Biomedical subjects
Publications and source records attributed to D Lu.
Determination of selenium in human hair by GFAAS has been described in this paper, Hairs from 120 middle school teachers were determined. The results are 0.15-1.00 mg/kg and the median is 0.43 mg/kg. The sensitivity of this method is 2.96 ng/mL and the relative standard deviation is 2.4%-6.7%.
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In this paper, the carbonic anhydrase II (CA II) enzyme active site is modeled using ab initio calculations and molecular dynamics simulations to examine a number of important issues for the enzyme function. It is found that the Zn2+ ion is dominantly tetrahedrally coordinated, which agrees with X-ray crystallographic studies. However, a transient five-fold coordination with an extra water molecule is also found. Studies of His64 conformations upon a change in the protonation states of the Zn-bound water and the His64 residue also confirm the results of an X-ray study which suggest that the His64 conformation is quite flexible. However, the degree of water solvation is found to affect this behavior. Water bridge formation between the Zn-bound water and the His64 residue was found to involve a free energy barrier of 2-3 kcal/mol and an average lifetime of several picoseconds, which supports the concept of a proton transfer mechanism through such a bridge. Mutations of various residues around the active site provide further insight into the corresponding experimental results and, in fact, suggest an important role for the solvent water molecules in the CA II catalytic mechanism.
In the H. influenzae type b (Hib) genome, two putative adhesin B genes, HI0119 and HI0362, have been identified on the basis of homology to the adhesin B (FimA) of Streptococcus parasanguis. We expressed and characterized one of them, HI0119, from a non-typeable H. influenzae strain (NTHI). This 37 kDa protein was selectively isolated from an H. influenzae surface protein (water) extract by elution from a celite matrix with EDTA. The adhesin B protein is 97.7% identical to that of H. influenzae, strain Rd, has 23.7% identity and 47.8% similarity to FimA of Streptococcus parasanguis but is distinguished from the FimA family by the absence of the N-terminal lipid anchor consensus sequence LXXC, the presence of a C-terminal disulfide-bonded domain, and a central histidine-rich domain. Recombinant fusion protein bound specifically to celite. Antisera raised against fusion protein recognized a 37 kDa protein from whole cell extracts of H. influenzae on Western blots. A truncated mutant lacking the C-terminal disulfide-bonded domain and a Cys308 to Ser mutant were constructed and expressed as fusion proteins. Both mutants retained celite binding. However, purified fusion proteins could not, unlike H. influenzae, bind Hep2 cells, suggesting that HI0119 may not be an adhesin in this organism.
A single-chain antibody phage display library was constructed from spleen cells of mice immunized with a soluble form of a human vascular endothelial growth factor (VEGF) receptor, kinase insert domain-containing receptor (KDR). After two rounds of biopanning, >90% of the clones recovered were specifically reactive to KDR. Subsequent selection identified two clones that blocked VEGF binding to KDR. The clones were expressed in Escherichia coli and purified as soluble single-chain Fv (scFv) antibodies. The affinities of the scFv for binding to KDR were determined by BIAcore analysis (2.1 x 10(-9)-5.9 x 10(-9) M). One scFv, p1C11, was shown to inhibit VEGF-induced KDR phosphorylation and VEGF-stimulated DNA synthesis in human umbilical vein endothelial cells. There is much experimental evidence to suggest that the VEGF/KDR/Flk-1 pathway plays an important role in tumor angiogenesis, a process that is essential for tumor growth and metastasis. The antibodies discussed here, which block VEGF binding to KDR, have potential clinical application in the treatment of cancer and other diseases where pathological angiogenesis is involved.
Angiotensin II (Ang II) exerts chronic stimulatory actions on tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH), and the norepinephrine transporter (NET), in part, by influencing the transcription of their genes. These neuromodulatory actions of Ang II involve Ras-Raf-MAP kinase signal transduction pathways (Lu, D., H. Yang, and M.K. Raizada. 1997. J. Cell Biol. 135:1609-1617). In this study, we present evidence to demonstrate participation of another signaling pathway in these neuronal actions of Ang II. It involves activation of protein kinase C (PKC)beta subtype and phosphorylation and redistribution of myristoylated alanine-rich C kinase substrate (MARCKS) in neurites. Ang II caused a dramatic redistribution of MARCKS from neuronal varicosities to neurites. This was accompanied by a time-dependent stimulation of its phosphorylation, that was mediated by the angiotensin type 1 receptor subtype (AT1). Incubation of neurons with PKCbeta subtype specific antisense oligonucleotide (AON) significantly attenuated both redistribution and phosphorylation of MARCKS. Furthermore, depletion of MARCKS by MARCKS-AON treatment of neurons resulted in a significant decrease in Ang II-stimulated accumulation of TH and DbetaH immunoreactivities and [3H]NE uptake activity in synaptosomes. In contrast, mRNA levels of TH, DbetaH, and NET were not influenced by MARKS-AON treatment. MARCKS pep148-165, which contains PKC phosphorylation sites, inhibited Ang II stimulation of MARCKS phosphorylation and reduced the amount of TH, DbetaH, and [3H]NE uptake in neuronal synaptosomes. These observations demonstrate that phosphorylation of MARCKS by PKCbeta and its redistribution from varicosities to neurites is important in Ang II-induced synaptic accumulation of TH, DbetaH, and NE. They suggest that a coordinated stimulation of transcription of TH, DbetaH, and NET, mediated by Ras-Raf-MAP kinase followed by their transport mediated by PKCbeta-MARCKS pathway are key in persistent stimulation of Ang II's neuromodulatory actions.
Deficiency of blood coagulation factor V or tissue factor causes the death of mouse embryos by 10.5 days of gestation, suggesting that part of the blood coagulation system is necessary for development. This function is proposed to require either generation of the serine protease thrombin and cell signaling through protease-activated receptors or an activity of tissue factor that is distinct from blood clotting. We find that murine deficiency of prothrombin clotting factor 2 (Cf2) was associated with the death of approximately 50% of Cf2(-/-) embryos by embryonic day 10.5 (E10.5), and surviving embryos had characteristic defects in yolk sac vasculature. Most of the remaining Cf2(-/-) embryos died by E15.5, but those surviving to E18.5 appeared normal. The rare Cf2(-/-) neonates died of hemorrhage on the first postnatal day. These studies suggest that a part of the blood coagulation system is adapted to perform a developmental function. Other mouse models show that the absence of platelets or of fibrinogen does not cause fetal wastage. Therefore, the role of thrombin in development may be independent of its effects on blood coagulation and instead may involve signal transduction on cells other than platelets.
Recent studies have documented an increased risk of therapy-related myelodysplastic syndrome or acute myelogenous leukemia (t-MDS/AML) after autologous bone marrow transplant (ABMT) for non-Hodgkin's lymphoma (NHL). To develop methods to identify patients at risk for this complication, we have investigated the predictive value of clonal bone marrow (BM) hematopoiesis for the development of t-MDS/AML, as defined by an X-inactivation based clonality assay at the human androgen receptor locus (HUMARA), in a group of patients undergoing ABMT for NHL from a single institution (Dana-Farber Cancer Institute, Boston, MA). One hundred four female patients were analyzed. At the time of ABMT, the prevalence of polyclonal hematopoiesis was 77% (80/104), of skewed X-inactivation pattern (XIP) was 20% (21/104), and of clonal hematopoiesis was 3% (3/104). To determine the predictive value of clonality for the development of t-MDS/AML, a subgroup of 78 patients with at least 18 months follow-up was analyzed. As defined by the HUMARA assay, 53 of 78 patients had persistent polyclonal hematopoiesis, 15 of 78 had skewed XIP, and 10 of 78 (13.5%) either had clonal hematopoiesis at the time of ABMT or developed clonal hematopoiesis after ABMT. t-MDS/AML developed in 2 of 53 patients with polyclonal hematopoiesis and in 4 of 10 with clonal hematopoiesis. We conclude that a significant proportion of patients have clonal hematopoiesis at the time of ABMT and that clonal hematopoiesis, as detected by the HUMARA assay, is predictive of the development of t-MDS/AML (P = .004).
Human factor Xa specifically cleaves the anticoagulant protein S within the thrombin-sensitive domain. Amino-terminal amino acid sequencing of the heavy chain cleavage product indicates cleavage of protein S by factor Xa at Arg60, a site that is distinct from those utilized by alpha-thrombin. Cleavage by factor Xa is unaffected by the presence of hirudin and is completely blocked by tick-anticoagulant-peptide and D-Glu-Gly-Arg-chloromethyl ketone, the latter two being specific inhibitors of factor Xa. The cleavage requires the presence of phospholipid and Ca2+, and is markedly inhibited by the presence of factor Va. Factor Xa-cleaved protein S no longer possesses its activated protein C-dependent or -independent anticoagulant activity, as measured in a factor VIII-based activated partial thromboplastin time clot assay. The apparent binding constant for protein S binding to phospholipid (Kd approximately 4 nM +/- 1.0) is unaffected by factor Xa or thrombin cleavage, suggesting that the loss of anticoagulant activity resulting from cleavage is not primarily due to the loss of membrane binding ability. Cleavage and inactivation of protein S by factor Xa may be an additional way in which factor Xa exerts its procoagulant effect, after the initial stages of clot formation.
Hypertension produces pathophysiological changes that are often responsible for the mortality associated with the disease. However, it is unclear whether normalizing blood pressure (BP) with conventional therapy is effective in reversing the pathophysiological damage. The duration and initiation of treatment, site of administration, and agent used all appear to influence the reversal of the pathophysiological alterations associated with hypertension. We have previously established that retrovirally mediated delivery of angiotensin II type 1 receptor antisense (AT1R-AS) attenuates the development of high BP in the spontaneously hypertensive (SH) rat model of human essential hypertension. Our objective was to determine whether this attenuation of high BP is associated with prevention of other pathophysiological changes induced by the hypertensive state. Intracardiac delivery of AT1R-AS in neonates prevented the development of hypertension in SH rats for at least 120 days. Contractile experiments demonstrated an impaired endothelium-dependent vascular relaxation (acetylcholine) and an enhanced contractile response to vasoactive agents (phenylephrine and KCl) in the SH rat renal vasculature. In addition, the voltage-dependent K+ current density, which is believed to contribute to smooth muscle resting membrane potential and basal tone, was decreased in renal resistance artery cells of the SH rat. AT1R-AS treatment prevented each of these renal vascular alterations. Finally, AT1R-AS delivery prevented the pathological alterations observed in the SH rat myocardium, including left ventricular hypertrophy, multifocal fibrosis, and perivascular fibrosis. These observations demonstrate that viral-mediated delivery of AT1R-AS attenuates the development of hypertension on a long term basis, and this is associated with prevention of pathophysiological changes in SH rats.
The objective of this review is to examine the role of neuronal angiotensin II (Ang II) receptors in vitro. Two types of G protein-coupled Ang II receptors have been identified in cardiovascularly relevant areas of the brain: the AT1 and the AT2. We have utilized neurons in culture to study the signaling mechanisms of AT1 and AT2 receptors. Neuronal AT1 receptors are involved in norepinephrine (NE) neuromodulation. NE neuromodulation can be either evoked or enhanced. Evoked NE neuromodulation involves AT1 receptor-mediated, losartan-dependent, rapid NE release, inhibition of K+ channels and stimulation of Ca2+ channels. AT1 receptor-mediated enhanced NE neuromodulation involves the Ras-Raf-MAP kinase cascade and ultimately leads to an increase in NE transporter, tyrosine hydroxylase and dopamine beta-hydroxylase mRNA transcription. Neuronal AT2 receptors signal via a Gi protein and are coupled to activation of PP2A and PLA2 and stimulation of K+ channels. Finally, putative cross-talk pathways between AT1 and AT2 receptors will be discussed.
A disturbance in the frontal-striatal-thalamic circuitry has been proposed for schizophrenia, but this concept has been based primarily on indirect evidence from psychopharmacology and analogies with animal research. Diffusion tensor imaging, a new MRI technique that permits direct assessment of the large axon masses stretching from the prefrontal cortex to the striatum, was used to study white matter axon bundles. Diffusion tensor images, high-resolution structural MRI and positron emission tomography scans with 18-fluorodexoyglucose were obtained on five patients with schizophrenia and six age- and sex-matched normal controls. Significantly lower diffusion anisotropy in the white matter of the prefrontal cortex in schizophrenic patients than in normal controls was observed in statistical probability maps. Co-registered PET scans revealed significantly lower correlation coefficients between metabolic rates in the prefrontal cortex and striatum in patients than in controls. These twin findings provide convergent evidence for diminished fronto-striatal connectivity in schizophrenia.
Chronic stimulation of brain neurons by angiotensin II (Ang II) results in a increase in norepinephrine (NE) uptake. This involves stimulation of transcription of NE transporter and tyrosine hydroxylase genes and is associated with translocation of signaling molecules and transcription factors from the cytoplasmic compartment into the neuronal nucleus (). We report here that the phosphorylation of p62, a glycoprotein nucleoporin of the nuclear pore complex (NPC), by MAP kinase is involved in this process. Ang II caused a time-dependent translocation of signal transducers and activators of transcription (STAT3) from the cytoplasmic compartment into the nucleus. This translocation was attenuated by pretreatment with antisense oligonucleotide (AON) to MAP kinase. Ang II also stimulated phosphorylation of p62, and a maximal phosphorylation of 12-fold was observed with 100 nM Ang II. This stimulation was blocked by losartan, an AT1 receptor subtype-specific antagonist. The conclusion that MAP kinase is involved in Ang II-induced phosphorylation of p62 and nuclear translocation of STAT3 is supported by the following. (1) p62 phosphorylation was blocked by a peptide that competes with p62 as a MAP kinase substrate both in vitro and in vivo; (2) AON to MAP kinase attenuated Ang II stimulation of p62 phosphorylation; and (3) in addition, it also blocked nuclear translocation of STAT3. Intracellular loading of the peptide containing MAP kinase substrate consensus of the p62 reduced Ang II stimulation of p62 phosphorylation and nuclear translocation of STAT3 in both in vivo and in vitro experiments. These observations suggest that Ang II-induced phosphorylation of p62 may accelerate the activity of the NPC, which would result in an increase in the nuclear transport of transcription factors and signaling molecules. This will stimulate transcriptional processes associated with Ang II regulation of NE neuromodulation.
OBJECTIVE: To determine the polymorphism of DXS102 and use it in gene diagnosis in hemophilia B. METHODS: Amp-FLP and linkage analysis on 234 chromosomes. RESULTS: Eight alleles were found at DXS102 locus. The number of AC dinucleotide repeats ranged from 13 to 21. And the observed heterozygosity, calculated heterozygosity and polymorphism information content(PIC) were 0.87, 0.80 and 0.80, respectively. It was noted that the difference of the allele frequencies of DXS102 in Chinese and European populations was significant. By using the linkage analysis of the DXS102 locus, a family with a hemophilia B patient receiving gene therapy in 1994 was analyzed and a carrier in that family was then detected. CONCLUSION: The polymorphism of DXS102 locus reveals significant difference between Chinese and European populations. DXS102 locus can be used as a promising marker for gene diagnosis in hemophilia B family.
OBJECTIVE: Sexual transmission of HIV is the most common route of HIV transmission throughout the world. To prevent sexually transmitted HIV infection, a vaccine is urgently needed. A previous report demonstrated the targeted immunization of the iliac lymph nodes with simian immunodeficiency virus (SIV) subunits protects rhesus macaques from rectal challenge with SIV. We sought to determine whether this immunization strategy could protect rhesus macaques from vaginal challenge with SIV. DESIGN: Macaques were immunized with either whole-killed SIV or envelope and core subunit antigen vaccines. Using three independent groups, with three macaques in each group, macaques were immunized by the targeted iliac lymph-node (TILN) route, injecting the vaccine close to the iliac lymph nodes that drain the genital tract. RESULTS: The TILN immunization procedure induced high-titer SIV-specific immunoglobulin (Ig) G antibodies in serum in all animals and anti-SIV IgG and IgA antibodies in the cervicovaginal secretions of most animals. After a series of three or four TILN immunizations, the animals were intravaginally challenged with SIVmac251. All animals became virus isolation-positive, except one animal immunized with SIV p27 and gp120. This animal was virus isolation-negative but SIV DNA proviral sequences were detected in peripheral blood mononuclear cells. CONCLUSIONS: In this series of studies, reliable protection from vaginal transmission of SIV was not achieved by the TILN immunization procedure.
A 43-year-old man with oligoblastic leukemia and t(3;8) variant translocation is reported. At first he was classified as refractory anemia with excess of blasts in transformation according to the FAB criteria for myelodysplastic syndrome. Remission was obtained after intensive chemotherapy. After 8 months, a relapse occurred as overt M2 AML. At presentation chromosome study of bone marrow cells using R- and G-bandings revealed 45,X, -Y,t(3;8)(q29;q22) in 35 of the 42 metaphases analyzed and 46,XY,t(3;8) in one metaphase in addition to normal karyotype in the other six metaphases. However, RT-PCR assay showed no AML1/ETO fusion transcript. At relapse, a karyotype of 46, XY,t(3;8), deletion(4)(p14), add(7)(q32) was observed in all abnormal cells indicating a clonal karyotypic evolution. We believed that this case should be diagnosed as an early form of M2 AML initially. It may be the first case of oligoblastic leukemia with t(3;8) variant translocation. Further study is needed to elucidate its molecular entity.
Peripheral acute leukemia (PAL) is extremely rare. We report on the first case of acute megakaryocytic leukemia presenting with PAL and complex chromosomal abnormalities. At diagnosis, the patient had 10.5-21% marrow blasts and 55-60% peripheral blasts which expressed CD42b and CD61. Two related clones with the karyotype of 48,X,-X,+3,+9,del(9)(q12q31) x 2,+17,i(17)(q10)/ 49,idem, +18 were revealed by conventional cytogenetics, but no AML-1/ETO fusion transcript was detected by RT-PCR assay. The significance of this case is discussed concisely.
The role of time symmetry in the design of amplitude-modulated (shaped) pulses for spin-1 excitation is examined. The quaternion calculus is used to calculate the quaternion elements (Euler-Rodrigues parameters) of each shaped pulse. In this manner, it is shown how the simplicity and compactness of the Euler-Rodrigues parametrization can be used to significantly expedite a computer search for optimal time-symmetric shaped pulses. Theoretical and experimental tests of a new class of symmetric quadrupole-shaped (SQUASH) pulses identified by this procedure show a significant improvement in both excitation bandwidth and efficiency in comparison to the time-asymmetric QUASH shaped pulse previously identified.