Triterpene acids from the leaves of Perilla frutescens and their anti-inflammatory and antitumor-promoting effects

Nine triterpene acids, viz., six of the ursane type, ursolic acid (1), corosolic acid (2), 3-epicorosolic acid (3), pomolic acid (4), tormentic acid (5) and hyptadienic acid (6), and three of the oleanane type, oleanolic acid (7), augustic acid (8) and 3-epimaslinic acid (9), among which 1 constituted the most predominant triterpene acid, were isolated and identified from ethanol extracts of the leaves of red perilla [Perilla frutescens (L.) Britton var. acuta Kudo] and green perilla [P. frutescens (L.) Britton var. acuta Kudo forma viridis Makino]. These eight compounds, 1, 2, 4-9, were evaluated for their inhibitory effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation (1 microg/ear) in mice. All the compounds tested showed a marked anti-inflammatory effect, with a 50% inhibitory dose (ID50) of 0.09-0.3 mg per ear. In addition, an evaluation against the Epstein-Barr virus early antigen (EBV-EA) activation induced by TPA showed five compounds, 1-3, 5 and 9, with a potent inhibitory effect on EBV-EA induction (91-93% inhibition at 1x10(3) mol ratio/TPA). Furthermore, compound 5 exhibited strong antitumor-promoting activity in an in vivo two-stage carcinogenesis test of mouse tumor by using 7,12-dimethylbenz(a)anthracene (DMBA) as an initiator and TPA as a promoter.     

Whole-mount silver staining of Arabidopsis and maize: a new method for staining secondary wall thickenings in tracheary elements

Secondary wall thickenings in tracheary elements were specifically stained by incubation of Arabidopsis and maize in Silver Stain Plus (Bio-Rad) staining solution, after pretreatment with SDS and ethanol solution. Scanning electron microscopic analysis of sections of celery revealed that silver particles were deposited on the secondary wall thickenings, indicating that the staining was due to the deposition of silver through the interaction of the stain with lignin. This method is more sensitive than the acidified phloroglucinol method.     

Nucleolin and the packaging signal, psi, promote the budding of human immunodeficiency virus type-1 (HIV-1)

Gag proteins of human immunodeficiency virus type 1 (HIV-1) play a pivotal role in the budding of the virion, in which the zinc finger motifs of the gag proteins recognize the packaging signal of genomic RNA. Nucleolin, an RNA-binding protein, is identified as a cellular protein that binds to murine leukemia virus (MuLV) gag proteins and regulates the viral budding, suggesting that HIV-1 gag proteins, the packaging signal, psi and nucleolin affect the budding of HIV-1. Here we report that nucleolin enhances the release of HIV-1 virions which contain psi. Furthermore, nucleolin and gag proteins form a complex incorporated into virions, and nucleolin promotes the infectivity of HIV-1. Our results suggest that an empty particle which contains neither nucleolin nor the genomic RNA is eliminated during the budding process, and this mechanism is beneficial for escape from the host immune response against HIV-1.     

Structure-activity relationship of synthetic truncated analogues of vasoactive intestinal peptide (VIP): an enhancement in the activity by a substitution with arginine

In order to develop potent shortened analogues of vasoactive intestinal peptide (VIP), the structure-activity relationship of C-terminally truncated analogues of VIP was investigated by examining the binding activity to rat lung VIP receptors and relaxation of smooth muscle in isolated mouse stomach. VIP(1-27) showed VIP receptor binding activity comparable to that of VIP but the activity of VIP(1-26) was reduced to one-third of VIP. The receptor binding activity of VIP(1-26) to VIP(1-23) was reduced in proportion to the decrease in amino acid residues. There was a significant correlation between the number of amino acid residues and VIP receptor binding activities of VIP and its C-terminally truncated analogues. VIP(1-22) and VIP(1-21) exhibited little binding activity even at high concentrations, suggesting the requisite of 23 amino acid residues as the minimal essential sequence for the conservation of VIP receptor binding activity. The chemical modification of VIP(1-23) generated a potent analogue, [Arg(15, 20, 21), Leu(17)]-VIP(1-23), that displayed a 22-fold higher receptor binding activity and 1.6-fold more potent relaxation of mouse stomach than VIP(1-23) did. In conclusion, it was shown that [Arg(15, 20, 21), Leu(17)]-VIP(1-23) could be a relatively potent and stable agonist of VIP receptors. The present study has provided further insight into the structure-activity relationship of VIP to generate novel shortened VIP analogues having a high affinity to VIP receptors and potent pharmacological activity.     

Growth inhibitory alkaloids from mesquite (Prosopis juliflora (Sw.) DC.) leaves

Plant growth inhibitory alkaloids were isolated from the extract of mesquite [Prosopis juliflora (Sw.) DC.] leaves. Their chemical structures were established by ESI-MS, 1H and 13C NMR spectra analysis. The I50 value (concentration required for 50% inhibition of control) for root growth of cress (Lepidium sativum L.) seedlings was 400 microM for 3'-oxo-juliprosopine, 500 microM for secojuliprosopinal, and 100 microM for a (1:1) mixture of 3-oxo-juliprosine and 3'-oxo-juliprosine, respectively. On the other hand, the minimum concentration exhibiting inhibitory effect on shoot growth of cress seedlings was 10 microM for 3'-oxo-juliprosopine, 100 microM for secojuliprosopinal, and 1 microM for a (1:1) mixture of 3-oxo-juliprosine and 3'-oxo-juliprosine, respectively. Among these compounds, a (1:1) mixture of 3-oxo-juliprosine and 3'-oxo-juliprosine exhibited the strongest inhibitory effect on the growth of cress seedlings.     

AtHKT1 facilitates Na+ homeostasis and K+ nutrition in planta

Genetic and physiological data establish that Arabidopsis AtHKT1 facilitates Na(+) homeostasis in planta and by this function modulates K(+) nutrient status. Mutations that disrupt AtHKT1 function suppress NaCl sensitivity of sos1-1 and sos2-2, as well as of sos3-1 seedlings grown in vitro and plants grown in controlled environmental conditions. hkt1 suppression of sos3-1 NaCl sensitivity is linked to higher Na(+) content in the shoot and lower content of the ion in the root, reducing the Na(+) imbalance between these organs that is caused by sos3-1. AtHKT1 transgene expression, driven by its innate promoter, increases NaCl but not LiCl or KCl sensitivity of wild-type (Col-0 gl1) or of sos3-1 seedlings. NaCl sensitivity induced by AtHKT1 transgene expression is linked to a lower K(+) to Na(+) ratio in the root. However, hkt1 mutations increase NaCl sensitivity of both seedlings in vitro and plants grown in controlled environmental conditions, which is correlated with a lower K(+) to Na(+) ratio in the shoot. These results establish that AtHKT1 is a focal determinant of Na(+) homeostasis in planta, as either positive or negative modulation of its function disturbs ion status that is manifested as salt sensitivity. K(+)-deficient growth of sos1-1, sos2-2, and sos3-1 seedlings is suppressed completely by hkt1-1. AtHKT1 transgene expression exacerbates K(+) deficiency of sos3-1 or wild-type seedlings. Together, these results indicate that AtHKT1 controls Na(+) homeostasis in planta and through this function regulates K(+) nutrient status.