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Biomedical subjects

H Guan

Publications and source records attributed to H Guan.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Antisense monocyte chemotactic protein-1 gene inhibits vein graft intimal hyperplasia in rabbits].

OBJECTIVE: To identify the effect of in vivo local expression of recombine antisense MCP-1 gene on the development of vein graft neointima formation. METHODS: Jugular vein-to-artery bypass grafting was performed on 20 New Zealand white rabbits, of which 4 grafts were transferred with LNCX vectors, 6 grafts with antisense MCP-1 (200 micrograms) by cationic liposome, and 4 grafts as controls. Fourteen days after surgery grafts were harvested. The expression of antisense MCP-1 and its effect on MCP-1 in vein grafts were detected by dot blot. Grafts were processed for morphologic evaluation and immunohistochemistry analysis. RESULTS: Antisense MCP-1 was expressed in local gene delivery group, meanwhile MCP-1 expression in vein grafts was significantly inhibited (test group, 1.227 +/- 0.362; controls, 1.981 +/- 0.394, P < 0.05). Monocytes/macrophages adherence and infiltration were prominently reduced (test group, 24.3% +/- 2.7%; controls, 36.8% +/- 2.8%, P < 0.05), and intimal hyperplasia was markedly reduced [test group, (0.65 +/- 0.08) mm2; controls, 1.27 +/- 0.15) mm2, P < 0.05]. CONCLUSION: Local expression of antisense MCP-1 in vein graft significantly reduced intimal hyperplasia with inhibition of MCP-1 expression and prevention of monocytes/macrophages infiltration.

Animals↗
PubMed2001

[Inquiries about methods of primary eye care and prevention of blindness].

OBJECTIVE: To inquire about the methods of developing primary eye care (PEC) and prevention of blindness. METHODS: The methods of developing PEC and prevention of blindness in recent 10 years were analyzed retrospectively. RESULTS: Five grades of PEC network were established. The training courses 1 007 times were held in Nantong, and the epidemiological survey of the blind was carried out for 6 817 259 people. The blind persons were 13 496 in number, and the prevalence of blindness was 0.20%. Cataract operations were performed on 83.16% of the treatable cataract blind persons. The successful rate of cataract surgery was 98.22%. Eight counties became the national advanced counties of prevention of blindness. Nantong city became the first national advanced city of prevention of blindness in 1997. CONCLUSIONS: PEC is the basis of prevention of blindness. To bring PEC into line with the primary health care (PHC) is the key point of developing PEC. Affordable operation, promising quality of the operative procedure and combination of survey and treatment are the three essential factors of developing PEC and prevention of blindness. To create national advanced county and city is the motive force of developing prevention of blindness.

Adult↗
PubMed2001

[The significance of thrombosis after experimental pulmonary thromboembolism].

OBJECTIVE: To study the significance of thrombosis after experimental pulmonary thromboembolism (PTE). METHODS: Acute PTE models of rabbits were established with injection of autologous blood clots (0.04 g/kg) stabilized in a temperature-controlled (70 degrees C) of distilled water for 10 minutes through the femoral vein, then the regulation of thrombosis was explored at dissection and upon microscopic examination after PTE. Moreover, the coagulability of blood and the plasma level of thromboxane A2(TXA2) and endothelin (ET) were examined. RESULTS: Thrombotic propensity was found at 1 h, and fresh thrombosis started to form at 24 h following clots infusion. Emboli were completely or partly dissolved at 5 d and organized at 10 and 14 d after clots infused. Prothrombin time was significantly lower [(7.15 +/- 0.06)s], and fibrinogen was higher [(5.86 +/- 1.50) g/L] at 24 h post-clots, compared with pre-clots [(7.34 +/- 0.19)s, (3.37 +/- 1.02) g/L] (P < 0.05). Venous plasma level of TXA2 began to increase at 5 min [(2.5 +/- 0.7) micrograms/L] and continued to rise to its maximum at 15 min [(2.5 +/- 0.6) micrograms/L], then declined at 60 min after clots infusion. The level of ET in both arterial and venous blood increased at 5 d post-clots [(0.84 +/- 0.15) micrograms/L and (0.23 +/- 0.05) micrograms/L] separately, while most of emboli resolved. CONCLUSIONS: There is thrombus formation after autologous-blood-clots-induced PTE. Furthermore, thrombus formation, fibrinolysis and organization may always interact on each other consistently, and control the pathogenesis of PTE. Abnormalities of ET metabolism occur after PTE and the major mediator of TXA2 plays an important role in the early phase of PTE.

Animals↗
PubMed2001

[Fractionated-clamping for thoracoabdominal aortic aneurysm repair: report of 13 cases].

OBJECTIVE: Fractionated-clamping was applied to aneurysm repair in patients with thoracoabdominal aortic aneurysm(TAA), and its effects in decreasing operative mortality and severe complications such as renal failure and hemiplegia were discussed. METHODS: Using improved shunting and cross-clamping technique, we repaired 13 thoracoabdominal aortae and their branches (9 males and 4 females). TAA Crawford type: type I one case, type II two cases, type III two cases and type IV three cases. TAA dissection Debakey type: type I one case, type III four cases (including 2 of ruptured aneurysm) and aorta stenosis one case. RESULTS: Twelve procedures were performed successfully. One patient died of cardiac attack immediately before accomplishment of the operation with a operative mortality rate of 7.7% (1/13). Operative complications included acute necrotizing pancreatitis (1 case), ARDS (1), thoracic cavity bleeding (2), hemiplegia (1), and acute renal failure (1). The incidence rate of complications was significantly lower than that reported elsewhere. CONCLUSIONS: Fractionated-clamping for thoracoabdominal aortic aneurysm repair is a renovation on the basis of Crawford procedure and aorta bypass method. Clinical results demonstrated that the procedure decreases the surgical mortality and the incidence rate of dangerous complications. Fractionated clamping for aorta replacement is a reasonable procedure under general anesthesia at normal temperature.

Acute Kidney Injury↗
PubMed2001

Combined intraoperative iliac artery stents and femoro-popliteal bypass for multilevel atherosclerotic occlusive disease.

OBJECTIVE: To review our preliminary experience and evaluate our early results of a combined intraoperative iliac angioplasty and stenting with infrainguinal revascularization in multilevel atherosclerotic occlusive disease. METHODS: From July 1999 to April 2000, intraoperative iliac angioplasty and stenting combined with simultaneous femoro-popliteal bypass were performed on 12 lower extremities of 10 patients suffering from multilevel atherosclerotic occlusive disease. There were 8 men and 2 women, average 72 years. The indications for procedures included disabling claudication in 3 and rest pain in 7 patients. RESULTS: Eleven iliac angioplasty and stent procedures combined with simultaneous 9 femoro-popliteal by-pass and 3 femoro-femoral-popliteal bypass were performed in 12 limbs of 10 patients. Angioplasty and stent placement was technically successful in all patients. One contralateral femoral-popliteal bypass was failure after femoro-femoral-popliteal bypass. There were no additional instances of procedural or postoperative morbidity or mortality. Mean follow-up was 5 months (range 1 approximately 10 months). During the follow-up period, one femoro-infrapopliteal graft became occluded after 7 months and above-knee amputation was required. The cumulative primary patency rate of stented iliac arteries, femoro-femoral bypass grafts and femoro-popliteal bypass grafts were 100% (11/11), 100% (3/3) and 90.9% (10/11) in the follow-up period, respectively. The amputation rate was 8.3% (1/12). CONCLUSIONS: Intraoperative iliac artery PTA and stent placement can be safely and effectively performed simultaneously with infrainguinal revascularization for multilevel atherosclerotic occlusive disease by skilled vascular surgeon, using a portable C arm fluoroscopy inthe operating room. Furthermore, iliac artery PTA and stenting was valuable adjunct to distal bypass either to improve inflow and outflow, or to reduce the extent of traditional surgical intervention, and also, any angioplasty and stenting-related complications can be immediately corrected as well.

Aged↗
PubMed2000

Polymerization of nontemplate bases before transcription initiation at the 3' ends of templates by an RNA-dependent RNA polymerase: an activity involved in 3' end repair of viral RNAs.

The 3' ends of RNAs associated with turnip crinkle virus (TCV), including subviral satellite (sat)C, terminate with the motif CCUGCCC-3'. Transcripts of satC with a deletion of the motif are repaired to wild type (wt) in vivo by RNA-dependent RNA polymerase (RdRp)-mediated extension of abortively synthesized oligoribonucleotide primers complementary to the 3' end of the TCV genomic RNA. Repair of shorter deletions, however, are repaired by other mechanisms. SatC transcripts with the 3' terminal CCC replaced by eight nonviral bases were repaired in plants by homologous recombination between the similar 3' ends of satC and TCV. Transcripts with deletions of four or five 3' terminal bases, in the presence or absence of nonviral bases, generated progeny with a mixture of wt and non-wt 3' ends in vivo. In vitro, RdRp-containing extracts were able to polymerize nucleotides in a template-independent fashion before using these primers to initiate transcription at or near the 3' end of truncated satC templates. The nontemplate additions at the 5' ends of the nascent complementary strands were not random, with a preference for consecutive identical nucleotides. The RdRp was also able to initiate transcription opposite cytidylate, uridylate, guanylate, and possibly adenylate residues without exhibiting an obvious preference, flexibility previously unreported for viral RdRp. The unexpected existence of three different repair mechanisms for TCV suggests that 3' end reconstruction is critical to virus survival.

Base Pairing↗
PubMed2000

Involvement of conserved aspartate and glutamate residues in the catalysis and substrate binding of maize starch synthase.

Chemical modification of maize starch synthase IIb-2 (SSIIb-2) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC), which modifies acidic amino acid residues, resulted in a time- and concentration-dependent inactivation of SSIIb-2. ADPGlc was found to completely protect SSIIb-2 from inactivation by EDAC. These results suggest that glutamate or aspartate is important for SS activity. On the basis of the sequence identity of SS, conserved acidic amino acids were mutagenized to identify the specific amino acid residues important for SS activity. Three amino acids (D21, D139, and E391) were found to be important for SS activity. D21N showed 4% of the wild-type enzyme activity and a 10-fold decrease in the affinity for ADPGlc, while the conservative change from D21 to E resulted in a decrease in V(max) and no change in affinity for ADPGlc, suggesting that the negative charge is important for ADPGlc binding. When sites D139 and E391 were changed to their respective amide form, no SS activity was detected. With the conservative change, D139E showed a decrease in V(max) and no changes in apparent K(m) for substrates. E391D showed a 9-fold increase in K(m) for ADPGlc, a 12-fold increase in apparent K(m) for glycogen, and a 4-fold increase in apparent K(m) for amylopectin. The circular dichroism analysis indicates that these kinetic changes may not be due to a major conformation change in the protein. These results provide the first evidence that the conserved aspartate and glutamate residues could be involved in the catalysis or substrate binding of SS.

Amino Acid Sequence↗
PubMed2000

Analysis of cis-acting sequences involved in plus-strand synthesis of a turnip crinkle virus-associated satellite RNA identifies a new carmovirus replication element.

Satellite RNA C (satC) is a 356-base subviral RNA associated with turnip crinkle virus (TCV). A 3'-proximal element (3'-UCCCAAAGUAU) located 11 bases from the 3' terminus of satC minus strands can function as an independent promoter in an in vitro RNA-dependent RNA polymerase (RdRp) transcription system. Furthermore, in the absence of a 5'-proximal element, the 3'-proximal element is required for complementary strand synthesis in vitro. Site-directed mutagenesis was conducted to investigate the functional significance of this element and the 3' minus-strand terminal sequence "3'-OH-CCCUAU," which contains the minus-strand 3'-end sequence "3'-OH-CC(1-2)(A/U)(A/U)(A/U)" found in all carmovirus RNAs. Single mutations in the 3'-terminal sequence, which we have named the carmovirus consensus sequence (CCS), suppressed satC plus-strand synthesis to undetectable levels in protoplasts while still permitting some minus-strand synthesis. However, single and multiple mutations introduced into the 3'-proximal element had little or no effect on satC accumulation in protoplasts. In vivo genetic selection (SELEX) of the minus-strand 3'-terminal 21 bases revealed that all satC species accumulating in plants contained the 3' CCS. In addition, the 3'-proximal element preferentially contained a sequence similar to the CCS and/or polypurines, suggesting that this element may also contribute to accumulation of satC in vivo.

Brassica↗
PubMed2000

Requirement of a 5'-proximal linear sequence on minus strands for plus-strand synthesis of a satellite RNA associated with turnip crinkle virus.

Viral RNA replication begins with specific recognition of cis-acting RNA elements by the viral RNA-dependent RNA polymerase (RdRp) and/or associated host factors. A short RNA element (3'-AACCCCUGGGAGGC) located 41 bases from the 5' end of minus strands of satellite RNA C (satC), a 356-base subviral RNA naturally associated with turnip crinkle virus (TCV), was previously identified as important for plus-strand synthesis using an in vitro RdRp assay (H. Guan, C. Song, A. E. Simon, 1997, RNA 3, 1401-1412). To examine the functional significance of this element in RNA replication, mutations were introduced into the consecutive C residues in the element. A single mutation of the 3'-most C residue resulted in undetectable levels of satC plus strands when transcripts were assayed in protoplasts and suppressed transcription directed by the element in vitro. However, satC minus strands were detectable at 6 h postinoculation (hpi) of protoplasts, accumulating to about 10% of wild-type levels at 24 hpi. This mutation, when in the plus-sense orientation, had little or no effect on minus-strand synthesis from full-length satC plus strands in vitro, suggesting that the 5'-proximal RNA element is required for satC plus-strand synthesis. In addition, in vivo genetic selection revealed a strict requirement for 10 of the 14 nucleotides of the element, indicating that the primary sequence is essential for RNA accumulation.

5' Untranslated Regions↗
PubMed2000

Transplant vasculopathy: viral anti-inflammatory serpin regulation of atherogenesis.

BACKGROUND: Surgical and ischemic injury to the artery wall initiates vascular wound-healing responses that stimulate atherosclerotic plaque growth. The plasminogen activators have cellular chemotactic, adhesion, and proteolytic activity. Serp-1 is a secreted myxoma virus glycoprotein serpin that binds and inhibits plasminogen activators. We have examined the effects of Serp-1 on plaque growth and inflammatory cell invasion in animal models after balloon injury and after aortic allograft transplant. METHODS: We used histologic analysis to assess 4 animal models of angioplasty-mediated injury and 2 models of aortic allograft transplant for intimal hyperplasia and cellular invasion. We assessed plasminogen activator (uPA and tPA) and inhibitor (PAI-1) expression in rat iliofemoral arteries after balloon injury using Western blot, enzyme activity, and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: Plaque growth after balloon injury decreased after Serp-1 treatment in all balloon-injury models tested. Transplant vasculopathy also significantly decreased in 2 rat models of aortic allograft transplant. Infusion of a Serp-1 active site mutant, that lacked plasminogen activator inhibiting activity, did not inhibit plaque growth. Quantitative RT-PCR detected increased transcription of PAI-1 mRNA. Increased PAI-1 protein and enzyme-inhibitory activity was also detected in Serp-1-treated arteries by activity assay and Western blot. CONCLUSIONS: Thrombolytic serpins are central regulatory agents in vascular wound-healing responses. Investigation of the inhibitory mechanisms of viral serpins may provide new insights into atherogenesis.

Angioplasty, Balloon↗
PubMed2000

Lipoxygenase-dependent mechanisms in hypertension.

This study was designed to examine the contribution of lipoxygenase products to mechanisms of vascular contraction and elevated blood pressure in rats with aortic coarctation-induced hypertension. In cytosolic fractions of aortae taken from hypertensive rats, 12-lipoxygenase protein was increased as compared to normotensive controls. Aortic rings from hypertensive, but not from normotensive rats, exhibited a basal tone which was reduced 74+/-12 and 71+/-22%, respectively, by the lipoxygenase inhibitors cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (CDC, 10(-5) mol/L) and 5,8,11-eicosatriynoic acid (ETI, 10(-5) mol/L). CDC (8 mg/kg s.c.) did not affect the blood pressure of normotensive rats but decreased that of hypertensive rats from 182+/-6 to 151+/-10 mm Hg. The blood pressure lowering effect of CDC was blunted in hypertensive rats pretreated with indomethacin or antibodies against 5,6-dihydro-prostaglandin I2. These data suggest contribution of lipoxygenase-derived products to mechanisms underlying aortic smooth muscle basal tone and elevated blood pressure in rats with aortic coarctation-induced hypertension. The vasodepressor effect of CDC depends on a mechanism involving vasodilatory prostaglandins.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2000

Adaptive portal CT reconstruction: a simulation study.

In radiotherapy, radiation treatment beams contain valuable information for patient setup verification. These beams may be used for portal CT reconstruction. However, direct use of the beam data for reconstruction may yield inadequate CT images simply because these beams cover only a part of the patient body. In this study, we use the treatment beams in addition to a set of regular CT projection beams to reconstruct a locally enhanced portal CT image. This approach is called adaptive portal CT reconstruction. A computer simulation demonstrated the advantages of the approach. The image reconstruction was carried out by the multilevel scheme algebraic reconstruction technique. Results indicated that the image quality of adaptive portal CT reconstruction is equivalent to that obtained from a full set of projections. This proposed technique should be not only valuable for three-dimensional radiotherapy verification, but also applicable to diagnostic CT imaging.

Computer Simulation↗
PubMed2000

[Unsuccessful operative treatment of acute thoracic and thoracolumbar injuries with neurologic deficit].

OBJECTIVE: To analyze the main factors for unsuccessful operative treatment of acute thoracic and thoracolumbar injuries with neurologic deficit. METHODS: 82 patients with acute thoracic and thoracolumbar injuries with neurologic deficit who had had unsuccessful operations in other hospitals were reviewed. Clinical materials and radiographs including plane and functional films and CT scans were analyzed. RESULTS: In the 82 patients 30 had unsuccessful reduction or spinal deformity, and 31 canal encroachment. In 12 pedicle screws located out of the pedicle, 2 penetrated the canal and 3 pressed against the aorta. 41 patients who complained back pain, 16 had mechanical spinal instability, and 3 neurological instability. CONCLUSION: The main factors for unsuccessful operative management include inappropriate selection of surgical indications and inaccurate use of surgical technique.

Acute Disease↗
PubMed2000

[Report of 4 cases for treating optic nerve inflammation through total ethmoidectomy under nasal endoscope].

OBJECTIVE: The curative effect of treating optic nerve inflammation through total ethmoidectomy under nasal endoscope is evaluated. METHOD: The operations through total ethmoidectomy under nasal endoscope for 4 patients who had optic nerve inflammation has been done. RESULT: Two patients have apparent effect while the other two patients are effective, and the symptoms such as snuffle, eye distension and headache are well remitted. CONCLUSION: Towards the sufferer who had both optic nerve inflammation and intercurrent nasosinusitis, when conservative treatment was invalid or the patient was relapsed after surgery, it is necessary to do the operation in season and its effective rate is satisfactory. Total ethmoidectomy under nasal endoscope is safety and reliable.

Adult↗
PubMed1999

Essential arginine residues in maize starch synthase IIa are involved in both ADP-glucose and primer binding.

The arginine-specific reagent phenylglyoxal inactivated the activity of maize starch synthase IIa (SSIIa), due to the modification of at least one arginine residue out of a possible 42. The addition of ADPGlc completely protected SSIIa from the inactivation, indicating that arginine may be involved in the interaction of this anionic substrate with SSIIa. However, site-directed mutagenesis of the conserved Arg-214 in SSIIa showed that this amino acid is important for apparent affinity of SSIIa for its primer (amylopectin and glycogen), as evidenced by a marked increase in the K(m) for primer upon substitution of this amino acid with no concomitant change in V(max), K(m) for ADPGlc, or secondary structure. Therefore, Arg-214 of SSIIa appears to play a role in its primer binding.

Adenosine Diphosphate↗
PubMed1999

Analysis of purified maize starch synthases IIa and IIb: SS isoforms can be distinguished based on their kinetic properties.

Since starch synthases IIa (SSIIa) and SSIIb have not been purified from plant tissue, their structure-function relationships have not been well characterized. Therefore, we have expressed these SS genes in Escherichia coli, purified them to apparent homogeneity, and studied their kinetic properties. In addition, the N-terminally truncated forms of these enzymes were studied in an attempt to understand the function of the diverse N-terminal sequences in SS. Our results show that, like SSI, the N-terminal extensions of SSIIa and SSIIb are not essential for catalytic activity and no extensive changes in their kinetic properties are observed upon their N-terminal truncation. Each isoform of SS can be distinguished based on its kinetic properties. Maize SSI and maize SSIIb exhibit higher Vmax with glycogen as a primer, while the converse is true for SSIIa. However, the specific activity of SSIIb is at least two- to threefold higher than that for either SSI or SSIIa. Although SSIIb exhibits the highest maximal velocity of the isoforms compared, its apparent affinity for primer is twofold lower than the affinity of SSI and SSIIa for primer. Perhaps these differences in primer affinity, primer preference, and maximal velocities all contribute in some way to the different structure(s) of starch during its synthesis. Expression and purification of maize SS has now provided us a useful tool to address the role(s) of SS in starch synthesis and starch structure.

Adenosine Diphosphate Glucose↗
PubMed1999

Identification of the soluble starch synthase activities of maize endosperm.

This study identified the complement of soluble starch synthases (SSs) present in developing maize (Zea mays) endosperm. The product of the du1 gene, DU1, was shown to be one of the two major soluble SSs. The C-terminal 450 residues of DU1 comprise eight sequence blocks conserved in 28 known or predicted glucan synthases. This region of DU1 was expressed in Escherichia coli and shown to possess SS activity. DU1-specific antisera detected a soluble endosperm protein of more than 200 kD that was lacking in du1- mutants. These antisera eliminated 20% to 30% of the soluble SS activity from kernel extracts. Antiserum against the isozyme zSSI eliminated approximately 60% of the total soluble SS, and immunodepletion of du1- mutant extracts with this antiserum nearly eliminated SS activity. Two soluble SS activities were identified by electrophoretic fractionation, each of which correlated specifically with zSSI or DU1. Thus, DU1 and zSSI accounted for the great majority of soluble SS activity present in developing endosperm. The relative activity of the two isozymes did not change significantly during the starch biosynthetic period. DU1 and zSSI may be interdependent, because mutant extracts lacking DU1 exhibited a significant stimulation of the remaining SS activity.

Amino Acid Sequence↗