Biomedical subjects

Y Zhao

Publications and source records attributed to Y Zhao.

At least 397 records · Page 22Linked to original sources

PubMed2000

[Stress-corrosion test of laser welded ceramic alloys].

OBJECTIVE: The corrosion properties of dental material are very critical. This study is to investigate the corrosion properties of laser welded basemetalalloys. METHODS: The precise stainless rod molds had been made in size of phi 3 mm x 4 mm, with which 20 wax patterns were made. They were invested with inner investment (Bellavest) and outer investment (phosphate and gypsum). Then they were casted with CW-PA (Ni-Cr-Nb) alloys. All casted alloy rods were ultra-sonic washed in distilled water. Every two rods were contacted longitudinally by a special welding jig. Laser welding machine (DL-2002) was used to weld them at 305 V, 20 ms. The specimens were divided into 2 groups as following: 1. The group of stress-corrosion: 5 laser welded samples were subjected to the stress-corrosion test under 261.44 MPa in the 37 degrees C artificial saliva for 3 months in a special stress-corrosion test jig. After that, the ultimate tensile strength (UTS) was tested, the surface microcrack at the fusion zone (FZ), the heat affecting zone (HAZ) and the interface zone was observed with SEM (ARMY-1845, USA), the elements were also analyzed with EPMA (ARMY-1845, USA) at the fusion zone (FZ), the parent metal zone and the interface zone. 2. The other 5 laser welded samples were made as the controlled group. No special treatment were done to them, and the UTS was also tested, the surface of the micro crack and the elements at the FZ, the HAZ, parent metal zone and the interface zone were observed and analyzed with SEM, EPMA as well. RESULTS: The study showed us that the UTS of the stress-corrosion group was 502.48 +/- 12.49 MPa, while that of the controlled group was 446.05 +/- 82.50 MPa, there was no significant difference (P > 0.05). There was no microcrack on any sample's surface at the FZ, the HAZ and the interface zone. The main elements of the FZ were Ni(56.63%), Cr(19.36%), Nb (6.57%), Si(6.01%), Al(0.32%) and Mo(11.11%), while the elements of the parent metal zone were Ni(60.77%), Cr (20.59%), Nb(5.03%), Si(3.95%), Al(0.37%) and Mo(9.29%) respectively. CONCLUSION: The results suggest that the corrosion properties of laser welded alloys are excellent.

Corrosion↗

PubMed2000

[Effects of chincap therapy for early anterior crossbite].

OBJECTIVE: To analysis the effects of chincap therapy for early anterior crossbite and mandibular prognathism. METHODS: 136 patients anterior crossbite and mandibular prognathism aged from 3 to 14 years old at the start of treatment were treated with active chincap with bilateral force of 700 to 1000 gram. Every patient wore chin cap 12 to 14 hours daily, and most of those patients used removable appliances to open the crossbite of incisors. According to the age of patients, they were divided into four groups, C1 (3-5 years old), C2 (6-8 years old), C3 (9-11 years old) and C4 (12-14 years old). When the treatment ended after two years, we analyzed the models by measuring the length of maxillary on the models before and after treatment (U1 and U2 that's the distance between the tip of 1|1 and the distal plane of 6|6 or V|V and the overjet before and after treatment (L1 and L2). Then we calculated the obtained distance for the mandible related to the maxillary position X(X = (L2-L1)-(U2-U1)) and analyzed treating time and mandibular retreating speed in the four groups. RESULTS: The obtained distance for the mandible related to the maxillary position in C1, C2, C3 and C4 groups were 3.27 +/- 0.99 mm, 4.62 +/- 1.33 mm, 4.43 +/- 1.28 mm and 2.63 +/- 0.92 mm respectively, and the treating time in four groups were 8.92 +/- 2.66 months, 10.47 +/- 2.21 months, 13.07 +/- 2.00 months, 20.50 +/- 3.96 months respectively. The retreating speed of the mandible related to the maxillary position in the four groups were 0.37 mm/month, 0.44 mm/month, 0.34 mm/month and 0.13 mm/month respectively. The effects of the treatment in C1, C2 and C3 groups (3-11 years old) were remarkable, especially in C1 group (3-5 years old). CONCLUSION: The effects of chincap therapy for early anterior crossbite and mandibular prognathism were remarkable, especially for the very early crossbite patients.

Adolescent↗

PubMed2000

[Effects of bite force lost on the expression of IL-6 in the rat periodontium].

OBJECTIVE: In order to explain the molecular mechanism of periodontium remodeling the expression of IL-6 in the rat periodontal ligament fibroblasts (PDLC) and the alveolar bone osteoblasts under normal and bite force lost was studied. METHODS: To establish a rat model of different bite force for the study, left maxillary molars of rats were extracted and the left mandibular molar area was used as the bite force lost. The animals were sacrificed after 6 hours, 1, 2, 3 days and 1, 2, 3, 4 weeks. The prepared tissue specimens were processed for the study of the change in the histologic morphology and the expression of IL-6 protein in PDLC and osteoblasts with HE staining and immunohistochemistry techniques. RESULTS: In the group of bite force lost, the loosely arrangement of periodontal ligaments and the resorption of alveolar bone were observed in histological study, the expression of IL-6 in PDLC and osteoblasts was enhanced apparently than that in the group of normal bite force by using immunohistochemistry techniques. In the group of lost bite force, the expression of IL-6 in PDLC enhanced with time regularly: The expression of IL-6 was strengthened after 3 days, and reached the peak after 2 weeks, then, decreased after that and restored to normality in 4 weeks. While in osteoblasts of the group of bite force lost, the expression of IL-6 was strengthened just after 2 weeks. CONCLUSION: Bite force lost induce the expression of IL-6 enhanced apparently in PDLC and osteoblasts, it suggests that IL-6 may play important roles in the effect of bite force on periodontium remodeling. It approaches initially the molecular mechanism of periodontium remodeling, demonstrates that the histologic morphology is closely related to the mechanical condition.

Alveolar Bone Loss↗

PubMed2000

[The investigation of the testing method on fracture toughness of dental adhesive resins].

OBJECTIVE: The testing method for mode I fracture toughness (GIC) of dental adhesive resins was investigated. METHODS: The dental adhesive resins were placed between two Co-Cr alloy plates to make up test specimen, so test specimen had a metal/adhesive resin/metal construction. The category of adhesive resins, the dimensions of test specimen and testing speed were used as the variants. The testing method for mode I fracture toughness (GIC) was investigated by using double cantilever beam (DCB) testing. The correlation between the GIC and each factor was analysed by regression analysis. RESULTS: In all test specimens, it was found that the values of fracture toughness (GIC, GIR) at the process of crack propagation were nearly constant. Therefore, it was found that fracture toughness (GIC) at maximal load might only be measured to evaluate an adhesive resin. On the values of GIC, there was no effect from the dimensions of the test specimens, width (b = 3.5 mm), thickness (2 hm = 2.4 mm), initial crack length (ao = 10-19 mm) and testing speed(Vc = 0.1 mm/min, 0.2 mm/min). But, it was found that the fracture toughness was influenced by thickness of adhesive layer (hr). In case of SB, the value of GIC had a tendency to increase as the adhesive layer became thicker, and then the crack propagating area observed as cohesive failure became remarkably rougher. In case of PV, the values for hr = 100 and 200 microns were similar, however, that for hr = 20 microns somewhat decreased resulting in an interfacial failure. By the way, cohesive failures of hr = 100 and 200 microns were observed as similar flat surfaces. CONCLUSION: Fracture toughness was not influenced very much by the dimensions of test specimen, but was influenced by thickness of adhesive layer. Thus, it was recognized that this testing method was more effective for evaluating the adhesive resin.

Materials Testing↗

PubMed2000

[Production, partial purification and characterization of methamidophos-degrading enzyme from methylotroph WB-1].

After cultivation for 20 h in the inorganic salt medium with methamidophos as sole carbon and nitrogen source, Methylotroph WB-1 could produce methamidophos-degrading enzyme in larger amounts. The enzyme was partially purified by sonication disruption, Tween-20 extraction, heat treatment(9 min at 60 degrees C), DEAE-cellulose 32 and CM-cellulose32 chromatography with 22.8 times purification and 78.8% recovery. Activity staining showed single violate band corresponding to that of protein staining. Optimum pH of the enzyme was 9.0; poor substrate specificity was showed. It was strongly inhibited by Hg2+, Mn2+ and Cu2+, but not by Co2+ and Zn2+; it also exhibited poor stability.

Aeromonas↗

PubMed2000

[Studies on the trehalose-producing by Colloides CB39].

A bacterium which had the ability of producing sugar produced sugar at low temperature (18 degrees C) was selected from the water of Tianchi in Changbai mountain. The sugar was identified to be trehalose by methods of thin-layer chromatography, reaction of producing osazyone, capillary electrophoresis and infrared spectrum. It was also been found that the trehalose produced by this bacterium (identified to be a new species of Colloides Sp. CB39) was exocrine. At 18 degrees C, its trehalose content in culture solution was 256 mg/g dry weight of the strain. This characteristic is different from that of other strains, which had been proved to have the ability of producing trehalose. then the strain CB39 was induced by ultraviolet in order to abstain mutants which can produce trehalose in high level at usual temperature. The mutant strain 5 that could produce trehalose in high level at usual temperature (25 degrees C) was selected from all the mutant strains. The value of its productivity of trehalose is 416.7 mg/g dry weight of the strain. (At the same temperature, trehalose productivity of mutant strain 5 was eight times of that of the wild type strain CB39).

Bacteria↗

PubMed2000

[Cloning and tissue expressive pattern analysis of the human ribosomal S6 kinase-RPS6KA5 cDNA].

Human ribosomal protein S6 kinase includes two protein families: P90RSK and P70S6K, they participate in two different signaling pathways. When the two kinases were inhibited by their antibodies or rapamycin, the proliferation of cells was arrested. However, their analog, the immunosupressant FK-506, can inhibit the proliferation of fibroblast PBL1 without interfering with the activities of P90RSK, P70S6K and MAPK. We take the tactics of "homolog screening" to demonstrate whether there are some novel proteins which can substitute for the known P90RSK and P70S6K or other pathways without interfering with the known P90RSK and P70S6K. With the conserved sequence of mouse p90RSK as a probe, we screened the homologous sequence in NCBI EST database and got three human EST fragments. With the assembled contig as a probe to screen human brain cDNA library, a full-length cDNA of 3833 bp was attained. It contains a completed open reading frame from 165 bp to 2570 bp encoding 802 amino acids. The putative protein has higher homology with other members of p90RSK family. The gene was named RPS6KA5, the accession number in GenBank is AF090421. Northern hybridization showed the gene expressed in 16 human tissues tested, and the gene was localized in 14q31-32.1 by RH mapping. Another novel P70S6K gene has also been cloned. Thus, our initial presumption that there is an analog of known P90RSK and P70S6K in human beings was proved.

Amino Acid Sequence↗

PubMed2000

[Nucleotide sequence analysis of E2 major protective antigen encoding region of 12 strains of hog cholera virus(HCV)].

cDNA fragments, of HCV envelope glycoprotein E2 major gene of 11 field strains isolated in China in different time and 1 French reference strain(Thiveral) were amplified respectively with RT-PCR method and sequenced. The fragments amplified located by the 5' 2485 to 2708 of E2 major domains B and C and encoded 75 amino acid residues of E2 glycoprotein. All the products amplifield by RT-PCR from 12 strains in the study were same size of 224 bp. Comparing 12 sequences with other 9 references strains sequence reported before using software DNAstar, it was found that Hog Cholera Virus could be classified in two groups by analysis of phylogenetic tree. Strains Brescia, Gpe, Ald, Thiverval, C, CW, HCLV, HCVSM, BJCY1/96, BJTX3/96, BJSY2/96, HeNXH2/98, HeNZZ1/82 and GDGZ1/95 were assigned to group A and were 85.7%-100% for nucleotide sequence and 83.8%-100% for amino acid sequence in homology; but strains HCVF98, HCVF94, HeBHH2/95, LN1/84, SZGM1/85, SCCD1/79 and Alfort were assigned to group B and were 84.3%-100% for nucleotide sequence and 85.1%-100% for amino acid sequence in homology; and 21 strains of HCV were 78.1%-100% for nucleotide sequence and for 78.4%-100% amino acid sequence in homology. Homology were 99.1% for nucleotide sequence and 100% for amino acid sequence between strains HCLV in our study and strains C reported by Rijn's in the Netherlands. It's showed our method of sequencing is reliable. There were obvious differences between the two groups in sequences of envelope glycoprotein E2 major gene, especially in the amino acid substitutions of sites 713 and 729 respectively, and it is showed the two groups of HCV field strains might vary genetically in some extents. The results of other report of challenging of the partial field strains showed that the Chinese stock vaccine virus(HCLV) has good immunity.

Amino Acid Sequence↗

PubMed2000

[Affection of exogenous gibberellic acid (GA3) on endogenus hormones of Panax quinquefolium seed during its morphological after ripening period].

According to the determination of endogenus hormones variation of Panax quinquefolium seed during its morphological afterripenging period, and the affection of exo-GA3 on the endogenus hormones dynamics, it suggested that exo-GA3 couldn't be used for accelerate the growth of Panax quinquefolium embryo, but was helpful in relieving seed dormancy during physiological afterripening period.

Abscisic Acid↗

PubMed2000

[Biological effects of supplements on soil properties and the growth of Panax quinquefolium].

This paper suggests that the physical and chemical characteristics of soil in American ginseng field were greatly improved after utilization of supplement on soil. Compared with the contrast, the soil gravity ratio decreased from 0.812 g/cm3 to 0.715 g/cm3, while the soil porosity increased from 69.36% to 73.03%. These improvements are benefit for the growth of Panax quinquefolium. Biological observations show that the fresh weight of ginseng root enhanced 53.8%, and the content of total saponins in root enhanced 0.5%-1% (get to 8.28%).

Carbon↗

PubMed2000

[Study on chemical constituents of essential oil of Biota orientalis by GC-MS].

The essential oil was extracted from Biota orientalis (L) Endl by using steam distillery, analyzed with SE-54(30 m x 0.25 mm I.d) fused silica capillary column. The optimum separate and analytical conditions were researched. The amount of the components from the essential oil was determinated by monoliration method. The separated components were identified by GC-MS. There are 33 components which are make up 80% of the total essential oil were separated and identified.

Alkenes↗

PubMed2000

[Effect of ethyl acetate extract of Eclipta prostrata on mice of normal and immunosupression].

OBJECTIVE: The regulatory effects of ethyl acetate extract of Eclipta prostrata (EAEEP) on immune function were studied. METHODS: The experimental immunosuppressive mice models were induced by injection of cyclophosphamide or hydrocartisone. RESULTS: The index of spleen in normal mice were decreased significantly. So was the level of hemolysin in serum, Delayed trpe hypersensitivity was also inhibited at the same condition. But EAEEP can increase all these indexes in immunosuppressive mice. CONCLUSION: EAEEP possesses obvious regulatory action on immune function in mice.

Acetates↗

PubMed2000

[Long-term observation on two types of surgical operations for idiopathic hemifacial spasm].

OBJECTIVE: To evaluate and compare the long-term curative effects of two types of surgical operations, microvascular decompression (MVD) and microneurovascular decompression neurocombing neurotraction draw (MVDCTD) for idiopathic hemifacial spasm (IHFS). METHODS: Five hundred and fifty-four patients with complete medical records and with at least 3-year followed-up had been collected since 1985. RESULTS: Of 148 MVD-treated cases with the longest follow-up of 13 years and 9 months, 117 cases were free of symptoms, giving a 79.05% cure rate. Thirty-one patients had recurrence of the symptoms, giving a 20.95% recurrence rate. Of 406 cases treated by MVDCTD with the longest follow-up of 12 years and 3 months, 374 were cured, giving a 92.12% cure rate, and 32 had recurrences of symptoms, giving a 7.88% recurrence rate. Most of them recurred within 2 years after the operation. Complications were sensorineural hearing loss in 31 patients (23 temporary, 8 permanent), temporary tinnitus in 22, temporary postoperative facial weakness in 78, and postoperative meningitis in 34 (3.13%, 33 cases were controlled with antibiotics and 1 patient died). CONCLUSION: The vascular compression at the root of the facial nerve is a main cause of IHFS, and the abnormal function of the facial nucleus is also one of the causes. MVDCTD for IHFS is characterized by its high curative rate, low recurrent rate and stable long-term effect, and is superior to the MVD.

Adult↗

PubMed2000

[Change of 5-fluorouracil penetration in blood-pancreatic barrier of rats after high-dose radiotherapy].

OBJECTIVE: The high-dose intraoperative radiotherapy has become an important therapy to control local recur of pancreatic carcinoma. But the relevant effect of high-dose radiotherapy on chemotherapy is not clear now. METHODS: We studied the effect of high-dose radiotherapy to the penetration of 5-FU (5-Fluorouracil) in blood-pancreatic barrier of rats after the pancreatic region of the rats had treated with 10(Gy) external beam radiotherapy, the penetration ratio (PR) of 5-FU in the pancreatic tissue was investigated with HPLC assay. RESULTS: We found the PR increased with the time processing. And reached the peak on the 6th day, (PR = 0.8300 +/- 0.1662, P < 0.05). Then, the PR began to descend and was 0.7028 on the 10th day. But it was still significantly higher than control group (P < 0.05). CONCLUSION: After the treatment of high-dose radiotherapy, in addition to chemotherapy on the 4th day, and finished the course on the 10th day, the effect of radiotherapy may improve chemotherapy significantly.

Animals↗

PubMed2000

[Effect of low dose gossypol treatment on male sperm nuclear basic protein].

OBJECTIVE: Study on human sperm nuclear basic proteins after low dose of gossypol treatment. METHODS: Twenty-three men with normal fertility were divided into two groups. The experimental group included 15 men which were treated daily with gossypol (15 mg/d for 12 weeks and treated with 10 mg/d for 32 weeks continuously), 8 men were used in the control group. Semen was collected at 1, 4, 8, 12, 16, 24, 36 and 44 weeks after gossypol treatment and 10 weeks after stopping treatment. Total nuclear basic protein (TNBP) was extracted and TH/TP, HP1/(HP2+HP3) ratios were determined by scanning microdensitometry following electrophoresis of TNBP in polyacrylamide gels. RESULTS: The TH/TP ratio of control and the gossypol treated group were 0.17 +/- 0.07 and 0.63 +/- 0.79(P < 0.05); The HP1/(HP2+HP3) ratio of control and gossypol treated group were 1.05 +/- 0.21 and 1.47 +/- 0.18 (P < 0.01). These two parameters were returned to normal after 10 weeks of stopping gossypol treatment. CONCLUSIONS: The interruption of histone-to-protamine replacement reaction (HPRR) and alteration of nuclear basic proteins induced by low dose gossypol treatment might lead to infertility. Changes of HPRR and nuclear basic protein were reversible after stopping gossypol treatment.

Adult↗

PubMed2000

[Coexpression of the preS1(1-42) and the Core(1-144) antigen of HBV in E. coli].

OBJECTIVE: To study the therapeutic T cell vaccine for the treatment of chronic hepatitis B. METHODS: The genes of HBcAg (1-144) and preS1 Ag (1-42) were amplified and fused by PCR. This fusion gene was inserted in the prokaryotic expression vector pET-11d and expressed in E. coli. RESULTS: It was showed by SDS-PAGE that the protein molecular weight of the coexpression product was about 20,000, twenty percent of all bacteria protein. The monoclone antibody against Core and preS1 antigen could react with this fused protein by Western-blot technique respectively. The fused gene was verified by sequencing. Under the immune electron microscopy, this fused protein is a typical particle of HBcAg but in an aggregated form. CONCLUSIONS: The results may aid for studying T cell immunotherapeutic vaccine to chronic hepatitis B.

Artificial Gene Fusion↗

PubMed2000

Inhibitory effect of fluvastatin on aortic intimal thickening in normocholesterolemic rabbits.

OBJECTIVE: The anti-atherosclerotic effect of fluvastatin at does insufficient to lower serum cholesterol on the catheter-induced intimal thickering and possible mechanism were investigated in abdominal aorta of rabbits. METHODS: Fifty-six rabbits were randomly divided into eight groups (n = 7, each). Fluvastatin was given mixed with food at daily dose of 8 mg/kg starting 5 days before catheterization. Light microscope, immunohistochemistry, transmission electron microscope and RT-PCR assay were applied to assess vascular smooth muscle cell (VSMC) proliferation and apoptosis, as well as oncogene expression in vascular wall. RESULTS: At day 10 and day 15 after catheter induced denudation intima/media (I/M) thickness ratio was obviously higher, and also the percentage of PCNA-positive cells and TUNEL-positive cells in media was significantly higher compared with controls. The intimal hyperplasia was mostly composed of alpha-SM-actin-positive cells. In rabbits given fluvastatin I/M ratio and the percentage of these positive cells significantly decreased compared with those without fluvastatin. The overexpression of proto-oncogene H-ras mRNA and decreased expression of anti-oncogene p53 mRNA were found after vascular injury, whereas fluvastatin significantly reduced H-ras mRNA and increased p53 mRNA expression. CONCLUSION: Proliferation of VSMC in the media and the migration to the intima can be inhibited, and apoptosis of VSMC be induced by short-term use of fluvastatin after balloon catheter denudation, independent of serum lipid change. The underlying mechanism is presumably associated with the influence of fluvastatin on oncogene expression in the injured vascular wall.

Animals↗

PubMed2000

[Studies on the infrared and fluorescence spectra of europium-lanthanum-o-aminobenzoate-2,2'-dipyridyl complexes].

A series of mixed rare earth complexes of europium and lanthanum with o-aminobenzoate and 2,2-dipyridyl were synthesized by the reaction of EuCl3 and LaCl3 with o-aminobenzoate and 2,2' dipyridyl in solution. Their infrared and fluorescence spectra were investigated. The results showed that the chemical bonds have been formed between the two ligands with rare-earth ions. The fluorescence spectra excited by 343 nm UV-light indicated that the emission intensity for europium ions can be greatly enhanced if a part of europium ions in europium complexes were substituted by lanthanum ions. This paper discussed the luminance, mechanism of too.

2,2'-Dipyridyl↗