Effects of nitrogen dioxide exposure on prostacyclin synthesis in lung and thromboxane A2 synthesis in platelets in rats

Effects of nitrogen dioxide (NO₂) exposure on prostacyclin (PGIP₂) synthesis in the rat lung and thromboxane A₂ (TXA₂) synthesis in the platelets were studied. Male Wistar rats were exposed to 10 ppm NO₂ for 1, 3, 5, 7 and 14 days. PGI₂ synthesizing activity of homogenized lung decreased. The damage of PGI₂ synthesizing activity reaches its maximum at 3 days. At 14 days, PGI₂ synthesizing activity returned to the normal level. The activity of PGI₂ synthetase decreased significantly. The formation of lipid peroxides due to NO₂ exposure may cause the depression of PGI₂ synthesizing activity of lung. On the other hand, platelet TXA₂ synthesizing activity increased. This increased TXA₂ synthesizing activity lasted at least till 3 days. Then, it returned to the normal level. The counts of platelet were decreased significantly by 1, 3, 5 and 7 days NO₂ exposure. Then the decreased counts of platelet returned to the normal level at 14 days NO₂ exposure. These results indicate that the depression of PGI₂ synthesizing activity lung by NO₂ exposure cause an increase in TXA₂ synthesizing activity of platelets. It may contribute to induce platelet aggregation and to the observed decrease in the number of platelets during NO₂ exposure.     

Elevation of Cyclic AMP-Dependent Protein Kinase Activity during Migration of Primary Mesenchyme Cell in Sand Dollar Blastulae

Concetration of intracellular cyclic AMP (cAMP), and activities of adenylate cyclase and cAMP-dependent protein kinase were examined in swimming and mesenchyme blastulae and primary mesenchyme cells (PMCs) of the sand dollar, Clypeaster japonicus , respectively. In mesenchyme blastulae, the concentration of cAMP increased 45% from that in swimming blastulae. PMCs contained a concentration of cAMP 40% higher than that in whole embryos at the mesenchyme blastula stage. The activity of adenylate cyclase in mesenchyme blastulae was 100% higher than that in swimming blastulae. The activites of cAMP-dependent protein kinase in whole embryos at the above two developmental stages, on the other hand, were quite similar to each other. However, in PMCs the activity of the enzyme was conspicuously higher than that in these embryos, and it reached 190% higher than that in these embryos. Inhibition of cAMP-dependent protein kinase activity by a synthetic inhibitor, H8, caused severe inhibition of PMC migration but it did not exert any effect on PMC ingression. These results suggest that the cAMP-dependent protein kinase activity is involved in PMC migration, but not in PMC ingression.     

Changes in the lysosome structure during the formation of zoospores inTrebouxia potteri

Summary Changes in the lysosome structures were examined by electron microscopy during the formation of zoospores inTrebouxia potteri. Lysosomes in vegetative cells were homogeneously filled with electron-dense material. At the beginning of zoospore formation, lysosomes invaginated or evaginated to take up mitochondria, ER, or cytoplasmic ground plasma. The ingested organelles became disorganized within the lysosomes. During this disruption of these organelles, the lysosomal contents became heterogeneous, suggesting a decrease in the amount of enzymes within the lysosomes. Golgi bodies and ER seemed to be involved with the disruption of the organelles, probably supplying some substances necessary for the functioning of the lysosomes. Amount of electron-dense materials decreased and, finally, only one to three small spherical aggregates remained in the lysosomes. Then the lysosomes appeared to shrink via loss of watery substances or cutting off of electron-transparent regions. After these changes in lysosome structure, nuclei started to divide successively for formation of the zoospores. The possibility is proposed that the drastic cytoplasmic changes operated by lysosomes trigger the following morphogenetic events in the formation of zoospores.Abbreviations ER endoplasmic reticulum - TGN trans Golgi network     

The augmentative effect of a protein-bound polysaccharide (PSK) on tumoricidal activity of the soluble factor produced by a streptococcal preparation (OK-432)-activated macrophages

The enhancement of antitumor activities of the tumoricidal soluble factor (SF) from a streptococcal preparation (OK-432)-activated macrophages by the pretreatment with a protein-bound polysaccharide (PSK) was investigated in tumor-bearing mice.Two-step stimulations with OK-432 atin vivo priming andin vitro eliciting were required for the production of the tumoricidal SF by macrophages, and the tumoricidal activity of the SF apparently correlated with the uptake of OK-432 by macrophages at priming phase.Tumoricidal activity of the SF from OK-432-activated macrophages in proteose-peptone (P-P)-pretreated mice significantly decreased with the development of the tumor, whereas in PSK-pretreated mice did not. Pretreatment of tumor-bearing mice with PSK saved a decrease in the macrophages carrying Ia^k or asialo GM1 antigens and an increase in wheat germ agglutinin (WGA) receptors. Furthermore, the uptake of OK-432 by macrophages at priming phase was enhanced. The tumoricidal activity of the SF from OK-432-activated macrophages was augmented.Thus, PSK may restore the depressed functions of macrophages, and the combination therapy with PSK and OK-432 may be effective to enhance the production of tumoricidal SF in tumor-bearing mice.     

1H NMR studies on ferricytochromec 3 fromDesulfovibrio vulgaris Miyazaki F and its interaction with ferredoxin I

Summary The¹H NMR signals of the heme methyl, propionate and related chemical groups of cytochromec ₃ fromDesulfovibrio vulgaris Miyazaki F (D.v. MF) were site-specifically assigned by means of ID NOE, 2D DQFCOSY and 2D TOCSY spectra. They were consistent with the site-specific assignments of the hemes with the highest and second-lowest redox potentials reported by Fan et al. (Biochemistry,29 (1990) 2257–2263). The site-specific heme assignments were also supported by NOE between the methyl groups of these hemes and the side chain of Val¹⁸. All the results contradicted the heme assignments forD.v. MF cytochromec ₃ made on the basis of electron spin resonance (Gayda et al. (1987)FEBS Lett.,217 57–61). Based on these assignments, the interaction of cytochromec ₃ withD.v. MF ferredoxin I was investigated by NMR. The major interaction site of cytochromec ₃ was identified as the heme with the highest redox potential, which is surrounded by the highest density of positive charges. The stoichiometry and association constant were two cytochromec ₃ molecules per monomer of ferredoxin I and 10⁸ M^–2 (at 53 mM ionic strength and 25°C), respectively.     

The periodic change in adenosine 3′,5′-monophosphate concentration in sea-urchin eggs

The level of adenosine 3′,5′-monophosphate (cyclic AMP) in the eggs of the sea urchin, Anthocidaris crassispina, was found to change periodically after fertilization. The minimum and maximum levels of cyclic AMP were 1.0·10^?7 M and 1.5·10^?6 M, respectively. The activity of adenylate cyclase in a 105 000 × g precipitate reached a plateau at 20 min after fertilization and stayed constant for at least 2 h. It was also found that 1.0 mM CaCl₂ increased the activity of adenylate cyclase in the same precipitate from unfertilized eggs. In contrast, phosphodiesterase activity changed periodically and correlated with cyclic AMP levels in the eggs. Up to a concentration of 1.5·10^?6 M cyclic AMP, phosphodiesterase activity was low, but it became activated when the level of cyclic AMP rose beyond this level. These results indicate that the change in the intracellular level of cyclic AMP is regulated mainly by the change in phosphodiesterase activity.     

Membrane-potential- and surface-potential-induced absorbance changes of merocyanine dyes added to chromatophores from Rhodopseudomonas sphaeroides

(1) Three analogs of merocyanine dyes added to suspensions of chromatophore vesicles showed absorbance changes responding to the change in surface potential induced by salt addition and to the change in membrane potential induced by illumination. (2) The extent of the light-induced absorbance changes of the dyes was linearly related, in the presence and absence of uncouplers, to that of carotenoid spectral shift which is an intrinsic probe of the intramembrane electric field. (3) Comparison of the merocyanine absorbance changes induced by salt addition with those induced by illumination indicated that the surface potential change in the outer surface of chromatophore membranes during illumination was very small. (4) Judging from the spectra of these absorbance and from the low permeabilities of the dyes to membrane, the absorbance change are attributed to change in distribution of the dyes between the medium and the outer surface region in chromatophore membranes. The extent of the light-induced absorbance changes of merocyanine dyes depended on the salt concentration of the medium. The types of dependence were different among three merocyanine analogs. This is explained by the mechanism mentioned above assuming appropriate parameters. It is suggested that, under continuous illumination, an equilibrium of the electrochemical potential of H⁺ is reached between the bulk aqueous phase and the outer surface region in the membrane where the merocyanine dyes are distributed.     

Ribosomal protein modification in Escherichia coli

Summary Among mutants of E. coli selected for temperaturesensitive growth, four were found to possess alterations in ribosomal proteins L7/L12. Of these, three apparently lack protein L7, the acetylated form of protein L12. Genetic analyses have revealed that the mutation responsible for this alteration maps at a locus around 34 min of the current E. coli genetic map, which is clearly different from the location for the structural gene for protein L7/L12 which is situated at 89 min. Hence, the gene affected in these mutants was termed rimL. Tryptic and thermolysin fingerprints of the protein L12 purified from the rimL mutants showed a profile indistinguishable from that of wild-type protein. It was found that the acetylase activity specific for protein L12 was negligible, when assayed in vitro, in the high-speed supernatant prepared from mutant cells. These results indicated that the three mutants contain mutations in the gene rimL that codes for an acetylating enzyme specific for ribosomal protein L12.Previous paper in this series is Isono and Isono (1980)