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Biomedical subjects

L Han

Publications and source records attributed to L Han.

At least 127 records · Page 7Linked to original sources
PubMed1994

Cloning and characterization of polyketide synthase genes for jadomycin B biosynthesis in Streptomyces venezuelae ISP5230.

Hybridizing fragments in the genomic DNA of Streptomyces venezuelae ISP5230, which produces the jadomycin group of angucycline antibiotics, were detected by probing with actI DNA from Streptomyces coelicolor A3(2). The hybridizing regions were isolated from a 16.5 kb insert of S. venezuelae DNA recovered from a genomic library cloned in a lambda replacement vector. Subcloning and sequencing of a 4.8 kb segment of the insert, containing regions hybridizing to actIII as well as actI, identified five open reading frames (ORFs). The deduced polypeptide products of the ORFs closely resemble in sequence the components of streptomycete type-II polyketide synthases (PKSs): the ORF1 product corresponds to the ketoacyl synthase, and the ORF2 product to a polypeptide closely related to the ketoacyl synthase and involved in determining chain length; the ORF3 product matches the acyl carrier protein; ORF4 encodes a bifunctional cyclase/dehydrase; and ORF5 encodes a ketoreductase. Integration into the chromosomal DNA of a plasmid containing a segment of the ORF2-ORF4 region severely depressed jadomycin B biosynthesis; since the integrant showed no change in growth or spore pigmentation, the cloned PKS genes are presumed to encode enzymes in the pathway for jadomycin biosynthesis.

Amino Acid Sequence↗
PubMed1994

Tannins of theaceous plants. V. Camelliatannins F, G and H, three new tannins from Camellia japonica L.

Two new complex tannins, camelliatannins F (3) and G (4), were isolated from the leaves of Camellia japonica L. (Theaceae), and their structures, each consisting of an epicatechin unit and a C-glucosidic ellagitannin moiety, were elucidated. A new dimeric hydrolyzable tannin, named camelliatannin H (5), was isolated from the fruits of this plant. Camelliins A (6) and B (7), and camelliatannin A (1) and 3 were also isolated from the fruits.

Carbohydrate Sequence↗
PubMed1994

[Surgical treatment and diagnosis of adult bronchogenic cysts].

Between 1974 and 1993, 22 adults with bronchogenic cysts were operated in our hospital: 14 men and 8 women, ranging from 11 to 62 years old. The location was mediastinal in 13 (59.1%) and intrapulmonary in 9 (40.9%). Cysts were symptomatic (chest pain and recurrent bronchiolitis) in 20 patients (91%). The perioperative complications include infection in lungs and in the cysts and dysphagia due to esophageal compression. Chest pain was the main symptom in mediastinal cyst and recurrent infection of lungs in intrapulmonary cysts. Plain chest radiographs showed round shadows. Occasional air-fluid levels, peripheral calcification may be found. Operation is the best method for treating cysts. All cysts were completely excised. No perioperative, late complication or recurrence developed in our patients. Operation was recommended in most instances to confirm the diagnosis, to relieve symptoms, and to prevent complications.

Adolescent↗
PubMed1994

Selenium supplement in the prevention of pregnancy induced hypertension.

The effect of selenium (Se) supplement on pregnancy was studied in 52 pregnant women with high risk factors of pregnancy induced hypertension (PIH). They were given natural Se dietetic liquid (100 micrograms/d) for 6-8 weeks during late pregnancy, and 48 controls were given placebo. They received similar routine prenatal care. The results revealed that Se supplement on the pregnant women prevented and decreased the incidence of PIH and gestational edema, and elevated the mother's blood Se level by 0.1008 +/- 0.091 ppm in the treated group while decreased by 0.0402 +/- 0.046 ppm in the control group (P < 0.01). The umbilical blood Se level was 0.2756 +/- 0.100 ppm in the treated group and 0.1544 +/- 0.051 ppm in the control (P < 0.01). The differences of the neonatal birth weight and the amount of postpartum hemorrhage between the two groups were not significant.

Adult↗
PubMed1993

Pyruvate enhances recovery of rat hearts after ischemia and reperfusion by preventing free radical generation.

Pyruvate protects myocardium from ischemic and anoxic injury, effects that have been attributed to beneficial metabolic alterations. Pyruvate also reacts with hydrogen peroxide in vitro, and pyruvate prevents free radical injury in other organs. Hearts supplied with 2 mM of pyruvate with glucose during reperfusion recovered significantly more mechanical function (81%) than those provided with 2 mM of acetate (which does not react with free radicals) and glucose (49%) or glucose alone (27%). Pyruvate significantly reduced free radical generation during reperfusion as measured with electron spin resonance using the spin-trap 5,5-dimethyl-1-pyrroline-1-oxide. In a model of direct oxidant stress, hearts were perfused with 0.28 mM of hydrogen peroxide. In this model, loss of function was almost entirely prevented by addition of 2 mM of pyruvate. From these results we conclude an important mechanism of protection when pyruvate is supplied during reperfusion is limitation of oxygen-derived free radical damage.

Animals↗
PubMed1993

[Effect of selenium supplement on prevention of pregnancy-induced hypertension].

We studied the effect of selenium supplement on 52 pregnant women with high risk factors of pregnancy-induced hypertension (PIH) who were given the natural Se dietetic liquid (100 micrograms/day) for 6-8 weeks during late pregnancy and 48 controls. They were subjected to the same prenatal care. Se supplement on the pregnant women prevented or lowered the incidence of PIH and gestational edema. Se supplement on the pregnant women elevated the mother's blood Se level (0.1008 +/- 0.091 ppm in the treated group vs 0.0402 +/- 0.046 ppm in the control group, P < 0.01) and umbilical blood Se level (0.2756 +/- 0.1 ppm in the treated group vs 0.1544 +/- 0.051 ppm in the controls, P < 0.01). The difference of the neonatal birth weight and the amount of postpartum hemorrhage between the two groups were not significant.

Adult↗
PubMed1993

[Image analysis of effects of 4 drugs on coronary occlusion and myocardial reperfusion injury].

Myocardial infarction induced by coronary occlusion (O model) and reperfusion (R model) and the effects of nitroglycerin (Nit), propranolol (Pro), lidocaine (Lid), nifedipine (Nif), and saline were studied in rats by image analysis and weighing methods. The results showed that the myocardial infarct size (MIS) in R and O models were 27 +/- 8% and 39 +/- 6%, respectively (P < 0.01). The roundness and the distances from the border of the infarct zone (IZ) to endocardium or epicardium in R model were greater than those in O model, while the gray level difference between normal and infarct myocardium (delta G) in the R model was less than that in O model. MIS of Nit group in O and R models were 23 +/- 12% and 16 +/- 7%, respectively, which were significantly less than those in Lid, Nif groups, and saline. The reduction of MIS was also found in Pro group in both models. The results suggested that early restoration of blood flow resulted in the salvage of injured myocardium and Nit and Pro were found to have beneficial effects in both models.

Animals↗
PubMed1992

The effects of various clinical factors on marginal enamel micro-cracks produced around composite restoration.

In this study, enamel micro-cracks produced around composite restorations were observed on surfaces and vertical sections, using a stereomicroscope and a scanning electron microscope (SEM). The effects of various clinical factors, i.e. the curing system, the marginal form and the polishing period after filling, on the incidence of marginal enamel micro-cracks were examined. Enamel micro-cracks were observed on all of the class 1 and 5 composite restorations when the cavity had no marginal bevel and the restorations were polished immediately after filling. Enamel micro-cracks distributed approximately parallel to the cavity margin and located 0.01-0.3 mm from the restored cavity margin. The occurrence of enamel micro-cracks was higher in light-cured composite resin restorations than in chemical-cured ones, for non-beveled cavities when polished 10 min or 24 hours after filling. The occurrence of micro-cracks was reduced by marginal beveling and delayed polishing.

Composite Resins↗
PubMed1991

Inhibition of Moloney murine leukemia virus-induced leukemia in transgenic mice expressing antisense RNA complementary to the retroviral packaging sequences.

Recombinant plasmids pLP psi as and pCP psi as were constructed by positioning the Moloney murine leukemia virus (M-MuLV) proviral packaging (psi) sequences in reverse orientation under the transcriptional regulation of lymphotropic promoter/regulatory elements from the M-MuLV long terminal repeat or the cytomegalovirus immediate-early region. Linear fragments containing the antisense psi and the appropriate transcriptional regulatory sequences from these plasmids were introduced into the mouse germ line by zygote microinjection. The chromosomal integration, germ-line transmission, and lymphocyte-directed expression of the antisense psi RNA were confirmed. Control (nontransgenic) and transgenic mice containing either the pLP psi as or the pCP psi as sequences were infected with M-MuLV on the day of birth and assayed for signs of leukemia between 12 and 14 weeks of age with standard assay procedures. While 31% (11 of 36) of the control, nontransgenic, mice developed leukemia, none of the antisense psi transgenic mice developed any symptoms of leukemia. The pCP psi as sequences were also introduced into mouse NIH 3T3 cells and stably transformed cell lines were isolated. When infected with M-MuLV these cells were shown to produce virus devoid of packaged viral RNA.

Animals↗
PubMed1991

Interspecific hybridization of Streptomyces by electrofusion.

Two auxotrophic mutants of S. rimosus and S. griseus were obtained through nitrosoguanidine treatment. The equal volume of two protoplast containing 10(9)/ml were mixed and put in the fusion chamber of Shimadzu somatic hybridizer-SSH-C11. Fifteen seconds after protoplast pearl chains were formed through electrophoresis under high-frequency electric field (800 V/cm 1 MHz), it was turned into high DC pulse field (6 kV/cm) for 20 seconds immediately to make the protoplast to be fused. Colonies were raised on regeneration medium R3. 34971 colonies were selected and transferred to basic medium containing two antibiotics. Nine of them were prototrophic fusant with double resistance. They had good biological characteristics of parent strain, such as faster growth rate, higher productivity and stronger microbial activity. Bioautographic result showed that it can produce bioactive characteristics that their parents do not have.

Anti-Bacterial Agents↗
PubMed1989

[Studies on the chemical constituents of Ardisia crenata Sims].

A new bergenin derivative isolated from the root of Ardisia crenata was determined to be 11-o-syringylbergenin by spectral methods. Other compounds were identified as spinasterol, series fatty acids, beta-sitosterol-beta-D-glucoside, norbergenin and sucrose respectively. The last three were obtained for the first time from the genus of Ardisia.

Benzopyrans↗