Distinct susceptibility of developing neurons to death following Bax overexpression in the chicken embryo.

Bax is a proapoptotic protein that is required for programmed cell death (PCD) of many neuronal populations. Here we show that, during an early period of retinal PCD and in naturally occurring sensory and motor neuron (MN) death in the spinal cord, Bax delivery results in enhanced death of these neural populations. In contrast, Bax overexpression fails to enhance an early phase of MN death that occurs in the cervical spinal cord, although overexpressed Bax appears to be activated in dying MNs. Bax overexpression does not also affect the survival of immature neurons prior to the PCD period. Taken together, these data provide the first in vivo evidence suggesting that Bax appears to act selectively as an executioner only in neurons undergoing PCD. Furthermore, although Bax appears to mediate the execution pathway for PCD, the effect of Bax overexpression on susceptibility to death differs between different neuronal populations.

New bisdesmosidic triterpene saponins from the roots of Pulsatilla chinensis.

Further phytochemical analysis aimed at the triterpene saponin constituents of the roots of Pulsatilla chinensis has resulted in the isolation of four new bisdesmosidic triterpene saponins whose aglycons are based on the lupane skeleton (1-4), together with three known saponins (5-7). The structures of the new compounds were determined by spectroscopic analysis and acid-catalyzed hydrolysis.

Flavonol glycosides and steroidal saponins from the leaves of Cestrum nocturnum and their cytotoxicity.

Phytochemical analysis of the leaves of Cestrum nocturnum (Solanaceae) resulted in the isolation of two new flavonol glycosides (1, 2) and seven steroidal saponins (3-9), including four new ones (4, 6, 7, and 9). The structures of the new compounds were determined by spectroscopic analysis, including 2D NMR data, and the results of hydrolytic cleavage. Cytotoxic activities of the isolated compounds against human oral squamous cell carcinoma-(HSC-2) cells and normal human gingival fibroblasts are reported.

A new factor from Bacillus mesentericus which promotes the growth of Bifidobacterium.

It was reported previously that supernatants of cultures of Bacillus mesentericus TO-A promote the growth of Bifidobacterium species. In this study, a new growth-promoting factor, BM-1, was purified from the supernatant of such a culture and its chemical structure was determined. BM-1 was identified as 3,3-dihydroxyazetidine, and it promoted the growth of several strains of Bifidobacterium.

Direct detection of antipyrine metabolites in rat urine by (13)C labeling and NMR spectroscopy.

Antipyrine is a useful probe to evaluate variation of in vivo activities of oxidative hepatic drug-metabolizing enzymes. Here we describe a new approach using (13)C labeling and NMR spectroscopy for the direct and simultaneous detection of all phase I and phase II metabolites of antipyrine in rat urine. [C-methyl-(13)C]Antipyrine was synthesized and administered orally to rats (100 mg/kg), and the 0- to 24-h postdose urine was analyzed by 100-MHz (13)C NMR spectroscopy under the conditions of distortionless enhancement by polarization transfer without any pretreatments such as deconjugation, chromatographic separation, and solvent extraction. Consequently, all the major metabolites in urine were successfully detected with favorable signal-to-noise ratios in the limited acquisition time (30 min). The assignments of the resonances were performed by enzymic modification and spiking authentic samples. The reproducibility of the NMR detection was sufficient for the quantitative evaluation of the metabolic profile. Effects of 3-methylcholanthrene on antipyrine metabolism were examined by this approach to evaluate variation of in vivo phase I and phase II metabolism of antipyrine in rats. The present approach is useful and practical to evaluate variation of in vivo activities of conjugation enzymes as well as oxidation enzymes responsible for the formation of antipyrine metabolites in rats. This direct approach would enhance the value of the antipyrine test because of the simplicity and convenience.

Studies on the stereoselective internal acyl migration of ketoprofen glucuronides using 13C labeling and nuclear magnetic resonance spectroscopy.

Internal acyl migration reactions of drug 1beta-O-acyl glucuronides are of interest because of their possible role in covalent binding to serum proteins and consequent allergic reactions as well as their influence on drug disposition. An approach using 13C labeling and nuclear magnetic resonance (NMR) spectroscopy has been used to investigate in situ the kinetics of acyl migration and hydrolysis of 1beta-O-acyl glucuronides of enantiomeric ketoprofens (KPs) in phosphate buffer solutions at 37 degrees C. Apparent first-order degradation of the 1beta-O-acyl glucuronide labeled in the ester carbonyl carbon and the sequential appearance of 2-, 3-, and 4-O-acyl isomers as both alpha- and beta-anomeric forms were observed for each enantiomer. All of the positional isomers and anomers were characterized using two-dimensional NMR spectroscopy (heteronuclear multiple bond correlation, correlated spectroscopy, totally correlated spectroscopy) of the reaction mixtures. The overall degradation rate constants (hr-1) of (R)- and (S)-KP glucuronides were 1.07 +/- 0.154 and 0.55 +/- 0.034, respectively. To evaluate in detail the stereoselective reactivity, a kinetic model describing the rearrangement reactions was constructed, and the kinetics were simulated using a theoretical approach. Only the acyl migration, 1beta-->2beta, was found to have significant stereoselectivity. The rate constants (hr-1) for 1beta-->2beta migration of (R)- and (S)-KP glucuronides were 1.04 +/- 0.158 and 0. 52 +/- 0.029, respectively. The results may suggest that (R)-KP glucuronide could be more susceptible to covalent binding to proteins via acyl migration than the corresponding antipode. This stereoselective reactivity may be responsible for the stereoselective pharmacokinetics of KP. The direct approach using 13C labeling and NMR spectroscopy could also provide insight into the reactivities of other labile drug acyl glucuronides and their isomeric glucuronides.

Proton NMR study on a histone-like protein, HU alpha, from Escherichia coli and its complex with oligo DNAs.

It was confirmed that the flexible arm region of HU alpha forms an antiparallel beta-sheet and that all of the residues of phenylalanines, together with some of leucines and/or valines, form a hydrophobic core within the dimer of HU alpha. HU alpha protein alone is thermally labile and melts at 38 degrees C, but it becomes remarkably stabilized and melts at 59 degrees C in the presence of DNA. Several resonances from both HU alpha and DNA perturbed by their complex formation, notably those of His C-2 and C-4 protons, downfield shifted C alpha protons in the antiparallel beta-sheet, as well as Arg C delta and Lys C epsilon protons. The results indicated that a beta-sheet region of HU alpha binds to DNA, and also showed that rapid equilibrium occurs on the NMR time scale between bound and unbound states of HU alpha. A few intermolecular nuclear Overhauser effects (NOEs) were also observed between the protein and H1' protons of DNA in the complex, suggesting that HU alpha binds primarily to the minor groove of DNA.

Conformational recognition of RA-XII by 80S ribosomes: a differential line broadening study in 1H NMR spectroscopy.

1H NMR spectroscopy has been used to demonstrate specific binding of rat 80S ribosomes to the major conformer of an antitumor bicyclic hexapeptidic glucoside, RA-XII, isolated from Rubia cordifolia, in a fast exchange process.

[Application of 13C label-nuclear magnetic resonance (NMR) tracer techniques to clinical chemistry. Metabolic rate of benzoic acid to hippuric acid].

A new tracer technique, in which a 13C-labeled compound as a biological tracer and 13C nuclear magnetic resonance (NMR) as an analytical tool are used, is proposed. In order to verify the applicability of the method to clinical chemistry. [1-13C]benzoic acid was administered and [1'-13C]hippuric acid excreted in the urine was quantitated by NMR, by using [1-13C]hippuric acid as an internal standard.