Growth Analysis and Reproductive Allocation of Japanese Forbs and Grasses in Relation to Organ Toughness under Trampling

Abstract: The growth and reproduction of Japanese forbs ( Artemisia princeps and Piantago asiatica ) and grasses ( Digitaria ad-scendens and Eleusine indica ) treated to 25 tramplings (3 g m^-2) per week were investigated in relation to the toughness (tensile strength) of organs. The perennial erect forb, A. princeps , was the most sensitive to trampling in terms of a remarkable depression of plant size and relative growth rate (RGR). RGR and net assimilation rate (NAR) of trampled A. princeps were negative. This was promoted by a loss of organs due to a reduced toughness of organs following trampling. In contrast to this species which did not flower after trampling, the perennial rosette forb, P. asiatica , maintained its plant biomass, NAR, RGR and reproduction under trampling because of tougher organs. However, NAR without trampling was lower in P. asiatica due to a larger leaf dry mass per leaf area (LMA), which could contribute to leaf toughness under trampling. The annual tussock grass, D. adscendens , which has a greater RGR than that of another grass, E. indica , without trampling was intolerant to trampling in terms of decreased biomass and RGR under trampling due to more sensitive organs, although it maintained an ability to reproduce. On the other hand, E. indica showed a marked trampling tolerance, with hardly reduced plant biomass and RGR. This species showed increased toughness of organs when trampled and frequently formed inflorescences in the growing period and produced similar biomass allocation to reproductive organs to untrarnpled plants. Between the grasses, RGR without trampling was slower in E. indica , partly because of its larger LMA. These results suggest that plants face a dilemma between trampling tolerance and efficient assimilative capacity and/or growth rate.     

Visualization of Sialidase Activity in Mammalian Tissues and Cancer Detection with a Novel Fluorescent Sialidase Substrate

Sialidase removes sialic acid from sialoglycoconjugates and plays crucial roles in many physiological and pathological processes. Various human cancers express an abnormally high level of the plasma membrane-associated sialidase isoform.Visualization of sialidase activity in living mammalian tissues would be useful not only for understanding sialidase functions but also for cancer diagnosis. However, since enzyme activity of mammalian sialidase is remarkably weak compared with that of bacterial and viral sialidases, it has been difficult to detect sialidase activity in mammalian tissues. We synthesized a novel benzothiazolylphenol-based sialic acid derivative (BTP-Neu5Ac) as a fluorescent sialidase substrate. BTP-Neu5Ac can visualize sialidase activities sensitively and selectively in acute rat brain slices. Cancer cells implanted orthotopically in mouse colons and human colon cancers (stages T3-T4) were also clearly detected with BTP-Neu5Ac. The results suggest that BTP-Neu5Ac is useful for histochemical imaging of sialidase activities.     

The influence of feeding on the metabolic activity of Antarctic krill (Euphausia superba Dana)

Summary The influence of feeding on the metabolic activity of juvenile krill was assessed from 24h experiments in which krill were incubated with various concentrations of diatoms (Chaetoceros calcitrans, Phaeodactylum tricornutum, Thalassiosira eccentrica, Fragilariopsis vanheurkii), newly hatched Artemia nauplii and latex beads. Krill fed on the larger food more efficiently, with reluctant feeding on latex beads. Feeding of krill expressed as clearance rates was poorly correlated with their oxygen uptake rates. Instead, a positive correlation was found between the oxygen uptake rates and ingestion rate (except for latex beads). The result implies that the specific dynamic action is the major cause of the increased oxygen uptake of krill. Krill fed diatoms increased both ammonia and phosphate excretion with increasing ingestion rate, but only phosphate excretion was increased in parallel with ingestion rate for those fed Artemia nauplii. Assuming the daily ration of krill in the field is 5% of the body weight, and the major food source is phytoplankton, oxygen uptake, ammonia excretion and phosphate excretion rates of wild krill are estimated to be 1.6, 4.5 and 7.8, respectively, times the rates of non-feeding krill in 24h laboratory experiments. Krill offered various kinds of food showed different metabolic quotients (O/N, N/P and O/P ratios). While no functional relationship was seen between the metabolic quotient and the ingestion rate of krill fed Artemia nauplii, those fed Fragilariopsis showed a progressive decrease in O/N, N/P, and O/P ratios as their ingestion rates increased.     

Regulation of melatonin 1a receptor signaling and trafficking by asparagine-124.

Melatonin is a pineal hormone that regulates seasonal reproduction and has been used to treat circadian rhythm disorders. The melatonin 1a receptor is a seven- transmembrane domain receptor that signals predominately via pertussis toxin-sensitive G-proteins. Point mutations were created at residue N124 in cytoplasmic domain II of the receptor and the mutant receptors were expressed in a neurohormonal cell line. The acidic N124D- and E-substituted receptors had high-affinity (125)I-melatonin binding and a subcellular localization similar to the neutral N124N wild-type receptor. Melatonin efficacy for the inhibition of cAMP by N124D and E mutations was significantly decreased. N124D and E mutations strongly compromised melatonin efficacy and potency for inhibition of K(+)-induced intracellular Ca(++) fluxes and eliminated control of spontaneous calcium fluxes. However, these substitutions did not appear to affect activation of Kir3 potassium channels. The hydrophobic N124L and N124A or basic N124K mutations failed to bind (125)I-melatonin and appeared to aggregate or traffic improperly. N124A and N124K receptors were retained in the Golgi. Therefore, mutants at N124 separated into two sets: the first bound (125)I-melatonin with high affinity and trafficked normally, but with reduced inhibitory coupling to adenylyl cyclase and Ca(++) channels. The second set lacked melatonin binding and exhibited severe trafficking defects. In summary, asparagine-124 controls melatonin receptor function as evidenced by changes in melatonin binding, control of cAMP levels, and regulation of ion channel activity. Asparagine-124 also has a unique structural effect controlling receptor distribution within the cell.     

Overlapping and distinct roles of STAT4 and T-bet in the regulation of T cell differentiation and allergic airway inflammation

T-bet and STAT4 play critical roles in helper T cell differentiation, especially for Th1 cells. However, it is still unknown about the relative importance and redundancy of T-bet and STAT4 for Th1 differentiation. It is also unknown about their independent role of T-bet and STAT4 in the regulation of allergic airway inflammation. In this study, we addressed these issues by comparing T-bet-deficient (T-bet(-/-)) mice, STAT4(-/-) mice, and T-bet- and STAT4-double-deficient (T-bet(-/-)STAT4(-/-)) mice on the same genetic background. Th1 differentiation was severely decreased in T-bet(-/-) mice and STAT4(-/-) mice as compared with that in wild-type mice, but Th1 differentiation was still observed in T-bet(-/-) mice and STAT4(-/-) mice. However, Th1 cells were hardly detected in T-bet(-/-)STAT4(-/-) mice. In contrast, the maintenance of Th17 cells was enhanced in T-bet(-/-) mice but was reduced in STAT4(-/-) mice and T-bet(-/-)STAT4(-/-) mice. In vivo, Ag-induced eosinophil and neutrophil recruitment into the airways was enhanced in T-bet(-/-) mice but was attenuated in STAT4(-/-) mice and T-bet(-/-)STAT4(-/-) mice. Ag-induced IL-17 production in the airways was also diminished in STAT4(-/-) mice and T-bet(-/-)STAT4(-/-) mice. These results indicate that STAT4 not only plays an indispensable role in T-bet-independent Th1 differentiation but also is involved in the maintenance of Th17 cells and the enhancement of allergic airway inflammation.     

The oncogenic role of GASC1 in chemically induced mouse skin cancer

Gene amplified in squamous cell carcinoma (SCC) 1 (GASC1), also known as KDM4C/JMJD2C, encodes a histone demethylase that specifically demethylates lysine residues (H3K9, H3K36, and H1.4K26) and plays a crucial role in the regulation of gene expression as well as in heterochromatin formation. GASC1 is located at human chromosome 9p23–24, where frequent genomic amplification is observed in human esophageal cancer, and its aberrant expression is detected in a variety of human cancers, such as breast, colon, and prostate. Therefore, it is highly likely that GASC1 contributes to the genesis and/or development of cancer. However, there is a lack of direct evidence of GASC1 having an oncogenic function. In this study, we aimed to clarify the role of GASC1 in the skin SCC carcinogenesis. For this purpose, we generated Gasc1-heterozygous mice (Gasc1 ^+/−) with reduced expression of Gasc1. On the basis of our results, Gasc1 ^+/− mice displayed a significantly lower incidence and multiplicity of both benign and malignant tumors induced by the two-stage skin carcinogenesis protocol than wild-type mice. In addition, the volume of carcinoma was significantly lower in Gasc1 ^+/− mice. Consistent with these observations, knocking down of Gasc1 resulted in reduced cell viability of SCC cells in vitro. Our findings clearly demonstrated that GASC1 has an oncogenic role in skin carcinogenesis.

     

Influence of Lactic Acid Bacteria on Longevity of Caenorhabditis elegans and Host Defense against Salmonella enterica Serovar Enteritidis

This study aimed to develop a convenient model to investigate the senescence of host defenses and the influence of food and nutrition. A small soil nematode, Caenorhabditis elegans, was grown for 3 days from hatching on a lawn of Escherichia coli OP50 as the normal food source, and subsequently some of the nematodes were fed lactic acid bacteria (LAB). The life spans of worms fed LAB were significantly longer than the life spans of those fed OP50. To investigate the effect of age on host defenses, 3- to 7-day-old worms fed OP50 were transferred onto a lawn of Salmonella enterica serovar Enteritidis for infection. The nematodes died over the course of several days, and the accumulation of salmonella in the intestinal lumen suggested that the worms were infected. The 7-day-old worms showed a higher death rate during the 5 days after infection than nematodes infected at the age of 3 days; no clear difference was observed when the worms were exposed to OP50. We then investigated whether the LAB could exert probiotic effects on the worms' host defenses and improve life span. Seven-day-old nematodes fed LAB from the age of 3 days were more resistant to salmonella than worms fed OP50 until they were infected with salmonella. This study clearly showed that LAB can enhance the host defense of C. elegans and prolong life span. The nematode appears to be an appropriate model for screening useful probiotic strains or dietetic antiaging substances.     

Regression of abdominal aortic aneurysm by inhibition of c-Jun N-terminal kinase

Abdominal aortic aneurysm (AAA) is a common disease among elderly people that, when surgical treatment is inapplicable, results in progressive expansion and rupture of the aorta with high mortality. Although nonsurgical treatment for AAA is much awaited, few options are available because its molecular pathogenesis remains elusive. Here, we identify JNK as a proximal signaling molecule in the pathogenesis of AAA. Human AAA tissue showed a high level of phosphorylated JNK. We show that JNK programs a gene expression pattern in different cell types that cooperatively enhances the degradation of the extracellular matrix while suppressing biosynthetic enzymes of the extracellular matrix. Selective inhibition of JNK in vivo not only prevented the development of AAA but also caused regression of established AAA in two mouse models. Thus, JNK promotes abnormal extracellular matrix metabolism in the tissue of AAA and may represent a therapeutic target.