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Biomedical subjects

W Gao

Publications and source records attributed to W Gao.

At least 217 records · Page 12Linked to original sources
PubMed1993

GCR1, a transcriptional activator in Saccharomyces cerevisiae, complexes with RAP1 and can function without its DNA binding domain.

In Saccharomyces cerevisiae, efficient expression of glycolytic and translational component genes requires two DNA binding proteins, RAP1 (which binds to UASRPG) and GCR1 (which binds to the CT box). We generated deletions in GCR1 to test the validity of several different models for GCR1 function. We report here that the C-terminal half of GCR1, which includes the domain required for DNA binding to the CT box in vitro, can be removed without affecting GCR1-dependent transcription of either the glycolytic gene ADH1 or the translational component genes TEF1 and TEF2. We have also identified an activation domain within a segment of the GCR1 protein (the N-terminal third) that is essential for in vivo function. RAP1 and GCR1 can be co-immunoprecipitated from whole cell extracts, suggesting that they form a complex in vivo. The data are most consistent with a model in which GCR1 is attracted to DNA through contact with RAP1.

Base Sequence↗
PubMed1993

The dynamics of aging and mortality in the People's Republic of China, 1957-1990.

The Strehler-Mildvan modification of the Gompertz relationship between aging and mortality predicts a negative linear relationship between the theoretical logarithm of the mortality rate at birth (log R0) and the exponential rate of increase (alpha) in the age-specific mortality rates under specified conditions. This prediction has been generally validated using mortality data from the United States with respect to general and many disease-specific age-specific mortality rates by the method of longitudinal Gompertzian analysis. Estimated age-specific mortality rates from the People's Republic of China for seven years from 1957 to 1990 were analyzed using the method of longitudinal Gompertzian analysis. The results in this population further validate the Strehler-Mildvan modification of the Gompertz relationship between aging and mortality.

Adolescent↗
PubMed1993

Development of a new method for hepatic rearterialization in rat orthotopic liver transplantation. Reduction of liver injury and improvement of surgical outcome by arterialization.

The purpose of this study was to develop a simple new method for rearterialization to compare rearterialized and nonarterialized models of liver transplantation in the rat in the same laboratory with the same surgeon. Hepatic rearterialization in the rat was completed by connecting the proper hepatic artery with a splint of polyethylene tubing (PE 10). With this technique, no extrahepatic arteries or modification of other organs was required. Further, the recipient's gastroduodenal artery remained intact to minimize bile duct hypoxia, and the anastomosis was completed rapidly (< 3 min). Postoperative arterial thrombosis and bile duct necrosis occurred with low frequencies with this model (< 15%). For comparison, the nonarterialized model of Kamada was used. With the nonarterialized method, survival of livers stored for 24 hr in cold University of Wisconsin solution was approximately 85% (6/7), whereas survival of livers stored for 48 hr was poor (< 10%; 1/16). Rearterialization improved survival following 48 hr of storage in UW solution from less than 10% to 50% (3/6), and reduced early enzyme release (AST) by about 50%. Rearterialization also reduced enzyme release following 24 hr of cold storage by about 50%. We conclude that this new technique is a simple and reliable method for hepatic artery reconstruction that may be particularly useful in studying the mechanism of primary graft non-function. These data are consistent with the hypothesis that hepatic rearterialization minimizes hypoxic injury to parenchymal cells postoperatively, most likely by increasing oxygen delivery.

Animals↗
PubMed1993

Tn5-Mob transposon mediated transfer of salt tolerance and symbiotic characteristics between Rhizobia genera.

Rhizobium meliloti 042B is a fast-growing, salt-tolerant and high efficiency nitrogen-fixing symbiont with alfalfa. Bradyrhizobium japonicum USDA110 grows slowly, and cannot grow in YMA medium containing 0.1M NaCl, but nodulates and fixed nitrogen efficiently with soybean. Eighty-six transconjugants, called SR, were obtained by inserting Tn5-Mob randomly into genomes of 042B using pSUP5011 and helper plasmid RP4. Selecting 4 SR strains randomly and introducing DNA fragment of SR into USDA110 with helper plasmid R68.45 by triparental mating, 106 transconjugants, called BSR, were constructed. Most of BSR strains had the fast-growing phenotype and could tolerate 0.3-0.5M NaCl generally. Some of them produced melanine. When soybean and alfalfa were inoculated with these transconjugants BSR, 47 out of 90 BSR were found to nodulate in both of these plants, but no nitrogenase activity was observed with alfalfa; 26 strains could only nodulate and fix nitrogen in soybean; 13 strains could nodulate in alfalfa but did not fix nitrogen; 4 strains failed to nodulate in either soybean or alfalfa. Among them, 4 transconjugants which tolerated and fixed nitrogen efficiently in soybean were constructed.

Conjugation, Genetic↗
PubMed1992

Reperfusion rather than storage injury predominates following long-term (48 h) cold storage of grafts in UW solution: studies with Carolina Rinse in transplanted rat liver.

Both storage injury and reperfusion injury have been reported in association with liver transplantation; however, which predominates is not clear. Therefore, these studies were designed to evaluate whether Carolina Rinse, which minimizes reperfusion injury following orthotopic liver transplantation in the rat, would be effective after long-term (48 h) storage of grafts in University of Wisconsin (UW) cold storage solution where sufficient time for development of storage injury exists. Livers were rinsed with either Ringer's solution or Carolina Rinse solution immediately prior to completion of implantation surgery. In the Ringer's group, 30-day survival was high following 24 h of cold storage (4/5) but was very low after 48 h (1/16). Importantly, survival was increased significantly (5/14) when grafts were rinsed with Carolina Rinse following 48 h of cold storage. In both groups, parenchymal cells appeared normal by scanning electron microscopy, excluded trypan blue, and released SGOT at values only slightly above the normal range immediately (i.e., less than 5 min) after 48 h of cold storage. However, SGOT values rose steadily during the 1st hour postoperatively following reperfusion in the Ringer's rinse group and reached levels around 1,000 U/l. In addition, nonparenchymal cells were not labelled with trypan blue following storage, but significant labelling occurred within 1 h. Both SGOT release and nonparenchymal cell injury were reduced significantly when grafts were rinsed with Carolina Rinse prior to completion of surgery. Liver injury assessed histologically 24 h postoperatively was also reduced about 50% by Carolina Rinse. Oxidative stress appeared to be involved, since radical adducts, most likely of lipid origin, were trapped during the first 5 min after reperfusion with the spin trapping technique and detected by electron paramagnetic resonance spectroscopy. Lipid radical formation was reduced nearly completely on reperfusion by Carolina Rinse. Since Carolina Rinse improved survival of liver grafts following long periods of cold storage and reduced lipid radical formation and hepatocellular injury, we concluded that a reperfusion injury rather than a storage injury predominates following orthotopic transplantation of livers stored for long periods of time in cold UW solution.

Adenosine↗
PubMed1992

The second generation of Carolina Rinse, solution II, improves graft survival following orthotopic liver transplantation in the rat by preventing reperfusion injury.

Carolina Rinse solution was designed to minimize reperfusion injury following orthotopic liver transplantation. Carolina Rinse blocks reperfusion-induced endothelial cell killing, diminishes postoperative enzyme release and improves survival dramatically. Adenosine and mildly acidotic pH were identified as key components. Here we report results with a simplified formulation, Carolina Rinse II, which contains extracellular inorganic ions similar to Ringer's solution, adenosine, as well as antioxidants and radical scavengers (allopurinol, glutathione and desferrioxamine). In this study, 44 rat livers were explanted and stored for 12 h in University of Wisconsin (UW) cold storage solution (non-survival conditions). Control livers were rinsed with 15 ml cold Ringer's solution just prior to completion of implantation surgery. In this control group, average 30-day survival was poor (8%). However, survival was increased to around 60% when grafts were rinsed with Carolina Rinse II. Survival was not improved significantly by rinsing the graft with Ringer's solution containing antioxidants and radical scavengers with adenosine omitted (about 30%). Peak SGOT values of nearly 3000 U/l, measured 1-3 days postoperatively in the Ringer's rinse control group, were decreased 4- to 5-fold both by Carolina Rinse II and by Ringer's solution containing antioxidants. On the other hand, the addition of adenosine to Ringer's solution improved survival (around 60%) but did not decrease the postoperative elevation of serum enzymes significantly. Thus, it appears that adenosine was necessary for optimal survival whereas antioxidants and radical scavengers were needed to prevent injury to the transplanted graft. These data were consistent with the hypothesis that at least two mechanisms, one involving the liver and a second one non-hepatic, are responsible for post-transplant pathophysiology. Carolina Rinse II also reduced the postoperative elevation in serum enzymes 2- to 3-fold in livers stored under survival conditions (e.g., for 8 h in UW solution). This study demonstrated convincingly that a very simple rinse solution, Carolina Rinse II, improved survival significantly and minimized graft injury following orthotopic liver transplantation.

Animals↗
PubMed1992

Food restriction increases detoxification of polycyclic aromatic hydrocarbons in the rat.

It is well known that food restriction diminishes tumor formation, but mechanisms responsible are difficult to define because multiple physiological changes result from dietary alterations. Studies in this report were designed to focus specifically on the effects of food restriction on hepatic metabolism of polycyclic aromatic hydrocarbons following liver transplantation. By placing livers from food-restricted and untreated rats into naive controls, the effects of diet could be restricted to the liver. After a 15 min infusion of [3H]benzo[a]pyrene under these conditions, food restriction increased polar metabolites in liver (70 pmol/g) and blood (8 pmol/ml) compared to controls approximately 2-fold. Four hours after liver transplantation, levels of polar metabolites in blood were diminished by approximately 50% but were still approximately 2-fold higher in the food-restricted than in the control group. Lung, kidney, spleen, adrenal, ovary, colon, heart and brain also contained higher levels of polar metabolites in the food-restricted than in the control group. The more hydrophobic glucuronides and sulfate conjugates accounted for most of the elevation in polar metabolites in blood from the food-restricted group. In spite of the increase in circulating metabolites in blood of food-restricted animals, DNA binding in liver, lung and kidney was identical in tissues from control and food-restricted groups. In order to evaluate the hypothesis that food restriction stimulated the release of hepatic benzo[a]pyrene metabolites, a liver perfusion model was employed. Maximal rates of release of polar metabolites into the effluent perfusate were approximately 30 and approximately 45 nmol/g/h in livers of control and food-restricted rats respectively. Moreover, rates of metabolism of the model compound p-nitroanisole and glucuronidation of p-nitrophenol were also approximately 2-fold higher in livers from food-restricted than control rats. However, rates of monooxygenation were the same in microsomes prepared from livers of food-restricted or control animals. These results support the hypothesis that food restriction enhances the supply of cofactors which stimulate metabolism of polycyclic aromatic hydrocarbons. This detoxification process may be an important mechanism involved in the protective action of reduced food intake.

Animals↗
PubMed1992

Evidence that free radicals are involved in graft failure following orthotopic liver transplantation in the rat--an electron paramagnetic resonance spin trapping study.

The purpose of these studies was to determine whether free radicals were formed as a consequence of reperfusion during orthotopic liver transplantation and whether their formation was related to graft failure. Grafts were stored for 18 hr in Euro-Collins solution or for 48 hr in University of Wisconsin solution (nonsurvival conditions) and reperfused with blood containing the spin trap alpha-phenyl N-tert-butylnitrone (PBN). Venous blood samples (4-5 ml) were collected, and serum was extracted with chloroform and methanol (2:1) and analyzed for radical adducts by electron paramagnetic resonance (EPR) spectroscopy. In samples from livers stored under nonsurvival conditions, EPR spectra were detected indicating the presence of PBN radical adducts. In contrast, radical adduct formation was 3- to 4-fold lower in similar experiments performed with untransplanted livers or with livers stored under survival conditions (1 hr in Ringer's solution or 24 hr in UW solution). Oxygen radicals are more likely involved in the production of radical adducts because formation was nearly completely prevented by superoxide dismutase plus catalase or Carolina rinse, which contains glutathione, desferrioxamine mesylate, and allopurinol. Radical adduct formation was much greater in a blood-free perfusion system where oxygen delivery was high, suggesting that blood elements are not necessary for radical adduct formation. An inverse correlation between survival of livers stored in UW solution and radical adduct signal was observed in this study. Thus, it is concluded that free radicals formed during reperfusion are involved in the mechanism of graft failure following liver transplantation in the rat.

Animals↗
PubMed1990

[Determination of water soluble silicon from herbal drugs].

This article has set up a method for silicon determination by ammonium molybdate-ferrous sulfate-sodium carbonate spectrophotometry. The method is simple, convenient, quick, effective and free of the influence of phosphate ion and reducing agents such as vitamin C and so on. By this method water soluble silicon has been determined in 38 herbal drugs.

Drugs, Chinese Herbal↗
PubMed1989

Effect of fatty acids on formation, distribution, storage, and release of benzo(a)pyrene phenols and glucuronides in the isolated perfused rat liver.

The hydroxylation of benzo(a)pyrene and conjugation, storage, and release of benzo(a)pyrene phenols and glucuronides by the perfused rat liver were studied in the presence and absence of acute addition of physiological concentrations of common dietary fatty acids. The actions of fatty acids on the oxidation and conjugation of benzo(a)pyrene in the intact liver were compared with their actions on microsomes isolated from rat liver. Rats were treated with beta-naphthoflavone to stimulate polycyclic aromatic hydrocarbon metabolism. Long-chain fatty acyl CoA compounds (palmitoyl CoA, oleoyl CoA, linolenoyl CoA; 50 microM) inhibited hydroxylation of benzo(a)pyrene by isolated microsomes by about 45%; however, long-chain fatty acids did not affect overall rates of hydroxylation of benzo(a)pyrene by the perfused liver at concentrations ranging up to 300 microM. The medium-chain acyl CoA compound, octanoyl CoA, also did not affect benzo(a)pyrene hydroxylation in microsomes or liver. Although fatty acids did not alter rates of hydroxylation, the ratio of free benzo(a)pyrene phenols to glucuronides (F/G ratio) increased about 60% (P less than 0.05) in livers perfused with long-chain fatty acids (palmitate, oleate, linolenate). Inhibition of glucuronidation was not observed with the medium-chain fatty acid, octanoate. Benzo(a)pyrene phenols and glucuronides accumulated linearly in the liver at rates of approximately 40 nmol/g/h. A second action of both long- and medium-chain length fatty acids was to increase rates of release of benzopyrene phenols into the perfusate by 50 to 80%. Fatty acids did not effect release of benzo(a)pyrene phenols and glucuronides into bile. Taken together, these data support the hypothesis that fatty acids displace carcinogenic metabolites of benzo(a)pyrene from binding sites in the liver which enter the circulation and travel to target tissues.

Acyl Coenzyme A↗
PubMed1989

[Effect of high-frequency oscillation on hypoxic pulmonary vasoconstriction].

We studied the effect of high-frequency oscillatory ventilation (HFO) on hypoxic pulmonary vasoconstriction (HPV) in mongrel dogs. Arterial blood gas as well as pulmonary and systemic hemodynamic variables were measured. Using a double-lumen endotracheal catheter, the right lung was ventilated by controlled mechanical ventilation (CMV) and the left lung was ventilated by CMV (controlled group, n = 5), HFO (HFO group, n = 6) and a combined use of CMV and HFO (combined group, n = 6). Under the same condition as in HFO group, chest was opened and the left pulmonary arterial flow was determined by electromagnetic method (opened thorax group, n = 4). Bilateral lungs were ventilated with pure oxygen during the control period. The right lung was ventilated with pure oxygen while the left lung was ventilated with pure nitrogen afterward during the study. There was no significant change in arterial oxygen partial pressure due to delayed HPV in HFO group or combined group between 30 and 120 minute values. Although there was an increase in mean pulmonary arterial pressure in combined group, in HFO group it was not observed. At the same time, the decrease in pulmonary flow was minimum in open thorax group. Authors conclude that HFO interferes with the effect of HPV to a certain extent.

Animals↗
PubMedDate not supplied

Percutaneous closure of perimembranous ventricular septal defects with the eccentric Amplatzer device: multicenter follow-up study.

Using an Amplatzer membranous eccentric occluder, 186 patients with an average weight of 43.5 kg (range 12.5-77) underwent attempted catheter closure of a perimembranous venricular septal defect (PMVSD). Their age ranged from 3 to 51 years, with the an average age being 15.9 years. The patients were divided into three groups according to morphology of PMVSD: 106 patients with single PMVSD, 63 patients with single PMVSD with aneurysmatic formation, and 17 patients with multiple VSD with aneurysmatic formation. Using angiography, PMVSDs were measured to be between 2.5 and 12 mm, with an average of 5.1 mm. In the third group of patients, we did not measure the size of PMVSD and a device was selected according to the size of entry to the aneurysm. The device was successfully implanted in all patients. The immediate closure rate was 90% in the first group, increasing to 100% at 1 month and remained at that level during follow-up. The immediate closure rate in the second group was 98% and remained the same during follow-up. The immediate closure rate in the third group was 89% and during 1 year of follow-up remained the same. There was no clinical evidence of hemolysis and no incidence of device embolization or bacterial endocarditis after implantation. Before the procedure, all patients showed normal electrocardiogram (ECG) or left ventricle enlargement. After the procedure (at least 3 months later) ECG showed left anterior hemiblock (LAH) in nine patients, complete right bundle branch block in eight patients, and incomplete right bundle branch block in seven patients. A complete heart block (CHB) developed in 2 patients after the procedure (1.07%). The first patient developed LAH immediately after closure and CHB within 24 hours, The heart rate was 28 beats per minute. After treatment with steroids and atropine, CHB changed to sinus rhythm with LAH within 2 months. One year later, the ECG revealed the same findings. The second patient developed CHB immediately after the procedure and was on temporary pacing for 1 week. After 1 month, the patient recovered to sinus rhythm and ECG showed LAH.

Adolescent↗