Divergence time estimates of mammals from molecular clocks and fossils: Relevance of new fossil finds from India

This paper presents a brief review of recent advances in the classification of mammals at higher levels using fossils and molecular clocks. It also discusses latest fossil discoveries from the Cretaceous — Eocene (66–55 m.y.) rocks of India and their relevance to our current understanding of placental mammal origins and diversifications.     

MutantHFE genotype leads to significant iron overload in patients with liver diseases from western Romania

The present study aimed at assessing the frequency ofHFE mutations (C282Y, H63D and S65C) in western Romanian patients with liver disease of diverse aetiologies suspected of iron overload. A total of 21 patients, all Romanian residents hospitalized with clinical suspicion of iron overload and liver disease, were assayed for C282Y, H63D and S65C mutations, serum ferritin and viral hepatitis markers. Overall, 9 out of the 21 patients (42.86%) were found to harbour mutations in theHFE gene: 4 homozygotes C282Y (19.0%), 1 compound heterozygote C282Y/H63D (4.8%), 1 single heterozygote C282Y (4.8%), 2 single heterozygotes H63D (9.5%), 1 single heterozygote S65C (4.8%), and 12 wild-type cases (57.1%). Among the subgroup of 10 patients with the most prominent signs of iron overload (hyperferritinaemia and/or hepatocyte iron score ≥ 1), without hepatocellular carcinoma, theHFE genotypes were conclusive in 5 cases (50%). They had significantly increased ferritin levels compared to wild-type cases (P = 0.029). The inclusion of iron studies during routine clinical visits, coupled with the availability ofHFE genotyping for family and population studies, should facilitate the early detection of hereditary haemochromatosis in Romania.     

Physical microhabitat requirements of freshwater pearl mussels,Margaritifera margaritifera (L.)

Surface sediment diatoms from the east coast of Lake Tanganyika were analysed using ordination and classification techniques, and compared with assemblages previously described from the northern part of the lake. Grain-size analyses were performed on subsamples. Four groups of diatom assemblages were recognised. The first group clusters samples taken in the north, far from the Rusizi river mouth. The second group comprises samples taken on silty sediment along the Tanzanian coast, including one sample taken near the mouth of the Malagarazi river and those from the northernmost part of the lake. The third group comprises surface sediments along the Burundian coast (near Ramba and Magara), and the fourth is characterised by epipsammic taxa. A sample taken near the central arm of the Malagarazi river is included in the latter group. The impact of small rivers on the diatom assemblages in the surface sediments is restricted to the mouth area.     

Transport of amino acids and ammonium in mycelium of Agaricus bisporus.

Mycelium of Agaricus bisporus took up methylamine (MA), glutamate, glutamine and arginine by high-affinity transport systems following Michaelis-Menten kinetics. The activities of these systems were influenced by the nitrogen source used for mycelial growth. Moreover, MA, glutamate and glutamine uptakes were derepressed by nitrogen starvation, whereas arginine uptake was repressed. The two ammonium-specific transport systems with different affinities and capacities were inhibited by NH(+)(4), with a K(i) of 3.7 microM for the high-velocity system. The K(m) values for glutamate, glutamine and arginine transport were 124, 151 and 32 microM, respectively. Inhibition of arginine uptake by lysine and histidine showed that they are competitive inhibitors. MA, glutamate and glutamine uptake was inversely proportional to the intracellular NH(+)(4) concentration. Moreover, increase of the intracellular NH(+)(4) level caused by PPT (DL-phosphinotricin) resulted in an immediate cessation of MA, glutamine and glutamate uptake. It seems that the intracellular NH(+)(4) concentration regulates its own influx by feedback-inhibition of the uptake system and probably also its efflux which becomes apparent when mycelium is grown on protein. Addition of extracellular NH(+)(4) did not inhibit glutamine uptake, suggesting that NH(+)(4) and glutamine are equally preferred nitrogen sources. The physiological importance of these uptake systems for the utilization of nitrogen compounds by A. bisporus is discussed.     

Chlamydia isopodii sp. n., an obligate intracellular parasite of Porcellio scaber

In an ultrastructural study of the hepatopancreas of Porcellio scaber, an obligate intracellular parasite, Chlamydia, was noted in the epithelial cells. Although the infection was found to extend the entire length of the hepatopancreas, it was most extensive in the glandular region. Indirect immunofluorescence testing revealed no cross-reactivity with either lymphogranuloma venereum or psittacosis antisera.     

Redox study of electron donation to P-680 in Photosystem II

Flash-induced absorption changes at 820 nm were studied as a function of redox potential in Tris-extracted Photosystem II oxygen-evolving particles and Triton subchloroplast fraction II particles. The rereduction kinetics of P-680+ in both preparations showed biphasic recovery phases with half-times of 42 and 625 microseconds at pH 4.5. The magnitude of the 42 microseconds phase of P-680+ rereduction was strongly dependent on the redox potential of the medium. This absorption transient, attributed to electron donation from D1 (the secondary electron donor in oxygen-inhibited chloroplasts), titrated as a single redox component with a midpoint potential of +240 +/- 35 mV. The experimentally determined midpoint potential was found to be independent of pH over the tested range 4.5-6.0. In contrast, the magnitude of the 625 microseconds phase of P-680+ rereduction was independent of redox potential between +350 and +100 mV. These results are interpreted in terms of a model in which an alternate electron donor with Em approximately equal to 240 mV, termed D0, serves as a rapid donor (t 1/2 less than or equal to 2 microseconds) to P-680+ in Tris-extracted and Triton-treated Photosystem-II preparations. According to this model, the slower electron donor, D1, is functional only when D0 becomes oxidized.     

Rapid quantitative analysis of binary mixtures of Escherichia coli strains using pyrolysis mass spectrometry with multivariate calibration and artificial neural networks

Pyrolysis mass spectrometry (PyMS) and multivariate calibration were used to show the high degree of relatedness between Escherichia coli HB101 and E. coli UB5201. Next, binary mixtures of these two phenotypically closely related E. coli strains were prepared and subjected to PyMS. Fully interconnected feedforward artificial neural networks (ANNs) were used to analyse the pyrolysis mass spectra to obtain quantitative information representative of the level of E. coli UB5201 in E. coli HB101. The ANNs exploited were trained using the standard back propagation algorithm, and the nodes used sigmoidal squashing functions. Accurate quantitative information was obtained for mixtures with >3% E. coli UB5201 in E. coli HB101. To remove noise from the pyrolysis mass spectra and so lower the limit of detection, the spectra were reduced using principal components analysis (PCA) and the first 13 principal components used to train ANNs. These PCA-ANNs allowed accurate estimates at levels as low as 1% E. coli UB5201 in E. coli HB101 to be predicted. In terms of bacterial numbers, it was shown that the limit of detection for PyMS in conjunction with ANNs was 3 × 10⁴ E. coli UB5201 cells in 1·6 × 10⁷ E. coli HB101 cells. It may be concluded that PyMS with ANNs provides a powerful and rapid method for the quantification of mixtures of closely related bacterial strains.