A Subset of Cytokinin Two-component Signaling System Plays a Role in Cold Temperature Stress Response in Arabidopsis

A multistep two-component signaling system is established as a key element of cytokinin signaling in Arabidopsis. Here, we provide evidence for a function of the two-component signaling system in cold stress response in Arabidopsis. Cold significantly induced the expression of a subset of A-type ARR genes and of GUS in Pro_ARR7:GUS transgenic Arabidopsis. AHK2 and AHK3 were found to be primarily involved in mediating cold to express A-type ARRs despite cytokinin deficiency. Cold neither significantly induced AHK2 and AHK3 expression nor altered the cytokinin contents of wild type within the 4 h during which the A-type ARR genes exhibited peak expression in response to cold, indicating that cold might induce ARR expression via the AHK2 and AHK3 proteins without alterations in cytokinin levels. The ahk2 ahk3 and ahk3 ahk4 mutants exhibited enhanced freezing tolerance compared with wild type. These ahk double mutants acclimated as efficiently to cold as did wild type. The overexpression of the cold-inducible ARR7 in Arabidopsis resulted in a hypersensitivity response to freezing temperatures under cold-acclimated conditions. The expression of C-repeat/dehydration-responsive element target genes was not affected by ARR7 overexpression as well as in ahk double mutants. By contrast, the arr7 mutants showed increased freezing tolerance. The ahk2 ahk3 and arr7 mutants showed hypersensitive response to abscisic acid (ABA) for germination, whereas ARR7 overexpression lines exhibited insensitive response to ABA. These results suggest that AHK2 and AHK3 and the cold-inducible A-type ARRs play a negative regulatory role in cold stress signaling via inhibition of ABA response, occurring independently of the cold acclimation pathway.     

Evolutionary inferences based on ITS rDNA and actin sequences reveal extensive diversity of the common lichen alga Asterochloris (Trebouxiophyceae,Chlorophyta)

The genus Asterochloris is one of the most common lichen photobionts. We present a molecular investigation of 41 cultured strains, for which nuclear-encoded ITS rDNA and partial actin I sequences were determined. The loci studied revealed considerable differences in their evolutionary dynamics as well as sequence variation. As compared to ITS data, the actin sequences show much greater variation, and the phylogenies yield strong resolution and support of many internal branches. The partitioning of ITS dataset into several regions yielded better node resolution. We recognized 16 well-supported monophyletic lineages, of which one represents the type species of the genus (Asterochloris phycobiontica), and six correspond to species previously classified to the genus Trebouxia (T. erici, T. excentrica, T. glomerata, T. irregularis, T. italiana and T. magna). Only 15% of isolated photobionts considered in our study could be assigned with certainty to previously described species, emphasizing amazing cryptic variability in Asterochloris. Concurrently with the formal delimitation of the genus Asterochloris, we propose new combinations for the former Trebouxia species; furthermore, T. pyriformis is reduced to a synonym of A. glomerata. The present knowledge of global diversity of Asterochloris algae is discussed.     

Arabidopsis cytokinin receptor mutants reveal functions in shoot growth, leaf senescence, seed size, germination, root development, and cytokinin metabolism

We used loss-of-function mutants to study three Arabidopsis thaliana sensor histidine kinases, AHK2, AHK3, and CRE1/AHK4, known to be cytokinin receptors. Mutant seeds had more rapid germination, reduced requirement for light, and decreased far-red light sensitivity, unraveling cytokinin functions in seed germination control. Triple mutant seeds were more than twice as large as wild-type seeds. Genetic analysis indicated a cytokinin-dependent endospermal and/or maternal control of embryo size. Unchanged red light sensitivity of mutant hypocotyl elongation suggests that previously reported modulation of red light signaling by A-type response regulators may not depend on cytokinin. Combined loss of AHK2 and AHK3 led to the most prominent changes during vegetative development. Leaves of ahk2 ahk3 mutants formed fewer cells, had reduced chlorophyll content, and lacked the cytokinin-dependent inhibition of dark-induced chlorophyll loss, indicating a prominent role of AHK2 and, particularly, AHK3 in the control of leaf development. ahk2 ahk3 double mutants developed a strongly enhanced root system through faster growth of the primary root and, more importantly, increased branching. This result supports a negative regulatory role for cytokinin in root growth regulation. Increased cytokinin content of receptor mutants indicates a homeostatic control of steady state cytokinin levels through signaling. Together, the analyses reveal partially redundant functions of the cytokinin receptors and prominent roles for the AHK2/AHK3 receptor combination in quantitative control of organ growth in plants, with opposite regulatory functions in roots and shoots.     

Natural infection of Cryptosporidium muris (Apicomplexa: Cryptosporiidae) in Siberian chipmunks

Coprologic examination of nine Siberian chipmunks (Eutamias sibiricus) imported from Southeast Asia revealed infection with Cryptosporidium sp. Experimental inoculation of BALB/c mice proved their susceptibility to the infection. Infected mice shed oocysts 14-35 days postinfection. Oocyst morphology was similar to that reported for C. muris in previous studies, oocysts were 8.1 (7.0-9.0) x 5.9 (5.0-6.5) microns. Clinical signs were absent in naturally infected chipmunks and experimental mice. Histologic examinations of mice revealed numerous developmental stages of C. muris in the glandular stomach. Analysis of partial small subunit rRNA gene sequences confirmed identity of these isolates as C. muris. Our results represent the first report of C. muris in members of the family Sciuridae.     

Ribo-, xylo-, and arabino-configured adenine-based nucleoside phosphonates: synthesis of monomers for solid-phase oligonucleotide assembly

Adenine-based, regioisomeric nucleoside phosphonates with ribo, xylo and arabino configuration were synthesized in the protected form suitable for the phosphotriester-like, solid-phase synthesis of oligonucleotides. Phosphonate moiety was protected by 4-methoxy-1-oxido-2-picolyl group and the furanose hydroxyl by the dimethoxytrityl group.     

Actions of a novel synthetic natriuretic peptide on hemodynamics and ventricular function in the dog

Dendroaspis natriuretic peptide (DNP) is a recently discovered peptide with structural similarity to known natriuretic peptides. DNP has been shown to possess potent renal actions. Our objectives were to define the acute hemodynamic actions of DNP in normal anesthetized dogs and the acute effects of DNP on left ventricular (LV) function in conscious chronically instrumented dogs. In anesthetized dogs, DNP, but not placebo, decreased mean arterial pressure (141 +/- 6 to 109 +/- 7 mmHg, P < 0.05) and pulmonary capillary wedge pressure (5.8 +/- 0.3 to 3.4 +/- 0.2 mmHg, P < 0.05). Cardiac output decreased and systemic vascular resistance increased with DNP and placebo. DNP-like immunoreactivity and guanosine 3',5'-cyclic monophosphate concentration increased without changes in other natriuretic peptides. In conscious dogs, DNP decreased LV end-systolic pressure (120 +/- 7 to 102 +/- 6 mmHg, P < 0.05) and volume (32 +/- 6 to 28 +/- 6 ml, P < 0.05) and LV end-diastolic volume (38 +/- 5 to 31 +/- 4 ml, P < 0.05) but not arterial elastance. LV end-systolic elastance increased (6.1 +/- 0.7 to 7.4 +/- 0.6 mmHg/ml, P < 0.05), and Tau decreased (31 +/- 2 to 27 +/- 1 ms, P < 0.05). The effects on hemodynamics, LV function, and second messenger generation suggest synthetic DNP may have a role as a cardiac unloading and lusitropic peptide.     

Ependyma as a Possible Morphological Basis of Ischemic Preconditioning Tolerance in Rat Spinal Cord Ischemia Model: Nestin and Fluoro-Jade B Observations

1. To test our hypothesis that a transient nonlethal ischemic insult benefits the lumbosacral spinal cord ischemic injury, nestin, the marker of proliferating cells, and Fluoro-Jade B, the marker of degenerating cells, were used in rats. Morphological outcome was evaluated after 12-min ischemia versus 12-min ischemia preconditioned by 3-min ischemic period and 30-min recirculation (IPC), in each group followed by 2, 3, and 4 days of posttreatment survival. 2. Twelve-minute ischemia, inducing nestin-positivity in ependyma and reactive astrocytes at the L(1-3) spinal cord segments, shows this region as the viable region of spinal cord in all postischemic survival periods. On the other hand, abundance of Fluoro-Jade B-positive cells, distributed throughout the dorsal horn and intermediate zone of L4-S2 segments, points out the most injured spinal cord region by ischemia. 3. After the same ischemic insult in IPC rats only a few nestin-positive ependymal cell and reactive astrocytes appeared beside the nestin-positive vessels in the lower lumbar and sacral spinal cord segments of all survival periods. The appearance of nestin-positive cells in the spinal cord segments, which "should have been affected" by ischemia indicates protection of this region by the IPC treatment. 4. The number and density evaluation of Fluoro-Jade B fluorescent cells of L4-S2 segments after ischemia and IPC confirmed that degenerating cells were significantly reduced in the IPC rats in all survival periods. 5. Our results showing the immunohistochemical response of epemdyma, committed to the presence of viable tissue, indicate that the ependymal cells may contribute to the ischemic resistance in the IPC rats.     

Synthesis of glycosyl amino acids by light-induced coupling of photoreactive amino acids with glycosylamines and 1-C-aminomethyl glycosides

The glycosylamines of O-acetyl-protected GlcNAc and chitobiose, as well as two partially unprotected 1-C-aminomethyl glucosides, were photochemically coupled with orthogonally protected N-aspartyl-5-bromo-7-nitroindoline derivatives. The reactions proceeded under neutral conditions by irradiation with near-UV light. The glycosyl asparagines with N- or C-glycosyl linkages were afforded in 60-85% yield on a 10-70 mg scale. Moreover, the ability of a highly photoreactive N-glutamyl-4-methoxy-7-nitroindoline derivative to acylate amino saccharides was tested. Upon irradiation in the presence of a dimeric 1-C-aminomethyl glycoside, or a glycosylamine, the corresponding glycosyl glutamines were obtained in 50% and 30% yield, respectively. Preparations of the photoreactive aspartates and the 1-C-aminomethyl glycosides are also described.     

Fluvastatin in the therapy of acute coronary syndrome: Rationale and design of a multicenter, randomized, double-blind, placebo-controlled trial (The FACS Trial)[ISRCTN81331696

BACKGROUND: Activation of inflammatory pathways plays an important contributory role in coronary plaque instability and subsequent rupture, which can lead to the development of acute coronary syndrome (ACS). Elevated levels of serum inflammatory markers such as C-reactive protein (CRP) represent independent risk factors for further cardiovascular events. Recent evidence indicates that in addition to lowering cholesterol levels, statins also decrease levels of inflammatory markers. Previous controlled clinical trials reporting the positive effects of statins in participants with ACS were designed for very early secondary prevention. To our knowledge, no controlled trials have evaluated the potential benefits of statin therapy, beginning immediately at the time of hospital admission. A previous pilot study performed by our group focused on early initiation of cerivastatin therapy. We demonstrated a highly significant reduction in levels of inflammatory markers (CRP and interleukin-6). Based on these preliminary findings, we are conducting a clinical trial to evaluate the efficacy of another statin, fluvastatin, as an early intervention in patients with ACS. METHODS: The FACS-trial (Fluvastatin in the therapy of Acute Coronary Syndrome) is a multicenter, randomized, double-blind, placebo-controlled study evaluating the effects of fluvastatin therapy initiated at the time of hospital admission. The study will enroll 1,000 participants admitted to hospital for ACS (both with and without ST elevation). The primary endpoint for the study is the influence of fluvastatin therapy on levels of inflammatory markers (CRP and interleukin-6) and on pregnancy associated plasma protein A (PAPP-A). A combined secondary endpoint is 30-day and one-year occurrence of death, nonfatal myocardial infarction, recurrent symptomatic ischemia, urgent revascularization, and cardiac arrest. CONCLUSION: The primary objective of the FACS trial is to demonstrate that statin therapy, when started immediately after hospital admission for ACS, results in reduction of inflammation and improvement of prognosis. This study may contribute to new knowledge regarding therapeutic strategies for patients suffering from ACS and may offer additional clinical indications for the use of statins.