A split-pot experiment with sorghum to test a root water uptake partitioning model

Correct modeling of root water uptake partitioning over depth is an important issue in hydrological and crop growth models. Recently a physically based model to describe root water uptake was developed at single root scale and upscaled to the root system scale considering a homogeneous distribution of roots per soil layer. Root water uptake partitioning is calculated over soil layers or compartments as a function of respective soil hydraulic conditions, specifically the soil matric flux potential, root characteristics and a root system efficiency factor to compensate for within-layer root system heterogeneities. The performance of this model was tested in an experiment performed in two-compartment split-pot lysimeters with sorghum plants. The compartments were submitted to different irrigation cycles resulting in contrasting water contents over time. The root system efficiency factor was determined to be about 0.05. Release of water from roots to soil was predicted and observed on several occasions during the experiment; however, model predictions suggested root water release to occur more often and at a higher rate than observed. This may be due to not considering internal root system resistances, thus overestimating the ease with which roots can act as conductors of water. Excluding these erroneous predictions from the dataset, statistical indices show model performance to be of good quality.     

Chromosome banding and genome compartmentalization in fishes

The diploid chromosome number of the Chinese raccoon dog varies from 54 (no B chromosomes) to 58 (4 B chromosomes). The B chromosomes are totally heterochromatic. An electron microscopic study was made of the synaptonemal complexes (SC) in spermatocytes of these animals. The SC karyotype consists of 27 regular chromosome pairs (autosomes and the sex chromosomes) plus the B chromosomes. The Bs pair effectively with one another at pachytene, but the SC axes of the B chromosomes are much denser than those of the A chromosomes. Depending on the number of Bs, both bivalents and multivalents have been observed. When three B chromosomes are present in a cell, parallel alignment of all three SCs can be seen. Formation of multivalents indicates high homology among these supernumerary heterochromatic chromosomes. Fusiform bulges are found along unpaired regions of all chromosomes which are particularly pronounced in diplotene.     

Purification and subunit structure of RNA polymerases I and II from Dictyostelium discoideum vegetative cells

Summary A purification procedure to obtain RNA polymerases I (or A) and II (or B) from Dictyostelium discoideum amoeba has been developed. The enzymes were solubilized from purified nuclei and separated by DEAF-Sephadex chromatography. RNA polymerases I and II were further purified by a second chromatography on DEAE-Sephadex followed by chromatographies on phosphocellulose and heparin-sepharose. The specific activities of purified RNA polymerases I and II are 92 units/ mg protein and 70 units/ mg protein, respectively. The subunit structure of both RNA polymerases were analyzed by polyacrylamide gel electrophoresis under denaturing conditions after glycerol gradient centrifugation of the enzymes. The putative subunits of RNA polymerase I have molecular weights of 180 000,125 000,43 000,40 000,34 000, 31 000, 25 000,19 000, 17 000 and 14 000. The putative subunits of RNA polymerase II have molecular weights of 200 000 (170 000), 130 000, 33 000, 25 000, 19 000, 17 000, 15 000, 13 000. There are three polypeptides with common molecular weight in Dictyostelium RNA polymerases I and 11. The subunit of 25 000 daltons of both enzymes has common immunological determinants with RNA polymerase II from crustacean Artemia.Abbreviations TLCK tosyl-lysine-chloromethyl-ketone - DPT diazophenylthioether     

Nucleotide substitutions at the -6 position in the promoter region of the factor IX gene result in different severity of hemophilia B Leyden: consequences for genetic counseling

Mutations in the promoter region of the factor IX gene result in hemophilia B Leyden, which is characterized by considerable improvement in the disease after puberty. We have found that distinct nucleotide substitutions at the -6 position in the Leyden-specific (LS) region are associated with a different severity of hemophilia B. The proband (aged 2) from one family is a severe hemophiliac with factor IX activity (F.IXC) and antigen (F.IXAg) levels less than 1.0U/dl. F.IXC and F.IXAg levels in two affected uncles are approximately 30% of normal levels. The LS region was targeted for analysis because the phenotypes suggested the inheritance of a factor IX Leyden gene. An abnormal TaqI digestion pattern was found in amplified DNA from the proband, and sequencing showed a G (-6) to C transversion that was linked to the disease in the family. In another family, two brothers (aged 8 and 9) suffer from mild hemophilia with F.IXC ranging from 7 to 10 U/dl and F.IXAg from 3 to 4 U/dl. They are the only documented members of the family with a bleeding tendency. Denaturing gradient gel electrophoresis on amplified fragments from one of the patient's genomic DNA corresponding to the 8 exons and flanking sequences of the factor IX gene suggested a defect only in a segment from the 5 region. This segment showed an altered TaqI digestion pattern, and sequencing demonstrated a G(-6) to A transition that was traced to the patients's mother and a grandmother. The different phenotypes associated with the G (-6) to A purine nucleotide transition compared with a G(-6) to C transversion provide evidence that this area is directly involved in the regulation of the human factor IX gene expression in vivo by binding of regulatory factors. The ability to predict that the conditions of a hemophilia B patient will improve with age has important implications for genetic counseling of the family. Therefore, the LS region should always be included when scanning the factor IX gene for mutations.     

Immunophenotyping of mitotic cells from long-term cultures of chorionic villi

Chromosomal mosaicism in chorionic villus samples (CVS) may arise from different sources, such as clonal diversity within the chorionic tissue or contamination with maternal cells. To determine the origin of karyotyped cells, we compared the immunocytochemical features of mitotic cells in CVS long-term cultures with histological sections of their tissue of origin, i.e. chorionic villi. Immunolabelling of intermediate filaments specific for epithelial cells (cytokeratin) and mesenchymal cells (vimentin) established that mitoses yielded from CVS long-term cultures indeed stem from independently growing clones derived from both the epithelial and mesenchymal parts of the chorionic villi. Thus, mosaicism in CVS cultures may reflect true genetic heterogeneity within the biopsy. However, epithelial chorionic cells undergo in vitro metaplasia leading to co-expression of cytokeratins and vimentin. Fetal-specific immune markers (-HCG and SP1-glycoprotein) are not reliably expressed in CVS cell culture.     

Fishers' Knowledge Reveals Ecological Interactions Between Fish and Plants in High Diverse Tropical Rivers

Ecosystems - Frugivory and seed dispersal by fish is an important mutualistic interaction in complex and species-rich tropical rivers. The local ecological knowledge (LEK) held by fishers can...     

Population structure of mud flounder Paralichthys orbignyanus from the south-western Atlantic Ocean

The mud flounder Paralichthys orbignyanus (Pleuronectiformes, Paralichthyidae) inhabits shallow waters of low salinities and mud bottoms in the temperate marine coastal regions of the Bonaerensean Ecoregion of the Argentinean Biogeographic Province in the south-western Atlantic Ocean. Specimens of P. orbignyanus were collected from Lagoa dos Patos (LDP) (southern Brazil), Mar Chiquita (MCH) and Marisol (MAR) both located in Buenos Aires (Argentina), and San Antonio Oeste (SAO) in the San Matías Gulf, Rio Negro (Argentina). A fragment of the mitochondrial DNA of the Control Region and seven microsatellite loci were characterized. In the Control Region, P. orbignyanus showed high variability, low nucleotide diversity, mild population expansion and a coalescence time of 35,000 years before the present. Flounders provided evidence of a genetic structure between the sampling sites LDP, MCH, MAR vs. SAO. On the other hand, P. orbignyanus displayed a lower to moderate contemporary genetic structure among all samples except between LDP and MCH. With no evidence of isolation by distance, this analysis supports a model of limited gene flow that is likely to be associated with a consistent larvae retention in all sampling sites. In addition, the present connectivity is ascribed to a lower migration process from SAO in the San Matías Gulf congruent with the prevailing littoral drift.     

Contribution of the different planktonic microbial assemblages to ETS activity in the Ligurian frontal area: north-west Mediterranean Sea

Spatial and size distribution of micro-organisms and their ETSactivity has been investigated in Ligurian Sea surface watersalong the Nice-Calvi transect across frontal areas from 18 to37 km offshore (TOMOFRONT 1 and 2 cruises, April 1988 and April-May1989 respectively). Aplastidic and plastidic nanoflagellatesand aplastidic picoflagellates were present in numbers closeto 0.25 x 10⁴ cells ml^–1, whereas plastidic picoflagellatesaccounted for about half this number. Correlations have beenevidenced between plastidic and aplastidic micro-organisms withinthe same size group, suggesting that they belong to a well-definedecosystem. The highest correlation between total ETS activityand abundance of the considered size groups was observed fornanoflagellates (r = 0.94, n = 22, and r = 0.90, n = 22 foraplastidic and plastidic cells respectively). The importanceof the role of nanoflagellates in surface waters, with respectto the overall ETS activity, was supported by results from sizefractionation which assigned to the 3–10 µm sizerange a 73.3% contribution to overall ETS activity. Resultsemphasize analysing global ETS activity of natural samples inorder to derive relationships between the different populationspresent in the sampled water. It is suggested that couplingflow cytometry to the ETS approach should be very helpful inthat respect.