Photoperiod regulates corticosterone rhythms by altered adrenal sensitivity via melatonin-independent mechanisms in Fischer 344 rats and C57BL/6J mice

Most species living in temperate zones adapt their physiology and behavior to seasonal changes in the environment by using the photoperiod as a primary cue. The mechanisms underlying photoperiodic regulation of stress-related functions are not well understood. In this study, we analyzed the effects of photoperiod on the hypothalamic-pituitary-adrenal axis in photoperiod-sensitive Fischer 344 rats. We first examined how photoperiod affects diurnal variations in plasma concentrations of adrenocorticotropic hormone (ACTH) and corticosterone. ACTH levels did not exhibit diurnal variations under long- and short-day conditions. On the other hand, corticosterone levels exhibited a clear rhythm under short-day condition with a peak during dark phase. This peak was not observed under long-day condition in which a significant rhythm was not detected. To analyze the mechanisms responsible for the photoperiodic regulation of corticosterone rhythms, ACTH was intraperitoneally injected at the onset of the light or dark phase in dexamethasone-treated rats maintained under long- and short-day conditions. ACTH induced higher corticosterone levels in rats examined at dark onset under short-day condition than those maintained under long-day condition. Next, we asked whether melatonin signals are involved in photoperiodic regulation of corticosterone rhythms, and rats were intraperitoneally injected with melatonin at late afternoon under long-day condition for 3 weeks. However, melatonin injections did not affect the corticosterone rhythms. In addition, photoperiodic changes in the amplitude of corticosterone rhythms were also observed in melatonin-deficient C57BL/6J mice, in which expression profiles of several clock genes and steroidgenesis genes in adrenal gland were modified by the photoperiod. Our data suggest that photoperiod regulates corticosterone rhythms by altered adrenal sensitivity through melatonin-independent mechanisms that may involve the adrenal clock.     

Assessment of Benzene-Induced Hematotoxicity Using a Human-Like Hematopoietic Lineage in NOD/Shi-scid/IL-2R��null Mice

Despite recent advancements, it is still difficult to evaluate in vivo responses to toxicants in humans. Development of a system that can mimic the in vivo responses of human cells will enable more accurate health risk assessments. A surrogate human hematopoietic lineage can be established in NOD/Shi-scid/IL-2Rγ^null (NOG) mice by transplanting human hematopoietic stem/progenitor cells (Hu-NOG mice). Here, we first evaluated the toxic response of human-like hematopoietic lineage in NOG mice to a representative toxic agent, benzene. Flow cytometric analysis showed that benzene caused a significant decrease in the number of human hematopoietic stem/progenitor cells in the bone marrow and the number of human leukocytes in the peripheral blood and hematopoietic organs. Next, we established chimeric mice by transplanting C57BL/6 mouse-derived bone marrow cells into NOG mice (Mo-NOG mice). A comparison of the degree of benzene-induced hematotoxicity in donor-derived hematopoietic lineage cells within Mo-NOG mice indicated that the toxic response of Hu-NOG mice reflected interspecies differences in susceptibilities to benzene. Responses to the toxic effects of benzene were greater in lymphoid cells than in myeloid cells in Mo-NOG and Hu-NOG mice. These findings suggested that Hu-NOG mice may be a powerful in vivo tool for assessing hematotoxicity in humans, while accounting for interspecies differences.     

Tissue organization of fasciated lateral roots of Arabidopsis mutants suggestive of the robust nature of outer layer patterning

In three temperature-sensitive mutants of Arabidopsis, root redifferentiation 1 (rrd1), rrd2, and root initiation defective 4 (rid4), formation of fasciated lateral roots was previously observed under high temperature conditions of 28°C. When lateral roots were induced from explants of very young seedlings of these mutants by culture with exogenously supplied auxin at 28°C, expansion of lateral root primordia leading to lateral root fasciation occurred reproducibly and semi-synchronously with a high frequency. This experimental system allowed us to examine how radial organization of root tissues is altered in association with expansion of primordia. Analysis with various tissue-specific reporter genes indicated that in the fasciated lateral roots, cell files of the stele are increased markedly while the numbers of cortical and epidermal cell layers are not changed. This suggests that radial organization during root primordium development involves a mechanism that makes outer layer patterning more robust than inner layer patterning against unusual enlargement of the morphogenetic field.     

Differential expression of oxidation-specific epitopes and apolipoprotein(a) in progressing and ruptured human coronary and carotid atherosclerotic lesions

The relationships between oxidation-specific epitopes (OSE) and lipoprotein (a) [Lp(a)] and progressive atherosclerosis and plaque rupture have not been determined. Coronary artery sections from sudden death victims and carotid endarterectomy specimens were immunostained for apoB-100, oxidized phospholipids (OxPL), apo(a), malondialdehyde-lysine (MDA), and MDA-related epitopes detected by antibody IK17 and macrophage markers. The presence of OxPL captured in carotid and saphenous vein graft distal protection devices was determined with LC-MS/MS. In coronary arteries, OSE and apo(a) were absent in normal coronary arteries and minimally present in early lesions. As lesions progressed, apoB and MDA epitopes did not increase, whereas macrophage, apo(a), OxPL, and IK17 epitopes increased proportionally, but they differed according to plaque type and plaque components. Apo(a) epitopes were present throughout early and late lesions, especially in macrophages and the necrotic core. IK17 and OxPL epitopes were strongest in late lesions in macrophage-rich areas, lipid pools, and the necrotic core, and they were most specifically associated with unstable and ruptured plaques. Specific OxPL were present in distal protection devices. Human atherosclerotic lesions manifest a differential expression of OSEs and apo(a) as they progress, rupture, and become clinically symptomatic. These findings provide a rationale for targeting OSE for biotheranostic applications in humans.Oxidative pathways in the subendothelial space activate pro-inflammatory, immunogenic, and atherogenic processes, resulting in endothelial dysfunction, plaque growth and destabilization, platelet activation, and thrombosis, ultimately leading to clinical events (1). A variety of oxidation-specific epitopes (OSE) are generated during oxidative modification of plaque components. These epitopes are not only expressed on modified lipoproteins but also on apoptotic cells and proteins in the extracellular matrix of atherosclerotic vessels (2).Extensive experimental data exists defining the role of oxidation in both progression and regression of atherosclerosis. Atherosclerotic lesions of hypercholesterolemic animal models, which represent primarily early and intermediate stage atherosclerosis, contain significant amounts of OSE, often in proportion to plaque burden. OSE in the vessel wall of atherosclerotic animals can also be imaged with nuclear and magnetic resonance techniques using murine and human oxidation-specific antibodies, such as MDA2, E06, and IK17 (3–5). Dietary interventions in hypercholesterolemic animals that promote regression result in more rapid removal of OSE than apoB, which occurs prior to plaques diminishing significantly in size, and is associated with markers of plaque stabilization, such as increased collagen and smooth muscle cell (SMC) expression, and a decrease in reactive oxygen species and macrophages (6–8).Despite this wealth of animal data on the relationship of OSE and atherosclerosis, relatively little is known about their relationship to clinically relevant advanced, unstable, or ruptured plaques. Furthermore, a systematic analysis of the presence of OSE in human lesions has not been performed to date. Therefore, the purpose of this study was to determine the presence and relative distribution of well-characterized OSE in various stages of human atherosclerotic lesions, including native coronary lesions, carotid endarterectomy samples, and material from carotid and saphenous vein graft (SVG) embolic protection filters. Such knowledge may have significant clinical implications with the emergence in the clinical and translational arenas of oxidative biomarkers, molecular imaging, and therapeutic approaches, including immune modulation and vaccine approaches targeting these moieties (9–12), broadly characterized as “biotheranostic” (biomarker, therapeutic, diagnostic imaging) applications.     

High abundance of ammonia-oxidizing archaea in acidified subtropical forest soils in southern China after long-term N deposition

Nitrification has been believed to be performed only by autotrophic ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) until the recent discovery of ammonia-oxidizing archaea (AOA). Meanwhile, it has been questioned whether AOB are significantly responsible for NH(3) oxidation in acidic forest soils. Here, we investigated nitrifying communities and their activity in highly acidified soils of three subtropical forests in southern China that had received chronic high atmospheric N deposition. Nitrifying communities were analyzed using PCR- and culture (most probable number)-based approaches. Nitrification activity was analyzed by measuring gross soil nitrification rates using a (15) N isotope dilution technique. AOB were not detected in the three forest soils: neither via PCR of 16S rRNA and ammonia monooxygenase (amoA) genes nor via culture-based approaches. In contrast, an extraordinary abundance of the putative archaeal amoA was detected (3.2?×?10(8) -1.2?×?10(9) g?soil(-1) ). Moreover, this abundance was correlated with gross soil nitrification rates. This indicates that amoA-possessing archaea rather than bacteria were predominantly responsible for nitrification of the soils. Furthermore, sequences of the genus Nitrospira, a dominant group of soil NOB, were detected. Thus, nitrification of acidified subtropical forest soils in southern China could be performed by a combination of AOA and NOB.     

Photoperiod regulates dietary preferences and energy metabolism in young developing Fischer 344 rats but not in same-age Wistar rats

The effects of photoperiod on dietary preference were examined using young growing Fischer 344 and Wistar rats, which are seasonal and nonseasonal breeders, respectively. Rats were provided a low-fat, high-carbohydrate diet (LFD: 66/10/24% energy as carbohydrate/fat/protein) and high-fat, low-carbohydrate diet (HFD: 21/55/24% energy as carbohydrate/fat/protein) simultaneously under long- (LD: 16 h light/day) and short-day (SD: 8 h light/day) conditions for 3 wk. Fischer 344 rats preferred the LFD to the HFD under the LD condition, whereas preference for both diets was equivalent under the SD condition. Consequently, their body weight and total energy intake exhibited 11-15 and 10-13% increases, respectively, under the LD condition. Calculation of energy intake from macronutrients revealed that rats under the LD condition consumed 20-24 and 9-13% higher energy of carbohydrates and proteins, respectively, than those under the SD condition. In contrast, Wistar rats preferred the LFD to the HFD irrespective of photoperiod and exhibited no photoperiodic changes in any parameters examined. Next, Fischer 344 rats were provided either the LFD or HFD for 3 wk under LD or SD conditions. Calorie intake was 10% higher in the rats fed the LFD than those fed the HFD under SD condition. However, rats under LD condition exhibited 5-10, 14, and 64% increases in body weight, epididymal fat mass, and plasma leptin levels, respectively, compared with those under the SD condition irrespective of dietary composition. In conclusion, photoperiod regulates feeding and energy metabolism in young growing Fischer 344 rats via the interactions with dietary macronutrient composition.     

Quercetin glycosides prevent dexamethasone-induced muscle atrophy in mice

Although quercetin has numerous biological benefits, including preventing muscle atrophy due to disuse, no reports have been published to date about the preventive effects and molecular mechanisms underlying drug-induced muscle atrophy. Highly soluble and bioavailable quercetin glycosides (QGs) were used to examine the inhibition of dexamethasone (DEX)-induced muscle atrophy in vivo. Male BALB/cCrSlc mice were treated with or without QGs for 7 days ad libitum, followed by addition of DEX to their drinking water for a further 7 days. The weight of gastrocnemius (GM) adjusted by body weight was significantly decreased on day 7 after DEX treatment. DEX-induced decrease of GM weight was improved by QG co-administration on day 7. The mRNA levels of muscle atrophy-related genes in the gastrocnemius were significantly lowered by QGs on day 1. In particular, the expression of myostatin, a master regulator of muscle mass homeostasis, was suppressed to that of the control level. In murine C2C12 myotubes, quercetin elevated the phosphorylation of Akt, which are downstream of the myostatin pathway, as well as expression of atrogenes. We demonstrated the protective effect of QGs in DEX-induced muscle atrophy, which might depend on the suppression of myostatin signaling.     

Gastric and intestinal phenotypic correlation between exocrine and endocrine components in human stomach tumors

We have previously suggested that an origin of a stomach cancer is from a progenitor cell specializing toward exocrine cell (Exo-cell) lineages. To clarify whether our hypothesis is correct or not, we analyzed the expression of Exo-cell and endocrine cell (End-cell) markers in a series of lesions for comparison. We evaluated chromogranin A (CgA) expression in 37 early and 73 advanced stomach cancers, in 30 stomach adenomas, in 8 carcinoid tumors, and in 4 endocrine cell carcinomas (ECCs) with assessment of gastric and/or intestinal (G/I) phenotypes in both Exo-cell and End-cell by immunohistochemistry. CgA expression was observed in 10.8% of the early and 16.4% of the advanced stomach cancers, respectively. The End-cell G/I phenotypes were in line with the Exo-cell counterparts in the CgA-positive stomach cancerous areas, and there was strong association between Cdx2 expression and the intestinal End-cell markers. All of the adenoma cases had the intestinal Exo-cell phenotypic expression, with the positive link between Exo-cell and End-cell G/I phenotypes. All stomach carcinoids had CgA expression but no expression of Exo-cell markers. In conclusion, most stomach cancers might develop from a progenitor cell specializing towards Exo-cell lineages, but some cases possessed both Exo-cell and End-cell markers with maturely differentiated phenotypes. In such cases, Exo-cell and End-cell phenotypes were found to correlate strongly, suggesting the possibility of histogenesis from "cancer stem cells".     

Oral administration of D-aspartate,but not L-aspartate,depresses rectal temperature and alters plasma metabolites in chicks

Aims

L-Aspartate (L-Asp) and D-aspartate (D-Asp) are physiologically important amino acids in mammals and birds. However, the functions of these amino acids have not yet been fully understood. In this study, we therefore examined the effects of L-Asp and D-Asp in terms of regulating body temperature, plasma metabolites and catecholamines in chicks.

Main methods

Chicks were first orally administered with different doses (0, 3.75, 7.5 and 15 mmol/kg body weight) of L- or D-Asp to monitor the effects of these amino acids on rectal temperature during 120 min of the experimental period.

Key findings

Oral administration of D-Asp, but not of L-Asp, linearly decreased the rectal temperature in chicks. Importantly, orally administered D-Asp led to a significant reduction in body temperature in chicks even under high ambient temperature (HT) conditions. However, centrally administered D-Asp did not significantly influence the body temperature in chicks. As for plasma metabolites and catecholamines, orally administered D-Asp led to decreased triacylglycerol and uric acid concentrations and increased glucose and chlorine concentrations but did not alter plasma catecholamines.

Significance

These results suggest that oral administration of D-Asp may play a potent role in reducing body temperature under both normal and HT conditions. The alteration of plasma metabolites further indicates that D-Asp may contribute to the regulation of metabolic activity in chicks.     

RNase HI stimulates the activity of RnlA toxin in Escherichia coli

A type II toxin–antitoxin system in Escherichia coli, rnlA‐rnlB, functions as an anti‐phage mechanism. RnlA is a toxin with an endoribonuclease activity and the cognate RnlB inhibits RnlA toxicity in E. coli cells. After bacteriophage T4 infection, RnlA is activated by the disappearance of RnlB, resulting in the rapid degradation of T4 mRNAs and consequently no T4 propagation, when T4 dmd is defective: Dmd is an antitoxin against RnlA for promoting own propagation. Previous studies suggested that the activation of RnlA after T4 infection was regulated by multiple components. Here, we provide the evidence that RNase HI is an essential factor for activation of RnlA. The dmd mutant phage could grow on ΔrnhA (encoding RNase HI) cells, in which RnlA‐mediated mRNA cleavage activity was defective. RNase HI bound to RnlA in vivo and enhanced the RNA cleavage activity of RnlA in vitro. In addition, ectopic expression of RnlA in ΔrnlAB ΔrnhA cells has less effect on cell toxicity and RnlA‐mediated mRNA degradation than in ΔrnlAB cells. This is the first example of a direct factor for activation of a toxin.