Activation of extracellular signal-regulated kinase by ultraviolet is mediated through Src-dependent epidermal growth factor receptor phosphorylation. Its implication in an anti-apoptotic function.

Ultraviolet (UV) irradiation stimulates stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), which is a member of the mitogen-activated protein kinase (MAPK) superfamily and implicated in stress-induced apoptosis. UV also induces the activation of another MAPK member, extracellular signal-regulated kinase (ERK), which is typically involved in a growth-signaling cascade. However, the UV-induced signaling pathway leading to ERK activation, together with the physiological role, has remained unknown. Here we examined the molecular mechanism and physiological function of UV-induced ERK activation in human epidermoid carcinoma A431 cells that retain a high number of epidermal growth factor (EGF) receptors. UV-induced ERK activation was accompanied with the Tyr phosphorylation of EGF receptors, and both responses were completely abolished in the presence of a selective EGF receptor inhibitor (AG1478) or the Src inhibitor PP2 and by the expression of a kinase-dead Src mutant. On the other hand, SAPK/JNK activation by UV was partially inhibited by these inhibitors. UV stimulated Src activity in a manner similar to the ERK activation, but the Src activation was insensitive to AG1478. UV-induced cell apoptosis measured by DNA fragmentation and caspase 3 activation was enhanced by AG1478 and an ERK kinase inhibitor (U0126) but inhibited by EGF receptor stimulation by the agonist. These results indicate that UV-induced ERK activation, which provides a survival signal against stress-induced apoptosis, is mediated through Src-dependent Tyr phosphorylation of EGF receptors.     

Magnesium Supplementation did not Affect the Increasing Bone Zinc Concentration in Rats Given Excess Calcium as Carbonate

We investigated the effect of magnesium supplementation on zinc distribution in rats given excess calcium as carbonate. Rats were given a control diet (5 g/kg calcium and 0.5 g/kg magnesium), a high calcium diet (HC, 25 g/kg calcium and 0.5 g/kg magnesium) or the high calcium diet supplied with magnesium (HCM, 25 g/kg calcium and 2.5 g/kg magnesium) for 4 weeks. Calcium carbonate and magnesium oxide were used for increasing these mineral concentrations in diets. Although feed intake did not differ among the groups, the excess calcium suppressed feed efficiency, irrespective of dietary magnesium concentration. Femoral magnesium concentration was lower in the HC group than in the control and the HCM groups. Femoral zinc concentration was higher in the HC group and the HCM group than in the control group. The zinc concentration in the kidney was lower in the HC group and the HCM group than in the control group. The excess calcium did not affect zinc concentration in plasma and other tissues such as the liver, testis, and spleen, irrespective of dietary magnesium. These results suggest that the increasing bone zinc and the decreasing renal zinc do not result from magnesium insufficiency in rats given excess calcium as carbonate.     

Studies on the Metabolism of Aspergilli

This report is concerned with the time course of changes of several enzymes during endogenous respiration. It was observed that enzymes such as deaminases, amidases and transaminases found in the mycelia increased in activity more or less during endogenous respiration. It was assumed that enzyme formation occurred as the result of glucose starvation or depression of carbohydrate metabolism during endogenous respiration of the mold mycelia on buffer solution.     

Enzymatic Production of Urocanic Acid by Achromobacter liquidum

To develop an efficient method for the production of urocanic acid, optimal conditions for the production of microbial L-histidine ammonia lyase and for the conversion of L-histidine to urocanic acid by this enzyme were studied. A number of microorganisms were screened to test their ability to form and accumulate urocanic acid from L-histidine. Achromobacter liquidum was selected as the best organism. With this organism, enzyme activity as high as 2.0 units/ml could be produced by a shaking culture at 30 C in a medium containing glucose, urea, potassium phosphate, L-histidine, yeast extract, peptone, and inorganic salts. Appropriate addition of a surface-active agent to the reaction mixture shortened the time required for the conversion. A large amount of L-histidine was converted stoichiometrically to urocanic acid in 48 h at 40 C. Accumulated urocanic acid was readily isolated in pure form by ordinary procedures with isoelectric precipitation. Yields of isolated urocanic acid of over 92% from L-histidine were easily attainable. When the culture of Achromobacter liquidum was added to DL-histidine, D-histidine and urocanic acid were simultaneously obtained in high yields.     

Regeneration of the respiratory epithelium]

It is very important to clarify the mechanism of the regeneration of the respiratory epithelium in not only Oto-Naso-Laryngology but also in the field of chest medicine and surgery. Because of the experimental study carried out on dogs, involving the curing process of the tracheal anastomosis site, a scanning electron microscopic study showed that after two weeks, ciliated cells could be seen making a thin layer. It took nine weeks or more till the whole tracheal anastomosis site was completely covered by the ciliated epithelial cells. Having reviewed the experimental papers concerning the regeneration of the respiratory epithelium which have been published since 1953, a conclusion has been reached that after the injury of the respiratory mucosa, the existence of the basement membranes remains were covered by the migration of the traditional epithelium from the margin of the wound and four weeks later, the wound was covered by the normal epithelium. It has been stated up until now that the differentiation of the epithelium was covered from basement cells, but in fact, it seems to occur from the secretory cells. This has been demonstrated by the culture process of the respiratory epithelium. From these facts, the cultured respiratory epithelium cells are very important in elucidating carcinogenesis.     

Primary structure of Vicia angustifolia proteinase inhibitor

The complete amino acid sequence (72 amino acid residues) of a double-headed proteinase inhibitor from seeds of Vicia angustifolia L. var. segetalis Koch has been determined and compared with those of other double-headed inhibitors of known structure. Sequencing was performed by conventional methods with the aid of the fragments produced by reduction and S-carboxymethylation of the enzymatically modified inhibitors, and also using tryptic and chymotryptic peptides. The positions of the 14 half-cystine residues agreed among all the reported primary structures of the legume double-headed inhibitors. However, V. angustifolia inhibitor possessed extensive amino acid differences compared to the others. The phylogenetic relationship among these inhibitors was established using the unweighted pair-group method and revealed that the V. angustifolia inhibitor and the peanut inhibitor B-III had diverged at a relatively earlier stage compared to the other inhibitors.     

Purification and characterization of W-protein. A DNA-binding protein showing high affinity for the W chromosome-specific repetitive DNA sequences of chicken

A protein component, which binds with high affinity to the W chromosome-specific XhoI family repetitive DNA of chicken (Tone, M., Sakaki, Y., Hashiguchi, T., and Mizuno, S. (1984) Chromosoma (Berl.) 89, 228-237), was detected in the 0.35 M NaCl extract of the female chicken liver nuclei. This protein, designated as W-protein, was substantially purified by phosphocellulose, hydroxyapatite, and DEAE-Toyopearl column chromatography. Molecular weight of W-protein was estimated to be about 72,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but it seems to form multimeric structure having apparent molecular weight of about 2.3 X 10(6) under nondenaturing conditions. W-Protein binds strongly to both 0.7- and 1.1-kb repeating units of the XhoI family, both of which show curved DNA characteristics, and weakly to the AATAT-satellite sequence of Drosophila melanogaster. Stable binding of W-protein requires greater than or equal to 300 base pairs of the 0.7-kilobases sequence, or more than 14 tandem repeats of the 21-base pair internal repeating unit of the 0.7-kilobase sequence. DNA footprint analysis and effects of some DNA-binding compounds suggest that the DNA double helix wraps around W-protein or its multimeric form contacting through A-T-rich minor grooves. A possible role of W-protein in the formation of W heterochromatic body is discussed.     

Spontaneous and flow-induced Ca2+ transients in retracted regions in endothelial cells

Changes in intracellular calcium concentration ([Ca2+]i) and focal adhesion sites of cultured bovine aortic endothelial cells (BAECs) were simultaneously visualized in real time. Local [Ca2+]i transients were observed at the rear edges of spontaneously migrating BAECs. Furthermore, the majority of starting regions of [Ca2+]i transients retracted continuously. Frequency of [Ca2+]i transients increased with the application of fluid flow. The majority of starting regions of flow-induced [Ca2+]i transients retracted following the occurrence of [Ca2+]i transients. In addition, retracted areas were distributed in the upstream regions of the cell. Application of GdCl3, a mechanosensitive cation channel blocker, resulted in a clear reduction of [Ca2+]i transients and rear retractions in cases of spontaneous and flow-induced BAEC migration. Flow-induced directional rear retractions were also inhibited. Consequently, we conclude that local [Ca2+]i transients play an important role in the migration of BAECs with respect to rear retraction. Furthermore, flow-induced [Ca2+]i transients regulate directional rear retraction under flow conditions.