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Biomedical subjects

N Li

Publications and source records attributed to N Li.

At least 415 records · Page 23Linked to original sources
PubMed1990

The tyrosine phosphorylated carboxyterminus of the EGF receptor is a binding site for GAP and PLC-gamma.

Phospholipase C-gamma (PLC-gamma) and GTPase activating protein (GAP) are substrates of EGF, PDGF and other growth factor receptors. Since either PLC-gamma or GAP also bind to the activated receptors it was suggested that their SH2 domains are mediating this association. We attempted to delineate the specific region of the EGF receptor that is responsible for the binding, utilizing EGF receptor mutants, PLC-gamma, and a bacterially expressed TRP E fusion protein containing the SH2 domains of GAP. As previously shown, tyrosine autophosphorylation of the wild-type receptor wsa crucial in mediating the association and in agreement, a kinase negative EGF receptor could bind PLC-gamma or TRP E GAP SH2, but only when cross tyrosine phosphorylated by an active EGF receptor kinase. The importance of autophosphorylation for association was confirmed by demonstrating that a carboxy-terminal deletion of the EGFR missing four autophosphorylation sites bound these proteins poorly. To study the role of EGF receptor autophosphorylation further, a 203 amino acid EGF receptor fragment was generated with cyanogen bromide that contained all known tyrosine autophosphorylation sites. This fragment bound both TRP E GAP SH2 and PLC-gamma but only when tyrosine phosphorylated. This data localizes a major binding site for SH2 domain containing proteins to the carboxy-terminus of the EGF receptor and points to the importance of tyrosine phosphorylation in mediating this association.

Animals↗
PubMed1990

Intraoperative coronary venography in observing changes of portal blood flow after portal-azygos disconnection.

Intraoperative coronary venography was performed in 24 patients before and after portal-azygos disconnection for portal hypertension. Before the procedure the portal vein was found to be communicated with cardial and esophageal veins by two pathways, i,e., from the esophageal and gastric branches of the coronary vein to the esophageal varices, with the latter branches by way of the gastric intramural venula. The portal blood flow was postulated to be hepatofugal because the portal trunk could not be seen venographically. Coronary venography done after the disconnection revealed no pericardial and esophageal varices and the portal vein with hepatopetal blood flow. We conclude that the operation had the advantage of complete disconnection between the portal vein and the cardio-esophageal varices, thus preventing the bleeding from the varix and increasing hepatopetal blood flow.

Adult↗
PubMed1990

[The changes of beta-glucuronidase in rabbit model with calcium bilirubinate stone].

The aim of the present study is to determine the beta-glucuronidase changes in bile and hepatobiliary tissue of rabbit model having pigment gallstone by means of biochemical and enzymehistochemical assay methods. The result showed both of the bacterial and non-bacterial beta-glucuronidase take part in the course of pigment gallstone formation. The bacterial beta-glucuronidase level increased quickly before the formation of gallstone, then decreased with control of bacterial infection. Non-bacterial beta-glucuronidase increased slowly in pro-formation stage of gallstone, then kept high level for long period of time. The relationship between beta-glucuronidase and pigment gallstone formation is also discussed.

Animals↗
PubMed1990

[An epidemiological study on coronary sudden death in Beijing].

An epidemiological study on coronary sudden death (CSD) had been carried out in defined areas of Beijing, covering a population of approximately 700,000, for a period of two years, 1984 to 1985. A total of 201 cases of CSD had been registered. The data showed: 1) half of the coronary death in the population were CSD and the rate of CSD increased with age; 2) the rate of CSD in males was higher than that in females; 3) most cases of CSD had a history of cardiovascular diseases; 4) 85% of CSD cases died within 6 hours after acute onset; 5) about half of the CSD cases had predominant symptoms with lower specificity. Some issues about the diagnostic criteria of CSD and cardiac-pulmonary resuscitation outside hospital in the communities of Beijing were discussed in detail.

Adult↗
PubMed1989

[Mucus histochemical study of bilirubin cholangiolithiasis in rabbit model].

Sulfated mucopolysaccharides have an important role in pigment gallstone formation. In this experiment, the animal model of bilirubin cholangiolithiasis was made with Japanese hybrid big-ear white rabbits. The source, nature, quantity and distribution of sulfated mucopolysaccharides in the cause of bilirubin cholangiolithiasis were observed by means of mucous histochemical study. There were three characteristic pathologic changes observed in this experiment: 1. In normal condition, the sulfated mucopolysaccharides were secreted by epithelium of biliary tracts and the quantity was minimum. When bacterial infection was present in the biliary tracts, they were secreted mainly by the proliferative glands in submucosa of the bile duct; 2. In 26 rabbits where the bilirubin cholangiolithiasis developed, there were many proliferative glands in submucosa of the bile duct. Most of the glands produced sulfonated acid mucin. In 5 rabbits where the gallstones did not develop in the stone growing stage, the proliferative glands were not present in the bile duct. It was suggested that there was a close relationship between the proliferative glands and the formation of bilirubin cholangiolithiasis, and 3. The glands in submucosa of the biliary tract provided the refuge where the bacteria could not be cleaned out easily and so it was difficult to control the infection of the biliary tract.

Animals↗
PubMed1989

[The selective cytotoxicity of monoclonal antibody conjugated with mitomycin C on human gastric cancer cells].

The murine monoclonal antibody (MoAb)3H11 against human gastric cancer was purified with affinity column and conjugated with Mitomycin C (MMC). The binding activity of MoAb in the conjugate retained more than 90% of the original MoAb 3H11 when the molar ratios of MMC to 3H11 was 7-8:1. The killing rate of 3H11-MMC conjugate on human gastric cancer cells BGC 823 was increased significantly than that of free MMC in vitro. The selective cytotoxicity was verified with the following results: (1) the cytotoxicity of the conjugate was much higher than that of normal mouse IgG (nMuIgG) conjugated with MMC; (2) when breast cancer cells MCF-7 was used as target cells instead of BGC 823 cells, much lower cytotoxicity of the conjugate was observed; (3) the cytotoxicity of the conjugate on BGC823 cells could be blocked when the target cells was preincubated with MoAb 3H11, but not with MoAb 3G9 which did combine with BGC823 cells at binding sites different from MoAb 3H11. Nude mice were inoculated with BGC823 cells as a model of gastric cancer and treated with conjugate 3H11-MMC, nMuIgG-MMC, MMC or PBS (ip). It was shown that the time of tumor formation and the rate of tumor growth in 3H11-MMC conjugate treated animals were significantly different from that in control groups. The rate of inhibition of tumor weights was 60.4% for the conjugate 3H11-MMC treated group which was significantly higher than for other groups.

Animals↗
PubMed1989

[Observation of oral glucose-insulin releasing test in liver cirrhosis].

In order to investigate the disorders of carbohydrate metabolism and insulin secretion as well as their correlation in patients with liver cirrhosis, we performed an oral glucose tolerance test on 30 patients with liver cirrhosis proven by history, clinical findings, liver function test, radioisotope liver scanning, ultrasonic examination, gastroscopy, barium esophagogram and liver biopsy, compared with 20 healthy controls. Blood glucose and immunoreactive insulin were determined in both groups at 60 min intervals for 180 min. Results showed marked glucose intolerance with peak value 60 min after glucose load in cirrhotic patients with normal fasting blood glucose. Plasma IRI levels were significantly higher in cirrhotic patients than in normal subjects after glucose load (P less than 0.05), especially 180 min after (P less than 0.01). Twelve of 30 cases (40%) showed an abnormal OGTT curve. Of the 12 cases seven (23.3%) showed a diabetic OGTT curve, five (16.7%) an impaired OGTT curve. While eighteen of 30 cases (60%) showed an abnormal OGIRT curve. Among the 18 cases one (3.3%) presented hypersecretic OGIRT curve, twelve (40.0%) with delayed and prolonged peak, and five (16.7%) with hypersecretic OGIRT curve and delayed, prolonged peak.

Adult↗
PubMed1988

The Gram-Charlier and multipole expansions in accurate X-ray diffraction studies: can they be distinguished?

The Gram-Charlier temperature factor formalism has been applied to a set of accurate low-temperature data on bis(pyridine)(meso-tetraphenylporphinato)iron(II), and to a theoretical set of static structure factors on the hexaaquairon(II) ion. The refinements are compared with the multipole treatment for atomic asphericity due to chemical bonding. In a treatment of the experimental data in which only the iron atom asphericity is considered, the 'thermal motion' formalism is as efficient as the multipole formalism in accounting for the observations. It is slightly less efficient when applied to the static theoretical data, though model maps based on the two treatments are remarkably similar. A high-order Gram-Charlier refinement of the porphyrin data, followed by a multipole refinement of all data with the Gram-Charlier parameters initially fixed, and later varied, shows that simultaneous refinement of anharmonic and aspherical effects is possible, though the resulting separation may not be accurate. A combined Gram-Charlier multipole refinement on the static data, however, leads to non-significant thermal parameters. It is concluded that the statistical Gram-Charlier formalism is remarkably successful in representing bonding effects in the valence charge density if these are not specifically accounted for in the scattering formalism. Statistical anharmonic thermal motion formalisms should only be used for X-ray data analysis in combination with a formalism accounting for the effect of bonding on the atomic charge density.

Chemical Phenomena↗
PubMed1988

The Sino-MONICA-Beijing Study: report on results between 1984 and 1986.

The Beijing Heart Lung and Blood Vessel Medical Center has participated in the World Health Organisation MONICA project since 1981. Our study, named Sino-MONICA-Beijing, has been carried out in Beijing and covers a population approximately of 700,000. After a 2-year pilot study, the project started formally January 1, 1984. This paper presents the organization and methodology of the study, with emphasis on the monitoring system and on how events were found. The main results of the cardiovascular disease (CVD) event monitoring are as follows: average annual mortality from all causes, for the 3-year period of 1984-86 was 319/100,000 for men and 238/100,000 for women aged 25-64; from CVD 119/100,000 for men and 101/100,000 for women; from ischemic heart disease 29/100,000 for men and 14/100,000 for women; and from cerebrovascular disease 59/100,000 for men and 52/100,000 for women. Preliminary experience has shown that Sino-MONICA-Beijing is a well-standardized project of long-term surveillance of CVD in the communities of Beijing.

Adult↗
PubMed1987

Chloroplast genome characterization in the red alga Griffithsia pacifica.

It has been suggested that cyanobacteria served as the ancestors for rhodophytic algae whose chloroplasts contain chlorophyll a and phycobilins, and that a rodophyte served as the plastid source for chromophytic plants that contain chlorophylls a and c. Although organellar DNA has been used to assess phylogenetic relatedness among terrestrial plants and green algae whose chloroplasts contain chlorophylls a and b, few data are presently available on the molecular profile of plastid DNA in chromophytes or rhodophytes. In this study the chloroplast genome of the rhodophytic, filamentous alga Griffithsia pacifica has been characterized. DNA was purified from isolated chloroplasts using protease k treatment and sodium dodecyl sulfate lysis followed by density centrifugation in Hoechst-33258 dye-CsCl gradients. Single and double restriction enzyme digests demonstrate that the DNA prepared from purified chloroplasts has a genome size of about 178 kilobase pairs (kb). A restriction map of this chloroplast genome demonstrates that it is circular and, unlike the chloroplast DNA (cpDNA) in most other plants, contains only a single ribosomal DNA operon. DNA was also purified from the mitochondria that co-isolated with chloroplasts. Mitochondrial DNA consists of molecules that range in size from 27 to 350 kb based on restriction endonuclease digestion and electron microscopic analysis.

Chloroplasts↗
PubMed1986

Human chromosome hot points. V. The effect of four nucleosides on chromosomes in folate-free medium.

Human lymphocytes from 18 healthy adults were cultured in minimal essential medium without folic acid. The addition of 4 mM cytidine or 1 mM guanosine to cultures 24 h prior to harvest produced a statistically significant increase in hot point 3p14 breaks. An excess of 3 mM adenosine or thymidine had no such effect on the hot point. The mechanism of the effects of nucleosides on hot points was discussed.

Adult↗
PubMed1986

Endogenous microbial dissemination following severe burns in rats.

This study suggests that damage to the intestinal lining, an important mechanical barrier against bacterial invasion, is the main factor leading to the dissemination of endogenous microbes. Reduced phagocytic activity of Kupffer cells and compromised opsonic function also appear to contribute to the process.

Animals↗
PubMed1986

Pulmonary surfactant activity after severe steam inhalation injury in rabbits.

Lung water content, Pao2, surface tension (in terms of hysteresis) and lecithin content of both bronchial irrigation fluid and lung homogenates were determined after severe steam inhalation injury in rabbits. At the time of a decrease in Pao2 and an increase in lung water content there was a moderate fall in pulmonary surfactant activity; as shown by a progressive decrease in the area of the hysteresis loop and a decrease of the lecithin content in both bronchial irrigation fluid and lung homogenate. It is proposed that a fall in pulmonary surfactant activity plays an important role in the pathogenesis of pulmonary oedema after inhalation injury. Successive determinations of lecithin content and/or surface tension of bronchial irrigation fluid are recommended as early diagnostic and prognostic aids in severe inhalation injury.

Animals↗
PubMed1985

Human chromosome hot points. IV. Uridine-induced hot-point breaks at 3p14 and 16q23-24 and increased expression of fragile site Xq27 in folate-free medium.

Peripheral lymphocytes from 16 healthy adults, 9 pregnant women, and 3 fragile X syndrome patients were cultured in Eagle's minimum essential medium without folic acid (MEM-FA). The addition of 2 mM, 4 mM, or 8 mM uridine 24 h or 72 h prior to harvest resulted in increases of chromosome gaps or breaks, especially at hot points 3p14, 16q23-24, and at fragile site Xq27. Pregnant women showed higher frequencies of 3p14 breaks and total chromosome breaks than men and non-pregnant women. The other chromosome regions, such as 6q26, 7q23, 7q35, 6p25, Xp22, 14q23 and 11p13, also frequently showed gaps or breaks. The results indicated that the unbalance of nucleotide pools was one of the causes of chromosome breakages. The higher frequencies of chromosome gaps and breaks under the condition of thymidylate stress may be due to the misincorporation of uracil instead of thymine into DNA.

Adult↗
PubMed1985

Anaerobic infections of burns.

From August 1980 to June 1982, 102 burn wound specimens taken from 34 patients were studied for anaerobic cultures. Fifteen instances (14.7 per cent) from 8 patients were positive and altogether 12 species were found. The predominant anaerobes were Bacteroides melaninogenicus, Peptococcus, Bacteroides fragilis, and other strains of Bacteroides and Peptostreptococcus. They were mostly discovered in electric burn wounds and burn wounds affecting the perianal and oral areas. Wounds with anaerobic infection usually appeared gaseous, necrotic and ischaemic with foul odour. Nineteen blood samples from 10 burn patients were also studied for anaerobic cultures, and two were positive, one caused by Bacteroides and the other by mixed infection of Peptococcus and Serratia, indicating that the anaerobes played an important role in burn infections. It seems necessary to perform anaerobic culture studies in burn patients as a routine. A comparative study between anaerobic culture and indirect immuno-fluorescence method was undertaken for Bact. fragilis and Bact. melaninogenicus in 47 burn wounds. It showed that the immunofluorescence method was a more rapid, simple, sensitive and specific diagnostic method.

Adolescent↗