Biomedical subjects

Y C Li

Publications and source records attributed to Y C Li.

At least 91 records · Page 5Linked to original sources

PubMed1997

Propofol induces a lowering of free cytosolic calcium in myocardial cells.

BACKGROUND: The intravenous anaesthetic drug propofol has been shown to depress myocardial contractility. Ketamine, on the other hand, is a well-documented cardiovascular stimulant. These differences could possibly be due to different effects of the drugs on the calcium homeostasis of the myocardium. METHODS: The fluorescent intracellular probe fura-2 acetoxymethyl ester (fura-2/AM) was used in this in vitro investigation to study the influence of intravenous anaesthetic drugs on free cytosolic calcium concentration in suspensions of isolated rat myocardial cells. RESULTS: Addition of 0.5-2.0 micrograms/mL propofol resulted in a significant and dose-dependent decrease of free cytosolic calcium concentration in the myocardial cells, while addition of 0.25-2.5 micrograms/mL ketamine did not affect this concentration significantly. CONCLUSION: The results imply that the previously demonstrated negative inotropic effect of propofol could possibly be related to its influence on calcium availability in the myocardium.

Anesthetics, Intravenous↗

PubMed1997

Cloning and characterization of the vitamin D receptor from Xenopus laevis.

The Vitamin D receptor (VDR), a member of the nuclear receptor superfamily, mediates the effects of 1,25-dihydroxyvitamin D3 on mineral ion homeostasis. Although the mammalian and avian VDRs have been extensively studied, little is known about the VDR in lower vertebrate species. To address this, we have isolated the Xenopus laevis VDR (xVDR) complementary DNA. Overall, the xVDR shares 79%, 73%, 73%, and 75% identity at the amino acid level with the chicken, mouse, rat, and human VDRs, respectively. The amino acid residues and subdomains important for DNA binding, hormone binding, dimerization, and transactivation are mostly conserved among all VDR species. The xVDR polypeptide can heterodimerize with the mouse retinoid X receptor alpha, bind to the rat osteocalcin vitamin D response element (VDRE), and induce vitamin D-dependent transactivation in transfected mammalian cells. Northern analysis reveals two xVDR messenger RNA species of 2.2 kb and 1.8 kb in stage 60 Xenopus tissues. In the adult, xVDR expression is detected in many tissues including kidney, intestine, skin, and bone. During Xenopus development, xVDR messenger RNA first appears at developmental stage 13 (pre-neurulation), increasing to maximum at stages 57-61 (metamorphosis). Our data demonstrate that, in Xenopus, VDR expression is developmentally regulated and that the vitamin D endocrine system is highly conserved during evolution.

Aging↗

PubMed1996

Neonatal jaundice and molecular mutations in glucose-6-phosphate dehydrogenase deficient newborn infants.

Molecular mutations of the glucose-6-phosphate dehydrogenase (G6PD) gene and clinical manifestations of neonatal jaundice in 112 male and 50 female Chinese neonates with G6PD deficiency were studied. In the 112 males, the nucleotide (nt) 1376 (G-->T) mutation was the dominant type (50.0%), followed by nt 1388 (G-->A) (16.1%), nt 493 (A-->G) (8.0%), nt 1024 (C-->T) (6.2%), nt 95 (A-->G) (5.4%), nt 392 (G-->T) (1.8%), nt 487 (G-->A) (1.8%), nt 871 (G-->A) (0.9%), and nt 1360 (C-->T) (0.9%). The nt 871 variant has not been reported in Taiwan before. The occurrence rates for nt 1376, nt 1388, nt 493, nt 95, and nt 1024 mutations in the 50 females were 44.0%, 18.0%, 12.0%, 6.0%, and 6.0%, respectively. The type of G6PD mutation in 10 male and 7 female neonates has not been identified yet. Although G6PD deficient neonates had higher frequency of phototherapy than G6PD normal neonates in both sexes, a significant difference in the prevalence of hyperbilirubinemia (peak bilirubin > or = 15.0 mg/dl) between G6PD deficient and normal neonates was found only in males. Further analysis showed that duration of phototherapy was longer in G6PD deficient male neonates than in the control group, while the outcome of phototherapy was better in subjects with non-nt 1376 mutations than subjects with the nt 1376 mutation. Most (78.3%) of the 23 G6PD deficient neonates who subsequently suffered from neonatal hyperbilirubinemia carried the nt 1376 mutation. The results of this study indicate that the nucleotide substitution at 1376 is the most common and important mutation for G6PD deficiency in Chinese neonates in Taiwan.

Base Sequence↗

PubMed1996

High-level production of uniformly ¹⁵N- and ¹³C-enriched fusion proteins in Escherichia coli.

An approach to produce 13C- and 15N-enriched proteins is described. The concept is based on intracellular production of the recombinant proteins in Escherichia coli as fusions to an IgG-binding domain, Z, derived from staphylococcal protein A. The production method provides yields of 40-200 mg/l of isotope-enriched fusion proteins in defined minimal media. In addition, the Z fusion partner facilitates the first purification step by IgG affinity chromatography. The production system is applied to isotope enrichment of human insulin-like growth factor II (IGF-II), bovine pancreatic trypsin inhibitor (BPTI), and Z itself. High levels of protein production are achieved in shaker flasks using totally defined minimal medium supplemented with 13C(6)-glucose and (15NH4)2SO4 as the only carbon and nitrogen sources. Growth conditions were optimized to obtain high protein production levels and high levels of isotope incorporation, while minimizing 13C(6)-glucose usage. Incorporation levels of 13C and/or 15N isotopes in purifies IGF-II, BPTI, and Z were confirmed using mass spectrometry and NMR spectroscopy. More than 99% of total isotope enrichment was obtained using a defined isotope-enriched minimal medium. The optimized systems provide reliable, high-level production of isotope-enriched fusion proteins. They can be used to produce 20-40 mg/l of properly folded Z and BPTI proteins. The production system of recombinant BPTI is state-of-the-art and provides the highest known yield of native refolded BPTI.

Animals↗

PubMed1996

Influence of alkaline buffers on cytoplasmic pH in myocardial cells exposed to metabolic acidosis.

The influence of different clinically used alkaline buffers on cytoplasmic pH in normal as well as acidotic rat myocardial cells was investigated in this study by means of the fluorescent intracellular probe 2',7'-bis-(carboxyethyl)-5,6-carboxyfluorescein acetoxymethyl ester (BCECF-AM). It was shown that both sodium bicarbonate and Tris buffer mixture (Tribonat) caused a significant and dose-dependent acidification of the cytoplasm of suspended myocardial cells with normal initial intracellular pH. This decrease was followed by a slow increase during the observation period. The initial cytoplasmic pH value was more easily reached when Tris buffer mixture was used. Ringer's acetate also caused a decrease of intracellular pH, but this change persisted and was further amplified during the experiment. Carbicarb in larger dosages as well as pure trometamol (Tris) caused a pronounced dose-dependent and lasting intracellular alkalinization. Intracellular acidosis was achieved by preincubating the cells in sodium acetate. Addition of sodium bicarbonate caused an initial and dose-dependent acidification of the cytoplasm followed by a slow increase to values slightly above the induced acidosis. In contrast, Tris buffer mixture showed a tendency towards an initial acidification only when larger dosages were used, and correction of the induced acidosis was possible by use of moderate to large volumes. Ringer's acetate produced a lasting and dose-dependent decrease of cytoplasmic pH, while Carbicarb and pure trometamol caused an immediate, pronounced and persistent alkalinization. Myocardial cells with low initial cytoplasmic pH due to preincubation in an acid buffer also showed an early decrease of intracellular pH after addition of sodium bicarbonate and Tris buffer mixture. In the case of sodium bicarbonate correction of the acid-base disturbance was not achieved during the observation period, while this was accomplished by use of larger volumes of Tris buffer mixture. Carbicarb in larger volumes caused an increase in intracellular pH. The most significant and persistent increases of cytoplasmic pH was achieved by use of pure trometamol. In conclusion, the present in vitro study implies that Tris buffer mixture (Tribonat) is well-suited for correction of intracellular acidosis since it acts without causing a pronounced initial intracellular acidosis or a later potentially hazardous huge cytoplasmic alkalinization.

Animals↗

PubMed1996

A new ultrasonic method for measuring minute motion activities of rats.

A new ultrasonic method is presented for measuring the minute motion activities of rats. A pair of low-cost 40 kHz ultrasonic transducers are used to transmit ultrasound toward a rat and receive the ultrasound reflected from the rat. The relative motion of the rat modulates the phase difference between the transmitted and received ultrasound signals. An 8-bit digital phase meter was designed to record the phase difference signal which was used to reconstruct the relative motion waveform of the rat in an 8751 single-chip microcomputer. The reconstructed data are then sent to a PC-AT microcomputer for further processing. This method employs a spectrum analysis for the reconstructed data and can measure three minute motion activities including locomotor activity (LMA), tremor and myoclonia. Finally, the method has been tested with real animal experiments. The main advantages of this new method are that it is non-invasive, non-contact, low cost and high precision. This new method could also be profitably employed for other behavioral studies and offer potential for research in basic medicine.

Animals↗

PubMed1996

The MoAb-V kappa IIIb cross-reactive idiotope on A27a (Humkv325) encoded kappa chains maps to framework region 3. off.

The monoclonal antibody MoAb-V kappa IIIb binds a cross-reactive idiotopic (CRI) determinant on light (L) chains encoded by the V kappa IIIb subgroup A27a (Humkv325) gene segment. The aim of this study was to localize the MoAb-V kappa IIIb CRI. Mutational analyses involving region exchanges between a CRI-positive V kappa IIIb chain and a CRI-negative V kappa 1 chain indicate that the MoAb-V kappa IIIb CRI is located in framework region (FR) 3 of A27a (Humkv325) encoded L chains. CRI-positive kappa chains unpaired with a heavy (H) chain are reactive with MoAb-V kappa IIIb, indicating that the CRI is located on the kappa chain alone without involvement of H chain residues. Combinatorial antibodies composed of non-parental L and H chain pairings are reactive with MoAb-V kappa IIIb only when the L chain is A27a (Humkv325) encoded. The CRI, therefore, is not readily perturbed by H chain interactions. When the FR3 from a CRI-positive kappa chain replaced the FR3 in a CRI-negative lambda chain, the determinant was no longer detectable with MoAb-V kappa IIIb. It is possible, therefore, to exchange regions between kappa chains from different families and retain the CRI structure, however the determinant is lost when placed in a more foreign background such as a lambda chain. These data more precisely define the interaction between MoAb-V kappa IIIb and its CRI, and indicate that there are limits within which antibody FRs can be shuffled and still retain their native structural features.

Amino Acid Sequence↗

PubMed1996

Effect of tris buffer on free cytosolic calcium in myocardial cells.

OBJECTIVE: To study the effect of tris buffer on free cytosolic calcium in vitro. DESIGN: Open, randomized, control trial of dispersed rat myocardial cells. SETTING: Experimental laboratory in a large university hospital. SUBJECTS: Dispersed myocardial cells from Sprague-Dawley rats. INTERVENTIONS: The influences of pure trometamol (tris) and a tris butter mixture, as well as conventional sodium bicarbonate on free cytosolic calcium in suspended rat myocardial cells were studied with the fluorescent intracellular probe fura-2. MEASUREMENTS AND MAIN RESULTS: Addition of pure trometamol (tris) resulted in a significant increase of free cytosolic calcium in myocardial cells suspended in a buffer containing 1.25 mM of ionized calcium. The actions of trometamol display a dose-dependency in relation to the concentration of external ionized calcium since the ionized calcium response was reduced in a buffer with 0.5 mM of extracellular ionized calcium. Furthermore, removal of external ionized calcium totally prevented trometamol induced increases of ionized calcium, indicating that this increase is dependent on transmembrane ionized calcium fluxes. When tris buffer mixture was investigated in 1.25 mM of calcium, as well as 0.5 mM of external ionized calcium, a decrease of ionized calcium was noted initially, followed by an increase during the observation period. Addition of sodium bicarbonate to the two experimental settings resulted in a more prominent initial decrease of ionized calcium, followed by a slower increase which did not reach the initial values during the 20-min observation period. Extracellular pH was also included as a variable. When the cells were suspended in a buffer containing 1.25 mM of ionized calcium with a pH of 6.80 instead of 7.40 (as above), addition of pure trometamol also resulted in an increase of ionized calcium; however, after 20 mins this increase was smaller as compared with the results above. When tris buffer mixture as well as sodium bicarbonate was added, initial decreases of ionized calcium were recorded, followed by smaller increases during the observation period, compared with the increase in buffers with a pH of 7.40. CONCLUSIONS: Pure trometamol (tris) induces an increase in free cytosolic calcium in suspended myocardial cells.

Animals↗

PubMed1996

The determination of radioisotope levels in municipal sewage sludge.

Sludge samples from 25 municipal waste water treatment plants have been analyzed to determine the level of environmentally present, man-made, gamma-ray emitting radioisotopes. Samples were freeze dried and separated into dried sludge, liquid-soluble and liquid-insoluble components. These were counted in the low background level, whole body counter at Missouri University using a standard intrinsic-Germanium spectrometer. After freeze drying, the liquid effluents from the samples were not found to have statistically significant levels of radioactivity. Using log-normal analysis, the dried sludge was found to have 0.0016 +/- 0.0022 Bq g-1 (0.04 +/- 0.06 pCi g-1) of 137Cs and 0.001 +/- 0.003 Bq g-1 (0.03 +/- 0.08 pCi g-1) of 60Co. These data can be used to determine if sewage effluents from nuclear facilities have levels of radioactivity above that expected from the environment.

Sewage↗

PubMed1995

Human type-alpha transforming growth factor undergoes slow conformational exchange between multiple backbone conformations as characterized by nitrogen-15 relaxation measurements.

Human type-alpha transforming growth factor (hTGF alpha) is a small mitogenic protein containing 50 amino acids and three disulfide bonds. It has both sequence and structural homology with epidermal growth factor (EGF). While the three-dimensional structures of hTGF alpha and other EGF-like proteins have been studied extensively, relatively little is known about conformational dynamics of these molecules. In this paper we describe nuclear relaxation measurements which probe the molecular dynamics of hTGF alpha in aqueous solution at neutral pH. In order to characterize conformational dynamics of hTGF alpha on both the fast (i.e., sub-nanosecond) and intermediate nitrogen-15 chemical-exchange (i.e., microsecond) time scales, we measured nitrogen-15 relaxation parameters at pH 7.1 +/- 0.1 and a temperature of 30 +/- 0.5 degrees C. Measurements of nitrogen-15 longitudinal (R1) and transverse (R2) relaxation rates, and 1H-15N heteronuclear NOE effects, were then interpreted using an extended Lipari-Szabo analysis [Lipari, G., & Szabo, A. (1982) J. Am. Chem. Soc. 104, 4546-4559; Clore, G. M., Szabo, A., Bax, A., Kay, L. E., Driscoll, P. C., & Gronenborn, A. M. (1990) J. Am. Chem. Soc. 112, 4989-4991] to provide estimates of the locations and amplitudes of fast internal motions and the locations of nitrogen-15 chemical-exchange line broadening. These results demonstrate that, under conditions of pH and temperature at which it is tightly bound by the EGF receptor, hTGF alpha is a highly dynamic molecule. Indeed, some 40% of the backbone amide groups of hTGF alpha, including many at the interface between the two subdomains, exhibit significant nitrogen-15 chemical-exchange line broadening indicative of interconversions between multiple protein conformations on the microsecond time scale. The distribution of these sites on the three-dimensional protein structure suggests that these dynamic fluctuations are due to (i) partial unfolding of the core beta-sheet, (ii) hinge-bending motions between the N- and C-terminal subdomains, and/or (iii) disulfide bond isomerization in the solution structure of hTGF alpha at neutral pH.

Amino Acid Sequence↗

PubMed1995

A transcriptional enhancer of the glutamine synthetase gene that is selective for retinal Müller glial cells.

This article demonstrates that the chicken glutamine synthetase (GS) promoter contains cis-acting elements that direct transcription to retinal Müller glial cells. The transient assay system developed to identify these elements involved electroporation of intact retinal tissue with GS-beta-galactosidase fusion genes followed by preparation of primary cultures and histochemical assay of cells expressing beta-galactosidase. Plasmids containing beta-galactosidase under transcriptional control by two different viral promoters are expressed primarily in neuronal cells after transfection of intact embryonic d 12 retina. In sharp contrast, expression is primarily in Müller glia after transfection with a GS-beta-galactosidase fusion gene. Although GS is glucocorticoid inducible, steroid hormone is not required to achieve Müller cell-selective expression of the GS-beta-galactosidase fusion gene. Deletion studies indicate that multiple cis-acting elements located between nucleotides-436 and -61 relative to the GS transcription start site contribute to produce Müller cell selectivity. Moreover, these upstream elements enhance expression of a heterologous promoter in Müller cells not neurons. These results indicate that an enhancer located between 61 and 436 nucleotides upstream of the transcription start site contributes to Müller cell-selective expression of the GS gene in the retina.

Animals↗

PubMed1995

Assessing the behavioral impact of a diagnostic decision support system.

This paper describes a prototype for research to evaluate the impact of diagnostic decision support systems on the behavior of physicians. Several indices that can be used to quantify the magnitude of impact are proposed. A large medical diagnostic knowledge base in internal medicine (the Iliad knowledge base) was used in this evaluation. The impact on behavior when different inference models are run against this knowledge base is evaluated for two different case domains and physician's specialties.

Analysis of Variance↗

PubMed1994

Transactivation of the 'promoterless' luciferase-encoding vectors pXP1 and pXP2 by C/EBP alpha.

Transactivation of the firefly luciferase-encoding vectors, pXP1 and pXP2, by the alpha isoform of CCAAT/enhancer-binding protein (C/EBP) is reported. Thus, these vectors are not 'promoterless' in every cellular context, and transactivation by C/EBP or a closely related factor should be considered as a possible explanation for the relatively high background levels of luciferase production that are occasionally observed after transfection of certain cells with these or other similar vectors.

Animals↗

PubMed1994

Overcoming solvent saturation-transfer artifacts in protein NMR at neutral pH. Application of pulsed field gradients in measurements of 1H-15N Overhauser effects.

Artifacts due to solvent saturation-transfer effects result in incorrect measurements of 1H-15N heteronuclear NOE (HNOE). These artifacts are commonly observed in aqueous protein solutions at neutral pH. We describe the application of pulsed field gradients (PFGs) together with long recycle delays in overcoming errors in HNOE measurements which arise from H2O solvent preirradiation and solvent saturation transfer. Even in the absence of explicit solvent irradiation, the HNOE pulse sequence itself results in a nonequilibrium spin-state distribution of solvent nuclei which can then be transferred by chemical exchange into amide-proton sites. This effect can be avoided by using PFGs for suppression of solvent H2O together with a recycle delay sufficiently long for the magnetization of water to relax back to equilibrium values during the preparation period. These effects were studied in 15N-enriched human type alpha transforming growth factor at pH 7.1. Comparisons of PFG-HNOE experiments with and without selective H2O irradiation and with different recycle times provide estimates of the effects of solvent irradiation on HNOE measurements, which are different for different amide nitrogen-15 nuclei. The amplitudes of these artificial HNOE enhancements are roughly correlated with solvent accessibilities of amide sites in the three-dimensional structure of hTGF alpha.

Artifacts↗

PubMed1994

Effects of brewer's yeast on glucose tolerance and serum lipids in Chinese adults.

This study was designed to investigate the supplemental effects of brewer's yeast on serum glucose and lipids in Chinese adults. Twenty-two participants (8 males and 14 females) were recruited from Pingtung city. Mean age of the group was 51 yr, and fasting values of total cholesterol and glucose were from 3.21 to 6.90 and 4.3 to 6.2 mmol/L, respectively. Before supplementation, a 75 g oral glucose load was administered after an overnight (9 h) fast. Blood was drawn before and at 30, 60, 90, and 120 min after the glucose load. The subjects were randomly assigned into either brewer's yeast or torula yeast group and consumed 10 g yeast powder daily for 12 wk. Brewer's yeast demonstrated a beneficial effect on decreasing serum triacylglycerol values (p < 0.05). The brewer's yeast supplemented group had an increment at 0 min (p < 0.01) and significant decrements at 60 (p < 0.05) and 90 (p < 0.01) min of oral glucose tolerance test (OGTT). However, after 12-wk supplementation, torula yeast increased glucose values at both 0 and 30 min (p < 0.05) after a glucose load. Brewer's yeast and torula yeast addition significantly altered glucose concentrations at 60 min after the glucose dosage (p < 0.05). Brewer's yeast had significantly decreasing effects on insulin output both at 90 (p < 0.05) and 120 min (p < 0.01) after the glucose load. Likewise, serum insulin contents decreased at 90 min (p < 0.01) after supplementation in the group given torula yeast. Brewer's yeast supplementation had beneficial effects both on serum triacylglycerol and on 60-min and 90-min glucose values of OGTT.

Adult↗

PubMed1994

Clinical evaluation of a renal mass diagnostic expert system.

In this paper, we describe our clinical evaluation of the diagnostic accuracy of the renal mass diagnostic system (RMDS) and of seven physicians. To investigate the value of intravenous urography (IVU) and/or retrograde urography (RU) in diagnosing renal parenchymal tumors and tumors of the renal pelvis, RMDS and the seven physicians were tested with and without the information regarding IVU/RU at two different times. From this study we believe that RMDS can help residents in making more accurate presurgical renal mass diagnosis, and may eliminate the need for IVU/RU in the diagnosing process for a specific group of patients.

Adolescent↗

PubMed1994

A high-precision ultrasonic system for vertical movement counts in rats.

A microcomputer-aided ultrasonic system was used to measure vertical displacement of rats in response to drug injection. The system utilizes an inexpensive PC/AT microcomputer for data collection and can distinguish between number of vertical movements of small (i.e., greater than 5 mm, but less than 15 mm), and large (i.e., greater than 15 mm) displacements. In addition, rest time denotes the time elapsed for the vertical motion of less than 5-mm displacements. As little as 0.32 mg/kg of d-amphetamine increased the average amount of both small and large activity (i.e., number of movements), but decreased the average amount of rest time in rats. On the contrary, as little as 2.5 mg/kg of chlorpromazine decreased the average amount of both small and large activity, but increased the rest time in rats. When the animal activity was measured with an infrared light system, the activity responses to drugs were not detectable. Thus, it appears that the ultrasonic method provides a high-precision system for measuring animal behaviors.

Animals↗

PubMed1994

The cross-reactive idiotopes recognized by the monoclonal antibodies 9G4 and LC1 are located in framework region 1 of two non-overlapping subsets of human VH4 family encoded antibodies.

The monoclonal anti-idiotopic antibodies LC1 and 9G4 bind two non-overlapping sets of VH4 encoded antibodies. 9G4 exclusively binds VH4-21 encoded antibodies, while LC1 binds antibodies derived from VH4 family gene segments V71-2, V71-4, VH4-18, VH72-1 and V2-1. The VH4-21 gene segment is utilized by most cold agglutinin (CA) antibodies with I/i specificity, while antibodies encoded by other VH4 gene segments are associated not with CA disease, but primarily with rheumatoid-factor (RF) activity. We previously determined that the idiotope to which 9G4 binds in VH4-21-derived antibodies is located in framework region 1 (FR1). In the present study, by using mutational analysis involving individual framework- and complementarity-determining region exchanges between VH4-21- and V71-2-encoded antibodies, we have found that the idiotope to which LC1 binds in V71-2-derived antibodies also maps to FR1. The LC1 idiotope is heavy (H)-chain associated, but requires pairing with a light (L) chain for LC1 binding. Recombinant antibodies composed of a variety of kappa (kappa) and lambda (lambda) L chains paired with either a V71-2 or VH4-21 chain were produced in the baculovirus expression system. LC1 bound all of the kappa-containing antibodies but did not bind the V71-2-encoded H chain alone nor to the two lambda-containing antibodies. This experiment demonstrates that not all light chains exert equivalent influence on the conformation of the H-chain idiotope. These results indicate that the FR1 of VH4-encoded antibodies is immunogenic and suggest a physiological role of FR1 during an immune response.

Amino Acid Sequence↗