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Biomedical subjects

L Yang

Publications and source records attributed to L Yang.

At least 343 records · Page 19Linked to original sources
PubMed1999

Novel highly oxygenated bisabolane sesquiterpenes from Cremanthodium discoideum.

Five new highly oxygenated bisabolane sesquiterpenes (1-5) were isolated from Cremanthodium discoideum. Their structures were elucidated on the basis of spectroscopic analysis and chemical transformations. The structure and relative stereochemistry of 1 were determined by single-crystal X-ray crystallography on the acetate derivative, 1a. Compound 1 showed antibacterial activity against Bacillus acidilatici and Bacillus subtilis.

Anti-Bacterial Agents↗
PubMed1999

Retinoic acid receptor antagonist BMS453 inhibits the growth of normal and malignant breast cells without activating RAR-dependent gene expression.

To elucidate the role of RAR-dependent gene transcription in inhibiting breast cell growth, we have investigated the ability of retinoids to suppress growth of normal, immortal, and malignant breast cells. We compared the ability of all trans retinoic acid (atRA) to activate retinoid receptors in normal, immortal, and malignant breast cells, with its ability to inhibit the growth of these cells. Our studies demonstrate that normal breast cells are more sensitive to the growth inhibitory effect of atRA than are immortal nonmalignant breast cells and breast cancer cells. atRA activated RAR-dependent gene transcription in both atRA-sensitive and -resistant breast cells as determined by transfection of a RARE-containing reporter gene. These results demonstrate that activation of RAR-dependent gene transcription by atRA is not sufficient to inhibit growth in atRA-resistant breast cancer cells. To determine whether activation of RAR-dependent gene transcription by atRA is necessary for growth inhibition, we tested the growth suppressive effect of a retinoid (BMS453) which binds RAR receptors and transrepresses AP-1 but does not activate RAR-dependent gene expression. This retinoid inhibited the growth of normal breast cells (HMEC and 184) and T47D breast cancer cells. Breast cancer cells which were resistant to atRA, were also resistant to BMS453. Normal human breast cells were most sensitive to the anti-proliferative effects of BMS453. These results indicate that in some breast cells RAR-dependent transactivation is not necessary for retinoids to inhibit growth. Instead, retinoids may suppress growth by inhibiting transcription factors such as AP-1 through transcription factor crosstalk.

Antineoplastic Agents↗
PubMed1999

Determination of the genotype of a panel of human tumor cell lines for the human homologues of yeast cell cycle checkpoint control genes: identification of cell lines carrying homoallelic missense base substitutions.

A number of human homologues of yeast cell cycle checkpoint control genes have been identified recently. In this study, the sequence alterations in six of such novel human genes (hRAD1, hRAD9, hRAD17, hHUS1, CHK1 and CHES1) were analyzed by PCR-single-strand conformational polymorphism (PCR-SSCP) method on a panel of 25 human tumor cell lines in an attempt to search for possible in vivo cases where any of the checkpoint-related genes are altered in human systems. For hRAD9, hHUS1 or CHK1, no SSCP variant was detected in any of the cell lines tested, indicating a high stability of these genes in human cancer. Most of the SSCP variants found in the other three genes were due to single nucleotide base substitutions. Two cell lines were found to be homozygous for missense-type base substitutions, i.e., Saos-2 was homoallelic for 1637T-->G in hRAD17; and COLO320DM for 1189G-->A in CHES1, indicating a possible use of these cell lines for further study. The former nucleotide change in hRAD17, which causes a change of amino acid from arginine to lysine at codon 546, was supposed to be polymorphic. Considering that lysine, but not arginine, is the amino acid that is well conserved among fission yeast, mouse and monkey at the corresponding position, coexistence of both alleles in human may have a functional or selectional implication.

Alleles↗
PubMed1999

Autologous peripheral blood stem cell transplantation for Waldenstrom's macroglobulinemia.

We report a 50-year-old male patient with Waldenstrom's macroglobulinemia poorly responsive to conventional chemotherapy, who went on to receive high-dose melphalan as conditioning before autologous PBSC infusion. Autologous hematopoiesis was reconstituted 5 weeks after transplant. Complete remission was confirmed by blood and marrow examination. The patient remains well at 12 months, with no detectable monoclonal IgM in his serum and absence of plasmacytoid lymphocytes in his marrow. Our results suggest that, at least in this case, high-dose chemotherapy with autologous PBSC support was an effective therapeutic approach for Waldenstrom's macroglobulinemia.

Hematopoietic Stem Cell Transplantation↗
PubMed1999

Determination of genetic relationships among five indigenous Chinese goat breeds with six microsatellite markers.

Microsatellite variation was analyzed in five Chinese indigenous goat breeds, which include four Cashmere breeds (Tibetan, Neimonggol, Liaoning, Taihang) and one Hubei local breed (Matou) used for meat production. Five ovine and one bovine microsatellites, selected from eight ovine microsatellites and five bovine microsatellites were suitable for use in this study. With these six microsatellites, allele frequencies, heterozygosity, polymorphism information content (PIC) and effective allele number were calculated. A neighbor-joining tree was constructed using Nei's standard genetic distance (1978). In the tree, Neimonggol and Liaoning were grouped together, then with Taihang; while Tibetan and Matou individually had their own branch. The genetic relationship of five breeds corresponds to their history and geographic origins.

Animals↗
PubMed1999

Metabolism and functional effects of sphingolipids in blood cells.

We examined the sphingolipid metabolism of peripheral blood cells, i. e. platelets, erythrocytes, neutrophils and mononuclear cells. A distinguishing characteristic of sphingolipid metabolism in these highly differentiated cells was their high sphingosine (Sph) kinase activity. The occurrence of [3H]sphingosine 1-phosphate (Sph-1-P) from [3H]Sph (actively incorporated from the outside) in the blood cells was strong, long-lasting, and independent of cell activation. Hence, the possibility of Sph-1-P playing a second messenger role is remote in these cells. About 40% of platelet Sph-1-P could be released extracellularly by 12-O-tetradecanoylphorbol 13-acetate, possibly through mediation by protein kinase C. On the other hand, in erythrocytes, neutrophils and mononuclear cells a significant percentage of Sph-1-P formed inside the cell was discharged without stimulation, whereas the stimulation-dependent release was marginal. In contrast to active [3H]Sph conversion to [3H]Sph-1-P, formation of [3H]sphingomyelin was barely detectable in the blood cells; this was especially true for anucleate platelets and erythrocytes. The Sph --> Sph-1-P pathway may become predominant over the Sph --> Cer --> sphingomyelin pathway during late-stage differentiation into platelets or erythrocytes. Sph and its methylated derivative, N, N-dimethylsphingosine, induced apoptosis not only in neutrophils but also in mononuclear cells, whereas Sph-1-P elicited Ca2+ mobilization in platelets. Our results suggest that all blood cells may remove plasma Sph, which is harmful or suppressive to cellular functions, and change it into Sph-1-P, acting as the source of plasma Sph-1-P, which may play a variety of important roles in blood vessels.

Apoptosis↗
PubMed1999

Haplotype analysis of families with erythropoietic protoporphyria and novel mutations of the ferrochelatase gene.

Ferrochelatase, the enzyme that catalyzes the terminal step in the heme biosynthetic pathway, is the site of the defect in the human inherited disease erythropoietic protoporphyria. Molecular genetic studies have shown that the majority of erythropoietic protoporphyria cases are transmitted in dominant fashion and that mutations underlying erythropoietic protoporphyria are heterogeneous. We performed haplotype analysis of American families that shared recurrent ferrochelatase gene mutations yet had forbearers from several European countries. This was to gain insight into whether these mutations represent mutational hotspots at the ferrochelatase gene, or propagation of ancestral alleles bearing the mutations. Two recurrent mutations were found to occur on distinctive chromosome 18 haplotypes, consistent with being hotspot mutations. On the other hand, we found three sets of two unrelated families that shared the same haplotypes bearing these mutations, which could reflect geographic dispersion of ancestral mutant alleles. In addition, we report novel mutations associated with erythropoietic protoporphyria: g(+ 1)-->t transversion of the exon 4 donor site, g(+ 1)-->a transition of the exon 6 donor site, and t(+ 2)-->a substitution at the exon 9 donor site; these mutations are predicted to cause splicing defects of the associated exons. We also identified a g(+ 5)-->a transition of the exon 1 donor site in four unrelated families with erythropoietic protoporphyria, and a G(- 1)-->A substitution at the exon 9 donor site in an additional family. The probability that these sequence changes are normal polymorphisms was virtually excluded (p < 0.0001) by their absence in 120 ferrochelatase alleles from 30 normal subjects and 30 individuals with manifested erythropoietic protoporphyria with or without a known mutation.

Alternative Splicing↗
PubMed1999

Mono- and sesquiterpenes and antifungal constituents from Artemisia species.

In addition to beta-sitosterol and alpha-amyrin detected in all the investigated species, the extract of the aerial parts of Artemisia giraldii var. giraldii gave stigmasterol, daucosterol, sesamine, luteolin, eupafolin, hispidulin, eupatilin, belamcanidin, pinitol, artemin, ridentin, and a new antifungal monoterpene (named santolinylol) while that of the aerial parts of A. mongolica afforded sesamine, eupafolin, eupatilin, matricarin, and a new germacranolide (3-oxo-11 alpha H-germacra-1(10)E,4Z-dien-12,6 alpha-olide), and that of the aerial parts of A. vestita yielded stigmasterol, daucosterol, umbelliferone, scopolin, scoparone, and isoscopoletin-O-glucoside. Pinitol, first reisolated from Artemisia genus, was shown to inhibit the growth of the human pathogenic fungi Candida albicans, Aspergillus flavus, A. niger, Geotrichun candidum, Trichophyton rubrum, and Epidermophyton floccosum. Umbelliferone was also active against Candida tropicalis, A. flavus, G. candidum, T. rubrum, and E. floccosum. The flavones hispidulin and belamcanidin were almost equally inhibitory to the growth of A. flavus, G. candidum, T. rubrum, and E. floccosum, and santolinylol to C. albicans, A. flavus, A. niger, G. candidum, T. rubrum, and E. floccosum. In addition, ridentin was active against the growth of the plant pathogenic fungus Cladosporium cucumerinum.

Antifungal Agents↗
PubMed1999

Dose-dependent response to IFN-gamma in muscle flap microcirculation.

In this study, the authors attempted to determine the effects of intraarterial administration of various doses of Interferon-gamma (IFN-gamma) on microcirculation in a rat muscle flap model. In Group 1 (control), 0.6 ml vehicle solution-PBS-BSA, in Group 2 0.6 ml IFN-gamma (25 ng/ml), in Group 3 0.6 ml IFN-gamma (50 g/ml), in Group 4 0.6 ml IFN-gamma (100 g/ml), were injected. The diameter of the cremaster arterioles and venules, red blood cell velocities, the number of rolling leukocytes and lymphocytes, sticking leukocytes and lymphocytes, capillary perfusion, and endothelial edema index were evaluated. Deterioration of flow hemodynamics was confirmed by a significant decrease in flow velocity in the main artery (A1) (47 percent in Group 3 and 65 percent in Group 4). All dosages of IFN-gamma caused a statistically significant decrease in rolling leukocytes, but this effect was more obvious in the 25 ng/ml group. Injury to the vascular endothelium was confirmed by a two-fold increase in transmigrating leukocytes in the 100 ng/ml group. This was accompanied by 60 percent and 75 percent drops in capillary perfusion, and by 12 percent and 24 percent drops in the endothelial edema index in Groups 3 and 4, respectively. The results indicate that direct intraarterial administration of IFN-gamma in doses higher than 25 ng/ml may be toxic to muscle flaps.

Animals↗
PubMed1999

Endocardial abscesses in children: case report and review of the literature.

The rarity of perivalvular abscesses arising as a complication of bacterial endocarditis in the pediatric population limits its recognition and awareness of its often malignant course. The diagnosis depends on a combination of clinical criteria, including persistent fever and bacteremia, the presence of an atrioventricular block and persistent embolic phenomenon, and transthoracic or transesophageal echocardiographic confirmation. Because of the infrequency of perivalvular abscesses in children, there is no consensus on a treatment strategy. Early detection and intervention with antibiotics and surgical debridement are recommended to decrease the morbidity and mortality associated with this disease. A case of a 14-year-old boy with an aortic root abscess is presented, along with review of other cases reported in the last 20 years in children in relation to risk factors, clinical features, diagnosis, therapy, and mortality.

Abscess↗
PubMed1999

Distinct effect of retroviral-mediated IFN-alpha gene transfer on human erythroleukemic and CD34+ cell growth and differentiation.

Human interferon-alpha (IFN-alpha) has been used in the management of leukemia, but its diverse adverse effects may influence the ability of IFN-alpha to treat this disease. We constructed two retroviral vectors, LSN-IFN-alpha and LNC-IFN-alpha, in which IFN-alpha cDNA was driven by viral LTR and CMV promoters, respectively. After transduction into the PA317 and PG13 retroviral packaging cells, high titers of retrovirus were produced and were used to infect K562 and human BM CD34+ hematopoietic cells. The IFN-alpha gene expression in transduced K562 cells was confirmed by Northern blot, RT-PCR, RIA, and biologic assay. Cell proliferation and cell viability in IFN-alpha-transduced K562 cells were significantly suppressed as compared with control K562 cells. Although the IFN-alpha expression in K562 cells did not affect BCR/ABL expression, it apparently upregulated the production of adhesion molecules (VLA-4 and Mac-1). We evaluated the effect of IFN-alpha gene transfer on human CD34+ cells infected with LSN-IFN-alpha retrovirus with the aid of fibronectin (FN) fragment CH-296 and growth factors. RIA showed that IFN-alpha-transduced CD34+ cells produced 72.2+/-15 U/ml of IFN-alpha compared with 4.3+/-1.2 U/ml in control CD34+ cells. Methylcellulose clonogenic assay indicated that IFN-alpha-transduced CD34+ cells produced similar numbers of burst-forming units-erythrocytes (BFU-E)/colony-forming units-GM (CFU-GM) colonies as compared with control CD34+ cells. Selected colonies expressed IFN-alpha and neo(r) mRNA, as measured by RT-PCR. These studies indicate that retrovirus-mediated IFN-alpha gene transfer may provide a useful tool for studying the effect of IFN-alpha gene transfer on leukemic cells and long-lived CD34+ cells.

Antigens, CD↗
PubMed1999

Sphingosine 1-phosphate formation and intracellular Ca2+ mobilization in human platelets: evaluation with sphingosine kinase inhibitors.

Sphingosine 1-phosphate (Sph-1-P) is considered to play a dual role in cellular signaling, acting intercellularly as well as intracellularly. In this study, we examined the role of Sph-1-P as a signaling molecule in human platelets, using DL-threo-dihydrosphingosine (DHS) and N,N-dimethylsphingosine (DMS), inhibitors of Sph kinase and protein kinase C. Both DMS and DL-threo-DHS were confirmed to be competitive inhibitors of Sph kinase obtained from platelet cytoplasmic fractions. In intact platelets labeled with [3H]Sph, stimulation with 12-O-tetradecanoylphorbol 13-acetate or thrombin did not affect [3H]-Sph-1-P formation. While both DMS and DL-threo-DHS inhibited not only [3H]Sph-1-P formation but also protein kinase C-dependent platelet aggregation, staurosporine, a potent protein kinase inhibitor, only inhibited the protein kinase C-dependent reaction. Hence, it is unlikely that Sph kinase activation and the resultant Sph-1-P formation are mediated by protein kinase C in platelets. Furthermore, Ca2+ mobilization induced by platelet agonists that act on G protein-coupled receptor was not affected by DMS or DL-threo-DHS. Our results suggest that Sph-1-P does not mediate intracellular signaling, including Ca2+ mobilization, in platelets.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1999

Interferon-gamma improves muscle flap microcirculation in double-strand RNA-induced inflammation.

Endothelial cell (EC) activation and subsequent expression of leukocyte adhesion molecules are initial events in multiple pathological processes. Viral double-strand ribonucleic acid (dsRNA) induces EC adhesion protein expression and leukocyte adhesion in vitro. Interferon-gamma (IFN-gamma) has been demonstrated to modulate the expression of certain adhesion proteins. The purpose of this study was to measure the inflammatory response to a viral mimetic--a synthetic dsRNA, polyinosinic-polycytidylic acid (poly-I:C)-on the microcirculation of a muscle flap in a rat model and to determine whether IFN-gamma attenuated the response. Two-stage surgery to create a cremaster muscle end-organ tube flap was performed on 18 male Sprague-Dawley rats in three groups. After intra-arterial injection into the abdominal aorta, the reagents (phosphate-buffered saline-bovine serum albumin [PBS-BSA] in groups I and II, and IFN-gamma in group III) were kept for 1 hour in this end-organ system. During the second stage at 16 hours, after injection into the penile vein (PBS-BSA in group I, poly-I:C in groups II and III), the flap was prepared for intravital microscopic measurement. The following parameters were measured: red blood cell velocity; vessel diameter; number of functional capillaries; and number of rolling, sticking, and transmigrating neutrophils and lymphocytes. Wilcoxon's rank sum test was used for statistical comparison. Poly-I:C caused a 70% increase in the main artery diameter and a 7% increase in velocity. But as a consequence of dynamic activation of leukocyte interaction, a 30% drop in functional capillary perfusion was observed. Injury to the entire vascular endothelium was confirmed by a 160% increase in transmigrating leukocytes. Treatment with IFN-gamma inhibited the poly-I:C-induced inflammation, as shown by 88%, 63%, and 85% decreases in rolling, sticking, and transmigrating leukocytes respectively, and by a 28% increase in capillary perfusion. Treating the system with IFN-gamma in advance, inhibited poly-I:C-induced inflammation, shown by marked decreases in rolling, adhering, and transmigrating leukocytes, and a notable increase in perfused capillaries. These observations reflect an inhibitory effect of IFN-gamma on leukocyte adhesion molecule expression in vascular endothelium in response to dsRNA in a muscle flap at the microcirculatory level.

Animals↗
PubMed1999

Cloning and characterization of adeno-associated virus type 5.

Adeno-associated virus type 5 (AAV5) is distinct from other dependovirus serotypes based on DNA hybridization and serological data. To better understand the biology of AAV5, we have cloned and sequenced its genome and generated recombinant AAV5 particles. The single-stranded DNA genome is similar in length and genetic organization to that of AAV2. The rep gene of AAV5 is 67% homologous to AAV2, with the majority of the changes occurring in the carboxyl and amino termini. This homology is much less than that observed with other reported AAV serotypes. The inverted terminal repeats (ITRs) are also unique compared to those of the other AAV serotypes. While the characteristic AAV hairpin structure and the Rep DNA binding site are retained, the consensus terminal resolution site is absent. These differences in the Rep proteins and the ITRs result in a lack of cross-complementation between AAV2 and AAV5 as measured by the production of recombinant AAV particles. Alignment of the cap open reading frame with that of the other AAV serotypes identifies both conserved and variable regions which could affect tissue tropism and particle stability. Comparison of transduction efficiencies in a variety of cells lines and a lack of inhibition by soluble heparin indicate that AAV5 may utilize a distinct mechanism of uptake compared to AAV2.

Amino Acid Sequence↗
PubMed1999

Activation of ERK by Ca2+ store depletion in rat liver epithelial cells.

In rat liver epithelial (WB) cells, Ca2+ pool depletion induced by two independent methods resulted in activation of extracellular signal-regulated protein kinase (ERK). In the first method, Ca2+ pool depletion by thapsigargin increased the activity of ERK, even when rise in cytosolic Ca2+ was blocked with the Ca2+ chelator BAPTA-AM. For the second method, addition of extracellular EGTA at a concentration shown to deplete intracellular Ca2+ pools also increased ERK activity. In each instance, ERK activation, as measured by an immunocomplex kinase assay, was greatly reduced by the tyrosine kinase inhibitor genistein, suggesting that Ca2+ store depletion increased ERK activity through a tyrosine kinase pathway. The intracellular Ca2+-releasing agent thapsigargin increased Fyn activity, which was unaffected by BAPTA-AM pretreatment, suggesting that Fyn activity was unaffected by increased cytosolic free Ca2+. Furthermore, depletion of intracellular Ca2+ with EGTA caused inactivation of protein phosphatase 2A and protein tyrosine phosphatases. ANG II-induced activations of Fyn, Raf-1, and ERK were augmented in cells pretreated with BAPTA-AM, but ANG II-induced expression of the dual-specificity phosphatase mitogen-activated protein kinase phosphatase-1 was blocked by BAPTA-AM pretreatment. Together these results indicate that ERK activity is regulated by the balance of phosphorylation vs. dephosphorylation reactions in intact cells and that the amount of Ca2+ stored in intracellular pools plays an important role in this regulation.

Angiotensin II↗
PubMed1999

Retrovirus-mediated HO gene transfer into endothelial cells protects against oxidant-induced injury.

Heme oxygenase (HO)-1 is a stress protein that has been implicated in defense mechanisms against agents that may induce oxidative injury, such as endotoxins, heme, and cytokines. Overexpression of HO-1 in cells might, therefore, protect against oxidative stress produced by certain agents, specifically heme, by catalyzing its degradation to bilirubin, which by itself has antioxidant properties. We report for the first time the successful transduction of human HO-1 gene into rat lung microvessel endothelium using replication-defective retroviral vector. Cells transduced with human HO-1 gene exhibited a 2.1-fold increase in HO-1 protein level, which was associated with a 2.3-fold elevation in enzyme activity compared with that in nontransduced cells. The cGMP content in transduced endothelial cells was increased by 2.9-fold relative to that in nontransduced cells. Moreover, human HO-1 gene-transduced endothelial cells acquired substantial resistance to toxicity produced by exposure to heme and H(2)O(2) compared with that in nontransduced cells. The protective effect of enhancement of HO-1 activity against heme and H(2)O(2) was reversed by pretreatment with stannic mesoporphyrin, a competitive inhibitor of HO. These data demonstrate that the induction of HO-1 in response to injurious stimuli represents an important mechanism for moderating the severity of cell damage. Regulation of HO activity in this manner may have clinical applications.

3T3 Cells↗
PubMed1999

Growth hormone releasing substances: types and their receptors.

A series of structurally diverse growth hormone (GH) releasing substances have been synthesized that are distinct from the naturally occurring GH releasing hormone (GHRH). These synthetic molecules range from the family of GH releasing peptides and mimetics such as MK-0677. The physiological importance of these molecules and their receptor is exemplified by studies in the elderly. For example, when MK-0677 was administered chronically to 70- to 90-year-old subjects, once daily, the age-related reduced amplitude of GH pulses was reversed to that of the physiological profile typical of young adults. In 1996, the synthesis of (35)S-MK-0677 was reported and used as a ligand to characterize a common receptor (GH secretagogue receptor [GHS-R]) for the GH releasing substances. The GHS-R is distinct from the GHRH receptor. Subsequently, the GHS-R gene was cloned and shown to encode a unique G-protein coupled receptor with a deduced protein sequence that was 96% identical in human and rat. Because of the physiological importance of the GHS-R, a search for family members (FMs) was initiated and its molecular evolution investigated. Three FMs GPR38, GPR39 and FM3 were isolated from human genomic libraries. To accelerate the identification of other FMs, a vertebrate organism with a compact genome distant in evolutionary terms from humans was exploited. The pufferfish (Spheroides nephelus) genome provides an ideal model for the discovery of human genes. Three distinct full-length clones encoding proteins of significant sequence identity to the human GHS-R were cloned from the pufferfish. Remarkably, the pufferfish gene with highest sequence homology to the human receptor was activated by the hexapeptide and non-peptide ligands. These intriguing results show that the structure and function of the ligand binding pocket of the human GHS-R has been highly conserved in evolution ( approximately 400 million years) and strongly suggests that an endogenous natural ligand has been conserved. This new information is consistent with a natural ligand for the GHS-R playing a fundamentally important and conserved role in physiology.

Aged↗