Pre-treatment of Caco-2 cells with zinc during the differentiation phase alters the kinetics of zinc uptake and transport(2)

The Caco-2 cell model was used to study the efficiency of absorption and endogenous excretion of zinc (Zn) regulated by dietary Zn concentration. Cells were seeded onto high pore-density membranes and maintained in medium supplemented with 10% FBS. After confluence, cells were treated with 5 or 25 μmol Zn/L for 7 d, and Zn uptake and transport were measured in both apical (AP) and basolateral (BL) directions by using ⁶⁵Zn. Similar cells were labeled with ⁶⁵Zn and the release of Zn to the AP and BL sides was measured. The AP uptake of Zn in cells exposed to 25 μmol Zn/L was slower (p < 0.05) than that in cells exposed to 5 μmol Zn/L. The AP to BL transport rate in the 25 μmol Zn/L group was only 40% (p < 0.05) of that in the 5 μM group. In contrast, the rate of BL Zn uptake was 4-fold higher in cells treated with 25 μmol Zn/L than in those treated with 5 μmol Zn/L (p < 0.05). The BL to AP transport rate was 2-fold higher in cells treated with 25 μmol Zn/L than in those treated with 5 μmol Zn/L (p < 0.05). Basolateral uptake was 6 to 25 times greater (p < 0.05) than AP uptake for cells treated with 5 and 25 μmol Zn/L, respectively. The rate of Zn release was enhanced about 4-fold (p < 0.05) by 25 μmol Zn/L treatment. Release to the BL side was 10 times greater than to the AP side. Zn-induced metallothionein (MT), thought to down-regulate AP to BL Zn transport, was 4-fold higher (p < 0.001) in the 25 μmol Zn/L group than in the 5 μM group, but the rate of BL Zn release was higher in cells treated with 25 μmol Zn/L than in those treated with 5 μmol Zn/L (p < 0.05). Induced changes in transport rates by media Zn concentrations could involve the up- and/or down-regulation of Zn influx and efflux proteins such as the ZIP and ZnT families of Zn transporters.     

Potentials of radio-frequency field gradient NMR microscopy in environmental science

An understanding of transport, flow, diffusivity and mass transfer processes is of central importance in many fields of environmental biotechnology such as biofilm, bioreactor and membrane engineering, soil and groundwater bioremediation, and wastewater treatment. Owing to its remarkable sensitivity to molecular displacements and to its noninvasive and nondestructive character, pulsed field gradient (PFG) nuclear magnetic resonance (NMR) can be a valuable tool for investigating such processes. In conventional NMR microscopy, spatial encoding is achieved by using static magnetic field gradients (B ₀ gradients). However, an interesting alternative is to use radio-frequency magnetic field gradients (RF or B ₁ gradients). Although the latter are less versatile than the former, RF field gradient microscopy is particularly suitable for dealing with heterogeneous systems such as porous media because of its quasi-immunity to background static magnetic field gradients arising from magnetic susceptibility inhomogeneities, unlike the B ₀ gradients microscopy. Here, we present an overview of basic principles and the main features of this technique, which is still relatively unused. Different examples of diffusion imaging illustrate the potentialities of the method in both micro-imaging and the measurement of global or local diffusion coefficients within membranes and at liquid–solid interfaces. These examples suggest that a number of environmental problems could benefit from this technique. Different future prospects of application of B ₁ gradient NMR microscopy in environmental biotechnology are considered. Journal of Industrial Microbiology & Biotechnology (2001) 26, 53–61. Received 09 February 2000/ Accepted in revised form 07 August 2000     

Development of a novel diffusion-based method to estimate the size of the aggregated Abeta species responsible for neurotoxicity

beta-Amyloid peptide (Abeta) is the primary protein component of senile plaques in Alzheimer's disease and is believed to be responsible for the neurodegeneration associated with the disease. Abeta is toxic only when aggregated, however, the size and structure of the aggregated species associated with toxicity is unknown. In the present study, we developed a diffusion-based method to simultaneously separate and detect the biological activity of toxic Abeta oligomers and used the method to examine the relationship between size of aggregated protein and toxicity to SH-SY5Y cells. From these measurements, the effective diffusivity and hydrodynamic radius of the toxic oligomeric species of Abeta could be determined. A sensitivity analysis was performed to examine the effects of model assumptions used in data analysis on the effective diffusivity calculated. The method provides a new estimate of the size of small toxic Abeta species associated with fibril formation. This work contributes to our understanding of the relationship between Abeta structure and toxicity and with further refinements may aid in our ability to design agents which alter the Abeta aggregation/dissociation processes associated with neurotoxicity.     

Use of SAMPL for a study of DNA polymorphism,genetic diversity and possible gene tagging in bread wheat

Selective Amplification of Microsatellite Polymorphic Loci (SAMPL) technology was used in bread wheat for the first time for a study of genetic diversity, genotype identification and gene tagging. The diversity studies involved 55 wheat genotypes and two SAMPL primer pairs (SAMPL-6 and SAMPL-7, each with a M-CAG primer), which together gave 43 polymorphic bands out of a total of 87 SAMPL bands. The average polymorphic information content (PIC) of SAMPL primers was 0.221 and that of SAMPL markers was 0.264. The marker index of SAMPL markers was 9.61. The genetic similarity (GS) coefficients for 1,485 pairs of genotypes ranged from 0.35 to 0.96 with an average of 0.65. A dendrogram was prepared on the basis of a similarity matrix using the UPGMA algorithm, which corresponded well with the results of principal component analysis (PCA). From a total of 55 genotypes, 54 could be distinguished using the SAMPL banding patterns of both primers. For gene tagging, 568 bands from a total of 1,185 SAMPL bands detected polymorphism between each of the three pairs of parents differing for grain protein content (GPC), pre-harvest sprouting tolerance (PHST) and grain weight (GW). An association of six bands with GPC, of seven bands with PHST and four bands with GW was observed using bulked segregant analysis (BSA). Received: 5 April 2001 / Accepted: 17 May 2001     

Overall concordance correlation coefficient for evaluating agreement among multiple observers

Accurate and precise measurement is an important component of any proper study design. As elaborated by Lin (1989, Biometrics 45, 255-268), the concordance correlation coefficient (CCC) is more appropriate than other indices for measuring agreement when the variable of interest is continuous. However, this agreement index is defined in the context of comparing two fixed observers. In order to use multiple observers in a study involving large numbers of subjects, there is a need to assess agreement among these multiple observers. In this article, we present an overall CCC (OCCC) in terms of the interobserver variability for assessing agreement among multiple fixed observers. The OCCC turns out to be equivalent to the generalized CCC (King and Chinchilli, 2001, Statistics in Medicine 20, 2131-2147; Lin, 1989; Lin, 2000, Biometrics 56, 324-325) when the squared distance function is used. We evaluated the OCCC through generalized estimating equations (Barnhart and Williamson, 2001, Biometrics 57, 931-940) and U-statistics (King and Chinchilli, 2001) for inference. This article offers the following important points. First, it addresses the precision and accuracy indices as components of the OCCC. Second, it clarifies that the OCCC is the weighted average of all pairwise CCCs. Third, it is intuitively defined in terms of interobserver variability. Fourth, the inference approaches of GEE and the U-statistics are compared via simulations for small samples. Fifth, we illustrate the use of the OCCC by two medical examples with the GEE, U-statistics, and bootstrap approaches.     

Study of the serum albumin-polyethyleneglycol interaction to predict the protein partitioning in aqueous two-phase systems

The theoretical framework based only on the excluded volume forces is not enough to explain the bovine serum albumin partitioning behaviour in aqueous biphasic systems. The goal of this work is to look at the phase separation via the polymer effect on the water structure. Our findings suggest that polyethyleneglycol 600-protein interaction is conducted by van der Waals forces between the hydrophobic surfaces from PEG and protein molecules, which implies the rupture of hydrogen bonds from the structured water in their neighbours. Therefore, the protein will concentrate in the most water-structured phase (polyethyleneglycol) in order to reach the minimal free energy condition. When polyethyleneglycol molecular weight increases, its exclusion from protein surface prevails, thus pushing the bovine serum albumin to the bottom phase.     

Ingestion of crude oil: effects on digesta retention times and nutrient uptake in captive river otters

Studies following the Exxon Valdez oil spill in Prince William Sound, Alaska indicated that river otters (Lontra canadensis) from oiled regions displayed symptoms of degraded health, including reduced body weight. We examined the fate of ingested oil in the digestive tract and its effects on gut function in captive river otters. Fifteen wild-caught males were assigned to three groups, two of which were given weathered crude oil in food (i.e., control, 5 ppm day⁻¹, and 50 ppm day⁻¹) under controlled conditions at the Alaska Sealife Center. Using glass beads as non-specific digesta markers and stable isotope analysis, we determined the effects of ingested oil on retention time and nutrient uptake. Our data indicated that oil ingestion reduced marker retention time when we controlled for activity and meal size. Fecal isotope ratios suggested that absorption of lipids in the oiled otters might have been affected by reduced retention time of food. In addition, a dilution model indicated that as much as 80% of ingested oil was not absorbed in high-dose animals. Thus, while the ingestion of large quantities of weathered crude oil appears to reduce absorption of oil hydrocarbons and may alleviate systemic effects, it may concurrently affect body condition by impacting digestive function. Accepted: 18 May 2000     

The D' measure of overall gametic disequilibrium between pairs of multiallelic loci

Abstract The D ' coefficient is one of the most commonly used measures of the extent of gametic disequilibrium between multiallelic loci. It has been suggested that the range of the D ' measure of overall disequilibrium between pairs of multiallelic loci depends on allele frequencies, except under some very restricted conditions. Nevertheless, the problem of dependence of the range of D ' has not been characterized under a wide set of possible polymorphisms. Evaluation of the utility of D ' as a measure of the strength of overall disequilibrium between all possible pairs of alleles at two multiallelic loci requires better knowledge of its range than is currently available. In this work, the conditions of polymorphism under which the range of D ' is frequency independent are given. It is found that the range of D ' is more often independent of allelic frequencies than is commonly thought. Furthermore, the range of D ' undergoes only small fluctuations as a function of the polymorphisms at the loci. Numerical cases and microsatellite data from humans are used for illustration. These observations indicate that the D ' coefficient is a useful tool for the estimation and comparison of the extent of overall disequilibrium across pairs of multiallelic loci.     

森林流域土壤饱和渗透系数与有效孔隙度模型的研究

以长白山自然保护区内未受扰动的两种典型原始森林土壤为对象,通过野外选取原状土样,在实验室内测定其饱和渗透系数和有效孔隙度,利用回归分析法分别建立了森林土壤内饱和渗透系数和有效孔隙度随深度变化的数学模型,即Ｋｓ（ｚ）＝Ｋ０－ｆ１ｌｎａ１ｚ和ω（ｚ）＝ω０－ｆ２ｌｎａ２ｚ．将所得出的对数模型与Ｂｅｖｅｎ所提出的指数模型进行比较表明,在森林流域内对数模型不仅适用范围比指数模型广,而且精度明显高于指数模型,它更接近于野外实际情况．