Characterizing the conversion kinetics of carbamazepine polymorphs to the dihydrate in aqueous suspension using Raman spectroscopy

In an aqueous environment, polymorphic forms I-III of carbamazepine all convert to the dihydrate. This study investigated the conversion of each polymorphic form individually and of a mixture of forms III and I to the dihydrate. Two batches of form I with different crystal morphology were used. Samples were dispersed independently in water at 23+/-1 degrees C and recovered at various timepoints varying from 10 to 210 min. Scanning electron microscopy, X-ray powder diffraction and Raman spectroscopy were used to characterize the initial polymorphic forms and the recovered samples after 210 min. Raman spectroscopy combined with partial least squares analysis was used to generate quantitative models of binary and ternary mixtures of the different polymorphic forms with the dihydrate. On the basis of these models the conversion kinetics of the polymorphic forms I-III were characterized. First-order kinetics with an unconverted portion were used to model the data (R2> or =0.95). The unconverted portions ranged from 16 to 51% after dispersion for 210 min. The conversion kinetics were similar between polymorphic forms with comparable crystal morphology, but differed significantly between batches of the same polymorph (form I) with different crystal morphology. Furthermore, the conversion of forms III and I in the aqueous suspension was not influenced by the presence of the other polymorph when dispersed together.

Observation of the surface stress induced in microcantilevers by electrochemical redox processes

The potential-induced surface stress of a solid electrode was investigated in an electrochemical cell. Gold-coated atomic force microscopy microcantilevers were used as working electrodes to measure the current-potential response (by cyclic voltammetry) and simultaneous bending characteristics in solutions of NaNO3 and K3Fe(CN)6/NaNO3. The observed changes of differential surface stress at a microcantilever electrode were attributed to electrochemical-potential-induced changes in surface charge density, ion adsorption/desorption, and electron transfer across the electrode surface. The potential dependent change in stress shows promise for the study of microscopic properties at the solid-electrolyte interface.

Adsorption of trinitrotoluene on uncoated silicon microcantilever surfaces

We measured the adsorption characteristics of trinitrotoluene (TNT) on piezoresistive silicon microcantilever surfaces under ambient air using a well-characterized TNT vapor generator. This allowed us to quantify the adsorption parameters and to estimate the sticking coefficient. The sticking coefficient initially increases with TNT exposure time and then levels off around 0.3. Atomic force microscopy images of silicon surfaces exposed to TNT revealed "island" formation of the adsorbate on the silicon surface. At low exposure times, mainly the number density of islands increased with exposure time; at longer exposure times, the size (in particular, height) of the islands grew, corresponding to the higher sticking coefficients. These observations can be qualitatively explained via the difference between TNT-surface and TNT-TNT interactions mediated by water molecules.

Synthesis and characterization of a brush-like copolymer of polylactide grafted onto chitosan

A brush-like poly(DL)-lactide grafted onto chitosan as the backbone was investigated. The graft copolymerization was carried out with triethylaluminum as catalyst in toluene at 70 degrees C. It was found that a greater lactide content in the feeding ratio results in a higher grafting percentage. FTIR spectrometry, (1)H NMR, DSC scanning, and wide-angle X-ray scattering, respectively, are used to characterize these branch copolymers. A copolymer has a definite melting point when the molar feeding ratio of lactide to chitosan is more than 10:1, and the deltaH of the copolymers increases with the feed ratio of lactide to chitosan in feeding.

Exposure to 2.45 GHz electromagnetic fields induces hsp70 at a high SAR of more than 20 W/kg but not at 5W/kg in human glioma MO54 cells

PURPOSE

To determine potential hazards from exposure to a high-frequency electromagnetic field (HFEMF) at 2.45 GHz by studies of the expression of heat-shock protein 70 (hsp70) in MO54 cells.

METHOD

MO54 cells were exposed to a HFEMF at average specific absorption rates (SAR) of 5, 20, 50 and 100 W/kg, using input powers of 0.8, 3.2, 7.8 and 13 W, at a temperature of up to 39 degrees C. An annular culture dish provided three levels of exposure for a given input power, designated inner, middle and outer rings. Two control groups were used: the first was subjected to sham exposure and the second was a temperature control, used to determine the effect of high temperature using incubation in a conventional incubator at 39 degrees C. Cell survival was determined in intervals up to 24 h. Protein was extracted from MO54 cells in both groups after 2, 4, 8 and 16 h exposure times. Changes in the hsp70 protein levels were analysed by Western blots.

RESULTS

Little or no cell death was observed in the sham-exposed cells, nor for incubation at 39 degrees C for up to 16 h. Cell survival decreased to about 30% after exposure to HFEMF for 24 h at an average SAR of 100 W/kg. A slight increase in hsp70 was observed in cells in both the inner and outer rings of the plate after exposure at SAR levels of 25 and 78 W/kg, respectively, for 2 h. With increasing exposure time, hsp70 expression increased except for an SAR of 5 W/kg. In the raised temperature control at 39 degrees C, hsp70 expression also increased as the incubation time increased. However, the expression level of hsp70 for the HFEMF exposure was greater than that for the raised temperature control.

CONCLUSION

HFEMF can produce an increased level of hsp70 expression in MO54 cells at SAR levels above 20 W/kg, even when the effect of raised temperature is taken into account.

A dipolar coupling based strategy for simultaneous resonance assignment and structure determination of protein backbones

A new approach for simultaneous protein backbone resonance assignment and structure determination by NMR is introduced. This approach relies on recent advances in high-resolution NMR spectroscopy that allow observation of anisotropic interactions, such as dipolar couplings, from proteins partially aligned in field ordered media. Residual dipolar couplings are used for both geometric information and a filter in the assembly of residues in a sequential manner. Experimental data were collected in less than one week on a small redox protein, rubredoxin, that was 15N enriched but not enriched above 1% natural abundance in 13C. Given the acceleration possible with partial 13C enrichment, the protocol described should provide a very rapid route to protein structure determination. This is critical for the structural genomics initiative where protein expression and structural determination in a high-throughput manner will be needed.

Liquid chromatography with multi-channel electrochemical detection for the determination of epigallocatechin gallate in rat plasma utilizing an automated blood sampling device

A liquid chromatography method with multi-channel electrochemical detection was developed for the determination of epigallocatechin gallate (EGCG) in rat plasma. After administration of EGCG, blood samples were periodically collected by Culex (an automated blood sampling robot). EGCG was extracted from 50 microl of diluted blood (blood and saline at a ratio of 1:1) with ethyl acetate. Chromatographic separation was achieved within 10 min using a C8 (150x4.6 mm) 5 microm column with a mobile phase containing 20 mM sodium monochloroacetate, pH 2.8 and 12% acetonitrile at a flow-rate of 1.2 ml/min. A four-channel detector with glassy carbon electrodes was used with applied potentials of +700, 600, 500, 400 mV vs. Ag/AgCl. The limit of detection was 2 ng/ml at a signal-to-noise ratio of 3:1 and the limit of quantitation was 5 ng/ml. The calibration curve was linear over the range of 5-800 ng/ml. The intra- and inter-assay precisions were in the range of 1.3-4.5% and 2.2-4.4%, respectively. Using this method it was possible to determine plasma concentration following a single dose of EGCG to rats with good accuracy and precision. Thus the pharmacokinetic properties of EGCG in rats can be examined for intravenous, intraperitoneal and oral dosing.

Effect of thinking on intracranial blood flow velocities

OBJECTIVE

To determine the effect of thinking on intracranial blood flow velocities.

METHODS

Transcranial Doppler (TCD) was used to measure the blood flow velocities of the cerebral arteries, when 10 normal persons were at rest and during thinking.

RESULTS

The mean flow velocities (MFVs) of the cerebral arteries during thinking were significantly higher than those at rest, especially in the MCA and ACA. The MFVs were raised from between 10.3% to 14.3%.

CONCLUSIONS

Thinking can increase the blood flow velocities of cerebral arteries significantly.

Robinlin: a novel bioactive homo-monoterpene from Robinia pseudoacacia L. (Fabaceae)

A bioactivity-directed fractionation of the ethanolic extracts of Robinia pseudoacacia L. (Fabaceae) afforded robinlin (1), a novel homo-monoterpene. The structure of 1 was elucidated by spectral analyses of the parent compound as well as its derivatives; 1 showed strong bioactivity in the brine shrimp lethality test (BST).

Functionalized xenon as a biosensor

The detection of biological molecules and their interactions is a significant component of modern biomedical research. In current biosensor technologies, simultaneous detection is limited to a small number of analytes by the spectral overlap of their signals. We have developed an NMR-based xenon biosensor that capitalizes on the enhanced signal-to-noise, spectral simplicity, and chemical-shift sensitivity of laser-polarized xenon to detect specific biomolecules at the level of tens of nanomoles. We present results using xenon "functionalized" by a biotin-modified supramolecular cage to detect biotin-avidin binding. This biosensor methodology can be extended to a multiplexing assay for multiple analytes.

Mutation and abnormal expression of the fragile histidine triad gene in nasopharyngeal carcinoma

OBJECTIVE

To determine alterations of fragile histidine triad (FHIT) gene in nasopharyngeal carcinoma and the correlation of FHIT gene with nasopharyngeal carcinogenesis.

STUDY DESIGN

Prospective study.

METHODS

A total of 28 nasopharyngeal carcinoma and 16 normal nasopharyngeal epithelium specimens were examined for abnormalities of FHIT gene by nested reverse-transcriptase-polymerase chain reaction and DNA sequencing.

RESULTS

The deletion of FHIT gene was not observed in 16 normal nasopharyngeal epithelium specimens. In 28 cases of nasopharyngeal carcinoma tissues, 12 (42.9%) exhibited FHIT aberrant transcripts. Complementary DNA sequencing revealed exonic deletion, small DNA insertion, synonymous mutation in exon 8, or frameshift mutation in exon 5.

CONCLUSIONS

The present results suggest that the FHIT gene may play an important role in the pathogenesis of nasopharyngeal carcinoma and may be one of the candidate tumor suppressor genes in nasopharyngeal carcinoma.

Nuclear magnetic resonance in the era of structural genomics

Current interests in structural genomics, and the associated need for high through-put structure determination methods, offer an opportunity to examine new nuclear magnetic resonance (NMR) methodology and the impact this methodology can have on structure determination of proteins. The time required for structure determination by traditional NMR methods is currently long, but improved hardware, automation of analysis, and new sources of data such as residual dipolar couplings promise to change this. Greatly improved efficiency, coupled with an ability to characterize proteins that may not produce crystals suitable for investigation by X-ray diffraction, suggests that NMR will play an important role in structural genomics programs.

[Comparison of stepwise and pulse induced cisplatin-resistant ovarian cancer cell sublines]

OBJECTIVE

To investigate the mechanism responsible for acquired cisplatin resistance induced in human ovarian cancer cell lines by different methods.

METHODS

Two resistant cell lines, Skov3/CDDP-P and Skov3/CDDP-50, were established by pulse or stepwise exposures of ovarian cancer cell line Skov3 to cisplatin (CDDP) for 10-12 months with the drug sensitivity monitored by MTT test. The growth rate and cell cycle were compared. The intracellular drug concentration was measured by FACS after 1 hour incubation in 20 mumol/L ADM. The drug-resistance-associated genes: MDR1, MRP, LRP and GST-pi were monitored by RT-PCR and western blotting.

RESULTS

The resistance indexes (RI) of Skov3/CDDP-P and Skov3/CDDP-50 were 3.7 and 48.6 to cisplatin, 4.0 and 33.0 to Taxol, 2.2 and 7.3 to adriamycin, 1.5 and 3.4 to VP16, and the intracellular ADM concentration was lowered by 34.6% and 47.2% respectively. Both resistant cell lines grew slowly and exhibited changes in morphology and cell cycle. The expression of the resistance-associated genes MDR1, MRP and LRP was enhanced in both resistant cell lines. However, Skov3/CDDP-50 showed greater increase in MDR1 but Skov3/CDDP-P showed more in MRP. There were no significant changes in GST-pi expression either at mRNA or protein level. The TOPO II activity decreased slightly in both resistant cell lines.

CONCLUSION

Stepwise induction of cisplatin resistance in ovarian cancer is more readily acquired in which multiple drug-resistance-associated genes are involved.

Conformational analysis of a flexible oligosaccharide using residual dipolar couplings

We present a new approach to the analysis of the conformational and the motional properties of an oligosaccharide, methyl 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside. The approach relies on an order matrix analysis of residual dipolar couplings in the solution state. By combining a number of different types of couplings, (1)D(CH), (2)D(CH), and D(HH), an order matrix is solved for each ring of the trimannoside. The resulting order parameters indicate the internal motion at the alpha (1,3) linkage to be limited, while significant motion is suggested at the alpha (1,6) linkage. Two structures for the trimannoside were determined by aligning the order tensor principal axes obtained from two different orienting media, bicelles and phage. The very similar conformations at the alpha (1,3) linkage of these two structures confirm that the internal motion at the alpha (1,3) linkage is small and the conformation is a good representation of a single preferred structure. The different conformations at the alpha (1,6) linkage suggest that the motional amplitudes are large and the conformations must be viewed as virtual conformers. Compared with traditional NMR methods, data acquisition is easy and data analysis is straightforward.

A unique mRNA initiated within a middle intron of WHSC1/MMSET encodes a DNA binding protein that suppresses human IL-5 transcription

Human interleukin (IL)-5 gene transcription is regulated by several transcription factor binding sites, including CLE 0, GATA, and a region from position -123 to -92 known as response element (RE)-II. By expression cloning, a partial protein was identified that bound to concatamers of RE-II. Recombinant protein derived from this initial complementary DNA (cDNA) encoding the partial protein specifically bound to RE-II-containing oligonucleotides in electromobility shift assays. The complete sequence (3,649 bp) was determined by 5' rapid amplification of cDNA ends and comparisons to existing ESTs, and found to be identical to the 3' half of Wolf-Hirschhorn syndrome candidate 1, (WHSC1; also known as Multiple Myeloma SET domain [MMSET]). The full-length protein contains an SET domain and two plant homeodomain-type zinc fingers. Transcription initiation of RE-II binding protein (RE-IIBP) messenger RNA (mRNA) uniquely occurred within the middle of WHSC1 near a region that exhibits complex mRNA splicing. RE-IIBP reactive polyclonal antisera identified proteins in human T-cell nuclear protein extracts of 62 and 66 kD that were consistent with the length of the longest open reading frame in RE-IIBP. In contrast, WHSC1 is predicted to encode a protein of 136 kD. In activated human Jurkat and murine D10.G4.1 T cells, expression of full-length and truncated forms of RE-IIBP repressed RE-II promoter activity of a 5X-RE-II luciferase reporter construct by as much as 75%. In addition, RE-IIBP expressed in activated D10.G4.1 T cells inhibited endogenous murine IL-5 production. The repressor activity of RE-IIBP is consistent with the presence of an SET domain that is found in other proteins that act as gene silencers.

Rapid determination of protein folds using residual dipolar couplings

Over the next few years, various genome projects will sequence many new genes and yield many new gene products. Many of these products will have no known function and little, if any, sequence homology to existing proteins. There is reason to believe that a rapid determination of a protein fold, even at low resolution, can aid in the identification of function and expedite the determination of structure at higher resolution. Recently devised NMR methods of measuring residual dipolar couplings provide one route to the determination of a fold. They do this by allowing the alignment of previously identified secondary structural elements with respect to each other. When combined with constraints involving loops connecting elements or other short-range experimental distance information, a fold is produced. We illustrate this approach to protein fold determination on (15)N-labeled Eschericia coli acyl carrier protein using a limited set of (15)N-(1)H and (1)H-(1)H dipolar couplings. We also illustrate an approach using a more extended set of heteronuclear couplings on a related protein, (13)C, (15)N-labeled NodF protein from Rhizobium leguminosarum.

Asitrocin, (2,4)-cis- and trans-asitrocinones: novel bioactive mono-tetrahydrofuran acetogenins from Asimina triloba seeds

Asitrocin (1) and the mixture of (2,4)-cis- and trans-asitrocinones (2 and 3), new bioactive Annonaceous acetogenins, were isolated from the seeds of Asimina triloba by activity-directed fractionation using the brine shrimp lethality test. Asitrocin and the mixture of (2,4)-cis- and trans-asitrocinones have a configuration of erythro/trans/threo from C-15 to C-20, the mono-THF moiety with two flanking hydroxyl groups. The structures were determined by spectroscopic methods. These acetogenins showed potent bioactivities in the brine shrimp lethality test (BST) and among six human solid tumor cell lines with notable selectivity for the prostate (PC-3) and the pancreatic (MIA PaCa-2) cell lines at 10-100 times the potency of adriamycin.

[Precise map of allelic loss on chromosome 3p14 in nasopharyngeal carcinoma]

OBJECTIVE

To determine the precise allelic loss on chromosome 3p14 and discuss the possible relations between loss of heterozygosity (LOH) and EBV infection, clinical stage and clinic-pathology of nasopharyngeal carcinoma (NPC).

METHODS

Six high dense microsatellite marker on chromosome 3p14 were selected to examine LOH in 32 cases of NPC.

RESULTS

23 of 32 (71.9%) tumors were deleted for at least one locus of six loci. High frequencies of LOH (> 40%) were observed at loci D3S1300(50.0%), D3S1313(46.4%) and D3S1312(44.4%). 12 cases showed LOH in one contiguous and nonrandom region. The smallest common deletion region seems likely to lie between D3S1313 and D3S1312. Relations between LOH on 3p14 and clinical stage and EBV infection were observed. The frequency of LOH was 70.0% in 30 cases of poor-differentiated squamous cell carcinoma. 2 cases of vesicular nucleus cell carcinoma had LOH at two loci.

CONCLUSION

The high deletion rate on 3p14 in NPC indicates that there might be a putative tumor suppressor gene related to the development and progression of NPC.

[The effects of the receptor antagonist of glutamic acid on the brain tissue of severely scalded rats]

OBJECTIVE

To explore the influence of glutamic acid on burned rat brain tissue and the effects of the receptor antagonist of glutamic acid.

METHODS

Rats inflicted with 30% TBSA III degree scalding injury were taken as the model. The water content, K(+), Na(+), Ca(2+), Mg(2+), nitric oxide metabolites (NO(2)(-)/NO(3)(minus sign))concentrations of scalded rat brain were determined at 2, 6, 12 and 24 postburn hours (PBH). Morphological and histochemical studies of the brain tissue were carried out with LM and EM.

RESULTS

The water content, Na(+), Ca(2+)and NO(2)(minus sign)/NO(3)(minus sign) concentrations of the brain tissue after scalding injury were higher than those in control group. But intracerebral ATP enzyme decreased postburn. It was found by EM examination that there existed swelling of capillary endothelium, nerve cells and some intracytoplasmic mitochondria. There appeared pinosome on capillary wall. After the administration of receptor antagonist of glutamic acid, D-2-amino-group-7-phosphoenanthate (D-AP7), the brain water content, Na(+), Ca(2+)and NO(2)(-)/NO(3)(-) concentrations in brain tissue, and the capillary wall pinosome decreased, and the swelling of nerve cells ameliorated.

CONCLUSION

There might be postburn increased cerebral microvascular permeability, ischemic injury of cerebral tissue cells and the development of brain edema. The postburn alterations in the morphology and metabolism of brain tissue were correlated with the over secretion of glutamic acid. And the excitatory toxic effects of glutamic acid were mediated by its receptor. The receptor antagonist of glutamic acid D-AP7 might ameliorate postburn cerebral injury.

Direct measurement of 1H-1H dipolar couplings in proteins: a complement to traditional NOE measurements

An intensity-based constant-time COSY (CT-COSY) method is described for measuring 1H-1H residual dipolar couplings of proteins in weakly aligned media. For small proteins, the overall sensitivity of this experiment is comparable to the NOESY experiment. In cases where the 1H-1H distances are defined by secondary structure, such as 1H(alpha)-1H(N) and 1H(N)-1H(N) sequential distances in alpha-helices and beta-sheets, these measurements provide useful orientational constraints for protein structure determination. This experiment can also be used to provide distance information similar to that obtained from NOE connectivities once the angular dependence is removed. Because the measurements are direct and non-coherent processes, such as spin diffusion, do not enter, the measurements can be more reliable. The 1/r3 distance dependence of directly observed dipolar couplings, as compared with the 1/r6 distance dependence of NOEs, also can provide longer range distance information at favorable angles. A simple 3D, 15N resolved version of the pulse sequence extends the method to provide the improved resolution required for application to larger biomolecules.

[The selection of taxol resistance associated genes in ovarian cancer cell line by mRNA DD]

OBJECTIVE

One of the main reasons of the treatment failure for ovarian cancer is the emergence of drug resistance in which several genes involved. The purpose of the study was to select the genes related to Taxol resistance in ovarian cancer.

METHODS

Resistant ovarian cancer cell line, Skov3/Taxol-25, was established by interval exposure Skov3 to Taxol. mRNA was compared between Skov3 and Skov3/Taxol-25 by mRNA DD.

RESULTS

Skov3/Taxol-25 showed 44 times increase resistance to Taxol after 12 months of induction. There were 22 new differential bands obtained from Skov3/Taxol-25 as compared with Skov3. 18 bands were special by repeated PCR. In the 5 sub-clones, three clones were homologous to the known gene. 105/106 base pair of clone 1 were homologous to tPA (tissue plasminogen activator), 261/268 of clone 3 to Kiaa 0372, and 406/409 of clone 18 to LDLC. The other 2 ESTs were new gene segments, which were banked to Genbank with the number of AF120327 and AF120328. The identification by RT-PCR revealed that both tPA and Kiaa0372 were special genes from Skov3/Taxol-25, while LDLC was pseudopositive.

CONCLUSION

Several genes were involved in the resistance to Taxol in ovarian cancer. The enhanced expression of tPA indicated the increased ability of metastasis after the acquisition of resistance to taxol.