Search PubMed⌕ Search

Biomedical subjects

H Wu

Publications and source records attributed to H Wu.

At least 451 records · Page 25Linked to original sources
PubMed1998

Peptidergic activation of transcription and secretion in chromaffin cells. Cis and trans signaling determinants of pituitary adenylyl cyclase-activating polypeptide (PACAP).

Pituitary adenylyl cyclase-activating polypeptide (PACAP) is a potent endogenous secretagogue for chromaffin cells. Chromogranin A is the major soluble core component in secretory vesicles. Since chromogranin A is secreted along with catecholamines, we asked whether PACAP regulates expression of the chromogranin A gene in PC12 rat chromaffin cells, so as to resynthesize the just-secreted protein, and whether such biosynthetic regulation is coupled mechanistically to catecholamine secretion. PACAP activated the endogenous chromogranin A gene by four- to fivefold. Proportional results (seven- to eightfold activation) were obtained with a transfected 1,200-bp mouse chromogranin A promoter/luciferase reporter construct. A series of chromogranin A promoter 5' deletion mutant/luciferase reporter constructs narrowed down the PACAP response element to a proximal region containing the cAMP response element (CRE box), at (-71 bp)5'-TGACGTAA-3'(-64 bp). Site-directed point mutations of the CRE site suppressed PACAP-induced trans-activation of the promoter. Thus, the proximal CRE box is entirely necessary for the chromogranin A promoter response to PACAP. Transfer of the CRE box to a neutral, heterologous promoter also conferred activation by PACAP, suggesting that the CRE domain is also sufficient to mediate the transcriptional response to PACAP. Expression of a dominant-negative mutant (KCREB) of the CRE-binding factor CREB markedly diminished trans-activation of the chromogranin A promoter by PACAP. Cotransfection of expression plasmids encoding the protein kinase A inhibitor, or an inactive protein kinase A (PKA) catalytic beta subunit, inhibited both forskolin and PACAP activation of chromogranin A transcription, revealing that PACAP-induced trans-activation is highly dependent on PKA. By contrast, inhibition of protein kinase C (by chronic exposure to phorbol ester) had no effect on transcriptional activation by PACAP. The potent PACAP/vasoactive intestinal peptide (VIP) type I receptor antagonist PACAP6-38 impaired both chromogranin A transcription or catecholamine secretion triggered by PACAP38, while the PACAP/VIP type II receptor antagonist (p-Chloro-D-Phe6, Leu17)-VIP had little or no ability to antagonize the PACAP38 effect. The agonist VIP was approximately 100- to 1,000-fold less potent than PACAP in stimulating either secretion or transcription. Thus, PACAP-evoked chromogranin A transcription and catecholamine secretion are likely mediated by the PACAP/VIP type I receptor isoform. Although the calcium channel antagonists Zn2+ (100 microM), nifedipine (10 microM), or ruthenium red (10 microM), or the cytosolic calcium chelator BAPTA-AM (50 microM) each strongly impaired PACAP-induced secretion, transcriptional activation of chromogranin A remained unaltered. Therefore, we propose that PACAP signals to chromogranin A transcription through the CRE in cis, and through PKA and CREB in trans. By contrast, a pathway involving cytosolic calcium entry through L-type voltage-dependent channels is required for PACAP to evoke catecholamine secretion.

Animals↗
PubMed1998

The anemic Friend virus gp55 envelope protein induces erythroid differentiation in fetal liver colony-forming units-erythroid.

The gp55 envelope proteins of the spleen focus-forming virus initiate erythroleukemia in adult mice. Because the gp55 from the polycythemic strain (gp55-P), but not from the anemic strain (gp55-A), activates the erythropoietin receptor (EpoR) for proliferation of hematopoietic cell lines, the mechanism by which gp55-A initiates erythroleukemia has remained a mystery. We show here that gp55-A activates the EpoR in fetal liver cells. In contrast to previous studies using bone marrow cells from phenylhydrazine-treated, anemic mice, we find that both gp55-A and gp55-P induce erythroid differentiation from colony-forming unit-erythroid (CFU-E) progenitors in fetal liver cells. The effects on CFU-Es of both gp55-A and -P are mediated by the EpoR, because no colonies are seen upon expression of either gp55 in EpoR-/- fetal liver cells. However, only gp55-P induces erythroid bursts from burst-forming unit-erythroid progenitors and only gp55-P induces Epo independence in Epo-dependent cell lines. Using chimeric gp55 P/A proteins, we extend earlier work showing that the transmembrane sequence determines the capacity of gp55 proteins to differentially activate EpoR signaling. We discuss the possibilities for different signaling capacities of gp55-A and -P in fetal liver and bone marrow-derived erythroid progenitor cells.

Animals↗
PubMed1998

[Shadow bands in PCR amplification of trinucleotide repeats and their elimination].

OBJECTIVE: To explore a method for eliminating the shadow bands in PCR amplification of trinucleotide repeats. METHODS: CTG trinucleotide repeat sequence in the 3'-untranslated region of the human myotonin protein kinase gene was used as templates DNA in PCR amplification, and the effects of Taq DNA polymerase alone and its mixture with Pwo DNA polymerase on occurrence of the shadow bands' were compared. The PCR products containing(CTG)5, both from Taq DNA polymerase and from Taq+Pwo polymerase amplification, were cloned into pBluecript KS and sequenced on ALF express TM DNA sequencer respectively. RESULTS: The PCR of DNA sequence containing CTG repeats frequently produced a main band (usually darker) and a shadow band (lighter) that differed from the main band by 3 base pairs when Taq DNA polymerase was used alone. However, when the mixture of Taq DNA polymerase and Pwo DNA polymerase was used, the shadow bands usually disappeared. In the 4 clones containing PCR products amplificated by Taq DNA polymerase, one clone contained only 4 CTG repeats. However, this kind of decrease of repeat copy was not observed in the 5 clones containing PCR products amplified by using mixture of Taq+Pwo DNA polymerase. CONCLUSION: The results of this experiment demonstrate that shadow bands occur during the PCR. Pwo DNA polymerase in known to possess not only DNA polymerase activity, but also 3'-5' exonuclease activity, or proofreading ability. The mixture of Taq DNA polymerase and Pwo DNA polymerase has higher processivity than Taq DNA polymerase itself. This explain the effect on eliminating or reducing the occurrence of shadow bands in polymerase chain reaction.

Adult↗
PubMed1998

Identification and partial purification of human double strand RNase activity. A novel terminating mechanism for oligoribonucleotide antisense drugs.

We have identified a double strand RNase (dsRNase) activity that can serve as a novel mechanism for chimeric antisense oligonucleotides comprised of 2'-methoxy 5' and 3' "wings" on either side of an oligoribonucleotide gap. Antisense molecules targeted to the point mutation in codon 12 of Harvey Ras (Ha-Ras) mRNA resulted in a dose-dependent reduction in Ha-Ras RNA. Reduction in Ha-Ras RNA was dependent on the oligoribonucleotide gap size with the minimum gap size being four nucleotides. An antisense oligonucleotide of the same composition, but containing four mismatches, was inactive. When chimeric antisense oligonucleotides were prehybridized with 17-mer oligoribonucleotides, extracts prepared from T24 cells, cytosol, and nuclei resulted in cleavage in the oligoribonucleotide gap. Both strands were cleaved. Neither mammalian nor Escherichia coli RNase HI cleaved the duplex, nor did single strand nucleases. The dsRNase activity resulted in cleavage products with 5'-phosphate and 3'-hydroxyl termini. Partial purification of dsRNase from rat liver cytosolic and nuclear fractions was effected. The cytosolic enzyme was purified approximately 165-fold. It has an approximate molecular weight of 50,000-65,000, a pH optimum of approximately 7.0, requires divalent cations, and is inactivated by approximately 300 mM NaCl. It is inactivated by heat, proteinase K, and also by a number of detergents and several organic solvents.

Animals↗
PubMed1998

Stochastic modeling of the dynamics of CD4+ T-cell infection by HIV and some Monte Carlo studies.

In this paper, we develop a stochastic model for the interaction between CD4+ T cells and the human immunodeficiency virus (HIV) virus by taking into account the basic biological mechanism as described in [1-4]. We studied this stochastic model through extensive Monte Carlo simulations. Our results show that, in some cases, there is a positive probability that the virus will be eliminated by the process. We have also shown that, at the earlier stage of the infection, the probability distributions of the CD4+ T cells and free HIV are skewed; however, these distributions will eventually converge to the Gaussian distributions after several years. A real-data example is given to illustrate the application of our model.

CD4-Positive T-Lymphocytes↗
PubMed1998

Activation of development in mammals: is there a role for a sperm cytosolic factor?

In mammalian oocytes, fertilization-associated calcium [Ca2+]i oscillations are responsible for the activation of development. The mechanism(s) by which the sperm triggers the initial [Ca2+]i rise and supports long-lasting oscillations is not resolved. It has been proposed that the sperm may interact with receptors in the oocyte's plasma membrane and engage intracellular signaling pathways that result in Ca2+ release. A different line of investigation suggests that upon sperm-oocyte fusion, a sperm cytosolic factor is released into the oocyte which interacts with unknown cytosolic targets, and generates [Ca2+]i oscillations. We will discuss the most recent evidence for both lines of thought and demonstrate that injections of sperm crude extracts (SF) into mammalian oocytes trigger [Ca2+]i oscillations that support in vitro parthenogenetic development to the blastocyst stage.

Animals↗
PubMed1998

Serological and genomic characterization of human rotaviruses detected in China.

A total of 1,385 stool specimens were collected from children with diarrhea at two hospitals in Wuhan, Hubei Province, China, in 1994 and 1995, and screened for rotavirus by polyacrylamide gel electrophoresis of viral RNA. Group A rotavirus was detected with high frequency; 56.5% (87/154) and 40.8% (502/1,231) of the specimens collected in 1994 and 1995, respectively, were positive for rotavirus. Assignment of G serotype and P type (VP4 genotype) of group A rotavirus by ELISA with monoclonal antibodies and/or PCR, respectively, showed that strains of G2-P[4] and G1-P[8] specificity were predominant in 1994 and in 1995, respectively. In contrast, a single strain was found to have a P[9] type specificity, and no G4 strain was detected. Unusual combinations of RNA pattern-subgroup-G serotype-P type, such as long pattern-subgroup I-G1-P[8], short pattern-subgroup II-G3-P[4] and short pattern-subgroup I-G1-P[4], were detected in four specimens. Nucleotide sequences of the VP8* and/or NSP5 genes from two Chinese P[8] strains 470 and 582 and one Chinese P[9] strain 512 as well as five Japanese P[9] strains (K8, AU1, M318, 0264, and 0265) were determined and compared with the published sequences of the corresponding gene. In the phylogenetic tree of VP8* sequences of P[9] strains, which formed two clusters each having strain K8 or AU-1 as the representative strain, the Chinese P[9] strain was found in the cluster represented by AU-1, although it was most distantly related to other strains. While NSP5 sequences of human strains with P[9] specificity were related to simian and bovine strains, that of Chinese P[8] strains was most closely related to those of porcine strains. A single group C rotavirus (No. 208) was detected. Nucleotide sequences of its VP4, VP6, VP7, and NSP4 genes were very similar to those of group C human rotaviruses detected worldwide.

Amino Acid Sequence↗
PubMed1998

Injection of a porcine sperm factor induces activation of mouse eggs.

Injection of sperm preparations into mammalian oocytes and eggs has been shown to elicit persistent [Ca2+]i oscillations that closely resemble fertilization-associated Ca2+ release. However, the ability of these sperm fractions to initiate egg activation has not been clearly demonstrated. In the present experiments, mouse eggs injected with a porcine sperm preparation were evaluated for early and late events of activation. Events monitored included, among early events, the generation of [Ca2+]i oscillations and cortical granule exocytosis and, among late events, the decrease in histone H1 and myelin basic protein kinase activities, polar body extrusion, pronuclear formation, and cleavage to the two-cell stage. Injection of sperm fractions consistently evoked [Ca2+]i oscillations that, in turn, initiated all events of activation. Uninjected control eggs or eggs injected with buffer or heat-treated sperm fractions failed to show Ca2+ responses or activation. In addition, injection of sperm fractions into recently ovulated eggs (experiments were concluded within 15 hr after human chorionic gonadotropin administration) induced high rates of activation, while similarly aged eggs exposed to 7% ethanol for 5 min, a known parthenogenetic treatment, failed to activate. Together these results indicate that injection of sperm fractions elicits [Ca2+]i oscillations that are capable of initiating normal egg activation. These results support the hypothesis that a sperm component participates in the generation of fertilization-associated [Ca2+]i oscillations.

Animals↗
PubMed1998

Experimental study on temperature distribution within a wide-gap continuous free-flow electrophoresis chamber.

The temperature distribution within a wide-gap (3 mm) continuous free-flow electrophoresis (CFFE) chamber was investigated by direct measurements. The walls of the chambers consisted of Plexiglas and thermocouples were used as temperature sensors. The study of different operating and heat dissipating conditions revealed that lateral temperature gradients arise in CFFE chambers in addition to an axial increase in temperature of 0.25 degrees C per Watt of electric power and per minute of residence time in the absence of cooling.

Buffers↗
PubMed1998

Recurrent psammocarcinoma of the peritoneum with complete response to tamoxifen therapy.

Psammocarcinoma is a rare type of serous carcinoma arising from the ovary or peritoneum, characterized by massive psammoma body formation, invasiveness, and low-grade cytological features. A case of primary peritoneal psammocarcinoma is presented. Aspects of clinical presentation, diagnosis, and management are described. Emphasis is placed on successful management of recurrent disease using tamoxifen therapy.

Antineoplastic Agents, Hormonal↗
PubMed1998

Changes of gastric nitric oxide in neonatal rats with hypoxic-ischemic encephalopathy.

In order to study the changes of nitric oxide (NO) in gastric wall in hypoxic neonatal rats, the activity of nitric oxide synthase (NOS) of gastric wall was measured and the NADPH-diaphorase biochemistry test was taken to show the distribution of NOS in the gastric wall of neonatal rats. The results showed that compared with normal rats, NOS had no significant changes in the acute hypoxic rats (P > 0.05). However, in hypoxic-ischemic encephalopathy (HIE) neonatal rats, the activity of NOS was markedly increased (P < 0.01), and the NOS positive reactive products were markedly increased in the gastric muscle, but no changes in the mucosal and submucosal layers were observed. The results suggest that the decreased gastric motivation and the gastric mucosal lesions caused by asphyxia are associated with the changes of NO in gastric wall.

Animals↗
PubMed1998

The role for endothelin in mesangial proliferative glomerulonephritis.

To understand the effect of endothelin (ET) on the mesangium and matrix proliferation on the basis of hyperlipidemia, the model of mesangial proliferative glomerulonephritis (MSPGN) was established by intravenously giving calf serum albumin (250 mg/L) to the rabbits fed on feed containing 1% cholesterol for 4-8 weeks. Our results showed that in the 4th week of the experiment, the ET level in experiment group was significantly higher than that of normal controls (P < 0.01) and the pathological examination revealed development of MSPGN. In the 8th week of the experiment, the ET level was further elevated and pathological study demonstrated local glomerular sclerosis and infiltration of lymphocytes of interstitia. We are led to conclude that ET, as a newly identified hormone, is involved in the pathogenesis and development of MSPGN and acts as an important regulator in the proliferation of mesangium and accumulation of matrix of basal membrane.

Animals↗
PubMed1998

The bacterial inhibitory ability and in vivo drug release pattern of a new drug delivery system: ciprofloxacine/tricalcium phosphate delivery capsule.

The bacterial inhibitory ability of a new drug delivery system (DDS): Ciprofloxacine/tricalcium phosphate delivery capsule (CTDC), its in vivo drug release pattern, and the influence of ultrasonic irradiation on its drug release were investigated. It was found that CTDC had a strong and sustained inhibitory ability to some common pathogens of bone and joint infections, such as staphylococcus aureus, escherichia coli and pseudomonas aeruginosa. In vivo drug-release study in animals demonstrated a high concentration of ciprofloxacine in the bone tissue surrounding CTDC which was placed in the greater trochanter of the rabbit and continued to release ciprofloxacine for at least 5 weeks and the blood level of ciprofloxacine was low. In vivo study also showed ultrasonic irradiation could increase the amount of ciprofloxacine released from CTDC, which may be an economical, effecient and safe new method to achieve the control of drug release from DDS.

Animals↗
PubMed1998

Ticlopidine-associated aplastic anemia. A case report and review of literature.

Serious hematologic complications associated with ticlopidine have been reported, including aplastic anemia. We report here an additional case of fatal aplastic anemia due to ticlopidine. A 66-year-old male patient developed fever and pancytopenia 2 months after ticlopidine was started. Despite the administration of granulocyte colony-stimulating factor (G-CSF) and broad-spectrum antibiotics, as well as aggressive red cell and platelet transfusions, the patient died 16 days after admission due to septic shock. Eighteen other cases of ticlopidine-induced aplastic anemia published in the English literature are also reviewed and presented here. Eight of the total 19 patients (including the one reported here) have died, mostly due to infection. Of the seven who received supportive treatment only, four had spontaneous recovery. Nine cases were treated with G-CSF or granulocyte-macrophage colony-stimulating factor (GM-CSF), and response was observed in only four of them. Several other cases were treated with high-dose corticosteroids or androgens; however, it was not possible to evaluate the efficacy of these treatments because of the limited number of cases. In the absence of satisfactory treatment for ticlopidine-induced aplastic anemia at present, it may be reasonable to try antilymphocyte globulin or cyclosporine. Also, great efforts should be made in the prevention and management of infection accompanying this disease.

Adrenal Cortex Hormones↗
PubMed1998

Unilateral hippocampal lesions in newborn and adult rats: effects on spatial memory and BDNF gene expression.

Subcortical damage at birth often produces more severe deficits than similar lesions in an adult. In the present study, effects of unilateral electrolytic hippocampal ablations made on postnatal day 1 or in 3-month-old adult rats, were compared. Exploratory behavior and spatial navigation in the Morris water maze (MWM) were assessed 8 and 20 weeks after hippocampal damage. Rats with neonatal damage did not respond to novelty in the environment and did not learn to find the hidden platform in the MWM. Rats lesioned as adults did learn the water maze task, but slower than controls. We hypothesized that behavioral deficits observed in rats lesioned at birth, may be due, in part, to neurochemical dysfunction of the contralateral hippocampus. Specifically, cholinergic and GABAergic neurotransmission were assessed by measuring choline-acetyltransferase (ChAT) and GABAdecarboxylase (GAD) activity. In addition, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) mRNA levels were assayed in the remaining (contralateral) hippocampus. Of these molecules, only BDNF gene expression was significantly reduced (by 30%) at 8 and 20 weeks after neonatal and adult unilateral ablation. The similar reduction in BDNF mRNA in both treatment groups does not correspond with the lesion's differential effect on memory function. However, the more severe learning impairment after neonatal lesion may reflect increased dependence on trophins during development.

Aging↗
PubMed1998

Cytogenetic effects of energetic ions with shielding.

In order to understand the effects of shielding on the induction of biological damages by charged particles, we conducted experiments with accelerated protons (250 MeV) and iron particles (1 GeV/u). Human lymphocytes in vitro were exposed to particle beams through polyethylene with various thickness, and chromosomal aberrations were determined using FISH technique. Dose response curves for chromosome aberrations were obtained and compared for various particle types. Experimental results indicated that for a given absorbed dose at the cell, the effectiveness of protons and iron particles in the induction of chromosomal aberrations was not significantly altered by polyethylene with thickness up to 30-cm and 15-cm respectively. Comparing with gamma rays, charged particles were very effective in producing complex chromosomal damages, which may be an important mechanism in alterating functions in non dividing tissues, such as nervous systems.

Chromosome Aberrations↗
PubMed1998

Intravascular ultrasound predictors of angiographic restenosis in lesions treated with Palmaz-Schatz stents.

OBJECTIVES: This study sought to evaluate the clinical, procedural, preinterventional and postinterventional quantitative coronary angiographic (QCA) and intravascular ultrasound (IVUS) predictors of restenosis after Palmaz-Schatz stent placement. BACKGROUND: Although Palmaz-Schatz stent placement reduces restenosis compared with balloon angioplasty, in-stent restenosis remains a major clinical problem. METHODS: QCA and IVUS studies were performed before and after intervention (after stent placement and high pressure adjunct balloon angioplasty) in 382 lesions in 291 patients treated with 476 Palmaz-Schatz stents for whom follow-up QCA data were available 5.5 +/- 4.8 months (mean +/- SD) later. Univariate and multivariate predictors of QCA restenosis (> or = 50% diameter stenosis at follow-up, follow-up percent diameter stenosis [DS] and follow-up minimal lumen diameter [MLD]) were determined. RESULTS: Three variables were the most consistent predictors of the follow-up angiographic findings: ostial lesion location, IVUS preinterventional lesion site plaque burden (plaque/total arterial area) and IVUS assessment of final lumen dimensions (whether final lumen area or final MLD). All three variables predicted both the primary (binary restenosis) and secondary (follow-up MLD and follow-up DS) end points. In addition, a number of variables predicted one or more but not all the end points: 1) restenosis (IVUS preinterventional lumen and arterial area); 2) follow-up DS (QCA lesion length); and 3) follow-up MLD (QCA lesion length and preinterventional MLD and DS and IVUS preinterventional lumen and arterial area). CONCLUSIONS: Ostial lesion location and IVUS preinterventional plaque burden and postinterventional lumen dimensions were the most consistent predictors of angiographic in-stent restenosis.

Adult↗