In Vivo Substitution of Choline for Sodium Evokes a Selective Osmoinsensitive Increase of Extracellular Taurine in the Rat Hippocampus

Recent investigations have demonstrated that taurine and phosphoethanolamine (PEA) are the amino acids most sensitive to microdialysis-perfusion with reduced concentrations of NaCl. The aim of the present work was to assess the importance of Na+ deficiency in evoking this response. Further, the previously described selectivity of replacement of Cl- with acetate with respect to amino acid release was reinvestigated. The hippocampus of urethane-anesthetized rats was dialyzed with Krebs-Ringer bicarbonate buffer, and amino acid concentrations of the perfusate were determined. Choline chloride was then stepwise substituted for NaCl, and, in some cases, mannitol (122 mM) was included in low sodium-containing media. In other experiments, NaCl was replaced with sodium acetate. The dialysate levels of taurine increased selectively in response to Na+ substitution. The elevation of taurine was linearly related to the increase in choline chloride, and maximal levels amounted to 335% of basal levels. The increase in extracellular taurine was not inhibited by perfusion with medium made hyperosmotic with mannitol. Replacement of Cl- with acetate stimulated the release of taurine to 652% of resting levels. In addition, PEA levels increased to 250% of control concentration. Other amino acids were unaffected by Cl- substitution. The results show that taurine transport is considerably more sensitive to Na+ depletion than glutamate transport, which also is known to be Na+ dependent. The taurine increase evoked by low Na+ is not caused by cellular swelling as it was unaffected by hyperosmolar medium. Finally, substitution of acetate for Cl- causes a specific elevation of extracellular taurine and PEA, possibly as a result of cytotoxic edema.     

Loss of bovine papillomavirus DNA replication control in growth-arrested transformed cells.

The bovine papillomavirus type 1 (BPV-1) genome replicates as a plasmid within the nuclei of BPV-1-transformed murine C127 cells at a constant multiple copy number, and spontaneous amplification of the viral DNA is rarely observed. We report here that a mutant BPV-1 plasmid within a contact-inhibited C127 cell line replicated as a stable multicopy plasmid in exponentially growing cells but amplified to a high level in confluent cell culture. In situ hybridization analysis revealed that most of the mutant viral DNA amplification occurred in a minor subpopulation of cells within the culture. These consisted of giant nondividing cells with greatly enlarged nuclei, a cell form which was specifically induced in stationary-phase cultures. These observations indicated that expression of a viral DNA replication factor was cell growth stage specific. Consistent with this hypothesis, considerable amplification of wild-type BPV-1 DNA associated with characteristic giant cell formation was observed in typical wild-type virus-transformed C127 cultures following a period of growth arrest achieved by serum deprivation. Further observations indicated that induction of the giant-cell phenotype was dependent on BPV-1 gene expression and implicated a viral E1 replication factor in this process. Moreover, heterogeneity in virus genome copy numbers within the giant-cell population suggested a complex regulation of induction of DNA synthesis in these cells. It appears that this process represents a mechanism employed by the virus to ensure maximal viral DNA synthesis within a growth-arrested cell. Fundamental questions concerning the integration of the virus-cell control circuitry in proliferating and resting cells are discussed.     

Activation of rat liver microsomal glutathione S-transferase by hydrogen peroxide: role for protein-dimer formation.

The mechanism of oxygen radical-dependent activation of hepatic microsomal glutathione S-transferase by hydrogen peroxide was studied. Glutathione S-transferase activity in liver microsomes was increased 1.5-fold by incubation with 0.75 mM hydrogen peroxide at 37 degrees C for 10 min, and the increase in activity was reversed by incubation with dithiothreitol. Purified glutathione S-transferase was also activated by hydrogen peroxide after incubation at room temperature, and the increase in the activity was also reversed by dithiothreitol. Immunoblotting with anti-microsomal glutathione S-transferase antibodies after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of hydrogen peroxide-treated microsomes or purified glutathione S-transferase revealed the presence of a glutathione S-transferase dimer. These results indicate that the hydrogen peroxide-dependent activation of the microsomal glutathione S-transferase is associated with the formation of a protein dimer.     

Nachweis humoraler und lokaler Antikörper nach Einsatz einer bordetella Bronchiseptica-Lebendvakzine am Schwein

The aim of this work was to prove if a Bordetella bronchiseptica living vaccine is able to induce humoral and local antibodies in pigs. The living vaccine was compared with a killed Bordetella bronchiseptica adjuvans vaccine. The results show that piglets of sows vaccinated parenterally with living vaccine and killed adjuvans vaccine develop a stronger humoral immune reaction than piglets vaccinated locally with living vaccine. Sows immunized parenterally with living vaccine permint their piglets in the first three weeks colostral antibodies like sows immunized with killed adjuvans vaccine. The living vaccine induces especially local antibodies.     

Armaments and ornaments: an evolutionary explanation of traits of dual Utility

Secondary sexual characters in many species function both in male-male competition and as cues for female choice. Based on a literature compilation of existing knowledge of traits with this dual function, we propose that they commonly arise through intersexual selection processes and serve as honest signals to other males regarding fighting ability or dominance. Faking these traits, here called armaments, (i.e. weapons and status badges) is difficult, as they are constantly put to trial in male-male contests. Females that subsequently utilize them as indicators of male phenotypic quality when selecting a partner will benefit by acquiring males of higher quality to father their offspring. Thus, evolution of armaments through male-male competition is seen as a usually initiating process, whereas female choice later may assume a role as an additional selective factor. The reverse, that males use information from traits evolved through female choice, is, however, also possible. The traditional view of independently evolved and temporarily unordered intra- and intersexual selection processes fails to explain dual trait functions. Moreover, our model may more satisfyingly than traditional ones explain how trait honesty and trait genetic variance are maintained: theoretical and empirical evidence suggests that such honesty and variation are more easily maintained under male-male competition than under female choice.     

Drought signal transduction in plants

Water deficit is one of the most common environmental limitations of crop productivity by affecting growth through alterations in metabolism and gene expression. The mechanisms involved in drought perception and signal transduction pathways are poorly understood. The participation of the plant hormone abscisic acid (ABA) has been well established. ABA levels increase when there are changes in the environment that result in cellular dehydration. Different approaches have been taken to understanding the molecular responses to desiccation and how ABA regulates gene expression. Recent efforts have identified particular topics of importance in the dissection of the signal transduction pathway which are summarized as follows: physiological approaches: identification of signalling molecules. Genetic approaches: the use of mutants, and Molecular approaches: promoter analysis.     

Colonial breeding and speciation in birds

Summary It was recently suggested that bird species which breed colonially might be under stronger sexual selection, have faster rates of evolution and might therefore speciate more rapidly than bird species which do not. If true, then colonial taxa should contain more species than non-colonial taxa, other things being equal. When similarity through common descent is accounted for, there is little evidence for an association between the number of species in a clade and whether it is colonial or not.     

Immunoaffinity column clean-up for the high-performance liquid chromatographic determination of aflatoxins B1, B2, G1, G2, M1 and Q1 in urine

A method for the determination of aflatoxins B₁, B₂, G₁, G₂, M₁ and Q₁ in human urine has been developed. The 10-ml urine samples were automatically cleaned up on immunoaffinity columns and analysed by high-performance liquid chromatography (HPLC), including post-column derivatization with bromine and fluorescence detection. Average aflatoxin recoveries were: B₁ 103%, B₂ 106%, G₁ 98% and G₂ 96% in the range 6.8–73 pg/ml of urine and M₁ 103% and Q₁ 100% in the range 18–97 pg/ml of urine. The relative standard deviations were all between 1% and 21%. The determination limits of aflatoxins in urine were 6.8 pg/ml for B₁, B₂, G₁ and G₂ and 18 pg/ml for M₁ and Q₁.