Membrane fluidity of microsomal and thymocyte membranes after X-ray and UV irradiation

A brief literature review shows that ionizing radiation in biological membranes and in pure lipid membranes causes malondialdehyde formation, indicating lipid peroxidation processes. With respect to membrane fluidization by ionizing radiation, in pure lipid membranes rigidization effects are always reported, whereas contradictory results exist for biological membranes. Starting from the assumption that membrane proteins at least partly compensate for radiation effects leading to a rigidization of membrane lipid regions, pig liver microsomes, as a representative protein-rich intracellular membrane system, were irradiated with X-rays or UV-C with doses up to 120 Gy at a dose rate of 0.67 Gy min^–1 and up to 0.73 J cm^–2 at an exposure rate of 16.2 mJ cm^–2 min^–1, respectively. For both irradiation types a weak but significant positive correlation between malondialdehyde formation and membrane fluidity is revealed throughout the applied dose ranges. We conclude that the membraneous protein lipid interface increases its fluidity under radiation conditions. Also, thymocyte ghosts showed an increased fluidity after X-ray irradiation. Fluidity measurements were performed by the pyrene excimer method.     

Starvation-Induced Stress Resistance in Lactococcus lactis subsp. lactis IL1403

Carbohydrate-starved cultures of Lactococcus lactis subsp. lactis IL1403 showed enhanced resistance to heat, ethanol, acid, osmotic, and oxidative stresses. This cross-protection seems to be established progressively during the transitional growth phase, with maximum resistance occurring when cells enter the stationary phase. Chloramphenicol or rifamycin treatment does not abolish the development of a tolerant cell state but, on the contrary, seems to provoke this response in L. lactis subsp. lactis.     

Biologie und Verhalten zentralasiatischer Schneefinken (Montifringilla) und Erdsperlinge (Pyrgilauda)

Snow Finches and Mountain-steppe Sparrows differ in habitat selection, feeding, social and vocal behaviour. For these reasons, separation of the genusMontifringilla intoMontifringilla andPyrgilauda is recommended.     

Phylogenetic relationships among eutherian orders estimated from inferred sequences of mitochondrial proteins: Instability of a tree based on a single gene

The phylogenetic relationships among Primates (human), Artiodactyla (cow), Cetacea (whale), Carnivora (seal), and Rodentia (mouse and rat) were estimated from the inferred amino acid sequences of the mitochondrial genomes using Marsupialia (opossum), Aves (chicken), and Amphibia (Xenopus) as an outgroup. The overall evidence of the maximum likelihood analysis suggests that Rodentia is an outgroup to the other four eutherian orders and that Cetacea and Artiodactyla form a clade with Carnivora as a sister taxon irrespective of the assumed model for amino acid substitutions. Although there remains an uncertainty concerning the relation among Artiodactyla, Cetacea, and Carnivora, the existence of a clade formed by these three orders and the outgroup status of Rodentia to the other eutherian orders seems to be firmly established. However, analyses of individual genes do not necessarily conform to this conclusion, and some of the genes reject the putatively correct tree with nearly 5% significance. Although this discrepancy can be due to convergent or parallel evolution in the specific genes, it was pointed out that, even without a particular reason, such a discrepancy can occur in 5% of the cases if the branching among the orders in question occurred within a short period. Due to uncertainty about the assumed model underlying the phylogenetic inference, this can occur even more frequently. This demonstrates the importance of analyzing enough sequences to avoid the danger of concluding an erroneous tree.     

Cloning and characterization of the platypus mitochondrial genome

The vertebrate mitochondrial genome is highly conserved in size and gene content. Among the chordates there appears to be one basic gene arrangement, but rearrangements in the mitochondrial gene order of the avian lineages have indicated that the mitochondrial genome may be more variable than once thought. Different gene orders in marsupials and eutherian mammals leave the ancestral mammalian order in some doubt. We have investigated the mitochondrial gene order in the platypus (Ornithorhynchus anatinus), a representative of the third major group of mammals, to determine which mitochondrial gene arrangement is ancestral in mammals. We have found that the platypus mtDNA conforms to the basic chordate gene arrangement, common to fish, amphibians, and eutherian mammals, indicating that this arrangement was the original mammalian arrangement, and that the unusual rearrangements observed in the avians and marsupials are probably lineage-specific. Correspondence to: N.J. Gemmell     

Analysis of the regulation of penicillin biosynthesis in Aspergillus nidulans by targeted disruption of the acvA gene

To analyse the regulation of the biosynthesis of the secondary metabolite penicillin in Aspergillus nidulans, a strain with an inactivated acvA gene produced by targeted disruption was used. acvA encodes -(l--aminoadipyl)-l-cysteinyl-d-valine synthetase (ACVS), which catalyses the first step in the penicillin biosynthetic pathway. To study the effect of the inactivated acvA gene on the expression of acvA and the second gene, ipnA, which encodes isopenicillin N synthase (IPNS), A. nidulans strain XEPD, with the acvA disruption, was crossed with strain AXB4A carrying acvA-uidA and ipnA-lacZ fusion genes. Ascospores with the predicted non-penicillin producing phenotype and a hybridization pattern indicating the presence of the disrupted acvA gene, and the fusion genes integrated in single copy at the chromosomal argB locus were identified. Both fusion genes were expressed at the same level as in the non-disrupted strain. Western blot analysis (immunoblotting) revealed that similar amounts of IPNS enzyme were present in both strains from 24 to 68 h of a fermentation run. In the acvA disrupted strain, IPNS and acyl-CoA: 6-aminopenicillanic acid acyltransferase (ACT) specific activities were detected, excluding a sequential induction mechanism of regulation of the penicillin biosynthesis gene ipnA and the third gene aat.     

Phloem translocation of Fe,Cu, Mn,and Zn in Ricinus seedlings in relation to the concentrations of nicotianamine,an endogenous chelator of divalent metal ions,in different seedling parts

During the first 8 days of germination the Ricinus seedling is supplied with all nutrients by the endosperm via phloem transport. In 4- to 8-days-old seedlings the concentrations and contents of Fe, Cu, Mn and Zn, and nicotianamine (NA) in the endosperm, cotyledons, hypocotyl and roots were estimated. From the data obtained translocation rates and flow profiles for the metals were established. The main sink for Fe, Mn and Zn were the cotyledons whereas Cu was mainly imported into the hypocotyl. Maximum flow rates occurred between days 5 and 7, for Zn between days 6 and 8.The time kinetics of NA and divalent metal ion concentrations and contents are interpreted as co-transport. The role of NA as transport vehicle of micronutrients in the sieve tubes is discussed.