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Biomedical subjects

B Yu

Publications and source records attributed to B Yu.

At least 73 records · Page 4Linked to original sources
PubMed2000

Intragenic complementation and the structure and function of argininosuccinate lyase.

Argininosuccinate lyase (ASL) catalyzes the reversible hydrolysis of argininosuccinate to arginine and fumarate, a reaction important for the detoxification of ammonia via the urea cycle and for arginine biosynthesis. ASL belongs to a superfamily of structurally related enzymes, all of which function as tetramers and catalyze similar reactions in which fumarate is one of the products. Genetic defects in the ASL gene result in the autosomal recessive disorder argininosuccinic aciduria. This disorder has considerable clinical and genetic heterogeneity and also exhibits extensive intragenic complementation. Intragenic complementation is a phenomenon that occurs when a multimeric protein is formed from subunits produced by different mutant alleles of a gene. The resulting hybrid protein exhibits greater enzymatic activity than is found in either of the homomeric mutant proteins. This review describes the structure and function of ASL and its homologue delta crystallin, the genetic defects associated with argininosuccinic aciduria and current theories regarding complementation in this protein.

Amino Acid Metabolism, Inborn Errors↗
PubMed2000

The effects of the lower extremity joint motions on the total body motion in sit-to-stand movement.

OBJECTIVE: The purpose of this study is to investigate the effects of lower extremity joint angular motions on the whole body linear motions in a sit-to-stand movement using a biomechanical model that describes the whole body linear velocity vector as functions of lower extremity joint angular velocities. DESIGN: Two-dimensional video analysis of whole body and joint kinematics. BACKGROUND: A biomechanical model that describes the whole body linear motions as functions of lower extremity joint angular motions is needed to provide clinically relevant information in clinical services and scientific research. METHODS: The linear velocity vector of the whole body motion during the sit-to-stand movement was partitioned into horizontal and vertical components and expressed as functions of lower extremity joint angular velocities for 10 healthy subjects. The coefficient of joint contribution to the whole body linear velocity vector was determined for each joint in each direction. RESULTS: The ankle and hip angular motions are critical to the development of the forward horizontal velocity of the whole body during the sit-to-stand movement. The knee and hip angular motions are critical to the development of the upward vertical velocity of the whole body during the sit-to-stand movement. CONCLUSIONS: The hip, knee, and ankle joint angular motions have various roles in whole body motions in different directions of the sit-to-stand movement. RELEVANCE: The model and the results of this study can be applied to study the control strategies, falls, and assessments of functional impairments in the sit-to-stand movement.

Adult↗
PubMed2000

Characterization of IL-4 and IL-13 signals dependent on the human IL-13 receptor alpha chain 1: redundancy of requirement of tyrosine residue for STAT3 activation.

IL-4 and IL-13 are pleiotropic cytokines whose biological activities overlap with each other. IL-13 receptor alpha chain 1 (IL-13R alpha 1) is necessary for binding to IL-13, and the heterodimer composed of IL-13R alpha 1 and IL-4R alpha chain transduces IL-13 and IL-4 signals; however, the functional mapping of the intracellular domain of IL-13R alpha 1 is not fully understood. In this study, we constructed wild and mutated types of human IL-13R alpha 1, and analyzed IL-4 and IL-13 signals using an IL-13R alpha 1-transfected human B cell line. Expression of IL-13R alpha 1 evoked STAT3 activation by IL-4 and IL-13, and in stimulated human B cells, on which IL-13R alpha 1 was highly expressed, IL-4 and IL-13 induced STAT3 activation. Replacement of the two tyrosine residues completely abolished STAT3 activation, although replacing either tyrosine residue alone retained it. Furthermore, we found that the Box1 region and the C-terminal tail of IL-13R alpha 1 were critical for binding to Tyk2, and activation of Jak1, Tyk2, the insulin receptor substrate-1 and STAT6 respectively. These results suggest that STAT3 activation is involved with IL-4 and IL-13 signals in human B cells along with the activation of STAT6, and that there is a unique sequence in IL-13R alpha 1 to activate STAT3.

Animals↗
PubMed2000

Ethanol stimulates glucose uptake and translocation of GLUT-4 in H9c2 myotubes via a Ca(2+)-dependent mechanism.

Short-term exposure to ethanol impairs glucose homeostasis, but the effects of ethanol on individual components of the glucose disposal pathway are not known. To understand the mechanisms by which ethanol disrupts glucose homeostasis, we have investigated the direct effects of ethanol on glucose uptake and translocation of GLUT-4 in H9c2 myotubes. Short-term treatment with 12.5-50 mM ethanol increased uptake of 2-deoxyglucose by 1.8-fold in differentiated myotubes. Pretreatment of H9c2 myotubes with 100 nM wortmannin, an inhibitor of phosphatidylinositol 3-kinase, had no effect on ethanol-induced increases in 2-deoxyglucose uptake. In contrast, preincubation with 25 microM dantrolene, an inhibitor of Ca(2+) release from the sarcoplasmic reticulum, blocked the stimulation of 2-deoxyglucose uptake by ethanol. Increased 2-deoxyglucose uptake after ethanol treatment was associated with a decrease in small intracellular GLUT-4 vesicles and an increase in GLUT-4 localized at the cell surface. In contrast, ethanol had no effect on the quantity of GLUT-1 and GLUT-3 at the plasma membrane. These data demonstrate that physiologically relevant concentrations of ethanol disrupt the trafficking of GLUT-4 in H9c2 myotubes resulting in translocation of GLUT-4 to the plasma membrane and increased glucose uptake.

Adipocytes↗
PubMed2000

Effect of peroxovanadate compound on phenylalanine hydroxylase gene expression.

Vanadium, a trace element in human cells and regarded as an essential nutrient, plays an active role in all tissues. It is known that peroxovanadate-nicotinic acid (POV), a complex compound of vanadium, can decrease hyperglycemia; however, its biochemical mechanism remains unclear. The object of the present study is to explore the hypoglycemia mechanism of POV at gene molecular levels. Rats rendered diabetic with streptozotocin were treated with POV. Total RNA was isolated from rat liver, and phenylalanine hydroxylase (PAH) mRNA abundance was determined by reverse transcriptase-polymerase chain reaction. PAH activity, blood glucose, and lipid levels were measured. Significantly increased hepatic PAH activity and corresponding mRNA with concomitant hyperglycemia and hyperlipemia were found in diabetic rats. These levels returned to normal after POV treatment and accompanied by negative glucosuria, normoglycemia, and normolipemia. The results from the current study indicates one of the mechanisms of POV action is to inhibit PAH gene expression and PAH activity, thus decreasing gluconeogenesis and hyperglycemia. At the same time, POV is able to promote diabetic recovery by lowering hyperlipemia.

Animals↗
PubMed2000

DNA testing for haemochromatosis: diagnostic, predictive and screening implications.

Since 1996, the identification of the HFE gene has enabled DNA testing for hereditary haemochromatosis (HH). The range of DNA testing available includes: (1) diagnostic, (2) predictive (also called presymptomatic testing) and (3) screening. Access to DNA testing has been facilitated by an Australian Medicare rebate, the first available for genetic disorders. Despite the availability of HFE DNA testing in HH, it remains necessary to interpret results in the context of the clinical picture. Traditional markers based on phenotype (transferrin ferritinsaturation, and liver biopsy) are still required in some circumstances. We report our experience with HFE DNA testing using a semi-automated approach, which allows multiplexing for the two common mutations (C282Y and H63D). Screening a cohort of beta-thalassaemia major and sickle cell anaemia patients of predominantly Mediterranean origin showed that these individuals do not have the common C282Y mutation. This excluded C282Y as a factor in the pathogenesis of iron overload in these haemoglobinopathies. It also showed that the C282Y mutation is of limited value when investigating HH in certain ethnic groups. An Australian family studied illustrated the relative contribution of C282Y and H63D in iron overload. A recently reported third mutation (S65C) in the HFE gene was detected in a low frequency in the populations tested.

Aged↗
PubMed2000

[Genes of micrometastasis in bone marrow of patients with colorectal cancer].

OBJECTIVE: To detect the gene of micrometastasis in bone marrow of patients with colorectal cancer. METHODS: PCR-SSCP/silver stain technique was used to find out the metastatic cancer cells in 51 bone marrow samples in different time. RESULTS: The total positive rate of mutations of p53 and K-ras in bone marrow was 37.25% before operation. The incidence of mutations was obviously correlated with Duke's stage and lymphatic metastasis. After postoperative chemotherapy mutation in 11 patients turned to be negative. CONCLUSIONS: Detection of micrometastasis in bone marrow may contribute to early diagnosis of blood stream metastasis of colorectal cancer.

Bone Marrow Neoplasms↗
PubMed2000

[Total meso-rectal excision in low anterior resection with double stapling technique].

OBJECTIVE: To elucidate the value of total meso-rectal excision (TME) in low anterior resection with double stapling technique. METHODS: During January 1993 to October 1998, 306 cases of rectal lesions were treated by total meso-rectal excision in low anterior resection (LAR) with double stapling technique. Among the patients with rectal cancer, 235 (78.86%) were treated by low anterior resection and 97 (41.28%) by ultra-low anterior resection. RESULTS: No operative death was noted, and anastomotic leakage occurred in 9 (2.94%) patients. Ureter injury occurred in 2 (0.65%) patients. 32 (10.46%) patients suffered from anastomotic stenosis, 31 mm diameter of stapler for 27 (12.68%) patients and 33 mm diameter of stapler for 5 patients (5.38%). Local recurrence occurred in 20 (6.71%) patients: Dukes'B 4 (2.33%) patients, Dukes'C 9 (12.5%) patients, and Dukes'D 7 (53.85%) patients. CONCLUSIONS: Total meso-rectal excision can effectively reduce the local recurrence rate after LAR with double stapling technique. Since the recurrence is closely related to the stage of the disease, early detection, early diagnosis and early treatment are extremely important.

Adult↗
PubMed2000

[Expression of thymidylate synthase gene and recurrence of colorectal carcinoma: their relation and clinical significance].

OBJECTIVE: To study the relationship between expression of thymidylate synthase (TS) gene and recurrence of colorectal carcinoma and its effect on clinical treatment. METHODS: RT-PCR was used to detect the expression of TS gene in primary foci, para-tumoral intestine mucosa, local recurrence, abdominal-pelvic dissemination and hepatic metastasis in 68 cases of colorectal carcinoma, and TS protein was examined with western blot. RESULTS: In 68 cases of colorectal carcinoma, the expression of TS gene in primary foci was 22.1% (15/68); and the positive rates of TS gene expression in local recurrence, abdominal-pelvic dissemination and hepatic metastasis were 88.5% (23/26), 85.0% (17/20), 40.9% (9/20) respectively. The rates of TS protein expression in primary foci, local recurrence, abdominal-pelvic dissemination and hepatic metastasis were 22.1% (15/68), 84.6% (22/26), 80.0% (16/20), 36.4% (8/22) respectively. The negative expression of TS gene and TS protein was detected in paratumoral intestinal mucosa. The results of TS gene and TS protein expression were identical with those the two methods. The positive rates of TS gene and TS protein expression in diversified recurrence foci and metastasis were higher than those in primary foci (P < 0.01). The differences of TS gene and TS protein expression rates between recurrence and hepatic metastasis were significant (P < 0.01). The expression rates of TS gene and TS protein in local recurrence and abdominal-pelvic dissemination tissues were higher than those in hepatic metastasis. CONCLUSION: Overexpression of TS gene plays an important role in the process of local recurrence and abdominal-pelvic dissemination of colorectal carcinoma.

Adult↗
PubMed2000

[Myocardial apoptosis induced by delayed fluid resuscitation in a burned rat model].

OBJECTIVE: To explore the possibility and the mechanism of myocardial apoptosis induced by delayed fluid resuscitation in a burned rat model and its relationship with nitric oxide (NO) and oxygen-derived free radicals. METHODS: In a rat model with 30% III degree burn, the genomic DNA of the myocardial tissue was detected with ApoAlert(TMLM)-PCR Ladder Assay Kit and visualized with agarose gel electrophoresis. Meanwhile, the NO and the content of unsaturated fatty acids were measured. RESULTS: In rats receiving delayed fluid resuscitation following burn, the myocardial genomic DNA exhibited DNA ladder-index of apoptosis, and the contents of myocardial NO and unsaturated fatty acid were much lower than those in rats receiving immediate resuscitation (P < 0.05). CONCLUSION: The myocardial tissue undergoes apoptosis in burned rats receiving delayed fluid resuscitation, and the decreased NO and the production of oxygen-derived free radicals are also observed in this process.

Animals↗
PubMed2000

[Expressions of five protein kinase C isoforms in salivary adenoid cystic carcinoma].

OBJECTIVE: The protein kinase C (PKC) family of isoforms plays the key role in the regulation of cellular events, including cell proliferation, differentiation and canceration. Previous work from our laboratory has shown the alteration of PKC and its inhibitor activities in salivary adenoid cystic carcinoma (SACC) [Sun Changfu, et al. West China Journal of Stomatology, 1998, 16(3): 201-203]. This study aimed to further explore the relationship between PKC isoforms and canceration of SACC. METHODS: Expressions of five isoforms of PKC (alpha, beta I, beta II, epsilon and delta) were examined in cytosolic and membranous fraction of specimen homogenates from SACCs and were compared with the adjacent normal tissues by immunoblotting. Equal amounts of cytosolic and membrane protein from control and experimental groups were simultaneously subjected to sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE), transferred to nitrocellulose membranes, and reacted with first and second antibodies; Color development and image analysis were performed. RESULTS: 1. Cytosolic PKC-alpha, PKC-beta I, and PKC-beta II were expressed in SACCs and adjacent normal tissues. The Expressions of these three cytosolic isoforms were reduced significantly in SACCs compared with the adjacent normal tissues; 2. Membranous PKC-alpha was only detected in SACCs and the membranous translocation of cytosolic PKC-alpha was also seen. 3. The expressions of PKC-epsilon and PKC-delta were not detected in both SACCs and adjacent normal tissues. CONCLUSION: There was close relationship between changes of expression of PKC isoforms (alpha, beta I, beta II) and carcinogenesis of SACC. We postulated that there may be relationship between the membranous translocation of PKC-alpha and hematogenous lung metastasis in SACC.

Carcinoma, Adenoid Cystic↗
PubMed2000

[DNA damage and c-myc gene expression of NIH3T3 cell induced by superoxide anion].

OBJECTIVE: To study the DNA damage, membrane lipid peroxidation, and c-myc gene expression of NIH3T3 cell induced by superoxide anion(O2.-). METHODS: The superoxide anion(O2.-) was produced by reactive system of xanthine-xanthine oxidase (X-XO) and the DNA-EB complex, malondialdehyde (MDA) content and expression of c-myc gene were measured by means of fluorescence, thiobarbituric acid (TBA) assay and DNA-RNA situ hybridization with digoxigenin labeled probes respectively. RESULTS: The O2.- of high concentration(X: 20 micrograms, XO: 2 x 10(-3) U) reacted with isolated DNA from NIH3T3 cell directly which caused DNA damage obviously. When the O2.- of high concentration reacted with whole NIH3T3 cell, the amount of MDA increased and fluorescence intensity of DNA-EB complex decreased which mean lipid peroxidation of membrane and gene damage of the cell respectively. When the producing O2.- of high concentration reactive system existing FeSO4, the phenomena mentioned above showed obviously. Enough amount of catalase showed the inhibit effects, but it could not completely inhibit the DNA damage of whole cell. The c-myc gene expression was observed in the cell treated with O2.- of middle (X: 4 micrograms, XO: 4 x 10(-4) U) and high concentration, but it was not observed in the cell treated with O2.- of low concentration(X: 0.4 micrograms, XO: 4 x 10(-5) U). CONCLUSIONS: DNA damage of the whole cell induced by extracellular O2.- was able to act through the pathway of membrane lipid peroxidation in which hydrogen peroxide is important and the other pathways such as signal transduction of the cell might also be existed. The expression of c-myc gene of NIH3T3 cell induced by O2.- was related closely to the concentration of O2.-.

Animals↗
PubMed2000

[High temperature Raman spectra and micro-structure study of lithium metaborate and its melt].

Lithium metaborate (LiBO2) is studied by high temperature Raman spectroscopy from room temperature up to 1,673 K, and spectra drawing in different temperature are got. By analyzing, it focus on the phase transition, it is that the endless chains of BO3 triangles transform into rings of (B3O6)3- at about 1,123 K, and then the different kind of phase balance's motion occurs after 1,273 K which implies that both endless chain and ring have changed to CRN. In the drawing, the variation of peak's area rate implies the micro-structure information, and shows the process from order to disorder.

English Abstract↗
PubMed2000

[Developments of high temperature Raman spectroscopic techniques].

High temperature Raman spectroscopy (HTRS) is contemporarily a useful tool to study micro-structure of various materials under high temperature. Developments of HTRS techniques are well reviewed. In order to realize the determinations of metallurgical melts, the modified instrumentation for high temperature determination purpose based on JY U1000 Raman spectrometer in Shanghai Enhanced Lab of Ferrometallurgy (SELF) is introduced. It is assembled as macro-Raman with time-resolved detect system by using pulsed Copper Vapor Laser(CVL). This is the first set of its kind in domestic and some further modifications are proposed.

Hot Temperature↗
PubMed1999

pH-dependent peptide binding properties of the type I diabetes-associated I-Ag7 molecule: rapid release of CLIP at an endosomal pH.

MHC class II molecules and invariant chain assemble at a neutral pH in the endoplasmic reticulum and are transported to a low pH compartment where the invariant chain is trimmed to the class II-associated invariant chain peptide (CLIP). For many major histocompatibility complex class II molecules, DM is required for rapid removal of CLIP, which allows binding of antigenic peptides. Since I-Ag7 confers susceptibility to type I diabetes in NOD mice, the biochemical requirements for peptide loading were examined using soluble I-Ag7 expressed in insect cells. I-Ag7 formed long-lived complexes with naturally processed peptides from transferrin and albumin, whereas several peptides that represent T cell epitopes of islet autoantigens were poor binders. I-Ag7-peptide complexes were not sodium dodecyl sulfate (SDS) resistant, indicating that SDS sensitivity may be an intrinsic property of I-Ag7. Complexes of I-Ag7 and CLIP formed at a neutral pH, but rapidly dissociated at pH 5. This rapid dissociation was due to a poor fit of M98 of CLIP in the P9 pocket of I-Ag7, since substitution of M98 by a negatively charged residue greatly enhanced the stability of the complex. These biochemical properties of I-Ag7 result in the rapid generation of empty molecules at an endosomal pH and have a global effect on peptide binding by I-Ag7.

Amino Acid Sequence↗
PubMed1999

Disordered water within a hydrophobic protein cavity visualized by x-ray crystallography.

Water in the hydrophobic cavity of human interleukin 1beta, which was detected by NMR spectroscopy but was invisible by high resolution x-ray crystallography, has been mapped quantitatively by measurement and phasing of all of the low resolution x-ray diffraction data from a single crystal. Phases for the low resolution data were refined by iterative density modification of an initial flat solvent model outside the envelope of the atomic model. The refinement was restrained by the condition that the map of the difference between the electron density distribution in the full unit cell and that of the atomic model be flat within the envelope of the well ordered protein structure. Care was taken to avoid overfitting the diffraction data by maintaining phases for the high resolution data from the atomic model and by a resolution-dependent damping of the structure factor differences between data and model. The cavity region in the protein could accommodate up to four water molecules. The refined solvent difference map indicates that there are about two water molecules in the cavity region. This map is compatible with an atomic model of the water distribution refined by using XPLOR. About 70% of the time, there appears to be a water dimer in the central hydrophobic cavity, which is connected to the outside by two constricted channels occupied by single water molecules approximately 40% of the time on one side and approximately 10% on the other.

Computer Simulation↗
PubMed1999

An online locus-specific mutation database for familial hypertrophic cardiomyopathy.

The aim of this locus-specific mutation database was to provide an online resource that contains summarised and updated information on familial hypertrophic cardiomyopathy (FHC)-associated mutations and related data, for researchers and clinicians. It also serves as a means of publishing previously unpublished data, which could be of value in understanding genotype/phenotype correlations. There are 123 FHC-associated mutations catalogued along with ancillary information. By implementing the cgi/http method, remote users can query the database via the HTML interface on the Web browser and obtain data of relevance to them. The online service is available on http://www.angis.org.au/Databases/Heart.

Alternative Splicing↗