Change in plasma amino acid concentrations during breath-hold diving at high altitude

We studied the plasma concentration of various amino acids in 6 Italian sport divers in Italy and at approximately 4,500 m altitude in Peru; 6 Peruvian inhabitants were examined for comparison. We attempted to create a situation of pronounced hypoxia in muscles by breath-hold diving at altitude. The diving reflex diverts blood away from muscles while diving increases central oxygen tension and prevents loss of consciousness. Differences in certain amino acids, probably related to diet, were noted between Italy and Peru. Increases in concentration of plasma alanine and some branched-chain amino acids occurred after breath-hold diving. These changes were similar to those seen after prolonged hard exercise, even though physical work was low. Hypoxia in muscles, common during hard work and during breath-hold diving at altitude, might thus be the stimulus for amino acid release from working muscles.     

Similarities in Restriction Fragment Patterns of Mitochondrial DNAs of PhytophthoraSpecies Strongly Depend on the Restriction Enzyme Used Due to Heterogeneous Base Distribution and Sequence Conservation

Mitochondrial DNAs of six morphologically different Phytophthora species were digested with 15 restriction enzymes. The numbers of restriction fragments obtained differed considerably from those theoretically expected for random base distribution. Enzymes with relatively many G and C in their recognition sequences produced significantly larger numbers of fragments. Moreover, fragments generated by most of these enzymes were more often shared by two or more species than those from enzymes with more A and T in their recognition sequence. It is concluded that base distribution in mitochondrial DNA of Phytophthora is heterogeneous,AT-rich stretches occurring scattered over the mitochondrial genome and GC-rich regions present in conserved sequences, presumably genes. A practical consequence for taxonomic RFLP studies is that optimal enzymes can be selected, depending on the desired level of resolution.     

A Cytochrome c Peroxidase Isolated from Thiobacillus thiooxidans

High phytin containing particles were isolated from rice bran by a combination of a differetial centrifugation and an aqueous two phase system, using dextran 500 and polyethylene glycol 6000. The isolated particles consisted mainly of phytic acid, potassium and magnesium. The chemical composition and electron microscopic observation of the isolated particles confirmed that the electron dense material, which is embedded in aleurone particles of matured rice grains, is potassium and magnesium salts of phytic acid.     

Requirement for non-regulated, constitutive calcium influx in macrophage survival signaling

The phosphatidylinositol-3-kinase (PI3K)/AKT axis and the Nuclear Factor kappa B (NFκB) pathway play critical roles in macrophage survival. In cells other than macrophages proper operation of those two pathways requires Ca²⁺ influx into the cell, but if that is the case in macrophages remains unexplored. In the present work we used THP-1-derived macrophages and a pharmacological approach to examine for the first time the role of constitutive, non-regulated Ca²⁺ influx in PI3K/AKT and NFκB signaling. Blocking constitutive function of Ca²⁺-permeable channels with the organic channel blocker SKF96365 completely prevented phosphorylation of IκBα, AKT and its downstream target BAD in TNFα-treated macrophages. A similar effect was observed upon treating macrophages with the calmodulin (CAM) inhibitor W-7 or the calmodulin-dependent kinase II (CAMKII) inhibitor KN-62. In addition, pre-treating macrophages with SKF96365 significantly enhanced TNFα-induced apoptosis. Our findings suggest that in THP-1-derived macrophages survival signaling depends, to a significant extent, on constitutive Ca²⁺ influx presumably through a mechanism that involves the CAM/CAMKII axis as a coupling component between constitutive Ca²⁺ influx and activation of survival signaling.     

Math3 and NeuroD regulate amacrine cell fate specification in the retina

The basic helix-loop-helix genes Math3 and NeuroD are expressed by differentiating amacrine cells, retinal interneurons. Previous studies have demonstrated that a normal number of amacrine cells is generated in mice lacking either Math3 or NEUROD: We have found that, in Math3-NeuroD double-mutant retina, amacrine cells are completely missing, while ganglion and Müller glial cells are increased in number. In the double-mutant retina, the cells that would normally differentiate into amacrine cells did not die but adopted the ganglion and glial cell fates. Misexpression studies using the developing retinal explant cultures showed that, although Math3 and NeuroD alone only promoted rod genesis, they significantly increased the population of amacrine cells when the homeobox gene Pax6 or Six3 was co-expressed. These results indicate that Math3 and NeuroD are essential, but not sufficient, for amacrine cell genesis, and that co-expression of the basic helix-loop-helix and homeobox genes is required for specification of the correct neuronal subtype.     

Analysis of mutations induced by carbon ions in Arabidopsis thaliana

To investigate the nature of mutations induced by accelerated ions in higher plants, the effects of carbon-ion-irradiation were compared with those of electron-irradiation in Arabidopsis thaliana. Point-like mutations and rearrangements were induced at a similar frequency after carbon-ion-irradiation, whereas point-like mutations were more frequently induced after electron-irradiation. Sequence analysis revealed that carbon-ion-induced point-like mutations were mostly short deletions. In the case of rearrangements, deletions, inversions, insertions, and translocations were found. The estimated frequency of deletion induction was comparable to that of fast neutrons. Analysis of chromosome breakpoints revealed that carbon ions frequently deleted small regions around the breakpoints, whereas electron-irradiation often duplicated these regions. Moreover, for both types of radiation, broken ends with microhomologies were frequently rejoined. Results of the breakpoint and broken end analyses suggest that non-homologous end-joining (NHEJ) leads to the rejoining of double strand breaks (dsbs) after cells are exposed to both types of radiation, but the type of NHEJ that occurs as a result of damage is different. The results indicated that carbon-ion-induced mutations are most likely nulls and that the induced rearrangements may arise through a unique mechanism. These findings indicate that accelerated ions are a useful mutagen for both forward and reverse genetics for plants.     

Repair Kinetics of Abasic Sites in Mammalian Cells Selectively Monitored by the Aldehyde Reactive Probe (ARP)‡

Abstract

Human methylpurine N-glycosylase (MPG) activity was investigated by monitoring abasic (AP) sites resulting from removal of alkylated bases. The amount of AP sites in MMS-treated HeLa cells transiently increased at 3 h, then gradually decreased to 40% at 24 h. The presence of adenine, an inhibitor of AP endonucleases, in the repair incubation of MMS-treated cells induced moderate accumulation of AP sites, suggesting inhibition of the activities of MPG as well as AP endonucleases by adenine metabolites.

     

Dysregulation of gene expression in the artificial human trisomy cells of chromosome 8 associated with transformed cell phenotypes

A change in chromosome number, known as aneuploidy, is a common characteristic of cancer. Aneuploidy disrupts gene expression in human cancer cells and immortalized human epithelial cells, but not in normal human cells. However, the relationship between aneuploidy and cancer remains unclear. To study the effects of aneuploidy in normal human cells, we generated artificial cells of human primary fibroblast having three chromosome 8 (trisomy 8 cells) by using microcell-mediated chromosome transfer technique. In addition to decreased proliferation, the trisomy 8 cells lost contact inhibition and reproliferated after exhibiting senescence-like characteristics that are typical of transformed cells. Furthermore, the trisomy 8 cells exhibited chromosome instability, and the overall gene expression profile based on microarray analyses was significantly different from that of diploid human primary fibroblasts. Our data suggest that aneuploidy, even a single chromosome gain, can be introduced into normal human cells and causes, in some cases, a partial cancer phenotype due to a disruption in overall gene expression.     

Physiological Studies on Thiobacilli

NADPH-cytochrome c oxidoreductase obtained from the cells of Thiobacillus thiooxidans displayed the pH optimum of 8.7 and was completely inactivated by heating at 60°C for 10 min. Enzymatic activity was proportional to protein concentration and linear with time. The Km for NADPH was found to be 2.13 × 10^?5 m. The enzyme was specific for NADPH and transferred electrons to cytochrome c and some dyes. p-Chloromercuribenzoate, EDTA and acryflavin inhibited the reductase activity.