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Biomedical subjects

H Ni

Publications and source records attributed to H Ni.

At least 19 recordsLinked to original sources
PubMed2006

Fibrinogen and von Willebrand factor-independent platelet aggregation in vitro and in vivo.

BACKGROUND: Fibrinogen (Fg) has been considered essential for platelet aggregation. However, we recently demonstrated formation of occlusive thrombi in Fg-deficient mice and in mice doubly deficient for Fg and von Willebrand factor (Fg/VWF(-/-)). METHODS AND RESULTS: Here we studied Fg/VWF-independent platelet aggregation in vitro and found no aggregation in citrated platelet-rich plasma of Fg/VWF(-/-) mice. Surprisingly, in Fg/VWF(-/-) plasma without anticoagulant, adenosine diphosphate induced robust aggregation of Fg/VWF(-/-) platelets but not of beta(3)-integrin-deficient (beta(3) (-/-)) platelets. In addition, beta(3) (-/-) platelets did not significantly incorporate into thrombi in Fg/VWF(-/-) mice. This Fg/VWF-independent aggregation was blocked by thrombin inhibitors (heparin, hirudin, PPACK), and thrombin or thrombin receptor activation peptide (AYPGKF-NH(2)) induced aggregation of gel-filtered Fg/VWF(-/-) platelets in 1 mm Ca(2+) PIPES buffer. Notably, aggregation in PIPES buffer was only 50-60% of that observed in Fg/VWF(-/-) plasma. Consistent with the requirement for thrombin in vitro, hirudin completely inhibited thrombus formation in Fg/VWF(-/-) mice. These data define a novel pathway of platelet aggregation independent of both Fg and VWF. Although this pathway was not detected in the presence of anticoagulants, it was observed under physiological conditions in vivo and in the presence of Ca(2+)in vitro. CONCLUSIONS: beta(3) integrin, thrombin, and Ca(2+) play critical roles in this Fg/VWF-independent aggregation, and both plasma and platelet granule proteins contribute to this process.

Animals↗
PubMed2006

Valproic acid adjunctive therapy for HIV-associated cognitive impairment: a first report.

In vitro and animal model data demonstrate that valproic acid (VPA) can ameliorate HIV-associated neurotoxicity. The authors conducted a pilot 10-week placebo-controlled study of VPA 250 mg twice daily in 22 HIV-infected individuals with (n = 16) and without (n = 6) cognitive impairment. VPA was safe and well tolerated, with trends toward improved neuropsychological performance and brain metabolism in the impaired subjects.

AIDS Dementia Complex↗
PubMed2006

Effects of number of diffusion gradient directions on derived diffusion tensor imaging indices in human brain.

BACKGROUND AND PURPOSE: The effects of a number of diffusion-encoding gradient directions (NDGD) on diffusion tensor imaging (DTI) indices have been studied previously with theoretic analysis and numeric simulations. In this study, we made in vivo measurements in the human brain to compare different clinical scan protocols and to evaluate their effects on the calculated DTI indices. METHODS: Fifteen healthy volunteers were scanned with a 1.5T MR scanner. Single-shot DTI images were acquired using 3 protocols different in NDGD and number of excitations (NEX) for each direction (NDGD/NEX = 6/10, 21/3, 31/2). Means and standard error of mean (SEM) were calculated and compared in 6 regions of interest (ROIs) for mean diffusivity (D), fractional anisotropy (FA), diffusion tensor eigenvalues (lambda(1), lambda(2), and lambda(3)), and correlation coefficients (r) of these indices among the 3 DTI protocols. RESULTS: At the ROI level, no significant differences were found for the mean and SEM of D and FA among protocols (P > .05). The 6-NDGD protocol, however, yielded higher values for lambda(1) and lambda(2) and lower values for lambda(3) in most ROIs (P < .05) compared with the other protocols. At the voxel level, the correlation between the protocols r(21-31) were higher than r(6-21) and r(6-31) in most ROIs. The correlation of FA among 3 protocols also increased with increasing anisotropy. CONCLUSION: For ROI analyses, different NDGDs lead to similar values of FA and D but different eigenvalues. However, different NDGDs at the voxel level provide varying values. The selection of the NDGD, therefore, should depend on the focus of different DTI applications.

Adult↗
PubMed2005

Vitronectin stabilizes thrombi and vessel occlusion but plays a dual role in platelet aggregation.

The role of vitronectin (Vn) in thrombosis is currently controversial; both inhibitory and supportive roles have been reported. To monitor directly the function of Vn in thrombotic events at the site of vascular injury, we studied Vn-deficient (Vn-/-) and wild-type (WT) control mice with two real-time intravital microscopy thrombosis models. In the mesenteric arteriole model, vessel injury was induced by ferric chloride. We observed unstable thrombi and a significantly greater number of emboli in Vn-/- mice. Vessel occlusion was also delayed and frequent vessel re-opening occurred. In the cremaster muscle arteriole model, vessel injury was induced by a nitrogen dye laser. We observed significantly fewer platelets, lower fibrin content, and unstable fibrin within the thrombi of Vn-/- mice. To define further the role of Vn in thrombus growth, we studied platelet aggregation in vitro. Consistent with our in vivo data, the second wave of thrombin-induced aggregation of gel-filtered platelets was abolished at a low concentration of thrombin in Vn-/- platelets. Interestingly, adenosine diphosphate (ADP)-induced platelet aggregation was significantly increased in Vn-/- platelet-rich plasma (PRP) and this effect was attenuated by adding purified plasma Vn. We also observed increased platelet aggregation induced by shear stress in Vn-/- whole blood. These data demonstrate that Vn is a thrombus stabilizer. However, in contrast to released platelet granule Vn which enhances platelet aggregation, plasma Vn inhibits platelet aggregation.

Adenosine Diphosphate↗
PubMed2005

Differential expression of prostaglandin E receptor subtype EP2 in rat uterus during early pregnancy.

PGE2 is essential for mammalian female reproduction. This study was to examine the expression of EP2 gene in the rat uterus during early pregnancy, delayed implantation and artificial decidualization by in situ hybridization and immunohistochemistry. There was no detectable EP2 mRNA expression in the uterus from days 1 to 4 of pregnancy (day 1 = day of vaginal sperm). A low level of EP2 immunostaining was observed in the luminal and glandular epithelium from days 1 to 4 of pregnancy. Both EP2 mRNA and protein expression were highly detected in the luminal epithelium at implantation sites on day 6 of pregnancy. EP2 expression decreased from day 7 of pregnancy and was undetectable on days 8 and 9 of pregnancy. After delayed implantation was terminated by estrogen treatment and the embryo implanted, both EP2 mRNA and protein expression were strongly observed in the luminal epithelium at the implantation site. There was no detectable EP2 expression in both control and decidualized uteri. In conclusion, these data suggest that EP2 expression at implantation site may play an important role during embryo implantation in rats.

Animals↗
PubMed2004

Visualization and quantitation of peroxisomes using fluorescent nanocrystals: treatment of rats and monkeys with fibrates and detection in the liver.

Peroxisome proliferation in the liver is a well-documented response that occurs in some species upon treatment with hypolipidemic drugs, such as fibrates. Typically, liver peroxisome proliferation has been estimated by direct counting via electron microscopy, as well as by gene expression, enzyme activity, and immunolabeling. We have developed a novel method for the immunofluorescent labeling of peroxisomes, using an antibody to the 70-kDa peroxisomal membrane protein (PMP70) coupled with fluorescent nanocrystals, Quantum Dots. This method is applicable to standard formalin-fixed, paraffin-embedded tissues. Using this technique, a dose-dependent increase in PMP70 labeling was evident in formalin-fixed liver sections from fenofibrate-treated rats. In formalin-fixed liver sections from cynomolgus monkeys given ciprofibrate, quantitative image analysis showed a statistically significant increase in PMP70 labeling compared to control; the increase in hepatic PMP70 protein levels was corroborated by immunoblotting using total liver protein. An increase in hepatic peroxisome number in ciprofibrate-treated monkeys was confirmed by electron microscopy. An advantage of the Quantum Dot/PMP70 method is that a single common protocol can be used to label peroxisomes from several different species, and many of the common problems that arise with immunolabeling, such as fading and low signal strength, are eliminated.

Animals↗
PubMed2003

Expression of regulator of G-protein signalling protein 2 (RGS2) in the mouse uterus at implantation sites.

Establishment of an active dialogue between the maternal endometrium and the implanting blastocyst is essential for successful implantation. The aim of this study was to identify genes that are explicitly expressed at implantation sites of the mouse uterus by subtractive hybridization. One expressed sequence tag of the genes identified showed 92% identity to the regulator of G-protein signalling protein 2 (RGS2). The full cDNA sequence of this gene was amplified by PCR and subsequently registered in GenBank. The sequence of its open reading frame encoding 211 amino acids was the same as that of mouse RGS2, with the exception of four amino acids. Northern blot analysis showed that the expression of this gene was much higher at implantation sites than at inter-implantation sites on days 5-8 of pregnancy. In situ hybridization localized this mRNA predominantly to the stromal cells at the implantation sites. These results indicate that RGS2 has a role during implantation, possibly by regulating the intracellular Ca(2+) mobilization and T-cell proliferation at the maternal-fetal interface.

Animals↗
PubMed2002

Recreational injury and its relation to socioeconomic status among school aged children in the US.

OBJECTIVES: This study described epidemiologic patterns of recreational injuries among school aged children in the US and assessed the relation of these patterns to socioeconomic status. METHODS: Combined data from the 1997-98 National Health Interview Surveys for 38 458 children aged 6-17 years regarding non-fatal recreational injury episodes that received medical attention, reported by a household adult, were analysed. Logistic regression analysis was used to assess the association between recreational injury and socioeconomic status while controlling for confounding factors. RESULTS: The annualized rate of recreational injury was 91.2 episodes per 1,000 children, with an increased risk associated with a higher family income status or being non-Hispanic white. For children from not poor families, most injury episodes occurred in sport facilities, whereas for children from poor and near poor families, most occurred outside the home. CONCLUSION: Recreational injury is a significant health problem for school aged children in the US. Non-Hispanic white children and children from affluent families are at increased risk of recreational injury.

Adolescent↗
PubMed2001

Ordered water and ligand mobility in the HIV-1 integrase-5CITEP complex: a molecular dynamics study.

A 2 ns molecular dynamics simulation has been carried out for the HIV-1 integrase-5CITEP complex in order to understand the role of water in defining the ligand's binding mode and to address issues of binding site flexibility and ligand motion. Although the ligand retains considerable mobility within the active site, a structural water molecule bridging 5CITEP with Asp 64 and Asn 155 is identified in the simulation. Consideration of this water molecule could open a route to new HIV-1 integrase inhibitors.

Binding Sites↗
PubMed2001

Amino acid substitution(s) in the stem-anchor region of langat virus envelope protein attenuates mouse neurovirulence.

The identification of variants that are unable to bind membrane receptor preparations (MRPs) has previously been shown to select attenuated yellow fever and Japanese encephalitis viruses. In this study, this methodology has been extended to the tick-borne serocomplex of flaviviruses. Langat (LGT) virus strain TP21 was bound to mouse or human brain MRPs and viruses that escaped binding were isolated and characterized. In addition, variant viruses escaping neutralization by the monoclonal antibody (MAb) 9F9 were also isolated. All of the variant viruses were attenuated for mouse neurovirulence (> or =13-fold). Sequence analysis of the prM/E region of the variant viruses identified mutations within the stem-anchor region of the E protein in variants isolated following incubation with mouse or human brain MRPs at a pH > or = 7.0. The MAb 9F9 variants and MRP variants isolated at pH 5.0, which should induce a conformational shift in the viral E protein, had nearly identical mutations in the prM/M protein immediately N-terminal to the prM/E cleavage site. MAb 9F9 neutralized none of the variant viruses and hemagglutination inhibition assays suggest that the variant virus surface proteins have slightly different conformations compared to the parental virus. These data support previous work indicating that the stem-anchor region of the E protein is important to the surface architecture of the tick-borne flaviviruses. In addition, this study demonstrates that the M protein is at least partially solvent accessible on the virion surface and that the M protein plays a role in maintaining the conformation of the M/E surface complex.

Amino Acid Sequence↗
PubMed2001

Increased thrombogenesis and embolus formation in mice lacking glycoprotein V.

The glycoprotein (GP) Ib-V-IX complex plays a critical role in initiating platelet adhesion to von Willebrand factor (vWF) at the site of vascular injury. The complex also forms a high-affinity binding site for thrombin. Using an intravital microscopy mouse model, it was previously established that vWF plays a critical role in mediating platelet adhesion and thrombus formation following mesenteric arteriolar injury induced by ferric chloride. Further characterization of this model showed that these thrombotic events were also thrombin dependent. Using this vWF- and thrombin-dependent model, this study shows that GP V gene deficiency significantly accelerates both platelet adhesion and thrombus formation in mice following arteriolar injury. The time required for vessel occlusion in GP V-deficient (GP V(-/-)) mice was significantly shorter than that in wild-type mice. Interestingly, large emboli were also produced in GP V(-/-) mice, but not in wild-type mice, causing frequent downstream occlusion. However, when the 2 genotypes were compared in the in vitro perfusion chamber where thrombin was inhibited by heparin, no significant differences were found in either initial single-platelet adhesion or thrombus volume. These results demonstrate that GP V(-/-) mice have accelerated thrombus growth in response to vascular injury and suggest that this is caused by enhanced thrombin-induced platelet activation rather than enhanced binding of GPIb-V-IX to vWF. Absence of GP V also compromises thrombus stability.

Animals↗
PubMed2001

Nonproliferating bystander CD4+ T cells lacking activation markers support HIV replication during immune activation.

HIV replicates primarily in lymphoid tissue and immune activation is a major stimulus in vivo. To determine the cells responsible for HIV replication during Ag-driven T cell activation, we used a novel in vitro model employing dendritic cell presentation of superantigen to CD4(+) T cells. Dendritic cells and CD4(+) T cells are the major constituents of the paracortical region of lymphoid organs, the main site of Ag-specific activation and HIV replication. Unexpectedly, replication occurred in nonproliferating bystander CD4(+) T cells that lacked activation markers. In contrast, activated Ag-specific cells were relatively protected from infection, which was associated with CCR5 and CXC chemokine receptor 4 down-regulation. The finding that HIV replication is not restricted to highly activated Ag-specific CD4(+) T cells has implications for therapy, efforts to eradicate viral reservoirs, immune control of HIV, and Ag-specific immune defects.

Antigen Presentation↗
PubMed2001

Genetic variation in the 3' non-coding region of dengue viruses.

The 3' non-coding region (3'NCR) of strains of dengue 1 (DEN 1), DEN 2, DEN 3, and DEN 4 viruses, isolated in different geographical regions, was sequenced and compared to published sequences of the four dengue viruses. A total of 50 DEN 2 strains was compared: 7 West African strains, 3 Indonesian mosquito strains, 1 Indonesian macaque isolate, and 39 human isolates from Southeast Asia, the South Pacific, and the Caribbean and Americas. Nucleotide sequence alignment revealed few deletions and no repeat sequences in the 3' NCR of DEN 2 viruses and showed that much of the 3' NCR was well conserved. The strains could be divided into two groups, sylvatic and human/mosquito/macaque, based on nucleotide sequence homology. A hypervariable region was identified immediately following the NS5 stop codon, which involved a 2-10 nucleotide deletion in human, mosquito, and macaque isolates compared with the sylvatic strains. The DEN 2 3'NCR was also compared with 3'NCR sequences from strains of DEN 1, DEN 3, and DEN 4 viruses. DEN 1 was found to have four copies of an eight nucleotide imperfect repeat following the NS5 stop codon, while DEN 4 virus had a deletion of 75 nucleotides in the 3'NCR. We propose that the variation in nucleotide sequence in the 3'NCR may have evolved as a function of DEN virus transmission and replication in different mosquito and non-human primate/human host cycles. The results from this study are consistent with the hypothesis that DEN viruses arose from sylvatic progenitors and evolved into human epidemic strains. However, the data do not support the hypothesis that variation in the 3'NCR correlates with DEN virus pathogenesis.

3' Untranslated Regions↗
PubMed2001

Distribution and declines in cardiac allograft radionuclide left ventricular ejection fractions in relation to late mortality.

BACKGROUND: Cardiac allograft left ventricular ejection fraction (LVEF) is an important measure of left ventricular systolic function. Despite widespread use of LVEF after transplantation, its normal range and prognostic value in cardiac allografts has not been defined. METHODS: We conducted a retrospective cohort study among 292 consecutive adult heart transplant patients. Left ventricular ejection fractions were performed at 1, 3, 12, 24, and 48 months after transplantation using radionuclide ventriculography. Endomyocardial biopsies assessed rejection, right heart catheterization assessed loading conditions, and angiography assessed allograft coronary artery disease. We used Cox proportional hazards model to examine the predictive value of LVEF on late mortality. RESULTS: Of the patients who survived > or =4 years, the mean allograft LVEF decreased 4.7 units at 3 months, from 63.8 to 59.7; an additional 4.1 units at 12 months, from 59.7 to 55.6 (p < 0.001); and remained stable afterward. These changes were not associated with concurrent changes in loading conditions, episodes of rejection, or development of allograft coronary artery disease. Left ventricular ejection fraction lower than the 95% normal limit (<40%) at 12 months was inversely associated with risk for late cardiac mortality (relative risk = 3.5, 95% confidence interval = 1.0-12.2), while controlling for recipient age, sex, donor age, and rejection episodes. CONCLUSIONS: The cardiac-allograft LVEF frequently decreases in the first year after transplantation. The 95th percentile of allograft LVEF value (<40%) at Year 1 predicts late cardiac mortality among transplant recipients.

Adult↗
PubMed2001

Characterization of NF-kappaB expression in Hodgkin's disease: inhibition of constitutively expressed NF-kappaB results in spontaneous caspase-independent apoptosis in Hodgkin and Reed-Sternberg cells.

Although the neoplastic cells of classical Hodgkin's disease (CHD) demonstrate high levels of constitutively active nuclear NF-kappaB, the precise physiologic and clinical significance of NF-kappaB expression is currently undefined. Expression of active NF-kappaB p65(Rel A) was evaluated in patient samples of CHD and nodular lymphocyte predominance Hodgkin's disease. The action of the chemical NF-kappaB inhibitors gliotoxin and MG132 and the effect of NF-kappaB inhibition utilizing an adenovirus vector carrying a dominant-negative IkappaBalpha mutant (Ad5IkappaB) were then demonstrated in CHD cell lines (L428, KMH2, and HS445). Hodgkin and Reed-Sternberg (HRS) cells from all patient and cell line specimens showed strong immunopositivity for active p65(Rel A). Expression was also seen in lymphocytic/histiocytic cells from all cases of nodular lymphocyte predominance Hodgkin's disease. After chemical NF-kappaB inhibition, p65(Rel A) was significantly reduced in nuclear extracts from cultured HRS cells as revealed by electrophoretic mobility shift assays. Furthermore, chemical NF-kappaB inhibition resulted in time- and concentration-dependent apoptosis in HRS cells. With the exception of MG132-induced apoptosis in HS445, apoptosis by chemical NF-kappaB inhibition was not significantly altered by preincubation with various caspase inhibitors (z-DQMD-FMK, z-DEVD-FMK, z-VAD-FMK, z-VEID-FMK, and z-IETD-FMK). Regardless of the chemical inhibitor used, no significant change in caspase-3 functional activity was found in CHD cell lines. HRS cells infected with Ad5IkappaB also showed a marked increase in spontaneous apoptosis compared with wild type adenovirus-infected and control cells. Overall, the inhibition of active NF-kappaB in HRS cells resulting in spontaneous caspase-independent apoptosis demonstrates a critical role for NF-kappaB in HRS cell survival and resistance to apoptosis.

Adenoviridae↗
PubMed2001

Analysis of expression of nuclear factor kappa B (NF-kappa B) in multiple myeloma: downregulation of NF-kappa B induces apoptosis.

Nuclear factor-kappa B (NF-kappa B) is an important transcription factor that regulates survival in many cells. Activated NF-kappa B has been shown to protect some haematopoietic neoplastic cells from apoptosis. In the present study, we analysed NF-kappa B status in 13 primary samples from patients with multiple myeloma (MM) and in four myeloma cell lines including U266, RPMI 8226, HS-Sultan and K620. Constitutive activation of NF-kappa B was evaluated by either immunohistochemistry or immunofluorescence using a monoclonal mouse anti-human p65 (Rel A) antibody, which recognizes the unbound, active form of p65 (Rel A). Constitutively active NF-kappa B was present in all MM patient samples as well as in all four myeloma cell lines. Inhibition of constitutively active NF-kappa B, by either proteasome inhibitors (MG132, gliotoxin) or inhibitors of I kappa B phosphorylation (Bay117082, and Bay117085), induced apoptosis as demonstrated by both flow cytometric analysis and light microscopic morphological evaluation. This chemically induced apoptosis was associated with decreased DNA binding of nuclear NF-kappa B as determined by the electrophoretic mobility shift assay. In addition, adenovirus vector with dominant negative I kappa B alpha (Ad5I kappa B) was used for inhibition of NF-kappa B in the U266 cell line. Compared with wild-type, super-repressor-treated cells showed an increased level of apoptosis. These results suggest that constitutive expression of NF-kappa B plays an important role in plasma cell survival in MM.

Adenoviridae↗