Biomedical subjects

Y Kong

Publications and source records attributed to Y Kong.

At least 73 records · Page 4Linked to original sources

PubMed2000

[Pharmacological studies of trilex on treatment of pharyngitis].

Trilex consisted of three species: Ilex latifolia, Ilex asprella and Ilex rotunda. Trilex had the antipyretic effects, decreased the rat body temperature about 0.8 degree C on yeast induced hyperthermia. Trilex could obviously enhance the threshold of hot plate induced pain in mice. The maximum threshold increased 43.8%. Trilex could also inhibit acetic acid induced inflammatory ooze in mice abdominal cavity. The inhibitory rate was 34.8%. These results showed that trilex had antipyretic, analgesic and anti-inflammatory effects. It could be used to treat acute and chromic pharyngitis.

Analgesics↗

PubMed1999

Distinctive expression and functions of the type 4 endothelial differentiation gene-encoded G protein-coupled receptor for lysophosphatidic acid in ovarian cancer.

Endothelial differentiation gene (edg)-encoded G protein-coupled receptors (Edg Rs)-1, -3, and -5 bind sphingosine 1-phosphate (S1P), and Edg-2 and -4 bind lysophosphatidic acid (LPA). Edg Rs transduce signals from LPA and S1P that stimulate ras- and rho-dependent cellular proliferation, enhance cellular survival, and suppress apoptosis. That high levels of LPA in plasma and ascitic fluid of patients with ovarian cancer correlate with widespread invasion suggested the importance of investigating expression and functions of Edg Rs in ovarian cancer cells (OCCs) as compared with nonmalignant ovarian surface epithelial cells (OSEs). Analyses of Edg Rs by semiquantitative reverse transcription-PCR, a radioactively quantified variant of PCR, and Western blots developed with monoclonal antibodies showed prominent expression of Edg-4 R in primary cultures and established lines of OCCs but none in OSEs. In contrast, levels of Edg-2, -3, and -5 were higher in OSEs than OCCs. LPA stimulated proliferation and signaled a serum response element-luciferase reporter of immediate-early gene activation in OCCs but not OSEs, whereas S1P evoked similar responses in both OSEs and OCCs. Pharmacological inhibitors of Edg R signaling suppressed OCC responses to LPA. A combination of monoclonal anti-Edg-4 R antibody and phorbol myristate acetate, which were inactive separately, evoked proliferative and serum response element-luciferase responses of OCCs but not OSEs. Thus the Edg-4 R may represent a distinctive marker of OCC that transduces growth-promoting signals from the high local concentrations of LPA characteristic of aggressive ovarian cancer.

Female↗

PubMed1999

Dual mechanisms for lysophospholipid induction of proliferation of human breast carcinoma cells.

Endothelial differentiation gene-encoded G protein-coupled receptors (Edg Rs) Edg-1, Edg-3, and Edg-5 bind sphingosine 1-phosphate (S1P), and Edg-2 and Edg-4 Rs bind lysophosphatidic acid (LPA). LPA and S1P initiate ras- and rho-dependent signaling of cellular growth. Cultured lines of human breast cancer cells (BCCs) express Edg-3 > Edg-4 > Edg-5 > or = Edg-2, without detectable Edg-1, by both assessment of mRNA and Western blots with rabbit and monoclonal mouse anti-Edg R antibodies. BCC proliferation was stimulated significantly by 10(-9) M to 10(-6) M LPA and S1P. Luciferase constructs containing the serum response element (SRE) of growth-related gene promoters reported mean activation of BCCs by LPA and S1P of up to 85-fold. LPA and S1P stimulated BCC secretion of type II insulin-like growth factor (IGF-II) by 2-7-fold, to levels at which exogenous IGF-II stimulated increased proliferation and SRE activation of BCCs. All BCC responses to LPA and S1P were suppressed similarly by pertussis toxin, mitogen-activated protein kinase kinase inhibitors, and C3 exoenzyme inactivation of rho, suggesting mediation by Edg Rs. Monoclonal anti-IGF-II and anti-IGFR1 antibodies suppressed proliferation and SRE reports of BCCs to LPA and S1P by means of up to 65%. Edg Rs thus transduce LPA and S1P enhancement of BCC growth, both directly through SRE and indirectly by enhancing the contribution of IGF-II.

Animals↗

PubMed1999

Ligand binding on ladder lattices.

The ligand binding problems on two-dimensional ladders, which model many important binding phenomena in molecular biology, are studied in details. The model is represented by four parameters, the interactions between ligands when bound to adjacent sites on opposite legs of the ladder (tau), the interactions between bound ligands in the longitudinal direction of the ladder (sigma), the number of binding sites that are covered by a bound ligand (m), and the intrinsic binding constant (K). The partition functions of ring ladders are approached with the transfer matrix method. A general relation is derived which connects the partition function of a linear ladder with that of a ring ladder. The results obtained apply to the general situation of multivalent binding, in which m>1. Special attention is paid to the case where the ligand covers one site (m=1). In this case explicit formulas are given for the partition functions of ring and linear ladders. Closed-form expressions are obtained for various properties of the system, including the degree of binding (theta), the midpoint in the binding isotherm (1/square root(tau sigma)), the initial and end slopes of the Scatchard plots (2sigma + tau - 4 and -sigma2 tau, respectively). From these closed-form formulas, sigma and tau may be extracted from experimental data. The model reveals certain features which do not exist in one-dimensional models. Using the general method discussed in [1], the recurrence relation is found for the partition functions. The analytical solution found for this model provides test cases to verify the numerical results for more complex two-dimensional models.

Journal Article↗

PubMed1999

Reactive oxygen species: the unavoidable environmental insult?

Reactive oxygen species (ROS) are generated by a variety of sources from the environment (e.g., photo-oxidations and emissions) and normal cellular functions (e.g., mitochondrial metabolism and neutrophil activation). ROS include free radicals (e.g., superoxide and hydroxyl radicals), nonradical oxygen species (e.g., hydrogen peroxide and peroxynitrite) and reactive lipids and carbohydrates (e. g., ketoaldehydes, hydroxynonenal). Oxidative damage to DNA can occur by many routes including the oxidative modification of the nucleotide bases, sugars, or by forming crosslinks. Such modifications can lead to mutations, pathologies, cellular aging and death. Oxidation of proteins appears to play a causative role in many chronic diseases of aging including cataractogenesis, rheumatoid arthritis, and various neurodegenerative diseases including Alzheimer's Disease (AD). Our goal is to elucidate the mechanism(s) by which oxidative modification results in the disease. These studies have shown that (a) cells from old individuals are more susceptible to oxidative damage than cells from young donors; (b) oxidative protein modification is not random; (c) some of the damage can be prevented by antioxidants, but there is an age-dependent difference; and (d) an age-related impairment of recognition and destruction of modified proteins exists. It is believed that mechanistic insight into oxidative damage will allow prevention or intervention such that these insults are not inevitable. Our studies are also designed to identify the proteins which are most susceptible to ROS damage and to use these as potential biomarkers for the early diagnosis of diseases such as AD. For example, separation of proteins from cells or tissues on one- and two-dimensional gels followed by staining for both total protein and specifically oxidized residues (e.g., nitrotyrosine) may allow identification of biomarkers for AD.

Adult↗

PubMed1999

Expression and characterization of chimeric hepatitis B surface antigen particles carrying preS epitopes.

Many studies have provided evidence that hepatitis B surface antigen (HBsAg) including preS1 and preS2 sequences could be an ideal candidate for a new hepatitis B virus (HBV) vaccine with higher efficacy. However, the large (L) protein containing the entire preS region expressed in mammalian cells is not efficiently assembled into particles and secreted. Here we report an alternative approach to include the dominant epitopes of preS1 and preS2 to the small (S) protein as fusion proteins by the recombinant DNA technology. Three fusion proteins containing preS2(120-146) and preS1(21-47) at the N-terminus and/or truncated C-terminus of S protein were expressed using the recombinant vaccinia virus system. All these fusion proteins were efficiently secreted in the particulate form, and displayed S, preS1 and/or preS2 antigenicity. Further analysis showed that these chimeric HBsAg particles elicited strong antibody responses against S, preS1 and preS2 antigens in BALB/c mice, suggesting that they could be promising candidates for a new recombinant vaccine to induce broader antibody response required for protection against hepatitis B viral infection.

Animals↗

PubMed1999

Lysophosphatidic acid and sphingosine 1-phosphate protection of T cells from apoptosis in association with suppression of Bax.

Members of a subfamily of G protein-coupled receptors (GPCRs), encoded by five different endothelial differentiation genes (edgs), specifically mediate effects of lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) on cellular proliferation and differentiation. Mechanisms of suppression of apoptosis by LPA and S1P were studied in the Tsup-1 cultured line of human T lymphoblastoma cells, which express Edg-2 and Edg-4 GPCRs for LPA and Edg-3 and Edg-5 GPCRs for S1P. At 10-10 M to 10-7 M, both LPA and S1P protected Tsup-1 cells from apoptosis induced by Abs to Fas, CD2, and CD3 plus CD28 in combination. Apoptosis elicited by C6 ceramide was inhibited by S1P, but not by LPA, in part because ceramide suppressed expression of Edg-2 and Edg-4 surface receptors for LPA without affecting Edg-3 surface receptors for S1P. At 10-9 M to 10-7 M, LPA and S1P significantly suppressed cellular levels of the apoptosis-promoting protein Bax, without altering the levels of Bcl-xL or Bcl-2 assessed by Western blots and immunoassays. Transfections of pairs of antisense plasmids for Edg-2 plus Edg-4 and Edg-3 plus Edg-5, and hygromycin selection of transfectants with reduced expression of the respective Edg R proteins in Western blots, inhibited both protection from apoptosis and reduction in cellular levels of Bax by LPA and S1P. Thus, LPA and S1P protection from apoptosis is mediated by distinct Edg GPCRs and may involve novel effects on Bax regulatory protein.

Animals↗

PubMed1999

An efficient in vivo recombination cloning procedure for modifying and combining HSV-1 cosmids.

A helper virus-free herpes simplex virus type-1 (HSV-1) plasmid vector system developed recently may have applications in gene therapy and basic physiological studies. This system might be improved by mutating specific HSV-1 genes in the packaging system and by creating large vectors. An in vivo recombination cloning procedure is reported that supports the routine manipulation of relatively large DNAs such as the five cosmids that comprise this helper virus-free HSV-1 packaging system. In vivo recombination cloning is carried out by transforming overlapping DNA fragments into a specific RecA+ Escherichia coli, BJ5183. The cloning efficiency was improved by using a modified version of the Hanahan transformation procedure, and the background was lowered by either using vectors with different combinations of ends (5' overhangs, 3' overhangs, blunt ends) or by treating the vector with calf intestinal phosphatase. The range of usable overlap sizes is from 251 bp to 18 kb with 500 bp to 5 kb preferred. This procedure supports the routine construction and mutation of HSV-1 cosmids, by use of up to six different DNA fragments, and the construction of plasmids up to 65 kb in size. This procedure may also have applications to other vector systems and to studies on large viruses.

Cloning, Molecular↗

PubMed1999

Approach to withdrawal from tacrolimus in a fully allogeneic murine skin graft model.

With few exceptions, transplant patients must take immunosuppressants throughout their lives. In this study, we used anti-T-cell receptor (TCR/CD3) monoclonal antibodies (mAbs) to induce immunological tolerance to alloantigens after withdrawal from tacrolimus in a fully allogeneic murine skin graft model. Skin grafts from AKR donor mice were maintained in C57BL/6 recipients by administering tacrolimus for one month. Anti-T-cell receptor (TCR) alphabeta mAb was administered to recipient mice on the day of withdrawal from tacrolimus administration. Seven days after mAb administration, the recipient mice were treated with various combinations of the following treatments: low-dose whole body irradiation, AKR bone marrow transfer (BMT), and anti-CD3 mAb administration. The control recipient mice did not receive treatment with either mAb, nor any other treatment. All the control recipient mice showed rejection of AKR skin grafts 42 days after tacrolimus withdrawal (mean skin graft survival: 77 days). Mice treated with a combination of anti-TCR alphabeta antibody, low-dose irradiation and AKR BMT showed stable chimerism in their peripheral blood lymphocytes and significantly prolonged skin graft survival (mean skin graft survival: >151.2+/-15.3 days). Mice given the combination of anti-TCR alphabeta mAb, anti-CD3 mAb, low-dose irradiation, and AKR BMT exhibited more stable chimerism but had earlier skin graft rejection (mean skin graft survival: 116.7+/-17.6 days) than the mice that did not receive anti-CD3 mAb. These results suggest that anti-TCR alphabeta mAb, but not anti-CD3 mAb, in combination with low-dose irradiation and BMT, is useful for long-lasting allograft survival after withdrawal from tacrolimus in mice with fully allogeneic skin grafts.

Animals↗

PubMed1999

A recombinant 10-kDa protein of Taenia solium metacestodes specific to active neurocysticercosis.

Neurocysticercosis (NCC) is an important cause of neurological disease worldwide. A 10-kDa antigen of Taenia solium metacestodes (TsMs) has been shown to be specific for immunodiagnosis of NCC. Screening of a TsM complementary DNA (cDNA) library isolated a cDNA encoding this protein. The cloned cDNA contained a 258-bp complete open-reading frame that encodes an 86-amino acid polypeptide with a calculated molecular weight of 9582 Da. It showed 73% homology with a 10-kDa antigen of T. crassiceps. The recombinant protein was expressed bacterially as a fusion protein at a high level. In immunoblot with recombinant protein, 97% (184/190) of sera from patients with active NCC showed strong reactivity, whereas 14% (4/29) of those from patients with chronic calcified NCC reacted weakly. In 180 sera from other patients with parasitic infections and from normal controls, it showed 98% specificity. A single recombinant TsM antigen has a high potential for serological differentiation of active NCC.

Amino Acid Sequence↗

PubMed1999

Timing of treatment for myocardial reperfusion injury.

Early reperfusion of acute myocardial infarctions halts cell death due to ischemia but causes further injury, probably by oxidant mechanisms. We identified the window of opportunity during which antioxidants must be present in therapeutic concentrations to prevent reperfusion injury during 90 min of ischemia and 48 h of reperfusion in 57 dogs. We examined the effect on myocardial infarct size of intravenous infusion of N-2-mercaptopropionyl glycine (MPG), a diffusible antioxidant with a plasma half-time of 7 min, by using a series of protocols with a range of timing. Whereas infusions of MPG for > or =3 h reduced infarct size by approximately 50%, infusions for 1 h only (the first, second or third hours of reperfusion) caused only small reductions. A statistical analysis that focused on identifying components of group membership responsible for differences revealed that duration of treatment was a major determinant of infarct size. If begun any time within the first hour of reperfusion, infusions of > or =3 h markedly diminished infarct size. Because reperfusion injury proceeds for the first 3 h of reperfusion, but decreases thereafter, adequate protection is needed for > or =3 of the first 4 h of reperfusion, but more prolonged protection is not necessary.

Animals↗

PubMed1999

Age-dependent infectivity of orally transferred juvenile Fasciola hepatica.

Juvenile Fasciola hepatica is infective when administered orally. To determine whether the age of juveniles is a factor in infectivity by oral transfer, experimental mice were challenged orally with immature F. hepatica that had been grown in donor mice for 12, 14, 16, and 18 days. Experimental mice were examined for infections 12 16 days after the oral transfers. The infection success in experimental mice decreased with the age of juveniles. The worm recovery also decreased according to the age of juveniles. None of the juveniles was infective when grown for longer than 11 days. Once infected, orally transferred worms continued to grow. Juvenile age was a significant factor in determining the infectivity of orally transferred juvenile F. hepatica.

Age Factors↗

PubMed1999

Lens epithelium and fiber Na,K-ATPases: distribution and localization by immunocytochemistry.

PURPOSE: To use immunofluorescence and immunogold techniques to identify the catalytic subunits of the Na,K-ATPases of the lens and to determine their location in the cells of the epithelium and cortex of bovine and human lenses. METHODS: Frozen sections of capsulated and decapsulated bovine and human lenses were prepared, blocked, and treated with affinity-purified polyclonal rabbit antibodies to the Na,K-ATPase catalytic subunit isoforms with subsequent treatment with fluorescein isothiocyanate-labeled goat anti-rabbit IgG and visualization of the fluorescence by light microscopy. An immunogold-labeled goat anti-rabbit IgG was used to detect, by electron microscopy, the binding of the same affinity-purified polyclonal antibodies to thin sections of decapsulated lenses that had been fixed and embedded in Lowicryl K4M. The results were confirmed by staining of western blot analysis of sodium dodecyl sulfate-polyacrylamide gel separations of enriched membrane preparations from bovine and human lenses. RESULTS: The three common catalytic subunits of the Na,K-ATPases are present in the plasma membranes of lens epithelium, lens fibers, or both. The data indicate a polarized distribution of the alpha1 and alpha3 catalytic subunit isoforms in central epithelium. In the cortical fibers, the alpha2 isoform is present around the interdigitations. The alpha3 isoform is found in the interdigitation-free regions of human cortical fibers. CONCLUSIONS: This unique distribution of Na,K-ATPases precludes the popular pump-leak model for lens monovalent cation homeostasis. The functional significance of the distribution of Na,K-ATPases in the lens epithelium and superficial fibers is currently under investigation.

Amino Acid Sequence↗

PubMed1998

Requirements for stimulating naive CD8+ T cells via signal 1 alone.

In the absence of costimulation, TCR recognition of peptide/MHC complexes is generally considered to be nonimmunogenic. In agreement with this view, naive TCR transgenic CD8+ cells failed to respond to specific peptides presented by MHC class I (Ld) molecules bound to mouse RBC. However, peptide/Ld complexes presented by cell-sized beads or bound to plastic led to overt proliferative responses in the absence of added cytokines. Significantly, equivalent strong proliferative responses occurred when mouse RBC were fixed with glutaraldehyde before Ld coupling. The implication therefore is that the intensity of signaling via the TCR is a reflection of the mobility of the ligand being recognized; TCR signaling is weak when the ligand can move laterally on the cell membrane but strong when the ligand is immobilized.

Animals↗

PubMed1998

Natural forms of shed tumor gangliosides.

Gangliosides shed by tumor cells are immunosuppressive molecules, but the mechanisms of shedding are poorly understood. We therefore conducted a comprehensive study of shedding to identify the natural forms of shed gangliosides. By chemical detection and mass spectrometric analysis of the gangliosides of YAC-1 murine lymphoma cells, we first confirmed that all major ganglioside species are released. Then, by the combination of metabolic and cell surface radiolabeling, we further demonstrated that gangliosides are released directly from the cell plasma membrane, i.e. by shedding. Ultracentrifugation separated the conditioned medium of metabolically radiolabeled cells cultured in either serum-free or serum-containing medium into: (1) a pellet of 100-200 nm membrane vesicles (visualized by electron microscopy) containing nearly one-third of total shed gangliosides; and (2) the supernatant, which contained soluble gangliosides (two-thirds of the total shed gangliosides). Although the ganglioside concentration in the conditioned medium (6-14x10-8 M) was above the critical micelle concentration of purified YAC-1 gangliosides (<1x10-8 M), by gel filtration >90% of the soluble gangliosides were found in monomeric form (MW <2 kDa) and only <10% in micelles (130 kDa). Ultrafiltration of fresh conditioned medium likewise showed the existence of monomers, and the findings were confirmed in human Daoy medulloblastoma and mouse MEB4 melanoma cells. Thus, in their natural states, shed tumor cell gangliosides exist in three forms: membrane vesicles, micelles, and monomers.

Animals↗

PubMed1998

A double stain for total and oxidized proteins from two-dimensional fingerprints.

Oxidative modification of proteins plays a major role in the etiology of aging and age-related diseases. For example, in Alzheimer's disease, although evidence points to oxidation of proteins as a causative factor in loss of cognitive abilities, it is not known which specific proteins of the brain are most susceptible to these modifications. Thus, it is of interest to identify the specific proteins which are susceptible to oxidation in vivo. Two-dimensional protein fingerprint methods offer the analytical potential for resolution of thousands of individual proteins from tissues, and the oxidized proteins can be visualized with immunological probes. Sensitive methods permit recovery and sufficient amino acid sequencing to identify these proteins. However, for such analyses it is essential to simultaneously analyze both protein content and level of oxidation. We have evaluated several approaches, identified the sources of artifacts and interferences, and developed a double-staining procedure that allows visualization and quantitation of total protein patterns as well as the specific oxidized proteins from two-dimensional protein fingerprints. The method has been applied to cells grown in culture and to tissue extracts from young and old animals.

Age Factors↗

PubMed1998

Lipophilic siderophores of Mycobacterium tuberculosis prevent cardiac reperfusion injury.

Reperfusion injury, which occurs upon the reintroduction of blood flow to an ischemic organ, is responsible for considerable damage in heart attacks and strokes. However, no treatment for reperfusion injury is currently available. A major cause of reperfusion injury is the iron-mediated generation of hydroxyl radical (.OH). In this study we have explored the capacity of novel iron chelators called "exochelins" to prevent reperfusion injury. Exochelins, siderophores of Mycobacterium tuberculosis, are unique iron chelators because they are lipid soluble, and hence able to enter cells rapidly. In the iron-free state, exochelins prevented .OH formation. Desferri-exochelins prevented oxidative injury to cultured cardiac myocytes, and did so more rapidly and effectively than the nonlipid soluble iron chelator deferoxamine. The capacity of various desferri-exochelins to protect myocytes from oxidative injury varied directly with their solubility in lipid. Infused into isolated rabbit hearts during reperfusion after a period of ischemia, desferri-exochelins dramatically improved systolic and diastolic left ventricular function, preserved coronary flow, reduced release of the cardiac enzyme lactic dehydrogenase, and reduced myocardial concentrations of .OH metabolites. Thus, highly diffusible desferri-exochelins block injury caused by .OH production and have potential for the treatment of reperfusion injury.

Animals↗

PubMed1998

Crystal structures of the Klenow fragment of Thermus aquaticus DNA polymerase I complexed with deoxyribonucleoside triphosphates.

The crystal structures of the Klenow fragment of the Thermus aquaticus DNA polymerase I (Klentaq1) complexed with four deoxyribonucleoside triphosphates (dNTP) have been determined to 2.5 A resolution. The dNTPs bind adjacent to the O helix of Klentaq1. The triphosphate moieties are at nearly identical positions in all four complexes and are anchored by three positively charged residues, Arg659, Lys663, and Arg587, and by two polar residues, His639 and Gln613. The configuration of the base moieties in the Klentaq1/dNTP complexes demonstrates variability suggesting that dNTP binding is primarily determined by recognition and binding of the phosphate moiety. However, when superimposed on the Taq polymerase/blunt end DNA complex structure (Eom et al., 1996), two of the dNTP/Klentaq1 structures demonstrate appropriate stacking of the nucleotide base with the 3' end of the DNA primer strand, suggesting that at least in these two binary complexes, the observed dNTP conformations are functionally relevant.

Binding Sites↗