Optimization of microalgal production in a shallow outdoor flume

The marine diatom Cyclotella cryptica was grown over a period of 13 months in a 48-m(2) shallow outdoor flume. The use of foil arrays at intervals of 1.2 m to effect systematic vertical mixing in the flume was found to significantly enhance microalgal production (p = 0.006). Average photosynthetic efficiencies (based on visible irradiance) with and without the foil arrays in place were 9.6 +/- 0.8 and 7.5 +/- 0.5% (+/-95% confidence intervals), respectively. A cost-benefit analysis indicated that the foil arrays were cost-effective if the value of the algae exceeded about $2.28 kg(1) of ash-free dry weight (AFDW). Parallel experiments performed in four 9.2-m(2) flumes showed that production was maximized when the cells were grown on a 2-day batch cycle between harvests rather than on a 1- or 3-day batch cycle. The optimum initial concentration (immediately after harvesting) of the algae was negatively correlated with the time interval between harvests and ranged from approximately 39 g AFDW/m(3) on a 3-day cycle to 213 g AFDW/m(3) on a 1-day cycle. The increase in production resulting from growth on a 2-day rather than a 1-day batch cycle was about 19% and was statistically significant at p = 0.0003. Growth of C. cryptica over a total period of 122 days during the 13-month study in the 48-m(2) flume under near-optimal conditions (2-day batch cycle, initial concentration 155 g AFDW/m(3)) resulted in an average production rate (+/-95% confidence interval) of 29.7 +/- 2.7 g AFDW/m(2) d.     

Clonal nature of murine hemopoietic blast cell colonies

Murine hemopoietic blast cell colonies obtained from spleen cells of 5-fluorouracil (5-FU)-treated mice give rise to many multilineage colonies including granulocyte - erythrocyte - macrophage - megakaryocyte (GEMM) colonies in secondary cultures. Progenitor cells for blast cell colonies are considered to be more primitive than colony forming units (CFU)-GEMM. To determine whether they are clonal, we examined the phosphoglycerate kinase-1 (PGK-1) isozyme type of colonies originally grown from spleen cells of 5-FU-treated mice which had PGK-1 isozyme mosaicism. PGK assays of whole secondary colonies derived from one blast cell colony showed that they were either of type A or type B but not both. These results suggest that murine hemopoietic blast cell colonies are clonal.     

Chromosomal localization of the Epstein-Barr virus (EBV) genome in Bloom's syndrome B-lymphoblastoid cell lines transformed with EBV

The localization of the Epstein-Barr virus (EBV) genome in chromosomes of human B-lymphoblastoid cell lines (LCLs) transformed with EBV, and the effect of EBV DNA on the level of sister chromatid exchange (SCE) in Bloom's syndrome (BS) B-LCLs, were examined with chromosomal in situ hybridization techniques using a ³H-EBV DNA probe. EBV DNA was detected in chromosomes 1–5 and 13–15 at specific G band regions in BS as well as in normal B-LCLs, regardless of SCE. Several chromosomal sites (1p31, 1q31, 4q22–24, 5q21, 13q21, 14q21) carrying EBV DNA seemed to be very characteristic in normal as well as in BS B-LCLs. There was no statistically significant difference in silver grain counts due to EBV DNA and their distribution in different chromosomes or groups among normal and BS B-LCLs with normal and high SCE. These findings strongly indicate that EBV infection did not introduce a correcting factor for BS SCE.     

Optimum conditions for ursodeoxycholic acid production from lithocholic acid by Fusarium equiseti M41.

Ursodeoxycholic acid dissolves cholesterol gallstones in humans. In the present study optimum conditions for ursodeoxycholic acid production by Fusarium equiseti M41 were studied. Resting mycelia of F. equiseti M41 showed maximum conversion at 28 degrees C, pH 8.0, and dissolved oxygen tension of higher than 60% saturation. Monovalent cations, such as Na+, K+, and Rb+, stimulated the conversion rate more than twofold. In the presence of 0.5 M KCl, the initial uptake rate and equilibrium concentration of lithocholic acid (substrate) were enhanced by 5.7- and 1.7-fold, respectively. We confirmed that enzyme activity catalyzing 7 beta-hydroxylation of lithocholic acid was induced by substrate lithocholic acid. The activity in the mycelium was controlled by dissolved oxygen tension during cultivation: with a dissolved oxygen tension of 15% and over, the activity peak appeared at 25 h of cultivation, whereas the peak was delayed to 34 and 50 h with 5 and 0% dissolved oxygen tension, respectively. After reaching the maximum, the 7 beta-hydroxylation activity in the mycelium declined rapidly at pH 7.0, but the decline was retarded by increasing the pH to 8.0. Several combinations of operations, such as pH shift (from pH 7 to 8), addition of 0.5 M KCl, and dissolved oxygen control, were applied to the production of ursodeoxycholic acid in a jar fermentor, and a much larger amount of ursodeoxycholic acid (1.2 g/liter) was produced within 96 h of cultivation.     

Ectoenzyme release from rat liver and kidney by phosphatidylinositol-specific phospholipase C

Ectoenzyme release from rat liver and kidney by phosphatidylinositol (PI)-specific phospholipase C of Bacillus thuringiensis was studied. Alkaline phosphatase and 5'-nucleotidase were released from rat kidney slices to extents of up to 60% and 30%, respectively. Release of alkaline phosphatase was observed at lower amounts of PI-specific phospholipase C than that of 5'-nucleotidase. Both enzymes were more easily released from microsomal fractions or free cells. From kidney cells, alkaline phosphatase was released without cell lysis, and more than 80% release of alkaline phosphatase was observed at 3.8% hydrolysis of PI. Isoelectric focusing profiles of alkaline phosphatase released by PI-specific phospholipase C were significantly different from the control in the cases of both rat liver and kidney. Lubrol-solubilized alkaline phosphatase was eluted at the void volume of a Toyopearl HW-55 column, while the enzyme obtained by further treatment with PI-specific phospholipase C was eluted in the lower-molecular-weight region corresponding to 100,000-110,000 daltons. Furthermore, Lubrol-solubilized phosphatase became more thermostable on treatment with PI-specific phospholipase C.     

New pteridine substrates for dihydropteridine reductase and horseradish peroxidase.

The oxidation of 4,5-diaminopyrimidin-6(1H)-one, 5,6,7,8-tetrahydropteridin-4(3H)-one, its 6-methyl and cis-6,7-dimethyl derivatives, and 6-methyl- and cis-6-7-dimethyl-5,6,7,8-tetrahydropterins, by horseradish peroxidase/H2O2 is enzymic and follows Michaelis-Menten kinetics, and its Km and kcat. values were determined. This oxidation of 5,6,7,8-tetrahydropterins produces quinonoid dihydropterins of established structure, and they are known to be specific substrates for dihydropteridine reductase. By analogy the peroxidase/H2O2 oxidation of the 5,6,7,8-tetrahydropteridin-4(3H)-ones should produce similar quinonoid dihydro species. The quinonoid species derived from 5,6,7,8-tetrahydropteridin-4(3H)-one and its 6-methyl and cis-6,7-dimethyl derivatives are shown to be viable substrates for human brain dihydropteridine reductase, and apparent Km and Vmax. values are reported.     

Studies on the interactions between phospholipids and membrane-bound enzymes in microsomes. Effects of phospholipases C on the glucose-6-phosphatase system of rat liver microsomes

The role of phospholipids in the glucose-6-phosphatase system, including glucose-6-P phosphohydrolase and glucose-6-P translocase, was studied in rat liver microsomes by using phospholipases C and detergents. In the time course experiments on detergent exposure, the maximal activation of glucose-6-P phosphohydrolase varied according to the nature of the detergent used. On treatment of microsomes with phospholipase C of C. perfringens, the activity of glucose-6-P phosphohydrolase without detergent (i.e. without rupture of translocase activity) was gradually decreased with the progressive hydrolysis of phosphatidylcholine and phosphatidylethanolamine on the microsomal membrane, and was restored by incubation of these microsomes with egg yolk phospholipids. The extent of decrease in this phosphohydrolase activity in the detergent-exposed microsomes (with rupture of translocase activity) also varied depending on the detergent used (Triton X-114 or taurocholate). When 66% of the phosphatidylinositol on the membrane was hydrolyzed by phosphatidylinositol-specific phospholipase C of B. thuringiensis, the inhibition of glucose-6-P phosphohydrolase activity without detergent was very small. Although the inhibition of enzyme activity with detergent was apparently greater than that without detergent, the enzyme activity was stimulated by the breakdown of phosphatidylinositol when the enzyme activity was measured at lower concentration (0.5 mM) of substrate, glucose-6-P. The latency of mannose-6-P phosphohydrolase, a plausible index of microsomal integrity, remained above 70% after the hydrolysis of phosphatidylcholine, phosphatidylethanolamine, or phosphatidylinositol. The results show that the glucose-6-phosphatase system requires microsomal phospholipids for its integrity, suggesting that there exists a close relation between phosphatidylinositol and glucose-6-P translocase.     

Effect of alpha-fluoromethylhistidine on the histamine content of the brain of W/Wv mice devoid of mast cells: turnover of brain histamine

In the brains of W/Wv mutant mice that have no mast cells, the histidine decarboxylase (HDC) level is as high as in the brain of congenic normal mice (+/+), but the histamine content is 53% of that of +/+ mice. The effects of alpha-fluoromethylhistidine (alpha-FMH) on the HDC activity and histamine content of the brain of W/Wv and +/+ mice were examined. In both strains, 30 min after i.p. injection of alpha-FMH the HDC activity of the brain had decreased to 10% of that in untreated mice. The histamine content decreased more gradually, and after 6 h about half of the control level remained in +/+ mice, whereas histamine had disappeared almost completely in W/Wv mice. It is concluded that the portion of the histamine content that was depleted by HDC inhibitor in a short time is derived from non-mast cells, probably neural cells. The half-life of histamine in the brain of W/Wv mice was estimated from the time-dependent decrease in the histamine content of the brain after administration of alpha-FMH: 48 min in the forebrain, 103 min in the midbrain, and 66 min in the hindbrain.