Pharmacokinetics and anti-inflammatory pharmacodynamics of prednisolone in cynomolgus monkey

The purpose was to investigate whether the pharmacokinetics and pharmacodynamics of prednisolone in the non-human primate was an appropriate surrogate for man. After single intravenous doses of 0.03, 0.3, and 3 mg kg(-1), prednisolone demonstrated a dose-dependent clearance and volume of distribution. When corrected for concentration-dependent protein binding, the free clearance was linear at the tested dose levels. The protein binding-corrected volume of distribution was similar across doses. The serum half-life was estimated as being between 2 and 4 h. Prednisolone exhibits near complete inhibition of the cytokines TNF-alpha, IL-1beta, IL-6 and IL-8 with very similar IC50 estimates from 0.09 to 0.16 microg ml(-1) (from 0.24 to 0.44 microM). The monkey demonstrated a similar pharmacokinetics-pharmacodynamics profile of prednisolone when compared with man (from the literature).

[Distribution of hepatitis B virus genotypes and subgenotypes among chronically infected patients in Xinjiang Uighur.]

OBJECTIVE

To investigate the distribution of Hepatitis B virus genotypes and subgenotypes among patients with chronic hepatitis B in Xinjiang Uighur.

METHODS

The HBV genotypes and subgenotypes were analyzed by PCR-restriction fragment length polymorphism in 109 patients with chronic hepatitis B.

RESULTS

Two HBV genotypes, genotype C (45.9%) and genotype C/D (29.4%) were prevalent, genotype B (8.3%) and genotype D (16.5%) were also found in Xinjiang Uighur. Genotype C had two subgenotypes, C1 (54%) and C2 (46%). Genotype B had only one subgenotype, i.e. Ba. The subgenotype C2 was associated with cirrhosis and hepatocellular carcinoma.

CONCLUSION

In Uygurs, the most common HBV genotypes were C and C/D, and the subgenotype C2 was associated with cirrhosis and hepatocellular carcinoma.

An archaeal histone-like protein mediates efficient p53 gene transfer and facilitates its anti-cancer effect in vitro and in vivo

The improvement of the transfection efficiency of the non-viral-based gene delivery systems is a key issue for the application in gene therapy. We have previously described an archaeal histone-like protein-based (HPhA) gene delivery system and showed that HPhA formed stable non-covalent complexes with nucleic acids and improved their delivery by using beta-galactosidase as a reporter gene. In this study, the wild-type p53 gene was transfected into the cancer cells using the HPhA as a vector, and the expression level and the activity of p53 gene were evaluated both in vitro and in vivo. Gene expression was determined by real-time reverse transcriptase-PCR and western blotting analysis. The cellular growth inhibition and apoptosis of HPhA-mediated p53 transfection were assessed by XTT (sodium 3'-[1-(phenylaminocarbonyl)-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzene sulfonic acid hydrate) assay and annexin V-FITC (fluorescein isothiocyanate) staining, respectively. Further more, transfection of HPhA/p53 into CNE (nasopharyngeal carcinoma cell line)-xenografted nude mice was performed and tumor growth was measured. The present study demonstrates that HPhA enhances the efficiency of p53 gene transfer and antitumor activity compared with the widely used Lipofectamine. These results demonstrate that HPhA enhances the in vitro and in vivo efficiency of p53 gene transfer and suggest that it may be served as a promising tool for gene delivery and gene therapy.

[Study on the body mass index reference norm for defining overweight and obesity in school-age children and adolecents with Uygur and Han ethnic backgrounds in Urumqi]

OBJECTIVE

To construct and compare the body mass index (BMI) cutoff points for defining overweight and obesity in school-age children and youths with Uygur and Han ethnic backgrounds in Xinjiang, China.

METHODS

A total number of 9146 boys and girls in Urumqi, Xinjiang, aged 7-18 years, were recruited by stratifying and clustering sampling from April to June 2004. Demographic and anthropometric data, including body weight and standing height, were collected. Questionnaires and standard methods were used and BMI was calculated by weight/height2. BMI centile curves with age were drawn according to gender and ethnicity, using LMS software (Tim cole and Huiqi Pan) which were making the centile curves passing through 25 kg/m2 and 30 kg/m2, and 24 kg/m2 and 28 kg/m2 at age of 18 for overweight and obesity respectively.

RESULTS

The age and sex specific BMI centile curves were drawn for children with Uygur and Han ethnicities. Data showed that BMI increased with age. The centile of BMI curves, P94.46 and P99.58 for Uygur boys, P92.44 and P99.64 for Uygur girls, P85.05 and P97.26 for Han boys, P90.92 and P99.03 for Han girls, which passing through 25 kg/m2 and 30 kg/m2 by IOTF recommendation at age 18, were constructed. Under the basis of WGOC recommendation, the points that passing through 24 kg/m2 and 28 kg/m2 at age 18 were P90.54 and P98.86 for uygur boys, P86.96 and P98.77 for uygur girls, P78.98 and P94.72 for Han boys, P86.15 and P97.56 for Han girls. The BMI cutoff points for defining overweight and obesity were suggested.

CONCLUSION

To the best of our knowledge, the present study established the BMI cutoff points for Uygur ethnic school-aged children and youths for identifying overweight and obesity. There was ethnic difference in the BMI distribution with age. We recommended using the BMI cutoff points proposed by the current study to identify those overweight and obese children in Urumqi.

Ethnic differences in body mass index and prevalence of obesity in school children of Urumqi City, Xinjiang, China

OBJECTIVE

To investigate the prevalence of obesity and distribution of body mass index (BMI) in school children of four ethnic groups in Urumqi, Xinjiang, China.

METHODS

A total of 55508 school children of Han, Hui, Uygur and Kazak nationalities aged 8-18 years were selected by a cluster sampling from a districts of Urumqi City for anthropometric measurement and demographic survey. Prevalence of obesity and overweight and distribution of body mass index (BMI) by gender, age, and nationality were analyzed and compared. Cutoff points of BMI for defining obesity and overweight were based on the proposal set by the Working Group on Obesity in China (WGOC) to assess age-, gender- and nationality-specific prevalence of obesity and overweight.

RESULTS

Prevalence of obesity was 5.34%, 6.78%, 3.39 %, and 1.22% for boys and 2.61%, 1.83%, 1.78%, and 1.40% for girls of Han, Hui, Uygur and Kazak nationalities, respectively. Prevalence of obesity tended to decrease with age overall, whereas that of overweight increased with age in Han children.

CONCLUSIONS

Prevalence of obesity in school children in Urumqi varies with their nationalities and is lower than that of an average national level and a level of western countries. Obesity is more prevalent in boys than in girls of Urmuqi overall, which is just the opposite in Kazak children. Han boys and Hui girls have the highest prevalence of obesity and Kazak boys and girls have the lowest ones. Prevalence of obesity decreases with age, but that of overweight shows a different trend.

Retrograde cerebral perfusion of oxygenated, compacted red blood cells attenuates brain damage after hypothermia circulation arrest of rat

BACKGROUND

It was proved that higher haematocrit (Hct) might improve the function of brain after hypothermia circulation arrest (HCA). In the present study we established a new rat HCA model and investigated whether retrograde cerebral perfusion of oxygenated, compacted red blood cells (RBC) could attenuate brain injury after HCA.

METHODS

A new rat HCA model was developed and rats were randomly distributed into three groups: HCA group, HCA combined with retrograde cerebral perfusion of oxygenated, compacted red blood cell group (HCArcp group), and sham operation group (sham op. group). Animals both in the HCA group and in the HCArcp group underwent HCA 90 min at 18 degrees C. Brain damage after HCA was evaluated with light microscopy and electron microscopy. Immunohistochemistry and RT-PCR techniques were used to measured the different expressions of the C-Fos, Bcl-2, Bax mRNA and protein among the groups. Additionally we measured the wet/dry ratio of the brain in order to evaluate the oedema degree after HCA.

RESULTS

The new HCA model of rat we developed was comparable to the clinical setting not only in terms of the intubation, anaesthesia method and materials employed but also in terms of the priming volume in relation to body weight. The number of injured neurones in the hippocampus CA1 and parietal cortex, but not in the thalamus of the HCA group, was significantly greater than that of the HCArcp group (P<0.05). The mean score of mitochondrion of the hippocampus CA1 in the HCA group was significantly higher than in the HCArcp group (P<0.05). The expression of C-Fos, Bax mRNA and protein in the hippocampus CA1 and/or parietal cortex area was higher in the HCA group than in the HCArcp group (P<0.05). Expression of the mRNA and protein of Bcl-2 was higher in the HCArcp group than in the HCA group (P<0.05). The degree of oedema after HCA between the HCA group and HCArcp group had no significant difference (P>0.05).

CONCLUSIONS

We established a new rat model of HCA comparable to the clinical setting. Retrograde cerebral perfusion of oxygenated, compacted RBC is a simple, effective, and safe method to protect the brain during HCA. Adjusting the gene expression in relation to apoptosis might contribute to the neuroprotective effects of a retrograde cerebral infusion of oxygenated, compacted RBC.

Screening and identification of target genes differentially expressed in HepG2 cells treated with arsenic trioxide by suppression subtractive hybridization technique

AIM: To clone and identify human genes differentially expressed in human hepatocarcinoma HepG2 cells treated with arsenic trioxide by constructing a subtractive cDNA library with suppression subtractive hybridization (SSH) technique, and to elucidate the molecular mechanism of arsenic trioxide in the regulation of liver cells.

METHODS: The mRNA was isolated from HepG2 cells treated with arsenic trioxide and PBS, respectively, and then cDNA was synthesized. After digestion of restriction enzyme RsaI, small sizes cDNA were obtained. Then the tester cDNA was subdivided into two portions and each was ligated with a different cDNA adaptor. After the tester cDNA was hybridized with driver cDNA (twice) and underwent nested polymerase chain reaction (PCR) (twice), the DNA fragment was subcloned into T/A plasmid vectors to establish the subtractive cDNA library. Amplification of the library was performed in E. coli strain JM109. The amplified cDNA was sequenced and analyzed in GenBank with BLAST search after colony PCR.

RESULTS: The subtractive cDNA library of genes differentially expressed in HepG2 cells treated with arsenic trioxide was constructed successfully. The amplified library contained 109 positive clones. Colony PCR showed that these clones all contained 200-1 000 bp inserts. Thirty-six clones were analyzed by sequencing and bioinformatics. The results showed there were 15 coding sequences with known function and 6 novel ones with unknown function.

CONCLUSION: A subtractive cDNA library of genes differentially expressed in HepG2 cells treated with arsenic trioxide was constructed successfully using SSH technique.

Aplastic anaemia associated with parvovirus B19 infection

Parvovirus B19 involvement was investigated in 30 children with severe aplastic anaemia. Active or recent parvovirus B19 infection, as shown by B19 DNA viraemia, positive B19 specific IgM antibodies, or both, was diagnosed in six patients. There were no other plausible causes. We suggest that parvovirus B19 infection might be associated with severe aplastic anaemia.

[Addition internal standard method in chromatographic quantitative analysis]

Internal standard method is a conventional chromatographic quantitative method which requires one or several internal standards added. The internal standard component must not be contained in the sample and need a good separation between the internal standard and sample components. In many cases selecting an internal standard is not convenient or even restricted by the seperation of components. In this paper, we try to combine the internal standard method and the addition method to form a new chromatographic quantitation method named addition internal standard method. The principles of addition internal standard method are suitable to not only chromatographic quantitation but also polarography etc. The related theory and foundation of the method are defined. The operation steps and the conditions suitable to the method are discussed. The advantages and disadvantages of this method are explained in detail.

[Study on the determination of NO, AsH3, COS and other impurities in cracked gas by chromatography/mass spectrometry method]

The selected ion monitoring(SIM) mode of capillary column gas chromatography coupled with mass spectrometry has been used for the determination of NO, AsH3, COS, thio-ether, thio-alcohol etc. in gases from catalytic cracking of heavy oils. The interference of CO, CO2, ethylene, ethane and N2 which affected the determination of NO was eliminated by chromatographic separation and subtraction of responses. The interference to the determination of selected ion was studied. Only C2H5SH was affected at m/z = 62 and the interference could be eliminated by using the ions at m/z = 47. The impurities in practical sample gas were determined. The detection limit of NO was 100 nL/L. The detection limits of other impurities were between 15 nL/L and 50 nL/L.

Catalytic mechanism of quinoprotein methanol dehydrogenase: A theoretical and x-ray crystallographic investigation

The catalytic mechanism of the reductive half reaction of the quinoprotein methanol dehydrogenase (MDH) is believed to proceed either through a hemiketal intermediate or by direct transfer of a hydride ion from the substrate methyl group to the cofactor, pyrroloquinoline quinone (PQQ). A crystal structure of the enzyme-substrate complex of a similar quinoprotein, glucose dehydrogenase, has recently been reported that strongly favors the hydride transfer mechanism in that enzyme. A theoretical analysis and an improved refinement of the 1.9-A resolution crystal structure of MDH from Methylophilus methylotrophus W3A1 in the presence of methanol, reported earlier, indicates that the observed tetrahedral configuration of the C-5 atom of PQQ in that study represents the C-5-reduced form of the cofactor and lends support for a hydride transfer mechanism for MDH.

Solvolytic enolization of scytalone

[reaction--see text] The major conformation of scytalone has an envelope shape with C3 forming the flap and the C3 hydroxyl in the equatorial position as determined by quantum mechanical calculations and corroborated by NMR. The C2 axial pro-R is slower to exchange with solvent than the equatorial pro-S hydrogen. Modeling the transition state for enolate formation points to a deprotonation through the flipped envelope conformation in which the C3-hydroxyl and the C2 pro-S hydrogen are axial.

Synthesis and structural analysis of the active enantiomer of famoxadone, a potent inhibitor of cytochrome bc1

Famoxadone is a newly commercialized fungicide and potent Qo-site inhibitor of cytochrome bc1. The S-(-)-enantiomer of famoxadone (the active component) was synthesized by two routes and was analyzed computationally and by X-ray crystallography. The molecule displays an extended conformation with flexibility in the structure imparted by the two terminal phenyl groups. In the crystal lattice, intermolecular hydrogen bonds occur between the NH and the oxygen atoms of the heterocycle.

Stereochemistry of the enolization of scytalone by scytalone dehydratase

In D(2)O, scytalone exchanges its two C2 hydrogen atoms for deuterium atoms at different rates. At pD 7.0 and 25 degrees C, half-lives for the exchanges are 0.8 and 10 days for the pro-S and pro-R hydrogens, respectively. The differential exchange rates allow for the preparation of multiple scytalone samples (through incubation of scytalone in D(2)O and then back exchanging with H(2)O) having differential levels of deuterium enrichment at the C2 pro-S and pro-R positions. From these samples, the stereochemical preference for hydrogen abstraction during the dehydration reaction mediated by the enzyme scytalone dehydratase was determined. At pH 7. 0, deuterium at the pro-S position has little effect on enzyme catalysis, whereas deuterium at the pro-R position produces kinetic isotope effects of 2.3 (25 degrees C), 5.1 (25 degrees C), and 6.7 (6.8 degrees C) on k(cat), k(cat)/K(m), and the single-turnover rate, respectively. The results are fully consistent with the enzyme catalyzing a syn elimination through an E1cb-like mechanism. The syn elimination is compatible with the interactions realized between a scytalone boat conformation and key active site residues as modeled from multiple X-ray crystal structures of the enzyme in complexes with inhibitors.

Role of a critical water in scytalone dehydratase-catalyzed reaction

Scytalone dehydratase (EC 4.2.1.94) catalyzes the dehydration of two important intermediates in the biosynthesis of melanin, and it functions without metal ions or any cofactors. Using molecular orbital theory, we have examined the role of a critical water molecule in the mechanism of scytalone dehydratase. The water, together with an internal hydrogen bonding, contributes significantly to the stabilization of the transition state (or the enolate intermediate). The role of two active site tyrosines (Tyr-50 and Tyr-30) is (i) to hold the critical water in place so that it may stabilize the transition state without much structural rearrangement during the catalytic reaction, and (ii) to polarize the water, making it a better general acid. The stereochemistry of the scytalone dehydratase-catalyzed dehydration is also discussed.

Conformation of coenzyme pyrroloquinoline quinone and role of Ca2+ in the catalytic mechanism of quinoprotein methanol dehydrogenase

The ab initio structures of 2,7,9-tricarboxypyrroloquinoline quinone (PQQ), semiquinone (PQQH), and dihydroquinone (PQQH2) have been determined and compared with ab initio structures of the (PQQ)Ca2+, (PQQH)Ca2+, and (PQQH2)Ca2+ complexes as well as the x-ray structure of (PQQ)Ca2+ bound at the active site of the methanol dehydrogenase (MDH) of methyltropic bacteria. Plausible mechanisms for the MDH oxidation of methanol involving the (PQQ)Ca2+ complex are explored via ab initio computations and discussed. Considering the reaction of methanol with PQQ in the absence of Ca2+, nucleophilic addition of methanol to the PQQ C-5 carbonyl followed by a retro-ene elimination is deemed unlikely due to large energy barrier. A much more favorable disposition of the methanol C-5 adduct to provide formaldehyde involves proton ionization of the intermediate followed by elimination of methoxide concerted with hydride transfer to the oxygen of the C-4 carbonyl. Much the same transition state is reached if one searches for the transition state beginning with Asp-303-CO2-general-base removal of the methanol proton of the (PQQ)Ca2+O(H)CH3 complex concerted with hydride transfer to the oxygen at C-4. For such a mechanism the role of the Ca2+ moiety would be to (i) contribute to the formation of the ES complex (ii) provide a modest decrease in the pKa of methanol substrate,; and (iii) polarize the oxygen at C-5.

Non-enzymatic and enzymatic hydrolysis of alkyl halides: a haloalkane dehalogenation enzyme evolved to stabilize the gas-phase transition state of an SN2 displacement reaction

The semiempirical PM3 method, calibrated against ab initio HF/6-31+G(d) theory, has been used to elucidate the reaction of 1, 2-dichloroethane (DCE) with the carboxylate of Asp-124 at the active site of haloalkane dehalogenase of Xanthobacter autothropicus. Asp-124 and 13 other amino acid side chains that make up the active site cavity (Glu-56, Trp-125, Phe-128, Phe-172, Trp-175, Leu-179, Val-219, Phe-222, Pro-223, Val-226, Leu-262, Leu-263, and His-289) were included in the calculations. The three most significant observations of the present study are that: (i) the DCE substrate and Asp-124 carboxylate, in the reactive ES complex, are present as an ion-molecule complex with a structure similar to that seen in the gas-phase reaction of AcO- with DCE; (ii) the structures of the transition states in the gas-phase and enzymatic reaction are much the same where the structure formed at the active site is somewhat exploded; and (iii) the enthalpies in going from ground states to transition states in the enzymatic and gas-phase reactions differ by only a couple kcal/mol. The dehalogenase derives its catalytic power from: (i) bringing the electrophile and nucleophile together in a low-dielectric environment in an orientation that allows the reaction to occur without much structural reorganization; (ii) desolvation; and (iii) stabilizing the leaving chloride anion by Trp-125 and Trp-175 through hydrogen bonding.

Nonenzymatic and enzymatic hydrolysis of alkyl halides: a theoretical study of the SN2 reactions of acetate and hydroxide ions with alkyl chlorides

The SN2 displacements of chloride ion from CH3Cl, C2H5Cl, and C2H4Cl2 by acetate and hydroxide ions have been investigated, using ab initio molecular orbital theory at the HF/6-31+G(d), MP2/6-31+G(d), and MP4/6-31+G(d) levels of theory. The central barriers (calculated from the initial ion-molecule complex) of the reactions, the differences of the overall reaction energies, and the geometries of the transition states are compared. Essential stereochemical changes before and after the displacement reactions are described for selected cases. The gas phase reactions of hydroxide with CH3Cl, C2H5Cl, and C2H4Cl2 have no overall barrier, but there is a small overall barrier for the reactions of acetate with CH3Cl, C2H5Cl, and C2H4Cl2. A self-consistent reaction field solvation model was used to examine the SN2 reactions between methyl chloride and hydroxide ion and between 1,2-dichloroethane and acetate in solution. As expected, the reactions in polar solvent have a large barrier. However, the transition state structures determined by ab initio calculations change only slightly in the presence of a highly polar solvent as compared with the gas phase. We also calibrated the PM3 method for future study of an enzymatic SN2 displacement of halogen.

Ab initio quantum mechanics analysis of imidazole C-H...O water hydrogen bonding and a molecular mechanics forcefield correction

While it is well established that classical hydrogen bonds play an important role in enzyme structure, function and dynamics, the role of weaker, but 'activated' C-H donor hydrogen bonds is poorly understood. The most important such case involves histidine which often plays a direct role in enzyme catalysis and possesses the most acidic C-H donor group of the standard amino acids. In the present study, we obtained optimized geometries and hydrogen bond interaction energies for C-H...O hydrogen bonded complexes between methane, ethylene, benzene, acetylene, and imidazole with water at the MP2-FC/6-31++G(2d,2p) and MP2-FC/aug-cc-pVDZ/MP2-FC/6-31++G(2d,2p) levels of theory. A strong linear relationship is obtained between the stability of the various hydrogen bonded complexes and both separation distances for H...O and C----O. In general, these calculations indicate that C-H...O interactions can be classified as hydrogen bonding interactions, albeit significantly weaker than the classical hydrogen bonds, but significantly stronger than just van der Waals interactions. For instance, while the electronic energy of stabilization at the MP2-FC/aug-cc-pVDZ/MP2-FC/6-31++G(2d,2p) level of theory of a water O-H...O water hydrogen bond is 4.36 kcal/mol more stable than the methane C-H...O water interaction, the water-water hydrogen bond is only 2.06 kcal/mol more stable than the imidazole Ce-H...O water hydrogen bond. Neglecting this latter hydrogen bonding interaction is obviously unacceptable. We next compare the potential energy surfaces for the imidazole Ce-H...O water and imidazole Na-H...O hydrogen bonded complexes computed at the MP2/6-31++G(2d,2p) level of theory with the potential energy surface computed using the AMBER molecular mechanics program and forcefields. While the Weiner et al and Cornell et al AMBER forcefields reasonably account for the imidazole N-H...O water interaction, these forcefields do not adequately account for the imidazole Ce-H...O water hydrogen bond. A forcefield modification is offered that results in excellent agreement between the ab initio and molecular mechanics geometry and energy for this C-H...O hydrogen bonded complex.

Is strong hydrogen bonding in the transition state enough to account for the observed rate acceleration in a mutant of papain?

Nitriles are good inhibitors for the cysteine protease papain. However, a single amino acid mutation (Gln-19 --> Glu-19) in the active site makes the mutant enzyme a good catalyst for nitrile hydrolysis. A theoretical approach was used to examine the differential transition state stabilization in the papain mutant relative to the wild-type enzyme. Based on this study, we concluded that strong hydrogen bonding in the transition state is responsible for the observed rate enhancement of 4 x 10(5).

Catalytic role of the alpha-carboxylate of the Glu residue of glutathione in glutathione S-transferases

The recently proposed catalytic role of the alpha-carboxylate of the Glu residue of glutathione in glutathione S-transferases (Widersten et al, Biochemistry 35, 7731-7742 (1996)) was examined. Based on structural considerations, it is clear that conformational changes in both glutathione and glutathione S-transferase are required. Recent kinetic studies by Ricci and coworkers (Ricci et al, J. Biol. Chem. 271, 16187-16192 (1996) and Caccuri et al, J. Biol. Chem. 271, 16193-16198 (1996)) may provide the missing evidence for these conformational changes. Possible ways to test this hypothesis are discussed.

A molecular dynamics study of the effect of carbon tetrachloride on enzyme structure and dynamics: subtilisin

Developing enzymes that are functional in highly concentrated halocarbon solutions, such as carbon tetrachloride, may prove useful in the development of new strategies for environmental remediation and monitoring of pollutant plumes, as well as in developing 'green' processes. Doing so will require gaining an understanding of the underlying structural and dynamic effects on enzymes induced by such solvents. Herein we report a 714 ps molecular dynamics simulation of the enzyme subtilisin Carlsberg and its waters of crystallization in a periodic box of carbon tetrachloride. The crystal structure from aqueous solution was used as the starting structure for our simulation using the AMBER program and forcefield. The calculated time-averaged structure is similar to the aqueous X-ray structure except for significant differences in loop (or turn) regions, resulting in many extra intra-protein hydrogen bonding interactions. Since carbon tetrachloride is a non-polar solvent and cannot interact strongly with the protein and water molecules, the water molecules stay very close to the protein surface throughout the simulation. The mobility of most of the waters was therefore very low. A few water molecules underwent significant lateral motion during the simulation, but never wandered far from the protein surface. Waters were either hydrogen bonded to protein polar groups, other water and/or counterions. Some of the surface waters participated in the formation of water-mediated hydrogen bonding networks. The increase in total number of intra-protein hydrogen bonds and the formation of water-mediated hydrogen bonding networks in carbon tetrachloride is consistent with the generally observed increase in thermostability and reduced flexibility of proteins in non-aqueous solutions. Several possible carbon tetrachloride binding sites on the protein surface are predicted.

Clinical evaluation of the diagnostic value of measuring IgG antibody to 3 mycobacterial antigen preparations in the capillary blood of children with tuberculosis and control subjects

SETTING

Department of Paediatrics in a University Hospital.

OBJECTIVE

To evaluate ABC-ELISA as serodiagnostic tests for tuberculosis in children.

DESIGN

An avidin-biotin-peroxidase conjugated anti-human immunoglobulin (ABC) enzyme-linked immunosorbent assay (ELISA) was established to measure serum immunoglobulin G (IgG) antibodies to polymerized old tuberculin (OT), tuberculin purified protein derivative (PPD) and the 30,000 dalton (30 kDa) native antigen of Mycobacterium tuberculosis, in 122 tuberculosis patients and 187 healthy children.

RESULTS

In those patients who had received less than 3 months of chemotherapy the sensitivities of the tests based on OT, PPD and the 30 kDa antigen were 40.3%, 50.0% and 36.1% respectively; the positive predictive values were 92.6%, 94.7% and 93.8% respectively and the negative predictive values were 58.6%, 62.9% and 57.2% respectively.

CONCLUSION

The ABC-ELISA may be useful for the diagnosis of pulmonary and extrapulmonary tuberculosis in groups of children with a high prior probability of tuberculosis. Antibodies to the 30 kDa antigen persisted longer than did those to OT and PPD.

Mechanism of gas-phase aldose-ketose isomerization: A study using tandem mass spectrometry and theoretical calculations

Fast-atom bombardment tandem mass spectrometry and the semiempirical molecular orbital method were used to investigate the mechanism of gas-phase aldose-ketose isomerization process in lithiated 1,3 linked disaccharide isomers. Both the 1,3 hydrogen shift and hydride transfer mechanisms were investigated. Our experimental and theoretical calculations support the latter. The hydride transfer mechanism in these lithium-coordrnated systems is similar to the xylose isomerase catalyzed aldose-ketose isomerization.

Theoretical examination of the mechanism of aldose-ketose isomerization

Two mechanisms for an aldose-ketose isomerization have been examined using high level ab initio and semiempirical molecular orbital methods. The proton transfer pathway via an enediol intermediate is shown to be favored in the absence of a metal ion, while the hydride transfer pathway becomes favored in the presence of a metal ion. Our calculations explain why the proton transfer pathway is operative in most aldose-ketose isomerization reactions. These calculations also provide further support for the previously proposed metal ion-mediated hydride transfer mechanism for xylose isomerase.

[Observation of three anti-M. tuberculosis antibodies in children with tuberculosis during chemotherapy]

Earlobe blood from 122 children with tuberculosis and 187 healthy children were assayed for anti-OTIgG, anti-PPDIgG and anti-Ag6IgG by ABC-ELISA. We found that the mean levels and sensitivity of anti-OTIgG and anti-PPDIgG decreased significantly in patients receiving more than 3 months of chemotherapy, but the anti-Ag6IgG remained constant. 18 patients were followed up for 12 months. among them 6 patients had a conversion from negative of anti-Ag6IgG to positive results. It is suggested that IgG to various M. tuberculosis antigens changes differently during the chemotherapy.

The effect of gossypol on ATPase activity of the kidney

The results of the present study have shown no change in the activity of ATPase of the renal cortex of rats administered gossypol for half a year. The Na+, K+-ATPase activity of the cellular membrane of renal cortex of guinea pigs fed with gossypol for 5 or 9 weeks is significantly altered. It seems possible to diminish or to delay the inhibition by allowing the guinea pigs a potassium-rich diet ad libitum. In vitro, gossypol inhibits significantly the activity of ATPase of the brain and the kidney of rats and guinea pigs uncompetitively. However, the inhibition of the ATPase of human fetus kidney is of a mixed type.