Pellicle of Paramecium caudatum as Revealed by Freeze Etching

SYNOPSIS. Freeze etching study of Paramecium caudatum surface reveals a regular pattern formed by depressions equipped with a single or paired cilia. This picture is consistent with the generally accepted concept of Paramecium cortex based on conventional methods of study. The surface of the ciliate is covered with small globular particles ∼14 nm in diameter, which have been found also on the plasma membrane of other cells. In the areas where the tips of trichocysts are attached to the pellicle, the globular particles are arranged into circles 0.4 μm in diameter. The whole surface of Paramecium is covered by a smooth thin layer which, always chipped off during fracturing, is detectable only after etching.     

提高生物课堂教学有效性——新课程背景下探究教学法的灵活运用

新课程的实施需要运用探究教学法,广大高中生物教师对这一教法的运用还在摸索之中。通过拟从探究教学法的运用,对提高高中生物课堂教学有效性的作用,提出实践性的教学建议。     

A method for determining the position and size of optimal sequence regions for phylogenetic analysis

The availability of fast and accurate sequencing procedures along with the use of PCR has led to a proliferation of studies of variability at the molecular level in populations. Nevertheless, it is often impractical to examine long genomic stretches and a large number of individuals at the same time. In order to optimize this kind of study, we suggest a heuristic procedure for detection of the shortest region whose informational content can be considered sufficient for significant phylogenetic reconstruction. The method is based on the comparison of the pairwise genetic distances obtained from a set of sequences of reference to those obtained for different windows of variable size and position by means of a simple index. We also present an approach for testing whether the informative content in the stretches selected in this way is significantly different from the corresponding content shown by the larger genomic regions used as reference. Application of this test to the analysis of the VP1 protein gene of foot-and-mouth-disease type C virus allowed us to define optimal stretches whose informative content is not significantly different from that displayed by the complete VP1 sequence. We showed that the predictions made for type C sequences are valid for type O sequences, indicating that the results of the procedure are consistent. Correspondence to: J. Dopazo     

Skin Tattooing As A Novel Approach For DNA Vaccine Delivery

Nucleic acid-based vaccination is a topic of growing interest, especially plasmid DNA (pDNA) encoding immunologically important antigens. After the engineered pDNA is administered to the vaccines, it is transcribed and translated into immunogen proteins that can elicit responses from the immune system. Many ways of delivering DNA vaccines have been investigated; however each delivery route has its own advantages and pitfalls. Skin tattooing is a novel technique that is safe, cost-effective, and convenient. In addition, the punctures inflicted by the needle could also serve as a potent adjuvant. Here, we a) demonstrate the intradermal delivery of plasmid DNA encoding enhanced green fluorescent protein (pCX-EGFP) in a mouse model using a tattooing device and b) confirm the effective expression of EGFP in the skin cells using confocal microscopy.     

Mechanism of the binding of 2-(4'-hydroxyphenylazo)benzoic acid to bovine serum albumin

The mechanism of the binding of 2-(4'-hydroxyphenylazo)benzoic acid (HABA) to bovine serum albumin was studied by relaxation methods as well as the binding isotherm using gel chromatography. A single relaxation was observed over a wide range of HABA concentration except at the extremes of high concentration where another slow process was observed. The concentration dependence of the reciprocal relaxation time of the fast process decreased monotonically with increase in concentration of HABA at constant polymer concentration. The data were analyzed on the basis of Brown's domain structure model and were found to be consistent with a sequential binding mechanism. The azohydrazon tautomerism of HABA was identified with the intramolecular step of the complex. The activation parameters of the step, determined from the temperature dependence of the relaxation time of the fast process, showed that this step is rate limited by an enthalpy barrier in both forward and backward directions. Comparison of the activation parameters with those of other serum albumin-ligand systems suggests that there is an enthalpy-entropy compensation in the activation process of the intramolecular step with the compensation temperature at about 270 K; the enthalpy-entropy compensation is thought to be related to the hydrophobic nature of the ligand.     

A new method for the improvement of data production in phytochemical analysis

Introduction – The use of the average analytical signal for the construction of curves by the least squares method (LSM) over the standard addition method (SAM) is widespread. It would be advantageous, however, to find a way to avoid intermediary averages, which are known to be the cause of significant increases in standard deviations (SD). Objective – To develop a protocol that uses all gathered data to create curves by LSM over SAM. To use Excel^® for the estimation of y = mx + b and R² rather than using LSM equations for the SD of m, x and b. Methodology – The level of lead (II) in the bark (cork) of Quercus suber Linnaeus was determined using differential pulse anodic stripping voltammetry (DPASV). Three current samples were taken for each of the four standard additions. These signals were combined for adjustment by LSM. The results were compared with those obtained after averaging the current for each addition, and the expression of uncertainty in the measurements determined. Results – The new method shows an expanded uncertainty of ± 0.3321 μg/g (nearly 1.42%). The difference between the results obtained by the new and the old method is 0.01 μg/g (23.41 and 23.40 μg/g). The limit of detection changed approximately from 4.8 to 4 μg/g and the relative SD approximately from 9 to 6%. Conclusion – The absence of intermediary averages in curves improved the determination of lead (II) in cork by DPASV. Estimation of SD only with LSM equations produced results that were significantly worse. The changes are large enough to transform an apparently internally non‐validated procedure (repeatability for precision) into an internally validated procedure. Copyright © 2009 John Wiley & Sons, Ltd.