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Biomedical subjects

C Dong

Publications and source records attributed to C Dong.

At least 91 records · Page 5Linked to original sources
PubMed1999

NMR structure of the complex between the zinc finger protein NCp10 of Moloney murine leukemia virus and the single-stranded pentanucleotide d(ACGCC): comparison with HIV-NCp7 complexes.

The structure of the 56 amino acid nucleocapsid protein NCp10 of retrovirus MoMuLV, which contains a single CX(2)CX(4)HX(4)C-type zinc finger, has been determined previously by NMR. The important role of NCp10 (or NCp7 for HIV-1) in the retroviral life cycle seems mainly related to their preferential binding to single-stranded nucleic acids. We report here the structure of the complex formed between the biologically active (14-53)NCp10 and the oligonucleotide d(ACGCC) in aqueous solution determined by 2D (1)H NMR based methods. The aromatic residue Trp(35) of NCp10 directs nucleic acid complexation as shown by its complete fluorescence quenching upon addition of d(ACGCC). (1)H and (31)P NMR studies support the insertion of Trp(35) between the G(3) and C(4) bases. A total of 577 NOE distance restraints, of which 40 were intermolecular, were used for the structure determination. The zinc finger provides a well-defined surface for the binding of d(ACGCC) through hydrophobic interactions and tryptophan stacking on the guanine. This latter interaction was also observed in the NMR-derived structures of the complexes between NCp7, which contains two successive zinc fingers, and single-stranded DNA and RNA, supporting the proposal for a major role played by aromatic residues of NCp proteins in nucleic acid recognition. Upon binding to the nucleotide a new loop in NCp10 that participates in the intermolecular interaction is formed. Additional interactions provided by positively charged residues surrounding the zinc finger appear necessary for tight binding. The structure of the complex NCp10-d(ACGCC) gives a structural explanation for the loss of virus infectivity following point mutations in the finger domain.

Amino Acid Sequence↗
PubMed1999

New method for detection of heart allograft rejection: validation of sensitivity and reliability in a rat heterotopic allograft model.

BACKGROUND: Patients with inflammatory heart muscle diseases would benefit from a safe, convenient, rapidly performed diagnostic technique with real-time results not involving tissue removal. We have performed a detailed evaluation of detection of heart allograft rejection by autofluorescence in a heterotopic abdominal rat heart allograft model ex vivo. METHODS AND RESULTS: Recipient rats with allograft (Lewis to Fisher 344; n=71) and isograft (Lewis to Lewis; n=33) hearts, treated with cyclosporine or untreated, were killed at days 2, 4, 7, 14, 21, 28, and 56 after transplant. Nontransplant controls with (n=24) or without (n=24) immunosuppressive therapy were also studied. When the rats were killed, autofluorescence spectra were acquired under blue-light excitation from midtransverse ventricular sections of native and transplanted hearts. Corresponding sections were then evaluated pathologically by a modified International Society for Heart and Lung Transplantation (ISHLT) grading schema. The spectral differences between rejecting and nonrejecting hearts were quantified by linear discriminant functions, producing scores that decreased progressively with increasing severity of tissue rejection. Mean+/-SD discriminant function scores were 2.9+/-1.6, 1.8+/-2.2, -0.1+/-2.8, -1.2+/-2.3, and -2.3+/-3.0 for isografts and allograft ISHLT grades 0, I, II, and III, respectively (Spearman rank-order correlation -0.6; P<0.001, test for trend). Cyclosporine had no detectable effect on the spectra. CONCLUSIONS: The correlation between changes in autofluorescence spectra and ISHLT rejection grade strongly supports the possibility of catheter-based, fluorescence-guided surveillance of rejection.

Animals↗
PubMed1999

Familial risks in cervical cancer: is there a hereditary component?

The Swedish Family-Cancer Database was used to analyze familial relationships in mothers and daughters in invasive and in situ cervical cancers from years 1958-1994, including a total of 125,000 in situ and 14,000 invasive cancers. In situ cancers were diagnosed on average 10 years earlier than invasive cancers. Familial relative risks (FRRs) were calculated separately for mothers and daughters, and were between 1.8 and 2.3 for the 2 forms. The risks were only slightly modified by age of onset, except at higher ages where there was no familial risk; in mothers, the risks increased if more than one daughter was affected. Aggregation of in situ cases among sisters was observed in families. Heritability estimates were between 0.11 and 0.15 for in situ and 0.22 and 0.34 for invasive cervical cancer. A comparison of cancers in mothers and daughters showed an association between cervical cancer and many cancer types observed in immunosuppressed patients, suggesting a role for a mild form of immunosuppression, in addition to sexual behavior leading to human-papilloma-virus infections, in familial cervical cancer.

Adolescent↗
PubMed1999

Protection of cardiomyocytes by pinacidil during metabolic inhibition and hyperkalemia.

The objective of this study is to understand the mechanism underlying the cardioprotective effects of pinacidil, an ATP-sensitive K+ channel (K(ATP)) opener. We examined the effects of 10 microM pinacidil in cultured chicken cardiomyocytes. Pinacidil caused a concentration-dependent delay in metabolic inhibition-induced increase in intracellular calcium concentration ([Ca2+]i) and creatine phosphokinase release, and this action was antagonized by glyburide, a K(ATP) blocker. Neither verapamil, an L-type Ca2+ channel blocker, nor bepridil, a Na+-Ca2+ exchange inhibitor, affected the time course of increase in [Ca2+]i induced by metabolic inhibition. Pinacidil did not have an effect on the amplitude of K+-induced increase in [Ca2+]i, but accelerated the rate of decline following peak stimulation. In contrast, glyburide reduced the amplitude of K+-induced increase in [Ca2+]i and prolonged the rate of decline. These results provide direct evidence that pinacidil protects cardiomyocytes from metabolic inhibition-induced injury by cyanide (CN) through a delay in the onset of increase in [Ca2+]i, rather than by inhibition of the L-type Ca2+-channels or by alteration of Na+-Ca2+ exchange.

Adenosine Triphosphate↗
PubMed1999

Application of the dual-micropipet technique to the measurement of tumor cell locomotion.

The objective of this work was to characterize tumor cell locomotion in response to chemotactic stimulation using a dual-micropipet assay. The assay involves two micropipets. An individual A2058 human melanoma cell was retained, without pressure gradient, in a pipet of approximately 14 micrometers i.d. A solution of type IV collagen, chosen as the chemotactic source, was placed in another pipet (approximately 10 micrometers o.d.) with zero pressure at the pipet tip. The smaller pipet was then inserted into the larger one containing the melanoma cell. The initial chemoattractant concentration (C0) and the distance between the tip of the small pipet and the cell surface (delta) provided a gradient (C0/delta) for tumor cell locomotion toward stimulation. This novel assay provides a direct measure of cell movement: cyclic pseudopod protrusion (Lp) and subsequent cell locomotion (Lc). The influences of different adhesion substrates on cell locomotion were also studied. The peak length in Lp precedes the highest locomotion velocity (dLc/dt) by an apparent lag time. C0/delta influences pseudopod protrusion frequency (fp) and dLc/dt, but not significantly on Lp. Substrate adhesions affect dLc/dt, but apparently not Lp or fp. In conclusion, pseudopod protrusion and substrate adhesion are two necessary but mutually independent factors in tumor cell locomotion. dLc/dt correlates with changes in C0/delta, which is in significant correlation with fp but not Lp.

Chemotaxis↗
PubMed1999

Hepatitis C virus envelope glycoprotein E1 originates in the endoplasmic reticulum and requires cytoplasmic processing for presentation by class I MHC molecules.

We investigated whether hepatitis C virus envelope glycoprotein E1 is transported from the endoplasmic reticulum (ER) to the cytoplasm of infected cells for class I MHC processing. Target cells expressing E1 were killed by CTL lines from a hepatitis C virus-infected chimpanzee, and synthetic peptides were used to define an epitope (amino acids 233-GNASRCWVA-241) presented by the Patr-B*1601 class I MHC molecule. An unusually high concentration (>100 nM) of this nonameric peptide was required for target cell lysis, but this could be reduced at least 1000-fold by replacing the asparagine at amino acid position 234 (Asn234) with aspartic acid (Asp), the anticipated anchor residue for NH2-terminal peptide binding to Patr-B*1601. Conspicuously, position 234 is part of an N-glycosylation motif (Asn-Xaa-Ser/Thr), suggesting that the Asn234 to Asp substitution might occur naturally within the cell due to deglycosylation/deamidation of this amino acid by the cytosolic enzyme peptide N-glycanase. In support of this model, we demonstrate that presentation of the epitope depended on 1) cotranslational synthesis of E1 in the ER, 2) glycosylation of the E1 molecule, and 3) a functional TAP transporter to shuttle peptide from the cytosolic to ER compartment. These results indicate for the first time that during infection of the host, viral envelope glycoproteins originating in the ER are processed in the cytoplasm for class I MHC presentation. That a posttranslational change in amino acid sequence from Asn to Asp alters the repertoire of peptides presented to CD8+ CTL has implications for the design of antiviral vaccines.

Animals↗
PubMed1999

Black-white differences in postprandial triglyceride response and postheparin lipoprotein lipase and hepatic triglyceride lipase among young men.

Black-white differences in serum triglycerides and high-density lipoprotein (HDL) cholesterol concentrations are known. However, the metabolic basis for these differences is not clear. This study determined the magnitude of postprandial triglyceride concentrations, lipoprotein lipase and hepatic triglyceride lipase activities in postheparin plasma, and serum lipid and lipoprotein cholesterol concentrations in healthy young adult black men (n = 22) and white men (n = 28). Postprandial triglyceride concentrations were measured at 2, 3, 4, 5, 6, and 8 hours after a standardized test meal. Serum lipid and lipoprotein cholesterol concentrations were similar between the races in this study sample. However, incremental (above basal) increases in triglycerides were significantly greater in white men versus black men at 2 hours (P = .01) and tended to be greater at 3 hours (P = .12) and 4 hours (P = .06) after the fat load. In a multivariate analysis that included age, race, apolipoprotein E (apoE) genotype, fasting triglycerides, obesity measures, alcohol intake, and cigarette use, fasting triglycerides (P = .04) and, to a lesser extent, race (P = .07) were associated independently with the 2-hour incremental increase in triglycerides. The incremental triglyceride response correlated inversely with HDL cholesterol in both whites (r = -.38, P = .04) and blacks (r = -.59, P = .004). Lipoprotein lipase activity was higher (P = .049) and hepatic triglyceride lipase activity lower (P = .0001) in black men compared with white men; racial differences persisted after adjusting for the covariates. While lipoprotein lipase activity tended to associate inversely with the postprandial triglyceride concentration in both races, hepatic triglyceride lipase activity tended to correlate positively in whites and inversely in blacks. These results suggest that compared with whites, blacks may have an efficient lipid-clearing mechanism that could explain the black-white differences in lipoproteins found in the population at large.

Adult↗
PubMed1999

Molecular basis of T-cell differentiation.

In summary, a multitude of regulatory systems are employed to cause the selective activation of target cytokine genes in Th1 and Th2 effector cells. These mechanisms involve both positive and negative regulation and employ at least three kinds of mechanisms. In the first, selective expression of transcription factors such as GATA3 in Th2 cells and the homeobox gene HLX in Th1 cells occurs, and appears in both cases to play a causal role. Another example of this would be c-maf, discovered by the Glimcher laboratory. A second mechanism is by the selective accumulation of protein through posttranscriptional mechanisms. Thus, junB accumulates in Th2 cells despite the fact that the junB mRNA levels are not different between Th1 and Th2 cells. Finally, the selective use of signaling pathways, in the case studied here MAP kinase pathways, leads to the selective activation of target genes. We believe that transcriptional up-regulation of rac2 leads to the coupling of both the p38 and JNK MAP kinase pathways to the T-cell receptor and/or costimulatory receptors, thereby providing a lineage-specific signal.

Cell Differentiation↗
PubMed1999

Influence of cell deformation on leukocyte rolling adhesion in shear flow.

Blood cell interaction with vascular endothelium is important in microcirculation, where rolling adhesion of circulating leukocytes along the surface of endothelial cells is a prerequisite for leukocyte emigration under flow conditions. HL-60 cell rolling adhesion to surface-immobilized P-selectin in shear flow was investigated using a side-view flow chamber, which permitted measurements of cell deformation and cell-substrate contact length as well as cell rolling velocity. A two-dimensional model was developed based on the assumption that fluid energy input to a rolling cell was essentially distributed into two parts: cytoplasmic viscous dissipation, and energy needed to break adhesion bonds between the rolling cell and its substrate. The flow fields of extracellular fluid and intracellular cytoplasm were solved using finite element methods with a deformable cell membrane represented by an elastic ring. The adhesion energy loss was calculated based on receptor-ligand kinetics equations. It was found that, as a result of shear-flow-induced cell deformation, cell-substrate contact area under high wall shear stresses (20 dyn/cm2) could be as much as twice of that under low stresses (0.5 dyn/cm2). An increase in contact area may cause more energy dissipation to both adhesion bonds and viscous cytoplasm, whereas the fluid energy input may decrease due to the flattened cell shape. Our model predicts that leukocyte rolling velocity will reach a plateau as shear stress increases, which agrees with both in vivo and in vitro experimental observations.

Adsorption↗
PubMed1999

Neocognitron's parameter tuning by genetic algorithms.

The further study on the sensitivity analysis of Neocognitron is discussed in this paper. Fukushima's Neocognitron is capable of recognizing distorted patterns as well as tolerating positional shift. Supervised learning of the Neocognitron is fulfilled by training patterns layer by layer. However, many parameters, such as selectivity and receptive fields are set manually. Furthermore, in Fukushima's original Neocognitron, all the training patterns are designed empirically. In this paper, we use Genetic Algorithms (GAs) to tune the parameters of Neocognitron and search its reasonable training pattern sets. Four contributions are claimed: first, by analyzing the learning mechanism of Fukushima's original Neocognitron, the correlations amongst the training patterns are claimed to affect the performance of Neocognitron, tuning the Neocognitron's number of planes is equivalent to searching reasonable training patterns for its supervised learning; second, a GA-based supervised learning of the Neocognitron is carried out in this way, searching the parameters and training patterns by GAs but specifying the connection weights by training the Neocognitron; third, other than traditional GAs which are unsuitable for the large searching space of training patterns set, the cooperative coevolution is incorporated to play this role; fourth, an effective fitness function is given out when applying the above methodology into numeral recognition. The evolutionary computation in our initial experiments is implemented based on the original training pattern set, e.g. the individuals of the population are generated from Fukushima's original training patterns during initialization of GAs. The results prove that our correlation analysis is reasonable, and show that the performance of a Neocognitron is sensitive to its training patterns, selectivity and receptive fields, especially, the performance is not monotonically increasing with respect to the number of training patterns, and this GA-based supervised learning is able to improve Neocognitron's performance.

Cognition↗
PubMed1999

[Isolating candidate inserted fragment from positive fused phage clones using quantitative PCR].

OBJECTIVE: To isolate quickly and exactly the specific inserted fragment from fused phage clones which were obtained from cDNA library by hybridization. METHODS: According to the amplification principle of quantitative polymerase chain reaction (PCR) and based on the difference of original template quantity,target cDNA fragment was isolated and identified by two PCRs. RESULTS: A positive clone with specific cDNA fragment of HumGT-H1 gene was obtained from a two-phage fused clone by using this method,and the inserted fragment was verified to be the 5' cDNA sequence of HumGT-H1,1.9kb in length. So another hybridization screening is not necessary. CONCLUSION: The method presented is effective and rapid in gene cloning and can greatly save time and materials.

Bacteriophages↗
PubMed1999

Endometrial cancer in the family-cancer database.

Endometrial cancer was studied in the Swedish Family-Cancer Database, updated in 1999 to cover individuals born after 1934 with their biological parents, totaling 9.6 million persons. Cancer data were obtained from the Swedish Cancer Registry from 1958 to 1996 and included over 20,000 cases of endometrial cancer. Seventy-six families were identified in which both the mother and the daughter had endometrial cancer, giving a familial standardized incidence ratio (SIR) of 3.19 for daughters and 2.78 for mothers. The risk depended inversely on the age at diagnosis, and the risk was almost 10 in daughters who were diagnosed before age 50 when their mothers were also diagnosed before that age. The discordant cancer site that associated with endometrial cancer between the two generations was colon, with a SIR of 1.44-1.68. However, when the maternal endometrial cancer was diagnosed before age 50, increased SIRs were observed in daughters or sons for rectal, pancreatic, nervous system, breast, and ovarian cancers. Second cancers were followed in females diagnosed with endometrial cancer, and the highest overall risks were observed for ovarian and connective tissue cancers; colorectal cancers were also clearly in excess. Among the other family members of the 76 families in which both mother and daughter were affected with endometrial cancer, there were 11 cases of colorectal cancer. When a sister was affected in such families, the SIR of endometrial cancer was 31.40, and the median diagnostic age was several years lower than in endometrial cancer families in which no colorectal cancers were found. Many of these families may have hereditary nonpolyposis colorectal carcinoma syndrome. However, the risk of endometrial cancer was increased even in families presenting no colorectal cancers.

Adolescent↗
PubMed1999

Bax and apoptosis in acute and chronic rejection of rat cardiac allografts.

Apoptosis is associated with acute rejection, transplant vascular disease, and the "Quilty effect" in cardiac allografts. However, the causality and mechanisms of apoptosis in the pathogenesis of vascular injury are poorly understood. In the current study, the Lewis-to-F344 rat cardiac allograft model was utilized as a means to immunohistochemically evaluate the expression of Bax, Bcl-2, and factor VIII-related antigen in transplant vascular disease. Apoptosis was detected by in situ labeling of fragmented DNA using in situ terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) in native hearts and grafted hearts of allogeneic and syngeneic recipients. Bax immunostaining was detected in 50% of endothelial cells, in 60% of infiltrating leukocytes associated with acute rejection in the myocardium, and in certain other parenchymal cells, considering all cardiac allografts. More than 75% of infiltrating leukocytes in the intima of vessel walls immunostained positive for Bax. Bcl-2 immunopositivity was not detected in native hearts, allo allo-, or syngrafts. On Days 2, 4, 7, and 14 after transplantation, TUNEL positivity was detected in only about 1% of leukocytes in the interstitial infiltrates, despite the fact that rather severe rejection was observed in Day 14 allografts. The number of apoptotic leukocytes increased significantly by Days 28 and 56 after transplantation, although the severity of histopathological rejection did not increase as compared with Day 14. The apoptotic leukocytes remained isolated or in small clusters, mainly perivascular. TUNEL positivity colocalized with Bax expression in these cells. TUNEL staining was also observed in certain parenchymal cells in the interstitium and in randomly distributed inflammatory cells in vessel walls. TUNEL positivity was detected in rare luminal endothelial cells in transverse sections of vessel walls (about 10% of cells in <1/10 of the vessels studied). Nuclear TUNEL positivity was observed in Bax-negative cardiomyocytes in ischemically damaged areas of myocardium in both allografts and syngrafts. In summary, increased expression of Bax was observed in rat cardiac allografts. The colocalization of TUNEL and Bax suggests that endothelial cell injury and infiltrating leukocyte apoptosis may be regulated in part by the apoptosis-promoting protein, Bax. In the current model, myocyte death due to ischemia and surgical injury in syngrafts and allografts does not seem to involve Bax.

Animals↗
PubMed1999

[Study on spectrophotometric determination of trace nitrite with brilliant cresol blue].

A new spectrophotometric method for the determination of trace nitrite was studied. The method is based on the diazo-reaction of brilliant cresol blue with nitrite. The linear range for the determination is 0.5-12 microg NO2(-)/25 mL. The detection limit is 0.5 microg NO2(-)/25 mL. The method has been used for the determination of trace nitrite in water. The mechanism of the reaction was discussed.

Benzenesulfonates↗
PubMed1998

Defective T cell differentiation in the absence of Jnk1.

The c-Jun NH2-terminal kinase (JNK) signaling pathway has been implicated in the immune response that is mediated by the activation and differentiation of CD4 helper T (TH) cells into TH1 and TH2 effector cells. JNK activity observed in wild-type activated TH cells was severely reduced in TH cells from Jnk1-/- mice. The Jnk1-/- T cells hyperproliferated, exhibited decreased activation-induced cell death, and preferentially differentiated to TH2 cells. The enhanced production of TH2 cytokines by Jnk1-/- cells was associated with increased nuclear accumulation of the transcription factor NFATc. Thus, the JNK1 signaling pathway plays a key role in T cell receptor-initiated TH cell proliferation, apoptosis, and differentiation.

Animals↗
PubMed1998

Impairment of T and B cell development by treatment with a type I interferon.

Type I interferons alpha and beta, naturally produced regulators of cell growth and differentiation, have been shown to inhibit IL-7-induced growth and survival of B cell precursors in vitro. After confirming an inhibitory effect on B lymphopoiesis in an ex vivo assay, we treated newborn mice with an active IFN-alpha2/alpha1 hybrid molecule to assess its potential for regulating B and T cell development in vivo. Bone marrow and splenic cellularity was greatly reduced in the IFN-alpha2/alpha1-treated mice, and B lineage cells were reduced by >80%. The bone marrow progenitor population of CD43+B220+HSA- cells was unaffected, but development of the CD19+ pro-B cells and their B lineage progeny was severely impaired. Correspondingly, IL-7-responsive cells in the bone marrow were virtually eliminated by the interferon treatment. Thymus cellularity was also reduced by >80% in the treated mice. Phenotypic analysis of the residual thymocytes indicated that the inhibitory effect was exerted during the pro-T cell stage in differentiation. In IFN-alpha/beta receptor-/- mice, T and B cell development were unaffected by the IFN-alpha2/alpha1 treatment. The data suggest that type I interferons can reversibly inhibit early T and B cell development by opposing the essential IL-7 response.

Animals↗
PubMed1998

In vitro side-view imaging technique and analysis of human T-leukemic cell adhesion to ICAM-1 in shear flow.

The objective of the present study is to apply a novel side-view imaging technique to investigate T-leukemic Jurkat cell adhesion to a surface-immobilized ICAM-1 in shear flow, a ligand for leukocyte LFA-1. Images have revealed that Jurkat cell adhesion on ICAM-1 under flow conditions in vitro is quasistatic. The cell-substrate contact length steadily increased with time during the initial cell attachment to the ICAM-1-coated surface and subsequently decreased with time as the trailing edge of the cell membrane peeled away from the substrate under the influence of fluid shear forces. Changes in flow shear stresses, cell deformability, or substrate ligand strength resulted in a significant change in the characteristic adhesion binding time and contact length. A 3-D flow field with shear stresses acting on an adherent cell was calculated by using finite element methods based on cell shapes obtained from the in vitro images. The maximum shear stress acting on an actual cell body was found to be 3-5 times greater than the upstream inlet wall shear stress and was influenced by the extent of cell deformation within the flow channel. Therefore, the application of such a side-view imaging technique has provided a practical assay to study the mechanics of cell-surface adhesion in 3-D. The elongation of cells in shear flow tempers hydrodynamic shear forces on the cell, which affects the transients in cell-surface adhesion.

Biomechanical Phenomena↗