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Biomedical subjects

Y Du

Publications and source records attributed to Y Du.

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

Apolipoprotein E is essential for amyloid deposition in the APP(V717F) transgenic mouse model of Alzheimer's disease.

We quantified the amount of amyloid beta-peptide (Abeta) immunoreactivity as well as amyloid deposits in a large cohort of transgenic mice overexpressing the V717F human amyloid precursor protein (APP(V717F+/-) TG mice) with no, one, or two mouse apolipoprotein E (Apoe) alleles at various ages. Remarkably, no amyloid deposits were found in any brain region of APP(V717F+/-) Apoe(-/-) TG mice as old as 22 mo of age, whereas age-matched APP(V717F +/-) Apoe(+/-) and Apoe(+/+) TG mice display abundant amyloid deposition. The amount of Abeta immunoreactivity in the hippocampus was also markedly reduced in an Apoe gene dose-dependent manner (Apoe(+/+) > Apoe(+/-) >> Apoe(-/-)), and no Abeta immunoreactivity was detected in the cerebral cortex of APP(V717F+/-) Apoe(-/-) TG mice at any of the time points examined. The absence of apolipoprotein E protein (apoE) dramatically reduced the amount of both Abeta(1-40) and Abeta(1-42) immunoreactive deposits as well as the resulting astrogliosis and microgliosis normally observed in APP(V717F) TG mice. ApoE immunoreactivity was detected in a subset of Abeta immunoreactive deposits and in virtually all thioflavine-S-fluorescent amyloid deposits. Because the absence of apoE alters neither the transcription or translation of the APP(V717F) transgene nor its processing to Abeta peptide(s), we postulate that apoE promotes both the deposition and fibrillization of Abeta, ultimately affecting clearance of protease-resistant Abeta/apoE aggregates. ApoE appears to play an essential role in amyloid deposition in brain, one of the neuropathological hallmarks of Alzheimer's disease.

Alzheimer Disease↗
PubMed1999

Rat B(2) sequences are induced in the hippocampal CA1 region after transient global cerebral ischemia.

Global brain ischemia causes cell death in the CA1 region of the hippocampus 3-5 days after reperfusion. The biological pathway leading to such delayed neuronal damage has not been established. By using differential display analysis, we examined expression levels of poly(A) RNAs isolated from hippocampal extracts prepared from rats exposed to global ischemia and found an up-regulated transcript, clone 17a. Northern blot analysis of clone 17a showed an approximately 35-fold increase in the ischemic brain at 24 h after four-vessel occlusion. Rapid amplification of cDNA ends of clone 17a revealed a family of genes (160-540 base pairs) that had the characteristics of rodent B(2) sequences. In situ hybridization demonstrated that the elevated expression of this gene was localized predominantly in the CA1 pyramidal neurons. The level of expression in the CA1 region decreased dramatically between 24 and 72 h after ischemia. The elevated expression of clone 17a was not observed in four-vessel occlusion rats treated with the compound LY231617, an antioxidant known to exert neuroprotection in rats subjected to global ischemia. Since delayed neuronal death has the characteristics of apoptosis, we speculate that clone 17a may be involved in apoptosis. We examined the expression level of clone 17a in in vitro models of apoptosis using cerebellar granule neurons that were subjected to potassium removal, glutamate toxicity, or 6-hydroxydopamine treatment and found that clone 17a transcripts were induced in cerebellar granule neurons by glutamate or 6-hydroxydopamine stimulation but not potassium withdrawal.

Amino Acid Sequence↗
PubMed1999

Preparation of chitooligosaccharides from chitosan by a complex enzyme.

Chitosan of 24% degree of acetylation was depolymerized by a mixture of cellulase, alpha amylase, and proteinase to give the title oligosaccharides. The removal of products by membrane separation permitted yield maximization of products having degree of polymerization in the 3-10 range.

Chitin↗
PubMed1999

Localization on a physical map of the NKC-linked Cmv1 locus between Ly49b and the Prp gene cluster on mouse chromosome 6.

The Cmv1 locus controls NK cell-mediated resistance to infection with murine CMV. Our recent genetic analysis of backcross mice demonstrated that the NK gene complex (NKC)-linked Cmv1 locus should reside between the Ly49 and Prp gene clusters on distal mouse chromosome 6. We have aligned yeast artificial chromosome (YAC) inserts in a contig spanning the interval between the Ly49 and Prp gene clusters. This YAC contig includes 13 overlapping YAC inserts that span more than 2 megabases (Mb) in C57BL/6 (B6) mice. Since we have identified genomic clones that span the Ly49-Prp gene region, we hypothesize that at least one should contain the Cmv1 locus. To narrow the Cmv1 critical region, we developed novel NKC genetic markers and used these to genotype informative backcross and intra-NKC recombinant congenic mouse DNA samples. These data suggest that Cmv1 resides on a single YAC insert within an interval that corresponds to a physical distance of approximately 390 kb. This high resolution, integrated physical and genetic NKC map will facilitate identification of Cmv1 and other NKC-linked loci that regulate NK cell-mediated immunity.

Animals↗
PubMed1999

[HLA-DQA1 genes involved in the genetic susceptibility to duodenal ulcer in Wuhan Hans]

OBJECTIVE: To study the genetic susceptibility of HLA-DQA1 alleles to duodenal ulcer in Chinese Hans from Wuhan and its nearby regions. METHODS: Seventy patients with duodenal ulcer and fifty healthy controls were examined for HLA-DQA1 genotypes. HLA-DQA1 typing was carried out by digesting the locus specific polymerase chain reaction amplified products with alleles specific restriction enzymes (PCR-RFLP), Apal I, Basj I, Hph I, Fok I, Mbo II and Mnl I. RESULTS: The allele frequency of DQA1 0301 in patients with duodenal ulcer (64.3%) was significantly higher than that in healthy controls (36%). In contrast, the allele frequency of DQA1 0102 in patients with duodenal ulcer (8.6%) was significantly lower than that in healthy controls (26%). CONCLUSION: These findings suggest that DQA1 0301 is a susceptible gene for duodenal ulcer in Wuhan Hans while DQA1 0102 is its resistant gene, and there are immunogenetic differences in HLA-DQA1 locus between duodenal ulcer patients and healthy controls.

Journal Article↗
PubMed1999

A short conserved motif is required for repressor domain function in the myeloid-specific transcription factor CCAAT/enhancer-binding protein epsilon.

CCAAT/enhancer-binding protein epsilon (C/EBPepsilon) is expressed almost exclusively in the myeloid lineage of the hematopoietic system and functions during terminal differentiation of neutrophils and macrophages, and in the regulation of cytokine gene expression in macrophages and T cells. We have undertaken a series of structure/function studies on the murine C/EBPepsilon polypeptide to investigate the mechanism by which C/EBPepsilon activates transcription. Studies with deletion mutants and fusion proteins consisting of C/EBPepsilon sequences joined to the Gal4 DNA-binding protein identified two transcriptional activation domains in C/EBPepsilon. Removal of sequences between the two activation domains or sequences between the second activation domain and the C-terminal DNA binding domain significantly increased the activity of C/EBPepsilon, suggesting the presence of two separate regulatory domains (designated RD-1epsilon and RD-2epsilon). RD-1epsilon behaved as a classic active repressor domain being capable of inhibiting adjacent activation domains irrespective of their origin and when linked to a heterologous DNA binding domain. Mutagenesis studies revealed a short motif in RD-1epsilon that appears to be a target site for protein-protein interactions and is conserved in repressor domains from C/EBPbeta, Sp3, c-Fos, and FosB. The juxtaposition of activation and repressor domains may permit C/EBPepsilon to function as a transcriptional activator or repressor at different stages of myeloid differentiation or as an inducible transcriptional activator of cytokine genes.

Amino Acid Sequence↗
PubMed1999

Caspase-3-like proteases and 6-hydroxydopamine induced neuronal cell death.

Neurotoxicity induced by 6-hydroxydopamine (6-OHDA) is believed to be due, in part, to the production of reactive oxygen species (ROS) and/or an inhibition of mitochondrial function. However, little is known about the ensuing intracellular events which ultimately result in cell death. Here we show that exposure to relatively low concentrations of 6-OHDA induces apoptosis of cerebellar granule neurons (CGN). 6-OHDA-induced apoptosis of CGN is associated with activation of a caspase-3-like protease. Western blots of cytosolic extracts from 6-OHDA-treated CGN reveal a translocation of cytochrome c from mitochondria to the cytosol, which precedes activation of the protease detected by Ac-DEVD-pNA. DNA laddering can be blocked by caspase inhibitors zVAD-FMK and Ac-DEVD-CHO, however cell death can only be attenuated for a short time period in the presence of these inhibitors. Our data suggest that 6-OHDA-induced apoptosis of CGN involves activation of a caspase-3-like protease. In contrast to the neurotoxicity induced by MPP+, however, the peptide inhibitors zVAD-FMK and Ac-DEVD-CHO can only attenuate early neuronal death induced by 6-OHDA. At later time points, neuronal death lacking DNA laddering occurs even in the presence of the peptide inhibitor zVAD-FMK or Ac-DEVD-CHO.

1-Methyl-4-phenylpyridinium↗
PubMed1999

Structure of the human Lanosterol synthase gene and its analysis as a candidate for holoprosencephaly (HPE1).

Holoprosencephaly (HPE) is the most common birth defect of the brain in humans. It involves various degrees of incomplete separation of the cerebrum into distinct left and right halves, and it is frequently accompanied by craniofacial anomalies. The HPE1 locus in human chromosome 21q22.3 is one of a dozen putative genetic loci implicated in causing HPE. Here, we report the complete gene structure of the human lanosterol synthase (LS) gene, which is located in this interval, and present its mutational analysis in HPE patients. We considered LS an excellent candidate HPE gene because of the requirement for cholesterol modification of the Sonic Hedgehog protein for the correct patterning activity of this HPE-associated protein. Despite extensive pedigree analysis of numerous polymorphisms, as well as complementation studies in yeast on one of the missense mutations, we find no evidence that the LS gene is in fact HPE1, implicating another gene located in this chromosomal region in HPE pathogenesis.

Base Sequence↗
PubMed1999

Adventitia as a source of inducible nitric oxide synthase in the rat aorta.

In the current study we used in vitro and in vivo models to determine the sites of nitric oxide production in rat aortic tissue following cytokine stimulation. In vitro studies in which intact rat aortic rings were incubated with endotoxin (1 microg/mL) or interferon-gamma (600 U/mL) indicated that the expression of inducible nitric oxide synthase (iNOS) activity was increased as measured by Northern blot analysis or determination of nitrite production. In situ hybridization showed iNOS mRNA in the endothelium and adventitia of the incubated aortic rings but not in the media. Immunohistochemical staining showed a similar localization for iNOS protein in the incubated rings. Additional studies were performed in which bacterial endotoxin (4 mg/kg) was administered to rats, and iNOS expression was assayed using in situ hybridization and immunohistochemistry. Clear increases in iNOS mRNA and protein were found in aortic tissue. Endothelial and adventitial cells were the major source of iNOS, with relatively low amounts of iNOS mRNA present in medial smooth muscle, consistent with in vitro findings. These studies indicate that the aortic adventitia is a potential source of NO, and suggest that the adventitial fibroblast may have an important paracrine role in regulating arterial structure and function.

Animals↗
PubMed1999

Sodium salicylate and 17beta-estradiol attenuate nuclear transcription factor NF-kappaB translocation in cultured rat astroglial cultures following exposure to amyloid A beta(1-40) and lipopolysaccharides.

In recent years inflammatory mechanisms have become increasingly appreciated as important steps in the Alzheimer's pathogenic pathway. There is accumulating evidence that amyloid beta-peptide (A beta), the peptide product of the cleavage of amyloid precursor protein, may promote or exacerbate local inflammation by stimulating glial cells to release immune mediators. In addition, clinical studies using nonsteroidal antiinflammatory drugs have found a reduced risk for Alzheimer's disease with their use. Here we show that the neurotoxic A beta, a major plaque component, and lipopolysaccharides (LPS), an immune reaction-triggering portion of bacterial membranes, are both potent activators of the nuclear transcription factor NF-kappaB in primary rat astroglial cells. The activation was found to be concentration- and time-dependent and could be attenuated in the presence of NF-kappaB decoy nucleotides. The pretreatment by either 17beta-estradiol (1-10 microg) or sodium salicylate (3-30 mM) reduced the A beta (LPS)-induced activation of NF-kappaB by 48 (50%) and 60% (50%) of activated levels, respectively. In addition, 17beta-estradiol (10 microM) and sodium salicylate (10 mM) were able to attenuate the increase in interleukin-1beta levels following exposure to 25 microM A beta. Our data suggest that the aberrant gene expression is at least in part due to A beta-induced activation of NF-kappaB, a potent immediate-early transcriptional regulator of numerous proinflammatory genes; this event takes place in astroglial cells. The results of our experiments provide a further understanding of the effects of estrogen and aspirin on astroglial cells exposed to A beta and LPS.

Amyloid beta-Peptides↗
PubMed1999

The effects of beta-bungarotoxin on the morphogenesis of taste papillae and taste buds in the mouse.

Although it has been long accepted that innervation by a taste nerve is essential for maintenance of taste buds, it is not clear what role, if any, innervation plays in the morphogenesis of taste papillae and taste bud development. The following study was undertaken to determine what effects lack of sensory innervation have on the development of taste papillae and the formation of taste buds in the mouse. Timed-pregnant female mice (n = 3) at gestational day 12 (gd12) were anesthetized and a 1 microl solution (1 microg/microl) of beta-bungarotoxin (beta-BTX), a neurotoxin that disrupts sensory and motor neuron development, was injected into the amniotic cavity of two embryos per dam. Two shams were injected with PBS. Fetuses were harvested at gd18, 1 day before birth, and four beta-BTX-injected embryos, two shams and two controls were fixed in buffered paraformaldehyde. Serial sections were examined for the presence and morphology of taste papillae and taste buds. No nerve profiles were observed in beta-BTX-injected tongues. Although circumvallate papillae were present on beta-BTX tongues, only five fungiform papillae could be identified. Taste buds were present on a large percentage of fungiform papillae profiles (24%) and on circumvallate papillae in sham and control fetuses; in contrast, no taste buds were associated with taste papillae in beta-BTX fetuses. These results implicate a significant role for innervation in taste papillae and taste bud morphogenesis.

Animals↗
PubMed1999

Identification of genomic regions controlling experimental autoimmune uveoretinitis in rats.

The present study attempts to identify specific genetic loci contributing to experimental autoimmune uveoretinitis (EAU) susceptibility in F2 progeny of resistant Fischer (F344/N) and susceptible Lewis (LEW/N) inbred rats. F2 progeny of F344/N x LEW/N inbred rats were immunized with the R16 peptide of interphotoreceptor retinoid-binding protein (IRBP). A genome-wide scan was conducted using 125 simple sequence length polymorphism markers in selected F2 animals that developed severe eye disease or remained unaffected to identify phenotype:genotype co-segregation. The F2 population (n = 1287) demonstrated a wide range of histologically assessed EAU scores (assessed on a scale of 0-4). The disease incidence and severity were not consistent with a simple Mendelian inheritance model. Of the F2 hybrid rats, 60% developed EAU, implying the existence of a potent susceptibility locus with incomplete penetrance associated with the LEW genome or a more complex polygenic model of inheritance. Two genomic regions, on chromosomes 4 and 12, showed strong genetic linkage to the EAU phenotype (P < 0.0016), suggesting the presence of susceptibility loci in these chromosomal regions. In conclusion, we have identified two genomic candidate intervals from D4Arb8 to D4Mit17 on chromosome 4 and from the chromosome end to D12Arb8 on chromosome 12, that appear to influence EAU susceptibility in LEW/F344 rats. Further analysis of these genomic regions may lead to identification of the susceptibility genes and to characterization of their function.

Animals↗
PubMed1999

Paracrine role of adventitial superoxide anion in mediating spontaneous tone of the isolated rat aorta in angiotensin II-induced hypertension.

The relationship between vascular generation of superoxide anion and spontaneous tone observed in the isolated aorta was studied in hypertensive rats infused with angiotensin II. Aortic rings from hypertensive, but not from sham-operated rats, demonstrated oscillatory spontaneous tone that represented 52+/-5.6% of the maximal contraction to KCl. Spontaneous tone was prevented by calcium-free buffer or by blocking calcium influx through L-type calcium channels with nifedipine. The production of superoxide anion measured by lucigenin chemiluminescence was up to 15-fold higher than in sham-operated rat aorta. The adventitial site of production of superoxide anion was suggested by the fact that lucigenin chemiluminescence was 5.5-fold higher from the adventitia than from the intima. This was confirmed histochemically by demonstrating that the adventitia was the site of reduction of nitroblue tetrazolium as well as immunohistochemical staining of NAD(P)H oxidase subunit proteins. A causal link between superoxide anion production by NAD(P)H oxidase and the spontaneous tone is suggested by the fact that superoxide dismutase or the inhibitor of NAD(P)H oxidase, diphenylene iodonium, decreased both superoxide anion production and spontaneous tone. L-NAME or removal of the endothelium from the aorta had no significant effect on superoxide anion levels or spontaneous tone. However, although superoxide dismutase decreased superoxide anion levels in the presence of L-NAME or in endothelium-denuded rings, it no longer inhibited the tone. This suggests that the effect on tone of superoxide anion originating in the adventitia is mediated by inactivating endothelium-derived nitric oxide, which promotes smooth muscle calcium influx and spontaneous tone. The adventitia is not a passive bystander during the development of hypertension, but rather it may have an important role in the regulation of smooth muscle tone.

Acridines↗
PubMed1999

Distribution of granulocyte colony-stimulating factor (G-CSF) and G-CSF-receptor mRNA and protein in the human fetus.

Granulocyte colony-stimulating factor (G-CSF) promotes neutrophil proliferation, differentiation, and survival. It acts by binding to specific cell-surface receptors (G-CSF-R), which are expressed on cells of granulocytic lineage, human endothelial cells, and placenta. It has been postulated that the administration of recombinant G-CSF (rG-CSF) to preterm neonates might be useful in treating infections or in reducing nosocomial infections. Whereas it is known that G-CSF and G-CSF-R are present in the developing fetal bone marrow and liver, no information is available as to the existence or distribution of nonhematopoietic G-CSF-R in other tissues of the developing human fetus. We hypothesized that G-CSF and its receptor might be expressed in various fetal tissues, as has been shown for other growth factors such as erythropoietin and fibroblast growth factor. Therefore, we studied the anatomical distribution of mRNA-encoding G-CSF and G-CSF-R, using RT-PCR and in situ RT-PCR in a variety of human fetal tissues ranging from 8 to 24 weeks postconception. The cellular distributions of the corresponding proteins were determined by immunohistochemistry. Both G-CSF and G-CSF-R were present in nearly every organ and tissue examined, but in discrete cellular localizations. G-CSF-R in kidney and intestine underwent changes in anatomical distribution with fetal development. These results indicate that G-CSF and G-CSF-R have wide anatomical expression in the developing human fetus.

Fetus↗
PubMed1999

Concentrations of granulocyte colony-stimulating factor in human milk after in vitro simulations of digestion.

Human milk contains proteins that survive digestion in the neonatal gastrointestinal tract. Our group and others have reported that granulocyte colony-stimulating factor (G-CSF), a hematopoietic cytokine that influences neutrophil proliferation and differentiation, is present in human milk. We also reported that specific receptors for G-CSF are expressed on the villous enterocytes of neonates. However, the physiologic role of milk-borne G-CSF is not known. Thus, we sought to evaluate the capacity of human milk to protect G-CSF against proteolytic degradation after exposure to gastric secretions obtained from preterm (PT) and term (T) neonates at pH concentrations of 3.2, 5.8, and 7.4. Specifically, we examined degradation of 1) endogenous G-CSF in PT (n = 15) and T (n = 15) human milk; 2) recombinant human G-CSF (rhG-CSF) added to a protein-free buffer (n = 10, 5 PT and 5 T); and 3) rhG-CSF added to human milk (n = 12, 6 PT and 6 T), various commercially prepared infant formulas (n = 15), and cow's milk (n = 5). Endogenous G-CSF and rhG-CSF added to human milk resisted degradation at 1 and 2 h. However, when rhG-CSF was added to commercial formulas, >95% was degraded at 1 and 2 h at each pH level. Similarly, approximately 60% of rhG-CSF added to cow's milk was degraded at I and 2 h. We conclude that 1) endogenous G-CSF and rhG-CSF added to human milk are protected from degradation after exposure to gastric secretions at physiologic pH levels, 2) rhG-CSF added to infant formulas is not protected from degradation, and 3) it is likely that the G-CSF present in human milk is biologically available to the neonate.

Digestion↗
PubMed1999

[HLA-DQA1 genes involved in the genetic susceptibility to duodenal ulcer in Wuhan Hans].

OBJECTIVE: To study the genetic susceptibility of HLA-DQA1 alleles to duodenal ulcer in Chinese Hans from Wuhan and its nearby regions. METHODS: Seventy patients with duodenal ulcer and fifty healthy controls were examined for HLA-DQA1 genotypes. HLA-DQA1 typing was carried out by digesting the locus specific polymerase chain reaction amplified products with alleles specific restriction enzymes (PCR-RFLP), Apal I, Basj I, Hph I, Fok I, Mbo II and Mnl I. RESULTS: The allele frequency of DQA1 0301 in patients with duodenal ulcer (64.3%) was significantly higher than that in healthy controls (36%). In contrast, the allele frequency of DQA1 0102 in patients with duodenal ulcer (8.6%) was significantly lower than that in healthy controls (26%). CONCLUSION: These findings suggest that DQA1 0301 is a susceptible gene for duodenal ulcer in Wuhan Hans while DQA1 0102 is its resistant gene, and there are immunogenetic differences in HLA-DQA1 locus between duodenal ulcer patients and healthy controls.

Adolescent↗