The alpha(1,3)fucosyltransferases FucT-IV and FucT-VII exert collaborative control over selectin-dependent leukocyte recruitment and lymphocyte homing

E-, P-, and L-selectin counterreceptor activities, leukocyte trafficking, and lymphocyte homing are controlled prominently but incompletely by alpha(1,3)fucosyltransferase FucT-VII-dependent fucosylation. Molecular determinants for FucT-VII-independent leukocyte trafficking are not defined, and evidence for contributions by or requirements for other FucTs in leukocyte recruitment is contradictory and incomplete. We show here that inflammation-dependent leukocyte recruitment retained in FucT-VII deficiency is extinguished in FucT-IV(-/-)/FucT-VII(-/-) mice. Double deficiency yields an extreme leukocytosis characterized by decreased neutrophil turnover and increased neutrophil production. FucT-IV also contributes to HEV-born L-selectin ligands, since lymphocyte homing retained in FucT-VII(-/-) mice is revoked in FucT-IV(-/-)/FucT-VII(-/-) mice. These observations reveal essential FucT-IV-dependent contributions to E-, P-, and L-selectin ligand synthesis and to the control of leukocyte recruitment and lymphocyte homing.

Enflurane actions on spinal cords from mice that lack the beta3 subunit of the GABA(A) receptor

BACKGROUND

Gamma-aminobutyric acid type A (GABA(A)) receptors are considered important in mediating anesthetic actions. Mice lacking the beta3 subunit of this receptor (beta3-/-) have a higher enflurane minimum alveolar concentration (MAC) than wild types (+/+). MAC is predominantly determined in spinal cord.

METHODS

The authors measured three population-evoked responses in whole spinal cords, namely, the excitatory postsynaptic potential (pEPSP), the slow ventral root potential (sVRP), and the dorsal root potential. Synaptic and glutamate-evoked currents from motor neurons in spinal cord slices were also measured.

RESULTS

Sensitivity of evoked responses to enflurane did not differ between +/+ and -/- cords. The GABA(A) receptor antagonist bicuculline significantly (P < 0.05) attenuated the depressant effects of enflurane on pEPSP, sVRP and glutamate-evoked currents in +/+ but not -/- cords. The glycine antagonist strychnine elevated the pEPSP to a significantly greater extent in -/- than in +/+ cords, but the interactions between strychnine and enflurane did not differ between -/- and +/+ cords.

CONCLUSIONS

Similar enflurane sensitivity in spinal cords from -/- and +/+ mice was coupled with a decreased role for GABA(A) receptors in mediating the actions of enflurane in the former. This finding implies that other anesthetic targets substitute for GABA(A) receptors. Increase in glycine receptor-mediated inhibition was found in -/- cords, but the glycine receptor does not appear to be a substitute anesthetic target. This mutation thus led to a quantitative change in the molecular basis for anesthetic depression of spinal neurotransmission in a fashion not predicted by the mutation itself. The results argue against an immutable dominant role for GABA(A) receptors in mediating spinal contributions to MAC.

Human T-cell leukemia virus type I tax protein induces the expression of anti-apoptotic gene Bcl-xL in human T-cells through nuclear factor-kappaB and c-AMP responsive element binding protein pathways

Human T-cell leukemia virus type I (HTLV-I) is the etiologic agent of adult T-cell leukemia (ATL), which is an aggressive form of human T-cell malignancy. The viral protein, Tax, immortalizes human T-cells and inhibits various types of apoptosis, and is thought to play crucial roles in the development of ATL. We have recently demonstrated that Tax induces the constitutive expression of the anti-apoptotic protein, Bcl-xL, in a mouse T-cell line. The mouse, however, is not a natural host of HTLV-I, and HTLV-I does not induce this malignancy in mice. We thus examined whether Tax also activates the expression of Bcl-xL in human T-cells. Expression of Tax in a human T-cell line, Jurkat, induced the expression of the Bcl-xL gene, but did not significantly affect the expression of the other apoptosis-related genes, Bcl-2 and Bax. Transient transfection assays showed that Tax stimulated human Bcl-xL promoter activity in Jurkat cells. Deletion of the two potential nuclear factor (NF)-kappaB binding sites in the human Bcl-xL promoter significantly decreased Tax-induced transactivation. In addition to NF-kappaB, Tax activates transcription through the c-AMP responsive element binding protein (CREB). Tax mutants segregating these two pathways showed that both the NF-kappaB and CREB pathways of Tax are required for maximum activation of a human Bcl-xL promoter, nevertheless, NF-kappaB alone was sufficient for that of a mouse Bcl-xL promoter. Northern blot analysis showed that all the human T-cell lines expressing Tax had higher levels of Bcl-xL mRNA than HTLV-I-uninfected ones. Furthermore, the sample from one patient with ATL expressed higher levels of Bcl-xL mRNA compared with levels from uninfected peripheral blood mononuclear cells. Our results suggest that Tax induces the expression of Bc-xL through the NF-kappaB and CREB pathways in HTLV-I-infected human T-cells, and then inhibits apoptosis, and such inhibition is necessary for the infected cells to advance to the leukemia in vivo.

The I-antigens of Ichthyophthirius multifiliis are GPI-anchored proteins

The parasitic ciliate Ichthyophthirius multifiliis has abundant surface membrane proteins (i-antigens) that when clustered, trigger rapid, premature exit from the host. Similar antigens are present in free-living ciliates and are GPI-anchored in both Paramecium and Tetrahymena. Although transmembrane signalling through GPI-anchored proteins has been well-documented in metazoan cells, comparable phenomena have yet to be described in protists. Since premature exit of Ichthyophthirius is likely to involve a transmembrane signalling event, we sought to determine whether i-antigens are GPI-anchored in these cells as well. Based on their solubility properties in Triton X-114, the i-antigens of Ichthyophthirius are amphiphilic in nature and partition with the detergent phase. Nevertheless, following treatment of detergent lysates with phospholipase C, the same proteins become hydrophilic. Concomitantly, they are recognized by antibodies against a cross-reacting determinant exposed on virtually all GPI-anchored proteins following cleavage with phospholipase C. Finally, when expressed in recombinant form in Tetrahymena thermophila, full-length i-antigens are restricted to the membrane, while those lacking hydrophobic C-termini are secreted from the cell. Taken together, these observations argue strongly that the i-antigens of Ichthyophthirius multifiliis are, in fact, GPI-anchored proteins.

Suppressive effect of tranilast on interleukin-5 prolonged eosinophils survival via apoptosis

Tranilast has long been used clinically to treat allergic diseases such as bronchial asthma. To further clarify the antiinflammatory machanism, we examined the ability of tranilast to counteract the prolongation of eosinophil survival induced by interleukin (IL)-5. Tranilast reduced the IL-5 prolonged survival of eosinophils at the concentration range of 30 microg/ml to 100 microg/ml. The DNA extracted from eosinophils cultured with tranilast showed signs of fragmentation that was comparable with apoptosis. Electron-microscopic analysis of activated eosinophils cultured with 100 microg/ml of tranilast also revealed morphologic features of apoptosis. These data suggest that tranilast may act in vivo on activated eosinophils to reduce inflammation in allergic diseases.

Investigation of infection risk and the value of urine endotoxin during extracorporeal shock wave lithotripsy

OBJECTIVE

To clarify the infection risks and the value of endotoxin determination in urine during extracorporeal shock wave lithotripsy (ESWL).

METHODS

According to the distribution and complications of upper urinary calculi, 164 patients were divided into five groups. Group A consisted of 48 patients with 1 to 4 renal calculi, which were or less than 2 cm in diameter. Group B was composed of 24 patients with renal calculus larger than 2 cm in diameter or one to multiple renal calculi. Group C was composed of 22 patients with 1 to 3 renal calculi accompanied by 1 to 2 ureteric calculi. Group D consisted of 51 patients with 1 to 3 ureteric calculi that were 0.5 to 1.2 cm in diameter, respectively. Group E included 19 patients with complicated renal calculus, such as casting and staghorn renal calculus. Urine and blood samples of these patients were obtained before and after ESWL, respectively. Their urine samples were proven sterile prior to treatment. All samples were cultured for bacteria and investigated for endotoxin concentration by the limulus lysate test.

RESULTS

No significant difference in serum endotoxin was noted before and after ESWL. Blood bacterial cultures were all negative in all patients after ESWL, similar to those before ESWL. Significant increases in urine endotoxin after ESWL compared with that before ESWL in patients of Groups B, C and E were observed, respectively (P < 0.05). There was no significant difference in urine endotoxin after ESWL compared with that before ESWL in patients of Groups A and D. The positive incidences of urine bacterial culture were significantly increased (P < 0.05) in Groups B and C and very significantly increased (P < 0.01) in Group E compared with those in Groups A and D.

CONCLUSIONS

Urinary infection risk following ESWL was lower in patients with one to several renal calculi, which were less than 2 cm in diameter and did not interfere obviously with the urine flow or in patients with 1 to 3 ureteric calculi that were 0.5 to 1.2 cm in diameter. The risk was higher in those with complicated calculi, such as casting, staghorn renal calculus, renal calculus larger than 2 cm in diameter or renal calculi accompanied by ureteric calculi. For patients with higher infection risk after ESWL, prophylactic antibiotics are necessary even if bacteriuria is not present before ESWL. Endotoxin determination in urine is a reliable, sensitive and simple method for the diagnosis of bacterial infection in patients undergoing ESWL.

[Quantum chemistry Ab initio calculation of vibration spectrum of beta-elemene]

In this study, ab initio calculation of vibration spectrum of beta-elemene has been performed at RHF/6-31G* level. Comparison with the experimental results, we succeed in assignment of normal modes of the fundamental frequency of the molecule. We have also discussed the characteristic vibrations, and scaled theoretical frequencies empirically.

A Schiff base is a major DNA adduct of crotonaldehyde

Previous studies have demonstrated that the reaction of crotonaldehyde with DNA produces Michael addition products, and these have been detected in human tissues as well as tissues of untreated laboratory animals. A second class of crotonaldehyde-DNA adducts releases 2-(2-hydroxypropyl)-4-hydroxy-6-methyl-1,3-dioxane (paraldol, 12) upon hydrolysis, and these adducts are quantitatively more significant than the Michael addition adducts in vitro. In this study, we demonstrate that the major source of the paraldol-releasing DNA adducts of crotonaldehyde is a Schiff base. Reaction of crotonaldehyde with DNA, followed by treatment with NaBH(3)CN and enzyme hydrolysis, resulted in the formation of N(2)-(3-hydroxybutyl)dG (10), identified by its UV, MS, and proton NMR. Reactions of crotonaldehyde or paraldol with dG demonstrated that the Schiff base precursor to N(2)-(3-hydroxybutyl)dG is N(2)-(3-hydroxybutylidene)dG (7), identified by UV, LC-APCI-MS, and MS/MS. Four isomers of N(2)-(3-hydroxybutylidene)dG were observed. The (R)- and (S)-isomers were identified by reactions of chiral paraldol with dG; each existed as a pair of interconverting (E)- and (Z)-isomers. These data indicate that the structure of the major Schiff base DNA adduct in crotonaldehyde-treated DNA is N(2)-(3-hydroxybutylidene)dG (7). This adduct is unstable at the nucleoside level and accounts for more than 90% of the paraldol released from crotonaldehyde-treated DNA. However, the adduct is stable in DNA and therefore is a likely companion to the Michael addition adducts in human DNA.

Successful Engraftment in Two Adult Patients with Severe Aplastic Anemia Using Nonmyeloablative Conditioning Followed by Unrelated HLA-Mismatched Cord Blood Transplantation

Umbilical cord blood as an alternative source of hematopoietic stem cells and nonmyeloablative conditioning are very exciting new developments in transplantation. We report here mixed chimerism in two adult patients with severe aplastic anaemia using nonmyeloablative conditioning and two-antigen mismatched cord blood transplantation resulting in satisfactory clinical response. Our results suggest that such transplant is possible with minimal toxicity.

AlaArg motif in the carboxyl terminus of the gamma(1)34.5 protein of herpes simplex virus type 1 is required for the formation of a high-molecular-weight complex that dephosphorylates eIF-2alpha

The gamma(1)34.5 protein of herpes simplex virus (HSV) type 1 functions to prevent the shutoff of protein synthesis mediated by the double-stranded-RNA-dependent protein kinase PKR. This is because gamma(1)34.5 associates with protein phosphatase 1 (PP1) through its carboxyl terminus, forming a high-molecular-weight complex that dephosphorylates the alpha subunit of translation initiation factor eIF-2 (eIF-2alpha). Here we show that Val193Glu and Phe195Leu substitutions in the PP1 signature motif of the gamma(1)34.5 protein abolished its ability to redirect PP1 to dephosphorylate eIF-2alpha and replication of mutant viruses was severely impaired. The gamma(1)34.5 protein, when expressed in Sf9 cells using a recombinant baculovirus, was capable of directing specific eIF-2alpha dephosphorylation. Deletions of amino acids 258 to 263 had no effect on activity of gamma(1)34.5. However, deletions of amino acids 238 to 258 abolished eIF-2alpha phosphatase activity but not PP1 binding activity. Interestingly, deletions in the AlaArg motif of the carboxyl terminus disrupted the high-molecular-weight complex that is required for dephosphorylation of eIF-2alpha. These results demonstrate that gamma(1)34.5 is functionally active in the absence of any other HSV proteins. In addition to a PP1 binding domain, the carboxyl terminus of gamma(1)34.5 contains an effector domain that is required to form a functional complex.

The electrochemically induced conformational transition of disulfides in bovine serum albumin studied by thin layer circular dichroism spectroelectrochemistry

The conformational transition of disulfides in bovine serum albumin (BSA) induced by electrochemical redox reaction of disulfides were monitored by in-situ circular dichroism (CD) spectroelectrochemistry, with a long optical path thin layer cell and analyzed by a singular value decomposition least square (SVDLS) method. Electrochemical reduction of disulfides drives the left-handed conformation of disulfides changed into the right-handed. At open circuit, eight of the 17 disulfides were of left-handed conformation. Four of the 17 disulfides took part in the electrochemical reduction with an EC mechanism. Only one-fourth of the reduced disulfides returned to left-handed conformation in the re-oxidation process. Some parameters of the electrochemical reduction process, i.e. the number of electrons transferred and electron transfer coefficient, n = 8, alpha n = 0.15, apparent formal potential, E1(0') = -0.65(+/-0.01) V, standard heterogeneous electron transfer rate constant, k1(0) = (2.84 +/- 0.14) x 10(-5) cm s(-1) and chemical reaction equilibrium constant, Kc = (5.13 +/- 0.12) x 10(-2), were also obtained by double logarithmic analysis based on the near-UV absorption spectra with applied potentials.

Compositional and functional changes of pulmonary surfactant in a guinea-pig model of chronic asthma

Recent studies have found that severe surfactant dysfunction occurs during an asthma attack, but the changes in surfactant in a guinea-pig model of chronic asthma have not been studied. We therefore analysed the surfactant recovered from guinea-pigs after repeated inhalation of ovalbumin to see if the surfactant recovered from chronic asthmatic lungs would be intrinsically altered. Guinea pigs immunized through repeated inhalation of aerosolized ovalbumin (OA) were exposed to the antigen once a week for a month. Twenty-four hours after the last challenge the alveolar wash was recovered. We calculated saturated phosphatidylcholine (Sat-PC) and total protein (TP) pool sizes in alveolar spaces. Surfactant subtype conversion of large aggregate surfactant (LA) to small aggregate surfactant was studied in vitro by means of the surface area cycling technique. The phospholipid composition of LA was analysed by thin layer chromatography and the surface activity of LA was also determined. We found decreased surfactant pool sizes, decreased ratio of Sat-PC to TP in alveolar lavages in asthma groups, and surface activity of the surfactant recovered from asthmatic lungs to be inferior to that of the controls. Accelerated surfactant subtype conversion in vitro was also noted in the lungs of asthmatic animal models. In addition, the changes in phospholipid compositions which were similar to the pattern of acute lung injury suggested that alveolar inflammation might be involved in the pathogenesis of chronic asthma. These results indicate that surfactant is intrinsically abnormal in chronically asthmatic lungs.

Transfusion of peripheral blood stem cells from donor homozygous for a shared HLA-haplotype: avoiding fatal transfusion-associated graft-versus-host disease while preserving anti-leukemic effect

BACKGROUND

Fatal transfusion-associated graft-versus-host disease was observed in immunocompetent patients transfused with blood from donors homozygous for a shared haplotype with the recipient (the P-F1 barrier). We tested whether it was possible to carry out successful transplantation in a patient with relapsed acute myeloid leukemia, using peripheral blood stem cells from his HLA-homozygous brother (HLA A2, B46, DRB1 901) who shared a haplotype with the patient (HLA A2, B46,75, DRB1 901,12).

METHODS

A CD34 positively selected cell fraction (5.46x 10(6) CD34 cells/kg) was infused first, followed by subsequent infusion of graded doses of donor T cells (total 7.25x10(7) T cells/kg). Nonmyeloablative chemotherapy with idarubicin and cytarabine was given during the transplantation to reduce the leukemic burden and facilitate engraftment. Polymerase chain reaction with the VNTR primers, D1S80, was used to detect engraftment.

RESULTS

Complete remission (>300days) and successful donor engraftment (90%) were achieved.

CONCLUSIONS

Peripheral blood stem cells transplantation from a donor with a homozygous shared haplotype is possible with a minimal preparative regimen.

[Using fluorescence PCR analysis for early diagnosis and carriers detection of Chinese Wilson's disease]

OBJECTIVE

To diagnose the pre-symptomatic cases of Chinese Wilson's disease(WD) and detect the potential carriers by using fluorescence PCR technique.

METHODS

Screening the high frequency spot Arg778Leu of WD gene mutation in 66 Chinese WD patients, 55 healthy family members and 30 controls, and selecting 3 random samples (2 from WD patients, 1 from controls) for DNA sequencing to testify the accuracy of fluorescence PCR.

RESULTS

Among 66 Chinese WD cases, 5 were found homozygous for mutation of Arg778Leu and 21 were compound heterozygous; the gene mutation rate was totally 39.4%. Out of 55 healthy family members, 12 were found heterozygous, and it was confirmed that 11 of these 12 individuals were WD gene carriers but not pre-symptomatic patients. The results of direct DNA sequencing consisted with those results detected by fluorescence PCR.

CONCLUSION

The Arg778Leu mutation in exon 8 is the high frequency spot of Chinese Wilson's disease gene. Fluorescence PCR analysis is a rapid, accurate gene diagnostic method and demonstrates a high detecting rate.

Interleukin (IL)-4/IL-9 and exogenous IL-16 induce IL-16 production by BEAS-2B cells, a bronchial epithelial cell line

Previous studies have suggested that bronchial epithelial cells may perpetuate airway inflammation. We have reported that the bronchial epithelial cell line BEAS-2B can produce interleukin (IL)-16, a potent chemoattractant for CD4+ T cells. IL-16 is thought to regulate airway inflammation in asthmatics. Recent studies showed that IL-4 induces inflammatory cytokines in bronchial epithelial cells and that IL-9 is a candidate gene for development of asthma. The present study demonstrated that BEAS-2B cells produced specifically IL-16 by synergistic effects of IL-4 + IL-16, or IL-9 + IL-16, and that the synthesized IL-16 induced migration of CD4+ T cells. This study is a first report indicating that IL-16 production may be maintained by an autocrine machinery by epithelial cell-derived IL-16 with IL-4 and IL-9 in asthma.

[Landscape change in middle Heihe River Basin]

Using GIS and a landscape structure analysis program FRAGSTATS, this paper dealt with the landscape change in the middle Heihe River Basin during the past 20 years. During the past 20 years, the landscape elements had a complex change of landscape structure and an apparent transition of landscape composition, but the landscape in a whole still displayed a pattern of sharply contrast between oasis landscape and desertification landscape. Human activities significantly changed the distribution and allocation of the limited water resource in the basin, leading to an acute contradiction between desertification and oasisfication. Moreover, the transitional area between desertification and oasisfication was very sensitive to these processes. The decrease of Shannon's diversity index and evenness index manifested the intensive management and reconstruction of landscape by human beings, which improved the socioeconomic benefits of the region on one hand, but decreased the landscape heterogeneity and landscape diversity, leading to the decrease of eco-environmental benefits of some areas in the basin on the other hand. The research method and technology used in this paper were also discussed.

CD40 signaling replaces CD4+ lymphocytes and its blocking prevents chronic rejection of heart transplants

Chronic rejection remains the major obstacle to long term survival in heart transplant recipients. The cellular and molecular mechanisms that underlie chronic rejection are not known, and their discovery can form the basis of clinical intervention. Several investigators have suggested that the development of chronic rejection in solid organ transplants is dependent on help mediated by CD4(+) lymphocytes. Importantly, the mechanism through which help is provided has not been fully delineated in transplant rejection. Using a murine heterotopic heart transplant model without immunosuppression, this study defines the functional role of CD4(+) lymphocytes in chronic rejection. In an MHC class II-mismatched model, we demonstrate that chronic rejection was absolutely contingent on the presence of CD4(+) lymphocytes. Importantly, here we report that signaling through CD40 can replace the requirement of CD4(+) lymphocytes, demonstrated by the development of chronic rejection in CD4 knockout recipients treated with a CD40-activating mAb (FGK45). The return of rejection appears to be a CD8(+) lymphocyte-dependent process, noted by the absence of rejection in FGK45-treated recombinase-activated gene knockout (CD4(+) and CD8(+) lymphocyte-deficient) recipients. The CD40 signaling pathway works independently of B7-CD28 costimulation, as indicated by the development of severe chronic rejection in CD28 knockout recipients. Importantly, this study provides evidence that CD40 ligand-targeted therapies may prevent chronic rejection only in strain combinations where CD4(+) lymphocyte help is absolutely required.

[Advance in study of artificial nerve]

OBJECTIVE

To review the advance in materials of nerve conduit and Schwann cell transplantation for preparation of artificial nerve with tissue engineering technique.

METHODS

Recent literatures about artificial nerve, nerve conduit and Schwann cell transplantation were extensively reviewed.

RESULTS

Many biomaterials such as silicon, dacron, expanded polytetrafluoroethylene(ePTFE), polyester and chitin could be used as nerve conduits to repair nerve defect, the degradable biomaterials were better. The nerve conduit with intrinsic filaments could be used to bridge an extended gap in peripheral nerve. Purified and cultured Schwann cells were still bioactive. Axonal regeneration could be enhanced after implantation of Schwann cells into nerve conduit.

CONCLUSION

The ideal artificial nerve is composed of three dimensional biodegradable nerve conduit and bioactive Schwann cells, Schwann cells can be distributed in nerve conduit just like Bünger's band.

Increased levels of surfactant protein A and D in bronchoalveolar lavage fluids in patients with bronchial asthma

Surfactant proteins (SP)-A and SP-D are collagen-like glycoproteins belonging to the "collectin" class of C-type lectins, which are primarily synthesized in type II cells. Recent studies reported the possibility of local production of SP-A and SP-D in the airways, but the amounts of surfactant proteins in patients with bronchial asthma have not been studied. The composition of surfactant proteins in mild, stable asthmatics in the first lavage as bronchial lavage (BL) and the second and third lavages consecutively as alveolar lavages (AL) were therefore, analysed separately. The co-relationships in the BL between the amounts of surfactant proteins and those of fucose, which is one of the markers of submucosal secretion were also analysed. Increased amounts of SP-A in BL and AL of in asthmatics were found as compared with those in controls. A high concentration of SP-D in the AL asthma patients was also found. The levels of SP-A correlated with those of fucose in patients with bronchial asthma (r=0.849, p<0.01). The observations in the present study suggested that surfactant protein A may be secreted from the airways with allergic inflammation in a different manner from the alveoli. The increased levels of surfactant proteins A and D may play a protective role in an allergic inflammation in the pathogenesis of bronchial asthma.

Assessment of optic nerve compression in Graves' ophthalmopathy. The usefulness of a quick T1-weighted sequence

PURPOSE

Diagnosis of optic nerve compression can be difficult in patients with equivocal clinical signs. We examined the usefulness of a quick coronal MR sequence performed at a predetermined plane as a screening tool for selecting patients at high risk of optic nerve compression.

MATERIAL AND METHODS

Direct coronal images of the orbit were obtained in 37 patients with Graves' disease in a predetermined plane. The muscular indices (MI) of each orbit were calculated. Mann-Whitney U-Wilcoxon rank sum test was used to assess if there was any statistically significant difference between patients with and without signs of optic nerve compression. The ROC curve was used to identify a value useful for discriminating patients with a higher risk of developing optic nerve compression.

RESULTS

There was a statistically significant difference (p<0.05) in the MI between patients with and without optic nerve compression. An MI of -0.48 had 100% sensitivity, 89% specificity and 91% accuracy in identifying patients with optic nerve compression. CONCLUSION. A quick coronal MR image obtained at the mid-orbital plane is useful in screening patients with Graves' disease for optic nerve compression.

Identification of DNA adducts of acetaldehyde

Acetaldehyde is a mutagen and carcinogen which occurs widely in the human environment, sometimes in considerable amounts, but little is known about its reactions with DNA. In this study, we identified three new types of stable acetaldehyde DNA adducts, including an interstrand cross-link. These were formed in addition to the previously characterized N(2)-ethylidenedeoxyguanosine. Acetaldehyde was allowed to react with calf thymus DNA or deoxyguanosine. The DNA was isolated and hydrolyzed enzymatically; in some cases, the DNA was first treated with NaBH(3)CN. Reaction mixtures were analyzed by HPLC, and adducts were isolated and characterized by UV, (1)H NMR, and MS. The major adduct was N(2)-ethylidenedeoxyguanosine (1), which was identified as N(2)-ethyldeoxyguanosine (7) after treatment of the DNA with NaBH(3)CN. The new acetaldehyde adducts were 3-(2-deoxyribos-1-yl)-5,6,7, 8-tetrahydro-8-hydroxy-6-methylpyrimido[1,2-a]purine-10(3H)one (9), 3-(2-deoxyribos-1-yl)-5,6,7,8-tetrahydro-8-(N(2)-deoxyguanosyl+ ++)- 6-methylpyrimido[1,2-a]purine-10(3H)one (12), and N(2)-(2, 6-dimethyl-1,3-dioxan-4-yl)deoxyguanosine (11). Adduct 9 has been previously identified in reactions of crotonaldehyde with DNA. However, the distribution of diastereomers was different in the acetaldehyde and crotonaldehyde reactions, indicating that the formation of 9 from acetaldehyde does not proceed through crotonaldehyde. Adduct 12 is an interstrand cross-link. Although previous evidence indicates the formation of cross-links in DNA reacted with acetaldehyde, this is the first reported structural characterization of such an adduct. This adduct is also found in crotonaldehyde-deoxyguanosine reactions, but in a diastereomeric ratio different than that observed here. A common intermediate, N(2)-(4-oxobut-2-yl)deoxyguanosine (6), is proposed to be involved in formation of adducts 9 and 12. Adduct 11 is produced ultimately from 3-hydroxybutanal, the major aldol condensation product of acetaldehyde. Levels of adducts 9, 11, and 12 were less than 10% of those of N(2)-ethylidenedeoxyguanosine (1) in reactions of acetaldehyde with DNA. As nucleosides, adducts 9, 11, and 12 were stable, whereas N(2)-ethylidenedeoxyguanosine (1) had a half-life of 5 min. These new stable adducts of acetaldehyde may be involved in determination of its mutagenic and carcinogenic properties.

Conformational transition of DNA in electroreduction studied by in situ UV and CD thin layer spectroelectrochemistry

Electrochemically induced three conformational transitions of calf thymus DNA from B10.4 to Z10.2-DNA and from B10.2 to B10.4 and to C-DNA in 10 mM phosphate buffer solution (pH 7.21) at glassy carbon electrode are found and studied by in situ circular dichroism (CD) thin layer spectroelectrochemistry with singular value decomposition least square (SVDLS) analysis. It indicates that the so-called B10.2 form and the C-form of DNA may be composed of B10.4 and left-A DNA and of B10.4 and right-A DNA, respectively. The irreversible electrochemical reduction of adenine and cytosine groups in the DNA molecule is studied by UV-Vis spectroelectrochemistry. Some electrochemical parameters alpha n = 0.17, E0' = -0.70 V (vs. Ag/AgCl), and the standard heterogeneous electron transfer rate constant, k0 = 1.8 x 10(-5) cm s(-1), are obtained by double logarithmic analysis and non-linear regression.