Four New Diterpenoid Alkaloids from The Roots of Aconitum coreanum

Four new hetisine‐type C₂₀‐diterpenoid alkaloids, named as coreanines A–D ( 1 – 4 ), were isolated from the roots of Aconitum coreanum, together with thirteen known alkaloids ( 5 – 17 ). Their structures were elucidated by extensive spectroscopic methods including IR, HR‐ESI‐MS and NMR techniques. All the isolated compounds were screened for the acetylcholinesterase (AChE) inhibitory effects, and none of them showed considerable inhibitory activity.     

The putative tumor suppressor LRP1B, a novel member of the low density lipoprotein (LDL) receptor family, exhibits both overlapping and distinct properties with the LDL receptor-related protein

The low density lipoprotein receptor-related protein-deleted in tumor (LRP1B, initially referred to as LRP-DIT) was cloned and characterized as a candidate tumor suppressor. It is a new member of the low density lipoprotein receptor gene family. Its overall domain structure and large size (approximately 600 kDa) are similar to LRP and suggest that it is a multifunctional cell surface receptor. Herein, we characterize a series of ligands for the receptor using cell lines that stably express it as a domain IV minireceptor (mLRP1B4). Ligands of LRP including receptor-associated protein, urokinase plasminogen activator, tissue-type plasminogen activator, and plasminogen activator inhibitor type-1 each demonstrate binding, internalization, and degradation via mLRP1B4. Interestingly, the kinetics of ligand endocytosis is distinctly different from that of LRP, with LRP1B exhibiting a markedly diminished internalization rate. In addition, tissue expression analysis reveals that the LRP1B gene is expressed in brain, thyroid, and salivary gland. These studies thus extend the physiological roles of members of the LDL receptor family.     

Cardiac restricted overexpression of kinase-dead mammalian target of rapamycin (mTOR) mutant impairs the mTOR-mediated signaling and cardiac function

Mammalian target of rapamycin (mTOR) is a key regulator for cell growth through modulating components of the translation machinery. Previously, numerous pharmacological studies using rapamycin suggested that mTOR has an important role in regulating cardiac hypertrophic growth. To further investigate this assumption, we have generated two lines of cardiac specific mTOR transgenic mice, kinase-dead (kd) mTOR and constitutively active (ca) mTOR, using alpha-myosin heavy chain promoter. alpha-Myosin heavy chain (alphaMHC)-mTORkd mice had a near complete inhibition of p70 S6k and 4E-BP1 phosphorylation, whereas alphaMHC-mTORca had a significant increase in p70 S6k and 4E-BP1 phosphorylation. Although the cardiac function of alphaMHC-mTORkd mice was significantly altered, the cardiac morphology of these transgenic mice was normal. The cardiac hypertrophic growth in response to physiological and pathological stimuli was not different in alphaMHC-mTORkd and alphaMHC-mTORca transgenic mice when compared with that of nontransgenic littermates. These findings suggest that the mTOR-mediated signaling pathway is not essential to cardiac hypertrophic growth but is involved in regulating cardiac function. Additional analysis of cardiac responses to fasting-refeeding or acute insulin administration indicated that alphaMHC-mTORkd mice had a largely impaired physiological response to nutrient energy supply and insulin stimulation.     

Differentiated pressor and sympathetic responses to dual brain stimulation: ventromedial hypothalamus versus locus coeruleus

Sensitivity of the ventromedial hypothalamus (VMH) to electrical stimulation was compared with that of the locus coeruleus (LC) in urethane-anesthetized rats. Based not only on current strengths required to elicit threshold effects, but also on magnitude of pressor responses to suprathreshold stimulation, the LC was consistently more sensitive than the VMH. Despite this greater pressor sensitivity, splanchnic nerve firing increased almost equally upon stimulation of either brain area. Similar comparisons made in other rats following bilateral adrenalectomy or pretreatment with a vasopressin antagonist showed no significant alteration of pressor and sympathetic responsiveness to stimulation of either the LC or the VMH. When frequency of neural firing was recorded from a lumbar sympathetic trunk instead of the splanchnic nerve, increases in sympathetic nerve activity produced by LC stimulation were significantly larger than those produced from the VMH. The results suggest that greater pressor sensitivity of the LC is due, at least in part, to stronger constriction in vascular beds innervated by the lumbar sympathetic chains.     

Cloning,expression, and purification of an antiviral protein from Pseudomonas fluorescens CZ and its antagonistic activity against tobacco mosaic virus

The antiviral alkaline phosphatase L (AapL) protein of Pseudomonas fluorescens CZ was expressed in Escherichia coli, purified using the Ni-NTA column, and its antiviral activity against tobacco mosaic virus (TMV)-infected Nicotiana was tested. The recombinant protein (360?µg/mL) showed stability and most effective suppression in vitro (94.85%) against TMV.     

Mechanisms of Metabonomic for a Gateway Drug: Nicotine Priming Enhances Behavioral Response to Cocaine with Modification in Energy Metabolism and Neurotransmitter Level

Nicotine, one of the most commonly used drugs, has become a major concern because tobacco serves as a gateway drug and is linked to illicit drug abuse, such as cocaine and marijuana. However, previous studies mainly focused on certain genes or neurotransmitters which have already been known to participate in drug addiction, lacking endogenous metabolic profiling in a global view. To further explore the mechanism by which nicotine modifies the response to cocaine, we developed two conditioned place preference (CPP) models in mice. In threshold dose model, mice were pretreated with nicotine, followed by cocaine treatment at the dose of 2 mg/kg, a threshold dose of cocaine to induce CPP in mice. In high-dose model, mice were only treated with 20 mg/kg cocaine, which induced a significant CPP. ¹H nuclear magnetic resonance based on metabonomics was used to investigate metabolic profiles of the nucleus accumbens (NAc) and striatum. We found that nicotine pretreatment dramatically increased CPP induced by 2 mg/kg cocaine, which was similar to 20 mg/kg cocaine-induced CPP. Interestingly, metabolic profiles showed considerable overlap between these two models. These overlapped metabolites mainly included neurotransmitters as well as the molecules participating in energy homeostasis and cellular metabolism. Our results show that the reinforcing effect of nicotine on behavioral response to cocaine may attribute to the modification of some specific metabolites in NAc and striatum, thus creating a favorable metabolic environment for enhancing conditioned rewarding effect of cocaine. Our findings provide an insight into the effect of cigarette smoking on cocaine dependence and the underlying mechanism.     

Efficient expression of human soluble guanylate cyclase in Escherichia coli and its signaling-related interaction with nitric oxide

Soluble guanylate cyclase (sGC), as a nitric oxide (NO) sensor, is a critical heme-containing enzyme in NO-signaling pathway of eukaryotes. Human sGC is a heterodimeric hemoprotein, composed of a α-subunit (690 AA) and a heme-binding β-subunit (619 AA). Upon NO binding, sGC catalyzes the conversion of guanosine 5′-triphosphate (GTP) to 3′,5′-cyclic guanosine monophosphate (cGMP). cGMP is a second messenger and initiates the nitric oxide signaling, triggering vasodilatation, smooth muscle relaxation, platelet aggregation, and neuronal transmission etc. The breakthrough of the bottle neck problem for sGC-mediated NO singling was made in this study. The recombinant human sGC β1 subunit (HsGCβ619) and its truncated N-terminal fragments (HsGCβ195 and HsGCβ384) were efficiently expressed in Escherichia coli and purified successfully in quantities. The three proteins in different forms (ferric, ferrous, NO-bound, CO-bound) were characterized by UV–vis and EPR spectroscopy. The homology structure model of the human sGC heme domain was constructed, and the mechanism for NO binding to sGC was proposed. The EPR spectra showed a characteristic of five-coordinated heme-nitrosyl species with triplet hyperfine splitting of NO. The interaction between NO and sGC was investigated and the schematic mechanism was proposed. This study provides new insights into the structure and NO-binding of human sGC. Furthermore, the efficient expression system of E. coli will be beneficial to the further studies on structure and activation mechanism of human sGC.     

Ocular findings in patients with chronic renal failure undergoing haemodialysis

The aim of this paper was to evaluate the ocular findings in patients with chronic renal failure (CRF) undergoing haemodialysis (HD). In 64 patients undergoing haemodialysis (30 female and 34 male), aged 24-83 years (mean 58 years) on haemodialysis 1-213 months (mean 47 months) complete ocular examination were performed: visual acuity (VA), intraocular pressure (IOP), biomicroscopic examination and fundoscopy. On right eye sixty-nine percent of patents had VA 0.6 or better, and on left eye 84% of patients had VA 0.6 or better. Mean IOP before dialysis was 15 mmHg and after dialysis was 14 mmHg. In 9 patients (14%) we found corneo-conjunctival calcium deposits. No correlation of ocular calcification and parathyroid hormone (PTH) level or calcium and phosphate product were observed. 39 (60%) patients had cataract. Hypertensive vascular changes were seen in 44 (68%) patients and in 6 (7%) patients age-related macular degeneration. Seven patients had diabetes mellitus and in 5 diabetic retinopathy was observed. Patients with CRF or who are receiving HD represent unique group of patients. Pathologic change could be found in many tissue and organs, therefore we suggest ocular examination more frequently in dialysis patients.     

The C-terminal domain of nucleolin accelerates nucleic acid annealing

We report that the abundant nucleolar protein nucleolin accelerates nucleic acid annealing. Nucleolin accelerates annealing of complementary oligonucleotides and of oligonucleotides that contain a limited number of mismatches. The annealing activity of nucleolin can be localized to a C-terminal region consisting of two RNA binding domains (RBD3 and RBD4) and the RGG(9) domain (RBD3-RBD4-RGG(9)). This same region mediates self-association of nucleolin. The RGG(9) domain of nucleolin, believed to mediate interactions between nucleolin and several ribosomal proteins, is neither sufficient for self-association, as determined by small-angle X-ray scattering, nor can it independently accelerate annealing. Acceleration of nucleic acid annealing by nucleolin is likely to depend on self-association of nucleolin molecules bound to nucleic acid.