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H Hao

Publications and source records attributed to H Hao.

At least 55 records · Page 3Linked to original sources
PubMed1995

GM1 antibody in Guillain-Barre syndrome after Campylobacter jejuni infection.

Fecal culture of Campylobacter jejuni was prepared by the method of Skirrow, and serum class specific antibodies (IgG, IgM and IgA) to Campylobacter jejuni and serum class specific antibodies (IgG IgM) to GM1 were prepared with solid phase enzyme linked immunasorbent assay in 16 cases of Guillain-Barre syndrome (GBS), 32 controls with other neurological diseases (disease controls) and 90 normal controls. The results showed that the incidence of Campylobacter jejuni infection, especially recent infections, in the group with Guillain-Barre syndrome was much higher than that in the two control groups, and that the positive rate of GM1 antibody was also much higher in the GBS group than in the two control groups. The results suggest that Campylobacter jejuni infection may be one of the important precipitating factors of Guillain-Barre syndrome and play an important role in the epidemiological pattern of Guillain-Barre syndrome in China. It damages the myelin of peripheral nerves through induction of GM1 antibody production.

Adult↗
PubMed1994

Regulation of human DNA polymerase delta during the cell cycle.

The expression of polymerase delta (pol delta) during the cell cycle was studied in Molt 4 cells separated by counter-flow centrifugal elutriation. Northern blotting showed that pol delta mRNA levels increased by 3-fold at the G1/S border. Levels of pol delta protein determined by Western blotting also peaked at the G1/S border with qualitatively similar changes as the mRNA levels. Thus, pol delta gene expression appears to be regulated during the cell cycle at the transcriptional level. The mRNA half-life for pol delta was determined to be about 8 h and the protein half-life about 10 h. Parallel examination of the expression of proliferating cell nuclear antigen showed that the mRNA levels also increased about 2-fold at the G1/S border, while the protein levels of proliferating cell nuclear antigen increased steadily through the whole cell cycle period, and remained high at G2/M. Analysis of pol alpha expression showed qualitatively similar behavior as pol delta, but the magnitude of the changes were higher. Pulse labeling of cells metabolically arrested in G1,S, or G2/M with 32Pi showed that pol delta is a phosphoprotein and that it is most actively phosphorylated during the S phase.

Cell Cycle↗
PubMed1994

Dihydrofolate reductase of Drosophila. Cloning and expression of a gene with a rare transcript.

Traditionally, dihydrofolate reductase (DHFR) has been isolated and the corresponding gene cloned from drug-resistant cell lines which have amplified DHFR genes after selection. A Dhfr sequence has now been obtained by nested polymerase chain reaction (PCR) from Drosophila bearing a single gene copy. Using the PCR-amplified partial cDNA as a probe, Dhfr was cloned by screening a Drosophila genomic library. It consists of regulatory regions as well as a 599-nucleotide coding region with a single 50-base pair (bp) intron and encodes a protein of 182 amino acids. Previously we have shown that the enzyme has kinetic properties characteristic of both "prokaryotic" and "eukaryotic" DHFRs. Here we show that the organization of Drosophila Dhfr is strikingly different from its mammalian counterparts and most similar to that of mosquito. A 790-bp transcript was detected by Northern blot analysis, with a single transcription start site located 27 bp upstream of ATG codon. The Drosophila genome contains a single Dhfr copy at 89E and a selected cell line has not amplified the gene. Confirmation of the identity of this gene has been obtained by kinetic studies of recombinant DHFR over-expressed in Escherichia coli cells.

Amino Acid Sequence↗
PubMed1994

DNA polymerase delta is involved in the cellular response to UV damage in human cells.

We have used antibodies specific for either polymerase delta (pol delta) or its accessory protein, proliferating cell nuclear antigen (PCNA), to demonstrate that they can markedly inhibit the capacity of HeLa nuclear extracts to effect repair of UV-damaged plasmid DNA. This provides the first unambiguous evidence for the involvement of pol delta in DNA repair synthesis. The mRNA levels of both pol delta and PCNA were significantly stimulated subsequent to UV irradiation of cultured cells, providing the first evidence that the cellular response to UV damage may involve regulation of pol delta and PCNA at the gene level. Thus, DNA polymerase delta and its accessory proteins, in addition to their function in replicative DNA synthesis, also function in DNA repair synthesis.

Catalysis↗
PubMed1994

N omega-nitro-L-arginine inhibits vasodilations and elevations of both cyclic AMP and cyclic GMP levels in rat aorta induced by calcitonin gene-related peptide (CGRP).

Our previous studies showed that vasodilations and elevations of both cyclic AMP and cyclic GMP levels in rat aorta induced by rat calcitonin gene-related peptide (rCGRP) are inhibited by hemoglobin and methylene blue, blockers of the endothelium-derived relaxant factor (EDRF, now recognized as nitric oxide [NO]). In the present study, we used N omega-nitro-L-arginine (L-NNA), a selective inhibitor of nitric oxide synthase, to test whether rCGRP-induced relaxations and cyclic AMP and cyclic GMP responses in rat aorta require de novo synthesis of NO. L-NNA (30 microM, 15 min) inhibited by 84, 76 and 73% the relaxations induced by rCGRP at 1, 10 and 100 nM, respectively. D-NNA (30 microM), which does not inhibit nitric oxide synthase, did not block rCGRP-induced vasorelaxations. Addition of L-arginine (3 mM) 5 min before L-NNA completely prevented the L-NNA-inhibition of CGRP-induced relaxations. L-NNA (30 microM, 15 min) also inhibited the elevations of both cyclic AMP and cyclic GMP levels caused by CGRP (100 nM). The data suggest that de novo synthesis of nitric oxide from its precursor L-arginine is required for rCGRP to induce vasodilations and elevations of both cyclic AMP and cyclic GMP levels in rat aorta.

Amino Acid Oxidoreductases↗
PubMed1994

Nitroglycerin (exogenous nitric oxide) substitutes for endothelium-derived nitric oxide in potentiating vasorelaxations and cyclic AMP elevations induced by calcitonin gene-related peptide (CGRP) in rat aorta.

Rat calcitonin gene-related peptide (rCGRP) causes endothelium-dependent vasorelaxations via a dual signal transduction mechanism involving elevations of both cyclic AMP and cyclic GMP levels in rat aorta. These responses are all dependent on de novo synthesis of nitric oxide (NO) in endothelial cells and appear to involve a mechanistic link between cyclic GMP and cyclic AMP responses in smooth muscle cells. The present study determined whether NO from an exogenous source (i.e. added nitroglycerin) could substitute for endogenous NO in rCGRP-induced responses in endothelium-denuded aorta. Nitroglycerin (1 microM) significantly elevated cyclic GMP levels by 20-fold and 3.3-fold and cyclic AMP levels by 26% and 22% at 1 and 2 min, respectively. By itself, rCGRP (100 nM) did not significantly elevate cyclic AMP levels. In combination, however, nitroglycerin and rCGRP caused more-than-additive cyclic AMP elevations (41% above basal at 1 and 2 min). Nitroglycerin also potentiated rCGRP-induced vasorelaxations in endothelium-denuded rings, thus uncovering a direct (endothelium-independent) relaxant effect of rCGRP in rat aorta. The data indicate that exogenous NO can substitute for endogenous NO in rCGRP-induced relaxant and cyclic AMP responses in aorta. This nitroglycerin-induced potentiation of CGRP effects likely involves inhibition of cyclic-GMP-inhibited-phosphodiesterase in smooth muscle cells, thus allowing cyclic AMP to accumulate and mediate the direct vasodilator effects of rCGRP.

Animals↗
PubMed1993

An analysis of autopsy findings in 108 patients who died after valve replacement.

The pathological findings and the causes of death were reviewed in 108 patients who had received 142 heart valve prostheses (52 mechanical and 90 bioprostheses) at the National Cardiovascular Center in Osaka, Japan, from 1977 to 1991. Rheumatic heart disease was the major underlying disease (60.2%), and the age distribution at death ranged from 21 to 80-year-old. Survival duration after the surgery extended from 0 day to 9 years. Thirty-three patients (30.6%) died of perioperative complications such as myocardial haemorrhage and damage, or from heart failure which had been evident prior to the operation, a cause of death which pre-dominated in patients who died within 1 week of surgery (15/17; 88.2%). Thirty-eight patients (35.2%) died of prostheses-related problems such as prosthetic valve failure (cuspal tears and calcifying destruction of the xenograft), thromboembolism, and prosthetic valve endocarditis. Endocarditis was frequent in patients who had survived longer than 1 year (25/33; 75.8%). None of the patients died of prostheses-related problems within 1 week. Non-infectious valve failure was more common in patients with bioprostheses than in those with mechanical valves; thromboembolism showed the opposite association. Prosthetic valve infective endocarditis was nearly equal in frequency in both types of valve.

Adult↗
PubMed1993

Detection of enteroviral genome and its significance in cardiomyopathy.

Myocarditis is an important disease that can lead to dilated cardiomyopathy (DCM). Using the polymerase chain reaction (PCR), we examined whether viral genomes were present specifically in the hearts of viral myocarditis or DCM patients in our autopsy series and compared the results with their clinicopathological features. We applied three different criteria of myocarditis to fully describe the histological features. The presence of a viral genome was detected by PCR but was not specific in DCM or myocarditis. PCR might be helpful in the diagnosis of viral myocarditis, when combined with other clinical information.

Adult↗
PubMed1992

Molecular cloning of the cDNA for the catalytic subunit of human DNA polymerase delta.

The cDNA of human DNA polymerase delta was cloned. The cDNA had a length of 3.5 kb and encoded a protein of 1107 amino acid residues with a calculated molecular mass of 124 kDa. Northern blot analysis showed that the cDNA hybridized to a mRNA of 3.4 kb. Monoclonal and polyclonal antibodies to the C-terminal 20 residues specifically immunoblotted the human pol delta catalytic polypeptide. A multiple sequence alignment was constructed. This showed that human pol delta is closely related to yeast pol delta and the herpes virus DNA polymerases. The levels of pol delta message were found to be induced concomitantly with DNA pol delta activity and DNA synthesis in serum restimulated proliferating IMR90 cultured cells. The human pol delta gene was localized to chromosome 19 by Southern blotting of EcoRI digested DNA from a panel of rodent/human cell hybrids.

Amino Acid Sequence↗
PubMed1992

Structural and functional relationships of human DNA polymerases.

A continuing theme of our laboratory has been the understanding of human DNA polymerases at the structural level. We have purified DNA polymerases delta, epsilon and alpha from human placenta. Monoclonal antibodies to these polymerases were isolated and used as tools to study their immunochemical relationships. These studies have shown that while DNA polymerases delta, epsilon and alpha are discrete proteins, they must share common structural features by virtue of the ability of several of our monoclonal antibodies to exhibit cross-reactivity. A second approach we have taken is the molecular cloning of human DNA polymerase delta and epsilon. We have cloned the DNA polymerase delta cDNA, and this has allowed us to compare its primary structure to those of human polymerase alpha and other members of this polymerase family. Multiple sequence alignments have revealed that human DNA polymerase delta is also closely related to the herpes virus family of DNA polymerases. In situ hybridization has shown that the human DNA polymerase delta gene is localized to chromosome 19 q13.3-q13.4. In order to further determine the functional regions of the DNA polymerase delta structure we are currently expressing human pol delta in E. coli and baculovirus systems. Other work in our laboratory is directed toward examining the expression of DNA polymerase delta during the cell cycle.

Amino Acid Sequence↗
PubMed1992

N omega-nitro-L-arginine blocks the second phase but not the first phase of the endothelium-dependent relaxations induced by substance P in isolated rings of pig carotid artery.

Endothelium-dependent relaxations can be evoked by a variety of stimuli, among them substance P (SP), which is found in sensory nerve fibers supplying the adventitia-media junction of most muscular arteries. This study determined the role of endothelium-derived nitric oxide as a mediator of endothelium-dependent relaxations to SP in isolated rings of the pig carotid artery suspended in organ chambers for isometric tension recording. SP (10(-12)-10(-7) M) caused concentration-dependent relaxations of arteries precontracted with norepinephrine (10(-7) M). The relaxations were characterized by a partially transient relaxation (phase 1) and a sustained relaxation of the artery (phase 2). The inhibitor of nitric oxide formation, N omega-nitro-L-arginine (L-NNA) methyl ester caused a gradual increase in tension, the phase I response at 3 x 10(-10) to 3 x 10(-7) M SP was shifted to the right, but the maximal relaxation was comparable in the presence of L-NNA. However, the sustained relaxation after addition of substance P (phase II) was lost and tension in the presence of L-NNA returned to a level above that induced by L-NNA and norepinephrine (10(-9) M). These results suggest that the endothelium-dependent relaxations to SP, particularly the prolonged relaxation (phase II), are due to de novo synthesis of nitric oxide and hence fully abolished by a specific inhibitor.

Animals↗