidenced by visible, EPR, and resonance Raman spectroscopy. When reconstituted into artificial vesicles, the purified mutants pumped protons with normal efficiency and responded to the membrane pH and electrical gradients in a manner similar to that of wild type. Furthermore, the EPR spectra and Mn quantitation analysis of mutants grown in high Mn indicated no significant alteration in the Mn/Mg site. These results suggest that Asp407 does not play a critical role in proton translocation or in Mn/Mg binding.

Aspartic Acid↗
PubMed1997

Effects of maternal oral administration of monosodium glutamate at a late stage of pregnancy on developing mouse fetal brain.

Monosodium glutamate (MSG) was shown to penetrate placental barrier and to distribute to embryonic tissues using [3H]glutamic acid ([3H]Glu) as a tracer. However, the distribution is not even; the uptake of MSG in the fetal brain was twice as great as that in the maternal brain in Kunming mice. Other maternal mice were given per os MSG (2.5 mg/g or 4.0 mg/g body weight) at 17-21 days of pregnancy, and their offspring behaviors studied. The results showed that maternal oral administration of MSG at a late stage of pregnancy decreased the threshold of convulsion in the litters at 10 days of age. Y-maze discrimination learning was significantly impaired in the 60-day-old filial mice. On the other hand, no significant difference in spatial learning or tail flick latency was measured between the experimental animals and the controls. The filial mice of MSG-treated mothers could either not grasp a rope tightly, or grasped the rope tightly but could not crawl along the rope at the beginning of the training. However, such mice, after training, could grasp and crawl along the rope as well as controls. Obvious neuronal damage was not detected in the periventricular organs or the hypothalamus under a light microscope. The rate of weight gain for experimental animals was greater than for controls throughout the period from 20 to 90 days. Mating of treated males with treated females resulted in pregnancies and normal offspring, indicating that oral administration of MSG at a late stage of pregnancy did not affected the reproductive capacity of the offspring. The possible differences and relationship between MSG-induced damage to developing human and rodent brain are discussed.

Administration, Oral↗
PubMed1997

Scanning Transmission X-Ray Microscopy: A New Method for the Investigation of Aggregation in Silica

During the preparation of silica by acidification of water glass, primary silica particles form extended and ramified aggregates. The growing aggregates form a gel, a tenuous network of interconnected aggregates. After aging and drying of the wet gel, porous silica is obtained. To study the extremely vulnerable aggregates only noninvasive methods are allowed. Moreover, because of the colloidal scale many methods based on (atomic or molecular scale) spectroscopy are not informative. Scanning transmission x-ray microscopy (STXM), using high-brilliance synchrotron radiation at 3.25 nm (380 eV) and 2.60 nm (480 eV) as an X-ray source, provides a new technique to obtain direct images of wet or solved aggregates at a 50-5000 nm scale. The 50 nm resolution is sufficient to provide excellent images of fractal structures. In this paper the principles of STXM are discussed in relation to investigations of wet gel systems like silica gel.

Journal Article↗
PubMed1997

Genetically engineered bacteria: electrochemical sensing systems for antimonite and arsenite.

A bacterial sensing system that responds selectively to antimonite and arsenite has been investigated. The bacteria used in these studies have been genetically engineered to produce the enzyme beta-galactosidase in response to these ions. This is accomplished by using a plasmid that incorporates the gene for beta-galactosidase (reporter gene) under the control of the promoter of the ars operon. This plasmid also encodes for the ArsR protein, a regulatory protein of the ars operon, which, in the absence of antimonite or arsenite, restricts the expression of beta-galactosidase. In the presence of antimonite or arsenite the ArsR protein is released from the operator/ promoter region of the ars operon and beta-galactosidase is expressed. The activity of this enzyme was monitored electrochemically using p-aminophenyl beta-D-galactopyranoside as the substrate. The bacterial sensing system responds selectively to arsenite and antimonite (and to a lesser extent arsenate) and shows no significant response to phosphate, sulfate, nitrate, and carbonate.

Antimony↗
PubMed1997

Endothelin reactivity and receptor profile of pulmonary vessels in postobstructive pulmonary vasculopathy.

Chronic ligation of one pulmonary artery results in pulmonary vascular remodeling and bronchial angiogenesis, collectively known as postobstructive pulmonary vasculopathy (POPV). To determine whether the reactivity of pulmonary vessels to endothelins (ET) was altered in POPV and to explore potential mechanisms, we ligated the left main pulmonary artery of 18 rats. Four weeks later, using a lung explant technique, we compared POPV lungs with controls for contractile responses of intrapulmonary vessels to ET-1 and ET-3 and for relaxant responses to ET-1 and sodium nitroprusside (SNP) after precontraction with U-46619. Morphometric measurements were made on vessels studied pharmacologically. Competition receptor binding studies with 125I-labeled ET-1 and unlabeled ET-1 and BQ-123 were performed using membrane proteins of pulmonary vessels. We found, in arteries, that contractile responses to ET-1 and ET-3 were significantly increased and that relaxant responses to ET-1 but not to SNP were reduced; in veins, only relaxation to SNP was increased. Morphometry showed that arteries and veins in POPV had reduced diameters without altered muscle thickness. Receptor binding studies showed that the proportion of ETA receptors in arteries was significantly increased in POPV (66%) vs. controls (54%). We conclude that, in POPV, the increase in reactivity to ET-1 and ET-3 is primarily related to an augmented proportion of ETA receptors.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗