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Biomedical subjects

K Wei

Publications and source records attributed to K Wei.

At least 37 records · Page 2Linked to original sources
PubMed2000

Genetic evidence for obesity loci involved in the regulation of body fat distribution in obese type 2 diabetes rat, OLETF.

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese type 2 diabetes in human. Obesity is essential for the onset of type 2 diabetes in this rat. Our present investigation was designed to identify quantitative trait loci (QTLs) contributing to obesity by performing a whole-genome search using 214 F(2) intercross progeny between OLETF and F344 rats. We have identified six QTLs responsible for adiposity indices of fat pads on rat chromosomes 2 (Obs1 for mesenteric fat), 4 (Obs2 for retroperitoneal fat), 8 (Obs3 for mesenteric fat), 9 (Obs4 for retroperitoneal fat), and 14 (Obs5 and Obs6 for retroperitoneal fat), demonstrating that the adiposity indices of individual fat pads were under the control of different genes. As expected, the OLETF allele corresponds to increased adiposity indices for all QTLs, except for Obs3, in which the F344 allele leads to an increase in the index.

Adipose Tissue↗
PubMed2000

Triptolide and chemotherapy cooperate in tumor cell apoptosis. A role for the p53 pathway.

Triptolide (PG490), a diterpene triepoxide, is a potent immunosuppressive agent extracted from the Chinese herb Tripterygium wilfordii. We have previously shown that triptolide blocks NF-kappaB activation and sensitizes tumor necrosis factor (TNF-alpha)-resistant tumor cell lines to TNF-alpha-induced apoptosis. We show here that triptolide enhances chemotherapy-induced apoptosis. In triptolide-treated cells, the expression of p53 increased but the transcriptional function of p53 was inhibited, and we observed a down-regulation of p21(waf1/cip1), a p53-responsive gene. The increase in levels of the p53 protein was mediated by enhanced translation of the p53 protein. Additionally, triptolide induced accumulation of cells in S phase and blocked doxorubicin-mediated accumulation of cells in G(2)/M and doxorubicin-mediated induction of p21. Our data suggest that triptolide, by blocking p21-mediated growth arrest, enhances apoptosis in tumor cells.

Animals↗
PubMed2000

Monte Carlo simulation of single-cell irradiation by an electron microbeam.

A model is presented for irradiation of a cellular monolayer by an electron microbeam. Results are presented for two possible window designs, cells plated on the vacuum-isolation window and cells plated on Mylar above the vacuum-isolation window. Even for the thicker dual-membrane window that facilitates tissue culture and allows the target cell to be centered relative to the electron beam, the majority of the calculated beam spreading was contained in a volume typical of the mammalian HeLa cell line. None of the 10(4) electrons simulated at 25 keV were scattered into the spatial region occupied by neighbors of the target cell. Dose leakage was largest at 50 keV where the mean energy deposited in all neighbors was 21% of that deposited in the target cell. This ratio was reduced to 5% at 90 keV, the highest beam energy simulated. Lineal energy spectra of energy deposition events scored in the nucleus of the target cell became progressively more like the gamma-ray spectrum as the electron beam energy increased. Hence, our simulations provide strong support for the feasibility of a low-LET, single-cell irradiator.

Cell Nucleus↗
PubMed2000

Ribozyme-catalyzed tRNA aminoacylation.

The RNA world hypothesis implies that coded protein synthesis evolved from a set of ribozyme catalyzed acyl-transfer reactions, including those of aminoacyl-tRNA synthetase ribozymes. We report here that a bifunctional ribozyme generated by directed in vitro evolution can specifically recognize an activated glutaminyl ester and aminoacylate a targeted tRNA, via a covalent aminoacyl-ribozyme intermediate. The ribozyme consists of two distinct catalytic domains; one domain recognizes the glutamine substrate and self-aminoacylates its own 5'-hydroxyl group, and the other recognizes the tRNA and transfers the aminoacyl group to the 3'-end. The interaction of these domains results in a unique pseudoknotted structure, and the ribozyme requires a change in conformation to perform the sequential aminoacylation reactions. Our result supports the idea that aminoacyl-tRNA synthetase ribozymes could have played a key role in the evolution of the genetic code and RNA-directed translation.

Acylation↗
PubMed2000

Quantification of the physiological relevance of a coronary stenosis using myocardial contrast echocardiography.

MCE can be used in the catheterization laboratory or in the operating room to provide rapid assessments of the functional significance of a coronary stenosis from direct arterial injections of microbubbles. In the past few years, the development of more stable microbubble contrast agents, and a better understanding of the interactions between ultrasound and microbubbles have led to the development of a truly non-invasive approach to quantify MBF using venous infusions. Furthermore, additional insights into the physiology of coronary stenosis, particularly as it affects MBV, have been obtained using MCE.

Blood Flow Velocity↗
PubMed2000

Relation between regional function and coronary blood flow reserve in multivessel coronary artery stenosis.

In the setting of chronic coronary stenoses, percent wall thickening (%WT) both at rest and during catecholamine stimulation can be abnormal despite normal resting myocardial blood flow (MBF). We hypothesized that this phenomenon is related to abnormal MBF reserve. Accordingly, 15 dogs were studied between 7 and 10 days after placement of Ameroid constrictors around the proximal coronary arteries and their major branches, at a time when collateral development had not yet occurred. %WT and MBF were measured at rest, after 0.56 mg/kg of dipyridamole, and at incremental doses of dobutamine (5-40 microgram. kg(-1). min(-1)). Resting %WT and MBF were normal in all four sham dogs. Resting transmural MBF was normal in all segments in the 11 study dogs, despite reduced (-2 SD of normal) %WT (<30%) in 40 of 82 segments. MBF reserve was reduced (<3) in segments with reduced %WT, and a close coupling was noted between resting %WT and MBF reserve. All segments showed an increase in %WT with dobutamine up to a dose of 20 microgram. kg(-1). min(-1), above which those with abnormal endocardial MBF reserve showed a "biphasic" response. It is concluded that, in the presence of chronic coronary stenoses, abnormalities in resting %WT as well as inducible reduction in %WT during pharmacological stress are related to the degree of abnormal MBF reserve.

Animals↗
PubMed2000

Assessment of resting perfusion with myocardial contrast echocardiography: theoretical and practical considerations.

BACKGROUND: The aim of this study was to perform a quantitative comparison between myocardial contrast echocardiography (MCE) and single-photon emission computed tomography (SPECT) in patients with prior myocardial infarction (MI). We also wanted to determine the optimal method for the intravenous administration of an ultrasound contrast agent in the clinical setting. METHODS AND RESULTS: Seventeen patients with resting perfusion defects in a single vascular territory on SPECT were studied. MCE was performed with intermittent harmonic imaging during continuous infusions of a second-generation ultrasound contrast agent (Sonovue, Bracco Diagnostics) in all 17 patients and after bolus injection in 8 of them. During continuous infusions, the video intensity (VI) ratio between the abnormal and normal myocardium at a pulsing interval (PI) of 8 cardiac cycles correlated well with the activity ratio between these segments on SPECT (r = 0.73, P <.01). When information regarding microbubble velocity (MV) denoted as change in VI with increasing PIs was added, the correlation with SPECT activity ratio improved (P <.05) significantly (r = 0.87, P <.0001). Higher microbubble doses resulted in higher VI during continuous infusions with good myocardial opacification and no far-field attenuation until the highest dose was reached. With bolus injections, the VI ratio between the abnormal and normal myocardium at PI of 1 and 5 cardiac cycles showed a modest correlation (r = 0.46 and r = 0.48, respectively, P <.05) with activity ratios between these regions on SPECT. When a dose of microbubbles administered as a bolus produced adequate myocardial opacification, it invariably resulted in far-field attenuation. CONCLUSIONS: In patients with prior MI, quantitative assessment of resting perfusion defects on MCE correlates well with regional activity on SPECT. Continuous infusions offer an advantage over bolus injections because they can provide an assessment of both relative VI and MV. Adjustment of the microbubble infusion rate produces adequate myocardial opacification without attenuation.

Coronary Circulation↗
PubMed2000

[Assessment of the effects of dipyridamole and dobutamine on coronary microcirculation using myocardial contrast echocardiography].

OBJECTIVES: To evaluate the effects of dipyridamole and dobutamine on myocardial blood flow (MBF) and myocardial blood volume (MBV), and their ability to detect non-flow-limiting coronary stenoses with myocardial contrast echocardiography (MCE). METHODS: Thirteen closed-chest dogs were studied at 7-10 days after placement of ameroid constrictors around proximal coronary arteries and their branches. MBF was measured with radiolabeled microspheres and myocardial plateau video intensity (VI, which indicates relative MBV) and microbubble velocity (beta) were measured with MCE at rest, after dipyridamole (0.56 mg/kg), and during peak dobutamine dose (30-40 micrograms.kg-1.min-1). RESULTS: The effects of both agents on MBF were similar in abnormal and normal segments. Plateau VI increased more and beta increased less with dobutamine than dipyridamole (P < 0.05), but the plateau VI ratios and beta ratios between abnormal and normal segments were almost identical during both drugs (P < NS), resulting in similar perfusion defects. Excellent linear relations were found between the plateau VI ratio or beta ratio and MBF (derived from radiolabeled microspheres) ratio from abnormal and normal beds during dipyridamole and dobutamine. CONCLUSION: Although the effect of dipyridamole and dobutamine on MBV is different, they unmask MBF reserve to a similar extent. Thus, the quantification of stenosis severity is identical using both agents with MCE.

Animals↗
PubMed2000

[The application of auro-galvano-form ceramic crowns in clinic].

OBJECTIVE: To evaluate the effects of auro-galvano-form ceramic crown in clinic. METHODS: The Ni-Cr alloy high-gold alloy and auro-galvano-form ceramic crowns were made respectively. Every kind was 200 pieces. 600 piece crowns were in total for 298 patients. The color of ceramic crowns was checked with Shade Eye. The color, fitness and fracture of ceramic crowns were checked in clinic. RESULTS: The results showed the aurogalvano-form ceramic crowns was similar to high-gold alloy ceramic crowns in color and fitness in clinic (P > 0.05). The effects of them were better than Ni-Cr alloy ceramic crowns in color and fitness significantly (P < 0.05). The fracture of 600 ceramic crowns was not found out in two years. CONCLUSIONS: The effects of auro-galvano-form ceramic crowns were perfect in color, fitness and fracture. It can be used in clinic.

Adolescent↗
PubMed2000

[Myocardial protection and immunoregulation of minor bupleurum decoction and its decomposed preparations on coxsackie B3m viral myocarditis in mice].

OBJECTIVE: To study the effect of Minor Bupleurum Decoction (MBD) and its decomposed preparations, decomposition-1 (DC-1) and decomposition-2 (DC-2) in myocardial protection and immunoregulation on coxsackie virus B3m induced myocarditis in mice. METHODS: Murine model of experimental myocarditis caused by coxsackie virus B3m was developed in Balb/c mice, and were treated by MBD, DC-1 and DC-2. Natural killer (NK) cell activity, T-lymphocyte subsets and histopathological change of myocardium were examined at various times after MBD, DC-1 and DC-2 were taken. RESULTS: (1) MBD and DC-2 could increase the NK cell activity significantly, and also regulate the T-lymphocyte subsets, while DC-1 did not have this kind of effect; (2) All MBD, DC-1 and DC-2 could protect myocardium obviously, the effect of MBD is better than those of its decomposed preparations. CONCLUSION: MBD and DC-2 had bi-directional regulation on NK cell activity and T-cell subsets, all the 3 groups could obviously protect myocardium.

Adjuvants, Immunologic↗
PubMed2000

[Raman and infrared spectroscopic investigation of SO4(2-)/TiO2 solid acids].

The structure, crystal phase transition and surface acid centers of SO4(2-)/TiO2 solid acids calcined at different temperatures were studied by IR and Raman spectroscopy. The results showed that SO4(2-) is combined with metal ions of TiO2 in a chelating bidentate mode. When the calcination temperature is below 500 degrees C, the samples possess stable structure with anatase as the main crystal phase, and there are two types of acid sites (Lewis and Bronsted acid) on the samples, the amount of B acid is about twice as that of L acid. When the temperature is above 500 degrees C, surface SO4(2-) desorb gradually with increasing calcination temperature, leading to crystal phase transition from anatase to rutile and the surface B acid sites fade away.

Acids↗
PubMed2000

[Comparative studies on the spectral behavior between SO4(2-)/TiO2 and TiO2 photocatalysts].

The differences of spectral behavior between SO4(2-)/TiO2 and TiO2 photocatalysts were studied by using IR, Raman as well as UV-Vis diffuse reflectance spectroscopy(DRS). The results showed that both L and B acid sites exist on SO4(2-)/TiO2 photocatalyst while only L acid sites on TiO2 photocatalyst. As compared with unmodified TiO2, the sulfated TiO2 (SO4(2-)/TiO2) exhibits higher resistance to crystal phase transition from anatase to rutile, higher resistance to growth of crystal grain. As the results of sulfation, SO4(2-)/TiO2 samples possess higher anatase content, smaller crystal grain, and the blue-shifted band edge of adsorption spectra, which increases the optical absorption threshold value and yield larger redox potential.

Adsorption↗
PubMed2000

[Characterization of the Pt/CeO2-ZrO2/Al2O3 catalysts by spectra].

The performance of Pt/Al2O3 catalysts with CeO2-ZrO2 in difference ways was studied by NIR-FT-Raman, BET, H2 chemisorption, XRD. It shows that the dispersion of Pt on Al2O3 is improved with the increasing of dispersion of CeO2-ZrO2 on the surface of Al2O3, owing to the strong interacting between CeO2-ZrO2 and Pt. And adding with salts is priority.

Aluminum Oxide↗
PubMed1999

Immobilized sample amplification for quantitative determination of retroviruses.

Immobilized sample amplification (ISA) is a novel method for amplification, detection, monitoring, and quantitative determination of nucleic acids from a minute amount of sample. We present here a novel quantitative ISA assay for retroviruses using a replication-defective recombinant retrovirus as a model retrovirus. Samples, as small as 5 to 10 microl or as large as 1 ml or more in volume, are readily immobilized on a nylon or polyester matrix. Retroviral RNA is directly amplified following the rehydration of the immobilized samples, thus eliminating the needs for retroviral RNA extraction. An ISA assay of a 10-microl viral sample generates results equal to or better than that of RT-PCR on equivalent amount RNA isolated from larger sample volumes. Recovery of RNA from small volumes, such as 10 microl, is almost impossible, whereas ISA assay detects retroviruses from as small as 1 to 5 microl of viral samples containing 10(4) cfu/ml determined by colony-forming assay. Extraction of RNA from a small amount of infectious viral samples not only is a difficult, biohazardous procedure, but also introduces random errors which contribute to variability in viral quantitation. Since the ISA method eliminates the isolation/extraction of the nucleic acids, it significantly shortens the handling time for the biohazardous materials and simplifies the procedure for analyzing small quantities of biological samples. This method detects less than 10 infectious retroviral particles as determined by both colony-forming assay and electron microscope studies. The format and protocol of this quantitative ISA assay can be easily automated to fit into numerous platforms, thus making it attractive for laboratory automation.

3T3 Cells↗
PubMed1999

Mapping and characterization of quantitative trait loci for non-insulin-dependent diabetes mellitus with an improved genetic map in the Otsuka Long-Evans Tokushima fatty rat.

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type, non-insulin-dependent diabetes mellitus (NIDDM) in humans. We have previously reported four quantitative trait loci (QTLs) responsible for NIDDM on Chromosomes (Chrs) 7, 14, 8, and 11 (Nidd1-4/of for Non-insulin-dependent diabetes1-4/oletf) by a whole-genome search in 160 F2 progenies obtained by mating the OLETF and the Fischer-344 (F344) rats. Our present investigation was designed to identify and characterize novel QTLs affecting NIDDM by performing a genome-wide linkage analysis of genes for glucose levels and body weight and analysis for gene-to-gene and gene-to-body-weight interactions on an improved genetic map with a set of 382 informative markers in the 160 F2 progenies. We have identified seven novel QTLs on rat Chrs 1 (Nidd5 and 6/of), 5 (Nidd7/of), 9 (Nidd8/of), 12 (Nidd9/of), 14 (Nidd10/of) and 16 (Nidd11/of) which, together with the Nidd1-4/of, account for a total of approximately 60% and approximately 75% of the genetic variance of the fasting and postprandial glucose levels, respectively, in the F2. While the OLETF allele corresponds with increased glucose levels as expected for the novel QTLs except Nidd8 and 9/of, the Nidd8 and 9/of exhibit heterosis: heterozygotes showing significantly higher glucose levels than OLETF or F344 homozygotes. There are epistatic interactions between Nidd1 and 10/of and between Nidd2 and 8/of. Additionally, our results indicated that the Nidd6 and 11/of could also contribute to an increase of body weight, and that the other five QTLs could show no linkage with body weight, but Nidd8,9, and 10/of have an interaction with body weight.

Animals↗
PubMed1999

Identification of novel non-insulin-dependent diabetes mellitus susceptibility loci in the Otsuka Long-Evans Tokushima fatty rat by MQM-mapping method.

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type, non-insulin-dependent diabetes mellitus (NIDDM) in humans. We have previously identified 11 quantitative trait loci (QTLs) responsible for NIDDM susceptibility on Chromosomes (Chrs) 1, 5, 7, 8, 9, 11, 12, 14, and 16 (Nidd1-11/of for Non-insulin-dependent diabetes 1-11/oletf) by using the interval mapping method in 160 F(2) progenies obtained by mating the OLETF and the Fischer-344 (F344) rats. MQM-mapping, which was applied for QTL analysis based on multiple-QTL models, is reported to be more powerful than interval mapping, because in the process of mapping one QTL the genetic background, which contains the other QTLs, is controlled. Application of MQM-mapping in the F(2) intercrosses has led to a revelation of three novel QTLs on rat Chrs 5 (Nidd12/of), 7 (Nidd13/of), and 17 (Nidd14/of), in addition to Nidd1-11/of loci. The three QTLs, together with the Nidd1-11/of, account for a total of approximately 70% and approximately 85% of the genetic variance of the fasting and postprandial glucose levels, respectively, in the F(2). While the OLETF allele corresponds with increased glucose levels as expected for Nidd12 and 14/of, the Nidd13/of exhibits heterosis: heterozygotes showing significantly higher glucose levels than OLETF or F344 homozygotes. There is epistatic interaction between Nidd2 and 14/of. Additionally, our results indicated that the novel QTLs could show no linkage with body weight, but Nidd12/of has an interaction with body weight.

Animals↗
PubMed1999

Potential advantage of flash echocardiography for digital subtraction of B-mode images acquired during myocardial contrast echocardiography.

Optimal assessment of myocardial perfusion with contrast echocardiography by using B-mode imaging often requires image alignment and background subtraction, which are time consuming and need extensive expertise. Flash echocardiography is a new technique in which primary images are gated to the electrocardiogram and secondary images are obtained by transmitting ultrasound pulses in rapid succession after each primary image. Myocardial opacification is seen in the primary image and not in the secondary images because of ultrasound-induced bubble destruction. Because the interval between the primary and first few secondary images is very short, cardiac motion between these images should be minimal. Therefore we hypothesized that 1 or more secondary images could be subtracted from the primary image without the need for image alignment. The ability of ultrasound to destroy microbubbles was assessed by varying the sampling rate, line density, and mechanical index in 6 open-chest dogs. The degree of translation between images was quantified in the x and y directions with the use of computer cross-correlation. At sampling rates of 158 Hz or less and a mechanical index of more than 0.6, videointensity rapidly declined to baseline levels by 25 ms. Significant translation between images was noted only at intervals of more than 112 ms. It is concluded that flash echocardiography can be used for digital subtraction of baseline from contrast-enhanced B-mode images without image alignment. Background subtraction is therefore feasible on-line, potentially eliminating the need for off-line image processing in the future.

Animals↗