Biomedical subjects

H Li

Publications and source records attributed to H Li.

At least 595 records · Page 33Linked to original sources

PubMed2000

Natural killer cells determine the outcome of B cell-mediated autoimmunity.

Natural killer (NK) cells can affect the outcome of adaptive immune responses. NK cells, but not NK1.1+T cells, were found to participate in the development of myasthenia gravis (a T cell-dependent, B cell- and antibody-mediated autoimmune disease) in C57BL/6 mice. The requirement for NK cells was reflected by the lack of a type I helper T cell response and antibodies to the acetylcholine receptor in both NK1.1+ cell-depleted and NK cell-deficient IL-18-/- mice. These findings establish a previously unrecognized link between NK cells and autoreactive T and B cells.

Amino Acid Sequence↗

PubMed2000

Point mutations alter the mechanical stability of immunoglobulin modules.

Immunoglobulin-like modules are common components of proteins that play mechanical roles in cells such as muscle elasticity and cell adhesion. Mutations in these proteins may affect their mechanical stability and thus may compromise their function. Using single molecule atomic force microscopy (AFM) and protein engineering, we demonstrate that point mutations in two beta-strands of an immunoglobulin module in human cardiac titin alter the mechanical stability of the protein, resulting in mechanical phenotypes. Our results demonstrate a previously unrecognized class of phenotypes that may be common in cell adhesion and muscle proteins.

Amino Acid Substitution↗

PubMed2000

BID-dependent and BID-independent pathways for BAX insertion into mitochondria.

In the absence of an apoptotic signal, BAX adopts a conformation that constrains the protein from integrating into mitochondrial membranes. Here, we show that caspases, including caspase-8, can initiate BAX insertion into mitochondria in vivo and in vitro. The cleavage product of caspase-8, tBID, induced insertion of BAX into mitochondria in vivo, and reconstitution in vitro showed that tBID, either directly or indirectly, relieved inhibition of the BAX transmembrane signal-anchor by the NH2-terminal domain, resulting in integration of BAX into mitochondrial membrane. In contrast to these findings, however, Bid-null mouse embryo fibroblasts supported Bax insertion into mitochondria in response to death signaling by either TNFalpha or E1A, despite the fact that cytochrome c release from the organelle was inhibited. We conclude, therefore, that a parallel Bid-independent pathway exists in these cells for mitochondrial insertion of Bax and that, in the absence of Bid, cytochrome c release can be uncoupled from Bax membrane insertion.

Amino Acid Chloromethyl Ketones↗

PubMed2000

A pivotal role of nitric oxide in endothelial cell dysfunction.

The functional role of the vascular endothelium is a subject of growing interest and appreciation. Some of the key functions of the endothelium are modulated by the activity and expression of endothelial nitric oxide synthase (eNOS), suggesting a role for this enzyme in endothelial dysfunction. Several well-known angiogenic stimulators exert their effect only in the presence of the functional eNOS. In this setting NO production is responsible for the scalar podokinetic cell motility, which is a prerequisite for the acquisition of vectorial movement when guidance cues are applied. The mode of this NO action appears to lie in the accelerated turnover of focal adhesions through the process of activation/inactivation of protein tyrosine phosphatases. Localization of eNOS to the caveolar domains, in the proximity of clustered beta1 integrins, provides an additional level of regulatory complexity through the modulation of caveolar dynamics and the state of caveolin oligomerization. Therefore, eNOS serves various important functions in the endothelium and is a putative target for therapeutic interventions.

Animals↗

PubMed2000

Human immunoglobulin VH4 sequences resolved by population-based analysis after enzymatic amplification and denaturing gradient gel electrophoresis.

Exhaustive gene identification followed by assignment of the genes identified to corresponding loci is a key step in elucidating the physical structure of a multigene family. However, problems occur in this process because genes in a multigene family usually share a high degree of sequence identity and are highly polymorphic. To address these problems, an efficient population-based approach was developed. Using this approach, sequences in the human immunoglobulin VH4 family were amplified by PCR with family-specific primers. Denaturing gradient gel electrophoresis (DGGE) was used to separate the resulting sequences with either very similar or identical sizes and differing by as little as 1 base pair (bp). Eighteen distinct bands and 21 banding patterns were observed in the samples collected from 41 unrelated individuals. Of the 18 bands, 12 were polymorphic. No sample had all 18 bands. The estimated frequencies for the alleles represented by the 18 bands ranged from 1.2 to 100%. The 18 sequences differed from each other by 1-19 bases (0.7 to 13%) within the 145-146-bp amplified region. Sequences in eight bands (44%) were not reported previously. These results were used to assign the majority (14 out of 18) of the VH4 sequences to 10 loci. This PCR-DGGE method, in conjunction with a population-based assay, may also be used to study other multigene families including those involved in the development of the immune system.

Base Sequence↗

PubMed2000

Mechanisms of pertussis toxin-induced myelomonocytic cell adhesion: role of CD14 and urokinase receptor.

Pertussis toxin (PTX) has been shown previously to promote myelomonocytic cell adhesion in serum. The aim of the present study was to identify, using transforming growth factor-beta1 and 1, 25-(OH)2 vitamin D3 (TGF-beta1/D3)-primed U937 cells, the PTX-binding site(s) and the adhesion molecule(s) responsible for PTX-induced myelomonocytic cell adhesion. Monoclonal antibodies (mAbs) directed against CD14, CD11b, CD18 or urokinase receptor (uPAR) significantly inhibited PTX-induced primed U937 cell adhesion in serum in a concentration-dependent manner. However, only anti-CD14 and anti-CD18 mAbs were able to prevent the myeloid cells from binding to PTX-coated plates and significantly inhibited a PTX-induced rise of [Ca2+]i in primed U937 cells. A receptor-isolation study showed that biotinylated PTX recognized a 48 000-molecular weight protein in primed U937 cell lysates, which could be specifically blocked by excess unlabelled PTX or by anti-CD14 mAb. On the other hand, mAb directed against uPAR significantly blocked PTX-induced myeloid cell adhesion to serum and to immobilized vitronectin, a major extracellular matrix protein in serum. Taken together, our data suggest that PTX may bind to cell-surface CD14 to induce myelomonocytic cell adhesion to vitronectin in serum via uPAR activation, which may represent a pathogenetic mechanism for the respiratory tract infection induced by Bordetella pertussis.

Bone Marrow Cells↗

PubMed2000

Protein binding of NADH on chemical preconditioning.

Chemical preconditioning, an emerging neuroprotective strategy described in recent years, results in preserved energy metabolism during hypoxia via yet unknown mechanisms. The hypoxic increase of NADH content is attenuated by preconditioning. The goal of the present study was to investigate whether attenuation of the hypoxic NADH increase is due to a shift between free and protein-bound NADH. NADH in solution has a fluorescence maximum at 469.2 nm. In untreated mouse hippocampal slices, lambda(control onset) is 456.2 +/- 5.3 nm in CA1 (mean +/- SD; p < 0.01 vs. solution) and 454.6 +/- 6.1 nm in CA3 [p < 0.01 vs. solution, not significant (NS) to lambda(control onset) in CA1]. In slices prepared from animals pretreated in vivo with 20 mg/kg 3-nitropropionate, lambda(preconditioning onset) is 439.2 +/- 5.0 nm (p < 0.001 vs. control) in CA1 and 434.2 +/- 6.4 nm in CA3 (p < 0.001 vs. control; NS to lambda(preconditioning onset) in CA1). In controls, the fluorescence maximum shifts to lambda(control hypoxia) 458.2 +/- 1.3 nm in CA1 (NS vs. onset) and 456.0 +/- 3.6 nm in CA3 (NS vs. onset). On preconditioning with 3-nitropropionate, lambda(preconditioning hypoxia) shifts to 446.4 +/- 4.3 nm in CA1 (p < 0.03 vs. onset) and 438.6 +/- 6.9 nm in CA3 (p < 0.03 vs. onset). Posthypoxic decay of free and protein-bound NADH is diminished after preconditioning. We conclude that the free NADH level is reduced on an increase of hypoxic tolerance by chemical preconditioning. Reduction of free NADH content is maintained during hypoxia after preconditioning.

Animals↗

PubMed2000

Expression of Rh30 and Rh-related glycoproteins during erythroid differentiation in a two-phase liquid culture system.

BACKGROUND: To gain insight into the formation of the Rh complex during erythroid differentiation, the ways in which Rh30 and Rh-related glycoproteins, especially Rh50, were produced in a modified two-phase liquid culture system were studied. STUDY DESIGN AND METHODS: A mononuclear cell fraction from fresh peripheral blood was first cultured in a medium supplemented with conditioned medium collected from the culture of a bladder carcinoma cell line (5637) for 7 days. Nonadherent cells were then collected for culture in a secondary medium containing 2 U per mL of erythropoietin to initiate erythroid differentiation. The expression of Rh30 and Rh50 during secondary culture (16 days) was monitored by flow cytometry. RESULTS: D+ cells appeared after Day 4 and increased to 70 percent by Day 8. On Day 12, 90 percent of the total cells became D+ and remained so until the end of the culture. A similar expression profile was obtained for Rh50. As determined from mean fluorescence intensities recorded in flow cytometry, the number of both D and Rh50 antigenic sites per cell increased as the differentiation progressed. Rh-related glycoprotein, CD47, had expression patterns significantly different from those of Rh30 and Rh50. In addition, the cultured cells produced partially glycosylated protein (approx. 32 kDa) in Rh50. CONCLUSION: Expressions of Rh30 and Rh50 occur simultaneously during erythroid differentiation, and both proteins are most actively synthesized at the last stage of the differentiation. In contrast, CD47 may be involved in expression of Rh30 in a different manner from Rh50. The two-phase liquid culture system will be an excellent model for studying the interaction among the components of the Rh complex during protein synthesis and complex assembly on the cell membrane.

Anion Exchange Protein 1, Erythrocyte↗

PubMed2000

Genetics of brugada, long QT, and arrhythmogenic right ventricular dysplasia syndromes.

This article outlines the up-to-date understanding of the molecular basis of primary ventricular arrhythmias. Two disorders have recently been well described at the molecular level, the long QT syndromes and Brugada syndrome, and this article reviews the current scientific knowledge of each disease. A third disorder, arrhythmogenic right ventricular dysplasia, which is on the cusp of understanding, will also be described.

Arrhythmogenic Right Ventricular Dysplasia↗

PubMed2000

Perinatal lethal form of Gaucher's disease presenting with hemosiderosis.

A term infant with hydrops fetalis presented with hypotonia, massive splenomegaly, renal failure, and severe hyperferritinemia. Multiple organ failure, myoclonus, and opisthotonus ensued and she died at 15 days of age. High rounded forehead, large open fontanel, and a small recessed chin led to initial premortem diagnosis of Zellweger syndrome, but her plasma profile of long chain fatty acid was normal. Her subsequent clinical course and findings of postmortem examinations were consistent with perinatal lethal form of Gaucher's disease (PLGD). The diagnosis was confirmed by deficiency of enzyme beta-glucocerebrosidase in white blood cells and in cultured fibroblasts. In addition to the crossover features of Zellweger phenotype, this infant exhibited a number of unusual features including, severe hyperferritinemia, rapid progression of splenomegaly, and absence of icthyosis.

Fatal Outcome↗

PubMed2000

Ovarian cancer gene therapy: repeated treatment with thymidine kinase in an adenovirus vector and ganciclovir improves survival in a novel immunocompetent murine model.

OBJECTIVE: Our purpose was to assess the effect of multiple injections of the system of herpes simplex virus thymidine kinase in an adenovirus vector and ganciclovir on survival in a murine model of human epithelial ovarian cancer. STUDY DESIGN: In this work we tested the ability of the system of thymidine kinase delivered by an adenovirus vector and ganciclovir to treat ovarian cancer in a novel murine model for epithelial ovarian cancer, SaskMouse. SaskMouse was developed by injecting LM-1 cells, a murine epithelial ovarian cancer cell line, intraperitoneally into a syngeneic C57BL/6N x C3H/He mouse strain. The cells developed into multiple cancer implants on different abdominal organs, leading to ascites and rapid death. The model has an intact immune system, as evidenced by the inability of different human cancer cells to develop into cancers when injected into the mice intraperitoneally. RESULTS: The system of thymidine kinase delivered by an adenovirus vector and ganciclovir was applied to SaskMouse. Mice were either untreated (group 1), treated with one intraperitoneal injection of adenovirus- thymidine kinase at 250 plaque-forming units/cell (group 2), or treated with two intraperitoneal injections of adenovirus-thymidine kinase at 250 plaque-forming units/cell on days 0 and 23 (group 3). Survivals were 23 +/- 2, 27 +/- 2, and 35 +/- 4 days, respectively (P <.05). Antiadenoviral antibodies were assayed both in the serum and in the peritoneal fluid of treated mice. Despite high antibody titers in serum, there were no detectable antibodies in the peritoneal fluid. CONCLUSION: Our data suggest that multiple intraperitoneal injections of the combination of thymidine kinase delivered by an adenovirus vector and ganciclovir are effective in prolonging survival in the presence of ovarian cancer. There are potential implications for other abdominal malignancies.

Adenoviridae↗

PubMed2000

The influence of human intervertebral disc tissue on the metabolism of osteoblast-like cells.

Extensive studies have been performed to evaluate different factors that may affect on spinal interbody fusion, but the role of intervertebral disc tissue in the fusion process remains unclear. To study the influence of intervertebral disc tissue on osteoblast metabolism, we harvested disc tissue from patients who had undergone spinal surgery. The nucleus pulposus and annulus fibrosus were separately co-cultured with osteoblast-like cells SaOS-2 by means of culture inserts or organ culture. We assayed alkaline phosphoatase activity, 3H-thymidine incorporation into the DNA, and production of collagen type I, IL-1beta, IL-6, IL-10, and TNF-alpha. Exposure of the nucleus pulposus (NP) to osteoblast-like cells revealed stimulation of alkaline phosphatase production, 3H-thymidine incorporation and collagen type I production. Exposure of the annulus fibrosus (AF) stimulated 3H-thymidine incorporation and collagen type I production, but did not affect ALP activity. IL-6 was detected after application of NP and AF. Interleukin IL-10, IL-1beta and TNF-alpha were all below detection levels after application of disc tissue. Our findings show that frozen disc tissue stimulates the metabolism of osteoblast-like cells in vitro.

Adolescent↗

PubMed2000

Preparation and evaluation of a sustained-release formulation of nifedipine HPMC tablets.

A nifedipine (NF) polyethylene glycol (PEG) solid dispersion was prepared. Using this solid dispersion, NF hydroxypropylmethylcellulose (HPMC) matrix tablets were prepared. Both the high-viscosity grade HPMC (Methocel K15M) and low-viscosity grade HPMC (Methocel K100) were applied in the tablets to form the matrix. The dissolution and absorption of NF from the tablet were evaluated as a formulation that had a sustained release over 24 hr. The Hixson-Crowell equation and Higuchi equation were used to investigate the dissolution mechanism, and the erosion and diffusion codependent mechanism was established. Adalat GITS 30 was used as a reference dosage form. Each beagle dog was also administered an intravenous injection to obtain the pharmacokinetics parameters. The Loo-Riegelman method was applied to study the in vitro/in vivo correlation of the tested tablets and Adalat GITS 30, and significant correlation was proved. Absolute bioavailability and comparative bioavailability of the tested tablet were studied. The results indicated that the NF HPMC tablet could be an ideal 24-hr sustained-release formulation.

Absorption↗

PubMed2000

Analysis of candidate-host immunogenetic determinants in herpes simplex virus-associated Mollaret's meningitis.

Infection due to herpes simplex virus (HSV) is associated with recurrent aseptic meningitis (Mollaret's meningitis); however, the neuropathogenesis of this disease remains unknown. We collected 20 cerebrospinal fluid (CSF) specimens that were positive for HSV DNA by using polymerase chain reaction (PCR) assay from patients with a clinical diagnosis of Mollaret's meningitis. Patients were predominantly female (female:male, 22:1), with an average age of 32.8 years (range, 18-46 years). Using direct sequence analysis of HSV PCR products obtained from the CSF, we determined that all of the patients were infected with HSV type 2. In addition, we evaluated polymorphisms in 2 human genomic loci, which are associated with either severe or recurrent microbial infections (interferon-gamma receptor [IFN-gammaR] and mannose binding lectin [MBL]); these host genes were also amplified directly from the CSF specimens. No mutations were found in exons 2 or 3 of the IFN-gammaR gene (n=20). In contrast, there were 4 (20%), 4 (20%), and 0 mutations found in codons 52, 54, and 57, respectively, in exon 1 of MBL (n=20). A significantly higher frequency of codon 52 mutations (P=.04) was observed, compared with racially matched control patients.

Adolescent↗

PubMed2000

Construction of ELISA system to quantify human ST2 protein in sera of patients.

The human ST2 gene can be specifically induced by growth stimulation in fibroblastic cells, and can also be induced by antigen stimulation in Th2 cells. The gene encodes a soluble secreted protein, ST2, and a transmembrane protein, ST2L, which are closely related to the interleukin-1 receptor. To gain insight into the biological roles of the ST2 gene, three monoclonal antibodies (MAbs) against human ST2 gene products were obtained. To obtain these antibodies, immunization was carried out using two different immunogens: purified soluble human ST2 protein (hST2), and COS7 cells, which express the extracellular portion of human ST2L. 2A5 and FB9 MAbs were derived from the immunization with soluble hST2, and HB12 was derived from the COS7 cell immunization. All three antibodies were shown to detect native forms of the human ST2 gene products by immunoprecipitation, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). In the competitive ELISA using biotinylated and nonlabelled MAbs, neither FB9 nor HB12 affected the binding of 2A5 to ST2 gene products. Based on this result, we constructed a sandwich ELISA system using 2A5 and FB9 to measure the concentration of soluble hST2 in sera. The ELISA, combined with the flow cytometry using these antibodies, will be a useful tool for elucidating the functions of human ST2 gene products in individuals.

Animals↗

PubMed2000

Associations between uncoupling protein 2, body composition, and resting energy expenditure in lean and obese African American, white, and Asian children.

BACKGROUND: Little is known about genes that affect childhood body weight. OBJECTIVE: The objective of this study was to examine the association between alleles of the mitochondrial uncoupling protein 2 (UCP2) gene and obesity because UCP2 may influence energy expenditure. DESIGN: We related UCP2 genotype to body composition and resting energy expenditure in 105 children aged 6-10 y. Overweight children and nonoverweight children of overweight parents were genotyped for a 45-base pair deletion/insertion (del/ins) in 3'-untranslated region of exon 8 and for an exon 4 C to T transition. RESULTS: Eighty-nine children were genotyped for the exon 8 allele: 50 children had del/del, 33 had del/ins, and 6 had ins/ins. Mean (+/-SD) body mass index (BMI; in kg/m(2)) was greater for children with del/ins (24.1 +/- 5.9) than for children with del/del (20.4 +/- 4.8; P < 0.001). BMI of ins/ins children (23.7 +/- 7.8) was not significantly different from that of del/ins children. A greater BMI in del/ins children was independent of race and sex. Body composition was also different according to UCP2 genotype. All body circumferences and skinfold thicknesses examined were significantly greater in del/ins than in del/del children. Body fat mass as determined by dual-energy X-ray absorptiometry was also greater in del/ins than in del/del children (P < 0.005). For 104 children genotyped at exon 4, no significant differences in BMI or body composition were found among the 3 exon 4 genotypes. Neither resting energy expenditure nor respiratory quotient were different according to UCP2 exon 4 or exon 8 genotype. CONCLUSIONS: The exon 8 ins/del polymorphism of UCP2 appears to be associated with childhood-onset obesity. The UCP2/UCP3 genetic locus may play a role in childhood body weight.

Asian People↗

PubMed2000

Uncoupling proteins 2 and 3 with age: regulation by fasting and beta3-adrenergic agonist treatment.

In rodents, adaptive thermogenesis in brown adipose tissue (BAT) serves both to regulate body mass after hyperphagia and to conserve energy during food deprivation. In addition to uncoupling protein 1 (UCP1), UCP3 and possibly UCP2 may have a role in energy homeostasis in BAT. We examined basal levels of UCP2 and UCP3 mRNA with age and regulation of UCP1, UCP2, and UCP3 mRNA by two conditions known to modulate energy homeostasis: fasting and beta3-adrenergic agonists. UCP1, UCP2, and UCP3 mRNA levels were unchanged between 3, 24, and 31 months of age in BAT, and UCP2 and UCP3 mRNA levels were unchanged between 6 and 24 months of age in retroperitoneal white adipose tissue (RTWAT). Following a 2-day fast, there were sizable reductions in BAT UCP1 and UCP3 mRNA, but these decreases with fasting were significantly less in the older compared with the young rats. Fasting had no effect on UCP2 mRNA levels at any age. The beta3-adrenergic agonist, CL316,243, increased BAT UCP1 and UCP3 mRNA equally in both young and old rats. The beta3-adrenergic agonist did not increase UCP2 mRNA in BAT but did increase expression in RTWAT of both young and old rats. In summary, these data indicate that the expression of the three uncoupling proteins is unchanged with age. Although the upregulation of these uncoupling proteins by beta3-adrenergic agonist treatment is maintained with age, the downregulation by fasting is diminished with age. The parallel regulation of UCP1 and UCP3 expression in BAT suggests that UCP3, like UCP1, may have a role in energy homeostasis in BAT. The diminished downregulation of UCP1 and UCP3 expression in BAT by fasting suggests that energy conservation in response to food deprivation is impaired with age, and this may contribute to an inability of older animals to maintain body mass during periods when food is limited.

Adipose Tissue, Brown↗

PubMed2000

Adequacy of home care and hospital readmission for elderly congestive heart failure patients.

Readmission to acute care facilities is a frequent and costly problem among older adults with congestive heart failure (CHF). The study reported in this article tested the hypothesis that adequate home care, operationalized as patient-perceived adequacy of formal and informal assistance, is associated with lower readmission to acute care facilities. The study followed 253 elderly (age 65 and older) Medicare patients discharged to their homes after hospitalization for CHF, through structured telephone interviews at two, six, 10, and 14 weeks postdischarge. Study findings point to the importance of home care in reducing the high risk of readmission among elderly patients. The findings raise implications for practice, policy, and research.

Aged↗