Robust, tunable biological oscillations from interlinked positive and negative feedback loops     

Tsai TY  Choi YS  Ma W  Pomerening JR  Tang C  Ferrell JE 《Science (New York, N.Y.)》2008,321(5885):126-129

A simple negative feedback loop of interacting genes or proteins has the potential to generate sustained oscillations. However, many biological oscillators also have a positive feedback loop, raising the question of what advantages the extra loop imparts. Through computational studies, we show that it is generally difficult to adjust a negative feedback oscillator's frequency without compromising its amplitude, whereas with positive-plus-negative feedback, one can achieve a widely tunable frequency and near-constant amplitude. This tunability makes the latter design suitable for biological rhythms like heartbeats and cell cycles that need to provide a constant output over a range of frequencies. Positive-plus-negative oscillators also appear to be more robust and easier to evolve, rationalizing why they are found in contexts where an adjustable frequency is unimportant.  相似文献   

Thyroid hormone action: a cell-culture system responsive to physiological concentrations of thyroid hormones   总被引：19，自引：0，他引：19  

H H Samuels  J S Tsai  R Cintron 《Science (New York, N.Y.)》1973,181(106):1253-1256

Cells from a rat pituitary tumor cell line will respond in vitro to physiological concentrations of L-thyroxine and L-triiodothyronine. The cells are grown in a cultutre medium that contains serum from a hypothyroid calf. Dose-response relationships of a vacriety of thyronine derivatives indicate that this system has a specificity of response which is similar to that observed in vitro.  相似文献   

A central repository for published plasmids     

Fan M  Tsai J  Chen B  Fan K  LaBaer J 《Science (New York, N.Y.)》2005,307(5717):1877

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Determination of naringin in rat blood,brain, liver,and bile using microdialysis and its interaction with cyclosporin a,a p-glycoprotein modulator     

Tsai TH 《Journal of agricultural and food chemistry》2002,50(23):6669-6674

To determine naringin levels in various biological fluids, we developed an in vivo microdialysis technique coupled with a microbore HPLC system to investigate the pharmacokinetics of naringin and its interaction with cyclosporin A in rat blood, brain, liver, and bile. After naringin administration, naringin was undetectable in the brain; the distribution ratios of area under the curve (AUC) of liver over that in blood (AUC(liver)/AUC(blood)) and of AUC of bile over that in blood (AUC(bile)/AUC(blood)) of naringin were 5.39 +/- 0.94 and 29.17 +/- 3.58, respectively. When cyclosporin A (20 mg/kg) was concomitantly administered with naringin (30 mg/kg), the naringin was detected in brain dialysate, but the distribution ratios of liver and bile showed no statistical difference. These results suggest that naringin was concentrated in the liver and bile by the processes of active transport. The blood-brain barrier penetration of naringin may be enhanced by P-glycoprotein inhibitor; however, the pathway of hepatobiliary excretion of naringin may not be related to the P-glycoprotein.  相似文献   

Visibility Variation with Air Qualities in the Metropolitan Area in Southern Taiwan     

Tsai  Ying I.  Lin  Yi H.  Lee  Suen Z. 《Water, air, and soil pollution》2003,144(1-4):19-40

Principal component analysis (PCA) was used to analyze variationsin visibility compared with (1) variations in meteorological variables in the period 1961 to 1998, and (2) criteria air pollutant (SO₂, CO, O₃, NO_x and PM₁₀) concentrations monitored between 1994 and 1998, in the Kaohsiungmetropolitan area. Whilst average visibility during the 1960'sexceeded 20km, it had deteriorated to 5–10 km in theperiod 1994 to 1998. PCA identified seven components witheigenvalues greater than one. The principal componentsidentified accounted for variability related to PM₁₀concentration, ozone-related pollutants, oil combustion,and traffic emissions. Furthermore, spatial and temporalvariations in PM₁₀ were consistent throughout thecity. Variation in SO₂ levels followed a similarpattern at Tsoying, Shanming, Chiankin and Chiancheng.Industrial pollution and traffic emissions, SO₂, COand NO_x, from the Hsiaokang area remained within thearea. However, similar patterns of SO₂ andNO_xat Fengshan and Jenwu indicate that industrial emissionsfrom the latter were probably transported to the former.Much of the first principal component is based onPM₁₀ variability, suggesting that, of the fivecriteria pollutants studied, PM₁₀ is the majorcontributor to visibility deterioration. It is known thatPM_2.5 concentration is more closely associated withvisibility changes than is PM₁₀. However, becausePM₁₀ and PM_2.5 are strongly associated inKaohsiung, a targeting reduction in PM₁₀ may imply areduction in visibility.  相似文献   

Analysis of ambient lead concentrations around three secondary lead smelters     

Eric Chia-Ei Tsai 《Water, air, and soil pollution》1987,33(3-4):321-329

Ambient Pb concentrations measured over a 30 mo span around three secondary Pb smelters in the City of Winnipeg, Manitoba, Canada are statistically analyzed. The results obtained are compared with the provincial regulatory air quality guideline. The contribution of smelter emissions to high Pb levels that exceed the provincial guideline is also demonstrated. It is concluded, by inference, that the Secondary Lead Smelter National Emission Standards Regulations were effectively implemented.  相似文献   

Urine hemojuvelin in cats with naturally occurring kidney disease     

Hwei Jing  Wei-Li Hsu  Vin-Cent Wu  Han-Ju Tsai  Shang-Feng Tsai  Pei-Shiue Jason Tsai  Tai-Shuan Lai  Ya-Jane Lee 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2020,34(3):1222-1230

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Substitution of Chaetoceros muelleri by Spirulina platensis meal in diets for Litopenaeus schmitti larvae     

Barbarito J. Jaime-Ceballos  Alfredo Hernndez-Llamas  Tsai Garcia-Galano  Humberto Villarreal 《Aquaculture (Amsterdam, Netherlands)》2006,260(1-4):215-220

The nutritional response of Litopenaeus schmitti larvae to substitution of Chaetoceros muelleri by Spirulina platensis meal (SPM) was evaluated. The substitution levels (S) were 0%, 25%, 50%, 75% and 100%, dry weight basis. Final larval length (FL) ranged from 1.98 to 3.16 mm for the different substitution levels. There was a significant relationship between S and FL, described by the following quadratic equation: FL = 2.853 + 0.01598S − 0.000233S². The substitution level (S) yielding maximum FL was 34.2%. Development index (DI) values ranged from 2.84 to 3.93 and were dependent on substitution level. The corresponding equation was DI = 3.799 + 0.00945S − 0.000189S² (P < 0.01). Maximum DI was obtained at 25.0% substitution. Survival was high (82–87%) and no significant differences were found between treatments. Protein digestibility of either microalgae was high, with 92% for SPM and 94% for C. muelleri, with no significant differences between them. The results in this study indicate that an adequate balance of nutrients in relation to the requirements of the species is critical. To simultaneously improve FL and DI, a 30% substitution of C. muelleri by SPM is suggested. This is equivalent to feeding 0.15 mg larvae^− 1 day^− 1 dry weight basis of a 70% C. muelleri/30% SPM diet, representing 0.078 mg protein larvae^− 1 day^− 1, 0.026 mg lipids larvae^− 1 day^− 1 and 2.732 J larvae^− 1 day^− 1.  相似文献   

Genetic Characterization of Brazilian Annual <Emphasis Type="Italic">Arachis</Emphasis> Species from Sections <Emphasis Type="Italic">Arachis</Emphasis> and <Emphasis Type="Italic">Heteranthae</Emphasis> using RAPD Markers     

Silvana?CresteEmail author  Siu?Mui?Tsai  José?F.?M.?Valls  Marcos?A.?Gimenes  Catalina?Romero?Lopes 《Genetic Resources and Crop Evolution》2005,52(8):1079-1086

The genus Arachis is divided into nine taxonomic sections. Section Arachis is composed of annual and perennial species, while section Heteranthae has only annual species. The objective of this study was to investigate the genetic relationships among 15 Brazilian annual accessions from Arachis and Heteranthae using RAPD markers. Twenty-seven primers were tested, of which nine produced unique fingerprintings for all the accessions studied. A total of 88 polymorphic fragments were scored and the number of fragments per primer varied from 6 to 17 with a mean of 9.8. Two specific markers were identified for species with 2n = 18 chromosomes. The phenogram derived from the RAPD data corroborated the morphological classification. The bootstrap analysis divided the genotypes into two significant clusters. The first cluster contained all the section Arachis species, and the accessions within it were grouped based upon the presence or absence of the ‘A’ pair and the number of chromosomes. The second cluster grouped all accessions belonging to section Heteranthae.  相似文献   

Socio-economic differences in weight-control behaviours and barriers to weight control     

Siu J  Giskes K  Turrell G 《Public health nutrition》2011,14(10):1768-1778

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