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Biomedical subjects

S Yang

Publications and source records attributed to S Yang.

At least 469 records · Page 26Linked to original sources
PubMed1995

Detection of p21ras mutations in colorectal adenomas and carcinomas by enzyme-linked immunosorbent assay.

BACKGROUND: Point mutations of the ras protooncogene, primarily within codons 12 and 13, are commonly identified in colorectal carcinomas and large adenomas. Despite data suggesting that ras genotyping may have clinical significance with respect to colorectal cancer screening and prognosis, more widespread use has been limited because of the lack of a suitable assay system. The principal objective of this study was to assess the feasibility and validity of a qualitative enzyme-linked immunosorbent assay (ELISA) for detecting the four most common ras mutations in human colorectal tumors at the protein (p21ras) level. METHODS: Tissue homogenates (11-121 micrograms) from endoscopically or surgically resected colorectal adenomas, carcinomas, and normal mucosae were evaluated by a commercially available ELISA (Oncogene Science, Inc. Cambridge, MA) for mutant p21ras containing arginine position 12 (arg12), valine position 12 (val12), aspartate position 12 (asp12), and aspartate position 13 (asp13) amino acid substitutions. Portions of the same tissue from an initial series of 27 specimens also were subjected to mutant-enriched polymerase chain reaction (PCR) and/or PCR amplification with subsequent DNA sequence analysis to validate the ELISA data. RESULTS: Forty-seven adenomas, 9 carcinomas, and 14 normal mucosae were assayed. Mutations were identified in 16 (34%) of the adenomas (7-asp12, 7-val12, 2-asp13), 3 (33%) of the carcinomas (1-asp12, 1-arg12, 1-asp13), and none of the normal mucosae by ELISA: Polymerase Chain Reaction and DNA sequencing analyses demonstrated identical results for 21 of the 23 (91%) and 14 of 16 (88%) homogenates tested, respectively. The ELISA demonstrated an overall sensitivity of 80-86%, specificity of 90-92%, positive predictive value of 86-100%, and negative predictive value of 86-91%. CONCLUSIONS: The ELISA is a feasible and valid approach for identifying p21ras mutations in human colorectal adenomas and carcinomas.

Adenoma↗
PubMed1995

Extended therapy with intravenous arginine butyrate in patients with beta-hemoglobinopathies.

BACKGROUND: Enhanced production of fetal hemoglobin lessens the severity of beta-thalassemia and sickle cell disease. Intravenous infusion of arginine butyrate can increase the number of reticulocytes containing fetal hemoglobin in patients with these disorders, and it has induced a substantial increase in hemoglobin in one patient with thalassemia. We therefore tested the efficacy of this agent in patients with beta-hemoglobinopathies. METHODS: We treated 10 patients with severe beta-thalassemia or sickle cell disease with arginine butyrate at an initial dose of 500 mg per kilogram of body weight per day (final dose, 2000 mg per kilogram per day), 6 days per week, for a mean (+/- SD) of 10 +/- 1.2 weeks (range, 9 to 13). A hematologic response was defined as an increase in the hemoglobin concentration of at least 2 g per deciliter in patients with thalassemia and as a twofold increase in the fetal hemoglobin concentration in patients with sickle cell disease. RESULTS: Increase in gamma-globin messenger RNA and in reticulocytes containing fetal hemoglobin but not in hemoglobin were observed in the patients with thalassemia. A small, unsustained increase in fetal hemoglobin was observed in two patients with sickle cell disease. Drug toxicity was minimal at standard doses. One patient had a grand mal seizure after inadvertently receiving 2000 mg of arginine butyrate per kilogram over a period of six hours. CONCLUSIONS: Ten weeks of intravenous arginine butyrate did not produce a hematologic response in 10 patients with either severe beta-thalassemia or sickle cell disease.

Adolescent↗
PubMed1995

Regulation of cAMP-dependent protein kinase: enzyme activation without dissociation.

It has become axiomatic that, in contrast to other protein kinases, cAMP-dependent protein kinase (cAPK) is activated only when its catalytic (C) and regulatory (RII2) subunits dissociate. To directly evaluate this postulation, the ability of cAMP to dissociate the holoenzyme form of cAPK was examined by measuring the rotational mobility of the carboxyfluorescein-labeled C subunit (CFC) complexed to the dimeric RII2 regulatory subunit under equilibrium conditions. The rotational mobility was determined from an analysis of the time-resolved emission anisotropy of the CFC subunit. The time-resolved anisotropy decays were best fitted by a sum of two exponentials for both the free CFC subunit and the RII2CFC2 complex (holoenzyme). In the absence of cAMP, the two rotational correlation times (phi F and phi S) were 1.7 +/- 0.3 and 18.3 +/- 0.7 ns for the free CFC subunit and 2.3 +/- 0.1 and 93 +/- 2 ns for the RII2CFC2 complex, respectively. The faster rotational correlation times can be attributed to the localized rotations of the label and the slower rotational correlation times to the global rotations of the entire molecule. The addition of cAMP had no significant effect on either the fast or the slow rotational correlation time of the RII2CFC2 complex (phi F = 2.0 +/- 0.2 ns and phi S = 93 +/- 9 ns). Control experiments established that the RII2CFC2 complex was fully activated by cAMP at the same concentrations (0.2-0.4 microM) used for the anisotropy measurements. Together, the results demonstrate (1) that cAMP can induce the catalytic activity of cAPK without subunit dissociation and (2) that cAMP binding to holoenzyme is insufficient to explain its in vivo dissociation.

Catalysis↗
PubMed1995

Micellar liquid chromatographic separation of sulfonamides in physiological samples using direct on-column injection.

A mixture of twelve sulfonamides was separated by micellar liquid chromatography (MLC) using sodium dodecyl sulfate (SDS) micelles and a hydrophilic endcapped C18 column. Retention behavior and selectivity pattern of sulfonamides in MLC were examined with the change of SDS concentration and volume fraction of an organic modifier (1-propanol). The suitable condition was found to be 0.070 M SDS and 6.0% 1-propanol for the separation of these twelve sulfonamides. Under this condition, the isocratic separation of the sulfonamides was achieved within 15 min with a relatively high column efficiency for MLC (ca. 7000 plates/25 cm column). Retention times of these twelve sulfonamides were found to be very repeatable, which is due to the highly reproducible retention behavior in MLC. The same twelve sulfonamides were successfully separated in the spiked physiological fluids (human urine and cow milk) through direct on-column injection by MLC.

Animals↗
PubMed1995

Linear solvation energy relationships in micellar liquid chromatography and micellar electrokinetic capillary chromatography.

Linear solvation energy relationships (LSERs) were used to evaluate and characterize chemical interactions that influence retention behavior in micellar liquid chromatography (MLC) and micellar electrokinetic capillary chromatography (MEKC). High correlations were found between solutes' capacity factors in MLC and in MEKC, as well as binding constants to micelles and their solvatochromic parameters using two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium cholate (SC), and one cationic surfactant, tetradecyltrimethylammonium bromide (C14TAB). Surprisingly, in the C14TAB MLC system capacity factor (k') vs. solvatochromic parameters gives better correlation than log k' vs. solvatochromic parameters, which is an opposite behavior to that observed in the SDS MLC system. The capacity factors in the C14TAB MLC system were characterized using LSERs with and without organic modifiers. It was found that the addition of a small amount of short-chain alcohols (e.g., 7% 2-propanol or 5% butanol) does not significantly change the high correlations between k' vs. solvatochromic parameters. The changes in the coefficients with the volume fraction of organic solvents were explained by comparing the differences in chemical natures between mobile phase and stationary phase. Stationary phase shows a significant effect on the chemical interactions in MLC through LSER study using a diphenyl column and a C8 column. LSERs were also used to characterize retention behavior in MEKC. High correlations between the logarithm of solutes' capacity factors and their solvatochromic parameters were observed for a group of 25 uncharged substituted aromatic compounds and polycyclic aromatic hydrocarbons with SDS and SC micelles. It was found that solutes' size and basicity are the two dominant factors that influence the migration behavior in MEKC.

Chromatography, Liquid↗
PubMed1995

Chemical selectivity in micellar electrokinetic chromatography: characterization of solute-micelle interactions for classification of surfactants.

The influence of surfactant type on migration behavior and chemical selectivity in micellar electrokinetic chromatography (MEKC) is investigated through linear solvation energy relationships (LSER) and functional group selectivities. In LSER modeling, solutes' capacity factors are correlated with their structural descriptors such as size, dipolarity, and hydrogen-bonding abilities. Using the LSER methodology, useful information about the nature of solute interactions with different types of surfactant aggregates can be obtained since capacity factor in MEKC is directly related to solute distribution between the bulk aqueous solvent and micelles. High correlations were observed for different LSER models of migration behavior in MEKC for a group of 60 uncharged aromatic compounds of non-hydrogen bonding (NHB), hydrogen-bonding acceptor (HBA) bases, and hydrogen-bonding donor (HBD) acids. In two anionic, hydrocarbon micellar systems of sodium dodecyl sulfate (SDS) and sodium cholate (SC), retention is primarily influenced by the size of molecules and their hydrogen bond accepting basicity. Their dipolarity/polarizability and hydrogen bond donating acidity play minor roles. Capacity factors of solutes in SDS and SC systems increase with their size and decrease for stronger hydrogen bond acceptor bases. These results are similar to those observed for other systems where hydrophobic interactions play a major role, e.g., solute distribution in the 1-octanol-water solvent system or retention in reversed phase LC. In MEKC with an anionic fluorocarbon surfactant, lithium perfluorooctanesulfonate (LiPFOS), however, size and solute HBD acidity are the two predominant factors. The LSER results indicate that compounds find the SDS micellar environments slightly less cohesive (i.e., more apolar) than the SC micelles, while the LiPFOS micelles are the most cohesive among the three surfactant aggregates and 1-octanol provides the least cohesive environment. The fluorocarbon micelles of LiPFOS, on the other hand, are the strongest hydrogen bond donor acids, followed by SDS, SC, and 1-octanol, respectively. The SC micelles have the most hydrogen bond acceptor basic characteristics, followed by 1-octanol, SDS, and LiPFOS micelles. It can be concluded that selectivity differences between these surfactant types in MEKC is primarily due to hydrogen-bonding interactions rather than the dipolar interactions. Comparing the perfluorinated and the hydrocarbon surfactants, even solute size can play a role in selective migration patterns. In addition, information from polar and hydrophobic group selectivities confirm the LSER conclusions about the underlying interactions that control migration behavior and chemical selectivity in MEKC.(ABSTRACT TRUNCATED AT 400 WORDS)

Chromatography, Liquid↗
PubMed1995

Establishment of a human hepatocyte line derived from primary culture in a collagen gel sandwich culture system.

A human hepatocyte line (HHY41) was established from normal human liver tissue. This cell line was derived from a primary culture of human hepatocytes maintained between two layers of collagen gel for 4 weeks. It differs from other human hepatocyte lines in that transfection with the simian virus 40 gene was not used for cellular transformation and nonhepatocellular coculture cells were not present. HHY41 cells have proliferated freely in serum and hormone-supplemented medium after more than 1 year in continuous culture, exhibiting typical morphological characteristics of hepatocytes. HHY41 cells retain glucose-6-phosphatase activity. They also retain the ability to secrete liver-specific proteins such as albumin, transferrin, and alpha-fetoprotein. Northern blot analysis confirmed the presence of albumin mRNA. Cytochromes P450 induced by polycyclic aromatic hydrocarbons are maintained in these cells. Detection of cell surface antigens revealed that HHY41 cells express alpha 1 beta 1-integrin, which is expressed by normal hepatocytes and not by bile duct epithelial cells. High-molecular-weight cytokeratin, a marker for bile duct cells, is also absent in HHY41. Cytogenetic analysis showed hyperdiploid karyotype with a consistent deletion in the short arm of chromosome 1. HHY41 can be considered a new human hepatocyte line which retains liver-specific functions of differentiated hepatocytes. Derived from normal liver tissue, not a hepatocellular carcinoma, it provides a new model system for studying the regulation of cell growth and differentiated functions in human hepatocytes.

Adult↗
PubMed1995

Effects of superior mesenteric artery stenosis on splanchnic and systemic hemodynamics in conscious rats with biliary cirrhosis.

BACKGROUND/AIMS: Since portal tributary blood flow is increased in portal hypertension due to cirrhosis, a reduction in mesenteric arterial blood flow should decrease portal pressure. METHODS: Calibrated stenosis of the superior mesenteric artery was performed in bile duct ligated rats, using a 22-gauge needle. Arterial stenosis was performed 4 weeks after bile duct ligation. Hemodynamic studies were performed in the 5th week following bile duct ligation in conscious rats. RESULTS: At that time, no digestive tract alterations were observed. In rats with mesenteric arterial stenosis, portal pressure was 12.2 +/- 2.0 mmHg; this value was lower than in rats with cirrhosis without arterial stenosis (14.5 +/- 1.1 mmHg) but higher than normal rats (5.8 +/- 0.7 mmHg). In rats with cirrhosis with mesenteric arterial stenosis, portal tributary and mesenteric blood flows were lower than in rats with cirrhosis without arterial stenosis and not significantly different from normal rats. In rats with mesenteric stenosis, cardiac index was significantly lower than in rats with cirrhosis and not significantly different from normal rats. CONCLUSION: This study shows that calibrated superior mesenteric arterial stenosis normalized portal tributary blood flow and reduced but did not normalize the degree of portal hypertension.

Animals↗
PubMed1995

Atrial inflow can alter regurgitant jet size: in vitro studies.

Recent studies have attempted to predict the severity of regurgitant lesions from color Doppler jet size, which is a function of orifice momentum for free jets. Jets of mitral and tricuspid regurgitation, however, are opposed by flows entering the atria. Despite their low velocities, these counterflows may have considerable momentum that can limit jet penetration. The purpose of this study was to address the hypothesis that such counterflow fields influence regurgitant jet size. Steady flow was driven through 2.4- and 5.1-mm-diameter circular orifices at 2 to 6 m/s. At a constant orifice velocity and flow rate, the velocity of a uniform counterflow field was varied from 5 to 30 cm/s. Jet dimensions were measured by both fluorescent dye visualization and Doppler color flow mapping. The results showed that despite its relatively low velocities, counterflow dramatically curtailed jet length and area. Jet dimensions were functions of the ratio of jet to counterflow momentum. Thus, atrial inflow may participate in determining jet size and can alter the relation between jet size and lesion severity in mitral and tricuspid regurgitation.

Algorithms↗
PubMed1995

Effect of silicone sound speed and intraocular lens thickness on pseudophakic axial length corrections.

We compared the sound speeds of SLM-1/UV (990 M/sec at 35 degrees Celsius [degrees C]), SLM-2/UV (1090 M/sec at 35 degrees C), and Perspex CQ poly(methyl methacrylate)(2658 M/sec at 35 degrees C). Methods are presented to determine the correction of axial length (CAL) factors for axial length measurements made on pseudophakes with AMO PhacoFlex Si-18, Si-26 (SLM-1/UV), and AMO PhacoFlex II SI-20 or SI-30 (SLM-2/UV) silicone intraocular lenses (IOLs). A CAL is required to avoid potential errors with secondary IOL power predictions; CALs, which are strongly dependent on the material sound speed and less so on lens thickness, ranged from -0.65 mm to -1.20 mm for SLM-1/UV silicone IOLs and from -0.35 mm to -0.55 mm for SLM-2/UV silicone IOLs. The sound speeds of IOL materials varied insignificantly between ambient room temperature (23 degrees C) and intraocular temperature (35 degrees C).

Artifacts↗
PubMed1995

Induction of proinflammatory cytokines by a soluble factor of Propionibacterium acnes: implications for chronic inflammatory acne.

Although many cytokines have been implicated in the development and persistence of inflammatory immune responses, it is unknown if any of these are important in inflammatory acne. This study investigated the production of the proinflammatory cytokines interleukin-8 (IL-8), IL-1 beta, and tumor necrosis factor alpha (TNF-alpha) by human monocytic cell lines, ThP-1 and U937, and by freshly isolated peripheral blood mononuclear cells from acne patients. Both Propionibacterium acnes and supernatants obtained from 72-h P. acnes cultures could induce significant concentrations of IL-1 beta, TNF-alpha, and IL-8 by both cell lines and by peripheral blood mononuclear cells as determined by enzyme-linked immunosorbent assay. There was no significant difference between acne and non-acne subjects. Endotoxin quantification and addition of polymyxin B to assays indicated no lipopolysaccharide (LPS) contamination. P. acnes supernatant was fractionated into components with molecular weights of < 3,000, < 10,000, and < 30,000 and assayed for the ability to induce IL-8 and TNF production in ThP-1 cells. Nearly 90% of the original activity was found in the < 30,000-molecular-weight fraction, 50% was in the < 10,000-molecular-weight fraction, and only 15% remained in the < 3,000-molecular-weight fraction. The effluent from the < 3,000-molecular-weight fraction contained about 70% activity, indicating that the inducing factor was not retained in the membrane. Incubation of P. acnes supernatant with various concentrations of mutanolysin or lysozyme resulted in a loss of 60% of the original activity. The addition of jimson lectin, which binds peptidoglycan, resulted in a loss of 70% of the activity in a dose-response manner, whereas peanut lectin had little or no effect on the activity. Heating of the P. acnes supernatant to 65 degrees C also had no effect on the activity. Blocking of CD14, a receptor for both LPS and peptidoglycan, reduced cytokine production by > 50%, suggesting that the soluble stimulating factor may be a secreted form of peptidoglycan-polysaccharide.

Acne Vulgaris↗