PubMed Health⌕ Search

Biomedical subjects

W B Liu

Publications and source records attributed to W B Liu.

15 recordsLinked to original sources
PubMed2006

Strengthening of a Pd-free high gold dental alloy for porcelain bonding by a pre-firing heat treatment.

OBJECTIVES: The purpose of the present investigation was to report a Pd-free high gold alloy for porcelain bonding based on the ternary system of Au-Pt-Zn with a nominal composition of 86Au-11Pt-1.5Zn-0.5In-0.7Rh-0.2Fe-0.1Ir (wt.%). Emphasis was put on the effect of a pre-firing heat treatment on the mechanical properties of the alloy. METHODS: The strengthening effect of the pre-firing heat treatment was investigated by means of hardness measurement, tensile testing, X-ray diffraction, optical microscopy and scanning electron microscopy. RESULTS: Experimental results showed that both the hardness and tensile strength of the alloy can be significantly improved after heat treatment at the temperature of 980 degrees C for 15 min. The strengthening could be attributed to homogenization of microstructure and alloying elements and precipitation of new fine particles. SIGNIFICANCE: The cast framework of the present new Pd-free alloy could be heat treated before actual firing, and this would improve the processing properties of the alloy during firing.

Dental Alloys↗
PubMed2003

Pathotypical and genotypical characterization of strains of Newcastle disease virus isolated from outbreaks in chicken and goose flocks in some regions of China during 1985-2001.

Twenty-nine strains of Newcastle disease virus (NDV) isolated from outbreaks in chicken and goose flocks in several regions of China during 1985-2001 were characterized pathotypically and genotypically. All except one of these strains were velogenic. For genotyping, phylogenetic tree analysis (nt 47-420), restriction site mapping (nt 334-1682) and residue substitution analysis (residues 4-124) of the F gene were performed using sequences of our isolates and sequences of selected NDV strains from GenBank. The results revealed that most of these newly characterized strains belonged to six novel genetic groups that were designated as VIf, VIg, VIIc, VIId, VIIe and IX. The genotype IX viruses, to which the China challenge strain F48E8 used for vaccine evaluation belonged, were found only in China and still induced sporadic infections in certain areas. Isolates belonging to group VIf and VIg were distinct from previously reported members of genotype VI, with genetic distance from 2.5 to 12.1%. Subgenotype VIIc, VIId and VIIe viruses, which were distributed in clusters in the phylogenetic tree distinct from members of subgenotypes VIIa and VIIb, were responsible for disease outbreaks in chicken and goose flocks and circulated predominantly in southern China in recent years. Finally, cross-protective testing showed that specific-pathogen free (SPF) chickens vaccinated with La Sota vaccines can be fully protected against challenge by strains from genetic groups VIb, VIg, VIId and IX, indicating that the antigenic differences between strains of various genotypes are insufficient to change the cross-protection conferred by the commonly used vaccine.

Amino Acid Sequence↗
PubMed2001

[Effects of praeruptorin C on vascular hypertrophy, [Ca2+]i, collagen content and NO in renovascular and spontaneously hypertensive rats].

AIM: To study the effects of praeruptorin C (pra-C), a pure constituent isolated from "Qian-Hu", the roots of Peucedanum praeruptorum Dunn. (Umbelliferae), on vascular hypertrophy, collagen content, transient [Ca2+]i, NO and vascular response of the thoracic aorta of renovascular and spontaneously hypertensive rats (RHR, SHR). METHODS: RHR and SHR were given pra-C 20 mg.kg-1.d-1 for 9 weeks, ig. Blood pressure of both rats were measured using tail cuff manometry. Under inverted microscopy the length and width of the smooth muscle cells were measured by using computer software MICC (Dongnan University). [Ca2+]i of smooth muscle cell (SMCs) was measured with Fura-2/AM. By measuring the specific aminoacid hydroxyproline content, the collagen content was obtained. By using Griess reagent, the NO in the smooth muscle cells (SMCs) was measured. RESULTS: The intermedia of the thoracic aorta in RHR was enlarged than that of the normal and pra-C groups. The size (length x width) of the SMCs of thoracic aorta from RHR increased 73.4 microns vs nomal 34.5 microns and pra-C 34 microns. The collagen content of thoracic aorta was 39% +/- 6.8% dry weight in RHR, they were 26.5% +/- 3% dry weight in normal and 25.6% +/- 1.1% dry weight in pra-C, RHR vs pra-C. The resting [Ca2+]i of single cell of SMCs was (62 +/- 6) nmol.L-1. In Hanks solution containing CaCl2 1 mmol.L-1, the resting [Ca2+]i of SMCs was (150 +/- 8) nmol.L-1 in normal. (226 +/- 11) nmol.L-1 in RHR. In presence of KCl 60 mmol.L-1, NE 10 mumol.L-1, ANG II 100 nmol.L-1 and ATP 30 mumol.L-1 the [Ca2+]i of SMCs were increased by 128%; 132%; 233% and 152% in RHR, respectively. The pra-C group was similar to the normal group. The resting [Ca2+]i of SMCs was (71 +/- 6) nmol.L-1 in control of SHR, in Hanks solution containing CaCl2 1 mmol.L-1. The resting [Ca2+]i of SMCs was (160 +/- 8) nmol.L-1 in normal, and (362 +/- 18) nmol.L-1 in SHR. In presence KCl 60 mmol.L-1 and NE 10 mumol.L-1 the [Ca2+]i of SMCs were increased by 235% and 200% in SHR, respectively. Pra-C group was similar to normal group. NO of SMCs was decreased 76% in SHR, pra-C group was nearly normal. The pra-C improved vascular responses of the thoracic aorta of RHR. CONCLUSION: These results indicate that pra-C improved the vascular hypertrophy by decreasing the size of SMCs cells, collagen content. SMCs [Ca2+]i and increasing NO production.

Animals↗
PubMed2000

Tetrandrine inhibits inward rectifying potassium current in cultured bovine aortic endothelial cells.

AIM: To study the effect of tetrandrine (Tet) on inward rectifying potassium current in cultured bovine aortic endothelial cells. METHODS: Inward rectifying potassium current (IRK) was observed by the whole cell patch-clamp technique. RESULTS: IRK was inhibited by Tet in a concentration-dependent manner and recovered to normal after wash with drug-free external solution. IRK was reduced from (582 +/- 48) pA to (221 +/- 40) pA at a holding potential of -70 mV by Tet 30 mumol/L. IC50 was 2.8 mumol/L. CONCLUSION: Tet inhibited inward rectifying potassium current in cultured bovine aortic endothelial cells.

Alkaloids↗
PubMed1998

Methylation and gene mutation in eukaryotic DNA.

5-methylcytosine (m5C) as a rare base exists in eukaryotic genomes, which is a normal constitution in many eukaryotic DNA and the existence of m5C is a feature of eukaryotic DNA. Under regular physiological conditions, cytosine of eukaryotic DNA is usually methylated. Up to the present, many people consider that the m5C may be mutation hotspots by the deamination leading to gene mutation. Our study indicated that the spontaneous mutation caused by the transition of G.C --> A.T, in eukaryotic DNA, may result from the tautomer changing of base pairs and may also be cause by other factor actions, however it could not be caused by the deamination of m5C.

Base Sequence↗
PubMed1997

[Effect of sanchinoside Rg1 on experimental thrombosis and its mechanisms].

The effect of sanchinoside Rg1 on generation of thrombosis and its mechanism was studied. Rg1 was shown to markedly inhibit experimental thrombosis formation induced by extra corporeal shunt between the carotid artery and jugular vein. After Rg1 infusion, the activity of t-PA was found to be increased, so did the percentage of active-type t-PA, but the activity of PA-I decreased. Further data in our study indicate that incubation of endothelial cells with Rg1 for 24 h caused significant increase of NO production. This effect was found to be dose-dependent. These observations suggest that Rg1 is a potent anti-thrombosis substance and can enhance the function of fibrinolysis system and stimulate vascular endothelial cells to release NO.

Animals↗
PubMed1994

A temperature-sensitive mutant of human p53.

We discovered that the human 'hot-spot' p53 mutant 143Ala is temperature sensitive for the binding of two DNA elements and for mediating the transcription of a downstream luciferase reporter gene. At 32.5 degrees C, 143Ala possesses strong DNA binding ability. In addition, its transcriptional activities are stronger than those of wild-type p53. At 37.5 degrees C, however, both the mutant's DNA binding and transcriptional activation functions are greatly reduced or abolished. The activity differences correlate with the presence of two conformational states of p53, which are recognized by monoclonal antibodies: at 32.5 degrees C, 143Ala is recognized by PAb1620, which is specific for the wild-type conformation, whereas at 37.5 degrees C, 143Ala is almost undetectable by PAb1620-mediated immunoprecipitation. Although 143Ala's binding to p53 DNA recognition elements and its activation of reporter gene transcription at 32.5 degrees C is markedly higher than that of the wild-type p53, 143Ala inhibited proliferation less robustly than wild-type p53 and it did not increase inhibition of ras-induced focus formation. These results indicate a partial correlation between the events involved in transcriptional activation and events involved in the proliferation suppression of p53. 143Ala therefore will be of use in dissecting the relationship between the structure of p53 and its different cellular functions.

Animals↗
PubMed1994

[The morphological changes in trabecular architecture of bone in severe primary hyperparathyroidism].

By histomorphometry bone biopsy specimens were evaluated from 10 patients with severe primary hyperparathyroidism (PHPT). The data suggest that the mean trabecular width and trabecular bone volume were slightly, but not significantly increased. As indices of bone remodeling activity, both trabecular osteoid surface and trabecular resorption surface were significantly increased indeed, indicating high bone turn-over occurred in PHPT. The dynamic study showed that much more trabecular bone surface was covered either with single or double tetracycline labels in PHPT than in control. The overproduction of osteoid in the patients leads to the accumulation of osteoid on the trabecular surface. Moreover, the mean osteoid width seemed to be thicker in PHPT than in control, suggesting the co-existence of osteomalacia, which might be a possible explanation for eucalcemia usually seen in the majority. Part of chinese PHPT patients.

Adenoma↗
PubMed1994

[Trabecular connectivity in primary hyperparathyroidism].

By bone histomorphometry, 10 cases of primary hyperparathyroidism (PHPT) were used to study the trabecular connectivity, which in a few literatures was mentioned to be reserved somehow. Our data suggest that in comparison with the normal control (10 subjects) the nodes (N.Nd), the number of terminus (N.Tm), the total strut length (TSL), the length between the nodes (Nd.Nd), trabecular separation (Tb.Sp) and trabecular thickness (Tb.Th) were significantly increased while no significance was found in N.Nd/N.Tm, Tm.Tm and TBV. The correlation analyses indicate that there is no correlation between the variables in the normal controls. In contrast, however, TBV and Tb.Th showed negative correlations with N.Tm and Tm.Tm. Besides these, there were positive correlations between N.Nd/N.Tm and TBV or Tb.Th, and a negative correlation between N.Nd/N.Tm and Tb.Sp. The results suggest that to certain degree the trabecular connectivity in PHPT be destructed while the three dimensional architecture be reserved. Our data seem to be different from those reported previously. It may be due to the severity of PHPT in our patients.

Adolescent↗
PubMed1994

[Effects of pollution with fluoride on bone dynamics of periosteum in iliac of domestic pigs].

Studies on bone dynamic parameters of iliac periosteum and endosteum in domestic pigs with fluorosis caused by coal-burning contamination were conducted. Bone dynamics of 12 pigs with experimental fluorosis and nine controls both labelled with double tetracycline was investigated. Results showed the distance between two labels on iliac periosteum of domestic pigs with fluorosis shortened and, rates of mineralization and bone matrix formation slowed. It suggested fluorosis played significantly inhibitory roles in bone formation on the periosteal membrane of pig iliac.

Air Pollution↗
PubMed1991

[Chemical studies of coumarins from Glycyrrhiza uralensis Fisch].

This paper reports the isolation and identification of eight crystalline substances (I, II, III, IV, V, VI, VII, VIII) from the root of Glycyrrhiza uralensis Fisch. Besides the known compounds liquiritin, hexacosance, beta-sitosterol, licoricone liquiritigenin and etc, a new constituent, named neoglycyrol was obtained by sillica gel and polyamide column chromatographic method. Its chemical structure was elucidated by means of chemical and spectrometric analysis (UV, IR, NMR and MS). Neoglycyrol, C21H18O6, yellow needles with mp 263.5-265 degrees C, possesses one methoxyl, one isopentenyl and two hydroxyls. Its diacetate derivative is C25H22O8 with mp 202-203.5 degrees C. Its dimethyl ether derivative is C23H22O6 with mp 207-208.5 degrees C. Its structure was found to be VII.

Coumarins↗