PubMed Health⌕ Search

Biomedical subjects

J N Yang

Publications and source records attributed to J N Yang.

14 recordsLinked to original sources
PubMed2001

Illuminant cues in surface color perception: tests of three candidate cues.

Many recent computational models of surface color perception presuppose information about illumination in scenes. The models differ primarily in the physical process each makes use of as a cue to the illuminant. We evaluated whether the human visual system makes use of any of three of the following candidate illuminant cues: (1) specular highlight, (2) full surface specularity [Lee, H. C. (1986). Method for computing the scene-illuminant chromaticity from specular highlights. Journal of the Optical Society of America A, 3(10), 1694-1699; D'Zmura, M., & Lennie, P. (1986). Mechanisms of color constancy. Journal of the Optical Society of America A, 3(10), 1662-1672], and (3) uniform background. Observers viewed simulated scenes binocularly in a computer-controlled Wheatstone stereoscope. All simulated scenes contained a uniform background plane perpendicular to the observer's line of sight and a small number of specular, colored spheres resting on the uniform background. Scenes were rendered under either standard illuminant D65 or standard illuminant A. Observers adjusted the color of a small, simulated test patch to appear achromatic. In a series of experiments we perturbed the illuminant color signaled by each candidate cue and looked for an influence of the changed cue on achromatic settings. We found that the specular highlight cue had a significant influence, but that the influence was asymmetric: greater when the base illuminant, CIE standard Illuminant A, was perturbed in the direction of Illuminant D65 than vice versa. Neither the full surface specularity cue nor the background cue had any observable influence. The lack of influence of the background cue is likely due to the placement of the test patch in front of the background rather than, as is typical, embedded in the background.

Color Perception↗
PubMed1997

An investigation of tomotherapy beam delivery.

Experimental simulations for tomotherapy beam delivery were performed using a computer-controlled phantom positioner, a cylindrical phantom, and a 6 MV x-ray slit beam. Both continuous helical beam and sequential segmented tomotherapy (SST) beam deliveries were evaluated. Beam junctioning problem due to couch indexing error or field width errors presented severe dose uniformity perturbations for SST, while the problem was minimized for helical beam delivery. Longitudinal breathing motions were experimentally simulated for helical and SST beam delivery. While motions reduced the dose uniformity perturbations for SST, small artifacts in dose uniformity can be introduced for helical beam delivery. With typical breath frequency and magnitude, for a slit beam of 2.0 cm width at 4 rpm, the dose uniformity perturbation was not significant. A running start/stop technique was implemented with helical beam delivery to sharpen the 20%-80% longitudinal dose fall-off from 1.5 to 0.5 cm. The latter was comparable to the corresponding dose penumbra of a conventional 6 MV 10 x 10 cm2 field. All together, helical beam delivery showed advantages over SST for tomotherapy beam delivery under similar delivery conditions.

Biophysical Phenomena↗
PubMed1997

Plasminogen activator system in osteoclasts.

To determine which genes of the plasminogen activator (PA) system were expressed in osteoclasts, RNA extracted from microisolated mouse osteoclasts was used as template for reverse transcribed polymerase chain reaction (RT-PCR) with gene-specific primer pairs. Using this approach, the expression of RNAs for tissue-type plasminogen activator, urokinase-type plasminogen activator, plasminogen activator inhibitor-1, plasminogen activator inhibitor-2, protease nexin, and urokinase receptor isoform 1 (uPAR1) were detected in mouse osteoclasts. The expression of uPAR RNA in osteoclasts was confirmed by in situ hybridization with a uPAR1 probe. RNA encoding the uPAR isoform 2 was not detected in mouse osteoclasts, but a novel unspliced uPAR RNA variant was detected in these cells. The novel uPAR variant and uPAR1 RNA were also detected in mouse calvarial osteoblasts, kidney, muscle, and the mouse macrophage cell line J774A.1 by RT-PCR. The presence of RNAs for most of the components of the PA system in osteoclasts suggests that it may have a functional role in this cell type.

Animals↗
PubMed1994

Mammalian osteoclasts express a transient potassium channel with properties of Kv1.3.

Previous studies have revealed that expression of K+ channels in osteoclasts correlates with cell morphology and is influenced by interaction with the extracellular matrix. In this study, we investigated the electrophysiological properties of an outwardly rectifying K+ channel in rat and mouse osteoclasts using patch-clamp techniques. Cell-attached patch recordings revealed a channel of approximately 14 pS conductance that opened upon depolarization, and had a reversal potential close to that predicted for a K+ channel. Channel activity was transient; inactivation of ensemble currents, like that of whole-cell currents, occurred as a single exponential process. Both single-channel and macroscopic currents exhibited use-dependent inactivation in response to repetitive depolarizations. Two scorpion toxins, margatoxin and charybdotoxin, blocked this transient K+ channel, with half-maximal inhibition at 200 pM and 5 nM, respectively. In contrast, dendrotoxin (500 nM) had little effect. In summary, the outwardly rectifying K+ channel in osteoclasts resembles the Shaker-related K+ channel, Kv1.3. When membrane potential was recorded in whole-cell configuration, charybdotoxin (50 nM) caused a depolarization of 5 to 10 mV from resting levels of -50 mV or more positive; therefore this K+ channel contributes to the membrane potential of osteoclasts under some conditions. To investigate the molecular nature of osteoclast K+ channels, we performed RT-PCR on osteoclast RNA using primers for Kv1.3 and the inward rectifier, IRK1. mRNA encoded by Kv1.3 and IRK1 was detected and message identity confirmed by restriction enzyme digestion and sequence analysis. We conclude that osteoclasts exhibit, in addition to the previously described inward rectifier, an outwardly rectifying K+ conductance with properties of the Kv1.3. channel.

Animals↗
PubMed1992

Endogenous Mtv-8 or a closely linked sequence stimulates rearrangement of the downstream V kappa 9 gene.

Mtv-8 is an endogenous retrovirus located 4.6 kb upstream of a V kappa region gene (called V kappa 9M) within the kappa-Ig locus. The proximity of these two genes resulted in several effects. Using a newly developed RNase protection assay for measuring transcription from a single endogenous provirus, we found that Mtv-8 transcription could be detected after juxtaposition of the kappa-enhancers to the normally silent provirus. Reciprocally, using the polymerase chain reaction we observed that the frequency of V kappa 9M rearrangement was 5- to 10-fold higher in spleens from Mtv-8-positive mice (BALB/c, C58.C, A/J, and B6) compared to spleens from mice that lacked the Mtv-8 provirus (C58, C.C58, NZB, and PERA/Ei). Molecular cloning and sequencing of the V kappa 9M gene from C.C58 mice (containing the kappa-locus from C58 mice on a BALB/c background) indicated that at least some Mtv-8-negative strains have a functional V kappa 9M gene. Together these data suggest that Mtv-8 or a closely linked gene enhances V kappa 9M rearrangement. Since Mtv-8 also reportedly produces a superantigen, it appears that Mtv-8 may influence both the T cell and B cell repertoires.

Amino Acid Sequence↗
PubMed1992

Interpersonal underpinnings of request strategies: general principles and differences due to culture and gender.

Several hypotheses derived from P. Brown and Levinson's (1987) politeness theory were tested with Ss from the United States and Korea. Ss imagined themselves in situations in which they were to make a request. They then indicated exactly what they would say in each situation and what their perceptions of the request size, the hearer's power, and the closeness of their relationship with the hearer were. Consistent with P. Brown and Levinson's theory, power, distance, and size contributed significantly to politeness. Significant predictor variable interactions suggested that an additive model is not appropriate. Finally, there was evidence of cultural and gender differences in the weighting of these predictor variables. These differences can partially account for cultural and gender differences in language use.

Adolescent↗
PubMed1991

The endogenous Mtv-8 provirus resides within the V kappa locus.

The endogenous Mtv-8 provirus previously has been mapped within approximately 0.52 centimorgan from several V kappa markers on mouse chromosome 6. Using Southern blotting and DNA from a recombinant backcross mouse from the C57BL/6 (Mtv-8 positive) and C58 (Mtv-8 negative) strains, Mtv-8 was localized to the same side of the crossover point as immunoglobulin kappa (Ig kappa)-V24 but on the opposite side of the crossover from Ig kappa-V10 and Ig kappa-V21. Molecular cloning and characterization of cellular DNA adjacent to Mtv-8 revealed a functional V kappa 9 gene approximately 4.6 kb downstream and in the same transcriptional orientation as the provirus. These data suggest that Mtv-8 is within the centromere-proximal portion of the V kappa locus.

Animals↗
PubMed1991

Role of the epithelium in airway smooth muscle responses to relaxant agonists.

We studied the role of the guinea pig tracheal epithelium in modulating tracheal smooth muscle responses to the relaxant agonists albuterol, sodium nitroprusside, and theophylline. We used an in vitro preparation that allowed separation of the fluids bathing the luminal (internal) and serosal (external) surfaces of the trachea, and bronchodilators were administered to either surface of carbachol-contracted tracheae. All three drugs produced dose-dependent relaxation. However, albuterol and nitroprusside were less potent (concentration that produced half-maximal effect increased by 100- and 32-fold, respectively) when given to the epithelial side with the epithelium intact compared with the epithelium denuded or compared with serosal administration with the epithelium intact. These differences were not observed for theophylline, where smooth muscle responses were independent of either the side of stimulation or of the presence or absence of the epithelium. Direct measurements of the diffusion of theophylline across the tracheal wall in the presence or absence of epithelium showed that after 5 h of incubation with a fixed luminal concentration of theophylline, only 1.7% had diffused across the tracheal wall with the epithelium intact. This increased to only approximately 3.3% when the epithelium was denuded. These results suggest that the epithelial is a relatively weak barrier for lipophilic agents but has a major role as a diffusion barrier to hydrophilic substances.

Albuterol↗
PubMed1991

A method for in vitro mapping of ultrasonic speed and density in breast tissue.

A method has been developed for mapping density and ultrasonic speed in 1 mm thick slices of soft tissue with a resolution of about 1 mm. Tests using phantom sections have verified the accuracy and resolution of the ultrasonic speed maps. The method has been applied to breast tissues of three patients including tumors and surrounding tissue. Fixing a specimen in 5% formaldehyde did not change the degree of local variation in ultrasonic speeds, and raised mean speeds by less than 0.8%. The densities with fixing remained almost unchanged at low tissue densities (0.93 g/cm3), but rose 1.5% for higher tissue density (greater than 1.00 g/cm3).

Female↗
PubMed1989

Effect of pH on pulmonary vascular tone, reactivity, and arachidonate metabolism.

We studied the effects of perfusate pH on pulmonary vascular tone, reactivity, and thromboxane and prostacyclin synthesis in isolated buffer-perfused rabbit lungs. Extracellular acidosis did not affect base-line vascular tone, but alkalosis had a biphasic effect. Increasing the perfusate pH from 7.40 to 7.65 caused vasodilation, whereas raising pH to 7.70-8.10 caused vasoconstriction. Removing calcium (Ca2+) from the perfusate completely prevented the vasoconstriction caused by alkalosis. Perfusate pH strikingly affected pulmonary vascular reactivity. Acidosis inhibited the vasoconstriction caused by thromboxane and potassium chloride (KCl) but did not affect the response to angiotensin II. Alkalosis, in contrast, augmented the vasoconstriction caused by thromboxane and angiotensin II but reduced the vasoconstriction caused by KCl. Changes in pH also altered thromboxane and prostacyclin synthesis after the infusion of exogenous arachidonic acid (AA) or the endogenous release of AA by the lipid peroxide tert-butyl hydroperoxide.

Angiotensin II↗
PubMed1987

The endogenous retrovirus Mtv-8 on mouse chromosome 6 maps near several kappa light chain markers.

Endogenous retroviruses are known to affect expression of cellular genes in the vicinity of their integration sites. The endogenous mouse mammary tumor provirus (Mtv-8) previously has been reported to reside on mouse chromosome 6 near the immunoglobulin kappa chain locus. Using pairs of mouse strains on the BALB/c (Mtv-8 positive) and C58 (Mtv-8 negative) backgrounds which are congenic for chromosome 6 genetic markers, we have confirmed the chromosome assignment of this provirus. Moreover, we have analyzed the N1 progeny of a (B6 X C58) X C58 backcross to determine the segregation of the Mtv-8 provirus with respect to polymorphisms in the Igk-VSer and Igk-J loci. The results with congenic and backcross mice together with results of others suggest that Mtv-8 is located approximately 0.52 cM from several closely linked kappa markers on chromosome 6.

Animals↗
PubMed1985

Use of microcomputers in medical practice management: a practical guide.

The decreasing cost and increasing availability of computers have created both concern and desire on the part of the non-computer professional. This article provides basic information to use in the selection of microcomputer hardware and software. It is slanted toward the small practitioner, one to four physicians, and provides practical guidelines, definitions, and examples relevant for a small practice.

Computers↗