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Biomedical subjects

W Su

Publications and source records attributed to W Su.

At least 127 records · Page 7Linked to original sources
PubMed1991

DNA looping between the origin of replication of Epstein-Barr virus and its enhancer site: stabilization of an origin complex with Epstein-Barr nuclear antigen 1.

Epstein-Barr nuclear antigen 1 (EBNA-1) is the only viral protein required to support replication of Epstein-Barr virus during the latent phase of its life cycle. The DNA segment required for latent replication, oriP, contains two essential binding regions for EBNA-1, termed FR and DS, that are separated by 1 kilobase pair. The FR site appears to function as a replicational enhancer providing for the start of replication at the DS site. We have used electron microscopy to visualize the interaction of EBNA-1 with its binding sites and to study the mechanism for communication between the FR and DS sites. We have found that DNA-bound EBNA-1 forms a DNA loop between the FR and DS sites. From these results, we suggest that EBNA-1 bound to the replicational enhancer acts by a DNA-looping mechanism to facilitate the initiation of DNA replication. Occupancy of the DS site alone is highly sensitive to competition with nonspecific DNA. In contrast, occupancy of the DS site by looping from FR is largely resistant to the competitor DNA. These experiments support the concept that enhancers act in cis from nearby sites to provide a high local concentration of regulatory proteins at their target sites and to stabilize regulatory interactions.

Animals↗
PubMed1991

Activity-induced decrease in early and late inhibitory synaptic conductances in hippocampus.

The use dependence of inhibitory postsynaptic potentials (IPSPs) and their underlying conductances was studied in area CA1 of the hippocampal brain slice preparation, using a two-pulse paradigm in which paired activation of two separate synaptic inputs resulted in changes in the second, or "primed" response. In intracellular current-clamp recordings, the "primed" response, normally triphasic, exhibited a larger, wider excitatory PSP (EPSP) component and greatly reduced or absent IPSP components. Maximal widening occurred when the interval between synaptic stimuli was between 200 and 250 msec. Hyperpolarization of the postsynaptic cell reversed both the early IPSP and the direction of change of the width of the "primed" EPSP response, suggesting that the changes in the "primed" waveform were not due to the addition of an unidentified inward current(s). Furthermore, the reduction of the IPSPs during the "primed" response could not be accounted for by the fact that the membrane potential of the postsynaptic cell was hyperpolarized and therefore closer to IPSP reversal potential. Using single-electrode voltage-clamp techniques, we found that the early inhibitory conductance generally decreased by approximately 50%, with little if any change in reversal potential. The late inhibitory conductance also showed a priming-induced decrease of approximately 95%. Finally, "primed" four-pulse bursts of stimuli induced a larger depolarization in the postsynaptic cell than did unprimed bursts, also with an optimal interval of about 250 msec. We conclude that activation of certain synaptic pathways in the hippocampus results in a temporal window of 200-300 msec during which inhibitory synaptic activity is depressed and excitatory synaptic transmission is maximally effective, especially if the excitation occurs in short bursts. Such a mechanism would endow the inhibitory synaptic components of the hippocampus with a "gating" function to control long-term synaptic modification at excitatory synapses in the same region.

Animals↗
PubMed1991

Changes in cutaneous microcirculation, hemorrheology and platelet aggregation function in dermatomyositis.

Marked disturbance of microcirculation was observed in 85 cases of dermatomyositis: decrease in number and irregular pattern of the capillaries, many being tortuous and dilated and having a slow and granular blood stream, as well as an increase of vascular permeability. The changes were more marked in cases with visceral disorders, or in active disease; however, there was no correlation between these changes and the duration of illness. Blood hyperviscosity was found in an hemorrheological study. The cause is considered to be due to high plasma viscosity, high fibrinogen levels, and increase of aggregation of erythrocytes and platelets. Modulation of microcirculation is advisable in the treatment of dermatomyositis.

Adolescent↗
PubMed1991

DNA looping between sites for transcriptional activation: self-association of DNA-bound Sp1.

The Sp1 protein activates transcription from many eukaryotic promoters. Sp1 can act in vivo from enhancer sites that are distal to the promoter and exhibit synergistic interaction with promoter-proximal binding sites. To investigate possible protein-protein interactions between DNA-bound Sp1 molecules, we have used electron microscopy to visualize the DNA-protein complexes. At the SV40 promoter, we observed the expected localized interaction at the Sp1 sites; in addition, we found that DNA-bound Sp1 served to associate two or more DNA molecules. At a modified thymidine kinase promoter, we observed a localized interaction at each of two binding locations that were separated by 1.8 kbp; in addition, we noted a substantial fraction of DNA molecules in which the distant binding regions were joined by a DNA loop. As judged by studies with mutant Sp1 proteins, the distant interactions depended on the glutamine-rich regions of Sp1 required for transcriptional activation. We conclude that DNA-bound Sp1 can self-associate, bringing together distant DNA segments. From the correlation between DNA looping in vitro and synergistic activation of the modified thymidine kinase promoter shown previously in vivo, we suggest that Sp1 exerts its transcriptional synergism by a direct protein-protein association that loops the intervening DNA. Our experiments support the DNA-looping model for the function of transcriptional enhancers.

Base Sequence↗
PubMed1991

The isolation and characterization of a Norwalk virus-specific cDNA.

Norwalk virus, an important cause of epidemic, acute, nonbacterial gastroenteritis in adults and children, has eluded adaptation to tissue culture, the development of an animal model, and molecular cloning. In this study, a portion of the Norwalk viral genome encoding an immunoreactive region was cloned from very small quantities of infected stool using sequence-independent single primer amplification. Six overlapping complementary DNA (cDNA) clones were isolated by immunologic screening. The expressed recombinant protein from a representative clone reacted with six of seven high titer. Norwalk-specific, postinfection sera but not with corresponding preinfection sera. Nucleic acid sequence for all clones defined a single open reading frame contiguous with the lambda gt11-expressed beta-galactosidase protein. Only oligonucleotide probes specific for the positive strand (defined by the open reading frame) hybridized to an RNaseA-sensitive, DNaseI-resistant nucleic acid sequence extracted from Norwalk-infected stool. Furthermore, RNA extracted from serial postinfection, but not preinfection, stools from three of five volunteers hybridized to a Norwalk virus cDNA probe. Clone-specific oligonucleotide probes hybridized with cesium chloride gradient fractions containing purified Norwalk virion. In conclusion, an antigenic, protein-coding region of the Norwalk virus genome has been identified. This epitope has potential utility in future sero- and molecular epidemiologic studies of Norwalk viral gastroenteritis.

Amino Acid Sequence↗
PubMed1991

[A study on immunization of polio vaccine. I. Observation on an improved immunization schedule].

This artical reports the result of serological observation on an improved immunization schedule of polio vaccine. The result shows that a good response can be obtained by immunizing an additional dose of the vaccine on the children of 18-24 month of age.serological convertion type I of neutralization antibody can be improved from 85% up to 96%, type II from 84% to 100%, and type III from 91% to 100%, with great increase of all the three types. The study proves that the additional immunization of the vaccine will effectively control over the incidence occurrence of the children who have received three doses of the vaccine within 3 years of age. An nation-wide extensive inoculation of the vaccine among the children who have received three doses of the vaccine is suggested. 81% of neonates inoculated with the vaccine within 24 hours after birth can discharge the polio-vaccine-virus through their intestinal canal and the inoculation has some effect on the improvement of the seroconversion obtained from the immunization of the three doses of the vaccine afterwards.

Antibodies, Viral↗
PubMed1991

[A study on immunization of polio vaccine. II. Comparison of responses obtained by different forms of polio vaccine].

A comparison study on the responses to the immunization of three different forms of polio vaccine, eg. Liquid I, Oral dragee candy I and Trivalent Oral dragee candy, on the susceptible children of 2-6 month of age was conducted in wujin County, Jiangsu Province The study showed no statistical difference between the responses to the three forms of the vaccine reaching 95-100%. For antibody GMT, Liquid I was the highest, with little difference between Liquid I and Oral dragee candy I and Trivalent Oral dragee candy vaccine in statistics. But, there was a significant statistical difference between Trivalent Oral dragee candy and Liquid I. Considering that it is not easy to inoculate the children of 2-4 months of age with oral dragee candy vaccine, it is suggested all the producers try their best to convert the present oral dragee candy form into Liquid.

Antibodies, Viral↗
PubMed1991

[Methanogens from feces of patients with intestine disorder].

Fecal specimens from 10 colorectal cancer, 1 duodenum diverticulosis and 2 healthy adults were examined. Nine fecal enrichments contained Methanobrevibacter. The percentage of methanogen positive individuals was 69% Methanobrevibacter were isolated from fecal enrichments of 4 colorectal cancer and 1 duodenum diverticulosis. The percentage of breath methane positive individuals and methane production had significantly increased in colorectal cancer patients. It will be hopeful that methane production in breath samples at the end of exhalation will became a rapid, simple and non-penetrative method for monitoring precancerous colonic or rectal carcinogenesis and monitoring the relapse of individuals with carcinosectomy.

Breath Tests↗
PubMed1991

[Application of cluster analysis to the classification of Radix scutellariae].

Ten samples of Radix Scutellariae from different habitats were analyzed by thin layer chromatography. From the analysis numerical characteristic features were obtained that represent the quality difference of samples. All of the multivariate data were treated with mathematic method of cluster analysis. Scutellaria bai alensis included in Chinese Pharmacopoeia was clearly differentiated from the other four varieties of herbs (S. rehderiana, S. viscidula, S. amoena, S. likiangensis).

Chromatography, Thin Layer↗
PubMed1990

DNA-looping and enhancer activity: association between DNA-bound NtrC activator and RNA polymerase at the bacterial glnA promoter.

The NtrC protein activates transcription of the glnA operon of enteric bacteria by stimulating the formation of stable "open" complexes by RNA polymerase (sigma 54-holoenzyme form). To regulate the glnA promoter, NtrC binds to sites that have the properties of transcriptional enhancers: the sites will function far from the promoter and in an orientation-independent fashion. To investigate the mechanism of enhancer function, we have used electron microscopy to visualize the interactions of purified NtrC and RNA polymerase with their DNA binding sites and with each other. Under conditions that allow the formation of open complexes, about 30% of DNA molecules carry both RNA polymerase and NtrC bound to their specific sites. Of these, about 15% form looped structures in which NtrC and the RNA polymerase-promoter complex are in contact. The length of the looped DNA is that predicted from the spacing that was engineered between the enhancer and the glnA promoter (390 base pairs). As expected for activation intermediates, the looped structures disappear when RNA polymerase is allowed to transcribe the DNA. We conclude that the NtrC enhancer functions by means of a direct association between DNA-bound NtrC and RNA polymerase (DNA-looping model). Association of DNA-bound proteins appears to be the major mechanism by which different types of site-specific DNA transactions are localized and controlled.

Bacterial Proteins↗
PubMed1990

DNA looping in cellular repression of transcription of the galactose operon.

Communication between distant DNA sites is a central feature of many DNA transactions. Negative regulation of the galactose (gal) operon of Escherichia coli requires repressor binding to two operator sites located on opposite sides of the promoter. The proposed mechanism for regulation involves binding of the repressor to both operator sites, followed by a protein-protein association that loops the intervening promoter DNA (double occupancy plus association). To assess these requirements in vivo, we have previously converted gal operator sites to lac and shown that both operator sites must be occupied by the homologous repressor protein (Lac or Gal) for negative regulation of the gal operon. We have now addressed more directly the need for protein-protein association by the use of the converted operator sites and a mutant Lac repressor defective in association of the DNA-binding dimers. We have compared the biological and biochemical activity of two Lac repressors: the wild-type (tetramer) I+ form, in which the DNA-binding dimer units are tightly associated; and the mutant Iadi repressor, in which the dimer units do not associate effectively. The I+ repressor is an efficient negative regulator of the gal operon in vivo, but the Iadi mutant is an ineffective repressor. Purified I+ repressor efficiently forms DNA loops between operator sites that we have visualized by electron microscopy; the Iadi repressor fails to form DNA loops, although the protein binds effectively to both operator sites. From the clear correlation between looping in vitro and repression in vivo, we conclude that regulation of the gal operon depends on the association of repressor proteins bound to the two operator sites.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA, Bacterial↗
PubMed1990

[Primary study of iontophoresis of zinc ion in treatment of retinitis pigmentosa].

We report here the preliminary effects of zinc iontophoresis in treatment of 26 Rp patients who had decreased zinc serum level or abnormal ratio of serum copper to zinc. Through more than 20 to 30 times of therapy, the vision of 15.38% eyes increased more than "3 lines", 4% eyes increased more than 5 degrees in the visual field, 13.46% eyes improved in dark adaptation threshold (greater than 1.0), the visual functions of the rest eyes were slightly improved or unimproved. The fundus didn't change before & after treatment. There were no changes of ERG in 8 eyes of 4 cases. In addition, the advantages and disadvantages between Zn iontophoresis and Zn compound taken orally, the improvement of vision by direct electric current therapy, the relationship between the metabolism of Zn element and Vit A and influence of Zn over the mechanism of dark adaptation were also briefly discussed.

Adaptation, Ocular↗
PubMed1989

Activity-induced depression of synaptic inhibition during LTP-inducing patterned stimulation.

In the hippocampus, patterns of electrical stimulation that approximate bursting neuronal activity during theta rhythm have been shown to induce a long-term potentiation (LTP) of excitatory synapses. In this study, a single subthreshold stimulus applied to one set of Schaffer/commissural fibers affected the response to a second stimulation delivered 200 ms later to a separate set of Schaffer/commissural fibers in the CA1 field of rat hippocampal slices. The first (priming) stimulus caused a prolongation of the synaptic response elicited by the second (primed) stimulus. In addition, the priming stimulation facilitated the induction of LTP by bursts of stimulation (4 pulses at 100 Hz) of the second afferent pathway. Analysis of the shape of the synaptic responses indicates that the prolongation is due to the removal of an inhibitory component rather than the addition of a novel excitatory component. Blockade of GABAA-ergic transmission with picrotoxin mimicked the priming effect in that it also widened synaptic responses and facilitated burst-induced LTP. We suggest that these patterns of stimulation result in a transient loss of inhibition during the primed stimulation. This, in turn, brings about a prolongation of the synaptic response that allows short bursts of excitatory synaptic activity to depolarize postsynaptic cells sufficiently to trigger LTP.

Animals↗
PubMed1989

Ocular survey of deaf-mute children.

Through routine ocular examination of 279 Deaf-mute students in Lie De School in Guangzhou in 1988 by visual chart, Yu Zi Ping Pseudoisochromatic plate, portable slit lamp and direct ophthalmoscope, 100 persons (35.8%) were found to have ocular defects in one or both eyes. The incidence of ocular defects was higher than that of the normal populations. Among the ocular abnormalities, fundus defects occupied 28.6%, error of refraction, 17.9%. 17.9% of the eyes had the vision lower than 1.0 and the error of refraction was the main cause. Cases of hereditary syndromes were found: Usher syndrome, 2 cases; Goldenhar syndromes, 2 cases (brother and sister); Waardenburg syndrome, 1 case; von Recklinghausen's syndrome, 1 case. In comparing with the other articles, the ocular defect, visual disturbance, error of refraction, way of examination as well as types and characteristics of some syndromes were briefly discussed. The importance of special examinations for diagnosis, early correction of refractive error, avoidance of consanguineal marriage among deaf-mutes were emphasized.

Adolescent↗
PubMed1986

Production, Purification, and Characterization of alpha-Galactosidase from Monascus pilosus.

A Monascus pilosus strain was selected for production of intracellular alpha-galactosidase. Optimum conditions for mycelial growth and enzyme induction were determined. Galactose was one of the best enzyme inducers. The enzyme was purified by ammonium sulfate precipitation, gel filtration, and ion exchange chromatography and was demonstrated to be homogeneous by slab gel electrophoresis. The molecular weight of this enzyme, estimated by gel filtration, was about 150,000. The optimum conditions for the enzyme reaction was pH 4.5 to 5.0 at 55 degrees C. The purified enzyme was stable at 55 degrees C or below and in buffer at pH 3 to 8. The activity was inhibited by mercury, silver, and copper ions. The kinetics of this enzyme, with p-nitrophenyl-alpha-d-galactoside as substrate, was determined: K(m) was about 0.8 mM, and V(max) was 39 mumol/min per mg of protein. Enzymatic hydrolysis of melibiose, raffinose, and stachyose was analyzed by thin-layer chromatography.

Journal Article↗