The formation and degradation of cyanobacterium Aphanizomenon flos-aquae blooms: the importance of pH, water temperature, and day length

Investigation of annual changes in phytoplankton community structure in a small artificial eutrophic pond was carried out from May 2002 to April 2003. A heavy bloom of Aphanizomenon flos-aquae var. klebahnii Elenk. (Cyanobacteria) persisted in most of the water column from June to the end of October. In November, the A. flos-aquae bloom suddenly crashed and green algae were predominant until the end of spring. Weekly monitoring suggested strong involvement of the changes in abiotic factors in the cyanobacterial bloom degradation. To clarify the effects of pH, water temperature, and day length on the growth of A. flos-aquae, laboratory batch experiments were conducted. The results showed that A. flos-aquae could not grow below pH 7.1 and 11°C, and the growth tended to be suppressed under a 10L:14D photoperiod. pH, water temperature, and day length are vital factors in the growth of A. flos-aquae and, additionally, grazing by cyclopoid copepods also seemed important in bloom collapse.     

Expression profile analysis of aorta-gonad-mesonephros region-derived stromal cells reveals genes that regulate hematopoiesis

The aorta-gonad-mesonephros (AGM) region is involved in the generation and maintenance of the first definitive hematopoietic stem cells (HSCs). A mouse AGM-derived cell line, AGM-S3, was shown to support the development of HSCs. To elucidate the molecular mechanisms regulating early hematopoiesis, we obtained subclones from AGM-S3, one of which was hematopoiesis supportive (S3-A9) and the other one of which was non-supportive (S3-A7), and we analyzed their gene expression profiles by gene chip analysis. In the present study, we found that Glypican-1 (GPC1) was highly expressed in the supportive subclone AGM-S3-A9. Over-expression of GPC1 in non-supportive cells led to the proliferation of progenitor cells in human cord blood when cocultured with the transfected-stromal cells. Thus, GPC1 may have an important role in the establishment of a microenvironment that supports early events in hematopoiesis.     

Photoreactions of Tyr8- and Gln50-mutated BLUF domains of the PixD protein of Thermosynechococcus elongatus BP-1: photoconversion at low temperature without Tyr8

We studied the photoreaction of a blue-light sensor PixD protein of Thermosynechococcus elongatus that has the blue-light-using flavin (BLUF) domain. The Tyr8 and Gln50 residues of the protein were modified to phenylalanine, alanine, or asparagine (Y8F, Y8A, Q50N, and Q50A) by site-directed mutagenesis. The following results were obtained. (1) At room temperature, blue-light illumination induced the red shift of the absorption bands of flavin in the wild-type (WT) protein but not in the Y8F, Y8A, Q50A, and Q50N mutant proteins, as reported [Okajima, K., et al. (2006) J. Mol. Biol. 363, 10-18]. (2) At 80 K, neither the Q50N nor the Q50A mutant protein accumulated the red-shifted form. (3) At 80 K, the Y8F protein photoaccumulated the red-shifted forms to an extent that was half that in the WT protein at a 43-fold slower rate, and the Y8A protein to the one-fourth the extent at a 137-fold slower rate. (4) The red-shifted form in the Y8F protein was stable below 240 K and became unstable above 240 K in the dark. (5) The illumination of the Y8F protein at 150 K accumulated the red-shifted form at the beginning, and the prolonged illumination accumulated the flavin anions by the secondary photoreaction. (6) The results indicate that Tyr8 is not indispensable for the accumulation of the red-shifted form at least at 80 K. (7) Photoconversion mechanisms in the WT and Tyr8-mutated proteins are discussed in relation to the schemes with and without the electron transfer between Tyr8 and flavin in the first step of the photoconversion.     

The Drosophila Toll-9 activates a constitutive antimicrobial defense

The Toll family of transmembrane proteins participates in signaling infection during the innate immune response. We analyzed the nine Drosophila Toll proteins and found that wild-type Toll-9 behaves similar to gain-of-function Toll-1. Toll-9 activates strongly the expression of drosomycin, and utilizes similar signaling components to Toll-1 in activating the antifungal gene. The predicted protein sequence of Toll-9 contains a tyrosine residue in place of a conserved cysteine, and this residue switch is critical for the high activity of Toll-9. The Toll-9 gene is expressed in adult and larval stages prior to microbial challenge, and the expression correlates with the high constitutive level of drosomycin mRNA in the animals. The results suggest that Toll-9 is a constitutively active protein, and implies its novel function in protecting the host by maintaining a substantial level of antimicrobial gene products to ward off the continuous challenge of microorganisms.     

A study of the native-denatured (N in equilibrium with D) transition in lysozyme. II. Kinetic analysis of protease digestion.

Kinetic analyses of the protease digestion of several chemical derivatives of lysozyme [EC 3.2.1.17] showed that only the D(denatured) state of the protein is digested and that the reaction velocity is proportional to the equilibrium constant (KD) of the N in equilibrium with D transition of the protein. Alteration of the net charge of lysozyme by acetylation caused a shift of the N in equilibrium with D transition to the right (ten-fold increase in KD compared to that of native enzyme). Both the formation of a lysozyme-inhibitor complex and the introduction of a covalent bond in the lysozyme molecule restricted the transition. The magnitude of the N in equilibrium with D transition is related to the susceptibility of lysozyme to protease digestion and it is estimated that the N in equilibrium with D transition in proteins is generally important in the intracellular catabolism of proteins.     

Irreversible inactivation of aspartate aminotransferases during transamination with L-propargylglycine

L-Propargylglycine serves as an amino acid substrate in the transamination reaction catalyzed by both cytosolic and mitochondrial aspartate aminotransferases from pig heart. Incubation of these isoenzymes with L-propargylglycine alone did not result in the inactivation of these enzymes. However, the presence of 2-oxoglutarate or pyruvate caused gradual irreversible inactivation of these isoenzymes. The inactivation was greatly accelerated by the presence of formate ion. Inactivation of both isoenzymes with L-[2-¹⁴C]propargylglycine resulted in stoichiometric incorporation of the radioactive molecule. Drastic changes in the absorption and circular dichroic spectra of the enzymes which took place during the inactivation also indicated that the modification by L-propargylglycine is restricted to the active site of these isoenzymes.     

Inhibitory effect of the extract from Zizyphus jujuba leaves on sweet taste responses of the chorda tympani in the rat and hamster

1. One of the fractions obtained from the extract of Zizyphus jujuba leaves suppressed the response of the chorda tympani to sucrose, both in the rat and hamster. 2. In the rat and man, suppressive effect was found to be significant in responses to various sugars and artificial sweeteners but not in some sweet amino acids.     

Immunological detection of a cysteine protease in the skin and other tissues

Summary Monospecific antibody directed to cysteine protease of 2-day-old rat epidermis recently characterized as being different from the proteases previously reported was produced in rabbits. By immunofluorescence microscopy and immunoperoxidase staining with an avidin-biotin-peroxidase method the protease was found to be present in the epidermis of rodents of different ages as well as that of humans, but not in the dermis. The staining in germinative cells was more intense than in cells in the superficial layers. It appeared as irregular patches in the nuclei and stained more diffusely in the cytoplasm where small granular components, strongly stained, were identified. The staining patterns in granular cells showed accumulation of the antigen in a granular form. The morphology and distribution of granules resembled those of keratohyalin-like granules in the nucleus and dense homogenous deposits in the cytoplasm. In cornified cells the reaction product was localized by the plasma membrane where concentration of the dense homogenous deposits occurred, suggesting that the cysteine protease is one component of the unique and characteristic structure of differentiated keratinocytes. In addition, the cysteine protease antigen having the same molecular weight as the epidermal enzyme was detected in liver, kidney and lung indicating a wider tissue distribution of the protease. The significance of the protease in regulation of cellular functions remains to be investigated.