Bacterially associated corrosion of aluminum surface in the air

Summary In a process of precision machining, corrosion of the surface of a precisely cut aluminum piece caused by bacteria was observed. A bacterium, Alcaligenes denitrificans, accumulated aluminum within the cell in granular form.     

Recall of sequences based on the position of the first cue stimulus in rats

We investigated the ability of rats to recall sequences of nose-poke holes with a modified serial reaction time task. In each trial, a sequence was randomly selected and the position of the first illuminated hole, which functioned as a cue stimulus, informed the rats whether the following sequence was a predictable one or not, based on prior training. The rats responded predictively only when the cues of the predictable sequences were presented. They did not show predictive responses when the cues of unpredictable sequences were presented, even though the unpredictable sequences partially had the same order of holes as the predictable sequences. These results indicate that the rats can recall sequences on the basis of presentation of the first cue stimulus informing predictable or unpredictable sequences. Recording neuronal activity while rats perform this behavioral task would be useful to elucidate neuronal mechanisms that mediate sequence recall.     

ESR analysis with long-chain alkyl spin labels in bovine blood platelets. Relationship between the increase in membrane fluidity by alcohols and phenolic compounds and their inhibitory effects on aggregation

Four spin-labeled probes (5-doxylstearic acid (5-NS), its methyl ester (5-NMS), 16-doxylmethylstearate (16-NMS) and 4-(N,N-dimethyl-N-pentadecyl)ammonium-2,2,6,6-tetramethylpiperidine-1-ox yl (CAT-15)) were used to monitor membrane fluidity change in bovine platelets induced by three alkyl alcohols, benzyl alcohol and two phenolic compounds. The relationship between the increase in membrane fluidity induced by these compounds and their inhibitory effects on platelet aggregation was observed. Experiments with the four probes showed that n-hexyl alcohol induced decreases in the order parameter of 5-NS and apparent rotational correlation times of the other probes at the same minimal alcohol concentration. The decreases were observed in the concentration range that inhibited aggregation. n-Amyl alcohol and n-butyl alcohol decreased the values of the parameters of the above mentioned only at higher concentrations that were dependent on their hydrophobicities. Like alkyl alcohols, benzyl alcohol and phenolic compounds decreased the values of the parameters in the concentration ranges in which these compounds inhibited platelet aggregation. The concentration of these compounds causing 50% inhibition of platelet aggregation, the IC50 values, and data on 5-NS-labeled platelets indicated that they inhibited aggregation and decreased the value of the order parameter at lower concentrations relative to their Poct values in comparison to the effective concentrations of alcohols. Phenolic compounds also decreased the values of the apparent rotational correlation times of 5-NMS and 16-NMS. These results indicate that the inhibition of platelet aggregation by alcohols and phenolic compounds is due to membrane perturbation in wide range in depths within the lipid bilayer.     

Effects of ethanol alone or after pretreatment with 20% ethanol on phospholipid metabolism in rat gastric mucosa

Changes in phospholipid metabolism in gastric mucosa caused by instillation of absolute ethanol (a cell-damaging agent) into the stomach of rats and the effects of pretreatment with 20% ethanol (a mild irritant) were investigated by using radioisotope-labeled fatty acids and glycerol. The labeled precursors were incorporated mainly into phosphatidylcholine and triacylglycerol, and also to lesser extents into phosphatidylethanolamine and phosphatidylinositol + phosphatidylserine. The instillation of absolute ethanol reduced the incorporation of fatty acids and glycerol into phospholipids within 15 min, indicating the inhibition by ethanol of de novo synthesis of phospholipids. Pretreatment with 20% ethanol caused the incorporation of fatty acids into phospholipids to be maintained after absolute ethanol instillation. These results suggest that the pretreatment with 20% ethanol may protect the cellular synthetic activity of phospholipids against damage by absolute ethanol. The incorporation of fatty acids into the free fatty acid fraction, monoacylglycerol and diacylglycerol was increased by absolute ethanol instillation, suggesting damage to the blood vessels of the gastric mucosa, and these changes were inhibited to some extent by the pretreatment with 20% ethanol.     

Changes in adhesive and migratory characteristics of hepatocellular carcinoma (HCC) cells induced by expression of alpha3beta1 integrin

The invasive and metastatic potentials of hepatocellular carcinoma are positively correlated with the expression level of alpha3beta1 integrin, a high-affinity adhesion receptor for laminin isoforms including laminin-5. In this study, we investigated changes in the adhesive and invasive behaviors of human HCC HepG2 cells after transfection with cDNA for alpha3 integrin in order to elucidate the direct involvement of this integrin in these cellular processes. We introduced cDNA for splice variants of alpha3 integrin (alpha3A and alpha3B) into the cells, and selected two transfectant clones (HepG2-3A and HepG2-3B), which express the alpha3A and alpha3B integrins, respectively. Both transfectant cells adhered almost equally to laminin-5-coated plates in an alpha3 integrin-dependent manner, indicating that transfected alpha3Abeta1 and alpha3Bbeta1 integrins were functionally active in these cells. The migratory and invasive potentials of the transfectant cells were assessed by scratch wound assay and in vitro chemoinvasion assay. The results demonstrated that the migration of HepG2-3A and HepG2-3B cells but not of mock transfectant (HepG2-M) cells was stimulated on the plates coated with laminin-5. Furthermore, HepG2-3A and HepG2-3B cells were found to be more invasive into laminin-5-containing matrices than were HepG2-M cells. These results strongly suggest that enhanced expression of alpha3beta1 integrin on HCC cells is directly involved in their malignant phenotypes such as invasion and metastasis.     

Adaptation of macrophages to exercise training improves innate immunity

The effects of 3-week exercise training on the functions of peritoneal macrophages from BALB/c mice were investigated. Lipopolysaccharide (LPS)-stimulated nitric oxide (NO) and proinflammatory cytokine production in macrophages from trained mice was markedly higher than those from control mice. Meanwhile, exercise training decreased the steady state level of β₂-adrenergic receptor (β₂AR) mRNA in macrophages. Overexpression of β₂AR in the macrophage cell line RAW264 by transfecting with β₂AR cDNA suppressed NO synthase (NOS) II expression but dose not influenced proinflammatory cytokine expression. When expression of transfected β₂AR in RAWar cells was downregulated by a tetracycline repressor-regulated mammalian expression system, NOS II mRNA expression was significantly increased; this suggested that the changes in the β₂AR expression level in macrophages associated with exercise training play a role in the regulation of NO production following LPS stimulation. These findings indicate that exercise training improves macrophage innate immune function in a β₂AR-dependent and -independent manner.     

A method for analyzing lipid-modified proteins with mass spectrometry

In protein analysis using mass spectrometry, proteins are usually separated by electrophoresis and digested within the gel with proteases such as trypsin. However, analysis of lipid-modified proteins is difficult due to the low recovery of lipid-modified peptide fragments from the gel as well as their low ionization efficiency during mass spectrometry. In this study, we developed a simple extraction method with n-dodecyl-β-d-maltoside following chloroform/methanol extraction that efficiently elutes lipid-modified fragments from gels. This method allowed us to analyze the structure of lipid-modified fragments, suggesting the applicability of the method for analysis of lipid-modified fragments by mass spectrometry.