从茶树种胚中提取总RNA方法的研究

茶树种胚中富含多糖和多酚类化合物,这增加了总RNA的提取难度.试验以茶树种胚为研究对象,通过对几种提取总RNA方法的比较与分析,认为用改进的CTAB-LjCl法提取茶树种胚总RNA的产率较高,质量好,可直接用于cDNA的合成、cDNA-AFLP分析等分子生物学实验操作.     

Extraction of condensed tannins from Mexican plant sources

Contents of total polyphenols, condensed tannins and proanthocyanidins, and their stability to various pH values and temperatures were studied in Mexican blueberry, cuautecomate fruit, garambullo fruit, aubergine, coffee pulp and residues of black grapes. Several aqueous extracts, obtained through a one-pass-extraction process, were analyzed using liquid chromatography in order to quantify the condensed tannin (proanthocyanidin) content responsible for their antioxidant activity and colour. All tested samples included high proanthocyanidin contents demonstrating that these Mexican fruits and vegetables are good sources of natural antioxidants, and they all could be considered as excellent functional foods due to their bioactivity measured as the condensed tannin level.     

A ninhydrin-based assay to quantitate the total protein content of tissue samples

Quantitation of small tissue samples for total protein content is essential for many biochemical analyses. In this study a ninhydrin method for measuring the total protein content of tissue hydrolysates is presented.The ninhydrin reagent is stable at room temperature for up to 1 month in the ethylene glycol-sodium acetate solvent system without the requirement for a nitrogen atmosphere. The reaction was very accurate and precise, with intra- and interassay variations of less than 3% when 5 microg of protein was assayed. All proteins that were investigated contributed the same color intensity per microgram protein as bovine serum albumin. This assay was several times more sensitive than the Coomassie reaction and linear over a greater range of protein concentration.     

Kinetics of protein agglomeration. A nephelometric method for the determination of total protein in biological samples

The kinetics of agglomeration of proteins precipitating in a viscous solution was measured by light scattering. The resulting transitory maximum was linearly proportional to the mass of protein over three orders of magnitude. The change in scattering intensity is described as a change in scattering symmetry due to a continuous in particle size.This method is both fast (minutes) and sensitive (30 ng protein) and is independent of the chemical composition of the different protein species and is barely influenced by size and shape of the proteins.By solubilising the protein in an alkaline dedecyl sulfate solution this method can be applied to all types of biological samples (e.g. tissue homogenates proteins) and also to all types of biological preparations containing detergents as well as urea, sucrose, salts and lipids.     

Measurement of the synthesis rates of collagens and total protein in rabbit muscle.

1. Collagen- and total-protein-synthesis rates were determined in rabbit muscle by continuous infusion of radioactive proline. 2. The precursor pool of free proline used for collagen synthesis was defined by measuring the specific radioactivity of hydroxy-proline in isolated type I procollagen. The specific radioactivities of type I procollagen were about 40% of those for free proline in the homogenate. 3. The mean ratio (+/- S.E.M.) between the fractional synthesis rates of muscle collagen and total protein was 0.99 +/- 0.10, where the total protein values were based on specific radioactivities of the homogenate free proline pools. 4. Types I, III and V collagen were solubilized by pepsin and isolated by fractional precipitation with NaCl. The fractional synthesis rates of types I and III collagens were very similar. Type V collagen samples had higher specific radioactivities than the other collagens, but this was not necessarily indicative of a higher rate of synthesis because of uncertainty about the cellular origin of this collagen and, hence, the specific radioactivity of its precursor proline pool.     

Correlation of oxidative transformations of hydrolyzable tannins and plant evolution

The progressive oxidative transformations in the biogenesis of hydrolyzable tannins, gallotannin (I) --> ellagitannin (II) --> dehydro ellagitannin (III) --> transformed dehydroellagitannin (IV), conform in several aspects to the evolutionary routes in the subclasses of Dicotyledonae, particularly in the Rosidae.     

Determination of total protein in hyperimmune serum samples by near-infrared spectrometry and multivariate calibration

In the present work, the determination of the total protein concentration in hyperimmune serum samples was performed through a partial least-squares near-infrared (NIR-PLS) method. The method was based on the chemometric treatment of the NIR spectra of samples. The influences of spectra preprocessing and spectral window utilized in the construction of PLS model were studied. Models were built using reference data of 19 samples selected through the use of hierarchical cluster analysis (HCA) of NIR spectra of samples and another 24 samples were employed for external validation of the method. A model with better prediction capacity was obtained after whole spectra preprocessing by multiplicative scattering correction (MSC) algorithm and using data in the spectral range of 2158-2209 nm. Under optimized conditions a RMSEP of 0.21 g dl⁻¹ and a quality coefficient value (QC) of only 5.8% were obtained for the prediction of total protein content in the samples used for external validation. Also, a determination coefficient, r², of 0.97 was obtained in the correlation of predicted and reference data of samples situated in the validation set.     

Inferring coancestry in population samples in the presence of linkage disequilibrium

In both pedigree linkage studies and in population-based association studies there has been much interest in the use of modern dense genetic marker data to infer segments of gene identity by descent (ibd) among individuals not known to be related, to increase power and resolution in localizing genes affecting complex traits. In this article, we present a hidden Markov model (HMM) for ibd among a set of chromosomes and describe methods and software for inference of ibd among the four chromosomes of pairs of individuals, using either phased (haplotypic) or unphased (genotypic) data. The model allows for missing data and typing error, but does not model linkage disequilibrium (LD), because fitting an accurate LD model requires large samples from well-studied populations. However, LD remains a major confounding factor, since LD is itself a reflection of coancestry at the population level. To study the impact of LD, we have developed a novel simulation approach to generate realistic dense marker data for the same set of markers but at varying levels of LD. Using this approach, we present results of a study of the impact of LD on the sensitivity and specificity of our HMM model in estimating segments of ibd among sets of four chromosomes and between genotype pairs. We show that, despite not incorporating LD, our model has been quite successful in detecting segments as small as 10(6) bp (1 Mpb); we present also comparisons with fastIBD which uses an LD model in estimating ibd.     

Variation in total phenols and condensed tannins in Eucalyptus: leaf phenology and insect grazing

Total phenols and condensed tannins in leaves of seven species of Eucalyptus ranged from 4–40% and 0–27% respectively of the leaf dry weight. The concentrations of these compounds were variable but usually high in young and older leaves throughout the growing season, and typically increased during winter, but no other trends with season or leafage were apparent. This pattern of seasonal variation in concentrations of total phenols and condensed tannins is different to that studied for other plant species. This difference may be related to repeated production of new leaves by Eucalyptus during the growing season, and the probability that these leaves will be attacked by herbivorous insects.     

Evidence for the presence of ferritin in plant mitochondria.

In this work, evidence for the presence of ferritins in plant mitochondria is supplied. Mitochondria were isolated from etiolated pea stems and Arabidopsis thaliana cell cultures. The proteins were separated by SDS/PAGE. A protein, with an apparent molecular mass of approximately 25-26 kDa (corresponding to that of ferritin), was cross-reacted with an antibody raised against pea seed ferritin. The mitochondrial ferritin from pea stems was also purified by immunoprecipitation. The purified protein was analyzed by MALDI-TOF mass spectrometry and the results of both mass finger print and peptide fragmentation by post source decay assign the polypeptide sequence to the pea ferritin (P < 0.05). The mitochondrial localization of ferritin was also confirmed by immunocytochemistry experiments on isolated mitochondria and cross-sections of pea stem cells. The possible role of ferritin in oxidative stress of plant mitochondria is discussed.     

The presence and activity of progesterone in the plant kingdom

Steroids are present in living organisms as one of the most essential groups of compounds. Continuous research has led to new discoveries and the revision of existing information concerning the occurrence and the role of steroids, both in animals and plants. This article will focus on reviewing the literature studying progesterone in the plant kingdom, including its discovery, its occurrence in different plant species as well as its biological activity and molecular basis of action. This review will present and discuss the current data in addition to introducing potential directions for further research on the subject of progesterone in plants.     

The digestion of dietary protein bound by condensed tannins in the gastro-intestinal tract of sheep

The digestion of dietary protein bound by condensed tannins (CTs) in ruminants was investigated by determining the extent of dissociation of insoluble ¹²⁵I-BSA + CT complexes administered to abomasally and intestinally fistulated sheep. The extent of dissociation was registered as the true digestibility of iodinated bovine serum albumin (¹²⁵I-BSA). The true digestibility of ¹²⁵I-BSA originally bound to Leucaena pallida CT (0.721) was lower (P<0.05) than that of ¹²⁵I-BSA originally bound to L. leucocephala CT (0.880) between the abomasum and terminal ileum. These results indicate that differences in the ability of CT to inhibit ¹²⁵I-BSA digestion in vivo matched the relative abilities of the same CT to bind BSA in vitro, indicating that the in vitro BSA-binding assay for ranking CT behaviour was biologically relevant in vivo. Furthermore, the true digestibility of CT-bound ¹²⁵I-BSA between the mouth and faeces permitted the prediction of the quantitative contribution that CT-bound dietary proteins make to improved nitrogen supply to the small intestines.     

Polyphenols, tannins and antioxidant activities of eight true mangrove plant species in South China

Background and aims

(i) compare the concentrations of total polyphenols (TP) and condensed tannins (CT), and CT profiles in different organs of mature trees and seedlings of eight true mangrove species in Hong Kong; (ii) examine the antioxidant activities of CT and (iii) relate the non-enzymatic antioxidative defence system with the vertical zonation pattern of mangrove species.

Methods

Mature trees and seedlings of eight species were collected from a Hong Kong mangrove swamp to determine TP and CT concentrations and the antioxidant activities of CT.

Results

According to TP concentrations, the true mangrove species could be broadly classified into three groups, (i) Lumnitzera racemosa and Aegiceras corniculatum > (ii) Heritiera littoralis, Excoecaria agallocha, Bruguiera gymnorrhiza and Kandelia obovata > (iii) Acanthus ilicifolius and Avicennia marina. The last two are pioneer species in the most foreshore location. They also had significantly lower antioxidant activities, CT concentrations and different CT profiles than the other six species in mid- and low-tides.

Conclusions

Classification of the eight true mangrove species into three groups based on polyphenols was similar to their vertical zonation from land to sea. The relationships between these antioxidants and zonation should be further verified by transplantation studies.     

Critical aspects in determining total radioactivity of biological samples

During measurements of radioactivity in some milk samples with liquid scintillation counter (about one year after the nuclear accident of Chernobyl) we have observed an increase of the values of scintillation fluid with the passing of time. Although this enhancement is absolutely small (about 2 c.p.m. in 500 min), it is very important for an exact measurement of samples at low counting, as those tested. Our protocol of measure provides for insertion of alternate blanks and samples in the automatic sample-holders of liquid scintillation counter. The values of measurement of samples are taken during the increase phase subtracting the value of blank interpolated on the increasing straight line from c.p.m. of sample. Finally, we report the collected values of the whole radioactivity in some milk samples: at least 5-6 nCi/L contrary to about 1 nCi/L of 137Cs reported by USL. In our opinion it is important to consider the whole radioactivity as measure of the overall biological danger of radioactive samples. In fact, this measurement takes into account also biologically very dangerous radionuclides as 3H, 14C, 90Sr.     

Multivariate logistic regression for predicting total culturable virus presence at the intake of a potable-water treatment plant: novel application of the atypical coliform/total coliform ratio

Predicting the presence of enteric viruses in surface waters is a complex modeling problem. Multiple water quality parameters that indicate the presence of human fecal material, the load of fecal material, and the amount of time fecal material has been in the environment are needed. This paper presents the results of a multiyear study of raw-water quality at the inlet of a potable-water plant that related 17 physical, chemical, and biological indices to the presence of enteric viruses as indicated by cytopathic changes in cell cultures. It was found that several simple, multivariate logistic regression models that could reliably identify observations of the presence or absence of total culturable virus could be fitted. The best models developed combined a fecal age indicator (the atypical coliform [AC]/total coliform [TC] ratio), the detectable presence of a human-associated sterol (epicoprostanol) to indicate the fecal source, and one of several fecal load indicators (the levels of Giardia species cysts, coliform bacteria, and coprostanol). The best fit to the data was found when the AC/TC ratio, the presence of epicoprostanol, and the density of fecal coliform bacteria were input into a simple, multivariate logistic regression equation, resulting in 84.5% and 78.6% accuracies for the identification of the presence and absence of total culturable virus, respectively. The AC/TC ratio was the most influential input variable in all of the models generated, but producing the best prediction required additional input related to the fecal source and the fecal load. The potential for replacing microbial indicators of fecal load with levels of coprostanol was proposed and evaluated by multivariate logistic regression modeling for the presence and absence of virus.