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Biomedical subjects

Y G Wu

Publications and source records attributed to Y G Wu.

13 recordsLinked to original sources
PubMed2001

Congenital lactic acidosis: evaluation of the properties of the a199t natural variant of human pyruvate dehydrogenase e1alpha by in vitro mutation.

One cause of congenital lactic acidosis is a mutation in the E1 alpha-subunit of the pyruvate dehydrogenase multienzyme complex. Little is known about the consequences of these mutations at the enzymatic level. Here we study the A199T mutation by expressing the protein in Escherichia coli. The specific activity is 25% of normal and the K(m) for pyruvate is elevated by 10-fold. Inhibitors of lactate dehydrogenase might be a useful therapy for patients with such mutations.

Acidosis, Lactic↗
PubMed2001

Medical image compression by discrete cosine transform spectral similarity strategy.

Due to the bandwidth and storage limitations, medical images must be compressed before transmission and storage. However, the compression will reduce the image fidelity, especially when the images are compressed at lower bit rates. The reconstructed images suffer from blocking artifacts and the image quality will be severely degraded under the circumstance of high compression ratios. In this paper, we present a strategy to increase the compression ratio with simple computational burden and excellent decoded quality. We regard the discrete cosine transform as a bandpass filter to decompose a sub-block into equal-sized bands. After a band gathering operation, a high similarity property among bands is found. By the utilization of similarity property, the bit rate of compression can be greatly reduced. Meanwhile, the characteristics of the original image are not sacrificed. Thus, it can avoid the misdiagnosis of diseases for doctors. Simulations are carried to different kind of medical images to demonstrate that the proposed method achieves better performance when compared to other existing transform coding scheme as the JPEG in terms of bit rate and quality. For the case of angiogram image, its peak signal-to-noise-ratio gain is 13.5 dB at the same bit rate of 0.15 bits per pixel when comparing to the JPEG compression. As to the other kind of medical images, their benefits are not so obvious as an angiogram image; however, the gains for them are still from 4-8 dB at high compression ratios. Two doctors from the Department of Radiology, National Cheng Kung University Hospital, Tainan, Taiwan, R.O.C., and Chang Gung Medical Hospital, Kaoshuing, Taiwan, R.O.C., are invited to verify the decoded image quality; the diagnoses of all the test images are correct when the compression ratios are below 20.

Algorithms↗
PubMed2000

Mutagenesis at asp27 of pyruvate decarboxylase from Zymomonas mobilis. Effect on its ability to form acetoin and acetolactate.

Pyruvate decarboxylase (PDC) is one of several enzymes that require thiamin diphosphate (ThDP) and a bivalent cation as essential cofactors. The three-dimensional structure of PDC from Zymomonas mobilis (ZMPDC) shows that Asp27 (D27) is close to ThDP in the active site, and mutagenesis of this residue has suggested that it participates in catalysis. The normal product of the PDC reaction is acetaldehyde but it is known that the enzyme can also form acetoin as a by-product from the hydroxyethyl-ThDP reaction intermediate. This study focuses on the role of D27 in the production of acetoin and a second by-product, acetolactate. D27 in ZMPDC was altered to alanine (D27A) and this mutated protein, the wild-type, and two other previously constructed PDC mutants (D27E and D27N) were expressed and purified. Determination of the kinetic properties of D27A showed that the affinity of D27A for ThDP is decreased 30-fold, while the affinity for Mg2+ and the Michaelis constant for pyruvate were similar to those of the wild-type. The time-courses of their reactions were investigated. Each mutant has greatly reduced ability to produce acetaldehyde and acetoin compared with the wild-type PDC. However, the effect of these mutations on acetaldehyde production is greater than that on acetoin formation. The D27A mutant can also form acetolactate, whereas neither of the other mutants, nor the wild-type PDC, can do so. In addition, acetaldehyde formation and/or release are reversible in wild-type ZMPDC but irreversible for the mutants. The results are explained by a mechanism involving thermodynamic and geometric characteristics of the intermediates in the reaction.

Acetaldehyde↗
PubMed2000

An adaptive 3-D discrete cosine transform coder for medical image compression.

In this communication, a new three-dimensional (3-D) discrete cosine transform (DCT) coder for medical images is presented. In the proposed method, a segmentation technique based on the local energy magnitude is used to segment subblocks of the image into different energy levels. Then, those subblocks with the same energy level are gathered to form a 3-D cuboid. Finally, 3-D DCT is employed to compress the 3-D cuboid individually. Simulation results show that the reconstructed images achieve a bit rate lower than 0.25 bit per pixel even when the compression ratios are higher than 35. As compared with the results by JPEG and other strategies, it is found that the proposed method achieves better qualities of decoded images than by JPEG and the other strategies.

Biomedical Engineering↗
PubMed1996

Laboratory evaluation on the toxic effects of bednets impregnated with permethrin against malaria mosquitos.

In the laboratory, bednets impregnated with 250mg ai/m2 and 500mg ai/m2 permethrin caused respectively the mean mortalities of 86.6% within 13 months and 87.2% within 17 months on laboratory-bred An. sinensis, while they caused average mortalities of 58.3% within 4 months and 73.8% within 10 months on An. dirus respectively. The bioassay results of KT50 and LT50 on the two species showed that KT50 is shorter than LT50 after exposure to the treated bednets. The ratio is 1:2.16 - 1:3.05. It was observed Anopheles had obviously secondary knocked down after exposure to the treated bednets and there is obvious resurgent after Anopheles have been knocked down. When the temperature goes up the resurgence gets shorter, the resurgence rate gets higher and the mortality gets lower. It showed that permethrin has stronger knocking down effect than killing effect.

Animals↗
PubMed1994

[Application of microsurgical technique in the intrasinus renalis pyeloureteroplasty in pelvic atresia in children].

Seven cases of pelvic atresia in children were treated by the intrasinus renalis pyeloureteroplasty with the application of microsurgical technique. The site of pelviureteric anastomosis was unobstructed and the hydronephrosis was greatly improved through postoperative examinations of intravenous urography and renogram. This procedure provides clear field, simple performance and high successful rate. The prevention of complete pelviureteric laceration and pelvic atresia in children, the advantages of the microsurgical technique, and the operation precautions are discussed.

Adolescent↗
PubMed1993

Experimental studies on peripheral nerve regeneration enhanced by nerve growth factor.

The effect of exogenous nerve growth factor (NGF) examined on the neural repair of adult rabbit sciatic nerve was evaluated in the present study. A nerve regeneration chamber was created by suturing the proximal and distal ends of a transected sciatic nerve into a silicone chamber. A gap of 6 mm in chamber was left after removal of a 3 mm piece of nerve in the distal ends and insertion of the proximal and distal stumps into the chamber. Animals were operated on bilaterally, one side of the chamber was filled with a 1 mg/ml NGF/normal saline (NS) (experimental) and the contralateral side with NS (control). The regenerated nerves from within the silicone chamber were dissected and fixed 1 to 5 weeks following surgery for histological studies at both the light microscopic and ultrastructural levels. The NGF chamber showed a more mature regenerated nerve based on a larger diameter of the regenerated nerve trunk, a great number of axons, and thicker myelin sheaths.

Animals↗
PubMed1989

Clinical application of the forearm island skin and fascia flap with posterior interosseous artery pedicle--report of 15 cases.

The present paper reported 15 cases, in which skin and fascia forearm island flap with posterior interosseous artery pedicle was applied. It was found that this flap has the advantages of stable vessels, abundance in blood supply and good circulation, without sacrificing the main arteries of the forearm. As a result, it is an ideal method for repair and reconstruction of the hand and forearm.

Adolescent↗
PubMed1988

Observations on renal function in workers exposed to lead.

Renal function was studied in 40 workers chronically exposed to lead at a smelter. The geometric means of lead were 40 (range 24.0 - 63.0) micrograms/dl in blood and 47 (range 19 - 115) micrograms/g creatinine or 71 (range 20 - 250) micrograms/l in urine, respectively. There were no significant differences between the lead-exposed group and a control group in the concentrations of beta 2-microglobulin in serum, urinary total protein and IgG, whereas the level of beta 2-microglobulin in urine was significantly higher in the lead-exposed group (p less than 0.01). No individual lead worker showed abnormally increased level of urinary beta 2-microglobulin. The significance of increased excretion of beta 2-microglobulin on the basis of the group remains to be elucidated.

Environmental Exposure↗