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Y Shi

Publications and source records attributed to Y Shi.

At least 649 records · Page 36Linked to original sources
PubMed1991

YY1 is an initiator sequence-binding protein that directs and activates transcription in vitro.

Regulation of eukaryotic messenger RNA transcription is governed by DNA sequence elements that serve as binding sites for sequence-specific transcription factors. These include upstream and downstream promoter-proximal elements, enhancers, repressors, and silencers, which modulate the rate of specific initiation by RNA polymerase II. In addition, the promoter-proximal region between -45 and +30 (relative to the start of initiation) contains two highly conserved motifs, the TATA sequence at around -30 and CA at +1. Although the TATA element-binding factor TFIID has been purified and cloned from several organisms and has provided invaluable insight into the process of transcription initiation and its regulation, little is known about factors that interact at the +1 region. We have recently shown that the adeno-associated virus type 2 P5 promoter +1 region (P5 + 1 element) binds transcription factor YY1. We report here that this sequence is necessary and sufficient for accurate basal transcription. Further, partially purified YY1 can restore basal level transcription from a P5 + 1 element in a HeLa extract depleted for YY1 or a Drosophila embryo extract devoid of YY1 activity, whereas a YY1-specific antibody can block the reactivation. Finally, using electrophoretic mobility shift assay, we have identified YY1-related factors that bind to two other transcription initiators in cellular genes.

Animals↗
PubMed1991

Transcriptional repression by YY1, a human GLI-Krüppel-related protein, and relief of repression by adenovirus E1A protein.

A sequence within the transcription control region of the adeno-associated virus P5 promoter has been shown to mediate transcriptional activation by the adenovirus E1A protein. We report here that this same element mediates transcriptional repression in the absence of E1A. Two cellular proteins have been found to bind to overlapping regions within this sequence element. One of these proteins, YY1, is responsible for the repression. E1A relieves repression exerted by YY1 and further activates transcription through its binding site. A YY1-specific cDNA has been isolated. Its sequence reveals YY1 to be a zinc finger protein that belongs to the GLI-Krüppel gene family. The product of the cDNA binds to YY1 sites. When fused to the GAL4 DNA-binding domain, it is capable of repressing transcription directed by a promoter that contains GAL4-binding sites, and E1A proteins can relieve the repression and activate transcription through the fusion protein.

Adenoviridae↗
PubMed1991

Evaluation of HemoQuant test and enteroclysis in estimating the sites of obscure gastrointestinal bleeding.

The HemoQuant test includes the measurement of total fecal hemoglobin (Hb) or porphyrin derived from heme, and of intestinal converted fraction (ICF) which is the performed porphyrin probably by bacteria during enterocolic transit. The mean +/- SD of HemoQuant in 31 healthy subjects was 0.57 +/- 0.49 mg Hb/g stool, values above 2 mg Hb/g stool are considered to be positive. In patients with upper GI bleeding (n = 44), small bowel bleeding (n = 11) and large bowel bleeding (n = 16), the ICF ranged 0.03-23%, 0.09-20.20% and 0.35-11.0%, respectively. There was major overlap in individual ICF due to some influencing factors such as the quantity of fecal blood and the enterocolic transit. We conclude that HemoQuant is a sensitive assay for detection of fecal occult blood, but ICF is not helpful in estimating the anatomic site of bleeding. Seventy-one patients with GI bleeding of obscure origin underwent enteroclysis. The results showed 77.5% had definite lesions in the small bowel, but 22.5% still were undefined. It is suggested that enteroclysis should be performed without delay if upper and lower GI endoscopic studies are negative.

Adult↗
PubMed1991

Nonlinear system identification by m-pulse sequences: application to brainstem auditory evoked responses.

The purpose of this paper is to introduce a method for characterizing the nonlinear behavior of the auditory system. The method uses an m-pulse sequence as the stimulus and employs a general nonlinear framework for the auditory system. Like Sutter's binary m-sequence approach, the m-pulse sequence approach is computationally efficient since calculation of the first-order input-output cross-correlation function is all that is necessary for obtaining the nonlinear characteristics of the system. The nonlinear system characteristics are reflected in pulse kernels in contrast to binary kernels associated with the binary m-sequence approach. By assuming the system under study is a third-order nonlinear system, binary and pulse kernels are shown to be related to Volterra kernels. The results suggest that the m-pulse sequence can be used to study the system nonlinear effects of varying the stimulus repetition rate more effectively than conventional methods. Preliminary physiological data obtained by applying m-pulse sequences to the brainstem auditory evoked response (BAER) clearly illustrates the feasibility of obtaining replicable evoked responses using this method.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1991

Negative regulation of the BZLF1 promoter of Epstein-Barr virus.

The Epstein-Barr virus BZLF1 gene product (ZEBRA) is a transcriptional activator whose expression in latently infected B cells is sufficient to induce the viral lytic cycle. Since there is no transcription of BZLF1 during latency, we carried out experiments to determine whether cis-acting negative elements in the BZLF1 promoter contribute to the lack of expression during this phase of the virus cycle. A series of deletion plasmids encompassing positions -551 to +14 of the BZLF1 promoter region were constructed and tested for the ability to drive chloramphenicol acetyltransferase (CAT) gene expression in the absence of inducing agents such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and anti-immunoglobulin. Expression from the intact 551-bp region was very weak in most of the cell lines tested, but deletion of 165 bp from the 5' end caused a sevenfold increase in expression of CAT. Within these 165 bp, a minimal 48-bp region was sufficient to down regulate the expression of a simian virus 40/CAT fusion plasmid. The 48-bp negative element consists of 7-bp dyad symmetry elements separated by 27 bp. The rightmost half of the dyad symmetry element partially overlaps a region which has a 14-of-15-bp homology to the human cytoskeletal gamma-actin promoter.

Animals↗
PubMed1991

Evidence for reduced fibrinolytic activity in unstable angina at rest. Clinical, biochemical, and angiographic correlates.

BACKGROUND: The goal of this study was to evaluate the role of the fibrinolytic system in patients with unstable angina at rest associated with transient electrocardiographic changes. METHODS AND RESULTS: Tissue plasminogen activator activity in plasma was comparable among patients with unstable angina (n = 17), patients with stable exertional angina (n = 10), and control patients with normal coronary arteriograms (n = 8). In contrast, plasminogen activator inhibitor-1 (PAI-1) activity in plasma was elevated in the unstable angina group (21.67 +/- 9.52 AU/ml) as compared with either the stable angina group (12.01 +/- 7.06 AU/ml, p less than 0.02) or the controls (12.49 +/- 8.54 AU/ml, p less than 0.02). Coronary angiography performed within 24 hours after the last anginal episode showed a similar extent of coronary artery disease in the unstable and stable angina groups. However, intracoronary thrombi were observed in eight patients in the unstable angina group while no thrombus was noted in the stable angina group (chi 2 = 7.22, p less than 0.01). CONCLUSIONS: We conclude that patients with unstable angina at rest have a reduced fibrinolytic activity and an increased incidence of intracoronary thrombi. It is postulated that elevated PAI-1 activity in the presence of coronary arterial wall injury may be an important factor leading to the development of acute coronary syndromes.

Angina Pectoris↗
PubMed1991

[A study on the male DNA special restricted fragment of bovine].

Bkm, which is related to sexes, is a satellite DNA of the female snake. After the genomic DNA of bovine was digested by Pst I, it was hybridized with Bkm sequence probe (p184) and subcloned in the vector pUC19. Recombinants were identified by the colony in situ and Southern blot hybridization. When we determined genomic DNA of bovine using the male DNA fragment, it was observed that the pattern of hybridization was different because of different sexes. The results showed that we could identify the sex of bovine by Southern blot hybridization with recombinants of male DNA special restricted fragment of bovine origin.

Animals↗
PubMed1991

[Relation between psychoactive drugs and body weight among inpatients].

A self-control study was conducted among 92 inpatients for the purpose of the establishment of the relationship between psychoactive and body weight, with the latter measured once a week, stepwise regression (alpha = 0.3) revealed: increase or decrease of body weight was associated not only with the kinds of medicines administered, but also with the types of the diseases, living standard, and therapeutic effects. The mechanism of body weight increase was explored and some suggestions were also given with regard to the prevention of the increase of body weight.

Adolescent↗
PubMed1991

[Consecutive observation of the plasma MDA, XO and UA levels and erythrocyte SOD in 10 cases of cardiopulmonary bypass].

The plasma malonaldehyde (MDA), xanthine oxidase (XO) and uric acid (UA) levels and erythrocyte superoxide dismutase (SOD) were measured in 10 cases during cardiopulmonary bypass (CPB) operation. These examinations were taken at pre-aortic clamping, 15 min after aortic clamping, 30, 60, 120 and 180 min after reperfusion respectively. The results showed that MDA, XO and UA rise but SOD decreases after reperfusion. We believe that a lot of oxygen free radicals (OFR) release during peri-operative period and the XO may be an important pathway of OFR release.

Cardiopulmonary Bypass↗
PubMed1991

Growth kinetics of Bu3 cells secreting HBsAg in microcarrier culture.

The genetically engineered mammalian cell (Bu3) secreting Hepatitis B surface antigen (HBsAg) was cultured on microcarriers semi-continuously. The growth model of Bu3 cells propagating on microcarriers, glucose consumption and lactate accumulation models were established. It is illustrated that the technology of anchorage-dependent Bu3 cell culture on microcarriers will give high yield and high HBsAg expression.

Animals↗
PubMed1990

Functional changes of the NADH respiratory chain in rat-liver mitochondria and the content changes of high-energy phosphate groups in rat liver and heart during the early phase of burn injury.

Using glutamate plus malate as substrates, the respiratory control ratio of liver mitochondria from burned male Sprague-Dawley rats with full skin thickness burns covering 20 per cent of the body surface area were increased at 45, 60, 75 and 90 min and using alpha-ketoglutarate, were increased at 60 and 75 min after burning, the peak being at 75 min postburn. The ADP/O ratio and the rate of ATP formation were also increased at about 75 min postburn and the ATP content in liver was increased at 120 min following burning. The ATP and creatine phosphate contents in heart tissue were increased at 120 min and at 105, 120 and 135 min postburn respectively. A sham-injured group acted as control. All the results suggested an increased oxidative phosphorylation coupling in some organs during the early phase of burn injury.

Adenosine Diphosphate↗
PubMed1990

Does antiplatelet therapy enhance myocardial salvage after coronary reperfusion?

The aim of this study was to test the hypothesis that either the cyclooxygenase inhibitor aspirin or the thromboxane A2 receptor antagonist sulotroban exerts a direct myocardial effect that enhances myocardial salvage afforded by reperfusion. Accordingly, 21 anesthetized dogs underwent suture occlusion of the left anterior descending coronary artery. At 2.5 h after occlusion, all dogs received intravenous streptokinase (20,000 U/kg body weight over 30 min) and were randomized to the following groups: group I (n = 7) received no additional treatment, group II (n = 7) received aspirin (5 mg/kg intravenously) and group III (n = 7) received sulotroban (10 mg/kg followed by 10 mg/kg per h intravenously). At 3 h after occlusion, the dogs underwent coronary reperfusion for the next 3 h. Myocardial infarct size as a percent of the hypoperfused zone was similar among dogs in group I (42 +/- 8%), group II (41 +/- 10%) and group III (45 +/- 11%). The incidence and the extent of myocardial hemorrhage were similar in all three study groups. Infarct size as a percent of the hypoperfused zone was significantly smaller in dogs without hemorrhage irrespective of treatment (35 +/- 9% versus 63 +/- 5%, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Myocardial protection with autoperfusion during prolonged coronary artery occlusion.

Passive transcatheter coronary arterial perfusion, i.e., autoperfusion, has been introduced for clinical use to ameliorate short episodes of myocardial ischemia during percutaneous transluminal coronary angioplasty. The primary goal of this study was to evaluate the cardioprotective effect of autoperfusion after prolonged coronary artery occlusion. Accordingly, in 24 anesthetized dogs, either the left anterior descending or left circumflex coronary artery was occluded for 6 hours. The dogs were randomized to a control group subjected to coronary artery occlusion alone (n = 13) or to a group treated with transcatheter autoperfusion (n = 11). The hypoperfused zone, i.e., risk area and infarct size, were measured by autoradiography and triphenyltetrazolium chloride staining, respectively. The hypoperfused zone was 30 +/- 2% and 29 +/- 2% in the control and treated (NS) groups, respectively. When infarct size was expressed as a percent of the hypoperfused zone, it was 84 +/- 5% in the control group and 25 +/- 9% in the group treated with transcatheter autoperfusion (p less than 0.001), showing a reduction of 70%. In addition, an in vitro study showed pressure-dependent flow during autoperfusion as reflected by close linear relationship between perfusion pressure and flow (Flow = 0.54 X Pressure + 16.16, r = 0.99, n = 16). These data suggest that although passive coronary arterial perfusion for 6 hours after coronary occlusion does not prevent myocardial necrosis, it markedly reduces myocardial infarction in the canine model.

Angioplasty, Balloon, Coronary↗