7-Oxo-24ξ(28)-dihydrocycloeucalenol,a potent inhibitor of plant sterol biosynthesis

Cycloeucalenol-obtusifoliol isomerase from higher plant cells catalyses the opening of the cyclopropane ring of cycloeucalenol yielding obtusifoliol. 7-Oxo-24ξ(28)-dihydrocycloeucalenol was not a substrate but behaved like a potent inhibitor of the isomerase. The inhibition was reversible and highly specific; the inhibitor needed the presence of the 7-oxo group, the cyclopropane ring and the absence of a 4β-methyl group to be active. Other enzymes involved in plant sterol biosynthesis such as 2, 3-oxidosqualene-cycloartenol cyclase and S-adenosyl methionine cycloartenol C-24 methyltransferase were not inhibited by 7-oxo-24ξ(28)-dihydrocycloeucalenol. In vivo treatment of a suspension of bramble cells growing in a liquid medium with 7-oxo-24ξ(28)-dihydrocycloeucalenol resulted in a strong accumulation of 9β 19-cyclopropyl sterols confirming that the main cellular target of the inhibitor is the cycloeucalenol-obtusifoliol isomerase.     

Benzofuran derivatives from two Encelia species

From Encelia actoni and E. virginensis two new benzofuran esters could be isolated. The unusual structure of the skeleton comprises an acetyl group at C-2 of the furan ring.     

The nature of “θ-carotene”

“θ-Carotene” has been isolated from Neurospora crassa and resolved into two isometric conjugated heptaene components, ξ-carotene and 7,8,11     

A benzoisofuranone derivative and carbazole alkaloids from Murraya koenigii and their antimicrobial activity

A benzoisofuranone derivative, 3xi-(1xi-hydroxyethyl)-7-hydroxy-1-isobenzofuranone, and a dimeric carbazole alkaloid, 3,3'-[oxybis(methylene)]bis(9-methoxy-9H-carbazole), along with six known carbazole alkaloids and three known steroids were isolated from the stem bark of Murraya koenigii. The structures of these compounds were established unambiguously by UV, IR, MS and a series of 1D and 2D NMR analyses. The minimum inhibitory concentrations (MIC) of these compounds were found to be in the range 3.13-100 microg/ml.     

Polyhydroxylated steroids from an endophytic fungus, Chaetomium globosum ZY-22 isolated from Ginkgo biloba

A novel polyhydroxylated C₂₉-sterol, 25ξ-methyl-22-homo-5α-cholest-7,22-diene-3β,6β,9α-triol, designated globosterol (1), together with one known tetrahydroxylated ergosterol (22E, 24R)-ergosta-7,22-diene-3β,5α,6β,9α-tetraol (2) has been isolated from the cultures of an endophytic fungus, Chaetomium globosum ZY-22 originated from the plant Ginkgo biloba. The structures and relative configurations of 1 and 2 were established on the basis of extensive spectroscopic analyses including 1D and 2D NMR (¹H-¹H COSY, HSQC, HMBC, and NOESY) experiments and comparison with the literature. Globosterol (1) possesses an unprecedented 25-methyl Δ²²-C₁₀-side chain and Δ⁷-3β,6β,9α-hydroxy-steroid nucleus, which represents the first example for C₂₉-steroids of the group.     

Antibacterial properties of bile acid oxazoline compounds

Chenooxazoline³ (50–100 μM) inhibited (>50%) both 7α and 7β-dehydroxylase activities in whole cells and cell extracts of $\text{Eubacterium}$ sp. V.P.I. 12708. Chenooxazoline (>50 μM) and methylchenooxazoline (>25 μM) but not lithooxazoline (≤100 μM) inhibited growing cultures of $\text{Eubacterium}$ sp. V.P.I. 12708. Chenooxazoline (100 μM) also inhibited the growth of certain members of the genera $\text{Eubacterium}$, $\text{Clostridium}$, $\text{Bacteroides}$ and $\text{Staphylococcus}$ but not $\text{Pseudomonas}$, $\text{Escherichia}$, $\text{Salmonella}$ or the eucaryotic microorganism, $\text{Saccharomyces cerevisiae}$ (_< 400 μM).     

Evidence for the transmission of information through electric potentials in injured avocado trees

Electrical excitability and signaling, frequently associated with rapid responses to environmental stimuli, have been documented in both animals and higher plants. The presence of electrical potentials (EPs), such as action potentials (APs) and variation potentials (VPs), in plant cells suggests that plants make use of ion channels to transmit information over long distances. The reason why plants have developed pathways for electrical signal transmission is most probably the necessity to respond rapidly, for example, to environmental stress factors.We examined the nature and specific characteristics of the electrical response to wounding in the woody plant Persea americana (avocado). Under field conditions, wounds can be the result of insect activity, strong winds or handling injury during fruit harvest. Evidence for extracellular EP signaling in avocado trees after mechanical injury was expressed in the form of variation potentials. For tipping and pruning, signal velocities of 8.7 and 20.9 cm/s, respectively, were calculated, based on data measured with Ag/AgCl microelectrodes inserted at different positions of the trunk. EP signal intensity decreased with increasing distance between the tipping and pruning point and the electrode. Recovery time to pre-tipping or pre-pruning EP values was also affected by the distance and signal intensity from the tipping or pruning point to the specific electrode position. Real time detection of remote EP signaling can provide an efficient tool for the early detection of insect attacks, strong wind damage or handling injury during fruit harvest.Our results indicate that electrical signaling in avocado, resulting from microenvironment modifications, can be quantitatively related to the intensity and duration of the stimuli, as well as to the distance between the stimuli site and the location of EP detection. These results may be indicative of the existence of a specific kind of proto-nervous system in plants.     

Stabilization of rat liver lysosomes by new anti-inflammatory steroids in vitro

Steroid acid esters, synthesized by modifying the 17-ketol side chain of prednisolone, were tested for their in vitro ability to stabilize heavy mitochondrial lysosomes prepared from rat liver. Membrane stabilization was determined by assessing capability of steroids to decrease extrusion of the marker enzymes (acid phosphatase, beta-glucuronidase and aryl sulfatase) from lysosomes incubated in hypo-osmotic sucrose-Tris acetate buffer. Results indicated that prednisolone (1) significantly inhibited the lysosomal release of acid phosphatase as did the new anti-inflammatory steroid, methyl 20-dihydroprednisolonate. Methyl prednisolonate exhibited weak membrane stabilization capacities and 20-dihydroprednisolonic acid, a metabolic product of methyl 20-dihydroprednisolonate, showed virtually no membrane stabilization.     

Flavones and isoflavones from the west African Fabaceae Erythrina vogelii

The CH(2)Cl(2)/MeOH extract of the stem bark of Erythrina vogelii (Fabaceae) from Nigeria has yielded two novel isoflavones, 7,4'-dihydroxy-8-(gamma,gamma-dimethylallyl)-2'zeta-(4'-hydroxyisopropyl)dihydrofurano[1',3':5,6]isoflavone (vogelin H) (1) and 7,4'-dihydroxy-8-[(2'zeta,3'-dihydroxy-3'-methyl)butyl]-2',2'-dimethyl-3',4'-dehydropyrano[1',4':5,6]isoflavone (vogelin I) (2), a novel flavone, 7,4'-dihydroxy-2',2'-dimethyl-3',4'-dehydropyrano[1',4':5,6]flavone (vogelin J) (3), and eight known flavonoids.     

Lipid-Modulated Sequence-Specific Association of Glycophorin A in Membranes

Protein association in lipid membranes is a complex process with thermodynamics directed by a multitude of different factors. Amino-acid sequence is a molecular parameter that affects dimerization as shown by limited directed mutations along the transmembrane domains. Membrane-mediated interactions are also important although details of such contributions remain largely unclear. In this study, we probe directly the free energy of association of Glycophorin A by means of extensive parallel Monte Carlo simulations with recently developed methods and a model that accounts for sequence-specificity while representing lipid membranes faithfully. We find that lipid-induced interactions are significant both at short and intermediate separations. The ability of molecules to tilt in a specific hydrophobic environment extends their accessible interfaces, leading to intermittent contacts during protein recognition. The dimer with the lowest free energy is largely determined by the favorable lipid-induced attractive interactions at the closest distance. Finally, the coarse-grained model employed herein, together with the extensive sampling performed, provides estimates of the free energy of association that are in excellent agreement with existing data.     

Statistical evaluation of ion-channel gating models based on distributions of log-likelihood ratios

The distributions of log-likelihood ratios (DeltaLL) obtained from fitting ion-channel dwell-time distributions with nested pairs of gating models (Xi, full model; Xi(R), submodel) were studied both theoretically and using simulated data. When Xi is true, DeltaLL is asymptotically normally distributed with predictable mean and variance that increase linearly with data length (n). When Xi(R) is true and corresponds to a distinct point in full parameter space, DeltaLL is Gamma-distributed (2DeltaLL is chi-square). However, when data generated by an l-component multiexponential distribution are fitted by l+1 components, Xi(R) corresponds to an infinite set of points in parameter space. The distribution of DeltaLL is a mixture of two components, one identically zero, the other approximated by a Gamma-distribution. This empirical distribution of DeltaLL, assuming Xi(R), allows construction of a valid log-likelihood ratio test. The log-likelihood ratio test, the Akaike information criterion, and the Schwarz criterion all produce asymmetrical Type I and II errors and inefficiently recognize Xi, when true, from short datasets. A new decision strategy, which considers both the parameter estimates and DeltaLL, yields more symmetrical errors and a larger discrimination power for small n. These observations are explained by the distributions of DeltaLL when Xi or Xi(R) is true.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细