Biomedical subjects

R Li

Publications and source records attributed to R Li.

At least 379 records · Page 21Linked to original sources

PubMed1997

[Study on the stunted culture of trees of Scaphium lychnophorum].

Taking these cultural practices, grafting by the ingraftment of side branch on the place of flowering with the dwarf stock, tip pruning on time to make branches growing and rational pruning etc can make the trees of Scaphium lychnbophorum dwafing effectively. The stunted trees are only high 3-5 m and their branches are only high about 1 m from the ground. Some of them first flower until five years after they are cultivated.

Malvaceae↗

PubMed1997

[The prognostic significance of regular bone marrow aspirations during induction chemotherapy in acute myeloid leukemia].

OBJECTIVE: To evaluate the prognostic significance of regular aspirations during induction chemotherapy in acute myeloid leukemia. METHODS: Regular bone marrow aspirations were performed during the first course of induction chemotherapy in 96 cases of de novo AML. RESULTS: Complete remission (CR) rate after the first course in patients with < or = 0.10 bone marrow blasts at the 7th day on chemotherapy was higher than that in patients with > 0.10 blasts (64.6% vs 40.0%, P < 0.05). Prolonged the chemotherapy course for a few more days in the latter group of patients increased CR rate from 25.0% to 50.0%. CR rate in patients with < or = 0.10 bone marrow blasts at the nadir of white blood cell count after chemotherapy was higher than that in patients with > 0.10 blasts (66.0% vs 25.8%, P < 0.005), and the refractory cases were significantly fewer in the former group of patients (7.5% vs 45.2%, P < 0.005). CONCLUSION: Regular bone marrow aspirations during induction chemotherapy were helpful in predicting the prognosis and guiding the treatment in AML.

Adolescent↗

PubMed1997

p53-induced p21 controls DNA replication.

The p21 protein, a regulator of cyclin-dependent kinases (CDKs), has been thought to be one of the key proteins to function in cell proliferation suppression upon DNA damage. In normal cells but not in many tumor cells, p21 forms a quaternary complex with a cyclin, a CDK and the proliferating cell nuclear antigen (PCNA), one of the DNA replication and repair factors, suggesting that this complex might play an important role in maintaining the integrity of the genome. Here, we have focused on the p21-PCNA interaction in the context of DNA replication or DNA repair, presenting the data from both in vitro and in vivo studies of the p21 function.

Antigens, Viral, Tumor↗

PubMed1997

Previous cesarean birth. A risk factor for placenta previa?

OBJECTIVE: To study the risk of placenta previa following a previous cesarean birth. STUDY DESIGN: We conducted a population-based, case-control study using 1990 North Carolina state birth certificate data. The study population included 342 women with a pregnancy complicated by placenta previa and 1,082 randomly selected controls. Analysis was restricted to women who reported one or more previous live births and delivered a singleton, live neonate. Adjusted odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated using logistic regression, controlling for maternal age, race, prior spontaneous or induced abortions and cigarette use. RESULTS: When the data were adjusted for maternal age, race, prior spontaneous or induced abortions, and cigarette use, women who had a previous cesarean birth and had a parity of 3 were 1.7 times more likely (OR 1.7, 95% CI 0.7, 4.2) and women of parity > or = 4 were 5.5 times more likely (OR 5.5, 95% CI 1.0, 30.1) to have placenta previa than women of parity 1 who had a previous cesarean birth. CONCLUSION: Women with a history of a previous cesarean birth and parity > or = 3 were at increased risk of having a pregnancy complicated by placenta previa.

Abortion, Induced↗

PubMed1997

[Intracytoplasmic sperm injection in the management of male infertility and idiopathic fertilization failure].

OBJECTIVE: To demonstrate the efficacy of intracytoplasmic sperm injection (ICSI) in treatment male infertility and idiopathic fertilization failure. METHODS: 31 couples received intracytoplasmic sperm injections because of severe oligo-astheno-teratospermia or idiopathic infertility. Ovarian stimulation was achieved by conventional protocol. Transvaginal ultrasound-guided oocyte collections were done 36 hours after hCG injection. Only matured oocytes were selected for microinjection. RESULTS: 237 oocytes were treated by intracytoplasmic sperm injection; normal fertilization and cleavage occurred in 132 of 213 oocytes which were survived (62.0% normal fertilization rate). From 1995 to 1996, clinical pregnancies were achieved in 8 cases (25.8%). The first ICSI baby was delivered on October 3, 1996. CONCLUSION: Intracytoplasmic sperm injection has improved the results of IVF-ET treatment in male and idiopathic infertility.

Adult↗

PubMed1997

[Polymorphism and pologenetic affinities of genotype in pathogenic yeast].

The classification of pathogenic yeast, which is one of the most common reasons of opportunistic infection in human body, will be useful for the epidemiological survey and clinical works. The genotypic polymorphism of intergenus, interspecies and intraspecies in 48 isolates, including Candida, Cryptococcus, Torulopsis, Trichosporon, Saccaromyces had been administered carefully with patterns amplified by RAPD (Randomly amplified polymorphic DNA) in 53 primers. The pologenetic affinities had been evaluated by similarity coefficients obtained from these profiles. The results indicated that there are significant difference among intergenus, interspecies and intraspecies in Candida and related yeast. The similarity coefficients among Candida and Crytococcus, Trichosporon were maintained about 80%. The similarity coefficients among interspecies of Candida ranged from 82%-87%, and ones of intraspecies of different Candida species were more than 90%. The genotypic typing of species except C. guilliermondii seems to be related to morphological classification.

Candida↗

PubMed1997

[Application of artificial humeral head in the treatment of tumor of upper end of humerus].

In order to restore the function of shoulder joint in patient with tumor of upper end of humerus, artificial humeral head replacement was performed. The materials included resinene, nylon-6 and large molecular polyethylene from 1978 to 1993, 14 patients were treated. The tumors involved in this group were giant cell tumor, synviosarcoma, bone cyst, osteochondroma, osteoblastoma, osteofibrosarcoma, osteosarcoma, chondrosarcoma, parosteosarcoma and malignant giant cell tumor. After resection of the tumor, the artificial prosthesis was implanted with bone cement. After 1 to 16 years follow-up, functions of the shoulder joint were reserved in 86% of the patients.

Adult↗

PubMed1997

[Color Doppler flow imaging study on the changes of collateral circulation between portal-superior vena cava and azygos vein before and after endoscopic ligation of the esophageal varix].

Color Doppler flow imaging (CDFI) was performed in 35 patients with portal hypertension and esophageal varix. Thirty subjects were served as control. After esophageal variceal ligation, CDFI observed that the portal-superior vena cava collateral veins were partialy blocked. The esophageal varices disappeared. The esophageal wall thinned. Diameter of left gastric vein enlarged and blood flow velocity decreased. Azygos diameter was reduced and blood flow velocity was decreased. Although diameter of portal vein was not changed, the blood flow velocity slightly increased. The results suggest that ligation treatment can have the tendency to increase blood flow of liver and stomach, which might aggravate gastric mucosal lesion.

Adolescent↗

PubMed1997

[The sonarographic diagnosis of prostatic and periprostatic cysts on high resolution transrectal ultrasound imaging].

The symptoms of prostatic and periprostatic cysts are nonspecific and digital rectal examination has no definite findings detected. The conventional radiological plain film cannot define the relationship of a cyst to the surrounding structures. The use of MRI as a means in detection is too expensive. To solve these problems, we detected 118 cysts in 73 patients by transrectal ultrasound (TRUS) and discussed the TRUS imaging findings of various prostate and periprostate cysts with illustrations from our clinical practice. We suggest that TRUS can be used routinely, because its distinct advantage of high resolution for minute nodular or cystic lesion detection with high quality image demonstrates the relationship of surrounding structures, and provides an outstanding novel diagnostic modality.

Adult↗

PubMed1996

Independent evolution of the prochlorophyte and green plant chlorophyll a/b light-harvesting proteins.

The prochlorophytes are oxygenic prokaryotes differing from other cyanobacteria by the presence of a light-harvesting system containing both chlorophylls (Chls) a and b and by the absence of phycobilins. We demonstrate here that the Chl a/b binding proteins from all three known prochlorophyte genera are closely related to IsiA, a cyanobacterial Chl a-binding protein induced by iron starvation, and to CP43, a constitutively expressed Chl a antenna protein of photosystem II. The prochlorophyte Chl a/b protein (pcb) genes do not belong to the extended gene family encoding eukaryotic Chl a/b and Chl a/c light-harvesting proteins. Although higher plants and prochlorophytes share common pigment complements, their light-harvesting systems have evolved independently.

Amino Acid Sequence↗

PubMed1996

Lack of a pharmacologic interaction between rifabutin and methadone in HIV-infected former injecting drug users.

Rifampin, an agent known to decrease the half-life of methadone, and rifabutin are two rifamycins that are structurally similar and share mechanisms of action. Hence the possibility of a drug-drug interaction between rifabutin and methadone was evaluated in 24 methadone-maintained, former injecting drug users infected with the human immunodeficiency virus. The study was an open-label, drug-drug interaction and safety trial in which patients were followed for 15 days. Each patient received rifabutin 300 mg as a single dose concomitantly with their individualized methadone dosage. No significant differences in methadone peak plasma concentration, time to peak plasma concentration, area under the plasma concentration-time curve, systemic clearance or renal clearance was observed in the presence of rifabutin. Seventy-five percent of the patients reported at least one symptom of narcotic withdrawal during the study, however, these symptoms were mild. A relationship between the development of narcotic withdrawal and methadone systemic exposure could not be established. Concurrent administration of rifabutin and methadone appeared to be safe in human immunodeficiency virus-infected injecting drug users maintained on stable doses of methadone and is not expected to produce any significant changes in the pharmacokinetics of methadone in these patients.

AIDS-Related Opportunistic Infections↗

PubMed1996

Leukocyte transmembrane potential in bipolar illness.

Abnormalities in ion regulation and distribution are commonly reported in bipolar disorder. In an effort to determine if these alter cellular physiological function, we determined the transmembrane potential (TMP) in mononuclear leukocytes from normal individuals and patients with bipolar illness either during normal phase or manic and hypomanic episodes. TMP was analyzed by flow cytometry using dihexyloxacarbocyanine iodide (DIOC6(3)), a cationic potential sensitive fluorescent dye. A normal range was established from measurements on leukocytes from 5 control individuals. TMP of manic and hypomanic patients was significantly hyperpolarized (P = 0.0036). The TMP of euthymic bipolar individuals was not different from normal controls. Pathologic moods in bipolar illness may be associated with altered cellular membrane physiology.

Acute Disease↗

PubMed1996

The role of p53 in the induction of polyploidity of myelomonocytic leukemic M1/2 cells.

p53 was shown to play a central role in the maintenance of genomic integrity. The present experiments suggest that p53 is involved in the control of cell ploidity. Using a p53 non-producer cell line, M1/2, that was reconstituted to express either wild type or mutant p53 protein, by infection with the temperature sensitive (Ts) p53Val135 virus, it was found that both loss of wild type p53 or overexpression of mutant p53, may be associated with the generation of cell polyploidity. Overexpression of mutant p53 protein enhanced the appearance of giant cells that further accumulated following gamma-irradiation. Expression of wild type p53 reduced the level of giant cells which accumulated in the parental M1/2 p53 non-producer cells following gamma-irradiation. This activity of the wild type p53 seems to be mediated by either the reduction in the rate of giant cell generation, as observed in M1/2 derived cell lines expressing low levels of wild type p53 protein or by facilitating their apoptosis, as observed in wild type p53 high-producer cells. The latter conclusion is further supported by the observation that isolated giant cells are directly induced to undergo apoptosis following wild type p53 expression.

Animals↗

PubMed1996

Expression of the human cytochrome c1 gene is controlled through multiple Sp1-binding sites and an initiator region.

It is widely accepted that nuclear genes that encode proteins of the oxidative-phosphorylation system are regulated by nuclear factors believed to be specific for such genes. In the present study we show that the promoter for the human cytochrome c1 gene is an exception, in that it involves only conserved Sp1 core elements and an initiator region. Maximal promoter activity within a 1.4-kb 5' flanking region of the cytochrome c1 gene is contained in a fragment (-72 to +18) that lacks TATA and CCAAT elements. The transcriptional start site was mapped to an initiator region by RNase protection of mRNA from human HepG2 cells, and by primer extension of in vitro-generated transcripts, to a sequence that is highly similar to the dihydrofolate reductase family of initiators. Deletion of this region (+1 to +18) severely impairs transcription initiation. Sp1 core elements centered at nucleotides -21 and -39 define the activation domain of the proximal promoter. Only the -39 element is protected from DNase I in the presence of crude nuclear extracts. However, transfection, gel-mobility-shift, supershift and in vitro-transcription experiments show that the -21 element binds Sp1 protein and contributes to transcription activation. No other functional oxidative-phosphorylation-specific response elements have been identified. These data implicate Sp1 as a single activating factor for an oxidative-phosphorylation gene.

3T3 Cells↗

PubMed1996

Abrogation of shedding of immunosuppressive neuroblastoma gangliosides.

Shedding of tumor cell gangliosides may contribute to tumor cell escape from host immune destruction. Thus, it would be of interest to block the shedding of these immunosuppressive molecules. To this end, we studied a ceramide analogue, D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP). D-PDMP is a potent inhibitor of glucosylceramide synthase and thereby the synthesis of cellular glycosphingolipids. Exposure of LAN-5 human neuroblastoma cells to 10 microM D-PDMP for 5 days almost completely abolished the shedding of gangliosides (from 240 to 8 pmol/10(8) cells/h), whereas cellular ganglioside synthesis was reduced by 90%. A shorter (3-day) treatment of LAN-5 cells with 10 microM D-PDMP was already effective in inhibiting shedding (by 86%) even while the cellular ganglioside content was still high. Specificity was evidenced by the only minimal effect of D-PDMP on the synthesis of sphingomyelin and phosphatidylcholine. Therefore, certain pharmacological agents, such as D-PDMP, may be useful in abrogating tumor ganglioside shedding and its consequent biological effects in vivo.

Cell Division↗

PubMed1996

Cyclic HIV protease inhibitors: synthesis, conformational analysis, P2/P2' structure-activity relationship, and molecular recognition of cyclic ureas.

High-resolution X-ray structures of the complexes of HIV-1 protease (HIV-1PR) with peptidomimetic inhibitors reveal the presence of a structural water molecule which is hydrogen bonded to both the mobile flaps of the enzyme and the two carbonyls flanking the transition-state mimic of the inhibitors. Using the structure-activity relationships of C2-symmetric diol inhibitors, computed-aided drug design tools, and first principles, we designed and synthesized a novel class of cyclic ureas that incorporates this structural water and preorganizes the side chain residues into optimum binding conformations. Conformational analysis suggested a preference for pseudodiaxial benzylic and pseudodiequatorial hydroxyl substituents and an enantiomeric preference for the RSSR stereochemistry. The X-ray and solution NMR structure of the complex of HIV-1PR and one such cyclic urea, DMP323, confirmed the displacement of the structural water. Additionally, the bound and "unbound" (small-molecule X-ray) ligands have similar conformations. The high degree of preorganization, the complementarity, and the entropic gain of water displacement are proposed to explain the high affinity of these small molecules for the enzyme. The small size probably contributes to the observed good oral bioavailability in animals. Extensive structure-based optimization of the side chains that fill the S2 and S2' pockets of the enzyme resulted in DMP323, which was studied in phase I clinical trials but found to suffer from variable pharmacokinetics in man. This report details the synthesis, conformational analysis, structure-activity relationships, and molecular recognition of this series of C2-symmetry HIV-1PR inhibitors. An initial series of cyclic ureas containing nonsymmetric P2/P2' is also discussed.

Animals↗

PubMed1996

The scl gene product is required for the generation of all hematopoietic lineages in the adult mouse.

Homozygosity for a null mutation in the scl gene causes mid-gestational embryonic lethality in the mouse due to failure of development of primitive hematopoiesis. Whilst this observation established the role of the scl gene product in primitive hematopoiesis, the death of the scl null embryos precluded analysis of the role of scl in later hematopoietic development. To address this question, we created embryonic stem cell lines with a homozygous null mutation of the scl gene (scl-/-) and used these lines to derive chimeric mice. Analysis of the chimeric mice demonstrates that the scl-/- embryonic stem cells make a substantial contribution to all non-hematopoietic tissues but do not contribute to any hematopoietic lineage. These observations reveal a crucial role for the scl gene product in definitive hematopoiesis. In addition, in vitro differentiation assays with scl-/- embryonic stem cells showed that the scl gene product was also required for formation of hematopoietic cells in this system.

Animals↗

PubMed1996

Sp1 activates and inhibits transcription from separate elements in the proximal promoter of the human adenine nucleotide translocase 2 (ANT2) gene.

Expression of the adenine nucleotide translocator 2 (ANT2) gene is growth regulated. We report a feature of the ANT2 promoter that involves a novel regulatory function for the Sp1 transfactor. We show that expression from the ANT2 proximal promoter is modulated through three Sp1 elements, two of which activate and one of which partially inhibits transcription. The inhibitor site, box C, is juxtaposed to transcription start (nucleotides -7 to -2). Sp1 bound to box C decreases transcription initiation. This was demonstrated by introducing mutations in box C which (a) increased chloramphenicol acetyltransferase expression in the transient transfection assay and (b) inhibited binding of both purified Sp1 and Sp1 in crude nuclear extracts. The activating elements (A and B boxes) are located at adjacent sites in the distal region of the proximal promoter. Mutation of either box inhibits transfection by 90%, indicating that they act in a synergistic manner. Supershift experiments with crude nuclear extracts showed that only Sp1 was bound to the three GC boxes. The finding that Sp1 acts as an activator/inhibitor within the same promoter region was verified in NIH3T3, HeLa, JEG3, and COS-1, indicating that this dual effect of Sp1 is widely preserved. These data suggest a unique role for Sp1 and raise the possibility that growth activation of the ANT2 gene is regulated by the interaction of Sp1 on the A, B, and C boxes.

3T3 Cells↗