Binocular rivalry from luminance and contrast.

Binocular rivalry is the phenomenon that when two incompatible images are simultaneously presented, one to each eye, the two images compete with each other to be the dominant percept. Studying the underlying neural mechanisms of binocular rivalry is useful for understanding the mechanisms of interocular inhibition. Levelt's Propositions, a set of four propositions that were originally published over fifty years ago, are not only useful for characterizing the perceptual dynamics of binocular rivalry, but can also provide a metric for assessing the common or differential neural mechanisms of binocular rivalry when diverse stimulus types are used. In the present study, we conducted a series of psychophysics experiments, where we compared the rivalry dynamics of two quite different types of stimuli. Orthogonal gratings, a classic type of rivalry stimulus, were contrasted with luminance patches, a type of rivalry stimulus that is relatively less studied. Our results showed that, similar to the orthogonal gratings, the alternate percepts in luminance-only rivalry were described by the modified Levelt's Propositions, despite the clearly slower alternation rates for luminance patches. However, unlike the mixed percepts observed during transitions between oriented gratings, fusion percepts during luminance rivalry were common, could be lustrous, and obeyed the same Propositions, suggesting a regime of tri-stability. Overall, both types of rivalry are consistent with recent models that posit separate binocular and monocular channels embedded within neural circuits that also accomplish contrast normalization. Finally, luminance rivalry is discussed in the contexts of binocular summation and suppression, as well as Fechner's paradox.

Prediction of human absorption of natural compounds by the non-everted rat intestinal sac model.

A major concern in natural drug research is that many substances with potent biological activity in vitro are unable to generate good activity in vivo owing to their poor water-solubility, poor permeability and/or poor stability. The permeability of drug candidates across the intestinal mucosa is one of the most important factors in defining drug bioavailability and biological activity. In order to screen promising compounds for further investigation, a non-everted rat intestinal sac model has been developed successfully to assay the permeability of natural compounds and to predict their human absorption. In this system, the drug solution was placed in non-everted intestinal sacs (NEIS), which were placed in an acceptor solution and the permeability of drug across intestine walls was determined. The feasibility of this method has been validated and demonstrated for 11 model compounds chosen from currently marketed drugs whose human fraction absorbed (Fa) data have been reported. The results of the studies indicate that a good relationship exists between the permeability of the model drugs and their corresponding Fa data. The permeability of 13 natural compounds was evaluated using this system. Only fraxinellone and vitexin-7-glucoside exhibited high intestinal permeability, and predictive of excellent human absorption, which awaits confirmation from further investigation in vivo. This model provides an alternative method to everted intestinal sacs for the evaluation of in vitro permeability in rats, and for estimating human absorption of drugs. It may therefore hold great promise for oral absorption screening of new drug candidates.

A pregnane steroid from Aglaia lawii and structure confirmation of cabraleadiol monoacetate by X-ray crystallography.

The pregnane steroid, (E)-aglawone, along with four known triterpenes, and a known sterol mixture were isolated from the bark of Aglaia lawii (Wight) Saldanha ex Ramamoorty (Meliaceae). The structural determination/identification was accomplished by a combination of 1D- and 2D-NMR spectroscopic techniques. The relative stereochemistry of the known triterpene, 20S,24S-epoxydammarane-3alpha,25-diol acetate, was also unequivocally determined for the first time by X-ray crystallography. The isolates were not active against various human cancer cell lines.

Isolation and characterization of cytotoxic saponin chloromaloside A from Chlorophytum malayense.

A cytotoxic steroidal glycoside was isolated from Chlorophytum malayense Ridley and its structure was characterized as a known compound, neohecogenin 3-O-beta-D-glucopyranosyl(1-->2)-[beta-D-xylopyranosyl(1-->3)]-beta-D- glucopyranosyl(1-->4)-beta-D-galactopyranoside (chloromaloside A). The structural identification was performed using 2D-NMR and LC/MS/MS analysis. The previous, erroneously assigned 1H-NMR spectral data were revised whereas the published 13C-NMR spectral assignments were confirmed. This compound showed in vitro cytotoxicity against several human cancer cell lines.

Liquid chromatography-electrospray ionization mass spectrometry study of the flavonoids of the roots of Astragalus mongholicus and A. membranaceus.

High-performance liquid chromatography-electrospray ionization mass spectrometry has been applied to analyze the flavonoids of Huangqi, the roots of Astragalus mongholicus and A. membranaceus. Eight flavonoids were identified as calycosin-7-O-beta-D-glucoside, calycosin-7-O-beta-D-glucoside-6"-O-malonate (2), ononin, (6aR,11aR)-3-hydroxy-9,10-dimethoxypterocarpan-3-O-bet a-D-glucoside, calycosin, (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavan-7-O-beta-D-glucoside, formononetin-7-O-beta-D-glucoside-6"-O-malonate and formononetin by direct comparison with the isolated standards from Huangqi. The existence of (6aR,11aR)-3-hydroxy-9,10-dimethoxypterocarpan, (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavan, astrapterocarpanglucoside-6'-O-malonate and astraisoflavanglucoside-6'-O-malonate was detected. This is the first report of flavonoid glycoside malonates in these two Astragalus species, and malonate 2 is a structurally completely identified new compound.

LC-ESI-MS study of the flavonoid glycoside malonates of red clover (Trifolium pratense).

High-performance liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) was applied to the analysis of the flavonoids and their glycoside malonates of the flowers and leaves of red clover (Trifolium pratense). Through LC-MS comparative studies on the plant extracts and their malonate-free extracts, approximately 20 flavonoid glycoside malonates were detected in the flower extract. Eight were identified as genistin 6' '-O-malonate (39), formononetin 7-O-beta-D-glucoside 6' '-O-malonate (40), biochanin A 7-O-beta-D-glucoside 6' '-O-malonate (41), trifoside 6' '-O-malonate (42), irilone 4'-O-beta-D-glucoside 6' '-O-malonate (43), pratensein 7-O-beta-D-glucoside 6' '-O-malonate (44), isoquercitrin 6' '-O-malonate (45), and 3-methylquercetin 7-O-beta-D-glucoside 6' '-O-malonate (46). About 15 other flavonoids and clovamides were proved to be present in this extract. The study also found that the flowers contained flavones as the major flavonoids, whereas the leaves had isoflavones as the major flavonoids. This is the first detection of the six malonates (39 and 42-46) in the extracts of red clover, and among them, 42, 43, and 46 are new compounds.

Megathyrin B: a cytotoxic diterpene from Isodon megathyrsus.

From the leaves of Isodon megathyrsus, a novel ent-kaurene diterpene, megathyrin B, was isolated and its structure determined as 1 alpha,7 beta,11 beta,15 beta-tetrahydroxy-ent-7 alpha,20-epoxy-kaur-16-ene by 1D- and 2D-NMR spectral analysis. Additionally, its stereochemistry was unambiguously assigned by X-ray crystallography. This compound was cytotoxic to the KB and KB-V cell lines.

Saniculoside N from Sanicula europaea L.

Extracts from the aerial parts of Sanicula europaea L. were investigated for their anti-HIV activity, and the 50% ethanolic extract was shown to exhibit the highest activity. A new triterpene saponin glycoside, 21 beta-(angeloyloxy)-3-O-[beta-D-arabinopyranosyl(1-->4)-beta- D-glucopyranosyl (1-->3)-beta-D-glucuronopyranosyl propyl ester]-3 beta,15,16,22 alpha,28 beta-pentahydroxy-delta(12)-oleanene, saniculoside N (1), in addition to the known phenolic acids, rosmarinic acid (2), and caffeic acid (3) were isolated as major components. Rosmarinic acid was established as the principal active substance.

Acylated C-21 steroidal bisdesmosidic glycosides from Caraluma umbellata.

From the whole plant of Caraluma umbellata, three new C-21 steroidal glycosides, named as carumbellosides III-V, were isolated and their structures elucidated by extensive spectroscopic experiments, devoid of any derivatisation, as caralumagenin 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-digitalopyranoside-20-O-be ta- D-glucopyranoside, caralumagenin 3-O-beta-D-glucopyranosy(1-->4)- beta-D-digitalopyranoside-20-O-(2-O- benzoyl)-beta-D-glucopyranoside and caralumagenin 3-O-[6-O-benzoyl-beta-D-glucopyranosyl(1-->4)]-beta-D- digitalopyranoside-20-O-(2-O-benzoyl)-beta-D-glucopyranoside. The determination of the absolute configuration of the aglycone as (20 R), the conformations of the sugars and the unambiguous assignments of their NMR spectroscopic signals were achieved by a combination of 2D-NMR techniques. The isolates were devoid of significant cytotoxity in the UIC human cancer cell panel.

Steroidal glycosides from the subterranean parts of Liriope spicata var. prolifera.

In a continuation of phytochemical studies on the underground organs of Liriope spicata var. prolifera, four new steroidal glycosides, lirioproliosides A-D, along with two known compounds, 25(S)-ruscogenin 1-O-[alpha-L-rhamnopyranosyl(1-->2)[beta-D-xylopyranosyl (1-->3)]-beta-D-fucopyranoside and ophiopogonin A, were identified. The structures of lirioproliosides A-D were established by a combination of spectroscopic and chemical methods as 25(S)-ruscogenin 1-O-[alpha-L-rhamnopyranosyl(1-->2)][beta-D-xylopyranosyl (1-->3)]-beta-D-fucopyranoside-3-O-alpha-L-rhamnopyranoside, 25(S)-ruscogenin 1-O-[3-O-acetyl-alpha-L-rhamnopyranosyl(1-->2)]-beta-D-fucopyranoside, 25(S)-ruscogenin (1-O-[2-O-acetyl-alpha-L-rhamnopyranosyl (1-->2)]-beta-D-fucopyranoside and ruscogenin (1-O-[2-O-acetyl-alpha-L-rhamnopyranosyl(1-->2)]-beta-D-fucopyranoside, respectively. Among these steroidal glycosides, ophiopogonin A and lirioprolioside B, and lirioproliosides C and D, were isolated as epimeric pairs.

Nigranoic acid, a triterpenoid from Schisandra sphaerandra that inhibits HIV-1 reverse transcriptase.

An A ring-secocycloartene triterpenoid, nigranoic acid (3,4-secocycloarta-4(28),24-(Z)-diene-3,-26-dioic acid, (1) was isolated from the stems of Schisandra sphaerandra, a Chinese traditional medicinal plant. Its structure elucidation and unambiguous NMR spectral assignment were achieved by the combination of 1D- and 2D-NMR techniques with the aid of computer modeling. Nigranoic acid showed activity in several anti-HIV reverse transcriptase and polymerase assays.

Further polyoxypregnanes from Marsdenia tenacissima.

Two new polyoxypregnanes, designated marstenacigenins A and B, along with a known compound, dresgenin, were isolated from the mild acid hydrolysate of the ethanol extract of the stems of Marsdenia tenacissima. Their structures were deduced by a combination of 1D and 2D NMR spectroscopic techniques as 12 beta-cinnamoyl-dihydrosarcostin and 12 beta,20-dibenzoyldihydrosarcostin, respectively.

[The clinical observation of early neonatal pure breast-feeding].

Through observation on the rate of physiological body weight loss, the percentage of body weight regaining and the incidence of infection in hospital of 160 newborns with rooming in and pure breast-feeding after uneventful delivery or caesarean section. The average rates of physiological body weight loss were 6.70% and 6.47% in pure breast-feeding group with normal delivery and caesarean section respectively, whereas 5.03% and 5.57% in mix feeding group. The percentage of body weight regaining at discharge were 34.00% and 53.33% in pure breast-feeding group compared with 11.46% and 40.00% in mix feeding group. The incidence of neonatal infection in hospital were 2.00% and 13.33% in pure breast-feeding group, instead 14.00% and 13.33% in mix feeding group. The results showed advantages and feasible of pure breast-feeding.