Biomedical subjects
Publications and source records attributed to S Yang.
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The cardiac function of 21 patients with cystic fibrosis was studied using radionuclides and M-mode echocardiography. The patients (mean age 13.2 years, range 4 to 27) had a wide range of clinical and pulmonary function abnormalities (mean Shwachman-Kulczycki score 62.1). Decreased right ventricular ejection fraction was found in 13 of 18 patients (72%); an additional four patients had abnormal septal motion on ECHO. Left ventricular ejection fraction was abnormal at rest in four patients (19%); an additional four patients had borderline low LVEF. The LV pre-ejection period to ejection time ratio increased significantly (i.e., worsening LV performance) with deterioration of S-K score, chest radiograph score, and forced expiratory volume in 1 second. Three of eight patients with normal LVEF at rest had an abnormal response to supine bicycle exercise: LVEF fell in two patients and was unchanged in one. Thus evidence of LV dysfunction was observed in seven of 21 (33%) of the patients; four at rest and in three only during exercise.
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In the presence of nitrobenzylthioinosine (NBMPR) a potent inhibitor of nucleoside transport, Roswell Park Memorial Institute 6410 cells proliferating in culture were protected from otherwise inhibitory concentrations of 9-beta-D-ribofuranosylpurine (nebularine); cellular uptake of nebularine was greatly reduced under these circumstances. Initial rates of nebularine uptake by Roswell Park Memorial Institute 6410 cells were inhibited by NBMPR, indicating that the latter interfered with nebularine transport. NBMPR protected mice against potentially lethal treatment regimens with nebularine, 4-amino-7-(beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine (tubercidin) or 4-amino-5-cyano-7-(beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine (toyocamycin); protection resulted when NBMPR was administered i.p. in advance of or simultaneously with nebularine, but not when NBMPR followed nebularine by 1 hr. Both NBMPR and its 5'-monophosphate protected mice against nebularine lethality when administered s.c.
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Fourteen population samples of Drosophila pavani were obtained from a number of localities in Chile. The populations sampled were dispersed over 7 degrees of latitude and 1800 meters of elevation, and were drawn at three different times. Sixteen electrophoretic loci were assayed for each population; eight of the loci were analyzed statistically for geographic variation; the other eight were essentially monomorphic. For all eight variable loci, variation in allelic frequencies among populations was highly significant. In all cases, a significant portion of the variation among populations was associated with variation in gross environmental variables (latitude, elevation, month of collection). The implications of the evidence were discussed, and the authors concluded that there was suggestive evidence for selection.
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A glucose biosensor based on an amperometric oxygen electrode has been developed. Polycarbonate and Silastic membranes were assembled (glued together) to form a multilayer sandwich glucose diffusion barrier. The effects of the glue layer composition and thickness of the Silastic membrane on sensor response parameters have been investigated in order to optimize the sensor. The parameters measured were the sensitivity, the concentration range of the linear dependence of the sensor response to glucose, and the long-term operation time. The sensors with the sandwich-type glucose diffusion membrane (Silastic membrane prepared from 20% Silastic suspension, glue layer prepared from polyurethane, 0.5 w/v % in ThF solution and standard polycarbonate membrane) demonstrated linearity of response up to 520 mg/dl glucose at 25 degrees C and up to 400 mg/dl at 37 degrees C. These sensor showed good reproducibility of response without significant interference effects (from 1 to 5% of the background current value). The long-term continuous operational time of the sensors was over 40 days at 37 degrees C, and over 60 days at 25 degrees C.
Current methods for assessing the severity of aortic stenosis depend primarily on measures of maximum systolic pressure drop at the aortic valve orifice and related calculations such as valve area. It is becoming increasingly obvious, however, that the impact of the obstruction on the left ventricle is equally important in assessing its severity and could potentially be influenced by geometric factors of the valve, causing variable degrees of downstream pressure recovery. The goal of this study was to develop a method for measuring fluid mechanical energy losses in aortic stenosis that could then be directly related to the hemodynamic load placed on the left ventricle. A control volume form of conservation of energy was theoretically analyzed and modified for application to aortic valve stenosis measurements. In vitro physiological pulsatile flow experiments were conducted with different types of aortic stenosis models, including a venturi meter, a nozzle, and 21-mm Medtronic-Hall tilting disc and St. Jude bileaflet mechanical valves. The energy loss created by each model was measured for a wide range of experimental conditions, simulating physiological variation. In all cases, there was more energy lost for the nozzle (mean = 0.27 J) than for any other model for a given stroke volume. The two prosthetic valves generated approximately the same energy losses (mean = 0.18 J), which were not statistically different, whereas the venturi meter had the lowest energy loss for all conditions (mean = 0.037 J). Energy loss correlated poorly with orifice pressure drop (r2 = 0.34) but correlated well with recovered pressure drop (r2 = 0.94). However, when the valves were considered separately, orifice and recovered pressure drop were both strongly correlated with energy loss (r2 = 0.99, 0.96). The results show that recovered pressure drop, not orifice pressure drop, is directly related to the energy loss that determines pump work and therefore is a more accurate measure of the hemodynamic significance of aortic stenosis.
BACKGROUND: To evaluate and optimize a modified small bowel follow-through examination (SBFT) by using an oral administration of a large amount (600 mL) of methylcellulose after taking a small amount of barium. METHODS: Ninety-nine normal subjects underwent modified SBFT with an oral administration of 600 mL of 0.5% methylcellulose after taking 100 mL of 120% or 100, 150, or 200 mL of 70% w/v barium. The transradiancy and distensibility of the bowel and the transit time were compared with those of 39 other normal subjects who underwent conventional SBFT with 500 mL of 70% w/v barium. RESULTS: Except for two subjects who developed diarrhea immediately after examination, no patients complained of acute symptoms, such as abdominal pain or vomiting. Modified SBFT was much superior to conventional series for obtaining good bowel transradiancy and rapid transit time (range = 37-49 min), but bowel distention was not significantly improved. The use of 150 mL of 70% w/v barium was better than the other three modified techniques for achieving good bowel transradiancy, rapid transit time, and less occurrence of flocculation. CONCLUSION: Modified SBFT is a simple method for easily improving the image quality in terms of bowel transradiancy and transit time.
Genes encoding four different C-terminal fragments of a Plasmodium falciparum merozoite surface antigen were generated: MSA1C-(Si,A), containing signal and anchor regions of MSA1; MSA1C-(Si,nA), containing the signal but not the anchor; MSA1C-(nSi,A), containing the anchor but not the signal, and MSA1C-(nSi,nA) containing neither the signal nor the anchor region. Each gene was inserted into the thymidine kinase region of vaccinia virus, under the control of a synthetic strong early/ late promoter. When the plasmodial genes were expressed in cells infected by the recombinant vaccinia virus, the two proteins containing the signal region were transported to the surface of infected cells. Infection of mice and rabbits with the latter recombinant viruses stimulated C-terminal-specific antibody levels that were 10-80-fold higher than those induced by the two recombinant viruses without the signal region. The combination of the signal and anchor regions with the C-terminal MSA1 protein also generated the most effective neutralization in a P. falciparum invasion assay.
PURPOSE: To introduce an updated accelerated photoaging model for application to intraocular lens (IOL) materials and to apply this model to determine the photostability of AMO PhacoFlex model SI-18NGB and PhacoFlex II model SI-20NGB silicone IOL materials over a simulated 50 years of exposure. SETTING: Research laboratory, AMO Surgical Products, Irvine, California, USA. METHODS: Previous photoaging models and aging parameters, including intraocular exposure intensity, daily exposure duration, and acceleration exponent were critically reviewed and analyzed, and an updated model was introduced. The test specimens were continuously irradiated with ultraviolet (UV) light in a Suntest UV chamber at an intensity of 8 mw/cm2 for 86 days to simulate 50 years of in vivo exposure. The silicone lenses were evaluated for focal length, resolution, and surface integrity, while regular slabs were tested for tensile strength, elongation, hardness, contact angle, and percentage light transmission. The UV-absorption capacity was monitored using ultrathin slabs (0.127 mm). Six replicate samples were used for each determination, and a two-sided t-test with significance set at P < .05 was used to evaluate the difference before and after aging. RESULTS: No significant difference in optical, physical, and surface properties of the lenses and lens materials was found. No change in UV-absorption capacity was observed after a simulated 50 years of accelerated photoaging. CONCLUSION: The AMO PhacoFlex SI-18NGB and PhacoFlex II SI-30NGB silicone lens materials resisted UV light degradation over 50 years of simulated exposure.
The effect of aortic outflow on the quantification of mitral regurgitation by the flow convergence method was investigated by both in vitro experiments and computational simulations. Digital analysis of the color Doppler M-mode images was compared with results obtained with laser Doppler anemometry, an engineering gold standard, and three-dimensional computational simulations. Regurgitant orifices of 3.2 and 6.4 mm in diameter were used with instantaneous aortic flow rates from 0 to 500 ml/sec, corresponding to net cardiac outputs of 0 to 5 L/min. In the absence of aortic outflow, a clear plateau was observed in plots of the calculated flow rate as a function of the distance from the orifice, indicating that there was a zone in which the hemispheric assumption was valid. As the aortic outflow was increased, the length of this plateau region decreased and then disappeared at high aortic flow rates. Farther from the orifice, beyond the plateau zone, the flow rate was overestimated and this overestimation increased with increasing aortic flow rate. Results showed excellent agreement between in vitro experiments and computational stimulations. This study demonstrated that aortic outflow has a dramatic effect on the flow convergence region and therefore must be considered in flow rate calculations.