Importance of interspecific competition in the abundance of Aphanizomenon flos-aquae (Cyanophyceae)

The population dynamics of Aphanizomenon flos-aquae var. klebahnii Elenk. (Cyanophyceae) was studied in an artificial pond for 32 months from May 2002 to December 2004. Our previous in vitro study showed that the lower limits of water temperature and pH for its growth are within the ranges of 11°–14°C and 7.1–7.4, respectively, and it appeared that these findings are applicable to the emergence and disappearance of Ap. flos-aquae in the pond. Based on the change in the water temperature, the emergence of Ap. flos-aquae in 2004 was expected to be in late April, whereas emergence occurred after a 1-month lag period. During this period, Ankistrodesmus falcatus (Corda) Ralfs (Chlorophyceae) dominated the phytoplankton assemblage, which raised the possibility that the growth of Ap. flos-aquae was restricted by the existence of An. falcatus. We conducted mixed cultures of Ap. flos-aquae and An. falcatus at four temperatures (14°, 19°, 24°, and 29°C). After 18 days of incubation, An. falcatus dominated at 14° and 29°C whereas Ap. flos-aquae dominated at 19°C. This result indicates that a slightly higher water temperature than the growth threshold value is needed for Ap. flosaquae to outcompete An. falcatus, which agrees with the field observation. Contrary to the results of the mixed culture, the summer phytoplankton assemblage was dominated by Ap. flos-aquae, and the population of An. falcatus was less or almost absent. This variation seemed to be partly caused by the difference in nutrient conditions; concentrations of dissolved inorganic nitrogen and phosphorus in the pond were far lower than those in the culture medium. The lack of nitrogen fixation of An. falcatus seemed to be a growth disadvantage during the summer when the concentration of dissolved inorganic nitrogen was low.     

Protective roles of redox-active protein thioredoxin-1 for severe acute pancreatitis

Severe acute pancreatitis is a disease with high mortality, and infiltration of inflammatory cells and reactive oxygen species have a crucial role in the pathophysiology of this disease. Thioredoxin-1 (TRX-1) is an endogenous redox-active multifunctional protein with antioxidant and anti-inflammatory effects. TRX-1 is induced in various inflammatory conditions and shows cytoprotective effects. The aim of the present study was to clarify the protective roles of TRX-1 in the host defense mechanism against severe acute pancreatitis. Experimental acute pancreatitis was induced by intraperitoneal administration of cerulein, a CCK analog, and aggravated by lipopolysaccharide injection in transgenic mice overexpressing human TRX-1 (hTRX-1) and control C57BL/6 mice. Transgenic overexpression of hTRX-1 strikingly attenuated the severity of experimental acute pancreatitis. TRX-1 overexpression suppressed neutrophil infiltration as determined by myeloperoxidase activity, oxidative stress as determined by malondialdehyde concentration, and cytoplasmic degradation of inhibitor of kappaB-alpha, thereby suppressing proinflammatory cytokines, tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6; a neutrophil chemoattractant, keratinocyte-derived chemokine; and inducible nitric oxide synthase in the pancreas. Administration of recombinant hTRX-1 also suppressed neutrophil infiltration, reduced the inflammation of the pancreas and the lung, and improved the mortality rate. The present study suggests that TRX-1 has potent antioxidant and anti-inflammatory actions in experimental acute pancreatitis and might be a new therapeutic strategy to improve the prognosis of severe acute pancreatitis.     

Isolation and characterization of a novel small cardioactive peptide-related peptide from the brain of Octopus vulgaris

A novel small cardioactive peptide (SCP)-related peptide (oct-SCPRP: Ser-Asn-Gly-Tyr-Leu-Ala-Leu-Pro-Arg-Gln-NH2) was isolated from the brain of the octopus (Octopus vulgaris). cDNA encoding this precursor protein was cloned. Oct-SCPRP was shown to evoke contraction in the radula protractor muscle, and the precursor protein was highly homologous to the SCP family in the Mollusk but did not encode a related peptide, SCPB. The expression of oct-SCPRP mRNA was present not only in the peripheral nervous system (PNS) which is a motor center for the control of feeding, but also in the central nervous system (CNS) which is capable of complex analysis, learning, and controls behaviors.     

Regulation of food intake by acyl and des-acyl ghrelins in the goldfish

Our recent research has indicated that intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) administration of n-octanoic acid-modified ghrelin (acyl ghrelin) stimulates food intake and locomotor activity in the goldfish. The manner in which peripherally administered acyl ghrelin regulates food intake, however, remains unclear. In contrast to acyl ghrelin, non-acylated ghrelin (des-acyl ghrelin) does not exert an orexigenic action or induce hypermotility. To this extent, the biological role of des-acyl ghrelin in fish is unknown. Given the possible involvement of afferent pathways in mediating the effects of acyl ghrelin, as is known to occur in rodents, we examined the effect of capsaicin, a neurotoxin which destroys primary sensory (vagal and splanchnic) afferents, on the orexigenic activity induced by i.p.-injected acyl ghrelin. Pretreatment with i.p.-injected capsaicin (0.16 micromol/g body weight (BW)) cancelled the orexigenic action of i.p.-injected acyl ghrelin (8 pmol/g BW), although i.p.-injected capsaicin alone did not affect food intake. The effect of des-acyl ghrelin on the orexigenic action of acyl ghrelin in the goldfish was also investigated. The i.c.v. and i.p. injection of des-acyl ghrelin at doses 3-10 times higher than that of acyl ghrelin suppressed the orexigenic action of i.c.v.- and i.p.-injected acyl ghrelin (doses of 1 and 8 pmol/g BW). In contrast, injection of des-acyl ghrelin alone did not show any inhibitory effect on food intake. These results suggest that, as is seen in rodents, circulating acyl ghrelin derived from peripheral tissues acts via primary sensory afferent pathways on feeding centers in the brain. The results also show that des-acyl ghrelin inhibits acyl ghrelin-induced orexigenic activity in goldfish.     

Differential inhibitory effects of mu-opioids on substance P- and capsaicin-induced nociceptive behavior in mice

The antinociceptive mechanisms of the selective mu-opioid receptor agonists [D-Ala2,NMePhe4,Gly(ol)5]enkephalin (DAMGO), H-Tyr-D-Arg-Phe-beta-Ala-OH (TAPA) or H-Tyr-D-Arg-Phe-beta-Ala-NH2 (TAPA-NH2) against substance P (SP)- or capsaicin-elicited nociceptive behaviors was investigated in mice. DAMGO, TAPA or TAPA-NH2 given intrathecally inhibited the nociceptive behaviors elicited by intrathecally administered SP or capsaicin, and these antinociceptive effects were completely eliminated by intrathecal co-administration with D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), a selective mu-opioid receptor antagonist. Pretreatment subcutaneously with naloxonazine, a selective mu1-opioid receptor antagonist, partially attenuated the antinociceptive effect of TAPA-NH2, but not DAMGO and TAPA, against SP. However, the antinociception induced by TAPA, but not DAMGO and TAPA-NH2, against capsaicin was significantly inhibited by naloxonazine. On the other hand, co-administration intrathecally with Tyr-D-Pro-Trp-Gly-NH2 (D-Pro2-Tyr-W-MIF-1), a selective mu2-opioid receptor antagonist, significantly attenuated the antinociceptive effects of DAMGO, but not TAPA and TAPA-NH2, against capsaicin, while the antinociceptions induced by three opioid peptides against SP were significantly inhibited by D-Pro2-Tyr-W-MIF-1. These results suggest that differential inhibitory mechanisms on pre- and postsynaptic sites in the spinal cord contribute to the antinociceptive effects of the three mu-opioid peptides.     

ATM-Chk2-p53 activation prevents tumorigenesis at an expense of organ homeostasis upon Brca1 deficiency

BRCA1 is a checkpoint and DNA damage repair gene that secures genome integrity. We have previously shown that mice lacking full-length Brca1 (Brca1(delta11/delta11)) die during embryonic development. Haploid loss of p53 completely rescues embryonic lethality, and adult Brca1(delta11/delta11)p53+/- mice display cancer susceptibility and premature aging. Here, we show that reduced expression and/or the absence of Chk2 allow Brca1(delta11/delta11) mice to escape from embryonic lethality. Compared to Brca1(delta11/delta11)p53+/- mice, lifespan of Brca1(delta11/delta11)Chk2-/- mice was remarkably extended. Analysis of Brca1(delta11/delta11)Chk2-/- mice revealed that p53-dependent apoptosis and growth defect caused by Brca1 deficiency are significantly attenuated in rapidly proliferating organs. However, in later life, Brca1(delta11/delta11)Chk2-/- female mice developed multiple tumors. Furthermore, haploid loss of ATM also rescued Brca1 deficiency-associated embryonic lethality and premature aging. Thus, in response to Brca1 deficiency, the activation of the ATM-Chk2-p53 signaling pathway contributes to the suppression of neoplastic transformation, while leading to compromised organismal homeostasis. Our data highlight how accurate maintenance of genomic integrity is critical for the suppression of both aging and malignancy, and provide a further link between aging and cancer.     

Binding of AlF-C, an Orc1-binding transcriptional regulator, enhances replicator activity of the rat aldolase B origin

A region encompassing the rat aldolase B gene (aldB) promoter acts as a chromosomal origin of DNA replication (origin) in rat aldolase B-nonexpressing hepatoma cells. To examine replicator function of the aldB origin, we constructed recombinant mouse cell lines in which the rat aldB origin and the mutant derivatives were inserted into the same position at the mouse chromosome 8 by cre-mediated recombination. Nascent strand abundance assays revealed that the rat origin acts as a replicator at the ectopic mouse locus. Mutation of site C in the rat origin, which binds an Orc1-binding protein AlF-C in vitro, resulted in a significant reduction of the replicator activity in the mouse cells. Chromatin immunoprecipitation (ChIP) assays indicated that the reduction of replicator activity was paralleled with the reduced binding of AlF-C and Orc1, suggesting that sequence-specific binding of AlF-C to the ectopic rat origin leads to enhanced replicator activity in cooperation with Orc1. Involvement of AlF-C in replication in vivo was further examined for the aldB origin at its original rat locus and for a different rat origin identified in the present study, which contained an AlF-C-binding site. ChIP assays revealed that both replication origins bind AlF-C and Orc1. We think that the results presented here may represent one mode of origin recognition in mammalian cells.